JP2009298872A - Method for producing elastomer composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing an elastomer composition which improves oil resistance and cold resistance of a crosslinked NBR composition, and an elastomer composition produced by the production method. <P>SOLUTION: The method for producing an elastomer composition includes: making a crosslinked acrylonitrile-butadiene rubber composition, a radical polymerizable monomer and a radical polymerization initiator coexist in supercritical carbon dioxide; thermally decomposing the radical polymerization initiator; and polymerizing the radical polymerizable monomer. The elastomer composition produced by the production method is also provided. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing an elastomer composition, and more particularly, a method for producing an elastomer composition containing a crosslinked acrylonitrile butadiene rubber composition capable of improving both oil resistance and cold resistance, and the production method. The present invention relates to an elastomer composition.

Acrylonitrile butadiene rubber (NBR) is used by adjusting the acrylonitrile content depending on the intended use. For example, NBR with a high acrylonitrile content is used for applications that require oil resistance and water resistance. However, although such NBR is excellent in oil resistance, it has a problem of low cold resistance. On the other hand, NBR having a low acrylonitrile content has a high butadiene content, and thus can improve cold resistance, but has a problem that oil resistance is remarkably inferior.
Thus, oil resistance and cold resistance are contradictory properties in NBR, and providing an NBR that satisfies both is a major challenge in the industry.

On the other hand, various techniques using supercritical materials such as carbon dioxide, water, propane and the like have been studied. For example, in Patent Document 1, when an additive is added to a polymer material such as rubber or plastic material, the additive is dissolved in a compressed fluid of a gaseous substance in a normal state (at normal temperature and normal pressure). Incorporating the additive into the polymeric material without using mechanical mixing means by bringing it into contact with the polymeric material. Other techniques for bringing a supercritical fluid into contact with a polymer are disclosed in Patent Documents 2 to 5 and the like.
However, the above patent documents do not disclose or suggest any technical idea of the present invention that improves the oil resistance and cold resistance by polymerizing a radical polymerizable monomer in a cross-linked NBR to form a composite.
US Pat. No. 4,820,752 JP 2002-146038 A JP 2001-316832 A Japanese Patent Laid-Open No. 11-348037 JP 2006-160945 A

  An object of the present invention is to provide a method for producing an elastomer composition which improves both oil resistance and cold resistance of an elastomer composition of a crosslinked acrylonitrile butadiene rubber composition, and an elastomer composition produced by the production method. is there.

The present invention is as follows.
1. Crosslinked acrylonitrile butadiene rubber composition, radical polymerizable monomer and radical polymerization initiator are allowed to coexist in supercritical carbon dioxide, and then the radical polymerization initiator is thermally decomposed to polymerize the radical polymerizable monomer. The manufacturing method of the elastomer composition characterized by the above-mentioned.
2. 2. The method for producing an elastomer composition according to 1 above, wherein the radical polymerizable monomer is a (meth) acrylate monomer.
3. 3. The method for producing an elastomer composition as described in 1 or 2 above, wherein the radical polymerization initiator is an organic peroxide.
4). 4. The method for producing an elastomer composition according to any one of 1 to 3, wherein a temperature at which the radical polymerization initiator is thermally decomposed is equal to or higher than a 20-hour half-life temperature of the radical polymerization initiator.
5. The elastomer composition manufactured by the manufacturing method in any one of said 1-4.

  According to the present invention, in the supercritical carbon dioxide, a crosslinked acrylonitrile butadiene rubber composition, a radical polymerizable monomer and a radical polymerization initiator are allowed to coexist, and then the radical polymerization initiator is thermally decomposed to produce the radical. Since it is characterized by polymerizing a polymerizable monomer, it becomes possible to produce an elastomer composition improved in both oil resistance and cold resistance.

Hereinafter, the present invention will be described in more detail.
The cross-linked acrylonitrile butadiene rubber composition (hereinafter referred to as cross-linked NBR composition) used in the present invention is a known acrylonitrile butadiene rubber (NBR) using a known vulcanization or cross-linking agent, vulcanization or cross-linking accelerator. What was manufactured by the manufacturing method of can be used.
For example, when sulfur is used as a vulcanizing agent, a sulfenamide vulcanization accelerator, a thiuram vulcanization accelerator, a thiazole vulcanization accelerator, or the like can be used as a vulcanization accelerator. On the other hand, the vulcanizing agent can be used in an amount of about 0.5 to 10 parts by mass and about 0.1 to 5 parts by mass of the vulcanization accelerator.
In addition, carbon black; inorganic fillers such as silica, calcium carbonate, and clay; various additives such as various oils, anti-aging agents, and plasticizers can be variously added to the crosslinked NBR composition depending on the application.

  As the radical polymerizable monomer used in the present invention, those that polymerize in the presence of various radical polymerization initiators can be used. Specific examples of such monomers include vinyl acetate, styrene and styrene derivatives, vinyl pyridine and derivatives thereof, various vinyl ethers, acrylonitrile, various acrylamides, various (meth) acrylic acids, various (meth) acrylic esters, vinyl carbazole, Various vinyl monomers such as maleic anhydride and various vinyl isocyanates can be used. These monomers may be used alone or in combination with other monomers. However, it is necessary to use it with care that maleic anhydride does not homopolymerize. In addition to those exemplified above, monomers described in, for example, “POLYMER HANDBOOK forth edition” II-310 pages (1999) JOHN WILEY & SONS INC. Table 1 can be used.

Among them, in the present invention, from the viewpoint of providing an elastomer composition with improved oil resistance, (meth) acrylates such as (meth) acrylic acid, (meth) acrylic acid metal salts, and (meth) acrylic acid esters Monomers are preferred. In the present specification, (meth) acrylic acid means acrylic acid or methacrylic acid. Among them, it is represented by a monomer having an acid group such as acrylic acid or methacrylic acid, or CH ₂ ═C (R) COOR ′ (wherein R represents hydrogen or a methyl group, and R ′ represents an alkyl group). In the (meth) acrylic acid ester, a monomer in which R ′ is an alkyl group having 1 to 3 carbon atoms is preferable. Particularly preferred are acrylic acid, methacrylic acid, and methyl methacrylate.

  As the radical polymerization initiator used in the present invention, various organic peroxides, various azo initiators, disulfide compounds such as tetramethylthiuram disulfide, and the like can be suitably used. Specific examples of the organic peroxide include diisobutyl peroxide, cumyl peroxyneodecanoate, di-n-propyl peroxydicarbonate, diisopropyl peroxydicarbonate, di-sec-butyl peroxydicarbonate, 1, 1,3,3-tetramethylbutylperoxyneodecanoate, di- (4-t-butylcyclohexyl) peroxydicarbonate, 1-cyclohexyl-1-methylethylperoxyneodecanoate, di (2- (Ethoxyethyl) peroxydicarbonate, di (2-ethylhexyl) peroxydicarbonate, t-hexylperoxyneodecanoate, dimethoxybutylperoxydicarbonate, t-butylperoxyneodecanoate, t-hexylper Oxypivalate, t-butyl peroxypivalate, di (3,3,5-trimethylhexanoyl) per Oxide, di-n-octanoyl peroxide, dilauroyl peroxide, distearoyl peroxide, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, disuccinic acid peroxide, 2,5 -Dimethyl-2,5-di (2-ethylhexanoylperoxy) hexane, t-hexylperoxy-2-ethylhexanoate, di (4-methylbenzoyl) peroxide, t-butylperoxy-2- Ethyl hexanoate, di (3-methylbenzoyl) peroxide, benzoyl (3-methylbenzoyl) peroxide, dibenzoyl peroxide, t-butyl peroxyisobutyrate, 1,1,1-di (t-butyl Peroxy) 2-methylcyclohexane, 1,1-di (t-hexylperoxy) -3,3,5-trimethylcyclohexane, 1,1-di (t-hexylperoxy) cyclohexane, 1,1-di ( t-heki Sylperoxy) -3,3,5-trimethylcyclohexane, 1,1-di (t-butylperoxy) cyclohexane, 2,2-di (4,4-di- (t-butylperoxy) cyclohexyl) propane, t-hexylperoxyisopropyl monocarbonate, t-butylperoxymaleic acid, t-butylperoxy-3,3,5-trimethylhexanoate, t-butylperoxylaurate, 2,5-dimethyl-2, 5-di- (3-methylbenzoylperoxy) hexane, t-butylperoxyisopropyl monocarbonate, t-butylperoxy 2-ethylhexyl monocarbonate, t-hexylperoxybenzoate, 2,5-dimethyl-2,5 -Di- (benzoylperoxy) hexane, t-butylperoxyacetate, 2,2-di- (t-butylperoxy) butane, t-butylperoxybenzoate, n-butyl4,4-di- (t -Butylperoxy) valerate Di (2-t-butylperoxyisopropyl) benzene, dicumyl peroxide, di-t-hexyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, t-butyl cumi Ruperoxide, di-t-butyl peroxide, p-menthane hydroperoxide, 2,5-dimethyl-2,5-di- (t-butylperoxy) hexyne-3, diisopropylbenzene hydroperoxide, 1,1 3,3-tetramethylbutyl hydroperoxide, cumene hydroperoxide, t-butyl hydroperoxide, t-butyltrimethylsilyl peroxide 2,3-di-methyl-2,3-diphenylbutane, and the like.

Specific examples of the azo initiator include 2-2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2-2′-azobis (2,4-dimethylvaleronitrile), 2,2 ′. -Azobisisobutyronitrile, 2-2'-azobis (2-methylbutyronitrile), 1,1'-azobis (cyclohexane-1-carbonitrile), 1-[(1-cyano-1-methylethyl) ) Azo] formamide, 2-2'-azobis {2-methyl-N- [1,1-bis (hydroxymethyl) -2-hydroxyethyl] propionamide}, 2-2'-azobis {2-methyl- N- [2- (1-hydroxybutyl)]-propionamide}, 2-2'-azobis [2-methyl-N- (2-hydroxyethyl) -propionamide], 2-2'-azobis (N- Butyl-2-methylpropionamide), 2-2'-azobis (N-cyclohexyl-2-methylpropionamide), 2-2'-azobis [2- (5-methyl-2-imidazolin-2-yl) propane ] Hydrochloride, 2-2'-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride, 2-2'-azobis [2- (2-imidazolin-2-yl) propane] disulfate di Hydrate, 2-2'-azobis [2- (3,4,5,6-tetrahydropyrimidin-2-yl) propane] dihydrochloride, 2-2'-azobis {2- [1- (2-hydroxy Ethyl) -2-imidazolin-2-yl] propane} dihydrochloride, 2-2'-azobis [2- (2-imidazolin-2-yl) propane], 2-2'-azobis (2-methylpropionamidine) ) Dihydrochloride, 2-2'-azobis [N- (2-carboxyethyl) -2-methylpropionamidine], 2-2'-azobis (2-methylpropionamidoxime), dimethyl 2-2'-azobis (2-methylpropionate), 4,4'-azobis (4-cyanovaleric acid), 2-2'-azobis (2,2,4-trimethyl) Lupentane).
Of these, use of an organic peroxide is desirable from the viewpoint of the effect of the present invention.

  In the production method of the present invention, a crosslinked NBR composition, a radical polymerizable monomer, and a radical polymerization initiator are allowed to coexist in supercritical carbon dioxide, and then the radical polymerization initiator is thermally decomposed to produce the radical polymerizable monomer. It is characterized by polymerizing. Next, the manufacturing method will be described in detail.

  There is no particular limitation on the method of introducing the above components into supercritical carbon dioxide. However, the method of coexisting the above components in a closed container filled with supercritical carbon dioxide, the composition of supercritical carbon dioxide and crosslinked NBR, or the like. A radically polymerizable monomer and a radical polymerization initiator after coexisting with the product, or after dissolving a radically polymerizable monomer and a radical polymerization initiator in supercritical carbon dioxide in advance, the crosslinked NBR composition And the like. The supercritical carbon dioxide can contain other components usually called an entrainer. Entrainers are usually added to adjust the solubility parameter of supercritical carbon dioxide, and one or more organic solvents and organic compounds (gas, liquid, solid) that can be dissolved in supercritical carbon dioxide can be arbitrarily selected. it can. For example, examples of the entrainer include methanol, ethanol, octane, various fatty acids, and the like. However, the entrainer is not limited to these.

The concentration of the crosslinked NBR composition is not particularly limited, but is, for example, 0.1 to 80% by volume in supercritical carbon dioxide, and more preferably 0.5 to 50% by volume.
The amount of the radically polymerizable monomer and the radical polymerization initiator added to the crosslinked NBR composition is not particularly limited, but the radically polymerizable monomer is 1 to 100 parts by mass, radicals with respect to 100 parts by mass of the crosslinked NBR composition. The polymerization initiator is preferably 0.001% by mass to 10% by mass with respect to the radical polymerizable monomer in order to achieve the object.

  In addition, it is preferable that the density | concentration of a radically polymerizable monomer shall be 1.0-60 mass% in supercritical carbon dioxide, and it is more preferable to set it as 3.0-50 mass%. This amount is defined as the amount of radical polymerizable monomer that must be present in the system being used for substantial processing over a substantial processing time with supercritical carbon dioxide. For example, in a batch-type process, it is preferable that 1.0 to 60% by mass of a radical polymerizable monomer coexist with the supercritical carbon dioxide in the processing container. Also, when the radical polymerizable monomer is continuously introduced into the supercritical carbon dioxide, it is preferable to adjust the radical polymerizable monomer so that the concentration is always in this range in the reaction system. If the amount of the radically polymerizable monomer is too small, it takes too much time for complexing, which is not preferable. On the other hand, if the amount is too large, it is difficult to dissolve in supercritical carbon dioxide, or it is difficult to form a composite, which is not preferable.

In the supercritical carbon dioxide, the above components are allowed to coexist, the radical polymerization initiator is thermally decomposed, and the radical polymerizable monomer is polymerized. The thermal decomposition of the radical thermal polymerization initiator may be performed simultaneously with the coexistence of the crosslinked NBR composition, the radical polymerizable monomer and the radical polymerization initiator, or the crosslinked NBR composition is impregnated with the radical polymerizable monomer and the radical polymerization initiator. It may be after letting.
The thermal decomposition of the radical polymerization initiator can be achieved, for example, by setting the temperature in the reaction system to be equal to or higher than the 20-hour half-life temperature of the radical polymerization initiator. The polymerization time is not particularly limited, but is preferably 5 times or more of the half-life time of the radical polymerization initiator at the system temperature. The pressure in the reaction system is preferably not less than the critical pressure of carbon dioxide and not more than 50 MPa. Polymerization of the radical polymerizable monomer forms a new polymer network in the crosslinked NBR composition. In addition, when the radical polymerization initiator has hydrogen abstraction ability, it is considered that hydrogen abstraction from the molecular chain of the crosslinked NBR composition occurs, and a part of the radical polymerizable monomer is grafted there. By the reaction mechanism, the crosslinked NBR composition and the polymer of the radical polymerizable monomer are combined. When a monomer having a carboxyl group in the molecule is used as the radical polymerizable monomer and the crosslinked NBR composition contains a reactive metal atom with a carboxyl group, at least a part of the carboxyl group and metal atom (cation) ) Can also form ionic bonds.

  After completion of the radical polymerization reaction, the pressure in the reaction vessel is lowered to turn carbon dioxide into a gas that is easily removed from the elastomer composition. In the present invention, since carbon dioxide is used as the supercritical fluid, no serious problem is caused in terms of safety or work environment.

In the elastomer composition of the present invention thus obtained, the composite rate defined by the following formula is preferably 3 to 100% by mass, and more preferably 5 to 80% by mass. The composite rate can be adjusted by controlling the amount of radical polymerizable monomer, the amount of radical polymerization initiator, the temperature and pressure of supercritical carbon dioxide, and the degree of impregnation of the radical polymerizable monomer.
Composite rate (mass%) = {(G ¹ −G ⁰ ) / G ⁰ } × 100
G ⁰ : mass (g) of the crosslinked NBR composition before introduction into supercritical carbon dioxide
G ¹ : mass of elastomer after completion of radical polymerization reaction (g)

FIG. 1 is a conceptual diagram for explaining the production method of the present invention.
In FIG. 1A, when the crosslinked NBR composition 102 before being introduced into the prepared supercritical carbon dioxide is allowed to coexist with a radical polymerizable monomer and a radical polymerization initiator in supercritical carbon dioxide, FIG. As shown in b), the radically polymerizable monomer 104 and the radical polymerization initiator 106 are impregnated into the dissolved or swollen crosslinked NBR composition 102. When the radical polymerization initiator 106 is thermally decomposed, the radical polymerizable monomer 104 is polymerized as shown in FIG. As the polymerization proceeds, the unreacted radical polymerizable monomer 104 in the system is supplied into the crosslinked NBR composition 102. Subsequently, when carbon dioxide is gasified by lowering the pressure in the reaction system or the like, the polymer of the crosslinked NBR composition 102 and the radical polymerizable monomer 104 is complexed as shown in FIG. An elastomer composition 108 is obtained.

  EXAMPLES Hereinafter, although an Example and a comparative example further demonstrate this invention, this invention is not restrict | limited to these examples.

Examples 1-6 and Comparative Examples 1-4
(Preparation of crosslinked NBR composition)
In the formulation (parts by mass) shown in Table 1, components other than the vulcanization accelerator and sulfur were kneaded at 80 ° C. for 5 minutes in a closed Banbury mixer, then released outside the mixer and cooled at room temperature. Subsequently, the composition was wound around an open roll, a vulcanization accelerator and sulfur were added, and the mixture was uniformly dispersed by a turning operation to obtain a sheet having a thickness of 2.5 mm. This was kneaded under the vulcanization conditions shown in Table 1 to obtain a crosslinked NBR composition.

[Table 1]

* 1: NBR (manufactured by Nippon Zeon Co., Ltd., Nipol DN401, amount of bound acrylonitrile 18.0% by mass)
* 2: NBR (manufactured by Nippon Zeon Co., Ltd., Nipol 1043, amount of bound acrylonitrile 29.0% by mass)
* 3: NBR (manufactured by Nippon Zeon Co., Ltd., Nipol 1042, amount of bound acrylonitrile 33.5% by mass)
* 4: NBR (manufactured by Nippon Zeon Co., Ltd., Nipol 1041, amount of bound acrylonitrile 40.5% by mass)
* 5: Carbon black (Toast Carbon Co., Ltd., Seast 3)
* 6: Zinc flower (Zonhua No. 3 manufactured by Shodo Chemical Industry Co., Ltd.)
* 7: Stearic acid (Chiba Fatty Acid Co., Ltd., industrial stearic acid)
* 8: Sulfur (Tsurumi Chemical Co., Ltd., powdered sulfur)
* 9: Vulcanization accelerator (Ouchi Shinsei Chemical Co., Ltd., Noxeller NS-F, Nt-butyl-2-bezothiazoylsulfenamide)

(Preparation of elastomer composition)
Sample 1 (10 mm wide, 50 mm long, 1 mm thick strip), glass filter paper carrying a radical polymerizable monomer shown in Table 2 below, and a radical polymerization initiator are placed in a pressure resistant container having a capacity of 45 ml. Carbon dioxide was injected therein, and the pressure and temperature shown in Table 2 were used. The treatment was performed for the time shown in Table 2, and then the carbon dioxide was discharged over 20 minutes and returned to normal pressure.

* 1: MMA (made by Wako Pure Chemical Industries, Ltd., methyl methacrylate)
* 2: MAA (made by Wako Pure Chemical Industries, Ltd., methacrylic acid)
* 3:% by mass relative to sample 1
* 4: DCP (manufactured by Nacalai Tex Corporation, dicumyl peroxide)

The following tests were conducted on the various elastomer compositions obtained above.
Measurement of glass transition temperature (Tg): Measured by DSC at a temperature rising rate of 10 ° C./min in a temperature range of −120 ° C. to 250 ° C.
Measurement of swelling degree of n-hexane: A sample was immersed in n-hexane at 20 ° C., taken out at regular intervals, and n-hexane on the surface was quickly wiped off and weighed. The volume of the swollen sample was calculated from the density of this sample and n-hexane. When the swelling volume became constant, the degree of swelling was determined by the following formula.
Swelling degree = {(volume of swollen sample) − (volume of original sample)} / (volume of original sample) × 100 (%)
The results are shown in Table 3, and the numerical values in Table 3 are shown in FIG.

[Table 3]

Referring to the graph of FIG. 2, the crosslinked NBR compositions of Comparative Examples 1 to 4 improved in oil resistance (n-hexane swelling degree) as the amount of bound acrylonitrile increased (Comparative Example 1 → Comparative Example 4). , Cold resistance (Tg) tends to decrease.
Referring to the results of Examples 1 to 3 of the present invention, it can be seen that the oil resistance is much improved as compared with Comparative Example 1. Further, as the amount of the radical polymerizable monomer used is increased (Example 1 → Example 3), although the cold resistance tends to decrease, the cold resistance decrease curve shown by the broken lines in Comparative Examples 1 to 4 It can be seen that the balance between oil resistance and cold resistance is well improved.
Further, referring to the results of Examples 4 to 6 of the present invention, it is understood that the cold resistance is further improved although it is similar to the results of Examples 1 to 3 described above.

  According to the present invention, improvement in oil resistance and cold resistance of the elastomer composition is achieved, and therefore it can be suitably used for various rubber products including tires and hoses.

It is a conceptual diagram for demonstrating the manufacturing method of this invention. It is a graph which shows oil resistance and cold resistance of the various elastomer compositions in an Example and a comparative example.

Explanation of symbols

102 Crosslinked NBR Composition 104 Radical Polymerizable Monomer 106 Radical Polymerization Initiator 108 Elastomer Composition

Claims (5)

  Crosslinked acrylonitrile butadiene rubber composition, radical polymerizable monomer and radical polymerization initiator coexist in supercritical carbon dioxide, and then the radical polymerization initiator is thermally decomposed to polymerize the radical polymerizable monomer. The manufacturing method of the elastomer composition characterized by the above-mentioned.   The method for producing an elastomer composition according to claim 1, wherein the radical polymerizable monomer is a (meth) acrylate monomer.   The method for producing an elastomer composition according to claim 1 or 2, wherein the radical polymerization initiator is an organic peroxide.   The method for producing an elastomer composition according to any one of claims 1 to 3, wherein a temperature at which the radical polymerization initiator is thermally decomposed is equal to or higher than a 20-hour half-life temperature of the radical polymerization initiator.   The elastomer composition manufactured by the manufacturing method in any one of Claims 1-4.

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