JP2006281698A - Foam molded product molding method and foam molded product molding apparatus - Google Patents

Abstract

A foam-molded article has properties such as a reduction in surface property due to entrainment of foaming gas into a skin layer and a reduction in product rigidity due to bubbles inside. An object of the present invention is to provide a molding means that ensures the surface property and rigidity of such a foam-molded product without being restricted by the product shape and thickness, and is preferably obtained by one injection device.
Filling a mold cavity as a first layer with a predetermined amount of molten resin containing a foaming agent, holding the mold cavity for a predetermined time, and molding the first layer; and elapse of the predetermined time Fully filled with a molten resin containing a foaming agent in the gap formed as the second layer, which is formed by expanding the mold cavity later, and expanding and holding the expanded mold cavity after the filling of the molten resin is completed. And forming a second layer by foaming the resin, and a step of opening the mold after a predetermined cooling time has elapsed and taking out the molded product, and sequentially molding the foam layer in the mold .
[Selection] Figure 2

Description

  The present invention relates to a molding method and a molding apparatus for a foam molded product in which a molten resin containing a foaming agent is filled in a mold cavity and foamed, and in particular, a foam molded product obtained by sequentially laminating foam layers in a mold is obtained. The present invention relates to a molding method and a molding apparatus.

BACKGROUND ART Foamed molded articles that exhibit excellent effects in physical properties such as weight reduction, heat insulation, and sound absorption due to a large number of bubbles in the resin have been used in various fields for a long time.
In particular, in recent years, a technique of foaming a resin has been used to reduce the amount of resin used in a product to reduce the weight, and the reduction in cost has led to a reduction in cost, further expanding the field of foam molded products. However, technical problems still remain, such as a decrease in surface properties due to the entrainment of foaming gas into the skin layer and a decrease in product rigidity due to bubbles inside.

As a molding method in which the surface property does not deteriorate due to entrainment of the foaming gas into the skin layer and the surface of the molded product is smooth and less rough, for example, Patent Document 1 discloses a pressurized gas body in a mold cavity prior to injection filling. A molding method (gas counter pressure method) is disclosed in which a molten resin containing a foaming agent is filled and molten resin containing a foaming agent is filled, and then a mold cavity is expanded to foam the resin to obtain a molded product.
Patent Document 1 describes that the pressurized gas body suppresses the bursting of bubbles caused by the foaming gas at the flow front of the molten resin flowing in the mold cavity, thereby preventing surface defects. (See Patent Document 1)

On the other hand, as a molding method aiming at both improvement of surface properties and ensuring of product rigidity, for example, in Patent Document 2, molten resin containing a foaming agent is filled in a mold in an unfoamed state, and then molded. A molding method is disclosed in which a mold cavity is enlarged so that a hollow portion is formed in a product, and a molten resin containing a foaming agent is filled in the hollow portion to obtain a molded product.
According to the method for molding a foam molded article disclosed in Patent Document 2, a molded article having a sandwich structure in which the surface layer is an unfoamed layer having a good surface property and the inside of the molded article is a foamed layer for the purpose of reducing the weight. It is possible to obtain (See Patent Document 2)
JP 54-053171 JP 54-021384

However, in the molding method (gas counter pressure method) described in the above-described conventional patent document 1, the surface property of the molded product is improved, but a pressurized gas body is injected into the mold to be in a pressurized state. Since the gas body supply device and the specially structured mold with the gas body sealing mechanism that prevents leakage of the injected gas body under pressure are used, the equipment cost is high and the product cost is high. There were problems such as incurring high and restricting the product shape.
In addition, the gas body cannot be completely discharged out of the mold, and there are problems such as the occurrence of a gas loss failure and a decrease in product rigidity.

To ensure product rigidity, use special molding materials with special foaming grades, reinforcing agents such as talc and glass fiber, or modifiers such as rubber, or increase the thickness of the molded product. It was necessary to devise such as inserting a reinforcing material.
However, if special molding materials with special foam grades or reinforcing agents added are used, there will be a problem of increased costs, and if the thickness of the molded product is increased or a reinforcing material is inserted, the dimensions of the molded product will be increased. There is a problem that the shape is restricted and the weight of the molded product increases and cannot be reduced in weight.

Moreover, in the molding method described in the above-described conventional Patent Document 2, the mold resin is first filled with a molten resin containing a foaming agent in an unfoamed state, and then the mold cavity is expanded so that a hollow portion is formed. Next, since the hollow portion is filled with a molten resin containing a foaming agent to form a foam molded product, a sandwich-like structure is formed, and the shape and minimum thickness of the molded product are restricted, and the application range is also limited. There was a problem.
In order to ensure product rigidity, a special dedicated molding device with two injection devices that can supply different molding materials to the skin layer to be molded first and the core layer to be molded next is necessary. Met.

  Therefore, the present invention is not limited by the shape and thickness of the molded product when molded by the injection molding method, and has rigidity without using a special molding material with a dedicated foam grade or reinforcing agent added. However, the basic object is to obtain a foam-molded article having a smooth surface by a molding apparatus having one injection apparatus.

For this reason, in the first method of the present invention, (a) a mold cavity serving as a first layer is filled with a predetermined amount of molten resin containing a foaming agent, and the mold cavity is held for a predetermined period of time. And (a) filling the molten resin containing a foaming agent into the gap that becomes the second layer formed by enlarging the mold cavity after the predetermined time, and filling the molten resin A step of enlarging and holding the expanded mold cavity after completion and foaming the resin to form the second layer;
(C) a step of opening a mold after a predetermined cooling time has elapsed and taking out a molded product, and sequentially molding foam layers in the mold.

According to the second method of the present invention, (a) the mold cavity serving as the first layer is fully filled with a molten resin containing a foaming agent, and the mold cavity is enlarged after the filling of the molten resin to fill the resin. Foaming and holding the expanded mold cavity for a predetermined time to mold the first layer;
(Ii) After the lapse of the predetermined time, the enlarged mold cavity is expanded to form a void portion to be a second layer, and a second layer is formed by filling a predetermined amount of molten resin containing a foaming agent. And (u) a step of opening the mold after a predetermined cooling time has elapsed and taking out the molded product, and sequentially molding the foam layers in the mold.

  In the above case, the filling method for each of the first layer and the second layer is a method in which the filling amounts of the first layer and the second layer are added in advance and plasticized and weighed, and the filling is sequentially performed in each filling step. Alternatively, the filling amount of the first layer may be plasticized and measured in advance, and the filling amount of the second layer may be plasticized and measured after the filling of the first layer is completed.

  In the third method of the present invention, in the first invention, the predetermined amount of the molten resin containing the foaming agent to be the first layer is set to a resin amount substantially the same as the mold cavity volume of the first layer. did.

  Further, in the fourth method of the present invention, in the second invention, the predetermined amount of the molten resin containing the foaming agent to be the second layer is set to be approximately the same as the mold cavity volume of the second layer. .

In the third and fourth methods of the present invention, the predetermined amount of the molten resin containing the foaming agent and the resin amount substantially the same as the mold cavity volume filled with the molten resin are the completion of the filling of the molten resin. After that, the filling pressure acts to suppress the foaming pressure, and foaming cannot be performed, and solidification is performed as it is by cooling, thereby forming a layer containing almost no foamed cells (bubbles). In this method, since the mold cavity volume is maintained after filling with the molten resin, foaming is performed according to the cooling and solidification shrinkage behavior of the resin to obtain an extremely low foamed layer. On the other hand, a method of obtaining an unfoamed layer by reducing the mold cavity volume according to the cooling and solidification shrinkage behavior of the resin and suppressing foaming may be used.
In the third and fourth methods of the present invention, a method of obtaining a low foam layer by enlarging the mold cavity volume by a minute amount after filling with a resin amount substantially the same as the mold cavity volume, or a mold after filling A method may be used in which a non-foamed layer is formed by applying a holding pressure (holding pressure) while maintaining the cavity volume.

And in the 5th method of this invention, the molten resin containing the foaming agent used as the 1st layer and the 2nd layer is made into the same thermoplastic resin material in any one of the methods 1-4 of this invention. .
In the present invention, the thermoplastic resin material used for the first layer and the second layer is not particularly limited, and is a resin in which the first layer and the second layer are joined and integrated in the mold. Preferred are olefin resins such as polypropylene and polyethylene, acrylic resins such as polystyrene and polymethyl acrylate, polyamide resins such as 6-nylon, polyester resins, ABS resins, polycarbonate resins, and thermoplastic elastomers. In particular, a high-flow polypropylene resin with improved fluidity that can obtain a high expansion ratio even if it is thin is preferable.

Moreover, it does not specifically limit as a foaming agent used for this invention, A chemical foaming agent and a physical foaming agent can be used. Examples of the chemical foaming agent include inorganic foaming agents represented by sodium bicarbonate and organic foaming agents represented by azodicarbonamide (ADCA).
Examples of the physical foaming agent include inert gas such as carbon dioxide, nitrogen, and a mixed gas of carbon dioxide and nitrogen, air, and the like. These foaming agents may be used alone or in combination.
In addition, when the foam nucleating agent is mixed with the foaming agent and molded, the bubbles become finer and the dispersibility is improved. Therefore, a highly rigid foam layer with a high foaming ratio can be realized. Examples of the cell nucleating agent include fine powders of inorganic substances such as iron oxide, calcium silicate, zinc stearate or magnesium stearate, organic acids such as citric acid and tartaric acid, fine powders such as aluminum silicate, glass fiber and talc. It is preferable to use selectively according to the resin material to be molded.

A molding apparatus according to the present invention includes a pair of molding dies composed of a movable mold and a fixed mold, a mold clamping device that opens and closes the movable mold with respect to the fixed mold, and the mold clamping device. Includes a mold clamping position setting unit that can set the opening / closing position of the movable mold in multiple stages, and a mold clamping speed setting unit that can vary the opening / closing speed of the movable mold according to the opening / closing position. And a mold clamping control unit for controlling the mold opening / closing position and mold opening / closing speed during mold opening / closing based on the set values of these two setting units,
One injection device for filling a mold cavity with a molten resin containing a foaming agent made of a thermoplastic resin material, and filling the mold cavity with the molten resin to be a first layer and a second layer in the injection device It has an injection setting unit that can set injection conditions such as quantity, filling speed, and filling pressure, and controls injection conditions such as the filling amount, filling speed, and filling pressure of the molten resin based on the set values of the setting unit. An injection control unit was provided, and a foamed layer was sequentially laminated and molded in the mold.

  In the present invention, since the movable mold is moved to enlarge and mold the mold cavity, it is preferable to employ a toggle mechanism that can control the moving position of the movable plate to 1/100 mm or less. The drive mechanism of the toggle mechanism includes a hydraulic drive type and an electric servo drive type, but the use of the electric servo drive type is more preferable in terms of control stability and flexibility.

Further, in the present invention, a predetermined amount of molten resin containing a foaming agent for each of the first layer and the second layer is plasticized and measured by adding the predetermined amounts of the first layer and the second layer in advance. In addition, since the filling method is performed sequentially in each filling step, the filling amount of the first layer can be accurately controlled, and the filling amount of the second layer after filling can be accurately maintained. It is preferable to use an electric servo drive type injection device having excellent characteristics for holding the position of the screw for suppressing the foaming pressure.
In addition, a predetermined amount of molten resin containing the first layer of foaming agent is plasticized and measured, and after completion of filling of the first layer, a predetermined amount of molten resin containing the second layer of foaming agent is plasticized and measured. Even in the case of the filling method, the drive of the injection device is preferably an electric servo type in terms of control stability and flexibility.
The filling rate of the molten resin is preferably set to, for example, 750 g / sec or more, which can suppress foaming of the foaming agent at the flow front in the mold cavity and prevent the occurrence of swirl marks.

  The mold used in the present invention preferably uses a half-pressing structure in which the molten resin filled in the mold does not leak even if the cavity volume is enlarged or reduced by a predetermined amount. Instead, as long as it is applicable to foam molding, other molds such as a flat push structure may be used.

According to the first method of the present invention, the mold cavity is filled with a molten resin containing a foaming agent that becomes the first layer in the mold-clamped state, and is held for a predetermined time, and then the mold is opened to open the mold cavity. Filling the gap formed by the first layer and the mold cavity with a molten resin containing a foaming agent to be the second layer, and then performing mold opening again to expand the mold cavity volume. By foaming the second layer, it is possible to obtain a foam-molded product having a first layer as a strength layer and a second layer as a lightweight layer and having a smooth surface and product rigidity.
And by setting appropriately the filling amount with respect to the mold cavity volume of the first layer and the mold cavity enlargement amount after filling the molten resin with respect to the void volume of the second layer, even if it is a general-purpose thermoplastic resin It is possible to achieve product rigidity and weight reduction by laminating foam layers having different foaming ratios.

According to the second method of the present invention, the first layer is foamed by filling a molten resin containing a foaming agent which becomes the first layer in the mold-clamped state, and performing mold opening to enlarge the mold cavity volume. Then, the mold opening is performed again, the mold cavity is enlarged, and the gap formed by the first layer and the mold cavity is filled with a molten resin containing a foaming agent to be the second layer, so that the lightweight layer It is possible to obtain a foam-molded product comprising a first layer as a first layer and a second layer as a strength layer, the lightweight layer being smooth and having product rigidity.
And even if it is a general-purpose thermoplastic resin by setting appropriately the amount of expansion of the mold cavity after filling the molten resin to the void volume of the first layer and the amount of filling of the mold cavity volume of the second layer It is possible to achieve product rigidity and weight reduction by laminating foam layers having different foaming ratios.

In particular, since the filling amount of the molten resin into the first layer according to the first invention and the second layer according to the second invention is substantially the same as the mold cavity volume, even if the molten resin containing a foaming agent is filled. A foamed structure and an unfoamed layer with almost no foamed cells (bubbles) to prevent the product rigidity from falling down more reliably, and to express high surface properties and transferability if the product design side is used. Can do.
Furthermore, in the above case, the first layer and the second layer are made of molten resin in which the same thermoplastic resin material, a foaming agent, and a cell nucleating agent are appropriately mixed, and the filling method is set in advance for the first layer and the second layer. A method of adding plastics and adding plasticity to measure and sequentially filling in each filling step, or preliminarily plasticizing and filling the filling of the first layer, and after completion of filling of the first layer Since the filling amount of the second layer is plasticized and weighed, a foamed molded product having a smooth surface and ensuring product rigidity can be obtained using a molding apparatus equipped with one injection device.

  Further, according to the molding apparatus of the present invention, the opening / closing position of the movable mold can be set in multiple stages by the mold clamping position setting section, and the opening / closing speed of the movable mold is set to the opening / closing position by the mold clamping speed setting section. It can be variably set accordingly. Moreover, injection conditions, such as the filling amount of 1st layer and 2nd layer molten resin, can be set by an injection setting part. The mold clamping control unit and the injection control unit control the position and speed of the movable mold during the mold opening / closing period, the amount of filled resin, the filling speed, the filling pressure, and the like based on the set values of the three setting parts. Therefore, each set value can be controlled more finely according to the product shape, molding conditions, and the like. As a result, when molding a foam molded product that is formed by laminating foam layers by the foam molding method, the molding device is controlled so that a foam molded product with a smooth surface and product rigidity can be stably obtained. It becomes possible to do.

  The best mode for carrying out the present invention will be described below in detail with reference to the accompanying drawings. First, the shaping | molding apparatus for demonstrating the shaping | molding method concerning this embodiment is demonstrated. FIG. 1 is an explanatory view schematically showing the overall configuration of a forming apparatus for carrying out the forming method according to the present embodiment, and FIGS. 2 and 3 are explanatory views schematically showing the outline of the forming method. . 4 and 5 are diagrams for explaining the mold clamping operation, where the horizontal axis represents time, and the vertical axis is based on the contact point (mold touch point) between the movable mold and the fixed mold. Indicates the position.

As shown in FIG. 1, a molding apparatus 100 used in an embodiment of the present invention is a horizontal mold clamping type, and includes a mold 10, a mold clamping apparatus 20, an injection apparatus 30, and a control apparatus 60.
The mold 10 includes a fixed mold 3 attached to the fixed platen 1 and a movable mold 4 attached to the movable platen 2, and the fixed mold 3 and the movable mold 4 are fitted in the fitting portion. The mold cavity is formed in the half-pressed structure in the fitted state. Then, the fitting portion of the half-press structure is formed over the entire circumference of the mold cavity, and even if the volume of the mold cavity is enlarged or reduced after filling with the molten resin, the resin filled in the mold cavity is removed from the mold 10. Prevents leakage.
The fixed mold 3 of the mold 10 includes a valve runner 37 shown in FIG. 1 and a hot runner using a heating manifold (not shown). The mold 10 configured in this manner has no runner (or sprue) left in the molded product and has a wide range of conformity to the product shape, and seals the foaming gas immediately before the mold cavity. The foaming gas in the mold does not escape.

  The mold clamping device 20 includes a fixed platen 1, a movable platen 2, a link drive mechanism 26 using an electric servomotor 25 as a drive source, a toggle type mold clamping mechanism 8 driven by the link drive mechanism 26, and an electric servomotor. The movable platen 2 is guided by a tie bar 7 installed between the fixed platen 1 and the end plate 5 so that it can be moved forward and backward together with the movable die 4 by a toggle type mold clamping mechanism 8. It is configured. A stroke sensor 74 for detecting the position of the crosshead 28 is attached to the crosshead drive shaft 27 of the link drive mechanism 26 provided in the mold clamping device 20. Further, as a mold opening / closing stroke sensor for detecting the mold opening / closing stroke, a movable platen position sensor 71 is arranged so as to detect the position of the movable platen 2.

The injection device 30 includes a barrel 32, a screw 34 provided in the barrel 32, and a hopper 38 that supplies a thermoplastic resin material into the barrel 32, and a screw moving means 40 that moves the screw 34 forward and backward, Screw rotating means 42 for rotating the screw 34 is provided. A heater (not shown) is attached to the outer peripheral surface of the barrel 32.
Then, the screw 34 is rotated by the screw rotating means 42 so that the thermoplastic resin material is supplied from the hopper 38 into the barrel 32, and the supplied thermoplastic resin material is attached to the barrel 32. It is heated by the heated heater and melted by being subjected to a kneading compression action by the rotation of the screw 34 and sent to the front of the screw 34. The molten resin sent to the front of the screw 34 is moved from the nozzle 39 attached to the tip of the barrel 32 and the valve gate 37 attached to the fixed die 3 to the die cavity by the screw 34 advanced by the screw moving means 40. Can be filled.

On the other hand, the control device 60 includes a microcomputer as a main part, a mold clamping control unit 61 that controls opening / closing of a mold and a mold clamping force, plasticizing a thermoplastic resin material, and filling a mold cavity with molten resin. The injection control part 63 which controls is provided.
The mold clamping control unit 61 of the mold clamping device 20 requires a mold clamping position setting unit (not shown) that can set the opening / closing position of the movable mold 4 in multiple stages as necessary, and the opening / closing speed of the movable mold 4. And a mold clamping speed setting unit that can be set to vary according to the mold opening / closing position, and based on the set values of these two setting parts, during the mold opening / closing period (that is, from the mold closing start to the final The opening / closing position and the opening / closing speed of the movable mold 4 are controlled during the period from mold clamping to mold opening completion. The mold clamping speed control unit can set the opening / closing speed of the movable mold 4 so as to change in multiple steps according to the opening / closing position of the movable mold 4, and also set so as to change continuously. You can also.
The opening / closing position of the movable mold 4 is based on the positional relationship data with the position of the cross head 28 corresponding to the position of the movable platen 2 stored in advance, and the position data of the cross head 28 detected during the mold closing operation. Is controlled by.

Next, a method for molding a foam molded product in which the molding apparatus 100 of the present invention is used to sequentially laminate and mold foam layers in a mold will be described.
The first molding method of the present invention includes the following steps.
(A) filling a mold cavity serving as a first layer with a predetermined amount of molten resin containing a foaming agent, and molding the first layer while holding the mold cavity for a predetermined time;
(B) Fully filled with a molten resin containing a foaming agent in the gap that becomes the second layer formed by enlarging the mold cavity after the predetermined time has elapsed, and after completion of the filling of the molten resin A step of forming the second layer by expanding and holding the mold cavity and foaming the resin.
(C) A step of opening the mold after a predetermined cooling time has elapsed and taking out the molded product.
And the 2nd method of this invention is equipped with the following process.
(A) The mold cavity that is the first layer is fully filled with a molten resin containing a foaming agent, and after completion of filling the molten resin, the mold cavity is expanded to foam the resin, and the expanded mold A step of forming the first layer while holding the cavity for a predetermined time.
(Ii) After the lapse of the predetermined time, the enlarged mold cavity is expanded to form a void portion to be a second layer, and a second layer is formed by filling a predetermined amount of molten resin containing a foaming agent. Process.
(Iii) A step of opening the mold after a predetermined cooling time has elapsed and taking out the molded product.

  According to the molding method including the above steps, the amount of filled resin with respect to the mold cavity volume of each layer and the amount of expansion of the mold cavity volume after filling with molten resin can be adjusted. They can be stacked sequentially in the mold. As a result, when molding foamed molded products by laminating foam layers using a foam molding method that fills mold cavities with molten resin containing a foaming agent, there is no restriction on the shape or thickness of the molded product, and it is lightweight and rigid. Thus, a molded product having a smooth surface can be obtained stably.

Hereafter, the detail of each process in the 1st shaping | molding method of this invention is demonstrated, referring explanatory drawing of FIG. FIG. 2 is an explanatory view schematically showing an outline of the molding method.
In the molding step of the first layer 51 in the step (a), as shown in FIG. 2A, the movable mold 4 and the fixed mold 3 are in contact with each other and a predetermined mold clamping force is applied. The mold cavity is filled with a predetermined amount of molten resin containing a foaming agent that has been plasticized and measured in advance. For example, when the amount of resin to be filled in the mold cavity is smaller than the volume of the mold cavity, the shortage of the filled resin is compensated by expansion of the foaming gas, and the expansion ratio corresponding to the ratio between the mold cavity volume and the filled resin amount is used. A foam layer consisting of a thin skin layer, a foamed core layer and a thin skin layer is obtained. On the other hand, when the resin volume is approximately the same as the mold cavity volume, the filling pressure is applied after the filling of the molten resin is completed. Thus, the foaming pressure is suppressed, foaming cannot be performed, and solidification is performed as it is by cooling, whereby an unfoamed layer containing almost no foamed cells (bubbles) can be obtained.

In the forming step of the second layer 52 in the step (A), after cooling and solidifying the first layer 51, as shown in FIG. 2B, the movable platen 2 is moved backward to enlarge the mold cavity to form a gap. Then, the formed void is fully filled with a molten resin containing a foaming agent. Then, as shown in FIG. 2C, the movable platen 2 is moved backward again after the filling is completed, the mold cavity is expanded and the filled molten resin is foamed to form the second layer 52. Here, the foam molding of the second layer 52 is performed in accordance with the balance between the timing for expanding the mold cavity according to the degree of formation of the surface skin layer and the growth rate of the foamed cell and the elongational viscosity of the resin. Adjust the enlargement speed as appropriate. Further, the mold cavity may be multi-stage controlled so that the formation of the foam nuclei and the growth of the foam cells are performed separately as necessary. Then, the product thickness and the expansion ratio are controlled by the amount of expansion of the mold cavity (S2 minus S1).
In this way, molded articles 53 having different foaming ratios such as an unfoamed layer and a foamed layer, a low foamed double layer, and a high foamed double layer in the mold are obtained.

  Then, after the molding process of the second layer 52, as shown in FIG. 2 (d), the movable mold 4 is retracted, the mold is opened and the mold 53 is extruded (molded). Product removal step (c)) One molding cycle is completed.

Next, details of each step in the second molding method of the present invention will be described with reference to the explanatory view of FIG. FIG. 3 is an explanatory view schematically showing an outline of the molding method.
In the molding process of the first layer 51 in the process (A), as shown in FIG. 3A, the movable mold 4 and the fixed mold 3 are in contact with each other and a predetermined clamping force is applied. The mold cavity is fully filled with a molten resin containing a foaming agent that has been plasticized and measured in advance. As shown in FIG. 3B, the movable platen 2 is moved backward after the filling to enlarge the mold cavity. The first layer 51 is obtained by foaming the resin and holding the enlarged mold cavity for a predetermined time to cool and solidify. Here, the foam molding of the first layer 51 is performed in accordance with the balance between the timing of expanding the mold cavity according to the degree of formation of the surface skin layer and the growth rate of the foamed cell and the elongational viscosity of the resin. Adjust the enlargement speed as appropriate. Further, the mold cavity may be multi-stage controlled so that the formation of the foam nuclei and the growth of the foam cells are performed separately as necessary. Then, the product thickness and the expansion ratio are controlled according to the amount of expansion of the mold cavity (S12 minus S11).

  In the forming step of the second layer 52 in the step (ii), after the first layer 51 is cooled and solidified, the movable platen 2 is moved backward to enlarge the mold cavity and form a gap as shown in FIG. Then, a predetermined amount of molten resin containing a foaming agent is filled in the gap and held. For example, when the amount of resin to be filled in the mold cavity is smaller than the volume of the mold cavity, the shortage of the filled resin is compensated by expansion of the foaming gas, and the expansion ratio corresponding to the ratio between the mold cavity volume and the filled resin amount is used. A foam layer consisting of a thin skin layer, a foamed core layer and a thin skin layer is obtained. On the other hand, when the resin volume is approximately the same as the mold cavity volume, the filling pressure is applied after the filling of the molten resin is completed. Thus, the foaming pressure is suppressed, foaming cannot be performed, and solidification is performed as it is by cooling, whereby an unfoamed layer containing almost no foamed cells (bubbles) can be obtained.

Then, after elapse of a predetermined cooling time after filling the second layer 52, as shown in FIG. 3 (d), the movable mold 4 is moved backward to open the mold, and the molded article 53 is extruded from the mold 10. The molded product is taken out (the step of taking out the molded product (U)), and one molding cycle is completed.
In this way, molded articles 53 having different foaming ratios such as an unfoamed layer and a foamed layer, a low foamed double layer, and a high foamed double layer in the mold are obtained.

  Since it is configured as described above, there is no restriction on the shape or thickness of the molded product, and there is no need to use a special resin material with a foam-only grade or a reinforcing agent, and it has rigidity and a smooth surface. It became possible to obtain a foam-molded article with the molding apparatus 100 including one injection apparatus 30.

Using the molding apparatus 100 shown in FIG. 1 (electrical die-pressed machine UBE-MD350DP manufactured by Ube Industries Co., Ltd.), the following conditions are set in the first method of the present invention and molding is performed. A test was conducted.
(1) Molded product resin material: polypropylene resin (melt flow rate (ISO-1133) 30 g / 10 min)
(2) Mold temperature: 30-40 ° C
(3) Resin temperature: 190-200 ° C
(4) Filling time: 1 layer = 0.9 seconds, 2 layers = 1.1 seconds (5) Foaming agent and bubble nucleating agent: 3% by mass of mixed foaming agent of sodium bicarbonate and citric acid (6) First Layer thickness and expansion ratio: 0.9 mm, expansion ratio = 1.0 (unfoamed)
(7) Second layer void thickness (S1): 1.3 mm
(8) Cavity enlargement dimension (difference between S2 dimension and S1 dimension) and expansion ratio: 1.1 mm, expansion ratio = approximately 1.8

  Then, even if the molding conditions were adjusted, it was possible to mold a molded product that could not be molded by the conventional method and molding apparatus. That is, the thickness of the first layer is 0.9 mm, the thickness of the second layer is 2.4 mm (gap thickness 1.3 mm, cavity enlargement dimension 1.1 mm), the wall thickness is 3.3 mm, and the expansion ratio is approximately 1. It was possible to obtain a foam molded article in which 0.8 foam layers were laminated.

  Needless to say, the present invention is not limited to the above embodiments, and various modifications and improvements can be made without departing from the scope of the present invention.

  The foam-molded product obtained by the foam-molded product molding method and foam-molded product molding apparatus according to the present invention is thin and rigid because the surface is smooth, less rough, rigid and lightweight. There are various uses such as required automobile interior parts and home appliances.

It is explanatory drawing which shows roughly the whole structure of the shaping | molding apparatus for demonstrating the shaping | molding method which concerns on embodiment of this invention. It is explanatory drawing which shows typically the outline of the shaping | molding method in the said 1st invention. It is explanatory drawing which shows typically the outline of the shaping | molding method in the said 2nd invention. It is a diagram for demonstrating the mold clamping operation | movement by the shaping | molding method of the said 1st invention. It is a diagram for demonstrating the mold clamping operation | movement by the shaping | molding method of the said 2nd invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 Fixed mold 4 Movable mold 10 Mold 20 Clamping apparatus 30 Injection apparatus 51 1st layer 52 2nd layer 53 Molded product 60 Control apparatus 61 Mold clamping control part 63 Injection control part 100 Molding apparatus

Claims (6)

Filling a mold cavity as a first layer with a predetermined amount of molten resin containing a foaming agent, holding the mold cavity for a predetermined time, and molding the first layer;
Fully filled with a molten resin containing a foaming agent in the gap that becomes the second layer formed by enlarging the mold cavity after the predetermined time has elapsed, and after the filling of the molten resin is completed, the expanded mold cavity Expanding and holding and foaming the resin to form the second layer;
A step of opening the mold after a predetermined cooling time has elapsed and taking out the molded product,
A molding method for a foam molded product, in which foam layers are sequentially laminated in a mold. The mold cavity serving as the first layer is fully filled with a molten resin containing a foaming agent, and after the completion of filling the molten resin, the mold cavity is expanded to foam the resin, and the mold cavity after expansion is predetermined. Holding the time and molding the first layer;
Expanding the mold cavity after the expansion for a predetermined time to form a void portion to be a second layer, filling a predetermined amount of molten resin containing a foaming agent, and molding the second layer;
A step of opening the mold after a predetermined cooling time has elapsed and taking out the molded product,
A molding method for a foam molded product, in which foam layers are sequentially laminated in a mold.   The method for molding a foam molded article according to claim 1, wherein a predetermined amount of the molten resin containing a foaming agent filled in the first layer is set to a resin amount substantially equal to a mold cavity volume of the first layer.   The method for molding a foam molded article according to claim 2, wherein a predetermined amount of the molten resin containing a foaming agent to be filled in the second layer is set to a resin amount substantially the same as the mold cavity volume of the second layer.   The method for molding a foam molded article according to any one of claims 1 to 4, wherein the molten resin containing a foaming agent used for each of the first layer and the second layer is the same thermoplastic resin material. A pair of molding dies composed of a movable mold and a fixed mold;
A mold clamping device for opening and closing the movable mold with respect to the fixed mold;
The mold clamping apparatus includes a mold clamping position setting unit that can set the opening / closing position of the movable mold in multiple stages, and a mold clamping speed setting unit that can change the opening / closing speed of the movable mold according to the opening / closing position. And a mold clamping control unit for controlling the mold opening / closing position and mold opening / closing speed during mold opening / closing based on the set values of these two setting units,
One injection device for filling a mold cavity with a molten resin containing a foaming agent made of a thermoplastic resin material;
The injection apparatus includes an injection setting unit that can set injection conditions such as a filling amount, a filling speed, and a filling pressure of the molten resin to be the first layer and the second layer into the mold cavity. Based on the set value, an injection control unit for controlling injection conditions such as the filling amount, filling speed and filling pressure of the molten resin is provided,
A molding device for foamed molded products, in which foam layers are sequentially laminated and molded in a mold.

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