JPH10305455A - Skin integrally pasting molding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To contrive to realize a low cost without executing a pre-shaping by a method wherein a mold, in which a plurality of branched flow passages are provided so as to scatteringly reach a resin on the front surface of a skin sheet, is used in order to end the injection of the resin before the arrival of the skin sheet to the temperature deformable by the fluid pressure of the melted resin and blowing an inert gas or the like in the mold after the above-mentioned temperature is reached in order to form the skin sheet and the resin and pasted the skin to the resin. SOLUTION: The core material flow passage 3a of the injection device 30 of a fixed mold 3 is connected with gates 3b branched to the expanding direction of a skin sheet S in the midway of the flow passage. In the fixed mold 3, a gas flow passage 3c for pouring a fluid such as an inert gas or the like from outside in a mold cavity is bored. After molds 3 and 4 are opened and the skin sheet S is set to the predetermined position to the mold cavity, the molds are closed under the state that the peripheral edge of the set skin sheet is held. After the completion of the injection and filling of a core material C in the mold cavity and the temperature of the skin sheet S rises to the temperature shapable by the melted resin C, a nitrogen gas is blown in the melted resin C or between the melted resin C and the inner surface of the mold so as to complete the shapings of the skin sheet S and of the core material in order to realize a low cost molding with the skin integrally pasted thereto without loss due to a pre-shaping.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for laminating a core material to obtain a molded product obtained by fusing and integrating a decorative skin material on the surface of a core material at the same time.
The present invention relates to a skin integral lamination molding method that can integrally mold a skin sheet directly with a molten resin without performing preforming, and can provide a high-quality molded product at low cost without impairing the feel of the skin sheet.

[0002]

2. Description of the Related Art In recent years, resin molded parts used for automobiles, home appliances, building materials, and the like have increased added value such as cushioning property, decorativeness, touch feeling, and the like, or have reduced cost by reducing the number of molding steps. For this reason, two-layer molding has been practiced in which a decorative skin material such as a skin sheet is integrally molded on the surface of a core layer resin as shown below. That is, when using an injection molding machine, a skin material is set between the opened molds, the mold is closed and the mold is closed, and then the mold cavity formed by the skin sheet and the mold is formed. The inside is injected and filled with a molten resin as a core material. Then, the holding pressure is supplied using the injection unit,
Cool for a specified time, open the mold and take out the product. From the mold clamping to the product removal in this method, the molding operation is performed by a normal injection molding method, and the mold is clamped with high pressure so that the resin does not leak during injection filling. A method using a press molding machine A skin sheet is set between both molds that have been opened, and while holding both molds at a predetermined mold opening amount, a space formed by the skin sheet and the molds After the molten resin as the core material is injected and filled, both dies are subjected to mold clamping press, and then cooled for a specified time, and the mold is opened to take out the product.

[0003] Conventionally, when performing integral lamination molding of the skin, the skin sheet is placed on a female mold while being heated to a deformable temperature and preliminarily shaped by a method such as vacuum pressure forming. In general, a preformed skin sheet is set in a mold and a molten resin is injection-molded. In particular, in the case of a molded article having a three-dimensional uneven surface structure, it has been considered that pre-shaping the skin sheet in advance is an essential condition.

[0004]

However, such a conventional method has the following problems. (1) In the prior art, in the manufacturing process including the pre-shaping, not only the manufacturing time of one cycle increases but also the manufacturing cost of the pre-shaping increases the overall cost and lowers the productivity. (2) In the prior art, if an attempt is made to shape the skin sheet with a resin pressure without preliminary shaping, the temperature near the flow path (gate), which has a long contact time with the injected molten resin, is high, and the flow at the end of flow ends. The skin sheet is locally stretched due to the low temperature and the gradient in the resin pressure, and the original purpose of the skin sheet, which is to decorate the surface of the molded article beautifully, cannot be sufficiently satisfied. (3) Even though the temperature of the skin sheet has not reached the specified temperature, the skin sheet was forcibly stretched and damaged without being able to withstand local stress.

[0005]

In order to solve the above problems, in the present invention, in the first invention, preliminary shaping is performed on a surface between a pair of left and right or upper and lower pairs of dies facing each other. After the mold is clamped with a skin sheet not to be interposed, the molten resin serving as a core material is injected and filled into a mold cavity space formed by the skin sheet and a mold having a gate among the two molds. A skin integral lamination molding method for integrally molding the skin material and the core material by blowing a fluid in the molten resin or between the molten resin and the mold inner surface,
A mold provided with a plurality of branched flow paths so that the molten resin to be injected and filled into the mold cavity is dispersed over almost the entire surface of the skin sheet is used, and the molten resin is melted through the flow paths. The resin is injected and filled, and the injection operation is completed before the temperature of the skin sheet reaches the deformable temperature due to the flowing pressure of the molten resin by the injected molten resin, and the skin sheet comes into contact with the molten resin and is applied. After the temperature is raised to a formable temperature, a fluid such as an inert gas is blown into the molten resin or between the molten resin and the inner surface of the mold to simultaneously mold and bond the skin sheet and the molten resin. And

In the second invention, the value of the 100% tensile stress at 70 ° C. is not more than ／ of the 100% tensile stress at around room temperature in the skin sheet of the first invention,
In addition, a skin sheet having a larger breaking elongation at 70 ° C. than at around room temperature was used.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, in the first invention, after a skin sheet not subjected to pre-shaping is interposed between a pair of opposed left and right or upper and lower molds, the mold is clamped. After injecting and filling a molten resin serving as a core material into a mold cavity space formed by the skin sheet and the mold having a gate among the two molds, the inside of the molten resin or the inside of the molten resin and the mold are filled. A method of integrally forming the skin material and the core material by blowing a fluid between them, wherein the molten resin injected and filled into the mold cavity is dispersed over substantially the entire surface of the skin sheet. Using a mold provided with a plurality of branched flow paths so as to pass through, the molten resin is injected and filled through the flow path, and the temperature of the skin sheet is melted by the injected molten resin. Temperature that can be deformed by the flow pressure of resin Completes the injection operation before reaching
After the skin sheet is brought into contact with the molten resin and heated to a temperature at which shaping is possible, a fluid such as an inert gas is blown into the molten resin or between the molten resin and the mold inner surface, and the skin sheet and Since the molding and bonding of the molten resin are performed at the same time, after the heat of the molten resin is transmitted to the skin sheet after the injection is completed and reaches a temperature at which shaping is possible, injection of a fluid such as an inert gas into the inert gas is performed. Due to the action of the fluid pressure, the shaping of the skin sheet, the shaping of the molten resin, and the lamination of the two are performed efficiently.

[0008] In the second invention, the skin sheet is provided with 7
The value of 100% tensile stress at 0 ° C.
Since a skin sheet which is not more than ／ of the 0% tensile stress and has a larger breaking elongation at 70 ° C. than near room temperature is employed, the skin sheet is uniformly 70 ° after injection filling.
Since it is easy to stretch to a high temperature exceeding C, shaping of the skin sheet becomes easy.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below in detail with reference to the drawings. 1 to 5 relate to an embodiment of the present invention,
FIG. 1 is an overall configuration diagram of an injection molding machine used in the present invention, and FIG.
3 is a longitudinal sectional view of a main part of a mold, FIG. 3 is a flowchart of a skin integral molding process, FIG. 4 is a longitudinal sectional view of a mold apparatus in an inner method, FIG. 5 is a longitudinal sectional view of a mold apparatus in an outer method, FIG.
Is a graph for explaining the time course of the temperature of the core material skin sheet.

As shown in FIG. 1, an injection molding machine 100 according to the present invention comprises a mold device 10, a mold clamping device 20, an injection device 30, and a control device 60. The mold apparatus 10
It comprises a fixed mold 3 attached to the fixed platen 1 and a movable mold 4 attached to the movable platen 2. The movable platen 2 and the movable mold 4 can be moved forward and backward by the mold clamping cylinder 22 of the mold clamping device 20. Be composed. The mold clamping device 20 includes a mold clamping cylinder 22 that operates to open and close the molds 3 and 4 of the mold device 10. The movable mold 4 is connected to the fixed mold 3 by a tie bar (not shown). You will be guided back and forth.

The injection device 30 has a screw 34 provided with a screw blade 36 spirally mounted on the outer periphery of a barrel 32. The screw 34 is rotatable by a forward / reverse rotation hydraulic motor 42 and an injection cylinder 40, and is freely rotatable forward and backward. The molten resin is injected into the mold cavity 5 formed between the molds 3 and 4 via the nozzle 39 while heating and melting and kneading the resin pellets supplied to the hopper 38. That is, the injection device 30 heats and compresses the resin raw material in the hopper 38 in the supply zone and the compression zone in the barrel 32, melts and measures in the measurement zone, and passes through the injection zone into the mold cavity 5 through the nozzle 39. It is configured to fire. Hydraulic oil supplied from a hydraulic supply source 50 is supplied to the injection cylinder 40 and the forward / reverse rotation hydraulic motor 42 at a constant pressure set by a hydraulic control valve 52 that has received an operation command from an injection control unit 61, and is driven. You.

On the other hand, as shown in FIG. 1, the control device 60 converts the pressure information measured by the resin pressure sensor 63 disposed on the fixed mold 3 and the core material resin temperature information measured by the temperature sensor 65. A mold clamping control unit 62 that inputs and provides an operation signal to the mold clamping cylinder 22 of the mold clamping device 20 via a hydraulic control valve 69, a timer 66 connected to the mold clamping control unit 62, and a mold clamping control unit 62 It is composed of an injection control unit 61 connected thereto. 70 is a hydraulic supply source.

In this embodiment, an injection molding machine having a direct pressure type mold clamping device is used. However, an injection molding machine of a toggle mold clamping device, a vertical injection molding machine, or an electric type mold clamping device is used. May be used.

FIG. 2 is a longitudinal sectional view of a main part of the mold according to the present invention.
Material flow path 3a of molten resin (core material) Q supplied from
The core material flow path 3a is provided between the two dies 3, 4
Is connected to the gate 3b branched into a plurality of pieces in the direction in which the skin sheet S sandwiched by the sheet 3 extends, and communicates with the mold cavity 5.

The fixed mold 3 has a gas flow path 3 c for injecting a fluid such as an inert gas into the mold cavity 5 from outside.
Is formed, and the mold cavity 5 is inserted through a gas injection nozzle 3d attached to the mold cavity 5 at the tip.
It is configured to be able to inject a fluid such as an inert gas into the inside.
In this embodiment, nitrogen gas is injected as an inert gas. However, another inert gas or a liquid which is liquid at normal temperature and becomes a gas in a resin and may be used. Further, the gas injection amount may be pressure control or volume control.

FIG. 3 is a flowchart showing the steps of the skin integral lamination molding of the present invention, and the operation is performed according to the steps shown in FIG. (1) First, the molds 3 and 4 of the mold apparatus 10 are opened, the skin sheet S is set at a predetermined position on the mold parting surface facing the mold cavity 5, and the periphery is gripped. Close both molds. The skin sheet S is a multi-layer or single-layer sheet based on PP (polypropylene), PE (polyethylene), ABS, or the like, and may have a raised material on its surface. In addition, the resin sheet is provided for the purpose of decorating the surface of the molded article beautifully and at the same time imparting weatherability, and for fusing and integrating with the core material. And if necessary, a cushion layer or the like may be provided on the back surface of the resin sheet.

(2) After the mold clamping is completed, injection is started while the mold clamping pressure is applied and the mold clamping state is maintained, and the core material Q is injected and filled into the mold cavity 5. Core material Q at this time
The injection filling amount is set to be equal to or more than the capacity that fills the volume surrounded by the skin sheet S and the mold 3. In the present invention, during the injection of the core material Q, the injection operation is completed before the time (t ₁ ) at which the temperature of the skin sheet S reaches the deformable temperature (T _S ) due to the flow pressure of the molten resin.

(3) When the injection filling of the core material Q is completed,
The amount of heat held by the core material Q injected and filled in the mold cavity 5 is transmitted to the skin sheet S, and the temperature of the skin sheet S becomes
As shown in FIG. Then, after the skin sheet is brought into contact with the molten resin and heated to a temperature (T _S ) at which the skin sheet can be shaped, nitrogen gas is blown into the molten resin or between the molten resin and the inner surface of the mold to form a skin sheet. Shaping of S and core material Q
The shape of the shape is completely made, and the two are integrated. Therefore, the temperature rise of the skin sheet S is monitored by the temperature sensor 65, and the skin sheet temperature T is measured every moment. In the inner method of gas injection (method of injecting gas into the molten resin) shown in FIG. Prior to this, a gas injection nozzle 3d for injecting nitrogen gas is placed in the molten resin. The skin sheet temperature T is set at a preset temperature T.
When it exceeds _S, the injection of nitrogen gas at a predetermined pressure and starts through the injection nozzle 3d, continues setting time t ₄ when preset. In the gas injection outer method shown in FIG. 5 (a method of performing gas injection between the molten resin and the inner surface of the mold (mold wall surface)), the above-described forward movement of the injection nozzle 3d is unnecessary, and the injection is not performed. The position of the nozzle 3d is a retreat position. The sealing pressure of the inert gas or the like is transmitted to the skin sheet S via the molten resin Q, and the shaping of the skin sheet S and the shaping of the molten resin Q are promoted. Matching proceeds simultaneously.

(4) When the set time t ₄ has elapsed, the gas injection is stopped, and the gas pressure in the mold cavity 5 is removed.
In the inner method, the advanced gas injection nozzle 3d is returned to the original retracted position, and the mold clamping force is released. (5) Then, the mold is opened and the molded product is taken out as a product.

In the above-described series of molding steps, the temperature of the skin sheet S is increased by receiving the heat of the injected molten resin Q, and the skin sheet S is shaped together with the shape of the molten resin Q. However, the deformation of the skin sheet S during the injection of the molten resin Q is minimized. After the injection of the molten resin Q is completed, the temperature of the skin sheet S further rises, and at the time when the temperature rise becomes uniform throughout the skin sheet S, gas injection with an inert gas is performed inside the molten resin. By performing (inner method) or between the molten resin Q and the mold wall surface (outer method), the deformation of the skin sheet S can be made uniform. As a result, the skin sheet S can be closed in a smooth initial state without preforming the skin sheet S, and the skin integral bonding molding can be performed.

In the above-mentioned forming step according to the present invention,
The skin sheet S has a 100% tensile stress at around 70 ° C., which is ／ of a 100% tensile stress at around room temperature.
In the following, a skin sheet of a material that is desirably 以下 or less, and whose elongation at break at 70 ° C. becomes larger than that near room temperature, preferably 1.5 times or more is selected. During molding, when the core material Q is injected, the skin sheet S easily reaches a temperature of 70 ° C. or higher due to the calorific value of the molten resin, but the temperature rising speed varies depending on the material, sheet thickness, and the like. It takes 3 to 5 seconds after contact with the molten resin to reach. For this reason, since the temperature of the skin sheet S is low during injection, it cannot be deformed by the pressure due to the flow of the molten resin, but it can be easily deformed after the temperature rise because the elastic modulus is lowered. Become. Therefore, when the skin sheet is selected as a material having a small decrease in the elastic modulus, the pressure of the injected gas may locally deform due to a pressure gradient transmitted to the skin sheet S via the resin. Furthermore, since the elongation at break after the temperature rise is larger than the elongation at break near room temperature, even if the rate of change of elongation when deforming according to the shape of the mold cavity is large, local breakage may occur. Is prevented. For this reason, by injecting the fluid such as the inert gas after the temperature of the skin sheet S has uniformly increased, it is possible to avoid local elongation and local damage during shaping as described in the problem to be solved.

[0022]

As described above, according to the method of the present invention, the skin sheet S can be integrally laminated and formed without preforming the skin sheet S. As a result, it is possible to eliminate the loss of energy and time required for pre-shaping, and to obtain a surface-integrated laminated body with a beautiful surface stably at low cost.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an injection molding machine according to an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of a main part of a mold according to the embodiment of the present invention.

FIG. 3 is a flowchart of a skin integral lamination molding process according to the embodiment of the present invention.

FIG. 4 is a longitudinal sectional view of a mold apparatus in an inner method according to an embodiment of the present invention.

FIG. 5 is a longitudinal sectional view of a mold device in an outer method according to an embodiment of the present invention.

FIG. 6 is a graph illustrating the time course of the temperature of the core material skin sheet according to the example of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixed board 2 Movable board 3 Fixed mold 3a Core material passage 3b Gate 3c Gas passage 3d Gas injection nozzle 4 Movable mold 5 Mold cavity 10 Mold device 20 Mold clamping device 22 Mold clamping cylinder 30 Injection device 32 Barrel 34 Screw 36 Screw Blade 38 Hopper 39 Nozzle 40 Injection Cylinder 42 Hydraulic Motor 50 Hydraulic Supply Source 52 Hydraulic Control Valve 60 Control Device 61 Injection Control Unit 62 Mold Clamp Control Unit 63 Resin Pressure Sensor 65 Temperature Sensor 66 Timer 69 Hydraulic Control Valve 70 Hydraulic Source 100 Injection molding machine Q Core material (molten resin) S Skin sheet

Claims (2)

[Claims] 1. A mold sheet is clamped between a pair of left and right dies or a pair of upper and lower dies, the surface of which is not preformed, and a gate is provided between the dies and the two dies. After injecting and filling a molten resin serving as a core material into a mold cavity space formed by a mold, a fluid is blown into the molten resin or between the molten resin and a mold inner surface to form the skin material and the mold. A skin integral lamination molding method for integrally molding a core material, wherein a plurality of flow paths are branched so that molten resin injected and filled into the mold cavity is dispersed over substantially the entire surface of the skin sheet. Using the arranged mold, the molten resin is injected and filled through the flow path, and before the temperature of the skin sheet reaches a deformable temperature due to the flowing pressure of the molten resin by the injected molten resin. Injection operation is completed and the skin After the sheet is brought into contact with the molten resin and heated to a temperature at which it can be shaped, a fluid such as an inert gas is blown into the molten resin or between the molten resin and the inner surface of the mold to melt the skin sheet. A method of integrally forming and bonding a skin, wherein resin molding and bonding are performed simultaneously. 2. 100% at 70 ° C. is applied to the skin sheet.
% Tensile stress value is 3/4 of 100% tensile stress around room temperature
2. The method according to claim 1, wherein the skin sheet has a breaking elongation at 70 [deg.] C. greater than that at around room temperature.