JPH03247632A - Polyolefin-based expanded material containing inorganic filler and production thereof - Google Patents

Abstract

PURPOSE:To obtain the subject expanded material excellent in flame retardancy and heat resistance and useful as a building material, etc., by blending a specified resin component with an inorganic filler, a flame retardant and a foaming agent, molding the resultant mixture, applying an ionizing radiation thereto for cross-linking and heating for expansion. CONSTITUTION:With 100 pts.wt. resin component (Provided that vinyl acetate content in resin component is 5-20wt.%) consisting of an ethylene-vinyl acetate copolymer alone or a mixture composed of the above-mentioned copolymer and two or more kinds of other polyolefin-based resins, 30-60 pts.wt. inorganic filler (e.g. aluminum hydroxide), 10-20 pts.wt. flame retardant (e.g. tetrabromobisphenol A) and 15-30 pts.wt. foaming agent (e.g. azodicarbonamide) are blended to obtain a composition. The resultant composition is molded, irradiated with an ionizing radiation so as to be cross-linked and heated at >=the decomposition temperature of the foaming agent for expansion, thus providing the objective expanded material.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention provides flame retardance by containing an inorganic filler and a flame retardant in a polyolefin resin component such as an ethylene-vinyl acetate copolymer resin. The present invention also relates to a polyolefin resin foam having a relatively large expansion ratio and a method for producing the same.

(Prior Art) Synthetic resin foams have conventionally been used for construction materials, transportation equipment such as automobiles, packaging materials, household daily necessities, and other store applications. BACKGROUND ART Polyolefin resin foams, which are one of the general-purpose resins that have properties such as high elasticity, heat insulation, electrical 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 flammable resin flame retardant, and various studies have been conducted. There are usually two ways to make this polyolefin resin flame retardant, one of which is to add a halogen flame retardant and a flame retardant aid;
Another method is to add inorganic fillers.

However, these flame retardant methods have advantages and disadvantages; the former has the problem of generating halogen-based toxic gases during combustion, which is not only harmful to the human body but also corrodes equipment; In this case, the effect cannot be obtained unless the amount of inorganic filler added to the resin component is large, and if the amount of inorganic filler added is large, gas dissipation during the foaming process However, there was a problem that a product with a high expansion ratio could not be obtained.

Therefore, in the technique described in Japanese Patent Publication No. 62-16217, an ethylene-vinyl acetate copolymer is used as the olefin resin, and if necessary, it is mixed with other thermoplastic resins to produce 100 parts by weight of this copolymer. 50% of the inorganic filler
This problem is solved by using a composition comprising ~100 parts by weight, a blowing agent, optionally a flame retardant and a flame retardant aid, and optionally a crosslinking agent.

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 inorganic substances than the polymer component, and is rather an inorganic foam. It is something that should be said. In other words, this technology allows ethylene-vinyl acetate copolymer resin to be mixed with a large amount of inorganic filler, and the mechanical properties do not deteriorate significantly.
It was completed by discovering that it also has excellent moldability, and in this case, as mentioned above, it is easy to add large amounts of inorganic fillers, flame retardants, and flame retardant aids, and as described below. Another aim is to obtain a particularly high foaming ratio at the stage of producing a foam using such a composition.

That is, when the crosslinking means before heating and foaming is chemical crosslinking, an ethylene-vinyl acetate copolymer resin with a relatively low vinyl acetate content (5 to 30% by weight) is used to form a foamable composition. By mixing a crosslinking agent into the foaming composition and controlling it to a predetermined value (0.07% by weight or less), paying attention to the fact that the foaming performance is affected by the amount of water contained in the foamable composition, When the crosslinking means is radiation irradiation, it is important to note that ethylene-vinyl acetate copolymer resins with a high content of vinyl acetate have a so-called low crystallinity and are easy to mix with inorganic fillers. By specifically using a relatively large amount (40 to 90% by weight), a high expansion ratio can be obtained.

(Problems to be Solved by the Invention) The present invention relates to improvements in the above-mentioned conventional techniques in which the crosslinking means is radiation irradiation.

In other words, when ethylene-vinyl acetate copolymer resin is selected as a synthetic resin into which an inorganic filler can be mixed, a resin with a high vinyl acetate content has a so-called low crystallinity and cannot be filled with a large amount of inorganic filler. However, on the other hand, it also has mechanically unfavorable properties such as i) a low melting point, ii) noticeable creep characteristics, and ij) a low initial elastic modulus. This obstinacy is passed on to the body as well.

The purpose of the present invention is to obtain a synthetic resin foam having flame retardancy while avoiding such characteristics as much as possible.

(Means for Solving the Problems) The first aspect 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 (however, the vinyl acetate content in the resin component is 5%).
-20% by weight), 30 to 60 parts by weight of an inorganic filler, and a flame retardant. The second aspect 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 (
However, the vinyl acetate content in the resin component is within the range of 5 to 20% by weight) 100 parts by weight, and 30 to 6 parts by weight of the inorganic filler.
0 parts by weight, a flame retardant, and a foaming agent, the resulting molded product is crosslinked by irradiation with ionizing radiation, and then the temperature is higher than the decomposition temperature of the foaming agent. The gist of this invention is a method for producing a polyolefin resin foam, which is characterized by heating and foaming.

However, since the present invention uses an ethylene-vinyl acetate copolymer resin with a high degree of crystallinity, that is, a resin with a low content of vinyl acetate, the amount of inorganic filler incorporated is necessarily low. However, it is possible to increase the foaming ratio of the foam for its height, and by doing so, it is possible to reduce the amount of resin component that occupies the unit volume of the resulting foam. The total amount of heat generated per volume can be suppressed.

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

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

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

Therefore, in the present invention, in a resin component consisting of an 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 must let it be within you.

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

The other polyolefin resins used in the present invention include polyethylene, ethylene-α-olefin copolymer,
Ethylene-acrylic acid copolymer, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer resin whose vinyl acetate content is different from the above-mentioned main vinyl acetate copolymer resin, ethylene-ethyl These include acrylate copolymers, ethylene-vinyl acetate-vinyl chloride copolymers, and the like.

Inorganic fillers used in the present invention include 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, etc. Examples include phosphates, sulfates such as gypsum, and one or more of these powders are used.

Therefore, the blending ratio must be 30 to 60 parts by weight; if it is less than 30 parts by weight, the desired effect cannot be obtained due to the mixing of inorganic fillers, and if it exceeds 60 parts by weight, It becomes difficult to obtain the desired foaming ratio.

In the present invention, as mentioned above, those having a high degree of crystallinity,
In other words, since a material with a low vinyl acetate content is used, the amount of inorganic filler added naturally decreases, but if this is used in combination with a flame retardant and a flame retardant aid, the expansion ratio at the foam manufacturing stage will increase. They found an optimal amount of 30 to 60 parts by weight as a blending ratio that can compensate for the improvement in .

The flame retardants used in the present invention are preferably halogenated flame retardants, such as bisphenol A tetrabromo, bisphenol A epichlorohydrin glycidyl etherified condensate, tetrabromo bisphenol A diglycidyl ether and brominated bisphenol adduct, poly-4, Products such as 4-isopropylidene bis(2,6-dibromophenyl) carbonate with a bromine content of 80% by weight or less are highly flame retardant but emit little smoke, so use one or more of them in combination. etc., and can be suitably employed.

Further, in the present invention, a flame retardant aid such as antimony dioxide may be used. The blending ratio of the above flame retardant is preferably 10 to 20 parts by weight; if it is less than 10 parts by weight, the flame retardant effect of the obtained foam will be reduced, and if it exceeds 20 parts by weight, the flame retardant will have a There is a tendency for harm to occur.

In addition, when a flame retardant aid is used in combination, the blending ratio should be 5 to 5.
Preferably, it is 10 parts by weight.

Examples of the blowing agent used in the present invention include organic blowing agents such as azodicarbonamide and N,N-dinitrosopentamethylenetetramine, and inorganic blowing agents such as sodium bicarbonate and ammonium carbonate. Usually 15~
It is 30 parts by weight.

The method for producing the 2-polyolefin resin foam of the present invention includes:
A resin component consisting of an ethylene-vinyl acetate copolymer resin on the ridges 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 parts by weight, 30 to 60 parts by weight of an inorganic filler, preferably 10 to 20 parts by weight of a flame retardant, and a blowing agent are mixed and prepared, and a Banbury mixer, The mixture is kneaded using a kneader mixer, roll mill, etc. to obtain a composition. Next, this composition is used to form, for example, into a sheet, or while being continuously formed into a sheet, the formed body is irradiated with ionizing radiation to crosslink it, and then heated using an infrared irradiation device or hot air. It is introduced into a furnace and heated and foamed. In this way, the polyolefin resin foam according to the first aspect of the present invention is obtained.

The dose when irradiating with 1 it release radiation in the method for producing a polyolefin resin foam according to item 2 of the present invention depends on the thickness of the irradiated molded product and the type of resin used, but is usually 0.5
~8 Mrad.

(Function) In the first aspect of the present invention, a resin component consisting of a mixture of an ethylene-vinyl acetate copolymer resin and two or more types of polyolefin resins is used, and the vinyl acetate content in the resin component is 5 to 20% by weight. Using a specific range of
100 parts by weight of this and 30 to 60 parts by weight of an inorganic filler are blended within a specific range, and a flame retardant is further added to this composition. Vinyl acetate content of vinyl copolymer resin (low,
Therefore, although the composition is made of a composition containing a correspondingly low amount of inorganic filler, the foaming ratio can be increased accordingly.

In addition, the method for producing a polyolefin resin foam according to the second aspect of the present invention uses the composition constituting the polyolefin resin foam according to the first aspect of the present invention as a material with a blowing agent added thereto, and kneading, molding, and ionizable Since general-purpose techniques such as crosslinking by radiation, heating, and foaming can be used, the polyolefin resin foam filled with the inorganic substance according to the first aspect of the present invention can be easily produced.

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

Commercially available ethylene-vinyl acetate copolymer resin (vinyl acetate content: 19%, density: 0.94, Ml.

2.5) 100 parts by weight of a resin component made by mixing 75 parts by weight with 25 parts by weight of commercially available low density polyethylene (density: 0.92, MI, 4.0) (The vinyl acetate content in the resin component is 14%), 30 to 110 parts by weight of aluminum hydroxide powder (trade name: Hisilite-H42M, manufactured by Showa Denko K.K.) as an inorganic filler, 25 parts by weight of azodicarbonamide as a blowing agent, and decabrom as a flame retardant. A composition is prepared by blending 15 parts by weight of diphenyl ether, 5 parts by weight of antimony trioxide as a flame retardant aid, and 2 parts by weight of lubricants and other additives, and the mixture is adjusted to a temperature range of 100 to 120°C. The mixture was kneaded with rolls, then press-molded into a sheet with a thickness of 2°51 using a hot press machine, and then cross-linked by irradiating this sheet with a dose equivalent to an absorbed dose of 5.5 Mrad using an electron beam accelerator. did. Next, this sheet was placed in an oven whose temperature was adjusted to 230°C and foamed by heating to obtain a foamed sheet.

Table 1 shows the test results regarding the properties and flame retardancy of the foams of Examples and Comparative Examples obtained in the manner described above. However, the 01 surface combustion test method was measured by attaching a foam sheet to a 22 cm square iron plate and using the method specified in JIS A-1321-1975.

■, total calorific value (cal/g) and total calorific value (cal/c
Measurement method c) involves heating and burning the foam sheet and measuring the amount of heat generated.

(Effects of the Invention) The first aspect of the present invention is a runo having a structure similar to that of a ridge,
Compared to conventional foams using ethylene-vinyl acetate copolymer resins with low crystallinity, i) the heat resistance of the foams is improved;

ii) It is advantageous against deformation due to creep.

ij) High initial elastic modulus and rigidity.

iv) Since the amount of additives such as inorganic fillers can be reduced and the expansion ratio can be improved, manufacturing costs can be reduced.

It has the following effects.

Moreover, since the second aspect of the present invention has the same structure as above, the polyolefin resin foam according to the second aspect of the present invention can be easily produced.

Claims (1)

[Claims] 1. 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 within the range of 5 to 20% by weight) ) 100 parts by weight and 3 parts by weight of inorganic filler
A polyolefin resin foam filled with an inorganic substance consisting of a composition mainly consisting of 0 to 60 parts by weight and a flame retardant. 2. A resin component consisting of an ethylene-vinyl acetate copolymer resin alone or a mixture with two or more other polyolefin resins (however, the vinyl acetate content in the resin component is within the range of 5 to 20% by weight) 100 weight part and inorganic filler 3
After molding a composition containing 0 to 60 parts by weight, a flame retardant, and a foaming agent, the resulting molded product is crosslinked by irradiation with ionizing radiation, and then the foaming agent is decomposed. A method for producing a polyolefin resin foam, which is characterized by foaming by heating to a temperature higher than that temperature.