JP2000109573A - Easily tearable sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a sheet having a high mechanical strength, and capable of providing an easily tearable container. SOLUTION: This easily torn sheet is obtained by molding a resin composition comprising (A) 95-60 wt.% styrenic resin, and (B) 5-40 wt.% olefinic resin, and has 10-100 gf Elmendorf tear strength. The easily torn sheet also has easily torn properties in one direction, and <=10 mm displacement in the MD(machine direction) in a diagonal tensile test.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an easily tearable sheet and a unidirectionally tearable container obtained therefrom.

[0002]

2. Description of the Related Art Styrene resin sheets are widely used as materials for manufacturing various containers because of their excellent moldability and rigidity. Therefore, in addition to the above properties, it is desired that the material be easily torn.

[0003] Japanese Patent Publication No. 8-16168 discloses such a sheet having easy tearing properties. A styrene-based resin, a polyolefin-based resin and a polyolefin-based resin are provided at any position on a polystyrene-based resin or polyolefin-based resin base sheet. A thermoplastic resin sheet provided with a resin composition sheet containing a blend of a modified polyolefin resin or the like is disclosed. However, since this sheet requires a process for providing an easy tearing band, the number of steps is increased,
Manufacturing costs rise. Further, when formed into a container, the strength of the easily tearable band is reduced, so that the durability of the container is inferior, and it is also insufficient in that it can be torn only at a portion where the easily tearable band exists.

[0004] It is an object of the present invention to provide an easily tearable sheet from which a container having high mechanical strength and easily tearable in one direction can be obtained. It is another object of the present invention to provide a container obtained from the easily tearable sheet.

[0005]

SUMMARY OF THE INVENTION The present invention relates to an easily tearable one-way tearable film having an Elmendorf tear strength of 10 to 100 gf and a deviation in the MD direction of 5 mm or less in an oblique tensile test. Provide a functional sheet. The present invention also provides a container formed by molding the above-mentioned easily tearable sheet.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The easily tearable sheet of the present invention has an Elmendorf tear strength of 10 to 100 gf, preferably 2 to 100 gf.
It is from 0 to 90 gf, particularly preferably from 30 to 80 gf. When the Elmendorf tear strength is 10 gf or more, the mechanical strength of the sheet and the container obtained therefrom can be increased,
When it is 100 gf or less, the tearability can be maintained, and the weight can be easily reduced when discarded as garbage. The Elmendorf tear strength is a strength determined by an Elmendorf tear test, and the test method is described in, for example, Dictionary of Plastics Molding and Processing Terminology (Industry Research Institute Co., Ltd., 560-56).
1).

The easily tearable sheet of the present invention has a deviation in the MD direction (sheet flow direction) of 10 in the oblique tensile test.
mm, preferably 5 mm, particularly preferably 3 mm. The "displacement in the MD direction" in the present invention is obtained by an oblique tensile test according to the following method. A square (5 × 5 cm) sheet having two sides parallel to the MD direction and two sides perpendicular to the MD direction as shown in FIG. 1 is prepared, and a cut is made from the corner B to the center point O. Thereafter, the corners A and C of the sheet are pulled in opposite directions to tear. In this case, the tear when straightly torn becomes a broken line X, but the tear when displaced becomes a broken line Y. In the case where the tear becomes the broken line Y, the shift r between the broken line X and the broken line Y is referred to as “displacement in the MD direction”.

The easily tearable sheet of the present invention can be obtained by molding a resin composition containing (A) a styrene resin and (B) an olefin resin.

The styrene resin as the component (A) includes a polymer of a styrene monomer and a copolymer of a styrene monomer and another monomer copolymerizable therewith.

As the styrene monomer, styrene,
Alkyl-substituted styrene such as 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 4-ethylstyrene, 4-t-butylstyrene, 2,4-dimethylstyrene, α-methylstyrene, α-methyl-4- One or more selected from α-alkyl-substituted styrene such as methylstyrene, halogenated styrene such as 2-chlorostyrene and 4-chlorostyrene, and the like can be given.

Other monomers copolymerizable with the styrene monomer include acrylic acid or methacrylic acid, methyl acrylate or methyl methacrylate, ethyl acrylate or ethyl methacrylate, butyl acrylate or butyl methacrylate, acrylic acid 2 Acrylic acid such as -ethylhexyl or 2-ethylhexyl methacrylate (C _1-
C ₈₎ esters or methacrylic acid (C ₁ ~C ₈₎ esters, acrylonitrile, maleic anhydride, maleimide,
One or more types selected from maleic acid or derivatives thereof such as N-substituted maleimide such as N-methylmaleimide and N-ethylmaleimide can be mentioned.

The styrene resin as the component (A) may be a rubber-modified styrene resin. Examples of the rubber used in the production of the rubber-modified styrene resin include non-styrene rubbers such as butadiene rubber, butadiene-isoprene rubber, butadiene-acrylonitrile rubber, ethylene-propylene rubber, isoprene rubber, acrylic rubber, and ethylene-vinyl acetate rubber; At least one selected from styrene rubbers such as butadiene rubber and styrene-isoprene rubber can be used. The butadiene rubber may be a high cis type having a high content of cis-1,4 structure or a low cis type having a low content of cis-1,4 structure. When the rubber-modified styrenic resin is used, the content of the rubber component in the resin is 1 to 2
It is preferably 0% by weight.

The polymerization form when the component (A) is made into a copolymer is not particularly limited, but may be a block copolymer,
It may be a random copolymer or a copolymer having a tapered block structure. As the component (A), polystyrene is preferable.

The content of the component (A) is preferably from 60 to
It is 95% by weight, particularly preferably 65-90% by weight, more preferably 70-80% by weight.

The olefin resin of the component (B) is a polymer containing a monoolefin having 2 to 8 carbon atoms as a main monomer component.
Linear low density polyethylene, polypropylene, ethylene-
Propylene random copolymer, ethylene-propylene block copolymer, polymethylpentene, polybutene-1
And the like. One or more selected from the above can be mentioned, and among these, polyethylene is preferable. The content of the component (B) is preferably 5 to 40% by weight, particularly preferably 10 to 40% by weight.
It is 35% by weight, more preferably 20 to 30% by weight.

The resin composition may further contain the following compatibilizers. When a component that also acts as a compatibilizing agent with the component (B) is used as the component (A), the compatibilizing can be sufficiently performed only by the action alone. There is no.

(C-1) A copolymer comprising a vinyl aromatic compound and a conjugated diene compound or a hydrogenated product thereof. Examples of the vinyl aromatic compound include monomers used in the component (A) described above, and examples of the conjugated diene compound include butadiene, chloroprene, and isoprene. (C-2) An epoxidized copolymer of a vinyl aromatic compound and a conjugated diene compound or a hydrogenated product thereof.
Examples of the copolymer composed of a vinyl aromatic compound and a conjugated diene compound include the copolymer (a).

The content of the compatibilizer is preferably from 0.1 to 100 parts by weight of the total amount of the components (A) and (B).
The amount is 20 parts by weight, particularly preferably 1 to 10 parts by weight.

The resin composition may further contain a heat stabilizer, an ultraviolet absorber, a phosphorus-based, sulfur-based or hindered phenol-based antioxidant, calcium phosphate, barium sulfate, talc, zeolite, a colorant, a fatty acid, if necessary. A lubricant such as an ester, an antistatic agent and the like can be blended.

The easily tearable sheet of the present invention is obtained, for example, by melt-kneading the above-mentioned resin composition or resin pellets obtained therefrom by a usual extruder, and extruding it through a circular die, a T-die or the like. Obtainable.

The easily tearable sheet of the present invention can be a laminated sheet of two or more layers in which a sheet obtained from the above resin composition is laminated on one or both sides of a synthetic resin sheet as a base material. In this case, the synthetic resin sheet serving as the base material is used and properties to be provided, for example, according to heat resistance, abrasion resistance, improvement of surface appearance, printability, etc.
It can be appropriately selected from desired materials. As the material of the synthetic resin sheet, polyolefin resin, polyester resin, polyamide resin, polysulfone resin,
One or more thermoplastic resins selected from polyether resins and polyketone resins can be mentioned. Known methods such as a co-extrusion method and a dry lamination method can be applied as a method for producing the laminated sheet.

The thickness of the easily tearable sheet of the present invention is preferably from 0.1 to 2.0 mm, particularly preferably from 0.2 to 1.
0 mm. When the easily tearable sheet of the present invention is the above-described laminated sheet, the thickness of the laminated sheet is in a range obtained by adding the thickness of the base material to the thickness.

The container of the present invention is formed by molding the above-mentioned easily tearable sheet. The shape and size of the container are not particularly limited as long as the container has an opening for inserting contents. Instead, it can be appropriately changed according to the application. Further, it may be a container including a main body and a lid. For forming the container, a known vacuum forming method or the like can be applied.

In the container of the present invention, a release agent such as an antistatic agent and silicone oil can be applied to the inner surface and / or the outer surface.

Although the container of the present invention can be used as a container in various fields, it is suitable, for example, as a confectionery container in which a large number of confections are evenly arranged and stored.

[0026]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto.

The details of the resin composition used below are as follows. (A) Component PS: polystyrene (“# 3” manufactured by Daicel Chemical Industries, Ltd.)
0)) (B) component LLDPE: Linear low-density polyethylene (“AF331R” manufactured by Nippon Polyolefin) LDPE: Low-density polyethylene (“JF124Z” manufactured by Nippon Polyolefin) HDPE: High-density polyethylene (Nippon Polyolefin “High-density Polyethylene ") (Compatibilizer) SBS: Styrene-butadiene block copolymer (" TR2003 "manufactured by Nippon Synthetic Rubber Co., rubber content 57% by weight) SEBS: Styrene-ethylene-butadiene block copolymer (" H1041 "manufactured by Asahi Kasei Corporation) Examples 1 to 6 and Comparative Examples 1 to 3 The compositions ((A) and (B) shown in Table 1 are expressed in% by weight. The compatibilizers are shown in parts by weight based on the total amount of (A) and (B). ) Was previously mixed in a V-blender. Thereafter, the mixture is fed to a single screw extruder and melt-kneaded. The extrusion temperature is 250 ° C. or less, the die width of the T die is 1500 mm, the lip opening is 600 μm, and the discharge rate is 45 kg / hour.
A sheet (0.2 mm thick) was obtained. Each of the sheets was subjected to measurement of Elmendorf tear strength and an oblique tensile test.
Table 1 shows the results.

The Elmendorf tear strength was determined by making a 2 cm cut in a sheet having a width of 3 cm and a length (length in the MD direction) of 10 cm, and measuring the tensile strength with Tensilon (manufactured by Orientec Co., Ltd.). The deviation in the MD direction due to the oblique tensile test was evaluated as linearity based on the following criteria. ：: The deviation in the MD direction is within 5 mm Δ: The deviation in the MD direction is more than 5 mm to 10 mm ×: The deviation in the MD direction exceeds 10 mm

[0029]

[Table 1]

The sheet of the example could be torn from any part in the MD direction. The balance between tear strength and linearity was also good. The sheet of the comparative example has a poor balance between tear strength and linearity, and it is difficult to tear the comparative examples 2 and 3, while the comparative example 1 is fragile and difficult to apply as a container.

[0031]

As described above, the easily tearable sheet of the present invention has high mechanical strength and easily tears. For this reason, when the molded product is applied to various containers, it has sufficient strength to hold the contents and can be easily torn by human hands at the time of disposal to reduce the weight.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a test method of an oblique tensile test.

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Claims (6)

[Claims] An Elmendorf tear strength of 10 to 100.
gf, deviation in MD direction in oblique tensile test is 10mm
An easily tearable sheet having tearing properties in one direction. 2. (A) 60 to 95% by weight of a styrene resin
And (B) an easily tearable sheet formed by molding a resin composition containing 40 to 5% by weight of an olefin resin. 3. The easily tearable sheet according to claim 2, wherein the component (A) is polystyrene and the component (B) is polyethylene. 4. The easily tearable sheet according to claim 2, wherein the resin composition further contains the following compatibilizer. (C-1) A copolymer comprising a vinyl aromatic compound and a conjugated diene compound or a hydrogenated product thereof. (C-2) An epoxidized copolymer of a vinyl aromatic compound and a conjugated diene compound or a hydrogenated product thereof. 5. The synthetic resin sheet as a base material, wherein
5. An easily tearable sheet, on which the easily tearable sheet according to any one of 4 to 4 is laminated. 6. A container formed by molding the easily tearable sheet according to claim 1.