JPH032894B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to blowing agent compositions. Azodicarbonamide is widely used as a blowing agent in the production of synthetic resin foams, but the decomposition temperature of commonly used azodicarbonamide is as high as approximately 200°C, so the atmosphere during foaming must be
The temperature is as high as 200 to 220°C, and metal oxides, metal salts of fatty acids, amines, etc. are added to lower the decomposition temperature. However, in the above method, azodicarbonamide could not be decomposed uniformly at low temperature while generating a large amount of gas, and a resin foam with poor thermal stability could not be obtained. In addition, soft vinyl chloride resin foam has good mechanical strength, appearance, and feel, so it is used in various applications such as vinyl leather, but plasticizers are added to give it flexibility. This migration to the surface causes the surface to become sticky during use, contaminates surrounding utensils, and the foam itself loses its plasticizer, resulting in a decrease in physical properties. In order to improve this drawback, ethylene-
It has been proposed to use a graft polymer obtained by graft polymerizing vinyl chloride onto a vinyl acetate copolymer. However, the above-mentioned graft polymer has poor heat resistance at high temperatures, and when producing foam using a blowing agent such as azodicarbonamide, it is dechlorinated because it is heated to 200-220°C, which is above the decomposition temperature of the blowing agent. The disadvantage was that the foam was colored by decomposition and the viscosity of the graft polymer was reduced, making it impossible to obtain a foam with uniform cells. In view of the above-mentioned drawbacks, the object of the present invention is to mainly contain azodicarbonamide,
The purpose of the present invention is to obtain a blowing agent composition that uniformly generates and decomposes a large amount of gas at low temperatures. The blowing agent composition consists of 100 parts by weight. The blowing agent composition in the present invention is formed by adding 1 to 100 parts by weight of zinc fatty acid and zinc hydroxide to 100 parts by weight of azodicarbonamide, but when the amount of zinc fatty acid and zinc hydroxide added is small, The effect of lowering the decomposition temperature of azodicarbonamide will be reduced, and conversely, too much will have a negative effect on the foam obtained, so
It is preferable to add up to 20 parts by weight. As the fatty acid zinc, a zinc salt of any fatty acid can be used, and examples thereof include zinc laurate, zinc palmitate, zinc stearate, zinc ricinoleate, zinc oleate, zinc undecylenate, and the like. The graft polymer used in the present invention is an ethylene-vinyl acetate copolymer with a vinyl acetate content of 10 to 55% by weight, and 20 to 55% of vinyl chloride in the polymer.
It is graft polymerized to 90% by weight, and if the content of vinyl acetate in the ethylene-vinyl acetate copolymer is less than 10% by weight, the flexibility of the graft polymer will decrease and a soft foam will not be obtained. figure,
If it exceeds 55% by weight, the mechanical properties of the foam will deteriorate, so it is limited to 10 to 55% by weight.
As the melt index of the ethylene-vinyl acetate copolymer decreases, the melt viscosity of the graft polymer increases, resulting in poor kneading and processability with the blowing agent composition; It is preferable that the amount of grafted vinyl chloride is less than 20% by weight, since the mechanical properties of the vinyl chloride will deteriorate, so it is preferable that the amount is 1 to 30 g/10 minutes.
If the amount exceeds 90% by weight, it becomes difficult to crosslink, so vinyl chloride is graft-polymerized so that it accounts for 20 to 90% by weight in the graft polymer, and preferably 40% by weight.
~89% by weight. In the present invention, the blowing agent composition is used when producing the foam of the graft polymer, and the amount of the blowing agent composition to be added may be appropriately determined depending on the density of the foam to be produced. , generally for 100 parts by weight of the graft polymer,
It is preferable to add 0.5 to 30 parts by weight. In the present invention, a foam is produced from the mixture obtained by mixing the above-mentioned graft polymer and a blowing agent composition, but any method may be adopted as the production method. A method of melt-kneading at a temperature below the decomposition temperature of the blowing agent composition, forming a molded body, irradiating the molded body with ionizing radiation to crosslink it, and then heating it to a temperature above the decomposition temperature of the blowing agent composition to foam it; An organic peroxide is added to the above mixture, melt-kneaded at a temperature below the decomposition temperature of the blowing agent composition to form a molded article, and then heated to a temperature above the decomposition temperature of the blowing agent composition to cause crosslinking and foaming. Examples include methods. Any method can be used to obtain the molded product by melt-kneading the above, such as an extruder, a calendar roll, an injection molding machine, etc., and the melt-kneading temperature is set to 140 to 160°C, which is the decomposition temperature of the blowing agent composition. Because the temperature is higher than the softening temperature of the graft polymer,
Preferably, the temperature is below 140°C. The shape of the molded product may be, for example, a sheet, rod, pellet, or tube shape. The foaming temperature may be higher than the decomposition temperature of the blowing agent composition; however, if the temperature is too high, the graft polymer will decompose and the resulting foam will be colored;
Preferably it is ℃. When cross-linking with the above-mentioned ionizing radiation, if the cross-linking density is low, gas will escape during foaming and a foam with a high magnification ratio will not be obtained. Therefore, it is preferable to carry out crosslinking so that the gel fraction is 20 to 70%. Furthermore, since the decomposition temperature of the blowing agent composition is as low as 140 to 160°C, the organic peroxide having a decomposition temperature of 150 to 190°C with a half-life of 1 minute is preferably used. , for example dicumyl peroxide,
n-butyl-4,4-bis(t-butylperoxy)
Examples include valeric acid, bis(t-butylperoxy)diisopropylbenzene, and the amount added is preferably 0.1 to 5.0 parts by weight per 100 parts by weight of the graft polymer. Further, stabilizers, plasticizers, lubricants, fillers, pigments, etc. which are generally used in vinyl chloride resins may be added to the above mixture. The structure of the present invention is as described above, and since the blowing agent composition contains 1 to 100 parts by weight of fatty acid zinc and zinc hydroxide each added to 100 parts by weight of azodicarbonamide, the decomposition temperature is 140 to 160°C. The decomposition is rapid and a large amount of gas is generated, and bubbles are uniform and low from resins with poor thermal stability such as vinyl chloride resins, ethylene-vinyl acetate copolymers, rubber, etc. Density foam can be obtained. The graft polymer is obtained by graft polymerizing an ethylene-vinyl acetate copolymer with a vinyl acetate content of 10 to 55% by weight so that vinyl chloride is 20 to 90% by weight in the resulting polymer, and the above-mentioned blowing agent is used. Since the composition is used as a blowing agent, the graft polymer can be heated to 160% without thermal decomposition.
It can be foamed at a relatively low temperature of ~200°C, and can produce a foam that is free from coloration and has uniform cells. In addition, the obtained foam is soft and has excellent elasticity, flexibility, feel, appearance, etc., and has the characteristics of vinyl chloride resin such as self-extinguishing property and chemical resistance, so it can be used for clothing, It can be suitably used for a wide range of applications such as leather for furniture, interior decoration, and various other molding applications, such as leather and seats. Next, the present invention will be explained with reference to examples. Example 1 and Comparative Example 1 100 parts by weight of azodicarbonamide and the specified amounts of zinc laurate, zinc stearate, zinc ricinoleate, zinc hydroxide, zinc oxide,
A blowing agent composition was obtained by mixing urea or citric acid in a mortar. The obtained composition was supplied to a differential thermal analyzer, and the temperature was increased at a rate of 5° C./min to measure the decomposition initiation temperature. The results are shown in Table 1. Also, put 1 g of the obtained composition into a test tube and heat it at 200°C.
The relationship between the heating time and the amount of gas generated was measured and is shown in Figure 1. The amount of gas generated in FIG. 1 is calculated per gram of azodicarbonamide.

[Table] Examples 2 and 3 and Comparative Examples 2 and 3 The compositions shown in Table 2 were kneaded at 90°C using a kneading roll, and then heated and pressed at 100°C using a press to form a 2 mm thick sheet. A foamable sheet was obtained.The foamable sheet obtained was irradiated with ionizing radiation in a predetermined amount shown in Table 2 to obtain a crosslinked sheet. The gel fraction of the crosslinked sheet is shown in Table 2. Next, the crosslinked sheet was supplied to a hot air dryer and heated under the conditions shown in Table 2 to obtain a foam. The density and condition of the foam are
Shown in the table. The gel fraction was determined by extracting the crosslinked sheet with tetrahydrofuran at 60°C for 48 hours, and the insoluble content was expressed as weight %.

【table】

[Table] Examples 4 to 7 and Comparative Examples 4 and 5 100 parts by weight of the graft copolymer shown in Table 3,
A formulation consisting of 18 parts by weight of azodicarbonamide, 2 parts by weight of zinc stearate and 1 part by weight of zinc hydroxide was extruded using a twin-screw extrusion having a diameter of 50 mm and equipped with a mold having a slit of 100 mm in length and 1.5 mm in width. It was fed to a machine and extruded at 100℃ at a rate of 10Kg/hr to a thickness of 1.3
A foamable sheet of mm was obtained. The obtained foamable sheet was irradiated with a predetermined amount of ionizing radiation shown in Table 3 to obtain a crosslinked sheet, which was then fed to a hot air dryer at 180°C.
A foamed sheet was obtained by heating for 4 minutes. Table 3 shows the gel fraction of the crosslinked sheet and the density and condition of the foamed sheet.

【table】

[Table] Examples 8 to 10 and Comparative Examples 6 to 9 An ethylene-vinyl acetate copolymer with a vinyl acetate content of 35% by weight and a melt index of 4 was grafted so that vinyl chloride was 55% by weight in the resulting polymer. A composition consisting of the polymerized graft polymer and predetermined amounts of diazocarbonamide, dicumyl peroxide, zinc laurate, zinc stearate, zinc oleate, and zinc hydroxide shown in Table 4 was heated at 90°C. The mixture was kneaded using a kneading roll, and then heated and pressed using a press at 100°C to obtain a foamable sheet with a thickness of 2 mm. The obtained foamable sheet was supplied to a hot air dryer at 180°C and heated for 4 minutes to obtain a foamed sheet. Table 4 shows the density, cell state and coloring state of the foam sheet.

[Table] Examples 11 to 14 and Comparative Examples 10 to 12 100 parts by weight of the graft polymer shown in Table 5, 18 parts by weight of azodicarbonamide, 2 parts by weight of zinc stearate, 1 part by weight of zinc hydroxide, and dicumyl A formulation consisting of 0.8 parts by weight of peroxide was applied to a length of 100 mm.
It was fed to a twin screw extruder with a diameter of 50 mm equipped with a mold with a slit of 1.5 mm in width and 10 mm in width at 100°C.
A foamed sheet with a thickness of 1.3 mm was obtained by extrusion at a rate of Kg/hr. The obtained foamable sheet was supplied to a hot air dryer at 180°C and heated for 4 minutes to obtain a foamed sheet. Table 5 shows the density and condition of the foam sheet.

【table】 [Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between heating time and gas generation amount for blowing agent compositions of the present invention and comparison. In the figure, 1 to 11 are the formulation numbers of the blowing agent composition.
shows the gas generation amount curve.

Claims (1)

[Claims] 1. A blowing agent composition comprising 100 parts by weight of azodicarbonamide, 1 to 100 parts by weight of fatty acid zinc, and 1 to 100 parts by weight of zinc hydroxide.