JPH07286081A - Highly heat-resistant rubber composition - Google Patents

Abstract

PURPOSE:To obtain a rubber composition thermally stable at high temperature over a long period of time. CONSTITUTION:A vulcanizable rubber composition which contains a rubber composite wherein a fluororubber having polymer units based on propylene hexafluoride and vinylidene fluoride and/or ethylene tetrafluoride and an acrylic rubber having cross-linkable hydroxyl groups or crosslinkable chlorine atoms in the molecule are mutually dispersed, an acid acceptor comprising a metal oxide and/or a metal hydroxide, and a vulcanization accelerator comprising a quaternary ammonium salt and/or a quaternary phosphonium salt.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a heat resistant and oil resistant composite rubber composition comprising 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. As a means for solving this problem, various studies have been conducted on a composition in which a high heat resistant rubber such as a fluororubber or a silicone rubber is mixed (JP-A-55-23).
128, JP-A-58-63740). Further, in order to increase the affinity with each component, a method of introducing a monomer having a high affinity for fluororubber or silicone rubber into a constituent monomer of acrylic rubber has also been attempted (Japanese Patent Laid-Open No. Hei 4).
-30963, JP-A-4-100846).

[0003]

However, in practice, acrylic rubber and fluororubber or silicone rubber have a poor chemical affinity, and it is difficult to obtain a uniform mixture in a micro state by ordinary mechanical kneading. Is. Further, it is difficult to form a good co-vulcanization state because the respective cross-linking groups are different. In addition, the cross-linking reaction with the co-vulcanizing agent forms not only the original purpose, that is, inter-molecular cross-linking of different polymers, but also intra-molecular cross-linking of the same kind of polymer, so that a rubber having a uniform and stable phase cannot be obtained. .

Therefore, the vulcanized compound thus obtained has not been able to bring out excellent heat resistance. Even if acrylic rubber containing a monomer with a high affinity is used, it is a compound consisting of components that are inherently poor in co-vulcanization, so the rubber obtained by vulcanization easily undergoes phase separation, which also results in long-term heat resistance. It hasn't reached its full potential.

[0005]

As a result of various studies to solve these problems, the present inventors have found that a fluororubber and an acrylic rubber having a crosslinkable group that can be directly crosslinked with the crosslinkable group of the fluororubber are used. The micro-dispersed composite is compounded with an acid acceptor and a vulcanization accelerator without using a vulcanizing agent, and is directly vulcanized between different polymers to ensure long-term stability at high temperatures. The inventors have found that a vulcanized rubber can be provided and completed the present invention.

That is, the present invention provides (A) a fluororubber having a polymerized unit based on 6-propylene propylene and vinylidene fluoride and / or 4-fluoroethylene, and a crosslinkable hydroxyl group or a crosslinkable chlorine atom in the molecule. A rubber composite in which acrylic rubber is mutually dispersed, (B) an acid acceptor comprising a metal oxide and / or a metal hydroxide, and (C) a quaternary ammonium salt and / or a fourth
The present invention relates to a vulcanizable rubber composition containing a vulcanization accelerator composed of a high-grade phosphonium salt. Such a rubber composition is obtained by mixing an acrylic rubber latex having a cross-linking group capable of directly bonding with the cross-linking group of the fluororubber in a latex state with the fluororubber in a latex state, followed by coagulation, or an acrylic rubber having the cross-linking group. A blend composition obtained by coating and polymerizing the constituent monomers with fluororubber latex as a seed, and then coagulating the mixture contains an acid acceptor comprising a metal oxide and / or a metal hydroxide, and a quaternary quaternary ammonium salt. A vulcanization accelerator comprising a salt and / or a quaternary phosphonium salt, and optionally, an antioxidant, a processing aid and a filler usually used in a rubber compound are mixed by using a mixer usually used in the rubber industry. Obtained by kneading.

Due to such a constitution, the vulcanizable rubber composition of the present invention has a durability in hot air aging which is at least twice as long as the durability time and twice as much as the temperature based on the temperature of the acrylic rubber which is usually commercially available. High heat resistance of 25 ° C. or higher can be obtained. Therefore, by using it for gaskets, seal materials, O-rings, hoses, and rubber parts in the industrial machinery field that require heat resistance, which are directly attached to automobile engines, their life can be greatly extended. .

[0008]

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.

[0009]

[Chemical 1]

It is a fluorine atom of, therefore, the preferable content ratio of 6-fluorinated propylene is 5 to 100% by weight,
Particularly, it is 50 to 100% by weight. In order to obtain a composite with acrylic rubber, its shape has an average particle size of 0.1 to 1
0 μm, preferably in the range of 0.2 to 0.5 μm in the form of fine particles and having a concentration of 40 to 80% by weight, preferably 50
Particularly preferably, the latex is uniformly dispersed in water in the range of ˜70% 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 acrylic ester as a main component include alkyl acrylates such as methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate and 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. Especially ethyl acrylate 30-7
The combined use of 0 mol% and 50 to 10 mol% of n-butyl acrylate is preferable 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 ratio of each component in the composite of fluororubber and acrylic rubber is 1 for fluororubber / acrylic rubber (weight ratio).
5-85 / 85-15, preferably 65-35 / 35
It is preferably 65. When the proportion of fluororubber decreases, the physical properties such as durability against hot air aging are insufficiently improved, and when the proportion of acrylic rubber decreases, the vulcanization rate becomes slow, and it tends to become unusable for practical use.

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, a metal hydroxide, ordinarily 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 fluororubber-acrylic rubber composite of the present invention is a latex coprecipitation method in which both latexes are mixed and then salted out, washed with water, and dried, or the fluororubber latex is used as a seed, and the monomers constituting the acrylic rubber component are mixed. It can be produced by salting out, latex washing with water and drying.

The acrylic rubber latex used in the latex coprecipitation method is produced, for example, by the following method.
The method is not limited to this.

In a 2 liter beaker, an anionic emulsifier,
5.0 g of dioctyl sulfosuccinate sodium salt 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 homomixer. 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 composite of fluororubber and acrylic rubber by the coprecipitation method is prepared by mixing and dispersing the fluororubber latex and the acrylic rubber latex in a predetermined ratio and then carrying out a normal salting-out operation using salt as a salting-out agent. It is produced by coagulating a polymer, washing with water and drying.

The composite of fluororubber and acrylic rubber by coating polymerization is obtained by coagulating the latex obtained by the following coating polymerization method by a normal salting-out operation using salt as a salting-out agent, washing with water, Manufactured by drying.

The polymer concentration is adjusted to 20% by weight in a polymerization vessel equipped with a 2 liter reflux cooling tube. 1200 g of fluororubber latex is charged and the temperature is raised to 70 ° C. under a nitrogen stream. To this, 10 g of a 10% aqueous solution of ammonium persulfate was added, and then the monomer mixture constituting the acrylic rubber component was mixed at a predetermined ratio by weight and the temperature in the polymerization vessel was adjusted to 8
Quantitatively add dropwise over 3 hours while maintaining the range of 0 to 82 ° C. After dripping, aging at the same temperature for 1 hour,
A coated polymerized latex is obtained.

The highly heat resistant rubber composition of the present invention comprises a complex of 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 In addition to the vulcanization accelerator consisting of a quaternary phosphonium salt, auxiliary materials added to ordinary rubber compounds, that is, antiaging agents such as diphenylamine derivatives and phenylenediamine derivatives, processing aids such as stearic acid, and carbon. Black, kaolin clay, talc,
It is prepared as an unvulcanized rubber composition by kneading a filler such as diatomaceous earth, a plasticizer and the like with an open mill roll, an internal mixer or the like which is usually used in the rubber industry.

To obtain a high heat resistant rubber by vulcanizing an 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 6 and Comparative Examples 1 to 4 The composites of fluororubber 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, and based on the following formulation The rubber composition of the present invention was prepared by blending other 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 fluororubber used in Examples 1 to 6 was a terpolymer of 6-propylene propylene, vinylidene fluoride and 4-fluoroethylene (average particle size 0.25 μm) with a concentration of 6
It is 0% by weight of latex (Technoflon TN latex manufactured by Audigmonte). Further, in Examples 1 to 4 and Comparative Examples 2 to 3, composites of fluororubber and acrylic rubber were prepared by the coating polymerization method, and in Examples 5 to 7 and Comparative Example 1, they were prepared by the coprecipitation method.

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 K6251).
K6253), air heating aging test (JIS K625
7) and compression set test (JIS K6262). The results are shown in Table 2.

(Formulations of Examples) Rubber component (Table 1) 100.0 parts Stearic acid 1.0 part Antiaging 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 5) Fluororubber * 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 (Ternary copolymer of ethyl acrylate, butyl acrylate, and methoxyethyl acrylate) * 5 Tsurumi Chemical Industry Co., Ltd. 325 mesh sulfur * 6 Nippon Oil & Fat Co., Ltd. aliphatic monocarboxylate * 7 Japan Oil and fats Co., Ltd. sodium monocarboxylic acid aliphatic * 8 Daikin Industries, Ltd. Daiel G-701
(Binary copolymer of 6-propylene fluoride and vinylidene fluoride)

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

According to the rubber composition of the present invention, it is possible to provide a highly durable rubber molded article which is excellent in long-term heat resistance and compression set resistance at high temperatures.

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

Claims (6)

[Claims] 1. A fluororubber having a polymerized unit based on (A) 6-fluoropropylene and vinylidene fluoride and / or 4-fluoroethylene, and an acrylic rubber having a crosslinkable hydroxyl group or a crosslinkable chlorine atom in its molecule. A rubber composite in which are mutually dispersed, (B) an acid acceptor comprising a metal oxide and / or a metal hydroxide, and (C) a fourth
A vulcanizable rubber composition containing a vulcanization accelerator composed of a quaternary ammonium salt and / or a quaternary phosphonium salt. 2. The rubber composition according to claim 1, wherein the composite of (A) is obtained by mixing and dispersing a fluororubber latex and an acrylic rubber latex in a latex state, and then salting out and coagulating the mixture. 3. The composite according to claim 1, wherein the composite of (A) is obtained by using fluororubber latex as a seed, coating and polymerizing a monomer constituting an acrylic rubber in an emulsion system, and then salting out and coagulating the monomer. Rubber composition. 4. The crosslinkable hydroxyl group or crosslinkable chlorine atom content of the acrylic rubber component in the composite (A) is 1 to 20.
The rubber composition according to claim 1, which is a mol%. 5. The rubber composition according to claim 1, wherein the metal oxide and the metal hydroxide of (B) are oxides and hydroxides of alkaline earth metals. 6. The rubber composition according to claim 1, wherein the quaternary ammonium salt of (C) is a chlorine salt or bromine salt of tetraalkylammonium.