JPH06104742B2 - Polyolefin resin foam filled with inorganic material and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention provides a flame-retardant property by containing an inorganic filler and a flame retardant in a polyolefin resin component such as ethylene-vinyl acetate copolymer resin. At the same time, it relates to a polyolefin resin foam having a relatively large expansion ratio and a method for producing the same.

(Prior Art) Conventionally, synthetic resin foams have been used in a wide range of applications such as building materials, transportation equipment such as automobiles, packaging materials, household daily necessities, etc., but are relatively inexpensive and chemically stable. Foams of polyolefin resins, which are one of the general-purpose resins having rich properties such as heat insulation, electric insulation, and light weight, have recently attracted attention.

However, in the field of application of building materials that require flame retardancy, it is necessary to make this flame-retardant resin flame-retardant, so various studies have been conducted. There are usually two ways to make this polyolefin resin flame-retardant, one of which is
This is a method of adding a halogen-based flame retardant and a flame retardant auxiliary agent, and another method is a method of adding an inorganic filler.

However, these flame-retardant means have advantages and disadvantages, and in the former case, there is a problem that halogen-based harmful gas is generated during combustion, which is not only harmful to the human body but also corrodes equipment. In that case, the effect cannot be obtained unless the amount of the inorganic filler added to the resin component is large, and when the amount of the inorganic filler added is large, the gas escapes in the foaming process. There is a problem that a high expansion ratio cannot be obtained.

Therefore, in the technology described in Japanese Patent Publication No. 62-16217, an ethylene-vinyl acetate copolymer is adopted as an olefin resin, and 100 parts by weight of this is mixed with another thermoplastic resin if necessary. Against this problem by using a composition comprising 50 to 100 parts by weight of an inorganic filler, a foaming agent, and optionally a flame retardant and a flame retardant auxiliary agent, and optionally a crosslinking agent. Has been resolved.

As shown in the detailed description and examples of the invention, the foam described in this prior art has a larger total amount of other components such as an inorganic substance than the polymer component. It should be said. That is, in this technique, the ethylene-vinyl acetate copolymer resin easily mixes a large amount of the inorganic filler, and the mechanical properties do not deteriorate so much,
It was completed by finding that it is also excellent in molding processability. In this case, as described above, it is easy to add a large amount of inorganic filler, flame retardant, flame retardant auxiliary agent, and as described below. In addition, it is aimed to obtain a particularly high expansion ratio at the stage of producing a foam using such a composition.

That is, when the cross-linking means in the pre-stage of the heat foaming is chemical cross-linking, one having a relatively low vinyl acetate content in the ethylene-vinyl acetate copolymer resin (5 to 30% by weight) is used,
By incorporating a cross-linking agent into the foamable composition and focusing on the fact that the foaming performance is affected by the amount of water contained in the foamable composition, this can be controlled to a predetermined value (0.07% by weight or less). When the crosslinking means is irradiation, ethylene-
Those with a high vinyl acetate content in the vinyl acetate copolymer resin have a low so-called crystallinity and are apt to mix with an inorganic filler, and those with a relatively high content (40-
90% by weight), each of which has a high expansion ratio.

(Problems to be Solved by the Invention) The present invention relates to an improvement in the case where the crosslinking means is irradiated with radiation, among the above-mentioned conventional techniques.

That is, when an ethylene-vinyl acetate copolymer resin is selected as a synthetic resin in which an inorganic filler can be mixed, one having a high vinyl acetate content as described above has a low so-called crystallinity and a large amount of an inorganic filler is filled. However, on the other hand, on the other hand, it also has mechanically unfavorable characteristics such as i) the melting point becomes low, ii) the creep characteristics remarkably appear, and iii) the initial elastic modulus is low. The body inherits the samurai.

The present invention has been made for the purpose of obtaining a synthetic resin foam having flame retardancy while avoiding such properties as much as possible.

(Means for Solving the Problems) 1 of the present invention is a resin component consisting of an ethylene-vinyl acetate copolymer resin alone or a mixture with two or more other polyolefin resins (provided that the vinyl acetate content in the resin component is 5 or less).
(Within the range of up to 20% by weight) 100 parts by weight, 30 to 60 parts by weight of an inorganic filler, and a polyolefin resin foam filled with an inorganic material composed of a composition containing a flame retardant as a main material. The second point of the present invention is ethylene-
100 parts by weight of a resin component consisting of vinyl acetate copolymer resin alone or a mixture of two or more other polyolefin resins (provided that the vinyl acetate content in the resin component is in the range of 5 to 20% by weight); 30 to 60 parts by weight of a filler, a flame retardant, and after molding using a composition containing a foaming agent, the resulting molded body is irradiated with ionizing radiation to crosslink,
The gist of the invention is a method for producing a polyolefin resin foam, which is characterized by heating the foaming agent to a temperature not lower than the decomposition temperature for foaming.

In the present invention, however, since an ethylene-vinyl acetate copolymer resin having a certain degree of crystallinity, that is, a resin having a low vinyl acetate content, is used, the inorganic filler is inevitably correspondingly low in blending. However, the foaming ratio of the foam can be increased, and by doing so, the amount of the resin component in the unit volume of the resulting foam can be reduced. The total calorific value per unit volume of can be suppressed.

Therefore, an effect equal to or greater than the effect achieved by the above-described conventional technique in which the amount of the resin component occupying in the unit volume of the foam is relatively reduced by mixing a large amount of the inorganic filler is achieved.

The ethylene-vinyl acetate copolymer resin used in the present invention preferably has a vinyl acetate content within the range of 10 to 20% by weight.

The ethylene-vinyl acetate copolymer resin may be used alone or as a mixture with two or more kinds of other polyolefin resins. In this case, the ethylene-vinyl acetate copolymer resin is preferably 50 to 75 parts by weight, and 100 parts by weight together with the other polyolefin resin. By doing so, the vinyl acetate content in the resin component can be kept within the range of 5 to 20% by weight.

In the present invention, however, in the resin component comprising the ethylene-vinyl acetate copolymer resin alone or a mixture with two or more other polyolefin resins, the vinyl acetate content in the resin component is in the range of 5 to 20 parts by weight. You have to be inside.

When the vinyl acetate content is less than 5 parts by weight, it becomes difficult to mix the inorganic filler, and when it exceeds 20 parts by weight, the obtained foam becomes too soft.

Examples of the other polyolefin resin used in the present invention include polyethylene, ethylene-α-olefin copolymers, ethylene-acrylic acid copolymers, ethylene-propylene copolymers, and ethylene-vinyl acetate containing the vinyl acetate as the main component. The vinyl acetate copolymer resin is an ethylene-vinyl acetate copolymer resin having a different vinyl acetate content, an ethylene-ethyl acrylate copolymer, an ethylene-vinyl acetate-vinyl chloride copolymer, or the like.

The inorganic filler used in the present invention includes hydrated metal compounds such as aluminum hydroxide and magnesium hydroxide, metal oxides such as alumina and titanium oxide, carbonates such as calcium carbonate and magnesium carbonate, calcium phosphate, potassium metaphosphate and the like. Examples thereof include phosphates and sulfates such as gypsum, and one or more of these powders are used.

However, the blending ratio must be 30 to 60 parts by weight, and if it is less than 30 parts by weight, the effect that can be obtained by mixing the inorganic filler cannot be obtained, and if it exceeds 60 parts by weight. It becomes difficult to obtain the desired expansion ratio.

In the present invention, as described above, the crystallinity is somewhat high,
That is, since the one having a low vinyl acetate content is used, the addition amount of the inorganic filler is naturally lowered, but when this is used in combination with the flame retardant and the flame retardant auxiliary, the expansion ratio in the production step of the foam is reduced. The optimum amount of 30 to 60 parts by weight has been found as a blending ratio that can be compensated by improving the above.

As the flame retardant used in the present invention, a halogen-based flame retardant is preferable, and bisphenol A tetrabromo, bisphenol A epichlorohydrin glycidyl etherified condensate, tetrabromobisphenol A diglycidyl ether and brominated bisphenol adduct, poly-4, 4-Isopropylidene bis (2,6-dibromophenyl) carbonate with a bromine content of 80% by weight or less has high flame retardancy but emits a small amount of smoke, so use one or more of them together. Etc. and can be suitably adopted.

Further, in the present invention, a flame retardant aid such as antimony trioxide may be used. The blending ratio of the above flame retardant is preferably 10 to 20 parts by weight, and if it is less than 10 parts by weight, the flame retardant effect of the resulting foam becomes low, and if it exceeds 20 parts by weight, the flame retardant has It tends to cause harmful effects.

When a flame retardant aid is used in combination, the blending ratio is 5
It is preferably 10 parts by weight.

Examples of the foaming agent used in the present invention include azodicarbonamide, N, N-dinitrosopentamethylenetetramine and other organic foaming agents, sodium bicarbonate, and inorganic foaming agents such as ammonium carbonate. Usually 15-30
Parts by weight.

The method for producing the 2 polyolefin resin foam of the present invention is
Resin component consisting of the above ethylene-vinyl acetate copolymer resin alone or a mixture with two or more other polyolefin resins (provided that the vinyl acetate content in the resin component is within the range of 5 to 20% by weight) 100 30 to 60 parts by weight of an inorganic filler, preferably 10 to 20 parts by weight of a flame retardant, and a foaming agent as a main component are mixed and prepared with respect to parts by weight, and a Banbury mixer, a kneader mixer, a roll mill. And the like are kneaded to obtain a composition. Then, using the composition, for example, after molding into a sheet or while continuously molding into a sheet, the molded body is irradiated with ionizing radiation to be crosslinked,
Then, it is introduced into an infrared irradiator or a hot-air stove to heat and foam. Thus, the polyolefin resin foam of 1 of the present invention can be obtained.

The dose for irradiating ionizing radiation in the method for producing a polyolefin resin foam according to 2 of the present invention is usually 0.5 to 8 Mrad, although it depends on the thickness of the article to be irradiated and the type of resin used.
Is.

(Function) In the first aspect of the present invention, a resin component comprising a mixture of an ethylene-vinyl acetate copolymer resin and two or more polyolefin resins is used, and the vinyl acetate content in the resin component is 5 to 20% by weight. In the range of 100 parts by weight, the inorganic filler is blended within a specific range of 30 to 60 parts by weight, and a flame retardant is further added to the composition as a main component. As a result, the ethylene-vinyl acetate copolymer resin has a low vinyl acetate content, and therefore is composed of a composition in which a low compounding amount of an inorganic filler corresponding thereto is compounded, but the expansion ratio is correspondingly increased. You can do it.

The method for producing a polyolefin resin foam according to the second aspect of the present invention uses a composition obtained by adding a foaming agent to the composition constituting the polyolefin resin foam according to the first aspect of the present invention as a material, and kneading, molding, and ionizing property. Since a general technique of crosslinking by radiation, heating, and foaming can be used, the polyolefin resin foam filled with the inorganic substance of the present invention can be easily manufactured.

(Examples) Examples of the present invention will be described below.

Commercially available ethylene-vinyl acetate copolymer resin (vinyl acetate content: 19%, density: 0.94, MI; 2.5) 75 parts by weight mixed with commercially available low density polyethylene (density: 0.92, MI; 4.0) 25 parts by weight 100 parts by weight of the resin component (vinyl acetate content in the resin component is about 14%) and aluminum hydroxide powder (trade name; Hydilite-H42M, Showa Denko KK) as an inorganic filler 30-110 parts by weight Parts, 25 parts by weight of azodicarbonamide as a foaming agent, 15 parts by weight of decabrom diphenyl ether as a flame retardant, 5 parts by weight of antimony trioxide as a flame retardant aid, and 2 parts by weight of a lubricant and other additives. To obtain a composition, which is kneaded with a mixing roll adjusted to a temperature range of 100 to 120 ° C., a sheet having a thickness of 2.5 mm is formed by press molding with a hot press machine, and then an electron beam accelerator is applied to the sheet. The absorbed dose is 5.5Mra Crosslinking was performed by irradiating a dose corresponding to d. Then this sheet 23
It is placed in an oven whose temperature is adjusted to 0 ° C and heated and foamed.
A foamed sheet was obtained.

Table 1 shows the test results for the properties and flame retardancy of the foams of the respective Examples and Comparative Examples obtained as described above. However ,. The surface sintering test method is a method in which a foam sheet is attached to a 22 cm square iron plate and the method is specified in JIS A-1321-1975.

． The total calorific value (cal / g) and total calorific value (cal / cc) are measured by sintering the foamed sheet and measuring the amount of heat generated.

(Effects of the Invention) Since 1 of the present invention is configured as described above,
I) The heat resistance of the foam is improved as compared with the conventional foam using the low crystallinity ethylene-vinyl acetate copolymer resin.

ii) Advantageous against deformation due to creep.

iii) The initial elastic modulus is high and rigidity is obtained.

iv) Since the amount of additives such as an inorganic filler is small and the expansion ratio can be mentioned, the manufacturing cost can be reduced.

And so on.

Further, since the second aspect of the present invention is configured as described above, the polyolefin resin foam of the second aspect of the present invention can be easily produced.

Claims (2)

[Claims] 1. A resin component comprising an ethylene-vinyl acetate copolymer resin alone or a mixture with two or more other polyolefin resins (provided that the vinyl acetate content in the resin component is 5 to 5).
Polyolefin resin foam filled with an inorganic material composed of a composition containing 100 parts by weight, 30 to 60 parts by weight of an inorganic filler, and a flame retardant as main components. 2. A resin component comprising an ethylene-vinyl acetate copolymer resin alone or a mixture with two or more other polyolefin resins (provided that the vinyl acetate content in the resin component is 5 to 5).
20% by weight) 100 parts by weight, 30 to 60 parts by weight of an inorganic filler, a flame retardant, and a foaming agent are used to obtain a molded product. A method for producing a polyolefin resin foam, which comprises irradiating the body with ionizing radiation to crosslink the body, and then heating the body above the decomposition temperature of the foaming agent to foam the body.