JP5168897B2 - Multilayer molding method of resin - Google Patents

Description

The present invention relates to multi-layer molding of a resin that is molded by injecting at least two kinds of resins into a mold cavity, and changes the shape of the second-layer molded product to be molded on the rising surface portion of the molded product when molding into multiple layers. It relates to a multilayer molding method.

  Conventionally, a resin multilayer molding method in which two or more kinds of resins are injected into a mold and molded is widely known, and multilayer molded products are used in a wide range of fields.

  Multi-layer molded products with a foam layer have also been produced in the past, but in recent years, the market has become widespread, especially because the amount of resin used can be reduced to reduce weight, and its use in many product fields. Being considered. Along with the fact that weight reduction leads to cost reduction, we have further expanded the field of foam products.

As a technique for molding a multilayer molded article having a foam layer, a multilayer molding method disclosed in Patent Document 1 or Patent Document 2 is known.

JP 54-86550 A

Japanese Patent Publication No.46-29637

In Patent Document 1, after molding the first layer of resin in the mold, the mold is slightly opened to enlarge the mold cavity, and the second layer of resin is injected into the expanded mold cavity. A multilayer molding method for foaming a resin is disclosed. Further, Patent Document 1 further discloses a foam molding method in which a mold cavity is appropriately enlarged as necessary when foaming a second layer of resin. According to the multilayer molding method disclosed in Patent Document 1, the resin for molding the first layer can be different from the resin for molding the second layer. For example, by foaming only the resin of the second layer, It is also possible to mold a high-functional foam-molded product that has both a soft feel and rigidity.

  Similarly, Patent Document 2 discloses a multilayer in which a first layer of resin is molded in a mold, a mold cavity is expanded, and a second layer of resin is injected into the expanded mold cavity for foaming. A molding method is disclosed. Therefore, in the same way as the multilayer molding disclosed in Patent Document 1, in the multilayer molding method disclosed in Patent Document 2, the resin for molding the first layer and the resin for molding the second layer can be different. As a result, it is possible to mold a highly functional multilayer molded product.

  In addition, in order to secure a gap necessary for injecting the resin of the second layer, a method of slightly opening the mold as described above is known as a method of enlarging the mold cavity. There are several methods, for example, a method of expanding a mold cavity by die replacement as shown in Patent Document 3 is known.

JP-A-6-134803

  The technique disclosed in Patent Document 3 is a method of changing a shape of a mold cavity by exchanging a part of a mold during molding.

By the way, when the mold cavity is expanded to form a void and a void is formed, and when the void is filled with the second resin and the second layer is molded, the molded product of the second layer is inevitable. In addition, a gap formed by opening a mold and a uniform gap in the mold opening and closing direction and a gap due to thermal contraction of the first resin are filled.
Therefore, when molding the second resin, it is easy to obtain a gap of a desired dimension in the mold opening / closing direction, but in directions other than the mold opening / closing direction, for example, the direction perpendicular to the mold opening / closing direction, etc. Only voids generated by thermal contraction of the first resin can be created, and as a result, the voids for filling the second resin cannot be enlarged greatly in the direction side.

However, depending on the shape of the desired molded product, a standing surface portion extending in the mold opening / closing direction may be formed in the mold cavity during molding, and the thickness dimension (so-called wall thickness dimension) of the standing surface portion is Since the dimensions are perpendicular to the mold opening / closing direction, a large gap cannot be formed. For this reason, when molding the second resin, the thickness dimension of the resin layer (sometimes referred to as a layer thickness dimension) is limited.

  In other words, in the above-described prior art, when a molded product having a standing surface portion is molded, particularly when the standing surface portion is parallel to the mold opening / closing direction or shifted by a small angle with respect to the mold opening / closing direction. Even if the mold is opened, there is only a slight gap formed in the standing surface portion, and there is a problem that the thickness of the second resin layer cannot be increased.

In particular, as the functionality of products has increased recently, the layer thickness dimension control of molded products has become strict, and there are cases in which it is required to increase the thickness of the second layer of resin molded at the standing surface.
In some cases, including the draft angle of the standing surface portion, the inclination angle of the standing surface portion (inclination angle from the mold opening / closing direction) cannot be increased. In such a case, the standing surface portion is parallel to the mold opening / closing direction, or The problem described above becomes serious because it is substantially parallel to the mold opening and closing direction.

In the multilayer molding method disclosed in the above-mentioned conventional patent document 1 or patent document 2, the thickness that can be molded in the second layer is limited by the shape of the molded product, so that the inclination angle of the standing surface portion is as large as possible. Then, the above-mentioned problem can be solved by such a method that the gap of the standing surface portion is opened even by slightly opening the mold, or the thickness of the first resin formed on the standing surface portion is increased to increase the amount of heat shrinkage. It was dealt with, but it did not lead to a fundamental solution.

  Further, in the multilayer molding method disclosed in Patent Document 3, the shape of the molded product molded in the second layer is determined by the shape of the molded product molded in the first layer as in Patent Document 1 or 2 described above. There is no end to it. However, in order to replace the mold during molding, a special mold exchanging device is required, which increases the size of the molding machine and increases the cycle time. Furthermore, there is a problem that a mold for replacement during molding is necessary and expensive.

The present invention has been made in view of the above problems, and a multilayer molded product in which the shapes of the first layer and the second layer are different for the purpose of expanding the use range of the multilayer molded product to a wider product field. The multilayer molding method which can manufacture is provided.

In order to achieve the above object, a method for multilayer molding of a resin according to the present invention includes:
(1) Filling the mold cavity with the first resin and molding the first layer, and forming the first layer and then expanding the volume of the mold cavity by mold opening operation In the resin multilayer molding method, comprising the step of filling the part with the second resin and molding the second layer, the mold opening and closing adjacent to the standing surface part extending in the mold opening and closing direction formed in the mold cavity placed incorporate nest to move freely advance and retreat in the direction as part of the mold cavity surface, in the time of forming the second layer, the shape of the mold cavity by retracting the telescopic relative to the mold cavity Change.

(2) In the multilayer molding method of (1),
When the second resin has foamability, after filling the resin, the volume of the mold cavity is further expanded by a mold opening operation, and the insert is moved backward with respect to the mold cavity by a driving device. The shape of the mold cavity is changed to foam the resin.

  According to the multilayer molding method of the present invention, it is possible to produce a multilayer molded product having different shapes of the first layer and the second layer without using a special device such as a mold changer and the like. The thickness of the second layer of the resin can be made larger than the conventional one.

  Also, when using a foamable resin as the resin for forming the second layer, the softness, cushioning, sound absorption and heat insulation can be changed by changing the layer thickness freely up and down to the standing surface. A multilayer molded article having improved properties can be obtained.

  Furthermore, since the position of the movable plate can be controlled with high accuracy by using the toggle type clamping mechanism as the clamping mechanism of the multilayer molding apparatus according to the present invention, the volume of the mold cavity can be controlled with high precision. It is possible to obtain a multilayer molded article having uniform and fine foamed cells and a highly accurate foaming ratio.

  Hereinafter, a preferred example of a mode for carrying out the present invention will be described in detail with reference to the drawings. 1 and 2 relate to an embodiment of the present invention, FIG. 1 is a cross-sectional view of a principal part schematically showing the configuration of a multilayer molding die, and FIG. 2 conceptually shows the overall configuration of the multilayer molding apparatus. It is explanatory drawing. 3 and 4 are conceptual diagrams for explaining the steps of the multilayer molding method according to the embodiment of the present invention.

  A multilayer molding apparatus 100 used in the embodiment shown in FIG. 2 includes a mold 10, a mold clamping apparatus 20, an injection apparatus 30, and a control apparatus 60.

  Hereinafter, the structure of the mold 10 will be described. 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. The fixed mold 3 and the movable mold 4 have a half-push structure in which the fitting parts are fitted together. The mold cavity 5 is formed in the fitted state.

The fitting portion of the half-pressing structure is formed over the entire circumference of the mold cavity, and even after the molten resin is filled, the mold cavity can be opened or closed slightly to increase or decrease the volume of the mold cavity. The resin filled in is prevented from leaking out of the mold 10.

  The fixed mold 3 constituting the mold 10 includes a hot runner for introducing a resin injected from a first injection unit 31 described later to the mold cavity 5 from the introduction port 3A, and a second injection described later. A hot runner for introducing the resin injected from the unit 32 into the mold cavity 5 through the introduction port 3B, and the former hot runner has a first valve gate 6A (also referred to as a first valve 6A). The latter hot runner includes a second valve gate 6B (sometimes referred to as a second valve 6B).

Hereinafter, the multilayer molding die 10 according to the present embodiment will be described.
In the multilayer molding die 10 according to the present embodiment, a frame-like slide core 7 is arranged as a nest in the die, and the slide core 7 is arranged so as to be adjacent to the standing surface portion 9 of the mold cavity 5. Part of the mold cavity surface is formed. In the present embodiment, as shown in FIG. 1, a slide core 7 (nesting) is incorporated as a part of the mold cavity 5, and the mold cavity is moved forward and backward. The shape (layer thickness dimension) of the 5 standing surface portions 9 can be changed.

In the embodiment of FIG. 1, the slide core 7 has a shape in which a flat plate extending in the mold opening / closing direction is assembled in a frame, and in the mold opening / closing direction processed on the mold cavity surface of the movable mold 4. By being inserted into an extending groove (sometimes referred to as a cylinder part), it is incorporated into the mold cavity surface and is supported and disposed so as to be slidable in the groove part.
In the embodiment shown in FIG. 1, a hydraulic cylinder is formed adjacent to the groove, and the slide core 7 can be moved forward or backward relative to the mold cavity 5 using the hydraulic cylinder as a driving device. Has been.
In this embodiment, in order to simplify the structure, the hydraulic cylinder as described above is used as a driving machine. However, the driving machine is a commercially available driving machine such as a general-purpose hydraulic cylinder or an electric cylinder. Alternatively, a driving method may be adopted by connecting a connecting flange or a cam (not shown) to the slide core.

According to the embodiment shown in FIG. 1, with the above-described configuration, the thickness of the standing surface portion 9 is increased (thickened) or decreased (thinned) by moving the slide core 7 forward or backward relative to the mold cavity 5. ).

In the embodiment shown in FIG. 1, hydraulic lines P1 and P2 are connected to the hydraulic cylinder. Then, the slide core 7 moves forward to the mold cavity side (fixed mold 3 side) by applying oil pressure to the hydraulic line P2 and extracting oil from P1, and the slide core 7 moves into the mold cavity. As the slide core 7 is inserted, the standing surface portion 9 is configured such that the thickness (dimension in the direction perpendicular to and intersecting the mold opening / closing direction) is reduced and the volume is reduced.
Further, the slide core 7 is retracted from being separated from the mold cavity 5 by applying oil pressure to the hydraulic line P1 and extracting the oil from P2, and only the portion where the slide core 7 is retracted is retreated. As a dimension, the thickness increases and the volume increases.

In the present invention, the flat slide core 7 assembled in the frame is nested, but the shape of the nested used in the present invention is not limited to this, and is necessary for the shape of the molded product. The shape may be determined according to the configuration to be performed.
For example, in the embodiment shown in FIG. 1, the slide core 7 is determined on a flat plate in accordance with the shape of the standing surface portion 9, and may be, for example, a prism or the like according to the requested purpose. good.

  Next, as shown in FIG. 2, the mold clamping device 20 includes a toggle-type mold clamping mechanism 21 driven by a fixed platen 1, a movable platen 2, and a link driving mechanism that is moved by a mold clamping servomotor 20B. I have. The movable platen 2 is guided by a tie bar (not shown) installed between the fixed platen 1 and the end plate, and can be moved forward and backward together with the movable die 4 by a toggle type mold clamping mechanism 21.

In the present embodiment, a stroke sensor (not shown) for detecting the position of the crosshead is attached to the crosshead drive shaft of the link drive mechanism provided in the mold clamping device 20, and the position of the movable platen 2 is determined. The movable platen position sensor (not shown) is arranged to detect the position of the movable platen 2 as a mold open / close stroke sensor for detecting the die open / close stroke.

  The multilayer injection device 30 shown in FIG. 2 includes two machines, a first injection unit 31 and a second injection unit 32, as the injection devices. The first injection unit 31 is built in the barrel 31A and the barrel 31A. A screw, a hopper for supplying a thermoplastic resin material to the barrel 31A, and a screw driving device 31C for moving the screw forward and backward or rotating are provided. A heater (not shown) is attached to the outer peripheral surface of the barrel 31A.

  Similarly, the second injection unit 32 is provided with a barrel 32A, a screw provided in the barrel 32A, a hopper for supplying a thermoplastic resin material to the barrel 32A, and a screw driving device 32C for moving the screw forward and backward. . A heater (not shown) is attached to the outer peripheral surface of the barrel 32A.

Further, in the first injection unit, the thermoplastic resin material is supplied from the hopper into the barrel 31A by rotating the screw, and the supplied thermoplastic resin material is supplied into the barrel 31A. It is heated by the attached heater, and melted by receiving a kneading compression action by the rotation of the screw and sent to the front of the screw.
The molten resin sent to the front of the screw can be filled into the mold cavity 5 by the screw from the nozzle 31B attached to the tip of the barrel 31A and the first valve 6A attached to the fixed mold 3.

  Similarly, in the second injection unit, the mold cavity 5 can be filled from the nozzle 32B attached to the tip of the barrel 32A and the second valve 6B attached to the fixed mold 3.

  The control device 60 controls the mold clamping control unit for controlling the opening and closing of the mold and the mold clamping force, and the first and second injection units to plasticize the thermoplastic resin material and mold the mold cavity 5 of the molten resin. The injection control part which controls filling to is provided.

  The mold clamping control unit of the mold clamping device 20 can set the opening / closing position of the movable mold 4 in multiple stages as required, and set the opening / closing speed of the movable mold 4 to be variable according to the mold opening / closing position as necessary. A mold clamping condition setting machine is provided, and based on the set value, the movable mold 4 during the mold opening / closing period (that is, during the period from the start of mold closing to the completion of mold opening after final mold clamping) The opening / closing position and opening / closing speed of the can be controlled. Further, the mold clamping condition setting machine can set the opening / closing speed of the movable mold 4 so as to change in multiple stages 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 controlled by the position data of the crosshead detected during the mold closing operation based on the positional relationship data of the crosshead corresponding to the position of the movable platen 2 stored in advance. It has become.

A preferred example of the multilayer molding method according to the present invention will be described below with reference to FIG.
First, as a first step, the mold 10 is clamped between the movable platen 2 and the fixed platen 1 by the mold clamping device 20 as shown in FIG. A mold cavity 5 is formed between 4.

Next, as the second step, as shown in FIG. 3B, the first resin is fed from the first injection unit 31 into the mold cavity 5 with the first valve 6A switched and opened. Fill. Then, after completion of filling, the first valve 6A is switched and closed for a predetermined time.
In the present embodiment, the resin to be filled as the first resin is a thermoplastic resin that is in a molten state. Accordingly, the resin filled in the mold cavity 5 is held there for a predetermined time and then cooled and solidified to form the first layer of the molded product. In this step, the cooling time of the first resin is set so that when the mold 10 is slightly opened and when the second resin is filled in the mold cavity in the step described later, This is the time required to solidify the first layer to such an extent that it will not be damaged.

Then, as shown in FIG. 3 (3), as shown in FIG. 3 (3), the slide core 7 is driven to change the shape of the mold cavity 5 to enlarge the thickness dimension of the standing surface portion 9. An air gap is generated between the mold cavity surface and the molded product made of the first resin. In addition, this space | gap part becomes new cavity space filled with 2nd resin mentioned later.
In the step shown in FIG. 3 (3), oil is supplied to the hydraulic line P1 to apply hydraulic pressure, and the oil is removed from the hydraulic line P2, so that the slide core 7 is moved in the direction of the anti-mold cavity 5 (anti-fixed mold). 3 side direction).

  In the present embodiment, the hydraulic cylinder method is selected as the driving method of the slide core 7 that is a nesting. However, the driving method of the nesting that can be applied to the present invention is not limited to this. A known drive system such as a pressure cylinder system, an electric system, a cam system, or a spring system can be employed. Further, in order to improve the movement accuracy of the movement amount of the slide core 7 which is a nesting, it is preferable to use a limit sensor for determining the forward limit and the backward limit, a movement amount detection sensor, or the like.

  Next, as a fourth step, the mold clamping device 20 is operated to move the movable mold 4 slightly in the direction of the anti-fixed mold 3 as shown in FIG. The volume is increased, a gap is formed between the molded product of the first layer and the mold cavity surface of the movable mold 3, and a gap is formed. This void portion also becomes a new cavity space filled with a second resin described later.

  In the present embodiment, after the completion of the third step, the process proceeds to the fourth step. However, in the third step and the fourth step, the nesting operation adversely affects the first layer and the mold opening operation of the molded product. May be performed within a range that does not give the same, or at the same time, or by changing the order of the steps (after entering the fourth step, the third step).

  Next, as a fifth step, as shown in FIG. 3 (5), the mold cavity 5 in which the second resin is expanded from the second injection unit 32 with the second valve 6B switched and opened. Fill inside. Then, after the filling is completed, the second valve 6B is switched and closed, and is held for a predetermined time to be cooled and solidified.

  When the second layer molded product is solidified to such an extent that it can be removed from the mold 10 by holding for a predetermined time, the process proceeds to the sixth step, and the mold clamping device 20 is operated as shown in FIG. As a result, the molded product is taken out from the mold 10. In the present embodiment, the layer thickness of the second resin formed by the standing surface portion 9 can be formed larger than that of the conventional case in the molded product portion of the second layer by the process described above.

  In the present invention, the thermoplastic resin material used for the first layer and the second layer is not particularly limited, but the first layer and the second layer are joined and integrated in the mold. 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. It is done.

  Hereinafter, another preferable example of multilayer molding according to the present invention will be briefly described with a focus on differences from the embodiment described with reference to FIG. The process illustrated in FIG. 4 is a suitable form when a resin in which a foaming agent is mixed in advance is used as the second resin for forming the second layer, as a resin having foamability.

First, the first to third steps are performed in the same manner as in the embodiment shown in FIG. As a fourth step, as shown in FIGS. 4 (4) to 4 (5), the second valve 6B is switched and opened while the slide core 7 is driven to increase the thickness dimension of the standing surface portion 9. In this state, the second resin is filled into the mold cavity 5 from the second injection unit 32.
In this case, preferably, the mold clamping device 20 is further operated to move the movable mold 4 in the direction of the anti-fixed mold 3 so that the second resin is foamed in the mold cavity 5 to a required magnification. Then, the volume of the mold cavity 5 may be further expanded so that it can expand.

Then, after the second layer of resin is filled, the second valve 6B is switched and closed for a predetermined time.

In addition, 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 the other embodiments of the present application, the resin for foaming is filled in the mold while driving the slide core 7, but the scope of application of the present invention is not limited thereto, for example, After the slide core 7 is moved to a predetermined position to increase the thickness dimension of the standing surface portion 9, the mold cavity is opened so that the second resin can be expanded and expanded to the required magnification by opening the mold 10. The volume of the mold cavity 5 may be expanded, or the mold core 5 may be opened to expand the volume of the mold cavity 5 so that the second resin can expand and expand to the required magnification. It may be moved to a predetermined position to increase the thickness dimension of the standing surface portion 9.

  In particular, when the second resin is a foamable resin, after filling the second resin, moving the slide core 7 in accordance with the foaming to create a void makes uniform foam bubbles. This is advantageous in that

  After the foaming is completed, the mold clamping device 20 is operated when the second layer of the foamed molded product is solidified to such an extent that it can be removed from the mold 10 as shown in FIG. 4 (7). Thus, the molded product is taken out from the mold 10.

  Note that the present invention is not limited to the above embodiments, and it goes without saying that various changes and improvements can be added without departing from the spirit of the present invention.

It is principal part sectional drawing which showed the general | schematic structure in order to demonstrate the structure of the metal mold | die for multilayer molding in connection with embodiment of this invention. It is explanatory drawing for demonstrating the whole structure of the multilayer shaping | molding apparatus to embodiment of this invention. It is a figure for demonstrating the process of the multilayer molding method in connection with embodiment of this invention. It is a figure for demonstrating the process of the multilayer molding method in connection with other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fixed platen 2 Movable platen 3 Fixed type | mold 4 Movable type | mold 5 Mold cavity 7 Slide core 9 Standing surface part 10 Multilayer molding die 20 Clamping device 21 Toggle type clamping mechanism 30 Multilayer injection device 31 1st injection unit 32 2nd Injection unit 3A First resin inlet 3B Second resin inlet 60 Control device 6A First valve (first valve gate)
6B Second valve (second valve gate)
P1 hydraulic line (for slide core, rod side)
P2 hydraulic line (for slide core, head side)
100 multilayer molding machine 20B servomotor for mold clamping 31A barrel (first injection unit)
31B nozzle (first injection unit)
31C Screw drive (first injection unit)
32A barrel (second injection unit)
32B nozzle (second injection unit)
32C screw drive (second injection unit)

Claims (2)

Filling the mold cavity with the first resin to form the first layer;
After molding the first layer, filling the second resin into the gap formed by expanding the volume of the mold cavity by mold opening operation, and molding the second layer,
In the multilayer resin molding method provided,
A second layer is formed by placing a nest that is movable in the mold opening / closing direction as a part of the mold cavity surface, adjacent to a standing surface portion formed in the mold cavity and extending in the mold opening / closing direction. A multilayer molding method for resin, wherein the insert is moved backward with respect to the mold cavity to change the shape of the mold cavity. When the second resin has foamability, after filling the resin, the volume of the mold cavity is further expanded by a mold opening operation, and the insert is moved backward with respect to the mold cavity by a driving device. The method for forming a resin multilayer according to claim 1, wherein the resin is foamed by changing the shape of the mold cavity.

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