JP2005041209A - Propylene resin foam sheet and container - Google Patents

Abstract

The present invention provides a propylene-based resin foam sheet in which a container having a beautiful appearance can be obtained in a wide processing temperature range, and a container obtained by vacuum forming the foam sheet.
A foamed layer made of a propylene-based resin and a non-foamed material made of a propylene-based resin exhibiting an endothermic curve having the highest peak and a melting peak having a half-value width Δw of 15 ° C. or higher in differential scanning calorimetry. And a container obtained by vacuum forming the foamed sheet.
[Selection] Figure 4

Description

The present invention relates to a propylene-based resin foam sheet having a foamed layer made of a propylene-based resin and a non-foamed layer made of a propylene-based resin, and a container obtained therefrom. In particular, the present invention relates to a propylene-based resin foam sheet excellent in secondary formability such as vacuum molding and a container obtained using the propylene-based resin 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.
Generally, a propylene-based resin foam sheet is shaped into a desired shape by vacuum forming or the like.
As an example of the propylene-based resin foam sheet, Patent Document 1 discloses a three-layer structure sheet in which non-foamed films are laminated on both surfaces of an intermediate foam layer.
However, conventional propylene-based resin foam sheets such as the above three-layer structure sheet can be successfully processed into a container only in a narrow processing temperature range, and it is possible to produce a container with a beautiful appearance from these conventional sheets. was difficult.

JP-A-5-208442

As a result of studies to develop a propylene-based resin foam sheet in which a container having a beautiful appearance can be obtained in a wide processing temperature range, the inventors have arrived at the present invention.

That is, the present invention relates to a foamed layer composed of a propylene-based resin and a non-propylene resin composed of a propylene-based resin exhibiting an endothermic curve having the highest peak and a melting peak having a half-value width Δw of 15 ° C. or higher in differential scanning calorimetry. A propylene-based resin foam sheet having a foam layer. Further, according to the present invention, the foamed layer is formed of a propylene-based resin having an endothermic curve having a melting peak having the highest peak and a half-value width Δw of 15 ° C. or more in differential scanning calorimetry on both surfaces of the foamed layer. The propylene-based resin foam sheet having a foam layer.
Furthermore, this invention is a container obtained from the said propylene-type resin foam sheet.
In the following description, the essential non-foamed layer is “made of a propylene-based resin having an endothermic curve having the highest peak in differential scanning calorimetry and a melting peak having a half-value width Δw of 15 ° C. or more”. This is defined as a DSC requirement. That is, the essential non-foamed layer may be referred to as “non-foamed layer satisfying DSC requirements”.

The propylene-based resin foam sheet of the present invention is excellent in secondary formability such as vacuum forming, and can form a container having an excellent appearance at a wide range of processing temperatures. A container obtained by vacuum forming is excellent in appearance.

The propylene-based resin foam sheet of the present invention has a foam layer made of a propylene-based resin. The expansion ratio of the foam layer is usually 1.5 to 40 times, and preferably 2 to 10 times. Since the expansion ratio is in the above range, the sheet of the present invention is excellent in heat insulation, light weight, and rigidity. The expansion ratio can be adjusted by appropriately changing the amount of foaming agent to be used and the physical conditions during sheet production.

The propylene resin constituting the foamed layer is not particularly limited, and examples thereof include a propylene homopolymer and a propylene copolymer containing 50 mol% or more of a monomer unit derived from propylene. 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 monomer units other than 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 a long-chain branched propylene resin or a propylene resin having a weight average molecular weight of 1 × 10 ⁵ or more as the propylene resin constituting the foamed layer, 50% by weight or more of the total propylene resin, finer bubbles can be formed. Since it can obtain the propylene-type resin foam sheet which has it, it is preferable.

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. As an example of a long-chain branched propylene-based resin satisfying the branching degree index [A] of 0.20 ≦ [A] ≦ 0.98, propylene PF-814 manufactured by Montel is listed.

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.
Branch index [A] = [η] _Br / [η] _Lin
Here, [η] _Br is the intrinsic viscosity of the propylene resin having a long chain branch, and [η] _Lin is a straight chain having the same monomer unit and the same weight average molecular weight as the propylene resin having the long chain branch. It is an intrinsic viscosity of a chain 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.
As an example of a method for polymerizing a propylene resin having a weight average molecular weight of 1 × 10 ⁵ or more, as described in JP-A No. 11-228629, a high molecular weight component is first polymerized and then a low molecular weight component is added. Examples include a polymerization method.

Among long-chain branched propylene resins or 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 at a temperature about 30 ° C. higher than the melting point of the resin. Is preferably 5 or more, more preferably 10 or more. The uniaxial melt extensional viscosity ratio is measured with an apparatus such as a uniaxial extensional viscosity measurement apparatus (for example, a uniaxial extensional viscosity measurement apparatus manufactured by Rheometrics Scientific) at an elongation strain rate of 1 sec ^−1. The uniaxial melt elongation viscosity after 0.1 seconds from the start of strain is η _0.1, and the uniaxial melt elongation viscosity after 5 seconds is η 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. Examples of such thermoplastic resins include olefin polymers other than propylene resins, ethylene-vinyl ester copolymers, ethylene- (meth) acrylic acid copolymers, ethylene- (meth) acrylic acid ester copolymers, polyesters. Resin, polyamide resin, polystyrene resin, acrylic resin, acrylonitrile resin, polyvinyl alcohol, ionomer resin and the like. Specific examples of olefin polymers include copolymerization of two or more monomers selected from olefin homopolymers having 6 or less carbon atoms such as ethylene, butene, pentene, and hexene, or 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 polymer include low density polyethylene, ultra low density polyethylene, linear low density polyethylene, and high density polyethylene. When the foam layer contains such a thermoplastic resin, the content is usually 10 wt% or less.

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 or resin used so that a desired foaming ratio can be obtained. 0.5 to 20 parts by weight.

The propylene-based resin foamed sheet of the present invention has a non-foamed layer made of a propylene-based resin showing an endothermic curve having the highest peak and a melting peak with a half-value width Δw of 15 ° C. or more in differential scanning calorimetry. . In other words, as described above, the sheet has a non-foamed layer that satisfies the DSC requirement.
The definition of “the highest peak” in the endothermic curve obtained by DSC measurement and the definition of its half-value width Δw are described below. The method for determining the highest peak and its half width will also be described below.
For the DSC measurement, a sample cut out from the non-foamed layer of the propylene-based resin foam sheet is used. The sample is set in a differential scanning calorimeter and the thermal operation shown below is performed.
Step (1): The temperature is raised from 30 ° C. to 200 ° C. at 10 ° C./min.
Step (2): Following step (1), hold at 200 ° C. for 5 minutes.
Step (3): Following step (2), the temperature is decreased from 200 ° C. to 30 ° C. at 10 ° C./min.
Step (4): Following step (3), hold at 30 ° C. for 5 minutes.
Step (5): Following step (4), the temperature is increased from 30 ° C. to 200 ° C. at 10 ° C./min.
In step (5), an endothermic curve indicating the relationship between the endothermic amount (vertical axis) and the temperature (horizontal axis) is created.
If the endothermic curve has only one melting peak, that peak is the “highest peak”. The length of the line segment between the apex of the peak and the intersection of the perpendicular line extending from the peak to the base line of the endothermic curve is defined as the “true height” of the peak.
When the endothermic curve has two or more melting peaks, the “highest peak” means the peak having the highest “true height” defined in the same manner as described above. Also in this case, the “true height” of the “highest peak” is defined in the same manner as described above.
In any case, at the “highest peak”, as shown in FIG. 4, the temperature width where the endothermic curve exists above the height of the midpoint of the line segment corresponding to “true height”. It is defined as “half-value width Δw”.

The full width at half maximum Δw of the endothermic curve of the propylene-based resin indicates the melting point distribution of the propylene-based resin. From the propylene-based resin foam sheet of the present invention having a non-foamed layer made of a propylene-based resin having a Δw of 15 ° C. or more, a container having an excellent appearance is produced by a secondary molding method such as vacuum molding in a wide temperature range. Can do. When Δw is smaller than 15 ° C., the processing temperature range in which a container having an excellent appearance can be manufactured becomes narrow, and it is necessary to strictly control the processing conditions. In light of the object of the present invention, it is preferable that the highest peak half-value width Δw is as large as possible, but the half-value width Δw is usually adjusted to a range of 15 ° C. to 30 ° C.

In this invention, the propylene-type resin foam sheet should just have the non-foamed layer which satisfy | fills the foaming layer which consists of propylene-type resin, and the said DSC requirements. The non-foamed layer propylene resin satisfying the DSC requirement may be a single type of propylene resin or a composite of two or more types of resins, and has the highest peak in differential scanning calorimetry. Further, it may be a composite showing an endothermic curve having a melting peak having a half width Δw of 15 ° C. or more.

  When producing the sheet of the present invention, the propylene-based resin used for forming the non-foamed layer satisfying the DSC requirement is the DSC measurement before sheet forming, which is the highest peak in the differential scanning calorimetry. Propylene-based resin which has been confirmed to show an endothermic curve having a melting peak with a half-value width Δw of 15 ° C. or higher, or the highest peak in the differential scanning calorimetry, and the half-value width Δw is 15 ° C. A composite of a plurality of propylene resins showing an endothermic curve having the melting peak as described above is selected. When the propylene-based resin used to form the non-foamed layer is a composite, each propylene-based resin constituting the composite is not necessarily the highest peak in differential scanning calorimetry and the half-value width Δw Is not required to be a propylene-based resin having an endothermic curve having a melting peak of 15 ° C. or higher, and is the highest peak when the differential scanning calorimetry is performed as a composite, and the half-value width Δw is 15 ° C. or higher. An endothermic curve having a melting peak may be shown. The DSC measurement here is performed by a method including the steps (1) to (5). In order to obtain such a composite, it is preferable to combine propylene resins having different melting points. Examples of such a combination of propylene resins include homopolypropylene and propylene-ethylene copolymer, homopolypropylene and propylene-ethylene-butene terpolymer. Thus, when mix | blending two types of propylene resin from which melting | fusing point differs, it is preferable that the difference of melting | fusing point of each propylene resin is 20 degreeC or more, and the compounding quantity is the range of 70 / 30-30 / 70 wt ratio. It is preferable that Moreover, the propylene-type resin which comprises the non-foamed layer which satisfy | fills the said DSC requirements may be the same as the propylene-type resin which comprises a foamed layer, and may differ. Moreover, the non-foamed layer satisfying the DSC requirement may contain a thermoplastic resin other than the propylene-based resin.

The propylene-based resin foamed sheet of the present invention may have at least one foamed layer made of propylene-based resin and at least one non-foamed layer satisfying the DSC requirement. For example, the sheet of the present invention may have two or more non-foamed layers that satisfy the DSC requirement, and may have one or more thermoplastic resin layers that do not satisfy the DSC requirement. Such a thermoplastic resin is not particularly limited as long as the properties specified in the DSC requirements are not satisfied. Examples of such materials include propylene resins and saponified ethylene-vinyl ester copolymers.

The layer structure of the propylene-based resin foam sheet is not particularly limited as long as it has at least one foamed layer made of propylene-based resin and one non-foamed layer that satisfies the DSC requirements. For example, it does not satisfy the DSC requirements. You may have a non-foaming layer. A non-foamed layer made of a propylene-based resin, which has an endothermic curve having a melting peak with a half-value width Δw of 15 ° C. or more, which is the highest peak in differential scanning calorimetry, on both surfaces of the propylene-based resin foam sheet. The embodiment having a foamed layer and having a foamed layer between these non-foamed layers is suitable for producing a container having an excellent appearance as well as the sheet itself being excellent in moldability. This is preferable.

In the aspect in which the propylene-based resin foam sheet has one or more non-foamed layers satisfying the DSC requirements and the non-foamed layers not satisfying the DSC requirements, the total weight of the non-foamed layers satisfying the DSC requirements is It preferably occupies 50% by weight or more of the total weight of all the non-foamed layers including the two types of non-foamed layers, and more preferably occupies 60% by weight or more.
In the total weight of all non-foamed layers in the propylene-based resin foamed sheet, when the proportion of the non-foamed layer satisfying the DSC requirement is too low, the appearance of the container obtained by secondary molding of the sheet is poor. Tend to be.

The thickness of the propylene-based resin foam sheet may be any thickness that can be secondarily formed by vacuum molding or the like, and is usually 0.1 to 3 mm. The thickness of the foamed layer and the non-foamed layer in the propylene-based resin foamed sheet made of the propylene-based resin and the non-foamed layer satisfying the DSC requirements is not particularly limited, but is foamed from the viewpoint of heat insulation. The layer thickness is preferably 0.1 mm or more, more preferably 0.3 mm or more. The thickness of the non-foamed layer that satisfies the DSC requirement is preferably 1 to 200 μm, more preferably 50 to 150 μm or less from the viewpoint of the balance between strength and lightness.

Each layer constituting the propylene-based resin foam sheet of the present invention may contain an additive. Examples of the additive include a filler (filler), an antioxidant, a light stabilizer, an ultraviolet absorber, a plasticizer, an antistatic agent, a colorant, a release agent, a fluidity-imparting agent, and a lubricant. In particular, by adding a filler to the non-foamed layer, the rigidity and heat resistance of the sheet can be improved. Specific examples of the filler include inorganic fibers such as glass fibers and carbon fibers, inorganic particles such as talc, clay, silica, titanium oxide, calcium carbonate, and magnesium sulfate. When using talc, it is preferable to use a talc having an average particle diameter in the range of 0.1 to 50 μm from the viewpoint of improving the rigidity and heat resistance by blending talc and the secondary formability of the foamed sheet. Talc is preferably blended in an amount of about 10 to 100 parts by weight per 100 parts by weight of the resin constituting the non-foamed layer.

The method for producing the propylene-based resin foam sheet of the present invention is not particularly limited, and is extruded while foaming a molten resin from a die such as a flat die (T die) or a circular die, and stretched along a mandrel or the like. A method of cooling is preferably used. It is also possible to perform stretching after the molten resin is extruded from a die and cooled and solidified. In addition, a method of further forming a layer by extrusion lamination on an extruded foam sheet, a method of melt-extrusion of a thermoplastic resin such as a propylene resin between layers to be laminated, and molding by sand lamination, and at least one of the layers to be laminated And a method of heating and melting the surface of the material with hot air or an infrared heater and bonding.
Among these methods, from the viewpoint of light weight and manufacturing cost of the obtained sheet, the foamed sheet and other layers are passed through a nip roll composed of two or more rolls, and hot air is blown from an air knife or the like at the nip portion. Particularly preferred is a heat bonding method in which at least one surface of the foam sheet or other layer to be laminated is heated and melted by contact, and then pressure-bonded by a nip roll.

Since the propylene-based resin foam sheet of the present invention is excellent in heat insulation, light weight, and heat resistance, it is subjected to secondary molding such as vacuum molding, pressure molding, vacuum pressure molding, etc., and food containers such as cups, trays, bowls, etc. Suitable for manufacturing parts containers.
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 a vacuum is formed using a mold such as a male mold, a female mold, and a male-female mold. Examples thereof include a method of forming by a secondary forming method such as forming, pressure forming, vacuum pressure forming, etc., and cooling and solidifying. 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 female mold with a male mold or a plug. The vacuum forming method is preferable because it is difficult to damage the foamed layer by molding, and deformation after molding is small.

When the propylene-based resin foam sheet of the present invention is molded by vacuum molding or the like and used as a food container or the like, it is preferable that a heat seal layer is provided in the innermost layer of the container. The heat seal layer preferably has an easy peel property. As a heat seal layer having such properties, 100 parts by weight of a thermoplastic resin, 0.5 to 160 parts by weight of fine particles having an average particle size of 0.05 to 20 μm selected from the group consisting of organic fine particles and inorganic fine particles, And a layer made of a resin composition containing. The thermoplastic resin used here is preferably a resin composed of 100 parts by weight of a propylene resin and 10 to 100 parts by weight of an ethylene resin.
Moreover, you may provide a layer by methods, such as apply | coating a coating liquid further, to the container obtained by shape | molding the propylene-type resin foam sheet of this invention.

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

[Example 1]
Two types and three layers of a propylene-based resin foam sheet were prepared by the method described below. This sheet was a sheet in which a non-foamed layer satisfying the DSC requirement was laminated on both surfaces of a propylene-based resin foamed layer.

[I] Pelination of propylene polymer Calcium stearate with respect to 100 parts by weight of propylene polymer powder comprising a high molecular weight component and a low molecular weight component obtained by the method disclosed in JP-A-11-228629 0.1 part by weight, phenolic antioxidant (trade name: Irganox 1010, manufactured by Ciba Specialty Chemicals) 0.05 part by weight, phenolic antioxidant (trade name: Sumilizer BHT, manufactured by Sumitomo Chemical Co., Ltd.) 0.2 part by weight was added and mixed. The mixture was kneaded at 230 ° C. to obtain pellets (i) having a melt flow rate (MFR) of 4.5 g / 10 min (230 ° C. 2.16 kgf).
The physical properties of the resulting propylene polymer are as follows.
High molecular weight component:
Intrinsic viscosity ([η] A) = 9.5 dl / g,
Ethylene unit content in component (A) (C2inA) = 2.9%
Low molecular weight components:
Intrinsic viscosity ([η] B) = 11 dl / g,
Ethylene unit content (C2inB) = 2.7%
Uniaxial extensional viscosity at 180 ° C. measured using a uniaxial extensional viscosity measuring device manufactured by Rheometrics η ₅ = 300000 Pa · s,
η _0.1 = 2900 Pa · s.

[II] Dry blend of three components listed under preparation of foam layer material (i), (ii) and (iii) at a weight ratio of (i) / (ii) / (iii) = 70/21/9 wt Thus, a foam layer material was obtained.
(i): propylene-based polymer pellets obtained by the above method;
(ii): Polypropylene 1 (Sumitomo Chemical Co., Ltd. polypropylene R101 MFR = 20 g / 10 min (230 ° C. 2.16 kgf))
(iii): Polypropylene 2 (manufactured by Sumitomo Chemical Co., Ltd. Polypropylene U101E9 MFR = 120 g / 10 min (230 ° C. 2.16 kgf))

[III] Preparation of the non-foamed layer material The five components listed below (iv), (v), (vi), (vii) and (viii) are converted into (v) / (vi) / (vii) / (viii ) = 21/30/20/29/5 was dry blended to obtain a non-foamed layer material.
(iv): Polypropylene 3 (Sumitomo Chemical Homopolypropylene FS2011DG2 Melting point 158 ° C. MFR 2.5 g / 10 min (230 ° C. 2.16 kgf))
(v): Polypropylene 4 (Sumitomo Chemical Propylene-Ethylene-Butene Copolymer W171 (monomer blending weight ratio propylene / ethylene / butene = 92.4 / 4.0 / 3.6) Melting point 129 ° C. MFR 6 g / 10 min ( 230 ° C. 2.16 kgf))
(vi): Polypropylene 5 (Long-chain branched homopolypropylene PF814, melting point 164 ° C. MFR 3 g / 10 min (230 ° C. 2.16 kgf) manufactured by Montel)
(vii): Talc masterbatch (manufactured by Sumitomo Chemical Co., Ltd., polypropylene base talc masterbatch MF110 talc content 70 wt%, melting point of base propylene resin 164 ° C.),
(viii): Titanium masterbatch (manufactured by Sumika Color Co., Ltd., polyethylene-based titanium masterbatch SPEM7A1155 titanium content 60 wt%)

[IV] Production of propylene-based resin foam sheet Using the sheet production apparatus shown in FIGS. 1 and 2, a propylene-based resin foam sheet was produced by the following method. Extrusion is performed by a sheet manufacturing apparatus (1) in which a 90 mmφ circular die (4) is attached to a 50 mmφ twin screw extruder (2) for foaming layer extrusion and a 32 mmφ single screw extruder (3) for non-foaming layer extrusion, A propylene-based resin foam sheet comprising two non-foamed layers and one foamed layer interposed therebetween was obtained. In the production, the foamed layer material and the non-foamed layer material prepared in the items [I] and [II] were used.

A raw material obtained by blending 2 parts by weight of a nucleating agent (Hydrocelol manufactured by Beilinger Ingelheim Chemicals Co., Ltd.) 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. Kneaded in a cylinder.

A pump (5) connected to a 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 (4).
The non-foamed layer material was melt-kneaded by a 32 mmφ single-screw extruder (3) and supplied to the circular die (4).

Inside the circular die (4), the material for the foam layer is introduced into the die from the head (7) of the 50 mmφ twin-screw extruder (2) and sent in the direction of the die exit by the flow path (9a). It branched through the path P and sent to the flow path (9b).
The material for the non-foamed layer is introduced into the die from the head (8) of the 32 mmφ single screw extruder (3), divided into flow paths (10a) and (10b), and then laminated on both sides of the flow path (9b). While being fed, it was sent in the direction of the die exit, and was laminated in the laminated portion (11a). The material for the non-foamed layer supplied to the flow paths (10a) and (10b) is branched in the middle by a divided flow path (not shown) similar to the path P and sent to the flow paths (10c) and (10d). Then, while being fed so as to be laminated on both surfaces of the flow path (9a), it was sent in the die exit direction and laminated in the lamination part (11b). The laminated resin (11a) and (11b) in the two-layered / three-layered molten resin is extruded from the outlet (12) of the circular die (4), and this release to atmospheric pressure allows the foamed layer to be used. Carbon dioxide gas impregnated in the material expanded, bubbles were formed to form a foamed layer, and two types and three layers of a propylene-based resin foamed sheet having a thickness of 1.2 mm were obtained.

The two- and three-layer foam sheet extruded from the die was taken up in a tube shape along a mandrel (6) having a maximum diameter of 210 mm, and expanded and cooled. The sheet was cut at one place on the circumference of the tubular foamed sheet to obtain a flat sheet having a width of 660 mm, and taken up by a take-up roll.

Using the propylene-based resin foam sheet obtained by the above method, a container was formed by vacuum forming. The vacuum forming was performed using a commercially available vacuum forming apparatus (vacuum / pneumatic forming machine WPB1200 made by cloth vacuum).
First, the propylene-based resin foam sheet (13) was sandwiched between clip members (14), and both surfaces of the sheet were heated by an infrared heater so that the surface was 160 ° C.
Thereafter, the plug (15) is moved to the propylene-based resin foam sheet side so that the propylene-based resin foam sheet and the plug are brought into contact with each other, and the female metal disposed on the back side of the sheet in a direction perpendicular to the propylene-based resin foam sheet surface. The plug was moved to the mold (16) side, and the propylene-based resin foam sheet was brought into contact with the female mold. Further, the plug was moved from the plane in which the propylene-based resin foam sheet was sandwiched between the clip members to the female mold side, and the propylene-based resin foam sheet was preshaped into a container shape.
After the propylene-based resin foam sheet was brought into contact with the surface of the female mold, 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 to form a container having the same shape as the female mold.
Thereafter, the molded sheet was solidified by air cooling with a fan, released from the clip member, and taken out from the female mold.
A container (opening diameter: 130 mm, edge width: 10 mm, bottom diameter: 60 mm, height: 50 mm) was obtained by trimming the end of the propylene-based resin foam sheet.
The result of having evaluated the obtained propylene-type resin foam sheet and the container obtained by vacuum-molding this foam sheet is shown to Tables 1-2.

[Comparative Example 1]
A propylene-based resin foam sheet was produced in the same manner as in Example 1 except that the following materials were used as the non-foamed layer constituting material, and then the foamed sheet was vacuum-molded to obtain a container. The results of evaluating these foam sheets and containers are shown in Tables 1-2.
[Preparation of non-foamed layer constituent material]
The four components listed below, (iv), (ix), (vii) and (viii) are dried at a weight ratio of (iv) / (ix) / (vii) / (viii) = 24/47/29/5 Blended to obtain a non-foamed layer material.
(iv): Polypropylene 3
(ix): Polypropylene 6 (Homopolypropylene W101MFR manufactured by Sumitomo Chemical 8 g / 10 min (230 ° C., 2.16 kgf))
(vii): Talc masterbatch
(viii): Titanium masterbatch

(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.

(Half width measurement)
Using a DSC (Differential Scanning Calorimeter DSC220 manufactured by Seiko Instruments Inc.), about 10 mg of a sample was set, and the thermal operation consisting of the following five steps was performed. Thus, an endothermic curve showing the relationship between the endothermic amount (vertical axis) and the temperature (horizontal axis) was created.
Step (1): The temperature is raised from 30 ° C. to 200 ° C. at 10 ° C./min.
Step (2): Following step (1), hold at 200 ° C. for 5 minutes.
Step (3): Following step (2), the temperature is decreased from 200 ° C. to 30 ° C. at 10 ° C./min.
Step (4): Following step (3), hold at 30 ° C. for 5 minutes.
Step (5): Following step (4), the temperature is increased from 30 ° C. to 200 ° C. at 10 ° C./min.
Using the obtained endothermic curve, the “highest peak” and its half-value width Δw were determined by the above procedure.

(Vacuum forming temperature range evaluation)
The temperature range in which the sheet can be formed by vacuum forming was evaluated. The evaluation was carried out by repeatedly performing vacuum forming while changing the sheet surface temperature at the time of molding by adjusting the heating time with an infrared heater at the time of vacuum forming, and evaluated whether or not the vacuum forming was possible by the appearance of the molded product. The surface temperature of the sheet was measured by attaching a thermocouple to the sheet surface. The sheet (13) was placed in a molding machine, heated by an infrared heater, molded, and the highest temperature was taken as the sheet surface temperature until it was removed from the mold.
The appearance of the molded product was visually observed and evaluated according to the following criteria.
(Evaluation results)
A: Good appearance of molded product B: The molded product is shaped into the shape of the mold, but the surface of the molded product is rough and has many irregularities C: The evaluation result that the molded product is not shaped into the shape of the mold is A The temperature range at that time was defined as a “temperature range in which vacuum forming is possible”.

The figure which showed the example of the apparatus for manufacturing the propylene-type resin foam sheet of this invention Sectional drawing of the example of the circular die | dye used when manufacturing the propylene-type resin foam sheet of this invention The figure which showed the example of the apparatus which vacuum-forms the propylene-type resin foam sheet of this invention The figure which showed an example of the method of calculating | requiring the half value width (DELTA) w from the endothermic curve obtained by DSC measurement in this invention. The figure which showed the other example of the method of calculating | requiring the half value width (DELTA) w from the endothermic curve obtained by DSC measurement in this invention.

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 Circular die 5 Carbon dioxide supply pump 6 Mandrel 7 Head of 50 mmphi biaxial extruder 8 Head 9a of 32 mmphi single screw extruder 9b Channel 10a Channel 10b Channel 10c Channel 10d Channel 11a Laminated portion (channel)
11b Laminate part (flow path)
12 Circular die outlet 13 Propylene resin foam sheet 14 Clip member 15 Plug 16 Female die

Claims (3)

A foamed layer made of a propylene-based resin and a non-foamed layer made of a propylene-based resin showing an endothermic curve having the highest peak and a melting peak having a half-value width Δw of 15 ° C. or higher in differential scanning calorimetry. Propylene resin foam sheet. A non-foamed layer made of a propylene-based resin showing an endothermic curve having a melting peak having the highest peak and a half-value width Δw of 15 ° C. or more in differential scanning calorimetry on both surfaces of the foamed layer. 1. The propylene-based resin foam sheet according to 1. A container obtained by vacuum forming the propylene-based resin foam sheet according to claim 1 or 2.

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