JPH03205437A - Tracking-resistant material - Google Patents

Abstract

PURPOSE:To obtain the title material improved in elongation without detriment to its tracking resistance by mixing a thermoplastic resin with a thermoplastic rubber, Mg(OH)2 and a polyether. CONSTITUTION:A composition is obtained by mixing 100 pts.wt. thermoplastic resin such as PE, an ethylene/vinyl acetate copolymer or polyethyl acrylate with 100-600 pts.wt. thermoplastic rubber such as an ethylene/propylene/diene terpolymer or a styrene/(ethylene)/butadiene/styrene copolymer. 100 pts.wt. this composition is mixed with 20-50 pts.wt. Mg(OH)2 in the form of a powder of a mean particle diameter of 1mum or less and a specific surface area of 5m<2>/g or more and 0.5-2 pts.wt. polyether such as polyoxymethylene, polyethylene oxide or polyoxacyclobutane.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) (Industrial Application Field) The present invention relates to improved tracking-resistant materials and heat-recoverable articles having excellent tracking-resistant properties.

(Prior Art) Examples of insulating materials used in salt-damaged areas and other contaminated areas include insulating materials in the form of sheets, tubes, etc. used for connecting outdoor cables, reinforcing cable terminals, preventing corrosion, waterproofing, or repairing.

When such insulating materials are used, salts, dust, etc. accumulate on the insulating materials, and if water from rainfall adheres to the insulating materials, a leakage current will flow, and the leakage current path will be disconnected due to the evaporation of the attached moisture due to Joule heat, causing damage to the area. A discharge occurs, and the surface of the insulator is carbonized by this discharge, and thereafter, due to the cumulative occurrence of carbonization, a phenomenon in which carbonization paths grow in a dendritic shape, so-called "tracking", is unavoidable.

As an organic insulating material that suppresses such tracking, a mixture of thermoplastic resin such as polyethylene (PE) and magnesium hydroxide (Mg(○(2)H)2) is known. Japanese Unexamined Patent Publication 1987-
No. 68346 FIi! , Japanese Unexamined Patent Publication No. 61-31446).

2. Can the occurrence of the trasoking phenomenon be delayed according to the insulating material containing magnesium hydroxide? The amount of magnesium hydroxide added to the +00 heavy area is normally 50 parts by weight or more, and in heavily polluted areas it is required to be 70 parts by weight or more.

When using this organic insulation + A material, if it is shaped into a sheet shape, tube shape, etc., or if a large amount of magnesium hydroxide is added, the mechanical properties may deteriorate, and in particular, it tends to have low elongation. .

Elongation in organic insulating materials is an important property, and low elongation can be a serious defect.

For example, if heat-shrinkable organic insulation material is desired, a mixture of thermoplastic resin and magnesium hydroxide powder is formed into a sheet, tube, etc., and then the shaped material is heated. After stretching, heat shrinkability (3) is imparted by maintaining this hot stretched state and cooling. If the elongation of this insulating material is small, the shaped article may break during hot stretching, and the heat-shrinkable article may not be attached.Also, even if the heat-shrinkable article is 777, the degree of hot stretching will be insufficient. Instead, I had to use a small heat shrink skewer.

(Problems to be Solved by the Invention) Accordingly, the present invention provides resistance to 1 and racking 1'1. One of its objectives is to provide a high growth rate of insulation interest while maintaining a 21% yield. A further object of the present invention is to provide a heat regenerating article which is excellent in i{ l-ranking properties and has a high degree of heat recovery.

(Means for Solving the Problems) In order to achieve the above two objects, the present inventor has made extensive studies and added two types of third components to the conventional binary mixture system of thermoplastic resin and magnesium hydroxide. It has been discovered that the elongation properties can be improved by specific blending, and the present invention has been completed.

That is, the anti-tragging +A material according to the present invention contains 100 to 60 parts by weight of thermoplastic rubber to 100 parts by weight of thermoplastic resin.
Furthermore, 20 to 50 parts by weight of magnesium hydroxide and 0.5 to 2 parts by weight of polyether are blended to 100 parts by weight of the total amount of these thermoplastic resins and thermoplastic rubber. It is what it is.

In addition, in the present invention, instead of polyether,
iO or SiOt) can be used. and,
This 1-racking resistant material is a thermoplastic resin flNIo
o For the coulometric part. Thermoplastic 1"" 100 to 600 parts by weight of rubber is blended, and magnesium hydroxide 1, 2
71 parts of 0 to 5011t and 20 to 100 parts by weight of silica are blended.

As the thermoplastic resin used in the present invention, those conventionally used as the main component of anti-tracking materials can be used as they are, and preferred specific examples include PE, ethylene-vinyl acetate copolymer, polyethyl acrylate, etc. can be mentioned.

These thermoplastic resins may be used alone or in combination of two or more. ．． l: may be used in combination.

(5) The thermoplastic resins include ethylene bromine/endentor polymer (EPDM), styrene-butadiene-styrene copolymer (SBS), styrene-ethylene-butadiene-styrene copolymer (SEBS), etc. Thermoplastic rubber is mixed.

The blending amount of the thermoplastic rubber is 100 to 600 parts by weight (preferably 101 parts by weight or more, more preferably 110 to 600 parts by weight) per 100 parts by weight of the thermoplastic resin.

By blending the rubber in such an amount, the dispersibility of magnesium hydroxide in the resulting cracking-resistant material is improved.
Then, the elongation of the material becomes large enough to be used in actual production. If the amount of rubber compounded is too small, the elongation is expected to improve, but if it is too large, the tensile strength decreases, so neither is preferable.

In addition, in the present invention, 20 to 50
Contains magnesium hydroxide from Jukeibu. If the amount of magnesium hydroxide is too small, i. t+- racking property cannot be expected, and if the compounding polish is too high, elongation tends to decrease despite the addition of thermoplastic rubber.

The amount of magnesium hydroxide blended in the present invention is small compared to conventional materials that require 50 parts by weight or more even when used in lightly polluted environments, and despite this, the tracking resistance is equal to or higher than that of conventional materials. It is a unique effect of the present invention that it is possible to obtain improvements in mechanical properties as well as exhibit properties.

The magnesium hydroxide used in the present invention has an average particle size of 1 μm or less and a specific surface area of 5 rrr.
It has been found that it is preferable to use a powder with a weight of less than 1/g (value measured by the BET method).

In addition, the use of magnesium hydroxide that has been surface-treated with fatty acids such as stearic acid or leicic acid or metal salts of fatty acids is advantageous in order to improve the mutual dispersibility (uniform mixability) of thermoplastic resin and thermoplastic rubber. There are some preferable ones. Surface treatments for magnesium hydroxide to improve dispersibility are already known, for example, in ``Interaction of Inorganic Substances and Polymers'' (Management Development Center Publishing Department, General Technology (7) Data Collection), Volumes 395-420. It is written on the page.

Of course, magnesium hydroxide powder subjected to such a surface treatment is commercially available under the trade name "Kismer" manufactured by Kyowa Kagaku Kogyo Co., Ltd., and these can also be obtained and used.

Furthermore, in the present invention, 0.5 to 2 parts by weight of polyether or 20 to 100 parts by weight of silica is blended with respect to 100 parts by weight of the total amount of both thermoplastic resin and thermoplastic rubber. Polyether or silica is used to improve the dispersibility of magnesium hydroxide in thermoplastic resins and thermoplastic rubbers. If the blending amount of polyether or silica deviates from each of the above ranges, the elongation and tracking resistance tend to decrease compared to when the above predetermined amount is blended, although the reason is not clear.

The polyether used in the present invention is a polymer represented by the general formula (■).

{-(CH2), 1o yo. - (D(8) "m" in the above general formula is 1 to 4, and "n" is 1
000 or less.

Specific examples of such polyethers include polyoxymethylene, polyethylene oxide, polyoxacyclobutane, polytetrahydrofuran, and the like.

The anti-tracking material of the present invention has four components as essential components: thermoplastic resin, thermoplastic rubber, magnesium hydroxide, and polyether, or has four components: thermoplastic resin, thermoplastic rubber, magnesium hydroxide, and silica. A certain amount is required, and a mixture of these may be used in granular or powdered form, but since it is used for connecting outdoor cables, etc.
It is used after being molded into a predetermined shape such as a seam shape or a tube shape.

The present invention further provides heat recoverable articles. This heat-recoverable article consists of four components: thermoplastic resin, thermoplastic rubber, magnesium hydroxide, and polyether, or four components: thermoplastic resin, thermoplastic rubber, magnesium hydroxide, and silica.
The anti-tracking material prepared by arranging the components as described above (9) is formed into a predetermined shape such as a seal shape or a tube shape. (may be expandable).

As a method of imparting heat shrinkability to a molded article made of thermoplastic resin or rubber, for example, the molded article is crosslinked (chemical crosslinking, radiation crosslinking, etc.), then the molded article is hot stretched,
A method of cooling while maintaining this stretched state is known.

Therefore, the heat-shrinkable article of the present invention can also be obtained by applying the above method to a certain shaped article made of a tracking-resistant material.

When applying such a method to obtain a heat-shrinkable article, the molded article made of the tracking-resistant material may have an elongation of up to about 1000%, depending on its formulation, molding method, etc. , the stretching ratio is correspondingly large, for example about 200! l) It can also be set to about 6. For this reason,
It is possible to obtain a material with a high heat shrinkage rate of approximately 70%.

(Example) (10) Hereinafter, the present invention will be explained in more detail with reference to Examples. In addition, all "parts" indicating the blending amount mean "parts by weight."

Example 1 20 parts of PE with a specific gravity of 0.96 (manufactured by Mitsui Petrochemical Industries, Ltd., trade name Mirason 67), 80 parts of EPDM (manufactured by Mitsui Petrochemical Industries, Ltd., trade name X65), 20 parts of magnesium hydroxide,
0.5 parts of polyethylene oxide as a polyether, pentaerythrityltetrakis (3-(3.5
- ditertiarybutyl-4-hydroxyphenyl) propionate] (manufactured by Ciba Geigy, trade name Irganox) and 2 parts of the black pigment red iron were mixed at a temperature of 40°C.
Knead with heated rolls, then knead with an inner diameter of 10 mm and a wall thickness of 1 m.
A tracking-resistant material is obtained by extrusion into a tube shape of m. In addition, the average particle size of magnesium hydroxide is 0.8μ.
A material having a specific surface area of 8 rrf/g (measured value by BET method) and no surface treatment was used.

Next, this tube is cross-linked by irradiating it with an electron beam of 10 Mrad, then heated to a temperature of 150°C, and stretched in the radial direction so that the inner diameter is 30 mm. Maintain the stretched state at room temperature (approximately 25
Cool to °C).

As a result, a heat-shrinkable tube (sample 1) having an inner diameter of 30 mm and a wall thickness of 0.9 mm was obtained.

Example 2 PE, EPDM, magnesium hydroxide, polyether (
Samples 2 to 7 were the same as sample 1, and test needles 8 and 9 used polyoxacyclobutane), except that the number of blended parts or the presence or absence of surface treatment with magnesium hydroxide were changed as shown in Table 1. Working in the same manner as in Example 1, eight types of heat-shrinkable tubes (Samples 2 to 9) were obtained.

In addition, in any case of Samples 2 to 9, the same antioxidant and pigment as in Example 1 were used, and the number of blended parts thereof was also the same as in Example 1.

Comparative Example The work was carried out in the same manner as in Example 1, except that the proportions of PE and magnesium hydroxide were set as shown in Table 1, and the proportions of antioxidant and pigment were 1 part each. A shrinkable tube (Sample 10) was obtained.

The heat-shrinkable tubes obtained in these Examples and Comparative Examples were tested in the manner described below, and the results are also listed in Table 1. In addition, the units of "tensile strength", "elongation", "tracking resistance" (abbreviated as "tracking resistance") and "arc resistance" in Table 1 are rkg/
crd”, “%”, “KV” and rs e Cl.

(A. Tensile strength and elongation test) According to JIS C 2132, punched with a No. 3 dumbbell, temperature 25°C, tensile speed 200mm/min
It was measured using a Schopper tensile tester under the following conditions.

(B. Tracking resistance test) According to ASTM D 2303, a sheet test piece (
A standard staining solution was poured over the sample (cut from a heat-shrinkable tube), a voltage was applied between the electrodes in contact with the test piece (starting voltage 2.5 KV), and the voltage was increased stepwise (l 3) to perform tracking. I saw the voltage at which the phenomenon started.

(C. Arc resistance test] JIS K 6 9 1 1 By the method prescribed in 2. Ru.

(Hereinafter, blank space) (l 4) Example 3 Particle size 0. The work was carried out in the same manner as in Example 1, except that 5 μm St○2 powder was used and the number of blended parts of each precept or the presence or absence of surface treatment with magnesium hydroxide was changed as shown in Table 2. A heat-shrinkable tube of ~22) was obtained. However, in both cases, the same antioxidants and pigments as those used in Example 1 were used, and the number of blended parts thereof was also the same as in Example 1.

The properties of these heat-shrinkable tissues are also listed in Table 2. Note that the method of characteristic testing is the same as in Example 1.

(Hereinafter, blank spaces) (1 6) (Effects of the Invention) The present invention is configured as described above, and in addition to the thermoplastic resin and magnesium hydroxide system, a thermoplastic rubber and polyether, or a thermoplastic rubber and silica are added. A tracking-resistant material with improved mechanical properties and a heat-recoverable article made from the material while maintaining the level of tracking resistance even though the amount of magnesium hydroxide used is small. can be provided.

Claims (3)

[Claims] (1) 100 to 600 parts by weight of thermoplastic rubber is blended with 100 parts by weight of thermoplastic resin, and 20 to 50 parts by weight of magnesium hydroxide is added to 100 parts by weight of the total amount of these thermoplastic resins and thermoplastic rubber. and polyether 0
．． A tracking resistant material containing 5 to 2 parts by weight. (2) 100 to 600 parts by weight of thermoplastic rubber is blended with 100 parts by weight of thermoplastic resin, and 20 to 50 parts by weight of magnesium hydroxide is added to 100 parts by weight of the total amount of these thermoplastic resins and thermoplastic rubber. and silica 20-1
A tracking-resistant material containing 0.00 parts by weight. (3) A heat-recoverable article formed by molding the anti-tracking material according to claim 1 or claim 2 into a predetermined shape.