JP4232228B2 - Plastic bubble sheet with excellent heat sealability and adhesion - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a bubble sheet made of plastic that has good low-temperature heat sealability and high adhesion to other objects. The present invention also relates to a method for heat-sealing the bubble sheet and a product obtained by the method. The present invention further relates to the use of the bubble sheet as a heat insulating material for glass windows.
[0002]
[Prior art]
A two-layered bubble sheet made of plastic as a material, formed by vacuum forming a cap film having a large number of dents, and a flat back film bonded to it to form a large number of sealed bubbles is mainly used for packaging. Widely used as cushioning material. There are various modes of changing the bubble sheet, and there are a bubble sheet in which a flat liner film is stuck on the top of the bubble to form a three-layer structure, and a two-layer structure in which two sheets are stacked. As the plastic material, polyethylene and overwhelmingly low density polyethylene LDPE are used.
[0003]
When using a bubble sheet, heat sealing is often performed, such as processing into a bag. For the heat seal, an impulse sealer is preferably used, but an electric heat type heat sealer that is inexpensive and easy to use is also often used. LDPE, which is most often used as the material for the bubble sheet, has poor heat sealability at low temperatures, so the sealing temperature must be increased (100 ° C or higher). There is a problem that it adheres to the surface, lowers workability, and impairs the appearance of the product. Improvements can be seen by applying plating or Teflon coating to the seal bar, or by adding an additive that enhances releasability such as a lubricant to the polyethylene material, but this is not a drastic measure.
[0004]
In addition to the cushioning material, the plastic foam sheet can also be used as a heat insulating material, such as sticking it to the window glass in winter to reduce the loss of heating energy. In this case, the attachment to the window glass is performed by a technique such as using a double-sided pressure-sensitive adhesive tape in the surrounding portion. If the area is large, use adhesive tape not only around but also inside. However, such sticking and peeling after use have poor workability, and there are various problems such as tape marks remaining on the window glass after peeling and difficult collection at the time of disposal. . When a low molecular weight component is contained in the material plastic, it tends to migrate to the surface of the bubble sheet and leave a mark on the part that is in close contact with the window glass (this is referred to as “grain residue”), which is also preferable. Absent.
[0005]
On the other hand, various attempts to improve or change the properties of polyethylene have been continued, and as one of the means, a monomer component to be copolymerized with ethylene has been selected. Specifically, α-olefins higher than ethylene, such as propylene, butene-1, and butadiene, are used, and ethylene trimer (C ₆ ) and tetramer (C ₈ ) are also used. Research has continued on polymerization methods, and there are various types such as conventional LDPE by radical polymerization, HDPE by Ziegler catalyst, single-site polymerization PE by metallocene catalyst, L-LDPE by ionic polymerization.
[0006]
Recently developed ethylene-higher α-olefin copolymer L-LDPE is a polymer obtained by copolymerizing ethylene with a small amount of hexene, hexadiene, octene, octadiene, etc., and has a relatively narrow molecular weight distribution. The inventors manufactured a bubble sheet using this copolymer polyethylene as a material, and the product has high heat-sealability even at low temperatures and good adhesion to other objects such as window glass, and does not use an adhesive. However, it was found that the adhesion was maintained.
[0007]
[Problems to be solved by the invention]
Therefore, the object of the present invention is to utilize the above-mentioned knowledge obtained by the inventors, and first provide a bubble sheet that has a good heat seal processability as a cushioning material for packaging and gives a beautiful product regardless of the heat seal machine. There is to do. Next, as a heat insulating material for window glass, it is possible to affix without the help of an adhesive tape, and therefore, to provide a bubble sheet that does not have a fundamental problem in use of the adhesive tape.
[0008]
[Means for Solving the Problems]
The basic mode of the plastic foam sheet of the present invention is that a cap film (2) having a number of dents and a flat back film (1) are bonded together as shown in a plane in FIG. 1 and a cross section in FIG. Te, in the bubble sheet formed comprising two layers constituting the multiple sealed bubble (4), a cap film and (2) to one or both of the back film (1), ethylene and octadiene as monomers and characterized by using the linear low density polyethylene is a binary copolymer prepared by high pressure ion polymerization using.
[0009]
As shown in FIG. 3, a modified embodiment of the plastic foam sheet of the present invention is obtained by laminating a cap film (2) having a large number of dents and a flat back film (1) to form a large number of sealed bubbles (4 In the three-layered bubble sheet in which a flat liner film (3) is also applied to the top of the bubble, as a monomer on one or both of the back film (1) and the liner film (3) It is characterized by using a linear low density polyethylene which is a binary copolymer produced by high pressure ionic polymerization using ethylene and octadiene.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
As the α-olefin copolymerized with ethylene to obtain a linear low density polyethylene, various mono- and di-olefins can be used, and as described above, C ₄ to C ₈ α-olefins are used. However, according to the inventors' experience, octadiene was optimal. Several grades have been announced by manufacturers of synthetic resins, so you can choose one with the appropriate physical properties from them. When these relatively high-grade olefins are copolymerized with ethylene by high-pressure ionic polymerization, the resulting polymer has less carbon chain branching and narrow molecular weight distribution than conventional LDPE by high-pressure radical polymerization. However, it is also a kind of L-LDPE, which has improved low-temperature heat sealability and high adhesion. The difference from normal, that is, L-LDPE in which no special α-olefin is copolymerized is that there are many small branches on the straight chain, which is considered to affect the physical properties. The linear low density polyethylene, which is a binary copolymer obtained by copolymerization by high-pressure ionic polymerization using ethylene and octadiene as monomers , is used in the present invention. It can be said that it resembles the properties of polyethylene polymerized using a metallocene catalyst known as a site catalyst. However, it does not show self-adhesiveness like polyethylene with a metallocene catalyst.
[0011]
In a special aspect of the air bubble sheet of the present invention, only one of the cap film and the back film in the above-described two-layer air bubble sheet, or only one of the back film and the liner film in the above three-layer air bubble sheet, Linear low density polyethylene, the remaining film is conventional polyethylene, the remaining film is made of conventional polyethylene, and the melting point of linear low density polyolefin is at least 5 ° C. lower than the melting point of conventional polyethylene.
[0012]
Here, “ordinary polyethylene” refers to LDPE and L-LDPE that are usually used for the production of cellular sheets, and those that have a small amount of HDPE blended with them to achieve appropriate physical properties as cellular sheet materials. Means that the density falls within the range of about 0.91 to 0.93 g / cm ³ .
[0013]
The packaging method of the present invention uses the above-described special embodiment of the air bubble sheet, and the air bubble sheet is overlapped so that the low melting point polyethylene is located on the inner side and the high melting point polyethylene is located on the outer side. Heat-sealing in between.
[0014]
If heat sealing is performed in this manner, heat sealing can be performed in a state where the inner side is completely melted and fused and the outer side is one step before the complete melting. More specifically, many ethylene / higher α-olefin copolymer films have a melting point slightly below 100 ° C., and ordinary polyethylene such as ordinary LDPE has a melting point slightly above 100 ° C. Since there are many, it is easy to obtain a melting point difference of 5 ° C. or more. As shown in FIG. 4, the bubble sheet formed by combining such materials is overlapped with the low melting point polyethylene layer (L) on the inside and the high melting point polyethylene layer (H) on the outside, and around 100 ° C. When the heat sealing is performed at the temperature of FIG. 4A (FIG. 4A), the inner fusion is complete, but on the outer side, the resin is completely melted by the seal bar (7), and the heat sealing proceeds.
[0015]
As a result, a seal product with a beautiful melted edge is obtained, and adhesion of the molten resin to the seal bar does not occur (FIG. 4B). If there is a melting point difference of 5 ° C or more, the temperature of the seal bar is kept lower than the higher melting point and higher than the lower melting point, even if the temperature control of the heat sealing device is not precise. There is no difficulty to do. If an appropriate amount of lubricant is added to the outer LDPE, even if the surface of the seal bar is somewhat rough, even if the surface of the steel material itself is not exposed, such as chrome plating, it will heat without trouble. The seal can continue.
[0016]
When both of the outer layers are formed of an ethylene / higher α-olefin copolymer film according to the present invention, the advantages brought about by the combination of the above melting point differences cannot be obtained. Thus, there is a benefit that a good heat seal can be realized even if an arbitrary superposition method is used.
[0017]
The use of the air bubble sheet of the present invention taking advantage of its high adhesion to other objects is the use as a heat insulating material for window glass. As shown in FIG. 5, water (6) is applied to the window glass (5) (FIG. 5A), and a bubble sheet is adhered onto the window glass (5B), as shown in FIG. It consists of attaching. Water evaporates away from the surroundings and even after passing through the bubble sheet itself, but the bubble sheet remains in close contact with the glass window after evaporation (FIG. 5C). In order to aim for the use as the heat insulating material, it is generally preferable to use a modified embodiment of the bubble sheet of the present invention, that is, a three-layer structure having a liner film. Even a two-layer structure consisting of a back film and a back film can withstand sufficient use. In that case, if the side where the bubbles are present is exposed, dust accumulates. Therefore, as shown in FIG. 6, the side of the bubbles is brought into contact with the window glass. After the water evaporates, it is possible to maintain close contact with the window glass due to the sucker effect of the bubbles. If a conventional bubble sheet made of LDPE is used in such a form, “grain residue” tends to occur, but if it is a bubble sheet according to the present invention, there is no concern.
[0018]
[Example 1]
The height of the cell having the two-layer structure shown in FIGS. 1 and 2, using a polyolefin obtained by copolymerizing ethylene and 48% by weight of octadiene as a cap film, and using conventional LDPE as a back film. 4 mm, diameter 10 mm, bubble pitch 11 mm, and a staggered plastic bubble sheet was manufactured. The film thicknesses are 50 μm cap film and 30 μm back film, respectively.
[0019]
This long sheet of bubble sheet was folded in half along the longitudinal direction, and heat sealed at a constant interval as shown in FIG. Heat sealing could be performed without any trouble, and a bag with a beautiful seal edge could be produced.
[0020]
[Example 2]
Using the copolymerized polyolefin used for the cap film in Example 1 for the back film and the liner film, and using conventional LDPE for the cap film, a plastic foam sheet having a three-layer structure shown in FIG. 3 was produced. The film thicknesses are a cap film 50 μm, a back film 30 μm, and a liner film 15 μm, respectively.
[0021]
A long 1 m wide sheet of this bubble sheet was cut into a length of 1.5 m and attached to the window glass with water. It adhered well to the entire surface and could be used as a heat insulating material as it was for 4 months in the winter season. When it was peeled off in the spring, it was easily peeled off, and no "grain residue" was found on the peeled trace.
[0022]
【The invention's effect】
The plastic air bubble sheet of the present invention has a basic structure of two-layer structure and a modified three-layer structure of ethylene and a specific higher α-olefin as a material of a part of the film. By using a copolymer by high-pressure ion polymerization, heat sealability at a low temperature can be enhanced, and a beautiful heat seal product can be obtained without using a special machine for heat sealing. This is a significant advantage considering that this type of foam sheet often undergoes heat sealing as a cushioning material for packaging.
[0023]
A special application of the plastic foam sheet of the present invention is to apply it to a window glass to make a seasonal heat insulating material. For this purpose, it is not necessary to use means such as a double-sided adhesive tape as in the prior art, and a sufficiently durable adhesion can be ensured by simply applying a bubble sheet after applying water. When exfoliating, it exfoliates quite easily, and there is no “grain residue” on the glass surface that tends to occur in the past.
[Brief description of the drawings]
FIG. 1 is a plan view showing a basic aspect of a plastic bubble sheet of the present invention.
FIG. 2 is a cross-sectional view of the plastic foam sheet of FIG.
FIG. 3 is a cross-sectional view similar to FIG. 2, showing a modified embodiment of the plastic bubble sheet of the present invention.
FIGS. 4A and 4B are diagrams for explaining good heat sealability of the plastic foam sheet of the present invention, where A is a state where a seal bar is applied, and B is a product obtained after heat sealing and fusing. FIG. Both are sectional views.
5 is an explanatory diagram of a method of using the bubble sheet of FIG. 3 as a heat insulating material for a window glass, wherein A is a stage where water is applied to the window glass, B is a stage where a bubble sheet is pasted thereon, C FIG. 4 is a cross-sectional view showing a state where the water sheet is dry and the bubble sheet is in close contact with the window glass.
6 is a cross-sectional view corresponding to FIG. 5C showing a situation where the bubble sheet of FIGS. 1 and 2 is used as a heat insulating material for a window glass.
[Explanation of symbols]
1 Back film 2 Cap film 3 Liner film 4 Bubble 5 Window glass 6 Water 7 Seal bar H High melting point polyethylene L Low melting point polyethylene

Claims (5)

In a two-layered bubble sheet formed by laminating a cap film having a large number of dents and a flat back film to form a large number of sealed bubbles, a single amount is provided for one or both of the cap film and the back film. A bubble sheet made of plastic with excellent heat-sealability and adhesion, characterized by using linear low-density polyethylene , a binary copolymer produced by high-pressure ion polymerization using ethylene and octadiene as the body . In a three-layered bubble sheet in which a cap film having a large number of dents and a flat back film are bonded together to form a large number of sealed bubbles, and a flat liner film is also applied to the top of the bubbles. Heat seal, characterized in that linear low density polyethylene , a binary copolymer produced by high pressure ionic polymerization using ethylene and octadiene as monomers , is used for one or both of the film and liner film Bubble sheet made of plastic with excellent properties and adhesion. In a two-layer foam sheet, only one of the cap film and the back film, or in a three-layer foam sheet, only one of the back film and the liner film uses high pressure ions using ethylene and octadiene as monomers. consists of a binary copolymer prepared by polymerizing linear low density polyethylene, the remaining film consists of polyethylene customary, at least 5 ° C. the melting point of the linear low density polyolefin is the melting point of the polyethylene customary combines low The bubble sheet according to claim 1 or 2. A packaging method comprising stacking the air bubble sheet according to claim 3 so that polyethylene having a low melting point is located on the inside and polyethylene having a high melting point is located on the outside, and heat-sealing the objects to be packaged therebetween. A method of using the air bubble sheet as a heat insulating material for a glass window, comprising adhering the air bubble sheet according to any one of claims 1 to 3 to a glass window coated with water and adhering without using an adhesive.

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