JP5123829B2 - 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, and the hardness and repulsive force of the flap part when applied to a widely used corrugated cardboard automatic sealing machine 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. However, the conventional air bubble sheet cannot withstand use as a substitute for corrugated cardboard due to insufficient rigidity.
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 cap film is composed of three or more layers having an intermediate layer in which at least both surfaces are in contact with other layers, and the intermediate layer is composed of homopolypropylene.
(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 °.

  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%.

  Here, the description of (a) discloses conditions found in the process of searching for an optimal balance of materials and composition from the viewpoint of resource saving.

  That is, when the cap film is composed of at least three layers having an intermediate layer in contact with other layers on both sides, and the intermediate layer is composed of homopolypropylene, it can be effectively improved from the viewpoint of strength. In particular, by applying a multilayer structure of three or more layers, it is possible to reduce the weight while ensuring the strength without unduly reducing the strength of the waist. 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.

  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.

  As a main raw material of the layer in contact with the intermediate layer, any of general-purpose synthetic resins may be used. Polypropylene containing an ethylene component, in particular, random polypropylene having an ethylene content of 3% or more, particularly in polypropylene, preferably ethylene content 5 When 10% super random polypropylene is used, it is possible to obtain a corrugated cardboard air bubble sheet that not only has excellent workability but also has high wear resistance and is resistant to repeated folding of the flap portion.

  One or both of the back film and the liner film may have a layer made of homopolypropylene. In that case, it is good also as a 2 layer thing which protrudes the layer which consists of a homopolypropylene on the surface.

  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 an automatic sealing machine for A-type cardboard, which is widely used for manufacturing a general cardboard box B, for example.

  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 cap film is composed of three or more layers having an intermediate layer in which at least both surfaces are in contact with other layers, and the intermediate layer is composed of homopolypropylene. (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 °.

  In addition, although the bubble sheet A is typically shown in FIG. 3, the bubble sheet produced by the method according to a 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 made of the same or similar resin.

  The cap film 1 is composed of three layers in which the cap film 1 includes an intermediate layer 12 and outer layers 11 and 13, and the cap 10 can be formed in an arrangement as shown in FIG. For example, 55%. Specifically, the cap film 1 is made of the outer layers 11 and 13 made of, for example, polypropylene containing an ethylene component, more specifically super random polypropylene having an ethylene content of 5 to 10% in this embodiment. And the intermediate | middle layer 12 makes the cap film 1 itself excellent in rigidity by using a homo polypropylene in this embodiment. The cap film 1 specifically has a cap 10 formed with a particle size 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 the bubbles b together with the cap film 1. In this embodiment, polyethylene is used as an example, but various existing materials can be used. Of course, it is good also as what uses the super random polypropylene of ethylene content 5-10% similarly to the said outer side layers 11 and 13 grade | etc.,. Moreover, although the thickness ratio with respect to the whole thickness shall be set, for example to 35%, you may adjust thickness suitably or may comprise in a multilayer.

  The liner film 3 is disposed on the opposite side of the back film 2 through the cap film 1 and uses polyethylene as an example, as described above, but uses various existing materials. Is possible. Of course, it is good also as what uses the super random polypropylene of ethylene content 5-10% similarly to the said outer side layers 11 and 13 grade | etc.,. Moreover, although the thickness ratio with respect to the whole thickness shall be set to 10%, for example, you may adjust thickness suitably or may comprise 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.

  In particular, the air bubble sheet according to the present embodiment is preferably used as a good joint with the intermediate layer by using super random polypropylene having an ethylene content of 5 to 10% for the outer layers 11 and 13 in contact with the intermediate layer 12. In addition to being able to be manufactured, the strength of impact is effectively improved while maintaining high bending stiffness by suitably supplementing the properties of homopolypropylene, which is generally considered to be “hard and brittle”. ing.

<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 air bubble sheet A1 according to the present modification, as shown in FIG. 4, the cap film 1 and the back film 2 are the same as those in the above embodiment, and the liner film 3 is formed in two layers, and faces the surface. The surface layer 31 is made of the same homopolypropylene as the intermediate layer 12. The inner layer 32 in contact with the cap film may use polyethylene as in the above embodiment, but in order to achieve good adhesion with the surface layer 31, the same ethylene content 5 to 10 as the outer layers 11 and 13 is used. % Super random polypropylene.

  By setting it as such a structure, even if it is the same weight, the bubble sheet A1 which can achieve weight reduction is realizable by improving a bending strength and bending stiffness effectively.

  As mentioned above, although embodiment and the modification of this invention were demonstrated, the specific structure of each part is not limited only to embodiment mentioned above, A various deformation | transformation is possible in the range which does not deviate from the meaning of this invention. is there.

  For example, in the above-described embodiments and modifications, the cap film and the back film are disclosed as a single layer and two layers, but of course, it is possible to have three layers or more, and the liner film may be a multilayer of two layers or more. is there.

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

<Test material>
As Example 1, the cap sheet has a three-layer structure in which the thickness ratio from the entire thickness is 55%, the intermediate layer is made of homopolypropylene, and the thickness ratio from the entire thickness is 15%. The outer layer in contact with the surface was made of super random polypropylene having an ethylene content of 8%, and the total thickness ratio was 20%. Polyethylene was used for both the back sheet and the liner sheet, and the thickness ratio of the cap sheet, the back sheet and the liner sheet with respect to the total thickness was set to 35% and 10%, respectively. A bubble sheet was used in which the bubble particle size was 10 mm, the particle height was 4 mm, the pitch between the particles was 11.5 mm, and the bubble misalignment angle between adjacent rows was 60 °. The weight of the bubble sheet was 135 g per square meter.
As Comparative Example 1, polyethylene was used for the cap sheet, back sheet, and liner sheet, and the thickness ratios of the cap sheet, back sheet, and liner sheet to the total thickness were 55%, 35%, and 10%, respectively, as in Example 1. And a bubble sheet having a bubble particle size of 10 mm, a particle height of 4 mm, and a pitch between the particles of 11.5 mm was used. The weight of the bubble sheet was 150 g per square meter.

<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 measured.
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 and Comparative Example 1 in the test described above are shown in Table 1 below.

  As described above, Example 1 shows the conditions that can be used as a corrugated cardboard substitute, that is, the suitability of an A-type corrugated cardboard for an automatic sealing machine. And it turned out that it is the corrugated cardboard substitute bubble sheet excellent in intensity | strength, implement | achieving 10% of weight reduction with respect to the comparative example 1. FIG.

  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.

Explanatory drawing which concerns on arrangement | positioning of the grain 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 12 ... Intermediate layer 2 ... Back film 3 ... Liner film 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 cap film is composed of three or more layers having an intermediate layer in which at least both surfaces are in contact with other layers, and the intermediate layer is composed of homopolypropylene.
(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 °.   2. The corrugated cardboard substitute bubble sheet according to claim 1, wherein polypropylene containing an ethylene component is used as a main raw material of the layer in contact with the intermediate layer. The bubble sheet as a substitute for corrugated board according to claim 2, wherein the polypropylene containing the ethylene component is super random polypropylene having an ethylene content of 5 to 10%.   The bubble sheet as an alternative to corrugated cardboard according to claim 1 or 2, wherein one or both of the back film and the liner film has a layer made of homopolypropylene.

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