JPH10296800A - Method for molding injection molded piece and mold for injection molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an injection molding method for forming embossments as uniformly as possible on the surface of an injection molded piece even when the molded piece is long. SOLUTION: A molding method for an injection molded piece uses a mold 10 comprising a cavity 13, a fused resin injecting portion 14, and a pressurized fluid introducing portion (to which a distal end portion of a pressurized fluid introducing device 15 corresponds), wherein an embossing treatment for forming embossments on the surface of a molded piece is provided on at least a part of a cavity surface 16 of a mold constituting the cavity 13, and wherein the depth of the embossing treatment provided in the cavity surface 16 is varied depending on positions on the cavity surface, and a pressurized fluid is introduced from the pressurized fluid introducing portion into a fused thermoplastic resin injected from the fused resin injecting section 14 into the cavity, whereby embossments are formed on the surface of a molded piece 21 so molded to have a hollow section 22 therein.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for molding an injection-molded article having a surface formed with a grain and having a hollow portion, and a mold for injection molding suitable for manufacturing such an injection-molded article.

[0002]

2. Description of the Related Art Commercialization of an injection molded product having a hollow portion has been promoted.
In recent years, it has spread rapidly. For molding an injection-molded article having a hollow portion, an injection mold having a cavity, a molten resin injection portion, and a pressurized fluid introduction portion is used. Then, during or after completion of injection of the molten thermoplastic resin into the cavity from the molten resin injection section, the pressurized fluid is introduced from the pressurized fluid introduction section into the molten thermoplastic resin in the cavity, whereby the injection molded article is formed. Is molded. Such injection molding methods are classified into so-called full-shot injection molding methods in which the inside of a cavity is completely filled with a molten thermoplastic resin, and so-called short-shot injection molding methods in which the inside of a cavity is not completely filled with a molten thermoplastic resin. You. By the short shot injection molding method, for example, a pipe-shaped injection molded product such as a handle, a lever, or a paper press roller having a hollow portion having a large hollow ratio can be formed.
When forming a grain on the surface of the injection-molded product, a necessary portion (sometimes called a design surface) of a cavity surface of a mold constituting the cavity is subjected to grain processing. That is, for example, fine irregularities are formed on the design surface of the mold.

[0003]

In the short-shot injection molding method, during the initial stage of injection of the molten thermoplastic resin into the cavity, the injection between the molten thermoplastic resin injected into the cavity and the mold is performed. Does not proceed sufficiently, and the molten thermoplastic resin is kept at a relatively high temperature, so that the viscosity of the molten thermoplastic resin is low. Moreover,
In order to fill the cavity with the viscous molten thermoplastic resin, the filling pressure of the molten thermoplastic resin by the injection ram of the injection molding machine is high. Therefore, the molten thermoplastic resin immediately after injection into the cavity is strongly pressed against the cavity surface of the mold. As a result, the transferability of the cavity surface to the surface of the portion of the injection molded article located near the molten resin injection portion is improved. That is, the grained portion applied to the cavity surface of the mold is satisfactorily transferred to the surface of the injection molded product. However, a part of the injection molded product obtained as a result of the molten thermoplastic resin flowing in the cavity by the pressurized fluid introduced during or after the injection of the molten thermoplastic resin has a certain degree of solidification of the thermoplastic resin. The transferability of the cavity surface to the surface of the portion of the injection molded article is not so good because the film is formed at the time when the process proceeds to a certain extent. In other words, the textured portion applied to the cavity surface of the mold is not transferred sufficiently to the surface of the injection molded product, and the textured portion becomes noticeable.

As described above, the difference between the injection timing of the molten thermoplastic resin and the introduction timing of the pressurized fluid causes a difference in the transferability of the cavity surface to the surface of the injection molded product. Product value may be significantly impaired.
In particular, this difference in transferability occurs remarkably in the case of an injection-molded product having a textured design surface and a long injection-molded product. Conventionally, the following measures have been taken in order to deal with such a difference in transferability, but in reality, it is difficult to produce injection molded products.

[0005] If the pressure of the pressurized fluid to be introduced into the molten thermoplastic resin is increased, the molten thermoplastic resin injected into the cavity is strongly pressed against the cavity surface of the mold, so that the transferability is improved. . However, the method of recovering the pressurized fluid remaining in the hollow portion formed in the thermoplastic resin is complicated, and the production cost of the injection molded article increases with the installation of the recovery equipment. Further, there is a case where a hollow portion formed in the thermoplastic resin is communicated with the atmosphere before the mold is opened because removal of the decomposition gas generated from the molten thermoplastic resin is complicated. However, because it communicates with the atmosphere,
As the pressure of the pressurized fluid increases, the consumption of the pressurized fluid increases, which leads to an increase in the production cost of the injection molded product.

[0006] When the melting temperature of the thermoplastic resin is increased, the transferability is improved, but poor appearance such as silver stripes (also referred to as silver or silver wire) occurs due to thermal degradation of the thermoplastic resin. Further, although the transferability is improved even when the mold temperature is increased, the solidification time of the molten thermoplastic resin is prolonged, and the molding cycle is prolonged. As a result, productivity is significantly impaired.

Accordingly, it is an object of the present invention to eliminate the need to increase the pressure of a pressurized fluid, to increase the melting temperature of a thermoplastic resin, or to increase the mold temperature. Differences in the state of grain formation on the surface of the injection molded product are unlikely to occur even due to the difference between the timing and the time of introduction of the pressurized fluid. An object of the present invention is to provide an injection molding method capable of forming an injection mold, and a mold for injection molding suitable for carrying out the injection molding method.

[0008]

According to a first aspect of the present invention, there is provided a mold for injection molding comprising a cavity, a molten resin injection section, and a pressurized fluid introduction section. A mold for injection molding for introducing a pressurized fluid from a pressurized fluid introduction portion into a molten thermoplastic resin injected into a cavity from the above, thereby molding an injection molded product having a hollow portion. . Then, at least a part of the cavity surface of the mold that constitutes the cavity is subjected to a graining process for forming a grain on the surface of the injection molded product, and the depth of the graining performed on the cavity surface is reduced. It is characterized by being changed according to the position of the cavity surface.

In order to achieve the above object, a method for molding an injection-molded article according to the present invention comprises a cavity, a molten resin injection section, and a pressurized fluid introduction section. At least a part of the surface of the injection molded article is subjected to a graining process for forming a grain, and the depth of the graining performed on the cavity surface is changed according to the position of the cavity surface. Using a mold, pressurized fluid is introduced from the pressurized fluid introduction section into the molten thermoplastic resin injected into the cavity from the molten resin injection section, whereby a grain is formed on the surface, and the hollow section is formed. An injection-molded article having the following is molded.

[0010] The depth _Rz of the graining process performed on the cavity surface in the method for molding a mold for injection molding or an injection-molded article of the present invention is a value measured in accordance with the provisions of JIS B0601-1982. The ten-point average roughness.

In the method for molding a mold for injection molding or an injection-molded article according to the present invention, a so-called short shot injection in which the amount of the molten thermoplastic resin injected into the cavity does not completely fill the cavity. A molding method can be adopted, or a full-shot injection molding method using a mold provided with an overflow cavity (that is, the mold is provided with an overflow cavity communicating with the cavity, and the inside of the cavity is molten thermoplastic resin) (A full-shot injection molding method in which the molten thermoplastic resin removed by introducing a pressurized fluid into the molten thermoplastic resin flows into the overflow cavity). .

[0012] In the molding method of a mold or injection-molded article for the injection molding of the present invention is to vary the depth R _z of the grain finish by the position of the cavity surface, the depth R _z of the grain processing, continuous It may be gradually changed gradually, or may be changed stepwise (stepwise). Furthermore, when changing stepwise (stepwise), the depth _Rz of the graining at a certain stage may be gradually changed continuously.

The method of molding a mold or injection molded product for injection molding of the present invention is suitable for molding an injection molded product having a particularly long length, in which the grain formed on the surface needs to be made as uniform as possible. . Therefore, the depth _Rz of the graining applied to the cavity surface is changed along the direction in which the molten thermoplastic resin injected into the cavity flows by the pressurized fluid.
It is preferable to increase the depth sequentially. The direction in which the molten thermoplastic resin flows means the direction in which the entire molten thermoplastic resin flows. The depth _Rz may be continuously increased gradually, may be increased stepwise (stepwise),
In the latter case, the depth R _z of the graining at a certain stage
May be continuously deepened gradually. The average value of the depth _Rz of the texturing in the region of the cavity surface where the depth of the texturing applied to the cavity surface is the shallowest is R _L , and the cavity whose depth of the texturing applied to the cavity surface is the deepest Assuming that the average value of the depth _Rz of the graining in the surface region is _RH , the rate of change in the depth of the graining ( _RH / _RL ) depends on the injection molded product to be molded. 0.05 to 50, preferably 1.1 to 30.

The number of pressurized fluid introduction sections and molten resin injection sections to be provided in the mold may be any number as long as it is one or more. The positional relationship between the pressurized fluid introduction unit and the molten resin injection unit is essentially arbitrary, and the pressurized fluid introduction unit is disposed in the molten resin injection unit or in the vicinity of the molten resin injection unit. The pressurized fluid introduction section may be provided in the molten resin injection section or near the molten resin injection section, and may be provided on the cavity surface. It is preferable to gradually increase the depth _Rz of the embossed as the distance from the molten resin injection portion increases. The depth _Rz may be continuously and gradually increased, or may be increased stepwise (stepwise). In the latter case, the depth _Rz of the graining at a certain stage may be increased. The depth may be gradually increased continuously. The rate of change in the depth of embossing (R _H / R _L ) depends on the injection molded product to be molded.
It is desirably 1.05 to 50, preferably 1.1 to 30.

When the short shot injection molding method is adopted, after the injection of the molten thermoplastic resin is completed (including simultaneously with the completion of the injection), a pressurized fluid is introduced from a pressurized fluid introduction section,
The mean value R ₂ of the molten thermoplastic in the injection completion time of the resin molten thermoplastic resin in contact though not depth R _z of the embossed decorated with portions of the cavity surface, the heat of fusion at the completion of injection time of the molten thermoplastic resin it is preferred to deeper than the average value R ₁ of the depth R _z of the embossed decorated with portions of the cavity surface in contact with the thermoplastic resin. Alternatively, a pressurized fluid is introduced from the pressurized fluid introduction section during the injection of the molten thermoplastic resin, and the surface of the cavity surface that is not in contact with the molten thermoplastic resin when the injection of the molten thermoplastic resin is completed. the mean value R ₂ of the machining depth R _z, than the average value R ₁ of the molten thermoplastic resin in contact with the depth R _z of the embossed decorated with portions of the cavity surfaces at the completion of injection time of the molten thermoplastic resin Preferably, it is deep. Alternatively, a pressurized fluid is introduced from the pressurized fluid introduction portion during injection of the molten thermoplastic resin, and graining is performed on a portion of the cavity surface that is not in contact with the molten thermoplastic resin at the start of the introduction of the pressurized fluid. mean value R ₁ of the depth of the mean value R ₂ of R _z, the decorated with the depth of the embossing portion of the cavity surface in contact with molten thermoplastic resin introduced beginning of pressurized fluid R _z
It is preferable to make it deeper. The depth _Rz may be continuously and gradually increased, or may be increased stepwise (stepwise). In the latter case, the depth _Rz of the graining at a certain stage may be increased. The depth may be gradually increased continuously. still,
The change in the depth of the graining (R ₂ / R ₁ ) depends on the injection-molded product to be molded, but is preferably from 1.05 to 50, preferably from 1.1 to 30. In actual molding of an injection molded product, it may be difficult to strictly separate a portion of the cavity surface that is not in contact with the molten thermoplastic resin from a portion of the cavity surface that is in contact with the molten thermoplastic resin. it if can also occur where the the portion of the cavity surface depth average value R ₂ in contact slightly molten thermoplastic resin, all parts of the cavity surface depth average value R ₁ of the graining is contact with the molten thermoplastic resin It can also happen if not. Therefore, the boundary between the portion of the cavity surface not in contact with the molten thermoplastic resin and the portion of the cavity surface in contact with the molten thermoplastic resin is calculated from the volume of the molten thermoplastic resin to be injected and the volume of the cavity. Note that, in the alternative embodiment, the average of the depth _Rz of the graining process on the cavity surface forming the portion of the cavity near the molten resin injection portion, which is the region where the first molten thermoplastic resin is injected into the cavity, the value R _0, it is preferred to shallower than the depth average value R ₁ of the graining, for (R ₀ / R _1), it depends on the injection-molded article to be molded, 0.5
It is desirably 0.95 to 0.95. The first injection of the molten thermoplastic resin into the cavity means that 5% to 30% of the amount of the molten thermoplastic resin to be injected into the cavity is injected into the cavity. . Here, or which of the modes should be adopted may be determined as appropriate by conducting tests and the like depending on the shape, size, and the like of the injection molded product to be molded.

In the injection mold or injection molding method of the present invention, the shape of the injection molded article is essentially arbitrary, but the injection mold or injection molded article of the present invention is not limited to any shape. Injection molded products particularly suitable for the application of the molding method,
It is an elongated injection molded product. It is preferable that the length of the injection molded article having such a shape is in the range of 1 m to 2.5 m. When molding such an injection molded product, the length of the cavity needs to be in the range of 1 m to 2.5 m. Further, the position of the molten resin injection section in the mold is essentially arbitrary. However, the position of the molten resin injection section at the end of the cavity is important in view of the flow of the molten thermoplastic resin in the cavity. Is preferred.

In the method of molding a metal mold or an injection-molded product for injection molding of the present invention, the depth _Rz of the graining process performed on the cavity surface is 1 × 10 ⁻⁶ m to 1 × 10 ⁻⁴ m. Is preferably within the range. Note that the range of R _z, above R _H, R _L, all R _0, R _1, R _2, and the like.

As the thermoplastic resin suitable for use in the present invention, polystyrene resin, acrylonitrile-butadiene-styrene copolymer resin (ABS resin), AES
Resin, acrylonitrile-styrene copolymer resin (AS
Resin), methacrylic resin, polycarbonate resin, polysulfone resin, polyethersulfone resin, polyarylate resin, polyetherimide resin, polyamideimide resin, polyester resin (for example, polyethylene terephthalate resin and polybutylene terephthalate resin),
Modified polyphenylene oxide resin (for example, modified polyphenylene ether resin), polyimide resin, polyphenylene sulfide resin, POM resin, polyether ketone resin, polyether ether ketone resin, polyolefin resin such as polyethylene resin and polypropylene resin, and polyamide resin such as polyamide MXD6 resin Examples thereof include thermoplastic resins such as resins, polyacetal resins, polyester carbonate resins, liquid crystal polymers, and elastomers, and mixtures thereof, and alloy resin compositions comprising two or more of these resins.
If desired, a material obtained by mixing a fiber reinforcing material, a filler, a stabilizer, and the like with these resins can also be used.

The pressurized fluid suitable for use in the present invention is a gaseous or liquid fluid at normal temperature and normal pressure, and reacts or mixes with the molten thermoplastic resin when injected into the molten thermoplastic resin. Those that do not are desirable. In particular,
Nitrogen gas, carbon dioxide gas, air, helium gas, and other gaseous substances at room temperature, liquids such as water, and gases liquefied under high pressure can be used. Among them, inert gases such as nitrogen gas and helium gas Is preferred. Furthermore, as a pressurized fluid,
A foamable resin, a fiber-reinforced resin material, or the like can also be used. In this case, the hollow portion is filled with a foamable resin, a fiber-reinforced resin material, or the like, and such a structure is also included in the concept of the hollow portion in the present invention.

In carrying out the injection molding method of the present invention, the amount, temperature, pressure or injection speed of the molten thermoplastic resin injected into the cavity, the amount, pressure or speed of the pressurized fluid to be introduced, Various conditions such as the cooling time of the mold need to be appropriately selected and controlled depending on the type of the thermoplastic resin to be used, the shape of the mold, and the like, and cannot be uniquely determined.

The grain in the present invention refers to a dent or projection of a detailed pattern formed on the surface of an injection-molded article, and includes "pattern", "skin grain", "bumper grain" and the like. Examples of the grain pattern (design) include leather, woven fabric, wood grain, and grain. The cavity surface of the mold subjected to the graining may be a part (so-called design surface) of the cavity surface of the mold constituting the cavity, or may be the entire cavity surface, and should be molded. It depends on the grain forming position required for the injection molded product.

The graining method can be a known method. That is, graining by etching or graining by blasting may be used. In the case of graining by etching, for example, the mold is first degreased,
After the primary masking, an acid treatment is performed. Next, a photosensitive resin is applied to the cavity surface of the mold, and the photosensitive resin is subjected to a drying and heating treatment. Then, the photosensitive resin is exposed and developed, and the photosensitive resin is further subjected to a heat treatment. Next, a secondary masking process is performed, and after using the patterned photosensitive resin as an etching mask, an etching process is performed on the cavity surface of the mold, and then the etching mask is removed. If etching needs to be performed a plurality of times, the steps from the acid treatment step to the etching mask removal step are repeated as many times as necessary. Thereafter, etching is performed, masking is removed, and sand blasting is performed. In order to change the depth of the graining performed on the cavity surface depending on the position of the cavity surface, for example, the number of times of etching may be changed depending on the position of the cavity surface, or the etching conditions may be changed depending on the position of the cavity surface. Good. On the other hand, in the case of graining by blasting, a sharp abrasive or a spherical abrasive made of alumina-based abrasive, silicon carbide-based abrasive, glass beads, etc. is compressed at high speed using compressed air or centrifugal force. The cavity surface of the mold may be physically subjected to satin finish by sand blasting or shot blasting in which a fine rugged pattern is carved on the cavity surface by spraying onto the cavity surface.

In the present invention, the depth of the graining performed on the cavity surface is changed according to the position of the cavity surface. As a result, even when the difference between the injection timing of the molten thermoplastic resin and the introduction timing of the pressurized fluid causes a difference in the transferability of the cavity surface to the surface of the injection molded product, the formation of the grain on the surface of the injection molded product. Differences are less likely to occur in the state. That is,
The grain can be uniformly formed on the surface of the injection molded article.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on embodiments with reference to the drawings.

As shown in a schematic sectional view of FIG. 1A, an injection mold 10 having a cavity 13 for obtaining a long injection molded product having a total length of 1.95 m was used.
FIG. 1B shows a schematic cross-sectional view when the injection molded product is cut along the line BB in FIG. The mold 10 for injection molding includes a fixed mold part 11 and a movable mold part 12. FIG. 1A shows a state in which the mold is clamped. The mold 10 includes a cavity 13, a molten resin injection section (resin gate section) 14, and a pressurized fluid introduction device 15. Incidentally, in the mold in the embodiment, the pressurized fluid introduction device 15 is
Is disposed in the vicinity of.

A check valve (not shown) is provided at the distal end of the pressurized fluid introducing device 15, and the molten thermoplastic resin injected into the cavity 13 flows into the distal end of the pressurized fluid introducing device 15. It does not have a structure. Note that the distal end of the pressurized fluid introduction device 15 corresponds to a pressurized fluid introduction unit. The pressurized fluid introducing device 15 is connected to a pressurized fluid source (not shown) via a pipe. Further, the pressurized fluid introduction device 15 can be moved in the vertical direction in the drawing by moving means (not shown) formed of, for example, a hydraulic cylinder. Can communicate or stop communication.

A part of the cavity surface 16 of the mold constituting the cavity 13 is subjected to a graining process for forming a grain on the surface of the injection molded product. The depth of the graining performed on the cavity surface 16 is changed according to the position of the cavity surface 16. FIG. 1C shows a diagram of the cavity surface and the like. More specifically, the cavity surface 16A constituting the cavity portion 13A in the vicinity of the molten resin injection portion 14, which is the region where the first molten thermoplastic resin is injected into the cavity 13, has a depth of graining (R ₀ ) was set to R _z = 35 μm. In the cavity 13A, the filling pressure of the molten thermoplastic resin is high, the viscosity of the molten thermoplastic resin is low, and the transferability of the cavity surface 16A to the surface of the injection molded product is extremely excellent.
On the other hand, when the injection of the molten thermoplastic resin was completed, the depth (R ₁ ) of the graining performed on the portion 16 </ b> B of the cavity surface in contact with the molten thermoplastic resin was _Rz = 40 μm. The cavity portion 16B constitutes the cavity portion 13B. Further, when the injection of the molten thermoplastic resin is completed, the depth of the graining performed on the portion 16C of the cavity surface that is not in contact with the molten thermoplastic resin is represented by R _z =
The thickness was 45 μm. Here, such a cavity surface portion 1
6C constitutes cavity portion 13C.
In addition, as shown in FIG. 1B which is a schematic cross-sectional view of the injection molded article, a grain is formed on the surface 21A of the injection molded article 21 and no grain is formed on the surface 21B. . In order to form the surfaces 21A and 21B of the injection-molded article 21, as shown in FIG. 1C, the cavity surface portion 16D is not subjected to graining.

In the examples, a so-called short shot injection molding method was employed as the injection molding method. That is, the amount of the molten thermoplastic resin 20 injected into the cavity 13 is
The amount of the cavity 13 was not completely filled. Then, the molten thermoplastic resin 20 was injected from the molten resin injection portion 14 into the cavity 13 of the mold 10 in the mold clamped state shown in FIG. In the examples, as the thermoplastic resin, a polycarbonate resin (manufactured by Mitsubishi Engineering-Plastics Corporation, trade name: Iupilon MB43)
05HU black) was used. The temperature of the thermoplastic resin is 280 ° C. in a cylinder of an injection molding machine (not shown).
And plasticized. In addition, the injection pressure is 1500 kg
f / cm ² -G, and the mold temperature was 70 ° C. A state immediately after the start of injection of the molten thermoplastic resin 20 into the cavity 13 is shown in a schematic cross-sectional view in FIG.

Immediately after the injection of the molten thermoplastic resin was completed, the injection operation was stopped. This state is shown in a schematic cross-sectional view in FIG. At the same time, the final holding pressure is 3
A pressurized fluid consisting of compressed nitrogen gas of 5 kgf / cm ² -G was introduced into the molten thermoplastic resin 20 in the cavity 13 from the pressurized fluid introduction part which is the tip of the pressurized fluid introduction device 15. . FIG. 3A is a schematic cross-sectional view showing a state in which the pressurized fluid is being introduced into the molten thermoplastic resin 20. Cavity 1 for 100 seconds after introduction of pressurized fluid
After cooling the thermoplastic resin inside 3 (see FIG. 3B), moving means (not shown) for releasing the pressurized fluid in the hollow portion 22 formed inside the injection molded product 21 to the atmosphere. As a result, the pressurized fluid introduction device 15 was retracted, and the tip of the pressurized fluid introduction device 15 was separated from the mold 10. afterwards,
The mold 10 was opened, and the injection molded article 21 was taken out of the mold 10. The obtained injection-molded article had an excellent appearance quality with no noticeable grain spots on the appearance.

(Comparative Example) As a comparative example, a cavity surface of a mold constituting a cavity is subjected to a graining process for forming a grain on the surface of an injection molded product. A mold for injection molding in which the depth of the graining was fixed at 35 μm was used. Other than that, the structure of the mold was the same as that of the example, and injection molding was performed using the same thermoplastic resin as the example and under the same conditions as the example. Observation of the surface of the obtained injection-molded product revealed that the surface of the injection-molded product had uneven spots due to the difference in transferability, as described above.

Although the present invention has been described based on the preferred embodiments, the present invention is not limited to these embodiments. The structure of the mold, the depth of the graining process, the injection molding conditions, the thermoplastic resin used, the size of the injection molded product, the external shape, and the cross-sectional shape used in the examples are merely examples, and can be appropriately changed.

[0032]

According to the present invention, it is possible to obtain an injection-molded article having uniform appearance on its surface and excellent appearance quality without impairing productivity. According to the present invention, a grain can be reliably formed uniformly on the surface of an injection molded article having a particularly long length.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing a mold-clamped state of an injection mold according to the present invention, a schematic sectional view of an injection-molded product, and a diagram of a cavity surface of the mold.

FIG. 2 is a schematic cross-sectional view of a mold or the like showing a state immediately after the start of injection of a molten thermoplastic resin into a cavity and a state after the completion of injection of the molten thermoplastic resin.

FIG. 3 is a schematic cross-sectional view of a mold or the like showing a state in which a pressurized fluid is being introduced into a molten thermoplastic resin in a cavity, and a state after cooling the thermoplastic resin in the cavity.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Mold 11 ... Fixed mold part 12 ... Movable mold part 13 ... Cavity 14 ... Molten resin injection part (resin gate part) 15 ... Pressurized fluid introduction device 16 ... Mold cavity surface 20 ... Molten thermoplastic resin 21 ... Injection molded product 22 ... Hollow part

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shinji Koboko 5-6-1, Higashi-Hachiman, Hiratsuka-shi, Kanagawa Prefecture Inside the Technology Center of Mitsubishi Engineering Plastics Co., Ltd. (72) Inventor Hidehiko Kamano Higashi-Yawata, Hiratsuka-shi, Kanagawa 5-6-2 Mitsubishi Engineering Plastics Co., Ltd. Technology Center (72) Inventor Naoji Sekimoto 320, Fujii, Kamiyabe-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Hashimoto Forming Industry Co., Ltd. (72) Inventor Kaoru Urata 320, Fujii, Kamiyabe-cho, Totsuka-ku, Yokohama, Kanagawa Prefecture Inside (72) Inventor Akihiko Nakagawa 320, Fujii, Kamiyabe-cho, Totsuka-ku, Yokohama, Kanagawa Prefecture Inside Hashimoto Forming Industry Co., Ltd.

Claims (12)

[Claims] A pressurized fluid injection portion provided in the molten thermoplastic resin injected into the cavity from the molten resin injection portion; And introduce
Thus, an injection mold for molding an injection molded article having a hollow portion, wherein at least a part of the cavity surface of the mold that forms the cavity forms a texture on the surface of the injection molded article. Characterized in that the depth of the graining applied to the cavity surface is changed depending on the position of the cavity surface. 2. The method according to claim 1, wherein the depth of the graining applied to the cavity surface is gradually increased in the direction in which the molten thermoplastic resin injected into the cavity flows by the pressurized fluid. Item 2. A mold for injection molding according to Item 1. 3. The pressurized fluid introducing section is disposed in the molten resin injection section or in the vicinity of the molten resin injection section, and sequentially increases the depth of the graining performed on the cavity surface as the distance from the molten resin injection section increases. The mold for injection molding according to claim 1, wherein the mold is deepened. 4. The amount of the molten thermoplastic resin injected into the cavity is an amount that does not completely fill the cavity, and after the injection of the molten thermoplastic resin is completed, the pressurized fluid is introduced from the pressurized fluid introduction unit. When the injection of the molten thermoplastic resin is completed, the depth of the graining process applied to the portion of the cavity surface that is not in contact with the molten thermoplastic resin is changed to the cavity in contact with the molten thermoplastic resin when the injection of the molten thermoplastic resin is completed. 2. The injection molding die according to claim 1, wherein the depth of the surface processing is greater than the depth of the graining. 5. The cavity according to claim 1, wherein a length of the cavity is in a range of 1 m to 2.5 m, and the molten resin injection section is located at an end of the cavity.
14. The mold for injection molding according to item 13. 6. A depth R of a graining process performed on a cavity surface.
The injection mold according to any one of claims 1 to 5, wherein _z is in a range of 1 × 10 ⁻⁶ m to 1 × 10 ⁻⁴ m. 7. A mold having a cavity, a molten resin injection section, and a pressurized fluid introduction section, wherein at least a part of a cavity surface of a mold constituting the cavity is used to form a texture on the surface of an injection molded product. Using a mold for injection molding in which the graining process is performed and the depth of the graining process performed on the cavity surface is changed according to the position of the cavity surface, the molten resin is injected into the cavity from the molten resin injection part. A pressurized fluid is introduced into the thermoplastic resin from a pressurized fluid introduction unit,
Thus, a method of molding an injection-molded article, characterized by molding an injection-molded article having a grain formed on its surface and having a hollow portion. 8. The method according to claim 1, wherein the depth of the graining applied to the cavity surface is sequentially increased in the direction in which the molten thermoplastic resin injected into the cavity flows by the pressurized fluid. Item 8. A method for molding an injection molded article according to Item 7. 9. The pressurized fluid introducing section is disposed in or near the molten resin injection section, and sequentially increases the depth of the graining performed on the cavity surface as the distance from the molten resin injection section increases. The method for molding an injection-molded article according to claim 7, wherein the depth is increased. 10. The amount of the molten thermoplastic resin injected into the cavity is an amount that does not completely fill the cavity, and after the injection of the molten thermoplastic resin is completed, the pressurized fluid is introduced from the pressurized fluid introduction unit. When the injection of the molten thermoplastic resin is completed, the depth of the graining process applied to the portion of the cavity surface that is not in contact with the molten thermoplastic resin is changed to the cavity in contact with the molten thermoplastic resin when the injection of the molten thermoplastic resin is completed. The method of molding an injection-molded article according to claim 7, wherein the depth of the surface is made larger than the depth of the graining. 11. The method according to claim 7, wherein a length of the cavity is in a range of 1 m to 2.5 m, and the molten resin injection portion is located at an end of the cavity. The molding method of the injection molded article according to the above. 12. The method according to claim 7, wherein a depth _Rz of the graining performed on the cavity surface is in a range of 1 × 10 ⁻⁶ m to 1 × 10 ⁻⁴ m. A method for molding an injection-molded article according to any one of the preceding claims.