JPH07286083A - Vulcanizable acrylic rubber-fluororubber composition - Google Patents

Abstract

PURPOSE:To obtain a heat- and oil-resistant rubber composition with both ecomony and intermediate physical characteristics between those of an acrylic rubber and a fluororubber. CONSTITUTION:This composition consists of a rubber component (1) comprising a mixture of an acrylic rubber having cross-linkable hydroxyl groups or cross- likable chlorine atoms and a fluororubber having polymer units based on propylene hexafluoride and vinylidene fluoride and/or ethylene tetrafluoride, wherein the weight ratio of the acrylic rubber to the fluororubber is (0.5 to 99.5):(99.5 to 0.5), an acid acceptor (2) comprising a metal oxide and/or a metal hydroxide, and a vulcanization accelerator (3) comprising a quaternary ammonium alt and/or a quaternary phosphonium salt.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat- and oil-resistant composite rubber composition having an intermediate property between an acrylic rubber and a fluororubber composed of an acrylic rubber component and a fluororubber component.

[0002]

2. Description of the Related Art Acrylic rubber is a rubber material having heat resistance, oil resistance, and weather resistance, and is widely used as rubber parts for automobiles such as engine gaskets, oil hoses, air hoses, and O-rings. In recent years, as automobiles have become more sophisticated, more excellent heat resistance and higher durability are required. On the other hand, fluororubber has excellent performance in terms of heat resistance and oil resistance, but it is economically not used for general-purpose use in the field, and its use amount can be dramatically increased. Have difficulty. In order to solve these problems, various co-crosslinkable blends have been developed.

Blends of acrylic rubber and fluororubber are disclosed in JP-A-55-23128 and JP-A-58.
No. 63740 discloses an attempt to improve processing characteristics such as vulcanization characteristics by selecting a crosslinking agent that crosslinks both acrylic rubber and fluororubber. However, even if acrylic rubber and fluororubber are simply mixed and a crosslinking agent that crosslinks both acrylic rubber and fluororubber is used, it is difficult to disperse both rubber components in a stable state for a long period of time. However, the effect of preventing deterioration of characteristics such as mechanical strength due to deterioration over time is not sufficient.

As a means for improving these, for example, in Japanese Unexamined Patent Publication (Kokai) No. 4-100846, a fluorine-containing monomer having a high affinity for fluororubber is introduced into a constituent monomer of acrylic rubber, so that the interface between both rubber components is introduced. Although the technology to increase the affinity of and maintain a stable dispersion state is disclosed,
In any case, it is difficult to achieve sufficient cross-linking because different types of rubber components are cross-linked with one type of cross-linking agent, and even with this method, the effect of maintaining a stable dispersed state for a long time cannot be said to be sufficient. .

Further, Japanese Patent Application Laid-Open No. 5-287156 discloses a technique for improving dispersibility by blending an internally cross-linked acrylic rubber with fluororubber, but it is necessary for maintaining properties such as mechanical strength. It cannot be said that crosslinking between both rubber components has been sufficiently achieved, and it is difficult to maintain a stable dispersed state for a long time even by this method.

[0006]

In the blend of acrylic rubber and fluororubber, the crosslinking reaction by the co-vulcanizing agent is not only the purpose of the co-crosslinking but also the intermolecular crosslinking of different polymers and / or the crosslinkage of the same type of polymers. Since intramolecular crosslinking is also formed at the same time, it is not possible to obtain a blend having a uniform and stable phase, and the vulcanizable rubber composition prepared using this has a stable dispersed state for a long period of time. Is difficult.

[0007] In view of these points, as a result of extensive studies on a blend of acrylic rubber and fluororubber in order to obtain a rubber composition having stable dispersibility for a long period of time, as a result, a crosslinkable group capable of directly bonding with the crosslinkable group of fluororubber When using a vulcanizable rubber component obtained by mixing an acrylic rubber having a with a fluororubber containing a crosslinkable group, an intermediate physical property between the acrylic rubber and the fluororubber can be obtained without using a vulcanizing agent. The inventors have found that a rubber composition having a stable dispersed state for a long period of time can be obtained, and thus reached the present invention.

[0008]

That is, the present invention is
(A) Acrylic rubber / fluorine in a mixture with an acrylic rubber having a crosslinkable hydroxyl group or a crosslinkable chlorine atom and a fluororubber having polymerized units based on 6-fluoropropylene and vinylidene fluoride and / or 4-fluoroethylene The ratio of rubber is 0.5 to 99.5 by weight.
/99.5-0.5 rubber component (B) acid acceptor consisting of metal oxide and / or metal hydroxide and (C)
Vulcanizable acrylic rubber comprising a vulcanization accelerator comprising a quaternary ammonium salt and / or a quaternary phosphonium salt-
It relates to a fluororubber composition.

The rubber composition of the present invention exhibits characteristics in the intermediate range between fluororubber and acrylic rubber in terms of physical properties such as hot air aging durability, and can be provided at a price intermediate between those. This shows improved heat resistance in areas where the acrylic rubber content is high, and in areas where the fluororubber is high, it provides heat resistance and oil resistance by imparting economic efficiency without significantly impairing its outstanding properties. It can be widely used for rubber parts in the field of industrial machinery such as automobiles, etc.

[0010]

The composition of the fluororubber usable in the present invention is generally the same as that commercially available under the general name of fluororubber, and more specifically, a homopolymer of 6-fluorinated propylene or a fluoropolymer of the same. Vinylidene chloride and / or 4-
A copolymer with fluorinated ethylene is exemplified. 40 mol% of other vinyl monomer which can be copolymerized, if necessary.
Up to 20 mol%, usually up to 20 mol%. Examples of other vinyl monomers include ethylene, propylene, methyl vinyl ether, ethyl vinyl ether, butyl vinyl ether and phenyl vinyl ether. Further, the crosslinkable group of fluororubber is produced by the copolymerization of 6-fluoropropylene.

[0011]

[Chemical 1]

[0012] Therefore, the preferred content of 6-fluorinated propylene is 5 to 100% by weight,
Particularly, it is 50 to 100% by weight.

The acrylic rubber which can be used in the present invention comprises an acrylic acid ester as a main component and a copolymerizable monomer having a crosslinkable hydroxyl group or a crosslinkable chlorine atom as a crosslinking component, and if necessary, an acrylic acid ester. A copolymerizable vinyl monomer may be added.

Examples of the acrylate ester as a main component include alkyl acrylate esters such as methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, octyl acrylate; Acrylic acid 2
-Acrylic acid alkoxyalkyl esters such as methoxyethyl, 2-ethoxyethyl acrylate, 2-butoxyethyl acrylate, and 3-methoxypropyl acrylate can be used. Particularly, ethyl acrylate 30-
70 mol% and n-butyl acrylate 50 to 10 mol% are preferably used together in order to adjust cold resistance and oil resistance.

The copolymerizable monomer having a crosslinkable hydroxyl group or a crosslinkable chlorine atom to be a crosslinkable group is preferably a phenolic hydroxyl group in the case of a crosslinkable hydroxyl group, and an active chlorine atom in the case of a crosslinkable chlorine atom. Specifically, o,
m, p-hydroxystyrene, α-methyl-o-hydroxystyrene, o-cavicol, vinyl p, m-hydroxybenzoate, vinyl salicylate, eugenol, isoeugenol, p-isopropenylphenol, o,
Crosslinkable hydroxyl group-containing monomers such as m, p-allylphenol and 2,2- (o, m, p-hydroxyphenyl-4-vinylacetyl) propane; 2-chloroethyl vinyl ether, vinyl monochloroacetate, chloromethylstyrene, allyl. Monomers containing active chlorine atoms such as chloride can be used. Crosslinkable group-containing monomer content is 1
In the range of ˜20 mol%, particularly 2 to 10 mol% is preferable, and if it is less than 1 mol%, the vulcanization rate becomes too slow to be practically used, and if it exceeds 20 mol%, scorch easily occurs.
The storage stability of the final rubber compound is impaired.

As the vinyl monomer copolymerizable with the acrylic ester, for example, acrylonitrile, vinyl acetate, styrene, methacrylic acid alkyl esters, methacrylic acid alkoxyalkyl esters and the like can be used.

The acrylic rubber used in the present invention is obtained by coagulating a latex obtained by the following polymerization method by a usual salting-out operation using salt as a salting-out agent, followed by washing with water and drying. Manufactured.

In a 2 liter beaker, anionic emulsifier, dioctyl sulfosuccinate sodium salt 5.0
g is dissolved in 1250 g of deionized water, 300 g of the acrylic rubber-constituting monomer mixture is added thereto in total, and the mixture is emulsified using a small mixer. Next, the monomer emulsion is charged into a 2 liter polymerization vessel equipped with a reflux cooling tube and heated to 70 ° C. under a nitrogen stream. To this, 10 g of a 10% aqueous solution of ammonium persulfate is added to initiate polymerization.
After the initiation of the polymerization, the temperature in the polymerization vessel was changed from the initial 70 ° C to 80
C., and maintained in the range of 80 to 82.degree. C. for 2 hours to complete the polymerization reaction.

The mixing ratio (weight ratio) of the fluororubber and the acrylic rubber is 0.5 to 99.5 / 99.5 to 0.5, preferably 20 to 80/80 to 20. When the proportion of fluororubber decreases, the physical performance such as durability against hot air aging becomes insufficient, and when the proportion of acrylic rubber decreases, the vulcanization speed becomes slow and the economical efficiency is impaired.

The rubber composition of the present invention is characterized in that a vulcanizing agent is not used, and an acid acceptor and a vulcanization accelerator composed of a metal oxide and a metal hydroxide, which are usually used for compounding a halogen-containing rubber, are used. By compounding, fluororubber and acrylic rubber are directly vulcanized together. As the metal oxide, for example, magnesium oxide, zinc oxide, calcium oxide or the like can be used, and as the metal hydroxide, for example, magnesium hydroxide, zinc hydroxide, calcium hydroxide,
Aluminum hydroxide or the like can be used.

As the vulcanization accelerator, quaternary ammonium salts and quaternary phosphonium salts can be preferably used, and examples thereof include tetraethylammonium chloride, tetraethylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium bromide and n-dodecyl. Trimethylammonium chloride, n-dodecyltrimethylammonium bromide,
Octadecyl trimethyl ammonium bromide, cetyl dimethyl ammonium chloride, 1,6-diaza-
Quaternary ammonium salts such as bicyclo (5.4.0) undecene-7-cetylpyridinium sulfate, trimethylbenzylammonium benzoate; triphenylbenzylphosphonium chloride, triphenylbenzylphosphonium bromide, tricyclohexylbenzylphosphonium chloride, tricyclohexylbenzyl. Examples thereof include quaternary phosphonium salts such as phosphonium bromide.

The highly heat resistant rubber composition of the present invention comprises a rubber component comprising a specific fluororubber and an acrylic rubber, an acid acceptor comprising a metal oxide and / or a metal hydroxide, a quaternary ammonium salt and / or Alternatively, in addition to the vulcanization accelerator comprising a quaternary phosphonium salt, an auxiliary material added to a usual rubber compound, that is, an antiaging agent such as a diphenylamine derivative or a phenylenediamine derivative, a processing aid such as stearic acid, Carbon black, kaolin clay,
It is prepared as an unvulcanized rubber composition by kneading a filler such as talc and diatomaceous earth, a plasticizer and the like with an open mill roll, an internal mixer and the like which are usually used in the rubber industry.

To obtain a high heat resistant rubber by vulcanizing the unvulcanized rubber composition using a vulcanizing machine usually used in the rubber industry such as a hot press, an injection molding machine and a steam can. You can

Next, the present invention will be explained based on examples, but the present invention is not limited to such examples.

Examples 1 to 5 and Comparative Examples 1 to 6 Fluorine rubber and acrylic rubber shown in Table 1 were used as the main compounding ingredients of the rubber component, the acid acceptor and the vulcanization accelerator. The rubber composition of the present invention was prepared by mixing the auxiliary materials and using a 6-inch test roll. Acrylic rubber and fluororubber compositions as comparative examples were also prepared in the same manner using a 6-inch test roll based on the following comparative formulation.

The fluororubbers used in Examples 1 to 5 and Comparative Examples 1 to 4 are terpolymer solid rubbers of 6-fluoropropylene, vinylidene fluoride and 4-fluoroethylene (Technoflon manufactured by Audimonte). TN). The acrylic rubber (ACM) used in Comparative Example 5 was a terpolymer of ethyl acrylate, butyl acrylate, and methoxyethyl acrylate (50/25/25 molar ratio, Toa Akron AR- manufactured by Toupe Corporation). 840), and the fluororubber (FKM) used in Comparative Example 6 is a binary copolymer of 6-fluoropropylene and vinylidene fluoride (Daiel G-701 manufactured by Daikin Industries, Ltd.).

Each rubber composition was vulcanized using a hot press under the vulcanization conditions shown in Table 2 and each vulcanized rubber was subjected to an initial physical property test (JIS K6251, JIS).
K6253), air heating aging test (JIS K625
7) and compression set test (JIS K6262). The results are shown in Table 2.

(Composition of Examples) Rubber component (Table 1) 100.0 parts Stearic acid 1.0 part Anti-aging agent (diphenylamine derivative) * 1 2.0 parts MT carbon black (N990) 25.0 parts Oxidation Magnesium (acid acceptor) * 2 3.0 parts Calcium hydroxide (acid acceptor) * 3 9.0 parts n-dodecyltrimethyl ammonium bromide (vulcanization accelerator) 2.0 parts (Compound formulation of Comparative Example 4) Acrylic rubber * 4 100.0 parts Stearic acid 1.0 part Anti-aging agent (diphenylamine derivative) * 1 2.0 parts HAF carbon black (N550) 55.0 parts Fine powder sulfur * 5 0.3 parts Nonsar SK-1 * 6 0.3 parts Nonsal SN-1 * 7 3.0 parts (Compound formulation of Comparative Example 6) Fluorine rubber * 8 100.0 parts MT carbon black (N990) 20. Part of magnesium oxide (acid acceptor) * 2 3.0 parts of calcium hydroxide (acid acceptor) * 3 6.0 parts [Note] * 1 Uniroyal Corp. Naugard #
445 * 2 Kyowa Chemical Co., Ltd. Kyowamag 150 * 3 Omi Chemical Co., Ltd. Caldic 200
0 * 4 Toa Akron AR- manufactured by Toupe Corporation
840 * 5 Tsurumi Chemical Industry Co., Ltd. 325 mesh sulfur * 6 NOF Corporation potassium aliphatic monocarboxylate * 7 NOF Corporation sodium aliphatic monocarboxylate * 8 Daikin Industries Co., Ltd. Daiel G-701

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

The rubber composition of the present invention exhibits characteristics in the intermediate range between fluororubber and acrylic rubber in physical properties such as hot air aging durability and can be provided at a price intermediate between those. This gives improved heat resistance in areas where the acrylic rubber content is high, and in areas where there is much fluororubber, it provides heat resistance and oil resistance by imparting economic efficiency without significantly impairing its outstanding properties. It is possible to promote widespread use for rubber parts in the industrial machinery field, such as automobiles, that require high cost.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Masateru Yokotani 1-5-5 Chikko Shinmachi, Sakai City, Osaka Prefecture 11 Toupe Sakai Business Office

Claims (1)

[Claims] 1. A mixture of (A) an acrylic rubber having a crosslinkable hydroxyl group or a crosslinkable chlorine atom and a fluororubber having a polymerized unit based on 6-fluoropropylene and vinylidene fluoride and / or 4-fluoroethylene. A rubber component having a weight ratio of acrylic rubber / fluorine rubber of 0.5 to 99.5 / 99.5 to 0.5,
Vulcanizable acrylic rubber-fluorine comprising (B) an acid acceptor composed of a metal oxide and / or metal hydroxide and (C) a vulcanization accelerator composed of a quaternary ammonium salt and / or a quaternary phosphonium salt Rubber composition.