JPH06116234A - Crosslinking agent for ethylenic polymer, method for crosslinking and electric power cable - Google Patents

Abstract

PURPOSE:To provide the crosslinking agent used for ethylenic polymers, reducing the generation of scorches, low in vapor pressure, not producing solid thermal decomposition products, and having a high crosslinking performance. CONSTITUTION:The compound of formula I[R1 is mono-trivalent 0-20C aliphatic or aromatic hydrocarbon group; X is C(O), C(O)(OCH2-CH(R2)m-OC(O) (R2 is H, methy; (m) is 1-10), OC(O), (O-CH2-CH(R3)n-OC(O) (R3 is H, methy; (n) is 1-10); (p) is 1-3], e.g. t-butyl (1,1-dimethyl-2-hydroxyethyl) peroxide (DAPO)/ lauroyl chloride condensation product of formula II. This compound of formula I is obtained by reacting the DAPO with an organic acid chloride or alcohol chloroformate in the presence of a base such as pyridine. This crosslinking agent is used in an amount of 0.5-7 pts.wt., preferably 1-5 pts.wt., per 100 pts.wt. of an ethylenic polymer, when the ethylenic polymer is crosslinked.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an ethylene-based polymer crosslinking agent capable of preventing scorch and improving the degree of crosslinking when the ethylene-based polymer is heated and crosslinked with the crosslinking agent. The present invention relates to a cross-linking method used and an electric power cable having an insulating layer obtained by cross-linking an ethylene polymer with the same cross-linking agent.

[0002]

2. Description of the Related Art Dicumyl peroxide (DCP), di-t-butyl peroxide (DBP), di-t-amyl peroxide (DAM), t-butyl cumyl peroxide (BC) have been used as crosslinking agents for conventional ethylene polymers.
P), bis (α-t-butylperoxyisopropyl)
Benzene (DIP), 2,5-bis (t-butylperoxy) -2,5-dimethylhexane (25B), 2,5
Dialkyl peroxides such as -bis (t-butylperoxy) -2,5-dimethylhexyne-3 (25YB) are known. Of these, DBP and 25YB are high temperature decomposition crosslinking agents.

It is also known to add an anti-scorch agent to suppress scorch (premature crosslinking, burning) during kneading before crosslinking. As a scorch inhibitor, for example, Japanese Patent Publication No. 47-36866 discloses a method of adding a phenolic compound. On the other hand, examples of the crosslinking agent which has a low vapor pressure and is liquid at room temperature include, for example, Japanese Patent Publication No. 2-31106, 25 to 10% by weight of bis (α-t-butylperoxyisopropyl) benzene and 75 to 90% by weight. Disclosed is an organic peroxide mixture consisting of 10% isopropyl cumyl-t-butyl peroxide. Further, JP-A-54-132644 discloses dicumyl peroxide substituted with an alkyl group.

A rubber / plastic insulated power cable (hereinafter simply referred to as "power cable") is usually a cable core provided with an inner semiconductive layer and an insulator layer on the outer periphery of a conductor, or an inner semiconductive layer, an insulator layer and It has a cable core provided with an outer semiconductive layer. Each of these layers is formed by extrusion-coating a resin composition based on a polyethylene-based resin containing a crosslinking agent onto the outer periphery of the conductor with an extruder and then heating to crosslink the base resin.

[0005]

Among the above-mentioned conventional cross-linking agents, DCP, BCP, DIP, 25
Each of the Bs has a problem that they are likely to cause scorch. Also DB
P, BCP, 25B and 25YB have a problem that they are easily volatilized in the process of blending and kneading with an ethylene polymer.
Further, DAM has a problem that it is easily volatilized and its degree of crosslinking is low. Further, 25YB has a problem that 2,5-dihydroxy-2,5-dimethylhexyne-3 is deposited as a solid as a thermal decomposition product thereof and remains as a foreign substance in the crosslinked product. Further, the addition of the scorch inhibitor complicates the work, and the scorch preventing effect is not sufficient. Further Japanese Examined Fairness 2-31
The crosslinking agents disclosed in Japanese Patent Laid-Open No. 106 and Japanese Patent Laid-Open No. 54-132644 have a problem that scorch is likely to occur.

Further, conventionally, when a power cable having an insulating layer or a semiconductor layer of a crosslinked ethylene-based polymer is manufactured, and when the power cable is connected, a scorch phenomenon or a foreign substance is often generated in those layers. It was These reduce the reliability of the power cable. Particularly in recent years, with the increase in voltage, high density polyethylene having a high softening temperature has come to be used, and the problem of scorch has become more serious. Therefore, there is no scorch, and the crosslinking performance is high,
There is a demand for a cross-linking agent for ethylene polymers that does not generate foreign matter.

[0007]

Means for Solving the Problems As a result of a long-term study for the purpose of developing a cross-linking agent for an ethylene-based polymer satisfying the above-mentioned needs, the present inventors have found that the scorch is small,
The present invention has been completed by finding a cross-linking agent for ethylene polymers having a low vapor pressure, no generation of solid thermal decomposition products, and high cross-linking performance. The present invention has the general formula

[Chemical 4] The present invention relates to a cross-linking agent for an ethylene-based polymer, which is a compound represented by Furthermore, the present invention provides the general formula

[Chemical 5] The present invention relates to a method for crosslinking an ethylene-based polymer, which comprises using the compound represented by Furthermore, the present invention provides an ethylene-based polymer having the general formula

[Chemical 6] The invention relates to a power cable having an insulating layer obtained by crosslinking the compound represented by the formula (1) as a crosslinking agent.

In the present invention, the compound represented by the general formula (Formula 1) is, for example, t-butyl (1,1-dimethyl-2-hydroxyethyl) peroxide (DAPO).

[Chemical 7] A condensate of LAuroyl chloride (LA-PO),

[Chemical 8] Condensate of DAPO with acetic acid, propionic acid, butyric acid, hexanoic acid, octylic acid, decanoic acid, palmitic acid, acid chloride of stearic acid, condensate of DAPO with benzoyl chloride (BZ-PO),

[Chemical 9] Condensation product of DAPO with oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, succinic acid, acid chloride of dodecanedioic acid, DAPO with phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid A condensate with an acid chloride, a condensate with DAPO and hexyl chloroformate (HA-PO),

[Chemical 10] DAPO and butyl alcohol, octyl alcohol, decyl alcohol, undecyl alcohol, pentadecyl alcohol, ethylene glycol monomethyl ether,
Condensates of ethylene glycol monoethyl ether with chloroformate, DAPO with ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, butanediol, hexylene glycol with dichloroformate, etc. (Hereinafter, these are collectively referred to as "crosslinking agent of the present invention"). Most of the above-mentioned crosslinking agents of the present invention are compounds that are liquid at room temperature. Practically particularly preferred are BZ-PO and L.
It is A-PO.

The cross-linking agent of the present invention can be obtained by reacting DAPO with an acid chloride of an organic acid or a chloroformate of an alcohol in the presence of a base such as pyridine.

Examples of the ethylene polymer used in the present invention include low density polyethylene, high density polyethylene, ethylene propylene copolymer (EPR), ethylene butene copolymer, ethylene pentene copolymer, ethylene vinyl acetate copolymer (EVA), ethylene propylene diene. Copolymer (EPDM), chlorinated polyethylene, ethylene ethyl acrylate copolymer (EE
A), ethylene methyl methacrylate copolymer, ethylene glycidyl methacrylate copolymer (EGM
A), ethylene acrylonitrile copolymer and the like.

In cross-linking the ethylene-based polymer of the present invention, the cross-linking agent of the present invention is the ethylene-based polymer 100.
0.5 to 7 parts by weight, preferably 1 to 5 parts by weight is used with respect to parts by weight. If it is less than 0.5 parts by weight, the degree of crosslinking will be small, and if it is used in excess of 7 parts by weight, the degree of crosslinking will be too high and it will become brittle.

In the present invention, the cross-linking agent of the present invention may be used in combination with a peroxide which is conventionally known as a cross-linking agent. Examples of the peroxide that can be used in combination include isopropyl cumyl-t-butyl peroxide and D
CP, BCP, 25B, 25YB, DBP, DIP,
3,3,6,6,9,9-hexamethyl-1,2,4
Examples thereof include 5, -tetraoxycyclononane.

In the present invention, a crosslinking aid may be used in combination. As a crosslinking aid, 2,4-diphenyl-4
-Methyl-1-pentene (MSD), diisopropenylbenzene (DIB), ethylene glycol dimethacrylate, butylene glycol dimethacrylate, 1,3-
Butylene glycol dimethacrylate, trimethylolpropane trimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, polyethylene glycol dimethacrylate,
Pentaerythritol trimethacrylate, ethylene glycol diacrylate, butylene glycol diacrylate, 1,3-butylene glycol diacrylate,
Trimethylolpropane triacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, pentaerythritol triacrylate, triallyl cyanurate, triallyl isocyanurate, N,
Compounds such as N'-m-phenylene bismaleimide and polybutadiene can be mentioned.

In the present invention, various additives generally used in the cross-linking process, such as antioxidants, pigments, UV stabilizers, fillers, plasticizers and lubricants can be added. As the antioxidant, 4,4'-thiobis (3
-Methyl-6-t-butylphenol), 2,5-di-
t-butylhydroquinone, 2,6-di-t-butyl-p
-Phenol compounds such as cresol, phosphorus compounds or bis (2-methyl-4- (3-n-alkylthiopropionyloxy) -5-t-butylphenyl) sulfide, 2,2'-thiodiethylenebis- (3 -(3
Examples thereof include sulfur compounds such as 5-di-t-butyl-4-hydroxyphenyl) propionate), dilaurylthiopropionate and distearylthiopropionate. The blending amount of these antioxidants is usually 0.05 to 1.0 part by weight with respect to 100 parts by weight of the ethylene polymer.

In the present invention, the crosslinking temperature is generally 170.
-250 degreeC, Preferably 180-220 degreeC is used.

In the power cable of the present invention, at least one of its insulating layer and semiconductive layer is a resin obtained by crosslinking an ethylene polymer with the crosslinking agent of the present invention.

[0017]

The crosslinking agent of the present invention has the following features. That is, it has low volatility and, when used as a cross-linking agent for ethylene polymers, has high cross-linking efficiency and low scorch. Among the cross-linking agents of the present invention, those that are liquid at room temperature are easy to handle and there is no danger of contamination by foreign matter. Further, the electric power cable of the present invention has no scorch (burn) in the resin layer around the conductor, has a high degree of crosslinking (gel fraction), and does not generate a decomposition product harmful to electric characteristics, so that the electric characteristics ( Good AC breakdown strength). Since the degree of cross-linking is high as described above, a small amount of cross-linking agent (organic peroxide) is required to obtain the same degree of cross-linking, so gas generation due to the decomposition products of the cross-linking agent is reduced and the water tree is also reduced. You can

[0018]

EXAMPLES The present invention will be described in detail below with reference to examples and comparative examples. The abbreviations of the compounds used in the examples indicate the following compounds. BZ-PO: Condensate of DAPO and 2-benzoyl chloride (liquid, purity 97%) LA-PO: Condensate of DAPO and lauric acid chloride (liquid, purity 98%) AC-PO: DAPO and acetyl chloride Condensation product (liquid, purity 97%) AD-PO: Condensation product of DAPO and adipic acid chloride (liquid, purity 90%) IF-PO: Condensation product of DAPO and isophthalic acid chloride (melting point 61 ° C., purity 99) %) HA-PO: Condensate of DAPO and chloroformate of hexyl alcohol (liquid, purity 95%) EE-PO: Condensate of DAPO and chloroformate of ethylene glycol monoethyl ether (liquid, purity 92)
%) EG-PO: Condensation product of DAPO and ethylene glycol chloroformate (liquid, purity 87%) PE-PO: Condensation product of DAPO and polyethylene glycol (molecular weight 500) chloroformate (liquid, purity 89%) %) PG-PO: Condensate of DAPO and chloroformate of propylene glycol (liquid, purity 90%) OX-PO: Condensate of DAPO and oxalic acid chloride (liquid, purity 93%) DCP: Dicumyl peroxide (Nippon Oil & Fat, Perkmill D, melting point 39 ° C, purity 100%) DBP: Di-t-butyl peroxide (Nippon Oil & Fat, perbutyl D, liquid, purity 100%) TBP: 4,4'-thiobis (3-methyl) -6-t
-Butylphenol) MBS: Bis (2-methyl-4- (3-n-alkylthiopropionyloxy) -5-t-butylphenyl) sulfide TMP: Trimethylolpropane trimethacrylate TAIC: Triallyl isocyanurate DEG: Diethylene glycol dimethacrylate PB : Polybutadiene (molecular weight 2000) MSD: 2,4-diphenyl-4-methyl-1-pentene DAP: diallylphthalate DIB: m-diisopropenylbenzene

Example 1 Low density polyethylene (NUC-9, manufactured by Nippon Unicar Co., Ltd.)
025) 500 g and BZ-PO 20.6 as a crosslinking agent
g, and 1.0 g of TBP as an antioxidant were mixed to obtain a composition. This composition was kneaded using a heating roll at about 110 ° C. for about 20 minutes. The resulting kneaded product was subjected to a heating test with a curast meter (manufactured by Toyo Baldwin Co., Ltd .; JSR curast meter type III). The maximum torque value was measured at 180 ° C. Separately, the scorch time was measured at 155 ° C. The scorch time was 10% of the maximum torque value at 180 ° C., and the time from the minimum value was raised. The results are shown in Table 1. In Table 1, T90 is the time to reach 90% of the maximum torque value. Separately, 1000 g of the composition having the same composition as described above before kneading was put in a polyethylene bag having a thickness of 0.05 mm, sealed, and left at room temperature of about 15 ° C. for 30 days. Then, the composition was extracted with chloroform, and the reduction amount due to volatilization of the crosslinking agent was measured by gas chromatography.
The results are shown in Table 1 (the amount of volatilization is shown as a ratio to the added crosslinking agent).

Examples 2 to 13 and Comparative Examples 1 to 2 The procedure of Example 1 was repeated, except that the compounds shown in Table 1 were used instead of the crosslinking agent, the crosslinking aid and the antioxidant. . The results are shown in Table 1. From the comparison between Examples 1 to 13 and Comparative Example 1, it can be seen that the composition of the present invention has a higher degree of crosslinking and is less likely to cause scorch as compared with the composition using a conventional crosslinking agent. From the comparison between Examples 1 to 13 and Comparative Example 2, it can be seen that the composition of the present invention is less likely to volatilize than the conventional crosslinking agent having excellent scorch property.

[Table 1]

Example 14 In Example 1, instead of low density polyethylene, high density polyethylene (HDF60 manufactured by Ace Polymer Co., Ltd.) was used.
(80 V) 500 g, except that the same procedure as in Example 1 was performed. As a result, the scorch time was 12 minutes, the maximum torque value was 3.44 kgf · cm, and the T90 was 15 minutes.

Comparative Example 3 The procedure of Example 1 was repeated except that 7.3 g of DCP was used as the crosslinking agent in place of BZ-PO. As a result, the scorch time was 4 minutes, the maximum torque value was 3.73 kgf · cm, and the T904 was 4 minutes. From the comparison between Example 14 and Comparative Example 3, it can be seen that the composition of the present invention is less likely to cause scorch when using high-density polyethylene, as compared with the composition using a conventional crosslinking agent.

Example 15 Instead of the low density polyethylene in Example 1, an ethylene vinyl acetate copolymer manufactured by Tosoh Corporation (Ultrasen 6) was used.
25) The procedure of Example 1 was repeated except that 500 g was used. As a result, the scorch time was 12 minutes, the maximum torque value was 1.85 kgf · cm, and the T90 was 14 minutes.

Comparative Example 4 The procedure of Example 1 was repeated except that 7.3 g of DCP was used in place of BZ-PO as the crosslinking agent in Example 15. As a result, the scorch time was 4 minutes, the maximum torque value was 1.96 kgf · cm, and T904 was 4 minutes. From the comparison between Example 15 and Comparative Example 4, it is understood that the composition of the present invention is less likely to cause scorch even when the ethylene vinyl acetate copolymer is used, as compared with the composition using the conventional crosslinking agent.

Example 16 (Production of power cable) An inner semiconductive layer made of an ethylene vinyl acetate, acetylene black and BZ-PO (100/60 / 1.5 weight ratio) composition was formed on a conductor by using an extruder. Coated, then low density polyethylene, BZ-PO, TAIC and T
An insulating layer made of a BP (100/3 / 0.5 / 0.2 weight ratio) composition was extruded at 145 ° C. by using an extruder to cover it, and an inner semiconductive layer and an outer semiconductive layer having the same composition were coated. After extrusion coating, crosslink at 200 ° C for 10 minutes,
A 6 kV, 38 mm ² cross-linked polyethylene insulated power cable was manufactured. The AC breakdown voltage of the obtained power cable was 250 kV. Moreover, as a result of cutting out the cross-linked insulating portion and observing with a microscope, "burn" was not seen. Again 1
As a result of extracting the gel content for 5 hours in xylene at 30 ° C., the gel content was 91%.

Comparative Example 5 In Example 16, the insulating composition was replaced by low density polyethylene, DCP and TBP (100 instead of low density polyethylene, BZ-PO, TAIC and TBP compositions).
/2.5/0.2 weight ratio) was used and a power cable was manufactured and tested according to Example 8. The AC breakdown voltage of the obtained power cable was 200 kV. Moreover, "burning" was observed by observation with a microscope. As a result of extracting the gel content by extracting in xylene at 130 ° C. for 5 hours, the gel content was 88%. It can be seen from Example 16 and Comparative Example 5 that the power cable of the present invention has no scorch, has a high degree of cross-linking, and has improved electrical characteristics as compared with the conventional power cable.

Claims (3)

[Claims] 1. A general formula: An ethylene-based polymer cross-linking agent which is a compound represented by. 2. A general formula: A method for crosslinking an ethylene-based polymer, which comprises using the compound represented by the formula (1) as a crosslinking agent. 3. An ethylene-based polymer is represented by the general formula: A power cable having an insulating layer obtained by crosslinking the compound represented by the formula (1) as a crosslinking agent.