JP5682085B2 - Injection molding method for synthetic resin molded products - Google Patents

Description

The present invention relates to an injection molding method of a molded article having a body portion formed in thick plate of synthetic resin.

  Thick plate-like injection-molded products are used as molded products where appearance is important, such as display sample product storage container lids and compact container lid decorations. ing. This molded product is placed in the molding space of the molded product so that the gate trace of the injection can be positioned where it is not conspicuous or hidden so that the appearance of the molded product is not impaired. A gate is formed for a certain cavity by a side gate method.

  As described above, in the case of an injection molded product in which appearance is regarded as important, the body portion formed into a thick plate is generally injection molded by a side gate method. When the main body is injection-molded by the method, jetting that is defective molding occurs due to the scattering of the molten resin that is injected first into the cavity, and the line pattern due to this jetting appears on the surface of the molded product, There is a disadvantage that the appearance appearance of the molded product is deteriorated.

  As a conventional technique for solving this inconvenience, a technique disclosed in Japanese Patent Laid-Open No. 11-192644 (Patent Document 1) is such that a molten resin injected from a gate is placed in a cavity facing a side gate type gate. A collision protrusion is provided, and the molten resin injected into the cavity from the gate vigorously collides with the protrusion.

  In the prior art shown in this Patent Document 1, the molten resin injected from the gate into the cavity is collided with the protrusions, and the impingement of the injected molten resin is reduced by this collision to prevent the occurrence of scattering, Thus, jetting is prevented from occurring, and injection filling of the molten resin into the cavity is sequentially achieved from a location close to the gate.

JP 11-192644 A

  However, in the above-described prior art, the occurrence of jetting can be surely prevented by the collision of the molten resin projected into the cavity vigorously. When the molten resin that has accumulated in the foreground fills and flows into the cavity beyond this protrusion, the molten resin splits and exceeds the protrusion. There is a problem that the weld is generated on the downstream side of the protrusion, and this weld significantly impairs the appearance of the molded product.

  In particular, when a molded product is molded with a highly light-transmitting synthetic resin, not only is the jetting and weld visible as a flaw, but the jetting and weld are not affected by light transmitted through the molded product. Distortion will be given, and unpleasant distortion will occur in the appearance.

  In addition, when the main body 2 of a molded product 1 (hereinafter referred to as FIG. 8) molded with a highly light-transmitting synthetic resin is observed with a polarization type distortion inspection apparatus according to the conventional technique disclosed in Patent Document 1, the main body The distortion generating portion 13 is generated in the entire area 2. This is because the molten resin injected and filled into the cavity is injected from the gate and then flow-filled into the cavity sequentially over the protrusion, and its streamline is disturbed when it crosses the protrusion, It seems that this streamline turbulence causes the distortion generating portion 13 as it is.

  This distortion generating portion 13 causes distortion in the light beam transmitted through the molded article 1, which deteriorates the optical decoration effect exhibited by the synthetic resin having a high light transmission property. Due to changes in the action of external physical force such as pressure changes, deformation and deterioration of light transmission, etc. occur. For this reason, for example, the surface gloss of the main body 2 and spots appear, and the appearance appearance deteriorates. There was a problem that.

  Therefore, the present invention was devised to solve the above-mentioned problems in the prior art, and the technical problem is to make the surface of the molded product uniform gloss and appearance, thereby ensuring a good appearance. The purpose is to obtain.

A configuration example that solves the above technical problem is:
Providing at least one recess in the peripheral end of the back side of the main body, which is injection-molded into a thick plate with synthetic resin,
Side gate type gate marks are located at the peripheral end surface location of the main body portion close to the recess,
The surface of the main body has a uniform gloss and appearance without spots,
It is what .

In the configuration example of this, since the gloss and appearance of the surface of the body portion is uniform, without causing mottle by non-uniform, thereby Toka mottled color density, gloss of the surface unevenness, such as The appearance appearance will not deteriorate due to the above.

In the above-described configuration example , the synthetic resin for molding the main body can have high light transmittance.

  In the case of molding the main body part with a synthetic resin having a high light transmittance, there is little generation of a distortion generating part in the main body part that causes gloss and appearance spots on the surface of the main body part. The degree of inconvenient distortion of the transmitted light due to the generated portion is reduced, and thus the optical decorative effect exhibited by the molded product is hardly deteriorated.

Serving as the main constituent of the present invention,
It is an injection molding method of a molded product in which a thick plate-like main body portion is molded from a synthetic resin, and a concave portion is provided in a peripheral end portion of the main body portion,
A molding pin for recess molding is assembled to the peripheral end of the cavity, which is the molding space of the molded product body, so that it can be moved back and forth in the thickness direction, and the gate that faces the molding pin in the cavity close to the side gate system Provided in
In accordance with the timing when the molten resin injected from the gate into the cavity collides with the molding pin and the momentum is reduced, the molding pin is retracted from the cavity.
Advancing the molding pin into the cavity immediately before the cavity is filled with molten resin,
It is in.

In the serving main configuration of the present invention, at the beginning of the injection molding of the main body portion of the molded product, the molten resin injected into the cavity from the gate, without being scattered in the cavity, and an advanced position in the cavity It collides with the forming pin and becomes a lump. The molten resin that is subsequently injected merges with the molten resin that has become a lump.

  Therefore, even when the molten resin first injected into the cavity collides with the molding pin and the momentum is reduced to form a lump, the molding pin continues to be injected into the cavity even if the molding pin is retracted from the cavity. The molten resin merges without splashing into the massive molten resin.

  This flow of molten resin in the cavity in the filling direction does not cause splitting and merging because the molding pin has already retracted and retreated from the cavity. This is accomplished without disturbing the flow through the pins.

  When the molten resin is filled into the cavity, the molding pin is advanced and returned to the cavity just before the cavity is filled with the molten resin, that is, when there is a small space in the cavity that is not yet filled with the molten resin. To form a recess.

  At this time, a part of the molten resin in the cavity is pushed away by the advance of the molding pin, but since there is still a small space in the cavity, the increased change of the pushed molten resin Minutes are absorbed by the voids, and there is no problem in forming the recesses by the advancement of the forming pins.

Another embodiment of the present invention is a serving main configuration described above, the retraction timing of the forming pin, and around a time point of 5 wt% of the molten resin for molding the molded article is injected, the advancement timing for forming pin, In this case, 95% by weight of the molten resin for molding the molded product is set near the point of injection.

  In the case where the retraction timing of the molding pin is in the vicinity of the time when 5% by weight of the molten resin is injected, and the advancement timing of the molding pin is in the vicinity of the time when 95% by weight of the molten resin is injected, By setting the retraction timing of the molding pin around the time when 5% by weight of the molten resin is injected, a block of molten resin formed between the gate and the molding pin in the cavity is subsequently injected. The molten resin can be sized so that it can be stably merged without splashing, and the advancement timing of the molding pin is around the time when 95% by weight of the molten resin is injected, It is possible to stably form the concave portion with the molding pin, and it is possible to minimize the occurrence of turbulence in the streamline of the molten resin due to the advanced molding pin.

In serving the main structure of the present invention, by having a high light transmittance synthetic resin it is possible to mold the molded article.

  In the case of molding a molded product with a synthetic resin having high light transmittance, since the disturbance of the streamline of the filling flow into the cavity of the molten resin is small, it is possible to sufficiently reduce the generated strain generation part. Thus, distortion to the transmitted light is less distorted, and an excellent decorative effect due to an optical action such as a crystal effect exhibited by a highly light-transmitting synthetic resin can be obtained.

In serving the main structure of the present invention, it is possible to mold a molded article of hard synthetic resin.

  In the case where a molded product is molded from a hard synthetic resin, a molded product having excellent surface smoothness and gloss can be obtained.

Since the present invention has the above-described configuration, the following effects can be obtained.
In the molded product molded according to the present invention, the appearance of the molded product is not deteriorated due to color shading or surface gloss, etc., so that the appearance is good. Can be definitely obtained.

In the case where the main body is molded with a synthetic resin having high light transmittance, the optical decoration effect exhibited by the molded product is rarely deteriorated. An optical decoration effect can be exhibited effectively .

In the serving main configuration of the present invention, the main body portion formed in a molded article of the thick plate, it is possible to reliably prevent the occurrence of jetting and weld, defective molding due to jetting and weld Generation | occurrence | production can be blocked | prevented reliably and the molded article excellent in the external appearance can be obtained.

  Further, since the molding operation is the control of the advance and retreat of the molding pin with the timing, it is easy to implement and simple, and can be easily performed using an existing mold apparatus.

  Furthermore, the filling of the molten resin into the cavity is achieved in a state where there is no obstruction such as a molding pin, etc., so that there is little occurrence of a distortion generating portion, thereby stabilizing a good and excellent appearance appearance at the time of molding. Can be maintained.

In the main configuration of the present invention , the retraction timing of the molding pin is set near the time when 5% by weight of the molten resin is injected, and the advancement timing of the molding pin is set near the time when 95% by weight of the molten resin is injected. In this case, the retraction timing of the molding pin is in the vicinity of the time when 5% by weight of the molten resin is injected, so that the mass of the molten resin portion formed between the gate in the cavity and the molding pin Since the molten resin that is subsequently injected can be sized so that it can be stably joined without splashing, a stable molding operation can be obtained, and the advance timing of the molding pin can be By setting the vicinity of the point at which 95% by weight of the molten resin is injected, it is possible to stably form the concave portion with the molding pin, and the streamline of the molten resin with the advanced molding pin. The occurrence of disturbance, it is possible to minimize, can together be satisfactorily molded recess, to sufficiently suppress the generation of distortion generation portion by advancement of the forming pin.

In the main configuration of the present invention, in the case of molding a molded product with a synthetic resin having high light transmittance, it is possible to obtain an excellent decorative effect due to an optical action such as a crystal effect. A certain optical decoration effect can be obtained.

In the main structure of the present invention, a molded product made of a hard synthetic resin can be used to obtain a molded product with excellent surface smoothness and glossiness. Can be obtained.

It is the perspective view which fractured | ruptured partially which shows the example of 1 structure of the molded article by this invention. It is explanatory drawing which carried out the longitudinal cross-section which shows the state of the shaping | molding of the structural example of FIG. In FIG. 2, it is explanatory drawing which looked at the cutting arrow along the AA line. It is explanatory drawing illustrated longitudinally which shows the state just before shaping | molding completion. FIG. 5 is an explanatory view taken along the line BB in FIG. It is explanatory drawing illustrated longitudinally which shows the state which shaping | molding completed. It is explanatory drawing which made drawing the photograph of the polarization distortion test result of the molded article shape | molded by this invention. It is explanatory drawing which made drawing the photograph of the polarization distortion test result of the molded article shape | molded by the prior art.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows an example of the structure of a molded article 1 according to an embodiment of the present invention. The molded article 1 is injection-molded with a hard synthetic resin having a high light transmittance, and its main body 2 Has a thick plate shape, and a recess 3 is formed in a part of the peripheral end of the back surface thereof.

  As shown in FIG. 2, the fixed mold 9 and the movable mold 10 of the mold apparatus 8 are molded so that a side-gate type gate mark is located at the peripheral end surface portion of the molded product 1 close to the recess 3. A molding pin 11 for molding the recess 3 is arranged at a peripheral end portion of the cavity 12 which is a molding space of the main body 2 formed by matching, and is close to the molding pin 11 and faces the molding pin 11. As shown, a side gate type gate 5 having a runner 6 and a gate 5 is formed as an opening.

  The molding pin 11 is arranged on the movable mold 10 side so that the molten resin 7 injected into the cavity 12 from the gate 5 collides without being scattered, but it advances and retreats with respect to the cavity 12 as necessary. It is assembled to be movable. That is, the molding pin 11 is movable between a position where the molten resin 7 injected into the cavity 12 collides and a position where the flow of the molten resin 7 injected into the cavity 12 is not affected. It is.

  When the mold apparatus 8 is clamped and the molding pin 11 is advanced into the cavity 12 and the molten resin 7 is injected from the gate 5 into the cavity 12, the injected molten resin 7 is not scattered and the molding pin is injected. 11, the momentum decreases to form a lump (see FIG. 2), but the molding pin 11 is retracted from the cavity 12 in accordance with the timing when the injected molten resin 7 collides with the molding pin 11 (see FIG. 2). (See the downward arrow in FIG. 2).

  As described above, the timing of the backward movement of the molding pin 11 from the cavity 12 is the timing when the molten resin 7 injected first collides with the molding pin 11 to form a lump, as shown in FIG. In addition, it is the timing when the massive molten resin 7 is located between the molding pin 11 and the gate 5, and the massive molten resin 7 is located between the molding pin 11 and the gate 5 in this way. Thus, the molten resin 7 subsequently injected joins the bulk molten resin 7 while absorbing its momentum without scattering.

  The timing of the backward movement of the molding pin 11 from the cavity 12 is preferably a timing at which 5 weight percent of the resin material required for molding the molded product 1 is injected into the cavity 12. By retreating, the injected molten resin 7 is surely agglomerated before passing over the molding pin 11, and an appropriate merging operation of the subsequent molten resin 7 can be obtained.

  Since the injection of the molten resin 7 into the cavity 12 is continued with the molding pin 11 retracted from the cavity 12 (see FIG. 4), the filling flow operation of the molten resin 7 into the cavity 12 continues in the cavity 12. Is done. The filling and flowing operation of the molten resin 7 is performed in a state where the molding pin 11 is retracted from the cavity 12, so that the molten resin 7 can be filled and flowed without being obstructed by the molding pin 11, and therefore, the turbulence is prevented. The cavity 12 is filled while maintaining few streamlines.

  Immediately before the molten resin 7 is filled into the cavity 12 and the cavity 12 is filled with the molten resin 7, the molding pin 11 is moved forward (see the upward arrow in FIG. 4) to mold the recess 3. A part of the molten resin 7 in the cavity 12 is forcibly pushed away by the advancement of the molding pin 11 into the cavity 12, but at this timing, a slight space remains in the cavity 12 ( Therefore, the resin portion corresponding to the molten resin 7 that has been pushed away is quickly absorbed into the void.

  The timing of the forward movement of the molding pin 11 into the cavity 12 is preferably the timing at which 95 weight percent of the resin material required for molding the molded product 1 is injected into the cavity 12. As a result of the forward movement, it is possible to reliably leave a small space in the cavity 12, and to obtain a forward movement that does not hinder the molding pin 11.

  Even if the forward movement of the molding pin 11 into the cavity 12 is completed, the injection of the molten resin 7 into the cavity 12 is continued until the molten resin 7 is filled in the cavity 12 (see FIG. 6). At this point, the injection molding of the molded product 1 is completed. In this case, after the molding pin 11 has advanced into the cavity 12, the amount of the molten resin 7 injected into the cavity 12 is very small. Therefore, the streamline of the molten resin 7 injected into the cavity 12 is the molding pin. 11 is hardly disturbed.

  As described above, most of the main body 2 is molded with the molding pin 11 retracted from the cavity 12, so that the molten resin 7 filled in the cavity 12 can move over the molding pin 11. Therefore, no weld is generated. Similarly, most of the main body 2 is molded without disturbing the filling streamline by the molding pin 11, so that the distortion generating portion 13 is hardly molded.

  Therefore, when the molded product 1 is observed with a polarization-type distortion inspection apparatus, as shown in FIG. 7, almost no distortion generating portion 13 is generated as compared with the conventional example shown in FIG. The surface 1 of the present invention will exhibit a uniform gloss and appearance with no spots, and the molded product 1 will exhibit an excellent optical decoration effect with little distortion in transmitted light.

  The forward / backward movement of the molding pin 11 with respect to the cavity 12 can be achieved, for example, by providing a dedicated air cylinder and driving control of the air cylinder. However, the ejector pin is used as the molding pin 11 to operate the ejector pin. It is also possible to use it.

  In addition, since the recessed part 3 shape | molded in the molded product 1 of the example of illustration structure is a part which forms the assembly function part for assembling the molded product 1 to another structure via a shaft, this recessed part 3 In order to reinforce the mechanical strength of the opening edge portion, a reinforcing thick portion 4 for reinforcement is bulged and formed at the opening edge portion of the recess 3 in a spherical arc shape. It is not limited to what forms, and for example, it may be constituted by a part of the concavo-convex pattern formed on the back surface of the molded product 1.

  Further, the synthetic resin for molding the molded article 1 is not specified as a highly light-transmitting synthetic resin, and a synthetic resin having low or no light transmitting property can be used. It is also possible to use a synthetic resin. Examples of the resin that has high light transmittance and can ensure appropriate hardness include AS resin, but of course, the resin is not limited to this, and other appropriate resin can be selected. .

  As described above, the present invention can substantially eliminate the adverse effect of the molding pin provided in the cavity for preventing jetting on the molten resin injected and filled in the cavity. A wide range of usage expansion is expected for injection molded products that place importance on appearance.

DESCRIPTION OF SYMBOLS 1; Molded product 2; Main-body part 3; Concave part 4; Reinforcement thick part 5; Gate 6; Runner 7; Molten resin 8; Mold apparatus 9; ; Strain generation part

Claims (2)

A method for injection molding a molded article (1), wherein a thick plate-like main body (2) is molded from a synthetic resin, and a recess (3) is provided at a peripheral end of the main body (2). A molding pin (11) for molding the recess (3) is assembled to a peripheral end of the cavity (12), which is a molding space of the part (2), so as to be able to advance and retreat in the thickness direction, and in the cavity (12) A gate (5) facing the molding pin (11) is provided in a side gate manner, and the molten resin (7) injected from the gate (5) into the cavity (12) is formed by the molding pin (11). The molding pin (11) is retracted from the cavity (12) in accordance with the timing when the momentum is reduced and the molding resin is immediately filled with the molten resin (7). Advancing the pin (11) into the cavity (12) Injection molding method of a resin molded article. The retraction timing of the molding pin (11) is set in the vicinity of the time when 5% by weight of the molten resin (7) for molding the molded product (1) is injected, and the advancement timing of the molding pin (11) is set as the molding product. The method for injection molding a synthetic resin molded product according to claim 1, wherein 95% by weight of the molten resin (7) for molding (1) is injected in the vicinity.

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