JPH08142196A - Butt welding method for thermoplastic resin tube material - Google Patents

Abstract

PURPOSE: To alleviate the distortion generated at a boundary between the highly crystallized part and the amorphous part of a tube end and to improve the impact strength of the connected part by melting and connecting the vicinity of the connecting part of the tube material by holding the vicinity at the melting point or lower of the material to connect the material. CONSTITUTION: The tube end faces of the tube materials P1 , P2 of a molded form of a polyphenylene sulfide(PPS) to be connected are formed perpendicular to the axial direction of the tube material, the materials P2 , P2 are disposed at clamps 1, 2 and fixedly positioned. In this case, the materials P1 , P2 are so positioned that the distances from the tube end faces to the ends of liners 11, 12 of the clamps are 1 to 2mm. The grips of the materials P1 , P2 are heated by liners 11, 12 for a predetermined time. The temperatures of the grips are held at the temperature lower than 270 deg.C of the melting point of PPS, e.g. 200 deg.C, heated and melted. Thus, it is held at the lower temperature by 70 deg.C than the melting point of the PPS, thereby raising the impact strength twice as large as the strength.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for joining resin-molded pipe materials by butt welding, and more specifically to a thermoplastic resin pipe material (for example, PPS: used for clean applications such as transportation of ultrapure water). The present invention relates to a butt welding method suitable for joining polyphenylene sulfide molded articles and the like).

[0002]

2. Description of the Related Art As a method of joining pipes made of a thermoplastic resin such as PPS, for example, as shown in FIG. 3, a pair of clamps 31 and 32 grips the pipes P1 and P2, and the respective pipes P1 and P2 are held. After heating and melting the end portion of each of them by a heat source 33 such as a heater, the clamps 31 and 32 are moved toward each other so that the respective melted portions are abutted and fused at a predetermined pressure. Japanese Patent Laid-Open No. 5-318
594, JP-A 1-110128, or JP-A 61-20725).

[0003]

By the way, since PPS and the like are crystalline resins, when the PPS pipes are joined by the above-mentioned butt fusion, the crystallinity at the interface of the fusion-bonded portion becomes extremely high. Since the interface between the melted part and the non-melted part is cooled relatively rapidly, distortion may occur at this interface and the impact strength of the joint part may not be sufficiently obtained.

The present invention has been made in view of such a point, and in joining a crystalline thermoplastic resin pipe material such as PPS by butt fusion welding, a method capable of enhancing the impact resistance of the joined portion. For the purpose of providing.

[0005]

In order to achieve the above object, the present invention is a welding method in which each pipe end portion of a pair of pipe materials to be joined is heated and melted, and then the respective melted portions are butted and fused. In FIG. 1, the heater 11 in which the non-melted portion near the portion which becomes the fused portion at the pipe end portion of each pipe material is embedded in the liners 11 and 12 of the clamps 1 and 2 as shown in FIG.
It is characterized by performing the above-mentioned heat melting and butt fusion in a state where the non-melted portion is heated by a and 12a, and the non-melted portion is maintained at a temperature equal to or lower than the melting point of the thermoplastic resin.

Here, when the method of the present invention is applied to the joining of PPS pipes, the holding temperature of the non-melted portion of the pipe material is 140 ° C to 2 ° C.
It is preferable to set the temperature in the range of 50 ° C. and to keep the temperature at a position 1 to 2 mm away from the tube end surface.

In the case of joining PPS pipes, the reason why the temperature of the non-melting part is within the above range is that if the temperature of the non-melting part near the bonding part is too low, the vicinity of the interface between the melting part and the non-melting part This is because there is a risk that the non-melted portion will be softened and deformed if the temperature becomes too high and approaches the melting point (270 ° C.).

[0008]

Function: During fusion bonding, if the non-melted portion near the joint at the end of the pipe is kept at a temperature slightly lower than the melting point of the thermoplastic resin, the vicinity of the joint during the cooling process after fusion bonding Is gradually cooled, and as a result, the temperature gradient from the joint interface to the vicinity of the joint (non-melted portion) becomes gentle. As a result, the strain at the interface between the highly crystallized portion and the amorphous portion of the joint is relaxed. It

[0009]

FIG. 1 is an explanatory view of an embodiment of the butt welding method of the present invention. First, an apparatus (entire structure is not shown) used for carrying out the method of the present invention comprises a pair of clamps 1 and 2 facing each other and a heater 3 arranged between the clamps 1 and 2. .

The heater 3 is slidably or rotatably arranged with respect to the main body of the apparatus, and has a pair of clamps 1 and 1.
It is possible to selectively move to two positions, an intermediate position (use position) of 2 and a position (standby position) where the clamps 1 and 2 do not interfere with each other. The heater 3 used in this example is a cartridge type heater whose hot plate is made of aluminum, and
The heating temperature of ℃ or more can be set arbitrarily.

The pair of clamps 1 and 2 has a structure in which the liners 11 and 12 can be exchanged, and the liners can be exchanged to hold pipe materials having a plurality of different diameters. This each liner 1
1 and 12 are made of aluminum, and a plurality of cartridge heaters 11a..11a, 12a..12a are embedded at a constant pitch along the circumferential direction, and the clamps 1 and 2 grip the pipe materials P1 and P2. In this state, the grip portion can be maintained at a temperature slightly lower than the melting point of the thermoplastic resin forming the pipe material.

Next, the procedure of the embodiment of the method of the present invention is shown in FIG.
Explanation will be given with reference to (A). First, the pipe end surfaces of the PPS pipe materials P1 and P2 to be joined are set as the surfaces orthogonal to the axial direction of the pipe material, and the pipe materials P1 and P2 are arranged and positioned in the clamps 1 and 2, respectively. To do. At this time, the pipe materials P1 and P2 are lined up from the pipe end surface to the liners 11 and 12 of the clamps.
Position so that the distance to the end of is 1-2 mm,
In this state, the grips of the pipe materials P1 and P2 are attached to the liners 11 and 12
To heat for a certain period of time by
A temperature lower than the melting point of PS (270 ° C.), for example, 200
Hold at ° C.

Next, a heater 3 is arranged between the pipe materials P1 and P2, and the pipe ends of both are heated and melted. During this heating, a 1 mm gap is provided between each tube end surface and the heating plate of the heater 3. Then, after heating the heater for a predetermined time, the heater 3 is removed from between the pipe materials P1 and P2, and the pair of clamps 1 and 2 are moved relative to each other so that each melting portion of the pipe materials P1 and P2 is predetermined. Butt and fuse under pressure.

Next, specific numerical examples of the embodiment of the present invention will be described.
This will be described below. First, the joining target is PP with a nominal diameter of 25 mm.
The S pipe was used, and this pipe material was held in a clamp in the state shown in Fig. 1 (A) and fusion bonding was performed while keeping the vicinity of the joint warm.
The Charpy impact strength of the joint was measured for each of the two types of samples with different heat retention times and the sample subjected to fusion bonding without heat retention of the pipe material. The results shown in Table 1 below were obtained. Was obtained. However, the tube end was melted in a heating time of 45 s by non-contact heating (interval = 1 mm) at a heater temperature of 470 ° C., and the joining pressure was 0.9 MPa.

[0015]

[Table 1]

As is clear from this table, by holding the gripping portion of the pipe material, that is, the non-melting portion, at a temperature lower by about 70 ° C. than the melting point of PPS, the impact strength is about 2 with respect to the case without heat retention. It turned out to be about twice as expensive. From this, it was confirmed that the butt welding method of the present invention is an effective method for improving the impact resistance of the joint portion when joining the crystalline thermoplastic resin pipe material.

In the embodiment of the present invention described above, the pipe end surface of the pipe material to be joined is a flat surface orthogonal to the pipe axis, but as shown in FIG. 2, a slight chamfer C1 is formed on the inner peripheral edge of the pipe end surface. , C2 may be applied.

Although the hot plate of the heater 3 is made of aluminum, the material of the hot plate is not particularly limited, and the temperature can be raised to a temperature at which the end of the tube can be heated above the melting point, and
It suffices that the surface temperature of the heating plate has a variation of about ± 5 ° C., for example, iron, brass, or ceramics. Further, as the heat source, a casting heater may be used instead of the cartridge type.

Furthermore, in the above embodiments, since the melting point of PPS is high, the pipe end portion is heated and melted by non-contact heating with a gap provided between the hot plate and the pipe end face.
In the case of joining a resin having a relatively low melting point, heating and melting may be performed with the tube end surface in contact with the hot plate.

The method of the present invention is not limited to the joining of PPS pipes, but can be applied to the joining of pipe materials of any other thermoplastic resin. In particular, PEEK (polyether ether ketone), PES ( Polyether sulfone),
PET (polyethylene terephthalate) or PVDF
It is suitable for joining pipes made of crystalline thermoplastic resin such as (polyvinylidene fluoride).

[0021]

As described above, according to the butt welding method of the present invention, in joining a crystalline thermoplastic resin pipe material such as PPS, the vicinity of the joint portion of the pipe material is kept at a temperature equal to or lower than the melting point of the pipe material. By performing fusion bonding in the state of
Since the vicinity of the joint is gradually cooled after fusion bonding, the strain generated at the interface between the highly crystallized portion and the amorphous portion of the pipe end is relaxed, and the impact strength of the joint is improved. .

[Brief description of drawings]

FIG. 1 is an explanatory view of an embodiment of the method of the present invention.

FIG. 2 is a view showing a modified example of a pipe end surface of a pipe material used in an embodiment of the method of the present invention.

FIG. 3 is a diagram illustrating an example of a conventional butt welding method.

[Explanation of symbols]

 1, 2 Clamp 11, 12 Liner 11a, 12a Cartridge heater 3 Heater P1, P2 Tubing (made of PPS)

Claims (1)

[Claims] 1. A method for joining pipe materials formed of a thermoplastic resin, wherein each pipe end portion of a pair of pipe materials to be joined is heated and melted, and then the pipe end portions are butted against each other and fused. In the method, the non-melting portion in the vicinity of the portion that becomes the melting portion at the time of joining at the pipe end of each pipe material is heated, and the non-melting portion is maintained at a temperature equal to or lower than the melting point of the thermoplastic resin, A butt welding method for a thermoplastic resin pipe material, which comprises performing heat melting and the above butt fusion.