JPH04293946A - Ethylene-propylene copolymer rubber composition vulcanizeble in hot air - Google Patents

Abstract

PURPOSE:To prepare the title compsn. vulcanizable continuously in hot air and giving a vulcanizate which is free of surface tack and inside abnormal foaming and is excellent in heat resistance and compression set properties. CONSTITUTION:The title compsn. is prepd. by compounding 100 pts.wt. ethylene- propylene copolymer rubber having a propylene content of 25-45wt.% and a dicyclopentadiene content of 8-26wt.% with 0.05-10 pts.wt. org. peroxide.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is a crosslinked product that can be crosslinked in hot air, has no stickiness on the surface of the crosslinked product, does not cause abnormal foaming inside, and has excellent heat resistance and compression set. The present invention relates to an ethylene-propylene copolymer rubber composition capable of obtaining the following.

0002

[Prior Art] Ethylene-propylene copolymer rubber has no unsaturated groups in its main chain, and compared to general-purpose diene rubber,
It has excellent heat resistance and is often used in extruded products such as automobile water hoses, weather strips, and electric wires. On the other hand, ethylene-propylene-diene copolymer rubber (EP
DM) is used for sulfur crosslinking, but as heat resistance requirements increase, expectations for organic peroxide crosslinking are increasing. By the way, for crosslinking of rubber parts made by extrusion molding, generally a method of crosslinking in a batch manner in the presence of pressurized steam or a method of continuous crosslinking under hot air is adopted. In crosslinking using sulfur as a crosslinking agent, a crosslinked product with no surface stickiness can be obtained by the above crosslinking method, but in crosslinking using organic peroxide, when air (oxygen) comes into contact with the rubber, the crosslinking is sufficient. However, the crosslinked product did not suffer from softening and deterioration, and the surface of the crosslinked product became sticky, making it impossible to obtain a satisfactory rubber product. As a method to improve the adhesiveness of the crosslinked surface during continuous crosslinking of EPDM in hot air, a method of blending silicone rubber and a bismaleimide compound (Japanese Patent Publication No. 13093/1983) uses EPDM with a very high ethylene content. A method (Japanese Unexamined Patent Publication No. 75552/1983) has been proposed. However, EPDM
In the method of blending a bismaleimide compound with a bismaleimide compound, the melting point of the bismaleimide compound is high, which tends to cause poor dispersion during kneading, and great care is required to obtain a homogeneous product. In addition, resin-like EPD with high ethylene content
The use of M may impair the cold resistance of rubber products.

0003

[Problems to be Solved by the Invention] The present invention further improves the heat resistance and compression set characteristics of EPDM extruded products, and also creates a rubber composition that is crosslinked in hot air and has an appearance and performance that are satisfactory as a rubber product. The purpose is to provide something.

0004

[Means for Solving the Problems] The present invention provides (A) an ethylene-propylene copolymer rubber 1 having a propylene content of 25 to 45% by weight and a dicyclopentadiene content of 8 to 26% by weight.
(B) organic peroxide 0.05 to 10 parts by weight
The object of the present invention is to provide an ethylene-propylene copolymer rubber composition for hot air crosslinking, containing parts by weight.

The ethylene-propylene copolymer rubber (A) used in the present invention has a propylene content of 25 to 45% by weight, preferably 25 to 35% by weight, and 8 to 8% of dicyclopentadiene as the third component. 26% by weight, preferably 9 to 20% by weight of the copolymer. here,
When the propylene content is less than 25% by weight, the resulting rubber becomes resin-like and has poor cold resistance, while when it exceeds 45% by weight, the crosslinked surface becomes sticky and the crosslinking becomes insufficient. Further, when the dicyclopentadiene content is less than 8% by weight, the crosslinked surface becomes sticky, while when it exceeds 26% by weight, heat resistance deteriorates. Note that (A) used in the present invention
Ethylene-propylene copolymer rubber has a Mooney viscosity (
ML1+4, 100°C) of 10 to 150 is preferred.

[0006] The ethylene-propylene copolymer rubber (A) can also be further copolymerized with various polyenes as a fourth component. As this polyene, for example, 1
, 4-hexadiene, 1,6-octadiene, 2-methyl-1,5-hexadiene, 6-methyl-1,5-heptadiene, 7-methyl-1,6-octadiene; cyclohexadiene , methyltetrahydroindene, 5-vinylnorbornene, 5-ethylidene-2-norbornene, 5-methylene-2-norbornene, 5-isopropylidene-2-norbornene, 6-chloromethyl-5-isopropenyl-2-norbornene. Cyclic non-conjugated dienes such as 2,3-diisopropylidene-5-norbornene, 2-ethylidene-3-isopropylidene-5-norbornene, 2-propenyl-2,2-
norbornadiene, 1,3,7-octatriene, 1,
Trienes such as 4,9-decatriene can be exemplified. Among these, preferred polyenes are cyclic nonconjugated dienes and 1,4-hexadiene, especially 5-ethylidene-2-norbornene.

Next, as the organic peroxide (B) used in the present invention, di-t-butyl peroxide,
Di-t-amyl peroxide, t-butylcumyl peroxide, dicumyl peroxide, 1,4-(or 1,3-) di-t-butylperoxyisopropylbenzene, 2,2-di-t-butyl Peroxybutane, 2
, 5-dimethyl-2,5-di-(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di-(t-butylperoxy)hexane-3, n-butyl-4,4 −
Di-t-butyl valerate, 1,1-di-t-butylperoxycyclohexane, di-t-butylperoxy-
3,3,5-trimethylcyclohexane, 2,2-bis(4,4-di-t-butylperoxycyclohexyl)
Dialkyl peroxides such as propane; t-butylperoxyacetate, t-butylperoxyisobutyrate, t-butylperoxypivalate, t-butylperoxymaleic acid, t-butylperoxyneodecanoate, t-Butyl peroxybenzoate, di-
Peroxy esters such as t-butylperoxyphthalate, t-butylperoxydilaurate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, t-butylperoxyisopropyl carbonate;
Examples include ketone peroxides such as dicyclohexanone peroxide, and mixtures thereof. Among them, the temperature that gives a half-life of 1 minute is between 130℃ and 200℃.
Preference is given to using organic peroxides in the range of n
-butyl-4,4-di-t-butylvalerate, dicumyl peroxide, 2,5-dimethyl-2,5-di-(
t-butylperoxy)hexane, 2,5-dimethyl-
2,5-di-(t-butylperoxy)hexyne-3,
Organic peroxides such as di-t-butyl peroxide and 1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane can be preferably used. The amount of organic peroxide (B) is 0.05 to 10 parts by weight, preferably 1 to 7 parts by weight, per 100 parts by weight of component (A). If it is less than 0.05 parts by weight, hot air crosslinking will occur. There is a problem that the process does not proceed sufficiently and the mechanical strength and compression set are poor. On the other hand, if the amount exceeds 10 parts by weight, there is a problem that the elongation of the crosslinked product becomes small.

[0008] The rubber composition of the present invention may also be blended with an organic polymer other than component (A) having a double bond and an iodine value of 10 or more, preferably 20 or more and a glass transition temperature of 25°C or less. . By blending this organic polymer, the tackiness of the crosslinked surface upon hot air crosslinking can be improved. Specific examples of this organic polymer include butadiene rubber, styrene-butadiene rubber, chloroprene rubber, acrylonitrile-butadiene rubber, acrylic rubber, and EPDM other than component (A), preferably 1,2-polybutadiene, medium vinyl・High-vinyl-styrene-butadiene rubber, etc. may be mentioned. The amount of this organic polymer blended is preferably 1 to 50 parts by weight, more preferably 5 to 25 parts by weight, based on 100 parts by weight of component (A).

[0009] The rubber composition of the present invention also contains a highly reactive polyfunctional monomer having a melting point of 160°C or lower, preferably having a vinyl group, in order to improve the tackiness of the composition after hot air crosslinking. It is also possible to add polyfunctional monomers. Specific examples of polyfunctional monomers include allyl compounds such as triallyl isocyanurate, diallyl phthalate, diallyl itaconate, and tetraallyloxyethane;
Methacrylic compounds such as trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, ethylene dimethacrylate, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, and polyethylene glycol dimethacrylate; others include divinylbenzene, divinyltoluene, and the like. Among these, particularly preferred are triallylisocyanurate, trimethylolpropane triacrylate, and the like. The blending amount of the polyfunctional monomer is preferably 0 to 10 parts by weight, more preferably 0 to 5 parts by weight, based on 100 parts by weight of component (A).

Furthermore, an antioxidant can also be incorporated into the rubber composition of the present invention. The antioxidants include styrenated phenol, 2,6-di-t-butylphenol, 2,6-di-t-butyl-4-methylphenol, 2,6-di-t-butyl-p-ethylphenol. , 2,4,6-tri-t-butylphenol, butylhydroxyanisole, 1-hydroxy-3-methyl-4
-isopropylbenzene, mono-t-butyl-p-cresol, mono-t-butyl-m-cresol, 2,4-dimethyl-6-t-butylphenol, butylated bisphenol A, 2,2'-methylene-bis(4- Ethyl-6-
t-butylphenol), 4,4'-butylidene-bis(3-methyl-6-t-butylphenol), 2,2'
-methylene-bis(4-methyl-6-t-butylphenol), 2,2'-methylene-bis(4-ethyl-6-
t-butylphenol), 4,4'-methyl-bis(2
, 6-di-t-butylphenol), 2,2'-methylene-bis(4-methyl-6-t-nonylphenol),
4,4'-butylidene-bis(3-methyl-6-t-butylphenol), 2,2'-isobutylidene-bis(
4,6-dimethylphenol), 4,4'-thio-bis(3-methyl-6-t-butylphenol), bis(3
-methyl-4-hydroxy-5-t-butylbenzyl)
Sulfide, 4,4'-thio-bis(2-methyl-6-
t-butylphenol), 2,2'-thio-bis(4-
Methyl-6-t-butylphenol), 4,4'-thio-bis(6-t-butyl-3-methylphenol), 2
, 2-thio[diethyl-bis3-(3,5-di-t-butyl-4-hydroxyphenol)propionate],
Bis-[3,3-bis(4'-hydroxy-3'-t-
butylic acid] glycol ester, bis[2-(2-hydroxy-5-methyl-
3-t-butyl-benzyl)-4-methyl-6-t-butylphenyl] terephthalate, 1,3,5-tris(
3',5'-di-t-butyl-4'-hydroxybenzyl)isocyanurate, N,N'-hexamethylene-bis(3,5-di-t-butyl-4-hydroxy-hydrocinamide), n- Octadecyl-3-(4'-hydroxy-3',5'-di-t-butylphenol)propionate, tetrakis[methylene-3(3,5-di-t-
Butyl-4hydroxyphenyl)propionate] methane, 1,1'-bis(4-hydroxyphenyl)cyclohexane, 2,6-mono(α-methylbenzyl)phenol, di(α-methylbenzyl)phenol, tri(α
-methylbenzyl)phenol, bis(2'-hydroxy-3'-t-butyl-5'-methylbenzyl)4-methyl-phenol, 2,5-di-t-amylhydroquinone, 2,6-di-t -Butyl-α-dimethylamino-
Phenolic antioxidants such as p-cresol, 2,5-di-t-butylhydroquinone, diethyl ester of 3,5-di-t-butyl-4-hydroxybenzyl phosphate, catechol, and hydroquinone; 2-mercaptobenz imidazole, zinc salt of 2-mercaptobenzimidazole, 2-mercaptomethylbenzimidazole, 2
- Benzimidazole antioxidants such as zinc salt of mercaptomethylimidazole; aliphatic thioether antioxidants such as dimyristylthiopropionate, dilaurylthiodipropionate, distearylthiodipropionate, ditridecyl dipropionate Agents: Zinc or nickel salts of dibutyldithiocarbamic acid, zinc salts of diethyldithiocarbamic acid, zinc salts of ethyl-phenyl-dithiocarbamic acid, zinc salts of dimethyldithiocarbamic acid, metal salt-based antioxidants of diamyldithiocarbamic acid; 2,2, Quinoline antioxidants such as 4-trimethyl-1,2-dihydroquinoline or its polymer, 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline; others phenothiazine, 4-benzoyloxy-2 , 2,6,6-tetramethylpiperidine, bis(2,2,6,6-tetramethyl-4-piperidine) sebacate, N-(3'-hydroxybutylidene)-1-
Examples include naphthylamine. Among these antioxidants, 2,2,4-trimethyl-1,
2-dihydroquinoline polymer, 2-mercaptobenzimidazole, 2-mercaptoimidazole zinc salt, dibutyldithiocarbamate nickel salt, mono(α-methylbenzyl)phenol, di(α-methylbenzyl)phenol, tri(α-methylbenzyl) ) Phenol, 2,
6-di-t-butyl-4-methylphenol, N-(3
Preferred examples include '-hydroxybutylidene)-naphthylamine and a combination of at least two thereof. The blending amount of the antioxidant is 0 to 10 parts by weight, preferably 0 to 5 parts by weight, per 100 parts by weight of component (A).

The composition of the present invention may also contain a processing aid in order to improve the processing suitability of the rubber composition. Examples of processing aids include softeners, tackifiers, plasticizers, and the like. Specific examples of such processing aids include process oils, lubricating oils, paraffins, liquid paraffins, petroleum softeners and plasticizers such as vaseline;
Examples include synthetic polymer softeners and plasticizers such as atactic polypropylene and liquid polybutene. Among such processing aids, paraffinic process oils, liquid paraffins, and the like are preferred. The blending amount of the processing aid is about 200 parts by weight or less, preferably about 150 parts by weight or less, per 100 parts by weight of component (A).

[0012] Furthermore, various fillers can be added to the composition of the present invention. Examples of the filler include carbon black, silicic acid or silicates, calcium carbonate, talc, clay, etc. Among them, silicic acid and silicates are preferred. The blending amount of the filler is 200 parts by weight or less, preferably 1 part by weight, per 100 parts by weight of component (A).
It is about 80 parts by weight or less. Furthermore, the composition of the present invention may contain other additives such as a foaming agent and a foaming aid for the purpose of forming a foam. Examples of such blowing agents include inorganic blowing agents such as sodium bicarbonate, sodium carbonate, ammonium bicarbonate, ammonium carbonate, ammonium nitrite;
Nitroso compounds such as N,N'-dinitrosoterephthalamide and N,N'-dinitrosopentamethylenetetramine; azodicarbonamide, azobisisobutyronitrile, azocyclohexylnitrile, azodiaminobenzene, barium azodicarboxylate, etc. azo compounds; sulfonyl hydrazide compounds such as benzenesulfonylhydrazide, toluenesulfonylhydrazide, p,p'-oxybis(benzenesulfonylhydrazide), diphenylsulfone-3,3'-disulfonylhydrazide; calcium azide, 4,4'-diphenyl Azide compounds such as disulfonyl azide-p-toluenesulfonyl azide can be mentioned. Among them, nitroso compounds, azo compounds and azide compounds are preferably used. The amount of foaming agent blended is 0 per 100 parts by weight of the rubber component.
-30 parts by weight can be appropriately selected and used. The rubber composition of the present invention may also contain colorants, ultraviolet absorbers, flame retardants, and the like.

[0013] The method for preparing the rubber composition of the present invention is not particularly limited, but for example, (A) ethylene-propylene copolymer rubber and (B) organic peroxide (in addition, other materials used as necessary) may be used. Additives) can be added at the same time and kneaded, or component (A) and other additives can be mixed in advance and then component (B) can be added. Mixing is done using various extruders, Banbury mixers, kneaders,
This can be done by kneading with a roll or the like.

[0014]

[Examples] The present invention will be explained in more detail below with reference to Examples, but the present invention is not limited thereto. In addition, unless otherwise specified, parts and percentages in the examples are as follows.
It is based on weight. In addition, the following measurement method was used to evaluate the physical properties in the examples. Reference Example 1 (Preparation of ethylene-propylene copolymer rubber)
Table 1 shows the properties of the ethylene-propylene copolymer rubber used in the examples.

[0015]

[Table 1] Note) DCP = dicyclopentadiene ENB = 5-ethylidene-2-norbornene Reference example 2 (
Preparation of organic polymer) Table 2 shows the properties of the organic polymer used in the examples.

[0016]

[Table 2] Note) JSR RB805=manufactured by Japan Synthetic Rubber Co., Ltd., 1
, 2-polybutadiene rubber JSR SL574 = manufactured by Japan Synthetic Rubber Co., Ltd., high vinyl type SBR Vinyl content = measured by infrared absorption analysis. Glass transition temperature = Measured according to ASTM D3418-75.

Examples 1 to 5, Comparative Examples 1 to 4 Compounded rubbers (rubber compositions) were prepared according to the formulations shown in Table 3, and then crosslinked products were obtained. Namely, ethylene-propylene copolymer rubber, zinc white, stearic acid, filler, oil,
After kneading the anti-aging agent etc. for 10 minutes using a 1.7 liter Banbury mixer (manufactured by Kobe Steel, Ltd.), organic peroxide was added and kneaded using a 6-inch roll, after which the compounded rubber sheet was separated. The mixture was taken out and kept in a hot air gear oven at 200°C for 10 minutes to obtain a crosslinked sheet with a thickness of 2 mm. Moreover, the test piece for compression set was made by punching out a crosslinked sheet into a circular shape with a diameter of 29 mm, and stacking six sheets. Various physical properties were evaluated using this crosslinked sheet and test piece. The results are shown in Table 4. The evaluation methods for various physical properties are as follows.

Tensile Test, Hardness Test, Heat Aging Test The above crosslinked sheet was punched into No. 3 dumbbells according to JIS K6301, and the tensile strength and elongation were measured at a tensile speed of 500 mm/min and 25°C. Furthermore, the hardness HS (JIS A) of the crosslinked sheet was measured according to JIS K6301. In addition, the heat aging test was conducted using the No. 3 dumbbell at 125°C using a gear type aging tester in accordance with JIS K6301.
After heat aging for 70 hours, tensile strength, elongation, and hardness were measured and the rate of change was determined. Scraping of the crosslinked surface The sheet of the compounded rubber (uncrosslinked rubber sheet) was crosslinked with hot air at 250°C for 6 minutes in a gear type aging tester, and then taken out. Immediately after, the crosslinked surface was scratched with an HB pencil and the state of scratching was observed. did. This was used as an index of surface tackiness. ◎; No scratches at all ○; Only slight scratches △; Slight scratches ×; Persistent peeling Ta. The compression set rate is 2
5%, -30°C, 20 hours.

[0019]

[Table 3] Note) TAIC = triallyl isocyanurate, PW38
0 = Manufactured by Idemitsu Kosan Co., Ltd., Diana process oil (paraffin oil), Seast SO = Tokai Carbon Co., Ltd.
Made by FEF Carbon Black, Nip Seal VN3 =
Made by Nippon Silica Co., Ltd., wet silica, non-flex RD
= Seiko Kagaku Co., Ltd., quinoline anti-aging agent, Vesta P
P = Calcium carbonate, manufactured by Inoue Lime Industry Co., Ltd.; Percumil D = Dicumyl peroxide, manufactured by Nippon Oil & Fats Co., Ltd.

[0020]

[Table 4]

[0021] As is clear from Tables 3 and 4, Examples 1 to 4
It can be seen that even when No. 5 is continuously crosslinked in hot air, the crosslinked surface is sufficiently crosslinked and there is no stickiness, and a crosslinked product with excellent heat resistance and compression set can be obtained. On the other hand, Comparative Examples 1~
In No. 3, the crosslinked surfaces were not sufficiently crosslinked, and the crosslinked surfaces were easily scratched after being taken out immediately after crosslinking. Also, comparative example 4
indicates that the low-temperature compression set is extremely large.

[0022]

Effects of the Invention The ethylene-propylene copolymer rubber composition for hot air crosslinking of the present invention does not cause surface adhesion or abnormal internal foaming even when continuously crosslinked in hot air, and has excellent heat resistance, A crosslinked product with excellent compression set properties can be obtained. This cross-linked material is used for automobile water hoses, weather strips, etc.
It can be used for all kinds of purposes such as electric wires, heat-resistant hoses, heat-resistant belts, condenser caps, anti-vibration rubber, and rolls.

Claims (1)

[Claims] Claim 1: (A) 100 parts by weight of ethylene-propylene copolymer rubber containing 25-45% by weight of propylene and 8-26% by weight of dicyclopentadiene, (B
) An ethylene-propylene copolymer rubber composition for hot air crosslinking containing 0.05 to 10 parts by weight of an organic peroxide.