JPS6386719A - Ethylene-based elastomer composition - Google Patents

Abstract

PURPOSE:To obtain a crosslinkable elastomer capable of giving cured products of good balance in rubber phsical properties, by incorporating an ethylene-based elastomer with, as the curing agent, a combination of polycarboxylic acid compound and quaternary ammonium salt. CONSTITUTION:The objective composition can be obtained by incorporating (I) an ethylene-based elastomer prepared by copolymerization between (A) 50-85mol% of ethylene, (B) 50-15mol% of an acrylic ester, and (C) 0.5-1.0mol of an unsaturated glycidyl ester (e.g., glycidyl acrylate) (based on 100mol of the components A plus B) with (II) pref. 0.45-0.55mol, based on the component C in said elastomer, of curing agent, e.g., a combination of (D) a compoing containing two or more carboxyl groups (e.g., tetradecane diacid) and (E) a quaternary ammonium salt (e.g., cetyl trimethyl ammonium bromide).

Description

Detailed Description of the Invention <Industrial Application Field> The present invention relates to a crosslinkable ethylene-based elastomer composition, and more specifically to a copolymer composed of ethylene, an acrylic acid ester, and an unsaturated glycidyl ester. The present invention relates to a crosslinkable oil-resistant ethylene elastomer composition based on the present invention.

<Conventional technology> In recent years, with remarkable technological advances in various industries such as automobiles, home appliances, and machinery, the characteristics required of rubber materials used in various related parts have become diverse, and various special elastomers have been developed to meet these requirements. As is well known, it is being developed.

As a type of such special elastomers, for example, crosslinkable elastomer compositions mainly composed of ethylene copolymers made of ethylene, acrylic esters, and unsaturated glycidyl esters are known.

The required properties for such special elastomers have become more severe in recent years, including tensile strength, compression set,
Improvements in physical properties such as oil resistance are required, and optimizing the balance of these physical properties is an important point in practice. Since this composition contains unsaturated glycidyl ester (hereinafter referred to as the third component) as a crosslinking point, it can be vulcanized with conventionally known epoxy vulcanizing agents. Vulcanization systems have drawbacks such as slow vulcanization rate and large compression set.

As a method for solving these drawbacks, a vulcanization system using a dicarboxylic acid and a quaternary ammonium salt or a quaternary phosphonium salt is disclosed, for example, as seen in JP-A-61-26621.

However, the physical property balance of the ethylene elastomer using this vulcanization system is not necessarily in a satisfactory range.To solve this problem, the content of the third component of the ethylene elastomer has been changed, and Attempts to change the amount of the compound were considered.

Regarding the former, when the content of the third component is increased, the crosslinking reaction progresses excessively, and although the oil resistance is at a good level, the tensile strength and elongation are significantly reduced, and when the content of the third component is decreased, the crosslinking point tensile strength, oil resistance, and compression set.

Regarding the latter, if the amount of vulcanizing agent is increased, the tensile strength is good but the compression set is impaired, and if the amount of the vulcanizing agent is decreased, the tensile strength, compression set, and oil resistance are impaired.

<Problems to be Solved by the Invention> The purpose of the present invention is to improve the above-mentioned drawbacks and to develop an ethylene copolymer-based product which has an improved balance of physical properties such as tensile strength, elongation, compression set, and oil resistance. elastomer composition.

<Means for Solving the Problems> As a result of intensive studies on improving the above problems, the present inventors have determined that a copolymer having a specific structure and a specific vulcanizing agent are mixed in a certain ratio. The present invention has been achieved by discovering that by blending, the balance of physical properties such as tensile strength, elongation, compression set, and oil resistance can be improved.

That is, the present invention provides: (1) (a) 50 to 85 mol% ethylene (b)
50 to 15 mol% of acrylic acid ester and (c) 0.0% to 100 mol of both components (a) and (b) above.
An ethylene elastomer obtained by copolymerizing 5 to 1.0 moles of unsaturated glycidyl ester, and a compound containing two or more carboxyl groups in the molecule and
The present invention relates to a crosslinkable ethylene-based elastomer composition with an improved balance of physical properties such as tensile strength, elongation, compression set, and oil resistance, which is characterized by containing a class ammonium salt. The acrylic ester (b), which is a component of the ethylene elastomer in the present invention, is an ester consisting of an alcohol having 1 to 8 carbon atoms, and specifically, methyl acrylate, ethyl acrylate, n-butyl acrylate. , acrylic acid tart-
Examples include butyl and 2-ethylhexyl acrylate, and these may be used alone or in combination of two or more.

The molar ratio of (a) ethylene and (b) acrylic ester is 50 to 85:50 to 15, preferably 58 to 80.
:42-20.

(b) When the content of acrylic ester exceeds the upper limit, the embrittlement point becomes high, making it difficult to use it as an elastomer at low temperatures. On the other hand, if it is lower than the lower limit, the crystallinity of the copolymer will become high, making it impossible to obtain sufficient elasticity as an elastomer.

(c) Examples of unsaturated glycidyl esters include glycidyl acrylate, glycidyl methacrylate, itaconic acid diglycidyl ester, butenetricarboxylic acid triglycidyl ester, and p-styrenecarboxylic acid glycidyl ester, which are described in Japanese Patent Publication No. 46-45085. Illustrated.

The ethylene elastomer of the present invention can be produced by known methods, such as free radical initiated bulk polymerization, emulsion polymerization, or solution polymerization. A typical polymerization method is described in Japanese Patent Publication No. 46-45085. For example, it can be produced under conditions of a pressure of 500 kg/cj or more and a temperature of 40 to 300° C. in the presence of a polymerization initiator that generates free radicals.

The ethylene elastomer used in the present invention is made by copolymerizing the above-mentioned components, and has a melting index of 0.5 to 500 g/10 at 190°C as defined by JIS K6791.
min, preferably in the range from 0.5 to 50 g/10 min.

The amount of the third component (c) used in the present invention is 0.5 to 100 moles in total of both components (a) and (b).
The amount is 1.0 mol, preferably 0.6 to 0.8 mol. When the content of the third component exceeds the upper limit, the oil resistance is at a good level, but the tensile strength and elongation are significantly reduced, and when the content is below the lower limit, the tensile strength, oil resistance, and compression set are impaired.

Such ethylene elastomers are vulcanized by blending a compound having two or more carboxyl groups in the molecule and a quaternary ammonium salt in a specific ratio.

The compounds having two or more carboxyl groups in the molecule used in the present invention are usually selected from saturated and unsaturated aliphatic compounds, alicyclic compounds, aromatic compounds and low molecular weight polymers. Aliphatic dicarboxylic acids are preferred in terms of compression set, vulcanization rate, and compression set.

Representative compounds of aliphatic dicarboxylic acids include the following.

Among these, preferred are malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, octaniic acid, dodecanoic acid, tridecanoic acid, tetradecanionic acid, hexadecanionic acid, octadecanionic acid, taldolic acid, etc. Tetradecanonic acid is preferred.

The quaternary ammonium salt used in the present invention is a compound represented by the following general formula.

R5 to R4 in the above general formula have about 1 to 25 carbon atoms, such as alkyl, aryl, alkylaryl, and polyoxyalkylene groups.

X is an anionic halogen, preferably C1, Br5I
Anionic halogens such as

Specific examples of quaternary ammonium salts include cetyltrimethylammonium bromide, tetraethylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium iomade, n-dodecyltrimethylammonium bromide, and cetyldimethylbenzylammonium chloride. , methylcetyldibenzylammonium bromide, cetyldimethylethylammonium bromide, octadecyltrimethylammonium bromide, and among these, cetyltrimethylammonium bromide or octadecyltrimethylammonium bromide is preferred.

The compound containing two or more carboxyl groups in the molecule and the quaternary ammonium salt used in the present invention are each 0.4 to 0.6 mol per mol of unsaturated glycidyl ester in the copolymer. , preferably 0.45 to 0.
It is used in a proportion of 55 moles. If the proportion of these compounds exceeds the upper limit, compression set and processing stability will be impaired, while below this range, vulcanization will not proceed and tensile strength, compression set, and oil resistance will be impaired.

The effects of the present invention can be obtained by blending a specific amount of a compound having two or more carboxyl groups in the molecule and a quaternary ammonium salt into the ethylene elastomer having the specific structure described above. If one of them is out of range, good results will not be obtained.

In the present invention, vulcanization accelerators, processing aids, zinc white, stearic acid, reinforcing agents, fillers, softeners, anti-aging agents, processing aids, defoaming agents, etc. known in the rubber industry are used as necessary. can be added.

<Examples> The present invention will be described below with reference to Examples, but the present invention is not limited to these Examples.

Examples 1 to 3 and Comparative Examples 1 to 4 The ingredients and proportions (parts by weight) shown in Table 1 were kneaded using a mixing roll, and the resulting compositions were heated at 170°C.
Vulcanize using a steam press for 10 minutes, then 15 minutes.
Secondary vulcanization was performed for 4 hours in an open environment at 0°C.

Vulcanized rubber physical properties and oil resistance were measured according to JIS K6301. Oil resistance is 150 using JIS No. 3 oil.
The degree of volumetric swelling was measured after 70 hours at ℃.

The results are shown in Table 1.

<Effects of the Invention> As described above, according to the present invention, it is possible to provide an ethylene-based elastomer composition with an excellent balance of vulcanized rubber physical properties (tensile strength, elongation, oil resistance, compression set).

Claims (2)

[Claims] (1) (a) 50-85 mol% ethylene, (b) 50
~15 mol% acrylic ester and (c) the above (
The ethylene elastomer obtained by copolymerizing 0.5 mol to 1.0 mol of (c) unsaturated glycidyl ester with respect to the total 100 mol of both components a) and (b) contains 2 in the molecule.
1. A crosslinkable ethylene elastomer composition comprising a compound containing one or more carboxyl groups and a quaternary ammonium salt. (2) The amount of the compound containing two or more carboxyl groups in the molecule and the quaternary ammonium salt is 0.4 to 0 per mole of (c) unsaturated glycidyl ester in the copolymer. The ethylene-based elastomer composition according to claim 1, wherein the amount is .6 mol.