JPS614111A - Method of producing foamable plastic insulator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a foamed plastic insulator that is used as an insulator for communication cable insulated core wires, coaxial cables, and the like.

[Prior Art] The following three types of methods are known as methods for manufacturing foamed plastic insulators.

(1) A method using a chemical foaming agent.

(Method using 21 gas blowing agent.

(3) A method using a volatile liquid blowing agent.

In method (1), since the chemical blowing agent is uniformly dispersed, the gas is uniformly distributed when the blowing agent is decomposed. Furthermore, since the chemical foaming agent itself has a nucleation effect, a uniform and fine foamed plastic insulator can be obtained. however,
There is a problem that a residue remains after the blowing agent decomposes, which impairs the dielectric properties.

On the other hand, it is known that methods (a and 31) require the addition of certain substances as inorganic or organic nucleating agents in order to obtain uniform microbubbles, such as calcium carbonate, white carbon, Diatomaceous earth, clay, 2,3
-dihydro-1,4-7 talradione, phthalic acid hydrazide, and the like.

[Problems to be solved by the invention] When these substances are mixed with plastic, it is difficult to disperse them evenly, so screening using a fine screen mesh or dispersing agents such as wax and lubricants are required. , the dispersibility has been improved. However, the former has problems in terms of an increase in the T number, and the latter has problems in terms of effectiveness and the use of a large amount of dispersant. Furthermore, even if relatively good dispersion is obtained, secondary agglomeration may occur during foam production, clogging the screen mesh and significantly impairing foaming performance. There is a problem that it becomes necessary to replace the housing, and continuous and stable production cannot be performed.

The object of the present invention is to provide a manufacturing method capable of stably manufacturing a foamed plastic insulator for a long period of time by improving the dispersibility and secondary agglomeration of a nucleating agent.

-1″l!llI*t8ThM(7)f=IU] The manufacturing method of the present invention is a method for manufacturing a foamed plastic insulator by extruding a mixture of plastic containing a foaming agent and a nucleating agent. , the above mixture has the general formula R
A titanate coupling agent represented by -0-Ti-(OX)s (wherein R is an alkyne group and X is an acyl group, an alkynebenzenesulfonyl group, or a dialkylpyrophosphate group) forms a nucleus. 0.0 of agent content
It is characterized by being added in an amount of 5 to 5% by weight.

[Function J] Plastics used in the present invention include polyethylene, polypropylene, propylene-ethylene copolymer, ethylene-propylene copolymer, ethylene-α.
Polyolefins such as olefin copolymers are typical, and these can be used alone or in a mixture of two or more. Further, fluorine thread resins such as polytetrafluoroethylene, polyvinylidene fluoride, and Te1-rafluoroethylene-ethylene copolymers can also be used.

Representative examples of the door body foaming agent include nitrogen gas and carbon dioxide gas, and representative examples of the volatile liquid foaming agent include Freon.

Nucleating agents include inorganic substances and organic substances, and the former include calcium carbonate, white carbon, diatomaceous earth,
Examples include clay and talc, and the latter includes phthalic acid hydrazide. The nucleating agent is generally added in an amount of 0.5 to 10 parts by weight based on the iooma part of the plastic.

General formula R-0-Oi-(OX)3 ((IJ, f,
Examples of titanate coupling agents in which R is an alkyne group and X is an acyl group, an alkynebenzenesulfonyl group, or a dialkylpi [''phosphate group] include impropyl triisostearoyl titanate, impropyl tridodecibenzene; These include sulfonyl titanate, isopropyl tris(dioctyl bi-ophosphate) titanate-1-, bis(dioctyl pyrophosphate) oxyacetate titanate, tris(dioctyl pyrophosphate) ethylene titanate-1-, and the like.

The amount of these titanate-based coupling agents added must be in the range of 0.05 to 5% by weight relative to the nucleating agent; if it is less than 0.05% by weight, the desired effect cannot be achieved; If the amount exceeds %, the resin viscosity decreases, the bubble diameter increases, and bleeding occurs. The preferred range is 0.5-2% by weight.

The titanate coupling agent can be added by blending it with a nucleating agent in advance and mixing it with the plastic.
Either method may be used, such as adding it to the plastic together with a nucleating agent and kneading it.

In the present invention, in addition to the above-mentioned components, antioxidants, copper damage inhibitors, colorants, etc. may be added as necessary.

[Example] Example 1 Low density polyethylene (density: 0.921, melt index 0.217 / 10'min) 100 weight 1
3 parts by weight of Mistron paper talc as a nucleating agent, 0.003 parts by weight of bis(dioctylpyrophosphate) oxyacetate titanate (0.1 part by weight of a nucleating agent)
% by weight) and kneaded with a main single roll to obtain a foaming mixture.

Using a 65#IIφ extruder, nitrogen gas was injected into the center of the cylinder at a pressure of 2589/a/r, and a copper conductor with an outer diameter of 0.5 m was extruded and coated with an outer diameter of 0.8 mm. A foam insulated wire was manufactured. The extrusion temperature was 225°C, and the linear speed was 2000 m/min. IC0 Example 2: 100 parts by weight of polypropylene (density 0.890, melt flow rate: 2 g/min), and 3 parts by weight of calcined seaweed as a nucleating agent. 1% by weight of tris(dioctylpyrophosphate) ethylene titanate (1% by weight of the nucleating agent) and kneaded with a mixing roll.
It was used as a foaming mixture.

A foamed insulated wire was produced in the same manner as in Example 1 except that the extrusion temperature was 250°C.

Example 3-. □1. Engineering f, a, engineering. ,94318
．． .

To index: 0.9g/10m 1n), 1 part by weight of phthalic acid hydrazide and 0.03 parts by weight of isopropyl triisostearo titanate (0.3% by weight of the nucleating agent) were added as a nucleating agent. and mixing 1
The mixture was kneaded with coal to obtain a foaming mixture.

Using a 65IIIIIIφ extruder, Freon (R-114) was injected from the center of the cylinder at a pressure of 15 (1 g/CI!) and extruded to coat a copper conductor with an outer diameter of 2 m to produce a foam insulated wire with an outer diameter of 8 m. .

The extrusion temperature was 132° C., and the linear speed was 50 m/1n.

Comparative Example 1 As a nucleating agent, 3 parts by weight of calcium carbonate was added in place of Mistronbebatatar, and no titanate coupling agent was added. A foam insulated wire was manufactured in the same manner as in Example 1 in other respects.

Comparative Example 2 As a nucleating agent, 2 parts by weight of phthalic acid hydrazide was added instead of calcined clay, and 0.11 parts by weight of isopropyl triisostearoyl titanate (5.5% by weight of the nucleating agent) was added.
) was added. A foam insulated wire was manufactured in the same manner as in Example 2 in other respects.

In each example and each comparative example, continuous extrusion was carried out between two layers,
The head resin pressure, foaming degree, and cell diameter were measured at the beginning of extrusion and after 24 hours had passed. The results are shown in Table 1.

Table 1 [Effects of the Invention] As explained above, the present invention uses a nucleating agent and a titanium-based coupling agent in combination, which prevents secondary aggregation of the nucleating agent and provides a long service life. It becomes possible to produce a foam that is stable over time.

-Example 1

Claims (1)

[Claims] (1) In a method for producing a foamed plastic insulator by extruding a mixture of plastic containing a foaming agent and a nucleating agent, the mixture has the general formula R-O-Ti.
The titanate coupling agent represented by -(OX)_3 (in the formula, R is an alginic group, X is an acyl group, an alkynebenzenesulfonyl group, or a dialkylpyrophosphate group) has a content of nucleating agent. A method for producing a foamed plastic insulator, characterized in that the additive is added in an amount of 0.05 to 5% by weight.