JP2005131902A - Injection welding molding method for resin molding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a molding method which enhances bonding strength brought about by injection welding, by optimizing the property of a part, serving as a surface to be joined with a secondary molding, of a primary molding. <P>SOLUTION: The secondary molding is molded by injecting a secondary molding material as the same thermoplastic resin to the primary molding premolded from a thermoplastic resin such as a polyamide, so that the primary molding can be joined to the secondary molding by the injection welding while being remelted. Temperatures of molten resins when the primary and secondary moldings are molded are each set higher by the order of 50-100°C than a melting point of a material itself, and a difference between a temperature of a mold and a temperature of a molten resin when the primary molding is molded is set to be in the range of 220°C±20°C. According to such conditions, a skin layer of the part, serving as the surface to be joined with the secondary molding, of the primary molding is made ultrathin, so that the bonding strength brought about by the injection welding can be increased. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for injection-welding a thermoplastic resin molded product frequently used for molding a hollow container or the like, and in particular, a die slide injection method (Die Slide Injection = DSI method) or a die rotary injection method (Die Rotary Injection = DRI method). ), For example, if a primary molded body is molded, the mold is temporarily opened while the primary molded body remains in the cavity, and a cavity for molding the secondary molded body is formed by sliding the mold. It relates to an injection welding molding method in which a mold is clamped again after being secured, a secondary molding material is injected to form a secondary molded body, and simultaneously joined to the primary molded body by injection welding (fusion). It is.

  The die rotary injection method is a hollow product molding method based on a die rotation method based on the die slide injection method, and the mold performs primary molding and secondary molding while repeating normal rotation and inversion every 120 degrees, for example. The molding method is performed at the same time, and is a highly productive molding method in which one molded product is obtained for each opening and closing operation of the mold.

  For example, Patent Document 1 discloses a technique for molding a hollow container such as a reservoir tank disposed in an engine room of an automobile by an injection welding molding method based on a die slide injection method.

In the technique described in Patent Document 1, after molding the primary molded body and before molding the secondary bonding layer as the secondary molded body by injection of the secondary molding material, After attaching interior parts such as filters, the primary molded bodies are butted together, and then the secondary bonding layer is formed, so that the three parts are integrated while holding the interior parts between the primary molded bodies. We are trying to weld.
JP 2002-59454 A

  In the joining by injection welding as described above, for example, a welding mechanism or molding conditions for obtaining an appropriate welding strength is obtained, although it is said that a larger welding joint strength is obtained as compared with vibration welding widely used conventionally. The reality is that the correlation with the above has not been fully elucidated, and it is most important that there is no decrease or variation in weld joint strength, especially in order to ensure airtightness and pressure resistance as a hollow container. Nevertheless, sometimes the weld joint strength decreases and varies, and there is still room for improvement in terms of stability and reliability of the weld joint strength.

  In particular, there is clearly a temperature difference based on the time difference at the start of injection between the primary molded body and the secondary bonded layer that is the secondary molded body by injection of the secondary molding material. The secondary molded resin material is filled into a predetermined space while transferring heat to the surface of the primary molded body which has already been solidified at the interface and remelting a part thereof. For this reason, the properties of the portion to be the joint surface with the secondary bonding layer in the primary molded body is an important factor in improving the welded joint strength, and there is a strong demand for optimization of the properties of the portion.

  The present invention has been made paying attention to such problems, and optimizes the properties of the portion of the primary molded body that should become the joint surface with the secondary molded body, thereby strengthening the joint portion by injection welding. An object of the present invention is to provide an improved molding method.

  According to the first aspect of the present invention, by injecting a secondary molding material that is also a thermoplastic resin into a primary molded body that is previously molded with a primary molding material that is a thermoplastic resin, a secondary bonding layer is molded. The premise is an injection welding molding method in which a part of the primary molded body is remelted and welded to the secondary molded body by injection welding.

  Then, the molten resin temperature of the primary molding material at the time of molding the primary molded body is set to be about 50 to 100 ° C. higher than the melting point of the primary molding material itself, and at least the secondary bonding layer of the primary molded body It is characterized in that the skin layer of the part to be the joint surface is extremely thinned.

  The above-mentioned skin layer has a so-called amorphous structure formed by first contacting the mold and being cooled. However, the higher the molten resin temperature, the slower the solidification. It tends to be thinner.

  In the above-described method, as described in claim 2, after the two halved primary molded bodies that have been molded in advance with the primary molding material that is a thermoplastic resin are butted together, By injecting the secondary molding material, which is a plastic resin, and molding the secondary bonding layer as a secondary molded body, the primary molded bodies are joined by injection welding while remelting a part of the primary molded body. This method is also included.

  For example, two primary molded bodies that have been molded in advance are set in a mold, preheated, both primary molded bodies are butted together, and then a secondary molding material is injected to form a secondary molded body. Thus, the primary molded bodies are joined by injection welding while remelting a part of the primary molded bodies.

  Of course, as described in claim 3, the primary molded body and the welding joint by the secondary bonding layer may be continuously performed by a die slide injection method (including a die rotary injection method). .

  As the molding material, for example, as described in claim 6, one or both of the primary molding material and the secondary molding material is polyamide, polyacetal, or polyester.

  In this case, as described in claim 7, one or both of the primary molding material and the secondary molding material may be fiber reinforced resin having glass fibers or the like as reinforcing fibers.

  Therefore, in the invention according to the first aspect, the secondary molding material remelts the surface layer portion of the primary molded body during the secondary molding, and dissolves a special ultrathin skin layer on the outermost surface with good compatibility. However, the primary molded body and the secondary molded body are joined by injection welding by forming an amorphous structure weld layer on both interfaces. For this reason, the weld joint strength at the weld joint is greatly improved, and the variation is reduced, so that the weld joint strength can be stabilized.

  In particular, as described in claim 4, the molten resin temperature of the secondary molding material when molding the secondary molded body is set higher by about 50 to 100 ° C. than the melting point of the secondary molding material itself, or As described in 5, the temperature difference between the mold temperature and the molten resin temperature when molding the primary molded body is set in the range of 220 ° C. ± 20 ° C., thereby improving the welding joint strength and stabilizing effect. Becomes more prominent.

  1 and the following drawings show a preferred embodiment of the present invention. Here, an oil reservoir tank (hereinafter simply referred to as an oil reservoir tank for a power steering system) disposed in an engine room of an automobile as a hollow container that is a resin molded product. An example in the case of molding 1) (referred to as a tank) is shown.

  As shown in FIGS. 1 and 2, the tank 1 includes a halved upper tank 2 and a lower tank 3 as primary molded bodies, and a filter 4 that is an interior part. Each of the upper tank 2 and the lower tank 3 is formed in a substantially bottomed cylindrical shape which is a half-divided shape by polyamide (for example, nylon 6 (registered trademark)) which is a thermoplastic resin material, and the opening surfaces of both are abutted. The tank body is formed. An oil supply port 5 is formed in the upper tank 2, and a return tube 6 and an outlet tube 7 are integrally formed in the lower tank 3, and a filter 4 is positioned on the inner periphery of the lower tank 3 as will be described later. An annular groove 8 (see FIG. 3) is formed.

  The filter 4 is made of resin and has a cylindrical shape with an upper flange 9 and a lower flange 10 on the upper and lower sides. A mesh-like filter element 12 is integrally formed as a filter medium on the upper surface and the opening of the cylindrical portion 11. Yes. When the filter 4 is inserted into the lower tank 3, as shown in FIG. 3, the lower flange 10 engages with the annular groove 8, while the clamping piece 13 on the periphery of the upper flange 9 contacts the opening surface of the lower tank 3, The filter 4 is positioned with respect to 3.

  Then, the lower tank 3 and the upper tank 2 in which the filter 4 is inserted as described above are butted together while sandwiching the sandwiching pieces 13 of the upper flange 9 with the respective opening surfaces as butting surfaces, and the outer periphery of the butting portion By forming an annular belt portion 14 as a secondary bonding layer as a secondary molded body on the side, the upper tank 2, the filter 4 and the lower tank 3 are integrated by injection welding based on the molding of the belt portion 14. Will be.

  The tank 1 is formed by, for example, an injection molding method as shown in FIG. 4 and subsequent drawings based on a die slide injection method.

  The injection mold shown in FIG. 4 includes a movable mold 15 that moves forward and backward by an expansion / contraction operation of a mold clamping cylinder (not shown), and a slide mold that slides by an expansion / contraction operation of the shift cylinder 16 at a position facing the movable mold 15. The movable mold 15 has a cavity for forming the upper tank 2 described above, and the slide mold 17 has a cavity for forming the lower tank 3. Then, as shown in the figure, when the mold is clamped with the movable mold 15 and the slide mold 17 facing each other, both cavities are set to be offset by a predetermined amount.

  In the mold-clamped state of FIG. 4, the upper tank 2 and the lower tank 3 which are primary molded bodies are simultaneously injection-molded (primary molding) by injecting and filling molten resin materials such as polyamide which is the primary molding material into the cavities through the runners 18. To do. As a primary molding material which is a material of the upper tank 2 and the lower tank 3 which are primary molded bodies, for example, nylon 6 which is a typical polyamide (PA) is used as a matrix resin, and 30 wt% of a glass fiber filler is contained therein as a reinforcing fiber. (PA6-GF30, for example, reinforced nylon 6 CM1011G-30 manufactured by Toray Industries, Inc.) is used.

  After the molding, the upper tank 2 and the lower tank 3 are left in the cavities of the respective molds 15 and 17, and the molds are once opened as shown in FIG. 5 to remove the runner 18 and the non-product part region attached as the gate equivalent part. On the other hand, the filter 4 molded in advance in a separate process is fitted and inserted into the lower tank 3 for positioning.

  Subsequently, as shown in FIG. 6, the slide mold 17 is raised by a predetermined amount by the contraction operation of the shift cylinder 16 to offset the movable mold 15 and the slide mold 17, and the upper tank 2 and the slide mold on the movable mold 15 side are offset. Directly face the lower tank 3 on the 17th side. In this state, the movable mold 15 is advanced, and the molds 15 and 17 are clamped together with the movable mold 15 and the slide mold 17 being offset as shown in FIG. 7, and as shown in FIG. While sandwiching the opening surfaces of the upper tank 2 and the lower tank 3, a clamping piece 13 attached to the upper flange 9 of the filter 4 is sandwiched therebetween. As a result, as shown in FIG. 1, a cavity for forming the belt portion 14 as the secondary bonding layer is formed on the outer periphery of the abutting portion between the upper tank 2 and the lower tank 3.

  In this state, a molten resin material such as polyamide, which is a secondary molding material, is injected and filled into the cavity through the runner 19, whereby the belt portion 14, which is a secondary bonding layer, which is a secondary molded body, is injection-molded into a ring shape. (Secondary molding). The upper tank 2, the filter 4, and the lower tank 3 are joined by injection welding with the injection molding of the belt portion 14. As the secondary molding material, the same resin material as the primary molding material is used in consideration of compatibility.

  Thereafter, after the belt portion 14 is solidified, as shown in FIG. 8, the movable die 15 is moved backward to open the die, and the tank 1 as a molded product is taken out.

  In such injection welding molding of the tank 1, the temperature of the resin, which is the primary molding material, is increased to make the skin layers formed on the surfaces of the upper tank 2 and the lower tank 3 as the primary molding as thin as possible, and the secondary molding material It has been found that by increasing the resin temperature and forming a weld layer with a large amount of penetration into the primary molded body, the mechanical properties at the weld joint, that is, the joint strength by injection welding, are greatly improved.

  Here, primary molding conditions, that is, molding conditions of the upper tank 2 and the lower tank 3 that are primary molded bodies, and secondary welding conditions, that is, injection welding conditions that are molding conditions of the belt part (secondary bonding layer) 14 that is a secondary molded body. And, the correlation with the joint strength at the joint by injection welding after the secondary molding was investigated. Table 1 shows the results of a shear test at the joint by this injection welding.

  As shown in FIG. 9, the test piece (test piece) used for the shear test is the same as the tank 1 in the so-called half-shaped primary molded body 21 </ b> A obtained by bisecting the JIS No. 1 dumbbell-shaped test piece 21 in the radial direction. The material is primary molded, and then the primary molded body 21A is inserted into a cavity corresponding to the dumbbell-shaped test piece 21 of JIS No. 1, and the other half is a secondary molded body 21B, and the same material as the belt portion 14 described above. At the same time as molding in step (b), bonding was performed by injection welding, and a plurality of dumbbell-shaped test pieces 21 of JIS1 shown in FIG. The primary molding conditions and secondary molding conditions (injection welding conditions) for each sample (test piece) C to Q were as shown in Table 1.

  Each sample C to Q is formed by offsetting a notch 22 reaching the interface between the primary molded body 21A and the secondary molded body 21B as shown in FIG. The shear strength at the joint by injection welding was determined. At the same time, the fracture surface of each sample C to Q after the measurement of shear strength was observed using a scanning electron microscope. Separately from this, samples C to Q after injection welding were cut at the center, polished after being embedded in resin, and the structure of the joint portion by injection welding was observed with an optical microscope.

  FIG. 10 is a graph plotting the injection speed at the time of secondary molding and the resin temperature at the time of primary molding shown in Table 1 and showing the effect on the shear strength at the joint due to injection welding. As is clear from the figure, it is clearly shown that the shear strength increases as the resin temperature during the primary molding increases. On the other hand, there is no clear influence of the injection speed during secondary molding on the shear strength. As is apparent from the figure, it can be seen that the improvement of the shear strength greatly depends on the resin temperature during the primary molding.

  FIG. 11 is a graph plotting the injection temperature at the time of the secondary molding shown in Table 1 and showing the relationship with the shear strength at the joint by injection welding. As is apparent from the figure, the shear strength increases as the resin temperature in the secondary molding as well as in the primary molding increases, and if the resin temperature is 290 ° C. in both the primary molding and the secondary molding in relation to FIG. It can be seen that the shear strength increases to 40 MPa or more.

  12 and 13 show the observation results of the fracture surface described above, and in the case of low shear strength (29 MPa), the surface is smooth because the interface is insufficiently welded, as is apparent from FIG. It is well understood that ductile fracture is caused in the case of high shear strength (47 MPa) because the weld layer is formed as apparent from FIG.

  FIGS. 14 and 15 also show the results of the structure observation described above. In the case of low shear strength (29 MPa), a clear welded layer is not observed as apparent from FIG. 14, while the shear strength is high. As can be seen from FIG. 15, it was clearly observed that a weld layer having a thickness of about 8 μm or more was formed in the case (47 MPa).

  Thus, the higher the molten resin temperature of the primary molding material and the molten resin temperature of the secondary molding material, the better the compatibility at the welded part in the secondary molding, and the joining at the joined part by injection welding. It can be seen that the strength, that is, the shear strength is greatly improved. More specifically, as apparent from Table 1, samples L to N in which the molten resin temperature of the primary molding material and the molten resin temperature of the secondary molding material are both set to 290 ° C. have the highest shear strength, Samples O to Q in which the molten resin temperature of the primary molding material is set to 245 ° C., the molten resin temperature of the secondary molding material is set to 305 ° C., and the molten resin temperature of the primary molding material is 245 ° C. Samples I to K were set in this order in which the molten resin temperature of the molding material was set to 290 ° C.

  In other words, considering that the melting point of the PA6-GF30 material which is the primary molding material and the secondary molding material used in the present embodiment is 225 ° C., the molten resin temperature of the primary molding material is In order to improve the shear strength of the molded article, it is set to be about 50 to 100 ° C. higher than the melting point, and further, the molten resin temperature of the secondary molding material is similarly set to about 50 to 100 ° C. higher than the melting point. It turns out that it is advantageous. In particular, when the temperature difference between the normal set temperature of 70 to 90 ° C. of the mold at the time of primary molding and the molten resin temperature is set in the range of 220 ° C. ± 20 ° C., the effect of improving the shear strength tends to become more prominent. Become.

  As described above, the higher the resin temperature of the primary molded body, the slower the solidification in the mold, and the thickness of the amorphous structure skin layer formed on the outermost surface of the finally solidified primary molded body This is because the molten resin, which is the secondary molding material, dissolves the skin layer of the primary molded body with good compatibility during the secondary molding, and forms a welded layer, resulting in improved shear strength. Presumed to be. In addition, when the thickness of the skin layer of the outermost surface of each primary molded object was measured for each of the samples L to N having the highest shear strength, the average value was 0.039 mm. On the other hand, when the thickness of the skin layer on the outermost surface of the primary molded body of each of the other samples C to K and O to Q was measured, the average value was 0.063 mm.

  Thus, it can be seen that the higher the molten resin temperature, which is the molding condition of the primary molded body, and the smaller the thickness of the skin layer on the surface, the more the shear strength is improved.

The half sectional view which shows the structure of a reservoir tank as an example of the molded article shape | molded by the shaping | molding method which concerns on this invention. FIG. 2 is a half sectional perspective view of the reservoir tank shown in FIG. 1. The exploded view of the reservoir tank similarly shown in FIG. The schematic explanatory drawing of the mold clamping state at the time of shape | molding the reservoir tank shown in FIG. 1 by the die slide injection method. The schematic explanatory drawing when a mold is once opened from the state of FIG. FIG. 6 is a schematic explanatory diagram when the slide mold is slid from the state of FIG. 5. Schematic explanatory drawing when the mold is clamped again from the state of FIG. Schematic explanatory drawing when a mold is opened again from the state of FIG. Explanatory drawing of the test piece used for the measurement of the shear strength in the injection welding part of the molded article shape | molded by the shaping | molding method shown in FIGS. The graph which shows the relationship between secondary injection speed and shear strength. The graph which shows the relationship between secondary resin temperature and shear strength. The microscope picture of the fracture surface by shearing when the shear strength is 29 MPa. Similarly, a photomicrograph of a fracture surface caused by shearing when the shear strength is 47 MPa. The microscope picture of the weld part cross section of a primary molded object and a secondary molded object when shear strength is 29 Mpa. Similarly, the microscope picture of the weld part cross section of a primary molded object and a secondary molded object when shear strength is 47 Mpa.

Explanation of symbols

1 ... Reservoir tank (molded product or hollow container)
2 ... Upper tank (primary molded product)
3. Lower tank (secondary molded product)
4 ... Filter (interior parts)
13 ... clamping piece 14 ... belt part (secondary joining layer or secondary molded object)

Claims (7)

A part of the primary molded body is re-formed by injecting a secondary molded material, which is also a thermoplastic resin, into a primary molded body that has been molded in advance with a primary molding material that is a thermoplastic resin. An injection welding molding method for a resin molded product which is joined by injection welding with a secondary molded body while melting,
The molten resin temperature of the primary molding material at the time of molding the primary molded body is set to be about 50 to 100 ° C. higher than the melting point of the primary molding material itself, so that at least a joint surface with the secondary molded body of the primary molded body is formed. An injection welding molding method for a resin molded product, characterized in that the skin layer of the power portion is extremely thinned.   After butt-joining two half-shaped primary molded bodies molded in advance with a primary molding material that is a thermoplastic resin, a secondary molding material that is also a thermoplastic resin is injected into the vicinity of the butt portion to perform secondary molding. 2. The resin molded product according to claim 1, wherein the primary molded body is joined by injection welding while remelting a part of the primary molded body by molding a secondary bonding layer as a body. Injection molding method.   3. The method of injection welding molding of a resin molded product according to claim 2, wherein the molding of the primary molded body and the injection welding joining by molding of the secondary molded body are continuously performed by a die slide injection method.   The molten resin temperature of the secondary molding material at the time of molding the secondary molded body is set to be about 50 to 100 ° C higher than the melting point of the secondary molding material itself. Injection molding method for resin molded products.   The resin molded product according to any one of claims 1 to 4, wherein a temperature difference between a mold temperature and a molten resin temperature in molding the primary molded body is set in a range of 220 ° C ± 20 ° C. Injection welding molding method.   6. The resin molding according to claim 1, wherein at least one of the primary molding material and the secondary molding material is one of polyamide, polyacetal, and polyester. Injection molding method of products.   7. The method of injection-molding a resin molded product according to claim 1, wherein at least one of the primary molding material and the secondary molding material is a fiber reinforced resin.