Modified polyvinyl butyral as well as preparation method and application thereof

Abstract

The invention discloses modified polyvinyl butyral as well as a preparation method and application thereof. The modified polyvinyl butyral is obtained by carrying out condensation polymerization on an organic silicon polyurethane prepolymer of which two ends are connected with isocyanate groups, an organic silicon polyurethane prepolymer of which one end is connected with an isocyanate group and hydroxyl on the polyvinyl butyral. According to the invention, polyvinyl butyral is modified by the double-isocyanate-group-terminated organic silicon polyurethane prepolymer and the single-isocyanate-group-terminated organic silicon polyurethane prepolymer, so that a coating formed by the prepared organic silicon polyurethane modified polyvinyl butyral is good in water resistance and high in impact resistance; meanwhile, the advantages of the polyvinyl butyral coating, the organic silicon coating and the polyurethane coating are integrated, and the application range of the polyvinyl butyral is effectively widened.

Description

Technical Field

[0001] The present invention belongs to the technical field of coatings, and particularly relates to a modified polyvinyl butyral and its preparation method and application. Background Art

[0002] With the development of technology, while various electronic devices improve people's lives, new requirements and challenges are also put forward for the development of electronic devices. For example, high signal transmission intensity, good waterproof performance, good resistance to acid, alkali, and salt spray. In order to meet these performance requirements, the three-proof coatings used in electronic products have been continuously improved and developed.

[0003] According to the classification of existing three-proof coatings in the market, the most common three-proof coatings are divided into five categories. They are polyurethane resin type (UR), epoxy resin type (ER), silicone resin type (SR), acrylic resin type (AR), and parylene type (XY). These five types of three-proof coatings have their own advantages and disadvantages according to their main film-forming substances. Polyurethane resin type coatings have good dielectric properties and mechanical properties, as well as excellent moisture-proof, solvent-resistant, salt spray corrosion-resistant, chemical-resistant, and wear-resistant properties. However, the surface of the circuit board must be kept clean and dry before coating, and the polyurethane coating is prone to yellowing and has poor reparability. Epoxy resin type coating materials are based on epoxy resin and its modifiers, with high hardness, good moisture-proof and chemical corrosion-resistant properties, and good wear-resistant properties. However, internal stress will be generated during the curing process of epoxy resin materials, which is easy to cause damage to brittle components. In addition, the epoxy coating has poor toughness, is prone to powdering under outdoor exposure, and is difficult to repair and remove. Silicone resin type three-proof coating materials have good water-repellent properties, dielectric properties, excellent moisture and heat resistance, salt spray resistance, good thermal stability and weather resistance, a wide temperature range for the material, excellent high and low temperature resistance, controllable coating thickness, good flexibility, excellent electrical and anti-aging properties, and at the same time low surface tension, easy to remove and repair, but its thermal expansion coefficient is large and it is easy to wear. Acrylic resin type coatings are generally solvent-based acrylic resin coatings, which have the characteristics of easy coating and convenient repair, as well as good dielectric properties, mechanical properties, and anti-mildew properties. However, this type of coating has a high content of volatile solvents, is flammable, and has poor safety. Parylene type coatings are thin, up to the micron level; the coating is uniform, dense, pore-free, and has a low permeability; it shows chemical inertness and is resistant to solvents, acid, and alkali erosion; the material has excellent dielectric properties. However, the preparation of this type of coating requires special vacuum deposition equipment, and the preparation cost is relatively high; the coating has poor resistance to high temperature aging and ultraviolet aging; the coating is difficult to repair and remove; and because the film thickness of this type of coating is only 7-8μm, it is difficult to achieve the purpose of moisture-proof.

[0004] Polyvinyl butyral is a resin with strong binding force, high optical clarity, easy adhesion to various substrate surfaces, high toughness and high elasticity. It is often used as safety glass interlayer, adhesive and coating manufacturing. When polyvinyl butyral is used to prepare coatings, the coating has good impact resistance, cold resistance, water resistance and good adhesion to most substrates. It has good solubility in most strong polar solvents and is easy to remove and repair. However, the common polyvinyl butyral currently has a high hydroxyl content and high water absorption, and is not suitable for use as a three-proof coating and anti-corrosion coating. Summary of the invention

[0005] In view of the deficiencies in the prior art, the object of the present invention is to provide a modified polyvinyl butyral and a preparation method and application thereof, so as to solve the technical problems of poor water resistance and insufficient mechanical properties of existing coating materials.

[0006] To achieve the above object, the present invention adopts the following technical solution: In a first aspect, the present invention provides a modified polyvinyl butyral, which is a silicone polyurethane modified polyvinyl butyral, obtained by a condensation reaction between a silicone polyurethane prepolymer having isocyanate groups at both ends and a silicone polyurethane prepolymer having an isocyanate group at one end and a hydroxyl group on the polyvinyl butyral.

[0007] The present invention reacts a diisocyanate-terminated silicone polyurethane prepolymer with a part of hydroxyl groups on polyvinyl butyral to form a cross-linked network, thereby improving the mechanical properties of the polyvinyl butyral coating. At the same time, a monoisocyanate-terminated silicone polyurethane prepolymer reacts with the remaining hydroxyl groups to further reduce the content of hydroxyl groups in the polyvinyl butyral, thereby reducing the surface energy of the coating and improving the hydrophobicity.

[0008] Preferably, the molar ratio of the organosilicon polyurethane prepolymer with isocyanate groups at both ends to the hydroxyl group in polyvinyl butyral is (0.01-0.2):1, and the molar ratio of the organosilicon polyurethane prepolymer with isocyanate groups at one end to the hydroxyl group in polyvinyl butyral is (0.8-0.99):1.

[0009] In a second aspect, the present invention provides a method for preparing silicone polyurethane modified polyvinyl butyral, comprising the following steps: The hydroxyl-terminated polydimethylsiloxane is subjected to a first addition reaction with diisocyanate to generate an organosilicon polyurethane prepolymer having isocyanate groups at both ends, thereby obtaining a first reaction product; The hydroxyl-terminated polydimethylsiloxane and diisocyanate are subjected to a second addition reaction to generate an organosilicon polyurethane prepolymer having an isocyanate group at one end, thereby obtaining a second reaction product; Mix the polyvinyl butyral solution, the first reaction product, the second reaction product and a catalyst to carry out a third addition reaction to obtain an organosilicon polyurethane modified polyvinyl butyral.

[0010] Preferably, in the first addition reaction, the molar ratio of the hydroxyl-terminated polydimethylsiloxane to the diisocyanate is 1:(1 - 2).

[0011] Preferably, the reaction temperature of the first addition reaction is 70 - 100 °C, and the reaction time is 4 - 7 h.

[0012] Preferably, the second addition reaction includes: reacting the hydroxyl-terminated polydimethylsiloxane and the diisocyanate at 70 - 100 °C for 4 - 7 h to obtain a mixture; then, adding anhydrous ethanol to the mixture and continuing the reaction for 1 - 3 h to obtain the second reaction product.

[0013] Preferably, in the second addition reaction, the molar ratio of the hydroxyl-terminated polydimethylsiloxane to the diisocyanate is 1:(1.3 - 2); the molar ratio of the hydroxyl-terminated polydimethylsiloxane to the anhydrous ethanol is 1:(0.5 - 1).

[0014] Preferably, the diisocyanate includes one or more of hexamethylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate.

[0015] Preferably, the kinematic viscosity of the hydroxyl-terminated polydimethylsiloxane is 20 - 100 cst, and the molecular weight is 300 - 2000 g / mol.

[0016] Preferably, in the third addition reaction, the dosage of the first reaction product is 1% - 20% of the molar amount of hydroxyl groups in the polyvinyl butyral, the dosage of the second reaction product is 80% - 99% of the molar amount of hydroxyl groups in the polyvinyl butyral, and the dosage of the catalyst is 0.05% - 1% of the total mass of the polyvinyl butyral, the first reaction product and the second reaction product.

[0017] Preferably, the catalyst is an organotin catalyst.

[0018] Preferably, the reaction temperature of the third addition reaction is 70 - 100 °C, and the reaction time is 3 - 5 h.

[0019] In a third aspect, the present invention provides an application of the above-mentioned organosilicon polyurethane modified polyvinyl butyral in coatings.

[0020] The beneficial effects of the present invention are: (1)The modified polyvinyl butyral prepared in the present invention is an organosilicon polyurethane modified polyvinyl butyral. Compared with the polyvinyl butyral coating before modification, the coating formed by it has a lower water absorption rate, excellent hydrophobicity, water resistance and impact resistance, and to a certain extent makes up for the problems that the organosilicon three-proof coating is easy to wear and the polyurethane coating is difficult to repair. At the same time, it combines the advantages of polyvinyl butyral coating, organosilicon coating and polyurethane coating, and is suitable as a three-proof coating and anti-corrosion coating material, effectively broadening the application fields and scope of polyvinyl butyral.

[0021] (2)When the modified polyvinyl butyral provided by the present invention forms a coating, the organosilicon polyurethane chain segment can phase-separate and migrate to the coating surface to form a micro-nano structure with the polyvinyl butyral main chain, thereby effectively improving the hydrophobic and water-repellent properties of the coating. Description of the Drawings

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings of the embodiments will be briefly introduced below.

[0023] Figure 1 It is the Fourier infrared spectrogram of organosilicon polyurethane before and after modifying PVB in Example 1; Figure 2 It is the surface SEM diagram of the organosilicon polyurethane modified PVB coating in Example 1; Figure 3 It is the EDX element distribution diagram of the convex structure and non-convex structure on the surface of the organosilicon polyurethane modified PVB coating in Example 1; Figure 4 It is the water contact angle photo of organosilicon polyurethane before and after modifying PVB on a glass substrate in Example 1. Detailed Embodiments

[0024] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0025] Polyvinyl butyral has a large number of hydroxyl groups. If it is used directly as a coating, the coating will have a high water absorption rate, poor water resistance, and poor impact resistance. The present invention uses the hydroxyl groups in polyvinyl butyral as modified active sites, and reacts the hydroxyl groups with the blocked diisocyanate on the silicone polyurethane, which not only effectively reduces the hydroxyl content and improves water resistance, but also gives it the advantages of silicone resin coatings, polyurethane coatings and polyvinyl butyral coatings, and prepares a composite coating material with complementary properties, thereby making up for the various defects faced by existing three-proof coatings.

[0026] Specifically, an embodiment of the present invention provides a silicone polyurethane modified polyvinyl butyral, which is obtained by polycondensation reaction of a silicone polyurethane prepolymer having isocyanate groups at both ends and a silicone polyurethane prepolymer having isocyanate groups at one end with hydroxyl groups on polyvinyl butyral.

[0027] In some embodiments, the silicone polyurethane modified polyvinyl butyral has the structural formula shown in Formula I:

[0028] Formula I In the formula, R 1 is an aliphatic group, an alicyclic group or an aromatic group; R 2 It is polydimethylsiloxane.

[0029] The values ​​of x, n, m, and z in Formula I depend on the degree of polymerization of the raw material polyvinyl butyral. Polyvinyl butyral at any degree of polymerization can achieve the technical effect of the present invention, so the present invention does not limit the values ​​of x, n, m, and z. In some embodiments, x=0.79~0.82, n=0.0018~0.018, m=0.172~0.1782, and z=0~0.01. a and b are the average number of silicone polyurethane segments, and any values ​​thereof can achieve the technical effect of the present invention, so the present invention does not limit the values ​​of a and b. In some embodiments, a=2~8, and b=1~3.

[0030] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be described in further detail below.

[0031] In the following examples, all reaction raw materials were dried to remove water: solid raw materials were dried in a vacuum oven at 40° C. for 8 h to remove water, and liquid raw materials were dried over activated molecular sieves to remove water.

[0032] Example 1 A silicone polyurethane modified polyvinyl butyral is obtained by the polycondensation reaction of a silicone polyurethane prepolymer with isocyanate groups at both ends and a silicone polyurethane prepolymer with an isocyanate group at one end and the hydroxyl groups on the polyvinyl butyral. Its structural formula is as follows:

[0033] In the formula, x = 0.79 - 0.82, z = 0 - 0.01, n = 0.0018 - 0.018, m = 0.172 - 0.1782, a = 2 - 8, b = 1 - 3, y = 4 - 25.

[0034] The specific preparation method of the above silicone polyurethane modified polyvinyl butyral is as follows: Under nitrogen protection, 20 g of hydroxyl-terminated polydimethylsiloxane (kinematic viscosity 28 cst, molecular weight 400 g / mol) and 10.08 g of hexamethylene diisocyanate are added to a flask, and the temperature is raised to 80 °C and stirred for 4 h to form a silicone polyurethane prepolymer with isocyanate groups at both ends, obtaining a first reaction product.

[0035] Under nitrogen protection, 24 g of hydroxyl-terminated polydimethylsiloxane (kinematic viscosity 28 cst, molecular weight 400 g / mol) and 20.16 g of hexamethylene diisocyanate are added to a flask, the temperature is raised to 80 °C and stirred for 4 h, then 2.76 g of absolute ethanol is added to the flask, and stirred at 80 °C for 2 h to form a silicone polyurethane prepolymer with an isocyanate group at one end, obtaining a second reaction product.

[0036] Take 5 g of polyvinyl butyral (PVB, molecular weight 50000, hydroxyl content 18%) and stir it to dissolve in 150 g of cyclohexanone to obtain a polyvinyl butyral solution. Add 0.35 g of the first reaction product, 16.63 g of the second reaction product and 0.02 g of dibutyltin dilaurate to the polyvinyl butyral solution, and stir and reflux at 80 °C for 4 h. Rotate and evaporate the obtained solution to remove most of the solvent to obtain a silicone polyurethane modified polyvinyl butyral adhesive solution.

[0037] Figure 1 This is the Fourier transform infrared spectrum diagram of the silicone polyurethane modified polyvinyl butyral before and after modification in this example. As can be seen from the curve in Figure 1 The stretching vibration peak at 3520 cm -1 on the PVB is the characteristic peak of -OH. The characteristic peak at 3520 cm -1 on the modified PVB disappears, and a stretching vibration peak of -NH appears at 3340 cm -1 indicating that all the -OH on the side chain of PVB has reacted with the silicone polyurethane prepolymer to form urethane groups.

[0038] The polyvinyl butyral glue modified with silicone polyurethane prepared in this embodiment is coated on the PCB board to form a coating. Figure 2 This is a SEM image of the surface of the silicone polyurethane modified PVB coating. From the image, it can be seen that there are a large number of micro-nano protrusion structures with a size of tens of nanometers to several microns that are evenly distributed on the surface of the modified PVB coating.

[0039] EDX element analysis was performed on the convex and non-convex structures on the coating surface, such as Figure 3 As shown, (a) is the EDX element distribution on the surface of the raised structure part, and (b) is the EDX element distribution on the surface of the non-raised structure part. It can be seen that the distribution of Si and O elements in (a) is significantly higher than that in (b), indicating that the raised structure has a higher Si and O content than the non-raised structure, and the Si and O elements are provided by the silicone polyurethane prepolymer. This proves that the micro-nano raised structure on the coating surface is formed by the microphase separation and migration of the silicone polyurethane chain segment and PVB to the coating surface, that is, when the silicone polyurethane modified PVB prepared by the present invention forms a coating, the silicone polyurethane chain segment will migrate to the coating surface, effectively improving the hydrophobicity and water repellency of the coating, and can be directly used as a three-proof coating and an anti-corrosion coating.

[0040] Example 2 A silicone polyurethane modified polyvinyl butyral is prepared by the following steps: Under nitrogen protection, 20 g of hydroxyl-terminated polydimethylsiloxane (kinematic viscosity 28 cst, molecular weight 400 g / mol) and 10.08 g of hexamethylene diisocyanate were added to a flask, the temperature was raised to 80°C and stirred for reaction for 4 h to generate a silicone polyurethane prepolymer with isocyanate groups at both ends to obtain a first reaction product.

[0041] Under nitrogen protection, 24 g of hydroxyl-terminated polydimethylsiloxane (kinematic viscosity 28 cst, molecular weight 400 g / mol) and 20.16 g of hexamethylene diisocyanate were added to a flask, the temperature was raised to 80°C and stirred for reaction for 4 h, and then 2.76 g of anhydrous ethanol was added to the flask, and the reaction was stirred at 80°C for 2 h to generate a silicone polyurethane prepolymer with an isocyanate group at one end, thereby obtaining a second reaction product.

[0042] Take 5 g of polyvinyl butyral (PVB, molecular weight 50,000, hydroxyl content 18%) and stir it to dissolve in 150 g of cyclohexanone to obtain a polyvinyl butyral solution. Add 1.56 g of the first reaction product, 15.98 g of the second reaction product and 0.02 g of dibutyltin dilaurate to the polyvinyl butyral solution, and stir and reflux at 80 °C for 4 h. Rotate and evaporate the obtained solution to remove most of the solvent to obtain an organosilicon polyurethane-modified polyvinyl butyral adhesive solution.

[0043] Example 3 An organosilicon polyurethane-modified polyvinyl butyral is prepared by the following steps: Under nitrogen protection, add 20 g of hydroxyl-terminated polydimethylsiloxane (kinematic viscosity 28 cst, molecular weight 400 g / mol) and 10.08 g of hexamethylene diisocyanate to a flask, heat up to 80 °C and stir and react for 4 h to generate an organosilicon polyurethane prepolymer with isocyanate groups at both ends, obtaining the first reaction product.

[0044] Under nitrogen protection, add 24 g of hydroxyl-terminated polydimethylsiloxane (kinematic viscosity 28 cst, molecular weight 400 g / mol) and 20.16 g of hexamethylene diisocyanate to a flask, heat up to 80 °C and stir and react for 4 h, then add 2.76 g of absolute ethanol to the flask and stir and react at 80 °C for 2 h to generate an organosilicon polyurethane prepolymer with an isocyanate group at one end, obtaining the second reaction product.

[0045] Take 5 g of polyvinyl butyral (PVB, molecular weight 50,000, hydroxyl content 18%) and stir it to dissolve in 150 g of cyclohexanone to obtain a polyvinyl butyral solution. Add 3.11 g of the first reaction product, 15.11 g of the second reaction product and 0.02 g of dibutyltin dilaurate to the polyvinyl butyral solution, and stir and reflux at 80 °C for 4 h. Rotate and evaporate the obtained solution to remove most of the solvent to obtain an organosilicon polyurethane-modified polyvinyl butyral adhesive solution.

[0046] Example 4 An organosilicon polyurethane-modified polyvinyl butyral is prepared by the following steps: Under nitrogen protection, add 20 g of hydroxyl-terminated polydimethylsiloxane (kinematic viscosity 28 cst, molecular weight 400 g / mol) and 10.08 g of hexamethylene diisocyanate to a flask, heat up to 80 °C and stir and react for 4 h to generate an organosilicon polyurethane prepolymer with isocyanate groups at both ends, obtaining the first reaction product.

[0047] Under nitrogen protection, 24 g of hydroxyl-terminated polydimethylsiloxane (kinematic viscosity 28 cst, molecular weight 400 g / mol) and 20.16 g of hexamethylene diisocyanate were added to a flask. The temperature was raised to 80 °C and stirred for reaction for 4 h. Then, 2.76 g of absolute ethanol was added to the flask, and stirred at 80 °C for reaction for 2 h to generate a silicone polyurethane prepolymer with an isocyanate group at one end, obtaining the second reaction product.

[0048] 5 g of polyvinyl butyral (PVB, molecular weight 50,000, hydroxyl content 18%) was stirred and dissolved in 150 g of cyclohexanone to obtain a polyvinyl butyral solution. 6.28 g of the first reaction product, 13.35 g of the second reaction product and 0.02 g of dibutyltin dilaurate were added to the polyvinyl butyral solution, and stirred and refluxed at 80 °C for reaction for 4 h. The obtained solution was rotary evaporated to remove most of the solvent, obtaining a silicone polyurethane-modified polyvinyl butyral adhesive solution.

[0049] Example 5 A silicone polyurethane-modified polyvinyl butyral is prepared by the following steps: Under nitrogen protection, 24 g of hydroxyl-terminated polydimethylsiloxane (kinematic viscosity 28 cst, molecular weight 400 g / mol) and 13.44 g of hexamethylene diisocyanate were added to a flask. The temperature was raised to 80 °C and stirred for reaction for 4 h to generate a silicone polyurethane prepolymer with isocyanate groups at both ends, obtaining the first reaction product.

[0050] Under nitrogen protection, 24 g of hydroxyl-terminated polydimethylsiloxane (kinematic viscosity 28 cst, molecular weight 400 g / mol) and 20.16 g of hexamethylene diisocyanate were added to a flask. The temperature was raised to 80 °C and stirred for reaction for 4 h. Then, 2.76 g of absolute ethanol was added to the flask, and stirred at 80 °C for reaction for 2 h to generate a silicone polyurethane prepolymer with an isocyanate group at one end, obtaining the second reaction product.

[0051] 5 g of polyvinyl butyral (PVB, molecular weight 50,000, hydroxyl content 18%) was stirred and dissolved in 150 g of cyclohexanone to obtain a polyvinyl butyral solution. 0.21 g of the first reaction product, 16.63 g of the second reaction product and 0.02 g of dibutyltin dilaurate were added to the polyvinyl butyral solution, and stirred and refluxed at 80 °C for reaction for 4 h. The obtained solution was rotary evaporated to remove most of the solvent, obtaining a silicone polyurethane-modified polyvinyl butyral adhesive solution.

[0052] Example 6 A silicone polyurethane-modified polyvinyl butyral is prepared by the following steps: Under nitrogen protection, 24 g of hydroxyl-terminated polydimethylsiloxane (kinematic viscosity 28 cst, molecular weight 400 g / mol) and 13.44 g of hexamethylene diisocyanate were added to a flask, and the temperature was raised to 80 °C and stirred for reaction for 4 h to form a silicone polyurethane prepolymer with isocyanate groups at both ends, obtaining the first reaction product.

[0053] Under nitrogen protection, 24 g of hydroxyl-terminated polydimethylsiloxane (kinematic viscosity 28 cst, molecular weight 400 g / mol) and 20.16 g of hexamethylene diisocyanate were added to a flask, and the temperature was raised to 80 °C and stirred for reaction for 4 h. Then, 2.76 g of absolute ethanol was added to the flask, and the mixture was stirred for reaction at 80 °C for 2 h to form a silicone polyurethane prepolymer with an isocyanate group at one end, obtaining the second reaction product.

[0054] 5 g of polyvinyl butyral (PVB, molecular weight 50000, hydroxyl content 18%) was stirred and dissolved in 150 g of cyclohexanone to obtain a polyvinyl butyral solution. 1.02 g of the first reaction product, 15.98 g of the second reaction product, and 0.02 g of dibutyltin dilaurate were added to the polyvinyl butyral solution, and the mixture was stirred and refluxed at 80 °C for 4 h. The obtained solution was rotary evaporated to remove most of the solvent, obtaining a silicone polyurethane-modified polyvinyl butyral adhesive solution.

[0055] Example 7 A silicone polyurethane-modified polyvinyl butyral is prepared by the following steps: Under nitrogen protection, 24 g of hydroxyl-terminated polydimethylsiloxane (kinematic viscosity 28 cst, molecular weight 400 g / mol) and 13.44 g of hexamethylene diisocyanate were added to a flask, and the temperature was raised to 80 °C and stirred for reaction for 4 h to form a silicone polyurethane prepolymer with isocyanate groups at both ends, obtaining the first reaction product.

[0056] Under nitrogen protection, 24 g of hydroxyl-terminated polydimethylsiloxane (kinematic viscosity 28 cst, molecular weight 400 g / mol) and 20.16 g of hexamethylene diisocyanate were added to a flask, and the temperature was raised to 80 °C and stirred for reaction for 4 h. Then, 2.76 g of absolute ethanol was added to the flask, and the mixture was stirred for reaction at 80 °C for 2 h to form a silicone polyurethane prepolymer with an isocyanate group at one end, obtaining the second reaction product.

[0057] Take 5 g of polyvinyl butyral (PVB, molecular weight 50,000, hydroxyl content 18%) and stir it to dissolve in 150 g of cyclohexanone to obtain a polyvinyl butyral solution. Add 2.04 g of the first reaction product, 15.11 g of the second reaction product and 0.02 g of dibutyltin dilaurate to the polyvinyl butyral solution, and stir and reflux at 80 °C for 4 h. Rotavapor the obtained solution to remove most of the solvent to obtain an organosilicon polyurethane-modified polyvinyl butyral adhesive solution.

[0058] Example 8 An organosilicon polyurethane-modified polyvinyl butyral is prepared by the following steps: Under nitrogen protection, add 22.4 g of hydroxyl-terminated polydimethylsiloxane (kinematic viscosity 28 cst, molecular weight 400 g / mol) and 10.75 g of hexamethylene diisocyanate to a flask, heat up to 80 °C and stir and react for 4 h to generate an organosilicon polyurethane prepolymer with isocyanate groups at both ends, obtaining the first reaction product.

[0059] Under nitrogen protection, add 24 g of hydroxyl-terminated polydimethylsiloxane (kinematic viscosity 28 cst, molecular weight 400 g / mol) and 20.16 g of hexamethylene diisocyanate to a flask, heat up to 80 °C and stir and react for 4 h, then add 2.76 g of absolute ethanol to the flask and stir and react at 80 °C for 2 h to generate an organosilicon polyurethane prepolymer with an isocyanate group at one end, obtaining the second reaction product.

[0060] Take 5 g of polyvinyl butyral (PVB, molecular weight 50,000, hydroxyl content 18%) and stir it to dissolve in 150 g of cyclohexanone to obtain a polyvinyl butyral solution. Add 0.43 g of the first reaction product, 16.63 g of the second reaction product and 0.02 g of dibutyltin dilaurate to the polyvinyl butyral solution, and stir and reflux at 80 °C for 4 h. Rotavapor the obtained solution to remove most of the solvent to obtain an organosilicon polyurethane-modified polyvinyl butyral adhesive solution.

[0061] Example 9 An organosilicon polyurethane-modified polyvinyl butyral is prepared by the following steps: Under nitrogen protection, add 22.4 g of hydroxyl-terminated polydimethylsiloxane (kinematic viscosity 28 cst, molecular weight 400 g / mol) and 10.75 g of hexamethylene diisocyanate to a flask, heat up to 80 °C and stir and react for 4 h to generate an organosilicon polyurethane prepolymer with isocyanate groups at both ends, obtaining the first reaction product.

[0062] Under nitrogen protection, 24 g of hydroxyl-terminated polydimethylsiloxane (kinematic viscosity 28 cst, molecular weight 400 g / mol) and 20.16 g of hexamethylene diisocyanate were added to a flask. The temperature was raised to 80 °C and stirred for 4 h. Then, 2.76 g of absolute ethanol was added to the flask and stirred at 80 °C for 2 h to form a silicone polyurethane prepolymer with an isocyanate group at one end, obtaining the second reaction product.

[0063] 5 g of polyvinyl butyral (PVB, molecular weight 50000, hydroxyl content 18%) was stirred and dissolved in 150 g of cyclohexanone to obtain a polyvinyl butyral solution. To the polyvinyl butyral solution, 2.15 g of the first reaction product, 15.98 g of the second reaction product, and 0.022 g of dibutyltin dilaurate were added, and stirred and refluxed at 80 °C for 4 h. The resulting solution was rotary evaporated to remove most of the solvent, obtaining a silicone polyurethane-modified polyvinyl butyral adhesive solution.

[0064] Example 10 A silicone polyurethane-modified polyvinyl butyral is prepared by the following steps: Under nitrogen protection, 20 g of hydroxyl-terminated polydimethylsiloxane (kinematic viscosity 28 cst, molecular weight 400 g / mol) and 10.08 g of hexamethylene diisocyanate were added to a flask. The temperature was raised to 80 °C and stirred for 4 h to form a silicone polyurethane prepolymer with isocyanate groups at both ends, obtaining the first reaction product.

[0065] Under nitrogen protection, 24 g of hydroxyl-terminated polydimethylsiloxane (kinematic viscosity 28 cst, molecular weight 400 g / mol) and 20.16 g of hexamethylene diisocyanate were added to a flask. The temperature was raised to 80 °C and stirred for 4 h. Then, 2.76 g of absolute ethanol was added to the flask and stirred at 80 °C for 2 h to form a silicone polyurethane prepolymer with an isocyanate group at one end, obtaining the second reaction product.

[0066] 5 g of polyvinyl butyral (PVB, molecular weight 50000, hydroxyl content 18%) was stirred and dissolved in 150 g of cyclohexanone to obtain a polyvinyl butyral solution. To the polyvinyl butyral solution, 4.29 g of the first reaction product, 15.11 g of the second reaction product, and 0.022 g of dibutyltin dilaurate were added, and stirred and refluxed at 80 °C for 4 h. The resulting solution was rotary evaporated to remove most of the solvent, obtaining a silicone polyurethane-modified polyvinyl butyral adhesive solution.

[0067] Comparative Example 1 Take 5 g of polyvinyl butyral (PVB, molecular weight of 50,000, hydroxyl content of 18%) and stir it to dissolve in 50 g of cyclohexanone to obtain a polyvinyl butyral glue solution.

[0068] Performance test Hydrophobicity: Film the PVB glue solutions before and after the modification of silicone polyurethane in Example 1 on a glass substrate, and observe the water contact angle of the coating surface on a contact angle measuring instrument. Figure 4 (a) is a photo of the water contact angle after the PVB film is formed on the glass substrate, and (b) is a photo of the water contact angle after the modified PVB film is formed on the glass substrate. It can be found that the water contact angle of PVB on the glass substrate is 75±3°, while the water contact angle of the modified PVB on the glass substrate is 110±5°, and the water contact angle of the coating is significantly improved.

[0069] Adhesion: Film the modified PVBs in Examples 1 to 10 and the unmodified PVB in Comparative Example 1 on a PCB board respectively. According to the adhesion test requirements of GB / T 9286, use a cross-cut knife to apply uniform force perpendicular to the surface of the sample, and draw 11 parallel lines vertically and horizontally to form a grid. Apply tape on the grid to ensure complete contact with the paint film. Peel the tape at an angle of about 60° with the sample, and observe the peeling of the paint film in the grid. Grading: Grade 0: No peeling; Grade 1: Peeling <5%; Grade 2: Peeling <15%; Grade 3: Peeling <35%; Grade 4: Peeling <65%; Grade 5: Peeling >65%. Detection requirements: Grades 0 to 2 are qualified. The adhesion test results are shown in Table 1.

[0070] Water absorption rate: Film the PVBs before and after the modification in Example 1 on a copper sheet. According to the water absorption rate detection requirements of HG / T 3344-2012, soak the test piece in water at room temperature for 24 h, then take out the test piece, measure the mass change of the test piece, and calculate the water absorption rate of the glue film. It is found that the water absorption rate of PVB is 8.5±0.5%, and the water absorption rate of the modified PVB coating is 1±0.3%, which basically meets the water absorption rate requirements of the three-proof coating.

[0071] Film the modified PVBs in Examples 1 to 10 and the unmodified PVB in Comparative Example 1 on a PCB board respectively, and test the adhesion, water contact angle and water absorption rate of the coatings respectively according to the same test method as above. The test results are shown in Table 1.

[0072] Table 1

[0073] As can be seen from Table 1, the test results of the modified PVB of the present invention on the PCB board are grades 0 to 1, the water contact angle is greater than 100°, and the water absorption rate is less than 2.2%, meeting the performance requirements of the three-proof coating.

[0074] In summary, the present invention uses polyvinyl butyral (PVB) as the main body and is modified by a silicone polyurethane prepolymer capped with diisocyanate and a silicone polyurethane prepolymer capped with monoisocyanate. The coating formed by the silicone polyurethane-modified polyvinyl butyral has low water absorption, good water resistance, better impact resistance, good hydrophobicity, and good solubility in most strongly polar solvents. To a certain extent, it makes up for the problems of easy wear of silicone three-proof coatings and difficult repair of polyurethane coatings. At the same time, it combines the advantages of polyvinyl butyral coatings, silicone coatings, and polyurethane coatings, effectively broadening the application scope of polyvinyl butyral.

[0075] It should be noted that the above embodiments all belong to the same inventive concept. The descriptions of the embodiments have their own emphases. For the parts not described in detail in individual embodiments, reference can be made to the descriptions in other embodiments.

[0076] The above embodiments only represent the implementation modes of the present invention. The descriptions are relatively specific and detailed, but should not be construed as limiting the scope of the invention patent. It should be pointed out that for those of ordinary skill in the art, without departing from the inventive concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A modified polyvinyl butyral, characterized in that: The polyurethane prepolymer is obtained by polycondensation reaction of an organic silicon polyurethane prepolymer having isocyanate groups at both ends and an organic silicon polyurethane prepolymer having isocyanate groups at one end with the hydroxyl group on polyvinyl butyral.

2. The modified polyvinyl butyral according to claim 1, characterized in that The molar ratio of the organosilicon polyurethane prepolymer having isocyanate groups at both ends to the hydroxyl group in the polyvinyl butyral is (0.01-0.2):1, and the molar ratio of the organosilicon polyurethane prepolymer having isocyanate groups at one end to the hydroxyl group in the polyvinyl butyral is (0.8-0.99):

1.

3. A method for preparing the modified polyvinyl butyral according to any one of claims 1 to 2, characterized in that: The following steps are involved: The hydroxyl-terminated polydimethylsiloxane is subjected to a first addition reaction with diisocyanate to generate an organosilicon polyurethane prepolymer having isocyanate groups at both ends, thereby obtaining a first reaction product; The hydroxyl-terminated polydimethylsiloxane and diisocyanate are subjected to a second addition reaction to generate an organosilicon polyurethane prepolymer having an isocyanate group at one end, thereby obtaining a second reaction product; The polyvinyl butyral solution, the first reaction product, the second reaction product and a catalyst are mixed to carry out a third addition reaction to obtain silicone polyurethane modified polyvinyl butyral.

4. The method for preparing modified polyvinyl butyral according to claim 3, characterized in that: In the first addition reaction, the molar ratio of the hydroxyl-terminated polydimethylsiloxane to the diisocyanate is 1:(1-2).

5. The method for preparing modified polyvinyl butyral according to claim 3, characterized in that: The reaction temperature of the first addition reaction is 70-100° C., and the reaction time is 4-7 h.

6. The method for preparing modified polyvinyl butyral according to claim 3, characterized in that: The second addition reaction comprises: reacting hydroxyl-terminated polydimethylsiloxane and diisocyanate at 70-100° C. for 4-7 hours to obtain a mixture; then, adding anhydrous ethanol to the mixture and continuing the reaction for 1-3 hours to obtain the second reaction product.

7. The method for preparing modified polyvinyl butyral according to claim 6, characterized in that: The molar ratio of the hydroxyl-terminated polydimethylsiloxane to the diisocyanate is 1:(1.3-2); the molar ratio of the hydroxyl-terminated polydimethylsiloxane to the anhydrous ethanol is 1:(0.5-1).

8. The method for preparing modified polyvinyl butyral according to claim 3, characterized in that: The hydroxyl-terminated polydimethylsiloxane has a kinematic viscosity of 20-100 cst and a molecular weight of 300-2000 g / mol; the diisocyanate includes one or more of hexamethylene diisocyanate, isophorone diisocyanate, and diphenylmethane diisocyanate.

9. The method for preparing modified polyvinyl butyral according to claim 3, characterized in that: In the third addition reaction, the reaction temperature is 70-100°C and the reaction time is 3-5 h; The amount of the catalyst used is 0.05% to 1% of the total mass of the polyvinyl butyral, the first reaction product, and the second reaction product; the catalyst is an organic tin catalyst.

10. Use of the modified polyvinyl butyral according to any one of claims 1 to 2 in coatings.

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