A kind of high temperature resistant ear glue and preparation method thereof

Abstract

The present invention relates to the field of ear glue technology, and in particular to a high temperature resistant ear glue and a preparation method thereof. The ear glue prepared by the present invention using a dry composite process includes a PET layer, a glue layer arranged on both sides of the PET layer, and an MPP layer arranged outside the glue layer; wherein the MPP layer is a three-layer structure, which is a modified PP layer, a homopolymer PP layer, and a copolymer PP layer treated with corona from the outside to the inside. The ear glue of the present invention has excellent high temperature resistance and electrolyte resistance, and has a simple process, low investment cost, and can be produced according to the color requirements of customers.

Description

Technical Field

[0001] The invention relates to the technical field of tab glue, and in particular to a high temperature resistant tab glue and a preparation method thereof. Background Art

[0002] Tab glue is a material widely used in the field of lithium-ion batteries. The main function of tab glue is to bond to the tab of lithium-ion batteries, so that the tab of lithium-ion batteries has the performance of heat sealing with the PP layer (polypropylene layer) of the aluminum-plastic film. Tab glue is essentially a non-sticky film, which is completely controlled by temperature and time to make it fuse.

[0003] At present, most of the tab glues on the market are single-layer or three-layer tab glues. Among them, single-layer tab glue is generally made of polypropylene, which is in a molten state when sealed at high temperature and hot pressing, and has a certain fluidity, which often causes the metal conductor to contact the shell and cause short circuit or leakage; three-layer tab glue is a surface film layer / middle film layer / surface film layer structure, which is produced by extrusion and lamination process. When sealed at high temperature and hot pressing, the inner layer is easily deformed and leaks.

[0004] The three-layer lug glue that can withstand high temperatures on the market is mainly black lug glue, which is made by multi-layer co-extrusion process. During the production process, black masterbatch needs to be added to the raw materials of the film layers on both sides. It is extremely difficult to clean after use, which is not conducive to the subsequent production of other products. Therefore, it has great limitations. In addition, when using the multi-layer co-extrusion process, the surface film layer and the middle film layer need to be customized with related equipment, and the investment cost is relatively high. At present, the black lug glue on the market is exclusively monopolized by DNP and is expensive. Moreover, with the continuous improvement of people's requirements for personalization, people have put forward demands for the diversification of lug glue colors. Therefore, how to produce high-temperature resistant lug glue of different colors according to customer needs is also one of the research focuses.

[0005] The invention patent with authorization announcement number CN102208576B provides a tab glue and a preparation method thereof, wherein a tab glue with a surface film layer / middle film layer / surface film layer structure is prepared by a three-layer co-extrusion method, wherein the surface film layer is made of uncross-linked polyolefin, and the middle film layer is made of cross-linked polyolefin or a mixture of polyolefin, cross-linking agent, co-cross-linking agent and antioxidant as raw materials, so that the prepared tab glue does not stratify under long-term electrolyte immersion and does not deform during heat sealing. However, the production process has high requirements on equipment, especially for high-temperature resistant tab glue, and does not solve the customer's demand for diversified colors of tab glue.

[0006] In view of this, it is necessary to provide a new high temperature resistant ear glue and a preparation method thereof through research to solve the above problems. Summary of the invention

[0007] The first object of the present invention is to provide a high temperature resistant tab glue.

[0008] The second object of the present invention is to provide a method for preparing the above-mentioned high temperature resistant tab glue.

[0009] To achieve the above object, the technical solution of the present invention is:

[0010] The first aspect of the present invention provides a high temperature resistant ear glue, comprising a PET (polyethylene terephthalate) layer, a glue layer arranged on both sides of the PET layer, and an MPP (acid-modified polypropylene) layer arranged on the outside of the glue layer; the PET layer, the glue layer and the MPP layer are compounded together by a dry compounding process, and the single layer thicknesses are 10-30um, 2-5um, and 20-50um, respectively; wherein the MPP layer is a three-layer structure, which, from the outside to the inside, is a modified PP (polypropylene) layer, a homopolymer PP layer and a copolymer PP layer treated with corona, and the thickness ratio thereof is 1:(1-4):1.

[0011] Furthermore, the PET layer is made of a double-sided corona-treated PET film.

[0012] Furthermore, the color of the PET film can be selected according to customer needs.

[0013] Furthermore, the glue layer is made of anhydride-modified polypropylene solvent-based glue.

[0014] Furthermore, the modified PP layer is made of polypropylene graft-modified with one or more monomers selected from acrylic acid, methacrylic acid, maleic acid, maleic anhydride, α-methacrylic acid, methyl methacrylate and glycidyl methacrylate;

[0015] The homopolymer PP layer is made of polypropylene obtained by polymerizing a single propylene monomer;

[0016] The copolymerized PP layer subjected to corona treatment is prepared by subjecting propylene monomer and a small amount of ethylene (1-4%) monomer to copolymerization to obtain polypropylene, which is subjected to corona treatment.

[0017] Furthermore, the MPP layer is a modified PP layer, a homopolymer PP layer and a copolymer PP layer treated with corona, which are compounded together by casting or blowing.

[0018] Furthermore, the thickness of the MPP layer is 30-43 um, and in the single-layer MPP layer, the thickness ratio of the modified PP layer, the homopolymer PP layer and the corona-treated copolymer PP layer is 1:2:1.

[0019] The second aspect of the present invention provides a method for preparing the above-mentioned high temperature resistant tab glue, comprising the following steps:

[0020] S1. Preparation of MPP membrane

[0021] The raw materials are added into the hoppers of the extruder in the order of modified PP layer, homopolymer PP layer and copolymer PP layer by using the casting process, extruded and formed, and the outer side of the copolymer PP layer is corona treated to obtain MPP film, and 2 portions of MPP film are prepared for standby use;

[0022] The parameters of the casting process are as follows: melting temperature 200-260°C, cooling temperature 10-40°C, and drawing ratio (1-2):1;

[0023] S2, dry compound

[0024] Take a double-sided corona-treated PET film, apply a layer of glue on one side to form a glue layer, place the corona-treated side of the copolymer PP layer of the MPP film prepared in step S1 opposite to the glue layer, and compound on a compounding machine at a compounding temperature of 80-120°C; similarly, compound another MPP film on the other side of the PET film to obtain the above-mentioned high-temperature resistant ear glue.

[0025] Furthermore, in step S1, a film blowing process is used instead of a casting process to prepare the MPP film, and the parameters of the film blowing process are: a melting temperature of 200-260°C, a cooling temperature of 10-40°C, a blowing ratio of (1-3):1, and a pulling ratio of (1-2):1.

[0026] The advantages and beneficial effects of the present invention compared to the prior art are:

[0027] 1. The high temperature resistant ear glue of the present invention has a three-layer structure design of a modified PP layer, a homopolymer PP layer and a copolymer PP layer treated with corona, which effectively improves the high temperature resistance and bonding performance of the ear glue; the PET layer as the middle film layer has excellent high temperature resistance; the glue layer bonding the surface film layer and the middle film layer has excellent electrolyte resistance while playing an excellent bonding role;

[0028] 2. The present invention adopts a dry composite process to prepare high-temperature resistant ear glue. Not only is the preparation method simple, but there is no need to customize special equipment, which greatly reduces the investment cost and breaks the monopoly of foreign companies. In addition, the preparation process of the present invention can adjust production according to customer demand for color on the original production line, filling the gap in the market demand for the color of high-temperature resistant ear glue. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic diagram of the overall structure of the high temperature resistant tab glue according to an embodiment of the present invention;

[0030] Figure 2 Schematic diagram of the hierarchical structure of the MPP layer in an embodiment of the present invention. DETAILED DESCRIPTION

[0031] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0032] The abbreviations used in the present invention are as follows:

[0033] PET: Polyethylene terephthalate

[0034] PP: Polypropylene

[0035] MPP: Acid modified polypropylene

[0036] CPP: Cast Polypropylene

[0037] like Figure 1 The figure shows a high temperature resistant ear glue of the present invention, comprising a PET layer 1, a glue layer 2 arranged on both sides of the PET layer 1, and an MPP layer 3 arranged outside the glue layer 2; the thicknesses of the PET layer 1, the glue layer 2 and the MPP layer 3 are 10-30um, 2-5um, and 20-50um respectively; wherein the MPP layer 3 is a three-layer structure, such as Figure 2 As shown, from the outside to the inside are the modified PP layer 31, the homopolymer PP layer 32 and the corona-treated copolymer PP layer 33, and the thickness ratio thereof is 1:(1-4):1.

[0038] The PET layer 1 is made of a double-sided corona-treated PET film, and the PET film can be purchased according to the customer's requirements for color.

[0039] The glue layer 2 is made of anhydride-modified polypropylene solvent-based glue and has excellent electrolyte resistance.

[0040] The modified PP layer 33 is made of polypropylene grafted with one or more monomers selected from acrylic acid, methacrylic acid, maleic acid, maleic anhydride, α-methacrylic acid, methyl methacrylate and glycidyl methacrylate, and is used for heat sealing with the tabs later.

[0041] Furthermore, the MPP layer 3 is made of a modified PP layer 31, a homopolymer PP layer 32 and a corona-treated copolymer PP layer 33 by casting or blowing.

[0042] The homopolymer PP layer 32 is made of polypropylene polymerized from a single propylene monomer and is a support layer for the MPP layer 3;

[0043] The corona-treated copolymer PP layer 33 is made of polypropylene obtained by copolymerizing propylene monomer and a small amount of ethylene (1-4%) monomer and subjected to corona treatment, and is used for high-strength bonding with the PET layer 1 .

[0044] The present invention also provides a method for preparing the high temperature resistant ear glue, comprising the following steps:

[0045] S1. Preparation of MPP membrane

[0046] The raw materials are added into the hoppers of the extruder in the order of modified PP layer, homopolymer PP layer and copolymer PP layer by using the casting process, extruded and formed, and the outer side of the copolymer PP layer is corona treated to obtain MPP film, and 2 portions of MPP film are prepared for standby use;

[0047] The parameters of the casting process are as follows: melting temperature 200-260°C, cooling temperature 10-40°C, and pulling ratio (1-2):1.

[0048] Here, the MPP film can also be prepared by using a blown film process instead of a cast film process, and the parameters of the blown film process are: a melting temperature of 200-260° C., a cooling temperature of 10-40° C., a blowing ratio of (1-3):1, and a pulling ratio of (1-2):1;

[0049] S2, dry compound

[0050] Take a double-sided corona-treated PET film, apply a layer of glue on one side to form a glue layer, place the corona-treated side of the copolymer PP layer of the MPP film prepared in step S1 opposite to the glue layer, and compound on a compounding machine at a compounding temperature of 80-120°C; similarly, compound another MPP film on the other side of the PET film to obtain the high-temperature resistant ear glue of the present invention.

[0051] The present invention will be further described below by means of specific examples.

[0052] Example 1

[0053] A high temperature resistant ear glue comprises a PET layer, a glue layer arranged on both sides of the PET layer, and an MPP layer arranged outside the glue layer, with a total thickness of 100um; wherein the thicknesses of the PET layer, the glue layer and the MPP layer are 10um, 2um and 43um respectively; the MPP layer is a three-layer structure, which comprises a modified PP layer, a homopolymer PP layer and a copolymer PP layer treated with corona from the outside to the inside, and the thickness ratio is 1:2:1.

[0054] Example 2

[0055] The only difference compared with Example 1 is that the thicknesses of the PET layer, the glue layer and the MPP layer are 20 um, 3.5 um and 36.5 um respectively; the rest are the same as Example 1.

[0056] Example 3

[0057] The only difference compared with Example 1 is that the thicknesses of the PET layer, the glue layer and the MPP layer are 30um, 5um and 30um respectively; the rest are the same as Example 1.

[0058] Comparative Example 1

[0059] The only difference compared with Example 1 is that the PET layer is replaced by a PP layer of the same thickness, and the rest is the same as Example 1.

[0060] Comparative Example 2

[0061] The only difference compared to Example 1 is that the MPP layer is replaced by a cooking-grade CPP layer of equal thickness, and the rest is the same as Example 1.

[0062] Comparative Example 3

[0063] Commercially available products: The 100um thick black high-temperature resistant ear glue produced by DNP is produced using a three-layer co-extrusion casting process. The structure is MPP / PET / MPP, where the thickness of MPP and PET are 44um and 12um respectively.

[0064] Performance Testing

[0065] The high temperature resistant ear glues of Examples 1-3 and Comparative Examples 1-3 were subjected to high temperature resistance test and electrolyte resistance test respectively, and the test methods and judgment criteria were as follows:

[0066] (1) High temperature resistance test

[0067] Test method: Cut two pieces of ear glue with a size of 80mm×80mm, seal them together, the heat sealing temperature is 150℃ (the upper and lower metal heat sealing heads are heated, hard sealing), the heat sealing pressure is 0.2MPa, the heat sealing time is 2.5s, and the heat sealing retention thickness of the ear glue after sealing is tested;

[0068] Judgment criteria: If the retained thickness is greater than 170um, it is OK (passed); if the retained thickness is less than 170um, it is NG (failed);

[0069] (2) Electrolyte resistance test

[0070] Test method: completely immerse the sample in an electrolyte containing 1000ppm water and seal it with a container. Then immerse the container in a constant temperature water bath at 85℃ for 24 hours. Take out the container and cool it. Then rinse the sample film with tap water and observe the surface condition of the sample after peeling.

[0071] Judgment standard: If the surface after the tab glue and the tab liquid resistance are peeled off is white, it is OK (passed); if the surface is transparent and has no strength, it is NG (failed).

[0072] The results of the high temperature resistance test and the electrolyte resistance test of Examples 1-3 and Comparative Examples 1-3 are shown in Table 1 below:

[0073] Table 1

[0074] Test items Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 High temperature resistance test OK OK OK NG OK OK Electrolyte resistance test OK OK OK OK NG OK

[0075] As can be seen from Table 1, Examples 1-3 and Comparative Example 3 (commercially available products) have passed the high temperature resistance test and the electrolyte resistance test, but Comparative Example 3 is a black high temperature resistant ear glue produced by a three-layer co-extrusion process. As mentioned in the background technology, the production equipment needs to be specially customized and is difficult to clean after production. Therefore, it has great limitations and high investment costs, resulting in expensive products. In addition, it cannot meet people's demand for diversified color of ear glue; while Comparative Example 1 only passed the electrolyte resistance test but failed the high temperature resistance test. The difference compared to Example 1 is that Comparative Example 1 uses PP as the intermediate film layer, which is not as high temperature resistant as PET; while Comparative Example 2 passed the high temperature resistance test but failed the electrolyte resistance test. The difference compared to Example 1 is that Comparative Example 2 uses cooking grade CPP as the surface film layer, and its strength and bonding properties are poor, resulting in poor overall composite effect and electrolyte resistance.

[0076] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. The present invention may be subject to various changes and improvements without departing from the spirit and scope of the present invention. These changes and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A high temperature resistant ear glue, characterized in that: It includes a PET layer, a glue layer arranged on both sides of the PET layer, and an MPP layer arranged outside the glue layer; the PET layer, the glue layer and the MPP layer are compounded together by a dry compounding process, and the thickness of the single layer is 10-30um, 2-5um, and 30-43um respectively; wherein the MPP layer is a three-layer structure, which is a modified PP layer, a homopolymer PP layer and a copolymer PP layer treated with corona from the outside to the inside, and the thickness ratio is 1:2:1; The modified PP layer is made of polypropylene grafted with one or more monomers selected from acrylic acid, methacrylic acid, maleic acid, maleic anhydride, methyl methacrylate and glycidyl methacrylate; The MPP layer is a composite of a modified PP layer, a homopolymer PP layer and a copolymer PP layer treated with corona by means of casting or blowing.

2. The high temperature resistant ear glue according to claim 1, characterized in that: The PET layer is made of a double-sided corona-treated PET film.

3. The high temperature resistant ear glue according to claim 1, characterized in that: The glue layer is made of anhydride-modified polypropylene solvent-based glue.

4. A method for preparing a high temperature resistant ear glue according to any one of claims 1 to 3, characterized in that: The steps include: S1. Preparation of MPP membrane The raw materials are added into the hoppers of the extruder in the order of modified PP layer, homopolymer PP layer and copolymer PP layer by using the casting process, extruded and formed, and the outer side of the copolymer PP layer is corona treated to obtain MPP film, and 2 portions of MPP film are prepared for standby use; The parameters of the tape casting process are as follows: melting temperature 200-260°C, cooling temperature 10-40°C, and drawing ratio (1-2):1; S2, dry compound Take a double-sided corona-treated PET film, apply a layer of glue on one side to form a glue layer, place the corona-treated side of the copolymer PP layer of the MPP film prepared in step S1 opposite to the glue layer, and laminate on a laminating machine at a laminating temperature of 80-120° C. Similarly, another MPP film is compounded on the other side of the PET film to obtain the above-mentioned high temperature resistant ear glue.

5. The method for preparing a high temperature resistant ear glue according to claim 4, characterized in that: In the step S1, the MPP film is prepared by using a film blowing process instead of a casting process, and the parameters of the film blowing process are: a melting temperature of 200-260° C., a cooling temperature of 10-40° C., a blowing ratio of (1-3):1, and a pulling ratio of (1-2):1.

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