JPS63210113A - Production of acrylic elastomer - Google Patents

Abstract

PURPOSE:To obtain the title elastomer which can give a crosslinked rubber excellent in vulcanizability and transparency, by copolymerizing an (alkoxy)alkyl acrylate with a functional group-containing vinyl monomer by using a mercapto compound as a chain transfer agent. CONSTITUTION:A solution formed by dissolving 1-10pts.wt. polymerization initiator (B) such as purified azobisisobutyronitrile in a solvent is added to 10-900pts.wt. monomer mixture (A) comprising at least one vinyl monomer selected from among a 1-8C alkyl acrylate (a) and/or a 2-8C alkoxyalkyl acrylate (b) and a vinyl monomer or diene monomer (c) containing a functional group such as an epoxy group, COOH group, reactive halogen, OH group, NH2 group or the like, and the obtained mixture is solution-polymerized in the presence of 0.1-3mol.%, based on component A, chain transfer agent (C) comprising a mercapto compound such as an omega-mercaptoalkanol.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing an acrylic elastomer. More specifically, the present invention relates to a method for producing an acrylic elastomer that can provide a crosslinked rubber with excellent vulcanization properties and transparency.

[Prior Art] and [Problems to be Solved by the Invention] Conventional transparent materials with rubber-like elasticity deteriorate in transparency when vulcanized physical properties such as strength and elongation are improved; has the disadvantage that vulcanized physical properties deteriorate.

Therefore, the present inventors have conducted various studies in order to obtain a rubber material for acrylic elastomer that is excellent in both vulcanizable properties and transparency.

It has been found that this problem can be effectively solved by using a mercapto compound as a chain transfer agent during copolymerization of acrylic elastomer.

[Means for solving problems]

Therefore, the present invention relates to a method for producing an acrylic elastomer, and the method for producing an acrylic elastomer includes (a) an alkyl acrylate having an alkyl group having 1 to 8 carbon atoms and/or (b) an alkoxyalkyl group having 2 to 8 carbon atoms. Alkoxyalkyl acrylates with groups as well as (c
) At least one of the following monomers (a) Epoxy group-containing vinyl monomer (b) Carboxyl group-containing vinyl monomer (c) Reactive halogen-containing vinyl monomer (d) Diene monomer (ho ) A hydroxyl group-containing vinyl monomer (to) An amide group-containing vinyl monomer is solution-polymerized using a radical polymerization initiator in the presence of a mercapto compound chain transfer agent.

Examples of the alkyl acrylate as component (a) forming the copolymer include methyl acrylate, ethyl acrylate, n- or iso-propyl acrylate, n- or iso-butyl acrylate, n-amyl acrylate, n-hexyl acrylate, Alkyl acrylates having an alkyl group having 1 to 8 carbon atoms (including those having a substituent such as a cyano group) such as 2-ethylhexyl acrylate, n-octyl acrylate, and 2-cyanoethyl acrylate are used, and ethyl acrylate is preferably used. Acrylate or n-butyl acrylate is used.

Examples of the alkoxyalkyl acrylate of component (b) include methoxymethyl acrylate, ethoxymethyl acrylate, 2-methoxyethyl acrylate, 2-
Alkoxyalkyl acrylates having an alkoxyalkyl group having 2 to 8 carbon atoms, such as ethoxyethyl acrylate and 2-butoxyethyl acrylate, are used, and 2-methoxyethyl acrylate and 2-ethoxyethyl acrylate are preferably used.

These (a) components and/or (b) components are about 9
It is copolymerized and used at a ratio of 9.9 to 90 mol%, (
When both components .

A part of these components (,) and/or component (b), specifically up to about 10 mol %, may be substituted with other copolymerizable monomers and copolymerized. Examples of such copolymerizable monomers include vinyl chloride, vinylidene chloride, acrylonitrile, styrene, vinyl acetate, ethyl vinyl ether, butyl vinyl ether, alkyl methacrylate, and alkoxyalkyl methacrylate.

The following crosslinking agents are used depending on the type of component (e) forming the crosslinking points of the copolymer and its reactive group.

(a) Epoxy foundation' vinyl monomer allyl glycidyl ether, glycidyl acrylate,
Examples include glycidyl methacrylate, and examples of crosslinking agents include polyamines such as diethylenetriamine and metaphenylenediamine, polycarboxylic acids such as adipic acid, acid anhydrides such as pyromellitic anhydride and maleic anhydride, and polyamides. and sulfonamides are used.

(b) Carboxyl group-containing vinyl monomers such as acrylic acid, methacrylic acid, and itaconic acid are exemplified, and examples of crosslinking agents for these include polyepoxides such as ethylene glycol diglycidyl ether and 1,6-hexanesiol diglycidyl ether. , 1,4-butanediol,
Polyols such as 1,1,1-trimethylolpropane are used.

Instead of using these crosslinking agents, crosslinking may be performed only by heating.

(c) Reactive halogen-containing vinyl monomers 2-chloroethyl vinyl ether, monochloroacetic acid, etc. are exemplified, and crosslinking agents for these include, for example, diethylenetriamine,
Polyamines such as triethylenetetramine, polycarbamates such as hexamethylene diamine carbamate, etc. are used.

(d) Diene monomers divinylbenzene, piperylene, isoprene, pentadiene, vinylcyclohexene, chloroprene, butadiene, methylbutadiene, cyclopentadiene, methylpentadiene, ethylene glycol diacrylate, propylene glycol diacrylate, ethylene glycol dimethacrylate , propylene glycol dimethacrylate, etc. Examples of crosslinking agents include sulfur, organic peroxides such as benzoyl peroxide and dicumyl peroxide, azo compounds such as azobisisobutyronitrile, and divinylbenzene. , triallyl cyanurate, triallyl isocyanurate, etc. are used. Instead of using these crosslinking agents, crosslinking may be performed only by heating).

(e) Hydroxyl group-containing vinyl monomers Examples include hydroxyalkyl acrylate, hydroxyalkyl methacrylate, hydroxyalkoxy acrylate, and N-methylol acrylamide. Examples of crosslinking agents for these include polyisocyanates such as hexamethylene diisocyanate and tolylene diisocyanate. , polycarboxylic acids such as adipic acid, and alkoxymethylmelamines such as methoxymethylmelamine.

(f) Amide group-containing vinyl monomers such as acrylamide and methacrylamide are exemplified, and as a crosslinking agent for these, aminoformaldehyde and the like are used, for example. Alternatively, crosslinking may be effected only by heating.

The copolymerization of each of the copolymerizable monomer components is preferably carried out by a solution polymerization method, and is not preferably carried out by an emulsion polymerization method or a bulk polymerization method. This is because, in the emulsion polymerization method, residues of water-soluble polymerization initiators, emulsifiers, and salting-out agents are mixed into the copolymer disstomer, significantly reducing light transmittance. In the bulk polymerization method, as the polymerization rate increases, it becomes difficult to control the reaction conditions and gelation tends to occur during the reaction, so the polymerization rate is approximately 20 to 5.
The reaction must be stopped to within 0%. Therefore, the solution polymerization method is suitable as a method for producing a copolymer elastomer with high yield and good light transmittance. In the solution polymerization method, for example, benzene,
Toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, butyl acetate, etc. are used, and each monomer component is a commercially available monomer that is used by removing the polymerization inhibitor by a conventional method and then distilled under reduced pressure. As the agent, azobisisobutyronitrile, benzoyl peroxide, etc., which are commercially available products and purified by repeated recrystallization with pure ethanol, are used.

Specifically, the copolymerization reaction is carried out, for example, as follows. 100 parts by weight of solvent is charged into a flask each equipped with a reflux condenser, a dropping funnel, and a stirrer, and maintained at a predetermined temperature. In the dropping funnel there is a monomer mixture of about 10
A solution of about 1 to 10 parts by weight of a polymerization initiator dissolved in ~900 parts by weight is added dropwise over about 0.5 to 5 hours, and the reaction is continued for about 1 to 5 hours after the dropwise addition is completed. Under such reaction conditions, the polymerization rate is about 80 to 95%. In order to further increase the polymerization rate, approximately 1 to 5 overlapping parts of a polymerization initiator are added after the monomer mixture has been added dropwise, thereby increasing the polymerization rate to 9 g% or more.

When such a dropwise polymerization method is adopted, there is an advantage that the copolymerization ratio of monomers having different reactivities is not much different between the start and end of polymerization, and a copolymer elastomer with a uniform composition can be obtained. In addition, when copolymerizing monomers with extremely different reactivities, it is recommended to increase the concentration of the monomer with low reactivity at the beginning of the dropwise addition and lower the concentration at the later stage of the dropwise addition to achieve a relatively uniform composition. A copolymer elastomer is obtained.

When the copolymerization reaction is carried out using a mercapto compound as a chain transfer agent, the resulting copolymer elastomer is a crosslinked product with excellent vulcanization properties and transparency. give.

As the mercapto compound, ω-mercaptoalkanol, alkylmercaptan, allylmercaptan, mercaptocarboxylic acid, alkyldithiol, dithioglycerin, trithioglycerin, etc. are used, but preferably 2-mercaptoethanol, 3-mercaptopropanol, 4- An ω-mercaptoalkanol such as mercaptobutanol is used. These mercapto compounds are used in a proportion of about 0.1 to 3 mol 2 , preferably about 0.15 to 1 mol %, based on the monomer mixture.

Another advantage of using these mercapto compounds is that the copolymerization ratio of the crosslinkable group-containing monomer can be increased. In general, increasing this copolymerization ratio makes gelation easier, but by using this chain transfer agent,
Even if a relatively large amount of the crosslinkable group-containing monomer, about 0.1 to 10 mol %, is copolymerized, the copolymerization can be effected without gelation.

In the resulting acrylic elastomer, various crosslinking agents as described above may be used depending on the type of crosslinkable group-containing monomer copolymerized into the copolymer, but preferably hexamethylene diisocyanate, 2 , 4-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate or other diisocyanate compounds or 4.4', 4
Triisocyanate compounds such as '-trimethyl-3,3',3'-), diisocyanate 2,4,6-triphenyl cyanurate are used, and hexamethylene diisocyanate or its trimer is particularly preferably used. It will be done. These crosslinking agents.

When ω-mercaptoalkanol is used as a chain transfer agent, the number of isocyanate groups is about 1.0 to 2.0 with respect to the hydroxyl group bonded to the end of the copolymer (and the hydroxyl group derived from the hydroxyl group-containing monomer). It is used in an amount that gives an equivalent ratio of

Crosslinking of acrylic elastomer is carried out by adding the necessary ingredients to the acrylic elastomer and crosslinking agent, mixing and dispersing them using a roll mill or using a solvent such as benzene, toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, etc., and then volatilizing the solvent. After the crosslinkable formulation has been prepared, using methods and the like as necessary, the crosslinking is carried out under conditions commonly used for acrylic elastomers.

〔Effect of the invention〕

Acrylic elastomer has a tensile strength value of 10 to 20 =
It is as low as 11-kg/cJ, and in order to improve this point, measures have been taken such as adding fillers or increasing the number of crosslinking points. However, addition of fillers such as carbon black and white carbon results in impaired transparency. Furthermore, when the amount of copolymerization of the crosslinkable group-containing monomer is increased in order to increase the number of crosslinking points, gelation occurs during polymerization (see Comparative Examples 5-6).

However, according to the method of the present invention, by performing a copolymerization reaction using a mercapto compound as a chain transfer agent and crosslinking using a hexamethylene diisocyanate trimer in particular, the tensile strength (
30 to 63 kg/ff1) and good transparency can be obtained.

〔Example〕

Next, the present invention will be explained with reference to examples.

Examples 1 to 6, Comparative Examples 1 to 6 (blank below) Table 1 Example 2 4.4 0.2 0.4 Example 3 4.4 0.4 0.8 Example 4
8.8 0.2 0.4 Example 5
8.8 0.4 0.8 Example 6 11
．． 0 0.4 0.8 Comparative example 1 0.6
0.2 Comparative example 2 1.1 0.2 Comparative example 3 2,2 0.1 Comparative example 4 2.2 0.2 Comparative example 5 4,4 0.1 Comparative example 6 4,4 0.2 Thermometer Methyl ethyl ketone and azobisisobutyronitrile (AI
BN) and 2-mercaptoethanol in a predetermined molar ratio, and heated to 50°C for 3 hours while purging with nitrogen gas.
Heated for 0 minutes.

Next, a mixed solution of ethyl acrylate with a molar ratio of 100 and 2-hydroxyethyl acrylate (HEA) with a predetermined molar ratio was dropped from the dropping funnel at a dropping rate of 3 seconds per drop,
Heating and stirring were continued even after the dropwise addition was completed. After the reaction was completed, the reaction mixture was dissolved in methyl ethyl ketone and reprecipitated using hexane, which was repeated several times.

Hexamethylene diisocyanate was added to the copolymer thus obtained in a proportion such that the NGO10H ratio was 1, and the mixture was placed in a glass molding machine and heated to 60°C at 50°C.
After drying under vacuum for a minute, it was further crosslinked by heating at 120° C. for 60 minutes.

Example 7 In Example 5, the same molar ratio of n-butyl acrylate was used instead of ethyl acrylate.

Example 8 In Example 5, a part of ethyl acrylate (mole ratio 30) was substituted with n-butyl acrylate.

Regarding the transparent rubber-like elastic bodies obtained in the above Examples and Comparative Examples, in addition to the density, the tensile strength and elongation (measured using a JIS hardness meter on a hard sample with a thickness of 6 mm on a flat table), tensile strength, and elongation (automatic The results were obtained as shown in Table 2 below. In addition, the sample in Comparative Example 1 was highly adhesive and could not be peeled off from the glass molding machine, so it was impossible to mold the sample piece for measurement, and in Comparative Examples 5 and 6, the polymerization rate was high and the temperature could not be controlled. However, it turned into a gel during polymerization. Furthermore, stringiness was observed in Comparative Example 5, and there were many uncrosslinked portions, making it impossible to measure hardness and elongation.

(Margin below) Table 2 Example 2 40,8 1,140 13.9
460 Example 3 40.7 1.140 1
8.2 442 Example 4 44.0 1.15
1 27.7 230 Example 5 51,2
1,153 25.1 201 Example 6 68
,7 1,162 23.3 106 Example 7
31.6 1.141 6.5 898 Example 8 41.0 1,141 19.6
630 Comparative Example 2 - 1.124 4.3
-Comparative Example 3 31.5 1.125
6.1 68 Comparative Example 4 31.5 1.12
8 7.7 42 In addition, when measuring the adhesion of some of the measurement sample pieces using a surface property measuring machine, it was found that μ = 0.5 to 2.1 in Examples 3 to 5. ,
In all of Comparative Examples 3 and 4, μ>5.

Furthermore, when the transparency of the obtained rubber-like elastic body is measured as the light transmittance per 1 cm, for example, those of Example 2 and those of Comparative Example 3 have almost the same light transmittance in the wavelength range of 200 to 860 nm. Specifically, at 660 nm, they were 96.8% and 98.1%, respectively.

Examples 9 to 14 In Examples 1 to 6, instead of hexamethylene diisocyanate, its trimer was used in an NGO10H ratio of 1. The results of measuring the physical properties of the obtained transparent rubber-like elastic body are shown in Table 3 below.

Table 3 10 40.7 1.139 14.4
21711 41.0 1.147 26.
1 24712 65.3 1.160
63.1 10413 65.0 1.16
2 49.9 8514 69.0 1
．． 164 29.5 106 Furthermore, when the tackiness of some of the measurement sample pieces was measured using a surface property measuring device, it was found that μ=0.5 to 2.1 in Examples 11 to 13.

Examples 15-19 In Example 4, the same molar ratio of various crosslinking monomers was used instead of 2-hydroxyethyl acrylate, and as the crosslinking agent, various crosslinking agents were used in amounts of 5 moles. Note that crosslinking was performed at 60° C. for 50 hours.

Example 15) Glycidyl acrylate/diethylenetriamine Example 16) Acrylic 811/Ethylene glycol diglycidyl ether Example 17) Monochlorovinyl acetate diethylenetriamine Example 18) Methyl butadiene/Heat crosslinking (Example 19) Acrylamide /aminoformaldehyde The physical properties of the transparent rubber-like elastomer obtained are shown in Table 4 below.

Table 4 16 95.5 49.0 1.138 30.
2 11317 82.0 58.9 1.14
6 46.0 18018 92.0 56.
3 1.161 29.0 8019 88.
0 55.1 1.141 38.2 125
Procedural Amendment (Part 1, August 7, 1988)

Claims (1)

[Scope of Claims] 1. (a) an alkyl acrylate having an alkyl group having 1 to 8 carbon atoms and/or (b) an alkoxyalkyl acrylate having an alkoxyalkyl group having 2 to 8 carbon atoms; and (c) at least one The following monomers (a) Epoxy group-containing vinyl monomer (b) Carboxyl group-containing vinyl monomer (c) Reactive halogen-containing vinyl monomer (d) Diene monomer (e) Hydroxyl group-containing vinyl A method for producing an acrylic elastomer, which comprises solution polymerizing a (he)amide group-containing vinyl monomer using a radical polymerization initiator in the presence of a mercapto compound chain transfer agent. 2. The method for producing an acrylic elastomer according to claim 1, wherein the mercapto compound is ω-mercaptoalkanol. 3. The method for producing an acrylic elastomer according to claim 2, wherein the ω-mercaptoalkanol is 2-mercaptoethanol.