JPH03250037A - Rubber composition - Google Patents

Abstract

PURPOSE:To obtain a rubber composition improved in resistance to a fluorocarbon refrigerant by mixing a blend rubber containing a hydrogenated nitrile rubber and a chlorinated PE in a specified ratio with an organic peroxide. CONSTITUTION:An acrylonitrile/butadiene copolymer rubber is hydrogenated to obtain a hydrogenated nitrile rubber (a) having a content of the C-C double bonds in the main chain of 10% or below. 20-60wt.% component (a) is mixed with 80-20wt.% chlorinated PE (b) of a chlorine content of 30-40%, obtained by chlorinating a high density PE, to obtain a blend rubber. 100 pts.wt. said rubber is mixed with 1-10 pts.wt. organic peroxide (e.g. dicumyl peroxide) and optionally a polyfunctional compound, a reinforcing agent, a filler, a processing aid, an acid acceptor, an antioxidant, a plasticizer, etc., and the resulting mixture is kneaded, vulcanized at 150-200 deg.C for 3-60min, and optionally subjected to secondary vulcanization at 120-200 deg.C for 1-24hr.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a rubber composition. More specifically, the present invention relates to a rubber composition with excellent resistance to fluorocarbon refrigerants.

[Conventional technology]

Currently, nitrile rubber or hydrogenated nitrile rubber is used in rubber parts (O-rings, gaskets, etc.) of air conditioners that use Freon R12 (CCU, F,) as a refrigerant. 2 is about to be replaced by Freon R134a (CHzFCFz). However, nitrile rubber and hydrogenated nitrile rubber have the disadvantage of foaming upon contact with Freon R134a.

On the other hand, ethylene-propylene copolymer rubber has excellent resistance to Freon R134a, but it is said that ethylene-propylene copolymer rubber can ignite upon contact with Freon Old 2. It has its drawbacks.

As described above, there is currently an attempt to replace Freon R12 with Freon R134a, but there are various problems associated with this, and all Freon R12 is replaced by Freon R134a.
Currently, it will take a considerable amount of time before it is replaced by a. As a measure during this time, Freon R12 and Freon R
Therefore, there is a demand for a rubber composition that can be used with both Freon R12 and Freon R134a refrigerants, but currently no rubber composition has been provided that can meet these demands. .

In addition, the present applicant has previously proposed a rubber composition with excellent resistance to fluorocarbon gas made of chlorinated polyethylene and liquid polybutadiene (Japanese Unexamined Patent Publication No. 64-22948). −
CH, CHF3 azeotrope) or R502 (CHCn
F, -cc n F2CF, azeotrope).

[Problem to be solved by the invention]

An object of the present invention is to provide a rubber composition that exhibits excellent resistance to both Freon R12 and Freon R134a refrigerants.

[Means to solve the problem]

The object of the present invention is to provide hydrogenated nitrile rubber.

This is achieved by a rubber composition containing chlorinated polyethylene and an organic peroxide.

The hydrogenated nitrile rubber is hydrogenated copolymer rubber of acrylonitrile and butadiene.

Generally, those having a carbon-carbon double bond content of 10% or less in the molecular main chain are used, and commercially available products such as Nippon Zeon's Zetpol can be used as they are.

Furthermore, as the chlorinated polyethylene, chlorinated high-density polyethylene (chlorine content of about 30 to 40%, preferably about 30 to 35%) is generally used, and this is a commercially available product such as Showa Denko's Elaslene. can be used as is.

Both of these are used in a proportion of about 20 to 60% by weight, preferably about 30 to 50% by weight of hydrogenated nitrile rubber, and about 80 to 20% by weight, preferably about 70 to 50% by weight of chlorinated polyethylene. . If the blending ratio of hydrogenated nitrile rubber is higher than this, the CFC resistance will be R13.
4a property deteriorates and foaming occurs. On the other hand, below this range, the fluorocarbon R12 resistance deteriorates.

These blended rubbers are crosslinked with organic peroxides which are generally used in an amount of about 1 to 10 parts by weight, preferably about 2 to 8 parts by weight per 100 parts of blended rubber. Examples of organic peroxides include di-tert-butyl peroxide, dicumyl peroxide, tert-butylcumyl peroxide, 1,1-di(tert-butylperoxy)-3,3,5
-trimethylcyclohexane, 2,5-dimethyl-2,
5-di(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3,1,3-di(tert-butylperoxyisopropyl)benzene, 2 , 5-dimethyl-2,5-di(benzoylperoxy)hexane, tert-butylperoxybenzoate, tert-butylperoxyisopropyl carbonate, n-butyl-4,4-di(tert-butylperoxy)
Valerate etc. are used.

In addition to one or more essential components, the rubber composition contains polyfunctional compounds such as triallyl(iso)cyanurate, trimethylolpropane trimethacrylate, and triallyl trimellitate, carbon black, and fine particles as compounding agents for each rubber. Reinforcing agents such as silica, fillers such as talc, clay, graphite, and calcium silicate, processing aids such as stearic acid, palmitic acid, and paraffin wax, acid acceptors such as magnesium oxide, hydrotalcite, and epoxy resin, and aging Compounding agents commonly used in the rubber industry, such as inhibitors and plasticizers, may be added as appropriate.

Preparation of the rubber composition is performed using an intermix or kneader.

This is done by kneading using a mixer such as a Banbury mixer or an open roll, and vulcanization is done using an injection molding machine, compression molding machine, vulcanizing press, etc.
Generally, this is done by heating at about 150 to 200°C for about 3 to 60 minutes, and if necessary, heating at about 120 to 200°C.
Secondary vulcanization is carried out by heating at 0.degree. C. for about 1 to 24 hours.

〔Effect of the invention〕

When hydrogenated nitrile rubber and chlorinated polyethylene are blended, there is no problem in the compatibility between the two, and mixing is possible without causing microscopic interfacial peeling.

When such a blended rubber is crosslinked with an organic peroxide, properties that cannot be obtained with each rubber alone can be obtained.

In other words, a rubber composition is provided that exhibits excellent resistance to both Freon R12 and Freon R134a refrigerants.

Therefore, the rubber composition according to the present invention can be used in machines 1, such as air conditioners, that use Freon R12 or Freon R134a.
It can be suitably used as a molding material for rubber parts such as O-rings and gaskets used in refrigerators and the like.

〔Example〕

Next, the present invention will be explained with reference to examples.

Examples 1-2, Comparative Examples 1-3 Hydrogenated nitrile rubber (Z-pol 2010) [hydrogenated NBRI, chlorinated polyethylene (elasulene 302NA)
) [chlorinated PEI and MT carbon black [MT-
Magnesium oxide 5 parts by weight Hydrotalcite 10 Stearic acid
1 Hindered phenolic anti-aging agent l Hydroquinone anti-aging agent l Paraffin wax l Epoxy resin
2 polybutadiene
The formulation containing 2 dicumyl peroxide 5 triallylisocyanurate 3 was mixed using a 3Q kneader and oven rolls.

This rubber composition was heated and press-molded at 170°C for 20 minutes, and then oven-cured at 160°C for 3 hours.
A vulcanized sheet measuring 50 x 150 x 2 mm was molded.

For each obtained vulcanized sheet, JIS K-6301
In addition to measuring the normal physical properties according to the following immersion liquids (
A immersion test (25°C, 24 hours) was conducted in a mixture of chlorofluorocarbon refrigerants or refrigeration oil, and changes in hardness and volume were measured.After the immersion test, the rubber sheet was placed in an oven at 150°C. After heating for 1 hour, the external appearance was observed to see if foaming occurred.

Immersion liquid I: Freon R 12200g ■: Freon R 12100g + paraffin oil 100g ■:
200 g of Freon R134a (2): 100 g of Freon R134a + 100 g of polyglycol oil The results obtained are shown in the following table, along with the mixing ratios of hydrogenated NBR, chlorinated PE, and CD.

(Space below) Ratio-1 Ratio-2 Compound ≦ [Blend rubber, %] Hydrogenated NOR Chlorinated PE MT-CB [Normal physical properties] Hardness (JIS-A) Tensile strength (kgf/aJ) Elongation ( %) [After immersion in immersion liquid I] Hardness change (points) Volume change rate (phantom foaming state [after immersion in immersion liquid I] Change in hardness (points) Volume change rate (%) Foaming state [after immersion in immersion liquid ■] Hardness change (points) Volume change rate (%) Foaming state [after immersion in immersion liquid] Hardness change (points) Volume change rate (%) Foaming state too 67 50 33 00 33
50 67 10075 70 65
60 5576 75 76 76 752
13 210 212 207 221230
220 230 210 200-5 −
4 -3 -3 -3÷7.0 ÷6.3
+6.1 +6.5 +7.1 None None None
None Somewhat -5-4-3-4-4 +6.4 +5.7 +5.7 +6.2 +
5.6 None None None None None -7-4-2-2-1 +8.5 ÷5.6 +2.7 +2.0 +
1.5 Somewhat None None None -8-5-4-3-2 +lO,5+8.1 +3.2 +2.5 +
2.1 Yes Yes No No No

Claims (1)

[Claims] 1. About 20-60% by weight hydrogenated nitrile rubber and about 8
A rubber composition obtained by adding an organic peroxide to a blend rubber of 0 to 40% by weight of chlorinated polyethylene.