JP2001113655A - Laminated foam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated foam having a foam layer and a gas barrier resin layer, in which the gas barrier resin layer does not become extremely thin or is not destructed at the time of vacuum molding. SOLUTION: A laminated foam has as least one polyolefin foamed layer and a gas barrier resin layer and the gas barrier resin layer has a thickness of 10-200 μm and a thickness distribution Tmax/Tmin of 1.0-1.2 within a range of at least 25 cm2. This laminated foam is preferably. formed by laminating a polyolefin foamed sheet having the polyolefin foamed layer and a gas barrier resin film having the gas barrier resin layer by thermal fusion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated foam having a gas-barrier resin layer, and more specifically to a container such as a food container which is required to have gas-barrier properties, heat insulation, light weight, or the like. A sheet suitable for manufacturing the same.

[0002]

2. Description of the Related Art As a conventional foam sheet having a gas barrier resin layer, a foam sheet-forming material and a gas barrier resin layer-forming material are prepared by using separate extruders.
What is manufactured by the method of co-extrusion with two extrusion dies is known.

[0003]

However, according to the above-mentioned technology, it is difficult to adjust the thickness of the gas barrier resin layer alone. When a food container or the like is manufactured by vacuum forming the resin, an extremely thin portion of the gas barrier resin layer or a portion where the gas barrier resin layer is broken and does not exist may be generated, and quality may deteriorate in food preservation.

[0004] It is an object of the present invention to provide a laminated foam having a foam layer and a gas barrier resin layer, wherein the gas barrier resin layer does not become extremely thin or break when vacuum-formed. To provide.

[0005]

SUMMARY OF THE INVENTION The present invention provides at least one
A laminated foam comprising a polyolefin foam layer and at least one gas barrier resin layer, wherein the gas barrier resin layer has a thickness of 10 to 200 μm and a thickness distribution T
max / Tmin is 1.0 to 1.2 in a range of at least 25 cm ² .

[0006] With the above structure, a laminated foam can be obtained in which the gas barrier resin layer is not extremely thinned or broken during vacuum forming.

It should be noted that Tmax / Tmin is 1.0 to 1.
If the measurement range of ² is 25 cm ² or more, the wider the better, the better the uniformity is, which is preferable.

[0008] The above-mentioned laminated foam is preferably formed by laminating a polyolefin foam sheet having a polyolefin foam layer and a gas barrier resin film having a gas barrier resin layer by heat fusion. This provides a laminated foam that does not elute the organic solvent as compared with the case where the laminate is laminated using an adhesive.

The above-mentioned laminated foam further comprises at least one
A layer having a non-foamed layer of a polyolefin-based resin is preferable because vacuum formability is improved.

Here, the non-foamed layer is a layer having a foaming ratio of 1.0 to 1.5 times, preferably 1.0 to 1.1 times. The layer is not particularly limited as long as the properties are satisfied, but is preferably a layer having an expansion ratio of 2.5 to 40 times. Expansion ratio is 2.5
If it is less than twice, the properties as a foam, specifically lightness and heat insulation, will not be sufficient, and if it exceeds 40 times, it will be difficult to manufacture, and it will not be possible to suppress foam breakage during vacuum forming. The expansion ratio can be adjusted by the amount of the foaming agent to be used, the pressure reduction after forming the foam sheet, and the like.

The polyolefin resin constituting the non-foamed layer is a long-chain branched polypropylene or a long-chain branched polyolefin adhesive resin, and more preferably, the long-chain branched polypropylene or long-chain branched polyolefin adhesive resin has a degree of branching. It is preferable that the index [A] satisfies 0.20 ≦ [A] ≦ 0.98, since a laminated foam excellent in particularly appearance and vacuum moldability is obtained.

In particular, the branching index [A] of the long-chain branched polypropylene or the long-chain branched polyolefin adhesive resin.
Is more preferably in the range of 0.30 ≦ [A] ≦ 0.90, and in the range of 0.40 ≦ [A] ≦ 0.80, from the viewpoint of the appearance of the product, vacuum formability, and the like. More particularly preferred.

The branching index indicates the degree of long-chain branching, and is a numerical value defined by the following equation. Branching degree index [A] = [η] Br / [η] Lin Here, [η] Br is the intrinsic viscosity of the branched polypropylene, and [η] Lin is substantially the same in weight average molecular weight. It is the intrinsic viscosity of a tactic semicrystalline linear polypropylene.

Intrinsic viscosity, also known as limiting viscosity number, is in its most general sense a measure of the ability of a polymer molecule to enhance solution viscosity. The intrinsic viscosity depends on the size and shape of the dissolved polymer molecule. Thus, when comparing a non-linear polymer to a linear polymer of substantially the same weight average molecular weight, the intrinsic viscosity is a number that indicates the configuration of the non-linear polymer molecule. That is,
The ratio of the intrinsic viscosities described above is a measure of the degree of branching of the non-linear polymer, and was defined as a branching index. The method for measuring the intrinsic viscosity of long-chain branched polypropylene or long-chain branched polyolefin-based adhesive resin is described in Elliott et al. (J. App.
ly. Sci., 14, 2947-2963 (1970)]. In this specification, the intrinsic viscosity in each case is 135 ° C. for a sample dissolved in tetralin or orthodichlorobenzene.
It was measured in.

The laminated foam of the present invention has a low molecular weight organic compound having 3 to 4 carbon atoms in a content of 10,000 ppm or less, preferably 1000 ppm or less, more preferably 100 ppm or less.
pm or less is preferable because it does not cause any safety-related problems when used for the production of food containers.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Raw materials used in the present invention will be described. Examples of the polyolefin constituting the foamed layer include homopolymers of ethylene, propylene, butene and the like, copolymers using two or more of these monomers, and copolymers of at least one of these monomers with other monomers. Polymers. Examples of the copolymer include an ethylene-α-olefin copolymer and a propylene-α-olefin copolymer.

[0017] Polyethylene (PE) or a copolymer of ethylene and another monomer, that is, as the ethylene resin, for example, polyethylene such as low-density polyethylene and high-density polyethylene; ethylene-propylene copolymer, ethylene-butene-1 copolymer Polymer, ethylene-4-methyl-1
Ethylene-α such as pentene copolymer, ethylene-hexene-1 copolymer, ethylene-octene-1 copolymer, etc.
An olefin copolymer; an ethylene copolymer comprising a repeating unit derived from at least one vinyl monomer and a repeating unit derived from ethylene, such as an ethylene-methyl methacrylate copolymer and an ethylene-vinyl acetate copolymer. Coalescence, and mixtures thereof.

The propylene-α-olefin copolymer includes a propylene-α-olefin block copolymer,
Examples include propylene-based polymers such as propylene-α-olefin random copolymers and mixtures thereof. Examples of the α-olefin of the propylene-α-olefin block copolymer and the propylene-α-olefin random copolymer include ethylene, butene-1, and octene-1.
And α-olefins having 2 to 4 carbon atoms, such as

Among the polyolefins exemplified above, (a) a long-chain branched polypropylene, which has high uniformity of the foam and has excellent vacuum moldability as the multilayer polyolefin foam sheet of the present invention. (P
P), (b) In the first step, a crystalline PP having an intrinsic viscosity of 5 dl / g or more is synthesized, and in a second step, a crystalline PP having an intrinsic viscosity of less than 3 dl / g is continuously synthesized. Has a PP of 0.05 to 25 wt% and an intrinsic viscosity of 3 dl as a whole.
A suitable raw material is polypropylene having an Mw / Mg of less than 10 and Mw / Mn of less than 10. The commercially available product (a) is PF814 (manufactured by Montell).

The polyolefin constituting the polyolefin foam layer may be one kind or a mixture of two or more kinds. The polyolefin foam layer may contain a thermoplastic elastomer as long as the effects of the present invention are not significantly impaired.

The foaming agent used to form the foamed layer is preferably an inert substance such as water or carbon dioxide. In particular, when polypropylene is used as the resin constituting the foam layer, the use of carbon dioxide is preferred. By using carbon dioxide gas as a foaming agent, it is easy to obtain a laminated foam having a content of a low-molecular-weight organic compound having 3 to 4 carbon atoms of 100 ppm or less.

As the long-chain branched polypropylene forming the non-foamed layer, the above-mentioned product of Montell is available as a commercial product, and can be suitably used. The thickness of the non-foamed layer is not particularly limited as long as the surface smoothness, that is, the appearance is good, but is preferably 1 μm or more, more preferably 10 μm or more, and even more preferably 50 μm or more. . The upper limit of the thickness is appropriately set according to the thickness of the entire multilayer polyolefin foam sheet, the application, and the like. If it is too thick, the properties of the foamed layer will not be sufficiently exhibited.

The polyolefin-based adhesive resin having a long chain branch which is a preferable non-foaming layer constituting material in the present invention includes 1) unsaturated carboxylic acid, unsaturated carboxylic anhydride, epoxy group-containing vinyl monomer, A copolymer of at least one monomer selected from the group consisting of a saturated carboxylic acid ester and a vinyl ester with an olefin monomer; 2) an acid-modified olefin polymer grafted with an unsaturated carboxylic acid or an acid anhydride thereof; Coalescence and the like are exemplified.

1) at least one monomer selected from the group consisting of unsaturated carboxylic acids, unsaturated carboxylic anhydrides, epoxy group-containing vinyl monomers, unsaturated carboxylic esters and vinyl esters, and olefin monomers; Examples of the copolymer of ethylene- (meth)
Acrylic acid copolymer, ethylene- (meth) acrylic acid copolymer metal crosslinked product, ethylene-glycidyl methacrylate copolymer, ethylene-glycidyl methacrylate-vinyl acetate copolymer, ethylene-glycidyl methacrylate-methyl (meth) acrylate Copolymer, ethylene-
Examples thereof include (meth) acrylate copolymers, ethylene- (meth) acrylate-maleic anhydride copolymers, and ethylene-vinyl acetate copolymers.

Examples of the above 2) an acid-modified olefin polymer grafted with an unsaturated carboxylic acid or an acid anhydride thereof include a maleic anhydride-grafted ethylene polymer and a maleic anhydride-grafted propylene polymer. Coalescence is exemplified.

The polyolefin resin constituting the non-foamed layer may be one kind or a mixture of two or more kinds. The non-foamed layer may contain a thermoplastic elastomer as long as the effects of the present invention are not significantly impaired.

The gas barrier resin layer in the laminated foam of the present invention will be described. The gas barrier resin layer has a thickness of 10 to 200 μm, preferably 10 to 150 μm.
And more preferably 10 to 100 μm.

The resin forming the gas barrier resin layer is not particularly limited, but specific examples include the following.

Saponified polyvinyl esters such as polyvinyl alcohol; saponified ethylene-vinyl ester copolymers such as ethylene-vinyl alcohol copolymer; polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate and polyhydroxybenzoic acid Resin; nylon-6, nylon-
6,6, meta-xylene diamine-adipic acid condensation polymer,
Polymethylmethacrylimide, diethylenetriamine-
Polyamide resins such as adipic acid copolymers and salts thereof;
Aramid resins; acrylic resins such as polymethyl methacrylate, polyacrylic acid, sodium polyacrylate, poly-2-hydroxyethyl acrylate, poly-2-hydroxyethyl methacrylate, polyacrylamide, ethylene-acrylic acid copolymers and salts thereof Resins; halogen-containing resins such as polyvinyl chloride, polyvinylidene chloride, polyvinylidene fluoride, and polytetrafluoroethylene; polycarbonate resins, polysulfone resins, polyether sulfone resins, polyether ether ketone resins, polyphenylene ether resins, polyphenylene oxide resins, Engineering plastic resins such as polyarylene sulfide resin, polymethylene oxide resin, and polyacetal resin. Further, a so-called modified resin obtained by graft-modifying, cross-linking or modifying the terminal of a molecular chain of these resins may be used.

The gas barrier resin layer in the present invention can be formed by a method of forming a film from the above-mentioned resin or its composition from a molten state, or by drying a solution as a liquid film.

As a method for forming a resin or a composition thereof from a molten state into a film, a common extrusion method such as T-die molding, inflation molding, injection molding, blow molding, stretch blow molding, etc. may be used. , An extrusion lamination method, a dry lamination method, and the like, and are not limited thereto. In a preferred embodiment, the film obtained by these methods is subjected to a stretching process generally performed, for example, uniaxial stretching, zone stretching, flat sequential stretching, flat simultaneous biaxial stretching, and tubular simultaneous stretching.

The resin or its composition is dissolved in a solvent,
In order to obtain a film by a manufacturing method in which the obtained solution is formed into a liquid film and dried to produce a film, a resin containing a medium such as water or a composition thereof is coated on a release film to form a liquid film, and this is dried. A method of peeling off later or the like can be used.

As the above-mentioned coating method, direct gravure method, reverse gravure method, microgravure method, two roll beat coating method, bottom feed method 3
Examples of the method include a roll coating method such as the reverse coating method and the like, a doctor knife method, a die coating method, a dip coating method, a bar coating method, and a coating method combining these methods.

The resin constituting the laminated foam of the present invention includes:
It is preferred to incorporate other suitable additives. Examples of such additives include various additives described in “Separation and Analysis Techniques for Polymer Additives” published by Nippon Scientific Information, for example, antioxidants, light stabilizers, and the like. Agents, ultraviolet absorbers, anti-fog agents, anti-fog agents, plasticizers, antistatic agents, lubricants, colorants, fillers, nucleating agents and other high molecular compounds. These can be blended within a range that does not impair the effects of the present invention.

An example of the method for producing a laminated foamed sheet of the present invention will be described with reference to the drawings together with an example of a production apparatus suitable for production. FIG. 1 shows an example of a production apparatus suitable for producing a laminated foam of the present invention, and a state in which a laminated foam is produced using the apparatus. In this example, polypropylene is used for the foam layer, and a multi-layer polyolefin foam sheet having a non-foam layer on both sides of the foam layer is formed into a tube shape (cylindrical shape) by coextrusion, and is formed at two locations in the longitudinal direction. To obtain a multilayer foam having a gas-barrier resin layer by forming two multi-layer polyolefin foam sheets, supplying a gas-barrier resin film between them, and laminating them. For example, when a gas barrier resin single-layer film is used as the gas barrier resin film, the laminated foam obtained by this method has a non-foamed layer /
It has a seven-layer structure of foam layer / non-foam layer / gas barrier resin layer / non-foam layer / foam layer / non-foam layer. When a multilayer film composed of a gas barrier resin layer and another resin layer is used as the gas barrier resin film, a laminated foam including the layer structure of the multilayer film can be obtained. For example, adhesive resin layer /
When a gas barrier resin film having a three-layer structure of a gas barrier resin layer / adhesive resin layer is used, the obtained laminated foam has a non-foam layer / foam layer / non-foam layer / adhesive resin layer / gas barrier resin layer / Adhesive resin layer / non-foamed layer / foamed layer /
It has a structure called a non-foamed layer.

The multilayer gas barrier resin film is not limited to the three-layer structure described above, but has a structure such as a non-stretched polyolefin resin layer / adhesive resin layer / gas barrier resin layer / adhesive resin layer. Is also good.

The manufacturing apparatus 1 shown in FIG. 1 includes a first extruder 3 for extruding a foamed polypropylene layer, a second extruder 5 for extruding a non-foamed layer, an extrusion die 7, a mandrel 9, a cutter 30,
A roller 32, a raw gas barrier resin film 34, and the take-off roller 11 are provided.

The first extruder 3 is provided with a pump 6 for supplying carbon dioxide as a foaming agent. The polypropylene resin introduced from the hopper into the cylinder of the first extruder 3 is melted while being sent in the direction of the extrusion die 7 by a screw. The carbon dioxide gas is supplied to the molten resin when the resin is sufficiently melted, and is further uniformly dispersed and sent to the extrusion die 7. A configuration in which a known vent-type extruder is used as the first extruder and carbon dioxide gas is supplied under pressure from the vent hole without particularly requiring improvement of the extruder is a preferable embodiment.

The polyolefin resin constituting the non-foamed layer is melted by the second extruder 5 and sent to an extrusion die 7 (hereinafter sometimes simply referred to as a die). The type of the extrusion die 7 is not particularly limited as long as the internal structure is a structure suitable for forming a multilayer sheet. Flat dies such as T dies and coat hanger dies, circular dies such as straight dies, and crosshead dies are used. Is exemplified.

The multilayer foam sheet fed out of the extrusion die 7 in the form of a tube is preferably formed into a tube 15 having a predetermined diameter by the mandrel 9. By using a mandrel having a desired size, a foamed sheet having a desired width and thickness can be easily manufactured.

The multi-layer polypropylene foam sheet 15 having a non-foamed layer formed on both surfaces passing through the mandrel 9 is cut at two opposing portions of the tube by a cutter 30, and two flat sheets are formed by rollers 32. Fifteen, one
5 is assumed. Two multi-layer polypropylene foam sheets 15
Between them, a barrier resin film raw material 34 is disposed,
The unwound barrier resin film 36 is fed between the two multilayer polypropylene foam sheets 15 and pressed by the take-off roller 11 (lamination step) to form a laminated foam sheet S1. Gas barrier resin film 36
It is a suitable embodiment to provide a preheating step of heating the lamination surface before laminating the two with the two multilayer polypropylene foam sheets 15.

FIG. 4 is a view showing a sectional shape of a circular die suitable for carrying out the present invention used in the manufacturing apparatus shown in FIG.

The die used in this example is a circular die. The die 7 has resin flow paths 23a and 23b forming a foamed layer and resin flow paths 24, 24a, 24b, 24c and 24d forming a non-foamed layer.

The head 21 of the first extruder 3 is connected to the end of the die 7 in the direction of the resin flow path, and the head 22 of the second extruder 5 is connected to the side of the die 7 in the direction of the resin flow path. Head 21
The molten resin that forms the foamed layer supplied from the above first enters the channel 23a and is sent toward the die exit. On the way, it is branched by passing through the path P and sent to the flow path 23b.

On the other hand, the molten resin forming the non-foamed layer is the second resin.
It is supplied from the head 22 of the extruder 5 and
a, 24b, and supplied so as to adhere to both surfaces of the flow path 23b so as to cover both surfaces of the foam layer, and are multi-layered at 25a. The molten resin supplied to the flow paths 24a and 24b passes through a divided flow path (not shown) similar to the path P so as to cover both surfaces of the foam layer of the flow path 23a.
4c and 24d, and are multi-layered at 25b.

The molten resin having a three-layer cylindrical shape at 25 a and 25 b is extruded from a die outlet 26.
When the atmospheric pressure is released, the carbon dioxide gas in the resin constituting the foam layer expands, and bubbles are formed to form a foam layer.

FIG. 2 shows another example of a production apparatus suitable for producing a laminated foam of the present invention, and a state in which a laminated foam is produced using the apparatus. This example is different from the production apparatus shown in FIG. 1 in the supply of the gas barrier resin film and the lamination position. That is, using an extrusion device and a mandrel 9 having the same configuration as the device shown in FIG.
A multi-layer polyolefin foam sheet 15 formed by co-extrusion into a tubular (cylindrical) multi-layer polyolefin foam sheet 15 is continuously cut in the length direction at two locations,
The two multi-layer polyolefin foam sheets are laminated by a take-off roller 11 to form a laminated polyolefin foam sheet 50.
And Then, a gas barrier resin film 36 is supplied from a raw material (not shown) to a downstream position of the flow of the sheet via a guide roller 41, and is laminated on the laminated polyolefin foam sheet 50 by a pressure roller 42.
A laminated foam S3 having a gas barrier resin layer is obtained. The laminated foam S3 obtained by this method has a gas barrier resin layer / non-foamed layer / foamed layer / non-foamed layer / foamed layer /
It has a six-layer structure of a non-foam layer or a seven-layer structure of a gas barrier resin layer / non-foam layer / foam layer / non-foam layer / non-foam layer / foam layer / non-foam layer.

A gas barrier resin layer is further laminated on the opposite surface of the laminated polyolefin foam sheet 50, and is called gas barrier resin layer / non-foam layer / foam layer / non-foam layer / foam layer / non-foam layer / gas barrier resin layer. Layer structure or gas barrier resin layer / non-foamed layer / foamed layer / non-foamed layer / non-foamed layer /
An eight-layer laminated foam having a gas barrier resin layer on both sides of a foamed layer / non-foamed layer / gas barrier resin layer can also be obtained.

FIG. 2 shows an example in which a pressure roller 42 is provided for laminating the gas barrier resin film 36. However, without providing the pressure roller 42, the multi-layer polyolefin sheet is And taking over, and gas barrier resin film 36
Is also preferable from the viewpoint of simplification of the apparatus.

FIG. 3 shows another example of a production apparatus suitable for producing a laminated foam of the present invention, and a state in which a laminated foam is produced using the apparatus. In this example, a multilayered polyolefin foamed sheet formed in a tube (cylindrical) shape by coextrusion is continuously cut at one location in the length direction to form one multilayered polyolefin foamed sheet 15 and overlaid on one surface thereof. As described above, a gas-barrier resin film is supplied from a raw material (not shown) via a guide roller 41, and these are laminated using a take-off roller 11, whereby a laminated foam S2 having a gas-barrier resin layer is obtained. ing. The laminated foam S2 obtained by this method is:
Gas barrier resin layer / non-foamed layer / foamed layer / non-foamed layer 4
It has a layered structure. Here, the example in which the gas barrier resin film is laminated on only one side of the multilayer polyolefin foam sheet is shown. However, the gas barrier resin layer is supplied and laminated on both sides of the multilayer polyolefin foam sheet to form a gas barrier resin layer. A laminated foam having a five-layer structure of / non-foamed layer / foamed layer / non-foamed layer / gas barrier resin layer can also be obtained.

The manufacturing apparatus shown in FIG.
The flat die 7 includes one second extruder 5 and one extrusion die 7 which is a flat die.
Are provided with two extrusion openings 7a and 7b parallel to each other. The path P is formed so that the non-foamed layer constituting material is supplied to both sides of the foamed layer constituting material. When this apparatus is used, in the co-extrusion step, a polyolefin foamed layer constituent material and a polyolefin non-foamed layer constituent material are respectively supplied to the extrusion openings and co-extruded to form two layers of a non-foamed layer / foamed layer. Two multi-layer polyolefin foam sheets 15 having a structure are formed, and in the laminating step, a gas barrier resin film 36 is supplied from the raw fabric 34 to the space between the two multi-layer polyolefin foam sheets 15 and laminated. The body S4 is manufactured. The laminated foam S4 obtained by this method is preferably laminated so that the non-foamed layer is on the outside, and has a five-layer structure of non-foamed layer / foamed layer / gas barrier resin layer / foamed layer / non-foamed layer.

In the apparatus shown in FIG. 5, the foam layer forming material is first divided into two parts, and a die having a structure capable of supplying a non-foam layer forming material to both surfaces of each of the divided foam layer forming materials is provided. When co-extrusion is used, two multi-layer polyolefin foam sheets having a three-layer structure of a non-foamed layer / foamed layer / non-foamed layer can be formed. By supplying and laminating a gas barrier resin film between these multilayer foam sheets, seven layers of non-foam layer / foam layer / non-foam layer / gas barrier resin layer / non-foam layer / foam layer / non-foam layer A laminated foam having a structure can be obtained.

In the embodiment shown in FIG. 5, as in the case of manufacturing the foam laminated sheet S3 illustrated in FIG.
The multi-layer polyolefin foam sheet 15 is formed, and in the laminating step, the two multi-layer polyolefin foam sheets 15 are laminated by the take-off roller 11, and the gas barrier resin film is supplied on the downstream side thereof to form a pressure roller. It is also preferable to obtain a laminated foam having a gas-barrier resin layer as the outermost layer by laminating the foam.
The laminated foam obtained by this method has a four-layer structure of a gas barrier resin layer / non-foam layer / foam layer / non-foam layer or a gas barrier resin layer / non-foam layer / foam layer / foam layer / non-foam layer. It has a five-layer structure. Lamination may be performed by the take-up roller 11 without providing the pressure roller as described above.

FIG. 5 shows an example in which a gas barrier resin film is laminated from the outer surface side of one of the two multilayer polyolefin foam sheets. By supplying and laminating a gas barrier resin film from the outside of each, a gas barrier resin layer / non-foamed layer / foamed layer /
Lamination of a five-layer structure of a non-foaming layer / gas barrier resin layer or a six-layer structure having a gas barrier resin layer on both surfaces of a gas barrier resin layer / non-foam layer / foam layer / foam layer / non-foam layer / gas barrier resin layer A foam can also be obtained.
Furthermore, when the foamed layer constituting material is first divided into two parts and co-extruded using a die having a structure capable of supplying a non-foamed layer constituting material to both sides of each of the divided foamed layer constituting materials, the non-foamed layer / Two multi-layer polyolefin foam sheets having a three-layer structure of a foam layer / non-foam layer can be formed. If a gas barrier resin film is laminated on these two multi-layer polyolefin foam sheets, a gas barrier resin layer / non-foam layer / foam layer / non-foam layer / foam layer / non-foam layer 6
A laminated foam having a gas barrier resin layer on the outermost layer on one side of a seven-layer structure having a layer structure or a gas barrier resin layer / non-foam layer / foam layer / non-foam layer / non-foam layer / foam layer / non-foam layer; or Gas barrier resin layer / non-foamed layer / foamed layer /
7 layer structure of non-foaming layer / foaming layer / non-foaming layer / gas barrier resin layer or gas barrier resin layer / non-foaming layer / foaming layer / non-foaming layer / non-foaming layer / foaming layer / non-foaming layer / gas barrier resin A laminated foam having a gas barrier resin layer on the outermost layers on both surfaces having an eight-layer structure can be obtained.

When laminating the gas barrier resin film, in any case, as described above, the gas barrier resin film 36 of the laminated polyolefin foam sheet 50 is laminated.
, And at least one of the gas barrier resin film 36 surfaces, preferably the laminated polyolefin foam sheet 5
Preheating the surface of No. 0 is a preferred embodiment from the viewpoint of improving the adhesion.

In order to increase the expansion ratio, it is also a preferable embodiment that the sheet or tube extruded from the die is passed through a vacuum chamber to further expand the foam.

[0057]

〔Example〕

(Foam layer constituent material) As the foam layer constituent material, polypropylene by a two-stage polymerization method was used. Hereinafter, the polymerization method will be described.

(1) Synthesis of solid catalyst After replacing a 200 L stainless steel reaction vessel equipped with a stirrer with nitrogen, 80 L of hexane and titanium tetrabutoxy were used.
55 mol, 2.8 mol of diisobutyl phthalate and 98.9 mol of tetraethoxysilane were added to obtain a uniform solution. Next, 51 L of a diisobutyl ether solution of butylmagnesium chloride having a concentration of 2.1 mol / L was gradually dropped over 5 hours while maintaining the temperature in the reaction vessel at 5 ° C. After completion of the dropwise addition, the mixture was further stirred at room temperature for 1 hour, then subjected to solid-liquid separation at room temperature, and washed three times with 70 L of toluene. Next, toluene was added so that the slurry concentration became 0.6 kg / L, then a mixed solution of 8.9 mol of n-butyl ether and 274 mol of titanium tetrachloride was added, and 20.8 mol of phthalic chloride was further added. The reaction was performed at 110 ° C. for 3 hours. After completion of the reaction, washing was performed twice at 95 ° C. with toluene. Next, after adjusting the slurry concentration to 0.6 kg / L, 3.13 mol of diisobutyl phthalate, 8.9 mol of n-dibutyl ether and 137 mol of titanium tetrachloride were added, and the mixture was reacted at 105 ° C. for 1 hour. After the completion of the reaction, the mixture was subjected to solid-liquid separation at the same temperature, and then washed twice at 95 ° C. with 90 L of toluene. Next, after adjusting the slurry concentration to 0.6 kg / L, 8.9 mol of n-dibutyl ether and 137 mol of titanium tetrachloride were added, and the mixture was reacted at 95 ° C. for 1 hour. After the completion of the reaction, solid-liquid separation was performed at the same temperature, and washing was performed three times with 90 L of toluene at the same temperature. Then, after adjusting the slurry concentration to 0.6 kg / L, n-butyl ether 8.
9 mol and 137 mol of titanium tetrachloride were added, and the mixture was reacted at 95 ° C. for 1 hour. After completion of the reaction, solid-liquid separation was performed at the same temperature, and the solid was washed three times with 90 L of toluene at the same temperature, further washed three times with 90 L of hexane, and dried under reduced pressure to obtain 11.0 kg of a solid catalyst component.

The solid catalyst component comprises 1.9% by weight of titanium atoms,
20% by weight of magnesium atom, phthalate 8.6
Weight%, ethoxy group 0.05 weight%, butoxy group 0.2
It contained 1% by weight and had good particle properties without fine powder.

(2) Pre-activation of solid catalyst component: 1.5 L of n-hexane, 37.5 mmol of triethylaluminum, 37.5 mmol of t-butyl-, dehydrated and sufficiently dehydrated in a stainless steel autoclave having an internal volume of 3 L and having a stirrer
3.75 mmol of n-propyldimethoxysilane and 15 g of the above solid catalyst component were added, and the temperature in the vessel was adjusted to 5 to 15 ° C.
, 15 g of propylene was continuously supplied over 30 minutes to carry out preactivation.

(3) Polymerization of Propylene Polymer First Stage In a first polymerization vessel made of SUS and having a volume of 300 L, 57 kg / liquid propylene was added so as to maintain a polymerization temperature of 60 ° C. and a polymerization pressure of 27 kg / cm ² G. 1.3 mmol / h of triethylaluminum, 0.13 mmol / h of t-butyl-n-propyldimethoxysilane
Then, 0.51 g / h of the preactivated solid catalyst component was continuously supplied, and propylene polymerization was carried out in the substantial absence of hydrogen to obtain a polymer of 2.0 kg / h. At this time, the produced amount of the polymer was 3920 g per 1 g of the catalyst, and as a result of sampling and analyzing a part thereof, the intrinsic viscosity was 7.7 dL / g. The obtained polymer was continuously transferred to the second polymerization tank without being deactivated.

Second stage In a fluidized bed reactor with an internal volume of 1 m ³ equipped with a stirrer (second polymerization tank), the polymerization temperature is 80 ° C., and the polymerization pressure is 18 kg / c.
While supplying propylene and hydrogen so as to maintain m ² G and a hydrogen concentration of 8 vol% in the gas phase, the catalyst-containing polymer transferred from the first polymerization tank and triethylaluminum 60 mmol / h, t-butyl-n By continuing propylene polymerization continuously while supplying 6 mmol / h of -propyldimethoxysilane, a polymer of 18.2 kg / h was obtained. The intrinsic viscosity of this polymer is 1.9 dL /
g.

From the above results, the amount of polymer produced during the second stage polymerization was 31760 g per 1 g of the catalyst, the polymerization weight ratio of the first polymerization tank to the second polymerization tank was 11:89, and the second stage polymerization was carried out. The intrinsic viscosity of the polymer in the portion formed by the reaction was determined to be 1.2 dL / g.

(4) Pelletization of Polymer 100 parts by weight of the polymer powder obtained by the above two-step reaction was mixed with 0.1 part by weight of calcium stearate, and Irganox 1010 (trade name of Ciba Specialty Co., Ltd.).
(Chemicals) and 0.2 parts by weight of Sumilyzer BHT (Sumitomo Chemical Co., Ltd.) were added, mixed and melt-kneaded at 230 ° C. to obtain pellets having an MFR of 12.

(Material for non-foamed layer) As a material for non-foamed layer, polypropylene PF814 having a long-chain branch made by Montell (melting point: 159.0 ° C., crystallization temperature: 13)
0.1 ° C, MI 2.2 g / 10 min).

(Gas Barrier Resin Layer Constituent Material) Saponified ethylene-vinyl acetate copolymer having an ethylene content of 44 mol% and a saponification degree of 98% or more (EP-E1 manufactured by Kuraray Co., Ltd.)
05A: MFR = 5.5 g / 10 min) was applied to a gas barrier resin layer, polypropylene (Sumitomo Chemical Co. polypropylene F)
L8115: MFR = 7 g / 10 min) as the outermost layer, acid-modified polypropylene (Admer QF55, Mitsui Petrochemical Co., Ltd.)
1: MFR = 5.7 g / 10 min) was used as an adhesive layer, and the thickness configuration was (adhesive layer / barrier layer / adhesive layer / outermost layer = 10/30 /
10/50 (unit: μm)) to produce a gas barrier resin film having a thickness distribution Tmax / Tmin of 1.0 measured in a range of 25 cm ² of the coextruded film of 1.0. For producing a laminated foam.

[Comparative Example] The same material as that of the example was used as the foam layer forming material and the non-foaming layer forming material. The material constituting the gas barrier resin layer is the same as that in the example, but the film has a thickness distribution Tmax / Tmin measured in a range of 25 cm ^2.
= 1.3.

[Extrusion Foaming Test] An apparatus in which a 90 mmΦ circular die (7) was attached to a 50 mmΦ twin screw extruder (3) and a 32 mmΦ single screw extruder (5) was used. A raw material obtained by blending 1 part by weight of a nucleating agent (Hydrocerol manufactured by Beilinger Ingelheim Chemicals Co., Ltd.) with respect to 100 parts by weight of the propylene polymer used for the foamed layer was put into a hopper of an extruder (3) and melted. 1 part by weight of carbon dioxide gas was injected from the position where the process had progressed, the raw material and carbon dioxide gas were sufficiently kneaded and melted and fed to a die (7). The molten mixture to be a foamed layer and the molten resin to be a non-foamed layer fed by an extruder (5) are laminated and extruded in a die, and then cooled and expanded (blow-up) along a mandrel (9) installed immediately after. ) Is done. Thereafter, two slits are made in the cylindrical foamed sheet with a cutter, and two strips having the same width are formed into a flat sheet. During this time, a barrier resin film is supplied, and the sheet is pressure-bonded and laminated by a take-off roller (11). Wound up.

[Vacuum Forming] The obtained multilayer polyolefin foam sheet was heated at a surface temperature of 1 with a far-infrared heater.
The temperature was set to 30 ° C. to 160 ° C., and vacuum forming was performed using a cylindrical female mold.

[Evaluation of Appearance] The ratio of the area where appearance defects such as dents and uneven thickness were observed to the total surface area of the vacuum-formed product (area of defective appearance of molded product / total area of molded product) was determined. The higher the value of this ratio, the poorer the appearance, and the lower the value, the better the appearance. Table 1 shows the results of Examples and Comparative Examples.

[0071]

[Table 1]

[Brief description of the drawings]

FIG. 1 is a view showing an example of a production apparatus suitable for producing a laminated foam of the present invention and a form of producing a laminated foam.

FIG. 2 is a diagram showing a cross-sectional shape of a preferred circular die in the apparatus for producing a laminated foam of the present invention.

FIG. 3 is a view showing another example of a production apparatus suitable for producing a laminated foam of the present invention and a form of producing the laminated foam.

FIG. 4 is a view showing another example of a production apparatus suitable for producing a laminated foam of the present invention and a form of producing a laminated foam.

FIG. 5 is a view showing another example of a production apparatus suitable for producing a laminated foam of the present invention and a form of producing the laminated foam.

Claims (6)

[Claims] 1. A laminated foam comprising at least one polyolefin foam layer and at least one gas barrier resin layer, wherein the gas barrier resin layer has a thickness of 10 to 200 μm,
A laminated foam having a thickness distribution Tmax / Tmin of 1.0 to 1.2 in a range of at least 25 cm ² . 2. The laminated foam according to claim 1, wherein a polyolefin foam sheet having a polyolefin foam layer and a gas barrier resin film having a gas barrier resin layer are laminated by heat fusion. 3. The laminated foam according to claim 1, further comprising at least one non-foamed layer of a polyolefin resin. 4. The laminated foam according to claim 3, wherein the polyolefin resin constituting the non-foamed layer is a long-chain branched polypropylene or a long-chain branched polyolefin adhesive resin. 5. The laminate according to claim 4, wherein the long-chain branched polypropylene or long-chain branched polyolefin adhesive resin has a branching degree index [A] satisfying 0.20 ≦ [A] ≦ 0.98. Foam. 6. The laminated foam according to claim 1, wherein the content of the low-molecular-weight organic compound having 3 to 4 carbon atoms is 10,000 ppm or less.