JP2002011838A - Polypropylene resin laminated foam and molded product using it - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To have heat resistance, oil resistance, and heat insulation properties that can be used for microwave cooking, and to have excellent rigidity at a high temperature, and to further improve impact resistance at a low temperature than before. The present invention provides a novel polypropylene-based resin laminated foam capable of producing a good molded article, and a molded article using the same, which is excellent in each of the above-mentioned properties. SOLUTION: The laminated foam is a biaxially stretched polypropylene resin film on one or both sides of a foamed sheet formed from a mixed resin containing a polypropylene resin and an ethylene-α-olefin copolymer in a predetermined ratio. Were laminated. A molded article was produced by thermoforming the above-mentioned laminated foam.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel laminated foam of a polypropylene resin and a molded article using the same, which is suitably used for food packaging containers and the like.

[0002]

2. Description of the Related Art Conventionally, food packaging containers such as lunch boxes and bowls sold at convenience stores and supermarkets and other general packaging containers are made of expanded polystyrene in consideration of heat retention, heat insulation and container strength. Things have been widely used. However, recently, with the spread of microwave ovens to general households, and the spread of heating and cooking services such as lunch boxes using microwave ovens at convenience stores, especially in food packaging containers and foamed polystyrene containers, High heat resistance and oil resistance, which cannot be obtained, have been required.

A non-foamed polypropylene sheet container filled with a filler such as talc is now generally used as a food packaging container having excellent heat resistance and oil resistance and capable of microwave cooking. However, since the above-mentioned container is non-foamed, it has insufficient heat insulating properties. In particular, when the container is taken out after heating and cooking in a microwave oven, there is a problem that the wall surface and the bottom surface thereof become hot and dangerous. In addition, since the container contains a large amount of filler, there is also a problem that recycling is difficult.

[0004] In view of the above, foaming of a polypropylene-based resin which is excellent in heat resistance and oil resistance as compared with expanded polystyrene, has excellent heat insulating properties due to its foamed structure, and has excellent recyclability in most cases because it contains no filler. It has been considered to manufacture a molded article such as a food packaging container by thermoforming a sheet.

[0005]

However, according to studies made by the inventors, it has been found that a molded article obtained by thermoforming the above-mentioned foamed sheet of a polypropylene resin has insufficient impact resistance especially at a low temperature. It has been found that it has a problem that it is liable to be broken by an impact during transportation or the like. In other words, the food container is suitable for transportation and storage between the time the food is frozen and the time the food is stored in the store, approximately -2.
Excellent impact resistance over a wide temperature range, from a low temperature of 0 ° C. or less, particularly around −30 ° C., to a normal temperature range when food is displayed at a store or taken home from a store. It is necessary.

However, polypropylene resins are generally
Since the glass transition temperature is around 0 ° C., the glass is easily broken when subjected to an impact due to transportation or the like, particularly at a low temperature lower than the temperature. So the inventors first
In order to improve the impact resistance of molded products at low temperatures, a polypropylene-based resin is extruded and foamed with a mixed resin containing an ethylene-1-butene copolymer or an ethylene-1-octene copolymer at a predetermined ratio. Formed foam sheet,
Alternatively, it has been proposed to manufacture a molded article such as a food container by using a laminated foam obtained by laminating a non-foamed sheet (unstretched sheet) of a polypropylene resin on the foamed sheet (Japanese Patent Application Laid-Open No. 8-259721, JP-A-10-601
No. 44).

However, according to further studies by the inventors, it has been found that a molded product obtained by thermoforming a foamed sheet or a laminated foam made of the above-mentioned mixed resin is particularly in a high temperature state such as when cooking with a microwave oven. In the case of a container having a wide opening such as a lunch box container, a noodle container, and a curry container, rigidity cannot be maintained, and the entire container is bent or deformed by the weight of the contents. It has been found that this causes a new problem that the contents are easily spilled.

Further, in the foamed sheet or laminated foam made of the above-mentioned mixed resin, the effect of improving the low-temperature impact resistance of the molded product still remains, as is clear from the results of Examples and Comparative Examples described later. Not enough, e.g.
No. 4337 or JP-A-11-170455.
It has also been found that the same improvement effect as that of a laminated foam obtained by laminating a biaxially stretched film of a polypropylene-based resin on a foamed sheet of a normal polypropylene-based resin disclosed in Japanese Unexamined Patent Publication (Kokai) No. H10-284,028 can be obtained.

An object of the present invention is to provide heat resistance, oil resistance and heat insulation which can be used for microwave cooking, as well as excellent rigidity at high temperatures and further improved impact resistance at low temperatures. Another object of the present invention is to provide a novel polypropylene-based resin laminated foam capable of producing excellent molded articles. Further, the other objects of the present invention are excellent in each of the above-described properties, and can be suitably used for food packaging containers and the like.
It is to provide a new molded product.

[0010]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors first set forth a polypropylene resin, an ethylene-1-butene copolymer, and an ethylene-1-
Of a molded article made of a foam sheet formed from a mixed resin with an ethylene-α-olefin copolymer such as an octene copolymer,
In order to improve the rigidity at high temperatures, a biaxially stretched film formed of the same type of polypropylene resin and having the function of imparting rigidity to the molded product even at high temperatures such as after heating in a microwave oven is laminated on the foamed sheet. Considered to do.

The present inventors have found that not only the rigidity of the molded article at high temperatures is improved, but also the surprisingly the impact resistance of the molded article at low temperatures is significantly improved more than expected. Was completed. That is, the polypropylene-based resin laminated foam of the present invention is formed on at least one surface of a foamed sheet formed from a mixed resin containing 98 to 60% by weight of a polypropylene-based resin and 2 to 40% by weight of an ethylene-α-olefin copolymer. A biaxially stretched film of a polypropylene resin is laminated.

According to the laminated foam of the present invention, the biaxially stretched film of the polypropylene resin having the function of imparting rigidity to the molded product even at a high temperature as described above is laminated, whereby And the stiffness at high temperatures is improved. Further, according to the laminated foam of the present invention, (1) a laminated foam in which the biaxially stretched film is laminated with a foamed sheet of a general polypropylene resin (the above-mentioned Patent No. 2904337)
JP-A-11-170455), or (2) a foamed sheet of a polypropylene-based resin containing an ethylene-α-olefin copolymer alone, or a non-stretched and non-stretched foamed sheet. A laminated foam obtained by laminating foam sheets (both described in JP-A-8-25972)
No. 1, JP-A-10-60144, etc.), the impact resistance of the molded article at low temperature is remarkably improved as described above.

The reason for this is that the lamination of a biaxially stretched film having high strength and excellent impact resistance has the effect of improving the impact resistance of a molded article as a whole in a wide temperature range, and the effect of the foam sheet By adding an ethylene-α-olefin copolymer having good dispersibility to the constituent polypropylene resin to absorb the energy of impact, the effect of improving the impact resistance of the foamed sheet, especially at low temperatures, is synergistic. The inventors consider that it functions effectively.

That is, in the laminated foam of (1) in which a biaxially stretched film is laminated with a foamed sheet of ordinary polypropylene resin, the biaxially stretched film imparts impact resistance to a molded product. At low temperatures, the impact resistance of the foamed sheet is greatly reduced, so when an impact is applied to the molded product, cracks are first generated in the foamed sheet, which propagates to the biaxially stretched film and the entire molded product becomes Will break. On the other hand, in the case of (2) a foamed sheet of a polypropylene-based resin containing an ethylene-α-olefin copolymer alone or a laminated foam obtained by laminating a non-stretched and non-foamed sheet thereon, the ethylene-α-olefin copolymer is used. It is thought that the higher the content of the polymer, the higher the impact resistance at low temperatures.However, when the ethylene-α-olefin copolymer is contained in a large amount, the foaming property of the polypropylene resin deteriorates. Thus, there arises a problem that a good foamed sheet cannot be manufactured by, for example, an extrusion foaming method. Therefore, since the content ratio of the ethylene-α-olefin copolymer is limited to 40% by weight or less as described above, the effect of improving the impact resistance at low temperatures is limited.

On the other hand, in the laminated foam of the present invention, as described above, a synergistic effect of the two, ie,
(A) biaxially stretched film laminated on at least one side of the foam sheet, ethylene-α- at a predetermined ratio as described above
By incorporating an olefin copolymer, the impact resistance at low temperatures is improved to some extent, and the foamed sheet that has been improved is further reinforced, and (b) a foamed sheet whose impact resistance at low temperatures is further improved by this reinforcement is Cracks are less likely to occur even when subjected to impact at low temperatures, preventing cracks from propagating to the biaxially stretched film.As a result, the impact resistance of molded products at low temperatures is higher than before. It is a significant improvement.

Further, the molded article of the present invention is produced by thermoforming the above-mentioned laminated foam, and is excellent in each of the above-mentioned properties, so that it can be suitably used for food packaging containers and the like suitable for microwave cooking. .

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below. <Polypropylene resin laminated foam> (Foam sheet) The polypropylene resin laminated foam of the present invention contains 98 to 60% by weight of the polypropylene resin and 2 to 40% by weight of the ethylene-α-olefin copolymer as described above. And a biaxially stretched film of a similar polypropylene resin is laminated on at least one surface of a foamed sheet formed from a mixed resin containing

Among these, the non-crosslinked polypropylene resin is preferable as the polypropylene resin constituting the mixed resin from which the foamed sheet is based, and the non-crosslinked polypropylene resin includes (A) a free terminal length in the molecule. Polypropylene resin having a chain branch (hereinafter referred to as “resin (A)”), and (B) melt tension is 0.01 to 10 g
Polypropylene resin (hereinafter referred to as “resin
(B) ”] is preferably used.

Among them, the resin (A) is not limited, but, for example, its melt tension is 6 g or more.
Those in the range of 0 g or less are preferred. If the melt tension of the resin (A) is less than 6 g, good foaming properties cannot be obtained, and if it exceeds 40 g, the flowability becomes extremely poor or gels are easily formed, resulting in extrusion. Workability may be reduced. The melt tension of the resin (A) is preferably 20 to 30 even within the above range.
g is preferred.

Resin having long branch of free terminal as described above
As (A), for example, the trade name Pro-, which is sold as a foaming grade by Montell SDK Sunrise, Inc.
fax PF-814, Pro-fax SD-632
And the like. The resin (A) has good foaming properties when foamed by extrusion foaming or the like, and has a low density, a high foaming ratio, for example, a density of less than 0.3 g / cm ³ , and particularly excellent heat insulation properties. Suitable for forming foam sheets.

However, since the resin (A) is expensive and may cause an increase in product cost, a foamed sheet can be formed by using the resin (A) alone as a polypropylene resin. It is preferable to form the foamed sheet by using the resin (A) and the resin (B) in combination as the polypropylene resin. Also in that case, a foam sheet having a relatively low density and a high foaming ratio and excellent heat insulation properties can be formed. As the resin (B), its melt tension is
As described above, it is preferable to use one having a range of 0.01 to 10 g.

That is, if the melt tension of the resin (B) is less than 0.01 g, the tension is too low, so that the obtained foamed sheet tends to have an open cell structure. Conversely, if it exceeds 10 g, the melt viscosity of the resin becomes too low. As a result, it becomes difficult to lower the resin temperature to near the melting point. Therefore, in either case, the quality of the foam sheet may be reduced. Resin (B)
Melt tension of 0.1 g especially in the above range
Or more and less than 6 g, preferably 0.1 g or more and 3 g or less.
More preferably, it is less than g.

Examples of the resin (B) include general-purpose polypropylene resins such as a propylene homopolymer and an ethylene-propylene copolymer which satisfy the above conditions. The ratio of the resin (A) to the total amount of the resin (A) and the resin (B) is preferably in the range of 10 to 50% by weight. The reason is as follows. That is, the resin (A) is a non-crosslinked general-purpose polypropylene resin that is usually not very good in foaming property, that is, the function of the free terminal long-chain branch introduced in the molecule, that is, the foaming property of the resin (B) is improved. It contributes to obtaining a foam sheet with heat insulation, oil resistance and heat resistance. However, due to the above-mentioned long chain branch at the free end, there is a problem that, especially among polypropylene resins in which the physical properties of the product tend to decrease over time under the influence of air oxidation, the tendency appears strongly. . In addition, since it is expensive as described above, there is a problem that the manufacturing cost of the product is increased.

Therefore, it is known to add a stabilizer to reduce the influence of air oxidation.
(A) has a low stabilizing effect due to the addition of a stabilizer, so that it is necessary to add a larger amount than usual, and since the stabilizer has a function of increasing the bubble diameter, a large amount is added. This causes problems such as an increase in the open cell ratio and a decrease in surface smoothness, which adversely affects the quality of the product. Further, since a large amount of stabilizer is required, there is a problem that the production cost of the product is further increased.

Therefore, in order to minimize the addition amount of the stabilizer and make it less susceptible to air oxidation, the proportion of the resin (A) to the total amount of the resin (A) and the resin (B) is required. However, as described above, the content is preferably 50% by weight or less. On the other hand, the foaming property of the resin (B) is improved so that the density of the resin (B) is reduced to 0.
In order to form a foamed sheet having a low density of less than 3 g / cm ^3, a high expansion ratio, and an excellent heat insulating property, the resin (A)
And the ratio of the resin (A) to the total amount of the resin (B),
It is preferably at least 10% by weight.

As described above, the resin (B) usually has a low foaming property, but has a density of, for example, 0.1.
It is possible to produce a foam sheet having a relatively low expansion ratio of ³ g / cm ³ or more. Therefore, the foamed sheet may be formed by using the resin (B) alone as the polypropylene resin. Examples of the ethylene-α-olefin copolymer that forms a foamed sheet together with the above polypropylene resin include, for example, at least one α-olefin selected from the group consisting of 1-butene, 1-hexene, and 1-octene. One or two or more of certain ethylene-1-butene copolymers, ethylene-1-hexene copolymers, and ethylene-1-octene copolymers may be mentioned.

The ethylene-α-olefin copolymer is not limited to the above, but may have a density in the range of 0.85 to 0.90 g / cm ³ , particularly 0.86 to 0.90 g / cm ^3.
Those in the range of 0.88 g / cm ³ are preferably used. The density of the ethylene-α-olefin copolymer is 0.
If it is less than 85 g / cm ³ , the strength of the foamed sheet and the degree of lowering of the rigidity of the molded product at high temperature may be increased when added to the polypropylene resin. Conversely, if the density exceeds 0.90 g / cm ³ , the effect of improving the low-temperature impact resistance of the molded article may not be sufficiently obtained.

Examples of such an ethylene-α-olefin copolymer include, for example, Espleno NO416 (trade name) manufactured by Sumitomo Chemical Co., Ltd., and Kernel KS240 (ethylene-butene copolymer) manufactured by Nippon Polychem Co., Ltd. 1
-Hexene copolymer) and Affinity EG8100 (ethylene-1-octene copolymer) manufactured by Dow Chemical Company. As described above, the foamed sheet is obtained by melt-kneading a mixed resin containing 98 to 60% by weight of the polypropylene resin and 2 to 40% by weight of the ethylene-α-olefin copolymer using, for example, an extruder together with a foaming agent. And then extruded through a mold connected to the extruder tip.

The content of the polypropylene resin in the mixed resin is 98% by weight or less and the content of the ethylene-α-olefin copolymer is limited to 2% by weight or more. This is because, when the content ratio of the olefin copolymer is small, the effect of improving the impact resistance of the foamed sheet at a low temperature due to the addition of the copolymer cannot be obtained. Conversely, when the content of the polypropylene-based resin in the mixed resin is 60% by weight or more,
And the content of the ethylene-α-olefin copolymer is 4
As described above, when the content of the ethylene-α-olefin copolymer is larger than this range, the foaming property of the polypropylene-based resin deteriorates, and the content is limited to 0% by weight or less. This is because there is a problem that a good foam sheet cannot be manufactured.

Examples of the foaming agent used for extrusion foaming include various volatile foaming agents and decomposition type foaming agents. Among them, examples of the volatile foaming agent include one or more of hydrocarbons such as propane, butane, and pentane, and halogenated hydrocarbons such as tetrafluoroethane, chlorodifluoroethane, and difluoroethane. It is preferably used.

Examples of the decomposable foaming agent include organic foaming agents such as azodicarbonamide and dinitrosopentamethylenetetramine, and inorganic foaming agents such as citric acid and sodium bicarbonate (sodium bicarbonate). In some cases, carbon dioxide, nitrogen gas, water, etc. may be used alone or
The foaming agent can be used as a foaming agent in combination with the above-mentioned volatile foaming agents or the like, or in combination with the volatile foaming agent.

In order to adjust the cell diameter of the foamed sheet after foaming, an organic acid such as talc or citric acid and sodium bicarbonate (sodium bicarbonate) or a salt thereof and a bicarbonate may be added to the mixed resin. Various additives such as a pigment, a stabilizer, a filler, and an antistatic agent may be appropriately added in addition to the cell regulator such as a combination of the above as long as the effects of the present invention are not impaired. Of these, fillers are added to improve the strength, rigidity at high temperature, durability and heat resistance of molded articles. Examples of such fillers include talc, calcium carbonate, silica, alumina, and titanium oxide. And inorganic fillers such as clay. The amount of the inorganic filler to be added is preferably in the range of 5 to 50 parts by weight based on 100 parts by weight of the mixed resin.

The foam sheet thus formed preferably has a density in the range of 0.1 to 0.85 g / cm ³ . If the density of the foamed sheet is less than 0.1 g / cm ³ , the strength of the molded article and the rigidity at high temperatures may be reduced. Conversely, if it exceeds 0.85 g / cm ³ , the heat insulating property of the molded article may be reduced. May decrease. Note that the density of the foamed sheet is particularly 0.18 to 0.6 g / cm even within the above range.
More preferably, it is ³ .

Although the thickness of the foamed sheet depends on the specifications of the target molded product, the thickness of the foamed sheet is not more than 0.1 in consideration of thermoformability.
It is preferable to be within a range of 5 mm or more and less than 2 mm. (Biaxially stretched film) Examples of the polypropylene resin forming the biaxially stretched film laminated on at least one surface of the foamed sheet include a propylene homopolymer, and a block copolymer of propylene and another resin. Or a random copolymer alone or 2
The seeds are mixed and used.

Other olefins other than propylene include ethylene and α-olefins having about 4 to 10 carbon atoms.
One or more kinds of olefins (1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, etc.) are exemplified. Particularly preferred polypropylene resins include, for example, propylene homopolymer, propylene-ethylene random copolymer, and block copolymer containing a propylene component and a propylene-ethylene random copolymer component.

Further, other resins may be mixed with the polypropylene resin within a range not to impair the effects of the present invention.
Examples of the other resin include homopolymers or copolymers such as ethylene and α-olefin, olefin resins such as polyolefin wax and polyolefin elastomer, petroleum resins, and hydrocarbon resins such as terpene resins. Are used singly or as a mixture of two or more.

The above-mentioned polypropylene resin may contain, if necessary, an antistatic agent, an antifogging agent, an antiblocking agent,
Various additives such as an antioxidant, a light stabilizer, a crystal nucleating agent, a lubricant, a surfactant for imparting slipperiness and an anti-blocking property, and a filler, as long as the effects of the present invention are not impaired, It may be added. The film is, for example, melt-kneaded with the above-mentioned polypropylene-based resin using an extruder, and then extruded into a film through a mold connected to the extruder tip, and the extruded film is extruded in the resin extrusion direction ( It is manufactured by stretching (biaxial stretching) simultaneously or sequentially in two directions of a longitudinal direction (MD) and a direction perpendicular thereto (lateral direction, TD).

The thickness of the biaxially stretched film is 6 to 100 μm.
It is preferably within the range of m. If the thickness of the biaxially stretched film is less than 6 μm, the effect of improving the low-temperature impact resistance of the molded product or the effect of improving the rigidity at high temperature may be insufficient. In this case, a large amount of heat is required when the axially stretched film is laminated on a foam sheet to produce a laminated foam, or when the produced laminated foam is thermoformed to produce a molded product. Therefore, the production efficiency may be deteriorated, and the appearance of the molded article may be deteriorated. The thickness of the biaxially stretched film is more preferably 10 to 60 μm even within the above range.

The area stretch ratio of the biaxially stretched film, that is, the area stretch ratio = (MD direction stretch ratio) × (TD direction stretch ratio) is preferably in the range of 4 to 50 times. If the area stretching ratio is less than 4 times, the effect of improving the impact resistance of the molded article at low temperatures or the effect of improving the rigidity at high temperatures may be insufficient, and conversely, it exceeds 50 times. In such a case, when a molded article is produced by thermoforming the laminated foam, the heat shrinkage of the film becomes large, and the molding accuracy of the molded article may be reduced. The area stretching ratio of the biaxially stretched film is more preferably 16 to 32 times even in the above range.

The biaxially stretched film may be a single layer or may have a laminated structure of two or more layers. Further, other films having different compositions may be laminated for the purpose of improving adhesiveness, heat sealing properties, gas barrier properties, and the like within a range that does not impair the effects of the present invention. Further, for the purpose of improving the appearance of the molded article and improving the sense of quality, the surface of the biaxially stretched film may be directly printed, or the printed film may be laminated.

(Laminated Foam) The polypropylene resin laminated foam of the present invention is produced by laminating a biaxially stretched film on at least one side of the polypropylene resin foam sheet described above. Also, at least one side of the foamed sheet used for the above-mentioned lamination is a layer of a non-stretched and non-foamed polypropylene resin (hereinafter referred to as “non-foamed layer”) by a coextrusion method, a laminating method or the like in advance.
May be laminated.

That is, the laminated foam of the present invention basically includes the following seven types of laminated structures (actually, here, there are variations due to the laminated structure of a biaxially stretched film as described above). Although the description is complicated, the biaxially stretched films in the following categories include all those having such a laminated structure in addition to those having a single layer). Two-layer structure of biaxially stretched film / foam sheet.

A three-layer structure of biaxially stretched film / foamed sheet / biaxially stretched film. Three-layer structure of biaxially stretched film / non-foamed layer / foamed sheet. Four-layer structure of biaxially stretched film / non-foamed layer / foamed sheet / biaxially stretched film. Three-layer structure of biaxially stretched film / foamed sheet / non-foamed layer. Four-layer structure of biaxially stretched film / non-foamed layer / foamed sheet / non-foamed layer.

A five-layer structure of biaxially stretched film / non-foamed layer / foamed sheet / non-foamed layer / biaxially stretched film. The non-foamed layer interposed below and in the biaxially stretched film improves the adhesiveness between the foamed sheet and the biaxially stretched film, or the laminated biaxially stretched film or the formed biaxially stretched film. It functions as a layer for improving the surface smoothness of the side surface. The non-foamed layer exposed on the surface of the laminated foam may be colored or printed on the surface.

As a method for producing the laminated foam of the present invention by laminating the above-mentioned respective layers, a conventionally known general laminating method such as a thermal laminating method or a laminating method using a hot melt adhesive is employed. be able to. <Molded article> Examples of the thermoforming method for producing the molded article of the present invention from the laminated foam include, for example, vacuum molding and pressure molding, or matched mold molding as these applications, plug assist molding, and the like. Conventionally known various molding methods can be adopted.

The molded article of the present invention thus manufactured has heat resistance since the foamed sheet and the biaxially stretched film constituting the container are both formed of a polypropylene resin.
It has excellent oil and chemical resistance, and is easy to recycle. In addition, since the foamed sheet is contained, it is excellent in heat insulation and heat retention, and has a structure in which the foamed sheet is reinforced with a biaxially stretched film, so that it has excellent rigidity at high temperatures. Moreover, as described above, the addition of the ethylene-α-olefin copolymer to the polypropylene resin constituting the foamed sheet and the reinforcement with the biaxially stretched film combined with the impact resistance particularly at low temperatures. Are better.

Therefore, the molded article of the present invention is suitable as various containers. In particular, the food, which is the content, is delivered to each store from a distribution center in a state where the food is refrigerated or frozen, and is stored at a store or at home. It is most suitable for food packaging containers such as convenience stores that can be brought back to and used for heating and cooking in a microwave oven.

[0048]

The present invention will be described below based on examples and comparative examples. In addition, each characteristic of the polypropylene resin used in each Example of this invention and the comparative example, and the manufactured molded product was measured by the following methods, respectively. <Melt Tension Measurement> The melt tension of the polypropylene resin was measured as follows using a measuring device [Capillograph PMD-C] manufactured by Toyo Seiki Seisaku-sho, Ltd.

That is, in a state where the sample resin was heated to 230 ° C. and melted, the descent speed of the piston was set to 10 mm / min from the nozzle (diameter 2.095 mm, length 8 mm) of the piston extrusion type plastometer of the above apparatus. The string-like material was passed through a tension detection pulley located 35 cm below the nozzle while being extruded into a string while being maintained at a constant speed of min. The film was wound up while being gradually increased at an acceleration of about 66 m / min ² , and the tension at the time when the string was cut was used as the melt tension of the sample resin.

However, in the case where the cord was not cut even when the winding speed exceeded 60 m / min, the tension at the winding speed of 60 m / min was defined as the melt tension of the resin. <Low-Temperature Impact Resistance Test> The impact resistance at low temperature of the molded product was measured by measuring the long side of the molded product obtained by thermoforming the laminated foam.
Place 250 cc of water in a 5 mm x 155 mm short side x 25 mm deep tray-shaped pasta container, leave it in a constant temperature room set at -30 ° C for 24 hours or more to freeze the water inside, then drop in the same room A test was performed and evaluated.

In the drop test, an acrylic plate tilted at an angle of 75 ° was placed at a predetermined height on the collision surface, and a pasta container with the water inside frozen on top of the opening was placed downward. When the pasta container is dropped from the plate with the ice inside and tilted from the top of the plate and collides with the collision surface,
The operation of observing whether or not cracks occurred was performed while increasing the drop height by 50 mm. The low-temperature impact resistance of the molded article was evaluated based on the maximum drop height (mm) at which no crack occurred. <High-Temperature Rigidity Test> The rigidity of a molded product at a high temperature was determined by placing 200 g of cold rice in a pasta container having the same dimensions as above, and outputting 1
When heated for 1 minute in a microwave oven of 500 W, removed immediately, and pasted with pasted rice, one short side of the pasta container is fixed horizontally in a hollow with 30 mm in width sandwiched between two plate-shaped brackets. Next, how many mm the upper edge of the opposite short side hangs down from the horizontal position was measured and evaluated.

In each of the following Examples and Comparative Examples,
As a raw material for producing a foam sheet, the resin (A)
The resin of the following A-1 belonging to the following, the following B- belonging to the resin (B)
1 and the following three resins C-1 to C-3 belonging to the ethylene-α-olefin copolymer were blended in the proportions shown in Table 1 and dry-blended 9 to 9 of I to IX.
Any of the resin mixtures was used. <Resin A-1> Propylene-ethylene block copolymer manufactured by Montell SDK Sunrise, trade name SD632 Melt tension: 21.9 g Melt index (MI) value: 3 Density: 0.90 g / cm ³ ] <Resin B- 1> Propylene homopolymer manufactured by Montell SDK Sunrise, trade name: PM600A Melt tension: 0.8 g MI value: 7.5 Density: 0.90 g / cm ³ <Resin C-1> Ethylene manufactured by Dow Chemical 1-octene copolymer, trade name Affinity EG8100 Density: 0.87 g / cm ³ <Resin C-2> ethylene-1-butene copolymer manufactured by Sumitomo Chemical Co., Ltd., trade name Espleno NO416 Density: 0.87 g / cm ³ <Resin C-3> Ethylene-1-hexene copolymer manufactured by Nippon Polychem Co., Ltd., product name: Kernel KS240 Density: 0. 88 g / cm ³

[0053]

[Table 1]

Example 1 <Preparation of foamed sheet> The resin mixture of I in Table 1 was supplied to a hopper of a tandem extruder (diameter φ90-φ115) having first and second two extruders. While melting and mixing in the first extruder connected to the hopper, butane as a foaming agent was injected. Pressurized amount of butane is resin 1
2.0 parts by weight per 00 parts by weight.

Then, the melted and mixed mixture was continuously supplied from the first extruder to the second extruder, cooled uniformly in the second extruder, and connected to the tip of the second extruder. From a 240 mm bore cylindrical die
Foaming was performed while continuously extruding a cylindrical shape into the atmosphere at a discharge amount of 10 kg. Next, the obtained cylindrical foam was cooled from the inside of the cylinder along a mandrel having a diameter of 680 mm cooled with water at 20 ° C., and air was blown from an air ring larger than the outer shape of the cylinder. After cooling from the outside of the cylinder, it was cut with a cutter at two points on the circumference to produce a long foam sheet having the density and thickness shown in Table 2.

<Production of Laminated Foam> A biaxially stretched film of a polypropylene resin having a thickness and a draw ratio shown in Table 2 was placed on one side of the foamed sheet prepared as described above, while the respective MD directions were matched. The laminate was continuously laminated and integrated by a lamination method to produce a laminated foam. <Manufacture of molded article> The laminated foam is thermoformed by vacuum forming so that the film side surface is the inner surface side of the container, and the tray-shaped pasta container (long side 195 mm × (Short side 155 mm x depth 25 mm).

Example 2 The same polypropylene-based resin as used in Example 1 was used on both surfaces of the manufactured foam sheet by using the resin mixture of II in Table 1 as a raw material of the foam sheet. Was obtained in the same manner as in Example 1 except that the biaxially stretched films were continuously laminated and integrated while matching their MD directions, to obtain a pasta container as a foamed sheet, a laminated foam and a molded product.

Example 3 One side of the foam sheet, which is the inner side of the container, had a diameter of 65 mm.
A non-foamed layer of a polypropylene resin (trade name: PM600A, manufactured by Montell SDK Sunrise Co., Ltd.) is laminated by a co-extrusion method using an extruder, and the foam sheet is opposite to the outer surface side of the container. A biaxially stretched film of the same polypropylene resin as used in Example 1 was applied to one side of each side by thermal lamination.
A foamed sheet, a laminated foam, and a pasta container as a molded product were obtained in the same manner as in Example 1 except that the layers were continuously laminated and integrated while matching the direction D.

Example 4 A foamed sheet, a laminated foam and a pasta container as a molded product were obtained in the same manner as in Example 1 except that the resin mixture shown in Table 1 was used as a raw material of the foamed sheet. Example 5 A resin mixture of IV in Table 1 was used as a raw material of a foamed sheet, and two sides of a polypropylene resin having a thickness and a draw ratio shown in Table 2 were respectively applied to both surfaces of the produced foamed sheet by a thermal lamination method. A foamed sheet, a laminated foam, and a pasta container as a molded product were obtained in the same manner as in Example 1, except that the axially stretched films were continuously laminated and integrated while the respective MD directions were matched.

Example 6 A foamed sheet, a laminated foam and a pasta container as a molded product were obtained in the same manner as in Example 1 except that the resin mixture shown in Table 1 was used as a raw material of the foamed sheet. Example 7 The resin mixture of VI shown in Table 1 was used as a raw material for a foamed sheet, and the thickness and the stretching ratio shown in Table 2 were applied to one side of the manufactured foamed sheet, which is the outer surface side of the container, by a thermal lamination method. A foamed sheet, a laminated foam, and a pasta container as a molded product in the same manner as in Example 1 except that a biaxially stretched film of a polypropylene-based resin having the same is continuously laminated and integrated while matching their MD directions. I got

Example 8 A foamed sheet, a laminated foam and a pasta container as a molded product were obtained in the same manner as in Example 1 except that the resin mixture of VII in Table 1 was used as a raw material of the foamed sheet. Comparative Example 1 A pasta container as a molded product was manufactured using the same foamed sheet alone before laminating a film as in Example 1.

Comparative Example 2 A foamed sheet was prepared in the same manner as in Example 1 except that the resin mixture of VIII in Table 1 was used as a raw material of the foamed sheet. A container was manufactured. Comparative Example 3 A foamed sheet was produced in the same manner as in Example 1 except that the resin mixture of III in Table 1 was used as a raw material of the foamed sheet, and a pasta container as a molded article was manufactured using the foamed sheet alone. did.

Comparative Example 4 A non-foamed layer of the same polypropylene resin was laminated on one side of the same foamed sheet produced in Example 1 as the inner side of the container by the same coextrusion method as in Example 3. A laminated foam was used, and a pasta container as a molded product was manufactured using the laminated foam. Comparative Example 5 A foamed sheet, a laminated foam, and a pasta container as a molded product were obtained in the same manner as in Example 1 except that the resin mixture of IX in Table 1 was used as a raw material of the foamed sheet.

Comparative Example 6 A foamed sheet, a laminated foam and a pasta container as a molded product were obtained in the same manner as in Example 2 except that the resin mixture of VIII in Table 1 was used as a raw material of the foamed sheet. Table 2 shows the above results.

[0065]

[Table 2]

From the results of Comparative Examples 1 to 3 in the table, all of the molded products obtained by thermoforming the foam sheet alone have low rigidity at high temperature, and even if the polypropylene resin constituting the foam sheet is ethylene-α-olefin. Even when the copolymer was added (Comparative Examples 1 and 3), it was found that the impact resistance at low temperature was insufficient. This was the same for Comparative Example 4 in which only a non-stretched layer made of a polypropylene resin was laminated on one surface of the foamed sheet.

From the results of Comparative Examples 5 and 6, when the ethylene-α-olefin copolymer was not added to the polypropylene resin constituting the foamed sheet, it was assumed that a biaxially stretched film was laminated on one or both sides thereof. It was also found that the molded article had insufficient impact resistance at low temperatures. On the other hand, from the results of Examples 1 to 8, the laminated foam obtained by adding the ethylene-α-olefin copolymer to the polypropylene resin constituting the foamed sheet and laminating the biaxially stretched film on one or both surfaces thereof It was confirmed that all of the molded products manufactured from No. 4 were excellent in rigidity at high temperatures and extremely good in impact resistance at low temperatures.

[0068]

As described in detail above, according to the present invention,
To produce a good molded product that has heat resistance, oil resistance, heat insulation, excellent rigidity at high temperature, and more improved impact resistance at low temperature than before, which can be used for microwave cooking. The present invention has a specific effect of being able to provide a novel polypropylene-based laminated resin foam and a molded article using the same, which is excellent in each of the above-mentioned properties.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Eiji Asada 7-488-1 Nanjing Shumachi, Nara City, Nara Prefecture B202 (72) Inventor Masao Oi 2-6, Jonanmachi, Yamatokoriyama City, Nara Prefecture (72) Inventor Nishioka Taku 153-1 Kamitakino, Takino-cho, Kato-gun, Hyogo (72) Inventor Shizuo Sekiguchi F-term (reference) 3E033 AA10 BA14 BA16 BA30 BB08 CA03 CA08 FA04 GA03 4F074 AA17 AA24 AB02 BA37 CA22 CC03X CC04X CC04Y CE02 DA02 DA20 DA34 4F100 AK07A AK07B AK07C AK62A AK65A AK66A AL05A BA02 BA03 BA06 BA07 BA10B BA10C CA01 EC03 EC033 EH17 EH172 EJ02 EJ02A EJ022 EJ38A EJ38A EJ38A EJ38A EJ38A EJ38A EJ38A

Claims (6)

[Claims] (1) 98 to 60% by weight of a polypropylene resin
And 2 to 40% by weight of an ethylene-α-olefin copolymer
And a biaxially stretched film of a polypropylene-based resin laminated on at least one surface of a foamed sheet formed from a mixed resin containing: 2. The polypropylene resin laminated foam according to claim 1, wherein the density of the ethylene-α-olefin copolymer is 0.85 to 0.90 g / cm ³ . 3. The polypropylene resin laminated foam according to claim 1, wherein the α-olefin is at least one selected from the group consisting of 1-butene, 1-hexene, and 1-octene. 4. A polypropylene resin forming a foamed sheet, comprising: (A) a polypropylene resin having a free terminal long-chain branch in a molecule; and (B) a melt tension of 0.01 to 10.
The polypropylene-based resin laminated foam according to claim 1, wherein the foam is at least one selected from the group consisting of polypropylene-based resins within the range of g. 5. A foam sheet having a density of 0.1 to 0.85 g /
The polypropylene-based resin laminated foam according to claim 1, which is in a range of cm ³ . 6. A molded article produced by thermoforming the polypropylene resin laminated foam according to any one of claims 1 to 5.