JP2005041527A - Paper bag - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a paper bag, which has tensile strength and tear strength that are superior enough to allow the bag to hold when packed with articles, and is also excellent in waterproofness and mositureproofness. <P>SOLUTION: At least one surface of a craft paper K is laminated with a synthetic resin film P to form a sheet S, which is made into the paper bag 40 with the synthetic resin film P forming the inner surface of the bag 40 through gluing work. The synthetic resin film P is composed of a double synthetic resin layer consisting of a synthetic resin having waterproofness/mositureproofness and a synthetic resin having tensile strength, which are subjected to a coextrusion lamination process. The synthetic resin film P is processed by corona discharge, then is laminated, and is further processed by corona discharge. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a paper bag made of a sheet material manufactured by laminating, and particularly to a paper bag having waterproof and moistureproof properties and tear strength suitable as a packaging material.

  Conventionally, there are bags made of resin such as vinyl chloride and polyethylene, and paper bags. In general, a resin bag has an excellent effect on waterproofness and water resistance, but there is a problem that it is easy to break if a bag is filled with a hard object or even a relatively soft object. .

  In addition, simple paper bags can be made durable and hard to tear, but there are problems with waterproof and moisture resistance, products that are difficult to get wet with water, and products that deteriorate when exposed to oil, chemicals, etc. It is unsuitable as a bag for packing.

For this purpose, a bag body is formed by a composite of a resin film laminated on paper (also referred to as lamination), and a square-bottom bag that has tensile strength and tear strength and is suitable for packaging products is disclosed. Yes. (For example, see Patent Document 1)
Furthermore, in order to make an envelope and a storage device excellent in tear strength and burst strength, a laminated sheet having excellent tear strength and burst strength obtained by cold laminating a reinforced film made of a synthetic plastic material on paper, and the sheet The manufacturing system has already been released. (For example, see Patent Document 2)
Japanese Utility Model Publication No. 57-101749 (page 1-13, FIG. 6) JP-A-6-305085 (page 1-5, FIG. 2)

  If a paper bag is manufactured from a sheet material obtained by laminating a resin film on paper, a paper bag having better waterproof and moisture resistance and tear strength than a simple paper bag can be obtained. However, when storing a large amount of products in a paper bag, the hole was pierced or torn during carrying, and the strength was still insufficient.

  An object of the present invention is to provide a paper bag that is excellent in tensile strength and tear strength to the extent that a product can be stored in a bag in order to solve the above-described problems, and further excellent in waterproof and moisture-proof properties.

  In order to achieve the above object, the invention according to claim 1 is a paper bag comprising a sheet material obtained by laminating a synthetic resin film on at least one surface of a kraft paper, the synthetic resin film being an inner surface side, The resin film is characterized by comprising two synthetic resin layers obtained by co-extrusion and lamination of a synthetic resin having waterproof and moistureproof properties and a synthetic resin having tensile strength.

  According to the invention according to claim 1 having the above-described configuration, since two synthetic resin layers are further laminated on the kraft paper having excellent strength, the waterproof and moistureproof property is improved, and when the bag is formed, A paper bag having a further enhanced tensile strength and tear strength can be obtained.

  The invention according to claim 2 is characterized in that the synthetic resin film is subjected to a corona discharge treatment and then laminated, and the laminated sheet material is further subjected to a corona discharge treatment.

  According to the invention according to claim 2 having the above-described configuration, the adhesiveness between the kraft paper and the synthetic resin layer film at the time of laminating is improved, and the adhesiveness at the time of forming the bag body is also improved. A paper bag that does not easily peel off can be created.

  The invention according to claim 3 is characterized in that the kraft paper is subjected to a corona discharge treatment and then laminated.

  According to the invention which concerns on Claim 3 which has said structure, when adhere | attaching a kraft paper and a synthetic resin film by laminating so that the surfaces which carried out the corona discharge process may adhere | attach, further adhesive strength is provided. Can be improved.

  The invention according to claim 4 is characterized in that the two synthetic resin layers are polyethylene having a thickness of about 15 μm and stretched polypropylene having a thickness of 20 μm or more, and the total thickness of the synthetic resin film is 35 μm or more.

  According to the invention according to claim 4 having the above-described configuration, since two synthetic resin layers of polyethylene having waterproof and moisture-proof properties and stretched polypropylene having tensile strength are laminated on kraft paper, the waterproof and moisture-proof properties are excellent. In addition, a bag body excellent in tear strength can be formed.

  As described above, according to the present invention, the waterproof and moisture-proof property is improved because the synthetic resin layer having the waterproof and moisture-proof property and the synthetic resin layer having the tensile strength are laminated simultaneously on the kraft paper having excellent strength. At the same time, when a bag is formed, it can be a paper bag with further enhanced tensile strength and tear strength.

  The objective of obtaining a paper bag with good waterproof and moisture resistance and excellent tear strength was realized by laminating a synthetic resin with waterproof and moisture resistance and a synthetic resin with tensile strength on kraft paper at the same time.

  Hereinafter, an embodiment of a paper bag according to the present invention will be described with reference to FIGS.

  FIG. 1 is a schematic explanatory view showing the main configuration of the laminating process according to the present invention, and FIG. 2 is a schematic explanatory view showing the overall configuration of the laminating process.

  The laminating process according to the present invention will be described with reference to FIGS. The kraft paper K is taken out from the paper feed roll 1 around which the kraft paper K as a base material is wound, and is inserted into the anchor coater 3 through the guide roller 2. In the anchor coater 3, a predetermined anchor coating agent is applied, and a predetermined synthetic resin film is adhered to the base material surface to which the anchor coating agent is applied.

  The anchor coater 3 is provided with a rotating roller 31 in a tank 30 in which an anchor coating agent is stored so that the lower part of the roller is in the tank and the upper part of the roller is located outside the tank. It is the structure which made the press roller 32 mutually oppose and contact | abuts on the upper part, and forms a pair of feed roller. The kraft paper K is applied to the kraft paper K while the craft paper K is applied to the kraft paper K by passing the kraft paper K through the nip portion of the feed roller constituted by the rotary roller 31 and the press roller 32. K is sent out.

  Kraft paper K coated with a predetermined anchor coating agent is conveyed to the film laminating unit via guide roller 4 and dryer 5. In the film laminating portion, the synthetic resin film P sent out from the extruder 10 and the kraft paper K are laminated and laminated, and simultaneously fed into the nip portion between the nip roller 6 and the cooling roller 7 for pressure bonding. In addition, the laminated sheet material S is formed by cooling.

  The sheet material S on which the synthetic resin film P and the kraft paper K are laminated and laminated is wound around the winding roll 9 in a sheet shape via the guide roller 8.

  Since this is a laminating method in which the synthetic resin film P is pressed and bonded to the surface of the kraft paper K to which a predetermined anchor coating agent is applied, in order to improve its adhesion, the corona discharge treatment is applied to the bonding surface. Yes.

  In this embodiment, as shown in FIG. 1, a corona discharge device A1 composed of a discharge electrode 20 and a counter ground electrode roll 21 is disposed immediately after the extruder 10 and another corona discharge device A2 is laminated. Between the guide rollers 8A and 8B. The corona discharge device A1 is disposed in order to perform a corona discharge treatment on the synthetic resin film P before laminating to improve adhesion with the craft paper K as a base material. When the laminated sheet S is bonded and configured as a bag, the sheet S is disposed to improve the adhesion.

  Further, if the corona discharge device A3 is disposed and the kraft paper K is subjected to the corona discharge treatment and then laminated, the kraft paper surface subjected to the corona discharge treatment and the synthetic resin film similarly subjected to the corona discharge treatment are used. Adhesion strength can be further improved because the surfaces are laminated by adhesive pressure contact.

  When corona discharge occurs in the air, the generated electrons collide with the surface of the kraft paper or synthetic resin film, and in addition to the effects of secondary ozone and ultraviolet rays, the surface of the film is reactive and polar. High functional groups are generated, increasing surface wettability and reactivity. Polyolefin-based plastics such as polypropylene (PP) and polyethylene (PE) have the property that their surface polarity is small, chemically stable, and rarely immersed in organic solvents. When the surface treatment is not performed, the surface wettability is poor and the ink adhesion is often poor. Therefore, in order to obtain practical adhesiveness, it is necessary to perform surface treatment such as corona discharge treatment.

  Kraft paper K is a woody paper having a thickness of about 100 μm or more, and is originally a strong paper, but it is weak in waterproofness and water resistance, and is not suitable as a packaging material for products as it is. Therefore, a synthetic resin film such as polyethylene or polyester having excellent waterproof and moisture resistance can be laminated on the kraft paper K to obtain a sheet material that is strong and also excellent in waterproof and moisture resistance.

  In this embodiment, as shown in FIG. 2, a co-extrusion laminating process in which two types of synthetic resin film layers are laminated, polyethylene is selected as the first synthetic resin P1, and stretched polypropylene is selected as the second synthetic resin P2. The synthetic resin film P integrated with the kraft paper K serving as a base material is laminated together.

  Since the polyethylene is excellent in waterproof and moistureproof, and the stretched polypropylene is excellent in tensile strength, the first synthetic resin P1 has a polyethylene layer with a thickness of about 15 μm, and the second synthetic resin P2 has a thickness of about 20 μm or more. By integrally laminating the synthetic resin film P as a stretched polypropylene layer of kraft paper K, the thickness of the integrated synthetic resin film P becomes about 35 μm or more, and has excellent tear strength, and A sheet material S having excellent waterproof and moisture resistance can be obtained.

  Since the integrated synthetic resin film P is a sheet material S having a thickness of about 35 μm or more, and a laminated structure in which the thickness of the resin having the tensile strength is made thicker than the thickness of the resin having waterproof and moisture proof properties. It has been found that it is difficult to tear the sheet material S with both hands, and it is possible to make a paper bag that is not easily torn even if the product is stored in a full bag.

  As described above, a synthetic resin film obtained by laminating a first synthetic resin having waterproof and moisture proof properties and a second synthetic resin having tensile strength is integrally laminated on kraft paper K as a base material Therefore, by increasing each thickness, the waterproof / moisture-proof property and tear strength of the obtained sheet material S can be further increased. However, if the thickness of the resin film is made too thick, it becomes difficult to fold when forming the bag body, the operability is deteriorated, and the bag body itself is hardened. For this purpose, the sheet material S laminated in the kraft paper K with the first synthetic resin having waterproof / moisture resistance shown in this example being about 15 μm and the second synthetic resin having tensile strength being about 20 μm or more is used. If a paper bag is constituted by the above, it is preferable that a paper bag which is sufficiently soft as a bag body and which has excellent tear strength can be formed.

  In addition, since it is desirable that the thickness of the film subjected to the corona discharge treatment is 25 μm or more, from this point of view, the present embodiment in which two synthetic resin layers are provided and the total resin film thickness is about 35 μm or more is used. A synthetic resin film layer that can be easily subjected to discharge treatment can be obtained, which is preferable.

  As shown in FIG. 3, the sheet material S is a sheet obtained by laminating a synthetic resin film P composed of a first synthetic resin P1 and a second synthetic resin P2 on a kraft paper K. 4 is assembled into a bag body shown in FIG.

  The paper bag 40 is a bag body that is folded with the synthetic resin film P side as an inner surface and bonded to a seam, and forms a bag body that is excellent in waterproof and moistureproof properties and has excellent tear strength. For this reason, the bag is suitable for storing an anaerobic product, and even if the full product is stored in the bag, it is not torn or damaged.

  When the paper bag 40 is formed, as shown in FIG. 4A, the paper bag 40 is assembled in a cylindrical shape and overlapped by a predetermined width at the longitudinal adhesive portion S1. Thereafter, one of the four sides of the cylindrical body is folded at the folding portion S2 shown in FIG. 4B to form the bottom portion, and the paper bag 40 is formed. The formation procedure of the paper bag 40 will be described in more detail with reference to FIG.

  As shown in FIG. 5 (a), the kraft paper K of the sheet material S is on the outside and the synthetic resin film P is on the inside to form a cylindrical body 40a. And fold part S2 is folded and a bottom part is formed. First, as shown in FIG. 5 (b), trapezoidal bottom portions 41 and 42 facing each other are formed by folding the short side of the cylindrical body 40a. Thereafter, the trapezoidal bottom portions 43 and 44 on the long side are folded to form the bottom portion as shown in FIG. 5C, but the bottom portion 43 where the adhesive portion S1 is disposed is folded first, The paper bag 40 shown in FIG. 5D is completed by overlapping and folding the bottom portions 44 facing each other.

  At this time, the bottom portion 43 where the adhesive portion S1 is located is folded first, and then the opposing bottom portion 44 is overlapped and folded, so that the adhesive portion S1 portion is pressed from above. The body is formed, and the adhesive strength as the bag body can be maintained more firmly.

  Also, since the bottom 44b, which is also the synthetic resin film P layer, and the bottom 44a, which is the kraft paper layer, are simultaneously bonded to the bottom 43a where the synthetic resin film P layer appears, corona discharge treatment is performed on both sides. The applied paper bag 40 according to the present invention can maintain its adhesive strength more firmly.

  As a synthetic resin film, it is a two-layer synthetic resin film of polyethylene with excellent waterproof and moisture resistance and stretched polypropylene with excellent tensile strength. Combined with the strong adhesive strength described above, it has even better waterproof and moistureproof properties and tearing. Can exhibit strength.

  For this reason, the paper bag 40 according to the present invention is a paper bag that is effective when packaging or packaging products that dislike moisture, and has a high tensile strength and tear strength, so that the bag can store products in a full bag. It can be.

  Furthermore, even if the product is shipped or transported in a state where the product is fully packed, the bag is strong, so it will not be torn or damaged.

  In addition, since both sides are subjected to corona discharge treatment, the printability is excellent, and the information on the stored products can be easily printed.

It is a schematic explanatory drawing which shows the principal part structure of the lamination process which concerns on this invention. It is a schematic explanatory drawing which shows the whole structure of a lamination process. It is sectional drawing which shows the structure of a sheet | seat material. It is a schematic explanatory drawing of the paper bag which concerns on this invention. The assembly procedure of the paper bag which concerns on this invention is shown, (a) shows the place which formed the cylindrical body, (b) shows the middle of folding in a bottom part, (c) shows the last in which a bottom part is folded in. (D) shows a completed paper bag.

Explanation of symbols

1 Paper feed roll
3 Anchor coater
5 Dryer
6 Nip roller
7 Cooling roller
9 Winding roll 10 Extruder 20 Discharge electrode 21 Opposing ground electrode roll 40 Paper bag
A Corona discharge device
K kraft paper
P Synthetic resin film
S sheet material

Claims (4)

It consists of a sheet material laminated with a synthetic resin film on at least one surface of kraft paper, and is a paper bag with the synthetic resin film on the inner surface side,
The paper bag, wherein the synthetic resin film is composed of two synthetic resin layers obtained by coextrusion and lamination of a synthetic resin having waterproof and moisture resistance and a synthetic resin having tensile strength.   The paper bag according to claim 1, wherein the synthetic resin film is subjected to a corona discharge treatment and then laminated, and the laminated sheet material is further subjected to a corona discharge treatment.   The paper bag according to claim 1 or 2, wherein the kraft paper is subjected to a corona discharge treatment and then laminated. The two synthetic resin layers are polyethylene having a thickness of about 15 µm and stretched polypropylene having a thickness of 20 µm or more, and the total thickness of the synthetic resin film is 35 µm or more. Paper bag.

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