JP7085923B2 - Recycled styrene resin composition - Google Patents

Description

The present invention relates to a recycled styrene resin composition.

Thermoplastic resins such as styrene resin and olefin resin are generally used as lightweight, high-strength, and mass-produceable materials for housings and parts of various products such as home appliances and OA equipment. ..

When these products are disposed of after use, most of them have been disposed of without being remanufactured by landfill or incinerator, except for the parts that can be disassembled and recovered by hand. However, in recent years, from the viewpoints of enforcement of the Home Appliance Recycling Law, effective use of resources, formation of a recycling-oriented society, and reduction of carbon dioxide emissions, material recycling has been carried out in which the recovered recycled plastic is melt-kneaded and reused as a resin molded product. It is progressing.

Since the used resin composition recovered from home electric appliances is a mixed flake of the above resin composition, it is separated for each resin type through various sorting treatment steps and reused after melt-kneading.

The used resin composition is, for example, pulverized into resin flakes, and then utilizing the difference in specific densities, an olefin resin having a specific gravity of 1.0 or less, polystyrene and ABS having a specific densities of 1.05 to 1.10, and the like. It is separated into a heavy specific density resin having a specific density of 1.10 or more. Next, the mixed flakes of polystyrene and ABS are separated by an electrostatic sorter that utilizes the charge when the resin flakes are rubbed together.

These used resin compositions separated for each resin type contain a small amount of foreign substances such as metals and dissimilar resins, and have significantly better toughness physical properties such as impact strength and stretching characteristics than new resin. It is declining. As a countermeasure against such foreign substances, foreign substances are removed by using a metal screen mesh during extrusion molding, or an elastomer is added as a compatibilizer to the used resin composition to make dissimilar resins compatible with each other. Improvements may be made. In addition, a coloring pigment may be added to the used resin composition in order to conceal foreign substances generated on the surface of the resin molded product.

Usually, when processing a thermoplastic resin, it is necessary to plasticize the thermoplastic resin by heating from the outside, and the heating temperature at that time is generally a high temperature of 200 degrees or more. However, if the resin is maintained at a high temperature for a long time, the resin is decomposed and low molecular weight decomposition products are generated. This low molecular weight decomposition product stays in the vicinity of the die as a so-called "meyani" during extrusion molding, which causes the appearance of the resin molded product to be spoiled.

In addition, resin additives such as antioxidants that are added to the thermoplastic resin for the purpose of imparting long-term thermal stability are also gasified resins when the plasticized resin is poured into a mold during injection molding. Additives stay in the mold as tar, which causes the appearance of the resin molded product to be spoiled.

BHT (dibutylhydroxytoluene), which is an antioxidant, has been widely used as an additive for resins in the past. However, after BHT exerts its function as an antioxidant, a colored dimer is formed, so that BHT has a property of yellowing the resin over time. Further, since BHT is a low molecular weight molecule, it tends to volatilize during heating during molding or during use.

For this reason, in recent years, the use of BHT as an additive for resins has decreased, and antioxidants that are less likely to yellow over time and are less likely to be heated during molding or volatilized during use have been developed. As a result, recently, due to antioxidants, it is unlikely that tar will adhere to the mold during molding and yellowing over time will occur.

However, for example, since the life cycle of home appliances is generally about 10 years, many of the used resin compositions recovered from home appliances contain BHT added in the past. Therefore, the recycled resin composition obtained from such a used resin composition has problems such as tar adhesion to the mold during molding and yellowing over time.

As a method for removing unnecessary substances derived from a thermoplastic resin and a method for suppressing volatilization, in Patent Document 1 (Japanese Patent No. 37676474), in order to adsorb a discoloring substance (antioxidant dimer) that causes discoloration of a coating film. , A coating resin product containing a porous material (adsorbent selected from zeolite, activated clay, silica gel, clay clay and activated alumina) is disclosed.

Further, in Patent Document 2 (Japanese Unexamined Patent Publication No. 2002-69308), at least one of an alkali metal and an alkaline earth metal having a specific surface area of 50 mm ² / g or more is added to obtain a low molecular weight component in a thermoplastic resin or a low molecular weight component. A resin composition and a resin molded product capable of suppressing volatilization of a resin decomposition product are disclosed.

Further, in Patent Document 3 (Japanese Unexamined Patent Publication No. 2001-29966639), a gas adsorbent (formaldehyde, sulfur, cyanide, hydrogen chloride, etc.) that adsorbs a gas (formaldehyde, sulfur, cyanide, hydrogen chloride, etc.) that adversely affects photographic properties contained in the resin composition is described. A resin composition containing (silica, talc, etc.) and the like is disclosed.

Japanese Patent No. 3776474 Japanese Unexamined Patent Publication No. 2002-69308 Japanese Unexamined Patent Publication No. 2001-29966639

However, in the methods described in Patent Documents 1 to 3, it is not possible to sufficiently suppress the deterioration of the appearance design in the resin molded product produced from the recycled styrene resin composition obtained from the used styrene resin composition. was difficult.

The present invention has been made to solve the above problems, and an object of the present invention is to suppress deterioration of the appearance design of a resin molded product produced from a recycled styrene resin composition.

The resin composition of the present invention contains a used styrene resin composition and zeolite. Zeolites have an average pore size of 8.0 Å or more and less than 10 Å.

According to the present invention, it is possible to suppress deterioration of the appearance design of a resin molded product produced from a recycled styrene resin composition.

It is a schematic diagram which shows how BHT is adsorbed in a pore of a zeolite. It is a schematic diagram which shows how BHT is not adsorbed to the pore of a zeolite when the pore diameter of a zeolite is small. It is a schematic diagram which shows how BHT is desorbed to the pore of a zeolite when the pore diameter of a zeolite is large.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, in the drawing, the same reference numeral represents the same part or the corresponding part.

The regenerated styrene resin composition in the present embodiment contains a used styrene resin composition and zeolite. Zeolites have an average pore size of 8.0 Å or more and less than 10 Å.

With reference to FIG. 1, in the regenerated styrene resin composition of the present embodiment, BHT1 is adsorbed in the pores 3 of the zeolite 2. In the drawing, the whole image of zeolite is omitted, and only the zeolite around the pore 3 is drawn as zeolite 2.

In this way, BHT generated as a gas during molding of the regenerated styrene resin composition can be adsorbed in the pores of the zeolite having a pore diameter equivalent to that of the BHT molecule. This makes it possible to reduce the amount of BHT volatilization during molding using the used styrene resin composition. As a result, it is possible to prevent the BHT from adhering to the resin molded product after it becomes a tar and is deposited on the mold. Further, since BHT is adsorbed as a monomer in the zeolite pores, the formation of the BHT dimer, which is a colored component, is suppressed, and the discoloration of the resin molded product is suppressed. Therefore, it is possible to suppress deterioration of the appearance design of the resin molded product produced from the recycled styrene resin composition.

On the other hand, as shown in FIG. 2, when the pores 3 of the zeolite 2 are smaller than the BHT, the BHT1 is not adsorbed in the pores. Further, as shown in FIG. 3, when the pore 3 of the zeolite 2 is larger than the BHT 1, the BHT 1 adsorbed in the pore 3 is desorbed by heating during injection molding.

(Used thermoplastic resin composition)
The used styrene resin composition is not particularly limited as long as it is a styrene resin composition recovered from used products such as home appliances and OA equipment, but a metal removal process using eddy current or magnetic force, a specific gravity difference. It is preferable that the styrene-based resin composition has undergone a floating-sink sorting step using the above, an electrostatic sorting step utilizing the charging action of the plastic, and the like.

The used styrene resin composition is preferably a styrene resin composition recovered from scraps of used home appliances. By using such a used styrene-based resin composition, it is possible to promote a business of recycling waste plastics for home appliances, in which resin compositions derived from used home appliances are sorted and collected for each resin type.

In the present specification, the "styrene-based resin composition" is a composition containing a styrene-based resin. The content of the styrene resin in the styrene resin composition is, for example, 50 to 100% by mass.

(Styrene resin)
The "styrene-based resin" is a polymer obtained by polymerizing a plurality of monomers including a styrene-based monomer, and includes a structural unit derived from the styrene-based monomer. The ratio of the number of styrene-based monomers to the total number of plurality of monomers used to obtain the styrene-based resin is, for example, 40 to 100%.

The styrene-based monomer is a monomer containing styrene (styrene skeleton) in its composition. The styrene-based monomer may be styrene, a vinyl aromatic monomer other than styrene, or a mixture thereof.

Examples of vinyl aromatic monomers other than styrene include o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-tert-butylstyrene, and mixtures thereof. Styrene-based resin compositions using these monomers as raw materials are generally synthesized by radical polymerization, anionic polymerization, coordination anionic polymerization, and cationic polymerization. Further, when the synthesis method is classified by solvent, it is generally synthesized by a bulk polymerization method, a solution polymerization method, a suspension polymerization method, or an emulsion polymerization method.

Moreover, polystyrene is mentioned as a typical example of a styrene resin. Examples of polystyrene include general purpose polystyrene (GPPS) and crystalline polystyrene (SPS).

As another example of the styrene resin, for example, an acrylonitrile-styrene copolymer (AS resin), an acrylonitrile-butadiene-styrene copolymer (ABS resin), an acrylonitrile-ethylene propylene-styrene copolymer (AES resin), and the like. Acrylonitrile-chlorinated polyethylene-styrene copolymer (ACS resin), acrylate-styrene-acrylonitrile copolymer (ASA resin), silicon rubber-acrylonitrile-styrene copolymer (SAS resin), etc. Examples thereof include a copolymer containing acrylonitrile.

As another example of the styrene-based resin, a copolymer containing a styrene-based monomer and methyl methacrylate as a comonomer component such as a methyl methacrylate-styrene copolymer (MS resin) and a methyl methacrylate-butadiene-styrene copolymer (MBS resin). Examples include polymers.

Another example of the styrene-based resin is high impact polystyrene (HIPS) containing a styrene-butadiene copolymer (SB resin), polybutadiene, polyisoprene and the like. Impact-resistant polystyrene, which is often used in home appliances and OA equipment, can be synthesized by a bulk polymerization method in which a rubber component is generally dissolved in an organic solvent containing a styrene monomer and heat or a polymerization initiator is used.

Styrene-based resin parts used in home appliances and OA equipment also use resins recycled by home appliances and OA equipment manufacturers. In such a recycled resin, a thermoplastic elastomer may be blended with the recycled resin as a compatibilizer in order to improve the deterioration of physical properties due to the incompatible resin that could not be sorted out. Therefore, the regenerated styrene resin composition of the present embodiment may contain a thermoplastic elastomer.

In particular, since olefin-based resin compositions are often used in household appliances in addition to styrene-based resins, the thermoplastic elastomers (compounding agents) include, for example, block copolymers of styrene-based monomers and olefin-based monomers, and Examples thereof include modified polymers in which a functional group is added to these block copolymers.

Examples of the block copolymer of the styrene-based monomer and the olefin-based monomer include a styrene-butadiene-styrene block copolymer (SBS), a styrene-isoprene-styrene block copolymer (SIS), and a styrene-isobutylene-styrene block copolymer (Styline-isobutylene-styrene block copolymer). SIBS), and styrene-ethylenebutylene-styrene copolymer (SEBS) and styrene-ethylenepropylene-styrene copolymer (SEPS) hydrogenated thereto can be mentioned.

The modified polymer obtained by imparting a functional group to the block copolymer is, for example, an acid-modified SEBS obtained by graft-bonding maleic anhydride to SEBS, and the functional group (carboxyl group or the like) is the main chain. Examples thereof include a polymer graft-bonded to a polymer, or a polymer obtained by blocking a high-molecular-weight polymer such as polyurethane by utilizing a hydroxyl group at the end of the molecule.

(Zeolite)
Zeolite is a general term for crystalline aluminosilicates, and its composition is a porous substance represented by the general formula Me ₂ / X · O · Al ₂ O ₃ · mSiO ₂ · nH ₂ O, and metal ions are contained in the crystal structure. Have. In the chemical formula, Me is a metal ion such as sodium, potassium and calcium, X is a valence, and m and n are integers. For these zeolites, natural zeolite collected as a mineral resource, synthetic zeolite obtained by desorbing crystalline water by intensely heating crystalline hydrous aluminosilicate of alkali metal or alkaline earth metal, and coal ash are used as alkalis. There are artificial zeolites obtained by processing.

The zeolite used in this embodiment has an average pore diameter of 8 Å or more and less than 10 Å. Examples of zeolite having an average pore diameter of 8 Å or more and less than 10 Å include crystalline zeolite having a crystalline form such as X-type, Y-type, ultra-stabilized Y-type, and L-type.

The average pore diameter of zeolite can be measured by quantifying the amount of argon gas adsorbed on the sample surface using a fully automatic gas adsorption amount measuring device (manufactured by Quantachrome).

The zeolite may be any of natural zeolite, synthetic zeolite and artificial zeolite, and may be any of hydrophilic zeolite and hydrophobic zeolite.

Recycled styrene resin composition By blending zeolite with an average pore diameter of 8 Å or more and less than 10 Å, BHT is adsorbed in the zeolite pores during melt kneading and molding, reducing the volatilization amount of BHT and making it into a mold. It is possible to suppress the adhesion of tar. Further, since BHT is adsorbed as a monomer, the amount of BHT dimer produced can be reduced, and discoloration of the resin molded product over time can be suppressed.

When the average pore diameter is less than 8 Å, the pore diameter is too small for the size of the BHT molecule, and the effect of BHT adsorption cannot be obtained.

On the other hand, when the average pore diameter is 10 Å or more, the pore diameter is too large for the size of the BHT molecule, so that the BHT adsorbed by the high heat during melt-kneading cannot be efficiently carried in the pores. Further, when the average pore diameter is 10 Å or more, even low molecular weight additive molecules other than BHT may be adsorbed, and the physical properties such as fluidity, weather resistance, and heat resistance stability of the regenerated styrene resin composition may deteriorate. be.

Zeolites are adsorbents with an extremely narrow pore size distribution, so unlike other adsorbents with a wide pore size (silica gel, alumina, clay compounds, activated carbon, calcium carbonate, carbon black, etc.), they are molecules of a certain size. Can be selectively adsorbed in the pores. The general average pore diameter of zeolite is 3 Å or more and 15 Å or less, but in the present embodiment, the average pore diameter is further limited.

In Patent Document 1 (Japanese Patent No. 3776474), a zeolite having a pore diameter of 10 Å or more and 100 Å or less is used in order to adsorb a dimer of an antioxidant inside a pore. In the present embodiment, the tar component in question is a monomer of BHT, which is an antioxidant, and is not a target for adsorption of the porous material used in Patent Document 1.

Further, in Patent Document 2 (Japanese Unexamined Patent Publication No. 2002-69308), an alkali metal and an alkaline earth metal are used as adsorbents for adsorbing a contaminant generated from the thermoplastic resin composition, but BHT is used. It is not described to adsorb. Further, the adsorbed substance added in Patent Document 2 has no selectivity in the size of the molecule to be adsorbed, and other additives that maintain various physical characteristics of the resin composition and the resin molded product for a long period of time or improve the fluidity. It is expected that the resin composition will be adsorbed to the extent that it is difficult to suppress the volatilization of the generated substance while maintaining the physical characteristics of the resin composition.

Further, also in Patent Document 3 (Japanese Unexamined Patent Publication No. 2001-29966639), selective molecular adsorption by the pore size of the gas adsorbent is not considered.

The average particle size of the zeolite is not particularly limited, but the average particle size is preferably 0.1 to 100 μm, more preferably 0.1 to 10 μm. When zeolite having a large particle size is used, the impact strength of the resin molded product obtained from the regenerated styrene-based resin composition is lowered, and therefore, those in this range are preferable.

(Antioxidant)
In the present embodiment, the regenerated styrene resin composition preferably contains an antioxidant other than BHT. Examples of antioxidants other than BHT include phenol-based antioxidants other than BHT, phosphorus-based antioxidants, sulfur-based antioxidants, and the like.

Examples of the phenolic antioxidant other than BHT include antioxidants such as hindered, semi-hindart, and less hindered.

For example, stearyl 3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid, tetrakis [3- (3', 5'-di-t-butyl-4'-hydroxyphenyl) propionic acid]. Pentaerytritor, 2,2'-dimethyl-2,2'-(2,4,8,10-tetraoxaspiro [5.5] undecane-3,9-diyl) dipropane-1,1'-diyl-bis [3- (3-tert-Butyl-4-hydroxy-5-methylphenyl) propanoate], 2,4,6-tris (3', 5'-di-tert-butyl-4'-hydroxybenzyl) mecitylene, Known phenolic antioxidants such as 4,4'-butylidenebis (6-tert-butyl-m-cresol), 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, etc. Agent is used.

Among these, from the viewpoint of improving heat resistance, tetrakis [3- (3', 5'-di-t-butyl-4'-hydroxyphenyl) propionic acid] pentaerythritol, 2,2'-dimethyl-2,2 '-(2,4,8,10-tetraoxaspiro [5.5] undecane-3,9-diyl) dipropane-1,1'-diyl-bis [3- (3-tert-butyl-4-hydroxy) -5-Methylphenyl) propanoate] is preferred.

The antioxidant other than BHT is preferably an antioxidant having a higher molecular weight than BHT. Antioxidants having a molecular weight larger than that of BHT are less likely to be adsorbed in the pores of zeolite having a molecular weight of 8 Å or more and less than 10 Å. Therefore, the function of the antioxidant is effectively exhibited in the regenerated styrene resin composition, and the heat resistance stability of the regenerated styrene resin composition is enhanced.

Examples of the phosphorus-based antioxidant include tris phosphite (2,4-di-tert-butylphenyl) and 3,9-bis (octadecyloxy) -2,4,8,10-tetraoxa-3,9. -Diphosphaspiro [5.5] undecane, 3,9-bis (2,6-di-tert-butyl-4-methylphenoxy) -2,4,8,10-tetraoxa-3,9-diphosphaspiro [5.5] ] Known phosphorus-based antioxidants such as undecane, triphenyl phosphite, tris phosphite (4-nonylphenyl) can be used.

Among these, from the viewpoint of color stability, 3,9-bis (octadecyloxy) -2,4,8,10-tetraoxa-3,9-diphosphaspiro [5.5] undecane, 3,9-bis (2) , 6-Di-tert-butyl-4-methylphenoxy) -2,4,8,10-tetraoxa-3,9-diphosphaspiro [5.5] Undecane is preferred.

Examples of the sulfur-based antioxidant include bis [3- (dodecylthio) propionic acid] 2,2-bis [[3- (dodecylthio) -1-oxopropyloxy] methyl] -1,3-propanediyl, 3 , 3'-Ditridecylthiobispropionate, 2,4-bis (octylthiomethyl) -6-methylphenol, dioctadecyl 3,3'-thiodipropionate, and other known sulfur-based antioxidants can be used. ..

Among these, from the viewpoint of improving long-term heat resistance, bis [3- (dodecylthio) propionic acid] 2,2-bis [[3- (dodecylthio) -1-oxopropyloxy] methyl] -1,3-propane It is preferable to use diyl.

(Metal inactivating agent)
The regenerated styrene resin composition preferably further contains a metal deactivating agent and the same amount of a phosphorus-based antioxidant or a sulfur-based antioxidant as the phenol-based antioxidant. The regenerated styrene-based resin composition is liable to deteriorate because metal components that cause resin deterioration adhere to it during use or when it is crushed after recovery, or it is used in various parts as appearance parts. Therefore, it is necessary to improve the heat stability by combining a metal deactivating agent, another kind of antioxidant, and the like.

Examples of the metal inactivating agent include N- (2H-1,2,4-triazole-5-yl) salicylamide, bis-dodecanoate bis [N2- (2-hydroxybenzoyl) hydrazide], N, N'. -A known metal inactivating agent such as bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyl] hydrazine can be used.

[Other additives]
The regenerated styrene resin composition is, for example, a flame retardant, a flame retardant aid, a plasticizer, a mold release agent, a fluidity adjuster, an inorganic filler, a pigment, an antistatic agent, as long as the effect of the present embodiment is not impaired. , Conductive agents, antibacterial agents and other additives may be contained. For each of these, only one of them can be used alone, or two or more of them can be used in combination.

Examples of the flame retardant include brominated flame retardants such as ethylene bispentabromophenyl and ethylene bistetrabromophthalimide, phosphorus flame retardants such as triphenyl phosphate and tricresyl phosphate, and inorganic substances such as magnesium hydroxide and aluminum hydroxide. A flame retardant or a silicone flame retardant can be arbitrarily used.

As the flame retardant aid, for example, antimony trioxide, zinc borate, zinc tinate, zinc sulfide and the like can be arbitrarily used.

Examples of the plasticizer include phthalic acid-based, aliphatic dibasic acid-based, polyester-based, chlorinated paraffin-based, epoxy-based, phosphoric acid ester-based, trimellitic acid-based, pyromellitic acid-based, and ether ester-based plasticizers. Known substances can be used.

Examples of the fluidity adjusting agent include liquid paraffin, paraffin wax, polyethylene wax, stearic acid, behenic acid, stearyl alcohol, methylene bisstearic acid amide, ethylene bisstearic acid amide, zinc stearate, butyl stearate, and stearyl stearate. Known substances such as can be used.

Examples of the inorganic filler include carbon black, titanium black, titanium dioxide, barium carbonate, zinc flower, calcium carbonate, red iron oxide, alumina, silica, zinc oxide, aluminum oxide, magnesium oxide, antimony oxide, aluminum hydroxide, and hydroxide. Magnesium, zeolite, talc, mica, glass fiber, carbon fiber, sepiolite, potassium titanate, boron nitride, hydrotalcite, montmorillonite, barium sulfate, silas balloon and the like can be arbitrarily used.

<Manufacturing method of recycled styrene resin composition>
Hereinafter, an example of a method for producing the regenerated styrene resin composition according to the present embodiment will be described.

First, the used styrene resin composition is prepared in the state of a pulverized product (recycled plastic flakes) or the like, and is kneaded with other components such as zeolite. Examples of the kneading method include a method using an apparatus such as an extruder, a kneader, a Banbury mixer, a laboplast mill, a bead mixer, and a roll mill, and a solvent blending method. Kneading can be performed continuously or in batches. By such kneading, a regenerated styrene resin composition can be obtained.

The melt-kneaded resin composition is preferably pelletized by an extruder. As the extrusion molding machine, for example, a single shaft type, a multi-shaft type or a tandem type extrusion molding machine can be used.

It is preferable that the used styrene resin composition, such as a pulverized product, is surface-polished as a pretreatment before being kneaded with other components such as zeolite. This makes it possible to obtain a resin molded product having further excellent surface design.

Surface polishing of a used styrene resin composition is to remove stains adhering to the surface and dark-colored foreign substances such as other resins by polishing a crushed product of the used styrene resin composition. It is performed by rubbing the resin compositions against each other or by cutting with a metal solid (media) or a metal roller. By surface polishing, it is possible to obtain a resin molded product having high brightness and excellent appearance design from the regenerated styrene resin composition.

The method for producing a resin molded product from the regenerated styrene resin composition is not particularly limited, and for example, known methods such as injection molding and compression molding can be used.

Hereinafter, Examples and Comparative Examples will be described in detail, but the present invention is not limited thereto.

<Reference composition>
A twin-screw kneading extruder (TEX30α, manufactured by Japan Steel Works, Ltd.) was used at a cylinder temperature of 220 ° C. without adding an adsorbent component to 100 parts by mass of the used styrene resin composition recovered from home appliances. The strands were melt-kneaded, cooled with water, and pelletized to obtain pellets (reference composition).

<Example 1>
For 100 parts by mass of the used styrene resin composition recovered from home appliances, 1.0 part by mass of L-type zeolite (average pore diameter: 8.0 Å) (HSZ-500, manufactured by Tosoh Corporation) was used as an adsorbent. The added and mixed product was melt-kneaded at a cylinder temperature of 220 ° C. using a twin-screw kneading extruder (TEX 30α, manufactured by Japan Steel Works, Ltd.), and the strands were cooled with water and pelletized to obtain pellets.

<Example 2>
For 100 parts by mass of the used styrene resin composition recovered from home appliances, 5.0 parts by mass of L-type zeolite (average pore diameter: 8.0 Å) (HSZ-500, manufactured by Tosoh Corporation) was used as an adsorbent. The added and mixed product was melt-kneaded at a cylinder temperature of 220 ° C. using a twin-screw kneading extruder (TEX 30α, manufactured by Japan Steel Works, Ltd.), and the strands were cooled with water and pelletized to obtain pellets.

<Example 3>
Ultra-stabilized Y-zeolite (average pore diameter: 9.0 Å) (USKY-700, manufactured by Union Showa Co., Ltd.) as an adsorbent for 100 parts by mass of the used styrene resin composition recovered from home appliances. 1 part by mass was added and mixed, and the mixture was melt-kneaded at a cylinder temperature of 220 ° C. using a twin-screw kneading extruder (TEX 30α, manufactured by Japan Steel Works, Ltd.), and the strands were cooled with water and then pelletized to form pellets. Obtained.

<Example 4>
Ultra-stabilized Y-type zeolite (average pore diameter: 9.0 Å) (USKY-700, manufactured by Union Showa Co., Ltd.) as an adsorbent for 100 parts by mass of the used styrene resin composition recovered from home appliances. 0 parts by mass was added and mixed, and the mixture was melt-kneaded at a cylinder temperature of 220 ° C. using a twin-screw kneading extruder (TEX 30α, manufactured by Japan Steel Works, Ltd.), and the strands were cooled with water and then pelletized to form pellets. Obtained.

<Example 5>
5. Ultra-stabilized Y-zeolite (average pore diameter: 9.0 Å) (USKY-700, manufactured by Union Showa Co., Ltd.) as an adsorbent for 100 parts by mass of the used styrene resin composition recovered from home appliances. 0 parts by mass was added and mixed, and the mixture was melt-kneaded at a cylinder temperature of 220 ° C. using a twin-screw kneading extruder (TEX 30α, manufactured by Japan Steel Works, Ltd.), and the strands were cooled with water and then pelletized to form pellets. Obtained.

<Example 6>
For 100 parts by mass of the used styrene resin composition recovered from home appliances, 0.8 parts by mass of L-type zeolite (average pore diameter: 8.0 Å) (HSZ-500, manufactured by Tosoh Corporation) as an adsorbent, MFI type zeolite (average pore diameter: 6.0 Å) (Hisiv-3000, manufactured by Union Showa Co., Ltd.) 0.2 parts by mass was added and mixed, and a twin-screw kneading extruder (TEX 30α, Japan Steel Works, Ltd.) The strands were melt-kneaded at a cylinder temperature of 220 ° C., cooled with water, and pelletized to obtain pellets.

<Example 7>
3. Ultra-stabilized Y-zeolite (average pore diameter: 9.0 Å) (USKY-700, manufactured by Union Showa Co., Ltd.) as an adsorbent for 100 parts by mass of the used styrene resin composition recovered from home appliances. 0 parts by mass, X-type zeolite (average pore diameter: 10 Å) (13X, manufactured by Union Showa Co., Ltd.) 1.0 part by mass was added and mixed, and the mixture was mixed with a twin-screw kneading extruder (TEX 30α, Japan Steel Works, Ltd.). The strands were melt-kneaded at a cylinder temperature of 220 ° C., cooled with water, and pelletized to obtain pellets.

<Comparative Example 1>
MF1 type zeolite (average pore diameter: 6.0 Å) (Hisiv-3000, manufactured by Union Showa Co., Ltd.) 1.0 part by mass as an adsorbent with respect to 100 parts by mass of the used styrene resin composition recovered from home appliances. Was melt-kneaded at a cylinder temperature of 220 ° C. using a twin-screw kneading extruder (TEX 30α, manufactured by Japan Steel Works, Ltd.), and the strands were cooled with water and pelletized to obtain pellets.

<Comparative Example 2>
To 100 parts by mass of the used styrene resin composition recovered from home appliances, 1.0 part by mass of X-type zeolite (average pore diameter: 10 Å) (13X, manufactured by Union Showa Co., Ltd.) was added and mixed. Using a twin-screw kneading extruder (TEX 30α, manufactured by Japan Steel Works, Ltd.), melt-kneading was performed at a cylinder temperature of 220 ° C., and the strands were water-cooled and then pelletized to obtain pellets.

<Comparative Example 3>
To 100 parts by mass of the used styrene resin composition recovered from home appliances, 1.0 part by mass of Sepiolite (average pore diameter: 13 Å) (P-300, Omi Mining Co., Ltd.) was added and mixed. Using a shaft kneading extruder (TEX 30α, manufactured by Japan Steel Works, Ltd.), melt kneading was performed at a cylinder temperature of 220 ° C., and the strands were water-cooled and then pelletized to obtain pellets.

<Comparative Example 4>
To 100 parts by mass of the used styrene resin composition recovered from home appliances, 1.0 part by mass of silica gel (average pore diameter: 20 Å) (P-763, Mizusawa Chemical Industry Co., Ltd.) was added and mixed. Using a twin-screw kneading extruder (TEX 30α, manufactured by Japan Steel Works, Ltd.), melt-kneading was performed at a cylinder temperature of 220 ° C., and the strands were water-cooled and then pelletized to obtain pellets.

<Comparative Example 5>
MFI-type zeolite (average pore diameter: 6.0 Å) (Hisiv-3000, manufactured by Union Showa Co., Ltd.) 5.0 parts by mass with respect to 100 parts by mass of the used styrene resin composition recovered from home appliances. Was melt-kneaded at a cylinder temperature of 220 ° C. using a twin-screw kneading extruder (TEX 30α, manufactured by Japan Steel Works, Ltd.), and the strands were cooled with water and pelletized to obtain pellets.

<Comparative Example 6>
To 100 parts by mass of the used styrene resin composition recovered from home appliances, 5.0 parts by mass of X-type zeolite (average pore diameter: 10 Å) (13X, manufactured by Union Showa Co., Ltd.) was added and mixed. Using a twin-screw kneading extruder (TEX 30α, manufactured by Japan Steel Works, Ltd.), melt-kneading was performed at a cylinder temperature of 220 ° C., and the strands were water-cooled and then pelletized to obtain pellets.

<Comparative Example 7>
To 100 parts by mass of the used styrene resin composition recovered from home appliances, 5.0 parts by mass of Sepiolite (average pore diameter: 13 Å) (P-300, Omi Mining Co., Ltd.) was added and mixed. Using a shaft kneading extruder (TEX 30α, manufactured by Japan Steel Works, Ltd.), melt kneading was performed at a cylinder temperature of 220 ° C., and the strands were water-cooled and then pelletized to obtain pellets.

<Comparative Example 8>
To 100 parts by mass of the used styrene resin composition recovered from home appliances, 5.0 parts by mass of silica gel (average pore diameter: 20 Å) (P-763, Mizusawa Chemical Industry Co., Ltd.) was added and mixed. Using a twin-screw kneading extruder (TEX 30α, manufactured by Japan Steel Works, Ltd.), melt-kneading was performed at a cylinder temperature of 220 ° C., and the strands were water-cooled and then pelletized to obtain pellets.

〔evaluation〕
Using the pellets obtained in the reference composition, Examples 1 to 7 and Comparative Examples 1 to 8, a flat plate test piece was used by an injection molding machine under the conditions of a resin temperature (molding temperature) of 220 ° C. and a mold temperature of 60 ° C. Was produced. The BHT incidence and color difference were measured for each of these flat plate test pieces.

(Measurement of BHT incidence)
As described below, the amount of BHT generated by the regenerated styrene resin compositions (pellets) of the reference composition, Examples and Comparative Examples during molding was measured, and the BHT generation rate was determined.

The amount of BHT was measured for 15 mg of pellets by pyrolysis gas chromatography-mass spectrometry (Pylo-GC / MS) as the amount of BHT generated when the heating temperature was measured at 220 ° C. for 10 minutes.

Based on the measured value of the BHT amount, the BHT generation amount of the reference composition to which zeolite is not added is set to 100%, and the BHT generation of the regenerated styrene resin composition of Examples and Comparative Examples with respect to the BHT generation amount of the reference composition is set to 100%. The amount ratio (mass ratio) was determined as the BHT generation rate.

(Measurement of color difference)
The color difference was measured as follows.

Using the flat plate test piece (long side 80 mm × short side 20 mm × thickness 2 mm), the presence or absence of coloring of the resin molded product by the colored substance (BHT dimer) was evaluated. Specifically, the color difference of the resin molded product which was heated at 100 ° C. for 4 hours and then cooled at room temperature for 1 day was measured, and the presence or absence of coloring was evaluated from the measured value.

The color difference (synonymous with "color") was measured by color measurement with a spectrocolorimeter (CM-700d, manufactured by Konica Minolta Co., Ltd.). Calculate ΔEa ^* b ^* (color difference) from the measurement results using the following (Equation 1), and pass the case where the color difference is 1.5 or less, which is visually perceptible in NBS (US Standards Bureau) units (A). If it exceeds 1.5, it is evaluated as rejected (B) and shown in the table.

Here, the color measurement was performed in a 10-degree field of view using a D65 light source in the L ^* a ^* b ^* color system recommended by the International Commission on Illumination (CIE) in 1976. In Equation 1, L ^* indicates lightness, a ^* indicates color, and b ^* indicates saturation. In addition, the color difference calculation is based on "JIS Z 8781-4: 2013 (Color measurement-Part 4: CIE1976 L ^* a ^* b ^* )", and the respective differences in color values before and after heating are set to ΔL ^* and Δa ^*. , Δb ^* .

The measurement and evaluation results for the reference composition and Examples 1 to 7 are shown in Table 1. Table 2 shows the measurement and evaluation results for Comparative Examples 1 to 8.

From the results shown in Tables 1 and 2, for Example 1, the BHT generation rate was 78%, the color difference was 0.8, the BHT generation rate during molding was low, and the appearance was good. From this result, it was found that Example 1 was a regenerated styrene resin composition having an excellent appearance design on the surface of the molded product as compared with Comparative Examples 1 to 4 containing the same amount of zeolite as in Example 1. rice field.

Further, in Example 2, the BHT generation rate was 61% and the color difference was 0.6, the BHT generation rate during molding was low, and the appearance was good. From this result, it was found that Example 2 was a regenerated styrene resin composition having an excellent appearance design on the surface of the molded product as compared with Comparative Examples 5 to 8 containing the same amount of zeolite as in Example 2. rice field.

Further, in Example 3, the BHT generation rate was 79% and the color difference was 1.5, the BHT generation rate during molding was low, and the appearance was good. From this result, it was found that Example 3 was a regenerated styrene resin composition having an excellent appearance design on the surface of the molded product as compared with Comparative Examples 1 to 4 in which the amount of zeolite added was larger than that in Example 3. rice field.

Further, in Example 4, the BHT generation rate was 67%, the color difference was 0.8, the BHT generation rate at the time of molding was low, and the appearance was good. From this result, it was found that Example 4 was a regenerated styrene resin composition having an excellent appearance design on the surface of the molded product as compared with Comparative Examples 1 to 4 containing the same amount of zeolite as in Example 4. rice field.

Further, in Example 5, the BHT generation rate was 31% and the color difference was 0.7, the BHT generation rate during molding was low, and the appearance was good. From this result, it was found that Example 5 was a regenerated styrene resin composition having an excellent appearance design on the surface of the molded product as compared with Comparative Examples 5 to 8 containing the same amount of zeolite as in Example 5. rice field.

Further, in Example 6, the BHT generation rate was 32% and the color difference was 0.6, the BHT generation rate at the time of molding was low, and the appearance was good. From this result, it was found that Example 6 was a regenerated styrene resin composition having an excellent appearance design on the surface of the molded product as compared with Comparative Example 1 containing the same total amount of zeolite as in Example 6. That is, it was found that a zeolite having a pore diameter equivalent to that of BHT is effective even when combined with a zeolite having a pore diameter smaller than the size of BHT.

Further, in Example 7, the BHT generation rate was 33% and the color difference was 1.2, the BHT generation rate at the time of molding was low, and the appearance was good. From this result, it was found that Example 7 was a regenerated styrene resin composition having an excellent appearance design on the surface of the molded product as compared with Comparative Example 2 containing the same total amount of zeolite as in Example 7. That is, it was found that a zeolite having a pore diameter equivalent to that of BHT is effective even when combined with a zeolite having a pore diameter larger than the size of BHT.

As shown in Table 2, for Comparative Example 1, the BHT generation rate was 94% and the color difference was 2.9, the BHT generation rate during molding was high, the color difference was large, and the appearance design of the resin molded product was poor. rice field.

Further, in Comparative Example 2, the BHT generation rate was 94% and the color difference was 0.8, the color difference was small and the appearance design of the resin molded product was good, but the BHT generation rate during molding was high.

Further, in Comparative Example 3, the BHT generation rate was 95% and the color difference was 1.6, the BHT generation rate during molding was high, the color difference was large, and the appearance design of the resin molded product was poor.

Further, in Comparative Example 4, the BHT generation rate was 99% and the color difference was 0.4, the BHT generation rate during molding was high, the color difference was large, and the appearance design of the resin molded product was poor.

Further, in Comparative Example 5, the BHT generation rate was 99% and the color difference was 1.7, the BHT generation rate at the time of molding was high, the color difference was large, and the appearance design of the resin molded product was poor.

Further, in Comparative Example 6, the BHT generation rate was 45% and the color difference was 2.0, and the BHT generation rate at the time of molding was small, but the color difference was large and the appearance design of the resin molded product was poor.

Further, in Comparative Example 7, the BHT generation rate was 55% and the color difference was 2.0, and the BHT generation rate at the time of molding was small, but the color difference was large and the appearance design of the resin molded product was poor.

Further, in Comparative Example 8, the BHT generation rate was 70% and the color difference was 1.6, and the BHT generation rate at the time of molding was small, but the color difference was large and the appearance design of the resin molded product was poor.

Regarding the reference composition, the color difference was 2.3, the BHT generation rate during molding was high, the color difference was large, and the appearance design of the resin molded product was poor.

As shown in Tables 1 and 2, the BHT generation amount of Comparative Examples 1 and 5 was not 80% or less of the standard BHT generation amount to which the adsorbent was not added, and the zeolite having an average pore diameter of 6 Å was used. It can be seen that the BHT adsorption performance is poor. Further, from the results of Comparative Examples 2 to 4 and 6 to 8, none of the zeolites having an average pore diameter of 10 Å or more met the acceptance criteria (A) in the comprehensive judgment of the appearance design.

On the other hand, in Examples 1 to 7 in which zeolite having an average pore diameter of 8 Å or more and less than 10 Å was blended, the amount of BHT generated was reduced to 80% or less, and BHT volatilization was suppressed even in a high temperature state during melt kneading. I was able to. In addition, the color difference was 1.5 or less, and the overall design was excellent in appearance design.

Regarding the blending amount of zeolite, in Example 3, since zeolite is excellent in BHT adsorption performance, the addition of 0.1 parts by mass of zeolite also had an effect of reducing the amount of volatilization. In addition, although the effect of reducing the amount of volatilization was increased by increasing the blending amount of zeolite, the impact strength of the regenerated styrene resin composition decreased when zeolite exceeding 5.0 parts by mass was blended, so 100 parts by mass was used. The blending amount of zeolite with respect to the finished styrene resin composition is preferably 0.1 to 5.0 parts by mass.

It should be noted that the molded scraps of the resin molded product using the recycled styrene resin composition or the recycled product of the recycled styrene resin composition are recycled by crushing, heating and melting, or dissolving in an organic solvent. Even in the recycled material, the crystal structure of the zeolite in the resin is not destroyed. Therefore, it is considered that the volatilization of BHT during injection molding can be suppressed and the discoloration of the resin molded product can be suppressed for a long period of time.

That is, according to the above-mentioned regenerated styrene resin composition, the amount of BHT volatilized during injection molding is reduced, and BHT is adsorbed in the pores of the zeolite to suppress discoloration over time, thereby molding the resin. It is possible to prevent the appearance and design of the product from being impaired. Further, even when a molded end material of the above-mentioned recycled styrene resin composition or a resin containing a part or all of the recycled material is used, it is possible to produce a resin molded product having excellent appearance design.

The embodiments and examples disclosed this time should be considered to be exemplary and not restrictive in all respects. The scope of the present invention is shown by the scope of claims rather than the above description, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

1 BHT, 2 zeolite, 3 pores.

Claims (5)

Contains a used styrene resin composition and zeolite,
The zeolite has an average pore diameter of 8.0 Å or more and less than 10 Å .
The used styrene resin composition is a recycled styrene resin composition which is a styrene resin composition recovered from scraps of used home electric appliances . Contains a used styrene resin composition and zeolite,
The zeolite has an average pore diameter of 8.0 Å or more and less than 10 Å.
A regenerated styrene resin composition, wherein the zeolite is a zeolite having at least one crystal structure of X-type, Y-type, ultra-stabilized Y-type, and L-type. Contains a used styrene resin composition and zeolite,
The zeolite has an average pore diameter of 8.0 Å or more and less than 10 Å.
A regenerated styrene resin composition containing an antioxidant other than dibutylhydroxytoluene. The regenerated styrene resin composition according to claim 3 , wherein the antioxidant is a phenolic antioxidant. The regenerated styrene resin composition according to claim 4 , further comprising the metal deactivating agent and the same amount of the phosphorus-based antioxidant or the sulfur-based antioxidant as the phenol-based antioxidant.

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