JPH0384046A - Foaming agent for thermoplastic resin - Google Patents

Abstract

PURPOSE:To obtain a foaming agent for thermoplastic resins, containing chlorotetrafluoroethane and dichlorotrifluoroethane in a specific proportion, excellent in stability and capable of forming homogeneous foams with hardly any danger of destroying ozonosphere. CONSTITUTION:A foaming agent, containing (A) chlorotetrafluoroethane, [e.g. 1-chloro-1,2,2,2-tetrafluoroethane (CFC-124)] and (B) dichlorotrifluoroethane [e.g. 1,1-dichloro-1,2,2triifluoroethane (CFC-123b)] at (80-40):(20-60), preferably (70-50):(30-50) weight ratio of the components (A) to (B) and readily decomposable before reaching ozonosphere due to easy decomposability. The aforementioned foaming agent in an amount of 0.001-0.5mol based on 100g thermoplastic resin is mixed with, e.g. the above-mentioned resin melted by heating, at a high temperature under a high pressure, depressurized and expanded.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a blowing agent composition for thermoplastic resins.

In addition, in this specification, "%" means "% by weight"
” means.

Conventional technology and its problems As a blowing agent used in the production of thermoplastic resin foam, dichlorodifluoromethane (Freon-12) has conventionally been used.
, dichlorotetrafluoroethane (Freon-114) and other fluorocarbons have been used. however,
In recent years, it has been pointed out that certain types of fluorocarbons destroy the ozone layer in the stratosphere when released into the atmosphere, and as a result, have a serious negative impact on the earth's ecosystem, including humans. Therefore, international agreements have come to restrict the use and production of fluorocarbons, which pose a high risk of ozone layer depletion. Freon-12 mentioned above is subject to this restriction, and from this point of view as well, there is a need to develop new blowing agents that have no or low risk of causing ozone layer depletion problems. .

It is possible to use LPG instead of CFC, which has the above problems, but in this case, there is a big problem that a foamed product with uniform bubbles cannot be obtained, and there is also a risk of explosion. .

Means for Solving the Problems As a result of repeated research in view of the above-mentioned problems in the prior art, the present inventor has found that a composition consisting of tetrafluoroethane and dichlorotrifluoroethane is It has been found that it has unique foaming properties that are completely difficult to predict, and as a result, it exhibits excellent effects as a foaming agent for producing thermoplastic resin foams, leading to the completion of the present invention.

That is, the present invention provides the following composition: (1) A blowing agent for thermoplastic resins characterized by comprising chlorotetrafluoroethane and dichlorotrifluoroethane.

■The above item (1
) A blowing agent for thermoplastic resins as described in .

(2) The blowing agent for thermoplastic resins according to item (2) above, which comprises chlorotetrafluoro, 0 to 50% chlorotrifluoroethane, and 30 to 50% chlorotrifluoroethane.

In the blowing agent composition according to the present invention, it is essential to use chlorotetrafluoroethane and dichlorotrifluoroethane together.

Chlorotetrafluoroethane used in the present invention includes 1-chloro-1.2,2.2-tetrafluoroethane (Freon-124) and 1-chloro-1.1,2.2
-tetrafluoroethane (Freon-1 24 a).

Further, as the dichlorotrifluoroethane used in the present invention, 1,1-dichloro-1.2.2-trifluoroethane (Freon-123b), 1.

1-dichloro-2.2.2-trifluoroethane (Freon-123), 1,2-dichloro-1,2.

Examples include 2-trifluoroethane (Freon-123a).

Combination of Freon-124 and/or Freon-123a (hereinafter referred to as Freon-124 unless otherwise required) and Freon-123 and/or its isomer (hereinafter referred to as Freon-123 unless otherwise required) The ratio is usually about 80-40:20-60%, based on the total weight of both, and in order to obtain a more uniform foam, the ratio is 70-5%.
More preferably, the ratio is about 0:20 to 50%.

If the percentage of Freon-124 exceeds 80%, a foam with a low magnification ratio or poor foaming will occur.
If the percentage of Freon-123 exceeds 60%, the product will have a rough surface and a foam with large shrinkage and many wrinkles.

The foaming composition of the present invention may contain a stabilizer, if necessary.

The blowing agent composition of the present invention can be used in the same manner as known blowing agents for producing thermoplastic resin foams.

There are no particular restrictions on the thermoplastic resin used as the foaming raw material.

More specifically, thermoplastic resins include polystyrene,
Polystyrene copolymers made of styrene and other copolymerizable monomers (e.g., styrene-butadiene copolymers, styrene-acrylonitrile copolymers, styrene-methacrylate copolymers, etc.); low-density polyethylene (density = Approximately 0.910-0.925 g/cc c)
, medium density polyethylene (density = approximately 0.926 ~ 0.
940 g/cc), high density polyethylene (
density = about 0.941 to 0.965 g/CC), isotactic polypropylene, polybutene-1, polyolefin copolymers consisting of ethylene and/or other monomers copolymerizable with propylene (e.g., propylene-octene). -1-ethylene copolymer, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-ethyl acrylate copolymer, ethylene-vinyl chloride copolymer, etc.). Illustrated.

The amount of the blowing agent of the present invention to be used in the thermoplastic resin is the same as in the case of known blowing agents, and is appropriately determined depending on the type of thermoplastic resin, the density of the desired foam, etc. 0.001 to 0 per 100g
．． It is about 5 moles.

When producing a foam using the blowing agent of the present invention, it may be carried out in the same manner as known methods.

For example, (a) a method in which raw resin is heated and melted, a foaming agent is mixed under high temperature and high pressure, and after melting, the raw resin is extruded into a low pressure zone and foamed; (b) a method in which raw resin is heated and melted and foamed at high temperature and under high pressure. (e) A method of crosslinking the raw material resin with an electron beam, a chemical crosslinking agent, etc., adding a foaming agent thereto, and heating and foaming. Examples include.

Further, the blowing agent according to the present invention can be used in sheets, blocks, rods,
It can be used to manufacture foamed products in any form, such as pipes, coatings (wires, cables, etc.), molded products, etc.

Effect of the invention According to the present invention, the following effects are achieved.

Freon-124 and Freon-123 used in the present invention
is relatively easily decomposed and is easily decomposed before reaching the ozone layer, so the risk of causing ozone destruction is extremely low.

Furthermore, the blowing agent according to the present invention is nonflammable and therefore safe for use.

Furthermore, the foaming agent of the present invention using a mixture of Freon-124 and Freon-123 forms a foam with excellent stability and extremely uniformity compared to when each is used alone.

EXAMPLES Examples and comparative examples are shown below to further clarify the characteristics of the present invention.

Examples 1-5 and Comparative Examples 1-2 Polyethylene foam was produced in the manner shown below.

A resin raw material was prepared by adding 0.7 g of calcium carbonate fine powder as a foam nucleating agent to 100 g of granular polyethylene having a density of 0.92 g/CC.

Freon-124 and Freon-12 in the proportions shown in Table 1
A blowing agent according to the invention consisting of 3 was prepared. Table 1 also includes blowing agents outside the composition range of the present invention, Comparative Examples NG, 1 to 1.
It is also shown as 2.

The extruder used had a hopper, a metering section, a mixing section, a compression and melting section, and a screw extrusion section (inner diameter 40++
v+) is the main component, and a blowing agent injection hole is provided in the center of the cylinder.

The resin raw material was charged into the extruder from the hopper, and the foaming agent was injected into the heated resin raw material in the cylinder through the foaming agent injection hole and mixed uniformly with a screw. The amount of blowing agent used is polyethylene 10
The weight was 15g compared to 0g.

The polyethylene-foam nucleator-blowing agent mixture was heated to 130° C. from the blowing agent injection hole to the die attached to the extruder outlet and extruded into the atmospheric pressure region to form polyethylene foam.

Table 2 shows the physical properties of the obtained foam.

No. 1 table Blowing agent composition (%) 24 23 Example No.

0 0 5 5 0 0 0 0 0 0 comparative example shame 00 00 Table 2 Density Stability (g/cnf) (room temperature) exterior Example No.

1 0.03B 2 0.03B 3 0.035 4 0.039 5 0.030 Comparative example no.

1 0.040 2 0.029 5 4 3 6 0 Uniform and relatively uniform Low magnification foam surface Slightly rough 0 5 Poor foaming Surface rough In addition, in Table 2, the stability of the foam is calculated from the volume immediately after foaming to 100 In this case, the volume ratio after being left at room temperature for one day is shown.

As is clear from the results shown in Table 2, when the blowing agent composition of the present invention is used, a resin foam that is uniform, has a small convergence line, and has excellent dimensional stability can be obtained.

On the other hand, when Freon-124 alone or Freon-123 alone is used, the foaming ratio may be low or the product may have an inferior appearance.

(that's all)

Claims (2)

[Claims] (1) A blowing agent for thermoplastic resins, characterized by comprising chlorotetrafluoroethane and dichlorotrifluoroethane. (2) The blowing agent for thermoplastic resins according to claim (1), comprising 80 to 40% of chlorotetrafluoroethane and 20 to 60% of dichlorotrifluoroethane. Claim (2) comprising 70-50% of 3-chlorotetrafluoroethane and 30-50% of dichlorotrifluoroethane.
) A blowing agent for thermoplastic resins as described in .