JPH0221415B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing pre-expanded polypropylene (hereinafter abbreviated as PP) resin particles containing a specific compound. According to the present invention, the bubbles are fine and
Moreover, uniform pre-expanded particles of PP resin can be obtained. The cell diameter of pre-expanded synthetic resin particles used for in-mold foam molding should be at most 500 μm, considering the flexibility, cushioning properties, appearance, etc. of the foam after molding.
It is said that 300 μm or less is preferable. but,
Normally, in the case of PP resin, even if pre-foaming is performed by heating after containing a foaming agent in the resin particles, the cell diameter
Only expanded particles larger than 500 μm can be obtained. Therefore,
Conventionally, in the production of foams, for the purpose of making the cell diameter uniform and fine, it has been done to add a finely powdered inorganic substance such as talc, known as a so-called nucleating agent. This method was also carried out, but the cell diameter of the pre-expanded PP resin particles was the same as that without additives, or even larger, and there was no effect of making the cell diameter uniform and fine. However, according to the method of the present invention, it is possible to produce pre-expanded particles of PP resin in which the cells are uniformly fine. That is, the present invention is characterized by containing a foaming agent in PP resin particles made by adding a specific amount of a specific compound, and then heating and foaming the particles.
The present invention provides a method for producing pre-expanded PP resin particles. More specifically, the present invention provides a PP obtained by adding 0.01 to 2 parts by weight of one or more compounds selected from ethylene bis fatty acid amide, methylene bis fatty acid amide, glycerin ester of fatty acid, fatty acid amide, etc. as a specific compound. It is characterized by containing a foaming agent in resin particles and then heating them to produce pre-expanded PP resin particles.
The cells in the pre-expanded PP resin particles thus obtained are uniform and fine, and a cell diameter of 500 μm or less, and even 300 μm or less can be easily achieved. Further, as another effect of the present invention, there are great advantages in terms of foaming technology, such as a beautiful surface appearance of the foamed particles due to the miniaturization of the cells, and an improvement in the expansion ratio due to an increase in the foaming speed. Among the specific compounds used in the present invention, ethylene or methylene bis fatty acid amide has 10 to 10 carbon atoms.
ethylene or methylene bis fatty acid amides having 24 fatty acid residues, such as ethylene bis stearamide, ethylene bis palmitic acid amide, ethylene bis oleic acid amide, methylene bis stearic acid amide, methylene bis lauric acid amide, methylene bis Examples include palmitic acid amide, and preferably ethylene bis stearic acid amide, methylene bis stearic acid amide, etc. Furthermore, among the specific compounds used in the present invention, glycerin esters of fatty acids have 10 to 24 carbon atoms.
mono-, di-, or triglycerin esters of higher fatty acids and glycerin, such as lauric acid monoglyceride, lauric acid diglyceride,
Lauric acid triglyceride, palmitic acid monoglyceride, palmitic acid diglyceride, palmitic acid triglyceride, stearic acid monoglyceride, stearic acid diglyceride, stearic acid triglyceride, etc., preferably stearic acid monoglyceride, stearic acid diglyceride, stearic acid triglyceride, or one type thereof. It is a mixture of the above. Furthermore, among the specific compounds referred to in the present invention, fatty acid amides are saturated fatty acid amides having 10 to 24 carbon atoms,
For example, lauric acid amide, myristic acid amide,
Examples include palmitic acid amide, stearic acid amide, erucic acid amide, etc., and preferably stearic acid amide, palmitic acid amide, erucic acid amide, etc. In the present invention, the amount of the specific compound added is
The amount is 0.01 to 2 parts by weight per 100 parts by weight of PP resin. If the amount added is less than 0.01 part by weight, it will be difficult to achieve the desired effect of making the bubbles uniform and fine, and if it exceeds 2 parts by weight, the desired effect will be lost. Considering both economic efficiency and effectiveness, the preferred addition amount is 0.01
-0.5 parts by weight, more preferably 0.01-0.1 parts by weight. The specific compound of the present invention may be added by any commonly used method, but in particular
A masterbatch method of kneading into PP resin or a dry blend method is preferred. Compounds with a melting point above room temperature may be heated and liquefied before being added. Any method may be used as long as the specific compound of the present invention is uniformly added to the PP resin particles before foaming. The PP resin referred to in the present invention is polypropylene homopolymer obtained by stereoregular polymerization of propylene monomer, random or block polypropylene obtained by stereoregular copolymerization of propylene monomer with a small amount of ethylene or (and) butene, etc. These include copolymers and terpolymers. Among these, random copolymers or random terpolymers of ethylene and/or butene and propylene can be particularly preferably used. Note that the PP resin of the present invention is crosslinked,
Although any non-crosslinked case can be used, the non-crosslinked case is particularly useful. Furthermore, a small amount of other thermoplastic resin may be mixed with the PP resin, provided that the effect of making the cells uniform and fine, which is the object of the present invention, is not impaired. Furthermore, ultraviolet absorbers,
Additives such as antistatic agents, heat stabilizers, colorants, and inorganic fine powders may also be added as appropriate depending on the purpose. The blowing agent used in the present invention has a normal pressure boiling point of -50
It is a volatile organic blowing agent in the range of ~100℃,
For example, propane, butane, pentane, pentene,
Hydrocarbons such as hexane; methylene chloride, dichlorodifluoromethane, trichloromonofluoromethane, monochlorodifluoromethane, 1,2
-Halogenated hydrocarbons such as dichlorotetrafluoroethane and trichlorotrifluoroethane, and these blowing agents can be used alone or in combination of two or more. In the method for producing pre-expanded PP resin particles of the present invention, the method of incorporating a blowing agent into PP resin particles is similar to the method generally used for producing pre-expanded particles of cross-linked polyethylene. A so-called impregnation method is useful, in which a blowing agent is incorporated into resin particles by contacting them in a liquid or gas phase and controlling pressure and temperature. Further, heating and foaming can be carried out by contacting the material under a heat source such as superheated steam, an infrared lamp, or heated air for a certain period of time. In the present invention, by adding a specific amount of a specific compound to the pre-expanded particles of the PP resin, the pre-expanded particles have a uniform and fine cell diameter, a good surface appearance, and an improved expansion ratio. obtained by the present invention
Pre-expanded PP resin particles are used for the purpose of producing foam molded products by filling molds directly or by impregnating with inert gas to re-foam them and then heating them with steam, etc. In this case, When the pre-expanded particles of the present invention having uniform, fine cells are used, the properties of the molded product obtained, especially flexibility, cushioning properties, surface appearance, etc., are extremely excellent, and therefore the commercial value is increased. . Therefore, in order to use conventional synthetic resin pre-expanded particles for in-mold foam molding, one of the technical challenges has been to reduce the cell diameter of the pre-expanded particles as much as possible. For example, in the case of pre-foaming of polyethylene resin, a method of crosslinking the resin, in the case of polystyrene resin, a method of adding a nucleating agent and aging after impregnation with a blowing agent, etc., are used to form pre-foamed particles with uniform fine bubbles. has been obtained. However, pre-foaming of PP resin is a technology that has been tackled relatively recently in this industry, and many technical issues remain, but the present invention focuses on pre-foaming, which is particularly important among them. This solves the problem of uniformly reducing the size of bubbles in particles. As in the present invention, fatty acid amide is added to PP resin,
1 selected from compounds such as ethylene or methylene bis fatty acid amides, glycerin esters of fatty acids, etc.
It is not necessarily clear why the cells become uniform and fine when heated and pre-foamed after adding a specific amount of a seed or two or more compounds, but it is not clear why the cells become uniform and fine when heated and pre-foamed. The points of the above compound present in large numbers in the resin particles aggregate the impregnated blowing agent, forming a large number of foaming nuclei during heat foaming, and as a result, pre-expanded PP resin particles having uniform and fine bubbles are obtained. It is estimated that the Next, the present invention will be explained by examples. The evaluation scales shown in the following Examples and Comparative Examples are classified as follows. Cell diameter of pre-expanded particles (measured in accordance with JIS-K6402) Code Evaluation A Average cell diameter is less than 200 μm B Average cell diameter is 200 μm or more and less than 500 μm C Average cell diameter is 500 μm or more Cell uniformity of pre-expanded particles (Relative evaluation) Code Evaluation 〇 Homogeneous with small variation in average bubble diameter △ Slight variation in average bubble diameter, but homogeneous when observed with the naked eye × Large variation in average bubble diameter, even when observed with the naked eye Homogeneity of surface and appearance Code Evaluation A: The surface is smooth with a white pearl-like luster.B: There are minute irregularities on the surface, but it can be used as a product.C:The surface has irregularities, Compounds used in Examples and Comparative Examples are listed below. Stearic acid amide (manufactured by Kao Soap Co., Ltd.; Amide T) Ethylene bisstearic acid amide (Kao Soap Co., Ltd.; Amide T)
Co., Ltd.; Waxus EB-P) Mono- and diglycerides of stearic acid (Kao Soap Co., Ltd.; Atomul 84) Silica (Nippon Aerosil Co., Ltd.; Aerosil)
OX-50) Calcium silicate (manufactured by Tokuyama Soda Kogyo Co., Ltd.; Sorex CM) Butyl stearate (manufactured by Kao Soap Co., Ltd.; butyl stearate) Methylene bisstearamide (manufactured by Nippon Kasei Kogyo Co., Ltd.; Bisamide) Implemented Examples 1 to 13, Comparative Example 1 Sumitomo Noblen as polypropylene resin
Table-1 for WF942 (melt index 8.0)
Add the compound described in , dry blend it, and extrude it into pellets under normal conditions. To the resulting resin particles, add dichlorodifluoromethane as a blowing agent for 60 minutes.
After contact impregnation at .degree. C. for 4 hours, preliminary foaming was carried out using 2.5 kg/ ^cm.sup.2.G steam as a heat source. The obtained pre-expanded particles were evaluated according to the method described above, and the results are shown in Table 1. The results of the evaluation of the obtained pre-expanded particles according to the method described above are shown in Table 1, and it was found that the cells of the examples were beautiful expanded particles with uniform cells and fine cell diameters. On the other hand, when no specific compound was added, the foamed particles had a large cell diameter and had no commercial value, as shown in the comparative example. Incidentally, in both the above examples and comparative examples, no shrinkage was observed after foaming. The relationship between the average cell diameter of the expanded particles obtained in Examples 1 to 4, 5 to 7 and Comparative Example 1 and the amount of additive mixed is shown in FIG. According to FIG. 1, all examples showed smaller average cell diameters than Comparative Example 1, and both the Kao EB-P and Amide T mixed systems had low mixing parts of 0.1 parts by weight to 0.5 parts by weight. Shows the most excellent bubble refining effect. As the number of mixed parts increases, the bubble diameter tends to increase. Comparative Examples 2 to 5 PP resin particles were pre-foamed in the same manner as in Examples 1 to 13, except that calcium silicate, silica, butyl stearate, etc. were used as additive compounds. The foaming results and evaluation are shown in Table 2, and it is clear that these conventional foam control agents such as calcium silicate and silica and fatty acid ester lubricant butyl stearate have no effect on making the foam finer. I understand. Moreover, no shrinkage was observed after foaming in any case. Examples 14-20, Comparative Example 6 Sumitomo Noblen as polypropylene resin
Pre-foaming was carried out in the same manner as in Examples 1 to 13, except that Z131 (melt index 33.0) was used.
Pre-expanded PP resin particles with no shrinkage after foaming were obtained. The foaming results and evaluation are shown in Table 3, and it was found that in each example, the bubbles were more uniform and finer and the surface appearance was better than in the comparative example in which no compound was added.
The effectiveness of the compound of the present invention was demonstrated even when the PP resin was changed. Examples 21-24, Comparative Example 7 Pre-foaming was carried out in the same manner as in Examples 1-13, except that butane was used as the blowing agent and Sumitomo Noblen WF942 (melt index 8.0) was used as the polypropylene resin. Pre-expanded resin particles were obtained. The foaming results and evaluation are shown in Table 4, and in each example, compared to the comparative example in which no compound was added,
It was found that the bubbles were uniform and fine and the surface appearance was excellent, and it was found that the effect of the present invention was obtained even if the blowing agent was changed to butane, a saturated linear hydrocarbon.

【table】

【table】

【table】

【table】

【table】

【table】 [Brief explanation of drawings]

The drawing shows the relationship between the amount of additive mixed and the average cell diameter, where □ indicates no additive added, and ○ indicates Examples 1 to 4.
The amide T mixed system of
Represents an EB-P mixed system.

Claims (1)

[Claims] 1. One or more compounds selected from ethylene bis fatty acid amide, methylene bis fatty acid amide, glycerin ester of fatty acid, and fatty acid amide per 100 parts by weight of polypropylene resin.
A method for producing pre-expanded polypropylene resin particles with finer cells, which comprises adding a foaming agent to polypropylene resin particles in an amount of 0.01 to 2 parts by weight, and then heating and foaming the particles. 2. The method according to claim 1, wherein the polypropylene resin is a random copolymer of propylene and ethylene or/and butene. 3 Ethylene or methylene bis fatty acid amide is
Claim 1 which is ethylene bis stearic acid amide or methylene bis stearic acid amide
The method described in section. 4. The method according to claim 1, wherein the glycerin ester of fatty acid is stearic acid monoglyceride, stearic acid diglyceride, stearic acid triglyceride, or a mixture of one or more thereof. 5. The method according to claim 1, wherein the fatty acid amide is stearic acid amide or palmitic acid amide. 6. Claim 1 in which the polypropylene resin particles are formed by adding 0.01 to 0.1 part by weight of one or more compounds selected from ethylene or methylene bis fatty acid amide, glycerin ester of fatty acid, and fatty acid amide. The method described in section.