JPH0497B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a molded article having a desired shape by molding expanded polyolefin resin particles in a mold, and more specifically, the present invention relates to a method for manufacturing a molded article having a desired shape by molding expanded polyolefin resin particles in a mold. The present invention relates to a method for producing a resin foam. The method of molding a foam in a mold involves adding a foaming agent to a particulate base resin, foaming it by heating etc. to form foamed particles, and then filling the foamed particles into a mold having a desired shape. However, a common method is heat molding. This in-mold molding process yields a foam molded product with a complex shape, but since pre-expanded foamed particles are used, if the heating conditions during molding are low, the fusion between the particles will be insufficient. The molded product becomes brittle. Therefore, in order to obtain a molded article with good fusion bonding, it is necessary to heat the resin to a temperature higher than its softening temperature. Especially when using polyolefin resins such as polyethylene and polypropylene,
Since it is a crystalline polymer, it must be heated to a temperature higher than the melting point of the resin. Such strong heating conditions cause various disadvantages such as deterioration of the appearance of the molded product and increase in molding cost. The present inventors have solved these disadvantages and
The present invention was achieved as a result of intensive research aimed at inexpensively producing polyolefin-based in-mold foam molded articles with good fusion between particles. That is, the present invention provides a method in which polyolefin resin particles are made to contain a foaming agent and heated to form polyolefin resin foam particles, which are then filled into a mold and heat-molded.
This is a method for producing a polyolefin resin foam, which comprises coating or impregnating the polyolefin resin foam particles with an organic compound having a boiling point of 150°C or more and a melting point of 100°C or less. The present invention will be explained in detail below. The method of the present invention is applied to resin particles containing polyolefin resin as a main component. Polyolefin resins include polyethylene polymers and polypropylene polymers, but propylene and ethylene, which have a high melting point, This method is particularly effective for polypropylene resins such as random copolymers. The organic compound to be coated or impregnated onto the expanded particles has a boiling point of 150°C or higher, preferably 200°C or higher, and a melting point of 200°C or higher.
It is necessary that the temperature is 100°C or lower, preferably 80°C or lower. When the boiling point is less than 150°C, it is difficult to stably localize near the surface of the foamed particles due to volatilization from the surface of the foamed particles and diffusion into the resin, and therefore plasticizes only the vicinity of the particle surfaces and promotes fusion. Not suitable for purpose. When a large amount of such an organic compound is applied, it diffuses into the interior and deteriorates the physical properties of the foam, while when applied in a small amount, the resin cannot be sufficiently plasticized and the desired fusion cannot be promoted. I can't do it. Also, if the melting point exceeds 100°C, it will take time to melt and penetrate into the resin, which will reduce the ability to plasticize the particle surface during molding, and therefore it will not be possible to expect much improvement in the desired fusion. . In addition, in order to effectively plasticize the vicinity of the surface of the foamed particles during heat molding in a small amount to promote fusion, it is preferable that the compatibility between the polyolefin and the organic compound is good, and the solubility parameter value (SP value) is 6.0 to 6.0.
Preferably it is 10.0. Examples of organic compounds that meet the above conditions include phthalate ester compounds such as dibutyl phthalate, di-2-ethylhexyl phthalate, and butylbenzyl phthalate;
Aliphatic dibasic esters such as 2-ethylhexyl, di-2-ethylhexyl azelate, dibutyl sebacate; fatty acid esters such as butyl phenylstearate; glycerin esters such as soybean oil and coconut oil; diethylene glycol dibenzoate,
Aromatic carboxylic acid esters such as dipropylene glycol dibenzoate; liquid paraffin, chlorinated paraffin, and the like. These organic compounds may be used alone or in combination of two or more. The preferred amount of these organic compounds to be used differs depending on the plasticizing effect of each organic compound on the expanded polyolefin particles; if the plasticizing effect is large, a small amount can be used, and if the plasticizing effect is small, a large amount should be used. However, when each organic compound is used in an amount exceeding the optimum amount, the fusion is actually deteriorated. Therefore, usually foamed particles 100
0.01 to 10 parts by weight are used, preferably
It is 0.1 to 5 parts by weight. Even if more than 10 parts by weight is used, it is excessive and has little effect. Methods for coating or impregnating foamed particles with these organic compounds include (1) a method of adding an organic compound in the step of impregnating the foaming agent into the particles;
There are two methods: (2) a method in which particles are impregnated with a foaming agent and then coated on the particles; (3) a method in which particles are impregnated with a foaming agent, foamed, and then coated on the foamed particles. In (1), the blowing agents used include hydrocarbons such as propane, butane, pentane, and hexane, and halogenated carbon atoms such as dichlorodifluoromethane, trichloromonofluoromethane, and dichlorotetrafluoroethane. These mainly include organic compounds with low boiling points, such as organic compounds with a low boiling point. Methods for impregnating particles with these blowing agents include immersing the particles in a container containing a liquid blowing agent, and mixing the particles with the blowing agent in a container. There are methods such as bringing steam into contact with the particles and impregnating the particles with a blowing agent by suspending them in an aqueous medium in a container equipped with a stirrer. When added and mixed, the organic compound adheres to the particle surface as the blowing agent impregnates, but due to its large molecular weight, it is impregnated near the particle surface and remains near the surface of the expanded particle even after the subsequent foaming process. are doing. Regarding method (2), after impregnating the foaming agent as described above, the organic compound can be added to the container and mixed so that it exists near the particle surface, or the particles can be removed from the container. After that, the organic compound can be applied to the surface of the particles by placing the particles and the organic compound in a container equipped with a stirrer or a rotary container and mixing them. Method (3) involves applying the foamed particles to the foamed particles, and can be easily applied by mixing the foamed particles and the organic compound in a container equipped with a stirrer. In this way, if foamed polyolefin resin particles coated or impregnated with an organic compound having plasticizing ability are filled into a mold and heat-molded, the amount of heat transfer medium used can be reduced and the fusion rate can be improved. A molded article with high particle size and particles firmly fused together can be obtained. The present invention will be explained below using examples. Example 1 100 parts by weight of random copolymer particles of propylene and ethylene (ethylene content 4.1%, MI90) and 30 parts by weight of dichlorodifluoromethane were placed in a closed container and kept at a temperature of 60°C for 4 hours. After the resin particles were made to contain dichlorodifluoromethane, they were heated for 30 seconds in steam at a pressure of 1.7 Kg/cm ² (cage pressure, the same applies hereinafter) to form a random mixture of propylene and ethylene foamed to 11.9 times the original size. Polymer resin foam particles were obtained. Furthermore, the foamed particles are placed in a closed container.
The mixture was maintained at a temperature of 80° C. for 4 hours under air pressure of 25 kg/cm ² , and then heated for 30 seconds with steam at a pressure of 2.3 kg/cm ² to foam 35 times. The foamed particles thus obtained were placed in a closed container again under air pressure of 20 kg/cm ² .
After maintaining the temperature at 60℃ for 4 hours, the expanded particles and
3.5% by weight of di-2-ethylhexyl adipate was added to the foamed particles in a container equipped with a stirrer, and di-2-ethylhexyl adipate was applied to the surface of the foamed particles by stirring and mixing. These particles were filled into a mold and heated with steam at a pressure of 2.3 kg/cm ² and a temperature of 143° C. for 30 seconds to obtain a molded product with an expansion ratio of 45 times. A cut with a depth of approximately 5 mm was made on the surface of this compact using a cutter, and the cut section was broken by hand. (sum of number of particles)
When the ratio (hereinafter referred to as fusion rate) was investigated, it was 90%. Examples 2 to 6 After coating the organic compounds shown in Table 1 on the 35 times expanded particles of the random copolymer resin of propylene and ethylene obtained in Example 1, the particles were molded in the same manner as in Example 1, The fusion rate of the obtained foamed molded product was observed. Comparative Examples 1 to 5 The results are shown for cases in which no organic compound was applied in Example 1, and cases in which an organic compound with a lower boiling point than the compounds in Examples 1 to 6 was applied and molded in the same manner as in Example 1. Shown in conjunction with 1. Note that Comparative Example 1 is an example in which a vortex surplus amount of the organic compound to be applied is used. Comparative Example 6 The expanded particles obtained in Example 1 were filled into a mold without applying any organic compound, and the pressure was 2.8 Kg/cm ² and the temperature was
When heated with steam at 150° C. for 60 seconds (twice as long as in Example 1), a molded article with an expansion ratio of 45 times was obtained. The fusion rate of this molded body was 50%.

【table】

[Table] Examples 7 to 10 Similarly to Example 1, each compound shown in Table 2 was added to random copolymer particles of propylene and ethylene containing dichlorodifluoromethane in a container equipped with a stirrer. After applying by mixing, foaming was performed by heating with water vapor at a pressure of 1.7 kg/cm ² , and then the temperature was 80° C. under air pressure of 25 kg/cm ² .
After holding at ℃ for 4 hours, heating was performed for 30 seconds with steam at a pressure of 2.3 kg/cm ² to obtain expanded particles having the magnification shown in Table 2. These particles are each placed in a closed container.
After being maintained at a temperature of 60° C. for 4 hours under air pressure of 20 kg/cm ² , it was filled into a mold and heated for 30 seconds with steam at a pressure of 2.3 kg/cm ² to be molded. The obtained foamed molded articles each had a fusion rate shown in Table 2. Comparative Examples 6 and 7 The results when a compound with a low boiling point was applied are also shown in Table 2 as Comparative Examples 6 and 7.

【table】

[Table] Examples 11 to 14, Comparative Example 8 Low density polyethylene containing 10% by weight of dichlorodifluoromethane (MI = 1.5, gel fraction 50%)
was heated with steam to obtain expanded polyethylene particles. The foamed beads were kept in an air atmosphere at a pressure of 9 kg/cm ² and a temperature of 60° C. for 2 hours in a container, and then taken out, and the internal pressure of the foamed beads was 1.8 kg/cm ² .
The particles were coated with di-2-ethylhexyl adipate in the amounts shown in Table 3 by mixing in a container equipped with a stirrer, filled into a mold, and placed under pressure.
It was heated for 30 seconds with steam at a pressure of 1.5 Kg/cm ² and a temperature of 133°C, or a pressure of 2.0 Kg/cm ² and a temperature of 140°C to obtain a molded product 27 times larger. The fusion rates of these molded bodies were as shown in Table 3.

【table】

【table】

Claims (1)

[Scope of Claims] 1. In a method of forming polyolefin resin foam particles by adding a blowing agent to polyolefin resin particles and heating them, the foamed polyolefin resin particles are filled into a mold and heat-molded. A method for producing a polyolefin resin foam, which comprises coating or impregnating an organic compound with a boiling point of 150°C or higher and a melting point of 100°C or lower. 2. The manufacturing method according to claim 1, wherein the polyolefin resin particles are resin particles containing a polypropylene resin as a main component. 3. The manufacturing method according to claim 2, wherein the propyrefine resin particles are resin particles whose main component is a random copolymer resin of propylene and ethylene. 4. The manufacturing method according to claim 1, wherein the organic compound is liquid at room temperature. 5 Solubility parameter value of organic compound is 6.0~
10.0 The manufacturing method according to claim 1. 6. The manufacturing method according to claim 5, wherein the organic compound is a phthalate ester. 7. The manufacturing method according to claim 5, wherein the organic compound is a fatty acid ester. 8. The manufacturing method according to claim 5, wherein the organic compound is an aliphatic dibasic acid ester. 9. The manufacturing method according to claim 5, wherein the organic compound is an aromatic carboxylic acid ester. 10. The manufacturing method according to claim 5, wherein the organic compound is a fatty acid ester of glycerin. 11. The manufacturing method according to claim 5, wherein the organic compound is an aliphatic hydrocarbon or a chlorinated paraffin. 12. The manufacturing method according to claim 5, wherein the organic compound is an aromatic hydrocarbon. 13. The manufacturing method according to claim 1, wherein the polyolefin resin is foamed and then coated or impregnated with an organic compound.