JPH11106436A - Acrylic elastomer and its composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject elastomer copolymerized with a halogen- containing vinylic monomer and an epoxy group-containing vinylic monomer and giving a composition excellent in heat resistance, when compounded with a phenylamine antioxidant. SOLUTION: This elastomer preferably has a Mooney viscosity ML1+4 (100 deg.C) of about 5 pts or larger, and is obtained by copolymerizing (A) about 60-98.9 wt.% of a main component such as a 1-8C alkyl acrylate, a cyanoalkyl acrylate, a 2-8C alkoxyalkyl or alkylthioalkyl group-having alkoxyalkyl acrylate or alkylthioalkyl acrylate with (B) 1-5 wt.% of a halogen-containing vinylic monomer and (C) 0.1-0.3 wt.% of an epoxy group-containing vinylic monomer preferably by an emulsion polymerization method. The elastomer is compounded with a phenylamine antioxidant and calcium (hydr)oxide to obtain an acrylic elastomer composition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an acrylic elastomer and a composition thereof. More specifically, it relates to an acrylic elastomer having excellent heat resistance and a composition thereof.

[0002]

2. Description of the Related Art In conventional acrylic rubber, there is a restriction that the temperature range in which it is used is limited in terms of heat resistance and cold resistance, depending on the type of constituent monomers, particularly cross-linking site monomers. . In the case of halogen-containing acrylic rubber, both heat resistance and cold resistance are satisfactorily satisfied, especially when a phenylamine-based compound is used as an anti-aging agent, heat resistance is evaluated as suppressing the increase in rubber hardness. Although satisfied in that respect, the fact is that further improvement in heat resistance is demanded in relation to the intended use.

[0003] The present applicants have previously provided a vulcanizate which is a composition containing a halogen-containing acrylic rubber as a main component and a phenylamine-based compound as an antioxidant, and which has even more excellent heat resistance. For example, a halogen-containing acrylic rubber composition containing a halogen-containing acrylic rubber, a phenylamine-based antioxidant, and calcium hydroxide or calcium oxide has been proposed (JP-A-7-33943).

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a halogen-containing acrylic elastomer having improved heat resistance by incorporating a phenylamine-based antioxidant, wherein the heat-resistant acrylic elastomer is further improved. To provide.

[0005]

SUMMARY OF THE INVENTION The object of the present invention is as follows.
This is achieved by an acrylic elastomer obtained by copolymerizing 1 to 5% by weight of a halogen-containing vinyl monomer and 0.1 to 0.3% by weight of an epoxy group-containing vinyl monomer.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION An acrylic elastomer obtained by copolymerizing a halogen-containing vinyl monomer and an epoxy group-containing monomer is an alkyl acrylate having an alkyl group having 1 to 8 carbon atoms, a cyanoalkyl acrylate, a C2 to C2 alkyl group. 8
The main component (about 60 to 98.9% by weight) of an alkoxyalkyl acrylate or an alkylthioalkyl acrylate having an alkoxyalkyl group or an alkylthioalkyl group, and chloroethyl vinyl ether, chloroethyl acrylate, vinylbenzyl chloride, vinyl chloroacetate, allyl Chloroacetate or glycidyl acrylate, glycidyl methacrylate,
About 0.1 to 5% by weight, preferably about 1 to 3% by weight, of a halogen-containing vinyl monomer such as an addition reaction product of a glycidyl compound such as allyl glycidyl ester and monochloroacetic acid;
Glycidyl acrylate, glycidyl methacrylate,
The copolymerization is carried out using 0.1 to 0.3% by weight, preferably 0.1 to 0.2% by weight, of an epoxy group-containing vinyl monomer such as allyl glycidyl ester.

[0007] In this copolymerization reaction, the polymerization rate is about 90% or more, so that the ratio of each monomer used in the copolymerization reaction becomes almost the copolymerization rate. If the copolymerization ratio of the halogen-containing vinyl monomer is less than this, the normal physical properties of the vulcanizate obtained from this acrylic elastomer decrease, while if copolymerized at a higher ratio, the vulcanizate becomes brittle, Elongation starts to decrease. Further, if the copolymerization ratio of the epoxy group-containing vinyl monomer is smaller than this, the effect of further improving the heat resistance aimed at by the present invention is not obtained, while if copolymerized at a higher ratio, The compression set characteristic deteriorates, and this acrylic elastomer cannot be used as a vulcanization molding material for sealing materials such as O-rings, gaskets, and packings.

[0008] In each of these comonomers, other vinyl monomers may be used as long as the properties of the obtained copolymer are not impaired (about 30% by weight or less, preferably about 20% by weight or less). Olefin monomer, diene monomer and the like can be copolymerized. Other vinyl monomers include vinyl chloride, vinylidene chloride, acrylonitrile, styrene, vinyl acetate, ethyl vinyl ether, alkyl methacrylate, furfuryl acrylate, 2-acetoxyethyl acrylate,
2-propoxyethyl acrylate, 4-acetoxybutyl acrylate, 4-propoxybutyl acrylate, ethylene glycol dimethacrylate and the like are used. Further, a crosslinkable group-containing vinyl monomer such as a vinylsilyl group-containing acrylate may be copolymerized. Ethylene and propylene are used as olefin monomers, and divinylbenzene, isoprene, pentadiene, ethylidene norbornene and the like are used as diene monomers.

The copolymerization reaction is carried out in the presence of a generally used radical polymerization initiator by any method such as an emulsion polymerization method, a suspension polymerization method, a solution polymerization method and a bulk polymerization method. Is carried out by an emulsion polymerization method. The polymerization initiator is also used as a redox type. The resulting acrylic elastomer generally has a Mooney viscosity ML _{1 + 4} (100 ° C.) of about 5 pts or more, preferably about 10-100 pts.

JP-B-63-49689 discloses an alkyl acrylate as a main component and a halogen-containing monomer of 0.5%.
Acrylic elastomer obtained by copolymerizing 22% by weight, 0.5-2% by weight of an epoxy group-containing monomer and 0.1-1% by weight of an unsaturated carboxylic acid is described, and this acrylic elastomer has a large vulcanization rate. However, the scorch time is extremely short, and in this respect it is completely impractical. Also, in such an acrylic elastomer,
When the unsaturated carboxylic acid is not copolymerized, the heat resistance is improved, but the compression set characteristic is significantly deteriorated, and the scorch time is also reduced.

In the case of an acrylic elastomer copolymerized with 1 to 10% by weight of vinyl chloroacetate and 0.1 to 5% by weight of hydroxyalkyl (meth) acrylate described in JP-B-62-23762, scorch is used. Although there is no problem in terms of time, it is inferior to the acrylic elastomer of the present invention in heat resistance and compression set characteristics.

The acrylic elastomer of the present invention can be vulcanized preferably using the following vulcanization system. (a) Aliphatic alkali metal salts / sulfur-based alkali metal salts of fatty acids include saturated fatty acids having 1 to 18 carbon atoms, unsaturated fatty acids having 3 to 18 carbon atoms, and lithium such as aliphatic dicarboxylic acids and aromatic carboxylic acids. Salts, potassium salts, sodium salts and the like are used. Specifically, for example, potassium stearate, sodium stearate,
Examples include potassium oleate, sodium oleate, sodium 2-ethylhexanoate, sodium potassium tartrate, sodium propionate, sodium acetate and the like. Particularly preferred are potassium or sodium salts of fatty acids having 8 to 18 carbon atoms, with potassium salts generally tending to increase the vulcanization rate. (b) Trithiocyanuric acid / aliphatic alkali metal salt system As the aliphatic alkali metal salt, those described above are used. (c) Diamine or its carbamate / dibasic lead phosphite system As the diamine or its carbamate, hexamethylene diamine or its carbamate is preferably used. In addition to these, the following vulcanization systems are also used. (d) trithiocyanuric acid / dicyandiamide / dibasic phosphite system (e) trithiocyanuric acid / dicyandiamide / metal oxide system (f) trithiocyanuric acid / dicyandiamide / aluminum-containing compound system (g) trithiocyanuric acid / dicyandiamide / aliphatic Alkaline earth metal salt or zinc salt type (h) trithiocyanuric acid / dithiocarbamic acid metal salt / thiuram sulfide type (i) trithiocyanuric acid / dithiocarbamic acid metal salt / No. 4
Grade ammonium salt or phosphonium salt type (j) Trithiocyanuric acid / trimethylthiourea / metal oxide type (k) Trithiocyanuric acid / fatty acid alkaline earth metal salt or zinc salt type

These vulcanizing components are generally used in a proportion of about 0.1 to 10 parts by weight per 100 parts by weight of the acrylic elastomer, and the preferred range is, for example, about 0.2 to 1 part by weight depending on the components used and the combination thereof. Parts or about 1 to 5 parts by weight.

As the anti-aging agent, various ones are used depending on the intended use. Preferably, 4,4 '-(α,
α-Dimethylbenzyl) diphenylamine, octylated diphenylamine, phenylamine-based compounds such as phenyl-α-naphthylamine are acrylic elastomers 10
It is used in an amount of about 0.1 to 5 parts by weight, preferably about 1 to 2 parts by weight per 0 parts by weight. If the compounding ratio is less than this, the effect as an antioxidant is not exhibited, while if it is more than this, vulcanization is inhibited and the state properties of the vulcanized rubber are reduced.

[0015] In the above acrylic elastomer composition, if necessary, various vulcanization aids may be blended, and preferably, calcium hydroxide or calcium oxide may be blended. These compounds are converted to acrylic elastomers
When used in an amount of about 0.1 to 5 parts by weight, preferably 1 to 3 parts by weight per 100 parts by weight, the heat resistance can be further improved.

In the acrylic elastomer composition containing the above components as essential components, other necessary compounding agents are appropriately compounded. Speaking of fillers and reinforcing agents, for example, when used as a vulcanization molding material for various sealing materials, an O-ring,
Carbon black is mainly blended for applications such as packing, and diatomaceous earth and white carbon are mainly blended for applications such as oil seals. In addition, a lubricant or the like is used if necessary.

The composition is prepared using a closed kneader such as a kneader or a Banbury mixer or an open kneader such as an open roll.
It is performed by press vulcanization or injection molding vulcanization performed at 50 ° C. for about 1 to 30 minutes, and if necessary, about 150 to 200
Oven vulcanization or steam vulcanization at a temperature of about 1 to 22 hours is performed as secondary vulcanization.

[0018]

EFFECT OF THE INVENTION The scorch stability, the normal physical properties of the vulcanizate and the compression set characteristics are obtained by further copolymerizing a small amount of a glycidyl monomer into a halogen-containing acrylic elastomer containing a phenylamine-based antioxidant. Can be further improved without substantially impairing the heat resistance (particularly in terms of tensile strength).

[0019]

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

Examples 1-2, Comparative Examples 1-4 Comonomers (wt%) real-1 real-2 ratio-1 ratio-2 ratio-3 ratio-4 ethyl acrylate 97.8 97.8 98 97 96.75 97.8 vinyl chloroacetate 2 2 2 2 2 2 Glycidyl methacrylate 0.2 1 1 Allyl glycidyl ether 0.2 Methacrylic acid 0.25 3-Hydroxypropyl methacrylate 0.2 Elastomer Mooney viscosity (pts) 49 50 49 51 51 59

To 100 parts of each of these acrylic elastomers (weight, hereinafter the same), 60 parts of FEF carbon black (Examples 1-2) 50 parts (Comparative Examples 1-4) Calcium stearate 0.25 parts Sodium stearate 3 parts Sulfur 0.3 Part 4,4 '-(α, α-dimethylbenzyl) diphenylamine 1 part Stearic acid 1 part was mixed and kneaded with an 8-inch open roll.
Press vulcanization at 8 ° C. for 8 minutes and oven vulcanization (secondary vulcanization) at 175 ° C. for 4 hours were performed. About the kneaded material, Mooney
Scorch the (125 ° C.) with measured as scorch time t _5, the normal state physical properties and compression set for vulcanizates JIS
Measured according to K-6301, and combined with heat aging test (300 ° C,
175 hours later), and the results shown in the following Table 1 were obtained. Table 1 Measurement items actual -1 actual -2 ratio -1 Ratio -2 ratio -3 ratio -4 normal physical properties Hardness (JIS A) 70 71 70 72 72 71 Tensile strength (MPa) 18.1 18.2 17.1 18.9 17.4 17.2 elongation ( %) 380 380 400 300 350 370 Heat aging Hardness change (point) +14 +15 +14 +17 +16 +15 Change in tensile strength (%) -38 -38 -69 -33 -36 -45 Compression Permanent strain 150 ° C, 70 hours (%) 32 33 32 48 44 40 Mooney scorch Scorch time t ₅ (min) 11.6 11.8 12.4 9.2 2.5 11.5

Example 3, Comparative Example 5 Copolymerized monomer (% by weight) Example 3 Comparative Example 5 Ethyl acrylate 94.8 95 Chloroethyl vinyl ether 55 Glycidyl methacrylate 0.2 Elastomer Mooney viscosity (pts) 53 53

To 100 parts of each of these acrylic elastomers, 60 parts of FEF carbon black (Example 3) 50 parts (Comparative Example 6) 3 parts of sodium stearate 0.5 parts of trimercaptotriazine 4,4 '-(α, α-dimethyl 1 part of benzyl) diphenylamine and 1 part of stearic acid were blended and kneaded, vulcanized and measured in the same manner as in Example 1 to obtain the results shown in Table 2 below. Table 2 Measurement items Example 3 Comparative example 5 Normal physical properties Hardness (JIS A) 71 70 Tensile strength (MPa) 16.2 15.3 Elongation (%) 290 310 Heat aging resistance Change in hardness (points) +12 +12 Tensile strength Rate of change (%) -29 -45 Compression set 150 ° C, 70 hours (%) 21 21 Mooney scorch Scorch time t ₅ (min) 9.9 9.8

Example 4, Comparative Example 6 Comonomers (% by weight) Example 4 Comparative Example 6 Ethyl acrylate 72.8 73 n-butyl acrylate 25 25 Vinyl chloroacetate 22 Glycidyl methacrylate 0.2 Elastomer Mooney viscosity (pts) 39 39

Each of the components of Example 1 was blended with 100 parts of each of these acrylic elastomers, and kneading, vulcanization and measurement were carried out in the same manner to obtain the results shown in Table 3 below. Further, a change in hardness over time at 175 ° C. was measured, and a result as shown in the graph of FIG. 1 was obtained. Table 3 Measurement items Example 4 Comparative example 6 Normal physical properties Hardness (JIS A) 71 71 Tensile strength (MPa) 16.6 15.5 Elongation (%) 230 250 Heat aging resistance Hardness change (points) +12 +11 Tensile strength Rate of change (%) -30 -58 Compression set 150 ° C, 70 hours (%) 29 28 Mooney scorch Scorch time t ₅ (min) 8.6 9.3

Example 5, Comparative Example 7 Co-monomer (% by weight) Example 5 Comparative Example 7 Ethyl acrylate 47.8 48 n-butyl acrylate 25 25 2-methoxyethyl acrylate 25 25 Vinyl chloroacetate 22 Glycidyl methacrylate 0.2 Elastomer Mooney Viscosity (pts) 43 42

Each component of Example 1 was blended with 100 parts of each acrylic elastomer, and kneading, vulcanization and measurement were carried out in the same manner to obtain the results shown in Table 4 below. Table 4 Measurement items Example 5 Comparative example 7 Normal physical properties Hardness (JIS A) 73 72 Tensile strength (MPa) 16.0 15.5 Elongation (%) 230 260 Heat aging Hardness change (points) +13 +12 Tensile strength Rate of change (%) -26 -34 Compression set 150 ° C, 70 hours (%) 30 30 Mooney scorch Scorch time t ₅ (min) 7.2 6.5

Example 6, Comparative Example 8 To 100 parts of each acrylic elastomer of Example 4 or Comparative Example 6, 60 parts of FEF carbon black, 0.5 part of trimercaptotriazine, 1.5 parts of zinc dithiocarbamate, 4,4 '-(α, α- 1 part of dimethylbenzyl) diphenylamine and 1 part of stearic acid were blended and kneaded, vulcanized and measured in the same manner as in Example 1 to obtain the results shown in Table 5 below. Table 5 Measurement items Example 6 Comparative example 8 Normal physical properties Hardness (JIS A) 68 70 Tensile strength (MPa) 14.6 13.8 Elongation (%) 160 220 Heat aging resistance Hardness change (points) +13 +12 Tensile strength Rate of change (%) -28 -54 Compression set 150 ° C, 70 hours (%) 16 15 Mooney scorch Scorch time t ₅ (min) 7.4 7.9

Example 7, Comparative Example 9 100 parts of each acrylic elastomer of Example 4 or Comparative Example 6, 5 parts of FEF carbon black, 65 parts of diatomaceous earth, 28 parts of white carbon, 0.25 parts of potassium stearate, 3 parts of sodium stearate, 3 parts of sulfur 0.3 part Calcium hydroxide 1 part 4,4 '-(α, α-dimethylbenzyl) diphenylamine 1 part Stearic acid 1 part was blended, and kneading, vulcanization and measurement were carried out in the same manner as in Example 1. The result as shown in was obtained. Further, with respect to Example 7, a change in hardness over time at 175 ° C. was measured, and the result shown in the graph of FIG. 1 was obtained. Table 6 Measurement items Example 7 Comparative example 9 Normal physical properties Hardness (JIS A) 81 80 Tensile strength (MPa) 8.5 7.8 Elongation (%) 130 180 Heat aging Hardness change (points) +9 +8 Tensile strength Rate of change (%) +4 -27 Compression set 150 ° C, 70 hours (%) 78 79 Mooney scorch Scorch time t ₅ (min) 9.2 10.1

[Brief description of the drawings]

FIG. 1 is a graph showing a change in strength over time at 175 ° C.

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Claims (2)

[Claims] An acrylic elastomer obtained by copolymerizing 1 to 5% by weight of a halogen-containing vinyl monomer and 0.1 to 0.3% by weight of an epoxy group-containing vinyl monomer. 2. An acrylic elastomer composition comprising the acrylic elastomer according to claim 1 and a phenylamine-based antioxidant and calcium hydroxide or calcium oxide.