JP2637664B2 - Method for producing recycled expanded polystyrene resin molded article - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a recycled foamed molded article by regenerating a used foamed polystyrene resin molded article or a waste foamed molded article such as a defective product by-produced during molding. is there.

[0002]

2. Description of the Related Art Foamed polystyrene resin moldings are used in large quantities as buffer packaging materials for home appliances or as containers for transport of seafood and fresh foods. Has become a major social issue. Therefore, in recent years, various studies have been made in order to regenerate a used foamed polystyrene-based resin molded article and obtain foamed polystyrene-based regenerated resin particles capable of producing a good foamed molded article. .

Conventionally, a used foamed polystyrene resin molded product is crushed, heated and melted by an extruder, extruded from a die, cooled, and then cut to obtain a pellet. A method for producing regenerated foamable resin particles by impregnating a foaming agent such as butane, pentane or the like is known. There is also known a method for producing regenerated foamable resin particles by press-fitting and kneading a foaming agent into a molten resin in an extruder, extruding from a die, cooling and cutting.

[0004]

However, the expandable polystyrene resin particles produced by the above-mentioned conventional method are
In the case of a regenerated foam molded article that is foamed by heating with water vapor, not only the cells become extremely fine and the heat resistance is reduced, but also the adhesiveness between the pre-expanded particles is poor, so that a molded article having a satisfactory molded appearance is obtained. Can not. Further, this foamed molded article has disadvantages such as low mechanical strength.

Japanese Patent Publication No. 58-24449 discloses that polystyrene resin particles which have already been foamed are used as a raw material, an organic solvent is added thereto in a water-dispersed state, and the mixture is stirred at a temperature higher than the softening point of the resin. Has been proposed. In addition, Japanese Patent Publication No. 58-244
No. 50 discloses that the same resin particles are used as a raw material, a styrene monomer is gradually added thereto in an aqueous dispersion to be absorbed by foamed resin particles, and heated to carry out polymerization. A method of impregnating a blowing agent such as butane and pentane has been proposed. However, in the expandable polystyrene resin particles obtained by these methods, a large number of bubbles constituting the original foam disappear, and the resin particles have no bubbles at all.
Although the foam state, mechanical strength, and the like of a foam molded article obtained by foam molding the foam are improved to some extent, they are not always sufficient. Moreover, in these methods, the expanded polystyrene-based resin molded body is returned to the original state of the non-expanded resin particles and then regenerated as the expandable resin particles. Since heat energy is required, it is disadvantageous in terms of manufacturing cost.

As described above, in the conventional method, since the bubbles constituting the foam are once eliminated to produce resin particles containing no bubbles, the process is not only complicated, but also involves heating. For this reason, there is a problem that a large amount of energy is consumed, and the quality of the obtained recycled foam is deteriorated due to deterioration of the resin due to heating.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in order to solve the above-mentioned problems, and as a result, an inorganic gas was applied to foamed resin particles obtained by crushing a used foamed molded product under pressure. In the gas phase impregnation, the foamed particles are filled into a mold in a compressed state, and foamed, so that the normal cells of the foamed particles can be used as they are, without going through complicated steps of the molded body. Further, they have found that a high-quality regenerated foam molded article can be easily obtained without consuming a large amount of heat energy, and have completed the present invention.

Thus, according to the present invention, the foamed resin particles obtained by crushing the waste foamed polystyrene resin molded article are gas-phase impregnated with an inorganic gas at a moderate temperature at which the particles do not coalesce and under pressure. Inorganic gas is added to the foamed resin particles in an amount of 0.
5 mol / kg (resin) or more, and pressurized gas is used so that the foam volume of the inorganic gas-containing foam resin particles after filling in the mold is 70% or less of the original foam volume. Recycled foamed polystyrene, characterized in that a foamed molded product is obtained by introducing into a mold while compressing the mixture, introducing steam in a temperature range higher by 10 to 30 ° C. than the Vicat softening point of the base resin, and heating and fusing the steam. A method for manufacturing a resin molded article is provided.

In the present invention, the resin constituting the waste foamed polystyrene resin molded article used as a starting material is a styrene polymer, at least 50% by weight or more of a styrene component and another polymerizable unsaturated compound. And mixed resins thereof, crosslinked polymers of styrene and polyethylene or polypropylene, and reinforced resins obtained by adding an appropriate amount of a rubbery substance to these resins. Examples of the copolymerizable unsaturated compound include α-methylstyrene, acrylonitrile, an ester of acrylic acid or methacrylic acid with an alcohol having 1 to 8 carbon atoms, maleic acid, fumaric acid and 1 to 8 carbon atoms. Esters with an alcohol having an atom, maleic anhydride and the like, and as a small amount of a crosslinking agent, divinylbenzene, butadiene, polyethylene glycol dimethacrylate and the like can also be mentioned. A waste foamed polystyrene resin molded product is a foam molded product obtained by pre-foaming foamable resin particles obtained by impregnating the above polystyrene resin particles with a foaming agent, and then performing foam molding in a predetermined mold. In addition, after being used for various containers, cushioning packaging materials, and other certain uses, used foamed molded products to be discarded, and defective molded products produced as by-products when manufacturing these molded products. included.
In addition, as the waste expanded polystyrene resin molded article, it is also possible to use as a raw material a used molded article of a foamed molded article obtained by extrusion foaming the above resin, a defective molded article, cutting waste during trimming, and the like. is there.

[0010] In the resin constituting the foam molded article,
Various additives such as a filler, a plasticizer, a flame retardant, a lubricant, a coloring agent, an ultraviolet absorber, and an antioxidant may be contained. In the present invention, it is desirable to use a single resin type as the base resin of the waste expanded polystyrene resin molded article used as a starting material, but the thermal properties of the foam (foaming moldability) and the cell size (molding) Product appearance) are almost the same,
Two or more base resins may be used in combination.

Although the waste expanded polystyrene resin molded article has a different expansion factor depending on its use, in order to obtain a homogeneous regenerated expanded molded article by the method of the present invention, a molded article having substantially the same expansion factor is divided. It is desirable to use it separately as a raw material. Buffer packaging materials for home appliances, fish and shellfish containers, apple boxes, etc., which occupy the majority of waste foam molded products, are approximately 50-
It is a 60 times expanded molded article. However, as long as it is within such a range of variation, it can be used as a raw material of the present invention without any particular problem.

The waste foamed polystyrene resin molded product is crushed into foamed resin particles having a substantially spherical or cubic shape by a crusher or a cutter, or any other method. The average particle diameter of the foamed resin particles is appropriately determined depending on the size of the molded article to be regenerated and foamed.
５０50 mm, preferably about 10-30 mm.
If the average particle diameter is larger than 50 mm, the pipes will be clogged during pneumatic transportation, or the filling property of the mold will be poor. On the other hand, if the average particle size is smaller than 5 mm, the foam cells are destroyed when the foam molding is crushed, the closed cell ratio is reduced, and sufficient foaming property cannot be obtained at the time of foam molding. I can't get my body.

The closed cell ratio of the expanded resin particles used in the present invention must be 65% or more, preferably 80% or more. When a large amount of inappropriate fine particles generated when crushing the foam molded article is contained, it is desirable to remove the fine particles by sieving. Further, as the crushing machine or the cutting machine, the one which can obtain the desired foamed particles having a shape similar to a sphere or a cubic shape without breaking the bubbles of the foamed product as much as possible, suppressing the generation of fine particles, having a uniform particle diameter, and preferably a cubic shape is preferable. Used for

In the present invention, first, the foamed resin particles are gas-phase impregnated with an inorganic gas at a moderate temperature at which the particles do not coalesce and under pressure. As the inorganic gas in the present invention, carbon dioxide, nitrogen, air and the like are used,
These may be used alone or as a mixture. The impregnation treatment with an inorganic gas is performed in a pressure-tight container at a moderate temperature at which the foamed resin particles do not coalesce. Here, the mild temperature means a temperature at which coalescence does not occur between the foamed particles during the impregnation process and the foamed particles do not shrink, and specifically, at least 20 ° C. or more from the Vicat softening point of the base resin. Refers to the low temperature range. The preferred temperature range varies depending on the base resin of the foamed resin particles to be used, and also varies depending on the inorganic gas.However, it is usually possible to increase the substantial impregnation amount of the inorganic gas.
In view of the fact that the internal pressure of the pressure vessel can be set lower, the impregnation temperature is desirably lower, and is preferably 40 ° C. or lower. However, when the temperature is 0 ° C. or lower, energy consumption is industrially large for cooling usually, which is not preferable.
From the viewpoint of the impregnation rate of the inorganic gas, a high temperature is desirable, but in order to reduce the gas impregnation amount, it is preferably 5 to 40 ° C. in the case of carbon dioxide gas, and 5 to 30 ° C. in the case of nitrogen and air.
° C. When the impregnation is performed at a temperature higher than the Vicat softening point of the base resin −20 ° C., a large amount of gas is dissipated until foaming is performed, the foaming property is reduced, and a good foamed molded article is obtained. Absent.

Under such a mild temperature condition, the inorganic gas does not act as a solvent for the resin, so that there is no possibility that the foamed resin particles coalesce. Therefore, the gas impregnation with the inorganic gas can be performed while the foamed resin particles are left still. In addition, when the inorganic gas is impregnated by standing, the inorganic gas under pressure may be sucked by a pump or the like and passed through a temperature control chamber, and then returned to the lower part of the container and circulated.

An appropriate pressure for impregnating the foamed resin particles with the inorganic gas is 1 kg / cm ² G or more, preferably ^{2 to 10} kg / cm ^2.
G. The impregnation of the inorganic gas depends on the type of the inorganic gas, the impregnation pressure, the type of the base resin, the particle size of the foamed resin particles, etc., but at least the inorganic gas is 0.5 mol / kg.
(Resin) This is carried out until the above impregnation, and is usually achieved within one hour. In addition, the inorganic gas content in the expanded resin particles,
It can be determined by taking out the foamed resin particles under pressure in the container from the container and measuring the volume or weight of the inorganic gas that escapes from the foamed resin particles.

Since the escape of the inorganic gas from the foamed resin particles is relatively fast, the foamed resin particles impregnated with the inorganic gas are:
At the time of filling the mold, the inorganic gas is filled with at least 0.1%.
It is necessary to contain 5 mol / kg (resin) or more. When the inorganic gas content in the expanded resin particles is 0.5 mol /
If the weight is less than kg (resin), the foaming power is insufficient, and it is difficult to obtain a good foam molded article.

In the present invention, an inorganic gas is used. However, as long as the effects of the present invention are not impaired, a small amount of a volatile organic foaming agent can be used in combination. For example, the same effect can be obtained by using propane, butane, or the like in a small amount, for example, 0.2 or less with respect to 1 of the inorganic gas. Next, the foamed resin particles impregnated with the inorganic gas in this manner are filled in a molding die while being compressed using a pressurized gas. The porosity of normal pre-expanded particles is about 35-
40%. On the other hand, the foamed resin particles obtained by crushing the waste foamed polystyrene resin molded article used in the present invention have a large bulk and a porosity of about 50 to 60%. Therefore, in order to obtain sufficient foaming property during foam molding, it is necessary to reduce the space between foamed particles when filling the foamed resin particles into the molding. Therefore, in the present invention, the foamed resin particles filled in the mold are compressed so that the bulk of the foamed resin particles becomes 70% or less, more preferably 65% or less, and 40% or more of the original bulk. To supply. 70% compression of expanded resin particles
If it is less than the above range, the foaming power will be insufficient at the time of foam molding, the space between the foamed resin particles cannot be sufficiently filled, a gap will be formed, and the appearance of the foamed molded article will be deteriorated. On the other hand, compression is 40
%, The improvement effect is not so much recognized, although an excessive pressure vessel is required. Further, it shows a sign of overfilling, suppresses passage of water vapor during molding, and inhibits fusion between the foamed particles.

In the present invention, in order to maintain the compressed state of the foamed resin particles, it is desirable to maintain the inside of the mold before and during filling with the foamed resin particles in a pressurized state. The foaming multiple of the recycled foamed molded article obtained by heat molding the foamed resin particles is the foaming multiple of the original waste foamed resin molded article,
It is determined by the compression ratio of the expanded resin particles under pressure, and the multiple of the expanded particles in the mold becomes the expanded multiple of the regenerated expanded molded article. Therefore, it is necessary to previously set the internal pressure in the mold to a predetermined pressurized state, and then pressurize and fill the foamed resin particles.

In the present invention, as a gas used for filling the foamed resin particles under pressure and pressurizing the inside of the mold, an inorganic gas used at the time of gas phase impregnation can be used, but usually compressed air is preferably used. In the present invention, after the pressurized state of the mold is released and depressurized to return the internal pressure of the mold to atmospheric pressure, the gas between the foamed particles is exhausted, and the compressed foamed particles are expanded and restored. Then, steam is introduced into the mold and the foamed particles are heated and fused to form a foamed molded article. The gas between the foamed particles may be discharged by introducing steam while keeping the mold in a pressurized state so that the steam is allowed to flow. The foam molded body obtained by the heat molding is taken out of the mold after cooling with cooling water.

The water vapor used for heat molding the foamed resin particles is controlled so as to be in a temperature range higher by 10 to 30 ° C. than the Vicat softening point of the base resin, and more preferably by 10 to 2 ° C.
The temperature is controlled to be higher by 0 ° C. If the water vapor temperature at the time of molding is lower than the Vicat softening point + 10 ° C., the foaming rate is slow, and the escape of the inorganic gas to the outside becomes dominant, and a sufficient foaming effect cannot be obtained. As a result, high quality foaming A molded product cannot be obtained. In the case of a temperature range of not less than the Vicat softening point + 30 ° C., the appropriate foaming width becomes extremely narrow, and it is extremely difficult to obtain an industrially normal foamed molded product. In addition, the molding heating time varies depending on the size of the foam molded article, the number of times of foaming, and the like, but is generally about 10 to 180 seconds, and preferably about 15 to 90 seconds. In addition, as the steam, a steam-air mixed medium can be used.

As described above, the regenerated foam molded article of the present invention obtained by impregnating the foamed resin particles with the inorganic gas, filling the mold with pressure, and then subjecting the molded article to heat molding is a heat-insulating wall material for architectural use. It is suitably used as a flooring material, as a buried material in an EPS civil engineering method for improving soft ground for civil engineering, and the like. In these applications, the reclaimed foam molded article of the present application is formed into a relatively thick block shape or plate shape, and it is not necessary to mold it into a complicated shape. Can be. For these applications, the desired foaming multiple of the foamed molded product is about 40 to 50, and a buffer packaging material for used home electric appliances, or a transport container for fish and shellfish or fresh food, etc., is used as a raw material of the present invention. It is preferably used.

When the reclaimed foam obtained by the present invention is used for the above-mentioned architectural or civil engineering applications, it is necessary to impart self-extinguishing properties and flame retardancy to the foamed molded article. In order to impart self-extinguishing properties and flame retardancy to the regenerated foam molded article, a flame-retardant and, if necessary, a flame-retardant auxiliary agent may be added to the surface of the foamed resin particles, and the coated article may be subjected to foam molding. . As the flame retardant, a brominated alicyclic compound, a brominated aromatic compound, a brominated aromatic polymer, a brominated phenyl (meth) acrylate, and the like are suitably used. When the flame retardant is in a powder form, it is desirable to use a fine powder that passes 149 μm according to a JIS standard sieve from the viewpoint of adhesion to the particle surface. Further, in order to ensure the adhesion to the particles, the powdered flame retardant may be coated and spread after partially coating the liquid flame retardant having an appropriate viscosity. Further, a powdery flame retardant having a relatively low melting point may be heated and melted for coating. Such a flame retardant provides self-extinguishing properties when used in a relatively small amount, has good adhesion to foamed resin particle surfaces, does not inhibit fusion between foamed particles during molding, has good weather resistance, and has a resin base. Hexabromocyclododecane, tetrabromocyclooctane,
Tribromophenyl allyl ether, pentabromophenyl allyl ether, bisaryl ether of tetrabromobisphenol, bisdibromopropyl ether of tetrabromobisphenol, and the like are particularly preferably used. These flame retardants are used in an amount of 0.5 to the foamed resin particles.
To 2.0% by weight, more preferably 0.8 to 1.5% by weight
Used in the range. Further, a compound having, for example, an O—O, C—C, N ＝ N bond such as an organic peroxide is used as a flame retardant auxiliary in an amount of 0.1 to 0.5% by weight in combination with the flame retardant. You may. Preferred examples of the flame retardant aid include dicumyl peroxide, 1,1-diphenylbicyclohexyl, azodiisobutyronitrile, and the like.

Further, the foamed resin particles of the present invention are provided with a surface treatment agent such as a lubricant for improving the filling property into a molding die, a fusion promoter during molding, a molding cooling time shortening agent, an antistatic agent and a coloring agent. It may be coated. Specific examples include ethylene bis stearamide, higher fatty acid, higher fatty acid amide, edible oil, higher fatty acid triglyceride, higher fatty acid monoglyceride, paraffin wax, polyethylene wax, zinc stearate and the like.

The surface coating treatment is performed by using a ribbon blender, a tumbler, a Lodige mixer, a Nauter mixer, a super mixer or the like before the impregnation with the inorganic gas. Alternatively, if the container impregnated with the inorganic gas has a rotating or stirring function, the coating treatment may be performed simultaneously with the gas impregnation.

[0026]

Hereinafter, the present invention will be described with reference to examples.
Accordingly, the present invention is not limited, and various changes can be made within the scope of the present invention. An expanded molded article of expandable polystyrene resin particles used as a buffer packaging material for home appliances was crushed by a crusher to a particle diameter of about 10 to 20 mm, and this was used as a starting material for forming a recycled foam. The crushed foamed resin particles were subjected to a surface coating treatment using 1.2% by weight of bisallyl ether of tetrabromobisphenol as a flame retardant using a super mixer. The foamed particles coated with the flame retardant were placed in a pressure-resistant container having a capacity of 1000 ml, sealed, and kept at a predetermined pressure for 1 hour while controlling the temperature of the inorganic gas to impregnate the foamed resin particles with the inorganic gas. Next, the inner dimensions were 30 × 7.5 × 2.5, maintained in a pressurized state.
The foamed particles impregnated with the above-mentioned inorganic gas were filled in a mold having a cm cavity. After the resin particles were filled, the pressurized state of the mold was released, the inorganic gas in the mold was discharged, steam at a predetermined temperature was introduced, and the foam was heated and foamed to produce a regenerated foamed article.

Table 1 shows the impregnation conditions of the inorganic gas, the molding conditions in the mold, and the obtained regenerated foamed molded product. The waste foam molded article used as a starting material was a buffer packaging material for home appliances used once, and was used in Example 1, Comparative Examples 1, 2,
4, 5, and 6 are 55 times expanded products, Example 2, Comparative Example 3
Is a 40-fold expanded product, and Example 3 is a 60-fold expanded product. These base resins are polystyrene.

Example 4 is a 40-fold foam molded article of a copolymer of 92% styrene and 8% maleic anhydride. In all of Examples 1 to 4, there was no problem in production, and the obtained regenerated foamed molded product was of high quality with uniform and good fusion. The self-extinguishing property of the obtained regenerated foam molded article was evaluated in accordance with the combustion test method based on the oxygen index method of JIS K-7201, and as a result, the oxygen index was 26 or more, indicating that the article had good flame retardancy. On the other hand, in Comparative Example 1, the inorganic resin impregnation temperature was too high, and there was a sign that the foamed resin particles contracted. In Comparative Example 2, the compression of the foamed resin particles was insufficient at the time of filling the mold,
It was high magnification, and normal molding could not be performed. In Comparative Example 3, normal molding was not possible due to insufficient impregnation pressure of the inorganic gas. In Comparative Example 4, the steam temperature during molding was low, and the fusion between the foamed particles was poor. In Comparative Example 5, the steam temperature during molding was high, and the foamed molded product shrank. In Comparative Example 6, the expanded particles were excessively filled, and the fusion between the expanded particles was poor.

[0029]

[Table 1]

[0030]

According to the present invention, a foamed resin particle obtained by crushing a used foamed polystyrene resin molded body is impregnated with an inorganic gas under pressure in a gas phase, and the foamed particles are compressed and placed in a molding die. By using the normal cells of the foamed particles as they are, and performing the conventional complicated steps of volume reduction of waste foam, repellet, impregnation of foaming agent, prefoaming, and heat molding. A high-quality regenerated foamed molded article can be produced without using any heat energy. The recycled foam molded article obtained according to the present invention can be used in many fields including architectural applications and civil engineering applications.

The method for producing a regenerated foam molded article of the present invention can effectively recycle a large amount of used foam molded articles, and has a great effect as a disposal treatment measure or a method for effectively utilizing resources.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location B29K 105: 26 C08L 25:00

Claims (1)

(57) [Claims] 1. A foamed resin particle obtained by crushing a waste foamed polystyrene-based resin molded article is impregnated with an inorganic gas in a gaseous phase under a moderate temperature and under a pressure at which the particles are not coalesced, so that the foamed resin particles are At least 0.5 mol / kg (resin) of an inorganic gas is contained, and the foam volume of the foamed resin particles after filling in the mold is 70% of the original foam volume.
It is supplied into the mold while compressing using a pressurized gas so that the foamed molded body is heated and fused by introducing steam in a temperature range higher than the Vicat softening point of the base resin by 10 to 30 ° C. A method for producing a recycled foamed polystyrene resin molded article, characterized by being obtained.