CN116057074A

CN116057074A - Acrylic rubber excellent in roll processability, banbury processability, water resistance, strength characteristics and compression set resistance

Info

Publication number: CN116057074A
Application number: CN202180056883.6A
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: JPWO2021246510A1; WO2021246510A1; KR20230020409A

Abstract

The invention provides an acrylic rubber having excellent roll processability, banbury processability, water resistance, strength characteristics and compression set resistance. The acrylic rubber of the present invention has at least one reactive group selected from a carboxyl group, an epoxy group and a chlorine atom, has a number average molecular weight (Mn) of 10 to 50 tens of thousands, a ratio (Mw/Mn) of a weight average molecular weight (Mw) to a number average molecular weight (Mn) of 3.7 to 6.5, a methyl ethyl ketone insoluble content of 50 wt% or less, an ash content of 0.5 wt% or less and a total amount of magnesium and phosphorus in ash of 50 wt% or more based on an absolute molecular weight and an 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 composition and a rubber crosslinked product, and more particularly to an acrylic rubber excellent in roll processability and banbury processability and excellent in water resistance, strength characteristics and compression set resistance of the crosslinked product, a method for producing the same, a rubber composition comprising the same, 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 the field of automobiles.

For example, patent document 1 (single file book of international publication No. 2019/188709) discloses the following method: after repeating the vacuum degassing and nitrogen substitution by adding a monomer component composed of ethyl acrylate, butyl acrylate, methoxyethyl acrylate and monobutyl fumarate, water and sodium lauryl sulfate, emulsion polymerization was initiated by adding sodium aldehyde sulfoxylate and cumene hydroperoxide as an organic radical generator at normal pressure and normal temperature until the polymerization conversion rate reached 95% by weight, and the resultant was coagulated with a calcium chloride aqueous solution, filtered through a metal mesh, and dehydrated and dried by an extrusion dryer having a screw to produce an acrylic rubber. However, the acrylic rubber obtained by this method has problems of extremely poor roll processability and banbury processability, and poor storage stability and water resistance.

For example, patent document 2 (japanese patent application laid-open No. 2019-119772) discloses the following method: after a monomer emulsion is prepared from a monomer component comprising ethyl acrylate, butyl acrylate, methoxyethyl acrylate and monobutyl maleate, pure water and sodium lauryl sulfate and polyoxyethylene lauryl ether used as emulsifiers, a part of the monomer emulsion is put into a polymerization tank, cooled to 12 ℃ under a nitrogen stream, and then the remaining part of the monomer emulsion, ferrous sulfate, sodium ascorbate and an aqueous potassium persulfate solution used as an inorganic radical generator are continuously added dropwise for 3 hours, and then kept at 23 ℃ for 1 hour, emulsion polymerization is continued until the polymerization conversion reaches 97 wt% and then heated to 85 ℃, and then sodium sulfate is continuously added, thereby solidification and filtration are performed to obtain an aqueous pellet, and after 4 times of water washing, 1 time of acid washing and 1 time of pure water washing, a sheet-like acrylic rubber is continuously produced by an extrusion dryer with a screw, and crosslinked by an aliphatic polyamine compound 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 component comprising ethyl acrylate, caprolactone-added acrylate, cyanoethyl acrylate and vinyl chloride acetate was prepared, 1/4 of the amount of a monomer mixture comprising the above monomer component and n-dodecyl mercaptan as a chain transfer agent was emulsified with sodium lauryl sulfate, polyethylene glycol nonylphenyl ether and distilled water, polymerization was initiated by adding sodium sulfite and ammonium persulfate as an inorganic radical generator, the remaining part of the monomer mixture and a 2% ammonium persulfate aqueous solution were dropwise added while maintaining the temperature at 60℃for 2 hours, polymerization was further continued for 2 hours after the dropwise addition, and latex having a polymerization conversion of 96 to 99% was put into a sodium chloride aqueous solution at 80℃for coagulation, and then dried after sufficient water washing, to produce an acrylic rubber, crosslinked 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.

For example, patent document 4 (japanese patent application laid-open No. 2018-168343) discloses the following method: a monomer emulsion composed of a monomer component composed of ethyl acrylate, butyl acrylate and monobutyl fumarate, pure water, sodium lauryl sulfate, polyethylene glycol monostearate and n-dodecyl mercaptan as a chain transfer agent was prepared, then a part of the monomer emulsion and pure water were put into a polymerization tank, cooled to 12℃and then the remaining part of the monomer emulsion, ferrous sulfate, sodium ascorbate and an aqueous solution of potassium persulfate as an inorganic radical generator were continuously added dropwise over 2.5 hours, then the reaction was continued at 23℃for 1 hour, then industrial water was added, after heating to 85℃sodium sulfate was continuously added, thereby solidifying to give pellets, which were dried with hot air after washing 3 times with pure water, and acrylic rubber was produced by crosslinking with 2,2' -bis [4- (4-aminophenoxy) phenyl ] propane. However, the acrylic rubber obtained by this method has problems of insufficient roll processability and storage stability, and poor strength characteristics and water resistance of the crosslinked product, although it is excellent in stress relaxation property and extrusion processability.

Patent document 5 (japanese patent application laid-open No. 9-143229) discloses the following method: a monomer mixture composed of ethyl acrylate, a special acrylic ester and vinyl monochloroacetate, sodium lauryl sulfate as an emulsifier, n-octyl mercaptan as a chain transfer agent and water are added into a reaction vessel, after nitrogen substitution, ammonium bisulfide and sodium persulfate as an inorganic free radical generator are added to initiate polymerization, and the mixture is copolymerized at 55 ℃ for 3 hours at a reaction conversion of 93 to 96%, so that an acrylic rubber is produced, and crosslinked 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 it is composed of 50 to 99.9% by weight of at least one compound selected from alkyl acrylate and alkoxyalkyl acrylate, 0.1 to 20% by weight of a dicyclopentyl ester containing a radical-reactive group-containing unsaturated carboxylic acid, 0 to 20% by weight of other monovinyl system, mono1, 1-vinylidene (vinylidene) system And a copolymer composed of at least one monomer selected from the group consisting of mono-1, 2-vinylidene compounds, 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 copolymer being prepared by using tetrahydrofuran as a developing solvent. Further, regarding the number average molecular weight (Mn), it is described that it is 20 to 100 ten thousand, preferably 20 to 100 ten thousand, and if Mn is less than 20 ten thousand, the physical properties and processability of the sulfide are poor, and when it exceeds 120 ten thousand, the processability is poor, and regarding the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn), it is described that when it exceeds 10, the compression set resistance is large, which is not preferable. As specific examples thereof, the following manufacturing methods are disclosed: an acrylic rubber having 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 the weight average molecular weight (Mw) to the number average molecular weight (Mn) of 4.7 to 8 is obtained by adding, with varying addition amounts, a monomer component comprising ethyl acrylate, a radical crosslinkable dicyclopentenyl acrylate and the like, sodium lauryl sulfate as an emulsifier, potassium persulfate as an inorganic radical generator, octyl mercaptoacetate as a molecular weight regulator, and t-dodecyl mercaptan, and by solidifying in an aqueous solution of calcium chloride, and then washing with water and directly drying. Further, it is shown in examples and comparative examples that the number average molecular weight (Mn) of the obtained acrylic rubber is as high as 500 ten thousand when the amount of the chain transfer agent is small, the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) becomes narrow as 1.4, and that the number average molecular weight (Mn) is as small as 20 ten thousand and the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is extremely wide as 17 when the amount of the chain transfer agent is large. However, the acrylic rubber obtained by this method has such a problem that: compression set resistance and storage stability are poor, and since the radical-reactive group is contained, even if a proper molecular weight distribution (Mw/Mn) is obtained in a polymerization reaction using a radical generator, the molecular weight (Mw, mn) becomes too large and too complicated, and roll processability and Banbury processability are insufficient. In addition, the acrylic rubber obtained by this method has such a problem that: in the crosslinking reaction, sulfur as a crosslinking agent and a vulcanization accelerator were added and kneaded with a roll at 170 DEG C For 15 minutes 100kg/cm ² Is vulcanized and crosslinked with a Gill's oven at 175℃for 4 hours; there are problems in that long-time crosslinking is required, and the resulting crosslinked product is poor in compression set resistance, water resistance, and strength characteristics, and also poor in physical property change after thermal degradation, and the like.

Prior art literature

Patent literature

Patent document 1: single file book 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 circumstances of the prior art, and an object thereof is to provide an acrylic rubber which is excellent in roll processability and banbury processability and is excellent in water resistance, strength characteristics and compression set resistance of a crosslinked product, a method for producing the same, 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 made intensive studies in view of the above problems, and as a result, have found that an acrylic rubber containing a specific reactive group and having a specific range of a number average molecular weight (Mn) and a ratio (Mw/Mn) of a weight average molecular weight (Mw) to a number average molecular weight (Mn) based on an absolute molecular weight and an absolute molecular weight distribution measured by a GPC-MALS method, and having a limitation of an insoluble component amount of a specific solvent and an ash amount of a specific ash component, is excellent in roll processability and banbury processability, and a crosslinked product is highly excellent in water resistance, strength characteristics and compression set resistance.

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

The present inventors have found that, in GPC measurement of an acrylic rubber having such a reactive group and having a specific number average molecular weight (Mn), the above-mentioned conventional radical-reactive acrylic rubber obtained by copolymerizing ethyl acrylate, dicyclopentenyl acrylate or the like is not sufficiently dissolved in tetrahydrofuran used for GPC measurement, and each molecular weight and molecular weight distribution cannot be clearly and reproducibly measured, but by using a specific solvent having an SP value higher than that of tetrahydrofuran as an eluent, the cleanly dissolved and reproducibly measured can be obtained, and by specifying each specific value, the roll processability, banbury processability of the acrylic rubber, and the water resistance, strength characteristics and compression set resistance characteristics of a crosslinked product can be highly balanced.

Regarding roll processability, the present inventors have found that, in particular, it is important to widen the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the absolute molecular weight distribution, based on the number average molecular weight (Mn) of the absolute molecular weight measured by GPC-MALS method, and that the roll processability of the acrylic rubber and the strength characteristics of the crosslinked product can be highly balanced. The present inventors have found that it is not easy to widen the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the absolute molecular weight distribution, which is based on the absolute molecular weight measured by GPC-MALS method, by adding the chain transfer agent in the polymerization reaction after it is batchwise or by drying the aqueous pellet with high shear in a screw type biaxial extrusion dryer. Further, it is found that when the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is too large, 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 inventors found that: the amount of methyl ethyl ketone insoluble components of the acrylic rubber is generated during the polymerization reaction, and particularly, when the polymerization conversion is increased in order to improve the strength characteristics, the amount is rapidly increased, and the control is difficult, and the emulsion polymerization can be performed in the presence of a chain transfer agent in the latter half of the polymerization reaction to some extent to suppress the amount; and melt-kneading and extrusion-drying the acrylic rubber in a state substantially containing no water (water content less than 1 wt%) in a screw type biaxial extrusion dryer, wherein the rapidly increased methyl ethyl ketone insoluble component disappears and the amount of methyl ethyl ketone insoluble component deviation is reduced, whereby the banbury processability can be remarkably improved without impairing the roll processability of the acrylic rubber.

Regarding 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 remarkably excellent. The inventors found that: it is very difficult to reduce the ash content in the acrylic rubber, but the washing efficiency in hot water and the removal efficiency in dehydration of the aqueous pellets by the coagulation reaction performed by a specific method are high; and ash of a specific component is difficult to remove by washing but is easily reduced by this method and water resistance can be remarkably improved. The present inventors have found that, in particular, by increasing the ratio of the specific particle size of the aqueous aggregates produced in the coagulation step, and performing washing, dewatering and drying, the water resistance can be significantly improved without impairing the properties such as the roll processability, strength properties and compression set resistance of the obtained acrylic rubber. The present inventors have also found that if a specific emulsifier is used in emulsion polymerization of an acrylic rubber or a specific coagulant is used in coagulating an emulsion polymerization liquid, the acrylic rubber is excellent in water resistance and is remarkably improved in releasability from a metal mold or the like.

The present inventors have found that by increasing the specific gravity of an acrylic rubber, the roll processability, banbury processability, water resistance, strength characteristics and compression set resistance characteristics are excellent, and further the storage stability is significantly improved. The inventors found that: the acrylic rubber of the present invention having a specific reactive group is cohesive and hardly exhausts air, and when a large amount of air is involved in the pellet-like acrylic rubber in which the aqueous pellet is directly dried (the specific gravity becomes small), the storage stability is deteriorated, and when the pellet-like acrylic rubber is encapsulated by compression with a packer or the like, some of the air can be removed, and the storage stability can be improved; and, extrusion drying of the aqueous pellets under reduced pressure by a screw type biaxial extrusion dryer, and lamination by air-free sheet extrusion, can produce a rubber-coated acrylic rubber having a high specific gravity and remarkably excellent storage stability, which contains little air. The present inventors have also found that the specific gravity considering the content of air can be measured according to the a method of cross-linked rubber-density measurement using JIS K6268 having a buoyancy difference. It has also been found that the storage stability of the acrylic rubber can be further improved by a specific pH value.

The present inventors have also found that, after emulsifying a specific monomer component with water and an emulsifier, emulsion polymerization is initiated in the presence of a redox catalyst composed of an inorganic radical generator such as potassium persulfate and a reducing agent, and the emulsion polymerization is carried out in a batch manner during the polymerization without adding a chain transfer agent in the initial stage, so that the polymerization conversion rate is 90 wt% or more, whereby the acrylic rubber which can be produced can produce a high molecular weight component and a low molecular weight component in the absolute molecular weight and absolute molecular weight distribution measured by GPC, a wide molecular weight distribution can be formed while maintaining a high molecular weight, and the roll processability, crosslinkability, strength characteristics and compression set resistance characteristics of the acrylic rubber are highly balanced.

The present inventors have also found that by specifying the number of times of post-addition of the chain transfer agent in batches, the post-addition timing, the post-addition amount, the kind of the chain transfer agent, the kind of the reducing agent, the reducing agent added not only in the initial stage but also in batches, the ratio of the amount of the reducing agent added initially and post-addition, and the polymerization temperature, it is possible to produce an acrylic rubber in which the roll processability, the strength characteristics, the water resistance and the compression set resistance characteristics are further balanced.

The present inventors have further found that, when the emulsion polymerization liquid to which the chain transfer agent is added after the above-mentioned batch 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 the incorporation of carbon black and silica as fillers into a rubber composition comprising the acrylic rubber of the present invention, fillers and crosslinking agents provides excellent roll processability, banbury processability, storage stability and short-time crosslinking properties, and also provides crosslinked products having high water resistance, strength properties and compression set resistance. The present inventors have also found that an organic compound, a polyvalent compound or an ionic crosslinking compound, for example, a polyvalent ionic organic compound having a plurality of ion-reactive groups reactive with the ion-reactive groups of an acrylic rubber such as an amine group, an epoxy group, a carboxyl group or a thiol group, is preferable as the crosslinking agent, thereby making the roll processability, the banbury processability, the storage stability and the crosslinking property in a short period of time excellent and making the water resistance, the strength property and the compression set resistance of the crosslinked product highly excellent.

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

Thus, according to the present invention, there is provided an acrylic rubber having at least one reactive group selected from a carboxyl group, an epoxy group and a chlorine atom, wherein the number average molecular weight (Mn) based on the absolute molecular weight and the absolute molecular weight distribution measured by GPC-MALS method is in the range of 10 to 50 ten thousand, 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 methyl ethyl ketone insoluble component amount is 50% by weight or less, the ash content is 0.5% by weight or less, and the total amount of magnesium and phosphorus in the ash is 50% by weight or more.

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 specific gravity is preferably 0.8 or more.

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

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

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

In the acrylic rubber bag of the present invention, it is preferable to use a phosphate salt or a sulfate salt as an emulsifier for emulsion polymerization, and it is preferable to use an alkali metal salt or a group 2 metal salt of the periodic table as a coagulant to coagulate and dry the emulsion polymerized polymer. 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 containing no 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.

According to the present invention, there is provided a method for producing an acrylic rubber, comprising the steps of: emulsifying an acrylic rubber monomer component containing a monomer containing at least one reactive group selected from a carboxyl group, an epoxy group and a chlorine atom with water and an emulsifier; and

And a step of initiating polymerization in the presence of a redox catalyst comprising an inorganic radical generator and a reducing agent, adding a chain transfer agent in batch during the polymerization, and continuing the polymerization to perform emulsion polymerization.

According to the present invention, there is provided a method for producing an acrylic rubber, comprising the steps of: an emulsifying step of emulsifying an acrylic rubber monomer component containing a monomer having a reactive group selected from at least one of a carboxyl group, an epoxy group, and a chlorine atom with water and an emulsifier;

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

a coagulation step of bringing the emulsion polymerization liquid obtained into contact with a coagulation liquid to coagulate the emulsion polymerization liquid into aqueous pellets;

a cleaning step of cleaning the produced water-containing pellets;

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

And a rubber-coating step of laminating the extruded sheet-like dry rubber into a rubber-coated acrylic rubber as required.

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 emulsifier is preferably a phosphate salt or a sulfate salt.

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 by using an alkali metal salt or a group 2 metal salt of the periodic table as a coagulant, and then 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 be coagulated.

In the method for producing an acrylic rubber of the present invention, the coagulating liquid is preferably an aqueous magnesium salt solution.

In the method for producing an acrylic rubber of the present invention, it is preferable that the above-described dehydration and drying steps be performed by melt kneading and drying.

In the method for producing an acrylic rubber of the present invention, it is preferable that the above-mentioned melt kneading and drying are carried out in a state of substantially not containing 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 that the maximum torque of the screw type biaxial extrusion dryer at the time of melt kneading and drying is 25n·m 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.

According to the present invention, there is also provided a rubber composition containing a rubber component comprising the above-mentioned acrylic rubber, a filler and a crosslinking agent.

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

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

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

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.

The rubber composition of the present invention preferably further comprises an anti-aging agent. In the rubber composition of the present invention, the antioxidant is preferably an amine-based antioxidant.

According to the present invention, there is also provided a method for producing a rubber composition, comprising mixing a rubber component comprising the above-mentioned acrylic rubber, a filler and an antioxidant, if necessary, and then mixing a crosslinking agent.

According to the present invention, there is further provided a crosslinked rubber product obtained by crosslinking the 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, it is preferable that the crosslinking of the rubber composition is a crosslinking in which primary crosslinking and secondary crosslinking are performed.

Effects of the invention

According to the present invention, there are provided an acrylic rubber excellent in roll processability and banbury processability and having excellent water resistance, strength characteristics and compression set resistance of a crosslinked product, an efficient production method thereof, 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 manufacturing system for manufacturing 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 configuration of a transport cooling device as the cooling device of fig. 1.

Detailed Description

The acrylic rubber of the present invention is characterized by having at least one reactive group selected from the group consisting of carboxyl groups, epoxy groups and chlorine atoms, having a number average molecular weight (Mn) of 10 to 50 tens of thousands, a ratio (Mw/Mn) of weight average molecular weight (Mw) to number average molecular weight (Mn) of 3.7 to 6.5, a methyl ethyl ketone insoluble content of 50 wt.% or less, an ash content of 0.5 wt.% or less and a total amount of magnesium and phosphorus in ash of 50 wt.% or more, based on an absolute molecular weight and an 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 method that separates based on differences in molecular size. A multi-angle laser light scattering detector (MALS) and a differential refractive index detector (RI) are assembled in the device, and the GPC device is used for measuring the light scattering intensity and refractive index difference of a molecular chain solution classified by size according to the dissolution time, thereby sequentially calculating the molecular weight of solute and the content thereof, and finally obtaining the absolute molecular weight distribution and absolute average molecular weight value of the polymer substance.

< reactive group >

The acrylic rubber of the present invention is characterized by having at least one reactive group selected from the group consisting of a carboxyl group, an epoxy group and a chlorine atom.

The reactive group selected from at least one of a carboxyl group, an epoxy group and a chlorine atom is not particularly limited, but is preferably a reactive group having ion reactivity, more preferably a carboxyl group and an epoxy group, particularly preferably 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 highly improved.

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 usually in the range of 0.001 to 5% by weight, preferably 0.01 to 3% by weight, more preferably 0.05 to 1% by weight, and particularly preferably 0.1 to 0.5% by weight, based on the weight of the reactive group itself, and in this case, processability, crosslinkability, and strength characteristics when used as a crosslinked product, compression set resistance, oil resistance, cold resistance, water resistance and other characteristics are highly balanced, and therefore, it is preferable.

The acrylic rubber having at least one reactive group selected from the group consisting of a carboxyl group, an epoxy group and a chlorine atom of the present invention may be an acrylic rubber in which at least one reactive group selected from the group consisting of a carboxyl group, an epoxy group and a chlorine atom is introduced into an acrylic rubber in a post-reaction, and is preferably an acrylic rubber in which a monomer containing the reactive group is copolymerized.

< monomer component >

The monomer component of the acrylic rubber of the present invention is not particularly limited as long as it constitutes a usual acrylic rubber, and is preferably an acrylic rubber monomer component containing a monomer containing at least one reactive group selected from the group consisting of a carboxyl group, an epoxy group and a chlorine atom, more preferably composed of at least one (meth) acrylate selected from the group consisting of an alkyl (meth) acrylate and an 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 copolymerizable as necessary. In the present invention, "(meth) acrylate" is used as a term for esters of acrylic acid and/or methacrylic acid.

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 preferable, and an alkyl (meth) acrylate having an alkoxy group having 2 to 6 carbon atoms is more preferable.

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 preferable, and an alkoxyalkyl (meth) acrylate having an alkoxyalkyl group having 2 to 6 carbon atoms is more preferable.

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 them, methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate and the like are preferable, and methoxyethyl acrylate and ethoxyethyl acrylate are more preferable.

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

The 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 an ion-reactive group that participates in an ion 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 compression set resistance and water resistance of a 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 them, particularly, ethylenically unsaturated dicarboxylic acid monoester is preferable because it can further improve 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 includes ethylenically unsaturated dicarboxylic acids present as 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 them, 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; allyl glycidyl ether; vinyl ethers containing an epoxy group such as 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, aromatic vinyl compounds having a chloromethyl group, unsaturated amides having a chlorine atom, and chloroacetyl unsaturated monomers.

Specific examples of the unsaturated alcohol ester of a saturated carboxylic acid containing chlorine atoms 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, 2, 3-dichloropropyl (meth) acrylate, and the like. Specific examples of the chloroacyloxyalkyl (meth) acrylate include: 2- (chloroacetoxy) ethyl (meth) acrylate, 2- (chloroacetoxy) propyl (meth) acrylate, 3- (hydroxychloroacetoxy) propyl (meth) acrylate, and the like. Examples of the (chloroacetylcarbamoyloxy) alkyl (meth) acrylate include: 2- (chloroacetylcarbamoyloxy) ethyl (meth) acrylate, 3- (chloroacetylcarbamoyloxy) propyl (meth) acrylate, and the like. Specific examples of the unsaturated ether containing chlorine atom include: chloromethyl vinyl ether, 2-chloroethyl vinyl ether, 3-chloropropyl vinyl ether, 2-chloroethyl allyl ether, 3-chloropropyl allyl ether, and the like. Specific examples of the unsaturated ketone containing chlorine atom include: 2-chloroethyl vinyl ketone, 3-chloropropyl vinyl ketone, 2-chloroethyl allyl ketone, and the like. Specific examples of the chloromethyl aromatic vinyl compound include: p-chloromethylstyrene, m-chloromethylstyrene, o-chloromethylstyrene, p-chloromethyl-alpha-methylstyrene, etc. Specific examples of the unsaturated amide containing chlorine atom include N-chloromethyl (meth) acrylamide and the like. Further, 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 monomers such as styrene, α -methylstyrene, divinylbenzene, and the like; ethylenically unsaturated nitrile monomers such as acrylonitrile and methacrylonitrile; acrylamide monomers such as acrylamide and methacrylamide; olefin monomers such as ethylene, propylene, vinyl acetate, ethyl vinyl ether, butyl vinyl ether, and the like.

These other monomers are used singly or in combination, and the proportion of the total monomer components is usually controlled within a 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, and most preferably 0 to 10% by weight.

< acrylic rubber >

The acrylic rubber of the present invention has at least one reactive group selected from the group consisting of carboxyl groups, epoxy groups and chlorine atoms, and preferably consists of a combination unit containing at least one (meth) acrylate selected from the group consisting of the above-mentioned alkyl (meth) acrylate and alkoxyalkyl (meth) acrylate, at least one reactive group selected from the group consisting of carboxyl groups, epoxy groups and chlorine atoms, and other monomers, if necessary, each in the acrylic rubber in a ratio of: the binding unit derived from at least one (meth) acrylic acid ester selected from the group consisting of alkyl (meth) acrylate and alkoxyalkyl (meth) acrylate is usually in the range of 50 to 99.99% by weight, preferably 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, the binding unit derived from a monomer containing at least one reactive group selected from the group consisting of carboxyl group, epoxy group and chlorine atom is usually in the range of 0.01 to 10% by weight, preferably 0.05 to 8% by weight, more preferably 0.1 to 6% by weight, particularly preferably 0.5 to 5% by weight, most preferably 1 to 3% by weight, and the binding unit derived from another monomer is usually 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. When the monomer composition of the acrylic rubber falls within this range, the properties such as crosslinking property, compression set resistance, weather resistance, heat resistance, and oil resistance in a short time are highly balanced, and thus are preferable.

The measuring 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 can dissolve and measure the acrylic rubber of the present invention, and dimethylformamide-based solvents are preferable. The dimethylformamide-based solvent to be used is not particularly limited as long as it contains dimethylformamide as a main component, and the ratio of dimethylformamide to dimethylformamide in the dimethylformamide-based solvent is 100% by weight, preferably 95% by weight, and more preferably 97% by weight or more. In the present invention, lithium chloride and 37% concentrated hydrochloric acid are preferably added to dimethylformamide, respectively, so that the concentration of lithium chloride is 0.05mol/L and the concentration of hydrochloric acid is 0.01%.

The number average molecular weight (Mn) of the acrylic rubber of the present invention is preferably in the range of usually 100000 ～ 500000 (10 to 50. Mu.m), preferably 200000 ～ 480000 (20 to 48. Mu.m), more preferably 250000 ～ 450000 (25 to 45. Mu.m), particularly preferably 300000 ～ 400000 (30 to 40. Mu.m), and most preferably 350000 ～ 400000 (35 to 40. Mu.m) in terms of absolute molecular weight 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. If the number average molecular weight (Mn) of the acrylic rubber of the present invention is too small, the strength properties and compression set resistance properties are poor, whereas if it is too large, the roll processability, banbury processability, injection moldability and the like are poor, which is not preferable.

The weight average molecular weight (Mw) of the acrylic rubber of the present invention is not particularly limited, but is usually in the range of 1000000 ～ 3500000, preferably 1200000 ～ 3000000, more preferably 1300000 ～ 3000000, particularly preferably 1500000 ～ 2500000, and most preferably 1900000 ～ 2100000, in terms of absolute molecular weight 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. If 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 if it is 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 preferably in the range of usually 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, since the roll processability, strength characteristics, and compression set resistance of the acrylic rubber are highly balanced.

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 preferably 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, and most preferably 4.7 to 5.5, in terms of absolute molecular weight measured by GPC-MALS method, and in this case, the roll processability, the strength characteristics at the time of crosslinking, and the compression set resistance characteristics are highly balanced. If 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 if it is too large, the strength properties and compression set resistance properties are poor, and the roll processability is 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 is preferably 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, and most preferably 1.8 to 1.95, in terms of the absolute molecular weight distribution in the high molecular weight region measured by GPC-MALS method, the processability and strength characteristics of the acrylic rubber are highly balanced, and the change in physical properties during storage can be alleviated.

The ash content of the acrylic rubber of the present invention is preferably 0.5% by weight or less, more preferably 0.3% by weight or less, still more preferably 0.2% by weight or less, still more preferably 0.15% by weight or less, particularly preferably 0.14% by weight or less, and most preferably 0.13% by weight or less, and when the ash content is within this range, the water resistance, strength characteristics and processability of the acrylic rubber are highly balanced.

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

The ash content in the acrylic rubber of the present invention in the case of a high balance of water resistance, strength characteristics, processability and handleability is usually in the range of 0.0001 to 0.5% by weight, preferably 0.0005 to 0.3% by weight, more preferably 0.001 to 0.2% by weight, particularly preferably 0.005 to 0.14% by weight, and most preferably 0.01 to 0.13% by weight.

The total amount of magnesium and phosphorus 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, strength characteristics and workability of the acrylic rubber are highly balanced. When the total amount of magnesium and phosphorus in the ash of the acrylic rubber of the present invention is in this range, the metal adhesion is reduced, and the operability is excellent, which is preferable.

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

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

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

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

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

The acrylic rubber of the present invention uses a metal salt as a coagulant to be described later, preferably an alkali metal salt or a metal salt of group 2 of the periodic table, and in this case, in addition to water resistance and strength characteristics, mold releasability and workability can be improved to a high degree, and therefore, it is preferable. The water resistance of the acrylic rubber is preferably further highly balanced with respect to the ash content in the acrylic rubber and the total amount of sodium, magnesium, calcium, phosphorus and sulfur in the ash, because the water resistance, strength characteristics, mold releasability and workability of the acrylic rubber are more highly balanced with the use of the coagulant.

The amount of the insoluble component of methyl ethyl ketone 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, processability during kneading such as Banbury and injection moldability are improved to a high degree.

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

The acrylic rubber of the present invention is preferably obtained by melt kneading and drying the aqueous pellets produced by the solidification reaction in a state in which water is substantially removed (water content of less than 1% by weight) by a screw type biaxial extruder dryer, since the Banbury processability and strength characteristics are highly balanced.

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 usually in the range of 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, and in this case, productivity, storage stability, crosslinking characteristic stability of the crosslinked product, and the like are highly balanced, and therefore, it is preferable. 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 the influence on the storage stability including oxidative deterioration is large, which 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 by the solidification reaction under reduced pressure by a screw type biaxial extruder, or melt-kneading and drying under reduced pressure, because it is excellent in storage stability, injection moldability and strength characteristics and is highly balanced.

The glass transition temperature (Tg) of the acrylic rubber of the present invention is not particularly limited, and may be appropriately selected depending on the purpose of use of the acrylic rubber, and is usually 20 ℃ or less, preferably 10 ℃ or less, more preferably 0 ℃ or less, and in this case, 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 usually not more than 15000[ Pa.s ], preferably 1000 to 10000[ Pa.s ], more preferably 2000 to 5000[ Pa.s ], particularly preferably 2500 to 4000[ Pa.s ], and most preferably 2500 to 3000[ Pa.s ], and is suitably selected depending on the purpose of use, and in this case, the processability, oil resistance and shape retention are excellent, and therefore, it is preferable.

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

The ratio ([ eta ]100 ℃ C.) of the complex viscosity ([ eta ]100 ℃ C.) to the complex viscosity ([ eta ]60 ℃ C.) at 60 ℃ C. ([ eta ]100 ℃ C./[ eta ]60 ℃ C.) 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. The ratio of the complex viscosity at 100 ℃ ([ eta ]100 ℃) to the complex viscosity at 60 ℃ ([ eta ]60 ℃) ([ eta ]100 ℃/[ eta ]60 ℃) of the acrylic rubber of the present invention 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 is appropriately selected depending on the purpose of use, but is usually less than 1% by weight, preferably 0.8% by weight or less, more preferably 0.6% by weight or less, and in this case, the vulcanization characteristics of the acrylic rubber are optimum, and the characteristics such as heat resistance and water resistance are highly improved, and therefore, it is preferable.

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

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, and is preferably sheet-like or bale, and in this case, the handling property and storage stability are excellent, and therefore, it is preferable.

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

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

< method for producing acrylic rubber >

The method for producing the acrylic rubber is not particularly limited, and the acrylic rubber can be easily produced by the following production method. The manufacturing method includes, for example, the steps of: emulsifying an acrylic rubber monomer component containing a monomer having a reactive group selected from at least one of a carboxyl group, an epoxy group, and a chlorine atom with water and an emulsifier; and

and a step of initiating polymerization in the presence of a redox catalyst comprising an inorganic radical generator and a reducing agent, adding a chain transfer agent after the batch during the polymerization, and continuing the polymerization to perform emulsion polymerization.

In the present invention, the method for producing an acrylic rubber comprises the steps of: an emulsifying step of emulsifying an acrylic rubber monomer component containing a monomer having a reactive group selected from at least one of a carboxyl group, an epoxy group, and a chlorine atom with water and an emulsifier;

a cleaning step of cleaning the produced water-containing pellets;

a dehydration/drying step of dehydrating the washed aqueous pellets with a dehydration cylinder to a water content of 1 to 40 wt% and drying the aqueous pellets with the dryer cylinder to less than 1 wt%, using a dryer cylinder having a dehydration slit and a dryer cylinder under reduced pressure and a screw type biaxial extrusion dryer having a die at the tip end, and extruding a sheet-like dry rubber (sheet-like acrylic rubber) from the die; and

and a rubber-coating step of laminating the extruded sheet-like dry rubber into a rubber-coated acrylic rubber as required. The method for producing an acrylic rubber is preferable because it can produce an acrylic rubber having further excellent normal physical properties including crosslinkability, roll processability, banbury processability, water resistance, compression set resistance and strength characteristics and also excellent storage stability.

(monomer component)

The monomer component used in the present invention, which contains a 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 composed of at least one (meth) acrylate selected from the group consisting of an alkyl (meth) acrylate and an 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 copolymerizable as needed, and is the same as exemplified and preferred ranges of the monomer component described above. As described above, the amount of the monomer component used may be appropriately selected so that the composition of the acrylic rubber of the present invention becomes the composition described above in emulsion polymerization.

(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 dibasic phosphate salts are most preferable, since 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 dibasic 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 them, metal salts thereof are preferable, alkali metal salts thereof are more preferable, and sodium salts thereof are most preferable.

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

As specific examples of the alkoxypolyoxyethylene phosphate salt, there may be mentioned octyloxydioxyethylene phosphate, octyloxytrioxyethylene phosphate, octyloxytetraethylene phosphate, decyloxy tetraethylene phosphate, dodecyloxytetraethylene phosphate, tridecyloxytetraethylene phosphate, tetradecyloxy tetraethylene phosphate, hexadecyloxy tetraethylene phosphate, octadecyl tetraethylene phosphate, octyloxypentaethylene phosphate, decyloxy pentaethylene phosphate, dodecyloxypentaethylene phosphate, tridecyloxypentaethylene phosphate, tetradecyloxy pentaethylene phosphate, hexadecyloxy pentaethylene phosphate, octadecyl pentaethylene phosphate, octyloxyhexaethylene phosphate, decyloxy hexaethylene phosphate, dodecyloxyhexaethylene phosphate, tridecyloxyhexaethylene phosphate, tetradecyloxy hexaethylene phosphate, hexadecyloxy hexaethylene phosphate, octadecyl hexaethylene phosphate, octooxyoctaethylene phosphate, dodecyloxyoctaethylene phosphate, tridecyloxyoctaethylene phosphate, hexadecyloxy octaethylene phosphate, and the alkali metal salt of which are particularly preferable.

As specific examples of the alkoxypolyoxypropylene phosphate, there may be mentioned octyloxydioxy propylene phosphate, octyloxytrioxypropylene phosphate, octyloxytetraoxypropylene phosphate, decyloxy tetrapropylate, dodecyloxytetrapropylate, tridecyloxypropylate, tetradecyloxy tetrapropylate, hexadecyloxy tetrapropylate, octadecyloxypropylate, octyloxypentaoxypropylate, decyloxy pentapropylate, dodecyloxypentaoxypropylate, tridecyloxypentaoxypropylate, tetradecyloxy pentapropylate, hexadecyloxy pentapropylate, octadecyloxypentaoxypropylate, octyloxypropylate, decyloxy hexaoxypropylate, dodecyloxypropylate, tridecyloxypropylate, tetradecyloxy hexaoxypropylate, hexadecyloxy hexaoxypropylate, octadecyloxypropylate, octoxyoctaoxypropylate, decyloxy octaoxypropylate, dodecyloxypropylate, tridecyloxypropylate, octaoxypropylate, octaalkoxyl octaoxypropylate, octaalkoxyphosphate, and the alkali metal salts thereof, particularly preferred among them.

Specific examples of the alkylphenoxypolyoxyalkylene phosphate include alkylphenoxypolyoxyethylene phosphate and alkylphenoxypolyoxypropylene phosphate, and among these, alkylphenoxypolyoxyethylene phosphate is preferable.

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

Specific examples of the alkylphenoxypolyoxypropylene phosphate include metal salts such as methylphenoxy tetrapropoxy phosphate, ethylphenoxy tetrapropoxy phosphate, butylphenoxy tetrapropoxy phosphate, hexylphenoxy tetrapropoxy phosphate, nonylphenoxy tetrapropoxy phosphate, dodecylphenoxy tetrapropoxy phosphate, methylphenoxy pentapropoxy phosphate, ethylphenoxy pentapropoxy phosphate, butylphenoxy pentapropoxy phosphate, hexylphenoxy pentapropoxy phosphate, nonylphenoxy pentapropoxy phosphate, dodecylphenoxy pentapropoxy phosphate, methylphenoxy hexaoxypropoxy phosphate, ethylphenoxy hexaoxypropoxy phosphate, butylphenoxy hexaoxypropoxy phosphate, hexylphenoxy hexaoxypropoxy phosphate, nonylphenoxy hexaoxypropoxy phosphate, dodecylphenoxy hexaoxypropoxy phosphate, methylphenoxy octaoxypropoxy phosphate, ethylphenoxy octaoxypropoxy phosphate, butylphenoxy octaoxypropoxy phosphate, hexylphenoxy octaoxypropoxy phosphate, nonylphenoxy octaoxypropoxy phosphate, dodecylphenoxy octaoxypropoxy phosphate, and the like, and sodium salts thereof are particularly preferred.

As the phosphate ester salt, a mono-phosphate ester salt such as a sodium salt of di (alkoxypolyoxyalkylene) phosphate ester can be used alone or in combination with a di-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, with sodium lauryl sulfate being preferred.

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 method (mixing method) for mixing 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 (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, based on 100 parts by weight of the monomer component.

(inorganic radical generator)

As the polymerization catalyst used in the present invention, a redox catalyst composed of an inorganic radical generator and a reducing agent is used. 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, hydrogen peroxide, and the like, and among them, persulfates are preferable, potassium persulfate and ammonium persulfate are more preferable, and potassium persulfate is particularly preferable.

These inorganic radical generators may be used singly or in combination of two or more kinds, 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, and 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 2 reducing agents, and it is possible to further highly balance the banbury processability and roll processability and strength characteristics of the obtained acrylic rubber by combining the metal ion compound in a reduced state with the other reducing agents.

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 ferrous sulfate is preferable. These metal ion compounds in a 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 aldehyde bisulfite, and potassium bisulfite; metabisulfites such as sodium metabisulfite, potassium metabisulfite, sodium metabisulfite, potassium metabisulfite and the like; thiosulfate such as sodium thiosulfate and potassium thiosulfate; phosphorous acid or salts thereof such as phosphorous acid, sodium phosphite, potassium phosphite, sodium hydrogen phosphite, potassium hydrogen phosphite, etc.; pyrophosphorous acid or salts thereof such as pyrophosphorous acid, sodium pyrophosphate, potassium pyrophosphate, sodium hydrogen pyrophosphate, potassium hydrogen pyrophosphate, etc.; sodium formaldehyde sulfoxylate and the like. Among them, 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.

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

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

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

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

(post addition of chain transfer agent)

The present invention is characterized in that it is preferable to add the chain transfer agent in the course of polymerization in a batch mode without adding the chain transfer agent at the initial stage, whereby an acrylic rubber having a high molecular weight component and a low molecular weight component separated from each other can be produced, and the strength characteristics of the produced acrylic rubber are highly balanced with the processability at the time of kneading by 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-pentylmercaptan, n-hexylthiol, n-heptylthiol, n-octylthiol, n-decylthiol, n-dodecylthiol, n-tridecylthiol, n-tetradecylthiol, n-hexadecylthiol, n-octadecylthiol, sec-pentylmercaptan, sec-hexylthiol, sec-heptylthiol, sec-octylthiol, zhong Guiji thiol, sec-dodecylthiol, sec-tridecylthiol, sec-tetradecylthiol, sec-hexadecylthiol, sec-octadecylthiol, tert-pentylmercaptan, tert-hexylthiol, tert-heptylthiol, tert-octylthiol, tert-decylthiol, tert-dodecylthiol, tert-tridecylthiol, tert-tetradecylthiol, tert-hexadecylthiol, tert-octadecylthiol, etc., preferably n-octylthiol, n-dodecylthiol, tert-dodecylthiol, more preferably n-octylthiol, n-dodecylthiol.

These chain transfer agents can be used singly or in combination of two or more kinds. The amount of the chain transfer agent used is not particularly limited, but is 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, and 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, and thus are preferable.

The present invention is characterized in that the above chain transfer agent is not added at the initial stage of polymerization but is added in batches during polymerization, and the produced acrylic rubber contains a high molecular weight component and a low molecular weight component, and the molecular weight distribution is in a specific range, so that the strength characteristics and the processability of rolls and the like can be highly balanced, and therefore, it is preferable.

The number of times of adding the chain transfer agent after it is batchwise is not particularly limited, and is 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 acrylic rubber and the workability of the roll and the like can be highly balanced, and thus it is 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 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, which is preferable.

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

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

(post addition of reducing agent)

In the present invention, the redox catalyst can be added after the polymerization, and thus the strength characteristics of the produced acrylic rubber and the processability of rolls and the like can be highly balanced, which is preferable.

The above-mentioned reducing agent is exemplified and preferably in the same range as the reducing agent added after the polymerization. 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, and 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 highly balanced, and thus it is preferable.

The reducing agent added after the polymerization may be added continuously or batchwise, preferably batchwise. The number of times of adding the reducing agent after the batch during the polymerization is not particularly limited, but is usually 1 to 5, preferably 1 to 3, more preferably 1 to 2.

When the reducing agent added at the beginning of polymerization and during the course of polymerization is ascorbic acid or a salt thereof, the ratio of the amount of the ascorbic acid or a salt thereof added at the beginning to the amount of the ascorbic acid or a salt thereof added at the later stage is not particularly limited, and is usually in the range of 1/9 to 8/2, preferably in the range of 2/8 to 6/4, more preferably in the range of 3/7 to 5/5, based on the weight ratio of "the ascorbic acid or a salt thereof added at the earlier stage"/"the ascorbic acid or a salt thereof added at the later stage in a batch", and in this case, the productivity of the production of the acrylic rubber can be improved and the strength characteristics and the processability of the produced acrylic rubber can be highly balanced, and therefore, it is preferable.

The timing of the post-addition of the reducing agent is not particularly limited, and may be appropriately selected depending on the purpose of use, and is usually 1 hour or more, preferably 1 to 3 hours, more preferably 1.5 to 2.5 hours after the initiation of polymerization, and in this case, it is preferable to be able to make the productivity of the production of the acrylic rubber excellent and to highly balance the strength characteristics and processability of the produced acrylic rubber.

In the case where the reducing agent is added after being added in portions, the amount to be added per one time is not particularly limited, and may be appropriately selected depending on the purpose of use, but is usually in the range of 0.00005 to 0.5 parts by weight, preferably 0.0001 to 0.1 parts by weight, more preferably 0.0005 to 0.05 parts by weight, and particularly preferably 0.001 to 0.03 parts 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, and thus are preferable.

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

The polymerization conversion rate of the emulsion polymerization is preferably 90% by weight or more, more preferably 95% by weight or more, and the acrylic rubber produced at this time is excellent in strength characteristics and free from monomer odor. At the termination of the polymerization, a polymerization terminator may be used.

After the emulsion polymerization, the emulsion polymerization solution (emulsion) obtained can be coagulated and dried to separate the acrylic rubber. This can be done by including the following procedures, for example: a step of bringing the emulsion polymerization liquid after emulsion polymerization into contact with a coagulation liquid to produce an aqueous pellet; a cleaning step of cleaning the produced aqueous pellets; a dehydration step of dehydrating the washed aqueous granules; a drying step of drying the dehydrated aqueous pellets; and a step of coating the dried rubber with a coating agent as needed.

(coagulation step)

In the coagulation step after emulsion polymerization, the emulsion polymerization liquid obtained by the emulsion polymerization is brought into contact with the coagulation liquid, whereby coagulation can be caused to produce aqueous aggregates of the acrylic rubber.

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

The coagulant of the coagulant liquid to be used is not particularly limited, and a metal salt is usually used. Examples of the metal salt include: alkali metal, metal salt of group 2 of the periodic table, other metal salt, and the like are preferable, alkali metal and metal salt of group 2 of the periodic table are more preferable, metal salt of group 2 of the periodic table is particularly preferable, and magnesium salt is particularly preferable, and in this case, the water resistance, strength characteristics, mold releasability, and workability of the obtained acrylic rubber can be highly balanced, and therefore 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 of two or more, 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 coagulation of the acrylic rubber can be made sufficient, and when the acrylic rubber is crosslinked, compression set resistance and water resistance can be improved to a high degree, which is preferable.

In the coagulation step of the present invention, it is particularly preferable to concentrate the particle size of the produced aqueous aggregates in a specific region, because the cleaning efficiency and ash removal efficiency during dehydration are remarkably improved. The proportion of the produced aqueous pellet in the range of 710 μm to 6.7mm (6.7 mm without passing through 710 μm) is not particularly limited, but it is preferable that the water resistance of the acrylic rubber is remarkably improved when it is usually 30% by weight or more, preferably 50% by weight or more, more preferably 60% by weight or more, particularly preferably 70% by weight or more, and most preferably 80% by weight or more, relative to the total produced aqueous pellet. The proportion of the produced aqueous pellet in the range of 710 μm to 4.75mm (4.75 mm without passing through 710 μm) is not particularly limited, but is preferably 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 produced aqueous pellet, since 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 without passing through 710 μm) is not particularly limited, and it is preferable that the water resistance of the acrylic rubber is remarkably improved when the amount 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.

The means for forming the particle size of the aqueous pellet in the above range is not particularly limited, and the method of contacting the emulsion polymerization liquid with the coagulant may be, for example, a method of adding the emulsion polymerization liquid to a stirred coagulant (aqueous coagulant solution) or a method of specifying the coagulant concentration of the coagulant, the number of stirring of the stirred coagulant, or the circumferential speed.

The coagulant of the coagulant liquid to be used is usually used as 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 aggregates 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℃in this case, and it is preferable to produce uniform aqueous aggregates.

The method of bringing the emulsion polymerization liquid into contact with the coagulation liquid is not particularly limited, and may be, for example: the method of adding the coagulating liquid to the emulsion polymerization liquid, the method of adding the coagulating liquid to the stirred emulsion polymerization liquid, the method of adding the emulsion polymerization liquid to the coagulating liquid, the method of adding the emulsion polymerization liquid to the stirred coagulating liquid, and the like are preferable because the method of adding the emulsion polymerization liquid to the stirred coagulating liquid can significantly improve the washing efficiency and the dewatering efficiency of the produced aqueous pellets and the water resistance and the storage stability of the obtained acrylic rubber as described above.

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

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

The peripheral speed of the stirred coagulation liquid, that is, the speed of the outer periphery of the stirring blade of the stirring device is not particularly limited, and the particle size of the resulting aqueous aggregates can be reduced and uniform by intense stirring to a certain extent, and therefore, is preferably usually 0.5m/s or more, more preferably 1.5m/s or more, particularly preferably 2m/s or more, and most preferably 2.5m/s or more. On the other hand, the upper limit of the peripheral speed is not particularly limited, and it is preferable to control the coagulation reaction easily when it is usually 50m/s or less, preferably 30m/s or less, more preferably 25m/s or less, and most preferably 20m/s or less.

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, rotational speed and peripheral speed at the time of stirring of coagulation liquid, etc.) within specific ranges, the shape of the resulting aqueous pellet and the particle size of the pellet are made uniform and concentrated, and the removal of the emulsifier and coagulant at the time of washing and dehydration is remarkably improved, and as a result, the water resistance and storage stability of the produced acrylic rubber can be highly changed, which is preferable.

(cleaning step)

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

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

The amount of water to be added for washing is not particularly limited, but is preferably 50 parts by weight, more preferably 50 to 15000 parts by weight, still more preferably 100 to 10000 parts by weight, and even 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 water to be used is not particularly limited, but it is preferably hot water, usually 40 ℃ or higher, preferably 40 to 100 ℃, more preferably 50 to 90 ℃, particularly 60 to 80 ℃, and in this case, the cleaning efficiency can be significantly improved. The water used is at a temperature not lower than the lower limit, so that the emulsifier and the coagulant are released from the aqueous pellets, thereby further improving the cleaning efficiency.

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 desirable that the number of times of washing is large, but as described above, by setting the shape of the aqueous aggregates and the particle size of the aqueous aggregates within a specific range and/or setting the washing temperature within the above-described range, the number of times of washing can be significantly reduced.

(dehydration step)

The water-containing pellets after washing are particularly preferably subjected to a dehydration step of dehydrating the water-containing pellets before being transferred to a drying step, because removal of the emulsifier and the coagulant can be significantly improved.

The means for dehydrating the hydrous pellets is not particularly limited, and any conventional method may be used, and water can be discharged from the hydrous pellets using, for example, a centrifugal separator, a squeezer, a screw extruder, or the like. Since the acrylic rubber of the present invention has a strong adhesiveness, it can be dehydrated only to about 45 to 50% by weight by a centrifugal separator or the like, among these dehydrators, a press or a screw extruder which forcibly extrudes water from the aqueous pellet is preferable, and among these, a screw extruder is most preferable.

The water content of the dehydrated aqueous pellets is not particularly limited, but is usually in the range of 1 to 40% by weight, preferably 5 to 40% by weight, more preferably 5 to 35% by weight, and particularly preferably 10 to 35% by weight, and in this case, the removal efficiency of the emulsifier and the coagulant is remarkably improved, and the drying efficiency in the drying step is high, so that it is preferable.

(drying step)

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

In the present invention, the aqueous pellets can be melted, extruded and dried in a screw type biaxial extrusion dryer to obtain an acrylic rubber. The drying temperature (set temperature) of the screw type biaxial extrusion dryer 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.

In the present invention, it is preferable to melt and extrude the aqueous pellets under reduced pressure in a screw type biaxial extrusion dryer because the storage stability can be highly improved without impairing the roll processability and strength characteristics of the acrylic rubber. In order to remove air existing in the acrylic rubber at this stage and to improve the storage stability, the vacuum degree of the screw type biaxial extrusion dryer is preferably selected appropriately, and is usually in the range of 1 to 50kPa, preferably 2 to 30kPa, more preferably 3 to 20 kPa.

In the present invention, it is preferable to melt-knead and dry the aqueous pellets with almost water removed by a screw type biaxial extrusion dryer, because the banbury processability is highly improved without impairing the roll processability and strength characteristics of the acrylic rubber. The water content of the acrylic rubber is usually less than 1% by weight, preferably 0.8% by weight or less, and more preferably 0.6% by weight or less, as long as the water content is appropriately selected in a state of substantially removing water, which improves the banbury workability. In the present invention, "melt-kneading" or "melt-kneading and drying" means: in a screw type biaxial extrusion dryer, the acrylic rubber is kneaded (mixed) in a molten state or extruded in a molten state and dried at this stage; or extruding and drying the acrylic rubber by kneading the acrylic rubber in a molten (plasticized) state by a screw type biaxial extrusion dryer.

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

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

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

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

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

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

The water content of the dried acrylic rubber is not limited, but is usually less than 1% by weight, preferably 0.8% by weight, and more preferably 0.6% by weight or less.

The acrylic rubber of the present invention thus obtained is excellent in roll processability, strength characteristics and compression set resistance, and can be used for various applications. The shape of the acrylic rubber of the present invention is not particularly limited, and may be selected according to the purpose of use, and may be selected, for example, in the form of powder, pellet, strand, sheet, bale, etc., and is preferably in the form of sheet or bale, and its handling property and storage stability are excellent. The rubber-coated acrylic rubber can be produced by a rubber coating process of a conventional method, for example, by compressing a dried rubber in a packer. The pressure of the compression may be appropriately selected depending on the purpose of use, and is usually in the range of 0.1 to 15MPa, preferably 0.5 to 10MPa, and more preferably 1 to 5 MPa. The compression time is not particularly limited, but is usually in the range of 1 to 60 seconds, preferably 5 to 30 seconds, more preferably 10 to 20 seconds.

(dehydration and drying Process)

In the present invention, it is preferable to use 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 tip end, to dehydrate the washed aqueous pellets to a water content of 1 to 40% by weight with the dryer barrel, and to dry the aqueous pellets to a water content of less than 1% by weight with the dryer barrel, to extrude a sheet-like dried rubber (sheet-like acrylic rubber) from the die, to dry the sheet-like dried rubber, and to laminate the extruded sheet-like dried rubber into a rubber-in-bag type acrylic rubber as required, because it is possible to produce an acrylic rubber excellent in roll processability, strength characteristics and compression set resistance, and also excellent in banbury processability and water resistance.

In the present invention, the aqueous pellet fed to the screw type biaxial extrusion dryer is preferably free water removed (water removal) 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, in order to improve the dehydration efficiency.

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

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

The water content of the dehydrated aqueous pellet, that is, the water content of the aqueous pellet to be subjected to the dehydration and 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 put into the dehydration and drying step is not particularly limited, but is preferably in the range of usually 40℃or higher, preferably 40 to 100℃or higher, more preferably 50 to 90℃or lower, particularly preferably 55 to 85℃or lower, and most preferably 60 to 80℃or lower, since the aqueous pellet having a specific heat of 1.5 to 2.5 KJ/kg.K and being difficult to raise the temperature can be dehydrated and dried efficiently by using the screw type biaxial extrusion dryer as in the acrylic rubber of the present invention.

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

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

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

The removal of water from the hydrous pellets in the dewatering barrel is distinguished by the removal of water in a liquid state (drainage) from the dewatering slit and the removal of water in a vapor state (steam removal), and in the present invention, the drainage is defined as dewatering and the steam removal is defined as predrying.

In the dehydration of the hydrous pellets, the water discharged from the dehydration slit may be in any state of liquid (drain) or vapor (drain), and in the case of dehydration using a screw type biaxial extrusion dryer having a plurality of dehydration barrels, it is preferable to efficiently dehydrate the adhesive acrylic rubber by combining drain and drain. For a screw type biaxial extrusion dryer having 3 or more dehydration barrels, the dehydration barrel of the drainage type and the dehydration barrel of the steam discharge type may be appropriately selected depending on the purpose of use, and generally the dehydration barrel is increased in the case of reducing the ash content in the produced acrylic rubber and the steam discharge barrel is increased in the case of reducing the water content.

The setting temperature of the dehydration barrel may be appropriately selected depending on the monomer composition, ash content, water content, and operating conditions of the acrylic rubber, and is usually in the range of 60 to 150 ℃, preferably 70 to 140 ℃, more preferably 80 to 130 ℃. The set 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 ℃, and more preferably 110 to 130 ℃.

The water content after dehydration of the drainage type for extruding water from the hydrous pellets is not particularly limited, but is preferably a high balance between productivity and ash removal efficiency when it is usually 1 to 40% by weight, preferably 5 to 40% by weight, more preferably 5 to 35% by weight, particularly preferably 10 to 35% by weight.

In the present invention, when the dehydration is performed by using a centrifugal separator or the like, the acrylic rubber adheres to the dehydration slit portion and is hardly dehydrated (the water content is about 45 to 55% by weight), and the water content can be reduced to the above range by using a screw type biaxial extrusion dryer having a dehydration slit and forcibly extruding with a screw.

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

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

(drying of aqueous pellets in the dryer section)

The above-described drying of the dehydrated aqueous pellets is desirably performed by a screw type biaxial extrusion dryer having a plurality of dryer barrel sections at reduced pressure. Drying the acrylic rubber under reduced pressure is preferable because it improves the drying productivity and removes air existing inside the acrylic rubber, thereby producing an acrylic rubber having a high specific gravity and excellent storage stability. In the present invention, the acrylic rubber is melted and extrusion-dried under reduced pressure, whereby the storage stability can be highly improved. The storage stability of the acrylic rubber is related to the high specific gravity of the acrylic rubber, and when the storage stability is controlled to be high with the high specific gravity, the control can be performed by the degree of vacuum or the like in the extrusion drying.

The vacuum degree of the dryer cylinder may be appropriately selected, and is preferably 1 to 50kPa, more preferably 2 to 30kPa, and even more preferably 3 to 20kPa, since the aqueous pellets can be efficiently dried, and the air in the acrylic rubber can be removed and the storage stability of the acrylic rubber can be significantly improved.

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 not scorched or deteriorated, can be efficiently dried, and the amount of methyl ethyl ketone insoluble components in the acrylic rubber can be reduced.

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

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

In the present invention, the shear rate applied to the cylinder of the screw-type biaxial extrusion dryer in a state where the acrylic rubber does not substantially contain water is not particularly limited, and when the shear rate is usually 10[1/s ] or more, preferably 10 to 400[1/s ], more preferably 50 to 250[1/s ], the storage stability, roll processability, banbury processability, strength characteristics and compression set resistance of the obtained acrylic rubber are highly balanced, and therefore preferable.

In the screw type biaxial extrusion dryer used in the present invention, the shear viscosity of the acrylic rubber in the dryer barrel is not particularly limited, but is preferably in the range of usually 12000[ Pa.s ], preferably 1000 to 12000[ Pa.s ] or less, more preferably 2000 to 10000[ Pa.s ], particularly preferably 3000 to 7000[ Pa.s ], and most preferably 4000 to 6000[ Pa.s ] because the storage stability, roll processability, banbury processability and strength characteristics of the obtained acrylic rubber are highly balanced.

(extrusion of dried rubber from die head)

The dried rubber dehydrated and dried by the screw sections of the dehydration cylinder and the drying cylinder is transferred to a die section without rectification of the screw, and extruded from the die section into a desired shape. A perforated plate or a metal mesh may or may not be provided between the screw portion and the die portion.

By forming the die shape in a substantially rectangular shape, the extruded dry rubber is extruded into a sheet shape, and a dry rubber having a small air entrainment, a large specific gravity, and excellent storage stability is obtained, which is preferable.

The resin pressure of the die head is not particularly limited, but is preferably in the range of usually 0.1 to 10MPa, preferably 0.5 to 5MPa, more preferably 1 to 3MPa, because the air inclusion of the acrylic rubber is small (specific gravity is high) 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 water content can be preferably less than 1% by weight without causing a decrease in the molecular weight or scorching of the dried rubber.

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

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

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

The maximum torque of the screw type biaxial extrusion dryer to be used is not particularly limited, but is usually 30n·m or more, preferably 35n·m or more, and more preferably 40n·m or more. Further, the screw type biaxial extrusion dryer used in the present invention is preferably used because the maximum torque is usually 30 to 100n·m, preferably 35 to 75n·m, and 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.

The specific energy consumption of the screw type biaxial extrusion dryer to be used is not particularly limited, but is preferably in the range of usually 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 ], because the roll processability, banbury processability and strength characteristics of the obtained acrylic rubber are highly balanced.

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

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

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

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

(sheet-like Dry rubber)

The shape of the dried rubber extruded from the screw type biaxial extrusion dryer is preferably a sheet shape, since the specific gravity can be increased without involving air and the storage stability can be improved to a high degree. The sheet-like dry rubber extruded from the screw type biaxial extrusion dryer is usually cooled and cut to be used as a sheet-like acrylic rubber.

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

The width of the sheet-like dry rubber extruded from the screw type biaxial extrusion dryer may 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, but is usually 1500 to 6000[ Pa.s ], preferably 2000 to 5000[ Pa.s ], more preferably 2500 to 4000[ Pa.s ], and most preferably 2500 to 3500[ Pa.s ] at a complex viscosity ([ eta ]100 ℃) at 100℃and, in this case, the extrudability and shape retention as sheets are highly balanced, and therefore, it is preferable. That is, the extrusion properties can be further improved by the lower limit or more, and the breakage or fracture of the shape 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 directly folded for use, and is usually cut off for use.

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

The cutting temperature of the sheet-like dry rubber is not particularly limited, but is preferably 60℃or lower, more preferably 55℃or lower, and even more preferably 50℃or lower, because the cutting property and productivity are highly balanced.

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

The ratio of the complex viscosity at 100 ℃ ([ eta ]100 ℃) to the complex viscosity at 60 ℃ ([ eta ]60 ℃) ([ eta ]100 ℃/[ eta ]60 ℃) is not particularly limited, and it 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 the air inclusion is small at this time, and the cutting and productivity are highly balanced, so that 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 in order to reduce the heat conductivity of the sheet-like dry rubber to a very small level of 0.15 to 0.35W/mK, forced cooling by an air cooling system under an air-blowing or cooling system, a water-feeding system by spraying water, a dipping system by immersing in water, or the like is preferable, and an air cooling system under an air-blowing or cooling system is particularly preferable.

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

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

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

(lamination step)

In the present invention, the extruded sheet-like dry rubber may be cut and laminated into a rubber-covered acrylic rubber as needed.

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

The thus obtained rubber-coated acrylic rubber of the present invention is excellent in handling properties, roll processability, crosslinkability, strength properties and compression set resistance, and also excellent in storage stability, banbury processability and water resistance, as compared with the pellet-shaped acrylic rubber, and can be used by charging the rubber-coated acrylic rubber directly or after cutting a required amount into a banbury mixer, roll or the like.

< rubber composition >

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

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

The other rubber component 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 singly or in combination of two or more. The shape of the other rubber component 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 that does not impair the effect of the present invention, and is, for example, generally 70% by weight or less, preferably 50% by weight or less, and more preferably 30% by weight or less.

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

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

These fillers may be used singly or in combination, and the amount thereof may be appropriately selected within a range not to impair the effects of the present invention, but 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 2 or more reactive groups is preferable. As the crosslinking agent, either an ion-crosslinkable compound or a radical-crosslinkable compound may be used, but an ion-crosslinkable compound is preferable.

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 excellent in roll processability, banbury processability and crosslinking property in a short time, and the crosslinked product is highly excellent in water resistance, strength characteristics and compression set resistance, and therefore, is preferable. The "ion" of the ion-crosslinkable or multi-component ion is an ion-reactive ion, and is not particularly limited as long as it reacts with the ion-reactive group of the ion-reactive group-containing monomer of the above-mentioned acrylic rubber, and examples thereof include ion-crosslinkable organic compounds having an ion-reactive group such as an 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-bis-cinnamaldehyde-1, 6-hexamethylenediamine; 4,4 '-methylenedianiline, p-phenylenediamine, m-phenylenediamine, 4' -diaminodiphenyl ether, 3,4 '-diaminodiphenyl ether, 4' - (m-phenylenediisopropylidene) diphenylamine, 4'- (p-phenylenediisopropylidene) diphenylamine aromatic polyamine compounds such as 2,2' -bis [4- (4-aminophenoxy) phenyl ] propane, 4 '-diaminobenzanilide, 4' -bis (4-aminophenoxy) biphenyl, m-xylylenediamine, p-xylylenediamine, and 1,3, 5-benzenetriamine. Among these, hexamethylenediamine carbamate, 2' -bis [4- (4-aminophenoxy) phenyl ] propane and the like are preferable. Further, as the polyamine compound, carbonates thereof can be preferably used. These polyamine compounds are particularly preferably used in combination with carboxyl group-containing acrylic rubber or epoxy group-containing acrylic rubber.

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

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

These crosslinking agents may be used 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 blending amount of the crosslinking agent is within this range, the rubber elasticity can be made sufficient, and the mechanical strength of the rubber crosslinked product can be made excellent, which is preferable.

The rubber composition of the present invention may contain an antioxidant as needed. The type of the antioxidant is not particularly limited, and examples thereof include: other phenol-based antioxidants such as 2, 6-di-tert-butyl-4-methylphenol, 2, 6-di-tert-butylphenol, butylhydroxyanisole, 2, 6-di-tert-butyl-. Alpha. -dimethylamino-p-cresol, octadecyl-3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate, styrenated phenol, 2' -methylene-bis (6-. Alpha. -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-butyl-o-cresol), 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 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, and the like; imidazole-based antioxidants such as 2-mercaptobenzimidazole; quinoline antioxidants such as 6-ethoxy-2, 4-trimethyl-1, 2-dihydroquinoline; hydroquinone-based antioxidants such as 2, 5-di- (t-amyl) hydroquinone. Among these, amine-based antioxidants are particularly preferable.

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

The rubber composition of the present invention contains the rubber component containing the acrylic rubber of the present invention, the filler and the crosslinking agent as essential components, and optionally contains an anti-aging agent, and further optionally contains other additives commonly used in the art, for example, 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 amount 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 of the present invention, the filler, the crosslinking agent, and optionally the antioxidant and other compounding agents, and any means used in the conventional rubber processing field can be used in the mixing, for example, an open roll, a Banbury mixer, and various kneaders. The mixing order of the components may be a normal 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 rubber composition of the present invention is molded by a molding machine, such as an extruder, an injection molding machine, a compressor, or a roll, 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 that can be used for crosslinking of 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 further heated according to the shape, size, etc. of the rubber crosslinked product to carry out secondary crosslinking. 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 is preferably used as a sealing material such as an O-ring, a sealing material, a diaphragm, an oil seal, a shaft seal, a bearing seal, a mechanical seal, a wellhead seal, a seal for electric/electronic equipment, and a seal for air compression equipment, by effectively utilizing the above-mentioned characteristics; 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.

In addition, the rubber crosslinked product of the present invention is preferably used as an extrusion molded die product and a die crosslinked product useful for automobile use, for example: fuel hoses such as fuel tanks, oil filler hoses, exhaust hoses, paper hoses, oil hoses, and air hoses such as turbo charge air hoses and transmission control hoses; various hoses such as radiator hoses, heater hoses, brake hoses, air conditioner hoses, and the like.

< Structure of apparatus for producing acrylic rubber >

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

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

The emulsion polymerization apparatus 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 an emulsion polymerization reactor, water and an emulsifier are mixed with a monomer for forming an acrylic rubber, and emulsified while being properly stirred by a stirrer, 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 being batchwise during the polymerization to obtain an emulsion polymerization liquid. 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 shown 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 having a motor 32 and stirring blades 33, and a drive control unit not shown for controlling the rotational speed and rotational 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 the coagulation liquid to coagulate, whereby aqueous pellets can be produced.

In the coagulation device 3, for example, a method of adding the emulsion polymerization liquid to the stirred coagulation liquid can be used for the contact of the emulsion polymerization liquid with the coagulation liquid. That is, the stirring 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 solidification liquid filled in the stirring tank 30. The temperature control unit of the solidifying 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 not particularly limited, and 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. In the stirring liquid filled in the stirring tank 30, the stirring blade 33 is rotated about the rotation axis by the rotation power of the motor 32, whereby the solidification liquid can be caused to flow. The shape, size, number of the stirring vanes 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 to set the rotational speed and the rotational speed of the stirring blade 33 of the stirring device 34 to predetermined values. The stirring number of the coagulation liquid is, for example, usually 100rpm or more, preferably 200 to 1000rpm, more preferably 300 to 900rpm, and particularly preferably 400 to 800rpm by controlling the rotation of the stirring blade 33 by the drive control unit. 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 shown in fig. 1, the cleaning apparatus 4 includes, for example, a cleaning tank 40, a heating section 41 for heating the cleaning tank 40, and a temperature control section, not shown, for controlling the temperature in the cleaning agitation tank 40. In the cleaning device 4, the water-containing aggregates generated by the coagulation device 3 are mixed with a large amount of water and cleaned, whereby the ash content in the finally obtained acrylic rubber can be effectively reduced.

The heating unit 41 of the cleaning device 4 is configured to heat the inside of the cleaning tank 40. The temperature control unit of the cleaning apparatus 4 is configured 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 cleaning water in the cleaning tank 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 which performs 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 a water separator 43 capable of separating free water. As the water removing machine 43, a metal mesh, a screen, an electric screen, or the like is preferably used.

When the washed aqueous pellets are supplied to the screw type biaxial extrusion dryer 5, the temperature of the aqueous pellets is preferably 40 ℃ or higher, more preferably 60 ℃ or higher. For example, 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 can effectively perform the dehydration step and the drying step as subsequent steps, and can greatly reduce the water content of the finally obtained dried rubber.

The screw type biaxial extrusion dryer 5 shown in fig. 1 is configured to perform the above-described dehydration step and drying step. In addition, although a screw type biaxial extrusion dryer 5 is shown as a preferred example in fig. 1, a centrifugal separator, a squeezer, or the like may be used as a dryer for performing the dehydration step, and a hot air dryer, a reduced pressure dryer, an expansion dryer, a kneading dryer, or the like may be used as a dryer for performing 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 to have: a dewatering cylinder 53 having a function as a dewatering machine for dewatering the aqueous pellets washed by the washing device 4; the dryer barrel 54, which has a function as a dryer for drying the aqueous pellets, is further provided with a die 59 on the downstream side of the screw type biaxial extrusion dryer 5, which has a molding function for molding the aqueous pellets.

The structure of the screw type biaxial extrusion dryer 5 will be described below with reference to fig. 2. Fig. 2 shows a structure as a preferable specific example of the screw type biaxial extrusion dryer 5 shown in fig. 1. The above-described dehydration and drying process 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. The acrylic rubber is preferably dried by applying high shear to the acrylic rubber by this structure. The driving unit 50 is installed 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 first supply cylinder 52a and a second supply cylinder 52 b.

The dewatering cylinder 53 is composed of 3 dewatering cylinders, namely, a first dewatering cylinder 53a, a second dewatering cylinder 53b, and a third dewatering cylinder 53 c.

The dryer section 54 is composed of 8 dryer cylinders, i.e., a first dryer cylinder 54a, a second dryer cylinder 54b, a third dryer cylinder 54c, a fourth dryer cylinder 54d, a fifth dryer cylinder 54e, a sixth dryer cylinder 54f, a seventh dryer cylinder 54g, and an eighth 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, and heats the aqueous pellets in the respective cylinders 52a to 52b, 53a to 53c, 54a to 54h 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 may be employed in which high-temperature steam is supplied from a steam supply means to a steam flow jacket formed in each of the barrels 52a to 52b, 53a to 53c, 54a to 54h, or the like, but the present invention is not limited thereto. The screw type biaxial extrusion dryer 5 further includes a temperature control unit, not shown, which controls the set temperatures of the heating units 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 subjected to the drying treatment.

For example, the number of supply barrels provided in the supply barrel portion 52 is, for example, 1 to 3. In addition, when the number of the dehydrator cylinders of the dehydrator cylinder part 53 is preferably 2 to 10, more preferably 3 to 6, for example, dehydration of the aqueous pellets of the adhesive acrylic rubber can be efficiently performed, which is preferable. The number of the dryer cylinders of the dryer cylinder section 54 is preferably 2 to 10, more preferably 3 to 8, for example.

The pair of screws in the barrel unit 51 are rotationally driven by a driving 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 screw ridge portions and the screw groove portions are meshed with each other, whereby the dewatering efficiency and drying efficiency of the aqueous pellets can be improved.

In addition, the rotation directions of the pair of screws may be the same direction or different directions, and the pair of screws are preferably rotated in the same direction in terms of self-cleaning performance. The screw shape of the pair of screws is not particularly limited, and is not particularly limited as long as it is a shape required in each of the

cylinder portions

52, 53, 54.

The supply cylinder section 52 is a region for supplying the aqueous pellets into the cylinder unit 51. The first supply cylinder 52a of the supply cylinder section 52 has a feed port 55 for supplying the aqueous pellets into the cylinder unit 51.

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

The first to third 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. Dehydration slits 56a, 56b, 56c are formed in the respective dehydration cylinders 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 can be reduced and the dewatering of the aqueous pellets can be effectively performed.

The removal of water from the aqueous pellets in the respective dewatering cylinders 53a to 53c of the dewatering cylinder 53 includes both the removal in a liquid state from the

respective dewatering slits

56a, 56b, 56c and the removal in a vapor state. The dehydration cylinder 53 of the present embodiment is distinguished from a case where water is removed in a liquid state, which is referred to as drainage, and a case where water is removed in a vapor state, which is referred to as drainage.

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 dehydration cylinder section 53, which dehydration cylinder among the first to third dehydration cylinders 53a to 53c is used for the drainage or the steam discharge 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 dehydration cylinder for the drainage may be increased. In this case, for example, as shown in fig. 2, the first and second dewatering cylinders 53a, 53b on the upstream side are used for water discharge, and the third dewatering cylinder 53c on the downstream side is used for steam discharge. For example, in the case where the dewatering cylinder part has 4 dewatering cylinders, it is conceivable to drain water from the 3 dewatering cylinders on the upstream side and drain steam from the 1 dewatering cylinder on the downstream side. On the other hand, in the case of decreasing the water content, the dehydration cylinder in which the steam discharge is performed may be increased.

The setting temperature of the dewatering cylinder 53 is usually 60 to 150 ℃, preferably 70 to 140 ℃, more preferably 80 to 130 ℃, as described in the above dewatering and drying steps, and the setting temperature of the dewatering cylinder for dewatering in a discharged state is usually 60 to 120 ℃, preferably 70 to 110 ℃, more preferably 80 to 100 ℃, and the setting temperature of the dewatering cylinder for dewatering in a discharged state is usually 100 to 150 ℃, preferably 105 to 140 ℃, more preferably 110 to 130 ℃.

The dryer section 54 is a region in which the dehydrated aqueous pellets are dried under reduced pressure. Of the first to eighth dryer barrels 54a to 54h constituting the dryer barrel section 54, the second dryer barrel 54b, the fourth dryer barrel 54d, the sixth dryer barrel 54f, and the eighth dryer barrel 54h have

exhaust ports

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

exhaust ports

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

A vacuum pump, not shown, is connected to each end of each air passage, and the dryer cylinder 54 is depressurized to a predetermined pressure by operation of the vacuum pump. The screw extruder 5 has a pressure control unit, not shown, for controlling the operation of these vacuum pumps to control the vacuum level in the dryer barrel section 54.

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

As described above, the vacuum degree of the dryer cylinder 54 may be appropriately selected, and is usually set to 100 to 250 ℃, preferably 110 to 200 ℃, and more preferably 120 to 180 ℃.

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

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 by the dryer cylinder 54 is extruded and molded into a shape corresponding to a predetermined nozzle shape through the discharge port of the die 59. The acrylic rubber passing through the die 59 can be molded into various shapes such as a pellet, a column, a round bar, a sheet, etc., according to the nozzle shape of the die 59, and in the present invention, into a sheet. A perforated plate, a metal mesh, or the like may be provided between the screw and the die 59.

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

dewatering slits

56a, 56b, and 56c provided in the first to third dewatering cylinders 53a to 53c drain water and steam contained in the aqueous pellets, respectively, and dewater the aqueous pellets.

The aqueous pellets dehydrated by the dehydration cylinder section 53 are sent to the dryer cylinder section 54 by 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 to form 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 a not-shown vent pipe connected to each of the

exhaust ports

58a, 58b, 58c, and 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 rotation speed (N) of the pair of screws in the barrel unit 51 may be appropriately selected depending on each condition, and is usually 10 to 1000rpm, and from the viewpoint of being able to efficiently reduce the water content of the acrylic rubber and the amount of methyl ethyl ketone insoluble components, it is preferably 50 to 750rpm, more preferably 100 to 500rpm, and most preferably 120 to 300rpm.

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

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

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

The specific energy consumption in the cylinder unit 51 is not particularly limited, but is usually 0.1 to 0.25[ kw.h/kg ] or more, preferably 0.13 to 0.23[ kw.h/kg ], and 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[1/s ] or more, preferably 45 to 125[1/s ], and more preferably 50 to 100[1/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 in the dehydrator and the drying step in the dryer. As the cooling method of the cooling device 6, various methods including an air cooling method under an air blowing or cooling system, a water adding method by spraying water, a dipping method in water, and the like can be used. In addition, the rubber may also be cooled and dried by leaving it at room temperature.

As described above, the dried rubber discharged from the screw 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. A conveyor type cooling device 60 for cooling the sheet-shaped dry rubber 10 molded into a sheet shape, which is an example of the cooling device 6, will be described below with reference to fig. 3.

Fig. 3 shows a structure of a preferred conveyor 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 convey the sheet-like dry rubber 10 discharged from the discharge port of the die 59 of the screw extruder 5 and cool it by an air cooling method. 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 directly connected to the die 59 of the screw type extruder 5 shown in fig. 2, or is disposed in the vicinity of the die 59.

The transport cooling device 60 includes: a conveyor 61 that conveys the sheet-like dried rubber 10 discharged from the die 59 of the screw extruder 5 in the direction of arrow a in fig. 3; and a cooling unit 65 that blows cold 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 having the sheet-like dry rubber 10 carried thereon. 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 a conveyor belt 64.

The cooling unit 65 is not particularly limited, and may be configured to blow cooling air sent from a cooling air generating unit, not shown, to 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 cooling device 60 (the length of the portion capable of blowing out the 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 conveyor type cooling device 60 shown in fig. 3, the sheet-like dry rubber 10 discharged from the die 59 of the screw extruder 5 is conveyed by the conveyor 61, and cooling air is blown from the cooling unit 65 to the sheet-like dry rubber 10 to cool the sheet-like dry rubber 10.

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

conveyor

61 and 1 cooling unit 65 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 each 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 rubber bag. 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 rubber-coated acrylic rubber produced by the rubber coating device 7 are not particularly limited, and for example, approximately 20kg of a rubber-coated acrylic rubber having a substantially rectangular parallelepiped shape can be produced.

The rubber packing device 7 may also have, for example, a packer, and the rubber-packed acrylic rubber is produced by compressing cooled dry rubber with the packer.

In addition, in the case of producing the sheet-like dry rubber 10 by the screw extruder 5, a rubber-coated acrylic rubber in which the sheet-like dry rubber 10 is laminated may be produced. For example, a cutter mechanism for cutting the sheet-like dried 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 coating device 7 is constituted in the following manner, for example: the cooled sheet-like dry rubber 10 is continuously cut at predetermined intervals to produce a sheet-like dry rubber 16 of a predetermined size. By stacking a plurality of pieces of the sliced dried rubber 16 cut into a predetermined size by a cutting mechanism, a rubber-coated acrylic rubber in which the sliced dried rubber 16 is stacked can be produced.

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

Examples

The present invention will be described in more detail with reference to examples and comparative examples. In each example, "parts", "%" and "ratio" are weight basis unless otherwise specified. Further, various physical properties and the like were evaluated by the following methods.

[ monomer composition ]

Regarding the monomer composition in the acrylic rubber, use is made of ¹ H-NMR was used to confirm the monomer structure of each monomer unit in the acrylic rubberThe reactivity of the reactive groups remaining in the acrylic rubber and the content of each of the reactive groups 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. Specifically, since the polymerization reaction is an emulsion polymerization reaction, the polymerization conversion rate is approximately 100%, and the unreacted monomers cannot be confirmed, the content ratio of each monomer unit in the rubber is the same as the amount of each monomer used.

[ reactive group content ]

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

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

(2) The amount of epoxy group was calculated by dissolving the sample in methyl ethyl ketone, adding an equivalent amount of hydrochloric acid thereto to react with epoxy group, 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, and the generated chlorine was absorbed by water and titrated with silver nitrate.

[ Ash content ]

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

[ ash component amount ]

The ash content collected in the measurement of the ash content was pressed against titration filter paper having a diameter of 20mm, and XRF measurement was performed on the content (ppm) of each component in the acrylic rubber ash using ZSX Primus (manufactured by Physics Co.).

[ molecular weight and molecular weight distribution ]

The molecular weight (Mw, mn, mz) and the molecular weight distribution (Mw/Mn and Mz/Mw) of the acrylic rubber were determined by GPC-MALS method using, as a solvent, a solution in which lithium chloride and 37% concentrated hydrochloric acid were added to dimethylformamide to give a concentration of 0.05mol/L lithium chloride and a concentration of 0.01% hydrochloric acid, respectively, and an absolute molecular weight distribution in which a polymer region is a major point were measured by GPC-MALS method.

The structure of the gel permeation chromatograph multi-angle light scattering photometer of the present apparatus was composed of a pump (manufactured by LC-20ADOpt shimadzu corporation), a differential refractive optical detector (manufactured by Optilab rEX Huai Ya trickplay corporation) as a detector, and a multi-angle light scattering detector (manufactured by DAWN HELEOS Huai Ya trickplay corporation). Specifically, a multi-angle laser light scattering detector (MALS) and a differential refractive index detector (RI) were assembled in a GPC (Gel Permeation Chromatography) apparatus, and the molecular weight of a solute and its content were calculated and obtained in sequence by performing light scattering intensity and refractive index differences of a molecular chain solution classified into size according to elution time by a GPC apparatus. The measurement conditions and measurement methods using the GPC apparatus are as follows.

Column: TSKgel alpha-M2 root%

Manufactured by Tosoh corporation)

Column temperature: 40 DEG C

Flow rate: 0.8ml/mm

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

[ glass transition temperature (Tg) ]

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

[ amount of methyl ethyl ketone insoluble component ]

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

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

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

[ specific gravity ]

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

The measured value obtained by the following measuring method was the density, and the density of water was 1Mg/m ³ Specific gravity at that time. Specifically, the specific gravity of the rubber sample obtained by the a method of the JIS K6268 crosslinked rubber-density measurement is a value obtained by dividing the mass by the volume of the rubber sample including voids, and the density of the rubber sample obtained by dividing the density of the rubber sample obtained by the a method of the JIS K6268 crosslinked rubber-density measurement 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 on a hook on a chemical balance having an accuracy of 1mg using a fine nylon yarn having a mass of less than 0.010g so that the bottom edge of the test piece was 25mm above a distribution plate for the chemical balance, and the mass (m 1) to mg of the test piece was measured 2 times in the atmosphere.

(2) Next, 250cm of the solution was placed on a chemical balance-use dispensing 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 movement 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 2 times.

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

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

(Density of rubber sample without counterweight)

Density=m1/(m 1-m 2)

(Density of rubber sample when weight was used)

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

[ Water content ]

According to JIS K6238-1: the moisture content (%) was measured by the oven a (volatile matter measurement) method.

[pH]

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

[ Complex viscosity ]

The complex viscosity η is determined by: the complex viscosity η at each temperature was determined by measuring the temperature dispersion (40 to 120 ℃) at a deformation 473% and 1Hz using a dynamic viscoelasticity measuring device "Rubber Process Analyzer RPA-2000" (manufactured by alpha technologies Co.). Here, in the above dynamic viscoelasticity, the dynamic viscoelasticity at 60 ℃ is defined as the complex viscosity η (60 ℃) and the dynamic viscoelasticity at 100 ℃ is defined as the complex viscosity η (100 ℃), and the ratio η (100 ℃) to η (60 ℃) is calculated.

[ Mooney viscosity (ML1+4, 100 ℃)

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

[ Cross-Linkability ]

The change rate of the breaking strength of the rubber crosslinked material subjected to the secondary crosslinking for 2 hours and the breaking strength of the rubber crosslinked material subjected to the secondary crosslinking for 4 hours ((breaking strength of the rubber crosslinked material crosslinked for 4 hours/breaking strength of the rubber crosslinked material crosslinked for 2 hours). Times.100 was calculated, and the crosslinkability of the rubber sample was judged by 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-windability and the state of the rubber were observed when the rubber sample was rolled, and the roll processability of the rubber sample was evaluated on the basis of the following criteria.

And (3) the following materials: easy mixing, easy winding on the roller, no detachment from the roller is observed, and the surface of the rubber composition after mixing is smooth

And (2) the following steps: easy kneading, easy winding around the roll, no detachment from the roll, and slight irregularities on a part of the surface of the rubber composition after kneading

And ∈: easy kneading, excellent roll windability, and the surface of the rubber composition after kneading has a few projections and depressions

Delta: easy mixing, slightly poor roll windability, and rough surface of the rubber composition after mixing

X: the roll windability was also poor when a load was applied to kneading

[ Banbury processability ]

After the rubber sample was put into a banbury mixer heated to 50 ℃ for mastication for 1 minute, compounding agent a described in table 1 was put into the rubber mixture, the rubber mixture of the first stage was integrated, and the time until the maximum torque value was exhibited, that is, BIT (carbon black mixing time, black Incorporation Time) was measured, and banbury processability of the rubber sample was evaluated by an index of 100 in comparative example 2 (the smaller the index, the more excellent the processability).

[ evaluation of storage stability ]

The rubber sample was put into a constant temperature and humidity tank (SH-222 manufactured by espek) at 45 ℃ x 80% rh, the rate of change of the water content before and after 7 days of the test was calculated, and the storage stability of the rubber sample was evaluated by using an index of 100 in comparative example 2 (the smaller the index, the more excellent the storage stability).

[ evaluation of Water resistance ]

The cross-linked product of the rubber sample was immersed in distilled water at 85℃for 100 hours in accordance with JIS K6258 to conduct an immersion test, and the volume change rate before and after the immersion was calculated in accordance with the following formula, and the water resistance of the rubber sample was evaluated by an index of 100 in comparative example 2 (the water resistance was excellent as the index was smaller).

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 after 90 hours at 175℃was measured in a state where the rubber crosslinked product of the rubber sample was compressed by 25% in accordance with JIS K6262, and the compression set resistance of the rubber sample was evaluated according to the following criteria.

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

X: compression set of 15% or more

[ evaluation of physical Properties in Normal state ]

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

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

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

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

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

The amount of methyl ethyl ketone insoluble component at 20 points arbitrarily selected 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 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 the total of the 20 points of measurement is 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 all of the 20 points of measurement are within the range of the average value.+ -. 5 (1 of the 20 points of measurement is outside the range of the average value.+ -. 3, and all of the 20 points are 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 at 20 points of measurement being out of the range of + -5 of the average value

[ evaluation of processing stability Using Mooney scorch inhibition ]

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

Example 1

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

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

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

194 parts of hot water (70 ℃) was added to the coagulation tank in which the filtered aqueous pellets remained, stirred for 15 minutes, the aqueous pellets were washed, then the water was discharged, 194 parts of hot water (70 ℃) was added again, stirred for 15 minutes, and the aqueous pellets were washed (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. Next, the sheet-like dry rubber was cooled at a cooling rate of 200 ℃/hr 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 (first to third dehydrators), and 5 dryers (first to fifth dryers). The first dewatering cylinder discharges water, and the second and third dewatering cylinders discharge steam. The operating conditions of the screw type biaxial extrusion dryer are as follows.

Water content:

water content of the aqueous pellet after draining with the first dewatering barrel section: 20 percent of

Water content of the aqueous pellets after steam removal with the third dewatering barrel section: 10 percent of

Moisture content of the aqueous pellets after drying with the fifth dryer section: 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:

first dewatering barrel: 100 DEG C

A second dewatering barrel: 120 DEG C

Third dewatering barrel: 120 DEG C

First dryer barrel: 120 DEG C

Second dryer barrel: 130 DEG C

Third dryer barrel: 140 DEG C

Fourth dryer barrel: 160 DEG C

Fifth dryer barrel: 180 DEG C

Operating conditions:

diameter of screw (D): 132mm

Full length of screw (L): 4620mm

·L/D：35

Rotational speed of the screw: 135rpm

Extrusion amount of rubber from die: 700 kg/hr

Vacuum of the dryer barrel: 10kPa

Resin pressure in die: 2MPa of

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

The extruded sheet-like dry rubber was cooled to 50℃and then cut by a cutter, and 20 parts (20 kg) of the sheet-like dry rubber was laminated to obtain a rubber-coated acrylic rubber (A) before the temperature reached 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 using a Banbury mixer, and mixed at 50℃for 5 minutes (first-stage mixing). At this time, BIT was measured, and the Banbury processability of the acrylic rubber was evaluated, and the results are shown in Table 2-2.

Next, the resulting mixture was transferred 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: SEAST3 (HAF) in the table is carbon black (manufactured by eastern sea carbon Co., ltd.).

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

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

Example 2

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

Example 3

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

Example 4

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

Example 5

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

Example 6

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

Example 7

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

Example 8

Acrylic rubber (H) was obtained in the same manner as in example 6 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 1

Acrylic rubber (I) was obtained and evaluated for each characteristic in the same manner as in example 8, except that the amount of potassium persulfate as the inorganic radical generator was changed to 0.22 part, and the acrylic rubber was obtained in the form of a pellet without adding a chain transfer agent and without being subjected to rubber encapsulation by a packer. The results are shown in Table 2-2.

Comparative example 1

Acrylic rubber (J) was obtained and evaluated for each property in the same manner as in reference example 1 except that a coagulation reaction was carried out by adding a 0.7% aqueous magnesium sulfate solution to the stirred emulsion polymerization solution (stirring number: 100rpm, circumferential speed: 0.5 m/s) after emulsion polymerization. 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 194 parts of industrial water was added to 100 parts of the aqueous pellets after the coagulation reaction, the aqueous pellets having been discharged from the coagulation tank were washed after stirring at 25℃for 5 minutes, 194 parts of an aqueous sulfuric acid solution having a pH of 3 was added, the aqueous pellets were stirred at 25℃for 5 minutes, the water was discharged from the coagulation tank and then subjected to acid washing 1 more time, and then 194 parts of pure water was added and subjected to pure water washing 1 more time, whereby each characteristic was evaluated. The results are shown in Table 2-2.

Comparative example 3

To the monomer emulsion was continuously added 0.025 parts of n-dodecyl mercaptan as a chain transfer agent, and the aqueous pellet was washed as follows: acrylic rubber (L) was obtained in the same manner as in comparative example 2 except that 194 parts of industrial water was added only 2 times and the mixture was stirred at 25℃for 5 minutes in the coagulation tank, and then the water was discharged from the coagulation tank, whereby the properties were evaluated. The results are shown in Table 2-2.

[ Table 2-1]

[ Table 2-2]

As is clear from tables 2-1 and 2-2, the acrylic rubber (A) to (H) of the present invention has at least one reactive group derived from carboxyl groups, epoxy groups and chlorine atoms, has a number average molecular weight (Mn) of 10 to 50 tens of thousands based on the absolute molecular weight and the absolute molecular weight distribution measured by GPC-MALS method, has a ratio (Mw/Mn) of weight average molecular weight (Mw) to number average molecular weight (Mn) of 3.7 to 6.5, has a methyl ethyl ketone insoluble content of 50% by weight or less, has an ash content of 0.5% by weight or less, and has a total amount of magnesium and phosphorus in ash of 50% by weight or more, and the acrylic rubber (A) to (H) is remarkably excellent in normal physical properties including crosslinkability, roll processability, banbury processability, water resistance, compression set characteristics and strength characteristics, and also is remarkably excellent in storage stability (examples 1 to 8).

As is clear from tables 2 to 2, since the acrylic rubbers (A) to (L) produced under the conditions of examples, reference examples and comparative examples of the present application have any reactive group such as a carboxyl group, an epoxy group and a chlorine atom and have a specific region having a number average molecular weight (Mn) of 10 to 50 tens of thousands as measured by GPC-MALS, the acrylic rubbers (A) to (L) are excellent in normal physical properties including crosslinking property in a short period of time, compression set resistance and strength characteristics (examples 1 to 8, reference examples 1 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 properties, but are inferior in roll processability, banbury processability, water resistance and storage stability.

As is clear from table 2-2, in the case where the number average molecular weight (Mn) is in the range of 10 to 50 tens of thousands of specific regions 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, still more preferably 4 or more, and in this case, the roll processability can be remarkably improved without impairing the strength characteristics (comparison of examples 1 to 8 and comparative examples 1 to 3).

As is clear from tables 2-1 and 2-2, the acrylic rubber having the number average molecular weight (Mn) within the range of the specific region and having a wide Mw/Mn and excellent strength characteristics and roll processability can be obtained by: the inorganic radical generator was reduced and 1 polymerization chain was extended, and a chain transfer agent (n-dodecyl mercaptan) was added in portions (examples 1 to 8). In order to widen the Mw/Mn efficiently, the number of times of addition after batchwise was greatly affected, and the Mw/Mn was wider for 2 times than for 3 times of addition after batchwise (comparison of examples 3 to 5 and examples 6 to 8), but if the chain transfer agent was continuously added, the Mw/Mn was only slightly widened and the improvement of the roll processability was limited (comparative example 3). This is presumably because, although the GPC-MALS method does not show a standard double peak, the chain transfer agent is added after the batch, so that a high molecular weight component and a low molecular weight component can be obtained, mw/Mn can be widened, and roll processability can be significantly improved. In addition, although not shown in Table 2-1, in the present example, sodium ascorbate was added as a reducing agent 120 minutes after initiation of polymerization, and by doing so, the formation of high molecular weight components of the acrylic rubber became easier, and the Mw/Mn widening effect of the chain transfer agent added after the initiation was increased. On the other hand, although not shown in this example, too much addition of the chain transfer agent results in too wide Mw/Mn, and for example, if it is 10 or more, the low molecular weight component is present in large amounts, and the strength property and compression set resistance property are not preferable. Further, if an organic radical generator is used instead of an inorganic radical generator, mw/Mn becomes narrow, and roll processability is significantly lowered.

As is clear from tables 2 to 2, regarding the banbury workability of the acrylic rubber, it is related to the amount of the methyl ethyl ketone insoluble component, and the smaller the methyl ethyl ketone insoluble component, the more excellent the banbury workability. It is found that the banbury processability of the acrylic rubber is excellent particularly when the amount of the methyl ethyl ketone insoluble component is 50% by weight or less, preferably 30% by weight or less (comparison of examples 3 to 8 and comparative example 3 with reference example 1 and comparative examples 1 to 2), and is remarkably excellent when the amount of the methyl ethyl ketone insoluble component is 10% by weight or less, preferably 5% by weight or less (examples 1 to 2). It is found that the amount of methyl ethyl ketone insoluble matter in the acrylic rubber can be reduced by emulsion polymerization in the presence of a chain transfer agent (examples 3 to 8 and comparative example 3), and particularly when the polymerization conversion is improved in order to improve the strength characteristics, the amount of methyl ethyl ketone insoluble matter increases sharply, and therefore in examples 3 to 8 added after the chain transfer agent is performed in the latter half of emulsion polymerization, the formation of methyl ethyl ketone insoluble matter can be suppressed. Further, it was found that the Banbury processability of the produced acrylic rubber was significantly improved by drying the aqueous pellets with a screw type biaxial extrusion dryer to significantly reduce the amount of methyl ethyl ketone insoluble components of the acrylic rubber (comparison of examples 1 to 2 and examples 3 to 8). In the present invention, although not shown in the present example, it was confirmed that the methyl ethyl ketone insoluble component amount (comparative examples 1 to 2) which rapidly increased by emulsion polymerization without adding a chain transfer agent was melted and kneaded in a state of substantially not containing water (water content less than 1 wt%) in a screw type biaxial extrusion dryer to disappear, and the banbury processability was greatly improved without impairing the strength characteristics.

As is clear from tables 2 to 2, the acrylic rubbers (A) and (B) of examples 1 and 2 of the present invention are remarkably excellent in water resistance as compared with the acrylic rubbers (J) to (L) of comparative examples 1 to 3, and the acrylic rubbers (C) to (I) of examples 3 to 8 and reference example 1 are excellent. When the influence of the difference in the ion reactive groups on the water resistance was observed in examples 3 to 8 and reference example 1 having the same ash amount, it was found that the acrylic rubber (C, F) of examples 3 and 6 having a carboxyl group and the acrylic rubber (D, G) of examples 4 and 7 having an epoxy group were 2 times more excellent than the acrylic rubber (E, H, I) of examples 5 and 8 having a chlorine atom and reference example 17. It is understood that the acrylic rubbers (A) to (H) of the present invention, the acrylic rubber (I) of the reference example, and the acrylic rubber (J) to (L) of the comparative example each have an element content of more than 90% by weight in total of phosphorus, magnesium, sodium, calcium, and sulfur in ash, and that the acrylic rubber is excellent in water resistance, mold releasability, and other properties, and particularly, even if the ash content is the same, the water resistance in which the ratio of phosphorus to magnesium in ash is large is excellent (comparison of reference example 1 and comparative example 2).

As is clear from tables 2 to 2, the water resistance of the acrylic rubber was greatly affected by the ash component together with the ash component. It is found that, for example, the ash contents of examples 3 to 8, reference example 1 and comparative example 2 are the same, that is, 0.3 wt%, and that the acrylic rubber having a high content of phosphorus and magnesium in ash is extremely excellent in water resistance (comparison of examples 3 to 8 and reference example 1 with comparative example 2). This is considered to be because: the phosphorus and magnesium in the ash exist as insoluble salts, improving the water resistance of the acrylic rubber, and the improvement effect is particularly high when the phosphorus and magnesium are binary. In this example, although the sodium salt of dibasic phosphate was used as the emulsifier and the aqueous magnesium sulfate salt solution was used as the coagulant, the content of magnesium and phosphorus in the ash after washing the aqueous pellet produced by the coagulation method of the present invention was 70% by weight or more (examples 3 to 8), and the total amount of magnesium and phosphorus in the ash after further dehydration was 90% by weight or more (examples 1 to 2), so that the emulsifier was subjected to salt exchange during the coagulation reaction to remain as a water-insoluble magnesium phosphate salt, and the water resistance was not affected, and as a result, the water resistance of the acrylic rubber was greatly improved.

As is clear from tables 2-1 and 2-2, the ash content of the acrylic rubber was difficult to remove by washing when the phosphorus and magnesium components were large, and a large amount of the acrylic rubber remained in the washing of the aqueous pellet in the normal coagulation step (comparative example 1). However, it was found that even with ash containing a large amount of phosphorus and magnesium, the water resistance of the acrylic rubber can be improved by washing the obtained aqueous pellets with hot water (examples 3 to 8 and reference 1) and dehydrating the washed aqueous pellets to extrude the ash (examples 1 to 2) therein, by adding the emulsion polymerization liquid obtained by emulsion polymerization to the coagulating liquid, with the coagulating liquid being a concentrated aqueous solution (coagulating liquid) and stirring vigorously, to carry out the coagulation reaction. This is presumably because, although omitted in the examples of the present application, the aqueous aggregates generated in the coagulation step carried out in the examples of the present application are aggregated in the range of particle diameters as small as 710 μm to 4.75mm, thereby remarkably improving the cleaning efficiency in hot water and the ash removal efficiency at the time of dehydration and remarkably improving the water resistance of the acrylic rubber. In addition, although the ash content can be reliably reduced by the time of washing with water at room temperature up to the 3 rd time, the effect of reducing the ash content is hardly seen after the 4 th time, although the 3 rd time and the 4 th time are hardly different from each other. On the other hand, the ash content in the acrylic rubber was reduced until the 2 nd washing in hot water, and the washing effect after the 3 rd washing was hardly confirmed.

It was found that the acrylic rubber was more excellent in water resistance than the chlorine atom due to the reactive group, and the carboxyl group and the epoxy group (comparison of examples 3 to 4 and 5, and comparison of examples 6 to 7 and 8).

As is clear from tables 2-1 and 2-2, the acrylic rubbers (A) to (H) of the present invention are excellent in crosslinking property, roll processability, banbury processability, water resistance, compression set resistance and strength characteristics, and also remarkably excellent in storage stability (examples 1 to 8). The relationship between the storage stability of the acrylic rubber and the specific gravity of the acrylic rubber was large, and when the specific gravity was large, the acrylic rubber was not involved in air, and the storage stability was excellent (compared with examples 1 to 2, examples 3 to 8, and comparative examples 1 to 3). The acrylic rubber having a high specific gravity can be encapsulated by compressing the acrylic rubber in pellet form with a packer (examples 3 to 8), and more preferably, it is obtained by extruding the acrylic rubber into a sheet form without involving air with a screw type biaxial extrusion dryer, cutting the sheet at a specific temperature, and laminating the sheet to obtain the acrylic rubber in the form of an encapsulated form (examples 1 to 2). In the present invention, it was found that, in particular, as an acrylic rubber bag in which acrylic rubber sheets melt-kneaded under reduced pressure and dried were laminated, the storage stability was significantly improved without impairing the normal physical properties and water resistance including short-time crosslinkability, roll processability, compression set resistance, and strength characteristics (examples 1 to 2). The lower the ash content or the better the storage stability of the acrylic rubber when the pH is specified (examples 1 to 8).

As described above, the acrylic rubber (A) to (H) of the present invention has at least one reactive group derived from a carboxyl group, an epoxy group and a chlorine atom, has a weight average molecular weight (Mn) of 10 to 50 tens of thousands, a ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of 3.7 to 6.5, a methyl ethyl ketone insoluble content of 50 wt% or less, an ash content of 0.5 wt% or less and a total amount of magnesium and phosphorus in ash of 50 wt% or more, is highly balanced in normal physical properties including roll processability, banbury processability, water resistance, compression set resistance and strength characteristics, and is excellent in crosslinking property and storage stability.

[ regarding the particle size of the resulting hydrous pellets ]

Regarding the aqueous pellets produced in the coagulation step of examples 1 to 8, reference example 1 and comparative example 1, the ratio of the aqueous pellets to the amount of the aqueous pellets in the following range was measured using a JIS sieve: (1) 710 μm to 6.7mm (6.7 mm without passing through 710 μm); (2) 710 μm to 4.75mm (not passing 710 μm but 4.75 mm); (3) 710 μm to 3.35mm (not passing 710 μm but 3.35 mm). The results are shown below.

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

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

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

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

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

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

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

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

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

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

From these results, it was found that even when the same washing was performed, the amount of ash remaining in the acrylic rubber or the acrylic rubber was different depending on the size of the aqueous aggregates generated in the coagulation step, and that the specific ratio of (1) to (3) was large, the washing efficiency was high, the ash amount was low, and the water resistance was excellent (comparison between examples 3 to 8 of tables 2-2 and comparative example 1 of reference example 1). It was also found that the ash removal rate at the time of dehydration of 20 wt% was also high even when the specific proportion of the aqueous pellets of (1) to (3) was large, and the water resistance of the acrylic rubber was significantly improved by further reducing the ash content (comparison of examples 1 to 2 and comparative examples 3 to 8). Further, it is apparent from comparative example 8 and reference example 1 that the particle size of the aqueous pellets produced in the solidification step is not related to the presence or absence of the chain transfer agent.

For reference, the procedure was carried out in the same manner as in comparative example 1 (reference example 3) except that the emulsion polymerization liquid was added to the coagulation liquid in the coagulation step (reference example 2), and the coagulant concentration of the coagulation liquid was changed from 0.7% by weight to 2% by weight, except that the particle size ratio of the produced aqueous pellets and the ash content in the acrylic rubber were measured in the same manner as in comparative example 1. The results are shown below. The same conditions as in reference example 1 were set when the stirring number of the solidification liquid in reference example 3 was changed to 600rpm and the circumferential speed was increased from 0.5m/s to 3.1m/s and the conditions were changed to the conditions of intense rotation.

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

Reference example 3: 91 wt%, 70 wt%, 40 wt% and 0.41 wt% ash

From these results, it was found that the method (Lx. About.v.) of increasing the concentration of the coagulating liquid (2%) during the coagulation reaction and adding the emulsion polymerization liquid to the stirring coagulating liquid to carry out the coagulation reaction was changed to the method (Lx. About.v.) and the stirring of the coagulating liquid was vigorously carried out (stirring number 600 rpm/circumferential speed 3.1 m/s), whereby the particle diameter of the produced aqueous particles could be concentrated in a specific range of 710 μm to 4.75mm, and the water resistance could be greatly improved without impairing the properties of the acrylic rubber such as the normal physical properties including the crosslinkability, roll workability, compression set resistance and strength properties by significantly improving the washing efficiency with hot water and the removal efficiency of the emulsifier and coagulant during the dehydration to reduce the ash content of the acrylic rubber (examples 1 to 2).

Example 9

An 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 and 1.5 parts of mono-n-butyl fumarate and the emulsifier was changed to 1.8 parts of sodium tridecyloxy hexaoxyethylene phosphate as shown in Table 3-1, and the results are shown in Table 3-2. Further, 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 in table 3-1.

Example 10

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 results are shown in tables 3 to 2. Further, the post-dehydration (drainage) water content, maximum torque, specific power, specific energy consumption, shear rate, and shear viscosity of the screw type biaxial extrusion dryer are shown in table 3-1.

Example 11

An acrylic rubber (O) was obtained in the same manner as in example 9 except that the monomer components were changed to 28 parts of ethyl acrylate, 38 parts of N-butyl acrylate, 27 parts of methoxyethyl acrylate, 5 parts of acrylonitrile and 2 parts of allyl glycidyl ether, and the operating conditions of the screw-type biaxial extrusion dryer were changed to high shear (maximum torque 45n·m), and the properties (the compounding agent was changed to "formula 3"), and the results were evaluated as shown in table 3-2. Further, the post-dehydration (drainage) water content, maximum torque, specific power, specific energy consumption, shear rate, and shear viscosity of the screw type biaxial extrusion dryer are shown in table 3-1.

Example 12

An acrylic rubber (P) was obtained in the same manner as in example 11 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 n-butyl fumarate, and the properties (the compounding agent was changed to "formula 1") were evaluated, and the results are shown in Table 3-2. Further, 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 in table 3-1.

Example 13

An acrylic rubber (Q) was obtained in the same manner as in example 11 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. Further, 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 in table 3-1.

Example 14

An acrylic rubber (R) was obtained in the same manner as in example 10 except that the monomer components were changed to 28 parts of ethyl acrylate, 38 parts of N-butyl acrylate, 27 parts of methoxyethyl acrylate, 5 parts of acrylonitrile and 2 parts of allyl glycidyl ether, and the operating conditions of the screw-type biaxial extrusion dryer were changed to high shear (maximum torque 45n·m), and the properties (compounding agent was changed to "formula 3"), and the results were shown in table 3-2. Further, 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 in table 3-1.

Example 15

An acrylic rubber (S) was obtained in the same manner as in example 14 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. Further, 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 in table 3-1.

Example 16

An acrylic rubber (T) was obtained in the same manner as in example 14 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. Further, 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 in table 3-1.

[ Table 3-1]

[ Table 3-2]

As is clear from tables 3-1 and 3-2, by increasing the maximum torque of the screw type biaxial extrusion dryer to a specific region (high shear), and dehydrating and drying the aqueous pellets, the roll processability can be further remarkably improved without impairing the properties such as the crosslinkability, banbury processability, water resistance, compression set resistance, and strength properties of the acrylic rubber of the present invention (comparison of examples 11 to 16 with examples 9 to 10). From this, it was found that by drying the acrylic rubber composed of the high molecular weight component and the low molecular weight component emulsion-polymerized by adding the chain transfer agent later with high shear using a screw type biaxial extrusion dryer, the molecular weight distribution can be further moderately widened, and the roll processability can be further improved.

Further, the rubber samples were evaluated for the variation in the amount of methyl ethyl ketone insoluble components 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-mentioned standard.

When the deviation evaluation of the methyl ethyl ketone insoluble component amount was performed using the acrylic rubbers (M) to (T) obtained in examples 9 to 16 and the acrylic rubber (J) obtained in comparative example 1 as rubber samples, the results of the acrylic rubbers (a) to (H) of examples 9 to 16 of the present invention were all "", but the result of the acrylic rubber (J) of comparative example 1 was "×".

This is presumed to be because: the acrylic rubbers (M) to (T) are melt-kneaded by a screw type biaxial extrusion dryer, and melt-kneaded and dried in a state substantially free of moisture (water content less than 1 wt%) so that the amount of methyl ethyl ketone insoluble components is almost eliminated and the variation in the amount of methyl ethyl ketone insoluble components is almost eliminated, whereby the banbury processability can be remarkably improved without impairing the normal physical properties including crosslinkability, roll processability, compression set resistance and 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 9 and extrusion-dried, and the amount of methyl ethyl ketone insoluble component measured on the obtained acrylic rubber were reduced to substantially the same level as those of the acrylic rubber (M), and the banbury processability was improved, but the roll processability was evaluated as "x".

Regarding the (M) to (T) acrylic rubber compositions comprising the acrylic rubbers of examples 9 to 16, the mooney scorch storage stability was evaluated on the basis of the following criteria by measuring the mooney scorch time T5 (minutes) at a temperature of 125 ℃ in accordance with JIS K6300 by the above-described method for evaluating the processing stability by mooney scorch inhibition. The results were excellent.

And (3) the following materials: the Mooney scorch time t5 exceeds 2.0 minutes

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

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

In addition, regarding the acrylic rubbers (M) to (T), the cooling rate of the sheet-like dry rubber extruded from the screw type biaxial extrusion dryer was 40℃/hr or more as fast as about 200℃/hr as in example 1.

[ Release to Metal mold ]

The rubber compositions of the acrylic rubbers (M) to (T) obtained in examples 9 to 16 were pressed into a metal mold of 10 mm. Phi. Times.200 mm, crosslinked at a metal mold temperature of 165℃for 2 minutes, and then the rubber crosslinked product was taken out, and when the mold releasability was evaluated on the basis of the following criteria, the acrylic rubbers (M) to (T) were evaluated as excellent ".

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

And (2) the following steps: can be easily released from the metal mold but little mold residue is found

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

X: difficult to release from a metal mold

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 having at least one reactive group selected from the group consisting of a carboxyl group, an epoxy group and a chlorine atom,

the acrylic rubber has a number average molecular weight (Mn) of 10 to 50 tens of thousands, a ratio (Mw/Mn) of weight average molecular weight (Mw) to number average molecular weight (Mn) 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 a methyl ethyl ketone insoluble content of 50 wt% or less, an ash content of 0.5 wt% or less, and a total amount of magnesium and phosphorus in the ash 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 specific gravity of the acrylic rubber is 0.8 or more.

5. The acrylic rubber according to any one of claims 1 to 4, wherein the pH of the acrylic rubber is 6 or less.

6. The acrylic rubber according to any one of claims 1 to 5, wherein the acrylic rubber is sheet-like or bale-like.

7. The acrylic rubber according to any one of claims 1 to 6, wherein when the amount of methyl ethyl ketone insoluble component is measured at 20 points of the acrylic rubber, the measured values are all within a range of (average ± 5% by weight).

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 an 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 state substantially containing no moisture.

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 after the melt-kneading and drying, cooling is performed at a cooling rate of 40 ℃/hr or more.

14. The acrylic rubber according to any one of claims 1 to 13, wherein the aqueous pellet having a particle diameter in the range of 710 μm to 6.7mm is washed, dehydrated and dried at a ratio of 50% by weight or more.

15. A method for producing the acrylic rubber according to any one of claims 1 to 14, comprising the steps of:

Emulsifying an acrylic rubber monomer component containing a monomer having a reactive group selected from at least one of a carboxyl group, an epoxy group, and a chlorine atom with water and an emulsifier; and

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

an emulsifying step of emulsifying an acrylic rubber monomer component containing a monomer having a reactive group selected from at least one of a carboxyl group, an epoxy group, and a chlorine atom with water and an emulsifier;

a cleaning step of cleaning the produced water-containing pellets;

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

18. The method for producing an acrylic rubber according to claim 16 or 17, wherein the emulsifier is a phosphate salt or a sulfate salt.

19. The method according to any one of claims 16 to 18, wherein the polymerization solution produced in the emulsion polymerization step is coagulated by using an alkali metal salt or a group 2 metal salt of the periodic table as a coagulant, and dried.

20. The method for producing an acrylic rubber according to claim 19, wherein 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.

21. The method for producing an acrylic rubber according to any one of claims 16 to 20, wherein the coagulating liquid is an aqueous magnesium salt solution.

22. The method for producing an acrylic rubber according to any one of claims 16 to 21, wherein melt kneading and drying are performed in the dehydration and drying step.

23. The method for producing an acrylic rubber according to claim 22, wherein the melt kneading and drying are performed in a state substantially containing no moisture.

24. The method for producing an acrylic rubber according to claim 22 or 23, wherein the melt kneading and drying are performed under reduced pressure.

25. The method according to any one of claims 22 to 24, wherein the melt-kneaded and dried acrylic rubber is cooled at a cooling rate of 40 ℃/hr or more.

26. The method according to any one of claims 22 to 25, wherein a maximum torque of the screw type biaxial extrusion dryer at the time of melt kneading and drying is 25 n.m or more.

27. The method according to any one of claims 16 to 26, wherein the aqueous pellet having a particle diameter in the range of 710 μm to 6.7mm is washed, dehydrated and dried at a ratio of 50 wt% or more.

28. A rubber composition comprising a rubber component comprising the acrylic rubber according to any one of claims 1 to 14, a filler and a crosslinking agent.

29. The rubber composition according to claim 28, wherein the filler is a reinforcing filler.

30. The rubber composition according to claim 28, wherein the filler is a carbon black.

31. The rubber composition according to claim 28, wherein the filler is a silica type.

32. The rubber composition according to any one of claims 28 to 31, wherein the crosslinking agent is an organic crosslinking agent.

33. The rubber composition according to any one of claims 28 to 32, wherein the crosslinking agent is a multi-component compound.

34. The rubber composition according to any one of claims 28 to 33, wherein the crosslinking agent is an ion-crosslinkable compound.

35. The rubber composition according to claim 34, wherein the crosslinking agent is an ion-crosslinkable organic compound.

36. The rubber composition of claim 34 or 35, wherein the crosslinking agent is a polyionic organic compound.

37. The rubber composition according to any one of claims 34 to 36, wherein the ion of the ion-crosslinkable compound, the ion-crosslinkable organic compound or the polyion-organic compound as the crosslinking agent is at least one ion-reactive group selected from the group consisting of an amino group, an epoxy group, a carboxyl group and a thiol group.

38. The rubber composition according to claim 36, 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.

39. The rubber composition according to any one of claims 28 to 38, 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.

40. The rubber composition of any of claims 28-39, wherein the rubber composition further comprises an anti-aging agent.

41. The rubber composition according to claim 40, wherein the antioxidant is an amine-based antioxidant.

42. A process for producing a rubber composition, comprising mixing the rubber component comprising the acrylic rubber according to any one of claims 1 to 14, a filler and an anti-aging agent, if necessary, and then mixing the mixture with a crosslinking agent.

43. A rubber crosslinked product obtained by crosslinking the rubber composition according to any one of claims 28 to 41.

44. A rubber crosslinked according to claim 43 wherein the crosslinking of the rubber composition is performed after molding.

45. A rubber crosslinked according to claim 43 or 44 wherein the crosslinking of the rubber composition is a crosslinking which is a primary crosslinking and a secondary crosslinking.