JP2012171218A - Method of manufacturing injection molded product of thermoplastic resin having glittering material and injection molded product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an injection molded product that prevents orientation disorder of a glittering material even in a relative complicated shape such as a material having rib or boss, in molding a thermoplastic resin having the glittering material.SOLUTION: The injection molding machine uses a mold designed so that the thickness of a part 14 having the rib 12 or boss 13 is 0.1-3.0 mm thicker than a part 15 having no rib or boss, to mold the thermoplastic resin having the glittering material having <120 μm average particle diameter. The method of manufacturing the injection molding machine includes: a step of increasing the temperature of the mold to keep the temperature of the mold so that the temperature of the thermoplastic resin in a cavity is equal to or above the deflection temperature under load; a step of injecting and casting the molten thermoplastic resin into the cavity of the mold; and a step of hardening the thermoplastic resin by lowering the temperature of the mold.

Description

  The present invention relates to a method for producing an injection molded body of a thermoplastic resin having a glittering material, and an injection molded body.

  Conventionally, painting is often used as a means for improving the appearance quality of a resin molded product. However, painting has a large environmental impact due to emissions of volatile organic compounds and carbon dioxide, deterioration of recyclability, etc. In addition, it is necessary to select a resin with a high affinity with paint, or when using a resin with a low affinity In addition, there is a problem that the cost increases due to the necessity of primer treatment for increasing the affinity between the resin and the coating film, and the increase in man-hours. Also, parts that are susceptible to external irritation such as rubbing and bumping have a risk of peeling off the paint, making it difficult to apply the paint and making it difficult to improve the appearance quality. Because of these problems, painting alternative technologies are being studied in various fields.

  One of the painting alternative technologies is “a technology that creates a glittering feeling by kneading a material called a glittering material into a resin and molding it”. Compared to painting, the environmental impact is small, and cost reductions due to a reduction in man-hours can be expected.

  However, this technique has a problem that appearance failure occurs due to disorder of the glitter material, and in injection molding, the orientation of the glitter material may be disturbed due to the flow of resin in the mold cavity. .

  For example, when the flow front of resin flowing from different directions merges, the orientation of the glitter material is disturbed at the junction of the thermoplastic resin, resulting in a difference in the reflection intensity and reflection angle on the glitter material surface, and the appearance deteriorates To do.

  Also, if there are irregularities in the shape of the molded product, such as bosses and ribs, the orientation of the glittering material will be disturbed as the resin flow is disturbed in the corresponding part, so there is a difference in the reflection intensity and reflection angle on the surface of the glittering material. Occurs and the appearance deteriorates.

  Therefore, conventionally, techniques for improving the appearance have been studied.

  There is a technique in which the cause of occurrence of disorder in the orientation of the glittering material (ribs, bosses, etc.) is eliminated as much as possible during injection molding, and a desired shape is obtained by post-processing (see, for example, Patent Document 1).

  In addition, there is a technique in which the design rear surface of the molded product and the ribs are arranged so as to be spaced apart from each other so that the orientation surface of the glittering material due to the ribs is not generated on the design surface (see, for example, Patent Document 2).

  In addition, there is a technique in which a merged portion of resin is formed on a non-external portion of a molded product and is discarded later (for example, see Patent Document 3).

  FIG. 7 shows a conventional injection-molded article described in Patent Document 1. As shown in FIG. 7, the injection molded body 1 is molded from a thermoplastic resin material in which a gloss material is mixed, and after the molded body body 2 and the mounting portion 3 are separately molded, the molded body body 2 and the mounting body 1 are attached. The parts 3 are joined to each other. Thereby, at the time of injection molding of the molded body 2, since the recess is not formed in the mold, the flow of the resin material is not disturbed, and no weld mark is generated.

  FIG. 8 is a side view of a conventional resin molded product described in Patent Document 2. As shown in FIG. 8, the resin molded product 4 includes a main body portion 5 constituting a design surface and a reinforcing structure portion 6 protruding from the back surface of the main body portion 5, and these are integrally formed by injection molding. The reinforcing structure 6 includes a plurality of horizontal ribs 7 oriented in a direction intersecting the resin flow direction during injection molding, and vertical ribs 8 extending perpendicularly to the horizontal ribs 7 and connecting the horizontal ribs 7 to each other. The horizontal ribs 7 are connected to the back of the design, and the vertical ribs 8 are spaced from the back of the design. As a result, it is possible to prevent the weld line generated on the design surface side of the main body part 5 and the resin flows into the main body part 5 via the lateral rib 7 in which the gate part is set at the time of injection molding. Since the resin flows from the horizontal ribs 7 to the vertical ribs 8 and the inflow speed is reduced, the resin does not reach the design surface in a jet state, and poor appearance such as flow marks and sink marks can be prevented.

  FIG. 9 is a schematic view showing a state in which a molded product provided with a cut-out portion in the conventional molding method described in Patent Document 3 is molded. As shown in FIG. 9, the molded product 9 is a molded product having a corner at an outer edge portion, and the outer edge portion is extended to provide a cutout portion 10 to generate a weld at the cutout portion. Thereby, by removing the cut-out portion 10, a molded product without a weld line is obtained.

JP 2004-188885 A JP 2008-49652 A JP 2006-103052 A

  However, in the conventional method of Patent Document 1, the shape of the molded product is limited, the number of man-hours increases due to the need for molding or joining of another part, and a separate mold is required when molding another part. Therefore, there was a problem that the mold cost was high.

  In addition, the conventional method of Patent Document 2 has problems that the main body and the rib are formed apart from each other, so that the strength is low and the method cannot be applied to uses requiring strength.

  Further, the conventional method of Patent Document 3 has problems such as an increase in cost due to an increase in materials used, and an increase in environmental load because the cut-out portion becomes dust.

  In addition, when the average particle size of the glittering material is 120 μm or more, the number of particles per unit volume is small, so that the orientation state of the glittering material is difficult to visually recognize. It does not require much ingenuity, but it is far from the texture of the paint in terms of appearance quality. On the other hand, if the particle size of the glittering material is made small in order to achieve the same quality as the coating, the number of particles per unit volume increases, so that the orientation state of the glittering material is easily recognized visually. In this case, considerable contrivance is required in the mold shape and construction method.

  The present invention solves the above-mentioned conventional problems, and in order to produce a texture close to coating, a thermoplastic resin having a relatively small particle size, that is, a bright material having an average particle size of less than 120 μm, is provided with ribs and bosses. An object of the present invention is to provide a molded product in which the orientation disorder of the glittering material is suppressed when it is molded into a relatively complicated shape.

  In order to solve the above-described conventional problems, the method for producing a thermoplastic resin injection-molded body having a glittering material according to the present invention has a thickness of a portion having ribs or bosses in a range from 0.1 mm to 3 mm. A method of manufacturing an injection-molded body for molding a thermoplastic resin having a bright material having an average particle diameter of less than 120 μm using a mold designed to have a thickness of 0.0 mm thick, wherein the temperature of the mold is set to a cavity Increasing the temperature of the thermoplastic resin to a temperature at which the deflection temperature under the load can be maintained, a step of injecting and pouring the molten thermoplastic resin into the cavity, and lowering the temperature of the mold to reduce the temperature of the thermoplastic resin. An injection molded body is obtained by a method for producing an injection molded body including a curing step.

  Even when molding a thermoplastic resin having a bright material with an average particle size of less than 120 μm, the thickness of the portion having ribs or bosses is made 0.1 mm to 3.0 mm thicker than the thickness of the portion not having By using the designed mold and raising the mold temperature to a temperature that keeps the temperature of the thermoplastic resin in the cavity at or above the deflection temperature under load, ribs are introduced at the initial stage of the flow of the thermoplastic resin in the cavity. Even if the orientation of the glitter material is disturbed by the boss or the boss, the orientation of the disordered glitter material is not fixed, and the thermoplastic resin flows by the flow until the entire cavity is filled afterwards. The orientation disorder of the glittering material does not remain in the injection molded product.

  The method for producing an injection molded article of a thermoplastic resin according to the present invention is such that, when molding a thermoplastic resin having a bright material having an average particle size of less than 120 μm, the shape of the injection molded article to be obtained is a rib or a boss. Even with such a relatively complicated shape, the disordered orientation of the glittering material does not remain in the injection molded body, so that an injection molded body excellent in appearance quality can be obtained without coating.

External view of the surface of the injection-molded body in Embodiment 1 of the present invention External view of the back surface of the injection-molded body in Embodiment 1 of the present invention Schematic diagram showing the flow of thermoplastic resin in the cavity of the mold according to the first embodiment of the present invention. The schematic diagram which shows the flow of the thermoplastic resin in the cavity of the metal mold | die in Example 1. FIG. External view of the back surface of the injection-molded product in Example 4 The schematic diagram which shows the flow of the thermoplastic resin in the cavity of the metal mold | die in Example 4. Sectional view of a conventional injection molded product Side view of conventional resin molded product Schematic diagram showing the appearance of a molded product with a conventional cutout

  1st invention uses the metal mold | die designed in the shape which made thickness of the site | part which has a rib and boss | hub the thickness of 0.1 mm-3.0 mm thicker than the thickness of the site | part which does not have, and the temperature of a metal mold | die Even when molding a thermoplastic resin having a glitter material having an average particle size of less than 120 μm by raising the temperature of the thermoplastic resin in the cavity to a temperature that maintains the deflection temperature under load or higher, the flow of the thermoplastic resin in the cavity Even if the orientation of the glittering material is disturbed by ribs or bosses in the initial stage, the orientation of the disturbing glittering material is not fixed, and the thermoplastic resin flows by the flow of the thermoplastic resin until the entire cavity is filled thereafter. Since the glitter material flows so as to flow away, the disorder of orientation of the glitter material can be eliminated from the injection molded body.

  In the second invention, in particular, in the method of manufacturing an injection molded article according to the invention of claim 1, a speed difference is further increased by providing a gate in a part directly connected to a part where the thickness of the mold is increased. Therefore, the disorder of the orientation of the glittering material is more likely to disappear.

  The third invention is an injection-molded product obtained by the method for producing an injection-molded product according to the first or second invention.

  If the injection-molded product has a rib or boss, the flow rate of the thermoplastic resin at the relevant part changes, such as the flow of thermoplastic resin into the rib or boss, or the flow around the rib or boss. The flow of the thermoplastic resin is disturbed, and accordingly the orientation of the glittering material is disturbed, but even if the injection molded body has a shape having ribs or bosses, the method for producing an injection molded body according to claim 1 or 2, An injection-molded article excellent in appearance quality can be obtained.

  According to a fourth aspect of the present invention, there is provided an injection molded body manufacturing method or an injection molded body characterized in that the thermoplastic resin of claims 1 to 3 is ABS.

  ABS is often used after being painted, but it is difficult to apply the paint and improve the appearance quality because there is a risk that the parts that are subject to external rubbing and bumping may be peeled off. There was a problem.

  On the other hand, ABS is a resin that has a high gloss of products obtained among resins, is excellent in balance between strength and cost, and is desired to be used as an external part.

  In the method of the present invention, the appearance quality can be improved because the thermoplastic resin is ABS.

  According to a fifth aspect of the present invention, there is provided a method for manufacturing an injection-molded article, or an injection-molded article, wherein the thermoplastic resin of claims 1 to 3 is PP.

  Since PP has poor adhesion to a coating film, it is generally difficult to paint and it is difficult to improve the appearance quality. Further, in the case of coating, since a primer treatment for increasing the adhesion is required, there is a problem that the cost is higher than when coating other resins.

  On the other hand, PP is a resin that has high chemical resistance among resins, is excellent in cost, and is desired to be used as an external part that requires chemical resistance.

  In the method of the present invention, the appearance quality can be improved because the thermoplastic resin is PP.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is an external view of the surface of an injection molded body according to the first embodiment of the present invention, FIGS. 2 (1) and 2 (2) are external views of the back surface of the injection molded body, and FIG. 3 is a mold. It is a schematic diagram which shows the flow of the thermoplastic resin in the cavity.

  1 and 2, the injection-molded body 11 is made of a thermoplastic resin having a bright material having an average particle diameter of less than 120 μm, and the thickness of the portion 14 having the ribs 12 and the bosses 13 is smaller than the thickness of the portion 15 having no ribs. The thickness is increased from 1 mm to 3.0 mm.

  Next, the manufacturing method of the injection molded body of this Embodiment is demonstrated.

  First, in a state where the mold is opened, the temperature of the mold is raised to a temperature at which the thermoplastic resin can maintain a temperature higher than the deflection temperature under load. Next, the mold is closed, and the molten thermoplastic resin is injected and poured into the cavity of the mold.

  At this time, as shown in (1) to (7) of FIG. 3, the thermoplastic resin is injected from the gate 16 and preferentially flows in the cavity to the portion 14 having the ribs 12 and the bosses 13 having a large thickness. Then, it flows to the site | part 15 which does not have the rib 12 and the boss | hub 13 with thin thickness.

  At this time, the alignment disorder of the glitter material occurs on the surface of the injection molded body 11 when the thermoplastic resin reaches the portion 14 having the ribs 12 and the bosses 13 ((1) to (4) in FIG. 3). To do.

  However, when the flow front of the thermoplastic resin reaches the portion 15 that does not have the ribs 12 and the bosses 13 ((5) and (6) in FIG. 3), the orientation disorder of the glittering material is washed away together with the thermoplastic resin. Go to the thermoplastic flow front.

  Further, when the cavity is filled with the thermoplastic resin ((7) in FIG. 3), the alignment disorder of the glittering material disappears.

  When the entire inside of the cavity is filled with the thermoplastic resin, the temperature of the mold is lowered to cure the thermoplastic resin, the mold is opened, and the injection molded body 11 is obtained.

  As described above, in the present embodiment, the material to be used is a thermoplastic resin having a glittering material, and even if the shape of the injection molded body is a relatively complicated shape having ribs and bosses, the ribs and bosses are not used. Use a mold that is designed to have a thickness of 0.1 mm to 3.0 mm thicker than the thickness of the part that does not have, and the temperature of the mold exceeds the temperature at which the thermoplastic resin in the cavity is bent Even if the orientation of the glitter material is disturbed by ribs or bosses in the initial stage of the thermoplastic resin flow in the cavity, the orientation disorder of the glitter material is not fixed, and the entire inside of the cavity is thereafter fixed. Due to the flow until filling, the thermoplastic resin flows so as to be washed away together with the glitter material, so that the disorder of the glitter material does not remain in the injection molded body.

  Here, the glitter material of the present invention produces a glitter feeling by the action of reflection, transmission, refraction, and the like. Specifically, metallic pigments (aluminum powder, bronze powder, etc.) and pearl pigments (for mica). There are metal oxide-coated, alumina-coated metal oxide, glass-coated metal oxide, etc.), but it is not specified and is free from the required appearance, cost, etc. It is also possible to use a mixture of a plurality of these.

  Note that the glitter material has a higher glitter feeling as the aspect ratio is larger, and the disorder is less noticeable as the aspect ratio is smaller. In addition, the larger the particle size, the smaller the number of particles per unit volume of the thermoplastic resin, so it is difficult to recognize the disorder of orientation of the glitter material. It is desirable to use a material. In this case, the number of particles per unit volume increases, so that the disorder of the orientation of the glittering material can be easily seen. Therefore, the method of the present invention is particularly effective when the particle size is small.

  Also, the amount of the glittering material added to the thermoplastic resin is not particularly specified, but if it is too small, the glittering feeling cannot be obtained, and if it is too large, the mechanical strength of the injection molded product deteriorates. On the other hand, the weight ratio is preferably 0.2% to 7%.

  In addition, the thermoplastic resin of the present invention is not particularly specified, such as PP (polypropylene), ABS (acrylonitrile butadiene styrene copolymer resin), PS (polystyrene), PC (polycarbonate), PET (polyethylene terephthalate), It can be freely selected in consideration of cost, appearance, mechanical properties, etc.

  In addition to the glittering material, the thermoplastic resin of the present invention has other fillers and additives such as fibrous fillers, antioxidants, pigments, flame retardants, etc. in accordance with the performance desired to be imparted. May be.

  In addition, the ribs and bosses refer to projecting portions provided for reinforcement and joining with other parts. In this embodiment, the ribs and bosses have both ribs and bosses. It may be a shape having only.

  The thickness of the injection-molded body is not particularly specified, but is generally about 0.5 mm to 4.0 mm. The thicker one is 2.0 mm to 2.5 mm and the thinner one is 1.5 mm to 1. .8 mm is desirable from the viewpoints of strength, cost, and suppression of disorder in the alignment of the glittering material.

  In addition, if the difference in thickness in the injection-molded product is less than 0.1 mm, the disorder of orientation does not disappear, and if it exceeds 3.0 mm, the thickness of the molded product becomes thick, so that the strength can be maintained without ribs. Therefore, the range of 0.1 mm to 3.0 mm is desirable.

  In addition, the thickness between the part having ribs and bosses and the part not having them may be the thickness between them, or the same thickness as either, or the thickness may be gradually changed with an inclination. Is not particularly specified.

  Moreover, although the rib or boss | hub does not need to exist in the site | part between both, it is desirable for the volume which a rib and boss | occupy have less than the site | part which has a rib and boss | hub.

  The deflection temperature under load is also called a heat distortion temperature, and is obtained by the method of JIS K7191. Specifically, both ends of the test piece are supported in a heating bath, and the temperature of the heating medium is increased at a rate of 2 ° C./min while applying a predetermined bending stress (load) to the test piece by a central load rod, The temperature of the heating medium when the deflection of the test piece reaches a predetermined amount.

  In JIS K7191-2, three types of loads are described, but in the present invention, 0.45 MPa is used as a reference based on the JIS K7191-2 B method.

  In addition, the upper limit temperature of the mold of the present invention is not particularly specified, but if it is raised to the decomposition temperature of the thermoplastic resin, it will be altered, so it is necessary that the temperature be below the decomposition temperature.

  In order to keep the temperature of the thermoplastic resin in the cavity equal to or higher than the deflection temperature under load, the temperature of the mold is preferably set to +20 to 70 ° C. under the load deflection temperature, although it depends on the shape of the mold.

  The present invention will be described more specifically with reference to examples. In addition, this invention is not limited by this Example.

  The thickness difference of the mold, the temperature of the mold, the type of the thermoplastic resin, and the shape of the mold were verified as shown in [Table 1].

Example 1
In Example 1, molding was performed using a mold having the same shape as that of Embodiment 1 (referred to as mold A).

  Regarding the thickness, the thickness of the portion 14 having the ribs 12 and the bosses 13 was set to 2.2 mm, and the thickness of the portion 15 having no ribs was set to 1.8 mm. That is, the difference in thickness is 0.4 mm.

  The material used was a mixture of 0.5% aluminum powder having an average particle diameter of 40 μm and 3% mica-based pearl pigment having a particle diameter of 70 μm and ABS having a deflection temperature under load of 96 ° C.

  The mold temperature was set to 140 ° C. so that the ABS temperature in the cavity was higher than the deflection temperature under load.

  First, a short shot was made, and the flow of the thermoplastic resin in the cavity and the orientation state of the glittering material were visually confirmed.

  As shown in (1) to (7) of FIG. 3, the thermoplastic resin is injected from the gate 16 and preferentially flows in the cavity to the portion 14 having the ribs 12 and the bosses 13 having a large thickness. It flowed to a portion 15 having no thin rib 12 or boss 13.

  The alignment disorder of the glitter material occurred on the surface of the injection molded body 11 when the thermoplastic resin reached the portion 14 having the ribs 12 and the bosses 13 ((1) to (4) in FIG. 3).

  However, when the flow front of the thermoplastic resin reaches the portion 15 that does not have the ribs 12 and the bosses 13 ((5) and (6) in FIG. 3), the orientation of the disturbed glitter material is washed away together with the thermoplastic resin. It moved to the thermoplastic resin flow front.

  Further, when the cavity was filled with the thermoplastic resin ((7) in FIG. 3), the alignment disorder of the glittering material disappeared.

  Due to the high temperature of the mold, once the orientation of the glittering material is disturbed, the surface layer in contact with the mold is not cooled and solidified, and is easily flown by the subsequent flow of the thermoplastic resin, I think that the disorder in the orientation of the glitter material has disappeared.

  As described above, the mold is designed to have a thickness difference between the portion 14 having the ribs 12 and the bosses 13 and the portion 15 not having the ribs 12 and the portion 15 having no ribs, and the temperature of the mold is determined by the temperature of the thermoplastic resin. By setting the temperature to be equal to or higher than the deflection temperature, the alignment disorder of the glitter material of the injection molded body 11 could be eliminated.

  Next, the temperature of the mold was examined. At this time, parameters other than the mold temperature are not changed.

  As a result of the examination, as shown in [Table 2], it was confirmed that the temperature of the mold was 140 ° C. or higher and the temperature of the thermoplastic resin in the cavity was higher than the deflection temperature under load. Confirmed that disappeared.

  The flow of the thermoplastic resin in the cavity and the state of orientation of the glittering material were confirmed by short shots at a mold temperature of 80 ° C., which resulted in an orientation of x.

  The flow of the thermoplastic resin was the same, but the orientation of the glitter material was different.

  The disordered alignment of the glitter material occurred on the surface of the injection molded body 11 when the thermoplastic resin reached the portion 14 having the ribs 12 and the bosses 13.

  Thereafter, even if the thermoplastic resin flow front arrived at the portion 15 having no ribs 12 or bosses 13, the orientation disorder of the glittering material did not move as described above.

  Further, even when the entire cavity was filled with the thermoplastic resin, the alignment disorder of the glittering material did not move as described above.

  If the temperature of the mold is low, once the orientation of the glitter material is disturbed, the surface layer in contact with the mold is first cooled and solidified, so that the disorder of the disordered glitter material is fixed, and then the thermoplastic resin It is considered that the disorder of the orientation of the glittering material remained on the surface of the injection molded body without being caused to flow by the flow of.

  Therefore, the mold temperature needs to be a temperature that keeps the thermoplastic resin in the cavity at or above the deflection temperature under load.

(Example 2)
In Example 2, molding was performed using a mold (mold A) having the same shape as in the first embodiment.

  Regarding the thickness, the thickness of the portion 14 having the rib 12 and the boss 13 was 1.5 mm, and the thickness of the portion 15 not having the thickness was 2.5 mm. That is, the difference in thickness is 1.0 mm.

  The material used was a mixture of 0.3% aluminum powder having an average particle size of 5 μm and 1.5% mica-based pearl pigment having a particle size of 50 μm and PP having a deflection temperature under load of 112 ° C.

  The temperature of the mold was 140 ° C. so that the temperature of PP in the cavity was not less than the deflection temperature under load.

  First, a short shot was made, and the flow of the thermoplastic resin in the cavity and the orientation state of the glittering material were visually confirmed.

  Both the flow of the thermoplastic resin and the state of orientation of the glittering material were the same as in Example 1.

  As described above, the mold is designed to have a thickness difference between the portion 14 having the ribs 12 and the bosses 13 and the portion 15 not having the ribs 12 and the portion 15 not having the ribs, and the temperature of the mold is the load of the thermoplastic resin. By setting the temperature to be equal to or higher than the deflection temperature, the alignment disorder of the glitter material of the injection molded body 11 could be eliminated.

  Next, the temperature of the mold was examined. At this time, parameters other than the mold temperature are not changed.

  As a result of the examination, as shown in [Table 3], it was confirmed that the temperature of the mold was 140 ° C. or higher and the temperature of the thermoplastic resin in the cavity was higher than the deflection temperature under load. Confirmed that disappeared.

  The flow of the thermoplastic resin in the cavity and the state of orientation of the glittering material were confirmed by short shots at a mold temperature of 80 ° C., which resulted in an orientation of x.

  This was the same as in Example 1.

  Due to the low temperature of the mold, once the orientation of the glitter material is disturbed, the surface layer in contact with the mold is first cooled and solidified, so that the orientation of the disturbed glitter material is fixed, and the thermoplastic resin thereafter It is considered that the brilliant material remains on the surface of the injection molded body without being swept away by the flow.

  Therefore, the mold temperature needs to be a temperature that keeps the thermoplastic resin in the cavity at or above the deflection temperature under load.

(Example 3)
In Example 3, molding was performed using a mold having the same shape as that of Embodiment 1 (Mold A) and the same material as in Example 1.

  The mold temperature was fixed at 140 ° C. as a representative value of the temperature at which the ABS temperature in the cavity was equal to or higher than the deflection temperature under load, and the thickness was examined. At this time, parameters other than the thickness are not changed.

  As a result of the examination, as shown in [Table 4], it was confirmed that the alignment disorder disappeared when the difference in thickness was 0.1 mm or more.

  In addition, the difference in thickness, which was the result of orientation x, the thickness of the portion having ribs and bosses of 2.2 mm, the thickness of the portion not having 2.2 mm, and the thickness difference of 0 mm, was short shot in the cavity. The flow of the thermoplastic resin and the orientation of the glittering material were confirmed.

  FIG. 4 is a schematic diagram illustrating the flow of the thermoplastic resin in the cavity of the mold according to the third embodiment.

  The thermoplastic resin was injected from the gate and first flowed as shown in FIG.

  Thereafter, the orientation was not disturbed in the portion 15 having no rib 12 or boss 13, but the orientation was disturbed in the portion 14 having the rib 12 or boss 13 and was filled as shown in FIG. 4 (2).

  At this time, since the thermoplastic resin has the rib 12 and the boss 13 at the part where the thermoplastic resin flows last, the distance through which the orientation of the disturbed glitter material flows is insufficient, and the orientation of the glitter material from the injection molded body 11 is disturbed. Did not disappear.

  In addition, the thickness control of the mold is generally performed in units of 0.01 mm, the thickness of the portion 14 having the ribs 12 and the bosses 13 is 2.2 mm, and the thickness of the portion 15 not having the thickness is 2.11 mm. Even when a thickness difference of 0.09 mm was provided, a slight alignment disorder remained.

  Therefore, it is determined that a difference in thickness of 0.1 mm or more is necessary.

  Even if the difference in thickness is less than 0.1 mm, as in the case of the conventional patent document 3, if the shape to be cut out is formed on the outer edge of the injection molded body and the thermoplastic resin flows there, Although the disorder of orientation disappears, it is not a desirable method because of the increase in materials used and the increase in dust.

  Moreover, since the required intensity | strength can be ensured without providing the rib 12 because the thickness of the injection molded object 11 becomes thick in the range where the difference in thickness exceeds 3.0 mm, the necessity for providing a thickness difference becomes low. For this reason, in the present invention, 3.0 mm is defined as the upper limit.

Example 4
In Example 4, molding was performed using a mold (mold B) having a shape different from that of the first embodiment.

  (1) and (2) in FIG. 5 are external views of the back surface of the injection-molded product in Example 4, and FIG. 6 is a schematic diagram showing the flow of the thermoplastic resin in the cavity of the mold.

  In FIG. 5, the injection molded body 17 is designed such that the thickness of the portion 20 having the ribs 18 and the bosses 19 is thicker than the portion 21 not having the ribs 18 and the bosses 19.

  In the present embodiment, the thickness of the portion 20 having the ribs 18 and the bosses 19 is 2.4 mm, and the thickness 21 of the portion 21 not having the ribs 18 and the bosses 19 is 1.6 mm. That is, the difference in thickness is 0.8 mm.

  The material used was a mixture of 0.2% aluminum powder having an average particle diameter of 20 μm and 1% of mica-based pearl pigment having a particle diameter of 20 μm and PP having a deflection temperature under load of 80 ° C.

  The temperature of the mold was 120 ° C. so that the temperature of PP in the cavity was equal to or higher than the deflection temperature under load.

  First, a short shot was intentionally made, and the flow of the thermoplastic resin in the cavity and the state of orientation of the glittering material were visually confirmed.

  As shown in FIGS. 6 (1) to (6), the thermoplastic resin is injected from the gate 22 directly connected to the portion 20 having the rib 18 and the boss 19, and the portion 20 having the thick rib 18 and boss 19 is present. Flowed preferentially, and then flowed to a portion 21 having a small thickness.

  The alignment disorder of the glittering material occurred on the surface of the injection molded body 17 when the thermoplastic resin reached the portion 20 having the ribs 18 and the bosses 19 ((1) and (2) in FIG. 6).

  However, when the flow front of the thermoplastic resin reaches the portion 21 that does not have the ribs 18 and the bosses 19 ((3) to (5) in FIG. 6), the disordered glitter material orientation is washed away together with the thermoplastic resin. It moved to the thermoplastic resin flow front.

  Further, when the cavity was filled with the thermoplastic resin ((6) in FIG. 3), the alignment disorder of the glittering material disappeared.

  Due to the high temperature of the mold, once the orientation of the glittering material is disturbed, the surface layer in contact with the mold is not cooled and solidified, and is easily flown by the subsequent flow of the thermoplastic resin, I think that the disorder in the orientation of the glitter material has disappeared.

  Thus, the mold is designed to have a thickness difference between the portion 20 having the ribs 18 and the bosses 19 and the portion 21 not having the ribs 18 and the portion 21 having no ribs, and the temperature of the mold is the load of the thermoplastic resin. By setting the temperature to be equal to or higher than the deflection temperature, the alignment disorder of the glittering material of the injection molded body 17 could be eliminated.

  With this mold, the temperature of the mold was examined. At this time, parameters other than the mold temperature are not changed.

  As a result of the examination, as shown in [Table 5], it was confirmed that the temperature of the mold was 100 ° C. or higher and the temperature of the thermoplastic resin in the cavity was higher than the deflection temperature under load. Confirmed that disappeared.

  Next, the temperature of the mold was fixed at 120 ° C., and the thickness was examined. At this time, parameters other than the thickness are not changed.

  As a result of the investigation, as shown in [Table 6], it was confirmed that the alignment disorder of the glittering material disappeared when the difference in thickness was 0.1 mm or more.

  Thus, even when the shape of the mold changed, the tendency of the orientation state of the glittering material with respect to the temperature and thickness difference of the mold was the same.

  In this embodiment, the gate 22 is provided at a portion directly connected to the portion 20 having the rib 18 and the boss 19. The directly connected portion of the present invention refers to a portion where the thermoplastic resin flow front immediately after injection enters the thickest portion first. As in this embodiment, depending on the shape of the injection-molded body, it may not be directly connected to a thick part, but it is more desirable to provide a gate at the directly connected part because the alignment disorder is more likely to disappear. .

  As described above, the method for producing an injection molded article of a thermoplastic resin having a glitter material according to the present invention and the injection molded article produce a texture equivalent to painting by the glitter material in the thermoplastic resin without performing painting. Therefore, it can be applied to applications that require appearance quality. For example, it can be used for home appliances such as a vacuum cleaner, a refrigerator, an air conditioner, a washing machine, a hot water washing toilet seat, and a microwave oven. Moreover, it can be used not only for home appliances but also for other products such as automobile parts.

DESCRIPTION OF SYMBOLS 11 Injection molded object 12 Rib 13 Boss 14 The part which has a rib and a boss 15 The part which does not have a rib and a boss 17 The injection molded object 18 Rib 19 Boss 20 The part which has a rib and a boss 21 The part which does not have a rib and a boss

Claims (5)

A glitter material having an average particle size of less than 120 μm is used by using a mold designed to have a thickness of a portion having ribs and bosses 0.1 to 3.0 mm thicker than a portion having no ribs or bosses. In the method of manufacturing an injection-molded article for molding a thermoplastic resin having, a step of raising the temperature of the mold to a temperature at which the temperature of the thermoplastic resin in the cavity can be maintained above the deflection temperature under load; A method for producing an injection-molded article, comprising: a step of injecting and pouring the thermoplastic resin melted into a portion; and a step of lowering the temperature of the mold to cure the thermoplastic resin. The method for producing an injection-molded article according to claim 1, wherein a gate is provided at a portion directly connected to a portion where the thickness of the mold is increased. An injection-molded product obtained by the method for producing an injection-molded product according to claim 1 or 2. The said thermoplastic resin is ABS, The manufacturing method or injection molding body of the injection molded body of Claim 1 to 3 characterized by the above-mentioned. The said thermoplastic resin is PP, The manufacturing method or injection molded body of the injection molded body of Claim 1 to 3 characterized by the above-mentioned.

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