CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and benefits of Chinese Patent Application Serial No.

201210043637.X, filed with the State Intellectual Property Office of P. . China on February 24, 2012, the entire content of which is incorporated herein by reference.

FIELD

The present disclosure relates to the field of metal-plastic integrally molding, and more particularly to a method for producing a composite of a metal and a resin, and a metal-resin composite obtainable by the same.

BACKGROUND

In the fields of manufacture of articles such as automobiles, household appliances and industrial machines, a metal and a resin need to be firmly bonded together. Currently, in a conventional method, an adhesive is used at normal temperature or under heating to integrally bond a metal and a synthetic resin. One research direction is to integrally bond an engineering resin with high strength to a magnesium alloy, an aluminum alloy, or ferroalloys such as stainless steel directly without an adhesive.

Nano molding technology (NMT) is a technique of integrally bonding a metal and a resin, which allows the resin to be directly injection molded on a surface of a metal sheet by nano molding the surface of the metal sheet so as to obtain a metal-resin integrally molded product. For effective bonding of a metal and a resin, NMT may replace commonly used insert molding or zinc-aluminum or magnesium-aluminum die casting so as to provide a metal-resin integrally molded product with low cost and high performance. Compared with the bonding technology, NMT may reduce the whole weight of the product, and may ensure excellent strength of the mechanical structure, high processing rate, high output, and many appearance decoration methods, and consequently may apply to vehicles, IT apparatuses and 3C products. Japan Taisei Plas Co., Ltd. filed a series of patent applications, for example, CN1492804A, CN1717323A, CN101341023A and CN101631671 A, which propose a method for integrally molding a metal and a resin composition. In this method, by using a resin composition containing polyphenylene sulfide (PPS), polybutylene terephthalate (PBT) and polyamide (PA) with high crystallinity as an injection molding material, the resin composition is directly injection molded on a surface of a nano molded aluminum alloy layer to allow the resin composition to immerse in a nanoscale micropore, so as to obtain a metal-resin integrally molded product with a certain mechanical strength. However, because the resins used in this method are all highly crystalline resins, a longer cooling time and strict mold temperature should be needed in the course of molding to ensure the machinery performance, and on the other hand, highly crystalline resins often make the plastic surface hard to process, resulting in a significant difference from a metal element, when used in an appearance article.

Then, the prior art cannot solve the problems relating to the surface decoration of plastic articles, and the method for integrally molding a metal and a resin should be improved.

SUMMARY

Embodiments of the present disclosure seek to solve at least one of the problems existing in the prior art to at least some extent, particularly technical problems of complex molding process, strict conditions, the fact that the surface of the plastic layer is difficult to process, the surface decoration of a plastic article, and low mechanical strength when the plastic is a highly crystalline resin in nano molding technology (NMT).

According to a first aspect of the present disclosure, there is provided a method for producing a composite of a metal and a resin. The method comprises steps of:

A) forming nanopores in at least a part of the surface of a shaped metal; and

B) injection molding a thermoplastic resin directly on the surface of the shaped metal, wherein the thermoplastic resin includes a main resin and a polyolefin resin, the main resin includes a mixture of polyphenylene ether and polyphenylene sulfide, and the polyolefin resin has a melting point of about 65 ^° C to about 105 ^° C .

According to a second aspect of the present disclosure, there is provided a metal-resin composite, which is obtainable by the method according to the first aspect of the present disclosure.

According to a third aspect of the present disclosure, there is provided a metal-resin composite comprising : a shaped metal part; a plastic part made of a resin; an oxide layer formed between the metal part and the plastic part, wherein the oxide layer contains corrosion pores in the surface contacting the plastic part, and nanopores in the surface contacting the shaped metal part; the nanopores have an average pore size of about lOnm to about lOOnm and an average depth of about 0.5μιη to about 9.5μιη, and the corrosion pores have an average pore size of about 200nm to about 2000nm and an average depths of about 0.5μιη to about 9.5μιη; a part of the corrosion pores are communicated with a part of the nanopores; and a part of the resin is filled in the nanopores and corrosion pores.

In the method for integrally molding the metal and the resin according to an embodiment of the present disclosure, a non- crystalline resin with good surface gloss and good toughness namely a mixture of polyphenylene ether and polyphenylene sulfide, and a polyolefin resin with a melting point of about 65 ^° C to about 105 ^° C is also used. Therefore, injection molding at a specific mould temperature may be not required during the molding, subsequent annealing treatment may also be not required, the molding process may be simplified, and it may be ensured that the obtained metal-resin composite may have high mechanical strength and good surface treatment characteristics, thus solving the problem of the surface decoration of a plastic article, and meet the diverse requirements of customers.

Additional aspects and advantages of embodiments of present disclosure will be given in part in the following descriptions, become apparent in part from the following descriptions, or be learned from the practice of the embodiments of the present disclosure.

DETAILED DESCRIPTION

Reference will be made in detail to embodiments of the present disclosure. The embodiments described herein are explanatory, illustrative, and used to generally understand the present disclosure. The embodiments shall not be construed to limit the present disclosure.

According to a first aspect of the present disclosure, a method for producing a composite of a metal and a resin is provided. The method comprises steps of:

A) forming nanopores in at least a part of the surface of a shaped metal; and

B) injection molding a thermoplastic resin directly on the surface of the shaped metal, in which the thermoplastic resin includes a main resin and a polyolefm resin, the main resin includes a mixture of polyphenylene ether and polyphenylene sulfide, and the polyolefm resin has a melting point of about 65 ^° C to about 105 ^° C .

Because the resins used in the prior art are all highly crystalline resins, the surface of the plastic layer may be difficult to treat. In the present disclosure, based on this reason, a non-crystalline resin, which has a surface gloss and a toughness both superior to those of the highly crystalline resins in the prior art, is used as an injection molding material, and a polyolefm resin with a melting point of about 65 ^° C to about 105 ^° C is also used. Therefore, injection molding at a specific mould temperature may be not required during the molding, subsequent annealing treatment may also be not required, the molding process may be simplified, and it may be ensured that the obtained metal-resin composite may have high mechanical strength and good surface treatment characteristics, thus solving the problem of the surface decoration of a plastic article and meeting the diverse requirements of customers.

In the present disclosure, the mechanism of the metal-resin integrally molding is as follows: nanoscale micropores are formed in the surface of the metal sheet; a resin composition is melted on the surface of the metal sheet, at this time, a part of melted resin composition permeates into the nanoscale micropore; and then the metal and the resin composition are integrally injection molded.

Particularly, in step A), forming nanopores in a surface of a metal sheet comprises: anodizing at least a part of the surface of the shaped metal to form an oxide layer having the nanopores thereon. The anodizing technique is well known to those skilled in the art. In some embodiments, anodizing the surface of the metal sheet may comprise: placing the shaped metal as an anode in a H ₂ SO ₄ solution with a concentration of about 10wt% to about 30wt%; and electrolyzing the shaped metal at a temperature of about 10 ^° C to about 30 ^° C at a voltage of about 10V to about 100V for about lmin to about 40min to form the oxide layer with a thickness of about Ιμιη to about ΙΟμιη on at least a part of the surface of the shaped metal. An anodizing apparatus may be a well-known anodizing apparatus, for example, an anodizing bath.

By anodizing, the oxide layer formed with the nanopores is formed on the surface of the metal sheet. Preferably, the oxide layer has a thickness of about Ιμιη to about ΙΟμιη, more preferably about Ιμιη to about 5μιη.

The nanopores preferably have an average pore size of about lOnm to about lOOnm, more preferably have an average pore size of about 20nm to about 80nm, and most preferably have an average pore size of about 20nm to about 60nm. The nanopores have an average depth of about 0.5μιη to about 9.5μιη, preferably have an average depth of about 0.5μιη to about 5μιη. By optimizing the structure of the nanopores, the filling degree of the melted resin composition in the nanopores may be enhanced, and it may be ensured that the nanoscale micropore with this depth may be filled with the melted resin in a conventional injection molding process, which may not reduce the joining area between the resin and the oxide layer but may further improve the connection force between the resin and the metal because there are no gaps in the nanopores.

In one preferred embodiment, in step A), forming nanopores in a surface of a metal sheet may further comprise a step of: immersing the shaped metal having the oxide layer on the surface thereof in an etching solution to form corrosion pores in an outer surface of the oxide layer. At least a part of the corrosion pores are communicated with the nanopores. By a double-layer three-dimensional pore structure formed by the corrosion pores and the nanopores, the permeability of the resin composition may be further enhanced, and the connection force between the resin composition and the metal may be improved, thus further facilitating the molding.

The corrosion pores preferably have an average pore size of about 200nm to about 2000nm, more preferably have an average pore size of about 200nm to about lOOOnm, and most preferably has an average pore size of about 400nm to about lOOOnm. The corrosion pores have an average depth of about 0.5μιη to about 9.5μιη, preferably have an average depth of about 0.5μιη to about 5μιη. By optimizing the structure of the corrosion pores, direct injection of the resin composition and the bonding between the resin composition and the alloy during the injection molding may be further facilitated.

The etching solution may include any solution which may corrode the oxide layer. Generally, the etching solution may include a solution which may dissolve the oxide layer and have a concentration to be adjusted, for example, an acid/base etching solution. Preferably, the etching solution may be a single basic solution with a pH of about 10 to about 13 or a complex buffer solution. The single basic solution with a pH of about 10 to about 13 may include at least one selected from the group consisting of a Na ₂ C0 ₃ aqueous solution, a NaHC0 ₃ aqueous solution and a NaOH aqueous solution, preferably a Na ₂ C0 ₃ aqueous solution and/or a NaHC0 ₃ aqueous solution, thus allowing the corrosion pores to be uniformly distributed in the surface of the oxide layer and to have uniform pore size, and achieving better bonding performance between the resin layer and an aluminum alloy substrate as well as higher tensile strength and better integral bonding of an aluminum alloy composite structure. The Na ₂ C0 ₃ aqueous solution and/or the NaHC0 ₃ aqueous solution may have a solid content of about 0.1 wt% to about 15wt%. The complex buffer solution may be a mixed solution of a soluble hydrophosphate and a soluble base, for example, an aqueous solution of sodium dihydrogen phosphate and sodium hydroxide. The aqueous solution of sodium dihydrogen phosphate and sodium hydroxide may have a solid content of about 0.1 wt% to about 15wt%.

Immersing the metal sheet formed with the oxide layer on the surface thereof in an etching solution may comprise repeatedly immersing the metal sheet in the etching solution for 2 times to 10 times with each immersing lasting for about lmin to about 60min, and cleaning the metal sheet with deionized water after each immersing. Cleaning the metal sheet may comprise placing the metal sheet in a washing bath to wash the metal sheet for about lmin to about 5min, or placing the metal sheet in a washing bath to place the metal sheet for about lmin to about 5min.

It has been found by the inventors through many experiments that in the present disclosure, by using a polyolefin resin with a melting point of about 65 ^° C to about 105 ^° C in the non-crystalline main resin, the flowing capability of the resin in the nanoscale micropore in the surface of the metal sheet may be enhanced, thus ensuring strong adhesive force between the metal and the plastic as well as high mechanical strength of the metal-resin composite. Preferably, based on 100 weight parts of the thermoplastic resin, the amount of the main resin is about 70 weight parts to about 95 weight parts, and the amount of the polyolefin resin is about 5 weight parts to about 30 weight parts.

It has also been found by the inventors that the flowing capability of the resin may be enhanced by the inclusion of a flow improver in the thermoplastic resin, thus further enhancing the adhesive force between the metal and the plastic as well as the injection molding performance of the resin. Preferably, based on 100 weight parts of the thermoplastic resin, the thermoplastic resin may comprise about 1 weight part to about 5 weight parts of a flow improver. Preferably, the flow improver includes a cyclic polycarbonate.

It has also been found by the inventors that including fiberglass in thermoplastic resin may reduce contractibility rate of plastics. Preferably, based on 100 weight parts of the thermoplastic resin, the thermoplastic resin may comprise 10-30 weight parts of fiberglass.

As mentioned above, in present disclosure the main resin includes non-crystalline resin. Specifically, the main resin includes a mixture of polyphenylene ether (PPO) and polyphenylene sulfide (PPS). Preferably, a weight ratio of PPO and PPS is about 3: 1 to about 1:3, more preferably is 2: 1 - 1 : 1.

In the present disclosure, the polyolefin resin has a melting point of about 65 ^° C to about 105 ^° C . Preferably, the polyolefin resin may be a grafted polyethylene. More preferably, the polyolefin resin may be a grafted polyethylene with melting point of about 100 ^° C or about 105 ^° C .

In the present disclosure, the metal may be any metal commonly used in the prior art, and may be properly selected according to its application areas. For example, the metal may be at least one selected from the group consisting of aluminum, stainless steel and magnesium.

According to a second aspect of the present disclosure, a metal-resin composite is also provided, which is obtainable by the method according to the first aspect of the present disclosure.

According to a third aspect of the present disclosure, there is provided a metal-resin composite comprising : a shaped metal part; a plastic part made of a resin; an oxide layer formed between the metal part and the plastic part, wherein the oxide layer contains corrosion pores in the surface contacting the plastic part, and nanopores in the surface contacting the shaped metal part; the nanopores have an average pore size of about lOnm to about lOOnm and an average depth of about 0.5μιη to about 9.5μιη, and the corrosion pores have an average pore size of about 200nm to about 2000nm and an average depths of about 0.5μιη to about 9.5μιη; a part of the corrosion pores are communicated with a part of the nanopores; and a part of the resin is filled in the nanopores and corrosion pores.

In the metal-resin composite according to an embodiment of the present disclosure, the metal sheet and the plastic layer are of an integrally formed structure, which has strong adhesive force and high mechanical strength. As shown in Table 1, each metal-resin composite has a fracture strength of about 19MPa to about 22MPa, and an impact strength of about 270 J/m to about 350J/m.

In order to make the technical problem, the technical solution and the advantageous effects of the present disclosure more clear, the present disclosure will be further described below in detail with reference to examples thereof. It would be appreciated that particular examples described herein are merely used to understand the present disclosure. The examples shall not be construed to limit the present disclosure. The raw materials used in the examples and the comparative examples are all commercially available, without special limits. Example 1

(1) Pretreatment:

A commercially available A5052 aluminum alloy plate with a thickness of 1mm was cut into 18mm x 45mm rectangular sheets, which were then immersed in a 40g/L NaOH aqueous solution. The temperature of the NaOH aqueous solution was 40 ^° C . After lmin, the rectangular sheets were washed with water and dried to obtain pretreated aluminum alloy sheets.

(2) Surface Treatment 1 :

Each aluminum alloy sheet as an anode was placed in an anodizing bath containing a 20wt% H ₂ SO ₄ solution, the aluminum alloy was electrolyzed at a voltage of 20V at 18 ^° C for lOmin, and then the aluminum alloy sheet was blow-dried.

The cross section of the aluminum alloy sheet after the surface treatment 1 was observed by a metalloscope, to find out that an aluminum oxide layer with a thickness of 5μιη was formed on the surface of the electrolyzed aluminum alloy sheet. The surface of the aluminum alloy sheet after the surface treatment 1 was observed by an electron microscope, to find out that nanopores with an average pore size of about 40nm to about 60nm and a depth of Ιμιη was formed in the aluminum oxide layer.

(3) Surface Treatment 2:

500ml of 10wt% sodium carbonate solution (pH=12) with a temperature of 20 ^° C was prepared in a beaker. The aluminum alloy sheet after step (2) was immersed in the sodium carbonate solution, taken out after 5min, and placed in a beaker containing water to be immersed for lmin. After 5 cycles, after water immersing for the last time, the aluminum alloy sheet was blow-dried.

The surface of the aluminum alloy sheet after the surface treatment 2 was observed by an electron microscope, to find out that corrosion pores with an average pore size of 300nm to lOOOnm and a depth of 4μιη were formed in the surface of the immersed aluminum alloy sheet. It may also be observed that there was a double-layer three-dimensional pore structure in the aluminum oxide layer, and the corrosion pores were communicated with the nanopores.

(4) Molding:

46 weight parts polyphenylene ether (PPO) (ZhongLanChenGuang PPO LX 040), 23 weight parts polyphenylene sulfide (PPS) (SiChuanDeYang PPS-HC1), 3 weight parts fluidity improver cyclic polycarbonate (CBTIOO), 8 weight parts grafted polyethylene having a melting point of 65 ^° C (Arkema Lotader AX8900) and 20 weight parts fiberglass (Zhe Jiang JuS hi 988A) are weighed and mixed uniformly to obtain a resin mixture. Then, using an injection molding machine, the melted resin mixture was injection molded on the surface of the aluminum alloy sheet after step (3), to obtain a metal-resin composite SI in this example.

Example 2

A metal-resin composite S2 in this example was prepared by a method which is substantially the same as the method in Example 1, with the following exceptions.

In step (1), instead of the aluminum alloy plate in Example 1, a commercially available magnesium alloy plate with a thickness of 3mm was cut into 18mm x 45mm rectangular sheets.

In step (2), each magnesium alloy sheet as an anode was placed in an anodizing bath containing a 20wt% H ₂ SO ₄ solution, the magnesium alloy was electrolyzed at a voltage of 15V at 18°C for lOmin, and then the magnesium alloy sheet was blow-dried.

The cross section of the magnesium alloy sheet after the surface treatment 1 was observed by a metalloscope, to find out that a magnesium oxide layer with a thickness of 5μιη was formed on the surface of the electrolyzed magnesium alloy sheet. The surface of the magnesium alloy sheet after the surface treatment 1 was observed by an electron microscope, to find out that nano micropore with an average pore size of 20nm to 40nm and a depth of Ιμιη were formed in the magnesium oxide layer.

The surface of the magnesium alloy sheet after the surface treatment 2 was observed by an electron microscope, to find out that corrosion pores with an average pore size of 300nm to lOOOnm and a depth of 4μιη were formed in the surface of the immersed magnesium alloy sheet. It may also be observed that there was a double-layer three-dimensional pore structure in the magnesium oxide layer, and the corrosion pores were communicated with the nanopores.

After the above steps, the metal-resin composite S2 in this example was obtained.

Example 3

A metal-resin composite S3 in this example was prepared by a method which was substantially the same as the method in Example 1, with the following exceptions.

In step (2), each aluminum alloy sheet as an anode was placed in an anodizing bath containing a 20wt% H ₂ SO ₄ solution, the aluminum alloy was electrolyzed at a voltage of 40V at 18 ^° C for 1 Omin, and then the aluminum alloy sheet was blow-dried. The cross section of the aluminum alloy sheet after the surface treatment 1 was observed by a metalloscope, to find out that an aluminum oxide layer with a thickness of 5μιη was formed on the surface of the electrolyzed aluminum alloy sheet. The surface of the aluminum alloy sheet after the surface treatment 1 was observed by an electron microscope, to find out that nanopores with an average pore size of 60nm to 80nm and a depth of Ιμιη was formed in the aluminum oxide layer.

The surface of the aluminum alloy sheet after the surface treatment 2 was observed by an electron microscope, to find out that corrosion pores with an average pore size of 300nm to lOOOnm and a depth of 4μιη were formed in the surface of the immersed aluminum alloy sheet. It may also be observed that there was a double-layer three-dimensional pore structure in the aluminum oxide layer, and the corrosion pores were communicated with the nanopores.

After the above steps, the metal-resin composite S3 in this example was obtained.

Example 4

A metal-resin composite S4 in this example was prepared by a method which is substantially the same as the method in Example 1, with the following exceptions.

In step (4), 35 weight parts polyp henylene ether (PPO) (ZhongLanChenGuang PPO LX 040), 35 weight parts polyphenylene sulfide (PPS) (SiChuanDeYang PPS-HC1), 10 weight parts fluidity improver epoxide oligoester (CBT100), 8 weight parts grafted polyethylene having a melting point of 105 ^° C (Arkema Lotader AX8900) and 20 weight parts fiberglass (Zhe Jiang JuS hi 988A) were weighed, Then, using an injection molding machine, the melted resin mixture was injection molded on the surface of the aluminum alloy sheet after step (3), to obtain a metal-resin composite S4 in this example.

Example 5

A metal-resin composite S5 in this example was prepared by a method which were substantially the same as the method in Example 2, with the following exceptions.

In step (4), 59 weight parts polyphenylene ether (PPO) (ZhongLanChenGuang PPO LXR040), 30 weight parts polyphenylene sulfide (PPS) (SiChuanDeYang PPS-HCL), 3 weight parts fluidity improver epoxide oligoester (CBT100) and 8 weight parts grafted polyethylene having a melting point of 65 ^° C (Arkema Lotader AX8900) were weighed, and a resin mixture was obtained after even mixing. Then, using an injection molding machine, the melted resin mixture was injection molded on the surface of the aluminum alloy sheet after step (3), to obtain a metal-resin composite S5 in this example.

Comparative Example 1

A metal-resin composite DS1 in this example was prepared by a method which was substantially the same as the method in Example 1, with the following exceptions.

In step (4), 51 weight parts polyphenylene ether (PPO) (ZhongLanChenGuang PPO

LXR040), 26 weight parts polyphenylene sulfide (PPS) (SiChuanDeYang PPS-HCL), 3 weight parts fluidity improver epoxide oligoester (CBTIOO) and 20 weight parts fiberglass (Zhe Jiang JuS hi 988A) were weighed, and a resin mixture was obtained after even mixing. Then, using an injection molding machine, the melted resin mixture was injection molded on the surface of the aluminum alloy sheet after step (3), to obtain a metal-resin composite DS1 in this example. Comparative Example 2

A metal-resin composite DS2 in this example was prepared by a method which was substantially the same as the method in Example 1, with the following exceptions.

In step (4), 89 weight parts polyphenylene sulfide (PPS) (SiChuanDeYang PPS-HCL), 3 weight parts fluidity improver epoxide oligoester (CBTIOO) and 8 weight parts grafted polyethylene having a melting point of 105 ^° C(Arkema Lotader AX8900), and a resin mixture was obtained after even mixing. Then, using an injection molding machine, the melted resin mixture was injection molded on the surface of the aluminum alloy sheet after step (3), to obtain a metal-resin composite DS2 in this example.

Comparative Example 3

A metal-resin composite DS3 in this example was prepared by a method which was substantially the same as the method in Example 1, with the following exceptions.

In step (4), 91 weight parts polyphenylene sulfide (PPS) (SiChuanDeYang PPS-HCL), 3 weight parts fluidity improver epoxide oligoester (CBTIOO) and 8 weight parts grafted polyethylene having a melting point of 105 ^° C (Arkema Lotader AX8900) were weighed, and a resin mixture was obtained after even mixing. Then, using an injection molding machine, the melted resin mixture was injection molded on the surface of the aluminum alloy sheet after step (3), and the entire article was subjected to anneal treatment at 180 ^° C for 1 hour, to obtain a metal-resin composite DS3 in this example.

Comparative Example 4

A metal-resin composite DS4 in this example was prepared by a method which was substantially the same as the method in Example 1, with the following exceptions.

In step (4), 84 weight parts polyphenylene sulfide (PPS) (SiChuanDeYang PPS-HCL), 3 weight parts fluidity improver epoxide oligoester (CBT100), 8 weight parts grafted polyethylene having a melting point of 105 ^° C (Arkema Lotader AX8900) and 5 weight parts flexibilizer (Arkema Lotader AX8840) were weighed, and a resin mixture was obtained after even mixing. Then, using an injection molding machine, the melted resin mixture was injection molded on the surface of the aluminum alloy sheet after step (3), and the entire article was subjected to anneal treatment at 180 ^° C for 1 hour, to obtain a metal-resin composite DS4 in this example.

Performance test

1) The metal-resin composites S1-S4 and DS1-DS4 were fixed on a universal testing machine for tensile test to obtain maximum loads thereof respectively. The test results were shown in Table 1.

2) The impact strength of standard samples of the metal-resin composites S1-S4 and DS1-DS4 was tested using a cantilever beam impact tester according to the method disclosed in ASTM D256.

The test results were shown in Table 1.

Table 1

It may be seen from the test results in Table 1 that the metal-resin composites S1-S5 have a fracture strength of 19-22MPa, which indicates that the connection force between the metal sheet and the plastic layer in the metal-resin composites S1-S5 is very strong; and the metal-resin composites S1-S5 have an impact strength of 270-350J/m, which indicates that the metal-resin composites S1-S5 have high mechanical strength.

By comparing the test results of the metal-resin composite SI with the test results of the metal-resin composites DS3 and DS4, it may be seen that the toughness of the polyphenylene oxide resin used in the prior art is very poor, the toughness is still poor even being modified with a toughener.

Although explanatory embodiments have been shown and described, it would be appreciated by those skilled in the art that the above embodiments cannot be construed to limit the present disclosure, and changes, alternatives, and modifications can be made in the embodiments without departing from spirit, principles and scope of the present disclosure.