JPH0455440A - Production of flame retardant resin-crosslinked foam - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flame-retardant olefin resin crosslinked foam, and more specifically, to a flame-retardant cross-linked foam with a beautiful surface, uniform bubbles, and high thermal dimensional stability. The present invention relates to a method for producing a crosslinked resin foam.

Ryomai Nika I Flame-retardant olefin resin crosslinked foams highly filled with inorganic substances are known (Japanese Patent Publication No. 16217/1986, etc.).

By the way, conventionally known methods for manufacturing such crosslinked foams include chemical crosslinking using organic peroxides, azide compounds, silane compounds, etc., or crosslinking by irradiation with ionizing radiation such as electron beams or radiation. There is.

That is, a foamable resin composition containing a crosslinking agent such as an organic peroxide and a thermally decomposable blowing agent is formed into a sheet at a temperature below the temperature at which the blowing agent decomposes, and if desired, after pre-crosslinking by heating, A method of foaming by heating above the decomposition temperature of the blowing agent and chemical crosslinking, or a method of forming a foamable resin composition containing a thermally decomposable blowing agent into a sheet shape at a temperature below the decomposition temperature of the blowing agent and ionizing it. In this method, the material is crosslinked by irradiation with sexual radiation, and then heated to a temperature higher than the decomposition temperature of the foaming agent to cause foaming.

However, in chemical cross-linking methods using organic persulfides, etc., oxygen and radicals react with each other in the surface layer of the foam sheet during foaming, resulting in insufficient cross-linking reaction, especially in the skin layer, resulting in an uneven surface. The result is a rough foam. Crosslinking using a silane compound requires long-term treatment in hot water or steam to cause a crosslinking reaction, which poses problems in productivity and cost.

In addition, crosslinking methods using electron beams or radiation irradiation impart a certain degree of crosslinking before foaming, but foaming stability decreases when a large amount of hydrated metal oxide, flame retardant, or flame retardant aid is filled. Therefore, high crosslinking cannot be achieved, and the resulting foam has poor thermal dimensional stability.

The object of the present invention is to use a flame-retardant resin composition in which an olefin resin is filled with a hydrated metal oxide, a flame retardant, and a flame retardant aid, so as to have a beautiful surface, uniform bubbles, and heat resistance. An object of the present invention is to provide a method for producing a crosslinked foam with excellent dimensional stability.

As a result of intensive research to overcome the problems of the prior art, the present inventors discovered a resin composition containing an olefin resin, a hydrated metal oxide, a flame retardant, a flame retardant aid, and a pyrolytic blowing agent. When producing a flame-retardant crosslinked foam from a product, vinyl alkoxysilane is mixed with the composition, molded into a desired shape (usually a sheet shape) at a temperature below the decomposition temperature of the blowing agent, and this molded product is Using ionizing radiation, the olefin resin is radically crosslinked and the vinyl alkoxysilane is grafted onto the olefin resin, and the reacted molded product is heated to a temperature higher than the decomposition temperature of the blowing agent and foamed, and the vinyl alkoxy silane is It has been found that by causing condensation reaction crosslinking, it is possible to obtain a highly crosslinked, flame-retardant crosslinked foam that has a beautiful surface and uniform cells, and is highly crosslinked and has excellent thermal dimensional stability.

The present invention has been completed based on these findings.

・According to the present invention, a mixed raw material containing at least an olefin resin, a hydrated metal oxide, a flame retardant, a flame retardant aid, a pyrolytic blowing agent, and a vinyl alkoxysilane is used. , a step of molding into a desired shape at a temperature lower than the decomposition temperature of the pyrolytic foaming agent, irradiating the molded product with an electron beam or radiation to radically crosslink the olefin resin, and a step of causing a graft reaction of the olefin resin to the olefin resin, and heating the radically crosslinked molded product to a temperature higher than the decomposition temperature of the thermally decomposable blowing agent to foam it, and at the same time causing condensation reaction crosslinking with the vinyl alkoxysilane. Provided is a method for producing a flame-retardant resin crosslinked foam, comprising the steps of:

Hereinafter, the configuration of the present invention will be explained 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, and ethylene-vinyl acetate copolymer (EVA). Acrylic copolymer, ethylene-methyl methacrylate copolymer, ethylene-α-olefin copolymer (including linear low-density polyethylene), polypropylene, propylene-butene copolymer, propylene-ethylene copolymer, etc. , and mixtures thereof.

Examples of hydrated metal oxides include aluminum hydroxide, magnesium hydroxide, calcium hydroxide, barium hydroxide, tin oxide hydrate, basic magnesium carbonate, hydrotalcite, heart cru, talc, mica, and the like. Mention may be made of mixtures of these.

The hydrated metal oxide is blended in an amount of 40 to 500 parts by weight, preferably 50 to 300 parts by weight, per 100 parts by weight of the olefin resin. If it is less than 40 parts by weight, the effect of blending the inorganic powder will be small, and conversely, if the blending ratio is too large, it will be difficult to obtain a foam with a high expansion ratio, for example, when forming a foam. .

Examples of flame retardants include halogen-based flame retardants such as decabromodiphenyl ether, pentabromochlorocyclohexane, hexabromocyclododecane, 23,5.6
-Pentabromoethylbenzene, 1,2-bis(2,4
, 5-tribromophenoxy)ethane, chlorinated paraffin, hexachloropentacyclodecane, hexabromobenzene, and tetrabromobisphenol A derivatives.

These flame retardants can be used alone or in combination of two or more, but are usually 3 to 30 parts by weight, preferably 5 to 20 parts by weight, per 100 parts by weight of the olefin resin.
Add within the range of parts by weight.

By combining a flame retardant and a flame retardant aid, the flame retardant effect can be enhanced. Examples of flame retardant aids include:
Examples include antimony trioxide, sodium antimonate, tin oxide, and red phosphorus.

When using these flame retardant aids, the amount is usually 1 to 20 parts by weight, preferably 2 to 20 parts by weight, per 100 parts by weight of the synthetic resin.
The range is 15 parts by weight.

Examples of thermally decomposable blowing agents include azodicarbonamide, 4,4'-oxybis(benzenesulfonyl hydrazide), azobisisobutyronidenor, barium azodicarboxylate, etc., which are decomposed by heat to generate gas. Compounds can be exemplified.

The thermally decomposable blowing agent is usually blended in an amount of 2 to 30 parts by weight, preferably 5 to 25 parts by weight, per 100 parts by weight of the olefin resin.

Examples of the vinyl alkoxysilane include vinyltrimethoxysilane and vinyltriethoxysilane.

The blending amount of these vinyl alkoxysilanes is 0.2 to 2.5 parts by weight per 100 parts by weight of the olefin resin.
Preferably it is 0.7 to 1.5 parts by weight.

Furthermore, a reaction inhibitor such as mercaptan may be added to suppress polymerization between vinyl alkoxysilanes.

In addition, lubricants, colorants, antistatic agents, etc. can be added.

(Method for producing crosslinked foam) In the present invention, crosslinking by irradiation with ionizing radiation and chemical crosslinking by vinyl alkoxysilane are carried out in combination.

Specifically, a resin composition containing an olefin resin, a hydrated metal oxide, a flame retardant, a flame retardant aid, a vinyl alkoxysilane, and a pyrolyzable blowing agent is molded into a desired shape, usually a sheet. In the process of crosslinking by irradiating electron beams or radiation, grafting vinylalkoxysilane onto the olefin resin, and foaming by heating above the decomposition temperature of the blowing agent, condensation reaction crosslinking with vinylalkoxysilane is carried out at the same time as foaming. bring about

In order to form a foamable resin composition into a sheet or the like, it is usually carried out using an extruder at a temperature below the decomposition temperature of the foaming agent.

After giving the resin the viscoelasticity necessary for foaming by irradiating it with ionizing radiation (electron beam or radiation), it is heated to a temperature higher than the decomposition temperature of the foaming agent to foam, and cross-linked by the condensation reaction of the grafted vinylalkoxysilane. Do this.

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

The method of physical property testing is as follows.

<Degree of crosslinking; method for measuring gel fraction> A test piece was immersed in xylene at 130°C for 24 hours, and after drying the undissolved content, the weight was measured and evaluated as a ratio to the initial weight. However, the content of components that do not dissolve in xylene, such as aluminum hydroxide, was calculated and subtracted from the initial weight and dry weight.

<Flame retardancy test method> A foam test piece of 22 x 22 cm is the same size and has a thickness of 0.3 m.
JISA-1321-19 pasted on a galvanized iron plate of m
Measured according to the 75 Surface Burning Test Method.

tdθ: Time, temperature, and area that are indicators of the amount of heat generated during combustion CA: Smoke generation coefficient that is an indicator of the amount of smoke generated Here, tdθ=0 and CA<30 are indicators of noncombustible material.

Appearance> ○: Surface smoothness ×; Surface is not smooth but rough and thermal dimensional stability> A test piece of 150 x 150 mm was used, and the heat shrinkage rate (%) at 120° C. was measured in the vertical and horizontal directions.

[Example 1] 1 part by weight of aluminum hydroxide was added to 100 parts by weight of vinyl acetate-ethylene copolymer (vinyl acetate content 20% by weight).
50 parts by weight, 20 parts by weight of decabromidiphenyl ether as a flame retardant, 10 parts by weight of antimony trioxide, 1.2 parts by weight of vinyltrimethoxysilane, and 25 parts by weight of azodicarbonamide as a pyrolytic blowing agent and mixed thoroughly. After that, 2 m of resin was produced using a single screw extruder with a diameter of 65 mm.
A foamable resin composition raw sheet having a thickness fi of 1.5 mm was prepared by extrusion at .degree.

Next, this foamable resin composition sheet was irradiated with an electron beam of 3.4 Mrad using an electron beam irradiation machine to cause radical reaction crosslinking and graft reaction with vinyltrimethoxysilane.

Thereafter, this radically crosslinked foamable resin composition sheet was placed in a heating furnace set at about 250° C. and foamed to obtain a foam with a thickness of 5 mm (expansion ratio: 20 times).

When the degree of crosslinking of the foam thus obtained was measured by a gel fraction evaluation method, it was 30% for the foamable resin composition raw sheet after irradiation with an electron beam, and 65% after foaming. .

Further, the foam had uniform cells, excellent appearance and surface smoothness, high flame retardancy, and good heat resistance.

[Examples 2 to 5] Foams were obtained in the same manner as in Example 1, except that the proportions of aluminum hydroxide and azodicarbonamide used were changed as shown in Table 1.

[Example 6] Example 1 except that the olefin resin was changed to vinyl acetate-ethylene copolymer (vinyl acetate content: 15% by weight)
A foam was obtained in the same manner.

[Example 7] Example 1 except that the olefin resin was changed to vinyl acetate-ethylene copolymer (vinyl acetate content 25% by weight).
A foam was obtained in the same manner.

[Example 8] As olefin resins, 80 parts by weight of vinyl acetate-ethylene copolymer (vinyl acetate content 25% by weight) and low density polyethylene (density 0.922 g/C, melt index 4.0 g/min melting point peak) were used. A foam was obtained in the same manner as in Example 1, except that 20 parts by weight of the mixture (111°C) was used.

[Example 9] Very low density polyethylene (VLD) was used as the olefin resin.
A foam was obtained in the same manner as in Example 1, except that 100 parts by weight of PE (density 0.905 g/crtr, melt index 10 g/min) was used and the irradiation dose was 6.2 Mrad.

[Comparative Example 1] No vinyltrimethoxysilane was added and the irradiation dose was 4.
A foam with a thickness of 5 mm (expansion ratio of about 20 times) was obtained in the same manner as in Example 1, except that the foam was 5 Mrad. The gel fraction of this foam was 40%.

[Comparative Example 2] (Chemical crosslinking method) 1 part of aluminum hydroxide was added to 100 parts by weight of vinyl acetate-ethylene copolymer (vinyl acetate content 20% by weight).
50 parts by weight, 20 parts by weight of decabromidiphenyl ether as a flame retardant, 10 parts by weight of antimony trioxide, 1.2 parts by weight of vinyltrimethoxysilane, 25 parts by weight of azodicarbonamide as a pyrolytic blowing agent, 3 parts by weight of dicumyl peroxide. 0 parts by weight, kneaded at a temperature of 100 to 120°C in a small experimental kneader, formed into a sheet with a thickness of 1.5 mm using a hot press at 130°C, and heated at a temperature of 150°C using a hot press. Pre-crosslinking was carried out by heating under pressure at a temperature of
It was placed in a heating furnace set at 0°C and foamed to obtain a foam with a thickness of 5 mm (expansion ratio of about 20 times).

The results of Examples and Comparative Examples are collectively shown in Table 1.

(Left below) New Year's Day J-肱! According to the present invention, a flame-retardant foam with uniform cells having a beautiful surface can be obtained, and even a light-filled sheet for obtaining high ridge flame resistance can be stably foamed.

Then, during foaming or post-crosslinking, the foam becomes highly crosslinked, so that a crosslinked foam with excellent thermal dimensional stability can be obtained.

Claims (1)

[Claims] (1) A resin composition containing an olefin resin, a hydrated metal oxide, a flame retardant, a flame retardant aid, a pyrolytic blowing agent, and a vinyl alkoxysilane is heated at a temperature below the decomposition temperature of the pyrolytic blowing agent. molded into a desired shape, irradiating the obtained molded product with an electron beam or radiation to radically crosslink the olefin resin, and grafting the vinyl alkoxysilane onto the olefin resin;
Next, this radical reaction crosslinked molded product is heated to a temperature higher than the decomposition temperature of the thermally decomposable foaming agent to foam it, and condensation reaction crosslinking is caused by the vinyl alkoxysilane. Method of manufacturing foam.