JPH07216125A - Production of flame-retardant polyolefinic resin foam - Google Patents

Abstract

PURPOSE:To produce the subject foam which does not undergo discoloration due to tetrabromobisphenol A as, the flame retardant, during foaming by using tetrabromobisphenol A with a low phenol monomer content. CONSTITUTION:This resin foam which does not undergo discoloration due to tetrabromobisphenol A as the flame retardant, during foaming is produced by mixing a polyolefinic resin 'with azodicarbonamide as the blowing agent and tetrabromobisphenol A with a phenol monomer content of 0.2% or lower and thermally blowing the resulting compsn.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a flame-retardant polyolefin resin foam.

[0002]

2. Description of the Related Art Foams of polyolefin resin are generally excellent in flexibility and heat insulation property,
Used for various purposes such as packaging materials and vehicle interior materials. With the expansion of such applications, flame retardancy is often required. As a method of making a polyolefin resin foam flame-retardant, a method of heat-foaming a foaming resin composition in which a foaming polyolefin resin contains a flame retardant together with an organic thermal decomposition type foaming agent is well known.

In this case, azodicarbonamide is used as the organic thermal decomposition type foaming agent, and tetrabromobisphenol A is used as the flame retardant. In order to further improve the flame retardancy, tetrabromobisphenol A is used as an inorganic powder. It is known to use them in combination (for example, JP-A-51-134762).

[0004]

By the way, when tetrabromobisphenol A is used as a flame retardant, the foam is colored due to tetrabromobisphenol A in the foam molding process in which azodicarbonamide as a foaming agent is thermally decomposed. There was a problem of doing. Also, when tetrabromobisphenol A and inorganic powder are used together, the problem that the foam is colored is inevitable.

The present invention is directed to tetrabromobisphenol A.
It is an object of the present invention to provide a method for producing a flame-retardant polyolefin resin foam that does not develop color by eliminating the occurrence of color development of the foam due to

[0006]

Means for Solving the Problems The inventors of the present invention have made earnest studies in order to eliminate the coloration of the foam due to tetrabromobisphenol A. As a result, the temperature of the heat-foaming molding was about the melting point of tetrabromobisphenol A. About 1 lower than 182 ℃
Even at a temperature of 60 ° C, the foam tends to be colored, and the higher the heating temperature, the more the coloring tends to become worse. The color development of the foam is due to the impure component remaining during the synthesis of tetrabromobisphenol A. That is, the present invention has been completed.

The method for producing a flame-retardant polyolefin-based resin foam of the present invention is a flame-retardant method by heating and foaming a foamable resin composition containing azodicarbonamide and tetrabromobisphenol A in a polyolefin-based resin. A method for producing a foam, comprising tetrabromobisphenol A having a content of deficiently polymerized phenol monomer of 0.25.
% Or less tetrabromobisphenol A is used.

In the present invention, the olefin resin means
Means a polymer or polymer of olefinic hydrocarbons,
For example, polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-styrene copolymer, propylene-styrene copolymer, propylene-
Examples thereof include styrene-ethylene-butadiene copolymer and vinyl chloride-ethylene copolymer. These resins can be used alone, or two or more kinds of them can be mixed or polymerized or crosslinked.

In the present invention, a thermal decomposition type foaming agent, azodicarbonamide, is used as the foaming agent, but other foaming agents, for example, physical foaming foaming agents such as organic gas, inorganic gas and water are also used. You can also The amount of tetrabromobisphenol A can be appropriately determined in consideration of the expansion ratio of the foam to be obtained, but usually the polyolefin resin 1
1 to 50 parts by weight, more preferably 5 parts by weight, relative to 00 parts by weight
-40 parts by weight.

Flame retardant tetrabromobisphenol A
Has a bromine content of 59% by weight of 2,2-bis (3,5-
Dibromo-4-hydroxyphenyl) propane,
It is necessary that the content ratio of the polymerization-deficient phenol monomer is 0.2% or less. Furthermore, the inorganic bromine content is 20 pp
It is preferable that the hydrolyzed bromine content is 40 ppm or less. Such tetrabromobisphenol A has a small amount of residual impure components, and does not cause the foam to develop color during foaming by heating. The content thereof is usually 1 to 50 parts by weight, and more preferably 2 to 50 parts by weight, based on 100 parts by weight of the polyolefin resin. 1
When it is less than 50 parts by weight, the flame retardant effect is small, and when it exceeds 50 parts by weight, further flame retardant effect cannot be expected. It should be noted that this tetrabromobisphenol A may be used in combination with other flame retardant and inorganic powder such as aluminum hydroxide.

The expandable resin composition of the present invention contains a stabilizer such as zinc stearate and an antioxidant such as a phenol type, a phosphorus type, an amine type and a sulfur type as long as the characteristics of the obtained foam are not impaired. Additives used in conventional expandable olefin-based resin compositions, such as metal damage inhibitors, fillers, antistatic agents, and pigments may be included. Further, a crosslinking agent and a crosslinking aid may be blended.

The foamable composition is foamed by being heated to a temperature not lower than the thermal decomposition temperature of the foaming agent at the same time as or after being molded into a predetermined shape such as a plate, a sheet or a tube without being crosslinked, Obtain a foam. As the crosslinking method, a method of irradiating an unfoamed molded article with ionizing radiation to cause a crosslinking reaction, and a method of adding a crosslinking agent to cause a chemical crosslinking reaction are adopted.

[0013]

In the method for producing a flame-retardant polyolefin-based resin foam of the present invention, tetrabromobisphenol A having a residual content of 0.25% or less of a poorly polymerized phenolic monomer and little residual impurities is used as a flame retardant. As a result, even at the time of foam molding at a high temperature exceeding 200 ° C,
The polyolefin resin foam does not develop color.

[0014]

Embodiments of the present invention will be described below. (Examples 1 to 7 and Comparative Examples 1 and 2) Tetrabromobisphenol A (frame cut 120G or flame cut) was added to 100 parts by weight of polyethylene having a melt index of 2.0 g / 10 minutes and a density of 0.920 g / cm ^3. Frame cut 120R (all manufactured by Tosoh Corporation), azodicarbonamide, zinc stearate, and aluminum hydroxide (Example 7 only) were blended in the amounts shown in Table 1. The content of the polymerization-deficient phenolic monomer in the frame cut 120G is 0.2%.
The content of the polymerization-deficient phenol monomer in R is 0.6%. Further, the flame-cut 120G has an inorganic bromine content of 7.5 ppm, the hydrolyzed bromine content is 7.5 ppm, and the flame-cut 120R has an inorganic bromine content of 25 p.
pm, hydrolyzed bromine content is 45 ppm.

This foamable composition was melt-kneaded by a plastograph, and then heated into a 3.0 mm sheet. The melt-kneading and pressing were performed below the decomposition temperature of the foaming agent. In the electron beam irradiation device, the unfoamed sheet was irradiated with an electron beam so that the absorbed dose was 5 Mrad to be crosslinked, and then the crosslinked sheet was heated and foamed in a heating oven at 210 ° C. Regarding the obtained foamed sheet, the oxygen index was measured, and the hue was visually determined. The case where the hue did not change as compared with the stage of the crosslinked sheet was marked with ◯, and the case where the hue changed was marked with x. The results are shown in Table 1.

[0016]

[Table 1]

As is clear from these results, the content of inorganic bromine is 20 ppm or less and the content of hydrolyzed bromine is 40 pp.
While the foamed sheets of Examples using tetrabromobisphenol A having m or less and a polymerization-deficient phenol monomer content of 0.5% or less did not have any color change,
Inorganic bromine content is over 20 ppm, hydrolyzed bromine content is over 40 ppm, and polymerization-deficient phenol monomer content is less than 0.
The foamed sheet of the comparative example using more than 5% of tetrabromobisphenol A was colored dark brown.

[0018]

According to the method for producing a foam of the present invention,
As a flame retardant, the use of tetrabromobisphenol A having an inorganic bromine content of 20 ppm or less, a hydrolyzed bromine content of 40 ppm or less, and a polymerization-deficient phenol monomer content of 0.5% or less may cause the temperature to exceed 200 ° C. Even when foam molding at high temperature, the foam does not develop color,
A foam having a good appearance can be produced.

Claims (1)

[Claims] 1. A method for producing a flame-retardant foam by heat-foaming a foamable resin composition comprising a polyolefin resin containing azodicarbonamide and tetrabromobisphenol A, wherein tetrabromobisphenol A is used. A method for producing a flame-retardant polyolefin-based resin foam, which comprises using tetrabromobisphenol A having a polymerization-deficient phenol monomer content of 0.25% or less.