JP2003012843A - Polystyrene-resin foamed material and production method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polystyrene-resin foamed material good in moldability and excellent in handleability and printability immediately after molding, and to provide a molded product thereof. SOLUTION: The polystyrene-resin foamed material is characterized in that a total content of volatile chemical materials extracted by a reprecipitation method with methanol is 1,800-4,000 ppm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polystyrene resin foam and a molded product thereof, and more specifically, it is suitable mainly for applications such as food containers such as instant noodle containers and packaging containers, and has good moldability and molding. The present invention relates to a polystyrene-based resin foam excellent in handleability and printability even immediately after that and a molded product thereof.

[0002]

2. Description of the Related Art Conventionally, polystyrene-based resin foams have been widely used as food containers and packaging containers because they are lightweight and have excellent heat insulating properties. On the other hand, it has been pointed out that styrene dimers and styrene trimers, which are of concern as environmental hormones, are eluted in foods in recent years in polystyrene resin foams used as food containers, particularly cup noodle containers. However, polystyrene is
As announced by the Environment Agency (currently the Ministry of the Environment) in October 2000, it is no longer a 67 item on the list of environmental hormones (endocrine disruptors), and its concern is disappearing.

As a method for producing a foamed sheet and a molded product in which styrene dimer and styrene trimer are difficult to elute,
A method is known in which a suspension polymerization raw material containing a small amount of styrene dimer and styrene trimer is used (JP-A-2000-95888 and JP-A-2000-15).
8507, etc.). However, the foamed sheet obtained by such a method and having a content of styrene dimer and styrene trimer of less than 1800 ppm has insufficient elongation, and when a reinforcing rib is provided on the upper surface of the container to increase the compressive strength, cracking occurs. May occur. Further, the polystyrene-based resin obtained by such a suspension polymerization method is a fine spherical, the extruder having a pellet-shaped resin supply device obtained by the conventional bulk polymerization, particularly single-screw extruder, discharge If the amount is not reduced, there is a problem that it is difficult for the resin raw material to bite into the extruder and a foamed sheet cannot be obtained under stable extrusion conditions.

Further, the fine spherical resin is supplied to a twin-screw extruder having a better resin biting than a single-screw extruder, melt-kneaded, extruded from a die having a strand shape, and then pelletized into pellets. However, there is a problem that the resin is thermally decomposed by melt-kneading in the twin-screw extruder, and volatile substances such as styrene dimer and styrene trimer contained in the resin increase.

Also, in food containers, especially cup noodle containers,
The outside is covered with a non-foamed film, and a product with a beautiful appearance is manufactured. The film surface of these containers is printed with characters and patterns by a curved surface printing machine, or a preprinted film is further laminated, which is colorful and has excellent surface gloss. However, the container used for curved surface printing is likely to be affected by curved surface printability due to its properties, such as spots on solid printed parts, conspicuous unevenness, blurring of letters and patterns, fading etc. Problems are likely to occur. As a method for improving these problems, slowing the speed of curved surface printing is performed. That is, it has been attempted to improve the printability by reducing the volume of container printing per minute.
In such a method, productivity is reduced. Further, as another method for improving printability, the printing pressure between the container and the printing roll is increased, but if the printing pressure is excessively increased, wrinkles are likely to occur in the container. Further, since the container is a foamed body, variations in container thickness and weight are likely to occur, and complicated fine adjustment of printing pressure is required.

Further, the curved surface printability of the container varies depending on the days after the container is molded, is the worst immediately after molding, becomes better as the days increase, and becomes constant in about 5 days.
The reason for this is not clear, but it is presumed that the film strength is weak because the air pressure inside the container immediately after molding is in a negative pressure state, and the container strength is lowered as a whole. From this, it is possible to improve the printing characteristics by keeping time after molding the container, but in this case, a place for storing the container is required. Therefore, it has been demanded that good printing be possible as soon as possible after the container is molded.

[0007]

DISCLOSURE OF THE INVENTION The present invention is intended to solve the above problems and has good moldability,
An object of the present invention is to provide a polystyrene resin foam excellent in handleability and printability immediately after molding and a molded product thereof.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies on polystyrene resin foams and molded products thereof in order to solve the above problems, and as a result, have found that polystyrene resins containing a specific amount of volatile substances. We have found that the foam has excellent moldability, handleability immediately after molding, and printability, and completed the present invention.

According to the present invention, the total amount of volatile substances extracted by the reprecipitation method with methanol is 1800 to 4000.
There is provided a polystyrene-based resin foam, a foamed sheet and a molded article thereof, which are characterized by being in ppm. Further, according to the present invention, the total amount of volatile substances extracted by the reprecipitation method with methanol is 2000 to 3500 p.
100 to 50% by weight of the polystyrene-based resin of the columnar pellet obtained by the bulk polymerization method, which is pm, and the total amount of volatile substances extracted by the reprecipitation method with methanol is 9
Polystyrene characterized in that 0 to 50 ppm by weight of spherical polystyrene resin obtained by the suspension polymerization method and 0 to 50% by weight are supplied to an extruder together with a foaming agent, melt-kneaded, and then extruded and foamed. A method for producing a resin foam is provided.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The polystyrene resin foam (hereinafter referred to as "foam") and the polystyrene resin foam molded product (hereinafter referred to as "molded product") of the present invention are extracted by a reprecipitation method with methanol. 18 total volatile substances
0 to 4000 ppm, preferably 2300 to 3
800 ppm, more preferably 2500-3800 p
pm.

Here, the total amount of volatile substances is obtained as follows. That is, first, 0.2 g of the sample (resin, foam or molded product) is dissolved in 10 ml of chloroform and dropped into 40 ml of methanol for reprecipitation. Next, 1 ml of an internal standard solution prepared by dissolving 0.2 g of eicosane in 100 ml of methyl ethyl ketone was added to the reprecipitation liquid, and N
O. Filter with 5A filter paper and make up to the internal standard solution. This is measured by a gas chromatography / mass spectrum (GC / MS) method, and all peak values are converted into an internal standard eicosane to determine the total amount of volatile substances. In the GC / MS method, GC17A (trade name) manufactured by Shimadzu Corporation is used as a measuring device, and the column is a column DB-1 (film thickness 0.1 μm, aperture 0.25).
mmφ, length 30 m), injection temperature 240 ° C., detection temperature 260 ° C., carrier gas He (pressure 80 psi),
The amount of the sample solution injected was 2 μl for measurement.

If the total amount of volatile substances in the foam and the molded product exceeds 4000 ppm, the strength immediately after molding the container by thermoforming cannot be obtained. That is, when a container immediately after molding is packed or pushed in with force when it is packed in a bag or box, the side surface of the container is dented or bent, which requires careful handling. Also, when a thermoplastic resin film is laminated on the outside of this container and a curved surface is printed on the surface of the film, the printing pressure cannot be endured during printing,
Wrinkles or faint prints on the container. Further, when the total amount of volatile substances is less than 1800 ppm, the elongation at the time of thermoforming into a container is insufficient, resulting in poor moldability. Specifically, when an attempt is made to form a container having reinforcing ribs on the upper surface of the container in order to obtain strength as a container, the container may crack.

The foam of the present invention may be a sheet-shaped polystyrene resin foam sheet (hereinafter referred to as "foam sheet"). The expansion ratio and the average thickness of the foam sheet are not particularly limited, but the expansion ratio is about 1.1 to 20 times, preferably about 2 to 15 times, and the average thickness is 0.6 to
It is about 3.0 mm. The foamed sheet may have a thermoplastic resin film (hereinafter referred to as “film”) laminated on at least one surface thereof in order to improve its strength and printability.

Examples of the film include those made of polystyrene resin, polypropylene resin, polyester resin, polyethylene resin, methacrylic resin and the like. The film may use these resins alone or in combination of two or more kinds. Above all, a high-impact polystyrene-based resin film in which a polystyrene-based resin contains a rubber component and has an effect of improving brittleness is preferable.

The molded product of the present invention is a molded product of the foamed product of the present invention. If a foamed sheet obtained by laminating the above-mentioned film is molded, a molded product having a laminated film is obtained. Examples of the molded product include a food container in the form of a donburi, a tray, a plate, and a packaging container in the form of a box, a cylinder, and the like.
When the molded product obtained by laminating films is such a container, the film may be provided inside or outside the container, or on both sides. When printing is performed on the outside of the container, the film is usually provided on the outside of the container.

The method for producing the foam of the present invention will be described below. The foam of the present invention includes a cylindrical pellet polystyrene resin obtained by a bulk polymerization method (hereinafter referred to as “cylindrical resin”) and a spherical polystyrene resin obtained by a suspension polymerization method (hereinafter, “ "Spherical resin")
Are supplied to an extruder together with a foaming agent, melt-kneaded, and then extrusion-foamed.

The columnar resin and the spherical resin as the base resin are not particularly limited, and examples thereof include a styrene homopolymer or a copolymer containing 50% by weight or more of styrene. Examples of the copolymer include styrene-maleic anhydride, styrene-methacrylic acid, styrene-acrylic acid (including acrylic acid ester), styrene-acrylonitrile copolymer resin, and acrylonitrile-butadiene-styrene terpolymer. Examples include polymer resins.

Examples of the copolymerization component in the copolymer include α-methylstyrene, ethylstyrene, isopropylstyrene, dimethylstyrene, paramethylstyrene,
Styrene derivatives such as t-butylstyrene, chlorostyrene and bromostyrene, esters of acrylic acid and methacrylic acid such as methyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate and cetyl methacrylate, or acrylonitrile,
Examples include various monomers such as dimethyl fumarate, ethyl fumarate, vinyltoluene, vinylxylene, butadiene, and maleic anhydride.

Other resins (for example, polyethylene resin, polypropylene resin, etc.) can be appropriately mixed with the base resin as long as the effects of the present invention are not impaired.
Both the suspension polymerization method and the bulk polymerization method are methods for producing polystyrene by opening the ethylene double bond portion of a styrene monomer to generate styrene molecules.

The suspension polymerization method, which is also called granular polymerization, is a method for producing a granular polymer (styrene polymer) by suspending styrene monomer in water in the form of oil droplets. In the suspension polymerization method, since a large amount of water is stirred, the heat generated during the polymerization is removed and the reaction temperature is kept uniform, and the temperature can be easily adjusted. On the other hand, since the polymerization reaction is carried out by dispersing them in the form of oil droplets, if the diameter of the oil droplets becomes large, dispersion in water becomes unstable, and it is difficult to obtain large particles. Also, the whole process including wastewater treatment becomes complicated, and in order to make spherical polystyrene into pellet polystyrene, it is fed to a twin-screw extruder, melt-kneaded, and then extruded from a die having a strand shape and then pelletized. Then, it is necessary to go through a pelletizing process, and it is difficult to construct a continuous process suitable for mass production.

The bulk polymerization method is a kind of solution polymerization in which the monomer itself is used as a solvent, and has the same shape as the shape of the reaction vessel after the reaction is formed. In practice, ethylbenzene contained in styrene monomer is often used as a solvent, and its bulky shape makes it industrially easy to manage and has high productivity. It is the mainstream method for producing general polystyrene resins. Has become. On the other hand, it is difficult to adjust the temperature and uniformly remove heat during the reaction, and since the solvent is the monomer itself, it is difficult to remove the solvent after the reaction. Further, since the product is lumpy, it is difficult to handle it as it is, and a step of making it into pellets through an extruder is required.

The columnar resin has a total amount of volatile substances of 200
0-3500 ppm, preferably 2200-33
It is 00 ppm. The spherical resin has a total amount of volatile substances of 900 to 2500 ppm, preferably 110.
It is 0 to 2200 ppm. If the total amount of volatile substances in the cylindrical resin exceeds 3500 ppm, or if the total amount of volatile substances in the spherical resin exceeds 2500 ppm, the strength immediately after molding the container by thermoforming cannot be obtained,
It is inferior in handleability, and when printing is performed on the film surface of a molded container in which films are laminated, it cannot withstand printing pressure and wrinkles occur in the container, or print fading occurs. Further, the total amount of volatile substances in the cylindrical resin is less than 2000 ppm, or the total amount of volatile substances in the spherical resin is 900 ppm.
When it is less than ppm, the uniform fluidity of the resin in the extruder is impaired, it becomes difficult to obtain a foamed sheet having a uniform thickness, and it becomes difficult to obtain a container having a uniform thickness. Further, depending on the molding die, cracks may occur in the rib portion.

The spherical resin has an average particle size of 0.25 to 2.5.
It is preferably mm, and more preferably 0.50 to 1.5 mm. Those having an average particle size of more than 2.5 mm are not preferable because they are likely to cause poor dispersion in the suspension polymerization method and reduce the yield. The average particle size is 0.25
If it is less than mm, it slips through between the cylindrical resin particles to be mixed and is accumulated in the lower part of the raw material tank first, which makes it difficult to extrude the mixed resin at a stable ratio, which is not preferable (FIG. 4).

The average particle size is JIS number Z-880.
1 standard sieve opening 2.36 mm (7.5 mesh), opening 2.00 mm (8.6 mesh), opening 1.70 mm (10 mesh), opening 1.40 mm
(12 mesh), opening 1.18 mm (14 mesh), opening 1.00 mm (16 mesh), opening 0.85 mm (18 mesh), opening 0.71 mm
(22 mesh), opening 0.60 mm (26 mesh), opening 0.50 mm (30 mesh), opening 0.425 mm (36 mesh), opening 0.355 m
m (42 mesh), opening 0.300 mm (50 mesh), opening 0.250 mm (60 mesh), opening 0.212 mm (70 mesh), opening 0.180
It was applied to a sieve of mm (83 mesh) in order and allowed to remain on the sieve, and it was determined from the average value of the openings of the top 5 sieves with a large distribution ratio.

The weight average molecular weight of the base resin is, for example, 20.
It is preferably about 10,000 to 450,000, more preferably about 250,000 to 400,000. When the weight average molecular weight of the base resin exceeds 450,000, elongation becomes insufficient and moldability is deteriorated, which is not preferable. Further, if the weight average molecular weight of the base resin is less than 200,000, the resulting foam tends to be brittle and the strength of the container is reduced, which is not preferable.

In the method of the present invention, only the columnar resin may be used, but since the strength of the molded product immediately after molding is increased and the handleability and the printability are further improved, the columnar resin and the spherical resin are used in combination. Preferably. The compounding amount of cylindrical resin is
It is 100 to 50% by weight, preferably 80 to 60% by weight. The compounding amount of the spherical resin is 0 to 50% by weight, and 20
-40% by weight is preferred. When the compounding amount of the columnar resin is less than 50% by weight, the moldability of the foam is deteriorated, and the resin does not bite into the screw of the extruder, and stable extrusion foaming may not be possible. In particular, the tendency is remarkable when a single-screw extruder is used.

In the method of the present invention, a foam can be produced by extruding and foaming the above base resin by a known extrusion foaming method. The extrusion foaming method is carried out by adding a base resin, a foaming agent and other additives to an extruder so as to obtain a desired density, melt-kneading the mixture, and then extruding it from a die of the extruder. A mixture of the base resin, the foaming agent and the additive is prepared in advance.
It may be supplied to the extruder. Further, the additive may be a so-called masterbatch product in which a resin of the same kind as the base resin is added in high concentration in advance.

The extruder used in the method of the present invention includes known ones, for example, a single screw extruder and a twin screw extruder. Among them, a single-screw extruder is preferable because it is excellent in extrusion stability under high pressure and little heat deterioration.
Examples of the foaming agent used in the method of the present invention include known foaming agents, for example, decomposable foaming agents, gaseous or volatile foaming agents.

Examples of the decomposition type foaming agent include inorganic decomposition type foaming agents such as ammonium carbonate, sodium bicarbonate, ammonium bicarbonate, ammonium nitrite, calcium azide, sodium azide and sodium borohydride, azodicarbonamide, azobis. Azo compounds such as sulforamide, azobisisobutyronitrile and diazoaminobenzene, nitroso compounds such as N, N′-dinitrosopentanemethylenetetramine and N, N′-dimethyl-N, N′-dinitrosoterephthalamide, Benzenesulfonyl hydrazide, p-toluenesulfonyl hydrazide and p, p'-oxybisbenzenesulfonyl semicarbazide, p-toluenesulfonyl semicarbazide, trihydrazinotriazine, barium azodicarboxylate, citric acid, etc. Is mentioned.

Examples of the gas blowing agent include nitrogen, carbon dioxide, propane, n-butane, i-butane, tert-butane, dimethyl ether and the like. The gas means a gas at normal temperature (20 ° C.) and normal pressure (1 atm). Examples of the volatile foaming agent include ether, petroleum ether, acetone, pentane, isopentane, hexane, isohexane, heptane, isoheptane, benzene, toluene and the like. Water can also be used as the foaming agent. These foaming agents may be used alone or in combination of two or more.

Among these foaming agents, n-butane and i-butane are particularly preferable. When the bubble size of the foam is about 40 μm or less, it is preferable to use nitrogen, carbon dioxide or water as the foaming agent. In particular, nitrogen and carbon dioxide are preferable because they are inexpensive. The amount of the foaming agent added is about 0.25 to 5.0 parts by weight with respect to 100 parts by weight of the base resin.

Further, in the method of the present invention, a cell regulator or the like may be added. Examples of the foam control agent include inorganic powders such as talc and silica, acidic salts such as polyvalent carboxylic acids, and reaction mixtures of polyvalent carboxylic acids with sodium carbonate or sodium bicarbonate. The addition amount of the cell regulator is 0.01 to 100 parts by weight of the base resin.
It is about 6.0 parts by weight. When the amount of the cell regulator is large, the cell membrane becomes vulnerable to heat, and the cell membrane may be broken during extrusion lamination, and as a result, the cell may become large. In order to prevent such an increase in bubbles, it is preferable to use nitrogen or carbon dioxide gas as a foaming agent.

Further, in the method of the present invention, an ultraviolet absorber, an antioxidant, a coloring agent, a lubricant, a flame retardant, an antistatic agent and the like may be added, if desired. The melt-kneaded resin is extruded and foamed from a die adjusted to a temperature suitable for foaming to obtain a foam. This foam can be formed into a sheet by directly extruding it into a sheet or once extruding it into a cylindrical shape and then cutting it at an arbitrary line.

The extruder barrel temperature at the time of producing the foam varies depending on the extruder used and the type of the base resin, but is preferably about 140 to 260 ° C. For laminating the film on the foamed sheet, a method of co-extruding and laminating the foamed sheet and the film, and a method of laminating the film on the foamed sheet using a heating roll, an adhesive or the like can be mentioned. Specifically, (1) a co-extrusion method in which a foamed sheet and a film are joined and laminated and then extruded from a die,
(2) A method of directly laminating a film extruded from an extruder by an inline or outline and directly laminating it on a foam sheet, or (3) a resin extruded from the extruder by an inline or outline binder As a method for laminating a film (which may be plain or printed) on a foamed sheet, (4) a film (which may be plain or printed) may be formed on a foamed sheet while being heated by a heating roll. Examples include a method of pressure bonding and laminating.

In the method for producing a molded article, the foam obtained by the above-mentioned method is used, for example, in an oven (at a temperature of 230 to 30).
After softening the foam in (0 ° C.), a desired molding die may be used for heat molding with a molding time of 3 to 20 seconds.

[0036]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

Example 1 100% by weight of a columnar resin GP-9 [manufactured by Toyo Styrene Co., Ltd., MI = 2.0] as a base resin and butane gas as a foaming agent (contains 50% each of normal and iso). Master batch product DSM-1401 containing 2.2 parts by weight and 0.7 parts by weight of powdered talc as a cell regulator.
A (manufactured by Toyo Styrene Co., Ltd.) was put in a single-screw extruder, the resin temperature was adjusted to 160 ° C., the resin was flown into a mold having a diameter of 170 mm, and the inside of the foamed sheet immediately after being extruded into a cylindrical shape from a slit was used. A foamed sheet was obtained by applying air to the outside to cool it and cutting it at a desired line. The conditions for applying air are as follows: the air temperature is 27 ° C, and the blowing amount is 1.
It was 5 m ³ / min and the outer side was 3.2 m ³ / min.

Then, the obtained foamed sheet was heat-molded at 230 ° C. for 15 seconds to obtain a dome-shaped molded product (FIG. 1) having a diameter of 150 mm and a depth of 80 mm. Also,
By heat-molding the obtained foamed sheet at 230 ° C. for 12 seconds, length 200 mm × width 100 mm × height 2
A 5 mm tray-shaped molded product (FIG. 2) was obtained. The content of volatile substances in the foam sheet is 3763 ppm,
The content of volatile substances in the molded product was 3796 ppm. The compression strength of the tray-shaped molded product immediately after molding was 598 gf.

Example 2 As a base resin, spherical resin HS-150 [manufactured by Sekisui Plastics Co., Ltd., MI = 2.0, average particle size = 0.76 mm]
20% by weight and 80% by weight of columnar resin GP-9 were used to obtain a foamed sheet and a molded product in the same manner as in Example 1. The content of volatile substances in the foamed sheet was 3277 ppm, and the content of volatile substances in the molded product was 3369 ppm. The compression strength of the tray-shaped molded product immediately after molding was 610 gf.

Example 3 A foamed sheet and a molded product were obtained in the same manner as in Example 1 except that 30% by weight of spherical resin HS-150 and 70% by weight of columnar resin GP-9 were used as the base resin. It was The content of volatile substances in the foam sheet is 3050ppm
And the content of volatile substances in the molded product is 3122
It was ppm. The compression strength of the tray-shaped molded product immediately after molding was 621 gf.

Example 4 A foamed sheet and a molded product were obtained in the same manner as in Example 1 except that 40% by weight of spherical resin HS-150 and 60% by weight of columnar resin GP-9 were used as the base resin. It was The content of volatile substances in the foam sheet is 2932ppm
And the content of volatile substances in the molded product is 2920
It was ppm. The compression strength of the tray-shaped molded product immediately after molding was 635 gf.

Example 5 As a base resin, 30% by weight of a spherical resin HS-150 having an average particle size of 0.95 mm and a columnar resin GP-
A foamed sheet and a molded product were obtained in the same manner as in Example 1 except that 70% by weight of 9 was used. The content of volatile substances in the foamed sheet was 3072 ppm, and the content of volatile substances in the molded product was 3163 ppm. In addition, the compression strength of the tray-shaped molded product immediately after molding is 636 g.
It was f.

Example 6 Foaming was carried out in the same manner as in Example 1 except that the columnar resin G0002 [manufactured by A & M Styrene Co., Ltd., MI = 2.0] was used as the base resin in an amount of 100% by weight. Sheets and moldings were obtained. The content of volatile substances in the foamed sheet was 3654 ppm, and the content of volatile substances in the molded product was 3,815 ppm. The compression strength of the tray-shaped molded product immediately after molding was 600 gf.

Example 7 Except that 20% by weight of spherical resin HS-150 and 80% by weight of columnar resin G0002 were used as the base resin,
A foamed sheet and a molded product were obtained in the same manner as in Example 1.
The content of volatile substances in the foam sheet is 3210pp
m, and the content of volatile substances in the molded product is 333
It was 5 ppm. The compression strength of the tray-shaped molded product immediately after molding was 608 gf.

Example 8 As a base resin, spherical resin HS-150 was used in an amount of 30% by weight and columnar resin G0002 was used in an amount of 70% by weight.
A foamed sheet and a molded product were obtained in the same manner as in Example 1.
The content of volatile substances in the foam sheet is 2985 pp
m, and the content of volatile substances in the molded product is 308
It was 0 ppm. The compression strength of the tray-shaped molded product immediately after molding was 615 gf.

Example 9 Except that 40% by weight of spherical resin HS-150 and 60% by weight of columnar resin G0002 were used as the base resin,
A foamed sheet and a molded product were obtained in the same manner as in Example 1.
The content of volatile substances in the foam sheet is 2880 pp
m, and the content of volatile substances in the molded product is 301
It was 4 ppm. The compression strength of the tray-shaped molded product immediately after molding was 621 gf.

Example 10 As a base resin, 30% by weight of a spherical resin HS-150 having an average particle size of 0.95 mm and a columnar resin G00 was used.
A foamed sheet and a molded product were obtained in the same manner as in Example 1 except that 70% by weight of 02 was used. The content of volatile substances in the foamed sheet was 3048 ppm, and the content of volatile substances in the molded product was 3296 ppm. The compression strength of the tray-shaped molded product immediately after molding is 627 g.
It was f.

Comparative Example 1 The same procedure as in Example 1 was carried out except that 100% by weight of a columnar resin G-9305 [manufactured by A & M Styrene Co., Ltd., MI = 1.7] was used as a base resin. To obtain a foamed sheet and a molded product. The content of volatile substances in the foamed sheet was 6126 ppm, and the content of volatile substances in the molded product was 6364 ppm. The compression strength of the tray-shaped molded product immediately after molding was 545 gf.

Comparative Example 2 70% by weight of a cylindrical resin G-9305 was used as a base resin.
A foamed sheet and a molded product were obtained in the same manner as in Example 1 except that 30% by weight of the spherical resin HS-150 was used. The content of volatile substances in the foam sheet is 575
It was 5 ppm, and the content of volatile substances in the molded product was 5840 ppm. The compression strength of the tray-shaped molded product immediately after molding was 568 gf.

Comparative Example 3 A base resin, which was obtained by a suspension polymerization method, was supplied to a twin-screw extruder, melt-kneaded, extruded from a strand-shaped mold, and then pelletized into pellets. Resin H
A foamed sheet and a molded product were obtained in the same manner as in Example 1 except that 100% by weight of RM-57 [manufactured by Toyo Styrene Co., Ltd., MI = 2.0] was used. The content of volatile substances in the foamed sheet was 1714 ppm, and the content of volatile substances in the molded product was 1756 ppm. In addition, the compression strength of the tray-shaped molded product immediately after molding is 615 g.
It was f.

Example 11 High-impact styrene resin E-641N (manufactured by Toyo Styrene Co., Ltd.) was extruded into a film form from an extruder equipped with a T-die, and the film was cooled before Example 1
By directly laminating on the surface of the foamed sheet, the foamed sheet obtained by laminating films was obtained. The thickness of this film was 140 μm. This foam sheet was used in Example 1.
Heat molding was carried out in the same manner as above to obtain a dombly-shaped molded product having a film formed on the outside. Immediately after molding, curved surface printing was performed on the film of the molded product. The results are shown in Table 2.

When the film was peeled from the foam sheet and the content of the volatile substance in the foam sheet was measured, it was 3
It was 777 ppm. The film was peeled off from the molded product, and the content of volatile substances in the molded product was measured and found to be 3802 ppm.

Example 12 A foamed sheet and a molded article obtained by laminating films were obtained in the same manner as in Example 11 except that the foamed sheet obtained in Example 2 was used, and curved surface printing was performed on the molded article. It was The results of curved surface printing are shown in Table 2. When the film was peeled from the foam sheet and the content of the volatile substance in the foam sheet was measured, it was 3298 ppm. The film was peeled off from the molded product, and the content of volatile substances in the molded product was measured and found to be 3396 ppm.

Example 13 A foamed sheet and a molded article obtained by laminating films were obtained in the same manner as in Example 11 except that the foamed sheet obtained in Example 3 was used, and the curved surface was printed on the molded article. It was The results of curved surface printing are shown in Table 2. The film was peeled off from the foam sheet, and the content of the volatile substance in the foam sheet was measured and found to be 3111 ppm. The film was peeled off from the molded product, and the content of volatile substances in the molded product was measured and found to be 3214 ppm.

Example 14 A foamed sheet and a molded article obtained by laminating films were obtained in the same manner as in Example 11 except that the foamed sheet obtained in Example 4 was used, and the curved surface was printed on the molded article. It was The results of curved surface printing are shown in Table 2. When the film was peeled off from the foam sheet and the content of the volatile substance in the foam sheet was measured, it was 3012 ppm. The film was peeled off from the molded product, and the content of volatile substances in the molded product was measured and found to be 3056 ppm.

Example 15 A foamed sheet and a molded article obtained by laminating films were obtained in the same manner as in Example 11 except that the foamed sheet obtained in Example 5 was used, and the curved surface was printed on the molded article. It was The results of curved surface printing are shown in Table 2. The film was peeled off from the foam sheet, and the content of the volatile substance in the foam sheet was measured and found to be 3111 ppm. The film was peeled off from the molded product, and the content of volatile substances in the molded product was measured and found to be 3222 ppm.

Example 16 A foamed sheet and a molded article obtained by laminating films were obtained in the same manner as in Example 11 except that the foamed sheet obtained in Example 6 was used, and the curved surface was printed on the molded article. It was The results of curved surface printing are shown in Table 2. When the film was peeled from the foam sheet and the content of the volatile substance in the foam sheet was measured, it was 3711 ppm. The film was peeled off from the molded product, and the content of volatile substances in the molded product was measured and found to be 3915 ppm.

Example 17 A foamed sheet and a molded article obtained by laminating films were obtained in the same manner as in Example 11 except that the foamed sheet obtained in Example 7 was used, and the curved surface was printed on the molded article. It was The results of curved surface printing are shown in Table 2. When the film was peeled from the foam sheet and the content of the volatile substance in the foam sheet was measured, it was 3295 ppm. The film was peeled off from the molded product, and the content of the volatile substance in the molded product was measured and found to be 3345 ppm.

Example 18 A foamed sheet and a molded article obtained by laminating films were obtained in the same manner as in Example 11 except that the foamed sheet obtained in Example 8 was used, and the curved surface was printed on the molded article. It was The results of curved surface printing are shown in Table 2. When the film was peeled from the foam sheet and the content of the volatile substance in the foam sheet was measured, it was 3015 ppm. The film was peeled off from the molded product, and the content of volatile substances in the molded product was measured and found to be 3111 ppm.

Example 19 A foamed sheet and a molded product obtained by laminating films were obtained in the same manner as in Example 11 except that the foamed sheet obtained in Example 9 was used, and the curved surface was printed on the molded product. It was The results of curved surface printing are shown in Table 2. When the film was peeled off from the foam sheet and the content of the volatile substance in the foam sheet was measured, it was 2974 ppm. The film was peeled off from the molded product, and the content of volatile substances in the molded product was measured and found to be 3152 ppm.

Example 20 A foamed sheet and a molded article obtained by laminating films were obtained in the same manner as in Example 11 except that the foamed sheet obtained in Example 10 was used, and curved surface printing was performed on the molded article. It was The results of curved surface printing are shown in Table 2. The film was peeled off from the foamed sheet, and the content of volatile substances in the foamed sheet was measured and found to be 3088 ppm. The film was peeled off from the molded product, and the content of volatile substances in the molded product was measured and found to be 3385 ppm.

Comparative Example 4 A foamed sheet and a molded article obtained by laminating films were obtained in the same manner as in Example 11 except that the foamed sheet obtained in Comparative Example 1 was used, and curved surface printing was performed on the molded article. It was The results of curved surface printing are shown in Table 2. When the film was peeled from the foam sheet and the content of the volatile substance in the foam sheet was measured, it was 6215 ppm. The film was peeled off from the molded product, and the content of volatile substances in the molded product was measured and found to be 6458 ppm.

Comparative Example 5 A foamed sheet and a molded article obtained by laminating films were obtained in the same manner as in Example 11 except that the foamed sheet obtained in Comparative Example 2 was used, and curved surface printing was performed on the molded article. It was The results of curved surface printing are shown in Table 2. The film was peeled off from the foam sheet, and the content of volatile substances in the foam sheet was measured and found to be 5888 ppm. Further, when the film was peeled off from the molded product and the content of the volatile substance in the molded product was measured, it was 6011 ppm.

Comparative Example 6 A foamed sheet and a molded article obtained by laminating films were obtained in the same manner as in Example 11 except that the foamed sheet obtained in Comparative Example 3 was used, and curved surface printing was performed on the molded article. It was The results of curved surface printing are shown in Table 2. The film was peeled off from the foam sheet, and the content of volatile substances in the foam sheet was measured and found to be 1759 ppm. The film was peeled off from the molded product, and the content of volatile substances in the molded product was measured and found to be 1785 ppm.

[Evaluation of Formability of Foamed Sheet] Examples 1-2
Regarding the moldability of the foamed sheets obtained in 0 and Comparative Examples 1 to 6, the following criteria were determined by visually observing 50 dombly-shaped molded articles obtained by thermoforming each foamed sheet. It was evaluated by. ◎ There is elongation during molding and no cracks occur in the molded product. ○ Elongation during molding is slightly low, but cracks do not occur in molded products. × There is no elongation during molding and cracks occur in the molded product.

[Evaluation of curved surface printability of a molded product immediately after molding]
Regarding the curved surface printability of the dombly-shaped molded articles obtained by forming the films obtained in Examples 11 to 20 and Comparative Examples 4 to 6 on the outside, 50 molded articles were molded within 30 minutes,
By performing curved surface printing on the film outside the container using a curved surface printing machine, and visually observing the printed surface,
The following criteria were evaluated. ◎ No wrinkles or scratches were seen on the printed surface, and the print was printed on the entire surface. ○ There are no wrinkles on the printed surface, and no blur is seen. △ There is no wrinkle on the printed surface, but faintness is observed. × There are wrinkles on the printed surface, and faintness is observed.

[Evaluation of compressive strength and handleability] Regarding the compressive strength of the foamed sheets obtained in Examples 1 to 10 and Comparative Examples 1 to 3, tray-shaped molding obtained by thermoforming each foamed sheet was carried out. Within 50 minutes after molding, 50 pieces of the product were tested for compressive strength (AIKOH ENGINEERING MO
DEL-1310DS) (Fig. 3), 10 mm
It was determined by measuring the repulsive force (compressive strength) (gf) when compressed.

The handleability of the molded product is based on the repulsive force when the molded product is manually deformed within 30 minutes after molding 50 tray-shaped molded products and the above-mentioned compression strength. Evaluated to. ◯: Compressive strength is 580 gf or more, and there is sufficient repulsive force even when the molded product is held and deformed by hand. X: Compressive strength is less than 580 gf, and repulsive force when the molded product is held and deformed by hand is weak. Table 1 shows measured values and evaluation results of the foamed sheets and molded products of Examples and Comparative Examples.

[0069]

[Table 1]

[0070]

[Table 2]

From Table 1, as in Examples 1 and 6, the foamed sheets produced by using only the columnar resin as the base resin have good moldability (⊚) and the compressive strength immediately after molding. It can be seen that the molded product is strong and easy to handle. Furthermore, by adding a spherical resin as the base resin and increasing the amount thereof, the compressive strength of the foamed sheets (foamed sheets of Examples 2 to 5 and Examples 7 to 10) immediately after molding is increased, and the handleability is further improved. It turns out that it becomes an excellent molded product.

Further, from Table 2, Example 1 and Example 6
It can be seen that the foamed sheets of Examples 11 and 16 in which a film is laminated on the foamed sheet of No. 11 are excellent in moldability and printability on a curved surface immediately after molding. Furthermore, by adding a spherical resin as the base resin and increasing the amount thereof, the printability of the foamed sheets (foamed sheets of Examples 12 to 15 and Examples 17 to 20) immediately after molding becomes more excellent. I understand.

[0073]

Industrial Applicability According to the present invention, it is possible to provide a polystyrene resin foam which is excellent in moldability and is excellent in handleability and printability immediately after molding, and a molded product thereof. This foam has high productivity and is very useful industrially. In addition, by using a base resin in which a columnar polystyrene-based resin obtained by bulk polymerization with many volatile substances is mixed with a spherical polystyrene-based resin obtained by suspension polymerization with few volatile substances, It is possible to provide a polystyrene resin foam-molded article which has good moldability and is excellent in handleability and printability immediately after molding.

[Brief description of drawings]

FIG. 1 is a view showing a molded product (a container of a doll shape) of the present invention.

FIG. 2 is a view showing a molded product (tray-shaped container) of the present invention.

FIG. 3 is a schematic view of a compressive strength measuring instrument in which the molded product of the present invention is set.

FIG. 4 is a schematic diagram showing how spherical resin slips through a mixed resin.

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Claims (8)

[Claims] 1. A polystyrene resin foam, characterized in that the total amount of volatile substances extracted by a reprecipitation method with methanol is 1800 to 4000 ppm. 2. A polystyrene resin foam sheet comprising the polystyrene resin foam according to claim 1. 3. The polystyrene resin foam sheet according to claim 2, wherein a thermoplastic resin film is laminated on at least one surface of the polystyrene resin foam sheet. 4. A volatile substance produced by thermoforming the polystyrene resin foam according to claim 1 or the polystyrene resin foam sheet according to claim 2 or 3, and extracted by a reprecipitation method with methanol. The total amount of
A polystyrene-based resin foam-molded product characterized by being 4000 ppm. 5. The polystyrene resin foam-molded article according to claim 4, wherein a layer of the thermoplastic resin film is formed on the outside of the molded article. 6. The total amount of volatile substances extracted by the reprecipitation method with methanol is 2000 to 3500 ppm,
The total amount of the polystyrene-based resin of the columnar pellet obtained by the bulk polymerization method is 100 to 50% by weight and the total amount of volatile substances extracted by the reprecipitation method with methanol is 900 to 250.
A polystyrene-based resin having 0 ppm, which is 0 to 50% by weight of a spherical polystyrene-based resin obtained by a suspension polymerization method, is supplied to an extruder together with a foaming agent, melt-kneaded, and then extrusion-foamed. Method for producing foam. 7. The method for producing a polystyrene resin foam according to claim 6, wherein the extruder is a single screw extruder. 8. The method for producing a polystyrene-based resin foam according to claim 6, wherein the spherical polystyrene-based resin obtained by the suspension polymerization method has an average particle size of 0.25 to 2.5 mm.