Polyester material as well as preparation method and application thereof

Abstract

The invention discloses a polyester material as well as a preparation method and application thereof. The polyester material is prepared from the following raw materials in parts by mass: 50 to 95 parts of polyester resin, 3 to 30 parts of polyester elastomer and 0 to 25 parts of flexibilizer, the melt index of the polyester elastomer is not higher than 100% of the melt index of the polyester resin, and the test conditions of the melt index are as follows: the test temperature is 20 DEG C higher than the melting point of the polyester resin, and the test pressure is 2.16 kg. The polyester material is suitable for surface metallization by wet electroplating, can be used for preparing a composite metal foil, and has the characteristics of high metal layer binding force, excellent electrochemical performance, low production cost and easiness in industrial application. The invention also provides a preparation method and application of the polyester material.

Description

Technical Field

[0001] This invention relates to the field of polymer materials and composite materials, and particularly to a polyester material, its preparation method, and its applications. Background Technology

[0002] Composite metal foil is a composite material with a "metal-polymer-metal" sandwich structure, widely used in current collectors for new energy batteries. The most common composite metal foils on the market are composite copper foil and composite aluminum foil, with composite copper foil being the most widely used. Commonly used polymer materials in composite copper foil include polyethylene terephthalate (PET), polypropylene (PP), and polyimide (PI). Although PI has good mechanical and heat resistance properties, its high cost limits its application in composite copper foil. In contrast, the cost advantage of PET and PP makes them the mainstream choice in the market.

[0003] Composite copper foil, by replacing part of the metallic copper with polymer materials, has the following advantages compared to traditional metal current collectors: (1) reduced dependence on metal resources; (2) lower unit price and density of polymer materials, which helps to reduce costs and weight; (3) higher flexibility; (4) greater potential for functionalization; and (5) improved puncture resistance of batteries: because polymer films have better deformation capabilities than metals, when a battery is punctured, the polymer film can effectively wrap the metal fracture, thereby preventing short circuits. Therefore, composite copper foil has attracted much attention in the field of new energy batteries.

[0004] The common process for preparing composite copper foil involves depositing a metal seed layer of tens of nanometers on the polymer surface by magnetron sputtering, followed by wet electroplating to thicken the copper layer. This process has the following problems: (1) Although the material cost of composite copper foil is low, the cost of magnetron sputtering equipment is high, which makes the production cost of composite copper foil still high; (2) Existing magnetron sputtering technology has problems such as uneven copper layer thickness and many surface pores during copper plating; (3) During the magnetron sputtering process, the surface temperature of the polymer film increases, which may cause polymer degradation and lead to a decrease in the mechanical properties of the material. Moreover, the more times the magnetron sputtering is performed, the more obvious the decrease in mechanical properties; (4) Magnetron sputtering involves a large number of vacuuming and temperature control operations, resulting in low production efficiency and difficulty in achieving continuous and efficient production.

[0005] Therefore, there is an urgent need to develop a polyester material suitable for wet electroplating to prepare metal layers, in order to solve the problems of poor adhesion between polyester and metal coating, low production efficiency and high cost, thereby promoting the industrial application of composite copper foil. Summary of the Invention

[0006] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes a polyester material suitable for surface metallization by wet electroplating, which can be used to prepare composite metal foils and has the characteristics of high metal layer adhesion, excellent electrochemical performance, low production cost, and easy industrial application.

[0007] The present invention also proposes a method for preparing the above-mentioned polyester material.

[0008] The present invention also proposes a polyester film.

[0009] The present invention also proposes a method for preparing the above-mentioned polyester film.

[0010] The present invention also proposes a composite metal foil.

[0011] The present invention also proposes a method for preparing the above-mentioned composite metal foil.

[0012] The present invention also proposes the application of the above-mentioned polyester materials, polyester films or composite metal foils in the preparation of current collectors or secondary batteries.

[0013] The first aspect of the present invention relates to a polyester material comprising the following raw materials in parts by weight: 50-95 parts polyester resin, 3-30 parts polyester elastomer, and 0-25 parts toughening agent; The melt index of the polyester elastomer is higher than that of the polyester resin, but not higher than 100% of the melt index of the polyester resin. The test conditions for the melt index are: the test temperature is 20°C above the melting point of the polyester resin, and the test pressure is 2.16 kg.

[0014] The polyester material according to the first aspect of the present invention has at least the following beneficial effects: Polyester elastomers have a higher melt index than polyester resins, giving them better flowability and migration during melt processing, allowing them to preferentially accumulate on the material surface. After roughening treatment before electroplating, certain areas of the polyester elastomer are more susceptible to corrosion, resulting in a uniform micro-pit structure on the surface. This provides a strong interlocking effect and more bonding sites for subsequent metal plating, effectively overcoming the problem of insufficient adhesion between traditional polyester materials and metal interfaces. The resulting composite copper foil exhibits excellent interfacial bonding strength and overall stability.

[0015] By limiting the melt index of the polyester elastomer to no more than 100% of the melt index of the polyester resin, the compatibility of the two during blending can be ensured, avoiding aggregation and uneven dispersion caused by excessive melt index differences. If the elastomer particle size is too large, it will not only lead to uneven material structure but also cause localized excessive corrosion during electroplating roughening, and even lead to film perforation. This invention ensures the uniform distribution of the elastomer in the matrix by reasonably controlling the melt index difference, maintaining the density and integrity of the material surface.

[0016] Adding toughening agents can further improve the toughness of the material. Specifically, POE, maleic anhydride-grafted POE, or maleic anhydride-grafted PA can be selected. Among them, the grafting rate of maleic anhydride graft modification can be controlled above 0.5wt% to improve compatibility and dispersibility.

[0017] The polyester material proposed in this invention can be used as a substrate for wet electroplating in the preparation process of composite copper foil. It can effectively improve the interfacial bonding strength between the metal coating and the polyester layer, reduce production costs, and has the advantage of mass production.

[0018] According to some embodiments of the present invention, the polyester resin is selected from aromatic polyesters.

[0019] According to some embodiments of the present invention, the polyester resin is selected from at least one of polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and poly(1,4-cyclohexanedimethyl terephthalate) (PCT).

[0020] According to some embodiments of the present invention, the Shore hardness of the polyester elastomer is 25D to 82D, for example, 50 to 72D.

[0021] According to some embodiments of the present invention, the polyester elastomer is selected from polyether-polyester block copolymers.

[0022] According to some embodiments of the present invention, the raw materials for preparation include: 55-95 parts of polyester resin and 5-25 parts of polyester elastomer. More specifically, they include: 70-95 parts of polyester resin and 5-25 parts of polyester elastomer.

[0023] The second aspect of the present invention relates to a method for preparing the above-mentioned polyester material, comprising the following steps: melting and extruding the raw material, and then pelletizing it to obtain the final product; In the melt extrusion process, the screw has 1 to 10 reverse threads in the plasticizing section.

[0024] Reverse threads can be continuously or intermittently installed in the plasticizing section. When intermittently installed, adjacent reverse threads can be spaced at least one turn of forward thread, and the reverse threads can be evenly or unevenly distributed. Reverse threads help improve the uniformity of component dispersion, but excessive numbers may cause material degradation and black spots. Typically, the number of reverse threads is controlled between 2 and 5. As the screw length increases, the number of reverse threads can be appropriately reduced.

[0025] This preparation method is simple, enables efficient large-scale production, and ensures uniform dispersion of raw materials. The prepared polyester material can be used to prepare composite copper foil, significantly enhancing the adhesion between the metal coating and the polymer layer, simplifying the electroplating process, reducing production costs, and improving production efficiency.

[0026] According to some embodiments of the present invention, the length-to-diameter ratio of the screw used for melt extrusion is greater than 36:1. A length-to-diameter ratio that is too low may affect the dispersion effect.

[0027] A third aspect of the present invention relates to a polyester film made from the aforementioned polyester material.

[0028] The aforementioned polyester film is made from the aforementioned polyester material, and therefore possesses at least all the beneficial effects of the embodiments described above. For example, the polyester elastomer can be uniformly dispersed in the polyester resin, thereby significantly enhancing the bonding force between the metal plating layer and the polymer layer during the preparation of composite copper foil, simplifying the electroplating process, effectively reducing production costs, and improving production efficiency.

[0029] According to some embodiments of the present invention, the thickness of the polyester film is 2~100μm, which can meet the design requirements of conventional composite copper foil. In actual use, the thickness can be adjusted according to specific application requirements.

[0030] According to some specific embodiments of the present invention, the thickness of the polyester film is 2~10μm.

[0031] The fourth aspect of the present invention relates to a method for preparing the above-mentioned polyester film, comprising the following steps: processing the polyester material by casting and stretching processes to obtain a polyester film.

[0032] The specific casting and stretching process parameters can be determined by referring to the mature processes of existing similar materials, and this invention does not limit them.

[0033] A fifth aspect of this invention relates to a composite metal foil, comprising the aforementioned polyester film and metal foil layers attached to both surfaces of the polyester film, wherein an intermediate conductive layer is provided between the metal foil layers and the polyester film. The intermediate conductive layer is used to deposit the metal foil layers via a wet electroplating process. The material of the intermediate conductive layer may be one or more alloys of nickel, copper, gold, and silver, and its thickness may be sufficient to meet conductivity requirements, for example, 20-500 nm.

[0034] According to some embodiments of the present invention, the thickness of a single metal foil layer is 0.5~2.5 μm. The metal foil layer can be prepared by a wet electroplating process. Due to the high purity of the plating layer and its excellent adhesion to the polyester film, high conductivity can be obtained with a relatively low metal thickness.

[0035] According to some embodiments of the present invention, the material of the metal foil layer is selected from one or more alloys of gold, silver, copper, cobalt, aluminum, nickel, chromium, magnesium, lithium and manganese.

[0036] According to some specific embodiments of the present invention, the material of the metal foil layer is selected from copper or aluminum.

[0037] The sixth aspect of the present invention relates to a method for preparing the above-mentioned composite metal foil, comprising the following steps: The polyester film is immersed in a solution to roughen and create pores; A conductive layer is deposited on both sides of the roughened film. After the intermediate conductive layer is deposited, wet electroplating is performed on both sides of the thin film to form a metal foil layer, thus obtaining a composite metal foil.

[0038] The relevant processes are mature technologies in this field and can be selected reasonably according to actual needs.

[0039] The seventh aspect of the present invention relates to the application of the above-mentioned polyester materials, polyester films or composite metal foils in the preparation of current collectors or secondary batteries.

[0040] Specifically, secondary batteries include lithium-ion batteries or sodium-ion batteries. Composite metal foils can be used as current collectors for the positive or negative electrodes of secondary batteries. For example, in lithium-ion and sodium-ion batteries, composite aluminum foil is typically used for the positive electrode current collector, while composite copper foil is typically used for the negative electrode current collector.

[0041] In this article, "multiple" includes two or more than two types.

[0042] In this document, all numerical ranges include endpoint values ​​and encompass any subrange within that range, such as ranges obtained by arbitrarily combining the numerical values ​​listed in the specific embodiments. Furthermore, "above" or "below" includes the numerical values ​​themselves.

[0043] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Detailed Implementation

[0044] The embodiments of the present invention are described in detail below. These embodiments are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0045] Unless otherwise specified, all raw materials or equipment mentioned are commercially available and can be purchased directly from the market.

[0046] Polyester: PBT, model TH6100, produced by Xinjiang Lanshan Tunhe Technology Co., Ltd., melting point 225℃, melt index 22g / 10min at 245℃ and 2.16kg.

[0047] Poly(cyclohexyldimethyl terephthalate): PCT, model 1631, manufactured by SK Chemicals, South Korea, melting point 268℃, melt index 18g / 10min at 288℃ and 2.16kg.

[0048] Polyester elastomer: Polyether-polyester block copolymer, TPEE 7246, DuPont, Shore hardness 72D. Melt index is 29 g / 10 min at 245℃ and 2.16 kg, and 35 g / 10 min at 288℃ and 2.16 kg.

[0049] Polyester elastomer: Polyether-polyester block copolymer, model TH3050, Xinjiang Lanshan Tunhe Technology Co., Ltd., Shore hardness 50D. Melt index is 47g / 10min at 245℃ and 2.16kg, and 126g / 10min at 288℃ and 2.16kg.

[0050] Examples 1-3 and Comparative Examples 1-2 The formulation of the polyester material is shown in Table 1.

[0051] The preparation method of polyester material is as follows, wherein the extrusion, casting, and stretching temperatures are selected according to the melting point of the polyester. If the melting point is high, a temperature close to the upper limit is selected; if the melting point is low, a temperature close to the lower limit is selected. The raw materials in the specified formula are fed into a twin-screw extruder via the main feeder, and after melt extrusion and pelletizing, polyester material is obtained. The extruder screw has a length-to-diameter ratio of 52, and the plasticizing section has 3 reverse threads, with 3 forward threads spaced between the reverse threads. The temperature setting range for each section of the extruder is 240~290℃.

[0052] The preparation method of composite copper foil is as follows: S1. Polyester material is processed by casting and stretching to obtain a polyester film with a thickness of 6μm. The casting temperature is 260~310℃, and the thickness after casting is 200μm. Biaxial stretching is then performed: at 180~220℃ and a wind speed of 25m / s, the X (transverse) stretch is 6 times and the time is 12 seconds; the Y (longitudinal) stretch is 6 times and the time is 12 seconds. S2. The polyester film is immersed in a roughening solution to roughen and corrode it to form micropores. The roughening solution consists of CrO3 400g / L, H2SO4 375g / L, roughening temperature 65℃, roughening time 12min. After roughening, it is neutralized (CP grade hydrochloric acid, 100mL / L) to clean the chromium remaining on the film surface. S3, Colloidal Palladium Activation Treatment: Impregnation Solution Composition: PL-5 colloidal palladium activator 1.5%, sodium sulfite 220g / L, CP grade hydrochloric acid 50mL / L, treatment temperature 40℃, treatment time 12min; S4: Degelatinization treatment: The treatment solution is 100 mL / L of CP grade hydrochloric acid, the treatment temperature is 40℃, and the treatment time is 2 min, so that the palladium particles adsorbed on the film surface have catalytic activity; S5. Nickel plating is performed on both sides of the polyester film after degumming treatment. The plating solution composition is: SHM-300A high phosphorus electroless nickel (produced by Sanhe Magnesium (Shenzhen) Technology Co., Ltd.) 150mL / L, SHM-300B high phosphorus electroless nickel (produced by Sanhe Magnesium (Shenzhen) Technology Co., Ltd.) 100mL / L, SHM-300C high phosphorus electroless nickel (produced by Sanhe Magnesium (Shenzhen) Technology Co., Ltd.) 100mL / L, temperature 40℃, time 4min, nickel plating thickness 20~500nm; S6. Perform wet electroplating on both sides of the nickel-plated film (plating solution composition: 210 g / L copper sulfate, 70 g / L CP grade sulfuric acid, 75 g / L CP grade hydrochloric acid) at a plating temperature of 30°C to form a single-layer copper layer with a thickness of 1 μm, thus obtaining a composite copper foil.

[0053] Comparative Example 3 Composite copper foil was prepared according to the method in Example 1, except that all the reverse threads of the extruder were replaced with forward threads, while the other parameters of the screw remained unchanged.

[0054] Comparative Example 4 Composite copper foil was prepared according to the method of Example 1, except that the plasticizing section of the extruder was continuously provided with 12 turns of reverse thread, while the other parameters of the screw remained unchanged.

[0055] Table 1 (parts by weight)

[0056] Test case 1. Adhesion of composite copper foil coating: The test sample is the composite copper foil prepared in the above-mentioned examples or comparative examples, with an area of ​​100mm×50mm. A peel force tester is used, the test speed is set to 2mm / min, and a 180° peel force test is performed. The maximum peel force N is recorded. The test is repeated 5 times and the average value is taken.

[0057] 2. Thermal Cycling: The prepared composite copper foil is kept at -50℃ for 24 hours, then heated to 50℃ at a rate of 2℃ / min and held at that temperature for 24 hours, and then cooled back to -50℃ at a rate of 2℃ / min. This constitutes one cycle. After one cycle, the adhesion between the electroplated layer and the resin is observed to see if it is loose. If not, the next cycle is performed, with a maximum of five cycles. The more thermal cycling cycles the product undergoes, the better its resistance to thermal shock.

[0058] 3. Bending resistance: After bending at 180°, record the number of times peeling or breaking occurs.

[0059] The test results are shown in Table 2.

[0060] Table 2

[0061] The present invention has been described in detail above with reference to the embodiments. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A polyester material, characterized in that, The preparation materials include the following raw materials in parts by weight: 50-95 parts polyester resin, 3-30 parts polyester elastomer, and 0-25 parts toughening agent; The melt index of the polyester elastomer is higher than that of the polyester resin, but not higher than 100% of the melt index of the polyester resin. The test conditions for the melt index are: the test temperature is 20°C above the melting point of the polyester resin, and the test pressure is 2.16 kg.

2. The polyester material according to claim 1, characterized in that, The polyester resin is selected from at least one of polyethylene terephthalate, polybutylene terephthalate, and poly(1,4-cyclohexanediol) terephthalate.

3. The polyester material according to claim 1, characterized in that, The polyester elastomer has a Shore hardness of 25D to 82D; and / or the polyester elastomer is selected from polyether-polyester block copolymers.

4. The polyester material according to claim 1, characterized in that, The raw materials for preparation include: 55-95 parts of polyester resin and 5-25 parts of polyester elastomer.

5. The method for preparing the polyester material according to any one of claims 1-4, characterized in that, Includes the following steps: The raw material is melt-extruded and then pelletized to obtain the final product. In the melt extrusion process, the screw has 1 to 10 reverse threads in the plasticizing section.

6. The preparation method according to claim 5, characterized in that, The length-to-diameter ratio of the screw used in the melt extrusion is greater than 36:

1.

7. A polyester film, characterized in that, It is made from the polyester material as described in any one of claims 1-4; Optionally, the thickness of the polyester film is 2 to 100 μm.

8. A composite metal foil, characterized in that, It includes the polyester film as described in claim 7, and a metal foil layer attached to both sides of the polyester film; an intermediate conductive layer is provided between the metal foil layer and the polyester film.

9. The composite metal foil according to claim 8, characterized in that, The metal foil layer is made of one or more alloys selected from gold, silver, copper, cobalt, aluminum, nickel, chromium, magnesium, lithium and manganese; And / or, the thickness of a single layer of the metal foil is 0.5~2.5μm.

10. The use of the polyester material as described in any one of claims 1-4, or the polyester film as described in claim 7, or the composite metal foil as described in any one of claims 8-9 in the preparation of current collectors or secondary batteries.

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