JP2001113654A - Multilayered polyolefin foamed sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayered polyolefin foamed sheet high in surface smoothness and excellent in secondary moldability such as vacuum moldability or the like. SOLUTION: A multilayered polyolefin foamed sheet has a foamed layer and a non-foamed layer and the foamed layer is a polyolefin foamed layer and the non-foamed layer is formed from long chain branched polyolefinic adhesive resin. The long chain branched polyolefinic adhesive resin pref. satisfies a degree-of-branching index [A] of 0.20<=[A]<=0.98.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-layer polyolefin foam sheet, and more particularly, to a sheet having excellent vacuum moldability and laminating properties when the same or different sheets are laminated to form a multilayer. The present invention relates to a multilayer polyolefin foam sheet having excellent lamination properties with a lid sheet when used as a container.

[0002]

2. Description of the Related Art Cups, trays, and other containers for home meal replacement (HMR), which are cooked foods to be heated in a microwave oven, are light in weight and have insulation properties so that they can be touched by hand after heating. Resin foam is used, and currently polystyrene foam is used.

[0003] However, the heat resistance of polystyrene is not yet sufficient, and polyolefin resin foams, particularly polypropylene foams having high heat resistance, have been of interest as an alternative.

[0004] Foams of polyolefins such as polyethylene and polypropylene are known. Known polyolefin foams include azodicarbonamide-based compounds, foams using chemical blowing agents such as nitroso compounds, foams using low-boiling aliphatic hydrocarbons such as propane and butane as blowing agents, and carbon dioxide. The foam used is known.

[0005]

However, the use of chemical blowing agents is not cost-effective. On the other hand, when carbon dioxide gas is used as a foaming agent, the foam is easily broken in the foaming step, and it is difficult to produce a foam itself. Polypropylene, which is easy to produce foam, is also known,
A foam sheet obtained by foaming carbon dioxide using such polypropylene has insufficient vacuum moldability, and thus has a problem in that, for example, vacuum molding of a food container causes foam breakage. In addition, since only those having high surface roughness can be obtained, the laminating property in the case of laminating the same type or different types of sheets to form a multilayer is not satisfactory.
In the case of a food container such as an MR, there is also a problem that a problem tends to occur in sealing between the lid and the lid sheet.

[0006] A foamed polyolefin sheet which is provided with a non-foamed layer on the surface to improve the appearance and is used for a surface covering material, a book case and the like is known (Japanese Patent No. 2820611). However, this method is characterized by adding a powdery filler to the non-foamed layer, and although the surface appearance is certainly improved, the secondary workability such as vacuum moldability is poor, and the It cannot be used for such purposes.

[0007] An object of the present invention is to provide high surface smoothness and excellent secondary workability such as vacuum formability, as well as multi-layering of itself, lamination with other materials, heat sealability and the like. An object of the present invention is to provide a multilayer polyolefin foam sheet having excellent secondary workability.

[0008]

The multilayer polyolefin foam sheet of the present invention has a foam layer and a non-foam layer, wherein the foam layer is a polyolefin foam layer, and the non-foam layer is a polyolefin-based material having a long-chain branch. It is characterized by being formed of an adhesive resin.

With the above-described structure, a multilayer polyolefin foam sheet having excellent vacuum moldability can be obtained. Moreover, since the non-foamed layer is made of a polyolefin-based adhesive resin, when this non-foamed layer is heated, a multilayered polyolefin foamed sheet can be formed by laminating a multi-layered polyolefin foamed sheet through this layer. In addition, the laminating property with other film materials and the like is improved, and the sealing property with the lid sheet when vacuum-formed to form a container is also excellent.

The above-mentioned polyolefin-based adhesive resin preferably has a branching degree index [A] satisfying 0.20 ≦ [A] ≦ 0.98.

When the branching index [A] is 0.20 ≦ [A] ≦
The long-chain branched polyolefin-based adhesive resin satisfying 0.98 has high strength in a molten state. By providing a non-foamed resin layer composed of this long-chain branched polyolefin-based adhesive resin on the surface, As a result, the effect of preventing the occurrence of unevenness due to bubbles (cells) formed by the foaming agent, and the occurrence of unevenness due to the destruction of the cells,
It is considered that a multilayer polyolefin foam sheet having high surface smoothness and excellent secondary workability such as vacuum moldability can be obtained.

The branching degree index [A] of the long-chain branched polyolefin adhesive resin is more preferably in the range of 0.30 ≦ [A] ≦ 0.90, and 0.40 ≦ [A] ≦ 0. 8
0 means that the surface smoothness, vacuum formability, etc.
A multi-layer polyolefin foam sheet having further excellent workability is obtained, which is particularly preferable.

The long-chain branched polyolefin-based adhesive resin is a resin having a functional group such as a carboxyl group or a hydroxyl group in a branched long chain. The adhesiveness between the resin and other materials, for example, a hot melt adhesive or a film substrate, is excellent.

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 long-chain branched polyolefin-based adhesive resin, and [η] Lin has substantially a weight average molecular weight. It is the intrinsic viscosity of the corresponding linear polyolefin which is the same. For example, in the case of a long-chain branched polyethylene-based adhesive resin, [η] Br is the intrinsic viscosity of the long-chain-branched polyethylene-based adhesive resin, and [η] Lin is the weight average of the long-chain-branched polyethylene-based adhesive resin. It is the intrinsic viscosity of high density polyethylene of substantially the same molecular weight. In the case of a long-chain branched polypropylene-based adhesive resin, [η] Br is the intrinsic viscosity of the long-chain-branched polypropylene-based adhesive resin, and [η] Lin is the weight average of the long-chain-branched polypropylene-based adhesive resin. It is the intrinsic viscosity of a predominantly isotactic semicrystalline linear polypropylene of substantially the same molecular weight.

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 measuring method of the intrinsic viscosity of the long-chain branched polyolefin adhesive resin is as follows.
Elliott et al. (J. App.Poly.Sci., 14, 2947-2963 (1970))
Is described. In the present specification, the intrinsic viscosity in each case is measured at 135 ° C. for a sample dissolved in tetralin or orthodichlorobenzene.

The weight average molecular weight (Mw) can be measured by various methods. Preferred methods are GPC method and
MLMcConnel, American Laboratory, May, 63-7
5 (1978), namely a low angle laser light scattering photometry.

The multilayer polyolefin foam sheet having high smoothness may have at least one foam layer and one non-foam layer, and preferably has a three-layer structure of non-foam layer / foam layer / non-foam layer. It was done. Since the sheet having such a structure has both sides formed of a non-foamed layer, both sides have high smoothness and excellent vacuum formability.

In the multilayer polyolefin foam sheet of the present invention, it is preferable that at least three non-foamed layers are formed.

The formation of the non-foamed layer between the foamed layers results in a multilayer polyolefin foamed sheet having further improved vacuum moldability.

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, and a foamed layer having a foaming ratio of 1.5 to 1.5 times. More than twice, preferably 2.5 to 40 times layers. If the expansion ratio is less than 2.5 times, the properties as a foam, specifically light weight, heat insulation, etc., will not be sufficient, and if it exceeds 40 times, the production will be difficult and the foam will break during vacuum forming. Can not be suppressed.
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.

Preferably, the polyolefin foam layer is formed of a polypropylene foam.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION As the polyolefin constituting the foamed layer, a homopolymer of ethylene, propylene, butene or the like, a copolymer using two or more of these monomers, and at least one of these monomers And other monomers. Examples of the copolymer include an ethylene-α-olefin copolymer and a propylene-α-olefin copolymer.

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) long-chain branched polypropylene, because the uniformity of the foam is high and the multi-layer polyolefin foam sheet of the present invention is particularly excellent in vacuum moldability. (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 polypropylene PF-814 (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 for forming the foamed layer is preferably an inert substance such as water or carbon dioxide gas in consideration of the influence on the environment. In particular, when polypropylene is used as the resin constituting the foam layer, the use of carbon dioxide is preferred.

Examples of the polyolefin adhesive resin having a long chain branch which forms a non-foamed layer include: 1) unsaturated carboxylic acid, unsaturated carboxylic anhydride, epoxy group-containing vinyl monomer, unsaturated carboxylic acid ester, vinyl ester And copolymers of one or more monomers selected from the group consisting of the above and an olefin monomer, and 2) an acid-modified olefin polymer grafted with an unsaturated carboxylic acid or an acid anhydride thereof.

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

The polyolefin-based adhesive resin having a long-chain branch constituting the non-foamed layer may be one type or a mixture of two or more types. The non-foamed layer may contain a thermoplastic elastomer as long as the effects of the present invention are not significantly impaired.

The thickness of the non-foamed layer is not particularly limited as long as the surface is smooth, that is, the appearance is good.
m, more preferably 10 μm or more, further preferably 50 μm or more. The upper limit of the thickness is the thickness of the entire multilayer foamed polyolefin sheet,
It is set appropriately according to the use and the like. If it is too thick, the properties of the foamed layer will not be sufficiently exhibited.

It is preferable that the multilayer foamed polyolefin sheet of the present invention contains other suitable additives. An example of such an additive is “Separation and Analysis Technology for Polymer Additives,” published by Japan Science Information.
Various additives can be used as described in, for example, antioxidants, light stabilizers, ultraviolet absorbers, anti-fog agents, anti-fog agents, plasticizers, antistatic agents, lubricants, coloring agents, fillers, Nucleating agents or other high molecular compounds can be mentioned.
These can be blended within a range that does not impair the effects of the present invention.

Examples of the antioxidant include 2,5-di-t-butylhydroquinone, 2,6-di-t-butyl-p-cresol, 4,4′-thiobis- (6-t-butylphenol), , 2'-Methylene-bis (4-methyl-6
-T-butylphenol), octadecyl-3- (3 ′
, 5'-Di-t-butyl-4'-hydroxyphenyl) propionate, 4,4'-thiobis- (6-t-
Phenolic antioxidants such as butylphenol), phenyldiisodecyl phosphite, diphenylisooctyl phosphite, triphenyl phosphite,
Trinonylphenyl phosphite, tris- (2,4
-Di-t-butylphenyl) phosphite, 4,4 '
-Phosphorus oxidation prevention such as isopropylidene diphenol alkyl phosphite, 1,1,3-tris (2-methyl-4-di-tridecyl) phosphite, 5-t-butylphenylbutanephenyldi (tridecyl) phosphite Agent, dilauryl 3,3'-thiodipropionate, ditridecyl 3,3'-thiodipropionate, dimyristyl 3,3'-thiodipropionate, distearyl 3,3'-thiodipropionate , Laurylstearyl 3,3'-thiodipropionate, bis [2-methyl-4-
(3-n-alkylthiopropionyloxy-5-t-
Butylphenyl] sulfide, pentaerythritol tetra (β-lauryl-thiopropionate) ester,
2-mercaptobenzimidazole, 2-mercapto-
And sulfur-based antioxidants such as 6-methylbenzimidazole.

An example of the method for producing a multilayer foamed polyolefin sheet of the present invention will be described with reference to the drawings. In this example, polypropylene using carbon dioxide as a foaming agent was used as a foaming layer, a long-chain branched polyolefin adhesive resin was used as a non-foaming layer, and a non-foaming layer / foaming layer / non-foaming layer was used. 1 shows a production example of a foamed polypropylene sheet having a layer structure.

FIG. 1 shows an example of an apparatus for producing a multilayer foamed polyolefin sheet of the present invention. Manufacturing equipment 1
Is an extruder 3 for extruding a foamed layer, an extruder 5 for extruding a non-foamed layer, and an extrusion die (hereinafter sometimes simply referred to as a die).
7, a mandrel 9, and a take-off roller 11.

The extruder 3 is provided with a pump 6 for supplying carbon dioxide as a foaming agent. The polypropylene resin charged into the cylinder of the extruder 3 from the hopper is
It is melted while being sent in the direction of the die 7 by the 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 die 7. A configuration in which a known vent-type extruder is used as the extruder and carbon dioxide gas is supplied under pressure from a vent hole is not particularly required to improve the extruder, and is a preferable embodiment.

The long-chain branched polyolefin adhesive resin constituting the non-foamed layer is melted by the extruder 5 and sent to the die 7. The type of the die 7 is not particularly limited as long as the internal structure is a structure suitable for forming a multilayer sheet. A flat die such as a T die and a coat hanger die, a circular die such as a straight die, and a crosshead die are used. Is exemplified.

The foamed layer constituent material and the non-foamed layer constituent material are laminated and extruded in the die 7 in a molten state.
The residence time in the extrusion die 7 after the lamination is preferably from 0.1 to 20 seconds, more preferably from 0.5 to 15 seconds.

The multi-layer foamed sheet sent out from the die 7 in the form of a tube is formed into a tube 15 having a predetermined diameter by the mandrel 9, and after cooling, folded by the take-off roller 11 and taken off. When this is cut at two folds, two three-layer foam sheets are obtained. In addition, a single wide sheet can be obtained by incising the tubular multilayered sheet at one place.

When two sheets of the obtained three-layered foamed sheet are laminated and bonded, a non-foamed layer / foamed layer / non-foamed layer / foamed layer / non-foamed layer, or a non-foamed layer / foamed layer / non-foamed layer A foamed sheet having three to four non-foamed layers having a structure of / non-foamed layer / foamed layer / non-foamed layer is obtained. Since the non-foamed layer formed of the adhesive resin is present on the surface of the foamed sheet having the three-layered or four-layered structure, the five-layered structure or the six-layered structure is strongly bonded by bonding two sheets of the non-foamed layer. A foamed sheet with a structure is obtained. The layers may be further laminated to form a multilayer structure.

A preferred embodiment of the structure of the die is shown in cross section in FIG. The die used in this example is a circular die. The die 7 has a resin flow path 23a, 23b forming a foamed layer and a resin flow path 2 forming a non-foamed layer.
4, 24a, 24b, 24c, 24d are formed.

A head 21 of the extruder 3 is connected to a source flow end of the die 7 in the resin flow direction, and a head 22 of the extruder 5 is connected to a source flow side. The molten resin forming the foam layer supplied from the head 21 first enters the flow path 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 supplied from the head 22 of the extruder 5,
It is divided into 24b, supplied so as to be laminated on both sides of the flow path 23b so as to cover both sides of the foam layer, and is 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.
c, 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.
By opening to the atmospheric pressure, the carbon dioxide gas in the resin constituting the foam layer expands, and bubbles are formed to form a foam layer.

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.

In each of the above examples, a single-screw extruder was used. However, a twin-screw extruder or the like can be used as an extruder for extruding at least one, and preferably, a foam layer constituent material. is there.

The multilayer polyolefin foam sheet of the present invention can be used for various applications, and specifically, food containers including microwave oven-compatible containers (HMR), heat insulating materials, cushioning materials for sports equipment, packing materials and the like. Examples of such uses include automotive parts such as insulating materials, vehicle ceiling materials, sealing materials, building materials, and resins that require lightness and heat insulation in the aerospace industry.

[0049]

〔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, fully dehydrated and degassed in a stainless steel autoclave with 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 (second polymerization tank) with a stirrer having an internal volume of 1 m ³ , a polymerization temperature of 80 ° C. and a polymerization pressure of 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 in 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 0.05 parts by weight of Sumilyzer BHT (manufactured by Sumitomo Chemical Co., Ltd.) were added and mixed and melt-kneaded at 230 ° C. to obtain pellets having an MFR of 12 g / 10 minutes. .

(Non-foamed layer constituent material) As a non-foamed layer constituent material, adhesive resin Admer LF500 (manufactured by Mitsui Petrochemical Industries, Ltd.), which is a polyolefin-based adhesive resin having a long chain branch (melting point 135 ° C, density 0) .89 g / cm ³ , M
FR 5.7 g / 10 min).

[Comparative Example] The same material as that used in the example was used as the foam layer constituting material. As the non-foaming layer constituting material, an adhesive resin which is a polyolefin adhesive resin having no long-chain branch (melting point: 120 ° C., density: 0.92 g / cm ³ , MFR
(3.5 g / 10 min).

[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, expanded along a mandrel (9) provided immediately after, and cooled. . Later, this cylindrical foam sheet is slit with a cutter,
Open the cylinder to make a flat sheet, take-off roller (11)
We picked it up.

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

[Evaluation of Appearance] The ratio of the area in which appearance defects such as dents and uneven thickness were recognized with respect to the total surface area of the vacuum-formed article (area of defective appearance of the molded article / total area of the molded article) 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.

[0062]

[Table 1]

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a preferred configuration of a production apparatus for a multilayer foamed polyolefin sheet.

FIG. 2 is a cross-sectional view illustrating a preferred configuration of a head in the apparatus for manufacturing a multilayer foamed polyolefin sheet.

Claims (6)

[Claims] 1. A foamed layer and a non-foamed layer, wherein the foamed layer is a polyolefin foamed layer, and the non-foamed layer is formed of a polyolefin-based adhesive resin having a long chain branch. Multi-layer polyolefin foam sheet. 2. The multilayer polyolefin foam sheet according to claim 1, wherein the polyolefin-based adhesive resin has a branching degree index [A] satisfying 0.20 ≦ [A] ≦ 0.98. 3. The non-foamed layer is at least two layers,
The multilayer polyolefin foam sheet according to claim 1 or 2, having a non-foam layer / foam layer / non-foam layer structure. 4. The multilayer polyolefin foam sheet according to claim 1, wherein at least three non-foamed layers are provided. 5. The multilayer polyolefin foam sheet according to claim 1, wherein the expansion ratio of the foam layer is 2.5 to 40 times. 6. The multilayer polyolefin foam sheet according to claim 1, wherein the polyolefin foam layer is formed of a polypropylene foam.