JP7459668B2 - Acrylic rubber sheet with excellent storage stability and processability - Google Patents

Description

The present invention relates to an acrylic rubber sheet having excellent storage stability and processability and a method for producing the same, an acrylic rubber veil formed by laminating the acrylic rubber sheet, a rubber mixture formed by mixing the acrylic rubber sheet or the acrylic rubber veil and a method for producing the same, and a cross-linked rubber product formed by cross-linking the same.

Acrylic rubber is a polymer whose main component is acrylic ester, and is generally known as a rubber with excellent heat resistance, oil resistance, and ozone resistance. It is widely used in fields such as automobiles, and is used with the addition of antioxidants as needed.

For example, in Patent Document 1 (International Publication No. WO 2018/139466), a monomer component containing ethyl acrylate, n-butyl acrylate, monobutyl fumarate, etc. is stirred with pure water, sodium lauryl sulfate, and polyoxyethylene dodecyl ether to obtain a monomer emulsion, and an aqueous solution of ferrous sulfate, sodium ascorbate, and potassium persulfate is continuously dropped over a period of 3 hours to obtain an emulsion polymerization liquid in which the polymerization conversion rate reaches 95%, and a 50% by weight aqueous dispersion of 3-(3,5-tert-butyl-4-hydroxyphenyl)stearyl propionate (50 parts of an aqueous solution of 0.2% by weight sodium lauryl sulfate and 50 parts of (3,5-di-tert-butyl-4-hydroxyphenyl)stearyl propionate is added. The method for producing crumb-like acrylic rubber, which can suppress contamination of the polymerization apparatus during polymerization and has excellent initial mechanical strength, is disclosed, in which a 50% by weight aqueous dispersion of 2,4-bis[(octylthio)methyl]-6-methylphenol (prepared by adding and mixing 50 parts by weight of 2,4-bis[(octylthio)methyl]-6-methylphenol to 50 parts by weight of an aqueous solution of 0.2% by weight sodium lauryl sulfate) is added, the temperature is raised to 85°C, and the mixture is coagulated with sodium sulfate to produce hydrous crumbs. The hydrous crumbs are then washed four times with industrial water, once with an acid of pH 3, and once with pure water, and then dried in a hot air dryer at 160°C for 10 minutes. It is also disclosed that this method allows the hydrous crumbs washed with a screw-type Oshida dryer to be dried at 150°C or higher. However, in addition to heat resistance, processability and storage stability under severe environments are also required.

Regarding the gel content of acrylic rubber, for example, Patent Document 2 (JP Patent No. 3599962) discloses an acrylic rubber composition having a gel fraction of 5% or less by weight, obtained by copolymerizing 95-99.9% by weight of alkyl acrylate or alkoxyalkyl acrylate with 0.1-5% by weight of a polymerizable monomer having two or more radically reactive unsaturated groups with different reactivity in the presence of a radical polymerization initiator, a reinforcing filler, and an organic peroxide-based vulcanizing agent, and excellent extrusion processability such as extrusion speed, die swell, and surface texture. The acrylic rubber used here, which has a very small gel fraction, is obtained by adjusting the polymerization liquid to pH 6-8 with sodium bicarbonate or the like, compared to acrylic rubber with a high acetone-insoluble gel fraction (60%) obtained in a polymerization liquid in the normal acidic range (pH 4 before polymerization, pH 3.4 after polymerization). Specifically, water, emulsifiers sodium lauryl sulfate and polyoxyethylene nonylphenyl ether, sodium carbonate, and boric acid are added and adjusted to 75°C, then t-butyl hydroperoxide, Rongalite, disodium ethylenediaminetetraacetate, and ferrous sulfate are added (pH at this time is 7.1), and then the monomer components of ethyl acrylate and allyl methacrylate are added dropwise to carry out emulsion polymerization, and the resulting emulsion (pH 7) is salted out using an aqueous sodium sulfate solution, washed with water, and dried to obtain acrylic rubber. However, acrylic rubbers that are mainly composed of (meth)acrylic acid esters have problems with handling, such as decomposing in the neutral to alkaline range and having poor storage stability, and acrylic rubbers that are emulsion polymerized at a pH from neutral to alkaline have problems with poor mechanical strength due to the loss of reactive groups (crosslinking points) such as carboxyl groups, epoxy groups, and chlorine atoms.

In addition, Patent Document 3 (International Publication WO 2018/143101) discloses a technology for improving the extrusion moldability, particularly the discharge amount, discharge length, and surface texture, of a rubber composition containing a reinforcing agent and a crosslinking agent, by emulsion polymerization of a (meth)acrylic acid ester and an ion-crosslinking monomer, using an acrylic rubber having a complex viscosity at 100°C ([η]100°C) of 3500 Pa·s or less and a ratio ([η]100°C/[η]60°C) of the complex viscosity at 60°C ([η]60°C) to the complex viscosity at 100°C ([η]100°C) of 0.8 or less. The technology discloses that the gel content of the tetrahydrofuran-insoluble portion of the acrylic rubber used in the technology is 80% by weight or less, preferably 5 to 80% by weight, and preferably exists as much as possible within the range of 70% or less, and that the extrusion property deteriorates when the gel content is less than 5%. It is also stated that the weight average molecular weight (Mw) of the acrylic rubber used is 200,000 to 1,000,000, and that if the weight average molecular weight (Mw) exceeds 1,000,000, the viscoelasticity of the acrylic rubber becomes too high, which is undesirable. However, there has been a demand for a product that has a high balance between high strength and processability during kneading such as Banbury mixing, and there has also been a demand for improved storage stability.

International Publication No. 2018/139466 pamphlet Patent No. 3599962 International Publication No. 2018/143101 pamphlet

The present invention was made in view of the above circumstances, and provides an acrylic rubber sheet with excellent storage stability and processability, a method for manufacturing the same, an acrylic rubber veil formed by laminating the acrylic rubber sheets, and an acrylic rubber sheet. Another object of the present invention is to provide a rubber mixture containing an acrylic rubber veil, a method for producing the same, and a crosslinked rubber product thereof.

As a result of intensive research conducted in consideration of the above problems, the inventors have found that an acrylic rubber sheet that contains an antioxidant with a specific structure that has a reactive group and that has a specific gel amount of a specific solvent-insoluble portion and a specific pH has excellent storage stability and processability. They have also found that the effects of the present invention can be further enhanced by specifying the type of sheet, the preferred specific antioxidant, and the complex viscosity and specific gravity at a specific temperature.

The present inventors also found that it is very important to uniformly disperse an anti-aging agent with a specific structure in an emulsion polymerization solution obtained by emulsion polymerization of a monomer component containing a (meth)acrylic acid ester and a reactive group-containing monomer. Although it has been difficult to improve the storage stability of acrylic rubber, it has been possible to dry the hydrated crumb at a specific temperature to a state that contains virtually no moisture (specific moisture content) using a specific screw extruder. We have also discovered that an acrylic rubber sheet with highly excellent storage stability and processability can be produced by melt-kneading a specific anti-aging agent and acrylic rubber and extruding it into a sheet.

The present inventors also discovered that when the polymerization conversion rate of emulsion polymerization is increased in order to improve the strength characteristics of acrylic rubber, the gel amount of specific solvent-insoluble components rapidly increases, which deteriorates the processability of acrylic rubber. After washing, the water-containing crumb is dried using a specific screw extruder to a state that contains virtually no water (specific water content), and then the dry rubber is melt-kneaded and extruded into a sheet, resulting in a rapid increase in emulsion polymerization. It has been found that the amount of gel insoluble in a specific solvent disappears, making it possible to produce an acrylic rubber sheet with excellent processability.

The present inventors have also discovered that by preparing an antioxidant-containing emulsion from water and an emulsifier for the specific antioxidant to be added to the emulsion polymerization liquid and by specifying the conditions for the antioxidant-containing emulsion, it is possible to further improve the storage stability and processability of the resulting acrylic rubber sheet.
The present inventors further discovered that the amount of gel (solvent-insoluble matter) in the acrylic rubber sheet varies greatly depending on the solvent used; for example, there is no correlation between the amount of gel of the tetrahydrofuran-insoluble matter and the amount of gel of the methyl ethyl ketone-insoluble matter, and that the effect of each insoluble matter on the acrylic rubber sheet also differs.

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

Thus, according to the present invention , there is provided an acrylic rubber sheet which comprises an acrylic rubber having a monomer composition comprising 70 to 99.9% by weight of bonding units derived from at least one (meth)acrylic ester selected from the group consisting of (meth)acrylic acid alkyl esters and (meth)acrylic acid alkoxyalkyl esters, 0.1 to 20% by weight of bonding units derived from reactive group-containing monomers, and 0 to 30% by weight of bonding units derived from other monomers, which contains 0.001 to 15% by weight of a hindered antiaging agent having a melting point of 90°C or less , has a gel amount of 10 % by weight or less of methyl ethyl ketone insoluble components , and has a pH of 2 to 6 .

In the acrylic rubber sheet of the present invention, the amount of acrylic rubber in the acrylic rubber sheet is preferably 85% by weight or more.

In the acrylic rubber sheet of the present invention, it is preferable that the ash content is 1% by weight or less.

In the acrylic rubber sheet of the present invention, the ash contains at least one element selected from the group consisting of sodium, sulfur, calcium, magnesium, and phosphorus , and the total content of these elements is 70% by weight or more of the total ash content. It is preferable.

In the acrylic rubber sheet of the present invention, it is preferable that the acrylic rubber sheet is a melt-kneaded sheet.

In the acrylic rubber sheet of the present invention, the hindered anti-aging agent is preferably a hindered phenol-based anti-aging agent.

In the acrylic rubber sheet of the present invention, the complex viscosity at 100°C ([η]100°C) is preferably in the range of 1500 to 6000 Pa·s.

In the acrylic rubber sheet of the present invention, it is preferable that the ratio ([η]100°C/[η]60°C) of the complex viscosity at 100°C ([η]100°C) to the complex viscosity at 60°C ([η]60°C) is 0.5 or more.

In the acrylic rubber sheet of the present invention, it is preferable that the ratio ([η]100°C/[η]60°C) of the complex viscosity at 100°C ([η]100°C) to the complex viscosity at 60°C ([η]60°C) is 0.8 or more.

In the acrylic rubber sheet of the present invention, the weight average molecular weight (Mw) is 100,000 to 5,000,000, and the ratio of z average molecular weight (Mz) to weight average molecular weight (Mw) (Mz/Mw) is 1. .3 or more is preferable.

In the acrylic rubber sheet of the present invention, the specific gravity is preferably 0.7 or more.

Further, according to the present invention, as a method suitable for manufacturing the above-mentioned acrylic rubber sheet,
At least one (meth)acrylic acid ester selected from the group consisting of (meth)acrylic acid alkyl ester and (meth)acrylic acid alkoxyalkyl ester 70 to 99.9% by weight, reactive group-containing monomer 0.1 an emulsion polymerization step in which a monomer component consisting of ~20% by weight and 0 to 30% by weight of other monomers is emulsified with water and an emulsifier and emulsion polymerized in the presence of a polymerization initiator to obtain an emulsion polymerization solution;
an antiaging agent addition step of adding a hindered antiaging agent with a melting point of 90° C. or less to the obtained emulsion polymerization liquid at a ratio of 0.001 to 15 parts by weight per 100 parts by weight of the monomer components ;
A coagulation step of adding the emulsion polymerization liquid to which the anti-aging agent has been added to the coagulation liquid being stirred to produce a water-containing crumb;
a cleaning step of cleaning the generated water-containing crumb;
The washed 40°C or higher water-containing crumb is melt-kneaded in a screw-type extruder equipped with a dehydration barrel having a dehydration slit, a drying barrel for drying under reduced pressure, and a die at the tip, and the water content is less than 1% by weight. Dehydration, drying, and molding process to extrude it as a sheet-like dry rubber,
A method of manufacturing an acrylic rubber sheet is provided.

In the method for producing an acrylic rubber sheet of the present invention , it is preferable that the hindered anti-aging agent is added to the emulsion polymerization solution as a hindered anti-aging agent-containing emulsion that is emulsified with warm water and an emulsifier.

In the method for producing an acrylic rubber sheet of the present invention, the emulsifier concentration of the hindered anti-aging agent-containing emulsion is preferably 1% by weight or more.

Thus, the present invention also provides an acrylic rubber veil formed by laminating the above-mentioned acrylic rubber sheets.

The present invention also provides a rubber mixture obtained by mixing the acrylic rubber sheet or acrylic rubber veil with a filler and a crosslinking agent.

According to the present invention, there is also provided a method for producing a rubber mixture, characterized in that a filler and a crosslinking agent are mixed into the acrylic rubber sheet or acrylic rubber veil using a mixer.

The present invention also provides a method for producing a rubber mixture in which the acrylic rubber sheet or acrylic rubber veil is mixed with a filler and then a crosslinking agent is mixed.

The present invention further provides a cross-linked rubber product obtained by cross-linking the above rubber mixture.

According to the present invention, an acrylic rubber sheet with excellent storage stability and processability, a method for producing the same, an acrylic rubber veil formed by laminating the acrylic rubber sheets, and a rubber mixture formed by mixing the acrylic rubber sheet or the acrylic rubber veil. A method for producing the same, and a crosslinked rubber product obtained by crosslinking the same are provided.

FIG. 1 is a diagram illustrating an example of an acrylic rubber production system used for producing an acrylic rubber sheet according to an embodiment of the present invention. FIG. 2 is a diagram showing the configuration of the screw-type extruder of FIG. 1. FIG. 2 is a diagram showing the configuration of a transport type cooling device used as the cooling device of FIG. 1. FIG.

Hereinafter, specific embodiments of the acrylic rubber sheet of the present invention and its manufacturing method will be described in detail. However, the present invention is not limited in the least by these embodiments.

<Monomer component>
The acrylic rubber sheet of the present invention is made of acrylic rubber having reactive groups. The reactive group is not particularly limited and is appropriately selected depending on the purpose of use, but preferably at least one functional group selected from the group consisting of a carboxyl group, an epoxy group, and a halogen group, more preferably a carboxyl group. The functional group is at least one functional group selected from the group consisting of epoxy groups, epoxy groups, and chlorine atoms, particularly preferably ion-reactive groups such as carboxyl groups and epoxy groups, and most preferably carboxyl groups. As for the acrylic rubber having such a reactive group, a reactive group may be introduced into the acrylic rubber by a post-reaction, but it is preferably one obtained by copolymerizing a reactive group-containing monomer.

The acrylic rubber constituting the acrylic rubber sheet of the present invention preferably contains (meth)acrylic ester, and is selected from the group consisting of (meth)acrylic acid alkyl ester and (meth)acrylic acid alkoxyalkyl ester. It is preferable that it contains at least one type of (meth)acrylic acid ester. In the present invention, "(meth)acrylic acid ester" is used as a general term for esters of acrylic acid and/or methacrylic acid.

Specific examples of preferred acrylic rubbers having reactive groups include those that are composed of at least one (meth)acrylic ester selected from the group consisting of (meth)acrylic acid alkyl esters and (meth)acrylic acid alkoxyalkyl esters, a reactive group-containing monomer, and other copolymerizable monomers as necessary.

There are no particular limitations on the (meth)acrylic acid alkyl ester, but it is usually a (meth)acrylic acid alkyl ester having an alkyl group with 1 to 12 carbon atoms, preferably a (meth)acrylic acid alkyl ester having an alkyl group with 1 to 8 carbon atoms, and more preferably a (meth)acrylic acid alkyl ester having an alkyl group with 2 to 6 carbon atoms.

Specific examples of (meth)acrylic acid alkyl esters 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, and cyclohexyl (meth)acrylate, with ethyl (meth)acrylate and n-butyl (meth)acrylate being preferred, and ethyl acrylate and n-butyl acrylate being more preferred.

The (meth)acrylic acid alkoxyalkyl ester is not particularly limited, but is usually an (meth)acrylic acid alkoxyalkyl ester having an alkoxyalkyl group of 2 to 12, preferably an (meth)acrylic acid alkoxyalkyl ester having an alkoxyalkyl group of 2 to 8, and more preferably an (meth)acrylic acid alkoxyalkyl ester having an alkoxyalkyl group of 2 to 6 carbon atoms.

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

At least one (meth)acrylic acid ester selected from the group consisting of these (meth)acrylic acid alkyl esters and (meth)acrylic acid alkoxyalkyl esters is used alone or in combination of two or more, and the proportion in the acrylic rubber is usually 50% by weight or more, preferably 70% by weight or more, more preferably 80% by weight or more, and most preferably 90% by weight or more. If the amount of (meth)acrylic acid ester in the monomer component is excessively small, the weather resistance, heat resistance, and oil resistance of the resulting acrylic rubber may decrease, which is not preferable. At least one (meth)acrylic acid ester selected from the group consisting of (meth)acrylic acid alkyl esters and (meth)acrylic acid alkoxyalkyl esters is used alone or in combination of two or more, and when the proportion in the acrylic rubber is usually in the range of 50 to 99.99% by weight, preferably 70 to 99.9% by weight, more preferably 80 to 99.5% by weight, and most preferably 87 to 99% by weight, the weather resistance, heat resistance, and oil resistance of the acrylic rubber sheet are highly balanced and suitable.

The reactive group-containing monomer is not particularly limited and is appropriately selected depending on the purpose of use, but monomers having at least one functional group selected from the group consisting of carboxyl group, epoxy group, and halogen group. A monomer having at least one functional group selected from the group consisting of a carboxyl group, an epoxy group, and a chlorine atom is more preferable, and a monomer having an ion-reactive group such as a carboxyl group or an epoxy group is preferable. Particularly preferred are monomers having a carboxyl group, most preferred.

There are no particular limitations on the monomer having a carboxyl group, but ethylenically unsaturated carboxylic acids can be suitably used. Examples of ethylenically unsaturated carboxylic acids include ethylenically unsaturated monocarboxylic acids, ethylenically unsaturated dicarboxylic acids, and ethylenically unsaturated dicarboxylic acid monoesters. Among these, ethylenically unsaturated dicarboxylic acid monoesters are particularly preferred because they can further improve the compression set resistance properties when the acrylic rubber is made into a rubber cross-linked product.

There are no particular limitations on the ethylenically unsaturated monocarboxylic acid, but ethylenically unsaturated monocarboxylic acids having 3 to 12 carbon atoms are preferred, such as acrylic acid, methacrylic acid, α-ethylacrylic acid, crotonic acid, and cinnamic acid.

There are no particular limitations on the ethylenically unsaturated dicarboxylic acid, but ethylenically unsaturated dicarboxylic acids having 4 to 12 carbon atoms are preferred, such as butenedioic acids such as fumaric acid and maleic acid, itaconic acid, and citraconic acid. Ethylenically unsaturated dicarboxylic acids also include those that exist as anhydrides.

The ethylenically unsaturated dicarboxylic acid monoester is not particularly limited, but it is usually an ethylenically unsaturated dicarboxylic acid having 4 to 12 carbon atoms and an alkyl monoester having 1 to 12 carbon atoms, preferably 4 to 6 carbon atoms. An ethylenically unsaturated dicarboxylic acid and an alkyl monoester having 2 to 8 carbon atoms, more preferably an alkyl monoester having 2 to 6 carbon atoms of butenedioic acid having 4 carbon atoms.

Specific examples of ethylenically unsaturated dicarboxylic acid monoesters include monomethyl fumarate, monoethyl fumarate, mono-n-butyl fumarate, monomethyl maleate, monoethyl maleate, mono-n-butyl maleate, monocyclopentyl fumarate, and fumarate. Butenedionic acid monoalkyl esters such as monocyclohexyl acid, monocyclohexenyl fumarate, monocyclopentyl maleate, monocyclohexyl maleate; itaconic acid such as monomethyl itaconate, monoethyl itaconate, mono n-butyl itaconate, monocyclohexyl itaconate Among these, mono-n-butyl fumarate and mono-n-butyl maleate are preferred, and mono-n-butyl fumarate is particularly preferred.

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

Examples of monomers having a halogen group include unsaturated alcohol esters of halogen-containing saturated carboxylic acids, (meth)acrylic acid haloalkyl esters, (meth)acrylic acid haloacyloxyalkyl esters, (meth)acrylic acid (haloacetylcarbamoyloxy)alkyl esters, halogen-containing unsaturated ethers, halogen-containing unsaturated ketones, halomethyl group-containing aromatic vinyl compounds, halogen-containing unsaturated amides, and haloacetyl group-containing unsaturated monomers.

Examples of unsaturated alcohol esters of halogen-containing saturated carboxylic acids include vinyl chloroacetate, vinyl 2-chloropropionate, and allyl chloroacetate. Examples of (meth)acrylic acid haloalkyl esters include chloromethyl (meth)acrylate, 1-chloroethyl (meth)acrylate, 2-chloroethyl (meth)acrylate, 1,2-dichloroethyl (meth)acrylate, 2-chloropropyl (meth)acrylate, 3-chloropropyl (meth)acrylate, and 2,3-dichloropropyl (meth)acrylate. Examples of (meth)acrylic acid haloacyloxyalkyl esters include 2-(chloroacetoxy)ethyl (meth)acrylate, 2-(chloroacetoxy)propyl (meth)acrylate, 3-(chloroacetoxy)propyl (meth)acrylate, and 3-(hydroxychloroacetoxy)propyl (meth)acrylate. Examples of (meth)acrylic acid (haloacetylcarbamoyloxy) alkyl esters include 2-(chloroacetylcarbamoyloxy) ethyl (meth)acrylic acid and 3-(chloroacetylcarbamoyloxy) propyl (meth)acrylic acid. Examples of halogen-containing unsaturated ethers include chloromethyl vinyl ether, 2-chloroethyl vinyl ether, 3-chloropropyl vinyl ether, 2-chloroethyl allyl ether, and 3-chloropropyl allyl ether. Examples of halogen-containing unsaturated ketones include 2-chloroethyl vinyl ketone, 3-chloropropyl vinyl ketone, and 2-chloroethyl allyl ketone. Examples of halomethyl group-containing aromatic vinyl compounds include p-chloromethylstyrene, m-chloromethylstyrene, o-chloromethylstyrene, and p-chloromethyl-α-methylstyrene. Examples of halogen-containing unsaturated amides include N-chloromethyl(meth)acrylamide. Examples of haloacetyl group-containing unsaturated monomers include 3-(hydroxychloroacetoxy) propyl allyl ether and p-vinylbenzyl chloroacetate.

These reactive group-containing monomers may be used alone or in combination of two or more, and their proportion in the acrylic rubber is usually 0.01 to 20% by weight, preferably 0.1 to 10% by weight, more preferably 0.5 to 5% by weight, and most preferably 1 to 3% by weight.

Other monomers that may be used as necessary are not particularly limited as long as they can be copolymerized with the above monomers, such as aromatic vinyl, ethylenically unsaturated nitriles, acrylamide monomers, and others. Examples include olefinic monomers. Examples of the aromatic vinyl include styrene, α-methylstyrene, and divinylbenzene. Examples of ethylenically unsaturated nitriles include acrylonitrile and methacrylonitrile. Examples of the acrylamide monomer include acrylamide and methacrylamide. Examples of other olefinic monomers include ethylene, propylene, vinyl acetate, ethyl vinyl ether, butyl vinyl ether, and the like.

These other monomers are used alone or in combination of two or more, and their proportion in the acrylic rubber is usually 0 to 30% by weight, preferably 0 to 20% by weight, more preferably 0. -15% by weight, most preferably 0-10% by weight.

<Acrylic rubber>
The acrylic rubber constituting the acrylic rubber sheet of the present invention is characterized by having reactive groups. The content of the reactive groups may be appropriately selected depending on the purpose of use, but when the weight ratio of the reactive groups themselves is usually in the range of 0.001 to 5 wt%, preferably 0.01 to 3 wt%, more preferably 0.05 to 1 wt%, and particularly preferably 0.1 to 0.5 wt%, it is suitable because properties such as processability, strength properties, compression set resistance, oil resistance, cold resistance, and water resistance are highly balanced.

Specific examples of the acrylic rubber constituting the acrylic rubber sheet of the present invention include at least one (meth)acrylic ester selected from the group consisting of (meth)acrylic acid alkyl ester and (meth)acrylic acid alkoxyalkyl ester; Consisting of a reactive group-containing monomer and other copolymerizable monomers as necessary, the proportions of each in the acrylic rubber are (meth)acrylic acid alkyl ester and (meth)acrylic acid alkoxyalkyl ester. At least one (meth)acrylic acid ester selected from the group consisting of usually 50 to 99.99% by weight, preferably 70 to 99.9% by weight, more preferably 80 to 99.5% by weight, particularly preferably is in the range of 87 to 99% by weight, and the reactive group-containing monomer is usually 0.01 to 20% by weight, preferably 0.1 to 10% by weight, more preferably 0.5 to 5% by weight, The amount of other monomers is particularly preferably in the range of 1 to 3% by weight, usually 0 to 30% by weight, preferably 0 to 20% by weight, more preferably 0 to 15% by weight, particularly preferably 0 to 10% by weight. % by weight. By setting the proportion of these monomers constituting the acrylic rubber within this range, the objects of the present invention can be achieved to a high degree, and when the acrylic rubber sheet is made into a crosslinked product, water resistance and compression set resistance properties can be significantly improved. Improved and suitable.

The weight average molecular weight (Mw) of the acrylic rubber constituting the acrylic rubber sheet of the present invention is not particularly limited, but is an absolute molecular weight measured by GPC-MALS, usually 100,000 to 5,000,000, preferably is in the range of 500,000 to 4,000,000, more preferably 700,000 to 3,000,000, most preferably 1,000,000 to 2,500,000 when mixing the acrylic rubber sheet. The workability, strength properties, and compression set resistance properties are highly balanced and suitable.

The ratio of the z-average molecular weight (Mz) to the weight-average molecular weight (Mw) (Mz/Mw) of the acrylic rubber constituting the acrylic rubber sheet of the present invention is not particularly limited, but The processability and strength properties of the acrylic rubber sheet are high when the absolute molecular weight distribution is usually 1.3 or more, preferably 1.4 to 5, and more preferably 1.5 to 2, with an emphasis on the molecular region. It is suitable because it is well-balanced and changes in physical properties during storage can be alleviated.

The glass transition temperature (Tg) of the acrylic rubber constituting the acrylic rubber sheet of the present invention is not particularly limited, but is usually 20°C or lower, preferably 10°C or lower, and more preferably 0°C or lower. The lower limit of the glass transition temperature (Tg) of acrylic rubber is not particularly limited, but is usually -80°C or higher, preferably -60°C or higher, and more preferably -40°C or higher. By setting the glass transition temperature at or above the above-mentioned lower limit, it is possible to obtain better oil resistance and heat resistance, and by setting the glass transition temperature at or below the above-mentioned upper limit, it is possible to obtain more excellent cold resistance and processability.

The content of acrylic rubber in the acrylic rubber sheet of the present invention is appropriately selected depending on the purpose of use, but is usually 85% by weight or more, preferably 90% by weight or more, more preferably 95% by weight or more, particularly preferably It is at least 97% by weight, most preferably at least 98% by weight.

<Anti-aging agent>
The acrylic rubber sheet of the present invention is characterized by containing a hindered antioxidant.

The hindered antioxidant used is not particularly limited as long as it is one that is normally used as an antioxidant for rubber having a hindered structure, but it is preferable that it is a hindered phenol-based antioxidant, since it can achieve high storage stability and heat resistance effects. The hindered structure is a structure having bulky substituents on both sides of a functional group that can exert the anti-aging function of the antioxidant. The bulky substituent is usually a substituent with 3 or more carbon atoms, preferably 4 carbon atoms, and specific examples include t-butyl groups and isobutyl groups, with t-butyl groups being preferred.

There are no particular limitations on the melting point of the hindered antioxidant, but it is usually preferred that it be 150°C or lower, preferably 100°C or lower, more preferably 90°C or lower, particularly preferably 80°C or lower, and most preferably 70°C or lower, since this provides excellent uniform fine dispersion with the acrylic rubber during melt kneading and can highly improve the storage stability and heat resistance of the acrylic rubber sheet.

The molecular weight of the hindered anti-aging agent is not particularly limited, but when it is usually 250 to 1000, preferably 300 to 800, more preferably 350 to 600, it has excellent uniform fine dispersibility with acrylic rubber. This is suitable because it can highly improve the heat resistance and storage stability of the sheet.

Suitable hindered phenol-based antioxidants include, for example, 2,6-di-t-butylphenol, 2,6-di-t-butyl-4-methylphenol, 2,6-di-t-butyl-α-dimethylamino-p-cresol, 3-(4-hydroxy-3,5-di-t-butylphenyl)butyl propionate, 3-(4-hydroxy-3,5-di-t-butylphenyl)hexyl propionate, 3-(4-hydroxy-3,5-di-t-butylphenyl)octyl propionate, 3-(4-hydroxy-3,5-di-t-butylphenyl)propionate, decyl 3-(4-hydroxy-3,5-di-t-butylphenyl)propionate, dodecyl 3-(4-hydroxy-3,5-di-t-butylphenyl)propionate, octadecyl 3-(4-hydroxy-3,5-di-t-butylphenyl)propionate, heptyl 3-(4-hydroxy-3,5-diisopropylphenyl)propionate, octyl 3-(4-hydroxy-3,5-diisopropylphenyl)propionate, dodecyl 3-(4-hydroxy-3,5-diisopropylphenyl)propionate, octadecyl 3-(4-hydroxy-3,5-diisopropylphenyl)propionate, 4,4'- Examples of the phenol include methylenebis(2,6-di-t-butylphenol), 2,6-di-t-butyl-4-(4,6-bis(octylthio)-1,3,5-triazin-2-ylamino)phenol, and the like. Preferred are 3-(4-hydroxy-3,5-di-t-butylphenyl)butyl propionate, 3-(4-hydroxy-3,5-di-t-butylphenyl)hexyl propionate, 3-(4-hydroxy-3,5-di-t-butylphenyl)octyl propionate, and 3-(4-hydroxy-3,5-di-t-butylphenyl)decyl propionate. 3-(4-hydroxy-3,5-di-t-butylphenyl) dodecyl propionate, 3-(4-hydroxy-3,5-di-t-butylphenyl) octadecyl propionate, more preferably 3-(4-hydroxy-3,5-di-t-butylphenyl) octyl propionate, 3-(4-hydroxy-3,5-di-t-butylphenyl) decyl propionate, 3-(4-hydroxy-3,5-di-t-butylphenyl) dodecyl propionate, 3-(4-hydroxy-3,5-di-t-butylphenyl) octadecyl propionate.

These hindered anti-aging agents can be used alone or in combination of two or more. The content of the hindered anti-aging agent in the acrylic rubber sheet is not particularly limited, but is usually 0.001 to 15% by weight, preferably 0.01 to 10% by weight, more preferably 0.1 to 5% by weight. , particularly preferably in the range from 0.3 to 3% by weight, most preferably from 0.5 to 2% by weight.

The acrylic rubber sheet of the present invention may contain anti-aging agents other than the hindered anti-aging agent within a range that does not impair the object of the present invention.

<Acrylic rubber sheet>
The acrylic rubber sheet of the present invention is characterized in that it is made of the above-mentioned acrylic rubber, contains the above-mentioned antioxidant, and has a specific gel amount and pH.

The thickness of the acrylic rubber sheet of the present invention is not particularly limited, but it is generally 1 to 40 mm, preferably 2 to 35 mm, more preferably 3 to 30 mm, and most preferably 5 to 25 mm for workability. , storage stability and productivity are highly balanced and suitable. In particular, when producing an acrylic rubber sheet that is inexpensive and greatly improves productivity, the thickness is usually in the range of 1 to 30 mm, preferably 2 to 25 mm, more preferably 3 to 15 mm, particularly preferably 4 to 12 mm.

The width of the acrylic rubber sheet of the present invention is appropriately selected depending on the intended use, but is usually in the range of 300 to 1200 mm, preferably 400 to 1000 mm, and more preferably 500 to 800 mm, which is particularly suitable for ease of handling.

The length of the acrylic rubber sheet of the present invention is not particularly limited, but a range of usually 300 to 1200 mm, preferably 400 to 1000 mm, and more preferably 500 to 800 mm is particularly suitable for excellent handling properties. be.

The amount of gel in the acrylic rubber sheet of the present invention is 50% by weight or less, preferably 30% by weight or less, more preferably 20% by weight or less, particularly preferably 10% by weight or less, most preferably 5% by weight or less, based on the insoluble content of methyl ethyl ketone. When it is less than % by weight, processability is highly improved and it is preferable. The amount of gel, which is the insoluble content of methyl ethyl ketone in the acrylic rubber veil, is related to the processability during kneading with Banbury, etc., but the characteristics of the amount of gel vary depending on the solvent used, especially when THF (tetrahydrofuran) is insoluble. There was no correlation with the amount of gel.

The storage stability of the acrylic rubber sheet of the present invention is highly improved when the pH is in the range of 6 or less, preferably in the range of 2 to 6, more preferably in the range of 2.5 to 5.5, particularly preferably in the range of 3 to 5. suitable.

The ash content of the acrylic rubber sheet of the present invention is not particularly limited, but is usually 1% by weight or less, preferably 0.5% by weight or less, more preferably 0.3% by weight or less, particularly preferably 0.2% by weight or less, and most preferably 0.15% by weight or less, which is suitable for excellent storage stability and water resistance.

The lower limit of the ash content of the acrylic rubber sheet of the present invention is not particularly limited, but is usually 0.0001% by weight or more, preferably 0.0005% by weight or more, more preferably 0.001% by weight or more, Particularly preferably, the amount is 0.005% by weight or more, and most preferably 0.01% by weight or more, since metal adhesion is suppressed and workability is excellent.

The content (total amount) of at least one element selected from the group consisting of sodium, sulfur, calcium, magnesium and phosphorus in the ash of the acrylic rubber sheet of the present invention is not particularly limited, but when the content is at least 30% by weight, preferably 50% by weight or more, more preferably 70% by weight or more, and particularly preferably 80% by weight or more, relative to the total ash content, the storage stability and water resistance are highly excellent and suitable.

The total amount of sodium and sulfur in the ash of the acrylic rubber sheet of the present invention is not particularly limited, but when the total amount of sodium and sulfur is 30% by weight or more, preferably 50% by weight or more, more preferably 70% by weight or more, and particularly preferably 80% by weight or more, the storage stability and water resistance are highly excellent and suitable.

The ratio of sodium to sulfur ([Na]/[S]) in the ash of the acrylic rubber sheet of the present invention is usually 0.4 to 2.5, preferably 0, although there is no particular limitation in terms of weight ratio. A range of 0.6 to 2, preferably 0.8 to 1.7, more preferably 1 to 1.5 is preferable because the water resistance is highly excellent.

The total amount of magnesium and phosphorus in the ash of the acrylic rubber sheet of the present invention is not particularly limited, but when the total amount of ash is usually 30% by weight or more, preferably 50% by weight or more, more preferably 70% by weight or more, and particularly preferably 80% by weight or more, the storage stability and water resistance are highly excellent and suitable.

The ratio of magnesium to phosphorus ([Mg]/[P]) in the ash of the acrylic rubber sheet of the present invention is a weight ratio, and there is no particular limitation, but it is usually 0.4 to 2.5, preferably 0. Storage stability and water resistance are within the range of .4 to 1.3, more preferably 0.4 to 1, particularly preferably 0.45 to 0.75, and most preferably 0.5 to 0.7. Highly excellent and suitable.

The specific gravity of the acrylic rubber sheet of the present invention is not particularly limited, but is usually 0.7 or more, preferably 0.8 to 1.4, more preferably 0.9 to 1.3, particularly preferably 0.95 to 1.25, and most preferably 1.0 to 1.2, and is therefore highly suitable for excellent storage stability.

The complex viscosity ([η]60°C) of the acrylic rubber sheet of the present invention at 60°C is not particularly limited, but is usually 15,000 Pa·s or less, preferably 2000 to 10,000 Pa·s, or more. Preferably, the range is from 2,500 to 7,000 Pa·s, and most preferably from 2,700 to 5,500 Pa·s, which is suitable for excellent workability, oil resistance, and shape retention.

The complex viscosity ([η] 100°C) of the acrylic rubber sheet of the present invention at 100°C is not particularly limited, but is usually 1500 to 6000 Pa·s, preferably 2000 to 5000 Pa·s, more preferably 2500 Pa·s. -4,000 Pa·s, most preferably 2,500 to 3,500 Pa·s, which is suitable for excellent workability, oil resistance, and shape retention.

The ratio of the complex viscosity at 100°C ([η] 100°C) to the complex viscosity at 60°C ([η] 60°C) of the acrylic rubber sheet of the present invention ([η] 100°C/[η] 60°C) Although not particularly limited, is usually 0.5 or more, preferably 0.6 or more, more preferably 0.7 or more, particularly preferably 0.8 or more, and most preferably 0.83 or more. Further, the ratio of the complex viscosity at 100°C ([η]100°C) to the complex viscosity at 60°C ([η]60°C) ([η]100°C/[η]60°C) is usually 0. 5 to 0.99, preferably 0.6 to 0.98, more preferably 0.75 to 0.95, particularly preferably 0.8 to 0.94, most preferably 0.83 to 0.93. It is preferable that the processability, oil resistance, and shape retention are highly balanced.

There are no particular limitations on the moisture content of the acrylic rubber sheet of the present invention, but when it is generally less than 1% by weight, preferably 0.8% by weight or less, and more preferably 0.6% by weight or less, the crosslinking characteristics are optimized and the properties such as heat resistance and water resistance are highly excellent and suitable.

The Mooney viscosity (ML1+4, 100°C) of the acrylic rubber sheet of the present invention is not particularly limited, but is usually suitable for achieving a high balance of processability and strength properties when it is in the range of 10 to 150, preferably 20 to 100, and more preferably 25 to 70.

The type of acrylic rubber sheet of the present invention is not particularly limited, but examples include blown sheets produced by a hollow molding method, cast sheets produced by a solution casting method, and melt-kneaded sheets produced by a melt extrusion method. Among these, melt-kneaded sheets are preferred in that they can maximize the storage stability effect of the hindered antioxidant.

<Method of manufacturing acrylic rubber sheet>
The method for producing the acrylic rubber sheet of the present invention is not particularly limited, but the acrylic rubber sheet can be easily produced by, for example, comprising: an emulsion polymerization step of emulsifying a monomer component consisting of at least one (meth)acrylic acid ester selected from the group consisting of (meth)acrylic acid alkyl esters and (meth)acrylic acid alkoxyalkyl esters, a reactive group-containing monomer, and, as necessary, other copolymerizable monomers, with water and an emulsifier, and emulsion-polymerizing the monomer component in the presence of a polymerization initiator to obtain an emulsion polymerization liquid; an antiaging agent adding step of adding a hindered antiaging agent to the obtained emulsion polymerization liquid; a coagulation step of contacting the emulsion polymerization liquid to which the antiaging agent has been added with a coagulation liquid to produce water-containing crumbs; a washing step of washing the produced water-containing crumbs; and a dehydration, drying, and molding step of dehydrating and drying the washed water-containing crumbs at 40° C. or higher using a screw-type extruder equipped with a dehydration barrel having a dehydration slit, a drying barrel for drying under reduced pressure, and a die at the tip to extrude a sheet-like dry rubber having a water content of less than 1% by weight.

(Emulsion polymerization process)
In the emulsion polymerization step in the method for producing an acrylic rubber sheet of the present invention, at least one (meth)acrylic ester selected from the group consisting of (meth)acrylic acid alkyl ester and (meth)acrylic acid alkoxyalkyl ester, a reactive A monomer component consisting of a group-containing monomer and other copolymerizable monomers as necessary is emulsified with water and an emulsifier, and emulsion polymerized in the presence of a polymerization initiator to obtain an emulsion polymerization solution. It is characterized by

The monomer components used are the same as those described above, and the amount used may be appropriately selected so as to obtain the monomer composition of the acrylic rubber that constitutes the acrylic rubber sheet.

The emulsifier used in emulsion polymerization is not particularly limited, but includes, for example, anionic emulsifiers, cationic emulsifiers, nonionic emulsifiers, etc., and preferably includes an anionic emulsifier.

There are no particular limitations on the anionic emulsifier; for example, salts of fatty acids such as myristic acid, palmitic acid, oleic acid, and linolenic acid; alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate; sulfuric esters such as sodium lauryl sulfate. salts, phosphate ester salts such as polyoxyalkylene alkyl ether phosphate ester salts; alkyl sulfosuccinates, and the like. Among these anionic emulsifiers, phosphate ester salts and sulfate ester salts are preferred, and phosphate ester salts are particularly preferred. Suitable phosphate ester salts include, for example, sodium lauryl phosphate, potassium lauryl phosphate, sodium polyoxyalkylene alkyl ether phosphate, and the like. Suitable sulfate ester salts include, for example, sodium lauryl sulfate, ammonium lauryl sulfate, sodium myristyl sulfate, sodium laureth sulfate, sodium polyoxyethylene alkyl sulfate, sodium polyoxyethylene alkylaryl sulfate, and sodium lauryl sulfate. Particularly preferred. These anionic emulsifiers can be used alone or in combination of two or more.

Examples of cationic emulsifiers include alkyltrimethylammonium chloride, dialkylammonium chloride, and benzylammonium chloride.

Nonionic emulsifiers are not particularly limited, but examples include polyoxyalkylene fatty acid esters such as polyoxyethylene stearic acid ester; polyoxyalkylene alkyl ethers such as polyoxyethylene dodecyl ether; polyoxyalkylene alkylphenol ethers such as polyoxyethylene nonylphenyl ether; polyoxyethylene sorbitan alkyl esters, etc., with polyoxyalkylene alkyl ethers and polyoxyalkylene alkylphenol ethers being preferred, and polyoxyethylene alkyl ethers and polyoxyethylene alkylphenol ethers being more preferred.

These emulsifiers can be used alone or in combination of two or more. The amount used is usually 0.01 to 10 parts by weight, preferably 0.1 to 5 parts by weight, and more preferably 1 to 3 parts by weight, per 100 parts by weight of the monomer component.

The monomer components, water, and emulsifier may be mixed in the usual manner, such as by stirring the monomers, emulsifier, and water using a stirrer such as a homogenizer or a disk turbine. The amount of water used is usually 1 to 1,000 parts by weight, preferably 5 to 500 parts by weight, more preferably 10 to 300 parts by weight, particularly preferably 15 to 150 parts by weight, and most preferably 20 to 80 parts by weight, per 100 parts by weight of the monomer components.

There are no particular limitations on the polymerization catalyst used, so long as it is one that is commonly used in emulsion polymerization. For example, a redox catalyst consisting of a radical generator and a reducing agent can be used.

Examples of radical generators include peroxides and azo compounds, with peroxides being preferred. As peroxides, inorganic peroxides and organic peroxides can be used.

Examples of inorganic peroxides include sodium persulfate, potassium persulfate, hydrogen peroxide, and ammonium persulfate. Among these, potassium persulfate, hydrogen peroxide, and ammonium persulfate are preferred, with potassium persulfate being particularly preferred.

The organic peroxide is not particularly limited as long as it is a known peroxide used in emulsion polymerization, and examples thereof include 2,2-di(4,4-di-(t-butylperoxy)cyclohexyl)propane, 1-di-(t-hexylperoxy)cyclohexane, 1,1-di-(t-butylperoxy)cyclohexane, 4,4-di-(t-butylperoxy)n-butyl valerate, 2,2-di-(t-butylperoxy)butane, t-butyl hydroperoxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide, paramenthane hydroperoxide, benzoyl peroxide, 1,1,3,3-tetramethylphenyl hydroperoxide, and the like. tetraethylbutyl hydroperoxide, t-butylcumyl peroxide, di-t-butyl peroxide, di-t-hexyl peroxide, di(2-t-butylperoxyisopropyl)benzene, dicumyl peroxide, diisobutyryl peroxide, di(3,5,5-trimethylhexanoyl)peroxide, dilauroyl peroxide, disuccinic acid peroxide, dibenzoyl peroxide, di(3-methylbenzoyl)peroxide, benzoyl(3-methylbenzoyl)peroxide, diisobutyryl peroxydicarbonate, di-n-propyl peroxydicarbonate, di (2-ethylhexyl)peroxydicarbonate, di-sec-butyl peroxydicarbonate, 1,1,3,3-tetramethylbutylperoxyneodecanate, t-hexylperoxypivalate, t-butylperoxyneodecanate, t-hexylperoxypivalate, t-butylperoxypivalate, 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanate, t-hexylperoxy-2-ethylhexanate, t-butylperoxy-3,5,5-trimethylhexanate, t-hexylperoxy Examples of the peroxyalkylene oxide include 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, t-butylperoxyacetate, t-hexylperoxybenzoate, t-butylperoxybenzoate, and 2,5-dimethyl-2,5-di(t-butylperoxy)hexane. Of these, diisopropylbenzene hydroperoxide, cumene hydroperoxide, paramenthane hydroperoxide, and benzoyl peroxide are preferred.
Examples of the azo compound include azobisisoptylonitrile, 4,4'-azobis(4-cyanovaleric acid), 2,2'-azobis[2-(2-imidazolin-2-yl)propane, 2,2'-azobis(propane-2-carboxamidine), 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropanamide], 2,2'-azobis{2-[1-(2-hydroxyethyl)-2-imidazolin-2-yl]propane}, 2,2'-azobis(1-imino-1-pyrrolidino-2-methylpropane), and 2,2'-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propanamide}.

These radical generators can be used alone or in combination of two or more, and the amount used is usually 0.0001 to 5 parts by weight, preferably 0.0001 to 5 parts by weight, based on 100 parts by weight of the monomer component. The amount ranges from 0.0005 to 1 part by weight, more preferably from 0.001 to 0.5 part by weight.

As the reducing agent, any reducing agent used in a redox catalyst for emulsion polymerization can be used without particular limitation, but in the present invention, it is particularly preferable to use at least two types of reducing agents. As the at least two types of reducing agents, for example, a combination of a metal ion compound in a reduced state and another reducing agent is suitable.

Examples of the metal ion compound in a reduced state include, but are not limited to, ferrous sulfate, sodium hexamethylenediaminetetraacetate, cuprous naphthenate, and the like. Among these, ferrous sulfate is preferred. These metal ion compounds in a reduced state can be used alone or in combination of two or more, and the amount used is usually 0.000001 to 0.000 parts per 100 parts by weight of the monomer components. 0.01 parts by weight, preferably 0.00001 to 0.001 parts by weight, more preferably 0.00005 to 0.0005 parts by weight.

Examples of reducing agents other than the metal ion compounds in a reduced state include, but are not limited to, ascorbic acid or its salts, such as ascorbic acid, sodium ascorbate, and potassium ascorbate; erythorbic acid or its salts, such as erythorbic acid, sodium erythorbate, and potassium erythorbate; sulfinates, such as sodium hydroxymethanesulfinate; sulfites, such as sodium sulfite, potassium sulfite, sodium hydrogensulfite, aldehyde sodium hydrogensulfite, and potassium hydrogensulfite; pyrosulfites, such as sodium pyrosulfite, potassium pyrosulfite, sodium hydrogensulfite, and potassium pyrosulfite; thiosulfates, such as sodium thiosulfate and potassium thiosulfate; phosphorous acid, sodium phosphite, potassium phosphite, sodium hydrogen phosphite, and potassium hydrogen phosphite, or phosphorous acid or its salts, such as pyrophosphorous acid, sodium pyrophosphite, potassium pyrophosphite, sodium hydrogen phosphite, and potassium hydrogen phosphite; pyrophosphorous acid or its salts, such as pyrophosphorous acid, sodium pyrophosphite, potassium pyrophosphite, sodium hydrogen phosphite, and potassium hydrogen phosphite; sodium formaldehyde sulfoxylate. Among these, ascorbic acid or its salts, sodium formaldehyde sulfoxylate, etc. are preferred, and ascorbic acid or its salts are particularly preferred.

These reducing agents other than metal ion compounds in a reduced state can be used alone or in combination of two or more, and the amount used is usually 0.001 parts by weight per 100 parts by weight of the monomer components. ~1 part by weight, preferably 0.005 to 0.5 part by weight, more preferably 0.01 to 0.3 part by weight.

A preferred combination of a metal ion compound in a reduced state and another reducing agent is ferrous sulfate and ascorbic acid or a salt thereof and/or sodium formaldehyde sulfoxylate, more preferably ferrous sulfate and ascorbate. and/or sodium formaldehyde sulfoxylate, most preferably a combination of ferrous sulfate and ascorbate. At this time, the amount of ferrous sulfate used is usually 0.000001 to 0.01 parts by weight, preferably 0.00001 to 0.001 parts by weight, and more preferably The amount of ascorbic acid or its salt and/or sodium formaldehyde sulfoxylate used is usually 0.001 to 1 part by weight per 100 parts by weight of the monomer component, in the range of 0.00005 to 0.0005 parts by weight. It is preferably in the range of 0.005 to 0.5 parts by weight, more preferably 0.01 to 0.3 parts by weight.

The amount of water used in the emulsion polymerization reaction may be just that used during the emulsification of the monomer components, but it is usually 10 to 1000 parts by weight, preferably 50 parts by weight, based on 100 parts by weight of the monomer components used in the polymerization. The amount is adjusted to be in the range of 500 parts by weight, more preferably 80 to 400 parts by weight, and most preferably 100 to 300 parts by weight.

The emulsion polymerization reaction may be carried out in a conventional manner, and may be carried out in a batch, semi-batch or continuous manner. The polymerization temperature and polymerization time are not particularly limited, and can be appropriately selected depending on the type of polymerization initiator used. The polymerization temperature is usually in the range of 0 to 100°C, preferably 5 to 80°C, more preferably 10 to 50°C, and the polymerization time is usually 0.5 to 100 hours, preferably 1 to 10 hours.

The polymerization conversion rate of the emulsion polymerization reaction is not particularly limited, but when it is usually 80% by weight or more, preferably 90% by weight or more, and more preferably 95% by weight or more, the produced acrylic rubber sheet has excellent strength properties. Moreover, it is suitable because there is no monomer odor. A polymerization terminator may be used to terminate the polymerization.

(Anti-aging agent addition process)
The antioxidant addition step in the method for producing an acrylic rubber sheet of the present invention is characterized by adding a hindered antioxidant to the emulsion polymerization liquid after the above-mentioned emulsion polymerization.

The amount of the hindered antioxidant used may be appropriately selected so as to be the content of the hindered antioxidant in the acrylic rubber sheet of the present invention, and is usually in the range of 0.001 to 15 parts by weight, preferably 0.01 to 10 parts by weight, more preferably 0.1 to 5 parts by weight, particularly preferably 0.3 to 3 parts by weight, and most preferably 0.5 to 2 parts by weight, per 100 parts by weight of the monomer component.

The method of adding the hindered antioxidant to the emulsion polymerization liquid is not particularly limited, but for example, by emulsifying the hindered antioxidant with an emulsifier and water and adding it as an emulsion containing a phenolic antioxidant, the antioxidant can be easily dispersed in the acrylic rubber and further finely dispersed in the screw extruder, maximizing the antioxidant effect, which is preferable.

The method of emulsifying the hindered anti-aging agent is not particularly limited, but it is produced by making an emulsion with water and an emulsifier, then adding the hindered anti-aging agent and stirring until it is uniformly dispersed. can.

The water used to emulsify the hindered anti-aging agent is preferably warm water, and its temperature is usually 40°C or higher, preferably 50 to 90°C, and more preferably 60 to 80°C, which is suitable for easily emulsifying the hindered anti-aging agent and enabling uniform dispersion.

The temperature of the water for emulsifying the hindered anti-aging agent is also higher than the melting point of the hindered anti-aging agent used, preferably above the melting point +5°C, more preferably above the melting point +10°C. This is suitable because it allows the agent to be easily emulsified and uniformly dispersed.

There are no particular limitations on the emulsifier used to emulsify the hindered antioxidant, but it is preferable to use the same emulsifier as that used when emulsifying the monomer components, as this ensures stability when isolating the acrylic rubber in the subsequent process. Specific examples include anionic emulsifiers, cationic emulsifiers, and nonionic emulsifiers, with anionic emulsifiers being preferred, phosphate ester salts being more preferred, and sulfate ester salts being particularly preferred.

The amount of emulsifier used to emulsify the hindered anti-aging agent may be appropriately selected depending on the molecular weight, melting point, SP value, etc. of the anti-aging agent used, but an amount of emulsifier in the range of usually 1% by weight or more, preferably 2 to 40% by weight, more preferably 3 to 30% by weight, particularly preferably 4 to 20% by weight, and most preferably 5 to 15% by weight, relative to the emulsion of water and emulsifier, is suitable for making the emulsification of the hindered anti-aging agent easy and enabling uniform dispersion.

The stirring time for emulsifying the hindered antioxidant is the time required for the antioxidant to be uniformly dispersed, and is not particularly limited, but is usually at least 1 hour, preferably 1 to 5 hours, more preferably 1 to 4 hours, and more preferably 1 to 3 hours.

In the phenolic antioxidant-containing emulsion thus obtained, which is added to the emulsion polymerization liquid, the phenolic antioxidant is uniformly dispersed. The uniform dispersion of the phenolic antioxidant in the phenolic antioxidant-containing emulsion can be judged, for example, as follows. A glass container is filled with the phenolic antioxidant-containing emulsion and then emptied. The glass container wall is observed after the phenolic antioxidant-containing emulsion has dripped down the wall. If the wall is clean, it is judged to be good uniform dispersion, and if white powder is attached, it is judged to be poor uniform dispersion. The phenolic antioxidant-containing emulsion once uniformly dispersed rarely re-solidifies even when left to stand, but if it becomes poorly dispersed, it can be stirred again and readjusted for use.

The content of the hindered antioxidant in the hindered antioxidant-containing emulsion is appropriately selected depending on the intended use, but it is usually suitable to have a content of 10 to 80% by weight, preferably 20 to 60% by weight, and more preferably 30 to 45% by weight, since this can highly improve the storage stability and heat resistance of the acrylic rubber sheet.

The emulsifier concentration of the emulsion containing a hindered anti-aging agent is not particularly limited, but is usually 2% by weight or more, preferably 3 to 15% by weight, more preferably 4 to 12% by weight, particularly preferably 5 to 10% by weight, most preferably Preferably, when the amount is in the range of 6 to 8% by weight, the storage stability, heat resistance, and water resistance of the acrylic rubber sheet can be highly balanced.

The pH of the emulsion containing a hindered antioxidant is not particularly limited, but is usually 6 or less, preferably 2 to 6, and more preferably 3 to 6, which is suitable for providing the acrylic rubber sheet with excellent storage stability and heat resistance.

The method of adding the hindered antioxidant or the emulsion containing the hindered antioxidant to the emulsion polymerization liquid is not particularly limited and may be done according to a conventional method.

(solidification process)
The coagulation step in the method for producing acrylic rubber of the present invention is a step in which the emulsion polymerization solution to which the hindered anti-aging agent is added is brought into contact with a coagulation solution to produce hydrous crumb.

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

The coagulant used is not particularly limited, but metal salts are usually used. Examples of metal salts include alkali metal salts, salts of metals from group 2 of the periodic table, and other metal salts, preferably alkali metal salts and salts of metals from group 2 of the periodic table, more preferably salts of metals from group 2 of the periodic table. Metal salts, particularly preferred are magnesium salts.

Examples of alkali metal salts include sodium salts such as sodium chloride, sodium nitrate, and sodium sulfate; potassium salts such as potassium chloride, potassium nitrate, and potassium sulfate; and lithium salts such as lithium chloride, lithium nitrate, and lithium sulfate. Of these, sodium salts are preferred, with sodium chloride and sodium sulfate being particularly preferred.

Examples of salts of metals in Group 2 of the periodic table include magnesium chloride, calcium chloride, magnesium nitrate, calcium nitrate, magnesium sulfate, and calcium sulfate, with calcium chloride and magnesium sulfate being preferred.

Other metal salts include, for example, 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 can be used alone or in combination of two or more, and the amount used is usually in the range of 0.01 to 100 parts by weight, preferably 0.1 to 50 parts by weight, and more preferably 1 to 30 parts by weight, per 100 parts by weight of the monomer component. When the coagulant is in this range, it is preferable because it can sufficiently coagulate the acrylic rubber while highly improving the compression set resistance and water resistance when the acrylic rubber sheet is crosslinked.

The coagulant concentration of the coagulating liquid used 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, particularly preferably 1.5 to 5% by weight. It is preferable that the particle size of the water-containing crumbs produced can be uniformly concentrated in a specific area.

There are no particular limitations on the temperature of the coagulation liquid, but a temperature of 40°C or higher, preferably 40 to 90°C, and more preferably 50 to 80°C, is generally preferred to produce uniform hydrous crumbs.

There are no particular limitations on the contact between the emulsion polymerization liquid and the coagulation liquid, but for example, either the method of adding the emulsion polymerization liquid to the stirred coagulation liquid or the method of adding the coagulation liquid to the stirred emulsion polymerization liquid may be used. However, the method of adding the emulsion polymerization liquid to the stirred coagulation liquid is preferable because it makes the shape and diameter of the water-containing crumbs that are generated uniform and focuses them in a specific area, significantly improving the washing efficiency of the emulsifier and coagulation agent.

The stirring speed (rotation speed) of the stirred coagulation liquid is expressed in terms of the rotation speed of the stirring blades of the stirring device installed in the coagulation bath in this invention, and although there are no particular limitations, it is usually 100 rpm or more, preferably 200 to 1000 rpm, more preferably 300 to 900 rpm, and particularly preferably in the range of 400 to 800 rpm.

A rotation speed that vigorously stirs the coagulation liquid to some extent is preferable because it allows the generated hydrous crumbs to be small and uniform in particle size. By setting the rotation speed above the lower limit, it is possible to prevent the generation of crumbs with excessively large and small particle sizes, and by setting the rotation speed below the upper limit, it is possible to more easily control the coagulation reaction.

The peripheral speed of the stirred coagulation liquid is expressed as the linear speed of the outer circumference of the stirring blade of the stirring device installed in the coagulation bath, and it is preferable to stir vigorously to a certain extent in order to produce small and uniform hydrous crumb particles, and the peripheral speed is usually 0.5 m/s or more, preferably 1 m/s or more, more preferably 1.5 m/s or more, particularly preferably 2 m/s or more, and most preferably 2.5 m/s or more. On the other hand, the upper limit of the peripheral speed is not particularly limited, but it is preferable that it is usually 50 m/s or less, preferably 30 m/s or less, more preferably 25 m/s or less, and most preferably 20 m/s or less, because this makes it easier to control the coagulation reaction.

By setting the above-mentioned conditions for the coagulation reaction in the coagulation process (contact method, solid content concentration of the emulsion polymerization liquid, concentration and temperature of the coagulation liquid, rotation speed and circumferential speed during stirring of the coagulation liquid, etc.) to a specific range, the formation The shape and diameter of the water-containing crumbs are uniform and concentrated in a specific area, and removal of emulsifiers and coagulants during washing and dehydration is greatly improved, which is preferable.

(Washing process)
The washing method is not particularly limited and may be any conventional method, for example, by mixing the produced water-containing crumbs with a large amount of water.

The amount of water used is not particularly limited, but it is suitable to effectively reduce the ash content in the acrylic rubber when the amount of water used per wash is usually 50 parts by weight or more, preferably 50 to 15,000 parts by weight, more preferably 100 to 10,000 parts by weight, and particularly preferably 150 to 5,000 parts by weight, per 100 parts by weight of the monomer component.

The temperature of the water used is not particularly limited, but the cleaning efficiency is improved when the temperature is usually 40°C or higher, preferably 40 to 100°C, more preferably 50 to 90°C, and most preferably 60 to 80°C. This is suitable because it can significantly improve the performance.

By setting the temperature of the washing water to the above-mentioned lower limit or higher, the emulsifier and coagulant are released from the water-containing crumbs, and the washing efficiency is further improved.

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

The number of washings is not particularly limited, and is usually 1 to 10 times, preferably multiple times, and more preferably 2 to 3 times. From the viewpoint of reducing the amount of residual coagulant in the final acrylic rubber, it is desirable to wash with water more frequently, but the number of washings can be significantly reduced by specifying the shape and diameter of the water-containing crumbs and/or setting the washing temperature within the above range.

(Dehydration, drying and molding process)
The dehydrating/drying/molding steps in the method for producing an acrylic rubber sheet of the present invention are characterized in that the washed water-containing crumbs having a temperature of 40°C or higher are dehydrated in the dehydrating barrel using a dehydrating barrel having a dehydration slit, a drying barrel under reduced pressure, and a screw-type extruder having a die at the tip thereof to a moisture content of 1 to 40% by weight, and then dried in the drying barrel to a moisture content of less than 1% by weight, and a sheet-like dried rubber is extruded through the die.

In the present invention, it is preferable that the hydrous crumb supplied to the screw extruder is one from which free water has been removed (drained) after washing.

In the method for producing an acrylic rubber sheet of the present invention, it is preferable to provide a draining step in which free water is separated from the water-containing crumbs after washing with a draining machine after the above-mentioned washing step and before the dehydrating and drying steps, in order to increase the dehydration efficiency.

As the drainer, any known device can be used without particular limitation, such as a wire mesh, a screen, an electric sieve, etc., preferably a wire mesh or a screen.

There are no particular limitations on the opening size of the drainer, but it is usually suitable for efficient draining with minimal loss of water-containing crumb when it is in the range of 0.01 to 5 mm, preferably 0.1 to 1 mm, and more preferably 0.2 to 0.6 mm.

The moisture content of the hydrous crumbs after draining, i.e., the moisture content (rate) of the hydrous crumbs fed into the dehydration, drying and molding process, is not particularly limited, but is usually in the range of 50 to 80% by weight, preferably 50 to 70% by weight, and more preferably 50 to 60% by weight.

The temperature of the hydrous crumbs after draining, i.e., the temperature of the hydrous crumbs fed into the dehydration, drying and molding process, is not particularly limited, but is usually 40°C or higher, preferably 40 to 100°C, more preferably 50 to 90°C, particularly preferably 55 to 85°C, and most preferably in the range of 60 to 80°C. This is suitable for efficiently dehydrating and drying hydrous crumbs such as the acrylic rubber of the present invention, which has a high specific heat of 1.5 to 2.5 KJ/kg·K and is difficult to raise in temperature, using a screw-type extruder.

Dehydration of hydrous crumbs (dehydration barrel part)
Dehydration of the hydrous crumb is carried out in a dehydration barrel provided with a dehydration slit in a screw extruder. The opening of the dehydration slit may be selected as appropriate depending on the conditions of use, but is usually in the range of 0.01 to 5 mm, preferably 0.1 to 1 mm, and more preferably 0.2 to 0.6 mm. In addition, it is preferable because there is little loss of water-containing crumbs and the water-containing crumbs can be efficiently dehydrated.

The number of dehydration barrels in a screw-type extruder is not particularly limited, but it is usually preferable to have more than one, preferably 2 to 10, and more preferably 3 to 6, in order to efficiently dehydrate the viscous acrylic rubber.

Water is removed from the wet crumb in the dewatering barrel in two ways: through the dewatering slit in liquid form (wastewater) or in vapor form (exhaust steam). In this invention, we distinguish between the two by defining wastewater as dewatering and exhaust steam as preliminary drying.

When using a screw-type extruder equipped with multiple dehydration barrels, a combination of drainage and exhaust steam can be used to efficiently dehydrate the viscous acrylic rubber and reduce its moisture content, which is preferable. Whether each barrel of a screw-type extruder equipped with three or more dehydration barrels is to be a drainage type dehydration barrel or an exhaust steam type dehydration barrel can be selected appropriately depending on the intended use, but typically, when the ash content in the acrylic rubber sheet to be produced is reduced, the number of drainage type barrels is increased, and when the moisture content is reduced, the number of exhaust steam type barrels is increased.

The set temperature of the dehydration barrel is appropriately selected depending on the monomer composition of the acrylic rubber, ash content, water content, operating conditions, etc., but is usually 60 to 150°C, preferably 70 to 140°C, more preferably 80 to 150°C. The temperature range is 130°C. The temperature setting of the dehydration barrel for dehydration in the drained state is usually 60 to 120°C, preferably 70 to 110°C, more preferably 80 to 100°C. The set temperature of the dehydration barrel for pre-drying in the exhaust steam state is usually in the range of 100 to 150°C, preferably 105 to 140°C, more preferably 110 to 130°C.

There are no particular limitations on the moisture content of the crumbs after dehydration in a drainage dehydration process that squeezes out moisture from the hydrous crumbs, i.e., after passing through a drainage dehydration barrel, but a moisture content of 1 to 45% by weight is usually preferred, 1 to 40% by weight, more preferably 5 to 40% by weight, particularly preferably 10 to 35% by weight, and most preferably 15 to 35% by weight, which provides a high level of balance between productivity and ash removal efficiency.

When dehydrating sticky acrylic rubber using a centrifuge or similar machine, the acrylic rubber adheres to the dehydration slits and is barely dehydrated (water content reaches approximately 45-55% by weight). However, in this invention, by using a screw-type extruder that has a dehydration slit and is forcibly squeezed by a screw, it is possible to reduce the water content to this extent.

When a drainage type dehydration barrel and a steam exhaust type dehydration barrel are used, the moisture content of the hydrous crumbs after dehydration in the drainage type dehydration barrel is usually 5 to 45% by weight, preferably 10 to 40% by weight, and more preferably 15 to 35% by weight, and the moisture content after pre-drying in the steam exhaust type dehydration barrel is usually 1 to 30% by weight, preferably 3 to 20% by weight, and more preferably 5 to 15% by weight.

By setting the moisture content after dehydration to above the lower limit, the dehydration time can be shortened and deterioration of the acrylic rubber can be suppressed, while by setting it below the upper limit, the ash content can be sufficiently reduced.

Drying of water-containing crumbs (drying barrel section)
The drying of the water-containing crumb after the dehydration is performed in a drying barrel section under reduced pressure.

The degree of vacuum in the drying barrel may be selected as appropriate, but a pressure of 1 to 50 kPa, preferably 2 to 30 kPa, and more preferably 3 to 20 kPa is suitable for efficient drying of the wet crumbs.

The set temperature of the drying barrel may be selected as appropriate, but a temperature in the range of 100 to 250°C, preferably 110 to 200°C, and more preferably 120 to 180°C is usually suitable to efficiently dry the acrylic rubber without discoloration or deterioration, and to reduce the amount of gel in the acrylic rubber sheet that is insoluble in methyl ethyl ketone.

The number of drying barrels in a screw-type extruder is not particularly limited, but is usually multiple, preferably 2 to 10, and more preferably 3 to 8. When there are multiple drying barrels, the degree of vacuum may be similar for all drying barrels or may be different. When there are multiple drying barrels, the set temperature may be similar for all drying barrels or may be different, but it is preferable to make the temperature of the discharge part (closer to the die) higher than the temperature of the introduction part (closer to the dehydration barrel) in order to increase the drying efficiency.

The moisture content of the dry rubber after drying is usually less than 1% by weight, preferably less than 0.8% by weight, more preferably less than 0.6% by weight. In the present invention, the hindered anti-aging agent and acrylic rubber are melt-kneaded and extruded in a screw type extruder with the water content of the dry rubber at this value (almost all water has been removed), thereby improving storage stability and heat resistance. This method is suitable because an acrylic rubber sheet with highly improved properties can be produced. In the present invention, it is also preferable that the acrylic rubber is melt-kneaded in a state in which most of the water has been removed, thereby reducing the gel amount of methyl ethyl ketone insoluble components in the acrylic rubber sheet and significantly improving the processability of the acrylic rubber sheet. It is.

Dry rubber (die part)
The dried rubber dehydrated and dried in the screw parts of the dewatering barrel and drying barrel is sent to a rectifying die part without a screw. A breaker plate and a wire mesh may or may not be provided between the screw part and the die part.

The dried rubber to be extruded is preferably extruded in sheet form using a roughly rectangular die shape, which results in less air entrapment, a higher specific gravity, and excellent storage stability.

The resin pressure in the die section is not particularly limited, but is usually in the range of 0.1 to 10 MPa, preferably 0.5 to 5 MPa, and more preferably 1 to 3 MPa, which is suitable for minimizing air entrapment (high specific gravity) and for excellent productivity.

Screw-type extruder and operating conditions The screw length (L) of the screw-type extruder used may be appropriately selected depending on the purpose of use, but is usually in the range of 3,000 to 15,000 mm, preferably 4,000 to 10,000 mm, and more preferably 4,500 to 8,000 mm.

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

The ratio (L/D) of the screw length (L) to the screw diameter (D) of the screw extruder used is not particularly limited, but is usually in the range of 10 to 100, preferably 20 to 80, and more preferably 30 to 60, which is suitable for reducing the moisture content to less than 1% by weight without causing a decrease in the molecular weight of the dried rubber or burning.

The rotation speed (N) of the screw extruder used may be selected appropriately depending on the various conditions, but a rotation speed of 10 to 1000 rpm, preferably 50 to 750 rpm, more preferably 100 to 500 rpm, and most preferably 120 to 300 rpm is suitable for efficiently reducing the water content and gel content of the acrylic rubber.

The throughput (Q) of the screw extruder used is not particularly limited, but is usually in the range of 100 to 1,500 kg/hr, preferably 300 to 1,200 kg/hr, more preferably 400 to 1,000 kg/hr, and most preferably 500 to 800 kg/hr.

The ratio (Q/N) between the extrusion amount (Q) and the rotation speed (N) of the screw type extruder used is not particularly limited, but is usually 2 to 10, preferably 3 to 8, more preferably ranges from 4 to 6.

Dry rubber sheet The dry rubber extruded from the screw extruder is in the form of a sheet, which is preferable because it does not trap air and can increase the specific gravity, resulting in highly improved storage stability. The dry rubber sheet extruded from the screw extruder is usually cooled and cut to be used as an acrylic rubber sheet.

The thickness of the sheet-like dry rubber extruded from a screw extruder is not particularly limited, but is usually in the range of 1 to 40 mm, preferably 2 to 35 mm, more preferably 3 to 30 mm, and most preferably 5 to 25 mm. It is suitable for certain situations due to its excellent workability and productivity. In particular, since the thermal conductivity of dry rubber sheets is as low as 0.15 to 0.35 W/mK, the thickness of dry rubber sheets is usually 1 to 30 mm when increasing cooling efficiency and dramatically improving productivity. The range is preferably 2 to 25 mm, more preferably 3 to 15 mm, particularly preferably 4 to 12 mm.

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

The temperature of the dry rubber extruded from the screw extruder is not particularly limited, but is usually in the range of 100 to 200°C, preferably 110 to 180°C, more preferably 120 to 160°C.

The moisture content of the dry rubber extruded from a screw extruder is not particularly limited, but is usually less than 1% by weight, preferably less than 0.8% by weight, more preferably less than 0.6% by weight.

The complex viscosity at 100°C ([η]100°C) of the sheet-like dry rubber extruded from the screw-type extruder 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 4000 Pa·s, and most preferably 2500 to 3500 Pa·s, which is suitable for achieving a high balance between extrudability as a sheet and shape retention. In other words, by setting it at or above the lower limit, the extrudability can be made superior, and by setting it at or below the upper limit, deformation or breakage of the sheet-like dry rubber can be suppressed.

The sheet-like dry rubber extruded from the screw extruder may be folded and used as is, but it is preferably cut and used.

There are no particular limitations on how to cut the dry rubber sheet, but since the acrylic rubber used in the acrylic rubber sheet of the present invention has strong adhesiveness, it is necessary to cut the dry rubber sheet in a continuous manner without drawing in air. It is preferable to do this after cooling.

There are no particular limitations on the cutting temperature of the dry rubber sheet, but a temperature of 60°C or less, preferably 55°C or less, and more preferably 50°C or less, is usually preferred as it provides a good balance between cuttability and productivity.

The complex viscosity of the dry rubber sheet at 60°C ([η]60°C) is not particularly limited, but is usually 15,000 Pa·s or less, preferably 2000 to 10,000 Pa·s, more preferably 2500 to 7000 Pa·s, and most preferably 2700 to 5500 Pa·s, which allows for continuous cutting without entraining air.

The ratio of the complex viscosity at 100°C ([η] 100°C) and the complex viscosity at 60°C ([η] 60°C) of the sheet-like dry rubber ([η] 100°C/[η] 60°C) is: Although not particularly limited, it is usually 0.5 or more, preferably 0.6 to 0.98, more preferably 0.75 to 0.95, particularly preferably 0.8 to 0.94, most preferably 0.83. A range of 0.93 to 0.93 is preferable because air entrainment is small and cutting and productivity are highly balanced.

There are no particular limitations on the method of cooling the dried rubber sheet, and it may be left at room temperature. Forced cooling methods such as air cooling under air conditioning, water spraying, and immersion in water are preferred in order to increase productivity, and air cooling under air blowing or cooling is particularly preferred.

In the air cooling method for dry rubber sheets, for example, the dry rubber sheets are extruded from a screw extruder onto a conveyor such as a belt conveyor, and are 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°C, preferably 5 to 25°C, more preferably 10 to 20°C. The length to be cooled is not particularly limited, but is usually in the range of 5 to 500 m, preferably 10 to 200 m, and more preferably 20 to 100 m. Although the cooling rate of the sheet-like dry rubber is not particularly limited, cutting is particularly easy when the cooling rate is usually 50°C/hr or more, more preferably 100°C/hr or more, and even more preferably 150°C/hr or more. This is suitable.

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

The acrylic rubber sheet thus obtained has superior operability and storage stability compared to crumb-like acrylic rubber, and can be used as it is or by laminating it into a bale.

<Acrylic rubber veil>
The acrylic rubber veil of the present invention is characterized in that it is formed by laminating and integrating the above-mentioned acrylic rubber sheets. The number of laminations is appropriately selected depending on the size or weight of the acrylic rubber veil.

The size of the acrylic rubber veil of the present invention is not particularly limited, but the width is usually in the range of 100 to 800 mm, preferably 200 to 500 mm, and more preferably 250 to 450 mm, the length is usually in the range of 300 to 1200 mm, preferably 400 to 1000 mm, and more preferably 500 to 800 mm, and the height is usually in the range of 50 to 500 mm, preferably 100 to 300 mm, and more preferably 150 to 250 mm.

Reactive group content, water content, ash content, amount and ratio of components in ash, specific gravity, gel content, pH, complex viscosity at 60°C ([η]60°C), and complex viscosity at 100°C of the acrylic rubber veil of the present invention Complex viscosity ([η] 100°C), ratio of complex viscosity at 100°C ([η] 100°C) to complex viscosity at 60°C ([η] 60°C) ([η] 100°C/[η ]60°C) and Mooney viscosity (ML1+4,100°C) are the same as the respective characteristic values of the acrylic rubber sheet.

Although the method for manufacturing the acrylic rubber veil of the present invention is not particularly limited, it can be easily manufactured by laminating the sheet-shaped dry rubber extruded from the screw type extruder after cooling and cutting.

There are no particular limitations on the lamination temperature of the dry rubber sheet, but a temperature of 30°C or higher, preferably 35°C or higher, and more preferably 40°C or higher, is usually suitable to allow air trapped during lamination to escape. The number of layers may be appropriately selected depending on the size or weight of the acrylic rubber veil.

The acrylic rubber bale of the present invention obtained in this manner has superior operability, storage stability, and water resistance compared to crumb-like acrylic rubber, and can be used as is or by cutting the required amount into bunburys, rolls, etc. It can be used by adding it to a mixer.

<Rubber mixture>
The rubber mixture of the present invention is characterized in that the acrylic rubber sheet or acrylic rubber veil is mixed with a filler and a crosslinking agent.

There are no particular limitations on the filler, but examples include reinforcing fillers and non-reinforcing fillers, with reinforcing fillers being preferred.

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

These fillers can be used alone or in combination of two or more, and the blending amount is appropriately selected within a range that does not impair the effects of the present invention. The amount is usually 1 to 200 parts by weight, preferably 10 to 150 parts by weight, and more preferably 20 to 100 parts by weight.

The crosslinking agent may be appropriately selected according to the type of reactive group contained in the acrylic rubber constituting the acrylic rubber sheet or acrylic rubber veil and the intended use, but is not particularly limited as long as it can crosslink the acrylic rubber sheet or acrylic rubber veil. For example, conventionally known crosslinking agents such as polyamine compounds such as diamine compounds and carbonates thereof; sulfur compounds; sulfur donors; triazine thiol compounds; polyepoxy compounds; organic ammonium carboxylate salts; organic peroxides; polycarboxylic acids; quaternary onium salts; imidazole compounds; isocyanuric acid compounds; organic peroxides; and triazine compounds may be used. Among these, polyamine compounds, ammonium carboxylate salts, metal dithiocarbamate salts, and triazine thiol compounds are preferred, and hexamethylenediamine carbamate, 2,2'-bis[4-(4-aminophenoxy)phenyl]propane, ammonium benzoate, and 2,4,6-trimercapto-1,3,5-triazine are particularly preferred.

When the acrylic rubber sheet or acrylic rubber veil used is composed of a carboxyl group-containing acrylic rubber, it is preferable to use a polyamine compound and its carbonate as a crosslinking agent. Examples of the polyvalent amine compound include aliphatic polyvalent amine compounds such as hexamethylenediamine, hexamethylenediamine carbamate, and N,N'-dicinnamylidene-1,6-hexanediamine; and aromatic polyvalent amine compounds such as 4,4'-methylenedianiline, p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-(m-phenylenediisopropylidene)dianiline, 4,4'-(p-phenylenediisopropylidene)dianiline, 2,2'-bis[4-(4-aminophenoxy)phenyl]propane, 4,4'-diaminobenzanilide, 4,4'-bis(4-aminophenoxy)biphenyl, m-xylylenediamine, p-xylylenediamine, and 1,3,5-benzenetriamine. Among these, hexamethylenediamine carbamate, 2,2'-bis[4-(4-aminophenoxy)phenyl]propane, etc. are preferred.

When the acrylic rubber sheet or acrylic rubber veil used is composed of an epoxy group-containing acrylic rubber, the crosslinking agent may be an aliphatic polyamine compound such as hexamethylenediamine, hexamethylenediamine carbamate, or the like, or a carbonate salt thereof; an aromatic polyamine compound such as 4,4'-methylenedianiline; an ammonium carboxylate salt such as ammonium benzoate or ammonium adipate; a metal dithiocarbamate salt such as zinc dimethyldithiocarbamate; a polycarboxylic acid such as tetradecanedioic acid; a quaternary onium salt such as cetyltrimethylammonium bromide; an imidazole compound such as 2-methylimidazole; an isocyanuric acid compound such as ammonium isocyanurate; and the like. Among these, ammonium carboxylate salts and metal dithiocarbamate salts are preferred, and ammonium benzoate is more preferred.

When the acrylic rubber sheet or acrylic rubber veil used is composed of a halogen atom-containing acrylic rubber, it is preferable to use sulfur, a sulfur donor, or a triazine thiol compound as a crosslinking agent. Examples of sulfur donors include dipentamethylene thiuram hexasulfide and triethyl thiuram disulfide. Examples of triazine compounds include 6-trimercapto-s-triazine, 2-anilino-4,6-dithiol-s-triazine, 1-dibutylamino-3,5-dimercaptotriazine, 2-dibutylamino-4,6-dithiol-s-triazine, 1-phenylamino-3,5-dimercaptotriazine, 2,4,6-trimercapto-1,3,5-triazine, and 1-hexylamino-3,5-dimercaptotriazine. Among these, 2,4,6-trimercapto-1,3,5-triazine is preferred.

These crosslinking agents can be used alone or in combination of two or more, and the amount thereof is usually 0.001 to 20 parts by weight, preferably 0.001 to 20 parts by weight, per 100 parts by weight of the acrylic rubber sheet or acrylic rubber veil. is 0.1 to 10 parts by weight, more preferably 0.1 to 5 parts by weight. By setting the amount of the crosslinking agent within this range, it is possible to obtain sufficient rubber elasticity and to obtain excellent mechanical strength as a crosslinked rubber product.

The rubber mixture of the present invention may contain other rubber components other than the acrylic rubber sheet or acrylic rubber veil, if necessary.

Other rubber components that may be used as needed are not particularly limited, and examples thereof include natural rubber, polybutadiene rubber, polyisoprene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, silicone rubber, fluororubber, olefin-based elastomers, styrene-based elastomers, vinyl chloride-based elastomers, polyester-based elastomers, polyamide-based elastomers, polyurethane-based elastomers, and polysiloxane-based elastomers. The shape of the other rubber components is not particularly limited, and may be, for example, powder, pellets, crumbs, sheets, veils, etc.

These other rubber components can be used alone or in combination of two or more. The amount of these other rubber components used is appropriately selected within a range that does not impair the effects of the present invention.

The rubber mixture of the present invention may be compounded with an anti-aging agent as necessary. Examples of the anti-aging agent include, but are not limited to, 2,6-di-t-butyl-4-methylphenol, 2,6-di-t-butylphenol, butylhydroxyanisole, 2,6-di-t-butyl-α-dimethylamino-p-cresol, octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, styrenated phenol, 2,2'-methylene-bis(6-α-methyl-benzyl-p-cresol), 4,4'-methylenebis( 2,6-di-t-butylphenol), 2,2'-methylene-bis(4-methyl-6-t-butylphenol), 2,4-bis[(octylthio)methyl]-6-methylphenol, 2,2'-thiobis-(4-methyl-6-t-butylphenol), 4,4'-thiobis-(6-t-butyl-o-cresol), 2,6-di-t-butyl-4-(4,6-bis(octylthio)-1,3,5-triazin-2-ylamino)phenol and other phenols. Phenolic antioxidants; phosphorous ester antioxidants such as tris(nonylphenyl)phosphite, diphenylisodecylphosphite, and tetraphenyldipropylene glycol diphosphite; sulfur ester antioxidants such as dilauryl thiodipropionate; phenyl-α-naphthylamine, phenyl-β-naphthylamine, p-(p-toluenesulfonylamido)-diphenylamine, 4,4'-(α,α-dimethylbenzyl)diphenylamine, Examples of the antiaging agents include amine-based antiaging agents such as butyl aldehyde, N,N-diphenyl-p-phenylenediamine, N-isopropyl-N'-phenyl-p-phenylenediamine, and butyraldehyde-aniline condensates; imidazole-based antiaging agents such as 2-mercaptobenzimidazole; quinoline-based antiaging agents such as 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline; and hydroquinone-based antiaging agents such as 2,5-di-(t-amyl)hydroquinone. Among these, amine-based antiaging agents are particularly preferred. The antiaging agent used here may be the same as or different from the antiaging agent used in the emulsion polymerization step.

These antioxidants can be used alone or in combination of two or more, and the amount of each is in the range of 0.01 to 15 parts by weight, preferably 0.1 to 10 parts by weight, and more preferably 1 to 5 parts by weight, per 100 parts by weight of the acrylic rubber sheet or acrylic rubber veil.

The rubber mixture of the present invention contains the acrylic rubber having reactive groups contained in the acrylic rubber sheet or acrylic rubber veil of the present invention, a filler, a crosslinking agent, and other rubber components and anti-aging agents as necessary, and can further contain other additives commonly used in the relevant technical field as necessary, such as crosslinking assistants, crosslinking accelerators, crosslinking retarders, silane coupling agents, plasticizers, processing aids, lubricants, pigments, colorants, antistatic agents, foaming agents, etc. These other additives can be used alone or in combination of two or more, and the amount of each additive is appropriately selected within a range that does not impair the effects of the present invention.

<Method for producing rubber mixture>
Examples of the method for producing the rubber mixture of the present invention include a method of mixing the acrylic rubber sheet or acrylic rubber veil of the present invention with the filler, crosslinking agent, and other compounding agents that can be contained as necessary. For this purpose, any means conventionally used in the rubber processing field, such as open rolls, Banbury mixers, various kneaders, etc., can be used. That is, using these mixers, the acrylic rubber sheet or acrylic rubber veil can be mixed with the filler, crosslinking agent, etc. by direct mixing, preferably by direct kneading.

In this case, the acrylic rubber sheet or acrylic rubber veil may be used as is or after being divided (cut, etc.).

There are no particular limitations on the mixing procedure for each component, but for example, after sufficiently mixing components that are difficult to react or decompose with heat, cross-linking agents, etc. that are easily reacted or decomposed with heat, are Two-stage mixing is preferred, in which mixing is performed at a low temperature for a short time. Specifically, it is preferable to mix the acrylic rubber sheet or acrylic rubber veil and the filler in the first stage, and then mix the crosslinking agent in the second stage. Other rubber components and anti-aging agents are usually mixed in the first stage, the crosslinking accelerator is mixed in the second stage, and other compounding agents may be selected as appropriate.
The Mooney viscosity (ML1+4,100°C; compound Mooney) of the rubber mixture of the present invention obtained in this way is not particularly limited, but is usually in the range of 10 to 150, preferably 20 to 100, more preferably 25 to 80. It is.

<Rubber cross-linked product>
The cross-linked rubber of the present invention is obtained by cross-linking the above-mentioned rubber mixture.

The crosslinked rubber product of the present invention is produced by molding the rubber mixture of the present invention in a molding machine corresponding to the desired shape, such as an extruder, injection molding machine, compressor, roll, etc., and then crosslinking by heating. It can be manufactured by performing a reaction and fixing the shape as a rubber crosslinked product. In this case, the crosslinking may be performed after pre-forming or at the same time as the molding. The molding temperature is usually 10 to 200°C, preferably 25 to 150°C. The crosslinking temperature is usually 100 to 250°C, preferably 130 to 220°C, more preferably 150 to 200°C, and the crosslinking time is usually 0.1 minute to 10 hours, preferably 1 minute to 5 hours. As the heating method, methods used for crosslinking rubber such as press heating, steam heating, oven heating, and hot air heating may be selected as appropriate.

The crosslinked rubber product of the present invention may be further heated to perform secondary crosslinking depending on the shape, size, etc. of the crosslinked rubber product. Secondary crosslinking varies depending on the heating method, crosslinking temperature, shape, etc., but is preferably carried out for 1 to 48 hours. The heating method and heating temperature may be selected as appropriate.

The rubber crosslinked product of the present invention is used as a sealing material such as an O-ring, a packing, a diaphragm, an oil seal, a shaft seal, a bearing sheath, a mechanical seal, a well head seal, a seal for electric/electronic equipment, and a seal for air compressor equipment. ; A unit cell equipped with a rocker cover gasket installed at the connection between the cylinder block and the cylinder head, an oil pan gasket installed at the connection between the oil pan and the cylinder head or transmission case, a positive electrode, an electrolyte plate, and a negative electrode. Various gaskets such as gaskets for fuel cell separators installed between a pair of sandwiched housings and gaskets for top covers of hard disk drives; Cushioning materials, anti-vibration materials; Wire sheathing materials; Industrial belts; Tubes and hoses; Sheets. ; etc. is suitably used.

The cross-linked rubber product of the present invention is also suitable for use as extrusion molded products and mold cross-linked products for automotive applications, such as fuel oil hoses for fuel tanks, such as fuel hoses, filler neck hoses, vent hoses, paper hoses, and oil hoses; air hoses, such as turbo air hoses and mission control hoses; radiator hoses, heater hoses, brake hoses, and air conditioner hoses.

<Equipment configuration used for manufacturing acrylic rubber sheet>
Next, the configuration of an apparatus used for manufacturing an acrylic rubber sheet according to an embodiment of the present invention will be described. FIG. 1 is a diagram schematically showing an example of an acrylic rubber manufacturing system having an apparatus configuration used for manufacturing an acrylic rubber sheet according to an embodiment of the present invention. For manufacturing the acrylic rubber sheet according to the present invention, for example, an acrylic rubber manufacturing system 1 shown in FIG. 1 can be used.

The acrylic rubber manufacturing system 1 shown in FIG. 1 is composed of an emulsion polymerization reactor (not shown), a coagulation device 3, a washing device 4, a drainer 43, a screw-type extruder 5, a cooling device 6, and a baling device 7.

The emulsion polymerization reactor is configured to perform the process related to the emulsion polymerization process described above. Although not shown in FIG. 1, this emulsion polymerization reactor includes, for example, a polymerization reaction tank, a temperature controller for controlling the reaction temperature, a motor, and a stirring device equipped with stirring blades. In an emulsion polymerization reactor, the monomer components for forming acrylic rubber are mixed with water and an emulsifier, and the mixture is appropriately stirred with a stirrer to form an emulsion, and emulsion polymerization is performed in the presence of a polymerization catalyst to form an emulsion polymerization solution. can be obtained. The hindered anti-aging agent or the emulsion containing the hindered anti-aging agent can be added to the emulsion polymerization solution as it is in the emulsion polymerization reactor. The emulsion polymerization reactor may be of a batch type, semi-batch type, or continuous type, and may be a tank type reactor or a tubular type reactor.

The coagulation apparatus 3 shown in FIG. 1 is configured to perform the processing related to the above-described coagulation process. As schematically illustrated in FIG. 1, the coagulation device 3 includes, for example, a stirring tank 30, a heating section 31 that heats the inside of the stirring tank 30, a temperature control section (not shown) that controls the temperature inside the stirring tank 30, It has a stirring device 34 including a motor 32 and stirring blades 33, and a drive control section (not shown) that controls the rotational speed and rotational speed of the stirring blades 33. In the coagulation device 3, water-containing crumb can be produced by bringing the emulsion polymerization liquid obtained in the emulsion polymerization reactor into contact with a coagulation liquid and coagulating it.

In the coagulation device 3, for example, the emulsion polymerization liquid and the coagulation liquid are brought into contact by a method in which the emulsion polymerization liquid is added to the coagulation liquid being stirred. That is, the stirring tank 30 of the coagulation device 3 is filled with a coagulation liquid, and the emulsion polymerization liquid is added to and brought into contact with the coagulation liquid to coagulate the emulsion polymerization liquid, thereby producing water-containing crumb.

The heating unit 31 of the solidification device 3 is configured to heat the solidification liquid filled in the stirring tank 30. The temperature control unit of the solidification device 3 is configured to control the temperature inside the stirring tank 30 by controlling the heating operation by the heating unit 31 while monitoring the temperature inside the stirring tank 30 measured by a thermometer. The temperature of the solidification liquid inside the stirring tank 30 is controlled by the temperature control unit to be normally 40°C or higher, preferably in the range of 40 to 90°C, and more preferably 50 to 80°C.

The agitator 34 of the solidification device 3 is configured to agitate the solidification liquid filled in the agitation tank 30. Specifically, the agitator 34 is equipped with a motor 32 that generates rotational power, and an agitator blade 33 that extends in a direction perpendicular to the rotation axis of the motor 32. The agitator blade 33 can cause the solidification liquid filled in the agitation tank 30 to flow by rotating around the rotation axis due to the rotational power of the motor 32. There are no particular limitations on the shape, size, or number of the agitator blades 33.

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

The cleaning device 4 shown in FIG. 1 is configured to perform the process related to the cleaning step described above. As shown in FIG. 1, the cleaning device 4 has, for example, a cleaning tank 40, a heating unit 41 that heats the inside of the cleaning tank 40, and a temperature control unit (not shown) that controls the temperature inside the cleaning tank 40. In the cleaning device 4, the amount of ash in the final acrylic rubber sheet can be effectively reduced by mixing the water-containing crumbs generated in the solidification device 3 with a large amount of water and cleaning them.

The heating unit 41 of the cleaning device 4 is configured to heat the inside of the cleaning tank 40. The temperature control unit of the cleaning device 4 is configured to control the temperature inside the cleaning tank 40 by controlling the heating operation of the heating unit 41 while monitoring the temperature inside the cleaning tank 40 measured by a thermometer. As described above, the temperature of the cleaning water in the cleaning tank 40 is usually controlled to be in the range of 40°C or higher, preferably 40 to 100°C, more preferably 50 to 90°C, and most preferably 60 to 80°C.

The water-containing crumbs washed by the washing device 4 are supplied to a screw type extruder 5 that performs a dehydration process and a drying process. At this time, it is preferable that the washed water-containing crumb is supplied to the screw extruder 5 through a drainer 43 capable of separating free water. As the drainer 43, for example, a wire mesh, a screen, an electric sieve, etc. can be used.

Further, when the water-containing crumb after washing is supplied to the screw extruder 5, the temperature of the water-containing crumb is preferably 40°C or higher, and more preferably 60°C or higher. For example, by setting the temperature of the water used for washing in the washing device 4 to 60° C. or higher (for example, 70° C.), the temperature of the water-containing crumb when supplied to the screw extruder 5 can be maintained at 60° C. or higher. Alternatively, the water-containing crumb may be heated to a temperature of 40° C. or higher, preferably 60° C. or higher when being transported from the washing device 4 to the screw extruder 5. This makes it possible to effectively carry out the dehydration step and drying step, which are subsequent steps, and to significantly reduce the water content of the finally obtained dried rubber.

The screw extruder 5 shown in FIG. 1 is configured to perform the processes related to the dehydration process and drying process described above. Although a screw type extruder 5 is shown as a preferable example in FIG. 1, a centrifugal separator, a squeezer, etc. may be used as the dehydrator for performing the process related to the dehydration process, and A hot air dryer, a vacuum dryer, an expander dryer, a kneader type dryer, etc. may be used as the dryer.

The screw extruder 5 is configured to mold the dried rubber obtained through the dehydration process and the drying process into a predetermined shape and discharge it. Specifically, the screw type extruder 5 includes a dehydration barrel section 53 that functions as a dehydrator for dehydrating the hydrous crumbs washed by the washing device 4, and a drying barrel section 53 that functions as a dryer for drying the hydrous crumbs. A barrel portion 54 is provided, and a die 59 having a molding function for molding a hydrous crumb is further provided on the downstream side of the screw extruder 5.

The configuration of the screw-type extruder 5 will be described below with reference to FIG. 2. FIG. 2 shows the configuration of a specific example suitable for the screw-type extruder 5 shown in FIG. 1. This screw-type extruder 5 can suitably carry out the above-mentioned dehydration and drying process.

The screw type extruder 5 shown in FIG. 2 is a twin screw type extrusion dryer including a pair of screws (not shown) in a barrel unit 51. The screw extruder 5 has a drive unit 50 that rotationally drives a pair of screws in a barrel unit 51. The drive unit 50 is attached to the upstream end (left end in FIG. 2) of the barrel unit 51. Further, the screw extruder 5 has a die 59 at the downstream end of the barrel unit 51 (the right end in FIG. 2).

The barrel unit 51 extends from the upstream side to the downstream side (from the left side to the right side in FIG. 2) and includes a supply barrel section 52, a dehydration barrel section 53, and a drying barrel section 54.

The supply barrel section 52 includes two supply barrels, namely, a first supply barrel 52a and a second supply barrel 52b.

The dehydration barrel section 53 is composed of three dehydration barrels, namely, a first dehydration barrel 53a, a second dehydration barrel 53b, and a third dehydration barrel 53c.

The drying barrel section 54 is composed of eight drying barrels, namely, a first drying barrel 54a, a second drying barrel 54b, a third drying barrel 54c, a fourth drying barrel 54d, a fifth drying barrel 54e, a sixth drying barrel 54f, a seventh drying barrel 54g, and an eighth drying barrel 54h.

In this way, the barrel unit 51 is composed of 13 divided barrels 52a-52b, 53a-53c, 54a-54h connected from the upstream side to the downstream side.

Further, the screw type extruder 5 individually heats each of the barrels 52a to 52b, 53a to 53c, and 54a to 54h to separate the hydrous crumbs in each barrel 52a to 52b, 53a to 53c, and 54a to 54h to a predetermined level. It has a heating means (not shown) for heating to a certain temperature. The number of heating means corresponds to each barrel 52a to 52b, 53a to 53c, and 54a to 54h. As such a heating means, for example, a configuration is adopted in which high temperature steam is supplied from a steam supply means to a steam distribution jacket formed in each barrel 52a to 52b, 53a to 53c, and 54a to 54h. It is not limited to this. Further, the screw type extruder 5 has a temperature control means (not shown) that controls the set temperature of each heating means corresponding to each barrel 52a to 52b, 53a to 53c, and 54a to 54h.

The number of supply barrels, dewatering barrels, and drying barrels constituting each barrel section 52, 53, and 54 in the barrel unit 51 is not limited to the embodiment shown in FIG. 2, but can be set according to the moisture content of the acrylic rubber hydrous crumbs to be dried, etc.

For example, the number of supply barrels installed in the supply barrel section 52 is, for example, 1 to 3. Further, the number of dehydration barrels installed in the dehydration barrel section 53 is preferably 2 to 10, for example, and more preferably 3 to 6, since water-containing crumbs of sticky acrylic rubber can be efficiently dehydrated. Further, the number of drying barrels installed in the drying barrel section 54 is preferably 2 to 10, and more preferably 3 to 8, for example.

The pair of screws in the barrel unit 51 are rotated by a driving means such as a motor stored in the drive unit 50. The pair of screws extend from the upstream side to the downstream side in the barrel unit 51, and are rotated to transport the wet crumb supplied to the supply barrel section 52 downstream while mixing it. The pair of screws is preferably a twin-shaft intermeshing type in which the peaks and valleys are intermeshed with each other, which can increase the dewatering and drying efficiency of the wet crumb.

The rotation directions of the pair of screws may be the same or different, but from the standpoint of self-cleaning performance, it is preferable that they rotate in the same direction. There are no particular limitations on the screw shape of the pair of screws, and they may have any shape required for each barrel portion 52, 53, 54.

The supply barrel section 52 is an area for supplying water-containing crumbs into the barrel unit 51. The first supply barrel 52a of the supply barrel section 52 has a feed port 55 for supplying hydrous crumb into the barrel unit 51.

The dehydration barrel section 53 is the area where liquid (serum water) containing coagulants and other substances is separated and discharged from the water-containing crumbs.

The first to third dehydration barrels 53a to 53c constituting the dehydration barrel section 53 have dehydration slits 56a, 56b, and 56c, respectively, for discharging moisture from the water-containing crumbs to the outside. A plurality of dewatering slits 56a, 56b, and 56c are formed in each of the dewatering barrels 53a to 53c, respectively.

The slit width, i.e., the mesh size, of each dewatering slit 56a, 56b, 56c may be appropriately selected according to the conditions of use, and is usually set to 0.01 to 5 mm. In order to minimize loss of moist crumb and to enable efficient dewatering of the moist crumb, it is preferably set to 0.1 to 1 mm, and more preferably 0.2 to 0.6 mm.

There are two ways to remove moisture from the water-containing crumbs in each of the dehydration barrels 53a to 53c of the dehydration barrel section 53: removing it in liquid form from the respective dehydration slits 56a, 56b, and 56c, and removing it in vapor form. . In the dehydration barrel section 53 of this embodiment, the case where water is removed in liquid form is defined as waste water, and the case where water is removed in vapor form is defined as exhaust steam.

In the dewatering barrel section 53, it is preferable to combine waste water and exhaust steam because it can efficiently reduce the moisture content of the adhesive acrylic rubber. In the dehydration barrel section 53, which dehydration barrel among the first to third dehydration barrels 53a to 53c is used to perform drainage or exhaust steam may be set as appropriate depending on the purpose of use, but it is usually manufactured. When reducing the amount of ash in the acrylic rubber, it is recommended to increase the number of dewatering barrels for draining water. In that case, for example, as shown in FIG. 2, drainage is performed in the first and second dehydration barrels 53a and 53b on the upstream side, and exhaust steam is performed in the third dehydration barrel 53c on the downstream side. Further, for example, when the dehydration barrel section 53 has four dehydration barrels, it is conceivable that, for example, three dehydration barrels on the upstream side perform drainage, and one dehydration barrel on the downstream side performs exhaust steam. On the other hand, when reducing the water content, it is preferable to increase the number of dehydration barrels for exhausting steam.

As described above in the dehydration and drying process, the set temperature of the dehydration barrel section 53 is usually in the range of 60 to 150°C, preferably 70 to 140°C, and more preferably 80 to 130°C. The set temperature of the dehydration barrel for dehydration in a drained state is usually in the range of 60 to 120°C, preferably 70 to 110°C, and more preferably 80 to 100°C. The set temperature of the dehydration barrel for dehydration in an exhausted steam state is usually in the range of 100 to 150°C, preferably 105 to 140°C, and more preferably 110 to 130°C.

The drying barrel section 54 is an area where the dehydrated hydrous crumbs are dried under reduced pressure. Of the first to eighth drying barrels 54a to 54h that make up the drying barrel section 54, the second drying barrel 54b, the fourth drying barrel 54d, the sixth drying barrel 54f, and the eighth drying barrel 54h each have a vent port 58a, 58b, 58c, and 58d for degassing. Each of the vent ports 58a, 58b, 58c, and 58d is connected to a vent pipe (not shown).

A vacuum pump (not shown) is connected to the end of each vent pipe, and the pressure inside the drying barrel section 54 is reduced to a predetermined level by the operation of the vacuum pump. The screw-type extruder 5 has a pressure control means (not shown) that controls the operation of the vacuum pumps to control the degree of reduced pressure inside the drying barrel section 54.

The degree of pressure reduction in the drying barrel section 54 may be selected as appropriate, but as described above, it is usually set to 1 to 50 kPa, preferably 2 to 30 kPa, and more preferably 3 to 20 kPa.

Further, the set temperature in the drying barrel portion 54 may be selected as appropriate, but as described above, it is usually set at 100 to 250°C, preferably 110 to 200°C, and more preferably 120 to 180°C.

The set temperatures of the drying barrels 54a-54h that make up the drying barrel section 54 may be similar or different, but it is preferable to set the temperature on the downstream side (die 59 side) higher than the temperature on the upstream side (dehydration barrel section 53 side) because this improves drying efficiency.

The die 59 is a metal mold placed at the downstream end of the barrel unit 51, and has an outlet of a predetermined nozzle shape. The acrylic rubber dried in the drying barrel section 54 passes through the outlet of the die 59 and is extruded into a shape that corresponds to the predetermined nozzle shape. In the present invention, the shape of the acrylic rubber passing through the die 59 can be extruded into a sheet shape by making the nozzle shape of the die 59 approximately rectangular. A breaker plate or wire mesh may or may not be provided between the screw and the die 59.

The screw-type extruder 5 according to this embodiment extrudes the water-containing crumbs of the raw acrylic rubber into a sheet-like dried rubber in the following manner.

The hydrous crumbs of acrylic rubber obtained through the washing process are fed from the feed port 55 to the feed barrel section 52. The hydrous crumbs fed to the feed barrel section 52 are sent from the feed barrel section 52 to the dehydration barrel section 53 by the rotation of a pair of screws in the barrel unit 51. In the dehydration barrel section 53, the hydrous crumbs are dehydrated by draining water contained in the hydrous crumbs and exhausting steam from the dehydration slits 56a, 56b, and 56c provided in the first to third dehydration barrels 53a to 53c, as described above.

The hydrous crumbs dehydrated in the dewatering barrel section 53 are sent to the drying barrel section 54 by rotation of a pair of screws in the barrel unit 51. The water-containing crumbs sent to the drying barrel section 54 are plasticized and mixed to become a melt, which generates heat and is conveyed to the downstream side while increasing its temperature. Then, the moisture contained in the molten acrylic rubber vaporizes, and the moisture (steam) is discharged to the outside through vent pipes (not shown) connected to the vent ports 58a, 58b, 58c, and 58d, respectively.

As described above, by passing through the drying barrel section 54, the water-containing crumb is dried and becomes a molten acrylic rubber, which is then fed to the die 59 by the rotation of a pair of screws in the barrel unit 51 and extruded from the die 59 as a sheet of dried rubber.

Here is an example of the operating conditions for the screw-type extruder 5 according to this embodiment.

The rotation speed (N) of the pair of screws in the barrel unit 51 may be appropriately selected depending on various conditions, and is usually set to 10 to 1000 rpm. From the viewpoint of efficiently reducing the water content and gel content of the acrylic rubber sheet, it is preferably set to 50 to 750 rpm, more preferably 100 to 500 rpm, and most preferably 120 to 300 rpm.

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

The cooling device 6 shown in FIG. 1 is configured to cool dried rubber obtained through a dehydration process using a dehydrator and a drying process using a dryer. As the cooling method by the cooling device 6, various methods can be adopted, including an air cooling method using ventilation or air conditioning, a water spraying method where water is sprayed, an immersion method where the device is immersed in water, and the like. Alternatively, the dried rubber may be cooled by leaving it at room temperature.

Hereinafter, as an example of the cooling device 6, a conveying cooling device 60 that cools a sheet-shaped dry rubber 10 formed into a sheet will be described with reference to FIG.

Figure 3 shows the configuration of a conveying type cooling device 60 suitable for the cooling device 6 shown in Figure 1. The conveying type cooling device 60 shown in Figure 3 is configured to cool the sheet-like dry rubber 10 discharged from the discharge port of the die 59 of the screw-type extruder 5 by air cooling while conveying it. By using this conveying type cooling device 60, the sheet-like dry rubber discharged from the screw-type extruder 5 can be appropriately cooled.

The conveying cooling device 60 shown in FIG. 3 is used, for example, by directly connecting it to the die 59 of the screw-type extruder 5 shown in FIG. 2 or by installing it near the die 59.

The conveying cooling device 60 has a conveyor 61 that conveys the sheet-like dried rubber 10 discharged from the die 59 of the screw-type extruder 5 in the direction of arrow A in FIG. 3, and a cooling means 65 that blows cold air onto the sheet-like dried rubber 10 on the conveyor 61.

The conveyor 61 includes rollers 62 and 63, and a conveyor belt 64 that is wound around these rollers 62 and 63 and on which the sheet-like dry rubber 10 is placed. The conveyor 61 is configured to continuously convey the sheet-like dry rubber 10 discharged from the die 59 of the screw extruder 5 onto a conveyor belt 64 to the downstream side (to the right in FIG. 3).

The cooling means 65 is not particularly limited, but has a configuration that can, for example, blow cooling air sent from a cooling air generating means (not shown) onto the surface of the sheet-like dry rubber 10 on the conveyor belt 64. Examples include.

The length L1 of the conveyor 61 and the cooling means 65 of the transport type cooling device 60 (the length of the portion where cooling air can be blown) is not particularly limited, but is, for example, 10 to 100 m, preferably 20 to 50 m. . Further, the conveyance speed of the sheet-like dry rubber 10 in the conveyance type cooling device 60 is determined by the length L1 of the conveyor 61 and the cooling means 65, the discharge speed of the sheet-like dry rubber 10 discharged from the die 59 of the screw extruder 5, It may be adjusted as appropriate depending on the target cooling rate, cooling time, etc., and is, for example, 10 to 100 m/hr, more preferably 15 to 70 m/hr.

According to the conveying type cooling device 60 shown in FIG. 3, the sheet-like dry rubber 10 discharged from the die 59 of the screw-type extruder 5 is conveyed by a conveyor 61 while cooling air is blown from a cooling means 65 onto the sheet-like dry rubber 10, thereby cooling the sheet-like dry rubber 10.

Note that the transport cooling device 60 is not particularly limited to a configuration including one conveyor 61 and one cooling means 65 as shown in FIG. 3, and may include two or more conveyors 61 and two or more corresponding It is also possible to have a configuration including a cooling means 65. In that case, the total length of each of the two or more conveyors 61 and the cooling means 65 may be within the above range.

The baling device 7 shown in FIG. 1 is configured to process the dried rubber extruded from the screw-type extruder 5 and cooled in the cooling device 6 to produce a bale, which is a single block. There are no particular limitations on the weight or shape of the acrylic rubber bales produced by the baling device 7, but for example, an approximately rectangular shaped acrylic rubber bale weighing about 20 kg is produced.

Further, the sheet-like dry rubber 10 produced by the screw extruder 5 may be laminated to produce an acrylic rubber veil. For example, a cutting mechanism for cutting the sheet-like dry rubber 10 may be provided in the baling device 7 disposed downstream of the transport type cooling device 60 shown in FIG. 3 . Specifically, the cutting mechanism of the baling device 7 continuously cuts the cooled dry rubber sheet 10 at predetermined intervals to process it into cut dry rubber sheets 16 of a predetermined size. It is configured as follows. By laminating a plurality of cut sheet-like dry rubber 16 cut into a predetermined size by a cutting mechanism, an acrylic rubber veil in which cut sheet-like dry rubber 16 is laminated can be manufactured.

When manufacturing an acrylic rubber veil in which cut sheet-like dry rubber 16 is laminated, it is preferable to laminate cut sheet-like dry rubber 16 at a temperature of 40° C. or higher, for example. By laminating the cut sheet-like dry rubber 16 at 40° C. or higher, good air release is achieved through further cooling and compression by its own weight.

The present invention will be explained in more detail below by giving Examples and Comparative Examples. In addition, "parts", "%" and "ratio" in each example are based on weight unless otherwise specified.

Various physical properties were evaluated according to the following methods.

[Monomer composition]
Regarding the monomer composition in acrylic rubber, the monomer composition of each monomer unit in acrylic rubber was confirmed by H-NMR, and it was confirmed that the activity of the reactive group remained in the acrylic rubber and its various reactions. The content of functional groups was confirmed by the following test method.
Moreover, the content ratio of each monomer unit in the acrylic rubber was calculated from the amount used in the polymerization reaction of each monomer and the polymerization conversion rate. Specifically, the polymerization reaction was an emulsion polymerization reaction, and the polymerization conversion rate was approximately 100%, with no unreacted monomers being observed. The amount used was the same as the amount used by the body.

[Reactive group content]
The reactive group content of the acrylic rubber was measured in the acrylic rubber sheet or acrylic rubber veil by the following method.
(1) The amount of carboxyl groups was calculated by dissolving an acrylic rubber sheet or acrylic rubber veil in acetone and performing potentiometric titration with a potassium hydroxide solution.
(2) The amount of epoxy groups was calculated by dissolving an acrylic rubber sheet or acrylic rubber veil in methyl ethyl ketone, adding a specified amount of hydrochloric acid to react with the epoxy groups, and titrating the amount of residual hydrochloric acid with potassium hydroxide.
(3) The amount of chlorine was calculated by completely burning an acrylic rubber sheet or an acrylic rubber veil in a combustion flask, absorbing the chlorine generated in water, and titrating it with silver nitrate.

[Anti-aging agent content]
The antioxidant content (%) in an acrylic rubber sheet or acrylic rubber veil is determined by dissolving the acrylic rubber sheet or acrylic rubber veil in tetrahydrofuran and performing gel permeation chromatography (GPC) measurement. Calculated based on the calibration curve.

[Ash content]
The ash content (%) in the acrylic rubber sheet or acrylic rubber veil was measured in accordance with JIS K6228 Method A.

[Ash content]
The amount (ppm) of each component in the acrylic rubber sheet or acrylic rubber veil ash was measured by pressing the ash sampled after the above-mentioned ash content measurement onto a titration filter paper of Φ20 mm and subjecting it to XRF measurement using a ZSX Primus (manufactured by Rigaku Corporation).

[Gel amount]
The gel amount (%) of the acrylic rubber sheet or acrylic rubber veil is the amount of insoluble matter in methyl ethyl ketone, and was determined by the following method.
Weigh approximately 0.2 g (Xg) of an acrylic rubber sheet or acrylic rubber veil, immerse it in 100 ml of methyl ethyl ketone, and leave it for 24 hours at room temperature.Then, use an 80-mesh wire mesh to filter out the insoluble matter in methyl ethyl ketone. The dry solid content (Yg) obtained by evaporating and solidifying the filtrate in which only the rubber component soluble in methyl ethyl ketone was dissolved was weighed and calculated using the following formula.

Gel volume (%) = 100 x (X-Y)/X

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

[Glass transition temperature (Tg)]
The glass transition temperature (Tg) of the acrylic rubber was measured using a differential scanning calorimeter (DSC, product name "X-DSC7000", manufactured by Hitachi High-Tech Science).

[pH]
The pH of the acrylic rubber sheet or acrylic rubber veil was measured with a pH electrode after dissolving 6 g (±0.05 g) of acrylic rubber in 100 g of tetrahydrofuran, adding 2.0 ml of distilled water, and confirming complete dissolution.

[Moisture content]
The water content (%) of the acrylic rubber sheet or acrylic rubber veil was measured in accordance with JIS K6238-1: Oven A (volatile matter measurement) method.

[Molecular weight and molecular weight distribution]
The weight average molecular weight (Mw) and molecular weight distribution (Mz/Mw) of the acrylic rubber are absolute molecular weight and absolute molecular weight distribution measured by the GPC-MALS method using a solution in which lithium chloride was added to dimethylformamide at a concentration of 0.05 mol/L and 37% concentrated hydrochloric acid was added at a concentration of 0.01%. Specifically, a multi-angle laser light scattering photometer (MALS) and a differential refractometer (RI) were incorporated into a GPC (Gel Permeation Chromatography) device, and the light scattering intensity and refractive index difference of the molecular chain solution size-fractionated by the GPC device were measured over the elution time, thereby sequentially calculating and determining the molecular weight of the solute and its content. The measurement conditions and method using the GPC device are as follows.
Column: 2 TSKgel α-M (φ7.8 mm × 30 cm, Tosoh Corporation)
Column temperature: 40°C
Flow rate: 0.8 ml/mm
Sample preparation: 5 ml of solvent was added to 10 mg of sample, and the mixture was gently stirred at room temperature (dissolution was visually confirmed), followed by filtration using a 0.5 μm filter.

[Complex viscosity]
The complex viscosity η of the acrylic rubber sheet or acrylic rubber veil was measured at each temperature by measuring the temperature dispersion (40 to 120°C) at a strain of 473% and 1 Hz using a dynamic viscoelasticity measuring device "Rubber Process Analyzer RPA-2000" (manufactured by Alpha Technology Co., Ltd.). Here, the dynamic viscoelasticity at 60°C of the above-mentioned dynamic viscoelasticity was taken as the complex viscosity η(60°C), and the dynamic viscoelasticity at 100°C was taken as the complex viscosity η(100°C), and the values of η(100°C)/η(60°C) and η(60°C)/η(100°C) were calculated.

[Storage stability evaluation]
The storage stability of the rubber sample was determined by placing the rubber mixture of the rubber sample in a constant temperature and humidity chamber at 45°C x 80% RH for 7 days, and using the rubber sample before and after the test as the rubber mixture in a rubber vulcanization tester (moving die rheometer MDR; A crosslinking test was conducted at 180°C for 10 minutes using a 100% polyester resin (manufactured by Alpha Technology), and the rate of change in crosslinking density, which is the difference between the maximum torque (MH) and the minimum torque (ML) (MH-ML), was calculated and compared. Evaluation was made using an index setting Example 1 as 100 (the smaller the index, the better the storage stability).

[Workability evaluation]
The processability of the rubber sample was determined by putting the rubber sample into a Banbury mixer heated to 50°C, masticating it for 1 minute, and then adding compounding agent A of the rubber mixture formulation listed in Table 2 to form the first stage rubber mixture. The time required for integration to show the maximum torque value, that is, BIT (Black Incorporation Time), was measured and evaluated using an index with Comparative Example 1 set as 100 (the smaller the index, the better the workability).

[Normal physical property evaluation]
The normal physical properties of the rubber sample were evaluated by measuring the breaking strength, 100% tensile stress, and breaking elongation of the rubber crosslinked product of the rubber sample according to JIS K6251 using the following criteria.
(1) Breaking strength was evaluated as ◎ if it was 10 MPa or more, and × if it was less than 10 MPa.
(2) 100% tensile stress was evaluated as ◎ for 5 MPa or more and × for less than 5 MPa.
(3) The elongation at break was evaluated as ◎ when 150% or more and as × when less than 150%.

[Adjustment of anti-aging agent-containing emulsion]
The antiaging agent-containing emulsion to be added to the emulsion polymerization solution after emulsion polymerization is prepared by adding a predetermined amount of water at a predetermined temperature and a predetermined amount to an adjustment tank with stirring blades, and adding a predetermined amount of emulsifier while stirring, based on the conditions listed in Table 1. Next, add 1 part of anti-aging agent to the emulsion, stir for 2 hours, then measure the pH. If the pH is not within the range of 3 to 6, adjust it within the range with sulfuric acid or sodium hydroxide. It was adjusted and made to fit. The entire amount of the prepared antiaging agent-containing emulsion was added to the emulsion polymerization solution after emulsion polymerization.

[Example 1]
In a mixing container equipped with a homomixer, 46 parts of pure water, 74.5 parts of ethyl acrylate, 17 parts of n-butyl acrylate, 7 parts of methoxyethyl acrylate, and 1.5 parts of mono-n-butyl fumarate. 1.8 parts of octyloxydioxyethylene phosphate sodium salt was added as an emulsifier and stirred to obtain a monomer emulsion.

Next, 170 parts of pure water and 3 parts of the monomer emulsion obtained above were charged into a polymerization reaction tank equipped with a thermometer and a stirring device, and the mixture was cooled to 12° C. under a nitrogen stream. Next, the remainder of the monomer emulsion, 0.00033 parts of ferrous sulfate, 0.264 parts of sodium ascorbate, and 0.22 parts of potassium persulfate were continuously added dropwise into the polymerization reaction tank over 3 hours. . After that, the reaction was continued while maintaining the temperature inside the polymerization reaction at 23℃, and after confirming that the polymerization conversion rate had reached approximately 100%, hydroquinone was added as a polymerization terminator to stop the polymerization reaction. Then, anti-aging emulsion 1 of the anti-aging agent (IRG1076) listed in Table 1 prepared previously as an anti-aging agent-containing emulsion was added to obtain an anti-aging emulsion polymerization solution containing an anti-aging agent.

The above anti-aging agent was added to a 2% aqueous magnesium sulfate solution (coagulation liquid) heated to 80°C and vigorously stirred (600 rotations: circumferential speed 3.1 m/s) in a coagulation tank equipped with a thermometer and a stirring device. The added emulsion polymerization solution was heated to 80° C. and added continuously to coagulate the polymer, which was then filtered to obtain water-containing crumb.

Next, 194 parts of warm water (70°C) was added to the coagulation tank and stirred for 15 minutes, after which the water was drained off, and 194 parts of warm water (70°C) was added again and stirred for 15 minutes to wash the wet crumbs. The washed wet crumbs (wet crumb temperature 65°C) were fed to a screw-type extruder, dehydrated and dried, and extruded into a sheet-like dry rubber with a width of 300 mm and a thickness of 10 mm. The sheet-like dry rubber was then cooled at a cooling rate of 200°C/hr using a conveying cooling device directly connected to the screw-type extruder.

The screw-type extruder used in this Example 1 is composed of one supply barrel, three dehydration barrels (first to third dehydration barrels), and five drying barrels (first to fifth drying barrels). The first and second dehydration barrels discharge water, and the third dehydration barrel discharges steam. The operating conditions of the screw-type extruder were as follows:

Water Content:
Moisture content of wet crumbs after draining in the second dewatering barrel: 20%
Moisture content of the wet crumb after steaming in the third dewatering barrel: 10%
Moisture content of the wet crumbs after drying in the fifth drying barrel: 0.4%
Rubber Temperature:
Temperature of the wet crumbs fed into the first feed barrel: 65° C.
Temperature of rubber discharged from the screw extruder: 140°C
Set temperature for each barrel:
First dehydration barrel: 90°C
Second dehydration barrel: 100° C.
Third dehydration barrel: 120°C
First drying barrel: 120° C.
Second drying barrel: 130° C.
Third drying barrel: 140° C.
Fourth drying barrel: 160° C.
Fifth drying barrel: 180° C.
Operating conditions:
Diameter of the screw in the barrel unit (D): 132 mm
Total length of the screw in the barrel unit (L): 4620 mm
・L/D: 35
・Rotation speed of the screw in the barrel unit: 135 rpm
・Rubber extrusion rate from die: 700 kg/hr
・Die resin pressure: 2 MPa

The extruded sheet-like dried rubber was cooled to 50°C and then cut with a cutter to obtain an acrylic rubber sheet (A). The reactive group content, ash content, ash component content, specific gravity, gel content, glass transition temperature (Tg), pH, antioxidant content, water content, molecular weight, molecular weight distribution, and complex viscosity of the obtained acrylic rubber sheet (A) were measured and are shown in Tables 3-1 and 3-2.

The obtained acrylic rubber sheet (A) was laminated to obtain 20 parts (20 kg) before the temperature fell below 40°C to obtain an acrylic rubber veil (A). The reactive group content, ash content, ash component content, specific gravity, gel content, glass transition temperature (Tg), pH, antioxidant content, water content, molecular weight, molecular weight distribution, and complex viscosity of the obtained acrylic rubber veil (A) were measured.

Next, 100 parts of the acrylic rubber sheet (A) and compounding agent A of "Compound 1" in Table 2 were added using a Banbury mixer and mixed at 50°C for 5 minutes. At this point, a processability evaluation was performed and the results are shown in Table 3-2. Next, the resulting mixture was transferred to a roll at 50°C, and compounding agent B of "Compound 1" in Table 2 was blended and mixed to obtain a rubber mixture. At this point, a storage stability evaluation was performed and the results are shown in Table 3-2. The crosslinking (vulcanization) conditions were 10 minutes at 180°C for the primary vulcanization and 2 hours at 180°C for the secondary vulcanization.

The obtained rubber mixture was put into a mold measuring 15 cm long, 15 cm wide and 0.2 cm deep, and pressed at 180° C. for 10 minutes while applying a press pressure of 10 MPa for primary crosslinking. The crosslinked product was further heated in a gear type oven at 180° C. for 2 hours to cause secondary crosslinking, thereby obtaining a sheet-like crosslinked rubber product. Then, a test piece of 3 cm x 2 cm x 0.2 cm was cut out from the obtained sheet-like crosslinked rubber product and its normal physical properties were evaluated, and the results are shown in Tables 3-1 and 3-2.

[Example 2]
The same procedure as in Example 1 was repeated except that the monomer components were changed to 4.5 parts of ethyl acrylate, 64.5 parts of n-butyl acrylate, 29.5 parts of methoxyethyl acrylate, and 1.5 parts of mono n-butyl fumarate, the emulsifier was changed to nonylphenyloxyhexaoxyethylene phosphate sodium salt, and the antioxidant-containing emulsion was changed to antioxidant emulsion 2. An acrylic rubber sheet (B) and an acrylic rubber veil (B) were obtained and their properties were evaluated. The results for the acrylic rubber sheet (B) are shown in Tables 3-1 and 3-2.

[Example 3]
The monomer components were added to 48.25 parts of ethyl acrylate, 50 parts of n-butyl acrylate, and 1.75 parts of mono-n-butyl fumarate, the emulsifier was added to tridecyloxyhexoxyethylene phosphate sodium salt, and Acrylic rubber sheet (C) and acrylic rubber veil (C) were obtained in the same manner as in Example 1 except that the anti-aging agent-containing emulsion was changed to anti-aging emulsion 3. ) was evaluated. The results for the acrylic rubber sheet (C) are shown in Tables 3-1 and 3-2.

[Example 4]
The temperature of the first dehydration barrel of the screw type extruder was changed to 100°C and the temperature of the second dehydration barrel was changed to 120°C so that drainage was performed only in the first dehydration barrel, and An acrylic rubber sheet (D) and an acrylic rubber veil (D) were obtained in the same manner as in Example 3, except that the water content of the water-containing crumb after drainage was changed to 30%, and their properties were evaluated. The results for the acrylic rubber sheet (D) are shown in Tables 3-1 and 3-2.

[Example 5]
The same procedure as in Example 4 was carried out 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 an acrylic rubber sheet (E) and an acrylic rubber veil (E) were obtained and their properties were evaluated (the compounding ingredients were changed to "Compound 3"). The results for the acrylic rubber sheet (E) are shown in Tables 3-1 and 3-2.

[Example 6]
The same procedure as in Example 4 was carried out 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 chloroacetate, and an acrylic rubber sheet (F) and an acrylic rubber veil (F) were obtained and their properties were evaluated (the compounding ingredients were changed to "Compound 4"). The results for the acrylic rubber sheet (F) are shown in Tables 3-1 and 3-2.

[Example 7]
An acrylic rubber sheet (G) and an acrylic rubber veil (G) were obtained in the same manner as in Example 6, except that the anti-aging emulsion was changed to anti-aging emulsion 4, and their properties were evaluated. The results for the acrylic rubber sheet (G) are shown in Tables 3-1 and 3-2.

[Example 8]
An acrylic rubber sheet (H) and an acrylic rubber veil (H) were obtained in the same manner as in Example 6 except that the anti-aging emulsion was changed to anti-aging emulsion 5, and their properties were evaluated. The results for the acrylic rubber sheet (H) are shown in Tables 3-1 and 3-2.

[Comparative example 1]
In a mixing container equipped with a homomixer, 46 parts of pure water, 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 chloroacetate. 0.709 parts of sodium lauryl sulfate and 1.82 parts of polyoxyethylene dodecyl ether (molecular weight 1500) were added as emulsifiers and stirred to obtain a monomer emulsion.

Next, 170 parts of pure water and 3 parts of the monomer emulsion obtained above were added to a polymerization reaction tank equipped with a thermometer and a stirrer, and cooled to 12°C under a nitrogen stream. Next, the remaining part of the monomer emulsion, 0.00033 parts of ferrous sulfate, 0.264 parts of sodium ascorbate, and 0.22 parts of potassium persulfate were continuously dropped into the polymerization reaction tank over a period of 3 hours. Thereafter, the reaction was continued while maintaining the temperature inside the polymerization reaction at 23°C, and it was confirmed that the polymerization conversion rate had reached approximately 100%, and the polymerization reaction was terminated by adding hydroquinone as a polymerization terminator, and the anti-aging emulsion 6 listed in Table 1 was added as an anti-aging agent-containing emulsion to obtain an emulsion polymerization liquid containing an anti-aging agent.

Next, the emulsion polymerization solution was heated to 80° C., and then a 0.7% aqueous sodium sulfate solution (coagulation solution) was continuously added to coagulate the polymer, which was then filtered to obtain a hydrous crumb. 194 parts of industrial water was added to 100 parts of the obtained water-containing crumb, and the mixture was stirred at 25°C for 5 minutes. The water-containing crumb was washed four times by draining water from the coagulation tank, and then 194 parts of sulfuric acid aqueous solution with a pH of 3 was added. After adding 194 parts of pure water and stirring at 25°C for 5 minutes, draining water from the coagulation tank and washing with acid once, add 194 parts of pure water and washing with pure water once, and then stir at 25°C for 5 minutes. The mixture was dried in a hot air dryer to obtain crumb-like acrylic rubber (I) with a water content of 0.4% by weight. The properties of the obtained crumb-like acrylic rubber (I) were evaluated and shown in Tables 3-1 and 3-2.

[Comparative example 2]
A crumb-like acrylic rubber (J) was obtained in the same manner as in Comparative Example 1, except that the anti-aging emulsion was changed to anti-aging emulsion 7 shown in Table 1. The properties of the obtained crumb-like acrylic rubber (J) were evaluated and shown in Tables 3-1 and 3-2.

Tables 3-1 and 3-2 show that the acrylic rubber of the present invention is made of reactive group-containing acrylic rubber, contains a hindered anti-aging agent, has a gel content of methyl ethyl ketone insoluble matter of 50% by weight or less, and has a pH of 6 or less. It can be seen that the acrylic rubber sheets (A) to (H) have significantly superior storage stability and processability, as well as excellent strength properties (Examples 1 to 8).

As for storage stability, since the antioxidant content of the acrylic rubber sheets (A) to (H) is the same as that of the crumb-like acrylic rubber (I), it is believed that the difference in the storage stability effect is due to the phenol-based antioxidant being uniformly and finely dispersed within the acrylic rubber sheets (A) to (H) (comparison between Examples 1 to 8 and Comparative Example 1). In addition, after the storage stability test, no change in color was observed in the acrylic rubber sheet of the present invention, but the crumb-like acrylic rubbers (I) to (J) were yellowed.

Tables 3-1 and 3-2 also show that the acrylic rubber sheets (A) to (H) of the present invention can prevent phenolic aging by adding water and an emulsifier to the phenolic antiaging agent added to the emulsion polymerization solution. By making an emulsion containing a phenolic anti-aging agent, and making the emulsifier concentration of the emulsion containing a phenolic anti-aging agent above a certain level, and making the water temperature at the time of emulsion preparation above a certain level or above the melting point of the phenolic anti-aging agent, storage stability can be significantly improved. (Comparison between Examples 1 to 7 and Example 8).

In terms of processability, in this invention, the polymerization conversion rate of emulsion polymerization is increased to improve strength properties, but as the polymerization conversion rate is increased, the amount of gel from the methyl ethyl ketone insoluble components increases rapidly, worsening the processability of the acrylic rubber. However, by drying to a state where there is essentially no moisture (water content less than 1%) in the screw-type extruder and then melt-kneading the dried rubber, the rapidly increasing gel from the methyl ethyl ketone insoluble components disappears. However, it is difficult to make acrylic rubber, which has a large specific heat and reactive groups, essentially moisture-free, and this can be achieved by adjusting the temperature of the water-containing crumbs fed in and the various conditions of the screw-type extruder, as shown in the examples.

From Tables 3-1 and 3-2, it can be seen that the acrylic rubber sheets (A) to (H) which further contain a phenolic antioxidant with a specific melting point and have specific gravity, gel amount, glass transition temperature (Tg), pH, antioxidant content, water content, weight average molecular weight (Mw), ratio of z-average molecular weight (Mz) to weight average molecular weight (Mw) (Mz/Mw), complex viscosity at 100°C η (100°C), complex viscosity at 60°C η (60°C), and ratio of complex viscosity at 100°C to 60°C (η100°C/η60°C) within specific ranges, have excellent storage stability, processability, and normal physical properties including strength properties (Examples 1 to 8).

In addition, the evaluated characteristic values of the acrylic rubber veils (A) to (H) of the present invention in which the acrylic rubber sheets (A) to (H) are laminated are the same as the characteristic values of each of the laminated acrylic rubber sheets. Met.

1 Acrylic rubber manufacturing system 3 Coagulation device 4 Cleaning device 5 Screw extruder 6 Cooling device 7 Baling device

Claims (19)

a monomer composition of 70 to 99.9% by weight of bonding units derived from at least one (meth)acrylic ester selected from the group consisting of (meth)acrylic acid alkyl esters and (meth)acrylic acid alkoxyalkyl esters; A hindered anti-aging agent made of acrylic rubber consisting of 0.1 to 20% by weight of bonding units derived from reactive group-containing monomers and 0 to 30% by weight of bonding units derived from other monomers , and having a melting point of 90°C or less. An acrylic rubber sheet containing 0.001 to 15% by weight of methyl ethyl ketone, a gel amount of methyl ethyl ketone insoluble matter of 10 % by weight or less, and a pH of 2 to 6 . The acrylic rubber sheet according to claim 1, wherein the amount of acrylic rubber in the acrylic rubber sheet is 85% by weight or more. The acrylic rubber sheet according to claim 1 or 2, wherein the ash content is 1% by weight or less. The acrylic rubber according to claim 3, wherein the ash contains at least one element selected from the group consisting of sodium, sulfur, calcium, magnesium, and phosphorus , and the total content of these elements is 70% by weight or more of the total ash content. sheet. The acrylic rubber sheet according to any one of claims 1 to 4, wherein the acrylic rubber sheet is a melt-kneaded sheet. The acrylic rubber sheet according to any one of claims 1 to 5, wherein the hindered anti-aging agent is a hindered phenol-based anti-aging agent. The acrylic rubber sheet according to any one of claims 1 to 6, which has a complex viscosity ([η] 100°C) at 100°C in the range of 1500 to 6000 Pa·s. The ratio of the complex viscosity at 100°C ([η] 100°C) to the complex viscosity at 60°C ([η] 60°C) ([η] 100°C/[η] 60°C) is 0.5 or more. The acrylic rubber sheet according to any one of claims 1 to 7. The acrylic rubber sheet according to any one of claims 1 to 8, in which the ratio ([η]100°C/[η]60°C) of the complex viscosity at 100°C ([η]100°C) to the complex viscosity at 60°C ([η]60°C) is 0.8 or more. The weight average molecular weight (Mw) is 100,000 to 5,000,000, and the ratio of z average molecular weight (Mz) to weight average molecular weight (Mw) (Mz/Mw) is 1.3 or more. 9. The acrylic rubber sheet according to any one of Item 9. The acrylic rubber sheet according to any one of claims 1 to 10, which has a specific gravity of 0.7 or more. an emulsion polymerization step of emulsifying a monomer component consisting of 70 to 99.9% by weight of at least one (meth)acrylic acid ester selected from the group consisting of (meth)acrylic acid alkyl esters and (meth)acrylic acid alkoxyalkyl esters, 0.1 to 20% by weight of a reactive group-containing monomer, and 0 to 30% by weight of other monomers with water and an emulsifier, and emulsion-polymerizing the resulting monomer component in the presence of a polymerization initiator to obtain an emulsion polymerization liquid;
an antioxidant addition step of adding a hindered antioxidant having a melting point of 90° C. or less to the obtained emulsion polymerization liquid in a ratio of 0.001 to 15 parts by weight per 100 parts by weight of the monomer component ;
a coagulation step of adding the emulsion polymerization liquid containing the antioxidant to a coagulation liquid being stirred to produce water-containing crumbs;
A washing step of washing the produced hydrous crumbs;
A dehydration, drying and molding process in which the washed water-containing crumbs having a temperature of 40°C or higher are melt-kneaded in a screw-type extruder equipped with a dehydration barrel having a dehydration slit, a drying barrel for drying under reduced pressure, and a die at the tip, and extruded as a sheet-like dry rubber having a water content of less than 1% by weight;
A method for producing an acrylic rubber sheet comprising the steps of: 13. The method for producing an acrylic rubber sheet according to claim 12, wherein the hindered anti-aging agent is added to the emulsion polymerization solution as a hindered anti-aging agent-containing emulsion obtained by emulsifying warm water and an emulsifier. The method for producing an acrylic rubber sheet according to claim 12 or 13, wherein the emulsifier concentration of the hindered antioxidant-containing emulsion is 1% by weight or more. An acrylic rubber veil formed by laminating the acrylic rubber sheets according to any one of claims 1 to 11. A rubber mixture obtained by mixing the acrylic rubber sheet according to any one of claims 1 to 11 or the acrylic rubber veil according to claim 15 with a filler and a crosslinking agent. A method for producing a rubber mixture, comprising mixing a filler and a crosslinking agent into the acrylic rubber sheet according to any one of claims 1 to 11 or the acrylic rubber veil according to claim 15 using a mixer. A method for producing a rubber mixture, which comprises mixing the acrylic rubber sheet according to any one of claims 1 to 11 or the acrylic rubber veil according to claim 15 with a filler and then mixing a crosslinking agent. A crosslinked rubber product obtained by crosslinking the rubber mixture according to claim 16.
A crosslinked rubber product made by crosslinking.