JP3255026B2 - Skin integral molding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for integrally forming a skin by molding a resin for a core layer and simultaneously fusing and integrating a decorative skin material on the surface of the resin for the core layer.

[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. Therefore, two-layer molding has been performed in which a decorative skin material is integrally molded on the surface of the core layer resin as described 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 a mold cavity formed by the skin material 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 by using the injection unit, the cooling is performed for a specified time, the mold is opened, and the product is taken out. 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 material is set between both molds that have been opened, and while holding both molds at a predetermined mold opening amount, a space is formed between the skin material and the mold. Then, after injecting and filling the molten resin to be the core material, both molds are subjected to mold clamping press, and then cooled for a specified time,
Open the mold and take out the product.

[0003]

However, such a conventional method has the following problems. (1) In the above-mentioned method, when the core material is injected, usually 300
Since high-pressure resin pressure exceeding kgf / cm ² and high-temperature molten resin flow are applied to the skin material, the skin material is severely damaged, resulting in quality deterioration and poor appearance. For example, in the case of the foamable skin material, the cushioning property is lost due to the collapse of the foamed layer, and in the case of the brushed skin material, the feeling of touch and the sense of quality are lost due to the fall of the hair. (2) Also in the above method, the skin material is damaged because the skin material comes into contact with the high-temperature molten resin, and high pressure is applied to the skin material during the mold clamping press. In addition, since the core material is injected with the mold open widely, for example, the parting surface has a sheared edge structure.
A mold structure that does not leak resin is required, which increases the cost of the mold, necessitates mold maintenance for preventing wear of the shear edge portion, and lowers productivity. (3) In addition, since it is necessary to set the skin material in the mold open state, it is necessary to hold the skin material during injection of the core material or during the mold clamping press. Must be installed, which complicates operation and increases costs. (4) In recent years, particularly in the field of injection molded products, there has been a strong demand for weight reduction and cost reduction. In order to realize this, there is a trend in the industry to respond to the demand for thinner products. The tendency is seen. Therefore, in the above method, the resin flow path of the core material in the mold cavity is narrowed, so that an increase in resin pressure is inevitable. In addition, in the above method, the cost increase due to the high functionality of the auxiliary equipment of the mold is unavoidable, the cooling and solidification of the core material resin is fast, and a high-speed, high-pressure mold clamping load is required for shaping, In any case, in the conventional molding method, molding defects due to damage to the skin material have been a serious problem.

[0004]

Means for Solving the Problems In order to solve the above-mentioned problems, according to the present invention, after a skin material is interposed between a pair of opposed left and right or upper and lower molds, the mold is clamped, and Injection-filling a molten resin serving as a core material into a mold cavity formed by the skin material and the two dies, a skin integral molding method of integrally molding the skin material and the core material,
After spraying a wetting liquid per skin material of 0.01 to 0.1 ml / cm 2 onto the skin material, the amount of the molten resin obtained by adding the amount of cooling solidification shrinkage of the molten resin of the core material is injected and filled. Means that the resin pressure in the mold cavity is 70-1
The mold clamping pressure was controlled so as to be in the range of 50 kgf / cm2.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, after a skin material is interposed between a pair of left and right or upper and lower molds facing each other and the mold is clamped, a mold formed by the skin material and the two molds is used. In a method for integrally molding the skin material and the core material by injection-filling a molten resin serving as a core material into a mold cavity, the skin material is previously wetted, and then the core material is melted. The amount of the molten resin obtained by adding the amount of cooling, solidification, and shrinkage of the resin was injection-filled. As a result, the following preferable molding is performed. By injecting the core material while the skin material is wet,
The skin material is warmed by the heat of the resin of the core material, and as a result, water evaporation of the skin material occurs. At this time, the heat of vaporization largely removes the resin heat from the core material received by the skin material, so that the skin material is significantly cooled and damage of the skin material is prevented. further,
By actively adjusting the wet state of the skin material to an optimal state, the effect of preventing damage to the skin material is stabilized, and as a result, a stable supply of a molded article having excellent appearance properties is achieved. After injecting and filling the amount of resin to which the amount of cooling, solidification, and shrinkage has been added, for example, by controlling the mold clamping pressure in an appropriate resin pressure range according to the shape of the molded product, the characteristics of the core material resin and the skin material, the resin cooling Uniform overall pressure-holding action from the mold clamping side according to the solidification behavior is performed, and uniformity of the adhesion of the skin material to the core material without causing deformation or warpage and without damaging the skin material be able to. At the same time, by minimizing the pressure load on the skin from the start of injection to the completion of cooling, damage to the skin is prevented. Furthermore, at the time of injection filling, the mold shows a mold opening behavior, which has a high degassing effect, achieves complete filling of the mold cavity with the resin by reducing the pressure and promoting the resin flow, and evaporates from the skin material. Excess gas containing moisture is also discharged. By controlling the mold opening at the time of core material injection, resin leakage is prevented together with the sealing effect on the parting surface of the skin material, and it is possible to operate with a normal mold without the need for a special mold. Initial cost is low and cost can be reduced. By using mold opening control and mold clamping pressure control together,
Hold the skin material with moderate tension control,
Hold while applying moderate tension to the skin material,
It is possible to obtain a molded product with high decorative performance, which prevents local elongation of the skin material and extends uniformly over the entire core material without wrinkles or entanglement.

[0006]

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.
Is an explanatory view showing an example of a wetting process, FIG. 3 is a flowchart of a skin integral molding process (first embodiment), and FIG. 4 is a resin pressure in a mold cavity, a holding time, and a degree of damage of a skin material in the skin integral molding process. FIG. 5 is a flowchart of a skin integral molding process (second embodiment).

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 2 and 4 of the mold device 10. The movable mold 4 is connected to the fixed mold 2 by a tie bar (not shown). You will be guided back and forth.

The injection device 30 includes a screw 32 having a screw blade 36 spirally mounted on the outer periphery of a barrel 32. The screw 34 is rotatable by a forward / reverse hydraulic motor 42 and an injection cylinder 40, and can be freely moved back and forth. The molten resin is injected into the mold cavity 5 formed between the molds 2 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 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 via 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 receives 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 detects the pressure information measured by the resin pressure sensor 63 disposed on the fixed mold 3 and the amount of mold opening between the two molds 3, 4. A mold clamping control unit 62 that inputs position information of the position sensor 64 and supplies an operation signal to the mold clamping cylinder 22 of the mold clamping device 20 via the hydraulic control valve 69, and receives an output signal of the mold clamping control unit 62. A hydraulic control valve 69 for the mold clamping cylinder 22 to be operated, a timer 65 connected to the mold clamping control unit 62,
2 and an injection control unit 61 connected to the control unit 2. 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 having a toggle mold clamping device, or an injection molding machine having a vertical injection molding machine or an electric type mold clamping device is used. A molding machine may be used.

FIG. 2 shows an embodiment of the wetting process. FIG. 2 (a) shows a case where a wetting liquid is sprayed on the surface of the skin material S, whereby the skin material S becomes wet. After being set at a predetermined position facing the mold cavity, the mold is closed. In FIG. 2B, after the wetting liquid is sprayed on the mold cavity surface of the movable mold 4 that comes into contact with the skin material S, the skin material S is set at a predetermined position, and the mold is closed.
In addition to these methods, the surface of the skin material S may be wetted by the method described below. For example, the wetting liquid is applied to both the surface of the skin material S and the mold cavity surface. The surface side of the skin material S is immersed or brought into contact with the wetting liquid. With the skin material S set, the wetting liquid is spray-coated on the skin material S or the mold cavity surface. That is, it is sufficient that the surface of the skin material S is in a wet state before the injection of the core material resin Q or during the injection filling.
Use any of the above methods as needed. In the present embodiment, a method in which the wetting liquid is sprayed by the spray robot 80 is used. The degree of the wet state, that is, in the present embodiment, the spray amount of the wetting liquid depends on the core material resin Q.
It is important to adjust the molded product to be in a dry state at the time of cooling and solidification of the molded product or at the time of removing the molded product. Skin material S
The purpose of wetting is to prevent the skin material S from being damaged. Here, the factors that cause damage to the skin material are roughly classified into three factors: "temperature", "pressure", and "time", all of which are received from the core material molten resin.

The "pressure" and "time" will be described in detail in the following description with reference to FIG. 4, and here, "humidity" suitable for the purpose of wetting the skin material S will be described. Will be described.

"Temperature" means the resin temperature. "Temperature", that is, the lower the core material molten resin temperature, the more the skin material S
Although the degree of damage of the core material is small, if it is too low, plasticization and flow failure of the core material resin are caused, resulting in molding failure. Therefore, it is important to select a temperature condition suitable for the resin characteristics. For example, in the case of PP resin, the temperature is set to around 200 to 230 ° C.
Therefore, reducing the amount of heat received by the skin material from the resin is an important point for preventing damage to the skin material. To achieve this, for example, the following method is considered. That is, the conventional method is a method of cooling a mold. For example, the surface layer of the skin material is cooled by lowering the mold temperature using a temperature controller or the like. If it is too much, the resin fluidity is reduced and the quality of the molded product is reduced. Therefore, in order to prevent this, a two-stage temperature control in which the skin material side and the core material side are separately cooled can be considered,
In addition to the increase in cost, the skin material and the mold only conduct heat transfer by contact, so that the cooling efficiency is poor, and there have been many drawbacks in that the expected effect of preventing the skin material from being damaged cannot be obtained. On the other hand, in the method of the present invention, by making the skin material S and the mold cavity surface in a wet state, the wetting solution evaporates with the core material holding calorie, and the heat absorption due to heat of vaporization at that time has a high cooling effect. And the surface layer of the skin material S is significantly cooled,
The amount of heat received from the resin is reduced, thereby preventing the skin material S from being damaged.

Further, the wetting effect of the present invention can prevent damage to the skin material S and allow only the required surface layer of the skin material S to be cooled, so that the core material Q during the flow behavior in the mold cavity can be cooled. Since it does not cause a decrease in fluidity, the quality of the molded article does not decrease. Here, the skin material S
Alternatively, if the spray amount on the mold cavity surface is insufficient (that is, if the wet state is too small), the cooling effect (wet effect) due to the wet state is insufficient, and if the spray amount is too large (the wet state is too small). If it is excessive), a separate drying step is required after the completion of molding, which is troublesome, and new defects are induced by the vaporized gas. Therefore,
During molding, in order to maintain and exert an appropriate wetting effect, it is necessary to actively adjust the amount of wetting so that the molded product is in a dry state at the time of cooling and solidifying the core material resin Q or at the time of removing the molded product. There is.

When the mold is cooled to a room temperature or lower, for example, the mold causes dew condensation, which makes it possible to wet the skin material S. The core material Q
There are many disadvantages such as defects due to moisture adhesion to the machine, machine troubles such as rust, and deterioration of molded product quality due to resin flow decrease,
Not preferred. In the embodiment of the present invention, in consideration of the above points, the spray amount is set to 0.01 to 0.1 ml / cm ² per skin material S, and the mold temperature is set to 20 to 30 in consideration of resin fluidity.
60 ° C.

The wetting liquid in the present invention may be any liquid that evaporates and evaporates due to the heat of the core material Q resin, is safe and has no corrosiveness, and can be supplied stably. In order to provide a satisfactory and low-cost supply of water or, if necessary, a wetting effect or a rust-preventive effect, a liquid to which an additive was added was used. In the examples of the present invention, rust did not occur in the mold, but consideration should be given to plating treatment and changing the material of the mold as necessary so that rust does not occur in the mold. .

FIG. 3 shows a first embodiment of the molding step of the method for integrally molding the skin of the present invention, and the operation is performed according to the step shown in FIG. First, the molds 3 and 4 of the mold apparatus 10 are opened, and a skin material S that has been subjected to wet treatment in advance at a predetermined position facing the mold cavity 5 on the mold parting surface.
Is set, the periphery is gripped, the mold is closed, and a low-pressure mold clamping state is set. Then, the core material Q is injected and filled into the mold cavity 5,
The resin pressure in the mold cavity 5 during injection filling is detected by the resin pressure sensor 63, and the resin pressure is, for example, 70 to 150 kg.
The mold clamping control unit 62 issues an operation command to the mold clamping cylinder 22 to control the mold clamping pressure so that the resin pressure is selected from a preset pressure range of f / cm ² . When setting the skin material S, it is desirable to maintain a slight tension state (tensile state) so that the skin material S does not loosen. In the molding process of FIG. 3, the process shifts to the mold clamping pressure in response to a timeout signal after a predetermined time set by the timer 65 from the start of injection of the core material Q.
The mold clamping pressure is controlled so as to be a low resin pressure selected from a predetermined pressure range of gf / cm ² . After the cooling is completed, the mold is opened and the product is taken out.

FIG. 4 is a graph showing the correlation between the resin pressure in the mold cavity, the holding time, and the degree of damage to the skin material. (A) in the figure is a region where the degree of damage of the skin material S is extremely large (non-formed region), (B) is a region where the degree of damage is extremely small (non-defective region), and (C) is a possibility of damage depending on set conditions. Indicates an unstable region (boundary region). As described above, there are three factors that cause damage to the skin material: “temperature”, “pressure”, and “time”, all of which are received from the core material molten resin. “Temperature” is as described above.

"Pressure" means "resin pressure in the mold cavity". In the present invention, since the resin pressure in the mold cavity is set by mold clamping pressure control, it also means "mold clamping pressure". Is done. In this case, the smaller the "pressure", the less damage to the skin material, but the amount of mold opening during injection filling increases, and resin leakage occurs. To prevent this, a specially designed mold that does not cause resin leakage If it is, the cost increases. Furthermore, the shaping ability becomes insufficient, and in particular, when the weight and cost are reduced by reducing the thickness of the core material, the insufficient ability becomes remarkable. Therefore, high pressure is required during molding, but the skin material is likely to be damaged. From the above, it is necessary to perform control in consideration of “pressure” and “time” at the same time. In the conventional method using an injection molding machine, FIG.
Since the operation is performed in the region D, the damage of the skin material is large,
Molding failure could not be avoided.

However, as a result of various studies and studies by the present applicant, it has been found that if the pressure is extremely short, the skin material S is not significantly damaged even under a considerably high pressure state. For short time, the upper limit of resin pressure is 1
It was found that it could be up to 50 kgf / cm ² (region (E) in FIG. 4). As can be seen from FIG. 4, as the time (holding time) increases, the allowable pressure for avoiding damage to the skin material S sharply decreases, so it is important to control the holding time in the high pressure state as short as possible. Yes,
For that purpose, the time must be within the allowable time range (5 in this embodiment).
It is desirable to set injection conditions in advance so that injection filling can be performed within seconds. In the region (F) of FIG. 4 where the resin pressure is 50 kgf / cm ² or less, the skin damage is slight even when the resin pressure is maintained for a long time, but a small mold clamping pressure control is performed to reduce the resin pressure. For this reason, the amount of mold opening during injection filling becomes large, resin leakage is large, and there is a problem in operation.

Here, for example, by gripping the peripheral portion of the skin material S with the mold parting surface, there is a sealing effect on the parting surface of the skin material S. Therefore, it differs depending on the material and thickness of the skin material. Generally, mold opening is 0.5 ~
If it is about 1 mm, resin leakage does not occur without using a mold having a special structure. Therefore, in order to keep the mold opening to this level, the lower limit of the resin pressure during injection filling is 70 kgf.
/ Cm ² is appropriate and the range of resin pressure during injection filling is 7
0 to 150 kgf / cm ² .

During the injection filling, the filling flow of the core material resin Q is promoted by the expansion of the mold cavity space (core material resin flow path) by the mold opening behavior corresponding to the injection filling and the degassing effect. Achieved low pressure and complete filling of resin into the mold cavity, and also enabled short-time filling. The effect of the short-time filling also effectively works to facilitate the setting range of the injection conditions for minimizing the injection filling time described above. Further, the mold opening behavior also serves to discharge the remaining surplus part that has acted on the moist cooling effect, of the gas that the moist skin material S has evaporated and vaporized by the heat of the core material resin. This prevents molding defects due to the filling of the gas in the mold cavity, and promotes stable evaporation and guarantees a stable and continuous wetting effect. In addition, since the periphery of the skin material is held at the low pressure mold clamping on the parting surface of the mold, the tension control of the skin material S corresponding to the injection filling of the core material resin (the skin material S is subjected to the mold parting with the extension of the filling). Slides along the surface)
Is made. On the other hand, 2 by the conventional injection molding machine
In the layer forming method, since the skin material is completely fixed on the parting surface, tension control cannot be performed. As a result, the skin material is locally stretched, and tears and uneven surface properties occur. Further, in the two-layer molding method using a conventional press molding machine, means for fixing the skin material is separately required, and there is a problem that the method is complicated.

In the present invention, as described above, the process enters the mold clamping pressure step based on the time-out signal of the timer 65 which is started simultaneously with the start of injection. The set time in this case is the maximum allowable holding time (5 in this embodiment) determined from the skin material characteristics.
(Within seconds) according to the shape of the molded product. Therefore, it may be simultaneous with the completion of injection. In the mold clamping pressure step, mold clamping pressure control is performed so as to maintain the resin pressure at a preset pressure within a pressure range of, for example, ^{2 to} 50 kgf / cm ² . The reason is that, as described above, FIG.
(F), the upper limit is 50 kgf / cm ²
The reason is that if it is 50 kgf / cm ² or less, the damage to the skin material S is extremely small even if it is continued for a long time.
If the weight is less than kgf / cm ² , the core material resin Q will have insufficient pressure holding (forming and holding) capability. When the cooling of the core material resin Q is completed, the mold is opened and the product is taken out. If necessary, trimming of the periphery of the skin material Q and cutting of the gate and the runner are performed. In this way, the skin material properties are mainly
When performing integral skin molding based on core material resin characteristics, molded product shape, etc., the most suitable combination of pressure range and holding time is selected and set, mold clamping pressure control is performed, and the amount of resin cooling solidification shrinkage is added. By simultaneously performing injection and filling control for filling the amount of resin into the mold cavity,
Achieves low pressure, short time filling, complete filling and full and uniform pressure-holding action of the mold-clamp side corresponding to the cooling, solidification and shrinkage behavior of the resin. A good skin-integrated molded product in which the skin material S and the core material Q are uniformly adhered to each other without any damage to the skin material is obtained.

Furthermore, by using the skin material S in a wet state, which is the most important feature of the present invention, a high-quality integrated skin product having extremely excellent surface properties can be formed in synergy with the wet cooling effect. Can be obtained stably without being affected by disturbance factors. In this case, by adjusting the wet state to the ideal state, continuous evaporation and vaporization of the wet liquid occurs from the start of the injection of the core material Q to the completion of the cooling, and as a result, the cooling action of the skin material by absorbing the heat of vaporization. (Wetting effect)
Is maintained, and damage due to the temperature rise of the skin material is prevented.
The surplus of the vaporized gas is discharged from the gap between the two molds that have opened. By realizing such a stable wet state, a more stable supply of a high-quality molded product can be achieved.

Therefore, according to the present invention, in addition to the above, for example, the following forming pattern can be implemented. The control pattern of the resin pressure during molding is set in three steps according to the shape of the molded product, the type of the skin material S, etc. within the allowable pressure range.
The number of steps is changed to four steps (two steps in FIG. 3).
For example, in molding for the purpose of lowering the pressure during injection filling and further enhancing the shaping ability, the pressure is set to be low during injection filling within a range where the resin does not leak, and after filling is completed, the pressure is temporarily changed to a high pressure state, and thereafter, A control pattern for maintaining the low pressure state again may be used. The mold opening during injection filling is detected, and during injection, the mold opening is controlled so as not to cause resin leakage. After filling is completed, mold clamping pressure control is performed. Furthermore, you may implement combining the said method. The resin pressure and the mold clamping pressure are balanced by the mold opening behavior.As a result, utilizing the linear relationship, a mold clamping pressure corresponding to the allowable resin pressure is set, and the set mold clamping pressure is set during molding. Control based on pressure.

FIG. 5 shows a second embodiment of the molding step of the method for integrally molding skin according to the present invention. In this method, after the surface material S that has been wet-treated is set at a predetermined position facing the mold cavity, a mold clamping operation is performed, the mold is held open at a predetermined mold opening position, and then the core material Q is injected. Perform At this time, in the present embodiment, since the peripheral portion of the skin material S holds the parting surface, resin leakage occurs due to the sealing effect of the parting surface of the skin material S without using a mold having a special structure. There was nothing. In this case, the mold opening varies depending on the type and thickness of the skin material S, but it is sufficient if the mold opening is approximately 1 mm or less. In the present embodiment, the mold opening is set to 0.5 mm. In addition, even with such a small mold opening amount, it has sufficient ability to hold the skin material,
Although there was no displacement of the skin material S, the skin material may be held by means such as needle insertion or suction if necessary.

During injection filling, the mold sensor is detected by the position sensor 64 and an operation command is issued from the mold clamping control unit 62 to the mold clamping cylinder 22 so as to maintain the set mold opening, thereby controlling the mold clamping position. By doing so, it is possible to avoid resin leakage and to continue the load of the ability to hold the skin material. Further, by performing the injection in the mold open state, a degassing effect and an increase in the volume of the mold cavity, which is a flow path, are achieved, and low pressure and complete filling in a short time are achieved. That is, for example, when the mold opening amount is about 0.5 to 1 mm, the resin pressure is 1/3 to 1/3 as compared with the fully closed state (in the case of the conventional molding method).
Since the pressure can be reduced to about 1/5 (satisfies the acceptable range (E) in FIG. 4), the effect of preventing skin damage during filling is also remarkable. In this embodiment, as in the case of the first embodiment, it is desirable to previously set injection conditions that allow short-time filling. In addition, by setting the micro mold opening amount, the skin material periphery is held,
The tension control of the skin material S corresponding to the core material Q filling is realized.

Further, the holding of the mold open also serves to discharge the surplus surplus gas that has contributed to the moist cooling effect, of the gas in which the moist skin material S has been evaporated and vaporized by the heat of the core material resin. This prevents molding defects due to the filling of the gas in the mold cavity, and promotes stable evaporation and guarantees a stable and continuous wetting effect.

Upon completion of the injection, the process enters the mold clamping pressure step, detects the resin pressure in the mold cavity, and controls the mold clamping pressure (mold clamping pressure) so as to fall within the set pressure range of the resin pressure. Also in this case, similarly to the first embodiment of FIG. 3, in order to avoid damage to the skin material S and to surely shape the resin of the core material, the resin pressure is, for example, as shown in FIG. 2 to 50 kgf /
The pressure range is as low as about ² cm ² . After the cooling of the core material resin Q is completed, the mold is opened to take out the product. In addition,
By holding the opening amount of the small mold of, for example, about 0.5 to 1 mm within a range where the resin does not leak, the core material resin Q is almost completely filled (just pack) in the mold cavity when the injection filling is completed. Since there is no discontinuity in the resin flow when the process proceeds to the mold holding pressure step, non-uniformity of the skin material due to defects such as flow marks does not occur at all. This is an effect obtained by injecting and filling a resin amount obtained by adding an appropriate mold opening amount and a cooling solidification shrinkage amount of the resin. Therefore, the same effect is obtained in the first embodiment.

As described above, the mold clamping pressure is controlled and the mold opening is set in the most suitable pressure range based on the core material properties, the shape of the molded product, etc., with the skin material properties as the main components, and the cooling solidification shrinkage of the resin is added. By simultaneously performing injection filling control to inject the filled resin amount into the mold cavity, it is possible to achieve low pressure, short time just pack filling, and uniform uniformity from the mold clamping side corresponding to the resin's cooling solidification shrinkage behavior. Due to the pressure-holding action, at the same time as the shaping action of the core material Q, a uniform close contact action between the skin material S and the core material Q without deformation, warpage, or damage to the skin material is performed. Furthermore, by using the skin material S in the wet state adjusted to the ideal state most intended by the present invention, the endothermic heat of vaporization due to continuous evaporation of the wet liquid during the period from the start of injection of the core material Q to the completion of cooling. By the action, the cooling effect (wetting effect) of the skin material is maintained, and damage to the skin material is prevented. Evaporated gas (excess)
Is discharged from the gap between the two molds in the mold open state. As a result, a more stable supply of a high-quality molded product having excellent surface properties is realized.

Therefore, according to the present invention, other than the above, for example, the following forming patterns are possible. The control pattern of the resin pressure during the mold clamping pressure is changed in multiple steps within the allowable pressure range according to the shape of the molded product. Alternatively, the mold clamping pressure is controlled based on the mold clamping pressure corresponding to the allowable resin pressure. The injection operation is performed in parallel with the mold clamping operation as long as the resin does not leak. However, when the injection is completed, it is necessary to maintain an appropriate mold opening. Further, it is combined with the above operation.

In addition to the integral skin molding method using an injection molding machine, the present method can be carried out in an integral skin molding method using, for example, press molding or blow molding. That is, any machine capable of controlling the resin pressure during molding can be used in combination with the wet skin material of the present invention.

There is no particular limitation on the skin material S, and it is selectively used depending on the required performance. One example is shown below. In order to obtain a texture and softness, a resin sheet such as a PP resin or a PE resin, a two-layer sheet in which a foam layer such as a foamed PP is attached to the back of a leather or a cloth are used. . In addition, in order to give a feeling of touch and luxury, use a two-layer sheet having a raised layer such as synthetic fiber or cloth on the surface of a resin sheet such as PP or PE, and foam on the back of the resin sheet if necessary. A layer may be provided. In the present embodiment, a sheet material is used as the skin material, but a material preliminarily formed into a shape roughly in accordance with the shape of a molded product may be used.

As for the core material Q, a thermoplastic resin such as PP or PE is used, and talc, fiber or the like is added as necessary.

In the present invention, a mold having a normal mold structure is used for the purpose of obtaining a skin-integrated molded article having excellent surface properties at a lower cost. However, resin leakage does not occur even when the mold is opened. It is possible to use a mold with a special structure. In this case, the cost is slightly higher.However, by realizing a large mold opening, the resin pressure can be reduced thoroughly, thus preventing damage to the skin material. If a weight is placed on the surface (mainly for damage prevention rather than cost reduction), a great effect can be expected.

[0035]

As described above, according to the method of the present invention, the following excellent effects are achieved. (1) The cooling effect of evaporating and vaporizing the wetting liquid is skillfully used to prevent damage to the skin material, and molding can be performed without impairing the fluidity of the core resin in the mold cavity. I have. (2) Damage to the skin material (foamable skin material loses soft feeling due to collapse of foam layer, brushed skin material loses feel and luxury due to hair fall, surface of skin material due to local stretching An integrated skin-molded article having very excellent appearance performance without uneven properties, breakage, wrinkles, etc.) can be stably obtained. (3) A good molded product without deformation and warpage can be obtained by uniform pressure-holding action from the mold clamping side in accordance with the cooling, solidification and shrinkage behavior of the resin.

[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 an explanatory diagram illustrating an example of a wetting process according to an example of the present invention.

FIG. 3 is a diagram showing a step of forming the integral skin (first step) according to the embodiment of the present invention;
15 is a flowchart of Example).

FIG. 4 is a graph showing a correlation between a resin pressure in a mold cavity, a holding time, and a degree of damage to a skin material in a skin integral molding step according to an example of the present invention.

FIG. 5 is a diagram showing a step of forming the integral skin according to the embodiment of the present invention (second embodiment);
15 is a flowchart of Example).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixed board 2 Movable board 3 Fixed mold 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 Reference Signs List 50 hydraulic supply source 52 hydraulic control valve 60 control device 61 injection control unit 62 mold clamping control unit 63 resin pressure sensor 64 position sensor 65 timer 69 hydraulic control valve 70 hydraulic supply source 80 spray robot 100 injection molding machine Q core material S skin material

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-64-61213 (JP, A) JP-A-8-1556023 (JP, A) JP-A-2-307722 (JP, A) JP-A-3-3 264317 (JP, A) JP-A-08-27042 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B29C 45/14-45/77

Claims (1)

(57) [Claims] A mold material is clamped by interposing a skin material between a pair of left and right or upper and lower molds facing each other, and then a core material is inserted into a mold cavity formed by the skin material and the two molds. Injection-filling the molten resin to form the skin material and the core material integrally, in which the skin material is sprayed with a wetting liquid per skin material of 0.01 to 0.1 ml / cm2. Thereafter, the amount of molten resin obtained by adding the amount of cooling, solidification, and shrinkage of the molten resin of the core material is injected and filled, and the resin pressure in the mold cavity is reduced to 70 to 1 during molding.
A method for integrally molding a skin, wherein a mold clamping pressure is controlled so as to be in a range of 50 kgf / cm ² .