JP2005081796A - Propylene resin foam sheet and container - Google Patents

Abstract

【Task】
Provided is a propylene-based resin foam sheet excellent in design and rigidity.
[Solution]
Non-foamed layer 1 containing 100 parts by weight of propylene-based resin and 10 to 100 parts by weight of talc, 100 parts by weight of propylene-based resin and 1 to 100 parts by weight of pigment, and containing no talc A propylene-based resin foam sheet produced by coextrusion having a foam layer 2, wherein at least one surface of the propylene-based resin foam sheet is a non-foam layer 2, and the foam layer, the non-foam layer 1 and the non-foam layer 2 A propylene-based resin foam sheet, wherein the weight ratio is foam layer: non-foam layer 1: non-foam layer 2 = 100: (50-100) :( 5-20).
[Selection figure] None

Description

The present invention relates to a propylene-based resin foam sheet excellent in design and rigidity and a container obtained by vacuum forming the foam sheet.

Propylene-based resin foam sheets are excellent in heat insulation, light weight, heat resistance, recyclability, and the like, and therefore demand is increasing as packaging containers for foods. However, when a propylene-based resin foam sheet is used as a packaging container, the rigidity is often insufficient. In order to solve such a problem, a propylene-based resin foam sheet having a foam layer and a non-foam layer containing talc in both outer layers is disclosed (for example, see Patent Document 1).

Japanese Patent Laid-Open No. 11-277696

In a packaging container, design is emphasized in addition to rigidity. In particular, when used as a container for food packaging, the food of the contents looks delicious and a design property that enhances the consumer's willingness to purchase is required.
As a method for imparting design properties to the propylene-based resin foam sheet, a method of pasting a film or a colored film printed on the foam sheet, or a surface layer of the foam sheet disclosed in Patent Document 1, that is, a talc-containing non-foam layer is used. A method of coloring a talc-containing non-foamed layer by adding a pigment to the constituent material is mentioned.

However, when the film is bonded to the foamed sheet as in the former, vacuum forming becomes difficult and the appearance of the resulting container often becomes poor. In addition, when the talc-containing non-foamed layer is colored as in the latter case, the surface of the resulting container is inferior in gloss, and it is often impossible to obtain a container that enhances consumers' willingness to purchase.
Therefore, as a result of studies to develop a propylene-based resin foam sheet having excellent design properties and rigidity and a container having excellent design properties and rigidity obtained by molding a propylene-based resin foam sheet, the present invention has been achieved. It was.

That is, the present invention comprises a foamed layer composed of a propylene-based resin, a non-foamed layer 1 containing 100 parts by weight of a propylene-based resin and 10 to 100 parts by weight of talc, 100 parts by weight of a propylene-based resin, and 1 to 100 parts by weight of a pigment. A propylene-based resin foam sheet produced by coextrusion having a non-foamed layer 2 containing no talc, wherein at least one side of the propylene-based resin foam sheet is the non-foamed layer 2, and the foamed layer, the non-foamed layer 1 and Propylene-based resin foam sheet, wherein the weight ratio of the non-foamed layer 2 is foamed layer: non-foamed layer 1: non-foamed layer 2 = 100: (50-100) :( 5-20) A container obtained by vacuum forming a resin foam sheet, wherein the non-foamed layer 2 is located inside the container, and the container for food packaging It is a vessel.

The propylene-based resin foam sheet of the present invention is a propylene-based resin foam sheet having gloss on the surface, excellent design properties, and excellent rigidity. Since the propylene-based resin foam sheet has good secondary processability such as vacuum forming, the container obtained by vacuum-forming such a propylene-based resin foam sheet has a glossy surface and a beautiful design It is a container with excellent properties and rigidity. Such a container is suitably used for food packaging.

The propylene-based resin foam sheet of the present invention has a foam layer made of a propylene-based resin. The foaming ratio of the foamed layer is usually 2 times or more, and is preferably 4 to 10 times, more preferably 5 to 10 times, from the viewpoint of the balance between heat insulation, lightness, and rigidity. The expansion ratio can be adjusted by appropriately changing the amount of the foaming agent to be used and the processing conditions during sheet production.

The propylene resin constituting the foam layer is not particularly limited, and examples thereof include a propylene homopolymer and a propylene copolymer containing 50 mol% or more of propylene-derived repeating units. The copolymer may be any of a block copolymer, a random copolymer, and a graft copolymer. As an example of the propylene-based copolymer that is preferably used, a copolymer of ethylene or an α-olefin having 4 to 10 carbon atoms and propylene can be given. Examples of the α-olefin having 4 to 10 carbon atoms include 1-butene, 4-methylpentene-1, 1-hexene, and 1-octene. The content of repeating units other than those derived from propylene in the propylene-based copolymer is preferably 15 mol% or less for ethylene and 30 mol% or less for α-olefins having 4 to 10 carbon atoms. One type of propylene resin may be used, or two or more types may be mixed and used.

By using 50% by weight or more of the total propylene resin, a long chain branched propylene resin or a high molecular weight propylene resin having a weight average molecular weight of 1 × 10 ⁵ or more as the propylene resin constituting the foamed layer is obtained. A sheet having a foamed propylene-based resin foam layer can be obtained.

Here, the long-chain branched propylene-based resin refers to a propylene-based resin having a degree of branching index [A] satisfying 0.20 ≦ [A] ≦ 0.98.
An example of a long-chain branched propylene resin satisfying a branching index [A] of 0.20 ≦ [A] ≦ 0.98 is a propylene resin PF-814 manufactured by Basel.

The degree of branching index indicates the degree of long chain branching in a polymer, and is a numerical value defined in the following formula.
Branching degree index [A] = [η] _Br / [η] _Lin
Here, [η] _Br is the intrinsic viscosity of the propylene-based resin having long chain branches, and [η] _Lin is a linear chain having the same composition and the same weight average molecular weight as the propylene-based resin having long chain branches. This is the intrinsic viscosity of the propylene resin.
Intrinsic viscosity, also called intrinsic viscosity, is a measure of the ability of a polymer to enhance solution viscosity. Intrinsic viscosity depends in particular on the molecular weight of the polymer molecules and the degree of branching. Therefore, by comparing the intrinsic viscosity of a polymer having long chain branches with the intrinsic viscosity of a linear polymer having the same weight average molecular weight as that of the polymer having long chain branches, the degree of branching of the polymer having long chain branches can be determined. It can be a scale. The method for measuring the intrinsic viscosity of a propylene-based resin is described by Elliott et al. [J. Appl. Polym. Sci. , 14, 2947-2963 (1970)], for example, a propylene resin is dissolved in tetralin or orthodichlorobenzene, and the intrinsic viscosity at 135 ° C. Can be measured.
The weight average molecular weight (Mw) of the propylene-based resin can be measured by various commonly used methods. L. The method disclosed by McConnel in American Laboratory, May, 63-75 (1978), that is, a low-angle laser light scattering intensity measurement method is particularly preferably used.
Examples of a method for polymerizing a high molecular weight propylene resin having a weight average molecular weight of 1 × 10 ⁵ or more include the method described in JP-A No. 11-228629.

Among long-chain branched propylene resins or high molecular weight propylene resins having a weight average molecular weight of 1 × 10 ⁵ or more, the uniaxial melt extensional viscosity ratio η ₅ / η _0.1 measured under the following conditions in the vicinity of the melting point + 30 ° C. is 5 The propylene-type resin which is the above is preferable, More preferably, it is 10 or more resin. The uniaxial melt extensional viscosity ratio is a value measured using an apparatus such as a uniaxial extensional viscosity measurement apparatus (for example, a uniaxial extensional viscosity measurement apparatus manufactured by Rheometrics, Inc.) at an extension strain rate of 1 sec ⁻¹ . the uniaxial melt elongation viscosity after 0.1 seconds from the strain initiation and eta _0.1, the uniaxial melt elongation viscosity after 5 seconds and eta _5. By using a propylene resin having such uniaxial extensional viscosity characteristics, a propylene resin foam sheet having finer bubbles can be produced.

The foam layer of the propylene-based resin foam sheet of the present invention may contain one or more thermoplastic resins other than the propylene-based resin. Other thermoplastic resins include olefin resins other than propylene resins, ethylene-vinyl ester copolymers, ethylene- (meth) acrylic acid copolymers, ethylene- (meth) acrylic acid ester copolymers, polyester-based resins. Examples thereof include resins, polyamide resins, polystyrene resins, acrylic resins, acrylonitrile resins, polyvinyl alcohol, ionomer resins and the like. When the foamed layer contains other thermoplastic resin, the content thereof is a level that does not hinder the effects of the present invention, and is usually 10 wt% or less. Specific examples of olefin resins include copolymerization of olefin homopolymers having 6 or less carbon atoms such as ethylene, butene, pentene, and hexene, or two or more monomers selected from olefins having 2 to 10 carbon atoms. Olefin copolymers and the like. The olefin copolymer may be a block copolymer, a random copolymer, or a graft copolymer. Examples of the ethylene resin that is one kind of olefin polymer include low density polyethylene, ultra-low density polyethylene, linear low density polyethylene, and high density polyethylene.

As the foaming agent used for forming the foamed layer of the propylene-based resin foamed sheet of the present invention, either a so-called chemical foaming agent or a physical foaming agent may be used, or these may be used in combination. Examples of the chemical foaming agent include a thermal decomposition type foaming agent that decomposes to generate nitrogen gas (azodicarbonamide, azobisisobutyronitrile, dinitrosopentamethylenetetramine, p-toluenesulfonylhydrazide, p, p'- Oxy-bis (benzenesulfonyl hydrazide) and the like, and pyrolytic inorganic foaming agents that decompose to generate carbon dioxide (sodium hydrogen carbonate, ammonium carbonate, ammonium bicarbonate, etc.) . Specific examples of the physical foaming agent include propane, butane, water, carbon dioxide gas, and the like. Of the above-exemplified foaming agents, water, carbon dioxide, and the like are suitably used because they are substances that are inert to high temperature conditions and fire. In this embodiment, the amount of the foaming agent used is appropriately selected according to the type of foaming agent and resin used so that a desired foaming ratio can be obtained, and foaming is usually performed with respect to 100 parts by weight of the propylene resin. 0.5 to 20 parts by weight of the agent.

The propylene-based resin foam sheet of the present invention has a non-foamed layer 1 containing 100 parts by weight of a propylene-based resin and 10 to 100 parts by weight of talc.
By setting the content of talc within the above range, when the foamed sheet of the present invention is molded into a container, a container having excellent rigidity can be obtained. If the blending amount of talc is too small, it will be difficult to obtain the rigidity required for use as a container, and if it is too large, the dispersion of talc will be poor, so that there will be a tendency that the rigidity commensurate with the content cannot be obtained. The talc contained in the non-foamed layer 1 preferably has an average particle diameter in the range of 0.1 to 50 μm from the viewpoints of rigidity, heat resistance, vacuum formability of the foamed sheet, and the like.

The propylene-based resin foam sheet of the present invention has a non-foamed layer 2 containing 100 parts by weight of a propylene-based resin and 1 to 100 parts by weight of a pigment and containing no talc.
The amount of the pigment contained in the non-foamed layer 2 is in the range of 1 to 100 parts by weight, although the optimum blending amount differs for each target color. When the blending amount is too small, the color becomes light, and when the blending amount is too large, the color becomes too dark or the weight becomes heavy. For example, when the non-foamed layer 2 is white, red, yellow, or the like, it is preferable to add 1 to 15 parts by weight of the pigment with respect to 100 parts by weight of the propylene-based resin, and 10 to 50 parts by weight for dark red and black. It is preferable.
The pigment to be used is not particularly limited, and a known inorganic or organic pigment can be used. As an inorganic pigment, any one of red and dark red pigments containing cadmium (Cd) or iron oxide (Fe ₂ O ₃ ), titanium (Ti), barium (Ba), zinc (Zn), calcium carbonate (CaCO ₃ ) And white pigments containing silica, yellow pigments containing any of silica (Si), titanium (Ti) and iron sulfate (FeSO ₄ ), black pigments containing carbon or iron tetroxide (Fe ₃ O ₄ ), and the like.
As organic pigments, red pigments containing any of azo compounds, anthraquinone compounds, perylene compounds, azo compounds, benzimidazoline compounds, yellow pigments containing isoindolinone compounds, aniline compounds And black pigments containing

The non-foamed layer 2 does not contain talc. When talc is contained, the reason for this is not clear, but the surface glossiness is lost, so that the design is inferior.

The propylene-based resin foam sheet of the present invention is the non-foamed layer 2 on at least one side. A molded product such as a container obtained by molding such a foamed sheet by a method such as vacuum molding is a molded product containing a pigment and containing no talc on the non-foamed layer 2 side and having excellent gloss. The non-foamed layer 2 may be one side of the foamed sheet or both sides. In the case where the non-foamed layer 2 is one side of the foamed sheet, the non-foamed layer 2 may be molded so that the glossy side of the molded product is required.

When the propylene-based resin foam sheet of the present invention is produced by a method of extruding from a circular die and expanding with a mandrel, the surface of the propylene-based resin foam sheet that contacts the mandrel is preferably the non-foamed layer 1. Since the non-foamed layer 1 containing talc and the mandrel come into contact with each other when the propylene-based resin foam sheet is taken up, the take-up becomes smooth and the appearance of the resulting foamed sheet is improved.

The propylene-based resin constituting the non-foamed layer 1 and the non-foamed layer 2 may be the same as or different from the propylene-based resin constituting the foamed layer. Similarly to the foamed layer, the non-foamed layer 1 and the non-foamed layer 2 may contain other thermoplastic resins other than the propylene-based resin as long as the effects of the present invention are not impaired.

The propylene-based resin foam sheet of the present invention may have at least one foamed layer made of propylene-based resin, non-foamed layer 1 and non-foamed layer 2, respectively, and a foamed layer made of other than propylene-based resin, A non-foamed layer other than the non-foamed layer 1 and the non-foamed layer 2 may be provided. The resin constituting the non-foamed layer other than the non-foamed layer 1 and the non-foamed layer 2 is not particularly limited, and examples thereof include propylene-based resins and saponified ethylene-vinyl ester copolymers.

The propylene-based resin foam sheet is not particularly limited as long as at least one side is the non-foamed layer 2, but has two foam layers 1, and the two layers of the non-foamed layer 1 are between the two layers. A configuration in which the foam layer is located is preferable from the viewpoint of the bending rigidity of the foam sheet. Further, in order to obtain a foam sheet having more excellent gloss, the non-foamed layer 2 is preferably adjacent to the non-foamed layer 1. By setting it as such a structure, it is estimated that the gloss of the non-foamed layer 2 can be made more conspicuous by the non-foamed layer 1 containing talc.

In the propylene-based resin foam sheet of the present invention, the weight of the non-foamed layer 1 and the non-foamed layer 2 is 50 to 100 parts by weight of the non-foamed layer 1 with respect to 100 parts by weight of the foamed layer. ~ 20 parts by weight. The weight of each layer is the total weight of the corresponding layers when there are one or more foamed layers, non-foamed layers 1 and non-foamed layers 2 respectively.
When the weight of the non-foamed layer 1 is too light, the appearance of the foamed sheet and the container obtained by molding the foamed sheet tends to be poor. When the weight is too heavy, the basis weight of the foamed sheet becomes large and light weight Tend to be impaired.
If the weight of the non-foamed layer 2 is too light or too heavy, the gloss of the foamed sheet and the container obtained by molding the foamed sheet tends not to be excellent.

Although the thickness of the propylene-type resin foam sheet of this invention is not specifically limited, Usually, it is 0.1-3 mm. If the thickness of the foamed sheet is too thin, the heat insulating property tends to be insufficient, and if it is too thick, secondary forming such as vacuum forming tends to be difficult.

Each layer which comprises the propylene-type resin foam sheet of this invention may contain an additive to such an extent that the effect of this invention is not inhibited. However, the non-foamed layer 2 does not contain talc. Examples of the additive include an antioxidant, a light stabilizer, an ultraviolet absorber, a plasticizer, an antistatic agent, a release agent, a fluidity imparting agent, a lubricant, and a filler.
When the non-foamed layer 2 contains a filler other than talc, it is preferable that the particle size of the contained filler is small in order to maintain surface gloss.

The method for producing the propylene-based resin foam sheet of the present invention is not particularly limited as long as it is a co-extrusion method, and a flat die (T die) in a state in which materials constituting each layer melt-kneaded by an extruder are laminated. A method is preferably used in which a foamed layer is extruded from a die such as a circular die while being foamed and cooled while being stretched along a mandrel or the like as necessary. It is also possible to perform stretching after the molten resin is extruded from a die and cooled and solidified. The propylene-based resin foam sheet of the present invention obtained by the coextrusion method is excellent in vacuum formability.

Since the propylene-based resin foam sheet of the present invention is excellent in surface gloss, heat insulation, light weight, and heat resistance, secondary molding such as vacuum molding, pressure molding, vacuum pressure molding, etc. is performed, such as cups, trays, bowls, etc. It is molded into containers of various shapes and is suitably used for food packaging and electronic component packaging. Since the propylene-based resin foam sheet of the present invention is excellent in secondary moldability, a container having a beautiful shape can be obtained.
When using the obtained container as a container for food packaging, it is preferable from the viewpoint of design that the non-foamed layer 2 is located inside the container, that is, the side in contact with the food to be packaged. The food packaged in the container of the present invention that is excellent in glossiness will inspire consumers to purchase.

As a method of producing a container by secondary molding of a foam sheet, the foam sheet is heated and softened by an infrared heater or the like, and then, using a mold such as a male mold, a female mold, or a male-female mold, a vacuum is formed. Examples thereof include a method of forming and cooling and solidifying by a secondary forming method such as forming, pressure forming, and vacuum pressure forming. When vacuum-forming or vacuum-pressure forming using a male-female pair, or a plug and female mold similar in shape to a male mold, the male mold is always brought into close contact with the female mold by vacuum and at the same time the male mold contacts the foamed sheet. It is not necessary to make it, and it can be pre-shaped with a male mold before the female mold and the sheet come into contact with each other, or it can be molded with the male mold immediately after the female mold and the sheet are brought into close contact with each other by vacuum or compressed air. Alternatively, the sheet can be formed by sucking a vacuum from the female mold while blowing the sheet to the female mold with compressed air, and finally pushing the inside of the container with a male mold or a plug. The vacuum forming method is preferred because it is difficult to damage the foamed layer by molding and deformation after molding is small.

EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, this invention is not limited to an Example at all.

[Example 1]
By the method shown below, a three-kind / four-layer propylene-based resin foamed sheet in which a non-foamed layer 1 is laminated on both sides of a propylene-based resin foamed layer and a non-foamed layer 2 is further laminated on one non-foamed layer 1 Produced.

(Propylene polymer pelletization)
With respect to 100 parts by weight of the propylene polymer powder obtained by the method disclosed in JP-A-11-228629, 0.1 part by weight of calcium stearate, phenolic antioxidant (trade name: Irganox 1010, Ciba Specialty) Chemicals) 0.05 parts by weight, phenolic antioxidant (trade name: Sumilizer BHT, manufactured by Sumitomo Chemical Co., Ltd.) 0.2 parts by weight, mixed, kneaded at 230 ° C., melt flow rate A pellet (i) having an (MFR) of 4.5 g / 10 min (230 ° C., 2.16 kgf) was obtained.
The physical properties of the resulting propylene polymer are as follows.
Properties of propylene polymer: Intrinsic viscosity ([η] of component (A) (high molecular weight component of the two components contained in the propylene polymer obtained by the method disclosed in JP-A-11-228629) A) = 9.5 dl / g, ethylene unit content in component (A) (C2inA) = 2.9%, intrinsic viscosity of component (B) ([η] B) = 11 dl / g, component (B) The ethylene unit content (C2inB) in the (low molecular weight component of the two components contained in the propylene polymer obtained by the method disclosed in JP-A-11-228629) = 2.7%. Η ₅ = 300,000 Pa · s at 180 ° C. and η _0.1 = 2900 Pa · s measured using a uniaxial extensional viscosity measuring device manufactured by Rheometrics.

(Foam layer material)
Propylene polymer pellet (i) obtained by the above method, propylene resin (ii) (manufactured by Sumitomo Chemical Co., Ltd., polypropylene R101 MFR = 20 g / 10 min (230 ° C. 2.16 kgf)), propylene resin (Iii) Polypropylene U101E9 MFR = 120 g / 10 min (230 ° C. 2.16 kgf) manufactured by Sumitomo Chemical Co., Ltd. was dried at a weight ratio of (i) / (ii) / (iii) = 70/21/9 wt. Blended to obtain a foam layer material.

(Material for non-foamed layer 1)
Propylene resin (iv) (Homopolypropylene FS2011DG2 MFR 2.5 g / 10 min (230 ° C. 2.16 kgf) manufactured by Sumitomo Chemical Co., Ltd.) and propylene resin (v) (Propylene-ethylene manufactured by Sumitomo Chemical Co., Ltd.) Copolymer W151 MFR 8 g / 10 min (230 ° C. 2.16 kgf)), propylene resin (vi) (long-chain branched homopolypropylene PF814 MFR 3 g / 10 min (230 ° C. 2.16 kgf) manufactured by Basel), talc master batch (Vii) (Sumitomo Chemical Co., Ltd. block polypropylene base talc masterbatch MF110 talc content 70 wt%), titanium masterbatch (viii) (Tokyo Ink Co., Ltd. titanium masterbatch PPM2924 titanium content 60 wt% Random PolyPro Pyrene-based MFR 30 g / 10 min (230 ° C. 2.16 kgf)) is dried at a weight ratio of (iv) / (v) / (vi) / (vii) / (viii) = 12/15/30/43/5 Blended to obtain a material for the non-foamed layer 1.

(Material for non-foamed layer 2)
Propylene resin 6 (ii) (Homopolypropylene R101 made by Sumitomo Chemical Co., Ltd.) and cadmium pigment masterbatch (ix) for candy (1T1040, manufactured by Sumika Color Co., Ltd.) Pigment content 30 wt% Random polypropylene base MFR 30 g / 10 min (230 C. 2.16 kgf)) was dry blended at a weight ratio of (ii) / (ix) = 100/100 to obtain a non-foamed layer 2 material.

(Propylene-based resin foam sheet manufacturing method)
Using the foam layer material, the non-foam layer 1 material, and the non-foam layer 2 material, a 50 mmφ twin-screw extruder (2) for extruding the foam layer and a 32 mmφ single-screw extruder for extruding the non-foam layer 1 1 (3), non-foamed layer 2 Extrusion molding is performed by a device (1) having a 90 mmφ circular die (5) attached to a 32 mmφ single screw extruder 2 (4) for extrusion, and propylene-based resin foaming is performed as follows A sheet was obtained.

A raw material obtained by blending 2 parts by weight of a nucleating agent (Baylinger Ingelheim Chemicals Hydrocerol) with 100 parts by weight of the foam layer material was put into a hopper of a 50 mmφ twin screw extruder (2) and heated to 180 ° C. Kneading in a cylinder.

The pump (6) connected to the liquefied carbon dioxide gas cylinder when the foam layer material and the nucleating agent are sufficiently melt-kneaded and compatible in the 50 mmφ twin screw extruder (2), and the nucleating agent is decomposed and foamed by heat. Further, 1 part by weight of carbon dioxide gas was injected as a physical foaming agent. After carbon dioxide gas injection, the mixture was further kneaded and impregnated with carbon dioxide gas, and then supplied to the circular die (5).
The material for the non-foamed layer 1 was melt-kneaded by a 32 mmφ single-screw extruder (3) and supplied to the circular die (5).
The material for the non-foamed layer 2 was melt-kneaded by a 32 mmφ single-screw extruder (4) and supplied to the circular die (5).

As shown in FIG. 2, in the circular die (5), the foam layer material is introduced into the die from the head (8) of the 50 mmφ twin screw extruder, and sent to the die exit direction by the flow path (11a). On the way, it branched through the path P and sent to the flow path (11b).
The material for the non-foamed layer 1 is introduced into the die from the head (9) of the 32 mmφ single-screw extruder (3), divided into flow paths (12a) and (12b), and then on both sides of the flow path (11b). While being fed so as to be laminated, it was sent in the direction of the die exit, and joined in a multilayer shape in (14a). The material for the non-foamed layer 1 supplied to the flow paths (12a) and (12b) is branched in the middle by a divided flow path (not shown) similar to the path P, and flows into the flow paths (12c) and (12d). After being sent, it was sent in the direction of the die exit while being supplied so as to be laminated on both surfaces of the flow path (11a), and merged in multiple layers in the flow path (14b).

The material for the non-foamed layer 2 is introduced into the die from the head (10) of the 32 mmφ single screw extruder (4), and is supplied to the outer surface of the channel (12a) by the channel (13a) while being laminated. It was sent in the direction of the outlet and merged in multiple layers at (14a). The material for the non-foamed layer 2 supplied to the flow path (13a) is branched by a divided flow path (not shown) similar to the path P in the middle and sent to the flow path (13b). 12c) was sent in the die exit direction while being supplied so as to be laminated on the outer surface, and merged in a multilayer shape in the flow path (14b).
The molten resin having a cylindrical shape of a three-kind / four-layer structure in the flow paths (14a) and (14b) is extruded from the outlet (15) of the circular die (5), and is released to the atmospheric pressure, thereby being used for the foam layer. The carbon dioxide gas impregnated in the material expanded, bubbles were formed, and a foam layer was formed.

The tube-shaped foam sheet of three types and four layers extruded from the die was taken along a mandrel (7) having a maximum diameter of 700 mm, and expanded and cooled. The layer structure of the tubular foamed sheet was the non-foamed layer 1, the foamed layer, the non-foamed layer 1, and the non-foamed layer 2 from the mandrel side. The sheet-like foamed sheet is cut at two locations on the circumference to form two flat sheets with a width of 1080 mm, taken up by a take-up roll, and a propylene-based resin foamed sheet with a thickness of 1.2 mm is obtained. Obtained.

Using the propylene-based resin foam sheet obtained by the above method, a container was formed by vacuum forming. For vacuum forming, a commercially available vacuum forming apparatus (vacuum / pneumatic forming machine WPB1200 manufactured by Cloth vacuum) was used.
First, the propylene-based resin foam sheet (16) was sandwiched between clip members (17) so that the non-foamed layer 2 was on the plug side.
A foam sheet heated in advance with an infrared heater to have a surface of 150 ° C. was quickly placed between the plug and the female mold.
In the propylene-based resin foam sheet (16), the plug (18) is moved in the vertical direction with respect to the propylene-based resin foam sheet (16) until the bottom portion of the propylene-based resin foam sheet (16) contacts the female mold. Then, the propylene-based resin foam sheet was pre-shaped into a container shape. Furthermore, the female mold and the propylene-based resin foam sheet were brought into close contact with each other by vacuum suction from the female mold, and shaped into a container shape.
Thereafter, the propylene-based resin foam sheet shaped into a container shape was solidified by air cooling with a fan, and after releasing from the clip member, it was taken out from the female mold.
A container (opening diameter: 200 mm, edge width: 15 mm, bottom diameter: 150 mm, height: 30 mm) was obtained by trimming the end of the propylene-based resin foam sheet.
Table 1 shows the results of evaluation of the obtained propylene-based resin foam sheet and the container obtained by vacuum forming the foam sheet.

[Comparative Example 1]
A propylene-based resin foam sheet was produced in the same manner as in Example 1 except that the non-foam layer 1 material of Example 1 was used as the non-foam layer 2 material. Obtained. Table 1 shows the evaluation results of the foam sheet and the container.

[Comparative Example 2]
A propylene-based resin foam sheet was produced in the same manner as in Example 1 except that the following composition was used as the material for the non-foamed layer 1, and the foamed sheet was vacuum formed to obtain a container. Table 1 shows the results of evaluation of these foam sheets and containers.
(Material for non-foamed layer 1)
Propylene resin (x) (Sumitomo Chemical Co., Ltd. block polypropylene AW161C MFR 8 g / 10 min (230 ° C. 2.16 kgf)), Propylene resin (xi) (Sumitomo Chemical Co., Ltd. block polypropylene AH161C MFR 3 g / 10 min (230 ° C. 2.16 kgf)), ethylene resin (xii) (low density polyethylene G201 MFR 2 g / 10 min (190 ° C. 2.16 kgf) manufactured by Sumitomo Chemical Co., Ltd.), titanium master batch (viii) (Tokyo Ink) Titanium masterbatch PPM2924 (made by Co., Ltd.) was dry blended at a weight ratio of (x) / (xi) / (xii) / (viii) = 49/21/30/5 to obtain a material for the non-foamed layer 1 .

(Measurement of foaming ratio)
Using a submersible density meter (automatic hydrometer model D-H100, manufactured by Toyo Seiki Seisakusho Co., Ltd.), the specific gravity of the propylene-based resin foam sheet sampled to 20 mm × 20 mm was measured, and each material constituting the foam sheet was measured. The expansion ratio was calculated using the density.

(Vacuum forming container appearance evaluation)
The appearance of the container obtained by vacuum forming was visually evaluated.
(Evaluation results)
○: Good appearance with gloss. Excellent design.
Δ: Slightly glossy. Slightly inferior in design.
X: Appearance defect without gloss. Inferior in design.

(Container rigidity evaluation)
A container was placed on a 25 cm square (weight 1.2 kg) flat plate with the opening facing down, and a flat plate of the same shape was placed on the container. The container was crushed from the top of the flat plate using an autograph (model AGS-500D, manufactured by Shimadzu Corporation) equipped with a circular jig with a tip having a diameter of 10 cm. The time change of the load applied to the container was measured with the horizontal axis as the time and the vertical axis as the load, and the total of the strength of the yield point appearing first and the load of the flat plate placed on the container was measured as the container rigidity.

Diagram of an apparatus for producing the propylene-based resin foam sheet of the present invention Sectional drawing of the circular die used when manufacturing the propylene-type resin foam sheet of this invention Diagram of an apparatus for vacuum forming the propylene-based resin foam sheet of the present invention (A) Cross-sectional view of a container obtained by vacuum forming the propylene-based resin foam sheet of the present invention (b) A container obtained by vacuum-forming the propylene-based resin foam sheet of the present invention was viewed from the opening side. Figure

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 The apparatus which manufactures a propylene-type resin foam sheet 2 50 mmphi biaxial extruder 3 32 mmphi single screw extruder 4 32 mmphi single screw extruder 5 Circular die 6 Carbon dioxide gas supply pump 7 Mandrel 8 Head of 50 mmphi biaxial extruder 9 32 mmphi single screw extrusion Head 10 of machine (3) Head 11 of 32 mmφ single screw extruder (4) 11a Channel 11b Channel 12a Channel 12b Channel 12c Channel 12d Channel 13a Channel 13b Channel 14a Channel 14b Channel 15 Circular die Outlet 16 Propylene resin foam sheet 17 Clip member 18 Plug 19 Female mold

Claims (3)

Non-foamed layer 1 containing 100 parts by weight of propylene-based resin and 10 to 100 parts by weight of talc, 100 parts by weight of propylene-based resin and 1 to 100 parts by weight of pigment, and containing no talc A propylene resin foam sheet produced by coextrusion having a foam layer 2, wherein at least one side of the propylene resin foam sheet is a non-foam layer 2, and the foam layer, the non-foam layer 1, and the non-foam layer 2 A propylene-based resin foam sheet, wherein the weight ratio is foam layer: non-foam layer 1: non-foam layer 2 = 100: (50-100) :( 5-20). A container obtained by vacuum forming the propylene-based resin foam sheet according to claim 1, wherein the non-foamed layer 2 is located inside the container. The container according to claim 2, wherein the container is for food packaging.