JP2023031571A - Polyolefin-based uniaxial vertically-stretched film - Google Patents

Abstract

[Problem] To provide a polyolefin longitudinally uniaxially stretched film to which an antifogging agent has been added, which has practical heat-sealing properties even when the heat-sealed surface is subjected to a corona treatment for exhibiting antifogging properties. .
At least two layers in which a heat seal layer 30 is laminated on one side of a substrate layer 20 mainly made of polypropylene resin, and an antifogging agent is added to either the substrate layer 20 or the heat seal layer 30 is stretched in the longitudinal direction by stretching between rolls, the heat seal layer 30 is subjected to corona treatment, the wet tension on the surface of the heat seal layer 30 is 32 mN / m or more, and the heat seal layer 30 is at 190 ° C. It consists of linear low-density polyethylene having a melt flow rate of 1 to 10 g/10 min measured under a load of 2.16 kg and a density of 0.860 to 0.935 g/cm ³ .
[Selection drawing] Fig. 1

Description

TECHNICAL FIELD The present invention relates to a polyolefin film, and more particularly to a longitudinally uniaxially stretched polyolefin film in which the heat seal layer is subjected to corona treatment for anti-fogging properties.

BACKGROUND ART In the packaging of various articles including food, a film and articles are supplied simultaneously by an automatic packaging machine, and filling, packaging and sealing are continuously performed. Stretched film is sometimes used as a film used for packaging this type of article, and various properties such as strength to withstand processing and distribution, heat-sealing properties, and easy-to-cut properties are required for suitable use as packaging bags. performance is required.

In addition, when the film is used as a packaging bag for food, an anti-fogging agent is sometimes added to the film because water droplets may adhere to the inside of the bag due to moisture emitted from the food. At that time, in order to develop antifogging properties on the heat-sealed surface of the film, corona treatment is performed to promote bleeding of the antifogging agent. However, when the heat-sealing surface is subjected to corona treatment, heat-sealing cannot be performed at the same temperature as before corona treatment, and heat-sealing must be performed at a higher temperature.

As a technique for solving the above problems, for example, it is composed of a heat seal layer and a base material layer, and the heat seal layer is composed of a propylene-based polymer and a propylene/1-butene copolymer, ethylene and an α- Laminated films composed of two or more copolymers selected from the group consisting of copolymers with olefins and copolymers of 1-butene and α-olefins having 3 or 5 to 20 carbon atoms are known. (See Patent Document 1).

Further, it has two or more layers, and at least one surface layer is derived from a propylene-based copolymer component and an α-olefin having a content of monomer units derived from an α-olefin of 1 to 5% by weight. A propylene-based copolymer containing a propylene-based copolymer component having a monomer unit content of 20 to 40% by weight, and a ethylene-derived monomer unit content of 6 to 20% by weight. A multilayer film made of a certain propylene-ethylene copolymer is known (see Patent Document 2).

Both the films described in Patent Documents 1 and 2 are biaxially stretched films. A biaxially stretched film is formed by performing longitudinal stretching by inter-roll stretching, in which the film is stretched by a difference in roll speed, and then transverse stretching and heat setting in a tenter oven. In this type of film, the heat setting temperature can be raised to lower the heat-sealing initiation temperature, but with biaxially oriented films, a tenter oven can provide a sufficient amount of heat, so the heat-sealing initiation temperature should be lowered appropriately. be able to. Therefore, even if the heat-sealing surface is subjected to corona treatment, it is possible to maintain a low heat-sealing initiation temperature.

By the way, for packaging bags, a uniaxially stretched film excellent in easy-to-cut properties is preferably used from the viewpoint of easy opening. Uniaxially stretched films include longitudinally uniaxially stretched films only longitudinally stretched and laterally uniaxially stretched films only laterally stretched. The longitudinally uniaxially stretched film is formed by heat setting by heating rolls after longitudinal stretching by stretching between rolls. When trying to lower the heat-sealing initiation temperature of a longitudinally uniaxially stretched film, it is necessary to raise the heat setting temperature of the heating roll. However, in the heating by the heating roll, since the film contacts the heating roll at a high temperature, the film melts and sticks to the heating roll, resulting in peeling traces and poor appearance.

Therefore, in order to avoid the poor appearance of the film due to heat setting, it is necessary to perform heat setting in a temperature range in which the film does not melt, but it is not possible to apply a sufficient amount of heat to the film. Therefore, it was inevitable that the longitudinally uniaxially stretched film had a higher heat sealing temperature than the biaxially stretched film. Moreover, when the heat-sealing surface of the longitudinally uniaxially stretched film is subjected to corona treatment, the heat-sealing temperature becomes even higher, which is also a problem.

WO2016/027885 JP 2017-205909 A

The present invention has been proposed in view of the above situation, and in a longitudinally uniaxially stretched film to which an antifogging agent is added, heat sealing that is practical even if corona treatment is performed to develop antifogging properties on the heat sealing surface. To provide a polyolefin-based longitudinally uniaxially stretched film having properties.

That is, the invention of claim 1 consists of at least two layers in which a heat seal layer is laminated on one side of a base material layer mainly made of polypropylene resin, and either the base material layer or the heat seal layer A polyolefin longitudinally uniaxially stretched film containing an antifogging agent, stretched in the longitudinal direction by stretching between rolls, and corona-treated on the heat seal layer so that the surface of the heat seal layer has a wet tension of 32 mN/m or more. The heat-seal layer has a melt flow rate of 1 to 10 g/10 min and a density of 0.860 to 0.935 g/cm ³ measured under a load of 2.16 kg at 190°C. The present invention relates to a polyolefin-based longitudinally uniaxially stretched film made of density polyethylene.

The invention of claim 2 is composed of at least two layers in which a heat seal layer is laminated on one side of a base material layer mainly made of polypropylene resin, and either the base material layer or the heat seal layer is antifogging. A polyolefin-based longitudinally uniaxially stretched film containing a polyolefin agent, stretched in the longitudinal direction by stretching between rolls, and subjecting the heat seal layer to corona treatment so that the heat seal layer surface has a wet tension of 32 mN / m or more, , the heat seal layer contains at least 50% by weight of linear low-density polyethylene (A) and a polypropylene-based resin (B), and the linear low-density polyethylene (A) is loaded at 190 ° C. A melt flow rate measured at 2.16 kg is 1 to 10 g/10 min, a density is 0.860 to 0.935 g/cm ³ , and the polypropylene resin (B) is propylene having a melting point of less than 135°C. - A polyolefin longitudinally uniaxially stretched film characterized by being selected from at least one of ethylene random copolymers, propylene-ethylene-butene random copolymers, and propylene-ethylene block copolymers.

The invention of claim 3 relates to the polyolefin-based longitudinally uniaxially stretched film of claim 1 or 2, wherein the heat seal initiation temperature between the heat seal layers is 155°C or less.

The invention of claim 4 relates to the polyolefin-based longitudinally uniaxially stretched film according to any one of claims 1 to 3, wherein a surface layer is laminated on the other surface side of the base material layer.

According to the polyolefin-based longitudinally uniaxially stretched film according to the invention of claim 1, it is composed of at least two layers in which a heat seal layer is laminated on one side of a base material layer mainly composed of polypropylene resin, and the base material layer or the heat Either one of the seal layers contains an antifogging agent, is stretched in the longitudinal direction by stretching between rolls, and the heat seal layer is subjected to corona treatment so that the heat seal layer surface has a wet tension of 32 mN/m or more. The polyolefin-based longitudinally uniaxially stretched film, wherein the heat seal layer has a melt flow rate of 1 to 10 g/10 min measured under a load of 2.16 kg at 190° C., and a density of 0.860 to 0.935 g/cm. Since it is made of linear low-density polyethylene that is ³ , even if the heat-sealing surface is subjected to corona treatment, it is possible to appropriately suppress the increase in the heat-sealing start temperature, and to suppress the occurrence of poor appearance due to peeling marks. can be obtained, good anti-fogging properties can be obtained, and a polyolefin-based longitudinally uniaxially stretched film having practical heat-sealing properties can be obtained.

According to the polyolefin-based longitudinally uniaxially stretched film according to the invention of claim 2, it is composed of at least two layers in which a heat seal layer is laminated on one side of a base material layer mainly composed of polypropylene resin, and the base material layer or the heat Either one of the seal layers contains an antifogging agent, is stretched in the longitudinal direction by stretching between rolls, and the heat seal layer is subjected to corona treatment so that the heat seal layer surface has a wet tension of 32 mN/m or more. A polyolefin-based longitudinally uniaxially stretched film, wherein the heat seal layer contains at least 50% by weight or more of a linear low-density polyethylene (A) and a polypropylene-based resin (B), and the linear low-density polyethylene (A) has a melt flow rate of 1 to 10 g/10 min and a density of 0.860 to 0.935 g/cm ³ measured under a load of 2.16 kg at 190° C. The polypropylene resin (B) is selected from at least one propylene-ethylene random copolymer or propylene-ethylene-butene random copolymer having a melting point of less than 135 ° C., or a propylene-ethylene block copolymer, so the heat sealing surface is corona treated Even if it is applied, it is possible to appropriately suppress the increase in the heat sealing start temperature, and it is possible to suppress the occurrence of poor appearance due to peeling marks, and it is possible to obtain good antifogging properties. A polyolefin longitudinally uniaxially stretched film having heat sealability is obtained. Moreover, it is possible to effectively suppress the occurrence of delamination between the base material layer and the heat seal layer.

According to the polyolefin-based longitudinally uniaxially stretched film according to the invention of claim 3, in the invention of claim 1 or 2, the heat seal initiation temperature between the heat seal layers is 155 ° C. or less, so heat sealing is easy and practical. Excellent.

According to the polyolefin-based longitudinally uniaxially stretched film according to the invention of claim 4, in the inventions of claims 1 to 3, the surface layer is laminated on the other side of the base material layer, so that it can be used as a product such as a packaging bag. can enhance sexuality.

1 is a schematic cross-sectional view of a polyolefin-based longitudinally uniaxially stretched film according to one embodiment of the present invention. FIG. It is the schematic of the stretching process between rolls.

FIG. 1 shows a polyolefin longitudinally uniaxially stretched film 10 according to one embodiment of the present invention, comprising at least two layers in which a heat seal layer 30 is laminated on one side of a base material layer 20 mainly made of polypropylene resin. Become. The illustrated longitudinally uniaxially stretched film 10 is composed of three layers in which a surface layer 40 is laminated on the other surface side of a substrate layer 20 . The longitudinally uniaxially stretched film 10 is not limited to two layers or three layers, and may be an appropriate multilayer film. This longitudinally uniaxially stretched film 10 is suitably used as a packaging material for various articles such as foods, daily necessities, and parts.

The longitudinally uniaxially stretched film 10 of the present invention contains an antifogging agent in either the substrate layer 20 or the heat seal layer 30, and is stretched in the longitudinal direction by stretching between rolls. Stretching between rolls stretches a film uniaxially by a speed difference between rolls. The draw ratio in stretching between rolls is preferably 2 to 15 times, more preferably 3 to 10 times, and still more preferably 3 to 6 times. If the draw ratio is too low, uneven drawing tends to occur, and if the draw ratio is too high, breakage may occur during the drawing process.

In the embodiment, as shown in FIG. 2, a film F co-extruded from a film forming machine 50 such as a T-die is wound through a plurality of rolls R, and passed through a preheating section 51 for preheating the film F. After the film F is longitudinally uniaxially stretched in the winding direction (MD) by the speed difference between the stretching section 52 composed of the roll R1 rotating at a low speed and the roll R2 rotating at a high speed, it is stretched in the heat setting section 53. is heated to a predetermined temperature. In FIG. 2, reference character Fr denotes a film roll around which the film F is wound.

In the longitudinally uniaxially stretched film 10, the heat seal layer 30 is subjected to corona treatment so that the surface of the heat seal layer 30 has a wet tension of 32 mN/m or more. The corona treatment of the heat-sealing layer 30 is a treatment for promoting bleeding of the anti-fogging agent contained in the base material layer 20 or the heat-sealing layer 30 to develop anti-fogging properties on the heat-sealed surface. If the wetting tension on the surface of the heat seal layer 30 is less than 32 mN/m, the corona treatment may be insufficient and the bleeding of the antifogging agent may be insufficient.

The wetting tension on the surface of the heat seal layer 30 rises or rises to a saturation point in proportion to the power applied for corona treatment. Therefore, the amount of discharge (W·min/m ² ) is used as a parameter of wetting tension. The amount of discharge is the input power per unit time and per unit area, and is obtained based on the following formula (i). In the formula for calculating the amount of discharge, P (W) is discharge power, L (m) is discharge electrode length, and v (m/min) is film speed.

The base material layer 20 is mainly composed of a polypropylene-based resin, and the thickness of the layer occupying the longitudinally uniaxially stretched film 10 is formed relatively thicker than the other layers to increase the stiffness (rigidity) of the film. It is a layer that is imparted to obtain bag-making aptitude. Examples of the polypropylene-based resin forming the base material layer 20 include propylene homopolymer, propylene-ethylene random copolymer, propylene-ethylene block copolymer, and the like.

The heat-sealing layer 30 is a layer that becomes the inner surface side when the longitudinally uniaxially stretched film 10 is made into a packaging bag, and is heat-sealed between the heat-sealing layers. In the heat seal layer 30, the heat seal initiation temperature between the heat seal layers is preferably 155°C or less. If the heat-sealing start temperature is higher than 155° C., heat-sealing must be performed at a high temperature during bag making, which is not practical.

In the longitudinally uniaxially stretched film 10 of the first embodiment, the heat seal layer 30 has a melt flow rate (MFR) of 1 to 10 g/10 min measured with a load of 2.16 kg at 190 ° C., and a density of 0.860 to It consists of linear low density polyethylene of 0.935 g/cm ³ . If the MFR of the linear low-density polyethylene is too low, it may lead to poor appearance and poor moldability. There is a risk. If the density of the linear low-density polyethylene is too low, blocking may occur more easily due to the lowering of the melting point. There is a risk that it will lead to a decline.

In the longitudinally uniaxially stretched film 10 of the second embodiment, the heat seal layer 30 is configured to contain at least 50% by weight or more of the linear low density polyethylene (A) and the polypropylene resin (B).

The linear low-density polyethylene (A) has a melt flow rate of 1 to 10 g/10 min and a density of 0.860 to 0.935 g/cm ³ measured at 190° C. under a load of 2.16 kg. On the other hand, the polypropylene resin (B) is selected from at least one propylene-ethylene random copolymer or propylene-ethylene-butene random copolymer having a melting point of less than 135°C, or a propylene-ethylene block copolymer. . By adding the polypropylene-based resin (B) to the linear low-density polyethylene (A), it is possible to prevent the heat-seal initiation temperature from dropping too much. Therefore, it is possible to adjust the heat-sealing start temperature by adjusting the blending ratio of the polypropylene-based resin (B). Further, since the polypropylene-based resin (B) is a resin composition of the same type as the base material layer 20 mainly composed of polypropylene-based resin, it is possible to more effectively suppress the occurrence of delamination.

The surface layer 40 is a layer laminated on the other surface side of the base material layer 20, that is, on the surface opposite to the surface on which the heat seal layer 30 is laminated, and is mainly composed of a polypropylene-based resin. The surface layer 40 serves as the outer surface when the longitudinally uniaxially stretched film 10 is made into a packaging bag. The surface layer 40 can be made to function as a printed layer by applying appropriate printing, and the practicality of products such as packaging bags can be enhanced. The surface layer 40 may be subjected to a surface treatment such as corona treatment as necessary to improve the printing performance of the film surface. The polypropylene-based resin forming the surface layer 40 is selected from propylene-based polymers such as propylene homopolymers and copolymers of propylene and other olefins such as ethylene and butene.

In the longitudinally uniaxially stretched film 10 of the present invention, any one or a plurality of layers of the base layer 20, the heat seal layer 30, and the surface layer 40 are subjected to recycling such as material recycling and chemical recycling in order to be an environmentally friendly product. Raw materials and biomass-derived polyolefin resins may also be included. Examples of biomass-derived polyolefin resins include polyethylene-based resins obtained by processing plant raw materials. Specifically, a linear low-density polyethylene system produced by a known resinification process after producing ethanol through alcohol fermentation by yeast from a sugar solution extracted from plant raw materials such as sugarcane and ethyleneizing it. Resin. The greater the weight ratio of the biomass-derived polyolefin resin, the greater the contribution to the reduction of the environmental load.

[Preparation of polyolefin-based longitudinally uniaxially stretched film]
Each material described later is blended, melted, kneaded, and two layers (base layer and heat seal layer) or three layers (surface layer and base layer) are formed by a T-die method using a co-extrusion T-die film forming machine. A sheet is produced by coextrusion on the heat seal layer), longitudinally uniaxially stretched in the winding direction (MD) by a roll stretching machine, and the heat seal layer is subjected to corona treatment to produce polyolefin-based longitudinal films of Prototype Examples 1 to 30. A uniaxially stretched film was obtained.

In each of Prototype Examples 1 to 30, the blending ratio of the resin was blended so as to be 100% by weight for each layer. Prototype Examples 1 to 8 and 11 to 30 were produced with a sheet thickness of 250 μm and the longitudinal uniaxial stretching ratio was 5 times. Prototype Example 10 was produced with a sheet thickness of 300 μm, the longitudinal uniaxial stretching ratio was set to 6 times, and the film thickness of each of Prototype Examples 1 to 30 was set to 50 μm. The amount of discharge in the corona treatment was 5 W·min/m ² for Prototype Example 20, 40 W·min/m ² for Prototype Example 21, and 20 W·min/m ² for Prototype Examples 1 to 19 and 22 to 30. The wet tension was adjusted to 32 mN/m or more. In addition, the thickness of each produced film was measured based on the film thickness measuring method based on JISK7130 (1999).

[Materials used]
The following resins were used as resin compositions for the surface layer, substrate layer, and heat seal layer. As the characteristics of each resin, the melt flow rate (MFR) is a value measured at 230 ° C., 2.16 kg load or 190 ° C., 2.16 kg load in accordance with JIS K 7210 (2014), and the density is JIS K 7112 (1999 ) is a value measured in accordance with The anti-fogging agent used was "Antex SA-300F" manufactured by Toho Chemical Industry Co., Ltd.

Resin A1: Linear low-density polyethylene (manufactured by Prime Polymer Co., Ltd.: "SP2040", MFR (190°C, 2.16 kg load): 3.8 g/10 min, density 0.918 g/cm ³ , melting point 116°C
Resin A2: Linear low-density polyethylene (manufactured by Japan Polyethylene Co., Ltd.: "KS340T", MFR (190°C, 2.16 kg load): 3.5 g/10 min, density 0.88 g/cm ³ , melting point 60°C
Resin A3: Linear low-density polyethylene (manufactured by Prime Polymer Co., Ltd.: "SP2540", MFR (190°C, 2.16 kg load): 3.8 g/10 min, density 0.924 g/cm ³ , melting point 120°C
Resin A4: Linear low-density polyethylene (manufactured by Ube Maruzen Polyethylene Co., Ltd.: "3540F", MFR (190°C, 2.16 kg load): 4.0 g/10 min, density 0.931 g/cm ³ , melting point 123°C
Resin A5: Linear low-density polyethylene (manufactured by Ube Maruzen Polyethylene Co., Ltd.: "4040F", MFR (190°C, 2.16 kg load): 4.0 g/10 min, density 0.938 g/cm ³ , melting point 126°C
Resin A6: Linear low-density polyethylene (manufactured by Ube Maruzen Polyethylene Co., Ltd.: "4540F", MFR (190°C, 2.16 kg load): 4.0 g/10 min, density 0.944 g/cm ³ , melting point 128°C
Resin A7: Linear low-density polyethylene (manufactured by Ube Maruzen Polyethylene Co., Ltd.: "1520F", MFR (190°C, 2.16 kg load): 2.0 g/10 min, density 0.913 g/cm ³ , melting point 114°C
Resin A8: Linear low-density polyethylene (manufactured by Ube Maruzen Polyethylene Co., Ltd.: "715FT", MFR (190°C, 2.16 kg load): 4.0 g/10 min, density 0.913 g/cm ³ , melting point 113°C
Resin A9: Linear low-density polyethylene (manufactured by Ube Maruzen Polyethylene Co., Ltd.: "022GS", MFR (190°C, 2.16 kg load): 8.0 g/10 min, density 0.904 g/cm ³ , melting point 102°C
Resin A10: Linear low-density polyethylene (manufactured by Ube Maruzen Polyethylene Co., Ltd.: "015AN", MFR (190°C, 2.16 kg load): 14.0 g/10 min, density 0.911 g/cm ³ , melting point 103°C

Resin B1: Low-density polyethylene (manufactured by Ube Maruzen Polyethylene Co., Ltd.: "F222", MFR (190°C, 2.16 kg load): 2.0 g/10 min, density 0.922 g/cm ³ , melting point 110°C

Resin C1: high-density polyethylene (Keiyo Polyethylene Co., Ltd.: "M8500", MFR (190°C, 2.16 kg load): 5.0 g/10 min, density 0.962 g/cm ³ , melting point 135°C

・ Resin D1: Propylene-ethylene random copolymer (manufactured by Japan Polypropylene Corporation: "WFW4M", MFR (230 ° C., 2.16 kg load): 7.0 g / 10 min, melting point 135 ° C.
・ Resin D2: Propylene-ethylene random copolymer (manufactured by Japan Polypropylene Corporation: "WFX4M", MFR (230 ° C., 2.16 kg load): 7.0 g / 10 min, melting point 125 ° C.

・ Resin E1: propylene-ethylene-butene random copolymer (manufactured by Japan Polypropylene Corporation: "FW4BT", MFR (230 ° C., 2.16 kg load): 7.0 g / 10 min, melting point 139 ° C.
・ Resin E2: propylene-ethylene-butene random copolymer (manufactured by Japan Polypropylene Corporation: "FX4G", MFR (230 ° C., 2.16 kg load): 5.0 g / 10 min, melting point 126 ° C.
・ Resin E3: propylene-ethylene-butene random copolymer (manufactured by Japan Polypropylene Corporation: "FX4E", MFR (230 ° C., 2.16 kg load): 5.0 g / 10 min, melting point 132 ° C.

Resin F1: Propylene homopolymer (manufactured by Japan Polypropylene Corporation: "FL203D", MFR (230°C, 2.16 kg load): 3.0 g/10 min, density 0.90 g/cm ³
・ Resin F2: Propylene homopolymer (manufactured by Japan Polypropylene Corporation: "FY6", MFR (230 ° C., 2.16 kg load): 2.4 g / 10 min, melting point 160 ° C.

・ Resin G1: propylene-ethylene block copolymer (manufactured by Japan Polypropylene Corporation: "BC6DRF", MFR (230 ° C., 2.16 kg load): 2.5 g / 10 min, melting point 165 ° C.

[Prototype example 1]
The film of Prototype Example 1 is composed of two layers, a substrate layer and a heat-seal layer having a layer thickness ratio of 7:1. 5% by weight, and the heat seal layer was composed of 70% by weight of resin A1 and 30% by weight of resin D2.

[Prototype example 2]
The film of Prototype Example 2 is composed of three layers, namely, a surface layer, a substrate layer, and a heat-seal layer having a layer thickness ratio of 1:6:1. was composed of 99.5% by weight of resin F1 and 0.5% by weight of antifog agent, and the heat seal layer was composed of 100% by weight of resin A1.

[Prototype Example 3]
The film of Prototype Example 3 was the same as the film of Prototype Example 2 except that the heat seal layer contained 85% by weight of Resin A1 and 15% by weight of Resin D2.

[Prototype example 4]
The film of Prototype Example 4 was the same as the film of Prototype Example 2 except that the heat seal layer contained 70% by weight of Resin A1 and 30% by weight of Resin D2.

[Prototype Example 5]
The film of Prototype Example 5 was the same as the film of Prototype Example 2 except that the heat seal layer contained 50% by weight of Resin A1 and 50% by weight of Resin D2.

[Prototype Example 6]
The film of Prototype Example 6 was the same as the film of Prototype Example 2 except that the heat seal layer contained 30% by weight of Resin A1 and 70% by weight of Resin D2.

[Prototype Example 7]
The film of Prototype Example 7 was the same as the film of Prototype Example 2 except that the heat seal layer contained 15% by weight of Resin A1 and 85% by weight of Resin D2.

[Prototype Example 8]
The film of Prototype Example 8 was the same as the film of Prototype Example 2 except that the heat seal layer contained 100% by weight of resin D2.

[Prototype Example 9]
The film of Prototype Example 9 was the same as the film of Prototype Example 4 except that the longitudinal uniaxial stretch ratio was 3 times.

[Prototype Example 10]
The film of Prototype Example 10 was the same as the film of Prototype Example 4 except that the longitudinal uniaxial stretch ratio was 6 times.

[Prototype Example 11]
The film of Prototype Example 11 was the same as the film of Prototype Example 4 except that the heat seal layer contained 70% by weight of Resin A2 and 30% by weight of Resin D2.

[Prototype Example 12]
The film of Prototype Example 12 was the same as the film of Prototype Example 4 except that the heat seal layer contained 60% by weight of resin A3 and 40% by weight of resin D2.

[Prototype Example 13]
The film of Prototype Example 13 was the same as the film of Prototype Example 4 except that the heat seal layer contained 70% by weight of Resin A4 and 30% by weight of Resin D2.

[Prototype Example 14]
The film of Prototype Example 14 was the same as the film of Prototype Example 4 except that the heat seal layer contained 85% by weight of Resin A5 and 15% by weight of Resin D2.

[Prototype Example 15]
The film of Prototype Example 15 was the same as the film of Prototype Example 4 except that the heat seal layer contained 70% by weight of Resin A6 and 30% by weight of Resin D2.

[Prototype Example 16]
The film of Prototype Example 16 was the same as the film of Prototype Example 4 except that the heat seal layer contained 70% by weight of Resin A7 and 30% by weight of Resin D2.

[Prototype Example 17]
The film of Prototype Example 17 was the same as the film of Prototype Example 4 except that the heat seal layer contained 70% by weight of resin A8 and 30% by weight of resin D2.

[Prototype Example 18]
The film of Prototype Example 18 was the same as the film of Prototype Example 4 except that the heat seal layer contained 70% by weight of Resin A9 and 30% by weight of Resin D2.

[Prototype Example 19]
The film of Prototype Example 19 was the same as the film of Prototype Example 4 except that the heat seal layer contained 70% by weight of Resin A10 and 30% by weight of Resin D2.

[Prototype example 20]
The film of Prototype Example 20 was the same as the film of Prototype Example 16 except that the amount of discharge in the corona treatment was 5 W·min/m ² .

[Prototype Example 21]
The film of Prototype Example 21 was the same as the film of Prototype Example 16 except that the amount of discharge in the corona treatment was 40 W·min/m ² .

[Prototype Example 22]
The film of Prototype Example 22 was the same as the film of Prototype Example 4 except that the heat seal layer contained 70% by weight of resin B1 and 30% by weight of resin D2.

[Prototype Example 23]
The film of Prototype Example 23 was the same as the film of Prototype Example 4 except that the heat seal layer contained 70% by weight of resin C1 and 30% by weight of resin D2.

[Prototype Example 24]
The film of Prototype Example 24 was the same as the film of Prototype Example 4 except that 30% by weight of Resin D1 was used instead of Resin D2 in the heat seal layer.

[Prototype Example 25]
The film of Prototype Example 25 was the same as the film of Prototype Example 4 except that 30% by weight of resin E1 was used instead of resin D2 in the heat seal layer.

[Prototype Example 26]
The film of Prototype Example 26 was the same as the film of Prototype Example 4 except that 30% by weight of resin E2 was used instead of resin D2 in the heat seal layer.

[Prototype Example 27]
The film of Prototype Example 27 was the same as the film of Prototype Example 4 except that 30% by weight of resin E3 was used instead of resin D2 in the heat seal layer.

[Prototype Example 28]
The film of Prototype Example 28 was the same as the film of Prototype Example 4 except that 15% by weight of Resin D2 and 15% by weight of Resin E2 were used instead of Resin D2 in the heat seal layer.

[Prototype Example 29]
The film of Prototype Example 29 was the same as the film of Prototype Example 4 except that 30% by weight of Resin F2 was used instead of Resin D2 in the heat seal layer.

[Prototype Example 30]
The film of Prototype Example 30 was the same as the film of Prototype Example 4 except that 30% by weight of resin G1 was used instead of resin D2 in the heat seal layer.

Regarding the longitudinally uniaxially stretched films of Prototype Examples 1 to 30, the resin composition of each layer, sheet thickness, stretch ratio, film thickness, layer thickness ratio (layer ratio), and corona treatment discharge amount are shown in Tables 1 to 1. 5.

As a performance evaluation of the longitudinally uniaxially stretched films of Prototype Examples 1 to 30, the wet tension and the heat seal initiation temperature were measured to evaluate the antifogging property.

[Measurement of wet tension]
Wetting tension (mN/m) was measured using a wet tension test method based on JIS K 6768 (1999).

[Measurement of heat seal initiation temperature]
In the measurement of the heat seal initiation temperature (°C), a heat seal initiation temperature test conforming to JIS Z 1713 (2009) was used, and the heat seal initiation temperature after corona treatment of the longitudinally uniaxially stretched films of Prototype Examples 1 to 30 was measured. bottom. First, a test piece with a width of 50 mm and a length of 250 mm is cut from the film of each of Prototype Examples 1 to 30, and the heat seal layers of the two test pieces are overlapped with a heat seal tester (manufactured by Toyo Seiki Seisakusho Co., Ltd.; thermal gradient Using a tester), heat sealing was performed under the conditions of a heat sealing pressure of 0.34 MPa, a heat sealing time of 1.0 sec, and a temperature gradient (heating) of 5°C. After heat sealing, cut out a test piece with a width of 15 mm, open the test piece fused by heat sealing at 180 °, pinch the unsealed part in the chuck of a tensile tester (manufactured by Shimadzu Corporation; EZ-SX), The temperature at which the heat seal strength reached 3 N when the seal portion was peeled off at a tensile speed of 200 mm/min was determined as the heat seal initiation temperature. A sample with a measurement result of 155°C or less was evaluated as "good (◯)", and a sample with a temperature exceeding 155°C was evaluated as "failed (x)".

[Evaluation of antifogging property]
In the antifogging evaluation, first, 50 ml of room temperature distilled water was poured into a 100 ml beaker, and a test piece cut to 100 mm x 100 mm was placed on the beaker and stored in an atmosphere of 5°C for 60 minutes. After storage, the beaker was placed on the paper on which the characters were printed, and the degree of fogging inside the film covering the beaker was evaluated from how the characters were seen at that time. When evaluating the anti-fogging property, "excellent (◎)" indicates that there are no water droplets on the film and characters can be clearly recognized, and "good (○)" indicates that the characters can be recognized even though water droplets adhere to the film. ”, and the case where characters could not be recognized due to water droplets adhering to the film was evaluated as “improper (x)”.

Tables 6 to 10 show the measurement results of the longitudinally uniaxially stretched films of Prototype Examples 1 to 30. In Tables 6 to 10, in the comprehensive evaluation, when all the judgments of each measurement are good (〇) or higher, it is “good (〇)”, and when even one is not good (×), it is “impossible (×)”. and

[Results and discussion]
As shown in Tables 6 to 10, all of Prototype Examples 1 to 30 had a good wet tension of 32 mN/m or more. In addition, in the comprehensive evaluation, prototype examples 1 to 5, 9 to 13, 16 to 18, 20, 21, 26 to 28, 30 were "good (◯)", prototype examples 6 to 8, 14, 15, 19, 22 to 25 and 29 were "impossible (x)".

First, the three-layer longitudinally uniaxially stretched films of Prototype Examples 2 to 8 are examples in which the blending ratio of linear low-density polyethylene (resin A1) in the heat seal layer was changed from 100% by weight to 0% by weight. In Prototype Example 2 in which the blending ratio of Resin A1 was 100% by weight, both the heat seal initiation temperature and the antifogging properties were extremely good. On the other hand, in Prototype Examples 3 to 8 in which a propylene-ethylene random copolymer (Resin D2) was added to the heat seal layer, when the blending ratio of Resin A1 was 50% by weight or more (Prototype Examples 3, 4, and 5), properly suppresses the increase in the heat seal initiation temperature, and when the blending ratio of the resin A1 is less than 50% by weight (prototype examples 6, 7, and 8), sufficiently suppresses the increase in the heat seal initiation temperature. I couldn't do it.

The longitudinally uniaxially stretched films of Prototype Examples 9 and 10 are examples in which the draw ratio is changed with respect to Prototype Example 4, which is a non-defective product. The heat seal initiation temperature and the anti-fogging property were good both when the draw ratio was reduced (prototype example 9) and increased (prototype example 10) from that of prototype example 4.

The longitudinally uniaxially stretched films of Prototype Examples 11 to 19 are examples in which the resins A2 to A10 are used in place of the resin A1 in the heat-seal layer of the non-defective Prototype Example 4. In Prototype Example 14 using resin A5 and Prototype Example 15 using resin A6, sufficient antifogging properties were not obtained. Moreover, in Prototype Example 19 using resin A10, it was not possible to sufficiently suppress the increase in the heat sealing start temperature.

Comparing Prototype Examples 4, 11 to 13, 16 to 18 and Prototype Examples 14 and 15, in which both the heat seal initiation temperature and the antifogging property were good, showed that the resins A5 and A6 used in Prototype Examples 14 and 15 had a higher density than Resins A1 to A4 and Resins A7 to A9 used in Prototype Examples 4, 11 to 13, 16 to 18. Further, when comparing Prototype Examples 4, 11 to 13, 16 to 18 with Prototype Example 19, Resin A10 used in Prototype Example 19 ~Resin A4, Resin A7~MFR was higher than Resin A9.

The longitudinally uniaxially stretched films of Prototype Examples 20 and 21 are examples in which the amount of discharge in the corona treatment is changed with respect to Prototype Example 16, which is a non-defective product. The heat seal initiation temperature and the anti-fogging property were good both when the amount of discharge in the corona treatment was reduced (prototype example 20) and increased (prototype example 21) as compared with prototype example 16.

In the longitudinally uniaxially stretched films of Prototype Examples 22 and 23, resin B1 (low-density polyethylene) or resin C1 (high-density polyethylene) is used. In Prototype Example 22, the heat seal strength did not reach 3 N in the measurement of the heat seal initiation temperature, and the measurement was impossible. In Prototype Example 23, it was not possible to suppress an increase in the heat seal initiation temperature, and the antifogging property was also insufficient.

In the longitudinally uniaxially stretched film of Prototype Example 24, resin D1 (a propylene-ethylene random copolymer different from resin D2) was used instead of resin D2 (propylene-ethylene random copolymer) in the heat seal layer of good product Prototype Example 4. ) is used. In Prototype Example 24 using resin D1, it was not possible to sufficiently suppress an increase in the heat-sealing start temperature. Comparing Prototype Example 4 and Prototype Example 24, Resin D1 used in Prototype Example 24 was a propylene-ethylene random copolymer having a higher melting point than Resin D2 used in Prototype Example 4.

In the longitudinally uniaxially stretched films of Prototype Examples 25, 26, and 27, resin E1, resin E2, and resin E3 (propylene -ethylene-butene random copolymer). In Prototype Example 25 using resin E1, sufficient antifogging properties were not obtained, but in Prototype Examples 26 and 27, both the heat seal initiation temperature and antifogging properties were good. Comparing Prototype Examples 26 and 27 with Prototype Example 25, resin E1 used in Prototype Example 25 is a propylene-ethylene-butene random copolymer having a higher melting point than resins E2 and E3 used in Prototype Examples 26 and 27. was a coalescence.

The longitudinally uniaxially stretched film of Prototype Example 28 is an example in which resin D2 and resin E2 are used in place of resin D2 (propylene-ethylene random copolymer) in the heat-seal layer of Prototype Example 4, which is a non-defective product. Prototype Example 28 was excellent in both the heat seal initiation temperature and the antifogging properties.

In the longitudinally uniaxially stretched films of Prototype Examples 29 and 30, resin F2 (propylene homopolymer) and resin G1 ( propylene-ethylene block copolymer). In Prototype Example 29 using resin F2, it was not possible to prevent the heat-sealing start temperature from increasing, and the antifogging property was also insufficient. In Prototype Example 30 using resin G1, both the heat seal initiation temperature and the antifogging properties were good.

As can be understood from Prototype Examples 2 to 10, 22, and 23, the preferred blending ratio of the resin for the heat seal layer is at least 50% by weight of linear low-density polyethylene, including 100% by weight of linear low-density polyethylene. It is considered that it is more than that. Further, when the heat seal layer is not 100% by weight of linear low-density polyethylene, the other resin constituting the heat seal layer is propylene-ethylene having a melting point of less than 135° C., as understood from Prototype Examples 24 to 30. It is considered preferable to select from random copolymers or at least one of propylene-ethylene-butene random copolymers, or propylene-ethylene block copolymers.

Further, as understood from Prototype Examples 11 to 21, the preferred conditions for the linear low-density polyethylene used in the heat seal layer are that the melt flow rate (MFR) measured at 190° C. under a load of 2.16 kg is It is believed to be 1-10 g/10 min with a density of 0.860-0.935 g/cm ³ .

The longitudinally uniaxially stretched film of Prototype Example 1 has the same structure as that of Prototype Example 4 except that it consists of two layers, a substrate layer and a heat seal layer, and does not have a surface layer. In Prototype Example 1, the heat seal initiation temperature and antifogging performance are the same as in Prototype Example 4. Therefore, if the base layer and the heat seal layer have the same structure, a two-layer film and a three-layer film can be obtained. It is believed that the heat seal initiation temperature and anti-fogging performance of the film will be the same.

As described above, the longitudinally uniaxially stretched film of the present invention can appropriately suppress an increase in the heat-sealing start temperature even if the heat-sealing surface is subjected to corona treatment for anti-fogging properties. It is possible to prevent the film from melting and sticking to the heating roll even when the heat setting is performed by heating, thereby suppressing the occurrence of poor appearance due to peeling marks. In addition, the longitudinally uniaxially stretched film of the present invention can obtain good anti-fogging properties. Therefore, a polyolefin-based longitudinally uniaxially stretched film having practical heat-sealing properties can be obtained even if the heat-sealing surface is subjected to corona treatment to develop anti-fogging properties.

As described above, the polyolefin-based longitudinally uniaxially stretched film of the present invention appropriately suppresses an increase in the heat-sealing initiation temperature and has good antifogging properties. Therefore, it is highly practical and promising as a substitute for conventional polyolefin-based longitudinally uniaxially stretched films.

REFERENCE SIGNS LIST 10 polyolefin-based longitudinally uniaxially stretched film 20 base layer 30 heat seal layer 40 surface layer 50 film forming machine 51 preheating section 52 stretching section 53 heat setting section F, F1 film Fr film roll R, R1, R2 roll

Claims (4)

Consists of at least two layers in which a heat seal layer is laminated on one side of a base material layer mainly composed of polypropylene resin,
An antifogging agent is included in either the base material layer or the heat seal layer,
Stretched in the machine direction by stretching between rolls,
A longitudinally uniaxially stretched polyolefin film in which the heat seal layer is subjected to corona treatment and the surface of the heat seal layer has a wet tension of 32 mN/m or more,
The heat seal layer is made of linear low-density polyethylene having a melt flow rate of 1 to 10 g/10 min and a density of 0.860 to 0.935 g/cm ³ measured under a load of 2.16 kg at 190°C. A polyolefin-based longitudinally uniaxially stretched film characterized by: Consists of at least two layers in which a heat seal layer is laminated on one side of a base material layer mainly composed of polypropylene resin,
An antifogging agent is included in either the base material layer or the heat seal layer,
Stretched in the machine direction by stretching between rolls,
A longitudinally uniaxially stretched polyolefin film in which the heat seal layer is subjected to corona treatment and the surface of the heat seal layer has a wet tension of 32 mN/m or more,
The heat seal layer contains at least 50% by weight of linear low-density polyethylene (A) and a polypropylene-based resin (B),
The linear low-density polyethylene (A) has a melt flow rate of 1 to 10 g/10 min and a density of 0.860 to 0.935 g/cm ³ measured under a load of 2.16 kg at 190°C.
The polypropylene resin (B) is selected from at least one propylene-ethylene random copolymer or propylene-ethylene-butene random copolymer having a melting point of less than 135°C, or a propylene-ethylene block copolymer. A polyolefin longitudinally uniaxially stretched film characterized by: 3. The longitudinally uniaxially stretched polyolefin film according to claim 1, wherein the heat seal initiation temperature between the heat seal layers is 155[deg.] C. or less. 4. The polyolefin longitudinally uniaxially stretched film according to any one of claims 1 to 3, wherein a surface layer is laminated on the other side of the base layer.

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