JPH1180281A - Composition and method for crosslinking ethylene polymer and polymer composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a composition which has high scorch preventing effect and can give a molding having a high degree of crosslinking by mixing an organic peroxide with a piperidine derivative having a specified structure. SOLUTION: The ethylene polymer (A) to be crosslinked is polyethylene or the like. The organic peroxide (B) used is dicumyl peroxide or the like. The piperidine derivative used is represented by the formula (wherein R is H, a 1-8C alkyl, an alkoxyl or acetyl; n is 1-4; and X is (meth)acryloyloxy, 3-dodecyl-2,5-dionepyrrolidino or a 1-10C acyloxy when n is 1, is a 1-10C alkylenedicarboxyl when n is 2, is 1,2,3-propanetricarboxyl when n is 3, and is 1,2,3,4-butanetetracarboxyl when n is 4). It is desirable that 0.3-5 pts.wt. component B and 0.1-2 pts.wt. component C are used per 100 pts.wt. component A and that the ratio B:C is 1:0.02 to 1:1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composition and a method for crosslinking an ethylene-based polymer which can prevent scorch and improve the degree of crosslinking when heating and crosslinking the ethylene-based polymer. The present invention relates to a polymer composition containing a crosslinking composition as a main component. The crosslinked polyethylene-based polymer obtained here is useful as an insulating material for power cables.

[0002]

2. Description of the Related Art Conventionally, in the case of producing a crosslinked ethylene polymer molded article using an organic peroxide as a crosslinking agent, a scorch inhibitor is added to suppress occurrence of scorch (early crosslinking and burning) during molding. It is known. For example, α-methylstyrene dimer (JP-A-4-218546) or diisopropenylbenzene (JP-A-9-178944) is known as a scorch inhibitor.

[0003]

However, although the above scorch inhibitors have some degree of effect, they are not yet satisfactory. In recent years, there has been a demand for an improvement in productivity of crosslinked ethylene-based polymer molded articles, and specifically, an improvement in workability by preventing scorch. An object of the present invention is to provide a crosslinking composition, a crosslinking method, and a polymer composition of an ethylene-based polymer having a high scorch prevention effect and a high degree of crosslinking of a molded article.

[0004]

Means for Solving the Problems The present inventors have studied the above-mentioned problems of the conventional method for a long time, and as a result, have found a specific scorch inhibitor and completed the present invention. That is, the first invention relates to an organic peroxide and the following general formula (1)

Embedded image (Wherein, R represents hydrogen, an alkyl group or an alkoxy group having 1 to 8 carbon atoms, or an acetyl group. N is an integer of 1 to 4; when n is 1, X is an acryloyloxy group;
A methacryloyloxy group, a 3-dodecyl-2,5-dione-pyrrolidino group, an acyloxy group having 1 to 10 carbon atoms, and when n is 2, X is an alkylenedicarboxyl group having 1 to 10 carbon atoms, and n is 3 In the formula, X is 1,2,3-propanetricarboxyl group, and when n is 4, X is 1,
Represents a 2,3,4-butanetetracarboxyl group. And a compound for crosslinking an ethylene-based polymer.

[0005] A second invention is a method for crosslinking an ethylene polymer, which comprises mixing and heating the ethylene polymer and the crosslinking composition of the first invention. The third invention is a polymer composition containing an ethylene-based polymer and the crosslinking composition of the first invention as main components.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, specific examples of the compound represented by the general formula (1) are those having n = 1, for example, 4-
Methacryloyloxy-2,2,6,6-tetramethylpiperidine, N-methyl-4-methacryloyloxy-
2,2,6,6-tetramethylpiperidine, 3-dodecyl-1- (2,2,6,6-tetramethyl-4-piperidinyl) pyrrolidine-2,5-dione, 3-dodecyl-
1- (N-methyl-2,2,6,6-tetramethyl-4
-Piperidinyl) pyrrolidine-2,5-dione, 1-
(N-acetyl-2,2,6,6-tetramethyl-4-
Piperidinyl) -3-dodecyl-pyrrolidine-2,5-
Dione and n = 2 is, for example, bis (2,2,6,6-tetramethyl-4-piperidinyl)
Sebacate, bis (N-methyl-2,2,6,6-tetramethyl-4-piperidinyl) sebacate, bis (N-
Octyloxy-2,2,6,6-tetramethyl-4-
Piperidinyl) sebacate; and n = 3, for example, tris (2,2,6,6-tetramethyl-4-piperidinyl) 1,2,3-propanetricarboxylate; Those having n = 4 include, for example, tetrakis (2,2,6,6-tetramethyl-4-
Piperidinyl) 1,2,3,4-butanetetracarboxylate, tetrakis (N-methyl-2,2,6,6-
Tetramethyl-4-piperidinyl) 1,2,3,4-butanetetracarboxylate. Among these, 4-methacryloyloxy-2,2,6,6-tetramethylpiperidine and N-methyl-4-methacryloyloxy-2,2,6,6-tetramethylpiperidine have a large effect of preventing scorch, and It is preferable because the degree of crosslinking of the molded article is high.

Specific examples of the organic peroxide used in the present invention include dicumyl peroxide, t-butylcumyl peroxide, and 2,5-bis (t-butylperoxy).
-2,5-dimethylhexane, 2,5-bis (t-butylperoxy) -2,5-dimethylhexyne-3, di-
Dialkyl peroxides such as t-butyl peroxide, isopropylcumyl-t-butyl peroxide, bis (α-t-butylperoxyisopropyl) benzene, 1,1-bis (t-butylperoxy) cyclohexane, 1,1-bis ( t-butylperoxy)-
3,3,5-trimethylcyclohexane, 1,1-bis (t-butylperoxy) cyclododecane, n-butyl-4,4-bis (t-butylperoxy) valerate,
Ethyl-3,3-bis (t-butylperoxy) butyrate, 3,3,6,6,9,9-hexamethyl-1,
Examples include peroxyketals such as 2,4,5, -tetraoxycyclononane, and peroxyesters such as bis (t-butylperoxy) isophthalate, t-butylperoxybenzoate, and t-butylperoxyacetate.

[0008] Among these organic peroxides, dicumyl peroxide and bis (α-t-butylperoxyisopropyl) benzene are compatible with a compound of the general formula (1) to achieve both high degree of crosslinking and prevention of scorch. It is particularly preferable because it is possible.

The ethylene polymer used in the present invention includes, for example, polyethylene, ethylene propylene copolymer (EPR), ethylene butene copolymer, ethylene pentene copolymer, ethylene vinyl acetate copolymer (EVA), ethylene propylene diene copolymer (E
PDM), chlorinated polyethylene, ethylene ethyl acrylate copolymer (EEA), ethylene methyl methacrylate copolymer, ethylene glycidyl methacrylate copolymer (EGMA), ethylene acrylonitrile copolymer, and the like. Among them, polyethylene, ethylene propylene copolymer, ethylene vinyl acetate copolymer, ethylene ethyl acrylate copolymer, and ethylene glycidyl methacrylate copolymer have excellent effects of improving the degree of crosslinking.

In the present invention, the compounding ratio of the organic peroxide and the compound of the general formula (1) is usually 1: 0.0 by weight.
2-1: 1 is used. If the compounding ratio of the compound of the general formula (1) to the organic peroxide is less than 1: 0.02, the effect of suppressing scorch is not sufficient, and if it is more than 1: 1, the degree of crosslinking tends to decrease, which is not preferable. . A particularly preferred range is 1: 0.1 to 1: 0.5.

In crosslinking, the amount of the organic peroxide is usually 0.1 to 100 parts by weight of the ethylene polymer.
It is 3 to 5 parts by weight, preferably 1 to 3 parts by weight. At this time, if the amount of the organic peroxide is less than 0.3 parts by weight, the effect of improving the degree of crosslinking is not sufficient, and if it exceeds 5 parts by weight, the degree of crosslinking tends to be too high to be brittle. The compounding amount of the compound represented by the general formula (1) is usually 0.1 to 2 parts by weight, preferably 0.2 to 1 part by weight, based on 100 parts by weight of the ethylene-based polymer. At this time, the general formula (1)
If the compound represented by the formula (1) is less than 0.1 part by weight, the effect of preventing scorch is not sufficient, and if it exceeds 2 parts by weight, the effect does not increase so much and the degree of crosslinking tends to decrease.

When crosslinking the ethylene polymer using the crosslinking composition or the polymer composition of the present invention, various additives generally used in the crosslinking process, such as antioxidants, pigments, and ultraviolet stabilizers , A filler, a plasticizer, a lubricant, a crosslinking aid, and the like can be appropriately added.

For example, antioxidants include 4,4'-
Thiobis (3-methyl-6-t-butylphenol),
2,5-di-t-butylhydroquinone, 2,6-di-t
Phenol compounds such as -butyl-p-cresol, phosphorus compounds, and bis (2-methyl-4- (3-n-
Alkylthiopropionyloxy) -5-t-butylphenyl) sulfide, 2,2′-thiodiethylenebis (3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate), dilaurylthiopropionate And sulfur-based compounds such as distearylthiopropionate. The compounding amount of these antioxidants is usually 0.05 to 100 parts by weight of the ethylene polymer.
One part by weight is used. Although the antioxidant originally has a function of suppressing the crosslinking reaction, the crosslinking composition of the ethylene-based polymer of the present invention can achieve the effect of preventing scorch even in the presence of these.

In the present invention, the crosslinking temperature of the composition for crosslinking an ethylene polymer is generally 110 to 220 ° C., and preferably 130 to 200 ° C. in order to obtain an appropriate crosslinking time.

[0015]

The present invention will be described below in more detail with reference to examples and comparative examples. Abbreviations of organic peroxides and additives mean the following compounds. DCP: dicumyl peroxide (trade name, manufactured by NOF Corporation)
MTEMP: 4-methacryloyloxy-2,2,6
6-tetramethylpiperidine MMTEMP: N-methyl-4-methacryloyloxy-2,2,6,6-tetramethylpiperidine

Example 1 12.5 g of DCP and 2.5 g of MTEMP were mixed to obtain a composition for crosslinking an ethylene polymer. Low density polyethylene (manufactured by Nippon Unicar Co., Ltd., trade name: NUC-902)
5) 500 g and the composition for crosslinking were kneaded at about 110 ° C. for about 20 minutes using a heating roll. The obtained polymer composition was uniform, and no abnormality was observed in the surface state. It was subjected to a heating test with a curast meter (manufactured by Toyo Baldwin Co., Ltd., Model JSR Curast Meter III), and the maximum torque value was measured at 180 ° C. Separately, the scorch time was measured at 145 ° C. The scorch time A was a time that increased from the minimum value to 10% of the maximum torque value at 180 ° C. (this value indicates a measure of the processing time of the resin in molding). The scorch time B was the time required for the torque value to reach 0.4 kgf · cm (this value indicates the time at which the resin substantially started to crosslink). The results are shown in Table 1.

[0017]

[Table 1]

Example 2 The procedure of Example 1 was repeated, except that the amount of MTEMP added was changed. The results are shown in Table 1.

Embodiments 3 and 4 In Embodiments 1 and 2, MM was used instead of MTEMP.
The operation was performed in the same manner as in Example 1 except that TEMP was used. The results are shown in Table 1.

Comparative Example 1 Example 1 was repeated except that MTEMP was not used.
The operation was performed according to The results are shown in Table 1.

Comparative Example 2 The procedure of Example 1 was repeated, except that α-methylstyrene dimer (described as SD in the table) was used instead of MTEMP. The results are shown in Table 1.
From the results shown in Table 1, in the crosslinking method of the present invention, the scorch time is long, and in particular, the time for substantially starting the crosslinking in the scorch time B is long. This indicates that the resin can be prevented from adhering to the molding machine during the molding process.

[0022]

The composition for crosslinking an ethylene-based polymer of the present invention can be transported and stored in a state of being mixed with the ethylene-based polymer. Such use simplifies the crosslinking operation. The method for crosslinking an ethylene-based polymer using the composition for crosslinking an ethylene-based polymer of the present invention includes:
It has the following features. That is, in crosslinking,
The scorch time is longer than when cross-linking with the organic peroxide alone. Further, there is no possibility of causing a polymerization reaction during kneading. Further, the above effect can be obtained even in the presence of an antioxidant at the time of crosslinking. Further, the crosslinked ethylene-based polymer obtained by the present invention has a high degree of crosslinking (gel fraction) and good electrical properties, and thus is excellent as a covering material for power cables.

Claims (3)

[Claims] An organic peroxide and the following general formula (1): (Wherein, R represents hydrogen, an alkyl group or an alkoxy group having 1 to 8 carbon atoms, or an acetyl group. N is an integer of 1 to 4; when n is 1, X is an acryloyloxy group;
A methacryloyloxy group, a 3-dodecyl-2,5-dione-pyrrolidino group, an acyloxy group having 1 to 10 carbon atoms, and when n is 2, X is an alkylenedicarboxyl group having 1 to 10 carbon atoms, and n is 3 In the formula, X is 1,2,3-propanetricarboxyl group, and when n is 4, X is 1,
Represents a 2,3,4-butanetetracarboxyl group. And a compound for crosslinking an ethylene-based polymer. 2. A method for crosslinking an ethylene-based polymer, comprising mixing and heating an ethylene-based polymer and the crosslinking composition according to claim 1. 3. A polymer composition comprising an ethylene-based polymer and the crosslinking composition according to claim 1 as main components.