JPS5934730B2 - Mixed elastomer-vulcanized formulations - Google Patents

Description

[Detailed description of the invention] BACKGROUND OF THE INVENTION This invention relates to mixed elastomer vulcanizate formulations.

More particularly, it relates to vulcanized blends of mixed elastomers of fluoroelastomers and acrylic elastomers with improved vulcanization properties. In the technical field of heat-resistant elastomers such as fluoroelastomers and acrylic elastomers, there is a need for elastomers that exhibit good processability during kneading and molding, have satisfactory heat resistance, and are priced accordingly. It has been proposed to use a fluoroelastomer and an acrylic elastomer as a mixed elastomer (Japanese Patent Laid-Open No. 52-40558).
Publication No.).

However, it is known that when elastomers with completely different properties are mixed, a uniform mixed state cannot be obtained in many cases, and even in the most uniformly mixed state, microscopic phase separation occurs. It is often seen that the physical properties of the vulcanized product of a phase-separated elastomer mixture are inferior to those of the vulcanized product of each elastomer alone, and this also applies to the case of a mixed elastomer of fluoroelastomer and acrylic elastomer. Not an exception. In order to overcome these drawbacks, by using a carboxyl group-containing acrylic elastomer as the acrylic elastomer,
The present inventor has already proposed to form crosslinks between mixed elastomers and fluoroelastomers to prevent deterioration of the physical properties of the vulcanizate due to phase separation (Japanese Patent Application No. 1983-1999). No. 7365 (Unexamined Japanese Patent Publication No. 54-101847
(Reference).

Although this proposal solved many of the problems that had previously been considered and made it possible to obtain a vulcanizate with excellent physical properties, it had poor storage stability near room temperature and often caused scorch. It was found that there are still some problems that need to be resolved, such as a tendency to occur. As a result of various studies to further overcome such handling difficulties, the present invention has newly discovered that a vulcanized compound containing a mixed elastomer and a vulcanizing component described below can solve these problems. Ta. Mixed elastomer is fluoroelastomer 1 to 9
9.5 parts (weight, same below), preferably 40-99.
5 parts and carboxyl group-containing acrylic elastomer
Consisting of 99 to 0.5 parts, preferably 60 to 0.5 parts,
Other elastomers may also be mixed as long as they do not impede the purpose of the present invention.

Examples of the fluoroelastomer include vinylidene fluoride-hexafluoropropylene copolymer, particularly preferably an 85-60:15-40 mol% copolymer thereof, and vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene tripolymer. One or more types of original copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, etc. are used, and in addition, dichlorodifluoroethylene, perfluoroacrylic acid derivatives, perfluorovinyl ether, etc. are used. Copolymers with vinylidene are also used. The carboxyl group-containing acrylic elastomer contains 50 to 99.9% by weight of acrylic acid ester, 20 to 0.1% by weight of a carboxyl group-containing monomer, and 30 to 30% of other monomers copolymerizable with these comonomers. It consists of 0% by weight of copolymer.

Examples of acrylic esters include alkyl acrylates in which the alkyl group has 1 to 8 carbon atoms, such as methyl acrylate, ethyl acrylate, n- or isopropyl acrylate, n- or isobutyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate. , methoxymethyl acrylate, 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, etc., in which the alkyl group and alkylene group each have 1 to 4 carbon atoms, are used, with ethyl acrylate being particularly preferred. Examples of carboxyl group-containing monomers include acrylic acid, methacrylic acid, vinyl acetic acid, 4-vinylbenzoic acid,
4-allylbenzoic acid, styryl acetic acid, etc. are used, and acrylic acid and methacrylic acid are particularly preferred. In the carboxyl group-containing acrylic elastomer, other monomers that can be copolymerized with acrylic esters such as styrene, acrylonitrile, and vinyl acetate and the carboxyl group-containing monomer can also be copolymerized. Examples of carpoxyl group-containing acrylic elastomers include ethyl acrylate to acrylic acid copolymers and ethyl acrylate to methacrylic acid copolymers, particularly preferably 95 to 99
．． 5:5~O. A 5 mol % copolymer, an ethyl acrylate methyl acrylate acrylic acid ternary copolymer, and the like are used. The vulcanization system contains a vulcanizing agent for fluoroelastomers, a vulcanizing agent for acrylic elastomers, a vulcanization accelerator, an anti-scorch vulcanization accelerator, and a vulcanization accelerator. Vulcanizing agents for fluoroelastomers include aromatic groups substituted with two or more, preferably 2 to 4, active hydrogen-containing groups such as carboxyl groups, hydroxyl groups, amino groups, imino groups, and mercapto groups; Aliphatic or cycloaliphatic compounds are used.

Examples of such compounds include terephthalic acid, p-hydroxybenzoic acid, dihydroxynaphthalene, tetrahydroxyanthracene, 2,2'-hydroxybiphenyl, 4,4'-hydroxybiphenyl, catechol, p-
Aminophenol, p-phenylenediamine Hydroquinone, naphthoquinone, 2-mercaptobenzimidazole, 4,4'-diaminodiphenylmethane, phthalic acid imide, bisphenol A1 bisphenol S1 bisphenol AF1 4,4'-dihydroxy Examples include benzophenone. Among these vulcanizing agents, compounds having the following general formula are preferably used.

Here, X and Y are substituents containing active hydrogen such as carboxyl group, hydroxyl group, amino group, imino group, mercapto group, m and n are integers of 1 or more, and A is carbonyl group, sulfinyl group. group, sulfonyl group, alkylene group, perfluoroalkylene group, alkylidene group, or perfluoroalkylidene group, and the phenyl nucleus is further substituted with a substituent that does not contain active hydrogen, such as a halogen, nitro group, alkoxy group, or ester group. can be done.

Particularly preferred vulcanizing agents are polyhydroxy-substituted compounds, especially bisphenol type compounds, such as hexafluoroisopropylidene bis(4-hydroxyphenyl), also known as bisphenol AF, and bisphenol A.
Examples include isopropylidene bis(4-hydroxyphenyl), which is said to be

These vulcanizing agents for fluoroelastomers are used in an amount of 0.1 to 10 parts, preferably O. 5
~3 parts. If the proportion is less than this, the desired vulcanized density cannot be obtained, while if the proportion is greater than this, the rubber elasticity will be lost and the vulcanization time will tend to be prolonged. As a vulcanizing agent for acrylic elastomer,
Polyepoxy compounds having at least two epoxy groups in the molecule and having an epoxy equivalent weight of about 70 to 1000 are used.

Examples of polyepoxy compounds include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, glycerin triglycidyl ether, 2
・2-bis(4-glycidyloxyphenyl)propane 2,2-bis(4-glycidyloxyphenyl)hexafluoropropane, phthalic acid diglycidyl ether, novolac polyglycidyl ether, tris(epoxypropyl)isocyanurate , bisphenol A-epichlorohydrin condensation adduct, etc. are used. These polyepoxy compounds are used in an amount of 0.1 to 20 parts, preferably 0.5 to 20 parts, per 100 parts of mixed elastomer.
It is used in a proportion of 5 parts. If the vulcanizing agent is used in a proportion smaller than this, the desired vulcanizing effect cannot be obtained, while if it is used in a larger proportion, heat aging becomes significant. Vulcanizing agents for fluoroelastomers such as polyhydroxy compounds and vulcanizing agents for acrylic elastomers such as polyepoxy compounds can be kneaded simultaneously for each elastomer by ordinary rubber kneading operations, but It is preferable to knead the compound and the like into the fluoroelastomer and the polyepoxy compound into the acrylic elastomer, respectively, and then knead both. As the vulcanization accelerator, those belonging to the following categories are used.

Those belonging to the first and second categories are used. Those in the first and second categories are shown in the following general formulas. Here, R1 to R4 have 1 to 2 carbon atoms.
0 alkyl group, fluoroalkyl group, aralkyl group,
These are polyoxyalkylene groups, aryl groups, etc., and X is halogen, hydroxyl group, carboxyl group, carbonate group, sulfide group, etc. Examples of such quaternary ammonium salts include octadecyldimethylbenzylammonium chloride, octadecyldimethylbenzylammonium Examples of quaternary phosphonium salts include triphenylbenzylphosphonium chloride and tricyclohexylbenzylphosphonium chloride.

Instead of the quaternary ammonium halide or phosphonium halide, a tertiary amine of the formula RlR2R3N or a tertiary phosphine of the formula RlR2R3P and a tertiary phosphine of the formula R4
Equimolar mixtures with halides represented by X (R, ~R4 are as defined above, and X is halogen) can also be used equally. Those belonging to the third category are nitrogen-containing heterogeneous compounds represented by the general formula RN-RlX (where R is a group forming a heterocyclic ring together with N, and R and X are the same as defined above). These are nodular cyclic compound adducts, such as laurylpyridinium bromide, laurylisoquinolinium bromide, benzylisoquinolinium chloride, and the like.

A mixture of a nitrogen-containing heterocyclic compound represented by the formula RN and a halide represented by the formula RlX' (R.R and X are the same as defined above), such as isoquinoline and benzyl chloride or lauryl bromide. Equimolar mixtures and the like can equally be used. Belonging to the fourth category are the guanidines, such as guanidine or alkyl, acyl, aryl, aralkyl substitutions of guanidine, such as methylguanidine, acetylguanidine, diphenylguanidine, di-0-tolylguanidine, O-tolyl biguanide. Examples include the body.

The fluoroelastomer and acrylic elastomer used in the present invention clearly have different crosslinking reactions, so it is rare that the same vulcanization rate and density can be obtained with the same vulcanization accelerator. I can't bite. Therefore, when using these vulcanization accelerators, it is preferable to vary the accelerator concentration in each elastomer or to use two or more types of accelerators in combination. The vulcanization accelerator is used in an amount of 0.1 to 10 parts per 100 parts of mixed elastomer. If the proportion is less than this, the desired vulcanization promoting effect cannot be obtained, while if the proportion is greater than this, the vulcanization rate will be too fast, causing problems in terms of moldability. The vulcanization system also contains a vulcanization accelerating aid consisting of a metal oxide or hydroxide in order to accelerate the vulcanization of each mixed elastomer and provide aging stability to the fluoroelastomer.

Examples of metal oxides include oxides of divalent metals such as magnesium oxide, zinc oxide, lead oxide, and calcium oxide.
Examples of metal hydroxides include magnesium hydroxide,
Examples include hydroxides of divalent metals such as zinc hydroxide and calcium hydroxide. One or more of these metal oxides or hydroxides are used in an amount of 1 to 40 parts, preferably 1 to 20 parts, per 100 parts of the mixed elastomer. In addition to the above-mentioned vulcanization system components, a scorch-preventing vulcanization accelerator, specifically a hydrogen acid addition salt of ammonia or amines, is used as a vulcanization rate regulator.

When a mixed elastomer of a fluoroelastomer and an acrylic elastomer is cured using a vulcanization system consisting of each of the above-mentioned components, scorch phenomenon near room temperature, which is not observed when each elastomer is used alone, can be avoided. cause. It has been found that this scorch phenomenon is mainly caused by the acrylic elastomer in the mixed elastomer, and is caused by the action of the metal oxide or hydroxide alone blended into the mixed elastomer vulcanization system and the interaction with these metal compounds. It is presumed that this is due to the action of a strong basic substance such as quaternary ammonium hydroxide or quaternary phosphonium hydroxide formed from quaternary ammonium salt or quaternary phosphonium salt. Acidic substances such as benzoic acid and phthalic anhydride, which are scorch inhibitors normally used to suppress such scorch phenomenon, do not exhibit the desired scorch-preventing effect in the vulcanization system of the mixed elastomer of the present invention. Not only that, but it also reacted with the polyepoxy compound, which is the vulcanizing agent for the acrylic elastomer, resulting in a side effect of lowering the vulcanized density of the mixed elastomer. In contrast, hydrogen acid addition salts of ammonia or amines are neutralized with stronger bases, such as quaternary ammonium hydroxide and quaternary phosphonium hydroxide, to produce amines, which are weaker bases.

Therefore, it not only prevents the scorch phenomenon but also acts as a vulcanization accelerator, making it possible to suppress the types of side effects mentioned above. Therefore, these hydrogen acid addition salts of ammonia or amines are not simply scorch inhibitors, but are suitable to be called vulcanization rate modifiers.
Amines that can be used in the same way as ammonia include
Any amine, secondary or tertiary amine can be used, and it can be a polyamine as well as a monoamine.

Specifically, primary amines such as laurylamine, aniline, and guanidine, secondary amines such as di-n-butylamine, diisobutylamine, di-0-tolylguanidine, and diphenylguanidine, and tertiary amines such as triethylamine and pyridine. is exemplified. In addition, as hydrogen acid,
For example, inorganic hydrogen acids such as hydrochloric acid, sulfuric acid, boric acid, ferricianic acid or acetic acid, propionic acid, acrylic acid, methacrylic acid, chloroacetic acid, trichloroacetic acid, phenylacetic acid,
Examples include organic hydrogen acids such as benzoic acid. Examples of hydrogen acid addition salts of ammonia or amines include ammonium benzoate, ammonium sulfate, laurylamine hydrochloride, aniline hydrochloride, di-n-butylamine hydrochloride, diisobutylamine hydrochloride, triethylamine hydrochloride, and pyridine hydrochloride. , di-10-tolylguanidine hydrochloride, diphenylguanidine hydrochloride, ammonium tetrafluoroborate, di-10-tetrafluoroborate
Examples include tolylguanidine, ammonium ferricyanate, di-10-tolylguanidine ferricyanate, and dicatechol di-0-tolylguanidine borate.

These hydrogen acid addition salts of ammonia or amines are
It is used in a proportion of 0.01 to 20 parts per 100 parts of mixed elastomer. If the proportion used is less than this, no scorch prevention effect will be observed, and if the proportion is too large, vulcanization tends to be extremely slow. After adding fillers, pigments, porous substances, etc., which are generally known as compounding agents for rubber, to the elastomer and each component of the vulcanization system as necessary, the mixture is mixed with an arbitrary mixing device, such as two rolls for kneading rubber. The components are mixed using a Banbury mixer or the like to prepare an elastomer vulcanized compound.

Since this mixture has appropriate viscoelasticity, it is easier to perform mixing and extrusion operations than when the fluoroelastomer is used alone, and is therefore superior in processability. Regarding processability, it has been pointed out that fluoroelastomers in particular have the disadvantage of poor processability compared to other general-purpose elastomers.

That is, during roll processing, the lack of adhesion to the roll results in poor winding and often requires an unnecessarily long kneading time. Furthermore, during calendering, it is difficult to obtain a sheet-like product that is relatively thin and has a smooth surface, such as a thickness of 0.2 m1, due to poor flow of the elastomer. Furthermore, during extrusion processing, the so-called melt fracture phenomenon occurs, in which the surface is undulated in the shape of bamboo knots or spirals due to poor fluidity. For this reason, when processing fluoroelastomers, it has been necessary to select processing conditions with poor productivity. However, the mixed elastomer vulcanized compound of the present invention also has the effect of improving processability. In other words, in the case of roll processing, the workability is improved due to good winding around the roll and the fast kneading speed of the filler, and in the case of calendar processing, the flow is good and the sheet strength is high in a thin state. Therefore, it is possible to easily obtain thinner and smoother sheets, and in the case of extrusion processing, the extrusion pressure is as low as 20 kg/CrA (99 ± 2°C), which was observed when using fluoroelastomer alone. The phenomenon of melt fracture on the surface is no longer observed, and therefore the extrusion pressure can be increased to improve productivity (see Table 3), resulting in a significant improvement in processing formability. Vulcanization is approximately 150-200℃
It is carried out by heating at a temperature of about 1 to 30 minutes.

This vulcanization is performed using a conventional rubber molding press, extruder, or the like. If a vulcanizate with excellent heat resistance and dimensional stability is desired, it is preferable to further post-vulcanize at a temperature of about 170 to 240° C. for about 1 to 48 hours. The vulcanizate obtained by vulcanizing the elastomer vulcanizate according to the present invention has significantly higher physical properties, especially compression, compared to the case where other types of acrylic elastomers are mixed with fluoroelastomers. It shows an excellent value in terms of permanent deformation.

Therefore, vulcanizates of mixed elastomers of other types of acrylic elastomers and fluoroelastomers are unusable due to excessive deformation due to heat aging, such as in fields such as valve stem seals and O-rings. It can also be used effectively. Of course, in addition to these new fields of application, it can also be effectively used in conventional fields of use of heat-resistant rubber, such as oil seals, gaskets, and tubes. Next, the effects of the present invention will be explained with reference to Examples.

Example 1 (1) Fluoroelastomer: The components (1) to (3) above were kneaded using a two-roll kneader to prepare a vulcanized compound.

After initial vulcanization of this formulation at 180°C for 11 minutes, 20
Post-vulcanization was carried out at 0° C. for 20 hours. Example 2 In Example 1, the post-vulcanization conditions were 175° C. for 24 hours.

Example 3 In Example 1, 0.3 part of dicatechol di-0-tolylguanidine borate was used, and the initial vulcanization conditions were 190° C. and 8 minutes.

Example 4 In Example 3, the post-vulcanization conditions were 175° C. for 24 hours.

Comparative Example 1 In Example 1, dicatecol di-10-tolylguanidine borate was not used and the initial vulcanization time was 15 minutes.

Comparative example 2 In Comparative Example 1, the post-vulcanization conditions were 175° C. for 24 hours.

Example 5 In Example 1, 0.28 parts of triphenylbenzylphosphonium chloride was used and the initial vulcanization conditions were 190° C. for 15 minutes.

Example 6 In Example 5, the post-vulcanization conditions were 175° C. for 24 hours.

Comparative Example 3 In Example 5, the initial vulcanization conditions were 180° C. for 20 minutes without using dicatechol di-0-tolylguanidine borate.

Comparative example 4 In Comparative Example 3, the post-vulcanization conditions were 175° C. for 24 hours.

For the vulcanized formulations of the above Examples and Comparative Examples, the film scorch time (△
5: Time required to increase by 5 points, △35:35
time required to increase points) and JISK-6
The physical properties of the vulcanizate (compression set: vulcanized product compressed by about 25% at 175° C. for 70 hours) were measured in accordance with the test method of No. 301.

The results obtained are shown in Table 1 below. In addition, Example 1
, 3, 5 and comparative examples 1, 3 are shown in the drawings. Examples 7-1
0. Comparative Example 5 Vulcanized components having the formulation (parts by weight) shown in Table 2 below were kneaded using a two-roll kneader to prepare a vulcanized compound.

For each of these vulcanized compound samples 37, a Koka-type flow tester (temperature 957 soil 2°C, plunger cross-sectional area 1c) was used.
r! i, nozzle diameter 1m7! L) was used to measure its extrusion properties.

The results obtained are shown in .

The following Table 3: The vulcanized compound of Example 8 was press-cured at 190°C for 8 minutes, and then oven-cured at 175°C or 200°C for 24 hours. The physical properties of the vulcanized product were measured, and the following values were obtained. Ta.

Claims (1)

[Claims] 1 (A) 100 parts by weight of a mixture of a fluoroelastomer and a carboxyl group-containing acrylic elastomer, (B
) 0.1 to 10 parts by weight of an aromatic, aliphatic or alicyclic compound substituted with two or more active hydrogen-containing groups, (C) 0.1 to 20 parts by weight of a polyepoxy compound, (D) Quaternary ammonium salt, quaternary phosphonium salt, nitrogen-containing heterocyclic compound adduct or guanidines 0.1 to 10 parts by weight, (E
) 1 to 40 parts by weight of metal oxide or metal hydroxide and (F) 0.0 part of hydrogen acid addition salt of ammonia or amines
A mixed elastomer vulcanized formulation containing 1 to 10 parts by weight.