JPH0153295B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a blowing agent composition for water-crosslinkable polymers. More specifically, the present invention relates to a blowing agent composition suitable for obtaining a crosslinked foam of an olefinic polymer having a hydrolyzable silane group as a crosslinkable group. There are many known techniques for producing crosslinked foams of olefin polymers. A mixture of an olefin polymer and a blowing agent,
A method of crosslinking by irradiating with radiation and then heating and foaming. A method in which a peroxide crosslinking agent and a foaming agent are blended into an olefin polymer and then heated to effect crosslinking and foaming. However, none of these methods is perfect as a technique. That is, the radiation crosslinking method requires special and expensive crosslinking equipment, and furthermore, due to the functionality of industrially usable irradiation equipment, it is practically impossible to use it for thick molded products. . On the other hand, the peroxide crosslinking method requires careful control of processing temperature and conditions.
Such control is often difficult to achieve because it requires a precise balance between the activation temperature of the peroxide crosslinker and blowing agent and the softening temperature of the olefinic polymer. By the way, in addition to the above-mentioned radiation crosslinking method and peroxide crosslinking method, methods using water crosslinkable polymers are known as methods for producing crosslinked foams of olefinic polymers. That is, a silicone-grafted olefin polymer obtained by graft copolymerizing an unsaturated silane compound to an olefin polymer, or a copolymer mainly composed of an olefin hydrocarbon and an olefinic unsaturated silane compound, and a foamed A molded article of a composition consisting of an agent and a silanol condensation catalyst is foamed by heating, and crosslinking is achieved by immersing it in hot water or exposing it to a heated steam atmosphere before, after, or simultaneously with the foaming operation. This method is performed by However, as far as the present inventors know, there are disadvantages that are not suitable for industrial use, such as molded bodies having a non-uniform degree of crosslinking and the fact that it takes time to reach a stable degree of crosslinking. Particularly in the case of thick molded products, the degree of crosslinking changes over time depending on the environment and atmosphere in which the product is used, making it extremely difficult to maintain stable physical properties. With the aim of solving the above-mentioned drawbacks, the inventors of the present invention have conducted extensive research and found that by crosslinking and foaming a water-crosslinkable polymer using the following blowing agent composition in the presence of a silanol condensation catalyst, We discovered that it is possible to obtain a foam that is uniformly crosslinked to the inside.
The present invention has now been completed. The blowing agent composition of the present invention comprises azodicarbonamide and at least one hydrogen peroxide-added inorganic compound selected from the group consisting of carbonate hydrogen peroxide, borate hydrogen peroxide, and phosphate hydrogen peroxide. The amount of hydrogen peroxide-added inorganic compound added is usually 0.1 parts by weight or more per 1 part by weight of azodicarbonamide, preferably 0.1 to 2.0 parts by weight, and more preferably 0.5 parts by weight.
It is desirable to use ~1.0 part by weight. Specific examples of hydrogen peroxide-added inorganic compounds used by adding to azodicarbonamide include sodium percarbonate, potassium percarbonate, sodium perborate, potassium perborate, sodium perphosphate, potassium perphosphate, etc. These compounds can be obtained by a method of reacting hydrogen peroxide with sodium carbonate, potassium carbonate, sodium borate, potassium borate, sodium phosphate, or potassium phosphate, respectively. The water-crosslinkable polymer as used in the present invention refers to an olefin polymer in which a silane having a hydrolyzable organic group is bonded to the main chain or side chain, and includes an olefin polymer and an olefinic unsaturated silane. There are graft copolymers with compounds and random copolymers of olefinic hydrocarbons and olefinically unsaturated silane compounds, and specific examples include the following. 1 Graft copolymer of olefinic polymer and olefinic unsaturated silane compound (1) Olefinic unsaturated silane compound Olefinic unsaturated silane compound represented by the general formula RR′nSiY _3-o (where R is Olefinic hydrocarbon or hydrocarbonoxy group, R' is an aliphatic saturated hydrocarbon group, Y is a hydrolyzable organic group, n is 0.1 or 2. When there is more than one Y, they are not the same. ) Specific examples of this unsaturated silane compound include R such as vinyl,
Allyl, isopropenyl, butenyl, cyclohexenyl, Y is methoxy, ethoxy, formyloxy, acetoxy, propionoxy,
Alkyl, R′ is methyl, ethyl, propyl,
They are decyl and phenyl. The most preferred among these are vinyltrimethoxysilane, vinyltriethoxysilane, and vinyltriacetoxysilane. (2) Olefin-based polymers The olefin-based polymers that should become the backbone for graft copolymerization with the above unsaturated silane include polyethylene, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, polypropylene, chlorinated polyethylene, etc. It is wide-ranging. An olefinic unsaturated silane compound is graft copolymerized onto an olefinic polymer in the presence of a radical generator to obtain an olefinic polymer grafted with an unsaturated silane compound. 2 Random copolymer of olefin hydrocarbon and olefinic unsaturated silane compound The copolymerization of olefin hydrocarbon and the above-mentioned olefinic unsaturated silane compound is carried out using a polymerization initiator, and under any conditions under which polymerization of both occurs. You can do it with As a crosslinking method, unlike the known method of exposing to a water atmosphere, the present invention uses an azozoan as This method is characterized by the generation of water necessary for silane crosslinking at the same time as the decomposition of the dicarbonamide, and foaming and crosslinking are performed simultaneously. That is, since crosslinking is carried out by water generated from the blowing agent composition and the crosslinking is completed in a short time, there is no need to expose it to a water atmosphere before, during or after the foaming operation, and the production time can be shortened. Gas generation due to thermal decomposition of azodicarbonamide and water generation occur simultaneously, so the temporal and viscoelastic balance between foaming and crosslinking is very good. Therefore, the cells in the molded product are uniform, fine, and extremely elastic. It becomes a sponge. The blowing agent composition of the present invention is not only excellent in the above points as a blowing agent composition for water-crosslinkable polymers, but also generates a very large amount of gas effective for expansion, and is free from decomposition residues of azodicarbonamide. It also has the advantage of having less Table 1 shows the amount of gas generated after 20 minutes at 200°C from a blowing agent obtained by blending azodicarbonamide with sodium percarbonate. The amount of gas generated is determined by adding a blowing agent to a test tube connected to a gas burette and placing it in liquid paraffin.
It was dispersed in 10 ml and measured. For comparison, the same measurements were conducted for azodicarbonamide alone and sodium percarbonate alone. When other hydrogen peroxide-added inorganic compounds were similarly measured, almost the same gas amount increasing effect was observed. Although it is extremely difficult to elucidate the decomposition mechanism, the decomposition mechanism of azodicarbonamide, which is the first component of the blowing agent composition of the present invention, is somehow changed by the added hydrogen peroxide-added inorganic compound such as sodium percarbonate. it is conceivable that.

[Table] The blowing agent composition of the present invention increases the amount of gas generated per unit of azodicarbonamide blended, so azodicarbonamide can be used very effectively and the amount used can be reduced. can.
That is, when azodicarbonamide decomposes,
Since there are many parts to be gasified, there will be less decomposition residue, and in the foam manufacturing process, there will be almost no damage to molded products and molding equipment due to decomposition residue. In the present invention, the target resin is a water-crosslinkable polymer, but other rubbers and resins may be mixed and used. For example, polyethylene, polypropylene,
Olefin resins such as polybutene, vinyl copolymers such as ethylene-vinyl acetate, ethylene-vinyl alcohol, ethylene-propylene, propylene-butadiene, polybutadiene and butadiene mono or copolymers such as ABS, SBR, chlorinated polyethylene, etc. There is. In some cases, a peroxide crosslinking agent may be added to allow water crosslinking and peroxide crosslinking to be used together. Type of resin to be mixed,
Depending on the amount, ratio and degree of water crosslinking and peroxide crosslinking,
Foams with various physical properties can be obtained. Further, the blowing agent composition of the present invention may be further mixed with other blowing agents and used as a mixed blowing agent.
For example, dinitropentamethylenetetramine,
Heavy metal salt of azodicarbonamide, 4,4'-oxybis(benzenesulfonylhydrazide), p-
Organic blowing agents such as toluenesulfonyl hydrazide,
Examples include inorganic blowing agents such as sodium bicarbonate and ammonium carbonate, and volatile blowing agents. Further, known foaming aids such as urea, urea compounds, zinc white, and zinc stearate may be used in combination. The blowing agent composition of the present invention contains 100% water-crosslinkable polymer.
Usually 0.3 to 80 parts by weight is used, but the desired expansion ratio, molding method, type and amount of hydrogen peroxide-added inorganic compound to be used together, and in the case of a mixed blowing agent, the blowing agent to be mixed and its It may be changed as appropriate in consideration of various factors such as the amount of gas generated. In the present invention, calcium carbonate, magnesium carbonate, calcium sulfate, aluminum sulfate,
Inorganic fillers such as silica, talc, clay, and glass fiber, organic fillers such as wood flour, powdered cellulose, and wood pulp, crosslinking accelerators, antioxidants, ultraviolet absorbers, plasticizers, lubricants, flame retardants, and pigments. , coupling agents, nucleating agents, etc., may be used as necessary. The presence or absence of crosslinking or the degree of crosslinking in the foamed molded article was determined by measuring the gel fraction. (Method for Measuring Gel Fraction) A molded article weighing Wg was heated under xylene reflux for 10 hours and then dried in a hot air circulation oven at 100°C to obtain an insoluble component of W'g. Gel fraction (%)=W'/W×100 The present invention will be described in detail below with reference to Examples. Example 1 Water-crosslinkable polymer (manufactured by Mitsubishi Yuka Co., Ltd.: Linklon
LF-710A) 100 parts by weight, 1 part by weight of low-density polyethylene masterbatch containing 1% by weight of dibutyltin dilaurate, and azodicarbonamide
3.5 parts by weight, 2.0 parts by weight of sodium percarbonate, zinc white
Add 1.5 parts by weight and heat on roll mill to temperature 120-125
Mixed for 5 minutes at °C. The gel fraction of the mixture was 0% by weight. Next, the mixture was placed in a 10 mm deep and 120 mm square mold, heated at 160° C. for 10 minutes under a pressure of 120 Kg/cm ² , and then the pressure was removed to cause foaming. Specific gravity of foam molded products
At 0.065 g/cm ³ , the bubbles were uniform, fine, highly elastic, and beautiful white. Gel fraction is 75% by weight
It was hot. Comparative Example In Example 1, heating and foaming was carried out in the same manner as in Example 1 except that sodium percarbonate was omitted.
Gas leakage occurred from the surface of the foam, causing it to shrink. The molded article had a specific gravity of 0.28 g/cm ² and a gel fraction of 8% by weight. Example 2 A foamed molded article was obtained in the same manner as in Example 1 except that sodium percarbonate was replaced with sodium perborate. The specific gravity of the foam molded product is 0.068g/
The bubbles were ^uniform , fine, elastic, and beautiful white in size. The gel fraction was 75% by weight. Example 3 A foamed molded article was obtained in the same manner as in Example 1 except that sodium percarbonate was replaced with potassium perphosphate. The specific gravity of the foam molded product is 0.068g/
The bubbles were ^uniform , fine, elastic, and beautiful white in size. The gel fraction was 75% by weight. Example 4 Water-crosslinkable polymer (manufactured by Mitsubishi Yuka Co., Ltd.: Linklon
LF-710A) 100 parts by weight, 1 part by weight of low-density polyethylene masterbatch containing 1% by weight of dibutyltin dilaurate, and azodicarbonamide
3.5 parts by weight, 3.5 parts by weight of sodium percarbonate, zinc white
Add 2.0 parts by weight and 30 parts by weight of light calcium carbonate,
Mixed for 10 minutes on a roll mill at a temperature of 120-125°C. The gel fraction of the mixture was 0% by weight. Next, the mixture was placed in a 10 mm deep and 120 mm square mold, heated at 160° C. for 10 minutes under a pressure of 120 Kg/cm ² , and then the pressure was removed to cause foaming. Specific gravity of foam molded products
The bubbles were 0.071 g/cm ³ and were uniform, fine, highly elastic, and beautiful white. Gel fraction is 58% by weight
It was hot. Example 5 Water-crosslinkable polymer (manufactured by Mitsubishi Yuka Co., Ltd.: Linklon
LF-710A) 80 parts by weight, low density polyethylene
20 parts by weight, 0.8 parts by weight of a low-density polyethylene masterbatch containing 1% by weight of dibutyltin dilaurate and 0.2 parts by weight of dicumyl peroxide,
3.5 parts by weight of azodicarbonamide, 2.0 parts by weight of sodium percarbonate, and 1.5 parts by weight of a urea-based auxiliary agent were added and mixed on a roll mill at a temperature of 120 to 125°C for 5 minutes.
The gel fraction of the mixture was 0% by weight. Next, the mixture was taken out as a sheet from the mill and heated and foamed in a 180°C salt bath for 8 minutes. The foamed molded product had a specific gravity of 0.068 g/cm ³ , the bubbles were uniform, fine, and had a beautiful white color with high elasticity. The gel fraction was 80% by weight. Example 6 Water-crosslinkable polymer (manufactured by Mitsubishi Yuka Co., Ltd.: Linklon
To 100 parts by weight of LF-710A), 1.2 parts by weight of a low-density polyethylene masterbatch containing dibutyltin dilaurate, 3.5 parts by weight of azodicarbonamide, 1.0 parts by weight of sodium percarbonate, and 1.0 parts by weight of sodium perborate were added, and the mixture was heated on a roll mill. and mixed for 5 minutes. The gel fraction of the mixture was 0% by weight. The mixture was then removed from the mill as a sheet and foamed by heating in a gear oven at a temperature of 220° C. for 5 minutes. The resulting foamed molded product had a specific gravity of 0.065 g/cm ³ , the cells were uniform and fine, and the foam was a beautiful white product with high elasticity. Gel fraction is 65
It was in weight%.

Claims (1)

[Scope of Claims] 1. At least one hydrogen peroxide-added inorganic compound selected from the group consisting of carbonate hydrogen peroxide, borate hydrogen peroxide, and phosphate hydrogen peroxide is added to azodicarbonamide. A foaming agent composition for a water-crosslinkable polymer. 2. The blowing agent composition according to claim 1, wherein the hydrogen peroxide-added inorganic compound is sodium percarbonate. 3. The blowing agent composition according to claim 1, wherein the hydrogen peroxide-added inorganic compound is sodium perborate.