JP2003034745A - Silane-crosslinked polyolefin molded article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a silane-crosslinked polyolefin molded article which does not induce the deterioration of appearance or of electrical properties caused by the deposit of a low molecular weight compound to a die. SOLUTION: An electrical cable is obtained by forming on a conductor 1 a silane-crosslinked polyethylene insulator 2 of which the intermolecular crosslinking is formed by reacting moisture with a polyethylene graft- copolymerized with a silane compound and the insulator 2 is extrusion-molded from a composition to which 0.005-5 pts.wt. each of a fluorine-based lubricant, a fluorine rubber and at least either of polyethylene glycol or a fatty acid ester based on 100 pts.wt. of polyethylene are introduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silane-crosslinked polyolefin molded product, and in particular, during molding such as extrusion, poor appearance or electrical characteristics due to adhesion of low molecular weight molecules contained in the polyolefin to a die. The present invention relates to a silane-crosslinked polyolefin molded product that does not cause deterioration.

[0002]

2. Description of the Related Art Polyolefins such as polyethylene, ethylene-vinyl acetate copolymer, ethylene-propylene copolymer and the like are graft-copolymerized with an organic silane compound in the presence of a radical initiator, and the resulting graft-copolymer is prescribed. Molded products obtained by molding in the shape of (1) and allowing water to act on them to crosslink the molecules are widely used.

This cross-linking method called silane cross-linking uses a small amount of an organic peroxide as a graft initiator to act on a polyolefin in a molding machine such as an extruder, thereby grafting a silane compound such as vinylalkoxysilane onto the polyolefin. After copolymerization, the basis of the reaction is to cause the cross-linking reaction by exposing the molded product discharged from the molding machine to high temperature and high humidity or hot water.

The cross-linking reaction is generally pre-mixed in the molded product or accelerated by a silanol condensation catalyst permeated from the surface of the molded product. The alkoxy silane graft-copolymerized with the polymer is generally used. It is carried out by causing hydrolysis and condensation reaction in the presence of the catalyst, thereby promoting intermolecular bonding of the polymer.

This cross-linking method is simpler and less expensive in terms of equipment and process than the peroxide cross-linking in which an organic peroxide is mixed with a polyolefin and thermally decomposed to cross-link the molecules. It is costly and therefore is most suitable as a method for crosslinking a molded article such as an insulating coating of an electric wire cable.

[0006]

However, according to the conventional molded article based on silane cross-linking, since the Guft reaction in the molding machine is carried out at a high temperature, the low molecular weight substance contained in the polyolefin is precipitated by this high temperature. , The deposited low molecular weight substance may adhere to the die of the molding machine and become stagnant.Therefore, the low molecular weight substance oxidized and deteriorated by the stagnant damages the appearance of the molded product discharged from the molding machine, or A streak on the surface of the molded product may cause problems such as frequent occurrence of water trees under flooding.

Accordingly, it is an object of the present invention to provide a silane-crosslinked polyolefin molded product which does not cause a poor appearance or a deterioration in electrical properties due to the adhesion of low molecular weight substances to a die.

[0008]

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention is constructed by molding a composition of a polyolefin graft-copolymerized with a silane compound and crosslinking the polyolefin by allowing water to act. In the silane-crosslinked polyolefin molded product described above, the composition contains 0.005 parts by weight of a fluorine-based lubricant, a fluorine rubber, and at least one of polyethylene glycol and a fatty acid ester per 100 parts by weight of the polyolefin.
The present invention provides a silane-crosslinked polyolefin molded product, characterized in that the silane-crosslinked polyolefin molded product is contained in an amount of 5 to 5 parts by weight each.

In the present invention, the reason why a fluorine-based lubricant, a fluororubber, and / or polyethylene glycol and a fatty acid ester are combined and mixed into the polyolefin is that these combinations form a thin coating film on the inner surface of the die. And, it was found that the formed coating film acts to prevent the adhesion of low molecular weight substances to the die.

However, in order to bring out this action without harmful effects, it is necessary to set the compounding amount of these compounds to 0.005 to 5 parts by weight per 100 parts by weight of the polyolefin. If the amount of each compound is less than 0.005 parts by weight, the effective coating film formation and the effect of preventing the adhesion of low molecular weight substances due to it cannot be obtained.
When it exceeds 5 parts by weight, blooming of these compounds occurs on the surface of the molded product, resulting in deterioration of appearance.

As a secondary effect of the addition of these compounds, prevention of stagnation of the polyolefin resin due to formation of a coating film on a metal surface such as a screw or a barrel in a molding machine such as an extruder or an injection machine, and molding The effect of preventing the generation of water trees due to the generation of amber for early crosslinking in the aircraft can be mentioned.

Examples of the fluorine-based lubricant include polytetrafluoroethylene powder, tetrafluoroethylene-vinylidene fluoride-hexafluoropropylene terpolymer, and the like. In particular, the latter compound is the most preferable material for the present invention. Becomes As the fatty acid ester, stearic acid ester, palmitic acid ester, oleic acid ester, montanic acid ester, erucic acid ester, behenic acid ester, lauric acid ester, ricinoleic acid ester or the like is used.

Further, as the polyolefin, low-density polyethylene, medium-density polyethylene, high-density polyethylene; ultra-low-density polyethylene by ion polymerization, linear low-density polyethylene, ethylene propylene rubber, ethylene butene binary or ternary copolymer Coal, polypropylene, chlorinated polyethylene, chlorosulfonated polyethylene; polyethylene and polypropylene polymerized with metallocene catalysts; vinyl acetate, acrylic acid ester, methacrylic acid ester, propylene, octene and other ethylene copolymers, or maleic anhydride Polyolefins grafted with functional groups including epoxy and epoxy are used, and these are
The 1 type, or 2 or more types are mixed and used.

The polyolefin used in the present invention is 2,2-thio-diethylenebis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] or pentaerythrityl for improving heat aging resistance. -Tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], octadecyl 3- (3,3
5-di-t-butyl-4-hydroxyphenyl) propionate, 2,4-bis-[(octylthio) methyl]
-O-cresol, 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino) -1,3,5-triazine, bis [2-methyl-4] -{3-n-alkyl (C12 or C14) thiopropionyloxy} -5-t-butylphenyl] sulfide and 4,4'-thiobis (3-methyl-6-t
-Butylphenol), it is preferable to include one or more kinds of antioxidants selected from the group, and the addition amount thereof is preferably set to 0.05 to 0.5 parts by weight per 100 parts by weight of the polyolefin. .

In addition to these antioxidants, polyolefins include dilaurylthiodipropionate, dimyristylthiodipropionate, distearylthiodipropionate, ditridecylthiodipropionate and tetrakis (methylenedodecylthiopionate). Propionate)
It is preferable to include one or more kinds of antioxidants selected from methane, and the preferable addition amount thereof is set to 0.05 to 0.5 parts by weight per 100 parts by weight of the polyolefin.

When the above-mentioned two groups of antioxidants are used in combination, the antiaging effect becomes synergistically improved as compared with the case of using the above-mentioned group of antioxidants alone.
Furthermore, it is possible to effectively suppress metal damage, which is a deterioration phenomenon of polyolefin due to contact with metal.

The reason for setting the preferable addition amount of each of the above-mentioned antioxidants to 0.05 to 0.5 parts by weight is that if the amount is less than 0.05 parts by weight, the antiaging effect and the metal damage in the case of combined use will be obtained. The preventive effect is not sufficient, while
This is because when it exceeds 0.5 parts by weight, a so-called bloom phenomenon occurs in which these antioxidants are deposited on the surface of the molded product.

As the silane compound added to the polyolefin for graft copolymerization, it is preferable to use an organic silane compound having a vinyl group such as vinyltrimethoxysilane or vinyltriethoxysilane. Examples of the radical initiator for grafting to dicumyl peroxide include dicumyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3,2,5-dimethyl-2,5-di ( t-Butylperoxy) hexane, α, α′-bis (t-butylperoxy-m-isopropyl) benzene, m- (t-butylperoxyisopropyl) -isopropylbenzene or p- (t-butylperoxyisopropyl) ) -Organic peroxides such as isopropylbenzene are mainly used. One or more of these will be used in combination.

The amount of the above-mentioned radical initiator added to the polyolefin is preferably 0.05 to 0.15 parts by weight with respect to 100 parts by weight of the polyolefin, and if the amount added is less than this, a sufficient degree of crosslinking is obtained. On the contrary, when the content exceeds this range, voids due to the decomposed components of the radical initiator are generated.

It is preferred to add a silanol condensation catalyst to accelerate the crosslinking reaction, for example:
Carboxylates of metals such as tin, zinc, iron, lead and cobalt,
Organic bases, inorganic acids or organic acids are used. Specifically, dibutyltin dilaurate, dibutyltin diacetate, dibutyltin dioctaate, stannous acetate, stannous carbylate, lead naphthenate, zinc carbylate, cobalt naphthenate, ethylamine, dibutylamine, hexylamine, pyridine , Sulfuric acid, hydrochloric acid, toluenesulfonic acid,
Acetic acid, stearic acid, maleic acid, etc. are used,
The amount used is often set to 0.01 to 0.1 parts by weight per 100 parts by weight of polyolefin.

The following two methods may be mentioned as suitable manufacturing means for applying the molded product of the present invention to the use of electric wires and cables. That is, one of them is a two-shot or a method called SIOPLUS in which a masterbatch containing a silanol condensation catalyst in a high concentration is prepared, and this is supplied to an extruder together with a polyolefin having a silane compound grafted thereto in advance and extrusion-molded. The other one is to supply an additive containing a silanol condensation catalyst and a radical initiator to the polyolefin in the extruder, whereby the graft reaction of the silane compound to the polyolefin and the extrusion molding of the electric wire cable can be performed. This is a method called one shot or monosil which is performed simultaneously in the extruder.

As a method of causing the silanol condensation catalyst to act on the polyolefin, a method of infiltrating the silanol catalyst from the surface of the molded polyolefin is possible. Further, when applying the present invention to an electric wire cable, a conductor filled with a water-tight compound is used in order to prevent water running in the conductor when water acts, or a shield is provided inside or outside the insulator. Various types of cable configurations are possible, such as forming a semiconductive layer of
It is possible to add carbon black in order to improve the weather resistance of the molded product, or to add other additives such as general lubricants, colorants and inorganic fillers.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the silane-crosslinked polyolefin molded product according to the present invention will be described below. Figure 1
The structural example of the electric wire cable which applied the molding of this invention is shown, (a) is the example which formed the silane bridge | crosslinking polyethylene insulator 2 on the conductor 1, (b) is the watertightness on the conductor 1. An example is shown in which the compound 3 is applied and formed, and the silane crosslinked polyethylene insulator 2 is formed thereon.

In addition, (c) shows that the inner semiconductive layer 4 is formed on the conductor 1, and the silane crosslinked polyethylene insulator 2 is formed on the inner semiconductive layer 4.
Is an example of a high voltage cable that has formed, and (d)
Shows an example of a high-voltage cable in which the outer semiconductive layer 5 is formed on the insulator 2 of the cable of (c).

Table 1 summarizes the contents of the examples and comparative examples of the present invention and the evaluation of the results of these examples.

[0026]

[Table 1]

In Examples 1 to 5 and Comparative Examples 1 to 5 in Table 1, first, polyethylene, or polyethylene and a carbon masterbatch were charged into a 130 mm extruder at 200 ° C., and other components were dissolved. By injecting methoxysilane from the lower part of the hopper of the extruder, extrusion molding of the cable and graft copolymerization of the silane compound with polyethylene were simultaneously performed.

This cable has the structure of FIG. 1 (c), and the size of the conductor 1 of the annealed copper wire and the thickness of the insulator 2 are 60 mm 2 and 4.5 mm, respectively.
An internal semiconductive layer 4 having a thickness of 0.7 mm is formed between them. Next, attach the cable obtained above to 8
It was left in an atmosphere of 0 ° C. × 95% steam for 24 hours, thereby obtaining a predetermined silane-crosslinked polyethylene insulated cable.

Separately from the above, the components of Examples 6 and 7 and Comparative Example 6 were prepared in the same manner as above, but with a thickness of 60 mm.
2.5 mm thick insulator 2 on conductor 1 of annealed copper stranded wire 2
1 (a) to form a cable, and then leave it in an atmosphere of 80 ° C. × 95% steam for 24 hours to manufacture a predetermined cable.

The test methods and evaluation methods for each characteristic shown in Table 1 are shown below. -Extrusion appearance: Evaluation was made based on the appearance of extrusion (presence of damage) when the insulator 2 was continuously extruded for 100 hours, and the presence or absence of adhesion of low molecular weight substances to the die. -Blood of additive: In the above extrusion, it was evaluated based on the presence or absence of a deposit on the cable surface.

[0031]   ・ Bow Tightly     Number of occurrences: The cable sample poured into the conductor was immersed in warm water at 90 ° C.                       Then, apply AC voltage of 50Hz × 9kV between the conductor and water 5                     It is applied for 00 days, and after 500 days, the cable insulator 2                     Thinly slice the cross section and boil with methylene blue solution                     Color and use an optical microscope to measure                     The number of utilites was counted.

According to Table 1, all of Examples 1 to 7 containing a fluorine-based lubricant, a fluororubber, a polyethylene glycol and a fatty acid ester in the polyolefin insulation 2 based on the combination of the present invention have an extruded appearance, an addition. In comparison with the good results in all the properties of the agent bloom and the number of occurrence of bouttitley, in the case of Comparative Example 1 which does not contain them, good results are obtained in the extrusion appearance and the number of occurrence of boutite trie. Not obtained.

Further, Comparative Example 2 containing the above compound in an amount exceeding the specified amount of the present invention, Comparative Example 3 containing no fluorine-based lubricant,
In the case of No. 5 and Comparative Examples 4 and 6 not containing fluororubber, good results were not obtained in two characteristics out of the three characteristics, showing a remarkable difference from the Examples. There is. Table 1 clearly shows the effect of the addition of the fluorine-based lubricant, the fluorine rubber, the polyethylene glycol and / or the fatty acid ester and the significance of setting the addition amount thereof.

[0034]

As described above, according to the silane-crosslinked polyolefin molded product of the present invention, a fluorine-based lubricant, a fluororubber, and at least one of polyethylene glycol and a fatty acid ester are respectively contained in the molded polyolefin. By including 0.005 to 5 parts by weight per 100 parts by weight of the polyolefin, it is possible to provide a molded product that does not cause a poor appearance or a decrease in electrical properties due to the adhesion of low molecular weight substances to the die. , Its usefulness is great.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a configuration example of an electric wire cable to which a silane-crosslinked polyolefin molded product according to the present invention is applied.

[Explanation of symbols]

1 conductor 2 Silane cross-linked polyethylene insulator 3 Watertight compound 4 Internal semi-conductive layer 5 External semiconductive layer

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C08L 71:02) (72) Inventor Junichi Abe 5-1-1 Hidaka-cho, Hitachi-shi, Ibaraki Hitachi Cable (72) Inventor, Masaru Hanawa, 5-1-1, Hidaka-cho, Hitachi-shi, Ibaraki Hitachi Cable Co., Ltd. F-term in Hidaka factory (reference) 4F071 AA14 AA26 AA27 AA39 AA77 AC10 AE05 AF36 AH19 4J002 BD122 BD153 BN041 CH024 EH036 EU187 EV047 EV067 FD077 FD202 FD203 FD204 FD206 GQ00

Claims (4)

[Claims] 1. A silane-crosslinked polyolefin molded article, which is molded from a polyolefin composition graft-copolymerized with a silane compound and is formed by crosslinking the polyolefin by allowing water to act thereon, wherein the composition is a fluorine-based compound. A silane-crosslinked polyolefin molded article, characterized by containing 0.005 to 5 parts by weight of a lubricant, fluororubber, and at least one of polyethylene glycol and fatty acid ester per 100 parts by weight of the polyolefin. 2. The fluorine-based lubricant is tetrafluoroethylene-vinylidene fluoride-hexafluoropropylene 3
The silane-crosslinked polyolefin molded product according to claim 1, which is a former copolymer. 3. The composition comprises 2,2-thio-diethylenebis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], pentaerythrityl-tetrakis [3- (3. , 5-Di-t-butyl-4-hydroxyphenyl) propionate], octadecyl 3-
(3,5-di-t-butyl-4-hydroxyphenyl)
Propionate, 2,4-bis-[(octylthio) methyl] -o-cresol, 2,4-bis (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino) -1, 3,5-triazine, bis [2-methyl-4- {3-n-alkyl (C12 or C14) thiopropionyloxy} -5-t-butylphenyl] sulfide and 4,4'-thiobis (3-methyl- 6-
The silane-crosslinked polyolefin molded product according to claim 1, wherein each of the one or more antioxidants selected from (t-butylphenol) is contained in an amount of 0.05 to 0.5 parts by weight based on 100 parts by weight of the polyolefin. 4. The composition comprises 2,2-thio-diethylenebis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], pentaerythrityl-tetrakis [3- (3. , 5-Di-t-butyl-4-hydroxyphenyl) propionate], octadecyl 3-
(3,5-di-t-butyl-4-hydroxyphenyl)
Propionate, 2,4-bis-[(octylthio) methyl] -o-cresol, 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-
Butylanilino) -1,3,5-triazine, bis [2
-Methyl-4- {3-n-alkyl (C12 or C1
4) Thiopropionyloxy} -5-t-butylphenyl] sulfide and 4,4'-thiobis (3-methyl-6-t-butylphenol), one or more antioxidants selected from 100 parts by weight of said polyolefin. 0.05 to 0.5 part by weight, per dilauryl thiodipropionate, dimyristyl thiodipropionate, distearyl thiodipropionate,
One or more antioxidants selected from ditridecylthiodipropionate and tetrakis (methylenedodecylthiopropionate) methane are added to the polyolefin 1
The silane-crosslinked polyolefin molded product according to claim 1, characterized in that it is contained in an amount of 0.05 to 0.5 part by weight per 100 parts by weight.