JPH04309545A - Cross-linkable polypropylene composition and method for cross-linking - Google Patents

Abstract

PURPOSE:To prepare the title compsn. which has a low volatile content, is cross-linked at a high cross-linking efficiency, and is highly safe by compounding polypropylene with a specific difunctional peroxymonocarbonate and a silane compd. CONSTITUTION:The title compsn. comprises 60-98 pts.wt. polypropylene, 1-20 pts.wt difunctional peroxymonocarbonate of formula I (wherein R<1> and R<2> are each 1-5C alkyl, cyclohexyl, or cyclohexyl substd. by a 1-4C or lower alkyl; and(n)is 4-8), and 1-20 pts.wt. silane compd. of formula II (wherein R<3> is vinyl, acryloxy, or methacryloxy; Y is a hydrolyzable monovalent org. group; and R<4> is R<3> or Y). 100 pts. wt. mixture consisting of the compsn. and polypropylene is mixed with 0.5-1 pt.wt. difunctional peroxymonocarbonate and 0.5-3 pts.wt. silane compd., and the resulting mixture is allowed to undergo grafting and is brought into contact with water in the presence of a silanol condensation catalyst to cross-link.

Description

[Detailed description of the invention]

0001

FIELD OF THE INVENTION The present invention relates to a composition for crosslinking polypropylene and a crosslinking method. Specifically, the present invention relates to a polypropylene crosslinking composition comprising polypropylene, a specific bifunctional peroxymonocarbonate, and a silane compound, and a polypropylene crosslinking method using the composition.

0002

BACKGROUND OF THE INVENTION Conventionally, polypropylene has tertiary hydrogen in its molecule, so even if an attempt is made to cross-link it with a radical generator such as an organic peroxide, the molecular chain collapses and a cross-linked product cannot be obtained. Methods have been reported in which various additives are added for the purpose of crosslinking polypropylene. For example, in Japanese Patent Application Laid-open No. 160852 of 1992, the temperature at which the half-life is 1 minute is 1
A method using an organic peroxide and a silane compound at 55 to 170°C is disclosed, and preferred examples of the organic peroxide include t-butylperoxyisopropyl monocarbonate and 2,2-bis(t-butylperoxy)butane. ing.

0003

[Problems to be Solved by the Invention] However, these organic peroxides have a small molecular weight and are volatilized during blending or crosslinking, resulting in a problem that the original crosslinking efficiency cannot be obtained. Moreover, this volatility causes a bad odor during compounding or crosslinking. Furthermore, since organic peroxides are generally flammable, there is a risk that volatilized organic peroxide vapor may ignite during work, causing decomposition and fire.

[0004] Furthermore, since the amount of organic peroxide added is small when crosslinking polypropylene, a polypropylene masterbatch containing a high concentration of organic peroxide is strongly required in order to uniformly disperse it in polypropylene. Organic peroxides with a high carbon content have the disadvantage that they volatilize during blending and storage, making it impossible to obtain the desired crosslinked product. The object of the present invention is to provide a polypropylene crosslinking composition that has low volatility, high activity per unit, does not volatilize during storage, high crosslinking efficiency during crosslinking, and high safety, and crosslinking using the composition. The purpose is to provide a method.

[0005]

[Means for Solving the Problems] As a result of various studies to solve the above object, the present inventors confirmed that the object can be achieved by using a specific bifunctional peroxymonocarbonate in polypropylene, and the present invention has been completed. completed.

That is, the first aspect of the present invention is polypropylene 6
0 to 98 parts by weight, general formula (wherein R1 or R2 represents a cyclohexyl group substituted with an alkyl group having 1 to 5 carbon atoms, a cyclohexyl group, or an alkyl group having 4 or less carbon atoms, and n is 4 to 8 ) Difunctional peroxymonocarbonates 1 to 2 represented by
0 parts by weight

and represented by the general formula R3R4SiY2 (wherein R3 is a vinyl group, acryloxy group or methacryloxy group, Y is a hydrolyzable monovalent organic group, and R4 is the same group as R3 or the same group as Y). The second aspect of the present invention is a polypropylene crosslinking composition comprising 1 to 20 parts by weight of a silane compound, and the second aspect of the present invention is a mixture of the composition and polypropylene, in which 0.05 parts by weight of a difunctional peroxymonocarbonate is added to 100 parts by weight of the mixture.
~1 part by weight and a silane compound in an amount of 0.5 to 3 parts by weight to cause a graft reaction, and then the resulting grafted product is crosslinked by reacting with water in the presence of a silanol catalyst. The present invention relates to a method for crosslinking polypropylene.

The polypropylene used in the present invention is, for example, homopolypropylene, a copolymer of propylene and an α-olefin such as ethylene or butene-1, and can be used alone or in combination. Further, synthetic rubber such as ethylene/propylene/non-conjugated diene copolymer rubber may be mixed and used as required.

Specific bifunctional peroxymonocarbonates represented by the above general formula used in the present invention include, for example, 1,6-bis(t-butylperoxycarboxy)butane, 1,6-bis(t-butylperoxycarboxy)
Hexane, 1,6-bis(t-hexylperoxycarboxy)hexane, 1,6-bis(t-octylperoxycarboxy)hexane, 1,6-bis(2-cyclohexylisopropylperoxycarboxy)hexane, 1,6-bis(t-butyl) Among them, 1,6-bis(t-butylperoxycarboxy)hexane is particularly preferred in terms of efficiency.

In the composition of the present invention, the content of the specific difunctional peroxymonocarbonate is 1 to 20 parts by weight. If it is less than 1 part by weight, the effect as a masterbatch will be small, and if it exceeds 20 parts by weight, the uniformity of the composition will be impaired.

Examples of the silane compound represented by the above general formula used in the present invention include vinyltris(β-methoxyethoxy)silane, vinyltriethoxysilane, vinyltrimethoxysilane, and γ-methacryloxypropyltrimethoxysilane. In the composition of the present invention, the content of the silane compound is 1 to 20 parts by weight. The composition of the present invention can be produced in a conventional kneader such as a Banbury mixer, a Henschel mixer, or a kneader under controlled conditions at low temperatures.

The above composition is mixed with polypropylene during crosslinking, and the proportion of the difunctional peroxymonocarbonate is 0.0 parts by weight per 100 parts by weight of the mixture.
They are mixed in an amount of 5 to 1 part by weight. If the amount of the bifunctional peroxymonocarbonate is less than 0.05 part by weight, the graft reaction will not proceed sufficiently, and if it exceeds 1 part by weight, the polypropylene disintegration reaction will be more dominant than the graft reaction.

Further, in the mixture of the composition of the present invention and polypropylene, the amount of the silane compound is 0.5 to 3 parts by weight based on 100 parts by weight of the mixture. If it is less than 0.5 parts by weight, the graft reaction will not proceed sufficiently, and if it exceeds 3 parts by weight, the performance will not change, which is not economically preferable. The grafting reaction of the present invention is carried out in a single-screw or multi-screw extruder at 160° C.
Performed at ~200°C.

The crosslinking reaction of the present invention is carried out by bringing the silane-treated grafted product into contact with moisture in the presence of a silanol condensation catalyst. As the silanol condensation catalyst for promoting crosslinking of the grafted product, compounds commonly used as silanol catalysts, such as dibutyltin dilaurate and dibutyltin dioctoate, can be used.

In addition to the specific bifunctional peroxymonocarbonate and silane compound, the polypropylene crosslinking resin composition of the present invention contains various commonly used fillers, reinforcing agents, plasticizers, processing aids, pigments, and flame retardants. A curing agent and the like can be added as necessary.

[0016]

EXAMPLES Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples. Examples: The number in the middle represents parts by weight. The evaluation method used in Examples and Comparative Examples was as follows. Crosslinking rate: The obtained sheet was placed in a 100 mesh wire gauze and extracted in boiling m-xylene for 6 hours, and the ratio of the weight of the extracted residue to the weight before extraction was defined as the crosslinking rate.

(Example 1) MFR (amount of molten resin discharged in 10 minutes when a load of 2.16 kg is applied at 230°C) 1.0 g/100 parts by weight of homopolypropylene for 10 minutes was added with 1,6-bis(t -butylperoxycarboxy)hexane and γ-methacryloxypropyltrimethoxysilane were blended in the proportions shown in Table 1, and then mixed in a Henschel mixer at room temperature and 250 rpm for 3 minutes to obtain 100 kg of a polypropylene crosslinking composition. (Example 2) The procedure of Example 1 was repeated except that 1,6-bis(t-butylperoxycarboxy)hexane and γ-methacryloxypropyltrimethoxysilane were changed to the proportions shown in Table 1. 100 kg of a crosslinking composition was obtained.

(Example 3) Same as Example 1 except that 1,6-bis(t-hexylperoxycarboxy)hexane was used instead of 1,6-bis(t-butylperoxycarboxy)hexane. 100 kg of a propylene crosslinking composition was obtained. (Example 4) In Example 1, 1,6-bis(t-butylperoxycarboxy)hexane was replaced with 1,6-bis(t-butylperoxycarboxy)hexane.
100 kg of a polypropylene crosslinking composition was obtained in the same manner as in Example 1 except that -bis(2-cyclohexylisopropylperoxycarboxy)hexane was used.

(Comparative Example 1) A polypropylene crosslinking composition was prepared in the same manner as in Example 1, except that t-butylperoxyisopropyl monocarbonate was used instead of 1,6-bis(t-butylperoxycarboxy)hexane. Obtained 100Kg. (Comparative Example 2) In Example 1, instead of 1,6-bis(t-butylperoxycarboxy)hexane, 2,5
-bis(isopropyloxycarbonolperoxy)2
, 100 kg of a polypropylene crosslinking composition was obtained in the same manner as in Example 1, except that 5-dimethylhexane was used.

[0020]

[Table 1]

(Example 5) A mixture of 100 parts of the polypropylene crosslinking composition obtained in Example 1 and 900 parts of the homopolypropylene used in Example 1 was melted at 200°C in a single screw extruder with a diameter of 40 mm. Processing yielded grafted pellets. Next, 90 parts of the grafted pellets, 10 parts of a mixture of 100 parts of homopolypropylene and 1 part of dibutyltin laurate were mixed in a 40 mm diameter extruder equipped with a T-die for 2 hours.
Sheeting was performed at 50° C. to obtain a sheet with a thickness of 0.25 mm. This sheet was crosslinked by immersing it in boiling water for 30 minutes, and the crosslinking rate was measured according to the method described above. The results are shown in Table 2.

(Example 6) In Example 5, Example 1
Crosslinking was carried out according to Example 5, except that the crosslinking composition of Example 2 was used instead of the polypropylene crosslinking composition of
The crosslinking rate is shown in Table 2. (Example 7) Crosslinking was carried out in the same manner as in Example 5, except that the crosslinking composition of Example 3 was used instead of the polypropylene crosslinking composition of Example 1, and the crosslinking ratio was determined in Table 2.
It was shown to. (Example 8) Crosslinking was carried out in the same manner as in Example 5, except that the crosslinking composition of Example 4 was used instead of the polypropylene crosslinking composition of Example 1, and the crosslinking ratio was determined in Table 2.
It was shown to.

(Comparative Example 3) In Example 5, Example 1
Crosslinking was carried out according to Example 5, except that the crosslinking composition of Comparative Example 1 was used instead of the polypropylene crosslinking composition of
The crosslinking rate is shown in Table 2. (Comparative Example 4) Crosslinking was carried out in the same manner as in Example 5, except that the crosslinking composition of Comparative Example 2 was used instead of the polypropylene crosslinking composition of Example 1, and the crosslinking ratio was determined in Table 2.
It was shown to.

[0024]

[Table 2]

From Table 2, it was confirmed that the polypropylene crosslinking composition and crosslinking method of the present invention exhibited a high crosslinking rate. (Example 9) 78 parts of homopolypropylene, 20 parts of 1,6-bis(t-butylperoxycarboxy)hexane, and 2 parts of γ-methacryloxypropyltrimethoxysilane were mixed in a Henschel mixer at room temperature and 250 rpm for 3 minutes to cross-link polypropylene. 100 kg of the composition for use was obtained. Next, 100g of this is 20cm in diameter and 1.5cm deep.
After uniformly dispersing the mixture in a cm Petri dish, the mixture was left open in a constant temperature bath at 30° C. for 30 days, and the weight loss rate was measured compared to that immediately after mixing. The results are shown in Table 3.

(Comparative Example 5) The weight loss rate was determined in the same manner as in Example 9, except that t-butylperoxyisopropyl monocarbonate was used instead of 1,6-bis(t-butylperoxycarboxy)hexane. The results are shown in Table 3. (Reference Example 1) In Example 9, homopolypropylene 9
The weight loss rate was measured according to Example 1, except that 8 parts of γ-methacryloxypropyltrimethoxysilane and 2 parts of γ-methacryloxypropyltrimethoxysilane were used, and 1,6-bis(t-butylperoxycarboxy)hexane was not used. It is shown in Table 3.

[0027]

From Table 3, it was confirmed that the polypropylene crosslinking composition of the present invention showed almost no weight loss and had low volatility. This means that the risk of ignition, decomposition, and fire caused by volatilized peroxide vapor during mixing, storage, and crosslinking can be significantly reduced.

[0029]

[Effects of the Invention] The specific bifunctional peroxymonocarbonate of the present invention has a large molecular weight and is difunctional, so
It is characterized by low volatility and high activity per unit. Therefore, in a composition blended with polypropylene and a silane compound, there is no concern that it will volatilize during storage, and since volatility is low even during crosslinking, it has high crosslinking efficiency and low odor, and furthermore, volatilized peroxide It has the characteristic of greatly reducing the risk of ignition, decomposition, and fire caused by steam.

Claims (2)

[Claims] Claim 1: 60 to 98 parts by weight of polypropylene General formula (wherein R1 or R2 represents an alkyl group having 1 to 5 carbon atoms, a cyclohexyl group, or a cyclohexyl group substituted with an alkyl group having 4 or less carbon atoms, and n is 4-8) Bifunctional peroxymonocarbonates 1-8
20 parts by weight and the general formula R3R4SiY2 (wherein R3 is a vinyl group, acryloxy group or methacryloxy group, Y is a hydrolyzable monovalent organic group, R4 is R
A polypropylene crosslinking composition comprising 1 to 20 parts by weight of a silane compound represented by the same group as 3 or the same group as Y. 2. In the mixture of the composition of claim 1 and polypropylene, the bifunctional peroxymonocarbonate is 0.05 to 1 part by weight and the silane compound is 0.5 to 3 parts by weight based on 100 parts by weight of the mixture. 1. A method for crosslinking polypropylene, which comprises mixing the mixture to cause a graft reaction, and then bringing the obtained grafted product into contact with water in the presence of a silanol condensation catalyst for crosslinking.