JP3791179B2 - Acrylic rubber composition for seal molding - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to an acrylic rubber composition for seal molding. More specifically, the present invention relates to an acrylic rubber composition for seal molding that is particularly excellent in wear resistance and durability.
[0002]
[Prior art]
When acrylic rubber vulcanized molded products are used as sealing materials, halogen-containing ethyl acrylate polymers are used to improve the heat resistance and extend the life of the seals. Is inferior in low temperature characteristics. When halogen-containing ethyl acrylate-n-butyl acrylate-2-methoxyethyl acrylate terpolymer or halogen-containing n-butyl acrylate-2-methoxyethyl acrylate copolymer is used instead of halogen-containing ethyl acrylate, low temperature characteristics Although improved, the heat resistance deteriorates and the seal life is shortened. Furthermore, in the case of a halogen-containing n-butyl acrylate polymer, a decrease in oil resistance is observed.
[0003]
When a halogen-containing ethyl acrylate-n-butyl acrylate copolymer is used, the low-temperature characteristics are good, but the heat resistance is slightly deteriorated. There are still problems that must be improved in terms of wear resistance and durability.
[0004]
[Problems to be solved by the invention]
An object of the present invention is an acrylic rubber composition for seal molding mainly composed of a halogen-containing ethyl acrylate-n-butyl acrylate copolymer, which not only has excellent heat resistance and low temperature characteristics, but also wear resistance. Another object is to provide a material with significantly improved durability.
[0005]
[Means for Solving the Problems]
The object of the present invention is to have a copolymer composition comprising 60 to 99.8% by weight of ethyl acrylate and n-butyl acrylate, 0.1 to 10% by weight of a crosslinking site halogen-containing monomer and 0 to 30% by weight of other vinyl compounds. Ethyl acrylate and n-butyl acrylate are halogen-containing ethyl acrylate-n-butyl acrylate copolymer and alkali copolymerized at a ratio of 60 to 80 % by weight of ethyl acrylate and 40 to 20 % by weight of n-butyl acrylate, respectively. This is achieved by an acrylic rubber composition for seal molding containing a metal or alkaline earth metal oxide or hydroxide, carbon fiber and a fatty acid metal soap / sulfur vulcanizing agent.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
As the acrylic rubber for seal molding, considering heat resistance, low temperature characteristics, oil resistance, etc., ethyl acrylate is about 60 to 80 % by weight, preferably about 70 to 80% by weight and n-butyl acrylate is about 40 to 20 % by weight. %, Preferably having a copolymer composition of about 30 to 20% by weight. Since the copolymerization reaction for obtaining such a copolymer is carried out at a favorable reaction rate of about 90% or more, it is considered that the charging ratio of each acrylate monomer is almost the copolymer composition thereof.
[0007]
The ethyl acrylate-n-butyl acrylate copolymer having such a copolymer composition has a halogen group in the copolymer as a crosslinkable group. As such a halogen-containing ethyl acrylate-n-butyl acrylate copolymer, ethyl acrylate and n-butyl acrylate having the above-mentioned copolymerization ratio are the main components (about 60 to 99.8% by weight), and (1) 2-chloroethyl Vinyl ether, 2-chloroethyl acrylate, vinyl benzyl chloride, (2) vinyl chloroacetate, allyl chloroacetate, (3) glycidyl compounds such as glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether and monochloroacetic acid An addition reaction product, or (4) an alkenyl ester of an α- or β-halogen-substituted aliphatic monocarboxylic acid, a haloalkyl ester of (meth) acrylic acid, a haloalkylalkenyl ester, a haloalkylalkenyl ketone or a haloacetoxyalkyl ester. A copolymer obtained by copolymerizing about 0.1 to 10% by weight, preferably about 1 to 5% by weight of a crosslinking site halogen-containing monomer such as tellurium or a haloacetyl group-containing unsaturated compound is used. In addition, other general vinyl compounds can be copolymerized within a range of about 30% by weight or less.
[0008]
Such halogen-containing ethyl acrylate-n-butyl acrylate copolymer (halogen-containing acrylic rubber) includes alkali metal or alkaline earth metal hydroxide or oxide, carbon fiber and fatty acid metal soap / sulfur vulcanizing agent. It is added as an essential component.
[0009]
Examples of the alkali metal or alkaline earth metal hydroxide or oxide include calcium hydroxide, magnesium hydroxide, calcium oxide, magnesium oxide, zinc oxide, and the like, and about 0.5 to 10 weights per 100 parts by weight of the halogen-containing acrylic rubber. Parts, preferably about 1 to 4 parts by weight, and the combination improves the heat resistance of the halogen-containing acrylic rubber.
[0010]
Carbon fibers having an average fiber diameter of about 5 to 20 μm, preferably about 10 to 15 μm and an average fiber length of about 15 to 100 μm, preferably about 20 to 40 μm, are about 1 per 100 parts by weight of the halogen-containing acrylic rubber. -30 parts by weight, preferably about 5-20 parts by weight. The blending of carbon fibers not only improves the heat resistance but also greatly contributes to the improvement of wear resistance and durability.
[0011]
As the vulcanization system, fatty acid metal soap / sulfur system is used. As the fatty acid metal soap, generally an alkali metal salt of a fatty acid, for example, a saturated fatty acid having 1 to 18 carbon atoms, an unsaturated fatty acid having 3 to 18 carbon atoms, a lithium salt such as an aliphatic dicarboxylic acid and an aromatic carboxylic acid, a potassium salt, Sodium salt or the like is used. More specifically, potassium stearate, sodium stearate, potassium oleate, sodium oleate, sodium 2-ethylhexanoate, sodium potassium tartrate, sodium propionate, sodium acetate and the like can be mentioned. Particularly preferred is a potassium salt or sodium salt of a fatty acid having 8 to 18 carbon atoms, and the potassium salt generally shows a tendency to increase the vulcanization rate.
[0012]
In the halogen-containing acrylic rubber composition containing the above components as essential components, other necessary compounding agents are appropriately blended. Speaking of fillers and reinforcing agents, for example, when used as a vulcanization molding material for various sealing materials, carbon black is mainly blended for uses such as O-rings and packings, and mainly for applications such as oil seals. Soil, white carbon, etc. are blended and used. In addition, graphite or the like is added as a lubricating filler. In addition, vulcanization aids, lubricants, and the like are blended and used as necessary.
[0013]
The composition is prepared using a sealed kneader such as a kneader or a Banbury mixer or an open kneader such as an open roll, and the vulcanization thereof is generally performed at about 150 to 250 ° C. for about 1 to 30 minutes. The press vulcanization or injection molding vulcanization is performed, and if necessary, oven vulcanization or steam vulcanization is performed as secondary vulcanization at about 150 to 200 ° C. for about 1 to 22 hours.
[0014]
【The invention's effect】
The acrylic rubber composition for seal molding according to the present invention is not only excellent in heat resistance and low-temperature characteristics, but can provide a vulcanized molded product with significantly improved wear resistance and durability.
[0015]
【Example】
Next, the present invention will be described with reference to examples.
[0016]
Comparative Example 1
To 100 parts by weight of a chlorine-containing ethyl acrylate-n-butyl acrylate (weight ratio 84:16) copolymer,
15 parts by weight of dry silica
FEF carbon black 15 〃
Diatomaceous earth 40 〃
Stearic acid 1 〃
Graphite 5 〃
Anti-aging agent CD 2 〃
Calcium hydroxide 2 〃
Carbon fiber (average fiber diameter 13μm, average fiber length 30μm) 5 〃
Sulfur 0.3 〃
Sodium stearate 3.5 〃
After kneading with an open roll, press vulcanization at 180 ° C for 10 minutes and oven vulcanization (secondary vulcanization) for 15 hours at 150 ° C for 15 hours, and then add a sheet-like test piece and an oil seal. Sulfur molded.
[0017]
For sheet-shaped test pieces, JIS K has normal physical properties, heat resistance (175 ° C, change in hardness after 500 hours) and oil resistance (volume change rate after being immersed in JIS No. 3 oil at 150 ° C for 70 hours). -6301 and low temperature properties measured according to ASTM D-1329 TR test. Further, the oil seal was subjected to a wear test (room temperature, 3000 rpm, 30 minutes, dry condition) and a durability test (product diameter 80 mm, 150 ° C., 8000 rpm, engine oil condition).
[0018]
Example 1
Using a chlorine-containing ethyl acrylate-n-butyl acrylate (weight ratio 74:26) copolymer, the same kneading, vulcanization and testing as in Comparative Example 1 were performed.
[0019]
Example 2
In Example 1 , the amount of carbon fiber was changed to 10 parts by weight.
[0020]
Example 3
In Example 1 , the amount of carbon fiber was changed to 20 parts by weight.
[0021]
Example 4
Using a chlorine-containing ethyl acrylate-n-butyl acrylate (weight ratio 65:35) copolymer, the same kneading, vulcanization and testing as in Example 1 were performed.
[0022]
The measurement results in the above Comparative Example 1 and each Example are shown in the following Table 1.
Table 1
Measurement item ratio- 1 actual- 1 actual- 2 actual- 3 actual- 4
[Normal physical properties]
Hardness (JIS A) 82 81 81 82 81
Tensile strength (MPa) 9.0 9.1 8.8 8.6 8.2
Elongation (%) 110 110 100 90 100
[Heat-resistant]
Change in hardness (points) +5 +6 +6 +6 +6
[Oil resistance]
Volume change rate (%) +19 +22 +22 +22 +27
[Low temperature characteristics]
TR-10 (℃) -15 -19 -19 -19 -21
[Abrasion resistance]
Wear width (mm) 0.85 0.85 0.80 0.80 0.85
[durability]
Leak time (hrs)-800 850 850 800
[0023]
Comparative Example 2
In Comparative Example 1 , the amount of graphite was changed to 10 parts by weight, and calcium hydroxide and carbon fiber were not used.
[0024]
Comparative Example 3
In Example 1 , the amount of graphite was changed to 10 parts by weight, and calcium hydroxide and carbon fiber were not used.
[0025]
Comparative Example 4
In Example 4 , the amount of graphite was changed to 10 parts by weight, and calcium hydroxide and carbon fiber were not used.
[0026]
Comparative Example 5
The chlorine-containing ethyl acrylate polymer was kneaded, vulcanized and measured in the same manner as in Example 1.
[0027]
Comparative Example 6
In Comparative Example 5 , calcium hydroxide was not used.
[0028]
Comparative Example 7
In Comparative Example 5 , the amount of graphite was changed to 10 parts by weight, and no carbon fiber was used.
[0029]
Comparative Example 8
In Comparative Example 5 , the amount of graphite was changed to 10 parts by weight, and calcium hydroxide and carbon fiber were not used.
[0030]
Comparative Example 9
About chlorine-containing ethyl acrylate-n-butyl acrylate-2-methoxyethyl acrylate (weight ratio 42:27:30) terpolymer, the amount of graphite was changed to 10 parts by weight in the formulation of Comparative Example 1 , and calcium hydroxide Kneading was performed without using carbon fiber, and vulcanization and measurement were performed.
[0031]
The measurement results in Comparative Examples 2 to 9 are shown in Table 2 below.
Table 2
Comparative example
Measurement item 2 3 4 5 6 7 8 9
[Normal physical properties]
Hardness (JIS A) 82 81 81 83 81 81 83 81
Tensile strength (MPa) 9.3 9.1 8.8 9.3 9.2 8.7 9.1 8.2
Elongation (%) 140 140 150 110 110 150 150 180
[Heat-resistant]
Hardness change (points) +9 +9 +9 +5 +10 +6 +10 +14
[Oil resistance]
Volume change rate (%) +19 +22 +27 +12 +12 +12 +12 +18
[Low temperature characteristics]
TR-10 (℃) -15 -19 -21 -12 -12 -12 -12 -25
[Abrasion resistance]
Wear width (mm)-1.0-1.0-0.8 1.0 1.2
[durability]
Leak time (hrs)-330-500 400 400 300-

Claims (1)

It has a copolymer composition consisting of ethyl acrylate and n-butyl acrylate 60 to 99.8% by weight, crosslinking site halogen-containing monomer 0.1 to 10% by weight, and other vinyl compounds 0 to 30% by weight, and ethyl acrylate and n-butyl Acrylate is a halogen-containing ethyl acrylate-n-butyl acrylate copolymer, alkali metal or alkaline earth metal copolymerized in a proportion of 60 to 80 % by weight of ethyl acrylate and 40 to 20 % by weight of n-butyl allylate, respectively. An acrylic rubber composition for molding a seal, comprising an oxide or hydroxide of the above, carbon fiber and a fatty acid metal soap / sulfur vulcanizing agent.