JPH0839673A - Mold and method for thermally fusing foamed plastic sheet - Google Patents

Abstract

PURPOSE:To improve the thermally fused part of a foamed plastic sheet, especially, a soft polyurethane foam sheet so as not to form a stress conc. part becoming a defect against pulling to the thermally fused part. CONSTITUTION:In a mold for thermally fusing a foamed plastic sheet having a pressing surface consisting of a pressing plane 4 and the shoulder part 5 continuing thereto, the angle Y formed by the plane 5 forming the shoulder part and the pressing surface 4 is 135-170 deg. and a plurality of grooves connecting the pressing plane and a leg part are formed to the surface of the shoulder part 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sealing die for a foamed plastic sheet, particularly for a polyurethane foam sheet, and a method for heat-sealing a polyurethane foam sheet by the heat-sealing die.

[0002]

2. Description of the Related Art With the advent of various foamed plastics, the foamed plastics have come to be used in various fields by taking advantage of their features such as light weight, heat insulation and bulkiness. Along with this, processing such as adhesion has come to be added to foamed plastics and foamed plastic sheets. Thermal bonding is often used for bonding. However, the foamed sheet thus fused is apt to be broken at a stress-concentrated point in the vicinity of the fused portion when a tensile stress is applied thereto.

In recent years, clothes are carried in a state where they are hung on a hanger for the purpose of rationalizing the transportation. In this case, a flexible polyurethane foam sheet is attached to the hanger in order to prevent the clothes from falling due to falling or shifting. Have been devised to cover. The polyurethane foam sheet for hangers used for this purpose is obtained by folding a flat polyurethane foam sheet into two layers, and heat-bonding both ends of the hangers, which are shoulders, to form a bag-shaped molded body.
When the hanger is coated with the molded product, the molded product is stretched and coated, but at this time, a fracture often occurs at the heat-sealed portion of the molded product.

In order to heat-bond the polyurethane foam sheet in the production of this molded product, a heating mold having a pressing protrusion whose cross-sectional shape is shown in FIG. 3C has been used. Since the polyurethane foam sheet molded body heat-sealed by this mold is likely to break at the heat-sealed portion, an improved mold has been devised to form a groove on the pressing plane at the upper end of the pressing protrusion. It was Although the tensile strength of the fusion-bonded part was improved to some extent by this, it is not yet satisfactory.

[0005]

DISCLOSURE OF THE INVENTION The object of the present invention has been improved such that the heat-sealed portion of a foamed plastic sheet, in particular a flexible polyurethane foam sheet, does not have a stress concentration portion which would be a defect against pulling. It is to provide a mold for heat fusion. Another object of the present invention is to provide a method for fusing a foamed plastic sheet, particularly a flexible polyurethane foam sheet, which is free from defects with respect to tensile stress, by using the above improved heat-sealing die.

[0006]

DISCLOSURE OF THE INVENTION The present invention is a mold for heat-sealing a foamed plastic sheet, the pressing surface of which comprises a pressing flat surface 4 and a shoulder portion 5 following the pressing flat surface. The angle Y formed by the flat surface 5 forming the portion and the pressing flat surface 4 is 135 to 170 °, and a plurality of grooves for connecting the pressing flat surface and the leg portions are formed on the surface of the shoulder portion 5 to form a heat fusion mold. Is. The shoulder portion 5 extends from the pressing plane to the protrusion leg portion 3
It may be formed of a convex curved surface that is smoothly connected to the bottom. Further, according to the present invention, a plurality of polyurethane foam sheets to be fused are sandwiched between the pressing projection 2 and the pressure plate of the heat fusion mold, and the polyurethane foam sheet is used as a fusion mold and a pressure plate. It is a method for adhering a polyurethane foam sheet in which pressure is applied between the two and the heat is applied from the protrusions of the die for fusion.

The features of the mold of the present invention will be described below. The difference between the conventional mold and the mold of the present invention is apparent by comparing FIG. 3 showing the cross section of the pressing protrusion 2 which is the heat-sealed portion of the mold. FIG. 3C shows the pressing protrusion 2 of the conventional mold.
FIG. 4 is a cross-sectional view of the pressing plane 4, which is a horizontal plane, and the projection leg portion 3 that is substantially perpendicular to the pressing plane 4 form a sharp edge substantially orthogonal to each other. On the other hand, in the mold of the present invention, as shown in (a) and (b) of the cross-sectional shape, the pressing plane 4 and the leg portion 3 are not directly connected to each other, but the shoulder portion 5 is interposed therebetween. Is provided. In the example of (a), the shoulder is flat,
That is, the cross section has a linear shape, and the example (b) has a convex curved surface with a smooth shoulder. Therefore, in the cases of (a) and (b), there are no sharp edges. The presence of such shoulders has the following effects. That is, FIG. 4 shows an enlarged cross-sectional view of the state of the heat-sealed portion of the flexible polyurethane foam sheet heat-sealed by the respective molds of FIG. The shaded portion means the molten state. FIG. 4C is an enlarged cross-sectional view of the fused portion of the polyurethane foam sheet fused by the conventional mold (FIG. 3C). The melted portion and the non-melted portion are distinctly separated from each other at the portion corresponding to the edge portion of the mold, and the thickness of the sheet, and thus the density, changes discontinuously. On the other hand, the fusion-bonded portion of the heat-fusion-bonded product of the mold of the present invention ((a) and (b) in FIG.
As shown in (a) and (b), there is a mixed region where the melting ratio changes continuously between the molten part and the non-melted part, and the thickness and density of the sheet change continuously. are doing. For this reason, when tensile stress is applied, stress concentrates at the density discontinuity corresponding to the edge in FIG. 4C, and breakage easily occurs. In contrast, in the cases of (A) and (B) Has no stress concentration, and this part does not become a defect against tensile stress.

In the mold of the present invention, as shown in FIG. 1, a plurality of grooves 6 for connecting the pressing plane and the legs may be formed on the surface of the shoulder portion 5. The groove 6 further improves the strength of the fused portion.

The height from the flange surface to the pressing plane in the protrusion of the mold of the present invention is not particularly limited and is determined in consideration of the thickness of the foamed plastic sheet. For example, in the case of a flexible polyurethane foam sheet having a thickness of 4 mm, about 4 to 7 mm is preferable. Pressing plane 4
The width is also not particularly limited, and is preferably 2 to 4 mm for a flexible polyurethane foam sheet for hangers. If it is larger than this, the fusion zone becomes wide and the design is inferior in appearance, and if it is smaller than this, the fusion strength tends to be insufficient. The thickness of the protrusion is between 1.1 and 3 times the width of the pressing plane.

The angle Y ((a) in FIG. 3) formed by the plane 5 forming the shoulder and the pressing plane is 135 to 170 °, preferably 135 to 160 °. If the shoulder is a curved surface, the cross section is the same curve everywhere,
In addition, the curve may be smooth, that is, a curve having no inflection point.

The material for forming the mold is preferably a material having a high specific heat, and any material having a high thermal conductivity can be used, but aluminum, copper or brass can be used.

A foamed plastic sheet is fused using the mold of the present invention as follows. The foamed plastic sheets are overlapped with the portions to be bonded together, set between the mold and the pressure plate, and then the foamed plastic sheet is sandwiched between the pressure plate and the mold, and the protrusions of the mold are pressed against each other. Here, the mold is heated to a predetermined temperature. Then, pressure is applied for a predetermined time to fuse the foamed sheet of the protruding portion.

The protrusion may be preheated as described above, or a high voltage is applied in a pulsed manner to rapidly heat the pressing surface portion when the protrusion and the pressure plate are pressed. You may do it.

The heating temperature of the protrusions should be higher than the softening point of the foamed plastic sheet to be heat-sealed, and if the foamed plastic sheet is a flexible polyurethane foam, it is preferably about 230 to 330 ° C. Pressurized pressure is 5 to 20 kg / cm ² , preferably 8 to 15 kg
/ Cm ² . Pressurization time depends on the type of foamed plastic,
It should be judged according to the mold temperature, the pressurizing pressure, and each device, and the fusion state,
On the contrary, from the viewpoint of productivity, the temperature and pressure should be set so that the pressurizing time is about 0.5 to 2 seconds.

Although not an essential condition, the surface of the protrusion and the pressure plate which are in contact with the fused portion of the foamed plastic sheet to be fused are subjected to permanent mold release processing (for example, coating with a fluororesin sheet), or It is preferable to apply the release agent every time.

Next, specific examples of the present invention will be shown by examples. Example 1 A flexible polyurethane foam sheet containing a polyether polyol and tolylene diisocyanate as main components (apparent density: 20 kg / m ³ , thickness: 4 mm) corresponding to (a) in FIG. 3 with the following specifications: Shoulder shape: plane Angle between shoulder and pressing plane Y: 160 ° Width of pressing plane: 2 mm Shape of groove provided on shoulder: width 0.3 mm, depth 0.3 mm,
Pitch 1.5 mm Thickness of protrusion: 4 mm Height of protrusion: 5 mm Material: Aluminum and a flat plate made of aluminum and fusion-bonded.
Heat fusion is assumed to be used for a hanger cover, and the flexible polyurethane foam sheet is folded in two and stacked, set between a pressure plate and a mold, sandwiched between the pressure plate and the mold to apply pressure, and a straight line is formed. Heat-bonded into a shape.

The fusion conditions were as follows: surface temperature of the pressing plane: 280 ° C. (set heating by a heater), pressure: 10 kg / cm ^2, pressurization time: 0.7 seconds.

In order to evaluate the strength of the fusion-bonded portion, a strip having a linear fusion-bonded portion in the center and having a lengthwise direction perpendicular thereto was cut out as a test piece. The dimensions of the strip are 16 cm in length and 7 cm in width (including the fused part in the full width).
Met. Five test pieces were prepared and the breaking strength was measured with a tensile tester. The average strength was 0.90 kgf.

Comparative Example 1 Conventional Die Corresponding to (c) of FIG. 3 Width of pressing plane = thickness of protrusion: 4 mm Height of protrusion: 5 mm Groove shape in pressing plane: width 0.3 mm, Depth 0.3 mm, pitch 1.5 mm Material: The same flexible polyurethane foam sheet was fused under the same conditions using aluminum and a flat plate made of aluminum. The average tensile strength of the obtained fused sheet is 0.65.
It is kgf.

[Brief description of drawings]

FIG. 1 is an overall view of a mold for heat fusion.

FIG. 2 is an enlarged perspective view of a heat-sealed portion of a mold.

FIG. 3 is a sectional view showing the shape of a heat-sealed portion of a mold.

FIG. 4 is a model view of an enlarged cross section of a fused portion of a foamed plastic sheet heat-sealed with a mold having the cross-sectional shape of FIG.

[Explanation of symbols]

1 flange, 2 pressing protrusions, 3 legs, 4 pressing plane, 5 shoulders, 6 grooves, 7
Heater wire, 8 insulation, 9 support.

Claims (6)

[Claims] 1. A mold for heat-sealing a foamed plastic sheet, the pressing surface of which comprises a pressing flat surface 4 and a shoulder portion 5 following the pressing flat surface 4. 2. The mold for heat-sealing a foamed plastic sheet according to claim 1, wherein an angle Y formed by the flat surface 5 forming the shoulder portion and the pressing flat surface 4 is 135 to 170 °. 3. The mold for heat-sealing a foamed plastic sheet according to claim 1, wherein the shoulder portion 5 has a convex curved surface which is smoothly connected from the pressing plane to the protrusion leg portion 3. 4. The mold for heat-sealing a foamed plastic sheet according to claim 1, wherein a plurality of grooves connecting the pressing plane and the legs are formed on the surface of the shoulder portion 5. 5. The mold for heat fusion according to claim 1, wherein the foamed plastic sheet is a flexible polyurethane foam sheet. 6. A plurality of polyurethane foam sheets to be fused are sandwiched between the pressing protrusion 2 and the pressure plate of the heat-sealing die according to any one of claims 1 to 4, and the polyurethane foam sheet is A method for fusing a polyurethane foam sheet, comprising applying pressure between a fusing die and a pressure plate and fusing with heat from a protrusion of the fusing die.