JP4976530B2 - Polypropylene resin laminate foam and molded product thereof - Google Patents

Description

  The present invention relates to, for example, a polypropylene-based resin laminated foam suitably used as a storage container, particularly a long-term storage container, and a molded product thereof. More specifically, it is a polypropylene resin laminated foam used in a polypropylene resin laminated foam container excellent in heat resistance and oil resistance that can be cooked in a microwave oven, and particularly for preserved foods such as instant ramen or instant foods, etc. The present invention relates to a polypropylene-based resin laminated foam suitably used as a food container for long-term storage.

  Containers made of polystyrene resin foam sheets, which are mainly used as food containers for storage such as instant noodle containers, are not heat-resistant and cannot be cooked by range-up. 2. Description of the Related Art Polypropylene resin laminated foam containers having heat insulation properties are widely used as containers such as pasta for lunch boxes and lunch boxes (for example, Patent Document 1).

  In Patent Document 1, an intermediate layer of a biaxially stretched polypropylene resin film (hereinafter sometimes abbreviated as “OPP film”) is provided on at least one surface of a base material layer made of a polypropylene resin foam sheet to ensure strength. A laminated foam of polypropylene resin having a surface layer of an unstretched polypropylene resin film is disclosed.

JP 2001-315277 A

  However, when such a polypropylene-based resin laminated foam container is stored and used as an instant food container for a long period of time, depending on the long-term storage environment, there is a problem of aroma transfer property that the noodles of the contents may smell from the outside of the container. I found out. Here, the translucency is a phenomenon in which an odor outside the container permeates the container material and smells the contents such as instant noodles.

  On the other hand, the resin-laminated foam container needs to have good adhesive strength between the respective layers, and particularly between the base material layer of the polypropylene resin foam sheet and the layer laminated with the base material layer. It is important to prevent bubble swelling during thermoforming and bubble swelling due to heating during microwave cooking due to a decrease in adhesive strength.

  In addition, Patent Document 1 laminates a biaxially stretched polypropylene resin film on a base material layer made of a foamed sheet of polypropylene resin to improve the strength of the container. When molding foam sheets, biaxially stretched polypropylene resin films with poor moldability are easy to cool, elongation during molding is reduced and thermoformability is deteriorated, and there is no problem with molded products with shallow bottoms. It was difficult to form a deep drawing product. Therefore, when forming a deep-drawn molded article such as a bag, a non-stretched polypropylene resin film having good moldability (hereinafter sometimes abbreviated as “CPP film”) is made of a polypropylene resin foam sheet. It had to be laminated to the layer.

  An object of the present invention is a polypropylene-based resin laminate foam having heat resistance and heat insulation capable of range-up, good adhesion strength between layers, and capable of preventing fragrance as much as possible. In addition, the present invention provides a polypropylene resin foam-molded article that is suitably used for containers for long-term storage such as preserved food containers such as instant noodles. In addition to the above-mentioned problems, the present invention provides a polypropylene-based resin laminated foam and instant noodles that can form deep-drawn molded articles such as straw while ensuring strength by laminating stretched polypropylene-based resin films. It exists in providing the said polypropylene resin foaming molded article used suitably for containers for long-term storage, such as a preservation | save food container.

  As a result of diligent study, the present inventor laminated a film of polyethylene terephthalate (PET) material, which is the least expensive of barrier materials, on a polypropylene resin foam sheet via a polypropylene resin film as a countermeasure for aroma transfer. By molding, it was possible to provide a low-cost polypropylene-based resin laminate foam having heat resistance and heat insulation that can be ranged up, good adhesion strength between each layer, and no fragrance. .

The present invention is a polypropylene resin laminate foam in which a non-foamed thermoplastic resin film is laminated on a polypropylene resin foam sheet,
The thermoplastic resin film is constituted by dry laminating an aromatic polyester resin film and a polypropylene resin film,
The polypropylene resin laminated foam is characterized in that the polypropylene resin film constituting the thermoplastic resin film is laminated with the polypropylene resin foam sheet.

Further, in the present invention, by using such a foam, a surface layer of the non-foamed thermoplastic resin film is disposed on the inner surface side of the container, and a base material layer of a polypropylene resin foam sheet is disposed on the outer surface side thereof. And a food container in which a base material layer is laminated,
The thermoplastic resin film layer, the aromatic polyester resin film layer and the polypropylene resin film layer are laminated via an adhesive layer,
The polypropylene resin film layer is laminated with the polypropylene resin foam sheet, and the aromatic polyester resin film layer is disposed on the inner surface side of the container,
A food container can be provided.

Since the present invention is a polypropylene resin laminated foam in which an aromatic polyester resin film is laminated, a foam molded product obtained by thermoforming this polypropylene resin laminated foam is a preserved food container such as instant noodles. It can be suitably used as a container for long-term storage such as heat resistance and heat insulation, and can prevent fragrance transfer.
In the present invention, the polypropylene resin film constituting the thermoplastic resin film is laminated on the polypropylene resin foam sheet, and the aromatic polyester resin film is dry laminated on the polypropylene resin film via an adhesive layer. Since the adhesive strength is improved as compared with the polypropylene resin foam sheet laminated with the aromatic polyester resin film, the bubble expansion during thermoforming and the microwave oven Generation | occurrence | production of the bubble swelling by the heating at the time of cooking can be prevented.

  Moreover, since this invention is the structure where the polypropylene resin film was covered with the aromatic polyester resin film and laminated | stacked on the said polypropylene resin foam sheet, the said polypropylene resin film was made into the biaxially stretched polypropylene resin film. Even when foamed sheets are molded, biaxially stretched polypropylene resin films with poor moldability are difficult to cool, and the elongation during molding is improved. Compared with the case of lamination, the moldability can be greatly improved while improving the strength of a molded product such as a container. Further, since deep drawing can be performed, a bucket-shaped or bowl-shaped molded article usually used as an instant noodle container can be easily molded.

FIG. 1 is a schematic sectional view showing a laminated structure of a polypropylene resin laminated foam according to an embodiment of the present invention. FIG. 2 is a schematic view showing a laminating process of the laminated foam sheet. FIG. 3 is a schematic cross-sectional view of the dimension definition showing a container thermoformed using the laminated foam sheet.

(Polypropylene resin laminate foam)
FIG. 1 is a schematic sectional view showing a laminated structure of a polypropylene resin laminated foam according to an embodiment of the present invention. 1 is a polypropylene resin foam sheet, and 2 is a non-foamed thermoplastic resin film. This polypropylene-based resin laminated foam has a structure in which a polypropylene-based resin foam sheet 1 and a non-foamed thermoplastic resin film 2 are laminated. In this embodiment, the polypropylene resin foam sheet 1 includes the foam layer 10 and the non-foam layer 11, but is not necessarily limited thereto.

The thermoplastic resin film 2 is configured by dry laminating an aromatic polyester resin film 20 and a polypropylene resin film 21, and 22 is an adhesive layer.
The polypropylene resin film 21 is laminated with the polypropylene resin foam sheet 1. In this embodiment, the polypropylene resin film 21 is composed of a biaxially stretched polypropylene resin film for improving the strength.

  Such a polypropylene-based resin laminate foam is thermoformed and used as a foam molded product, and is particularly suitable for use as a food foamed product such as a food container, especially as a storage food foamed container such as instant noodles. It is done.

For example, a food product in which a surface layer of the non-foamed thermoplastic resin film is disposed on the inner surface side of the container, and a base material layer of the polypropylene resin foam sheet is disposed on the outer surface side, and the surface layer and the base material layer are laminated. A container for
The thermoplastic resin film layer, the aromatic polyester resin film layer and the polypropylene resin film layer are laminated via an adhesive layer,
The polypropylene resin film layer is laminated with the polypropylene resin foam sheet, and the aromatic polyester resin film layer is disposed on the inner surface side of the container,
The food container can be suitably used as an instant noodle container or a lunch container that can be ranged up, has heat resistance and heat insulation, prevents fragrance transfer, and may be stored for a long period of time.

(Polypropylene resin foam sheet)
Of the laminated foam of the present invention, the polypropylene resin foam sheet 1 may be composed of only the foam layer 10 or may be a laminate of the foam layer 10 and the non-foam layer 11. Further, by thermally laminating a thermoplastic resin film on the surface of the non-foamed layer 11, the adhesiveness of the thermal laminate is improved, no bubbles are generated, and the production efficiency can be increased. Are preferably laminated. If the thickness of the non-foamed layer on which the thermoplastic resin film is thermally laminated is thin, the effect of improving the adhesiveness when the thermoplastic resin film is thermally laminated is small, and if it is thick, the foaming ratio of the foamed sheet 1 is lowered. Therefore, the heat insulating property is deteriorated and the weight of the foamed sheet 1 is increased, so that it is preferably 5 to 200 μm, more preferably 10 to 100 μm.
Of the laminated foams of the present invention, as the polypropylene resin forming the foamed layer 10 of the polypropylene resin foam sheet 1, an uncrosslinked polypropylene resin is preferable. Non-crosslinked polypropylene resins include (A) polypropylene resins having free end long chain branching in the molecule and a melt tension of 6 g or more and 40 g or less (hereinafter referred to as “resin (A)”), and (B ) From a polypropylene resin (hereinafter referred to as “resin (B)”) having a melt tension of 0.01 g or more and less than 6 g and a ratio Mw / Mn of weight average molecular weight Mw to number average molecular weight Mn of 3 to 8 At least one selected from the group is preferably used.

  Among them, the preferable range of the melt tension of the resin (A) is 6 g or more and 40 g or less because good foamability cannot be obtained when the melt tension is less than 6 g. On the other hand, when the melt tension exceeds 40 g, the fluidity is extremely deteriorated or gel is likely to be formed, and the extrusion processability may be lowered. The melt tension of the resin (A) is particularly preferably 20 to 30 g even within the above range in consideration of the balance between foamability and extrusion processability.

Examples of the resin (A) having such a free-end long chain branch include trade names Pro-fax PF-814 and Pro-fax SD-632, which are sold as foaming grades by Sun Allomer. The resin (A) has good foamability when foamed by extrusion foaming or the like, for example, its density is low density, such as less than 0.3 g / cm ³ , high foaming ratio, particularly excellent heat insulation Suitable for forming the sheet 1.

  Therefore, the foamed layer 10 may be formed by using the resin (A) alone, but the resin (A) is expensive and may increase the product cost. For this reason, it is usually preferable to form the foamed layer 10 by using the resin (A) and the resin (B) in combination as a polypropylene resin. Even in that case, it is possible to form the foam layer 10 having a relatively low density and a high expansion ratio and excellent heat insulation. The preferable range of the melt tension of the resin (B) is set to 0.01 g or more and less than 6 g as described above for the following reason. That is, since the tension is too low when the melt tension is less than 0.01 g, the resulting foamed layer 10 tends to have an open cell structure. On the other hand, if it is 6 g or more, the melt viscosity of the resin becomes so high that it is difficult to lower the resin temperature to near the melting point. For this reason, in any of these cases, the quality of the foam sheet 1 may be deteriorated. In view of the balance between the tension and the melt viscosity, the resin (B) has a melt tension of preferably 0.1 g or more and less than 6 g, and more preferably 0.1 g or more and less than 3 g, even within the above range. Is more preferable.

In the present invention, the melt tension of the resin was measured as follows using a measuring apparatus “Capillograph PMD-C” manufactured by Toyo Seiki Seisakusho.
First, in a state where the sample resin is heated to 230 ° C. and melted, the lowering speed of the piston is constant at 10 mm / min from the piston extrusion plastometer nozzle (2.095 mm diameter, 8 mm length) of the above apparatus. Extruded into a string while maintaining the speed. Next, the string-like material is passed through a tension detection pulley located 35 cm below the nozzle, and then the winding speed is increased with an acceleration of about 66 m / min ² using a winding roll. I wound it up. Then, when the test was performed until the string-like material was cut, the maximum tension detected by the tension detection pulley was used as the melt tension of the sample resin.
However, when the string-like material was not cut even when the winding speed exceeded 60 m / min, the tension at the winding speed of 60 m / min was used as the melt tension of the resin.

Examples of the resin (B) include those satisfying the above conditions among general-purpose polypropylene resins such as a homopolymer of propylene and an ethylene-propylene copolymer. The ratio of the resin (A) to the total amount of the resin (A) and the resin (B) is preferably 10 to 50% by weight, and more preferably 10 to 40% by weight. The reason for this is as follows.
In other words, the resin (A) has a function of improving the foaming property of the non-crosslinked general-purpose polypropylene resin, which is usually not very foamable, that is, the resin (B) by the action of free-end long chain branching introduced into the molecule. Have And it contributes in order to obtain the foaming layer 10 provided with heat insulation, oil resistance, and heat resistance. However, a polypropylene resin having a free end long chain branch has a problem that it is inferior in rigidity as compared to a general-purpose polypropylene resin having no free end long chain branch. In addition, since a polypropylene resin having a free-end long chain branch is expensive, the production cost of the product is increased.

Therefore, the ratio of the resin (A) to the total amount of the resin (A) and the resin (B) is preferably 50% by weight or less, particularly 40% by weight or less as described above. On the other hand, by improving the foamability of the resin (B) described above, as in the case of the resin (A) alone, the density is low density such as less than 0.3 g / cm ³ and the foaming ratio is high, and the heat insulation property. In order to form the foam layer 10 excellent in the above, the ratio of the resin (A) to the total amount of the resin (A) and the resin (B) is preferably 10% by weight or more.

As described above, although the resin (B) is usually not very foamable, it is possible to produce a foamed layer 10 having a relatively low foaming ratio such as a density of 0.3 g / cm ³ or more. It is. Therefore, the foamed layer 10 may be formed using the resin (B) alone as a polypropylene resin. As the polypropylene resin forming the non-foamed layer 11, the polypropylene resin of the above (A) and (B) can be used, but the foaming property is not necessary, so the cost is low. (B) or the polypropylene resin described later It is preferable to use the resin used for the film.
The polypropylene resin foam sheet 1 is manufactured by a known extrusion foam molding method.
For example, the foam sheet 1 consisting only of the foam layer 10 is obtained by melt-kneading the polypropylene resin for the foam layer 10 together with a foaming agent using an extruder, and then extruding and foaming through a die connected to the tip of the extruder. Manufactured by doing. The foamed sheet 1 in which the foamed layer 10 and the non-foamed layer 11 are laminated is connected to the extruder for the foamed layer 10 and the extruder for the non-foamed layer 11, and the respective extrudates are supplied to the joining die. And then extruded and foamed through a mold connected to a converging die.

  There are circular slit dies, T-shaped dies, etc., but a cylindrical foam obtained by extrusion foaming through a circular slit die is cut at one or two or more locations on the circumference of the foam sheet 1. Preferably it is manufactured. Examples of the foaming agent used for extrusion foaming include various volatile foaming agents, decomposable foaming agents, carbon dioxide, nitrogen gas, and water. Among these, examples of the volatile blowing agent include one or more hydrocarbons such as propane, butane and pentane, and halogenated hydrocarbons such as tetrafluoroethane, chlorodifluoroethane and difluoroethane. Preferably used. As butane, normal butane or isobutane may be used alone, or normal butane and isobutane may be used in any proportion.

  Examples of the decomposable foaming agent include inorganic foaming agents such as an organic foaming agent such as azodicarbonamide and dinitrosopentamethylenetetramine, a combination of an organic acid such as citric acid or a salt thereof, and a bicarbonate such as sodium bicarbonate. Type foaming agents. Any one of these foaming agents may be used alone, or two or more thereof may be used in combination.

  Various additives may be appropriately added to the polypropylene resin in advance or when melt-kneading with an extruder as long as the effects of the present invention are not impaired. Examples of the additive include an air conditioner, a pigment, a stabilizer, an antistatic agent and the like for adjusting the size of the air bubbles during foaming, such as citric acid and sodium bicarbonate. For example, inorganic fillers such as talc, calcium carbonate, silica, alumina, titanium oxide, and clay can be added to improve the strength, rigidity at high temperatures, durability, and heat resistance of molded products. It is preferable to blend at a ratio of about 40 parts by weight or less, preferably about 30 parts by weight or less with respect to 100 parts by weight of the resin. In the present invention, it is more preferable to use a polypropylene resin foam sheet not containing an inorganic filler. This is because, when a polypropylene resin foam sheet containing a filler in excess of 40 parts by weight with respect to 100 parts by weight of the polypropylene resin foam forming the polypropylene resin foam sheet is used, the open cell ratio of the foam layer is increased. Insufficient strength. Furthermore, there is much generation of residual ash when thermal recycling is performed. As described above, when a large amount of filler having a high thermal conductivity is contained, the open cell ratio is high, so that the heat insulating property is insufficient when applied to a molded product for food, particularly an instant food container.

The foamed layer 10 thus formed preferably has a density of 0.1 to 0.85 g / cm ³ . If the density of the foamed layer 10 is less than 0.1 g / cm ³ , the strength of the molded product and the rigidity at high temperature may be reduced. Conversely, if it exceeds 0.85 g / cm ³ , the heat insulating property of the molded product May decrease. The density of the foamed layer 10 is preferably 0.18 to 0.6 g / cm ³ even in the above range, considering the balance between the strength and rigidity of the molded product and the heat insulation.

  The thickness of the foamed layer 10 is preferably 0.3 to 5 mm considering the strength, heat insulation and thermoformability of the molded product, although it depends on the specifications of the target molded product. More preferably, it is 3 mm.

(Thermoplastic resin film)
The thermoplastic resin film used in the present invention is constituted by laminating the aromatic polyester resin film 20 and the polypropylene resin film 21 as described above. It is preferable that the aromatic polyester-based resin film 20 and the polypropylene-based resin film 21 are dry laminated with the adhesive layer 22 interposed therebetween. As an adhesive used when dry laminating, any adhesive can be used as long as it can adhere the polypropylene resin film 21 and the aromatic polyester film 20, but a urethane adhesive is used. preferable.

  Examples of the aromatic polyester resin that forms the aromatic polyester resin film include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polycyclohexanedimethyl terephthalate (PCT). For example, an aromatic polyester resin as described in JP-A-2001-219523 can be used. That is, any one obtained by polycondensation of a dicarboxylic acid component and a diol component can be used. Moreover, what is obtained by the transesterification etc. of an aromatic polyester homopolymer and / or an aromatic polyester copolymer can also be used.

  As the dicarboxylic acid component, dicarboxylic acid or a derivative capable of forming an ester thereof can be used. Examples of this derivative include ester derivatives such as dimethyl ester or diethyl ester, and salts such as diammonium salt. Component units of dicarboxylic acid in the polymer include those derived from aromatic dicarboxylic acids such as phthalic acid, terephthalic acid and isophthalic acid or derivatives capable of forming esters thereof, oxalic acid, succinic acid, adipic acid, sebacic acid Derived from aliphatic dicarboxylic acids such as diesters and derivatives capable of forming esters thereof, or derived from alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid and 1,3-cyclohexanedicarboxylic acid, or derivatives capable of esterification thereof What is done. These may contain one or more of them in the polymer.

  As the diol component, aliphatic and aromatic diols (including divalent phenols) can be used. The component unit of the diol in the polymer is an aliphatic diol such as ethylene glycol, propylene glycol, cyclohexanedimethanol, neopentyl glycol, trimethylene glycol, diethylene glycol, 1,4-butanediol, or an ester-forming derivative thereof. Can be derived, derived from alicyclic diols such as 1,4-cyclohexanedimethanol and 1,3-cyclohexanedimethanol, or esterable derivatives thereof, and can form aromatic diols such as bisphenol A or esters thereof And those derived from various derivatives.

  The aromatic polyester resin may contain a small amount of component units derived from polyfunctional compounds such as pyromellitic acid, trimellitic acid, trimesic acid, glycerin, and pentaerythritol. Moreover, the molecular terminal may be sealed with a component unit derived from a monofunctional compound such as a small amount of benzoic acid.

In the present invention, among the aromatic polyester resins, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polycyclohexanedimethyl terephthalate (PCT) and the like are preferable, but polyethylene terephthalate resin is more preferable. Among polyethylene terephthalate resins, PETG, which is excellent in formability when laminated with a polypropylene resin foam sheet, particularly with an OPP film, is optimal. PETG is polyethylene terephthalate containing 1,4-cyclohexanedimethanol as a glycol unit. As PETG, the brand name "Easter PETG6763" (made by Eastman Chemical Japan Co., Ltd.) can be used, for example. Its glass transition temperature is 82 ° C. and density is 1.26 g / cm ³ . Moreover, it is also possible to use a brand name "Easter PETG5011" (Eastman Chemical Japan Co., Ltd. product). Its glass transition temperature is 82 ° C. and density is 1.26 g / cm ³ .

  The thickness of the aromatic polyester resin film is preferably 5 to 70 μm. If the thickness is less than 5 μm, there is a fear that the effect of preventing the fragrance transfer of the molded product is small. Conversely, if the thickness exceeds 70 μm, lamination with a hot roll becomes difficult and the cost increases. 10-50 micrometers is more preferable.

  Examples of the polypropylene resin that forms the polypropylene resin film include a propylene homopolymer, a block copolymer of propylene and another resin, a random copolymer, or the like alone or two kinds. As described above, they are used in combination.

  Examples of resins other than propylene include ethylene and α-olefins having 4 to 10 carbon atoms (1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, etc.), 1 type or 2 types or more are mentioned. Particularly suitable polypropylene resins include, for example, propylene homopolymer, propylene-ethylene random copolymer, propylene-ethylene-α-olefin random copolymer, and propylene component and propylene-ethylene random copolymer component. Examples thereof include a block copolymer.

  In addition, other resins may be mixed with the polypropylene resin as long as the effects of the present invention are not impaired. Examples of such other resins include homopolymers or copolymers such as ethylene and α-olefin, olefin resins such as polyolefin wax and polyolefin elastomer, and hydrocarbon resins such as petroleum resins and terpene resins. However, it is used individually by 1 type or in mixture of 2 or more types.

  Moreover, you may add suitably various additives to a polypropylene resin as needed in the range which does not impair the effect of this invention. Examples of the additive include an antistatic agent, an antifogging agent, an antiblocking agent, an antioxidant, a light stabilizer, a crystal nucleating agent, a lubricant, a surfactant for the purpose of imparting slipping property and antiblocking property, and the like. It is done.

  As the polypropylene resin film used in the present invention, either an unstretched polypropylene resin film (CPP film) or a biaxially stretched polypropylene resin film (OPP film) can be used, but when an OPP film is used, It is preferable because the strength of the container or the like can be improved.

  In order to produce an OPP film, first, a polypropylene resin is melt-kneaded using an extruder, and then extruded into a film form through a mold connected to the tip of the extruder. Then, the OPP film is formed by stretching (biaxial stretching) the extruded film sequentially or simultaneously in the two directions of the resin extrusion direction (longitudinal direction, MD) and the direction orthogonal to it (transverse direction, TD). Is manufactured.

  Among the above, in the sequential biaxial stretching method, first, a resin melted using an extruder is extruded into a film form from a T die connected to the tip of the extruder, and then cooled and solidified on a cooling roll. Next, after stretching in the MD direction using a heated roll stretching machine, a method of stretching in the TD direction using a tenter transverse stretching machine is performed. Examples of the simultaneous biaxial stretching method include a tenter method and a tubular inflation method. The stretching amount of the OPP film is not particularly limited, but the area stretching ratio, that is, the area stretching ratio = (stretching ratio in the MD direction) × (stretching ratio in the TD direction) is preferably 4 to 50 times.

  If the area stretch ratio is less than 4 times, the effect of improving the drawdown of the laminated foam by laminating the OPP film, or the effect of improving the strength of the molded product, the rigidity at high temperature, etc. may be insufficient. There is. On the other hand, when the area stretch ratio exceeds 50 times, the thermoformability of the laminated foam may be lowered. The area stretch ratio is 15 to 35 times, especially within the above range, considering the balance between the effect of improving drawdown, the effect of improving the strength and rigidity of the molded product, and the thermoformability of the laminated foam. Preferably there is.

  Moreover, it is preferable that the draw ratio of MD direction and TD direction is 2-10 times. If the draw ratio is less than 2, the effect of improving the drawdown of the laminated foam by laminating the OPP film or the effect of improving the strength of the molded product, the rigidity at high temperature, etc. may be insufficient. is there. On the other hand, when the draw ratio exceeds 10 times, the thermoformability of the laminated foam may be reduced. The draw ratio in the MD direction and the TD direction is particularly within the above range in consideration of the effect of improving drawdown, the effect of improving the strength and rigidity of the molded product, and the thermoformability of the laminated foam. It is preferably 3 to 9 times.

  The thickness of the polypropylene resin film is preferably 5 to 50 μm. In particular, when an OPP film is used as the polypropylene resin film, the thickness is preferably 5 to 50 μm. If the thickness is less than 5 μm, the effect of improving the drawdown of the laminated foam and preventing the corrugation and the effect of improving the rigidity of the molded product at high temperature may be insufficient. On the contrary, when the thickness of the OPP film exceeds 50 μm, even if the polypropylene resin film is covered with the aromatic polyester resin film, the polypropylene resin film is laminated on the foam sheet to form a laminated foam. A large amount of heat is required when producing or when a molded product is produced by thermoforming the produced laminated foam. For this reason, there exists a possibility that manufacturing efficiency may worsen. In addition, the foamed sheet is attacked by heat, and a part that is locally stretched at the time of thermoforming may be generated, which may deteriorate the appearance of the molded product. The thickness of the polypropylene resin film is preferably 6 to 45 μm even in the above range, considering the balance of the above characteristics.

  As a preferable OPP film, a propylene-ethylene random copolymer having an ethylene content of 1 to 4% by weight or an ethylene content of 0.5 to 3.0% by weight and a 1-butene content of 4 to 15% by weight It is an OPP film formed of a propylene-based copolymer having a relatively low melting point such as a propylene-ethylene-1-butene random copolymer. By using this OPP film, the deep drawability is further improved (JP-A-7-241906, etc.). A preferable range of the thickness of the film is about 20 to 45 μm.

  The surface of the polypropylene-based resin film may be subjected to a surface treatment such as a corona discharge treatment in order to improve, for example, printability. The polypropylene resin film is not limited to a single layer. For example, a laminated film obtained by laminating two or more OPP films such as OPP films made of polypropylene resins having different compositions or OPP films having different stretching ratios may be used. In that case, it is preferable to set the thickness of each layer so that the total thickness of all the OPP films falls within the above-described preferable range.

  A CPP film can also be used as the polypropylene resin film. Examples of the polypropylene resin forming the CPP film include the same polypropylene resin as in the case of the OPP film. The same is true in that other resins can be mixed with the polypropylene resin within a range that does not impair the effects of the invention. The other resin types are the same as in the previous case. Further, the types of additives that may be added to the polypropylene resin are the same as in the previous case.

  The CPP film is produced by melt-kneading a polypropylene resin using an extruder and then extruding the film through a mold connected to the tip of the extruder without substantially stretching.

  The total thickness of the thermoplastic resin film obtained by dry laminating the aromatic polyester resin film and the polypropylene resin film is preferably 10 to 100 μm. When it exceeds 100 μm, lamination with a hot roll becomes difficult. If it is less than 10 μm, the effect of preventing the fragrance transfer of the molded product is small, and the strength is not improved. 20-80 micrometers is more preferable.

(Other preferred configurations)
In the present invention, in addition to the above configuration, for example, a colorant can be added to the adhesive layer 22 to obtain a colored adhesive layer. Thereby, coloring is easy, there is little usage-amount of a coloring agent, and it leads to a cost reduction.

The printing can be performed on the surface of the aromatic polyester resin film or the surface of the polypropylene resin film on the adhesive layer 22 side, but preferably on the surface of the polypropylene resin film on the adhesive layer 22 side. . In the case of solid printing, it is possible to color the adhesive layer 22 as described above.
Although it is possible to print on the surface of the polypropylene resin film on the polypropylene resin foam sheet side, depending on the printing ink, adhesion to the foam sheet may be insufficient, resulting in poor adhesion when trying to laminate the film rather than thermal lamination. In some cases, floating (delamination) may occur or bubbles may be generated during thermoforming. If the configuration is such that the printing is made on the surface of the adhesive layer 22 side of the polypropylene resin film, the polypropylene resin film is dry laminated with the aromatic polyester resin film and has a laminated structure with excellent adhesiveness. (Delami) and bubble generation can be prevented.

(Method for producing laminated foam)
As a method for producing the laminated foam of the present invention by laminating each of the above layers, the thermal laminating method is suitably employed as described above.
For example, in FIG. 2, the thermoplastic resin film 2 is thermally laminated on the foam sheet 1 by the heat roll 5 and the pressure roll 6 to form the laminated foam 3. It is preferable to preheat the foamed sheet 1 and the thermoplastic resin film 2 with the heater 7 before pressure bonding with a hot roll.

(Method for forming laminated foam)
The thermoforming method for producing the molded product of the present invention from the above-mentioned laminated foam includes, for example, conventionally known molding such as vacuum molding, pressure molding, match mold molding, plug assist molding, etc. as these applications. The method can be adopted.
In the present invention, the aromatic polyester resin film layer may be formed on either the inner surface side or the outer surface side of the container, but is preferably formed so as to be on the inner surface side of the container. For example, when a molded container is used as a container for instant noodles, the container is used by being sealed with a lid having barrier properties. At this time, when the aromatic polyester-based resin film layer is located on the inner surface side of the container, the lid is sealed to the aromatic polyester-based resin film layer, and the contents are sealed with a material having a barrier property. Sex is prevented. On the other hand, when a film layer widely used in a foamed polystyrene container or the like is placed outside the container, the lid material is sealed to the foamed sheet layer, and as a result, the polypropylene foam layer is sandwiched between the barrier materials. There may be a problem of aroma transfer from to the contents.

  In addition, in the said embodiment, what used the non-foamed layer in the surface of the polypropylene resin foam sheet was used, However, The polypropylene resin foam sheet in which the non-foam layer is not formed can also be used. When a non-foamed layer is formed as the surface layer of the polypropylene resin foam sheet as in this embodiment, the influence of air bubbles on the foam sheet surface is reduced when heat laminating, the adhesiveness is improved, and the productivity is increased. Can be raised.

Example 1
For the foam layer, 25 parts by weight of polypropylene resin (A) (Sun Allomer, trade name “SD632”, melt tension: 21.9 g), Polypropylene Resin (B) (Sun Allomer, trade name “PM600A”, melt tension: 0 .8 g) 75 parts by weight and 0.19 parts by weight of a bubble regulator (trade name “Fine Cell Master SSCPO410K” manufactured by Dainichi Seika Kogyo Co., Ltd.) were dry blended. Next, this mixture was supplied to a hopper of a tandem extruder (caliber 90 mm to 115 mm) having first and second extruders. While this mixture was melted and kneaded in the first extruder, butane (isobutane / normal butane = 65/35) was injected as 1 part by weight per 100 parts by weight of the resin. Further, the melt-kneaded molten mixture was continuously supplied from the first extruder to the second extruder, cooled uniformly to 178 ° C. by the second extruder, and then supplied to the joining die at an extrusion rate of 123 kg / hour. On the other hand, as a polypropylene resin for a non-foamed layer, 100 parts by weight of a product name “J104WA” manufactured by Mitsui Chemicals Co., Ltd. is supplied to a single screw extruder and melted, and then cooled to 188 ° C. Supplied to the die. Extrusion foaming was performed in a cylindrical shape from an annular mold connected to the tip of the converging die. The obtained cylindrical foam was cooled and molded along a mandrel cooled with water at 50 ° C., and cut with a cutter attached to the rear part of the mandrel to produce a polypropylene resin foam sheet. The obtained foamed sheet has a thickness of 1.17 mm (foam layer thickness 1.09 mm, non-foam layer thickness 0.08 mm), density 0.34 g / cm ³ (foam layer 0.30 g / cm ³ ), basis weight 400 g / m. ² (foamed layer 328 g / ^{m 2,} the non-foamed layer 72 g / ^{m 2)} was. The foamed sheet is provided with an 80 μm non-foamed PP resin layer on the surface thereof.

On the other hand, an aromatic polyester-based resin film (PetG film, manufactured by Eastman Chemical Japan, trade name “Easter PETG6763”) having a thickness of 30 μm and a polypropylene-based resin film (OPP film, manufactured by Santox Co., Ltd., trade names “ MF20Z ") dry-laminated thermoplastic film (adhesive for dry lamination: polyurethane ether adhesive, coating amount during coating (wet state) 15-17 g / m ² , coating amount after drying 3.5-5 g / m ² ) was prepared.

  Next, as shown in FIG. 2, the dry-laminated thermoplastic resin film is laminated by a hot roll so that the polypropylene resin film (OPP film) side is in contact with the non-foamed layer side surface of the polypropylene resin sheet 1. A laminated foam sheet was obtained. This laminated foam sheet had good adhesive strength between the respective layers, and no bubble (bubble expansion) was observed during thermoforming.

  The hot roll has a diameter of 300 mm, a hot roll temperature of 180 ° C., a pressure rubber roll (compression roll) diameter of 180 mm, a roll speed (laminate speed) of 6 m / min, and a pressurization amount of 120 N / cm of linear pressure.

  Next, the laminated foam sheet is plug-assisted molded with a single molding machine so that the aromatic polyester resin film (PETG film) side is inside the container, and a deep-drawn molded container for yakisoba (instant noodle container) Was molded. As shown in FIG. 3, this container 4 is a bucket-shaped molded product having a diameter 140 mm of the opening 40, a diameter 125 mm of the bottom 41, and a height of 45 mm. Reference numeral 42 denotes a side wall.

[Comparative Example 1]
A laminated foam sheet was obtained in the same manner as in Example 1 except that the thermoplastic resin film laminated on the polypropylene resin foam sheet was a single film of an OPP film (manufactured by Santox Co., Ltd., MF20Z) having a thickness of 30 μm. Next, in the same manner as in Example 1, a deep-drawn bucket-shaped molded product having the structure shown in FIG. 3 was molded. This laminated foam sheet also had good adhesion strength between the respective layers, and no bubble (bubble expansion) was observed during thermoforming.

(Evaluation of fragrance transfer)
20 g of dried pork flakes were put in each container of the bucket-shaped molded product according to Example 1 and Comparative Example 1 above, covered with aluminum foil, and the periphery was sealed with wax to prepare a container to be evaluated. These containers were sealed together with 16 g of paradichlorobenzene (trade name “Neopara Ace”, manufactured by Este Chemical Co., Ltd.) in a sealed metal container, and stored in an oven at 30 ° C. for 3 days. Thereafter, the container to be evaluated is taken out from the sealed metal container, and the concentration of paradichlorbenzene in the container and the measurement of the adhesion ratio of paradichlorbenzene adsorbed on the dried pork flakes are measured by gas chromatography / mass spectrometry. (GCMS).

Analytical instruments used in the gas chromatography / mass spectrometry method (GCMS) are headspace sampler JHS-100 manufactured by Nippon Analytical Industries, Ltd., and GCMS-QP5000 manufactured by Shimadzu Corporation. The GCMS analysis conditions are as follows. :
Column: DB-5 (manufactured by J & W) φ0.25 mm × 60 mm film thickness 0.25 μm
Split ratio: 10
Inlet temperature: 240 ° C
Interface temperature: 260 ° C
Column temperature: 40 ° C. (3 min) to 15 ° C./min to 200 ° C. (0 min) to 25 ° C./min to 240 ° C. (3 min)
Carrier gas; helium (1.0 ml / min)
Analysis; TIC mode

  Table 1 shows the measurement results. According to Table 1, in the container of Example 1, the concentration of paradichlorbenzene in the container is significantly lower than that in Comparative Example 1, and there is no odor on the dried pork flakes, and the adhesion of paradichlorbenzene is sufficiently prevented. It is recognized that

The present invention is used as a polypropylene resin laminated foam container that is excellent in heat resistance and oil resistance and can be stored for a long period of time. In particular, it is suitably used as a foaming container for foods having excellent heat resistance and oil resistance that can be cooked in a microwave oven. Moreover, it is suitably used as a food container for long-term storage such as preserved food such as instant ramen or instant food.
Among them, the polypropylene-based resin laminated foam of the present invention in which a laminated film of an aromatic polyester-based resin film and an OPP film is laminated as a thermoplastic resin film, the aromatic polyester-based resin film prevents transferability, and the OPP film However, it improves the strength of the container, and there is no deterioration in formability seen when only OPP films are laminated, enabling deep-drawing molding. It is easy to mold a molded product.

DESCRIPTION OF SYMBOLS 1 Polypropylene-type resin foam sheet 10 Foam layer 11 Non-foam layer 2 Thermoplastic resin film 20 Aromatic polyester-type resin film 21 Polypropylene-type resin film 22 Adhesive layer

Claims (5)

The foamed layer and the non-foamed layer and the foamed polypropylene resin sheet are laminated, non-foaming thermoplastic resin film is a method for producing a laminated polypropylene resin laminate foam,
The thermoplastic resin film is constituted by dry laminating an aromatic polyester resin film and a polypropylene resin film,
The polypropylene resin film is composed of a biaxially stretched resin film,
The polypropylene-based resin laminate foam , wherein the polypropylene-based resin film is covered with the aromatic polyester-based resin film , and is heat-laminated and laminated on the non-foamed layer of the polypropylene-based resin foam sheet. Body manufacturing method . The method for producing a polypropylene resin laminate foam according to claim 1, wherein the aromatic polyester resin film is composed of polyethylene terephthalate containing 1,4-cyclohexanedimethanol as a glycol unit. The foamed layer and the non-foamed layer and the foamed polypropylene resin sheet are laminated, non-foaming thermoplastic resin film is a method for producing a laminated polypropylene resin laminate foam,
The thermoplastic resin film is configured by dry laminating the aromatic polyester resin film and the biaxially stretched polypropylene resin film via an adhesive layer,
The foam sheet has a thickness of 0.3 to 5 mm,
The thickness of the non-foamed layer is 5 to 200 μm,
The thickness of the aromatic polyester resin film is 5 to 70 μm, the thickness of the biaxially stretched polypropylene resin film is 5 to 50 μm,
The method for producing a polypropylene resin laminated foam according to claim 1 or 2, wherein the adhesive layer is a layer capable of bonding the biaxially stretched polypropylene resin film and the aromatic polyester film. The manufacturing method of the foaming molded product formed by thermoforming the polypropylene resin laminated foam of any one of Claims 1 thru | or 3. A method for producing a storage container for a deep-drawn molded product obtained by thermoforming the polypropylene-based resin laminated foam according to claim 4,
The surface layer of the non-foamed thermoplastic resin film is disposed on the inner surface side of the storage container, and the base material layer of the polypropylene resin foam sheet is disposed on the outer surface side, and the surface layer and the base material layer are laminated. A storage container,
The thermoplastic resin film layer, the aromatic polyester resin film layer and the polypropylene resin film layer are laminated via an adhesive layer,
The polypropylene resin film layer is laminated with the polypropylene resin foam sheet, and the aromatic polyester resin film layer is disposed on the inner surface side of the container,
A method for producing a storage container.

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