JP2001348453A - Thermoplastic resin sheet and container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermoplastic resin sheet excellent in heat insulating properties. SOLUTION: The thermoplastic resin sheet has a thermoplastic resin foam layer having an expansion ratio of at least 3 and at most 40, a density of a cell wall in the direction of the thickness of at least 8 pieces/mm and a ratio of the density of a cell wall of the foam of at least 2 and less than 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoplastic resin sheet having excellent heat insulating properties and a container formed by molding the same.

[0002]

2. Description of the Related Art Resin foams are widely used as architectural / civil engineering materials, air-conditioning equipment parts, refrigeration / refrigeration equipment parts, vehicle / marine materials, container / packaging materials, etc., taking advantage of their excellent heat insulating properties. . Further, in order to improve the heat insulating property of the resin foam, improvement of the cell structure of the resin foam has been studied.
For example, Japanese Patent Application Laid-Open No. H11-245928 discloses that the maximum diameter of bubbles inside a polypropylene-based resin foam sheet is 5 mm.
By setting the cell size to be less than or equal to 00 μm, the cell shape is made to be close to a spherical shape. Further, by setting the number of cells having a substantially spherical shape to be 50% or more of the total cell number per unit area of the cross section of the foamed sheet, It has been reported that a suitable heat insulating property of a food container obtained by molding can be ensured.

[0003]

However, only by reducing the maximum diameter of the cells, there is a limit in improving the heat insulating properties of the resin foam, and it is difficult to obtain sufficient heat insulating properties. In view of the above-mentioned problems of the related art, an object of the present invention is to provide a thermoplastic resin sheet and a container that are more excellent in heat insulation.

[0004]

Means for Solving the Problems The present inventors have found that the above object can be achieved by providing a thermoplastic resin foam layer having a novel cell structure in a thermoplastic resin sheet. Reached. That is, the present invention is characterized by having a foamed thermoplastic resin layer having an expansion ratio of 3 to 40 times, a cell wall density in the thickness direction of 8 cells / mm or more, and a cell wall density ratio of 2 to less than 6. To provide a thermoplastic resin sheet.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The thermoplastic resin sheet according to the present invention is characterized by the expansion ratio of the foamed layer, the cell wall density in the thickness direction of the foamed layer, and the cell wall density ratio of the foamed layer. The resin sheet has an expansion ratio of 3 to 40 times, a cell wall density in the thickness direction of 8 cells / mm or more,
It is characterized by having a thermoplastic resin foam layer having a cell wall density ratio of 2 or more and less than 6. In the foamed thermoplastic resin layer, heat is easily transmitted through a resin portion having a high thermal conductivity, and is less likely to be transmitted through a bubble portion having a low thermal conductivity. Therefore, from the viewpoint of heat insulation, the higher the foaming ratio of the foamed layer, the better. However, when an attempt is made to form a foamed layer having a foaming ratio of more than 40 times, it is generally difficult to form a foamed layer having a foaming ratio of more than 40 times, because bubbles are likely to occur during the formation process. Therefore, in the present invention, the expansion ratio of the foam layer is set to 3 times or more and 40 times or less. The expansion ratio of the foam layer is preferably 3 times or more and 10 times or less. If the foaming ratio of the foamed layer is less than 3 times, the heat insulating property of the thermoplastic resin foam sheet will be insufficient. The expansion ratio of the foam layer can be adjusted by adjusting the amount of the foaming agent used and the physical conditions at the time of molding.

In the present invention, the cell wall density of the foam layer is:
It is defined as follows: This will be described below by taking the cell wall density in the thickness direction of the foam layer as an example. First, one cross section in the thickness direction of the foamed layer is enlarged to a magnification at which each bubble portion can be clearly recognized using a scanning electron microscope (SEM). Next, on the enlarged image, the number of cell walls where one straight line in the thickness direction of the foam layer intersects (that is, the wall of the resin that defines the bubbles) is counted. Based on the result, the number of cell walls existing per 1 mm in the thickness direction of the foam layer is determined. In this way, a total of 2 mm or more apart from each other
The number of cell walls existing per 1 mm in the thickness direction of the foamed layer in the portion of 0 or more is determined. The average value of the obtained cell wall numbers is defined as the cell wall density in the thickness direction of the foamed layer. The cell wall density in a direction other than the thickness direction of the foam layer is defined in the same manner.

Further, in the present invention, the cell wall density ratio of the foamed layer is defined by the following equation. Cell wall density ratio r = T / S where T is the cell wall density in the thickness direction of the foam layer,
S is the minimum value of the cell wall density in the direction perpendicular to the thickness direction of the foam layer.

[0008] In the thermoplastic resin sheet of the present invention having a thermoplastic resin foam layer having an expansion ratio of 3 times or more and 40 times or less, the cell wall density in the thickness direction of the foam layer is 8 cells / mm or more. The ratio is 2 or more and less than 6. By simultaneously setting the cell wall density in the thickness direction of the foam layer and the cell wall density ratio of the foam layer within such a range, a sheet having excellent heat insulating properties can be obtained. When the cell wall density ratio is less than 2, the heat flow transmitted in the thickness direction of the foam layer is large, and the heat insulation in the thickness direction becomes insufficient. In order to achieve better heat insulating properties, the cell wall density in the thickness direction of the foam layer should be 10
The number is preferably not less than 15 pieces / mm, more preferably not less than 15 pieces / mm, and still more preferably not less than 20 pieces / mm. From the viewpoint of heat insulation, the higher the cell wall density in the thickness direction of the foam layer, the better, and there is no particular upper limit. However, since a foam layer having a cell wall density exceeding 10,000 cells / mm is generally difficult to form with today's technology, the cell wall density in the thickness direction of the foam layer is 10,000 cells / mm.
mm or less.

It is preferable from the viewpoint of heat insulation that the bubbles in the foam layer have a shape that is thin in the thickness direction of the foam layer and long in the direction perpendicular to the thickness direction of the foam layer. Further, it is preferable that the projected shape in the thickness direction of the foam layer is a disc-shaped bubble that is close to a circular shape, rather than a rod-shaped bubble that is long in one direction perpendicular to the thickness direction of the foam layer. When the disc-shaped bubbles overlap in the thickness direction of the foam layer, heat flow in the thickness direction can be more efficiently blocked, and excellent heat insulating properties are exhibited.

[0010] In the thermoplastic resin sheet of the present invention, the horizontal cell wall density ratio of the foam layer defined below is preferably 0.3 or more and 3 or less. When the horizontal cell wall density is in this range, the transfer of heat in the thickness direction of the foam layer is particularly efficiently suppressed, and the heat insulating property is particularly excellent. The horizontal cell wall density is more preferably 0.5 or more and 2 or less, and particularly preferably 0.7 or more and 1.5 or less.

In the thermoplastic resin sheet of the present invention, the horizontal cell wall density ratio of the foamed layer is defined by the following equation. Horizontal cell wall density ratio R = M / L where M is the cell wall density in any one direction perpendicular to the thickness direction of the foam layer, L is perpendicular to the thickness direction of the foam layer,
And the cell wall density in the direction perpendicular to the direction in which M was measured. The cell wall density of the foamed layer is defined by the same method as the above-described cell wall density.

[0012] In the foamed layer of the thermoplastic resin sheet of the present invention, the average cell diameter is preferably in the range of 1 µm to 100 µm. When the average cell diameter of the foam layer is in this range, heat conduction due to convection of gas in the cells is well suppressed, and the thermoplastic resin sheet has excellent heat insulating properties.

In the present invention, the average cell diameter of the foam layer is defined and determined by the following method. First, among the directions perpendicular to the thickness direction of the foam layer, the cross section of the foam layer along the direction in which the cell wall density is minimum is enlarged and observed by SEM. The maximum length of each of 20 or more of the bubbles observed in the visual field is measured, and the average value is defined as the average major axis L of the bubbles in the foam layer. D defined by the following formula is the average cell diameter of the foam layer in the present invention. d = L / r (where L is the average major diameter of cells in the foamed layer, and r is the cell wall density ratio of the foamed layer.)

The content of the hydrocarbon having 3 to 4 carbon atoms in the foamed layer is preferably 10,000 ppm or less, preferably 1 ppm or less.
000 ppm or less, more preferably
pm or less is particularly preferred.

The thermoplastic resin constituting the foamed layer is not particularly limited as long as it can form and maintain the above-mentioned cell structure, but ethylene, propylene, butene, pentene,
Polyolefin resins such as olefin homopolymers having 2 to 6 carbon atoms such as hexene and olefin copolymers composed of two or more monomers selected from olefins having 2 to 10 carbon atoms are exemplified. The copolymer may be any of a block copolymer, a random copolymer, and a graft copolymer. These polyolefin-based resins may be only one kind or a blend of two or more kinds. From the viewpoint of heat resistance, a polypropylene-based resin is preferable, and in order to improve moldability, it is preferable that a small amount of polyethylene is blended in the polypropylene-based resin. Further, as long as the function and effect of the present invention are not impaired, a polymer compound other than the polyolefin type resin can be blended.

Particularly preferred polypropylene resins include propylene homopolymer and 5
Propylene copolymers containing 0 mol% or more can be mentioned. Preferred examples of the copolymerization 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, since a foamed layer having a highly uniform cell structure can be formed, (a) a long-chain branched polypropylene and (b) a first
In the second step, a crystalline polypropylene having an intrinsic viscosity of 5 dl / g or more is synthesized. In the second step, a crystalline polypropylene having an intrinsic viscosity of less than 3 dl / g is continuously synthesized. 0.5 to 25% by weight, the overall intrinsic viscosity is less than 3 dl / g, and Mw / Mn is 10
Polypropylene that is less than is preferred.

The thermoplastic resin sheet of the present invention is composed of the foamed layer and other layers, even if it has a single-layer structure composed of only the foamed layer, unless the heat insulating property is significantly impaired. It may have a multilayer structure. The thermoplastic resin sheet of the present invention preferably has at least one layer each of the foamed layer and a thermoplastic resin non-foamed layer laminated thereon, and more preferably has a non-foamed layer / foamed layer /
It has a three-layer structure of a non-foam layer or a five-layer structure of a non-foam layer / foam layer / non-foam layer / foam layer / non-foam layer. In the present invention, 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. In the sheet having the three-layer structure or the five-layer structure illustrated above, since the openings of the bubbles that are open on the foam layer surface are covered with the non-foam layer, the heat flow between the outside air and the inside of the foam layer is reduced. Excellent heat insulation.

When the thermoplastic resin sheet of the present invention has a non-foamed layer, the thermoplastic resin constituting the non-foamed layer is not particularly limited as long as the heat insulating property of the sheet is not significantly impaired, but ethylene, propylene, butene, pentene And polyolefin-based resins such as olefin copolymers composed of two or more monomers selected from olefins having 2 to 6 carbon atoms such as hexene and olefins having 2 to 10 carbon atoms. . The copolymer may be any of a block copolymer, a random copolymer, and a graft copolymer. These polyolefin-based resins may be only one kind or a blend of two or more kinds. As the polyolefin resin of the non-foamed layer, a polyolefin resin having a long chain branch is preferable, and a long chain branched polypropylene is particularly preferable.

The polyolefin resin constituting the non-foamed layer has a branching index [A] of 0.20 ≦ [A].
Long-chain branched polyolefin resins satisfying ≦ 0.98 are particularly preferred. The branching index [A] is 0.20 ≦ [A] ≦
The long-chain branched polyolefin resin satisfying 0.98 has a high strength in a molten state, and by providing this non-foamed layer as a surface layer of the thermoplastic resin sheet of the present invention, destruction of air bubbles, particularly near the surface of the foamed layer This can prevent the occurrence of irregularities due to the destruction of the bubbles. As a result, diffusion of heat in the thickness direction of the sheet can be suppressed, and a thermoplastic resin sheet having high heat insulating properties can be obtained. An example of such a preferred polyolefin-based resin is polypropylene PF-814 manufactured by Montell Co., which is commercially available.

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. This is the intrinsic viscosity of a linear polyolefin having the same repeating unit as the base 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. Poly. Sc
i. , 14, 2947-2693 (1970)]. The intrinsic viscosity of polypropylene can be measured, for example, at 135 ° C. on a sample dissolved in tetralin or orthodichlorobenzene.
The weight average molecular weight (Mw) can be measured by various methods. L. Ameri by McConnel
can Laboratory, May, 63-75.
(1978), that is, a low-angle laser light scattering intensity measurement method is particularly preferably used.

The foaming agent used to form the foamed layer may be any as long as it can form a foamed layer satisfying the above conditions, but is preferably an inert substance such as water and carbon dioxide. In particular, when a polypropylene resin is used as the foam layer constituent resin, the use of carbon dioxide gas is preferable, and the amount of addition is 0.5 to 8 parts by weight based on 100 parts by weight of the foam layer constituent resin. Is preferable.
Further, a citric acid-based nucleating agent is added as a nucleating agent to the resin 10 constituting the foam layer.
It is advisable to add 0.1 to 0.5 parts by weight based on 0 parts by weight.

The thickness of the foam layer is preferably 0.2 mm or more in order to achieve sufficient heat insulation. From the viewpoint of heat insulation, the thicker the foam layer, the better. In a thermoplastic resin sheet having a non-foamed layer on at least the surface, the thickness of the non-foamed layer is not particularly limited as long as the surface has smoothness, that is, good appearance, and is appropriately set according to the use of the sheet. However, it is preferable that the thickness is 1 μm or more,
More preferably 10 μm or more, even more preferably 50 μm
m or more. If the non-foamed layer is too thick, the lightness of the thermoplastic resin sheet is impaired, which is not preferable.

[0024] The thermoplastic resin sheet of the present invention can contain additives as appropriate. Additives include antioxidants, light stabilizers, ultraviolet absorbers, antifoggants, antifog agents, plasticizers, antistatic agents, lubricants, colorants, dioxin inhibitors,
Examples include an ethylene gas absorbent, a deodorant, a freshness maintaining agent, and an antibacterial agent. These can be blended as long as the effects of the present invention are not impaired. These additives may be added to any of the foamed layer, the non-foamed layer and both as long as the characteristics of the thermoplastic resin sheet of the present invention are not impaired. In addition, as for the method of compounding these additives, it is possible to use a material obtained by previously kneading the constituent materials of the resin composition of the present invention and the additives as a resin composition, or to manufacture the thermoplastic resin sheet of the present invention. At times, a master batch of additives or the additives themselves can be blended by dry blending.

Examples of antioxidants include 2,5-di-t
-Butylhydroquinone, 2,6-di-t-butyl-p
-Cresol, 4,4'-thiobis- (6-t-butylphenol), 2,2'-methylene-bis (4-methyl-6-t-butylphenol), octadecyl-3-
(3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionate, 4,4'-thiobis- (6-t
-Butyl phenol) and other phenolic antioxidants,
Phenyl diisodecyl phosphite, diphenyl isooctyl phosphite, triphenyl phosphite, trinonyl phenyl phosphite, tris-
(2,4-di-t-butylphenyl) phosphite,
4,4'-isopropylidene diphenol alkyl phosphite, 1,1,3-tris (2-methyl-4-di-tridecyl) phosphite, 5-t-butylphenylbutanephenyl di (tridecyl) phosphite, etc. Phosphorus antioxidants, dilauryl 3,3'-thiodipropionate, ditridecyl 3,3'-thiodipropionate dimyristyl 3,3'-thiodipropionate, 3,
Distearyl 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-6-methylbenzimidazole, and other sulfur-based antioxidants.

The thermoplastic resin sheet according to the present invention may contain an inorganic filler for improving rigidity. The inorganic filler may be contained in one or both of the foamed layer and the non-foamed layer, but in order to improve the rigidity without significantly increasing the weight of the thermoplastic resin sheet, the non-foamed layer is preferably used. It is particularly preferred that only the inorganic filler is contained.
As the inorganic filler used for such purpose, silicon oxide,
Aluminum oxide, titanium oxide, magnesium oxide, aluminum hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, calcium sulfate, barium sulfate, magnesium sulfate, talc, clay, mica, etc. , Magnesium sulfate is preferred. The amount is preferably in the range of 5 to 150 parts by weight based on 100 parts by weight of the constituent resin. If the amount of the inorganic filler is less than 5 parts by weight, the rigidity is not sufficiently improved, and even if the inorganic filler is added in an amount exceeding 150 parts by weight, it is difficult to obtain the rigidity corresponding to the added amount.
The filling amount of the inorganic filler is particularly preferably 40 to 70 parts by weight with respect to 100 parts by weight of the constituent resin in consideration of the balance between the weight and rigidity of the sheet.

As a method for producing the thermoplastic resin sheet of the present invention, a molten resin is extruded from a die such as a flat die (T die or coat hanger die), a straight die, a circular die (crosshead die, etc.), and simultaneously foamed. For example, a method in which the resin is compressed by, for example, a specific roll pressure (linear pressure) while being stretched, and further stretched is preferably used. Further, it is also preferable to extrude the molten resin from the die as described above and then expand the resin, compress the resin by a specific roll pressure (linear pressure), and further stretch the resin using a tenter stretching machine or the like.

Here, the specific roll pressure (linear pressure) may be, for example, about 6 to 10 kgf / cm, and by applying such a roll pressure to the extruded and foamed resin, a characteristic is obtained. It becomes possible to obtain a thermoplastic resin foam layer having a cellular structure. Extrude a specific roll pressure (linear pressure)
As a method for giving the foamed resin, for example, a method using two winding rolls (nip rolls) can be mentioned.

The stretching method of the sheet-like resin includes the following (1)
A method of stretching the extruded resin using a tenter stretching machine, a method of (2) a method of pulling the resin extruded along an internal mandrel, and a method of (3) a method of inflating the resin extruded from a circular die by air blow, etc. No. These stretching methods may be used alone or in combination of two or more. In the method of stretching using a tenter stretching machine, the extruded and foamed resin is heated to about 130 to 170 ° C., and the resin is heated to its T
It is preferable to stretch the film in the direction D by a factor of 2 to 10 times. The diameter of the circular die is preferably 50 mmφ or more, more preferably 80 mmφ or more.
When stretching the resin extruded from the circular die, the stretching ratio is preferably 2 to 10 times, more preferably 2.5 to 10 times, and more preferably 3 to 10 times. Is particularly preferred. When the stretching ratio is smaller than 2, the surface of the sheet-like resin is likely to wrinkle. On the other hand, when the stretching ratio is more than 10 times, the sheet-like resin is easily broken at the time of stretching. Here, the stretching ratio means the ratio of the inner diameter of the sheet-like resin after being stretched along the inner mandrel or expanded by air blow to the diameter of the circular die.

In order to produce a thermoplastic resin sheet having an expansion ratio of 3 times or more and 40 times or less, the amount of the foaming agent may be appropriately adjusted so as to obtain a desired expansion ratio. Further, the cell wall density and the average cell diameter of the foamed layer can be adjusted by selecting a thermoplastic resin having an appropriate melt viscosity as a resin for the foamed layer.

An example of the method for producing a thermoplastic resin sheet of the present invention will be described with reference to the drawings. In this example, a polypropylene sheet having a three-layer structure of a non-foamed layer / foamed layer / non-foamed layer is manufactured using polypropylene as a foamed layer, long-chain branched polypropylene as a non-foamed layer, and carbon dioxide as a foaming agent.

FIG. 1 shows an example of an apparatus for producing a thermoplastic resin sheet according to the present invention. The manufacturing apparatus 1 includes an extruder 3 for extruding a foam layer constituent material, an extruder 5 for extruding a non-foam layer constituent material, a die 7, a mandrel 9, and a take-up roll (nip roll) 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. The polypropylene containing the blowing agent is 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 polypropylene 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 (T die, coat hanger die, etc.), a straight die, a circular die (crosshead die, etc.), and the like. Is exemplified.

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

The three-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 a mandrel 9, cooled, and then taken up by a take-up roller (nip roll) 11. When this is cut at both folds, two three-layer sheets are obtained. In addition, when the sheet is cut open only at one of the folded portions, a sheet having a three-layer structure with one wide sheet is obtained.

When two sheets of the obtained three-layer structure are laminated and bonded, a non-foamed layer / foamed layer / non-foamed layer / foamed layer /
A sheet having a five-layer structure of a non-foamed layer is obtained. Further, they can be laminated to form a multilayer structure.

A preferred form of the die structure 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 2 for forming a foamed layer.
3a, 23b, a resin flow path 24 forming a non-foamed layer,
24a, 24b, 24c and 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 of the die 7. 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 adhere to 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-layered 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 production of the thermoplastic resin sheet of the present invention,
The discharge amount (Q: kg / h · mm) of the molten resin and the diameter (D: mmφ) of the die 7 are such that Q / D ≧ 0.3 kg / h ·
mm, Q / D ≧ 0.6 kg
/ H · mm is more preferable. The lip clearance of the die exit 26 is preferably 0.5 to 3 mm, more preferably 1 to 2 mm. The taper angle of the die exit is preferably 0 ° to 5 °, and 0 °
It is more preferable that it is 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 °, and more preferably 50 ° to 70 °.

In order to increase the expansion ratio, it is preferable to pass the sheet extruded from the die through a vacuum chamber. The foamed layer is further foamed in the vacuum chamber, and a thermoplastic resin sheet having a foamed layer with a high expansion ratio can be obtained.

In each of the above examples, a single-screw extruder is used, but a twin-screw extruder may be used. In particular, as an extruder for extruding a foam layer constituent material, 2
It is preferred to use a screw extruder.

The thermoplastic resin sheet having a foamed layer having a larger cell wall density ratio is obtained by, for example, further stretching a thermoplastic resin sheet having a foamed layer obtained by foaming under stretching conditions (hereinafter referred to as a foamed sheet). It can be manufactured by a method. This additional stretching is preferably performed after the foam sheet has been preheated. As a method of stretching the foam sheet, a general stretching method, for example, uniaxial stretching, zone stretching, flat sequential stretching, flat simultaneous biaxial stretching,
Examples include tubular simultaneous stretching. In order to improve the heat insulation of the entire foam sheet, it is particularly preferable that the stretching is simultaneous biaxial stretching.

The thermoplastic resin sheet of the present invention may have a layer (hereinafter referred to as an additional layer) other than the non-foamed layer laminated on the foamed layer as long as the heat insulating property is not impaired. By providing such an additional layer, bending stiffness,
Improves mechanical properties such as compressive strength, surface scratch resistance, and dimensional stability, and functions such as heat resistance, heat insulation, gas barrier properties, and moldability, and improves gloss, surface smoothness, and appearance. Properties can be imparted to the thermoplastic resin sheet of the present invention. Additional layers include layers composed of woven, non-woven, knitted, sheets, films, meshes, and the like.
The thermoplastic resin sheet of the present invention may have an adhesive layer or an adhesive resin layer for bonding the layers.

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. The additional layer may be a surface layer or an inner layer of the thermoplastic resin sheet of the present invention.

Examples of the thermoplastic resin constituting the additional layer include a polyolefin resin, an ethylene-vinyl ester copolymer, a polyester resin, and a polyamide resin.

The thermoplastic resin sheet of the present invention has, as an additional layer, a layer composed of a thermoplastic resin film containing a dioxin inhibitor in order to reduce the load on the environment when the sheet is incinerated. Is preferred. When the thermoplastic resin sheet of the present invention is applied to a food container, the sheet is made of an unstretched polypropylene film (C
It is preferable to have additional layers such as PP), an oriented polypropylene film (OPP), and an ethylene-vinyl ester copolymer (EVOH) film.
Further, when the thermoplastic resin sheet of the present invention is used for packaging of easily degradable products such as fruits, vegetables, and fresh flowers, a thermoplastic resin film containing an ethylene gas absorbent, a freshness-retaining agent, a deodorant, an antibacterial agent, and the like Such layers can be used as additional layers. The film constituting this additional layer may be a single-layer film or a multilayer film. The thickness of each of these films is 10 to 10
The thickness is preferably 0 μm, and the total thickness when used as a multilayer film is preferably 50 to 200 μm. Specific examples of additional layers when the thermoplastic resin sheet of the present invention is applied to a food container include 50 to 100 μm
Thick CPP film, polypropylene (PP) layer / adhesive layer / EVOH layer / three-type four-layer multilayer film of 100 μm thickness of adhesive layer, PP layer / adhesive layer / EVOH layer / adhesive layer / P
A 100 μm-thick, three-layer, five-layer film having a thickness of 100 μm, such as a PP layer / adhesive layer / nylon layer / EVOH layer / adhesive layer / PP layer, having a thickness of 100 μm, may be used.

Examples of the additional layer include a method of bonding a sheet (or film) corresponding to the layer to the foamed layer or the non-foamed layer via an adhesive layer, and a method of bonding the additional layer to a foamed layer. And a method of fusing on a non-foamed layer.

As a method of laminating via an adhesive layer, a method of coating and laminating a sheet (or film) as an additional layer and / or a foamed or non-foamed layer can be mentioned. Further, a sheet (or film) obtained by laminating an adhesive resin sheet (or film) on a sheet (or film) serving as an additional layer is used, and the adhesive resin is heated and melted to form a foamed layer or a non-foamed layer. It is also possible to use a bonding method. Conversely, an adhesive resin sheet (or film) may be laminated in advance on a foamed layer or a non-foamed layer, and then heated and melted to adhere to an additional layer sheet.

As a method of forming the additional layer on the foamed layer or the non-foamed layer by fusion, for example, a method of forming the additional layer on the foamed layer or the non-foamed layer by extrusion and laminating, And a method in which at least one surface of a foamed layer (and / or a non-foamed layer) to be bonded to the sheet to be bonded to the layer is heated and melted for bonding.

Examples of the adhesive resin include (1) one or more monomers selected from the group consisting of unsaturated carboxylic acids or anhydrides thereof, epoxy group-containing vinyl monomers, unsaturated carboxylic esters, and vinyl esters; Examples include a copolymer with an olefin monomer and (2) an acid-modified olefin-based polymer obtained by grafting an unsaturated carboxylic acid or an anhydride thereof. As a specific example of the former, 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- (meth) Examples thereof include a methyl acrylate copolymer, an ethylene- (meth) acrylate copolymer, an ethylene- (meth) acrylate-maleic anhydride copolymer, and an ethylene-vinyl acetate copolymer. Specific examples of the latter include, for example, acid-modified olefin polymers grafted with unsaturated carboxylic acids or anhydrides, such as maleic anhydride-grafted ethylene polymers and maleic anhydride-grafted propylene polymers. Is mentioned.

The thermoplastic resin sheet of the present invention can be used for various purposes by performing processing such as molding as required. Specifically, a microwave-compatible container (HM
R) and other food containers, heat insulation materials, cushioning materials such as sports equipment and packing materials, shock-absorbing materials to prevent the bottles and containers from being damaged by transportation and storage when transported and stored, and subjected to adhesive processing. It can be used for all kinds of heat insulating labels, automotive parts such as vehicle ceiling materials, sealing materials, building materials, and applications using resins that require heat insulating properties in the aerospace industry. In particular, it can be suitably used as a food container such as a microwave oven-compatible container. For example, the thermoplastic resin sheet of the present invention can be formed into a container such as a tray, a cup, a cup, and a box. As described above, since the thermoplastic resin sheet of the present invention has excellent heat insulating properties, a container formed by molding the same has excellent heat insulating properties. Therefore, the container formed by molding the thermoplastic resin sheet of the present invention is suitably used, for example, as a container for food which is heated and cooked in a microwave oven or the like.

As a method for forming the thermoplastic resin sheet of the present invention, for example, the thermoplastic resin sheet is heated and softened by an infrared heater or the like, and then a mold such as a male mold, a female mold, and a male-female mold pair is used. Then, it is shaped by vacuum forming, pressurized air, vacuum pressurized air, etc., and cooled and solidified, or the heat of the present invention is used between two fittable molds without using vacuum or pressurized technology. There is a method in which a plastic resin sheet is supplied and shaped by pressing.

[0056]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments and the like specifically showing the configuration and effects of the present invention will be described below. [Example 1] A thermoplastic resin sheet comprising three layers of a non-foamed layer / foamed layer / non-foamed layer was prepared by the following method, and the physical properties thereof were evaluated. Table 1 shows the results. (Foam layer constituent material) The foam layer constituent material is a 70/30 weight ratio of polypropylene and polyethylene by a two-stage polymerization method.
The mixture obtained by pellet blending 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. 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. 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. Next, 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 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: 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 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 thereto, and 15 g of propylene was continuously supplied over 30 minutes while keeping the temperature in the tank at 5 to 15 ° C. to perform preactivation.

(3) Polymerization of Propylene Polymer First Stage In a 300 L polymerization tank made of stainless steel, liquid propylene was supplied at 57 kg / h so as to maintain a polymerization temperature of 60 ° C. and a polymerization pressure of 27 kg / cm ² G. While feeding, 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 tank without deactivation.

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 continuously while supplying 6 mmol / h of h, t-butyl-n-propyldimethoxysilane, a polymer of 18.2 kg / h 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 of the first polymerization tank to the second polymerization tank was 11/89, and the second stage polymerization reaction was carried out. The intrinsic viscosity of the polymer in the portion formed by was determined to be 1.2 dL / g.

(4) Pelletization of polymer For 100 parts by weight of the polymer powder obtained by the above two-step reaction, 0.1 parts by weight of calcium stearate and 0.0% of Irganox 1010 (trade name, manufactured by Ciba-Geigy) are used.
5 parts by weight and 0.2 parts by weight of a trade name Sumilizer BHT (manufactured by Sumitomo Chemical Co., Ltd.) were added, mixed and melt-kneaded at 230 ° C. to obtain a pellet having an MFR of 12.

(5) Blend of foam layer constituent materials Polypropylene obtained by the above method and polyethylene (Sumikasen G20, trade name, manufactured by Sumitomo Chemical Co., Ltd.)
A dry blend of the pellets of 1) at a weight ratio of 70/30 was obtained.

(Material for Non-foamed Layer) As a material for the 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).

(Extrusion foaming) 50 mmΦ twin screw extruder (3)
And a device in which a 90 mmΦ circular die (7) was attached to a 32mmΦ single screw extruder (5). 70/30 of propylene polymer / polyethylene used for foam layer
(Weight ratio) A raw material obtained by blending 1 part by weight of a nucleating agent (Hydrocelol manufactured by Beilinger Ingelheim Chemicals Co., Ltd.) with respect to 100 parts by weight of the mixture was charged into a hopper of an extruder (3), and a position where melting was advanced. , 1 part by weight of carbon dioxide was injected, and the raw material and carbon dioxide were sufficiently kneaded and melted and fed to a die (7). The above molten mixture to be a foamed layer and the molten resin to be a non-foamed layer fed by an extruder (5) are laminated in a die and extruded.
Cooled along the mφ mandrel (9) and expanded 2.3 times. Thereafter, a slit was made in the cylindrical foam sheet with a cutter, and the cylinder was opened to form a flat foam sheet, which was wound by a winder (11). Incidentally, the take-up roll (nip roll) pressure at this time was about 6.8 kgf / cm.

Example 2 The thermoplastic resin sheet of Example 1 and a CPP 70 μm film (non-stretched PP manufactured by Tocelo Co., Ltd.)
Film RXC-3 # 70 type) was laminated with a sand lamination (fused PP temperature: 290 ° C., processing speed: 40 m / min, sand layer thickness: 40 μm, nip pressure: 5 kgf / cm ² ) of a molten PP resin (PP FW263A manufactured by Sumitomo Chemical), The physical properties were evaluated. Table 1 shows the results.

Example 3 The thermoplastic resin sheet of Example 1 and a barrier multilayer film having a thickness of 100 μm (PP layer / adhesive layer / barrier layer / adhesive layer / PP layer = 30/5/30/5)
/ 30 μm thick PP layer: Sumika PPFL8115, Adhesive layer: Mitsui Chemicals ADMER QF551, Barrier layer: Kuraray EVAL EVOH-E105A coextruded and manufactured with a three-layer five-layer film) by molten PP resin (Sumitomo Chemical) PP FW263A) (melting PP temperature 29
0 ° C, processing speed 40m / min, sand layer thickness 40μ
m, nip pressure 5 kgf / cm ² )
The physical properties were evaluated. Table 1 shows the results.

Example 4 The thermoplastic resin sheet of Example 1 and a barrier multilayer film having a thickness of 100 μm (PP layer / adhesive layer / barrier layer / adhesive layer / PP layer = 30/5/30/5)
/ 30 μm thickness PP layer: Sumika PP FLX80E3, Adhesive layer: Mitsui Chemicals Admar QF551, Barrier layer: Kuraray Eval EVOH-E105A coextruded and manufactured with three types of five-layer film by molten PP resin (Sumitomo Chemical) PP FW263A) (molten PP temperature 2)
90 ° C, processing speed 40m / min, sand layer thickness 40μ
m, nip pressure 5 kgf / cm ² )
The physical properties were evaluated. Table 1 shows the results.

Example 5 The thermoplastic resin sheet of Example 1 and a barrier multilayer film having a thickness of 100 μm (PP layer / adhesive layer / nylon layer / barrier layer / adhesive layer / PP layer = 32.
5/5/5/20/5 / 32.5 μm thick PP layer: PP FLX80E3 manufactured by Sumika, adhesive layer: Admer QF551 manufactured by Mitsui Chemicals, nylon layer: Nylon resin 50 manufactured by Ube Industries
23FD, barrier layer: EVAL EVOH-E made by Kuraray
105A co-extruded to produce four types of six-layer film)
Of molten PP resin (PP FW263A manufactured by Sumitomo Chemical) at a molten PP temperature of 290 ° C. and a processing speed of 40 m / m
in, sand layer thickness 40 μm, nip pressure 5 kgf / cm
² ) Lamination was carried out, and the physical properties were evaluated. Table 1 shows the results.

Example 6 A thermoplastic resin sheet was prepared in the same manner as in Example 1 except that the following resin composition was used as the non-foaming layer constituting material, and its physical properties were evaluated.
Table 1 shows the results. (Non-foamed layer constituent material) As a non-foamed layer constituent material, polypropylene PF814 having a long chain branch manufactured by Montell Corporation
(Melting point 159.0 ° C crystallization temperature 130.1 ° C M
I 2.2 g / 10 min) and talc (magnesium silicate main component, trade name Hayashi Kasei Micron White # 50)
00S) is dry blended at a mixing ratio of 60/40 wt%, and the co-axial twin screw extruder (Ikegai PCM45 45 mmφ,
L / D30), 200 rpm, die temperature 240
C., and a resin composition granulated and dried was used.

Example 7 A thermoplastic resin sheet was prepared in the same manner as in Example 1 except that the following resin composition was used as the non-foaming layer constituting material, and the physical properties thereof were evaluated.
Table 1 shows the results. (Non-foamed layer constituent material) As a non-foamed layer constituent material, polypropylene PF814 having a long chain branch manufactured by Montell Corporation
(Melting point 159.0 ° C crystallization temperature 130.1 ° C M
I 2.2 g / 10 min) and magnesium sulfate (Mosh Heidi SN manufactured by Ube Materials) in a blending ratio of 60/40 wt%, and the same direction twin screw extruder (Ikegai PCM45 45 mmφ, L / D30) 200
A resin composition granulated at a rpm of 240 ° C. and a die temperature and dried was used.

[Embodiment 7]

Comparative Example 1 The properties of a commercially available polypropylene foam sheet having a thickness of 1.2 mm and a foaming ratio of the foam layer of 2.5 times were evaluated. Table 1 shows the results.

Comparative Example 2 The physical properties of a commercially available polypropylene foam sheet having a thickness of 3 mm and an expansion ratio of the foam layer of 3 times were evaluated. Table 1 shows the results.

(Cell Wall Density of Foam Layer in Thickness Direction) After cooling the foam sheet with liquid nitrogen, it was cut in the thickness direction with a razor, and the cross section of the foam layer was photographed with a scanning microscope. The magnification was adjusted so that each bubble existing in the visual field of the electron microscope was clearly recognized. On the obtained enlarged image, the number of cell walls where one straight line in the thickness direction of the foam layer intersected was counted. Based on the result, the length of the foam layer in the thickness direction is 1 mm
The number of cell walls per hit was determined. By such a method, the number of cell walls existing per 1 mm in the thickness direction of the foam layer in a total of 20 or more portions separated from each other by 1 mm or more was obtained. By calculating the average value of the obtained cell wall numbers, the cell wall density in the thickness direction of the foam layer was obtained.

(Cell Wall Density Ratio) After cooling the foam sheet with liquid nitrogen, the foam layer was cut with a razor in a direction perpendicular to the thickness direction of the sheet, and the cross section was photographed with a scanning microscope. The magnification was adjusted so that each bubble actually present in the visual field of the electron microscope could be recognized independently of each other. The cell wall density ratio of the foam layer was determined by the following equation. Cell wall density ratio r = T / S where T is the cell wall density in the thickness direction of the foam layer,
S is the minimum value of the cell wall density in the direction perpendicular to the thickness direction of the foam layer.

(Horizontal Cell Wall Density) After cooling the foamed sheet with liquid nitrogen, the foamed layer was cut with a razor in a direction parallel to the thickness direction of the sheet, and the cross section was photographed with a scanning microscope. The magnification was adjusted so that each bubble actually present in the visual field of the electron microscope could be recognized independently of each other. The cell wall density ratio of the foam layer was determined by the following equation. Horizontal cell wall density ratio R = M / L where M is the cell wall density in any one direction perpendicular to the thickness direction of the foam layer, L is perpendicular to the thickness direction of the foam layer,
And the cell wall density in the direction perpendicular to the direction in which M was measured.

(Average Cell Diameter) Among the directions perpendicular to the thickness direction of the foam layer, the cross section of the foam layer along the direction in which the cell wall density is minimum is enlarged and observed by SEM, and is observed in the visual field. The maximum length of each of 20 or more of the bubbles was measured, and the average value was determined. The average cell diameter of the foam layer was determined by the following equation. d = L / r (where L is the average major diameter of cells in the foamed layer, and r is the cell wall density ratio of the foamed layer.)

(Thermal Conductivity) J was measured using a thermal conductivity measuring device (AUTO-II series HC-074) manufactured by Eiko Seiki Co., Ltd.
The thermal conductivity was measured based on IS A1412. (Low temperature plate temperature 20 ° C, high temperature plate temperature 30 ° C, Tem
property Equiridium 0.2 ° C, B
etween Block HEM Equil 49μ
V, HFMPercent Change 2.0%, M
in Number of Block 4, Calcul
ation Blocks 3) The foam sheet to be measured should be 200 mm x 200 m as much as possible.
m, the measurement was performed on one sheet in Example 1 and Comparative Example 2, and the measurement was performed on three sheets in Example 2;
Comparative Example 1 was measured in a state where two sheets were stacked.

[0081]

[Table 1]

[Brief description of the drawings]

FIG. 1 is a model diagram showing a preferred configuration of a thermoplastic resin sheet manufacturing apparatus.

FIG. 2 is a cross-sectional view illustrating a preferred configuration of a head in a thermoplastic resin sheet manufacturing apparatus.

Claims (6)

[Claims] 1. A thermoplastic resin foam layer having an expansion ratio of 3 to 40 times, a cell wall density in a thickness direction of 8 cells / mm or more, and a cell wall density ratio of 2 to less than 6. Thermoplastic resin sheet. 2. The foam layer has an average cell diameter of 1 μm or more and 10 μm or more.
The thermoplastic resin sheet according to claim 1, wherein the thickness is 0 µm or less. 3. The thermoplastic resin sheet according to claim 1, wherein the thermoplastic resin constituting the foamed layer is a polypropylene resin. 4. An expansion ratio laminated on the foam layer is 1.0.
The thermoplastic resin sheet according to any one of claims 1 to 3, wherein the thermoplastic resin sheet has a non-foamed layer of a polyolefin resin having a thickness that is twice or more and 1.5 times or less. 5. The thermoplastic resin sheet according to claim 4, wherein the non-foamed layer is made of a polyolefin resin having a long chain branch. 6. A container formed by molding the thermoplastic resin sheet according to any one of claims 1 to 5.