JP4925609B2 - Thermoplastic resin foam sheet and method for producing the sheet container - Google Patents

Description

  The present invention relates to a foamed sheet made of a thermoplastic resin and a method for producing the foamed sheet container. More specifically, it is preferably used for manufacturing various packaging containers, and is a foam sheet made of a thermoplastic resin, particularly excellent in cold resistance, heat insulation, oil resistance, heat resistance, rigidity, etc., and excellent in biodegradability. Thermoplastic resin foam sheet suitable for manufacturing trays, cups, bowls, dishes, containers, boxes (hereinafter collectively referred to as containers) by the next molding method, and better heat resistance than this foam sheet The present invention relates to a manufacturing method for a container.

  Depending on the type, commercially available food is stored in a resin container, refrigerated and frozen at a low temperature of 10 to -30 ° C., stored and transported, and when eaten, the temperature of 100 to 120 ° C. with a microwave oven is used for each container. Some are cooked in These food containers are required to have heat resistance so that they do not deform when cooked to the above temperature range with a microwave oven, and also have oil resistance that is not easily eroded by oils, seasonings, etc. contained in food. Is done. Also, cold resistance and impact resistance are required so that the container containing the food is not damaged even if it is shocked from the outside in a state where it is refrigerated and frozen at a low temperature.

  As a container for storing food to be cooked by a microwave oven, a container made by molding (molding) a polypropylene resin sheet by a thermoforming method has been conventionally used. Since polypropylene resin is excellent in heat resistance, the container is less deformed when heated in a microwave oven. However, since polypropylene resin is inferior in cold resistance, food is stored in this container and stored in a refrigerator / freezer at a low temperature of 10 to −30 ° C. or during cargo handling work in the transportation process by a frozen vehicle. There is a disadvantage that cracks and cracks occur due to external impacts such as dropping, collision, vibration, etc., and it is unbearable for cooking with a microwave oven. In order to improve this defect, a thermoforming sheet made of a resin composition in which a polyethylene resin and an inorganic filler are blended with a polypropylene resin has been proposed (Patent Document 1). However, the container obtained from this sheet is still insufficient in cold resistance and heat resistance.

  Foamed sheets made from high-density polyethylene resin are excellent in heat insulation, impact resistance, rigidity, and the like, and are used as containers, cardboard materials, and the like. Foamed sheets made from ordinary high-density polyethylene resins have the disadvantage that uniform foam cells are difficult to form, and a method using a polyethylene resin with a high melt viscosity has been proposed as a method to remedy this defect. ing. When the melt viscosity is high, a large load is applied to the extruder motor when the foamed sheet is produced by the extruder, making it difficult to produce the foamed sheet. As a technique for solving this problem, there has been proposed a foam sheet made of a resin composition in which two types of polypropylene resins are blended with a high-density polyethylene resin (Patent Document 2). However, according to experiments by the inventors, it has been found that the container obtained from the foamed sheet is still insufficient in cold resistance and heat resistance.

The containers are discarded after use, and in many cases, the discarded items are incinerated or crushed and landfilled in a landfill. Since the incineration heat is high when the resin is incinerated, there is a drawback of damaging the incinerator. Therefore, a method of reducing the amount of resin used by foaming is employed. When landfilled in a landfill, the resin is difficult to corrode and decompose, so there is a disadvantage that it remains semipermanently, so photodegradable resins and biodegradable resins have been proposed and partially put into practical use. It has the disadvantage of high cost and the usage is much less than expected.
Japanese Patent Laid-Open No. 2-80454 JP 2001-213989 A Japanese Patent No. 3029612 JP 2004-189833 A

In view of the above situation, the present inventors have developed a resin sheet excellent in cold resistance, heat insulation, oil resistance, heat resistance, rigidity, etc., excluding conventional defects, and excellent in biodegradability, and heat resistance from this resin sheet. As a result of intensive studies aimed at providing a method for producing a container having excellent properties, the present invention has been completed. That is, the object of the present invention is a foamed sheet made of a thermoplastic resin, which has excellent extrusion characteristics at the time of foam sheet production, excellent cold resistance, heat insulation, oil resistance, heat resistance, rigidity, etc., and excellent biodegradability. dish by secondary molding, containers, trays, thermoplastic resin foamed sheet suitable for producing such as boxes, and to provide a method for producing superior container in heat resistance.

In order to solve the above problems, in the first invention, the polylactic acid (A) having a weight average molecular weight of 50,000 or more is 20 to 90% by weight, the density is 0.90 to 0.96, and the MFR is 1 to 20 g / 10 minutes. (A) styrene-butadiene-styrene block copolymer with respect to 100 parts by weight of the total amount of the two components consisting of 10 to 80% by weight of the homopolypropylene (B) (the total amount of the two components is 100% by weight) 1 to 20 weights of compatibilizer (C) selected from the group consisting of: (b) hydrogenated product of styrene-butadiene-styrene block copolymer , and (c) styrene-isoprene-styrene block copolymer A resin composition obtained by partially blending is used as a raw material resin composition, the expansion ratio is 1.1 to 3.0 times, and the thickness is 0.5 to 3.0 mm. Foam seam made of plastic resin To provide.

In the second invention, the polylactic acid (A) having a weight average molecular weight of 50,000 or more is 20 to 90% by weight, the density is 0.90 to 0.96, and the MFR is 1 to 20 g / 10 min. (A) styrene-butadiene-styrene block copolymer, (b) styrene-based on 100 parts by weight of the total amount of the two components consisting of 10 to 80% by weight (the total amount of the two components is 100% by weight) butadiene - styrene block copolymer hydrogenated product of, and, (c) a styrene - isoprene - styrene block copolymer, compatibilizing agent selected from the group consisting of (C) 1 to 20 parts by weight is compounded comprising resin The composition is a raw material resin composition, the expansion ratio is 1.1 to 3.0 times, the thickness is 0.5 to 3.0 mm, and the mold temperature at the time of thermoforming is 105 to 115 ° C. Temperature range, container molding Wherein the annealing 10-20 seconds, to provide a method for producing a thermoplastic resin foam sheet steel container.

The present invention is as described in detail below, exhibit the special excellent effects as follows, utility value on that industry is extremely large.
1. Since the foamed sheet made of thermoplastic resin according to the present invention is a raw material resin in which homopolypropylene is blended with polylactic acid at a specific ratio, it has excellent extrusion characteristics during the production of the foamed sheet.
2. Since the thermoplastic resin foam sheet according to the present invention contains an appropriate amount of a compatibilizer,
Even when homopolypropylene that is incompatible with polylactic acid is blended, there is no fluffing on the surface of the foamed sheet, and the foamed sheet has a beautiful appearance and has excellent moldability, cold resistance, heat insulation, impact resistance, etc. Are better.
3. The foamed sheet made of thermoplastic resin according to the present invention is excellent in chemical resistance because it is blended with homopolypropylene , and is hardly eroded by oils, seasonings and the like contained in food.
4). Thermoplastic resin foam sheet according to the present invention, easily biodegraded because it contains the polylactic acid, since cheaper homopolypropylene than polylactic acid are blended in the polylactic acid, the raw material cost is cheap.
5. The thermoplastic resin foam sheet according to the present invention is excellent in cold resistance and rigidity, so it can be stored in a refrigerator / freezer at a low temperature or during a cargo handling operation in the transportation process by a freezer vehicle. Cracks and cracks are less likely to occur due to external impacts such as dropping, collision, and vibration.
6). Since the thermoplastic resin foam sheet according to the present invention is excellent in heat resistance, it is suitable for producing containers for various foods that are heated and cooked by a microwave oven.
7 . The foamed sheet made of the thermoplastic resin according to the present invention has a foaming ratio in the range of 1.1 to 3.0 times , and the amount of the material resin used can be reduced, so that the cost of the product can be reduced.
8 . Since the container manufactured from the foamed sheet made of thermoplastic resin according to the present invention contains bubbles and the amount of the material resin used is small, the incinerator is less likely to damage the incinerator during the incineration process after recovery. Also, the amount of black smoke per volume generated during incineration is small and air pollution can be reduced.
9 . The container made of a thermoplastic resin foam sheet produced by the method according to the second invention of the present invention is particularly excellent in heat resistance, and is therefore suitable as a container for storing various foods that are heated and cooked with a microwave oven.

Hereinafter, the present invention will be described in detail.
The raw material resin of the thermoplastic resin foam sheet according to the present invention includes polylactic acid (A) {hereinafter sometimes referred to as resin (A)} and homopolypropylene (B) {hereinafter referred to as resin (B). The two components that may be described are essential.

  In the present invention, the polylactic acid (A) refers to a resin having a monomer unit derived from L-lactic acid and / or D-lactic acid as a main component. Here, the “main component” means that these monomer units are contained in an amount of 75 mol% or more and contain other monomer units of less than 25 mol%. Examples of other monomer units include glycol compounds, dicarboxylic acids, hydroxycarboxylic acids, and lactones. Glycol compounds include ethylene glycol, propylene glycol, butanediol, heptanediol, hexanediol, octanediol, nonanediol, decanediol, 1,4-cyclohexanemimethanol, neopentylglycol, glycerin, pentaerythritol, bisphenol A. Polyethylene glycol, polypropylene glycol and polytetramethylene glycol. Dicarboxylic acids include oxalic acid, adipic acid, sebacic acid, azelaic acid, dodecanedioic acid, malonic acid, glutaric acid, cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, bis (p-carboxyphenyl) ) Methane, anthracene dicarboxylic acid, 4,4, -diphenyl ether dicarboxylic acid, 5-sodium sulfoisophthalic acid, 5-tetrabutylphosphonium isophthalic acid and the like. Examples of hydroxycarboxylic acids include glycolic acid, hydroxypropionic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxycaproic acid, hydroxybenzoic acid, etc., and lactones include caprolactone, valerolactone, propiolactone, undecalactone, 1,5-oxepan-2-one and the like can be mentioned. The proportion of other monomer units is particularly preferably 0 to 10 mol%.

  In order to obtain a foam sheet exhibiting particularly high heat resistance, it is preferable to use a polylactic acid (A) having a high optical purity of the lactic acid component. Among the total lactic acid components of the polylactic acid resin, those containing 80% or more of L-form are preferable. If the proportion of D-form is large, it becomes amorphous and is difficult to crystallize during product annealing, and heat resistance is not improved. A more preferable ratio of the L isomer ratio is 90% or more, and particularly preferable is 95% or more.

  The polylactic acid (A) is not particularly limited as long as it can be formed into a film and has physical properties enough to withstand practical use. The melting point is preferably 120 ° C. or higher, and more preferably 150 ° C. or higher. The melting point of polylactic acid (A) can be measured with a differential scanning calorimeter. The polylactic acid (A) has a molecular weight of preferably 50,000 or more, more preferably 100,000 or more, and particularly preferably 200,000 or more. Here, the weight average molecular weight refers to a molecular weight measured by gel permeation chromatography (GPC).

  Polylactic acid (A) can be produced by a conventionally known production method. A typical method is a method of ring-opening polymerization of lactide, which is an anhydrous cyclic dimer of lactic acid (lactide method), but a direct polymerization method of lactic acid may also be used.

The homopolypropylene (B) preferably has a density of 0.90 to 0.96 and an MFR (measured according to JIS K7210) of 1 to 20 g / 10 min. If the MFR is less than 1 g / 10 minutes, the fluidity is poor and it is difficult to produce a foamed sheet. If the MFR exceeds 20 g / 10 minutes, when a container is produced from the foamed sheet by a thermoforming method, the drawdown becomes large, which is not preferable. . Homopolypropylene ( B ) can be easily produced by a conventionally known production method. For example, propylene gas is purified to a purity of 95% or more, for example, propylene is blown into a solvent to which a triethylaluminum and titanium trichloride-based Ziegler-Natta catalyst is added at a temperature of 30 to 70 ° C., and the pressure is from atmospheric pressure to 5 kg / cm 2. Polymerization is started as a range of ² . The ratio of the stereoregular components (isotactic and atactic) of the resin can be adjusted by the type and concentration of the catalyst, the molar ratio of triethylaluminum to titanium trichloride, the reaction temperature, the reaction time, and the like.

  The foamed sheet made of a thermoplastic resin according to the present invention is made from a resin composition containing the two components of the resin (A) and the resin (B) described above. The blending ratio of the two components is 20 to 90% by weight of the resin (A) and 10 to 80% by weight of the resin (B) (the total amount of the two components is 100% by weight). When the proportion of the resin (A) is less than 20% by weight, the biodegradability of the foamed sheet becomes poor, and when the proportion of the resin (A) exceeds 90% by weight, the strength, heat resistance, moldability, etc. of the foamed sheet Is not preferable. In the above range, the resin (A) is preferably 30 to 70% by weight and the resin (B) is 30 to 70% by weight.

The compatibilizing agent (C) is a component for improving the mutual solubility of the two components of the insoluble resin (A) and the resin (B). Specifically, (a) a styrene-butadiene-styrene block copolymer (manufactured by Asahi Kasei Co., Ltd., trade name: Toughprene), (b) a hydrogenated product of styrene-butadiene-styrene block copolymer , and (c) Examples thereof include a styrene-isoprene-styrene block copolymer (manufactured by Kuraray Co., Ltd., trade name: HIBLER 5127).

The compounding amount of the compatibilizer (C) is in the range of 1 to 20 parts by weight with respect to 100 parts by weight of the total amount of the two resin components {resin (A) and resin (B)} . When the blending amount is less than 1 part by weight, the function as a compatibilizing agent is not exhibited, and when it exceeds 20 parts by weight, the strength, heat resistance, etc. of the foamed sheet are lowered, which is not preferable. In the above range, 2 to 10 parts by weight is particularly preferable, and 3 to 6 parts by weight is particularly preferable.

In the raw material resin composition, the crystallization accelerator (D), the nucleating agent (E), the antioxidant, the metal deactivator, and the phosphorus stabilizer are added to the raw material resin composition as necessary. , UV absorbers, light stabilizers, fluorescent brighteners, metal soaps, antacid adsorbent stabilizers, crosslinking agents, chain transfer agents, nucleating agents, lubricants, plasticizers, fillers (other than crystallization accelerators) Various resin additives such as reinforcing agents, pigments, dyes, flame retardants, and antistatic agents.

The crystallization accelerator (D) functions to increase the crystallization speed of the foam sheet. Examples of the crystallization accelerator (D) include talc, sodium bicarbonate, a mixture of talc and titanium dioxide. The crystallization accelerator (D) has a mean particle size of 0.3 to 10.0 μm, and the total amount of the two resin components {resin (A) and resin (B)} is 100 weight. The range is 0.1 to 10 parts by weight with respect to parts. If the blending amount is less than 0.1 part by weight, the function as a crystallization accelerator cannot be exhibited, and if it exceeds 10 parts by weight, the fluidity of the raw resin component is lowered, and neither is preferable. Particularly preferred in the above range is 2 to 8 parts by weight.

The nucleating agent (E) creates a bubble start part and makes it easy to control the size of the bubbles in the foam sheet. Preferred nucleating agents include citric acid, a mixture of citric acid and sodium bicarbonate, and the like. Similarly to the crystallization accelerator (D), the nucleating agent (E) is in the form of granules having an average particle size of 0.3 to 10.0 μm, and the blending amount thereof is two resin components {resin (A) And resin (B)} are preferably selected in the range of 0.01 to 1 part by weight with respect to 100 parts by weight of the total amount . The crystallization accelerator (D) and the nucleating agent (E) are mixed with the above various resin additives and melt kneaded and granulated, or dry blended with the obtained granular raw resin mixture. preferable.

  The method of blending the crystallization accelerator (D), the nucleating agent (E), the above resin additive and the like into the raw material resin composition containing the two resins and the compatibilizer (C) is a melt-kneading method. In general, the mixing / melting sequence and the method thereof are not particularly limited. The heating temperature at the time of melt-kneading varies depending on the type of the raw material resin, but if selected in the range of 150 to 300 ° C., the raw material resin composition is sufficiently melted and is not thermally decomposed and sufficiently foamable. Is preferable in that it can be obtained. Examples of the apparatus for melt kneading the raw material resin composition include a kneader, a Banbury mixer, a Brabender, a single screw extruder, a twin screw extruder, and the like.

  Next, a method for producing the foamed sheet according to the present invention from the raw material resin composition will be described. The foam sheet is formed by mixing a granular thermoplastic resin with a crystallization accelerator (D), a nucleating agent (E), and the resin additive, a step of plasticizing the mixture in an extruder, and a plasticized mixture. Each step of mixing (introducing or press-fitting) a foaming agent to prepare a foamable mixture, plasticizing the foamable mixture in an extruder, foaming and extruding from an extruder die, and continuously producing a foamed sheet It is manufactured by the method containing.

  The foaming agent is a material that is mixed with a raw material resin composition in a molten state in a melt-kneader and changes in phase from solid to gas, liquid to gas, or gas itself. Used to control). As for the foaming agent dissolved in the raw material resin composition, those that are liquid at room temperature undergo a phase change into a gas depending on the resin temperature and dissolve in the molten resin, and those that are a gas at room temperature dissolve in the molten resin without any phase change. The foaming agent dispersed and dissolved in the molten resin expands inside the sheet when the molten resin is extruded from the extrusion die into a sheet, and thus expands inside the sheet, forming a large number of fine closed cells in the sheet. A foam sheet is obtained. The foaming agent acts as a plasticizer that lowers the melt viscosity of the raw resin composition as a secondary effect, and lowers the temperature for bringing the raw resin composition into a plasticized state.

  Examples of the blowing agent include aliphatic hydrocarbons such as propane, butane, pentane, hexane, and heptane; alicyclic hydrocarbons such as cyclobutane, cyclopentane, and cyclohexane; chlorodifluoromethane, difluoromethane, trifluoromethane, and trichlorofluoro Methane, dichloromethane, dichlorofluoromethane, dichlorodifluoromethane, chloromethane, chloroethane, dichlorotrifluoroethane, dichloropentafluoroethane, tetrafluoroethane, difluoroethane, pentafluoroethane, trifluoroethane, dichlorotetrafluoroethane, trichlorotrifluoroethane Halogenated hydrocarbons such as tetrachlorodifluoroethane and perfluorocyclobutane; inorganic gases such as carbon dioxide, nitrogen and air; And the like. These foaming agents may be one kind or a mixture of two or more kinds.

  The amount of the foaming agent to be added varies depending on the type of foaming agent, the target foaming ratio of the foamed sheet, etc., but is preferably selected in the range of 1 to 20% by weight with respect to the raw material resin composition. The higher the amount of foaming agent mixed, the larger the foam will become, due to the combined effect of the higher pressure in the foam and the lower resistance of the foam wall against the plasticizing action of the foam. The magnification also increases. A preferable mixing amount of the blowing agent is 2 to 15% by weight.

  The step of preparing the foamable mixture and the step of foaming the foamable mixture can be performed in an extruder. That is, a thermoplastic resin composition blended with a crystallization accelerator (D) and a nucleating agent (E) is melted with an extruder and mixed (introduced or pressed) from the middle of the extruder cylinder. The extruder may be either a single screw extruder or a twin screw extruder. The extruder die may be a T die or a circular (circular) die.

The foamed sheet made of thermoplastic resin produced by the above method has a foaming ratio of 1.1 to 3.0 times and a thickness of 0.5 to 3.0 mm. If the foaming ratio of the foamed sheet is less than 1.1 times , the secondary processed product is inferior in heat insulation, cold resistance, buffering properties, etc., and if the foaming ratio exceeds 3.0 times, the rigidity is inferior. Absent. Particularly preferred within the above range is 1.5 to 2.7 times. Also, if the thickness of the foamed sheet is less than 0.5 mm, the secondary processed product is inferior in rigidity, impact strength, elastic modulus, heat insulation, etc. If the thickness exceeds 3.0 mm, the foamed sheet is foamed. Not only is it difficult to produce a cell-formed foam sheet, but the amount of raw material resin used is increased, and the secondary processability is inferior. Particularly preferred within the above range is 0.7 to 2.8 mm.

The thermoplastic resin foam sheet according to the present invention may be obtained by laminating a non-foamed layer (film) made of a thermoplastic resin on one or both surfaces of the foam sheet for the purpose of improving surface properties, rigidity, thermoformability and the like. it can. Laminated (film) thermoplastic resins include polylactic acid, modified polyphenylene ether resins, polyethylene resins, polypropylene resins, polyethylene terephthalate resins, polybutylene terephthalate resins, polyamide resins, acrylic resins, and polyvinyl chloride. Resin, polycarbonate resin and the like. The method for laminating the non-foamed layer on the foamed sheet is not particularly limited, and (a)
After the foam sheet is manufactured, a non-foamed film prepared separately is laminated by a heating method or a method using an adhesive, (b) a method of extruding the non-foamed film directly from the T-die onto the foam sheet surface, etc. Is mentioned. Particularly preferred is a method in which the non-foamed resin is polylactic acid and laminated by the method (b).

Thermoplastic resin foam sheet according to the present invention, the proportion of raw material resin two-component, the proportion of the compatibilizer (C), and by defining the characteristics of the foamed sheet, the secondary processability, or plug molding method or a vacuum It is possible to obtain a molded product that is excellent in processability when obtaining a final product by a thermoforming method such as a molding method or a pressure forming method, and has no thickness unevenness. Examples of thermoforming methods include plug molding, matched mold molding, straight molding, drape molding, plug assist molding, plug assist reverse draw molding, air slip molding, snapback molding, reverse Examples thereof include a draw molding method, a plug and ridge molding method, and a ridge molding method.

Next, a container can be manufactured from the thermoplastic resin foam sheet according to the first invention of the present invention described above by the thermoforming method described above. According to the study by the present inventors, it has been found that the heat resistance of a container produced from a thermoplastic resin foam sheet by a thermoforming method depends on the degree of crystallinity. It was also found that the crystallinity of the container depends on the mold surface temperature and the annealing time when the container is manufactured by thermoforming. Hereinafter, the manufacturing method of a container is demonstrated according to the method which concerns on 2nd invention.

It was found that the preferable mold surface temperature and annealing time were in the range of the mold surface temperature of 105 to 115 ° C., and the annealing time after container molding was 10 to 20 seconds. If the mold surface temperature is less than 105 ° C., it depends on the annealing time, but the molded product is difficult to crystallize, the heat resistance of the product container is not improved, and if the mold surface temperature exceeds 115 ° C., the product container It tends to be in a softened state, and neither is preferable. A particularly preferable range of the mold surface temperature is 107 to 113 ° C. Also, if the annealing time is less than 10 seconds, depending on the mold surface temperature, the molded product is difficult to crystallize, and the heat resistance of the product container is not improved. In addition to welding, the molding cycle is lengthened, both of which are undesirable. The annealing of the product container refers to maintaining the state where the product container after thermoforming with the molding die is not released from the molding die for a predetermined time.

EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited to the following description examples. In the following described examples, evaluation of various properties of the resin composition containing as a raw material of (A) ~ (E), and various properties of the thermoplastic resin foam sheet was carried out by the method described below .

<Raw resin, auxiliary material>
A: Polylactic acid (made by Mitsui Chemicals, trade name: Lacia H-400, having a weight average molecular weight of 200,000).
B: Polypropylene (manufactured by Nippon Polypro Co., Ltd., brand name: FY4), having a density of 0.9 g / cm ³ and MFR of 5 g / 10 min.
C: Styrene-butadiene-styrene block copolymer (manufactured by Asahi Kasei Co., Ltd., trade name: Toughprene).
D: Talc (manufactured by Dainichi Seika Co., Ltd., brand name: OK4070-70-N, average particle diameter is 3 μm).
E: Baking soda-citric acid (manufactured by Eiwa Kasei Co., Ltd., trade name: Cerbon SC / K).

(A) Extrusion characteristics: 40 mmφ, L / D = 36 twin screw extruder (manufactured by Plastic Engineering Laboratory Co., Ltd., model: BT-40-S2-36L), cylinder temperature set to 200 ° C., Evaluation was made based on the load on the extruder motor and the temperature of the screw tip resin when extruded at 40 rpm. In a relative comparison, a case where the load on the extruder motor was low was indicated as ◯, a case where the load on the extruder motor was high was indicated as x, and an intermediate between ○ and x was indicated as △.
(B) Foaming ratio: Measured according to JIS K6767.
(C) Appearance of sheet: The foamed sheet made of thermoplastic resin is visually observed, and wrinkles parallel to the extrusion direction (corrugated lines) and those where no fluff is observed are indicated by ○, and wrinkles parallel to the extrusion direction (corrugated lines) And those with crispness were indicated as x, and those between ◯ and x as △.

(D) Drawdown Resistance: The thermoplastic resin foam sheet, batch difference forming device (Kansai automatic molding machine manufactured by model: PK450V) using a fixed by a clamp dimension of 50 cm × 50 cm, The foam sheet with a thickness of 1.0 mm is heated from the top and bottom of the foam sheet at a heater set temperature of 300 ° C. for 15 seconds, and the drawdown property is evaluated by a visible light laser displacement sensor (Keyence Corporation, model: BL-300). did. Blowing amount sag of the sheet central portion ○ those less than 20 mm, sag amount × of not less than 20 mm, and displayed respectively.

(E) Moldability: A foam sheet made of thermoplastic resin is fixed by a clamp having a size of 50 cm × 50 cm using a batch type differential pressure molding machine (manufactured by Kansai Automatic Molding Machine Co., Ltd., model: PK450V) Heated from the top and bottom of a foam sheet with a thickness of 1.0 mm for 15 seconds with a heater set temperature of 300 ° C, and took a 20 cm x 25 cm x 3 cm lunch box-type container using a test mold and differential pressure molding Molded by the method (a method of reducing the pressure from the male mold side). About the obtained container, the appearances, such as the presence or absence of uneven thickness, the type-determined situation, were visually observed, and “good” as a whole, “poor” as poor, and “mid” between “good” and “good” as “△”.
( F ) Heat-resistant temperature: Commercially available salad oil (Nisshin Oil Industries, trade name: Nisshin Salad Oil) was put in an oil bath, the temperature was raised from 50 ° C. to 5 ° C., and the container was immersed for 1 minute at each temperature. After removal, the appearance was visually observed. The maximum temperature (° C.) at which no deformation was observed in any part of the container was defined as the heat resistant temperature.
( G ) Comprehensive evaluation: A case where all of the evaluation items (a) and (c) to (f) are good, ○, any inferior one is ×, and an intermediate between ○ and × is Δ , Respectively.

[Example 1 to Example 14, Comparative Example 1 to Comparative Example 4]
<Manufacture of foam sheet>
The raw material resin ( A ) and the resin (B) are weighed in the proportions shown in Table 1 to give a total of 100 parts by weight, and the auxiliary raw materials ( C ) (compatibilizer) and ( D ) (crystallization accelerator) ) Were weighed in the proportions shown in Table 1 and uniformly mixed with a ribbon blender to obtain a mixture. To this mixture, 0.5 part by weight of auxiliary raw material ( E ) (nucleating agent) was weighed and added, and uniformly mixed with a ribbon blender to obtain a blend. This blend was supplied to a hopper of a twin screw extruder (model: BT-40-S2-36L, manufactured by Plastic Engineering Laboratory Co., Ltd.) having a 40 mmφ, L / D = 36, and a cylinder temperature set to 200 ° C. , 1-5 parts by weight of carbon dioxide gas as a foaming agent is injected and mixed from the middle of the extruder cylinder to 100 parts by weight of the plasticized compound , and extruded from a circular die (75 mmφ) under atmospheric pressure to form a mandrel. While being taken, air was blown into the mandrel at 0.15 m ³ / min to draw and cool to obtain a cylindrical foam sheet, which was cut open with a cutter to obtain a foam sheet having a width of 700 mm.

<Production of raw material mixture, foam sheet, evaluation test of foam sheet>
By the above-described method, the raw material mixture, the production of the foamed sheet, and the foamed sheet were subjected to the evaluation test by the method described above, and the evaluation results are shown in Table-1.

From Table 1 above, the following becomes clear.
(1) Polylactic acid (A), homopolypropylene (B), and compatibilizing agent (C) that have a blending ratio satisfying the requirements specified in claim 1 are used as a raw material in the extrusion characteristics at the time of foam sheet production. Excellent (see Examples 1 to 14).
(2) The foamed sheet satisfying the requirements defined in claim 1 in terms of the blending ratio of the polylactic acid (A), the homopolypropylene ( B ) and the compatibilizer (C), the foaming ratio, etc. There is little draw down at the time of manufacturing a container by the next shaping | molding method, and it is excellent in a moldability (refer Example 1-Example 14).
(3) On the other hand, even if the blending ratio of the polylactic acid (A) and the homopolypropylene (B) satisfies the requirements defined in claim 1, the blending ratio of the compatibilizing agent (C) is defined in claim 1. Those that do not satisfy the requirements to perform are inferior in extrusion characteristics, sheet appearance, drawdown properties, and moldability during secondary molding (see Comparative Example 1) .
(4) Further, when the blending ratio of the polylactic acid (A) and the homopolypropylene (B) is outside the range specified in claim 1, the extrusion characteristics at the time of manufacturing the foamed sheet, the appearance of the sheet, the drawdown property, It is inferior to the moldability at the time of the next molding (see Comparative Example 2, Comparative Example 3, and Comparative Example 4) .

[Examples 15 to 28, Comparative Examples 5 to 7]
The above Examples 1 to 14 and a thermoplastic resin foam sheet obtained in Comparative Example 2 to Comparative Example 4, a batch difference forming device (Kansai automatic molding machine manufactured by model: PK450V) a Used, fixed by clamps with dimensions of 50 cm x 50 cm, heated from above and below the foam sheet with a thickness of 1.0 mm for 15 seconds with a heater set temperature of 300 ° C, 20 cm x 25 cm x 3 cm The lunch box type container was molded by a differential pressure molding method (a method of depressurizing from the male mold side) with a test mold.

The details of the molding conditions of the containers and the evaluation test results for the obtained containers are shown in Table 2.
The evaluation items in Table-2 were as follows.
(I) Crystallinity (%): An X-ray diffraction apparatus (manufactured by Shimadzu Corporation)
Model: XRD-7000), target Cu-Kα, tube voltage 40 KV, tube current 40 mA, divergence 1.00 degree, scattering 1.00 degree, receiving 0.3 mm, scanning range 5 to 35 degrees, scanning speed The measurement was performed under the condition of 2 degrees / minute. The obtained measurement data intensity is subjected to Lorentz polarization factor correction, and is separated into crystalline integrated intensity (Icr) and amorphous integrated intensity (Ia), and the crystal portion occupying the sample based on the ratio Concentration, that is, crystallinity (X) was calculated by the following formula (I). The crystallinity is a value obtained by adding the values of polylactic acid (A), homopolypropylene (B), compatibilizer (C), crystallization accelerator (D) and nucleating agent (E).

(J) Heat-resistant temperature (° C.): A commercially available salad oil (Nisshin Oil Industries, trade name: Nisshin Salad Oil) is put in an oil bath, and the temperature is raised by 5 ° C. in the range of 90 ° C. to 130 ° C. The container was taken out after being immersed for 1 minute at a temperature, and the appearance was visually observed. The maximum temperature (° C.) at which no deformation was observed in any part of the container was defined as the heat resistant temperature.
(K) Microwave oven heating test: The contents of the inner lunch box of the curtain (rice and side dish) are placed in the container storage part, a lid made of biaxially oriented polystyrene is covered, and the microwave oven (made by Sharp Corporation, model: RE-6000) is inside. And set to 1400 W and heated for 50 seconds. After heating, it was taken out from the microwave oven, and the presence or absence of deformation of the container was visually observed. A case where no deformation was observed in any part of the container was indicated as ◯, and a case where deformation was observed was indicated as △.
(L) Cold resistance: The tap water was stored in the container storage part, placed in a freezer of a freezer set to −20 ° C. (model: CR-221BSE) and left for 24 hours to freeze the tap water. . The container was taken out from the freezer, dropped from a height of 80 cm onto the concrete floor, and the presence or absence of cracking of the container was visually observed. A sample in which no cracks were observed was indicated as ◯, and a sample in which cracks were observed was indicated as ×.

From Table 2 above, the following becomes clear.
(1) polylactic acid (A), meets the requirements proportion of homopolypropylene (B) and compatibilizer (C) is defined in claim 1, the container produced molded under the conditions defined in claim 4 is carried out Compared to those of Examples 1 to 14, the heat resistant temperature is increased by 10 to 30 ° C. and excellent in mold releasability, microwave heating test, and cold resistance (see Examples 15 to 28). .
(2) When the content ratio of homopolypropylene (B) is high in the raw material resin composition, the degree of crystallinity of the molded product after annealing tends to be high ( see Examples 15 to 28).
(3) On the other hand, when the proportion of polylactic acid (A) is larger than the range specified in claim 1, the container was welded to the mold when the molded container was released from the mold. In addition, it was difficult to release, and a microwave heating test and a cold resistance evaluation test could not be performed (see Comparative Example 5).
(4) When the proportion of homopolypropylene (B) is larger than the range specified in claim 1, the compatibilizer (C) is inferior in cold resistance even if the compatibilizer (C) satisfies the range specified in claim 1 (comparison). See Example 6 and Comparative Example 7).

[Example 29 to Example 37, Comparative Example 8 to Comparative Example 11]
The thermoplastic resin foam sheet obtained in the example described above in Example 6, batch difference forming device (Kansai automatic molding machine manufactured by model: PK450V) using a size of 50 cm × 50 cm Fix with a clamp, heat from a top and bottom of a foam sheet with a thickness of 1.0 mm for 15 seconds with a heater set temperature of 300 ° C, and take a 20cm x 25cm x 3cm lunch box type container with a single take test mold It shape | molded by the pressure forming method (method to reduce pressure from the male die side). Molded products were obtained by variously changing the mold surface temperature, the annealing time of the molded product (container) after differential pressure molding, as described in Table-3. The obtained molded product was subjected to an evaluation test (crystallinity, heat resistant temperature , microwave heating test, cold resistance), and the evaluation results are shown in Table 3 .

From Table 3 above, the following becomes clear.
(1) When the mold surface temperature is in the range of 105 to 115 ° C. and the annealing time is 10 seconds to 20 seconds, the crystallinity of the container is increased or the heat resistance is excellent (Examples 29 to See Example 37).
(2) On the other hand, when the mold surface temperature is set to 120 ° C., even if the annealing time is set to 20 seconds, the crystallinity is not increased and the container is softened so that it is difficult to release from the mold. (See Comparative Example 8).
(3) Further, when the mold surface temperature is 100 ° C. , even if the annealing time is 30 seconds, the crystallinity of the container does not increase, and the heat resistant temperature is inferior to that of the example (see Comparative Example 9 ).
(4) Further, when the mold surface temperature is set to 80 ° C. or lower , the heat-resistant temperature is not improved at all (see Comparative Examples 10 and 11).

  The foamed sheet made of thermoplastic resin according to the present invention is lightweight, excellent in cold resistance, heat insulation, oil resistance, heat resistance, rigidity, etc., and also excellent in biodegradability, by a thermoforming method such as vacuum forming or pressure forming. Many secondary molded articles (containers) can be obtained. Containers include trays, cups, bowls, dishes, containers, boxes and the like. In particular, since containers manufactured under specific molding conditions are excellent in heat resistance, they store pre-cooked food, and are refrigerated and frozen at a low temperature of 10 to -30 ° C., stored and transported, and used for eating. It is suitable as a container for frozen cooked food that is cooked by a microwave oven at a temperature of 100 to 120 ° C.

Claims (4)

Polylactic acid (A) having a weight average molecular weight of 50,000 or more, 20 to 90% by weight, density of 0.90 to 0.96, MFR of 1 to 20 g / 10 min of homopolypropylene (B) of 10 to 80% by weight (2 (A) styrene-butadiene-styrene block copolymer and (b) styrene-butadiene-styrene block copolymer with respect to 100 parts by weight of the total amount of the two components comprising 100% by weight of the total amount of the components) hydrogenated products, and, (c) a styrene - isoprene - styrene block copolymer, compatibilizing agent selected from the group consisting of (C) 1 to 20 formed by parts resin composition blended raw material resin composition A foamed sheet made of a thermoplastic resin, characterized in that the expansion ratio is 1.1 to 3.0 times and the thickness is 0.5 to 3.0 mm.   The crystallization accelerator (D) 0.1 to 10 parts by weight and the nucleating agent (E) 0.01 to 1 part by weight are further blended with 100 parts by weight of the raw material resin composition. The foamed sheet made of thermoplastic resin as described in 1. Polylactic acid (A) having a weight average molecular weight of 50,000 or more, 20 to 90% by weight, density of 0.90 to 0.96, MFR of 1 to 20 g / 10 min of homopolypropylene (B) of 10 to 80% by weight (2 (A) styrene-butadiene-styrene block copolymer and (b) styrene-butadiene-styrene block copolymer with respect to 100 parts by weight of the total amount of the two components comprising 100% by weight of the total amount of the components) hydrogenated products, and, (c) a styrene - isoprene - styrene block copolymer, compatibilizing agent selected from the group consisting of (C) 1 to 20 formed by parts resin composition blended raw material resin composition The foaming ratio is 1.1 to 3.0 times, the thickness is 0.5 to 3.0 mm, the mold temperature at the time of thermoforming is set to a temperature range of 105 to 115 ° C., and after the container molding 10-20 seconds Characterized by-ring, method for producing a thermoplastic resin foam sheet steel container.   The crystallization accelerator (D) 0.1 to 10 parts by weight and the nucleating agent (E) 0.01 to 1 part by weight are further blended with 100 parts by weight of the raw material resin composition. The manufacturing method of the container made from the foamed sheet made from a thermoplastic resin of description.