JPS62227631A - Manufacture of beads method polystyrene in-mold foam molded body - Google Patents

Abstract

PURPOSE:To make it possible to reduce the gap between beads even in the interior of a molded body under the molding conditions same as that of conventional method by a method wherein more than one kind of polystyrene-based resin prefoamed beads having different foaming capacities are mixed and filled into an in-mold molding die for molding by heating. CONSTITUTION:More than one kind of prefoamed beads having different foaming capacities are mixed at the certain fixed ratio. The mixing ratio may properly be determined in accordance with the degree of desired improvement of the gap between beads. More than one kind of the prefoamed beads are mixed and then filled into the mold of an ordinary molding machine for polystyrene-based resin in-mold foam molding and foam-molded by heating with steam in the similar manner as ordinary polystyrene in-mold foam molding. As a result, a molded body faithful to the mold can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a method for producing a bead-processed polystyrene foam molded article, and more particularly to a method for producing a molded article with fewer intergranular gaps.

"Prior Art and Problems" Bead-process polystyrene foam moldings have been used for a variety of purposes, such as cushioning materials, packaging containers, and heat insulating materials.

These molded bodies have not only physical properties (buffer coefficient, compressive strength, compressive creep, bending strength, etc.) that can be used as cushioning materials and packaging containers, but also their appearance and external properties after slicing.
Internal appearance is also an important quality, and improvements in these are strongly desired. However, the reality is that no molded product has yet been proposed that satisfies these requirements.

"Means for Solving the Problems" The present invention relates to a method for producing in-mold foam molded products made of bead-processed polystyrene that can easily improve the weaknesses of the above-mentioned prior art, especially the internal intergranular gaps. As a result of extensive research in order to achieve the above objective, the inventors discovered that by performing in-mold foam molding by mixing two or more types of pre-foamed beads with different foaming abilities, molding can be achieved under the same molding conditions as before. They discovered that the intergranular spaces can be reduced to the inside of the body, and completed the present invention.

That is, the present invention relates to the production of an in-mold foamed article using a bead method, which is characterized in that two or more types of pre-expanded polystyrene resin particles having different foaming abilities are mixed, filled into an in-mold mold, and then heated and molded. The content is the method.

The present invention involves (a) producing two or more types of pre-foamed beads with different pre-expansion ratios in the normally carried out pre-foaming process in the process of in-mold foam molding of bead-method polystyrene resin; , mix in a certain proportion, (b)
Pre-foamed beads with the same expansion ratio are mixed under different curing conditions, such as those with different curing times, curing temperatures, and curing pressures, in a fixed ratio (Ha) ) Mixing two or more types of pre-foamed beads with different foaming agent contents and different expansion ratios at a constant ratio; (d) Two or more types of pre-foamed beads with different surface properties using additives. By a method such as mixing, i.e.,
Production of in-mold foam molded products of polystyrene resin using bead method, characterized by mixing two or more types of pre-foamed beads with different foaming abilities and foaming behaviors, filling an in-mold mold, and performing heat foam molding. The present invention provides a method.

As the polystyrene pre-expanded particles used in the present invention, any commercially available bead-shaped expandable polystyrene resins can be used.

For example, the base resin may be anything that can be subjected to normal in-mold molding, such as a polystyrene homopolymer, a copolymer of styrene and maleic anhydride, α-methylstyrene, or butadiene, or a graft copolymer of polystyrene and styrene.

Pre-expanded particles can be produced without any special efforts if they are used for bead-shaped expandable polystyrene resins.

The curing method used in the production of ordinary bead-shaped expandable polystyrene resin is sufficient, such as storing the pre-expanded beads in a silo and leaving them at room temperature, or using a silo with hot air circulation. 0 For example, the average curing time is preferably 20 to 30 hours, and when two types of beads with different curing times are mixed, the difference in curing time between the two is about 7 to 10 hours. If it gives good results.

Two or more types of pre-expanded particles with different foaming abilities produced by the above method are mixed at a certain ratio, but there is no particular restriction on the mixing ratio (it may be determined as appropriate depending on the desired degree of improvement in interparticle pores). For example, 40 to 60 beads of two types
Mix within the range of %.

From the viewpoint of manufacturing molded products of stable quality, it is desirable to always mix at a constant ratio. Examples of mixing equipment include Narako mixer, ribbon blender, and other commercially available mixing equipment, or those with foaming capacity. A mixed transport device, etc. in combination with a blower equipment that can send a fixed amount of pre-foamed beads from a storage tank of different sizes is used.

The molding machine and mold used in the present invention are those for ordinary polystyrene-based in-mold foam molding. For example, E
These are regular forming machines, vacuum forming machines, and molds for PS.

Two or more types of pre-foamed beads with different foaming capacities are mixed and filled into the mold of a molding machine, and heated and foamed with water vapor of 0.4 to 2.0 kg/cd CG>, similar to normal polystyrene foam molding. It can be molded to obtain a molded product according to the mold. ``The molded product obtained by the present invention can be used for various purposes, such as cushioning materials, packaging containers, heat insulating materials, and heat insulating materials, as well as conventional purposes, especially since there are few intergranular gaps between beads. It is suitable for hot wire cutting of blocks and lost wanx casting methods.

"Action/Effect" As explained above, by using two or more types of pre-foamed beads with different foaming abilities and performing in-mold molding under conventional molding conditions, the intergranular gap of the molded product obtained is This not only improves the internal and external appearance, but also
Other physical properties (compressive strength, tensile strength, etc.) can also be improved. The reason why internal interparticle gaps are reduced by mixing and molding two or more types of pre-foamed beads with different foaming abilities is not necessarily clear, but it is presumed as follows.

Pre-foamed beads are filled into a mold and foamed by steam heating, but if the beads are completely close-packed, there will be almost no gaps between the particles.

However, in reality, there are variations in the size of the beads, and the beads may line up in a line on the mold surface, so it seems that the packing state is different from close packing. Therefore, it is considered that intergranular gaps are more likely to occur than in the case of close packing. At that time, if all the pre-foamed beads have the same foaming ability, they will foam at the same position as filled, but if pre-foamed beads with different foaming abilities are mixed and filled, there will be a difference in foaming ability. It is thought that the pre-foamed beads with high capacity grow quickly, the filling position shifts and the interparticle gaps decrease.

"Examples" The present invention will be described in detail below with reference to Examples, but the present invention is not limited in any way by these.

Example 1 A: Preparation of pre-expanded beads Expandable polystyrene beads (manufactured by 111 Fuchi Kagaku Co., Ltd., Kanepal GM, average particle size 1, 2Φ) were heated with steam using a small pressure batch type pre-expanding machine. By pre-foaming conditions as shown in Table 1, foaming ratios of 92x and 82x were obtained.
Seed pre-expanded beads were obtained and aged for 24 hours at room temperature.

B; Preparation of molded body Using a block molding machine manufactured by Toyo Kikinzoku Co., Ltd. PS-1809-4V, a mixture of the above two pre-foamed beads at a ratio of 50150 was mixed into a mold for a block (dimensions 1840s*X
92 Qm x 42 Qmm) and heat-molded. Table 1 shows the intergranular gaps and other evaluation results of the obtained molded bodies.

Intergranular gap evaluation method: Three samples as shown in FIG. 1 were cut from a 1820+uX920■-×420 dragon molded block, the number of through holes was counted, and evaluation was made using a five-point method.

Comparative Example 1 Pre-expanded beads with an expansion ratio of 84 times were obtained in the same manner as in Example 1, a molded body was produced using the beads, and the interparticle gaps and other properties of the obtained molded body were evaluated in the same manner. The results are shown in Table 1.

Table 1 From the results shown in Table 1, the molded product of Example 1 has an intergranular gap one rank higher than that of Comparative Example 1, and has a specific gravity distribution of 5.
．． It has increased by 5%.

Example 2, Comparative Example 2 Pre-expanded beads with an expansion ratio of 84 times were obtained in the same manner as in Example 1, and two types of beads were obtained, one after curing at room temperature for 24 hours and one after curing for 17 hours. A molded product was obtained according to Example 1 under the molding conditions shown in Table 2, and the intergranular gaps and other properties of the molded product were evaluated.

At the same time, for comparison, the same operation was performed using beads that had been cured for 24 hours, and the physical properties of the molded bodies were evaluated.

The results are shown in Table 2.

Table 2 From the results shown in Table 2, the molded product of Example 2 was improved by one rank in terms of interparticle gap evaluation, and the specific gravity distribution was 11% better than that of Comparative Example 2.

"Effects" As mentioned above, when two or more types of pre-foamed beads with different foaming abilities are mixed and in-mold foam molding is performed, interparticle gaps and other physical properties are improved under the same conditions as before.

In other words, with conventional technology 4+j, it was possible to somehow improve the intergranular spacing by increasing steam heating, that is, consuming a large amount of energy, but if the present invention is used, the conventional equipment will not be improved in any way. A molded article with improved intergranular gaps can be produced very advantageously and efficiently under almost conventional production conditions.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing a method of preparing a test sample used for evaluating intergranular gaps. Patent applicant Kanebuchi Chemical Industry Co., Ltd. Agent: Patent attorney Kenji Itami, -C-゛

Claims (1)

[Claims] 1. A method for producing an in-mold foamed product using a bead method, which comprises mixing two or more types of pre-expanded polystyrene resin particles having different foaming capacities, filling the mixture into a mold for in-mold molding, and heating and molding the mixture.