JP4466254B2 - Plastic bubble sheet and manufacturing method thereof - Google Patents

Description

Industrial application fields

The present invention relates to an improvement of a plastic bubble sheet (hereinafter abbreviated as “bubble sheet”). In particular, the present invention relates to a bubble sheet that can be easily torn by hand without using a tool such as a cutter or a scissors, and also relates to a manufacturing method thereof.

A plastic film formed by plastic processing of a plastic film to form a large number of cap-shaped protrusions, and a flat plastic back film fused to the bottom of the cap to form a large number of sealed air chambers. Sheets are widely used as cushioning packaging materials, and as curing materials for walls and floors for moving and remodeling, because of their cushioning performance. Since this type of air bubble sheet also has heat insulation properties, it is used as a building material and as a curing sheet for placing concrete.

In the conventional bubble sheet, the shape of the cap is generally circular. This is based on the convenience of manufacturing, specifically, the convenience when manufacturing the manufacturing apparatus of the bubble sheet. The dominant technology for producing bubble sheets today is a vacuum forming roll in which a large number of cap-shaped cavities are provided on the outer surface of a metal cylinder that is rotatably supported, and the bottoms of these cavities are connected to a vacuum source. The cap film is formed by vacuum forming the melt-extruded film, and the back-film film, which is separately melt-extruded, is pressed on the bottom surface of the formed cap film with a pressure roll made of an elastic material. The process of fusing. Drilling is the most efficient way to provide this large number of cavities (even thousands of small form rolls).

Another feature that is not common to the conventional bubble sheets is that the circular caps are arranged in a staggered manner. Assuming that a circular cap is used and the air cushion volume per unit area is increased with the intention of ensuring the desired buffer performance and heat insulation performance, more practically speaking, the unit area It is an inevitable choice if the projected area of the surrounding cap is to be widened. When the caps are arranged in a grid pattern, the cap diameter must be reduced and the total volume of the air chamber is also reduced.

There is a usage that tries to improve the efficiency of heating by sticking the bubble sheet temporarily (only in the severe cold season) to the window glass. In this case, the window is usually rectangular, so the circular cap is aesthetically pleasing. ,not appropriate. Furthermore, the fact that the caps are arranged in a staggered pattern is not suitable as a heat insulating material for windows. The applicant has already developed and proposed a heat-insulating sheet that is used by being temporarily attached to a window glass, which is attached only by wetting the window glass with water (Patent Document 1). In addition to the circular air chamber, the heat insulating sheet includes a rectangular pyramid, and has high transparency and is beautiful.
JP2002-3655

The inventors have been concerned with the realization of a bubble sheet having a cap whose planar shape is not a circular single point, but a rectangle or a square (hereinafter represented by the term “ square shape ”). Utilizing recent advances in metalworking technology and trying to form cavities with a computer-controlled milling machine in particular, it has become possible to efficiently manufacture square-shaped cavities for vacuum forming rolls. Therefore, what should be done about the dimensional relationship between the side and height of the square cap, and what should be the shape of the four tops that tend to become weak points of the cap because it becomes thin during film molding? Focused on solving the problem.

Furthermore, if the cap is a square cap, by arranging the caps in a straight line, the fusion part between the cap film and the back film is placed between the cap steps in a line in the width direction. Easy to tear at this part because the line-of-sight cap line-to-line, line-to-line and line-to-line and line-to-line are consistently visible. Then, paying attention to the great convenience for the use of the bubble sheet, a means that can easily realize this ease of tearing was sought. Since the conventional air bubble sheet has a staggered arrangement of caps as described above, tearing is difficult if there is a cap in the direction of tearing. If it is forcibly torn, the cut will not be straight, and it will not hit the cross section of the cap.

When the conventional manufacturing method is used, the longitudinal direction of the product bubble sheet is the extending direction of the plastic material and is easily torn to some extent, but the width direction is a direction perpendicular to the stretching and is not easily torn. This is also because of the vacuum forming roll manufacturing method described above, it is convenient to arrange the circular cavities arranged in a staggered pattern on a line parallel to the axis of the roll. Although the caps are lined up in the width direction so that the gaps can be seen, it is difficult to tear in that direction, and the cap is hindered in the longitudinal direction. Therefore, the present situation is that the air bubble sheet product does not tear in any direction. However, attempts have been made to produce a tearable bubble sheet by selecting a plastic material for the bubble sheet, and this has been achieved to some extent. However, since such a material is weak, the strength of the bubble sheet itself is lowered as a whole, which is not practical.

An object of the present invention is to provide a bubble sheet having a square cap, a high crushing strength of the cap, and a practical performance as a cushioning material or a heat insulating material. Secondly, in such a foam sheet, it is easy to tear in the width direction, or in the longitudinal direction, or both in the width direction and in the longitudinal direction, and during work using the foam sheet, for example, When packing for moving, the object is to provide a bubble sheet that can be torn by hand without using scissors or a cutter, and has a beautiful cut surface.

The bubble sheet of the present invention that achieves the first object described above is obtained by fusing a flat plastic back film to the bottom surface of a cap film formed by plastic processing of a plastic film to form a large number of cap-shaped protrusions. In the air bubble sheet formed of a large number of sealed air chambers, the planar shape of the cap is square, and the caps are linearly arranged at equal intervals in at least one of the width direction and the longitudinal direction of the plastic air bubble sheet. The four tops of the cap are rounded, and the radius of curvature (R) is relative to the height (H) of the cap.
0.2H ≦ R ≦ 0.4H
And the height (H) of the cap is relative to the length (W) of one side,
0.3W ≦ H ≦ 0.5W
It is characterized by being in the range of

The foam sheet of the present invention that achieves the second object is the above-mentioned foam sheet that achieves the first object, and further, a fusion surface between the cap film and the back film between the cap steps, and fusion surface between the cap film and the back film which is between the rows and rows, in one or both, as run their substantially central, continuously or intermittently ridges which cross-sectional shape of the film changes abruptly It is easy to tear along this strip.

The air bubble sheet of the present invention in which a square cap having a square shape is arranged linearly can take a large projected area of the cap per unit area even though the cap is square. The air chamber volume can be increased, and high performance is exhibited as a cushioning material or a heat insulating material. The square cap is particularly suitable when used as a heat insulating material for windows, and realizes heat insulation with high aesthetics.

Square caps are arranged in a straight line, and the fusing surface between the cap film and the back film between the cap steps and the fusing surface between the cap film and the back film between the rows. In one or both of them, a continuous or intermittently formed strip having a sudden change in the cross-sectional shape of the film so as to run approximately in the middle of them can be easily torn along this strip. In addition, since it can be torn by hand without using a cutter or scissors, the packing and curing work can be efficiently performed. The cut is straight and beautiful because there is no cap.

One aspect of the bubble sheet according to the present invention is that, as shown in FIG. 1, a step in which the caps are arranged in a line in the width direction of the plastic bubble sheet and the caps are arranged at equal intervals is repeated in the longitudinal direction. By arranging the caps at the corresponding positions between the stages, the rows formed by the caps arranged in a straight line at equal intervals in the longitudinal direction of the plastic bubble sheet are repeated in the width direction as a whole. A pattern is formed. In the figure, MD indicates the longitudinal direction of the product bubble sheet, and TD indicates the width direction.

As shown in FIG. 2, another aspect of the bubble sheet according to the present invention is such that the cap is arranged in a longitudinal direction in which the caps are formed in a line in the width direction of the plastic bubble sheet and arranged at equal intervals. The caps are arranged at positions shifted by a half pitch between each stage, thereby forming a zigzag pattern as a whole.

As shown in FIG. 3, in another aspect of the bubble sheet according to the present invention, a row in which the caps are arranged in a straight line at equal intervals in the longitudinal direction of the plastic bubble sheet is repeated in the width direction. At the same time, the caps are arranged at positions shifted by a half pitch between each row, thereby forming a zigzag pattern as a whole.

The radius of curvature (R) that defines the roundness of the top of the cap is within the range of 0.2H ≦ R ≦ 0.4H with respect to the height (H) of the cap, as shown in FIG. is necessary. From the standpoint of avoiding thinning of the top and becoming a weak point of the cap, it is better that the radius of curvature (R) is large. However, the cap has a substantially square planar shape, that is, a rectangular air chamber for buffering and heat insulation. It is desirable that the radius of curvature (R) is as small as possible. The above range is defined as a compromise between the two. When the height (H) of the cap is increased, the plastic material of the portion forming the cap of the cap sheet tends to be stretched and thinned, and accordingly, the curvature radius (R) of the top portion needs to be increased. .

As shown in FIG. 4B, the height (H) of the cap is suitably in the range of 0.3 W ≦ H ≦ 0.5 W with respect to the length (W) of one side of the cap. is there. The higher the air chamber formed by the cap, the more advantageous in general for buffering and heat insulation. However, as mentioned above, if the height is increased, the cap portion becomes thinner and weaker. There is a limit. The ratio between the cap height (H) and the cap length (W) is determined in consideration of the balance between performance and strength.

In order to facilitate tearing of the bubble sheet, the cap film and back film fusion surface between the cap steps and / or the cap film and back between the cap rows The strip provided on the surface to be fused with the film and having a rapidly changing cross-sectional shape of the film may be formed as follows. That is, on the outer surface of a metal cylinder that is rotatably supported, a number of approximately square cavities and continuous or intermittent running between the tiers of cavities, or between tiers and between rows. The cap film was formed using a vacuum forming roll provided with a concave groove and the bottom of these cavities connected to a vacuum source, and the back film was manufactured from an elastic body against the molded cap film. Is a manufacturing method comprising continuously or intermittently forming strips in which the cross-sectional shape of the film changes rapidly on the fusion surface between the cap film and the back film.

If the strip formed by the molding operation as described above is schematically shown, the back film (2) melt-extruded to the cap film (1) molded by vacuum molding is as shown in FIG. When pressed and fused by a pressure roll, the cap film softens due to the heat of the back film and is pressed into the recesses provided in the vacuum forming roll, resulting in continuous or intermittent protrusions. Article (3) is made. When a shearing stress is applied to the cap film / back film fusion portion, the portion having such a sudden change in cross-sectional shape is likely to be broken due to the stress concentration. In this way, it can be easily torn between the steps of the cap and between the rows. On the other hand, tearing due to such a mechanism is caused by shearing stress, and since it is less sensitive to tensile stress in the plane direction, the performance of the bubble sheet as a cushioning material is likely to deteriorate. There is no.

Such strips for tearing can be arbitrarily provided in one or both of MD and TD in the case of the cap arrangement (grid pattern) of FIG. In the case of the cap arrangement (staggered) of FIGS. 2 and 3, it can be provided only on one of MD and TD that is consistent. It is usually a good idea to provide a TD that needs to be torn.

Using a polyethylene (density: 0.92 g / cm ³ , MFR: 2) as a material, an air bubble sheet having square caps arranged in a grid pattern as shown in FIG.
Cap film extrusion thickness: 35μm
One side of the cap (W): 7.5 mm, height (H): 2.5 mm, curvature radius of the top (R): 1 mm
Back film extrusion thickness: 25μm
This foam sheet product has a square cap arranged in an orderly manner, has a beautiful appearance, and has improved transparency compared to a foam sheet with a circular cap. The crushing strength was 60N.

A V-shaped groove having a width of 500 μm and a depth of 500 μm was provided in the vacuum forming roll in which the bubble sheet was manufactured in Example 1 so as to penetrate between the steps of the cavity for forming the cap. Using this vacuum forming roll, a bubble sheet having a grid arrangement of caps but having tearing protrusions only in the TD direction was produced. This bubble sheet could be easily torn by applying a force in the shear direction by hand, and its cross section was straight and beautiful.

The top view which shows the bubble sheet | seat which has a grid-like cap arrangement | sequence which is a typical aspect of this invention. The top view which shows the bubble sheet which has the cap arrangement | sequence which is a zigzag form in MD direction which is another aspect of this invention. The top view which shows the bubble sheet | seat which has the cap arrangement | sequence which is a zigzag form in the TD direction which is another aspect of this invention. The top part curvature radius (R), height (H), and the length of one side (W) of the cap in the bubble sheet of this invention are shown, A is sectional drawing, B is a top view. The typical sectional view showing the shape of the portion provided in the air bubble sheet of the present invention in order to make tearing easy, and the shape of the cross section changed abruptly to make stress easy to concentrate.

Explanation of symbols

MD Longitudinal direction TD Width direction R Curvature radius of cap H Height W Length of one side 1 Cap film 2 Back film 3 Projection

Claims (8)

A plastic film formed by plastic processing of a plastic film to form a large number of cap-shaped protrusions, and a flat plastic back film fused to the bottom of the cap to form a large number of sealed air chambers. In the sheet, the planar shape of the cap is a square, the caps are arranged in a straight line at equal intervals in at least one of the width direction and the longitudinal direction of the plastic bubble sheet, and the four top portions of the cap are rounded. The radius of curvature (R) is in the range of 0.2H ≦ R ≦ 0.4H with respect to the height (H) of the cap, and the height (H) of the cap is the length (W) of one side. On the other hand, a plastic bubble sheet characterized by being in the range of 0.3 W ≦ H ≦ 0.5 W. The steps of the cap array are repeated in the longitudinal direction in which the caps are arranged in a straight line at equal intervals in the width direction of the plastic bubble sheet, and the caps are arranged at corresponding positions between the steps. 2. The plastic foam sheet according to claim 1, wherein a row of caps arranged in a straight line at equal intervals in the longitudinal direction of the plastic foam sheet is repeated in the width direction to form a grid-like pattern as a whole. The caps are arranged in a line in the width direction of the plastic bubble sheet, and the steps formed by arranging the caps at regular intervals are repeated in the longitudinal direction, and the caps are arranged at positions shifted by a half pitch between each step. The plastic air bubble sheet according to claim 1, wherein a staggered pattern is formed as a whole. The caps are arranged in rows in which the caps are linearly arranged at equal intervals in the longitudinal direction of the plastic bubble sheet, and the rows are repeated in the width direction, and the caps are arranged at positions shifted by a half pitch between each row. Thus, the plastic bubble sheet according to claim 1, wherein a staggered pattern is formed as a whole. The cap film and back film fusion surface between the cap tiers and the cap film and back film fusion surface between the rows and rows, one or both of which are approximately The plastic foam sheet according to claim 2, wherein a strip portion in which the cross-sectional shape of the film changes rapidly so as to run in the center is formed continuously or intermittently, and it is easy to tear along the strip portion. On the fusion surface between the cap film and the back film between the cap steps, a strip where the cross-sectional shape of the film suddenly changes is formed continuously or intermittently so as to run almost in the middle of them. The plastic foam sheet according to claim 3, which is easily torn along the strip. On the fusion surface between the cap film and the back film between the rows of caps, a strip with a sudden change in the cross-sectional shape of the film is formed continuously or intermittently so as to run almost at the center of them. The plastic foam sheet according to claim 4, wherein the plastic foam sheet is easy to tear along the strip. A method for producing a plastic bubble sheet that is easy to tear along a continuous or intermittently provided strip according to any one of claims 5 to 7, wherein the metal cylinder is rotatably supported. A plurality of substantially square cavities and continuous or intermittent ridges running in one or both of the cavity steps and between the rows and rows, the bottom of the cavity A cap film is formed using a vacuum forming roll connected to a vacuum source, and the back film is pressed and fused to the formed cap film with a pressure roll made of an elastic body. A manufacturing method comprising continuously or intermittently forming a strip having a sudden change in the cross-sectional shape of a film on a fusion surface between a film and a back film.

Images