JPH10211633A - Sandwich molding method of resin molded article, molding device thereof, and resin molded article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To heighten the secondary resin packing in the boss part of a resin sandwich molded article. SOLUTION: A sub-cavity 8 is continuously connected through a leading-out passage 7 to a recessed part 6 corresponding to a boss part. The volume of the sub-cavity 8 is made variable by moving a piston 12. When a primary and a secondary resins 13 and 14 injected from a two-color molder consisting of a primary and a secondary cylinders 1 and 2 fill a cavity 3, the piston 12 is retreated from the sub-cavity 8 so as to enlarge the volume of the sub-cavity in order to pull the primary resin 13 from within the recessed part 6 in the enlarged sub-cavity 8, resulting in leading the secondary resin 14 in the recessed part 6 through the above-mentioned pulling-in.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for sandwich molding a resin molded article having a protrusion.

[0002]

2. Description of the Related Art A sandwich molding technique for a resin molded product uses a two-color molding machine to simultaneously or at a later timing with a primary resin for forming a skin layer (surface layer) in the same cavity. ) Injects secondary resin for molding to form a resin molded product with a double inner / outer structure. Use foamable resin for the core layer to reduce product weight and material usage, It is effective to reduce total cost by using inexpensive resin,
Since the core layer is formed of a high-strength material, and the skin layer is made of an expensive material having excellent slidability or a good feel, the added value can be increased.

[0003]

When a two-color molding machine is used to form a rectangular thin product as shown in FIG. 8, for example,
At the distal end portion A, the core layer 19 is narrow and thin, but is wide and thick at the central portion B. The core layer 19 is narrow and thick at the proximal end portion C near the gate 5.
9 are not evenly distributed. Further, when the boss portion is integrally formed on the surface of the thin plate product, the secondary resin among the injected resins is concentrated at the central portion of the cavity and has a product shape having a small protrusion such as a boss or a seat. In the cavity, as illustrated in FIG. 9, although the primary resin 13 for forming the skin layer enters the concave portion 6 corresponding to the boss portion as the protrusion, the secondary resin 14 extends into the concave portion 6. Since the boss does not penetrate sufficiently and the boss is formed only in the skin layer having no core layer or in a structure containing almost no core layer, the advantage of the sandwich molding is not utilized in the protrusion.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a sandwich molding technique which allows a secondary resin to be filled in a projecting portion, the structure comprising at least the projecting portion in a product-shaped main cavity having the projecting portion. In the corresponding space, a sub-cavity having a variable volume is continuously provided via a lead-out path, and the first and second resins corresponding to the amount exceeding the volume of the main cavity from the two-color molding machine are provided in the main cavity. In the step of injecting, when a predetermined amount of resin is filled in the main cavity, a part of both resins filled in the main cavity by expanding the volume of the sub-cavity is introduced into the sub-cavity, and Method of sandwich molding of resin molded product to draw secondary resin into space corresponding to protrusion of main cavity, product-shaped main cavity with protrusion, and main cavity And a two-color molding machine for injection first resin and a second resin within, to the main cavity,
A sandwich molding apparatus for a resin molded product, in which at least a space corresponding to the protruding portion is provided with a variable-volume sub-cavity via a lead-out path, and which is capable of controlling the volume expansion timing of the sub-cavity, is formed by the above-described method. And resin molded products. In the device, the sub-cavity can be made variable in volume by the reciprocating operation of a piston fitted in the sub-cavity, the maximum volume of the sub-cavity can be made variable, and the volume expansion speed of the sub-cavity can be made variable. .

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a sandwich molding apparatus and method for a resin molded product and a molded product according to the present invention will be described with reference to the drawings. FIG. 1 shows a molding apparatus according to the present invention, wherein 1 is a primary cylinder, 2 is a secondary cylinder, 3 is a main cavity formed in a mold 4, and the main cavity 3 has a width of 120 mm. Length 200mm, thickness 6.5
The gate 5 is provided at the center of one side surface. On the upper surface of the main cavity 3, there is formed a concave portion 6 corresponding to a boss which is a protrusion of a molded product. The concave portion 6 has a cylindrical shape with a diameter of 40 mm and a height of 40 mm. , Sub-cavity 8 through outlet path 7
Is provided. The gate 5 is connected via a sprue 9 formed in the mold 4 to a nozzle 10 having an inner / outer dual structure having an outlet of the secondary cylinder 2 coaxially arranged in the outlet of the primary cylinder 1. The primary cylinder 1, the secondary cylinder 2, and the nozzle 10 form a two-color molding machine. In the sub-cavity 8, a position where a piston 12 forcibly advanced and retracted by a hydraulic cylinder 11 advances to the sub-cavity 8 until it occupies the entire area in the sub-cavity 8, The sub-cavity 8 is moved so as to move between the retracted position and the sub-cavity 8 so that the volume of the sub-cavity 8 can be changed.

[0006] From a device provided with a two-color molding machine having the primary cylinder 1 and the secondary cylinder 2, a primary resin for forming a skin layer and a secondary resin for forming a core layer are injected. The secondary resin injected from the cylinder 2 fills the central portion of the primary resin injected from the primary cylinder 1. Although the injection timing is set so that the primary resin starts injection slightly earlier than the secondary resin and ends slightly later than the secondary resin, it can be changed. In the examples, the primary resin forming the skin layer has a melt index value of 9.2 (value at a temperature of 190 ° C. and a load of 2.16 kg measured according to ASTM D1239).
(G / 10 minutes), and the secondary resin forming the core layer has a melt index value of 3.6.
(G / 10 min) high impact polystyrene was used. The molding conditions were a cylinder temperature of 190 ° C., an injection speed of 67 mm / sec, a time difference between the injection of the primary resin and the injection of the secondary resin of 1.5 seconds, and injection filling for both the primary resin and the secondary resin. Resin pressure at the time and holding pressure after injection filling 30M
pa, the mold temperature was 60 ° C., and the cooling time was 85 seconds.

First, as a comparative example, the primary resin 13 and the secondary resin 14 are moved under the above-mentioned conditions while the piston 12 is advanced and the piston 12 is stopped while completely occupying the space in the sub-cavity 8. Into the main cavity 3,
The molded article was examined. As a result, the injection pattern in which the secondary resin 14 slightly advanced into the recess 6 was obtained as shown in FIG.

Next, as an example, in order to mold by the method of the present invention, before filling the resin, the piston 12 is advanced into the sub cavity 8 in the same manner as described above, and the primary resin 13 is 2, the piston 12 is retracted from the sub-cavity 8 as shown in FIG. 3, and the total volume of the primary resin and the secondary resin is reduced from the two-color molding machine as shown in FIG. It was added so as to exceed the amount, and at the end of the injection, control was performed so that only the primary resin was injected. Piston 12
Is retracted from the sub-cavity 8, the sub-cavity 8 is enlarged, and the primary resin 13 in the concave portion 6 is sucked into the enlarged sub-cavity 8 through the lead-out path 7,
Accordingly, the secondary resin 14 is drawn into the recess 6 together with the primary resin 13, and the primary resin 13 and the secondary resin 14 are filled into the recess 6. Inspection of the molded product revealed that the core layer was at least 50% or more at each point of 30 mm, 20 mm, and 10 mm from the tip within the boss, and the core was extended to the tip of the protruding portion, which was impossible with conventional means. It was confirmed that a layer could be formed.
FIG. 4 shows the filling ratio of the secondary resin at each point of the comparative example in which the piston was not operated and the embodiment in which the piston was operated. The resin filled in the sub-cavity 8 may be cut and separated at the outlet path 7 after the completion of molding.

Thus, the primary resin 13 and the secondary resin 1
4 is filled in the concave portion 8, the boss portion of the molded product also has a structure having the same characteristics as the base, the base and the core layer of the boss are continuous with each other, and the integral element is also high. . By exchanging the mold with a mold mounted on an existing device, the present invention can be implemented using the existing device.

Since the filling pattern of the secondary resin greatly depends on the balance of the rheological properties with the primary resin, for example, when the secondary resin has a higher viscosity than the primary resin, the ratio of the secondary resin is small, and 5 (a), the secondary resin 14 does not spread over a wide area, and in the opposite case, the secondary resin 14 spreads over a wide area, as shown in FIG. 5 (b), and is mostly occupied by the secondary resin 14. If the combination of primary resin and secondary resin changes even in the same cavity shape, the filling pattern of the secondary resin will of course be different, and the entire cavity and the shape of the concave portion are, for example, thin and long or thick and short. Even if it changes to, the filling pattern into the cavity and the concave portion will be greatly different. Therefore, consideration is given to controlling the timing, speed, stroke, and the like of operating the piston based on the difference in the balance between the two rheologies.

Since a hydraulic circuit is indispensable for the molding machine, a hydraulic cylinder can be suitably used for the operation of the piston. The injection timing is determined by, for example, picking up an injection start signal of a two-color molding machine, and setting a delay operation. Can be easily controlled. In addition, the operation of the piston can use an actuator other than the hydraulic cylinder, and it is desirable that the operation timing and speed can be adjusted according to the shape of the main cavity. Further, as illustrated in FIG. 6A, for example, the volume of the sub-cavity can be reduced by limiting the retreat amount of the piston 12 by using the spacer 15 to reduce the amount of the primary resin drawn into the sub-cavity 8. As shown in FIG. 6B, the amount of advance is suppressed by using the spacer 16 so that the space 17 is formed in the sub-cavity 8.
After the resin has flowed into the interior, the maximum volume of the sub-cavity and the amount of change in volume can be adjusted, for example, by retracting the piston and forcibly retracting the piston. Of course, a plurality of sub-cavities having different sizes may be prepared and exchanged. In the above embodiment, the piston is forcibly retracted by the hydraulic cylinder when the volume of the sub-cavity is increased, but the piston and the piston rod of the hydraulic cylinder are not connected, and the hydraulic cylinder moves the piston in the sub-cavity. The piston in the advanced state can be retracted by the pressure of the resin injected into the main cavity. or,
As a variable volume structure that not only continuously changes the volume of the sub-cavity but also provides, for example, an opening and closing mechanism in the lead-out path, and switches the minimum volume of the sub-cavity when the opening and closing mechanism is closed to the maximum by opening the opening and closing mechanism No problem.

In the above embodiment, the sub-cavity is provided only in the concave portion, but as shown in FIG.
The sub-cavity 18 is also provided continuously at the distal end of the main cavity 3 away from the gate 5, so that the secondary resin in the main cavity 3 can be distributed to the distal end side. In this case, the sub-cavity 18 connected to the tip not only forcibly retracts the piston but also pushes back with the pressure of the resin injected into the main cavity to change the volume of the sub-cavity. A constant volume structure in which the volume does not change may be used.

Further, the sub-cavities are formed not only in the protruding direction of the protruding portion but also laterally with respect to the protruding direction, or as shown in FIG. , 8 are provided one by one, and the arrangement of the sub-cavities, the number thereof, the structure of variable volume, and the like can be appropriately changed without departing from the spirit of the present invention. By providing a large number of sub-cavities, it is not impossible to introduce the secondary resin to the tip of the protruding portion extending like an arm. In the method of the present invention, the injection timing of the primary resin and the secondary resin and the expansion timing of the sub cavity are appropriately changed according to conditions such as the type of the resin and the form required by the product.

[0014]

According to the sandwich molding method of the present invention, the primary resin is drawn into the sub-cavity by enlarging the volume of the sub-cavity, and the secondary resin is moved into the recess by riding the flow of the primary resin being drawn. Can be filled. Also, an apparatus provided with a piston which advances and retracts with respect to the sub-cavity can easily carry out the resin sandwich molding method of the present invention, and the molded article formed by the method has a core layer formed in a protruding portion. As a result, the characteristics of the protrusion are at the same level as the mother. If the volume of the cavity is made variable by the reciprocating movement of the piston, the structure is simple because the movable part is only the piston, so that a plurality of sub-cavities can be provided for one protruding portion, and the volume expansion speed of the sub-cavity can be increased. If it is variable, it can respond to different protrusions. Further, in the resin molded product of the present invention, the advantage of sandwich molding can be utilized even in the projecting portion.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an apparatus for performing a resin sandwich molding method according to the present invention.

FIG. 2 is an explanatory diagram of an ejection pattern in a state where the volume of a sub cavity is minimum.

FIG. 3 is an explanatory diagram of an injection pattern in a state where the volume of a sub cavity is enlarged.

FIG. 4 is a comparison table showing a difference between a comparative example and an example.

FIG. 5 is an explanatory view exemplifying a difference in an ejection pattern due to a combination having a different viscosity.

FIG. 6 is an explanatory diagram of a modified example.

FIG. 7 is an explanatory diagram of a modified example.

FIG. 8 is an explanatory view showing a typical example of a sandwich molded product.

FIG. 9 is an explanatory diagram of a conventional example.

[Explanation of symbols]

1. primary cylinder, 2. secondary cylinder, 3. main cavity, 4. mold, 5. gate, 6. recess, 7.
..Outlet path, 8 ·· Sub cavity, 9 ·· Sprue, 1
Nozzle, 11 hydraulic cylinder, 12 piston, 13 primary resin, 14 secondary resin, 15, 16
..Spacers, 17 spaces, 18 cavities,
19. The core layer.

Claims (7)

[Claims] 1. A variable-capacity sub-cavity is connected to at least a space corresponding to the projecting portion of a product-shaped main cavity having a projecting portion via a lead-out path,
In the main cavity, at the stage of injecting the first and second resins corresponding to the amount exceeding the volume of the main cavity from a two-color molding machine, when the main cavity is filled with a predetermined amount of resin, A method of sandwich molding a resin molded product in which the volume of the sub-cavity is increased, a part of both resins filled in the main cavity is introduced into the sub-cavity, and the secondary resin is drawn into a space corresponding to a protrusion of the main cavity. . 2. A product-shaped main cavity having a protrusion, and a two-color molding machine for injecting a first resin and a second resin into the main cavity, wherein at least the protrusion is provided in the main cavity. A sandwich molding device for resin molded products that has a variable capacity sub-cavity connected to the space corresponding to the part via a lead-out path, and the timing of volume expansion of the sub-cavity can be controlled. 3. The sandwich molding apparatus for a resin molded product according to claim 2, wherein the sub-cavity has a variable volume by an advance / retreat operation of a piston fitted into the sub-cavity. 4. The resin molding sandwich molding apparatus according to claim 2, wherein a plurality of the sub-cavities are provided in a space corresponding to one protruding portion. 5. The sandwich molding apparatus for a resin molded product according to claim 2, wherein a maximum volume of the sub-cavity is variable. 6. The sandwich molding apparatus for a resin molded product according to claim 2, wherein the volume expansion speed of said sub cavity is variable. 7. A resin molded article formed by the molding method according to claim 1.