JP4802389B2 - Plastic hollow plate, manufacturing method and manufacturing apparatus thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a plastic hollow plate, and also relates to a manufacturing method and a manufacturing apparatus thereof. The present invention provides a plastic hollow plate that is lightweight, has high rigidity, and has little physical property directivity.
[0002]
[Prior art]
A plastic bubble sheet made of plastic, typically polyethylene, and a cap film in which a large number of caps are formed by vacuum forming and a flat back film are bonded together to form a large number of sealed air chambers. It is mainly used in the field of shock-absorbing packaging and partly as a heat insulating material.
[0003]
On the other hand, there is a product called “corrugated cardboard plastic” (abbreviated as “corrugated plastic”) having a structure in which plastic is extruded from a harmonica die and a large number of parallel ribs are connected between two sheets. In this corrugated plastic, a sufficiently rigid plastic hollow plate can be produced if the sheet and ribs are sufficiently thick.
[0004]
A corrugated plastic type plastic hollow plate has a remarkable directionality in terms of physical characteristics and workability. For example, from the viewpoint of workability, it is easy to bend along the rib direction, but in a direction crossing it. Bending is difficult. Such directionality is preferable depending on the application, but it is often required that the directionality is small.
[0005]
As a plastic hollow plate having a low directionality with respect to physical properties and processability, a three-layer product in which the top of the cap sheet is joined to another flat liner sheet in the above-mentioned bubble sheet type Can be adopted. That is, if the thickness of each film constituting the bubble sheet is increased, the rigidity is increased and the film can be used as a plastic hollow plate. FIG. 1 shows the structure of such a bubble sheet type plastic hollow plate.
[0006]
However, the production of a bubble sheet type plastic hollow plate has a problem that it is difficult to avoid warping of the product. The occurrence of this warp is considered to be caused by the manufacturing process. As described above, the production of the three-layered bubble sheet is made by first forming the cap sheet by vacuum forming, pasting the back sheet to the bottom surface of the cap, that is, the open cell side, and attaching the liner sheet that connects the tops of the caps. Follow the order of matching. If a sheet having a high temperature is bonded to a sheet having a low temperature, the degree of shrinkage is larger in the latter when cooled, and warping inevitably occurs due to a so-called bimetal effect. The bubble sheet type plastic hollow plate is asymmetric in terms of structure and thermal history with respect to the center plane of the product. For this reason, warpage occurs both in the width direction and in the length direction of the hollow plate.
[0007]
[Problems to be solved by the invention]
An object of the present invention is to solve the above-mentioned problems relating to the production of a bubble sheet type plastic hollow plate and to provide a method for producing a plastic hollow plate in which the warp is eliminated to a practically acceptable level. Providing an apparatus for carrying out the manufacturing method is also included in the object of the present invention.
[0008]
[Means for Solving the Problems]
The plastic hollow plate manufacturing method of the present invention includes a cap sheet (I) having a large number of caps, a flat back sheet (II) bonded to the cap bottom of the cap sheet, and a top of the cap as shown in FIG. In the method for producing a plastic hollow plate composed of three layers of another flat liner sheet (III) bonded together, the method comprises the following steps.
A) A cap sheet having a large number of caps by vacuum forming a plastic sheet in a thermoplastic state using a forming roll provided with a number of dents in a rotating metal cylinder and the bottom of the dent connected to a vacuum suction source. Forming,
B) A back sheet is bonded to a cap sheet to form a two-layer product,
C) The two-layer product is made into an elastic body with a uniform temperature distribution,
D) Stretching the two-layer product in the elastic body state in the width direction on the stretching means in the width direction by an amount substantially corresponding to the shrinkage of the liner sheet,
E) The two-layer product stretched in the width direction is passed through a mountain-shaped passage where the cap side is expanded, and is expanded in the flow direction by an amount substantially commensurate with the shrinkage of the liner sheet. The liner sheet in a thermoplastic state is bonded to form a three-layer product, and F) the three-layer product is contracted as the liner sheet contracts.
[0009]
The plastic hollow plate manufacturing apparatus of the present invention for carrying out the above method is an apparatus having the following components as essential components as shown in FIG.
A) a forming roll (2) having a number of dents and vacuum suction means for forming a plastic sheet for the cap sheet (I) in a thermoplastic state into a cap sheet by vacuum forming;
(B) a pressure roll (3) for attaching a back sheet (II) to the bottom surface of the cap sheet (I) formed on the forming roll to obtain a two-layer product;
C) Heating means (4) for contacting the smooth side of the two-layer product and heating the two-layer product to a uniform temperature, such as a heated roll group or oven,
D) Stretching means (5) for stretching the two-layer product heated to a uniform temperature in the width direction,
E) Means for forming a mountain path for expanding the cap side by contacting the smooth side of the two-layer product extending in the width direction, and f) Liner sheet (III) on the cap side of the two-layer product A pressure roll (8) for laminating and forming a three-layer product (V).
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The production method of the present invention succeeded in significantly reducing warpage as a result by reducing the influence of heat shrinkage that causes distortion on the product plastic hollow plate as follows.
[0011]
That is, first, when the cap sheet and the back sheet are bonded together, a higher temperature back sheet is bonded to the cap sheet that has been slightly cooled by touching the vacuum forming roll, so that the cooling shrinkage of the back sheet is greater. However, considering the cross section, the cap sheet is inside the concentric circle and the back sheet is outside, so as far as the flow direction is concerned, the back sheet with larger shrinkage is placed in a longer path in advance. In the latter two-layer product, the warpage in the flow direction is small.
[0012]
In the bilayer product, the strain in the width direction remains, but it is reduced by subsequent heating and stretching. This heating is performed on the two-layer product so that strict temperature control such as ± 1 ° C. is realized over the entire length in the width direction and over a certain length in the length direction. As a means, an array of heating rolls is appropriate, but an oven may be used.
[0013]
The most common means for stretching the two-layer product subjected to temperature control in the width direction is a tenter frame as shown. Another effective means is an expander roll. By running the two-layer product along the surface of the spindle-shaped roll, the sheet shape is expanded in the middle, and stretching in the width direction is performed. If attention is paid to the liner sheet, it is inevitable that a slight neck-in occurs after being pushed out from the T-die, and accordingly, the shrinkage rate during cooling also varies slightly depending on the location in the width direction. Since this difference is unique to the plastic material and the T-die, the curvature of the expander roll may be changed depending on the location.
[0014]
Since the stretched two-layer product is in an elastic state at the time when the liner sheet is bonded, when the liner sheet is cooled and contracts after bonding, the two-layer product also contracts, causing the liner sheet to contract. Follow. In this way, the warp in the three-layer product, particularly the warp in the width direction, is reduced.
[0015]
When the liner sheet is bonded to the top of the cap of the two-layer product, as shown in FIG. 4, the cap side is expanded by passing the mountain-shaped passage through the two-layer product, and the bonding is performed in that state. This chevron shape is similar to the relationship between the cap sheet and the back sheet in a vacuum forming roll, and allows a longer path for liner sheets that are hotter and have greater shrinkage on cooling, in other words. For example, a liner sheet is supplied to the long side to prepare for contraction in the longitudinal direction.
[0016]
There can be various modes for forming a mountain path. The illustrated example is a combination of the scallop stencil plate (6) and the two regulating rolls (7A, 7B). In addition to this, one large-diameter roll is disposed along a mountain path. A group of small-diameter rolls and an endless belt supported by a plurality of rolls can be used. These are preferable because the equipment is complicated, but sliding with the back sheet can be avoided. The small-diameter roll group can adjust the shape and length of the mountain path, which is advantageous.
[0017]
In this way, in the present invention, when the three layers are stacked, the length of the sheet to be supplied is changed in advance according to the difference in the degree of cooling and shrinkage of each layer, and the strain is reduced by heating and stretching. And the final strain remaining in the plastic hollow plate as a whole was successfully removed.
[0018]
Even with the above-described process, warping may not be completely eliminated because strain remains. As a countermeasure, it is recommended to anneal the three-layer product, that is, to maintain the product at a temperature lower than the softening point of the material for several minutes to several tens of minutes and then cool it slowly. .
[0019]
Since the three types of sheets constituting the plastic hollow plate of the present invention, that is, the plastic sheets for the cap sheet, the back sheet, and the liner sheet are all processed in a thermoplastic state, the T-die is used. It is advantageous to use melt extruded plastic sheets. As shown in FIG. 2, if all three sheets are melt-extruded and supplied from T-dies (1A, 1B, 1C), a complete in-line operation is possible.
[0020]
However, the same processing conditions, that is, the state of being thermoplasticized, can also be realized by winding these separately-manufactured sheets on a reel and then feeding them out to contact a heating roll and heating them to a required temperature. In some cases, direct melt extrusion from the above-mentioned T-die and plasticization with a heating roll can be used in combination. One or two of the three types of sheets are supplied from the T-die, and the remaining two or one is heated by a heating roll.
[0021]
The material for the plastic hollow plate of the present invention is not particularly limited as long as it is thermoplastic and can be made into a sheet, but polyethylene and polypropylene, which are particularly useful as materials for the plastic foam sheet, are also suitable here. It can be used. The behavior of heat shrinkage is unique to each plastic material, and it is safe to use the same material for the three layers, but if you fully understand the behavior, you can adjust the above-mentioned stretching ratio accordingly. It is also possible to use a combination of different materials.
[0022]
The sheet thickness and basis weight of the product, as well as the cap diameter and height, placement and density, etc., are the physical properties desired in relation to the plastic hollow plate application, such as the buckling strength in the plane direction, perpendicular to the plane. It is selected according to the compressive strength in the direction and processing characteristics such as cutting, bending, and other workability. With regard to automotive interior materials, packaging box materials, etc. that are currently being deployed as plastic hollow plate applications, the sheet thicknesses are generally in the following ranges,
Cap sheet: 250-1500 μm,
Back sheet: 125-800 μm,
Liner sheet: 125-1200 μm
This thickness corresponds to 450 to 3000 g / m ² in basis weight.
[0023]
The cap diameter is generally in the range of 3-15 mm and the height is generally in the range of 3-15 mm accordingly. Arrangement can be arbitrarily selected, such as staggered arrangement, lattice arrangement, and oblique lattice arrangement. The staggered arrangement performed on the bubble sheet is preferable in that it has no directionality, but the lattice arrangement is advantageous for cutting and bending. Products with no characteristic directionality are caps arranged in a square grid, but if it is rather desirable to have some directionality in the vertical and horizontal directions, the density of the cap should be reduced. What is necessary is just to change with directions.
[0024]
Needless to say, an optional additive such as a colorant, a filler, an antioxidant, an antistatic agent, an antibacterial agent, and a combustion aid can be added to the plastic hollow plate of the present invention.
[0025]
【Example】
Using HIPP “Sumitomo Noblen” (manufactured by Sumitomo Chemical) as the material, the plastic hollow structure using the apparatus shown in FIG. 2 and all three types of sheets are extruded and supplied from the T-die. A board was produced. The extrusion thickness of the three types of sheets is as follows:
Cap sheet: 670 μm
Back sheet: 370 μm
Liner sheet: 635 μm
The caps have an outer diameter of 5 mm, a pitch of 8 mm, and a 15 ° inclined arrangement.
[0026]
The two-layer product obtained by bonding the cap sheet and the back sheet was soaked with a soaking roll so that the temperature difference in the width direction was within 100 ± 1 ° C. This was stretched 2.5% in the transverse direction in a tenter. The temperature of the two-layer product stretched with a tenter dropped to about 90 ° C., and a liner sheet having a temperature of about 230 ° C. was placed thereon and bonded with a pressure roll to form a three-layer product. The subsequent annealing is performed by staying for about 5 seconds in a heating tunnel with an infrared heating lamp arranged on the extension of the same tenter and having an ambient temperature of about 150 ° C., and then cooling to room temperature over 1 minute. It was. After cooling, the edge was cut off to a width of 1000 mm and cut into a standard length of 2000 mm.
[0027]
The resulting three-layer plastic hollow plate has a thickness of 5 mm and a basis weight of 1500 g / m ² . The warpage and mechanical strength of this product were measured. To warp, cut a 100cm square sample from the product, place it on a flat plate, measure the height of the highest part,
Warpage = {(height-plate thickness) / 100 (each side)} × 100 (%)
Calculated as The results are as follows.
Warpage: 1.5% in the width direction and 1.0% in the length direction
Buckling strength in the plane direction: 1.3 MPa
Compressive strength of method perpendicular to the plane: 46.4 Pa (MD), 49.4 Pa (TD)
[0028]
【The invention's effect】
If a plastic hollow plate is produced according to the production method of the present invention, the shrinkage of the back sheet and liner sheet occurring in the course of production is anticipated in advance, and the sheet material is stacked in a form giving the corresponding elongation, and the cap sheet / back sheet By taking the steps of manufacturing the two-layer product and the three-layer product to which the liner sheet is added, a hollow plate in which the final warpage of the hollow plate is substantially eliminated can be obtained.
[Brief description of the drawings]
FIG. 1 is a perspective view for explaining the structure of a plastic hollow plate of the present invention.
2 is a cross-sectional view of the main part of the apparatus for explaining the outline of the method and apparatus for producing a hollow plate of the present invention. FIG. 3 shows a width direction extending means (tenter frame) portion of the apparatus of FIG. Plan view.
4 is a side view showing a part of a flow direction expanding means (kamaboko stencil) of the apparatus of FIG. 2;
[Explanation of symbols]
1A, 1B, 1C T-die 2 Forming rolls 3, 8 Pressure roll 4 Heating means 5 Stretching means (tenter frame)
6 Kamaboko template 7A, 7B Regulating roll 9 Annealing-cooling device I Cap sheet
II Back seat
III Liner sheet
IV Two-layer product V Three-layer product
VI Plastic hollow plate

Claims (8)

A plastic hollow composed of three layers: a cap sheet having a large number of cap-shaped protrusions, a flat back sheet bonded to the cap bottom of the cap sheet, and another flat liner sheet bonded together by connecting the top of the cap. A method for producing a plate, comprising the following steps:
A) A plastic sheet in a thermoplastic state is vacuum formed using a forming roll in which a number of dents are provided in a rotating metal cylinder and the bottom of the dent is connected to a vacuum suction source, and a number of cap-shaped protrusions are formed. Forming a cap sheet,
B) A back sheet is bonded to a cap sheet to form a two-layer product,
C) The two-layer product is made into an elastic body with a uniform temperature distribution,
D) Stretching the two-layer product in the elastic body state in the width direction on the stretching means in the width direction by an amount substantially corresponding to the shrinkage of the liner sheet,
E) The two-layer product stretched in the width direction is passed through a mountain-shaped passage where the cap side is expanded, and is expanded in the flow direction by an amount substantially commensurate with the shrinkage of the liner sheet. The liner sheet in a thermoplastic state is bonded to form a three-layer product, and F) the three-layer product is contracted as the liner sheet contracts. The manufacturing method of the plastic hollow plate which implements the following processes following the processes prescribed | regulated to Claim 1.
G) Annealing the contracted three-layer product to remove the strain, and then cooling to obtain a product. The production method according to claim 1 or 2, wherein one, two or three plastic sheets for a cap sheet, a back sheet and a liner sheet are used in a thermoplastic state melt-extruded from a T-die. 2. One, two, or three plastic sheets for a cap sheet, a back sheet, and a liner sheet are used by bringing a ready-made sheet out of a reel and making contact with a heating roll to be in a thermoplastic state. Or the manufacturing method of 2. The production method according to claim 1 or 2, wherein the stretching ratio by the stretching apparatus is selected from a range of 0.1 to 6%. Plastic hollow plate (VI) manufacturing equipment with the following components as essential components:
A) Forming roll (2) having a number of dents and vacuum suction means for forming a plastic sheet for a cap sheet in a thermoplastic state into a cap sheet by vacuum forming;
B) A pressure roll (3) for obtaining a two-layer product (IV) by attaching a back sheet to the bottom surface of the cap sheet formed on the forming roll.
C) heating means (4) for contacting the smooth side of the two-layer product and heating the two-layer product to a uniform temperature;
D) Stretching means (5) for stretching the two-layer product heated to a uniform temperature in the width direction,
E) Means for forming a mountain-shaped passage for expanding the cap side by contacting the smooth side of the two-layer product extending in the width direction, and f) A liner sheet being bonded to the cap side of the two-layer product A pressure roll (8) for making a three-layer product (V). One of the following means to form a mountain path,
・ One large diameter roll,
-A group of small diameter rolls arranged along a mountain path,
An endless belt supported by a plurality of rolls, and a slab plate (6) arranged in the width direction,
The manufacturing apparatus of Claim 6 which is a combination with two control rolls (7A, 7B). A manufacturing apparatus having the following components in addition to the components defined in claim 6.
G) An annealing-cooling device (9) for annealing and cooling the three-layer product to obtain a product.

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