Ultraviolet-curable polyvinylidene fluoride adhesive and preparation method therefor

Abstract

Disclosed in the present invention are an ultraviolet-curable polyvinylidene fluoride adhesive and a preparation method therefor. The adhesive comprises the following raw materials in parts by weight: 20-45 parts of an active diluent, 1-3.5 parts of a photoinitiator, 20-60 parts of a polyvinylidene fluoride prepolymer, 10-30 parts of a filler, and 0.1-3.5 parts of a silane coupling agent. The preparation method comprises: (1) preparing a polyvinylidene fluoride resin; (2) preparing a polyvinylidene fluoride prepolymer; and (3) preparing an ultraviolet-curable polyvinylidene fluoride adhesive. The ultraviolet-curable polyvinylidene fluoride adhesive of the present invention has the advantages of good temperature resistance and humidity resistance, good dielectric properties and a low surface energy, and solves the problem in the prior art of poor bonding effect between an ultraviolet-curable adhesive and a low-surface-energy material, and the preparation method has a simple process and is environmentally friendly.

Description

Ultraviolet light curing polyvinylidene fluoride adhesive and preparation method thereof TECHNICAL FIELD

[0001] The present application relates to the field of ultraviolet light curing adhesive, in particular to an ultraviolet light curing polyvinylidene fluoride adhesive and a preparation method thereof. BACKGROUND

[0002] With the development of lightweight electronic products such as mobile phones, computers and cameras, the plastic parts in electronic products are upgraded, and low surface energy plastics are widely used. Many parts need to be bonded with adhesives, among which UV adhesives are widely used due to their simple and efficient bonding process, environmental protection and no pollution. However, the traditional UV adhesive has the disadvantages of poor adhesion to low surface energy plastics, weak electrochemical stability, poor temperature and humidity resistance.

[0003] The PVDF adhesive has excellent weather resistance, low surface energy, good electrochemical stability, temperature and humidity resistance, and excellent bonding performance. However, the traditional PVDF adhesive needs to be used with polar solvents, which causes serious environmental pollution, complex processing technology and high energy consumption. In addition, the existing PVDF adhesive used in electronic products is prone to delamination and failure under high temperature and humidity conditions, and has poor adhesion to low surface energy plastic substrates.

[0004] CN102994012A discloses a preparation method of an adhesive for bonding fluoroplastic. The product uses polyvinylidene fluoride and trifluoroethylene copolymer, polyvinyl glycidyl ether, resorcinol-formaldehyde resin, triethyl citrate, polysiloxane resin, reinforcing silica, benzene and acetone as raw materials, and uses a melting tank and a stirring tank as equipment to prepare the adhesive for bonding fluoroplastic. The preparation method has simple production process, uses general equipment, and the product has excellent bonding properties, high temperature resistance, chemical resistance, high impact strength, and is very convenient to use. It is mainly used for bonding between fluoroplastic products, and can also be used for bonding between fluoroplastic products and other materials. However, it needs to be used with a large amount of organic solvent, which can cause environmental pollution, and the curing process is complicated, which can cause incomplete solvent evaporation, affecting the mechanical properties and bonding properties of the adhesive film. At the same time, the compatibility of polyvinylidene fluoride with other resins in the adhesive is poor, which can cause uneven dispersion of various resins in the adhesive film and unstable performance.

[0005] For example, CN112375169A discloses a new binder synthesis method, comprising the following steps: (1) fill the reaction kettle with inert gas, add reaction raw materials; (2) add deionized water, initiator and emulsifier in the reaction kettle; (3) introduce monomer vinylidene fluoride and monomer ethylene into the reaction kettle; (4) heat for 10-30h; (5) reduce the pressure after the reaction is completed; (6) the reaction product is obtained after condensation, washing, separation, drying and crushing. The F atoms in PVDF are replaced by H atoms, the crystallinity is reduced, the flexibility is improved, and the probability of HF elimination reaction is reduced, effectively avoiding the gelation of the slurry; the amount of vinylidene fluoride is reduced, which not only reduces the material cost, but also reduces the damage of F in VDF to the equipment; and the adhesion is strong, and other PVDF does not need to be compounded to increase the adhesion. The disadvantage is that the reaction time of polyvinylidene fluoride is too long, the production efficiency is low, the adhesion of the prepared solvent-based adhesive is poor, the bonding effect with polar materials is not ideal, which limits its application range, and the thermal stability is weak. A large amount of organic solvent is needed when used, which is easy to cause environmental pollution, and the curing process is complicated. SUMMARY

[0006] In order to overcome the defects of the prior art, the purpose of the present application is to develop a kind of product, and the electrochemical performance of the ultraviolet curing polyvinylidene fluoride adhesive with excellent temperature and humidity resistance and good adhesion to low surface energy plastics and its preparation method.

[0007] In order to solve the above technical problems, one of the technical solutions adopted by the present application is: an ultraviolet curing polyvinylidene fluoride adhesive, the raw material composition thereof is: active diluent 20-45 parts, photoinitiator 1-3.5 parts, polyvinylidene fluoride prepolymer with conjugated double bond 20-60 parts, filler 10-30 parts, silane coupling agent 0.1-3.5 parts.

[0008] As a preferred embodiment of the present application, the active diluent is at least one of propenyl pyrrolidone, methyl vinyl sulfone, methacrylamide, vinyl pyrrolidone, propylene neopentyl glycol dipropenoate, trimethylolpropane triacrylate, norbornene acrylate.

[0009] As a preferred embodiment of the present application, the photoinitiator is at least one of 2,4,6-trimethylbenzoyl diphenyl phosphine oxide, 1-hydroxycyclohexyl phenyl ketone, 2,4,6-trimethylbenzoyl phenyl ethyl phosphonate.

[0010] As a preferred embodiment of the present application, the silane coupling agent is at least one of aminopropyl triethoxysilane and gamma-aminopropyl trimethoxysilane.

[0011] As a preferred embodiment of the present application, the filler is at least one of silicon dioxide, calcium oxide, calcium carbonate, and mica.

[0012] As a preferred embodiment of the present application, the polyvinylidene fluoride prepolymer having conjugated double bonds is prepared by the following method:

[0013] (1) polymerizing 500-700 parts of deionized water, 5-15 parts of a dispersant, 0.5-2 parts of an initiator, 1-3 parts of a chain transfer agent, 70-90 parts of a vinylidene fluoride monomer, and 5-25 parts of an acrylic ester monomer at a reaction temperature of 30-90°C, a reaction time of 4-8 hours, and a reaction pressure of 4-8 MPa, and then filtering, washing, and drying the product to obtain a polyvinylidene fluoride resin;

[0014] (2) reacting the polyvinylidene fluoride resin obtained in step (1) in an alkaline solution at a reaction temperature of 40-80°C for 0.5-3 hours, and then filtering, washing, and drying the product to obtain a polyvinylidene fluoride prepolymer having conjugated double bonds.

[0015] As a preferred embodiment of the present application, the dispersant is at least one of methyl cellulose, polyethylene glycol, sodium dodecylbenzenesulfonate, and sodium dodecyl sulfate.

[0016] As a preferred embodiment of the present application, the initiator is at least one of azobisisobutyronitrile, di-tert-butyl peroxide, t-butyl benzoyl, methyl ethyl ketone peroxide, and dicyclohexyl peroxydicarbonate.

[0017] As a preferred embodiment of the present application, the chain transfer agent is at least one of acetone, secondary dodecyl mercaptan, acetic acid, n-butanol, and butyl acetate.

[0018] As a preferred embodiment of the present application, the acrylic ester monomer is at least one of methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, and hydroxyethyl acrylate.

[0019] In the present application, the reactive diluent can be one or a mixture of several of norbornene acrylate, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, 2-phenoxyethyl acrylate, lauric acid acrylate, trimethylolpropane triacrylate, 1,6-hexanediol diacrylate, propoxyl neopentyl glycol diacrylate, cyclodecane dimethylol diacrylate, polyethylene glycol (200) diacrylate, vinyl pyrrolidone, propyl pyrrolidone, vinyl formamide, methyl acrylamide, methyl vinyl sulfone, phenyl vinyl sulfone. As a preferred embodiment of the present application, the reactive diluent is at least one of propyl pyrrolidone, methyl vinyl sulfone, methyl acrylamide, vinyl pyrrolidone, propoxyl neopentyl glycol diacrylate, trimethylolpropane triacrylate, norbornene acrylate.

[0020] In the present application, the photoinitiator can be one or a mixture of several of 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1-(4-methylthiophenyl)-2-morpholin-1-propanone, 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2-hydroxy-4-(2-hydroxyethoxy)-2-methylpropiophenone, benzoin dimethyl ether, 2,4,6-trimethylbenzoyldiphenyl phosphine oxide, 2-phenylbenz-2-dimethylamine-1-(4-morpholinobenzyl) butanone, phenyl bis(2,4,6-trimethylbenzoyl) phosphine oxide, 2,4,6-trimethylbenzoyl phenyl phosphinic acid ethyl ester, benzophenone, 2-isopropylthioxanthone. As a preferred embodiment of the present application, the photoinitiator is at least one of 2,4,6-trimethylbenzoyldiphenyl phosphine oxide, 1-hydroxycyclohexyl phenyl ketone, 2,4,6-trimethylbenzoyl phenyl phosphinic acid ethyl ester.

[0021] In the present application, the silane coupling agent can be one or a mixture of two of aminopropyl triethoxysilane, γ-aminopropyl methyldiethoxysilane, γ-aminopropyl triethoxysilane, γ-glycidyl ether propyl trimethoxysilane. As a preferred embodiment of the present application, the silane coupling agent is at least one of aminopropyl triethoxysilane, γ-glycidyl ether propyl trimethoxysilane.

[0022] The present application improves the bonding performance of the ultraviolet light curing adhesive and the low surface energy material by optimizing the polymerization formula, and has the advantages of excellent temperature and humidity resistance, excellent dielectric performance, and low surface energy, solves the problem of poor bonding effect of the ultraviolet light curing adhesive and the low surface energy material in the prior art. The polyvinylidene fluoride prepolymer in the present application has conjugated double bonds, under the action of ultraviolet light initiator, the double bonds of the polyvinylidene fluoride prepolymer and the double bonds of the polar diluent occur addition reaction crosslinking and curing, forming a crosslinked network structure, greatly improving the molecular weight and the number of polar functional groups of the polymer, effectively improving the bonding performance between the polymer and the substrate; the present application can effectively control the hardness of the adhesive film by flexibly adjusting the functionality of the diluent, greatly widening the application scene of the adhesive film. Compared with the solvent type adhesive, the present application does not contain volatile solvent, is more friendly to the environment, the ultraviolet light curing process is simple, and the formed crosslinked network structure has better thermal stability and mechanical properties. In the present application, the introduction of the comonomer acrylate can enhance the ability of the polyvinylidene fluoride resin to dissolve in the active diluent, also can reduce the crystallinity of the polyvinylidene fluoride resin to increase its toughness, and at the same time prevent the polyvinylidene fluoride resin from removing too much HF in the alkaline environment to affect the performance of the polyvinylidene fluoride resin. The ultraviolet light curing polyvinylidene fluoride adhesive of the present application has excellent temperature and humidity resistance, excellent dielectric performance, and low surface energy after ultraviolet light curing, and solves the problem of poor bonding effect of the ultraviolet light curing adhesive and the low surface energy material, and is especially suitable for the bonding of electronic or industrial products of low surface energy materials such as polypropylene, polyethylene and fluoroplastic, and has good bonding effect.

[0023] Compared with the prior art, the present application has the following advantages:

[0024] 1、Compared with the traditional solvent type homopolymerization polyvinylidene fluoride adhesive, the introduction of the comonomer acrylate can enhance the ability of the polyvinylidene fluoride resin to dissolve in the solvent, also can reduce the crystallinity of the polyvinylidene fluoride resin to increase its toughness, and at the same time prevent the polyvinylidene fluoride resin from removing HF in the alkaline environment to affect the performance of the polyvinylidene fluoride resin, the product after ultraviolet light curing has a contact angle of more than 97 degrees, and the dielectric constant of the adhesive film is more than 4.2.

[0025] 2、The present application solves the problem of poor bonding effect of the prior art ultraviolet curing adhesive and low surface energy material. The polyvinylidene fluoride resin in the present application has conjugated double bonds after HF treatment with alkali solution. Under the action of ultraviolet light initiator, the double bonds of the polyvinylidene fluoride prepolymer and the double bonds of the polar diluent occur addition reaction crosslinking and curing, forming a crosslinked network structure, introducing a large number of polar functional groups and greatly increasing the molecular weight, effectively improving the bonding strength of the adhesive and the substrate, forming the cured bonding of the adhesive and the substrate, and having good adhesion to low surface energy plastics. Compared with traditional ultraviolet light adhesive prepolymers such as polyurethane acrylate, epoxy acrylate and polyacrylate, the C-F bond energy of the polyvinylidene fluoride prepolymer is higher, the corrosion resistance is better, the dielectric performance is better, the surface energy is lower, and the adhesion to low surface energy plastics is better. The PP-PP room temperature bonding strength is above 7.3MPa, and the PP-PP "double 85" bonding strength is 6.57MPa.

[0026] 3. The present application can effectively control the hardness of the adhesive film by flexibly adjusting the functionality of the diluent, greatly widening the application scenarios of the adhesive film. Compared with solvent-based adhesives, the present application does not contain volatile solvents, is more environmentally friendly, has a simple ultraviolet curing process, high production efficiency, and the formed crosslinked network structure has better thermal stability and mechanical properties. At the same time, the ultraviolet curing adhesive can flexibly adjust the types and proportions of the polar diluent, and more easily control the molecular weight and various properties of the adhesive.

[0027] The second technical scheme adopted by the application is a preparation method of an ultraviolet curing polyvinylidene fluoride adhesive, comprising the following steps:

[0028] (1) Polymerize deionized water 500-700 parts, dispersing agent 5-15 parts, initiator 0.5-2 parts, chain transfer agent 1-3 parts, vinylidene fluoride monomer 70-90 parts and acrylic ester monomer 5-25 parts by weight parts, the reaction temperature is 30-90℃, the reaction time is 4-8h, the reaction pressure is 4-8MPa, after the reaction, the product is filtered, washed and dried to obtain polyvinylidene fluoride resin;

[0029] (2) React the polyvinylidene fluoride resin obtained in step (1) in an alkali solution, the reaction temperature is 40-80℃, the reaction time is 0.5-3h, the obtained product is filtered, washed and dried to obtain polyvinylidene fluoride prepolymer with conjugated double bonds;

[0030] (3) according to the weight parts, the active diluent 20-45 parts, photo initiator 1-3.5 parts, stirring at 75-95 ℃, 200-500 rpm for 3-5 min, cooling to 50-70 ℃, adding the step (2) obtained by the polyvinyl fluoride prepolymer with conjugated double bond 20-60 parts, filler 10-30 parts and silane coupling agent 0.1-3.5 parts, stirring at 200-500 rpm for 3-5 min, the UV-curable polyvinyl fluoride adhesive is obtained.

[0031] Preferably, the dispersant is at least one of methyl cellulose, polyethylene glycol, sodium dodecyl benzene sulfonate, and sodium dodecyl sulfate.

[0032] Preferably, the initiator is at least one of azobisisobutyronitrile, di-tert-butyl peroxide, t-butyl benzoyl, methyl ethyl ketone peroxide, and dicyclohexyl peroxydicarbonate.

[0033] Preferably, the chain transfer agent is at least one of acetone, secondary dodecyl mercaptan, acetic acid, n-butanol, and butyl acetate.

[0034] Preferably, the acrylate monomer is at least one of methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, and hydroxyethyl acrylate.

[0035] Preferably, the mass ratio of the polyvinyl fluoride resin to the alkali solution is 1:10-50.

[0036] Preferably, the active diluent is at least one of propenyl pyrrolidone, methyl vinyl sulfone, methyl methacrylamide, vinyl pyrrolidone, propoxyl neopentyl glycol dipropyl acrylate, trimethylolpropane triacrylate, and norbornene acrylate.

[0037] Preferably, the photo initiator is at least one of 2,4,6-trimethyl benzoyl diphenyl phosphine oxide, 1-hydroxycyclohexyl phenyl ketone, and 2,4,6-trimethyl benzoyl phenyl phosphonate ethyl ester.

[0038] Preferably, the silane coupling agent is at least one of aminopropyl triethoxysilane and γ-aminopropyl trimethoxysilane.

[0039] Preferably, the filler is at least one of silicon dioxide, calcium oxide, calcium carbonate, and mica.

[0040] The present application improves the bonding performance of the UV-curable adhesive with low surface energy materials by optimizing the polymerization formula and parameters such as polymerization temperature, time, and feeding mode, and has the advantages of excellent temperature and humidity resistance, dielectric performance, and low surface energy, thereby solving the problem of poor bonding effect of the UV-curable adhesive with low surface energy materials in the prior art.

[0041] The method has the advantages of:

[0042] 1. The problem of poor bonding effect of the prior art ultraviolet curing adhesive and low surface energy materials is solved. The polyvinylidene fluoride resin is obtained by copolymerizing a vinylidene fluoride monomer and an acrylate monomer, the polyvinylidene fluoride resin is dehydrofluorinated in an alkaline environment to form a polyvinylidene fluoride prepolymer with conjugated double bonds, the polyvinylidene fluoride prepolymer is dissolved in a polar active diluent containing double bonds, and the double bonds of the polyvinylidene fluoride prepolymer and the double bonds of the polar diluent are crosslinked and cured under the action of an ultraviolet light initiator to form a crosslinked network structure. The process is simple, green and environmentally friendly, the polymerization reaction is mild and stable, and there is no strong exothermic phenomenon, which is suitable for large-scale production. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be further described in detail below with examples. It should be understood that the following description is only used to explain the present application and does not limit the present application.

[0044] Example 1

[0045] An ultraviolet curing polyvinylidene fluoride adhesive, with 1g per part, has the following composition: 7g of vinylpyrrolidone, 15g of propylpyrrolidone, 12g of methyl vinyl sulfone, 2g of 2,4,6-trimethylbenzoyl diphenyl phosphate, 1g of 1-hydroxycyclohexyl phenyl ketone, 30g of polyvinylidene fluoride resin prepolymer, 30g of silica powder (average particle size 10um), 2g of aminopropyl triethoxysilane, and 1g of gamma-aminopropyl trimethoxysilane.

[0046] The preparation method is as follows: 7g of vinylpyrrolidone, 15g of propylpyrrolidone, and 12g of methyl vinyl sulfone are added to a mixing tank, the mixing tank is heated to 80℃, then 2g of 2,4,6-trimethylbenzoyl diphenyl phosphate and 1g of 1-hydroxycyclohexyl phenyl ketone are added, stirred at a speed of 400rpm for 3min, then cooled to 70℃, 30g of polyvinylidene fluoride resin prepolymer prepared in step (2), 30g of silica powder (average particle size 10um), 2g of aminopropyl triethoxysilane, and 1g of gamma-aminopropyl trimethoxysilane are added, and stirred at a speed of 300rpm for 3min to obtain the ultraviolet curing polyvinylidene fluoride adhesive product.

[0047] The polyvinylidene fluoride resin prepolymer is prepared as follows:

[0048] (1) into the reaction kettle in turn 600 g of deionized water, 8 g of 1 wt% concentration of methyl cellulose, 2.5 g of acetone and 1 g of di-t-butyl peroxide, then 80 g of vinylidene fluoride monomer and 20 g of methyl acrylate are added to the reaction kettle for supercritical polymerization reaction, the reaction pressure is 4.5 MPa, the reaction temperature is 52℃, the reaction time is 4 h, after the reaction, the polymerization product is filtered, washed and dried to obtain polyvinylidene fluoride resin powder;

[0049] (2) the obtained polyvinylidene fluoride resin powder is added into 5 wt% NaOH solution, the mass ratio of polyvinylidene fluoride resin powder to NaOH solution is 1:10, heated at 50℃ water bath for 1 h for HF removal treatment, filtered, the polyvinylidene fluoride powder treated by HF removal is washed and dried to obtain polyvinylidene fluoride resin prepolymer containing conjugated double bond.

[0050] Example 2

[0051] An ultraviolet curing polyvinylidene fluoride adhesive, the raw material composition is: 7 g of methacrylamide, 10 g of vinyl pyrrolidone, 4 g of propylene neopentyl glycol dipropylene acrylate, 0.5 g of 2, 4, 6-trimethyl benzoyl diphenyl phosphine oxide, 1 g of 2, 4, 6-trimethyl benzoyl phenyl phosphonic acid ethyl ester, 35 g of polyvinylidene fluoride resin prepolymer, 20 g of silicon dioxide powder (average particle size 10 um), 2.6 g of γ-aminopropyl trimethoxysilane;

[0052] The preparation method is: 7 g of methacrylamide, 10 g of vinyl pyrrolidone, 4 g of propylene neopentyl glycol dipropylene acrylate are added into the mixing tank, the mixing tank is heated to 80℃, then 0.5 g of 2, 4, 6-trimethyl benzoyl diphenyl phosphine oxide and 1 g of 2, 4, 6-trimethyl benzoyl phenyl phosphonic acid ethyl ester are added, stirred at 300 rpm for 5 min, then cooled to 75℃, 35 g of polyvinylidene fluoride resin prepolymer prepared by step (2), 20 g of silicon dioxide powder (average particle size 10 um) and 2.6 g of γ-aminopropyl trimethoxysilane are added, stirred at 300 rpm for 5 min, to obtain the ultraviolet curing polyvinylidene fluoride adhesive product.

[0053] The polyvinylidene fluoride resin prepolymer is prepared by the following method:

[0054] (1) into the reaction kettle in turn 650 g of deionized water, 10 g of 1 wt% concentration of polyethylene glycol, 2.5 g of acetone and 1.1 g of methyl ethyl ketone peroxide, then 80 g of vinylidene fluoride monomer and 15 g of ethyl acrylate are added to the reaction kettle for supercritical polymerization reaction, the reaction pressure is 5 MPa, the reaction temperature is 48℃, the reaction time is 7 h, after the reaction, the polymerization product is filtered, washed and dried to obtain polyvinylidene fluoride resin powder;

[0055] (2) The obtained polyvinylidene fluoride resin powder is added into a 5wt% NaOH solution, the mass ratio of the polyvinylidene fluoride resin powder to the NaOH solution is 1:30, and the obtained mixture is heated in a 40°C water bath for 2h for HF removal treatment, then filtered, and the polyvinylidene fluoride resin powder after the HF removal treatment is washed and dried to obtain a polyvinylidene fluoride resin prepolymer containing conjugated double bonds.

[0056] Example 3

[0057] An ultraviolet light-curable polyvinylidene fluoride adhesive, the raw material composition of which is 13g of methyl vinyl sulfone, 10g of vinyl pyrrolidone, 8g of trimethylolpropane triacrylate, 9g of norbornene acrylate, 0.7g of 2,4,6-trimethylbenzoyl diphenyl phosphate, 1g of 2,4,6-trimethylbenzoyl phenyl ethyl phosphonate, 40g of the polyvinylidene fluoride resin prepolymer, 15g of calcium carbonate powder (average particle size 10um), and 0.8g of γ-aminopropyl trimethoxysilane per 1g.

[0058] The preparation method is as follows: 13g of methyl vinyl sulfone, 10g of vinyl pyrrolidone, 8g of trimethylolpropane triacrylate, and 9g of norbornene acrylate are added into a mixing tank, the mixing tank is heated to 85°C, then 0.7g of 2,4,6-trimethylbenzoyl diphenyl phosphate and 1g of 2,4,6-trimethylbenzoyl phenyl ethyl phosphonate are added, and stirred at a speed of 400rpm for 4min, then cooled to 65°C, 40g of the polyvinylidene fluoride resin prepolymer prepared in step (2), 15g of calcium carbonate powder (average particle size 10um), and 0.8g of γ-aminopropyl trimethoxysilane are added, and stirred at a speed of 400rpm for 4min to obtain an ultraviolet light-curable polyvinylidene fluoride adhesive product.

[0059] The preparation method of the polyvinylidene fluoride resin prepolymer is as follows:

[0060] (1) 580g of deionized water, 12g of polyethylene glycol with a concentration of 1wt%, 2.3g of sec-dodecyl mercaptan, and 1.2g of azobisisobutyronitrile are sequentially added into a reaction kettle, then 75g of vinylidene fluoride monomer and 10g of hydroxyethyl acrylate are added into the reaction kettle for supercritical polymerization reaction, the reaction pressure is 5.5MPa, the reaction temperature is 65°C, and the reaction time is 6h, after the reaction, the polymerization product is filtered, washed, and dried to obtain polyvinylidene fluoride resin powder;

[0061] (2) The obtained polyvinylidene fluoride resin powder is added to a 5wt% NaOH solution, the mass ratio of the polyvinylidene fluoride resin powder to the NaOH solution is 1:20, and the obtained polyvinylidene fluoride resin powder is heated in a water bath at 45°C for 1.5h for HF removal treatment, filtered, washed, and dried to obtain the polyvinylidene fluoride resin prepolymer containing conjugated double bonds.

[0062] Example 4

[0063] An ultraviolet light-curable polyvinylidene fluoride adhesive, with a feed composition of 7g of norbornene acrylate, 10g of methacrylamide, 8g of vinyl pyrrolidone, 8g of trimethylolpropane triacrylate, 1g of 2,4,6-trimethylbenzoyl diphenyl phosphate, 1.2g of 2,4,6-trimethylbenzoyl phenyl ethyl phosphonate, 50g of the polyvinylidene fluoride resin prepolymer, 25g of calcium carbonate powder (average particle size 10um), and 1g of γ-aminopropyl trimethoxysilane per 1g.

[0064] The preparation method is as follows: 7g of norbornene acrylate, 10g of methacrylamide, 8g of vinyl pyrrolidone, and 8g of trimethylolpropane triacrylate are added to a mixing tank, the mixing tank is heated to 80°C, 1g of 2,4,6-trimethylbenzoyl diphenyl phosphate and 1.2g of 2,4,6-trimethylbenzoyl phenyl ethyl phosphonate are added, stirring is performed at a speed of 500rpm for 3min, then the temperature is lowered to 55°C, 50g of the polyvinylidene fluoride resin prepolymer prepared in step (2), 25g of calcium carbonate powder (average particle size 10um), and 1g of γ-aminopropyl trimethoxysilane are added, stirring is performed at a speed of 500rpm for 3min, and an ultraviolet light-curable polyvinylidene fluoride adhesive product is obtained.

[0065] The polyvinylidene fluoride resin prepolymer is prepared as follows:

[0066] (1) 530g of deionized water, 10g of polyethylene glycol with a concentration of 1wt%, 1.2g of sec-acetic acid, and 1.8g of dicumyl peroxide are sequentially added to a reaction kettle, then 80g of vinylidene fluoride monomer and 8g of butyl acrylate are added to the reaction kettle for supercritical polymerization reaction, the reaction pressure is 5.3MPa, the reaction temperature is 66°C, the reaction time is 8h, and after the reaction is completed, the polymerization product is filtered, washed, and dried to obtain polyvinylidene fluoride resin powder;

[0067] (2) The obtained polyvinylidene fluoride resin powder is added to a 5wt% NaOH solution, the mass ratio of the polyvinylidene fluoride resin powder to the NaOH solution is 1:50, and the obtained polyvinylidene fluoride resin powder is heated in a water bath at 55°C for 0.75h for HF removal treatment, filtered, washed, and dried to obtain the polyvinylidene fluoride resin prepolymer containing conjugated double bonds.

[0068] Example 5

[0069] An ultraviolet light curing polyvinylidene fluoride adhesive, with a feed composition of 7g of methyl vinyl sulfone, 10g of vinyl pyrrolidone, 3g of trimethylolpropane triacrylate, 7g of methacrylamide, 2g of 2,4,6-trimethylbenzoyl diphenyl phosphate, 1g of 2,4,6-trimethylbenzoyl phenyl ethyl phosphonate, 45g of polyvinylidene fluoride resin prepolymer, 30g of calcium carbonate powder (average particle size 10um), 1.8g of γ-aminopropyl trimethoxysilane per 1g;

[0070] The preparation method is: 7g of methyl vinyl sulfone, 10g of vinyl pyrrolidone, 3g of trimethylolpropane triacrylate, 7g of methacrylamide are added into a mixing tank, the mixing tank is heated to 80℃, then 2g of 2,4,6-trimethylbenzoyl diphenyl phosphate and 1g of 2,4,6-trimethylbenzoyl phenyl ethyl phosphonate are added, stirred at a speed of 500rpm for 3min, then cooled to 60℃, 45g of polyvinylidene fluoride resin prepolymer prepared in step (2), 30g of calcium carbonate powder (average particle size 10um), 1.8g of γ-aminopropyl trimethoxysilane are added, stirred at a speed of 500rpm for 3min, to obtain the ultraviolet light curing polyvinylidene fluoride adhesive product.

[0071] The preparation method of the polyvinylidene fluoride resin prepolymer is as follows:

[0072] (1) 630g of deionized water, 10g of polyethylene glycol with a concentration of 1wt%, 1.5g of n-butanol and 0.8g of azobisisobutyronitrile are sequentially added into a reaction kettle, then 80g of vinylidene fluoride monomer and 16g of methacrylic acid ethyl ester comonomer are added into the reaction kettle for supercritical polymerization reaction, the reaction pressure is 7.0MPa, the reaction temperature is 78℃, the reaction time is 6h, after the reaction is completed, the polymerization product is filtered, washed and dried to obtain polyvinylidene fluoride resin powder;

[0073] (2) The obtained polyvinylidene fluoride resin powder is added into a 5wt% NaOH solution, the mass ratio of the polyvinylidene fluoride resin powder to the NaOH solution is 1:40, heated at 60℃ water bath for 0.5h for HF removal treatment, filtered, the polyvinylidene fluoride powder after HF removal treatment is washed and dried to obtain polyvinylidene fluoride resin prepolymer containing conjugated double bonds.

[0074] Comparative Example: The product is prepared according to the method of Example 1 of Chinese Patent Publication No. CN112375169A.

[0075] Performance test:

[0076] The properties of the products obtained from Examples 1-5 and Comparative Example 1 were tested, and the specific properties are shown in Table 1.

[0077] PP-PP room temperature bonding strength test: according to GB / T7124-2008 adhesive tensile shear strength test standard.

[0078] PP-PP "double 85" bonding strength test: after curing, the bonding sample was placed in a high temperature and high humidity oven, and the bonding strength was tested after being placed at 85℃ and 85% relative humidity for 1000h according to GB / T5170-2016 standard, and compared with the bonding strength measured at room temperature.

[0079] Contact angle test: according to GB / T30447-2013 contact angle measurement method.

[0080] Dielectric constant test: according to GB / T31838.6-2021 dielectric constant test.

[0081] As can be seen from the data in Table 1, the ultraviolet light cured polyvinylidene fluoride adhesive prepared by Examples 1-5 of the present application has strong hydrophobic property and low surface energy, and has good adhesion with low surface energy plastic PP (polypropylene), and the dielectric constant of the adhesive film is high, which can be widely used in electronic product bonding field.

[0082] Table 1 Properties of products of Examples 1-5 and Comparative Example 1

Claims

1. An ultraviolet light-cured polyvinylidene fluoride adhesive, characterized by comprising: The raw material composition comprises, by weight fraction, 20-45 parts of active diluent, 1-3.5 parts of photoinitiator, 20-60 parts of polyvinylidene fluoride prepolymer with conjugated double bond, 10-30 parts of filler, and 0.1-3.5 parts of silane coupling agent.

2. The ultraviolet light-cured polyvinylidene fluoride adhesive according to claim 1, wherein The active diluent is at least one of propenyl pyrrolidone, methyl vinyl sulfone, methacrylamide, vinyl pyrrolidone, propoxyl neopentyl glycol dipropyl acrylate, trimethylolpropane triacrylate, norbornene acrylate.

3. The ultraviolet light-cured polyvinylidene fluoride adhesive according to claim 1, wherein The photoinitiator is at least one of 2,4,6-trimethyl benzoyl diphenyl phosphine oxide, 1-hydroxycyclohexyl phenyl ketone, and 2,4,6-trimethyl benzoyl phenyl phosphonic acid ethyl ester.

4. The ultraviolet light-cured polyvinylidene fluoride adhesive according to claim 1, wherein The silane coupling agent is at least one of aminopropyl triethoxysilane and gamma-aminopropyl trimethoxysilane.

5. The ultraviolet light-cured polyvinylidene fluoride adhesive according to claim 1, wherein the polyvinylidene fluoride resin is polyvinylidene fluoride-hexafluoropropene copolymer. The filler is at least one of silicon dioxide, calcium oxide, calcium carbonate, and mica.

6. The ultraviolet light-cured polyvinylidene fluoride adhesive according to claim 1, wherein The polyvinylidene fluoride prepolymer with conjugated double bond is prepared by the following method: (1) by weight fraction, deionized water 500-700 parts, dispersant 5-15 parts, initiator 0.5-2 parts, chain transfer agent 1-3 parts, vinylidene fluoride monomer 70-90 parts, and acrylic ester monomer 5-25 parts are subjected to polymerization reaction, the reaction temperature is 30-90℃, the reaction time is 4-8h, the reaction pressure is 4-8MPa, after the reaction is completed, the product is filtered, washed, and dried to obtain polyvinylidene fluoride resin; (2) the polyvinylidene fluoride resin obtained in step (1) is subjected to reaction in alkali solution, the reaction temperature is 40-80℃, the reaction time is 0.5-3h, the obtained product is filtered, washed, and dried to obtain polyvinylidene fluoride prepolymer with conjugated double bond.

7. The ultraviolet light-cured polyvinylidene fluoride adhesive according to claim 6, wherein The dispersant is at least one of methyl cellulose, polyethylene glycol, sodium dodecyl benzene sulfonate, and sodium dodecyl sulfate.

8. The ultraviolet light-cured polyvinylidene fluoride adhesive according to claim 6, wherein The initiator is at least one of azobis isobutyronitrile, di-tert-butyl peroxide, tert-butyl benzoyl, methyl ethyl ketone peroxide, and dicyclohexyl peroxydicarbonate.

9. The ultraviolet light-cured polyvinylidene fluoride adhesive according to claim 6, wherein The chain transfer agent is at least one of acetone, secondary dodecyl mercaptan, acetic acid, n-butanol, and butyl acetate.

10. The ultraviolet light-cured polyvinylidene fluoride adhesive according to claim 6, wherein The acrylic ester monomer is at least one of methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, and hydroxyethyl acrylate.

11. A method for preparing an ultraviolet light-cured polyvinylidene fluoride adhesive, characterized by, The method comprises the following steps: (1) by weight fraction, deionized water 500-700 parts, dispersant 5-15 parts, initiator 0.5-2 parts, chain transfer agent 1-3 parts, vinylidene fluoride monomer 70-90 parts, and acrylic ester monomer 5-25 parts are subjected to polymerization reaction, the reaction temperature is 30-90℃, the reaction time is 4-8h, the reaction pressure is 4-8MPa, after the reaction is completed, the product is filtered, washed, and dried to obtain polyvinylidene fluoride resin; (2) the polyvinylidene fluoride resin obtained in step (1) is subjected to reaction in alkali solution, the reaction temperature is 40-80℃, the reaction time is 0.5-3h, the obtained product is filtered, washed, and dried to obtain polyvinylidene fluoride prepolymer with conjugated double bond. (3) according to weight parts, the active diluent 20-45 parts, photo initiator 1-3.5 parts, in 75-95 DEG C, 200-500 rpm under stirring 3-5 min, cooling to 50-70 DEG C, the obtained in step (2) has 20-60 parts of polyvinyl fluoride prepolymer with conjugated double bond, filler 10-30 parts and silane coupling agent 0.1-3.5 parts, stirring 3-5 min under 200-500 rpm, the UV curing polyvinyl fluoride adhesive is obtained.

12. The method for preparing the UV-curable polyvinylidene fluoride adhesive as described in claim 11, characterized in that, The dispersant is at least one of methyl cellulose, polyethylene glycol, sodium dodecyl benzene sulfonate, and sodium dodecyl sulfate.

13. The method for preparing the UV-curable polyvinylidene fluoride adhesive as described in claim 11, characterized in that, The initiator is at least one of azobisisobutyronitrile, di-tert-butyl peroxide, tert-butyl benzoyl, methyl ethyl ketone peroxide, and dicyclohexyl peroxydicarbonate.

14. The method for preparing the UV-curable polyvinylidene fluoride adhesive as described in claim 11, characterized in that, The chain transfer agent is at least one of acetone, secondary dodecyl mercaptan, acetic acid, n-butanol, and butyl acetate.

15. The method for preparing the UV-curable polyvinylidene fluoride adhesive as described in claim 11, characterized in that, The acrylate monomer is at least one of methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, and hydroxyethyl acrylate.

16. The method for preparing the UV-curable polyvinylidene fluoride adhesive as described in claim 11, characterized in that, The mass ratio of the polyvinyl fluoride resin to the alkali solution is 1:10-50.

17. The method for preparing the UV-curable polyvinylidene fluoride adhesive as described in claim 11, characterized in that, The active diluent is at least one of propenyl pyrrolidone, methyl vinyl sulfone, methyl acrylamide, vinyl pyrrolidone, propoxy neopentyl glycol dipropyl acrylate, trimethylolpropane triacrylate, and norbornene acrylate.

18. The method for preparing the UV-curable polyvinylidene fluoride adhesive as described in claim 11, characterized in that, The photo initiator is at least one of 2,4,6-trimethyl benzoyl diphenyl phosphine oxide, 1-hydroxycyclohexyl phenyl ketone, and 2,4,6-trimethyl benzoyl phenyl phosphonate ethyl ester.

19. The method for preparing the UV-curable polyvinylidene fluoride adhesive as described in claim 11, characterized in that, The silane coupling agent is at least one of aminopropyl triethoxysilane and γ-aminopropyl trimethoxysilane.

20. The method for preparing the UV-curable polyvinylidene fluoride adhesive as described in claim 11, characterized in that, The filler is at least one of silicon dioxide, calcium oxide, calcium carbonate, and mica.

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