JP5202244B2 - Air bubble sheet for corrugated cardboard - Google Patents

Description

  The present invention relates to an air bubble sheet for corrugated cardboard that is preferably used for packaging and the like.

  The present applicant has already proposed a bubble sheet that can be used as a substitute for cardboard (see, for example, Patent Document 1).

  At this time, the present inventors have presented a sheet-like material that is softer than what has been conventionally called plastic corrugated cardboard. However, if the properties of such a sheet-like material are set too soft, it becomes difficult to handle in the same way as so-called corrugated cardboard. However, there was a case that could not be sealed well because it was not enough.

  On the other hand, what is conventionally called a plastic corrugated cardboard is not only hard but also has a large repulsive force and cannot be used in an automatic sealing machine for A-type cardboard boxes. These machines are usually designed to bend a sheet through a guide roll or an arm, put a crease and then apply a tape or a hot melt. However, if the hardness or repulsive force is too large, there are problems that the tape is peeled off by that force, and the bonded surface is peeled off before the hot melt is cooled and solidified.

  The inventors of the present invention have a bending strength measured by the method specified in JIS K 7203 of 0.001 MPa or more and 10 MPa or less, and measured the bending stiffness twice in succession by the method specified in JIS K 7106 for the same specimen. If the air bubble sheet is set so that the second numerical value is 50% or more, more preferably 65% or more of the first numerical value, the hardness of the flap portion is within the range where the above-mentioned peeling problem does not occur. It was found that the repulsive force was sufficient and it was possible to apply the above-mentioned automatic sealing machine.

  However, in order to satisfy the above conditions with a conventional two-layer or three-layer bubble sheet and to have a certain level of independence when a box is made, the weight per unit area must be considerably large. Did not get.

  The increase in weight is not preferable from the increase in the estimated amount of carbon dioxide generated due to the recently implemented Containers and Packaging Recycling Law and the increase in raw materials used.

  Accordingly, the present inventors have further pursued a search to produce a bubble sheet that is as light as possible and has a low environmental load while satisfying the above conditions.

  Therefore, first, the present inventors paid attention to the balance of the thicknesses of the cap film, the back film, and the liner film in order to reduce the weight without unduly reducing the strength (strength) of the bubble sheet. As an extension, the inventors have taken into consideration the particle arrangement of the bubbles and obtained knowledge that is the basis of the present invention.

Incidentally, a product such as a bubble sheet was originally a two-layer product of a cap film and a back film in view of its formation. However, when such a bubble sheet is used to make a bag with the cap film on the inside, the grains in the bag interfere with each other, making it difficult to put the contents. In order to improve this, a thin film was stuck on the top of the cap film at the beginning of the three-layer bubble sheet. Thus, the thickness of the liner film in the conventional three-layer bubble sheet is at most 10 to 15% of the total sheet thickness of all the layers, and its existence significance and configuration are completely different from those of the present invention.
Japanese Patent Application No. 2004-34594

  The present invention has been made on the basis of the above circumstances and knowledge, and it is difficult to apply to a widely used automatic sealing machine for A-type corrugated cardboard, and it is mainly applied to the automatic sealing machine. In addition, it is intended to solve the problem that the weight per unit area tends to increase if it is developed, and it can be appropriately packed using the automatic sealing machine as an alternative to corrugated cardboard. The purpose of the present invention is to provide an air bubble sheet that is suitable for corrugated cardboard and has a low level of environmental impact.

In order to achieve this object, the present invention employs the following configuration. That is, the air bubble sheet for corrugated cardboard according to the present invention comprises three layers of a cap film, a back film, and a liner film, and is characterized by satisfying all the following conditions (a) to (d). .
(A) The thickness of the liner film is 20 to 45% of the total sheet thickness of the cap film, the back film, and the liner film 3 layers.
(B) The bending strength measured by the method defined in JIS K 7203 is 0.001 MPa or more and 10 MPa or less.
(C) When bending stiffness is measured twice by the method defined in JIS K 7106, the second numerical value is 50% or more of the first numerical value.
(D) As shown in FIG. 1, when the bubble particle arrangement is D, the bubble arrangement pitch is P, the bubble arrangement pitch between adjacent rows is θ, and P = 1. 05D to 1.3D, θ = 50 ° to 65 °.

  Here, the description about the bending strength of (b) and the description of the bending stiffness of (c) are the conditions for causing the bubble sheet to exhibit strength characteristics equivalent to that of cardboard, in other words, an automatic sealing machine for cardboard. However, it is based on the knowledge obtained after many trials and errors as described above.

  That is, if the bending strength shown in (b) exceeds 10 MPa, the hardness and repulsive force of the bubble sheet are excessively increased and the surface once bonded by the automatic sealing machine is liable to be peeled off. On the other hand, when the pressure is less than 0.001 MPa, the waist becomes extremely weak, so that the measurement defined in JIS K 7203 is practically impossible. It can cause a situation where the flap cannot be closed and the tape cannot be fixed properly. Further, when the characteristic value related to the bending stiffness shown in (b) is less than 50%, it becomes easy to fold, and automatic sealing is impossible practically due to the fall of the flap. The larger the characteristic value regarding bending stiffness, the better. However, no matter what film material is used, there is an upper limit due to the nature of the substance, and there is virtually no 100%.

  On the other hand, the description regarding the thickness in (a) and the description regarding the grain arrangement in (d) disclose conditions found in the process of searching for an optimal balance between thickness and grain arrangement from the viewpoint of resource saving. It is.

  That is, when the thickness ratio of the liner film deviates from 20% to 45%, the structural balance in terms of strength is lost, and it is difficult to reduce the weight without unduly reducing the strength of the waist. . Further, if the bending strength is improved, the interval between the bubbles should be narrow, but a wider one is advantageous for increasing the sealing property of the bubbles since a sufficient fusion allowance can be obtained. According to the study of the present inventor, the condition range of (d) described above has the best balance in practical use, and both waist strength and weight reduction can be achieved. When the thickness of the liner film is 10% or less, the air bubble sheet tends to bend toward the liner film side, and when it is thicker than 45%, it tends to bend toward the back film side.

  With the air bubble sheet having such a configuration, there is an effect that a sealing work having no practical problem can be performed on the corrugated cardboard automatic sealing machine by satisfying the conditions (b) and (c). In addition to the above, the conditions (a) and (d) are satisfied, so that the structural strength balance is good, and a moderate amount of independence when a box is made is realized using less material. It becomes possible to do.

  One or both of the back film and the liner film may be a multilayer of two or more layers. As a preferable aspect in that case, the side in contact with the cap film in the multilayer sheet may be a sealant layer, and the outer side may be a uniaxial or biaxially stretched polypropylene. That is, one or both of the back film and the liner film may be formed by attaching a uniaxial or biaxially stretched film having a required thickness to the cap film via the sealant layer. If the thicknesses of the liner film and the back film satisfy the above numerical values in the bonded state, it is possible to make an air bubble sheet having excellent strength while being lighter. Such a bubble sheet has high transparency and excellent cosmetics.

  As a material for the cap film, the back film, and the liner film, any of general-purpose synthetic resins may be used. In particular, a random polypropylene having an ethylene content of 3% or more, particularly an ethylene content of 5 to 10% in polypropylene (PP). When super random polypropylene is used, it is possible to obtain an air bubble sheet that is not only excellent in workability but also has excellent wear resistance and is resistant to repeated folding of the flap portion.

  When the air bubble sheet is composed of three layers of a cap film made of the same or similar resin, a back film and a liner film, the weight ratio of the liner film is used instead of the thickness of the liner film. Numerical limitation equivalent to that of the invention according to item 1 can be established. That is, the following can be cited as an invention in this case.

An air bubble sheet as an alternative to corrugated cardboard, comprising three layers of a cap film, a back film and a liner film made of the same or similar resin, and satisfying all the following conditions (a) to (d).
(A) The weight ratio of the liner film to the total weight of the cap film, the back film, and the liner film is 20 to 45%.
(B) The bending strength measured by the method defined in JIS K 7203 is 0.001 MPa or more and 10 MPa or less.
(C) When bending stiffness is measured twice by the method defined in JIS K 7106, the second numerical value is 50% or more of the first numerical value.
(D) When the bubble particle arrangement is D for the bubble diameter, P for the bubble pitch in the same row, and θ for the bubble shift angle between adjacent rows, P = 1.05D to 1.3D, θ = 50 ° to 65 °.

  Since the present invention is configured as described above, it can be applied to a corrugated cardboard automatic sealing machine, and is excellent in structural balance for securing the strength of the waist. It is possible to provide an air bubble sheet that can be used instead of corrugated cardboard and has a low environmental load.

  As shown in FIG. 2, a corrugated cardboard bubble sheet A (hereinafter referred to as a bubble sheet) A according to the present embodiment forms a box B that can be suitably applied to packing and transporting packages. The box B is formed in the same manner as a normal cardboard box by, for example, an A-type cardboard automatic sealing machine widely used for manufacturing a general cardboard box.

  Here, the air bubble sheet A according to the present embodiment includes three layers of a cap film 1, a back film 2, and a liner film 3 as shown in FIG. 3, and satisfies all the following conditions (a) to (d). It is characterized by this. (A) The thickness of the liner film 3 is 20 to 45% of the total sheet thickness of the three layers of the cap film 1, the back film 2, and the liner film 3. (B) The bending strength measured by the method defined in JIS K 7203 is 0.001 MPa or more and 10 MPa or less. (C) When bending stiffness is measured twice by the method defined in JIS K 7106, the second numerical value is 50% or more of the first numerical value. (D) When the particle arrangement of the bubbles b is D, the diameter of the bubbles b is P, the arrangement pitch of the bubbles b in the same row is P, and the deviation angle of the bubbles b between adjacent rows is θ, P = 1.05 D-1 .3D, θ = 50 ° to 65 °.

  In addition, although the bubble sheet A is typically shown in FIG. 3, the bubble sheet produced by the normal manufacturing method is actually used. That is, it should be noted in the bubble sheet manufacturing technique that the shape of the molded cap does not match the vacuum-molded mold shape. The cap film at the time of the production of the bubble sheet has just been molded from the molten state by the mold and is still at a high temperature, and the back film stuck to this is in contact in the molten state. It is at a high temperature. As a result of the air sealed in the space of a certain volume contracting due to a decrease in temperature, the shape of the bubble sheet contracts accordingly. That is why, as is well-known, none of the products are stretchy. To understand the outline, assuming that the air temperature at the time of bubble formation is 100 ° C. and the environmental temperature of the bubble sheet product is 20 ° C., the volume of the internal air is reduced to 78.5%. Should be. When actually measured, although it varies somewhat depending on the temperature conditions during production, the basis weight of the bubble sheet, the ratio of each film thickness, etc., it is generally in the range of 70 to 85%.

  Since bubble sheet products are always in this situation, they are used as a buffering agent, and when a load is applied in the surface direction, the air bubbles bulge out laterally by the air inside the bubble under pressure. , Calm down in a state where a "body blister" has occurred. In this way, the bubbles when functioning as a buffer are even lower than the height given by the mold cavity minus the amount of bubble volume reduction due to air cooling and shrinkage. In order to measure this state, for example, 10 sheets of air bubbles of length x 100 mm in width are stacked with 1 mm thick paper sandwiched between them, and a weight of 200 g is applied from the top. , And subtract the amount of cardboard to calculate the average bubble height.

  Hereinafter, the configuration of the bubble sheet A will be described. Of course, the cap film 1, the back film 2 and the liner film 3 shown below may be made of different materials within the range shown below, or may be made of the same or similar resin.

  The cap film 1 can form the cap 10 in an arrangement as shown in FIG. 1. In this embodiment, for example, super random polypropylene having an ethylene content of 5 to 10% is used. The thickness ratio with respect to the total thickness is set to 42%, for example. The cap film 1 specifically has a cap 10 formed with a particle diameter D of 10 mm, a particle height of 4 mm, a distance between particles, that is, a pitch P of 11.5 mm, and bubbles b between adjacent rows, The displacement angle θ of the cap 10 is set to 60 ° (FIG. 1).

  The back film 2 can form air bubbles b together with the cap film 1, and in the present embodiment, super random polypropylene having an ethylene content of 5 to 10% is similarly used. In addition, the thickness ratio with respect to the total thickness is set to 22%, for example.

  The liner film 3 is disposed on the opposite side of the back film 2 with the cap film 1 interposed therebetween, and the same as described above, super random polypropylene having an ethylene content of 5 to 10% is used. Moreover, although the thickness ratio with respect to the whole thickness shall be set to 36%, for example, what is necessary is just to set to 20-45% by adjusting thickness suitably or comprising in a multilayer.

  As described above, according to the bubble sheet A instead of corrugated cardboard according to the present embodiment, the above-described configuration allows the corrugated cardboard automatic sealing machine to meet the above conditions (b) and (c). Not only can the sealing work be carried out without any problem in practice, but the structural strength balance is improved by satisfying the conditions (a) and (d). It becomes possible to realize moderate self-supporting property when B is made using a small amount of material.

<Modification>
Hereinafter, although the modification of the said embodiment is demonstrated, while the same code | symbol is attached | subjected to the component equivalent to this embodiment, the detailed description shall be abbreviate | omitted.

  That is, in the bubble sheet A1 according to this modification, as shown in FIG. 4, both the back film 2 and the liner film 3 are two layers, and the layers in contact with the cap film 1 are sealant layers 21 and 31. In this embodiment, the outer side is the stretched polypropylene layers 22 and 32 made of biaxially stretched polypropylene. The stretched polypropylene layers 22 and 32 may be uniaxially stretched polypropylene layers instead of the biaxially stretched polypropylene layers.

  By adopting such a configuration, a uniaxial or biaxially stretched film having a required thickness is bonded to the cap film 1 via the sealant layers 21 and 31, and the liner film 3 in that state is formed. In addition, since the thickness of the back film 2 satisfies the above numerical value, the air bubble sheet A1 that is light in weight and further excellent in strength is realized. Moreover, such a bubble sheet A1 has high transparency and excellent cosmetics.

  Although the embodiment of the present invention has been described above, the specific configuration of each unit is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

  For example, in the above-described embodiment, the configuration in which the liner film and the back film are formed as a single layer and two layers is disclosed.

  In addition, the specific configuration of each part is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

  Examples of the present invention will be described in detail below, but the present invention is not limited to these examples.

  In this example, using Example 1 corresponding to the bubble sheet of the above embodiment, and Comparative Example 1 and Comparative Example 2 as test materials, tests for bending strength and bending stiffness are performed as described below. The suitability of the A-type cardboard box for the automatic sealing machine was investigated.

<Test material>
As Example 1, the material of the cap sheet, the back sheet, and the liner sheet is super random polypropylene whose ethylene content is 8%, and the thickness ratio of the cap sheet, the back sheet, and the liner sheet to the total thickness is 42% and 22%, respectively. And 36%, a bubble sheet in which the bubble particle size is 10 mm, the particle height is 4 mm, the pitch between the particles is 11.5 mm, and the deviation angle of the bubbles between adjacent rows is 60 ° is used. It was. The weight of the bubble sheet was 125 g per square meter.
As Comparative Example 1, the cap sheet, the back sheet, and the liner sheet are made of polyethylene, and the thickness ratio of the cap sheet, the back sheet, and the liner sheet to the total thickness is 55%, 35%, and 10%, respectively. A bubble sheet having a diameter of 10 mm, a grain height of 4 mm, and a pitch between grains of 11.5 mm was used. The weight of the bubble sheet was 150 g per square meter.

 As Comparative Example 2, the cap sheet, the back sheet, and the liner sheet are made of polyethylene, and the thickness ratio of the cap sheet, the back sheet, and the liner sheet to the total thickness is 55%, 35%, and 10%, respectively. An air bubble sheet having a diameter of 10 mm, a grain height of 4 mm, and a pitch between grains of 11.5 mm was used as two layers.

<Test method>
The bending strength measured by the method defined in A-type JIS K 7203 and the bending stiffness measured by the method defined in JIS K 7106 were continuously performed twice.
And the KTB-100 of Kyoto Seisakusho Co., Ltd. was used as an automatic sealing machine of A type corrugated cardboard, and the suitability for the automatic sealing machine was investigated with respect to Example 1, Comparative Example 1 and Comparative Example 2. In the table, as the evaluation of the suitability of the A-type corrugated cardboard for the automatic sealing machine, “◯” was entered for those that obtained the result that they could be used in the same manner as corrugated cardboard, and “X” was marked for those that did not show suitability for some reason.

<Test results>
The results of Example 1, Comparative Example 1, and Comparative Example 2 in the test described above are shown in Table 1 below.

  As described above, Example 1 shows conditions that can be used as a corrugated cardboard substitute, excellent bending strength, and excellent characteristics that the second numerical value is 50% or more of the first numerical value in two tests. It was found that this was an excellent corrugated cardboard substitute cell sheet that realized a weight reduction of 20% for Comparative Example 1 and 30% to 5% for Comparative Example 2.

  Further, in Example 1, the automatic sealing machine can easily perform the process of closing the flap and fixing the tape. However, in Comparative Example 1, since the flap collapses, the flap part is a guide roller of the automatic sealing machine. It was found that it was not suitable for processes such as flap closure and tape fastening. In addition, although the comparative example 2 showed the suitability with respect to an automatic sealing machine compared with the comparative example 1, from the weight of 350g per square meter, it was evaluated that it was a thing lacking in practicality. Specifically, the weight of the three-layered corrugated paper is normally 160 to 340 g per square meter, but since Comparative Example 2 is more than that, it is equivalent to the corrugated paper in terms of transportation surface and the like. It was impossible to handle.

Explanatory drawing which concerns on arrangement | positioning of the bubble in the bubble sheet of this invention. The external view of the box formed of the bubble sheet which concerns on one Embodiment of this invention. FIG. 3 is a schematic cross-sectional view according to the embodiment. The typical sectional view concerning the modification of the embodiment.

Explanation of symbols

A, A1 ... Corrugated cardboard bubble sheet (bubble sheet)
DESCRIPTION OF SYMBOLS 1 ... Cap film 2 ... Back film 3 ... Liner film 21, 31 ... Sealant layer 22, 32 ... Stretched polypropylene layer b ... Air bubble

Claims (4)

An air bubble sheet for corrugated cardboard, comprising three layers of a cap film, a back film, and a liner film, and satisfying all of the following conditions (a) to (d).
(A) The thickness of the liner film is 20 to 45% of the total sheet thickness of the cap film, the back film, and the liner film 3 layers.
(B) The bending strength measured by the method defined in JIS K 7203 is 0.001 MPa or more and 10 MPa or less.
(C) When bending stiffness is measured twice by the method defined in JIS K 7106, the second numerical value is 50% or more of the first numerical value.
(D) When the bubble particle arrangement is D for bubble diameter, P for bubble arrangement pitch in the same row, and θ for the bubble shift angle between adjacent rows, P = 1.05D to 1.3D, θ = 50 ° to 65 °.   The corrugated cardboard according to claim 1, wherein one or both of the back film and the liner film is a multilayer of two or more layers, the side in contact with the cap film in the multilayer sheet is a sealant layer, and the outside is a uniaxial or biaxially oriented polypropylene. Alternative bubble sheet.   3. The corrugated cardboard substitute bubble sheet according to claim 1 or 2, wherein super random polypropylene having an ethylene content of 5 to 10% is used as a main raw material of the sheet. An air bubble sheet as an alternative to corrugated cardboard, comprising three layers of a cap film, a back film and a liner film made of the same or similar resin, and satisfying all the following conditions (a) to (d).
(A) The weight ratio of the liner film to the total weight of the cap film, the back film, and the liner film is 20 to 45%.
(B) The bending strength measured by the method defined in JIS K 7203 is 0.001 MPa or more and 10 MPa or less.
(C) When bending stiffness is measured twice by the method defined in JIS K 7106, the second numerical value is 50% or more of the first numerical value.
(D) When the bubble particle arrangement is D for bubble diameter, P for bubble arrangement pitch in the same row, and θ for the bubble shift angle between adjacent rows, P = 1.05D to 1.3D, θ = 50 ° to 65 °.

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