JPH0583575B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for producing expandable styrenic resin particles. More specifically, it relates to a method for manufacturing a molded product having a cell structure in which foamed particles are completely fused together at their interfaces during the molding process, and the gap between particles is minimized. . [Prior Art] Expandable styrenic resin particles are prepared by adding a blowing agent such as a readily volatile aliphatic hydrocarbon, such as n
- impregnation with pentane etc. in an aqueous suspension;
Alternatively, it can be produced by impregnating polystyrene resin particles with a small amount of a solvent such as toluene or cyclohexane that is soluble in an aqueous suspension together with a blowing agent such as butane or propane, which is constantly in the gaseous state. The expandable styrenic resin particles thus manufactured are used as a raw material for manufacturing expanded styrenic resin molded bodies. In order to produce expandable styrenic resin molded products industrially and economically, expandable styrenic resin particles are made into pre-expanded particles using water vapor, etc., and the pre-expanded particles are formed into a wall surface having a desired shape with a large number of small holes. The pre-expanded particles are filled into a closed mold with holes, and a heating medium such as steam is ejected from the small holes in the mold to heat the particles to a temperature higher than the softening point of the pre-expanded particles and fuse them together. The foamed styrene resin molded article having the desired shape is produced by taking it out from the mold. [Problems to be Solved by the Invention] The expandable styrenic resin particles produced as described above coalesce and become agglomerated in the pre-foaming process, so they cannot be used in particle transfer pipes or mold cavities. It blocks the filling hole and becomes an obstruction. Therefore, there is a need for expandable styrenic resin particles that do not agglomerate when pre-foamed. For this purpose, for example, metal soap,
Methods are used in which the surface is coated with talc powder, wax, etc., but the pre-expanded particles of expandable styrenic resin particles whose surface has been coated by these methods do not close the gaps between particles in the mold cavity during molding. It is difficult to fill the mold completely, and foaming is suppressed by the accumulation of steam drainage generated during heating, and the resulting molded product contains a large amount of moisture immediately after molding because the particles do not fuse together sufficiently. Since the filling condition of the pre-expanded particles near the mold wall surface is poor, the porosity is high, and there are problems such as the occurrence of more drainage in this area and the generation of particle gaps on the surface of the molded product. When the molded product obtained in this way is used, for example, as a packaging material for electrical products, it must be thoroughly dried. When used for materials, containers, etc., there are drawbacks such as moisture infiltration during use even after sufficient drying, resulting in decreased heat insulation and water leakage. Furthermore, since the foaming of the molded product is not sufficient, there are other drawbacks such as poor appearance of the product and spoiling its image as a packaging material. [Means for Solving the Problem] The present inventors aimed to improve the drawbacks of the above-mentioned prior art, and the inventors of the present invention aimed to improve the drawbacks of the above-mentioned prior art. As a result of intensive research in order to obtain a molded product with as little amount as possible, the present invention was completed. That is, the present invention provides HLB (hydrophile) for expandable styrenic resin particles containing 1 to 20 parts by weight of one or more blowing agents.
-Liphophile Balance) 0.01 to 0.3 parts by weight of a nonionic surfactant having a value of 7 or more is coated, for example, in an aqueous solution or in an aqueous dispersion state, and then the moisture adhering to the surface is dried to reduce the surface moisture to 0.5% or less. A method for producing expandable styrenic resin particles is provided. The expandable styrenic resin particles in the present invention are resin particles obtained by adding a blowing agent during polymerization, or impregnating it after polymerization, such as a polymer of styrene alone or other polymers containing styrene as the main component. These are polymer particles that can be foamed by adding a foaming agent that is liquid or gaseous at room temperature to a copolymer with a vinyl monomer in advance during polymerization, or by impregnating it after polymerization and then heating. may be contained. As the blowing agent, an easily volatile hydrocarbon having a boiling point lower than the softening point of the resin particles is used, and one type or a mixture of two or more types is preferably used that does not dissolve the resin particles or only slightly swells them. There is no problem even if it is. For example, it is propane, butane, pentane, or a substance containing these as the main component, and a part thereof may be substituted with hexane, hebutane, cyclohexane, methyl chloride, freon, etc. The amount of blowing agent is 1 to 20 parts by weight. The nonionic surfactant used as a coating agent in the present invention has an HLB value of 7 or more, preferably 9 or more.
20, and nonionic surfactants with an HLB of less than 7 tend to be oil-soluble and cannot be used for the purpose of the present invention. For example, water-soluble polyoxyethylene alkyl ether, polyoxyethylene alkyl phenol ether, polyoxy Examples of nonionic surfactants belonging to these include ethylene alkyl ester and polyoxyethylene sorbitan alkyl ester, such as polyoxyethylene lauryl ether with an HLB value of 12.1 to 17.3, and HLB value 11.9.
~17.5 polyoxyethylene cetyl ether,
Polyoxyethylene oleyl ether with an HLB value of 13.3 to 16.6, polyoxyethylene stearyl ether with an HLB value of 12.7 to 16.5, polyoxyethylene tallow fatty acid ether with an HLB value of 13.0, HLB value of 13.6 to
Polyoxyethylene octyl phenol ether with HLB value 13.3~18.7, polyoxyethylene laurate with HLB value 13.1~17.7, HLB value 13.8~
18.1 Polyoxyethylene Palminate, HLB
Polyoxyethylene stearate with a value of 13.6 to 18.2, polyoxyethylene oleate with an HLB value of 13.5 to 17.2, polyoxyethylene sorbitan monolaurate with an HLB value of 16.7, polyoxyethylene sorbitan monopalmitate with an HLB value of 15.6, HLB
Polyoxyethylene sorbitan monostearate has an HLB value of 14.9, and polyoxyethylene sorbitan monooleate has an HLB value of 15.0. The coating material is applied to expandable styrenic resin particles.
0.01-0.3 parts by weight are used. If it is less than 0.01 part by weight, it will not have the effect of smoothing the surface of the molded product, and if it exceeds 0.3 part by weight, the grain boundaries on the surface of the molded product will be in a molten state, resulting in poor appearance. The HLB value is from industrial book “Surfactant Handbook” P307
It can be measured in 327 ways. The nonionic surfactant is coated on expandable styrenic resin particles, for example, in an aqueous solution or in a state dispersed in water, and then the water is dried. For example, coating with a liquid nonionic surfactant that does not contain water causes uneven coating and has no effect on smoothing the surface of the molded product, whereas an aqueous solution or dispersion provides uniform coating and Surprisingly, the present inventors have found that by drying the surface moisture to 0.5% by weight or less, preferably 0.1% by weight or less after coating, the surface of the molded product has no particle gaps and has an excellent appearance. discovered. If the surface moisture exceeds 0.5% by weight, particles will appear on the surface of the molded product, resulting in poor appearance and reduced product value. There are various coating methods. For example, the coating agent can be attached to the surface of the resin particles by sufficiently mixing the expandable styrenic resin particles and an aqueous solution or dispersion of a nonionic surfactant using a blender or the like. In this case, it is okay to impregnate and coat the expandable styrenic resin particles with an antistatic agent, zinc stearate, talc, calcium carbonate, or other anti-agglomeration agent during pre-foaming, or a water repellent after the coating process. do not have. Furthermore, as a coating method, expandable styrene resin particles impregnated with a blowing agent in an aqueous suspension are dehydrated using, for example, a centrifugal dehydrator, and then a nonionic surfactant or its aqueous solution or dispersion is added to the resin using a blender or the like. It is advantageous to apply the coating agent to the surface of the particles. In this case, since the nonionic surfactant also has an antistatic effect, it may be mixed with other antistatic agents for coating, if necessary. There are various drying methods, and it is possible to dry the moisture adhering to the expandable styrenic resin particles together with the nonionic surfactant. Moisture on the surface of the resin particles can be measured using a Karl Fischer moisture meter using a methanol dehydrated solvent. [Example] The present invention will be explained below with reference to Examples. Example 1 In a pressure-resistant reactor equipped with a stirrer and a temperature detection tube, 100 parts by weight of styrene monomer, 110 parts by weight of water, 0.15 parts by weight of tricalcium phosphate, 0.005 parts by weight of sodium dodecylbenzenesulfonate, and benzoyl peroxide. 0.25 parts by weight tert-butyl perbenzoate
Add 0.1 part by weight and add 0.5Kg/ ^cm2 of nitrogen while stirring.
The temperature was raised to 90°C under pressure, and polymerization was carried out for 5 hours. Next, 1.8 parts by weight of cyclohexane and 8.5 parts by weight of butane were added, the temperature was raised to 105°C, and impregnation with the blowing agent was carried out for 6 hours. This was cooled to room temperature to obtain spherical expandable polystyrene resin particles. After drying the particles, sieve them to obtain particles of 14 to 20 mesh,
Next, 0.09 parts by weight of zinc stearate was added, stirred with a ribbon blender, and then taken out. To 100 parts by weight of the expandable polystyrene resin particles obtained by the above method, 1 part by weight of a 5% polyoxyethylene oleyl ether (HLB value 15.4, manufactured by NOF KK) aqueous solution was stirred in a container so as to uniformly coat the surface. After drying the moisture in a dryer, expandable polystyrene resin particles coated with the polyoxyethylene oleyl ether were obtained. The expandable polystyrene resin particles were heated with steam in a batch pre-expanding machine to obtain pre-expanded particles with an apparent volume approximately 60 times larger. After curing and drying the pre-expanded particles in the air for 24 hours,
(manufactured by KK) using a mold with cavity dimensions of 300 mm to 450 mm x 20 mm. Table 1 shows the internal melting rate, internal state, surface state, and internal moisture content of the obtained molded body. (The marks ◎, 〇, and △ in the internal state in the table indicate the state of grain gaps in a flat plate cut out from the center of the molded body to 300 mm x 450 mm x 5 mm. ◎ indicates no gap, and 〇 indicates slight gap. , △ means that there are gaps, and the marks ◎, 〇, and △ indicate the surface smoothness and the state of interparticle gaps, where ◎ is excellent, 〇 is good, and △.
means slightly poor. In addition, the internal melting rate indicates the rate of fusion between foamed particles on the fractured surface of a molded body. The number of particles torn inside is expressed as a percentage of the total number of particles. In addition, internal moisture was determined by dividing the difference between the molded weight immediately after molding and the weight after drying at 40°C for 24 hours by the weight after drying. ) Example 2 5% polyoxyethylene stearyl ether (HLB value 15.3,
1 part by weight of an aqueous solution (manufactured by NOF KK) was coated and dried. Pre-foaming and molding were performed in the same manner as in Example 1.
The results are shown in Table 1. Example 3 Expandable polystyrene resin particles obtained in Example 1
5% polyoxyethylene lauryl ether (HLB value 16.2,
0.2 parts by weight and 3.2 parts by weight of an aqueous solution (manufactured by NOF KK) were coated and dried. Pre-foaming and molding were performed in the same manner as in Example 1. The results are shown in Table 1. Example 4 Expandable polystyrene resin particles obtained in Example 1
100 parts by weight was coated with 1 part by weight of a 5% polyoxyethylene octyl phenol ether (HLB value 16.2, manufactured by NOF KK) aqueous solution in the same manner as in Example 1, and dried. Pre-foaming and molding were performed in the same manner as in Example 1. The results are shown in Table 1. Example 5 Expandable polystyrene resin particles obtained in Example 1
100 parts by weight was coated with 1 part by weight of a 5% aqueous solution of polyoxyethylene nonylphenol ether (HLB value 17.1, manufactured by NOF KK) in the same manner as in Example 1, and dried. Pre-foaming and molding were performed in the same manner as in Example 1. The results are shown in Table 1. Example 6 Expandable polystyrene resin particles obtained in Example 1
100 parts by weight was coated with 1 part by weight of a 5% polyoxyethylene stearate (HLB value 13.6, manufactured by NOF KK) aqueous solution in the same manner as in Example 1, and dried. Pre-foaming and molding were performed in the same manner as in Example 1.
The results are shown in Table 1. Comparative Example 1 The expandable polystyrene resin particles obtained in Example 1 were pre-foamed in the same manner as in Example 1 without using a nonionic surfactant. The results are shown in Table 1. Example 7 Expandable polystyrene resin particles obtained in Example 1
Add 10% by weight to 100 parts by weight in the same manner as in Example 1,
0.5% and 20% by weight of polyoxyethylene lauryl ether (HLB value 16.2) aqueous solutions, respectively.
Parts by weight, 0.3 parts by weight, and 0.25 parts by weight were coated and dried.
Pre-foam molding was carried out in the same manner as in Example 1. The results are shown in Table 1. Comparative Example 2 Expandable polystyrene resin particles obtained in Example 1
To 100 parts by weight, 10% polyoxyethylene lauryl ether (HLB value) was added in the same manner as in Example 1.
16.2) 0.5 parts by weight of the aqueous solution was coated, and preliminary foaming and molding were performed in the same manner as in Example 1 without drying the water. The results are shown in Table 1. Comparative Example 3 Expandable polystyrene resin particles obtained in Example 1
100 parts by weight was coated with 0.08 parts by weight of liquid polyoxyethylene nonylphenol ether (HLB value 15.0, manufactured by NOF KK) in the same manner as in Example 1. Pre-foaming and molding were performed in the same manner as in Example 1. The results are shown in Table 1. Comparative Example 4 Expandable polystyrene resin particles obtained in Example 1
100 parts by weight was coated with 1 part by weight of a 5% aqueous dispersion of polyoxyethylene nonylphenol ether (HLB value 5.7, manufactured by NOF KK) in the same manner as in Example 1, and dried. Pre-foaming and molding were performed in the same manner as in Example 1. The results are shown in Table 1.

【table】

〔Effect of the invention〕

The effects of the present invention are summarized as follows. In the present invention, coalescence and agglomeration of each particle during the pre-foaming process are extremely rare, and there is almost no problem in the molding process. Furthermore, the foamable styrenic resin molded product obtained by the present invention has excellent surface smoothness, exhibits an excellent appearance with significantly fewer particle gaps, and has even particle gaps on the flat plate surface cut out thinly in the center. This method provides a molded product with almost no oxidation, so the moisture content immediately after molding is low, and the water absorption rate of the molded product is extremely low. In addition, the molded product has significant advantages such as a lower amount of electrical charge than conventional products.

Claims (1)

[Scope of Claims] 1. HLB [hydrophilic-lipophilic balance (hydrophile-lipophile balance)] 0.01 to 0.3 parts by weight of a nonionic surfactant with a value of 7 or more is coated as a coating agent in an aqueous solution or water dispersion state on the surface of expandable styrenic resin particles, and then dried to remove moisture adhering to the surface. A method for producing expandable styrenic resin particles, characterized in that the surface water content is 0.5% by weight or less. 2. Claim 1, wherein the nonionic surfactant is an ether type nonionic surfactant, and the nonionic surfactant is polyoxyethylene alkyl ether, polyoxyethylene alkyl phenol ether, or a mixture thereof. The method for manufacturing the expandable styrenic resin particles described above. 3 The polyoxyethylene alkyl ether is polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene oleyl ether, polyoxyethylene stearyl ether, polyoxyethylene tallow fatty acid ether, and the polyoxyethylene alkyl phenol ether is polyoxyethylene The method for producing expandable styrenic resin particles according to claim 2, which is octyl phenol ether or polyoxyethylene nonyl phenol ether. 4. Claim 1, wherein the nonionic surfactant is an ester type nonionic surfactant, and the nonionic surfactant is polyoxyethylene alkyl ester, polyoxyethylene sorbitan alkyl ester, or a mixture thereof. A method for producing expandable styrenic resin particles. 5 The polyoxyethylene alkyl ester is polyoxyethylene laurate, polyoxyethylene palmitate, polyoxyethylene stearate, polyoxyethylene oleate, and the polyoxyethylene sorbitan alkyl ester is polyoxyethylene sorbitan monolaurate, polyoxy Ethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate,
The method for producing expandable styrenic resin particles according to claim 4, which is polyoxyethylene sorbitan monooleate.