A modified PVB resin, its preparation method and use

Abstract

This invention relates to the field of polymer materials technology, and in particular to a modified PVB resin, its preparation method, and its applications. The method includes the following steps: mixing an aqueous solution of polyvinyl alcohol, an acidic catalyst, and n-butyraldehyde to undergo a partial acetalization reaction to obtain an intermediate; mixing the intermediate, an organic solvent, an alkaline catalyst, and an aromatic halogenated etherifying agent to undergo an etherification reaction to obtain the modified PVB resin; the molar amount of the aromatic halogenated etherifying agent added is 1-5% of the molar amount of hydroxyl groups in the intermediate. This invention, through a two-step reaction process of "partial acetalization followed by controlled etherification," and controlling the hydroxyl content of the intermediate to 25-30% and the molar amount of the etherifying agent added to 1-5% of the molar amount of hydroxyl groups in the intermediate, prepares a modified PVB resin. This resin exhibits good processing fluidity, and films made from it possess low haze, high light transmittance, good mechanical properties, and heat resistance, making it suitable for applications such as interlayer films in laminated glass.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to a modified PVB resin, its preparation method, and its applications. Background Technology

[0002] Polyvinyl butyral (PVB) resin is widely used as an interlayer, coating, and adhesive for safety glass due to its excellent transparency, toughness, adhesion, and weather resistance. Currently, PVB resin is typically produced from polyvinyl alcohol (PVA) and n-butyral through a one-step acetalization reaction under an acidic catalyst (e.g., patents CN107936149B and US5384346A). While this method is simple, it has inherent drawbacks in practical applications. Because PVA molecules retain a large number of highly reactive hydroxyl groups, these hydroxyl groups readily undergo intermolecular or intramolecular thermal crosslinking reactions during subsequent melt processing (such as extrusion and calendering). This crosslinking leads to an abnormally high melt viscosity and deteriorated processing fluidity. PVB films produced in this way commonly exhibit appearance defects such as "crystal points" or "fisheyes," accompanied by significantly reduced transparency and uneven mechanical properties, hindering their application in high-end safety glass and other fields.

[0003] To overcome the aforementioned problems, various improvement schemes have been explored in this field. For example, patent CN110903585B employs a physical blending method, adding fillers such as graphene to the PVB matrix to improve heat resistance or barrier properties. However, this type of physical modification method does not eliminate the cross-linking active source of hydroxyl groups from the chemical structure, thus failing to fundamentally solve the problems of poor processing flowability and low transparency, and may even introduce new defects due to poor compatibility between the filler and the matrix. Another approach involves chemical modification of PVA or PVB, such as co-acetalization or directly introducing etherification groups. However, these chemical modification methods typically face challenges such as difficulty in controlling the reaction process, uncontrollable product molecular structure, numerous side reactions, and difficulty in achieving a balance between different properties, resulting in poor batch-to-batch stability of product performance and hindering industrial application.

[0004] Therefore, how to effectively suppress thermal crosslinking during processing while maintaining the excellent properties of PVB resin itself, and synergistically improve the resin's processing fluidity, product transparency, and mechanical properties, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to address the problems existing in the prior art by providing a modified PVB resin, its preparation method, and its application. By first performing a partial acetalization reaction to control the hydroxyl content of polyvinyl alcohol within a specific range, and then performing low-degree aromatic etherification to end-cap the residual hydroxyl groups, the hydroxyl crosslinking in subsequent processing is effectively inhibited, thereby improving the resin's processing fluidity, optical transparency, mechanical properties, and heat resistance.

[0006] To achieve the above objectives, the present invention provides a method for preparing modified PVB resin, comprising the following steps: S1. Mix polyvinyl alcohol aqueous solution, acidic catalyst and n-butyraldehyde, and carry out partial acetalization reaction to obtain intermediate; S2. Mix the intermediate, organic solvent, alkaline catalyst and aromatic halogenated etherifying agent, and carry out etherification reaction to obtain modified PVB resin; the molar amount of aromatic halogenated etherifying agent added is 1-5% of the molar amount of hydroxyl groups in the intermediate.

[0007] In an optional embodiment, in S1, the degree of polymerization of the polyvinyl alcohol is 500-3000 and the degree of alcoholysis is 98-99.9 mol%; the polyvinyl alcohol is dispersed in deionized water and stirred and dissolved at 90-95°C to obtain a polyvinyl alcohol aqueous solution, the mass concentration of the polyvinyl alcohol aqueous solution being 8-15%.

[0008] In an optional embodiment, during S1, the polyvinyl alcohol aqueous solution is cooled to 10-20°C before adding the acidic catalyst and n-butyraldehyde.

[0009] In an optional embodiment, in S1, the acidic catalyst is selected from at least one of hydrochloric acid solution, sulfuric acid, and p-toluenesulfonic acid; the amount of the acidic catalyst is 2-5% of the mass of polyvinyl alcohol.

[0010] In an optional embodiment, in S1, the hydroxyl content of the intermediate is 25-30% by controlling the amount of n-butyraldehyde added.

[0011] In an optional embodiment, in S1, the partial acetalization reaction is carried out at a temperature of 10-20°C, a stirring rate of ≥500 r / min, and a time of 2-4 h. After the partial acetalization reaction is completed, the intermediate is obtained by neutralization, precipitation, washing, and drying.

[0012] In an optional embodiment, in S2, the organic solvent is selected from at least one of dimethyl sulfoxide, N,N-dimethylformamide, and ethanol; the alkaline catalyst is selected from at least one of sodium hydroxide, potassium hydroxide, and sodium methoxide; and the aromatic halogenated etherifying agent is a halomethylbenzene derivative, preferably selected from at least one of chloromethylbenzene and bromomethylbenzene.

[0013] In an optional embodiment, in S2, the molar amount of the aromatic halogenated etherifying agent added is 1-5% of the molar amount of hydroxyl groups in the intermediate, and the dropping rate of the aromatic halogenated etherifying agent is 0.5-1.0 mL / min; the molar ratio of the alkaline catalyst to the aromatic halogenated etherifying agent is (1.0-1.2):1.

[0014] In an optional embodiment, in S2, the etherification reaction is carried out under an inert atmosphere at a temperature of 40-60°C. During the reaction, samples are taken every 2 hours, and the reaction progress is monitored using a Fourier transform infrared spectroscopy (FTIR). The samples are prepared using the KBr pellet method, and the scanning range is 4000-400 cm⁻¹. -1 The resolution is 4cm. -1 By monitoring 3300-3400cm -1 The degree of etherification reaction is determined by the relative decreasing trend of the intensity of the stretching vibration peak of the hydroxyl group (-OH). When the intensity of this characteristic peak does not change significantly between two consecutive samples, the reaction is considered to have reached its endpoint. After the etherification reaction is completed, the modified PVB resin is obtained by precipitation, washing, and drying.

[0015] The present invention also provides a modified PVB resin, prepared according to the preparation method described above.

[0016] The present invention also provides the application of the modified PVB resin in the preparation of interlayer films for laminated glass.

[0017] The present invention also provides a PVB film, which is prepared by mixing modified PVB resin and plasticizer in a weight ratio of (50-70):(30-50), followed by melt extrusion and calendering. The plasticizer is selected from at least one of triethylene glycol di-2-ethylhexanoate and dioctyl adipate.

[0018] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention adopts a two-step reaction process of “partial acetalization first and then controlled etherification”. First, polyvinyl alcohol and n-butyraldehyde are partially acetalized to control the hydroxyl content of the intermediate in the range of 25-30%. Then, the residual hydroxyl groups are end-capped by low-degree etherification using an aromatic halogenated etherifying agent (the molar amount of the etherifying agent added is 1-5% of the molar amount of hydroxyl groups in the intermediate). This inhibits the occurrence of hydroxyl crosslinking in the subsequent melt processing from the molecular structure and improves the processing fluidity of the resin.

[0019] (2) The modified PVB resin prepared by the present invention has improved glass transition temperature, melt flow rate, haze, transmittance, tensile strength and elongation at break of the film made therefrom, and achieves synergistic improvement of processing fluidity, optical transparency, mechanical properties and heat resistance.

[0020] (3) The preparation method of the present invention has mild process conditions, easy-to-control reaction process, independent operation of each step, few side reactions, controllable molecular structure, good product performance repeatability, and is suitable for industrial production. Detailed Implementation

[0021] The following embodiments are provided to better understand the present invention and are not limited to the described embodiments. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0022] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0023] In the following examples and comparative examples of the present invention, the polyvinyl alcohol is PVA-1799, the degree of polymerization is 1700, and the degree of alcoholysis is 99 mol.

[0024] In the following embodiments and comparative examples of the present invention, "parts" refers to "parts by mass".

[0025] In the following embodiments and comparative examples of this invention, the hydroxyl content was determined by acetylation titration. The specific steps are as follows: Weigh 0.5 g of the dried sample to be tested and place it in an Erlenmeyer flask. Add 10 mL of a pyridine-acetic anhydride mixture (the volume ratio of pyridine to acetic anhydride is 3:1). Attach a reflux condenser and reflux in an oil bath at 115 °C for 1 h. After the reaction is complete, cool and add 10 mL of deionized water. Continue reflux for 10 min to completely hydrolyze the excess anhydride. Cool to room temperature and titrate with 0.5 mol / L sodium hydroxide standard solution using phenolphthalein as an indicator until a pink color is reached, which is the endpoint. Record the titration volume. Simultaneously, perform a blank experiment (without adding the dried sample to be tested, all other steps are exactly the same). The formula for calculating the hydroxyl content (OH%) is as follows: OH% = [(V 空白 -V 样品 )×C NaOH [×17.01] / (1000×m 样品 ) × 100%. Where, V 空白 V is the titration volume (mL) for the blank experiment. 样品 C is the titration volume (mL) of the sample to be tested. NaOH The concentration of the sodium hydroxide standard solution is (mol / L), m 样品 The mass (g) of the dried sample to be tested.

[0026] Example 1 This embodiment provides a method for preparing modified PVB resin, including the following steps: 100 parts of polyvinyl alcohol (PVA) were dispersed in 900 parts of deionized water, and the solution was heated to 95°C and stirred for 2 hours to prepare a 10% PVA aqueous solution. The PVA aqueous solution was cooled to 12°C, and 3 parts of 30% hydrochloric acid solution (3% of the PVA mass) were added. Under stirring at 500 rpm, 45.0 parts of n-butyraldehyde were slowly added dropwise over 1 hour using a constant pressure dropping funnel, and the reaction was carried out at 15°C for 3 hours. After the reaction was completed, the solution was neutralized to pH 7 with 10% sodium hydroxide aqueous solution. The reaction solution was poured into 5 times its volume of vigorously stirred deionized water to precipitate the precipitate. After standing, the precipitate was filtered, and the filter cake was washed with deionized water until the filtrate was neutral. The filter cake was then dried in a vacuum drying oven at 60°C for 12 hours to obtain an intermediate. The hydroxyl content of the intermediate was determined to be 27.3%.

[0027] Take 100 parts of the above intermediate and add 500 parts of dimethyl sulfoxide. Stir in a 60°C water bath until completely dissolved. Add sodium hydroxide (the molar ratio of sodium hydroxide to subsequent chloromethylbenzene is 1.1:1), and purge with nitrogen for protection. Dissolve chloromethylbenzene (the molar amount added is 1% of the molar amount of hydroxyl in the intermediate) in 20 parts of dimethyl sulfoxide, transfer to a constant pressure dropping funnel, and add it dropwise to the reaction solution at a rate of 0.8 mL / min under a nitrogen atmosphere. After the addition is complete, continue the reaction at 60°C. During the reaction, take samples every 2 hours and monitor the reaction progress using Fourier transform infrared spectroscopy (FTIR). Samples are prepared using the KBr pellet method, and the scanning range is 4000-400 cm⁻¹. -1 The resolution is 4cm. -1 By monitoring 3300-3400cm -1 The degree of etherification reaction was determined by the relative decreasing trend of the intensity of the hydroxyl (-OH) stretching vibration peak. When the intensity of this characteristic peak did not change significantly between two consecutive samples, the reaction was considered to have reached its endpoint. After the reaction was completed, the mixture was cooled to room temperature and precipitated in 2000 parts of deionized water under vigorous stirring. After filtration, the obtained solid was washed three times each with deionized water and anhydrous ethanol, and then dried in a vacuum drying oven at 60℃ for 24 hours to obtain the modified PVB resin, denoted as PVB-M1.

[0028] Example 2 This embodiment is basically the same as Embodiment 1, except that the molar amount of chloromethylbenzene added is adjusted to be 2% of the molar amount of hydroxyl in the intermediate.

[0029] The modified PVB resin obtained in this embodiment is denoted as PVB-M2.

[0030] Example 3 This embodiment is basically the same as Example 1, except that the molar amount of chloromethylbenzene added is adjusted to be 3.5% of the molar amount of hydroxyl in the intermediate.

[0031] The modified PVB resin obtained in this embodiment is denoted as PVB-M3.

[0032] Example 4 This embodiment is basically the same as Example 1, except that the molar amount of chloromethylbenzene added is adjusted to be 5% of the molar amount of hydroxyl in the intermediate.

[0033] The modified PVB resin obtained in this embodiment is denoted as PVB-M4.

[0034] Example 5 This embodiment is basically the same as Example 2, except that the amount of n-butyraldehyde added is adjusted to 57.7 parts. The hydroxyl content of the intermediate was determined to be 24.8%.

[0035] The modified PVB resin obtained in this embodiment is denoted as PVB-M5.

[0036] Example 6 This embodiment is basically the same as Example 1, except that the amount of n-butyraldehyde added is adjusted to 36.5 parts. The hydroxyl content of the intermediate was determined to be 30.1%.

[0037] The modified PVB resin obtained in this embodiment is designated as PVB-M6.

[0038] Comparative Example 1 This comparative example provides a method for preparing PVB resin, including the following steps: 100 parts of polyvinyl alcohol (PVA) were dispersed in 900 parts of deionized water, heated to 95°C and stirred for 2 hours to prepare a 10% PVA aqueous solution. The PVA aqueous solution was cooled to 15°C, and 3 parts of 30% hydrochloric acid solution (3% of the PVA mass) were added. Under stirring at 500 rpm, 53.4 parts of n-butyraldehyde were slowly added dropwise over 1 hour using a constant pressure dropping funnel, and the reaction was carried out at 15°C for 5 hours. After the reaction was completed, the solution was neutralized to pH 7 with 10% sodium hydroxide aqueous solution. The reaction solution was poured into 5 times its volume of vigorously stirred deionized water to precipitate the precipitate. After standing, the precipitate was filtered, and the filter cake was washed with deionized water until the filtrate was neutral. The filter cake was then dried in a vacuum drying oven at 60°C for 12 hours to obtain PVB resin, denoted as PVB-C1. The hydroxyl content of PVB-C1 was determined to be 26.0%.

[0039] Comparative Example 2 The intermediate prepared in Example 1 was used as the PVB resin in this comparative example, denoted as PVB-C2. The hydroxyl content of PVB-C2 was determined to be 27.3%, consistent with the intermediate in Example 1.

[0040] Comparative Example 3 This comparative example is basically the same as Example 2, except that chloromethylbenzene is replaced with an equimolar amount of chloroethane.

[0041] The modified PVB resin obtained in this comparative example is denoted as PVB-C3.

[0042] Comparative Example 4 This comparative example provides a method for preparing a modified PVB resin, comprising the following steps: Take 100 parts of polyvinyl alcohol (PVA) and add 500 parts of dimethyl sulfoxide. Stir in a 60°C water bath until completely dissolved. Add sodium hydroxide (the molar ratio of sodium hydroxide to chloromethylbenzene is 1.1:1), and purge with nitrogen for protection. Dissolve chloromethylbenzene (the molar amount added is 2% of the molar amount of hydroxyl groups in the PVA) in 20 parts of dimethyl sulfoxide, transfer to a constant pressure dropping funnel, and add it dropwise to the reaction solution at a rate of 0.8 mL / min under a nitrogen atmosphere. After the addition is complete, continue the reaction at 60°C. During the reaction, take samples every 2 hours and monitor the reaction progress using Fourier transform infrared spectroscopy (FTIR). Samples are prepared using the KBr pellet method, and the scanning range is 4000-400 cm⁻¹. -1 The resolution is 4cm. -1 By monitoring 3300-3400cm -1 The degree of etherification reaction was determined by the relative decreasing trend of the peak intensity of the hydroxyl (-OH) stretching vibration; when the intensity of this characteristic peak did not change significantly between two consecutive samples, the reaction was considered to have reached its endpoint. After the reaction was completed, the mixture was cooled to room temperature, and precipitated by adding 2000 parts of deionized water under vigorous stirring. After filtration, the obtained solid was washed three times each with deionized water and anhydrous ethanol, and then dried in a vacuum drying oven at 60℃ for 24 hours to obtain the intermediate. The hydroxyl content of the intermediate was determined to be 36.3%.

[0043] 100 parts of the intermediate were dispersed in 900 parts of deionized water, heated to 95℃ and stirred for 2 hours to prepare an aqueous solution with a mass concentration of 10%. The aqueous solution was cooled to 12℃, and 3 parts of 30% hydrochloric acid solution (3% of the intermediate mass) were added. Under stirring at 500 r / min, 37.4 parts of n-butyraldehyde were slowly added dropwise over 1 hour using a constant pressure dropping funnel, and the reaction was carried out at 15℃ for 3 hours. After the reaction was completed, the solution was neutralized to pH=7 with 10% sodium hydroxide aqueous solution. The reaction solution was poured into 5 times its volume of vigorously stirred deionized water to precipitate the precipitate. After standing, the precipitate was filtered, and the filter cake was washed with deionized water until the filtrate was neutral. The filter cake was then dried in a vacuum drying oven at 60℃ for 12 hours to obtain the modified PVB resin, denoted as PVB-C4. The hydroxyl content of PVB-C4 was determined to be 27.1%.

[0044] Comparative Example 5 This comparative example is basically the same as Example 1, except that the amount of chloromethylbenzene added is adjusted to be 0.5% of the amount of hydroxyl in the intermediate.

[0045] The modified PVB resin obtained in this comparative example is denoted as PVB-C5.

[0046] Comparative Example 6 This comparative example is basically the same as Example 1, except that the amount of chloromethylbenzene added is adjusted to be 8% of the amount of hydroxyl in the intermediate.

[0047] The modified PVB resin obtained in this comparative example is denoted as PVB-C6.

[0048] Experimental Example 1 The PVB resins prepared in Examples 1-6 and Comparative Examples 1-6 were subjected to film formation and performance testing, as detailed below: 1. Thin film preparation Weigh 60 parts of resin and 40 parts of plasticizer (triethylene glycol di-2-ethylhexanoate), and mix them in a high-speed mixer for 10 minutes. The mixture is then melt-blended and extruded into granules using a twin-screw extruder (length-to-diameter ratio 40:1) at 180-200℃. After drying the granules in an oven at 80℃ for 4 hours, they are hot-pressed for 5 minutes at 180℃ and 10MPa using a flat vulcanizing machine. The mixture is then held under pressure and cooled to room temperature to obtain a transparent film with a thickness of 0.76 mm.

[0049] 2. Performance Testing (1) Glass transition temperature (Tg) determination: Differential scanning calorimetry (DSC) was used. 5-10 mg of resin sample was weighed into an aluminum crucible and heated from -20 °C to 150 °C at a rate of 10 °C / min under a nitrogen atmosphere (flow rate 50 mL / min). The DSC curve was recorded and the midpoint of the curve inflection zone was taken as the Tg value.

[0050] (2) Melt flow rate (MFR) determination: The melt flow rate of the resin was determined at 180℃ and 2.16kg load according to GB / T 3682.1-2018 standard. The result is expressed as g / 10min.

[0051] (3) Thin film optical performance test: According to GB / T 2410-2008 standard, the haze and transmittance of the thin film sample with a thickness of 0.76 mm were tested.

[0052] (4) Mechanical property testing of film: According to GB / T 1040.3-2006 standard, the film is cut into standard dumbbell-shaped strips (type V) with a gauge length of 25 mm and a tensile speed of 50 mm / min. The tensile strength and elongation at break are tested. Each sample is tested 5 times and the average value is taken.

[0053] (5) Visual observation: Visually observe the appearance of the film after hot pressing under natural light, and record defects such as crystal points, fish eyes, and turbidity.

[0054] In addition, the hydroxyl content of the PVB resins prepared in Examples 1-6 and Comparative Examples 1-6 was determined by acetylation titration.

[0055] The test results are recorded in Table 1.

[0056] Table 1 Test Results

[0057] The test results in Table 1 show that: The product exhibits optimal overall performance when the hydroxyl content of the final resin is within the range of 24-30%. The modified PVB resin obtained in the embodiments of this invention has a hydroxyl content of 24.3-29.8%, all falling within this preferred range (achieved by controlling the hydroxyl content of the intermediate to 25-30% and the addition of an aromatic halogenated etherifying agent to 1-5% of the molar amount of hydroxyl in the intermediate), thus obtaining optimal overall performance. Comparative Example 5 has a hydroxyl content of 27.2%, very close to the 26.8% of Example 2, but due to its excessively low addition of an aromatic halogenated etherifying agent (only 0.5% of the molar amount of hydroxyl in the intermediate), it failed to effectively cap the resin, resulting in increased haze and spots. This indicates that simply controlling the total amount of hydroxyl is insufficient; sufficient etherification capping is also necessary. In Comparative Example 6, the hydroxyl content was reduced to 25.1%, which is within the preferred range. However, the molar amount of the aromatic halogenated etherifying agent added was too high (8% of the molar amount of hydroxyl in the intermediate), resulting in an excessively high Tg and a sharp decrease in elongation at break. This demonstrates that a lower hydroxyl content is not necessarily better; the specific 1-5% window of this invention is crucial. Although the hydroxyl content of Comparative Example 1 was 26.0%, due to the use of a traditional one-step synthesis method, the distribution of hydroxyl groups in its molecular structure differed from that of this invention (potentially making it easier to form intramolecular / intermolecular hydrogen bonds or crosslinks), resulting in a significantly lower MFR and higher haze.

[0058] Furthermore, the modified PVB resins (PVB-M1 to PVB-M6) prepared in Examples 1-6 of this invention have a glass transition temperature (Tg) of 69-78℃ and a melt flow rate (MFR) of 4.5-6.2 g / 10 min. The films prepared from these resins exhibit a haze ≤1.0%, light transmittance ≥90%, tensile strength ≥27 MPa, and elongation at break ≥250%, and after hot pressing, they are transparent, uniform, and defect-free. This indicates that the modified PVB resins prepared using the two-step method of "partial acetalization followed by controlled aromatic etherification" of this invention can effectively inhibit hydroxyl crosslinking during subsequent processing, significantly improving the resin's processing fluidity, optical transparency, and mechanical properties.

[0059] Compared to Comparative Example 1, taking Example 2 as an example, the MFR increased from 3.2 g / 10 min to 5.8 g / 10 min, the haze decreased from 1.5% to 0.8%, the transmittance increased from 88.5% to 90.8%, the Tg increased from 68℃ to 72℃, and the tensile strength increased from 25.0 MPa to 28.5 MPa. This demonstrates that the method of the present invention achieves synergistic improvement in processing fluidity, optical properties, heat resistance, and mechanical strength. Although the performance of Comparative Example 2 is better than that of Comparative Example 1, its MFR (4.0 g / 10 min) and haze (1.2%) are still lower than those of the examples, and a small number of fine crystal points are present in the film, proving that the etherification end-capping step is necessary to eliminate residual hydroxyl crosslinking activity. The MFR of Comparative Example 3 is improved, but the Tg decreases instead of increasing (66℃), indicating that the introduction of aromatic structures plays a key role in improving the heat resistance of the resin. Comparative Example 4 showed a significant decrease in MFR to 2.1 g / 10 min, with a haze as high as 3.5%. The film exhibited obvious fisheye and streaks, indicating that the "acetalization followed by etherification" process sequence of this invention has a non-obvious technical effect, and changing the sequence leads to performance degradation. Comparative Example 5 had a haze of 1.8%, and the film showed localized blurred spots, indicating insufficient end-capping when etherification was too low, failing to effectively inhibit crosslinking. Comparative Example 6 showed an increased Tg to 80°C, but a sharp decrease in elongation at break to 180%, poorer film toughness, and a drop in melt flow rate to 3.0 g / 10 min, indicating that excessive etherification impairs processing fluidity and mechanical toughness.

[0060] In summary, this invention utilizes a two-step reaction process of "partial acetalization followed by controlled etherification," controlling the hydroxyl content of the intermediate to 25-30% and the molar amount of the etherifying agent to be 1-5% of the molar amount of the intermediate hydroxyl content, to prepare a modified PVB resin. This resin exhibits good processing fluidity, and films made from it possess low haze, high light transmittance, good mechanical properties, and heat resistance, making it suitable for applications such as interlayer films in laminated glass.

[0061] Finally, it should be noted that the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a modified PVB resin, characterized in that, Includes the following steps: S1. Mix polyvinyl alcohol aqueous solution, acidic catalyst and n-butyraldehyde, and carry out partial acetalization reaction to obtain intermediate; S2. Mix the intermediate, organic solvent, alkaline catalyst and aromatic halogenated etherifying agent, and carry out etherification reaction to obtain modified PVB resin; the molar amount of aromatic halogenated etherifying agent added is 1-5% of the molar amount of hydroxyl groups in the intermediate.

2. The preparation method according to claim 1, characterized in that, In S1, the degree of polymerization of the polyvinyl alcohol is 500-3000, and the degree of alcoholysis is 98-99.9 mol%; the mass concentration of the polyvinyl alcohol aqueous solution is 8-15%.

3. The preparation method according to claim 1, characterized in that, In S1, the acidic catalyst is selected from at least one of hydrochloric acid solution, sulfuric acid, and p-toluenesulfonic acid; the amount of the acidic catalyst is 2-5% of the mass of polyvinyl alcohol.

4. The preparation method according to claim 1, characterized in that, In S1, the amount of n-butyraldehyde added is controlled to make the hydroxyl content of the intermediate 25-30%.

5. The preparation method according to claim 1, characterized in that, In S1, the temperature of the partial acetalization reaction is 10-20℃, the stirring rate is ≥500r / min, and the time is 2-4h.

6. The preparation method according to claim 1, characterized in that, In S2, the organic solvent is selected from at least one of dimethyl sulfoxide, N,N-dimethylformamide, and ethanol; the alkaline catalyst is selected from at least one of sodium hydroxide, potassium hydroxide, and sodium methoxide; and the aromatic halogenated etherifying agent is selected from at least one of chloromethylbenzene and bromomethylbenzene.

7. The preparation method according to claim 1, characterized in that, In S2, the molar ratio of the alkaline catalyst to the aromatic halogenated etherifying agent is (1.0-1.2):

1.

8. The preparation method according to claim 1, characterized in that, In S2, the etherification reaction is carried out under an inert atmosphere at a temperature of 40-60°C.

9. A modified PVB resin, characterized in that, Prepared by the preparation method according to any one of claims 1-8.

10. The use of the modified PVB resin according to claim 9 in the preparation of interlayer films for laminated glass.

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