JPS6211746A - Flame-retardant electrical material composition having excellent high-speed moldability - Google Patents

Abstract

PURPOSE:To obtain the titled composition having excellent mechanical strength, electrical characteristics and abrasion resistance, by adding a specific amount of an inorganic flame-retardant to a resin component obtained by compounding a specific ethylene-ethyl acrylate copolymer with a specific ethylene-alpha-olefin copolymer at a specific ratio. CONSTITUTION:The objective composition can be produced by compounding (A) 70-97 (wt)% ethylene-ethyl acrylate copolymer having a melt index (MI) of 0.2-5g/10 min, preferably 0.5-2g/10 min and an ethyl acrylate content of 5-20%, preferably 10-17% with (B) 3-30T ethylene-alpha-olefin copolymer (preferably propylene, etc.) having an MI of <=2g/10 min, preferably 0.01-1.8g/10 min, a density of 0.94-0.97g/cm<3> and a melt-tension (MT) at 190 deg.C satisfying the formula MT>=6.0XMI<-0.314>, and mixing 100pts. (wt.) of the obtained resin composition with (C) 40-150pts., preferably 70-120pts. of an inorganic flame- retardant (preferably magnesium hydroxide, etc., having an average particle diameter of <=20mum). EFFECT:A non-polluting composition having low smoking tendency. USE:Insulation material for communication cable.

Description

Detailed Description of the Invention <Industrial Application Field> The present invention is based on ethylene-ethyl acrylate copolymer and high-density polyethylene, which has excellent mechanical strength and electrical properties, and has excellent wear resistance and high-speed molding. The present invention relates to a composition for flame-retardant electrical materials with improved properties.

<Prior art> It is well known that polyolefin resins have excellent mechanical strength, electrical properties, and chemical resistance, are easy to extrude, and are suitable for electrical wire insulation, cable sheathing, and other uses. This is where I am.

However, polyolefin resins are easily flammable, and flame retardation is required in the above-mentioned applications.

Conventionally, methods of blending various flame retardants have been proposed for the purpose of making polyolefin resins flame retardant. among them,
Most commonly, a halogen flame retardant or a combination of the halogen flame retardant and antimony oxide is used. This system has the advantage of having a high flame retardant effect with a small amount of blending, and less deterioration in mechanical strength and electrical properties. However, this system generates a large amount of smoke and toxic rogens gas during combustion, which is not only harmful to the human body, but also has the problem of corroding surrounding equipment due to its corrosive nature. There is.

On the other hand, it is well known that hydrates of inorganic metal compounds such as magnesium hydroxide and aluminum hydroxide are effective as low-smoke flame retardants that do not generate harmful gases during combustion.

However, when the above-mentioned inorganic flame retardant is blended with a polyolefin resin, for example, as a polyolefin resin,
Although ethylene-vinyl acetate copolymers provide high flame retardancy, they have problems in that they have poor electrical properties, heat resistance, and low-temperature properties. On the other hand, blend systems of polyethylene, polypropylene, ethylene-propylene copolymers, etc., which have excellent electrical properties, and the above-mentioned inorganic flame retardants have a drawback of poor flame retardancy.

On the other hand, it is well known that the blended system of ethylene-ethyl acrylate copolymer and the above-mentioned inorganic flame retardant has high flame retardancy, excellent electrical properties, heat resistance, and low popularity properties, and is rapidly becoming a W1. It is becoming more important.

(For example, JP-A-51-132254, JP-A-56-13
No. 682, No. 60-13832, etc.0) However, when the above composition is applied to fields where the coating thickness is thin and high-speed extrusion processing is performed, such as insulation of communication cables, it is difficult to obtain a smooth coating appearance. However, there are problems in that there are no pores and the wear resistance is significantly reduced, and improvement of these problems is desired.

<Problems to be solved by the invention> In view of the above points, the present invention has been developed as a result of intensive studies,
Provides a low-smoke, non-polluting, flame-retardant electrical insulating composition with particularly excellent electrical properties, mechanical strength, abrasion resistance, and high-speed processability, and is used as an insulating material for communication cables, etc. It is.

<Means for Solving the Problems> The present invention provides: (a) a melt index of 0.2 or more! M/
10 minutes, ethylene-ethyl acrylate copolymer 70-97 with an ethyl acrylate content in the range of 5-20% by weight
weight and b) melt index is 29710 minutes or less, density is in the range of 0.94 to 0.97 t/cWP, and melt index (MI) and melt tension (MT) at 190°C are expressed by the following formula MT≧6. Ethylene-α-olefin copolymer satisfying OXMI-” 3~Note 0 C) A flame-retardant electrical material composition containing 40-150 parts by weight of an inorganic flame retardant and having excellent high-speed moldability. This is what we provide.

The ethylene-ethyl acrylate copolymer (hereinafter simply abbreviated as EEA), which is component a) of the present invention, has an ethyl acrylate (hereinafter simply abbreviated as EA) content in the range of 5 to 20% by weight and is melt-resistant. The index (hereinafter simply abbreviated as MI) needs to be in the range of 0.2 to !M/10 minutes.

If the above MI is less than 0.2 g/10 min, extrusion processing is difficult, and if it exceeds 5 t/10 min, the mechanical strength will decrease, and it is particularly preferable to use a MI in the range of 0.5 to 2 P/10 min. be.

In addition, when the EA content is less than 5% by weight, when the inorganic flame retardant described below is added in a sufficient amount to make it flame retardant,
Not only the mechanical strength is significantly reduced, but also the wear resistance is deteriorated. On the other hand, if the KA content exceeds 20% by weight, the resin will become soft and have poor abrasion resistance. From the above points, a particularly preferable EA content is in the range of 10 to 17% by weight.

The purpose of blending the ethylene-α-olefin copolymer, component b) of the present invention, is to improve the smoothness of the cable during high-speed molding and the abrasion resistance of the finished cable.

The above-mentioned ethylene-α-olefin copolymers include copolymers of ethylene and α-olefins having 3 to 12 carbon atoms, and mixtures thereof; specific α-olefins include propylene, phthene-1,4-methyl Penten-1,
hexene-1, octene-1, decene-1, dodecene-1
I can name the first prize. Particularly preferred among these are propylene and butene-1.

The content of the α-olefin is preferably 2 molt or less.

Its density is 0.94 t/1wi'~0.97f/l-
range, MI is 2.0 f/10 min or less, preferably 0.
01f/l0min to 1.8f710min, and MI and melt tension (MT) at 190°C are as follows: MT≧6.
It is necessary that it be within a specific range that satisfies o M I -a 3 * 4.

If the above-mentioned density is less than 0.94 f/shoulder, a sufficient effect of improving wear resistance cannot be obtained, and if it exceeds 0.97 fit-, it is difficult to industrially manufacture, and if the MI is 29/
This is because if the heating time exceeds 10 minutes, the degree of decrease in mechanical strength increases.

Furthermore, the relationship between the MI of the ethylene-α-olefin copolymer of the present invention and the melt tension (MT) at 190°C, that is, the range MT≧6.0M (MT) as shown in FIG.
Only by satisfying 1314 can a coating with a smooth appearance be obtained during high-speed molding.

Similarly, the EA content and melt tension were measured as follows.

EA content: determined from the absorbance of 860 crn-'' attributed to fiEA using infrared absorption spectroscopy (IR: manufactured by JASCO Corporation). However, the calibration curve was calculated using nuclear magnetic resonance spectroscopy (NM).
R: JEOL Ltd.] was used to determine the EA concentration, and 8 of the IR
It was determined by correlation with the absorbance at 60 cm-''.

Melt tension: Melt tension tester (newly manufactured by Toyo Seiki) at 190℃ L/D = 8.0m/2
．． 095 van (using D orifice, extrusion speed 20
txs/min, quick take-up with rolls with a roll diameter of 50mmφ 1
It was determined under the condition of 0.00 rpm.

The inorganic flame retardants that are component C) of the present invention include aluminum hydroxide, magnesium hydroxide, zirconium hydroxide, basic magnesium carbonate, dolomite, hydrotalcite, calcium hydroxide, barium hydroxide, and hydrated tin oxide. hydrates of inorganic metal compounds such as borax, zinc borate, zinc metaborate, barium metaborate, tribasic lead sulfate, basic lead sulfite, dibasic lead phosphite, zinc carbonate, magnesium carbonate. Examples include calcium, calcium carbonate, barium carbonate, magnesium oxide, molybdenum oxide, zirconium oxide, tin oxide, antimony oxide, red phosphorus, and at least one of these is used.

Among these, magnesium hydroxide and aluminum hydroxide are particularly advantageous in terms of flame retardancy and economy. The particle size of these flame retardants varies depending on the type, but for magnesium hydroxide, aluminum hydroxide, etc., the average particle size is preferably 20 μm or less.

The amount of the inorganic flame retardant is 40 to 150 parts by weight, preferably 70-12 parts by weight, based on 100 parts by weight of the polyolefin resin.
It is in the range of 0 parts by weight. If the amount of the flame retardant is less than 40 parts by weight, the flame retardant effect will be small, and if it exceeds 150 parts by weight, mechanical strength and elongation will decrease, and abrasion resistance will also deteriorate.

Furthermore, in addition to the above-mentioned inorganic flame retardants, general inorganic fillers such as clay, silica, and talc may be used in combination.

Furthermore, it is preferable to subject the surface of the inorganic flame retardant to a surface treatment such as coating with a fatty acid such as stearic acid, oleic acid, palmitic acid, or a metal salt thereof, wax, organic silane, organic borane, organic titanate, or the like.

The flame-retardant electrical insulating composition of the present invention may contain other olefin polymers, such as ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylate, to the extent that the characteristics of the present invention are not impaired. Acid copolymers, high density and low density ethylene homopolymers, ethylene tofuropyrene, silane-1, pentene-1, except within the scope of the present invention
hexene-1,4-methylpentene-1, octene-1
There is no problem in adding copolymers with α-olefins having 3 to ↓2 carbon atoms such as decene-1, propylene homopolymers, or copolymers of propylene with other α-olefins.

Furthermore, in the present invention, in order to improve the flame retardant effect, the inorganic flame retardant may be used in combination with a small amount of an organic flame retardant such as a halogen flame retardant or a phosphorus flame retardant.

Further, conventional additives such as various stabilizers such as antioxidants, ultraviolet absorbers, and copper damage inhibitors, pigments, crosslinking agents, crosslinking aids, blowing agents, and nucleating agents may be added.

Resin used in Examples> a) Acid component EEA) and comparative resin type EA
Including 1 (ffifr%) MI (f/10 minutes) A
15.6 0.8B
13.2 0.5C16,
72.4 D4.50.3 E 24.8 5.6b
) component (ethylene-α-olefin copolymer) G fuden-1 0.950 0.05 ' 6
4oUF pI Butene-10,9605,
o' E750CttJ Budden-1 0
．． 950 0.36 “E803
'K Silane-10,9350,24 Shiraishi AR4Y
Butt': ``Using the above components a) and b), magnesium hydroxide (trade name:
In the case of Kisuma 5B, manufactured by Kyowa Kagaku Co., Ltd., each compounded ingredient was mixed in a Henschel mixer (manufactured by Mitsui and Miike Seisakusho).
Mix the mixture with
0°C, screw rotation speed 200 rpm), and then pelletized with a high-speed wire coating machine (manufactured by Japan Steel Works, Ltd.: 65 φ extruder, "/D = 26, set temperature 230°C, screw rotation speed 33 rpm, core wire. Preheating 1201:, coating speed 10
Table 1 shows the results of evaluating the physical properties of the cable. Table 1 also shows the results of test pieces prepared and evaluated using the above pellets.

In addition, when the inorganic flame retardant is aluminum hydroxide (product name: Heijirai 42STV, manufactured by Showa Light Metal Co., Ltd.), the temperature of the twin-screw extruder during pelletization is set at 150°C.
The wires were coated in the same manner as above, with the high-speed wire coating machine set at 150° C., and the electrical properties and other physical properties were evaluated.

In addition, each test method is as follows.

1. Tensile strength and elongation Using the above-mentioned blended pellets, roll kneading with an oven roll at 160°C, and then using a hot press molding machine with a side of 150 gourds,
JIS 6301 3 from 1m thick square sheet
Test specimens were punched out from No. 1 dumbbells, and measurements were taken using a tensile tester (manufactured by Toyo Baldwin) at a tensile speed of 200 m/min.

2. Oxygen index Using the above-mentioned blended pellets, roll kneading with open rolls at 160 ° C., then molding with a hot press molding machine with a side of 150 mm,
Create a square sheet with a thickness of 1fi and use ASTM D28
It was measured by the method specified in 63.

3. Dielectric constant and dielectric voltage connection Create a sheet with a thickness of 1 m using the same method as above, and JIS
The method specified in K6760 (however, the measurement frequency I
MHz, measurement temperature: 23°C).

4. Volume resistivity Create a sheet with a thickness of 1fi using the same method as above, and
It was measured according to the method specified in TMD-257.

5. Surface roughness and high-speed formability) The surface roughness of the wire coating obtained above was measured using a universal surface profile measuring device (manufactured by Kosaka Institute) at a scanning distance of 4fi and a scanning speed of 2gi/sec.

6. Abrasion properties The wire coating obtained above was abraded using a Nema type abrasion tester (newly manufactured by Toyo Seiki Seisakusho) using an abrasion rod with a diameter of 4 mφ and a load of 3002 until the abrasion rod reached the conductor. The number of times was calculated.

Examples 1 to 3 and Comparative Examples 1 to 2 Using an ethylene-ethyl acrylate copolymer resin as component a) and an ethylene-α-olefin copolymer as component b), Flame retardant (magnesium hydroxide: hereinafter referred to as Mg(O)T)! We observed the effect of the amount of addition.

As a result, if the amount of inorganic flame retardant added is less than the range of the present invention, the oxygen index will be low and the flame retardance will be poor; if it is in excess, mechanical properties such as tensile strength and elongation will be affected. The mechanical strength will be reduced and the abrasion resistance will also be poor.

Examples 4-5 and Comparative Examples 3-4 a) Various EEA resins (B, C, D, E) and the ethylene-α-olefin copolymer (F) used in Example 1
) to observe the effects of KA content and MI.

As a result, when the EA content and MI are slightly lower than the range of the present invention, the tensile strength and elongation are low, and the oxygen index is also low. On the other hand, if the EA content and MI exceed the ranges of the present invention, the tensile strength and elongation will be low, and the abrasion resistance will also be poor.

Examples 6 to 7 and Comparative Examples 5 to 7 Addition of component b) using EEA resin (A) as component a) and ethylene-α-olefin copolymer (F) as component b) The effect of quantity was observed.

As a result, (b) the surface roughness and abrasion resistance of the cable were inferior in the case where no acid component was added, and although the physical properties of the cable were slightly improved even when 2 parts by weight was added, the improvement effect was poor and the result was unsatisfactory. Met.

On the other hand, if component b) is added in excess beyond the scope of the present invention, mechanical strength such as tensile strength and elongation will be poor.

Examples 8 to 9 and Comparative Examples 8 to 9 The EEA resin (A) was used as the a) component, and various ethylene-α-olefin copolymers (G
,H.

■, J) was used to observe the influence of MT and MI of component b).

As a result, in any case outside the scope of the present invention, the surface roughness of the cable increases, making it impossible to put it into practical use. In particular, those with a small MT are inferior in both tensile strength and elongation.

Comparative Example 10 In Comparative Example 10, the density of the ethylene-α-olefin copolymer was outside the range of the present invention, resulting in poor wear resistance.

Evaluation was carried out in the same manner as in Example 2, except that the flame retardant in Example 2 was replaced with aluminum hydroxide (hereinafter abbreviated as AL (OH)s) from magnesium hydroxide.

In addition, the results of evaluation in the same manner as in Comparative Example 5 (Comparative Example 11 ) and b] Acid component added in the same manner as in Example 10,
The evaluation results (Comparative Example 12) are shown in Table 1.

As a result, the EVA resin had a small volume resistivity and poor electrical properties. Furthermore, when component b) was not added, the surface roughness and abrasion resistance of the cable were poor.

As mentioned above, the EEA comprising the specific scope of the present invention
A composition comprising a resin and an ethylene-α-olefin copolymer can improve mechanical strength, electrical properties, and cable physical properties in a well-balanced manner.

<Operations and Effects of the Invention> As described above, the composition for flame-retardant electrical materials of the present invention contains an EEA resin with a specific MI and EA content and a high density.
Since the base material is a resin component made from an ethylene-α-olefin copolymer that satisfies a special relational expression between MI and MT within a specific MI range, it has excellent mechanical strength, electrical properties,
It has excellent high-speed formability (represented by the surface roughness of the cable) and abrasion resistance.

In addition, by using inorganic flame retardants such as aluminum hydroxide and magnesium hydroxide, no harmful gases are generated during combustion, resulting in a low-smoke, non-polluting flame-retardant composition that is highly flame-retardant. This meets the needs of today.

Since the composition of the present invention has excellent various electrical properties, it can be used as electrical materials such as electrical insulation materials and covering materials for electric wires, communication cables, etc., with or without crosslinking. . In particular, cables for various power plants, including nuclear power plants, which specify the amount of corrosive gas,
Suitable for locations that require a high degree of flame retardancy, such as fire-resistant electric wires and general house wiring.

[Brief explanation of drawings]

The figure is a diagram showing the relationship between melt index (MI) and melt tension (MT) of the ethylene-α-olefin copolymer used in the present invention. Patent applicant: Japan Petrochemical Co., Ltd. Ryoji Yosera, Pa. (V MIC9y% power)

Claims (2)

[Claims] (1)a) Ethylene-ethyl acrylate copolymer having a melt index of 0.2 to 5 g/10 min and an ethyl acrylate content of 5 to 20% by weight, 70 to 97% by weight
and b) Melt index less than 2g/10min, density 0
．． in the range of 94 to 0.97 g/cm^3, and the melt index (MI) and melt tension at 190°C (MT
) is the following formula MT≧6.0×MI^-^0^. ^3^1^4
Ethylene-α-olefin copolymers 3 to 30 that satisfy
100 parts by weight of a resin component consisting of c) 40 to 150 parts by weight of an inorganic flame retardant, and the composition has excellent high-speed moldability. (2) The composition for flame-retardant electrical materials having excellent high-speed processability according to claim 1, wherein the inorganic flame retardant is magnesium hydroxide or aluminum hydroxide.