KR19980076076A - Expandable resin composition for electric wire - Google Patents

Abstract

The present invention is for a wire containing 100 parts by weight of base resin, 0.3 to 2.0 parts by weight of foaming agent, 0.03 to 1.0 parts by weight of nucleating agent, 1.0 to 5.0 parts by weight of wax, 0.1 to 1.0 parts by weight of antioxidant and 0.1 to 1.0 parts by weight of metal deactivator. It relates to a foamable resin composition.

The resin composition of the present invention is prepared by pre-mixing a blowing agent, a nucleating agent and a wax in a powder state during the mixing process and then extruding it with the base resin.

Description

Expandable resin composition for electric wire

1-1 is an enlarged photograph of a cell cross section of the expandable resin produced in Example 1 of the present invention.

1-2 is an enlarged photograph of the cell cross section of the foamable resin produced according to Example 2 of the present invention.

1-3 is an enlarged photograph of a cell cross section of a general foamable resin produced by Comparative Example 1 of the present invention.

2 shows the screw configuration of the extruder used in the present invention as compared to the conventional one.

The present invention relates to a foamable resin composition for electric wire, and more particularly, the present invention is a resin composition containing a polyolefin resin, a foaming agent, a nucleating agent, an antioxidant, a metal deactivator and a wax, but the maximum foaming performance is the same as that of a conventional resin. It relates to a resin composition that simplifies the manufacturing process.

Currently used communication cable is manufactured by coating a foamed polyolefin to the copper used as a conductor to excellent currency characteristics. In general, the expandable polyolefin-based resin produces a compound by mixing and dispersing a blowing agent in the base resin, and then generates a plurality of uniform and fine cells generated by the thermal decomposition of the blowing agent introduced through a separate extrusion process. You should be able to. In order to generate a lot of uniform and fine cells, the type, content and dispersion degree of the foaming nucleating agent, which play an important role in the selection of excellent foaming agent and cell formation, are very important factors. These two main additives must be uniformly dispersed and distributed in the base resin and mixed without premature decomposition of the blowing agent in the final resin.

Currently, the direction of improvement of the expandable resin used as an insulator of communication cable is a compositional aspect of uniformly manufacturing fine cells in the base resin for the purpose of foaming within a maximum of 50%, that is, the base resin used through mixing of other base resins. It has been focused on improving the performance of chemical foaming agents (eg, azodicarbonamides), which are the most important additives in the strengthening of the melt strength and the preparation of the expandable resin. For example, Japanese Patent Laid-Open No. 52-11235 discloses 100 parts by weight of high density polyethylene having a density of 0.94-0.96 gcm 3 and a MI (melt index) of 0.1-2.0 g / 10 min, and a density of 0.91-0.93 g. A resin composition is disclosed in which a foaming agent is blended into a composition of a ternary system consisting of 10 to 40 parts by weight of low-density polyethylene having a size of 3 cm and a MI of greater than 7.0 g / 10 minutes, and 5 to 40 parts by weight of a high density polyethylene having an MI of 0.1 g / 10 minutes or less. In Japanese Patent Laid-Open No. 54-40253, 100 parts by weight of a high density polyethylene having a density of 0.94 to 0.98 g 3, 1 to 15 parts by weight of isobutylene-isopurene copolymer, 0.5 to ethylene-propylene elastomer (rubber) A foam composition having a uniform bubble by mixing 15 parts by weight is disclosed.

However, in the conventional method for obtaining the above-mentioned good foam insulation, the method of mixing several kinds of base resins in order to obtain a foaming agent having uniform fine independent bubbles has a limitation in selecting resin for foam insulation of electric wires. In addition, the mixing for homogeneous dispersion of these is not only very difficult, but also requires a lot of effort, the size of the bubbles generated in the foam does not exceed any certain system and economical disadvantages are also undesirable. In addition, a white residue (cyanuric acid) due to incomplete deterioration during the extrusion foaming process, which is a problem of a commonly used chemical foaming agent (for example, azodicarbonamide) itself, is deposited inside the compressor, resulting in die pressure. There is a problem that affects the appearance of the insulator in the rise or foreign matter. Recently, to solve this problem, a non-plateout type modified azodicarbonamide foaming agent mainly modified with a conventional blowing agent is mainly used. Modified products are generally used products in which 35 to 45 parts by weight of silicate is mixed. However, the homogeneous dispersion in the base resin is difficult due to the adhesive properties of the silica mixed in the blowing agent.

In other words, the poor dispersibility in the resin of the foaming agent means that the spacing between the particles of the foaming agent in the resin is non-uniform, so that a large and non-uniform bubble is formed in the foam during foaming and thus the mechanical properties of the insulator during foam insulation of the wire Deteriorates electrical characteristics (withstand voltage).

In addition, the nucleation agent that controls the formation of bubbles and the size of bubbles by effectively forge nucleation of the gas generated by decomposition of the blowing agent in the resin, if the dispersibility in the resin is not good, when forming a large and non-uniform bubble during the foaming properties of the foam Lowers.

According to the conventional manufacturing method of the foamable resin for the electric wire, in consideration of the difficulty in dispersing the inorganic material that acts as a nucleating agent in most cases, the master batch of the blowing agent is prepared, and then re-extruded together with the base resin. A foamable resin was prepared. However, in the case of such a manufacturing method, the manufacturing cost increases due to the expansion of the manufacturing step, and the melting point of the high density polyethylene or polypropylene is high when the bay resin is a high density polyethylene or a polypropylene instead of the low density polyethylene when the master batch of the foaming agent is manufactured. Therefore, when the blowing agent is mixed, some of the blowing agents are degraded prematurely, resulting in a non-uniform quality of the foam, thereby limiting the selection of the base resin.

It is an object of the present invention to provide a good foamable resin composition for electric wires having a uniform and fine read bubble, which is produced without using a foaming agent masterbatch, unlike the existing manufacturing method.

Therefore, the inventors of the present invention selected a finer foam product and a nucleating agent for the production of the foamable resin composition for the electric wire in order to achieve the above object compared to the existing product, and selected and used wax oxide of a specific molecular weight in order to maximize the dispersibility. Additives, such as antioxidants and metal deactivators, were used in batches when pelletized after the reactor in which high density polyethylene, which is a mainly used base resin, is produced. This eliminates the need for the production of a master medium in which antioxidants are added separately during the final product production, and the foaming range of 30 to 50% is achieved only by manufacturing the product through the compounding process of adding the base resin, foaming agent and wax in a batch. Invented a foamable resin composition for electric wire that can produce a foam having a large number of uniform and fine independent bubbles and excellent mechanical properties.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

The base resin used in the present invention is an olefin-based polyolefin resin. For example, the density of a polymerized from ethylene and an α-olefin having 4 or more carbon atoms is 0.92 to 0.96 g 3 and MI (Melt Index) of 0.4 to 1.0 g. Low density polyethylene, medium density polyethylene, or high density polyethylene, which is 10 minutes.

The blowing agent used in the present invention is a modified azodicarbonamide having a decomposition temperature of 190 to 210 ° C. and a particle size of 1 to 4 μm, and its content is 0.3 to 2.0 parts by weight based on 100 parts by weight of the base resin. to be.

The nucleating agent used in the present invention acts as a foaming nucleation agent and bubble size adjusting agent in the foam, preferably silicate, calcium carbonate or zinc stearate, and the amount is 0.03 to 1.0 parts by weight, preferably 100 parts by weight of the base resin. Preferably it is 0.05-0.08 weight part, and the particle size is 2-3 micrometers.

The wax used in the present invention is a low molecular weight polyethylene, a low molecular weight vinyl acetate copolymer or a low molecular weight acrylic acid copolymer having a softening point of 60 to 110 ° C, preferably 80 to 95 ° C, and a number average molecular weight of 2,000 to 4,000. , This is a surface-oxidized product to increase the fluidity and dispersibility of the blowing agent and the nucleating agent mixed with the base resin to give excellent dispersibility in the base resin. As for the usage-amount in manufacturing foamable resin, 1.0-5.0 weight part is preferable with respect to 100 weight part of base resins.

Antioxidants used in the present invention are 4,4'-thiobis (2-t-butyl-5methylphenol), pentaerythryl-tetrakis- [3- (3,5-di-t-butyl-4 -Hydroxyphenyl) -propiode], 2,2'-methylenebis [4-methyl-6- (1'-methylcyclohexyl) phenol] or tris (2,4-di-t-butylphenyl) force Pit and the like are preferred, and the metal inert agent is N, N'-bis (β-3,5-di-t-butyl-4-hydroxyphenyl-propiodo) hydrazide, oxalic acid-bis (benzylidene hydrazide ) Or 2,2'-oxamido bis- [ethyl3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], and the like, in the preparation of the foamable resin, the additive The addition amount of these is 0.1-1.0 weight part, respectively, Preferably it is 0.15-0.2 weight part with respect to 100 weight part of base resins. In the above-mentioned antioxidants, when the base resin is produced in each plant, the product introduced during the pelletization process is used in the compounding process.

The most important compounding process in the present invention rearranges the kneading block so that the dispersing performance is maximized in the screw configuration of the extruder in order to improve the dispersing performance of the blowing agent and the nucleating agent instead of the general extruder. In addition, the L / D (length / diameter) of the device is slightly longer than the previous one to improve the dispersion performance. The blowing agents, nucleating agents and dispersants used are preblended in a Henschel mixer prior to compounding, and then the additives in the form of powder mixed with the base resin in advance are added to the extruder during the final product production. The final extrusion is to produce a product. At this time, unlike the existing production process, the foaming agent masterbatch that requires a separate manufacturing process is not necessary, and even a simple manufacturing process contains many fine and uniform independent bubbles during foam insulation and has high thermal stability and excellent physical properties. A resin can be obtained.

The manufacturing process of the above-mentioned expandable resin according to the present invention is summarized and illustrated in comparison with the existing process as follows.

Existing Process

Process applied to the present invention

As shown above, the existing process requires a separate blowing agent masterbatch process and a separate quality control process, while the improved manufacturing process applied to the present invention is a simplified process that does not require a separate blowing agent masterbatch process and quality control process to be.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the present invention is not limited by these examples.

Example 1

In the first stage, 43 parts by weight of commercialized modified azodicarbonamide (40 parts by weight of pure azodicarbonamide, 60 parts by weight of silicate group, UNIROYAL AZ-130) and wax (product of ALLIED SIGNAL, trade name AC-6) Mix 57 parts by weight in a Henschel mixer at room temperature for 2 minutes at low speed and 3 minutes at high speed. In the second step, 100 parts by weight of high-density polyethylene (density 0.949 g / cm 3, 0.8 g / 10 min, Samsung Synthetic Co., Ltd., product name 3150SN) to which 2,500 ppm of an antioxidant and a metal deactivator are added, respectively, for the preparation of the expandable resin and 3 parts by weight of the mixture of the pre-blended powder blowing agent and the wax prepared in step 1 were trained and extruded at a temperature of 145 ° C. or lower with a single-axis continuous drill extruder specially designed to improve dispersibility.

The foamed resin prepared as described above was prepared in a foam skin insulated wire under the following conditions, the insulator characteristics were evaluated and the results are shown in Table 1.

* Production equipment for Form / Skin Insulated Core: Kobe (Japan), Extrusion Foam Line Diameter 65mm, Skin Extrusion Line Diameter 40mm.

Processing condition

Wire rod: 0.4mm wire

-Processing temperature (℃): Extruder: C1 / C2 / C3 / C4 / C5 / H1 / H2 = 151/174/180/182/173/174/175

Vertical Extruder: C1 / C2 / C3 / C4 / H / D = 169/220/230/240/250

Screw (rpm): Main extruder: 22

Vertical Extruder: 60

Speed (mm / min): 2,000

Insulation thickness (min): foam insulation layer 0.12

Skin layer 0.05 (skin insulation material: HDPE with density 0.949, melt index 0.8)

Conductor insulation outer diameter (mm): 0.74

Example 2

In the first step, the foamability for electric wire was the same as in Example 1 except that the wax used to improve the dispersing performance was replaced with polyethylene wax having a number average molecular weight of more than 5,000 (trade name: AC-735, manufactured by ALLIED SIGNAL). Resin was manufactured and the insulator characteristic evaluation was performed.

Comparative Example 1

Unlike Examples 1 and 2, LDPE (density 0.920g / cm 3, MI 4.0g / 10min Samsung General Chemical Co., Ltd., product name 610L) was sufficiently melted at 115 ° C. or lower in a Banbury mixer, and 100 parts by weight of molten LDPE was melted. 24 parts by weight of modified azodicarbonamide (40 parts by weight of pure azodicarbonamide, 60 parts by weight of silicate group mixed product, trade name AZ-130) and wax (manufactured by ALLIED SIGNAL, trade name AC-6) 28 parts by weight of the mixture is kneaded, finely pulverized by a crusher, and then extruded by an extruder at a temperature of 120 ° C. or lower to prepare a foaming agent masterbatch. In the second step, 100 parts by weight of HDPE (density 0.949 g / cm 3, MI 080 g / 10 min., Samsung Total Chemical Co., Ltd., product name 3150SN) to which 2,500 ppm of an antioxidant and a metal deactivator were added, respectively, for the preparation of the expandable resin, 7 parts by weight of the prepared foaming agent master batch was kneaded and extruded at a temperature of 145 ° C. or lower with a continuous kneading extruder to prepare a foamable resin for electric wire.

TABLE 1

* Insulator tensile strength and elongation are measured by KS C-3001 method.

Claims (8)

An electric wire comprising 100 parts by weight of base resin, 0.3 to 2.0 parts by weight of foaming agent, 0.03 to 1.0 part by weight of nucleating agent, 1.0 to 5.0 parts by weight of wax, 0.1 to 1.0 part by weight of antioxidant and 0.1 to 1.0 part by weight of metal deactivator. Foamable resin composition for use. The method of claim 1, The base resin is a foamable resin composition for electric wires, characterized by low density polyethylene, medium density polyethylene or high density polyethylene having a density of 0.92 to 0.96 g 3 and polymerized from ethylene and an α-olefin having 4 or more carbon atoms, and MI (0.4 to 1.0 g / 10 minutes). . The method of claim 1, Foaming agent is a foamed resin composition for electric wires, characterized in that the modified azodicarbonamide having a particle size of 1 ~ 4㎛. The method of claim 1, The nucleating agent is a silicate, calcium carbonate or zinc stearate, and the foamable resin composition for electric wires, characterized in that the particle size is 2 ~ 3㎛. The method of claim 1, The wax has a softening point of 60 to 110 ° C., and is a low molecular weight polyethylene, a low molecular weight vinyl acetate copolymer, or a low molecular weight acrylic acid copolymer having a number average molecular weight of 2,000 to 4,000. The method of claim 1, Antioxidants include 4,4'-thiobis (2-t-butyl-5methylphenol), pentaerythryl-tetrakis- [3- (3,5-di-t-butyl-4-hydroxyphenyl) -Propiode], 2,2'-methylenebis [4-methyl-6- (1'-methylcyclohexyl) phenol] or tris (2,4-di-t-butylphenyl) phosphite Expandable resin composition for electric wires The method of claim 1, Metal deactivators include N, N'-bis (β-3,5-di-t-butyl-4-hydroxyphenyl-propiodo) hydrazide, oxalic acid-bis (benzylidene hydrazide) or 2,2 ' -Oxamido bis- [ethyl3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] The expandable resin composition for electric wires, characterized by the above-mentioned. The method of claim 1, A foamable resin composition for electric wires, which is prepared by pre-mixing a blowing agent, a nucleating agent and a wax in a powder state during the mixing process of a resin composition and then extruding it with a base resin.