JP7489028B2 - Integrated structure of copper material and PPS resin composition and its manufacturing method - Google Patents

Description

The present invention relates to an integrated structure of copper material and PPS resin composition and a method for manufacturing the same. More specifically, the present invention relates to an integrated structure of copper material and PPS resin composition that is used in the electrode lead-out portion of a lithium ion battery or the like, and in particular has a seal structure that can prevent foreign substances such as water molecules from entering the electrolyte from the outside, and a method for manufacturing the same.

Some lithium ion batteries (hereinafter referred to as "LIBs") use copper for the positive electrode material and aluminum alloy for the negative electrode material in order to collect electricity from the positive and negative electrodes immersed in the electrolyte and extract the electricity from the LIB's main container to the outside. This electrode material needs to be sealed at the fixed joint with the LIB's container material to prevent the electrolyte from leaking, and for this purpose, an O-ring or the like is generally used. The applicant has proposed a structure in which, instead of the O-ring structure, copper or aluminum alloy electrode material is inserted into an injection mold and the resin of the container lid material is injected into it to seal it, and a manufacturing method for the structure (see Patent Documents 1, 5, etc.). That is, the joint surface (fixing surface) between the aluminum alloy (hereinafter referred to as "Al alloy") rod-shaped object for the negative electrode pull-out and the synthetic resin battery lid that supports it, and the joint surface (fixing surface) between the copper rod-shaped object for the positive electrode pull-out and the battery lid are improved. The inventors have proposed a chemical conversion treatment method for metal surfaces and a synthetic resin composition for use therein, which improves the bonding surface (adhesive surface) between the metal and resin parts and minimizes the number of water and oxygen molecules that pass through ultra-fine gaps.

LIBs are excellent secondary batteries and are already in practical use around the world. However, for example, in Japan's natural environment, their stored capacity tends to drop rapidly after about five years. One of the reasons for this is said to be the intrusion of foreign matter such as moisture into the electrolyte, which should be completely anhydrous, and this is also said to be one of the causes of deterioration. In particular, the bonding surface between the above-mentioned metal and resin parts has a problem in that the adhesive strength of the dissimilar materials, metal and resin, cannot withstand changes over time due to differences in linear expansion coefficients, etc. Furthermore, for the above-mentioned reasons, the seal between the above-mentioned metal and resin is required to have high gas sealing properties and durability against repeated creep stress caused by thermal stress. The inventors of the present invention (hereinafter referred to as "the inventors") have proposed that the synthetic resin used for the extraction electrode material (copper material and Al alloy material) of the above-mentioned LIB and the lid material bonded (fixed) thereto is a polyphenylene sulfide resin (Poly Phenylene Sulfide Resin, hereinafter referred to as "PPS")-based composition "for example, SGX120 (Tosoh Corporation, head office: Tokyo, Japan)" (hereinafter referred to as "SGX120"). The surfaces of both or one of the proposed "copper material and Al alloy material" are subjected to a specific chemical conversion treatment (see Patent Documents 1, 4, and 5).

Among the techniques proposed by the inventors in the past, there is one using an injection molding machine as a technique for strongly and directly bonding metal and crystalline thermoplastic resin, that is, a bonding technique called "injection bonding method" or "injection bonding technique" that is already known to many injection molding related engineers. Among these injection bonding techniques, there is "NMT" and "New NMT" that the inventors developed and named (see Patent Documents 11 and 12, etc.). In the manufacture of LIBs, if this NMT or New NMT is used, when an Al alloy or pure copper material is inserted into an injection molding die and a PPS resin composition (for example, "SGX120") is used for injection bonding, the bonding strength (shear bonding strength) between the resin part and the metal part is about 40 MPa in both cases, and it has been found that the bonding strength is very strong. Therefore, it was thought that these injection bonding techniques related to Al alloys and copper materials could be used for a technology that can not only seal liquid between the inside of the LIB battery box and the outside air, but can even seal gas.

Based on this technical idea, the invention described in Patent Document 1 was developed by designing a structural plan for the LIB lid and disclosing the structure. However, the injection joining technology described in Patent Document 1 and used for the electrode lead-out portion of the LIB lid was only related to Al alloys. At that time, the surface treatment method for injection joining of Al alloys had been improved, and the inventors invented the NMT2 treatment method. Although the invention described in Patent Document 1 proposes and discloses a structural plan for the LIB lid, the basis of the chemical conversion treatment is a new surface treatment method called NMT2 treatment, which was developed mainly for Al alloy materials. The gas sealing property of the joint surface of the injection joint of this NMT2-treated Al alloy material and PPS resin "SGX120" is high. At that time, the gas sealing property of the joint surface of the injection joint of C1100 copper treated with the new NMT treatment was more than one order of magnitude higher than the conventional O-ring sealing method in a helium gas leakage experiment, and it was not unusable. However, the gas sealing performance of the injection-bonded aluminum alloy material and PPS resin "SGX120" is two orders of magnitude higher than when C1100 copper material is used. Therefore, for gas sealing, only technology using aluminum alloy material was used.

(Gas sealing technology using injection bonding materials)
Thus, what is described in Patent Document 1 was mainly an invention about an injection joining technology related to an Al alloy, and disclosed the high performance of the gas sealing property of an Al alloy and a resin, which was found by an experiment. Further development was carried out on an injection joining product using this Al alloy. A test was conducted to confirm the strength of the wet heat resistance of the joint of this injection joining product. This test was conducted on an injection joining product (a test piece for joint strength) having the shape shown in FIG. 1 attached to this specification, and a high temperature and humidity test was conducted in which the injection joining product was exposed to an environment of a temperature of 85° C. and a humidity of 85% for 8,000 hours. In this high temperature and humidity test, the shear joint strength between the metal and resin parts was hardly reduced, and a joining method with high wet heat resistance was realized (see Patent Document 2). Similarly, a specific shape design method has already been proposed as an injection joining product in which the joint strength between the metal and resin does not decrease even when subjected to 3,000 cycles of temperature shock of -50° C./+150° C. (see Patent Document 3). In short, if the battery cover of the LIB is made of a PPS resin composition and the electrode lead part is made of an Al alloy material, there will be no decrease in the strength of the joint and no inclusion of moisture or other foreign matter if the injection joining technology disclosed in Patent Documents 1, 2, 3, etc. is used. In other words, the speed at which gas leaks, or more precisely the speed at which water molecules, oxygen molecules, etc. enter and leave the inside of the battery body, at the part where the Al alloy metal rod penetrates the resin plate is significantly reduced, achieving something close to a complete gas seal.

On the other hand, when the inventors performed the chemical conversion treatment (for example, the treatment method described in Patent Document 1) recommended at the time for injection bonding of pure copper C1100 and the PPS resin composition "SGX120," the shear bond strength was about 40 MPa. The inventors confirmed that the gas sealing performance of this bond was superior to that of conventional silicone rubber O-rings. However, for the reasons mentioned above, the proposed battery cover structure for LIB described in Patent Document 1 did not use the injection bonding technology for the copper part. For this reason, they later proposed an invention that improved the chemical conversion treatment of the copper electrode (see Patent Document 5). And even later, they proposed a further improvement on this invention (see Patent Document 4).

(Changes in surface treatment methods for injection joining of copper materials (preliminary testing and development history of the present invention))
On the other hand, the method for measuring the bonding strength between metal and resin in an injection-bonded product has been internationally standardized as ISO19095, which is a public standardization of the method that the inventors have been using in experiments since the beginning. The injection-bonded product for measuring the shear bonding strength is shown in FIG. 1. That is, the shear bonding strength of copper or copper alloy disclosed in the above-mentioned Patent Document 5 and Patent Document 4 is a measured value before it was standardized by ISO19095. However, since it is a numerical value obtained from a test piece of the same shape as shown in FIG. 1 and is the same shear bonding strength, it can be used as a similar numerical index as an evaluation index of the present invention. Whether or not the surface treatment method for strengthening the bonding strength has been improved was judged by whether or not the shear bonding strength of the injection-bonded product by this test method has improved. However, with this measurement test method, the numerical value tends to saturate once the bonding strength becomes strong to a certain extent. For example, if the above-mentioned "SGX120" which is a PPS-based resin is used, even if the chemical conversion treatment of copper or copper alloy is improved, the maximum value is 41 to 42 MPa, and no numerical value higher than that can be obtained. The inventors found that when the improvement progressed and the shear bond strength exceeded 38 MPa, it became difficult to evaluate the improvement thereafter. In other words, in the case of hard metal materials, not limited to copper or copper alloys, it was found that the effect and evaluation of gas sealing property, which is thought to be related to the true strength of the bond, cannot be correctly evaluated only by the above-mentioned method of measuring the shear bond strength.

In response to this, the inventors proposed a new concept of a joint strength measurement method called "shear joint tackiness", that is, a method of measuring the maximum external force that can be withstood without breaking by repeatedly applying the same numerical value of external force in the shear direction 300 times (details will be described later). This evaluation method was then used as an evaluation index for the development of new treatment methods. That is, after making the invention described in Patent Document 4, the inventors developed various new treatment methods using this evaluation method as an evaluation method for the development of new treatment methods. Therefore, C1100 copper pieces were also injection-joined using the three new surface conversion treatment methods described in Patent Document 4 to obtain test pieces with the shape shown in Figure 1, and a confirmation test was conducted to measure the "shear joint tackiness" value of each of these. As a result, it was found that all three types of surface treatment products described in Patent Document 4 were clearly improved over previous products, and that one of the three surface treatment products was particularly superior.

Similarly, C1100 copper pieces treated with the three surface treatment methods described in Patent Document 4 were used to obtain injection-bonded products with the above-mentioned "SGX120," and the bonding strength between the metal and the resin was measured. All three types of test pieces had a sufficiently high shear bonding strength of about 40 MPa. In addition, for a simple high-temperature, high-humidity test, the test pieces were immersed in a household electric kettle and in pure water at a temperature of 98°C for 72 hours, and only one of the three types showed a shear bonding strength of 38 MPa after 72 hours of immersion, indicating high resistance to moist heat. One of the excellent test pieces is shown in Figure 5 as a 100,000-fold electron microscope photograph. When observing this electron microscope photograph, the surface is covered entirely with whiskers with a diameter of about 10 nm, and many of the whiskers grow while tangled, and the shape of these whiskers is just like human hair.

The whiskers were found to be copper oxide using an analytical electron microscope. As far as the inventors know, metal pieces whose entire surface is covered with dense whiskers, as in the electron microscope photograph (hereinafter referred to as "electron microscope photograph") shown in Patent Document 4, are rare. In the present invention, in order to measure the "shear joint tackiness" of the three types mentioned above, three types including the copper pieces with dense whiskers were created again, and injection joints of "SGX120" were created with these and their "shear joint tackiness" was measured. As a result, not only were the measurement results of all three types higher than those described in Patent Document 5, which is the basic invention of the copper surface treatment, but the dense whisker type type was higher than the other two types. In short, this whisker type type, as an injection joint using "SGX120", a PPS resin composition, showed high values in all of the shear joint strength, shear joint tackiness, and joint strength and wet heat resistance, close to those of an injection joint using an Al alloy.

[Development history of the present invention]
Through this process, we have searched for a treatment method that further improves the shear joint ductility by fine-tuning the surface treatment method that produces copper pieces that generate whiskers among the chemical treatment methods described in Patent Document 4 and further fine-tuning the chemical treatment through trial and error. We have positioned this as an improved invention of the invention described in Patent Document 4, and named it the "latest new NMT treatment method 1" for copper in this invention. We have determined that C1100 copper can be treated with this "latest new NMT treatment method 1" and used for LIB. In short, the injection joint using this copper piece not only has a high shear joint strength of about 42 MPa, but also has moist heat resistance to the joint strength. And since this injection joint showed a high "shear joint ductility" value of 35.3 MPa, we predicted that the gas sealing property of the joint surface would also be high. The reason for this is that the injection-bonded product of the Al alloy and the PPS resin composition not only has a high shear bond strength of about 40 MPa, but also has resistance to wet heat and the "shear bond tackiness" value is high, the same as the 35.3 MPa obtained with the C1100 copper material. In short, with this improvement, the injection-bonded product has high values for shear bond strength, shear bond tackiness, and bond strength wet heat resistance, all of which are equivalent to those of the injection-bonded product using the Al alloy.

[Bondability of whisker-type copper surface]
Basically, Al alloy and copper material have physicochemically equivalent joining properties with PPS resin, so it was presumed that the gas sealing properties at the joints are similar. However, with the current technology, it is not possible to observe whether the injected resin flows and penetrates into the ultra-fine uneven surface of the copper material, where whiskers grow like hair, in a short time. This is because the depth of the recesses with such fine unevenness period in the electron microscope photograph (see, for example, Figure 4) of the Al alloy surface where an injection joint of Al alloy and PPS resin close to perfect sealing was realized is obviously shallower than the depth of the recesses (here, the thickness of the whisker layer) obtained from the photograph of the whisker surface (see, for example, Figure 5).

In short, the surface on which the whiskers are formed is not a simple ultrafine uneven surface shape. In other words, in terms of gas sealing, there is a possibility that nano-level spaces remain at the base of the whiskers, and it is presumed that this whisker structure may have slightly inferior gas sealing properties even if the bonding strength is the same. Therefore, in the present invention, a surface treatment method that produces a non-whisker type surface for C1100 copper pieces that has exactly the same shear bonding strength and "shear bonding ductility" value as copper pieces treated to have a whisker type has also been developed. As a result of improving these surface treatment methods, it was expected that the gas sealing properties on the copper electrode side would be reliably improved compared to those described in Patent Document 4, and would exhibit performance almost equivalent to that of the aluminum electrode part. Based on this result, the structural proposal for the LIB battery cover shown in Figure 8 was developed. For this reason, the shape example of this structure using the new surface treatment method is greatly simplified from the structural proposal for the LIB battery cover shown above (the structure shown in Figure 11 described in Patent Document 1).

(Other issues with copper surface treatment methods)
The aqueous solution of surface treatment used for copper material having the above-mentioned whisker-shaped surface contains a very small amount of chromium nitrate hydrate at a concentration of 0.1%. When a large amount of copper pieces are treated with this treatment solution, the treatment solution deteriorates and needs to be replaced with a new solution, generating waste liquid. Naturally, waste water containing trivalent chromium is generated, although at a very low concentration, and since this cannot be discharged into the natural environment, investment is required for waste water treatment equipment. Since the amount of chromium contained in the waste water is very low, the cost of treatment is not large, but at least the investment cost is incurred. The inventors of the present invention thought that a high level of environmental conservation should be demonstrated at a level that meets or exceeds the legal standard, not from the viewpoint of cost consciousness, but from the viewpoint of environmental protection. Therefore, it is desirable to change the treatment solution used for treating the copper material surface to one that does not contain chromium. Moreover, the injection joint between the copper material treated with this and the PPS resin must have an injection joint strength equal to or greater than that of the one treated with the treatment solution containing chromium. The chemical conversion treatment method of the present invention has also been achieved in the creation of this joint. As described below, the treatment methods using these chromium-free treatment solutions are referred to as "latest new NMT treatment method 2" and "latest new NMT treatment method 3" (described below) in Table 1. Copper oxide whiskers were not formed on the surfaces of the copper materials treated by these two new treatment methods.

(Injection joining technology)
The above-mentioned "injection joining technology" will be described in detail again. The technology of strongly joining metal and synthetic resin is required not only in the parts manufacturing industry such as automobiles, home appliances, and various industrial equipment, but also in a wide range of industrial fields, and many adhesives have been developed for this purpose. Such joining technology is a core technology in all manufacturing industries. On the other hand, joining methods that do not use adhesives when joining metal and resin have been studied and proposed in the past. The inventors developed and named them, and they are the above-mentioned "NMT (abbreviation of Nano Molding Technology)" and "New NMT (abbreviation of New Nano Molding Technology)". The NMT in this invention is a joining technology between an Al alloy that has been surface-treated by a specific chemical conversion treatment and a resin composition, and is a method in which a crystalline thermoplastic resin is injected into an Al alloy piece that has been inserted in an injection molding die in advance, a resin part is molded, and the molded product and the Al alloy piece are joined at the same time. The new NMT in this invention is a similar joining technology between all metal types including Al alloys and resin compositions, and differs from NMT in that the basic theory regarding the surface treatment method for metals performed before insertion is different. The inventors have referred to this joining of a solid material such as a metal material and a thermoplastic resin via an injection molding machine, or the technology thereof, as "injection joining" or "injection joining technology."

(N.M.T.)
The inventors of the present invention have stipulated the following four or five conditions as necessary conditions for the establishment of NMT, an injection joining technology using aluminum alloys. First, the following (1) and (2) are necessary conditions for the aluminum alloy side. The chemical treatment of the aluminum alloy surface to satisfy these two points is called "NMT treatment".
(1) The entire surface is covered with ultrafine recesses having a diameter of 20 to 50 nm.
(2) A water-soluble amine compound is chemically adsorbed onto the surface layer.
Next, the following two or three points are necessary conditions for the resin composition to be injected.
(3) The resin composition used is a resin composition containing a highly crystalline thermoplastic resin as a main component.
(4) The highly crystalline thermoplastic resin undergoes a chemical reaction with amine molecules at high temperatures.
(5) The resin composition contains, as a minor component resin, a resin that is compatible with the main component resin, or a resin that is not compatible with the main component resin but can become compatible or partially compatible with the main component resin by adding a third component resin.
The above conditions (1) to (4) are essential requirements, and adding the above condition (5) will further increase the injection joining strength. NMT, which satisfies the above conditions (1) to (5) and selects hydrazine hydrate as the amine compound in the above condition (2), is a commercially available NMT.

(NMT2, NMT5 to NMT8)
The present inventors discovered that a strong bonding strength can be obtained by injection bonding a PBT (polybutylene terephthalate) resin composition to an NMT-treated Al alloy. Then, the inventors discovered that a PPS resin composition can be injection bonded to an NMT-treated Al alloy (Patent Document 12). Next, as described in Patent Document 1, the inventors developed an "NMT2" treatment method by improving the surface treatment method for Al alloys, and discovered that the injection bonding strength between this treated product and the above-mentioned PBT resin and PPS resin is improved. In particular, the inventors discovered for the first time that the shear bonding strength of a product using PPS resin is about 40 MPa, and that the shear bonding strength of the injection bonded product is maintained at 37 to 40 MPa when the injection bonded product is exposed to a temperature of 85°C and a humidity of 85% for 6,000 to 8,000 hours or more, resulting in a metal-resin integrated product with the highest degree of wet heat resistance. The inventors named this technology NMT2.

The inventors had considered NMT2 to be the most advanced injection bonding technology between Al alloys and PPS resins, but problems still emerged in subsequent experiments. That is, if an Al alloy is treated with NMT2 and then stored for more than one week before the injection bonding process of a PPS resin composition is performed, the wet heat resistance of the shear bonding strength tends to decrease. The applicant's largest implementation of NMT2 was in the manufacture of an Al alloy body for an Al alloy smartphone. At this time, it was found that if the chemically treated Al alloy is stored for more than one week, the desired bonding strength cannot be obtained; more precisely, the shear bonding strength is obtained, but its long-term heat resistance decreases. As a countermeasure, the NMT2 treatment method was improved and chemical treatment methods called NMT5, NMT7, NMT8 treatment methods, etc. for various Al alloys were developed. When these new treatment methods are used, the above-mentioned effective storage period is more than four weeks. In addition, when new NMT processing methods (described below) named by the inventors, such as NMT5-Oxy, NMT7-Oxy, NMT5-Ano, and NMT7-Ano processing methods, are used for various Al alloys, the aforementioned effective storage period extends to several months or more, completely eliminating the weaknesses of NMT2 (Patent Document 2).

(New NMT)
The present inventors invented a new NMT capable of injection bonding various metal materials and resin compositions, and invented and proposed its fundamental processing method for each type of metal (Patent Documents 5 to 9). That is, it was disclosed as an injection bonding technology that can handle almost all types of practical metals supplied on the market, such as Mg alloys, Al alloys, copper, stainless steel, general steel materials, special steel plates, etc. The highly crystalline thermoplastic resin used here was the same as the injection bonding resin for NMT.

The conditions for establishing "New NMT" are defined by the inventors as the following five necessary conditions. Of these, the following three are necessary conditions for the metal materials used. And chemical processing that satisfies these three points ((1) to (3) below) is called "New NMT processing". In other words,
(i) the metal material has a fine rough surface with a period of 0.8 to 10 μm, and (ii) the rough surface has an ultrafine uneven surface shape with a period of 5 to 300 nm (preferably 50 to 100 nm), and
(iii) the surface layer is covered with a thin layer of a hard ceramic material such as a metal oxide or metal phosphate;
The following two points are necessary for the injected resin:
(iV) Use of a resin composition mainly composed of a highly crystalline thermoplastic resin;
(V) The resin composition contains, in addition to the highly crystalline thermoplastic resin as the main component, a minor resin, which is either a resin that is compatible with the main component resin, or a third resin that is incompatible with the main component resin but promotes at least partial compatibility with the main component resin.

The new NMT was developed for all metals. The first invention for which a patent application was filed for the new copper NMT was the invention described in Patent Document 5, and the improvement of the surface chemical conversion treatment method was achieved through the treatment method described in Patent Document 1, and then the treatment method described in Patent Document 4, as mentioned above. The invention described in Patent Document 4 is that, among the surface treatment methods for C1100 copper disclosed therein, there is a treatment in which short copper oxide whiskers cover the copper plate surface as an ultra-fine uneven surface like hair. When this copper plate is used to injection-bond with "SGX120", the shear bonding strength is about 40 MPa. When this is left at a temperature of 85°C and a humidity of 85% for 3,000 hours, and then dried and measured, the shear bonding strength decreases to 32 MPa. However, based on the results of this extremely harsh accelerated test, it was determined that the bonding strength is sufficiently high for practical use in the general atmospheric environment on the surface of the earth, and has high resistance to moisture and heat. These disclosed inventions are the latest surface treatment methods related to injection joining technology for copper materials that the present inventors are aware of.

WO2012/070654 Patent Publication 2019-188651 Patent Publication 2019-217704 Patent Publication 2017-132243 WO2008-047811 WO2008-069252 WO2008-081933 WO2008-078714 WO2009-011398 WO2009-116484 JP2003-103563A WO2004-041532

[Gas sealing properties of copper materials and resin]
The methods described in the above-mentioned Patent Documents 1, 2, and 3 provide nearly perfect gas sealing to the battery lid structure itself, including the electrode lead-out portion of the LIB. That is, the injection joint formed by the PPS resin and the Al alloy bar has nearly perfect helium gas sealing, and the injection joint formed by the PPS resin composition and the copper bar is shaped as shown in FIG. 11 described in Patent Document 1. That is, the copper bar is wrapped with an Al alloy thin plate having a thickness of about 1 mm, and the copper and the Al alloy are joined by "tight fit" accompanied by plastic deformation. If this is used as a member for the positive electrode lead-out portion, and is subjected to advanced surface treatment for Al alloy material and injection-joined with the PPS resin "SGX120", the copper-resin joint also has helium gas sealing properties equivalent to those of the above-mentioned Al alloy-used member. That is, Patent Document 1 already shows a plan to achieve almost perfect gas sealing between the electrolyte part of the LIB and the outside air, but it relies solely on an excellent surface treatment method for the Al alloy material and includes a processing step that is somewhat troublesome for use as an electrode lead member for a LIB.

The present invention discloses a significant advance in copper injection joining technology, and shows that the same technology can be used more simply as the copper electrode lead of an LIB, making it easier to produce LIBs with long life. In addition, the injection joining products using copper material according to the present invention include both products in which an aqueous solution containing a small amount of trivalent chromium is used as one of the surface treatment solutions for the copper material (the copper material surface is covered with whisker hairs) and products in which no chromium material is used as a treatment solution at all. Both have the same data on the bonding strength between the copper material and the resin, but the gas sealing properties of the bonding surface layer are high in both cases, but there is a possibility that they are slightly different. It is difficult to determine how this slight difference will affect the life of the LIB when it is finally commercialized. First of all, from the perspective of advanced environmental issues, it is better to avoid products that use treatment solutions containing chromium compounds.

In light of the above background, the present invention achieves the following objects.
An object of the present invention is to provide an integrated structure of a copper material and a PPS resin composition, which has high gas sealing properties, and a method for producing the same.
Another object of the present invention is to provide an integrated structure of a copper material and a PPS resin composition, which has high shear joint strength and shear joint toughness, and a method for producing the same.
Still another object of the present invention is to provide an integrated structure of a copper material and a PPS resin composition, which has high shear bonding strength and shear bonding tackiness, without using an aqueous solution containing chromium nitrate hydrate as one of the treatment solutions in a surface treatment step of the copper material, and a method for producing the same.

In order to solve the above problems, the present invention takes the following measures.
The integrated structure of the copper material and the PPS resin composition of the present invention 1 is
A structure in which a surface-treated copper piece and a specific polyphenylene sulfide-based resin composition are directly bonded and integrated,
The polyphenylene sulfide-based resin composition is a resin composition in which the main component of the resin portion is polyphenylene sulfide resin, the secondary component is modified polyolefin resin, and 15 to 25% by weight of short glass fibers as a reinforcing material component is added to the resin composition,
The bonding strength between the copper material and the polyphenylene sulfide-based resin composition is 40 MPa or more as measured by shear bonding strength using an injection-bonded product as specified by the International Organization for Standardization (ISO 19095), and
The injection-bonded product has a shear bonding viscosity of 33 MPa or more, which is defined as a tensile strength at which the product does not break even when an external force in a shear direction is applied 300 times continuously and repeatedly;
The copper material is a pure copper material having a purity of 99.90% or more,
The thickness of the polyphenylene sulfide resin composition bonded to the copper material is essentially 1 mm or less.

The integrated structure of copper material and PPS-based resin composition of Invention 2 is characterized in that, in Invention 2, the copper material is a rod-shaped member forming a negative electrode lead-out portion, a rod-shaped member made of an aluminum alloy that has been surface-treated by a chemical conversion treatment forms a positive electrode lead-out portion, the lead-out portions of the negative electrode portion and the positive electrode portion constitute a battery lid in which the lead-out portions of the negative electrode portion and the positive electrode portion penetrate to the outside, and the material of the battery lid is the polyphenylene sulfide-based resin composition, which is a structure around the electrode lead-out portions of a lithium-ion battery.

The method for producing an integrated structure of a copper material and a PPS-based resin composition according to the third aspect of the present invention is characterized in that, in the first or second aspect of the present invention, the copper material having a chemically treated surface is inserted into a die for injection molding, and the polyphenylene sulfide-based resin composition is injected into the die, thereby directly integrating the copper material with the polyphenylene sulfide-based resin composition.

The above-mentioned components constituting the present invention, the manufacturing method, reasons and concepts thereof will be described below.
[PPS resin composition used in the present invention]
All the resins used are resins for injection bonding, and are resin compositions whose main component is a crystalline thermoplastic resin described in the NMT theory and the new NMT theory, and whose secondary component is at least a different polymer. Specifically, when the main component is PPS, a modified polyolefin resin is used as the secondary component, and a small amount of a third component resin is added to increase the affinity between the PPS and the modified polyolefin resin. In short, the crystallization speed of the PPS molecules during quenching is significantly slower than that of a single resin composition, making injection bonding easier. Through this process, the above-mentioned "SGX120" and the like are listed as PPS-based resin compositions most suitable for injection bonding, as described above.

[Injection joining technology]
In the present invention, the injection joining refers to a process in which a copper material and/or an aluminum alloy is inserted into an injection mold, the injection mold is closed, and a PPS resin composition is injected into the cavity to join the metal and the PPS resin composition. The injection molding conditions are those generally required for PPS resin compositions.
[Aluminum alloy (Al alloy)]
Any general pure aluminum or aluminum alloy may be used, regardless of whether it is an Al-Cu, Al-Mn, Al-Si, or Al-Mg wrought or cast material. It is preferable to use a general-purpose standardized aluminum.

[Copper material]
The copper material used in the present invention can be any pure copper material. It is preferable to use a standardized one that is widely used. The preferred method of chemical conversion treatment of the surface is the new NMT type treatment method described in detail in Patent Document 4, or an improved chemical conversion treatment method (will be described in detail in the experimental examples described later). Among them, the treatment method in which whiskers are formed on the surface of the C1100 copper piece is preferred. The shear joint strength of the injection joint (shape shown in FIG. 1) of the C1100 copper material treated in this way and the above-mentioned "SGX120" is about 42 MPa, and the "shear joint ductility" value is 35.3 MPa. However, this surface treatment method includes an immersion step using an aqueous solution containing a small amount of trivalent chromium. After the entire immersion treatment, the surface of the copper material has a surface shape in which copper oxide whiskers grow densely like hair. However, evidence that the whiskers themselves contain chromium has not been confirmed, at least until the time of the invention of the present invention.

Generally speaking, there are no laws or regulations that prohibit the use of metal materials treated with a treatment solution containing chromium. If these products themselves were to be prohibited, important materials that support modern society, such as special steels including stainless steels and chromium-treated galvanized steel sheets, would be prohibited. To be precise, the process of manufacturing them inevitably produces chromium-containing wastewater and waste, so in newly proposed products such as this invention, the treatment process of wastewater and waste generated in the manufacturing process should be legally regulated and its management strengthened. For this reason, the idea of environmental protection has arisen that the manufacturing process itself should be changed to one that does not use chromium agents. This invention was developed based on this idea and also takes into consideration the future environment. In other words, it does not include a judgment on whether to make it a legal compliance type that only requires wastewater treatment and waste treatment in compliance with public regulations, or to go beyond that. This invention includes both as technologies that can be used. That is, in the examples of the present invention described below, the treatment method includes a chromium-containing treatment solution, which is called "Latest New NMT Treatment Method 1," while the treatment methods that do not include chromium-containing substances in the treatment solution are called "Latest New NMT Treatment Method 2" and "Latest New NMT Treatment Method 3."

In short, the inventors have also developed a new and excellent new NMT treatment method for C1100 that has an ultrafine uneven surface without using a chromium-containing treatment solution. The injection joint (test piece) of the shape shown in Figure 1 described in ISO19095 was made of "SGX120", C1100 copper pieces treated with this new surface treatment method, and copper pieces covered with copper oxide whiskers. The shear joint strength of the copper pieces treated with the new surface treatment method was 41.4 MPa, and the "shear joint tackiness" value was 35.3 MPa, while the shear joint strength when using copper pieces covered with copper oxide whiskers was 42.6 MPa and the "shear joint tackiness" value was 35.3 MPa, which are almost the same values. The copper material treatment method using a chromium-free treatment solution at this time was the "latest new NMT treatment method 2" mentioned above. Additionally, the latest copper treatment method, "New NMT Treatment Method 3," which also uses a chromium-free treatment solution, is a treatment method that improves the instability of the surface-treated products from Treatment Method 2 above, where the color tone of the appearance varies slightly when dried.

[-50℃/+150℃ temperature shock test of injection joining technology using several thousand cycles]
The linear expansion coefficient of Al alloy is 2.3×10 ^-5 K ^-1 , that of copper is 1.8×10 ^-5 K ^-1 , and that of the molded "SGX120" is approximately 4×10 ^-5 K ^-1 . Therefore, when an integrated product of Al alloy and "SGX120" is subjected to a temperature change, an internal stress in the opposite direction to the joining force is generated near the joining surface. In short, the difference in linear expansion coefficient of the joined product of Al alloy and "SGX120" is about 1.7×10 ^-5 K ^-1 , and the difference in linear expansion coefficient of the joined product of copper and "SGX120" is about 2.2×10 ^-5 K ^-1 . When the shape of these injection joined products is that shown in Figure 1, the joining surface is 10 mm x 5 mm, or ^0.5 cm2, and when an environmental temperature change of, for example, 200°C is applied, the dimensions that result will be 1.7 x 10 ^-5 K ^-1 x 200°C = 0.0034 = 0.34% for products using Al alloy, and 2.2 x 10 ^-5 K ^-1 x 200°C = 0.0044 = 0.44% for products using C1100 copper, compared to before the temperature change.

The longest part of this joint surface is 11.2 mm, so in the case of Al alloy material, this length will deviate by 0.038 mm, and in the case of copper material, it will be 0.049 mm. If this is repeated thousands of times, the outer periphery of the joint surface will eventually become unable to maintain its bonding strength, and the bonding strength will decrease. In the case of the above temperature change, thermoplastic resin molded products have creep properties, and if the temperature change progresses slowly, the internal stress that should be generated by the difference in linear expansion coefficient is hardly observed. In short, when the temperature changes slowly, the resin part near the joint surface is forcibly loaded with tensile and compressive forces due to the deformation of the metal material, so the tangled pattern of the amorphous part in the resin (the part where the polymer is tangled and shaped) changes, causing a slight change in shape and relieving the internal stress that has occurred. This is the explanation of the creep phenomenon itself, but for that reason, the temperature changes between early morning and early afternoon during the day, and the large but slow temperature changes in the four seasons will not lead to breakage even if there is a difference in linear expansion coefficient as mentioned above due to creep.

However, in the case of LIBs, they are subject to drastic temperature changes during use, for example, when used in winter in cold regions such as Alaska and Siberia. In cold regions, the outside temperature is about -50°C when the car is parked, and when driving, the LIB generates heat, and the heat from the engine and the interior heater can reach as high as 80°C. Such temperature changes are temperature shocks rather than temperature changes. This temperature shock is not directly related to the creep properties and does not affect them. Therefore, medium-sized LIBs used for mobile machines must be able to withstand a temperature shock test of about 3,000 cycles at -50°C/+100°C. Using the method described in Patent Document 3, a temperature shock test of 3,000 cycles was performed on an injection-bonded product of an Al alloy and "SGX120", and the bonded surface was observed. Once the shape (test piece) shown in Figure 1 is created, the resin part is scraped off and the shape is changed to the shape shown in Figures 6 and 7, with the resin part being 2 mm or 1 mm thick instead of the original 3 mm thickness of Figure 1.

Then, the objects in the shapes of Fig. 1, Fig. 6, and Fig. 7 were subjected to a temperature shock test of 3,000 cycles at -50°C/+150°C all at once, and after that, all were broken and the traces of the joint surface on the metal side were observed. In the case of the 3 mm thick resin part (test piece) in Fig. 1, which used an Al alloy treated with NMT5 to 7, the four corners of the joint surface of 10 mm x 5 mm and an area of 0.5 ^cm2 were clear with no resin powder, and black resin powder remained in the center. The above-mentioned "SGX120" is a black resin containing carbon black, and the fact that the resin powder remains in the center of this joint surface indicates that the joint surface was maintained in the black part. The four corners of the rectangular joint that are not black are parts where the resin part has already been extracted from the fine recesses on the metal surface and had zero joint strength. In other words, the above-mentioned temperature shock test indicates that the peeling had progressed to the point of almost breaking. In the part of the joint with a thickness of 2 mm shown in Fig. 6, only a small part without resin powder was observed in two of the four corners, and the joint strength was lost in a very small area. In the portion of the joint shown in FIG. 7 where the thickness is 1 mm, no resin loss occurred at all, including at the four corners.

From these results, the inventors have determined that, when the resin thickness is 1.5 mm, and the thickness is less than 1.5 mm, the resin molding will continue to bond to such an excellent surface-treated Al alloy, regardless of the bonding area, even if there are several thousand temperature shock cycles. On the other hand, a similar experimental test was also conducted with C1100 copper pieces. That is, this is the experimental example "A5" in the examples described later, and this experiment was conducted by injection bonding with the above-mentioned "SGX120". This was conducted by creating only the shape (test piece) shown in Figure 7 and subjecting it to a temperature shock test of 3,000 cycles at -50°C/+150°C. As mentioned above, the difference in linear expansion coefficient between the copper material and "SGX120" is greater than that of the Al alloy material, so it was predicted that if this temperature shock test was conducted on pieces with a resin thickness of 3 mm and 2 mm, the results would be worse than the experimental results for the Al alloy. In the experiment, it was observed whether slight peeling would occur at the bonding surface in an injection bonded product (test piece) with a resin thickness of 1 mm in the shape shown in Figure 7.

The results are shown in the examples below. If the resin thickness at the joint is 1 mm, it can be said that the joint structure can withstand this rigorous temperature shock test, regardless of the joint area. In the present invention, the resin thickness is 1 mm or less, and the design of the injection joint with "SGX120" containing both copper and Al alloy material can be done according to the basic design method described in Patent Document 3. The cross-sectional shape shown in Figure 8 is an example of the shape when applied to the lid of the main container of the LIB.

[Injection joining and annealing process]
In the injection joining of the present invention, as described above, a mold for injection joining is prepared, a surface-treated metal piece is inserted into the open mold, and the injection mold is closed to inject the molten resin. There is no technical feature that needs special attention for this injection joining operation. If anything, it is the temperature of the injection mold and the pressure retention time. The mold temperature may be within the temperature range specified by the resin manufacturer, but it is basically better to set it higher within this range. Specifically, when using the above-mentioned "SGX120", the mold temperature is preferably around 140°C. And, it is preferable that the obtained injection-joined product is not cooled as it is to be used as the final product, but is heated (annealed) at 150°C x 1 hour within a few hours to sufficiently advance the crystallization of the resin and then complete the entire injection joining process. For the above reasons, it is preferable that the integrated structure of the copper material and the PPS resin composition of the present invention is annealed after injection molding.

[Measurement of shear joint strength and shear joint viscosity]
ISO19095 specifies the method of measuring the tensile lap-shear strength and tensile strength between a metal part and a resin molded part in an injection-bonded product. According to this, a method of measuring the shear bond strength by tensile breaking an object (test piece) with a tensile tester as shown in FIG. 1, and a method of measuring the tensile bond strength by tensile breaking an object with a tensile tester as shown in FIG. 2 are described. The basis of this ISO standard for shear bond strength is a strength test method that the present inventors have used and proposed since the invention described in Patent Document 12. This method of measuring tensile bond strength is one that the present inventors have started to use around 2015 after going through various processes. Neither of these can be measured by the method specified in the Japanese Industrial Standards (JIS) (JISK6849, 6850), which was the conventional method of measuring adhesive strength and bond strength, so the inventors proposed a new standard and it was specified as an international industrial standard (ISO19095).

[About "shear joint viscosity"]
Furthermore, the present inventors proposed a new method of recording and evaluating the joining strength, not only the shear joining strength but also the "shear joining tackiness (force)", and placed more importance on this "shear joining tackiness" than on the value of the shear joining strength. That is, this was done by using the PPS resin composition "SGX120" to prepare an injection-jointed product (a product with the shape shown in FIG. 1), applying an external force in the shear direction to the joint surface, and measuring the resistance to the external force. In this case, regardless of the metal type, the shear joining strength was a maximum of 39 to 42 MPa, and no more was observed. In short, even if the type of metal material and the surface treatment method are variously changed, in the experiment using the above-mentioned "SGX120", if a breaking test is performed on a test piece with the shape shown in FIG. 1, a value that seems to be the upper limit value is reached. Therefore, if the surface treatment method of the metal alloy pieces is further improved and the shear joining strength is evaluated, it becomes difficult to determine whether an improvement has been made or whether it has worsened rather than improved when the shear joining strength approaches about 40 MPa.

For this reason, the inventors proposed a new measurement called "shear joint tackiness (force)" and decided that if the value of this measurement is high, a better surface treatment method has been achieved. This "shear joint tackiness (force)" is a type of fatigue test for joints. In this invention, "shear joint tackiness" refers to the results (shear joint strength) obtained by the following experimental method. First, a test piece (shaped as shown in Figure 1) is broken using a tensile tester, and the "shear joint strength" is measured and determined in advance. Then, a test is conducted in which a tensile force of about 75% of this "shear joint strength" is repeatedly applied to this test piece 300 times. The load is applied using a tensile tester and the operating software of the control device of the tester is set. The operating software sets the maximum tensile force to 75% of the "shear joint strength" value, the minimum tensile force to about 2/3 of the maximum tensile force, and the tensile speed to ±10 mm/min as one cycle.

If the specimen does not break under the 300 cycles of continuous repeated load, the maximum tensile load is increased by about 2 MPa and the test is repeated 300 times. If the specimen still does not break, the same operation is repeated by applying about 2 MPa. This repetition is continued until the specimen shown in FIG. 1 breaks. If the specimen breaks, the maximum tensile force before the break is expressed in MPa or in kg/0.5 ^cm2 , which is a gravity unit. In this experiment of the present invention, this is called "shear joint tenacity". The reason for the kg/ ^0.5 cm2 display is that the force display of the tensile tester is kg and the joint area of the joint surface of the shape shown in FIG. 1 is 0.5 ^cm2 .

The integrated structure of the copper material and PPS resin composition of the present invention not only has strong shear joint strength and shear joint toughness, but also has moist heat resistance against its shear breaking force. Furthermore, it was found that the physicochemical properties of both of these materials give the joint surface layer a high gas sealing ability. In particular, a new surface treatment method for copper materials was developed, and both new surface treatment methods were established using a treatment solution containing an aqueous solution of a trivalent chromium compound and a surface treatment solution that does not contain chromium compounds. These chemically treated Al alloy materials and LIBs using copper materials can seal the intrusion of water molecules into the electrolyte at a practical level.

FIG. 1 is an external view of an injection-bonded product for measuring the shear bond strength between a metal part and a resin part in a metal-resin bonded integrated product defined in ISO19095. FIG. 2 is an external view of an injection-bonded product for measuring the tensile bond strength between a metal part and a resin part in a metal-resin bonded integrated product defined in ISO19095. FIG. 3 is an external view of an auxiliary jig used when measuring the shear joint strength of a metal-resin integrated product as specified in ISO19095. 4A and 4B are electron microscope photographs of the surface of the A5052Al alloy of Experimental Example A-1 after chemical conversion treatment, where FIG. 4A is a photograph at a magnification of 1,000, FIG. 4B is a photograph at a magnification of 10,000, and FIG. 4C is a photograph at a magnification of 100,000. FIG. 5 is an electron microscope photograph of the surface-treated C1100 copper taken at a magnification of 100,000 times, and is a photograph of the surface after the chemical conversion treatment of Experimental Example A-4. FIG. 6 shows a test piece in which the upper part of the joint surface of the resin part in the shape shown in FIG. 1 has been machined to reduce the thickness from the original 3 mm to 2 mm. FIG. 7 shows a test piece in which the upper part of the joint surface of the resin part in the shape shown in FIG. 1 has been machined to reduce the thickness from the original 3 mm to 1 mm. FIG. 8 shows an example of the shape of the injection-jointed product according to the present invention, and is a cross-sectional view when applied to the lid of the main container of an LIB.

The embodiment of the integrated structure of copper material and PPS resin composition of the present invention will be explained as an experimental example in the following examples.

Hereinafter, examples of the integrated structure of the copper material and the PPS resin composition of the present invention will be described as experimental examples. The equipment and test methods used in the experiments are outlined below.
(a) Measurement of bonding strength 1
The breaking force when the injection bonded product (FIGS. 1 and 2) was tensile broken by a tensile tester was taken as the shear bond strength and tensile bond strength. However, the auxiliary jig shown in FIG. 3 was used for measuring the shear bond strength. The tensile tester used was "AG-500N/1kN (manufactured by Shimadzu Corporation (headquarters: Kyoto, Japan))" and measurements were taken at a pulling speed of 10 mm/min. The measurement method was in accordance with the method specified in ISO19095.
(b) Measurement of bonding strength 2
The above-mentioned "shear joint tackiness" value was measured using an injection joint (test piece shown in Figure 1) according to ISO 19095, with the above-mentioned tensile tester "AG-500N/1kN" at a pulling speed of ±10 mm/min. The specific operation method of the tester is as described above.
(c) Electron Microscope Observation Observation was performed at 1 to 2 KV using SEM-type electron microscopes "S-4800 (manufactured by Hitachi High-Technologies Corporation, headquartered in Tokyo, Japan)" and "JSM-6700F (manufactured by JEOL Ltd., headquartered in Tokyo, Japan)".

[Experimental Example A] Surface treatment method for metal pieces [Experimental Example A-1] Surface treatment for A5052 Al alloy (referred to as "NMT7 treatment" in this invention)
A 1.5 mm thick A5052 Al alloy plate was cut into 45 mm x 18 mm to obtain Al alloy pieces. In an immersion tank, an aqueous solution containing 10% aluminum degreaser "NA-6 (manufactured by Meltex Inc. (headquarters: Tokyo, Japan))" (hereinafter referred to as "NA-6") was set at 60°C, and the Al alloy pieces were immersed for 5 minutes, and then rinsed with public tap water (Ota City, Gunma Prefecture). Next, in another immersion tank, a 10% caustic soda aqueous solution at 40°C was prepared, and the Al alloy pieces were immersed for 1 minute and rinsed. Next, in another immersion tank, an aqueous solution containing 1% aluminum chloride hydrate and 5% hydrochloric acid at 40°C was prepared, and the Al alloy pieces were immersed for 6 minutes, and then rinsed with water. Next, in another immersion tank, an aqueous solution containing 2% ammonium difluoride and 10% sulfuric acid at 40°C was prepared, and the Al alloy pieces were immersed for 4 minutes, and then rinsed with water. Next, in another immersion tank, a 1.5% caustic soda aqueous solution at 40°C was prepared, and the Al alloy pieces were immersed in this for 1 minute, and then washed with water. Next, in another immersion tank, a 3% nitric acid aqueous solution at 40°C was prepared, and the Al alloy pieces were immersed in this for 1.5 minutes, and then washed with water. Next, in another immersion tank, a 3.5% hydrazine hydrate aqueous solution at 60°C was prepared, and the Al alloy pieces were immersed in this for 1 minute, and then in another immersion tank, a 0.5% hydrazine hydrate aqueous solution at 33°C was immersed for 6 minutes, and then washed with water. Next, the Al alloy pieces that had been subjected to the above chemical conversion treatment were placed in a hot air dryer set at 67°C for 15 minutes to dry, and then wrapped together in clean aluminum foil and stored.

The NMT7 treatment was carried out on A5052 plate pieces in the same manner as above. The aluminum alloy pieces obtained by this chemical conversion treatment were observed under an electron microscope. Figure 4 shows the electron microscope photograph (hereinafter referred to as the electron microscope photograph), and the electron microscope photograph at 1,000 times is shown in Figure 4 (a), the electron microscope photograph at 10,000 times is shown in Figure 4 (b), and the electron microscope photograph at 100,000 times is shown in Figure 4 (c). What was found by observing the photograph at 1,000 times was that there were high parts that looked like small hills and wide flat parts, and it can be observed that the mountain parts and the flat parts form a large uneven surface with a period of several tens of μm. When this part was observed visually, the reason why this part appeared to be a matte surface (pear-skinned) was due to the presence of this rough surface. In the electron microscope photograph at 10,000 times, there was a fine uneven surface with a period of several μm, which was the grain boundary of the metal crystal that became a recess. What is clear from the 100,000x electron microscope photographs is an ultra-fine uneven surface with a period of 30 to 100 nm, and looking at the metal surface as a whole, the surface of the chemically treated aluminum alloy piece has a triple uneven surface shape.

[Experimental Example A-2] Surface treatment of A6061Al alloy (referred to as "NMT8 treatment" in the present invention)
A 1.5 mm thick A6061 Al alloy plate was cut into 45 mm x 18 mm to obtain Al alloy pieces. In an immersion tank, an aqueous solution containing 10% of the aluminum degreaser "NA-6" was set to 60°C, and the Al alloy pieces were immersed for 5 minutes and then rinsed with public tap water (Ota City, Gunma Prefecture). Next, in another immersion tank, a 10% concentration aqueous caustic soda solution was prepared at 40°C, and the Al alloy pieces were immersed in this for 1 minute, and then rinsed with water. Next, in another immersion tank, an aqueous solution containing 1% concentration aluminum chloride hydrate and 5% concentration hydrochloric acid was prepared at 40°C, and the Al alloy pieces were immersed in this for 1 minute, and then rinsed with water. Next, in another immersion tank, an aqueous solution containing 2% concentration ammonium difluoride and 10% concentration sulfuric acid was prepared at 40°C, and the Al alloy pieces were immersed in this for 1 minute, and then rinsed with water. Next, in another immersion tank, a 1.5% concentration caustic soda solution at 40°C was prepared, and the Al alloy pieces were immersed in this for 2 minutes, and then washed with water. Next, in another immersion tank, a 3% concentration nitric acid solution at 40°C was prepared, and the Al alloy pieces were immersed in this for 1.5 minutes, and then washed with water. Next, in another immersion tank, a 3.5% concentration hydrated hydrazine solution at 60°C was prepared, and the Al alloy pieces were immersed in this for 1 minute, and then in another immersion tank, a 0.5% concentration hydrated hydrazine solution at 33°C was immersed for 4.5 minutes, and then washed with water. Next, in another immersion tank, a 1.5% concentration hydrogen peroxide solution was prepared, and the Al alloy pieces were immersed in this for 1 minute, and then thoroughly washed with water. Next, in another immersion tank, a 0.2% concentration triethanolamine solution at 40°C was prepared, and the Al alloy pieces were immersed in this for 5 minutes, and then thoroughly washed with water. Next, the aluminum alloy pieces that had been subjected to the above chemical conversion treatment were dried in a hot air dryer set at 67° C. for 15 minutes, and then wrapped together in clean aluminum foil and stored.

[Experimental Example A-3] Surface treatment of A1100Al alloy (NMT7 treatment)
A1100Al alloy plate with a thickness of 1.5 mm was cut into 45 mm x 18 mm to obtain Al alloy pieces. In an immersion tank, an aqueous solution containing 10% of the aluminum degreaser "NA-6" was set at 60°C, and the Al alloy pieces were immersed for 5 minutes, and then washed with public tap water (Ota City, Gunma Prefecture). Next, in another immersion tank, a 10% concentration aqueous caustic soda solution at 40°C was prepared, and the Al alloy pieces were immersed in this for 1 minute, and then washed with water. Next, in another immersion tank, an aqueous solution containing 1% concentration of hydrated aluminum chloride and 5% concentration of hydrochloric acid at 40°C was prepared, and the Al alloy pieces were immersed in this for 10 minutes, and then washed with water. Next, in another immersion tank, an aqueous solution containing 2% concentration of ammonium difluoride and 10% concentration of sulfuric acid at 40°C was prepared, and the Al alloy pieces were immersed in this for 1 minute, and then washed with water. Next, in another immersion tank, a 1.5% concentration caustic soda aqueous solution at 40°C was prepared, and the alloy pieces were immersed in this for 2 minutes, and then washed with water. Next, in another immersion tank, a 3% concentration nitric acid aqueous solution at 40°C was prepared, and the Al alloy pieces were immersed in this for 2 minutes, and then washed with water. Next, in another immersion tank, a 3.5% concentration hydrazine hydrate aqueous solution at 60°C was prepared, and the Al alloy pieces were immersed in this for 1 minute, and then in another immersion tank, a 0.5% concentration hydrazine hydrate aqueous solution at 33°C was immersed for 4 minutes, and then washed with water. Next, the Al alloy pieces that had been subjected to the above chemical conversion treatment were placed in a hot air dryer set at 67°C for 15 minutes to dry, and then wrapped in clean aluminum foil and stored.

[Experimental Example A-4] Surface treatment of C1100 copper (referred to as "New New NMT" in this invention: similar surface treatment method described in Patent Document 4: using a treatment agent containing chromium)
A 1.5 mm thick C1100 copper plate was cut into 45 mm x 18 mm, and a 2 mm diameter hole was drilled at the end to obtain a copper plate piece. The above-mentioned copper plate piece tied with a resin-coated wire for gardening was immersed in an aqueous solution containing 10% of the aluminum degreaser "NA-6" at 60°C in an immersion tank for 5 minutes, and then washed with public tap water (Ota City, Gunma Prefecture). Next, a 1.5% concentration aqueous caustic soda solution at 40°C was prepared in another immersion tank, and the copper plate piece was immersed in this for 1 minute, and then washed with water. Next, a 10% concentration aqueous nitric acid solution at 40°C was prepared in another immersion tank, and the copper plate piece was immersed in this for 1 minute, and then washed with water. Next, a 3% concentration aqueous solution containing nitric acid and 0.25% concentration ferric nitrate hydrate was prepared in another immersion tank, and the copper plate piece was immersed in this for 10 minutes, and then washed with water. Next, in another immersion tank, an aqueous solution containing 2% potassium permanganate, 3% caustic potassium, and 0.1% chromium nitrate hydrate was prepared at 70°C, and the copper plate was immersed in this for 35 minutes, and then washed with water. Next, in another immersion tank, an aqueous solution containing 5% sodium chlorite and 10% caustic soda was prepared at 55°C, and the copper plate was immersed in this for 20 minutes, and then washed with water. Next, the copper plate that had been subjected to the above chemical conversion treatment was dried in a hot air dryer set at 80°C for 15 minutes, and then wrapped in clean aluminum foil and stored. An electron microscope photograph of the surface of the copper plate is shown in Figure 5, and the whiskers are densely packed and formed like hair (this is the same treatment method described in Patent Document 4).

[Experimental Example A-5] Surface treatment of C1100 copper (referred to as "the latest type of new NMT 1" in this invention: treatment agent containing chromium is also used)
A 1.5 mm thick C1100 copper plate was cut into 45 mm x 18 mm, and a 2 mm diameter hole was drilled at the end to obtain a copper plate piece. In an immersion tank, an aqueous solution containing 10% of the aluminum degreaser "NA-6" was set to 60 ° C., and the copper plate piece was immersed for 5 minutes, and then washed with public tap water (Ota City, Gunma Prefecture). Next, in another immersion tank, a 10% concentration aqueous solution of nitric acid at 40 ° C. was prepared, and the copper plate piece was immersed in this for 3 minutes, and then washed with water. Next, in another immersion tank, an aqueous solution containing 3% concentration of nitric acid and 0.25% concentration of ferric nitrate hydrate at 40 ° C. was prepared, and the copper plate piece was immersed in this for 25 minutes, and then washed with water. Next, in another immersion tank, an aqueous solution containing 2% concentration of potassium permanganate, 3% concentration of caustic potash, and 0.1% concentration of chromium nitrate hydrate at 70 ° C. was prepared, and the copper plate piece was immersed in this for 15 minutes, and then washed with water. Next, in another immersion tank, an aqueous solution containing 5% sodium chlorite and 10% caustic soda at 55°C was prepared, and the copper plate pieces were immersed in this for 8 minutes and then washed with water. Next, the copper plate pieces that had undergone the above chemical conversion treatment were placed in a hot air dryer set at 80°C for 15 minutes to dry them. These were then wrapped together in clean aluminum foil and stored.

[Experimental Example A-6] Surface treatment of C1100 copper (referred to as "the latest type of new NMT 2" in this invention).
A 1.5 mm thick C1100 copper plate was cut into 45 mm x 18 mm, and a 2 mm diameter hole was drilled at the end to obtain a copper plate piece. In an immersion tank, an aqueous solution containing 10% aluminum degreaser "NA-6" was heated to 60°C, and the copper plate piece was immersed for 5 minutes while hanging from a resin-coated gardening wire, and then washed with public tap water (Ota City, Gunma Prefecture). Next, in another immersion tank, a 10% concentration aqueous solution of nitric acid at 40°C was prepared, and the copper plate piece was immersed in this for 3 minutes, and then washed with water. Next, in another immersion tank, an aqueous solution containing 3% concentration of nitric acid and 0.25% concentration of ferric nitrate hydrate was prepared at 40°C, and the copper plate piece was immersed in this for 25 minutes, and then washed with water. Next, in another immersion tank, an aqueous solution containing 2% potassium permanganate and 3% caustic potassium at 70°C was prepared, and the copper plate pieces were immersed in this for 15 minutes, and then washed with water. Next, in another immersion tank, an aqueous solution containing 5% sodium chlorite and 10% caustic soda at 55°C was prepared, and the copper plate pieces were immersed in this for 8 minutes, and then washed with water. Next, the copper plate pieces were placed in a hot air dryer set at 50°C for 20 minutes, and then placed in a hot air dryer set at 67°C for 10 minutes to dry the copper plate pieces. The dried copper plate pieces were wrapped together in clean aluminum foil and stored.

In addition, in the copper pieces obtained by this chemical conversion treatment, a line-shaped area with a slightly different color tone was observed about 5 mm from the end of the copper piece opposite the hole. Since the wet copper pieces obtained after the full liquid treatment were forced to dry by hanging them in a dryer, it is presumed that this area with a different color tone was caused by concentrated alkaline ions remaining at the end where the attached water remained last, which caused some kind of change in the fine shape and chemical change. The inventors thought that such color changes caused by the drying process should be avoided because they could cause quality variations. Therefore, in this experimental example A6, the water washing after the final process should be done carefully, of course, with sufficient washing with ion exchange water, etc. Furthermore, such unevenness of the copper plate surface was not seen in the above experimental examples A4 and A5. Experimental example A7, which will be described later, is a new idea to replace the alkaline substances remaining in the washing water by immersing the copper plate in a very dilute aqueous solution of water-soluble amine for a short time, and this immersion improved the unevenness of the copper plate surface.

[Experimental Example A-7] Surface treatment of C1100 copper (referred to as "the latest type of new NMT 3" in this invention)
A 1.5 mm thick C1100 copper plate was cut into 45 mm x 18 mm, and a 2 mm diameter hole was drilled at the end to obtain a copper plate piece. In an immersion tank, an aqueous solution containing 10% of the aluminum degreaser "NA-6" was set to 60 ° C., and the copper plate piece was immersed for 5 minutes, and then washed with public tap water (Ota City, Gunma Prefecture). Next, in another immersion tank, a 10% concentration aqueous solution of nitric acid at 40 ° C. was prepared, and the copper plate piece was immersed in this for 3 minutes, and then washed with water. Next, in another immersion tank, an aqueous solution containing 3% concentration of nitric acid and 0.25% concentration of ferric nitrate hydrate at 40 ° C. was prepared, and the copper plate piece was immersed in this for 25 minutes, and then washed with water. Next, in another immersion tank, an aqueous solution containing 2% concentration of potassium permanganate and 3% concentration of caustic potash was prepared at 70 ° C., and the copper plate piece was immersed in this for 15 minutes, and then washed with water. Next, in another immersion tank, prepare an aqueous solution containing 5% sodium chlorite and 10% caustic soda at 55°C, immerse the copper plate piece in this for 8 minutes, and then rinse with water.Next, in another immersion tank, prepare an aqueous solution of diethanolamine (DEA) at 0.02% at 40°C, immerse the copper plate piece in this for 0.5 minutes, and then rinse with water.Next, place in a hot air dryer set at 50°C for 20 minutes, and then place in a hot air dryer set at 67°C for 10 minutes to dry the copper plate piece, and then wrap it in clean aluminum foil and store it.

[Experimental Example B] An injection-bonded product having the shape shown in FIG. 1 was produced, and the bonding strength between the metal and resin was measured. Using the Al alloy pieces and copper plate pieces obtained in Experimental Examples A1 to A3 and Experimental Examples A4 to A7, and the PPS resin composition "SGX120" described above as the injection resin, an injection-bonded product was produced. The values of "shear bond strength" and "shear bond tackiness" of the produced injection-bonded product were measured. The results are shown in Table 1. From Table 1, it can be seen that the NMT7 and NMT8 treated products, which are developed from the NMT2 treatment method, show a shear bond strength of about 40 MPa for Al alloys in general, and the "shear bond tackiness" value shows about 85% of the shear bond strength, showing a sufficiently high bond strength. In addition, the shear bond strength of the A1100 Al alloy, which contains 1% impurity close to pure aluminum, is somewhat low because the Al alloy material is somewhat soft (low hardness).

On the other hand, among the C1100 copper-containing products A4 to A7, A4 and A5 are of the type that form whiskers on their surface, and use a treatment solution containing chromium ions to form whiskers. A4 is the same treatment product as the surface treatment method described in Patent Document 4, and A5 is an improved product used in the present invention, which has improved "shear joint viscosity." Although a chromium ion-containing aqueous solution that requires strict wastewater treatment is used, it is presumed that having a whisker-type surface may result in some advantageous situations, and it is therefore usable in the present invention.

The above experiments A6 and A7 shown in Table 1 used a treatment solution that did not contain chromium ions, and the treatment method for A6 was almost the same as A5 (the only difference was that a treatment solution that did not contain chromium ions was used). The treatment methods for A6 and A7 in the above experiments did not result in whisker formation, but the shear joint strength and shear joint ductility were comparable to those of the treatments that did result in whisker formation. As mentioned above, the copper piece A6 had a part with a different color tone about 5 mm from the end, and the injection joint surface contained this uneven part. From Table 1, it can be seen that there was no particular abnormality in the shear joint strength of A6, and the shear joint ductility was not particularly bad. Next, the treatment method of experimental example A7 was carried out with this countermeasure. That is, the surface was washed by immersing it in a dilute amine aqueous solution for a short time. This washing with a dilute amine aqueous solution eliminated the unevenness, at least when observed with the naked eye.

[Experimental Example C] Conducting a moist heat resistance test using an injection-bonded product of the shape shown in FIG. 1 Judging from the results shown in Table 1, the injection-bonded products of the PPS resin composition "SGX120" using C1100 copper according to Experimental Examples A5 and A6 are judged to be usable for the integrated structure of the copper material and the PPS resin composition of the present invention. Specifically, for example, when used for the lid of a battery box using these as a part of an LIB, it is optimal because the structure of the bonding surface layer does not change due to moisture in the air. In short, the important evaluation index is that if the bonding strength of the bonding part between the copper material and the resin molding decreases when placed in a humid atmosphere for a long period of time, it cannot be put into practical use. Therefore, a high temperature and high humidity test was conducted, which is a severe accelerated test, by exposing the product to 85% humidity at a temperature of 85°C for 1000 hours. The results are shown in Table 2. In this test, after removing the test piece from the high temperature and humidity tester, it was subjected to primary drying at 80°C for 48 hours, and then secondary drying at 150°C for 4 hours. After cooling, the shear bond strength was measured. The drying process at 150°C was performed to completely expel moisture contained in the PPS resin composition "SGX120" in a diffused state to the outside.

From the results in Table 2, both the shear joint strength and the shear joint ductility have decreased from the values before being put into the high-temperature, high-humidity tester, but they are still very high for a severe high-temperature, high-humidity test. This tendency of decrease in the strength of the Al alloy and copper material is quite similar to the data of the injection joint of the NMT2-treated Al alloy and the PPS resin composition "SGX120" shown in Patent Document 1, and the same high-temperature, high-humidity test. In the case of the Al alloy, the shear joint strength reached its lowest value in the first 500 hours or so, and the shear joint strength up to 1000 hours recovered slightly and returned to 37-39 MPa. After that, the joint strength was measured for 6,000 to 8,000 hours, but there was no change in the joint strength. This is presumed to be a process phenomenon in which aluminum rust is generated by water molecules and oxygen molecules invading the Al alloy side at the joint surface, filling the gap and moving towards a completely sealed type. In the case of copper, if the copper rust generated here is caused by copper oxide, it would have reacted with oxygen molecules to generate it. Judging from the above measured values, what occurred in 500 hours in the case of Al alloy material may have taken as long as 1000 hours in the case of copper. If this reasoning is correct, this high temperature and high humidity resistance test conducted at a temperature of 85°C and a humidity of 85% may lead to improved gas sealing properties as the test progresses. In any case, when this invention is applied to LIBs, the batteries are considered to be all-weather resistant, which should be favorable for extending the battery life.

[Experimental Example D] Thousand cycles of temperature shock test at -50°C/+150°C Several injection-bonded pieces (shape shown in FIG. 1) of the C1100 copper pieces prepared in Experimental Examples A5 and A6 and the PPS resin composition "SGX120" were prepared, and then the resin part was scraped off to make the shape shown in FIG. 7, with the thickness of the resin part reduced from 3 mm of the original shape in FIG. 1 to 1 mm. Then, a temperature shock test of 3,000 cycles at -50°C/+150°C was performed, and then the resin part was forcibly peeled off from the metal part using nippers or the like. As a result, the bonded surface of the metal part had black resin powder attached to the entire surface, including the four corners, and no resin loss occurred. From this result, it was determined that "SGX120" would continue to bond to C1100 copper with excellent surface treatment if the resin thickness was 1 mm or less, even if there were several thousand cycles of temperature shock, regardless of the bonded area.

On the other hand, as described above in Patent Document 3, a similar experimental test was conducted on an Al alloy, and in this invention, if the resin part thickness is based on about 1 mm in the case of an injection-joined product using the aforementioned PPS resin composition "SGX120," it can be fully expected that the injection-joined product will be able to withstand a temperature shock test of 3,000 cycles at -50°C/+150°C.

Figure 8 shows a cross-sectional view of an example of the structure of the lid of the LIB body. That is, it is an example of an integrated structure of copper material and PPS resin composition according to the present invention, and is an example of use in the lid of a LIB box. Whether the metal material of the drawer is a long plate or a round bar, it is surrounded by resin, and the basic thickness of the resin part that joins with the metal is about 1 mm. Since the joining area is wide and easy to obtain, it has good gas sealing properties. In the above test, the temperature shock 3,000 cycle test was performed with a 200°C difference of -50°C/+150°C, but in reality, when considering the actual usage environment of the LIB, a 150°C difference of -50°C/+100°C is thought to be sufficient.

The above-mentioned example was applied to the copper electrode for drawing out from the main body of the LIB, but it is not limited to this and can also be used in the construction and manufacture of parts for other products such as electrical equipment as long as it uses copper members and a PPS composition.

Claims (3)

A structure in which a surface-treated copper piece and a specific polyphenylene sulfide-based resin composition are directly bonded and integrated,
The polyphenylene sulfide-based resin composition is a resin composition in which the main component of the resin portion is polyphenylene sulfide resin, the secondary component is modified polyolefin resin, and 15 to 25% by weight of short glass fibers as a reinforcing material component is added to the resin composition,
The bonding strength between the copper material and the polyphenylene sulfide-based resin composition is 40 MPa or more as measured by shear bonding strength using an injection-bonded product as specified by the International Organization for Standardization (ISO 19095), and
The injection-bonded product has a shear bonding viscosity of 33 MPa or more, which is defined as a tensile strength at which the product does not break even when an external force in a shear direction is applied 300 times continuously and repeatedly;
The copper material is a pure copper material having a purity of 99.90% or more,
a thickness of the polyphenylene sulfide resin composition bonded to the copper material is essentially 1 mm or less. The integrated structure of a copper material and a PPS resin composition according to claim 1,
the copper material is a rod-shaped member forming a negative electrode lead-out portion, and the aluminum alloy rod-shaped member that has been surface-treated by a chemical conversion treatment forms a positive electrode lead-out portion, the negative electrode part and the positive electrode part form a battery lid in which the lead-out portions of the negative electrode part and the positive electrode part penetrate to the outside, and the battery lid is made of the polyphenylene sulfide-based resin composition, which is a structure around the electrode lead-out portion of a lithium ion battery. 2. The method for producing an integrated structure of a copper material and a PPS resin composition according to claim 1 ,
The method for producing a copper member having a chemically treated surface is inserted into an injection molding die, and the polyphenylene sulfide-based resin composition is injected into the die, thereby directly integrating the copper member with the polyphenylene sulfide-based resin composition.

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