JPH0379641A - Expandable composition - Google Patents

Abstract

PURPOSE:To obtain the subject composition, containing two kinds of foaming agents having different decomposition temperatures in a polyolefin and useful as highly expanded polyolefin insulated electric wires excellent in electrical characteristics and mechanical strength. CONSTITUTION:The objective composition composed of 100 pts.wt. polyolefin having <55%, preferably 20-51% swelling ratio, 0.2-2 pts.wt., preferably 0.6-1.4 pts.wt. foaming agent (e.g. p,p-oxybisbenzenesulfonyl hydrazide) having 150-170 deg.C, preferably 160 deg.C decomposition temperature and 0.2-2 pts.wt., preferably 0.6-1.4 pts.wt. foaming agent (e.g. azodicarbonamide) having 190-220 deg.C, preferably 205 deg.C decomposition temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a foamable composition for highly foamed polyolefin insulated wires having excellent electrical properties and mechanical strength.

[Conventional technology]

Foamed polyolefin, especially foamed polyethylene insulated wire, in which a conductor core wire is coated with a polyolefin foam, has been put to practical use in various applications including communication cables.

The foamed polyolefin insulation is generally manufactured by screw extrusion with plastic using a suitable blowing agent.

In recent years, improvements in the electrical properties of cables and reduction in cable diameter have been required, and for this reason, foam insulated wires have also been required to have a high degree of foaming with a degree of foaming of 50% or more. The elasticity of the plastic is a factor in achieving high foaming, and it has been found that the swelling ratio of the plastic, which is an index of elasticity, has a significant relationship in obtaining a highly foamed plastic insulator.

Here, the swelling ratio: SR is defined as the outer diameter of the extrudate obtained when measuring the melt index 2Ml with a melt indexer specified in JIS K6760 or ASTM D123B-70, and ds is the outer diameter of the extrudate set in the melt indexer. It is expressed by the following equation (a), where do is the inner diameter of the orifice.

d.

Note: Both ds and do use values measured at room temperature.

Further, the degree of foaming is defined by the following formula (+).

ρ 0 ρ0: Density of resin before foaming ρ: Density of foam However, on the other hand, when the degree of foaming is increased, the mechanical strength of the foam decreases, making it more susceptible to damage during manufacturing or use of electric wires. The problem arises.

In order to solve this problem, a ``method for producing highly foamed polyolefin insulated wire'' (Japanese Patent Publication No. 5B-11047) was developed in which the conductor is coated with foaming polyolefin containing a foaming agent and a material with a swelling ratio of 55% or more. Proposed.

(Problems to be Solved by the Invention) According to the manufacturing method disclosed in the above publication, the swelling ratio is 55.
A highly foamed insulator with a foaming degree of 55% or more is obtained using a foaming polyolefin containing a material of 55% or more.

The above publication lists low density polyethylene (LDPE), high density polyethylene (HDPE), polypropylene, etc. as polyolefins with a swelling ratio of 55% or more, and provides reference examples of these polyolefins and polyolefins with a swelling ratio of 55% or more.
Various insulated wires were manufactured using less than 5% polyolefin, and the degree of foaming and properties of the insulators were investigated, and the results are clearly shown in the tables. According to this, for example, as is clear from the table of Reference Example 1, DP with a swelling ratio of less than 55%
The bubble diameter of the Snake is more than twice that of the LDPH with a swelling ratio of 55% or more, and there is a considerable difference in the bubble diameter of the LDPH with a swelling ratio of less than 55%.
In E, it is written that the adhesion to the conductor and the appearance are poor. In addition, in the table of Reference Example 2, the blend resin body with a foaming degree of less than 55% has a bubble diameter that is more than twice as large as that of a resin body with a foaming degree of 55% or more, and is determined to be poor in terms of adhesion to the conductor and appearance. ing.

Furthermore, based on these results, the swelling ratio of 5
It has been determined that less than 5% polyolefin is not practical for highly expanded polyolefin insulated wire.

Therefore, in view of the above points, an object of the present invention is to provide a new technology that can be used for highly foamed polyolefin insulated wires having a foamed insulator with a degree of foaming of 55% or more even when polyolefin has a swelling ratio of less than 55%. be.

[Means to solve the problem]

In order to achieve the above object, the present inventors made extensive research efforts and found that polyolefin 1 with a swelling ratio of less than 55%
00 parts by weight and a blowing agent with a decomposition temperature of 150 to 170°C.
2 to 2 parts by weight and 0 blowing agent with a decomposition temperature of 190 to 220°C
．． If the foamable composition is made of 2 to 2 parts, a highly foamed insulator with a degree of foaming of at least 55% or more can be obtained, and the adhesion to the conductor and appearance are also good, and it can be put to practical use as a highly foamed polyolefin insulated wire. They discovered what they could do and developed the present invention.

That is, the present invention uses 100 parts by weight of a polyolefin with a swelling ratio of less than 55%, 0.2 to 2 parts by weight of a blowing agent with a decomposition temperature of 150 to 170°C, and 0.2 to 2 parts by weight of a blowing agent with a decomposition temperature of 190 to 220°C. A foamable composition comprising:

Therefore, the swelling ratio of the polyolefin used in the present invention is preferably less than 55%, preferably about 10 to 53%, particularly about 20 to 51%. There is no particular restriction on polyolefin as long as it has a swelling ratio of less than 55%.
Examples include low density polyethylene (LDPE), high density polyethylene (HD, PE), medium density polyethylene (MDPE), and polypropylene. The blending ratio of one or more of these polyolefins in the composition is 100 parts by weight in total.

The blowing agent has a decomposition temperature of 150-170℃ and 190-220℃
Two types of these are used. In the former blowing agent, the decomposition temperature is 150-170'C, preferably 152-168'C.
, particularly preferably about 160°C, for example, P, P-
Oxybisbenzenesulfonyl hydrazide (OBSH)
can be mentioned.

The decomposition temperature of the latter blowing agent is 190 to 220°C, preferably 192 to 218°C, particularly preferably about 205°C, such as azodicarbonamide (A0CA). The mixing ratio of both foaming agents is 0.2 to 2 parts, preferably 0.4 to 1.61 parts, particularly preferably 0.6 to 1.4 parts.

In addition, it is sufficient for the composition of the present invention to consist of the above-mentioned polyolefin and two types of blowing agents, but in addition, plate-out inhibitors (for example, silica), antioxidants, copper damage inhibitors, etc. may be added as additives. You may. The blending ratio of additives is
0.02 to 1.0 double wall, preferably 0.04 to 0.5
Parts by weight.

Note that there are no limitations to the method of producing a highly foamed polyolefin insulated wire using the above foamable composition, and for example, it may be carried out by simultaneously extrusion coating a foamed insulating layer and a non-foamed layer (seeds, etc.) onto a conductor core wire. .

(Example) Hereinafter, the present invention will be explained in more detail with reference to Examples.
These do not limit the present invention in any way.

Examples 1 to 3/Comparative Examples 1 to 2 Next, Examples and Comparative Examples demonstrate that the foamable composition of the present invention using a polyolefin with a swelling ratio of less than 55% has good foaming uniformity and a high foaming degree. Clarify by.

A foamable material made of a polyolefin and a blowing agent having the swelling ratio and blending ratio as shown in Table 1 was prepared, and the foaming uniformity and degree of foaming were examined, and the results are shown in Table R.
It was shown to.

However, the swelling ratio: SR and degree of foaming are expressed by the above formula (a),
(b).

In addition, as a reference example, the characteristics of a composition using a polyolefin with a swelling ratio of 60% are also listed.

(The following is a blank space) [Effects of the Invention] As explained above, the foaming property of the present invention consists of 100 parts by weight of polyolefin with a swelling ratio of less than 55% and 0.2 to 0.2 parts of a blowing agent with a decomposition temperature of 150 to 170°C. 2 parts by weight and 0.2 to 2 parts by weight of a blowing agent with a decomposition temperature of 190 to 220°C, the polyolefin has a swelling ratio of less than 55%, which was previously considered to be impractical for highly foamed polyolefin insulated wires. Even if the foaming degree is 55%
A foamed insulator having the above-described high foaming and good foaming uniformity can be obtained.

Therefore, the selection range of materials used for highly foamed polyolefin insulated wires is widened, which greatly contributes to enriching the technology for the wires.

Claims (1)

[Claims] 100 parts by weight of a polyolefin with a swelling ratio of less than 55%, 0.2 to 2 parts by weight of a blowing agent with a decomposition temperature of 150 to 170°C, and 0.2 to 2 parts of a blowing agent with a decomposition temperature of 190 to 220°C.
A foamable composition comprising parts by weight.