JPWO2018216804A1 - Method of joining resin molded products - Google Patents

Abstract

A joining method for joining a resin molded product made of a resin composition, wherein a joining of a first molded product (101) transmitting laser light and / or a second molded product (102) absorbing laser light is scheduled. After irradiating the irradiation surface (101a) and / or the irradiation surface (102a) with vacuum ultraviolet light, the irradiation surface (101a) and the irradiation surface (102a) are arranged so as to be in contact with each other, and the laser is irradiated from the first molded article (101) side. The laser light that has been irradiated and transmitted through the first molded article (101) is absorbed by the irradiation surface (102a) of the second molded article (102), and is heated and melted to perform laser welding.

Description

  The present invention relates to a method for joining resin molded articles, which is performed by irradiating ultraviolet light and then performing laser welding.

  BACKGROUND ART Conventionally, resin molded products obtained by injection molding a thermoplastic resin have been used in various fields such as automobile parts, electric / electronic device parts, and daily necessities. Such a resin molded product may be used as a composite molded product in which a plurality of resin molded products are joined to each other for the purpose of forming a three-dimensional hollow body and simplifying the process of assembling parts.

  In order to join resin molded products, various joining techniques such as adhesives and heat welding are provided. However, the technique of joining the resin molded product with an adhesive can be performed without deforming the resin molded product. However, in general, it takes several hours to cure the adhesive, resulting in poor productivity and flow path. In a three-dimensional hollow body having a fine hollow portion such as a part, there is a problem that the adhesive leaks into the hollow portion and the groove is buried. The technique of heat-welding resin molded products can be joined in a matter of minutes, but welding techniques such as hot plate welding, vibration welding, and ultrasonic welding cause burrs or thermal deformation on the joined resin molded products. In some cases, or damage to components housed inside. Although the use of laser welding as disclosed in Patent Document 1 suppresses burrs, deformation, and the effects on internal components, these heat welding techniques melt the surfaces of the resin molded articles to be joined together to form a joint. Since it is solidified in a melted state, there is a problem that molded products made of resins having high chemical affinity (compatibility), that is, basically limited to joining of the same material.

  In addition, there is provided a technique of processing and joining a resin molded product by vacuum ultraviolet light (VUV) (see Patent Literature 2-5 and Non-Patent Literature 1). According to this technique, it takes several minutes to several tens of minutes to join the resin molded products, but deformation of the joined resin molded products is small. However, Patent Literatures 2 and 3 and Non-Patent Literature 1 assume that a resin molded product is made of an amorphous resin such as polymethyl methacrylate (PMMA) resin or cyclic olefin resin, and the bonding strength is 1 MPa or less. . Patent documents 4 and 5 assume silicone bonding.

  Furthermore, a double molding (double shot molding) technique in which a resin molded article is primarily molded with the resin composition, and the resin molded article is additionally molded with the resin molded article to form a final resin molded article. Is provided. By the technique of double molding, resin molded articles combining materials of different properties or materials of different colors are integrally molded and used for various products. However, in double molding, in order to secure the strength of the portion where the resin is joined by the secondary molding, mechanical reinforcement such as provision of an anchor such as a through hole or an undercut may be provided at the joining portion. In addition, in double molding, since the step of inserting the primary molded product into the mold and then performing the secondary molding is performed, it is necessary to perform the shape design taking into account the installation in the mold and the release. There was a problem that the degree of freedom was poor. Furthermore, when performing double molding by housing electronic components and the like inside a composite molded product, these components are placed in a mold together with the primary molded product and secondary molding is performed. In some cases, double molding cannot be applied as a joining technique because parts housed inside may be damaged depending on pressure and pressure.

Japanese Patent Publication No. 9-510930 JP 2006-187730 A JP 2009-173894 A JP 2011-148104 A JP 2013-147018 A

Yoshinao Taniguchi and 4 others, "Jointing of cycloolefin polymer by photosurface activation: Evaluation of joining strength and application to microchannel", Surface Technology, Surface Technology Association, 2014, Vol. 65, No. 5, p. 36-41

  On the other hand, molded articles requiring mechanical strength, heat resistance and chemical resistance include thermoplastic crystalline resins such as polybutylene terephthalate (PBT) resin and polyphenylene sulfide (PPS) resin, which have robust and stable properties. Can be used. In addition, when a composite molded article is produced by joining resin molded articles made of a resin composition, the deformation of the resin molded article due to joining is small, and a composite molded article having high joining strength can be manufactured with high productivity. Is required.

  The above-mentioned technology of processing and joining resin molded products with vacuum ultraviolet light was able to suppress deformation of the resin molded products to a small extent.However, joining of resin molded products made of amorphous resin and curing of silicone adhesives were difficult. It was assumed, and sufficient bonding strength could not be secured.

  On the other hand, when the resin composition is joined by double molding, a large amount of heat is required to melt the resin of the primary molded article, so that a sufficient welding state cannot be obtained and the joining strength may not be secured. Was. In particular, when a crystalline thermoplastic resin composition is used for a primary molded product, a larger amount of heat is required to melt the crystallized resin. In addition, in order to join resins having low compatibility, it is necessary to reinforce with a physical structure such as an anchor in order to increase the joining strength. Naturally, such a reinforcing structure is provided in a resin molded product. Since there is a need to secure such a space, there is a problem in that the design is restricted and the degree of freedom in shape is reduced. And, in the joining by heat welding, since it is a technique of melting only the surface layer portion of the resin molded article and joining, it is difficult to reinforce with a physical anchor in the first place, and it is difficult to join resins having low compatibility with each other. That is as described above.

  The present invention has been proposed in view of the above-described circumstances, and relates to a resin molded article manufactured using a resin composition, which is capable of obtaining a high bonding strength while suppressing deformation of the resin molded article to be small. An object of the present invention is to provide a joining method for manufacturing a molded product with high productivity and high degree of freedom in shape.

  The method for joining a resin molded article according to the present invention is a joining method for joining a resin molded article made of a resin composition, wherein the first molded article made of a resin composition that transmits a laser beam and / or a laser beam is absorbed. After irradiating the region of the second molded product made of the resin composition to be joined with ultraviolet light to the region where bonding is to be performed, and arranging the region of the second molded product in contact with the region of the first molded product, The first molded article is irradiated with laser light to absorb the laser light transmitted through the first molded article in the area of the second molded article, and the interface where the areas of the first molded article and the second molded article are in contact with each other Is heated and melted, and then cooled and solidified to join the first molded article and the second molded article. The heating and melting of the interface between the first molded article and the second molded article in contact with the region may include stirring the resin composition constituting the first molded article and the second molded article at the interface.

The resin composition may include a thermoplastic crystalline resin. The ultraviolet light may be vacuum ultraviolet light. Furthermore, the resin composition constituting the first molded article and the second molded article may have a melt viscosity of 300 Pa · s or less measured at a melting point of the resin + 30 ° C. and 1000 sec ⁻¹ . The resin compositions forming the first molded article and the second molded article may be the same or different.

According to the present invention, a composite molded article produced by laser welding has high bonding strength. In addition, it is possible to manufacture a composite molded product excellent in productivity and shape flexibility while suppressing deformation of the resin molded product, particularly deformation of the hollow portion in the resin molded product constituting the three-dimensional hollow body.
Furthermore, according to the present invention, even when the resin compositions constituting the plurality of resin molded articles before being joined are made of different materials, the resin composition has high joining strength, small deformation, productivity and shape freedom. An excellent composite molded article can be manufactured.

It is a figure showing roughly a series of steps of a joining method of a resin molding. It is a photograph which shows the example of a vacuum ultraviolet light irradiation apparatus. It is a figure showing the shape of the composite molded article produced in the example.

  Hereinafter, embodiments of a method for joining resin molded articles according to the present invention will be described in detail with reference to the drawings. In the present embodiment, it is assumed that a composite molded article in which a resin molded article obtained by injection-molding a resin composition is joined by laser welding is produced, and a thermoplastic resin composition is used as the resin composition. In a resin molded product joined by laser welding, for convenience, the side that transmits laser light is referred to as a first molded product, and the side that absorbs laser light is referred to as a second molded product.

The thermoplastic resin composition comprises a composition containing a thermoplastic crystalline resin and / or a thermoplastic amorphous resin. As the thermoplastic crystalline resin, for example, polyoxymethylene (POM), polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyphenylene sulfide (PPS), or liquid crystal polymer (LCP) may be used. As the thermoplastic amorphous resin, for example, polycarbonate (PC), cyclic polyolefin (COP), or cyclic polyolefin copolymer (COC) may be used. Thermoplastic crystalline resins are generally opaque, but resins with low crystallinity may be translucent or transparent. In addition, the thermoplastic resin composition includes various fillers generally added to the resin composition, such as fillers such as glass fibers, antioxidants and stabilizers, nucleating agents, lubricants, plasticizers, release agents, and coloring agents. The additive may be added in a range that does not significantly impair the laser transmittance of the first molded article. The viscosity of the thermoplastic resin composition can be appropriately selected according to the thickness of the resin molded product to be obtained, within a range where the necessary moldability is obtained, but the resin is easily mixed at the bonding interface of laser welding. In light of the viewpoint, the melt viscosity of the thermoplastic resin composition is preferably low, and the melt viscosity at 1000 sec ^-1 measured at the melting point + 30 ° C is preferably 300 Pa · s or less. The lower limit of the melt viscosity is not particularly limited. However, if the melt viscosity is extremely low, there is a concern that the physical properties of the resin may be deteriorated due to an excessively low molecular weight.

  In the present embodiment, a first molded article and a second molded article produced by injection molding of a resin composition are arranged such that respective joining scheduled areas (surfaces irradiated with vacuum ultraviolet light) are in contact with each other, The first molded article made of a resin composition that transmits laser light is irradiated with a laser beam toward the joining area, and a laser beam is applied to the second molded article made of the resin composition that absorbs the laser light. Light is absorbed to generate heat at the interface of the region where the first molded article and the second molded article are to be joined, and after heating and melting, they are cooled and solidified to join them. The joining planned area of the first molded article and the second molded article includes opposing surfaces whose surfaces can come into contact with each other. Since the opposing surface of the second molded article and the opposing surface of the first molded article are in close contact with each other without gaps, the melted interface is efficiently welded, so that these opposing surfaces have corresponding shapes. ing. For example, if the opposing surface of the first molded product is substantially flat, the opposing surface of the second molded product is also substantially flat corresponding thereto. Further, the facing surface may be a surface having irregularities. For example, if the opposing surface of the first molded product has an uneven shape, the opposing surface of the second molded product also has a corresponding uneven shape.

FIG. 1 is a diagram schematically illustrating a series of steps of the present embodiment. Figure 1 (a), the first molded product 10 ₁ and providing a second molded article 10 _2, a first molded article with ultraviolet light irradiation device 20 10 ₁ of the irradiated surface 10 ₁ a and the second irradiating ultraviolet light (UV) to the irradiated surface 10 ₂ a of the molded product 10 _{2. 1} and a radiation surface 10 of the first molded product 10 _1, and the second molded product 10 _second irradiation surface 10 ₂ a, an area (opposing surface) of the bonding is scheduled together.

  Here, ultraviolet light refers to light having a wavelength of 380 nm or less. In particular, ultraviolet light having a wavelength of 200 nm or less is called vacuum ultraviolet light (VUV). Note that the vacuum ultraviolet light does not necessarily have to be irradiated in a vacuum, but since ultraviolet light in the wavelength range has a large absorption by air, when irradiated in air, the distance over which the vacuum ultraviolet light propagates Need to be shorter. It is preferable to use vacuum ultraviolet light because the shorter the wavelength of ultraviolet light is from the viewpoint of bonding strength, the more advantageous it is to use vacuum ultraviolet light. Whether or not to emit light may be appropriately adjusted depending on the type of resin used.

  In FIG. 1A, an ultraviolet light irradiation device 20 is a vacuum ultraviolet light irradiation device having a light source 21 such as a Xe excimer lamp and a reflector 22 for reflecting light emitted from the light source 21 toward an irradiation object. is there. FIG. 2 is a photograph showing an example of a vacuum ultraviolet light irradiation device. The vacuum ultraviolet light irradiation device shown in this photograph can irradiate ultraviolet light upward from an opening formed in the upper surface of the housing. Hereinafter, the ultraviolet light irradiation device 20 and the ultraviolet light may be referred to as the vacuum ultraviolet light irradiation device 20 and the vacuum ultraviolet light.

As shown in FIG. 1 (a), first molded product 10 ₁ has a generally flat illumination surface 10 ₁ a, the second molded product 10 ₂ has a substantially flat illumination surface 10 ₂ a. In this embodiment, the vacuum ultraviolet light irradiation toward the vacuum ultraviolet light irradiation device 20 in the first molded product 10 ₁ of the irradiated surface 10 1 _a and the irradiation surface 10 2 _a of the second molded product 10 _2. Such irradiation treatment, the first molded product 10 ₁ of the irradiated surface 10 ₁ a and the second irradiated surface 10 ₂ a of the molded product 10 _2, to a predetermined depth from the irradiated surface 10 ₁ a and the irradiation surface 10 ₂ a treatment layer 11 ₁ and the processing layer 11 ₂ that property changes of the resin composition is formed.

In this embodiment, the irradiation time of the first molded product 10 ₁ and the second molded product 10 ultraviolet light to ₂ (vacuum ultraviolet light) can be set as appropriate in consideration of the illuminance on the irradiated surface. For example, when irradiating ultraviolet light (vacuum ultraviolet light) under the conditions of an irradiation distance of 10 mm and an illuminance of 6 mW / cm ² , the irradiation time may be, for example, 7 minutes, but is not limited to 7 minutes, and is 0 minutes. The time may be longer than 15 minutes. Further, the time may be 30 seconds or more and 10 minutes or less (for example, 1 minute or more and 8 minutes or less). By irradiation with ultraviolet light, since that deterioration of the first molded product 10 ₁ of the irradiated surface 10 1 _a and the second molded product 10 _second irradiation surface 10 2 _a proceeds, the rather bonding strength may be lowered, the 1 irradiation of the ultraviolet light to the molded article 10 ₁ and the second molded product 10 ₂ is preferably within a predetermined time.

Since the illuminance varies depending on the irradiation distance (distance from the light source to the irradiation surface) and the output of the irradiation device, the irradiation condition of the ultraviolet light is based on the irradiation energy amount obtained from the product of the illuminance and the irradiation time. You may decide. The irradiation energy amount may be at 0.1 J / cm ² or more 10J / cm ² or less, also 0.5 J / cm ² or more 6J / cm ² or less (e.g., 1 J / cm ² or more 3J / cm ² or less) It may be. That is, when the illuminance is increased by increasing the output of the irradiation device and shortening the irradiation distance, the irradiation time can be shortened, so that the processing can be performed in a shorter time. However, in that case, there is a possibility that processing unevenness is likely to occur due to the influence of unevenness or warpage of the bonding surface. The irradiation of ultraviolet light, not must be both the first molded product 10 ₁ and the second molded product 10 _2, first forming 10 ₁ or the second molded product 10 ₂ either to only one Irradiation.

As shown in FIG. 1 (b), arranging the first molded product 10 ₁ and the second molded product 10 ₂ vacuum ultraviolet light is irradiated so that respective irradiation surface 10 1 _a and the irradiation surface 10 2 _a contact .

Here, in order to secure higher bonding strength, the operation of placing the first molded product 10 ₁ and the second molded product 10 _2, first forming 10 ₁ and the second molded product 10 ₂ to ultraviolet light ( It is desirable that the irradiation be performed in as short a time as possible after the step of irradiating (vacuum ultraviolet light) (see FIG. 1A) is completed. The time is, for example, preferably within 10 days, more preferably within 1 day, further preferably within 2 hours, particularly preferably within 30 minutes, most preferably within 5 minutes.

As shown in FIG. 1 (c), by using a laser beam irradiation apparatus 30 irradiates a laser beam from the first molded product 10 ₁ side, the laser beam transmitted through the first molded product 10 ₁ second forming 10 by being absorbed into _2, and heating the interface of the irradiated surface 10 ₁ a and the irradiation surface 10 ₂ a is, the resin composition constituting the first molded product 10 ₁ and the second molded product 10 ₂ is heated and melted. In the figure, a laser beam 200 emitted from a laser beam irradiation device 30 is focused so that a focus point 201 is located near the interface between the irradiation surface 10 ₁ a and the irradiation surface 10 ₂ a.

As shown enlarged in the vicinity of the first molded product 10 ₁ and the second molded product 10 _{and second} focal point 201 in FIG. 1 (d), constituting the first molded product 10 ₁ and the second molded product 10 ₂ The resin composition is melted at the laser beam converging point 201 located near the interface between the irradiation surface 10 ₁ a and the irradiation surface 10 ₂ a to form a fusion portion 12. In the melting section 12, by receiving the energy of the further laser beam while the resin composition is melted, the molten metal flow (stirring) 12a is generated at the interface, the first molded product 10 ₁ and the second molded product 10 ₂ Are in a mixed state.

Here, the higher the compatibility of the resin composition constituting the first molded product 10 ₁ and the second molded product 10 _2, but still are cooled and solidified in a state where the interface is mixed, the compatibility is resin composition In the case of the combination, the resin composition undergoes phase separation in the process of cooling and solidifying by ordinary laser welding, and sufficient bonding properties cannot be obtained. However, as in the present embodiment, the irradiation of the pre-ultraviolet light, if the first molded product 10 ₁ and the second molded product 10 _second surface if activated, the compatibility of the resin composition constituting each Is low, the mixture is cooled and solidified while maintaining a mixed state of the interfaces. Accordingly, the first molded product 10 ₁ and the second molded product 10 ₂ are joined integrally, so constituting a single composite molded article (e.g., three-dimensional hollow bodies). Note that, even in the case of a combination of highly compatible resin compositions, if irradiation with ultraviolet light is performed as in this embodiment, mixing of the resin at the interface is promoted, and ultraviolet light is emitted. Even better bonding properties can be obtained than when no irradiation is performed.

  In recent years, demands for integrating and integrating multiple components for miniaturization and weight reduction have led to the demand for so-called dissimilar composite moldings, which are made by joining resin molded products made of resins with low compatibility. Has also become. The joining method of the present embodiment is excellent in joining strength, productivity, and shape freedom even in the production of a composite molded article by dissimilar material joining.

The first molded product 10 ₁ and the bonding between the second molded product 10 _2, the processing layer 11 _second treatment layer 11 ₁ and the second molded product 10 ₂ of first molded product 10 ₁ is activated by the vacuum ultraviolet light It is heated, melted and stirred by the energy of laser light. Therefore, the connection of the first molded product 10 ₁ and the second molded product 10 ₂ are mechanically robust, which is chemically stable.

In this embodiment, the processing layer 11 ₁ and the processing layer 11 ₂ is formed on the first molded article 10 ₁ and the second molded product 10 _2, melting and stirring only treatment layer 11 ₁ and the processing layer 11 ₂ by laser welding to the first molded product 10 ₁ is intended to connect the second molded product 10 _2. Therefore, since excessive heat, pressure, vibration, etc. are not applied to the entire molded product, deformation and burrs due to joining are suppressed, and even if components are housed inside, they may be damaged. Nor.

  In the present embodiment, a thermoplastic resin composition containing a thermoplastic crystalline resin and / or a thermoplastic amorphous resin can be used as the resin composition. Examples of the thermoplastic crystalline resin include polyoxymethylene (POM), polybutylene terephthalate (PBT) resin, polyethylene terephthalate (PET) resin, polyphenylene sulfide (PPS) resin, and liquid crystal polymer (LCP) having robust and stable properties. Such thermoplastic crystalline resins can be used, and examples of the thermoplastic amorphous resin include thermoplastic amorphous resins such as polycarbonate (PC), cyclic polyolefin (COP), and cyclic polyolefin copolymer (COC). Resin can be used. In particular, a thermoplastic crystalline resin can be used for producing a resin molded product requiring mechanical strength, heat resistance, and chemical resistance.

An example to which the above-described embodiment is applied will be described. FIG. 3 shows the shape of the composite molded product. In the example of FIG. 3, the laser-transmissible resin composition to prepare a first shaped article 10 ₁ of the injection molded to 40 × 10 × 1mm, 50 × 13 × injection molded laser absorptive resin composition to produce a second molded product 10 ₂ 3 mm, the first molded product 10 ₁ of 40 × 10 mm irradiated surface 10 ₁ a and the respective vacuum ultraviolet light irradiation surface 10 ₂ a of the second 50 × 13 mm of the molded product 10 ₂ (Wavelength 172 nm, output voltage 16 kV, irradiation distance 10 mm (illuminance 6 mW / cm ² ), irradiation time 7 minutes). By irradiation with vacuum ultraviolet light, the first molded product 10 ₁ of the irradiated surface 10 ₁ a and the second irradiated surface 10 ₂ a of the molded product 10 _2, to a predetermined depth from the irradiated surface 10 ₁ a and the irradiation surface 10 ₂ a treatment layer 11 ₁ and the processing layer 11 ₂ that property changes of the resin composition is formed.

After irradiation with vacuum ultraviolet light to the first molded product 10 ₁ and the second molded product 10 _2, first molded product 10 ₁ of the irradiated surface 10 ₁ a and the second molded product 10 _second irradiation surface 10 ₂ a from each other 10 in contact with an area of × 10 mm, it was first molded article 10 ₁ and be overlapped portion of the predetermined distance from the second molded product 10 ₂ each longitudinal end disposed. Then, at a substantially central portion of the overlapping portion, the laser beam from the first molded product 10 ₁ side (wavelength 940 nm, output 24W, a beam diameter 1.6 mm, the scanning speed of 20 mm / sec) and, in the longitudinal direction of the composite molded article irradiated so as to scan in a perpendicular direction against the first molded product 10 ₁ and the second molded product 10 ₂ laser welding to form a molten part 12 in the region of 1.6 mm × 6 mm, to prepare a composite molded article .

A combination of the following resin compositions was used for the first molded article and the second molded article.
-Example 1
First molded product: PBT Duranex (registered trademark) 2002 manufactured by Wintech Polymer Co., Ltd. (non-reinforced PBT resin composition, melt viscosity at 250 ° C., 1000 sec ⁻¹ 260 Pa · s)
Second molded product: PPS DURAFIDE (registered trademark) 1130A1 (PPS resin composition reinforced with 30% by mass of glass fiber, melt viscosity at 310 ° C., 1000 sec ⁻¹ at 350 sec · ¹ ) manufactured by Polyplastics Co., Ltd.
-Example 2
First molded product: PBT Duranex (registered trademark) 2002 manufactured by Wintech Polymer Co., Ltd. (non-reinforced PBT resin composition, melt viscosity at 250 ° C., 1000 sec ⁻¹ 260 Pa · s)
Second molded product: PPS DURAFIDE (registered trademark) 1130A6 (PPS resin composition reinforced by 30% by mass of glass fiber, melt viscosity at 310 ° C., 1000 sec ⁻¹ at 220 sec · ¹ ) manufactured by Polyplastics Co., Ltd.

In addition, as Comparative Example 1, the same operation as in Example 1 except that vacuum ultraviolet light irradiation was not performed before laser welding was also evaluated. In addition, as a combination of resin compositions having high compatibility, bonding of the same materials was also evaluated. Specifically, as Example 3, PBT Duranex (registered trademark) 2002 (non-reinforced PBT resin composition, 250 ° C., 1000 sec ⁻¹ ) manufactured by Wintech Polymer Co., Ltd. Of Comparative Example 2 except that the melt viscosity at 260 Pa · s was used, and Comparative Example 2 was the same as Example 3 except that vacuum ultraviolet light was not irradiated before laser welding. The operation was also evaluated.

  The composite molded product of Example 1 was subjected to a tensile test at 5 mm / min using a tensile tester (manufactured by Shimadzu Corporation, Autograph AG-20kNXDplus) to measure the tensile shear strength. Was 12.1 MPa for the composite molded product of Example 2 and 18.5 MPa for the composite molded product of Example 2, whereas it was 0 MPa (no bonding) in Comparative Example 1. The composite molded product of Example 3 had a pressure of 32.0 MPa, while Comparative Example 2 had a pressure of 28.2 MPa.

  As in Comparative Example 1, in the case of ordinary laser welding without irradiation with ultraviolet light, it was not possible to join a resin molded product made of a PBT resin composition and a PBT resin composition, which are dissimilar materials with low compatibility. In Example 1 and Example 2 in which laser welding was performed after the irradiation, the composite molded article in which resin molded articles of different materials were joined to each other had sufficient bonding strength. In addition, in Example 2, a higher bonding strength was obtained than in Example 1, and it is understood that a lower melt viscosity of the resin composition is more advantageous in terms of bonding strength. This is considered to be due to the easiness of the molten metal flow (stirring) at the molten interface. Further, as can be seen from a comparison between Comparative Example 2 and Example 3, even in laser welding using a combination of the same materials, even higher bonding strength was obtained by performing a pretreatment by ultraviolet light irradiation.

Further, as Example 4, evaluation was also made on the same operation as in Example 1 except that the combination of the resin compositions was changed as follows and the output of the laser beam during welding was set to 30 W.
First molded product: PBT Duranex (registered trademark) 2002 manufactured by Wintech Polymer Co., Ltd. (non-reinforced PBT resin composition, melt viscosity at 250 ° C., 1000 sec ⁻¹ 260 Pa · s)
Second molded product: PPS DURAFIDE (registered trademark) 0220A9 (non-reinforced PPS resin composition, 310 ° C., melt viscosity at 1000 sec ⁻¹ 500 Pa · s) manufactured by Polyplastics Co., Ltd.

Further, in order to confirm the influence of the wavelength of ultraviolet light, as Example 5, in the same manner as in Example 4 except that ultraviolet light having a wavelength of 254 nm was irradiated for 7 minutes at an illuminance of 6 mW / cm ² instead of vacuum ultraviolet light. The operation and the comparative example 3 were also evaluated in the same manner as in Example 4 except that vacuum ultraviolet light was not irradiated before laser welding.

  The composite molded article produced as described above was subjected to a tensile test at 5 mm / min using a tensile tester (manufactured by Shimadzu Corporation, Autograph AG-20kNXDplus), and the tensile shear strength was measured. As a result, in Example 4, 19.8 MPa was obtained. In Example 5, it was 11.0 MPa, and in Comparative Example 3, it was 9.8 MPa. By irradiating ultraviolet light, particularly vacuum ultraviolet light as pretreatment, it was confirmed that the bonding strength of laser welding was increased. .

In addition, as a resin composition, PBT Duranex (registered trademark) 2002 (a non-reinforced PBT resin composition manufactured by Wintech Polymer Co., Ltd., melted at 250 ° C. and 1000 sec ⁻¹ ) is used for both the first molded article and the second molded article. Example 6 and Example 6, each operated in the same manner as Example 4, Example 5, and Comparative Example 3 except that a laser beam output during welding was set to 24 W using a combination of the same materials having a viscosity of 260 Pa · s). As a result of evaluation of Example 7 and Comparative Example 4, the tensile shear strength was 27.2 MPa in Example 6 irradiated with vacuum ultraviolet light, 15.7 MPa in Example 7 irradiated with ultraviolet light, and (vacuum) ultraviolet. In Comparative Example 4 in which no light was irradiated, the pressure was 10.1 MPa, and, similarly to the tendency in Examples 4, 5, and Comparative Example 3 in which bonding was performed using dissimilar materials, ultraviolet light, Irradiates vacuum ultraviolet light And, the bonding strength of the laser welding that increases was confirmed.

10 ₁ First molded product 10 ₂ Second molded product 12 Melting part 12a Hot water flow (stirring)
20 UV light irradiation device (Vacuum UV light irradiation device)
30 Laser light irradiation device

Claims (6)

A joining method for joining a resin molded product made of a resin composition,
Irradiating ultraviolet light to a region where bonding is planned, of a first molded product made of a resin composition that transmits laser light and / or a second molded product made of a resin composition that absorbs laser light,
After arranging the area of the second molded article in contact with the area of the first molded article,
Irradiating a laser beam from the first molded product side, the laser light transmitted through the first molded product is absorbed in the region of the second molded product,
After heating and melting the interface where the regions of the first molded article and the second molded article are in contact with each other with a laser beam, solidify by cooling, and join the first molded article and the second molded article. Method.   The heating and melting by the laser light at the interface where the regions of the first molded article and the second molded article are in contact with each other is to stir the resin composition constituting the first molded article and the second molded article at the interface. The bonding method according to claim 1, comprising:   The bonding method according to claim 1, wherein the resin composition includes a thermoplastic crystalline resin.   The bonding method according to claim 1, wherein the ultraviolet light is vacuum ultraviolet light. The resin composition constituting the first molded article and / or the second molded article has a melting viscosity of 300 Pa · s or less measured at a melting point of + 30 ° C. and 1000 sec ^−1. The joining method according to the paragraph.   6. The resin composition according to claim 1, wherein the resin composition constituting the first molded article and the resin composition constituting the second molded article are resin compositions mainly composed of different resins. The joining method according to the paragraph.