JPH03258516A - Hollow molded body with thick-walled reinforcing part and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a molded body excellent in strength by a structure wherein thick-walled reinforcing parts are provided at the important positions of the hollow molded body. CONSTITUTION:Before the filling of molten thermoplastic resin, which is injected in the cavity 6 of a mold 5, gas under pressure is forced in the cavity 6 in order to produce a hollow part 1 in the molten thermoplastic resin. Next, by locally squeezing the hollow part 1 through the protrusion of some part of the mold 5 in the cavity 6 so as to locally weld the front surface part 2 and the rear surface part 3 under the condition that the hollow part 1 of the obtained hollow molded part is pinched between the parts 2 and 3 in order to form thick-walled reinforcing parts 4.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a thermoplastic resin molded article used as a base material for a reflector for a parabolic antenna, etc. This invention relates to a hollow molded body that requires a location with excellent properties and a method for manufacturing the same.

[Prior art] Conventionally, even if the molded product has a thick appearance, the entire molded product has been made hollow so that it does not suffer from sink marks, warping, twisting, etc. like a solid molded product. A thermoplastic resin hollow molded article is known.

The method for manufacturing the above-mentioned hollow molded body is to inject molten thermoplastic resin into the cavity of a mold, and before the cavity is filled with the injected molten thermoplastic resin, pressurized gas is injected into the cavity. There is a known method of entering three times (Japanese Patent Publication No. 57-149 [No. 18, Japanese Patent Publication No. 1-598H]).

[Problems to be Solved by the Invention] Even if the molded product has a thick external appearance, if the entire molded product is hollow and the actual wall thickness of the whole is small, it may cause shrinkage, warping, etc.
This has the advantage that defects such as twisting do not occur.

However, when the entire molded body is made hollow, the actual wall thickness of the entire body becomes smaller, so when a load is concentrated on the central part, for example, there is a problem that the strength of that part is insufficient and it is easy to break. be.

In order to solve the problem in item L, it would be possible to leave the relevant part as thick so that sufficient strength can be maintained, but if this is done, defects such as sink marks will occur in that part. cause problems.

Problem E will be explained in more detail by taking as an example a thermoplastic resin body used as a base material for a reflector for a parabolic antenna.

The molded body used as the base material of this reflector for a parabolic antenna is of N thickness so that it has a rigidity that can maintain the accuracy of the reflective surface even when wind pressure is applied. In addition, since a thick molded product is likely to suffer from sink marks, warpage, twisting, etc., the foamed molded product prevents these from occurring and prevents the accuracy of the reflective surface from decreasing due to these occurrences.

However, since it is a foamed body, it is necessary to take a long molding cycle in order to suppress deformation due to secondary foaming and maintain the precision of the reflective surface, making it difficult to promote mass production.

The above problem can be solved by using a hollow molded body as the base material of the reflector so that it can be molded without using foam molding while preventing shrinkage, warping, twisting, etc. If this is done, the problem arises that the strength necessary for attaching the reflector cannot be maintained.

That is, the back of the molded body is provided with a boss or other protrusion for connecting the reflector to the support and support, but if it is a hollow molded body as described above, the overall wall thickness will be thinner. If a concentrated external force is applied to this attachment part due to wind pressure or the like, there is a problem that the attachment part may crack.

On the other hand, if the wall thickness in the vicinity of the attachment part is left thick and sufficient strength is applied to the vicinity of the attachment part, sink marks or the like will occur in the area, making it impossible to maintain high precision of the reflective surface.

The present invention has been made in view of the above-mentioned problems, and is designed to prevent defects such as sink marks from occurring even if thick-walled parts with excellent strength are partially left in thermoplastic resin hollow-molded products. The problem to be solved is to

[Means for Solving the Problems] In order to solve the above problems, in the invention of claim 1, at least the surface portion 2 and the surface portion 3 sandwiching the hollow portion 1 of the hollow molded body made of thermoplastic resin. A hollow molded body with a thick reinforcement part is obtained in which one part is pressed by crushing the hollow part 3, and the front part 2 and the back part 3 of the pressed part are crimped to form a thick reinforcement part 4. (See Figures 1 and 2). In addition, in the invention of claim 3, before the inside of the cavity 6 of the mold 5 is filled with the injected molten thermoplastic resin, pressurized gas is injected into the cavity 6 to fill the molten thermoplastic resin. After forming the hollow part 1 in the hollow part 1, a part of the mold 5 is projected into the cavity 6 to partially crush the hollow part 1, so that the surfaces of the hollow molded body sandwiching the hollow part 1 are obtained. A measure is taken in which the part 2 and the back part 3 are partially crimped to form a thick reinforced part 4 (see FIG. 3).

[Function] The thick reinforcing portion 4 in the invention of claim 1 is similar to the surface portion 2.
The combination of the back surface portion 3 and the back surface portion 3 forms a thick portion with excellent strength. Then, a portion of at least one of the front surface portion 2 and the back surface portion is pressed into the hollow portion 1, and the front surface portion 2 and the back surface portion 3 of the pressed portion are crimped to form the thick reinforced portion 4. By assuming that the thick part is not left as a thick part from the time of forming the hollow part 1, but is formed after forming the hollow part 1,
This is to prevent the occurrence of sink marks, etc.

In claim 3, the thick reinforcement portion 4 is formed by crushing the hollow portion 1 after forming the hollow portion 1.
Similar to the above, this is to prevent the occurrence of sink marks, etc., but to explain this further: - After forming the cavity 1, the injected molten thermoplastic resin is slightly cooled and thickened. By forming the flesh reinforcement portion 4, it can be formed without causing sink marks or the like.

[Embodiment] First, an embodiment of the invention of claims 1 and 2 will be described with reference to FIG.

The hollow molded body with thick reinforcing portion according to this example is a molded body used as a base material of a reflector for a parabolic antenna, and on the back side 3 side, a reflector constructed using this molded body is provided. A mounting portion 7 is provided for connecting the support to a pillar, support, or the like. The mounting portion 7 in this embodiment is a boss projecting toward the back side, as shown in the figure.

A thick reinforced portion 4 is formed adjacent to the attachment portion 7.

In this thick reinforcement part 4, the vicinity of the attachment part 7 of the back surface part 3 is pressed by crushing the hollow part 1, and this pressed part is crimped to the front surface part 2.

In this example, since the object is a molded body used as a base material of a reflector for a parabolic antenna, in order to obtain smoothness of the surface part 2 which becomes a reflective surface, the thick reinforcement part 4 is made as described in The back surface part 3 side is pushed in and formed.

However, when the object is a molded product that does not require strict maintenance of the smoothness of the surface part 2, the thick reinforced part may be formed by pushing in the front part 2 side or pushing in both the front part 2 and the back part 3. It can also be set to 4.

The front surface portion 2 and the back surface portion 3 are crimped together in the thick reinforced portion 4 by heating and softening at least the side to be pushed into the thick reinforced portion 4.
By this, the surface part 2 is
This can be done by bringing the and back surface portion 3 into pressure contact and fusing them together.

The thick reinforcing portion 4 may be formed at a location where reinforcement is required depending on the intended use of the molded product.

In this embodiment, the thick reinforced portion 4 is provided below -E of each attachment portion 7, but this may be provided on the left and right sides of the attachment portion 7 or the entire periphery of the attachment portion 7.

Since this molded body has a substantially uniform wall thickness throughout, the hollow portion 1 is also formed over the entire body. However, in a molded article having a partially thick portion, it is sufficient to form the hollow portion l only in the thick portion.

Moreover, the hollow part 1 has a substantial wall thickness (
Each thickness of the front surface part 2 and back surface part 3) is 0.8 to 8.0 mm.
, ¥ is preferably about 1.0 to 3.0 mm. If this substantial wall thickness is too large, it will be difficult to sufficiently prevent sink marks, etc., and if it is too small, it will be difficult to maintain the necessary strength.

The wood acid form is composed of thermoplastic resin,
The thermoplastic resin may be any thermoplastic resin that can be generally injection molded, and commonly used flame retardants,
Additives and fillers such as plasticizers, oxidizing soil protectors, stabilizers, ultraviolet absorbers, reinforcing fillers, calcium carbonate, talc, and clay can be used.

Specific examples of thermoplastic resins include polyphenylene ether resins, polyolefin thread resins (polyethylene, polypropylene, copolymers using these, etc.), polystyrene resins, AS resins, ABS resins, PMMA resins, and PC resins. , AAS resin, AC5 resin, polyamide resin, POM resin, and the like.

In addition, in the case of a molded product used as a base material for a reflector for a parabolic antenna, such as the molded product of this example, among the above-mentioned thermo-OT plastic resins, because it has strength and is difficult to change over time,
Polyphenylene ether-based resins are preferred. This polyphenylene ether resin is poly(2,6 dimethyl 1,4 phenylene)
Examples include ether, a copolymer of poly(2,6 dimethyl 1,4 phenylene) ether and 2,3,6-drimethylphenol, and the like. Further, these may be modified with a compound capable of co-polymerizing with a styrene compound or a rubbery polymer. Furthermore, it may be a polymer alloy in which polyphenylene ether and other resin are mixed using a compatibilizing agent such as maleic anhydride. Other resins include, for example, polyolefin resin, A
Examples include BS resin, AS resin, polyamide, hydrogenated styrene-butadiene copolymer, and polyphenylene sulfide.

The molded product shown in FIGS. 1 and 2 is used as a reflector for a parabolic antenna by laminating a conductive film on the surface portion 2 side and finishing the surface with a decorative layer.

Next, taking as an example the case of manufacturing a molded body used as a base material for a reflector for a parabolic antenna as explained in FIGS. The invention in section 2 will be explained.

The hollow cylindrical body with thick wood reinforcement is manufactured by injection molding, and FIG. 3 is an explanatory diagram showing the procedure.

First, as shown in (a), molten thermoplastic resin is injected into the cavity 6 of the mold 5 from the injection nozzle 8.

This thermoplastic resin is as described above.

After injecting a certain amount of molten thermoplastic resin, before the inside of cavity 6 is completely filled with molten thermoplastic resin, (b
), pressurized gas is forced into the cavity 6 from a gas nozzle 9 built into the injection nozzle 8. The pressurized gas enters the molten thermoplastic resin and expands it to form the hollow portion 1.

The pressurized gas may be any gas that does not liquefy due to the temperature of the molten thermoplastic resin and the pressure at the time of injection and does not react with the molten thermoplastic resin, such as air or an inert gas such as 1 2 nitrogen gas. can be used, and inert gas is particularly suitable.

Pressure injection of pressurized gas stops the injection of molten thermoplastic resin,
Although the pressurized gas may be used alone, the injection may be performed simultaneously with the injection of the molten thermoplastic resin while the injection of the molten thermoplastic resin continues, or the both may be performed in combination.

In addition to using the gas nozzle 9 built into the injection nozzle 8 as shown, a pipe-shaped needle (not shown) is inserted into the cavity 6 and pressurized gas is injected through this needle. You can also do that.

When the necessary amount of pressurized gas is injected in this way, (C
), when the formation of the hollow part 1 is completed, the molten thermoplastic resin is brought into close contact with the inner surface of the cavity 6 by the pressure of the pressurized gas, and the basic shape of the molded article is determined. In particular, the pressure of the pressurized gas improves the close contact of the molten thermoplastic resin to the inner surface of the cavity 6, so that good mold reproducibility can be obtained. Therefore, when the object to be molded is a molded body used as a base material of a reflector for a parabolic antenna, the accuracy of the reflecting surface is improved.

Next, while the molten thermoplastic resin around the hollow part 1 is in a softened state, as shown in FIG. The slide portion 10 is made to protrude into the cavity 6. Then, of the front surface part 2 and the back surface part 3 located on both sides of the hollow part 1, the vicinity of the mounting part 7 of the back surface part 3 located on the slide part IO side is pushed into the hollow part 1, and is crimped with the front surface part 2. Thus, the thick reinforced portion 4 is formed. Figure 4 (1) and (b)
) are enlarged views of the state before and after the slide portion lO protrudes into the cavity 6. Further, FIG. 5 is a diagram showing the positional relationship between the mounting portion 7 and the slide portion 10 of the molded body.

In the illustrated example, the slide portion 10 is provided on the back surface 3 side of the molded body, but the slide portion 10 may be provided on the surface portion 2 side, or on both the front surface portion 2 side and the back surface portion 3 side. You can also. That is, when forming the thick reinforcement part 4,
In addition to pushing the back part 3 into the hollow part 1, it is also possible to push the front part 2 or both the front part 2 and the back part 3 into the hollow part l.

Further, the thick reinforcement portion 4 can be formed not only near the recess 1 portion 7 (=J) but also at other locations.

After forming the thick reinforcement part 4 in this way, the molded body is sufficiently cooled and solidified, the pressurized gas in the hollow part 1 is exhausted, and the slide part 10 is retreated to its original position, and the gold 5 is removed. If it is opened and taken out, a hollow molded body with a thick wood reinforcement part can be obtained. The pressurized gas in the hollow part 1 can be discharged by separating the injection nozzle 8 from the mold 5, but by keeping the injection nozzle 8 in close contact with the mold 5 and allowing the gas to flow backward from the gas nozzle 9 and collecting it as appropriate. can also be done.

Next, embodiments of the invention according to claims 3 and 4 will be described.

Example 1 A mold for a molded product with a straight fi of 45 mm used as a base material for a reflector for an offset parabolic antenna explained in FIGS. 1 and 2 was attached to an injection molding machine and molded. The injection molding machine was of a built-in type with a gas nozzle, and the gas nozzle was capable of emitting 200 kgf/c+n2 of nitrogen gas.

The thermoplastic resin used was a modified polyphenylene ether resin (“Silon 220Zj” manufactured by Asahi Kasei Corporation).
Heat resistance: 90°C, UL95υ-O).

Resin temperature 280'O1 Injection pressure 350 kgf/Cm
? When the cavity was filled with 90% of its volume, nitrogen gas was injected at 200 kgf/cm2 to form a hollow part.

After forming the hollow part, while maintaining the pressurized gas pressure in the hollow part, a slide part located near the attachment part (boss) on the back side of the molded body is made to protrude into the hollow part, and the back part of the molded body is was pushed into the hollow part, and the back and front parts were crimped to form a thick reinforced part.

The molded body was attached at four locations, and thick reinforcing sections were formed near each location as shown in FIG. 2.

5 6 After sufficiently cooling and solidifying, the pressurized gas in the hollow part is discharged, the mold is opened, the molded body is taken out, and the surface precision of the surface side (Root Mean 5 square: RMS = @
MkZ)2/n) was measured using a three-dimensional measuring device.

In addition, Me-10 metal was press-fitted into the four mounting parts and attached to a fixed oil fixture, and the displacement (runout) was measured by applying a surface pressure of 10 kg.

The results are shown in Table 1.

Example 2 Molding was carried out in the same manner as in Example 1 except that the molding cycle time (cooling time) was changed, and the obtained molded product was measured.

The results are shown in Table 1.

Example 3 ABS resin (Stylac LO manufactured by Asahi Kasei Corporation)
IJ), resin temperature 250°C, injection pressure 260°C.
Molding and measurement were carried out in the same manner as in Example 1 except that kgf/cm2 was used.

The results are shown in Table 1.

Example 4 PS resin (“Stylon 400j” manufactured by Asahi Kakogyo Co., Ltd.
), resin temperature 235°C, injection pressure 210 kg
Molding and measurement were carried out in the same manner as in Example 1 except that f/cm7 was used.

The results are shown in Table 1.

Example 5 Using a compound of polypropylene mixed with 30% talc, the resin temperature was 200°C and the injection pressure was 200°C.
Molding and measurement were carried out in the same manner as in Example 1 except that kgf/cm2 was used.

The results are shown in Table 1.

Using the same mold as in Example 1, molding was performed without operating the slide section.

A blend of the thermoplastic resin used in Example 1 and 0.5% by weight of a blowing agent (powdered Azocica-Bonamide) was placed in the cylinder of an injection molding machine, and after cross-melting, the resin temperature was increased to 240°. Foam molding was performed under the conditions of C1 injection pressure of 320 Jf/cm2 and cooling time of 180 seconds to obtain a 78 molded product with an expansion ratio of 1.05.

Attach the above molded body to a fixing jig in the same manner as in Example 1,
Measurements similar to those in Example 1 were performed.

The results are shown in Table 1.

Comparative Example 2 Molding and measurement were carried out in the same manner as Comparative Example 1 except that the cycle time was changed.

The results are shown in Table 1.

Comparative Example 3 Molding and measurement were performed in the same manner as in Comparative Example 1, except that the same resin as that used in Example 3 was used as the thermoplastic resin.

The results are shown in Table 1.

Comparative Example 4 Molding and measurement were performed in the same manner as in Comparative Example 1, except that the same resin as that used in Example 4 was used as the thermoplastic resin.

The results are shown in Table 1.

Comparative Example 5 200 kgf/cm2 during molding in the same manner as in Example 1
Molding and measurement were performed in the same manner as in Comparative Example 1, except that a hollow portion was formed by pressurizing nitrogen gas and the cycle time was 110 seconds.

The results are shown in Table 1.

(The following is a blank space) 9 0 Table 1 [Effects of the Invention] The present invention is as described below, and has the following effects.

(1) According to the invention of claim 1, since the hollow molded body has the thick reinforcing portions 4 at key points, the hollow portion 1 increases the wall thickness of the front surface portion 2 and the back surface portion 3. Even if the material is thin, the thick reinforcing portion 4 can provide the necessary strength, resulting in a molded product with excellent strength. In addition, there is no occurrence of sink marks or the like, and a good appearance can be obtained.

(2) According to the invention of claim 2, the mounting portion 7 of the boss etc.
Since the surrounding area is reinforced by the thick reinforcing part 4, the parabolic antenna reflector formed using this molded body as a base material has good stability when attached to a column or support using the mounting part 7, and the thick reinforcement part 4 is reinforced by the wind. There is no strong shaking, and there is no risk that the hydro-powered molded body applied to the mounting portion 7 will break.

(3) According to the invention of claim 3, by using the mold 5 equipped with the slide portion 10, the thick reinforcing portion 4 can be formed simultaneously with the molding of the hollow molded body. An increase in the number of steps for forming the thick reinforced portion 4 can be prevented.

(4) According to the invention of claim 4, by forming a hollow molded body, it is possible to efficiently manufacture a molded body used as a base material of a reflector for a parabolic antenna, and the accuracy of the reflecting surface thereof It can also be set in 42 directions.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view showing an embodiment of the invention according to claims 1 and 2, FIG. 2 is a rear view thereof, and FIGS. 3(a) to (d)
) is an explanatory diagram showing the procedure of the invention of claims 3 and 4 performed in the order of (a) to (d), and FIGS.
b) is an enlarged view showing the state before and after the φ hollow part of the slide part is thickened, and FIG. 5 is an enlarged view showing the positional relationship between the slide part and the mounting part. 1: Hollow part, 2: Surface part, 3: Back part, 4: Thick reinforcement part, 5: Mold, 6: Cavity, 7: Mounting part, 8: Injection nozzle, 9: Gas nozzle, 10 Ni-Ride part . 3rd 0 q) Lf') (f) COCr-0

Claims (1)

[Scope of Claims] 1) At least a part of the front surface and the back surface of the thermoplastic resin hollow molded body sandwiching the hollow part is pressed by crushing the hollow part, and the front surface and the back surface of the pressed part are pressed together. 1. A hollow molded article with a thick-walled reinforcing section, characterized in that parts are crimped to form a thick-walled reinforcing section. 2) A molded body used as a base material for a reflector for a parabolic antenna, which has a mounting part on the back side for connecting to other parts, and the vicinity of the mounting part on the back side has a hollow part. 2. The hollow molded article with a thick-walled reinforcing portion according to claim 1, wherein the hollow molded article is crushed and pressed to form the thick-walled reinforcing portion. 3) Before the inside of the mold cavity is filled with the injected molten thermoplastic resin, pressurized gas is injected into the cavity to form a hollow part in the molten thermoplastic resin, and then the mold cavity is filled with the injected molten thermoplastic resin. By projecting the hollow part into the cavity and partially crushing the hollow part, the front part and the back part of the obtained hollow molded body sandwiching the hollow part are partially crimped to form a thick reinforced part. A method for producing a hollow molded body with a thick reinforced part, characterized by: 4) Using a mold for molding a molded body used as a base material for a reflector for a parabolic antenna, the mold part around the attachment part for connecting to other members, which is formed on the back side of the molded body, is 4. The method for producing a hollow molded body with a thick reinforcement part according to claim 3, wherein the hollow molded body is made to protrude into the cavity.