JPH0356517A - Production of silane-grafted copolymer and insulated electric wire therefrom - Google Patents

Abstract

PURPOSE:To obtain the title copolymer capable of giving insulated electric wires of good appearance by reaction of a combination of an organic unsaturated silane and free radical generator with a polymer blend containing a three- component polymer of ethylene, propylene and ethylidene norbornene at specified proportion. CONSTITUTION:A reaction is carried out between [A] 100 pts.wt. of a polymer blend of (1) 30 - 50 wt.% of a three-component copolymer made up of (a) ethylene plus propylene [ the molar ratio ethylene/propylene = ( 70 : 30 ) - ( 95 : 5 )] and (b) ethylidene norbornene, (2) 43 - 69 wt.% of an ethylene-methyl methacrylate copolymer and (3) 1 - 7 wt.% of powdered polyethylene, [B] 1 - 5 pts.wt. of an organic unsaturated silane and [C] 0.1 - 1 pt.wt. of a free radical generator, thus obtaining the objective silane-grafted copolymer of high rigidity and good in extrusion formability. The present copolymer is put to extrusion coating on a conductor in the presence of a silanol condensation catalyst followed by bringing water into contact with the coated conductor to effect crosslinking, thus obtaining the other objective insulated electric wires in high productivity.

Description

DETAILED DESCRIPTION OF THE INVENTION <<Industrial Application Field>> The present invention relates to an improved polyolefin rubber tIA edge wire and a manufacturing method.

<Prior Art> Conventionally, a simple method for crosslinking polyolefins such as polyethylene and ethylene propylene rubber involves grafting an organic unsaturated silane onto the polyolefin in the presence of a free radical generator, and then grafting the polyolefin with an organic unsaturated silane in the presence of a free radical generator. The so-called silane crosslinking method, in which silane graftomer is crosslinked by contacting it with water in the presence of a silanol condensation catalyst, is generally known. For example, Japanese Patent Publication No. 48-1711, Japanese Unexamined Patent Publication No. 57-49109, etc. Although it is possible to produce polyolefin rubber insulated wires with rubber elasticity using this method, the following problems make it difficult to put it into practical use. That is, in general, polyolefins having rubber elasticity have a low softening temperature of around 40°C, and the left end of the polyolefin may cause blocking at the throat of the extruder hopper during storage or during extrusion processing. Pellet adhesion to the screw feed section of the machine caused fluctuations in the extrusion rate or a gradual decrease in the extrusion rate, which hindered stabilization and caused major problems in practical application. Another method is to use a rubber vulcanization process to manufacture polyolefin rubber insulated wires, but the mechanical strength is low and the vulcanization process affects the cable manufacturing speed. Economic problems are unavoidable, that is, external forces are applied to the coating layer immediately after extrusion coating in the trading machine or winding drum, causing permanent deformation of the coating layer, so sufficient cooling and vulcanization steps are taken. There is a need. For this reason, it is necessary to slow down the cable manufacturing speed and make the cooling water tank significantly longer, which inevitably leads to economic problems. <<Problem to be solved by the invention>> The present invention solves these problems, and even if it is a polyolefin-based material with rubber elasticity, the strength does not decrease, the hardness is hard, and the extrusion stability is low. An object of the present invention is to provide an insulated wire having good rubber elasticity and good appearance as a shaped product. (Means for solving the problem) The present invention has a molar ratio of ethylene and propylene of 70/30.
~95/5, terpolymer with ethylidenenorbornene (EPDM) 30-50 fU amount%, and ethylene-methyl methacrylate copolymer (EMMA) 43-69
1 to 5 parts by weight of an organic unsaturated silane and 0.1 to 1 part by weight of a free radical generator are reacted with 100 parts by weight of a base polymer consisting of 1 to 7 parts by weight of polyethylene powder and 1 to 7 parts by weight of powdered polyethylene. A method for producing an insulated wire, characterized in that the silane graftomer obtained by the above method is extrusion coated onto a conductor in the presence of a silanol condensation catalyst, and crosslinked by contacting with moisture. be. The present invention will be explained in detail below. The EPDM used in this invention has a molar ratio of ethylene to brobylene of 70/30 to 95/5. And the iodine value of ethylidenenorbornene, the third commandment, is 5 to 25. For 50 to 30% by weight of such EPDM, ethylene-methyl methacrylate copolymer CEMM^) and an appropriate amount of powdered polyethylene are used as the base polymer of the invention. However, in general, EPDM is more expensive than the latter, so increasing the latter within the range of 50 to 30% by weight is economically advantageous as well as improving mechanical strength. It is. When the EPDM content is less than 30% by weight, the rubber elasticity is lost and the mechanical strength becomes weak. Furthermore,
The reason for adding an appropriate amount of powdered polyethylene is to impregnate the liquid organic unsaturated silane and disperse it uniformly when adding an appropriate amount of the organic unsaturated silane and free radical generator to be reacted, which will be described in detail later. This is for the purpose of being able to do something. If powdered polyethylene is not used, the liquid will simply adhere to the surface of the pellets, so it will not adhere to the walls in the hopper during extrusion or drip into the hopper, making it impossible to uniformly disperse it.

Therefore, the amount of powdered ethylene depends on the amount of organic unsaturated silane as a liquid, but preferably 1 to 7%. Appropriate amounts of organic unsaturated silane and a free radical generator are added to the base polymer with these characteristics and reacted to obtain a silane graftomer. This is coated on a conductor in the presence of a silanol condensation catalyst, brought into contact with moisture, and subjected to a crosslinking reaction to obtain a silane crosslinked insulated wire with rubber elasticity as in a conventional method. In this invention, the organic unsaturated silane used is general 2RR'SiYx (R is a monovalent olefinically unsaturated hydrocarbon group, Y is a hydrolyzable organic group, R゜ is an aliphatic unsaturated hydrocarbon A monovalent hydrocarbon group other than Y or the same as Y) is used. It is preferable to use an organic unsaturated silane represented by the general formula RSiY, where R' is the same as Y, and it is preferable to use, for example, vinyltrimethoxysilane, vinyltriethoxysilane, etc. The amount of organic unsaturated silane used is
1 to 5 parts by weight, preferably 2.5 to 00 parts by weight
It is 3.5 parts by weight. If it is less than 1 part by weight, sufficient grafting will not occur, while if it is more than 5 parts by weight, it will not only result in poor shape but also become uneconomical. Next, as a free radical generator, an organic peroxide with a strong polymerization initiating effect, such as DCP (dicumyl peroxide), is used. The amount of this free radical generator used is 10
0.01 to 1 part by weight, preferably 0.01 to 1 part by weight, preferably 0.01 to 1 part by weight.
It is 1 to 0.3 parts by weight. If it is too small, the grafting reaction will be insufficient, and if it is too large, the extrusion properties will deteriorate and the shaped surface will deteriorate. (Example) The present invention will be specifically explained below using examples. EPD with physical properties as shown in Table 1 for use in pace polymers
M and the resins shown in Table 2 were used to make the composite mixture shown in Table 3. Table 1 Table-2 Ethylene-methyl methacrylate copolymer (C) and powdered polyethylene (D) 3 parts by weight of vinyltrimethoxysilane 0.2 parts by weight of dicumyl peroxide per 100 parts by weight of one set of these base polymers Mix parts and make 50 cabinets of L/D 22φ
A silane graftomer was obtained by strand canting and granulation using a single-screw extruder at a material temperature of 200 to 220'C. Furthermore, a catalyst masterbatch (100 parts by weight of the resin C in Table 2, 1 part by weight of dibutyltin dilaurate and 4 parts by weight of an antioxidant was kneaded into pellets) was added to 100 parts by weight of the above silane graftomer. The results are shown in Table 3. However, those with poor strand cutability and those with poor extruded appearance were evaluated by kneading them with a roll after extrusion to prepare a press sheet. <<Effects of the Invention>> As is clear from the above examples, EPDM/
EMMA cross-linked insulated wires can be manufactured uniformly without any reduction in productivity, and its industrial value is extremely large.

Claims (2)

[Claims] (1) Molar ratio of ethylene and propylene is 70/30 to 9
Terpolymer with ethylidene norbornene (E
Base polymer 10 consisting of 30-50% by weight of PDM), 43-69% by weight of ethylene-methyl methacrylate copolymer (EMMA) and 1-7% by weight of powdered polyethylene.
A method for producing a silane graftomer, which comprises reacting 1 to 5 parts by weight of an organic unsaturated silane and 0.1 to 1 part by weight of a free radical generator. (2) A method for producing an insulated wire, which comprises extrusion coating the silane graftomer according to claim 1 onto a conductor in the presence of a silanol condensation catalyst, and crosslinking the conductor by contacting it with moisture.