JPH07241921A - Manufacture of curved pipe - Google Patents

Abstract

PURPOSE:To decrease the plant installation cost when a curved pipe is manufactured and improve the dimensional accuracy and the surface appearance of the curved pipe obtd. by providing a method for obtaining the curved by means of injection molding process by using only an ordinary injection molding apparatus needed for molding a straight pipe and a heating device and a tool needed for processing the curved pipe. CONSTITUTION:In a method for manufacturing a curved pipe by molding a crystalline resin, a pipe-like molding is manufactured by injection molding of the crystalline resin at a mold temp. being lower than the glass transition temp. of the resin and bending processing is performed by heating the pipe-like molding obtd, at a temp. being at least the glass transition temp.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a bent pipe with simple equipment.

[0002]

2. Description of the Related Art Bent pipes have an undercut in their shape, and in many cases, they cannot be formed by a normal die. For this reason, conventionally, when it is impossible to mold with a normal mold, a bent pipe is manufactured by a blow molding method, a gas assist molding method, an injection molding method by the lost core method, a method of welding several injection molded parts, or the like. Was there.

[0003]

However, when the blow molding method or the gas assist molding method is used, it is difficult to obtain the dimensional accuracy and surface appearance of the inner surface of the pipe, so that the application of the obtained pipe is restricted and the equipment cost of the processing machine is reduced. Will be huge. Further, the injection molding method by the lost core method is an ideal method for manufacturing a bent pipe, but the equipment cost is high. In addition, the method of welding several injection-molded parts has the problem that the number of parts increases and the number of processing steps increases.Furthermore, dimensional accuracy and There is also a problem with the surface appearance. Therefore, the present invention provides a method for obtaining a bent pipe by an injection molding method using only a normal injection molding facility required for molding a straight pipe, and a heating device and a jig required for processing a bent pipe. The present invention aims to reduce the equipment cost when manufacturing a bent pipe and improve the dimensional accuracy and surface appearance of the obtained bent pipe.

[0004]

That is, the present invention provides a method for producing a bent pipe by molding a crystalline resin, wherein the crystalline resin is injection molded at a mold temperature lower than the glass transition temperature of the resin. The present invention provides a method for producing a bent pipe, characterized in that after the pipe-shaped molded body is manufactured by the above, the obtained pipe-shaped molded body is heated to a glass transition temperature or higher to be bent.

As the above-mentioned crystalline resin, polyarylene sulfide (hereinafter referred to as PAS resin) typified by polyphenylene sulfide (hereinafter referred to as PPS resin), polyethylene terephthalate, polybutylene terephthalate, polyamide resin, polyacetal resin and these And a copolymer containing as a main component.
Also, two or more of these may be used in combination. Among these crystalline resins, the PAS resin is a resin that belongs to the category of slow crystallization rate, and is particularly suitable because the preheating condition for bending in the present invention is wide.

The above PAS resin has the repeating unit-(-Ar
It is an essentially crystalline polymer mainly composed of -S-)-(wherein Ar is an arylene group).
Examples of the arylene group include p-phenylene group, m-phenylene group, o-phenylene group, substituted phenylene group,
p, p'-diphenylene sulfone group, p, p'-biphenylene group, p, p'-diphenylene ether group, p,
P′-diphenylenecarbonyl group, naphthalene group and the like are preferable. The PAS resin may be a homopolymer consisting of the same repeating unit or a copolymer containing a small amount of different kinds of repeating units. The homopolymer preferably has a repeating unit of a p-phenylene sulfide group using a p-phenylene group as an arylene group. Further, as the copolymer, p-
A copolymer mainly containing a phenylene sulfide group and containing an m-phenylene sulfide group is preferably used. Among such homopolymers, those containing p-phenylene sulfide groups in an amount of 70 mol% or more, preferably 80 mol% or more are particularly preferable as the crystalline resin used in the present invention. The PAS resin may be either a block polymer or a random polymer, but the block polymer is excellent in heat resistance and mechanical properties. As the PAS resin, a polymer having a substantially linear structure obtained by polycondensation of a monomer mainly composed of a bifunctional halogen aromatic compound can be preferably used. A polymer having a partially crosslinked structure with a small amount of a crosslinking agent such as a polyhaloaromatic compound having three or more halogen substituents at the time of polycondensation can be preferably used, and a linear structure having a relatively low molecular weight can be used. It is also possible to use a polymer in which the melt viscosity is increased by heating the polymer at a high temperature in the presence of oxygen to cause a crosslinking reaction to improve the moldability. The melt viscosity of the PAS resin that can be used in the present invention is not particularly limited, but in consideration of mechanical strength, fluidity during injection molding, etc., the melt viscosity (temperature 310 ° C., shear rate 1200 /
Second) is preferably 100 to 5000 poise, more preferably 200 to 3000 poise.

The crystalline resin may be further blended with a fibrous, powdery or plate-like filler depending on the purpose. As the fibrous filler, glass fiber, asbestos fiber, carbon fiber, silica fiber, silica-alumina fiber, zirconia fiber, boron nitride fiber, silicon nitride fiber, boron fiber, potassium titanate fiber, stainless steel, aluminum, titanium, copper Inorganic fibrous substances such as metal fibers such as brass. Of these, a particularly representative fibrous filler is glass fiber. Further, as the particulate filler, carbon black, silica, quartz powder, glass beads, glass powder, calcium silicate, aluminum silicate, kaolin, talc, clay, silicate such as diatomaceous earth, wollastonite, Iron oxide, titanium oxide, zinc oxide, oxides of metals such as alumina, calcium carbonate,
Examples thereof include carbonates of metals such as magnesium carbonate, sulfates of metals such as calcium sulfate and barium sulfate, and further, silicon carbide, silicon nitride, boron nitride, various metal powders and the like.

Examples of the plate-like filler include mica, glass flakes, various metal foils and the like. These inorganic fillers can be used alone or in combination of two or more. By using a fibrous filler, particularly glass fiber, in combination with a granular and / or plate-like filler, it is possible to improve the mechanical strength, dimensional accuracy, electrical properties, etc. of the bent pipe obtained in the present invention in a well-balanced manner. .
When using these fillers, it is desirable to use a sizing agent or a surface treatment agent together. Examples of the sizing agent and the surface treatment agent include functional compounds such as epoxy compounds, isocyanate compounds, titanate compounds, and silane compounds.

Further, a small amount of a thermoplastic resin can be added to the above crystalline resin within the range in which its characteristics are not lost. The thermoplastic resin is preferably a thermoplastic resin that is stable at high temperatures, and examples thereof include polyolefin-based (co) polymers, polycarbonates, ABS, polyphenylene oxides, polyalkyl acrylates, polyacetals, polysulfones, polyether sulfones, polyether imides, Examples thereof include polyether ketone and fluororesin. These thermoplastic resins can also be used as a mixture of two or more kinds.

Further, the above-mentioned crystalline resin includes known additives generally added to synthetic resins such as stabilizers such as antioxidants and ultraviolet absorbers, antistatic agents, flame retardants, dyes and pigments. Colorants, lubricants, release agents and the like can be added. Further, in the present invention, a crystallization accelerator, a crystal nucleating agent, etc. may be appropriately added in order to enhance the performance of the crystalline resin.

In the present invention, the above-mentioned crystalline resin is injection-molded at a mold temperature lower than the glass transition temperature of the resin to produce a pipe-shaped molded body. The shape of the pipe-shaped molded body obtained at this time is not particularly limited, and a shape that is advantageous for processing the intended bent pipe may be selected within a range where injection molding is possible. For example, in consideration of moldability and workability, the shape of a straight pipe, a straight pipe with a branch, or the like is advantageous. In addition, the pipe-shaped molded body,
It may have a complicated shape as long as it can be injection-molded, and for example, a molded body having a complicated shape having flange portions at both ends can be used. The mold temperature is not particularly limited as long as it is lower than the glass transition temperature of the crystalline resin, but in the case of PPS resin, for example, 80 ° C. or lower is preferable. In the present invention,
The pipe-shaped molded product obtained by injection molding is heated to a temperature not lower than the glass transition temperature of the above crystalline resin and bent before the crystallization of the crystalline resin proceeds. In addition, in this specification, the heating for performing the bending is referred to as preheating. The heating temperature and heating time for this preheating are not limited because the suitable condition range varies depending on the characteristics of the crystalline resin, the heating method, and the crystallinity and rigidity of the pipe-shaped molded body. As an example of the case of PPS resin, preferably 100 ° C. or higher, more preferably 120 ° C. to 160 ° C.
At 0 ° C for 0.5 to 3.0 minutes. If the heating temperature of the preheating is too high, the crystallization of the crystalline resin will proceed before the bending work, which makes the work difficult. In the case of PPS resin, it is preferably 160 ° C. or lower.
Although the optimum heating temperature and heating time cannot be uniquely limited as described above, taking the case of PPS resin as an example,
An example of the relationship between the heating temperature and the heating time is as follows. i) heating temperature 120 ° C; heating time 1.5 to 2.5 minutes ii) heating temperature 140 ° C; heating time 1.0 to 1.7 minutes iii) heating temperature 160 ° C; heating time 0.5 to 0.9 When the above-mentioned bending process is performed for a minute, a pressurized fluid can be injected into the pipe-shaped molded body in order to prevent the molded body from being significantly deformed. That is, if a bending process is performed without applying pressure to the inside of the pipe-shaped molded body, a flat bent pipe is usually obtained. Therefore, when it is desired to manufacture a bent pipe having a good cylindrical shape, it is preferable to pressurize the inside of the pipe with a pressurizing fluid when performing bending. The type of the pressurized fluid is not particularly limited, but air, nitrogen, etc. are preferable because they are easy to handle. The fluid pressure by the pressurized fluid is not particularly limited as long as it is atmospheric pressure or more, but 1.2 kg / cm ² to 6 kg /
cm ² is preferable. When performing the bending process, it is preferable to use a bending jig for fixing the shape. The structure and shape of the bending jig can be determined according to the shape of the formed pipe-shaped formed body or the bent pipe to be obtained, and are not particularly limited. The bending jig may be made of any material as long as it retains its strength at the heating temperature. However, considering that it may be preheated when it is attached to the jig, it has good thermal conductivity. Those made of metal are preferable. In the present invention, after the bending process is completed, if desired, the pipe is left to stand still or heated while being fixed with a bending jig to accelerate the crystallization of the crystalline resin, thereby improving the shape retention performance and strength of the pipe. You can also let it. The heating temperature and heating time in this crystallization heating step also cannot be particularly limited because they differ depending on the crystallinity of the pipe-shaped molded article, etc., but particularly in the case of PPS resin, the heating time is preferably 120 ° C. or higher, The heating time is 0.5 minutes or more.
In addition, if the above-mentioned preheating is performed at a temperature of 120 ° C. or higher,
Subsequent crystallization heating can be carried out at that temperature. As a heating method for performing the above preheating and crystallization heating, a method using a hot air bath, a far infrared heating furnace, a hot wire heating furnace, or the like is preferable. In order to carry out the method of the present invention industrially advantageously, it is preferable to carry out the preheating, the bending and the crystallization heating continuously.

According to the manufacturing method of the present invention, bent pipes having various shapes can be obtained, and the shape is not limited. For example, a U-shaped pipe, a U-shaped pipe, a pipe having a bent portion, a pipe having an enlarged diameter in the central portion, and the like can be produced by using a linear pipe-shaped molded body,
A T-shaped pipe, a Y-shaped pipe, or the like can be manufactured by using a straight pipe-shaped molded body with a branch. Also,
When processing, not only simple bending, but also denting, flattening, twisting a part of the pipe,
It is possible to perform processing such as thinning.

[0013]

In the present invention, a bent pipe is manufactured using a crystalline resin. This crystalline resin has the property that crystallization does not proceed below the glass transition temperature. Therefore, when the crystalline resin is molded at a mold temperature lower than the glass transition temperature and then heated to the glass transition temperature or higher, the obtained molded article has extremely flexible properties while crystallization does not proceed. . The present invention utilizes this property, and first, a crystalline resin is injection-molded at a mold temperature lower than the glass transition temperature to produce a pipe-shaped molded body.
Next, while the obtained pipe-shaped molded body is not crystallized and has flexibility, it is bent by using a bending jig or the like. Then, heating is further continued to promote crystallization, whereby the shape of the obtained bent pipe is maintained and the strength is improved. In the present invention, a bent pipe can be produced in this manner using only ordinary injection molding equipment, a bending jig and a heating means.

[0014]

According to the present invention, since a bent pipe can be manufactured by using ordinary injection molding equipment, the bent pipe can be manufactured very easily and at low cost. That is, according to the manufacturing method of the present invention,
Compared with the conventional method of manufacturing bent pipes, the manufacturing equipment cost can be reduced significantly, the number of parts processing steps does not increase, and the bent pipes obtained have excellent dimensional accuracy, surface appearance, etc. And has a feature that the dimensional accuracy of the inner surface of the pipe is excellent. Therefore,
The method of the present invention can be used in various industrial fields, and its technical value is high.

[0015]

EXAMPLES The present invention will be described below in greater detail by giving Examples, but the present invention is not limited thereto.

Example 1 Fortron 0220A9 (manufactured by Polyplastics Co., Ltd.) which is a filler-unfilled grade as a PPS resin;
The linear pipe 1 shown in FIG. 1 was injection molded at a mold temperature of 55 ° C. using a glass transition temperature of 90 ° C.). Next, the obtained straight pipe 1 was fixed to the jig 2 made of aluminum shown in FIG. 2, placed in a hot air bath (not shown) at 100 ° C. to 160 ° C., and preheated for a predetermined time. Then pipe 1
Bending was performed while injecting air of 1.5 kg / cm 2 pressure into the pipe 1 from one end (flange) 1 a of the above as shown by an arrow A in FIG. A plug (not shown) was attached to the other end (flange) 1b of the pipe 1 to prevent air from leaking. When the pipe 1 was preheated for a predetermined time, the pipe 1 became flexible enough to be bent, so the pipe 1 was bent as shown in FIG. 3B. At this time, when a suitable condition range (heating temperature and heating time) of preheating until the pipe 1 becomes flexible and crystallization progresses and becomes rigid to the extent that bending cannot be performed, it was found that it was 2 ~ 1.5 minutes at 120 ° C for 3 minutes
2.5 minutes, 140 ° C for 1-1.5 minutes, 160 ° C for 3 minutes
It was 0 to 45 seconds. As shown in FIG. 3 (b), the bent pipe 1 is held in the jig 2 while being fixed,
The resin was crystallized by heating at the same temperature for a predetermined period of time to improve the strength of the bent pipe 1.
Table 1 shows the production conditions and workability of the obtained bent pipe. The surface appearance and dimensional accuracy of the molded product after processing were almost the same as those of the molded product obtained by ordinary injection molding. The straight pipe 1 shown in FIGS. 1 (a) and 1 (b) is a hollow cylindrical pipe having flanges 1a and 1b at both ends. The hollow cylindrical portion 1c has an inner diameter of 15 mm and a wall thickness of 1.2 mm. The length is 120 mm. Also, the jig 2
As shown in FIGS. 2A and 2B, is composed of a clamp base 3 for fixing the linear pipe and a movable block 4 for movably holding the linear pipe. The movable block 4 moves the block 4. It has a shaft 4a with a screw and a stopper 4b for restraining the movement of the block 4. FIGS. 3A and 3B show an example of bending work, but the shape of the bent pipe that can be manufactured in this embodiment is not limited to this. For example, as shown in FIG. 4 (a), a straight pipe having a branched portion is formed, and the branched portion of the pipe is bent to manufacture a bent pipe as shown in FIG. 4 (b). be able to. Further, as shown in FIG. 5 (a), a straight pipe is formed, and the pipe is curved, thereby
A bent pipe as shown in (b) can be manufactured. Further, it is also possible to manufacture a pipe having a bulged central portion as shown in FIG. 6B by forming a straight pipe as shown in FIG. 6A and bulging the central portion of the pipe. it can.

Example 2 A bent pipe was manufactured under the same conditions as in Example 1 except that the mold temperature during injection molding of the pipe 1 was set to 80 ° C. The suitable preheating condition range was the same as in Example 1. In Table 2,
The manufacturing conditions and workability of the obtained bent pipe are shown.

Example 3 A bent pipe was manufactured under the same conditions as in Example 1 except that the mold temperature during injection molding of the pipe 1 was set to 18 ° C. The suitable preheating condition range was the same as in Example 1. In Table 3,
The manufacturing conditions and workability of the obtained bent pipe are shown.

Example 4 Example 1 except that Fortron 1140A1 (manufactured by Polyplastics Co .; glass transition temperature 90 ° C.) filled with 40% by weight of glass fiber was used as the PPS resin.
Bent pipe was manufactured under the same conditions as. Suitable preheating condition ranges were 120 ° C. for 2 to 2.5 minutes, 140 ° C. for 1 to 1.5 minutes, and 160 ° C. for 30 to 45 seconds.
Table 4 shows the manufacturing conditions and workability of the obtained bent pipe.

Example 5 A bent pipe was manufactured under the same conditions as in Example 4 except that the mold temperature during injection molding of the pipe 1 was set to 80 ° C. The preferred preheating condition range was the same as in Example 4. In Table 5,
The manufacturing conditions and workability of the obtained bent pipe are shown.

Example 6 As the PPS resin, Fortron 0220A9 (manufactured by Polyplastics Co., Ltd .; glass transition temperature 90 ° C.) which is an unfilled grade and Fortron 1140A1 (Polyplastics stock which is 40% by weight of glass fiber filled grade) A bent pipe was manufactured under the same conditions as in Example 1 except that a glass fiber having a glass fiber concentration of 5% by weight was blended with a glass transition temperature of 90 ° C.). Suitable preheating condition ranges are 100 ° C for 2-3 minutes, 120 ° C for 1.5-2 minutes, and 140 ° C for 1-1.5.
Min, 160 ° C for 30-45 seconds. Table 6 shows the manufacturing conditions and workability of the obtained bent pipe.

Example 7 A bent pipe was manufactured under the same conditions as in Example 6 except that the mold temperature during injection molding of the pipe 1 was set to 80 ° C. The preferred preheating condition range was the same as in Example 6. In Table 7,
The manufacturing conditions and workability of the obtained bent pipe are shown.

Example 8 A bent pipe was manufactured under the same conditions as in Example 6 except that the mold temperature during injection molding of the pipe 1 was set to 18 ° C. The preferred preheating condition range was the same as in Example 6. In Table 8,
The manufacturing conditions and workability of the obtained bent pipe are shown.

Comparative Example 1 As the PPS resin, a non-filling grade Fortron 0220A9 (manufactured by Polyplastics Co., Ltd .; glass transition temperature 90 ° C.) was used to mold the straight pipe shown in FIG. 1 at 100 ° C. Injection molded at temperature. Next, the pipe was fixed to the jig shown in FIG. 3 and preheated in an air thermostat of 100 ° C. to 160 ° C. for bending, but the pipe was not flexible and a bent pipe could not be manufactured. Table 9 shows the manufacturing conditions and workability of the pipe.

Comparative Example 2 Bending under the same conditions as in Comparative Example 1 except that Fortron 1140A1 (manufactured by Polyplastics Co., Ltd .; glass transition temperature 90 ° C.), which is a 40% by weight glass fiber filling grade, was used as the PPS resin. I tried to manufacture a pipe, but I could not manufacture a bent pipe because the pipe was not flexible. Table 10 shows the manufacturing conditions and workability of the pipe.

Comparative Example 3 For PPS resin, Fortron 0220A9 (made by Polyplastics Co., Ltd .; glass transition temperature 90 ° C.) which is an unfilled grade and Fortron 1140A1 (Polyplastics stock, which is a filled grade of 40% by weight of glass fiber) An attempt was made to manufacture a bent pipe under the same conditions as in Comparative Example 1 except that a blend of a glass transition temperature of 90 ° C. manufactured by the company and a glass fiber concentration of 5% by weight was used, but the pipe was not flexible. I couldn't make a bent pipe.
Table 11 shows the manufacturing conditions and workability of the pipe.

The criteria for determining the workability in the table below are as follows. × Non-softening: hardly softened and could not be processed. B: Somewhat bad; it was not softened sufficiently and could not be processed into a desired shape. ○ Machining: It was softened sufficiently and could be processed into the desired shape. × Crystallization: Softened once, but could not be processed because crystallization proceeded and solidified.

[0028]

[Table 1]

[0029]

[Table 2]

[0030]

[Table 3]

[0031]

[Table 4]

[0032]

[Table 5]

[0033]

[Table 6]

[0034]

[Table 7]

[0035]

[Table 8]

[0036]

[Table 9]

[0037]

[Table 10]

[0038]

[Table 11]

[Brief description of drawings]

FIG. 1 (a) is a front view of a linear pipe injection-molded in Example 1, and FIG. 1 (b) is a side view of the linear pipe shown in FIG. 1 (a).

2 (a) is a front view of a jig used in Example 1, and FIG. 2 (b) is a side view of the jig shown in FIG. 2 (a).

FIG. 3 (a) is a front view showing a state where a straight pipe is held by a jig, and FIG. 3 (b) is a front view showing a state where the straight pipe is bent.

FIG. 4 (a) is a conceptual diagram of a pipe having a branched portion, and FIG. 4 (b) is a conceptual diagram of a pipe in which a branched portion of a straight pipe having a branched portion is bent.

5 (a) is a conceptual diagram of a straight pipe, and FIG. 5 (b) is a conceptual diagram of a curved pipe.

6 (a) is a conceptual diagram of a straight pipe, and FIG. 6 (b) is a conceptual diagram of a pipe in which a central portion of the linear pipe is inflated.

[Explanation of symbols]

 1 straight pipe 1a straight pipe one end (flange) 1b straight pipe other end (flange) 1c straight pipe hollow cylindrical portion 2 jig 3 clamp base 4 movable block 4a screwed shaft 4b stopper

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Claims (6)

[Claims] 1. A method for producing a bent pipe by molding a crystalline resin, wherein a pipe-shaped molded body is manufactured by injection molding the crystalline resin at a mold temperature lower than the glass transition temperature of the resin. After that, the bent pipe is manufactured by heating the obtained pipe-shaped molded body to a glass transition temperature or higher to perform bending. 2. The method for producing a bent pipe according to claim 1, wherein a polyphenylene sulfide resin is used as the crystalline resin. 3. The method for producing a bent pipe according to claim 1, wherein a pressurized fluid is injected into the pipe-shaped molded body when performing bending work. 4. After completion of bending, heating to a temperature above the processing temperature and below the melting point of the resin to accelerate crystallization of the crystalline resin improves the shape retention performance and strength of the pipe in a short time. The bent pipe manufacturing method according to claim 1, wherein the bent pipe is manufactured. 5. The mold temperature during injection molding is 80 ° C. or lower, and the processing temperature during bending is 100 ° C. or higher, according to any one of claims 2 to 4. Method for manufacturing the described bent pipe. 6. A mold temperature during injection molding is 80 ° C. or lower, and a processing temperature during bending is 120 ° C. to 16 ° C.
It is 0 degreeC, Any one of Claims 2-4 characterized by the above-mentioned.
A method for manufacturing a bent pipe according to the item.