JP3825348B2 - Injection molding apparatus and method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an injection molding apparatus and method, and more particularly, to an apparatus and method for molding a resin molded article having a multilayer structure in which a core layer resin is coated with a skin layer resin, and in particular, a rigid vinyl chloride resin. The present invention also relates to an injection molding apparatus and method that can cope with the above.
[0002]
[Prior art]
Conventionally, a resin molded product having a multilayer structure in which a resin for a core layer (inner layer) is coated with a resin for a skin layer (outer layer) has been widely used, and an injection molding apparatus and method for manufacturing such a resin molded product As described in, for example, JP-A-1-141711, JP-A-10-151645, and the like, various proposals have been conventionally made.
[0003]
[Problems to be solved by the invention]
However, conventional resin molded products with a multilayer structure are manufactured using a resin with good fluidity and thermal stability, and a resin molding with a multilayer structure using a hard vinyl chloride resin with poor fluidity and thermal stability. Goods were not obtained. That is, in the conventional molding apparatus, the flow path of the resin for the skin layer and the flow path of the resin for the core layer are arranged concentrically via the leg portions of the spider, and the resin flowing through the outer flow path When the vinyl chloride resin with poor fluidity is used, the resin stays in the vicinity of the legs and changes in quality because it merges after passing through the narrow flow path formed between the legs. However, this deteriorated resin hinders smooth injection operation and causes frequent molding defects.
[0004]
In addition, a conventional injection molding apparatus for injection molding of a multilayer resin-molded product is provided with a flow path opening / closing mechanism for controlling the injection timing and injection amount of the core layer resin and the skin layer resin. Resin stagnation is likely to occur in the flow path opening / closing mechanism, and it has been difficult to injection mold a multilayer structure resin molded product using a hard vinyl chloride resin.
[0005]
Therefore, the present invention has a multilayer structure in a stable state even when a hard vinyl chloride resin lacking fluidity and thermal stability is used by widening the resin flow path in the spider and making the resin flow and shape smooth. An object of the present invention is to provide an injection molding apparatus and method capable of injection molding a resin molded product.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the injection molding apparatus of the present invention includes a core layer resin and a skin layer resin injected from the first injection unit and the second injection unit, respectively, with respect to the cavity formed in the mold. An injection molding apparatus for molding a resin molded product having a multilayer structure in which a core layer resin is coated with a skin layer resin by injection injection through an injection nozzle, wherein the injection nozzle has a first portion in the center. An outer cylinder in which a ring-shaped second resin flow path is formed between an inner cylinder provided with a resin flow path, a coaxial double cylinder structure with respect to the inner cylinder, and an outer peripheral surface of the inner cylinder; A spider having a plurality of legs that are concentrically assembled with the inner cylinder, and a resin that is provided on one of the legs of the spider and is injected from the first injection unit through the outer cylinder, and A first resin introduction path for introduction into the first resin flow path; A second resin introduction path for introducing the resin injected from the second injection unit into the second resin flow path from the rear end portion of the outer cylinder; and the first resin flow path provided at the front end of the outer cylinder; An operation of injecting a predetermined amount of resin in a preset order with the first injection unit and the second injection unit. Control means for performing control, and the spider is provided with a second resin flow path having an opening area corresponding to 55 to 80% of the annular flow path over the entire circumference , and the spider The leg portion is characterized in that the cross-sectional shape in the cylinder circumferential direction is an elliptical shape or a water droplet shape having a long axis in the resin flow direction, and the upstream side and the downstream side in the resin flow direction are respectively sharpened .
[0007]
Furthermore, in the injection molding device of the present invention, the first resin flow path is a core layer resin flow path, the second resin flow path is a skin layer resin flow path, the skin layer resin and the core layer The resin for use is a hard vinyl chloride resin, and the leg portions of the spider are provided in two locations of the same shape at positions facing each other across the inner cylinder, and the first resin introduction path is provided in one of them. and this provided, at at least one position of the connection block for pre Symbol barrel or to the injection nozzle communicating resin flow passage of the first injection unit and second injection unit, circulating a temperature regulating fluid It is characterized by having a passage that can.
[0008]
The injection molding method of the present invention is an injection molding method for molding a resin molded product in which a core layer is covered with a skin layer using the injection molding apparatus configured as described above. A step of injecting a sufficient amount of the skin layer resin into the cavity portion from the merge nozzle portion to operate the second injection unit in a state where the external injection unit is stopped to form the outer surface of the resin molded product, and the skin layer resin. In the initial stage when the first injection unit is injected into the cavity portion, the core layer resin is simultaneously injected from the central portion of the merging nozzle portion by operating the first injection unit. The core layer tree remaining in the merging nozzle portion by the skin layer resin that stops the operation of the first injection unit when injected into the part and is continuously injected from the second injection unit. Is injected into the cavity portion, and the skin layer resin is injected into the injection port portion of the cavity portion to cover the core layer resin. Further, each of the skin layer resin and the core layer resin is hard. It is a vinyl chloride resin, and is characterized by adjusting the injection temperature from the first injection unit and the second injection unit within a range of 190 to 220 ° C.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
1 to 5 show an embodiment of an injection molding apparatus according to the present invention. FIG. 1 is a sectional view of an injection nozzle, and FIG. 2 shows a spider leg and a first resin introduction path in the injection nozzle. 3 is a sectional view taken along the line III-III in FIG. 2, FIG. 4 is a sectional view taken along the line IV-IV in FIG. 2, and FIG. 5 is a sectional view taken along the line V-V in FIG.
[0010]
First, as shown in FIG. 1, the injection molding apparatus includes a core layer resin and a skin in which a predetermined amount is injected from a first injection unit 11 and a second injection unit 12 in a predetermined order. By injecting and injecting the layer resin into the cavity of the mold through the injection nozzle 13, the resin for the multilayer structure in which the core layer resin is coated with the skin layer resin is formed. The injection nozzle 13 has a ring shape between the inner cylinder 15 provided with the first resin flow path 14 at the center and the outer peripheral surface of the inner cylinder 15 in a coaxial double cylinder structure with respect to the inner cylinder 15. And an outer cylinder 17 forming the second resin flow path 16. The inner cylinder 15 and the outer cylinder 17 are fixed to each other in a concentric manner by being assembled to a spider 19 having legs 18 at two locations, and the inner cylinder portion 15a of the spider 19 is connected to the inner cylinder 15 integrally. The outer cylinder portion 17 a of the spider 19 is integrally connected to the outer cylinder 17.
[0011]
One leg portion 18 of the spider 19 has a first resin introduction path 20 through which the resin injected from the first injection unit 11 passes through the outer cylinder 17 and is introduced into the first resin flow path 14. Is provided, and is connected to the first injection unit 11 via an external flow path 21 formed in the first connection block 25. The second resin flow path 16 is connected to the second injection unit 12 via the second resin introduction path 22 on the upstream side of the spider 19.
[0012]
A merge nozzle portion 23 communicating with the first resin flow path 14 and the second resin flow path 16 is provided at the distal end of the outer cylinder 17, and the distal end of the merge nozzle portion 23 is in pressure contact with the mold. Resin is injected into the cavity. The front end of the first resin flow path 14 is in direct communication with the inside of the merging nozzle portion 23 in a state of being slightly reduced in diameter, and the front end of the second resin flow path 16 is also connected to the inner cylinder 15 and the outer cylinder 17 It communicates directly with the inside of the confluence nozzle portion 23 via a conical channel 16a therebetween.
[0013]
Further, a temperature adjusting fluid passage 24 is provided inside the outer cylinder 17, and a fluid for adjusting the resin temperature in the injection nozzle 13 such as cooling air is introduced into the passage 24 to increase the resin temperature. Can be prevented. Further, a temperature adjusting fluid passage 24 a is provided in the first connection block 25 provided with the external flow path 21 connected to the first resin flow path 14, and the second connection block 26 outside the spider 19 is provided in the second connection block 26. Temperature control fluid passages 24b are respectively provided, and the passages 24a and 24b also pass through the external flow path 21 by introducing a refrigerant such as cooling air or opening to the outside air, for example. The resin flowing from one resin introduction path 20 to the first resin flow path 14 and the resin flowing from the second resin introduction path 22 to the second resin flow path 16 can be adjusted to the optimum temperature.
[0014]
The temperature in the injection nozzle 13 can be appropriately adjusted according to the resin raw material to be injection-molded. However, when molding a multilayer resin molded product made of hard vinyl chloride resin, the first injection unit 11 and the second It is preferable that the temperature of the resin injected into the cavity portion from the two injection units 12 is set to 190 to 220 ° C, preferably 200 to 210 ° C. If this injection temperature is less than 190 ° C, it will be difficult to spread hard vinyl chloride resin with poor flowability to the end of the cavity, and conversely if it exceeds 220 ° C, the hard vinyl chloride resin will be baked and altered. Problem occurs.
[0015]
As shown in FIGS. 2 to 5, the spider 19 cuts the metal cylindrical body 31 to leave the first resin flow path 14 at the center of the cylindrical body and the portions that become the legs 18. A pair of arc-shaped second resin flow paths 16, a first resin introduction path 20 connected to the rear end of the first resin flow path 14 through one leg 18, and the first resin introduction path 20 A connecting recess 32 provided for connecting the side channel 21 to the outer peripheral surface of the cylindrical body, and an assembly recess 33 provided concentrically with the first resin channel 14 for assembling the distal end side of the inner cylinder 15. And a conical portion 34 for guiding the resin introduced from the second resin introduction passage 22 to the ring-shaped second resin passage 16 so as to protrude upstream of the second resin passage 16. .
[0016]
The leg portion 18 can be smoothly branched to both sides of the leg portion without causing the resin flowing through the second resin flow path 16 to stay, and the resin after passing through the leg portion can be smoothly joined without remaining. It is formed in a shape that can For example, as shown in FIG. 3, the cross-sectional shape in the cylinder circumferential direction of the leg portion 18 is an elliptical shape or a water droplet shape having a long axis in the resin flow direction, and the upstream side 18 a and the downstream side 18 b in the resin flow direction are respectively It has a sharpened optimum shape. As shown in FIG. 2, the second resin flow path 16 of the spider 19 is a ring-shaped flow path divided by a pair of legs 18, and the narrowest central portion is about 122 degrees. It is formed in a circular arc shape, and the opening area of the pair of second resin flow paths 16 in this portion is about 68% (= 244 degrees / 360 degrees) of the annular flow path over the entire circumference. The opening area is preferably set to 55 to 80% of the annular flow path over the entire circumference. When the opening area is less than 55%, there is no significant difference from the opening area of the spider used in the conventional apparatus, and the resin is spider 19. There is a risk of staying when passing through. If this value exceeds 80%, it becomes difficult to form the first resin introduction path 20 in the leg portion 18, the strength of the leg portion 18 is reduced, and the inner cylinder 15 is the same as the outer cylinder 17. There arises a problem that the core cannot be supported.
[0017]
Furthermore, although it is possible to provide the legs 18 at three or more locations, considering the case of a hard vinyl chloride resin having a difficulty in fluidity, it is desirable to reduce it as much as possible, and the entire resin flow is uniform. In order to achieve this, it is preferable to arrange the same shape at equal intervals. In particular, as shown in the present embodiment, one leg portion is provided at a position where the first resin introduction path 20 is formed, and a leg having the same shape is provided at a position facing the leg portion with the inner cylinder 15 interposed therebetween. By providing the portion, it is possible to minimize the number of divisions of the resin flow while maintaining the strength as the spider 19, suppress the resin stagnation, and make the entire resin flow uniform.
[0018]
The injection nozzle 13 formed in this way operates the first injection unit 11 and the second injection unit 12 in a preset order by control means (not shown) so as to inject a preset amount of resin. By operating, a multilayer structure resin molded product in which the core layer resin is coated with the skin layer resin in the cavity portion in the mold can be injection molded.
[0019]
In addition, since each channel of the injection nozzle 13 is not provided with a channel opening / closing mechanism such as a valve, the resin can be prevented from staying in the channel, and hard vinyl chloride lacking in fluidity and thermal stability. Even if resin is used, a multilayer structure resin molded product can be injection-molded in a stable state.
[0020]
FIG. 6 is a diagram showing changes in the flow rates of the core layer resin and skin layer resin when injection molding a multilayer resin molded product. FIGS. 7 to 9 show the inside of the cavity at each stage during injection molding. It is a schematic sectional drawing for demonstrating the state of this resin.
[0021]
As an example, a molding process in which the core layer resin is injected from the first injection unit 11 and the skin layer resin is injected from the second injection unit 12 will be described. First, in the first injection step A shown in FIG. 6, the second injection unit 12 is operated with the first injection unit 11 stopped, and the skin layer resin P <b> 1 is removed from the second resin introduction path 22 through the spider 19. And introduced into the second resin flow path 16. This skin layer resin P1 spreads in a ring shape by the conical portion 34 of the spider 19, flows in the second resin flow path 16 in the state of being divided into two by the leg portion 18 and joined again, and from the joining nozzle portion 23, It is injected into the cavity portion 42 of the mold 41 through the injection port 43.
[0022]
At this time, the core layer resin P2 in the first resin flow path 14 is pushed into the first resin flow path 14 by the injection pressure of the skin layer resin P1, and thus flows into the merge nozzle portion 23. Never do. The amount of skin layer resin P1 injected is set to an amount sufficient to form the outer surface of the resin molded product, and a fixed amount is injected according to the size, shape, thickness, etc. of the molded product. Is done. In the initial stage of the first injection process A, as shown in FIG. 7, the skin layer resin P1 is injected into a part of the cavity portion 42, and then the second injection process B is started.
[0023]
In the second injection step B shown in FIG. 6, the first injection unit 11 is operated in a state where the second injection unit 12 is operated, and the core layer resin P <b> 2 is moved from the external channel 21 to the first resin introduction channel 20. Through the first resin flow path 14. The core layer resin P <b> 2 flows through the first resin flow path 14, flows out from the tip of the resin P <b> 2 to the merging nozzle portion 23, and is injected into the cavity portion 42 of the mold 41 from the merging nozzle portion 23. At this time, the core layer resin P2 is injected in a predetermined amount according to conditions such as the volume and thickness of the resin molded product.
[0024]
The core layer resin P2 in the second injection step B is injected into the cavity portion 42 from the merging nozzle portion 23 in a state where the outer side is surrounded by the skin layer resin P1. When the skin layer resin P1 and the core layer resin P2 are injected into the cavity portion 42 at the same time, the externally injected skin layer resin P1 contacts the peripheral wall of the cavity portion 42. The part is cooled to become a solidified skin layer, and the newly injected skin layer resin P1 sequentially advances to the end portion, and the core layer resin P2 is disposed on the inner side of the fluid skin layer resin P1. The filling progresses from the inlet 43 to the end portion.
[0025]
Therefore, in the second injection step B, as shown in FIG. 8, the core layer resin is placed inside the cavity portion 42 with the skin layer resin P1 in contact with substantially the entire peripheral wall of the cavity portion 42. P2 is injected.
[0026]
Finally, in the third injection step C shown in FIG. 6, the first injection unit 11 is stopped when a preset amount of the core layer resin P2 is injected into the cavity portion 42, and before this stop or Later, by controlling the operation of the second injection unit to reduce the resin flow rate, a small amount of skin layer resin P3 is injected from the second resin flow path 16 into the cavity portion 42 through the merge nozzle portion 23.
[0027]
At this time, when the skin layer resin P3 flows into the merging nozzle portion 23 from the second resin flow path 16, it flows out into the merging nozzle portion 23 in the previous second injection step B and into the merging nozzle portion 23. The remaining core layer resin P2 is extruded in the direction of the cavity portion 42, and then injected into the injection port 43 portion of the cavity portion so as to cover the core layer resin P2.
[0028]
Accordingly, the amount of the skin layer resin P3 in the third injection step C is almost independent of the shape of the resin molded product and the like, and the core layer resin P2 remaining in the merge nozzle portion 23 is transferred to the cavity portion 42. After the extrusion injection, the amount is set such that the core layer resin P2 in the injection port 43 portion of the cavity portion 42 can be covered.
[0029]
By performing the third injection step C, as shown in FIG. 9, the cavity layer 42 is filled with the core layer resin P2 inside the skin layer resins P1 and P3. Is taken out from the mold 41 in the usual procedure, whereby a resin molded article having a multilayer structure in which the core layer resin is coated with the skin layer resin can be obtained.
[0030]
In each step, when the resin temperature rises above the set temperature, the whole is cooled by blowing air from the outside of the injection nozzle 13 with a fan or the like, or the temperature adjusting fluid passages 24, 24a, 24b are provided. In this case, it is possible to prevent the resin from being deteriorated due to a temperature rise by circulating cooling air or the like through these passages. That is, when molding a resin molded product having a multilayer structure made of hard vinyl chloride resin, the temperature of the resin injected from the first injection unit and the second injection unit into the cavity is 190 to 220 ° C., preferably 200 to 200 ° C. It adjusts so that it may exist in the range of 210 degreeC.
[0031]
The injection nozzle 13 can be formed by combining a plurality of members according to processing conditions and the like, and is preferably manufactured on the basis of an injection molding apparatus for hard vinyl chloride resin. Further, the control means can be used simply by setting the operation order of the first injection unit 11 and the second injection unit 12 based on a timer or the like to the control means normally used in a general injection molding apparatus. .
[0032]
Further, the core layer resin and the skin layer resin can be used in combination with any synthetic resin that can be injection-molded. The same synthetic resin and the core layer resin are colorless or of any color tone. It is also possible to use one having a specified color tone as the resin for the skin layer. At this time, by injecting the skin layer resin from the second resin flow path 16 on the second injection unit 12 side, the core layer resin remaining in the merging nozzle portion 23 is more reliably pushed out to the cavity portion 42. be able to.
[0033]
【The invention's effect】
As described above, the molding apparatus of the present invention is not provided with a channel opening / closing mechanism in each channel through which the core layer resin and skin layer resin flow, and the spider resin flow channel through which the external skin layer resin flows. As the resin flowed smoothly, the multilayer resin molded product can be injection-molded in a stable state using the method of the present invention even when using a hard vinyl chloride resin that lacks fluidity and thermal stability. Can do.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an injection nozzle showing an embodiment of an injection molding apparatus of the present invention.
FIG. 2 is a side view of a spider.
3 is a cross-sectional view taken along line III-III in FIG.
4 is a cross-sectional view taken along line IV-IV in FIG.
5 is a cross-sectional view taken along line VV in FIG.
FIG. 6 is a diagram showing changes in the flow rates of the core layer resin and skin layer resin when injection molding a multilayer structure resin molded product.
FIG. 7 is a schematic cross-sectional view for explaining the state of the resin in the cavity part in the first injection step.
FIG. 8 is a schematic cross-sectional view for explaining the state of the resin in the cavity part in the second injection step.
FIG. 9 is a schematic cross-sectional view for explaining the state of the resin in the cavity in the third injection step.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... 1st injection unit, 12 ... 2nd injection unit, 13 ... Injection nozzle, 14 ... 1st resin flow path, 15 ... Inner cylinder, 16 ... 2nd resin flow path, 16a ... Conical flow path, 17 ... Out Cylinder, 18 ... Leg, 19 ... Spider, 20 ... First resin introduction path, 21 ... External flow path, 22 ... Second resin introduction path, 23 ... Merge nozzle part, 24, 24a, 24b ... Temperature control fluid passage , 25 ... 1st connection block, 26 ... 2nd connection block, 31 ... Metal cylinder, 32 ... Connection recessed part, 33 ... Assembly recessed part, 34 ... Conical part, 41 ... Mold, 42 ... Cavity part, 43 ... Inlet

Claims (7)

The core layer resin is injected by injecting the core layer resin and the skin layer resin injected from the first injection unit and the second injection unit through the injection nozzles into the cavity formed in the mold, respectively. An injection molding apparatus for molding a resin molded product having a multilayer structure coated with a resin for a skin layer, wherein the injection nozzle includes an inner cylinder provided with a first resin flow channel at a central portion, and the inner cylinder An outer cylinder forming a ring-shaped second resin flow path between the inner cylinder and the outer peripheral surface of the inner cylinder, and a plurality of legs that are assembled concentrically with the outer cylinder and the inner cylinder And a first resin introduction path for introducing the resin injected from the first injection unit through the outer cylinder into the first resin flow path. And the resin injected from the second injection unit A second resin introduction path for introducing the second resin flow path, and a merging nozzle portion provided at the tip of the outer cylinder and communicating with the first resin flow path and the second resin flow path. And a control means for controlling the first injection unit and the second injection unit to perform an operation of injecting a predetermined amount of resin in a preset order, and the spider Is formed with a second resin flow channel having an opening area corresponding to 55 to 80% of the annular flow channel over the entire circumference , and the spider legs have a cross-sectional shape in the cylinder circumferential direction with a resin flow. An injection molding apparatus characterized by having an elliptical shape or a water droplet shape having a major axis in the direction, wherein the upstream side and the downstream side in the resin flow direction are each sharpened .   The injection molding apparatus according to claim 1, wherein the first resin flow path is a core layer resin flow path, and the second resin flow path is a skin layer resin flow path.   2. The injection molding apparatus according to claim 1, wherein each of the skin layer resin and the core layer resin is a hard vinyl chloride resin.   The leg part of the spider is provided with two parts having the same shape at positions facing each other across an inner cylinder, and the first resin introduction path is provided in one of the two parts. The injection molding apparatus described. A passage through which a temperature control fluid can be circulated is provided in at least one of the outer cylinders or a connection block for communicating the injection nozzle with the resin flow paths of the first injection unit and the second injection unit. it is injection molding apparatus according to claim 1, wherein. An injection molding method for molding a resin molded article in which a core layer is covered with a skin layer using the injection molding apparatus according to any one of claims 1 to 5, wherein the first injection unit is first stopped. In a state where the second injection unit is actuated to inject a sufficient amount of the skin layer resin into the cavity portion from the merge nozzle portion to form the outer surface of the resin molded product, and the skin layer resin enters the cavity portion. The first injection unit is actuated at the initial injection stage, and the core layer resin is injected simultaneously from the central portion of the merging nozzle portion. A predetermined amount of the core layer resin is injected into the cavity portion. When the operation of the first injection unit is stopped, the core layer resin remaining in the merging nozzle portion is injected into the cavity portion by the skin layer resin continuously injected from the second injection unit. Extruded with injected, injection molding method characterized by covering the resin core layer by injecting a resin for the skin layer to the inlet section of the cavity portion. The resin for the skin layer and the resin for the core layer are each a hard vinyl chloride resin, and the temperature of each resin injected from the first injection unit and the second injection unit into the cavity portion is adjusted within a range of 190 to 220 ° C. The injection molding method according to claim 6 .

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