CN116096759A

CN116096759A - Acrylic rubber excellent in injection moldability and banbury processability

Info

Publication number: CN116096759A
Application number: CN202180056254.3A
Authority: CN
Inventors: 增田浩文; 川中孝文
Original assignee: Zeon Corp
Current assignee: Zeon Corp
Priority date: 2020-06-23
Filing date: 2021-06-04
Publication date: 2023-05-09
Also published as: WO2021261213A1; KR20230027037A; JPWO2021261213A1

Abstract

The present invention provides an acrylic rubber excellent in injection moldability and banbury processability. 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, the weight average molecular weight (Mw) of the acrylic rubber of the present invention is 100 to 500 tens of thousands, the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is in the range of 1.5 to 3, the gel amount is 50% by weight or less, the ash content is 0.0001 to 0.3% by weight, and the total amount of sodium, sulfur, calcium, magnesium and phosphorus in the ash is 80% by weight or more.

Description

Acrylic rubber excellent in injection moldability and banbury processability

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 having a high balance of injection moldability, banbury processability, strength characteristics, compression set resistance and water resistance, 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 fields of automobiles and the like.

For example, patent document 1 (japanese patent application laid-open No. 11-12427) discloses an acrylic rubber and a crosslinking composition excellent in extrusion processability and scorch characteristics, which are produced by: 100 parts of a monomer component comprising a monomer having a carbon-carbon double bond introduced into a side chain such as ethyl acrylate, butyl acrylate, methoxyethyl acrylate, acrylonitrile and allyl methacrylate, cyclopentenyloxyethyl acrylate, etc., 4 parts of sodium lauryl sulfate, 0.25 part of a terpene hydroperoxide as an organic radical generator, 0.01 part of ferrous sulfate, 0.025 part of sodium ethylenediamine tetraacetate, 0.04 part of sodium formaldehyde sulfoxylate, and 0.01 to 0.05 part of t-dodecyl mercaptan as a chain transfer agent were added to an autoclave after nitrogen substitution, the reaction was carried out at a reaction temperature of 30 degrees until the conversion of the monomer mixture became 100%, the resulting latex was coagulated by adding a 0.25% aqueous calcium chloride solution, the coagulated product was washed with water sufficiently, dried at about 90℃for 3 hours, and crosslinked by using an organic peroxide such as 1, 3-bis (t-butylperoxy isopropyl) benzene. However, the acrylic rubber obtained by the present method is insufficient in injection moldability and banbury processability, and has problems of poor storage stability, compression set resistance, water resistance and strength characteristics.

Further, patent document 2 (japanese patent application laid-open No. 5-86137) discloses a method for producing an acrylic rubber, in which polymerization is initiated by an organic radical generator, and a chain transfer agent is added to a monomer emulsion and continuously fed. Specifically, an emulsion was prepared by mixing and stirring one fifth of a mixture of monomers including 2- (2-cyanoethoxy) ethyl acrylate, n-butyl acrylate, vinyl chloride, allyl glycidyl ether and other crosslinkable monomers with an appropriate amount of n-dodecyl mercaptan, and one half of 1 part by weight of polyoxyethylene lauryl ether, 4 parts by weight of sodium lauryl sulfate, 0.7 part by weight of disodium hydrogen phosphate and 0.3 part by weight of sodium dihydrogen phosphate, and after the temperature reached 15 ℃, 0.005 parts by weight of iron (II) sodium ethylenediamine tetraacetate, 0.02 parts by weight of tetrasodium ethylenediamine tetraacetate, 0.02 parts by weight of sodium carving and 0.02 parts by weight of sodium dithionite were added, and polymerization was initiated by dropwise adding a 0.2% by weight aqueous solution of t-butyl hydroperoxide as an organic radical generator at a rate of 1.5 parts per hour, and the polymerization was carried out by dropwise adding a mixture of the remaining monomers and n-dodecyl mercaptan and an emulsifier solution for 3 hours while maintaining the temperature at 15 ℃ until the monomer conversion rate reached 99% by emulsion. The patent document also describes that the copolymer latex obtained is put into an aqueous solution of calcium chloride at 85 ℃, the copolymer is separated, and after sufficient washing, the copolymer is dried to obtain a copolymer rubber as a target, and sulfur crosslinking is performed. However, the acrylic rubber obtained by the present method is insufficient in injection moldability, and has problems of poor storage stability, water resistance and strength characteristics.

Further, in patent document 3 (pamphlet of international publication No. 2019/188709), a method of producing an acrylic rubber is disclosed as follows: the emulsion polymerization was initiated at normal pressure and normal temperature by adding a monomer component composed of ethyl acrylate, butyl acrylate, methoxyethyl acrylate and monobutyl fumarate, water and sodium lauryl sulfate, and repeatedly deaerating under reduced pressure and replacing nitrogen, then adding sodium formaldehyde sulfoxylate and cumene hydroperoxide as an organic radical generator, and after the emulsion polymerization was performed until the polymerization conversion became 95% by weight, the mixture was coagulated with a calcium chloride aqueous solution, and dehydrated and dried with an extrusion dryer having a screw. However, the acrylic rubber obtained by this method has problems of poor injection moldability, storage stability and water resistance.

Further, patent document 4 (pamphlet of international publication No. 2018/117037) discloses a method for producing an acrylic rubber as follows: adding monomer component formed from ethyl acrylate and mono-n-butyl fumarate, water and sodium dodecyl sulfate, implementing 3 times of vacuum degassing and nitrogen substitution to fully remove oxygen, then adding azobis (isobutyronitrile) and ethyl 2-methyl-2-phenyl tellurium propionate as organic free radical generator, initiating polymerization reaction at normal pressure and 50 deg. C, making polymerization conversion rate be up to 89%, solidifying by means of calcium chloride solution, washing with water and drying. However, the acrylic rubber obtained by this method has problems of poor injection moldability, banbury processability, storage stability and water resistance.

On the other hand, as a method for producing an acrylic rubber using an inorganic radical generator, for example, patent document 5 (japanese patent application laid-open No. 2019-119772) discloses the following method: the method comprises the steps of preparing a monomer emulsion from monomer components comprising ethyl acrylate, butyl acrylate, methoxyethyl acrylate and monobutyl maleate by using pure water and sodium lauryl sulfate and polyoxyethylene lauryl ether as emulsifiers, then charging a part of the monomer emulsion into a polymerization reaction tank, cooling down to 12 ℃ under a nitrogen stream, continuously dropwise adding the rest of the monomer emulsion, ferrous sulfate, sodium ascorbate and aqueous potassium persulfate solution as an inorganic free radical generator for 3 hours, continuously performing emulsion polymerization at 23 ℃ until the polymerization conversion reaches 97% by weight, continuously adding sodium sulfate after heating to 85 ℃, solidifying the mixture, performing filtration separation to obtain aqueous granules, performing 4 times of water washing on the aqueous granules, performing 1 time of acid washing and 1 time of pure water washing, continuously preparing acrylic rubber into a sheet by using an extrusion dryer with a screw, and performing crosslinking by using aliphatic polyamine compounds such as hexamethylenediamine carbamate. However, the sheet-like acrylic rubber obtained by the method has poor injection moldability and storage stability, and the crosslinked product has a problem of poor water resistance.

Patent document 6 (japanese patent application laid-open No. 1-135811) discloses the following method: a1/4 amount of a monomer mixture comprising a monomer component comprising ethyl acrylate, caprolactone-added acrylate, cyanoethyl acrylate and vinyl chloride, and n-dodecyl mercaptan as a chain transfer agent was emulsified with sodium lauryl sulfate, polyethylene glycol nonylphenyl ether and distilled water, and polymerization was initiated by adding sodium sulfite and ammonium persulfate as an inorganic radical generator, and the remaining part of the monomer mixture and a 2% ammonium persulfate aqueous solution were added dropwise while maintaining the temperature at 60℃for 2 hours, and a latex having a polymerization conversion rate of 96 to 99% was added to a sodium chloride aqueous solution at 80℃for further 2 hours after the addition, coagulated, and then dried after washing with water sufficiently to produce an acrylic rubber, and crosslinked by sulfur. However, the acrylic rubber obtained by the present method has problems of poor injection moldability, storage stability and water resistance.

Patent document 7 (japanese patent application laid-open No. 62-64809) discloses a sulfur-vulcanizable acrylic rubber comprising a copolymer of 50 to 99.9 wt% of at least one compound selected from alkyl acrylate and alkoxyalkyl acrylate, 0.1 to 20 wt% of a dicyclopentadienyl group-containing ester of an unsaturated carboxylic acid, 0 to 20 wt% of at least one of other monovinyl-based, mono1, 1-vinylidene-based and mono1, 2-vinylidene-based unsaturated compounds, wherein the copolymer has a number average molecular weight (Mn) in terms of polystyrene in which tetrahydrofuran is used as a developing solvent of 20 to 120 ten thousand, and a ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of 10 or less. As specific examples thereof, the following 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 weight average molecular weight (Mw) to number average molecular weight (Mn) of 4.7 to 8 is obtained by changing and adding a monomer component containing ethyl acrylate, a radical crosslinkable dihydro-dicyclopentene 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. Moreover, in practice Examples, comparative examples show: if the amount of the chain transfer agent is small, the number average molecular weight (Mn) is as large as 500 ten thousand, the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is as small as 1.4, and if the amount of the chain transfer agent is large, the number average molecular weight (Mn) is as small as 20 ten thousand, and the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is extremely varied to 17. However, the acrylic rubber obtained by this method is poor in injection moldability, and has the following problems in the crosslinking reaction: sulfur and a vulcanization accelerator as a crosslinking agent are added and kneaded by a roll, and it is necessary to use a roll having a weight of 100kg/cm ² Crosslinking at 170 ℃ for 15 minutes, and further crosslinking in a gill oven at 175 ℃ for a long period of time such as 4 hours; there are also problems such as poor water resistance, compression set resistance and strength characteristics, and poor physical property change after thermal degradation of the resulting crosslinked product.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open No. 11-12427;

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

patent document 3: international publication No. 2019/188709;

patent document 4: international publication No. 2018/117037;

patent document 5: japanese patent application laid-open No. 2019-119772;

Patent document 6: japanese patent laid-open No. 1-135811;

patent document 7: japanese patent laid-open No. 62-64809.

Disclosure of Invention

Problems to be solved by the invention

The present invention has been made in view of the above-described circumstances of the prior art, and an object thereof is to provide an acrylic rubber having a high balance of injection moldability, banbury processability, water resistance, compression set resistance and strength characteristics, 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 having a specific reactive group and having a weight average molecular weight (Mw) and a ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) in a specific range and having a gel amount, an ash amount, and an ash amount in a specific range is highly excellent in injection moldability, banbury workability, water resistance, compression set resistance, and strength characteristics. In particular, it was found that the acrylic rubber of the present invention is remarkably excellent in any of the properties of injection moldability, shape formability, fusion property and releasability.

The present inventors have also found that an acrylic rubber having a reactive group such as a carboxyl group, an epoxy group or a chlorine atom capable of reacting with a crosslinking agent or the like and having a weight average molecular weight (Mw) within a specific range is highly excellent in compression set resistance and strength characteristics. The present inventors have also found that, in GPC measurement of the reactive group-containing acrylic rubber, the reactive group-containing acrylic rubber is not sufficiently dissolved in tetrahydrofuran used in GPC measurement of the radical-reactive acrylic rubber obtained by copolymerizing ethyl acrylate with dicyclopentene acrylate or the like in the conventional art described above, 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 a developing solvent, measurement can be performed completely and reproducibly, and by specifying these characteristic values, injection moldability, water resistance, compression set resistance and strength characteristics of the acrylic rubber can be highly controlled.

The present inventors have found that in order to highly balance the strength characteristics and injection moldability of an acrylic rubber, it is important to set the weight average molecular weight (Mw) of the acrylic rubber to a large range and to set the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) to a specific region. In order to produce such an acrylic rubber, it has been found that when emulsion polymerization is carried out using only an organic radical generator, the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is small, and injection moldability is poor, but it can be achieved by adding a chain transfer agent in batches during the polymerization. On the other hand, it is found that the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the acrylic rubber emulsion-polymerized using the inorganic radical generator is too large, and the injection molding is poor.

The present inventors have also found that an acrylic rubber having a high balance of injection moldability, banbury processability, strength characteristics and compression set resistance can be produced by drying an acrylic rubber under specific shearing conditions by a specific extrusion dryer, without impairing the weight average molecular weight (Mw) of the acrylic rubber, by increasing the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn).

The inventors found that the banbury processability was related to the gel content of the specific solvent insoluble component. It has been found that the gel amount of the acrylic rubber is generated in emulsion polymerization, and particularly when the polymerization conversion rate is increased in order to improve the strength characteristics, the gel amount of the specific solvent insoluble component is drastically increased to make it difficult to control, and the banbury workability of the acrylic rubber is deteriorated, but by performing emulsion polymerization in the presence of a chain transfer agent in the final stage of the polymerization reaction, gelation can be prevented to some extent to improve the banbury workability; further, by melt kneading in a state substantially containing no water (water content of less than 1 wt%) in a screw type biaxial extrusion dryer and extrusion drying, the gel amount of the specific solvent insoluble component which increases rapidly in emulsion polymerization can be eliminated and the variation in gel amount can be reduced, and the banbury processability can be remarkably improved without impairing the strength characteristics of the obtained acrylic rubber.

The inventors found that the ash content and the ash component have a great influence on the water resistance. In particular, it has been found that ash removal from acrylic rubber produced using a large amount of an emulsifier or a coagulant is very difficult, but it has been found that the coagulation by a specific method can significantly improve the cleaning efficiency of the produced aqueous pellets and the ash removal efficiency at the time of dehydration, and as a result, the ash content of the acrylic rubber can be reduced and the water resistance can be significantly 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 washing, dehydrating and drying the aqueous aggregates, the water resistance can be significantly improved without impairing the properties such as injection moldability, 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 can significantly improve releasability from a mold or the like.

The present inventors have also found that an acrylic rubber contains no air and has a large specific gravity, is excellent in injection moldability, water resistance, strength characteristics and compression set resistance, and is remarkably excellent in storage stability. The inventors found that: in the case of such an acrylic rubber which does not contain air (has a high specific gravity) and is excellent in storage stability, the specific gravity can be slightly increased to improve the storage stability by compressing the dried rubber, which is produced by washing and dehydrating the aqueous pellets produced in the coagulation reaction and then directly drying them, with a high-pressure packing machine or the like, and it is preferable to extrude the dried rubber, which is produced by drying the aqueous pellets produced in the coagulation step in a specific extrusion dryer under reduced pressure without containing air, into a sheet form, whereby an acrylic rubber which is remarkably excellent in storage stability can be produced. The present inventors have also found that when an acrylic rubber having a specific pH is used, which is polymerized under a condition in which the emulsion polymerization liquid is not neutral, the storage stability can be further improved, and that by forming the acrylic rubber into a sheet-like or bag-like shape, the storage stability of the acrylic rubber can be further improved.

The present inventors have also found that an acrylic rubber excellent in injection moldability, water resistance, compression set resistance and strength characteristics can be efficiently produced by: emulsifying a specific monomer component comprising a monomer having a specific reactive group with water and an emulsifier, and then initiating emulsion polymerization in the presence of a redox catalyst comprising an organic radical generator such as dicumyl hydroperoxide and a reducing agent, and adding a chain transfer agent in batches during the polymerization without adding the chain transfer agent initially; solidifying the emulsion polymerization solution subjected to emulsion polymerization by a specific method; the aqueous pellets produced in the coagulation reaction are dehydrated after being washed and before being subjected to the drying step.

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

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

Thus, the present invention provides 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, wherein the acrylic rubber has a weight average molecular weight (Mw) of 100 to 500 tens of thousands, a ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of 1.5 to 3, a gel amount of 50 wt% or less, an ash content of 0.0001 to 0.3 wt%, and a total amount of sodium, sulfur, calcium, magnesium and phosphorus in the ash of 80 wt% or more.

In the acrylic rubber of the present invention, it is preferable that the acrylic rubber is formed of the following bonding units: binding units derived from at least one (meth) acrylate selected from the group consisting of alkyl (meth) acrylates and alkoxyalkyl (meth) acrylates; binding units derived from monomers containing at least one reactive group selected from the group consisting of carboxyl groups, epoxy groups, and chlorine atoms; and binding units from other monomers used as desired.

In the acrylic rubber of the present invention, it is preferable that 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 50 to 99.99% 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 0.01 to 10% by weight, and the binding unit derived from other monomer is 0 to 40% by weight.

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 gel amount is preferably 10% by weight or less.

In the acrylic rubber of the present invention, it is preferable that all values of the gel amount at 20 points are arbitrarily measured within a range of (average value.+ -. 5% by weight).

In the acrylic rubber of the present invention, the gel amount is preferably an amount of methyl ethyl ketone insoluble component.

In the acrylic rubber of the present invention, the ash content is preferably 0.2% by weight or less.

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, the complex viscosity at 100 ℃ (. Eta.100 ℃) is preferably 15000[ Pa.s ] or less.

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

The acrylic rubber of the present invention is preferably produced by emulsion polymerization using a phosphate salt or a sulfate salt as an emulsifier, and is preferably produced by solidifying and drying a polymerization liquid obtained by emulsion polymerization using an alkali metal salt or a group 2 metal salt of the periodic table as a coagulant. The acrylic rubber of the present invention is preferably obtained by melt-kneading and drying after solidification, and it is preferable that the melt-kneading and drying are carried out in a state where substantially no moisture is contained, and the melt-kneading and drying are carried out under reduced pressure. Further, in the acrylic rubber of the present invention, it is preferable that the acrylic rubber is cooled at a cooling rate of 40℃per hour or more after the above-mentioned melt kneading and drying.

In the acrylic rubber of the present invention, it is preferable that the acrylic rubber is obtained by washing, dehydrating and drying an aqueous pellet having a particle diameter of 710 μm to 6.7mm in a proportion of 50% by weight or more.

According to the present invention, there is also 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 containing at least one reactive group selected from a carboxyl group, an epoxy group and a chlorine atom, using water and an emulsifier;

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

a coagulation step of adding the emulsion polymerization liquid obtained to the stirred coagulation liquid to coagulate the emulsion polymerization liquid, thereby producing an aqueous pellet;

a cleaning step of cleaning the produced aqueous pellets;

a dehydration step of dehydrating the washed hydrous pellets to a water content of 1 to 50% by weight; and

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

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

In the method for producing an acrylic rubber of the present invention, it is preferable that in the dehydration step and the drying step, a dehydration cylinder having a dehydration slit, a dryer cylinder under reduced pressure, and a screw type biaxial extrusion dryer having a die head at the tip end are used, the washed aqueous pellets are dehydrated to a water content of 1 to 40% by weight using the dehydration cylinder, and then dried to less than 1% by weight using the dryer cylinder, and the dried rubber is extruded from the die head.

In the method for producing an acrylic rubber of the present invention, the number of stirring of the stirred coagulation liquid is preferably 200rpm or more.

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

In the method for producing an acrylic rubber of the present invention, it is preferable to perform emulsion polymerization using a phosphate salt or a sulfate salt as an emulsifier in the emulsion polymerization step.

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

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 solidified by contacting with a solidifying agent, and then melt-kneaded and dried.

In the method for producing an acrylic rubber of the present invention, it is preferable that the above-mentioned melt kneading and drying are performed in a state of substantially not containing moisture.

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

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

In the method for producing an acrylic rubber of the present invention, 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.

The present invention also provides a rubber composition containing a rubber component containing the 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 above-mentioned 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, the crosslinking agent is preferably 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 amino groups, epoxy groups, carboxyl groups and thiol groups.

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

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

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

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.

The invention also provides a rubber crosslinked product which is formed 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, the crosslinking of the rubber composition is preferably a crosslinking in which primary crosslinking and secondary crosslinking are performed.

Effects of the invention

According to the present invention, an acrylic rubber having a high balance of injection moldability, banbury processability, water resistance, compression set resistance and strength characteristics, an efficient production method thereof, a high-quality rubber composition comprising the acrylic rubber, and a crosslinked rubber product obtained by crosslinking the acrylic rubber can be provided.

Drawings

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

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

Fig. 3 is a diagram showing a structure of a transport type cooling device that can be used 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, a weight average molecular weight (Mw) of 100 to 500 tens of thousands, a ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of 1.5 to 3, a gel content of 50 wt.% or less, an ash content of 0.0001 to 0.3 wt.%, and a total amount of sodium, sulfur, calcium, magnesium and phosphorus in the ash of 80 wt.% or more.

< 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 an ion-reactive group is preferable, and an epoxy group and a carboxyl group are more preferable, and a carboxyl group is particularly preferable, and in this case, the crosslinkability in a short period of time, the compression set resistance and the water resistance of the crosslinked product can be improved to a high degree, and therefore, it is preferable.

The content of at least one reactive group selected from the group consisting of carboxyl groups, epoxy groups and chlorine atoms in the acrylic rubber of the present invention is not particularly limited, and may be appropriately selected depending on the purpose of use, and is 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 a crosslinked product is produced, compression set resistance, oil resistance, cold resistance, water resistance and the like are highly balanced, and thus are 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 obtained by introducing at least one reactive group selected from the group consisting of a carboxyl group, an epoxy group and a chlorine atom into an acrylic rubber by a subsequent reaction, and is preferably an acrylic rubber obtained by copolymerizing a monomer containing the reactive group.

< monomer component >

The monomer component of the acrylic rubber of the present invention is not particularly limited as long as it is a monomer component having the above-mentioned reactive group and constituting a usual acrylic rubber, and is preferably 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, more preferably is composed of the following monomers: at least one (meth) acrylate selected from the group consisting of alkyl (meth) acrylates and alkoxyalkyl (meth) acrylates; a monomer containing at least one reactive group selected from a carboxyl group, an epoxy group and a chlorine atom; and other monomers that can be copolymerized as desired. 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 preferably used. More preferably, an alkyl (meth) acrylate having an alkyl group having 2 to 6 carbon atoms is used.

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

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

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

These 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 of two or more, and the proportion of these 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, and may be appropriately selected depending on the purpose of use, and a monomer having an ion-reactive group is preferable, a monomer having a carboxyl group and an epoxy group is more preferable, and a monomer having a carboxyl group is further preferable, 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, and therefore, it is preferable.

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

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 -ethylacrylic acid, crotonic acid, cinnamic acid, and the like.

The ethylenically unsaturated dicarboxylic acid is not particularly limited, but an ethylenically unsaturated dicarboxylic acid having 4 to 12 carbon atoms is preferable, and examples thereof include butenedioic acid such as fumaric acid and maleic acid, itaconic acid and citraconic acid. In addition, the ethylenically unsaturated dicarboxylic acid also comprises ethylenically unsaturated dicarboxylic acids in the form of anhydrides.

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

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

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

The monomer having a chlorine atom is not particularly limited, and examples thereof include: unsaturated alcohol esters of saturated carboxylic acids containing chlorine atoms, chloroalkyl (meth) acrylates, chloroacyloxy alkyl (meth) acrylates, (chloroacetylcarbamooxy) alkyl (meth) acrylates, unsaturated ethers containing chlorine atoms, unsaturated ketones containing chlorine atoms, aromatic vinyl compounds containing chloromethyl groups, unsaturated amides containing chlorine atoms, unsaturated monomers containing chloroacetyl groups, and the like.

Specific examples of unsaturated alcohol esters of saturated carboxylic acids 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 a chlorine atom include: chloromethyl vinyl ether, 2-chloroethyl vinyl ether, 3-chloropropyl vinyl ether, 2-chloroethyl allyl ether, 3-chloropropyl ether, and the like. Specific examples of the unsaturated ketone containing a chlorine atom include: 2-chloroethyl vinyl ketone, 3-chloropropyl vinyl ketone, 2-chloroethyl vinyl acetone, and the like. Specific examples of the chloromethyl group-containing aromatic vinyl compound include: p-chloromethylstyrene, m-chloromethylstyrene, o-chloromethylstyrene, p-chloromethyl-alpha-methylstyrene, etc. Specific examples of the unsaturated amide containing a chlorine atom include N-chloromethyl (meth) acrylamide and the like. Specific examples of the chloroacetyl group-containing 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, most preferably 1 to 3% by weight.

The monomer other than the above-described monomer (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 is a monomer copolymerizable with the above-described monomer, and examples thereof include: aromatic vinyl such as styrene, α -methylstyrene, divinylbenzene, etc.; ethylenically unsaturated nitriles such as acrylonitrile and methacrylonitrile; acrylamide monomers such as acrylamide and methacrylamide; olefin monomers such as ethylene, propylene, vinyl acetate, ethyl vinyl ether, butyl vinyl ether, and the like.

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

Acrylic rubber >, a rubber composition

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, preferably comprising the above monomer component, and having a weight average molecular weight (Mw), a ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) (Mw/Mn), a gel amount, an ash amount and an ash component amount within specific ranges.

The monomer of the acrylic rubber of the present invention is composed of the following monomers: at least one (meth) acrylate selected from the group consisting of alkyl (meth) acrylates and alkoxyalkyl (meth) acrylates; a monomer containing at least one reactive group selected from a carboxyl group, an epoxy group and a chlorine atom; and, as for the proportion of the binding units derived from other monomers contained as needed, regarding the proportion of each binding unit in the acrylic rubber, the binding unit derived from at least one (meth) acrylic ester selected from the group consisting of alkyl (meth) acrylates and alkoxyalkyl (meth) acrylates is usually in the range of 50 to 99.99% by weight, preferably in the range of 62 to 99.95% by weight, more preferably in the range of 74 to 99.9% by weight, particularly preferably in the range of 80 to 99.5% by weight, most preferably in the range of 87 to 99% by weight, and the binding unit derived from a monomer containing at least one reactive group selected from the group consisting of carboxyl groups, epoxy groups and chlorine atoms is usually in the range of 0.01 to 10% by weight, preferably in the range of 0.05 to 8% by weight, more preferably in the range of 0.1 to 6% by weight, particularly preferably in the range of 0.5 to 5% by weight, most preferably in the range of 1 to 3% by weight, and the binding unit derived from other monomers is usually in the range of 0 to 40% by weight, preferably in the range of 0 to 30% by weight, more preferably in the range of 0 to 20% by weight, particularly preferably in the range of 0 to 15% by weight, most preferably in the range of 0 to 10% by weight. When the monomer composition of the acrylic rubber is within this range, 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 weight average molecular weight (Mw) of the acrylic rubber of the present invention is preferably in the range of 100 to 500. Mu.m, more preferably 110 to 400. Mu.m, still more preferably 120 to 300. Mu.m, particularly preferably 150 to 250. Mu.m, most preferably 160 to 220. Mu.m, and the injection moldability, strength characteristics and compression set resistance of the acrylic rubber are highly balanced. If the weight average molecular weight (Mw) of the acrylic rubber is too large, injection moldability is poor, and if the weight average molecular weight (Mw) of the acrylic rubber is too small, strength characteristics and compression set resistance are poor, so that both are not preferable.

The number average molecular weight (Mn) of the acrylic rubber of the present invention is not particularly limited, but is usually in the range of 30 to 150 million, preferably 35 to 130 million, more preferably 40 to 110 million, particularly preferably 50 to 100 million, most preferably 55 to 75 million, and in this case, the injection moldability, strength characteristics and compression set resistance of the acrylic rubber are highly balanced, and thus preferable.

The z-average molecular weight (Mz) of the acrylic rubber of the present invention is not particularly limited, and may be appropriately selected depending on the purpose of use, and is usually 150 ten thousand or more, preferably 200 ten thousand or more, more preferably 250 ten thousand or more, and particularly preferably 300 ten thousand or more. The z-average molecular weight (Mz) of the acrylic rubber of the present invention is preferably in the range of from 150 to 600 tens of thousands, preferably from 180 to 550 tens of thousands, more preferably from 200 to 500 tens of thousands, particularly preferably from 220 to 450 tens of thousands, and most preferably from 250 to 400 tens of thousands, since the injection moldability, banbury processability, strength characteristics and compression set resistance of the acrylic rubber are highly balanced.

The acrylic rubber of the present invention has a ratio (Mw/Mn) of weight average molecular weight (Mw) to number average molecular weight (Mn) of 1.5 to 3, preferably 1.8 to 2.7, more preferably 2 to 2.6, and particularly preferably 2.2 to 2.6, and in this case, the injection moldability of the acrylic rubber and the strength characteristics at the time of crosslinking and compression set resistance are highly balanced, and therefore, it is preferable. In particular, when the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the acrylic rubber of the present invention is within this range, the acrylic rubber is excellent in any of the properties of shape formability, fusion property and releasability in injection moldability, and the strength properties and compression set resistance as a crosslinked product are also highly balanced, and therefore, it is preferable. The ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the acrylic rubber is not preferable because it is too large or too small, since injection moldability is poor.

The molecular weight distribution of the acrylic rubber of the present invention in the high molecular weight region is not particularly limited, but is usually 1.3 or more, preferably 1.4 or more, more preferably 1.5 or more, particularly preferably 1.6 or more, and most preferably 1.7 or more in terms of the ratio (Mz/Mw) of the z-average molecular weight (Mz) to the weight-average molecular weight (Mw), and in this case, the deterioration of the releasability and the shape formability (burr generation) when the weight-average molecular weight (Mw) becomes too small can be prevented. The acrylic rubber of the present invention is preferably one in which the molecular weight distribution (Mz/Mw) of the high molecular weight region is usually 4 or less, preferably 3 or less, more preferably 2.5 or less, particularly preferably 2.2 or less, and most preferably 2 or less, because the deterioration of the shape formability (insufficient shape) and the fusion property when the weight average molecular weight (Mw) becomes excessively large can be prevented. Further, the acrylic rubber of the present invention is preferably used because it has a molecular weight distribution (Mz/Mw) in a high molecular weight region of usually 1.3 to 3, preferably 1.4 to 2.5, more preferably 1.5 to 2.2, particularly preferably 1.6 to 2, and most preferably 1.7 to 1.9, and in this case, injection moldability and banbury processability can be improved to a high degree without impairing the strength characteristics of the acrylic rubber.

The measurement of the molecular weight (Mn, mw, mz) and the molecular weight distribution (Mw/Mn, mz/Mw) of the acrylic rubber of the present invention is not particularly limited, and the measurement is preferably performed because each characteristic can be more accurately obtained when the molecular weight is the absolute molecular weight (Mn, mw, mz) or the absolute molecular weight distribution (Mw/Mn, mz/Mw) by GPC-MALS method.

The measuring solvent for GPC-MALS method for measuring the molecular weight (Mn, mw, mz) and molecular weight distribution (Mw/Mn, mz/Mw) of the acrylic rubber of the present invention is not particularly limited as long as it can dissolve the acrylic rubber of the present invention and measure it, and dimethylformamide-based solvent is preferable. The dimethylformamide-based solvent to be used is not particularly limited as long as it is a solvent containing dimethylformamide as a main component, and dimethylformamide may be used as 100% or a polar substance may be added to dimethylformamide. The proportion of dimethylformamide in the dimethylformamide-based solvent is 90% by weight or more, preferably 95% by weight or more, and more preferably 97% by weight or more. The compound to be added to dimethylformamide is not particularly limited, but in the present invention, a solution in which lithium chloride is added to dimethylformamide at a concentration of 0.05mol/L and 37% concentrated hydrochloric acid is added at a concentration of 0.01% is particularly preferable.

The gel content of 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, based on the amount of methyl ethyl ketone insoluble component, and in this case, processability and injection moldability at the time of kneading of banbury and the like are improved to a high degree.

The value at the time of arbitrarily measuring the gel amount of the acrylic rubber of the present invention at 20 is not particularly limited, and the value at all 20 measured is in the range of (average value.+ -. 5) wt%, preferably the value at all 20 measured is in the range of (average value.+ -. 3) wt%, and in this case, there is no processability variation, and the respective physical properties of the rubber mixture and the rubber crosslinked product are stable, so that it is preferable. Further, when the gel amount of the acrylic rubber at 20 is arbitrarily measured, a value at all 20 points within a range of ±5 of the average value means that the gel amount at 20 points measured is all within a range of (average value-5) to (average value +5) wt%, for example, when the average value of the gel amounts measured is 20 wt%, the measured value at all 20 points is within a range of 15 to 25 wt%.

The acrylic rubber of the present invention is preferably one obtained by melt-kneading and drying the aqueous pellets produced in 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 extrusion dryer, because the banbury processability and strength characteristics are highly balanced.

The ash content of the acrylic rubber of the present invention is preferably 0.3% by weight or less, more preferably 0.2% by weight or less, still more preferably 0.18% by weight or less, particularly preferably 0.15% by weight or less, and most preferably 0.13% by weight or less, and in this range, the water resistance, storage stability, strength characteristics, processability and injection moldability as 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 handling property is excellent, and further, the injection moldability, particularly the release property is excellent, so that it is preferable.

The ash content of the acrylic rubber of the present invention in a highly balanced state of water resistance, storage stability, strength characteristics, processability, handleability and fusion and release properties of injection moldability is usually in the range of 0.0001 to 0.3% by weight, preferably 0.0005 to 0.2% by weight, more preferably 0.001 to 0.18% by weight, particularly preferably 0.005 to 0.15% by weight, most preferably 0.01 to 0.13% by weight.

The total amount of sodium, magnesium, calcium, phosphorus and sulfur in the ash of the acrylic rubber of the present invention is preferably 80% by weight or more, more preferably 90% by weight or more, still more preferably 95% by weight or more, and in this case, the water resistance, the fusion property by injection molding and the release property of the acrylic rubber are highly improved.

The total amount of magnesium and phosphorus in the ash of the acrylic rubber of the present invention is not particularly limited, and is appropriately selected depending on the purpose of use, but is usually 30% by weight or more, preferably 50% by weight or more, more preferably 70% by weight or more, particularly preferably 80% by weight or more, and most preferably 90% by weight or more, and in this case, the water resistance, strength characteristics, fusion and release properties of injection molding, and processability of the acrylic rubber are highly balanced, and therefore, are 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 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 10% by weight or more, preferably 20 to 90% by weight, more preferably 30 to 80% by weight, particularly preferably 40 to 70% by weight, and most preferably 50 to 60% by weight.

The ratio of magnesium to phosphorus ([ Mg ]/[ P ]) in ash of the acrylic rubber of the present invention is not particularly limited, and is preferably in the range of usually 0.4 to 2.5, preferably 0.45 to 1.2, more preferably 0.45 to 1, particularly preferably 0.5 to 0.8, and most preferably 0.55 to 0.7 in terms of weight ratio, and the water resistance, strength characteristics, fusion property and releasability of injection molding, and processability of the acrylic rubber are highly balanced in this case, and thus are preferable.

Here, the ash in the acrylic rubber mainly comes from an emulsifier used in emulsion polymerization by emulsifying a monomer component and a coagulant used in coagulation of an emulsion polymerization liquid, but the total ash amount, the content of each component in the ash, and the like are changed 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.

In order to highly balance the water resistance, strength characteristics, fusion and release properties of the acrylic rubber by injection molding, and processability, as the emulsifier, an anionic emulsifier, a cationic emulsifier or a nonionic emulsifier, which will be described later, is particularly preferably used, an anionic emulsifier is preferably used, and a phosphate salt or a sulfate salt is more preferably used. The water resistance of the acrylic rubber is mainly related to the ash content in the acrylic rubber and the total amount of sodium, magnesium, calcium, phosphorus and sulfur in the ash, and the use of the above-described emulsifier is preferable because the water resistance, strength characteristics, fusion and release properties in injection molding, and processability of the acrylic rubber can be further highly balanced.

In order to highly balance the water resistance, strength characteristics, fusion and release properties of injection molding, and processability of the acrylic rubber, it is particularly preferable to use a metal salt described later, and it is preferable to use an alkali metal salt or a metal salt of group 2 of the periodic table as a coagulant. The water resistance of the acrylic rubber is mainly related to the ash content in the acrylic rubber and the total amount of sodium, magnesium, calcium, phosphorus and sulfur in the ash, and by using the above-described coagulant, the water resistance, strength characteristics, fusion and release properties of injection molding, and processability of the acrylic rubber are further highly balanced, and therefore preferable.

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

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 not more than 15000[ Pa.s ], preferably from 1000 to 10000[ Pa.s ], more preferably from 2000 to 8000[ Pa.s ], particularly preferably from 3000 to 5000[ Pa.s ], and most preferably from 3500 to 4000[ Pa.s ], and in this case, processability, oil resistance, injection moldability and shape retention are excellent, and therefore, are preferred.

The ratio of the complex viscosity at 100 ℃ ([ eta ]100 ℃) to the complex viscosity at 60 ℃ ([ eta ]60 ℃) of the acrylic rubber of the present invention ([ eta ]100 ℃/[ eta ]60 ℃) is 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, and more preferably 0.7 or more. The ratio of the complex viscosity at 100 ℃ ([ eta ]100 ℃) to the complex viscosity at 60 ℃ ([ eta ]60 ℃) of the acrylic rubber of the present invention ([ eta ]100 ℃/[ eta ]60 ℃) is usually 0.5 to 0.99, preferably 0.55 to 0.95, more preferably 0.6 to 0.9, particularly preferably 0.65 to 0.85, most preferably 0.7 to 0.8, and in this case, the processability, oil resistance and shape retention 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, it is preferable that air is hardly present in the interior and the storage stability is excellent. The specific gravity of the acrylic rubber molded article 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, which has a great influence on the storage stability including oxidative deterioration and the like, and is not preferable.

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

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

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

The pH of the acrylic rubber of the present invention is not particularly limited, and is preferably 6 or less, more preferably 2 to 6, still more preferably 2.5 to 5.5, and most preferably 3 to 5, as long as it is appropriately selected depending on the purpose of use, 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 is 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 may be appropriately selected depending on the purpose of use, but is usually in the range of 1 to 40mm, preferably 2 to 35mm, more preferably 3 to 30mm, most preferably 5 to 25mm, and in this case, the handling property, storage stability and productivity are highly balanced, and therefore preferable. The width of the sheet-like acrylic rubber of the present invention can be appropriately selected depending on the purpose of use, and is usually in the range of 300 to 1200mm, preferably 400 to 1000mm, more preferably 500 to 800mm, and in this case, the sheet-like acrylic rubber is particularly excellent in handling properties, and is therefore preferable. The length of the sheet-like acrylic rubber sheet of the present invention is not particularly limited, but is usually in the range of 300 to 1200mm, preferably 400 to 1000mm, more preferably 500 to 800mm, and in this case, the sheet-like acrylic rubber sheet is particularly excellent in handleability, 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 examples thereof include the following steps:

a cleaning step of cleaning the produced aqueous pellets;

(emulsification Process)

The emulsification step in the method for producing an acrylic rubber of the present invention is a step 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, using water and an emulsifier.

(monomer component)

The monomer component used in the present invention is 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, and is preferably composed of the following monomers: at least one (meth) acrylate selected from the group consisting of alkyl (meth) acrylates and alkoxyalkyl (meth) acrylates; a monomer containing at least one reactive group selected from a carboxyl group, an epoxy group, and a chlorine atom; and other monomers copolymerizable as needed, the above monomer components are the same as exemplified and preferred ranges of the monomer components already described. As described above, the amount of the monomer component used may be appropriately selected for each monomer in emulsion polymerization, and the composition of the acrylic rubber of the present invention may be the same.

(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 esters such as polyoxyalkylene alkyl ether phosphate; alkyl sulfosuccinates, and the like. Among these anionic emulsifiers, phosphate salts and sulfate salts are preferable, phosphate salts are particularly preferable, and divalent phosphate salts are most preferable, since the water resistance, strength characteristics, mold releasability, and processability of the resulting acrylic rubber can be highly balanced. The phosphate and sulfate are preferably alkali metal salts of phosphate and sulfate, and more preferably sodium salts of phosphate and sulfate, and in this case, the water resistance, strength characteristics, mold releasability, and processability of the resulting acrylic rubber can be highly balanced.

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

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

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

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

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

Specific examples of the alkylphenoxypolyoxyethylene phosphate salt include metal salts such as methylphenoxy tetraoxyethylene phosphate, ethylphenoxytetraoxyethylene phosphate, butylphenoxy tetraoxyethylene phosphate, hexylphenoxy tetraoxyethylene phosphate, nonylphenoxy tetraoxyethylene phosphate, dodecylphenoxy tetraoxyethylene phosphate, octadecylphenoxy tetraoxyethylene phosphate, methylphenoxy pentaoxyethylene phosphate, ethylphenoxypentaoxyethylene phosphate, butylphenoxy pentaoxyethylene phosphate, hexylphenoxy pentaoxyethylene phosphate, nonylphenoxy pentaoxyethylene phosphate, dodecylphenoxy pentaoxyethylene phosphate, methylphenoxy hexaoxyethylene phosphate, ethylphenoxyhexaoxyethylene phosphate, butylphenoxy hexaoxyethylene phosphate, hexylphenoxy hexaoxyethylene phosphate, nonylphenoxy hexaoxyethylene phosphate, ethylphenoxyoctaoxyethylene phosphate, butylphenoxy octaoxyethylene phosphate, hexylphenoxy octaoxyethylene phosphate, nonylphenoxy octaoxyethylene phosphate, dodecylphenoxy octaoxyethylene phosphate, and the like, and sodium salts thereof are particularly preferred.

Specific examples of the alkylphenoxypolyoxypropylene phosphate include metal salts such as methylphenoxy tetrapropoxy phosphate, ethylphenoxytetrapropoxy 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 hexaoxyprop phosphate, hexylphenoxy hexaoxyprop phosphate, nonylphenoxy hexaoxyprop phosphate, dodecylphenoxy hexaoxyprop phosphate, methylphenoxy octaoxyprop phosphate, ethylphenoxy octaoxyprop phosphate, butylphenoxy octaoxyprop phosphate, hexylphenoxy octaoxyprop phosphate, nonylphenoxy octaoxyprop phosphate, dodecylphenoxy octaoxyprop phosphate, and the like, and alkali metal salts thereof are particularly preferred.

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

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

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

(emulsion polymerization Process)

The emulsion polymerization step in the method for producing an acrylic rubber of the present invention is as follows: polymerization is initiated in the presence of a redox catalyst comprising an organic radical generator and a reducing agent, and a chain transfer agent is added after the polymerization is carried out in batches in the polymerization process, and the polymerization is continued to obtain an emulsion polymerization solution.

(organic radical generator)

The polymerization catalyst used in the present invention is preferably a redox catalyst comprising an organic radical generator and a reducing agent, because the injection moldability and strength characteristics of the resulting acrylic rubber can be improved to a high degree. In particular, the use of an organic radical generator is preferable because the injection moldability of the produced acrylic rubber can be improved to a high degree.

The organic radical generator is not particularly limited as long as it is an organic radical generator generally used in emulsion polymerization, and examples thereof include organic peroxides and azo compounds.

The organic peroxide is not particularly limited as long as it is a known organic peroxide used in emulsion polymerization, examples thereof include 2, 2-bis (4, 4-di- (t-butylperoxy) cyclohexyl) propane, 1-di- (t-hexylperoxy) cyclohexane, 1-di- (t-butylperoxy) cyclohexane, n-butyl 4, 4-di- (t-butylperoxy) valerate, 2-di- (t-butylperoxy) butane, t-butylhydroperoxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide, terpene hydroperoxide, benzoyl peroxide, 1, 3-tetraethyl butylhydroperoxide, t-butylcumyl peroxide, di-t-butyl peroxide, di-t-hexyl peroxide, di (2-t-butylperoxy isopropyl) benzene, dicumyl peroxide, diisobutyryl peroxide bis (3, 5-trimethylhexanoyl) peroxide, dilauroyl peroxide, disuccinic acid peroxide, dibenzoyl peroxide, bis (3-methylbenzoyl) peroxide, benzoyl (3-methylbenzoyl) peroxide, diisobutyryl peroxydicarbonate, di-n-propyl peroxydicarbonate, bis (2-ethylhexyl) peroxydicarbonate, di-sec-butyl peroxydicarbonate, 1, 3-tetramethylbutyl peroxyneodecanoate, t-hexyl peroxypivalate, t-butyl peroxypivalate, 2, 5-dimethyl-2, 5-bis (2-ethylhexanoylperoxy) hexane, 1, 3-tetramethylbutylperoxy-2-ethylhexanoate, t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-3, 5-trimethylhexanoate, t-hexylperoxyisopropyl monocarbonate, t-butylperoxyisopropyl monocarbonate, t-butylperoxy-2-ethylhexyl monocarbonate, 2, 5-dimethyl-2, 5-bis (benzoyl peroxy) hexane, t-butylperoxyacetate, t-hexylperoxybenzoate, t-butylperoxybenzoate, 2, 5-dimethyl-2, 5-bis (t-butylperoxy) hexane, and among these, diisopropylbenzene, cumene hydroperoxide, terpene hydroperoxide, benzoyl peroxide, and the like are preferable.

As the azo compound, there is used, examples thereof include azobisisobutyronitrile, 4' -azobis (4-cyanovaleric acid), 2' -azobis [2- (2-imidazolin-2-yl) ] propane, 2' -azobis (propane-2-formamidine), 2' -azobis [ N- (2-carboxyethyl) -2-methylpropionamide ]: 2,2' -azobis {2- [1- (2-hydroxyethyl) -2-imidazolin-2-yl ] propane }, 2' -azobis (1-imino-1-pyrrolidinyl-2-methylpropane) and 2,2' -azobis { 2-methyl-N- [1, 1-bis (hydroxymethyl) -2-hydroxyethyl ] propionamide }, and the like.

These organic radical generators may be used singly or in combination, and the amount thereof is usually in the range of 0.0001 to 5 parts by weight, preferably 0.0005 to 1 part by weight, more preferably 0.001 to 0.5 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 used in a usual emulsion polymerization, and it is preferable to use at least two reducing agents, and it is preferable to combine a metal ion compound in a reduced state with the other reducing agents because the injection moldability and strength characteristics of the resulting acrylic rubber can be further highly balanced.

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

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

The reducing agents other than these metal ion compounds in a 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 with the other reducing agent 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, relative to 100 parts by weight of the monomer component, and the amount of the ascorbic acid or a salt thereof and/or sodium formaldehyde sulfoxylate is usually in the range of 0.001 to 1 part by weight, preferably 0.005 to 0.5 parts by weight, more preferably 0.01 to 0.1 part by weight, relative to 100 parts by weight of the monomer component.

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

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

The emulsion polymerization is exothermic and the polymerization reaction can be shortened by increasing the temperature without control, but in the present invention, the emulsion polymerization temperature is usually controlled to 35℃or less, preferably 0 to 35℃and more preferably 5 to 30℃and particularly preferably 10 to 25℃and 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)

In the present invention, it is preferable that the chain transfer agent is not added at an initial stage but added in a batch after the polymerization process, because 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 injection moldability.

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, in which case the effect of the chain transfer agent can be stably exhibited, and the injection moldability of the produced acrylic rubber can be highly improved, and is therefore preferable.

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

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

The present invention is preferably characterized in that the chain transfer agent is not added at the beginning of polymerization but is added in batches during polymerization, whereby a high molecular weight component and a low molecular weight component of the produced acrylic rubber can be produced, and the molecular weight distribution can be made to fall within a specific range, and the strength characteristics and injection moldability can be highly balanced.

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

The period 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 generally preferably in the range of 35 to 150 minutes, most preferably 40 to 120 minutes after initiation of the polymerization, since the strength characteristics of the produced acrylic rubber can be highly balanced with the injection moldability at this time, usually after initiation of the polymerization for 20 minutes, preferably after 30 minutes, more preferably 30 to 200 minutes, particularly preferably 35 to 150 minutes, after initiation of the polymerization.

The amount of the chain transfer agent added after the batch 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 of the produced acrylic rubber can be highly balanced with the injection moldability.

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

(post addition of reducing agent)

In the present invention, the reducing agent of the above-mentioned redox catalyst can be added later in the polymerization process, whereby the strength characteristics of the produced acrylic rubber can be highly balanced with the injection moldability, and is preferable.

The above-mentioned reducing agent is exemplified by the same preferable range as the reducing agent added later in the polymerization process. 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 is appropriately selected depending on the purpose of use, but is usually in the range of 0.0001 to 1 part by weight, preferably 0.0005 to 0.5 part by weight, more preferably 0.001 to 0.5 part by weight, particularly preferably 0.005 to 0.1 part by weight, most preferably 0.01 to 0.05 part by weight, based on 100 parts by weight of the monomer component, and in this case, the productivity of the production of the acrylic rubber is excellent, and the strength characteristics and injection moldability of the produced acrylic rubber can be highly balanced, and therefore, it is preferable.

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

The ratio of the amount of the initially added ascorbic acid or a salt thereof to the amount of the post-added ascorbic acid or a salt thereof when the reducing agent added after the initiation of polymerization and during the polymerization is ascorbic acid or a salt thereof is not particularly limited, but is usually in the range of 1/9 to 8/2, preferably 2/8 to 6/4, more preferably 3/7 to 5/5, in terms of the weight ratio of "the initially added ascorbic acid or a salt thereof"/"the post-added ascorbic acid or a salt thereof in a batch", and in this case, the productivity of the acrylic rubber production is excellent and the strength characteristics of the produced acrylic rubber can be highly balanced with the injection moldability, and thus is preferable.

The period of 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 after the initiation of polymerization, preferably 1 to 3 hours after the initiation of polymerization, more preferably 1.5 to 2.5 hours after the initiation of polymerization, and in this case, the productivity of the production of the acrylic rubber is excellent and the strength characteristics of the produced acrylic rubber can be highly balanced with the injection moldability, which is preferable.

The amount of the reducing agent added in each of the batch-wise post-addition is not particularly limited and may be appropriately selected depending on the purpose of use, but is preferably in the range of usually 0.00005 to 0.5 part by weight, preferably 0.0001 to 0.1 part by weight, more preferably 0.0005 to 0.05 part by weight, particularly preferably 0.001 to 0.03 part by weight, based on 100 parts by weight of the monomer component, since the strength characteristics of the produced acrylic rubber can be highly balanced with the injection moldability.

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

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. In terminating the polymerization, a polymerization terminator may be used.

(coagulation step)

The coagulation step in the method for producing an acrylic rubber of the present invention is as follows: the emulsion polymerization solution obtained above was added to the stirred coagulation solution and coagulated to produce an aqueous pellet.

The solid content concentration of the emulsion polymerization liquid used in the coagulation reaction is not particularly limited, and is usually adjusted to 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. The metal salt may be, for example, an alkali metal, a metal salt of group 2 of the periodic table, or other metal salt, and is preferably an alkali metal salt, or a metal salt of group 2 of the periodic table, more preferably a metal salt of group 2 of the periodic table, and particularly preferably a magnesium salt, and in this case, the water resistance, strength characteristics, fusion and releasability in injection molding, and processability of the obtained acrylic rubber can be highly balanced, and therefore, it is preferable.

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

Examples of the metal salt of group 2 of the periodic table include: magnesium chloride, calcium chloride, magnesium nitrate, calcium nitrate, magnesium sulfate, calcium sulfate, etc., preferably calcium chloride, magnesium sulfate.

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

These coagulants may be used singly or in combination, and the amount thereof is usually in the range of 0.01 to 100 parts by weight, preferably 0.1 to 50 parts by weight, more preferably 1 to 30 parts by weight, relative to 100 parts by weight of the monomer component. When the coagulant is in this range, the coagulation of the acrylic rubber can be made sufficient, and the compression set and water resistance at the time of crosslinking the acrylic rubber can be highly improved, so that it is preferable.

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

The method for producing the aqueous pellets having the particle diameter in the above range is not particularly limited, and for example, a method of adding the emulsion polymerization liquid to the stirred coagulant (aqueous coagulant solution) or a method of bringing the emulsion polymerization liquid into contact with the coagulant by specifying the coagulant concentration of the coagulant, the number of stirred coagulants, and the peripheral speed.

The coagulant used is usually used in the form of an aqueous solution, and the concentration of the coagulant in the aqueous solution is usually in the range of 0.1 to 20% by weight, preferably 0.5 to 15% by weight, more preferably 1 to 10% by weight, and particularly preferably 1.5 to 5% by weight, and in this case, the particle size of the resulting aqueous pellets can be uniformly concentrated in a specific region, which is preferable.

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

As a method of bringing the emulsion polymerization liquid into contact with the coagulation liquid, a method of adding the emulsion polymerization liquid to the stirred coagulation liquid is preferable because the washing efficiency and the dewatering efficiency of the produced aqueous pellets can be remarkably improved and the water resistance and the storage stability of the obtained acrylic rubber can be highly improved.

The stirring number (rotation number) of the coagulation liquid to be stirred, that is, the rotation number of the stirring blade of the stirring device is not particularly limited, and is usually 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 number of revolutions is a number of revolutions at which stirring is performed vigorously to some extent, the particle size of the resulting aqueous pellets can be reduced and the particle size of the aqueous pellets can be made uniform, it is preferable that the number of revolutions is not less than the above-mentioned lower limit, and the formation of pellets having excessively large and excessively small particle sizes can be suppressed, and the coagulation reaction can be controlled more easily by setting the number of revolutions to not more than the above-mentioned upper limit.

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

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

(cleaning step)

The cleaning step in the method for producing an acrylic rubber of the present invention is a step of cleaning the aqueous pellet produced as described above.

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

The amount of water to be added for washing is not particularly limited, but is usually 50 parts by weight or more, preferably 50 to 15000 parts by weight, more preferably 100 to 10000 parts by weight, still more preferably 500 to 5000 parts by weight per 1 part by weight of the monomer component, and in this case, the ash content in the acrylic rubber can be effectively reduced, which is preferable.

The temperature of water to be used is not particularly limited, and warm water is preferably used, and is usually 40 ℃ or higher, preferably 40 to 100 ℃, more preferably 50 to 90 ℃, particularly 60 to 80 ℃, and the cleaning efficiency is most preferably improved. When the temperature of the water to be used is not less than the lower limit, the emulsifier and the coagulant are released from the aqueous pellet, 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 not particularly limited, but 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 by setting the shape of the aqueous aggregates and the particle size of the aqueous aggregates to the specific ranges and/or setting the washing temperature to the above-described ranges, the number of times of washing can be significantly reduced.

(dehydration step)

The dehydration step in the method for producing an acrylic rubber of the present invention is a step of dehydrating the washed aqueous pellet to a water content of 1 to 50% by weight.

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

The dehydrator is not particularly limited, and for example, a centrifuge, a squeezer, a screw extruder, or the like can be used, and particularly, the screw extruder is preferable because the water content of the water-containing pellets can be highly reduced. In a centrifuge or the like, the adhesive acrylic rubber adheres between the wall surface and the slit, and usually only about 45 to 55 wt% of the acrylic rubber is dehydrated. In contrast, a screw extruder is preferable because it has a structure to forcedly gradually extrude water.

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

(drying step)

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

The method for drying the dehydrated aqueous pellets is not particularly limited, and can be carried out using, for example, a screw type biaxial extrusion dryer. The screw type biaxial extrusion dryer to be used is not particularly limited as long as it is an extrusion dryer having two screws, and in the present invention, in particular, an acrylic rubber obtained by drying an aqueous pellet under high shear conditions using a screw type biaxial extrusion dryer having two screws is preferable because injection moldability, banbury processability and strength characteristics are highly balanced.

In the present invention, the acrylic rubber can be obtained by melting the aqueous pellets in a screw type biaxial extrusion dryer and extrusion-drying the pellets. 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, it is preferable to dry the acrylic rubber efficiently without scorching or deterioration.

In the present invention, it is preferable to highly improve the storage stability without impairing the injection moldability and strength characteristics of the acrylic rubber when the aqueous pellet is melt kneaded and dried under reduced pressure in a screw type biaxial extrusion dryer. In this stage, the vacuum degree of the screw type biaxial extrusion dryer is preferably selected appropriately for the purpose of removing air existing in the acrylic rubber to improve the storage stability, 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 highly improve the banbury processability without impairing the injection moldability and strength characteristics of the acrylic rubber when the aqueous pellet is melt kneaded and dried in a state where water is substantially removed by a screw type biaxial extrusion dryer. 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 so that the banbury processability can be highly improved. In the present invention, the term "melt kneading" or "melt kneading and drying" means kneading (mixing) the acrylic rubber in a molten state or extruding the acrylic rubber in a molten state in a screw type biaxial extrusion dryer, and drying the acrylic rubber in this stage, or kneading, extruding and drying the acrylic rubber in a molten (plasticized) state in 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 in the range of 5 to 125n·m, preferably 10 to 100n·m, more preferably 10 to 50n·m, particularly preferably 15 to 45n·m, and in this case, the injection moldability, banbury processability and strength characteristics of the produced acrylic rubber can be highly balanced, and thus it is preferable.

The specific energy consumption (specific energy) of the screw type biaxial extrusion dryer used in the present invention is not particularly limited, but is usually in the range of 0.01 to 0.3[ kw.h/kg ], preferably 0.05 to 0.25[ kw.h/kg ], more preferably 0.1 to 0.2[ kw.h/kg ], and the injection moldability, banbury processability and strength characteristics of the acrylic rubber obtained at this time are highly balanced, and therefore preferable.

The specific power (specific power) of the screw type biaxial extrusion dryer used in the present invention is not particularly limited, but is usually in the range of 0.1 to 0.6[ A.h/kg ], preferably 0.15 to 0.55[ A.h/kg ], more preferably 0.2 to 0.5[ A.h/kg ], and the injection moldability, 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 5 to 150[1/s ] or more, preferably 10 to 100[1/s ], more preferably 25 to 75[1/s ], and the storage stability, injection moldability, 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, injection moldability, banbury processability and strength characteristics of the acrylic rubber obtained at this time are highly balanced, and therefore, it is preferable.

In the present invention, the acrylic rubber is cooled after melt-kneading and drying. The cooling rate is usually 40℃/hr or more, preferably 50℃/hr or more, more preferably 100℃/hr or more, and particularly preferably 150℃/hr or more, and in this case, the acrylic rubber is excellent in storage stability, injection molding, banbury workability, strength characteristics, water resistance and compression set resistance, and scorch stability can be significantly improved, which is preferable.

The acrylic rubber of the present invention thus obtained is excellent in injection moldability, banbury processability, strength characteristics and water resistance, and can be used for various applications. The shape of the acrylic rubber of the present invention is not particularly limited, and may be selected according to the purpose of use, and examples thereof include: powder, pellet, strand, sheet, gel pack, etc., and the sheet or gel pack is excellent in handling property and storage stability, and is therefore preferable.

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

The method for producing a sheet-like or rubber-coated acrylic rubber of the present invention is not particularly limited, and a sheet-like or rubber-coated acrylic rubber can be easily produced by using a dehydrator cylinder having a dehydration slit, a dryer cylinder under reduced pressure, and a screw type biaxial extrusion dryer having a die at the tip end, dehydrating the above-mentioned washed aqueous pellets to a water content of 1 to 40% by weight with the dehydrator cylinder, and then drying the aqueous pellets to less than 1% by weight with the dryer cylinder, and extruding the sheet-like dried rubber from the die, and further, by laminating and rubber-coating the extruded sheet-like dried rubber, a rubber-coated acrylic rubber can be easily produced.

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

(Water removal Process)

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

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

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

The water content of the aqueous pellet after the water removal, that is, the water content of the aqueous pellet charged in 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 charged in the dehydration and drying step is not particularly limited, but is usually 40 ℃ or higher, preferably 40 to 100 ℃, more preferably 50 to 90 ℃, particularly preferably 55 to 85 ℃, and most preferably 60 to 80 ℃, and in this case, it is preferable to efficiently dehydrate and dry the aqueous pellet having a specific heat as high as 1.5 to 2.5KJ/kg·k and having a temperature hardly increased as in the acrylic rubber of the present invention using a screw type biaxial extrusion dryer.

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

The dewatering of the aqueous pellets is carried out by means of a dewatering barrel in a screw-type twin-screw extrusion dryer with dewatering slits. The holes of the dewatering slit may be appropriately selected depending on the conditions of use, and are 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, so that it 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 liquid water (drainage) from the dewatering slit and the removal of vapor state water (drainage), and in the present invention, drainage is defined as dewatering and drainage is defined as predrying.

In the dehydration of the hydrous pellets, the water discharged from the dehydration slit may be in any of a liquid state (drain) and a vapor state (drain), and in the case of using a screw type biaxial extrusion dryer having a plurality of dehydration barrels, it is preferable to combine drain and drain to efficiently dehydrate the adhesive acrylic rubber. The screw type biaxial extrusion dryer having three or more dewatering barrels may be a dewatering type dewatering barrel or a steam-discharging type dewatering barrel, and is appropriately selected according to the purpose of use, and generally, the dewatering type barrel is increased when the ash content in the produced acrylic rubber is reduced, and the steam-discharging type barrel is increased when the water content is reduced.

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

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

The dehydration of the acrylic rubber having the tackiness of the reactive group is carried out by using a centrifuge or the like, and the acrylic rubber adheres to the dehydration slit portion and is hardly dehydrated (the water content is about 45 to 55% by weight), but in the present invention, the water content can be reduced to the above range by using a screw type biaxial extrusion dryer having a dehydration slit and forcibly extruded by 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 is usually 5 to 40% by weight, preferably 10 to 40% by weight, more preferably 15 to 35% by weight, and the water content after pre-drying in the steam discharge type dehydrator cylinder is usually 1 to 30% by weight, preferably 3 to 20% by weight, more preferably 5 to 15% by weight.

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

(drying of aqueous pellets in the dryer section)

The above-described drying of the dehydrated aqueous pellets is performed in a dryer barrel section under reduced pressure by a screw type biaxial extrusion dryer having a dryer barrel section. Drying under reduced pressure is preferable because the drying efficiency is improved, and the air existing in the acrylic rubber can be removed to produce an acrylic rubber having a high specific gravity and excellent storage stability. In the present invention, the acrylic rubber is melted under reduced pressure and extrusion-dried, whereby the storage stability of the acrylic rubber can be highly improved. The storage stability of the acrylic rubber is closely related to the specific gravity of the acrylic rubber, and can be controlled, and in the case of controlling the storage stability to be high with a large specific gravity, the degree of vacuum of extrusion drying or the like can be controlled.

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

The setting temperature of the dryer cylinder may be appropriately selected, and is usually in the range of 100 to 250 ℃, preferably 110 to 200 ℃, more preferably 120 to 180 ℃, and in this case, it is preferable to reduce the gel amount of methyl ethyl ketone insoluble components in the sheet-like or bag-like acrylic rubber, since scorching and deterioration of the acrylic rubber do not occur and drying can be performed efficiently.

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

The moisture content of the dried rubber after drying is usually less than 1% by weight, preferably 0.8% by weight or less, more preferably 0.6% by weight or less. In the present invention, in particular, it is preferable to melt-extrude the dried rubber in a screw type biaxial extrusion dryer so that the water content of the dried rubber is at this value (the state where water is substantially removed), because the gel content of methyl ethyl ketone insoluble components of the sheet-like or bag-like acrylic rubber can be reduced. In the present invention, the acrylic rubber obtained by melt-kneading or melt-kneading and drying by a screw type biaxial extruder is preferably a sheet-like or bag-like acrylic rubber, and since the strength properties are highly balanced with the Banbury processability. In the present invention, the term "melt kneading" or "melt kneading and drying" means kneading (mixing) the acrylic rubber in a molten state in a screw type biaxial extrusion dryer, extruding the acrylic rubber in a molten state and drying the acrylic rubber at this stage, or kneading, extruding and drying the acrylic rubber in a molten (plasticized) state in a screw type biaxial extrusion dryer.

In the present invention, the shear rate applied to the cylinder of the screw-type biaxial extrusion dryer in a state where the above-mentioned acrylic rubber does not substantially contain water is not particularly limited, but is usually 5[1/s ] or more, preferably 10 to 400[1/s ], more preferably 20 to 250[1/s ], and the resulting sheet-like or gel-coated acrylic rubber is highly balanced in terms of storage stability, injection moldability, banbury processability, strength characteristics and compression set resistance, and therefore is preferred.

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

(extrusion of dried rubber from die head)

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

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

The resin pressure at the die section is not particularly limited, but is usually in the range of 0.1 to 10MPa, preferably 0.5 to 5MPa, more preferably 1 to 3MPa, and in this case, the air inclusion of the acrylic rubber in the form of a sheet or a bag is small (specific gravity is high), and productivity is excellent, so that it is preferable.

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

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

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

The maximum torque of the screw type biaxial extrusion dryer to be used is not particularly limited, but is usually in the range of 5 to 125n·m, preferably 10 to 100n·m, more preferably 10 to 50n·m, and particularly preferably 15 to 45n·m, and in this case, it is preferable to be able to highly balance the injection moldability, banbury processability and strength characteristics of the produced sheet-like or gel-coated acrylic rubber.

The specific energy consumption of the screw type biaxial extrusion dryer to be used is not particularly limited, but is usually in the range of 0.01 to 0.3[ kw.h/kg ] or more, preferably 0.05 to 0.2[ kw.h/kg ], more preferably 0.1 to 0.2[ kw.h/kg ], and the injection moldability, banbury processability and strength characteristics of the sheet-like or gel-coated acrylic rubber obtained at this time are highly balanced, and therefore, it is preferable.

The specific power of the screw type biaxial extrusion dryer to be used is not particularly limited, but is usually not less than 0.1 to 0.6[ A.multidot.h/kg ], preferably 0.15 to 0.55[ A.multidot.h/kg ], more preferably 0.2 to 0.5[ A.multidot.h/kg ], and the injection moldability, banbury processability and strength characteristics of the sheet-like or gel-coated acrylic rubber obtained at this time are highly balanced, and therefore, it is preferable.

The shear rate of the screw type biaxial extrusion dryer used is not particularly limited, but is usually 5 to 150[1/s ] or more, preferably 10 to 100[1/s ], and more preferably 25 to 75[1/s ], and the resulting sheet-like or gel-coated acrylic rubber is preferably highly balanced in terms of storage stability, injection moldability, banbury processability and strength characteristics.

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

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

(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 generally cooled and cut to be used as a sheet-like acrylic rubber.

The thickness of the sheet-like dry rubber extruded from the screw type biaxial extrusion dryer is not particularly limited, but is usually in the range of 1 to 40mm, preferably 2 to 35mm, more preferably 3 to 30mm, most preferably 5 to 25mm, and in this case, the handling property and productivity are excellent, and therefore, it is preferable. In particular, since the thermal conductivity of the sheet-like dry rubber is as low as 0.15 to 0.35W/mK, the thickness of the sheet-like dry rubber is usually in the range of 1 to 30mm, preferably 2 to 25mm, more preferably 3 to 15mm, particularly preferably 4 to 12mm 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 can be appropriately selected depending on the purpose of use, and is usually in the range of 300 to 1200mm, preferably 400 to 1000mm, more preferably 500 to 800 mm.

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

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

The sheet-like dry rubber extruded from the screw type biaxial extrusion dryer is not particularly limited, but is usually in the range of 1500 to 6000[ Pa.s ], preferably 2000 to 5000[ Pa.s ], more preferably 2500 to 4500[ Pa.s ], and most preferably 3000 to 4000[ Pa.s ], and in this case, the extrudability and shape retention as a sheet are highly balanced, and therefore preferable. That is, by setting the complex viscosity to the lower limit or more, a rubber having more excellent extrudability can be produced, and by setting the complex viscosity to the upper limit or less, collapse or fracture of the shape of the sheet-like dry rubber can be suppressed.

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

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

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

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

The ratio of the complex viscosity at 100 ℃ ([ eta ]100 ℃) to the complex viscosity at 60 ℃ ([ eta ]60 ℃) ([ eta ]100 ℃/[ eta ]60 ℃) of the sheet-like dry rubber is not particularly limited, and is appropriately selected according to the purpose of use, and is usually 0.5 or more, preferably 0.6 or more, more preferably 0.7 or more, and the ratio of the complex viscosity at 100 ℃ ([ eta ]100 ℃) to the complex viscosity at 60 ℃ ([ eta ]60 ℃) ([ eta ]100 ℃/[ eta ]60 ℃) of the sheet-like dry rubber is also usually 0.5 to 0.99, preferably 0.55 to 0.95, more preferably 0.6 to 0.9, particularly preferably 0.65 to 0.85, most preferably 0.7 to 0.8, and in this case, the air entanglement is small, and the cutting and the 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 the thermal conductivity of the sheet-like dry rubber is extremely small and is 0.15 to 0.35W/mK, so that forced cooling by an air cooling system under ventilation or cold air, a water spraying system, a dipping system in water, or the like is preferable, and an air cooling system under ventilation or cold air is particularly preferable in order to improve productivity.

In the air cooling system of the sheet-like dry rubber, for example, the sheet-like dry rubber can be extruded from a screw extruder onto a conveyor such as a 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, particularly preferably 150℃per hour or more, and in this case, the sheet-like dry rubber is preferably cut off easily. 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 the acrylic rubber composition is excellent in processing stability.

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 superior to pellet-like acrylic rubber in handleability, injection moldability, crosslinking property, strength characteristics and compression set resistance, and also superior in storage stability, banbury workability and water resistance, and can be used as it is or by lamination and encapsulation.

(lamination step)

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

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

The rubber-covered acrylic rubber of the present invention thus obtained is superior to the pellet-shaped acrylic rubber in terms of handling properties, injection moldability, crosslinkability, strength characteristics and compression set resistance, and also superior in terms of storage stability, banbury workability and water resistance, and can be used by directly cutting or cutting the rubber-covered acrylic rubber into a desired amount and putting it into a banbury mixer, a roll or the like.

< rubber composition >

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

The acrylic rubber of the present invention may be used alone as the rubber component as the main component of the rubber composition of the present invention, or the acrylic rubber of the present invention and other rubber components may be used in combination as required. The content of the acrylic rubber of the present invention in the rubber component may be selected according to 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 these other rubber components may be any of a pellet, a strand, a bale, a sheet, a powder, and the like. The content of the other rubber component in the whole rubber component may be appropriately selected within a range not to impair the effect of the present invention, and is, for example, generally 70% by weight or less, preferably 50% by weight or less, more preferably 30% by weight or less.

The filler contained in the rubber composition is not particularly limited, and examples thereof include: reinforcing fillers, non-reinforcing fillers, and the like are preferable, and reinforcing fillers are preferable because the rubber composition is excellent in injection moldability, banbury processability, and crosslinking property in a short time, and the crosslinked product is highly 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, barium sulfate, and the like.

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

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

The organic crosslinking agent is not particularly limited, but is preferably an ion-crosslinkable organic compound, and particularly preferably a polyion organic compound. When the crosslinking agent is a polyion organic compound (polyion crosslinkable compound), the rubber composition is excellent in injection moldability, banbury processability and crosslinking property in a short period of time, and the crosslinked product is highly excellent in water resistance, strength characteristics and compression set resistance, and therefore is preferable. The "ion" of the ion-crosslinkable or multi-element ion is an ion reactive ion, and is not particularly limited as long as it is an ion that reacts with a reactive group of the 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, a polythiol compound, and the like, and a polyamine compound and a polythiol compound are preferable, and a polyamine compound is more preferable.

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

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

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 acrylic rubber containing an epoxy group.

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

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

These antioxidants may be used singly or in combination, and the amount thereof is 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, a filler and a 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 singly 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 method that can be used in the conventional rubber processing field can be used for mixing, for example, an open roll, a Banbury mixer, various kneaders, and the like. The mixing step of the components may be carried out in a usual manner in the rubber processing field, and it is preferable to sufficiently mix components which are not easily reacted or decomposed by heat, and then mix a crosslinking agent or the like of the components which are easily reacted or decomposed by heat at a temperature which does not cause reaction or decomposition in a short period of time.

< rubber Cross-Linked substance >)

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

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

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

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

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

The rubber crosslinked product of the present invention is also preferably used as an extrusion molded product and a die crosslinked product used in automobiles, for example, various hoses such as fuel oil hoses such as fuel tanks, fuel oil hoses, air hoses such as turbine air hoses and emission control hoses, radiator hoses, heater hoses, brake hoses, air conditioning hoses, and the like.

Device structure used in the manufacture of acrylic rubber

Next, a device structure used for manufacturing 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 production system having an apparatus structure used in the production of acrylic rubber according to an embodiment of the present invention. For example, the acrylic rubber production system 1 shown in fig. 1 can be used for the production of the acrylic rubber of the present invention.

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

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

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

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

The heating unit 31 of the solidifying apparatus 3 has a structure for heating the solidification liquid filled in the stirring tank 30. The temperature control unit of the solidifying apparatus 3 has the following structure: the temperature in the agitation tank 30 is controlled by controlling the heating operation by the heating section 31 while monitoring the temperature in the agitation tank 30 measured by the thermometer. The temperature of the solidification liquid in the stirring tank 30 is controlled by the temperature control unit to be in the range of usually 40 ℃ or higher, preferably 40 to 90 ℃, and more preferably 50 to 80 ℃.

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

The drive control unit of the solidifying apparatus 3 has a structure for controlling the rotation drive of the motor 32 of the stirring device 34 and setting the rotation number and rotation speed of the stirring blade 33 of the stirring device 34 to predetermined values. The rotation of the stirring blade 33 is controlled by the drive control unit so that the stirring number of the coagulation liquid is, for example, usually 100rpm or more, preferably 200 to 1000rpm, more preferably 300 to 900rpm, and particularly preferably 400 to 800 rpm. The rotation of the stirring blade 33 is controlled by the drive control unit so that the peripheral speed of the coagulation 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 has a structure for performing the above-described cleaning process.

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

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

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

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

The screw type biaxial extrusion dryer 5 shown in fig. 1 has a structure in which the above-described dehydration step and drying step are performed. Fig. 1 shows a screw type biaxial extrusion dryer 5 as a preferable example, and a centrifugal separator, a squeezer, or the like may be used as a dehydrator for performing the treatment in the dehydration step, and a hot air dryer, a decompression dryer, an expansion dryer, a kneader type dryer, or the like may be used as a dryer for performing the treatment in the drying step.

The screw type biaxial extrusion dryer 5 has a structure in which the dried rubber obtained in the dehydration step and the drying step is molded into a predetermined shape and discharged. Specifically, the screw type biaxial extrusion dryer 5 has a structure including a dehydrator cylinder 53 and a dryer cylinder 54, and further includes a die 59 on the downstream side of the screw type biaxial extrusion dryer 5, wherein the dehydrator cylinder 53 has a function as a dehydrator for dehydrating the aqueous pellets washed by the washing device 4, the dryer cylinder 54 has a function as a dryer for drying the aqueous pellets, and the die 59 has a molding function for molding the aqueous pellets.

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

The screw type biaxial extrusion dryer 5 shown in fig. 2 is a biaxial screw type extrusion dryer having a pair of screws not shown in the figure in a barrel unit 51. The screw type biaxial extrusion dryer 5 has a drive unit 50 for rotationally driving a pair of screws in a barrel unit 51. With this configuration, the acrylic rubber can be dried by applying an optimal shear, which is preferable. 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 two supply cylinders, i.e., a first supply cylinder 52a and a second supply cylinder 52 b.

Further, the dewatering cylinder section 53 is constituted by three 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.

In this way, the barrel unit 51 is constituted by connecting 13 separate barrels 52a to 52b, 53a to 53c, 54a to 54h from the upstream side to the downstream side.

The screw type biaxial extrusion dryer 5 further includes heating means, not shown, for heating the respective cylinders 52a to 52b, 53a to 53c, 54a to 54h individually to heat 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 a heating unit, for example, the following structure may be adopted: the steam supply means supplies high-temperature steam or the like to the steam flow shields formed in the respective cylinders 52a to 52b, 53a to 53c, 54a to 54h, but the present invention is not limited thereto. The screw type biaxial extrusion dryer 5 further includes a temperature control mechanism, not shown, for controlling the set temperatures of the heating units corresponding to the respective cylinders 52a to 52b, 53a to 53c, and 54a to 54 h.

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

respective cylinder sections

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

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

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

The rotation direction of the pair of screws may be the same direction or different directions, and the same direction rotation is preferable from the viewpoint of self-cleaning performance. The screw shape of the pair of screws is not particularly limited, and may be any shape required for the

respective cylinder portions

52, 53, 54.

The supply cylinder section 52 is a region in which the aqueous pellets are supplied into the cylinder unit 51. The 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. A plurality of

dewatering slits

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

The slit width, that is, the hole of each

dewatering slit

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

The removal of moisture from the aqueous pellets in each of the dewatering barrels 53a to 53c of the dewatering barrel section 53 includes two forms: from each of the

dewatering slots

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

The 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 dehydrator cylinder 53, the first to third dehydrator cylinders 53a to 53c may be set to which dehydrator cylinder to drain water or steam depending on the purpose of use, and in general, the dehydrator cylinder to drain water may be increased in the case of reducing the ash content in the produced acrylic rubber. In this case, for example, as shown in fig. 2, the water is discharged through the first and second dewatering cylinders 53a and 53b on the upstream side, and the steam is discharged through the third dewatering cylinder 53c on the downstream side. Further, for example, in the case where the dewatering cylinder portion 53 has four dewatering cylinders, the following means can be considered: drainage is performed through three dewatering barrels on the upstream side, and steam drainage is performed through one dewatering barrel on the downstream side. On the other hand, in the case of decreasing the water content, a dehydration cylinder in which steam discharge is performed may be increased.

As described in the above-described dehydration and drying steps, the set temperature of the dehydration barrel section 53 is usually in the range of 60 to 150 ℃, preferably 70 to 140 ℃, more preferably 80 to 130 ℃, the set temperature of the dehydration barrel for dehydration in a water discharge state is usually 60 to 120 ℃, preferably 70 to 110 ℃, more preferably 80 to 100 ℃, and the set temperature of the dehydration barrel for dehydration in a steam discharge state is usually 100 to 150 ℃, preferably 105 to 140 ℃, more preferably 110 to 130 ℃.

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

respective exhaust ports

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

exhaust ports

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

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

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

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

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

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

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

dewatering slits

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

The aqueous pellets dehydrated by the dehydration cylinder section 53 are conveyed to the dryer cylinder section 54 by the rotation of a pair of screws in the cylinder unit 51. The water-containing pellets sent to the dryer section 54 are plasticized and mixed to become 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 an unillustrated exhaust pipe connected to the

exhaust ports

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

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

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

The number of rotations (N) of the pair of screws in the barrel unit 51 may be appropriately selected depending on the respective conditions, and is usually 10 to 1000rpm, preferably 50 to 750rpm, more preferably 100 to 500rpm, and most preferably 120 to 300rpm, from the viewpoint of efficiently reducing the water content of the acrylic rubber and the amount of methyl ethyl ketone insoluble components.

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

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

The maximum torque in the cylinder unit 51 is not particularly limited, but is usually in the range of 5 to 125 N.m, preferably 10 to 100 N.m, more preferably 10 to 50 N.m, and particularly preferably 15 to 45 N.m.

The specific energy consumption in the cylinder unit 51 is not particularly limited, but is usually 0.01 to 0.3[ kw.h/kg ] or more, preferably 0.05 to 0.25[ kw.h/kg ], and more preferably 0.1 to 0.2[ kw.h/kg ].

The specific power in the cylinder unit 51 is not particularly limited, but is usually 0.1 to 0.6[ A.multidot.h/kg ] or more, preferably 0.15 to 0.55[ A.multidot.h/kg ], and more preferably 0.2 to 0.5[ A.multidot.h/kg ].

The shear rate in the barrel unit 51 is not particularly limited, but is usually 5 to 150[1/s ] or more, preferably 10 to 100[1/s ], and more preferably 25 to 75[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 has a structure for cooling the dried rubber obtained through the dehydration step by the dehydrator and the drying step by the dryer. As the cooling system of the cooling device 6, various systems including an air cooling system under ventilation or cool air, a water spraying system by spraying water, a dipping system by dipping in water, and the like can be used. In addition, the dried rubber may also be cooled by being left 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, and the like 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-like dry rubber 10 molded into a sheet shape will be described below with reference to fig. 3 as an example of the cooling device 6.

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

The conveying type cooling device 60 shown in fig. 3 can be used, for example, by being directly connected to the die 59 of the screw type extruder 5 shown in fig. 2 or being disposed in the vicinity of the die 59.

The conveying type cooling device 60 includes a conveyor 61 for conveying the sheet-like dry 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 for blowing cool air to the sheet-like dry rubber 10 on the conveyor 61.

The conveyor 61 has

rollers

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

rollers

62, 63 and carrying the sheet-like dry rubber 10 thereon. The conveyor 61 has a structure in which the sheet-like dry rubber 10 discharged from the die 59 of the screw extruder 5 is continuously conveyed to the downstream side (right side in fig. 3) on a conveyor belt 64.

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

The length L1 of the conveyor 61 and the cooling unit 65 of the transport cooling device 60 (the length of the portion to which cooling air can be blown) 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 is cooled by blowing cooling air from the cooling unit 65 to the sheet-like dry rubber 10 while conveying the sheet-like dry rubber 10 discharged from the die 59 of the screw type extruder 5 by the conveyor 61.

The transport cooling device 60 is not particularly limited to the configuration having one conveyor 61 and one cooling unit 65 as shown in fig. 3, and may have a configuration having two or more conveyors 61 and two or more cooling units 65 corresponding thereto. In this case, the total length of each of the two 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 has the following structure: the dried rubber extruded from the screw extruder 5 and cooled by the cooling device 6 is processed to produce a bale as a block. 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 packing device 7 has a structure for packing 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 has, for example, a packer, and can compress the cooled dry rubber by the packer, thereby producing a rubber-packed acrylic rubber.

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 can be produced. For example, a cutting device for cutting the sheet-like dry rubber 10 may be provided in the rubber packing device 7 disposed downstream of the conveyor-type cooling device 60 shown in fig. 3. Specifically, the cutting apparatus of the glue wrapping device 7 has, for example, the following structure: the cooled sheet-like dried rubber 10 is continuously cut at predetermined intervals to produce a sheet-like dried rubber 16 of a predetermined size. The cut sheet-like dried rubber 16 cut into a predetermined size by a cutting device is stacked in a plurality of sheets, whereby a rubber-coated acrylic rubber in which the cut sheet-like dried rubber 16 is stacked can be produced.

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

Examples

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

[ monomer component ]

Regarding the monomer components in the acrylic rubber, the monomer structure of each monomer unit in the acrylic rubber was confirmed by 1H-NMR, and the reactive residue of the reactive group and the content of each reactive group in the acrylic rubber were confirmed by the following method. The content ratio of each monomer unit in the acrylic rubber is calculated from the amount used in the polymerization reaction of each monomer and the polymerization conversion rate. Specifically, since the polymerization reaction is an emulsion polymerization reaction and the polymerization conversion rate is almost 100% that any unreacted monomer 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 the rubber sample in acetone and performing potential difference titration with potassium hydroxide solution.

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

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

[ Ash content ]

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

[ ash component amount ]

Regarding each component amount (%) in the acrylic rubber ash, the ash collected at the ash measurement was pressed against a titration filter paper of Φ20mm, and the XRF measurement was performed on the component amount (ppm) using ZSX Primus (manufactured by the company corporation), and the amount was calculated as the ratio in the ash.

[ molecular weight and molecular weight distribution ]

The molecular weights (Mw, mn, mz) and molecular weight distributions (Mw/Mn and Mz/Mw) of the acrylic rubber are absolute molecular weights and absolute molecular weight distributions measured by GPC-MALS method using a solution obtained by adding lithium chloride to dimethylformamide at a concentration of 0.05mol/L and adding 37% concentrated hydrochloric acid at a concentration of 0.01% as a solvent. The term "GPC-MALS method" as used herein refers to the following. GPC (gel permeation chromatography: gel permeation chromatography) is one of liquid chromatography that separates based on differences in molecular size, specifically, "GPC-MALS method" is the following method: a multi-angle laser light scattering photometer (MALS) and a differential Refractometer (RI) were assembled in a GPC (Gel Permeation Chromatography) apparatus, and the light scattering intensity and refractive index difference of a molecular chain solution separated by size using a GPC apparatus were measured according to the elution time, whereby the molecular weight of a solute and the content thereof were sequentially calculated, and finally the absolute molecular weight distribution and absolute average molecular weight values of a polymer substance were obtained.

The gel permeation chromatography multi-angle light scattering photometer used as the device was composed of a pump (manufactured by LC-20ADOpt corporation, shimadzu corporation), a differential refractometer (manufactured by Optilab rEX Wyatt Technology Corporation) as a detector, and a multi-angle light scattering detector (manufactured by DAWN HELEOS Wyatt Technology Corporation).

Thus, the molecular weight and the content of the solute are sequentially calculated and obtained. The measurement conditions and measurement methods using the GPC apparatus are as follows.

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

Column temperature: 40 DEG C

Flow rate: 0.8ml/mm

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

[ glass transition temperature (Tg) ]

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

[ gel amount ]

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

About 0.2g (Xg) of an acrylic rubber was weighed, immersed in 100ml of methyl ethyl ketone, left at room temperature for 24 hours, and then filtered through an 80-mesh wire net to remove insoluble components of methyl ethyl ketone, thereby obtaining a filtrate, namely, a filtrate in which only a rubber component dissolved in methyl ethyl ketone was dissolved, and the filtrate was evaporated and dried to be solidified, and the obtained dry solid component (Yg) was weighed and calculated by the following formula.

Gel amount (%) =100× (X-Y)/X

[ specific gravity ]

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

The measured value obtained by the following measuring method was the density, 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 method a according to JIS K6268 crosslinked rubber-density measurement is a value obtained by dividing the volume of voids containing the rubber sample by the mass, and is a value obtained by dividing the density of the rubber sample obtained by the method a according to JIS K6268 crosslinked rubber-density measurement by the density of water (the same value is obtained if the density of the rubber sample is divided by the density of water, and the unit is lost). Specifically, the specific gravity of the rubber sample can be determined by the following procedure.

(1) 2.5g of a test piece was cut out from a rubber sample which was left to stand at a standard temperature (23 ℃ C.+ -. 2 ℃ C.) for at least 3 hours, and the test piece was hung on a hook on an analytical balance having an accuracy of 1mg using a fine nylon wire having a mass of less than 0.010g so that the bottom edge of the test piece was 25mm above the scale pan for the analytical balance, and the mass (m 1) of the test piece was measured 2 times in the atmosphere until mg.

(2) Next, 250cm of the sample was placed on a scale pan for analytical balance ³ The test piece was immersed in the distilled water cooled to the standard temperature after the boiling in the beaker having a capacity, bubbles adhering to the surface of the test piece were removed, the swinging of the pointer of the balance was observed within a few seconds, it was confirmed that the pointer was not gently deflected by convection, and the mass (m 2) of the test piece in water was measured in mg for 2 times.

(3) In addition, 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 (m 3) of the weight in water and the mass (m 4) of the test piece and the weight are measured 2 times in mg units.

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

(Density of rubber sample when weight is not used)

Density=m1/(m 1-m 2)

(Density of rubber sample when weight is used)

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

[ Water content ]

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

[pH]

Regarding the pH, after 6g (+ -0.05 g) of the acrylic rubber was dissolved with 100g of tetrahydrofuran, 2.0ml of distilled water was added and complete dissolution was confirmed, and then measurement was performed by a pH electrode.

[ Complex viscosity ]

The complex viscosity η 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" (ALPHATECHNOLOGY Co., LTD.). Here, the dynamic viscoelasticity at 60 ℃ among the above-mentioned dynamic viscoelasticity is defined as the complex viscosity η (60 ℃) and the dynamic viscoelasticity at 100 ℃ is defined as the complex viscosity η (100 ℃), and the ratio η (100 ℃) to η (60 ℃) is calculated.

[ Mooney viscosity (ML1+4, 100 ℃)

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

[ injection moldability ]

Regarding injection moldability, shape formability, releasability and fusion were observed and scored using a small injection molding machine (SLIM 15-30: DAIHAN CO., LTD), and the total score of these was evaluated based on the following criteria. Regarding the shape formability and releasability, a mold of 3 cylindrical shapes (A: 4 mm. Phi., B:3 mm. Phi., C:2 mm. Phi.) having diameters different from each other with a shaft length of more than 150mm was prepared, the rubber composition was flowed into the mold under the conditions of a screw temperature of 90℃for 30 seconds and an injection pressure of 7MPa, crosslinked at a mold temperature of 170℃for 1 minute for 30 seconds, and then the molded article of the cylindrical shape after injection molding was taken out, and the molded article of the cylindrical shape and the mold were observed and scored according to the following criteria. Regarding the fusion property, a mold was prepared which simulates a fusion observation zone in which a 5mm phi tube was connected to each of both ends in the longitudinal direction and having a thickness of 0.5 mm. Times.width of 5 mm. Times.length of 40mm, and the rubber composition was flowed into the fusion observation zone from the 5mm phi tube in the mold under the conditions of a screw temperature of 90℃for 30 seconds and an injection pressure of 7MPa, crosslinked at a mold temperature of 170℃for 1 minute for 30 seconds, and then the fusion condition of the rubber composition in the fusion observation zone was observed and scored by the following criteria.

(shape Forming Property)

5, the method comprises the following steps: in A, B, C, a cylindrical molded article could be produced, and the shape of the distal end portion of the entire molded article was formed to completely follow the mold, and the formation of burrs was not confirmed

4, the following steps: although a cylindrical molded body can be produced in A, B, C, in C, only a small portion of the distal end portion of the molded body does not completely follow the mold shape

3, the method comprises the following steps: a, B a cylindrical molded article can be produced, and C a half or more of the molded articles can be produced

2, the method comprises the following steps: a, B a cylindrical molded article can be produced, but even half of the molded articles in C cannot be produced

1, the method comprises the following steps: a can produce a molded article, but B cannot produce a molded article at all

0 point: a was not able to produce a molded article

(Release property)

5, the method comprises the following steps: can be easily released from the mold without leaving residues in the mold

4, the following steps: can be easily released from the mold, but it was confirmed that there was very little residue in the mold

3, the method comprises the following steps: can be easily released from the mold, but has a little residue in the mold

2, the method comprises the following steps: is not easy to be stripped from the mould, and has no residue in the mould

1, the method comprises the following steps: is not easy to be stripped from the mould, and has residues in the mould

0 point: is not easy to be stripped from the mould

(fusibility)

5, the method comprises the following steps: complete fusion

0 point: incomplete fusion (poor fusion)

Comprehensive evaluation

And (3) the following materials: full score (15 score)

And (2) the following steps: 14 minutes

And ∈:13 minutes

Delta: 11-12 minutes

X: less than 10 minutes

[ Banbury processability ]

Regarding the banbury processability of the rubber sample, the rubber sample was put into a banbury mixer heated to 50 ℃ for mastication for 1 minute, and then, compounding agent a for compounding the rubber mixture described in table 1 was put into the mixer, the rubber mixture in the first stage was integrated, and the time to show the maximum torque value, i.e., BIT (Black Incorporation Time) was measured, and an index of 100 was calculated based on comparative example 2, and evaluated based on the following criteria.

And (3) the following materials: 20 or less

And (2) the following steps: more than 20 and less than 40

And ∈: greater than 40 and less than 60

Delta: more than 60 and less than 80

X: greater than 80

[ evaluation of storage stability ]

Regarding the storage stability of the rubber sample, the rubber sample was put into a constant temperature and humidity tank (SH-222 manufactured by ESPEC Co., ltd.) 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 index was calculated to be 100 in comparative example 2, and the evaluation was performed on the basis of the following.

And (3) the following materials: 20 or less

And (2) the following steps: more than 20 and less than 50

And ∈: greater than 50 and less than 90

Delta: greater than 90 and less than 100

X: greater than 100

[ evaluation of Water resistance ]

The water resistance of the rubber sample was evaluated as follows: the crosslinked 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 measured, and the index was calculated to be 100 in comparative example 2, and evaluated according to the following criteria.

And (3) the following materials: 1 or less

And (2) the following steps: more than 1 and less than 5

And ∈: more than 5 and less than 10

Delta: more than 10 and less than 50

X: greater than 50

[ compression set resistance ]

Regarding the compression set resistance of the rubber sample, the compression set rate was measured after the rubber crosslinked product of the rubber sample was left to stand at 175℃for 90 hours in a state of 25% compression in accordance with JIS K6262, and evaluated by 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 ]

Regarding the normal physical properties of the rubber sample, 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 evaluated by the following criteria.

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

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

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

[ evaluation of deviation of gel amount ]

Regarding the evaluation of the deviation of the gel amount of the rubber sample, the gel amount at 20 points arbitrarily selected from 20 parts (20 kg) of the rubber sample was measured, and the evaluation was performed based on the following criteria.

And (3) the following materials: calculating the average value of the gel amounts at 20 points, wherein all the 20 points are within the range of + -3 of the average value

And (2) the following steps: calculating the average value of the gel amounts at 20 points of measurement, wherein all of the 20 points of measurement are within the range of the average value.+ -. 5 (at least 1 of the 20 points of measurement is outside the range of the average value.+ -. 3, but all of the 20 points are within the range of the average value.+ -. 5)

X: calculating the average value of the gel amount at 20 measured points, wherein at least 1 of the 20 measured points is out of the range of +/-5 of the average value

[ evaluation of processing stability based on Mooney scorch inhibition ]

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

Example 1

As shown in Table 2-1, 46 parts of pure water, 48.5 parts of ethyl acrylate, 50 parts of n-butyl acrylate and 1.5 parts of mono-n-butyl fumarate as monomer components, and 1.8 parts of sodium tridecyloxy hexaoxyethylene phosphate as 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 as described above were charged into a polymerization reaction tank having a thermometer and a stirring device, cooled to 12℃under a nitrogen stream, and then 0.00033 parts of ferrous sulfate, 0.02 parts of sodium ascorbate and 0.0045 parts of diisopropylbenzene hydroperoxide as an organic radical generator were added to initiate polymerization. The polymerization was continued by keeping the temperature in the polymerization vessel at 23℃and continuously dropping the remaining part of the monomer emulsion over 3 hours, adding 0.012 parts of n-dodecyl mercaptan after 50 minutes from the start of the reaction, adding 0.012 parts of n-dodecyl mercaptan after 100 minutes, adding 0.4 parts of sodium L-ascorbate after 120 minutes, and terminating the polymerization by adding hydroquinone as a polymerization terminator when the polymerization conversion reached about 100%, to obtain an emulsion polymerization solution.

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

194 parts of warm water (70 ℃) was added to the solidification tank in which the filtered aqueous pellets remained, and the mixture was stirred for 15 minutes, after washing the aqueous pellets, the water was discharged, 194 parts of warm water (70 ℃) was added again, and the mixture was stirred for 15 minutes, and washing of the aqueous pellets was performed (the total number of washing times was 2). The washed aqueous pellet (aqueous pellet temperature: 65 ℃ C.) was fed to a screw type biaxial extrusion dryer 15, dehydrated and dried, and a sheet-like dried rubber having a thickness of 10mm was extruded at a width of 300 mm. 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 one supply cylinder, three dehydration cylinders (first to third dehydration cylinders), and five dryer cylinders (first to fifth dryer cylinders). 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. The water content, maximum torque, specific power, specific energy consumption, shear rate and shear viscosity after dehydration (drainage) of the screw type biaxial extrusion dryer are shown in table 2-1.

Water content:

water content of the aqueous pellet after drainage through the first dewatering barrel: 20 percent of

Moisture content of the aqueous pellets after steam venting through the third dewatering barrel: 10 percent of

Moisture content of the dried aqueous pellets by the fifth dryer barrel: 0.4%

Rubber temperature:

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

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

Set temperature of each barrel:

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

Revolution of screw: 135rpm

Vacuum of the dryer barrel: 10kPa

Extrusion amount of rubber from die: 700 kg/hr

Resin pressure at die: 2MPa of

Maximum torque in screw type biaxial extrusion dryer: 40 N.m

The extruded sheet-like dried rubber was cooled to 50℃and then cut by a cutter, and laminated to 20 parts (20 kg) before 40℃or lower, to obtain a rubber-covered acrylic rubber (A). The reactive group content, ash component content, gel content, pH, specific gravity, glass transition temperature (Tg), water content, molecular weight distribution, and complex viscosity at 100℃and 60℃of the resulting rubber-coated acrylic rubber (A) were measured and are shown in tables 2-2. Further, the storage stability test of the rubber-coated 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 rubber-coated acrylic rubber (a) and the compounding agent a of "compounding 1" described in table 1 were charged into a banbury mixer, and mixed at 50 ℃ for 5 minutes (first-stage mixing). BIT was measured at this time, and the Banbury processability was evaluated, and the results are shown in Table 2-2. Next, the obtained mixture was transferred to a roller at 50℃and blended with the compounding agent B of "compounding 1" shown in Table 1, followed by mixing (second stage mixing) to obtain a rubber composition. The obtained rubber compositions were evaluated for injection moldability, and the results are shown in tables 2-2.

TABLE 1

1: SEAST3 (HAF) in the table is carbon black (manufactured by Donghai carbon Co., ltd.).

The NocracCD in the tables is 4.4' -bis (. Alpha.,. Alpha. -dimethylbenzyl) diphenylamine (manufactured by Dain Chemie Co., ltd.).

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

Then, the remaining rubber composition was put into a mold having a length of 15cm, a width of 15cm and a depth of 0.2cm, and the mold 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 at 180℃for 2 hours by a Gill oven, and secondary crosslinking was performed, whereby a sheet-like crosslinked rubber product was obtained. Then, a test piece of 3 cm. Times.2 cm. Times.0.2 cm was cut out from the resulting sheet-like rubber crosslinked material, and the water resistance, compression set resistance and normal physical properties were evaluated. These results are shown in Table 2-2.

Example 2

A rubber-coated acrylic rubber (B) 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 as shown in table 2-1, and each characteristic was evaluated (the compounding agent was changed to "compounding 2" (see table 1)). These results are shown in Table 2-2.

Example 3

The procedure of example 1 was repeated except that the post-addition of n-dodecyl mercaptan was changed to a total of 3 times of adding 0.008 parts after 50 minutes, adding 0.008 parts after 100 minutes and adding 0.008 parts after 120 minutes, to obtain a rubber-covered acrylic rubber (C), and each property was evaluated. These results are shown in Table 2-2.

Example 4

The procedure of example 2 was repeated except that the post-addition of n-dodecyl mercaptan was changed to a total of 3 times of adding 0.008 parts after 50 minutes, adding 0.008 parts after 100 minutes and adding 0.008 parts after 120 minutes, to obtain a rubber-coated acrylic rubber (D), and each property was evaluated. These results are shown in Table 2-2.

Example 5

The procedure of example 1 was repeated except that the maximum torque of the screw type biaxial extrusion dryer was changed to 15 N.multidot.m as shown in Table 2-1 to obtain a rubber-covered acrylic rubber (E), and each of the characteristics was evaluated. These results are shown in Table 2-2.

Example 6

A rubber-coated acrylic rubber (F) was obtained in the same manner as in example 2 except that the maximum torque of the screw type biaxial extrusion dryer was changed to 15n·m, and each characteristic was evaluated. These results are shown in Table 2-2.

Example 7

A rubber-coated acrylic rubber (G) was obtained in the same manner as in example 5 except that the water content after dehydration in the dehydration cylinder portion of the screw type biaxial extrusion dryer was set to 30% by weight, and each characteristic was evaluated. These results are shown in Table 2-2.

Example 8

A rubber-coated acrylic rubber (H) was obtained in the same manner as in example 6 except that the water content after dehydration in the dehydration cylinder portion of the screw type biaxial extrusion dryer was set to 30% by weight, and each characteristic was evaluated. These results are shown in Table 2-2.

Example 9

A rubber-covered acrylic rubber (I) was obtained in the same manner as in example 2, except that the washed aqueous pellets were dried to a water content of 0.4% by using a hot air dryer at 160 ℃ to obtain a pellet-like acrylic rubber (I), and then the pellet-like acrylic rubber was packed in a 300×650×300mm packer and compacted at a pressure of 3MPa for 25 seconds to obtain a rubber-covered acrylic rubber. The properties of the rubber-covered acrylic rubber bag were evaluated, and these results are shown in Table 2-2.

Example 10

A rubber-in-bag acrylic rubber (J) 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 each characteristic was evaluated (the compounding agent was changed to "compounding 3" (see table 1)). These results are shown in Table 2-2.

Example 11

A rubber-coated acrylic rubber (K) was obtained in the same manner as in example 9 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 characteristic was evaluated (the compounding agent was changed to "compounding 4" (see table 1)). These results are shown in Table 2-2.

Example 12

A rubber-coated acrylic rubber (L) was obtained in the same manner as in example 11, except that the post-addition of n-dodecyl mercaptan was changed to a total of 3 times of adding 0.008 parts after 50 minutes, adding 0.008 parts after 100 minutes, and adding 0.008 parts after 120 minutes, and each characteristic was evaluated. These results are shown in Table 2-2.

Example 13

The procedure of example 11 was repeated except that 0.0048 parts of diisopropylbenzene hydroperoxide was changed and 0.024 parts of n-dodecylmercaptan was continuously added to the monomer emulsion, and the subsequent addition was not performed, to obtain a rubber-covered acrylic rubber (M), and each characteristic was evaluated. These results are shown in Table 2-2.

Comparative example 1

An acrylic rubber in pellet form (N) was obtained in the same manner as in example 13, except that a coagulation reaction was carried out by adding a 0.7% aqueous solution of magnesium sulfate to the stirred emulsion polymerization solution (stirring number: 100rpm, circumferential speed: 0.5 m/s) after emulsion polymerization, and the acrylic rubber was not subjected to rubber-packing by a packer to obtain a pellet-like acrylic rubber, and each property was evaluated. These results are shown in Table 2-2.

Comparative example 2

The procedure of comparative example 1 was repeated except that the amount of diisopropylbenzene hydroperoxide was changed to 0.005 part and a chain transfer agent was not added, to obtain a pellet-like acrylic rubber (O), and each property was evaluated. These results are shown in Table 2-2.

[ Table 2-1]

[ Table 2-2]

As is clear from tables 2 to 2, the acrylic rubber (A) to (M) of the present invention having at least one reactive group selected from carboxyl groups, epoxy groups and chlorine atoms, having a weight average molecular weight (Mw) of 100 to 500 ten thousand, a ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of 1.5 to 3, a gel content of 50% by weight or less, an ash content of 0.0001 to 0.3% by weight, and a total content of sodium, sulfur, calcium, magnesium and phosphorus in the ash content of 80% by weight or more is excellent in injection moldability, banbury processability, water resistance, compression set resistance and normal physical properties including strength characteristics, and also excellent in storage stability (examples 1 to 13).

As is clear from tables 2 to 2, the acrylic rubbers (A) to (O) of examples and comparative examples of the present application are excellent in compression set resistance by having a plasma-reactive group such as a carboxyl group, an epoxy group or a chlorine atom, and the weight average molecular weights (Mw) of the acrylic rubbers (A) to (O) produced under the conditions of examples and comparative examples of the present application are all far greater than 100 ten thousand, so that the normal physical properties including strength characteristics are also excellent (examples 1 to 13 and comparative examples 1 to 2). However, the acrylic rubbers (N) to (O) were poor in injection moldability, banbury processability, water resistance and storage stability (comparative examples 1 to 2).

As is clear from tables 2 to 2, the injection moldability is greatly affected by the molecular weight distribution (Mw/Mn) of the acrylic rubber, and comparative example 2 is Mw/mn=1.3/injection moldability: example 13 was Mw/mn=1.55/injection moldability: delta, example 12 is Mw/mn=1.99/injection moldability: examples 3 to 11 were Mw/mn=2.39 to 2.45/injection moldability: for example 1 to 2, mw/mn=2.91 to 2.94/injection moldability: as described above, the acrylic rubber of the present invention is most excellent in Mw/Mn close to 2.4, and is excellent in injection moldability. It is also found that the molecular weight distribution (Mz/Mw) focused on the high molecular weight region is sufficiently enlarged, the number average molecular weight (Mn), the weight average molecular weight (Mw) and the z average molecular weight (Mz) are sufficiently enlarged, and the injection moldability can be improved without impairing the strength characteristics when the Mw/Mn of the present invention is within the range of the Mw/Mn (comparison of examples 1 to 13 and comparative example 2).

As is clear from tables 2-1 and 2-2, the acrylic rubbers (A) to (M) having a molecular weight distribution (Mw/Mn) in a specific range, which are excellent in injection moldability, without impairing the strength characteristics, can be produced by using specific amounts of an organic radical generator and a chain transfer agent, in particular, n-dodecyl mercaptan as the chain transfer agent (examples 1 to 13). Further, as is clear from tables 2-1 and 2-2, by adding a chain transfer agent (n-dodecyl mercaptan) in a batch manner after the initial addition of no chain transfer agent (n-dodecyl mercaptan) as compared with the continuous addition of a chain transfer agent (n-dodecyl mercaptan) (example 13), injection moldability can be improved without impairing strength characteristics (examples 1 to 12). The reason for this is presumed to be as follows: by elongating 1 polymer chain without adding a chain transfer agent at the initial stage and reducing the amount of an organic radical generator, and adding a chain transfer agent during polymerization, although two peaks are not clearly formed in the GPC chart, the high molecular weight component and the low molecular weight component can be produced in good balance, and the molecular weight distribution (Mw/Mn) can be brought into a specific range, thereby highly balancing the strength characteristics with the injection moldability. In order to effectively expand the molecular weight distribution (Mw/Mn), the number of times of batch post-addition was greatly affected, and the molecular weight distribution (Mw/Mn) when the number of times of batch post-addition was 2 was larger than that when the number of times of batch post-addition was 3 (comparison of examples 9 to 11 with example 12). In addition, although not shown in tables 2-1 and 2-2, in the examples of the present application, sodium ascorbate was added as a reducing agent 120 minutes after the start of polymerization, whereby a high molecular weight component of the acrylic rubber was easily produced, and the effect of increasing the molecular weight distribution (Mw/Mn) by the addition of the chain transfer agent was increased.

It is also clear from tables 2-1 and 2-2 that when the drying of the aqueous pellets is changed from direct drying to screw type biaxial extrusion dryer and the operation is performed under normal conditions, the molecular weight distribution (Mw/Mn) is not changed (comparison between examples 5 to 8 and examples 9 to 11), but the molecular weight distribution (Mw/Mn) of the acrylic rubber is enlarged by setting the drying conditions of the screw type biaxial extrusion dryer to be optimum for shearing, and the injection moldability of the acrylic rubber can be further improved (comparison between examples 3 to 4 and example 12), but the improvement effect of the injection moldability is gradually reduced if the molecular weight distribution (Mw/Mn) is excessively large (comparison between examples 1 to 2 and examples 5 to 8). It is also clear that, although not shown in examples and comparative examples of the present application, if a redox catalyst containing an inorganic radical generator is used, the molecular weight distribution (Mw/Mn) of the resulting acrylic rubber is too large, and the injection moldability is poor. The reason for this is considered as follows: in the case of an organic radical generator, the polymerization catalyst exists in the micelle of emulsion polymerization, polymerization proceeds continuously in the micelle, and in the case of an inorganic radical generator, the polymerization catalyst exists outside the micelle, polymerization proceeds outside the micelle, and thus, these differences in molecular weight distribution occur, affecting injection moldability.

As is clear from tables 2 to 2, the acrylic rubbers (A) to (M) of the present invention are excellent in water resistance (comparison of examples 1 to 13 with comparative examples 1 to 2), among these, acrylic rubbers (A) to (F) > acrylic rubbers (G) to (H) > acrylic rubbers (I) to (J) > acrylic rubbers (K) to (M), particularly acrylic rubbers (A) to (F) are excellent (comparison of examples 1 to 13), and these have a great influence on the ash amount in the acrylic rubbers (comparison of examples 1 to 13 with comparative examples 1 to 2).

As is clear from tables 2-1 and 2-2, the amount of ash in the acrylic rubber was significantly reduced by increasing the concentration of the coagulating liquid (2%) during the coagulation reaction, changing the method to a method in which the emulsion polymerization liquid was added to the stirred coagulating liquid (Lx ∈) and increasing the stirring change of the coagulating liquid (stirring number 600 rpm/circumferential speed 3.1 m/s) (comparison of examples 9 to 13 with comparative example 1). The reason for this is presumed to be as follows: in particular, by adding an emulsion polymerization liquid to a very vigorously stirred coagulation liquid to carry out a coagulation reaction, and the data will be described later, the particle size of the aqueous aggregates produced in the coagulation reaction is concentrated in the range of particle sizes as small as 710 μm to 4.75mm, whereby the washing efficiency with warm water and the removal efficiency of an emulsifier and a coagulant at the time of dehydration are remarkably improved, the ash content in the acrylic rubber is reduced, and the water resistance is remarkably improved. In addition, it is found that the gray components of examples 9 to 13 are the same level, but the acrylic rubbers (I) to (J) are more excellent than the acrylic rubbers (K) to (M). The reason for this is as follows: in terms of water resistance, even though each of the acrylic rubber has an ion-reactive group, the acrylic rubber having a carboxyl group and an epoxy group is more excellent in water resistance than the acrylic rubber having a chlorine atom (comparison of examples 9 to 10 and examples 11 to 13).

It is also clear from tables 2-1 and 2-2 that, in terms of water resistance, the ash content in the acrylic rubber can be further reduced significantly by dehydrating (squeezing out moisture) the aqueous pellets before drying them (comparison of examples 1 to 8 with examples 9 to 13), and that, in the case where more moisture is squeezed out of the aqueous pellets such that the water content after dehydration is 20%, the ash content can be further reduced significantly by significantly improving the water resistance of the acrylic rubber (comparison of examples 1 to 6 with examples 7 to 8) compared with the case where the water content after dehydration is 30%.

Further, as is clear from tables 2-1 and 2-2, in the ash components of the acrylic rubbers (A) to (M) of the invention and the acrylic rubbers (N) to (O) of the comparative examples, the total amount of phosphorus (P), magnesium (Mg), sodium (Na), calcium (Ca) and sulfur (S) is 80% by weight or more or 90% by weight or more, and if the ash content can be reduced, the water resistance can be improved. When the content of the ash is within this range, the releasability of the acrylic rubber is remarkably excellent. It is also clear from tables 2 to 2 that the ash content of the acrylic rubber (A) to (M) of the present invention, which was coagulated and washed and dehydrated by the method of the present invention, was 80% or more or 90% or more in terms of phosphorus (P) and magnesium (Mg) (examples 1 to 13 and comparative examples 1 to 2). From this, it was found that the emulsifier and coagulant used in the production of the ash in the acrylic rubber did not remain directly, but the sodium phosphate salt of the emulsifier and magnesium sulfate (MgSO) of the coagulant at the time of the coagulation reaction ₄ ) Although salt exchange was performed to form a magnesium phosphate salt which was hardly soluble in water and was not sufficiently removed in the washing step, ash content in the acrylic rubber was reduced by dehydration (extrusion of water from the aqueous pellet) in a screw type biaxial extrusion dryer (examples 1 to 8), and when more water was extruded from the aqueous pellet to a water content of 20% as compared with the case where the water content after dehydration was 30%, the ash content was further reduced and the water resistance of the acrylic rubber was remarkably improved (comparison of examples 1 to 6 and examples 7 to 8).

In terms of water resistance, data are omitted in the examples of the present application, and if a phosphate salt is used as an emulsifier, it is difficult to reduce the number of times of washing in the washing step, particularly in the normal temperature washing, and the number of times of washing is hardly reduced, but the hot water washing can be performed to improve the water resistance, and on the other hand, the water resistance is more excellent than the ash having a large amount of sulfur (S) and sodium (Na) generated by using a sulfate salt such as sodium lauryl sulfate as an emulsifier, particularly, the water resistance is more excellent by 5 times or more if the ash amount is the same. In addition, in the case of using a sulfate salt such as sodium lauryl sulfate as an emulsifier, it was confirmed that the coagulation reaction of the present invention was performed, and warm water washing and dehydration were performed, whereby the ash content was reduced to 0.1 wt% or less, and the water resistance was also significantly improved. In addition, the acrylic rubber obtained by emulsion polymerization using the phosphate salt or the sulfate salt as an emulsifier is significantly more excellent in handling properties such as mold release properties.

As is clear from tables 2-1 and 2-2, the Banbury processability was related to the gel amount (comparison of examples 1 to 13 with comparative examples 1 to 2). It can be seen that: by performing emulsion polymerization in the presence of a chain transfer agent, the gel amount of methyl ethyl ketone insoluble components of the acrylic rubber can be reduced (comparison of examples 9 to 13 with comparative examples 1 and 2), and particularly when the polymerization conversion is increased in order to improve the strength characteristics, the gel amount increases sharply, so in examples 9 to 13 in which a chain transfer agent is added after the latter half of the polymerization reaction, the formation of methyl ethyl ketone insoluble component gels can be suppressed. Further, by drying the aqueous pellets with a screw type biaxial extrusion dryer, the gel content of the acrylic rubber can be significantly reduced, and the banbury processability can be significantly improved without impairing the strength characteristics of the produced acrylic rubber (comparison of examples 1 to 8 and examples 9 to 13). In the present invention, although not shown in the present example, it was confirmed that the gel amount of methyl ethyl ketone insoluble component (comparative examples 1 to 2) which increases sharply by emulsion polymerization without adding a chain transfer agent was eliminated by melt kneading in a screw type biaxial extrusion dryer in a state substantially containing no water (water content less than 1% by weight), and the banbury processability was greatly improved.

As is clear from tables 2 to 2, the acrylic rubbers (A) to (M) of the present invention were excellent in injection moldability, banbury processability, water resistance, compression set resistance and strength characteristics, and also excellent in storage stability (examples 1 to 13). The specific gravity of the rubber-encapsulated acrylic rubber (A) to (M) was far greater than that of the pellet-like acrylic rubber (N) to (O) in terms of storage stability, which depends on the specific gravity, that is, the amount of air involved (comparison of examples 1 to 8, examples 9 to 13 and comparative examples 1 to 2). The rubber-coated acrylic rubber having a high specific gravity can be obtained by compacting the acrylic rubber in pellet form by a packer to obtain the rubber coating (examples 9 to 13), and more preferably by extruding the rubber coating in sheet form by a screw type biaxial extrusion dryer and laminating the rubber coating (examples 1 to 8). It is also found that the smaller the ash content, the better the storage stability of the acrylic rubber (examples 1 to 13). The results of example 13 in Table 2-2 were the same except that the specific gravity of the acrylic rubber (M) of example 13 was as low as 0.769 when the characteristic value of the pellet-like acrylic rubber after direct drying was measured without using a baler. In the present invention, it is found that, in particular, a rubber-coated acrylic rubber obtained by laminating sheet-like acrylic rubber obtained by melt kneading and drying under reduced pressure can significantly improve the storage stability without impairing the normal physical properties including injection moldability, banbury workability, water resistance, compression set resistance, and strength characteristics (examples 1 to 8). In addition, regarding the storage stability of the acrylic rubber, it is also important that the pH is 6 or less.

[ regarding the particle size of the resulting hydrous pellets ]

The aqueous pellets produced in the coagulation step in examples 1 to 13 and comparative examples 1 to 2 were measured for the proportions of (1) 710 μm to 6.7mm (not passing 710 μm but passing 6.7 mm), (2) 710 μm to 4.75mm (not passing 710 μm but passing 4.75 mm), (3) 710 μm to 3.35mm (not passing 710 μm but passing 3.35 mm) using a JIS sieve. These results are shown below.

Example 1: (1) 91 wt%, (2) 91 wt%, (3) 84 wt%

Example 2: 96 wt%, (2) 95 wt%, and (3) 89 wt%

Example 3: (1) 91 wt%, (2) 85 wt%, and (3) 79 wt%

Example 4: (1) 93 wt%, (2) 90 wt%, and (3) 84 wt%

Example 5: (1) 95 wt%, (2) 93 wt%, and (3) 90 wt%

Example 6: (1) 89 wt%, (2) 85 wt%, and (3) 79 wt%

Example 7: 96 wt%, (2) 94 wt%, and (3) 87 wt%

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

Example 9: (1) 95 wt%, (2) 94 wt%, and (3) 91 wt%

Example 10: (1) 89 wt%, (2) 86 wt%, and (3) 83 wt%

Example 11: (1) 95 wt%, (2) 94 wt%, and (3) 88 wt%

Example 12: (1) 93 wt%, (2) 93 wt%, and (3) 90 wt%

Example 13: (1) 93 wt%, (2) 89 wt%, and (3) 78 wt%

Comparative example 1: (1) 17 wt%, (2) 3 wt%, (3) 0 wt%

Comparative example 2: (1) 10 wt%, (2) 2 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 produced in the coagulation step, and that the aqueous aggregates having a high specific ratio of (1) to (3) were high in washing efficiency, low in ash content and excellent in water resistance (comparison between examples 9 to 13 and comparative examples 1 to 2 in Table 2-2). It is also found that the water-containing pellets having a high specific ratio of (1) to (3) have a high ash removal rate during dehydration, and that the examples (examples 1 to 6) having a dehydration rate (water content) of 20 wt% have a lower ash content than the examples (examples 7 to 8) having a dehydration rate (water content of 30 wt%) to improve the water resistance of the acrylic rubber.

In addition, as a reference, the procedure was carried out in the same manner as in comparative example 1 (reference example 1) except that the emulsion polymerization liquid was added to the coagulation liquid in the coagulation step, and the coagulant concentration of the coagulation liquid was changed from 0.7% by weight to 2% by weight, in addition to the above, the particle size ratios (1) to (3) of the produced aqueous pellets and the ash content (4) in the acrylic rubber were measured in the same manner as in comparative example 1 (reference example 2). These results are shown below.

Reference example 1: (1) 91 wt%, (2) 57 wt%, (3) 25 wt%, (4) 0.51 wt%

Reference example 2: (1) 92 wt%, (2) 75 wt%, (3) 42 wt%, (4) 0.40 wt%

Regarding the acrylic rubber compositions comprising the sheet-like acrylic rubbers (A) to (H) of examples 1 to 8, the Mooney scorch storage stability was evaluated by the following criteria by measuring the Mooney scorch time t5 (minutes) at a temperature of 125℃in accordance with JIS K6300 by the above-mentioned method of evaluating the processing stability based on the Mooney scorch inhibition. The results were excellent.

And (3) the following materials: the Mooney scorch time t5 is more than 3.3 minutes

And (2) the following steps: the Mooney scorch time t5 is 2 to 3.3 minutes

X: the Mooney scorch time t5 is less than 2 minutes

The cooling rate of the sheet-like acrylic rubbers (A) to (H) extruded from the screw type biaxial extrusion dryer was 40℃/hr or more, and was as high as about 200℃/hr in practice as in example 1.

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 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 above-mentioned reference.

When the acrylic rubbers (a) to (H) obtained in examples 1 to 8 and the acrylic rubber (O) obtained in comparative example 2 were evaluated for the gel amount deviation as rubber samples, the results of the acrylic rubbers (a) to (H) were all "excellent", and the result of the acrylic rubber (O) was "x".

This is presumed to be because: the acrylic rubbers (a) to (H) were melt kneaded and dried by a screw type biaxial extruder, and the gel amount of methyl ethyl ketone insoluble components was almost eliminated, and the gel amount was hardly deviated, so that the banbury processability was remarkably improved. Although not shown in the present embodiment, it is known that: the acrylic rubber (O) of comparative example 2 was subjected to emulsion polymerization and coagulation washing until a pellet-like acrylic rubber was obtained, and the pellet-like acrylic rubber was fed into a screw type biaxial extrusion dryer under the same conditions as in example 1, and extrusion-dried to obtain an acrylic rubber, which was reduced in gel amount and gel amount deviation to a level substantially equivalent to those of the acrylic rubber (a), and was significantly improved in banbury processability.

[ Release of mold ]

The rubber compositions of the acrylic rubbers (A) to (H) obtained in examples 1 to 8 were pressed into a 10 mm. Phi. Times.200 mm mold, and the crosslinked rubber product obtained by crosslinking at a mold temperature of 165℃for 2 minutes was taken out, and when mold releasability was evaluated based on the following criteria, the acrylic rubbers (A) to (H) were all evaluated to be excellent.

And (3) the following materials: can be easily released from the mold without leaving residues in the mold

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

Delta: can be easily released from the mold, but has a little residue in the mold

X: difficult to be peeled from the 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 a carboxyl group, an epoxy group and a chlorine atom, wherein the acrylic rubber has a weight average molecular weight (Mw) of 100 to 500 tens of thousands, a ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of 1.5 to 3, a gel amount of 50 wt.% or less, an ash content of 0.0001 to 0.3 wt.%, and a total amount of sodium, sulfur, calcium, magnesium and phosphorus in the ash of 80 wt.% or more.

2. The acrylic rubber according to claim 1, wherein the acrylic rubber is composed of the following bonding units: binding units derived from at least one (meth) acrylate selected from the group consisting of alkyl (meth) acrylates and alkoxyalkyl (meth) acrylates; binding units derived from monomers containing at least one reactive group selected from the group consisting of carboxyl groups, epoxy groups, and chlorine atoms; and binding units from other monomers used as desired.

3. The acrylic rubber according to claim 1 or 2, wherein the binding unit derived from at least one (meth) acrylic ester selected from the group consisting of alkyl (meth) acrylate and alkoxyalkyl (meth) acrylate is 50 to 99.99% 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 0.01 to 10% by weight, and the binding unit derived from other monomer is 0 to 40% by weight.

4. An acrylic rubber according to any one of claims 1 to 3, wherein the reactive group is an ion-reactive group.

5. The acrylic rubber according to any one of claims 1 to 4, wherein the gel amount of the acrylic rubber is 10% by weight or less.

6. The acrylic rubber according to any one of claims 1 to 5, wherein all values of the gel amount at any measured 20 are in the range of (average ± 5% by weight).

7. The acrylic rubber according to any one of claims 1 to 6, wherein the gel amount is an amount of methyl ethyl ketone insoluble component.

8. The acrylic rubber according to any one of claims 1 to 7, wherein the ash content of the acrylic rubber is 0.2% by weight or less.

9. The acrylic rubber according to any one of claims 1 to 8, wherein the specific gravity of the acrylic rubber is 0.8 or more.

10. The acrylic rubber according to any one of claims 1 to 9, wherein the acrylic rubber has a complex viscosity ([ η100 ] c) of 15000[ pa-s ] or less at 100 ℃.

11. The acrylic rubber according to any one of claims 1 to 10, wherein the pH of the acrylic rubber is 6 or less.

12. The acrylic rubber according to any one of claims 1 to 11, wherein the acrylic rubber is sheet-like or bale-like.

13. The acrylic rubber according to any one of claims 1 to 12, wherein the acrylic rubber is emulsion-polymerized using a phosphate salt or a sulfate salt as an emulsifier.

14. The acrylic rubber according to any one of claims 1 to 13, wherein the acrylic rubber is obtained by coagulating and drying a polymerization liquid obtained by emulsion polymerization using an alkali metal salt or a group 2 metal salt of the periodic table as a coagulant.

15. The acrylic rubber according to any one of claims 1 to 14, wherein the acrylic rubber is obtained by melt kneading and drying after solidification.

16. The acrylic rubber according to claim 15, wherein the melt-kneading and drying are performed in a state substantially containing no moisture.

17. The acrylic rubber according to claim 15 or 16, wherein the melt-kneading and drying are performed under reduced pressure.

18. The acrylic rubber according to any one of claims 15 to 17, wherein the acrylic rubber is cooled at a cooling rate of 40 ℃/hr or more after the melt kneading and drying.

19. The acrylic rubber according to any one of claims 1 to 18, wherein the acrylic rubber is obtained by washing, dehydrating and drying an aqueous pellet having a particle diameter in the range of 710 μm to 6.7mm in a proportion of 50% by weight or more.

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

a cleaning step of cleaning the produced aqueous pellets;

21. The method for producing an acrylic rubber according to claim 20, wherein the acrylic rubber according to any one of claims 1 to 19 is produced.

22. The method for producing an acrylic rubber according to claim 20 or 21, wherein in the dehydration step and the drying step, a dehydration cylinder having a dehydration slit, a dryer cylinder under reduced pressure, and a screw type biaxial extrusion dryer having a die at a tip end portion are used, the washed aqueous pellets are dehydrated to a water content of 1 to 40% by weight using the dehydration cylinder, and then dried to less than 1% by weight using the dryer cylinder, and the dried rubber is extruded from the die.

23. The method for producing an acrylic rubber according to any one of claims 20 to 22, wherein the number of stirring of the stirred coagulation liquid is 200rpm or more.

24. The method for producing an acrylic rubber according to any one of claims 20 to 23, wherein a peripheral speed of the stirred coagulation liquid is 1m/s or more.

25. The method for producing an acrylic rubber according to any one of claims 20 to 24, wherein emulsion polymerization is performed using a phosphate salt or a sulfate salt as an emulsifier in the emulsion polymerization step.

26. The method according to any one of claims 20 to 25, wherein the polymerization solution produced in the emulsion polymerization step is coagulated and dried by using an alkali metal salt or a group 2 metal salt of the periodic table as a coagulant.

27. The method according to any one of claims 20 to 26, wherein the polymerization liquid produced in the emulsion polymerization step is solidified by contacting with a solidifying agent, and then melt-kneaded and dried.

28. The method for producing an acrylic rubber according to claim 27, wherein the melt kneading and drying are performed in a state substantially containing no moisture.

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

30. The method according to any one of claims 27 to 29, wherein the acrylic rubber after melt-kneading and drying is cooled at a cooling rate of 40 ℃/hr or more.

31. The method according to any one of claims 20 to 30, wherein the aqueous pellets having a particle diameter in the range of 710 μm to 6.7mm are washed, dehydrated and dried at a ratio of 50 wt% or more.

32. A rubber composition comprising a rubber component comprising the acrylic rubber according to any one of claims 1 to 19, a filler and a crosslinking agent.

33. The rubber composition according to claim 32, wherein the filler is a reinforcing filler.

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

35. The rubber composition according to claim 32, wherein the filler is a silica type.

36. The rubber composition according to any one of claims 32 to 35, wherein the crosslinking agent is an organic crosslinking agent.

37. The rubber composition according to any one of claims 32 to 36, wherein the crosslinking agent is a multi-component compound.

38. The rubber composition according to any one of claims 32 to 37, wherein the crosslinking agent is an ion-crosslinkable compound.

39. The rubber composition according to claim 38, wherein the crosslinking agent is an ion-crosslinkable organic compound.

40. The rubber composition of claim 38 or 39, wherein the cross-linking agent is a polyionic organic compound.

41. The rubber composition according to any one of claims 38 to 40, 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.

42. The rubber composition according to claim 40, 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.

43. The rubber composition according to any one of claims 32 to 42, 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.

44. The rubber composition of any of claims 32 to 43, wherein the rubber composition further comprises an anti-aging agent.

45. The rubber composition according to claim 44, wherein the antioxidant is an amine-based antioxidant.

46. A process for producing a rubber composition, comprising mixing the rubber component comprising the acrylic rubber according to any one of claims 1 to 19, a filler and an anti-aging agent, if necessary, and then mixing the mixture with a crosslinking agent.

47. A rubber crosslinked product obtained by crosslinking the rubber composition according to any one of claims 32 to 45.

48. A rubber crosslinked according to claim 47 wherein the crosslinking of the rubber composition is performed after molding.

49. The rubber crosslinked according to claim 47 or 48 wherein the crosslinking of the rubber composition is a crosslinking that performs primary crosslinking and secondary crosslinking.