Polyvinyl butyral resin as well as preparation method and application thereof

Abstract

The invention relates to polyvinyl butyral resin as well as a preparation method and application thereof. The polyvinyl butyral resin is prepared from the following raw materials: polyvinyl alcohol, n-butyraldehyde and a composite antioxidant; the composite antioxidant comprises an antioxidant A and an antioxidant B; the antioxidant A comprises a hindered phenol antioxidant; and the antioxidant B comprises a phosphite ester antioxidant. The compatibility of the phosphite ester antioxidant and the PVB resin is high. Therefore, the PVB resin can obtain good high-temperature yellowing resistance by using the low-content composite antioxidant.

Description

Technical Field

[0001] The invention belongs to the technical field of high molecular polymer synthesis, and in particular relates to a polyvinyl butyral resin and a preparation method and application thereof. Background Art

[0002] Polyvinyl butyral (PVB) is a new type of synthetic resin with excellent optical and mechanical properties and good bonding properties to a variety of materials. It is currently widely used in the automotive, construction, aerospace, and military fields. PVB research and industrialization in my country began in the 1960s, but development has been relatively slow, with product brands mainly consisting of low-end products. In recent years, with the rapid development of the photovoltaic industry, PVB resin has attracted much attention as the core material for photovoltaic films. Photovoltaic films need to be exposed to harsh environments such as high temperature, high humidity, and strong ultraviolet rays outdoors for a long time. Their performance directly determines the product's light transmittance, mechanical strength, and service life. At present, my country's high-end PVB resins that can be used for photovoltaic-grade films mainly rely on imports and lack mature preparation processes. Domestic products generally have problems such as severe yellowing at high temperatures.

[0003] Conventional PVB resin is difficult to use in photovoltaic-grade films primarily because it is prone to yellowing at high temperatures. Yellowing at high temperatures is primarily caused by thermal oxidative aging, residual butyraldehyde self-polymerization, and ultraviolet-induced photooxidation. Yellowing not only affects the material's appearance but also significantly reduces the film's light transmittance, further irreversibly impacting other properties. Therefore, PVB for film applications places extremely high demands on the resin's thermal stability and anti-yellowing properties.

[0004] The main reasons why PVB resin turns yellow at high temperatures include the lack of a suitable antioxidant system, high residual sodium content in the resin, and high butyraldehyde content. Existing technologies for improving PVB yellowing mainly include the following two categories: (1) using multiple water washing processes to fully remove butyraldehyde and sodium residues in the system, but this technology will inevitably bring about the problems of high energy consumption and wastewater treatment (CN107880158A, JP2006-47974A); (2) improving yellowing by adding antioxidants (CN111533832A, CN103865218A), but this technology often requires the addition of a large amount of antioxidants, which is not conducive to the further preparation of high-performance films (low-content antioxidants have limited effect on improving yellowing, while high-content antioxidants will lead to a decrease in the mechanical, optical and other properties of PVB films); (3) without adding additional additives, improving yellowing by controlling the precipitation time and particle size of the PVB resin in the preparation process (CN113880971A), but this technology only maintains good yellowing resistance at high temperatures for a short time and cannot guarantee its yellowing resistance under long-term use.

[0005] Therefore, developing a PVB resin with few impurities and high temperature yellowing resistance is of great significance for achieving the localization of photovoltaic PVB film. Summary of the Invention

[0006] To solve the above technical problems, the present invention provides a polyvinyl butyral resin and a preparation method and application thereof. The PVB resin is resistant to yellowing at high temperatures, and the preparation method of the PVB resin is simple, environmentally friendly, and easy to operate.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a polyvinyl butyral resin, wherein the raw materials for preparing the polyvinyl butyral resin include: polyvinyl alcohol, n-butyraldehyde and a composite antioxidant; the composite antioxidant includes antioxidant A and antioxidant B; the antioxidant A includes a hindered phenol antioxidant; and the antioxidant B includes a phosphite antioxidant.

[0009] In the present invention, a composite antioxidant is added to the raw materials for preparing the PVB resin. In the composite antioxidant, antioxidant B comprises a phosphite antioxidant. Phosphite antioxidants are highly compatible with PVB resin. Therefore, even with a low content of the composite antioxidant, the PVB resin can achieve excellent high-temperature yellowing resistance.

[0010] Preferably, the mass ratio of n-butyraldehyde to polyvinyl alcohol is (0.5-0.8):1, such as 0.55:1, 0.6:1, 0.65:1, 0.7:1 or 0.75:1, etc.

[0011] Preferably, the mass ratio of the composite antioxidant to polyvinyl alcohol is (0.001-0.006):1, for example, 0.0015:1, 0.002:1, 0.0025:1, 0.003:1, 0.0035:1, 0.004:1, 0.0045:1, 0.005:1 or 0.0055:1, etc.

[0012] Preferably, the mass ratio of the antioxidant A to the antioxidant B is (1-9):1, for example, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1 or 8:1.

[0013] In the present invention, if the amount of antioxidant B is too small, the anti-yellowing effect is not obvious; if the amount of antioxidant B is too large, it will affect the processing and film-making performance of subsequent products.

[0014] Preferably, the antioxidant A includes antioxidant 1076 and / or antioxidant 1010.

[0015] Preferably, the polyvinyl alcohol comprises any one or a combination of at least two of polyvinyl alcohol 1599, polyvinyl alcohol 1799, polyvinyl alcohol 2499, polyvinyl alcohol 1788 or polyvinyl alcohol 2488.

[0016] Preferably, the antioxidant B comprises any one or a combination of at least two of trisphosphite (TNPP) antioxidant, bisphenyl A phosphite (BAP) or poly(dipropylene glycol) phenyl phosphite (DHOP).

[0017] Preferably, the trisphosphite antioxidant comprises any one or a combination of at least two of tris(1,2,2,6,6-pentamethylpiperidyl) phosphite, tris(nonylphenyl) phosphite or tris(2,4-di-tert-butylphenyl) phosphite.

[0018] Preferably, the antioxidant B has a molecular weight of 500-2500 g / mol, such as 600 g / mol, 700 g / mol, 800 g / mol, 900 g / mol, 1000 g / mol, 1200 g / mol, 1400 g / mol, 1600 g / mol, 1800 g / mol, 2000 g / mol, 2100 g / mol, 2200 g / mol, 2300 g / mol or 2400 g / mol, etc.

[0019] In the present application, if the antioxidant B is a polymer, the molecular weight is the number average molecular weight.

[0020] In the present application, by selecting an antioxidant B with a suitable structure and a relatively large molecular weight, the higher molecular weight can further improve the compatibility of the PVB resin with the composite antioxidant, and further improve the high-temperature yellowing resistance. If the molecular weight is too small, the high-temperature yellowing resistance decreases.

[0021] In a second aspect, the present application provides a method for preparing the polyvinyl butyral resin according to the first aspect, the method comprising the following steps:

[0022] mixing the polyvinyl alcohol aqueous solution, the composite antioxidant and n-butyl aldehyde to perform acetalization to obtain the polyvinyl butyral resin.

[0023] Preferably, before the mixing, the polyvinyl alcohol aqueous solution is subjected to vacuumization under reduced pressure and pressurized hot filtration treatment.

[0024] Preferably, the polyvinyl alcohol aqueous solution has a mass concentration of 8-12%, such as 8.5%, 9%, 9.5%, 10%, 10.5%, 11% or 11.5%, etc.

[0025] In the present invention, pretreatment of the polyvinyl alcohol aqueous solution by vacuuming and hot-filtering under reduced pressure can reduce the sodium and aldehyde contents in the PVB resin and improve its high-temperature yellowing resistance. The specific principle is that the pretreatment removes low-boiling-point, low-molecular-weight impurities through vacuuming, thereby reducing the ash content of the raw polyvinyl alcohol. This reduction in raw material ash further reduces the high-temperature yellowing index of the resulting PVB, thereby improving its high-temperature yellowing resistance.

[0026] Preferably, the method for preparing the polyvinyl alcohol aqueous solution comprises the following steps:

[0027] The polyvinyl alcohol is dissolved in deionized water at 85-95° C., and subjected to reduced pressure, vacuuming, and pressurized hot filtration. The filtered filtrate is diluted to a mass concentration of 8-12% to obtain the polyvinyl alcohol aqueous solution.

[0028] The 85-95°C, for example, 87°C, 89°C, 90°C, 92°C or 94°C.

[0029] Preferably, the acetalization step comprises:

[0030] The composite antioxidant is dissolved in n-butyraldehyde to obtain a mixed solution A, the polyvinyl alcohol solution is mixed with the mixed solution A to obtain a mixed solution B, an acidic substance is added, and the mixture is heated to 40-60° C. and kept warm for 6-8 hours.

[0031] The temperature is raised to 40-60°C, such as 42°C, 45°C, 47°C, 50°C, 53°C, 55°C or 58°C.

[0032] The heat preservation is 6-8 hours, such as 6.2 hours, 6.5 hours, 7 hours, 7.2 hours or 7.5 hours, etc.

[0033] Preferably, the acidic substance includes any one of hydrochloric acid, sulfuric acid or acetic acid, or a combination of at least two of them.

[0034] Preferably, the heating rate is 5-15°C / 50min, for example, 6°C / 50min, 7°C / 50min, 8°C / 50min, 9°C / 50min, 10°C / 50min, 11°C / 50min, 12°C / 50min, 13°C / 50min or 14°C / 50min, etc.

[0035] Preferably, when the polyvinyl alcohol aqueous solution is mixed with the mixed solution A, the temperature of the polyvinyl alcohol aqueous solution is below 65°C, for example, 50°C, 52°C, 55°C, 58°C, 60°C or 63°C.

[0036] Preferably, when the acidic substance is added, the temperature of the mixed solution B is 5-20°C, such as 7°C, 10°C, 12°C, 15°C or 18°C.

[0037] Preferably, the acetalization reaction further includes a water washing post-treatment step.

[0038] Preferably, the water washing post-treatment is performed with the assistance of ultrasound.

[0039] In the present invention, the high-temperature yellowing resistance of PVB resin is improved by ultrasound assistance. The specific principle is: the ultrasonic cavitation effect is used to improve the cleaning efficiency of sodium, and the thermal effect of ultrasound is used to promote the dissolution of sodium and aldehyde attached to the sample surface in water, thereby improving the washing efficiency.

[0040] Preferably, the water washing times are 3-6 times, for example 4 times or 5 times.

[0041] Preferably, the washing is performed using deionized water.

[0042] Preferably, the mass ratio of deionized water to polyvinyl alcohol in a single water washing is (4-6):1, such as 4.2:1, 4.5:1, 5:1, 5.5:1 or 5.7:1.

[0043] Preferably, the frequency of the ultrasound is 20-40 kHz, such as 22 kHz, 25 kHz, 30 kHz, 32 kHz or 35 kHz.

[0044] In the present invention, the frequency of ultrasound must be controlled within a specific range. If the ultrasound frequency is too low, the ultrasonic energy is high, and the bubbles generated are larger and fewer in number. This can also cause a significant thermal effect, increase sample viscosity, and thus hinder the cleaning effect. Conversely, high-frequency ultrasound has relatively low energy and can generate smaller and more numerous bubbles, which can improve the cleaning effect.

[0045] Preferably, the single ultrasound time is 10-30 min, for example, 12 min, 15 min, 18 min, 20 min, 22 min, 25 min or 28 min.

[0046] Preferably, the temperature of the ultrasound is 30-50°C, such as 32°C, 35°C, 40°C, 43°C or 45°C.

[0047] In the present invention, the temperature of the ultrasound needs to be controlled within a specific range. If the ultrasound temperature is too low, it is not conducive to the washing of sodium; if the ultrasound temperature is too high, the viscosity of the sample will increase, thereby reducing the cleaning effect.

[0048] In a third aspect, the present invention provides a use of the polyvinyl butyral resin described in the first aspect in a photovoltaic-grade adhesive film.

[0049] Compared with the prior art, the present invention has at least the following beneficial effects:

[0050] The water consumption of the water washing process of the present application is 25 times less than that of the conventional PVB resin preparation process; the sodium content and butyl aldehyde residue of the obtained PVB resin are less; and the yellowing index of the PVB after high-temperature baking at 180°C for 4h is less than 20 at a lower amount of composite antioxidant. DETAILED DESCRIPTION

[0051] For the purpose of facilitating the understanding of the present application, the present application is illustrated by the following examples. It should be apparent to those skilled in the art that the examples are only for the purpose of facilitating the understanding of the present application and should not be regarded as specific limitations of the present application.

[0052] Some of the preparation raw materials used in the following examples and comparative examples of the present application are listed as follows.

[0053] PVA1799 was purchased from Anhui Wanwei Group Co., Ltd.;

[0054] DHOP was purchased from Nanjing Milan Chemical Co., Ltd.

[0055] Example 1

[0056] The present example provides a polyvinyl butyral resin and a preparation method thereof.

[0057] The preparation method comprises the following steps:

[0058] PVA1799 (350g) and 3.5L of deionized water were added to a 5L three-necked flask, heated to 90°C, and dissolved to form a uniform PVA aqueous solution, which was clear and transparent.

[0059] Subsequently, a pre-refining process was carried out, the PVA aqueous solution was reduced in pressure to less than 1Pa, and then air was extracted for 30min to remove organic volatile components, and then pressure filtration was carried out, and then deionized water was added to dilute the mass concentration of the PVA aqueous solution to 10%.

[0060] Subsequently, it was cooled to 50°C, and about 287mL (230g) of n-butyl aldehyde (the composite antioxidant in the n-butyl aldehyde was antioxidant 1076 and DHOP, and the mass ratio of antioxidant 1076 and DHOP was 1:1; the mass ratio of the total amount of antioxidant to PVA was 0.003:1) was added by using a constant pressure dropping funnel. An ice water bath was used to reduce the temperature to 12°C, and the whole process was kept at a uniform speed of stirring, and 100mL of 5M hydrochloric acid was added at a speed of 13mL / min, and then the temperature was increased from 12°C to 50°C in stages, and the temperature gradient was 10°C per 50min. The reaction was continued at 50°C for 6h. After the reaction was completed, the temperature was reduced to 40°C and then filtered.

[0061] The filtered solid was placed in a beaker and deionized water (2 L) was quickly added, a 15% mass content NaOH solution was used to adjust the pH to 11, after stirring for 30 min the solution was filtered, the filtered solid was crushed and deionized water was added for additional washing under ultrasonic for 3 times (2 L deionized water each time, the frequency of ultrasonic was 40 kHz, the temperature of ultrasonic was 50 °C). Finally the solid was collected and dried in an oven at 50 °C for use, obtaining the polyvinyl butyral resin.

[0062] Example 2

[0063] The present example provides a polyvinyl butyral resin and a preparation method thereof.

[0064] The preparation method comprises the following steps:

[0065] PVA1799 (350 g) and 3.5 L deionized water were added to a 5 L three-necked flask, heated to 85 °C, and dissolved to form a uniform PVA aqueous solution, which was clear and transparent.

[0066] Subsequently, a pre-refining process was carried out, the PVA aqueous solution was reduced in pressure to less than 1 Pa, and then pumped for 30 min to concentrate the solution, then pressurized and hot filtered, and then deionized water was added to dilute the mass concentration of the PVA aqueous solution to 8%.

[0067] Then it was cooled to 50 °C, and about 350 mL (280 g) of n-butyraldehyde (the complex antioxidant in n-butyraldehyde was antioxidant 1010 and BAP, and the mass ratio of antioxidant 1010 and BAP was 9:1; the mass ratio of the total amount of antioxidant to PVA was 0.006:1) was added with a constant pressure dropping funnel. The temperature was reduced to 12 °C with an ice water bath, and the whole process was kept at a uniform speed stirring, 100 mL of 5M hydrochloric acid was added at a speed of 13 mL / min, and then the temperature was gradually increased from 12 °C to 50 °C, with a gradient of 5 °C per 50 min. The reaction was continued at 50 °C for 8 h. After the reaction was completed, the temperature was lowered to 40 °C and filtered.

[0068] The filtered solid was placed in a beaker and deionized water (2 L) was quickly added, a 15% mass content NaOH solution was used to adjust the pH to 11, after stirring for 30 min the solution was filtered, the filtered solid was crushed and deionized water was added for additional washing under ultrasonic for 3 times (2 L deionized water each time, the frequency of ultrasonic was 40 kHz, the temperature of ultrasonic was 50 °C). Finally the solid was collected and dried in an oven at 50 °C for use, obtaining the polyvinyl butyral resin.

[0069] Example 3

[0070] The present example provides a polyvinyl butyral resin and a preparation method thereof.

[0071] The preparation method comprises the following steps:

[0072] PVA1799 (350 g) and 3.5 L of deionized water were added to a 5 L three-necked flask and heated to 95° C. to dissolve the PVA to form a uniform PVA aqueous solution. The solution was clear and transparent.

[0073] Then, a pre-refining process was carried out, in which the PVA aqueous solution was decompressed to a pressure below 1 Pa and then evacuated for 30 minutes to concentrate the solution. The solution was then pressurized and hot filtered, and deionized water was added to dilute the PVA aqueous solution to a mass concentration of 12%.

[0074] The mixture was then cooled to 50°C and approximately 219 mL (175 g) of n-butyraldehyde (the composite antioxidant in n-butyraldehyde was antioxidant 1010 and tris(2,4-di-tert-butylphenyl)phosphite, with a mass ratio of 5:1 between antioxidant 1010 and tris(2,4-di-tert-butylphenyl)phosphite; the mass ratio of the total antioxidant to PVA was 0.001:1) was added using a constant pressure dropping funnel. The temperature was lowered to 12°C using an ice-water bath. While stirring was maintained throughout, 100 mL of 5M hydrochloric acid was added dropwise at a rate of 13 mL / min. The temperature was then increased in stages from 12°C to 50°C, with a temperature increase of 15°C every 50 minutes. The reaction was continued at 50°C for 7 hours. After the reaction was completed, the mixture was cooled to 40°C and filtered.

[0075] The filtered solid was placed in a beaker and quickly added with 2 L of deionized water. The pH was adjusted to 11 using a 15% by mass NaOH solution. After stirring for 30 minutes, the solution was filtered. The filtered solid was crushed and washed three additional times with deionized water (2 L of deionized water each time, at an ultrasonic frequency of 30 kHz and a temperature of 40° C.). Finally, the solid was collected and dried in an oven at 50° C. for later use, thereby obtaining the polyvinyl butyral resin.

[0076] Example 4

[0077] This embodiment provides a polyvinyl butyral resin and a preparation method thereof. The only difference from Example 1 is that the composite antioxidant is antioxidant 1076 and tris(2,4-di-tert-butylphenyl) phosphite.

[0078] Example 5

[0079] This embodiment provides a polyvinyl butyral resin and a preparation method thereof. The only difference from Example 1 is that the composite antioxidant is antioxidant 1076 and BAP.

[0080] Example 6

[0081] This embodiment provides a polyvinyl butyral resin and a preparation method thereof. The only difference from Example 1 is that the mass ratio of antioxidant 1076 to DHOP is 5:1.

[0082] Example 7

[0083] This embodiment provides a polyvinyl butyral resin and a preparation method thereof. The only difference from Example 1 is that the mass ratio of antioxidant 1076 to DHOP is 9:1.

[0084] Example 8

[0085] This embodiment provides a polyvinyl butyral resin and a preparation method thereof. The only difference from Example 1 is that the mass ratio of antioxidant 1076 to DHOP is 10:1.

[0086] Example 9

[0087] This embodiment provides a polyvinyl butyral resin and a preparation method thereof. The only difference from Example 1 is that the mass ratio of antioxidant 1076 to DHOP is 1:2.

[0088] Example 10

[0089] This embodiment provides a polyvinyl butyral resin and a preparation method thereof, which is different from Example 6 only in that no pre-refining process is performed.

[0090] The preparation method specifically comprises the following steps:

[0091] PVA1799 (350 g) and 3.5 L of deionized water were added to a 5 L three-necked flask and heated to 90° C. to dissolve the PVA to form a uniform PVA aqueous solution. The solution was clear and transparent.

[0092] The mixture was then cooled to 50°C without any pre-refining process. Approximately 287 mL (230 g) of n-butyraldehyde (the composite antioxidant in n-butyraldehyde consists of antioxidant 1076 and DHOP, with a mass ratio of 5:1; the mass ratio of the total antioxidant to PVA is 0.003:1) was added using a constant pressure dropping funnel. The temperature was lowered to 12°C using an ice-water bath. While stirring constantly, 100 mL of 5M hydrochloric acid was added dropwise at a rate of 13 mL / min. The temperature was then increased in stages from 12°C to 50°C, with a temperature increase of 10°C every 50 minutes. The reaction was continued at 50°C for 6 hours. After the reaction was completed, the temperature was lowered to 40°C and filtered.

[0093] The filtered solid was placed in a beaker and quickly added with 2 L of deionized water. The pH was adjusted to 11 using a 15% by mass NaOH solution. After stirring for 30 minutes, the solution was filtered. The filtered solid was crushed and washed three additional times with deionized water (2 L of deionized water each time, at an ultrasonic frequency of 40 kHz and a temperature of 50° C.). Finally, the solid was collected and dried in an oven at 50° C. for later use, thereby obtaining the polyvinyl butyral resin.

[0094] Example 11

[0095] This embodiment provides a polyvinyl butyral resin and a preparation method thereof, which differs from Example 6 only in that ultrasonic treatment is not performed during the deionized water washing process.

[0096] The preparation method specifically comprises the following steps:

[0097] PVA1799 (350 g) and 3.5 L of deionized water were added to a 5 L three-necked flask and heated to 90° C. to dissolve the PVA to form a uniform PVA aqueous solution. The solution was clear and transparent.

[0098] Then, a pre-refining process is carried out, in which the PVA aqueous solution is decompressed to a pressure below 1 Pa and then evacuated for 30 minutes to remove organic volatiles, followed by pressurized hot filtration, and deionized water is added to dilute the PVA aqueous solution to a mass concentration of 10%.

[0099] The mixture was then cooled to 50°C and approximately 287 mL (230 g) of n-butyraldehyde (the composite antioxidant in n-butyraldehyde was antioxidant 1076 and DHOP, with a mass ratio of 5:1 between antioxidant 1076 and DHOP; the mass ratio of the total antioxidant to PVA was 0.003:1) was added using a constant pressure dropping funnel. The temperature was lowered to 12°C using an ice-water bath. While stirring constantly, 100 mL of 5M hydrochloric acid was added dropwise at a rate of 13 mL / min. The temperature was then increased in stages from 12°C to 50°C, with a temperature increase of 10°C every 50 minutes. The reaction was continued at 50°C for 6 hours. After the reaction was completed, the mixture was cooled to 40°C and filtered.

[0100] The filtered solid was placed in a beaker and quickly added with 2 L of deionized water. The pH was adjusted to 11 using a 15% by mass NaOH solution. After stirring for 30 minutes, the solution was filtered. The filtered solid was crushed and washed three additional times with 2 L of deionized water each time at 50°C. Finally, the solid was collected and dried in an oven at 50°C until ready for use, thereby obtaining the polyvinyl butyral resin.

[0101] Example 12

[0102] This embodiment provides a polyvinyl butyral resin and a preparation method thereof, which is different from Example 6 only in that the frequency of ultrasound is 20 kHz.

[0103] Example 13

[0104] This embodiment provides a polyvinyl butyral resin and a preparation method thereof, which is different from Example 6 only in that the ultrasonic temperature is 30°C.

[0105] Example 14

[0106] This embodiment provides a polyvinyl butyral resin and a preparation method thereof. The only difference from Example 6 is that the composite antioxidant is antioxidant 1010 and DHOP.

[0107] Example 15

[0108] This embodiment provides a polyvinyl butyral resin and a preparation method thereof, which differs from Example 6 only in that the mass ratio of the composite antioxidant to PVA is 0.001:1.

[0109] Example 16

[0110] This embodiment provides a polyvinyl butyral resin and a preparation method thereof, which differs from Example 6 only in that the mass ratio of the composite antioxidant to PVA is 0.009:1.

[0111] Comparative Example 1

[0112] This comparative example provides a polyvinyl butyral resin and a preparation method thereof. The difference from Example 1 is that no pre-refining process is performed, the n-butyraldehyde does not contain any antioxidant, ultrasonic treatment is not performed during the deionized water washing process, and the number of deionized water washings is 5 times.

[0113] Comparative Example 2

[0114] This comparative example provides a polyvinyl butyral resin and a preparation method thereof. The difference from Example 1 is that n-butyraldehyde contains only antioxidant 1076, the mass ratio of antioxidant 1076 to PVA is 0.006:1, and ultrasonic treatment is not performed during the deionized water washing process.

[0115] Comparative Example 3

[0116] This comparative example provides a polyvinyl butyral resin and a preparation method thereof. The difference from Example 1 is that n-butyraldehyde contains only antioxidant 1076, the mass ratio of antioxidant 1076 to PVA is 0.006:1, and the number of deionized water washings is 5 times.

[0117] Comparative Example 4

[0118] This comparative example provides a polyvinyl butyral resin and a preparation method thereof. The difference from Example 1 is that n-butyraldehyde contains only antioxidant 1076, and the mass ratio of antioxidant 1076 to PVA is 0.006:1.

[0119] Comparative Example 5

[0120] This comparative example provides a polyvinyl butyral resin and a preparation method thereof. The only difference from Example 1 is that n-butyraldehyde contains only antioxidant 1076, and the mass ratio of antioxidant 1076 to PVA is 0.003:1.

[0121] Comparative Example 6

[0122] This comparative example provides a polyvinyl butyral resin and a preparation method thereof. The difference from Example 1 is that n-butyraldehyde contains only antioxidant 1076, and the mass ratio of antioxidant 1076 to PVA is 0.001:1.

[0123] Comparative Example 7

[0124] This comparative example provides a polyvinyl butyral resin and a preparation method thereof. The only difference from Example 1 is that the composite antioxidant is antioxidant 1076 and dodecyl mercaptan, and the mass ratio of the composite antioxidant to PVA is 0.003:1.

[0125] Comparative Example 8

[0126] This comparative example provides a polyvinyl butyral resin and a preparation method thereof. The only difference from Example 1 is that n-butyraldehyde contains only DHOP, and the mass ratio of DHOP to PVA is 0.003:1.

[0127] Test Method

[0128] Sodium content detection: The sodium content of the prepared polyvinyl butyral resin was detected using an inductively coupled plasma optical emission spectrometer (ICP-OES). The specific steps are as follows: weigh approximately 10 mg of PVB sample, add 1 mL of sulfuric acid, heat, and allow to react fully (the color turns black or reddish-brown), then add 3-4 mL of concentrated nitric acid and react until the solution turns light yellow (if the color turns reddish-brown again, add more nitric acid), and dilute to 25 mL with deionized water for ICP-OES testing.

[0129] Butyraldehyde content detection: The butyraldehyde content in polyvinyl butyral resin was detected by gas chromatography-mass spectrometry (GC-MS). -6 The butyraldehyde content in the PVB sample can be inferred by comparing the peak time and integrated area.

[0130] Standard butyraldehyde sample preparation: Butyraldehyde was diluted to a specific volume of DMSO and its concentration was diluted to 2×10 - 6 g / ml, this concentration is close to the target value and is easy to compare.

[0131] Preparation of the sample to be tested: 100 mg of PVB was dissolved in 1 mL of DMSO. The low-boiling-point substances in the sample (such as butyraldehyde) were converted into gas by heating and evaporation. The obtained gaseous sample entered the gas chromatography column. The peak time, molecular weight and peak area of ​​butyraldehyde were detected by GC-MS. The butyraldehyde content of the sample to be tested can be obtained by the following formula using the external standard one-point method:

[0132] That is (the butyraldehyde content of the sample to be tested is proportional to the butyraldehyde peak area of ​​the sample to be tested):

[0133]

[0134] (C(butyraldehyde content of standard sample)) / (C(butyraldehyde content of test sample)) = butyraldehyde peak area of ​​standard sample / butyraldehyde peak area of ​​test sample. The peak area corresponding to the standard sample is the peak area when the butyraldehyde content is 20 ppm.

[0135] Yellowing index: After baking the polyvinyl butyral prepared at 180°C for 4 hours, the PVB sample was melted and pressed into sheets, and the yellowing index was tested using a yellow index meter.

[0136] Test results

[0137] The test results of the embodiments of the present invention and the comparative examples are shown in Table 1.

[0138] Table 1

[0139]

[0140]

[0141] The test results show that:

[0142] (1) It can be seen from Examples 1 to 16 that the present invention can achieve good high-temperature yellowing resistance of PVB resin by adding a composite antioxidant comprising a hindered phenol antioxidant and a phosphite antioxidant to the raw materials for preparing polyvinyl butyral resin. The use of a low content of the composite antioxidant can achieve good high-temperature yellowing resistance of the PVB resin. After baking at 180°C for 4 hours, the yellowing index is less than 20.

[0143] (2) By comparing Example 1 with Examples 4-5, it can be seen that the yellowing index of the present invention is reduced to 7.3 by further selecting antioxidant B (DHOP) with a suitable structure and a relatively large molecular weight.

[0144] (3) By comparing Example 1 with Examples 6-9, it can be seen that the yellowing index of the present invention is reduced to 5.2 by further adjusting the mass ratio of antioxidant A to antioxidant B to 5:1.

[0145] (4) By comparing Example 6 and Example 11, it can be seen that in the present invention, if ultrasonic treatment is not performed during the deionized water washing process, the sodium content and butyraldehyde content increase significantly, and the yellowing index increases to 15.5.

[0146] (5) By comparing Example 6 with Examples 12-13, it can be seen that in the present invention, by controlling the frequency and temperature of ultrasonic treatment, the sodium content and butyraldehyde content are further reduced, and the high temperature yellowing resistance is improved.

[0147] (6) It can be seen from Example 1 and Comparative Examples 5, 7-8 that when the composite antioxidant containing hindered phenol antioxidants and phosphite antioxidants is not used, the PVB resin cannot simultaneously have good high-temperature yellowing resistance and a low composite antioxidant dosage.

[0148] In summary, the present invention adds a composite antioxidant comprising a hindered phenol antioxidant and a phosphite antioxidant to the raw materials for preparing polyvinyl butyral resin, and uses a low content of the composite antioxidant to enable the PVB resin to obtain good high-temperature yellowing resistance.

[0149] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A polyvinyl butyral resin, characterized in that The raw materials for preparing the polyvinyl butyral resin include: polyvinyl alcohol, n-butyraldehyde and a composite antioxidant; The composite antioxidant comprises antioxidant A and antioxidant B; The antioxidant A includes a hindered phenol antioxidant; The antioxidant B includes a phosphite antioxidant.

2. The polyvinyl butyral resin according to claim 1, characterized in that The mass ratio of n-butyraldehyde to polyvinyl alcohol is (0.5-0.8):1; Preferably, the mass ratio of the composite antioxidant to polyvinyl alcohol is (0.001-0.006):1; Preferably, the mass ratio of the antioxidant A to the antioxidant B is (9-1):

1.

3. The polyvinyl butyral resin according to claim 1 or 2, characterized in that The antioxidant A includes antioxidant 1076 and / or antioxidant 1010; Preferably, the polyvinyl alcohol includes any one of polyvinyl alcohol 1599, polyvinyl alcohol 1799, polyvinyl alcohol 2499, polyvinyl alcohol 1788 or polyvinyl alcohol 2488, or a combination of at least two thereof.

4. The polyvinyl butyral resin according to any one of claims 1 to 3, characterized in that The antioxidant B includes any one or a combination of at least two of triphosphite antioxidants, bisphenol A phosphite or poly (dipropylene glycol) phenyl phosphite; Preferably, the triphosphite antioxidant includes any one or a combination of at least two of tris(1,2,2,6,6-pentamethylpiperidinyl)phosphite, tris(nonylphenyl)phosphite or tris(2,4-di-tert-butylphenyl)phosphite; Preferably, the molecular weight of the antioxidant B is 500-2500 g / mol.

5. A method for preparing a polyvinyl butyral resin according to any one of claims 1 to 4, characterized in that: The preparation method comprises the following steps: The polyvinyl alcohol aqueous solution, the composite antioxidant and n-butyraldehyde are mixed to carry out acetalization reaction to obtain the polyvinyl butyral resin.

6. The method for preparing polyvinyl butyral resin according to claim 5, wherein: Before the mixing, the polyvinyl alcohol aqueous solution is subjected to reduced pressure vacuuming and pressurized hot filtration treatment; Preferably, the mass concentration of the polyvinyl alcohol aqueous solution is 8-12%.

7. The method for preparing a polyvinyl butyral resin according to any one of claims 5 or 6, wherein: The preparation method of the polyvinyl alcohol aqueous solution comprises the following steps: The polyvinyl alcohol is dissolved in deionized water at 85-95° C., and subjected to reduced pressure, vacuuming, and pressurized hot filtration. The filtered filtrate is diluted to a mass concentration of 8-12% to obtain the polyvinyl alcohol aqueous solution.

8. The method for preparing a polyvinyl butyral resin according to any one of claims 5 to 7, wherein: The steps of the acetalization reaction include: Dissolve the composite antioxidant in n-butyraldehyde to obtain a mixed solution A, mix the polyvinyl alcohol solution with the mixed solution A to obtain a mixed solution B, add an acidic substance, and heat to 40-60°C and keep warm for 6-8 hours; Preferably, the acidic substance includes any one of hydrochloric acid, sulfuric acid or acetic acid, or a combination of at least two thereof; Preferably, the heating rate is 5-15°C / 50min; Preferably, when the polyvinyl alcohol aqueous solution is mixed with the mixed solution A, the temperature of the polyvinyl alcohol aqueous solution is below 65°C; Preferably, when the acidic substance is added, the temperature of the mixed solution B is 5-20°C.

9. The method for preparing a polyvinyl butyral resin according to any one of claims 5 to 8, wherein: The acetalization reaction further includes a water washing post-treatment step; Preferably, the water washing post-treatment is performed with the assistance of ultrasound; Preferably, the number of water washings is 3-6 times; Preferably, the washing is performed with deionized water; Preferably, the mass ratio of deionized water to polyvinyl alcohol in the single water washing is (4-6):1; Preferably, the frequency of the ultrasound is 20-40 kHz; Preferably, the single ultrasound time is 10-30 minutes; Preferably, the temperature of the ultrasound is 30-50°C.

10. Use of the polyvinyl butyral resin according to any one of claims 1 to 4 in a photovoltaic-grade adhesive film.

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