CN116057085A

CN116057085A - Acrylic rubber excellent in roll processability, banbury processability, water resistance, strength characteristics and compression set resistance

Info

Publication number: CN116057085A
Application number: CN202180057541.6A
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: 2023-05-02
Also published as: WO2021246516A1; JPWO2021246516A1; KR20230020399A

Abstract

The invention provides an acrylic rubber which is excellent in roll processability, banbury processability, water resistance, strength characteristics and compression set resistance. The acrylic rubber of the present invention comprises a binding unit derived from at least one (meth) acrylic acid ester selected from the group consisting of alkyl (meth) acrylate and alkoxyalkyl (meth) acrylate, a binding unit derived from a monomer containing at least one reactive group selected from the group consisting of carboxyl groups, epoxy groups and chlorine atoms, and a binding unit derived from another monomer used as required, and the weight average molecular weight (Mw) of the acrylic rubber is 1000000 ～ 3500000, the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is in the range of 3.7 to 6.5, the amount of methyl ethyl ketone insoluble components is 50 wt.% or less, the amount of ash is 0.15 wt.% or less, and the total amount of sodium, magnesium, calcium, phosphorus and sulfur in the ash is 50 wt.% or more, based on the absolute molecular weight and absolute molecular weight distribution measured by GPC-MALS method.

Description

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

Technical Field

The present invention relates to an acrylic rubber, a method for producing the same, a rubber molded article, a rubber composition, and a rubber crosslinked product, and more particularly, to an acrylic rubber excellent in roll processability, banbury processability, and water resistance, strength characteristics, and compression set resistance of a crosslinked product, a method for producing the same, an acrylic rubber molded article obtained by molding the acrylic rubber, 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, in which a monomer component comprising ethyl acrylate, butyl acrylate, methoxyethyl acrylate and monobutyl fumarate, water and sodium lauryl sulfate are charged, deaeration under reduced pressure and nitrogen substitution are repeated, then, sodium formaldehyde sulfoxylate and cumene hydroperoxide as an organic radical generator are added, emulsion polymerization is initiated at normal pressure and normal temperature, emulsion polymerization is performed until the polymerization conversion reaches 95% by weight, then, solidification is performed with a calcium chloride aqueous solution, filtration is performed with a metal mesh, and dehydration and drying are performed with an extrusion dryer having a screw, thereby producing an acrylic rubber. However, the acrylic rubber obtained by this method has problems of extremely poor roll processability and 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: the method comprises the steps of preparing a monomer emulsion from monomer components comprising ethyl acrylate, butyl acrylate, methoxyethyl acrylate and monobutyl maleate by using pure water and sodium lauryl sulfate and polyoxyethylene lauryl ether as emulsifiers, then charging a part of the monomer emulsion into a polymerization reaction tank, cooling down to 12 ℃ under a nitrogen stream, continuously dropwise adding the rest of the monomer emulsion, ferrous sulfate, sodium ascorbate and aqueous potassium persulfate solution as an inorganic free radical generator over 3 hours, then maintaining at 23 ℃ for one hour, continuously performing emulsion polymerization, heating to 85 ℃ after the polymerization conversion reaches 97 wt%, continuously adding sodium sulfate, solidifying, filtering to obtain water granules, subjecting the water granules to four times of water washing, one time of acid washing and one time of pure water washing, continuously manufacturing acrylic rubber into a sheet shape by using an extrusion dryer with a screw, and crosslinking by using aliphatic polyamine compounds such as hexamethylenediamine carbamate. However, the sheet-like acrylic rubber obtained by this 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: a monomer composition comprising ethyl acrylate, caprolactone-added acrylate, cyanoethyl acrylate and vinyl chloride is prepared by emulsifying 1/4 of a monomer mixture comprising the monomer composition 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 to initiate polymerization, dropwise adding the rest of the monomer mixture and a 2% ammonium persulfate aqueous solution at 60 ℃ for 2 hours while maintaining the temperature, continuing to polymerize for 2 hours after dropwise adding, adding a latex with a polymerization conversion of 96-99% into a sodium chloride aqueous solution at 80 ℃ for coagulation, sufficiently washing with water, and drying to prepare an acrylic rubber, and crosslinking with sulfur. However, the acrylic rubber obtained by this 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 the above monomer components, pure water, sodium lauryl sulfate, polyethylene glycol monostearate and n-dodecyl mercaptan as a chain transfer agent was prepared from ethyl acrylate, butyl acrylate and monobutyl fumarate, then a part of the monomer emulsion and pure water were put 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, then the reaction was continued at 23℃for one hour, then industrial water was added, after heating to 85℃and continuously adding sodium sulfate at 85℃to effect coagulation, to obtain aqueous pellets, which were washed three times with pure water, 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 this 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 comprising ethyl acrylate, a special acrylic ester and vinyl monochloride, sodium lauryl sulfate as an emulsifier, n-octyl mercaptan as a chain transfer agent and water are added into a reaction vessel, nitrogen substitution is performed, ammonium bisulfide and sodium persulfate as an inorganic radical generator are added to initiate polymerization, copolymerization is performed at 55 ℃ for 3 hours at a reaction conversion rate of 93-96%, acrylic rubber is produced, and crosslinking is performed with sulfur. However, the acrylic rubber obtained by this 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:is prepared from at least one compound of 50-99.9 wt% of alkyl acrylate and alkoxy alkyl acrylate, 0.1-20 wt% of ester containing dihydro-dicyclopentadienyl of unsaturated carboxylic acid with free radical reactive group, 0-20 wt% of other monovinyl and monovinylidene (vinylidenecH) ₂ A copolymer comprising a monomer composed of at least one of a 1, 2-vinylidene (vinyl-ch=ch-) based unsaturated compound, wherein the copolymer has a polystyrene-equivalent number average molecular weight (Mn) of 20 to 120 tens of thousands and a ratio (Mw/Mn) of a weight average molecular weight (Mw) to a number average molecular weight (Mn) of 10 or less, the ratio being based on tetrahydrofuran as an eluting solvent. The following is also described: the number average molecular weight (Mn) is 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, and if Mn is more than 120 tens of thousands, the processability is poor, and if Mn is more than 10, compression set becomes large with respect to the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn), 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 is added, polymerized, and has a 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, and is sufficiently washed with water and directly dried after being solidified in a calcium chloride aqueous solution. Further, it is shown in examples and comparative examples that when the amount of the chain transfer agent is small, the number average molecular weight (Mn) of the obtained acrylic rubber is as high as 500 ten thousand, the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is as narrow as 1.4, and when the amount of the chain transfer agent is large, the number average molecular weight (Mn) is as low as 20 ten thousand, the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) becomes very wide, reaching 17. However, the acrylic rubber obtained by this method has the following problems: compression set resistance and storage stability are poor, and since the radical-reactive group is contained, even when the radical is used The polymerization reaction of the radical generator gives a suitable molecular weight distribution (Mw/Mn), and the molecular weights (Mw, mn) are too large and too complicated, and the roll processability and the Banbury processability are insufficient. In addition, the acrylic rubber obtained by this method has the following problems: in the crosslinking reaction, sulfur and a vulcanization accelerator as a crosslinking agent are added, and after kneading with a roll, 100kg/cm of the mixture is used ² The vulcanization press of (2) is carried out at 170℃for 15 minutes and further in a Gill oven at 175℃for 4 hours, and the resulting crosslinked product also has problems such as poor compression set resistance, water resistance and strength characteristics, and poor 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 actual state of the prior art, and an object thereof is to provide an acrylic rubber excellent in roll processability, banbury processability and in water resistance, strength characteristics and compression set resistance of a crosslinked product, a method for producing the same, an acrylic rubber molded article obtained by molding the acrylic rubber, a rubber composition comprising 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 is composed of a binding unit containing a specific monomer component of a specific reactive group-containing monomer, and is excellent in roll processability, banbury processability, and water resistance, strength characteristics and compression set resistance of a crosslinked product, based on an absolute molecular weight and an absolute molecular weight distribution measured by GPC-MALS method, and a ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is in a specific range, and a specific solvent insoluble component amount and a specific ash amount are limited.

The present inventors have found that an acrylic rubber having an ion-reactive group such as a carboxyl group, an epoxy group, a chlorine atom, or the like capable of reacting with a crosslinking agent and having a weight average molecular weight (Mw) of an absolute molecular weight measured by GPC-MALS method in a specific range on the high molecular weight side is excellent in short-time crosslinkability, strength characteristics, and compression set resistance.

The present inventors have found that an acrylic rubber having the above reactive group cannot be sufficiently dissolved in tetrahydrofuran used in the GPC measurement of the radical reactive acrylic rubber obtained by copolymerizing ethyl acrylate, dicyclopentenyl acrylate, or the like in the above conventional technique, and each molecular weight and molecular weight distribution cannot be measured cleanly and satisfactorily, but by using a specific solvent having an SP value higher than that of tetrahydrofuran as an eluting solvent, the acrylic rubber can be sufficiently dissolved and can be measured satisfactorily, and by setting each characteristic value to a specific value, the roll processability, banbury processability, and the water resistance, strength characteristics, and compression set resistance of a crosslinked product can be highly balanced.

Regarding roll processability, the present inventors found that it is particularly important to make the weight average molecular weight (Mw) of the absolute molecular weight measured by GPC-MALS method within a specific range and to expand the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the absolute molecular weight distribution, so that the roll processability of the acrylic rubber and the strength characteristics of the crosslinked product can be highly balanced. The present inventors have also found that it is not easy to set the weight average molecular weight (Mw) of the absolute molecular weight measured by GPC-MALS method to a specific range and to expand the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the absolute molecular weight distribution, but it can be achieved by adding the chain transfer agent in the polymerization reaction after it is batchwise or by drying the aqueous pellet at high shear in a screw type biaxial extrusion dryer. In addition, it was found that when the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is too wide, the low molecular weight component becomes excessive and the strength characteristics are lowered.

Regarding the banbury processability, the present inventors found that the smaller the amount of methyl ethyl ketone insoluble component of the acrylic rubber, the more excellent. The present inventors have found that the amount of methyl ethyl ketone insoluble components of an acrylic rubber is drastically increased during polymerization, particularly when the polymerization conversion is increased in order to improve the strength characteristics, and it is difficult to control, but by performing emulsion polymerization in the presence of a chain transfer agent, the inhibition can be performed to a certain extent, and the drastically increased methyl ethyl ketone insoluble components can be remarkably improved in banbury processability without impairing the roll processability of the acrylic rubber by melt kneading and extrusion drying the acrylic rubber in a state substantially free of moisture (moisture content less than 1% by weight) in a screw type biaxial extrusion dryer.

Regarding the water resistance, the present inventors found that when the amount of ash in the acrylic rubber is small and the ash is a specific component, it is extremely excellent. Although it is quite difficult to reduce the ash content in the acrylic rubber, the present inventors found that the washing efficiency in hot water and the ash removal efficiency at the time of dehydration of the aqueous pellets subjected to the coagulation reaction using the specific method are high, and that the ash of the specific component is difficult to remove in washing, by using the same method, the ash content can be easily reduced, and the water resistance can be remarkably improved. The present inventors have found that, particularly, 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 of the obtained acrylic rubber can be significantly improved without impairing the properties such as roll processability, banbury processability, strength properties and compression set resistance. Further, the present inventors have found that when a specific emulsifier is used in emulsion polymerization of an acrylic rubber or a specific coagulant is used in the case of coagulating an emulsion polymerization liquid, it is possible to remarkably improve releasability from a metal mold or the like while making the water resistance of the acrylic rubber excellent.

The present inventors have found that by increasing the specific gravity of an acrylic rubber, it is possible to improve the roll processability, banbury processability, water resistance, strength characteristics and compression set resistance and also to greatly improve the storage stability. The present inventors have found that the acrylic rubber of the present invention having a specific reactive group has tackiness and air is difficult to discharge, and a large amount of air is involved in the pellet-like acrylic rubber obtained by directly drying the aqueous pellets (specific gravity becomes small) and the storage stability is poor, but by rubber-packing the pellet-like acrylic rubber with a packer or the like, some air can be discharged and the storage stability can be improved, and by extrusion-drying the aqueous pellets under reduced pressure with a screw type biaxial extrusion dryer and extruding and laminating in the form of a sheet containing no air, the production of a rubber-packed acrylic rubber containing little air, having a high specific gravity and significantly improved storage stability can be achieved. Furthermore, the present inventors have found that the specific gravity of the content of air added can be measured according to the a method of JIS K6268 crosslinked rubber-density measurement using the difference in buoyancy. Further, it has been found that by setting the pH within a specific range, the storage stability of the acrylic rubber can be further improved.

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

Further, the present inventors have found that, by emulsifying a specific monomer component with water and an emulsifier, initiating emulsion polymerization in the presence of a redox catalyst composed of an inorganic radical generator such as potassium persulfate and a reducing agent, adding a chain transfer agent in batches during the polymerization without adding the chain transfer agent initially, and performing emulsion polymerization until the polymerization conversion becomes 90% by weight or more, an acrylic rubber which can be produced can produce a high molecular weight component and a low molecular weight component in an absolute molecular weight and absolute molecular weight distribution measured by GPC, and can widen the molecular weight distribution while maintaining a high molecular weight, thereby highly balancing the roll processability, crosslinkability, strength characteristics and compression set resistance of the acrylic rubber.

The inventors have found that by specifying the number of times of post-addition of the chain transfer agent in batches, the timing of post-addition, the amount of post-addition, the type of chain transfer agent, the type of reducing agent, the ratio of the amounts of the reducing agent to be added initially and post-added in batches, the initial and post-addition amounts, and the polymerization temperature, an acrylic rubber having a more balanced roll processability, strength characteristics, water resistance and compression set resistance can be produced.

Further, the present inventors have found that when the emulsion polymerization liquid obtained by adding the chain transfer agent in portions is coagulated and dried, an acrylic rubber having further improved roll processability, short-time crosslinkability, strength characteristics and compression set resistance can be produced by melt-kneading and drying the acrylic rubber under high shear conditions using a specific extrusion dryer.

The present inventors have further found that by blending carbon black and silica as fillers in the rubber composition comprising the acrylic rubber or the acrylic rubber molded body, the filler and the crosslinking agent of the present invention, the roll processability, the banbury processability and the short-time crosslinking property are more excellent, and the water resistance, the strength characteristics and the compression set resistance of the crosslinked product are highly excellent. Further, the present inventors have found that, by preferably using an organic compound, a polyvalent compound or an ionic crosslinking compound as a crosslinking agent, for example, a polyvalent ionic organic compound having an ion-reactive group such as a plurality of amine groups, epoxy groups, carboxyl groups or thiol groups which reacts with the ion-reactive group of the acrylic rubber, it is possible to make the roll processability, the banbury processability and the crosslinking property in a short period of time excellent, and the crosslinked product is highly excellent in water resistance, strength characteristics and compression set resistance.

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

Thus, according to the present invention, there can be provided an acrylic rubber comprising a binding unit derived from a (meth) acrylic acid ester selected from at least one of an alkyl (meth) acrylate and an alkoxyalkyl (meth) acrylate, a binding unit derived from a monomer having a reactive group selected from at least one of a carboxyl group, an epoxy group and a chlorine atom, and a binding unit derived from another monomer used as required, wherein the weight average molecular weight (Mw) of the acrylic rubber is 1000000 ～ 3500000, the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is in the range of 3.7 to 6.5, the amount of methyl ethyl ketone insoluble components is 50% by weight or less, the amount of ash is 0.15% by weight or less, and the total amount of sodium, magnesium, calcium, phosphorus and sulfur in the ash is 50% by weight or more, based on the absolute molecular weight and absolute molecular weight distribution measured by GPC-MALS method.

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

In the acrylic rubber of the present invention, the measurement solvent by GPC-MALS method is preferably dimethylformamide-based solvent.

In the acrylic rubber of the present invention, the amount of methyl ethyl ketone insoluble component is preferably 10% by weight or less.

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

In the acrylic rubber of the present invention, the specific gravity is preferably 1 or more.

In the acrylic rubber of the present invention, the pH is preferably 6 or less.

The acrylic rubber of the present invention is preferably produced by emulsion polymerization using a phosphate salt or a sulfate salt as an emulsifier, and is preferably produced by solidifying and drying a polymerization liquid obtained by emulsion polymerization using an alkali metal salt or a group 2 metal salt of the periodic table as a coagulant. The acrylic rubber of the present invention is preferably melt-kneaded and dried after solidification, and the melt-kneaded and dried are preferably carried out in a state substantially free of moisture, and the melt-kneaded and dried are preferably carried out under reduced pressure. The acrylic rubber of the present invention is preferably cooled at a cooling rate of 40℃per hour or more after the 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 wt% 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 a monomer component including a (meth) acrylic acid ester selected from at least one of an alkyl (meth) acrylate and an alkoxyalkyl (meth) acrylate, a monomer containing a reactive group selected from at least one of a carboxyl group, an epoxy group, and a chlorine atom, and, if necessary, another monomer, with water and an emulsifier;

an emulsion polymerization step of initiating emulsion polymerization in the presence of a redox catalyst comprising an inorganic radical generator and a reducing agent, adding a chain transfer agent and a reducing agent in batches during the polymerization, and continuing the emulsion polymerization until the polymerization conversion becomes 90 wt% or more to obtain an emulsion polymerization solution; a coagulation step of adding the obtained emulsion polymerization liquid to a stirred coagulation liquid, and coagulating the emulsion polymerization liquid to produce an aqueous pellet;

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

and a dehydration/drying step of dehydrating the washed aqueous pellets in a dehydration cylinder to a water content of 1 to 40 wt% and drying the same in the drying cylinder to less than 1 wt%, using a dehydration cylinder having a dehydration slit, a drying cylinder under reduced pressure, and a screw type biaxial extrusion dryer having a die at the front end, and extruding the dried rubber from the die.

The method for producing an acrylic rubber of the present invention is preferably a method for producing an acrylic rubber as described above.

In the method for producing an acrylic rubber of the present invention, the coagulant concentration of the coagulant is preferably 0.1 to 20% by weight.

In the method for producing an acrylic rubber of the present invention, the number of stirring of the stirred coagulation liquid is preferably 200rpm 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, it is preferable to perform emulsion polymerization using a phosphate salt or a sulfate salt as an emulsifier in the emulsion polymerization step.

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

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 stirred to coagulate the polymerization liquid.

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 and solidified, and then melt kneaded and dried.

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

In the method for producing an acrylic rubber of the present invention, the melt kneading and drying are preferably performed under reduced pressure.

In the method for producing an acrylic rubber of the present invention, the melt-kneaded and dried acrylic rubber 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, 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 can be provided an acrylic rubber molded article obtained by molding the acrylic rubber.

In the acrylic rubber molded body of the present invention, the acrylic rubber molded body is preferably a sheet or a bag.

Further, according to the present invention, there can be provided a rubber composition comprising a rubber component, a filler and a crosslinking agent, wherein the rubber component comprises the acrylic rubber and/or the acrylic rubber molded body.

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 ionic crosslinkable compound, the ionic crosslinkable organic compound or the polyionic organic compound as the crosslinking agent is preferably at least one ion-reactive group selected from the group consisting of an amine group, an epoxy group, a carboxyl group and a thiol.

In the rubber composition of the present invention, the crosslinking agent is preferably at least one polyion compound selected from the group consisting 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, comprising mixing a rubber component comprising the acrylic rubber or the acrylic rubber molded product, a filler, and an antioxidant, if necessary, and then mixing a crosslinking agent.

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, there can be provided an acrylic rubber excellent in roll processability, banbury processability and in water resistance, strength characteristics and compression set resistance of a crosslinked product, an efficient production method thereof, an acrylic rubber molded article obtained by molding the acrylic rubber, a high-quality rubber composition comprising the acrylic rubber, and a crosslinked rubber obtained by crosslinking the composition.

Drawings

Fig. 1 is a diagram schematically showing an example of an acrylic rubber production system for producing an acrylic rubber according to an embodiment of the present invention.

Fig. 2 is a view showing the structure of the screw extruder of fig. 1.

Fig. 3 is a diagram showing a structure of a transport type cooling device serving as the cooling device of fig. 1.

Detailed Description

The acrylic rubber of the present invention is characterized by comprising a binding unit derived from a (meth) acrylic acid ester selected from at least one of an alkyl (meth) acrylate and an alkoxyalkyl (meth) acrylate, a binding unit derived from a monomer having a reactive group selected from at least one of a carboxyl group, an epoxy group and a chlorine atom, and a binding unit derived from another monomer used as required, wherein the weight average molecular weight (Mw) of the acrylic rubber is in the range of 1000000 ～ 3500000, the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is in the range of 3.7 to 6.5, the amount of methyl ethyl ketone insoluble components is 50 wt% or less, the amount of ash is 0.15 wt% or less, and the total amount of sodium, magnesium, calcium, phosphorus and sulfur in the ash is 50 wt% or more, based on the absolute molecular weight and absolute molecular weight distribution measured by GPC-MALS method. The term "GPC-MALS method" as used herein refers to the following. GPC (gel permeation chromatography ) is a liquid chromatography that separates based on differences in molecular size. The "GPC-MALS method" is the following method: by installing a multi-angle laser light diffuser (MALS) and a differential refractive index detector (RI) in this apparatus, the light scattering intensity and refractive index difference of a molecular chain solution having been differentiated in size by the GPC apparatus are measured in accordance with the elution time, whereby the molecular weight of the solute and the content thereof are sequentially calculated, and finally the absolute molecular weight distribution and absolute average molecular weight value of the polymer substance are obtained.

< monomer component >

The acrylic rubber of the present invention is a polymer comprising a binding unit composed of at least one (meth) acrylic acid ester selected from the group consisting of alkyl (meth) acrylates and alkoxyalkyl (meth) acrylates, a monomer containing at least one reactive group selected from the group consisting of carboxyl groups, epoxy groups and chlorine atoms, and other monomers copolymerizable as needed. 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 alkyl (meth) acrylate is not particularly limited, and an alkyl (meth) acrylate having an alkyl group having 1 to 12 carbon atoms is generally 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 generally 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.

At least one (meth) acrylic acid ester selected from these alkyl (meth) acrylate and alkoxyalkyl (meth) acrylate may be used alone or in combination of two or more, 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 monomer containing at least one reactive group selected from the group consisting of a carboxyl group, an epoxy group and a chlorine atom is not particularly limited, but is preferably a monomer having a functional group that participates in an ionic reaction, more preferably a monomer having a carboxyl group and 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 the crosslinked product can be improved to a high degree, and therefore, it is preferable.

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, ethylenically unsaturated dicarboxylic acid monoester is particularly preferred from the viewpoint of further improving compression set resistance when the acrylic rubber is formed into a rubber crosslinked product.

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, the ethylenically unsaturated dicarboxylic acid also comprises ethylenically unsaturated dicarboxylic acids in the form of anhydrides.

The ethylenically unsaturated dicarboxylic acid monoester is not particularly limited, and examples thereof include alkyl monoesters having 1 to 12 carbon atoms of ethylenically unsaturated dicarboxylic acids having 4 to 12 carbon atoms, preferably alkyl monoesters having 2 to 8 carbon atoms of ethylenically unsaturated dicarboxylic acids having 4 to 6 carbon atoms, and more preferably alkyl monoesters having 2 to 6 carbon atoms of butenedioic acid having 4 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, chloroacyloxy alkyl (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 chloracetyl unsaturated monomer include 3- (hydroxychloroacetoxy) propyl allyl ether, p-vinylbenzyl chloroacetate, and the like.

These monomers containing at least one reactive group selected from the group consisting of a carboxyl group, an epoxy group and a chlorine atom 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, and most preferably 1 to 3% by weight.

The monomer other than the above (simply referred to as "other monomer" in the present invention) that can be used together with the above-described monomers as needed is not particularly limited as long as it can be copolymerized with the above-described monomer, and examples thereof include: aromatic vinyl such as styrene, α -methylstyrene, divinylbenzene, etc.; ethylenically unsaturated nitriles 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 alone or in combination of two or more, and the ratio in the total monomer components 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 is composed of a combination unit of at least one (meth) acrylic acid ester selected from the group consisting of the above-mentioned alkyl (meth) acrylate and alkoxyalkyl (meth) acrylate, a monomer containing at least one reactive group selected from the group consisting of a carboxyl group, an epoxy group and a chlorine atom, and other monomers used as needed, and the proportions of each of them in the acrylic rubber are as follows: the binding unit derived from at least one (meth) acrylic acid ester selected from the group consisting of alkyl (meth) acrylates and alkoxyalkyl (meth) acrylates 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 a monomer containing at least one reactive group selected from the group consisting of carboxyl groups, epoxy groups and chlorine atoms 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 other monomers 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, 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 at least one reactive group selected from the group consisting of carboxyl groups, epoxy groups and chlorine atoms 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 generally 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, particularly preferably 0.1 to 0.5% by weight, based on the weight of the reactive group itself, and in this case, processability and 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 measurement solvent for the GPC-MALS method for measuring the absolute molecular weight and the absolute molecular weight distribution of the acrylic rubber of the present invention is not particularly limited as long as it is a solvent capable of dissolving and measuring the acrylic rubber of the present invention, and is preferably a dimethylformamide-based solvent. The dimethylformamide-based solvent to be used is not particularly limited as long as it is a solvent containing dimethylformamide as a main component, and may be dimethylformamide 100% or the ratio of dimethylformamide in the dimethylformamide-based solvent is 90% by weight, preferably 95% by weight, more preferably 97% by weight or more. 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 concentrated hydrochloric acid at a concentration of 37% is added at a concentration of 0.01% is particularly preferable.

The weight average molecular weight (Mw) of the acrylic rubber of the present invention is preferably in the range of 1000000 ～ 3500000, preferably 1200000 ～ 3000000, more preferably 1300000 ～ 3000000, particularly preferably 1500000 ～ 2500000, most preferably 1900000 ～ 2100000, in terms of absolute molecular weight as measured by GPC-MALS, and in this case, the roll processability, strength characteristics and compression set resistance of the acrylic rubber are highly balanced. 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, whereas when too large, the roll processability, banbury processability, injection moldability and the like are poor, which is not 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, and the absolute molecular weight measured by GPC-MALS method is generally in the range of 100000 ～ 500000, preferably 200000 ～ 480000, more preferably 250000 ～ 450000, particularly preferably 300000 ～ 400000, and most preferably 350000 ～ 400000, and in this case, the roll processability, strength characteristics, and compression set resistance of the acrylic rubber are highly balanced, and therefore preferable. When the number average molecular weight (Mn) of the acrylic rubber of the present invention is too small, the strength characteristics and compression set resistance are poor, whereas when too large, the roll processability, banbury processability, injection moldability and the like are poor, which is not preferable.

The z-average molecular weight (Mz) of the acrylic rubber of the present invention is not particularly limited, and is generally in the range of 1500000 ～ 6000000, preferably 2000000 ～ 5000000, more preferably 2500000 ～ 4500000, and particularly preferably 3000000 ～ 4000000, in terms of the absolute molecular weight in the high molecular weight region as measured by GPC-MALS method, and in this case, the roll processability, strength characteristics and compression set resistance of the acrylic rubber are highly balanced, and therefore preferable.

The acrylic rubber of the present invention has a weight average molecular weight (Mw) to number average molecular weight (Mn) ratio (Mw/Mn) in the range of 3.7 to 6.5, preferably 3.8 to 6.2, more preferably 4 to 6, particularly preferably 4.5 to 5.7, most preferably 4.7 to 5.5, as measured by GPC-MALS method, and in this case, the roll processability and the strength characteristics at the time of crosslinking and compression set resistance are highly balanced, and therefore preferred. 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 poor, and when it is too large, the strength characteristics and compression set resistance are poor, and the roll processability is also insufficient, which is not preferable.

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 it is preferable that the acrylic rubber has a high balance of processability and strength characteristics and can mitigate physical property changes during storage, in terms of an absolute molecular weight distribution in a high molecular weight region measured by GPC-MALS method, usually 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.

The ash content of the acrylic rubber of the present invention is preferably 0.15 wt% or less, more preferably 0.14 wt% or less, and even more preferably 0.13 wt% 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 not less than 0.0001 wt%, preferably not less than 0.0005 wt%, more preferably not less than 0.001 wt%, particularly preferably not less than 0.005 wt%, most preferably not less than 0.01 wt%, 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 at the time of highly balancing water resistance, strength characteristics, processability and handleability is usually in the range of 0.0001 to 0.15% by weight, preferably 0.0005 to 0.15% by weight, more preferably 0.001 to 0.14% by weight, particularly preferably 0.005 to 0.13% by weight, most preferably 0.01 to 0.13% by weight.

The total amount of sodium, magnesium, calcium, phosphorus and sulfur in the ash of the acrylic rubber of the present invention is preferably 50% by weight or more, more preferably 60% by weight or more, still 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 of the acrylic rubber can be 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 the 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.

The ash in the acrylic rubber is mainly derived from an emulsifier used for emulsion polymerization by emulsifying a monomer component and a coagulant used for coagulation of 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 various conditions of the subsequent steps.

When an anionic emulsifier, a cationic emulsifier or a nonionic emulsifier, preferably an anionic emulsifier, more preferably a phosphate or a sulfate is used as an emulsifier in emulsion polymerization to be described later, the acrylic rubber of the present invention is preferable because it can improve the mold releasability and workability in addition to the water resistance and strength characteristics. 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, but the use of the above-mentioned emulsifier is preferable because the water resistance, strength characteristics, mold releasability and workability of the acrylic rubber can be further highly balanced.

When a metal salt, preferably an alkali metal salt or a metal salt of group 2 of the periodic table is used as a coagulant to be described later, the acrylic rubber of the present invention is preferable because it can improve the mold releasability and workability of a metal mold to a high degree in addition to the water resistance and strength characteristics. 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, but the use of the above-mentioned coagulant is preferable because the water resistance, strength characteristics, mold releasability and workability of the acrylic rubber are further highly balanced.

The amount of methyl ethyl ketone insoluble component in the acrylic rubber of the present invention is preferably 50% by weight or less, more preferably 30% by weight or less, still 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, workability in kneading such as Banbury is highly improved.

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

The acrylic rubber of the present invention is preferably used in a screw type biaxial extrusion dryer for the aqueous pellet produced in the coagulation reaction, because the Banbury processability and the strength characteristics are highly balanced when the melt kneading and drying are carried out in a state in which water is substantially removed (the water content is less than 1% by weight).

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 that the storage stability is greatly affected, including oxidative deterioration and the like, and is not preferable.

The specific gravity of the acrylic rubber of the present invention is obtained by dividing the mass by the volume including voids, that is, 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 by a screw type biaxial extrusion dryer under reduced pressure or melt kneading and drying under reduced pressure, because it is particularly excellent in storage stability, injection moldability, strength characteristics and other characteristics and is 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 it is preferable that the complex viscosity is suitably selected depending on the purpose of use, and 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.

The complex viscosity ([ eta ]100 ℃) of the acrylic rubber of the present invention at 100℃is not particularly limited, and it is preferable that the complex viscosity is suitably selected depending on the purpose of use, and 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, the processability, oil resistance and shape retention are excellent.

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 water content of the acrylic rubber of the present invention is not particularly limited, and may be 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 water resistance are highly improved, and thus, it is preferable.

The pH of the acrylic rubber of the present invention is not particularly limited, and is preferably selected appropriately according to 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, in which case the storage stability of the acrylic rubber is highly improved.

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 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.

< 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:

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

(monomer component)

The monomer components used in the present invention are the same as exemplified and preferred ranges of the above monomer components. The amount of the monomer component used is also 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 2-valent phosphate salts are most preferable, in which case the water resistance, strength characteristics, mold releasability and workability of the resulting acrylic rubber can be highly balanced. The phosphate and sulfate are preferably alkali metal salts of phosphate and sulfate, more preferably sodium salts of phosphate and sulfate, and in this case, the water resistance, strength characteristics, mold releasability and workability of the resulting acrylic rubber can be highly balanced.

The 2-valent 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: octoxydioxyethylene phosphate, octoxytrioxyethylene phosphate, octoxytetraethylene phosphate, decoxytetraethylene phosphate, dodecoxytetraethylene phosphate, tridecyloxytetraethylene phosphate, tetradecyloxytetraethylene phosphate, hexadecyloxytetraethylene phosphate, octadecyl tetraethylene phosphate, octoxypentaethylene phosphate, decoxypentaethylene phosphate, dodecoxypentaethylene phosphate, tridecyloxypentaethylene phosphate, tetradecyloxy pentaethylene phosphate, hexadecyloxy pentaethylene phosphate, octadecyl pentaethylene phosphate, octoxyhexaethylene phosphate, decyloxy hexaethylene phosphate, dodecoxyhexaethylene phosphate, tridecyloxy hexaethylene phosphate, tetradecyloxy hexaethylene phosphate, hexadecyloxy hexaethylene phosphate, octadecyl hexaethylene phosphate, octoxyoctaethylene phosphate, decaoxy octaethylene phosphate, dodecoxyoctaethylene phosphate, tridecyloxy octaethylene phosphate, tetradecyloxy octaethylene phosphate, hexadecyloxy octaethylene phosphate, and the like, among these, alkali metal salts thereof are preferable, and sodium 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 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 such as 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 hexaoxyethylene phosphate, ethylphenoxy octaoxyethylene phosphate, butylphenoxy octaoxyethylene phosphate, hexylphenoxy octaoxyethylene phosphate, nonylphenoxy octaoxyethylene phosphate, dodecylphenoxy octaoxyethylene phosphate, etc., among these, alkali metal salts are preferred, and sodium salts are particularly preferred.

Specific examples of the alkylphenoxypolyoxypropylene phosphate salt include: among these, 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, and dodecylphenoxy octaoxypropylene phosphate, and alkali metal salts thereof are particularly preferred, and sodium salts thereof are particularly preferred.

As the phosphate ester salt, a 1-valent phosphate ester salt such as a di (alkoxypolyoxyalkylene) phosphate ester sodium salt can be used alone or in combination with a 2-valent 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 alone or in combination of two or more, 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 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 alone or in combination of two or more, 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 generally used in emulsion polymerization, and it is preferable to use at least two reducing agents, since 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 and roll processability and strength characteristics of the resulting acrylic rubber.

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, potassium bisulfite, etc.; 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 of two or more, 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.

The preferred combination of the metal ion compound in the reduced state with the reducing agent other than the metal ion compound is a combination of ferrous sulfate with ascorbic acid or a salt thereof and/or sodium formaldehyde sulfoxylate, more preferably a combination of ferrous sulfate with ascorbic acid or a salt thereof. In this case, the amount of the ferrous sulfate to be used 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 to be 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 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, based on 100 parts by weight of the monomer component used for the polymerization, only in the emulsification of the monomer component.

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 according to 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 can be shortened even if the temperature is increased without control, but in the present invention, the emulsion polymerization temperature is preferably controlled to be not higher than 35℃in general, preferably to be 0 to 35℃and more preferably to be 5 to 30℃and particularly preferably to be 10 to 25℃so that the strength characteristics of the produced acrylic rubber and the processability in kneading such as Banbury can be highly balanced.

(post addition of chain transfer agent)

The present invention is characterized in that it is preferable to be able to produce an acrylic rubber having a high molecular weight component separated from a low molecular weight component by adding the chain transfer agent in a batch after the polymerization process without adding the chain transfer agent at the beginning, and the strength characteristics of the produced acrylic rubber are highly balanced with the processability in kneading with rolls or the like.

The chain transfer agent to be used is not particularly limited as long as it is a chain transfer agent 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-pentyl thiol, n-hexyl thiol, n-heptyl thiol, n-octyl thiol, n-decyl thiol, n-dodecyl thiol, n-tridecyl thiol, n-tetradecyl thiol, n-hexadecyl thiol, n-octadecyl thiol, sec-pentyl thiol, sec-hexyl thiol, sec-heptyl thiol, sec-octyl thiol, zhong Guiji thiol, sec-dodecyl thiol, sec-tridecyl thiol, sec-tetradecyl thiol, sec-hexadecyl thiol, sec-octadecyl thiol, tert-amyl thiol, tert-hexyl thiol, tert-heptyl thiol, tert-octyl thiol, tert-decyl thiol, tert-dodecyl thiol, tert-tridecyl thiol, tert-tetradecyl thiol, tert-hexadecyl thiol, tert-octadecyl thiol, and the like, preferably n-octyl thiol, n-dodecyl thiol, tert-dodecyl thiol, more preferably n-octyl thiol, and n-dodecyl thiol.

These chain transfer agents can be used each alone or in combination of two or more. 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.

The present invention is characterized in that the chain transfer agent is preferably added in batches during the polymerization without adding the chain transfer agent at the beginning of the polymerization, so that the high molecular weight component and the low molecular weight component of the obtained acrylic rubber can be produced, and the molecular weight distribution can be made to be in a specific range, and the strength characteristics of the acrylic rubber and the processability of rolls and the like can be highly balanced.

The number of times of post-addition of the chain transfer agent in batches 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 batch-wise 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 20 minutes or later, preferably 30 minutes or later, more preferably 30 to 200 minutes, particularly preferably 35 to 150 minutes, and most preferably 40 to 120 minutes after the initiation 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, and thus are preferable.

The amount of the chain transfer agent added in each of the batch-wise 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, 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.

The chain transfer agent is not particularly limited, and 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 terminated.

(post addition of reducing agent)

In the present invention, the reducing agent of the above-mentioned redox catalyst can be added later in the polymerization process, and thus the strength characteristics of the produced acrylic rubber and the processability of rolls and the like can be highly balanced, and thus it is preferable.

The reducing agent added later in the polymerization process 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 are also highly balanced, and therefore, it is preferable.

The reducing agent added later in the polymerization process may be either of continuous addition or batch addition, and is preferably added in batches. The number of times when the reducing agent is added in the polymerization process after it is batchwise is not particularly limited, but is usually 1 to 5 times, preferably 1 to 3 times, more preferably 1 to 2 times.

When the reducing agent added later in the polymerization initiation and polymerization process is ascorbic acid or a salt thereof, the ratio of the amount of the initially added ascorbic acid or a salt thereof to the amount of the later added ascorbic acid or a salt thereof is not particularly limited, and is usually in the range of 1/9 to 8/2, preferably 2/8 to 6/4, more preferably 3/7 to 5/5, in terms of the weight ratio of "the initially added ascorbic acid or a salt thereof"/"the ascorbic acid or a salt thereof added later in a batch", and in this case, the productivity of the production of the acrylic rubber is excellent, and the strength characteristics and the processability of the produced acrylic rubber are also 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 preferably in the range of 1 to 3 hours, more preferably 1.5 to 2.5 hours after the initiation 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 are also highly balanced, so that it is preferable.

The amount of the reducing agent added in each of the batch-wise 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, 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 continued for usually 30 minutes or more, preferably 45 minutes or more, more preferably 1 hour or more, and then ended.

The polymerization conversion rate of the emulsion polymerization is preferably 90% by weight or more, more preferably 95% by weight or more, and in this case, the produced acrylic rubber is excellent in strength characteristics and free from off-flavors. In terminating the polymerization, a polymerization terminator may be used.

After emulsion polymerization, the emulsion polymerization solution (emulsion) obtained is coagulated and dried, and the acrylic rubber can be separated.

(coagulation step)

In the coagulation step after emulsion polymerization, the emulsion polymerization liquid obtained in the emulsion polymerization is added to the stirred coagulation liquid, and coagulated, whereby aqueous pellets of the acrylic rubber can be produced.

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

The coagulant used as the coagulant liquid is not particularly limited, and a metal salt is usually 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 workability 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 and water resistance in the case of crosslinking the acrylic rubber can be highly improved.

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

The method for forming the particle size of the aqueous pellet in the above range is not particularly limited, and for example, the method can be performed as follows: the method of contacting the emulsion polymerization liquid with the coagulant is to add the emulsion polymerization liquid to the stirred coagulant liquid (coagulant aqueous solution); or the coagulant concentration of the coagulant, the stirring number of the stirred coagulant, and the peripheral speed are specified.

The coagulant used is usually used in the form of an aqueous solution, and the concentration of the coagulant in the aqueous solution is usually in the range of 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, and in this case, the particle size of the resulting aqueous pellets can be uniformly concentrated in a specific region, which is preferable.

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, it is preferable to produce uniform aqueous pellets.

The stirring number (rotation number) of the coagulation liquid to be stirred, that is, the rotation number of the stirring blade of the stirring device is not particularly limited, and is usually in the range of 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 water-containing aggregates to be produced can be made small and uniform when the number of revolutions is a number of revolutions with which stirring is intense to some extent, it is preferable that the number of revolutions is not less than the lower limit, and the particle size of the aggregates to be produced can be suppressed from being excessively large or excessively small, and the coagulation reaction can be controlled more easily by 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 since the particle size of the resulting aqueous granules can be made small and uniform when the stirring is intense to some extent, it is preferably 0.5m/s or more, more preferably 1m/s or more, still 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 (contact method, solid content concentration of emulsion polymerization liquid, concentration and temperature of coagulation liquid, number of revolutions and peripheral speed of coagulation liquid at the time of stirring, etc.) in a specific range, the shape and pellet size of the produced aqueous pellets are uniform and concentrated, and the removal efficiency of the emulsifier and coagulant at the time of washing and dewatering is remarkably improved, and as a result, the water resistance and storage stability of the produced acrylic rubber can be highly improved, which is preferable.

(cleaning step)

The aqueous pellets produced in the above-described coagulation reaction are preferably washed with hot water before drying.

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

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

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 ℃, and particularly 60 to 80 ℃, and thus the cleaning efficiency can be significantly improved, and is most preferable. When the temperature of the hot water to be used is not less 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 pellet and the particle size of the aqueous pellet 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-drying Process)

In the present invention, a screw type biaxial extrusion dryer having a dewatering barrel with a dewatering slit, a dryer barrel under reduced pressure, and a die head at the tip is preferably used, and the above-mentioned washed aqueous pellets are dewatered to a water content of 1 to 40% by weight in the dewatering barrel and dried to less than 1% by weight in the dryer barrel, and the dried rubber is extruded from the die head, whereby an acrylic rubber excellent in roll processability, strength characteristics, compression set resistance, banbury processability, and water resistance can be produced.

In the present invention, the aqueous pellets supplied to the screw type biaxial extrusion dryer are preferably aqueous 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 hydrous pellets by a water remover, because the water removal efficiency can be improved.

As the dewatering machine, a known dewatering machine can be used without particular limitation, and examples thereof include a wire mesh, a screen mesh, an electric screen classifier, and the like, and a wire mesh and a screen mesh 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 efficiently 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 ℃, more preferably 50 to 90 ℃, particularly preferably 55 to 85 ℃, and most preferably 60 to 80 ℃, and in this case, the aqueous pellet having a specific heat of up to 1.5 to 2.5KJ/kg·k, which is not liable to be increased in temperature, can be dehydrated and dried efficiently using a 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 in a dewatering barrel in a screw type twin screw extrusion dryer having dewatering slots. 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 efficiently performed, which is preferable.

In the present invention, the removal of water from the hydrous pellets in the dehydration cylinder is distinguished by the fact that the water is removed from the dehydration slit in a liquid state (drain) and removed in a vapor state (drain), and the drain is defined as dehydration and the drain is defined as predrying.

In the dehydration of the hydrous pellets, the water discharged from the dehydration slit may be in either a liquid state (drain) or a vapor state (vapor discharge), but in the case of using a screw type biaxial extrusion dryer having a plurality of dehydration barrels, it is preferable to combine drain and vapor discharge to efficiently dehydrate the adhesive acrylic rubber. In a screw type biaxial extrusion dryer having 3 or more dehydration barrels, it is sufficient to appropriately select whether each dehydration barrel is a drainage type dehydration barrel or a steam discharge type dehydration barrel depending on the purpose of use, and in general, the drainage type barrel is increased when the ash content in the produced acrylic rubber is reduced, and the steam discharge type barrel is increased when the water content is reduced.

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 preferably 1 to 40% by weight, more preferably 5 to 40% by weight, still 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.

In the case of dehydration of an adhesive acrylic rubber having a reactive group, when dehydration is performed using a centrifuge or the like, the acrylic rubber adheres to the dehydration slit portion and is hardly dehydrated (the dehydration is performed to about 45 to 55% by weight of water content), but in the present invention, the water content can be reduced to the above range by using a screw type biaxial extrusion dryer having a dehydration slit and capable of forcibly extruding with a screw.

For dehydration of the aqueous pellets in the case of having a water-draining type dehydrator cylinder and a steam-draining type dehydrator cylinder, the water content after water draining in the water-draining type dehydrator cylinder section 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 in the steam-draining type dehydrator cylinder section 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 the acrylic rubber under reduced pressure is preferable because the productivity of drying can be improved, and air existing in the acrylic rubber can be removed, and an acrylic rubber having a high specific gravity and excellent storage stability can be produced. 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 is mainly related to the specific gravity of the acrylic rubber, and can be controlled by the specific gravity. However, when the storage stability of the acrylic rubber having a large specific gravity is controlled to a high level, the storage stability of the acrylic rubber can be controlled by the degree of vacuum of the extrusion dryer or the like.

The vacuum degree of the dryer cylinder may be appropriately selected, and is usually 1 to 50kPa, preferably 2 to 30kPa, more preferably 3 to 20kPa, and in this case, it is preferable to be able to effectively dry the aqueous pellets, remove air from the acrylic rubber, and significantly improve the storage stability of the acrylic rubber.

The setting temperature of the dryer cylinder may be appropriately selected, and is usually in the range of 100 to 250 ℃, preferably 110 to 200 ℃, more preferably 120 to 180 ℃, and in this case, the acrylic rubber is preferably dried efficiently without scorching or deterioration, and the amount of methyl ethyl ketone insoluble components in the acrylic rubber can be reduced.

The number of the dryer cylinders in the screw type biaxial extrusion dryer is not particularly limited, but is usually plural, preferably 2 to 10, more preferably 3 to 8. The vacuum level in the case of having a plurality of dryer barrels may set all of the dryer barrels to an approximate vacuum level, or may be changed for each barrel. In the case of having a plurality of dryer cylinders, the set temperature may be set to be approximately the temperature of all the dryer cylinders, or may be changed for each cylinder, and it is preferable that the temperature of the discharge portion (the side close to the die head) is higher than the temperature of the introduction portion (the side close to the dryer cylinder), because the drying efficiency can be improved.

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 particularly 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 almost removed), because the amount of methyl ethyl ketone insoluble components of the acrylic rubber can be reduced. In the present invention, an acrylic rubber obtained by melt-kneading or melt-kneading and drying with a screw type biaxial extruder is preferable because the two properties of strength and Banbury processability are highly balanced. In the present invention, "melt kneading" or "melt kneading and drying" means kneading (mixing) the acrylic rubber in a molten state in a screw type biaxial extrusion dryer or extruding the acrylic rubber in a molten state and drying the acrylic rubber at this stage, or kneading the acrylic rubber in a molten (plasticized) state in a screw type biaxial extrusion dryer and extruding and drying the acrylic rubber.

In the present invention, the shear rate applied to 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 in the range of 10[ l/s ] or more, preferably 10 to 400[ l/s ], more preferably 50 to 250[ l/s ], and in this case, the storage stability, roll processability, banbury processability, strength characteristics and compression set resistance of the obtained acrylic rubber are highly balanced, and therefore preferred.

In the screw type biaxial extrusion dryer used in the present invention, the shear viscosity of the acrylic rubber in particular in the dryer barrel is not particularly limited, but is usually in the range of 12000[ Pa.s ] or less, 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 the storage stability, roll processability, banbury processability and strength characteristics of the obtained acrylic rubber are highly balanced, and therefore, are preferable.

(extrusion of dried rubber from die head)

The dehydrated and dried rubber is conveyed to a screw-free corrected die section in the screw sections of the dehydrator cylinder and the dryer cylinder, and extruded into a desired shape from the die section. A perforated plate or a metal mesh may or may not be provided between the screw portion and the die portion.

The extruded dry rubber is preferably extruded into a sheet shape by forming the die shape into a substantially rectangular shape, because the air involved is less, the specific gravity is high, and the storage stability is excellent.

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 acrylic rubber is preferable because less air is involved (high specific gravity) and productivity is excellent.

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 molecular weight of the dried rubber is not lowered and scorch is not caused, and the water content can be made smaller than 1 wt% and is therefore preferable.

The number of revolutions (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 acrylic rubber and the amount of methyl ethyl ketone insoluble components can be efficiently 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 number (N) of the screw type biaxial extrusion dryer to be used is not particularly limited, and 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 acrylic rubber can be highly balanced, and therefore, it is preferable.

The specific energy consumption (specific energy) 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 ] or more, 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 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 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 40 to 150[1/s ] or more, preferably 45 to 125[1/s ], and 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 to be used is not particularly limited, but is usually 4000 to 8000[ Pa.s ] or less, preferably 4500 to 7500[ Pa.s ], and more preferably 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.

In the present invention, it is preferable to use an extrusion dryer having a twin screw, because it is possible to dehydrate, dry and mold under high shear conditions.

The acrylic rubber of the present invention thus obtained is particularly excellent in storage stability, roll processability, banbury processability, strength characteristics, water resistance and compression set resistance, and is therefore preferred.

In the acrylic rubber of the present invention, the cooling rate after drying 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 at the same time, scorch stability can be significantly improved, which is preferred.

< acrylic rubber molded body >

The acrylic rubber molded body of the present invention is obtained by molding the above-mentioned acrylic rubber, and is usually obtained by molding a pellet-like acrylic rubber obtained by solidifying an acrylic rubber emulsion polymerization solution obtained by emulsion polymerization and directly drying the same into a predetermined shape, and the characteristic value (physical property value) of the acrylic rubber itself can be maintained even if the acrylic rubber molded body is produced. The acrylic rubber molded article of the present invention thus obtained is usually uncrosslinked.

The shape of the acrylic rubber molded article of the present invention is not particularly limited, and may be appropriately selected depending on the manner of use, and examples thereof include strands, sheets, and bales, and acrylic rubber sheets or bales, which are preferably sheet-like, are preferable, and their handling properties and storage stability are excellent.

The specific gravity of the acrylic rubber molded article 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 molded article 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, because the productivity, storage stability, and crosslinking characteristic stability of the crosslinked product are highly balanced.

The acrylic rubber molded article of the present invention is preferably obtained by drying an acrylic rubber under reduced pressure by a screw type biaxial extrusion dryer or by melt kneading and drying under reduced pressure, because the characteristics such as storage stability, roll processability and strength characteristics are particularly excellent and highly balanced.

The acrylic rubber molded article of the present invention is preferably obtained by melt-kneading and drying an acrylic rubber in a screw type biaxial extruder in which water is almost removed, and in this case, the banbury processability and strength characteristics are highly balanced.

The ash content, ash content (total amount of sodium, magnesium, calcium, phosphorus and sulfur, total amount of magnesium and phosphorus, magnesium amount or phosphorus amount), ash content ratio, complex viscosity at 60 ℃ ([ eta ]60 ℃), complex viscosity at 100 ℃ ([ eta ]100 ℃), ratio of complex viscosity at 100 ℃ ([ eta ]100 ℃) to complex viscosity at 60 ℃ ([ eta ]60 ℃), methyl ethyl ketone insoluble component amount, methyl ethyl ketone insoluble component deviation amount, water content, pH and Mooney viscosity (ML1+4, 100 ℃) of the acrylic rubber of the present invention are the same as those exemplified and preferred ranges of the above acrylic rubber.

The thickness of the acrylic rubber sheet of the present invention 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, most preferably 5 to 25mm, and in this case, the handling property, storage stability and productivity are highly balanced, and therefore preferred. The width of the acrylic rubber sheet 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 handling properties are particularly excellent, and therefore, it is preferable. The length of the 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 acrylic rubber sheet is particularly excellent in handling properties, and is therefore preferable.

The size of the acrylic rubber bag of the present invention 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 250mm, and these ranges are appropriate. The shape of the acrylic rubber bag of the present invention is not limited, and may be appropriately selected depending on the purpose of use of the acrylic rubber bag, and in many cases, a rectangular parallelepiped shape is preferable.

The acrylic rubber content of the acrylic rubber molded article of the present invention may be appropriately selected depending on the purpose of use, and is usually 90% by weight or more, preferably 95% by weight or more, more preferably 97% by weight or more, and in this case, the strength characteristics and the workability of rolls and the like are highly balanced, and thus are preferable.

The acrylic rubber molded article of the present invention is excellent in handleability, storage stability, roll processability, banbury processability, strength characteristics and compression set resistance, and can be used as it is or after cutting.

< method for producing acrylic rubber molded article >

The method for producing the acrylic rubber molded product is not particularly limited as long as the acrylic rubber is molded, and a method for producing an acrylic rubber sheet including a dehydration-drying-molding step is preferable: after the washing step of the method for producing an acrylic rubber, the washed aqueous pellets are dehydrated in a dehydration cylinder to a water content of 1 to 40% by weight, and then dried in the drying cylinder to less than 1% by weight, and a sheet-like dried rubber is extruded from a die, using a dehydration cylinder having a dehydration slit, a drying cylinder under reduced pressure, and a screw type biaxial extrusion dryer having a die at the front end; further, a method for producing an acrylic rubber bag further comprising a step of laminating and coating the extruded sheet-like dry rubber.

(emulsion polymerization step, coagulation step, and cleaning step)

The emulsification step, emulsion polymerization step, coagulation step and cleaning step in the method for producing an acrylic rubber molded body are the same as those described in the method for producing an acrylic rubber. The same applies except that the dried rubber extruded in the dehydration-drying step is specified to be sheet-like

(dehydration-drying-Forming Process)

The dehydration-drying-molding step in the method for producing an acrylic rubber molded body is characterized in that a dehydration barrel having a dehydration slit, a dryer barrel under reduced pressure, and a screw type biaxial extrusion dryer having a die at the front end are used, the 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 less than 1% by weight, and a sheet-like dry rubber is extruded from the die; the same description as that of the dehydration-drying step of the above-described acrylic rubber production method applies, except that the die is formed into a substantially rectangular parallelepiped shape and extruded in a sheet form.

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 acrylic rubber molded body is preferable because less air is involved (specific gravity is high) and productivity is excellent.

Screw type biaxial extrusion dryer and operating conditions

Sheet-like dry rubber

The shape of the dried rubber extruded from the screw type biaxial extrusion dryer is preferably in a sheet form because air is not involved at this time, the specific gravity can be increased, and the storage stability is highly improved. The sheet-like dry rubber extruded from the screw type biaxial extrusion dryer is generally cooled and cut to be used as an acrylic rubber sheet.

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 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, particularly preferably 4 to 12mm, with an improvement in cooling efficiency and a significant improvement in productivity.

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 the lower limit or more, and the shape collapse and fracture of the sheet-like dry rubber can be suppressed by the upper limit or less.

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

The sheet-like dried rubber is not particularly limited, and since the acrylic rubber of the acrylic rubber molded article of the present invention has strong adhesiveness, it is preferable to cool the sheet-like dried rubber and then cut the sheet-like dried rubber in order to cut the sheet-like dried rubber continuously without involving air.

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 in its complex viscosity ([ eta ]60 ℃) at 60℃and is usually not more than 15000[ Pa.s ], preferably 2000 to 10000[ Pa.s ], more preferably 2500 to 7000[ Pa.s ], and most preferably 2700 to 5500[ Pa.s ], and in this case, it is preferable to cut continuously without involving air.

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 at this time, air inclusion is low and cutting and productivity are highly balanced, and therefore, it is preferable.

The method for cooling 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 and is 0.15 to 0.35W/mK, forced cooling by air cooling with air blowing or cooling by air, watering by water spraying, immersing in water, and the like is preferable, and air cooling by air blowing or cooling by air cooling 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 extruder onto a conveyor such as a conveyor belt, 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 molded article. 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 particularly 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 acrylic rubber sheet thus obtained is excellent in handling properties, roll processability, banbury processability, crosslinkability, water resistance, strength characteristics and compression set resistance, and also excellent in storage stability, as compared with the pellet acrylic rubber, and can be used as it is or after lamination and encapsulation.

(lamination step)

The method for producing the acrylic rubber bag of the present invention is not particularly limited, and it is preferable to laminate the acrylic rubber sheets to obtain an acrylic rubber bag having less air entrainment and excellent storage stability.

The lamination temperature of the acrylic rubber sheet 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 acrylic rubber bag. The acrylic rubber bag of the present invention is integrated by the self weight of the laminated acrylic rubber sheets.

The acrylic rubber bag of the present invention thus obtained is superior to the pellet-like acrylic rubber in handling property, roll processability, banbury processability, crosslinkability, water resistance, strength characteristics and compression set resistance, and also superior in storage stability, and can be used as it is or cut into a desired amount to be 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 containing the acrylic rubber or the acrylic rubber molded product, a filler, and a crosslinking agent.

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 or the acrylic rubber molded product 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 to 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 each alone or in combination of two or more. The shape of these other rubber components may be any of a pellet, a strand, a bale, a sheet, a powder, and the like. The content of the other rubber component in the whole 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 short-time crosslinkability, 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, thermal 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 alone or in combination of two or more, and the amount thereof may be appropriately selected within a range that does not 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. As the crosslinking agent, either a polyvalent compound or a monovalent compound may be used, and a polyvalent compound having two or more reactive groups is preferable. 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 is an ion that reacts with an 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 amine 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 a carboxyl group-containing acrylic rubber or acrylic rubber molded body, or an epoxy group-containing acrylic rubber or acrylic rubber molded body.

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-six amino 3, 5-two mercapto three triazine. These triazine thiol compounds are particularly preferably used in combination with an acrylic rubber or an acrylic rubber molded body containing chlorine atoms.

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

These crosslinking agents may be used alone or in combination of two or more, 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.

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 and bisphosphite; 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 polycondensate; 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 alone or in combination of two or more, 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 above-mentioned acrylic rubber of the present invention and/or the acrylic rubber molded article of the present invention, a filler and a crosslinking agent 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 lubricant, a pigment, a colorant, an antistatic agent, a foaming agent, and the like, as required. These other compounding agents may be used alone or in combination of two or more kinds, and the compounding amounts thereof may be appropriately selected within a range that does not impair 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 and/or the acrylic rubber molded product of the present invention, a filler, a crosslinking agent, and optionally an antioxidant and other compounding agents, and any method available in the conventional rubber processing field can be used at the time of mixing, and for example, an open roll mill, a Banbury mixer, various kneaders, and the like can be used. The mixing order of the components may be in accordance with 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 at a temperature at which no reaction or decomposition occurs in a short period of time.

< 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 simultaneously with 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. As the heating method, a method for crosslinking the rubber such as pressing heating, steam heating, oven heating, and hot air heating may be appropriately selected.

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 are properly selected.

The rubber crosslinked product of the present invention maintains tensile strength, elongation, hardness, etc. as basic properties of rubber, while also having 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, sealing materials, diaphragms, oil seals, shaft seals, bearing seals, mechanical seals, wellhead seals, seals for electrical and electronic equipment, and seals for air compression equipment; a rocker cover gasket mounted at a joint portion of the cylinder block and the cylinder head, an oil pan gasket mounted at a joint portion of the oil pan and the cylinder head or the transmission case, a gasket for a fuel cell spacer mounted between a pair of cases sandwiching a unit cell having a positive electrode, an electrolyte plate and a negative electrode, a gasket for a top cover of a hard disk drive, and the like; 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 for fuel oil hoses such as fuel hoses, filler neck hoses, exhaust hoses, paper hoses, and fuel tanks such as oil hoses, as extrusion molded products and mold crosslinked products used for automobiles; an air hose such as a turbo air hose and a transmission hose; various hoses such as radiator hoses, heater hoses, brake hoses, air conditioner hoses, and the like.

< construction of apparatus for producing acrylic rubber and acrylic rubber molded article >

Next, a device structure for producing the acrylic rubber and the acrylic rubber molded body according to an embodiment of the present invention will be described. Fig. 1 is a diagram schematically showing an example of an acrylic rubber production system having an apparatus structure for producing an acrylic rubber and an acrylic rubber molded body 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 above-described treatment in the emulsion polymerization step. 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 the mixture is emulsified while being properly stirred by a stirrer, and an emulsion polymerization reaction is initiated in the presence of a redox catalyst composed of an inorganic radical generator and a reducing agent, and a chain transfer agent is added after the polymerization in batches, whereby an emulsion polymerization solution can be obtained. The emulsion polymerization reactor may be any of a batch type, a semi-batch type, and a continuous type, and may be any of a tank type reactor and a tube type reactor.

The coagulation apparatus 3 shown in fig. 1 is configured to perform the above-described treatment in the coagulation step. 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 shown 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 shown for controlling the rotation number and rotation speed of the stirring blades 33. In the coagulation apparatus 3, the emulsion polymerization liquid obtained in the emulsion polymerization reactor is brought into contact with a coagulation liquid to coagulate the emulsion polymerization liquid, whereby aqueous pellets can be produced.

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 therewith 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 solidification apparatus 3 is configured to control the temperature in the stirring tank 30 by controlling the heating operation of the heating unit 31 while monitoring the temperature in the stirring 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 has a motor 32 that generates rotational power and a stirring blade 33 that extends in a direction perpendicular to the rotation axis of the motor 32. The stirring blade 33 can rotate about a rotation axis by the rotation power of the motor 32 in the coagulation liquid filled in the stirring tank 30, thereby allowing the coagulation 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 to control the rotational drive of the motor 32 of the stirring device 34 and set the rotation number and rotation speed of the stirring blade 33 of the stirring device 34 to predetermined values. The rotation of the stirring blade 33 is controlled by the drive control unit so that the stirring number of the solidification liquid is, for example, usually 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 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 amount of ash in the finally obtained acrylic rubber can be effectively reduced by mixing the water-containing pellets produced in the coagulation device 3 with a large amount of water and cleaning the same.

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 to control the temperature in the cleaning tank 40 by controlling the heating operation of the heating unit 41 while monitoring the temperature in the cleaning tank 40 measured by 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. In this case, the washed aqueous pellets are preferably fed to the screw type biaxial extrusion dryer 5 after passing through the water separator 43 capable of separating free water. The water removing machine 43 may be, for example, a metal mesh, a screen, an electric sieving machine, or the like.

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

The screw type biaxial extrusion dryer 5 shown in fig. 1 is configured to perform the above-described dehydration step and drying step. In fig. 1, a screw type biaxial extrusion dryer 5 is shown as a preferable example, but a centrifugal separator, a squeezer, or the like may be used as a dehydrator for performing the treatment in the dehydration step, or a hot air dryer, a reduced pressure dryer, an expansion dryer, a kneader type dryer, or the like may be used as a dryer for performing the treatment 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: a dewatering cylinder section 53 having a function as a dewatering machine for dewatering the aqueous pellets washed by the washing apparatus 4; a dryer section 54 having a function as a dryer for drying the aqueous pellets; also provided is a die 59 having a molding function for molding the aqueous pellets on the downstream side of the screw type biaxial extrusion dryer 5.

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-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 cylinder 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 by applying 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.

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

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 constituted by connecting 13 divided barrels 52a to 52b, 53a to 53c, 54a to 54h from the upstream side to the downstream side.

The screw type biaxial extrusion dryer 5 further includes heating means, not shown, for heating the respective cylinders 52a to 52b, 53a to 53c, 54a to 54h individually, and for heating the aqueous pellets in the respective cylinders 52a to 52b, 53a to 53c, 54a to 54h individually to a predetermined temperature. The heating units have numbers corresponding to the respective barrels 52a to 52b, 53a to 53c, 54a to 54 h. As such heating means, for example, a structure is employed in which high-temperature steam or the like is supplied from the steam supply means to the steam flow shields formed in the respective cylinders 52a to 52b, 53a to 53c, 54a to 54h, but the invention is not limited thereto. The screw type biaxial extrusion dryer 5 further includes a temperature control means, not shown, for controlling the set temperatures of the heating means corresponding to the barrels 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 be supplied to the barrel portion 52 is, for example, 1 to 3. The number of the dehydrator cylinders of the dehydrator cylinder 53 is preferably 2 to 10, and in the case of 3 to 6, it is more preferable because dehydration of the aqueous pellets of the adhesive acrylic rubber can be efficiently performed. 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 unit such as a motor housed 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 the rotation driving, 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 flight portion and the groove portion are in mesh with each other, whereby the dewatering efficiency and drying efficiency of the aqueous pellet can be improved.

The rotation direction of the pair of screws may be the same direction or different directions, and from the viewpoint of self-cleaning performance, a form in which the screws rotate in the same direction is preferable. The screw shape of the pair of screws 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 in which a liquid (slurry) containing a coagulant or the like is separated from the aqueous pellet and discharged.

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 efficiently performed.

The removal of water from the hydrous pellets in each of the dewatering cylinders 53a to 53c of the dewatering cylinder 53 is both in the case of removing water in a liquid state from each of the

dewatering slits

56a, 56b, 56c and in the case of removing water in a vapor state. In the dehydrator cylinder 53 of the present embodiment, the case of removing water in a liquid state is defined as drain, and the case of removing water in a vapor state is defined as drain.

The dehydration cylinder 53 is preferable because the water content of the adhesive acrylic rubber can be reduced efficiently by combining drainage and steam discharge. In the dewatering cylinder section 53, which of the 1 st to 3 rd dewatering cylinders 53a to 53c is used for dewatering or discharging steam is appropriately set 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 dewatering can 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. For example, in the case where the dewatering cylinder portion 53 has 4 dewatering cylinders, a mode in which water is discharged from the 3 dewatering cylinders on the upstream side and steam is discharged from the 1 dewatering cylinder on the downstream side can be considered. On the other hand, in the case of decreasing the water content, a dehydration cylinder for discharging steam may be added.

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 that performs dehydration in a water discharge state is usually 60 to 120 ℃, preferably 70 to 110 ℃, more preferably 80 to 100 ℃, and the setting temperature of the dehydration barrel that performs dehydration in a steam discharge 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. The 2 nd, 4 th, 6 th, and 8 th dryer barrels 54b, 54d, 54f, and 54h constituting the dryer barrel section 54 have

exhaust ports

58a, 58b, 58c, 58d for degassing, respectively. The

exhaust ports

58a, 58b, 58c, and 58d are connected to exhaust pipes, not shown.

Vacuum pumps, not shown, are connected to the ends of the respective exhaust pipes, and the interior of the dryer cylinder 54 is depressurized to a predetermined pressure by the operation of these vacuum pumps. The screw extruder 5 has a pressure control unit, not shown, for controlling the operation of these vacuum pumps and controlling the vacuum level in the dryer barrel section 54.

The vacuum degree in the dryer cylinder 54 may be appropriately selected, and is usually set to 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 set to a value close to each other, or may be set to be different from each other, and when the temperature on the downstream side (die 59 side) is set to be higher than the temperature on the upstream side (dehydration cylinder section 53 side), the drying efficiency is preferably improved.

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 into a shape corresponding to a predetermined nozzle shape by passing through the discharge port of the die 59. The acrylic rubber passing through the die 59 can be molded into various shapes such as pellets, columns, round bars, sheets, etc., depending on the nozzle shape of the die 59, and in the present invention, into sheets. Between the screw and the die 59, a perforated plate, a metal mesh, or the like may be provided.

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

dewatering slits

56a, 56b, and 56c provided in the 1 st to 3 rd dewatering cylinders 53a to 53c, respectively, as described above, drain and discharge the water contained in the aqueous pellets, and dewater the aqueous pellets.

The hydrous 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 water-containing pellets sent to the dryer section 54 are plasticized and mixed into a melt, and are sent downstream while being heated by heat release. 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 the dryer barrel 54 to obtain a melt of the acrylic rubber, which is supplied to the die 59 by the rotation of the pair of screws in the barrel 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 number of rotations (N) of the pair of screws in the barrel unit 51 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, from the viewpoint of being able to efficiently reduce the water content of the acrylic rubber and the amount of methyl ethyl ketone insoluble components.

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 number of revolutions (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 cylinder unit 51 is not particularly limited, but is usually in the range of 0.1 to 0.25[ kw.h/kg ] or more, 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 0.2 to 0.6[ A.multidot.h/kg ] or more, preferably 0.25 to 0.55[ A.multidot.h/kg ], and 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 40 to 150[ l/s ] or more, preferably 45 to 125[ l/s ], and 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 4000 to 8000[ Pa.s ] or less, preferably 4500 to 7500[ Pa.s ], and more preferably 5000 to 7000[ Pa.s ].

The cooling device 6 shown in fig. 1 is configured to cool the dried rubber obtained through the dehydration step by a dehydrator and the drying step by a dryer. As the cooling method by the cooling device 6, various methods including an air cooling method by blowing or cooling air, a water spraying method, a dipping method in water, and the like can be employed. 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 extruder 5 is extruded into various shapes such as pellets, columns, round bars, sheets, etc., according to the nozzle shape of the die 59, and is molded into a sheet in the present invention. Hereinafter, a description will be given of a conveyor type cooling device 60 as an example of the cooling device 6 with reference to fig. 3, and the conveyor type cooling device 60 cools the sheet-shaped dry rubber 10 molded into a sheet shape.

Fig. 3 shows a structure of a preferred transport type cooling device 60 as the cooling device 6 shown in fig. 1. The conveying type cooling device 60 shown in fig. 3 is configured to cool by an air cooling method while conveying the sheet-like dry rubber 10 discharged from the discharge port of the die 59 of the screw extruder 5. By using this conveyor cooling device 60, the sheet-like dry rubber discharged from the screw extruder 5 can be cooled appropriately.

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

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

The conveyor 61 has

rollers

62, 63, and a conveyor belt 64 wound around these

rollers

62, 63 in tension and on which the sheet-like dry rubber 10 is placed. The conveyor 61 is configured to continuously convey the sheet-like dry rubber 10 discharged from the die 59 of the screw extruder 5 to the downstream side (right side in fig. 3) on the conveyor belt 64.

The cooling unit 65 is not particularly limited, and examples thereof include a cooling unit having a structure capable of blowing cooling air sent from a cooling air generating unit, 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 unit 65 of the transport 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 dry 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 unit 65, the discharge speed of the sheet-like dry rubber 10 discharged from the die 59 of the screw extruder 5, the target cooling speed, the 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 conveying type cooling device 60 shown in fig. 3, the sheet-like dry rubber 10 is cooled by blowing cooling air from the cooling unit 65 to the sheet-like dry rubber 10 while conveying the sheet-like dry rubber 10 discharged from the die 59 of the screw extruder 5 by the conveyor 61.

The transport cooling device 60 is not particularly limited to the configuration having 1

conveyor

61 and 1 cooling unit 65 as shown in fig. 3, and may have a configuration having 2 or more conveyors 61 and 2 or more cooling units 65 corresponding thereto. In this case, the total length of the 2 or more conveyors 61 and the cooling unit 65 may be set to the above range.

The glue coating device 7 shown in fig. 1 is constituted as follows: the dried rubber extruded from the screw extruder 5 and cooled by the cooling device 6 is processed to produce a one-piece bale. As described above, the screw extruder 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 carry out rubber coating on the dried rubber thus molded into various shapes. The weight, shape, etc. of the acrylic rubber bag manufactured by the rubber bag forming apparatus 7 are not particularly limited, and for example, an acrylic rubber bag having a substantially rectangular parallelepiped shape of about 20kg can be manufactured.

The rubber packing device 7 has, for example, a packer, and can compress cooled dry rubber by the packer to manufacture an acrylic rubber packing.

In addition, in the case of producing the sheet-like dry rubber 10 by the screw extruder 5, an acrylic rubber bag 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 packing 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. By stacking a plurality of sliced dried rubbers 16 cut into a predetermined size by a cutting mechanism, an acrylic rubber bag in which the sliced dried rubbers 16 are stacked can be manufactured.

In the case of producing an acrylic rubber bag 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, air can be discharged satisfactorily 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, use is made of ¹ The monomer structure of each monomer unit in the acrylic rubber was confirmed by H-NMR, and the residual reactivity of the reactive group 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 rate is approximately 100% which cannot be confirmed by the unreacted monomers, 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 or the acrylic rubber molded body is measured by the following method.

(1) The carboxyl group amount was calculated by dissolving a sample (acrylic rubber or acrylic rubber molded body) in acetone and potentiometric titration with potassium hydroxide solution.

(2) The amount of epoxy groups was calculated by dissolving a sample in methyl ethyl ketone, adding a predetermined amount of hydrochloric acid thereto to react with epoxy groups, and titrating the amount of residual hydrochloric acid 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 or the acrylic rubber molded body was measured according to JIS K6228A method.

[ ash component amount ]

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

[ molecular weight and molecular weight distribution ]

The molecular weights (Mw, mn, mz) and molecular weight distributions (Mw/Mn and Mz/Mw) of the acrylic rubber are absolute molecular weights and absolute molecular weight distributions measured by GPC-MALS method using, as a solvent, a solution in which lithium chloride was added to dimethylformamide at a concentration of 0.05mol/L and 37% concentrated hydrochloric acid was added at a concentration of 0.01%.

The structure of the gel permeation chromatography multi-angle light scattering photometer as a main device was composed of a pump (manufactured by LC-20ADOpt corporation, shimadzu corporation) and a differential refractive light detector (manufactured by Optilab re Huai Ya trickplay company) as a detector, and a multi-angle light scattering detector (manufactured by DAWN HELEOS Huai Ya trickplay company).

Specifically, a multi-angle laser light scattering device (MALS) and a differential refractive index detector (RI) were mounted in a GPC (Gel Permeation Chromatography) apparatus, and the light scattering intensity and refractive index difference of a molecular chain solution having been separated in size by the GPC apparatus were measured in accordance with the elution time, whereby the molecular weight of a solute and the content thereof were calculated and obtained in order. 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 or acrylic rubber molded article) 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, inc.).

[ amount of methyl ethyl ketone insoluble component ]

The amount (%) of the insoluble component in methyl ethyl ketone in the acrylic rubber or the acrylic rubber molded article was determined by the following method.

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

Methyl ethyl ketone insoluble component amount (%) =100× (X-Y)/X

[ specific gravity ]

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

The measured value obtained by the following measuring method was the density, but the density of water was set to 1Mg/m ³ To obtain specific gravity. Specifically, the specific gravity of the rubber sample obtained by the method a according to JIS K6268 crosslinked rubber-density measurement is a value obtained by dividing the mass of the rubber sample by the volume of voids containing the rubber sample, and the density of the rubber sample obtained by dividing the density of water by the method a according to JIS K6268 crosslinked rubber-density measurement is a value obtained by dividing the density of the rubber sample by the density of water (when the density of the rubber sample is divided by the density of water, the numerical values are the same, and the unit disappears). 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 from a hanger on a chemical balance having an accuracy of 1mg so that the bottom edge of the test piece was 25mm or more from the chemical balance tray using a fine nylon wire having a mass of less than 0.010g, and the mass (m 1) of the test piece was measured in the atmosphere 2 times until mg.

(2) Next, 250cm of the sample was placed on a chemical balance tray ³ The beaker was filled with distilled water which was boiled and cooled to a standard temperature, the test piece was immersed therein, bubbles adhering to the surface of the test piece were removed, the swinging of the pointer of the balance was observed for several seconds, it was confirmed that the pointer was not slowly swung by convection, and the mass (m 2) of the test piece in water was measured in mg units for 2 times.

(3) In addition, when the density of the test piece is less than 1Mg/m ³ When the test piece was floated in water, a weight was added to the test piece, and the mass of the weight in water (m 3), the mass of the test piece, and the mass of the weight (m 4) were measured 2 times in mg units.

(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 ) The calculated density divided by the density of water (1.00 Mg/m ³ ) The specific gravity of the rubber sample was determined.

(Density of rubber sample when weight is not used)

Density=m1/(m 1-m 2)

(Density of rubber sample when heavy object 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]

Regarding the pH, after 6g (+ -0.05 g) of acrylic rubber or an acrylic rubber molded body was dissolved with 100g of tetrahydrofuran, 2.0ml of distilled water was added thereto, and after confirming complete dissolution, measurement was performed with a pH electrode.

[ Complex viscosity ]

The complex viscosity η was measured by measuring temperature dispersion (40 to 120 ℃) at a deformation of 473% and 1Hz using a dynamic viscoelasticity measuring device "rubber processing analyzer RPA-2000" (manufactured by alpha technologies Co., ltd.), and the complex viscosity η at each temperature was obtained. Here, the dynamic viscoelasticity at 60 ℃ and the dynamic viscoelasticity at 100 ℃ are taken as the complex viscosity η (60 ℃) and the complex viscosity η (100 ℃) respectively, and the ratio η (100 ℃) and 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 ]

The crosslinking property of the rubber sample was determined by calculating the rate of change in the breaking strength of the rubber crosslinked material subjected to 2 hours of secondary crosslinking and the breaking strength of the rubber crosslinked material subjected to 4 hours of secondary crosslinking ((breaking strength of the 4-hour crosslinked rubber crosslinked material/breaking strength of the 2-hour crosslinked rubber crosslinked material) ×100) 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 ]

The roll processability of the rubber sample was evaluated by observing the roll-winding property and the state of the rubber when the rubber sample was rolled, according to the following criteria.

And (3) the following materials: easy kneading, easy winding around the roll, no detachment from the roll was observed, and the surface of the rubber composition after kneading was smooth

O: the rubber composition was easily kneaded and easily wound around a roll, and detachment from the roll was not observed, and irregularities were slightly observed on the surface of a part of the rubber composition after kneading.

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

Delta: the rubber composition was easily kneaded, and the roll-windability was slightly poor, and the surface of the kneaded rubber composition was rough.

X: the kneading is loaded and the roll windability is poor

[ Banbury processability ]

The banbury processability of the rubber samples was evaluated as follows: the rubber sample was put into a banbury mixer heated to 50 ℃ and plasticated for 1 minute, and then compounding agent a of the formulation of the rubber mixture shown in table 1 was put into the mixer, and the time until the rubber mixture in the first stage was integrated and the maximum torque value, that is, BIT (Black Incorporation Time, carbon black mixing time) was measured, and the evaluation was made using an index of comparative example 2 as 100 (the smaller the index was, the more excellent the processability was).

[ evaluation of storage stability ]

For the storage stability of the rubber sample, the change rate of the water content before and after the test was calculated by putting the rubber sample into a constant temperature and humidity tank (SH-222 manufactured by espek) at 45 ℃ x 80% rh, and the evaluation was performed using the index of comparative example 2 as 100 (the smaller the index, the more excellent the storage stability).

[ evaluation of Water resistance ]

For the water resistance of the rubber sample, the crosslinked product of the rubber sample was immersed in distilled water at 85℃for 100 hours in accordance with JIS K6258, and the volume change rate before and after immersion was calculated according to the following formula, and the evaluation was performed using the index of comparative example 2 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 evaluated according to JIS K6262, by measuring the compression set after leaving the rubber crosslinked product of the rubber sample to stand at 175℃for 90 hours in a state of being compressed by 25%.

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 normal physical properties of the rubber sample were measured according to JIS K6251, and the breaking strength, 100% tensile stress and elongation at break of the rubber crosslinked product of the rubber sample were evaluated according to the following criteria.

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

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

(3) The 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 insoluble methyl ethyl ketone ]

For the evaluation of the deviation of the methyl ethyl ketone insoluble content of the rubber sample, the methyl ethyl ketone insoluble content at 20 points arbitrarily selected from 20 parts (20 kg) of the rubber sample was measured, and the evaluation was performed based on the following criteria.

And (3) the following materials: calculating the average value of the methyl ethyl ketone insoluble component amounts at 20 points of measurement, wherein all the 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 methyl ethyl ketone insoluble component amounts at 20 points of measurement, wherein the total of the 20 points of measurement is within the range of the average value.+ -. 5 (1 at 20 points of measurement is outside the range of the average value.+ -. 3, but the total of the 20 points is within the range of the average value.+ -. 5)

X: calculating the average value of the methyl ethyl ketone insoluble component amounts at 20 points of measurement, 1 in the 20 points of measurement being out of the range of.+ -. 5 of the average value

[ 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

In a mixing vessel having a homogenizer, as shown in Table 2-1, 46 parts of pure water was added, and 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 stirred to obtain a monomer emulsion, 1.8 parts of sodium octoxyethylenephosphate as an emulsifier.

Into a polymerization reaction vessel equipped with a thermometer and a stirring device, 170 parts of pure water and 3 parts of the monomer emulsion obtained above were charged, 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 rate reached approximately 100%, to obtain an emulsion polymerization solution.

Next, in a solidification tank having a thermometer and a stirring device, in 350 parts of a 2% aqueous magnesium sulfate solution (solidification liquid using magnesium sulfate as a solidification agent) heated to 80 ℃ and vigorously stirred at 600 revolutions (circumferential speed 3.1 m/s) of a stirring blade of the stirring device, the emulsion polymerization liquid obtained above was heated to 80 ℃ and continuously added to solidify the polymer, to obtain a solidified slurry containing aggregates of acrylic rubber as a solidified material and water. The pellets were filtered from the resulting slurry, while 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 stirred for 15 minutes, the aqueous pellets were washed, then the water was discharged, 194 parts of hot water (70 ℃) was added again and stirred for 15 minutes, and washing of the aqueous pellets was performed (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 15, dehydrated and dried, and a sheet-like dried rubber having a width of 300mm and a thickness of 10mm was extruded. 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 15.

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 drying drum: 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

Full length of screw (L): 4620mm

·L/D：35

Revolution of screw: 135rpm

Vacuum of the dryer barrel: 10kPa

The amount of rubber extruded from the 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 resultant was laminated to obtain an acrylic rubber (A) (acrylic rubber bag) before the temperature was lowered to 40℃or lower. 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 "formula 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 compounded with the compounding agent B of "formula 1" and mixed (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 metal 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, and secondary crosslinking was performed, 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 order to evaluate the crosslinkability. 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 the inorganic radical generator was changed to 0.21 part, and 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, whereby the properties were evaluated. The results are shown in Table 2-2.

Reference example 1

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 packed in a 300X 650X 300mm packer and compacted at a pressure of 3MPa for 25 seconds to obtain rubber-covered acrylic rubber. The properties of the acrylic rubber (C) were evaluated (the compounding agent was changed to "formula 2"), and the results are shown in Table 2-2.

Reference example 2

Acrylic rubber (D) was obtained in the same manner as in reference example 1 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 characteristic was evaluated (the compounding agent was changed to "formula 3"). The results are shown in Table 2-2.

Reference example 3

Acrylic rubber (E) was obtained in the same manner as in reference example 1 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 "formula 4"). The results are shown in Table 2-2.

Reference example 4

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 rubber-covered acrylic rubber. The properties of the acrylic rubber (F) were evaluated (the compounding agent was changed to "formula 2"), and the results are shown in Table 2-2.

Reference example 5

Acrylic rubber (G) was obtained in the same manner as in reference example 4 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 characteristic was evaluated (the compounding agent was changed to "formula 3"). The results are shown in Table 2-2.

Reference example 6

Acrylic rubber (H) was obtained in the same manner as in reference example 4 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 "formula 4"). The results are shown in Table 2-2.

Reference example 7

Acrylic rubber (I) was obtained and evaluated for each characteristic in the same manner as in reference example 6 except that the amount of potassium persulfate as the inorganic radical generator was changed to 0.22 part, and the acrylic rubber was obtained in the form of a pellet by not adding a chain transfer agent and not being rubber-packed by a packer. The results are shown in Table 2-2.

Comparative example 1

An acrylic rubber (J) was obtained in the same manner as in reference example 7 except that a 0.7% aqueous magnesium sulfate solution was added to the stirred emulsion polymerization solution (stirring number 100rpm, circumferential speed 0.5 m/s) after emulsion polymerization to carry out a coagulation reaction, and each characteristic was evaluated. The results are shown in Table 2-2.

Comparative example 2

The emulsifier was changed to 0.709 part of sodium lauryl sulfate and 1.82 parts of polyoxyethylene lauryl ether, the coagulation liquid was changed to 0.7% sodium sulfate aqueous solution, and the cleaning method was changed to: acrylic rubber (K) was obtained in the same manner as in comparative example 1, except that the washing of the aqueous pellets in which 194 parts of industrial water was added to 100 parts of the aqueous pellets after the coagulation reaction and the aqueous pellets were stirred at 25℃for 5 minutes and then discharged from the coagulation tank, then 194 parts of an aqueous sulfuric acid solution having a pH of 3 was added and stirred at 25℃for 5 minutes, and after 1 acid washing was performed by discharging water from the coagulation tank, 194 parts of pure water was added and 1 pure water washing was performed, and the properties were evaluated. The results are shown in Table 2-2.

Comparative example 3

Acrylic rubber (L) was obtained in the same manner as in comparative example 2 except that 0.025 parts of n-dodecyl mercaptan as a chain transfer agent was continuously added to the monomer emulsion, and the aqueous pellet was washed by adding 194 parts of industrial water only 2 times and then draining the water from the coagulation tank after stirring at 25℃for 5 minutes in the coagulation tank. 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 rubber (A) to (B) of the present invention comprises a binding unit derived from a (meth) acrylic acid ester selected from at least one of an alkyl (meth) acrylate and an alkoxyalkyl (meth) acrylate, a binding unit derived from a monomer having a reactive group selected from at least one of a carboxyl group, an epoxy group and a chlorine atom, and a binding unit derived from another monomer used as required, and the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is in the range of 3.7 to 6.5, the amount of methyl ethyl ketone insoluble components is 50% by weight or less, the amount of ash components is 0.15% by weight or less, the total amount of sodium, magnesium, calcium, phosphorus and sulfur in the ash components is 50% by weight or more, and the adhesive rubber composition has excellent rolling processability, primary processability, green processability, permanent set and storage stability (Table 1) and excellent water resistance (normal state 2) on the basis of the absolute molecular weight and absolute molecular weight distribution (Mw) measured by GPC-MALS method.

It is clear from tables 2 to 2 that the acrylic rubbers (A) to (L) produced under the conditions of examples, reference examples and comparative examples of the present invention have a carboxyl group, an epoxy group and a plasma-reactive group such as a chlorine atom, and the weight average molecular weight (Mw) of the absolute molecular weight measured by GPC-MALS method is more than 100 ten thousand and has a large value, so that they are excellent in both crosslinking property in a short period of time, compression set resistance and normal physical properties including strength characteristics (examples 1 to 2, reference examples 1 to 7 and comparative examples 1 to 3). However, the acrylic rubbers (J) to (L) of comparative examples 1 to 3 are excellent in crosslinking property, compression set resistance and strength characteristics, but are inferior in roll processability, banbury processability, water resistance and storage stability (comparative examples 1 to 2), and are inferior in roll processability, water resistance and storage stability (comparative example 3).

As is clear from table 2-2, regarding the roll processability, when the weight average molecular weight (Mw) is between 100 ten thousand and 350 ten thousand and the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is large, it is preferably 3.5 or more, more preferably 3.7 or more, and still more preferably 4 or more, the roll processability can be significantly improved without impairing the strength characteristics (comparison of examples 1 to 2 with comparative examples 1 to 3).

As is clear from tables 2-1 and 2-2, the acrylic rubber having a large Mw and a wide Mw/Mn, which is excellent in strength characteristics and roll processability, can be obtained by extending one polymer chain with an inorganic radical generator and adding a chain transfer agent (n-dodecylmercaptan) in portions and thereafter (examples 1 to 2 and reference examples 1 to 6). Further, it was found that the number of times of batch post-addition of the chain transfer agent was significantly affected in order to efficiently enlarge Mw/Mn, and that Mw/Mn, which was 2 times of batch post-addition, was wider than 3 times (comparison of reference examples 1 to 3 and reference examples 4 to 6), but when the chain transfer agent was continuously added, the Mw/Mn was slightly enlarged and improvement in roll processability was limited (comparative example 3). This is presumably because, although the GPC-MALS method is not completely bimodal in the drawing, the chain transfer agent is added after the chain transfer agent is added in portions, so that the Mw/Mn is widened and the roll processability is greatly improved. In addition, although not shown in table 2-1, in the present example, sodium ascorbate as a reducing agent was added 120 minutes after the start of polymerization, whereby a high molecular weight component of the acrylic rubber was easily produced, and the effect of enlarging Mw/Mn of the chain transfer agent added after the start of the polymerization was increased. Further, although not shown in table 2-1, when an organic radical generator is used instead of an inorganic radical generator, mw/Mn becomes small, and roll processability is remarkably lowered, which is not preferable.

As is clear from tables 2 to 2, the acrylic rubber has excellent banbury workability in which the amount of methyl ethyl ketone insoluble components is related to the banbury workability, and the methyl ethyl ketone insoluble components are small. Further, it was found that the banbury workability of the acrylic rubber was excellent particularly when the amount of methyl ethyl ketone insoluble component was 50 wt% or less, preferably 30 wt% or less (comparison of reference examples 1 to 6 and comparative example 3 with reference example 7 and comparative examples 1 to 2), and was extremely excellent when the amount of methyl ethyl ketone insoluble component was 10 wt% or less, preferably 5 wt% or less (examples 1 to 2). It is also found that the amount of methyl ethyl ketone insoluble components in the acrylic rubber can be reduced by emulsion polymerization in the presence of a chain transfer agent (reference examples 1 to 6 and comparative example 3), and particularly when the polymerization conversion is increased in order to improve the strength characteristics, the amount of methyl ethyl ketone insoluble components increases sharply, so that in reference examples 1 to 6, in which a chain transfer agent is added after the latter half of the polymerization, the formation of methyl ethyl ketone insoluble components can be suppressed. Further, it was found that the amount of methyl ethyl ketone insoluble components of the acrylic rubber can be significantly reduced by drying the aqueous pellets using a screw type biaxial extrusion dryer, and thus the banbury processability of the produced acrylic rubber can be significantly improved (comparison of examples 1 to 2 with reference examples 1 to 6). In the present invention, although not shown in the present example, it was confirmed that the amount of methyl ethyl ketone insoluble component (comparative examples 1 to 2) which increases sharply in emulsion polymerization due to the absence of the addition of the chain transfer agent was eliminated by melt kneading in a screw type biaxial extrusion dryer in a state of substantially containing no moisture (water content less than 1% by weight), and the banbury processability was greatly improved without impairing the strength characteristics.

As is clear from Table 2-2, the acrylic rubbers (A) to (B) of examples 1 to 2 of the present invention are excellent in water resistance, and the acrylic rubbers (C) to (I) of reference examples 1 to 7 are excellent in water resistance, relative to the acrylic rubbers (J) to (L) of comparative examples 1 to 3. It is also clear that the acrylic rubber (C, F) of reference examples 1 and 4 having carboxyl groups and the acrylic rubber (D, G) of reference examples 2 and 5 having epoxy groups are twice as excellent as the acrylic rubber (E, H, I) of reference examples 3, 6 and 7 having chlorine atoms in terms of the influence of the difference in the ion reactive groups on the water resistance from the reference examples 1 to 7 having the same ash amount. The acrylic rubbers (a) to (B) according to the examples of the present invention, the acrylic rubbers (C) to (I) according to the reference examples, and the acrylic rubbers (J) to (L) according to the comparative examples each have a total element content of more than 90% by weight of phosphorus, magnesium, sodium, calcium, and sulfur in ash, and are excellent in properties such as water resistance and mold releasability, but particularly even if the ash content is the same, the rubber having a large proportion of phosphorus and magnesium in ash is excellent in water resistance (comparison of reference example 7 and comparative example 2).

Further, as is clear from tables 2 to 2, the water resistance of the acrylic rubber is greatly affected by the ash content. In the ash content of the acrylic rubber, ash containing a large amount of phosphorus and magnesium is difficult to remove during cleaning as compared with ash containing a large amount of sodium and sulfur, and a large amount of ash remains during cleaning of the aqueous pellets subjected to the normal coagulation step (comparison of comparative example 1 and comparative example 2). However, it was also found that even with ash having a large content of phosphorus and magnesium, the coagulation reaction can be carried out by adding an emulsion polymerization liquid after emulsion polymerization to a coagulating liquid by preparing a concentrated aqueous solution (coagulating liquid) from the coagulating agent and stirring vigorously, washing the resultant aqueous pellets with hot water (reference examples 1 to 7), and dehydrating the washed aqueous pellets (examples 1 to 2). It is also known that even if the ash amount is the same, the water resistance of the acrylic rubber can be significantly improved by increasing the contents of phosphorus and magnesium in the ash and by setting the ratio of phosphorus to magnesium to a specific range (comparison of reference examples 1 to 7 and comparative example 2). It was found that the water resistance of the acrylic rubber was different depending on the type of the reactive group, and that the carboxyl group and the epoxy group were superior to the chlorine atom (comparison of reference examples 1 to 2 and 3, and comparison of reference examples 4 to 5 and 6). In addition, although not shown in tables 2-1 and 2-2, in the production of the acrylic rubber similar to comparative example 2 (the ash content of sodium and sulfur is high), the water resistance can be significantly improved by performing the coagulation reaction and the washing in the same manner as in reference example 3, and further, the index of the water resistance can be improved to about 10 to 15 by dehydrating and drying the washed aqueous pellets by a screw type biaxial extrusion dryer in the same manner as in example 1, whereby the ash content can be 0.15 wt% or less, preferably 0.13 wt% or less. In addition, although the ash content can be reliably reduced up to the 3 rd time in the water washing at room temperature, the ash content reduction effect after the 4 rd time is hardly seen, although the 3 rd time and the 4 th time are hardly different from each other, with respect to the influence of the number of washing times on the ash content in the acrylic rubber. On the other hand, in the washing in hot water, the ash content in the acrylic rubber was reduced until the 2 nd time, and the washing effect after the 3 rd time was hardly seen.

As is clear from tables 2 to 2, the acrylic rubbers (a) to (B) of the present invention are excellent in crosslinking property, roll processability, banbury processability, water resistance, compression set resistance and strength characteristics, and also are remarkably excellent in storage stability (examples 1 to 2). It was also found that the storage stability of the acrylic rubber was greatly related to the specific gravity of the acrylic rubber, and when the specific gravity was large, the acrylic rubber did not trap air, and the storage stability was excellent (comparative examples 1 to 2, reference examples 1 to 6, and comparative examples 1 to 3). The acrylic rubber having a high specific gravity can be obtained by compacting the acrylic rubber in pellet form by a packer and rubber-wrapping (reference examples 1 to 6), and more preferably by extruding the acrylic rubber into a sheet without involving air by a screw type biaxial extrusion dryer, cutting the sheet at a specific temperature, and laminating the sheet to obtain rubber-wrapped (examples 1 to 2). In the present invention, it was found that, in particular, the acrylic rubber bag obtained by laminating the acrylic rubber sheets melt-kneaded and dried under reduced pressure, the storage stability was significantly improved without impairing the short-time crosslinkability, roll processability, compression set resistance, normal physical properties including strength characteristics, and water resistance (examples 1 to 2). Further, it is found that the storage stability of the acrylic rubber is more preferable when the ash content is smaller or the pH is within a specific range (examples 1 to 2).

From these results, it is apparent that the acrylic rubber (a) to (B) of the present invention comprises a binding unit derived from a (meth) acrylic acid ester selected from at least one of an alkyl (meth) acrylate and an alkoxyalkyl (meth) acrylate, a binding unit derived from a monomer having a reactive group selected from at least one of a carboxyl group, an epoxy group and a chlorine atom, a ratio (Mw/Mn) of a weight average molecular weight (Mw) to a number average molecular weight (Mn) of 3.7 to 6.5, an amount of methyl ethyl ketone insoluble components of 50 wt% or less, an amount of ash of 0.15 wt% or less, and a total amount of sodium, magnesium, calcium, phosphorus and sulfur in ash of 50 wt% or more, and that the adhesive rubber has a rolling processability, a water resistance, a banbury processability, a water resistance, a compression set and physical properties including a compression set property, and a high balance property, and a normal state stability, which are also excellent in terms of the weight average molecular weight (Mw) and the weight distribution, as measured by GPC-MALS method.

[ regarding the particle size of the resulting hydrous pellets ]

Regarding the aqueous pellets produced in the coagulation step of examples 1 to 2, reference examples 1 to 7 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 JIS sieves. 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%

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

Reference example 2: (1) 91 wt%, (2) 90 wt%, and (3) 83 wt%

Reference example 3: (1) 93 wt%, (2) 91 wt%, and (3) 89 wt%

Reference example 4: (1) 95 wt%, (2) 89 wt%, and (3) 80 wt%

Reference example 5: (1) 92 wt%, (2) 92 wt%, (3) 88 wt%

Reference example 6: (1) 94 wt%, (2) 93 wt%, (3) 87 wt%

Reference example 7: (1) 90 wt%, (2) 89 wt%, and (3) 88 wt%

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

From the results, it was found that even when the same washing was performed, the amount of ash remaining in the acrylic rubber or the acrylic rubber bag was different depending on the size of the aqueous aggregates generated in the coagulation step, and that the washing efficiency of the aqueous aggregates having a large specific ratio of (1) to (3) was high, the amount of ash was reduced, and the water resistance was excellent (comparison between reference examples 1 to 7 and comparative example 1 of tables 2-2). Further, it was found that the ash removal rate at the time of dehydration of 20 wt% was also high even when the specific proportions of (1) to (3) were large, the ash amount was further reduced, and the water resistance of the acrylic rubber was significantly improved (comparison of examples 1 to 2 with reference examples 1 to 7). In addition, it is understood from the comparison of reference example 6 and reference example 7 that the particle size of the aqueous pellets produced in the solidification step is independent of the presence or absence of the chain transfer agent.

Further, for ease of reference, the particle size ratio of the aqueous pellets produced in reference example 8 and reference example 9 and the ash content in the acrylic rubber were measured. In reference example 8, the procedure was carried out in the same manner as in comparative example 1 except that the emulsion polymerization liquid was added to the coagulation liquid in the coagulation step; the procedure of comparative example 1 was repeated except that the emulsion polymerization solution was added to the coagulation solution and the coagulant concentration of the coagulation solution was changed from 0.7% by weight to 2% by weight in referential example 9. The results are shown below. When the stirring number of the solidification liquid of reference example 9 was changed to 600rpm and the circumferential speed was increased from 0.5m/s to 3.1m/s, the same conditions as those of reference example 7 were employed.

Reference example 8: (1) 90 wt%, (2) 55 wt%, and (3) 22 wt%, and ash content 0.55 wt%

Reference example 9: 91 wt%, 70 wt%, 40 wt% and 0.41 wt% ash

From this result, it was found that the method (Lx ∈) of adding the emulsion polymerization liquid to the stirred coagulation liquid was changed from the method (Lx ∈) of increasing the concentration of the coagulation liquid (2%) in the coagulation reaction to the method of adding the emulsion polymerization liquid to the stirred coagulation liquid (stirring number 600 rpm/circumferential speed 3.1 m/s), and the particle size of the resulting aqueous pellets was concentrated in a specific range of 710 μm to 4.75mm, whereby the cleaning efficiency by hot water cleaning and the removal efficiency of the emulsifier and coagulant during dehydration were significantly improved, the ash content of the acrylic rubber was reduced, and the water resistance was significantly improved without impairing the properties such as crosslinking property, roll workability, compression set resistance, and normal physical properties including strength characteristics of the acrylic rubber (examples 1 to 2).

Example 3

Acrylic rubber (M) 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, 1.5 parts of mono-n-butyl fumarate and 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, in table 3-1, 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 are shown.

Example 4

Acrylic rubber (N) 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, in table 3-1, 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 are shown.

Example 5

An acrylic rubber (O) 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 the operating conditions of the screw-type biaxial extrusion dryer were changed to high shear (maximum torque 45n·m), and the properties (compounding agent was changed to "formula 3"), and the results were evaluated as shown in table 3-2. In addition, in table 3-1, 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 are shown.

Example 6

An acrylic rubber (P) was obtained in the same manner as in example 5 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 "formula 1"), and the results are shown in table 3-2. In addition, in table 3-1, 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 are shown.

Example 7

An acrylic rubber (Q) was obtained in the same manner as in example 5 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 (compounding agent was changed to "formula 2"), and the results are shown in table 3-2. In addition, in table 3-1, 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 are shown.

Example 8

Acrylic rubber (R) was obtained in the same manner as in example 4 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 (compounding agent was changed to "formula 3"), and the results were evaluated as shown in table 3-2. In addition, in table 3-1, 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 are shown.

Example 9

An acrylic rubber (S) was obtained in the same manner as in example 8 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 (compounding agent was changed to "formula 1"), and the results are shown in Table 3-2. In addition, in table 3-1, 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 are shown.

Example 10

An acrylic rubber (T) was obtained in the same manner as in example 8 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 (compounding agent was changed to "formula 2"), and the results are shown in table 3-2. In addition, in table 3-1, 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 are shown.

[ Table 3-1]

[ Table 3-2]

As is clear from tables 3-1 and 3-2, the roll processability of the acrylic rubber of the present invention can be remarkably improved without impairing the properties such as crosslinking property, banbury processability, water resistance, compression set resistance and strength characteristics by dehydrating and drying the aqueous pellets by increasing the maximum torque of the screw type biaxial extrusion dryer to a specific region (making high shear) (comparison of examples 3 to 4 with examples 5 to 10). Further, it was found that the acrylic rubber composed of a high molecular weight component and a low molecular weight component, which was emulsion polymerized by adding a chain transfer agent thereto, was dried by applying shear using a screw type biaxial extruder dryer, and the molecular weight distribution was further appropriately enlarged, and the roll processability was further improved. On the other hand, it is clear that although not shown in tables 3-1 and 3-2, when the molecular weight distribution (Mw/Mn) is excessively increased, for example, to 10 or more by adding a chain transfer agent excessively, the low molecular weight component of the acrylic rubber is excessive, and the strength characteristics and compression set resistance are poor, which is not preferable.

Further, the variation in the amount of methyl ethyl ketone insoluble component was evaluated for each rubber sample 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 evaluation of the amount of methyl ethyl ketone insoluble component of the rubber sample was performed based on the above reference.

When the acrylic rubbers (a) to (B) and (M) to (T) obtained in examples 1 to 10 and the acrylic rubber (J) obtained in comparative example 1 as rubber samples were evaluated for the deviation of the methyl ethyl ketone insoluble component amounts, the results of the acrylic rubbers (a) to (B) and (M) to (T) of examples 1 to 10 of the present invention were all "good", and the result of the acrylic rubber (J) of comparative example 1 was "×".

From this, it is assumed that the acrylic rubbers (a) to (B) and (M) to (T) are melt-kneaded by a screw type biaxial extruder, and melt-kneaded and dried in a state substantially free from moisture (water content less than 1 wt%) so that the amount of methyl ethyl ketone insoluble component is almost eliminated and the deviation of the amount of methyl ethyl ketone insoluble component is almost eliminated, whereby the banbury processability can be remarkably improved without impairing the crosslinkability, roll processability, compression set resistance and normal physical properties including strength characteristics.

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

Regarding the acrylic rubber compositions comprising the acrylic rubbers (A) to (B) and (M) to (T) of examples 1 to 10, the Mooney scorch storage stability was evaluated on the basis of the following criteria according to the method for evaluating the processing stability based on the Mooney scorch inhibition described above, by measuring the Mooney scorch time T5 (minutes) at a temperature of 125℃according to JIS K6300. 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

The cooling rate of the sheet-like dry rubber extruded from the screw type biaxial extrusion dryer was as high as that of example 1, and was approximately 200 ℃/hr, and was 40 ℃/hr or more for both the acrylic rubbers (a) to (B) and (M) to (T).

[ mold releasability of Metal mold ]

The rubber compositions of the acrylic rubbers (A) to (B) and (M) to (T) obtained in examples 1 to 10 were press-fitted into a 10 mm. Phi. Times.200 mm metal mold, crosslinked at a metal mold temperature of 165℃for 2 minutes, and then the rubber crosslinked product was taken out, and mold releasability was evaluated on the basis of the following criteria, and at this time, the acrylic rubbers (A) to (B) and (M) to (T) were all "excellent", i.e., good evaluation.

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

And (2) the following steps: the mold can be easily released from the mold, but it was confirmed that there was little mold residue

Delta: can be easily released from a metal mold, but has a small amount of mold residues

X: difficult to release from metal molds

Description of the reference numerals

1: acrylic rubber manufacturing system

3: coagulation device

4: cleaning device

5: screw extruder

6: cooling device

7: glue packaging device

Claims

1. An acrylic rubber comprising a binding unit derived from a (meth) acrylic acid ester, a binding unit derived from a monomer having a reactive group, and a binding unit derived from another monomer used as required,

the (methyl) acrylic ester is selected from at least one of (methyl) acrylic acid alkyl ester and (methyl) acrylic acid alkoxy alkyl ester, the reactive group is selected from at least one of carboxyl, epoxy and chlorine atom,

The weight average molecular weight (Mw) of the acrylic rubber is 1000000 ～ 3500000, the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is in the range of 3.7 to 6.5 based on the absolute molecular weight and the absolute molecular weight distribution measured by GPC-MALS method,

the acrylic rubber has an amount of methyl ethyl ketone insoluble components of 50 wt% or less, an ash content of 0.15 wt% or less, and a total amount of sodium, magnesium, calcium, phosphorus, and sulfur in the ash content of 50 wt% or more.

2. The acrylic rubber according to claim 1, wherein the reactive group is an ion-reactive group.

3. The acrylic rubber according to claim 1 or 2, wherein the measuring solvent of the GPC-MALS method is a dimethylformamide-based solvent.

4. The acrylic rubber according to any one of claims 1 to 3, wherein the amount of methyl ethyl ketone insoluble components is 10% by weight or less.

5. The acrylic rubber according to any one of claims 1 to 4, wherein the values when the amount of insoluble components of methyl ethyl ketone at 20 is measured are all in the range of (average ± 5% by weight).

6. The acrylic rubber according to any one of claims 1 to 5, wherein the specific gravity of the acrylic rubber is 1 or more.

7. The acrylic rubber according to any one of claims 1 to 6, wherein the pH of the acrylic rubber is 6 or less.

8. The acrylic rubber according to any one of claims 1 to 7, wherein the acrylic rubber is emulsion-polymerized using a phosphate salt or a sulfate salt as an emulsifier.

9. The acrylic rubber according to any one of claims 1 to 8, wherein the acrylic rubber is obtained by coagulating and drying the emulsion-polymerized polymer liquid using an alkali metal salt or a group 2 metal salt of the periodic table as a coagulant.

10. The acrylic rubber according to any one of claims 1 to 9, wherein the acrylic rubber is obtained by melt kneading and drying after solidification.

11. The acrylic rubber according to claim 10, wherein the melt-kneading and drying are performed in a substantially moisture-free state.

12. The acrylic rubber according to claim 10 or 11, wherein the melt-kneading and drying are performed under reduced pressure.

13. The acrylic rubber according to any one of claims 10 to 12, wherein the acrylic rubber is cooled at a cooling rate of 40 ℃/hr or more during the melt kneading and drying.

14. The acrylic rubber according to any one of claims 1 to 13, 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.

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

an emulsion polymerization step of initiating emulsion polymerization in the presence of a redox catalyst comprising an inorganic radical generator and a reducing agent, adding a chain transfer agent and a reducing agent in batches during the polymerization, and continuing the emulsion polymerization until the polymerization conversion becomes 90 wt% or more to obtain an emulsion polymerization solution;

a coagulation step of adding the obtained emulsion polymerization liquid to a stirred coagulation liquid, and coagulating the emulsion polymerization liquid to produce an aqueous pellet;

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

and a dehydration-drying step of dehydrating the washed aqueous pellets in a dehydration cylinder to a water content of 1 to 40 wt% and drying the same in the drying cylinder to less than 1 wt%, and extruding the dried rubber from the die head, using a dehydration cylinder having a dehydration slit, a drying cylinder under reduced pressure, and a screw type biaxial extrusion dryer having a die head at the front end.

16. The method for producing an acrylic rubber according to claim 15, wherein the method for producing an acrylic rubber produces the acrylic rubber according to any one of claims 1 to 14.

17. The method for producing an acrylic rubber according to claim 15 or 16, wherein the coagulant concentration of the coagulant is 0.1 to 20% by weight.

18. The method for producing an acrylic rubber according to any one of claims 15 to 17, wherein the number of stirring of the stirred coagulation liquid is 200rpm or more.

19. The method for producing an acrylic rubber according to any one of claims 15 to 18, wherein a peripheral speed of the stirred coagulation liquid is 1m/s or more.

20. The method according to any one of claims 15 to 19, wherein emulsion polymerization is performed using a phosphate salt or a sulfate salt as an emulsifier in the emulsion polymerization step.

21. The method for producing an acrylic rubber according to any one of claims 15 to 20, wherein the polymerization liquid produced in the emulsion polymerization step is coagulated and dried by using an alkali metal salt or a group 2 metal salt of the periodic table as a coagulant.

22. The method for producing an acrylic rubber according to claim 21, wherein the polymerization liquid produced in the emulsion polymerization step is coagulated by adding the polymerization liquid to an aqueous solution containing a coagulant containing an alkali metal salt or a group 2 metal salt of the periodic table and stirring the mixture.

23. The method according to any one of claims 15 to 22, wherein the polymerization liquid produced in the emulsion polymerization step is brought into contact with a coagulant to be coagulated, and then melt kneaded and dried.

24. The method for producing an acrylic rubber according to claim 23, wherein the melt kneading and drying are performed in a state substantially free of moisture.

25. The method for producing an acrylic rubber according to claim 23 or 24, wherein the melt kneading and drying are performed under reduced pressure.

26. The method according to any one of claims 23 to 25, wherein the acrylic rubber after melt-kneading and drying is cooled at a cooling rate of 40 ℃/hr or more.

27. The method according to any one of claims 15 to 26, wherein the aqueous pellet having a particle diameter in the range of 710 μm to 6.7mm in a proportion of 50 wt.% or more is washed, dehydrated and dried.

28. An acrylic rubber molded article obtained by molding the acrylic rubber according to any one of claims 1 to 14.

29. The acrylic rubber molded body according to claim 28, wherein the acrylic rubber molded body is a sheet or a bag.

30. A rubber composition comprising a rubber component comprising the acrylic rubber according to any one of claims 1 to 14 and/or the acrylic rubber molded body according to claim 28 or 29, a filler, and a crosslinking agent.

31. The rubber composition according to claim 30, wherein the filler is a reinforcing filler.

32. The rubber composition according to claim 30, wherein the filler is a carbon black.

33. The rubber composition according to claim 30, wherein the filler is a silica type.

34. The rubber composition of any of claims 30-33, wherein the cross-linking agent is an organic cross-linking agent.

35. The rubber composition according to any one of claims 30 to 34, wherein the crosslinking agent is a multi-component compound.

36. The rubber composition according to any one of claims 30 to 35, wherein the crosslinking agent is an ion-crosslinkable compound.

37. The rubber composition according to claim 36, wherein the crosslinking agent is an ion-crosslinkable organic compound.

38. The rubber composition of claim 36 or 37, wherein the crosslinking agent is a polyionic organic compound.

39. The rubber composition according to any one of claims 36 to 38, wherein the ion of the ion-crosslinkable compound, ion-crosslinkable organic compound or polyion-organic compound as the crosslinking agent is at least one ion-reactive group selected from the group consisting of amino group, epoxy group, carboxyl group and thiol.

40. The rubber composition according to claim 38, wherein the crosslinking agent is at least one polyionic compound selected from the group consisting of a polyamine compound, a polyepoxide compound, a polycarboxylic acid compound, and a polythiol compound.

41. The rubber composition according to any one of claims 30 to 40, 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.

42. The rubber composition of any of claims 30-41, wherein the rubber composition further comprises an anti-aging agent.

43. A rubber composition according to claim 42, wherein the anti-aging agent is an amine-based anti-aging agent.

44. A process for producing a rubber composition comprising mixing a rubber component comprising the acrylic rubber according to any one of claims 1 to 14 or the acrylic rubber molded body according to claim 28 or 29, a filler and an antioxidant optionally used, and then mixing the resulting mixture with a crosslinking agent.

45. A rubber crosslinked product obtained by crosslinking the rubber composition according to any one of claims 30 to 43.

46. A rubber crosslinked according to claim 45 wherein the crosslinking of the rubber composition is performed after molding.

47. The rubber crosslinked according to claim 45 or 46 wherein the crosslinking of the rubber composition is a crosslinking that performs primary crosslinking and secondary crosslinking.