JP3300436B2 - Method for joining tubular molded articles made of polyarylene sulfide - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for fusion joining a tubular molded article made of polyarylene sulfide, in which the beads formed inside the fusion joint are small, and despite this, the joining strength is relatively high and the heat is high. The present invention relates to a fusion bonding method that is not easily deteriorated and has good workability.

[0002]

2. Description of the Related Art Various techniques have been developed for a fusion joining method of a tubular molded article made of a thermoplastic resin. A typical example is a socket method in which a portion to be welded is formed in a socket shape and then combined and melt-bonded; a hot plate coated with a fluororesin or the like is brought into contact with the portion to be welded to melt the portion to be welded. There is a method such as pressure bonding.

[0003] However, any of the methods has a problem in that the joint portion has a shape different from that of other portions. That is, in the socket method, a gap generated between bonding surfaces is unavoidable, and particularly when used in an ultrapure water application field, it causes microbial growth and accumulation of fine particles, and is not suitable for use. In addition, in the method using a hot plate, in accordance with the pressure bonding, a swelling portion is formed on both the inner surface and the outer surface of the tube at the joint called a bead by those skilled in the art, and particularly the inner bead is similar to the depression in the case of the socket method. This may cause the growth of microorganisms and accumulation of fine particles. When a hot plate is used, a method is known in which a support called a core, such as a fluororesin, is inserted so as not to generate an inner bead. Then it is impossible to insert or remove it into the pipe. Also, if the size of the core is made smaller than the inner diameter of the pipe, and insertion and removal are easier, beads will be formed only at the interval between the inner diameter of the pipe and the core,
The height of the bead must be 1 mm or more. In addition, in the case of joining elbows, teeth and the like, it is very difficult to insert and remove the core, and there is a disadvantage that workability is poor.

[0004] Japanese Patent Application Laid-Open No. 62-279925 discloses a method for eliminating an inner bead. The method is a method of specifying the shape of the bonding surface and suppressing the hot-melt fluororesin from the outside with hot air in order to suppress thermal deterioration. The shape is formed obliquely inward from the outer peripheral surface of the joining surface toward the inner peripheral surface. However,
When such a method is applied to a tubular body made of polyarylene sulfide, the heating is performed by hot air, and despite the heat resistance of polyarylene sulfide, the oxidation reaction of sulfide is inevitable, resulting in thermal degradation. For example, it turns brown.

[0005]

When joining in a molten state, the higher the pressure, the higher the joining strength.
On the other hand, the bead increases. Therefore, it was difficult to have a small bead and a relatively high joining strength. The present invention relates to a method for joining a tubular body made of polyarylene sulfide, which has a small inner bead at a fusion joint, has a relatively high joining strength in spite of that, is hardly deteriorated by heat, and has good workability. Is to provide.

[0006]

The present invention differs from the prior art described above in that when the end face to be joined of the tubular body made of polyarylene sulfide is heated to a molten state in a non-contact state with the hot plate, the hot air differs from the hot air in the prior art described above. The air around the plate is low in temperature, and the temperature does not rise so much with radiant heat alone.
Focusing on the fact that lensulphide is not easily degraded by oxidative heat, we have found a bonding method with a small inner bead and high welding strength by joining it in a specific temperature range after melting it once. Based. Here, the welding strength capability is a percentage of the tensile strength of the joint surface obtained by cutting out a dumbbell piece from the joint portion and other portions from the joint pipe with respect to the other portions, that is, the tensile strength of the tubular molded body itself.

The gist of the present invention is that in joining tubular molded articles made of polyarylene sulfide, a pair of end faces to be joined are heated by a hot plate in a non-contact state, and the surface temperature of the end faces to be joined is increased. Is set to a temperature not lower than the melting endothermic peak temperature of polyarylene sulfide, but not higher than the melting endothermic peak temperature by 80 ° C., and keeping the hot plate away from the end face to be joined, and setting the melting start temperature of the resin to 10 ° C. A tube formed of polyarylene sulfide, wherein a pair of end faces to be joined are melt-pressed with a pressure of 50 to 1500 kPa at a temperature not lower than a temperature higher than a melting endothermic peak temperature. In the method of joining objects. Hereinafter, the present invention will be described in detail.

In the present invention, polyarylene sulfide means a polymer having-(-Ar-S-)-(where "-Ar-" means an arylene group) as a main constituent. Here, the arylene group is used in a broad sense and includes p-phenylene, m-phenylene, naphthylene,
4,4'-biphenylene or -Ph-CO-Ph-
(Where "-Ph-" means a phenylene group forth.), - Ph-O- Ph, -Ph-CH 2 -Ph-,
-Ph-SO ₂ -Ph-, etc., such as including divalent aromatic residue containing an aromatic ring at least two 6 carbon atoms. still,
A substituent such as an alkyl group or a carboxyl group may be introduced into each aromatic ring. These are homopolymers.
Or a random copolymer or a block copolymer.

Among them, those having a phenylene group, especially a paraphenylene group as a main component are preferred. Here, the main constituent element means 50 basic mol% or more when -Ar-S- is calculated as 1 basic mol. Preferably at least 70 base mol%, more preferably at least 90 base mol% is used. Preferably, a substantially straight-chain high molecular weight one is used. The term "substantially linear high molecular weight polyarylene sulfide" as used herein refers to a polymer obtained from a monomer mainly composed of a bifunctional monomer. Therefore, a small amount of a polyfunctional monomer may be present as a constituent unit.

The tubular molded article made of polyarylene sulfide in the present invention refers to a tubular molded article of a composition mainly composed of polyarylene sulfide in addition to polyarylene sulfide alone. The composition includes, for example, impact modifiers, reinforcing fibers, inorganic fillers, and the like. In addition, the tubular molded body refers to a molded body having a tubular portion, such as a pipe, a joint, a valve, or the like. As a molding method of the tubular molded body, a usual molding method such as extrusion molding and injection molding is employed.

The end face of the tubular body to be joined can be made smaller by providing a notch at its inner edge, referred to in the art as a "groove".
FIG. 1 is an example of a cross-sectional view of the tubular body 1 in the vicinity of a joint where no groove 6 is provided at the inner edge of the end face 2 to be joined. FIG. 2 shows a groove 6 provided at the inner edge of the end face 2 to be joined. FIG. 2 is an example of a cross-sectional view of the tubular body 1 near a joined portion. In FIG. 2, a groove 6 is provided at the inner edge of the end face 2 of the tubular body 1 to be joined. The groove is provided on the entire inner periphery of the joining surface.

The volume of the portion 6 notched by the groove is preferably equal to or less than the volume of the portion 3 remaining without being cut by the groove, and is preferably 1/20 or more thereof. Also, the end face 4 to be joined which is not cut off by the groove.
In extreme cases, only the outer periphery may be used, but it is preferable that the end face 4 to be joined without being notched by the groove is not only the outer periphery.

[0013] The thickness of the end face to be joined remaining without being notched by the groove is preferably at least about 1/3, more preferably at least 2/5 of the thickness of the pipe. The angle 5 is 10 to 70 °, more preferably 20 to 60.
°, particularly preferably in the range of 30 to 45 °.
In addition, it is desirable that the end face to be joined provided with the groove is removed so as to leave no shavings, and is finished.

[0014] A pair of end faces of the tubular molded body to be joined are heated in a non-contact state with a hot plate. That is, usually, the end faces to be joined are separated from each other, and a hot plate is arranged in the middle thereof to heat each end face. The surface temperature of the end face to be joined is not lower than the melting endothermic peak temperature of polyarylene sulfide but not higher than the melting endothermic peak temperature by 80 ° C. This is because if the temperature exceeds the melting endothermic peak temperature by 80 ° C., thermal deterioration is likely to occur. Here, the melting endothermic peak temperature is the melting endothermic peak of polyarylene sulfide when the temperature is raised at 10 ° C./minute by a differential scanning calorimeter (DSC) using “DSC30” manufactured by Metra Corporation.
Temperature.

As the heating plate, a known heating plate such as a metal heater in which a rod heater is embedded, a ceramic heater, a cast heater or the like is used. The distance between the end face of the tubular molded body to be joined and the hot plate varies depending on the type of hot plate, the temperature of the hot plate, the heating time and the like, but is usually several mm or less.
The heating time depends on the temperature of the hot plate and is not particularly limited, but is usually within 3 minutes, preferably 2 minutes.
Within minutes.

Then, the hot plate is joined at a predetermined temperature at which the polyarylene sulfide is in a molten state, away from the end face to be joined. The bonding temperature is 1 in DSC.
The temperature is higher than the melting start temperature of the polyarylene sulfide by 10 ° C. when the temperature is raised at 0 ° C./min and lower than the melting endothermic peak temperature. Preferably, the temperature is not lower than 15 ° C above the melting start temperature and not higher than 2 ° C below the melting endothermic peak temperature. Here, the melting start temperature is defined as DSC by "DSC 30" manufactured by Metra Corporation.
Is the temperature at which endothermic rises due to melting of polyarylene sulfide.

The joining is performed by crimping, and the pressure is usually 5
0 to 1500 kPa, more preferably 70 to 1200 k
Pa, even more preferably 100 to 500 kPa is employed. If the pressure is less than 50 kPa, sufficient welding strength cannot be obtained, and if it exceeds 1500 kPa, the bead becomes large. However, the welding strength can be reduced to 50% of the tensile strength of the tubular molded article itself by pressure bonding at the pressure shown in the present invention. % Or more and 80% or more and a small bead can be obtained by selecting appropriate conditions. In particular, when such a groove is provided, by the bonding method of the present invention, most of the remaining portion 3 which is not cut out by the groove is cut off by crimping. While filling, the part is melt-pressed to the extent that it appears as a bead on the outside of the tubular body, so that a joint surface having a smaller inner bead height and sufficient welding strength can be obtained.

[0018]

【Example】

[Test method] The tensile strength was measured in accordance with JIS-K6742 except that the material was polyphenylene sulfide instead of vinyl chloride resin. The end face temperature and the hot plate surface temperature were measured by a thermocouple and a contact type surface thermometer, respectively.

[0019]

Example 1 A melt viscosity at 310 ° C. and a shear rate of 200 / sec is 2.8 kPa · s, and a melting start temperature is 220
C. and polyphenylene sulfide having a melting peak temperature of 277.degree. C. were pelletized with a uniaxial pelletizer. The pellet was dried at 140 ° C. for 3 hours to remove water and volatile components. The resin temperature at the time of entering the die was 330 ° C., and about 310 ° C. at the exit of the die.

The outside mandrel was attached to the die of a small single screw extruder (35 mmφ), and the cylinder temperature 25
The pellets were passed through an extruder set at 0-330 ° C. Angular velocity π / 2 rad · sec ^-1 (screw rotation speed 15r
pm), while stretching 3% in the radial direction,
The pipe was formed by sizing and cooling with water. The obtained pipe had a smooth inner surface with an inner diameter of 26 mm and a thickness of 3 mm.

The inner groove angle of the two pipes is 30
° and a notch with a thickness of 1 mm from the inside of the end face to be joined to provide an inner groove. The end faces provided with the inner grooves were opposed to each other, and a ceramic heater having a surface temperature of 450 ° C. was placed between the end faces. After that, except for the heater, the pipes were 200 kP
a. The welding surface temperature at the time of pressing was 268 ° C.

The height of the bead on the inside of the obtained joint pipe is 0.9 mm, and the joint surface is not colored and has no evidence of thermal deterioration. Also, a dumbbell piece was cut out from this joint pipe from the joint and other places, and the tensile strength of the joint surface obtained was 52 MN / m ² (5.3 kg / m
m ² ), and the other portion, that is, the tensile strength of the tubular molded body itself was 62 MN / m ² (6.3 kg / mm ² ). Therefore, the welding strength capability of the joint surface was 84%.
Table 1 shows main conditions and physical properties together with other examples and comparative examples.

[0023]

[Table 1]

[0024]

Example 2 The internal groove angle of the pipe made of only polyphenylene sulfide used in Example 1 was 45 °, and 1 mm was removed from the inside of the end face to be joined. Others were carried out similarly to Example 1. Bee inside the obtained one
The height of the pad was 0.45 mm, and the joint surface was not colored and had no evidence of thermal deterioration. The tensile strength of the joint surface is 4
It was 9.3 MN / m ² (5.0 kg / mm ² ). Therefore, the welding strength capability of the joint surface was 80%.

[0025]

Embodiment 3 0.5 mm from the inside of the end face to be joined
Example 1 except that the heat was removed and the heating time during welding was 40 seconds.
As a result, the temperature of the welding surface at the time of pressing was 272 ° C., the height of the bead inside the obtained product was 0.9 mm, and the bonding surface was not colored and was thermally degraded. There is no evidence. The tensile strength of the joint surface is 52 MN / m ²
(5.3 kg / mm ² ). Therefore, the welding strength capability of the joint surface was 84%.

[0026]

[Comparative Example] A welding surface when pressing was performed in the same manner as in Example 1 except that 0.5 mm was removed from the inside of the end face to be joined in Example 1 and the heating time during welding was set to 50 seconds. Is 285 DEG C., the bead height inside is 1.2 mm, the joint surface is not colored and has no evidence of thermal degradation. The tensile strength of the joint surface was 62 MN / m ² (5.3 kg / mm ² ). Therefore, the welding strength capability of the joint surface was 100%.

[0027]

According to the present invention, there is provided a joining method in which no color change due to oxidative deterioration is observed, the inside bead is made 1 mm or less, and the welding strength capability of the joining surface is 50% or more. It became possible. In addition, the method is simple in operation, and can be easily performed in joining elbows, teeth, and the like. Therefore, it is particularly suitably used for joining ultrapure water pipes.

[0028]

[Brief description of the drawings]

FIG. 1 is an example of a cross-sectional view of a tubular body near a joint where no groove is provided at an inner edge of an end face to be joined.

FIG. 2 is an example of a cross-sectional view of a tubular body near a joint having a groove provided on an inner edge of an end face to be joined.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Tubular body 2 End face to be joined 3 Portion left without being notched by a groove 4 End face to be joined left without being cut by a groove 5 Groove angle 6 Groove

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Takeshi Kashiwadate 16 Nishikicho, Iwaki-shi, Fukushima Prefecture Nishiki Research Institute, Kureha Chemical Industry Co., Ltd. (56) References JP-A-51-4273 (JP, A) JP-A-1-110128 (JP, A) JP-A-2-2881928 (JP, A) JP-A-3-110134 (JP, A) JP-A-3-222722 (JP, A) JP-B-2-26848 (JP) , B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) B29C 65/00-65/82

Claims (3)

(57) [Claims] In joining a tubular molded article made of polyarylene sulfide, a pair of end faces to be joined are heated by a hot plate in a non-contact state, and the surface temperature of the end faces to be joined is reduced by the polyarylene sulfide. A temperature not lower than the melting endothermic peak temperature, but not higher than the melting endothermic peak temperature by 80 ° C., and not less than 10 ° C. higher than the melting start temperature of the resin by moving the hot plate away from the end face to be joined; And a temperature not higher than the melting endothermic peak temperature.
A method for joining a tubular molded article made of polyarylene sulfide, wherein a pair of end faces to be joined is melt-pressed with a pressure of 0 to 1500 kPa. 2. The method for joining tubular molded articles made of polyarylene sulfide according to claim 1, wherein a groove is provided at an inner edge of an end face to be joined and melted and heated. 3. The thickness of an end face to be joined remaining without being notched due to a groove is approximately １ ／ of the thickness of a pipe.
The method for joining tubular molded articles made of polyarylene sulfide according to claim 1, wherein the groove angle provided at the inner edge of the end face to be joined is 10 to 70 °.