JPS6026500B2 - Method for manufacturing polyolefin resin foam filled with inorganic material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an ethylene-vinyl acetate copolymer containing a high concentration of inorganic substances or a polyolefin resin foam mixed with the copolymer.

The purpose is to propose a method for producing a high expansion ratio foam made of an inorganic-filled polyolefin resin, and a method for obtaining a foam with very little resin deterioration and good quality.

Filling polyolefin resins with inorganic compounds has been carried out for the purpose of eliminating pollution, reducing combustion, and saving resources.

For example, hydrates such as Mg(OH)3 and Mg(OH)2(CH)2 can improve flame retardancy by separating water of crystallization at a specific temperature, and can be used as so-called halogen-based flame retardants. In comparison, it is attracting attention because it does not produce toxic gas when burned and is inexpensive. However, conventionally, when an inorganic-filled polyolefin resin molded product is heated and foamed under normal pressure, it is difficult to obtain a highly foamed product, and even if it is obtained, it is inevitably colored due to bubbles, coarse foam, or resin deterioration. .

The reason why a foam with a high expansion ratio cannot be obtained is due to the metal contained in the inorganic compound, or because inorganic compounds are generally basic, the decomposition temperature of the blowing agent is the decomposition temperature of the blowing agent when it does not contain an inorganic compound. lower than the temperature.

Therefore, the decomposition of the blowing agent begins before the crosslinking agent decomposes and a crosslinked structure is introduced into the polyolefin resin, and the decomposition gas of the blowing agent escapes from the surface of the inorganic-filled polyolefin resin molding. it is conceivable that. In order to obtain a highly foamed inorganic-filled polyolefin resin, there is a method of introducing a crosslinked structure under pressure to decompose the blowing agent, and then heating and expanding it under normal pressure, but continuous production is difficult and it is produced in a batch process. Production efficiency is low, prices tend to be high, and long foam products cannot be manufactured, so their uses are limited.

The present invention has been made as a result of intensive studies in view of the above situation, and the gist of the invention is to add an inorganic compound powder to an ethylene-vinyl acetate copolymer or a polyolefin resin mixed with the copolymer, and heat-decomposable foaming. In the method of mixing and molding a foaming agent and an organic peroxide to form an inorganic-filled resin molded product and then heating it to a temperature higher than the decomposition temperature of the foaming agent to form a foam, the ethylene-vinyl acetate copolymer is % vinyl acetate component, a melt index of 0.1 to 5, and an organic peroxide having a half-life temperature in 1 minute of 170 qo or less. It's in the way the body is manufactured.

In the present invention, 100 parts by weight of an ethylene-vinyl acetate copolymer having a vinyl acetate content of less than 4% by weight and a melt index of 0.1 to 10 min/polymer or a polyolefin resin mixed with the above copolymer is used. On the other hand, inorganic compound powder 5
An inorganic-filled polyolefin resin molded product containing 0 to 250 parts by weight of a thermally decomposable blowing agent and an organic peroxide whose half-life temperature per minute is 170 qo or less is heated above the decomposition temperature of the blowing agent under normal pressure. This can be carried out by foaming.

That is, the features of the present invention can only be realized by a combination of a special ethylene-vinyl acetate copolymer and a special organic peroxide.

In the present invention, the ethylene-vinyl acetate copolymer has a pinyl acetate content of less than 40% by weight and a melt index of 0.1 to 5 according to method E of ASTM D12 paper-57r.
It is within the range of 10 minutes in the evening.

Other polyolefin resins include one or two of polyethylene, ethylene-Q-olefin copolymer, ethylene-acrylic acid copolymer, ethylene-propylene copolymer, chlorinated polyethylene, chlorosulfonated polyethylene, polybutadiene, etc. A mixture of more than one species. Inorganic compounds in the present invention include aluminum hydroxide, magnesium hydroxide, basic magnesium carbonate, calcium hydroxide, tin oxide hydrate, zirconium oxide, calcium carbonate, magnesium carbonate, talc, clay, bentonite, athanolgite, and boric acid. barium, zinc borate,
Gypsum, etc., and one or a mixture of two or more thereof.

Moreover, the surface of the above-mentioned inorganic compound may be treated with a well-known fatty acid-based, silane-based, or titanate-based coupling agent.

These inorganic compounds are powders with an average particle size of 0.01 to 50 particles, preferably 0.05 to 10 particles. The amount added is 30 to 25 parts by weight, preferably 50 to 20 parts by weight, per 100 parts by weight of the polyolefin resin. The organic peroxide of the present invention is a crosslinking agent that decomposes when heated to generate radicals, and has a half-life temperature of 170 degrees per minute.
o or less, such as 2,4-dichlorobenzoyl peroxide, benzoyl oxide,
1,1-di, t-butylbaroxy 3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-dibenzoyl/dioxyhexane, n-butyl 4,
4-di-te91 butyl peroxyvalerate and the like.

Additionally, a crosslinking aid may be used if necessary. The thermally decomposable blowing agent of the present invention is a substance that decomposes when heated and generates gas relatively rapidly, such as azodicarbonamide,
One or two of dinitrosobentamethylenetetramine, P,P'-oxybisbenzenesulfonyl hydraside, etc.
It is a mixture of more than one species.

The mixing amount of the blowing agent is appropriately selected depending on the desired expansion ratio of the foam, or in the foam of the present invention, it is often added in an amount of 5 to 5 parts by weight based on 10 parts by weight of the polyolefin resin. .

The specific gravity of the foam obtained by this is 0.2 to 0.02
It is. Next, in the present invention, the vinyl acetate content of the ethylene-vinyl acetate copolymer is limited to less than 40% and the melt index is limited to 0.1 to 5 minutes/10 minutes. Although foams with relatively high expansion ratios can be obtained, these foams are too flexible and have extremely poor compression recovery properties, resulting in only foams with poor commercial value. Also, discoloration due to resin deterioration cannot be avoided. Furthermore, when this resin is used, there are problems such as adhesion to the molding machine and mutual adhesion of the foamable sheets, forming pellets, and handling of sheet-like materials. An ethylene monovinyl acetate copolymer with a vinyl acetate content of less than 4% by weight and a melt index of 0.1 to 5 min/min has crystallinity, a high expansion ratio, and a foam with excellent compression recovery. can get.

If the melt index is 5 minutes/10 minutes or more, the resin deteriorates significantly and a highly foamed product cannot be obtained.

This is thought to be because the molecular cleavage of the resin is greater than the introduction of a crosslinked structure by the crosslinking agent. Furthermore, if the melt index is less than 0.1 min/10 min, it is difficult to mix with additives such as inorganic compounds, resulting in decomposition and poor dispersion of blowing agents, crosslinking agents, etc. due to heat generation.

In the present invention, the above-mentioned polyolefin resin is mixed with the above-mentioned inorganic compound, a blowing agent, and an organic peroxide to form a molded product.

Additives such as a coloring agent, an anti-aging agent, an ultraviolet absorber, a reinforcing agent, a foaming aid, a crosslinking aid, and a lubricant may be added as necessary. In this step, the molding must be carried out under conditions in which the blowing agent and crosslinking agent do not decompose. The inorganic-filled polyolefin resin molded product thus obtained is subjected to infrared heating.
A highly foamed product is made under normal pressure by a single method such as hot air heating, hot plate heating, submerged or above liquid heating, or a combination of these methods. A more specific explanation will be given below based on Examples.

Example 1 Magnesium hydroxide commercially available as an inorganic compound powder (Kisuma YF: Kyowa Chemical Industry Co., Ltd.) was added to 10 parts by weight of A resin shown in Table 1 (vinyl acetate content 33%, melt index 1.0). ) 150 parts by weight, 25 parts by weight of azodicarbonamide as a blowing agent, organic peroxide PO-1 shown in Table 2, and 0.0 parts by weight of a phenolic antioxidant.
3 parts by weight, 0.0 parts by weight of trimethylolpropane triacrylate as a crosslinking aid. The Marugame weight portion was kneaded with a mixing roll of 90 to 100 qo, and press-molded at 100°C into a sheet with a thickness of 3 sides.

This sheet was placed in a 220 qo oven and foamed. The results are shown in Table-3. Example 2 Table Date 1 Table - 2 Taiichi 3 The compounding recipe shown in Example 1 was kneaded in a Pan Bali mixer at 90 to 100°C, then pelletized, and pelletized using a four-sided extruder.
It was molded into a sheet with a thickness of 3 mm and a medium thickness of 20 mm at a temperature of 0 to 100°C.

This sheet was placed in a heating foaming furnace to obtain a long foam. Its characteristics are shown in Table 3.

From Table 3, the foams obtained from Examples 1 and 2 both had high expansion ratios and were excellent in appearance and compression recovery properties. Comparative Examples 1 to 5 Foams were made using the same method as in Example 2 using the combinations of the resins and organic peroxides shown in Table 3, but the foaming was incomplete and the foaming was incomplete, with coloration considered to be due to resin deterioration. It was the body.

As described above, according to the present invention, it is possible to produce a flame-retardant foam that has high foaming properties, excellent compression recovery properties, and excellent appearance, and has great industrial value.

Claims (1)

[Claims] 1 An inorganic compound powder, a thermally decomposable blowing agent, and an organic peroxide are mixed and molded into an ethylene-vinyl acetate copolymer or a polyolefin resin mixed with the above copolymer to form an inorganic-filled molded product, and then foamed. In the method of forming a foam by heating above the decomposition temperature of the agent, the ethylene-vinyl acetate copolymer contains less than 40% by weight of a vinyl acetate component and has a melt index of 0.1 to 5, and is heated for 1 minute. A method for producing an inorganic-filled polyolefin resin foam, which comprises heating and foaming an inorganic-filled molded product containing an organic peroxide having a half-life temperature of 170° C. or less under normal pressure.