CN116034116A

CN116034116A - Acrylic rubber excellent in roll processability, strength characteristics and water resistance

Info

Publication number: CN116034116A
Application number: CN202180057051.6A
Authority: CN
Inventors: 增田浩文; 川中孝文
Original assignee: Zeon Corp
Current assignee: Zeon Corp
Priority date: 2020-06-05
Filing date: 2021-06-04
Publication date: 2023-04-28
Anticipated expiration: 2041-06-04
Also published as: CN116034116B; KR20230020402A; JPWO2021246511A1; WO2021246511A1

Abstract

The invention provides an acrylic rubber with excellent roller processability, strength characteristics and water resistance. The acrylic rubber of the present invention contains (meth) acrylic acid ester as a main component, a dimethylformamide-based solvent as an eluent, and has a weight average molecular weight (Mw) of 100 ten thousand or more, a ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of 3.4 or more, an ash content of 0.4% by weight or less, and a total amount of sodium, magnesium, calcium, phosphorus and sulfur in ash of 80% by weight or more, as measured by GPC-MALS method.

Description

Acrylic rubber excellent in roll processability, strength characteristics and water resistance

Technical Field

The present invention relates to an acrylic rubber, a method for producing the same, a rubber composition, and a rubber crosslinked product, and more particularly, to an acrylic rubber excellent in roll processability and excellent in strength characteristics and water resistance of the crosslinked product, a method for producing the same, a rubber composition containing the acrylic rubber, and a rubber crosslinked product obtained by crosslinking the same.

Background

Acrylic rubber is a polymer containing an acrylic ester as a main component, and is generally known as a rubber excellent in heat resistance, oil resistance and ozone resistance, and is widely used in fields related to automobiles, and the like.

For example, patent document 1 (pamphlet of international publication No. 2019/188709) discloses a method for producing an acrylic rubber as follows: the polymerization was carried out by adding a monomer component composed of ethyl acrylate, butyl acrylate, methoxyethyl acrylate and monobutyl fumarate, water and sodium lauryl sulfate, repeatedly degassing under reduced pressure and substituting nitrogen, adding sodium aldehyde sulfoxylate and cumene hydroperoxide as an organic radical generator, initiating emulsion polymerization at normal pressure and normal temperature, solidifying the mixture by a calcium chloride aqueous solution until the polymerization conversion rate reached 95% by weight, filtering the mixture by a wire mesh, and dehydrating and drying the mixture by an extrusion dryer having a screw. However, the acrylic rubber obtained by this method has problems of extremely poor roll processability and Banbury (Banbury) processability, and also poor storage stability and water resistance.

Patent document 2 (japanese patent application laid-open No. 2019-119772) discloses the following method: after a monomer emulsion was prepared from a monomer component comprising ethyl acrylate, butyl acrylate, methoxyethyl acrylate and monobutyl maleate using pure water and sodium lauryl sulfate and polyoxyethylene lauryl ether as emulsifiers, a part of the monomer emulsion was put into a polymerization tank and cooled to 12℃under a nitrogen stream, then the remaining part of the monomer emulsion, ferrous sulfate, sodium ascorbate and an aqueous potassium persulfate solution as an inorganic radical generator were continuously added dropwise over 3 hours, and thereafter, the emulsion polymerization was continued at 23℃for 1 hour until the polymerization conversion reached 97% by weight, and then, after heating to 85℃sodium sulfate was continuously added, thereby obtaining aqueous pellets by coagulation filtration, and after 4 times of washing with water, 1 time of washing with acid and 1 time of washing with pure water, the acrylic rubber was continuously produced into a sheet form by an extruder having a screw, and crosslinked with an aliphatic polyamine compound such as hexamethylenediamine amino formate. However, the sheet-like acrylic rubber obtained by the present method has problems of poor roll processability and poor water resistance of the crosslinked product.

Patent document 3 (japanese patent application laid-open No. 1-135811) discloses the following method: emulsion-liquefying 1/4 of a monomer mixture composed of a monomer component consisting of ethyl acrylate, caprolactone-added acrylate, cyanoethyl acrylate and vinyl chloride, and n-dodecyl mercaptan as a chain transfer agent with sodium lauryl sulfate, polyethylene glycol nonylphenyl ether and distilled water, adding sodium sulfite and ammonium persulfate as an inorganic radical generator, initiating polymerization, dropwise adding the remaining monomer mixture and a 2% ammonium persulfate aqueous solution for 2 hours while maintaining the temperature at 60 ℃, adding a latex having a polymerization conversion rate of 96 to 99% further for 2 hours after the dropwise addition to a sodium chloride aqueous solution of 80 ℃ for coagulation, then drying after sufficient water washing, and producing an acrylic rubber, and crosslinking by sulfur. However, the acrylic rubber obtained by the present method has problems of poor roll processability and storage stability, and poor strength characteristics and water resistance of the crosslinked product.

Patent document 4 (japanese patent application laid-open No. 2018-168343) discloses the following method: a monomer emulsion comprising a monomer component comprising ethyl acrylate, butyl acrylate and monobutyl fumarate, pure water, sodium lauryl sulfate, polyethylene glycol monostearate and n-dodecyl mercaptan as a chain transfer agent was prepared, a part of the monomer emulsion and pure water were fed into a polymerization tank and cooled to 12℃and then the remaining part of the monomer emulsion, ferrous sulfate, sodium ascorbate and potassium persulfate as an inorganic radical generator were continuously added dropwise over 2.5 hours, the mixture was kept at 23℃for further reaction for 1 hour, industrial water was added and heated to 85℃and then sodium sulfate was continuously added at 85℃to solidify to obtain pellets, and after 3-time washing with pure water, the pellets were dried with a hot air dryer to produce an acrylic rubber and crosslinked with 2, 2-bis [4- (4-aminophenoxy) phenyl ] propane. However, the acrylic rubber obtained by the method is excellent in stress relaxation property and extrusion processability, but has problems of insufficient roll processability and storage stability, and poor strength characteristics and water resistance of a crosslinked product.

Patent document 5 (japanese patent application laid-open No. 9-143229) discloses the following method: a monomer mixture composed of ethyl acrylate, a special acrylic ester and vinyl monochloroacetate, sodium lauryl sulfate as an emulsifier, n-octyl mercaptan as a chain transfer agent and water are added into a reaction vessel, after nitrogen substitution, ammonium bisulfide and sodium persulfate as an inorganic radical generator are added to initiate polymerization, and copolymerization is carried out at 55 ℃ for 3 hours until the reaction conversion is 93-96%, and an acrylic rubber is produced, and crosslinked with sulfur. However, the acrylic rubber obtained by the method has problems of poor storage stability, and poor strength characteristics and water resistance of the crosslinked product.

Patent document 6 (japanese patent application laid-open No. 62-64809) discloses an acrylic rubber which is excellent in processability, compression set and tensile strength and can be vulcanized with sulfur, and is characterized in that it is a copolymer composed of 50 to 99.9% by weight of at least one compound selected from alkyl acrylate and alkoxyalkyl acrylate, 0.1 to 20% by weight of a dihydrodicyclopentenyl group-containing ester of an unsaturated carboxylic acid having a radical reactive group, 0 to 20% by weight of at least one monomer selected from other monovinyl, monovinylidene (vinyl) and monovinylidene (vinyl) unsaturated compounds, and in that the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) in terms of polystyrene in which tetrahydrofuran is an eluent is 20 to 120 ten thousand or less is 10. Regarding number average The molecular weight (Mn) is also described as 20 to 100 tens of thousands, preferably 20 to 100 tens of thousands, and if Mn is less than 20 tens of thousands, the physical properties and processability of the sulfide are poor, if Mn is more than 120 tens of thousands, and if the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) (Mw/Mn) is more than 10, compression set becomes large, which is not preferable. As specific examples thereof, the following manufacturing methods are disclosed: an acrylic rubber containing a monomer component such as ethyl acrylate, a radical crosslinkable dicyclopentenyl acrylate, etc., sodium lauryl sulfate as an emulsifier, potassium persulfate as an inorganic radical generator, octyl mercaptoacetate as a molecular weight regulator, and t-dodecyl mercaptan as variables, having a polymerization number average molecular weight (Mn) of 53 to 115 ten thousand, a weight average molecular weight (Mw) of 354 to 626 ten thousand, and a ratio (Mw/Mn) of weight average molecular weight (Mw) to number average molecular weight (Mn) of 4.7 to 8, is sufficiently washed with water and directly dried after being solidified in a calcium chloride aqueous solution. Further, examples and comparative examples show: when the amount of the chain transfer agent is small, the number average molecular weight (Mn) of the resulting acrylic rubber is as large as 500 ten thousand, the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is narrowed to 1.4, and when the amount of the chain transfer agent is large, the number average molecular weight (Mn) is as small as 20 ten thousand, and the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) becomes extremely wide as 17. However, the acrylic rubber obtained by the present method has poor compression set resistance and storage stability, and also contains a radical-reactive group, and therefore, even if an appropriate molecular weight distribution (Mw/Mn) is obtained in a polymerization reaction using a radical generator, there is a problem that the molecular weight (Mw, mn) is large and too complicated, and the roll processability and banbury processability are insufficient. The acrylic rubber obtained by the method has the following problems: in the crosslinking reaction, after sulfur and a vulcanization accelerator are added as a crosslinking agent and kneaded with rolls, it is also necessary to use a total of 100kg/cm ² Is pressed at 170 ℃ for 15 minutes and then crosslinked with a gill oven at 175 ℃ for a long period of 4 hours; the resulting crosslinked product is inferior in compression set resistance, water resistance and strength characteristics, and also inferior in physical property change after thermal degradation.

Prior art literature

Patent literature

Patent document 1: international publication No. 2019/188709;

patent document 2: japanese patent application laid-open No. 2019-119772;

patent document 3: japanese patent laid-open No. 1-135811;

patent document 4: japanese patent application laid-open No. 2018-168343;

patent document 5: japanese patent laid-open No. 9-143229;

patent document 6: japanese patent laid-open No. 62-64809.

Disclosure of Invention

Problems to be solved by the invention

The present invention has been made in view of the above-described circumstances of the prior art, and an object thereof is to provide an acrylic rubber excellent in roll processability and having excellent strength characteristics and water resistance of a crosslinked product, a method for producing the same, a rubber composition containing the acrylic rubber, and a crosslinked rubber obtained by crosslinking the same.

Solution for solving the problem

The present inventors have conducted intensive studies on the above problems, and as a result, have found that an acrylic rubber contains (meth) acrylic acid ester as a main component, and that the weight average molecular weight (Mw) of the absolute molecular weight and the absolute molecular weight distribution and the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) measured by the GPC-MALS method are specified values, and that the ash content and the specific component content in ash are specified values, whereby the roll processability is excellent and the strength characteristics and the water resistance of a crosslinked product are highly excellent.

The present inventors have found that the roll processability of an acrylic rubber is closely related to the ratio (Mw/Mn) of the number average molecular weight (Mn), the weight average molecular weight (Mw) to the number average molecular weight (Mn) measured by GPC-MALS method, and that when they are respectively in a specific range, the roll processability can be significantly improved without impairing the strength characteristics. In particular, the larger the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn), the more improved the roll processability, but it was difficult to produce an acrylic rubber having a specific number average molecular weight (Mn) and a larger ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn), and the inventors have found that it is possible to obtain the acrylic rubber by adding the chain transfer agent not initially but intermittently during the polymerization. The present inventors have also found that the aqueous pellets produced in the coagulation reaction are dried at high shear by using a screw type biaxial extrusion dryer, whereby the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is greatly increased without impairing the number average molecular weight (Mn), and the roll processability is further improved.

The present inventors have also found that the water resistance of an acrylic rubber is greatly affected by the ash content and ash content in the acrylic rubber. Further, it has been found that it is difficult to reduce the ash content of an acrylic rubber in which an emulsifier and a coagulant are used in large amounts in emulsion polymerization, but the cleaning efficiency when the aqueous pellet produced by coagulation is cleaned with hot water and the ash removal efficiency when ash removal is performed by dehydration are remarkably improved, and as a result, the water resistance of the acrylic rubber can be remarkably improved. In particular, the present inventors have found that by increasing the ratio of the specific particle size of the aqueous aggregates produced in the coagulation step and washing, dehydrating and drying the aqueous aggregates, the water resistance can be significantly improved without impairing the properties such as the roll processability, strength properties and compression set properties of the obtained acrylic rubber. The present inventors have also found that when a specific emulsifier is used in emulsion polymerization of an acrylic rubber or when a specific coagulant is used in the case of coagulating an emulsion polymerization liquid, the acrylic rubber is excellent in water resistance and significantly improved in releasability from a mold or the like.

The present inventors have also found that an acrylic rubber having an ion-reactive group or a specific reactive group is more excellent in roll processability, strength characteristics and water resistance, and is also excellent in short-time crosslinkability and compression set resistance.

The present inventors have found that, in GPC measurement of an acrylic rubber, particularly an acrylic rubber having the above reactive group, tetrahydrofuran used in GPC measurement of a radical reactive acrylic rubber obtained by copolymerizing ethyl acrylate, dicyclopentenyl acrylate, or the like of the above conventional technique cannot be sufficiently dissolved and each molecular weight and molecular weight distribution cannot be measured perfectly and reproducibly, but by using a specific solvent having an SP value higher than that of tetrahydrofuran as an eluent, it is possible to perform measurement perfectly and reproducibly, and by specifying each characteristic value, it is possible to highly balance roll processability of an acrylic rubber, water resistance, strength characteristics, and compression set resistance characteristics of a crosslinked product.

The present inventors have also found that, by specifying the methyl ethyl ketone-insoluble component amount of the acrylic rubber, the roll processability, strength characteristics and water resistance are excellent, and the banbury processability is also excellent. The amount of methyl ethyl ketone-insoluble component of the acrylic rubber is generated during the polymerization reaction, and particularly, when the polymerization conversion is increased in order to improve the strength characteristics, it is drastically increased and difficult to control, but the inventors have found that: by performing emulsion polymerization in the presence of a chain transfer agent in the latter half of the polymerization reaction, the amount of components insoluble in methyl ethyl ketone can be suppressed to some extent; and melt-kneading the acrylic rubber in a substantially moisture-free state (water content of less than 1 wt%) in a screw-type biaxial extrusion dryer, and extrusion-drying the melt-kneaded acrylic rubber, whereby the rapidly increased methyl ethyl ketone-insoluble component disappears, and the banbury processability can be significantly improved without impairing the roll processability.

The present inventors have also found that by specifying the specific gravity of the acrylic rubber, the roll processability, strength characteristics and water resistance are excellent, and the storage stability is also excellent. An acrylic rubber, particularly an acrylic rubber having an ion-reactive group or a reactive group such as a carboxyl group, an epoxy group, or a chlorine atom that reacts with a crosslinking agent, has tackiness and is difficult to discharge air, and a large amount of air is involved in a pellet-like acrylic rubber obtained by directly drying an aqueous pellet (the specific gravity becomes small), and the storage stability is deteriorated, but the inventors have found that: by subjecting the pellet-like acrylic rubber to rubber encapsulation by compression under high pressure with a packer or the like, some air can be discharged and the storage stability can be improved; the aqueous pellets are preferably extrusion-dried under reduced pressure using a screw type biaxial extrusion dryer and extruded in the form of air-free pellets; and if necessary, laminating the extruded sheet-like acrylic rubber, whereby a rubber-coated acrylic rubber containing little air, having a large specific gravity, and significantly improved storage stability can be produced. The inventors of the present invention have also found that the specific gravity of the content of air added as described above can be measured according to JIS K6268 crosslinked rubber-density measurement A method using a difference in buoyancy. The present inventors have also found that the storage stability of the acrylic rubber can be further improved by specifying the pH.

The present inventors have also found that by increasing the cooling rate of the acrylic rubber which has been dried, the scorch stability of the rubber composition can be significantly improved without impairing the properties such as roll processability, water resistance, strength properties and compression set properties.

The present inventors have also found that the roll processability, strength properties and water resistance are further improved to a high degree by specifying the monomer composition of the acrylic rubber, the ratio of z-average molecular weight (Mz) to weight-average molecular weight (Mw) (Mz/Mw), the complex viscosity at 60 ℃ ([ eta ]60 ℃), the ratio of complex viscosity at 100 ℃ ([ eta ]100 ℃) to complex viscosity at 60 ℃ ([ eta ]60 ℃), and the shape, and the cross-linking property for a short time and each property of the resulting rubber cross-linked are further improved to a great degree by using a polyvalent organic compound as a cross-linking agent.

The present inventors have also found that by emulsion polymerizing a specific monomer component with water and an emulsifier, then initiating emulsion polymerization in the presence of a redox catalyst composed of an inorganic radical generator and a reducing agent such as potassium persulfate, intermittently adding a chain transfer agent during the polymerization without adding a chain transfer agent at the beginning, solidifying the resulting emulsion polymerization liquid under specific conditions, washing the aqueous pellets produced during the solidification reaction with hot water, and dehydrating and drying the washed aqueous pellets, the high molecular weight component and the low molecular weight component of the acrylic rubber that can be produced coexist to form a broad molecular weight distribution and form an ash component of the specific component, whereby the roll processability, strength characteristics and water resistance of the acrylic rubber are highly balanced.

The present inventors have also found that an acrylic rubber having further improved roll processability, strength characteristics and water resistance can be produced by melt-kneading and drying an acrylic rubber under high shear conditions using a specific extrusion dryer. Further, it has been found that by post-adding a reducing agent and a specific polymerization temperature, an acrylic rubber having a further balance among roll processability, strength characteristics and water resistance can be produced.

The present inventors have further found that by blending carbon black and silica as fillers in the rubber composition comprising the acrylic rubber of the present invention, the filler and the crosslinking agent, the roll processability, the banbury processability and the short-time crosslinking property are excellent, and the water resistance, the strength characteristics and the compression set resistance of the crosslinked product are highly excellent. The present inventors have also found that, as the crosslinking agent, an organic compound, a polyvalent compound or an ionic crosslinking compound is preferable, and that the polyvalent ionic organic compound having a plurality of ion-reactive groups reactive with the ion-reactive groups of the acrylic rubber, such as amino groups, epoxy groups, carboxyl groups or thiol groups, is excellent in roll processability, banbury processability and crosslinking properties in a short period of time, and the crosslinked product is highly excellent in water resistance, strength properties and compression set resistance.

The present inventors have completed the present invention based on these findings.

According to the present invention, there can be provided an acrylic rubber comprising (meth) acrylic acid ester as a main component, a dimethylformamide-based solvent as an eluent, wherein the weight average molecular weight (Mw) of the absolute molecular weight and the absolute molecular weight distribution measured by GPC-MALS method is 100 ten thousand or more, the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is 3.4 or more, the ash content is 0.4% by weight or less, and the total amount of sodium, magnesium, calcium, phosphorus and sulfur in the ash is 80% by weight or more.

In the acrylic rubber of the present invention, the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is preferably 3.5 or more.

In the acrylic rubber of the present invention, the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is preferably in the range of 3.7 to 6.5.

In the acrylic rubber of the present invention, it is preferable to have a reactive group.

In the acrylic rubber of the present invention, the reactive group is preferably a reactive group having an ion-reactive group.

In the acrylic rubber of the present invention, the reactive group is preferably at least one reactive group selected from a carboxyl group, an epoxy group and a chlorine atom.

In the acrylic rubber of the present invention, it is preferable that the acrylic rubber is composed of the following bonding units: binding units derived from a (meth) acrylate ester selected from at least one of an alkyl (meth) acrylate and an alkoxyalkyl (meth) acrylate, binding units derived from a reactive group-containing monomer, and binding units derived from other monomers.

In the acrylic rubber of the present invention, the ratio (Mz/Mw) of the z-average molecular weight (Mz) to the weight-average molecular weight (Mw) is preferably in the range of 1.3 to 3.

In the acrylic rubber of the present invention, the amount of the methyl ethyl ketone-insoluble component is preferably 50% by weight or less. Preferably, the complex viscosity at 60 ℃ (. Eta.60 ℃) is 15000[ Pa.s ] or less.

In the acrylic rubber of the present invention, it is preferable that the values when the amount of the methyl ethyl ketone-insoluble component at 20 points is measured are all within the range of (average ± 5% by weight).

In the acrylic rubber of the present invention, the ratio of the complex viscosity at 100 ℃ ([ eta ]100 ℃) to the complex viscosity at 60 ℃ ([ eta ]60 ℃) ([ eta ]100 ℃/[ eta ]60 ℃)) is preferably 0.8 or more.

In the acrylic rubber of the present invention, the specific gravity is preferably 0.8 or more.

In the acrylic rubber of the present invention, the acrylic rubber is preferably in the form of a sheet or a bag.

The acrylic rubber of the present invention is preferably an acrylic rubber obtained by emulsion polymerization using a phosphate salt or a sulfate salt as an emulsifier, and is preferably an acrylic rubber obtained by coagulating a polymerization solution obtained by emulsion polymerization using an alkali metal salt or a group 2 metal salt of the periodic table as a coagulant and drying the same. The acrylic rubber of the present invention is preferably an acrylic rubber obtained by melt-kneading and drying after solidification, and the melt-kneading and drying are preferably carried out in a state substantially free of moisture, and the melt-kneading and drying are preferably carried out under reduced pressure. Further, the acrylic rubber of the present invention is preferably an acrylic rubber obtained by cooling at a cooling rate of 40℃per hour or more after the above-mentioned melt-kneading and drying.

In the acrylic rubber of the present invention, it is preferable to wash, dehydrate and dry the aqueous pellet having a particle diameter in the range of 710 μm to 6.7mm in a proportion of 50% by weight or more.

Further, according to the present invention, there is provided a method for producing an acrylic rubber, comprising the steps of: an emulsifying step of emulsifying an acrylic rubber monomer component containing (meth) acrylic ester as a main component with water and an emulsifier; an emulsion polymerization step of initiating polymerization in the presence of a redox catalyst containing an inorganic radical generator and a reducing agent, intermittently adding a chain transfer agent during the polymerization, and continuing the polymerization to obtain an emulsion polymerization solution; a coagulation step of adding the obtained emulsion polymerization liquid to a stirred coagulation liquid to coagulate the emulsion polymerization liquid to produce aqueous pellets; a washing step of washing the produced water-containing pellets with hot water; a dehydration step of dehydrating the washed aqueous granules; and a drying step of drying the dehydrated aqueous pellets to less than 1% by weight.

The method for producing an acrylic rubber of the present invention is preferably to produce the above-mentioned acrylic rubber.

In the method for producing an acrylic rubber of the present invention, emulsion polymerization is preferably carried out using a phosphate salt or a sulfate salt as an emulsifier.

In the method for producing an acrylic rubber of the present invention, it is preferable to coagulate and dry the polymerization liquid produced in the emulsion polymerization step by using an alkali metal salt or a group 2 metal salt of the periodic table as a coagulant.

In the method for producing an acrylic rubber of the present invention, it is preferable that the polymerization liquid produced in the emulsion polymerization step is added to an aqueous solution containing a coagulant containing an alkali metal salt or a group 2 metal salt of the periodic table, and the mixture is stirred and coagulated.

In the method for producing an acrylic rubber of the present invention, it is preferable that the polymerization liquid produced in the emulsion polymerization step is brought into contact with a coagulant to solidify the polymerization liquid, and then melt-kneaded and dried.

In the method for producing an acrylic rubber of the present invention, it is preferable that the above-mentioned melt kneading and drying are carried out in a state of substantially free from moisture.

In the method for producing an acrylic rubber of the present invention, the above-mentioned melt kneading and drying are preferably carried out under reduced pressure.

In the method for producing an acrylic rubber of the present invention, the above-mentioned melt kneading and drying are preferably carried out by a screw type biaxial extrusion dryer.

In the method for producing an acrylic rubber of the present invention, it is preferable that the maximum torque of the screw type biaxial extrusion dryer at the time of melt kneading and drying is 20n·m or more.

In the method for producing an acrylic rubber of the present invention, the acrylic rubber after melt-kneading and drying is preferably cooled at a cooling rate of 40℃per hour or more.

In the method for producing an acrylic rubber of the present invention, the coagulant concentration of the coagulant is preferably 1% by weight or more.

In the method for producing an acrylic rubber of the present invention, it is preferable that the stirring speed of the stirred coagulation liquid is 100rpm or more.

In the method for producing an acrylic rubber of the present invention, the peripheral speed of the stirred coagulation liquid is preferably 1m/s or more.

In the method for producing an acrylic rubber of the present invention, the reducing agent is preferably added after the emulsion polymerization step.

In the method for producing an acrylic rubber of the present invention, it is preferable to wash, dehydrate and dry the aqueous pellet having a particle diameter in the range of 710 μm to 6.7mm in a proportion of 50 wt% or more.

Further, according to the present invention, there is provided a rubber composition comprising a rubber component, a filler and a crosslinking agent, wherein the rubber component comprises the acrylic rubber.

In the rubber composition of the present invention, the filler is preferably a reinforcing filler. In the rubber composition of the present invention, the filler is preferably carbon black. In the rubber composition of the present invention, the filler is preferably silica.

In the rubber composition of the present invention, the crosslinking agent is preferably an organic crosslinking agent. In the rubber composition of the present invention, the crosslinking agent is preferably a polyvalent compound. In the rubber composition of the present invention, it is preferable that the crosslinking agent is an ion-crosslinkable compound. In the rubber composition of the present invention, the crosslinking agent is preferably an ion-crosslinkable organic compound. In the rubber composition of the present invention, the crosslinking agent is preferably a polyionic organic compound.

In the rubber composition of the present invention, the ion of the ion-crosslinkable compound, ion-crosslinkable organic compound or polyion-crosslinkable organic compound as the crosslinking agent is preferably an ion-reactive group selected from at least one of amino group, epoxy group, carboxyl group and thiol group.

In the rubber composition of the present invention, the crosslinking agent is preferably a polyion compound selected from at least one of a polyamine compound, a polyepoxide compound, a polycarboxylic acid compound and a polythiol compound.

In the rubber composition of the present invention, the content of the crosslinking agent is preferably in the range of 0.001 to 20 parts by weight relative to 100 parts by weight of the rubber component.

In the rubber composition of the present invention, an antioxidant is preferably further contained. In the rubber composition of the present invention, the antioxidant is preferably an amine-based antioxidant.

Further, according to the present invention, there is provided a method for producing a rubber composition, wherein a rubber component containing the above-mentioned acrylic rubber, a filler and, if necessary, an anti-aging agent are mixed, and then a crosslinking agent is mixed.

Further, according to the present invention, there can be provided a crosslinked rubber product obtained by crosslinking the above-mentioned rubber composition. In the rubber crosslinked product of the present invention, the crosslinking of the rubber composition is preferably performed after molding. In the rubber crosslinked product of the present invention, the crosslinking of the rubber composition is preferably a crosslinking in which primary crosslinking and secondary crosslinking are performed.

Effects of the invention

According to the present invention, an acrylic rubber excellent in roll processability and in strength characteristics and water resistance of a crosslinked product, a method for efficiently producing the same, a high-quality rubber composition comprising the acrylic rubber, and a crosslinked rubber obtained by crosslinking the same can be provided.

Drawings

Fig. 1 is a diagram schematically showing an example of an acrylic rubber manufacturing system that can be used to manufacture an acrylic rubber according to an embodiment of the present invention.

Fig. 2 is a view showing the structure of the screw type biaxial extrusion dryer of fig. 1.

Fig. 3 is a diagram showing a structure of a conveying type cooling device that can be used as the cooling device of fig. 1.

Detailed Description

The acrylic rubber of the present invention is characterized in that it contains (meth) acrylic ester as a main component, a dimethylformamide-based solvent as an eluent, the weight average molecular weight (Mw) of the absolute molecular weight and the absolute molecular weight distribution measured by GPC-MALS method is 100 ten thousand or more, the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is 3.4 or more, the ash content is 0.4% by weight or less, and the total amount of sodium, magnesium, calcium, phosphorus and sulfur in ash is 80% by weight or more. The term "GPC-MALS method" as used herein refers to the following. GPC (gel permeation chromatography) is a type of liquid chromatography that separates based on differences in molecular size. The apparatus is equipped with a multi-angle laser light scattering photometer (MALS) and a differential Refractometer (RI), and the molecular weight of a solute and its content are sequentially calculated from the difference in light scattering intensity and refractive index of a molecular chain solution size-separated by a GPC apparatus according to elution time measurement, and finally the absolute molecular weight distribution and absolute average molecular weight value of a polymer substance are obtained.

< monomer component >

The acrylic rubber of the present invention is characterized by comprising (meth) acrylic acid ester as a main component, and the term "main component" as used herein means that the content of the acrylic rubber is usually 50% by weight or more, preferably 60% by weight or more, more preferably 70% by weight or more, and particularly preferably 80% by weight or more. In addition, in the present invention, "(meth) acrylate" is used as a term for esters of acrylic acid and/or methacrylic acid in general.

The acrylic rubber of the present invention preferably has an ion-reactive group or at least one reactive group selected from the group consisting of a carboxyl group, an epoxy group and a chlorine atom, and in this case, is excellent in crosslinking property and compression set resistance. The ion-reactive group is not particularly limited as long as it is a functional group that performs an ion reaction, and is preferably at least one functional group selected from the group consisting of a carboxyl group, an epoxy group, and a chlorine atom, more preferably an epoxy group and a carboxyl group, and particularly preferably a carboxyl group. The acrylic rubber having the reactive group may be one obtained by introducing the reactive group into the acrylic rubber by a subsequent reaction, but is preferably one obtained by copolymerizing a reactive group-containing monomer.

The preferable monomer component of the acrylic rubber of the present invention is composed of a (meth) acrylic acid ester selected from at least one of an alkyl (meth) acrylate and an alkoxyalkyl (meth) acrylate, a reactive group-containing monomer, and other monomers copolymerizable as needed.

The alkyl (meth) acrylate is not particularly limited, and an alkyl (meth) acrylate having an alkyl group having 1 to 12 carbon atoms is usually used, and an alkyl (meth) acrylate having an alkyl group having 1 to 8 carbon atoms is preferably used, and an alkyl (meth) acrylate having an alkyl group having 2 to 6 carbon atoms is more preferably used.

Specific examples of the alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, and the like, and among these, ethyl (meth) acrylate, n-butyl (meth) acrylate, and more preferably ethyl acrylate and n-butyl acrylate.

The alkoxyalkyl (meth) acrylate is not particularly limited, and an alkoxyalkyl (meth) acrylate having an alkoxyalkyl group having 2 to 12 carbon atoms is usually used, and an alkoxyalkyl (meth) acrylate having an alkoxyalkyl group having 2 to 8 carbon atoms is preferably used, and an alkoxyalkyl (meth) acrylate having an alkoxyalkyl group having 2 to 6 carbon atoms is more preferably used.

Specific examples of the alkoxyalkyl (meth) acrylate include methoxymethyl (meth) acrylate, methoxyethyl (meth) acrylate, methoxypropyl (meth) acrylate, methoxybutyl (meth) acrylate, ethoxymethyl (meth) acrylate, ethoxyethyl (meth) acrylate, propoxyethyl (meth) acrylate, butoxyethyl (meth) acrylate, and the like. Among these, methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate, and the like are preferable, and methoxyethyl acrylate and ethoxyethyl acrylate are more preferable.

These (meth) acrylic esters of at least one selected from the group consisting of alkyl (meth) acrylates and alkoxyalkyl (meth) acrylates may be used singly or in combination, and the proportion thereof in the total monomer components is usually in the range of 50 to 99.99% by weight, preferably 62 to 99.95% by weight, more preferably 74 to 99.9% by weight, particularly preferably 80 to 99.5% by weight, most preferably 87 to 99% by weight, and in this case, the acrylic rubber is highly excellent in weather resistance, heat resistance and oil resistance, and therefore is preferred.

The reactive group-containing monomer is not particularly limited as long as it has a functional group that participates in a reaction with a crosslinking agent or the like, and may be appropriately selected depending on the purpose of use, and is preferably a monomer having an ion-reactive group that participates in an ion reaction or a monomer having a reactive group selected from at least one of a carboxyl group, an epoxy group, and a chlorine atom, more preferably a monomer having a carboxyl group or an epoxy group, and even more preferably a monomer having a carboxyl group, and in this case, the crosslinkability in a short period of time and the compression set resistance and water resistance of a crosslinked product can be highly improved.

The monomer having a carboxyl group is not particularly limited, and an ethylenically unsaturated carboxylic acid can be preferably used. Examples of the ethylenically unsaturated carboxylic acid include ethylenically unsaturated monocarboxylic acid, ethylenically unsaturated dicarboxylic acid, and ethylenically unsaturated dicarboxylic acid monoester, and among these, the ethylenically unsaturated dicarboxylic acid monoester is particularly preferred because the compression set resistance when the acrylic rubber is made into a rubber crosslinked product can be further improved.

The ethylenically unsaturated monocarboxylic acid is not particularly limited, but preferably has 3 to 12 carbon atoms, and examples thereof include acrylic acid, methacrylic acid, α -ethacrylic acid, crotonic acid, cinnamic acid, and the like.

The ethylenically unsaturated dicarboxylic acid is not particularly limited, but preferably an ethylenically unsaturated dicarboxylic acid having 4 to 12 carbon atoms, and examples thereof include: butenedioic acids such as fumaric acid and maleic acid; itaconic acid; citraconic acid, and the like. In addition, ethylenically unsaturated dicarboxylic acids also include those which are present in the form of anhydrides.

The ethylenically unsaturated dicarboxylic acid monoester is not particularly limited, and examples thereof include monoesters of an ethylenically unsaturated dicarboxylic acid having 4 to 12 carbon atoms and an alkyl group having 1 to 12 carbon atoms, preferably monoesters of an ethylenically unsaturated dicarboxylic acid having 4 to 6 carbon atoms and an alkyl group having 2 to 8 carbon atoms, and more preferably monoesters of a butenedioic acid having 4 carbon atoms and an alkyl group having 2 to 6 carbon atoms.

Specific examples of the ethylenically unsaturated dicarboxylic acid monoester include: mono-alkyl butenedioates such as monomethyl fumarate, monoethyl fumarate, mono-n-butyl fumarate, monomethyl maleate, monoethyl maleate, mono-n-butyl maleate, monocyclopentyl fumarate, monocyclohexyl fumarate, monocyclohexenyl fumarate, monocyclopentyl maleate, monocyclohexyl maleate, and the like; mono-alkyl itaconates such as monomethyl itaconate, monoethyl itaconate, mono-n-butyl itaconate and monocyclohexyl itaconate, and among these, mono-n-butyl fumarate and mono-n-butyl maleate are preferable, and mono-n-butyl fumarate is particularly preferable.

Examples of the monomer having an epoxy group include: epoxy group-containing (meth) acrylates such as glycidyl (meth) acrylate; epoxy group-containing vinyl ethers such as allyl glycidyl ether and vinyl glycidyl ether.

Examples of the monomer having a chlorine atom include, but are not particularly limited to, unsaturated alcohol esters of saturated carboxylic acids having a chlorine atom, chloroalkyl (meth) acrylates, chloroacyloxyalkyl (meth) acrylates, (chloroacetylcarbamoyloxy) alkyl (meth) acrylates, unsaturated ethers having a chlorine atom, unsaturated ketones having a chlorine atom, chloromethyl aromatic vinyl compounds, unsaturated amides having a chlorine atom, and chloroacetyl unsaturated monomers.

Specific examples of the unsaturated alcohol ester of a saturated carboxylic acid containing a chlorine atom include vinyl chloroacetate, vinyl 2-chloropropionate, allyl chloroacetate, and the like. Specific examples of the chloroalkyl (meth) acrylate include chloromethyl (meth) acrylate, 1-chloroethyl (meth) acrylate, 2-chloroethyl (meth) acrylate, 1, 2-dichloroethyl (meth) acrylate, 2-chloropropyl (meth) acrylate, 3-chloropropyl (meth) acrylate, and 2, 3-dichloropropyl (meth) acrylate. Specific examples of the chloroacetoxy alkyl (meth) acrylate include 2- (chloroacetoxy) ethyl (meth) acrylate, 2- (chloroacetoxy) propyl (meth) acrylate, 3- (chloroacetoxy) propyl (meth) acrylate, and 3- (hydroxychloroacetoxy) propyl (meth) acrylate. Examples of the (chloroacetylcarbamoyloxy) alkyl (meth) acrylate include 2- (chloroacetylcarbamoyloxy) ethyl (meth) acrylate and 3- (chloroacetylcarbamoyloxy) propyl (meth) acrylate. Specific examples of the unsaturated ether containing chlorine atoms include chloromethyl vinyl ether, 2-chloroethyl vinyl ether, 3-chloropropyl vinyl ether, 2-chloroethyl allyl ether, and 3-chloropropyl allyl ether. Specific examples of the unsaturated ketone containing chlorine atom include 2-chloroethyl vinyl ketone, 3-chloropropyl vinyl ketone, and 2-chloroethyl allyl ketone. Specific examples of the chloromethyl aromatic vinyl compound include p-chloromethylstyrene, m-chloromethylstyrene, o-chloromethylstyrene, p-chloromethyl- α -methylstyrene, and the like. Specific examples of the unsaturated amide containing chlorine atom include N-chloromethyl (meth) acrylamide and the like. Specific examples of the chlorinated acetyl unsaturated monomer include 3- (hydroxychloroacetoxy) propyl allyl ether, p-vinylbenzyl chloroacetate, and the like.

These reactive group-containing monomers may be used singly or in combination, and the proportion thereof in the total monomer components is usually in the range of 0.01 to 10% by weight, preferably 0.05 to 8% by weight, more preferably 0.1 to 6% by weight, particularly preferably 0.5 to 5% by weight, most preferably 1 to 3% by weight.

The monomer other than the above-mentioned monomer (simply referred to as "other monomer" in the present invention) that may be used together with the above-mentioned monomers as needed is not particularly limited as long as it can be copolymerized with the above-mentioned monomer, and examples thereof include: aromatic vinyl monomers such as styrene, α -methylstyrene, divinylbenzene, and the like; ethylenically unsaturated nitrile monomers such as acrylonitrile and methacrylonitrile; acrylamide monomers such as acrylamide and methacrylamide; olefin monomers such as ethylene, propylene, vinyl acetate, ethyl vinyl ether, butyl vinyl ether, and the like.

These other monomers may be used singly or in combination of two or more, and the proportion thereof in the whole monomer component is usually controlled in the range of 0 to 40% by weight, preferably 0 to 30% by weight, more preferably 0 to 20% by weight, particularly preferably 0 to 15% by weight, most preferably 0 to 10% by weight.

< acrylic rubber >

The acrylic rubber of the present invention contains (meth) acrylic acid esters as a main component, and is preferably composed of binding units derived from at least one (meth) acrylic acid ester selected from the group consisting of alkyl (meth) acrylates and alkoxyalkyl (meth) acrylates, a reactive group-containing monomer, and other monomers, if necessary, in the following proportions: the binding unit derived from the (meth) acrylic acid ester of at least one selected from the group consisting of alkyl (meth) acrylate and alkoxyalkyl (meth) acrylate is usually in the range of 50 to 99.99% by weight, preferably in the range of 62 to 99.95% by weight, more preferably in the range of 74 to 99.9% by weight, particularly preferably in the range of 80 to 99.5% by weight, most preferably in the range of 87 to 99% by weight, and the binding unit derived from the reactive group-containing monomer is usually in the range of 0.01 to 10% by weight, preferably in the range of 0.05 to 8% by weight, more preferably in the range of 0.1 to 6% by weight, particularly preferably in the range of 0.5 to 5% by weight, most preferably in the range of 1 to 3% by weight, and the binding unit derived from the other monomer is usually in the range of 0 to 40% by weight, preferably in the range of 0 to 30% by weight, more preferably in the range of 0 to 20% by weight, particularly preferably in the range of 0 to 15% by weight, most preferably in the range of 0 to 10% by weight. When the monomer composition of the acrylic rubber is within this range, the properties such as crosslinking property, compression set resistance, weather resistance, heat resistance and oil resistance in a short time are highly balanced, and thus are preferable.

The content of the reactive group in the acrylic rubber of the present invention is not particularly limited, and may be appropriately selected depending on the purpose of use, and is usually in the range of 0.001 to 5% by weight, preferably 0.01 to 3% by weight, more preferably 0.05 to 1% by weight, and particularly preferably 0.1 to 0.5% by weight, and in this case, processability, crosslinkability, and strength characteristics, compression set resistance, oil resistance, cold resistance, water resistance and the like when a crosslinked product is produced are highly balanced, and thus preferable.

The weight average molecular weight (Mw) of the acrylic rubber of the present invention is 100 ten thousand or more, preferably 120 ten thousand or more, more preferably 150 ten thousand or more, based on the absolute molecular weight measured by GPC-MALS method using dimethylformamide as an eluent. When the weight average molecular weight (Mw) of the acrylic rubber of the present invention is too small, the strength characteristics and compression set resistance are poor, which is not preferable. The weight average molecular weight (Mw) of the acrylic rubber of the present invention is usually in the range of 100 to 350 ten thousand, preferably 120 to 300 ten thousand, more preferably 130 to 300 ten thousand, particularly preferably 150 to 250 ten thousand, most preferably 190 to 210 ten thousand, and in this case, the roll processability, strength characteristics and compression set resistance of the acrylic rubber are highly balanced and therefore preferable.

The number average molecular weight (Mn) of the acrylic rubber of the present invention is not particularly limited, and may be appropriately selected depending on the purpose of use, but it is preferable that the roll processability, strength characteristics and compression set resistance of the acrylic rubber are highly balanced in the range of usually 10 to 50, preferably 20 to 48, more preferably 25 to 45,particularly preferably 30 to 40,and most preferably 35 to 40,when the absolute molecular weight measured by GPC-MALS method using a dimethylformamide-based solvent as an eluent.

The z-average molecular weight (Mz) of the acrylic rubber of the present invention is not particularly limited, and may be appropriately selected depending on the purpose of use, but it is preferable that the roll processability, strength characteristics and compression set resistance of the acrylic rubber are highly balanced in the range of 150 to 600, preferably 200 to 500, more preferably 250 to 450,and particularly preferably 300 to 400,000, as measured by GPC-MALS method using dimethylformamide-based solvent as an eluent.

The ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the acrylic rubber of the present invention is 3.4 or more, preferably 3.5 or more, more preferably 3.6 or more, and particularly preferably 3.7 or more, in terms of an absolute molecular weight distribution measured by GPC-MALS method using a dimethylformamide-based solvent as an eluent. When the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the acrylic rubber of the present invention is too small, the roll processability is not preferable. The acrylic rubber of the present invention is preferably in a range of usually 3.7 to 6.5, preferably 3.8 to 6.2, more preferably 4 to 6, particularly preferably 4.5 to 5.7, and most preferably 4.7 to 5.5 in terms of the weight average molecular weight (Mw) and the number average molecular weight (Mn) in terms of the ratio (Mw/Mn), and in this case, the strength characteristics and compression set characteristics in the case of roll processability and crosslinking are highly balanced.

The ratio (Mz/Mw) of the z-average molecular weight (Mz) to the weight-average molecular weight (Mw) of the acrylic rubber of the present invention is not particularly limited, and may be appropriately selected depending on the purpose of use, and the processability and strength characteristics of the acrylic rubber are highly balanced and physical property changes during storage can be alleviated, in general, in the range of 1.3 to 3, preferably 1.4 to 2.7, more preferably 1.5 to 2.5, particularly preferably 1.8 to 2, most preferably 1.8 to 1.95, in terms of an absolute molecular weight distribution in a high molecular weight region measured by GPC-MALS method using a dimethylformamide-based solvent as an eluent.

The dimethylformamide-based solvent used as the measurement solvent in the GPC-MALS method is not particularly limited as long as it is a solvent containing dimethylformamide as a main component, and for example, 100% dimethylformamide or a solvent in which the proportion of dimethylformamide in the dimethylformamide-based solvent is 90% by weight or more, preferably 95% by weight or more, and more preferably 97% by weight or more can be used. The compound to be added to dimethylformamide is not particularly limited, but in the present invention, a solution in which lithium chloride is added to dimethylformamide at a concentration of 0.05mol/L and 37% concentrated hydrochloric acid is added at a concentration of 0.01% is particularly preferable.

The ash content of the acrylic rubber of the present invention is preferably 0.4% by weight or less, more preferably 0.3% by weight or less, still more preferably 0.2% by weight or less, still more preferably 0.18% by weight or less, particularly preferably 0.15% by weight or less, and most preferably 0.13% by weight or less, and in this range, the water resistance, strength characteristics and processability of the acrylic rubber are highly balanced.

The lower limit of the ash content of the acrylic rubber of the present invention is not particularly limited, and is appropriately selected depending on the purpose of use, but is usually 0.0001 wt% or more, preferably 0.0005 wt% or more, more preferably 0.001 wt% or more, still more preferably 0.003 wt% or more, particularly preferably 0.005 wt% or more, and most preferably 0.01 wt% or more, and in this case, the metal adhesion of the rubber is reduced and the handleability is excellent, and therefore, the acrylic rubber is preferable.

The ash content of the acrylic rubber of the present invention is usually in the range of 0.0001 to 0.4 wt%, preferably 0.0005 to 0.3 wt%, more preferably 0.001 to 0.2 wt%, still more preferably 0.003 to 0.18 wt%, particularly preferably 0.005 to 0.15 wt%, and most preferably 0.01 to 0.13 wt%, in the case where water resistance, strength characteristics, processability and handleability are highly balanced.

The total amount of sodium, magnesium, calcium, phosphorus and sulfur in the ash of the acrylic rubber of the present invention is preferably 80% by weight or more, more preferably 83% by weight or more, still more preferably 85% by weight or more, particularly preferably 87% by weight or more, and most preferably 90% by weight or more, and in this case, the water resistance of the acrylic rubber is highly improved. In addition, when the total amount of sodium, magnesium, calcium, phosphorus and sulfur in the ash of the acrylic rubber of the present invention is within this range, the metal adhesion is reduced, and the operability is excellent, so that it is preferable.

The total amount of magnesium and phosphorus in the ash of the acrylic rubber of the present invention is not particularly limited, and is appropriately selected depending on the purpose of use, but is usually 30% by weight or more, preferably 50% by weight or more, more preferably 70% by weight or more, particularly preferably 80% by weight or more, and most preferably 90% by weight or more, and in this case, the water resistance, strength characteristics and processability of the acrylic rubber are highly balanced and therefore preferable. When the total amount of magnesium and phosphorus in the ash of the acrylic rubber of the present invention falls within this range, the metal adhesion is reduced, and the operability is excellent, which is preferable.

The amount of magnesium in the ash of the acrylic rubber of the present invention is not particularly limited, and may be appropriately selected depending on the purpose of use, and is usually in the range of 10% by weight or more, preferably 15 to 60% by weight, more preferably 20 to 50% by weight, particularly preferably 25 to 45% by weight, and most preferably 30 to 40% by weight.

The amount of phosphorus in the ash of the acrylic rubber of the present invention is not particularly limited, and may be appropriately selected depending on the purpose of use, and is usually in the range of 10% by weight or more, preferably 20 to 90% by weight, more preferably 30 to 80% by weight, particularly preferably 40 to 70% by weight, and most preferably 50 to 60% by weight.

The ratio of magnesium to phosphorus ([ Mg ]/[ P ]) in ash of the acrylic rubber of the present invention is not particularly limited, and is preferably in the range of usually 0.4 to 2.5, preferably 0.45 to 1.2, more preferably 0.45 to 1, particularly preferably 0.5 to 0.8, and most preferably 0.55 to 0.7 in terms of weight ratio, and in this case, the water resistance, strength characteristics and workability of the acrylic rubber are highly balanced, as long as it is appropriately selected depending on the purpose of use.

Here, the ash in the acrylic rubber is mainly derived from an emulsifier used in emulsion polymerization by liquefying a monomer component and a coagulant used in coagulating an emulsion polymerization liquid, and the total ash amount, the content of magnesium and phosphorus in the ash, and the like vary not only depending on the conditions of the emulsion polymerization step and the coagulation step but also depending on the conditions of the subsequent steps.

As the emulsifier used in emulsion polymerization described later, an anionic emulsifier, a cationic emulsifier or a nonionic emulsifier is used, and an anionic emulsifier is preferably used, and a phosphate salt or a sulfate salt is more preferably used, and in this case, the acrylic rubber of the present invention can improve the water resistance and strength characteristics, and can improve the mold releasability and processability to a high degree, which is preferable. The water resistance of the acrylic rubber is mainly related to the ash content in the acrylic rubber and the total amount of sodium, magnesium, calcium, phosphorus and sulfur in the ash, and the use of the above-mentioned emulsifier is preferable because the water resistance, strength characteristics, mold releasability and processability of the acrylic rubber can be further highly balanced.

The coagulant to be described later is preferably a metal salt, preferably an alkali metal salt or a metal salt of group 2 of the periodic table, and in this case, the acrylic rubber of the present invention can improve the water resistance and strength properties, and can also improve the mold releasability and workability to a high degree. The water resistance of the acrylic rubber is mainly related to the ash content in the acrylic rubber and the total amount of sodium, magnesium, calcium, phosphorus and sulfur in the ash, and the use of the above-described coagulant is preferable because the water resistance, strength characteristics, mold releasability and workability of the acrylic rubber can be further highly balanced.

The glass transition temperature (Tg) of the acrylic rubber of the present invention is preferably selected appropriately according to the purpose of use of the acrylic rubber, and is usually 20 ℃ or lower, preferably 10 ℃ or lower, more preferably 0 ℃ or lower, since the processability and cold resistance are excellent. The lower limit of the glass transition temperature (Tg) of the acrylic rubber is not particularly limited, but is usually-80℃or higher, preferably-60℃or higher, and more preferably-40℃or higher. When the glass transition temperature is not lower than the lower limit, oil resistance and heat resistance can be further improved, and when the glass transition temperature is not higher than the upper limit, processability, crosslinkability and cold resistance can be further improved.

The complex viscosity ([ eta ]60 ℃) of the acrylic rubber of the present invention at 60℃is not particularly limited, and is preferably selected appropriately depending on the purpose of use, but is usually in the range of 15000[ Pa.s ] or less, preferably 1000 to 10000[ Pa.s ], more preferably 2000 to 5000[ Pa.s ], particularly preferably 2500 to 4000[ Pa.s ], most preferably 2500 to 3000[ Pa.s ], and in this case, the processability, oil resistance and shape retention are excellent, and therefore preferred.

The complex viscosity ([ eta ]100 ℃) of the acrylic rubber of the present invention at 100℃is not particularly limited, and is suitably selected depending on the purpose of use, but is usually in the range of 1500 to 6000[ Pa.s ], preferably 2000 to 5000[ Pa.s ], more preferably 2300 to 4000[ Pa.s ], particularly preferably 2500 to 3500[ Pa.s ], most preferably 2500 to 3000[ Pa.s ], and in this case, processability, oil resistance and shape retention are excellent, and therefore, it is preferable.

The ratio ([ eta ]100 ℃/[ eta ]60 ℃) of the complex viscosity ([ eta ]100 ℃) at 100 ℃ to the complex viscosity ([ eta ]60 ℃) of the acrylic rubber of the present invention is not particularly limited, and may be appropriately selected depending on the purpose of use, and is usually 0.5 or more, preferably 0.6 or more, more preferably 0.7 or more, particularly preferably 0.8 or more, and most preferably 0.83 or more. In addition, the ratio of the complex viscosity at 100 ℃ ([ eta ]100 ℃) to the complex viscosity at 60 ℃ ([ eta ]60 ℃) of the acrylic rubber of the present invention ([ eta ]100 ℃/[ eta ]60 ℃) is usually in the range of 0.5 to 0.99, preferably 0.6 to 0.98, more preferably 0.7 to 0.97, particularly preferably 0.8 to 0.96, most preferably 0.85 to 0.95, and in this case, the processability, oil resistance and shape retention are highly balanced, and therefore preferred.

The amount of the methyl ethyl ketone-insoluble component of the acrylic rubber of the present invention is not particularly limited, and is appropriately selected depending on the purpose of use, and is usually 50% by weight or less, preferably 30% by weight or less, more preferably 15% by weight or less, particularly preferably 10% by weight or less, and most preferably 5% by weight or less, and in this case, processability in kneading such as banbury is highly improved, which is preferred.

The value (deviation amount) when the component amount insoluble in methyl ethyl ketone of the acrylic rubber of the present invention at 20 is arbitrarily measured is not particularly limited, but is preferably in the range of (average value±5) wt% at 20, and is preferably in the range of (average value±3) wt% at 20, and in this case, there is no processability deviation, and the physical properties of the rubber composition and the rubber crosslinked product are stabilized. In addition, in the values when the methyl ethyl ketone-insoluble component amount of the acrylic rubber at 20 is arbitrarily measured, that all the 20 positions are within the range of ±5 wt% of the average value means that all the methyl ethyl ketone-insoluble component amounts at 20 positions are within the range of (average value-5) to (average value +5) wt%, and that all the measured values at 20 positions are within the range of 15 to 25 wt% when the average value of the methyl ethyl ketone-insoluble component amounts at 20 positions is 20 wt%, for example.

The acrylic rubber of the present invention is preferably an acrylic rubber obtained by melt-kneading and drying an aqueous pellet produced in a coagulation reaction in a state in which water is substantially removed (water content less than 1% by weight) by a screw type biaxial extrusion dryer, and in this case, the banbury processability and strength characteristics are highly balanced.

The water content of the acrylic rubber of the present invention is not particularly limited, and is appropriately selected depending on the purpose of use, but is usually less than 1% by weight, preferably 0.8% by weight or less, more preferably 0.6% by weight or less, and in this case, the vulcanization characteristics of the acrylic rubber are optimized, and the characteristics such as heat resistance and strand water resistance are highly improved, and therefore, it is preferable.

The pH of the acrylic rubber of the present invention is not particularly limited, and is appropriately selected depending on the purpose of use, and is usually 6 or less, preferably in the range of 2 to 6, more preferably 2.5 to 5.5, and most preferably 3 to 5, and in this case, the storage stability of the acrylic rubber is highly improved, and is therefore preferable.

The Mooney viscosity (ML1+4, 100 ℃) of the acrylic rubber of the present invention is not particularly limited, and may be appropriately selected depending on the purpose of use, and is usually in the range of 10 to 150, preferably 20 to 100, more preferably 25 to 70, and in this case, the processability and strength characteristics of the acrylic rubber are highly balanced, and therefore, it is preferable.

The specific gravity of the acrylic rubber of the present invention is not particularly limited, but is usually 0.7 or more, preferably 0.8 or more, more preferably 0.9 or more, particularly preferably 0.95 or more, and most preferably 1 or more, and in this case, air is hardly present in the interior, and the storage stability is excellent, and therefore, it is preferable. The specific gravity of the acrylic rubber of the present invention is preferably in the range of usually 0.7 to 1.6, preferably 0.8 to 1.5, more preferably 0.9 to 1.4, particularly preferably 0.95 to 1.3, and most preferably 1.0 to 1.2, since the productivity, storage stability, and crosslinking property stability of the crosslinked product are highly balanced. When the specific gravity of the acrylic rubber is too small, it means that the amount of air in the acrylic rubber is large, and oxidation degradation or the like is present, which is not preferable because it has a large influence on storage stability.

The specific gravity of the acrylic rubber of the present invention is a value obtained by dividing the mass by the volume including voids, that is, a value obtained by dividing the mass measured in air by the buoyancy, and is generally measured according to JIS K6268 crosslinked rubber-density measurement a method.

The acrylic rubber of the present invention is preferably obtained by drying the aqueous pellets produced in the coagulation reaction under reduced pressure by a screw type biaxial extrusion dryer or by melt kneading and drying under reduced pressure, because it is particularly excellent in storage stability, injection moldability and strength characteristics and is highly balanced.

The shape of the acrylic rubber of the present invention is not particularly limited, and may be appropriately selected depending on the purpose of use, and may be, for example, any of powder, pellet, strand, sheet, and bale, and is preferably in the form of a sheet or bale, and in this case, the handling property and storage stability are excellent, and therefore, it is preferable.

The thickness of the acrylic rubber of the present invention in the form of a sheet is not particularly limited, and may be appropriately selected depending on the purpose of use, but is usually in the range of 1 to 40mm, preferably 2 to 35mm, more preferably 3 to 30mm, and most preferably 5 to 25mm, and in this case, the handling property, storage stability and productivity are highly balanced, and therefore, it is preferable. The width of the sheet-like acrylic rubber of the present invention can be appropriately selected depending on the purpose of use, and is usually in the range of 300 to 1200mm, preferably 400 to 1000mm, more preferably 500 to 800mm, and in this case, the sheet-like acrylic rubber is particularly excellent in handling properties, and is therefore preferable. The length of the sheet-like acrylic rubber sheet of the present invention is not particularly limited, but is usually in the range of 300 to 1200mm, preferably 400 to 1000mm, more preferably 500 to 800mm, and in this case, the sheet-like acrylic rubber sheet is particularly excellent in handling properties, and is therefore preferable.

The size of the acrylic rubber of the present invention in the form of a rubber bag is not particularly limited, and may be appropriately selected depending on the purpose of use, and the width is usually in the range of 100 to 800mm, preferably 200 to 500mm, more preferably 250 to 450mm, the length is usually in the range of 300 to 1200mm, preferably 400 to 1000mm, more preferably 500 to 800mm, and the height (thickness) is usually in the range of 50 to 500mm, preferably 100 to 300mm, more preferably 150 to 250 mm. The shape of the rubber-coated acrylic rubber of the present invention is not limited, and may be appropriately selected depending on the purpose of use of the acrylic rubber coating, and in many cases, a rectangular parallelepiped is preferable.

< method for producing acrylic rubber >

The method for producing the acrylic rubber is not particularly limited, and for example, the acrylic rubber can be easily produced by a method comprising the steps of: emulsion polymerization step of emulsifying an acrylic rubber monomer component containing (meth) acrylic acid ester as a main component with water and an emulsifier, initiating polymerization in the presence of a redox catalyst comprising an inorganic radical generator and a reducing agent, intermittently adding a chain transfer agent during the polymerization, and continuing the polymerization to obtain an emulsion polymerization solution; a coagulation step of adding the obtained emulsion polymerization liquid to a stirred coagulation liquid to coagulate the emulsion polymerization liquid to produce aqueous pellets; a washing step of washing the produced water-containing pellets with hot water; a dehydration step of dehydrating the washed aqueous granules; and a drying step of drying the dehydrated aqueous pellets to less than 1% by weight.

(monomer component)

The monomer component containing (meth) acrylate as a main component used in the present invention is the same as the above-described examples and preferable ranges. The amount of the monomer component used is the same as described above, and in emulsion polymerization, each monomer may be appropriately selected so as to have the above composition of the acrylic rubber of the present invention.

(emulsifier)

The emulsifier used in the present invention is not particularly limited, and examples thereof include anionic emulsifiers, cationic emulsifiers, nonionic emulsifiers, and the like, and anionic emulsifiers are preferable.

The anionic emulsifier is not particularly limited, and examples thereof include: salts of fatty acids such as myristic acid, palmitic acid, oleic acid, and linolenic acid; alkylbenzene sulfonates such as sodium dodecylbenzene sulfonate; sulfate salts such as sodium lauryl sulfate, phosphate salts such as polyoxyalkylene alkyl ether phosphate salts; alkyl sulfosuccinates, and the like. Among these anionic emulsifiers, phosphate salts and sulfate salts are preferable, phosphate salts are particularly preferable, and divalent phosphate salts are most preferable, and in this case, the water resistance, strength characteristics, mold releasability and processability of the obtained acrylic rubber can be highly balanced, and thus preferable. The phosphate salt and the sulfate salt are preferably alkali metal salts of phosphate and alkali metal salts of sulfate, more preferably sodium salts of phosphate and sodium salts of sulfate, and in this case, the water resistance, strength characteristics, mold releasability and processability of the obtained acrylic rubber can be highly balanced, and thus are preferable.

The divalent phosphate is not particularly limited as long as it can be used as an emulsifier in emulsion polymerization, and examples thereof include alkoxypolyoxyalkylene phosphate and alkylphenoxypolyoxyalkylene phosphate, and among these, metal salts thereof are preferred, alkali metal salts thereof are more preferred, and sodium salts thereof are most preferred.

Examples of the alkoxypolyoxyalkylene phosphate include alkoxypolyoxyethylene phosphate and alkoxypolyoxypropylene phosphate, and among these, alkoxypolyoxyethylene phosphate is preferable.

Specific examples of the alkoxypolyoxyethylene phosphate salt include: among these, octyloxydioxyethylene phosphate, octyloxytrioxyethylene phosphate, octyloxytetraethylene phosphate, decyloxy tetraethylene phosphate, dodecyloxytetraethylene phosphate, tridecyloxytetraethylene phosphate, tetradecyloxy tetraethylene phosphate, hexadecyloxy tetraethylene phosphate, octadecyl tetraethylene phosphate, octyloxypentaethylene phosphate, decyloxy pentaethylene phosphate, dodecyloxypentaethylene phosphate, tridecyloxypentaethylene phosphate, tetradecyloxy pentaethylene phosphate, hexadecyloxy pentaethylene phosphate, octadecyl pentaethylene phosphate, octyloxyhexaethylene phosphate, decyloxy hexaethylene phosphate, dodecyloxyhexaethylene phosphate, tridecyloxyhexaethylene phosphate, tetradecyloxy hexaethylene phosphate, hexadecyloxy hexaethylene phosphate, octadecyl hexaethylene phosphate, octoyloxy octaethylene phosphate, decyloxy octaethylene phosphate, tridecyloxyoctaethylene phosphate, tetradecyloxy octaethylene phosphate, hexadecyloxy octaethylene phosphate, and octaalkoxyl octaethylene phosphate are particularly preferable, and their alkali metal salts are particularly preferable.

Specific examples of the alkoxypolyoxypropylene phosphate salt include: octyloxydioxypropene phosphate, octyloxytrioxypropene phosphate, octyloxytetraoxypropylene phosphate, decyloxy tetraoxypropylene phosphate, dodecyloxytetraoxypropylene phosphate, tridecyloxytetraoxypropylene phosphate, tetradecyloxy tetraoxypropylene phosphate, hexadecyloxy tetraoxypropylene phosphate, octadecyloxypropylene phosphate, octyloxypentaoxypropylene phosphate, decyloxy pentaoxypropylene phosphate, dodecyloxypentaoxypropylene phosphate, tridecyloxypentaoxypropylene phosphate, tetradecyloxy pentaoxypropylene phosphate, hexadecyloxy pentaoxypropylene phosphate, octadecyloxypentaoxypropylene phosphate, octyloxypropylene phosphate, decyloxy hexaoxypropylene phosphate, dodecyloxypropylene phosphate, tridecyloxy hexaoxypropylene phosphate, tetradecyloxy hexaoxypropylene phosphate, hexadecyloxy hexaoxypropylene phosphate, octadecyloxy hexapropylene phosphate, octoyloxy octapropylene phosphate, decyloxy octapropylene phosphate, tridecyloxy octaoxypropylene phosphate, tetradecyloxy octapropylene phosphate, hexadecyloxy octapropylene phosphate, octadecyl octapropylene phosphate, and the like, among these, alkali metal salts thereof are preferable, and sodium salts thereof are particularly preferable.

Specific examples of the alkylphenoxy polyoxyalkylene phosphate include alkylphenoxy polyoxyethylene phosphate and alkylphenoxy polyoxypropylene phosphate, and among these, alkylphenoxy polyoxyethylene phosphate is preferred.

Specific examples of the alkylphenoxypolyoxyethylene phosphate salt include: metal salts of methylphenoxy tetraoxyethylene phosphate, ethylphenoxy tetraoxyethylene phosphate, butylphenoxy tetraoxyethylene phosphate, hexylphenoxy tetraoxyethylene phosphate, nonylphenoxy tetraoxyethylene phosphate, dodecylphenoxy tetraoxyethylene phosphate, octadecylphenoxy tetraoxyethylene phosphate, methylphenoxy pentaoxyethylene phosphate, ethylphenoxy pentaoxyethylene phosphate, butylphenoxy pentaoxyethylene phosphate, hexylphenoxy pentaoxyethylene phosphate, nonylphenoxy pentaoxyethylene phosphate, dodecylphenoxy pentaoxyethylene phosphate, methylphenoxy hexaoxyethylene phosphate, ethylphenoxy hexaoxyethylene phosphate, butylphenoxy hexaoxyethylene phosphate, hexylphenoxy hexaoxyethylene phosphate, nonylphenoxy hexaoxyethylene phosphate, dodecylphenoxy hexaoxyethylene phosphate, methylphenoxy octaoxyethylene phosphate, ethylphenoxy octaoxyethylene phosphate, butylphenoxy octaoxyethylene phosphate, hexylphenoxy octaoxyethylene phosphate, nonylphenoxy octaoxyethylene phosphate, dodecylphenoxy octaoxyethylene phosphate, etc., among these, alkali metal salts thereof are particularly preferred, and sodium salts thereof are particularly preferred.

Specific examples of the alkylphenoxypolyoxypropylene phosphate salt include: metal salts such as methylphenoxy tetraoxypropylene phosphate, ethylphenoxy tetraoxypropylene phosphate, butylphenoxy tetraoxypropylene phosphate, hexylphenoxy tetraoxypropylene phosphate, nonylphenoxy tetraoxypropylene phosphate, dodecylphenoxy tetraoxypropylene phosphate, methylphenoxy pentaoxypropylene phosphate, ethylphenoxy pentaoxypropylene phosphate, butylphenoxy pentaoxypropylene phosphate, hexylphenoxy pentaoxypropylene phosphate, nonylphenoxy pentaoxypropylene phosphate, dodecylphenoxy pentaoxypropylene phosphate, methylphenoxy hexaoxypropylene phosphate, ethylphenoxy hexaoxypropylene phosphate, butylphenoxy hexaoxypropylene phosphate, hexylphenoxy hexaoxypropylene phosphate, nonylphenoxy hexaoxypropylene phosphate, dodecylphenoxy hexaoxypropylene phosphate, methylphenoxy octaoxypropylene phosphate, ethylphenoxy octaoxypropylene phosphate, butylphenoxy octaoxypropylene phosphate, hexylphenoxy octaoxypropylene phosphate, nonylphenoxy octaoxypropylene phosphate, dodecylphenoxy octaoxypropylene phosphate, and the like, and alkali metal salts thereof are particularly preferred, and sodium salts thereof are particularly preferred.

As the phosphate ester salt, a monovalent phosphate ester salt such as a di (alkoxypolyoxyalkylene) phosphate sodium salt can be used alone or in combination with a divalent phosphate ester salt.

Examples of the sulfate salt include sodium lauryl sulfate, potassium lauryl sulfate, ammonium lauryl sulfate, sodium myristyl sulfate, sodium polyoxyethylene alkyl sulfate, sodium polyoxyethylene alkylaryl sulfate, and the like, and sodium lauryl sulfate is preferable.

Examples of the cationic emulsifier include alkyl trimethyl ammonium chloride, dialkyl ammonium chloride, benzyl ammonium chloride, and the like.

Examples of the nonionic emulsifier include: polyoxyalkylene fatty acid esters such as polyoxyethylene stearate; polyoxyalkylene alkyl ethers such as polyoxyethylene lauryl ether; polyoxyalkylene alkylphenol ethers such as polyoxyethylene nonylphenyl ether; the polyoxyethylene sorbitan alkyl ester is preferably a polyoxyalkylene alkyl ether or a polyoxyalkylene alkylphenol ether, and more preferably a polyoxyethylene alkyl ether or a polyoxyethylene alkylphenol ether.

These emulsifiers may be used singly or in combination, and the amount thereof is usually in the range of 0.01 to 10 parts by weight, preferably 0.1 to 5 parts by weight, more preferably 1 to 3 parts by weight, relative to 100 parts by weight of the monomer component.

The mixing method (mixing method) of the monomer component, water and emulsifier may be a conventional method, and examples thereof include a method of stirring the monomer, emulsifier and water using a stirrer such as a homogenizer or a disk turbine. The amount of water to be used is usually in the range of 1 to 1000 parts by weight, preferably 5 to 500 parts by weight, more preferably 4 to 300 parts by weight, particularly preferably 3 to 150 parts by weight, and most preferably 20 to 80 parts by weight, relative to 100 parts by weight of the monomer component.

(inorganic radical generator)

The polymerization catalyst used in the present invention is characterized by using a redox catalyst comprising an inorganic radical generator and a reducing agent. In particular, the use of an inorganic radical generator is preferable because the processability of the produced acrylic rubber such as rolls can be improved to a high degree.

The inorganic radical generator is not particularly limited as long as it is an inorganic radical generator that can be generally used in emulsion polymerization, and examples thereof include: persulfates such as sodium persulfate, potassium persulfate, and ammonium persulfate; among these, hydrogen peroxide and the like are preferable, and potassium persulfate and ammonium persulfate are more preferable, and potassium persulfate is particularly preferable.

These inorganic radical generators may be used singly or in combination, and the amount thereof is usually in the range of 0.0001 to 5 parts by weight, preferably 0.0005 to 1 part by weight, more preferably 0.001 to 0.25 part by weight, particularly preferably 0.01 to 0.21 part by weight, most preferably 0.1 to 0.2 part by weight, relative to 100 parts by weight of the monomer component.

(reducing agent)

The reducing agent used in the present invention is not particularly limited as long as it is a reducing agent that can be generally used in emulsion polymerization, and it is preferable to use at least two reducing agents, and the combination of the metal ion compound in a reduced state and the reducing agent other than the same can further highly balance the banbury processability, roll processability and strength characteristics of the obtained acrylic rubber, and therefore is preferable.

The metal ion compound in the reduced state is not particularly limited, and examples thereof include ferrous sulfate, sodium iron hexamethylenediamine tetraacetate, cuprous naphthenate, and the like, and among these, ferrous sulfate is preferable. These metal ion compounds in the reduced state may be used singly or in combination, and the amount thereof is usually in the range of 0.000001 to 0.01 part by weight, preferably 0.00001 to 0.001 part by weight, more preferably 0.00005 to 0.0005 part by weight, relative to 100 parts by weight of the monomer component.

The reducing agent other than the metal ion compound in the reduced state used in the present invention is not particularly limited, and examples thereof include: ascorbic acid or its salts such as ascorbic acid, sodium ascorbate, potassium ascorbate, etc.; erythorbic acid or salts thereof such as erythorbic acid, sodium erythorbate, and potassium erythorbate; sulfinate salts such as sodium hydroxymethanesulfinate; sulfite such as sodium sulfite, potassium sulfite, sodium bisulfite, sodium acetaldehyde bisulfite, and potassium bisulfite; metabisulfites such as sodium metabisulfite, potassium metabisulfite, sodium metabisulfite, potassium metabisulfite and the like; thiosulfate such as sodium thiosulfate and potassium thiosulfate; phosphorous acid or salts thereof such as phosphorous acid, sodium phosphite, potassium phosphite, sodium hydrogen phosphite, potassium hydrogen phosphite, etc.; pyrophosphorous acid or salts thereof such as pyrophosphorous acid, sodium pyrophosphate, potassium pyrophosphate, sodium hydrogen pyrophosphate, potassium hydrogen pyrophosphate, etc.; sodium formaldehyde sulfoxylate, and the like. Among these, ascorbic acid or a salt thereof, sodium formaldehyde sulfoxylate, and the like are preferable, and ascorbic acid or a salt thereof is particularly preferable.

These reducing agents other than the metal ion compound in the reduced state may be used singly or in combination, and the amount thereof is usually in the range of 0.001 to 1 part by weight, preferably 0.005 to 0.5 part by weight, more preferably 0.01 to 0.1 part by weight, relative to 100 parts by weight of the monomer component.

Preferred combinations of the metal ion compound in the reduced state with a reducing agent other than it are combinations of ferrous sulfate with ascorbic acid or a salt thereof and/or sodium formaldehyde sulfoxylate, more preferably combinations of ferrous sulfate with ascorbic acid or a salt thereof. The amount of the ferrous sulfate used in this case is usually in the range of 0.000001 to 0.01 parts by weight, preferably 0.00001 to 0.001 parts by weight, more preferably 0.00005 to 0.0005 parts by weight, relative to 100 parts by weight of the monomer component, and the amount of the ascorbic acid or a salt thereof and/or sodium formaldehyde sulfoxylate used is usually in the range of 0.001 to 1 part by weight, preferably 0.005 to 0.5 parts by weight, more preferably 0.01 to 0.1 part by weight, relative to 100 parts by weight of the monomer component.

The amount of water used in the emulsion polymerization may be only that used in the emulsion polymerization of the monomer component, or may be adjusted to be in the range of usually 10 to 1000 parts by weight, preferably 50 to 500 parts by weight, more preferably 80 to 400 parts by weight, and most preferably 100 to 300 parts by weight, relative to 100 parts by weight of the monomer component used for polymerization.

The emulsion polymerization may be carried out by a conventional method, and may be carried out in any of batch, semi-batch, and continuous modes. The polymerization temperature and polymerization time are not particularly limited, and may be appropriately selected depending on the kind of the polymerization initiator used, and the like. The polymerization time is usually 0.5 to 100 hours, preferably 1 to 10 hours.

The emulsion polymerization is exothermic, and the polymerization reaction is shortened if the temperature is not controlled, but in the present invention, the emulsion polymerization temperature is usually controlled to 35℃or less, preferably 0 to 35℃and more preferably 5 to 30℃and particularly preferably 10 to 25℃and, in this case, the strength characteristics of the produced acrylic rubber and the processability during kneading such as Banbury are highly balanced, and therefore, it is preferable.

(post addition of chain transfer agent)

In the present invention, it is preferable that the chain transfer agent is not added initially but intermittently and thereafter during polymerization, because an acrylic rubber having a high molecular weight component and a low molecular weight component can be produced, and the strength characteristics of the produced acrylic rubber are highly balanced with the processability during kneading with rolls and the like.

The chain transfer agent to be used is not particularly limited as long as it is a chain transfer agent that can be generally used in emulsion polymerization, and for example, a thiol compound can be preferably used.

As the thiol compound, an alkyl thiol compound having 2 to 20 carbon atoms can be generally used, and an alkyl thiol compound having 5 to 15 carbon atoms is preferably used, and an alkyl thiol compound having 6 to 14 carbon atoms is more preferably used.

The alkyl thiol compound may be any of an n-alkyl thiol compound, a secondary alkyl thiol compound, and a tertiary alkyl thiol compound, and is preferably an n-alkyl thiol compound or a tertiary alkyl thiol compound, and more preferably an n-alkyl thiol compound, and in this case, the effect of the chain transfer agent can be stably exhibited, and the processability of the produced acrylic rubber such as rollers can be improved to a high degree, which is preferable.

Specific examples of the alkyl thiol compound include: n-pentylmercaptan, n-hexylthiol, n-heptylthiol, n-octylthiol, n-decylthiol, n-dodecylthiol, n-tridecylthiol, n-tetradecylthiol, n-hexadecylthiol, n-octadecylthiol, sec-pentylmercaptan, sec-hexylthiol, sec-heptylthiol, sec-octylthiol, zhong Guiji thiol, sec-dodecylthiol, sec-tridecylthiol, sec-tetradecylthiol, sec-hexadecylthiol, sec-octadecylthiol, tert-pentylmercaptan, tert-hexylthiol, tert-heptylthiol, tert-octylthiol, tert-decylthiol, tert-dodecylthiol, tert-tridecylthiol, tert-tetradecylthiol, tert-hexadecylthiol, tert-octadecylthiol, etc., preferably n-octylthiol, n-dodecylthiol, tert-dodecylthiol, more preferably n-octylthiol, n-dodecylthiol.

These chain transfer agents can be used singly or in combination of two or more kinds. The amount of the chain transfer agent used is not particularly limited, but is preferably in the range of usually 0.0001 to 1 part by weight, preferably 0.0005 to 0.5 part by weight, more preferably 0.001 to 0.5 part by weight, particularly preferably 0.005 to 0.1 part by weight, most preferably 0.01 to 0.06 part by weight, based on 100 parts by weight of the monomer component, and in this case, the strength characteristics and roll processability of the produced acrylic rubber are highly balanced.

In the present invention, it is preferable that the chain transfer agent is not added at the beginning of the polymerization but intermittently added during the polymerization, since the high molecular weight component and the low molecular weight component of the acrylic rubber can be produced and the molecular weight distribution is set to a specific range, and in this case, the strength characteristics and the processability of the roll or the like can be highly balanced.

The number of intermittent post-addition of the chain transfer agent is not particularly limited, and may be appropriately selected depending on the purpose of use, and is usually 1 to 5 times, preferably 2 to 4 times, more preferably 2 to 3 times, and particularly preferably 2 times, and in this case, the strength characteristics of the produced acrylic rubber and the workability of rolls and the like can be highly balanced, and thus are preferable.

The timing of starting the intermittent post-addition of the chain transfer agent is not particularly limited, and may be appropriately selected depending on the purpose of use, and is generally preferably in the range of from 30 minutes after the start of the polymerization, more preferably from 30 to 200 minutes after the start of the polymerization, particularly preferably from 35 to 150 minutes, most preferably from 40 to 120 minutes after the start of the polymerization, and in this case, the strength characteristics of the produced acrylic rubber and the processability of the roll or the like can be highly balanced.

The amount of the chain transfer agent added per one batch of the post-addition is not particularly limited, and may be appropriately selected depending on the purpose of use, but is preferably in the range of usually 0.00005 to 0.5 part by weight, preferably 0.0001 to 0.1 part by weight, more preferably 0.0005 to 0.05 part by weight, particularly preferably 0.001 to 0.03 part by weight, and most preferably 0.002 to 0.02 part by weight, based on 100 parts by weight of the monomer component, and in this case, the strength characteristics and roll processability of the produced acrylic rubber can be highly balanced.

After the addition of the chain transfer agent, the polymerization reaction can be continued for usually 30 minutes or more, preferably 45 minutes or more, more preferably 1 hour or more and then ended without any particular limitation.

(post addition of reducing agent)

In the present invention, the reducing agent of the redox catalyst can be added later during polymerization, and thus the strength characteristics of the produced acrylic rubber and the workability of rolls and the like can be highly balanced, which is preferable.

The reducing agent added after the polymerization is the same as the above-mentioned examples and preferable ranges of the reducing agent. In the present invention, as the reducing agent to be added later, ascorbic acid or a salt thereof is preferable.

The amount of the reducing agent to be added after the polymerization is not particularly limited, and may be appropriately selected depending on the purpose of use, but is usually in the range of 0.0001 to 1 part by weight, preferably 0.0005 to 0.5 part by weight, more preferably 0.001 to 0.5 part by weight, particularly preferably 0.005 to 0.1 part by weight, most preferably 0.01 to 0.05 part by weight, based on 100 parts by weight of the monomer component, and in this case, the productivity of the production of the acrylic rubber is excellent, and the strength characteristics and processability of the produced acrylic rubber can be highly balanced, and thus it is preferable.

The reducing agent to be added after the polymerization may be either continuous or batch-wise, and is preferably batch-wise. The number of times of adding the reducing agent intermittently and thereafter during the polymerization is not particularly limited, but is usually 1 to 5 times, preferably 1 to 3 times, and more preferably 1 to 2 times.

When the reducing agent added at the beginning of polymerization and the reducing agent added after the middle of polymerization are ascorbic acid or a salt thereof, the ratio of the amount of the ascorbic acid or a salt thereof added at the beginning to the amount of the ascorbic acid or a salt thereof added later is not particularly limited, and the ratio of the weight ratio of "the ascorbic acid or a salt thereof added at the beginning"/"the ascorbic acid or a salt thereof added intermittently" is usually in the range of 1/9 to 8/2, preferably in the range of 2/8 to 6/4, more preferably in the range of 3/7 to 5/5, and in this case, the productivity of the production of the acrylic rubber is excellent, and the strength characteristics and the workability of the produced acrylic rubber can be highly balanced, and therefore, it is preferable.

The timing of the post-addition of the reducing agent is not particularly limited, and may be appropriately selected depending on the purpose of use, and is usually in the range of 1 to 3 hours after the start of polymerization, preferably 1.5 to 2.5 hours after the start of polymerization, and in this case, the productivity of the production of the acrylic rubber is excellent, and the strength characteristics of the produced acrylic rubber and the workability of rolls and the like can be highly balanced, so that it is preferable.

The amount of the reducing agent added is not particularly limited and may be appropriately selected depending on the purpose of use, but is preferably in the range of usually 0.00005 to 0.5 part by weight, preferably 0.0001 to 0.1 part by weight, more preferably 0.0005 to 0.05 part by weight, particularly preferably 0.001 to 0.03 part by weight, based on 100 parts by weight of the monomer component, and in this case, the strength characteristics of the produced acrylic rubber and the workability of rolls and the like can be highly balanced.

The operation after the addition of the reducing agent is not particularly limited, and the polymerization reaction can be terminated after the polymerization reaction is continued for usually 30 minutes or more, preferably 45 minutes or more, more preferably 1 hour or more.

The polymerization conversion rate of the emulsion polymerization is not particularly limited, but is usually 90% by weight or more, preferably 95% by weight or more, and in this case, the produced acrylic rubber is preferable because it is excellent in strength characteristics and free from monomer odor. At the termination of the polymerization, a polymerization terminator may be used.

(coagulation step)

The coagulation step after emulsion polymerization is characterized in that the emulsion polymerization liquid obtained in the emulsion polymerization is added to the stirred coagulation liquid to coagulate the emulsion polymerization liquid, thereby producing aqueous pellets of the acrylic rubber.

The solid content concentration of the emulsion polymerization liquid used in the coagulation reaction is not particularly limited, and is usually adjusted to a range of 5 to 50 wt%, preferably 10 to 45 wt%, more preferably 20 to 40 wt%.

The coagulant used as the coagulant liquid is not particularly limited, and a metal salt can be generally used. The metal salt may be, for example, an alkali metal salt, a metal salt of group 2 of the periodic table, or other metal salt, and is preferably an alkali metal salt or a metal salt of group 2 of the periodic table, more preferably a metal salt of group 2 of the periodic table, and particularly preferably a magnesium salt, and in this case, the water resistance, strength characteristics, mold releasability, and processability of the resulting acrylic rubber can be highly balanced, and therefore, it is preferable.

Examples of the alkali metal salt include: sodium salts such as sodium chloride, sodium nitrate, and sodium sulfate; potassium salts such as potassium chloride, potassium nitrate, and potassium sulfate; among these, sodium salts are preferable, and sodium chloride and sodium sulfate are particularly preferable.

Examples of the metal salt of group 2 of the periodic table include magnesium chloride, calcium chloride, magnesium nitrate, calcium nitrate, magnesium sulfate, and calcium chloride and magnesium sulfate are preferable.

Examples of the other metal salt include zinc chloride, titanium chloride, manganese chloride, iron chloride, cobalt chloride, nickel chloride, aluminum chloride, tin chloride, zinc nitrate, titanium nitrate, manganese nitrate, iron nitrate, cobalt nitrate, nickel nitrate, aluminum nitrate, tin nitrate, zinc sulfate, titanium sulfate, manganese sulfate, iron sulfate, cobalt sulfate, nickel sulfate, aluminum sulfate, and tin sulfate.

These coagulants may be used singly or in combination, and the amount thereof is usually in the range of 0.01 to 100 parts by weight, preferably 0.1 to 50 parts by weight, more preferably 1 to 30 parts by weight, relative to 100 parts by weight of the monomer component. When the coagulant is in this range, the acrylic rubber can be sufficiently coagulated, and the compression set characteristics and water resistance in the case of crosslinked acrylic rubber can be highly improved, which is preferable.

In the coagulation step of the present invention, it is preferable that the particle size of the produced aqueous aggregates is concentrated in a specific region, because the cleaning efficiency and ash removal efficiency during dehydration are remarkably improved. The proportion of the produced aqueous pellets in the range of 710 μm to 6.7mm (not passing through 710 μm but passing through 6.7 mm) is not particularly limited, but is usually 30% by weight or more, preferably 50% by weight or more, more preferably 60% by weight or more, particularly preferably 70% by weight or more, and most preferably 80% by weight or more relative to the total of the produced aqueous pellets, and in this case, the water resistance of the acrylic rubber can be significantly improved, and is therefore preferred. The proportion of the produced aqueous pellet in the range of 710 μm to 4.75mm (not passing through 710 μm but passing through 4.75 mm) is not particularly limited, but is usually 30% by weight or more, preferably 50% by weight or more, more preferably 60% by weight or more, particularly preferably 70% by weight or more, and most preferably 80% by weight or more relative to the total amount of the produced aqueous pellet, and in this case, the water resistance of the acrylic rubber can be significantly improved, and is therefore preferred. Further, the proportion of the produced aqueous pellet in the range of 710 μm to 3.35mm (not passing through 710 μm but passing through 3.35 mm) is not particularly limited, but is usually 20% by weight or more, preferably 30% by weight or more, more preferably 40% by weight or more, particularly preferably 50% by weight or more, and most preferably 60% by weight or more relative to the total amount of the produced aqueous pellet, and in this case, the water resistance of the acrylic rubber can be significantly improved, and thus is preferred.

The method for forming the particle size of the aqueous pellet in the above-described range is not particularly limited, and for example, the method of adding the emulsion polymerization liquid to the stirred coagulation liquid (aqueous coagulant solution) or bringing the emulsion polymerization liquid into contact with the coagulant can be performed by specifying the coagulant concentration of the coagulation liquid, the stirring speed of the stirred coagulation liquid, and the peripheral speed of the stirred coagulation liquid.

The coagulant to be used is usually used in the form of an aqueous solution, and the concentration of the coagulant in the aqueous solution is not particularly limited, but is usually 0.1% by weight or more, preferably 0.5% by weight or more, more preferably 1% by weight or more, and particularly preferably 1.5% by weight or more. The coagulant concentration of the coagulant is preferably in the range of usually 0.1 to 20% by weight, preferably 0.5 to 15% by weight, more preferably 1 to 10% by weight, and particularly preferably 1.5 to 5% by weight, because the particle size of the resulting aqueous aggregates can be uniformly concentrated in a specific region.

The temperature of the coagulating liquid is not particularly limited, but is usually 40℃or higher, preferably 40 to 90℃and more preferably 50 to 80℃and, in this case, uniform aqueous aggregates can be produced, which is preferable.

The stirring speed (rotation speed) of the stirred coagulation liquid, that is, the rotation speed of the stirring blade of the stirring device is not particularly limited, and is usually 100rpm or more, preferably 200rpm or more, more preferably 200 to 1000rpm, particularly preferably 300 to 900rpm, and most preferably 400 to 800 rpm.

Since the particle size of the produced aqueous pellets can be made small and uniform when the rotational speed is a rotational speed at which stirring is intense to some extent, it is preferable that the rotational speed is not less than the lower limit, the particle size of the produced pellets can be suppressed from being excessively large or excessively small, and the coagulation reaction can be controlled more easily by setting the rotational speed to not more than the upper limit.

The peripheral speed of the stirred coagulation liquid, that is, the speed of the outer periphery of the stirring blade of the stirring device is not particularly limited, and when the stirring is vigorously performed to a certain extent, the particle size of the resulting aqueous granules can be made small and uniform, and therefore, it is preferably usually 0.5m/s or more, preferably 1m/s or more, more preferably 1.5m/s or more, particularly preferably 2m/s or more, and most preferably 2.5m/s or more. On the other hand, the upper limit of the peripheral speed is not particularly limited, but is usually 50m/s or less, preferably 30m/s or less, more preferably 25m/s or less, and most preferably 20m/s or less, and in this case, the coagulation reaction is easily controlled, and is therefore preferable.

By setting the above-mentioned conditions of the coagulation reaction (the addition method, the solid content concentration of the emulsion polymerization liquid, the concentration and temperature of the coagulation liquid, the rotational speed and peripheral speed of the coagulation liquid at the time of stirring, etc.) in a specific range, the shape and the pellet size of the produced aqueous pellets are uniform and concentrated, and as a result, the removal of the emulsifier and the coagulant at the time of washing and dehydration is remarkably improved, and as a result, the water resistance and the storage stability of the produced acrylic rubber can be highly improved, which is preferable.

(cleaning step)

The cleaning step in the method for producing an acrylic rubber of the present invention is characterized in that the aqueous pellet produced in the coagulation reaction is cleaned with hot water.

The washing method is not particularly limited, and can be performed by mixing the produced aqueous pellets with a large amount of hot water, for example.

The amount of hot water to be added for cleaning is not particularly limited, but is usually 50 parts by weight or more per 100 parts by weight of the monomer component, preferably 50 to 15000 parts by weight, more preferably 100 to 10000 parts by weight, still more preferably 500 to 5000 parts by weight, and in this case, the ash content in the acrylic rubber can be effectively reduced, which is preferable.

The temperature of the hot water to be used is not particularly limited, but is usually 40 ℃ or higher, preferably 40 to 100 ℃, more preferably 50 to 90 ℃, particularly preferably 60 to 80 ℃, and in this case, the cleaning efficiency can be significantly improved, and thus is most preferable. By setting the temperature of the water to be used to be equal to or higher than the lower limit, the emulsifier and the coagulant are released from the aqueous pellet, and the cleaning efficiency is further improved.

The washing time is not particularly limited, but is usually in the range of 1 to 120 minutes, preferably 2 to 60 minutes, more preferably 3 to 30 minutes.

The number of times of washing (water washing) is also not particularly limited, and is usually 1 to 10 times, preferably 1 to 5 times, and more preferably 2 to 3 times. In addition, from the viewpoint of reducing the residual amount of the coagulant in the finally obtained acrylic rubber, it is preferable that the number of times of washing is large, but by setting the shape of the aqueous aggregates and the particle size of the aqueous aggregates to a specific range and/or setting the washing temperature to the above-described range, the number of times of washing can be significantly reduced.

(dehydration step)

The dehydration step in the method for producing an acrylic rubber of the present invention is a step of dehydrating the washed aqueous pellet.

The method for dehydrating the aqueous pellet is not particularly limited as long as the method can extrude water from the aqueous pellet, and it can be usually performed using a dehydrator or the like. This is preferable because the amount of ash in the emulsifier and coagulant present in the aqueous pellet, which cannot be removed in the cleaning step, can be reduced, and the water resistance of the acrylic rubber can be significantly improved.

The dehydrator is not particularly limited, and for example, a centrifugal separator, a squeezer, a screw type biaxial extrusion dryer, or the like can be used, and particularly, the screw type biaxial extrusion dryer can highly reduce the water content of the aqueous pellet, and is therefore preferable. When a centrifuge or the like is used for the adhesive acrylic rubber, the acrylic rubber is adhered between the wall surface and the slit, and usually can be dehydrated only to about 45 to 55 wt%. In contrast, a screw type biaxial extrusion dryer is preferable because it has a mechanism for forcibly extruding water.

The water content of the dehydrated hydrous pellets is not limited, but is usually in the range of 1 to 50% by weight, preferably 1 to 40% by weight, more preferably 10 to 40% by weight, still more preferably 15 to 35% by weight. The dehydration time can be shortened by setting the water content after dehydration to the above lower limit or more, whereby deterioration of the acrylic rubber can be suppressed, and the ash content can be sufficiently reduced by setting the water content after dehydration to the above upper limit or less.

(drying step)

The drying step in the method for producing an acrylic rubber of the present invention is a step of drying the dehydrated aqueous pellet to less than 1% by weight.

The method for drying the dehydrated aqueous pellets is not particularly limited, and for example, the dehydrated aqueous pellets may be dried by direct drying, but is preferably performed by using a screw type biaxial extrusion dryer. The screw type biaxial extrusion dryer to be used is not particularly limited as long as it is an extrusion dryer having 2 screws, and in the present invention, particularly, it is preferable to dry the aqueous pellets under high shear conditions by using a screw type biaxial extrusion dryer having 2 screws, because the roll processability, banbury processability and strength characteristics of the obtained acrylic rubber can be highly balanced.

In the present invention, the acrylic rubber can be obtained by melting and extrusion-drying the aqueous pellets in a screw type biaxial extrusion dryer. The drying temperature (set temperature) of the screw type biaxial extrusion dryer is preferably selected as appropriate, since the drying temperature is usually in the range of 100 to 250 ℃, preferably 110 to 200 ℃, more preferably 120 to 180 ℃, and the drying can be effectively performed without scorching or deterioration of the acrylic rubber.

In the present invention, it is preferable that the aqueous pellet is melted and extrusion-dried under reduced pressure in a screw type biaxial extrusion dryer, since the roll processability and strength characteristics of the acrylic rubber are not impaired and the storage stability can be highly improved. In this stage, the vacuum degree in the screw type biaxial extrusion dryer, which is preferable for the purpose of removing air existing in the acrylic rubber and improving the storage stability, is usually in the range of 1 to 50kPa, preferably 2 to 30kPa, more preferably 3 to 20kPa, as long as it is appropriately selected.

In the present invention, it is preferable that the aqueous pellets are melt kneaded and dried in a state in which water is substantially removed by a screw type biaxial extrusion dryer, because the roll processability and strength characteristics of the acrylic rubber are not impaired and the banbury processability can be highly improved. The water content of the acrylic rubber is usually less than 1% by weight, preferably 0.8% by weight or less, and more preferably 0.6% by weight or less, as long as the water content is appropriately selected as a state in which the banbury workability can be highly improved. In addition, the "melt-kneading" or "melt-kneading and drying" as referred to in the present invention means that the acrylic rubber is kneaded (mixed) in a molten state or extruded in a molten state in a screw type biaxial extrusion dryer and dried at this stage; or kneading, extruding and drying the acrylic rubber in a molten (plasticized) state by a screw type biaxial extrusion dryer.

The maximum torque of the screw type biaxial extrusion dryer used in the present invention is not particularly limited, but is usually 20n·m or more, preferably 25n·m or more, more preferably 30n·m or more, particularly preferably 35n·m or more, and most preferably 40n·m or more. The maximum torque of the screw type biaxial extrusion dryer used in the present invention is usually 25 to 125n·m, preferably 30 to 100n·m, more preferably 35 to 75n·m, and particularly preferably 40 to 60n·m, and in this case, the roll processability, banbury processability, and strength characteristics of the produced acrylic rubber can be highly balanced, and therefore, it is preferable.

The specific energy consumption of the screw type biaxial extrusion dryer used in the present invention is not particularly limited, but is usually in the range of 0.1 to 0.25[ kw.h/kg ], preferably 0.13 to 0.23[ kw.h/kg ], more preferably 0.15 to 0.2[ kw.h/kg ], and in this case, the roll processability, banbury processability and strength characteristics of the obtained acrylic rubber are highly balanced and therefore preferable.

The specific power of the screw type biaxial extrusion dryer used in the present invention is not particularly limited, but is usually in the range of 0.2 to 0.6[ A.h/kg ], preferably 0.25 to 0.55[ A.h/kg ], more preferably 0.35 to 0.5[ A.h/kg ], and in this case, the roll processability, banbury processability and strength characteristics of the obtained acrylic rubber are highly balanced, and therefore preferable.

The shear rate of the screw type biaxial extrusion dryer used in the present invention is not particularly limited, but is usually in the range of 40 to 150[1/s ], preferably 45 to 125[1/s ], more preferably 50 to 100[1/s ], and in this case, the storage stability, roll processability, banbury processability and strength characteristics of the obtained acrylic rubber are highly balanced, and therefore preferable.

The shear viscosity of the acrylic rubber in the screw-type biaxial extrusion dryer used in the present invention is not particularly limited, but is usually in the range of 4000 to 8000[ pa·s ], preferably in the range of 4500 to 7500[ pa·s ], more preferably in the range of 5000 to 7000[ pa·s ], and in this case, the storage stability, roll processability, banbury processability and strength characteristics of the obtained acrylic rubber are highly balanced, and therefore preferable.

The acrylic rubber of the present invention is cooled after melt kneading and drying. The cooling rate is not particularly limited, but is usually 40℃per hour or more, preferably 50℃per hour or more, more preferably 100℃per hour or more, and particularly preferably 150℃per hour or more, and in this case, the acrylic rubber is excellent in storage stability, roll processability, banbury processability, strength characteristics, water resistance and compression set resistance, and can significantly improve scorch stability, and therefore is preferable.

The acrylic rubber of the present invention thus obtained is excellent in roll processability, strength characteristics and water resistance and can be used for various applications. The shape of the acrylic rubber of the present invention is not particularly limited, and may be appropriately selected depending on the purpose of use, and examples thereof include powder, pellet, strand, sheet, and gel pack, and the like, and the sheet, gel pack, and the like are excellent in handling property and storage stability, and thus are preferable.

(Process for producing sheet-like or rubber-coated acrylic rubber)

The method for producing a sheet-like or rubber-coated acrylic rubber of the present invention is not particularly limited, and a screw-type biaxial extrusion dryer having a dehydration barrel with a dehydration slit and a dryer barrel under reduced pressure and having a die at the tip end portion is used, and the above-mentioned washed aqueous pellets are dehydrated in the dehydration barrel to a water content of 1 to 40% by weight, and then dried in the dryer barrel to a water content of less than 1% by weight, and the sheet-like dried rubber is extruded from the die, whereby a sheet-like acrylic rubber can be easily produced, and the extruded sheet-like dried rubber can be laminated and rubber-coated to thereby easily produce a rubber-coated acrylic rubber.

In the present invention, the aqueous pellets supplied to the screw type biaxial extrusion dryer are preferably pellets from which free water (water removal) is removed after washing.

(Water removal Process)

In the present invention, it is preferable to provide a water removal step of separating free water from the washed aqueous pellets by a water remover in order to improve the dehydration efficiency.

The dewatering machine is not particularly limited, and a known dewatering machine can be used, and examples thereof include a wire mesh, a screen, and an electric screen, and a wire mesh and a screen are preferable.

The mesh of the dewatering machine is not particularly limited, but is usually in the range of 0.01 to 5mm, preferably 0.1 to 1mm, more preferably 0.2 to 0.6mm, and in this case, the loss of water-containing aggregates is small and water can be effectively removed, so that it is preferable.

The water content of the aqueous pellet after the water removal, that is, the water content of the aqueous pellet to be fed to the dehydration-drying step is not particularly limited, but is usually in the range of 50 to 80% by weight, preferably 50 to 70% by weight, more preferably 50 to 60% by weight.

The temperature of the aqueous pellet after the water removal, that is, the temperature of the aqueous pellet to be fed to the dehydration-drying step is not particularly limited, but is usually 40℃or higher, preferably 40 to 100℃or higher, more preferably 50 to 90℃or lower, particularly preferably 55 to 85℃or lower, and most preferably 60 to 80℃or lower, and in this case, the aqueous pellet having a specific heat of 1.5 to 2.5 KJ/kg.K and being hardly elevated in temperature can be dehydrated and dried efficiently by using the screw type biaxial extrusion dryer, and is therefore preferable.

(dehydration of aqueous pellets in the barrel section of the dehydrator)

The dewatering of the aqueous pellets is carried out by means of a dewatering barrel in a screw-type twin-screw extrusion dryer with dewatering slits. The mesh size of the dewatering slit may be appropriately selected depending on the conditions of use, and is usually in the range of 0.01 to 5mm, preferably 0.1 to 1mm, more preferably 0.2 to 0.6mm, and in this case, the loss of the aqueous pellets is small and the dewatering of the aqueous pellets can be efficiently performed, which is preferable.

The number of the dehydration cylinders in the screw type biaxial extrusion dryer is not particularly limited, but is usually plural, preferably 2 to 10, more preferably 3 to 6, and in this case, dehydration of the adhesive acrylic rubber can be effectively performed, which is preferable.

The removal of water from the hydrous pellets in the dewatering barrel has two forms of removal in a liquid state (drainage) from the dewatering slit and removal in a vapor state (drainage), and in the present invention, drainage is defined as dewatering and drainage is defined as predrying for the sake of distinction.

The water discharged from the dewatering slit during the dewatering of the hydrous pellets may be in any of a liquid state (drainage) and a vapor state (vapor discharge), and in the case of using a screw type biaxial extrusion dryer having a plurality of dewatering barrels, it is preferable to efficiently dewater the adhesive acrylic rubber by combining drainage and vapor discharge. The selection of the water-discharge type dehydrator cylinder or the steam-discharge type dehydrator cylinder of the screw type biaxial extrusion dryer having 3 or more dehydrator cylinders may be appropriately performed according to the purpose of use, and the water-discharge type cylinder is generally increased in the case of reducing the ash content in the produced sheet-like or rubber-coated acrylic rubber, and the steam-discharge type cylinder is increased in the case of reducing the water content.

The setting temperature of the dehydration barrel may be appropriately selected depending on the monomer composition, ash amount, water content, operating conditions and the like of the acrylic rubber, and is usually in the range of 60 to 150 ℃, preferably 70 to 140 ℃, more preferably 80 to 130 ℃. The setting temperature of the dehydration barrel for dehydration in a drained state is usually 60 to 120 ℃, preferably 70 to 110 ℃, more preferably 80 to 100 ℃. The set temperature of the dehydration barrel for dehydration in the vapor-exhausted state is usually in the range of 100 to 150 ℃, preferably 105 to 140 ℃, more preferably 110 to 130 ℃.

The water content after the water discharge type dehydration by extruding water from the hydrous pellets is not particularly limited, but is usually 1 to 40% by weight, preferably 5 to 40% by weight, more preferably 5 to 35% by weight, particularly preferably 10 to 35% by weight, and in this case, productivity and ash removal efficiency are highly balanced, and thus preferable.

When dehydration of the acrylic rubber having adhesiveness of the reactive group is performed using a centrifuge or the like, the acrylic rubber adheres to the dehydration slit portion and is hardly dehydrated (the water content is about 45 to 55% by weight), and in the present invention, the water content can be reduced to this point by using a screw type biaxial extrusion dryer having a dehydration slit and forcibly extruding with a screw.

Regarding the dehydration of the aqueous pellets in the case of having a drainage type dehydrator cylinder and a steam discharge type dehydrator cylinder, the water content after drainage of the drainage type dehydrator cylinder is usually 5 to 40% by weight, preferably 10 to 40% by weight, more preferably 15 to 35% by weight, and the water content after pre-drying of the steam discharge type dehydrator cylinder is usually 1 to 30% by weight, preferably 3 to 20% by weight, more preferably 5 to 15% by weight.

The dehydration time can be shortened by setting the water content after dehydration to the above lower limit or more, deterioration of the acrylic rubber can be suppressed, and the ash content can be sufficiently reduced by setting the water content after dehydration to the above upper limit or less.

(drying of aqueous pellets in the dryer section)

The above-described drying of the dehydrated aqueous pellets is preferably performed by a dryer barrel section of a screw type biaxial extrusion dryer having a dryer barrel section under reduced pressure. Drying under reduced pressure is preferable because it improves the production efficiency of drying and removes air present in the acrylic rubber, thereby enabling production of a sheet-like or bag-like acrylic rubber having a high specific gravity and excellent storage stability. In the present invention, the acrylic rubber is melted under reduced pressure and extrusion-dried, whereby the storage stability can be highly improved. The storage stability of the acrylic rubber can be controlled largely in relation to the specific gravity of the acrylic rubber, and in the case where the specific gravity is controlled so as to be high and the storage stability is high, the degree of vacuum or the like of the extrusion drying can be controlled.

The vacuum degree of the dryer cylinder is preferably 1 to 50kPa, more preferably 2 to 30kPa, and even more preferably 3 to 20kPa, since the drying cylinder is appropriately selected, and at this time, the aqueous pellets can be effectively dried, and the air in the acrylic rubber can be removed, so that the storage stability of the sheet-like or bag-like acrylic rubber is remarkably improved.

The setting temperature of the dryer cylinder is preferably selected as appropriate, and is usually in the range of 100 to 250 ℃, preferably 110 to 200 ℃, more preferably 120 to 180 ℃, in which case, scorching and deterioration of the acrylic rubber are not caused, and the drying can be effectively performed, and the amount of methyl ethyl ketone-insoluble components in the sheet-like or bale-like acrylic rubber can be reduced.

The number of the dryer cylinders of the screw type biaxial extrusion dryer is not particularly limited, but is usually plural, preferably 2 to 10, more preferably 3 to 8. In the case of having a plurality of dryer cylinders, the vacuum degree may be set to be similar for all the dryer cylinders, or may be changed for each cylinder. The set temperature in the case of having a plurality of dryer cylinders may be set to a similar temperature for all the dryer cylinders or may be changed for each cylinder, but it is preferable to set the temperature of the discharge portion (on the side closer to the die) higher than the temperature of the introduction portion (on the side closer to the dryer cylinder) to improve the drying efficiency.

The moisture content of the dried rubber after drying is usually less than 1% by weight, preferably 0.8% by weight or less, more preferably 0.6% by weight or less. In the present invention, it is preferable to melt-extrude the dried rubber in a screw type biaxial extrusion dryer so that the water content of the dried rubber is at this value (the state where water is substantially removed), because the amount of methyl ethyl ketone-insoluble component of the sheet-like or bale-like acrylic rubber can be reduced. In the present invention, the strength characteristics and the Banbury processability of the acrylic rubber melt-kneaded or melt-kneaded and dried by a screw type biaxial extruder are highly balanced, and therefore preferable. In addition, the "melt-kneading" or "melt-kneading and drying" as referred to in the present invention means that the acrylic rubber is kneaded (mixed) in a molten state or extruded in a molten state in a screw type biaxial extrusion dryer and dried at this stage; or kneading, extruding and drying the acrylic rubber in a molten (plasticized) state by a screw type biaxial extrusion dryer.

In the present invention, the shear rate of the acrylic rubber in a substantially water-free state in the dryer barrel of the screw type biaxial extrusion dryer is not particularly limited, but is usually 10[ l/s ] or more, preferably 10 to 400[ l/s ], and more preferably 50 to 250[ l/s ], and in this case, the resulting sheet-like or bag-like acrylic rubber is highly balanced in terms of storage stability, roll processability, banbury processability, strength characteristics and compression set resistance, and therefore, is preferable.

The shear viscosity of the acrylic rubber in the screw type biaxial extrusion dryer, particularly in the dryer barrel, used in the present invention is not particularly limited, but is usually not more than 12000[ pa·s ], preferably 1000 to 12000[ pa·s ], more preferably 2000 to 10000[ pa·s ], particularly preferably 3000 to 7000[ pa·s ], and most preferably 4000 to 6000[ pa·s ], and in this case, the resulting sheet-like or bag-like acrylic rubber is highly balanced in terms of storage stability, roll processability, banbury processability and strength characteristics, and is therefore preferable.

(extrusion of dried rubber from die section)

The dried rubber dehydrated and dried by the screw sections of the dehydrator cylinder and the dryer cylinder is transported to a die section without correction of the screw, and extruded from the die section in a desired shape. A perforated plate or a wire mesh may or may not be provided between the screw portion and the die portion.

The extruded dry rubber is preferably obtained by extruding the die into a sheet shape by forming the die into a substantially rectangular shape, because of which dry rubber having a small air entrainment, a large specific gravity and excellent storage stability is obtained.

The resin pressure of the die head is not particularly limited, but is usually in the range of 0.1 to 10MPa, preferably 0.5 to 5MPa, more preferably 1 to 3MPa, and in this case, the sheet-like or bag-like acrylic rubber is preferable because it is less involved in air (has a large specific gravity) and is excellent in productivity.

(screw type biaxial extrusion dryer and operating conditions)

The screw length (L) of the screw type biaxial extrusion dryer to be used may be appropriately selected depending on the purpose of use, and is usually in the range of 3000 to 15000mm, preferably 4000 to 10000mm, more preferably 4500 to 8000 mm.

The screw diameter (D) of the screw type biaxial extrusion dryer to be used may be appropriately selected depending on the purpose of use, and is usually in the range of 50 to 250mm, preferably 100 to 200mm, more preferably 120 to 160 mm.

The ratio (L/D) of the screw length (L) to the screw diameter (D) of the screw type biaxial extrusion dryer to be used is not particularly limited, but is usually in the range of 10 to 100, preferably 20 to 80, more preferably 30 to 60, and in this case, the water content can be preferably less than 1 wt% because the molecular weight of the dried rubber is not reduced or scorched.

The rotation speed (N) of the screw type biaxial extrusion dryer to be used may be appropriately selected depending on the respective conditions, and is usually 10 to 1000rpm, preferably 50 to 750rpm, more preferably 100 to 500rpm, and most preferably 120 to 300rpm, and in this case, the water content of the sheet-like or bale-like acrylic rubber and the amount of components insoluble in methyl ethyl ketone can be effectively reduced, which is preferable.

The extrusion amount (Q) of the screw type biaxial extrusion dryer to be used is not particularly limited, but is usually in the range of 100 to 1500 kg/hr, preferably 300 to 1200 kg/hr, more preferably 400 to 1000 kg/hr, and most preferably 500 to 800 kg/hr.

The ratio (Q/N) of the extrusion amount (Q) to the rotation speed (N) of the screw type biaxial extrusion dryer to be used is not particularly limited, but is usually in the range of 2 to 10, preferably 3 to 8, more preferably 4 to 6.

The maximum torque of the screw type biaxial extrusion dryer to be used is not particularly limited, but is usually 30n·m or more, preferably 35n·m or more, and more preferably 40n·m or more. Further, the maximum torque of the screw type biaxial extrusion dryer used in the present invention is usually in the range of 30 to 100n·m, preferably 35 to 75n·m, more preferably 40 to 60n·m, and in this case, the roll processability, banbury processability and strength characteristics of the produced sheet-like or bale-like acrylic rubber can be highly balanced, and therefore, it is preferable.

The specific energy consumption of the screw type biaxial extrusion dryer to be used is not particularly limited, but is usually in the range of 0.1 to 0.25[ kw.h/kg ], preferably 0.13 to 0.23[ kw.h/kg ], more preferably 0.15 to 0.2[ kw.h/kg ], and in this case, the roll processability, banbury processability and strength characteristics of the obtained sheet-like or gum-coated acrylic rubber are highly balanced, and therefore preferred.

The specific power of the screw type biaxial extrusion dryer to be used is not particularly limited, but is usually in the range of 0.2 to 0.6[ A.multidot.h/kg ], preferably 0.25 to 0.55[ A.multidot.h/kg ], more preferably 0.35 to 0.5[ A.multidot.h/kg ], and in this case, the roll processability, banbury processability and strength characteristics of the obtained sheet-like or bale-like acrylic rubber are highly balanced, and therefore, it is preferable.

The shear rate of the screw type biaxial extrusion dryer used is not particularly limited, but is usually in the range of 40 to 150[ l/s ], preferably 45 to 125[ l/s ], more preferably 50 to 100[ l/s ], and in this case, the resulting sheet-like or gel-coated acrylic rubber is highly balanced in terms of storage stability, roll processability, banbury processability and strength characteristics, and is therefore preferred.

The shear viscosity of the acrylic rubber in the screw-type biaxial extrusion dryer to be used is not particularly limited, but is usually in the range of 4000 to 8000[ Pa.s ], preferably 4500 to 7500[ Pa.s ], more preferably 5000 to 7000[ Pa.s ], and in this case, the resulting sheet-like or bag-like acrylic rubber is preferably highly balanced in storage stability, roll processability, banbury processability and strength characteristics.

In this way, in the present invention, it is preferable to use an extrusion dryer having a twin screw, because dehydration, drying, and molding under high shear conditions can be performed.

(sheet-like Dry rubber)

The shape of the dried rubber extruded from the screw type biaxial extrusion dryer is preferably a sheet shape, and in this case, the dried rubber can be highly improved in storage stability without involving air and has a large specific gravity. The sheet-like dry rubber extruded from the screw type biaxial extrusion dryer is generally cooled and cut to be used as a sheet-like acrylic rubber.

The thickness of the sheet-like dry rubber extruded from the screw type biaxial extrusion dryer is not particularly limited, but is usually in the range of 1 to 40mm, preferably 2 to 35mm, more preferably 3 to 30mm, most preferably 5 to 25mm, and in this case, the handling property and productivity are excellent, and therefore, it is preferable. In particular, since the thermal conductivity of the sheet-like dry rubber is as low as 0.15 to 0.35W/mK, the cooling efficiency is improved, and the productivity is remarkably improved, and the thickness of the sheet-like dry rubber is usually in the range of 1 to 30mm, preferably 2 to 25mm, more preferably 3 to 15mm, and particularly preferably 4 to 12 mm.

The width of the sheet-like dry rubber extruded from the screw type biaxial extrusion dryer can be appropriately selected depending on the purpose of use, and is usually in the range of 300 to 1200mm, preferably 400 to 1000mm, more preferably 500 to 800 mm.

The temperature of the dried rubber extruded from the screw type biaxial extrusion dryer is not particularly limited, but is usually in the range of 100 to 200 ℃, preferably 110 to 180 ℃, more preferably 120 to 160 ℃.

The water content of the dried rubber extruded from the screw type biaxial extrusion dryer is not particularly limited, but is usually less than 1% by weight, preferably 0.8% by weight or less, more preferably 0.6% by weight or less.

The sheet-like dry rubber extruded from the screw type biaxial extrusion dryer is not particularly limited in the complex viscosity ([ eta ]100 ℃) at 100℃and is usually in the range of 1500 to 6000[ Pa.s ], preferably 2000 to 5000[ Pa.s ], more preferably 2500 to 4000[ Pa.s ], most preferably 2500 to 3500[ Pa.s ], and in this case, the extrudability and shape retention as sheets are highly balanced and therefore preferred. That is, the extrusion properties can be further improved by setting the complex viscosity at 100 ℃ of the sheet-like dry rubber extruded from the screw-type biaxial extrusion dryer to the above lower limit or more, and the shape collapse and fracture of the sheet-like dry rubber can be suppressed by setting the complex viscosity at 100 ℃ of the sheet-like dry rubber extruded from the screw-type biaxial extrusion dryer to the above upper limit or less.

The sheet-like dry rubber extruded from the screw type biaxial extrusion dryer can be folded directly and used, and can be cut off normally.

The sheet-like dry rubber is not particularly limited, and the acrylic rubber of the present invention has strong adhesiveness, and therefore, in order to continuously cut the sheet-like dry rubber without involving air, it is preferable to cut the sheet-like dry rubber after cooling it.

The cutting temperature of the sheet-like dry rubber is not particularly limited, but is usually 60℃or lower, preferably 55℃or lower, more preferably 50℃or lower, and in this case, the cutting property and productivity are highly balanced, and therefore, it is preferable.

The sheet-like dry rubber is not particularly limited and is preferably cut continuously without involving air, since the sheet-like dry rubber has a complex viscosity ([ eta ]60 ℃) of usually not more than 15000[ Pa.s ], preferably in the range of 2000 to 10000[ Pa.s ], more preferably 2500 to 7000[ Pa.s ], and most preferably 2700 to 5500[ Pa.s ].

The ratio of the complex viscosity ([ eta ]100 ℃) at 100℃to the complex viscosity ([ eta ]60 ℃) at 60℃ ([ eta ]100 ℃/[ eta ]60 ℃) of the sheet-like dry rubber is not particularly limited, and is appropriately selected depending on the purpose of use, but is usually 0.5 or more, preferably 0.6 or more, more preferably 0.7 or more, particularly preferably 0.8 or more, most preferably 0.85 or more, and the upper limit is usually 0.98 or less, preferably 0.97 or less, more preferably 0.96 or less, particularly preferably 0.95 or less, most preferably 0.93 or less, and in this case, air inclusion is small, and the cutting property and productivity are highly balanced, and therefore, it is preferable.

The cooling method of the sheet-like dry rubber is not particularly limited, and the sheet-like dry rubber may be left at room temperature, and since the thermal conductivity of the sheet-like dry rubber is extremely small in the range of 0.15 to 0.35W/mK, forced cooling by an air cooling system under ventilation or air-conditioning equipment, a water spraying system, a dipping system in water, or the like is preferable, and an air cooling system under ventilation or air-conditioning equipment is particularly preferable in order to improve productivity.

In the air cooling system of the sheet-like dry rubber, for example, the sheet-like dry rubber can be extruded from a screw type biaxial extrusion dryer onto a conveyor such as a belt conveyor, and conveyed and cooled while blowing cold air. The temperature of the cold air is not particularly limited, but is usually in the range of 0 to 25 ℃, preferably 5 to 25 ℃, more preferably 10 to 20 ℃. The length of cooling is not particularly limited, and is usually in the range of 5 to 500m, preferably 10 to 200m, more preferably 20 to 100 m. The cooling rate of the sheet-like dry rubber is not particularly limited, but is usually 40℃per hour or more, preferably 50℃per hour or more, more preferably 100℃per hour or more, and particularly preferably 150℃per hour or more, and in this case, the sheet-like dry rubber is preferably easily cut and can be stored with good stability without involving air. In the present invention, the cooling rate of the sheet-like dry rubber is usually 40℃per hour or more, preferably 50℃per hour or more, more preferably 100℃per hour or more, and particularly preferably 150℃per hour or more, and in this case, the scorch stability when the acrylic rubber composition is produced is remarkably excellent, and thus it is preferable.

The cutting length of the sheet-like dry rubber is not particularly limited and may be appropriately selected depending on the purpose of use, and is usually in the range of 100 to 800mm, preferably 200 to 500mm, more preferably 250 to 450 mm.

The sheet-like acrylic rubber thus obtained is excellent in handling properties, roll processability, crosslinking properties, strength properties and compression set properties, and also excellent in storage stability, banbury processability and water resistance, as compared with the pellet-like acrylic rubber, and can be used as it is or laminated and packaged.

(lamination step)

The method for producing the rubber-covered acrylic rubber of the present invention is not particularly limited, and it is preferable to laminate the sheet-like acrylic rubber because the rubber-covered acrylic rubber is less involved in air and excellent in storage stability.

The lamination temperature of the sheet-like acrylic rubber is not particularly limited, but is usually 30℃or higher, preferably 35℃or higher, more preferably 40℃or higher, and in this case, air involved in lamination can be released, which is preferable. The number of laminated sheets may be appropriately selected according to the size or weight of the above-mentioned rubber-coated acrylic rubber. The rubber-covered acrylic rubber of the present invention is integrated by the self weight of the laminated sheet-like acrylic rubber.

The thus obtained rubber-coated acrylic rubber of the present invention is superior to the pellet-shaped acrylic rubber in handling property, and is excellent in roll processability, crosslinkability, strength characteristics and compression set resistance, and also in storage stability, banbury processability and water resistance, and can be used as it is or cut into a desired amount and put into a mixer such as a banbury, roll or the like.

< rubber composition >

The rubber composition of the present invention is characterized by comprising a rubber component, a filler and a crosslinking agent, wherein the rubber component comprises the acrylic rubber.

The acrylic rubber of the present invention may be used alone as the rubber component of the main component of the rubber composition of the present invention, or may be used in combination with other rubber components as required. The content of the acrylic rubber of the present invention in the rubber component may be appropriately selected depending on the purpose of use, and is, for example, usually 30% by weight or more, preferably 50% by weight or more, and more preferably 70% by weight or more.

The other rubber component that can be combined with the acrylic rubber of the present invention is not particularly limited, and examples thereof include natural rubber, polybutadiene rubber, polyisoprene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, silicone rubber, fluororubber, olefin elastomer, styrene elastomer, vinyl chloride elastomer, polyester elastomer, polyamide elastomer, polyurethane elastomer, polysiloxane elastomer, and the like.

These other rubber components can be used singly or in combination of two or more. The shape of these other rubber components may be any of a pellet shape, a strand shape, a bale shape, a sheet shape, a powder shape, and the like. The content of the other rubber component in the total rubber component may be appropriately selected within a range not to impair the effect of the present invention, and is, for example, generally 70% by weight or less, preferably 50% by weight or less, more preferably 30% by weight or less.

The filler contained in the rubber composition is not particularly limited, and examples thereof include reinforcing fillers and non-reinforcing fillers, and reinforcing fillers are preferable, and in this case, the rubber composition is excellent in roll processability, banbury processability and crosslinking property in a short period of time, and the crosslinked product is highly excellent in water resistance, strength characteristics and compression set resistance, and therefore is preferable.

Examples of the reinforcing filler include: carbon blacks such as furnace black, acetylene black, pyrolytic carbon black, channel black, and graphite; and silica such as wet silica, dry silica and colloidal silica. Examples of the non-reinforcing filler include quartz powder, diatomaceous earth, zinc oxide, basic magnesium carbonate, activated calcium carbonate, magnesium silicate, aluminum silicate, titanium dioxide, talc, aluminum sulfate, calcium sulfate, and barium sulfate.

These fillers may be used singly or in combination, and the amount thereof may be appropriately selected within a range not to impair the effects of the present invention, and is usually in a range of 1 to 200 parts by weight, preferably 10 to 150 parts by weight, more preferably 20 to 100 parts by weight, relative to 100 parts by weight of the rubber component.

The crosslinking agent used in the rubber composition is not particularly limited, and conventionally known crosslinking agents may be selected according to the purpose of use, and examples thereof include inorganic crosslinking agents such as sulfur compounds, organic crosslinking agents, and the like, and organic crosslinking agents are preferable. The crosslinking agent may be a polyvalent compound or a monovalent compound, and is preferably a polyvalent compound having 2 or more reactive groups. Further, the crosslinking agent may be either an ion-crosslinkable compound or a radical-crosslinkable compound, and is preferably an ion-crosslinkable compound.

The organic crosslinking agent is not particularly limited, but is preferably an ion-crosslinkable organic compound, and particularly preferably a polyion organic compound. When the crosslinking agent is a polyion organic compound (polyion crosslinkable compound), the rubber composition is particularly preferable because it is excellent in roll processability, banbury processability and crosslinking property in a short period of time, and the crosslinked product is highly excellent in strength characteristics and compression set resistance and also excellent in water resistance. The "ion" of the ion-crosslinkable or multi-element ion is an ion-reactive ion, and is not particularly limited as long as it can undergo an ion reaction with the ion-reactive group of the ion-reactive group-containing monomer of the above-mentioned acrylic rubber, and examples thereof include ion-crosslinkable organic compounds having an ion-reactive group such as an amino group, an epoxy group, a carboxyl group, and a thiol group.

Specific examples of the polyionic organic compound include a polyamine compound, a polyepoxide compound, a polycarboxylic acid compound, and a polythiol compound, and the polyamine compound and the polythiol compound are preferable, and the polyamine compound is more preferable.

Examples of the polyamine compound include: aliphatic polyamine compounds such as hexamethylenediamine, hexamethylenediamine carbamate, N' -biscinnamaldehyde-1, 6-hexamethylenediamine; 4,4 '-methylenedianiline, p-phenylenediamine, m-phenylenediamine, 4' -diaminodiphenyl ether, 3,4 '-diaminodiphenyl ether, 4' - (m-phenylenediisopropylene) diphenylamine, 4'- (p-phenylenediisopropylene) diphenylamine aromatic polyamine compounds such as 2,2' -bis [4- (4-aminophenoxy) phenyl ] propane, 4 '-diaminobenzanilide, 4' -bis (4-aminophenoxy) biphenyl, m-xylylenediamine, p-xylylenediamine, and 1,3, 5-benzenetriamine. Among these, hexamethylenediamine carbamate, 2' -bis [4- (4-aminophenoxy) phenyl ] propane and the like are preferable. Further, as the polyamine compound, carbonates thereof can be preferably used. These polyamine compounds are particularly preferably used in combination with carboxyl group-containing acrylic rubber or epoxy group-containing acrylic rubber.

As the polythiol compounds, preferably using triazine thiol compounds, can be cited for example, 6-three mercapto-s three triazine, 2-two amino-4, 6-two thiol-s three triazine, 1-two butyl amino 3, 5-two mercapto three triazine, 2-two butyl amino 4, 6-two thiol-s three triazine, 1-phenyl amino 3, 5-two mercapto three triazine, 2,4, 6-three mercapto-1, 3,5 three triazine, 1-hexyl amino 3, 5-two mercapto three triazine. These triazine thiol compounds are particularly preferably used in combination with an acrylic rubber containing chlorine atoms.

Examples of the other polyvalent organic compound include a polyvalent carboxylic acid compound such as tetradecanedioic acid, a metal dithiocarbamate such as zinc dimethyldithiocarbamate, and the like. These other polyvalent organic compounds are particularly preferably used in combination with an epoxy group-containing acrylic rubber.

These crosslinking agents may be used singly or in combination, and the amount thereof is usually 0.001 to 20 parts by weight, preferably 0.1 to 10 parts by weight, more preferably 0.1 to 5 parts by weight, relative to 100 parts by weight of the rubber component. When the amount of the crosslinking agent is in this range, the rubber elasticity can be made sufficient, and the mechanical strength as a crosslinked rubber product can be made excellent, which is preferable.

The rubber composition of the present invention may contain an antioxidant as needed. The type of the antioxidant is not particularly limited, and examples thereof include: other phenol-based antioxidants such as 2, 6-di-tert-butyl-4-methylphenol, 2, 6-di-tert-butylphenol, butylhydroxyanisole, 2, 6-di-tert-butyl- α -dimethylamino-p-cresol, octadecyl-3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate, styrenated phenol, 2' -methylene-bis (6- α -methyl-benzyl-p-cresol), 4' -methylenebis (2, 6-di-tert-butylphenol), 2' -methylene-bis (4-methyl-6-tert-butylphenol), 2, 4-bis [ (octylthio) methyl ] -6-methylphenol, 2' -thiobis- (4-methyl-6-tert-butylphenol), 4' -thiobis- (6-tert-butylphenol), 2, 6-di-tert-butyl-4- [4, 6-bis (octylthio) -1,3, 5-triazin-2-ylamino ] phenol; phosphite antioxidants such as tris (nonylphenyl) phosphite, diphenylisodecyl phosphite, tetraphenyl dipropylene glycol bisphosphite, etc.; thioester-based antioxidants such as dilauryl thiodipropionate; amine-based antioxidants such as phenyl- α -naphthylamine, phenyl- β -naphthylamine, p- (p-toluenesulfonamide) -diphenylamine, 4'- (α, α -dimethylbenzyl) diphenylamine, N-diphenyl-p-phenylenediamine, N-isopropyl-N' -phenyl-p-phenylenediamine, butyraldehyde-aniline condensate, and the like; imidazole-based antioxidants such as 2-mercaptobenzimidazole; quinoline antioxidants such as 6-ethoxy-2, 4-trimethyl-1, 2-dihydroquinoline; hydroquinone-based antioxidants such as 2, 5-di-t-amyl hydroquinone. Among these, amine-based antioxidants are particularly preferable.

These antioxidants may be used singly or in combination, and the amount thereof is usually in the range of 0.01 to 15 parts by weight, preferably 0.1 to 10 parts by weight, more preferably 1 to 5 parts by weight, relative to 100 parts by weight of the rubber component.

The rubber composition of the present invention contains the rubber component, filler and crosslinking agent of the acrylic rubber of the present invention as essential components, and optionally contains an anti-aging agent, and optionally contains other additives commonly used in the art, such as a crosslinking aid, a crosslinking accelerator, a crosslinking retarder, a silane coupling agent, a plasticizer, a processing aid, a slip agent, a pigment, a colorant, an antistatic agent, a foaming agent, and the like, as required. These other compounding agents may be used singly or in combination of two or more kinds, and the compounding amount thereof may be appropriately selected within a range not impairing the effects of the present invention.

The method for producing the rubber composition of the present invention includes a method of mixing the rubber component containing the acrylic rubber of the present invention, the filler, the crosslinking agent, and optionally the antioxidant and other compounding agents, and any method used in the conventional rubber processing field can be used at the time of mixing, for example, an open roll, a Banbury mixer, various kneaders, and the like. The mixing order of the components may be a usual order in the rubber processing field, and it is preferable that, for example, components which are not easily reacted or decomposed by heat are sufficiently mixed and then a crosslinking agent or the like which is a component which is easily reacted or decomposed by heat is mixed in a short time at a temperature at which the reaction or decomposition is not caused.

< crosslinked rubber >

The rubber crosslinked product of the present invention is obtained by crosslinking the rubber composition.

The rubber crosslinked product of the present invention can be produced by the following method: the rubber composition of the present invention is molded by a molding machine such as an extruder, an injection molding machine, a compressor, a roll, or the like, which corresponds to a desired shape, and is subjected to a crosslinking reaction by heating to fix the shape, thereby producing a rubber crosslinked product. In this case, the crosslinking may be performed after the preliminary molding, or may be performed at the same time as the molding. The molding temperature is usually 10 to 200℃and preferably 25 to 150 ℃. The crosslinking temperature is usually 100 to 250 ℃, preferably 130 to 220 ℃, more preferably 150 to 200 ℃, and the crosslinking time is usually 0.1 minutes to 10 hours, preferably 1 minute to 5 hours. The heating method may be any method used for crosslinking the rubber, such as pressing heating, steam heating, oven heating, and hot air heating, as appropriate.

The rubber crosslinked product of the present invention may be subjected to secondary crosslinking by further heating according to the shape, size, etc. of the rubber crosslinked product. The secondary crosslinking varies depending on the heating method, crosslinking temperature, shape, etc., and is preferably carried out for 1 to 48 hours. The heating method and the heating temperature may be appropriately selected.

The rubber crosslinked product of the present invention maintains tensile strength, elongation, hardness, etc. as basic properties of rubber, and has excellent compression set resistance and water resistance.

The rubber crosslinked material of the present invention can be preferably used as, for example, by effectively utilizing the above characteristics: sealing materials such as O-rings, packing, diaphragms, oil seals, shaft seals, bearing seals, mechanical seals, wellhead seals, seals for electrical-electronic devices, and seals for air compression devices; various gaskets such as a rocker arm cover gasket attached to a connecting portion between a cylinder block and a cylinder head, an oil pan gasket attached to a connecting portion between an oil pan and the cylinder head or a transmission case, a gasket for a fuel cell spacer attached between a pair of housings sandwiching a battery cell having a positive electrode, an electrolyte plate, and a negative electrode, and a gasket for a top cover of a hard disk drive; a buffer material and a vibration-proof material; a wire coating material; industrial belts; tubes/hoses; sheets, and the like.

The rubber crosslinked product of the present invention is preferably used as an extrusion molded product and a mold crosslinked product used in automobiles, for example, various hoses such as a fuel oil hose such as a fuel filler neck hose, an exhaust hose, a paper hose, and a fuel tank such as an oil hose, an air hose such as a turbo charge air hose and a mission control hose, a radiator hose, a heater hose, a brake hose, and an air conditioner hose.

< Structure of apparatus for producing acrylic rubber >

Next, a device structure for producing an acrylic rubber according to an embodiment of the present invention will be described. Fig. 1 is a diagram schematically showing an example of an acrylic rubber manufacturing system having an apparatus structure for manufacturing an acrylic rubber according to an embodiment of the present invention. In the production of the acrylic rubber of the present invention, for example, the acrylic rubber production system 1 shown in fig. 1 can be used.

The acrylic rubber production system 1 shown in fig. 1 is composed of an emulsion polymerization reactor, a coagulation device 3, a cleaning device 4, a water remover 43, and a screw type biaxial extrusion dryer, which are not shown.

The emulsion polymerization reactor is configured to perform the treatment in the emulsion polymerization step described above. Although not shown in fig. 1, the emulsion polymerization reactor includes, for example, a polymerization reaction tank, a temperature control unit for controlling a reaction temperature, and a stirring device having a motor and stirring blades. In the emulsion polymerization reactor, water and an emulsifier are mixed with a monomer component for forming an acrylic rubber, and then emulsion polymerization is initiated in the presence of a redox catalyst composed of an inorganic radical generator and a reducing agent while stirring properly with a stirrer, and a chain transfer agent is intermittently added during the polymerization to obtain an emulsion polymerization liquid. The emulsion polymerization reactor may be any of batch type, semi-batch type and continuous type, and may be any of a tank type reactor and a tube type reactor.

The coagulation device 3 shown in fig. 1 is configured to perform the processing in the coagulation step described above. As schematically illustrated in fig. 1, the solidification apparatus 3 includes, for example, a stirring tank 30, a heating unit 31 for heating the inside of the stirring tank 30, a temperature control unit not illustrated for controlling the temperature in the stirring tank 30, a stirring device 34 including a motor 32 and stirring blades 33, and a drive control unit not illustrated for controlling the rotational speed and rotational speed of the stirring blades 33. In the coagulation apparatus 3, the aqueous pellets can be produced by bringing the emulsion polymerization liquid obtained in the emulsion polymerization reactor into contact with a coagulation liquid to coagulate the emulsion polymerization liquid.

For example, the coagulation device 3 may be configured to contact the emulsion polymerization liquid with the coagulation liquid by adding the emulsion polymerization liquid to the stirred coagulation liquid. That is, the agitation tank 30 of the coagulation device 3 is filled with a coagulation liquid in advance, and an emulsion polymerization liquid is added to the coagulation liquid and brought into contact with the coagulation liquid to coagulate the emulsion polymerization liquid, thereby producing an aqueous pellet.

The heating unit 31 of the solidifying apparatus 3 is configured to heat the solidifying liquid filled in the stirring tank 30. The temperature control unit of the solidifying apparatus 3 is configured as follows: the temperature in the agitation tank 30 is controlled by controlling the heating operation of the heating portion 31 while monitoring the temperature in the agitation tank 30 measured by the thermometer. The temperature of the solidification liquid in the stirring tank 30 is controlled to be normally 40 ℃ or higher, preferably 40 to 90 ℃, and more preferably 50 to 80 ℃ by the temperature control unit.

The stirring device 34 of the solidifying apparatus 3 is configured to stir the solidification liquid filled in the stirring tank 30. Specifically, the stirring device 34 includes a motor 32 that outputs rotational power and stirring blades 33 that are deployed in a direction perpendicular to the rotation axis of the motor 32. The stirring blade 33 can rotate around a rotation axis by the rotation power of the motor 32 in the solidification liquid filled in the stirring tank 30, thereby allowing the solidification liquid to flow. The shape, size, number of the stirring blades 33, and the like are not particularly limited.

The drive control unit of the coagulation device 3 is configured as follows: the rotational drive of the motor 32 of the stirring device 34 is controlled so that the rotational speed and the rotational speed of the stirring blade 33 of the stirring device 34 are set to predetermined values. The rotation of the stirring blade 33 is controlled by the drive control unit so that the stirring speed of the solidification liquid is, for example, generally 100rpm or more, preferably 200 to 1000rpm, more preferably 300 to 900rpm, and particularly preferably 400 to 800 rpm. The rotation of the stirring blade 33 is controlled by the drive control unit so that the peripheral speed of the solidification liquid is usually 0.5m/s or more, preferably 1m/s or more, more preferably 1.5m/s or more, particularly preferably 2m/s or more, and most preferably 2.5m/s or more. Further, the rotation of the stirring blade 33 is controlled by the drive control unit so that the upper limit value of the peripheral speed of the solidification liquid is usually 50m/s or less, preferably 30m/s or less, more preferably 25m/s or less, and most preferably 20m/s or less.

The cleaning apparatus 4 shown in fig. 1 is configured to perform the processing in the above-described cleaning process. As schematically illustrated in fig. 1, the cleaning apparatus 4 includes, for example, a cleaning tank 40, a heating unit 41 for heating the interior of the cleaning tank 40, and a temperature control unit, not illustrated, for controlling the temperature in the cleaning tank 40. In the cleaning device 4, the water-containing aggregates generated in the coagulation device 3 are mixed with a large amount of water and cleaned, whereby the ash content in the finally obtained acrylic rubber can be effectively reduced.

The heating unit 41 of the cleaning device 4 is configured to heat the inside of the cleaning tank 40. The temperature control unit of the cleaning apparatus 4 is configured as follows: the temperature in the cleaning tank 40 is controlled by controlling the heating operation of the heating section 41 while monitoring the temperature in the cleaning tank 40 measured with the thermometer. As described above, the temperature of the washing water in the washing tub 40 is controlled to be generally 40 ℃ or higher, preferably 40 to 100 ℃, more preferably 50 to 90 ℃, and most preferably 60 to 80 ℃.

The aqueous pellets washed by the washing apparatus 4 are supplied to a screw type biaxial extrusion dryer 5 for performing a dehydration step and a drying step. At this time, the washed aqueous pellets are preferably supplied to the screw type biaxial extrusion dryer 5 through a water remover 43 capable of separating free water. The water remover 43 can use, for example, a wire mesh, a screen, an electric screen, or the like.

When the washed aqueous pellets are fed to the screw type biaxial extrusion dryer 5, the temperature of the aqueous pellets is preferably 40 ℃ or higher, more preferably 60 ℃ or higher. For example, the temperature of the aqueous pellets supplied to the screw type biaxial extrusion dryer 5 may be maintained at 60 ℃ or higher by setting the temperature of water used for washing in the washing device 4 to 60 ℃ or higher (for example, 70 ℃), or the aqueous pellets may be heated so that the temperature of the aqueous pellets is 40 ℃ or higher, preferably 60 ℃ or higher when the aqueous pellets are transported from the washing device 4 to the screw type biaxial extrusion dryer 5. This can effectively perform the dehydration step and the drying step as subsequent steps, and can greatly reduce the water content of the finally obtained dried rubber.

The screw type biaxial extrusion dryer 5 shown in fig. 1 is configured to perform the above-described dehydration step and the drying step. Although a screw type biaxial extrusion dryer 5 is illustrated in fig. 1 as a preferred example, a centrifugal separator, a squeezer, or the like may be used as a dehydrator for performing the processing in the dehydration step, and a hot air dryer, a reduced pressure dryer, an expansion dryer, a kneading type dryer, or the like may be used as a dryer for performing the processing in the drying step.

The screw type biaxial extrusion dryer 5 is configured to mold the dried rubber obtained through the dehydration step and the drying step into a predetermined shape and discharge the molded rubber. Specifically, the screw type biaxial extrusion dryer 5 is configured as follows: the apparatus comprises a dewatering cylinder 53 and a dryer cylinder 54, and further comprises a die 59 on the downstream side of the screw type twin screw extrusion dryer 5, wherein the dewatering cylinder 53 has a function as a dewatering machine for dewatering the aqueous pellets washed by the washing device 4, the dryer cylinder 54 has a function as a dryer for drying the aqueous pellets, and the die 59 has a molding function for molding the aqueous pellets.

The structure of the screw type biaxial extrusion dryer 5 will be described below with reference to fig. 2. Fig. 2 shows a structure as a preferable specific example of the screw type biaxial extrusion dryer 5 shown in fig. 1. The above-described dehydration step and drying step can be suitably performed by the screw type biaxial extrusion dryer 5.

The screw type biaxial extrusion dryer 5 shown in fig. 2 is a biaxial screw type extrusion dryer having a pair of screws not shown in the figure in a barrel unit 51. The screw type biaxial extrusion dryer 5 has a drive unit 50 that rotationally drives a pair of screws in a barrel unit 51. With this structure, the acrylic rubber can be dried with high shear, which is preferable. The drive unit 50 is mounted at the upstream end (left end in fig. 2) of the barrel unit 51. Further, the screw type biaxial extrusion dryer 5 has a die 59 at the downstream end (right end in fig. 2) of the barrel unit 51.

From the upstream side to the downstream side (from the left side to the right side in fig. 2), the barrel unit 51 has a supply barrel portion 52, a dehydration barrel portion 53, and a dryer barrel portion 54.

The supply cylinder portion 52 is composed of 2 supply cylinders, i.e., a 1 st supply cylinder 52a and a 2 nd supply cylinder 52 b.

The dewatering cylinder section 53 is composed of 3 dewatering cylinders, namely, a 1 st dewatering cylinder 53a, a 2 nd dewatering cylinder 53b, and a 3 rd dewatering cylinder 53 c.

The dryer section 54 is composed of 8 dryer cylinders, i.e., a 1 st dryer cylinder 54a, a 2 nd dryer cylinder 54b, a 3 rd dryer cylinder 54c, a 4 th dryer cylinder 54d, a 5 th dryer cylinder 54e, a 6 th dryer cylinder 54f, a 7 th dryer cylinder 54g, and an 8 th dryer cylinder 54 h.

As described above, the barrel unit 51 is configured by connecting 13 separate barrels 52a to 52b, 53a to 53c, and 54a to 54h from the upstream side to the downstream side.

The screw type biaxial extrusion dryer 5 further includes a heating device, not shown, for heating the respective cylinders 52a to 52b, 53a to 53c, 54a to 54h to heat the aqueous pellets in the respective cylinders 52a to 52b, 53a to 53c, 54a to 54h to a predetermined temperature. The heating device has a number corresponding to each barrel 52 a-52 b, 53 a-53 c, 54 a-54 h. As such a heating device, for example, a structure in which high-temperature steam or the like is supplied to the steam flow barriers formed in the respective cylinders 52a to 52b, 53a to 53c, 54a to 54h by a steam supply device may be employed, but the present invention is not limited thereto. The screw type biaxial extrusion dryer 5 further includes a temperature control device, not shown, for controlling the set temperatures of the heating devices corresponding to the respective cylinders 52a to 52b, 53a to 53c, and 54a to 54 h.

The number of supply cylinders, dewatering cylinders, and drying cylinders constituting the

respective cylinder sections

52, 53, and 54 in the cylinder unit 51 is not limited to the one shown in fig. 2, and may be set to a number corresponding to the water content of the aqueous pellets of the acrylic rubber to be dried.

For example, the number of supply barrels to the barrel portion 52 may be, for example, 1 to 3. The number of the dehydrators of the dehydrator cylinder 53 is preferably 2 to 10, for example, and when the number of the dehydrators of the dehydrator cylinder 53 is 3 to 6, dehydration of the water-containing pellets of the adhesive acrylic rubber can be performed efficiently, which is more preferable. The number of the dryer cylinders of the dryer cylinder section 54 is preferably 2 to 10, more preferably 3 to 8, for example.

The pair of screws in the barrel unit 51 are rotationally driven by a driving device such as a motor accommodated in the driving unit 50. The pair of screws extend from the upstream side to the downstream side in the barrel unit 51, and by rotationally driving the pair of screws, the aqueous pellets supplied to the supply barrel unit 52 can be conveyed to the downstream side while being mixed. The pair of screws are preferably biaxial meshing type in which the screw ridge portions and the screw groove portions are meshed with each other, whereby the dewatering efficiency and drying efficiency of the aqueous pellets can be improved.

The rotation direction of the pair of screws may be the same direction or different directions, and the rotation in the same direction is preferable from the viewpoint of self-cleaning performance. The screw shape of the pair of screws is not particularly limited, and is not particularly limited as long as it is a shape required in each of the

cylinder portions

52, 53, 54.

The supply cylinder section 52 is a region in which the aqueous pellets are supplied into the cylinder unit 51. The 1 st supply cylinder 52a of the supply cylinder section 52 has a feed port 55 for supplying the aqueous pellets into the cylinder unit 51.

The dewatering cylinder 53 is a region for separating and discharging a liquid (slurry) containing a coagulant or the like from the aqueous pellet.

The 1 st to 3 rd dewatering cylinders 53a to 53c constituting the dewatering cylinder 53 have

dewatering slits

56a, 56b, 56c for discharging the water of the aqueous pellets to the outside, respectively. A plurality of

dewatering slits

56a, 56b, 56c are formed in each dewatering cylinder 53a to 53 c.

The slit width, that is, the mesh width of each

dewatering slit

56a, 56b, 56c may be appropriately selected depending on the conditions of use, and is usually 0.01 to 5mm, preferably 0.1 to 1mm, more preferably 0.2 to 0.6mm, from the viewpoint that the loss of the aqueous pellets is small and the dewatering of the aqueous pellets can be effectively performed.

The removal of water from the hydrous pellets in each of the dewatering cylinders 53a to 53c of the dewatering cylinder 53 is performed in both a liquid form and a vapor form from the

dewatering slits

56a, 56b, 56 c. In the dehydrator cylinder 53 of the present embodiment, the form of removing water in a liquid state is defined as drainage, and the form of removing water in a vapor state is defined as drainage, for the purpose of distinction.

The combination of water discharge and steam discharge in the dehydrator cylinder 53 is preferable because the water content of the adhesive acrylic rubber can be effectively reduced. In the dewatering cylinder portion 53, which of the 1 st to 3 rd dewatering cylinders 53a to 53c is used for draining and which is used for draining steam is set appropriately according to the purpose of use, and in general, in the case of reducing the ash content in the produced acrylic rubber, the dewatering cylinder for draining water may be increased. In this case, for example, as shown in fig. 2, the 1 st and 2

nd dewatering cylinders

53a and 53b on the upstream side are used for water discharge, and the 3 rd dewatering cylinder 53c on the downstream side is used for steam discharge. Further, for example, in the case where the dewatering cylinder portion 53 has 4 dewatering cylinders, it is possible to consider, for example: drainage was performed with 3 dewatering cylinders on the upstream side, and steam was discharged with 1 dewatering cylinder on the downstream side. On the other hand, in the case of decreasing the water content, a dehydration cylinder in which steam discharge is performed may be increased.

As described in the above dehydration-drying step, the setting temperature of the dehydration barrel section 53 is usually in the range of 60 to 150 ℃, preferably 70 to 140 ℃, more preferably 80 to 130 ℃, the setting temperature of the dehydration barrel in which dehydration is performed in a drained state is usually in the range of 60 to 120 ℃, preferably 70 to 110 ℃, more preferably 80 to 100 ℃, and the setting temperature of the dehydration barrel in which dehydration is performed in a discharged steam state is usually in the range of 100 to 150 ℃, preferably 105 to 140 ℃, more preferably 110 to 130 ℃.

The dryer cylinder 54 is a region in which the dehydrated aqueous pellets are dried under reduced pressure. Of the 1 st to 8 th dryer barrels 54a to 54h constituting the dryer barrel section 54, the 2 nd dryer barrel 54b, the 4 th dryer barrel 54d, the 6 th dryer barrel 54f, and the 8 th dryer barrel 54h have

exhaust ports

58a, 58b, 58c, 58d for degassing, respectively. Exhaust pipes, not shown, are connected to the

exhaust ports

58a, 58b, 58c, 58d, respectively.

A vacuum pump, not shown, is connected to the end of each exhaust pipe, and the interior of the dryer cylinder 54 is depressurized to a predetermined pressure by the operation of these vacuum pumps. The screw type biaxial extrusion dryer 5 has a pressure control device, not shown, which controls the operation of these vacuum pumps to control the vacuum degree in the dryer barrel 54.

The vacuum degree in the dryer cylinder 54 may be appropriately selected, and is set to be generally 1 to 50kPa, preferably 2 to 30kPa, and more preferably 3 to 20kPa as described above.

The temperature to be set in the dryer barrel 54 may be appropriately selected, and is usually set to 100 to 250 ℃, preferably 110 to 200 ℃, and more preferably 120 to 180 ℃ as described above.

In each of the dryer cylinders 54a to 54h constituting the dryer cylinder section 54, the set temperature in all of the dryer cylinders 54a to 54h may be an approximate value or may be a different value, and it is preferable that the drying efficiency is improved when the temperature on the downstream side (the die 59 side) is set to be higher than the temperature on the upstream side (the dryer cylinder section 53 side).

The die 59 is a die disposed at the downstream end of the barrel unit 51, and has a discharge port having a predetermined nozzle shape. The acrylic rubber dried in the dryer cylinder 54 is extruded through the discharge port of the die 59 to be molded into a shape corresponding to a predetermined nozzle shape. The acrylic rubber passing through the die 59 can be molded into various shapes such as a pellet, a column, a round bar, a sheet, etc., depending on the nozzle shape of the die 59, and is molded into a sheet in the present invention. A perforated plate, a wire mesh, or the like may be provided between the screw and the die 59.

The aqueous pellets of the acrylic rubber obtained through the cleaning step are supplied from the feed port 55 to the supply cylinder portion 52. The aqueous pellets supplied to the supply cylinder section 52 are transported from the supply cylinder section 52 to the dehydration cylinder section 53 by rotation of a pair of screws in the cylinder unit 51. In the dewatering cylinder 53, as described above, the

dewatering slits

56a, 56b, and 56c provided in the 1 st to 3 rd dewatering cylinders 53a to 53c are used to drain and steam the water contained in the aqueous pellets, and the aqueous pellets are dewatered.

The aqueous pellets dehydrated in the dehydration cylinder section 53 are conveyed to the dryer cylinder section 54 by the rotation of a pair of screws in the cylinder unit 51. The aqueous pellets sent to the dryer section 54 are plasticized and mixed to form a melt, and are sent to the downstream side while being heated. Then, moisture contained in the melt of the acrylic rubber is vaporized, and the moisture (vapor) is discharged to the outside through exhaust pipes, not shown, connected to the

respective exhaust ports

58a, 58b, 58c, 58 d.

As described above, the aqueous pellets are dried by passing through the dryer cylinder 54, and thereby become a melt of the acrylic rubber, which is supplied to the die 59 by the rotation of the pair of screws in the cylinder unit 51, and extruded from the die 59.

Here, an example of the operating conditions of the screw type biaxial extrusion dryer 5 of the present embodiment is given.

The rotation speed (N) of the pair of screws in the barrel unit 51 may be appropriately selected depending on each condition, and is usually 10 to 1000rpm, and from the viewpoint of being able to effectively reduce the water content of the acrylic rubber and the amount of components insoluble in methyl ethyl ketone, it is preferably 50 to 750rpm, more preferably 100 to 500rpm, and most preferably 120 to 300rpm.

The extrusion amount (Q) of the acrylic rubber is not particularly limited, but is usually 100 to 1500 kg/hr, preferably 300 to 1200 kg/hr, more preferably 400 to 1000 kg/hr, and most preferably 500 to 800 kg/hr.

The ratio (Q/N) of the extrusion amount (Q) of the acrylic rubber to the rotation speed (N) of the screw is not particularly limited, but is usually 1 to 20, preferably 2 to 10, more preferably 3 to 8, particularly preferably 4 to 6.

The maximum torque in the barrel unit 51 is not particularly limited, and is usually in the range of 30 to 100n·m, preferably 35 to 75n·m, more preferably 40 to 60n·m.

The specific energy consumption in the barrel unit 51 is not particularly limited, but is usually in the range of 0.1 to 0.25[ kw.h/kg ], preferably 0.13 to 0.23[ kw.h/kg ], more preferably 0.15 to 0.2[ kw.h/kg ].

The specific power in the cylinder unit 51 is not particularly limited, but is usually in the range of 0.2 to 0.6[ A.multidot.h/kg ], preferably 0.25 to 0.55[ A.multidot.h/kg ], more preferably 0.35 to 0.5[ A.multidot.h/kg ].

The shear rate in the barrel unit 51 is not particularly limited, but is usually in the range of 40 to 150[ l/s ], preferably 45 to 125[ l/s ], more preferably 50 to 100[ l/s ].

The shear viscosity of the acrylic rubber in the cylinder unit 51 is not particularly limited, but is usually in the range of 4000 to 8000[ Pa.s ], preferably 4500 to 7500[ Pa.s ], more preferably 5000 to 7000[ Pa.s ].

The cooling device 6 shown in fig. 1 is constituted as follows: the dried rubber obtained through the dehydration step by a dehydrator and the drying step by a dryer is cooled. As the cooling method using the cooling device 6, various methods including an air cooling method under ventilation or a cold air system, a water spraying method, a dipping method in water, and the like can be used. In addition, the rubber may also be cooled and dried by leaving it at room temperature.

As described above, the dried rubber discharged from the screw type biaxial extrusion dryer 5 is extruded into various shapes such as pellet, columnar, round bar, sheet and the like according to the nozzle shape of the die 59, and is molded into a sheet in the present invention. A conveying type cooling device 60 for cooling the sheet-shaped dried rubber 10 molded into a sheet shape, which is an example of the cooling device 6, will be described below with reference to fig. 3.

Fig. 3 shows a structure of a conveyor type cooling device 60 which is preferable as the cooling device 6 shown in fig. 1. The transport cooling device 60 shown in fig. 3 is configured as follows: the sheet-like dried rubber 10 discharged from the discharge port of the die 59 of the screw type biaxial extrusion dryer 5 is cooled by an air cooling system while being conveyed. By using this conveyor type cooling device 60, the sheet-like dry rubber discharged from the screw type biaxial extrusion dryer 5 can be cooled appropriately.

The conveying type cooling device 60 shown in fig. 3 may be used in direct connection with the die 59 of the screw type biaxial extrusion dryer 5 shown in fig. 2, for example, or may be disposed in the vicinity of the die 59.

The conveying type cooling device 60 has a conveyor 61 that conveys the sheet-like dried rubber 10 discharged from the die 59 of the screw type biaxial extrusion dryer 5 in the direction of arrow a in fig. 3, and a cooling mechanism 65 that blows cool air to the sheet-like dried rubber 10 on the conveyor 61.

The conveyor 61 includes a roller 62, a roller 63, and a conveyor belt 64 wound around the roller 62 and the roller 63 in tension and carrying the sheet-like dry rubber 10 thereon. The conveyor 61 is constructed in the following manner: the sheet-like dried rubber 10 discharged from the die 59 of the screw type biaxial extrusion dryer 5 is continuously conveyed to the downstream side (right side in fig. 3) on a conveyor belt 64.

The cooling mechanism 65 is not particularly limited, and examples thereof include a cooling mechanism having a structure capable of blowing cooling air sent from a cooling air generating device, not shown, onto the surface of the sheet-like dry rubber 10 on the conveyor belt 64.

The length L1 of the conveyor 61 and the cooling mechanism 65 of the conveyor type cooling device 60 (the length of the portion capable of blowing cooling air) is not particularly limited, and is, for example, 10 to 100m, preferably 20 to 50m. The conveying speed of the sheet-like dried rubber 10 in the conveying type cooling device 60 may be appropriately adjusted according to the length L1 of the conveyor 61 and the cooling mechanism 65, the discharge speed of the sheet-like dried rubber 10 discharged from the die 59 of the screw type biaxial extrusion dryer 5, the target cooling speed, the target cooling time, and the like, and is, for example, 10 to 100 m/hr, and more preferably 15 to 70 m/hr.

According to the conveyor type cooling device 60 shown in fig. 3, the sheet-like dry rubber 10 is cooled by blowing cooling air from the cooling mechanism 65 to the sheet-like dry rubber 10 while conveying the sheet-like dry rubber 10 discharged from the die 59 of the screw type biaxial extrusion dryer 5 by the conveyor 61.

The transport cooling device 60 is not particularly limited to the configuration having 1 conveyor 61 and 1 cooling mechanism 65 shown in fig. 3, and may have a configuration having 2 or more conveyors 61 and 2 or more cooling mechanisms 65 corresponding thereto. In this case, the total length of each of the 2 or more conveyors 61 and the cooling mechanism 65 may be set to the above range.

The glue coating device 7 shown in fig. 1 is constituted as follows: the dried rubber obtained by extrusion molding in a screw type biaxial extrusion dryer 5 and cooling in a cooling device 6 was processed to produce a bale as a block. As described above, the screw type biaxial extrusion dryer 5 can extrude the dried rubber into various shapes such as pellets, columns, round bars, and sheets, and the rubber coating device 7 is configured to coat the dried rubber molded into various shapes. The weight, shape, etc. of the rubber-coated acrylic rubber produced by the rubber coating device 7 are not particularly limited, and for example, approximately 20kg of a rubber-coated acrylic rubber having a substantially rectangular parallelepiped shape can be produced.

The rubber packing device 7 may have, for example, a packer by which cooled dry rubber is compressed to manufacture rubber-packed acrylic rubber.

In addition, in the case of producing the sheet-like dry rubber 10 by the screw type biaxial extrusion dryer 5, a rubber-coated acrylic rubber in which the sheet-like dry rubber 10 is laminated can be produced. For example, a cutter mechanism for cutting the sheet-like dry rubber 10 may be provided in the rubber coating device 7 disposed downstream of the conveyor-type cooling device 60 shown in fig. 3. Specifically, the cutting mechanism of the glue wrapping apparatus 7 is configured as follows, for example: the cooled sheet-like dried rubber 10 is continuously cut at predetermined intervals, and processed into a sheet-like dried rubber 16 of a predetermined size. The cut sheet-like dried rubber 16 cut into a predetermined size by the cutting mechanism is laminated in a plurality of sheets, whereby a rubber-coated acrylic rubber in which the cut sheet-like dried rubber 16 is laminated can be produced.

In the case of producing a rubber-coated acrylic rubber in which the sliced dried rubber 16 is laminated, it is preferable to laminate the sliced dried rubber 16 at 40 ℃ or higher, for example. By stacking the sliced dried rubber 16 at 40 ℃ or higher, good air discharge can be achieved by further cooling and compression by its own weight.

Examples

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. Unless otherwise specified, "parts", "%" and "ratio" in each example are on a weight basis. The physical properties and the like of the various materials were evaluated by the following methods.

[ monomer composition ]

Regarding the monomer composition in the acrylic rubber, the polymerization is carried out by ¹ The H-NMR confirmed the monomer structure of each monomer unit in the acrylic rubber, and the activity of the reactive groups remaining in the acrylic rubber and the content of each reactive group were confirmed by the following method. The content ratio of each monomer unit in the acrylic rubber is calculated from the amount of each monomer used for polymerization reaction and the polymerization conversion rate. Specifically, since the polymerization reaction is an emulsion polymerization reaction and the polymerization conversion thereof is approximately 100% in which no unreacted monomer is confirmed, the content ratio of each monomer unit in the rubber is the same as the amount of each monomer used.

[ reactive group content ]

The content of the reactive group in the acrylic rubber was measured by the following method.

(1) The carboxyl group amount was calculated by dissolving a sample (acrylic rubber) in acetone and performing potential difference titration with a potassium hydroxide solution.

(2) The epoxy group amount was calculated by dissolving a sample in methyl ethyl ketone, adding a predetermined amount of hydrochloric acid thereto to react with the epoxy group, and titrating the residual hydrochloric acid amount with potassium hydroxide.

(3) The chlorine amount was calculated by completely burning the sample in a burning flask, absorbing the generated chlorine with water, and titrating with silver nitrate.

[ Ash content ]

The ash content (%) contained in the acrylic rubber was measured according to JIS K6228A method.

[ ash component amount ]

The amount (ppm) of each component in the acrylic rubber ash was obtained by pressing ash collected at the time of measuring the ash against titration filter paper having a diameter of 20mm, and measuring XRF using ZSX Primus (manufactured by Physics Co., ltd.).

[ molecular weight and molecular weight distribution ]

The weight average molecular weight (Mw) and the molecular weight distribution (Mw/Mn and Mz/Mw) of the acrylic rubber are the absolute molecular weight measured by GPC-MALS method and the absolute molecular weight distribution focusing on the high molecular region by using a solution in which lithium chloride is added to dimethylformamide at a concentration of 0.05mol/L and 37% concentrated hydrochloric acid is added at a concentration of 0.01% as a solvent.

The structure of the gel permeation chromatography multi-angle light scattering photometer used in the present apparatus was composed of a pump (manufactured by LC-20ADOpt corporation, shimadzu corporation) and a differential refractometer (manufactured by Optilabrex Huai Ya Studies corporation) as a detector, and a multi-angle light scattering detector (manufactured by DAWN HELEOS Huai Ya Studies corporation). Specifically, a multi-angle laser light scattering photometer (MALS) and a differential Refractometer (RI) were assembled in a GPC (Gel Permeation Chromatography) apparatus, and the light scattering intensity and refractive index difference of a molecular chain solution size-separated by a GPC apparatus were measured in accordance with the elution time, thereby sequentially calculating the molecular weight of a solute and the content thereof. The measurement conditions and measurement methods using the GPC apparatus are as follows.

Column: TSKgel alpha-M2 root (phi 7.8 mm. Times.30 cm, manufactured by Tosoh Co., ltd.)

Column temperature: 40 DEG C

Flow rate: 0.8ml/mm

Sample preparation: to 10mg of the sample (acrylic rubber) was added 5ml of the solvent, and the mixture was stirred slowly at room temperature (dissolution was visually confirmed). Then, filtration was performed using a 0.5 μm filter.

[ glass transition temperature (Tg) ]

The glass transition temperature (Tg) of the acrylic rubber was measured by a differential scanning calorimeter (DSC, product name "X-DSC7000", manufactured by Hitachi high technology, co., ltd.).

[ amount of methyl ethyl ketone-insoluble component ]

The amount (%) of the methyl ethyl ketone-insoluble component of the acrylic rubber was the amount of the methyl ethyl ketone-insoluble component, and was determined by the following method.

About 0.2g of an acrylic rubber (Xg) was weighed, immersed in 100ml of methyl ethyl ketone, left at room temperature for 24 hours, and then, components insoluble in methyl ethyl ketone were removed by filtration using an 80-mesh wire net to obtain a filtrate in which only a rubber component soluble in methyl ethyl ketone was dissolved, and the filtrate was evaporated and solidified to obtain a dry solid component (Yg), and the component was weighed and calculated by the following formula.

Component amount (%) =100× (X-Y)/X insoluble in methyl ethyl ketone

[ specific gravity ]

The specific gravity of the acrylic rubber was measured according to JIS K6268 crosslinked rubber-density measurement A method.

The measured value obtained by the following measuring method was the density, but the density of water was 1Mg/m ³ Is a specific gravity of (c). Specifically, the specific gravity of the rubber sample obtained by the method a according to JIS K6268 cross-linked rubber-density measurement is the specific gravity obtained by dividing the mass of the rubber sample by the volume containing voids, and the specific gravity obtained by dividing the density of the rubber sample obtained by the method a according to JIS K6268 cross-linked rubber-density measurement by the density of water (when the density of the rubber sample is divided by the density of water, the values are the same without units). Specifically, the specific gravity of the rubber sample was determined based on the following procedure.

(1) 2.5g of a test piece was cut out from a rubber sample left standing at a standard temperature (23 ℃ C.+ -. 2 ℃ C.) for at least 3 hours, and the test piece was hung on a hanger on a chemical balance having an accuracy of 1mg in such a manner that the bottom side of the test piece was 25mm higher than the tray for the chemical balance by using a fine nylon yarn having a mass of less than 0.010g, and the mass (m 1) of the test piece accurate to mg was measured twice in the atmosphere.

(2) Next, the volume placed on the tray for a chemical balance was 250cm ³ The beaker of (2) was filled with distilled water cooled to a standard temperature after boiling, the test piece was immersed therein, bubbles adhering to the surface of the test piece were removed, the movement of the pointer of the balance was observed for several seconds, it was confirmed that the pointer was not gently deflected by convection, and the mass (m 2) of the test piece in water was measured in mg twice.

(3) In addition, the density of the test piece is less than 1Mg/m ³ When the test piece was floating in water, a weight was attached to the test piece, and the mass (m 3) of the weight in water and the mass (m 4) of the test piece and the weight were measured twice in mg.

(4) Using the average value of each of m1, m2, m3, and m4 measured as described above, the density (Mg/m) was calculated based on the following formula ³ ) Dividing the calculated density by the density of water (1.00 Mg/m ³ ) The specific gravity of the rubber sample was obtained.

(Density of rubber sample when weight is not used)

Density=m1/(m 1-m 2)

(Density of rubber sample when weight is used)

Density=m1/(m1+m3-m 4)

[ Water content ]

Moisture content (%) according to JIS K6238-1: the measurement was performed by the oven a (volatile component measurement) method.

[pH]

After 6g (+ -0.05 g) of acrylic rubber was dissolved in 100g of tetrahydrofuran, 2.0ml of distilled water was added thereto, and after confirming complete dissolution, the pH was measured with a pH electrode.

[ Complex viscosity ]

The complex viscosity η was obtained by measuring the temperature dispersion (40 to 120 ℃) under the conditions of the strain 473% and 1Hz using a dynamic viscoelasticity measuring device "Rubber Process Analyzer RPA-2000" (manufactured by alpha technologies Co., ltd.), and obtaining the complex viscosity η at each temperature. Here, the dynamic viscoelasticity at 60 ℃ among the above-mentioned dynamic viscoelasticity is defined as the complex viscosity η (60 ℃) and the dynamic viscoelasticity at 100 ℃ is defined as the complex viscosity η (100 ℃), and the ratio η (100 ℃) to η (60 ℃) is calculated.

[ Mooney viscosity (ML1+4, 100 ℃)

Mooney viscosity (ML1+4, 100 ℃ C.) was measured according to the uncrosslinked rubber physical test method of JIS K6300.

[ Cross-Linkability ]

Regarding the crosslinkability of the rubber sample, the rate of change in the breaking strength of the rubber crosslinked material subjected to the secondary crosslinking for 2 hours and the breaking strength of the rubber crosslinked material subjected to the secondary crosslinking for 4 hours ((breaking strength of the 4-hour crosslinked rubber crosslinked material/breaking strength of the 2-hour crosslinked rubber crosslinked material) ×100) was calculated, and judged according to the following criteria.

And (3) the following materials: the change rate of the breaking strength is less than 10 percent

X: the change rate of the breaking strength is more than 10 percent

[ roll processability ]

Regarding the roll processability of the rubber sample, the roll-winding property and the state of the rubber when the rubber sample was rolled were observed, and evaluated according to the following criteria.

And (3) the following materials: the rubber composition was easily kneaded and wound around a roll, and separation from the roll was not observed, and the surface of the rubber composition after kneading was smooth

O: the kneading was easy, winding around the rolls was easy, separation from the rolls was not observed, and a small roughness was observed in a part of the surface of the rubber composition after kneading

And ∈: easy kneading, excellent roll windability, and slight surface irregularities of the kneaded rubber composition

Delta: the kneading is easy, the roll-winding property is slightly poor, and the surface of the rubber composition after the kneading is rough

X: is not easy to mix and has poor roll windability

[ Banbury processability ]

Regarding the banbury processability of the rubber sample, the rubber sample was put into a banbury mixer heated to 50 ℃ for mastication for 1 minute, and then, the compounding agent a blended in the rubber mixture described in table 1 was put into the mixer, the rubber mixture in the first stage was integrated, and the time until the maximum torque value was shown, i.e., BIT (Black Incorporation Time), was measured, and the index of comparative example 1 was evaluated as 100 (the smaller the index was, the more excellent the processability was).

[ evaluation of storage stability ]

Regarding the storage stability of the rubber sample, the rubber sample was put into a constant temperature and humidity tank (SH-222 manufactured by espek) at 45 ℃ x 80% rh, and the rate of change of the water content before and after 7 days of the test was calculated, and the evaluation was made with the index of comparative example 1 as 100 (the smaller the index, the more excellent the storage stability).

[ evaluation of Water resistance ]

Regarding the water resistance of the rubber sample, the cross-linked product of the rubber sample was immersed in distilled water at 85℃for 100 hours in accordance with JIS K6258 to conduct an immersion test, and the volume change rate before and after immersion was calculated in accordance with the following formula, and the evaluation was made with the index of comparative example 1 as 100 (the smaller the index, the more excellent the water resistance).

The volume change rate (%) = ((volume of test piece after immersion-volume of test piece before immersion)/volume of test piece before immersion) ×100 before immersion

[ compression set resistance ]

The compression set resistance of the rubber sample was measured in accordance with JIS K6262, and the compression set of the rubber crosslinked product of the rubber sample was measured at a state of 25% compression and left at 175℃for 90 hours, and evaluated in accordance with the following criteria.

And (3) the following materials: compression set of less than 15%

X: compression set of 15% or more

[ evaluation of physical Properties in Normal state ]

The rubber crosslinked product of the rubber sample was measured for breaking strength, 100% tensile stress and elongation at break according to JIS K6251, and evaluated according to the following criteria.

(1) Breaking strength was evaluated as excellent at 10MPa or more and as X at less than 10 MPa.

(2) 100% tensile stress, 5MPa or more was evaluated as excellent, and less than 5MPa was evaluated as X.

(3) Elongation at break was evaluated as excellent at 150% or more and as X at less than 150%.

[ evaluation of deviation of the amount of methyl ethyl ketone-insoluble component ]

Regarding the evaluation of the deviation of the methyl ethyl ketone-insoluble component amount of the rubber sample, the methyl ethyl ketone-insoluble component amount at 20 points arbitrarily selected from 20 parts (20 kg) of the rubber sample was measured and evaluated according to the following criteria.

And (3) the following materials: calculating the average value of the component amount insoluble in methyl ethyl ketone at 20 points of measurement, wherein all 20 points of measurement are within the range of + -3 of the average value

And (2) the following steps: calculating the average value of the component amounts insoluble in methyl ethyl ketone at 20 points of measurement, wherein all 20 points of measurement are within the range of the average value.+ -. 5 (at least 1 point of 20 points of measurement deviates from the range of the average value.+ -. 3, but all 20 points are within the range of the average value.+ -. 5)

X: calculating the average value of the component amount insoluble in methyl ethyl ketone at 20 points of measurement, wherein at least 1 point of the 20 points of measurement deviates from the average value by + -5

[ evaluation of processing stability based on Mooney scorch inhibition ]

The mooney scorch stability of the acrylic rubber composition was evaluated with respect to the cooling rate of the sheet-like acrylic rubber extruded from the screw type biaxial extrusion dryer described in japanese patent No. 6683189.

Example 1

As shown in Table 2-1, 46 parts of pure water, 4.5 parts of ethyl acrylate, 64.5 parts of n-butyl acrylate, 29.5 parts of methoxyethyl acrylate and 1.5 parts of mono-n-butyl fumarate as monomer components were added to a mixing vessel having a homogenizer, and 1.8 parts of sodium octoxyethylenephosphate as an emulsifier was added thereto and stirred to obtain a monomer emulsion.

170 parts of pure water and 3 parts of the monomer emulsion obtained above were charged into a polymerization reaction vessel equipped with a thermometer and a stirring device, and after cooling to 12℃under a nitrogen stream, 0.00033 parts of ferrous sulfate, 0.02 parts of sodium ascorbate, and 0.2 parts of potassium persulfate as an inorganic radical generator were added to initiate polymerization. The polymerization was continued by maintaining the temperature in the polymerization vessel at 23℃and continuously dropping the remaining portion of the monomer emulsion over 3 hours, adding 0.0072 part of n-dodecyl mercaptan after 50 minutes from the start of the reaction, adding 0.0036 part of n-dodecyl mercaptan after 100 minutes, and adding 0.4 part of sodium L-ascorbate after 120 minutes, and stopping the polymerization by adding hydroquinone as a polymerization terminator when the polymerization conversion reached approximately 100%, to obtain an emulsion polymerization solution.

Next, in a coagulation tank having a thermometer and a stirring device, the emulsion polymerization liquid obtained above, which was heated to 80 ℃, was continuously added to a 2% magnesium sulfate aqueous solution (coagulation liquid using magnesium sulfate as a coagulant) vigorously stirred at 600 revolutions (circumferential speed 3.1 m/s) with a stirring blade of the stirring device heated to 80 ℃ in 350 parts, and the polymer was coagulated to obtain a coagulated slurry containing aggregates of acrylic rubber as a coagulated material and water. The pellets were filtered from the resulting slurry, and water was drained from the solidified layer to obtain aqueous pellets.

194 parts of hot water (70 ℃) was added to the coagulation tank in which the filtered aqueous pellets remained, and the aqueous pellets were washed by stirring for 15 minutes, then the water was discharged, 194 parts of hot water (70 ℃) was added again, and the aqueous pellets were washed by stirring for 15 minutes (the total number of washing times was 2). The washed aqueous pellet (aqueous pellet temperature 65 ℃) was fed to a screw type biaxial extrusion dryer 5, dehydrated and dried, and a sheet-like dried rubber having a thickness of 10mm was extruded at a width of 300 mm. Then, the sheet-like dry rubber was cooled at a cooling rate of 200℃per hour using a conveyor type cooling device provided in direct connection with the screw type biaxial extrusion dryer 5.

The screw type biaxial extrusion dryer used in example 1 was composed of 1 feeder cylinder, 3 dehydrators (1 st to 3 rd dehydrators), and 5 dryer cylinders (1 st to 5 th dryer cylinders). The 1 st dewatering cylinder discharges water, and the 2 nd and 3 rd dewatering cylinders discharge steam. The operating conditions of the screw type biaxial extrusion dryer are as follows.

Water content:

water content of the aqueous pellets after draining in the 1 st dewatering barrel: 20 percent of

Water content of the aqueous pellets after steam venting in the 3 rd dewatering barrel: 10 percent of

Moisture content of the aqueous pellets after drying in the 5 th dryer barrel: 0.4%

Rubber temperature:

temperature of the aqueous pellets fed to the feed barrel: 65 DEG C

Temperature of rubber discharged from screw type biaxial extrusion dryer: 140 DEG C

Set temperature of each barrel:

1 st dewatering barrel: 100 DEG C

2 nd dewatering barrel: 120 DEG C

3 rd dewatering barrel: 120 DEG C

1 st dryer barrel: 120 DEG C

Dryer barrel 2: 130 DEG C

3 rd dryer barrel: 140 DEG C

4 th dryer barrel: 160 DEG C

5 th dryer barrel: 180 DEG C

Operating conditions:

diameter of screw (D): 132mm

Total length of screw (L): 4620mm

·L/D：35

Rotational speed of the screw: 135rpm

Vacuum of the dryer barrel: 10kPa

Extrusion amount of rubber extruded from die: 700 kg/hr

Resin pressure of die: 2MPa of

Maximum torque in screw type biaxial extrusion dryer: 15 N.m

The extruded sheet-like dried rubber was cooled to 50℃and then cut by a cutter, and 20 parts (20 kg) of the cut sheet-like dried rubber was laminated while the temperature was not lowered to 40℃or lower, to obtain a rubber-covered acrylic rubber (A). The reactive group content, ash component content, methyl ethyl ketone-insoluble component content, pH, specific gravity, glass transition temperature (Tg), water content, molecular weight distribution, and complex viscosity at 100℃and 60℃of the obtained acrylic rubber (A) were measured and are shown in tables 2-2. Further, the storage stability test of the acrylic rubber (A) was conducted to determine the water content change rate, and the results are shown in Table 2-2.

Next, 100 parts of the acrylic rubber (A) and the compounding agent A of "compounding 1" shown in Table 1 were charged into the Banbury mixer, and mixed at 50℃for 5 minutes (first-stage mixing). BIT was measured at this time, and the Banbury processability of the acrylic rubber was evaluated, and the results are shown in Table 2-2.

Next, the resulting mixture was moved to a roller at 50℃and blended with the compounding agent B of "compounding 1" (second stage mixing) to obtain a rubber composition. The roll processability at this time was evaluated, and the results are shown in Table 2-2.

TABLE 1

1: SEAST 3 (HAF) in the table is carbon black (manufactured by Tokida carbon Co., ltd.).

2: NOCRAC CD in the tables is 4,4' -bis (. Alpha.,. Alpha. -dimethylbenzyl) diphenylamine (manufactured by Dain Ind Chemie Co., ltd.).

3: rhenotran XLA-60 in the table is a vulcanization accelerator (manufactured by Langsheng Co.).

The obtained rubber composition was placed in a mold having a length of 15cm, a width of 15cm and a depth of 0.2cm, and was pressed at 180℃for 10 minutes while being pressurized by a pressing pressure of 10MPa, whereby primary crosslinking was performed, and the obtained primary crosslinked product was further heated by a Gill oven at 180℃for 2 hours to perform secondary crosslinking, whereby a sheet-like crosslinked rubber product was obtained. Then, a test piece of 3 cm. Times.2 cm. Times.0.2 cm was cut out from the resulting sheet-like crosslinked rubber, and the water resistance, compression set resistance and normal physical properties were evaluated. Further, the physical properties of the sheet-like rubber crosslinked product subjected to secondary crosslinking for 2 hours were measured in a normal state, and the crosslinkability was evaluated. The results are shown in Table 2-2.

Example 2

Acrylic rubber (B) was obtained in the same manner as in example 1 except that the emulsifier was changed to 1.8 parts of nonylphenoxy hexaoxyethylene phosphate sodium salt, the amount of potassium persulfate as an inorganic radical generator was changed to 0.21 part, and further, the post-addition of n-dodecyl mercaptan as a chain transfer agent was changed to 0.017 part after 50 minutes, 0.017 part after 100 minutes and 0.017 part after 120 minutes, and the properties were evaluated. The results are shown in Table 2-2.

Example 3

Acrylic rubber (C) was obtained in the same manner as in example 1 except that the monomer components were changed to 48.25 parts of ethyl acrylate, 50 parts of n-butyl acrylate and 1.75 parts of mono-n-butyl fumarate, the emulsifier was changed to 1.8 parts of sodium tridecyloxy hexaoxyethylene phosphate, and the washed aqueous pellets were dried to a water content of 0.4% by using a hot air dryer at 160℃to obtain pellet-like acrylic rubber, which was then filled into a 300X 650X 300mm packer and compacted at a pressure of 3MPa for 25 seconds to obtain a rubber-covered acrylic rubber. The properties of the acrylic rubber (C) were evaluated (the compounding agent was changed to "compounding 2"), and the results are shown in Table 2-2.

Example 4

Acrylic rubber (D) was obtained in the same manner as in example 3 except that the monomer components were changed to 28 parts of ethyl acrylate, 38 parts of n-butyl acrylate, 27 parts of methoxyethyl acrylate, 5 parts of acrylonitrile and 2 parts of allyl glycidyl ether, and each property was evaluated (the compounding agent was changed to "compounding 3"). The results are shown in Table 2-2.

Example 5

Acrylic rubber (E) was obtained in the same manner as in example 3 except that the monomer components were changed to 42.2 parts of ethyl acrylate, 35 parts of n-butyl acrylate, 20 parts of methoxyethyl acrylate, 1.5 parts of acrylonitrile and 1.3 parts of vinyl chloride acetate, and each property was evaluated (the compounding agent was changed to "compounding 4"). The results are shown in Table 2-2.

Example 6

Acrylic rubber (F) was obtained in the same manner as in example 2 except that the monomer components were changed to 48.25 parts of ethyl acrylate, 50 parts of n-butyl acrylate and 1.75 parts of mono-n-butyl fumarate, the emulsifier was changed to 1.8 parts of sodium tridecyloxy hexaoxyethylene phosphate, and the washed aqueous pellets were dried to a water content of 0.4% by using a hot air dryer at 160℃to obtain pellet-like acrylic rubber, which was then packed in a 300X 650X 300mm packer and compacted at a pressure of 3MPa for 25 seconds to obtain a rubber-covered acrylic rubber. The properties of the acrylic rubber (F) were evaluated (the compounding agent was changed to "compounding 2"), and the results are shown in Table 2-2.

Example 7

Acrylic rubber (G) was obtained in the same manner as in example 6 except that the monomer components were changed to 28 parts of ethyl acrylate, 38 parts of n-butyl acrylate, 27 parts of methoxyethyl acrylate, 5 parts of acrylonitrile and 2 parts of allyl glycidyl ether, and each property was evaluated (the compounding agent was changed to "compounding 3"). The results are shown in Table 2-2.

Example 8

Acrylic rubber (H) was obtained in the same manner as in example 7 except that the monomer components were changed to 42.2 parts of ethyl acrylate, 35 parts of n-butyl acrylate, 20 parts of methoxyethyl acrylate, 1.5 parts of acrylonitrile and 1.3 parts of vinyl chloride acetate, and each property was evaluated (the compounding agent was changed to "compounding 4"). The results are shown in Table 2-2.

Example 9

Acrylic rubber (I) was obtained in the same manner as in example 8, except that the amount of potassium persulfate as the inorganic radical generator was changed to 0.22 part, and 0.025 part of n-dodecyl mercaptan as a chain transfer agent was continuously added to the monomer emulsion, and the post-addition was not performed, to evaluate each characteristic. The results are shown in Table 2-2.

Comparative example 1

An acrylic rubber (J) was obtained in the same manner as in example 9, except that a solidification reaction was performed by adding a 0.7% aqueous magnesium sulfate solution to the stirred emulsion polymerization solution (stirring speed: 100rpm, circumferential speed: 0.5 m/s) after emulsion polymerization without adding a chain transfer agent, and a granulated acrylic rubber was obtained without being subjected to rubber encapsulation by a packer, and each characteristic was evaluated. The results are shown in Table 2-2.

Comparative example 2

The procedure of example 9 was repeated except that the emulsion polymerization was carried out by changing the emulsifier to 0.709 part of sodium lauryl sulfate and 1.82 parts of polyoxyethylene lauryl ether, the coagulation reaction was carried out by adding sodium sulfate to the stirred emulsion polymerization solution (stirring speed: 100rpm, circumferential speed: 0.5 m/s), the aqueous pellet was washed by adding 194 parts of industrial water in the washing step, the aqueous pellet was stirred in the coagulation tank at 25℃for 5 minutes, and then the water was discharged from the coagulation tank, the washing operation was carried out only 2 times, and the acrylic rubber in pellet form was obtained without being rubber-encapsulated by a packer, and the acrylic rubber (K) was obtained, and the characteristics were evaluated. The results are shown in Table 2-2.

[ Table 2-1]

[ Table 2-2]

As is clear from tables 2-1 and 2-2, the acrylic rubbers (A) to (I) of the present invention are excellent in roll processability, water resistance and normal physical properties including strength characteristics, and further excellent in Banbury processability, storage stability, crosslinkability and compression set characteristics, in terms of absolute molecular weight and absolute molecular weight distribution measured by GPC-MALS method using dimethylformamide-based solvents as an eluent, the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) being 3.4 or more, the ash content being 0.4% or less, and the total amount of sodium, magnesium, calcium, phosphorus and sulfur in ash being 80% or more, in terms of (meth) acrylic rubbers (A) to (I) being apparent from tables 2-1 and 2.

As is clear from tables 2-1 and 2-2, the acrylic rubbers (a) to (K) produced under the conditions of examples and comparative examples of the present application have an ion-reactive group or a reactive group selected from at least one of a carboxyl group, an epoxy group and a chlorine atom, and have a large weight average molecular weight (Mw), and therefore are excellent in crosslinkability, compression set resistance and normal physical properties including strength characteristics (examples 1 to 9 and comparative examples 1 to 2). However, the acrylic rubbers (J) to (K) were inferior in roll processability, banbury processability, water resistance and storage stability (comparative example 1), and in water resistance and storage stability (comparative example 2).

As is clear from tables 2 to 2, regarding the roll processability, the broader the molecular weight distribution was, the better the roll processability was (examples 1 to 9 and comparative example 2 and comparative example 1 were compared) in close relation to the molecular weight distribution (Mw/Mn) of the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn). In order to achieve a high balance of strength characteristics and roll processability, it is important that the weight average molecular weight (Mw) is high, and that the molecular weight distribution (the ratio of the z-average molecular weight (Mz) to the weight average molecular weight (Mw) (Mz/Mw)) that is a high molecular weight region is high.

As is clear from tables 2-1 and 2-2, an acrylic rubber having a large weight average molecular weight (Mw) and a wide Mw/Mn, which is excellent in strength characteristics and excellent in roll processability, can be produced by using a specific amount of an inorganic radical generator and a chain transfer agent, in particular n-dodecyl mercaptan (examples 1 to 9). As is clear from table 2-2, the roll processability (examples 1 to 8) can be further improved without impairing the strength characteristics by reducing the amount of the inorganic radical generator to be used and adding n-dodecyl mercaptan intermittently and thereafter without adding n-dodecyl mercaptan initially, as compared with continuously adding n-dodecyl mercaptan (example 9). This is because the length of one polymer chain is extended by reducing the inorganic radical generator and not adding a chain transfer agent at the beginning, and the high molecular weight component and the low molecular weight component are produced in good balance in GPC diagram although there are no clear two peaks, and the Mw is large and the Mw/Mn is wide, whereby the strength characteristics and the roll processability are highly balanced. In order to effectively expand Mw/Mn, the number of post-batch additions has a larger influence than the difference in the addition amount of the chain transfer agent after batch additions, and the number of post-batch additions is 2 times larger than the number of post-batch additions of 3 times (comparison of examples 3 to 5 and examples 6 to 8), and the continuous addition of the chain transfer agent limits the expansion of Mw/Mn to some extent (example 9). In addition, although not shown in table 2-2, in the present example, sodium ascorbate was added as a reducing agent 120 minutes after the start of polymerization, whereby the formation of the high molecular weight component of the acrylic rubber was facilitated, and the effect of enlarging Mw/Mn by the addition of the chain transfer agent was increased. On the other hand, although not shown in the examples of the present application, it was confirmed that the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) was not enlarged and the roll processability was poor when the polymerization was carried out using an organic radical generator.

As is clear from tables 2 to 2, the acrylic rubbers (A) to (I) of the present invention are excellent in overwhelming properties with respect to water resistance (comparison of examples 1 to 9 with comparative examples 1 to 2). As is clear from tables 2 to 2, the acrylic rubbers (A) to (I) excellent in roll processability and strength characteristics and greatly excellent in water resistance can be produced by adding a chain transfer agent to an emulsion polymerization liquid in a coagulation step of emulsion polymerization using an inorganic radical generator and continuously or intermittently followed by adding the chain transfer agent, not adding the coagulation liquid to the emulsion polymerization liquid, but adding the emulsion polymerization liquid to a stirred coagulation liquid to carry out a coagulation reaction, and more preferably by vigorously stirring the coagulation liquid (stirring speed: 600 rpm/peripheral speed: 3.1 m/s) and increasing the coagulant concentration of the stirred coagulation liquid (examples 1 to 9 are compared with comparative example 1). As will be described later, the present coagulation reaction produces aqueous pellets having a pellet diameter in the range of 710 μm to 4.75mm, and the removal efficiency of the emulsifier and coagulant in the washing and dewatering steps is improved to an overwhelming extent, and the ash content in the acrylic rubber is reduced, thereby greatly improving the water resistance.

As is clear from Table 2-2, the water resistance was more excellent when the ion-reactive group was a carboxyl group or an epoxy group than when the ion-reactive group was a chlorine atom (comparison between examples 3 to 4 and examples 6 to 7 and examples 5 and 8).

As is clear from tables 2 to 2, the total element amounts of phosphorus, magnesium, sodium, calcium and sulfur in the ashes of the acrylic rubbers (a) to (I) and the acrylic rubbers (J) to (K) of the comparative examples of the invention are all more than 90% by weight, and it is clear that the acrylic rubber is excellent in properties such as water resistance and mold releasability, but the acrylic rubber having a large proportion of phosphorus and magnesium in the ashes is excellent in water resistance (the ash amount of comparative example 1 is 2 times or more the ash amount of comparative example 2, but the water resistance is evaluated to the same extent).

Further, as is clear from tables 2 to 2, the acrylic rubber (a) to (B) dehydrated (water extruded) before drying the hydrous pellets had significantly reduced ash content and improved water resistance (comparison of examples 1 to 2 and examples 3 to 9). Further, it is known that the five elements phosphorus (P), magnesium (Mg), sodium (Na), calcium (Ca) and sulfur (S) account for a large proportion of the components in the ash of the acrylic rubber (a) to (B), but phosphorus (P) and magnesium (Mg) are almost all present as ash removal proceeds. This is presumably because the sodium phosphate salt as an emulsifier undergoes salt exchange with the magnesium sulfate as a coagulant to form magnesium phosphate, which is present in the aqueous pellet and cannot be sufficiently removed in the washing step, but can be reduced by dehydration (extrusion). It is also clear that phosphorus and magnesium do not deteriorate the water resistance of the components in the ash of the acrylic rubber in many cases (examples 1 to 9 and comparison of comparative example 1 and comparative example 2).

As is clear from tables 2 to 2, the acrylic rubbers (A) to (I) of the present invention are excellent in roll processability, water resistance and strength characteristics, and also excellent in Banbury processability, both roll processability and Banbury processability (examples 1 to 9). It is found that the banbury workability of the acrylic rubber is excellent in relation to the amount of the methyl ethyl ketone-insoluble component, and the banbury workability of the acrylic rubber having a small amount of the methyl ethyl ketone-insoluble component (comparison of examples 1 to 9 and comparative example 1). It is understood that the amount of methyl ethyl ketone-insoluble components of the acrylic rubber can be reduced by emulsion polymerization in the presence of a chain transfer agent (examples 3 to 8 and comparative example 2), and in particular, when the polymerization conversion is increased in order to improve the strength characteristics, the amount of methyl ethyl ketone-insoluble components increases sharply, and even then, in examples 3 to 8 added after the chain transfer agent, the formation of methyl ethyl ketone-insoluble components can be suppressed. Further, the amount of methyl ethyl ketone-insoluble components of the acrylic rubber can be significantly reduced by drying the aqueous pellets with a screw type biaxial extrusion dryer, thereby greatly improving the banbury processability of the produced acrylic rubber (comparison of examples 1 to 2 and examples 3 to 8). In the present invention, although not shown in the present example, it was confirmed that the amount of methyl ethyl ketone-insoluble component (comparative example 1) which increases sharply in emulsion polymerization without adding a chain transfer agent was eliminated by melt kneading in a screw type biaxial extrusion dryer in a state of substantially no moisture (moisture content less than 1% by weight), and the roll processability of the acrylic rubber was not impaired, and the banbury processability was greatly improved.

As is clear from tables 2 to 2, the acrylic rubbers (A) to (I) of the present invention are excellent in roll processability, water resistance and strength characteristics and also remarkably excellent in storage stability (examples 1 to 9). It is found that the storage stability of the acrylic rubber is closely related to the specific gravity of the acrylic rubber, and when the specific gravity is large, no air is trapped in the acrylic rubber, and the storage stability is excellent (comparison of examples 1 to 2, examples 3 to 9, and comparative examples 1 to 2). The acrylic rubber having a high specific gravity can be obtained by compacting the acrylic rubber in pellet form by a packer and rubber-packing (examples 3 to 9), and more preferably by extruding the acrylic rubber into a sheet by a screw type biaxial extrusion dryer and laminating the sheet and rubber-packing (examples 1 to 2). In the present invention, it was found that, in particular, a rubber-coated acrylic rubber obtained by laminating sheet-like acrylic rubber obtained by melt kneading and drying under reduced pressure, the storage stability was remarkably improved without impairing the short-time crosslinkability, roll processability, compression set resistance, normal physical properties including strength properties, and water resistance (examples 1 to 2). It is also clear that the storage stability of the acrylic rubber is more preferable when the ash content is smaller or the pH is specific (examples 1 to 9).

Further, as is clear from tables 2 to 2, the acrylic rubbers (A) to (K) of examples and comparative examples of the present application have a carboxyl group, an epoxy group, a plasma-reactive group such as a chlorine atom, and thus are excellent in crosslinking property and compression set resistance.

[ regarding the particle size of the resulting hydrous pellets ]

Regarding the aqueous pellets produced in the coagulation step of examples 1 to 9 and comparative example 1, the proportions of (1) 710 μm to 6.7mm (not passing through 710 μm but passing through 6.7 mm), (2) 710 μm to 4.75mm (not passing through 710 μm but passing through 4.75 mm), (3) 710 μm to 3.35mm (not passing through 710 μm but passing through 3.35 mm) with respect to the total amount of the aqueous pellets were measured using a JIS sieve. The results are shown below.

Example 1: (1) 90 wt%, (2) 90 wt%, (3) 87 wt%

Example 2: (1) 92 wt%, (2) 91 wt%, and (3) 89 wt%

Example 3: (1) 89 wt%, (2) 87 wt%, and (3) 83 wt%

Example 4: (1) 91 wt%, (2) 90 wt%, and (3) 83 wt%

Example 5: (1) 93 wt%, (2) 91 wt%, and (3) 89 wt%

Example 6: (1) 95 wt%, (2) 89 wt%, and (3) 80 wt%

Example 7: (1) 92 wt%, (2) 92 wt%, (3) 88 wt%

Example 8: (1) 94 wt%, (2) 93 wt%, (3) 87 wt%

Example 9: (1) 90 wt%, (2) 89 wt%, and (3) 88 wt%

Comparative example 1: (1) 15 wt%, (2) 1 wt%, (3) 0 wt%

From these results, it was found that the amount of ash remaining in the acrylic rubber was different even when the same cleaning was performed due to the difference in the sizes of the aqueous aggregates generated in the coagulation step, and that the aqueous aggregates having a large specific ratio of (1) to (3) were high in cleaning efficiency, low in ash amount and excellent in water resistance (comparison between examples 3 to 9 of Table 2-2 and comparative example 1). Further, it was found that the ash removal rate was also high when the water-containing pellets of a specific proportion of (1) to (3) were dehydrated to 20 wt%, the ash amount was further reduced, and the water resistance of the acrylic rubber was significantly improved (comparison of examples 1 to 2 and examples 3 to 9).

For reference, the procedure was carried out in the same manner as in comparative example 1 (reference example 2) except that the emulsion polymerization liquid was added to the coagulation liquid in the coagulation step (reference example 1), and the coagulant concentration of the coagulation liquid was changed from 0.7% by weight to 2% by weight, except that the particle size ratio of the produced aqueous pellets and the ash content in the acrylic rubber were measured in the same manner as in comparative example 1.

Reference example 1: (1) 90 wt%, (2) 55 wt%, and (3) 22 wt%, and ash content 0.55 wt%

Reference example 2: 91 wt%, 70 wt%, 40 wt% and 0.41 wt% ash

From these results, it was found that the ash content in the acrylic rubber was changed from the method (Lx ∈) of adding the emulsion polymerization liquid to the stirred coagulation liquid during the coagulation reaction to the method (Lx ∈) of adding the emulsion polymerization liquid to the stirred coagulation liquid, and the stirring of the coagulation liquid was vigorously performed (stirring speed 600 rpm/peripheral speed 3.1 m/s), whereby the particle size of the produced aqueous pellets was concentrated in a specific range of 710 μm to 4.75mm, the cleaning efficiency in hot water and the removal efficiency of the emulsifier and coagulant during dehydration were remarkably improved, the ash content of the acrylic rubber was reduced, and the properties such as the crosslinking property, roll processability, compression set resistance and normal physical properties including strength properties of the acrylic rubber were not impaired, and the water resistance was greatly improved (examples 1 to 2). In addition, it was confirmed that the presence or absence of the addition of the chain transfer agent has little effect on the particle size of the resulting aqueous pellet.

Example 10

Acrylic rubber (L) was obtained in the same manner as in example 2 except that the monomer components were changed to 74.5 parts of ethyl acrylate, 17 parts of n-butyl acrylate, 7 parts of methoxyethyl acrylate and 1.5 parts of mono-n-butyl fumarate, and the emulsifier was changed to 1.8 parts of sodium tridecyloxy hexaoxyethylene phosphate, as shown in Table 3-1, and the properties were evaluated, and the results are shown in Table 3-2. In addition, table 3-1 shows the post-dewatering (draining) water content, maximum torque, specific power, specific energy consumption, shear rate, and shear viscosity of the screw type biaxial extrusion dryer.

Example 11

Acrylic rubber (M) was obtained in the same manner as in example 1 except that the monomer components were changed to 74.5 parts of ethyl acrylate, 17 parts of n-butyl acrylate, 7 parts of methoxyethyl acrylate and 1.5 parts of mono-n-butyl fumarate, and the emulsifier was changed to 1.8 parts of sodium tridecyloxy hexaoxyethylene phosphate, and the properties were evaluated, and the results are shown in tables 3-2. In addition, table 3-1 shows the post-dewatering (draining) water content, maximum torque, specific power, specific energy consumption, shear rate, and shear viscosity of the screw type biaxial extrusion dryer.

Example 12

An acrylic rubber (N) was obtained in the same manner as in example 10 except that the monomer components were changed to 28 parts of ethyl acrylate, 38 parts of N-butyl acrylate, 27 parts of methoxyethyl acrylate, 5 parts of acrylonitrile and 2 parts of allyl glycidyl ether, and the operating conditions of the screw-type biaxial extrusion dryer were changed to high shear (maximum torque 45n·m), and the properties (the compounding agent was changed to "compounding 3") were evaluated, and the results are shown in table 3-2. In addition, table 3-1 shows the post-dewatering (draining) water content, maximum torque, specific power, specific energy consumption, shear rate, and shear viscosity of the screw type biaxial extrusion dryer.

Example 13

An acrylic rubber (O) was obtained in the same manner as in example 12 except that the monomer components were changed to 48.5 parts of ethyl acrylate, 50 parts of n-butyl acrylate and 1.5 parts of mono-n-butyl fumarate, and the properties (the compounding agent was changed to "compounding 1") were evaluated, and the results are shown in Table 3-2. In addition, table 3-1 shows the post-dewatering (draining) water content, maximum torque, specific power, specific energy consumption, shear rate, and shear viscosity of the screw type biaxial extrusion dryer.

Example 14

An acrylic rubber (P) was obtained in the same manner as in example 12 except that the monomer components were changed to 48.25 parts of ethyl acrylate, 50 parts of n-butyl acrylate and 1.75 parts of mono-n-butyl fumarate, and each characteristic was evaluated (the compounding agent was changed to "compounding 2"), and the results are shown in table 3-2. In addition, table 3-1 shows the post-dewatering (draining) water content, maximum torque, specific power, specific energy consumption, shear rate, and shear viscosity of the screw type biaxial extrusion dryer.

Example 15

An acrylic rubber (Q) was obtained in the same manner as in example 11 except that the monomer components were changed to 28 parts of ethyl acrylate, 38 parts of N-butyl acrylate, 27 parts of methoxyethyl acrylate, 5 parts of acrylonitrile and 2 parts of allyl glycidyl ether, and the operating conditions of the screw-type biaxial extrusion dryer were changed to high shear (maximum torque 45n·m), and the properties (the compounding agent was changed to "compounding 3"), and the results thereof were evaluated as shown in table 3-2. In addition, table 3-1 shows the post-dewatering (draining) water content, maximum torque, specific power, specific energy consumption, shear rate, and shear viscosity of the screw type biaxial extrusion dryer.

Example 16

An acrylic rubber (R) was obtained in the same manner as in example 15 except that the monomer components were changed to 48.5 parts of ethyl acrylate, 50 parts of n-butyl acrylate and 1.5 parts of mono-n-butyl fumarate, and each characteristic was evaluated (the compounding agent was changed to "compounding 1"), and the results are shown in table 3-2. In addition, table 3-1 shows the post-dewatering (draining) water content, maximum torque, specific power, specific energy consumption, shear rate, and shear viscosity of the screw type biaxial extrusion dryer.

Example 17

An acrylic rubber (S) was obtained in the same manner as in example 15 except that the monomer components were changed to 48.25 parts of ethyl acrylate, 50 parts of n-butyl acrylate and 1.75 parts of mono-n-butyl fumarate, and each characteristic was evaluated (the compounding agent was changed to "compounding 2"), and the results are shown in Table 3-2. In addition, table 3-1 shows the post-dewatering (draining) water content, maximum torque, specific power, specific energy consumption, shear rate, and shear viscosity of the screw type biaxial extrusion dryer.

[ Table 3-1]

[ Table 3-2]

As is clear from tables 3 to 2, the acrylic rubbers (N) to (S) of the present invention were excellent in Banbury workability, water resistance, storage stability, crosslinkability, compression set resistance and normal physical properties including strength characteristics, and also significantly improved in roll workability (comparison of examples 12 to 17 with examples 10 to 11). This is because the acrylic rubber composed of the high molecular weight component and the low molecular weight component obtained by emulsion polymerization with the chain transfer agent added later is dried with high shear using a screw type biaxial extrusion dryer, and further becomes an acrylic rubber having a balanced molecular weight and molecular weight distribution, and the roll processability can be significantly improved.

Further, the rubber samples were evaluated for the variation in the amount of the component insoluble in methyl ethyl ketone by the method described above. Specifically, the amount of methyl ethyl ketone-insoluble component at 20 selected arbitrarily from 20 parts (20 kg) of the rubber sample was measured, and the deviation of the amount of methyl ethyl ketone-insoluble component of the rubber sample was evaluated based on the above criteria.

When the acrylic rubbers (L) to (S) obtained in examples 10 to 17 and the acrylic rubber (J) obtained in comparative example 1 were used as rubber samples to evaluate the deviation of the component amounts insoluble in methyl ethyl ketone, the results of the acrylic rubbers (L) to (S) of examples 10 to 17 of the present invention were all "good", but the result of the acrylic rubber (J) of comparative example 1 was "×".

It is estimated from this that, with respect to the acrylic rubbers (L) to (S), by melt-kneading with a screw type biaxial extruder, melt-kneading and drying are performed in a state where substantially no moisture is present (the moisture content is less than 1% by weight), the component amount insoluble in methyl ethyl ketone is almost eliminated, and the component amount deviation insoluble in methyl ethyl ketone is almost eliminated, whereby the crosslinking property, roll processability, compression set resistance and normal physical properties including strength characteristics are not impaired, and the banbury processability can be remarkably improved.

On the other hand, it was found that the aqueous pellet produced after emulsion polymerization and coagulation washing under the conditions for producing the acrylic rubber (J) of comparative example 1 was fed into a screw type biaxial extrusion dryer under the same conditions as in example 10 and extrusion-dried to obtain an acrylic rubber, and the amount of methyl ethyl ketone-insoluble component were measured for the obtained acrylic rubber, and as a result, the amount of methyl ethyl ketone-insoluble component and the amount of methyl ethyl ketone-insoluble component were substantially the same as those of the acrylic rubber (L), and the banbury processability was improved, but the roll processability was evaluated as "x".

Regarding the acrylic rubber compositions comprising the acrylic rubbers (L) to (S) of examples 10 to 17, the Mooney scorch storage stability was evaluated on the basis of the following criteria by measuring the Mooney scorch time t5 (minutes) at a temperature of 125℃in accordance with JIS K6300 by the method of the above-mentioned evaluation of the processing stability based on the Mooney scorch inhibition. The results were excellent.

And (3) the following materials: the Mooney scorch time t5 is more than 2.0 minutes

And (2) the following steps: the Mooney scorch time t5 is 1.5 to 2.0 minutes

X: the Mooney scorch time t5 is less than 1.5 minutes

In addition, regarding the acrylic rubbers (L) to (S), the cooling rate of the sheet-like dried rubber extruded from the screw type biaxial extrusion dryer was as fast as approximately 200℃per hour as in example 1, and was 40℃per hour or more.

[ mold releasability to mold ]

The rubber compositions of the acrylic rubbers (L) to (S) obtained in examples 10 to 17 were pressed into a 10 mm. Phi. Times.200 mm mold, and the crosslinked rubber product crosslinked at the mold temperature of 165℃for 2 minutes was taken out, and when the mold releasability was evaluated on the basis of the following criteria, the acrylic rubbers (L) to (S) were evaluated as excellent.

And (3) the following materials: can be easily released from the mold without mold residue

And (2) the following steps: can be easily released from the mold, but very little mold residue was found

Delta: can be easily released from the mold, but with a small amount of mold residue

X: difficult to release from a mold

Description of the reference numerals

1: an acrylic rubber manufacturing system;

3: a coagulation device;

4: a cleaning device;

5: a screw type biaxial extrusion dryer;

6: a cooling device;

7: and a glue wrapping device.

Claims

1. An acrylic rubber comprising (meth) acrylic acid ester as a main component, a dimethylformamide-based solvent as an eluent, and having a weight average molecular weight (Mw) of 100 ten thousand or more, a ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of 3.4 or more, an ash content of 0.4% by weight or less, and a total amount of sodium, magnesium, calcium, phosphorus and sulfur in the ash content of 80% by weight or more, as measured by GPC-MALS method.

2. The acrylic rubber according to claim 1, wherein a ratio (Mw/Mn) of a weight average molecular weight (Mw) to a number average molecular weight (Mn) of the acrylic rubber is 3.5 or more.

3. The acrylic rubber according to claim 1 or 2, wherein a ratio (Mw/Mn) of a weight average molecular weight (Mw) to a number average molecular weight (Mn) of the acrylic rubber is in a range of 3.7 to 6.5.

4. An acrylic rubber according to any one of claims 1 to 3, wherein the acrylic rubber has a reactive group.

5. The acrylic rubber according to any one of claims 1 to 4, wherein the reactive group is an ion-reactive group.

6. The acrylic rubber according to any one of claims 1 to 5, wherein the reactive group is at least one reactive group selected from a carboxyl group, an epoxy group and a chlorine atom.

7. The acrylic rubber according to any one of claims 1 to 6, wherein the acrylic rubber is composed of the following bonding units: binding units derived from a (meth) acrylate ester selected from at least one of an alkyl (meth) acrylate and an alkoxyalkyl (meth) acrylate, binding units derived from a reactive group-containing monomer, and binding units derived from other monomers.

8. The acrylic rubber according to any one of claims 1 to 7, wherein a ratio (Mz/Mw) of z-average molecular weight (Mz) to weight-average molecular weight (Mw) of the acrylic rubber is in a range of 1.3 to 3.

9. The acrylic rubber according to any one of claims 1 to 8, wherein the amount of methyl ethyl ketone-insoluble component of the acrylic rubber is 50% by weight or less.

10. The acrylic rubber according to any one of claims 1 to 9, wherein the values when the amount of methyl ethyl ketone-insoluble component of the acrylic rubber at 20 is measured are all in the range of (average ± 5% by weight).

11. The acrylic rubber according to any one of claims 1 to 10, wherein the acrylic rubber has a complex viscosity ([ η60 ] c) of 15000[ pa-s ] or less at 60 ℃.

12. The acrylic rubber according to any one of claims 1 to 11, wherein a ratio of complex viscosity at 100 ℃ ([ η ]100 ℃) to complex viscosity at 60 ℃ ([ η ]60 ℃) ([ η ]100 ℃/[ η ]60 ℃)) of the acrylic rubber is 0.8 or more.

13. The acrylic rubber according to any one of claims 1 to 12, wherein the specific gravity of the acrylic rubber is 0.8 or more.

14. The acrylic rubber according to any one of claims 1 to 13, wherein the acrylic rubber is sheet-like or bale-like.

15. The acrylic rubber according to any one of claims 1 to 14, wherein the acrylic rubber is an acrylic rubber obtained by emulsion polymerization using a phosphate salt or a sulfate salt as an emulsifier.

16. The acrylic rubber according to any one of claims 1 to 15, wherein the acrylic rubber is one obtained by coagulating and drying a polymerization liquid produced in the emulsion polymerization step by using an alkali metal salt or a group 2 metal salt of the periodic table as a coagulating agent.

17. The acrylic rubber according to any one of claims 1 to 16, wherein the acrylic rubber is obtained by melt kneading and drying after solidification.

18. The acrylic rubber according to claim 17, wherein the melt kneading and drying are carried out in a state substantially free from moisture.

19. The acrylic rubber according to claim 17 or 18, wherein the melt-kneading and drying are performed under reduced pressure.

20. The acrylic rubber according to any one of claims 17 to 19, wherein the acrylic rubber is obtained by cooling at a cooling rate of 40 ℃/hr or more after the melt-kneading and drying.

21. The acrylic rubber according to any one of claims 1 to 20, wherein the acrylic rubber is obtained by washing, dehydrating and drying an aqueous pellet having a particle diameter in the range of 710 μm to 6.7mm in a proportion of 50% by weight or more.

22. A method for producing an acrylic rubber, comprising the steps of:

an emulsifying step of emulsifying an acrylic rubber monomer component containing (meth) acrylic ester as a main component with water and an emulsifier;

an emulsion polymerization step of initiating polymerization in the presence of a redox catalyst containing an inorganic radical generator and a reducing agent, intermittently adding a chain transfer agent during the polymerization, and continuing the polymerization to obtain an emulsion polymerization solution;

a coagulation step of adding the obtained emulsion polymerization liquid to a stirred coagulation liquid to coagulate the emulsion polymerization liquid to produce aqueous pellets;

a washing step of washing the produced water-containing pellets with hot water;

a dehydration step of dehydrating the washed aqueous granules; and

and a drying step of drying the dehydrated aqueous pellets to less than 1% by weight.

23. The method for producing an acrylic rubber according to claim 22, wherein the method for producing an acrylic rubber according to any one of claims 1 to 21 is carried out.

24. The method for producing an acrylic rubber according to claim 22 or 23, wherein emulsion polymerization is performed using a phosphate salt or a sulfate salt as an emulsifier.

25. The method for producing an acrylic rubber according to any one of claims 22 to 24, wherein the polymerization solution obtained after emulsion polymerization is coagulated and dried by using an alkali metal salt or a group 2 metal salt of the periodic table as a coagulant.

26. The method for producing an acrylic rubber according to claim 25, wherein the polymerization solution produced in the emulsion polymerization step is added to an aqueous solution containing a coagulant containing an alkali metal salt or a group 2 metal salt of the periodic table, and the mixture is stirred to coagulate the polymerization solution.

27. The method for producing an acrylic rubber according to any one of claims 22 to 26, wherein a polymerization liquid produced in the emulsion polymerization step is brought into contact with a coagulant to solidify the polymerization liquid, and then melt-kneaded and dried.

28. The method for producing an acrylic rubber according to claim 27, wherein the melt kneading and drying are performed in a state substantially free of moisture.

29. The method for producing an acrylic rubber according to claim 27 or 28, wherein the melt kneading and drying are performed under reduced pressure.

30. The method for producing an acrylic rubber according to any one of claims 27 to 29, wherein the melt kneading and drying are performed by a screw type biaxial extrusion dryer.

31. The method according to claim 30, wherein the maximum torque of the screw type biaxial extrusion dryer at the time of melt kneading and drying is 20 N.m or more.

32. The method for producing an acrylic rubber according to any one of claims 27 to 31, wherein the acrylic rubber after melt-kneading and drying is cooled at a cooling rate of 40 ℃/hr or more.

33. The method for producing an acrylic rubber according to any one of claims 22 to 32, wherein the coagulant concentration of the coagulant is 1% by weight or more.

34. The method for producing an acrylic rubber according to any one of claims 22 to 33, wherein a stirring speed of the stirred coagulation liquid is 100rpm or more.

35. The method according to any one of claims 22 to 34, wherein a peripheral speed of the stirred coagulation liquid is 1m/s or more.

36. The method for producing an acrylic rubber according to any one of claims 22 to 35, wherein a reducing agent is added later in the emulsion polymerization step.

37. The method according to any one of claims 22 to 36, wherein the aqueous pellets having a particle diameter in the range of 710 μm to 6.7mm in a proportion of 50 wt.% or more are washed, dehydrated and dried.

38. A rubber composition comprising a rubber component comprising the acrylic rubber according to any one of claims 1 to 21, a filler and a crosslinking agent.

39. The rubber composition according to claim 38, wherein the filler is a reinforcing filler.

40. The rubber composition according to claim 38, wherein the filler is a carbon black.

41. The rubber composition according to claim 38, wherein the filler is a silica type.

42. The rubber composition of any of claims 38-41, wherein the cross-linking agent is an organic cross-linking agent.

43. The rubber composition of any of claims 38 to 42, wherein the cross-linking agent is a multi-component compound.

44. The rubber composition according to any one of claims 38 to 43, wherein the crosslinking agent is an ion-crosslinkable compound.

45. The rubber composition according to claim 44, wherein the crosslinking agent is an ion-crosslinkable organic compound.

46. The rubber composition of claim 44 or 45, wherein the crosslinking agent is a polyionic organic compound.

47. The rubber composition according to any one of claims 44 to 46, wherein the ion of the ion-crosslinkable compound, the ion-crosslinkable organic compound or the polyion-organic compound as the crosslinking agent is an ion-reactive group selected from at least one of an amino group, an epoxy group, a carboxyl group and a thiol group.

48. The rubber composition according to claim 46, wherein the crosslinking agent is a polyion compound selected from at least one of a polyamine compound, a polyepoxide compound, a polycarboxylic acid compound, and a polythiol compound.

49. The rubber composition according to any one of claims 38 to 48, wherein the content of the crosslinking agent is in the range of 0.001 to 20 parts by weight relative to 100 parts by weight of the rubber component.

50. The rubber composition of any of claims 38-49, further comprising an anti-aging agent.

51. The rubber composition according to claim 50, wherein the antioxidant is an amine-based antioxidant.

52. A process for producing a rubber composition, comprising mixing a rubber component comprising the acrylic rubber according to any one of claims 1 to 21, a filler and, if necessary, an anti-aging agent, and then mixing a crosslinking agent.

53. A crosslinked rubber product obtained by crosslinking the rubber composition according to any one of claims 38 to 51.

54. A rubber crosslinked according to claim 53 wherein crosslinking of the rubber composition occurs after molding.

55. The rubber crosslink of claim 53 or 54, wherein the crosslinking of the rubber composition is a crosslinking that performs primary crosslinking and secondary crosslinking.