JPH06104744B2 - Method for producing highly filled composition foam - Google Patents

Description

TECHNICAL FIELD The present invention relates to an olefin resin crosslinked foam of a flame retardant, and more particularly to a method for producing a highly filled composition foam having no structural defect due to generation of water vapor or the like. .

2. Description of the Related Art Olefin-based resin cross-linked foams of flame retardants highly filled with inorganic substances are known (Japanese Patent Publication Nos. 62-16217 and 62-10253).
No.).

These highly-filled foams are formed by molding a foamable resin composition containing a crosslinking agent such as an organic peroxide and a pyrolyzable foam into a sheet at a temperature lower than the temperature at which the foaming agent decomposes and heating it if desired. After pre-crosslinking with a foaming agent, the foaming resin composition containing a thermally decomposable foam or a method of chemically cross-linking while foaming by heating above the decomposition temperature of the foaming agent is used as a sheet at a temperature lower than the temperature at which the foaming agent decomposes. It is manufactured by a method in which it is molded into a shape, irradiated with ionizing radiation and crosslinked, and then heated to a temperature above the decomposition temperature of the foaming agent to foam.

As the inorganic filler, a hydrated metal oxide is usually used from the viewpoint of flame retardancy.

By the way, inorganic powders such as hydrated metal oxides generally have a high hygroscopicity, and when the foamable resin composition is molded, because water is included, the water content in the composition is a system containing no inorganic material. Will be significantly higher than. In the foam molding process, this water may not only become steam in the foam forming step to generate bubbles in the composition but also change the cross-linking structure. In fact, the foaming property changes depending on the water content.

Heretofore, as a method for dealing with the above problem, it has been proposed to dry the raw material in a dry atmosphere or high temperature, or to dry the foamable composition by the same method. However, such a treatment method requires very large-scale equipment and labor, and has problems of workability and economical efficiency.

The object of the present invention is to use an olefin resin, a hydrated metal oxide, a flame retardant, a flame retardant resin composition filled with a flame retardant aid, and a simple means for water content. It is an object of the present invention to provide a method for producing a foamed body which is capable of achieving a high expansion ratio without removing abnormal foaming of the highly filled composition by removing it.

The inventors of the present invention have conducted extensive studies to overcome the above-mentioned problems of the prior art, and as a result, a resin composition containing an olefin resin, a hydrated metal oxide, a flame retardant, a flame retardant aid and a thermal decomposition type foaming agent. In the case of producing a flame-retardant crosslinked foam from a product, by mixing calcium oxide in the composition, it is possible to easily absorb the moisture in the composition by the calcium oxide, which causes structural defects due to generation of water vapor and the like. It was found that a foam having a high filling composition which does not exist can be obtained, and the present invention has been completed based on the finding.

Means for Solving the Problems Thus, according to the present invention, a resin composition containing an olefin resin, a hydrated metal oxide, a flame retardant, a flame retardant aid, a thermal decomposition type foaming agent and calcium oxide as a hygroscopic agent. , Molded into a desired shape at a temperature lower than the decomposition temperature of the heat-decomposable foaming agent, and the resulting molded article is irradiated with ionizing radiation to be crosslinked or chemically crosslinked, and then the crosslinked molded article is Provided is a method for producing a highly filled composition foam, which comprises heating to a temperature equal to or higher than the decomposition temperature of a thermal decomposition type foaming agent for foaming.

Hereinafter, the configuration of the present invention will be described in detail.

(Each component) Examples of the olefin resin used in the present invention include polyethylene (low to high density, ultra low density), ethylene-vinyl acetate copolymer (EVA), ethylene-ethyl acrylate copolymer, ethylene- Acrylic acid copolymer, ethylene-
Methyl methacrylate copolymer, ethylene-α-olefin copolymer (including linear low-density polyethylene), polypropylene, propylene-butene copolymer, propylene-ethylene copolymer, and the like, and mixtures thereof. be able to.

As the hydrated metal oxide, for example, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, barium hydroxide, tin oxide hydrate, basic magnesium carbonate, hydrotalcite, heart crew, talc, mica, etc.
And mixtures thereof.

The hydrated metal oxide is added in an amount of 40 to 500 parts by weight, preferably 50 to 30 parts by weight, based on 100 parts by weight of the olefin resin. If it is less than 40 parts by weight, the effect due to blending the inorganic powder is small, and conversely, if the blending ratio is too large, it becomes difficult to obtain a foam having a high expansion ratio, for example, when forming a foam. .

Examples of the flame retardant include halogen-based flame retardants such as decabromodiphenyl ether, pentabromonochlorocyclohexane, hexabromocyclododecane, and 2,3,5,6-
Examples thereof include pentabromoethylbenzene, 1,2-bis (2,4,5-tribromophenoxy) ethane, chlorinated paraffin, hexachloropentacyclodecane, hexabromobenzene, and tetrabromobisphenol A / derivative.

These flame retardants can be used alone or in combination of two or more, but usually added in an amount of 3 to 30 parts by weight, preferably 5 to 20 parts by weight, based on 100 parts by weight of the olefin resin. To do.

By combining the flame retardant and the flame retardant auxiliary, the flame retarding effect can be enhanced. As the flame retardant aid, for example,
Examples thereof include antimony trioxide, sodium antimonate, tin oxide, red phosphorus and the like.

When these flame retardants are used, the amount is usually 1 to 20 parts by weight, preferably 2 to 15 parts by weight, based on 100 parts by weight of the synthetic resin.

Examples of the thermal decomposition type foaming agent include compounds that generate gas by decomposing with heat such as azodicarbonamide, 4,4′-oxybis (benzenesulfonylhydrazide), azobisisobutyronitrile, and barium azodicarboxylate. Can be illustrated.

The thermal decomposition type foaming agent is usually added in an amount of 2 to 30 parts by weight, preferably 5 to 25 parts by weight, based on 100 parts by weight of the olefin resin.

In the present invention, calcium oxide is added as a hygroscopic agent. Calcium oxide reacts with water that is attached and contained in the composition to form calcium hydroxide.

CaO + H ₂ O → Ca (OH) ₂ calcium hydroxide must reach a high temperature of 400 ° C or higher.
Does not decompose to release water.

That is, under normal manufacturing conditions (processing temperature range) of an olefin-based resin cross-linked foam, dehydration does not occur, so that calcium oxide practically only acts as a hygroscopic agent.

Therefore, the use of calcium oxide as a hygroscopic agent has the following effects.

(1) The adverse effect of water can be easily removed without requiring special equipment.

(2) Adhered water and the like are retained in the composition in the form of calcium hydroxide, but are not re-released during the molding, crosslinking and foaming steps of the composition. On the other hand, when the foam is burned, calcium hydroxide releases water, so that the flame retarding effect is further enhanced.

(3) In the conventional method of drying in a dry atmosphere or at a high temperature, since there is a possibility of re-absorption of moisture, it is necessary to carry out a drying treatment just before processing. However, according to the method of adding calcium oxide, By properly adjusting the blending amount, it is possible to reduce or prevent the influence of new moisture absorption.

The mixing ratio of calcium oxide depends on the mixing ratio of the hydrated metal oxide and the amount of moisture absorption, but is usually 1 to 20 parts by weight, preferably 2 to 15 parts by weight with respect to 100 parts by weight of the olefin resin. Is. If the blending ratio is excessive, calcium hydroxide produced by reacting with water is alkaline, which may adversely affect the composite material.

In addition, a lubricant, a colorant, an antistatic agent, etc. can be added.

(Method for Producing Foam) In the present invention, a resin composition containing an olefin resin, a hydrated metal oxide, a flame retardant, a flame retardant aid, calcium oxide and a thermal decomposition type foaming agent is formed into a desired shape, usually It is formed into a sheet and irradiated with ionizing radiation (electron beam or radiation) to crosslink it, or it is chemically crosslinked with a chemical crosslinking agent such as peroxide that is contained in advance, and then it is heated to above the decomposition temperature of the foaming agent. Heat to foam.

In order to mold the foamable resin composition into a sheet or the like, it is usually carried out by an extruder at a temperature lower than the dividing temperature of the foaming agent. After viscoelasticity necessary for foaming is imparted to the resin by chemical crosslinking or irradiation with ionizing radiation, the resin is heated to a temperature equal to or higher than the decomposition temperature of the foaming agent to foam.

EXAMPLES The present invention will be described more specifically with reference to Examples and Comparative Examples below.

[Example 1] 150 parts by weight of aluminum hydroxide, 20 parts by weight of decabromodiphenyl ether as a flame retardant, and 10 parts of antimony trioxide as a flame retardant per 100 parts by weight of a vinyl acetate-ethylene copolymer (vinyl acetate-containing 25% by weight). Parts by weight, 25 parts by weight of azodicarbonamide as a thermal decomposition type foaming agent, and 10 parts by weight of calcium oxide as a hygroscopic agent, and after thoroughly mixing with a mixing roll heated to 130 ° C., with a heating press machine.
A 2 mm foamable resin composition sheet was prepared.

Next, the foamable resin composition sheet was irradiated with an electron beam of 5 Mrad with an electron beam irradiator to be crosslinked, and then 240 ° C.
And foamed by heating in a heating furnace.

Comparative Example 1 Example 1 except that calcium oxide was not added
A foam was obtained in the same manner as.

The results are shown in Table 1.

[Example 2] The foamable resin composition of Example 1 was blended with 1.5 parts by weight of digyl peroxide as a cross-linking agent, and similarly foamed without electron beam irradiation.

Comparative Example 2 Example 2 except that calcium oxide was not added.
A foam was obtained in the same manner as.

The results are shown in Table 1.

As is clear from Tables 1 and 2 above, in the case of crosslinking by electron beam irradiation (Example 1), the foaming ratio increased despite the large blending ratio of the hydrated metal oxide, Moreover, the generation of abnormal bubbles is suppressed. It can be inferred that the generation of abnormal bubbles is due to the suppression of microscopic structural defects generated by water vapor or the like in the foamable resin composition sheet. Also, in the case of chemical crosslinking (Example 2), a remarkable increase in foaming ratio is observed.

EFFECTS OF THE INVENTION According to the present invention, there is provided a highly filled composition foam having a high expansion ratio and having no structural defect due to generation of water vapor or the like despite the presence of a large amount of hygroscopic inorganic filler.

Claims (1)

[Claims] 1. A resin composition containing an olefin resin, a hydrated metal oxide, a flame retardant, a flame retardant aid, a thermal decomposition type foaming agent and calcium oxide as a hygroscopic agent at a decomposition temperature of the thermal decomposition type foaming agent. Molded into a desired shape at a temperature of less than, cross-linking by irradiating the obtained molded product with ionizing radiation or chemically cross-linked, and then the cross-linked molded product is decomposed at a temperature not lower than the decomposition temperature of the thermal decomposition type blowing agent A method for producing a highly-filled composition foam, which comprises heating to a temperature to cause foaming.