JP2003226864A - Rubber composition for sealing material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a rubber composition for sealing materials, having low permeability of carbon dioxide gas, especially a composition suitable for a hose, tube and diaphragm for carbon dioxide gas. <P>SOLUTION: The rubber composition for sealing materials is composed mainly of an epichlorohydrin rubber such as polyepichlorohydrin (CO), epichlorohydrin- ethylene oxide copolymer (ECO), epichlorohydrin-allyl glycidyl ether copolymer (GCO) and epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer (GECO) and crosslinked by using a polythiol crosslinking agent. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition for a sealing material used for molding a sealing material having a low carbon dioxide permeability, particularly a rubber composition for a sealing material suitable for a carbon dioxide gas hose, a tube, a diaphragm and the like. Regarding

[0002]

2. Description of the Related Art Most of the conventional refrigerants used in refrigerators, car air conditioners, etc. are, for example, 1, 1, 1, 2.
-A CFC gas such as tetrafluoroethane. Due to the problems of ozone layer depletion and environmental destruction such as global warming, the development of new refrigerants for these CFCs has been advanced recently. One of the leading candidates is carbon dioxide. Conventionally, in the case of a CFC gas refrigerant, a rubber composition for a sealing material such as acrylonitrile-butadiene rubber (NBR), hydrogenated NBR or EPDM has been used, but these rubber compositions are used for a carbon dioxide sealing material. If so, carbon dioxide will penetrate the rubber composition, resulting in swelling and foaming of the rubber composition. In order to reduce gas permeability in the sealing material, there is generally a method of adding a non-reinforcing filler such as mica or graphite, but this method tends to cause foaming of the rubber composition.

In addition, NBR, hydrogenated NBR or EPD
There is also a method of mixing M with a material having low carbon dioxide permeability.
However, these materials are NBR, hydrogenated NBR or EP.
The compatibility with DM is generally poor, and these mixtures have a problem of poor processability.

Further, there is a method of using a vinylidene fluoride resin, which is a material having a low carbon dioxide permeability, but it is inferior to a rubber material in processability and flexibility, and when used as a sealing material, the deformation followability is poor and the sealing medium is not This will cause a leak. Moreover, when the sealing material made of vinylidene fluoride resin is attached to a member that has been splined, it is likely to be damaged by the spline and the sealing performance cannot be maintained.

[0005]

DISCLOSURE OF THE INVENTION The present invention provides a rubber composition for a sealing material using carbon dioxide gas, which has a low carbon dioxide gas permeability and a small compression set.

[0006]

SUMMARY OF THE INVENTION The present invention is a rubber composition for a sealing material, characterized in that a rubber composition mainly composed of epichlorohydrin rubber is crosslinked with a polythiol crosslinking agent. The epichlorohydrin-based rubber is a polyepichlorohydrin (CO), epichlorohydrin-ethylene oxide copolymer (ECO), epichlorohydrin-allyl glycidyl ether copolymer (GCO) or epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer (GEC).
O) is used. Triazine thiol is preferably used as the polythiol cross-linking agent. Furthermore, the rubber composition for a sealing material is preferably blended with 0.5 to 10 parts by mass of metal oxide and 100 parts by mass or less of carbon black with respect to 100 parts by mass of the rubber component.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is a rubber composition for a sealing material, characterized in that a rubber composition mainly composed of epichlorohydrin rubber is crosslinked with a polythiol crosslinking agent.

(Rubber Component) In the present invention, the epichlorohydrin type rubber is a ring-opening polymer of a cyclic ether mainly containing epichlorohydrin. As the monomer, epichlorohydrin (hereinafter referred to as ECH), ethylene oxide (hereinafter referred to as EO), and allyl glycidyl ether (hereinafter referred to as AGE) are usually used.

From these monomers, ECH homopolymers such as polyepichlorohydrin (CO) and ECH-EO are obtained.
Copolymer epichlorohydrin-ethylene oxide copolymer (ECO), ECH-AGE copolymer epichlorohydrin-allyl glycidyl ether copolymer (GC
O), and also the ECH-EO-AGE terpolymer epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer (GECO). As the polymerization catalyst, a known organoaluminum-water catalyst, organoaluminum-phosphoric acid catalyst or polyphosphoric acid ester catalyst is used.

The CO and the ECO have excellent heat resistance and weather resistance as compared with a diene rubber having a double bond in the main chain. However, due to the fact that the main chain is an ether skeleton, ozone cracks are likely to occur due to heat deterioration and severe load deformation. Therefore, epichlorohydrin-allyl glycidyl ether copolymer (GCO) of the ECH-AGE copolymer and epichlorohydrin-ethylene of the ECH-EO-AGE terpolymer obtained by adding allyl glycidyl ether (AGE) to the copolymer component. The oxide-allyl glycidyl ether terpolymer (GECO) has improved thermal deterioration and ozone cracking property. However, if the amount of allyl glycidyl ether (AGE) is too large, curing type deterioration is likely to occur, and the amount of allyl glycidyl ether (AGE) is preferably 15 mol% or less of the copolymer.

(Mixing with other rubber component) In the present invention, the rubber component is the above-mentioned epichlorohydrin type rubber, a fluorine type thermoplastic elastomer, a fluorine type rubber, NBR, hydrogenated NBR or EPDM, and further polyisoprene, polybutadiene, styrene. A diene rubber such as a butadiene copolymer rubber can be mixed.

Here, two types of block type and kraft type can be used as the fluorine-based thermoplastic elastomer. The block type fluorine-based thermoplastic elastomer is
It is a thermoplastic elastomer in which a fluororubber component (soft segment) and a fluororesin component (hard segment) are block-bonded by utilizing telomerization by an iodine compound in radical polymerization of a fluoromonomer. The structure is such that the soft segment in the molecule is reinforced by the hard segment by chemical bonding. Here, the thermoplastic elastomer exhibits the properties of rubber at high temperature and the properties of resin at low temperature, and can be molded without crosslinking, and the molded product has rubber elasticity.

As the monomer constituting the soft segment, vinylidene fluoride, tetrafluoroethylene, hexafluoropropene, etc. are used. For example, vinylidene fluoride-hexafluoropropene-tetrafluoroethylene terpolymer segment etc. are formed. is doing. Further, examples of the monomer constituting the hard segment include vinylidene fluoride, ethylene, tetrafluoroethylene and the like. For example, polyvinylidene fluoride segment, tetrafluoroethylene-ethylene copolymer segment and the like are formed.

The fluorine-containing rubber is a highly fluorinated elastic copolymer such as vinylidene fluoride and hexafluoropropene, pentafluoropropene, trifluoroethylene, trifluorochloroethylene, tetrafluoro. One or two of ethylene, vinyl fluoride, perfluoro (methyl vinyl ether), perfluoro (propyl vinyl ether), etc.
One or more copolymers are exemplified.

When these rubber components are used as a mixture with the epichlorohydrin type rubber, they are used in an amount of less than 50% by weight, particularly less than 20% by weight, based on the whole rubber component.
Compatibility needs to be considered.

(Crosslinking Agent) In the rubber composition for a sealant of the present invention, a polythiol vulcanization accelerator is used as a crosslinking agent. Triazine thiol is particularly preferable, and specifically, 2,4,6-trimercapto-S-triazine, 2-dibutylamino-4,6-dimercapto-S-triazine, 2-anilino-4,6-dimercapto-S-. Examples include triazine. The polythiol vulcanization accelerator is blended in an amount of 0.1 to 3 parts by mass, more preferably 0.3 to 2.0 parts by mass, based on 100 parts by mass of the rubber component.

Triazinethiol forms crosslinks in epichlorohydrin rubber by the following reaction mechanism. Here, 2,4,6-trimercapto-S represented by the chemical formula (1) is used.
-Examples using triazine are shown.

[0018]

[Chemical 1]

Further, the following formula (2)
The same applies to dibutylamino-4,6-dimercapto-S-triazine (trade name: disnet DB) and 2-anilino-4,6-dimercapto-S-triazine (trade name: disnet AF) represented by the chemical formula (3). With a simple reaction mechanism,
It forms a bridge with epichlorohydrin.

[0020]

[Chemical 2]

[0021]

[Chemical 3]

By taking the above-mentioned cross-linking form, the thermal softening deterioration which is a defect of epichlorohydrin rubber is improved,
The compression set becomes small and secondary vulcanization becomes unnecessary.

(Acid acceptor) In order to accelerate the crosslinking reaction of the triazine thiol, it is preferable to add an acid acceptor. Examples of the acid acceptor include metal oxides, particularly oxides of Group II elements to Group IV elements, such as magnesium oxide, lead oxide, and zinc oxide. Acid acceptor is rubber component 1
0.1 to 8.0 parts by mass, preferably 1 to 5 parts by mass, is compounded with respect to 00 parts by mass.

(Vulcanization accelerator) The rubber composition of the present invention comprises:
Common vulcanization accelerators can be used. As a vulcanization accelerator, aldehydes such as hexamethylenetetramine
Ammonia-based vulcanization accelerators, guanidine-based vulcanization accelerators such as diphenyl / guanidine, 2-mercaptobenzothiazole, thiazole-based vulcanization accelerators such as dibenzothiazyl disulfide, cyclohexyl benzothiazyl sulfenamide, N- Sulfenamide vulcanization accelerators such as oxydiethylene benzothiazyl-2-sulfenamide, Nt-butyl-2-benzothiazole sulfenamide, tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetramethylthiuram・ Thiuram-based vulcanization accelerators such as monosulfide,
Dithioate vulcanization accelerators such as Zn-dimethyl dithiocarbamate, Zn-diethyl dithiocarbamate, Zn-di-n-butyl dithiocarbamate, ethylene
Thiourea-based vulcanization accelerators such as thiourea and diethyl thiourea are used. These vulcanization accelerators may be used either individually or in combination of two or more, but it is preferable that the vulcanization accelerator is blended in the range of 0.1 to 10 parts by mass with respect to 100 parts by mass of the rubber component.

(Filler) The rubber composition of the present invention preferably contains carbon black as a filler. Various grades of carbon black are used, such as SAF (N-110) and ISAF-LS (N-21.
9), ISAF-HM (N-220), ISAF-LM
(N-231), ISAF-HS (N-242), CF
(N-293), SCF (N-294), EPC (S-
300), MPC (S-301), HAF-LS-SC
(S-315), HAF-LS (N-326), HAF
(N-330), HAF-HS (N-347), SPF
(N-358), FF (N-440), XCF (N-4
72), FEF-LS (N-539), FEF (N-5
50), FEF-HS (N-568), HMF (N-6).
01), GPF (N-660), APF (N-68)
3), SRF-LM (N-761) or SRF-H
M (N-770) or the like can be used. Of these carbon blacks, the average particle size is 100 μm or less,
Particularly, those having a range of 20 to 50 μm are preferably used.
The blending amount of carbon black is 100 parts by mass or less, more preferably 10 to 7 parts by mass based on 100 parts by mass of the rubber component.
The range is 0 parts by mass.

In the present invention, silica can be used as a reinforcing agent. As the silica, both wet type white carbon and dry type white carbon can be used. For example, the trade name of silica is wet-type white carbon such as curverex, nipseal, tokuseal, vitaseal, and himeziel. In addition, dry type white carbon has Aerosil as a product name. Here, white carbon having an average particle size of 10 to 80 μm is preferably used, and the blending amount thereof is 30 with respect to 100 parts by mass.
It is preferable that the amount is less than 100 parts by mass.

In the present invention, non-reinforcing fillers such as calcium silicate, diatomaceous earth, alumina, bentonite, graphite, mica, calcium carbonate and zinc oxide can be used together with the above-mentioned reinforcing fillers. The filler is added in an amount of less than 50 parts by mass, preferably 10 to 30 parts by mass, based on 100 parts by mass of the rubber component.

(Plasticizer) In the present invention, a plasticizer may be added for the purpose of improving the fluidity, cold resistance and oil resistance of the epichlorohydrin rubber. D here as a plasticizer
BP, DOP, DOA, TP-95, TCP, W320
Etc. can be used. The plasticizer is blended in less than 30 parts by mass with respect to 100 parts by mass of the rubber component.

(Anti-aging agent) An anti-aging agent may be blended in order to improve the heat resistance and ozone resistance of the epichlorohydrin type rubber. As an anti-aging agent, for example, 2
-Mercaptobenzimidazole (MBI), 2,2
4-trimethyl-1,2-dihydroquinoline polymer (T
MDQ), nickel dibutyldithiocarbamate (Ni
DBC) is effective. For example, heat softening deterioration E
CO is preferably used in combination with NiDBC and MBI, and a small amount of TMDQ is used. When a large amount of MBI is added to hardening-deteriorated GCO and GECO, elongation and change in hardness after heat aging are increased, which is not preferable. The anti-aging agent is added in an amount of 3.0 parts by mass or less, more preferably 2 parts by mass or less, based on 100 parts by mass of the rubber component.

(Molding Method) The kneading method of the rubber composition of the present invention is the same as that for other rubbers, and a Banbury mixer, intermix and rolls are used. When a rapid-acting vulcanization accelerator is used, the rubber composition is likely to scorch, and it is preferable to avoid adding it in Banbury. The kneading temperature in the roll is preferably 40 to 80 ° C in consideration of adhesion. The die temperature for extrusion is usually 80 to 130 ° C, and the calendar temperature for rolling is usually 50 to 80 ° C.

The vulcanization temperature can usually be 120 to 180 ° C. In the case of epichlorohydrin rubber, the vulcanization rate is slow, and therefore the vulcanization time is shortened. Therefore, after vulcanization in order to further reduce the compression set, the temperature is about 180 to 260 ° C.
Oven vulcanization for about 1 to 24 hours, that is, secondary vulcanization is generally performed. However, in the present invention, since the polythiol-based cross-linking agent is used, the cross-linking speed is high and the secondary vulcanization is not required.

To prepare the rubber composition for a sealant, for example, a method of kneading each compounding component excluding the cross-linking agent with a kneader, then kneading with a heating roll and then adding the cross-linking agent is used. A method in which a compounding agent is added and mixed with a feeder from the middle of the shaft. Each compounding component excluding the cross-linking agent is introduced from the twin-screw extruder to the single-screw extruder, and then the cross-linking agent is added, and then a sheet shape is formed with a T-die. It is possible to adopt the method of processing into.

(Use of Rubber Composition) Since the vulcanized rubber composition of the present invention has excellent gas permeation resistance to carbon dioxide and low compression set, it is a sealing material that comes into contact with carbon dioxide, such as an O-ring and a gasket. In addition to being used as a packing, it can be effectively used as a molding die for a hose or a tube and a diaphragm.

[0034]

[Example] The composition for sealing material shown in Table 1 was kneaded at 130 ° C with a 10-inch open roll, and the kneaded product was heated to 170 ° C.
After press vulcanization for 20 minutes at room temperature, the sample obtained is size 1
The gas permeability and compression set (%) were evaluated by adjusting to 40 mm × 140 mm × 2 mm. The results are also shown in Table 1.

[0035]

[Table 1]

(Note 1) Gechron manufactured by Nippon Zeon Co., Ltd.
CHR1000 (Epichlorohydrin homopolymer, Mooney viscosity 70) (Note 2) ZP0020 (hydrogenated NB manufactured by Zeon Corporation)
R) (Note 3) NIPOLL1041 (NB manufactured by Zeon Corporation)
R) (Note 4) Carbon black ISAF (average particle size: 2
0-25 μm) (Note 5) Zithnet F (2,4,6-
(Trimercapto-S-triazine) (Note 6) Ouchi Shinko Chemical Co., Ltd. (dibenzyldithiocarbamine zinc salt) (Note 7) Ouchi Shinko Chemical Co., Ltd. (cyclohexylbenzothiazylsulfenamide) (Note 8) Ouchi Shinsei Kagaku Co. (diphenyl guanidine) The samples obtained in Table 1 were evaluated by the following methods.

(1) Gas permeability (carbon dioxide gas) Rubber cloth / plastic cloth test method-Part 10: Measurement was carried out in accordance with the gas permeability measuring method (K6404-10: 1999). The measurement principle is that a test piece is placed between two bahts of an airtight measurement cell and one surface of the test piece is exposed to carbon dioxide gas at a constant pressure, while carrier gas is introduced into the cell on the other surface. Flow at a constant speed to contact the test piece. The concentration of carbon dioxide gas in the carrier gas is measured by an analyzer provided at the outlet of the cell, and the transmittance of carbon dioxide gas in the test piece is measured from the result.

(2) Compression set (%) 120 in accordance with JIS K6262 (1997) "Test method for permanent set of vulcanized rubber and thermoplastic rubber".
Cylindrical shape of 25% compression at 70 ° C for 70 hours (height 12.5m
m, diameter 29.0 mm).

(Evaluation Results) Comparative Example 1 uses hydrogenated acrylonitrile-butadiene rubber as a rubber component and a combined system of ZTC and CZ as a vulcanization accelerator. The gas permeability of carbon dioxide is slightly improved, but the compression set is rather poor. Comparative Example 2 uses acrylonitrile-butadiene rubber as a rubber component and Z as a vulcanization accelerator.
It can be seen that the combined system of TC and CZ is adopted, and the gas permeability of carbon dioxide is considerably poor. On the other hand, in Example 1, epichlorohydrin was used as a rubber component and DISNET F (2,4,6-trimercapto-S-triazine) was used as a cross-linking agent, and the gas permeation resistance to carbon dioxide and the compression set were measured. It turns out that all are excellent.

The embodiments and examples disclosed this time must be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description but by the claims, and is intended to include meanings equivalent to the claims and all modifications within the scope.

[0041]

As described above, according to the present invention, a rubber composition mainly composed of polyepichlorohydrin type rubber is crosslinked with a polythiol type crosslinking agent, so that the compression set and carbon dioxide gas permeability are low, and O-rings, gaskets and packings are used. It is possible to obtain a rubber composition for a sealing material suitable for the above.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C08K 5/37 C08K 5/37 C08L 71/03 C08L 71/03 F16J 15/10 F16J 15/10 CY F Term (reference) 3J040 BA01 EA16 FA06 4H017 AA03 AA24 AA29 AA31 AB08 AB14 AB17 AC11 AD03 AE02 AE05 4J002 CH041 DA038 DE077 DE107 DE157 EV016 FD018 FD030 FD146 FD150 FD157 GJ02

Claims (5)

[Claims] 1. A rubber composition comprising an epichlorohydrin-based rubber as a main component, wherein a polythiol-based crosslinking agent is used,
A rubber composition for a sealing material, which is crosslinked. 2. The epichlorohydrin-based rubber is a polyepichlorohydrin (CO), an epichlorohydrin-ethylene oxide copolymer (ECO), an epichlorohydrin-allyl glycidyl ether copolymer (GCO) or an epichlorohydrin-ethylene oxide-allyl glycidyl ether ternary copolymer. The rubber composition for a sealing material according to claim 1, which is a polymer (GECO) or a mixture thereof. 3. The rubber composition for a sealing material according to claim 1, wherein the polythiol-based cross-linking agent is triazine thiol. 4. The rubber composition for a sealing material according to claim 1, wherein the metal oxide is mixed in an amount of 0.5 to 10 parts by mass with respect to 100 parts by mass of the rubber component. 5. The rubber composition for a sealing material according to claim 1, wherein 100 parts by mass or less of carbon black is mixed with 100 parts by mass of the rubber component.