JP2002316371A - Fiber-reinforced plastic cellular sheet and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin tenacious product suitable for a shock-absorbing packaging material high in the strength of the cell and provide a thick product having an enhanced bending strength in the direction vertical to the face and an enhanced buckling strength in the direction of the face, both of which are required by a variety of structural materials, by using inexpensive versatile resins while the thickness of a raw material is limited to an allowable thin level, in a plastic sheet in a plastic cellular sheet formed by sticking a plane plastic back sheet to a bottom surface of a cap of a cap sheet having many recesses by vacuum forming of a plastic sheet, and enclosing air into the cap to form many cells. SOLUTION: The fiber-reinforced plastic cellular sheet comprises the cap sheet reinforced by allowing knit fabric comprising fiber of a higher melting point than that of a plastic constituting the sheet to exist in a state of being stuck outside the cap by fusion weld to the cap sheet. The reinforced cap sheet may be that which holds the knit fabric under a state of being buried in the inside. If necessary, more one plane liner sheet is stuck in a long string of cap crests of the cap sheet and a three layer structure may be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic foam sheet (hereinafter abbreviated as "foam sheet") reinforced with fibers, and also relates to a method for producing the same.

[0002] In this technical field, when a material constituting an air bubble sheet is an appropriate thin film to be called a "film", a product is usually called a "air bubble sheet" and a material is called a "sheet". If is of a suitable thickness, the product is called a "bubble board". However, in this specification, the term "bubble sheet" is collectively referred to as a "bubble sheet" whether the constituent material is a thin film or a thick sheet. That is, the term "bubble sheet" encompasses not only "bubble sheet" in the art, but also "bubble board". The term "sheet" also includes "film" and "sheet" as referred to in the art.

[0003]

2. Description of the Related Art A plastic bubble formed by laminating a flat plastic back sheet on the bottom surface of a cap of a cap sheet having a large number of depressions formed by vacuum molding of a plastic sheet and forming air in the cap. Sheets are widely used in the field of packaging because of their cushioning power.

As a modification of these bubble sheets, there is a three-layer structure or a two-layer structure in which another flat liner sheet is attached by connecting the top of the cap of the cap sheet. There is also one in which two foam sheets are stacked.

[0005] The strength of the foam sheet as a cushioning material is determined by the crushing strength of the foam, which can be increased by using a high-strength plastic itself or by increasing the thickness of the plastic film or sheet of the material. There is nothing else. As a material for manufacturing the foam sheet, polyethylene, particularly low-density polyethylene, is widely used because of its high workability and low price. However, low density polyethylene does not have high strength. Regarding the thickness of the material, it is of course necessary to make it thinner in order to meet the general demand for weight reduction, and also to be required naturally from the viewpoint of effective use of resources and environmental issues, and it is also a factor that directly affects the cost. Therefore, it is difficult to increase the thickness.

In some cases, it is desired that the foam sheet has high rigidity as a sheet in addition to the strength of the foam. In a thin bubble sheet, so-called stiffness is required so that it can be easily handled. For thick foam sheets,
Since it is often used as a structural material, a bending strength with respect to a surface and a buckling strength in a surface direction are required. In answering such a demand, there is a similar problem as described above regarding the strength of the bubble.
Many plastics having high rigidity by themselves are brittle or poor in shock absorption, and generally have poor workability and are generally expensive.

[0007] Under such circumstances, the inventors have attempted to fiber-reinforce a foam sheet made of a general-purpose resin having high processability and low cost, as represented by conventional polyethylene. Such attempts have never been made before, but as a reinforcing material, not a woven or non-woven fabric,
This intent was achieved by utilizing a knit that is stretchable and easy to shape.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to utilize a low-cost general-purpose resin as a material in the field of a plastic foam sheet, utilizing the new technology developed by the inventors, and to reduce the thickness of the material. By using fiber reinforcement while keeping the thickness as thin as possible to the extent necessary, it is possible to provide a foam (highly defined foam sheet) in which the strength of bubbles is high, the rigidity as a whole is high, and the performance as a cushioning material can be satisfied.
Furthermore, it is an object of the present invention to provide a foam board (a narrowly defined foam board) in which not only the strength and the overall rigidity of the bubble but also the bending strength against the surface and the buckling strength in the surface direction are enhanced. Providing a method for producing them is also included in the object of the present invention.

[0009]

One embodiment of the fiber-reinforced plastic foam sheet of the present invention which achieves the above object has a number of depressions formed by vacuum forming a plastic sheet as shown in FIG. A plastic foam sheet formed by laminating a flat plastic back sheet (2) on the bottom surface of a cap of a cap sheet (1A) and forming a large number of air bubbles in the cap, wherein a fiber having a higher melting point than plastic. Is present in a state where the knitted fabric (4) is bonded to the outside or inside of the cap (outside in the illustrated example) by fusion with the cap sheet, thereby reinforcing the cap sheet. .

[0010] Another embodiment of the fiber-reinforced plastic foam sheet of the present invention is shown in FIG.
A flat plastic back sheet (2) is attached to the bottom surface of a cap of a cap sheet (1B) provided with a number of depressions by vacuum molding of a plastic sheet to form a number of air bubbles in the cap. In the plastic foam sheet, a knitted fabric (4) made of a fiber having a higher melting point than plastic is used for the cap sheet (1).
The cap sheet is reinforced by being buried inside B).

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, there are many variations of the foam sheet, and the present invention is applicable to them. The important thing is to connect the top of the cap of the cap sheet (1A) as shown in FIG.
A flat liner sheet (3) is laminated to form a three-layer structure, that is, a fiber-reinforced plastic foam sheet shown in FIG. 1 and a liner sheet (3) added thereto. A three-layer structure in which the top of the cap of the cap sheet (1B) is connected and another flat liner sheet (3) is attached, that is, the fiber-reinforced plastic foam shown in FIG. It is obtained by adding a liner sheet (3) to a sheet.

The method of the present invention for producing the fiber-reinforced plastic foam sheet having the structure shown in FIG. 1 according to the first-mentioned embodiment, as shown in FIG. Using a forming roll (5) in which these dents are provided and these dents are connected to a vacuum suction source,
A knitted fabric (4 ') and a sheet (7) of molten plastic extruded from an extruder (not shown) are superimposed on the surface of the forming roll such that the knitted fabric is on the side of the forming roll. Supply and continuous vacuum forming to form a cap sheet in which a knitted material is bonded to the outside of the cap by fusing with the cap sheet, and a sheet of molten plastic is formed on the bottom surface of the cap of the cap sheet by a back sheet (2). And press-bonding with a pressing roll (6) to form air bubbles, thereby obtaining a fiber-reinforced plastic foam sheet (9) product.

In this embodiment, the knitted fabric is deformed in accordance with the formation of the cap sheet, and a large number of knitted caps are formed according to the dents provided in the forming roll. When the molten plastic is formed, the plastic sheet is strongly pressed against the knitted fabric by vacuum suction, so that the plastic bites between the fibers of the knitted fabric, that is, the knitted fabric is bonded to the outside of the cap, Be one.

The method of the present invention for producing the fiber-reinforced plastic foam sheet having the structure shown in FIG. 2 is described below. As shown in FIG. 6, a large number of caps are placed on the surface of a rotatably installed cylinder. A forming roll (5) in which concave portions are provided and connected to a vacuum suction source, and a knitted fabric (4 ') is held on the surface of the forming roll with a knitted fabric (4') embedded inside a plastic sheet. (8) is supplied to form a cap sheet (1B) in which a knitted material is embedded by continuous vacuum forming, and a sheet of molten plastic is used as a back sheet (2) on the bottom surface of the cap of the cap sheet. It is brought into contact and pressed with a pressure roll (6) to form air bubbles, thereby obtaining a fiber-reinforced plastic foam sheet (9) product.

Various methods can be used to prepare the sheet (8) which holds the knitted fabric (4 ') embedded in the plastic sheet. One of them is 2
Each of the plastic films is extruded from the T-die of the book, the knitted fabric is sandwiched between the two sheets while the films are being melted, and pressed and integrated with appropriate pairs of rolls from both sides. . Another method is to form a single sheet by stacking a knitted fabric on one plastic, placing a molten plastic film on the knitted fabric, and fusing the knitted fabric with the heat to sandwich the knitted fabric. The method of burying the knitted fabric is not limited to heat fusion, of course.
A lamination method using an adhesive can also be employed.
Still another method is to use a knitted fabric made of a combination of two or more fibers having different melting points and heat the fiber before supplying it to a vacuum forming roll to melt the fiber having a lower melting point. By doing so, a knitted fabric made of fibers having a melting point higher than that of plastic is made to be buried inside the cap sheet.

A fiber reinforced foam sheet according to a modified embodiment in which the present invention is applied to a three-layer foam sheet, that is, FIGS. 3 and 4
In order to manufacture a product having the structure shown in (1), after performing any of the manufacturing methods described above, a sheet of molten plastic is supplied to the top of the cap of the cap sheet (1A or 1B). , Roll-pressing to form a liner sheet (3).

Since the fiber used for the knitted fabric is expected to have a reinforcing effect, it is desirable that the fiber state is maintained at the time of forming the cap. Therefore, the fiber is made of a material having a higher melting point than the plastic constituting the foam sheet. Should be used. Of course, it is necessary that the strength is high as much as the reinforcement effect is expected. Specifically, tough synthetic fibers such as nylon, polyester, aramid, ultrahigh molecular weight polyethylene, and polyetheretherketone are suitable, but natural fibers may be used. Glass fibers, rock wool, carbon fibers, and various metal fibers can also be used. Fiber thickness and fiber density in knitted fabric
It goes without saying that a wide range can be selected according to the thickness of the foam sheet to be reinforced and the desired degree of reinforcement.

[0018]

Example 1 A two-layer fiber-reinforced foam sheet having the structure shown in FIG. 1 was produced by the method shown in FIG. First, a knitted fabric was prepared by knitting an aramid fiber (Teijin's "Technola", 530 denier) with an 8 gauge (number of needles / inch) weft knitting machine in a flat knitting (sheeting structure). Low-density polyethylene "Sumikasen" (Sumitomo Chemical Industries, density 0.92g /
cc, MI = 0.8 g / 10 min) were extruded from two parallel T-dies so as to have a thickness of about 35 μm and 15 μm, respectively. To obtain a thin foam sheet product in which the above-mentioned nylon knitted material was fused.

The caps are staggered with a diameter of 10 mm, a height of 4 mm and a pitch of 12 mm. When the stiffness of this product was measured using a cantilever type test piece, the value of the bubble sheet made of a film of the same thickness was 1
In contrast to 10 kgf * mm, the product of the present invention was 250 kg.
kgf * mm. In order to measure the strength of bubbles as a cushioning material, one particle was cut from a bubble sheet, a load was applied between two plates, and the load at which the bubbles burst was measured.
The foam sheet without reinforcement stopped at 5.7 kg, but the product of the invention withstood until the load reached 12.1 kg.

[0020]

EXAMPLE 2 A two-layer fiber-reinforced foam sheet having the structure shown in FIG. 2 was produced by the method shown in FIG. 1x braided Tetron fiber (Toray's "Decitex 560")
A 1-ribbed knitted fabric is prepared, sandwiched between two melt-extruded polyethylene sheets having a thickness of 0.3 mm, and pressure-bonded with a pair of rolls to obtain a fiber-reinforced polyethylene sheet having a knitted fabric embedded therein. Obtained. The material is the same polyethylene as used in Example 1. This fiber-reinforced polyethylene sheet was softened by contacting it with a heat roll, and used as a cap sheet. The back film is another T-
It is of the same quality as the cap film extruded from the die and having a thickness of about 0.5 mm. Using these, a thick foam sheet having a cap diameter of 7.5 mm, a height of 5 mm, and a staggered arrangement of a pitch of 15 mm was manufactured.

For this product, the bending strength in the direction perpendicular to the surface was measured using a test piece having a width of 3 cm and a distance between supporting points of 9 cm.
When a three-point bending test in which a load was applied at the center at 0 mm was performed, the load resistance was 2,300 Pa. This value corresponds to 1.5 times that of the non-fiber reinforced foam sheet made of the same thickness sheet in comparison. Next, in order to examine the resistance to buckling in the plane direction, a test piece having a height of 5 cm was cut out, placed vertically, and a load was applied from above and below. n =
As a mean value of 5, a buckling load of 27.5 was obtained. this is,
Again, this is equivalent to three times the buckling resistance of the compared foam sheet.

[0022]

According to the fiber-reinforced foam sheet of the present invention, when forming the cap sheet of the foam sheet, the knitted fabric and the plastic material which follow the shape of the dent of the vacuum forming roll by virtue of the stretchability which is a characteristic of the knitted fabric. A cap sheet integrated with the sheet is formed. Fiber reinforcement on surfaces with irregularities is only possible with knitted fabrics,
Since the woven or non-woven fabric has a low deformability, it cannot follow a shape in which a large number of deep draws such as a cap of a bubble sheet are arranged.

In the fiber-reinforced cap sheet, not only the one in which the knitted material is buried inside, but also the one in which the knitted material is merely fused to the outside, the molten plastic bites into the knitted material at the time of forming the cap and is strongly integrated. Therefore, the reinforcing effect is maximized. When used as a cushioning material, the cap swells laterally when pressure is applied, but the knitted fabric effectively suppresses the deformation of the cap and prevents its rupture. The resistance to piercing is also significantly increased. If the physical properties of the knitted fabric are different in the vertical and horizontal directions, the product, the fiber-reinforced foam sheet, has anisotropy, and this anisotropy is useful depending on the application.

According to the present invention, a general-purpose plastic having high workability and low cost is used as the material of the foam sheet, and the strength of the foam is increased without increasing the thickness of the material. The air bubble sheet which increased was realized. When this is used as a cushioning material, it can withstand a stronger load and complete the cushioning action. Even when used as a structural material, for example, a building structural material, it is possible to provide a foam sheet having significantly improved resistance to bending in the direction perpendicular to the plane and buckling in the plane direction. As a result, not only can resources be effectively used, but also the burden on the environment is reduced, and buffer packaging with reduced costs is facilitated.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one embodiment of a fiber-reinforced plastic foam sheet of the present invention.

FIG. 2 is a cross-sectional view showing another embodiment of the fiber-reinforced plastic foam sheet of the present invention.

FIG. 3 shows the fiber-reinforced plastic foam sheet of FIG.
Sectional drawing which shows the modified aspect.

FIG. 4 shows the fiber-reinforced plastic foam sheet of FIG.
Sectional drawing which shows the modified aspect.

FIG. 5 is a conceptual cross-sectional view of an apparatus showing a method for manufacturing the fiber-reinforced plastic foam sheet of FIG.

FIG. 6 is a conceptual sectional view of an apparatus showing a method for producing the fiber-reinforced plastic foam sheet of FIG. 2;

[Explanation of symbols]

 Reference Signs List 1A, 1B Cap sheet 2 Back sheet 3 Liner sheet 4 Knitted material 4 'Knitted material 5 Forming roll 6 Crimping roll 7 Sheet of molten plastic 8 Sheet held with embedded knitted material 9 Fiber reinforced plastic foam sheet

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B65D 81/03 B29L 9:00 // B29L 9:00 B65D 81/14 C F-term (Reference) 3E066 AA12 AA22 BA02 CA01 CA08 CB03 CB04 KA20 MA06 4F100 AK01A AK01B AK01C AK01D AK06 AK47 AK48 BA03 BA04 BA07 BA10B BA10C BA10D DD21A DG01A DG01C DG11A DG11C DG13A DG13C DG18A DG18C DH00A DH00C EA021 EC032 EC14A EH171 EJ192 EJ241 EJ242 GB15 JA04A JA04C JK01 JK04 JL02 4F208 AD16 AD17 AG03 AG20 AM28 MA01 MB02 MG04 MG11 MH06 MH18 MJ05 MJ09

Claims (7)

[Claims] 1. A plastic formed by laminating a flat plastic back sheet on the bottom surface of a cap of a cap sheet provided with a number of depressions by vacuum molding of a plastic sheet, and forming a number of air bubbles in the cap. In the foam sheet, a knitted fabric made of a fiber having a higher melting point than plastic is present in a state of being bonded to the outside or inside of the cap by fusion with the cap sheet, thereby reinforcing the cap sheet. Fiber reinforced plastic foam sheet. 2. A plastic formed by bonding a flat plastic back sheet to the bottom surface of a cap of a cap sheet provided with a number of depressions by vacuum molding of a plastic sheet and forming a number of air bubbles in the cap. A fiber reinforced plastic foam sheet characterized in that a knitted fabric made of fibers having a melting point higher than that of plastic is buried inside the cap sheet to reinforce the cap sheet. 3. The cap sheet of the cap sheet is connected to another flat liner sheet, and the top of the cap sheet is attached.
The fiber-reinforced plastic foam sheet according to claim 1 or 2, which has a layer structure. 4. A method for producing a fiber-reinforced plastic foam sheet according to claim 1, wherein a number of cap-shaped depressions are provided on the surface of a rotatably installed cylinder, and these depressions are used as a vacuum suction source. Using a connected forming roll, a knitted fabric and a sheet of molten plastic are superimposedly supplied on the surface of the forming roll so that the knitted fabric is on the side of the forming roll, and continuous vacuum forming is performed to form a cap sheet. A fiber formed by fusing to a knitted material to form a cap sheet in which the knitted material is bonded to the outside of the cap, contacting a molten plastic sheet with the bottom surface of the cap of the cap sheet, and pressing with a roll to form bubbles. A method for producing a reinforced plastic foam sheet. 5. A method for producing a fiber-reinforced plastic foam sheet according to claim 2, wherein a number of cap-shaped depressions are provided on the surface of a rotatably installed cylinder, and these depressions are used as a vacuum suction source. Using a connected forming roll, supply a sheet of molten plastic with the knitted fabric embedded inside the surface of the forming roll to the surface of this forming roll, and by continuous vacuum forming, a cap with the knitted material embedded inside A method for producing a fiber-reinforced plastic foam sheet, comprising forming a sheet, bringing a molten plastic sheet into contact with the bottom surface of the cap of the cap sheet, and pressing the roll with a roll to form bubbles. 6. A method for producing a fiber-reinforced plastic foam sheet according to claim 2, wherein a knitted fabric knitted with two or more fibers having different melting points is used, and vacuum forming is performed. By heating this prior to feeding to the roll and melting the fiber with a lower melting point, a knitted fabric consisting of a fiber with a higher melting point than plastic is prepared in a state buried inside the cap sheet. The method for producing a fiber-reinforced plastic foam sheet according to claim 5, wherein 7. A method for producing a fiber-reinforced plastic foam sheet according to claim 3, wherein, after the step according to claim 4 or 5, the molten plastic sheet is applied to the top of the cap sheet. A method for producing a fiber-reinforced plastic foam sheet, comprising supplying and pressure-bonding with a roll to form a liner sheet.