JP2003246024A - Container molded from foamed laminated polystyrene resin sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a container molded from a foamed laminated styrene resin sheet which minimizes elution of a styrene dimer and a styrene trimer into a food soup, is excellent in container punching properties, and is prevented from being bored by the sticking of a chopstick and a fork. <P>SOLUTION: In the container, the foamed laminated polystyrene resin sheet is molded with a non-foamed polyester film (C) arranged inside. In the resin sheet, a non-foamed polystyrene resin film (B) 25-200 μm in thickness and 1,300 ppm or below in content of the styrene dimer and trimer is laminated at least on one surface of a foamed polystyrene resin sheet (A) 1,300 ppm or below in content of the styrene dimer and trimer, and the non-foamed polyester film (C) is laminated on the remaining surface of the film (B). <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polystyrene resin laminated foam sheet, a container and a laminated resin composition suitable for them.

[0002]

BACKGROUND OF THE INVENTION Polystyrene-based resin foam sheets are excellent in thermoforming, and the resulting molded products have a beautiful appearance, are lightweight, and have excellent heat insulating properties. Therefore, they are suitable for thermoforming of food containers and the like. It has been used in large quantities in recent years. However, some polystyrene resin sheets contain styrene dimer and styrene trimer, which are said to be suspected to be environmental hormones. Although new research results showing that they have no endocrine disrupting effects have been published, they tend to dislike what was once a social problem,
There is a social need to control the amount of food dissolved in soup. In particular, it was manufactured by bulk polymerization inside the container for the purpose of preventing cracking during molding of the container (punching workability), generation of fine powder due to contact between food and the inner wall of the container during product transportation, and perforation due to sticking chopsticks or forks. In a so-called laminated foam sheet container in which a film made of high-impact polystyrene is laminated, there is no technique for effectively suppressing the elution amount of styrene dimer and styrene trimer. Japanese Unexamined Patent Publication No. 2001-219523 discloses a laminated foam sheet in which a film obtained by laminating an aromatic polyester film and a polystyrene film is laminated on a polystyrene foam sheet, the purpose of which is to improve heat resistance and oil resistance. As in the present invention, there is no suggestion of the problem, the constitution and the effect of reducing the styrene dimer and styrene trimer of a container molded from an ordinary polystyrene foam sheet and improving the strength of the container.

[0003]

DISCLOSURE OF THE INVENTION According to the present invention, a polystyrene resin laminate in which styrene dimer and styrene trimer are hardly eluted into food soup, has excellent container punchability, and prevents perforation by sticking chopsticks or forks. The purpose is to obtain a container formed by molding a foamed sheet.

[0004]

Means for Solving the Problems As a result of intensive studies for solving the above-mentioned problems, the present inventors have found that a polystyrene-based resin non-foamed film (B) surface of a polystyrene-based resin laminated foamed sheet is formed inside. In the container, the content of styrene dimer and styrene trimer is 1300.
The content of styrene dimer and styrene trimer in the polystyrene-based resin laminated foam sheet of 1 ppm or less is 1300
Polystyrene-based resin non-foaming film (B) of ppm or less
It was found that by laminating the polyester resin non-foamed film (C) on the surface, the piercing strength of the container and the elution amount of the oligomer can be reduced.

That is, the present invention provides (1) a styrene dimer and a styrene trimer having a thickness of 25 to 200 μm on at least one surface of a polystyrene resin foam sheet (A) having a styrene dimer and styrene trimer content of 1300 ppm or less. Laminating a polystyrene-based resin non-foamed film (B) having a content of 1300 ppm or less,
Further, one of the polystyrene-based resin non-foamed films (B)
A polystyrene-based resin-laminated foamed sheet, which is characterized in that a polyester-based non-foamed film (C) is laminated on the surface of A container (claim 1) characterized in that the amount of styrene trimer eluted from heptane is 10 ppb or less, and (2) the container of claim 1 wherein the polyester non-foamed film (C) has a thickness of 10 to 50 µm. Item 2), (3) The polystyrene resin non-foamed film (B) is a laminate of two or more layers of polystyrene resin non-foamed film.
The container according to any one of claims 1 to 3, wherein the thickness of the polystyrene-based resin non-foamed film (B) is 80 to 200 µm (claim 4),
(5) Polystyrene-based resin The polystyrene-based resin composition used in the non-foamed film (B) is composed of a mixture of polystyrene-based resin and styrene-based rubber, and the total rubber component amount in the resin composition is 1 to 30% by weight. The container according to any one of claims 1 to 4 (claim 5),
(6) Polystyrene resin The container (claim 6) according to any one of claims 1 to 5, wherein the polystyrene resin used in the non-foamed film (B) is produced by suspension polymerization, and (7). ) The container (claim 7) according to any one of claims 1 to 6, wherein the styrene rubber used for the polystyrene resin non-foamed film (B) is a styrene-butadiene block copolymer.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the thickness of the polyester resin non-foamed film (C) laminated on the surface of the foamed sheet is preferably 10 to 50 μm, more preferably 2
It is 0 to 40 μm. If the thickness is less than 10 μm, pinholes may occur in the polyester resin non-foamed film due to stress during molding. Also, thickness 5
If it exceeds 0 μm, the cost becomes high, and wrinkles may be formed on the polyester resin non-foamed film during the molding of the container due to the difference in molding temperature between the polyester resin and the polystyrene resin. Furthermore, in order to obtain good molding processability, it is more preferably 40 μm or less.

As the polyester resin, polyethylene terephthalate obtained by polymerizing terephthalic acid and ethylene glycol, or amorphous polyester resin obtained by polymerizing terephthalic acid, ethylene glycol and cyclohexadimethanol can be used. Amorphous polyester resins are preferable in molding because they are superior in tensile elongation at break.

In the present invention, the content of styrene dimer and styrene trimer laminated inside the container is 1300.
Non-foaming polystyrene-based resin (B) with ppm or less
If the thickness is less than 15 μm, the strength of the film layer is insufficient,
It cannot prevent perforation caused by sticking chopsticks or forks.
Furthermore, in order to ensure the strength of the entire container, 80
It is preferably at least μm. Also, the thickness is 200 μm
If it exceeds, the cost becomes high, which is not preferable. As the polystyrene-based resin composition constituting the polystyrene-based resin non-foamed film (B), a polystyrene-based resin or a mixture of styrene-based rubber with the polystyrene-based resin is used. As the polystyrene-based resin, suspension polymerization or Those produced by solution polymerization are preferred.

Polystyrene resin non-foamed film (B)
The polystyrene-based resin used in the above may be a copolymer as long as it contains 50% by weight or more of styrene as long as the effects of the present invention are not impaired. As the copolymerization component,
Conjugated dienes such as 1,3-butadiene and isoprene, α
-Styrene derivatives such as methylstyrene, paramethylstyrene, t-butylstyrene and chlorostyrene, esters of acrylic acid and methacrylic acid such as methyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate and cetyl methacrylate, or acrylonitrile, dimethyl fumarate. Various monomers such as rate and ethyl fumarate may be mentioned, and these monomers may be used alone or in combination of two or more kinds.
Further, a difunctional monomer such as divinylbenzene or alkylene glycol dimethacrylate may be used in combination. Among these, polystyrene, which is a styrene homopolymer, and high-impact polystyrene, which is a copolymer with 1,3-butadiene, are preferable in terms of balance of heat resistance, mechanical properties, cost, and the like.

The weight average molecular weight of such a polystyrene resin is preferably 200,000 or more and 500,000 or less, more preferably 250,000 or more and 450,000 or less. When the weight average molecular weight is less than 200,000, the resulting laminated resin becomes brittle, which is not preferable. Further, if the weight average molecular weight exceeds 450,000, the workability at the time of stacking deteriorates. As the method for polymerizing the polystyrene resin, those produced by the suspension polymerization method or the solution polymerization method are preferable, and the suspension polymerization method is particularly preferable from the viewpoint of cost.

Polystyrene as a laminated film resin,
Examples of the styrene-based rubber mixed and used as the rubber component include a styrene-butadiene block copolymer, a styrene-isoprene block copolymer, a styrene-ethylene / butylene block copolymer and the like. Among these, cracks during container molding (punching workability),
From the point of view of cost reduction, fine powder generation due to contact between food and container inner wall during product transportation, and prevention of perforation due to sticking of chopsticks and forks, adhesiveness with polystyrene-based resin that is the base resin of foam sheet, and cost. A styrene-butadiene block copolymer is preferred. The styrene-butadiene block copolymer can be polymerized by solution polymerization (living anion polymerization method) using an alkali-based initiator. In addition, conjugated diene such as 1,3-pentadiene and isoprene may be used as a monomer other than styrene and butadiene as long as the effect of the present invention is not impaired.

The melt flow rate (hereinafter abbreviated as MFR) of styrene rubber at 200 ° C. and a load of 5 kgf is 5
The content of conjugated diene such as butadiene and isoprene is preferably 30 to 90% by weight. Styrene-based rubber outside this range has poor dispersibility in polystyrene-based resin, cracks during container molding (punching workability), generation of fine powder due to contact between food and container inner wall during product transport, holes due to sticking chopsticks or forks. It is difficult to obtain the effect of preventing perforations.

The polystyrene resin composition used in the non-foamed polystyrene resin film (B) of the present invention is preferably a mixture of polystyrene resin and styrene rubber, and the total amount of rubber components in the resin composition is It is preferably 1 to 30% by weight, more preferably 2 to 15% by weight. If the total amount of rubber components is less than 1% by weight, it is difficult to obtain the effect of preventing cracking during molding of the container, generation of fine powder due to contact between the food and the inner wall of the container during transportation of goods, and perforation by sticking chopsticks or forks. When it exceeds%, the laminating processability is deteriorated.

The resin composition for a polystyrene-based resin non-foamed film (B) thus obtained is laminated on a polystyrene-based resin foamed sheet (A) described below by various methods in a film state. You can The total content of styrene dimer and styrene trimer in the polystyrene resin non-foamed film (B) is 1300 p.
It is necessary to be pm or less, but the content of styrene dimer and styrene trimer in the laminated resin composition is also preferably 1300 ppm or less. Pinholes are generated not only in polyester films but also in non-foamed films, and when it exceeds 1300 ppm, the elution amount of styrene dimer and styrene trimer from the pinhole surface exceeds 10 ppb due to elution of styrene dimer and styrene trimer. there is a possibility.

The polystyrene resin foam sheet (A) used in the present invention must have a content of styrene dimer and styrene trimer of 1300 ppm or less. Manufactured by extrusion foaming. The polystyrene resin used here is not particularly limited, and bulk polymerization, suspension polymerization,
It is not particularly limited as long as it is produced by a usual polymerization method such as solution polymerization, but among these, those obtained by suspension polymerization and solution polymerization are preferable in that the content of styrene dimer and styrene trimer is small. .

The polystyrene-based resin foam sheet (A)
Examples of the blowing agent used in the production include aliphatic hydrocarbons such as propane, butane, isobutane, pentane, isopentane, and hexane, and alicyclic hydrocarbons such as cyclopentane and cyclohexane, and halogenated hydrocarbons. Examples include methyl chloride, methylene chloride, dichlorofluoromethane, chlorofluoromethane, chlorodifluoromethane, trichlorofluoromethane, trichlorotrifluoroethane, dichlorotetrafluoroethane and the like. The amount of the foaming agent is preferably 2 to 5 parts by weight with respect to 100 parts by weight of the polystyrene resin. These may be used alone or in combination of two or more, and may be added and impregnated at the time of producing the polystyrene resin, or may be added at the time of forming an extruded foam sheet.

The polystyrene resin foam sheet (A)
The nucleating agent used at the time of production is not particularly limited, and any nucleating agent that can be usually used can be used. Specific examples include talc, calcium carbonate, barium sulfate, silica,
Inorganic compounds such as titanium oxide, clay, aluminum oxide, bentonite, diatomaceous earth, etc., having an average particle size of 0.1 to 20 μm, preferably about 1 to 10 μm; organic acids such as citric acid, tartaric acid, oxalic acid, etc. Acids, such as those comprising a combination of acids such as boric acid and bicarbonates or carbonates such as sodium, potassium and ammonium. These nucleating agents are usually used alone, but two or more kinds may be used in combination. Among these, inorganic compounds such as talc, calcium carbonate, silica and alumina are preferable because they are inexpensive and easy to handle. Further, the polystyrene resin foam sheet (A) may contain a filler, a flame retardant, a coloring agent, an ultraviolet absorber, an antioxidant and the like.

The method for laminating the polystyrene resin non-foamed film (B) and the polyester resin non-foamed film (C) on the polystyrene resin foam sheet (A) of the present invention is not particularly limited. For example, a method in which a resin composition that has been formed into a film in advance is heat-fused and adhered to a foamed sheet that is supplied by a heat roll or the like, a method that adheres via an adhesive, a resin composition from a T-die to the surface of the foamed sheet Can be directly extruded and laminated, and the respective layers may be laminated by different methods.

In a particularly preferred embodiment, a polystyrene resin composition is used as a lamination method for obtaining good adhesion between the polystyrene resin non-foamed film (B) and the polyester resin non-foamed film (C) without damaging the film surface. The product is directly extruded on the surface of the foamed sheet (A) using a T-die to laminate the polystyrene resin non-foamed film (B1), and at the same time, the polystyrene resin non-foamed film (B2) and the polyester resin non-foamed film (C). A film obtained by laminating the above with an adhesive is laminated on the surface of the polystyrene resin non-foamed film (B1) so that the polyester resin non-foamed film (C) becomes the outermost surface, and then laminated and foamed by a cooling roll or the like. A method of cooling and fixing the sheet is adopted. Here, the polystyrene resin non-foamed film (B2) is a polystyrene resin non-foamed film (B2).
It is formed in order to obtain good adhesion between 1) and the polyester resin non-foamed film (C), and the thickness is in the case of laminating two or more layers of polystyrene resin non-foamed film on the foamed sheet (A). It is desirable that the polystyrene-based resin non-foamed film that is in direct contact with the foamed sheet (A) be thickest. In the above example, B2 ≦ B1 is preferable, and B2 <B
1 is more preferable. The thickness of the polystyrene resin non-foamed film (B) is the total thickness when it has two or more layers, and in the above example, (B) = (B1) + (B2).

The total content of styrene dimer and styrene trimer in the polystyrene resin laminated foam sheet thus obtained is preferably 1300 ppm or less. When it exceeds 1300 ppm, the elution amount of styrene dimer and styrene trimer from the container obtained from the polystyrene-based resin laminated foam sheet is significantly reduced,
It becomes difficult to obtain a container having a styrene dimer and a styrene trimer elution amount of heptane of 10 ppb or less.

The polystyrene-based resin laminated foam sheet container of the present invention can be manufactured by vacuum / pressure molding or the like as in the case of molding a normal foam sheet. The elution amount of styrene dimer and styrene trimer from the laminated foamed sheet container having the film surface inside as described above is extremely small, and the elution amount to heptane can be 10 ppb or less.

[0022]

EXAMPLES Next, 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. [Measurement of styrene dimer and styrene trimer in laminated resin composition] The laminated resin composition film or laminated foam sheet was dissolved in chloroform and measured by GC.

GC: Hewlett-Packard GC-
5890 Series II Column: J & W Scientific, DB-5 0.25m
mi.d.30m film thickness 0.25 micron Column temperature: 40 ° C (0.5 min) → 10 ° C / min → 100
℃ → 20 ℃ / min → 280 ℃ (15 minutes) Detector: FID [Measurement of elution amount of styrene dimer and styrene trimer] Food Sanitation Law, standard standards of equipment and containers and packaging, method of preparing test solution in dissolution test It measured according to regulation.

Polystyrene resin laminated foam sheet container (caliber 155 mm, bottom diameter 140 mm, depth 50 mm)
580 cc of heptane was placed in a conical shaped container having an inner volume of 850 cm ³ ) and left at 25 ° C. for 60 minutes to adjust the amount of styrene dimer and styrene trimer in heptane to G
It was measured by C / MS-SIM.

GC / MS: Made by Hewlett Packard
HP 6890 Series II / HP 5973.

Column: J-W Scientific DB-
5MS 0.25mm i.d.30m film thickness 0.25μ. Column temperature: 40 ° C (0.5 minutes) → 10 ° C / minute → 100
C → 20 ° C./min→280° C. (15 min). [Measurement of puncture strength] The puncture strength was measured according to the method specified by the Food Sanitation Law.

Polystyrene resin laminated foam sheet container (caliber 155 mm, bottom diameter 140 mm, depth 50 mm)
Of the inner volume of 850 cm ³ and the bottom of a conical shaped container) is cut out, and the non-foamed film laminated surface has a diameter of 1.0 m.
m, a semicircular needle with a tip shape radius of 0.5 mm is 50 ± per minute
The needle was pierced at a speed of 0.5 mm and the maximum load until the needle penetrated was measured. (Production example) 700 k of pure water was added to a reactor equipped with a stirrer.
g, tricalcium phosphate 1.05 kg, sodium dodecylbenzene sulfonate 46 g, sodium chloride 3.3 kg, and the mixture was stirred to form a water suspension, and then styrene 70
As a polymerization initiator at 0 kg, 1.33 kg of benzoyl peroxide, 1,1-bis-t-butylperoxy-
0.7 kg of 3,3,5-trimethylcyclohexane was dissolved, added to the reactor, heated to 98 ° C., and then polymerized for 4 hours. Next, the temperature was raised to 120 ° C., the temperature was maintained for 2 hours, and then the contents were taken out, dehydrated and dried to obtain a polystyrene resin. (Example 1) On the surface of a foamed sheet having a thickness of 2 mm, a foaming ratio of 8 and a number of 16 cells in the thickness direction, which was manufactured by a usual method from the suspension-polymerized polystyrene resin obtained in the manufacturing example.
Using a T-die, the suspension-polymerized polystyrene resin obtained in Production Example and a styrene-butadiene block copolymer (manufactured by Asahi Kasei Kogyo Co., Ltd .; "Tuffprene A", rubber content 60% by weight, MI = 13) were used. Extrude the mixture, 120
While laminating the film of μm, the thickness of 30
μm amorphous polyester film (Okura Industry Co., Ltd.)
And a 25 μm thick polystyrene (PS) film (Stylon D manufactured by Towa Kako Co., Ltd.) were laminated in advance with an adhesive so that the non-crystalline polyester film surface was the outermost surface. The amounts of styrene dimer and styrene trimer in the obtained laminated foam sheet and the laminated film portion were measured by gas chromatography.

Then, the laminated foamed sheet was heated in a furnace at 150 ° C. for 13 to 15 seconds using a small single-shot molding machine for molding polystyrene foamed sheet so that the laminated film was inside the container. With a mold whose temperature is adjusted to 60 ° C, the bore diameter is 155 mm, the bottom diameter is 140 mm, and the depth is 5.
A 0 mm container was molded, and the obtained container was punched out with a Thomson blade and taken out. The polyester film laminated on the surface of the molded product was visually observed for wrinkles, and those having no wrinkles were evaluated as ◯, those having wrinkles were evaluated as Δ, and those having severe wrinkles and not acceptable for practical use were evaluated as x. The elution amount and puncture strength of styrene dimer and styrene trimer from the obtained polystyrene-based resin laminated foam sheet container to n-heptane were measured. The measurement results are shown in Table 1. (Example 2) On the surface of the foamed sheet used in Example 1, using a T-die, the suspension-polymerized polystyrene resin obtained in the production example and a styrene-butadiene block copolymer (manufactured by Asahi Kasei Kogyo KK; Extruding a mixture of “Toughprene A”, rubber content 60% by weight, MI = 13),
A 120 μm film was laminated. 40 on the surface
A polyethylene terephthalate film (film manufactured by Towa Kako Co., Ltd.) having a thickness of μm was laminated using an adhesive to obtain a laminated foam sheet. The obtained laminated foam sheet was molded into a container by the same method as in Example 1, and the results of evaluation by the same method as in Example 1 are shown in Table 1. (Example 3) A laminated sheet was obtained and evaluated in the same manner as in Example 2 except that the thickness of the polyethylene terephthalate film (film manufactured by Towa Kako Co., Ltd.) used in Example 2 was changed to 50 μm. . (Example 4) The polyester film used in the laminated foam sheet obtained in Example 2 was 100μ (manufactured by Towa Kako).
A laminated foamed sheet and a container were prepared in the same manner except that the above-mentioned one was used, and the evaluation results are shown in Table 1. (Comparative Example 1) A laminated foam sheet and a container were manufactured in the same manner as in Example 1 except that the film obtained by previously laminating the 30 μm amorphous polyester film and the 25 μm PS film used in Example 1 with an adhesive was not laminated. Is made,
Evaluation was performed by the same method as in Example 1, and the results are shown in Table 1. (Comparative Example 2) The foamed sheet is a commercially available bulk-polymerized polystyrene resin, and the laminated film is a commercially available bulk-polymerized high-impact polystyrene (Asahi Kasei Co., Ltd .; Stylon HIPS,
A laminated foam sheet and a container were prepared and evaluated in the same manner as in Comparative Example 1 except that the rubber content was 7% by weight), and the results are shown in Table 1. (Comparative Example 3) A laminated foam sheet and a container were prepared and evaluated in the same manner as Comparative Example 2 except that a high impact film 25 μm (Stylon D manufactured by Towa Kako Co., Ltd.) was laminated on the surface of Comparative Example 2. Is shown in Table 1.

[0029]

[Table 1]

[0030]

EFFECTS OF THE INVENTION According to the present invention, polystyrene-based resin laminated foamed sheets having very little elution of styrene dimer and styrene trimer into food soup, excellent container punchability, and preventing perforation due to puncture of chopsticks or forks. It is possible to obtain a molded container.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 3E033 AA08 BA17 BA22 BB08 CA20                       FA01                 4F100 AK12A AK12B AK12D AK29B                       AK29D AK41C AL02B AL02D                       AN02B AN02D BA03 BA04                       BA07 BA10A BA10C BA15                       DJ01A GB16 JB08 JK01                       JL01 YY00A YY00B YY00C                       YY00D                 4J002 BC021 BC031 BC041 BC051                       BC061 BC071 BP012 GG01

Claims (7)

[Claims] 1. A thickness of 15 to 15 is provided on at least one surface of a polystyrene resin foam sheet (A) having a styrene dimer and styrene trimer content of 1300 ppm or less.
A polystyrene-based resin non-foaming film (B) having a styrene dimer and styrene trimer content of 200 μm of 1300 ppm or less is laminated, and a polyester-based non-foaming film (B) is further provided on the surface of one polystyrene-based resin non-foaming film (B). The polystyrene-based resin laminated foam sheet obtained by laminating C) is used as a polyester-based non-foamed film (C).
A polystyrene-based resin laminated foamed sheet molding container having a styrene dimer and styrene trimer elution amount of 10 ppb or less, which is molded so that its surface faces inward. 2. The container according to claim 1, wherein the polyester non-foamed film (C) has a thickness of 10 to 50 μm. 3. The container according to claim 1, wherein the polystyrene resin non-foamed film (B) is a laminate of two or more layers of polystyrene resin non-foamed film. 4. The container according to claim 1, wherein the polystyrene resin non-foamed film (B) has a thickness of 80 to 200 μm. 5. The polystyrene resin composition used for the polystyrene resin non-foamed film (B) comprises a mixture of polystyrene resin and styrene rubber,
The container according to any one of claims 1 to 4, wherein the total rubber component amount in the resin composition is 1 to 30% by weight. 6. The container according to claim 1, wherein the polystyrene resin used for the non-foamed polystyrene resin film (B) is produced by suspension polymerization. 7. The container according to claim 1, wherein the styrene rubber used for the polystyrene resin non-foamed film (B) is a styrene-butadiene block copolymer.