JP6344012B2 - Paper base sheet and half clear pack using the same - Google Patents

Description

  The present invention provides a paper base sheet excellent in adhesion between paper and resin and oil resistance, and using this sheet, a half clear pack excellent in heat sealability and curl resistance with a transparent film The purpose is to provide.

In recent years, as a packaging material used for over-the-counter sales of food side dishes such as croquettes and fried chicken, a transparent film is layered on a paper base sheet instead of the traditional polystyrene food pack. Half-clear packs that are sealed by heat-sealing the sides and opened in a bag shape with one side open are beginning to be used.
The half clear pack has the advantage that the front side is transparent film, so that the contents can be clearly seen, it is lightweight, and the back side is made of paper, so it can be printed, and also helps to reduce dust.

Conventionally, as a material of such a half clear pack, a heat-sealable OPP is used as a transparent film on the front side, and a paper itself or a resin that does not allow oil to pass through (oil resistance) as a paper base sheet on the back side. A paper base sheet having a layer laminated to paper is used.
As heat-sealable OPP used as a transparent film, a heat-sealable layer containing a low-melting resin such as random polypropylene or ethylene / α-olefin copolymer is laminated on a base layer made of homopolypropylene, and biaxial A stretched one is known.

However, in the half clear pack, since three sides are heat-sealed and one side is opened, a curling phenomenon caused by shrinkage of the heat-sealed portion is caused, and the half-clear pack is deformed and becomes bulky when a bag is stocked. There was a problem.
Further, since the compatibility between the oil-resistant paper base sheet and the heat-sealable OPP, which are generally used in the past, is poor, the heat-sealing performance is weak and there is a problem that it is easily peeled off during use.

  As a paper base sheet obtained by laminating and laminating a resin on a paper base material, a polypropylene resin having high pinhole resistance and low oil permeability is used in order to impart oil resistance to paper. In relation to this, a multilayer film composed of a polyethylene-based polymer and a propylene-based polymer excellent in adhesiveness with a paper base material has been provided (Patent Documents 1 and 2). There is room for improvement.

  Therefore, as a result of various studies on the composition of the laminate resin used in the paper base sheet constituting the half clear pack, the present inventors have adopted a specific resin composition, and the paper base sheet and the transparent film A half-clear pack paper base sheet that guarantees heat sealability, has good adhesion between the paper base and resin, does not impair the oil resistance of the paper base sheet, and does not cause curl even when three-way heat-sealed. The present invention has been found and obtained.

JP 2010-5851 JP2011-20372A

  The object of the present invention is to solve the above-mentioned conventional problems, ensure the adhesion between the paper substrate and the resin, provide a paper substrate sheet having oil resistance, and heat sealability with a transparent film, The object is to provide a half clear pack that does not cause a curl phenomenon.

  As a result of intensive studies to achieve the above object, the present inventors have adopted a specific resin composition, which has good adhesiveness to the resin that is laminated on the paper substrate, and improves the oil resistance of the paper substrate sheet. The present inventors have found that a half clear pack paper base sheet having good heat sealability between the paper base sheet and the transparent film and not causing a curl phenomenon can be obtained even during three-way heat sealing without damaging.

That is, according to the first invention, the paper base material sheet 2 is formed by laminating at least the adhesive resin layer 2c between the paper base material layer 2a and the surface resin layer 2b, and the adhesive resin layer has a melting point of 100 ° C. The polyethylene resin (C) is 55 to 95% by weight, and the composition includes a polyethylene resin (D) of 5 to 45% by weight having a density of 0.920 g / cm ³ or less and a melting point of 100 ° C. or less. There is provided a paper base sheet in which the surface resin layer is composed of a composition containing at least two kinds of 55 to 95% by weight of polypropylene resin (A) and 5 to 45% by weight of polyolefin resin (B).

  According to a second invention, there is provided a paper base sheet according to the first invention, wherein the polyolefin resin (B) constituting the surface resin layer is a polyethylene resin.

  Further, according to a third invention, there is provided a paper base sheet characterized in that, in the first or second invention, the polyethylene resin (D) is produced from a metallocene catalyst.

According to the fourth invention, in the first to third any one of the, melting points (T _D) of the polyethylene resin (D) constituting the the adhesive resin layer melting point (T _B) of the polyolefin resin (B) A paper base sheet characterized by satisfying the following formula (1) is provided.
25 ° C. ≦ T _B −T _D ≦ 65 ° C. Formula (1)

  According to a fifth invention, in any one of the first to third inventions, a transparent biaxially stretched polypropylene film 1 provided with a heat-sealable layer 1b on the outermost surface of a polypropylene-based substrate 1a is used as a surface resin. Provided is a paper base sheet characterized in that it is used in a half-clear pack formed by stacking layers 2b and heat-sealable layer 1b so that they face each other and heat-sealing the three sides to form a bag Is done.

  Furthermore, according to the sixth invention, according to any one of the first to fifth inventions, the transparent biaxially stretched polypropylene film 1 provided with the heat-sealable layer 1b on the outermost surface of the polypropylene-based substrate 1a, There is provided a half clear pack characterized in that it includes a paper base sheet that is formed in a bag shape by overlapping the resin layer 2b and the heat-sealable layer 1b so as to face each other and heat-sealing the three sides. The

  According to the present invention, it is possible to provide a paper base sheet having oil resistance while ensuring adhesion between the paper base and the resin. By using this paper base sheet, it is possible to provide a half clear pack that has good heat sealability with a transparent film and does not cause a curl phenomenon.

Sectional drawing which shows the layer structure of the half clear pack which concerns on this invention The figure which shows the half clear pack concerning this invention

  Hereinafter, the present invention will be described in detail.

1. FIG. 1 is a cross-sectional view of a paper base sheet and a half clear pack according to the present invention. The paper base sheet of the present invention comprises a paper base layer 2a, an adhesive layer resin 2b made of a specific resin composition, and a surface layer resin 2c.
The transparent film 1 is a transparent biaxially stretched polypropylene film that is biaxially stretched by providing a heat-weldable heat-sealable layer 1b on the surface of the polypropylene-based substrate 1a.
FIG. 2 shows a half clear pack according to the present invention. The half clear pack of the present invention is formed by superposing the paper base sheet 2 and the transparent film 1 such that the back surface is the paper base sheet 2 and the front surface is the transparent film 1, and the three end portions (three sides) ) Is heat sealed (part 3).

2. Paper base sheet (1) Surface resin layer 2b
The resin composition constituting the adhesive resin layer 2b contains 55 to 95% by weight of a polypropylene resin (A) and 5 to 45% by weight of a polyolefin resin (B) different from the polypropylene resin (A). To do.

(1-1) Polypropylene resin (A)
Examples of the polypropylene resin (A) include those containing 20 to 100% by weight of propylene units, and need to contain 0 to 20% by weight of ethylene / units and / or butene units.
Here, propylene units and ethylene and / or butene units are values measured by Fourier transform infrared analysis.
In the polypropylene resin used in the present invention, comonomer components other than ethylene and butene may be copolymerized with propylene. Examples of the comonomer include an α-olefin having 5 to 20 carbon atoms. Examples of the α-olefin having 5 to 20 carbon atoms include 1-hexene and 1-octene. One or more α-olefins copolymerized with propylene may be used. The comonomer copolymerized with propylene is preferably ethylene or 1-butene, more preferably ethylene.
That is, the polypropylene resin is a propylene homopolymer, a random copolymer of propylene and ethylene and / or butene, and the like, specifically, a propylene homopolymer, a propylene / ethylene random copolymer, a propylene / butene random. And copolymers, propylene / ethylene / butene ternary random copolymers, and the like. Of these, propylene / ethylene random copolymers are preferred.
Use of a polypropylene resin is preferable for improving the oil resistance of the half clear pack. As such a polypropylene resin, one having a melting point in the range of 120 ° C. to 180 ° C. is usually used. It is difficult to produce a polypropylene resin having a melting point exceeding 180 ° C., and if it is less than 120 ° C., the pinhole resistance is inferior, and the oil resistance is impaired.
The MFR of the polypropylene resin is 1 to 100 g / 10 minutes, preferably 5 to 75 g / 10 minutes, and more preferably 10 to 50 g / 10 minutes. If the MFR exceeds 100 g / 10 min, the heat resistance and pinhole property are inferior, so that the oil resistance is impaired. When the MFR is less than 1 g / 10 min, the extrusion load increases and the processability is inferior.

(1-2) Polyolefin resin (B)
The polyolefin resin (B) component is not particularly limited as long as it is a resin different from the polypropylene resin (A), but is preferably a polyethylene resin.
In particular, in order to prevent the occurrence of reduction and curling of delamination of the resin layer, the melting point (T _D) of the polyethylene resin (D) constituting the the adhesive resin layer melting point (T _B) of the polyolefin resin (B), the following It is preferable to satisfy the formula (1).
25 ° C. ≦ T _B −T _D ≦ 65 ° C. Formula (1)
The melting point in the present invention is a peak top temperature (Tm) on the highest temperature side in a DSC melting curve, which is measured using a differential scanning calorimeter in accordance with JIS-K7121.

  Examples of the polyethylene resin include branched low-density polyethylene (LDPE) obtained by a high-pressure method, linear low-density polyethylene (L-LDPE), metallocene polyethylene (m-LLDPE) obtained using a metallocene catalyst, and High density polyethylene (HDPE) and the like are known. Examples of such polyethylene resins include Harmolex series made by Japan polyethylene and Kernel series made by Japan polyethylene.

The melt flow rate (MFR), which is an index of the molecular weight of the polyolefin resin, is not particularly limited, but it is necessary that kneading, laminating and the like be performed stably.
The MFR of the polyethylene resin used for the component (B) is 1 to 50 g / 10 minutes, preferably 2 to 35 g / 10 minutes, and more preferably 5 to 25 g / 10 minutes. If the MFR exceeds 50 g / 10 min, the heat resistance and pinhole property are poor, and the oil resistance is impaired. When the MFR is less than 1 g / 10 min, the extrusion load increases and the processability is inferior.
Here, MFR is a value measured according to “Testing method for melt flow rate (MFR) and melt volume flow rate (MVR) of plastic-thermoplastic plastic” in JIS K7210-1999.

  In addition, it is also possible to use not only two types of component (A) and component (B) but also three or more types of resin compositions for the resin layer 2b.

(2) Adhesive resin layer 2c
The paper base sheet 2 of the present invention needs to have a configuration of three or more layers in which at least the adhesive resin layer 2c is added between the two layers of the paper base layer 2a and the surface resin layer 2b.
The resin composition constituting the adhesive resin layer 2c is a polyethylene resin (C) of 55 to 95% by weight having a melting point of 100 ° C. or higher, a polyethylene resin having a density of 0.920 g / cm ³ or lower and a melting point of 100 ° C. or lower ( D) 5 to 45% by weight is contained.

(2-1) Polyethylene resin (C)
The polyethylene resin (C) component is a polyethylene resin having a melting point of 100 ° C. or higher. As the polyethylene resin having a melting point corresponding to the component (C) of 100 ° C. or higher, a resin having a melting point of 100 ° C. or higher is selected from an ethylene homopolymer or a copolymer of ethylene and α-olefin. it can. When the melting point of polyethylene is less than 100 ° C., the heat resistance and pinhole resistance are inferior, so that the oil resistance is impaired.
Examples of ethylene homopolymers or copolymers of ethylene and α-olefin include branched low density polyethylene (LDPE) and linear low density polyethylene (L-LDPE) obtained by a high pressure method, among them metallocene catalysts. The obtained metallocene-based polyethylene (m-LLDPE), high-density polyethylene (HDPE), and the like are known, and as the component (C), linear low-density polyethylene (L-LDPE) is preferable. In particular, linear polyethylene low density polyethylene obtained from a metallocene catalyst is preferable from the viewpoint of high adhesive strength with a paper substrate and easy processability. An example of such a polyethylene resin is the Harmolex series made by Nippon Polyethylene.

The melt flow rate (MFR), which is an index of the molecular weight of the polyolefin resin, is not particularly limited, but it is necessary that kneading, laminating and the like be performed stably.
The MFR of the polyethylene resin used for the component (C) is 1 to 50 g / 10 minutes, preferably 2 to 35 g / 10 minutes, and more preferably 5 to 25 g / 10 minutes. If the MFR exceeds 50 g / 10 min, the heat resistance and pinhole property are poor, and the oil resistance is impaired. When the MFR is less than 1 g / 10 min, the extrusion load increases and the processability is inferior.
Here, MFR is a value measured according to “Testing method for melt flow rate (MFR) and melt volume flow rate (MVR) of plastic-thermoplastic plastic” in JIS K7210-1999.

(2-2) Polyethylene resin (D)
The polyethylene resin having a density of 0.920 g / cm ³ or less and a melting point of 100 ° C. or less used as the component (D) of the present invention is a melting point of a region called a so-called ultra-low density polyethylene or polyethylene elastomer among polyethylene resins. Is a polyethylene resin belonging to a very low special grade, and is preferably an ethylene / α-olefin copolymer. Here, the density is measured according to JIS K-7112.
A polyethylene resin obtained from a metallocene catalyst is preferred from the viewpoint that it has a low molecular weight and does not contain a low crystalline component, has a small solvent extraction component, and has a low odor and is a clean polyethylene material.
For example, a resin having a density of 0.920 g / cm ³ or less and a melting point of 100 ° C. or less can be selected from Kernel (registered trademark) series manufactured by Japan Polyethylene Corporation.
The density is preferably 0.860 g / cm ³ or more and 0.920 g / cm ³ or less, and more preferably 0.880 g / cm ³ or more and 0.910 g / cm ³ or less. When the density exceeds 0.920, the adhesion of the adhesive resin layer 2c is deteriorated. On the other hand, it is extremely difficult to produce a polyethylene resin having a density of less than 0.860.

  The melt flow rate (MFR) of the polyethylene resin used as the component (D) is 2 to 100 g / 10 minutes, and preferably 5 to 50 g / 10 minutes. When the MFR exceeds 100 g / 10 min, it is difficult to handle the resin due to stickiness, and when the MFR is less than 2 g / 10 min, the average molecular weight is large, so stable operation is performed during kneading or laminating. I can't.

(3) Paper base layer 2a
Examples of the paper substrate of the present invention include fine paper, thin paper, glassine paper and the like, and those having a weight of 5 to 50 g / m ² , preferably 10 to 30 g / m ² are used. If the weight is less than the lower limit, the strength decreases, and if the weight exceeds the upper limit, it is not suitable for a packaging material. The paper base layer is preferably subjected to surface treatment such as corona discharge treatment, ozone treatment, and low temperature plasma treatment.

(4) Laminating method As a method for producing a paper base sheet by laminating the resin layers 2c and 2b on the paper base layer 2a, a single laminating method, a tandem laminating method, a sandwich laminating method, a co-pressing laminating method, a dry laminating method. A known method such as a method can be used. Although the thickness of a paper base material layer is influenced also by the use of a packaging material, it is 5-100 micrometers normally, Preferably it is 10-50 micrometers. The thickness of the surface resin layer 2b is usually 5 to 30 μm, preferably 10 to 20 μm. The thickness of the adhesive resin layer is usually 5 to 30 μm, preferably 10 to 20 μm.

3. Half clear pack (1) Transparent film 1
As a transparent film used in the half clear pack of the present invention, a heat-sealable layer containing a low-melting resin such as random polypropylene or ethylene / α-olefin copolymer is laminated on a base layer made of homopolypropylene. A commercially available heat-sealable OPP biaxially stretched can be used.

(2) Heat sealing method About the method of heat sealing with the transparent film 1 and the following base material sheet 2, it manufactures according to a well-known method. The paper base sheet and the transparent film may have exactly the same shape, but in order to simplify the taking in and out of the food to be put in, the paper base sheet is more transparent than the transparent film at the end portion that is not heat-sealed. A shape that is several centimeters long and forms a chamfer is preferred. The main use of this half clear pack is for food packaging such as croquettes and fried foods, but it can also be used for other purposes.

  In the present invention, a base resin suitable as an adhesive resin layer and a surface layer resin is conceived, and an appropriate amount of low-melting polyethylene is blended, so that an adhesive resin layer 2c and a surface resin layer are formed between the paper substrate 2a and the adhesive resin layer 2c. It was possible to maintain the adhesive strength between the respective layers between the surface resin layer 2b and the transparent film 1 between 2b. Furthermore, curling resistance is also achieved by enabling low-temperature sealing between the paper base sheet 2 and the transparent film 1.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not construed as being limited to these examples.
In Examples and Comparative Examples, various physical properties of the constituent components were measured and evaluated according to the following evaluation methods, and the following resins were used.

1. Evaluation method (1) Melt flow rate (MFR):
The MFR of the polyethylene resin was measured at 190 ° C. and a load of 2.16 kg according to JIS K6922-2 (2005). In addition, about polypropylene resin, measurement temperature was performed at 230 degreeC. The unit is g / 10 minutes.
(2) Density:
It measured according to JIS K-7112.
(3) Melting point:
Measurement was performed using a differential scanning calorimeter in accordance with JIS K-7121, and the peak top temperature (Tm) on the highest temperature side in the DSC melting curve was taken as the melting point.
(4) Adhesive strength:
The obtained paper base sheet was cut into a 15 mm wide test piece, peeled off from the interface between the paper base and the resin layer on the paper base, and the sample was rotated at an angle of 90 degrees with a tensile tester manufactured by Toyo Seiki Co., Ltd. Was pulled at a tensile speed of 300 mm / min, and the tensile strength at that time was measured.

(5) Heat sealability:
The test pieces having a width of 15 mm are joined together, and the paper base sheet and the transparent film heat-sealable OPP) are placed so that the surface resin layer 2b of the paper base sheet and the heat-sealable layer 1b of the transparent film face each other. Toyo Seiki Co., Ltd. The upper seal bar of the upper sealer of the hot plate heat sealer manufactured by the overlay tester industry is 110 ° C., the lower seal bar is 30 ° C., heat sealed with a seal pressure of 2 kg / cm ² and a seal time of 1 second. The tensile strength of the heat seal part was measured with a tensile tester at a tensile speed of 300 mm / min.

(6) Curl property:
A paper base sheet and a transparent film (heat sealable OPP) are cut into a size of 10 cm in length and 15 cm in width and overlapped so that the surface resin layer 2b of the paper base sheet and the heat sealable layer 1b of the transparent film face each other. At the same time, heat-seal 10 samples at a sealing pressure of 2 kg / cm ² and a sealing time of 1 sec. To do.
Ten prepared samples were overlapped, and the height from the floor surface to the uppermost sample was measured, and the degree of curling was evaluated based on the height.
○: 5 mm or less from the floor surface Δ: 5 to 10 mm or less from the floor surface ×: 10 mm or more from the floor surface

(7) Oil resistance:
A paper base sheet and a transparent film (heat sealable OPP) are cut into a size of 10 cm in length and 15 cm in width and overlapped so that the surface resin layer 2b of the paper base sheet and the heat sealable layer 1b of the transparent film face each other. The three sides of the transparent film were heat-sealed with a tester industry hot plate type upper heat sealer width of 5 mm at 130 ° C and lower seal bar at 30 ° C, with a seal pressure of 2 kg / cm ² and a seal time of 1 second. To do.
30 edible oils were put into 9 prepared samples, one side was heat-sealed under the above conditions, put into a gear oven 50 ° C. manufactured by Suga Test Instruments Co., Ltd., and 3 pieces were taken out after 1 hour and 5 hours, The degree of oil penetration was observed and evaluated with the paper sheet surface facing up.
○: Oil leakage is not confirmed after 5 hours. Δ: Oil leakage is confirmed after 5 hours. ×: Oil leakage is confirmed after 1 hour.

2. Materials Used Materials (1) Material of the paper base sheet Paper base: 35 g of pure white paper resin a: Polypropylene resin “Product name PH943B manufactured by Sun Allomer Co., Ltd.”
Resin b: Polyethylene resin “trade name NH745N manufactured by Nippon Polyethylene Co., Ltd.”
Resin c: Polyethylene resin “Kernel KF360T manufactured by Japan Polyethylene Corporation”
Resin d: Polyethylene resin “Nippon Polyethylene Kernel KS340T”
Resin e: Polyethylene resin “Novatec LC607K manufactured by Nippon Polychem Co., Ltd.”
The physical properties of the resins a to e are summarized in Table 1.

[Example 1]
(1) Manufacture of paper base sheet 2 Resin at a molding temperature of 315 ° C. with a die width of 500 mm and a processing speed of 100 m / min using a 90 mmφ co-pressed single laminate molding machine manufactured by Modern Machinery Co., Ltd. 80 parts by weight of b and 20 parts by weight of resin d are mixed so that the resin composition is 7 μm, the molding temperature of the surface resin layer 2b is 285 ° C., 80 parts by weight of resin a and 20 parts by weight of resin b are mixed to 8 μm. A paper sheet was prepared by coextrusion lamination on a paper substrate.
(2) Heat sealable OPP
Biaxially stretched heat-sealable OPP (biaxially stretched polypropylene film) “Transparent film 1”, trade name FOH-L, film thickness 20 μm, was used as transparent film 1.
(3) Manufacture of a half clear pack A heat-sealable OPP adhesive layer is stacked on a paper base sheet 2 cut to 15 cm × 10 cm, and a heat plate heat sealer manufactured by Tester Sangyo Co., Ltd. with a 5 mm wide seal bar. The upper seal bar was heat-sealed at 110 ° C., the lower seal bar was 30 ° C., the seal pressure was 2 kg / cm ² , and the seal time was 1 second to prepare a half clear pack.
Table 2 shows the evaluation results of the obtained half clear pack and paper base sheet.

[Example 2]
A laminate was obtained in the same manner as in Example 1 except that 70 parts by weight of the resin b and 30 parts by weight of the resin d were mixed in the adhesive resin layer 2c in Example 1. The evaluation results of the obtained extrusion laminate are shown in Table 2.

[Example 3]
A laminate was obtained in the same manner as in Example 1 except that 60 parts by weight of resin b and 40 parts by weight of resin d were mixed as the adhesive resin layer 2c in Example 1. The evaluation results of the obtained extrusion laminate are shown in Table 2.

[Example 4]
A laminate was obtained in the same manner as in Example 1 except that 80 parts by weight of the resin e and 20 parts by weight of the resin d were mixed to constitute the adhesive resin layer 2c in Example 1. The evaluation results of the obtained extrusion laminate are shown in Table 2.

[Comparative Example 1]
A laminate was obtained in the same manner as in Example 1 except that 10 parts by weight of resin a and 90 parts by weight of resin b were mixed to constitute the surface resin layer 2b in Example 1. The evaluation results of the obtained extrusion laminate are shown in Table 2.

[Comparative Example 2]
A laminate was obtained in the same manner as in Comparative Example 1 except that the resin b was 100 parts by weight as constituting the adhesive resin layer 2c in Comparative Example 1. The evaluation results of the obtained extrusion laminate are shown in Table 2.

[Comparative Example 3]
A laminate was obtained in the same manner as in Comparative Example 1 except that 100 parts by weight of the resin e was used as the adhesive resin layer 2c in Comparative Example 1. The evaluation results of the obtained extrusion laminate are shown in Table 2.

[Comparative Example 4]
A laminated body was obtained in the same manner as in Example 1 except that the surface resin layer 2b and the adhesive resin layer 2c in Example 1 were constituted by 100 parts by weight of the resin a. The evaluation results of the obtained extrusion laminate are shown in Table 2.
[Comparative Example 5]
In Example 1, the surface resin layer 2b is composed of 80 parts by weight of resin a and 20 parts by weight of resin c, and the adhesive resin layer 2c is composed of 90 parts by weight of resin a and resin. A laminate was obtained in the same manner as in Example 1 except that 10 parts by weight of d was mixed. The evaluation results of the obtained extrusion laminate are shown in Table 2.

As is clear from Examples 1 to 4, the paper base sheet comprising the paper base layer, the adhesive resin layer, and the surface resin layer of the present invention has good adhesion between the paper base and the adhesive resin layer. Moreover, it turns out that the clear pack obtained from this invention is excellent in the heat-sealing property of a paper base material sheet and a transparent film, and is excellent in curl resistance and oil resistance.
On the other hand, in Comparative Example 1, since the polypropylene content constituting the surface resin layer was remarkably low, the curl increased due to the difference in thermal shrinkage after heat sealing with the OPP film.
In Comparative Examples 2 and 3, by not using a polyethylene resin having a density of 0.920 g / cm ³ or less and a melting point of 100 ° C. or less in the adhesive resin layer, the adhesive strength with the paper base material layer is impaired, As in Example 1, it can be seen that the curl of the clear pack is significantly impaired.
In Comparative Example 4, the clear pack curl is caused by the fact that the adhesive layer resin and the surface layer resin are polypropylene resins, the density of the adhesive resin layer is 0.920 g / cm ³ or less, and the melting point is 100 ° C. or less. Since polyethylene resin is not used, it turns out that the adhesive strength with a paper base material layer is impaired, and the sealing strength with an OPP film is also impaired.
In Comparative Example 5, polypropylene is used for the surface layer resin layer and the oil resistance is good, but since the polypropylene is used for the adhesive layer resin, the adhesive strength with the paper substrate is impaired.

Claims (5)

A paper base sheet 2 in which at least an adhesive resin layer 2c is laminated between the paper base layer 2a and the surface resin layer 2b, wherein the adhesive resin layer has a melting point of polyethylene resin (C) 55- 95% by weight and a composition containing 5 to 45% by weight of a polyethylene resin (D) having a density of 0.920 g / cm ³ or less and a melting point of 100 ° C. or less,
The surface resin layer is composed of a composition containing at least two kinds of 55 to 95% by weight of polypropylene resin (A) and 5 to 45% by weight of polyolefin resin (B) ,
Melting points (T _D) of the melting point of the polyolefin resin (B) (T _B) and the polyethylene resin constituting the adhesive resin layer (D), wherein a to Rukamimoto that satisfies the following formula (1) Material sheet.
25 ° C. ≦ T _B −T _D ≦ 65 ° C. Formula (1)   The paper base sheet according to claim 1, wherein the polyolefin resin (B) constituting the surface resin layer is a polyethylene resin.   The paper base sheet according to claim 1 or 2, wherein the polyethylene resin (D) is produced from a metallocene catalyst. A transparent biaxially stretched polypropylene film 1 provided with a heat-sealable layer 1b on the outermost surface of a polypropylene-based substrate 1a is overlaid so that the surface resin layer 2b and the heat-sealable layer 1b face each other. The paper base sheet according to any one of claims 1 to 3 , wherein the paper base sheet is used in a half-clear pack formed into a bag shape by heat sealing. A transparent biaxially stretched polypropylene film 1 provided with a heat-sealable layer 1b on the outermost surface of a polypropylene-based substrate 1a is overlaid so that the surface resin layer 2b and the heat-sealable layer 1b face each other. A half-clear pack comprising the paper base sheet according to any one of claims 1 to 4 , which is heat-sealed to form a bag.

Images