JP5249084B2 - Bonding method of resin molded products - Google Patents

Description

  The present invention relates to a method for joining resin molded products, in which two meltable resin molded products are welded.

  Resin-molded products are used in various fields because they have the characteristics of being inexpensive and lightweight without corrosion like metals and wood. Moreover, in order to save earth resources by recycling, most of the resin molded products are formed from thermoplastic resins. Various molding methods such as compression molding, transfer molding, injection molding, extrusion molding, and blow molding are used. Due to advances in molding machines and mold structures, it is possible to easily mold resin molded products with complex shapes. ing.

  However, it may be difficult to manufacture a molded article having a complicated shape by a single molding. In many cases, it is necessary to form a part of the molded product from a different kind of resin. In such a case, a plurality of molded products are respectively molded and then integrated by welding.

  The resin molded product is welded by heating the end surfaces of the pair of molded products to be welded, crimping them in a state where at least one end surface of the welded portion is melted, and cooling in that state. Is called. And, as a method of heating the end face of the portion to be welded, a method using a heated hot plate, a method in which a pair of molded products are vibrated in a pressed state and heated by frictional heat, etc. are known. It is called a welding method or a vibration welding method. Moreover, the method of vibrating using ultrasonic vibration is also called ultrasonic welding.

  Among them, the hot plate welding method is a method in which the welding end surfaces of a pair of molded products to be welded are brought into contact with the surface of a hot plate heated to a temperature higher than the temperature at which the molded product is melted, and the hot plate is retracted. The welding end surfaces of a pair of molded products are pressure-bonded to each other and cooled in that state. This hot plate welding method is particularly widely used because it has simple equipment and can be easily welded (Patent Documents 1 and 2).

  The hot plate welding method as described above is a method in which the resin molded product is bonded by pressing at the time of pressure bonding, and the thickness of the molten layer of two resin molded products is predicted, and the molten layer of one resin molded product and the other It is performed by a method of bonding by controlling the position where the molten layer of the resin molded product overlaps and pressing. In particular, in the latter method, it is said that a strong joint that hardly causes creep fracture is obtained by leaving a molten layer free of voids in the joint. “Creep rupture” refers to a phenomenon in which stress is generated when a load is applied to a resin molded product and breaks down over time. In general, the higher the generated stress, the shorter the breakage.

  The hot plate welding method as described above is a simple method and widely used. However, there is a problem that the creep rupture life of the resin product joined by hot plate welding is not stable.

JP 2000-198143 A JP 2002-28977 A

  The present invention has been made in order to solve the above-described problems, and the object thereof is to make it possible to reduce a decrease in the creep rupture life of a resin joined body obtained by welding two resin molded products. It is providing the joining method of a resin molded product.

  The inventors of the present invention have made extensive studies to solve the above problems. As a result, the inventors have found the cause of a decrease in the creep rupture life of the joined molded product, and have completed the present invention. Specifically, in the method of applying a strong pressure at the time of pressure bonding, since it is excessively compressed to the unmelted layer, it has been found that residual stress is generated at the interface between the joint and the resin molded product, and the life is shortened. . In addition, in the method of predicting the thickness of the melt layer of the two resin molded products, and joining them by controlling the position where the melt layer of one resin molded product and the melt layer of the other resin molded product overlap, As a result of the slightly different thickness of the molten layer each time, if too many molten layers are estimated, excessive pressure is applied to the interface between the joint and the resin molded product, and it remains at the interface between the joint and the resin molded product. Stress is generated. Further, when the molten layer is estimated too little, voids or the like may not be discharged as burrs and may remain in the joint, and thus the creep rupture life is not stable, and the present invention has been completed. More specifically, the present invention provides the following.

  (1) Heating the end surfaces of the two resin-molded products that can be welded and heating the end surfaces of the two resin-molded products; A method for joining resin molded products that are welded by being crimped to each other, wherein the pressure applied during the crimping is more than 0 MPa and 10 MPa or less, and the minimum thickness of the joined portion after welding is 100 μm or less. A method for joining resin molded products, comprising:

  (2) The method for joining resin molded products according to (1), wherein the pressure applied during the pressure bonding exceeds 0 MPa and is 5 MPa or less.

  (3) The method for joining resin molded products according to (1) or (2), wherein at least one of the two resin molded products contains a crystalline thermoplastic resin.

  (4) The method for joining resin molded products according to (3), wherein the crystalline thermoplastic resin is polyacetal.

  According to the present invention, the interface between the bonded portion after cooling and the resin molded product can be adjusted by adjusting the pressure applied when the two resin molded products that can be welded are bonded to each other in the range of more than 0 MPa to 10 MPa or less. It is possible to suppress the residual stress generated in. As a result, a decrease in creep rupture life due to the residual stress can be suppressed. Furthermore, the lifetime reduction by the residual stress of a junction part is not seen by making the pressure applied in the case of the crimping | compression-bonding of two resin molded products which can be welded to 5 Mpa or less.

  As described above, according to the present invention, since the resin molded product is joined by a method of applying pressure, there is no variation in life due to erroneous prediction of the thickness of the molten layer. In addition, since the present invention performs welding by controlling the pressure, the present invention can be more easily implemented than a method of predicting the melt layer thickness and controlling the overlapping position of the melt layers.

  Moreover, by joining so that the minimum thickness of the joint after the resin molded product is welded is in the range of 100 μm or less, no voids or the like remain in the joint after the welding. For this reason, the fall of the creep rupture life by voids etc. remaining in a junction part can be suppressed.

  As described above, according to the bonding method of the present invention, it is possible to prevent a decrease in creep rupture life due to residual stress generated at the interface between the bonded portion after cooling and the resin molded product. In addition, since the resin molded product is joined by a method of applying pressure, unlike the case of joining by controlling the position, it is possible to prevent fluctuations in the creep rupture life due to incorrect prediction of the thickness of the molten layer. Furthermore, it is possible to prevent defects such as voids from remaining in the joint portion of the resin molded product after welding, thereby reducing the creep rupture life. As a result, by using the joining method of the present invention, the joint has a stable and high creep rupture life at any time.

It is a figure which shows the joining method of this invention using the hot plate welding method. (A) It is a figure which shows the molded product before welding. (B) It is a figure which shows the resin welded goods after welding. It is a figure which represents typically the relationship between the pressure and time concerning the interface of a resin molded product and a junction part in the case of crimping | compression-bonding. (A) It is a figure which shows the resin test piece of an Example. (B) It is a figure which shows the resin welded goods of an Example. It is the schematic of the hot plate welding apparatus used in the Example. It is a figure which shows the relationship between a tensile stress and a creep rupture life. It is a figure which shows the relationship between the pressure in the case of crimping | bonding, and the refraction point of a creep rupture life line.

  Hereinafter, an embodiment of the present invention will be described in detail. However, the present invention is not limited to the following embodiment, and may be implemented with appropriate modifications within the scope of the object of the present invention. it can.

  In the method for joining resin molded products according to the present invention, two resin molded products are heated in a state where the end surfaces of the welded portions of the two resin molded products are heated and a molten layer is formed on the planned welded portions of the two resin molded products. A method for joining resin molded products that are welded by pressure-bonding the melt layers of the molded products to each other, wherein the pressure applied during pressure bonding is more than 0 MPa and not more than 10 MPa, more preferably not more than 5 MPa, There is no particular limitation as long as it is a method for joining resin molded products such that the minimum thickness of the joint of the resin molded products is 100 μm or less.

  In addition, as a method for joining resin molded products that are welded by pressing the melt layers of two resin molded products to each other in a state in which the end surface of the welded portion of the resin molded product is heated and a melt layer is formed on the weld planned portion, An example is a hot plate welding method. Hereinafter, the joining method of the present invention will be described by taking as an example the joining of the resin molded products of the present invention by the hot plate welding method in the case of joining two types of resin molded products that can be welded.

  As a joining method of the resin molded product of this invention using hot plate welding, the joining method provided with a joining preparation process, a heating process, a crimping | compression-bonding process, and a cooling process is mentioned, for example.

<Joint preparation process>
The “joining preparation step” is a step of producing a resin molded product made of a predetermined resin material and attaching the resin molded product to a hot plate welding apparatus or the like for welding.

[Resin material]
The resin contained in the resin molded product is not particularly limited, and a conventionally known thermoplastic resin can be used.

  One of the characteristics of the bonding method of the present invention is that no residual stress is left at the interface between the resin molded product after cooling after welding and the bonded portion. Therefore, if the bonding method of the present invention is used, the creep rupture life of the bonded portion can be stabilized even for a resin molded product containing a crystalline thermoplastic resin in which stress remains easily.

  Examples of the crystalline thermoplastic resin include polyolefin resins, polyester resins, polyacetal resins, polyphenylene sulfide resins, polyamide resins, and the like. Among these, polyacetal resin is particularly preferable. The resin molded product may be composed of a single crystalline thermoplastic resin, may be composed of two or more crystalline thermoplastic resin compositions, or is amorphous to the crystalline thermoplastic resin. The thermoplastic resin may be included.

  The two resin molded products may be resin molded products made of the same resin material or resin molded products made of different resin materials as long as they can be welded to each other.

[Molding process]
First, the above resin material is molded into a desired shape. The molding method is not particularly limited, and examples thereof include various molding methods such as compression molding, transfer molding, injection molding, extrusion molding, and blow molding. Moreover, the resin molded product obtained by a shaping | molding process needs to be equipped with a welding plan part. The planned welding part is provided so as to be able to be welded by abutting the planned welding parts of the two resin molded products. For example, it is a welding planned part like the welding planned parts 21 and 31 provided in the resin molded products 2 and 3 shown in FIG. Injection molding is an example of a molding method that facilitates molding of a resin molded product having a portion to be welded.

[Installation process]
This is a process of attaching to a hot plate welding apparatus or the like in order to weld two resin molded products. A conventionally well-known thing can be used for the hot plate welding apparatus etc. which attach a resin molded product. For example, the hot plate welding apparatus 1 provided with the upper jig | tool 11 and the lower jig | tool 12 as shown in FIG. 1 can be mentioned. As shown in FIG. 1A, one resin molded product 2 is attached to the upper jig 11, and the other resin molded product 3 is attached to the lower jig 12. If the resin molded products 2 and 3 are each hold | maintained at the upper jig | tool 11 and the lower jig | tool 12, the method of attaching will not be specifically limited.

  It attaches so that the welding planned part end surface 21 of the resin molded product 2 and the welding planned part end surface 31 of the resin molded product 3 face each other so that the melt layers of the two resin molded products can be easily pressed together. In addition, a predetermined space is provided between the end surfaces of the resin molded product 2 to be welded so that a hot plate can be inserted between the end surface 21 of the resin molded product 2 and the end surface 31 of the resin molded product 3. There is.

  Moreover, it attaches so that the welding planned part end surface 21 of the resin molded product 2 may become the lowest position in the Y direction in the resin molded product 2, and the welding planned part end surface 21 may become horizontal in the X direction. And it attaches so that the welding plan part end surface 31 of the resin molded product 3 may become the highest position in the Y direction in the resin molded product 3, and the welding planned part end surface 31 may become horizontal in the X direction. If the resin molded product 2 and the resin molded product 3 are not held in a state where they face each other without lateral displacement, the planned welding portion is not uniformly welded, and a high-quality bonded product cannot be obtained.

<Heating process>
The heating step is a step in which the welded portion end faces 21 and 31 of the resin molded products 2 and 3 are heated to form the melt layers 22 and 32 in the welded planned portions of the two resin molded products 2 and 3. First, a heating process is demonstrated using FIG.

  As shown in FIG. 1B, a hot plate 13 heated to a predetermined temperature in advance is formed of a resin molded product 2 held by the upper jig 11, and a resin molded product 3 held by the lower jig 12. It moves horizontally in the X direction so that it is located between.

  Next, an upper jig holding the resin molded product 2 by lifting means (not shown) capable of moving the upper jig 11 and the lower jig 12 in the ± Y direction while holding the resin molded products 2 and 3. The tool 11 is moved in the -Y direction, and the lower jig 12 holding the resin molded product 3 is moved in the + Y direction. And the welding plan part end surface 21 and the welding plan part end surface 31 are made to contact the hot platen 13, and the melt layers 22 and 32 are formed in a welding plan part.

[Heating conditions]
The heating conditions of the end surfaces 21 and 31 to be welded are not particularly limited, and the temperature of the hot plate 13 and the contact time between the hot plate 13 and the end surfaces 21 and 31 to be welded depend on the physical properties such as the melting point of the resin molded product to be welded. Based on this, change as appropriate. For example, the effect of the present invention can be enhanced by setting the heating conditions as follows.

  When the welded portion end faces 21 and 31 are brought into contact with the hot plate 13, the molten layers 22 and 32 are formed as described above. In the melted layers 22 and 32, the portion in contact with the hot plate 13 becomes the highest temperature, and becomes lower as it gets away from the hot plate 13. Accordingly, a temperature distribution is generated in the molten layer, and the viscosity becomes lower as the temperature becomes higher and the viscosity becomes higher as the temperature becomes lower. Here, it is divided into a large, low viscosity high temperature portion and a high viscosity low temperature portion.

  When the welded portion end surfaces 21 and 31 are brought into contact with the hot plate 13, the welded portion end surfaces 21 and 31 start to melt, and a low temperature portion is first formed in the molten layer. If the heating of the end surfaces 21 and 31 to be welded is further continued, the temperature in the vicinity of the end surfaces of the planned welding portion rises, and the portions of the molten layers 22 and 32 away from the hot plate 13 become the low temperature portions. Further, when the heating of the welding planned portions 21 and 31 is continued, the vicinity of the end surface of the welding planned portion becomes a high temperature portion, and the portions of the molten layers 22 and 32 away from the hot plate 13 become low temperature portions.

  As will be described later, in the method for joining resin molded products of the present invention, the molten layer 22 and the molten layer 32 are welded so as to be bonded to each other. At this time, when the state of the fusion part end faces 21 and 31 to be welded is roughly divided into two states, a low temperature part state and a high temperature part state, in the joining method of the present invention, the low temperature state melt layers are mutually appropriate. It is preferable to perform welding by pressure bonding. By discharging the molten layer in a high temperature state where voids are likely to be generated as burrs and not applying an excessive load to the unmelted layer, a product in which the creep rupture life is not lowered stably can be obtained.

<Crimping process>
The crimping step is a step of welding the two resin molded products by melting the molten layers 22 and 32 together. The crimping process will be described with reference to FIG.

  As shown in FIG. 1 (c), when the end surfaces 21 and 31 to be welded are sufficiently heated by the hot plate 13 to form the desired melt layers 22 and 32, resin molding is performed by lifting means (not shown). The upper jig 11 holding the product 2 is moved in the + Y direction, the lower jig 12 holding the resin molded product 3 is moved in the −Y direction, and the welded portion end surfaces 21 and 31 and the hot plate 13 are pulled apart. Then, the hot plate 13 moves so as to come off between the end surfaces 21 and 31 to be welded.

  Next, a predetermined pressure is applied to the upper jig 11 by a pressure means (not shown) while measuring the pressure applied to the joint portion of the resin molded product with the pressure measuring means P provided on the upper jig 11. The upper jig 11 holding the resin molded product 2 is moved in the −Y direction. Further, the lower jig 12 holding the resin molded product 3 is fixed. Due to this movement, the molten layer 22 approaches the molten layer 32 from the state of FIG. 2A, and the end surfaces 21 and 31 of the planned welding portion come into contact with each other. Thereafter, the molten layers 22 and 32 are overlapped, and finally, as shown in FIG. 2B, most of the molten layers 22 and 32 are discharged as burrs 5 between the resin molded product 2 and the resin molded product 3. The joint 4 having a thickness of 100 μm or less is formed.

[Conditions for crimping]
The bonding method of the present invention is characterized in that the pressure applied to the bonded portion during pressure bonding exceeds 0 MPa and is 10 MPa or less, more preferably 5 MPa or less. By applying a pressure in the above range and pressure bonding, residual stress generated at the interface between the resin molded product and the joint after cooling can be suppressed. As a result, a decrease in creep rupture life can be suppressed. In addition, it is a feature of the bonding method of the present invention that the minimum thickness of the bonded portion after cooling is 100 μm or less. By discharging most of the molten layer as burrs until the minimum thickness of the bonded portion becomes 100 μm or less, it is possible to prevent voids and the like generated in the molten layer from remaining in the bonded portion. It is possible to prevent the creep rupture life from being reduced due to defects. Thus, since the fall of the creep rupture life by the defect of a junction part can be suppressed, according to the joining method of this invention, the quality of the product which has a junction part is stabilized, and a creep rupture life is stabilized stably.

  Therefore, there is no particular limitation as long as the pressure applied in the pressure bonding is in the above range and the pressure is applied so that the thickness of the joint after cooling is in the above range, and the pressure bonding condition depends on the type of the resin material. It can be changed as appropriate.

  Further, since the bonding method of the present invention welds the resin molded products by controlling only the pressure, the thickness of the molten layer of two conventional resin molded products is predicted, and the molten layer of one resin molded product and the other This is easier than the method of controlling and bonding the position where the molten layer of the resin molded product overlaps. And the joining method of this invention has the equivalent creep fracture resistance compared with the said conventional method. Furthermore, in the joining method of the present invention, since the molten layer does not remain in the joint as compared with the conventional method described above, defects such as voids remain in the joint and the problem that the creep rupture life is reduced does not occur. With this joining method, the creep rupture life is high and stable.

FIG. 3 shows the resin molded product 2 and the resin molded product with the applied pressure P ₃ applied to the joint while measuring the pressure applied to the joint between the resin molded product 2 and the resin molded product 3 with the pressure measuring means P. 3 is a diagram schematically showing a change with time of a pressure applied to a joint portion when 3 is welded. One-dot chain line in FIG. 3, the applied pressure to be applied to the joint portion indicates the case of P _3. In FIG. 3, t ₀ to t ₁ are stages in which the molten layer 22 approaches the molten layer 32, and the molten layer 22 contacts the molten layer 32 at t ₁ . Until the molten layer 22 and the molten layer 32 come into contact with each other, the pressure applied to the joining portion is zero.

Start overlap from t ₁ in FIG. 3 and the molten layer 22 and the molten layer 32, consuming gradually pressure in the joint portion, the melt layer with a low viscosity is rapidly discharged. The pressure exerted on the overlapping start is P _1. From t ₁ to t ₂ , the overlap between the high-viscosity melt layers increases, and the melt layers become thinner while the melt layers are crushed. The crushed resin becomes burrs and is discharged from between the resin molded product and the resin molded product. Pressure on the joint portion rises gradually from t ₁ toward t _2. This is because, as described above, the tip of the molten layer is a low-viscosity high-temperature portion, and as the overlap of the molten layers increases and approaches the unmelted portion, it becomes a high-viscosity low-temperature portion. t ₂ is eliminated crushed melt layer, the discharge of the burr is substantially stopped point. At this point, pressure applied to the bonding portion is P _2.

t ₂ later, since the crushed melt layer is eliminated, the pressure applied to the bonding portion is rapidly increased. Then, control is not to apply more pressure to the joint portion at which point the applied pressure P ₃ set.

The applied pressure P ₃ is less 10MPa 7, if even more preferably at 5MPa or less, residual stress remaining in the bonding portion is small, it is possible to reduce the decrease in creep rupture life. The change when the thickness of the molten layer is reduced by the conventional method and a large pressure is applied to the joint portion is shown by a broken line. A point X indicates a case where the applied pressure is set too low. If it is set too low, butting will stop while the burrs are discharged while the molten layers overlap. If the molten layer is not discharged sufficiently, the creep rupture life may be shortened due to defects such as voids remaining in the molten layer.

In the case of FIG. 3, it is necessary to apply pressure to P ₂ or more. This is because the molten layer is not sufficiently discharged as burrs, and defects such as voids remain in the molten layer at the joint portion. Depending on the type of resin or the like, the value of P ₂ is different. Therefore, the applied pressure if it exceeds 0 MPa, P ₂ or more pressure is likely to take the junction.

From the above, applying pressure to set the following 10MPa from _{P 2,} even more preferably it should be set to 5MPa or less.

  The smaller the pressure applied at the time of crimping, the smaller the residual stress, which is preferable. However, if the pressure is too small, the molten layer at the portion to be welded cannot be discharged sufficiently as burrs. Since the molten layer remains in the joint, defects such as voids may remain in the joint, which is not preferable from the viewpoint of stabilizing the creep rupture life. Therefore, in the bonding method of the present invention, it is preferable to perform pressure bonding under conditions such that the molten layer does not substantially remain in the bonded portion.

  Note that “the molten layer does not substantially remain in the joint” means that the minimum thickness of the joint described later is in the range of 100 μm or less.

<Cooling process>
A cooling process is a process of taking out the resin molded product joined by cooling a joined part. The cooling process will be described with reference to FIG.

  After the resin molded products 2 and 3 are bonded, the resin molded products 2 and 3 are left until the molten layer at the bonded portion is solidified. The upper jig 11 is moved in the Y direction and the lower jig 12 is moved in the -Y direction, and the resin molded products 2 and 3 remaining on the lower jig 12 and connected to each other are taken out.

[Joint part]
In the bonding method of the present invention, since the minimum thickness of the bonded portion after cooling is 100 μm or less, it is possible to prevent defects such as voids from remaining in the bonded portion by discharging most of the molten layer as burrs. Instability of creep rupture life can be suppressed.

  Since the melted and hardened portion and the unmelted layer have different crystal structures, a boundary line appears at the boundary. The junction thickness is measured by measuring the distance between the boundary lines.

  Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

<Examples 1-4>
[Joint preparation process]
Using polyacetal (“Duracon M90-44” manufactured by Polyplastics Co., Ltd.) as the resin material, injection molding was performed under the following molding conditions, thereby producing a resin test piece as shown in FIG.
(Molding condition)
Molding machine: ROBOSHOT α-50C (manufactured by FUNUC)
Cylinder temperature: (nozzle) 200 ° C-200 ° C-180 ° C-160 ° C (hopper)
Injection speed: 10mm / s
Holding pressure: 60 MPa
Injection time + pressure holding time: 15 seconds Cooling time: 10 seconds Screw rotation speed: 100 rpm
Screw back pressure: 4MPa
Mold temperature: 80 ℃

  The two resin test pieces were attached to a hot plate welding apparatus (“PW-1” manufactured by Nakamori Industry Co., Ltd.). An outline of the hot plate welding apparatus is shown in FIG. In addition, FIG. 5 is a figure showing the hot plate welding apparatus in the time of the molten layer formation of the following heating process.

[Heating process]
Using the hot plate welding apparatus, the end face of the welded portion was brought into contact with a hot plate that had been heated to 260 ° C. in advance for 20 seconds to form a molten layer on the resin test pieces 6 and 7. FIG. 5 is a diagram showing a heating process. A stopper 8 is used to ensure the thickness of the molten layer. Then, a 0.1 mm thick fluororesin sheet 9 is sandwiched between the resin test piece and the hot plate in order to prevent a stringing phenomenon in which the resin is stretched into a string when the resin test piece is pulled away from the hot plate. The thickness of the molten layer was 0.8 mm as measured by spherulite observation of the cross section of the resin test piece once cooled after melting.

[Crimping and cooling process]
After separating the hot plate 13 from the end surfaces 21 and 31 to be welded, two resin test pieces were pressed against each other for 15 seconds. A spring is used for the pressure load means, and the target pressure (1.2 MPa in Example 1, 4.4 MPa in Example 2, 6.6 MPa in Example 3 and 6.6 MPa in Example 3 in consideration of the spring constant) (9.0 MPa) was set to stop at such a position. Finally, the resin welded product welded from the hot plate welding apparatus 1 was taken out. In all cases, the minimum thickness of the joint was 100 μm or less. The obtained resin welded product is shown in FIG.

  As described above, the bonding method of the present invention in which heat welding is performed by controlling only the pressure is easier than the conventional heat welding method in which the thickness of the molten layer is predicted and the overlapping position of the molten layer is controlled to perform pressure bonding. there were.

<Comparative Example 1>
A resin-welded article was produced in the same manner as in Example 1 except that the abutting position was set at the position of the unmelted layer during the pressure-bonding / cooling step and no pressure control was performed. In addition, the pressure applied between the test pieces at the time of pressure bonding was 33 MPa.

<Comparative example 2>
Resin welded articles were produced in the same manner as in Examples 1 to 4, except that the target pressure was changed to 16.3 MPa.

<Comparative Example 3>
In order to obtain a welded product that does not leave voids in the joint and does not cause excessive contact, the position of the welding allowance is controlled without using a spring by making a registration so that the molten layer thickness of the joint is about 50 μm. Produced a resin welded article in the same manner as in Example 1. Under this condition, in order to find the proper abutting position, the abutting position was changed and welded many times, and the creep rupture life was measured and confirmed. The proper welded product was obtained by changing the abutting position.

<Evaluation 1>
FIG. 6 shows the relationship between the tensile stress and the creep rupture life calculated for the resin welded products of Examples 1 to 4 and the resin welded products of Comparative Examples 1 to 3 based on the axial force / the minimum cross-sectional area perpendicular to the axis. .

  The resin welded products of Examples 1 to 4 were compared with the resin welded product of Comparative Example 1 in which excessive pressure was applied by position control and the resin welded product of Comparative Example 2 in which excessive pressure was applied by pressure control. The creep rupture life was high and stable. The resin welded products of Examples 1 and 2 had a particularly high creep rupture life and were stable, and had a creep rupture life as high and stable as the resin welded product of Comparative Example 3. The resin welded product of Comparative Example 3 is a high quality resin welded product obtained by repeating the production of the resin welded product many times. By performing welding as in Examples 1 and 2 as described above, a very excellent resin welded product can be obtained very easily.

  FIG. 7 shows the relationship between the pressure applied during crimping and the refraction point of the creep rupture life line. It was confirmed that the effect of the present invention was exhibited when the pressure applied during pressure bonding was 10 MPa or less, and that a very excellent resin welded product was obtained when the pressure was 5 MPa or less.

DESCRIPTION OF SYMBOLS 1 Hot plate welding apparatus 11 Upper jig | tool 12 Lower jig | tool 13 Hot plate 2, 3 Resin molded product 21, 31 End surface of welding part 22, 32 Molten layer 4 Joining part 5 Burr 6, 7 Resin test piece 8 Stopper 9 Fluoro resin Sheet

Claims (4)

The end surfaces of the two resin molded products that can be welded are heated, and the molten layers of the two resin molded products are pressure-bonded to each other in a state in which a melt layer is formed on the two resin molded products. A method of joining resin molded products that are welded by
The pressure applied at the time of the pressure bonding is more than 0 MPa and not more than 10 MPa, and the minimum thickness of the bonded portion formed by the molten layer that is not discharged even by the pressure bonding is not more than 100 μm. A method for joining resin molded products characterized by the above.   The method for joining resin molded products according to claim 1, wherein a pressure applied at the time of the pressure bonding is more than 0 MPa and not more than 5 MPa.   The method for joining resin molded products according to claim 1, wherein at least one of the two resin molded products includes a crystalline thermoplastic resin.   The method for joining resin molded products according to claim 3, wherein the crystalline thermoplastic resin is polyacetal.

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