JP2002104366A - Resin compositions of laminated-film for foam sheet, and laminated foam sheet and container of polystyrene- based resin laminated with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide polystyrene-based resin compositions having excellent workability when laminating a film onto a polystyrene-based-resin foam sheet, and resistant to the elution of styrene dimer or styrene trimer into the soup of precooked noodles when laminating the film inside the container of the precooked noodles, or the like, made of the polystyrene-based-resin foam sheet, a laminated foam sheet, and a container formed of this sheet. SOLUTION: This resin composition of the laminated-film is formed by adding a phenol-based oxidation inhibitor and/or a phosphorus-based working stabilizer into a compound of polystyrene-based resin and styrene-based rubber, and the laminated foam sheet and the container made of this sheet are formed by laminating the laminated-film with 20 or more times elongation of fusion at rupture at 250 deg.C in the resin composition of the laminated-film, over the foamed sheet of polystyrene-based resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polystyrene resin laminated foam sheet, a container and a laminated resin composition suitable for them.

[0002]

2. Description of the Related Art A foamed polystyrene resin sheet is characterized by being excellent in thermoforming, the appearance of the obtained molded article being beautiful, light-weight, and excellent heat insulating properties. In recent years it has been used in large quantities. Instant noodle cups are also mainly made of polystyrene resin foam sheets. However, the polystyrene resin sheet contains styrene dimer and styrene trimer, which are said to be suspected to be environmental hormones in part, and has a drawback that it is eluted into instant noodle soup. In particular, high impact 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 the noodles and the inner wall of the container during transportation, and prevention of piercing by chopstick piercing In a so-called laminated foam sheet container in which films made of polystyrene are laminated, the amount of styrene dimer and styrene trimer eluted is remarkably large. In order to solve these problems, a method of laminating a laminated film resin comprising a mixture of polystyrene and styrene rubber having a low content of styrene dimer and styrene trimer on a foamed sheet (Japanese Patent Application 2000
However, such a method has a problem in workability at the time of manufacturing a laminated film or laminating a film on a foamed sheet.

[0003]

DISCLOSURE OF THE INVENTION The present invention relates to a container molding method which improves the processability in the production of a laminated film or in laminating a film on a foamed sheet, and in which styrene dimer and styrene trimer are hardly eluted in instant noodle soup. A polystyrene-based resin laminated foam sheet, a container and a laminated resin composition suitable for preventing cracking at the time (punching workability), generation of fine powder due to contact between the noodle and the inner wall of the container during transportation of the product, and perforation due to sticking of chopsticks are obtained. The purpose is to:

[0004]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that a mixture of a polystyrene-based resin and a styrene-based rubber can be added to a phenolic antioxidant and / or a phosphorus-based processability. By adding a stabilizer, the laminated film resin composition characterized in that the melt elongation at break at 250 ° C. of the mixture to which the stabilizer is added is at least 20 times or more, by laminating the inside of a polystyrene resin foam sheet. The present inventors have found that the processability during film lamination is improved, and that the amount of styrene dimer and styrene trimer eluted into food soup is reduced, and the present invention has been completed.

That is, the present invention provides (1) a laminated film resin composition obtained by adding a phenolic antioxidant and / or a phosphorus-based processing stabilizer to a mixture of a polystyrene resin and a styrene rubber. A laminated resin composition for a polystyrene resin foam sheet, wherein the melt elongation at break at 250 ° C. of the film resin composition is at least 20 times (claim 1), (2) a polystyrene resin and a styrene rubber. A phenolic antioxidant and / or a phosphorus-based processing stabilizer are used in an amount of 0.01 to 100 parts by weight of the mixture.
2. The laminated resin composition for a polystyrene resin foam sheet according to claim 1, wherein the total rubber component amount in the laminated film resin composition is 1 to 0.5 parts by weight. 3. The laminated resin composition for a polystyrene resin foam sheet according to claim 1 or 2, wherein the polystyrene resin is produced by suspension polymerization. The laminated resin composition for a polystyrene resin foam sheet according to claim 1, 2 or 3.
(4) The styrene-based rubber is a styrene-butadiene block copolymer.
The laminated resin composition for a polystyrene resin foam sheet according to 2, 3, or 4 (Claim 5), (6) Claims 1, 2, 3,
A polystyrene resin laminated foam sheet obtained by laminating a laminated film comprising the laminated resin composition for a polystyrene resin foam sheet according to 4 or 5 on a polystyrene resin foam sheet (Claim 6), and (7). A container formed by laminating a laminated film comprising the laminated resin composition for a polystyrene-based resin foam sheet according to 3, 4 or 5 on a polystyrene-based resin foam sheet with the laminated film inside the laminated film. ), Concerning.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a polystyrene resin and a styrene rubber constituting a film resin composition which is preferably laminated inside a container are preferably those produced by suspension polymerization or solution polymerization. Is not particularly limited.

The polystyrene resin may be a copolymer as long as the effect of the present invention is not impaired, provided that styrene is contained in an amount of 50% by weight or more. As the copolymer 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 and dimethyl fuma And various monomers such as ethyl fumarate, and these monomers can be used alone or in combination of two or more.
Further, bifunctional monomers such as divinylbenzene and alkylene glycol dimethacrylate may be used in combination. As such a material, polystyrene which is a styrene homopolymer and high impact polystyrene which is a copolymer with 1,3-butadiene are preferable in balance of heat resistance, mechanical properties, cost and the like.

The weight average molecular weight of such a polystyrene resin is preferably from 200,000 to 500,000, and more preferably from 250,000 to 450,000. If the weight average molecular weight is less than 200,000, the obtained laminated resin becomes brittle, which is not preferable. On the other hand, when the weight average molecular weight exceeds 500,000, workability at the time of lamination decreases. As a method for polymerizing a polystyrene resin, suspension polymerization is preferred in terms of low content of styrene dimer and styrene trimer and cost.

Examples of the styrene rubber used by mixing the polystyrene as the laminated film resin include a styrene-butadiene block copolymer, a styrene-isoprene block copolymer, and a styrene-ethylene / butylene block copolymer. . Among these,
It has a large effect of preventing cracking (punching workability) during container molding, generation of fine powder due to contact between noodles and the inner wall of the container during transportation, and perforation caused by sticking of chopsticks. Styrene-butadiene block copolymer is preferred from the viewpoints of adhesiveness and cost. The styrene-butadiene block copolymer can be polymerized by solution polymerization (living anion polymerization method) using an alkali-based initiator. Note that conjugated dienes such as 1,3-pentadiene and isoprene may be used as monomers other than styrene and butadiene as long as the effects of the present invention are not impaired.

The melt flow rate (hereinafter abbreviated as MFR) of the styrene rubber at 200 ° C. under a load of 5 kgf is 5
To 30 is preferable, and the rubber component content is 30 to 90.
% By weight is preferred. Styrene-based rubber outside this range has poor dispersibility in polystyrene-based resin, cracking during container molding (punching workability), generation of fine powder due to contact between noodles and container inner wall during transportation of goods, perforation by sticking chopsticks, etc. May not be as effective.

The stabilizers used in the present invention include phenolic antioxidants and phosphorus processing heat stabilizers.
As phenolic antioxidants, n-octadecyl 3
-(3,5-di-t-butyl-4-hydroxyphenyl) propionate, pentaerythrityl-tetrakis (3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, Ciba Special Chemicals Co., Ltd. )
Irganox 1010), 2-t-
Butyl-6- (3-tert-butyl-2-hydroxy-5-
Methylbenzyl) -4-methylphenyl acrylate,
In addition to commercially available general compounds such as 2 (1- (2-hydroxy-3,5-di-t-pentylphenyl) ethyl) -4,6-di-t-pentylphenyl acrylate, vitamin C , Vitamin E, catechin and the like particularly suitable for food use are also used. As a phosphorus-based processing heat stabilizer, tris (2,4-di-t-butylphenyl) phosphite (Ciba Special Chemicals Co., Ltd., Irgaf)
General commercially available products such as os168) can be used. The stabilizer is generally blended with the resin before extrusion, but may be impregnated during suspension polymerization. Although the phenolic antioxidant and the phosphorus-based processing heat stabilizer can be used alone, the workability when laminating the laminated film resin composition on a polystyrene-based resin foam sheet, and the styrene dimer and styrene trimer in a food soup can be used. It is preferable to use two types in combination in that the amount of eluted is small. The amount of the stabilizer added is based on 100 parts by weight of the mixture of the polystyrene resin and the styrene rubber.
0.01 to 0.5 part by weight, preferably 0.03 to 0.5 part by weight.
0.4 parts by weight, more preferably 0.05 to 0.3 parts by weight.
Parts by weight. If the amount added is less than 0.01 parts by weight,
The laminated film resin composition has poor elongation at the time of melting, and is unfavorable from the viewpoint of processability, for example, the laminated film resin is torn during the production or lamination of the laminated resin film. In addition, the decrease in the amount of styrene dimer and styrene trimer eluted into the food soup is small. Further, even if added in an amount of more than 0.5 parts by weight, no further effect on the processability during lamination and the amount of styrene dimer and styrene trimer eluted into the food soup is observed, and the cost is reduced. Is also not preferred.

The laminated resin composition for a foamed polystyrene-based resin sheet of the present invention comprises a mixture of a polystyrene-based resin and a styrene-based rubber, and contains a total amount of rubber components in the resin composition.
(Content of rubber-forming components such as butadiene)
Is preferably 1 to 30% by weight, more preferably 2 to 1% by weight.
5% by weight. If the total rubber component content is less than 1% by weight, cracking of the laminated film at the time of film lamination or winding, cracking at the time of container molding, generation of fine powder due to contact between the noodles and the inner wall of the container during transportation of the product, and holes due to sticking of chopsticks The effect of preventing perforation and the like is hardly obtained.

Here, 250 of the laminated film resin composition is used.
A method for measuring the melt elongation at break at ℃ will be described. Toyo Seiki Capillograph, 1m diameter at the tip
m, 10 mm long, 250 mm cylinder with a bore of 10 mm and a length of 350 mm equipped with an orifice with an inflow angle of 45 degrees.
C. to fill about 15 g of the laminated film resin composition, and preheat for 5 minutes. After the preheating, the laminated film resin composition was 10 mm / mi using a piston having the same diameter as the cylinder.
The extrudate is extruded at a speed of n, and the extrudate is passed through a pulley for tension detection. The extrudate is wound while being accelerated from a start take-up speed of 5 m / min, and the take-up speed at which the extrudate is cut is measured. Here, the pick-up speed is 199.9.
The time required to change to m / min is set to 5 minutes,
Acceleration is measured at 40m / min ^2. The value obtained by dividing the take-up speed at break at the take-up speed at the start of take-off is defined as the melt elongation at break. The case where there is no break is also included in the present invention. In addition, as a measuring instrument, a Toyo Seiki Capillograph etc. are used.

The melt elongation at break of the laminated film resin composition of the present invention is at least 20 times, preferably at least 25 times, more preferably at least 30 times. When the melt elongation at break is less than 20 times, the elongation at the time of melting of the laminated film resin composition is poor, the laminated film resin composition is torn at the time of lamination, and the thickness of the laminated film cannot be controlled. Is not preferred.

The polystyrene-based resin foam sheet on which the laminated resin composition of the present invention is laminated has a polystyrene-based resin as a base resin and is produced by ordinary extrusion foaming. The polystyrene resin used herein is not particularly limited, and is not particularly limited as long as it is produced by a usual polymerization method such as bulk polymerization, suspension polymerization, and solution polymerization. Is preferred in that the content of styrene dimer and styrene trimer is small.

The foaming agents used in the production of the foamed polystyrene resin sheet include aliphatic hydrocarbons such as propane, butane, isobutane, pentane, isopentane and hexane, and cycloaliphatic hydrocarbons such as cyclopentane and cyclohexane. And halogenated hydrocarbons such as methyl chloride, methylene chloride, dichlorofluoromethane, chlorofluoromethane, chlorodifluoromethane, trichlorofluoromethane, trichlorotrifluoroethane, and dichlorotetrafluoroethane. The amount of the foaming agent is 100
It is preferable to use 2 to 5 parts by weight with respect to parts by weight. These may be used alone or in combination of two or more, and may be added and impregnated at the time of producing a polystyrene resin, or may be added at the time of forming an extruded foam sheet.

The nucleating agent used in the production of the polystyrene resin foam sheet is not particularly limited, and any nucleating agent that can be used normally can be used. Specific examples include inorganic compounds such as talc, calcium carbonate, barium sulfate, silica, titanium oxide, clay, aluminum oxide, bentonite, and diatomaceous earth, having an average particle size of 0.1 to 2
0 micron, preferably about 1 to 10 micron;
Organic acids such as citric acid, tartaric acid, oxalic acid, etc .; and those comprising a combination of an acid such as boric acid and a bicarbonate or carbonate such as sodium, potassium, ammonium and the like. These nucleating agents are generally used alone, but may be used in combination of two or more. Of these,
Inorganic compounds such as talc, calcium carbonate, silica, and alumina are preferred because they are inexpensive and easy to handle. Further, the polystyrene resin foam sheet may contain a filler, a flame retardant, a coloring agent, an ultraviolet absorber, an antioxidant, and the like.

The method of laminating the laminated film resin composition of the present invention so as to be inside the polystyrene resin foam sheet, especially inside the container, is not particularly limited. For example, a method of adhering to a foam sheet to which a resin composition previously formed into a film shape is supplied by a hot roll or the like so as to be on the inside of a container, or a method to supply a foam sheet to which a resin composition previously formed into a film shape is supplied. A method of bonding via an adhesive so as to be on the inside of the container, a laminated resin composition supplied from an extruder so as to be on the inside of the container is laminated on the supplied foam sheet in a plastic state. A method of fixing the laminated resin with a cooling roll or the like can be given. Among them, the method of laminating and fixing the laminated resin composition supplied from the extruder in a layered manner is preferable in terms of the number of manufacturing steps and cost.

By using the polystyrene resin laminated foam sheet of the present invention, the vacuum
Various containers can be manufactured by air pressure molding or the like. The amount of styrene dimer and styrene trimer eluted from the laminated foamed sheet container thus obtained is extremely small, and the amount of elution into heptane is preferably 300 p.
pb or less, more preferably 200 ppb or less.

The laminated sheet of the present invention can be suitably used as a bowl or cup for foods such as ramen, udon, yakisoba and the like.

[0021]

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 Melt Elongation at Break] Measurement of melt elongation at break described in the embodiment of the present invention was performed. The measurement was performed with a capillograph manufactured by Toyo Seiki Co., Ltd. [Measurement of Elution Amount of Styrene Dimer and Styrene Trimer] The measurement was carried out in accordance with the Food Sanitation Law, the standards for equipment and containers and packaging, and the method for preparing a test solution in an elution test.

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

GC / MS: manufactured by Hewlett-Packard
HP6890 Series II / HP5973.

Column: DB-, manufactured by J & W Scientific
5MS 0.25 mmi.d. × 30 m thickness 0.25 μm Column temperature: 40 ° C. (0.5 min) → 10 ° C./min→100
° C → 20 ° C / min → 280 ° C (15 minutes) [Punching workability] When a container molded from a laminated resin foam sheet is punched out with a Thomson blade and taken out, the case where cracks occur in the punched portion is × (fail), so If not, it was marked as ○ (pass). (Production Example) Pure water 700k in a reactor equipped with a stirrer
g, 1.05 kg of tribasic calcium phosphate, 46 g of sodium dodecylbenzenesulfonate, and 3.3 kg of sodium chloride.
To 0 kg, as a polymerization initiator, 1.33 kg of benzoyl peroxide, 1,1-bis-t-butylperoxy-
0.7 kg of 3,3,5-trimethylcyclohexane was dissolved and added to the reactor, and the temperature was raised to 98 ° C., and polymerization was carried out for 4 hours. Next, the temperature was raised to 120 ° C., the temperature was maintained for 2 hours, and then cooled. The contents were taken out, dehydrated and dried to obtain a polystyrene resin. (Examples 1 to 3) The surface of a foamed sheet having a thickness of 2 mm, an expansion ratio of 8 and a number of cells in the thickness direction of 10 manufactured by the usual method from the suspension-polymerized polystyrene resin obtained in the manufacturing example was treated with T. Suspension polymerized polystyrene resin obtained in the production example using a die, styrene-butadiene block copolymer,
A mixture of stabilizers having a composition as shown in Table 1 (the types of each compounding agent is shown in Table 2) was extruded, and a 120-micron film was laminated.

Next, the above-mentioned laminated foam sheet is heated in a furnace at 150 ° C. for 13 to 15 seconds using a small single-shot molding machine for molding a polystyrene foam sheet so that the laminated film is inside the container. 155 mm diameter, 140 mm bottom diameter, depth 5
A 0 mm container was formed, and the obtained container was punched out with a Thomson blade and taken out. The amount of styrene dimer and styrene trimer eluted into n-heptane from the obtained polystyrene resin laminated foam sheet container was measured by gas chromatography. Table 1 (Table 2) shows the results of the blending, the results of the measurement of melt elongation at break, the processability at the time of lamination, the punching property of the container, and the dissolution amount. Example 4 A mixture of 100 parts by weight of the suspension-polymerized polystyrene-based resin obtained in the production example and 1.5 parts by weight of a stabilizer was extruded with a 30 mm twin-screw extruder to obtain a suspension-polymerized polystyrene-based resin. And a master batch of stabilizer was prepared. A laminated film, a laminated foam sheet, and a container were produced in the same manner as in Example 1 except that the suspension-polymerized polystyrene resin, the styrene-butadiene block copolymer, and the masterbatch were mixed as shown in Table 1. Table 1 (Table 2) shows the results of the blending, the results of the measurement of melt elongation at break, the processability at the time of lamination, the punching property of the container, and the dissolution amount. (Example 5) A laminated film, a laminated foam sheet, and a container were produced in the same manner as in Example 1, except that the thickness of the laminated film was changed to 100 microns. Table 1 (Table 2) shows the results of the blending, the results of the measurement of melt elongation at break, the processability at the time of lamination, the punching property of the container, and the dissolution amount. Example 6 A mixture of the suspension-polymerized polystyrene resin, the styrene-butadiene block copolymer, and the stabilizer obtained in the production example in the composition shown in Table 1 was extruded into a 50 mm single screw with L / D = 32. The film was then extruded through a T-die to obtain a film having a thickness of 120 microns.

This film and the same foamed sheet as used in Example 1 were heat-pressed on a roll (surface temperature: 198 ° C.).
Were laminated with a laminator equipped with. Next, a container was formed from the obtained laminated foam sheet in the same manner as in Example 1. The amount of styrene dimer and styrene trimer eluted from the container was measured by gas chromatography. Table 1 (Table 2) shows the results of the blending, the results of the measurement of melt elongation at break, the processability at the time of lamination, the punching property of the container, and the dissolution amount. (Example 7) A laminated film, a laminated foam sheet, and a container were produced in the same manner as in Example 1, except that the phenol-based stabilizer was used alone. Table 1 (Table 2) shows the results of the blending, the results of the measurement of melt elongation at break, the processability at the time of lamination, the punching property of the container, and the dissolution amount. (Example 8) A laminated film, a laminated foamed sheet, and a container were produced in the same manner as in Example 1, except that the type of the stabilizer was changed to the phosphorus-based stabilizer alone. Table 1 (Table 2) shows the results of the blending, the results of the measurement of melt elongation at break, the processability at the time of lamination, the punching property of the container, and the dissolution amount. Comparative Example 1 Example 1 except that the laminated film was made from a commercially available bulk polymerized high impact polystyrene (Asahi Kasei; Stylon HIPS, rubber content 7% by weight).
A laminated film and a laminated foamed sheet container were produced in the same manner as described above. Table 1 (Table 2) shows the results of the blending, the results of the measurement of melt elongation at break, the processability at the time of lamination, the punching property of the container, and the dissolution amount. (Comparative Example 2) Example 1 except that the laminated film was produced only from the suspension-polymerized polystyrene obtained in the production example.
In the same manner as in the above, a laminated film, a laminated foam sheet and a container were produced. Table 1 (Table 2) shows the results of the blending, the results of the measurement of melt elongation at break, the processability at the time of lamination, the punching property of the container, and the dissolution amount. (Comparative Example 3) A laminated film, a laminated foam sheet, and a container were produced in the same manner as in Example 1 except that no stabilizer was added to the laminated film resin. Table 1 (Table 2) shows the results of the blending, the results of the measurement of melt elongation at break, the processability at the time of lamination, the punching property of the container, and the dissolution amount.

[0027]

[Table 1]

[0028]

[Table 2]

[0029]

According to the present invention, the processability during production of a laminated film or lamination on a foamed sheet is improved, and the amount of styrene dimer and styrene trimer eluted from a container can be greatly reduced.

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Claims (7)

[Claims] 1. A laminated film resin composition obtained by adding a phenolic antioxidant and / or a phosphorus-based processing stabilizer to a mixture of a polystyrene resin and a styrene rubber. A laminated resin composition for a polystyrene-based resin foam sheet, wherein the melt elongation at break at 20 ° C is 20 times or more. 2. A method according to claim 1, wherein 0.01 to 0.5 part of a phenolic antioxidant and / or a phosphorus-based processing stabilizer is added to 100 parts by weight of the mixture of the polystyrene resin and the styrene rubber. Item 4. The laminated resin composition for a polystyrene resin foam sheet according to Item 1. 3. The laminated resin composition for a foamed polystyrene resin sheet according to claim 1, wherein the total amount of the rubber components in the laminated film resin composition is 1 to 30% by weight. 4. The laminated resin composition for a foamed polystyrene resin sheet according to claim 1, wherein the polystyrene resin is produced by suspension polymerization. 5. The method according to claim 1, wherein the styrene rubber is a styrene-butadiene block copolymer.
5. The laminated resin composition for a polystyrene resin foam sheet according to 2, 3, or 4. 6. A polystyrene resin laminated foam sheet obtained by laminating a laminated film made of the laminated resin composition for a polystyrene resin foam sheet according to claim 1, 2, 3, or 4 on a polystyrene resin foam sheet. 7. A laminated film of a laminated polystyrene resin foam sheet obtained by laminating a laminated film comprising the laminated resin composition for a polystyrene resin foam sheet according to claim 1, 2, 3 or 4 on a polystyrene resin foam sheet. A container molded with the inside.