JPH07110891B2 - Method for producing acrylic copolymer elastomer - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a novel copolymer elastomer, and more particularly to a method for producing a novel acrylic copolymer elastomer excellent in fuel oil resistance. It is a thing.

[Prior Art] A polymer of an alkyl acrylate is known as an acrylic rubber. Acrylic rubber is widely used for oil seals and the like because it has excellent heat resistance and resistance to lubricating oil. However, acrylic rubber has no resistance to fuel oils that are stricter than lubricating oils such as gasoline, that is, fuel oils having a low aniline point, and the range of use is limited to lubricating oils. In order to improve the fuel oil resistance of acrylic rubber, it has been attempted to use a monomer having a highly polar functional group such as a cyano group or a fluorine-containing group as a copolymerization component. Therefore, there is a problem that the glass transition point of the copolymer is increased and the low temperature characteristics of the obtained copolymer elastomer are impaired.

[Problems to be Solved by the Invention] An object of the present invention is to provide a method for producing an acrylic elastomer having improved low temperature characteristics and improved resistance to fuel oil. The present inventors have improved the fuel oil resistance of the acrylic elastomer and used it at a low temperature by using an acrylic acid ester or a methacrylic acid ester having a specific structure as one component of the monomer constituting the acrylic elastomer. However, the present invention has been found to be improved.

[Means for Solving Problems] The present invention provides (A) at least one acrylic ester selected from an acrylic ester of an alkyl group having 2 to 4 carbon atoms,
89.5 to 50% by weight, (B) acrylic acid ester and / or methacrylic acid ester having the structure of the following formula (I), 10 to 50% by weight (Here, R ¹ is hydrogen or a methyl group, R ² is a cyano-substituted alkyl group, n is an integer of 1 or more, and the number average value thereof is 1 to 5.) (C) Crosslinkable monomer , 0.5 to 10% by weight, and (D) Monovinyl-based and monovinylidene-based unsaturated other than (A), (B) and (C) that can be copolymerized with the above (A), (B) and (C). The present invention relates to a method for producing an acrylic copolymer elastomer, which comprises copolymerizing at least one monomer selected from monomers in an amount of 0 to 15% by weight in the presence of a radical initiator.

In the present invention, the component (A) is at least one acrylic ester selected from an acrylic ester of an alkyl group having 2 to 4 carbon atoms, specifically, ethyl acrylate, propyl acrylate, isopropyl acrylate, acrylic acid. Examples include n-butyl, tert-butyl acrylate, and sec-butyl acrylate. Of these, ethyl acrylate and n-butyl acrylate are particularly preferable. The amount in the total monomers used is 94.5 to 50% by weight. When the content of the component (A) is less than 50% by weight, heat resistance and mechanical strength of the obtained copolymer elastomer are deteriorated, which is not preferable.

The component (B) is an acrylic acid ester and / or a methacrylic acid ester having a structure represented by the general formula (I).

(Here, R ¹ is hydrogen or a methyl group, R ² is a cyano group-containing alkyl group, n is an integer of 1 or more, and the number average value thereof is 1 to 5.) Specific examples of R ² include 2-cyanoethyl group, 1-cyanoethyl group, 1-cyanopropyl group, 2-cyanopropyl group, 3
Examples thereof include -cyanopropyl group, 4-cyanobutyl group, 6-cyanohexyl group, and 2-cyanoethyl group is particularly preferable. The acrylic acid ester or methacrylic acid ester of the component (B) usually has a different molecular weight when produced by the general production method described below, that is, the formula (I)
It is possible to use the mixture as it is, though it can be obtained as a mixture of different n. Of course, it does not matter if the acrylic ester or methacrylic ester separated by distillation or the like and having no molecular weight distribution is used. In the present invention, the number average value of n is 1 to 5. If the number average value of n is too large, the degree of unsaturation decreases, the polymerizability decreases, and the effect of improving fuel oil resistance is small, which is not preferable. The acrylic ester or methacrylic ester of the component (B) may contain cyanoalkyl acrylate or cyanoalkyl methacrylate represented by the following formula (II) in the production method, but if the amount is 20% by weight or less, There is no particular problem.

(Here, R ¹ is hydrogen or a methyl group, and R ² is a cyano group-containing alkyl group.) The acrylic ester or methacrylic ester of the component (B) is a compound having a structure represented by the formula (III) Known method for synthesizing acrylic acid ester or methacrylic acid ester by reacting with acrylic acid or methacrylic acid, or synthesis of known acrylic acid ester or methacrylic acid ester by reacting compound (III) with acryloyl halide or methacryloyl halide It can be easily synthesized by a method similar to the method.

(Here, R ² is a cyano group-containing alkyl group, and n is 1
It is the above integer, and the number average value is 1 to 5. The compound having a structure represented by the formula (III) and having a number average value of n of 1 to 5 is a monovalent cyano group-containing saturated alcohol having a structure of R ² OH and having ε-caprolactone as a catalyst. It is synthesized by a known method of ring-opening addition below.
The alcohols used in the ring-opening addition reaction of ε-caprolactone include 2-cyanoethyl alcohol, 1-cyanoethyl alcohol, 1-cyanopropyl alcohol, 2
-Cyanopropyl alcohol, 3-cyanopropyl alcohol, 4-cyanobutyl alcohol, 6-cyanohexyl alcohol and the like can be mentioned. As catalysts for ring-opening addition reaction, organotitanium compounds such as tetraethoxytitanium and tetrabutoxytitanium, organotin compounds such as di-n-butyltin dilaurate and dibutyltin oxide, tin halide compounds such as stannous chloride, and perchloric acid. It has been known.
The addition amount of ε-caprolactone in the above compound, that is, the number average value of n can be adjusted by changing the molar ratio of cyano group-containing saturated alcohol (R ² OH) and ε-caprolactone used in the reaction.

In the present invention, the amount of the component (B) in all monomers used is 5
It is 50% by weight, preferably 10 to 30% by weight. Ingredient (B)
When the amount is small, the effect of the present invention is not exhibited, and when the amount is too large, there arises a problem that the heat aging resistance and mechanical strength of the obtained copolymer elastomer are lowered.

The component (C) is a unit that acts as a cross-linking point during vulcanization in the copolymer elastomer of the present invention, and contains an active functional group such as an active halogen group, an epoxy group or a carboxylic acid in the molecule. Unsaturated compounds are used. Specific examples of the active halogen-containing unsaturated compound include 2-chloroethyl vinyl ether, vinyl chloroacetate, allyl chloroacetate, chloromethylstyrene, 2-chloroethyl acrylate, 2-chloroethyl methacrylate and the like. Examples of the epoxy group-containing unsaturated compound include allyl glycidyl ether, glycidyl acrylate, glycidyl methacrylate and the like. Examples of unsaturated carboxylic acids include acrylic acid, methacrylic acid, maleic acid, fumaric acid and itaconic acid. The amount of component (C) in all the monomers used is 0.5 to 10% by weight, preferably 0.5 to 5% by weight. These crosslinkable monomers can be used alone or as a mixture of two or more kinds. If the amount of the component (C) is small, the vulcanization cannot be sufficiently performed, and if it is too large, the vulcanization proceeds excessively and it is impossible to obtain a satisfactory vulcanized rubber sheet.

It is possible to further add the component (D) to the above essential components (A), (B) and (C) within a range not impairing the effects of the present invention. Ingredient (D) is the above essential ingredients (A), (B)
And (C), which are radically copolymerizable with (A), (B) and (C), other than monovinyl-based and monovinylidene-based unsaturated monomers, that is, one in the molecule. Is at least one monomer selected from monomers having a structure represented by the following, and examples thereof include alkyl acrylates other than the component (A) such as methyl acrylate and 2-ethylhexyl acrylate, Examples thereof include acrylic acid alkoxyalkyl esters such as methoxyethyl acrylate and ethoxyethyl acrylate, methacrylic acid esters such as methyl methacrylate and ethyl methacrylate, vinyl acetate, acrylonitrile, methacrylonitrile, and styrene. The maximum amount of the component (D) in all the monomers used, which does not impair the effects of the present invention, depends on the kind of the compound, but is at most 15% by weight.

The acrylic copolymer elastomer of the present invention can be obtained by a known method such as bulk polymerization, solution polymerization, emulsion polymerization or suspension polymerization by using a radical initiator which is usually used in the present invention for the monomer mixture. It can be easily manufactured. Emulsion polymerization is particularly preferable as the polymerization method.

As the radical polymerization initiator, usual radical initiators such as peroxides, redox compounds, persulfates and azo compounds can be used. Polymerization is possible in the temperature range of 0 to 100 ° C, preferably 5 to 80 ° C.

The copolymer elastomer obtained by the polymerization can be easily isolated by salting out using an aqueous solution of an inorganic salt such as calcium chloride or sodium chloride or by using a polymer insoluble solvent such as methanol.

The acrylic polymer elastomer produced by the method of the present invention can be vulcanized by a method similar to the commonly known vulcanization method of acrylic rubber. Vulcanization is performed on the copolymer elastomer by a vulcanizing agent selected depending on the type of the component (C) that acts as a crosslinking point, and if necessary, a vulcanization accelerator, a reinforcing agent, a filler, a plasticizer, an antiaging agent. , Stabilizers, etc. are added.

[Examples] The present invention will be specifically described below with reference to Examples, but the scope of the present invention is not limited thereto.

Synthesis Example 1 383.4 parts by weight of ethylene cyanohydrin and 148.2 parts by weight of ε-caprolactone were charged into a three-necked flask equipped with a stirrer and a condenser, and the temperature was raised with stirring. When the temperature reached 150 ° C., 0.075 parts by weight of tetrabutoxytitanium was added and the temperature was maintained at 150 ° C., and the reaction was carried out for about 5 hours under a nitrogen atmosphere. After the reaction, the conversion rates of ethylene cyanohydrin and ε-caprolactone were 8.9% and 98%, respectively. By further heating under reduced pressure, unreacted ethylene cyanohydrin was removed from the reaction product to obtain a caprolactone adduct having a hydroxyl group at the terminal. The average molecular weight of the obtained caprolactone addition compound was 370. Here, the conversion rates of ethylene cyanohydrin and ε-caprolactone were determined by using a gas chromatograph, and the molecular weight of the caprolactone addition compound was determined from the KOH value measured according to JIS K0070.

250 parts by weight of the obtained caprolactone oligomer, 65 parts by weight of acrylic acid, 500 parts by weight of toluene, 6.5 parts by weight of hydroquinone, and 3 parts by weight of sulfuric acid were charged into a flask equipped with a stirrer, a condenser and a separator to carry out an esterification reaction. went. The water produced by the reaction was distilled and condensed together with the solvent, removed from the system by a separator, and only the solvent was returned to the reaction system.
When the production of water stopped, the reaction was terminated by cooling. The resulting reaction solution was neutralized with a 20% aqueous sodium hydroxide solution, washed with a 20% aqueous sodium chloride solution several times, and the solvent was removed under reduced pressure to obtain the desired pale yellow acrylate. Table 1 shows the quantification of the terminal unsaturated group of the obtained acrylate ester and the molecular weight of the acrylate ester calculated from the nitrogen content. It was confirmed that the target acrylic acid ester was produced since these two were almost the same. This is represented by the formula (I) in which R ¹
= H, n corresponds to a compound having an average value of 3.0. The content of 2-cyanoethyl acrylate in the acrylic ester was 1% by weight or less.

Here, the quantification of the terminal unsaturated group is carried out by the morpholine method (for example, the method described on page 225 of "Polymer Experiment" Vol. According to, the nitrogen content was measured by elemental analysis. The amount of 2-cyanoethyl acrylate in the obtained acrylic ester was quantified by gas chromatography.

Synthesis Example 2 A caprolactone addition compound was synthesized in the same manner as in Synthesis Example 1 except that 355 parts by weight of ethylene cyanohydrin and 114 parts by weight of ε-caprolactone were used. After the reaction, the conversion of ethylene cyanohydrin and ε-caprolactone was 1 each.
2.8% and 100%, and the molecular weight of the obtained caprolactone addition compound was 210. 100 parts by weight of acrylic acid,
An esterification reaction was carried out in the same manner as in Synthesis Example 1 except that 10 parts by weight of hydroquinone was used to obtain the desired acrylic ester. Table 1 shows the amount of terminal unsaturated group measured by the same method as in Synthesis Example 1 and the molecular weight of the acrylic ester calculated from the nitrogen content. It was confirmed that the target acrylic acid ester was produced since these two were almost the same.

In this formula (I), R ¹ = H, the average value of n is
Corresponds to 1.6 compounds. The content of 2-cyanoethyl acrylate in the acrylic ester was 1% by weight or less.

Synthesis Example 3 A caprolactone addition compound was synthesized in the same manner as in Synthesis Example 2. After the reaction, the conversion rates of ethylene cyanohydrin and ε-caprolactone were 13.0% and 99%, respectively, and the obtained caprolactone addition compound had a molecular weight of 200. The esterification reaction was carried out in the same manner as in Synthesis Example 2 to obtain the desired acrylic ester. Table 1 shows the molecular weight of the acrylic ester calculated from the amount of terminal unsaturated group and nitrogen content measured by the same method as in Synthesis Example 1. It was confirmed that the target acrylic acid ester was produced since these two were almost the same. This corresponds to the compound of the formula (I) in which R ¹ = H and the number average value of n is 1.5. The content of 2-cyanoethyl acrylate in the acrylic ester was 6% by weight.

Synthesis Example 4 A caprolactone addition compound was synthesized in the same manner as in Synthesis Example 2. The conversion rates of ethylene cyanohydrin and ε-caprolactone after the reaction were 12.5% and 100%, respectively, and the obtained caprolactone addition compound had a molecular weight of 215. An esterification reaction was carried out in the same manner as in Synthesis Example 1 except that 125 parts by weight of methacrylic acid and 12.5 parts by weight of hydroquinone were used to obtain a desired methacrylic acid ester. Table 1 shows the molecular weight of the methacrylic acid ester calculated from the amount of terminal unsaturated group and nitrogen content measured by the same method as in Synthesis Example 1. It was confirmed that the target methacrylic acid ester was produced since these two were almost the same. This corresponds to the compound of formula (I) in which R ¹ = CH ₃ and the number average value of n is 1.6. The content of 2-cyanoethyl methacrylate in the methacrylic acid ester was 6% by weight or less.

Examples 1 to 11 and Comparative Examples 1 to 5 One-fifth of a mixture of the monomer mixture having the composition shown in Table 2 and n-dodecyl mercaptan (varied depending on the monomer composition for controlling the molecular weight) was used as sodium dodecylbenzenesulfonate 4 An emulsifier solution consisting of 1 part by weight, 1 part by weight sodium naphthalene sulfonate, 0.2 parts by weight tripotassium phosphate and 200 parts by weight distilled water was mixed and stirred to emulsify. The temperature of this emulsion was set to 10 ° C, 0.01 parts by weight of ferrous sulfate, 0.02 parts by weight of trisodium ethylenediaminetetraacetate,
Polymerization was initiated by adding 0.01 part by weight of paramenthane hydroperoxide.

Thereafter, while maintaining the temperature at 10 ° C., the remaining monomer mixture was added dropwise over about 6 hours, and 0.05 part by weight of paramenthane hydroperoxide was simultaneously added in portions. After the dropping of the monomer was completed, the polymerization was continued for another 4 hours and then cooled to complete the polymerization. The conversion of the monomer was 96-99%. The obtained copolymer latex was put into a sodium chloride aqueous solution at 80 ° C. to isolate the copolymer, which was thoroughly washed with water and then dried to obtain a copolymer elastomer.

The copolymer elastomers obtained in Examples 1 to 8 and Comparative Examples 1 and 2 were roll-kneaded in accordance with the composition shown in Table 3 and heated at 170 ° C for 2
A vulcanized rubber sheet was prepared by performing press vulcanization for 0 minutes.

Further, this was heat-treated in a gear oven at 150 ° C. for 4 hours, and then the physical properties of the vulcanized rubber were evaluated.

The copolymer elastomers obtained in Examples 9 to 11 and Comparative Examples 3 to 5 were roll-kneaded according to the formulations shown in Table 4.
A vulcanized rubber sheet was prepared by performing press vulcanization at 0 ° C for 20 minutes. Further, this was heat-treated in a gear oven at 150 ° C. for 4 hours, and then the physical properties of the vulcanized rubber were evaluated.

Table 5 shows physical properties of unvulcanized rubber and vulcanized rubber of Examples 1 to 10 and Comparative Examples 1 to 5. Mooney viscosity is JIS K630
0, physical properties of vulcanized rubber were evaluated according to JIS K6301. The fuel oil resistance was evaluated by measuring the volume change rate after immersing the vulcanized rubber in fuel oil C at 40 ° C. for 72 hours. The glass transition temperature was measured with a differential scanning calorimeter (DSC) at a temperature rising rate of 10 ° C / min using unvulcanized rubber as a sample.

[Effects of the Invention] From the above results, it is clear that a novel copolymer elastomer excellent in fuel oil resistance and cold resistance can be obtained by the production method of the present invention.

Claims (1)

[Claims] 1. A) at least one acrylic ester selected from the group consisting of (A) C2-4 alkyl group acrylic esters, 89.5 to 50% by weight, and (B) acrylic acid having the structure of the following formula (I). Ester and / or methacrylic acid ester, 10-50% by weight (Here, R ¹ is hydrogen or a methyl group, R ² is a cyano-substituted alkyl group, n is an integer of 1 or more, and the number average value thereof is 1 to 5.) (C) Crosslinkable monomer , 0.5 to 10% by weight, and (D) Monovinyl-based and monovinylidene-based unsaturated other than (A), (B) and (C) that can be copolymerized with the above (A), (B) and (C). A method for producing an acrylic copolymer elastomer, characterized in that 0 to 15% by weight of at least one monomer selected from monomers is copolymerized in the presence of a radical initiator.