JPS6147865B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an ethylene propylene diene copolymer composition with improved heat resistance. Ethylene propylene rubber, i.e. ethylene,
The rubber-like elastic material whose main component is a polymer obtained by copolymerizing propylene and, if necessary, a non-conjugated diene, has excellent ozone resistance and weather resistance among organic rubbers, and has a heat resistance of 120 to 150%. It is widely used in automobile parts, electrical parts, etc. because it can withstand temperatures at ℃. Silicone rubber is widely used in similar fields due to its high heat resistance of 170 to 250℃ and excellent ozone resistance and weather resistance, but it is expensive and
Weak mechanical properties limit its use. Therefore, it has been desired to develop a rubber-like elastic body having heat resistance intermediate between these two and sufficient mechanical properties. Attempts have been made to obtain a heat-resistant material intermediate between the two by blending ethylene propylene rubber and silicone rubber, but since the compatibility between the two is not good, no improvement in heat resistance can be seen by simply blending them. On the contrary, the mechanical properties were significantly deteriorated, and no good results were obtained. By introducing a mercapto group such as γ-mercaptopropyl group into polydiorganosiloxane, the main component of silicone rubber, and covulcanizing it with ethylene propylene copolymer, the lack of compatibility is solved and heat resistance is improved. Attempts have been made to do so, but in this case, it is extremely complicated to introduce a γ-mercaptopropyl group into a high molecular weight polydiorganosiloxane, and the heat resistance of the polydiorganosiloxane is reduced by the introduction. Regarding ethylene propylene copolymers, it is necessary to use a large amount of non-conjugated diene to make a copolymer with a high iodine value in order to perform covulcanization, which also reduces heat resistance. In the end, the improvement in heat resistance due to co-vulcanization was canceled out, and a product with very good heat resistance was not obtained. There is also a heat-resistant formulation in which carbon black is added to ethylene propylene rubber, but the color is limited to black and it is unsuitable for electrical insulation. It is known that the use of finely powdered silica as a reinforcing filler for ethylene propylene rubber has the effect of improving its wear resistance. However, since finely powdered silica has poor affinity with the ethylene propylene diene copolymer, it is difficult to blend 20 parts by weight or more with respect to 100 parts by weight of the latter. Therefore, there is a limit to the effect of improving wear resistance, and sufficient heat resistance cannot be obtained with this alone. Furthermore, if you try to incorporate more than 20 parts by weight of finely powdered silica, the Mooney level will increase significantly, making it difficult to handle the unvulcanized rubber.
In order to avoid this, it is necessary to add hydrocarbon-based process oil, which poses a problem of lowering heat resistance. The present inventors have made it possible to incorporate a large amount of fine powder silica by using fine powder silica whose surface has been treated with polyorganosiloxane as a reinforcing filler for ethylene propylene diene copolymer.
Furthermore, the inventors have discovered that the heat resistance, electrical insulation, and abrasion resistance of ethylene propylene rubber can be significantly improved, leading to the present invention. In addition, the present inventors have discovered that by adding polydiorganosiloxane, there is no need to use hydrocarbon-based process oil, which is a factor in reducing heat resistance, and that It has also been found that compression set at high temperatures can be significantly improved by using polydiorganosiloxane. That is, the present invention comprises (A) 100 parts by weight of a copolymer of ethylene, propylene, and a non-conjugated diene, (B) 10 to 200 parts by weight of finely powdered silica whose surface has been treated with polyorganosiloxane, and (C) an anti-aging agent. 1 to 20 parts by weight, (D) an organic peroxide, and (E) a polydiorganosiloxane with a degree of polymerization of 10 to 10,000 and in which 0 to 25 mol% of the total organic groups bonded to silicon atoms are alkenyl groups. 100 parts by weight of the heat-resistant composition. The copolymer (A) used in the present invention is a copolymer of ethylene, propylene, and a non-conjugated diene, and although the copolymerization ratio of ethylene and propylene is not particularly limited, it is usually Due to its physical properties, those containing 15 to 50 mol% of propylene units are used. Examples of non-conjugated dienes include dicyclopentadiene, ethylidenenorbornene, 1,
Examples include 4-hexadiene. The amount is
Usually, it is expressed by the iodine value due to the double bond contained in the copolymer due to the introduction of a non-conjugated diene, and an iodine value of 2 to 30 is generally used. In order to obtain excellent heat resistance, a material with a low iodine value is preferred, preferably 13 or less, particularly 7 or less. In order to obtain sufficient mechanical strength, it is preferable that the average molecular weight is 10,000 or more. The fine powder silica (B) used in the present invention is used to impart heat resistance to the composition of the present invention, and examples thereof include fumed silica, precipitated silica, silica aerogel, and calcined silica. Finely powdered silica having a specific surface area of 50 m ² /g or more is preferred because it provides excellent heat resistance through the treatment described below, and fumed silica or precipitated silica is preferred because it is easily available. By treating the surface of these fine powder silicas with polyorganosiloxane, it becomes possible to blend a large amount of fine powder silica into ethylene propylene diene copolymer, which is the purpose of the present invention. It is extremely effective in imparting heat resistance to compositions containing coalescence. There are hydroxyl groups that bond to silicon atoms on the surface of fine powdered silica, but when polyorganosiloxane is added and baked at high temperatures, some of the organic groups of the polyorganosiloxane are detached and water vapor in the atmosphere is released. The silanol group becomes a silanol group and condenses with the hydroxyl group on the surface of the silica, thereby forming a polyorganosiloxane layer on the surface of the finely powdered silica. As the polyorganosiloxane, polymethylsiloxane is preferred because it is easy to obtain and handle, does not require extremely high processing temperatures, and has excellent processing effects. The siloxane skeleton may be linear, cyclic, or branched. Cyclic polydimethylsiloxanes such as octamethylcyclotetrasiloxane and hexamethylcyclotrisiloxane are easy to synthesize and have considerable processing effects, but they are in the gas phase at processing temperatures, so there are limitations on equipment. It is a preferable surface treatment agent except for
However, it is easy to process, and a polymethylsiloxane layer can be easily formed on the surface of fine powdered silica, and the effect of improving heat resistance, which is the objective of the present invention, can be most effectively achieved. Substantially linear polymethylsiloxane with a degree of polymerization of 10 or more is most preferred because it is very easy to mix into the diene polymer and is also easily available like cyclic polydimethylsiloxane. Such polymethylsiloxanes may be completely linear or slightly branched, and the terminal groups may be trimethylsilyl or hydroxydimethylsilyl groups. If the degree of polymerization is less than 10, it tends to turn into a gas phase at high temperatures, resulting in equipment limitations, and it is difficult to form an effective polymethylsiloxane layer in a short baking time. Fine powdered silica can be treated by the usual method. For example, the surface of finely powdered silica is sufficiently sprinkled with polymethylsiloxane or its solvent solution, and when a solvent is used, the solvent is removed by heating under reduced pressure. After that, polymethylsiloxane is baked onto the surface of the finely powdered silica by heating it to a high temperature. Examples of the solvent include hydrocarbons such as toluene, xylene, n-hexane, n-heptane, and petroleum benzine, and halogenated hydrocarbons such as trichlene and 1,1,1-trichloroethane.
The baking temperature is the temperature at which methyl groups are eliminated, that is, 200°C or higher, but preferably between 250 and 350°C. The amount of finely powdered silica surface-treated with polyorganosiloxane is between 10 and 200 parts by weight, preferably between 20 and 100 parts by weight, per 100 parts by weight of the copolymer (A). This is because if the amount of fine powder silica is too small, there will be no heat resistance improving effect or reinforcing effect, and if it is too large, it will become hard and the physical properties after vulcanization will deteriorate. The anti-aging agent (C) used in the present invention, together with the surface-treated finely powdered silica (B), imparts heat resistance to the vulcanized composition. Anti-aging agents include phenol, imidazole, quinoline,
Amine-based, hydroquinone-based, zinc oxide, chlorinated polyethylene, etc. are known.
Any of them can be used in the present invention, and can be used alone or in combination, but since they have a synergistic effect with the surface-treated fine powder silica of (B) in improving heat resistance and do not cause coloring, 4,4'-thiobis(6-tertiarybutyl-
2-methylphenol), 2,2,4-trimethyl-1,2-dihydroquinoline polymer, 2-mercaptobenzimidazole, 2-mercaptobenzimidazole zinc salt, or zinc oxide. The amount of anti-aging agent added is 1 to 20 parts by weight, preferably 2 to 10 parts by weight, per 100 parts by weight of the copolymer (A). This is because if the amount added is too small, there will be no effect, and if the amount added is too large, the physical properties will be adversely affected. The organic peroxide (D) used in the present invention can be obtained by vulcanizing the copolymer (A), and when a polydiorganosiloxane containing an alkenyl group is used as (E), (E) and (A ) acts to co-vulcanize or crosslink (E). Examples of organic peroxides include dicumyl peroxide, ditertiarybutyl peroxide, 2,5-dimethyl-2,5-di(tertiarybutylperoxy)hexane, and 2,5-dimethyl-2,5-di(tertiarybutylperoxy). butyl)hexyne, di(tertiarybutylperoxy)diisopropylbenzene,
1,1'-di(tertiarybutylperoxy)-
Examples include 3,3,5-trimethylcyclohexane. The amount of organic peroxide to be added varies depending on the type of organic peroxide, and is not particularly limited.
Generally 0.5 to 5 parts by weight per 100 parts by weight of copolymer (A)
Parts by weight are used. If it is less than 0.5 parts by weight, a sufficient vulcanization rate cannot be obtained, and if it exceeds 5 parts by weight, it is not only ineffective, but also causes decomposition products to remain.
Heat resistance decreases. In order to easily and safely handle the organic peroxide, it may be kneaded with polydiorganosiloxane to form a paste, or it may be adsorbed onto a powder such as calcium carbonate or molecular sieve. The polydiorganosiloxane (E) used in the present invention improves the processability of the composition by improving the slippage between the copolymer (A) and the surface-treated fine powder silica (B), It is also intended to reduce internal heat generation during use after vulcanization. Traditionally, hydrocarbon-based process oils and plasticizers such as dioctyl sebatate have been used for this purpose. However, these have low heat resistance, and their frequent use has the disadvantage that the heat resistance of ethylene propylene rubber decreases. Although (E) is not essential in the present invention, by using it instead of process oil or plasticizer, it is possible to prevent a decrease in heat resistance caused by these.
As polydiorganosiloxane, the degree of polymerization is 10~
10,000, preferably 300 to 8,000 substantially linear ones are preferred. If the degree of polymerization is too low, before vulcanization,
Alternatively, there is a phenomenon in which polydiorganosiloxane is liberated from the composition after vulcanization, and if the degree of polymerization is too high, the viscosity is high and it is inconvenient to handle. Such polydiorganosiloxanes are broadly classified into those having an alkenyl group such as a vinyl group or allyl group bonded to a silicon atom, and those having no alkenyl group. When an alkenyl group-containing material is used, it can be partially covulcanized with the copolymer (A) by the action of the organic peroxide (D), or crosslinked alone (E). Significantly improves compression set at high temperatures. Further, there is no need to use a crosslinking aid such as an acrylic ester type. The amount of alkenyl group is
The amount of organic groups bonded to silicon atoms ranges from 25 mol % or less, preferably 2 per molecule to 10 mol % of the organic groups. This is because if there are too many alkenyl groups, the composition after vulcanization will become hard and the remaining alkenyl groups will impair heat resistance. The alkenyl group is preferably a vinyl group because it is easily available. Those containing no alkenyl group do not perform such co-vulcanization or crosslinking and are used simply as a lubricant. In the present invention, any of these may be used as the polydiorganosiloxane, or both may be used together. Examples of organic groups other than alkenyl groups bonded to the silicon atom of polydiorganosiloxane include alkyl groups such as methyl, ethyl, propyl, butyl, octyl, and decyl groups, aryl groups such as phenyl, and β. ―
Examples include aralkyl groups such as phenylethyl group and β-phenylpropyl group, substituted hydrocarbon groups such as halogenated alkyl groups, halogenated phenyl groups, and acylated alkyl groups. From the viewpoint of ease of handling the siloxane, a methyl group is preferred, and from the viewpoint of affinity for the copolymer (A), siloxanes having 40 mol% or less of phenyl groups in the siloxane group are also used. The amount of polydiorganosiloxane added in (E) is (A)
0 to 100 parts by weight per 100 parts by weight of the copolymer,
Preferably it is 5 to 50 parts by weight. Even if used in too large a quantity, no further effect can be expected, which is not only economically disadvantageous, but also causes a decrease in mechanical properties. This is because, in some cases, the polydiorganosiloxane may ooze out. In the composition of the present invention, fillers other than (B), colorants,
conductivity agents, crosslinking aids such as trimethylolpropane trimethacrylate, ethylene dimethacrylate, triallylisocyanurate, dibenzoylquinone dioxime, flame retardants, chlorinated materials such as chlorosulfonated polyethylene and chlorinated polyethylene It is also possible to add polymers and the like. Although the method for preparing the composition of the present invention is not particularly limited, the copolymer (A) and the surface-treated finely powdered silica (B) are usually mixed in a mixing device such as a Banbury mixer or a dough mixer. Generally, (E) and (C) are blended simultaneously or sequentially to mix well, and then (D) is blended using two rolls. According to the present invention, a rubber-like elastic body can be obtained which has superior processability and superior heat resistance and electrical properties after vulcanization compared to conventional ethylene propylene rubber. By vulcanization, the composition of the present invention can be used in automotive parts, electrical insulation materials, etc., which are used in a temperature range between conventional ethylene propylene rubber and silicone rubber.
Used as a wire coating material. Hereinafter, the present invention will be explained with reference to Examples. In Examples and Comparative Examples, all parts represent parts by weight. Comparative Example 1 100 parts of ethylene propylene diene copolymer (E-1) having an iodine number of 12 and the filler shown in Table 1 were charged into a Banbury mixer and mixed for 30 minutes to obtain compound samples 1a to 1f. Mooney viscosity of the formulation
When measured at 100℃, as shown in Table 1,
The Mooney viscosity of the sample using untreated finely powdered silica was significantly increased. This formulation contains a concentration of dicumyl peroxide adsorbed on calcium carbonate.
When 40% of the material was added and press vulcanization was performed at 160° C. for 20 minutes, a rubber-like elastic body with physical properties as shown in Table 1 was obtained. After heating this at 160°C for 72 hours, the physical properties were as shown in Table 1. at 200℃
Anything that has been heated for 24 hours will deteriorate significantly.
It was impossible to measure physical properties. The types and symbols of the fillers blended are as follows. P-1 Fumed silica with a specific surface area of 200 m ² /g P-2 Precipitated silica with a specific surface species of 240 m ² /g P-3 P-1 heat-treated with trimethylsilyl-terminated polydimethylsiloxane having a viscosity of 200 cst at 25°C P -4 P-2 heat-treated with trimethylsilyl-terminated polydimethylsiloxane with a viscosity of 200cst at 25°C P-5 P-1 heat-treated under pressure with octamethylcyclotetrasiloxane P-6 P-1 For sample 1d, which was heat-treated with polydimethylsiloxane end-blocked with hydroxydimethylsilyl groups and having a viscosity of 1000 cst at 25°C, the compression set at 100°C for 70 hours was 42%.

【table】

[Table] Example 1 Comparative example 1 except that the following anti-aging agent was added
In the same manner as above, formulation samples 11 to 16 were obtained. However, formulations 11 and 12 are comparative samples. Comparative example 1
Mooney viscosity and physical properties and electrical properties after vulcanization were measured in the same manner as described above. The heating test
The test was carried out at 200°C for 24 hours. The blending ratio and measurement results are shown in Table 2. Antiaging agent A-1 2,2,4-trimethyl-1,2-dihydroquinoline polymer A-2 2-mercaptobenzimidazole A-3 2-mercaptobenzimidazole zinc salt A-4 4,4'-thiobis( 6-tertiarybutyl-2-methylphenol) A-5 Zinc oxide Note that blend sample 26 uses an ethylene propylene diene copolymer (E-2) with an iodine value of 4, but As shown in the table, it showed extremely excellent heat resistance.

【table】

[Table] Example 2 Compound samples 21- Adjust 29, Mooney viscosity,
Physical properties and compression set after vulcanization were measured. The blending ratio and measurement results are shown in Table 4.

【table】

【table】

[Table] Example 3 An ethylene propylene diene copolymer (E-3) with an iodine value of 6 is end-blocked with a vinyldimethylsilyl group, and 10 mol% of the containing groups bonded to silicon atoms are vinyl groups. and the remainder is a methyl group,
Polydiorganosiloxane (S-
8) and the already described fine powder silica and anti-aging agent were added in the same manner as in Example 1 to obtain samples 31 to 33 with the formulations shown in Table 5. These samples were vulcanized in the same manner as Example 1. Mooney viscosity and compression set are shown in Table 5.

【table】

[Table] Example 4 Regarding sample 13 of Example 1 and sample 22 of Example 2, 55% of 2,5-dimethyl-2,5-ditertyabutylhexane was added instead of dicumyl peroxide.
Press vulcanization was performed at 160° C. for 30 minutes using parts by weight. When the obtained rubber elastic body was heated at 200° C. for 24 hours, as shown in Table 6, it exhibited the same heat resistance as Example 1 and Example 2.

【table】

Claims (1)

[Scope of Claims] 1 (A) 100 parts by weight of a copolymer of ethylene, propylene, and a non-conjugated diene, (B) 10 to 200 parts by weight of finely powdered silica whose surface has been treated with polyorganosiloxane, (C) Aging 1 to 20 parts by weight of an inhibitor, (D) an organic peroxide, and (E) a polydiorganosiloxane with a degree of polymerization of 10 to 10,000 and in which 0 to 25 mol% of the total organic groups bonded to silicon atoms are alkenyl groups. 0 to 100 parts by weight. Heat resistant composition. 2. The composition according to claim 1, wherein the polyorganosiloxane used in (B) is a substantially linear polymethylsiloxane having a degree of polymerization of 10 or more. 3. The composition according to claim 1, wherein the polyorganosiloxane used in (B) is a cyclic polydimethylsiloxane. 4. The composition according to claim 1, wherein the finely powdered silica (B) is fumed silica. 5. The composition of claim 1, wherein the finely divided silica in (B) is a precipitated silica. 6. The composition according to claim 1, wherein the amount of finely divided silica (B) is from 20 to 100 parts by weight. 7 (C) is 4,4′-thiobis(6-tertiarybutyl-2-methylphenol), 2,2,4-trimethyl-1,2-dihydroquinoline polymer, 2-
The composition of claim 1, wherein the composition is an antiaging agent selected from the group consisting of mercaptobenzimidazole, 2-mercaptobenzimidazole zinc salt, and zinc oxide. 8. The composition according to claim 1, wherein the alkenyl group in (E) is a vinyl group. 9. The composition according to claim 1, wherein the amount of alkenyl groups (E) is 2 or more in one molecule and 10 mol% or less of the total organic groups bonded to silicon atoms. 10. The composition according to claim 1, wherein the organic group other than the alkenyl group bonded to the silicon atom in (E) is a methyl group. 11 The iodine value of the copolymer (A) is 13 or less,
A composition according to claim 1. 12 The iodine value of the copolymer (A) is 7 or less,
A composition according to claim 1.