JP2000290379A - Crosslinked molded article sand its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a crosslinked molded article having a low hardness and excellent tensile and rubbery properties by exposing a composition comprising a silane-graft ethylene-α-olefin copolymer, polypropylene and an unsaturated aromatic α-methylalkenyl dimer to water in the presence of a silanol condensation catalyst. SOLUTION: The composition is molded into a desired shape and exposed to water to be crosslinked, giving the objective molded article. An ethylene- propylene copolymer is the most preferable as the ethylene-α-olefin copolymer. The polypropylene is preferably an ethylene copolymer prepared by copolymerizing a small amount of, e.g. 2-9 wt.%, ethylene. The wt. ratio of the ethylene-α-olefin copolymer to polypropylene is preferably (70/30)-(85/15). The aromatic α-methylalkenyl dimer is added usually in an amount of 0.05-5 wt.% of the ethylene-α-olefin copolymer. Examples of an organosilane compound for grafting are vinyltrimethoxysilane and vinyltriethoxysilane.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crosslinked molded article having low hardness and excellent tensile properties and rubbery properties, and a method for producing the same.

[0002]

2. Description of the Related Art An ethylene copolymer such as polyethylene, ethylene-vinyl acetate copolymer or ethylene propylene rubber, or a polyethylene derivative such as chlorinated polyethylene, and an organic silane compound are grafted in the presence of a free radical generator. The so-called silane water cross-linked product has been widely put into practical use by reacting and exposing to water in the presence of a silanol condensation catalyst after molding into a predetermined shape to form a cross-linked molded product.
In particular, cable insulators and pipes can be mentioned as silane water crosslinked products of polyethylene. A silane water crosslinked product of a blend of polyethylene and ethylene propylene rubber has been put to practical use as a flexible cable insulator.

[0003] However, a silane water crosslinked product comprising an ethylene copolymer has a lower tensile strength than its non-crosslinked product. In particular, this tendency is remarkable in a silane water crosslinked product of an ethylene propylene copolymer. Conventionally, in order to prevent such a decrease in tensile strength, an inorganic reinforcing agent such as carbon black or a crystalline polymer such as polyethylene has been added. In the former method of adding an inorganic reinforcing agent, foaming is performed due to the hygroscopicity of the reinforcing agent, the polymer is liable to scorch, the surface condition of the extruded body is roughened, and the extruded resin accompanying scorch is extruded. Workability will be reduced. In the latter method of adding a crystalline polymer such as polyethylene, hardness is increased and rubber properties such as compression set and permanent elongation are remarkably reduced.

[0004] The present applicant has proposed a method for producing a crosslinked molded article having low hardness and excellent tensile properties and rubber-like properties by forming a composition containing a silane-grafted ethylene-α-olefin copolymer and polypropylene into a predetermined shape. A method for producing a cross-linked molded article has been proposed in which after molding, the composition is exposed to moisture in the presence of a silanol condensation catalyst and crosslinked.
No. 0-120797).

[0005]

However, further improvements in elongation and tear strength are desired.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and is a crosslinked molded article having low hardness, excellent tensile properties and rubbery properties, and excellent elongation and tear strength. And a method for producing the same.

[0007]

The object of the present invention is to provide a composition comprising a silane-grafted ethylene-α-olefin copolymer, polypropylene and an unsaturated dimer of an aromatic α-methylalkenyl monomer. This is achieved by cross-linked moldings that have been cross-linked by exposure to moisture in the presence of a catalyst.

Another object of the present invention is to form a composition containing a silane-grafted ethylene-α-olefin copolymer, polypropylene and an unsaturated dimer of an aromatic α-methylalkenyl monomer into a predetermined shape and then form a silanol condensation catalyst. Is achieved by a method for producing a cross-linked molded article which is cross-linked by exposure to moisture in the presence of water.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, ethylene-α olefin copolymers include ethylene-butene-1 copolymer, ethylene-propylene copolymer, ethylene-hexene copolymer, ethylene-octene copolymer and the like. Although it can be mentioned, an ethylene-propylene copolymer is most preferable for achieving the object of the present invention. Although any type of ethylene-propylene copolymer can be used, a high-ethylene type copolymer having a propylene content of 20 to 35% by weight is preferable. The high ethylene type ethylene propylene copolymer can be pelletized, and the automation of the compound production process such as measurement and mixing is easy. Propylene content of 3
If it exceeds 5 parts by weight, pelletization tends to be difficult, and if it is less than 20 parts by weight, the rubber elasticity of the molded article tends to be lost.

As the polypropylene, it is preferable to use an ethylene copolymer type obtained by copolymerizing a small amount of an ethylene component, for example, 2 to 9% by weight. As the copolymerization method, either block copolymerization or random copolymerization may be used, but it is preferable to use block copolymerization in order to increase the strength of the crosslinked molded article. When the content of the ethylene component is as small as less than 2% by weight, the compatibility with the ethylene-α-olefin copolymer tends to decrease. The strength tends to decrease.

[0011] The weight ratio of the ethylene-α-olefin copolymer to the polypropylene in the polymer component (the former /
The latter is preferably in the range of 70 to 85/30 to 15, and when the content of polypropylene is less than 15% by weight, it tends to be difficult to increase the strength of the crosslinked molded article, and when it exceeds 30% by weight, the hardness is high. As a result, the rubber-like properties tend to decrease.

The organic silane compound is required to have a group which can be connected to a polymer and a group which can be silanol-condensed.
Vinyltriethoxysilane, vinyltriacetoxysilane, γ-methacryloxypropyltrimethoxysilane,
And ethylenically unsaturated silane compounds such as vinyl tris (2-methoxyethoxy) silane.

As the free radical generator, ethylene-
It is required to generate free radical sites in the α-olefin copolymer, and specifically, benzoyl peroxide, dichlorobenzoyl peroxide, dicumyl peroxide, di-tert-butyl peroxide, 2,5-dimethyl-2,5 -Di (peroxybenzoate) hexyne-
3,1,3-bis (tert-butylperoxyisopropyl) benzene, lauroyl peroxide, tert-butylperacetate, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3,2.5 -Dimethyl-
Organic peroxides such as 2,5-di (t-butylperoxy) hexane and tert-butylperbenzoate and peresters, and azo compounds such as azobis-isobutyronitrile and dimethylazodiisobutyrate can be mentioned.

Examples of the silanol condensation catalyst include organic tin compounds such as dibutyltin dilaurate, dibutyltin diacetate and dibutyltin dioctate.

The dimer of an aromatic α-methylalkenyl monomer is a dimer of an aromatic α-methylalkenyl monomer represented by the following chemical formula in the presence of an acidic catalyst or the like.

[0016]

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Here, R is an aryl group, an alkaryl group, a halogen-substituted aryl group or a halogen-substituted alkaryl group.

For example, α-methylstyrene represented by the following chemical formula

[0019]

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Chemical formula obtained by dimerizing

[0021]

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Α-methylstyrene dimer represented by the following formula, para-methyl-α-methylstyrene represented by the following chemical formula:

[0023]

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Chemical formula obtained by dimerizing

[0025]

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Para-methyl-α-methylstyrene dimer represented by the following formula:

In addition, dimer of para-ethyl-α-methylstyrene, dimer of para-isopropyl-α-methylstyrene, dimer of meta-ethyl-α-methylstyrene, meta-methyl-α-methylstyrene dimer Monomer, dimethyl-α-
Methylstyrene dimer, chloro-α-methylstyrene dimer, chloro-methyl-α-methylstyrene dimer, diethyl-α-methylstyrene dimer, methyl-isopropyl-α-methylstyrene dimer, etc. Can be given. The above dimers can be used alone or in combination of two or more.

The amount of the dimer of the aromatic α-methylalkenyl monomer to be added is 100 parts by weight of the ethylene-α-olefin copolymer.
0.05 to 5 parts by weight, preferably 0.1 to 5 parts by weight
If it is less than 0.05 part by weight, the effect of improving elongation and tensile properties is insufficient, and if it exceeds 5 parts by weight, the crosslinking reaction tends to be inhibited.

In the crosslinked molded article of the present invention, a fine polypropylene component of about 2 μm is uniformly dispersed in the ethylene-α-olefin copolymer component, and this fine polypropylene acts as a reinforcing component (organic polymer filler). A crosslinked molded article having low hardness and excellent tensile properties and rubber properties can be realized. In particular, in a production method in which polypropylene is blended with a graft polymer obtained by graft-reaction of an ethylene-α-olefin copolymer, and molding and crosslinking are performed, the polypropylene component is dispersed in a finer state, and further excellent tensile properties. Can be realized. Further, by adding a dimer of an aromatic α-methylalkenyl monomer, excellent elongation and tensile properties can be realized.

In the present invention, in addition to the above components, an antioxidant, a stabilizer, a coloring agent, a lubricant and the like may be appropriately compounded.
However, in the present invention, since polypropylene acts as a reinforcing component, it is not necessary to add an inorganic reinforcing agent such as carbon black. A small amount of carbon black may be added as a coloring agent.

The grafting reaction of the organic silane compound may be carried out using any of a kneader, Banbury and an extruder, but is most preferably carried out by an extruder which can be easily automated.

[0032]

EXAMPLES [Production Method I (Examples 1 to 3, Comparative Examples 1 to 1)
3)] (1) Blending Step According to the composition shown in Tables 1 and 2, the ethylene-propylene copolymer, polypropylene and black color batch were used in a total amount of 3.
Each was weighed so as to be 0.6 kg, sufficiently dry-blended, and then melt-mixed with a 30 mm extruder to produce mixed resin pellets. The temperature setting conditions of the extruder were as follows: cylinder 1: 160 ° C, cylinder 2: 220 ° C, cylinder 3: 220 ° C, head: 200 ° C.

(2) Silane grafting reaction step
100 parts by weight, 10 parts by weight of dicumyl peroxide, 10 parts by weight of α-methylstyrene dimer, 2,2-thio-diethylenebis [3- (3.5-di-t-butyl-4
-Hydroxyphenyl) propionate] (antioxidant) at 10 parts by weight and 4,4'-thiobis- (6-tert-butyl-3-methylphenol) (antioxidant) at 1 part by weight. Made

With respect to 2.04 kg of the mixed resin pellets prepared in the above (1), 52.4 g of a vinylsilane mixed solution was absorbed in the mixed resin pellets of the above (1) while being sufficiently mixed in a mixing vessel. . Next, the mixed resin pellets were charged into a 30 mm twin-screw extruder set to the same temperature as in the above (1), and a silane graft reaction was performed while melt-kneading to produce a graft polymer.

(3) Catalyst master batch mixing step A compound obtained by mixing and absorbing 1 part by weight of dibutyltin dilaurate with 100 parts by weight of ethylene propylene copolymer in a mixing vessel is melt-kneaded in the same manner as in (2) above. To produce a catalyst masterbatch.

(4) Sheet Forming Step The graft polymer produced in the above (2) and the catalyst masterbatch produced in the above (3) are mixed at a weight ratio of 1 / l to 1 / l.
The pellets weighed at a ratio of 9/1 were extruded into a sheet by a 40 mm extruder equipped with a T die, and then continuously passed through two rolls to adjust the thickness of the sheet to 2 mm. The temperature setting conditions for the extruder were the same as in (1) above.

(5) Crosslinking Step The sheet produced in the above (4) is heated at 80 ° C. in wet heat for 16 hours.
Allowed time to crosslink.

[Production method II (Examples 4 to 6, Comparative examples 4 to 6)
6)] (1) Silane Grafting Step of Ethylene Propylene Copolymer According to the blending of Tables 1 and 2, the ethylene propylene copolymer and the same vinylsilane mixed solution as in Production Method I were thoroughly mixed in a mixing vessel. While absorbing the resin. Next, the resin was charged into a 30 mm twin-screw extruder set at the same temperature as in the production method I, and a silane graft reaction was carried out while melt-kneading to produce a graft polymer of an ethylene-propylene copolymer.

(2) Kneading Step of Ethylene Propylene Copolymer Graft Polymer, Polypropylene and Black Color Batch The polypropylene and black color batch corresponding to the amount of the ethylene propylene copolymer graft polymer were weighed, and then the three were dry blended. did. This mixed resin was charged into a 30 mm twin-screw extruder set at the same temperature as in Production Method I, and was melt-mixed.

(3) Catalyst Masterbatch Mixing Step A catalyst masterbatch was produced in the same manner as in Production Method I (3).

(4) Sheet Forming Step A sheet having a thickness of 2 mm was extruded in the same manner as in Production Method I (4).

(5) Crosslinking Step Crosslinking was carried out in the same manner as in Production Method I (5).

The properties of the crosslinked sheets produced in Examples and Comparative Examples are shown in Tables 1 and 2. Tensile strength, elongation, and hardness (JIS.A) were measured according to the tensile test of Section 3 of JIS K6301. The tear strength is JIS K62
The measurement was performed according to No. 52 (angle with no cut). The compression set was measured according to the compression set test of JIS K 6301, section 10.

[0044]

[Table 1]

[0045]

[Table 2]

As is clear from the examples and comparative examples, the cross-linked molded article of the present invention has low hardness and excellent tensile properties, rubber-like properties, elongation, and tear strength. Since no inorganic reinforcing agent is used, a crosslinked molded article having a smooth surface state can be realized. Furthermore, while the same or better characteristics can be realized as compared with the conventional ethylene propylene rubber, the kneading and crosslinking processes are simplified, so that the productivity can be greatly improved.

[0047]

As described above, according to the present invention, it has low hardness, excellent tensile properties and rubbery properties, can be freely colored, and has excellent elongation and tear strength. A crosslinked molded article can be realized.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toshie Watanabe 1-1-1, Koriyama, Taishiro-ku, Sendai City, Miyagi Prefecture Inside Tohoku Rubber Co., Ltd. (72) Inventor Hiroshi Iwabuchi 1-1-1, Koriyama, Taishiro-ku, Sendai City, Miyagi Prefecture No. 1 Tohoku Rubber Co., Ltd. (72) Keiichi Kato 1-1-1, Koriyama, Taishiro-ku, Sendai City, Miyagi Prefecture F-term in the Tohoku Rubber Co., Ltd. 4F070 AA16 AB07 AB09 AB11 AC32 AC42 AC52 AC63 AC65 AE08 AE16 GA01 GB03 GC02 4J002 BB122 BB151 BB152 BB201 BN201 EA046 EZ047 FD207 GM00 GQ01

Claims (8)

[Claims] 1. A composition comprising a silane-grafted ethylene-α-olefin copolymer, polypropylene and an unsaturated dimer of an aromatic α-methylalkenyl monomer, which is exposed to moisture in the presence of a silanol condensation catalyst. A crosslinked molded article characterized in that it is crosslinked. 2. The content ratio by weight of the ethylene-α-olefin copolymer to polypropylene (the former / the latter) is 70 to 85.
The crosslinked molded article according to claim 1, wherein the ratio is / 30 to 15. 3. The crosslinked molded article according to claim 1, wherein the ethylene-α olefin copolymer is an ethylene propylene copolymer. 4. The crosslinked molded article according to claim 1, wherein the ethylene propylene copolymer has a propylene content of 20 to 35% by weight. 5. The polypropylene contains 2 to 9 ethylene components.
The crosslinked molded article according to claim 1, which is an ethylene copolymer type containing 1% by weight. 6. A composition containing a silane-grafted ethylene-α-olefin copolymer, polypropylene and an unsaturated dimer of an aromatic α-methylalkenyl monomer is formed into a predetermined shape, and then molded in the presence of a silanol condensation catalyst. A method for producing a crosslinked molded article, comprising exposing to water and crosslinking. 7. A graft reaction of a mixture containing an ethylene-α-olefin copolymer, polypropylene, an organic silane compound and an unsaturated dimer of an aromatic α-methylalkenyl monomer in the presence of a free radical generator, The method for producing a crosslinked molded article according to claim 6, wherein the reaction product is molded into a predetermined shape, and then exposed to moisture in the presence of a silanol condensation catalyst to perform crosslinking. 8. A graft reaction product obtained by subjecting an unsaturated dimer of an ethylene-α-olefin copolymer, an organosilane compound and an aromatic α-methylalkenyl monomer to a graft reaction in the presence of a free radical generator, and polypropylene. The method for producing a crosslinked molded article according to claim 6, wherein the blended product is molded into a predetermined shape and then exposed to moisture in the presence of a silanol condensation catalyst to effect crosslinking.