JPH10315265A - Integrally skin lamination molding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simultaneously realize the molding of a skin sheet and a molten resin and their lamination by a method wherein a fitst stage injection action is completed before the arrival of the temperature of the skin sheet to its deformable temperature by the fluid pressure of the molten resin and, after the temperature of the skin sheet has risen to its shapeable temperature through its contact with the molten resin, a second stage injection action and a dwell action are executed. SOLUTION: Under the condition that a mold clamping state is held by applying a mold clamping pressure after the completion of a mold clamping, a first stage injection is started so as to charge a core material in the cavity 5 of a mold through injection. The injection fill of the core material at this time is the volume of the molten resin, which fills the volume surrounded by the skin sheet (s) and the mold 3, for injection. The potential heat of the core material filling the cavity 5 of the mold is transmitted to the skin sheet (s). After the temperature of the skin sheet has risen to its shapable temperature through its contact with the molten resin, a second stage injection and filling is performed, resulting in contriving to completely shape the sin sheet (s) and the core material and turn them into an integral body.

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-mentioned problems, in the present invention, in the first invention, preforming is not performed between a pair of left and right dies or a pair of upper and lower dies. After clamping the mold with a skin sheet interposed, a 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 a skin material and the core material, wherein the molten resin injected and filled into the mold cavity is distributed over a substantially entire surface of the skin sheet and branched into a plurality of pieces. Using a mold provided with a flow path, the injection of the molten resin to be injected and filled into the mold cavity is performed in two stages, and in the first stage injection,
A volume of molten resin capable of filling a mold cavity space formed by the skin sheet and the mold provided with the plurality of flow paths branched out of the two molds in the two molds is applied to the flow path. The first stage 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 is added to the molten resin. After contacting and raising the temperature to a temperature at which shaping is possible, a second-stage injection operation and a pressure-holding operation are performed, and the molding and bonding of the skin sheet and the molten resin are performed simultaneously.

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, a mold sheet is clamped between a pair of left and right or upper and lower molds facing each other with a skin sheet not subjected to preforming being interposed therebetween. Injection-filling a molten resin serving as a core material into a mold cavity space formed by a sheet and a mold having a gate among the two molds, and integrally forming the skin material and the core material. A lamination molding method, comprising using a mold provided with a plurality of branched flow paths so that molten resin injected and filled into the mold cavity is dispersed over substantially the entire surface of the skin sheet. The injection of the molten resin to be injected and filled into the mold cavity is performed in two stages, and in the first stage injection, the skin sheet and the flow path branched into the plurality of the two dies are provided. Fills the mold cavity space formed by the Injecting and filling the molten resin in a volume amount capable of being performed through the flow path, and 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, the first stage After the injection operation is completed and the skin sheet is brought into contact with the molten resin and the temperature is raised to a shapeable temperature, a second-stage injection operation and a dwelling operation are performed to form and bond the skin sheet and the molten resin. Is performed at the same time, after the completion of the first-stage injection, the amount of heat of the molten resin is transmitted to the skin sheet and reaches a temperature at which shaping is possible. The shaping, the shaping of the molten resin, and the integrated lamination of both are efficiently performed.

[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.
FIG. 3 is a vertical sectional view of a main part of the mold at the time of completion of the first stage injection, FIG. 3 is a flowchart of a skin integral molding process, FIG. 4 is a vertical sectional view of a main part of the mold at the completion of second stage injection, and FIG. It is a graph which shows time progress of the temperature of a 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, and shows a state at the time of completion of the first stage injection. The fixed mold 3 is provided with a core material flow path 3a of the molten resin (core material) Q supplied from the nozzle 39 of the injection device 30,
The core material channel 3a is divided into a plurality of gates 3 in the extending direction of the skin sheet S sandwiched between the two molds 3, 4 in the middle.
b and is communicated to the mold cavity 5.

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. 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, the first stage 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. At this time, the injection filling amount of the core material Q is such that the molten resin having a capacity that satisfies the volume enclosed by the skin sheet S and the mold 3, that is, the volume of the injection molten resin C shown in FIG. In the present invention, during the injection of the core material Q, the injection operation of the first stage 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. FIG. 2 shows the state at this time, and the skin sheet S has not deformed yet and maintains a smooth original state.

(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 confirming that the skin sheet S has been brought into contact with the molten resin and has been heated to a temperature (T _S ) at which the skin sheet S can be shaped, the second-stage injection filling is performed, and the shaping and the core of the skin sheet S are performed. The shaping of the material Q is completely performed, 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.

That is, when the skin sheet temperature T exceeds the preset set temperature T _S , the second-stage injection filling by injecting the molten resin at a predetermined pressure is started, and from the preset set time t _1. injecting and filling until t _2. By the injection of the molten resin in the second stage, the amount of heat held by the molten resin Q is transmitted to the skin sheet S, and the shaping of the skin sheet S and the shaping of the molten resin Q are promoted. The bonding with Q proceeds at the same time. Skin sheet S and core material Q in mold cavity 5
Are shaped and fused as shown in FIG.

[0019] (4) When the second stage of the injection is complete, enter the pressure holding process, the pressure holding is performed during the time t ₂ to t _4. Then, when the time t ₄ has elapsed, the pressure holding is ended, and the cooling process is started. (5) After a cooling process for a certain time, the mold clamping force is removed,
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 increases due to the transfer of the retained heat of the molten resin Q injected by the first-stage injection.
The skin sheet S is shaped together with the shaping, but the deformation of the skin sheet S during the injection of the molten resin Q is minimized. Then, after the injection of the molten resin Q by the first injection is completed, the temperature of the skin sheet S further increases, and at the time when the increased temperature becomes uniform over the entire skin sheet S, the two-stage By starting the injection of the eyes, 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 a skin sheet made of a material having a small decrease in elastic modulus after temperature rise is selected, the pressure of the second-stage injection molten resin is transmitted to the skin sheet S via the first-stage injection resin. Local deformation may occur due to pressure gradients. 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 performing the second-stage injection after the temperature of the skin sheet S has uniformly increased, it is possible to avoid local elongation and local damage during shaping described in the problem to be solved.

[0023]

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 at the time of completion of a first-stage injection 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 main part of a mold at the time of completion of a second-stage injection according to the embodiment of the present invention.

FIG. 5 is a graph showing the time course of the temperature of the core material and the 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 flow path 3b Gate 4 Movable mold 5 Mold cavity 10 Mold device 20 Mold clamping device 22 Mold 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 clamping control unit 63 Resin pressure sensor 65 Temperature sensor 66 Timer 69 Hydraulic control valve 70 Hydraulic supply source 100 Injection molding machine C Injection Molten resin D Injection molten resin Q Core material (Molten resin) S Skin sheet

Claims (2)

[Claims] 1. A mold having a gate of the skin sheet and the two molds after a mold sheet is clamped between a pair of left and right molds or a pair of upper and lower molds facing each other, with a skin sheet not subjected to preforming being interposed therebetween. And a molten resin serving as a core material is injection-filled into the mold cavity space formed by the step (a), and the skin material and the core material are integrally molded. Injecting the molten resin to be injected and filled into the mold cavity using a mold provided with a plurality of branched flow paths so that the molten resin to be injected and filled is dispersed over almost the entire surface of the skin sheet. Is performed in two stages. In the first stage of injection, a mold cavity space formed by the skin sheet and a mold provided with a plurality of branched flow paths among the two molds is provided. A flow volume of molten resin that can fill Via injection filling
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, the first-stage injection operation is completed, and the skin sheet comes into contact with the molten resin and can be shaped. A skin integral lamination molding method comprising: performing a second-stage injection operation and a dwelling operation after the temperature is raised to a temperature; and simultaneously forming and laminating the skin sheet and the molten resin. 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.