Apparatus of manufacturing resin molded article and method of manufacturing resin molded article

Abstract

To provide a method of manufacturing a resin molded article capable of suppressing a weld line generated around a hole shape.SOLUTION: A method of manufacturing a resin molded article having a hole shape comprises the steps of: disposing a movable pin having a portion housed inside a hole provided on a surface of a mold core or a mold cavity, being capable of advancing toward the mold cavity or the mold core facing the hole, and having a shape corresponding to a shape that has filled the hole shape, in the hole on the surface of the mold core or the mold cavity; clamping the mold core and the mold cavity and injecting a molten resin into the cavity defined between the mold core and the mold cavity; advancing the movable pin into the cavity, and extruding the molten resin present in the moving direction of the movable pin into the cavity, to provide the hole shape corresponding to the shape of the movable pin to the molten resin; and retracting the movable pin to the inside of the hole after the molten resin solidifies and forms the resin molded article, and mold-opening the mold core and the mold cavity, to takeout the resin molded article.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a manufacturing method and manufacturing apparatus for a resin molded product having a hole shape formed by injection molding. [Background technology]

[0002] In recent years, materials that can achieve carbon neutrality and carbon offsets have been attracting attention as a way to create a sustainable society. Our company has also applied for a cellulose fiber composite resin under the previously mentioned Patent No. 6545145, and is currently investigating the development of high-concentration / high-biomass cellulose fibers in order to realize a sustainable society in the future.

[0003] On the other hand, when plant-derived materials such as cellulosic fibers are combined with resins, the following problems arise:

[0004] (1) Decreased fluidity during molding Cellulosic fibers have functional groups such as hydroxyl groups on the fiber surface, and these functional groups such as hydroxyl groups form hydrogen bonds that cause the cellulose fibers to bond with each other. As a result, by compounding cellulose fibers with resin, mechanical properties such as strength and elastic modulus are improved compared to the base resin. On the other hand, the bonding between the fibers increases the melt viscosity, and the flowability during injection molding deteriorates.

[0005] (2) Discoloration of resin due to thermal decomposition of fibers When the temperature of most cellulose-based fibers is increased, they begin to decompose without melting because their thermal decomposition temperature is lower than their melting point. Therefore, when the resin is heated in the molding machine cylinder to melt the base resin during injection molding, or when shear heat is generated during the resin flow, the cellulose-based fibers are thermally denatured and discolored to a brownish color.

[0006] (3) Occurrence of weld lines In order to prevent the fibers from turning brown due to thermal decomposition, resins containing cellulosic fibers must be molded at low temperatures. In this case, the low resin temperature narrows the range in which the resin can completely melt, and in molded products with holes, weld lines are more likely to occur when the resin passes through the holes. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2006-289835 A Summary of the Invention [Problem to be solved by the invention]

[0008] Of the three problems mentioned above, the occurrence of weld lines can occur even in resins that do not contain cellulosic fibers, and is a problem that can occur in resin molded products that include holes, regardless of the resin used.

[0009] 1(a) to (f) are schematic perspective views and schematic cross-sectional views showing a conventional manufacturing process of a resin molded product having a hole shape by injection molding. In each of (a) to (f), a schematic perspective view is shown in the upper part and a schematic cross-sectional view is shown in the lower part. For example, in a molded product 101 and a mold 102 as shown in FIG. 1, a molten resin is poured into a molded product cavity 109 between a mold consisting of a mold cavity 103 and a mold core 104, and the molten resin 108 flows into the molded product cavity 109 through a sprue 105, a runner 106, and a gate 107 as shown in FIG. 1(a). In the above process, when the molten resin 108 passes around a molded product hole 110, the molten resin 108 flows into different flow paths and is separated into molten resin 108a and molten resin 108b (FIG. 1(b)). After that, as shown in FIG. 1(c), when the molten resin 108a and the molten resin 108b reach a molded product hole 110a which is the farthest part from the gate 107 of the molded product hole 110, the molten resin 108a and the molten resin 108b which flowed into different flow paths join together while facing each other. At that time, as shown in Fig. 1(d), a weld line 111a begins to form between molten resin 108a and molten resin 108b, and a weld line 111b is formed along the flow direction of molten resin 108 where molten resin 108a and molten resin 108b flowing toward the flow end direction join together (Fig. 1(e)). Then, molten resin 108 that has completely filled up to the flow end cools and solidifies with weld line 111b remaining, and the molded product 101 that can be obtained has weld line 111b remaining (Fig. 1(f)).

[0010] One way to prevent the occurrence of weld lines in the molding process is to increase the resin temperature. However, as described above, resins containing cellulose-based fibers can discolor when their resin temperature increases. Therefore, if the resin temperature is increased to prevent the weld lines, a new problem of discoloration of the resin occurs. For this reason, it is important to take measures to prevent weld lines that do not involve an increase in the resin temperature when resins containing plant fibers such as cellulose-based fibers are used.

[0011] In addition, as mentioned above, resins containing cellulose fibers have poor fluidity, but if the resin temperature cannot be increased, concerns about filling properties will increase. In such cases, filling properties often become an issue before weld line suppression, so it is important to take measures to suppress weld lines and improve filling properties at the same time. Therefore, in order to apply these materials to products toward the creation of a sustainable society, it is important to suppress weld lines, taking into account that the fluidity of the materials themselves is poor, or that the fluidity is poor due to molding at low temperatures.

[0012] Therefore, an object of the present disclosure is to provide a manufacturing method for a resin molded product that can solve the above problems and suppress the occurrence of weld lines around the hole shape. [Means for solving the problem]

[0013] The manufacturing method of a resin molded product according to the present disclosure is a manufacturing method of a resin molded product having a hole shape, and includes the steps of: placing a movable pin, a portion of which is stored inside a hole provided in the surface of a mold core or mold cavity, capable of advancing from the hole toward the opposing mold cavity or mold core, and having a shape corresponding to the shape that fills the hole, in the hole on the surface of the mold core or mold cavity; clamping the mold core and the mold cavity to inject molten resin into the cavity defined between the mold core and the mold cavity; advancing the movable pin into the cavity and pushing out the molten resin in the direction of movement of the movable pin into the cavity, thereby imparting a hole shape to the molten resin that corresponds to the shape of the movable pin; and, after the molten resin has hardened to form a resin molded product, retracting the movable pin back inside the hole, opening the mold core and the mold cavity, and removing the resin molded product.

[0014] The manufacturing apparatus for a resin molded product according to the present disclosure is an apparatus for manufacturing a resin molded product having a hole shape, and comprises a mold having a mold core or mold cavity having a hole on its surface, a mold cavity or mold core corresponding to the mold core or mold cavity, a movable pin that can slide inside the hole and whose tip can advance from the hole toward the opposing mold cavity or mold core when the mold core and the mold cavity are clamped, and has a shape that corresponds to the shape that fills the hole, and a control device that can operate the movable pin. Effect of the Invention

[0015] By using the manufacturing method or manufacturing apparatus for a resin molded product according to the present disclosure, it is possible to provide a resin molded product that has no weld lines around the hole shape. In addition, when using a material with concerns about filling properties, it is possible to obtain a resin molded product that achieves both improved filling properties and no weld lines. In addition, when burrs remain around the hole shape by using the manufacturing method or manufacturing apparatus for a resin molded product according to the present disclosure, it is possible to remove the burrs. [Brief description of the drawings]

[0016] [Figure 1] 1(a) to 1(f) are schematic perspective views and schematic cross-sectional views showing a conventional manufacturing process for a resin molded product having a hole shape by injection molding. [Diagram 2] 5(a) and 5(b) are schematic cross-sectional views showing a process of a method for manufacturing a resin molded product having a hole shape using the manufacturing apparatus for a resin molded product according to the first embodiment. [Diagram 3] 1(a) to 1(f) are schematic perspective views and schematic cross-sectional views illustrating steps of a method for producing a resin molded product having a hole shape according to the first embodiment. [Figure 4] 10(a) to 10(g) are schematic perspective views and schematic cross-sectional views of steps of a method for producing a resin molded product having a hole shape according to a second embodiment. [Diagram 5] 11(a) to 11(e) are schematic cross-sectional views illustrating steps of a method for producing a resin molded product having a hole shape according to a third embodiment. [Figure 6]5(a) to 5(c) are schematic cross-sectional views showing an example of the cross-sectional shape of a movable pin. [Figure 7] 10(a) to 10(e) are schematic cross-sectional views illustrating steps of a method for producing a resin molded product having a hole shape according to a fourth embodiment. [Figure 8] 13(a) to 13(f) are schematic cross-sectional views illustrating steps of a method for producing a resin molded product having a hole shape according to a fifth embodiment. [Figure 9] 13(a) to 13(f) are schematic cross-sectional views illustrating steps of a method for producing a resin molded product having a hole shape according to a sixth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The manufacturing method of a resin molded product according to the first aspect is a manufacturing method of a resin molded product having a hole shape, and includes the steps of: placing a movable pin in the hole on the surface of the mold core or mold cavity, a portion of which is stored inside a hole provided in the surface of the mold core or mold cavity, which is capable of advancing from the hole toward the opposing mold cavity or mold core, and which has a shape corresponding to the shape that fills the hole shape; clamping the mold core and the mold cavity to inject molten resin into the cavity defined between the mold core and the mold cavity; advancing the movable pin into the cavity to extrude molten resin in the direction of movement of the movable pin into the cavity, thereby giving the molten resin a hole shape corresponding to the shape of the movable pin; and, after the molten resin has hardened to form the resin molded product, retracting the movable pin inside the hole, opening the mold core and the mold cavity, and removing the resin molded product.

[0018] The second aspect of the method for producing a resin molded product is the same as the first aspect, and further includes a step of retracting the movable pin inside the hole to provide a reserve space capable of being filled with molten resin from the hole to the tip of the movable pin retracted inside the hole, and in the step of imparting a hole shape to the molten resin, when a predetermined amount of molten resin has accumulated in the reserve space, the movable pin may be advanced from inside the hole into the cavity to extrude the molten resin accumulated in the reserve space into the cavity.

[0019] In the method for producing a resin molded product according to the third aspect, in the above-mentioned first or second aspect, in the step of imparting a hole shape to the molten resin, the tip of the movable pin may be brought into contact with the surface of the opposing mold cavity or mold core while penetrating the molten resin with the movable pin, thereby imparting a hole shape to the molten resin that corresponds to the shape of the movable pin.

[0020] In the manufacturing method for a resin molded product according to the fourth aspect, in the above-mentioned first or second aspect, in the step of imparting a hole shape to the molten resin, the tip of the movable pin may be stopped at a position that does not reach the surface of the opposing mold cavity or mold core, and a hole shape corresponding to the shape of the movable pin may be imparted to the molten resin.

[0021] A fifth aspect of the method for producing a resin molded product is any one of the first to third aspects above, and in the step of imparting a hole shape to the molten resin, the tip of the movable pin may be made concave, and the concave surface may be brought into contact with an opposing surface of the mold cavity or mold core to hold the molten resin within the concave surface and impart a hole shape corresponding to the shape of the movable pin to the molten resin.

[0022] A sixth aspect of the method for producing a resin molded product may be such that, in the step of imparting a hole shape to the molten resin in the above first to third and fifth aspects, while penetrating the molten resin with a movable pin, the tip of the movable pin is inserted into a recess pressed against the surface of the opposing mold cavity or mold core, thereby imparting a hole shape to the molten resin that corresponds to the shape of the movable pin.

[0023] The method for producing a resin molded product according to the seventh aspect, in any one of the first to sixth aspects above, may be capable of controlling the temperature of any location in the mold cavity or mold core facing the movable pin or the tip of the movable pin.

[0024] The method for producing a resin molded product according to an eighth aspect is any one of the first to seventh aspects, in which the movable pin may be independently operable.

[0025] A ninth aspect of the method for producing a resin molded article is any one of the first to eighth aspects, in which a filler composite resin may be used as the molten resin.

[0026] A tenth aspect of the method for producing a resin molded article is the same as the ninth aspect, and may further include using cellulosic fibers as the filler.

[0027] The method for manufacturing a resin molded product according to an eleventh aspect is any one of the third to tenth aspects above, in which, in the step of imparting a hole shape to the molten resin, the tip of the movable pin may begin to advance from a position on the same plane as the surface that will become the final product surface.

[0028] The manufacturing apparatus for a resin molded product of the twelfth aspect is an apparatus for manufacturing a resin molded product having a hole shape, and comprises a mold having a mold core or mold cavity having a hole on its surface, a mold cavity or mold core corresponding to the mold core or mold cavity, a movable pin that can slide inside the hole and whose tip can advance from the hole toward the opposing mold cavity or mold core when the mold core and the mold cavity are clamped, and has a shape that corresponds to the shape that fills the hole, and a control device that can operate the movable pin.

[0029] A thirteenth aspect of the present invention relates to an apparatus for producing a resin molded product according to the twelfth aspect, wherein the movable pin has a concave tip.

[0030] The apparatus for manufacturing a resin molded product according to a fourteenth aspect is the thirteenth aspect, wherein the cross-sectional shape of the movable pin along the sliding direction of the tip may be recessed into an arc shape, a trapezoid shape, or a triangle shape.

[0031] The manufacturing apparatus for resin molded products according to the 15th aspect is, in any one of the 12th to 14th aspects above, a mold cavity or mold core corresponding to the mold core or mold cavity has a recess biased against a surface of the mold cavity or mold core that faces the tip of the movable pin when the mold core and the mold cavity are clamped, and the movable pin may be insertable into the recess.

[0032] A sixteenth aspect of the present invention relates to an apparatus for producing a resin molded product according to the fifteenth aspect, wherein the biased recessed portion is biased by a spring.

[0033] The 17th aspect of the manufacturing apparatus for resin molded products is, in any one of the 12th to 16th aspects above, such that the temperature of the mold cavity or mold core facing the movable pin or the tip of the movable pin is not independently adjusted, but is set to a temperature equal to or lower than the temperature setting of the other mold core or mold cavity.

[0034] The manufacturing apparatus for resin molded products according to the 18th aspect may, in any one of the 12th to 17th aspects above, have a mechanism capable of adjusting the temperature of the mold cavity or mold core facing the movable pin or the tip of the movable pin so that the temperature is different from that of the other mold core or mold cavity.

[0035] In order to achieve the above object, an outline of a method for producing a resin molded product according to the present disclosure will be described below. (1) To suppress the occurrence of weld lines around holes in resin molded products while improving the resin filling amount. In any hole-shaped portion of a resin molded product, a recessed portion (hole) of the same shape as the hole shape is provided in either the mold cavity or the mold core, and a movable pin that can slide in the recessed portion (hole) and penetrate the molten resin by being inserted into the molten resin is installed in the recessed portion. Then, by arranging the movable pin in a state where it is recessed from the product surface, a reserve space into which the molten resin flows is provided in the cavity. After the molten resin is injected into the cavity, the molten resin reaches the reserve space and a predetermined amount flows in, and then the movable pin is advanced from the inside of the recessed portion (hole) into the cavity, and pressure is applied so that the molten resin reaches the filling end in the process of advancing to the product part surface. The movable pin is further advanced even after reaching the product part surface, and the movable pin is advanced until it penetrates the molten resin in the cavity and contacts the opposing mold. This makes it possible to improve the filling property of the resin and at the same time to provide a hole shape without a weld line.

[0036] In this case, there is no limitation as to whether the movable pin, the mold parts around the movable pin, and the mold parts facing the tip of the movable pin are temperature-controlled or not.

[0037] At this time, the number of movable pins is not limited, and multiple pins may be installed when the product has multiple hole shapes. The size of the reserve space in which the movable pins are retracted is not limited, but it is preferable to set it considering the volume that is left unfilled during normal molding. It is preferable that the unfilled volume and the reserve space volume are equal, but if the density of the final molded product is to be increased, the reserve space volume can be set larger than the unfilled volume. In addition, it is possible to set the reserve space volume smaller than the unfilled volume in consideration of the volume of the hole shape so that burrs do not occur on the hole shape and the product part surface. The volume of this reserve space is expected to be 80% to 120% of the unfilled volume, but is preferably 95% to 105%. It is preferable to adjust the unfilled volume ratio to this reserve space to an appropriate ratio by changing the VP switching value and the resin temperature.

[0038] (2) The tip shape of the movable pin removes burrs near the hole shape while suppressing the occurrence of weld lines around the hole shape in the resin molded product. In any hole-shaped portion of a resin molded product, a recessed portion having the same shape as the hole shape is provided in either the mold cavity or the mold core, and a movable pin that can slide along the recessed portion and penetrate the molten resin by being inserted into the molten resin is provided in the recessed portion. After the molten resin is injected, the molten resin reaches the hole shape, and after a predetermined amount of the molten resin has flowed in, the movable pin is advanced until it penetrates the molten resin in the cavity and contacts the opposing mold. At this time, the tip of the movable pin is concave, and when the tip of the movable pin contacts the opposing mold, the resin present on the inside of the concave shape and the outside of the movable pin are separated. This makes it possible to remove burrs near the hole shape and at the same time provide a hole shape without a weld line. In this case, there is no limitation as to whether the movable pin, the mold parts around the movable pin, and the mold parts facing the tip of the movable pin are temperature-controlled or not.

[0039] In addition, the tip position of the movable pin may be the same as the product part surface, or may be set back from the product part surface to provide a reserve space, and the disclosure of (1) may be used in combination; the tip position of the movable pin is not particularly limited. If an unfilled volume remains due to the product shape, material type, and molding conditions, the reserve space can be filled with resin by providing a reserve space. Therefore, if normal molding can sufficiently fill the space, it is desirable to set the tip position of the movable pin at the same position as the product part surface, and conversely, if an unfilled volume remains in normal molding, it is desirable to set the tip position of the movable pin back from the product part surface so that the volume of the reserve space is equivalent to the unfilled volume.

[0040] (3) The spring structure removes burrs around the hole shape while suppressing the occurrence of weld lines around the hole shape in plastic molded products. In any hole-shaped portion of a resin molded product, a recess (hole) of the same shape as the hole shape is provided in either the mold cavity or the mold core, and a movable pin that can slide in the recess (hole) and penetrate the molten resin by being inserted into the molten resin is installed in the recess. After the molten resin is injected, the molten resin reaches the hole shape, and after a predetermined amount of the molten resin flows in, the movable pin is advanced until it penetrates the molten resin in the cavity and contacts the opposing mold. At this time, a structure that is pushed in by a spring is provided in the opposing mold, so that the spring and the opposing part surface are pushed down by the compression force of the movable pin, and the molten resin that was in contact with the tip of the movable pin and the resin that was present outside the movable pin are separated. This makes it possible to remove burrs near the hole shape and at the same time provide a hole shape without a weld line.

[0041] In this case, there is no limitation as to whether the movable pin, the mold parts around the movable pin, and the mold parts facing the tip of the movable pin are temperature-controlled or not.

[0042] The tip position of the movable pin may be the same as the product part surface, or may be set back from the product part surface to provide a reserve space, and the tip position of the movable pin is not particularly limited. If an unfilled volume remains due to the product shape, material type, and molding conditions, the reserve space can be filled with resin by providing a reserve space. Therefore, if the volume can be sufficiently filled by normal molding, it is desirable to set the tip position of the movable pin at the same position as the product part surface, and conversely, if an unfilled volume remains by normal molding, it is desirable to set the tip position of the movable pin back from the product part surface so that the volume of the reserve space is equal to the unfilled volume.

[0043] As mentioned above, these disclosures may be used in combination without any problems, such as (1) and (2) or (1) and (3), depending on the application.

[0044] Hereinafter, embodiments will be described with reference to the accompanying drawings.

[0045] In the present disclosure, for example, pulp extracted from wood is crushed in advance to an average fiber particle size of 40±10 μm and a fiber length of 200±30 μm, and the powdered pulp (hereinafter, cellulose fiber) is mixed with a base material polypropylene in a kneader to form a composite integrated cellulose fiber composite resin (hereinafter, polypropylene (PP)-cellulose fiber).

[0046] The resin molded products used had a product shape of, for example, a rectangular shape with a width of 30 mm and a length of 400 mm with a variable thickness, a side gate with a thickness of 2 mm, and a runner length of 250 mm from the sprue to the gate.

[0047] In addition, a hydraulic cylinder is used for the movable pin drive section, and the drive of the movable pin is controlled by connecting a hydraulic pump capable of outputting a maximum pressure of 20 MPa and a control device capable of controlling the ON / OFF timing of the cylinder. In this disclosure, the hydraulic pressure of the hydraulic pump for driving the hydraulic cylinder was set to 15 MPa, and the hydraulic cylinder drive time was set to 1 second after the start of injection.

[0048] (Embodiment 1) In embodiment 1, the tip of the movable pin is recessed from the product part surface to provide a reserve space for molten resin to fill, and the tip shape of the movable pin is made flat with the product surface and the mold structure facing the movable pin is made the normal product part surface, thereby providing the reserve space to improve the filling of resin into the product and to impart a hole shape.

[0049] The product plate thickness is 1 mm and the resin temperature is 210°C to 230°C. 2(a) and (b) are schematic cross-sectional views showing a step of the method for manufacturing a resin molded product having a hole shape using the manufacturing apparatus for resin molded products according to embodiment 1. Figs. 3(a) to (f) are schematic perspective views and schematic cross-sectional views showing each step of the method for manufacturing a resin molded product having a hole shape according to embodiment 1.

[0050] First, the structure of the molding die for molding will be described. 2(a) and (b), a manufacturing apparatus 101 for a resin molded product having a hole shape according to the first embodiment includes a mold core 104 or mold cavity 103 having a carved portion (hole) 201 on its surface, a mold 102 having a corresponding mold cavity 103 or mold core 104, a movable pin 202, and a drive unit (control device) 203 capable of operating the movable pin 202. The movable pin 202 is capable of sliding inside the carved portion (hole) 201, and its tip is capable of advancing from the carved portion (hole) 201 toward the opposing mold cavity 103 or mold core 104 when the mold core 104 and the mold cavity 103 are clamped. The movable pin 202 has a shape corresponding to the shape that fills the hole shape. In the manufacturing method of a resin molded product using this manufacturing apparatus 101 for a resin molded product, molten resin 108 passes through a sprue 105, a runner 106, and a gate 107 and flows into a molded product cavity 109 defined between a mold core 104 and a mold cavity 103, as in normal injection molding. A dug portion (hole) 201 having the same shape as the hole shape is provided on the surface of the mold core corresponding to the hole shape portion of the resin molded product, and a movable pin 202 capable of sliding inside the dug portion 201 is installed in the dug portion 201. A movable pin drive unit 203 is installed on the back surface of the movable pin 202, and the movable pin 202 can be slid in the axial direction of the hole shape by controlling the drive unit 203.

[0051] Next, a method for manufacturing a resin molded product using this apparatus 101 for manufacturing a resin molded product will be described. 3(a) to 3(f) are schematic perspective views and schematic cross-sectional views of each step of the method for producing a resin molded product having a hole shape according to the first embodiment. (1) In a mold 102 consisting of a resin molded product 101, a mold cavity 103, and a mold core 104 as shown in Figure 3(a), a recessed portion (hole) 201 having the same shape as the hole shape and a movable pin 202 capable of sliding inside the recessed portion 201 are provided on the mold core 104 side of the part that will become the hole shape of the resin molded product 101, and the movable pin 202 is made to stop in a position recessed from the product part surface.

[0052] (2) When molten resin 108 is poured in under this condition, as shown in FIG. 3(a), the molten resin 108 passes through the sprue 105, the runner 106, and the gate 107, and flows into the molded product cavity 109, and then begins to flow into the dug-out portion 201, as shown in FIG. 3(b). (3) As shown in Fig. 3(c), when the molten resin flows a little downstream from the state where the dug portion 201 is completely filled, the molten resin 108c may not be able to flow due to the limit of the injection pressure of the molding machine. At this time, a hydraulic cylinder is used to advance the movable pin 202 until it contacts the surface of the mold cavity 103, as shown in Fig. 3(d). At this time, the molten resin 108 that has accumulated in the reserve space of the dug portion 201 starts to flow toward the product portion at the same time as the movable pin 202 advances, and the product portion can be completely filled before the movable pin 202 contacts the surface of the mold cavity 103, as shown in Fig. 3(e).

[0053] (4) Then, the molten resin 108 that has completely filled the flow end starts to cool and solidify, and when the molten resin 108 has sufficiently solidified, the movable pin 202 is retracted to the position before injection, as shown in Fig. 3(f). The amount of retraction at this time is the amount of molten resin 108 that accumulates in the dug portion 201, so it is desirable to set it taking into account the amount of resin flow from the injection molding machine.

[0054] By performing these steps, it is possible to obtain a completely filled resin molded product with no weld lines around the hole shape, such as a good PP-cellulose fiber product.

[0055] In addition, in the case of normal injection molding that does not use the flow of molten resin from the spare space according to the present disclosure, even if the resin temperature is set to 230°C, which is the upper limit of the recommended molding temperature for the molten resin used, for example, PP-cellulose fiber, the resin does not reach the end of the flow. In contrast, according to the manufacturing method of the resin molded product according to the first embodiment, not only can the product be completely filled at the same temperature, but also a completely filled resin molded product can be obtained even under conditions where the temperature is lowered to 210°C. Since the cellulose-based fiber discolors and turns brown due to the influence of heat, a resin molded product that can significantly suppress discoloration in the appearance of the molded product can be obtained by simply lowering the molding temperature by 20°C. Furthermore, even in a molded product where the molding temperature is lowered to 210°C, no weld lines are generated around the hole shape.

[0056] (Embodiment 2) In the manufacturing method of a resin molded product according to the second embodiment, the tip of the movable pin is recessed from the product part surface to provide a reserve space for filling with molten resin. Also, it differs from the first embodiment in that the tip shape of the movable pin is made flat with the product surface, and the forward movement of the movable pin is stopped before it comes into contact with the surface of the opposing mold, forming a hole shape that does not penetrate through. This makes it possible to improve the filling of the resin into the product and provide a hole shape by providing a reserve space.

[0057] In addition, the product plate thickness is 1 mm and the resin temperature is 210°C to 230°C. 4(a) to 4(g) are schematic perspective views and schematic cross-sectional views of each step of the method for producing a resin molded product having a hole shape according to the second embodiment. (1) In a mold 102 consisting of a resin molded product 101, a mold cavity 103, and a mold core 104 as shown in Figure 4(a), a recessed portion (hole) 201 having the same shape as the hole shape and a movable pin 202 capable of sliding inside the recessed portion 201 are provided on the mold core 104 side of the part that will become the hole shape of the resin molded product 101, and the movable pin 202 is made to stop in a position recessed from the product part surface.

[0058] (2) When molten resin 108 is poured in under this condition, as shown in FIG. 4(a), the molten resin 108 passes through the sprue 105, the runner 106, and the gate 107, and flows into the molded product cavity 109, and then begins to flow into the dug-out portion 201, as shown in FIG. 4(b). (3) As shown in Fig. 4(c), when the molten resin flows a little downstream from the state where the dug portion 201 is completely filled, the molten resin 108c may not be able to flow due to the limit of the injection pressure of the molding machine. At this time, a hydraulic cylinder is used to advance the movable pin 202 as shown in Fig. 4(d) and stop it before it comes into contact with the surface of the mold cavity 103. At this time, the molten resin 108 that has accumulated in the reserve space of the dug portion 201 starts to flow into the cavity that becomes the product portion at the same time as the movable pin 202 advances, and as shown in Fig. 4(e), the product portion can be completely filled before the movable pin 202 comes into contact with the surface of the mold cavity 103.

[0059] (4) Then, the molten resin 108 that has completely filled the flow end starts to cool and solidify, and when the molten resin 108 has sufficiently solidified, the movable pin 202 is retracted to the position before injection, as shown in Fig. 4(f). The amount of retraction at this time is the amount of molten resin 108 that accumulates in the dug portion 201, so it is desirable to set it taking into account the amount of resin flow from the injection molding machine.

[0060] By performing these steps, it is possible to obtain a completely filled resin molded product with no weld lines around the hole shape, such as a good PP-cellulose fiber product, as shown in Figure 4(g).

[0061] Furthermore, in the case of normal injection molding that does not use the flow of molten resin from the spare space according to the present disclosure, even if the resin temperature is set to 230°C, which is the upper limit of the recommended molding temperature for the molten resin used, for example, PP-cellulose fiber, the flow does not reach the end of the flow. In contrast, according to the manufacturing method for a resin molded product according to the first embodiment, not only can the product be completely filled at the same temperature, but a completely filled resin molded product can also be obtained even when the temperature is reduced to 210°C. Furthermore, no weld lines are generated around the hole shape even in a molded product where the molding temperature is reduced to 210°C.

[0062] (Embodiment 3) In embodiment 3, the tip of the movable pin is made the same as the product part surface, the tip shape of the movable pin is concave, and the mold structure facing the movable pin is a normal product part surface, so that the shape of the tip pin can be used to remove burrs around the hole shape and to impart the hole shape.

[0063] The product plate thickness is 4 mm, and the resin temperature is 200°C.

[0064] 5(a) to 5(e) are schematic cross-sectional views illustrating the steps of a method for producing a resin molded product having a hole shape according to the third embodiment. (1) In a mold 102 as shown in FIG. 5(a), a recessed portion (hole) 201 of the same shape as the hole is provided on the mold core 104 side of the mold core 104 in the portion that will become the hole shape of the resin molded product, and a movable pin 202a that is capable of sliding inside the recessed portion 201 and has a concave tip is placed in the recessed portion 201 at the same position as the tip of the product part surface.

[0065] 6(a) to 6(c) are schematic cross-sectional views showing an example of the cross-sectional shape of the movable pin 202a. The concave shape of the tip of the movable pin 202a may be trapezoidal as shown in FIG. 6(a), arcuate as shown in FIG. 6(b), or triangular as shown in FIG. 6(c) when viewed in cross section of the pin, and it does not matter if it is trapezoidal as shown in FIG. 6(a), arcuate as shown in FIG. 6(b), or triangular as shown in FIG. 6(c), as long as there is a distance in the axial direction of the movable pin 202a between the outermost part of the pin tip and any location inside. Among these, the trapezoidal shape is superior in terms of workability and burr cutting ability, while the arcuate and triangular shapes are superior in that the burrs to be removed are not taken to the pin side and can be smoothly removed. Therefore, it is possible to use them differently depending on the application. In these pin tip shapes, the distance between the pin tip and the most concave part (corresponding to the height of the outermost part) is not limited as long as it is equal to or greater than the thickness of the skin layer formed by the molten resin 108 during the flow, but is preferably 0.3 mm to 6 mm. In this example, the tip of the movable pin 202a is cut into a trapezoidal shape when viewed in cross section, and the distance (height) between the tip and the most recessed part (center) is 3 mm.

[0066] A movable pin driver 203 is provided on the rear surface of the movable pin 202a, and the movable pin can be slid in the axial direction of the hole shape by controlling the driver 203.

[0067] (2) When molten resin 108 is poured from the injection molding machine in this state, as shown in Figures 5(a) and (b), molten resin 108 passes through sprue 105, runner 106, and gate 107, and flows into molded product cavity 109, and passes through dug-out portion 201, as shown in Figure 5(c). Here, as shown in Figure 5(d), a hydraulic cylinder is used to advance movable pin 202a until it comes into contact with the surface of mold cavity 103.

[0068] (3) Then, the molten resin 108 that has completely filled the flow end starts to cool and solidify, and when the molten resin 108 has sufficiently solidified, as shown in FIG. 5(e), the movable pin 202a is retracted to the position before injection.

[0069] By performing these steps, it is possible to obtain a completely filled resin molded product with no weld lines around the hole shape, such as a good PP-cellulose fiber product.

[0070] When the plate thickness of a resin molded product increases, if the tip of the movable pin is flat, a large amount of molten resin is present at the tip of the movable pin while it is moving forward, and the tip of the movable pin cannot be pushed all the way to full contact with the facing mold, resulting in a thin layer of resin. Even in practice, for example, if a movable pin with a flat tip is used for a product shape with a plate thickness of 4 mm, resin burrs about 50 μm thick may remain on the molded product.

[0071] On the other hand, when a movable pin 202a with a concave tip is used, the molten resin present at the tip of the movable pin 202a is concentrated inside the concave tip, separating the molten resin inside the concave tip of the movable pin 202a and outside the movable pin, creating a portion of the outer periphery of the tip of the movable pin 202a where no resin layer is formed between the movable pin and the mold cavity 103. As a result, after the molten resin has completely solidified, it is separated into the product portion and the burr removal portion 108d, and a resin molded product without burrs or weld lines around the hole shape can be obtained.

[0072] (Embodiment 4) In embodiment 4, the tip of the movable pin is made the same as the product part surface, the tip shape of the movable pin is flat with the product surface, and the mold structure facing the movable pin has a spring structure that allows the movable pin to retract when compressed, thereby enabling the spring structure to remove burrs around the hole shape and to impart the hole shape.

[0073] The product plate thickness was 4 mm and the resin temperature was 200°C.

[0074] 7(a) to (e) are schematic cross-sectional views illustrating the steps of a method for producing a resin molded product having a hole shape according to the fourth embodiment. (1) In a mold 102 as shown in Fig. 7(a), a recessed portion (hole) 201 of the same shape as the hole is provided on the mold core 104 side of the portion that will become the hole shape of the resin molded product, and a movable pin 202 that can slide inside the recessed portion 201 is installed in the recessed portion 201 so that the tip of the movable pin 202 is in the same position as the product part surface. At this time, a movable pin drive unit 203 is installed on the back surface of the movable pin 202, and the movable pin can be slid in the axial direction of the hole shape by controlling the drive unit 203. In addition, a recessed portion 601 of the same shape as the movable pin 202 is installed coaxially opposite the recessed portion 201, and a push-in portion 602 that is biased by a spring structure and can move forward and backward is installed in the recessed portion.

[0075] Here, there are no restrictions on the number of turns, thickness, or material of the spring used for the pushing part 602, but it is sufficient to select one that can be pushed in by the compressive force of the movable pin 202 and is not completely pushed in during the flow process of the molten resin. Therefore, although it is not suitable when the molten resin is completely pushed in during the flow process, if the product part and the flash part can be separated, there is no problem if it is pushed in by the internal pressure of the molten resin before coming into contact with the movable pin 202.

[0076] (2) In this state, when molten resin 108 is poured from the injection molding machine, as shown in Fig. 7(a), molten resin 108 passes through sprue 105, runner 106, and gate 107, flows into molded product cavity 109, and passes through dug-in portion 201, as shown in Fig. 7(b) and (c). Then, as shown in Fig. 7(d), a hydraulic cylinder is used to advance movable pin 202 until it contacts the surface of push-in portion 602, and movable pin 202 is pushed in as it is until the spring of push-in portion 602 is completely retracted.

[0077] (3) Then, the molten resin 108 that has completely filled the flow end starts to cool and solidify, and when the molten resin 108 has sufficiently solidified, the movable pin 202 is retracted to the position before injection, as shown in Fig. 7(e). At this time, the pushing part 602 advances at the same time as the movable pin 202 retracts, and returns to the position before injection started while discharging the burr removing part 108d.

[0078] By performing these steps, it is possible to obtain a completely filled resin molded product with no weld lines around the hole shape, such as a good PP-cellulose fiber product.

[0079] In addition, in this product with a plate thickness of 4 mm, resin burrs of about 50 μm thickness remain in the resin molded product, but when the pushing part 602 is installed, the resin that was present at the tip of the movable pin 202 is concentrated inside the concave shape, so that the outer periphery of the tip of the movable pin 202 comes into complete contact with the mold cavity 103. As a result, after the molten resin has completely solidified, it separates into the product part and the burr removal part 108d, and a molded product without burrs or weld lines around the hole shape can be obtained.

[0080] (Embodiment 5) In embodiment 5, the tip of the movable pin is recessed from the product part surface to provide a reserve space for molten resin to fill, and the tip shape of the movable pin is concave and the mold structure facing the movable pin is the normal product part surface. By providing the reserve space, it is possible to improve the filling of resin into the product and to remove burrs around the hole shape and impart the hole shape by the tip pin shape.

[0081] For example, the product plate thickness is 4 mm, and the resin temperature is 190°C.

[0082] 8(a) to 8(f) are schematic cross-sectional views showing the steps of a method for producing a resin molded product having a hole shape according to the fifth embodiment. (1) In a mold 102 as shown in FIG. 8(a), a recessed portion (hole) 201 of the same shape as the hole is provided on the mold core 104 side of the mold core 104 in the portion that will become the hole shape of the resin molded product, and a movable pin 202a that is capable of sliding inside the recessed portion 201 and has a concave tip is brought to rest in the recessed portion 201 with the product part surface and the tip of the movable pin 202a recessed from the product part surface.

[0083] At this time, the concave shape of the tip of the movable pin 202a can be either arc-shaped or trapezoidal when viewed in cross section of the movable pin, and there is only a need for a distance (height) in the axial direction of the movable pin 202a between the outermost part of the tip of the movable pin and any location inside. There is also no restriction on the axial distance (height) between the tip of the movable pin and the most concave part as long as it is equal to or greater than the thickness of the skin layer formed by the molten resin 108 during its flow, but it is preferably 0.3 mm to 6 mm. In this example, the tip of the movable pin 202a is cut into a trapezoidal shape when viewed in cross section, and the distance between the tip and the most concave part is 3 mm.

[0084] Further, a movable pin driver 203 is provided on the rear surface of the movable pin 202a, and by controlling the driver 203, the movable pin 202a can be slid in the axial direction of the hole shape.

[0085] (2) When the molten resin 108 is poured in under this condition, as shown in Fig. 8(a) and (b), the molten resin 108 passes through the sprue 105, the runner 106, and the gate 107, flows into the molded product cavity 109, and starts to flow into the dug portion 201. As shown in Fig. 8(c), the molten resin may not be able to flow due to the limit of the injection pressure of the molding machine at a position slightly beyond the dug portion 201. Here, as shown in Fig. 8(d) and (e), the movable pin 202a is advanced using a hydraulic cylinder, and as shown in Fig. 8(e), the movable pin 202a is advanced to a point where it contacts the surface of the mold cavity 103. At this time, the molten resin 108 that has been accumulated in the preliminary space of the dug portion 201 starts to flow into the cavity that will become the product portion, and the cavity that will become the product portion is completely filled before the movable pin 202 contacts the surface of the mold cavity 103.

[0086] (3) Then, the molten resin 108 that has completely filled the flow end starts to cool and solidify, and when the molten resin 108 has sufficiently solidified, the movable pin 202a is retracted to the position before injection, as shown in Fig. 8(f). The amount of retraction at this time is the amount of molten resin 108 that accumulates in the spare space formed in the recessed portion 201, so it is desirable to set it taking into account the amount of resin flow from the injection molding machine.

[0087] By performing these steps, it is possible to obtain a completely filled resin molded product with no weld lines around the hole shape, such as a good PP-cellulose fiber product.

[0088] In addition, in the case of normal injection molding that does not use the flow of molten resin from the preliminary space according to the present disclosure, if the resin temperature is set to 190°C, which is the lower limit of the recommended molding temperature for the molten resin used, for example, PP-cellulose fiber, the resin does not fill to the end of the flow. In contrast, according to the manufacturing method of a resin molded product according to the fifth embodiment, the molten resin that has accumulated in the preliminary space formed by retracting the movable pin 202a is pushed out into the cavity that becomes the product part, and a resin molded product that is completely filled with molten resin at the same temperature is obtained. In addition, the molten resin that was present at the tip of the movable pin 202a is collected inside the concave shape of the tip, and after the molten resin has completely solidified, it is separated into the product part and the burr removal part 108d, and a resin molded product without burrs or weld lines around the hole shape can be obtained.

[0089] (Embodiment 6) In embodiment 6, the tip of the movable pin is recessed from the product part surface to provide a reserve space for molten resin to fill, and the tip shape of the movable pin is made flat with the product surface and the mold structure facing the movable pin has a spring structure that allows the movable pin to retreat by being compressed.By providing the reserve space, it is possible to improve the filling of resin into the product and to remove burrs around the hole shape and give the hole shape by the spring structure.

[0090] The product plate thickness was 4 mm and the resin temperature was 190°C.

[0091] 9(a) to 9(f) are schematic cross-sectional views showing the steps of a method for producing a resin molded product having a hole shape according to the sixth embodiment. (1) In a mold 102 as shown in Fig. 9(a), a recessed portion (hole) 201 of the same shape as the hole is provided on the mold core 104 side of the portion that will become the hole shape of the resin molded product, and a movable pin 202 that can slide inside the recessed portion 201 is installed in the recessed portion 201 at a position where the tip of the movable pin 202 is retreated from the product part surface and the product part surface. At this time, a movable pin drive unit 203 is installed on the back surface of the movable pin 202, and the movable pin can be slid in the axial direction of the hole shape by controlling the drive unit 203. In addition, a recessed portion 601 of the same shape as the movable pin 202 is installed coaxially opposite the recessed portion 201, and a push-in portion 602 that is biased by a spring structure and can move forward and backward is installed in the recessed portion.

[0092] Here, there are no restrictions on the number of turns, thickness, or material of the spring used for the pushing part 602, but it is sufficient to select one that can be pushed in by the compressive force of the movable pin 202 and is not completely pushed in during the flow process of the molten resin. Therefore, although it is not suitable when the molten resin is completely pushed in during the flow process, if the product part and the flash part can be separated, there is no problem if it is pushed in by the internal pressure of the molten resin before coming into contact with the movable pin 202.

[0093] (2) When molten resin 108 is poured in under this condition, as shown in Fig. 9(a), molten resin 108 passes through sprue 105, runner 106, and gate 107, flows into molded product cavity 109, and starts to flow into dug portion 201. As shown in Fig. 9(b), the molten resin may not be able to flow due to the limit of the injection pressure of the molding machine at a position slightly beyond dug portion 201. Here, as shown in Figs. 9(c) and 9(d), a hydraulic cylinder is used to advance movable pin 202 until it contacts push-in portion 602. At this time, as movable pin 202 advances, molten resin 108 that has accumulated in the spare space of dug portion 201 starts to flow into the cavity that will become the product portion, and as shown in Fig. 9(e), the product portion is completely filled before movable pin 202 contacts the surface of push-in portion 602. By continuing to push the movable pin 202 in until the spring of the pushing portion 602 is completely retracted, the product portion and the burr removal portion 108d are separated.

[0094] (3) Then, the molten resin 108 that has completely filled the flow end starts to cool and solidify, and when the molten resin 108 has sufficiently solidified, the movable pin 202 is retracted to the position before injection, as shown in Fig. 9(f). At this time, the pushing part 602 advances at the same time as the movable pin 202 retracts, and returns to the position before injection started while discharging the burr removal part 108d.

[0095] By performing these steps, it is possible to obtain a completely filled resin molded product with no weld lines around the hole shape, such as a good PP-cellulose fiber product.

[0096] In addition, in the case of normal injection molding that does not use the flow of molten resin from the preliminary space according to the present disclosure, if the resin temperature is set to 190°C, which is the lower limit of the recommended molding temperature for the molten resin used, for example, PP-cellulose fiber, the resin does not fill to the end of the flow. In contrast, according to the manufacturing method of the resin molded product according to the sixth embodiment, the molten resin that has accumulated in the preliminary space formed by retracting the movable pin 202 is pushed out into the cavity that becomes the product part, and a resin molded product that is completely filled with molten resin at the same temperature is obtained. In addition, the molten resin that was present at the tip of the movable pin 202 is collected inside the dug-out part 601, and after the molten resin has completely solidified, it is separated into the product part and the burr removal part 108d, and a resin molded product without burrs or weld lines around the hole shape can be obtained. [Explanation of symbols]

[0097] 101 Manufacturing equipment for resin molded products 102 Mold 103 Mold Cavity 104 Mold Core 105 sprue 106 Runner Gate 107 108 Molten Resin 109 Molded product cavity 110 Molded part hole 111 Weld line 201 Excavation section (hole) 202 Movable pin 203 Drive unit 601 Excavation 602 Push-in part

Claims

1. A method for manufacturing a resin molded product having a hole shape, comprising the steps of: a step of placing a movable pin in the hole in the surface of the mold core or the mold cavity, the movable pin being partially stored inside the hole and capable of advancing from the hole toward the opposing mold cavity or the mold core, the movable pin having a shape corresponding to the shape that fills the hole; clamping the mold core and the mold cavity to inject molten resin into a cavity defined between the mold core and the mold cavity; a step of advancing the movable pin into the cavity, and extruding molten resin in a direction of movement of the movable pin into the cavity, thereby imparting the hole shape corresponding to the shape of the movable pin to the molten resin; After the molten resin is cured to form a resin molded product, the movable pin is retracted to the inside of the hole to open the mold core and the mold cavity, and the resin molded product is removed. The method for producing a resin molded product comprising the steps of:

2. The method further includes a step of providing a spare space capable of being filled with molten resin from the hole to the tip of the movable pin that has been retracted inside the hole by retracting the movable pin inside the hole, 2. The method for manufacturing a resin molded product according to claim 1, wherein, in the process of imparting the hole shape to the molten resin, when a predetermined amount of molten resin has accumulated in the preliminary space, the movable pin is advanced from the inside of the hole into the cavity, thereby pushing out the molten resin accumulated in the preliminary space into the cavity.

3. 2. The method for manufacturing a resin molded product according to claim 1, wherein in the process of imparting the hole shape to the molten resin, the movable pin is caused to penetrate the molten resin while the tip of the movable pin is brought into contact with the opposing surface of the mold cavity or the mold core, thereby imparting the hole shape corresponding to the shape of the movable pin to the molten resin.

4. 2. The method for manufacturing a resin molded product according to claim 1, wherein in the process of imparting the hole shape to the molten resin, the tip of the movable pin is stopped at a position that does not reach the opposing surface of the mold cavity or the mold core, and the hole shape corresponding to the shape of the movable pin is imparted to the molten resin.

5. 2. The method for manufacturing a resin molded product according to claim 1, wherein in the process of imparting the hole shape to the molten resin, the tip of the movable pin is made concave, and the concave surface is brought into contact with the opposing surface of the mold cavity or the mold core to hold the molten resin within the concave surface and impart the hole shape corresponding to the shape of the movable pin to the molten resin.

6. 2. The method for manufacturing a resin molded product according to claim 1, wherein in the process of imparting the hole shape to the molten resin, while the movable pin penetrates the molten resin, the tip of the movable pin is inserted into a recess pressed against the opposing surface of the mold cavity or the mold core, thereby imparting the hole shape corresponding to the shape of the movable pin to the molten resin.

7. The method for producing a resin molded product according to claim 1 , wherein the temperature of any location in the mold cavity or the mold core facing the movable pin or the tip of the movable pin is controllable.

8. The method for producing a resin molded product according to claim 1 , wherein the movable pin is capable of being independently operated.

9. The method for producing a resin molded product according to claim 1 , wherein a filler composite resin is used as the molten resin.

10. The method for producing a resin molded product according to claim 9, wherein the filler is a cellulose-based fiber.

11. 7. The method for manufacturing a resin molded product according to claim 3, wherein in the step of imparting the hole shape to the molten resin, the movable pin starts to advance from a position where the tip of the movable pin is on the same plane as a surface that will become the surface of the final product.

12. An apparatus for manufacturing a resin molded product having a hole shape, comprising: A mold having a mold core or mold cavity with a hole on a surface thereof and a mold cavity or mold core corresponding to the mold core or mold cavity; a movable pin that is slidable inside the hole, and whose tip can move forward from the hole toward the opposing mold cavity or the mold core when the mold core and the mold cavity are clamped, and has a shape that corresponds to the shape that fills the hole; A control device capable of operating the movable pin; An apparatus for manufacturing a resin molded product comprising:

13. The apparatus for manufacturing a resin molded product according to claim 12 , wherein the movable pin has a concave tip.

14. The apparatus for manufacturing a resin molded product according to claim 13 , wherein the movable pin has a tip that is recessed in a cross section along the sliding direction into a circular arc shape, a trapezoid shape, or a triangle shape.

15. The manufacturing apparatus for resin molded products described in claim 12, wherein the mold cavity or the mold core corresponding to the mold core or the mold cavity has a recess biased against a surface of the mold cavity or the mold core that faces the tip of the movable pin when the mold core and the mold cavity are clamped, and the movable pin is insertable into the recess.

16. The apparatus for manufacturing a resin molded product according to claim 15, wherein the biased recess is biased by a spring.

17. A manufacturing apparatus for resin molding as described in claim 12, wherein the temperature of the mold cavity or mold core facing the movable pin or the tip of the movable pin is not independently adjusted, but is set to a temperature equal to or lower than the temperature setting of the other mold core or mold cavity.

18. The manufacturing apparatus for resin molded products according to claim 12, further comprising a mechanism for adjusting the temperature of the mold cavity or mold core facing the movable pin or the tip of the movable pin so that the temperature is different from that of the other mold core or mold cavity.

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