Water-based pressure-sensitive adhesive for expansion adhesive tape and preparation method of water-based pressure-sensitive adhesive

Abstract

The invention relates to a water-based pressure-sensitive adhesive for an expansion adhesive tape and a preparation method thereof. According to the invention, acrylic acid modified waterborne polyurethane, natural rubber emulsion, calcium stearate emulsion and PE wax emulsion are adopted as glue solution main bodies, and a certain amount of waterborne rosin resin emulsion and a waterborne curing agent (GA240) are added, so that the waterborne pressure-sensitive adhesive for the expansion adhesive tape, which takes waterborne polyurethane as a main body and has crosslinking capacity, is prepared. A novel expansion adhesive tape can be obtained after a modified PU film is coated with the mixed adhesive, and after the novel expansion adhesive tape is soaked in electrolyte for 30 days, the peel strength change rate of the novel expansion adhesive tape is smaller than 30%, and no falling trace exists.

Description

Technical Field

[0001] The present invention relates to an aqueous pressure-sensitive adhesive for an expansion tape and a preparation method thereof. Background Art

[0002] The lithium battery industry has currently become the mainstream in the new energy industry. Its excellent energy density, large upgrade space, excellent working adaptability under high-temperature conditions, and recyclability all make lithium-ion batteries play an irreplaceable role in the new energy field. In the process of manufacturing lithium-ion batteries, different types and kinds of bonding and sealing are required. The most commonly used methods can be divided into potting, glue sealing, and tape adhesion. Since traditional liquid lithium-ion batteries all contain flowing electrolytes, the substrates and the main body of the adhesives used in potting, glue sealing, and tape adhesion need to have a certain degree of electrolyte resistance. The quality of this property can directly determine the upper limit of the performance of the prepared lithium-ion batteries.

[0003] Although the currently disclosed patents mainly focus on improving the peel strength and electrolyte resistance of expansion tapes, the main problem of current expansion tapes is not the strength of the peel force of the pressure-sensitive adhesives used and the gap in their electrolyte resistance. The main material of the substrate used for expansion tapes is PU (polyurethane film), and the mainstream adhesive systems have poor compatibility with it, resulting in insufficient bonding strength, thus affecting the bonding strength between it and the battery cell, and further affecting its expansion rate and the service life of lithium-ion batteries. Therefore, there is an urgent need to design and provide a pressure-sensitive adhesive formulation that has excellent adhesion to the PU film, excellent electrolyte resistance, and excellent peel strength. Summary of the Invention

[0004] The purpose of the present invention is to solve the problem of insufficient bonding strength between the existing expansion tape substrate and the adhesive, and to provide an aqueous pressure-sensitive adhesive for an expansion tape and a preparation method thereof.

[0005] To achieve the above purpose, the technical solutions adopted by the present invention are as follows:

[0006] A preparation method of an aqueous pressure-sensitive adhesive for an expansion tape, the method being:

[0007] Step 1: Preparation of an acrylic acid-modified aqueous polyurethane emulsion solution: Using an acrylic acid-modified aqueous polyurethane emulsion as the raw material and deionized water as the solvent, an acrylic acid-modified aqueous polyurethane emulsion solution is prepared;

[0008] Step 2: Preparation of a natural rubber emulsion solution: Using a natural rubber emulsion as the raw material and deionized water as the solvent, a natural rubber emulsion solution is prepared;

[0009] Step 3: Preparation of a calcium stearate emulsion solution: Using a calcium stearate emulsion as the raw material and deionized water as the solvent, a calcium stearate emulsion solution is prepared;

[0010] Step 4: Preparation of PE wax emulsion: Using PE wax emulsion as raw material and deionized water as solvent, prepare a PE wax emulsion solution;

[0011] Step 5: Preparation of aqueous rosin resin emulsion solution: Using aqueous rosin resin emulsion as raw material and deionized water as solvent, prepare an aqueous rosin resin emulsion solution;

[0012] Step 6: Mix the solutions obtained in Steps 1 to 5 at 35°C, then add an aqueous curing agent (GA240) and mix evenly to obtain a glue solution. Control the concentration of the aqueous curing agent in the glue solution to be 1 g / L to 5 g / L; GA240 is a curing agent with an active ingredient of N,N,N',N'-tetrakis(oxiranylmethyl)-1,3-benzenediamine (common name: epoxidized m-xylenediamine);

[0013] Step 7: Coat the obtained glue solution on a PU substrate. The coating thickness is positively correlated with the viscosity and solid content of the obtained glue solution; after the coating process is completed, place the PU substrate in a vacuum drying oven at 150°C and dry it for 15 minutes to obtain an aqueous pressure-sensitive tape for expansion tape.

[0014] Further, in Step 1, the concentration of the acrylic acid-modified aqueous polyurethane emulsion solution is 300 g / L to 500 g / L.

[0015] Further, in Step 2, the concentration of the natural rubber emulsion solution is 200 g / L to 300 g / L.

[0016] Further, in Step 3, the concentration of the calcium stearate emulsion solution is 20 g / L to 100 g / L.

[0017] Further, in Step 4, the concentration of the PE wax emulsion solution is 10 g / L to 30 g / L.

[0018] Further, in Step 5, the concentration of the aqueous rosin resin emulsion solution is 30 g / L to 50 g / L.

[0019] Further, in Step 6, according to 100 parts of acrylic acid-modified aqueous polyurethane emulsion solution, 50 parts of natural rubber emulsion solution, 10 parts of calcium stearate emulsion solution, 5 parts of PE wax emulsion solution, and 20 parts of aqueous rosin resin emulsion solution.

[0020] The beneficial effects of the present invention compared with the prior art are as follows: The advantages of the present invention are the reasonable selection and use of the acrylic-modified waterborne polyurethane system, and the introduction of natural rubber latex, calcium stearate latex, PE wax latex, waterborne rosin resin latex and waterborne curing agent (GA240) into the system. Due to the introduction of the above five substances, a certain degree of cross-linked structure can be introduced into the system and the initial adhesion of the whole system can be improved. Moreover, the excellent adhesion between the acrylate-modified waterborne polyurethane and the PU film material can greatly improve the overall performance of the expansion tape. Description of the Drawings

[0021] Figure 1 Digital photo of the waterborne pressure-sensitive tape for expansion tape;

[0022] Figure 2 Digital photo of the waterborne pressure-sensitive tape for expansion tape expanding in the electrolyte;

[0023] Figure 3 Digital photo after being soaked in the electrolyte;

[0024] Figure 4 Peel strength diagram of the waterborne pressure-sensitive tape for expansion tape;

[0025] Figure 5 Peel strength diagram of the waterborne pressure-sensitive tape for expansion tape after soaking in the electrolyte;

[0026] Figure 6 Peel strength diagram of the waterborne pressure-sensitive tape for expansion tape;

[0027] Figure 7 Peel strength diagram of the waterborne pressure-sensitive tape for expansion tape after soaking in the electrolyte. Detailed Description of the Invention

[0028] The technical solutions of the present invention will be further described below in conjunction with the drawings and embodiments, but are not limited thereto. Any modification or equivalent replacement of the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention shall be covered by the protection scope of the present invention.

[0029] Example 1:

[0030] Expansion tape that can withstand soaking in the electrolyte for 30 days without falling off

[0031] Weigh 42.4 g of acrylic-modified waterborne polyurethane emulsion and disperse it in 100 mL of deionized water to prepare a solution with a concentration of 424 g / L of acrylic-modified waterborne polyurethane emulsion.

[0032] Weigh 24.3 g of natural rubber latex and disperse it in 100 mL of deionized water to prepare a solution with a concentration of 243 g / L of natural rubber latex.

[0033] Weigh 6.7 g of calcium stearate emulsion and disperse it into 100 mL of deionized water to prepare a solution with a calcium stearate emulsion concentration of 67 g / L.

[0034] Weigh 2.7 g of PE wax emulsion and disperse it into 100 mL of deionized water to prepare a solution with a PE wax emulsion concentration of 27 g / L.

[0035] Weigh 3.6 g of waterborne rosin resin emulsion and disperse it into 100 mL of deionized water to prepare a solution with a waterborne rosin resin emulsion concentration of 36 g / L.

[0036] Weigh 100 mL of acrylic-modified waterborne polyurethane emulsion solution, 50 mL of natural rubber emulsion solution, 10 mL of calcium stearate emulsion solution, 5 mL of PE wax emulsion solution, 20 mL of waterborne rosin resin emulsion solution and 0.7 mL of waterborne curing agent (GA240). The waterborne curing agent is added last. Heat the entire solution system to about 35 °C and stir vigorously at a stirring speed of 200 r / min to form a glue solution for a waterborne pressure-sensitive adhesive for an expansion tape.

[0037] Then, place the glue solution of the waterborne pressure-sensitive adhesive for an expansion tape in the air for natural defoaming. The defoaming process takes 1 h 30 min.

[0038] Finally, coat the obtained glue solution of the waterborne pressure-sensitive adhesive for an expansion tape on a PU substrate with a thickness of 40 μm. The coating thickness is 3 μm. After the coating process, place the coated PU substrate in a constant-temperature drying oven at 150 °C for 15 min.

[0039] Determination of peel strength: Use an electronic universal testing machine to measure the peel strength of the waterborne pressure-sensitive tape for an expansion tape under the condition of a test speed of 300 mm / min. After bonding this tape to the battery cell and placing it in the electrolyte for 30 d, measure its peel strength and conduct a comparison of the peel strength. The results are as follows: The peel force of the tape without being soaked in the electrolyte is 3.31 N / in; the peel strength of the tape after being soaked in the electrolyte is 3.05 N / in. The change rate of its peel strength is less than 30% and there is no any peeling trace.

[0040] The digital photo of the waterborne pressure-sensitive tape for an expansion tape is as Figure 1 shown. The digital photo of the waterborne pressure-sensitive tape for an expansion tape expanding in the electrolyte is as Figure 2 shown. The tape pasted on the copper foil surface shows a slight expansion phenomenon immediately after contacting the electrolyte. The digital photo of the tape of the expansion tape after being soaked in the electrolyte is as Figure 3 shown. An obvious expansion phenomenon occurs on the surface of the soaked tape. The peel strength curves of the waterborne pressure-sensitive tape for an expansion tape before and after being soaked in the electrolyte are as Figure 4 shown andFigure 5 as shown

[0041] Example 2:

[0042] Expansion tape that can be soaked in the electrolyte 21d without falling off

[0043] Weigh 42.4 g of acrylic-modified waterborne polyurethane emulsion and disperse it into 100 mL of deionized water to prepare a solution with a concentration of acrylic-modified waterborne polyurethane emulsion of 424 g / L.

[0044] Weigh 24.3 g of natural rubber latex and disperse it into 100 mL of deionized water to prepare a solution with a concentration of natural rubber latex of 243 g / L.

[0045] Weigh 4.2 g of calcium stearate emulsion and disperse it into 100 mL of deionized water to prepare a solution with a concentration of calcium stearate emulsion of 42 g / L.

[0046] Weigh 1.5 g of PE wax emulsion and disperse it into 100 mL of deionized water to prepare a solution with a concentration of PE wax emulsion of 15 g / L.

[0047] Weigh 4.5 g of waterborne rosin resin emulsion and disperse it into 100 mL of deionized water to prepare a solution with a concentration of waterborne rosin resin emulsion of 45 g / L.

[0048] Weigh 100 mL of acrylic-modified waterborne polyurethane emulsion solution, 50 mL of natural rubber latex solution, 10 mL of calcium stearate emulsion solution, 5 mL of PE wax emulsion solution, 20 mL of waterborne rosin resin emulsion solution and 0.7 mL of waterborne curing agent (GA240) solution. The waterborne curing agent is added last. Heat the entire solution system to about 35 °C and stir vigorously at a stirring speed of 200 r / min to form a glue solution for the waterborne pressure-sensitive adhesive of the expansion tape.

[0049] Then, place the glue solution of the waterborne pressure-sensitive adhesive for the expansion tape in the air for natural defoaming, and the defoaming process is 1 h 30 min.

[0050] Finally, coat the obtained glue solution of the waterborne pressure-sensitive adhesive for the expansion tape on a PU substrate with a thickness of 40 μm, and the coating thickness is 3 μm. After the coating process, place the PU substrate with the applied glue in a constant temperature drying oven at 150 °C for 15 min.

[0051] Measurement of peel strength: Use an electronic universal testing machine to measure the peel strength of the waterborne pressure-sensitive tape for the expansion tape under the condition of a test speed of 10 mm / min. After bonding this tape to the battery cell and placing it in the electrolyte for 21 d, test its peel strength and conduct a comparison of the peel strength. The results are as Figure 6 andFigure 7 As shown: the peel strength of the tape without electrolyte immersion is 4.27 N / 25 mm; the peel strength of the tape after electrolyte immersion is 3.79 N / 25 mm.

Claims

1. A method for preparing a water-based pressure-sensitive adhesive for an expansion tape, characterized in that: The method is: Step 1: Preparation of acrylic acid modified waterborne polyurethane emulsion solution: using acrylic acid modified waterborne polyurethane emulsion as raw material and deionized water as solvent to prepare acrylic acid modified waterborne polyurethane emulsion solution; Step 2: Preparation of natural rubber latex solution: using natural rubber latex as raw material and deionized water as solvent to prepare a natural rubber latex solution; Step 3: Preparation of calcium stearate emulsion solution: using calcium stearate emulsion as raw material and deionized water as solvent to prepare calcium stearate emulsion solution; Step 4: Preparation of PE wax emulsion: using PE wax emulsion as raw material and deionized water as solvent to prepare PE wax emulsion solution; Step 5: Preparation of an aqueous rosin resin emulsion solution: using an aqueous rosin resin emulsion as a raw material and deionized water as a solvent to prepare an aqueous rosin resin emulsion solution; Step 6: Mix the solutions obtained in steps 1 to 5 at 35° C., then add a water-based curing agent (GA240) and mix evenly to obtain a glue solution, wherein the concentration of the water-based curing agent in the glue solution is controlled to be 1 g / L to 5 g / L; Step 7: coating the above obtained adhesive solution on the PU substrate. After the coating process is completed, the PU substrate is placed in a vacuum drying oven at 150° C. and dried for 15 minutes to obtain a water-based pressure-sensitive tape for the expansion tape.

2. The method for preparing a water-based pressure-sensitive adhesive for an expansion tape according to claim 1, characterized in that: In step 1, the concentration of the acrylic acid modified aqueous polyurethane emulsion solution is 300 g / L to 500 g / L.

3. The method for preparing a water-based pressure-sensitive adhesive for an expansion tape according to claim 1, characterized in that: In step 2, the concentration of the natural rubber latex solution is 200 g / L to 300 g / L.

4. The method for preparing a water-based pressure-sensitive adhesive for an expansion tape according to claim 1, characterized in that: In step 3, the concentration of the calcium stearate emulsion solution is 20 g / L to 100 g / L.

5. The method for preparing a water-based pressure-sensitive adhesive for an expansion tape according to claim 1, characterized in that: In step 4, the concentration of the PE wax emulsion solution is 10 g / L to 30 g / L.

6. The method for preparing a water-based pressure-sensitive adhesive for an expansion tape according to claim 1, characterized in that: In step 5, the concentration of the aqueous rosin resin emulsion solution is 30 g / L to 50 g / L.

7. The method for preparing a water-based pressure-sensitive adhesive for an expansion tape according to claim 1, characterized in that: In step six, according to 100 parts of acrylic acid modified water-based polyurethane emulsion solution, 50 parts of natural rubber emulsion solution, 10 parts of calcium stearate emulsion solution, 5 parts of PE wax emulsion solution, and 20 parts of water-based rosin resin emulsion solution.

8. A water-based pressure-sensitive adhesive for an expansion tape prepared by the preparation method according to any one of claims 1 to 7.

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