Electrolyte-resistant hot melt adhesive and preparation method thereof

Abstract

The present invention discloses an electrolyte-resistant hot melt adhesive and a preparation method thereof. The hot melt adhesive comprises the following raw materials in parts by weight: 30-60 parts of polyolefin; 20-50 parts of tackifying resin; 5-20 parts of viscosity modifier; 10-30 parts of inorganic filler; and 0.1-1 parts of antioxidant. The inorganic filler is an inorganic layered compound, or a modified inorganic layered compound obtained by treating the inorganic layered compound with an organosilicon coupling agent or an organotitanium coupling agent. The present invention adds an inorganic layered compound that is very stable in the electrolyte to the raw materials of the polyolefin hot melt adhesive. The layered structure can form an inorganic barrier network structure in the resin matrix, thereby effectively reducing the swelling of the material in the electrolyte and reducing the effect of swelling on adhesion. On the other hand, the inorganic compound can improve the mechanical strength of the hot melt adhesive, reduce the initial surface tack, and accelerate the surface drying time.

Description

Technical Field

[0001] The present invention relates to the field of hot melt adhesive materials, and in particular to an electrolyte-resistant hot melt adhesive and a preparation method thereof. Background Art

[0002] Currently, lithium-ion batteries, especially lithium-ion power batteries, are one of the most important new energy sources. As a power battery, one of the most important performance characteristics is safety, so preventing short circuits within the battery is crucial. Typically, the positive and negative poles within the battery are derived through the positive and negative posts of the battery cell. The positive pole of the pole piece and the positive pole of the battery cell are connected by an aluminum adapter, and the negative pole of the pole piece and the negative pole of the battery cell are connected by a copper adapter. The connection between the adapter and the posts of the battery cell is achieved by laser welding. Laser welding can connect the corresponding metals together, but because laser welding is very hot and easily melts the above-mentioned metals, the molten metal welding slag must be ensured to prevent it from entering the battery cell. Therefore, the greatest risk is that metal residues will cause a direct short circuit between the positive and negative poles of the battery, resulting in rapid heating and fire or explosion.

[0003] In order to prevent the above-mentioned metal welding slag from entering the interior of the battery cell, the main solution at present is to stick tape on the surface of the adapter. The single-sided tape currently used is generally acrylic or rubber type, and the base material is mainly PET, PI or PPS type, which is compounded on the concave surface of the corresponding adapter by laminating. However, since the surface of the current adapter is not flat and the welding point is concave, the tape cannot be 100% adhered to the adapter. In addition, during the operation of the battery, the temperature is generally above 30 degrees, and the electrolyte (mainly various ester solvents) will slowly penetrate into the glue layer of the tape. Moreover, most of the tapes currently used are not resistant to electrolyte. During the long-term electrolyte erosion process, the tape will gradually fall off the adapter, thereby making the use of the tape to protect the adapter welding slag ineffective.

[0004] There are two main reasons for the above failures: 1) Current tapes cannot withstand long-term electrolyte (the electrolyte contains various strong and weak polar ester solvents). As time goes on, the tape gradually separates from the adapter; 2) Since the tape is glue coated on the substrate, the glue on the tape is in solid form. During the bonding process, there is no way to achieve 100% tight bonding with the substrate of the adapter. The electrolyte will still easily penetrate from the bonding interface, especially at high temperatures. The electrolyte is more likely to corrode the tape through the gaps in the interface, causing the tape to fail faster.

[0005] Patent CN104245872A discloses a hot melt adhesive for electrical devices, providing a hot melt adhesive having excellent solvent resistance and excellent adhesion to adherends containing battery electrolyte, and can contribute to the improvement of electrical device performance. The hot melt adhesive for electrical devices comprises an olefin-modified polymer (A), wherein the olefin-modified polymer (A) is a modified polymer having a silicon-containing functional group; the hot melt adhesive for electrical devices has excellent resistance to battery electrolyte (i.e., electrolyte resistance or solvent resistance), and also has improved hot melt adhesive adhesion to adherends containing electrolyte. Using silane-modified polyolefins, the mechanism of moisture curing is utilized, and the electrolyte resistance of the hot melt adhesive can be improved after curing and cross-linking, but the production and processing process of silane-modified polyolefins requires strict control of moisture, which increases the difficulty of the production process.

[0006] Patent CN111592841A discloses a UV-curable polyolefin hot melt adhesive and its preparation method, which relates to a UV-curable polyolefin hot melt adhesive for bonding battery packaging materials. The raw materials of the UV-curable polyolefin hot melt adhesive are composed of the following components: an olefin-modified polymer having a silicon-containing functional group, a polyolefin elastomer containing isoprene units, an ethylene-vinyl acetate copolymer, a photoinitiator, and an auxiliary agent. The polyolefin hot melt adhesive of the present invention has low viscosity and high initial adhesion. The polyolefin hot melt adhesive has lower requirements for the gluing temperature than the high-viscosity polyolefin hot melt adhesives on the market. It is not prone to stringing during the gluing process and has extremely high initial adhesion, shortening the holding time, helping to simplify the production process and improve production efficiency. It also has excellent electrolyte resistance. It can be used for bonding lithium-ion battery packaging materials, especially for bonding the folded edges of battery structures. Although the UV curing method is easy to operate, it is difficult to achieve complete irradiation in some complex gluing areas, and it is impossible to achieve sufficient curing and cross-linking.

[0007] Therefore, how to effectively improve the electrolyte resistance of hot melt adhesive without increasing the complexity of the hot melt adhesive production process has become a technical problem that needs to be urgently solved in this field. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide an electrolyte-resistant hot melt adhesive and a preparation method thereof in view of the deficiencies in the above-mentioned prior art.

[0009] In order to solve the above technical problems, the technical solution adopted by the present invention is: an electrolyte-resistant hot melt adhesive, comprising the following raw materials in parts by weight:

[0010]

[0011]

[0012] Wherein, the inorganic filler is an inorganic layered compound, or a modified inorganic layered compound obtained by treating an inorganic layered compound with an organic silicon coupling agent or an organic titanium coupling agent.

[0013] Preferably, the modified inorganic layered compound is prepared by the following method: adding an organic silicon coupling agent or an organic titanium coupling agent to isopropyl alcohol to obtain a modifier solution, then adding the inorganic layered compound to the modifier solution, stirring for 5-30 minutes, filtering, and drying the solid product at 30-60° C. for 10-60 minutes to obtain the modified inorganic layered compound;

[0014] The addition amount of the organic silicon coupling agent or organic titanium coupling agent is 1%-4% of the mass of the inorganic layered compound.

[0015] Preferably, the inorganic layered compound is at least one selected from talc, mica, graphite, graphene, montmorillonite, phosphate, silicate, and titanate.

[0016] Preferably, the inorganic filler is modified talc obtained by treating with coupling agent KH-550, and the preparation method is as follows: adding coupling agent KH-550 to isopropyl alcohol to obtain a modifier solution, then adding talc to the modifier solution, stirring for 10 minutes, filtering, and drying the solid product at 40° C. for 30 minutes to obtain the modified inorganic layered compound;

[0017] The addition amount of coupling agent KH-550 is 2% of the mass of talc powder.

[0018] Preferably, the polyolefin is at least one selected from polyethylene, polypropylene, polybutene, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, and amorphous polyalphaolefin.

[0019] Preferably, the tackifying resin is selected from at least one of rosin, rosin derivatives, terpene resins, petroleum resins, thermoplastic phenolic resins, and low molecular weight polystyrene.

[0020] Preferably, the viscosity modifier is selected from at least one of naphthenic mineral oil, hydrogenated polybutadiene, paraffin wax, microcrystalline wax, Fischer-Tropsch wax, polyethylene wax, oxidized polyethylene wax, polypropylene wax, and Sasol wax.

[0021] Preferably, the antioxidant is selected from at least one of antioxidant B215, antioxidant 1010, antioxidant 168, antioxidant 1076, and antioxidant 3114.

[0022] Preferably, the tackifying resin is C5 petroleum resin, the viscosity modifier is oxidized polyethylene wax, and the antioxidant is a mixture of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1.

[0023] The present invention also provides a method for preparing the electrolyte-resistant hot melt adhesive as described above, comprising the following steps:

[0024] S1. Preheat the reaction vessel to 100-150°C;

[0025] S2. Add polyolefin, tackifying resin, viscosity modifier, antioxidant and inorganic filler into the reaction vessel according to weight ratio, evacuate to -0.05~-0.2MPa, stir evenly, and react at 150-180℃ for 2-8h;

[0026] S3. After the reaction is completed, filter to obtain the electrolyte-resistant hot melt adhesive.

[0027] The beneficial effects of the present invention are:

[0028] The present invention provides an electrolyte-resistant polyolefin hot melt adhesive. An inorganic layered compound that is highly stable in electrolytes is added to the raw materials of the polyolefin hot melt adhesive. The layered structure forms an inorganic barrier network within the resin matrix, effectively reducing the material's swelling in the electrolyte and the effect of swelling on adhesion. Furthermore, the inorganic compound can improve the hot melt adhesive's mechanical strength, reduce initial surface tack, and accelerate surface drying time. Furthermore, in some embodiments of the present invention, surface modification of the inorganic layered compound with an organosilicon or organotitanium coupling agent can improve the compatibility of the inorganic compound with the resin matrix, resulting in a more uniform dispersion within the resin matrix, a better barrier network effect against electrolytes, a lower swelling rate, and less peel force attenuation.

[0029] The preparation method of the electrolyte-resistant hot melt adhesive provided by the present invention is simple and easy, has high repeatability, avoids the use of chemically cross-linked polyolefin materials, and effectively reduces the cost of raw materials and the complexity of the production process. DETAILED DESCRIPTION

[0030] The present invention is further described in detail below with reference to the embodiments so that those skilled in the art can implement the invention with reference to the description.

[0031] It should be understood that terms such as “having”, “including” and “comprising” used herein do not preclude the existence or addition of one or more other elements or combinations thereof.

[0032] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Materials and reagents used in the following examples are commercially available unless otherwise specified. In the following examples, where specific conditions are not specified, the experiments were conducted under conventional conditions or those recommended by the manufacturer. Reagents and instruments used, where the manufacturer is not specified, are commercially available conventional products.

[0033] The present invention provides an electrolyte-resistant hot melt adhesive comprising the following raw materials in parts by weight:

[0034]

[0035] The inorganic filler is an inorganic layered compound, or a modified inorganic layered compound obtained by treating the inorganic layered compound with an organic silicon coupling agent or an organic titanium coupling agent.

[0036] In a preferred embodiment, the modified inorganic layered compound is prepared by the following method: adding an organosilicon coupling agent or an organotitanium coupling agent to isopropyl alcohol to obtain a modifier solution, then adding the inorganic layered compound to the modifier solution, stirring for 5-30 minutes, filtering, and drying the solid product at 30-60°C for 10-60 minutes to obtain the modified inorganic layered compound; wherein the amount of the organosilicon coupling agent or organotitanium coupling agent added is 1%-4% by weight of the inorganic layered compound. By modifying the inorganic layered compound, the compatibility and dispersibility of the inorganic filler with the resin matrix can be improved.

[0037] The inorganic layered compound is selected from at least one of talc, mica, graphite, graphene, montmorillonite, phosphate, silicate and titanate.

[0038] In a preferred embodiment, the polyolefin is selected from at least one of polyethylene, polypropylene, polybutylene, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, and amorphous polyalphaolefin. As a matrix resin, the polyolefin provides the necessary bonding strength and cohesion.

[0039] In a preferred embodiment, the tackifying resin is selected from at least one of rosin, rosin derivatives, terpene resins, petroleum resins, thermoplastic phenolic resins, and low molecular weight polystyrene. The tackifying resin has good compatibility with the polyolefin main resin and can improve wetting properties and initial tack properties.

[0040] In a preferred embodiment, the viscosity modifier is selected from at least one of naphthenic mineral oil, hydrogenated polybutadiene, paraffin wax, microcrystalline wax, Fischer-Tropsch wax, polyethylene wax, oxidized polyethylene wax, polypropylene wax, and Sasol wax. The viscosity modifier is used to reduce the viscosity of the hot melt adhesive.

[0041] In a preferred embodiment, the antioxidant is selected from at least one of antioxidant B215, antioxidant 1010, antioxidant 168, antioxidant 1076, and antioxidant 3114, which is used to improve the thermal stability of the hot melt adhesive, prevent the physical properties of the hot melt adhesive from aging, and reduce color changes.

[0042] The present invention also provides a method for preparing the electrolyte-resistant hot melt adhesive, comprising the following steps:

[0043] S1. Preheat the reaction vessel to 100-150°C;

[0044] S2. Add polyolefin, tackifying resin, viscosity modifier, antioxidant and inorganic filler into the reaction vessel according to weight ratio, evacuate to -0.05~-0.2MPa, stir evenly, and react at 150-180℃ for 2-8h;

[0045] S3. After the reaction is completed, filter to obtain electrolyte-resistant hot melt adhesive.

[0046] The above is the overall concept of the present invention. The present invention is further described below through specific examples. It should be understood that these examples are used to illustrate the basic principles, main features and advantages of the present invention, and the present invention is not limited to the scope of the following examples. The implementation conditions adopted in the examples can be further adjusted according to specific requirements. The implementation conditions not specified are generally the conditions in routine experiments.

[0047] In the following examples and comparative examples, the polyolefin is polyethylene resin, brand Affinity GA1900, purchased from Dow; the tackifying resin is C5 petroleum resin, brand Wingtack 98, purchased from Cray Valley; the viscosity modifier is oxidized polyethylene wax, brand A-C1660, purchased from Honeywell; and the antioxidant is a mixture of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1, purchased from Tianjin Lianlong Company.

[0048] Example 1

[0049] An electrolyte-resistant hot melt adhesive, the preparation method of which comprises the following steps:

[0050] (1) Heat the reactor to 120°C;

[0051] (2) adding 50 parts by weight of polyolefin, 30 parts by weight of tackifying resin, 10 parts by weight of viscosity modifier, 10 parts by weight of inorganic layered compound, and 0.2 parts by weight of antioxidant into a reaction kettle, evacuating to -0.1 MPa, stirring, and reacting at a temperature of 150° C. for 4 hours. After the reaction is complete to form a clear liquid, filtering to obtain a polyolefin hot melt adhesive;

[0052] The inorganic layered compound is graphene, brand SE2430W-N, purchased from Changzhou Sixth Element Materials Technology Co., Ltd.

[0053] Example 2

[0054] An electrolyte-resistant hot melt adhesive, the preparation method of which comprises the following steps:

[0055] (1) Heat the reactor to 130°C;

[0056] (2) adding 50 parts by weight of polyolefin, 30 parts by weight of tackifying resin, 10 parts by weight of viscosity modifier, 5 parts by weight of inorganic layered compound, and 0.2 parts by weight of antioxidant into a reaction kettle, evacuating to -0.1 MPa, stirring, and reacting at a temperature of 160° C. for 4 hours. After the reaction is complete to form a clear liquid, filtering to obtain a polyolefin hot melt adhesive;

[0057] The inorganic layered compound is mica, which was purchased from Shijiazhuang Huabang Mineral Products Co., Ltd.

[0058] Example 3

[0059] An electrolyte-resistant hot melt adhesive, the preparation method of which comprises the following steps:

[0060] (1) Heat the reactor to 140°C;

[0061] (2) Add 50 parts by weight of polyolefin, 30 parts by weight of tackifying resin, 10 parts by weight of viscosity modifier, 10 parts by weight of inorganic layered compound, and 0.2 parts by weight of antioxidant into a reactor, evacuate to -0.1 MPa, stir, and react at a temperature of 170° C. for 4 hours. After the reaction is complete to form a clear liquid, filter to obtain a polyolefin hot melt adhesive;

[0062] Among them, the inorganic layered compound is talcum powder, brand 1. Purchased from Yiruishi Company;

[0063] Example 4

[0064] An electrolyte-resistant hot melt adhesive, the preparation method of which comprises the following steps:

[0065] (1) Heat the reactor to 150°C;

[0066] (2) Add 50 parts by weight of polyolefin, 30 parts by weight of tackifying resin, 10 parts by weight of viscosity modifier, 30 parts by weight of inorganic layered compound, and 0.2 parts by weight of antioxidant into a reaction kettle, evacuate to -0.1 MPa, stir, and react at a temperature of 180° C. for 4 hours. After the reaction is complete to form a clear liquid, filter to obtain a polyolefin hot melt adhesive;

[0067] Among them, the inorganic layered compound is talcum powder, brand 1. Purchased from Yiruishi Company;

[0068] Example 5

[0069] An electrolyte-resistant hot melt adhesive, the preparation method of which comprises the following steps:

[0070] (1) Heat the reactor to 150°C;

[0071] (2) Add 50 parts by weight of polyolefin, 30 parts by weight of tackifying resin, 10 parts by weight of viscosity modifier, 30 parts by weight of inorganic layered compound, and 0.2 parts by weight of antioxidant into a reaction kettle, evacuate to -0.1 MPa, stir, and react at a temperature of 180° C. for 4 hours. After the reaction is complete to form a clear liquid, filter to obtain a polyolefin hot melt adhesive;

[0072] Wherein, the inorganic layered compound is a surface-modified modified talc powder, and the brand of the original talc powder is 1. Purchased from Yiruishi Company. The surface modification method is as follows: After adding the inorganic layered compound into a high-speed stirrer, the coupling agent KH-550 diluted with isopropyl alcohol is added thereto for surface modification. The amount of coupling agent added is 2% (mass fraction) of the mass of talc powder. After stirring for 10 minutes, the mixture is placed in a 40°C oven and dried for 0.5 hours to obtain modified talc powder.

[0073] Comparative Example 1

[0074] A hot melt adhesive, the preparation method of which comprises the following steps:

[0075] (1) Heat the reactor to 120°C;

[0076] (2) Add 50 parts by weight of polyolefin, 45 parts by weight of tackifying resin, 5 parts by weight of viscosity modifier, and 0.5 parts by weight of antioxidant into the reactor, evacuate to -0.1 MPa, stir, and react at a temperature of 180°C for 4 hours. After the reaction is complete, a clear liquid is formed, which is filtered to obtain a hot melt adhesive.

[0077] The hot melt adhesives prepared in Examples 1-5 and Comparative Example 1 were subjected to performance tests. The test items and methods are as follows:

[0078] Melt viscosity is tested in accordance with HG / T 3660-1999.

[0079] Swelling rate: 0.5g of hot melt adhesive is immersed in 2.5g of electrolyte at 70°C for 7 days. The surface of the hot melt adhesive is wiped dry and the mass of the hot melt adhesive is weighed in mg. Swelling rate = (m - 0.5) / 0.5.

[0080] 180° peel strength before and after soaking was tested using the following method: On a 180°C heating platform, apply hot melt adhesive to aluminum foil using a scraper. The adhesive was then placed against the foil, removed, and cut into 1cm wide strips. The 180° peel strength of the strips before soaking was tested in accordance with GB / T 2790-1995. The soaked strips were placed in a 70°C electrolyte for 7 days, removed, dried, and tested in accordance with GB / T 2790-1995.

[0081] The test results are shown in Table 1:

[0082] Table 1

[0083]

[0084]

[0085] Inorganic layer compound has been added in embodiment 1-5, and wherein embodiment 5 has been modified to inorganic layer compound, and inorganic layer compound is not added in comparative example 1.The test result of table 1 shows, the use of inorganic layer compound can cause the decline of initial stripping force, but after swelling in electrolyte, the stripping force of embodiment 1 to embodiment 5 is all higher than comparative example, and swelling ratio is lower than comparative example, illustrates that the adding of inorganic layer compound can effectively reduce swelling ratio, strengthens the stripping force after blister.But the use of too much inorganic filler can cause initial stripping force lower, affects the size of stripping force after blister.Special, in embodiment 5, inorganic layer compound has been modified to, enhanced the compatibility of inorganic filler and resin, inorganic layer compound is dispersed more evenly in resin matrix, better to the barrier network effect of electrolyte, swelling ratio is lower, and stripping force decays less.

[0086] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the description and implementation methods. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to specific details.

Claims

1. An electrolyte-resistant hot melt adhesive, characterized in that: The invention comprises the following raw materials in parts by weight: 30-60 parts of polyolefin; 20-50 parts of tackifying resin; 5-20 parts of viscosity regulator; 10-30 parts of inorganic filler; 0.1-1 part of antioxidant; Wherein, the inorganic filler is an inorganic layered compound, or a modified inorganic layered compound obtained by treating an inorganic layered compound with an organic silicon coupling agent or an organic titanium coupling agent; The modified inorganic layered compound is prepared by the following method: adding an organic silicon coupling agent or an organic titanium coupling agent to isopropyl alcohol to obtain a modifier solution, then adding the inorganic layered compound to the modifier solution, stirring for 5-30 minutes, filtering, and drying the solid product at 30-60° C. for 10-60 minutes to obtain the modified inorganic layered compound; The amount of the organic silicon coupling agent or organic titanium coupling agent added is 1%-4% of the mass of the inorganic layered compound; The inorganic layered compound is selected from talc.

2. The electrolyte-resistant hot melt adhesive according to claim 1, characterized in that: The inorganic filler is a modified talc powder obtained by treating with a coupling agent KH-550. The preparation method is as follows: adding the coupling agent KH-550 to isopropyl alcohol to obtain a modifier solution, then adding the talc powder to the modifier solution, stirring for 10 minutes, filtering, and drying the solid product at 40° C. for 30 minutes to obtain the modified inorganic layered compound; The addition amount of coupling agent KH-550 is 2% of the mass of talc powder.

3. The electrolyte-resistant hot melt adhesive according to claim 1, characterized in that: The polyolefin is selected from at least one of polyethylene, polypropylene, polybutene, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, and amorphous polyalphaolefin.

4. The electrolyte-resistant hot melt adhesive according to claim 1, characterized in that: The tackifying resin is selected from at least one of rosin, rosin derivatives, terpene resins, petroleum resins, thermoplastic phenolic resins, and low molecular weight polystyrene.

5. The electrolyte-resistant hot melt adhesive according to claim 1, characterized in that: The viscosity modifier is selected from at least one of naphthenic mineral oil, hydrogenated polybutadiene, paraffin wax, microcrystalline wax, Fischer-Tropsch wax, polyethylene wax, oxidized polyethylene wax, polypropylene wax, and Sasol wax.

6. The electrolyte-resistant hot melt adhesive according to claim 1, characterized in that: The antioxidant is selected from at least one of antioxidant B215, antioxidant 1010, antioxidant 168, antioxidant 1076, and antioxidant 3114.

7. The electrolyte-resistant hot melt adhesive according to claim 1, characterized in that: The tackifying resin is C5 petroleum resin, the viscosity modifier is oxidized polyethylene wax, and the antioxidant is a mixture of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:

1.

8. A method for preparing an electrolyte-resistant hot melt adhesive according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1. Preheat the reaction vessel to 100-150°C; S2. Add polyolefin, tackifying resin, viscosity modifier, antioxidant, and inorganic filler into a reaction vessel according to weight ratio, evacuate to -0.05~-0.2MPa, stir evenly, and react at 150-180°C for 2-8h; S3. After the reaction is completed, filter to obtain the electrolyte-resistant hot melt adhesive.

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