JP7041834B2 - Molding method - Google Patents

Description

The present invention relates to a molding method for molding a composite molded body in which a skin sheet is integrated, and more particularly to an improvement in integrally molding a skin sheet having a solid layer such as synthetic leather.

For example, in the case of a lid panel for a luggage compartment of an automobile such as a floor panel of an automobile or a large board, a skin sheet such as a non-woven fabric is attached to the surface of the panel in order to improve the feel of the surface and give a design effect. It is used (for example, Patent Document 1, Patent Document 2, etc.).

On the other hand, with the diversification of utilization methods for automobile luggage compartments, etc., in addition to the conventional non-woven fabric-bonded panel, a resin sheet with a three-dimensional pattern such as a grain pattern is integrally welded. Etc. are also being requested. In this type of panel, synthetic leather or the like is used as the skin sheet.

For example, Patent Document 3 describes a molding method in which a coating layer (skin sheet) is heated and integrally attached at the time of blow molding. The skin sheet is made by adhering a non-woven fabric to soft PVC, and has an uneven pattern of a mold. Is described as being transcribed.

Japanese Unexamined Patent Publication No. 1-34720 Japanese Unexamined Patent Publication No. 2000-289095 Japanese Unexamined Patent Publication No. 62-255117

By the way, in a molding method in which a molten resin is generally sandwiched between molds and shaped, the molded product is cooled to a shape retention temperature in the mold, then released from the mold and further cooled to room temperature by natural heat dissipation. At this time, in order to promote cooling of the molded product in the mold, cold water is introduced into the jacket of the mold to lower the cavity surface temperature of the mold.

However, in the molding of the composite molded body in which the skin sheet is attached to the surface and integrated as described above, the molding conditions are different between the side to which the skin sheet is attached and the opposite side. Therefore, after being taken out from the mold, molding defects such as warpage tend to occur easily. The occurrence of warpage is not preferable from the viewpoint of stabilizing the product quality of the composite molded product.

The present invention has been proposed in view of such conventional circumstances, and an object of the present invention is to provide a molding method capable of molding a product having excellent quality stability without causing warpage during molding. And.

In order to achieve the above-mentioned object, in the molding method of the present invention, the skin sheet is placed between the split mold of one of the pair of split dies and the molten resin, and the skin sheet is attached to a part of the wall surface. A molding method for molding a worn hollow molded body, wherein the skin sheet has a resin layer that has substantially no voids or air bubbles, and is the same as the skin sheet in the pair of split dies. It is characterized in that the mold temperature of the facing first split mold is set higher than the mold temperature of the second split mold in direct contact with the molten resin within a temperature difference of 30 ° C. or less.

In the molding of a composite molded body having a skin sheet, the thermal conditions differ between the molten resin that comes into contact with the mold via the skin sheet and the molten resin that comes into contact with the mold without passing through the skin sheet on the opposite side. Therefore, molding defects such as warpage are likely to occur.

When the skin sheet is a material with voids and bubbles such as non-woven fabric and foamed resin, it functions as a heat insulating material, so the temperature of the mold on the side to which the skin sheet is attached is the temperature in the process until the molded product reaches room temperature. However, the temperature of the mold on the side where the skin sheet is not attached continues to be higher than the temperature of the mold, and due to this temperature difference, the shrinkage rate due to the cooling of the molten resin becomes uneven. As a result, molding defects such as warpage occur in the molded body after mold release.

In order to avoid such inconvenience, the applicant of the present application lowers the cavity surface temperature of one of the pair of split dies that forms the wall on the side to which the heat insulating sheet such as non-woven fabric is attached. However, we have previously proposed a method of blow molding while keeping the cavity surface temperature of the other mold for forming the wall on the side to which the heat insulating sheet is not attached higher than the cavity surface temperature of one mold (Japanese Patent Laid-Open No. 2000). -Refer to Gazette No. -238119). The temperature of the wall on the side where the heat insulating sheet of the molded product (hollow molded product) is attached is lowered from the beginning to the temperature of the wall on the side where the heat insulating sheet is not attached, and the molded product is cooled and released in the mold. By keeping the whole in an equilibrium state in the subsequent cooling process, it is possible to obtain a highly accurate hollow molded product without deformation strain.

However, when a skin sheet having a resin layer having no voids or bubbles such as synthetic leather is used, the wall on the side to which the heat insulating sheet such as a non-woven fabric is attached is formed at the above temperature setting (a pair of split dies). Even if the cavity surface temperature of one mold is lowered and the wall on the side where the heat insulating sheet is not attached is formed, the cavity surface temperature of the other mold is set higher than this), warpage and the like can be formed. The occurrence of defects cannot be eliminated.

Therefore, as a result of further studies by the applicant of the present application, in the case of a skin sheet having a resin layer having no voids or bubbles such as synthetic leather, the heat capacity of the skin sheet is larger than that of a heat insulating sheet such as a non-woven fabric, and it comes into contact with the skin sheet. It was concluded that thermal imbalance may occur due to the promotion of heat dissipation of the molten resin, which may cause warpage and the like. Further, in the case of an epidermis sheet having a resin layer having no voids or bubbles such as synthetic leather, the flexibility is lower than that of a heat insulating sheet such as a non-woven fabric, which may also affect the moldability. Guessed.

The invention of the present application was devised based on such findings. In the molding method of the present invention, the mold temperature of the first split mold facing the skin sheet is set higher than the mold temperature of the second split mold directly in contact with the molten resin, so that the skin sheet is set. The thermal imbalance caused by the heat capacity and the like is eliminated, and by raising the temperature of the skin sheet, flexibility is imparted to the skin sheet, and molding defects such as warpage are eliminated. If the temperature difference exceeds 30 ° C, warpage in the opposite direction may occur. Therefore, the mold temperature of the first split mold is set to the second split mold within the range of the temperature difference of 30 ° C or less. Set higher than the mold temperature of the mold.

According to the present invention, in the molding of a composite molded body in which a skin sheet having a resin layer having no voids or air bubbles like synthetic leather is attached to the surface and integrated, warpage or the like does not occur during molding, and the quality is improved. It is possible to provide a molding method capable of molding a product having excellent stability.

It is a schematic perspective view which shows the composite molded body to be molded and a part thereof enlarged and broken. It is a figure which shows the molding method of a composite molded body, and is the figure which shows the process of hanging a molten resin sheet. It is a figure which shows the shaping process of a molten resin sheet. It is a figure which shows the insertion process of a reinforcing material. It is a figure which shows the mold clamping process. It is a figure which shows the mold opening process.

Hereinafter, embodiments of the molding method to which the present invention is applied will be described in detail with reference to the drawings.

First, the configuration of the skin-integrated molded complex 1 molded by the molding method of the present embodiment will be described. As shown in FIG. 1, the skin-integrated composite 1 has a front surface FS and a back surface BF, and has a substantially rectangular parallelepiped shape. As shown in the enlarged fracture view in FIG. 1, the skin integrally molded composite 1 is a resin laminate 2 in which a first resin sheet 21 and a second resin sheet 22 are laminated, and a first resin sheet 21. Includes a skin sheet 23 provided on the front surface side. The front surface of the skin sheet 23 constitutes the front surface FS of the skin integrally molded composite 1. A hollow portion is formed between the first resin sheet 21 and the second resin sheet 22, and a parting at the time of resin molding is formed at the boundary between the first resin sheet 21 and the second resin sheet 22. A line PL is formed.

The first resin sheet 21 and the second resin sheet 22 are thermoplastic resins. The resin material is not limited, and may be a foamed resin or a non-foamed resin, but it is preferably formed from the non-foamed resin in order to secure the rigidity of the skin integrally molded composite 1. From the viewpoint of preventing variations in wall thickness due to drawdown, neck-in, etc. during molding, it is preferable to use a resin material with high melt tension, while improving transferability and followability to the mold. Therefore, it is preferable to use a resin material having high fluidity. As an example of the resin material of the first resin sheet 21 and the second resin sheet 22, any one of polyolefins such as polypropylene and polyethylene, acrylic derivatives such as polyamide, polystyrene and polyvinyl chloride, or a mixture of two or more kinds is used. Can be mentioned.

The first resin sheet 21 and the second resin sheet 22 may be molded using a resin material mixed with a glass filler for the purpose of increasing rigidity and strength. Examples of the glass filler include glass fiber, glass fiber cloth such as glass cloth and glass non-woven fabric, glass beads, glass flakes, glass powder, and milled glass. Examples of the type of glass include E glass, C glass, A glass, S glass, D glass, NE glass, T glass, quartz, low dielectric constant glass, high dielectric constant glass and the like. Not limited to the glass filler, talc, calcium carbonate, wollastonite, an inorganic filler such as a magnesium-based material, carbon fiber, or the like may be mixed to increase the rigidity.

The skin sheet 23 is configured for the purpose of improving the aesthetic appearance or decorativeness of the skin integrally molded complex 1 or protecting an object that comes into contact with the skin integrally molded composite 1. In the present embodiment, as the skin sheet 23, a skin sheet 23 having a resin layer having substantially no voids or bubbles is used. In this case, the skin sheet 23 may be composed of only the resin layer, or may be a laminated body including the resin layer. For example, synthetic leather in which a non-woven fabric or the like is lined (laminated) on a resin layer such as a polyvinyl chloride (PVC) layer is also suitable. Examples of the resin layer include a polyurethane (PU) layer and the like in addition to the PVC layer.

Further, the resin layer of the skin sheet 23 does not have substantially voids or bubbles, but this refers to a so-called solid layer. Specifically, it is a resin layer having a density of 90% or more with respect to the density (true density) when the resin layer is formed of a 100% resin material without containing any voids or bubbles. When the resin layer of the skin sheet 23 does not substantially contain voids or bubbles and has a density of 90% or more of the true density, the first resin sheet to be arranged on the back side thereof is used. Since it becomes difficult to shape the mold into a mold, it is preferable to make fine holes in the solid resin layer later, and the resin layer having such fine holes also has substantially voids and bubbles. It shall be contained in the resin layer which does not have.

The basis weight of the skin sheet 23 is arbitrary and may be appropriately selected depending on the intended use. For example, the basis weight of the entire skin sheet 23 is preferably about 500 g / m ² to 1000 g / m ² . In the case of the skin sheet 23 in which the resin layer is lined with a non-woven fabric, the basis weight of the resin layer is preferably about 400 g / m ² to 900 g / m ² , and the basis weight of the non-woven fabric is preferably about 50 g / m ² to 300 g / m ² .

Next, a method for molding the skin-integrated molding complex 1 will be described. As a configuration of the molding device, as shown in FIG. 2, the molding device 100 of the resin molded product has an extrusion device 120 and a mold clamping device 140 arranged below the extrusion device 120.

Further, as shown in FIG. 2, the extruder 120 includes two systems of molten resin extrusion mechanisms. That is, in the extruder 120, the cylinders 18A and 18B to which the hoppers 16A and 16B are attached, the hydraulic motors 20A and 20B connected to the cylinders 18A and 18B, respectively, and the accumulator 24A in which the cylinders 18A and 18B and the inside communicate with each other, respectively. , 24B and plungers 26A, 26B. The plungers 26A and 26B are interpolated in the accumulators 24A and 24B, respectively. By driving the plungers 26A and 26B, the plungers 26A and 26B are moved forward and backward in the accumulators 24A and 24B, whereby the contents of the accumulators 24A and 24B. The product is variable. The extruder 120 is provided with a hydraulic cylinder (not shown) for driving the plungers 26A and 26B.

In the extruder 120, the thermoplastic resin charged from the hoppers 16A and 16B is melted and kneaded by the rotation of the screw by the hydraulic motors 20A and 20B in the cylinders 18A and 18B, and the resin in a molten state (hereinafter, "molten resin"). Also referred to as) is transferred to the accumulators 24A and 24B and stored in a certain amount. The molten resin stored in the accumulators 24A and 24B is supplied to the T-die 28 through the valve 27 by driving the plungers 26A and 26B. That is, the plungers 26A and 26B are driven to reduce the internal volume of the accumulators 24A and 24B, and the molten resin stored inside the accumulators 24A and 24B is pressurized and sent to the T dies 28A and 28B to send the molten resin. It is designed to generate an extrusion pressure to.

The T-dies 28A and 28B push the supplied molten resin downward from the extrusion slit as continuous sheet-shaped molten resin sheets P and P. The extruded molten resin sheets P and P are sent downward while being sandwiched by a pair of rollers 40AA and 40AB and a pair of rollers 40BA and 40BB arranged at intervals, and are sent downward to the split dies 42A and 42B. It hangs down in between.

The mold clamping device 140 has split molds 42A and 42B. The split dies 42A and 42B are provided with sliding portions 43A and 43B, respectively. The sliding portions 43A and 43B face each other. The sliding portion 43A is slidable in a direction orthogonal to the molten resin sheet P (that is, in a horizontal direction), whereby is configured to be movable relative to the forming surface 116A of the split mold 42A. Similarly, the sliding portion 43B is slidable in a direction orthogonal to the molten resin sheet P (that is, in a horizontal direction), whereby the sliding portion 43B is configured to be movable relative to the forming surface 116B of the split mold 42B. ing.

In order to mold the skin integral molding composite 1, first, as shown in FIG. 2, the molten resin sheets P and P extruded from the T dies 28A and 28B (the first molten resin sheet and the second molten resin, respectively). An example of the sheet) is hung between the split molds 42A and 42B (an example of the first split mold and the second split mold, respectively).

Further, at this time, the skin sheet 23 is arranged between one of the molten resin sheets P and the split die 42B.

After that, by moving (sliding) the sliding portions 43A and 43B in the directions close to each other, the tips of the sliding portions 43A and 43B are brought into contact with the molten resin sheets P and P. As a result, a closed space is formed between the forming surface 116A of the split mold 42A and the molten resin sheet P, and a closed space is formed between the forming surface 116B of the split mold 42B and the molten resin sheet P (skin sheet 23). Will be done.

Although not shown, each of the split dies 42A and 42B has a built-in vacuum chamber, and a communication passage for vacuum suction is provided between the vacuum chamber and the forming surfaces 116A and 116B. Then, the air in the closed spaces SP1 and SP2 is sucked from the communication passage by the vacuum chamber. By this suction, as shown in FIG. 3, the pair of molten resin sheets P and P are pressed against the forming surfaces 116A and 116B, respectively, and formed (formed) into a shape along the forming surfaces 116A and 116B, respectively. At this time, the molten resin sheet P on the left side is shaped, and the skin sheet 23 is pressed together with the molten resin sheet P against the forming surface 116B of the split die 42B. As a result, the skin sheet 23 is welded to the molten resin sheet P.

Next, as shown in FIG. 4, the core material 3 is arranged between the split dies 42A and 42B while being held by the manipulator 90. Then, the core material 3 is pressed against the molten resin sheet P adsorbed on the forming surface 116B of the split die 42B. In this state, even if the holding of the core material 3 by the manipulator 90 is released, the core material 3 is separated from the molten resin sheet P and falls at least within a short period until the split dies 42A and 42B are molded. There is nothing to do.

Next, as shown in FIG. 5, the split dies 42A and 42B are molded to sandwich the molten resin sheets P and P. A pinch-off portion 118 is provided on the outer periphery of the split dies 42A and 42B so as to surround the forming surfaces 116A and 116B of the split dies 42A and 42B. The periphery of P is welded to form a parting line.

At this time, it is desirable not to blow air or the like between the molten resin sheets P and P. This is because the core material 3 may be deformed when air or the like is blown into it. The temperature conditions of the molten resin sheets P and P can be controlled to some extent by blowing air or the like, but when air or the like is not blown, one molten resin sheet P and the other molten resin sheet P can be controlled. Differences are likely to occur in temperature conditions, and the effect of the present invention is great.

Next, as shown in FIG. 6, the split dies 42A and 42B are opened to take out a molded product having a hollow portion, and burrs formed around the parting line are cut and removed by a cutter or the like. With the above, the skin integral molding complex 1 is completed.

In the above molding method, by appropriately setting the temperatures of the split dies 42A and 42B, warpage of the skin-integrated molded composite 1 to be molded is avoided. That is, the temperature difference between the mold temperature of the split mold 42B on the side (OUT side) to which the skin sheet 23 is joined is within 30 ° C. than the mold temperature of the split mold 42A on the opposite side (IN side). Increase in the range of.

As a specific temperature setting, the mold temperature of the split mold 42B is set to 50 ° C to 100 ° C, and the mold temperature of the split mold 42A is set to -5 ° C to -30 ° C with respect to the mold temperature of the split mold 42B. And.

In the case of the skin sheet 23 having a resin layer having no voids or bubbles like synthetic leather, the heat capacity of the skin sheet 23 is larger than that of a heat insulating sheet such as a non-woven fabric, and the heat dissipation of the molten resin in contact with the heat insulating sheet is promoted. Thermal imbalance occurs in this, which causes warpage and the like. By raising the mold temperature of the split mold 42B in contact with the skin sheet 23, heat dissipation of the molten resin is suppressed and the thermal imbalance is eliminated. In molding in the mold, the temperature of the surface in contact with both molds is important, and good molding is realized by matching these. By setting the temperature of the split dies 42A and 42B, the surface temperature of the skin sheet 23 and the surface temperature of the molten resin sheet P on the opposite side become equal to each other, which also has a good influence on the moldability. it is conceivable that. Further, when the skin sheet 23 is heated to a high temperature, the flexibility is increased and it becomes easy to follow the thermal behavior of the molten resin sheet P. As a result, the skin-integrated molded complex 1 after molding does not cause molding defects such as warpage, and is excellent in product quality stability.

Further, by raising the mold temperature of the split mold 42B in contact with the skin sheet 23, the skin sheet 23 and the molten resin sheet P, and further the molten resin sheet P and the core material 3 as a reinforcing material are surely welded. The effect of increasing the bonding strength can also be obtained. If the mold temperature of the split mold 42B is low, the pressure bonding between the skin sheet 23 and the molten resin sheet becomes insufficient, and there is a possibility that sufficient adhesiveness (bonding strength) cannot be obtained.

Although the embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to the above-described embodiments. For example, in the above embodiment, two molten resin sheets are supplied as molten resin to form a molded product, but a cylindrical parison is supplied as molten resin and molded by so-called blow molding. May be applied. However, in the case of blow molding, since the temperature can be controlled to some extent by blow air, the effect is greater when applied to a molding method in which two molten resin sheets are supplied to mold a molded product.

Next, examples of the present invention will be described based on specific experimental results.

The epidermis integral molding composite was molded by the method described in the embodiment of the molding destination of the epidermis integral molding composite. The skin sheet used was a laminate of a resin sheet (PVC) and a non-woven fabric (PET), with an overall thickness of 1 mm (PVC layer 0.5 mm + non-woven fabric layer 0.5 mm) and an overall texture of 800 g / m. ² (PVC layer 700 g / m ² + non-woven fabric layer 100 g / m ² ). In addition, in order to firmly shape the base material into the mold, innumerable small holes were made in the PVC layer.

The mold temperature on the skin sheet side (OUT side) and the mold temperature on the opposite side (IN side) are set as shown in Table 1, and the warp of the skin integrally molded composite taken out from the mold after molding is set. The tendency and the bonding state between the base material (molten resin sheet) and the skin sheet were investigated (Examples 1 to 9 and Comparative Examples 1 to 11). The results are also shown in Table 1. In Table 1, "concave" in the warp tendency column indicates a case where the central portion on the skin sheet side has a concave shape, and "convex" indicates a case where the central portion on the skin sheet side has a protruding shape. "Large" indicates that the product is not productive, such as rattling, "Small" indicates that the product is slightly warped, and "Small" indicates that the product is slightly warped but is within the permissible range. .. In addition, in the column of the bonding state between the base material and the skin sheet, "x" indicates a state in which the bonding is insufficient and easily peels off, and "△" indicates a state in which the bonding state is maintained to some extent, and if it is pulled strongly, it will peel off. "○" indicates a good bonding state in which it is difficult to peel off even if it is pulled strongly, and "◎" indicates a state in which it is firmly bonded so that it does not peel off at all even if it is pulled strongly.

As is clear from Table 1, by setting the mold temperature of the split mold 42A to -5 ° C to -30 ° C with respect to the mold temperature of the split mold 42B, a flat-shaped skin-integrated molded complex can be obtained. Has been done. Further, by setting the mold temperature of the split mold 42B to 50 ° C. or higher, the adhesiveness (bonding strength) between the base material (molded body obtained by molding and cooling the molten resin sheet) and the skin sheet is sufficiently secured. There is.

On the other hand, when the mold temperature of the split mold 42B is the same as or higher than the mold temperature of the split mold 42A, warpage occurs. In Comparative Example 5 in which the mold temperature of the split mold 42B is higher than the temperature difference of the split mold 42A of more than 30 ° C., warpage in the opposite direction occurs. Further, when the mold temperature of the split mold 42B is less than 50 ° C., the bonding strength between the base material and the skin sheet is insufficient. When the mold temperature of the split mold 42B is set to a temperature exceeding 100 ° C., there is no problem in terms of warpage and joining strength, but the load on the mold becomes large, for example, the life of the mold is shortened, or the device However, there is a possibility that problems such as the need for capital investment will arise.

1 Skin integral molding composite 2 Resin laminate 3 Core material 21 First resin sheet 22 Second resin sheet 23 Skin sheet 100 Molding device 120 Extruding device 140 Mold clamping device 16A, 16B Hopper 18A, 18B Cylinder 20A, 20B Hydraulic Motor 24A, 24B Accumulator 26A, 26B Plunger 28A, 28B T-die 40AA, 40AB, 40BA, 40BB Roller 42A, 42B Split mold 43A, 43B Sliding part 90 Manipulator 118 Pinch-off part FS Front side BF Back side P Molten resin sheet PL parting line

Claims (6)

A molding method in which a skin sheet is placed between a split mold of one of a pair of split molds and a molten resin, and a hollow molded body having the skin sheet attached to a part of a wall surface is formed.
The skin sheet has a resin layer that has substantially no voids or air bubbles.
The mold temperature of the first split mold facing the skin sheet of the pair of split molds is within a temperature difference of 30 ° C. or less from the mold temperature of the second split mold that is in direct contact with the molten resin. A molding method characterized by raising the temperature. Claim 1 is characterized in that a first molten resin sheet and a second molten resin sheet are supplied as the molten resin, and the skin sheet is arranged between the first molten resin sheet and the first split mold. The molding method described. The molding method according to claim 2, wherein a reinforcing material is interposed between the first molten resin sheet and the second molten resin sheet for molding. The molding method according to claim 3, wherein the reinforcing material is a foamed resin molded body. The molding method according to any one of claims 1 to 4, wherein the skin sheet is synthetic leather in which a non-woven fabric is laminated on the resin layer. The mold temperature of the first split mold is set to 50 ° C to 100 ° C, and the mold temperature of the second split mold is set to −5 ° C to −30 ° C with respect to the mold temperature of the first split mold. The molding method according to any one of claims 1 to 5, wherein the molding method is to be performed.

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