JPS58198540A - Production of expanded polyolefin particle - Google Patents

Abstract

PURPOSE:To obtain the titled expanded paricles which do not interface with waste water treatment and in which particles are not fused to one another, by adding a difficultly water-soluble fine inorg. powder and an anionic surfactant in combination as suspension stabilizers to expandable polyolefin resin particles contg. a volatile blowing agent. CONSTITUTION:Suspension stabilizers and pref. electrolytes and inorg. builder are added to expandable resin particles (e.g., ethylene/propylene random copolymer) contg. water-dispersed volatile blowing agent such as n-butane. The mixture is heated in a pressure vessel under pressure above the vapor pressure of the blowing agent at a temp. above the softening point of the particle, and a mixture of the particle and water is discharged into a zone under reduced pressure to obtain the titled expanded particles. As the suspension stabilizers, a difficultly water-soluble fine inorg. powder such as calcium tertiary phosphate and an anionic surfactant such as sodium alpha-olefinsulfonate are used in combination.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing foamed polyolefin particles, and more specifically, the present invention relates to a method for producing foamed polyolefin particles, and more specifically, to produce foamed polyolefin particles containing a volatile blowing agent dispersed in water in a pressure-resistant container. In a method for producing expanded polyolefin particles, the mixture of particles and water is released into a low pressure region after heating the particles to a softening temperature or higher under a pressure higher than the vapor pressure of a volatile blowing agent. The present invention relates to a method for obtaining polyolefin foamed particles in which particles are not fused together by using a poorly water-soluble inorganic fine powder and an anionic surfactant together as a turbidity stabilizer.

Methods for obtaining expanded polyolefin particles include a method of heating polyolefin particles containing a blowing agent in advance with a heating medium such as water vapor to form expanded particles, as shown in Japanese Patent Publication No. 48-84891, etc.; As seen in West German Patent Publication No. 2107688, Japanese Patent Publication No. 56-1844, etc., polyolefin particles containing a volatile blowing agent are dispersed in water in a pressure-tight airtight container, and the vapor pressure of the volatile blowing agent is higher than that of the volatile blowing agent. A known method is to obtain foamed particles by heating the polyolefin particles to a temperature higher than the softening temperature under pressure, and then releasing a mixture of the particles and water into a low-pressure atmosphere. The latter method is more efficient in that it can be performed continuously. However, when carrying out the latter method, polyolefin particles containing a blowing agent are dispersed in water and heated to a temperature above the softening point of the particles. The particles are extremely likely to fuse together, and as a result, it is difficult to obtain expanded particles in which the particles are not fused together. For this reason, it is necessary to use a suitable suspension stabilizer to prevent particles from fusing together. Regarding suspension stabilizers used when resin particles are suspended in water and impregnated with a blowing agent made of a low-boiling organic compound at high temperatures, many methods are used to produce expandable styrenic resin particles. It is being considered.

However, the present inventors have experimentally demonstrated that the suspension stabilizer used in the production of expandable styrenic resin particles is not necessarily suitable for polyolefin resins, and the amount required to maintain suspension stability is different. It was confirmed that Special Public Service 1974-11
Magnesium oxide shown in No. 497, Special Publication No. 55-38
Calcium hydroxide shown in No. 68, Special Publication No. 55-942
Calcium carbonate surface-treated with rosin shown in 7.
Even if 3 parts by weight of a suspension stabilizer such as a combination of magnesium birophosphate and methyl cellulose as shown in Japanese Patent Publication No. 56-85694 is used per part of the polyolefin resin particles, 50 parts by weight of butane cannot be impregnated at l 20 'C. When this happened, the particles fused together. Therefore, it is clear that it is necessary to study suspension stabilizers suitable for polyolefin resins. It can also be used as a suspension stabilizer for polyolefin resins, when an organic peroxide is added to the resin and crosslinked.
When a foaming agent is added to the resin to impregnate it, the suitable type naturally differs. Suitable suspension stabilizers include polyvinyl alcohol, N
- A method of using water-soluble polymers such as polyvinylpyrrolidone and methylcellulose, or a combination of these water-soluble polymers and an inorganic dispersant, is described in Equity N (561344+f), but when these water-soluble polymers are used, It is extremely difficult to remove water-soluble polymers from generated wastewater using wastewater treatment equipment, which is undesirable from the standpoint of environmental conservation.For this reason, the present inventors have developed a method that does not have this problem and is impregnated with a blowing agent into polyolefin particles. As a result of research into a suspension stabilizer with excellent suspension stability when carrying out suspension operations, the present invention was completed.

That is, the present invention involves the use of expandable polyolefin resin particles containing a volatile blowing agent dispersed in water in a pressure-resistant container under a pressure higher than the vapor pressure of the volatile blowing agent, and at a temperature higher than the softening temperature of the particles. In a method for producing expanded polyolefin particles in which a mixture of the particles and water is released into a low pressure region after being heated to , a poorly water-soluble inorganic fine powder and an anionic surfactant are used together as a suspension stabilizer. The gist is: This will be explained in detail below.

The polyolefin resin particles used in the present invention include ethylene homopolymers, propylene homopolymers, and copolymers containing 50% by weight or more of ethylene (for example, ethylene and vinyl acetate copolymers, ethylene and styrene copolymers). copolymers of ethylene and methyl methacrylate, copolymers of ethylene and other vinyl monomers), copolymers containing 50% by weight or more of propylene (e.g. copolymers of propylene and ethylene, etc.) Single or copolymer 50
Polymer mixtures containing 50% by weight or more of the above-mentioned polymers alone or mixtures with fillers containing 50% by weight or more of copolymers, those with crosslinks between ethylene or propylene molecules by organic peroxide or electron beam irradiation, etc. can be mentioned.

In the present invention, the volatile blowing agent is one that can swell or permeate the polymer particles.
Usually, those having a boiling point of -50°C to 120°C are used. For example, propane, butane, pentane, hexane,
Aliphatic hydrocarbons such as heptane, cycloaliphatic hydrocarbons such as cyclobutane, cyclobencune, and cyclohexane, and trifluorocarbons such as cyclobutane, cyclobencune, dichlorodifluoromethane, methyl chloride, dichlorotetrafluorene, etc. Examples include halogenated hydrocarbons such as carbon dioxide, ethyl chloride, and the like.

In the present invention, when dispersing expandable particles in water,
A poorly water-soluble inorganic fine powder and an anionic surfactant are used together as a suspension stabilizer, and more preferably an electrolyte inorganic bilge is used in addition to these. Examples of poorly water-soluble inorganic fine powder include tricalcium phosphate,
Calcium birophosphate, magnesium pyrophosphate, calcium silicate, calcium carbonate, magnesium carbonate, magnesium oxide, etc. are preferred, and tribasic calcium phosphate is particularly preferred. The finer the particle size of these fine powders, the smaller the amount used, which is preferable;
The following is sufficient. The suitable amount used varies depending on the type and particle size of the fine powder used, but when using particles with a particle size of 5 μ or less, it is preferably 0.1 to 5 parts per 100 parts by weight of the voliolefin-based particles, and 0. If it is less than 1 part, it is insufficient to prevent the particles from adhering to each other, and if it exceeds 5 parts, the inorganic fine powder remaining on the surface of the foamed particles will be removed when the resulting foamed particles are placed in a mold and molded. Since the fusion bonding between the comrades is inhibited, only a molded article with insufficient fusion strength can be obtained.

The anionic surfactant used in combination with the poorly water-soluble inorganic fine powder acts as a binder to make it easier for the poorly water-soluble inorganic fine powder to adhere to the surface of the polyolefin particles. Alkylarylsulfonic acid salts, higher alcohol sulfate ester salts, etc. are preferred, and sodium alkylsulfonates and sodium alkylbenzenesulfonates are particularly preferred. The optimum amount used varies depending on the type of surfactant used, but
For sodium α-olefin sulfonate, sodium dodecylbenzenesulfonate, etc., the amount of o and o o is preferably 0.5 part to 0.01 part, more preferably 0.01 part to 0.1 part.

In addition to these suspension stabilizers, if an electrolyte inorganic bilgu is used in combination, the suspension becomes even more stable.This is thought to be because the presence of the electrolyte improves the action of the surfactant, and it is used for this purpose. Examples include table salt, calcium chloride,
Pork salt, soda carbonate, etc. are suitable.

By using the suspension stabilizer in the above combination, it is possible to obtain expanded polyolefin particles that do not interfere with wastewater treatment and do not cause particles to fuse together. When the foamed particles obtained according to the present invention are placed in a mold and re-heated and molded, a foamed molded article with excellent particle-to-particle fusion strength can be obtained.

The present invention will be explained below with reference to Examples.

Example 1 Pure water at 2100mC in an autoclave with an internal volume of 3.5P and an opening pulp at the bottom! and ethylene-propylene random copolymer particles (ethylene content 4.5% by weight, Ml
9) 700y and! 118 As a stabilizer, tertiary phosphoric acid (manufactured by Taihei Kagaku Co., Ltd., particle size 0.5-2μ) 21y
, FF' silbenzenesulfonic acid sorg 0.01 ?
After adding 350 y of n-butane with stirring, the mixture was heated to 115°C. The pressure inside the autoclave at this time was 18 Kf/cr/l. Next, while maintaining the autoclave internal pressure at ~30° C. with nitrogen, the pulp at the lower blade of the autoclave was opened, and the mixture of granules and water was simultaneously released into the atmosphere at normal pressure. The obtained expanded particles are
No fusion of particles was observed, the particles were substantially composed of closed cells, and the foaming ratio was 40 times.

Table 1 shows the suspension stability when foamed particles were obtained in the same manner as in Example 1 except that the suspension stabilizer was changed.

Table 1 × Sodium α-olefin sulfonate (Lion Oil? T, L) × × ◎ Fusion of particles None at all ○ Almost none Comparative Example 1 Except for using only tribasic calcium phosphate as a suspension stabilizer When foaming was carried out in the same manner as in Example 1, the particles were fused together to form a foamed body.

Example 8 Foaming was carried out in the same manner as in Example 1 except that 420y of dichlorodifluoromethane was used as the JL agent and the temperature was raised to 135°C. There were no bubbles at all, and the foam consisted essentially of closed cells, with an expansion ratio of 42 times.

Patent applicant Kanebuchi Chemical Industry Co., Ltd. Agent: Patent attorney Makoto Asano -

Claims (4)

[Claims] (1) Expandable polyolefin resin particles containing a volatile blowing agent dispersed in water are heated in a pressure-resistant container to a temperature higher than the softening temperature of the particles under a JJII pressure higher than the vapor pressure of the volatile blowing agent. After 7 hours, the mixture of particles and water is discharged into a low pressure area. 1+ Production of lyolefin-based foamed particles Jj
In the method, poorly water-soluble inorganic fine powders 4 and 1 are used as suspension stabilizers.
The use of an ionic surfactant in combination with the five characteristics of beef, 9'J If'i, )j of polyolefin-based foamed particles.
7. ,l,. (2) The polyolefin-based particles are 714 ref [I] 9, which are the polyolefin-based particles; (3) Borif'robilene series In? - is efficient: /” Langum copolymer grains of Tl helenite are 1
, 1 permissible nl't 'F'' range Manufacturing power υ described in item 2,
. (4)! ! ! The manufacturing method according to claim 1, wherein a poorly water-soluble inorganic fine powder, an anionic surfactant, and an electrolyte inorganic bilge are used together as a turbidity stabilizer.