JP6376867B2 - COMPOSITE STRUCTURE USED FOR APPLICATION OF HEAT CYCLE FROM HOT TO LOW TEMPERATURE IN ENGINE COMPARTMENT AND MANUFACTURING METHOD - Google Patents

Description

The present invention, by injection molding, the aluminum composite material and polypropylene resin portion is integrally formed, double engagement structure that is used in applications where thermal cycling to low temperatures is repeated from the hot in the engine compartment, and a method for producing the same. More specifically, the present invention relates to a technique for improving the bondability between a resin portion and a metal material in a composite structure of a polypropylene resin and an aluminum material.

  In recent years, composite molded bodies in which a resin member and a metal member are integrated are used as parts for automobiles and electronic devices. Such a resin / metal composite molded body is manufactured mainly by placing a metal material in a mold and injecting a thermoplastic resin therein to integrally form the material. On the other hand, the resin / metal composite molded body also has a problem in that sufficient bonding strength cannot be obtained between the resin part that has been injection-molded and the metal material depending on the material used or a combination thereof.

  Therefore, various studies have been made in the past in order to improve the bondability between the resin portion and the metal material in the resin / metal composite molded body. For example, for a resin / metal composite molded body using an aluminum material or an aluminum alloy material as a metal material, a method of providing irregularities of nm to μm level on the surface of the metal material by chemical treatment (see, for example, Patent Documents 1 and 2) A method of applying alumite treatment to the surface (for example, see Patent Document 3) has been put into practical use. In the methods described in Patent Documents 1 to 3, the thermoplastic resin is introduced into fine irregularities and holes on the surface of the metal material at the time of injection molding, thereby improving the bondability between the resin portion and the metal material. .

  On the other hand, a resin / metal composite molded body has also been proposed in which a polyester-based resin layer is provided on a metal material to improve the bondability between the resin portion and the metal material (see Patent Document 4). In the resin / metal composite molded article described in Patent Document 4, an outermost layer made of a specific polyester resin is provided on the surface of a metal material, and an ABS (acryl-butadiene-styrene copolymer resin) resin is provided on the outermost layer. A resin such as ABS / polycarbonate alloy resin, polycarbonate resin and polyester elastomer resin is injection-molded and integrated.

JP 2007-144895 A JP 2009-144198 A International Publication No. 2004/055248 JP 2012-445920 A

  However, the conventional techniques described above have the following problems. That is, the conventional resin / metal composite molded body is a thermoplastic resin having a polar group in the molecule such as PBT (polybutylene terephthalate), PPS (polyphenylene sulfide), ABS and PA6 (nylon 6). When formed, it is relatively easy to integrally form, but when formed from a thermoplastic resin having no polar group in the molecule such as polyolefin resin, there is a problem that integral molding is difficult.

  Moreover, although the method of forming the fine unevenness | corrugation and hole in the metal material surface described in patent documents 1-4 is effective for PBT, PPS, ABS, etc. which were mentioned above, fluidity | liquidity like a polypropylene resin is possible. With a low resin, it is difficult for the resin to enter fine irregularities and holes, and it does not have a polar group that contributes to improving the bondability. Therefore, sufficient bonding strength cannot be obtained. In particular, the technique described in Patent Document 4 is a technique in which a polyester resin layer is formed on a metal surface and bonded to an ABS resin or a polycarbonate resin having a polar group, and thus has a low compatibility with polyester and has a polar group. If PP resin is not used, sufficient bonding force cannot be obtained.

  In recent years, resin-metal composite members have begun to be used in automobiles and the like. However, in applications such as engine compartments where thermal cycles from high to low temperatures are repeated, the above-described conventional technology provides sufficient bonding durability. Can't get.

  In this way, a composite molded body of a polypropylene material and a metal material that does not have a polar group in the molecule and is chemically stable cannot be sufficiently bonded by injection molding, and penetrates the resin part and the metal material. The present situation is that they are integrated by a method such as providing holes and mechanically joining the front and back surfaces with polypropylene resin through the through holes. Then, in this composite molded body using polypropylene resin, which is difficult to integrate with the conventional metal, the pressed metal material is injected as it is without being roughened and integrated with the resin. Development of technology that can do this is desired.

  Therefore, the present invention eliminates the need for surface treatment of the metal material prior to injection molding, and provides an aluminum composite material and composite structure in which a resin / metal composite structure excellent in bondability with an injection molded portion made of polypropylene resin can be obtained. And a manufacturing method thereof.

  The present inventor has intensively studied in order to solve the above-described problems and to join a polypropylene resin and an aluminum (alloy) material used for injection molding. As a result, by providing a polypropylene resin layer with a crystallinity of a specific value or less on the aluminum (alloy) material, the bondability with the injection molded part made of polypropylene resin is good, and even in an environment where the temperature cycle is repeated, The present inventors have found that a composite structure capable of maintaining a good bonding force can be realized, and have reached the present invention.

That is, in the composite structure used for the application in which the heat cycle from the high temperature to the low temperature in the engine compartment according to the present invention is repeated , the aluminum composite material and the injection molded portion made of polypropylene resin are integrally formed by injection molding. A composite structure, wherein the aluminum composite material is provided on at least a part of a surface of the base material made of aluminum or an aluminum alloy and the base material, and is subjected to a phosphoric acid chromate treatment, a chromate chromate treatment, and a coating type chromate treatment. A base treatment film formed by zirconium oxide treatment or titanium zirconium treatment, an adhesive layer provided on the base treatment film and containing a modified polypropylene resin having a polar group introduced thereon, and provided on the adhesive layer A polypropylene resin layer. When the heat of fusion is ΔH and the heat of fusion of a polypropylene resin having a crystallinity of 100% is ΔHpp (= 209 J / g), the degree of crystallinity Xc calculated by the following formula (A) is 40%. It is as follows.

Polypropylene resin forming the pre Symbol injection molding unit may also contain glass fibers or carbon fibers.
Moreover, the linear expansion coefficient of the said injection molding part is 20-100 (x10 < ^-6 > / degreeC), for example.

According to the present invention, a method for manufacturing a composite structure used for an application in which a heat cycle from a high temperature to a low temperature in an engine compartment is repeated includes a step of press-molding an aluminum composite into a predetermined shape, and a press-formed aluminum composite Is formed in an injection mold and a polypropylene resin is injected into the mold, thereby integrally forming an injection molded portion made of the polypropylene resin on the aluminum composite material. A base material made of aluminum or an aluminum alloy and provided on at least a part of the surface of the base material, and formed by phosphoric acid chromate treatment, chromate chromate treatment, coating chromate treatment, zirconium oxide treatment or titanium zirconium treatment A ground treatment film and a coating on the ground treatment film The polypropylene resin comprising a modified polypropylene resin having a polar group introduced therein and a polypropylene resin layer provided on the adhesive layer, and the polypropylene resin constituting the polypropylene resin layer has a heat of fusion of ΔH When the heat of fusion of a polypropylene resin having a crystallinity of 100% is ΔHpp (= 209 J / g), the one having a crystallinity Xc calculated by the above formula (A) of 40% or less is used.
Moreover, the polypropylene resin which forms the said injection molding part may contain glass fiber or carbon fiber.
In that case, the linear expansion coefficient of the injection molded part can be set to 20 to 100 (× 10 ⁻⁶ / ° C.).

  According to the present invention, a polypropylene resin layer having a crystallinity in a specific range is provided in a region where an injection molded part made of polypropylene resin on the surface of a base material made of aluminum or an aluminum alloy is formed. Even if surface treatment such as surface roughening or chemical solution immersion treatment is not performed, a resin / metal composite structure excellent in bondability between the injection molded part and the metal material can be produced.

It is sectional drawing which shows typically the structural example of the aluminum composite material of the 1st Embodiment of this invention. It is a figure which shows the manufacturing method of the aluminum composite material shown in FIG. 1 in the order of the process. It is a figure which shows the other manufacturing method of the aluminum composite material shown in FIG. 1 in the order of the process. It is sectional drawing which shows typically the structural example of the composite structure of the 2nd Embodiment of this invention. A and B are figures which show the shape of the test piece used for joining force evaluation, A is a bottom view, B is a side view. It is a figure which shows the cutout position of the test piece for joining force evaluation of a press-formed product.

  Hereinafter, embodiments for carrying out the present invention will be described in detail. Note that the present invention is not limited to the embodiments described below.

(First embodiment)
First, the aluminum composite material according to the first embodiment of the present invention will be described. FIG. 1 is a cross-sectional view schematically showing a configuration example of the aluminum composite material of the present embodiment. As shown in FIG. 1, the aluminum composite material 10 of this embodiment, the aluminum or the surface of the substrate 1 made of an aluminum alloy, a surface treatment film 2, an adhesive layer 3, and a polypropylene resin layer 4 is provided It has been.

[Substrate 1]
The base material 1 should just be an aluminum material or an aluminum alloy material, The kind, component composition, and shape are not specifically limited. Specifically, commonly used materials such as A1100, A3004, and A5052 can be used.

[Base treatment film 2]
The ground treatment film 2 is for improving adhesion with the adhesive layer 3 and obtaining more stable bonding strength. The base treatment film 2 may be formed at least in a portion where the adhesive layer 3 is formed, but may be formed in a portion where the adhesive layer 3 of the substrate 1 is not formed. It may be formed on the entire surface.

  As the base treatment for forming the base treatment film 2, phosphoric acid chromate treatment, chromic acid chromate treatment, coating-type chromate treatment, zirconium oxide treatment, titanium zirconium treatment and the like can be applied. By performing these surface treatments, a stable bonding force is maintained between the aluminum composite material and the injection-molded part even when used in environments with high humidity or when used in environments with large temperature changes. be able to.

[Adhesive layer 3]
The adhesive layer 3 is formed of a resin composition mainly composed of a modified polypropylene having a polar group introduced therein. The polar group introduced into the modified polypropylene that is the main component of the adhesive layer 3 may be any one that has good adhesion to the base material that has undergone the coating surface treatment. Specifically, —OH, —COOH , —O— group and NH ₂ group. The thickness of the adhesive layer 3 is not particularly limited, but is preferably as thin as possible in consideration of the influence on processability and the like, and further considering the adhesiveness between the base treatment film 2 and the polypropylene layer 4, it is 0. It is preferable to be about 5 to 5 μm.

[Polypropylene resin layer 4]
The polypropylene resin constituting the polypropylene resin layer 4 has a crystallinity Xc calculated by the following mathematical formula (A) of 40% or less. Here, ΔH in the following formula (A) is the heat of fusion (J / g) of the polypropylene resin constituting the polypropylene resin layer 4, and ΔHpp is the heat of fusion of the polypropylene resin having a crystallinity of 100% (= 209 J / g). .

  By setting the crystallinity Xc of the polypropylene resin layer 4 to 40% or less, a good bonding force can be stably obtained with an injection molded part made of polypropylene resin, and at 120 ° C. as in an engine room of an automobile. Good bonding strength can be maintained even in an environment where a temperature cycle in which the temperature cycle is as low as about −30 ° C. in winter is repeated. On the other hand, if the degree of crystallinity Xc of the polypropylene resin layer 4 exceeds 40%, a sufficient bonding force cannot be obtained with the injection-molded part made of polypropylene resin, or if it is used in an environment where the temperature cycle is repeated, The bonding strength with the molded part may be reduced.

  The melting point Tm of the polypropylene resin constituting the polypropylene resin layer 4 is preferably set to be equal to or lower than the injection molding temperature, and specifically preferably 120 to 200 ° C. Since the injection molding of polypropylene resin is usually performed in a temperature range of 200 to 240 ° C., the polypropylene resin formed on the base material 1 at the time of injection molding when the melting point of the resin constituting the polypropylene resin layer 4 is within this range. The layer 4 is melted and compatible with the injected polypropylene resin, and the polypropylene resin layer 4 and the injection molded part are integrated. As a result, a stronger bonding force can be obtained.

  Further, the thickness of the polypropylene resin layer 4 is not particularly limited, but when the metal material 1 is subjected to processing such as press molding after forming the polypropylene resin layer 4, it is 10 to 100 μm from the viewpoint of workability. It is desirable to do. Thereby, joining force with the injection molding part which consists of polypropylene resin can be improved, maintaining workability favorable. Furthermore, the polypropylene resin layer 4 can be provided on the entire surface of the substrate 1, but it is sufficient that it is provided at least on the portion where the injection molded part is formed.

[Production method]
Next, the manufacturing method of the aluminum composite material 10 mentioned above is demonstrated. FIG. 2 is a view showing a method of manufacturing the aluminum composite material 10 of the present embodiment in the order of steps. As shown in FIG. 2, when manufacturing the aluminum composite material 11, first, the surface of the aluminum material or aluminum alloy material to be the base material 1 is subjected to a ground treatment to form the ground treatment film 2. Next, a composition containing a modified polypropylene resin having a polar group is applied on the base treatment film 2 and baked at a temperature of about 120 to 250 ° C. as necessary to form the adhesive layer 3.

  Subsequently, the polypropylene resin film 41 is laminated on the adhesive layer 3 by, for example, a laminating method using a heating roll, and then heat-sealed, and then heated to a temperature of 160 ° C. or higher by a heating furnace or the like. The upper limit of the heating temperature at that time is not particularly limited, but when heated at 250 ° C. or higher, the decomposition of the polypropylene resin becomes significant. Therefore, the heating temperature when forming the polypropylene resin layer 4 is 250 It is preferable to set it as below ℃. Thereafter, it is rapidly cooled by air cooling or water cooling to form a polypropylene resin layer 4 having a crystallinity Xc of 40% or less.

  The thickness of the polypropylene resin film 41 can be appropriately selected according to the thickness of the polypropylene resin layer 4 to be formed. From the viewpoint of securing a bonding force that can withstand an impact when the resin is injected, The thickness is preferably 70 μm. If the thickness of the polypropylene resin film 41 forming the polypropylene resin layer 4 is thin, it is not only difficult to withstand the impact at the time of injection molding, but also expensive because quality control such as defects is difficult. On the other hand, when the thickness of the polypropylene resin film 41 exceeds 100 μm, the manufacturing cost may increase and processing characteristics such as cutting and drawing may be deteriorated.

  Moreover, the composite aluminum material 10 of this embodiment can also be formed using a polypropylene resin sheet provided with an adhesive layer. FIG. 3 is a view showing another manufacturing method of the aluminum composite material 10 of the present embodiment. Specifically, as shown in FIG. 3, a polypropylene resin sheet 42 having an adhesive layer 31 containing a modified polypropylene resin formed on one surface is applied to the surface of the base material 1 on which the base treatment film 2 is formed. The adhesive layer 31 is disposed on the substrate 1 side, heated at a heating temperature corresponding to the adhesive layer 31, and then heat-treated at a temperature of 160 ° C. or higher.

  Thereafter, the adhesive layer 3 and the polypropylene resin layer 4 having a crystallinity Xc of 40% or less are formed by quenching by air cooling or water cooling. As described above, when the polypropylene resin sheet 42 including the adhesive layer 31 is used, the adhesive layer 3 is formed on the substrate 1 by a simple method without using an adhesive paint, and has a strong bonding force. The resin layer 4 can be formed.

  Since the aluminum composite material of the present embodiment is provided with a polypropylene resin layer on a base material made of aluminum or an aluminum alloy, before forming an injection molded part made of polypropylene resin, surface roughening or chemical immersion treatment There is no need to surface-treat the substrate. Since this polypropylene resin layer is laminated on the base material via an adhesive layer mainly composed of a base treatment film and a modified polypropylene resin, it has excellent bondability with the base material. Furthermore, since the aluminum composite material of this embodiment has a crystallinity of the polypropylene resin layer of 40% or less, the aluminum composite material is excellent in bondability with an injection-molded part made of polypropylene resin, and in an environment where the temperature cycle is repeated. In this case, it is possible to suppress a decrease in bonding force.

(Second Embodiment)
Next, a composite structure according to the second embodiment of the present invention will be described. FIG. 4 is a diagram schematically illustrating a configuration example of the composite structure according to the present embodiment. As shown in FIG. 4, the composite structure of the present embodiment is obtained by integrally forming the injection molded portion 5 made of polypropylene resin by injection molding on the aluminum composite material 10 of the first embodiment described above.

[Injection molding part 5]
The injection molded part 5 is formed on the polypropylene resin layer 4 of the aluminum composite material 10. The kind and physical property of the polypropylene resin which forms the injection molding part 5 are not specifically limited, According to a use and a specification, it can select suitably and can be used. However, if the difference in the linear expansion coefficient between the base material 1 and the injection molded part 5 is large, cracks may occur in the injection molded part 5 due to changes in the temperature and the atmospheric temperature in the long term, and the bonding force may be reduced. . Therefore, it is desirable that the linear expansion coefficient of the injection-molded part 5 is as close as possible to the base material 1, and specifically, the linear expansion coefficient of the injection-molded part 5 is 20 to 100 (× 10 ⁻⁶ / ° C.). preferable. Thereby, it is possible to maintain excellent bonding strength over a long period of time.

  In order to make the injection-molded part 5 less susceptible to changes in the thermal environment, glass fibers or carbon fibers may be added to the polypropylene resin. In that case, although the addition amount of glass fiber or carbon fiber is not specifically limited, it is preferable to set it as 20-40 mass% per composition total mass, More preferably, it is 20-30 mass%. Thereby, the linear expansion coefficient of the injection molding part 5 can be made into half or less compared with what does not contain these fiber materials. In particular, when carbon fiber is contained in the injection molded part 5, a linear expansion coefficient close to that of a base material made of aluminum or an aluminum alloy can be obtained, so that a structure excellent in joining durability can be obtained.

  In addition, although the length of the carbon fiber and glass fiber contained in the injection molding part 5 is not specifically limited, It is preferable that it is 10 mm or less. When the fiber length exceeds 10 mm, the injection property of the polypropylene resin and the compatibility with the propylene resin layer 4 provided on the aluminum composite material 10 may be lowered.

[Production method]
Next, the manufacturing method of the resin / metal composite structure of this embodiment will be described. When manufacturing the composite structure of this embodiment, first, the aluminum composite material 10 is press-molded into a predetermined shape (press molding process). Next, the press-molded aluminum composite material 10 is placed in an injection mold, and a polypropylene resin is injected into the mold, so that an injection molded portion 5 made of polypropylene resin is integrally formed on the aluminum composite material 10 ( Injection molding process).

  Depending on the type of oil such as volatile press oil, the aluminum composite material 10 can be used for injection molding as it is without removing lubricating oil such as press oil adhering during processing, but generally after the press molding process. Then, after performing a degreasing step for removing oil adhering to the aluminum composite material 10, injection molding is performed. In addition, the shaping | molding method of the aluminum composite material 10 is not limited to press molding, Various processing methods, such as a bending process, can be applied. Further, the aluminum composite material 10 can be used as it is without being processed.

  The composite structure of the present embodiment uses an aluminum composite material having a polypropylene resin layer compatible with polypropylene resin, and an injection molded part made of polypropylene resin is formed in a portion where the polypropylene resin layer is provided. . As a result, a strong bonding force is obtained between the metal material and the injection-molded part, and the strength and hardness of the metal are utilized, and the three-dimensional shape-corresponding force by the injection molding of polypropylene resin is high. It is possible to realize a resin / metal composite molded body that is strong, excellent in design, and inexpensive.

  In fields such as automobiles, iron members, aluminum members or aluminum alloy members and a polypropylene resin part have been fastened by bolting so far. However, the composite structure of this embodiment has a resin part and a metal. The material can be integrated and produced. As a result, the cost can be reduced and the man-hours can be reduced because the bolt is omitted. Furthermore, the composite structure of this embodiment of the present embodiment can be applied to members that require strength, and further progress in weight reduction is expected.

  Hereinafter, the effects of the present invention will be specifically described with reference to Examples and Comparative Examples of the present invention. In this example, resin / metal composite assemblies of Examples and Comparative Examples were prepared by the following method, and the bonding strength was evaluated. 5A and 5B are views showing the shape of the test piece used for the bonding force evaluation, A is a bottom view, and B is a side view.

<Example 1>
An aluminum alloy material (5052H34) having a length of 300 mm, a width of 200 mm, and a thickness of 1 mm was degreased and then subjected to a phosphoric acid chromate treatment (Cr: 15 mg / m ² ). Thereafter, Unistor R200 (modified polypropylene adhesive) manufactured by Mitsui Chemicals, Inc. was applied by a bar coating method, and baked at 180 ° C. for 20 seconds to form an adhesive layer having a thickness of 3 μm. Next, a polypropylene film (Trefan 3301, thickness 30 μm) manufactured by Toray Industries, Inc. was bonded to the aluminum alloy material with an adhesive layer under a temperature condition of 120 ° C. using a heat laminating roll.

  Then, after heating at 170 degreeC for 30 second, it cooled with water and the aluminum composite material of Example 1 was produced. In addition, when the polypropylene film which heat-processed on the same conditions was analyzed using DSC (Differential Scanning Calorimetry: 7020) by Seiko Instruments Inc., crystallinity was 35%.

  Next, the aluminum composite material of Example 1 cut to a size of 25 mm in width and 100 mm in length was placed in a mold, and on the polypropylene resin layer, a polypropylene resin (Plastron PP- manufactured by Daicel Polymer Co., Ltd.) was placed. GF40: glass fiber content 40 mass%) was injection-molded to form an injection-molded portion having a length of 25 mm, a width of 100 mm, and a thickness of 3 mm, and a test piece having the shape shown in FIGS. 5A and 5B was obtained. At that time, the injection temperature was 230 ° C., and the injection time was 20 seconds. Moreover, after injection molding, it cooled at room temperature.

<Example 2>
The surface of an aluminum alloy material of the same type as in Example 1 was subjected to a chromate chromate treatment (Cr: 15 mg / m ² ), and then a similar adhesive layer was provided. Moreover, the aluminum composite material of Example 2 was produced using Torayfan ZK207 (thickness 50 micrometers) by Toray Industries, Inc. for a polypropylene film. In addition, about the aluminum composite material of Example 2, when the crystallinity degree of the polypropylene resin layer was measured by the same method as Example 1, it was 33%.

  Then, except that the glass fiber content of the polypropylene resin was 20% by mass, an injection molded part was formed by the same method and conditions as in Example 1 described above, and a test piece having the shape shown in FIGS. 5A and 5B was formed. Obtained.

<Example 3>
After the surface of an aluminum alloy material of the same type as in Example 1 was subjected to titanium zirconium treatment (Zr :: 15 mg / m ² ), an injection molded part was produced by the same method and conditions as in Example 1. In addition, Toray Industries, Inc. Treffan 9141 (thickness 20 micrometers) was used for the polypropylene film. Further, for the aluminum composite material of Example 3, the degree of crystallinity of the polypropylene resin layer was measured by the same method as in Example 1, and it was 38%.

<Example 4>
The surface of an aluminum alloy material of the same type as in Example 1 was subjected to a phosphoric acid chromate treatment (Cr :: 15 mg / m ² ), and then a modified polypropylene resin was applied under a temperature condition of 120 ° C. using a heat laminating roll. A polypropylene resin film (9710B, Toray Industries, Inc., thickness 50 μm) provided with an adhesive layer was press-bonded. Then, after heat-treating for 30 seconds at a temperature of 170 ° C., air cooling was performed to form a polypropylene resin layer on the surface of the aluminum alloy plate, and the aluminum alloy composite material of Example 4 was formed. With respect to the aluminum composite material of Example 4, the degree of crystallinity of the polypropylene resin layer was measured by the same method as in Example 1, and it was 25%.

  Using the aluminum composite material of Example 4 cut into a size of 25 mm in length, 100 mm in width, and 1 mm in thickness, an injection molded part was formed by the same method and conditions as in Example 1, and FIG. 5A and FIG. A test piece having the shape shown in 5B was obtained.

<Example 5>
A test piece was produced under the same conditions and method as in Example 1 except that the injection molded part was formed using a polypropylene resin not containing glass fiber.

<Comparative Example 1>
An aluminum alloy composite material was produced by the same method and conditions as in Example 1 described above, except that the base treatment was not performed on the aluminum alloy plate. And the polypropylene resin similar to Example 2 was injection-molded to this aluminum alloy composite material of Comparative Example 1 to form an injection-molded portion, and a test piece was produced.

<Comparative Examples 2 and 3>
In the same manner as in Example 1, after forming an adhesive layer on an aluminum alloy material and laminating a polypropylene film, an aluminum composite material of Comparative Example 2 was produced without performing reheating or subsequent rapid cooling. Moreover, the aluminum composite material of the comparative example 3 was produced without re-heat-processing and implementing only rapid cooling. The crystallinity of the polypropylene layer in these aluminum composites was 60% in Comparative Example 2 and 45% in Comparative Example 3, respectively, both exceeding the scope of the present invention.

  Using these aluminum composite materials of Comparative Examples 2 and 3, an injection molded part was formed under the same method and conditions as in Example 1 described above, and test pieces having the shapes shown in FIGS. 5A and 5B were produced.

<Comparative Example 4>
After the surface of the aluminum alloy material was subjected to phosphoric acid chromate treatment, a polypropylene resin was injection-molded into an aluminum composite material in which a resin layer was formed using a polyethylene terephthalate (PET) film. However, the polyethylene terephthalate resin layer and the injection-molded part made of polypropylene resin are bonded in appearance but have low bonding strength and cannot be integrated.

<Comparative Example 5>
After the surface of the aluminum alloy material is subjected to a chromate chromate treatment, an injection molded part made of polypropylene resin is used in the same manner and under the same conditions and conditions as in Example 2 without using an adhesive layer or a polypropylene resin layer. A test piece having the shape shown in FIGS. 5A and 5B was formed.

<Comparative Example 6>
The surface of an aluminum alloy material having a length of 25 mm, a width of 100 mm, and a thickness of 1 mm was etched with hydrochloric acid, and the generated smut was washed with nitric acid to roughen the average roughness Ra to 3 μm. Using this aluminum alloy material, injection molding was carried out under the same method and conditions as in Example 2 to form an injection molded part made of polypropylene resin, and test pieces having the shapes shown in FIGS. 5A and 5B were produced.

<Comparative Example 7>
Injection made of polypropylene resin by injection molding using the same method and conditions as in Example 2 using a surface of an aluminum alloy material having a length of 25 mm, a width of 100 mm, and a thickness of 1 mm formed with a 30 μm sulfate alumite film. A molded part was formed to produce a test piece having the shape shown in FIGS. 5A and 5B.

[Evaluation]
Using a tensile tester, a tensile test was performed on each of the test pieces of Examples and Comparative Examples, and the bonding strength was evaluated based on the tensile strength and the fracture mode. In particular, assuming severe use conditions of temperature change, (1) salt spray (according to JIS Z2371, 500 hours), (2) 85 ° C.-85% relative humidity, for each test piece of Examples and Comparative Examples Three types of endurance tests were conducted: exposure for 500 hours, (3) -30 ° C for 1 hour / + 120 ° C for 1 hour (switching 5 minutes), 300 cycles, and the degree of decrease in bonding force was investigated.

  FIG. 6 is a diagram showing a cut-out position of a test piece for evaluating the bonding strength of a press-formed product. Furthermore, in order to confirm that the injection molding can be performed as it is after the press molding, a rectangular shaped press product 20 shown in FIG. 6 is produced using each aluminum composite material of the example and the comparative example, and the processed product has a length of 25 mm. Then, a test piece 21 having a width of 100 mm was cut out, and a polypropylene resin was injection-molded by the same method, and the joining force was investigated. It was examined whether the same joining force could be obtained with an actual press-molded product.

  The above results are summarized in Table 1 below. In addition, in the evaluation results of the bonding strength shown in Table 1 below, “◯” indicates that the tensile strength is 1500 N or more, “Δ” indicates that the tensile strength is less than 1500 N and 1000 N or more, and “less” indicates that the tensile strength is less than 1000 N. × ”.

  Comparative Example 1 is an example in which the surface treatment was not performed on the surface of the aluminum alloy material. Initially, a bonding force close to that of the example was observed, but a decrease in the bonding force after the durability test was large. In Comparative Examples 2 and 3, a polypropylene resin layer was formed by providing an adhesive layer. In particular, this was a case where reheat treatment and subsequent rapid cooling were not performed, and the crystallinity of the polypropylene resin layer was the same as the crystallinity of the present invention. Since it exceeded, initial joining strength was also low compared with the Example, and joining force with an injection molding part was inferior. Further, even when the peeling interface was seen, the injection molded part was hardly left, and the joining force between the aluminum alloy material and the injection molded part was insufficient. This confirmed the effectiveness of adjusting the crystallinity.

  In all of Comparative Examples 4 to 7, the aluminum alloy material and the injection molded part were not joined, or even if they seemed to be joined, the joining force itself was low, and the joining strength in the tensile test was very small. These are considered to be difficult to use in harsh environments, especially since the decrease in bonding strength after the durability test was large.

  On the other hand, the test piece using the aluminum composite material of Examples 1-5 was able to maintain favorable joining force stably. However, in the test piece of Example 5, since the polypropylene resin forming the injection-molded portion does not contain any glass fiber, after the cooling and heating cycle, the bonding strength is reduced as compared with the test pieces of other examples. The proportion was slightly larger.

DESCRIPTION OF SYMBOLS 1 Base material 2 Ground treatment film 3 Adhesion layer 4 Polypropylene layer 5 Injection molding part 10 Aluminum composite material 20 Press-molded article 21 Test piece

Claims (6)

By injection molding, an injection molding unit consisting of A aluminum composite material and a polypropylene resin is a composite structure which is integrally formed,
The aluminum composite material is
A substrate made of aluminum or an aluminum alloy;
Provided on at least a part of the surface of the base material, a base treatment film formed by phosphoric acid chromate treatment, chromate chromate treatment, coating type chromate treatment, zirconium oxide treatment or titanium zirconium treatment;
An adhesive layer comprising a modified polypropylene resin provided on the base treatment film and introduced with a polar group;
A polypropylene resin layer provided on the adhesive layer;
Have
The polypropylene resin constituting the polypropylene resin layer is a crystal calculated by the following mathematical formula (A) when the heat of fusion is ΔH and the heat of fusion of a polypropylene resin having a crystallinity of 100% is ΔHpp (= 209 J / g). The degree of conversion Xc is 40% or less.
A composite structure used in applications where the heat cycle from high to low temperatures is repeated in the engine compartment .
Xc = (ΔH / ΔHpp) × 100 (A) The composite structure according to claim 1 , wherein the polypropylene resin forming the injection-molded portion contains glass fibers or carbon fibers. The composite structure according to claim 2 , wherein the injection molded part has a linear expansion coefficient of 20 to 100 (× 10 ⁻⁶ / ° C.). Pressing the aluminum composite material into a predetermined shape;
A step of placing the aluminum composite material press-molded in an injection mold and injecting a polypropylene resin into the mold to integrally form an injection molded portion made of the aluminum composite material and the polypropylene resin;
Have
As the aluminum composite material, a base material made of aluminum or an aluminum alloy and provided on at least a part of the surface of the base material, phosphoric acid chromate treatment, chromate chromate treatment, coating type chromate treatment, zirconium oxide treatment or titanium zirconium A base treatment film formed by treatment, an adhesive layer containing a modified polypropylene resin provided on the base treatment film and having a polar group introduced therein, and a polypropylene resin layer provided on the adhesive layer. The polypropylene resin constituting the polypropylene resin layer is calculated by the following equation (A), where ΔHpp is the heat of fusion and ΔHpp (= 209 J / g) is the heat of fusion of the 100% crystallinity polypropylene resin. Use a crystallinity Xc of 40% or less.
The manufacturing method of the composite structure used for the use in which the heat cycle from a high temperature to a low temperature in an engine compartment is repeated.
Xc = (ΔH / ΔHpp) × 100 (A) The method for producing a composite structure according to claim 4 , wherein the polypropylene resin forming the injection-molded part contains glass fibers or carbon fibers. The method for manufacturing a composite structure according to claim 5 , wherein the injection molded part has a linear expansion coefficient of 20 to 100 (× 10 ⁻⁶ / ° C.).

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