JP2002114856A - Crosslinked molded body and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a crosslinked molded product having good rubbery properties with low hardness and characteristics excellent in tear strength and tensile strength and provide a method for producing the same. SOLUTION: This crosslinked molded product comprises a composition containing a silane-grafted ethylene-α-olefin copolymer, a polypropylene and a metal salt of acrylic acid or methacrylic acid and is crosslinked by exposing to water in the presence of a silanol condensation catalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cross-linked molded article and a method for producing the same, and more particularly, to a cross-linked molded article having low hardness and good rubber properties, and excellent tear strength and tensile strength. The present invention relates to a manufacturing method for manufacturing.

[0002]

2. Description of the Related Art Grafting reaction is carried out between polyethylene or an ethylene-based copolymer such as ethylene-vinyl acetate copolymer or ethylene-propylene copolymer and an organic silane compound in the presence of a free radical generator. 2. Description of the Related Art A method for producing a molded article in which a product is molded into a predetermined shape and exposed to moisture in the presence of a silanol condensation catalyst to crosslink between molecules has been widely used.

This method, called the silane water cross-linking method, is particularly applicable to polyethylene or polyethylene and ethylene-ethylene.
It is used as a cross-linking method for cable insulation coated with a blend of propylene copolymer, etc.However, when an ethylene copolymer is selected as a polymer, a problem is that the tensile strength is lower than that of a non-cross-linked product. The drawback is that it decreases. In particular, when an ethylene-propylene copolymer is selected as the ethylene-based copolymer, the tensile strength is reduced to a level that cannot be practically used with a water-crosslinked product alone.

[0004] As a method of solving this problem,
A method of adding a reinforcing agent such as carbon black or a method of adding a crystalline polymer such as polyethylene has been adopted, but none of these methods is practically satisfactory.
That is, in the case of the former method, there is a problem of foaming due to moisture absorption of the reinforcing agent, or surface roughness and workability of the extruded body due to the property of accelerating scorch, while in the case of the latter method, hardness is increased. Alternatively, there is a problem of deterioration due to deterioration of rubber properties such as compression set and permanent elongation.

[0005] As a countermeasure to the above problem, a composition containing a silane-grafted ethylene-α-olefin copolymer and polypropylene is molded into a predetermined shape, and a composition is prepared by adding water to the composition in the presence of a silanol condensation catalyst. A method has been proposed in which the molecules are crosslinked by acting on each other (JP-A-10-120797). According to this method,
It is said that it is possible to provide a crosslinked molded article which has no problems of foaming and scorch, has low hardness and excellent rubber properties, and also has excellent tensile properties.

[0006]

However, according to the molded article obtained by the above-mentioned method, the tear strength is insufficient and the tensile strength is not always sufficient. In order to obtain a practical molded product, it is necessary to make the tear strength sufficient and to increase the tensile strength to a higher level.

Accordingly, an object of the present invention is to provide a cross-linked molded article having low hardness, good rubber properties, and excellent properties in tear strength and tensile strength, and a production method for obtaining the same. It is in.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a silane-grafted ethylene-α-
An olefin copolymer, polypropylene, and a molded product of a composition containing a metal salt of acrylic acid or methacrylic acid, wherein the molded product is cross-linked by exposure to moisture in the presence of a silanol condensation catalyst. A crosslinked molded article characterized by the following.

In order to achieve the above object, the present invention provides a composition comprising an ethylene-α-olefin copolymer, an organic silane compound, polypropylene, and a metal salt of acrylic acid or methacrylic acid. A graft reaction in the presence of an agent, molding the obtained reaction product into a molded product of a predetermined shape, and then exposing the molded product to moisture in the presence of a silanol condensation catalyst. It is intended to provide a method for producing a molded article.

The above ethylene-α-olefin copolymer and polypropylene have a weight ratio of the former of 70 to 70.
It is preferable to mix such that the latter becomes 85 to 85. When the amount of polypropylene is less than 15, it is difficult to increase the strength of the crosslinked molded article. Conversely, when the amount of polypropylene exceeds 30, the hardness increases and the rubber-like properties decrease.

It is preferable that the polypropylene contains an ethylene component. However, in order to ensure compatibility with the ethylene-α-olefin copolymer and to obtain sufficient physical properties at the lower limit, and to prevent a decrease in the strength of the crosslinked molded article due to a decrease in the strength of the polypropylene itself at the upper limit. The amount of the ethylene component contained is preferably set to 2 to 9% by weight.

In the present invention, the metal salt of acrylic acid mixed for improving the characteristics is represented by the following formula (1) when the metal is divalent, while the metal salt of methacrylic acid is represented by the formula (1) 2). In the formula, as the metal M,
Zinc, nickel, tin, magnesium, calcium, barium and the like can be mentioned, among which zinc is particularly preferred.

[0013]

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[0014]

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The mixing amount of these metal salts is as follows:
It is preferable to set within the range of 0.5 to 3 parts by weight based on 100 parts by weight of the mixture of the ethylene-α-olefin copolymer and polypropylene. If the amount of the metal salt is less than this, it is difficult to obtain a material having sufficient tear strength, while if the amount of the mixture exceeds this range, the moldability such as extrudability will be reduced.

Examples of the ethylene-α-olefin copolymer in the present invention include ethylene-propylene copolymer, ethylene-butene-1 copolymer, ethylene-hexene copolymer and ethylene-octene copolymer. used. As the organic silane compound, a compound having a group capable of grafting to a polymer and a group capable of silanol condensation in a molecule is used. Specifically, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriacetoxysilane, vinyltris ( 2-methoxyethoxy)
Silane or the like is used.

The free radical generator used in the production method of the present invention includes dicumyl peroxide, benzoyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-di ( Peroxybenzoate) hexyne-3, 1,3-bis (t-butylperoxyisopropyl) benzene, lauroyl peroxide, 2,5-dimethyl-2,5-di (tbutylperoxy) hexyne-3,2 Organic peroxides and peresters such as 5-dimethyl-2,5-di (t-butylperoxy) hexane, t-butylperbenzoate, t-butylperacetate, or azobis-isobutyronitrile, dimethylazodiisobutyi And azo compounds such as a rate.

Further, as a silanol condensation catalyst, dibutyltin dilaurate, dibutyltin diacetate,
Examples include organometallic compounds such as stannous acetate, cobalt naphthenate, tetrabutyl titanate, zinc stearate, barium stearate, and calcium stearate. Among these, use of an organotin compound is particularly preferable.

The method of using the silanol condensation catalyst is as follows.
In many cases, a silanol condensation catalyst prepared in advance when molding a mixture comprising a silane-grafted ethylene-α-olefin copolymer, polypropylene, and a metal salt of acrylic acid or methacrylic acid into a desired shape. Is used. In this case, the amount of the silanol condensation catalyst to be added is in the range of 0.01 to 0.1 part by weight based on 100 parts by weight of the ethylene-α-olefin copolymer from the viewpoint of balancing physical properties and processability. It is usually set to.

In the present invention, the reaction of grafting the organosilane compound to the ethylene-α-olefin copolymer is often carried out in a kneading facility such as a kneader or Banbury, or a molding facility such as an extruder. Will be It is possible to add other components such as antioxidants, stabilizers, colorants, plasticizers or lubricants to the composition.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of a cross-linked molded article and a method for producing the same according to the present invention will be described. Table 1 summarizes the contents of Examples and Comparative Examples of the present invention and the results of these Examples.

[0022]

[Table 1]

First, the implementation procedure is shown below for each step. (1) Blending Step Among the components shown in Examples and Comparative Examples in Table 1, dicumyl peroxide, zinc methacrylate, 2-thio-diethylenebis [3- (3,5-di-t-butyl-4) are used. -Hydroxyphenyl) propionate] (antioxidant),
4,4'-thiobis (6-t-butyl-3-methylphenol) (antioxidant) and black color batch (mixture of 94% by weight of polyethylene and 6% by weight of carbon black) dissolved in vinyltrimethoxysilane After preparing a mixed solution of vinylsilane by mixing, the mixed solution is added to a dry blend of an ethylene-propylene copolymer having a propylene content of 27% by weight and a polypropylene having an ethylene content of 3% by weight, and thoroughly mixed. As a result, a predetermined mixture in each of Examples and Comparative Examples was prepared.

(2) Silane Grafting Step The blend prepared in the above (1) is charged into a twin-screw extruder, and a silane grafting reaction is caused while melt-kneading, whereby a graft polymer for each Example and Comparative Example is obtained. Was prepared. The temperature conditions of the extruder are 160 ° C. for cylinder 1, 220 ° C. for cylinder 2, 220 ° C. for cylinder 3, and 200 ° C. for the head.

(3) Catalyst master batch preparation step One part by weight of dibutyltin dilaurate is added to 100 parts by weight of the ethylene-propylene copolymer in the mixing vessel, mixed and absorbed, and then melted in the same manner as in (2) above. A predetermined catalyst master batch was prepared by kneading.

(4) Sheet molding step After the catalyst master batch of (3) is mixed with the graft polymer obtained in the above (2) at the blending ratio shown in Table 1, this is mixed into a sheet by an extruder equipped with a T die. A sheet having a thickness of 2 mm was produced by extruding into a shape and subsequently rolling by two rolls continuously arranged on a T-die. The temperature condition of the extruder is the same as the above (2).

(5) Crosslinking Step The sheet obtained in the above (4) was allowed to stand in a moist heat at 80 ° C. for 16 hours, thereby producing a sheet-like crosslinked molded article of each of Examples and Comparative Examples.

The test method for each characteristic shown in Table 1 is as follows. ◇ Tensile strength, elongation: JIS K 6251 裂 Tear strength: JIS K 6252 ◇ Hardness: JIS K 6253 ◇ Compression set: JIS K 6262

According to Table 1, both Examples 1 and 2 have excellent tear strength and tensile strength, have an appropriate hardness level, and have sufficient rubber based on good compression set. It is recognized that it has the characteristic nature. On the other hand, when considering Comparative Examples, Comparative Example 1 has insufficient tensile strength and tear strength due to a small amount of polypropylene, and Comparative Example 2 has a low hardness due to an excessive amount of polypropylene. In addition to the increase, the compression set characteristic is insufficient.

Further, in the case of Comparative Examples 3 and 4,
Even if zinc methacrylate is not present or is present, the effect of improving the tear strength is not obtained due to the small amount, and the tensile strength tends to be insufficient. In the case of Comparative Example 5, the amount of methacrylic acid is low. Due to the excess, the compression set characteristics are lowered. When the Examples and Comparative Examples are compared, the significance of the existence of the metal methacrylate salt in the present invention is clear by comparing Example and Comparative Example 3 (and Comparative Example 4).

In practicing the present invention, as shown in the results of the other comparative examples, consideration should be given to the amount of each component. In the above embodiment, an example in which zinc methacrylate is blended has been described, but the same applies when using another metal methacrylate, or when using a metal acrylate instead of the metal methacrylate. Needless to say, an effect can be obtained.

[0032]

As described above, according to the crosslinked molded article and the method for producing the same according to the present invention, a silane-grafted ethylene-α-olefin copolymer, polypropylene, and a metal salt of acrylic acid or methacrylic acid are used. In order to obtain a cross-linked molded article by exposing the composition containing to water in the presence of a silanol condensation catalyst, a cross-linked molded article having low hardness and good rubbery properties, and having excellent tear strength and tensile strength is obtained. Can be provided. This greatly contributes to the improvement of the performance of the silane water crosslinked product.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Keiichi Kato 1-1-1 Koriyama, Taishiro-ku, Sendai-shi, Miyagi F-term in Tohoku Rubber Co., Ltd. (Reference) 4F071 AA14X AA15X AA20 AA32 AA32X AA77 AE09 AG05 BA09 BB06 BC01 4F073 AA05 BA07 BA08 BA09 BA10 EA11 EA59 EA71 4J026 AA12 AA13 AA14 AC01 AC15 AC18 BA25 BA43 BB03 DB05 DB15 DB24 EA08 GA06 GA08

Claims (5)

[Claims] 1. A molded product of a composition containing a silane-grafted ethylene-α-olefin copolymer, polypropylene, and a metal salt of acrylic acid or methacrylic acid, wherein the molded product is a silanol condensation catalyst. A crosslinked molded article which is crosslinked by exposure to moisture in the presence. 2. The composition according to claim 1, wherein the ethylene-α-olefin copolymer and the polypropylene are mixed in a proportion of 70 to 8;
2. The crosslinked molded article according to claim 1, wherein the weight ratio of the latter to 5 is 30 to 15. 3. The polypropylene according to claim 2, wherein the ethylene component is 2%.
The cross-linked molded article according to claim 1, wherein the content of the cross-linked molded article is from 9 to 9% by weight. 4. The metal salt of acrylic acid or methacrylic acid is used in an amount of 0.1 to 100 parts by weight of the total amount of the ethylene-α-olefin copolymer and the polypropylene.
2. The composition according to claim 1, wherein 5 to 3 parts by weight are mixed.
The crosslinked molded article according to the above item. 5. A composition comprising a mixture of an ethylene-α-olefin copolymer, an organic silane compound, polypropylene, and a metal salt of acrylic acid or methacrylic acid, which is subjected to a graft reaction in the presence of a free radical generator. A method for producing a crosslinked molded article, comprising: molding the obtained reactant into a molded article having a predetermined shape; and exposing the molded article to moisture in the presence of a silanol condensation catalyst.