Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2002-06-03
2004-08-31
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S237000, C524S262000, C524S506000, C524S565000, C524S571000, C524S261000, C526S336000
Reexamination Certificate
active
06784255
ABSTRACT:
TECHNICAL FIELD
This invention relates to a rubber composition for extrusion and molding and applications thereof.
BACKGROUND ARTS
An ethylene/&agr;-olefin
on-conjugated polyene copolymer rubber such as ethylene/propylene/diene copolymer rubber (EPDM) is widely used for automotive parts, household electric appliance parts, and the like thanks to superior weather ability, heat resistance and ozone resistance.
Among these, materials for sealant or fillers (packing) for automobiles and household electric appliances are the products manufactured by a continuous extrusion molding process.
Requirements for such rubber extrusion composition are continuous feed ability to extruder and no occurrence of crack or tear in a ribbon-like compound preformed prior to an extrusion during its storage.
During extrusion process, cross-sectional area of extrudate should not change, that is, die swell ratio should not vary. Variation in die swell ratio leads to change in cross-sectional shape of glass run or window frame products and may results in lowering of sealing performance and inferior products. Furthermore, in weather strip sponge products, the materials varying in the die swell ratio cause a big problem of uneven foaming since the variation means uneven viscoelastic state in the material.
In addition to these, in extrudate products of EPDM containing carbon black, trouble of foreign matter coming from unknown cause occurs very often. Analysis of a portion of the foreign matter for its cause survey often results in that the portion is composed of the same components to rubber substrate. Mysteriously this trouble naturally disappears, and occurs again sometimes.
On the other hand, there are many products manufactured by molding process in the rubber molding technology. Rubber vibration isolator obtained by injection is one of the products using a rubber composition for molding. Materials for injection are fed as a ribbon-like compound sheeted out using a roll. Tear of the ribbon lowers stability of material feeding and makes continuous production impossible. Such a material may show an abrupt viscosity increase in a feeder of the injection machine and leads to poor flow in a mold after injection. The products molded in such state often had a trouble such as an occurrence of crack during durability test.
Materials used for molding weather strip corner are required to have stable fluidity of the material. Changes of fluidity in each molding cause a serious problem due to poor adhesion at interface with straight parts of weather strip sponge or inferior appearance at joint area.
Fixing roll for copying machine, one of OA rolls, is a foam product having semi conductivity. It often had variation troubles in foaming and electric resistance due to unknown cause.
O-ring product also had troubles of uneven product shrinkage in each molding by unknown cause. Another problem was lowering in mechanical strength of product even with good product appearance.
Analysis of substrate for cause survey often resulted in no specific difference in the substrate composition. These phenomena are troublesome and mysterious because they naturally disappear after a while and the same troubles occur again sometimes.
At present, these trouble is considered to be caused by formation of a physical network originated in carbon black/rubber interface produced in the compound during mixing. That is, this network causes the troubles described above in molding a product.
To solve such problems, adding of polysulfide compounds including sulfur or sulfur compounds as radical scavenger has been disclosed in JP-A-H7-138379.
The addition of such sulfur or sulfur compounds at loading level of about 1.0×10
−2
mole per 100 weight parts of polymer in a mixer, however, causes start of cross linking by the presence of zinc oxide (ZnO) contained in the compound and leads to a problem of gelation (chemical burning). Loading level of about 1.0×10
−3
mole, {fraction (1/10)} of the above loading level, is safe in view of the burning in a mixer, but has little effect to solve the problems mentioned above.
DISCLOSURE OF THE INVENTION
First object of the invention is to solve such problems described above accompanied with conventional technology, and provide a rubber composition for extrusion to give a ribbon-like compound prepared prior to extrusion having no crack nor tear, stable cross sectional shape of extrudate, and foamed products with little variation in foaming, and also products made of the said rubber composition such as weather strip sponge, high extension seal, glass run channel, window frame and water hose for automobile.
Second object of the invention is to provide a rubber composition for molding to give a compound prepared for injection having no tear phenomenon, superior fluidity in a mold, in addition stable foaming and little variation in foaming in cast sponge, and also products made of the said composition with good surface texture and superior mechanical strength such as rubber vibration isolator, cast sponge, grommet, O-ring, packing, boots, window frame, break piston cup and OA roll products.
The invention includes the following disclosures.
(1) A rubber composition for extrusion comprising 100 weight parts of ethylene/&agr;-olefin
on-conjugated polyene copolymer rubber (A) composed of ethylene, &agr;-olefin having carbon atoms of 3-20 and non-conjugated polyene, and at least 30-300 weight parts of carbon black (B) and 1.0×10
−5
-5.0×10
−3
mol of alkoxysilane compound (C) shown by the following formula (I):
wherein, R is an alkyl group having carbon atoms of 1-4 or an alkoxy group having carbon atoms of 1-4, R
1
is an alkyl group having carbon atoms of 1-4 or phenyl group, n is 0, 1 or 2, R
2
is a bivalence of linear or branched hydrocarbon group having carbon atoms of 1-6, R
3
is an arylene group having carbon atoms of 6-12, m and p are 0 or 1 respectively, and m and p are not 0 at a same time, q is 1 or 2, D is —SCN or —SH when q is 1, and —Sx— when q is 2 (wherein x is an integer of 2-8).
(2) The rubber composition for extrusion according to item 1, wherein the ethylene/&agr;-olefin
on-conjugated polyene copolymer rubber (A) (i) comprises a unit (a) derived from ethylene and a unit (b) derived from &agr;-olefin having carbon atoms of 3-20 in a [(a)/(b)] molar ratio of 50/50-90/10, (ii) has an iodine value of 1-40, and (iii) has an intrinsic viscosity [&eegr;] measured in decalin at 135° C. of 2.0-4.5 dl/g.
(3) The rubber composition for extrusion according to item 1, wherein an amount of the carbon black (B) is 50-200 weight parts to 100 weight parts of the ethylene/&agr;-olefin
on-conjugated polyene copolymer rubber (A).
(4) The rubber composition for extrusion according to item 1, wherein an amount of the carbon black (B) is 61-200 weight parts to 100 weight parts of the ethylene/&agr;-olefin
on-conjugated polyene copolymer rubber (A).
(5) The rubber composition for extrusion according to item 1, wherein an amount of the carbon black (B) is 70-200 weight parts to 100 weight parts of the ethylene/&agr;-olefin
on-conjugated polyene copolymer rubber (A).
(6) The rubber composition for extrusion according to any one of items 1-5, wherein its apparent activation energy is 20-300 kJ/mol, and a change rate of the apparent activation energy is not higher than 40% even after processing in any rubber processing process.
(7) A rubber composition for extrusion, wherein it does not show any ribbon break nor ribbon crack, and has a change rate in die swell ratio not higher than 5% due to a rise of viscosity in an extruder.
(8) A weather strip sponge product, highly expanded seal product, glass run channel product, window frame product or water hose product for automobile characterized by comprising the rubber composition according to any one of items 1-7.
(9) A process for manufacturing a vulcanized rubber molding product comprising forming the rubber composition according to any one of items 1-7 to an intended shape using an extruder and vulc
Hosoya Mikio
Ishii Yuji
Kawasaki Masaaki
Nakahama Hidenari
Hu Henry S.
Mitsui Chemicals Inc.
Wu David W.
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