CN116157424A

CN116157424A - Acrylic rubber excellent in injection moldability

Info

Publication number: CN116157424A
Application number: CN202180056584.2A
Authority: CN
Inventors: 增田浩文; 川中孝文
Original assignee: Zeon Corp
Current assignee: Zeon Corp
Priority date: 2020-06-23
Filing date: 2021-06-04
Publication date: 2023-05-23
Also published as: CN116057073A; WO2021261216A1; KR20230027027A; JPWO2021261212A1; WO2021261212A1; JPWO2021261215A1; JPWO2021261216A1; CN116034118A; KR20230027021A; KR20230026335A; CN116113646A; WO2021261214A1; WO2021261215A1; KR20230027044A; JPWO2021261214A1

Abstract

The invention provides an acrylic rubber with excellent injection moldability. The acrylic rubber of the present invention comprises a binding unit derived from at least one (meth) acrylic acid ester selected from the group consisting of alkyl (meth) acrylates and alkoxyalkyl (meth) acrylates, a binding unit derived from an ion-reactive group-containing monomer, and a binding unit derived from another monomer which is optionally used, and has a weight average molecular weight (Mw) of 100 to 500 tens of thousands, a ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of 1.5 to 3, an ash content of 0.3 wt% or less, and a total amount of sodium, sulfur, calcium, magnesium, and phosphorus in the ash content of 80 wt% or more.

Description

Acrylic rubber excellent in injection moldability

Technical Field

The present invention relates to an acrylic rubber, a method for producing the same, a rubber composition and a rubber crosslinked product, and more particularly, to an acrylic rubber excellent in injection moldability, strength characteristics, compression set resistance and water resistance, a method for producing the same, a rubber composition comprising the same and a rubber crosslinked product obtained by crosslinking the same.

Background

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

For example, patent document 1 (japanese patent application laid-open No. 11-12427) discloses an acrylic rubber and a crosslinked composition excellent in extrusion processability and scorch characteristics, which are obtained by adding 100 parts of a monomer component containing a monomer having a carbon-carbon double bond introduced into a side chain such as ethyl acrylate, butyl acrylate, methoxyethyl acrylate, acrylonitrile, and allyl methacrylate, cyclopenteneoxyethyl acrylate, 4 parts of sodium lauryl sulfate, 0.25 part of a terpene hydroperoxide as an organic radical generator, 0.01 part of ferrous sulfate, 0.025 part of sodium ethylenediamine tetraacetate, 0.04 part of sodium formaldehyde sulfoxylate, and 0.01 to 0.05 part of tertiary dodecyl mercaptan as a chain transfer agent to an autoclave replaced with nitrogen, allowing the reaction temperature of 30 degrees to reach 100%, adding the obtained latex to a 0.25% aqueous potassium chloride solution, allowing the obtained latex to solidify, sufficiently washing the solidified product, drying the solidified product at about 90 ℃ for 3 hours, and crosslinking the crosslinked composition with 1, 3-bis (tert-butyl) benzene peroxide. However, the acrylic rubber obtained by the method has problems of insufficient injection moldability and Banbury processability, and also has problems of poor storage stability, compression set resistance, water resistance and strength characteristics.

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

Further, patent document 3 (pamphlet of international publication No. 2019/188709) discloses a method for producing an acrylic rubber, in which a monomer component composed of ethyl acrylate, butyl acrylate, methoxyethyl acrylate and monobutyl fumarate, water and sodium lauryl sulfate are added, deaeration under reduced pressure and nitrogen substitution are repeated, then, sodium formaldehyde sulfoxylate and cumene hydroperoxide as an organic radical generator are added, emulsion polymerization is initiated at normal pressure and normal temperature, emulsion polymerization is performed until the polymerization conversion reaches 95% by weight, and then, the resultant is coagulated with a calcium chloride aqueous solution, and dehydrated and dried by an extrusion dryer having a screw, to produce an acrylic rubber. However, the acrylic rubber obtained by this method has problems of poor injection moldability, storage stability, and water resistance.

Further, patent document 4 (pamphlet of international publication No. 2018/117037) discloses a method for producing an acrylic rubber as follows: adding monomer components composed of ethyl acrylate and mono-n-butyl fumarate, water and sodium dodecyl sulfate, carrying out reduced pressure degassing and nitrogen substitution for 3 times, fully removing oxygen, adding azobis (isobutyronitrile) and ethyl-2-methyl-2-phenyl tellurium (phenyl-nilanyl) propionate which are organic free radical generating agents, initiating polymerization reaction at normal pressure and 50 ℃, carrying out polymerization until the polymerization conversion rate reaches 89%, solidifying by using a calcium chloride solution, washing with water, and drying to prepare the acrylic rubber. However, the acrylic rubber obtained by this method has problems of poor injection moldability, banbury processability, storage stability, and water resistance.

On the other hand, as a method for producing an acrylic rubber using an inorganic radical generator, for example, patent document 5 (japanese unexamined patent publication No. 2019-119772) discloses a method in which a monomer component composed of ethyl acrylate, butyl acrylate, methoxyethyl acrylate and monobutyl maleate is made into a monomer emulsion using pure water and sodium lauryl sulfate and polyoxyethylene lauryl ether as emulsifiers, then a part of the monomer emulsion is put into a polymerization reaction tank, cooled to 12 ℃ under a nitrogen gas stream, then the remaining part of the monomer emulsion, ferrous sulfate, sodium ascorbate and an aqueous potassium persulfate solution as an inorganic radical generator are continuously added dropwise over 3 hours, then kept at 23 ℃ and continuously subjected to emulsion polymerization for 1 hour, after a polymerization conversion rate reaches 97 wt%, then sodium sulfate is continuously added, thereby setting and filtering to obtain an aqueous pellet, and after 4 times of water washing, 1 time of water washing, a sheet-like acrylic rubber is continuously produced by a screw extruder, a aliphatic diamine amide polyamine compound is crosslinked. However, the sheet-like acrylic rubber obtained by the present method has problems such as poor injection moldability and storage stability, and poor water resistance of the crosslinked product.

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

Patent document 7 (japanese patent application laid-open No. 62-64809) discloses a vulcanizable acrylic rubber characterized in that: is prepared from at least one of alkyl acrylate and alkoxyalkyl acrylate (50-99.9 wt.%), unsaturated carboxylic acid (0.1-20 wt.%), dihydro-dicyclopentenyl ester (0-20 wt.%), and other monovinyl or monovinylidene (vinyiidenecH) ₂ A copolymer comprising a monomer composed of at least one of a 1, 2-vinylidene (vinyl-ch=ch-) based unsaturated compound, wherein the copolymer has a polystyrene-equivalent number average molecular weight (Mn) of 20 to 120 ten thousand and a ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of 10 or less, using tetrahydrofuran as an eluting solvent. As specific examples thereof, disclosed is an acrylic rubber comprising, as variables, a monomer component comprising ethyl acrylate, a radical-crosslinkable dihydrodicyclopentenyl acrylate or the like, sodium lauryl sulfate as an emulsifier, potassium persulfate as an inorganic radical generator, and octyl thioacetate and t-dodecyl mercaptan as a molecular weight regulatorThe number average molecular weight (Mn) is 53 to 115 ten thousand, the weight average molecular weight (Mw) is 354 to 626 ten thousand, and the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is 4.7 to 8. Further, it is shown in examples and comparative examples that when the amount of the chain transfer agent is small, the number average molecular weight (Mn) is as large as 500 ten thousand, the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is as narrow as 1.4, and when the amount of the chain transfer agent is large, the number average molecular weight (Mn) is as small as 20 ten thousand, the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) becomes very wide, reaching 17. However, the acrylic rubber obtained by the present method has the following problems: poor injection moldability, and the use of 100kg/cm after mixing with rolls in the crosslinking reaction with sulfur and a vulcanization accelerator as crosslinking agents ² The vulcanization press of (2) is carried out at 170℃for 15 minutes and further in a Gill oven at 175℃for 4 hours, and the resulting crosslinked product has problems such as poor water resistance, compression set resistance and strength characteristics, and poor physical property change after thermal degradation.

Prior art literature

Patent literature

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

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

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

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

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

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

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

Disclosure of Invention

Problems to be solved by the invention

The present invention has been made in view of the actual circumstances of the prior art, and an object thereof is to provide an acrylic rubber excellent in injection moldability, water resistance, compression set resistance and strength characteristics, a method for producing the same, a rubber composition comprising the acrylic rubber, and a crosslinked rubber product obtained by crosslinking the same.

Solution for solving the problem

The present inventors have made intensive studies in view of the above problems, and as a result, have found that an acrylic rubber comprising a specific monomer component containing an ion-reactive group-containing monomer, having a weight average molecular weight (Mw) and a ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) within specific ranges and having an ash content and an ash content within specific ranges, is highly excellent in injection moldability, water resistance, compression set resistance and strength characteristics. In particular, it was found that the acrylic rubber of the present invention is remarkably excellent in any of the properties of shape formability, fusion property and mold releasability.

Further, the present inventors have found that emulsion polymerization is initiated in the presence of a redox catalyst comprising an organic radical generator such as diisopropylbenzene hydroperoxide and a reducing agent after emulsifying a specific monomer component containing an ion-reactive group-containing monomer with water and an emulsifier, and the emulsion polymerization is carried out by adding a chain transfer agent in portions during the polymerization without adding a chain transfer agent in the initial stage; solidifying the emulsion polymerization liquid subjected to emulsion polymerization by a specific method; and dehydrating the aqueous pellets produced in the coagulation reaction after washing and before entering the drying step, whereby an acrylic rubber excellent in injection moldability, water resistance, compression set resistance and strength characteristics can be efficiently produced.

In order to highly balance the strength characteristics and injection moldability of the acrylic rubber, the present inventors found that it is extremely important to make the weight average molecular weight (Mw) and the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the acrylic rubber in specific regions. In order to produce such an acrylic rubber, the present inventors have found that the above-mentioned acrylic rubber can be obtained by performing emulsion polymerization using only an organic radical generator, and that the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is narrow, and that the injection moldability is poor, but the above-mentioned acrylic rubber can be obtained by adding a chain transfer agent in batches during the polymerization. On the other hand, it is found that the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the acrylic rubber emulsion-polymerized using the inorganic radical generator is too wide and the injection molding is poor.

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

The present inventors have found that an acrylic rubber having a monomer-binding unit containing an ion-reactive group that reacts with a crosslinking agent, such as a carboxyl group, an epoxy group, or a chlorine atom, and having a weight average molecular weight in a specific range is remarkably excellent in compression set resistance and normal physical properties including strength characteristics.

The present inventors have found that an ion-reactive acrylic rubber obtained by copolymerizing an ion-reactive group-containing monomer cannot be sufficiently dissolved in tetrahydrofuran used in the GPC measurement of a radical-reactive acrylic rubber obtained by copolymerizing ethyl acrylate, dicyclopentenyl acrylate, and the like in the conventional art, and that each molecular weight and molecular weight distribution cannot be measured cleanly and satisfactorily, but can be sufficiently dissolved and satisfactorily measured by using a specific solvent having an SP value higher than that of tetrahydrofuran as an eluent, and that the injection moldability, water resistance, compression set resistance, and strength characteristics of the acrylic rubber can be highly controlled by setting each characteristic value within a specific range.

Regarding the water resistance, the present inventors found that it is greatly affected by the ash content and ash content in the acrylic rubber. It has also been found that, particularly when a large amount of an emulsifier or a coagulant is used, it is difficult to remove ash from the produced acrylic rubber, but by coagulating by a specific method, and by concentrating the particle size of the resultant aqueous aggregates in a specific region, the cleaning efficiency and ash removal efficiency at the time of dehydration can be remarkably improved, and as a result, the ash content of the acrylic rubber can be remarkably reduced and the water resistance can be improved. The inventors have found that not only the above ash amount or ash component amount, but also when a phosphate salt or a sulfate salt is used as an emulsifier and/or when an alkali metal salt or a group 2 metal salt of the periodic table is used as a coagulant, the water resistance of the acrylic rubber can be remarkably improved, and the mold releasability is remarkably excellent.

The present inventors have found that the smaller the gel amount of methyl ethyl ketone insoluble components in the acrylic rubber, the more excellent the injection moldability, compression set resistance and strength characteristics, and the more excellent the banbury workability. It has also been found that the gel amount of methyl ethyl ketone insoluble components in the acrylic rubber is rapidly increased during the polymerization reaction, particularly when the polymerization conversion is increased in order to improve the strength characteristics, and is difficult to control, but the emulsion polymerization can be suppressed to some extent by the presence of a chain transfer agent in the latter half of the polymerization reaction, and preferably the gel amount of the specific solvent insoluble components which is rapidly increased is eliminated by melt-kneading and drying the acrylic rubber in a state substantially containing no moisture in a screw-type biaxial extrusion dryer, whereby the banbury processability of the acrylic rubber can be significantly improved. In addition, the present inventors have found that the strength characteristics and banbury processability of the dried acrylic rubber are highly balanced by extruding the rubber in a molten state in a state in which water is almost removed (water content less than 1% by weight) by a screw type biaxial extrusion dryer.

The present inventors have found that the greater the specific gravity of the acrylic rubber, the more excellent the injection moldability, water resistance, strength characteristics and compression set resistance, and the more excellent the storage stability. Since the acrylic rubber of the present invention having a specific ion-reactive group such as a carboxyl group, an epoxy group and a chlorine atom is adhesive and has a high affinity for air, it is difficult to discharge the air once the air is trapped, and a large amount of air is trapped (the specific gravity becomes small) in the pellet-like acrylic rubber in which the aqueous pellets are directly dried, and the storage stability is deteriorated. The present inventors have found that by compacting and rubber-packing a pellet-shaped acrylic rubber with a high-pressure packer or the like, some air can be removed to improve the storage stability of the acrylic rubber, and preferably, an aqueous pellet is dried with a screw type biaxial extrusion dryer and extruded and laminated in a sheet form containing no air, whereby an acrylic rubber having remarkably excellent storage stability containing little air (having a high specific gravity) can be produced. The present inventors have also found that the specific gravity considering the content of this air can be measured according to JIS K6268 crosslinked rubber-density measurement a method using a difference in buoyancy. The present inventors have also found that an acrylic rubber dried under reduced pressure by a screw type biaxial extrusion dryer or melt-extruded and dried under reduced pressure is excellent in storage stability, injection moldability, strength characteristics and other characteristics and highly balanced.

The present inventors have also found that injection moldability, water resistance, compression set resistance and strength characteristics can be further improved highly by setting the monomer composition of the acrylic rubber, the kind of the ion-reactive group, the molecular weight distribution (Mz/Mw) focusing on the high molecular weight region, the complex viscosity at 60 ℃ ([ eta ]60 ℃), the ratio of the complex viscosity at 100 ℃ ([ eta ]100 ℃) to the complex viscosity at 60 ℃ ([ eta ]60 ℃), the specific element amount in ash, and the specific element amount ratio within specific ranges.

The present inventors have found that by using an organic compound having ionic crosslinkability as a crosslinking agent, the crosslinkability can be further improved and the properties of the resulting rubber crosslinked product can be further improved significantly.

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

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

Thus, according to the present invention, there is provided an acrylic rubber comprising a binding unit derived from a (meth) acrylic acid ester selected from at least one of an alkyl (meth) acrylate and an alkoxyalkyl (meth) acrylate, a binding unit derived from an ion-reactive group-containing monomer, and a binding unit derived from another monomer used as required, wherein the weight average molecular weight (Mw) of the acrylic rubber is 100 to 500 tens of thousands, the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is in the range of 1.5 to 3, the ash content is 0.3% by weight or less, and the total amount of sodium, sulfur, calcium, magnesium, and phosphorus in the ash is 80% by weight or more.

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

In the acrylic rubber of the present invention, the ratio (Mz/Mw) of z-average molecular weight (Mz) to weight-average molecular weight (Mw) is preferably 4 or less.

In the acrylic rubber of the present invention, the number average molecular weight (Mn) is preferably in the range of 40 to 110 tens of thousands.

In the acrylic rubber of the present invention, it is preferable that the weight average molecular weight (Mw), the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) (Mw/Mn), or the ratio of the z-average molecular weight (Mz) to the weight average molecular weight (Mw) (Mz/Mw) is the absolute molecular weight or the absolute molecular weight distribution as determined by GPC-MALS method.

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

In the acrylic rubber of the present invention, it is preferable that the monomer composition of the acrylic rubber is composed of 50 to 99.99% by weight of a binding unit derived from a (meth) acrylic acid ester selected from at least one of an alkyl (meth) acrylate and an alkoxyalkyl (meth) acrylate, 0.01 to 10% by weight of a binding unit derived from an ion-reactive group-containing monomer, and 0 to 40% by weight of a binding unit derived from another monomer.

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

In the acrylic rubber of the present invention, the gel amount is preferably 50% by weight or less.

In the acrylic rubber of the present invention, the gel amount is preferably 30% by weight or less.

In the acrylic rubber of the present invention, it is preferable that the total value of the gel amount at 20 is arbitrarily measured within the range of (average value.+ -. 5) wt%.

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

In the acrylic rubber of the present invention, the total amount of magnesium and phosphorus in ash is preferably 50% by weight or more.

In the acrylic rubber of the present invention, the ratio of magnesium to phosphorus ([ Mg ]/[ P ]) in ash is preferably in the range of 0.4 to 2.5 in terms of weight ratio.

In the acrylic rubber of the present invention, the complex viscosity at 60 ℃ (. Eta.60 ℃) is preferably 15000[ Pa.s ] or less.

In the acrylic rubber of the present invention, the ratio of the complex viscosity at 100 ℃ ([ eta ]100 ℃) to the complex viscosity at 60 ℃ ([ eta ]60 ℃) ([ eta ]100 ℃/[ eta ]60 ℃)) is preferably 0.7 or more.

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

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

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

Further, according to the present invention, there is provided a method for producing an acrylic rubber, comprising the steps of: an emulsifying step of emulsifying a monomer component composed of at least one (meth) acrylic acid ester selected from the group consisting of alkyl (meth) acrylates and alkoxyalkyl (meth) acrylates, an ion-reactive group-containing monomer, and other monomers used as needed, with water and an emulsifier; an emulsion polymerization step of initiating polymerization in the presence of a redox catalyst comprising an organic radical generator and a reducing agent, and adding a chain transfer agent after the batch during the polymerization to continue the polymerization to obtain an emulsion polymerization solution; a coagulation step of adding the emulsion polymerization liquid obtained to the stirred coagulation liquid and coagulating the emulsion polymerization liquid to form aqueous pellets; a cleaning step of cleaning the produced water-containing pellets; a dehydration step of dehydrating the washed aqueous pellets; and a drying step of drying the dehydrated aqueous pellets to less than 1% by weight.

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

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

In the method for producing an acrylic rubber of the present invention, it is preferable that the polymerization liquid produced in the emulsion polymerization step is solidified by contacting with a coagulant, and then the melt-kneading and drying are performed, preferably in a state substantially containing no water, and the melt-kneading and drying are performed, preferably under reduced pressure. In the method for producing an acrylic rubber of the present invention, the melt kneading and drying are preferably carried out by a screw type biaxial extrusion dryer, and the maximum torque of the screw type biaxial extrusion dryer at the time of the melt kneading and drying is preferably in the range of 5 to 125n·m. Further, in the method for producing an acrylic rubber of the present invention, the acrylic rubber after melt-kneading and drying is preferably cooled at a cooling rate of 40 ℃.

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

In the method for producing an acrylic rubber of the present invention, the number of stirring of the stirred coagulation liquid is preferably 100rpm or more.

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

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

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

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

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

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

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

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

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

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

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

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

Effects of the invention

According to the present invention, there are provided an acrylic rubber excellent in injection moldability, water resistance, compression set resistance and strength characteristics, a method for efficiently producing the same, a high-quality rubber composition comprising the acrylic rubber, and a crosslinked rubber product obtained by crosslinking the same.

Drawings

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

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

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

Detailed Description

The acrylic rubber of the present invention is characterized by comprising a binding unit derived from a (meth) acrylic acid ester selected from at least one of an alkyl (meth) acrylate and an alkoxyalkyl (meth) acrylate, a binding unit derived from an ion-reactive group-containing monomer, and a binding unit derived from another monomer used as required, wherein the weight average molecular weight (Mw) of the acrylic rubber is 100 to 500 ten thousand, the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is in the range of 1.5 to 3, the ash content is 0.3% by weight or less, and the total amount of sodium, sulfur, calcium, magnesium, and phosphorus in the ash is 80% by weight or more.

< monomer component >

The monomer component of the acrylic rubber of the present invention is composed of at least one (meth) acrylate selected from the group consisting of alkyl (meth) acrylates and alkoxyalkyl (meth) acrylates, an ion-reactive group-containing monomer, and other copolymerizable monomers used as required. In addition, in the present invention, "(meth) acrylate" is used as a term for esters of acrylic acid and/or methacrylic acid.

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

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

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

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

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

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

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

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

The ethylenically unsaturated dicarboxylic acid is not particularly limited, but preferably an ethylenically unsaturated dicarboxylic acid having 4 to 12 carbon atoms, and examples thereof include: and butenedioic acid such as fumaric acid and maleic acid, itaconic acid and citraconic acid. The ethylenically unsaturated dicarboxylic acid also includes an ethylenically unsaturated dicarboxylic acid present as an acid anhydride.

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

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

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

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

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

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

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

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

< acrylic rubber >

The acrylic rubber of the present invention is characterized by comprising the above monomer component, and by having a weight average molecular weight (Mw), a ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn), an ash amount, and an ash component amount within specific ranges.

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

The weight average molecular weight (Mw) of the acrylic rubber of the present invention is preferably in the range of 100 to 500 tens of thousands, preferably 110 to 400 tens of thousands, more preferably 120 to 300 tens of thousands, particularly preferably 150 to 250 tens of thousands, most preferably 160 to 220 tens of thousands, and in this case, the injection moldability, strength characteristics, and compression set resistance of the acrylic rubber are highly balanced, and therefore preferable.

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

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

The ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the acrylic rubber of the present invention is usually in the range of 1.5 to 3, preferably 1.8 to 2.7, more preferably 2 to 2.6, particularly preferably 2.2 to 2.6, and in this case, the injection moldability, the strength characteristics at the time of crosslinking, and the compression set resistance of the acrylic rubber are highly balanced, and therefore, are preferable. In particular, when the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the acrylic rubber of the present invention is within this range, any of the shape formability, the fusion property and the mold releasability of the acrylic rubber is also remarkably excellent, and the strength property and the compression set resistance as a crosslinked product are also highly balanced, so that it is preferable.

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

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

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

The ash content of the acrylic rubber of the present invention is 0.3% by weight or less, preferably 0.2% by weight or less, more preferably 0.18% by weight or less, particularly preferably 0.15% by weight or less, and most preferably 0.13% by weight or less, and when the ash content is within this range, the water resistance, storage stability, strength characteristics, processability and injection moldability as the acrylic rubber are highly balanced, and therefore, the acrylic rubber is preferable.

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

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

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

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

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

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

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

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

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

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

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

The complex viscosity ([ eta ]100 ℃) of the acrylic rubber of the present invention at 100℃is not particularly limited, and is suitably selected depending on the purpose of use, but is usually not more than 15000[ Pa.s ], preferably from 1000 to 10000[ Pa.s ], more preferably from 2000 to 8000[ Pa.s ], particularly preferably from 3000 to 5000[ Pa.s ], and most preferably from 3500 to 4000[ Pa.s ], and in this case, the processability, oil resistance, injection moldability and shape retention are excellent, and therefore, are preferred.

The ratio of the complex viscosity at 100 ℃ ([ eta ]100 ℃) to the complex viscosity at 60 ℃ ([ eta ]60 ℃) ([ eta ]100 ℃/[ eta ]60 ℃) of the acrylic rubber of the present invention is not particularly limited, and may be appropriately selected depending on the purpose of use, and is usually 0.5 or more, preferably 0.6 or more, and more preferably 0.7 or more. In addition, the ratio of the complex viscosity at 100 ℃ ([ eta ]100 ℃) to the complex viscosity at 60 ℃ ([ eta ]60 ℃) ([ eta ]100 ℃/[ eta ]60 ℃) of the acrylic rubber of the present invention is usually in the range of 0.5 to 0.99, preferably 0.55 to 0.95, more preferably 0.6 to 0.9, particularly preferably 0.65 to 0.85, most preferably 0.7 to 0.8, and in this case, the processability, oil resistance and shape retention are highly balanced, and therefore preferred.

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

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

When the acrylic rubber of the present invention is melt-kneaded and dried in a state in which water is almost removed (water content is less than 1% by weight) by using a screw type biaxial extrusion dryer, the banbury processability and strength characteristics are highly balanced, and thus it is preferable.

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

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

The acrylic rubber of the present invention is preferably produced by drying the aqueous pellets produced in the solidification step under reduced pressure or by melting and extrusion-drying under reduced pressure using a screw type biaxial extrusion dryer, because the acrylic rubber is particularly excellent in storage stability, injection moldability, strength characteristics and other characteristics and highly balanced.

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

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

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

The shape of the acrylic rubber of the present invention is not particularly limited, and may be any of powder, pellet, strand (strand), sheet, and bag, for example, and when it is preferably sheet or bag, it is excellent in handling property and storage stability, and is therefore preferable.

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

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

< method for producing acrylic rubber >

The method for producing the acrylic rubber is not particularly limited, and examples thereof include the following steps: an emulsifying step of emulsifying a monomer component composed of at least one (meth) acrylic acid ester selected from the group consisting of alkyl (meth) acrylates and alkoxyalkyl (meth) acrylates, an ion-reactive group-containing monomer, and other monomers used as needed, with water and an emulsifier; an emulsion polymerization step of initiating polymerization in the presence of a redox catalyst comprising an organic radical generator and a reducing agent, adding a chain transfer agent after the batch during the polymerization, and continuing the polymerization to obtain an emulsion polymerization solution; a coagulation step of adding the emulsion polymerization liquid obtained to the stirred coagulation liquid to coagulate the emulsion polymerization liquid to produce aqueous pellets; a cleaning step of cleaning the produced water-containing pellets; a dehydration step of dehydrating the washed aqueous pellets; and a drying step of drying the dehydrated aqueous pellets to less than 1% by weight.

(emulsification Process)

The emulsification step in the method for producing an acrylic rubber of the present invention is a step of emulsifying a monomer component composed of at least one (meth) acrylate selected from the group consisting of alkyl (meth) acrylates and alkoxyalkyl (meth) acrylates, an ion-reactive group-containing monomer, and other monomers used as needed, with water and an emulsifier.

(monomer component)

The monomer component used in the present invention is composed of at least one (meth) acrylate selected from the group consisting of alkyl (meth) acrylates and alkoxyalkyl (meth) acrylates, an ion-reactive group-containing monomer, and other copolymerizable monomers used as required, and is the same as exemplified and preferred ranges of the monomer components described above. As described above, the amount of the monomer component used is also appropriately selected so that the composition of the acrylic rubber of the present invention becomes the above-described composition in emulsion polymerization.

(emulsifier)

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

The anionic emulsifier is not particularly limited, and examples thereof include: salts of fatty acids such as myristic acid, palmitic acid, oleic acid, and linolenic acid; alkylbenzene sulfonates such as sodium dodecylbenzene sulfonate; sulfate salts such as sodium lauryl sulfate, phosphate salts such as polyoxyalkylene alkyl ether phosphate salts; alkyl sulfosuccinates, and the like. Among these anionic emulsifiers, phosphate salts, sulfate salts are preferable, phosphate salts are particularly preferable, and 2-valent phosphate salts are most preferable because the water resistance, strength characteristics, fusion and mold release properties of the resulting acrylic rubber, and processability can be highly balanced. The phosphate and sulfate are preferably alkali metal salts of phosphate and sulfate, more preferably sodium salts of phosphate and sulfate, and in this case, the water resistance, strength characteristics, mold releasability and workability of the resulting acrylic rubber can be highly balanced, and thus are preferable.

The 2-valent phosphate is not particularly limited as long as it can be used as an emulsifier in emulsion polymerization, and examples thereof include alkoxypolyoxyalkylene phosphate and alkylphenoxypolyoxyalkylene phosphate, and among these, metal salts thereof are preferred, alkali metal salts thereof are more preferred, and sodium salts thereof are most preferred.

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

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

Specific examples of the alkoxypolyoxypropylene phosphate include octyloxydioxy-propylene phosphate, octyloxytrioxypropylene phosphate, octyloxytetraoxypropylene phosphate, decyloxy-tetrapropoxy-phosphate, dodecyloxytetrapropoxy-phosphate, tridecyloxytetrapropoxy-phosphate, tetradecyloxy-tetrapropoxy-phosphate, hexadecyloxy-tetrapropoxy-phosphate, octadecyloxypropy-phosphate, octyloxypentaoxypropy-phosphate, decyloxy-pentapropy-phosphate, dodecyloxypentaoxypropy-phosphate, tridecyloxypentaoxypropy-phosphate, tetradecyloxy-pentapropy-phosphate, hexadecyloxy-pentapropy-phosphate, octadecyloxypentaoxypropy-phosphate, octyloxypropy-phosphate, decyloxy-hexaoxypropy-phosphate, dodecyloxypropy-phosphate, tridecyloxypropy-phosphate, tetradecyloxy-hexaoxypropy-phosphate, hexadecyloxy-hexaoxypropy-phosphate, octadecyloxypropy-phosphate, dodecyloxypropy-phosphate, tridecyloxypropy-oxypropy-phosphate, tridecyloxypropy-phosphate, octaalkoxyl-phosphate, and alkali metal salts thereof, especially preferred among these.

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

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

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

As the phosphate salt, a 1-valent phosphate salt such as a sodium salt of di (alkoxypolyoxyalkylene) phosphate can be used alone or in combination with a 2-valent phosphate salt.

Examples of the sulfate salt include sodium lauryl sulfate, potassium lauryl sulfate, ammonium lauryl sulfate, sodium myristyl sulfate, sodium polyoxyethylene alkyl sulfate, sodium polyoxyethylene alkylaryl sulfate, and the like, with sodium lauryl sulfate being preferred.

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

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

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

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

(emulsion polymerization Process)

The emulsion polymerization step in the method for producing an acrylic rubber of the present invention is a step of initiating polymerization in the presence of a redox catalyst composed of an organic radical generator and a reducing agent, and continuing polymerization by adding a chain transfer agent after batchwise during the polymerization to obtain an emulsion polymerization solution.

(organic radical generator)

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

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

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

Examples of the azo compound include azobisisobutyronitrile, 4' -azobis (4-cyanovaleric acid), 2' -azobis [2- (2-imidazolin-2-yl) propane ], 2' -azobis (propane-2-formamidine), 2,2' -azobis [ N- (2-carboxyethyl) -2-methylpropanamide ], 2' -azobis {2- [1- (2-hydroxyethyl) -2-imidazolin-2-yl ] propane }, 2' -azobis (1-imino-1-pyrrolidinyl-2-methylpropanamide }, 2' -azobis { 2-methyl-N- [1, 1-bis (hydroxymethyl) -2-hydroxyethyl ] propionamide }, and the like.

These organic radical generators may be used singly or in combination, and the amount thereof is usually in the range of 0.0001 to 5 parts by weight, preferably 0.0005 to 1 part by weight, more preferably 0.001 to 0.5 part by weight, relative to 100 parts by weight of the monomer component.

(reducing agent)

The reducing agent used in the present invention is not particularly limited as long as it is a reducing agent generally used in emulsion polymerization, and it is preferable to use at least two reducing agents, and it is preferable to combine a metal ion compound in a reduced state with the other reducing agents, because the injection moldability and strength characteristics of the resulting acrylic rubber can be further highly balanced.

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

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

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

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

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

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

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

(post addition of chain transfer agent)

The present invention is characterized in that the acrylic rubber having a high molecular weight component and a low molecular weight component separated from each other can be produced by adding the chain transfer agent in the course of polymerization in a batch manner without adding the chain transfer agent at the initial stage, and the strength characteristics and injection moldability of the produced acrylic rubber are highly balanced, so that it is preferable.

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

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

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

Specific examples of the alkyl thiol compound include n-pentyl thiol, n-hexyl thiol, n-heptyl thiol, n-octyl thiol, n-decyl thiol, n-dodecyl thiol, n-tridecyl thiol, n-tetradecyl thiol, n-hexadecyl thiol, n-octadecyl thiol, sec-pentyl thiol, sec-hexyl thiol, sec-heptyl thiol, sec-octyl thiol, zhong Guiji thiol, sec-dodecyl thiol, sec-tridecyl thiol, sec-tetradecyl thiol, sec-hexadecyl thiol, sec-octadecyl thiol, tert-amyl thiol, tert-hexyl thiol, tert-heptyl thiol, tert-octyl thiol, tert-decyl thiol, tert-dodecyl thiol, tert-tridecyl thiol, tert-tetradecyl thiol, tert-hexadecyl thiol, tert-octadecyl thiol, and the like, preferably n-octyl thiol, n-dodecyl thiol, tert-dodecyl thiol, more preferably n-octyl thiol, and n-dodecyl thiol.

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

The present invention is characterized in that the high molecular weight component and the low molecular weight component of the obtained acrylic rubber can be produced by adding the chain transfer agent in a batch manner during the polymerization without adding the chain transfer agent at the initial stage of the polymerization, and the molecular weight can be distributed in a specific range, and the strength characteristics and injection moldability are highly balanced, and therefore it is preferable.

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

The timing of starting the batch-wise post-addition of the chain transfer agent is not particularly limited, and may be appropriately selected depending on the purpose of use, and is usually 20 minutes or later, preferably 30 minutes or later, more preferably 30 to 200 minutes, particularly preferably 35 to 150 minutes, and most preferably 40 to 120 minutes after the start of polymerization, from the start of polymerization, and in this case, the strength characteristics and injection moldability of the produced acrylic rubber can be highly balanced, and thus are preferable.

The amount of the chain transfer agent added per 1 part by weight of the post-batch addition is not particularly limited, and may be appropriately selected depending on the purpose of use, but is preferably in the range of usually 0.00005 to 0.5 part by weight, preferably 0.0001 to 0.1 part by weight, more preferably 0.0005 to 0.05 part by weight, particularly preferably 0.001 to 0.03 part by weight, and most preferably 0.002 to 0.02 part by weight, based on 100 parts by weight of the monomer component, and in this case, the strength characteristics and injection moldability of the produced acrylic rubber can be highly balanced.

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

(post addition of reducing agent)

In the present invention, the reducing agent of the redox catalyst can be added after the polymerization, and by doing so, the strength characteristics and injection moldability of the produced acrylic rubber can be highly balanced, so that it is preferable.

The reducing agent added after the polymerization is in the same range as exemplified and preferred as the reducing agent described above. In the present invention, as the reducing agent to be added later, ascorbic acid or a salt thereof is preferable.

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

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

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

The timing of the post-addition of the reducing agent is not particularly limited, and may be appropriately selected depending on the purpose of use, and is usually in the range of 1 hour or later from the start of polymerization, preferably 1 to 3 hours, more preferably 1.5 to 2.5 hours after the start of polymerization, and in this case, the strength characteristics and injection moldability of the produced acrylic rubber can be highly balanced while the productivity of the production of the acrylic rubber is excellent, and thus it is preferable.

The amount of the reducing agent added per 1 part by weight of the post-batch addition is not particularly limited, and may be appropriately selected depending on the purpose of use, but is usually in the range of 0.00005 to 0.5 part by weight, preferably 0.0001 to 0.1 part by weight, more preferably 0.0005 to 0.05 part by weight, particularly preferably 0.001 to 0.03 part by weight, based on 100 parts by weight of the monomer component, and in this case, the strength characteristics and injection moldability of the produced acrylic rubber can be highly balanced, and thus are preferable.

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

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

(coagulation step)

The coagulation step in the method for producing an acrylic rubber of the present invention is a step of adding the emulsion polymerization liquid obtained as described above to a stirred coagulation liquid and coagulating the mixture to form aqueous pellets.

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

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

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

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

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

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

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

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

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

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

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

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

Since the particle size of the produced aqueous pellets can be made small and uniform when the number of revolutions is a number of revolutions with which the pellets are vigorously stirred to a certain extent, it is preferable that the particle size of the produced pellets is not less than the lower limit, and the coagulation reaction can be controlled more easily by not more than the upper limit.

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

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

(cleaning step)

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

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

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

The temperature of the water to be used is not particularly limited, but it is preferably hot water, usually 40℃or higher, preferably 40 to 100℃and more preferably 50 to 90℃and particularly 60 to 80℃because the washing efficiency can be remarkably improved. When the temperature of the water to be used is not less than the lower limit, the emulsifier and the coagulant are released from the aqueous pellet, thereby further improving the cleaning efficiency.

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

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

(dehydration step)

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

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

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

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

(drying step)

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

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

In the present invention, the acrylic rubber can be obtained by melting and extrusion-drying the aqueous pellets in a screw type biaxial extrusion dryer. The drying temperature (set temperature) of the screw type biaxial extrusion dryer may be appropriately selected, and is usually in the range of 100 to 250 ℃, preferably 110 to 200 ℃, more preferably 120 to 180 ℃, and in this case, it is preferable to dry the acrylic rubber efficiently without burning or deterioration.

In the present invention, it is preferable that the aqueous pellets produced in the solidification step are melt kneaded and dried under reduced pressure in a screw type biaxial extrusion dryer because the storage stability of the acrylic rubber can be highly improved without impairing the injection moldability and strength characteristics. In this stage, the vacuum degree in the screw type biaxial extrusion dryer is preferably selected appropriately for the purpose of improving the storage stability by removing air existing in the acrylic rubber, and is usually in the range of 1 to 50kPa, preferably 2 to 30kPa, more preferably 3 to 20 kPa.

In the present invention, it is preferable that the aqueous pellets produced in the solidification step are melt kneaded and dried in a state in which water is substantially removed by a screw type biaxial extrusion dryer, because the banbury processability of the acrylic rubber can be highly improved without impairing the injection molding and strength characteristics. The water content of the acrylic rubber is usually less than 1% by weight, preferably 0.8% by weight or less, and more preferably 0.6% by weight or less, as a state in which almost water is removed and the banbury processability is highly improved. In the present invention, "melt-kneading" or "melt-kneading and drying" means that the acrylic rubber is kneaded (mixed) in a molten state or extruded in a molten state in a screw type biaxial extrusion dryer and dried at this stage; or means that the acrylic rubber is kneaded in a molten (plasticized) state by a screw type biaxial extrusion dryer and extrusion-dried.

The maximum torque of the screw type biaxial extrusion dryer used in the present invention is not particularly limited, but is usually in the range of 5 to 125n·m, preferably 10 to 100n·m, more preferably 10 to 50n·m, particularly preferably 15 to 45n·m, and in this case, the injection moldability, banbury processability and strength characteristics of the produced acrylic rubber can be highly balanced, and thus are preferable.

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

The specific power of the screw type biaxial extrusion dryer used in the present invention is not particularly limited, but is usually 0.1 to 0.6[ A.h/kg ] or more, preferably 0.15 to 0.55[ A.h/kg ], and more preferably 0.2 to 0.5[ A.h/kg ], and in this case, the injection moldability, banbury processability and strength characteristics of the obtained acrylic rubber are highly balanced, and therefore preferable.

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

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

In the present invention, the cooling rate of the acrylic rubber after melt-kneading and drying is usually 40℃per hour or more, preferably 50℃per hour or more, more preferably 100℃per hour or more, particularly preferably 150℃per hour or more, and in this case, the scorch stability of the acrylic rubber composition is remarkably excellent, and thus it is preferable.

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

< method for producing sheet-like or rubber-coated acrylic rubber >

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

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

(Water removal Process)

In the present invention, it is preferable to provide a water removal step of separating free water from the washed aqueous pellets by using a water remover, because the water removal efficiency can be improved.

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

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

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

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

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

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

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

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

The water discharged from the dewatering slit during the dewatering of the hydrous pellets may be in any of a liquid state (drainage) and a vapor state (discharge) and, in the case of using a screw type biaxial extrusion dryer having a plurality of dewatering barrels, it is preferable to efficiently dewater the adhesive acrylic rubber by combining drainage and discharge. In a screw type biaxial extrusion dryer having 3 or more dehydration barrels, it is sufficient to appropriately perform the dehydration barrel as a drainage type dehydration barrel or a steam discharge type dehydration barrel depending on the purpose of use, but in general, the drainage type barrel is increased when the ash content in the produced acrylic rubber is reduced, and the steam discharge type barrel is increased when the water content is reduced.

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

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

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

In the dehydration of the aqueous pellet having the drainage type dehydration barrel and the steam discharge type dehydration barrel, the water content after drainage of the drainage type dehydration barrel section is usually 5 to 40% by weight, preferably 10 to 40% by weight, more preferably 15 to 35% by weight, and the water content after pre-drying of the steam discharge type dehydration barrel section is usually 1 to 30% by weight, preferably 3 to 20% by weight, more preferably 5 to 15% by weight.

When the water content after dehydration is not less than the lower limit, the dehydration time can be shortened, deterioration of the acrylic rubber can be suppressed, and when the water content is not more than the upper limit, the ash content can be further sufficiently reduced.

(drying of aqueous pellets in the dryer section)

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

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

The setting temperature of the dryer cylinder may be appropriately selected, and is usually in the range of 100 to 250 ℃, preferably 110 to 200 ℃, more preferably 120 to 180 ℃, and in this case, it is preferable that the drying cylinder is capable of efficiently drying without causing burning or deterioration of the acrylic rubber and reducing the gel amount of methyl ethyl ketone insoluble components in the sheet-like or gel-coated acrylic rubber.

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

The water content of the dried rubber after drying is usually less than 1% by weight, preferably 0.8% by weight or less, more preferably 0.6% by weight or less. In the present invention, in particular, in a screw type biaxial extrusion dryer, it is preferable to melt-extrude the dry rubber with the water content of the dry rubber at this value (in a state where water is substantially removed), because the gel amount of methyl ethyl ketone insoluble components of the sheet-like or rubber-coated acrylic rubber can be reduced. In the present invention, the acrylic rubber melt-kneaded or melt-kneaded and dried by using a screw type biaxial extruder is preferably a sheet-like or bag-like acrylic rubber, and thus both the strength characteristics and the banbury processability can be highly balanced, which is preferable. In the present invention, "melt-kneading" or "melt-kneading and drying" means that the acrylic rubber is kneaded (mixed) in a molten state or extruded in a molten state in a screw type biaxial extrusion dryer and dried at this stage; or means that the acrylic rubber is kneaded in a molten (plasticized) state by a screw type biaxial extrusion dryer and extrusion-dried.

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

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

(extrusion of dried rubber from die head)

The dried rubber dehydrated and dried by using the screw sections of the dehydration cylinder and the drying cylinder is fed to a screw-free correction die section, and extruded into a desired shape from the die section. A perforated plate or a metal mesh may or may not be provided between the screw section and the die section.

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

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

(screw type biaxial extrusion dryer and operating conditions)

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

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

The ratio (L/D) of the screw length (L) to the screw diameter (D) of the screw type biaxial extrusion dryer to be used is not particularly limited, but is usually in the range of 10 to 100, preferably 20 to 80, more preferably 30 to 60, and in this case, it is preferable to reduce the water content to less than 1% by weight without causing a decrease in the molecular weight or burning of the dried rubber.

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

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

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

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

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

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

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

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

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

(sheet-like Dry rubber)

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

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

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

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

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

The sheet-like dry rubber extruded from the screw type biaxial extrusion dryer is not particularly limited in the complex viscosity ([ eta ]100 ℃) at 100℃and is usually in the range of 1500 to 6000[ Pa.s ], preferably 2000 to 5000[ Pa.s ], more preferably 2500 to 4500[ Pa.s ], most preferably 3000 to 4000[ Pa.s ], and in this case, the extrudability and shape retention as sheets are highly balanced and therefore preferred. That is, the extrusion properties can be further improved by the lower limit or more, and the collapse and fracture of the shape of the sheet-like dry rubber can be suppressed by the upper limit or less.

The sheet-like dry rubber extruded from the screw type biaxial extrusion dryer may be used as it is in a folded state, but can be generally used as it is in a cut state.

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

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

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

The ratio of the complex viscosity at 100 ℃ ([ eta ]100 ℃) to the complex viscosity at 60 ℃ ([ eta ]60 ℃) ([ eta ]100 ℃/[ eta ]60 ℃) is not particularly limited, and is usually in the range of 0.5 or more, preferably 0.6 or more, more preferably 0.7 or more, as appropriate depending on the purpose of use, and the ratio of the complex viscosity at 100 ℃ ([ eta ]100 ℃) to the complex viscosity at 60 ℃ ([ eta ]60 ℃) ([ eta ]100 ℃/[ eta ]60 ℃) of the sheet-like dry rubber is usually in the range of 0.5 to 0.99, preferably 0.55 to 0.95, more preferably 0.6 to 0.9, particularly preferably 0.65 to 0.85, most preferably 0.7 to 0.8, and at this time, the air entanglement is small and the cutting and productivity are highly balanced, so that it is preferable.

The method for cooling the sheet-like dry rubber is not particularly limited, and the sheet-like dry rubber may be left at room temperature, and since the thermal conductivity of the sheet-like dry rubber is extremely small in the range of 0.15 to 0.35W/mK, forced cooling by air cooling with air blowing or cooling by air, watering by water spraying, immersing in water, and the like are preferable, and air cooling by air blowing or cooling by air cooling is particularly preferable in order to improve productivity.

In the air cooling system of the sheet-like dry rubber, for example, the sheet-like dry rubber can be extruded from a screw extruder onto a conveyor such as a conveyor belt, and conveyed and cooled while blowing cold air. The temperature of the cold air is not particularly limited, but is usually in the range of 0 to 25 ℃, preferably 5 to 25 ℃, more preferably 10 to 20 ℃. The length of cooling is not particularly limited, but is usually 40℃/hr or more, preferably 50℃/hr or more, more preferably 100℃/hr or more, particularly preferably 150℃/hr or more, and in this case, cutting is easy, and therefore, preferable. In the present invention, the cooling rate of the sheet-like dry rubber is usually 40℃per hour or more, preferably 50℃per hour or more, more preferably 100℃per hour or more, and particularly preferably 150℃per hour or more, and in this case, the scorch stability of the acrylic rubber composition is excellent, and therefore, it is preferable.

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

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

(lamination step)

The method for producing the rubber-covered acrylic rubber of the present invention is not particularly limited, and it is preferable to laminate the above-mentioned sheet-like acrylic rubber to obtain a rubber-covered acrylic rubber excellent in storage stability with less air inclusion.

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

The thus obtained rubber-coated acrylic rubber of the present invention is excellent in handling properties, injection moldability, crosslinkability, strength properties and compression set resistance, and also excellent in storage stability, banbury workability and water resistance, as compared with the pellet-shaped acrylic rubber, and the rubber-coated acrylic rubber can be used as it is or cut into a required amount to be put into a mixer such as a banbury, roll or the like.

< rubber composition >

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

The method for producing the rubber composition of the present invention includes a method of mixing the rubber component containing the acrylic rubber of the present invention, the filler, the crosslinking agent, and optionally the antioxidant and other compounding agents, and any means available in the conventional rubber processing field can be used for the mixing, for example, an open roll, a Banbury mixer, various kneaders, and the like. The mixing order of the components may be in accordance with a usual order in the rubber processing field, and it is preferable that, for example, components which are not easily reacted or decomposed by heat are sufficiently mixed and then a crosslinking agent or the like which is a component which is easily reacted or decomposed by heat is mixed at a temperature at which no reaction or decomposition occurs in a short period of time.

< crosslinked rubber >

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

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

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

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

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

The rubber crosslinked product of the present invention is preferably used as an extrusion molded product and a die crosslinked product for automotive applications, for example, in various hoses such as fuel oil hoses such as fuel tanks, filler neck hoses, exhaust hoses, paper hoses, oil hoses, air hoses such as turbo air hoses and transmission hoses, radiator hoses, heater hoses, brake hoses, and air conditioning hoses.

< Structure of apparatus for producing acrylic rubber >

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

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

The emulsion polymerization reactor is configured to perform the above-described treatment in the emulsion polymerization step. Although not shown in fig. 1, the emulsion polymerization reactor includes, for example, a polymerization reaction tank, a temperature control unit for controlling a reaction temperature, and a stirring device having a motor and stirring blades. In the emulsion polymerization reactor, water and an emulsifier are mixed with a monomer for forming an acrylic rubber, and the mixture is emulsified while being properly stirred by a stirrer, and an emulsion polymerization reaction is initiated in the presence of a redox catalyst composed of an organic radical generator and a reducing agent, and a chain transfer agent is added after the polymerization is batchwise, whereby an emulsion polymerization solution can be obtained. The emulsion polymerization reactor may be any of a batch type, a semi-batch type and a continuous type, and may be any of a tank type reactor and a tube type reactor.

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

In the coagulation device 3, for example, a method of adding the emulsion polymerization liquid to the stirred coagulation liquid can be used for the contact of the emulsion polymerization liquid with the coagulation liquid. That is, the agitation tank 30 of the coagulation device 3 is filled with a coagulation liquid in advance, and the emulsion polymerization liquid is added to the coagulation liquid and brought into contact with the coagulation liquid to coagulate the emulsion polymerization liquid, thereby producing the aqueous pellet.

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

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

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

The cleaning apparatus 4 shown in fig. 1 is configured to perform the above-described cleaning process.

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

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

The aqueous pellets washed by the washing apparatus 4 are supplied to a screw type biaxial extrusion dryer 5 for performing a dehydration step and a drying step. In this case, the washed aqueous pellets are preferably fed to the screw type biaxial extrusion dryer 5 after passing through the water separator 43 capable of separating free water. As the water removing machine 43, for example, a metal mesh, a screen, an electric screen, or the like can be used.

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

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

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

The structure of the screw type biaxial extrusion dryer 5 will be described below with reference to fig. 2.

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

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

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

The supply cylinder portion 52 is composed of 2 supply cylinders, i.e., a first supply cylinder 52a and a second supply cylinder 52 b.

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

The dryer section 54 is composed of 8 dryer cylinders, i.e., a first dryer cylinder 54a, a second dryer cylinder 54b, a third dryer cylinder 54c, a fourth dryer cylinder 54d, a fifth dryer cylinder 54e, a sixth dryer cylinder 54f, a seventh dryer cylinder 54g, and an eighth dryer cylinder 54 h.

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

The screw type biaxial extrusion dryer 5 further includes a heating unit, not shown, which heats the respective cylinders 52a to 52b, 53a to 53c, 54a to 54h individually, and heats the aqueous pellets in the respective cylinders 52a to 52b, 53a to 53c, 54a to 54h individually to a predetermined temperature. The heating units have numbers corresponding to the respective barrels 52a to 52b, 53a to 53c, 54a to 54 h. As such heating means, a structure may be employed in which high-temperature steam or the like is supplied from the steam supply means to the steam flow barriers formed in the respective cylinders 52a to 52b, 53a to 53c, 54a to 54h, but the invention is not limited thereto. The screw type biaxial extrusion dryer 5 further includes a temperature control unit, not shown, which controls the set temperatures of the heating units corresponding to the barrels 52a to 52b, 53a to 53c, and 54a to 54 h.

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

respective cylinder sections

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

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

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

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

cylinder portions

52, 53, 54.

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

The dewatering cylinder 53 is a region in which a liquid (slurry) containing a coagulant or the like is separated from the aqueous pellet and discharged.

The first to third dewatering cylinders 53a to 53c constituting the dewatering cylinder 53 have

dewatering slits

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

dewatering slits

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

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

dewatering slit

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

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

dewatering slits

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

The dehydration cylinder 53 is preferable because the water content of the adhesive acrylic rubber can be reduced efficiently by combining drainage and steam discharge. In the dehydrator cylinder 53, which dehydrator cylinder is used for the water discharge or the steam discharge in the first to third dehydrator cylinders 53a to 53c may be appropriately set according to the purpose of use, and in general, when the ash content in the produced acrylic rubber is reduced, the dehydrator cylinder for the water discharge may be increased. In this case, for example, as shown in fig. 2, the first and

second dewatering cylinders

53a and 53b on the upstream side are used for water discharge, and the third dewatering cylinder 53c on the downstream side is used for steam discharge. For example, in the case where the dewatering cylinder portion 53 has 4 dewatering cylinders, it is conceivable to drain water from the 3 dewatering cylinders on the upstream side and drain steam from the 1 dewatering cylinder on the downstream side. On the other hand, in the case of decreasing the water content, the dehydration cylinder in which the steam discharge is performed may be increased.

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

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

exhaust ports

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

exhaust ports

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

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

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

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

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

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

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

dewatering slits

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

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

exhaust ports

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

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

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

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

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

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

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

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

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

The shear rate in the barrel unit 51 is not particularly limited, but is usually 5 to 150[1/s ] or more, preferably 10 to 100[1/s ], and more preferably 25 to 75[1/s ].

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

The cooling device 6 shown in fig. 1 is configured to cool the dried rubber obtained through the dehydration step by a dehydrator and the drying step by a dryer. As the cooling method of the cooling device 6, various methods including an air cooling method with air blowing or cooling air, a water spraying method, a dipping method in water, and the like can be used. In addition, the rubber may also be dried by cooling at room temperature.

As described above, the dried rubber discharged from the screw extruder 5 is extruded into various shapes such as pellets, columns, round bars, sheets, etc., according to the nozzle shape of the die 59, and is molded into a sheet in the present invention. Next, a description will be given of a conveyor type cooling device 60 as an example of the cooling device 6 with reference to fig. 3, and the conveyor type cooling device 60 cools the sheet-shaped dry rubber 10 molded into a sheet shape.

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

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

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

The conveyor 61 has

rollers

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

rollers

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

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

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

According to the conveying type cooling device 60 shown in fig. 3, the sheet-like dry rubber 10 can be cooled by blowing cooling air from the cooling unit 65 to the sheet-like dry rubber 10 while conveying the sheet-like dry rubber 10 discharged from the die 59 of the screw extruder 5 by using the conveyor 61.

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

The glue coating device 7 shown in fig. 1 is constituted as follows: the dried rubber extruded from the screw extruder 5 and cooled by the cooling device 6 is processed to produce a one-piece rubber bag. As described above, the screw extruder 5 can extrude the dried rubber into various shapes such as pellets, columns, round bars, and sheets, and the rubber packing device 7 is configured to pack the dried rubber thus molded into various shapes. The weight, shape, etc. of the rubber-coated acrylic rubber produced by the rubber coating device 7 are not particularly limited, and for example, approximately 20kg of a rubber-coated acrylic rubber having a substantially rectangular parallelepiped shape can be produced.

The rubber packing device 7 has, for example, a packer, and can also produce a rubber-packed acrylic rubber by compressing the cooled dry rubber with the packer.

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

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

Examples

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

[ monomer composition ]

Regarding the monomer composition in the acrylic rubber, use is made of ¹ The monomer structure of each monomer unit in the acrylic rubber was confirmed by H-NMR, and the activity of the reactive groups remaining in the acrylic rubber and the content of each reactive group were confirmed by the following method. Further, the content ratio of each monomer unit in the acrylic rubber was calculated from the amount of each monomer used for polymerization reaction and the polymerization conversion. Specifically, since the polymerization reaction is an emulsion polymerization reaction, the polymerization conversion rate is about 100% which cannot be confirmed by the unreacted monomers, and therefore the content ratio of each monomer unit in the rubber is the same as the amount of each monomer used.

[ reactive group content ]

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

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

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

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

[ Ash content ]

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

[ ash component amount ]

The amount (%) of each component in the acrylic rubber ash was calculated as the ratio in the ash by pressing the ash collected when measuring the ash amount against titration filter paper of Φ20mm, and measuring the amount (ppm) of the component using ZSX Primus (manufactured by the company of the chemical Co., ltd.).

[ molecular weight and molecular weight distribution ]

The molecular weights (Mw, mn, mz) and molecular weight distributions (Mw/Mn and Mz/Mw) of the acrylic rubber are absolute molecular weights and absolute molecular weight distributions measured by GPC-MALS method using, as a solvent, a solution in which lithium chloride was added to dimethylformamide at a concentration of 0.05mol/L and 37% concentrated hydrochloric acid was added at a concentration of 0.01%. The term "GPC-MALS method" as used herein refers to the following. GPC (Gel Permeation Chromatography ) is one type of liquid chromatography that separates based on differences in molecular size, specifically, a method in which a multi-angle laser light scattering device (MALS) and a differential refractive index detector (RI) are mounted in a GPC (Gel Permeation Chromatography ) device, and the light scattering intensity and refractive index difference of a molecular chain solution whose size has been differentiated by the GPC device are measured in accordance with the elution time, whereby the molecular weight of a solute and the content thereof are sequentially calculated, and finally the absolute molecular weight distribution and absolute average molecular weight value of a polymer substance are obtained.

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

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

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

Column temperature: 40 DEG C

Flow rate: 0.8ml/mm

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

[ glass transition temperature (Tg) ]

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

[ gel amount ]

The gel content (%) of the acrylic rubber was determined as the amount of insoluble components with respect to methyl ethyl ketone by the following method.

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

Gel amount (%) =100× (X-Y)/X

[ specific gravity ]

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

The measured value obtained by the following measurement method was the density, but the density of water was set to 1Mg/m ³ To obtain specific gravity. Specifically, the specific gravity of the rubber sample obtained by the method a according to JIS K6268 crosslinked rubber-density measurement is a value obtained by dividing the mass by the volume of the void including the rubber sample, and the density of the rubber sample obtained by dividing the density of water by the method a according to JIS K6268 crosslinked rubber-density measurement is a value obtained by dividing the density of the rubber sample by the density of water (when the density of the rubber sample is divided by the density of water, the numerical values are the same, and the unit disappears). Specifically, the specific gravity of the rubber sample was determined based on the following procedure.

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

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

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

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

(Density of rubber sample when weight is not used)

Density=m1/(m 1-m 2)

(Density of rubber sample when heavy weight is used)

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

[ Water content ]

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

[pH]

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

[ Complex viscosity ]

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

[ Mooney viscosity (ML1+4, 100 ℃)

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

[ injection moldability ]

Regarding injection moldability, the shape formability, releasability and fusion property were observed and scored using a small injection molding machine (SLIM 15-30, manufactured by Kyowa Co., ltd.), and the injection moldability was comprehensively evaluated based on the total fraction thereof according to the following criteria. For the shape formability and the mold releasability, a metal mold was prepared which was used to simulate 3 cylindrical shapes (A: 4 mm. Phi., B:3 mm. Phi., C:2 mm. Phi.) having diameters of greater than 150mm, the rubber composition was flowed into the metal mold under the conditions of a screw temperature of 90℃for 30 seconds and an injection pressure of 7MPa, and after crosslinking at 170℃for 1 minute and 30 seconds, the molded article in the cylindrical shape was taken out, and the molded article in the cylindrical shape and the metal mold were observed and scored according to the following criteria. Regarding the fusion property, a metal mold having a shape of a fusion observation belt of 0.5mm x 5mm width x 40mm length was prepared in which 5mm Φ pipes were connected to both ends in the longitudinal direction, and the rubber composition was flowed into the metal mold from the 5mm Φ pipes under the conditions of a screw temperature of 90 ℃, an injection time of 30 seconds, and an injection pressure of 7MPa, and crosslinked at 170 ℃ for 1 minute and 30 seconds, and then the fusion state of the rubber composition in the fusion observation belt was observed, and the evaluation was performed on the basis of the following.

(shape Forming Property)

5, the method comprises the following steps: A. b, C can produce all cylindrical molded articles, and the shape of the tip end portion of all molded articles is formed to completely follow the mold, and burrs are not found to be formed

4, the following steps: A. b, C all can produce a cylindrical molded article, but in C, only a part of the tip end of the molded article cannot completely follow the shape of the metal mold

3, the method comprises the following steps: A. b can produce a cylindrical molded article, C can also produce more than half of the molded article

2, the method comprises the following steps: A. b can produce a cylindrical molded article, but in C, half of the molded article cannot be produced either

1, the method comprises the following steps: a enables the production of a molded article, but B does not enable the production of a molded article at all

0 point: a cannot produce a molded article

(mold release Property)

5, the method comprises the following steps: can be easily released from a metal mold without mold residue

4, the following steps: can be easily released from a metal mold but little mold residue is found

3, the method comprises the following steps: there is a small amount of mold residue that can be easily released from the metal mold

2, the method comprises the following steps: slightly difficult to release from a metal mold without mold residue

1, the method comprises the following steps: there is also mold residue, which is slightly difficult to release from the metal mold

0 point: difficult to release from metal molds

(fusibility)

5, the method comprises the following steps: can be completely fused

0 point: incomplete fusion (poor fusion)

Comprehensive evaluation

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

And (2) the following steps: 14 minutes

And ∈:13 minutes

Delta: 11-12 minutes

X: less than 10 minutes

[ Banbury processability ]

Regarding the Banbury processability of the rubber sample, the rubber sample was put into a Banbury mixer heated to 50℃for mastication for 1 minute, and then compounding agent A of the rubber mixture formulation shown in Table 1 was put into the mixer, and the time until the rubber mixture at the first stage was integrated to exhibit the maximum torque value, that is, BIT (Black Incorporation Time, carbon black mixing time) was measured, and the index of 100 in comparative example 2 was calculated and evaluated on the basis of the following criteria.

And (3) the following materials: 20 or less

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

And ∈: greater than 40 and less than 60

Delta: more than 60 and less than 80

X: greater than 80

[ evaluation of storage stability ]

Regarding the storage stability of the rubber sample, the rubber sample was placed in a constant temperature and humidity tank (SH-222 manufactured by espek) at 45 ℃ x 80% rh, the rate of change of the water content before and after 7 days of the test was calculated, the index of 100 was calculated as comparative example 2, and the evaluation was performed according to the following criteria.

And (3) the following materials: 20 or less

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

And ∈: greater than 50 and less than 90

Delta: greater than 90 and less than 100

X: greater than 100

[ evaluation of Water resistance ]

Regarding the water resistance of the rubber sample, the crosslinked product of the rubber sample was immersed in distilled water at 85℃for 100 hours according to JIS K6258 to conduct an immersion test, the volume change rate before and after the immersion was measured, and the index of 100 was calculated as comparative example 2, and evaluated according to the following criteria.

And (3) the following materials: is less than 1

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

And ∈: more than 5 and less than 10

Delta: more than 10 and less than 50

X: greater than 50

[ compression set resistance ]

The compression set resistance of the rubber sample was evaluated according to JIS K6262, by measuring the compression set after leaving the rubber crosslinked product of the rubber sample to stand at 175℃for 90 hours in a state of being compressed by 25%.

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

X: compression set of 15% or more

[ evaluation of physical Properties in Normal state ]

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

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

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

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

[ evaluation of deviation of gel amount ]

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

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

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

X: calculating the average value of the gel amounts at 20 positions, 1 in 20 positions being out of the range of + -5 of the average value

[ evaluation of processing stability based on Mooney scorch inhibition ]

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

Example 1

As shown in Table 2-1, in a mixing vessel having a homogenizer, 46 parts of pure water, 48.5 parts of ethyl acrylate, 50 parts of n-butyl acrylate and 1.5 parts of mono-n-butyl fumarate as monomer components, and 1.8 parts of sodium tridecyloxy hexaoxyethylene phosphate as emulsifier were added and stirred to obtain a monomer emulsion.

Into a polymerization reaction vessel equipped with a thermometer and a stirrer, 170 parts of pure water and 3 parts of the monomer emulsion obtained above were charged, and after cooling to 12℃under a nitrogen stream, 0.00033 parts of ferrous sulfate, 0.02 parts of sodium ascorbate, and 0.0045 parts of diisopropylbenzene hydroperoxide as an organic radical generator were added to initiate polymerization. The polymerization was continued by maintaining the temperature in the polymerization vessel at 23℃and continuously dropping the remaining portion of the monomer emulsion over 3 hours, adding 0.012 part of n-dodecyl mercaptan after 50 minutes, adding 0.012 part of n-dodecyl mercaptan after 100 minutes, and adding 0.4 part of sodium L-ascorbate after 120 minutes after the start of the reaction, and stopping the polymerization by adding hydroquinone as a polymerization terminator when the polymerization conversion reached approximately 100%, to obtain an emulsion polymerization solution.

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

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

The screw type biaxial extrusion dryer used in example 1 was composed of 1 feeder cylinder, 3 dehydrators (first to third dehydrators), and 5 dryers (first to fifth dryers). The first dewatering cylinder discharges water, and the second and third dewatering cylinders discharge steam. The operating conditions of the screw type biaxial extrusion dryer are as follows. The post-dewatering (draining) water content, maximum torque, specific power, specific energy consumption, shear rate, and shear viscosity of the screw type biaxial extrusion dryer are shown in table 2-1.

Water content:

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

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

Moisture content of the aqueous pellets after drying in the fifth dryer section: 0.4%

Rubber temperature:

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

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

Set temperature of each barrel:

first dewatering barrel: 100 DEG C

A second dewatering barrel: 120 DEG C

Third dewatering barrel: 120 DEG C

First dryer barrel: 120 DEG C

Second dryer barrel: 130 DEG C

Third dryer barrel: 140 DEG C

Fourth dryer barrel: 160 DEG C

Fifth dryer barrel: 180 DEG C

Operating conditions:

diameter of screw (D): 132mm

Full length of screw (L): 4620mm

·L/D：35

Revolution of screw: 135rpm

Vacuum of the dryer barrel: 10kPa

The amount of rubber extruded from the die: 700 kg/hr

Resin pressure in die: 2MPa of

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

The extruded sheet-like dried rubber was cooled to 50℃and then cut by a cutter, and 20 parts (20 kg) of the resultant was laminated before the temperature was lowered to 40℃or lower, to obtain a rubber-covered acrylic rubber (A). The reactive group content, ash component content, gel content, pH, specific gravity, glass transition temperature (Tg), water content, molecular weight distribution, and complex viscosity at 100℃and 60℃of the resulting rubber-coated acrylic rubber (A) were measured and are shown in tables 2-2. Further, the storage stability test of the rubber-coated acrylic rubber (A) was conducted to determine the water content change rate, and the results are shown in Table 2-2.

Next, 100 parts of the rubber-coated acrylic rubber (A) and the compounding agent A of "formula 1" shown in Table 1 were charged into a Banbury mixer, and mixed at 50℃for 5 minutes (first-stage mixing). At this time, BIT was measured, and the Banbury processability was evaluated, and the results are shown in Table 2-2. Subsequently, the obtained mixture was transferred to a roll at 50℃and blended with the compounding agent B of "formula 1" shown in Table 1, followed by mixing (second stage mixing) to obtain a rubber composition. The obtained rubber compositions were evaluated for injection moldability, and the results are shown in tables 2-2.

TABLE 1

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

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

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

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

Example 2

A rubber-coated acrylic rubber (B) was obtained in the same manner as in example 1 except that the monomer components were changed to 48.25 parts of ethyl acrylate, 50 parts of n-butyl acrylate and 1.75 parts of mono-n-butyl fumarate as shown in table 2-1, and each characteristic was evaluated (the compounding agent was changed to "formula 2" (see table 1)). These results are shown in Table 2-2.

Example 3

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

Example 4

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

Example 5

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

Example 6

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

Example 7

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

Example 8

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

Example 9

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

Example 10

A rubber-in-package acrylic rubber (J) was obtained in the same manner as in example 9 except that the monomer components were changed to 28 parts of ethyl acrylate, 38 parts of n-butyl acrylate, 27 parts of methoxyethyl acrylate, 5 parts of acrylonitrile, and 2 parts of allyl glycidyl ether, and each characteristic was evaluated (the compounding agent was changed to "formula 3" (see table 1)). These results are shown in Table 2-2.

Example 11

A rubber-coated acrylic rubber (K) was obtained in the same manner as in example 9 except that the monomer components were changed to 42.2 parts of ethyl acrylate, 35 parts of n-butyl acrylate, 20 parts of methoxyethyl acrylate, 1.5 parts of acrylonitrile, and 1.3 parts of vinyl chloride, and each characteristic was evaluated (the compounding agent was changed to "formula 4" (see table 1)). These results are shown in Table 2-2.

Example 12

The procedure of example 11 was repeated except that the post-addition of n-dodecyl mercaptan was changed to a total of 3 times of 0.008 parts after 50 minutes, 0.008 parts after 100 minutes and 0.008 parts after 120 minutes, to obtain a rubber-coated acrylic rubber (L), and each property was evaluated. These results are shown in Table 2-2.

Example 13

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

Comparative example 1

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

Comparative example 2

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

[ Table 2-1]

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[ Table 2-2]

As is clear from tables 2 to 2, the acrylic rubber (A) to (M) of the present invention is composed of a binding unit derived from at least one (meth) acrylic acid ester selected from the group consisting of alkyl (meth) acrylate and alkoxyalkyl (meth) acrylate, a binding unit derived from an ion-reactive group-containing monomer, and a binding unit derived from another monomer used as required, has a weight average molecular weight (Mw) of 100 to 500 ten thousand, a ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of 1.5 to 3, an ash content of 0.3% by weight or less, a total amount of sodium, sulfur, calcium, magnesium and phosphorus in ash of 80% by weight or more, and is excellent in injection moldability, water resistance, compression set and normal physical properties including strength characteristics, and also excellent in Banbury processability and storage stability (examples 1 to 13).

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

As is clear from tables 2 to 2, regarding the injection moldability, the molecular weight distribution (Mw/Mn) of the acrylic rubber was strongly affected, and in comparative example 2, mw/mn=1.3, the injection moldability was x; in example 13, mw/mn=1.55, injection moldability was Δ; in example 12, mw/mn=1.99, and injection moldability was good; in examples 3 to 11, mw/mn=2.39 to 2.45 and injection moldability was excellent; and in examples 1 to 2, the Mw/Mn=2.91 to 2.94 and the injection moldability was good, and it was found that the acrylic rubber of the present invention was most excellent in the vicinity of Mw/Mn of 2.4 and excellent in the injection moldability. It is also found that when the molecular weight distribution (Mz/Mw) focusing on the high molecular weight region is sufficiently broad, the number average molecular weight (Mn), the weight average molecular weight (Mw), and the z average molecular weight (Mz) are sufficiently large and are within the range of Mw/Mn of the present invention, the injection moldability can be improved without impairing the strength characteristics (comparison of examples 1 to 13 with comparative example 2).

As is clear from tables 2-1 and 2-2, the acrylic rubbers (A) to (M) having a molecular weight distribution (Mw/Mn) in a specific range, which are excellent in injection moldability, can be produced by using specific amounts of an organic radical generator and a chain transfer agent, in particular, n-dodecyl mercaptan as the chain transfer agent (examples 1 to 13). It is also clear from tables 2-1 and 2-2 that the injection moldability can be improved without impairing the strength characteristics by adding the chain transfer agent (n-dodecyl mercaptan) in a batch manner after the initial addition without the addition of the chain transfer agent (n-dodecyl mercaptan) as compared with the continuous addition of the chain transfer agent (n-dodecyl mercaptan) (example 13). This is presumed to be that 1 polymer chain is extended by reducing the amount of the organic radical generator without adding a chain transfer agent at the initial stage, and that the strength characteristics and injection moldability are highly balanced by adding a chain transfer agent during polymerization, whereby a high molecular weight component and a low molecular weight component can be produced in a well-balanced manner although there is no clear double peak in a GPC chart, and the molecular weight distribution (Mw/Mn) can be set in a specific range. In order to effectively widen the molecular weight distribution (Mw/Mn), the number of times of addition after batch was greatly affected, and the molecular weight distribution (Mw/Mn) of which the number of times of addition after batch was 2 was wider than that of 3 times (comparison of examples 9 to 11 with example 12). In addition, tables 2-1 and 2-2, although not shown, in the examples of the present application, sodium ascorbate, which is a reducing agent added 120 minutes after the start of polymerization, is likely to produce a high molecular weight component of the acrylic rubber, and the effect of widening the molecular weight distribution (Mw/Mn) of the chain transfer agent added later is increased.

Further, as is clear from tables 2-1 and 2-2, if the drying of the aqueous pellets is changed from direct drying to a screw type biaxial extrusion dryer and is operated under normal conditions, there is no change in the molecular weight distribution (Mw/Mn) (comparison of examples 5 to 8 with examples 9 to 11), and the molecular weight distribution (Mw/Mn) of the acrylic rubber is widened by setting the drying conditions of the screw type biaxial extrusion dryer to the most appropriate shearing, so that the injection moldability of the acrylic rubber can be further improved (comparison of examples 3 to 4 with example 12), but when the molecular weight distribution (Mw/Mn) is too wide, the effect of the injection moldability is reduced (comparison of examples 1 to 2 with examples 5 to 8). Further, it is understood that, although not shown in examples and comparative examples of the present application, when a redox catalyst of an inorganic radical generator is used, the molecular weight distribution (Mw/Mn) of the obtained acrylic rubber is too broad and the injection moldability is poor. This is considered to be because, in the case of using an organic radical generator, the polymerization catalyst is polymerized continuously in a certain micelle in the emulsion polymerized micelle, but in the case of using an inorganic radical generator, the polymerization catalyst is polymerized outside the micelle, and thus, a difference in these molecular weight distributions is generated, and injection moldability is affected.

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

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

Further, as is clear from tables 2-1 and 2-2, regarding the water resistance, by dehydrating (extruding moisture) before drying the aqueous pellets, the ash amount in the acrylic rubber can be further greatly reduced, the water resistance is remarkably improved (comparison of examples 1 to 8 and examples 9 to 13), and when the water content after dehydration is 20% compared with 30%, more moisture can be extruded from the aqueous pellets, and therefore the ash amount can be reduced, and the water resistance of the acrylic rubber is remarkably improved (comparison of examples 1 to 6 and examples 7 to 8).

Further, as is clear from tables 2-1 and 2-2, regarding the ash components of the acrylic rubbers (A) to (M) of the invention and the acrylic rubbers (N) to (O) of the comparative examples, the total amount of phosphorus (P), magnesium (Mg), sodium (Na), calcium (Ca) and sulfur (S) is 80% by weight or more or 90% by weight or more, and the ash content can be reduced and the water resistance can be improved. In addition, when the ash component is these components, the releasability of the acrylic rubber is particularly excellent. It is also clear from tables 2 to 2 that the ash components of the acrylic rubber (A) to (M) of the present invention, which were coagulated and washed and dehydrated by the method of the present invention, were 80% or more or 90% or more of phosphorus (P) and magnesium (Mg) (examples 1 to 13 and comparative examples 1 to 2). It is also found that the ash in the acrylic rubber is not directly remained as the emulsifier and coagulant used in the production, but is present in the aqueous pellet as a salt of sodium phosphate of the emulsifier and magnesium sulfate (MgSO 4) of the coagulant at the time of the coagulation reaction, and is not sufficiently removed in the washing step, but can be reduced by dehydration (water extrusion from the aqueous pellet) in a screw type biaxial extrusion dryer (examples 1 to 8), and when the water content after dehydration is 20% compared with 30%, more water can be extruded from the aqueous pellet, and therefore the ash amount can be reduced, and the water resistance of the acrylic rubber can be significantly improved (comparison of examples 1 to 6 and examples 7 to 8).

In the present example, although the data is omitted, the water resistance is hardly reduced in the washing step when the phosphate is used as the emulsifier, and particularly in the washing at ordinary temperature, the number of times of washing is hardly reduced, but the washing can be improved by hot water washing, and on the other hand, the water resistance is excellent as compared with ash having a large content of sulfur (S) and sodium (Na) components, and particularly 5 times or more when the amount of ash is the same. It was also confirmed that when a sulfate salt such as sodium lauryl sulfate is used as an emulsifier, the water resistance can be remarkably improved by performing the coagulation reaction of the present invention and performing hot water washing and dehydration to reduce the ash content to 0.1 wt% or less.

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

As is clear from tables 2 to 2, the acrylic rubber (A) to (M) of the present invention is excellent in injection moldability, banbury processability, water resistance, compression set resistance and normal physical properties including strength characteristics, and also is extremely excellent in storage stability. In particular, the acrylic rubbers (A) to (H) of the invention are particularly excellent in storage stability.

As is clear from tables 2-1 and 2-2, the storage stability was affected by the specific gravity of the rubber-coated acrylic rubber bags (A) to (M) which were much larger than the specific gravity of the granular acrylic rubber (N) to (O), that is, the amount of air involved (comparative examples 1 to 8, 9 to 13 and comparative examples 1 to 2). The rubber-coated acrylic rubber having a high specific gravity is obtained by compacting and coating a pellet-shaped acrylic rubber by a packer (examples 9 to 13), and more preferably by extruding and laminating the acrylic rubber into a sheet by a screw type biaxial extrusion dryer (examples 1 to 8). It is also clear that the smaller the ash content, the more preferable the storage stability of the acrylic rubber (examples 1 to 13). In addition, when the characteristic value of the pellet-shaped acrylic rubber directly dried without using a baler was measured for the acrylic rubber (M) of example 13, the results were the same as those of example 13 of Table 2-2 except that the specific gravity was as small as 0.769. In addition, it is also important for the storage stability of the acrylic rubber that the pH is 6 or less.

[ particle size of resulting hydrous pellets ]

Regarding the aqueous pellets produced in the coagulation step in examples 1 to 13 and comparative examples 1 to 2, the proportion of the amount of the aqueous pellets produced in the range of (1) 710 μm to 6.7mm (not passing 710 μm but passing 6.7 mm), (2) 710 μm to 4.75mm (not passing 710 μm but passing 4.75 mm), (3) 710 μm to 3.35mm (not passing 710 μm but passing 3.35 mm) to the total amount of the aqueous pellets produced was measured using a JIS sieve. These results are shown below.

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

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

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

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

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

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

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

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

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

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

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

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

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

Comparative example 2: (1) 10 wt%, (2) 2 wt%, (3) 0 wt%

From these results, it was found that even when the same washing was performed, the amount of ash remaining in the acrylic rubber was different depending on the size of the aqueous aggregates generated in the coagulation step, and that a large amount of the specific proportions of (1) to (3) had high washing efficiency, decreased ash amount, and excellent water resistance (comparison of examples 9 to 13 and comparative examples 1 to 2 of Table 2-2). It was found that the ash removal rate at the time of dehydration was also high in the water-containing pellets having a large specific proportion of (1) to (3), and the ash content (examples 1 to 6) having a dehydration rate (water content) of 20 wt% was lower than that having a dehydration rate (water content) of 30 wt% (examples 7 to 8), thereby improving the water resistance of the acrylic rubber.

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

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

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

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

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

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

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

In addition, regarding these sheet-like acrylic rubbers (A) to (H), the cooling rate of the sheet-like dried rubber extruded from the screw type biaxial extrusion dryer was practically as high as that of example 1, and was about 200℃per hour or more, and 40℃per hour or more.

Further, for each rubber sample, the deviation of the amount of methyl ethyl ketone insoluble component was evaluated by the method described above. Specifically, the amount of methyl ethyl ketone insoluble component at 20 selected arbitrarily from 20 parts (20 kg) of the rubber sample was measured, and the deviation evaluation of the amount of methyl ethyl ketone insoluble component of the rubber sample was performed based on the above reference.

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

This is presumably because the acrylic rubbers (a) to (H) were melt kneaded and dried by a screw type biaxial extruder, and the gel amount of methyl ethyl ketone insoluble components was almost lost and the gel amount was hardly deviated, whereby the banbury workability could be significantly improved.

On the other hand, it was found that the acrylic rubber (O) produced in comparative example 2 was fed into a screw type biaxial extrusion dryer under the same conditions as in example 1 to obtain an acrylic rubber, and the gel amount deviation measured on the obtained acrylic rubber were reduced to a level substantially equal to those of the acrylic rubber (a) and the banbury processability was significantly improved.

[ mold releasability from Metal mold ]

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

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

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

Delta: there is a small amount of mold residue that can be easily released from the metal mold

X: difficult to release from metal molds

Description of the reference numerals

1: acrylic rubber manufacturing system

3: coagulation device

4: cleaning device

5: screw extruder

6: cooling device

7: glue packaging device

Claims

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

the (meth) acrylic acid ester is at least one selected from the group consisting of alkyl (meth) acrylates and alkoxyalkyl (meth) acrylates,

the weight average molecular weight (Mw) of the acrylic rubber is 100 to 500 ten thousand, the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is in the range of 1.5 to 3, the ash content is 0.3 wt% or less, and the total amount of sodium, sulfur, calcium, magnesium and phosphorus in the ash is 80 wt% or more.

2. The acrylic rubber according to claim 1, wherein a ratio (Mz/Mw) of a z-average molecular weight (Mz) to a weight-average molecular weight (Mw) of the acrylic rubber is 1.3 or more.

3. The acrylic rubber according to claim 1 or 2, wherein a ratio (Mz/Mw) of z-average molecular weight (Mz) to weight-average molecular weight (Mw) of the acrylic rubber is 4 or less.

4. An acrylic rubber according to any one of claims 1 to 3, wherein the number average molecular weight (Mn) of the acrylic rubber is in the range of 40 to 110 tens of thousands.

5. The acrylic rubber according to any one of claims 1 to 4, wherein the weight average molecular weight (Mw), the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) (Mw/Mn), or the ratio of the z-average molecular weight (Mz) to the weight average molecular weight (Mw) (Mz/Mw) of the acrylic rubber is an absolute molecular weight or an absolute molecular weight distribution as determined by GPC-MALS method.

6. The acrylic rubber according to claim 5, wherein the measuring solvent of the GPC-MALS method is dimethylformamide-based solvent.

7. The acrylic rubber according to any one of claims 1 to 6, wherein the monomer composition of the acrylic rubber is composed of 50 to 99.99% by weight of a binding unit derived from a (meth) acrylic ester selected from at least one of an alkyl (meth) acrylate and an alkoxyalkyl (meth) acrylate, 0.01 to 10% by weight of a binding unit derived from an ion-reactive group-containing monomer, and 0 to 40% by weight of a binding unit derived from another monomer.

8. The acrylic rubber according to any one of claims 1 to 7, wherein the ion-reactive group is a carboxyl group or an epoxy group.

9. The acrylic rubber according to any one of claims 1 to 8, wherein the gel amount of the acrylic rubber is 50% by weight or less.

10. The acrylic rubber according to any one of claims 1 to 9, wherein the gel amount of the acrylic rubber is 30% by weight or less.

11. The acrylic rubber according to any one of claims 1 to 10, wherein all values of the gel amount at 20 are arbitrarily measured within a range of (average ± 5% by weight).

12. The acrylic rubber according to any one of claims 1 to 11, wherein the specific gravity of the acrylic rubber is 0.8 or more.

13. The acrylic rubber according to any one of claims 1 to 12, wherein the total amount of magnesium and phosphorus in ash of the acrylic rubber is 50% by weight or more.

14. The acrylic rubber according to any one of claims 1 to 13, wherein a ratio of magnesium to phosphorus ([ Mg ]/[ P ]) in ash of the acrylic rubber is in a range of 0.4 to 2.5 in terms of a weight ratio.

15. The acrylic rubber according to any one of claims 1 to 14, wherein the acrylic rubber has a complex viscosity ([ η60 ] c) of 15000[ pa-s ] or less at 60 ℃.

16. The acrylic rubber according to any one of claims 1 to 15, wherein a ratio of complex viscosity at 100 ℃ ([ η ]100 ℃) to complex viscosity at 60 ℃ ([ η ]60 ℃) ([ η ]100 ℃/[ η ]60 ℃)) is 0.7 or more.

17. The acrylic rubber according to any one of claims 1 to 16, wherein the acrylic rubber is in a sheet form or a bale form.

18. The acrylic rubber according to any one of claims 1 to 17, wherein the acrylic rubber is emulsion-polymerized using a phosphate salt or a sulfate salt as an emulsifier.

19. The acrylic rubber according to any one of claims 1 to 18, wherein the acrylic rubber is obtained by coagulating and drying the emulsion-polymerized polymer liquid using an alkali metal salt or a group 2 metal salt of the periodic table as a coagulant.

20. The acrylic rubber according to any one of claims 1 to 19, wherein the acrylic rubber is obtained by melt kneading and drying after solidification.

21. The acrylic rubber according to claim 20, wherein the acrylic rubber is obtained by the melt kneading and drying in a state substantially containing no moisture.

22. The acrylic rubber according to claim 20 or 21, wherein the acrylic rubber is obtained by the melt kneading and drying under reduced pressure.

23. The acrylic rubber according to any one of claims 20 to 22, wherein the acrylic rubber is cooled at a cooling rate of 40 ℃/hr after the melt-kneading and drying.

24. The acrylic rubber according to any one of claims 1 to 23, wherein the acrylic rubber is obtained by washing, dehydrating and drying an aqueous pellet having a particle diameter in the range of 710 μm to 6.7mm in a proportion of 50% by weight or more.

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

an emulsifying step of emulsifying a monomer component composed of a (meth) acrylic acid ester selected from at least one of an alkyl (meth) acrylate and an alkoxyalkyl (meth) acrylate, an ion-reactive group-containing monomer, and other monomers used as needed, with water and an emulsifier;

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

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

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

a dehydration step of dehydrating the washed aqueous pellets; and

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

26. The method for producing an acrylic rubber according to claim 25, which is a method for producing an acrylic rubber according to any one of claims 1 to 24.

27. The method for producing an acrylic rubber according to claim 25 or 26, wherein in the emulsion polymerization step, emulsion polymerization is performed using a phosphate salt or a sulfate salt as an emulsifier.

28. The method for producing an acrylic rubber according to any one of claims 25 to 27, wherein the polymerization liquid produced in the emulsion polymerization step is coagulated by contacting with a coagulant containing an alkali metal salt or a group 2 metal salt of the periodic table.

29. The method according to any one of claims 25 to 28, wherein the polymerization liquid produced in the emulsion polymerization step is solidified by contacting with a coagulant, and then melt-kneaded and dried.

30. The method for producing an acrylic rubber according to claim 29, wherein the melt kneading and drying are performed in a state substantially containing no moisture.

31. The method for producing an acrylic rubber according to claim 29 or 30, wherein the melt kneading and drying are performed under reduced pressure.

32. The method for producing an acrylic rubber according to any one of claims 29 to 31, wherein the melt kneading and drying are performed by a screw type biaxial extrusion dryer.

33. The method for producing an acrylic rubber according to claim 32, wherein the maximum torque of the screw type biaxial extrusion dryer at the time of melt kneading and drying is in the range of 5 to 125 N.m.

34. The method according to any one of claims 29 to 33, wherein the melt-kneaded and dried acrylic rubber is cooled at a cooling rate of 40 ℃/hr or more.

35. The method for producing an acrylic rubber according to any one of claims 25 to 34, wherein the coagulant concentration of the coagulant is 1% by weight or more.

36. The method for producing an acrylic rubber according to any one of claims 25 to 35, wherein the number of stirring of the stirred coagulation liquid is 100rpm or more.

37. The method for producing an acrylic rubber according to any one of claims 25 to 36, wherein the peripheral speed of the stirred coagulation liquid is 1m/s or more.

38. The method for producing an acrylic rubber according to any one of claims 25 to 37, wherein a reducing agent is added after the emulsion polymerization step.

39. The method according to any one of claims 25 to 38, wherein the aqueous pellets having a particle diameter in the range of 710 μm to 6.7mm in a proportion of 50 wt.% or more are washed, dehydrated and dried.

40. A rubber composition comprising: a rubber component comprising the acrylic rubber according to any one of claims 1 to 24, a filler and a crosslinking agent.

41. The rubber composition according to claim 40, wherein the filler is a reinforcing filler.

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

43. The rubber composition according to claim 40, wherein the filler is silica.

44. The rubber composition of any of claims 40 to 43, wherein the crosslinking agent is an organic crosslinking agent.

45. The rubber composition according to any one of claims 40 to 44, wherein the crosslinking agent is a multi-component compound.

46. The rubber composition of any of claims 40-45, wherein the crosslinking agent is an ionically crosslinkable compound.

47. The rubber composition according to claim 46, wherein the crosslinking agent is an ion-crosslinkable organic compound.

48. The rubber composition of claim 46 or 47, wherein the cross-linking agent is a polyionic organic compound.

49. The rubber composition according to any one of claims 46 to 48, wherein the ion of the ion-crosslinkable compound, the ion-crosslinkable organic compound or the polyion-organic compound as the crosslinking agent is at least one ion-reactive group selected from the group consisting of an amino group, an epoxy group, a carboxyl group and a thiol group.

50. A rubber composition as described in claim 48, wherein said crosslinking agent is at least one polyionic compound selected from the group consisting of a polyamine compound, a polyepoxide compound, a polycarboxylic acid compound and a polythiol compound.

51. The rubber composition according to any one of claims 40 to 50, wherein the content of the crosslinking agent is in the range of 0.001 to 20 parts by weight relative to 100 parts by weight of the rubber component.

52. The rubber composition of any of claims 40-51, wherein the rubber composition further comprises an anti-aging agent.

53. The rubber composition according to claim 52, wherein the antioxidant is an amine-based antioxidant.

54. A method for producing a rubber composition, wherein a rubber component comprising the acrylic rubber according to any one of claims 1 to 24, a filler, and an antioxidant, if necessary, are mixed, and thereafter a crosslinking agent is mixed.

55. A rubber crosslinked product obtained by crosslinking the rubber composition according to any one of claims 40 to 53.

56. The rubber crosslinked according to claim 55 wherein crosslinking of the rubber composition occurs after molding.

57. The rubber crosslinked according to claim 55 or 56 wherein the crosslinking of the rubber composition is a crosslinking that performs primary crosslinking and secondary crosslinking.