An intramolecularly plasticized poly(vinyl butyral) material and a method for its preparation

Abstract

This invention relates to an intramolecularly plasticized polyvinyl butyral (PVB) resin and its preparation method, belonging to the field of polymer materials. The specific preparation method is as follows: acetylated acid or glyoxylic acid first reacts with an alcohol compound to generate an aldehyde or ketone containing an ester group (internal plasticizer); then, polyvinyl alcohol (PVA) resin is dissolved in water, and an emulsifier, butyral, an acid catalyst, and the prepared internal plasticizer are added. An acetal reaction is then carried out within the range of 5-90 °C to obtain the intramolecularly plasticized PVB resin. The PVB resin prepared by this invention has a lower glass transition temperature and a higher melt index, significantly improving processing fluidity; it also improves its compatibility with external plasticizers and enhances the migration resistance of plasticizers. The resulting PVB film exhibits excellent mechanical properties and low water absorption, meeting the application requirements of photovoltaic laminated glass, automotive safety glass, and other fields.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology and relates to an intramolecularly plasticized modified polyvinyl butyral resin and its preparation method, which is particularly suitable for fields such as laminated glass and adhesives that require high water resistance and processing stability. Technical Background

[0002] Polyvinyl butyral (PVB) is a high molecular weight polymer produced by the acetal reaction of polyvinyl alcohol (PVA) and n-butyral using an acid catalyst. PVB is a ternary random polymer composed of three structural units: vinyl alcohol (VA) units, vinyl butyral (VB) units, and vinyl acetate (VAc) units. These structural units endow PVB resin with good flexibility and weather resistance, and it exhibits excellent adhesion to materials such as glass, metals, ceramics, and leather. Therefore, PVB is widely used in laminated glass, adhesives, and ceramic decals.

[0003] PVB resin has a refractive index similar to glass and exhibits exceptional adhesion and light transmittance to both inorganic and organic glass, making it a special material for manufacturing laminated safety glass. In 1935, an American polymer materials company synthesized the world's first PVB film. Laminated glass made using this film significantly surpassed existing glass made from other materials in terms of toughness, hardness, light transmittance, and other physical properties. Therefore, PVB films were widely used in automotive windshields. Laminated safety glass made from PVB films produced using extrusion molding or casting methods, bonded to glass under specific temperature and pressure conditions, boasts high transparency and mechanical strength, as well as water and aging resistance. When impacted by an external object, it only forms spiderweb-like cracks, with glass fragments remaining firmly adhered to the interlayer, effectively preventing shards from flying everywhere when the glass breaks. It offers excellent safety performance and can continue to be used for a certain period without obstructing vision.

[0004] However, pure PVB powder materials have certain limitations. First, pure PVB powder materials have relatively high hardness and insufficient flexibility, making it difficult to meet the flexibility requirements of specific applications. Second, due to the large number of polar groups in pure PVB materials, strong hydrogen bonds easily form between molecules, resulting in a high glass transition temperature, high melt viscosity, and poor melt flowability, which limits its applications. Therefore, a certain amount of plasticizer needs to be added when using PVB powder materials to increase chain mobility and enhance its plasticity. The addition of plasticizers can effectively lower the glass transition temperature of PVB and increase the mobility of molecular chains, enabling it to better meet the application requirements of high flexibility. In addition, the introduction of plasticizers can also improve the processing performance of PVB materials, enhance their moldability and processing stability, and make them easier to process into various shapes and sizes. External plasticizers (such as 3GO, 3G7, etc., whose structural formulas are shown below) usually have limited compatibility with PVB and are prone to diffusion migration and precipitation in humid and hot environments. Even if the plasticizer has good compatibility with PVB, it may still be extracted and lost when in contact with organic solvents. The migration and loss of plasticizers can lead to decreased flexibility, weakened adhesion, and increased optical haze in PVB films, severely impacting the long-term performance and service life of the product. Internal plasticizing, on the other hand, introduces flexible segments into the polymer backbone through chemical means to adjust the melt flow index, increase water resistance, and prevent plasticizer migration, thereby improving the product's processing performance and stability. Patent US5594069A uses long-chain acetal groups to modify a portion of polyvinyl butyral containing unreacted vinyl alcohol groups, reducing the size of the mixed polyvinyl butyral and improving its particle size distribution. US5137954A uses carbon numbers between C7 and C8. 15 Long-chain fatty aldehydes act as internal plasticizers, lowering their glass transition temperature T. g Patent CN108032579A uses dioctyl(2-ethylhexyl) 4,5-epoxytetrahydrophthalic acid as an internal plasticizer, covalently grafted into the PVB molecular chain, thereby improving the tensile strength, elongation at break, and melt index of the PVB film. US5019624A uses terminally etherified glyoxal / oxane as an internal plasticizer, producing polyvinyl acetal with excellent tensile strength and elongation at break, high internal plasticization, and improved water resistance and adhesion to glass and metals.

[0005] ;

[0006]

[0007] Therefore, intramolecular plasticization can be achieved by introducing flexible segments such as long carbon chains into the PVB molecular chain to improve the material's processing fluidity and water resistance, and to avoid the impact of external plasticizer migration and loss on material properties. However, traditional long-chain alkyl aldehydes (such as 2-ethylhexanal) have high aldehyde group reactivity, which can easily lead to problems such as excessively fast reaction rate, difficulty in controlling the degree of acetalization, and uneven distribution of condensation positions during acetalization. This results in uneven product structure and local cross-linking gelation. At the same time, the structure of pure long-chain alkyl internal plasticizers lacks ester groups similar to those in the external plasticizer structure, resulting in poor compatibility with the external plasticizer and ultimately affecting material properties.

[0008] This invention utilizes aldehydes or ketones containing ester groups as internal plasticizers to prepare PVB materials. The introduction of ester groups effectively reduces the reactivity of aldehyde groups, making the acetalization reaction more mild and controllable. Due to steric hindrance, ketone groups exhibit a slower condensation reaction with PVA, facilitating uniform distribution during PVB preparation. Simultaneously, ester groups possess good flexibility and polarity, enhancing the internal plasticizing effect of PVB, improving compatibility with external plasticizers in PVB resin, and increasing the material's water resistance, temperature resistance, and plasticizer migration resistance. Therefore, this invention selects aldehydes or ketones containing ester groups as internal plasticizers to prepare structurally uniform and stable intramolecularly plasticized PVB materials. Summary of the Invention

[0009] The object of this invention is to provide an intramolecularly plasticized polyvinyl butyral (PVB) resin, characterized by having a structure as shown in formula (I):

[0010]

[0011] (I)

[0012] Wherein, R1 is H or CH3, n is 0 or 2, and R2 is a straight-chain alkyl or branched alkyl with 4-12 carbon atoms.

[0013] x, y, z, and m are all integers, and the values ​​of y and z are related to the degree of acetalization.

[0014] The PVB resin provided by this invention is characterized by the addition of an internal plasticizer as shown in formula (II) during the synthesis process.

[0015]

[0016] (II)

[0017] Wherein, R1 is H or CH3, n is 0 or 2, and R2 is a straight-chain alkyl or branched alkyl with 4-12 carbon atoms.

[0018] The method for preparing the intramolecularly plasticized PVB resin of this invention is as follows:

[0019] S1. A mixture of levulinic acid or glyoxylic acid with an alcohol compound having 4-12 carbon atoms is subjected to an esterification reaction under acid catalysis. After washing, drying and purification under reduced pressure, an ester-containing aldehyde or ketone (internal plasticizer) is obtained.

[0020] The alcohol compounds mentioned therein include, but are not limited to, any one of butanol, hexanol, octanol, nonanol, decanol, lauryl alcohol, isobutanol, isohexanol, isooctanol, isononol, isodecanol, and isododecyl alcohol.

[0021] The acid catalyst can be any one or more of sulfuric acid, hydrochloric acid, and p-toluenesulfonic acid; the concentration is 0.1-99%.

[0022] The amount of acid catalyst used is 0.1-10 wt% of the total mass of levulinic acid or glyoxylic acid and alcohol compounds.

[0023] The molar ratio of the acetylpropionic acid or glyoxylic acid to the alcohol compound is 1:1 to 1:1.6.

[0024] The reaction temperature is 60-130 ℃.

[0025] The reaction time is 3-7 hours.

[0026] S2. Polyvinyl alcohol (PVA) resin is dissolved in water, and emulsifier, butyraldehyde, acid catalyst and internal plasticizer prepared in step S1 are added. An acetal reaction is carried out in the range of 5-90 °C to obtain intramolecularly plasticized PVB resin.

[0027] The reaction equation is as follows:

[0028]

[0029] Wherein, R1 is H or CH3, n is 0 or 2, and R2 is a straight-chain alkyl or branched alkyl with 4-12 carbon atoms.

[0030] x, y, z, and m are all integers, and the values ​​of y and z are related to the degree of acetalization.

[0031] The raw materials for preparing the intramolecularly plasticized modified polyvinyl butyral include: intramolecular plasticizer, polyvinyl alcohol (PVA), acid catalyst, butyral, emulsifier and alkaline solution.

[0032] The intramolecular plasticizer is an aldehyde or ketone containing an ester group, including but not limited to any one or more of butyl glyoxylate, hexyl glyoxylate, octyl glyoxylate, dodecyl glyoxylate, isobutyl glyoxylate, isooctyl glyoxylate, isododecyl glyoxylate, butyl levulinate, hexyl levulinate, octyl levulinate, dodecyl levulinate, isobutyl levulinate, isooctyl levulinate, and isododecyl levulinate, as well as other aldehydes or ketones that conform to the structure of the above general formula (II).

[0033] The molar ratio of the internal plasticizer to the total hydroxyl groups is 0.02:1-0.22:1.

[0034] The degree of polymerization of the raw material PVA is 300-2500, and the degree of alcoholysis is 86-99 mol.

[0035] The concentration of the PVA solution is 4-10 wt%.

[0036] The acid catalyst can be any one or more of hydrochloric acid, nitric acid, and sulfuric acid; the concentration is 0.1-99%.

[0037] The amount of acid catalyst used is 0.1-10 wt% of the total mass of the PVA solution.

[0038] The emulsifier may be one or more of Tween-80, fatty alcohol polyoxyethylene ether (AEO-9), and sodium dodecyl sulfate (SDS); the amount added is 0.1-2 wt% of the PVA mass.

[0039] The molar ratio of butyraldehyde to total hydroxyl groups is 0.10:1-0.41:1.

[0040] The alkaline solution can be any one or more of sodium hydroxide, potassium hydroxide, and sodium carbonate. Beneficial effects

[0041] (1) This invention provides an intramolecularly plasticized PVB resin, which utilizes an aldehyde or ketone containing an ester group as an intramolecular plasticizer to simultaneously introduce long-chain alkyl and ester groups onto the PVB chain, thereby achieving more efficient intramolecular plasticization and significantly reducing the glass transition temperature (T) of the PVB resin. g ), to improve low-temperature toughness.

[0042] (2) Compared with traditional 2-ethylhexanal modified PVB, the ester-containing aldehyde or ketone modified PVB resin prepared in this invention can significantly reduce water absorption and improve water resistance through the synergistic effect of ester group and long carbon chain, thereby reducing the impact of humid environment on product performance, delaying aging, extending product service life, and making it more suitable for long-term weather-resistant scenarios such as outdoor photovoltaics and building safety glass.

[0043] (3) The ester-containing aldehyde or ketone-modified PVB resin provided by the present invention has better processing fluidity and film-forming properties. The ester group and long carbon chain impart an internal lubrication effect to the system, which can significantly reduce the melt viscosity of PVB and increase the melt flow rate (MFR). Furthermore, intramolecular plasticization can improve the compatibility of PVB resin with external plasticizers and enhance the migration resistance of plasticizers. Attached Figure Description

[0044] The embodiments of the present invention will be described in detail with reference to the accompanying drawings, wherein...

[0045] Figure 1 In Example 1, isooctyl levulinate intramolecularly plasticized PVB (1B) 1 H NMR spectrum. Detailed Implementation

[0046] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; unless otherwise specified, the reagents and materials are commercially available.

[0047] The proton NMR spectra used in the examples were measured using a Bruker Ascend TM-400 NMR spectrometer.

[0048] Example 1

[0049] 1A. Preparation of isooctyl levulinate

[0050] 116.1 g (1.0 mol) of levulinic acid and 195.3 g (1.5 mol) of isooctanol were added to a 500 mL four-necked flask equipped with a stirrer, thermometer, and condenser, along with 2.9 g of p-toluenesulfonic acid as a catalyst. The mixture was stirred and refluxed at 125 °C for 6 h, with water continuously separated using a water separator until no more water precipitated. After the reaction was complete, the mixture was cooled to room temperature, washed with a 5% sodium carbonate aqueous solution until neutral, and then washed twice with saturated brine. After drying with anhydrous sodium sulfate, excess isooctanol was removed by vacuum distillation to obtain the target product. The yield was 89%.

[0051] 1B. Preparation of Internally Plasticized PVB

[0052] Preparation of intramolecularly plasticized modified PVB (B1): A suitable amount of polyvinyl alcohol PVA-2099 (produced by Sinopec Sichuan Chemical Co., Ltd., degree of polymerization 2000, degree of hydrolysis 99%) was placed in a 500 mL four-necked flask equipped with a stirrer and thermometer. Deionized water was added at 85-90℃ to prepare a 320 g, 8 wt% PVA solution. At 85-95℃, 0.26 g SDS was added to the PVA solution, and after stirring evenly, 10.8 g of 35% nitric acid and 14.99 g (0.07 mol) of isooctyl levulinate synthesized in 1A were added. After 5-7 min of reaction, the initially clear solution turned into a milky white liquid, and the reaction continued for 1 h. Butyraldehyde (10.31 g, 0.14 mol) was slowly added, and the reaction continued at the same temperature for approximately 4 h. The reaction mixture was then washed to pH 4.0, and the pH was adjusted to 10.0 using 45% KOH solution. This pH was maintained at 75 °C for 1 h, followed by washing with water to pH 7.0. Finally, the product was filtered and dried until the moisture content was less than 2%, with a yield of 83%. The product structure is shown in formula (Ⅲ):

[0053]

[0054] (III)

[0055] Example 2

[0056] 2A. Preparation of isooctyl glyoxylate

[0057] To a 500 mL four-necked flask equipped with a stirrer, thermometer, and condenser, 90.0 g (approximately 1.0 mol) of glyoxylic acid and 195.3 g (1.5 mol) of isooctanol were added sequentially, along with 1.8 g of p-toluenesulfonic acid as a catalyst. The mixture was stirred and refluxed at 120 °C for approximately 6 h, with water continuously separated using a water separator until no more water precipitated. After the reaction was complete, the mixture was cooled to room temperature, washed with a 5% sodium carbonate aqueous solution until neutral, then washed twice with saturated brine, dried over anhydrous sodium sulfate, and finally subjected to vacuum distillation to remove excess isooctanol, yielding the target product. The yield was 86%.

[0058] 2B. Preparation of Internally Plasticized PVB

[0059] Preparation of intramolecularly plasticized modified PVB (B2): A suitable amount of polyvinyl alcohol PVA-2099 (produced by Sinopec Sichuan Chemical Co., Ltd., degree of polymerization 2000, degree of hydrolysis 99%) was placed in a 500 mL four-necked flask equipped with a stirrer and thermometer. Deionized water was added at 85-90℃ to prepare a 320 g, 8 wt% PVA solution. At 85-95℃, 0.26 g SDS was added to the PVA solution, and after stirring evenly, 10.79 g of 35% nitric acid and 12.23 g (0.07 mol) of isooctyl glyoxylate synthesized in step 2A were added. After 5-7 min of reaction, the initially clear solution turned into a milky white liquid, and the reaction continued for 1 h. Butyraldehyde (10.31 g, 0.14 mol) was slowly added, and the reaction continued at the same temperature for approximately 4 h. The reaction mixture was then washed to pH 4.0, neutralized to pH 10.0 with 45% KOH solution, and maintained at this pH at 75 °C for 1 h. It was then washed with water to pH 7.0. Finally, the product was filtered and dried to a moisture content of less than 2%, with a yield of 82%. The product structure is shown in formula (Ⅳ):

[0060]

[0061] (IV)

[0062] Table 1 Formulation of Internal Plasticizers

[0063] Comparative Example

[0064] 144.22 g (2 mol) of n-butyraldehyde was added to a four-necked flask equipped with a stirrer, thermometer, and condenser. The temperature was raised to 40-50 °C, and 2.88 g of a 10% sodium hydroxide aqueous solution was added dropwise. The mixture was stirred for 2-4 h, and after neutralization and separation, 2-ethyl-2-hexenal was obtained. 2-Ethyl-2-hexenal was transferred to a high-pressure reactor, and 1.5 g of Pd / C catalyst was added. The mixture was hydrogenated at 2-3 MPa and 100-120 °C for 2-3 h. After the reaction was completed, the catalyst was removed by filtration, and then the product was subjected to vacuum distillation to obtain 2-ethylhexanal.

[0065] Table 2 Formulation of internally plasticized PVB resin in Example 3-Comparative Example 3

[0066]

[0067] Performance testing

[0068] 1. PVB resin

[0069] (1) Thermal performance test: The glass transition temperature (Tg) was determined using a differential scanning calorimeter. g The test results are shown in Table 3.

[0070] (2) Melt flow index test: Samples were prepared according to the national standard GB / T 3682-2000 and tested using a melt flow rate tester. First, about 6 g of sample was weighed and cut into small particles of 2 mm × 2 mm. The melt flow rate tester barrel was heated to the set value of 140 ℃ and stabilized for 10 min. The piston rod was pulled out and the sample to be tested was added. The piston rod was reinserted and compacted. After holding the temperature for 10 min, a 21.6 kg weight was added. The test was started when the lower mark ring was aligned with the barrel. The test time was 1 min per sample. The weight of the sample strip flowing out of the melt flow rate tester was measured as m1 and m2. The melt flow index was calculated using the following formula: Melt flow index = (m1 + m2) * 5 (unit: g / 10 min). The test results are shown in Table 3.

[0071] Table 3 Performance Tests of PVB Resin

[0072]

[0073] Table 3 shows that intramolecular plasticization can significantly reduce the T of PVB resin. g This increases the melt flow index, effectively improving the resin's low-temperature toughness and processing fluidity. Compared to 2-ethylhexanal-modified PVB resin (1D), the PVB resins (1B and 2B) provided by this invention, which are intramolecularly plasticized using ester-containing aldehydes or ketones, have a higher glass transition temperature (T0). g The plasticizing effect of 2-ethylhexanal-modified PVB resins (1D and 2D) decreased by 5.45-9.09%, while the melt index increased by 40-60%. Furthermore, the plasticizing effect of 2-ethylhexanal-modified PVB resins decreased, and the higher the degree of polymerization of PVA, the lower the T... g The higher the temperature, the worse the flowability. Pure PVB resin (3D) exhibits the highest TL. g And the worst melt flowability.

[0074] 2. PVB film

[0075] Weigh 100 parts by mass of intramolecularly plasticized PVB resin, 3-10 parts of 3G8, and 0.2 parts of antioxidant 1010. Mix them in a Banbury mixer at 110-130 °C for 10 min at a speed of 30-60 rpm to ensure uniform dispersion of the components. Then, add the mixture to a twin-screw extruder for melt blending. Set the extrusion temperature to 150-180 °C and the screw speed to 30-60 rpm. After extrusion, the molten material is cast into a film on cooling rollers, with the roller temperature controlled at 30-50 °C. After traction and setting, the resulting film is left at room temperature for 24 h to eliminate internal stress, ultimately yielding a PVB film of uniform thickness.

[0076] (1) Tensile strength and elongation at break test: Samples were prepared in accordance with the national standard GB / T 32020-2015 and tested using a universal testing machine. The test results are shown in Table 4.

[0077] (2) Water resistance test: Samples were prepared and water absorption rate was determined in accordance with the national standard GB / T 1034-2008. The test results are shown in Table 4.

[0078] (3) Migration resistance test: The prepared PVB film was cut into a certain size and weighed as W0. Then the sample was placed in an oven at 60 ℃, and the sample was taken out at intervals, cooled to room temperature, and weighed again as W1. The migration rate (M) of the plasticizer was calculated using the following formula, and the calculation results are shown in Table 4:

[0079]

[0080] Table 4 Performance Tests of PVB Films

[0081]

[0082] Table 4 shows that intramolecular plasticization significantly improves the toughness and water resistance of PVB films. Compared with films prepared by 2-ethylhexanal-modified PVB resin (1D), the PVB (1B and 2B) films provided by this invention, which are intramolecularly plasticized using ester-containing aldehydes or ketones, have a tensile strength of 24-26 MPa, an increase in elongation at break of 12.11-26.46%, and a decrease in water absorption of 15.38-23.08%. By comparing the properties of films prepared by 1D and 2D, it was found that the higher the degree of PVA polymerization, the higher the tensile strength of the PVB film, and the lower the elongation at break and water absorption. Pure PVB resin (3D) exhibits high tensile strength, low toughness, and low water resistance. Meanwhile, the presence of ester groups can improve the compatibility of PVB resin with external plasticizers, thereby enhancing the migration resistance of the plasticizers and improving the long-term stability of the film.

Claims

1. An intramolecularly plasticized polyvinyl butyral (PVB) resin, characterized in that... It has a structure as shown in equation (I): （I） Wherein, R1 is H or CH3, n is 0 or 2, and R2 is a straight-chain alkyl or branched alkyl with 4-12 carbon atoms. x, y, z, and m are all integers, and the values ​​of y and z are related to the degree of acetalization.

2. The PVB resin as described in claim 1, characterized in that... An internal plasticizer as shown in formula (II) was added during the synthesis process. （Ⅱ） 3. The PVB resin internal plasticizer as described in claim 2, wherein R1 is H or CH3, n is 0 or 2, and R2 is a straight-chain alkyl or branched-chain alkyl with 4-12 carbon atoms.

4. The PVB resin as described in claim 1 is prepared by dissolving polyvinyl alcohol (PVA) resin in water, adding emulsifier, butyraldehyde, acid catalyst and internal plasticizer, and stirring and reacting in the range of 5-90 °C.

5. The PVB resin internal plasticizer as described in claims 2 and 4, wherein the amount added during the PVB preparation process is such that the molar ratio of internal plasticizer to total hydroxyl groups is 0.02:1-0.22:

1.

6. The degree of polymerization of the raw material PVA as described in claim 4 is 300-2500, and the degree of alcoholysis is 86-99 mol.

7. The molar ratio of butyraldehyde to total hydroxyl groups as described in claim 4 is 0.10:1-0.41:

1.

8. In the PVB preparation method according to claim 4, the emulsifier may be one or more of Tween-80, fatty alcohol polyoxyethylene ether (AEO 9), and sodium dodecyl sulfate (SDS); the amount added is 0.1-2 wt% of the mass of PVB.

9. The acid catalyst as described in claim 4 may be hydrochloric acid, nitric acid, or sulfuric acid; with a concentration of 0.1-99%. Its dosage is 0.1-10 wt% of the total mass of the PVA solution.

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