JP2002166510A - Polyolefinic resin foamed sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyolefinic resin foamed sheet having a smooth surface by preventing breaking of foam in a foamed layer. SOLUTION: The polyolefinic resin foamed sheet is constituted by providing a polyolefinic resin non-foamed layer, which contains 10 wt.% or more of a polyolefinic resin selected from the group consisting of a long chain branched polyolefinic resin and a polyolefinic resin with a weight average mol.wt. of 1×105 or more and passed through a process melted from a solid state and subsequently re-solidified once or more, on at least the single surface of a polyolefinic resin foamed layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foamed polyolefin resin sheet having excellent surface smoothness.

[0002]

2. Description of the Related Art A foamed polyolefin resin sheet in which a non-foamed polyolefin resin layer is laminated on at least one surface of a foamed polyolefin resin layer is well known, and is used as a building / civil engineering material, a container for packaging and the like. However, during the production process, a phenomenon in which bubbles in the foamed layer of the polyolefin-based resin burst, that is, a so-called foam breakage, often occurs, and as a result, a foamed polyolefin-based resin sheet having poor surface smoothness may be obtained.

[0003]

DISCLOSURE OF THE INVENTION The present inventors have conducted intensive studies in order to solve this problem, and by laminating a layer made of a long-chain branched polyolefin-based resin on a polyolefin-based resin foamed layer, to obtain a smooth surface. It has been found earlier that a polyolefin-based resin foam sheet having excellent properties can be obtained.

However, according to a further study, the long-chain branched polyolefin-based resin is inferior in extrusion stability due to its high melt viscosity. It has been found that unevenness may occur, and that in the portion where the non-foamed layer is thin, poor appearance on the foamed layer surface cannot always be sufficiently improved. In particular, when a relatively thin non-foamed layer was to be formed, this tendency became remarkable, and it was found that the surface smoothness of the polyolefin resin foamed sheet was easily impaired. In view of the above findings of the present inventors, the purpose of the present invention is
A non-foamed layer made of a polyolefin resin is laminated on at least one surface of the polyolefin resin foam layer,
An object of the present invention is to provide a polyolefin resin foam sheet having excellent surface smoothness.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, the foamed layer made of a polyolefin resin has undergone at least one step of melting from a solid state and then re-solidifying. By laminating a non-foamed layer made of a long-chain branched polyolefin resin and / or a polyolefin resin having a weight average molecular weight of 1 × 10 ⁵ or more,
The present inventors have found that a polyolefin resin foam sheet having excellent surface smoothness can be obtained by effectively covering the thickness unevenness and appearance roughness of the foam layer, and completed the present invention.

That is, the present invention relates to a foamed polyolefin resin sheet comprising a non-foamed polyolefin resin layer laminated on at least one side of a foamed polyolefin resin layer, wherein the non-foamed layer comprises a long-chain branched polyolefin resin. And a polyolefin-based resin having a weight-average molecular weight of 1 × 10 ⁵ or more, and containing 10% by weight or more of a polyolefin-based resin that has undergone at least one step of melting and then re-solidifying from a solid state. To provide a polyolefin resin foam sheet. The process in which the resin is melted from the solid state and then re-solidified as described above may be hereinafter referred to as a “melting-re-solidification process”. Further, a polyolefin resin selected from the group consisting of the long-chain branched polyolefin resin and a polyolefin resin having a weight average molecular weight of 1 × 10 ⁵ or more, and subjected to at least one step of melting and then re-solidifying from a solid state, Hereinafter, it may be referred to as “re-solidified polyolefin resin”.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is a foamed polyolefin resin sheet having a non-foamed polyolefin resin layer laminated on at least one side of a foamed polyolefin resin layer. First, the polyolefin resin constituting the foamed layer in the polyolefin resin foam sheet of the present invention may be any polyolefin resin capable of forming and maintaining a foamed structure, for example, ethylene, propylene,
Examples include homopolymers of olefins having 2 to 6 carbon atoms such as butene, pentene, and hexene, and olefin copolymers composed of two or more monomers selected from olefins having 2 to 10 carbon atoms. The copolymer may be any of a block copolymer, a random copolymer, and a graft copolymer. For forming the polyolefin resin foam layer, even if only one kind of polyolefin resin is used,
You may blend and use more than one kind of polyolefin resin. From the viewpoint of heat resistance, a polypropylene-based resin is preferable, and a small amount of a polyethylene-based resin is preferably added to the polypropylene-based resin in order to improve moldability.

Particularly preferred polypropylene resins include propylene homopolymer and 5
Propylene copolymers containing 0 mol% or more can be mentioned. Preferred examples of the copolymer component with propylene in the propylene-based copolymer include ethylene and α-olefins having 4 to 10 carbon atoms. As the α-olefin having 4 to 10 carbon atoms, for example, 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 10% by weight or less for ethylene and 30% by weight or less for α-olefin.

Among the polypropylene resins, (a) a long-chain branched polypropylene and (b) a polypropylene having a weight-average molecular weight of 1 × 10 ⁵ or more, since a foamed layer having a highly uniform cell structure can be formed among polypropylene resins. A system resin is preferred. These polypropylene resins have a melting point of +
Under a temperature condition of 30 ° C., the elongation strain rate is 0.1 sec.
At c ^-1 , when a uniaxial melt extensional viscosity measurement was carried out by a device such as a Meissener type extension rheometer (for example, a Merten rheometer manufactured by Toyo Seiki), 1
Uniaxial melt extensional viscosity η ₁ , η at each point of 100 seconds
Those having a ratio of ₁₀₀ (η ₁₀₀ / η ₁ ) satisfying η ₁₀₀ / η ₁ ≧ 10 are particularly preferred.

As the foaming agent used for the polyolefin resin foam sheet of the present invention, any of a so-called chemical foaming agent and a physical foaming agent can be used. Decomposition type foaming agents (azodicarbonamide, azobisisobutyronitrile, dinitrosopentamethylenetetramine, p-toluenesulfonylhydrazide, p, p'-oxy-bis (benzenesulfonylhydrazide), etc.), heat for generating carbon dioxide gas Decomposable inorganic foaming agents (such as sodium bicarbonate, ammonium carbonate, ammonium bicarbonate) and the like;
Possible physical blowing agents include propane, butane,
Water, carbon dioxide and the like can be mentioned. Among these, water,
Substances that are inert to high-temperature conditions and fire, such as carbon dioxide, are preferred. In particular, when a polypropylene resin is used as the resin constituting the foam layer, the use of carbon dioxide gas is preferred.
In the present invention, the amount of the foaming agent used is not critical, and may be appropriately adjusted according to the type of the foaming agent, the type of the resin, and the like so as to obtain a desired expansion ratio.

Next, the polyolefin resin material constituting the non-foamed layer will be described. The polyolefin resin used for the non-foamed layer of the polyolefin resin foam sheet of the present invention is selected from the group consisting of a long-chain branched polyolefin resin and a polyolefin resin having a weight average molecular weight of 1 × 10 ⁵ or more, from the solid state. It is characterized by containing 10% by weight or more of a polyolefin-based resin (re-solidified polyolefin-based resin) which has been subjected to one or more steps of melting and then re-solidification (melt-re-solidification step). By using a re-solidified polyolefin-based resin as the material of the non-foamed layer to be laminated on the foamed layer, the non-foamed layer with less thickness unevenness can be easily and reliably formed based on the fact that the melt viscosity of the resin is reduced. Can be formed. As a result, foam breakage during foam layer formation can be more reliably prevented, and a foam sheet excellent in surface appearance can be obtained more efficiently.

In the present invention, a long-chain branched polyolefin resin is defined as having a branching degree index [A] of 0.20 ≦ [A] ≦
It refers to a polyolefin-based resin that satisfies 0.98, and has a molecular structure of ethylene, propylene, butene, pentene, a homopolymer of an olefin having 2 to 6 carbon atoms such as hexene, and a polymer having 2 to 10 carbon atoms. Examples include polyolefin-based resins such as olefin copolymers composed of two or more monomers selected from olefins. The copolymer may be any of a block copolymer, a random copolymer, and a graft copolymer. A polypropylene resin is particularly preferred from the viewpoint of heat resistance. Examples of the long-chain branched polyolefin-based resin having a branching degree index [A] satisfying 0.20 ≦ [A] ≦ 0.98 include polypropylene PF-814 manufactured by Montell.

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 where [η] _Br is the intrinsic viscosity of the polyolefin resin having a long chain branch, and [η] _Lin is the polyolefin having a long chain branch. It is the intrinsic viscosity of linear PO having the same repeating unit as the system resin and the weight average molecular weight. Intrinsic viscosity, also called the limiting viscosity number, is a measure of the ability of a polymer molecule to enhance solution viscosity. The intrinsic viscosity depends in particular on the molecular weight of the polymer molecules and on the degree of branching. Thus, when comparing a polymer with long chain branches to a linear polymer of the same weight average molecular weight, the intrinsic viscosity is a measure of the degree of branching of the polymer, and the ratio of the intrinsic viscosity is defined as the index of branching and the index of branching. did. The method for measuring the intrinsic viscosity of polypropylene is described in Elliott et al. [J. Appl. Polym. Sci. 14,29
47-2963 (1970)].
The intrinsic viscosity of polypropylene is, for example, 135 ° C. for a sample dissolved in tetralin or orthodichlorobenzene.
Can be measured. The weight average molecular weight (Mw) can be measured by various methods. L. M
American Labo by cConnell
The method disclosed in the literature, May, 63-75 (1978), that is, the low-angle laser light scattering intensity measurement method is particularly preferably used.

In the present invention, the weight average molecular weight is 1 × 1
0 The ⁵ or more polyolefin resin, the weight average molecular weight of 1 × 10 ⁵ or more ethylene, propylene, butene, pentene, homopolymers of olefin having 2 to 6 carbon atoms, such as hexene, and carbon atoms 2 to 10 And polyolefin resins such as olefin copolymers composed of two or more monomers selected from olefins. The copolymer may be any of a block copolymer, a random copolymer, and a graft copolymer. A polypropylene resin is particularly preferred from the viewpoint of heat resistance. Examples of the method of polymerizing a polypropylene resin having a weight average molecular weight of 1 × 10 ⁵ or more include the following methods. That is, the polymerization temperature is 60 ° C. and the polymerization pressure is 27 kg in the first stage.
/ Cm ² G under the conditions of liquid propylene 57kg / h,
1.3 mmol / h of triethylaluminum, 0.13 mmol / h of t-butyl-n-propyldimethoxysilane and 0.5 of the preactivated solid catalyst component.
The mixture was continuously supplied at 1 g / h to carry out propylene polymerization to obtain a polymer having an intrinsic viscosity of 7.7 dl / g. The obtained polymer was continuously transferred to the second stage without deactivating the catalyst. In the second stage, the polymerization temperature is 80 ° C. and the polymerization pressure is 18 kg.
/ Cm ² G, while supplying propylene and hydrogen so as to maintain a hydrogen concentration of 8 vol% in the gas phase, the catalyst-containing polymer and triethylaluminum transferred from the first step and 60 mmol / h, t- By continuing propylene polymerization while supplying 6 mmol / h of butyl-n-propyldimethoxysilane, the intrinsic viscosity is 7.7 dl.
/ G of polymer. The weight-average molecular weight of the polypropylene resin obtained by such a method was measured.
It was about 4 × 10 ⁵ . The weight-average molecular weight of the polypropylene-based resin can be adjusted by the amount of the monomer constituting the resin.

As an example of the process of melting and re-solidifying a polyolefin resin, a solid polyolefin resin, for example, in the form of a pellet is melted by a plasticizer (eg, an extruder) and extruded into an arbitrary shape such as a strand or a sheet. ,
Cooling and re-solidification. On the other hand, a molded article such as a film or sheet produced by an appropriate molding method such as extrusion molding using a long-chain branched polyolefin-based resin and / or a polyolefin-based resin having a weight-average molecular weight of 1 × 10 ⁵ or more, or the molded article. The offcuts generated during the production of the body can be recycled and used as the resolidified polyolefin-based resin in the method of the present invention.
In the present invention, when such a molded article or scrap material is recycled, the molded article or scrap material may be a long-chain branched polyolefin-based resin and / or a weight-average molecular weight unless the effects of the present invention are remarkably performed. ^May contain 1 × 10 ⁵ or more polyolefin-based resins other than polyolefin-based resins.

The re-solidified polyolefin resin may have undergone at least one melt-re-solidification step, and the number of times of the melt-re-solidification step is not particularly limited. It is preferable to use a recycled solidified polyolefin resin.

The polyolefin resin material forming the polyolefin resin non-foamed layer contains the above-mentioned resolidified polyolefin resin in an amount of 10% by weight or more. If the content of the re-solidified polyolefin resin is less than 10% by weight, the non-foamed layer to be formed tends to have uneven thickness, and the effect of preventing foam breakage at the time of forming the foamed layer may not be sufficiently obtained. As a result, a foamed sheet having poor surface smoothness can be easily obtained. Considering the deterioration of the resin due to the melt-resolidification process, the content of the resolidified polyolefin resin is more preferably from 20 to 80% by weight, and particularly preferably from 30 to 50% by weight.

The polyolefin-based resin material used for forming the non-foamed layer of the polyolefin-based resin may be composed of only the above-mentioned re-solidified polyolefin-based resin. And a polyolefin resin other than the re-solidified polyolefin resin.

The polyolefin resin usable in combination with the re-solidified polyolefin resin is selected from the group consisting of a long-chain branched polyolefin resin and a polyolefin resin having a weight average molecular weight of 1 × 10 ⁵ or more. And polyolefin-based resins that have not been subjected to the above. Further, a polyolefin resin other than a long-chain branched polyolefin resin having undergone or not undergoing a melt-resolidification process or a polyolefin resin having a weight-average molecular weight of 1 × 10 ⁵ or more is also applicable. Further, a polyolefin resin modified with a carboxylic acid or a carboxylic acid anhydride is also applicable. Furthermore, a copolymer of an olefin and a monomer polymerizable with the olefin, and a modified product thereof with a carboxylic acid or a carboxylic anhydride can also be applied.

Heat plasticization of the polyolefin resin material used for forming the non-foamed layer of the polyolefin resin can be carried out by melting and kneading the raw material resin using an ordinary plasticizer (eg, an extruder). . At this time, a desired additive can be blended.

The method for laminating the foamed layer and the non-foamed layer in the foamed polyolefin resin sheet of the present invention is not particularly limited as long as the features of the present invention are not lost. A flat die having a structure capable of laminating a layer made of a heat-plasticized polyolefin-based resin containing a re-solidified polyolefin-based resin but not containing a foaming agent, but containing a foaming agent, a straight die, a circular die, etc. A method of foaming a plasticized layer made of a polyolefin resin containing a foaming agent, a foamed polyolefin resin sheet and a non-foamed polyolefin resin sheet are separately prepared, and another thermoplastic resin such as polypropylene is interposed between these sheets. By lamination by melt extrusion and lamination An olefin-based resin foam sheet, a polyolefin resin non-foamed sheet was prepared separately, and a method of laminating through these sheets adhesive layer or an adhesive resin layer.

As long as the characteristics of the present invention are not lost, the foamed sheet of the present invention is a layer other than a polyolefin-based resin foamed layer and a non-foamed layer of a polyolefin-based resin containing 10% by weight or more of a resolidified polyolefin-based resin (hereinafter referred to as “additional layer”). May be laminated).

The additional layer may be coextruded with a foamed polyolefin resin layer and / or a non-foamed polyolefin resin layer, or may be laminated via an adhesive layer or an adhesive resin layer.

By laminating additional layers on the foamed sheet of the present invention, mechanical properties such as flexural rigidity, compressive strength, surface scratch resistance, dimensional stability, heat resistance, heat insulation, gas barrier properties, Functionality such as moldability can be improved, and properties such as gloss, surface smoothness, and appearance can be imparted.
Additional layers include layers composed of woven, non-woven, knitted, sheets, films, meshes, and the like. The polyolefin resin foam sheet of the present invention and the additional layer can be laminated via an adhesive layer or an adhesive resin layer.

The material of the additional layer can be appropriately selected according to the purpose. Examples thereof include thermoplastic resin, thermosetting resin, rubber, thermoplastic elastomer, natural fibers such as hemp, and the like. Minerals such as calcium silicate; In addition, wood, paper, synthetic paper made of polypropylene, polystyrene, or the like, a thin metal plate or metal foil of aluminum, iron, or the like can also be used. Such an additional layer may be provided with an uneven pattern such as a grain, printing or dyeing. Such additional layers may have a single-layer configuration or a multi-layer configuration comprising two or more layers.

Examples of the thermoplastic resin constituting the additional layer include a polyolefin resin, an ethylene-vinyl ester copolymer and a saponified product thereof, a polyester resin, a polyamide resin, and a halogen-containing resin. . When the polyolefin-based resin foam sheet of the present invention is applied to a food container, an unstretched polypropylene film (CPP),
It is preferable to have a layer such as an oriented polypropylene film (OPP) or an ethylene-vinyl ester copolymer film (EVOH) as an additional layer. The polyolefin-based resin foam sheet of the present invention may have, as an additional layer, a layer made of a thermoplastic resin film containing a dioxin inhibitor in order to suppress the load on the environment when the sheet is incinerated. preferable. When the polyolefin-based resin foam sheet of the present invention is used for packaging of easily degradable products such as fruits, vegetables, and fresh flowers, a thermoplastic resin containing an ethylene gas absorbent, a freshness-retaining agent, a deodorant, an antibacterial agent, etc. Layers such as films can be used as additional layers. The film to be laminated on the foamed sheet may be a single-layer film composed of a single film or a multilayer film composed of two or more laminated films. The thickness of the film to be laminated on the foamed sheet is preferably from 10 to 100 μm, and in the case of a multilayer film, preferably from 50 to 200 μm. Specific examples of the film to be laminated on the foamed sheet when the foamed polyolefin resin sheet obtained by the present invention is applied to a food container include a CPP film having a thickness of 50 to 100 μm, a CPP layer /
Adhesive layer / EVOH layer / Adhesive layer 100 μm thick three-layer four-layer film, CPP layer / Adhesive layer / EVOH layer / Adhesive layer / CPP layer 100-μm-thick three-layer five-layer film, CPP layer / Adhesive layer / Nylon layer / EVOH layer /
A 100 μm-thick, three-layer, five-layer multilayer film of an adhesive layer / CPP layer may be used.

In the foamed polyolefin resin sheet of the present invention, a non-foamed polyolefin resin material layer containing 10% by weight or more of a resolidified polyolefin resin is directly provided on at least one surface of the foamed polyolefin resin layer, , Or may be laminated indirectly, that is, via one or more additional layers.

In this case, as the additional layer provided between the foamed layer and the non-foamed layer, the above-mentioned long-chain branched polyolefin resin, which is a raw material resin of the resolidified polyolefin resin, and a weight average molecular weight of 1 × A layer made of a polyolefin resin selected from the group consisting of 10 ⁵ or more polyolefin resins is suitable. By interposing such a layer as an intermediate layer, a foamed sheet having excellent surface smoothness can be more stably obtained, and the obtained foamed sheet also has excellent surface smoothness.

The expansion ratio of the foam layer contained in the polyolefin resin foam sheet of the present invention is preferably from 2 times to 40 times. The expansion ratio of the foam layer of the foam sheet can be adjusted by adjusting the amount of the foaming agent to be used and the physical conditions at the time of molding. In addition, the thickness of the polyolefin resin foam sheet of the present invention is preferably 0.1 to 3 mm. The thickness of the non-foamed layer may be appropriately set according to the use of the sheet, and is not limited.
m or more, more preferably 10 μm
m or more, more preferably 50 μm or more.

The foamed polyolefin resin sheet of the present invention has at least one surface of a foamed polyolefin resin layer.
The gist of the invention is to have a non-foamed layer made of a polyolefin-based resin material containing 10% by weight or more of the re-solidified polyolefin-based resin. Most simply, one foamed layer and a non-foamed layer laminated on one side thereof And a foamed sheet having a foamed layer. Further, in the polyolefin resin foam sheet of the present invention, a foam sheet having a structure of non-foam layer / foam layer / non-foam layer in which a non-foam layer is laminated on both sides of the foam layer, A foamed sheet having a structure of non-foamed layer / foamed layer / non-foamed layer / foamed layer / non-foamed layer obtained by laminating via a foamed layer and further laminating a non-foamed layer outside both foamed layers can also be given as an example. it can. Furthermore,
A foamed sheet having a configuration of a non-foamed layer containing a re-solidified polyolefin resin / a non-foamed layer containing no re-solidified polyolefin resin / a foamed layer / a non-foamed layer containing no re-solidified polyolefin resin / a non-foamed layer containing a re-solidified polyolefin resin is also available. No.

Each layer of the foamed polyolefin resin sheet of the present invention may contain additives as appropriate. Additives include antioxidants, light stabilizers, UV absorbers,
Antifogging agent, antifog agent, plasticizer, antistatic agent, lubricant, coloring agent,
Examples include a dioxin inhibitor, an ethylene gas absorbent, a deodorant, a freshness maintaining agent, and an antibacterial agent. These can be blended within a range that does not impair the effects of the present invention. These additives may be blended in the foamed layer, the non-foamed layer and both in the sheet of the present invention.

An example of a method for producing the polyolefin resin foam sheet of the present invention will be described below with reference to the drawings. In this example, carbon dioxide gas was used as a foaming agent, melted in a first extruder, and melt-extruded with a twin-screw extruder on both surfaces of a heat-plasticized layer made of a polyolefin resin mixed with carbon dioxide gas. A thermoplastic resin comprising a resin composition obtained by melt-kneading 40 parts by weight of a long-chain branched polypropylene resin cooled and then re-solidified and 60 parts by weight of a polypropylene which has not been subjected to a melt-re-solidification process in a second extruder. The formed layers are laminated in a die and co-extruded, and the intermediate layer is foamed to produce a polyolefin resin foam sheet having a three-layer structure of non-foamed layer / foamed layer / non-foamed layer.

FIG. 1 shows an example of a production apparatus used for producing the polyolefin resin foam sheet of the present invention. The manufacturing apparatus 1 includes a first extruder 3 for extruding a foam layer constituent material, a second extruder 5 for extruding a non-foamed surface layer constituent material, a die 7, a mandrel 9, and a take-up roll 11.

The first extruder 3 is provided with a hopper for supplying resin and 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 melted while being sent to the die 7 by a screw. The carbon dioxide gas is supplied into the extruder at a position where the polypropylene resin in the extruder passes in a sufficiently molten state, and is uniformly dispersed in the molten polypropylene resin. The molten polypropylene resin containing the foaming agent is fed into the die 7. It is preferable that a known vent-type extruder is used as the first extruder, and carbon dioxide gas is supplied under pressure from the vent hole.

In a second extruder 5, 40 parts by weight of a long-chain branched polypropylene obtained by melt-extrusion with a twin-screw extruder, cooled and re-solidified, and 60 parts by weight of a polypropylene which has not been subjected to a melt-re-solidification process are melted. The kneaded resin composition,
The extruder 5 feeds the die 7.

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

The three-layer foamed sheet fed 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, is folded and taken up by the take-up roller 11. When this is cut at both folded portions, two three-layer foam sheets are obtained. When the sheet is cut open only at one of the folded portions, a three-layer foam sheet having one wide sheet is obtained.

When two sheets of the obtained three-layer foamed sheet are laminated and bonded, a non-foamed layer / foamed layer / non-foamed layer / non-foamed layer /
A foam sheet having six layers of foam layer / non-foam layer or five layers of non-foam layer / foam layer / non-foam layer / foam layer / non-foam layer is obtained. Further, three or more three-layer foamed sheets can be laminated.

The preferred structure of the die is shown in cross section in FIG.
The die in this example is a circular die. Die 7
Has a resin flow path 23a, 23b forming a foam layer,
Flow paths 24, 24a, 24b of resin forming a non-foamed layer,
24c and 24d are formed.

The head 21 of the first extruder 3 is connected to the end of the die 7 on the source flow side in the resin flow direction, and the head 22 of the second extruder 5 is connected to the 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 second extruder 5 and
It is divided into 4a and 24b, supplied so as to adhere to both sides of the flow path 23b so as to cover both sides of the foamed 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.
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.
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 the above method, the discharge amount of the molten resin (Q: k
g / hr · mm), and the internal diameter of the die 7 (D: mm)
Are preferably in a relationship of Q / D ≧ 0.3 kg / hour · mm, more preferably Q / D ≧ 0.6 kg / hour · mm. The lip clearance of the die exit 26 is preferably 0.5 to 3 mm, more preferably 1 to 2 mm. Die exit taper angle is 0 ° ~
The angle is preferably 5 °, more preferably 0 ° to 1 °. The length of the tapered land is preferably 10 mm or less, more preferably 5 mm or less.
The angle between the core of the die and the tapered land at the exit of the die is preferably 45 ° to 80 °.
It is more preferable that the angle is from 70 to 70 °.

In each of the above examples, the case where a single screw extruder is used has been described, but a twin screw extruder or the like may be used. In particular, it is preferable to use a twin-screw extruder as an extruder for extruding a foam layer constituent material. Further, in the above example, a case where a circular die is used as the die 7 has been described. However, as described above, the die used in the method of the present invention may have an internal structure that is suitable for forming a multilayer sheet. A flat die (T die, coat hanger die, etc.) and a straight die can also be applied.

The polyolefin-based resin foam sheet of the present invention can be used for various applications by performing processing such as molding as required. Specifically, food containers such as microwave oven-compatible containers (HMR), heat insulating materials, cushioning materials such as sports equipment and packing materials, heat insulating materials, automobile parts such as vehicle ceiling materials, sealing materials, building materials, and aerospace industry It can be used for applications that use resins that require heat insulation. In particular, it can be suitably used as a food container such as a microwave-compatible container in which a layer made of a barrier resin is laminated. Examples of food containers include trays, cups, cups,
Box and the like.

[0046]

According to the present invention, there is provided a foamed polyolefin resin sheet having excellent surface smoothness. The surface smoothness of the polyolefin resin foam sheet can be evaluated by the following method. The surface roughness is measured at a scan speed of 0.3 mm / sec over a length of 1 cm from an arbitrary point on the test piece (foamed sheet) according to the method of measuring the center line average roughness specified in JIS B0601. This measurement is performed at three arbitrary points, and the average value of the obtained surface roughness is defined as the surface roughness Ra of the foamed sheet. The smaller the Ra value is, the more excellent the foam sheet is in the surface smoothness. Ra is 4.8 in the conventional polypropylene resin foam sheet.
μm, but in the present invention, Ra was 3.8.
A sheet excellent in surface smoothness of not more than μm is provided.

[0047]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention.

Example 1 A foamed polyolefin-based resin sheet having a non-foamed layer / foamed layer / non-foamed layer was prepared in the following manner. (Foam layer constituent material) As the foam layer constituent material, polypropylene and polyethylene by the two-stage polymerization method are used in a weight ratio of 7
A mixture blended at 0/30 was used. Hereinafter, a method for producing and pelletizing the polypropylene, and a method for blending the constituent materials of the foamed layer 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 tetrabutoxy6.
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 separated into solid and liquid at room temperature, and the solid phase was washed three times with 70 L of toluene. Then, 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. In addition, 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, the slurry concentration was 0.6 kg / L.
Was adjusted to 3.13 mol of diisobutyl phthalate, n
8.9 mol of dibutyl ether and titanium tetrachloride 13
7 mol was added and the reaction was carried out at 105 ° C. for 1 hour. After completion of the reaction, solid-liquid separation was performed at the same temperature, and the solid phase was washed twice with 95 L of toluene at 95 ° C. twice. 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 reaction was carried out at a temperature of 1 hour. After completion of the reaction, solid-liquid separation was performed at the same temperature, and the solid phase was repeatedly washed with 90 L of toluene at the same temperature three times. Next, after adjusting the slurry concentration to 0.6 kg / L, 8.9 mol of n-butyl 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 the solid phase was repeatedly washed with 90 L of toluene at the same temperature three times, further washed with 90 L of hexane three times, and then dried under reduced pressure to obtain 11.0 kg of a solid catalyst component. Was.

The solid catalyst component comprises 1.9% by weight of titanium atom,
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 n-hexane 1.5, which was sufficiently dehydrated and degassed in a stainless steel autoclave having an internal volume of 3 L and equipped with a stirrer.
L, triethylaluminum 37.5 mmol, tert
3.75 mmol of -butyl-n-propyldimethoxysilane and 15 g of the above solid catalyst component were added, and
While maintaining the temperature at １５15 ° C., 15 g of propylene was continuously supplied over 30 minutes to perform preactivation.

(3) Propylene Polymerization First Stage In a 300 L polymerization vessel made of stainless steel, while supplying a polymerization temperature of 60 ° C. and a polymerization pressure of 27 kg / cm ² G, liquid propylene is supplied at a rate of 57 kg / h. 1.3 mmol / h of triethylaluminum, 0.13 mmol / h of t-butyl-n-propyldimethoxysilane
Further, 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. As a result of sampling and analyzing a part of the produced polymer, the intrinsic viscosity was 7.7 dl / g. The obtained polymer was continuously transferred to the second tank without deactivating the catalyst.

Second stage In a 1 m ³ fluidized bed reactor with a stirrer having an inner volume of 1 m ³ , propylene and hydrogen were added so as to maintain a polymerization temperature of 80 ° C., a polymerization pressure of 18 kg / cm ² G, and a hydrogen concentration of 8 vol% in the gas phase. While supplying, the catalyst-containing polymer transferred from the first tank and triethyl aluminum 60 mmol /
By continuing propylene polymerization while supplying 6 mmol / h of t-butyl-n-propyldimethoxysilane, 18.2 kg / h of a polymer was obtained. The intrinsic viscosity of this polymer was 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 between the first polymerization tank and the second polymerization tank was 11/89,
The intrinsic viscosity of the portion of the polymer formed by the step polymerization reaction was determined to be 1.2 dL / g.

(4) Pelletization of polypropylene By kneading in an extruder, 0.1 part by weight of calcium stearate and 100 parts by weight of the polypropylene powder obtained by the above two-step reaction, partially hindered phenol-based antioxidant 0.05 parts by weight of an agent (trade name: Irganox 1010, manufactured by Ciba Specialty Chemicals), a phenolic antioxidant (trade name: Sumilizer B)
HT, manufactured by Sumitomo Chemical Co., Ltd.)
Melt-kneading at a temperature of 12 ° C.
A pellet of g / 10 minutes was obtained.

(5) Blend of foam layer constituent materials Polypropylene pellets obtained through the above steps (1) to (4) and polyethylene (trade name: Sumikasen G)
201, manufactured by Sumitomo Chemical Co., Ltd.)
/ 30 was dry blended.

(Non-foamed layer constituent material) As a non-foamed layer constituent material, long chain branched polypropylene (trade name: Polypropylene PF814, manufactured by Montell Co .; melting point: 159.0)
° C; crystallization temperature: 130.1 ° C; MFR: 2.2 g / 1
0 minutes) with a co-rotating twin screw extruder (trade name: PCM45; manufactured by Ikegai Co., Ltd .; screw diameter: 45 mm; screw L /
D: 30), melt-kneaded at a screw rotation speed of 200 rpm, extruded into a strand at a die temperature of 240 ° C, cooled in water, re-solidified, cut with a cutter, and melted with 21 parts by weight of a resin pellet. A dry blend mixture of 49 parts by weight of long-chain branched polypropylene (Montel's polypropylene PF814), which has not been re-solidified, and 30 parts by weight of polyethylene (trade name: Sumikasen G201, manufactured by Sumitomo Chemical Co., Ltd.) is used. did.

(Extrusion foaming) 50 mmΦ twin screw extruder and 32
An apparatus in which a 90 mm circular die was attached to a single mm screw extruder was used. Polypropylene for foam layer /
A mixture obtained by blending 1 part by weight of a nucleating agent (trade name: Hydrocellol; manufactured by Boehringer Ingelheim Chemicals Co., Ltd.) with 100 parts by weight of a 70/30 (weight ratio) mixture of polyethylene into a 50 mmΦ twin screw extruder. The mixture was melted and kneaded, and 1 part by weight of carbon dioxide gas was further injected. After sufficiently kneading the resin mixture and carbon dioxide gas,
It was sent to a die temperature-controlled to 10 ° C. On the other hand, the dry blend mixture for the non-foamed layer was charged into a 32 mmφ single screw extruder, melt-kneaded, and sent to a die adjusted to 210 ° C. The resin composition for a foaming layer from a 50 mmΦ twin screw extruder and the resin composition for a non-foaming layer from a 32 mmΦ single screw extruder are laminated in a die and then extruded into a cylinder, and the extruded cylindrical sheet is placed immediately after the die. It was installed and expanded while cooling along a 210 mm outside diameter mandrel, which was cooled by circulating 6 ° C. water inside. The thus obtained cylindrical two- or three-layer foamed sheet was cut with a cutter, opened to obtain a flat two- or three-layer foamed sheet, and taken up by a take-off machine. The physical properties of the obtained foamed sheet were evaluated. Table 1 shows the results
Shown in

Example 2 A foamed sheet was prepared in the same manner as in Example 1 except that the following resin mixture was used as the non-foamed layer constituting material, and its physical properties were evaluated. Table 1 shows the results. Incidentally, the non-foamed layer of the obtained foamed sheet contained 48% by weight of the re-solidified polyolefin-based resin. (Non-foamed layer constituent material) Foamed layer having the same composition as the foamed layer in the foamed sheet prepared in Example 1 and long-chain branched polypropylene (Montel's polypropylene PF814)
The heat-plasticized non-foamed layer-forming resin is laminated on both outer layers of the heat-plasticized foamed-layer-forming resin, and the foamed layer-forming resin is foamed.
A non-foamed layer / foamed layer / non-foamed layer formed by taking out a sheet co-extruded from a die controlled at 0 ° C. while cooling and solidifying along a cooled internal mandrel by circulating water at 6 ° C. inside. Foamed layer = 80/2200/80 μm layered two-layer, three-layer foamed sheet, unstretched polypropylene layer / maleic anhydride-modified polypropylene layer / ethylene-vinyl ester copolymer saponified layer / maleic anhydride-modified polypropylene layer / Unstretched polypropylene layer =
Heat-plasticized constituent resin of each layer is laminated so as to have a layer structure of 25/10/30/10/25 μm,
A multilayer sheet formed by laminating a multilayer film having a thickness of 100 μm produced by co-extrusion from a die and cooling and solidifying by circulating water at 10 ° C. and taking it along a cooling roll cooled therein is scrapped. Resin material 35 obtained
Parts by weight of a long-chain branched polypropylene that has not been subjected to a melt-resolidification process (Montel's polypropylene PF8
14) 35 parts by weight of polyethylene and 30 parts by weight of polyethylene (trade name: Sumikasen G201, manufactured by Sumitomo Chemical Co., Ltd.)
A resin mixture was used.

Example 3 A resin (A) and a resin (B) described below were used as constituent materials of a non-foamed layer, and a non-foamed layer of the resin (A) / resin ( A three-layer five-layer polyolefin-based resin foam sheet having a configuration of non-foamed layer / foamed layer / foamed layer of resin (B) / non-foamed layer of resin (A) was prepared, and its physical properties were evaluated. Table 1 shows the results.

(Non-foamed layer constituent material) Resin (A) As the non-foamed layer constituent material (A), a long-chain branched polypropylene (trade name: polypropylene PF814; manufactured by Montell Co.) is a coaxial twin-screw extruder (trade name) : PCM45; manufactured by Ikegai Co., Ltd.), melt-kneaded at a screw rotation speed of 200 rpm, extruded into a strand at a die temperature of 240 ° C., cooled in water, re-solidified, and cut with a cutter, 21 parts by weight of resin pellets. And 49 parts by weight of pellets of long-chain branched polypropylene (Montell's polypropylene PF814) which has not been subjected to a melt-resolidification process, and 30 parts by weight of polyethylene (trade name: Sumikasen G201, manufactured by Sumitomo Chemical Co., Ltd.) The blend mixture was used. (Resin (B)) As the non-foamed layer constituent material (B), long chain branched polypropylene (trade name: polypropylene PF
814; manufactured by Montell).

(Extrusion foaming) 50 mmΦ2 for foam layer extrusion
A screw extruder, two 32 mmφ single screw extruders for non-foamed layer extrusion, and a device fitted with a 90 mmφ circular die were used. A mixture obtained by blending 1 part by weight of a nucleating agent (trade name: Hydrocellol; manufactured by Beilinger Ingelheim Chemicals) with respect to 100 parts by weight of a polypropylene / polyethylene 70/30 (weight ratio) mixture for a foam layer. Was injected into a 50 mmΦ twin screw extruder, and 1 part by weight of carbon dioxide gas was further injected while melting and kneading the mixture, and after sufficiently kneading the resin mixture and carbon dioxide gas, the mixture was fed to a die). On the other hand, the resin (A) for the non-foamed layer is
The resin (B) was charged into the other single-screw extruder into the other single-screw extruder, melt-kneaded, and fed into a die. A resin composition for a foamed layer from a 50 mmΦ twin screw extruder and a resin (A) and a resin (B) for a non-foamed layer are laminated in a die in a molten state, and then extruded into a cylindrical shape, and placed immediately after the die. Expanded while cooling along a mandrel with an outer diameter of 210 mm. The thus obtained cylindrical three-layered five-layer foamed sheet was cut with a cutter, opened to form a flat foamed sheet, and taken up by a take-off machine.

Comparative Example 1 A foamed sheet was prepared in the same manner as in Example 1 except that the following resin was used as the non-foamed surface layer constituting material, and its physical properties were evaluated. Table 1 shows the results. (Material for non-foamed surface layer) Long-chain branched polypropylene (melting point: 159.0 ° C; crystallization temperature: 130.1 ° C; MI)
A dry blend mixture of 70 parts by weight of pellets (230 ° C .: 2.2 g / 10 minutes) and 30 parts by weight of polyethylene (trade name: Sumikasen G201, manufactured by Sumitomo Chemical Co., Ltd.) was used.

The surface smoothness of the foamed sheet obtained in each example was evaluated by the following method. A test piece having a predetermined shape is set on a stylus-type roughness meter (trade name: Surfcom 570A; manufactured by Tokyo Seimitsu Co., Ltd.), and the test piece in the test piece is measured according to the center line average roughness measurement method specified in JIS B0601. The surface roughness was measured at a scan speed of 0.3 mm / sec over an area of 1 cm from an arbitrary point in FIG. This measurement was performed at three arbitrary points, and the average value of the obtained surface roughness was defined as the surface roughness Ra of the foamed sheet. The smaller the Ra value is, the more excellent the foam sheet is in the surface smoothness.

[0065]

[Table 1]

[Brief description of the drawings]

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

FIG. 2 is a cross-sectional view illustrating a preferred configuration of a head in a device for manufacturing a polyolefin resin foam sheet.

 ──────────────────────────────────────────────────続 き Continuing on the front page F term (reference) 4F100 AK03A AK03B AK03C AK03D AK03E AK04 AK07 AK07B AK07C AK62A AK62B AK62C AK62D AK62E AK66A AK66B AK66C AK66D AK66E BA02 BA01 BA07 BA01 BA02 GB33 JA07B JA07C JA07D JA07E JK15 YY00B YY00C YY00D YY00E

Claims (3)

[Claims] At least one side of the foamed polyolefin resin layer is selected from the group consisting of a long-chain branched polyolefin resin and a polyolefin resin having a weight average molecular weight of 1 × 10 ⁵ or more. A polyolefin-based resin foamed sheet comprising a polyolefin-based resin non-foamed layer containing 10% by weight or more of a polyolefin-based resin that has undergone at least one solidification process. 2. The long-chain branched polyolefin resin and the polyolefin resin having a weight average molecular weight of 1 × 10 ⁵ or more contained in the non-foamed layer are each a long chain branched polypropylene resin and a 1 × 10 ⁵ weight average molecular weight. The foamed polyolefin-based resin sheet according to claim 1, wherein the foamed polyolefin-based resin sheet is at least 10 ⁵ . 3. A layer comprising a polyolefin-based resin selected from the group consisting of a long-chain branched polyolefin-based resin and a polyolefin-based resin having a weight average molecular weight of 1 × 10 ⁵ or more, between a foamed layer and a non-foamed layer. The foamed polyolefin resin sheet according to any one of claims 1 to 2, wherein