Polyvinyl acetal molecular sequence distribution control method and polyvinyl acetal resin

Abstract

The invention discloses a polyvinyl acetal molecular sequence distribution control method and a polyvinyl acetal resin, wherein the obtained resin has a hydroxyl value of 17-20wt%, a c / i ratio range of a VA structural unit of 0.6 to 1.1, and an initial degradation temperature of more than 300° C. The invention has a simple process, low cost, less variation than the existing production process, a large adjustable range for the polyvinyl acetal molecular sequence distribution, and no need to modify the existing production equipment.

Description

Technical Field

[0001] The invention relates to the technical field of polymer materials, and in particular to a method for regulating and controlling the sequence distribution of polyvinyl acetal molecules, and polyvinyl acetal resin prepared by the method. Background Art

[0002] Polyvinyl acetal is the main material for the production of laminated glass and is widely used in the fields of automobiles, construction, photovoltaics, etc. Among them, the production and preparation of polyvinyl acetal resin is usually prepared by reacting polyvinyl alcohol resin with a certain proportion of aldehydes under the action of an acidic catalyst to produce an acetal reaction. Its molecular composition often includes three structural units: vinyl acetal (VB), vinyl alcohol (VA) and vinyl acetate (VAc). Among them, the VB unit mainly provides impact resistance, tensile strength, toughness, etc., the VA unit mainly provides bonding properties, and the VAc unit mainly provides water resistance. In this context, the sequence distribution of these three structural units in the molecular chain of polyvinyl acetal directly affects its macroscopic mechanical and bonding properties. In addition, the sequence distribution of the above structural units also directly affects the compatibility and distribution uniformity of the plasticizer in the process of manufacturing polyvinyl acetal film.

[0003] The regulation of polyvinyl acetal molecular sequence mainly includes two aspects: sequence length and length distribution of structural units. In previous technical research, the acetalization degree and hydroxyl content of polyvinyl acetal that were usually controlled only reflected the average value of the structural unit content. Even at the same VB or VA structural unit content, different samples can still show different sequence lengths and length distributions. Therefore, indicators such as acetalization degree and hydroxyl value cannot effectively reflect its sequence length and length distribution.

[0004] Patent CN102120785B reports that the fluidity of polyvinyl acetal can be regulated by adjusting the hydroxyl blockiness of the polyvinyl acetal molecular chain. It is reacted at a high acetal reaction temperature without additives such as emulsifiers. However, due to the low softening temperature and glass transition temperature of polyvinyl acetal, when the reaction temperature is higher than the softening temperature of polyvinyl acetal, problems such as large product particle size and reaction non-uniformity will occur. In addition, the hydroxyl blockiness also only reflects the average value of continuous VA structural units, and does not explain the distribution of the sequence length of the structural unit itself. Summary of the invention

[0005] In view of the deficiencies in the above-mentioned prior art, the main purpose of the present invention is to provide a method for regulating the molecular sequence distribution of polyvinyl acetal and to prepare polyvinyl acetal resins with different molecular sequence distributions.

[0006] In order to achieve the purpose, the present invention adopts the following technical scheme:

[0007] A method for regulating the molecular sequence distribution of polyvinyl acetal is characterized in that it comprises the following steps:

[0008] (1) Adding an acid catalyst, an aldehyde, and a penetrant into a polyvinyl alcohol aqueous solution within 5 minutes to 2 hours at a temperature range of 5 to 30°C;

[0009] (2) heating the reaction system to 40-60° C. and keeping the temperature to mature;

[0010] (3) adding alkali solution to the matured reaction system, stirring for 5 to 30 minutes, filtering, and obtaining a solid resin product;

[0011] (4) washing the solid resin product 1 to 10 times with a mixture of water and alcohol, and filtering to obtain a washed product;

[0012] (5) Drying the washed product at 40-60° C. to obtain a polyvinyl acetal resin.

[0013] Furthermore, in step (1), the solid content of polyvinyl alcohol in the polyvinyl alcohol aqueous solution is 8-10%.

[0014] Furthermore, in step (1), the aldehyde includes at least one of formaldehyde, acetaldehyde, butyraldehyde, valeraldehyde, isovaleraldehyde, hexanal, heptanal, octanal, nonanal, decanal, benzaldehyde and phenylacetaldehyde.

[0015] Furthermore, in step (1), the mass of the aldehyde is 50-60% of the mass of the polyvinyl alcohol.

[0016] Furthermore, in step (1), the acidic catalyst includes at least one of hydrochloric acid, sulfuric acid, nitric acid and p-toluenesulfonic acid.

[0017] Furthermore, in step (1), the penetrant is a multi-arm structure having multiple hydrophilic and lipophilic segments, including sulfonate penetrants such as sodium hexadecyl diphenyl oxide disulfonate, sodium dibutylnaphthalene sulfonate, sodium diisooctyl succinate sulfonate, sodium diisobutylnaphthalene sulfonate, and anionic multi-arm penetrants such as alkyl (aryl) sulfate ester penetrants, alkyl (aryl) phosphate ester penetrants such as triisobutyl phosphate, and nonionic multi-arm penetrants such as polyethylene glycol octylphenyl ether and nonylphenol polyoxyethylene ether.

[0018] Furthermore, in step (1), the amount of the penetrant added is 0.01 to 0.2 wt % of the mass fraction of the polyvinyl alcohol.

[0019] Furthermore, in step (1), the penetrant is added by dissolving it in aldehyde and then adding it together with the aldehyde.

[0020] Furthermore, in step (2), the heating rate of the reaction system is not less than 20°C / h, so as to achieve the purpose of accelerating the kinetics of the acetalization reaction. The heating method of the reaction system can be to place the solution obtained in step (1) directly in a 40-60°C water bath or oil bath environment and quickly heat it up.

[0021] Furthermore, in step (2), the heat preservation and aging is to continue the constant temperature reaction for 0.5 to 2 hours after the reaction system reaches the target temperature.

[0022] Furthermore, in step (3), the alkaline solution includes at least one of sodium hydroxide, potassium hydroxide and magnesium hydroxide.

[0023] Furthermore, in step (4), the alcohol includes at least one of methanol, ethanol, propanol, butanol, isobutanol, propylene glycol, n-butanol and n-octanol.

[0024] Furthermore, in step (4), the volume percentage of alcohol in the mixed solution of water and alcohol is 1 to 50%.

[0025] Furthermore, in step (4), the cleaning temperature is 20 to 50°C.

[0026] The polyvinyl acetal resin obtained by the present invention has the following characteristics: the hydroxyl value of the polyvinyl acetal resin is 17-20wt%, the c / i ratio of the VA structural unit thereof is in the range of 0.6-1.1, and the initial degradation temperature of the polyvinyl acetal resin is greater than 300°C.

[0027] The c / i ratio of the VA structural unit is defined as the ratio of the continuous VA structural unit (continuous VA, referred to as c-VA) to the isolated VA structural unit (isolated VA, referred to as i-VA). Figure 1 As shown, polyvinyl acetal was dissolved in deuterated d6-DMSO, and the signal peaks of different hydroxyl groups were measured by liquid nuclear magnetic resonance hydrogen spectrum. The signal peak ranges of c-VA and i-VA were 4.35-4.25 ppm and 4.25-4.15 ppm, respectively (as shown in FIG. Figure 2 The c / i ratio is the ratio of the integrated areas of the two characteristic peaks.

[0028] The hydroxyl value is tested by chemical titration.

[0029] The initial degradation temperature is tested by thermogravimetric analysis, and the temperature at the point where the mass begins to decrease in the thermogravimetric curve is the initial degradation temperature.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] The process of the present invention is simple, the cost is low, the change is smaller than that of the existing production process, the adjustable range of the molecular sequence distribution of polyvinyl acetal is large, and there is no need to change the existing production equipment. In addition, the reaction process of the present invention does not need to be carried out at high temperature, and under the effect of the addition of the penetrant, the reaction unevenness such as large product particles and reaction agglomeration will not occur. The present invention also has the characteristics and advantages of simple operation, no need to add other process equipment and high-priced raw materials, and has good market competitiveness. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is the molecular formula of polyvinyl acetal and the definitions of i-VA and c-VA;

[0033] Figure 2 Schematic diagram of the H-NMR spectrum of polyvinyl acetal and the characteristic peaks of i-VA and c-VA. DETAILED DESCRIPTION

[0034] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] Example 1

[0036] (1) Dissolve 100 g of polyvinyl alcohol with an average degree of polymerization of 1700 in 1 L of pure water and stir at 90°C for 1 h to fully dissolve it. Then cool it to 15°C, add 20 g of hydrochloric acid with a mass concentration of 36-38%, and stir it thoroughly to form a mixed solution. Add 57 g of butyraldehyde solution mixed with 0.05 g of sodium diisobutylnaphthalene sulfonate dropwise over 60 min. Keep at this temperature for 1 h.

[0037] (2) The reaction system was heated to 60°C at a heating rate of 40°C / h, and the reaction was stirred at this temperature for 2 h to obtain a solid-liquid mixture A.

[0038] (3) 40 mL of 15 wt% sodium hydroxide solution was added to the solid-liquid mixture A, and the mixture was stirred for 15 min. The mixture was centrifuged and dehydrated to obtain a solid product B.

[0039] (4) 1 L of a mixed solution of water and alcohol (methanol volume fraction of 10%) was added at a time, and the solid product B was repeatedly washed and filtered at 50° C. for 5 times, and then the solid product B was repeatedly washed and filtered at 25° C. for 2 times with 1 L of pure water. The solid product C was obtained by suction filtration.

[0040] (5) The solid product C is placed in a forced air drying oven and dried at 50° C. for 4 h to obtain a polyvinyl acetal resin product.

[0041] Example 2

[0042] Except that the mass of sodium diisobutylnaphthalenesulfonate in step (1) is 0.1 g, the remaining steps and conditions are the same as those in Example 1.

[0043] Example 3

[0044] Except that the mass of sodium diisobutylnaphthalenesulfonate in step (1) is 0.2 g, the remaining steps and conditions are the same as those in Example 1.

[0045] Example 4

[0046] Except that sodium diisobutylnaphthalene sulfonate in step (1) is replaced by sodium dodecyl sulfonate, the remaining steps and conditions are the same as those in Example 1.

[0047] Example 5

[0048] Except that the insulation temperature in step (2) is 40° C., the remaining steps and conditions are the same as those in Example 1.

[0049] Comparative Example 1

[0050] Except for adding 0 g of sodium diisobutylnaphthalenesulfonate in step (1), the remaining steps and conditions are the same as those in Example 1.

[0051] Comparative Example 2

[0052] Except for adding 0.5 g of sodium diisobutylnaphthalenesulfonate in step (1), the remaining steps and conditions are the same as those in Example 1.

[0053] Comparative Example 3

[0054] Except that the volume ratio of methanol / water in step (4) is 0:100, the remaining steps and conditions are the same as those in Example 1.

[0055] Comparative Example 4

[0056] Except that the insulation temperature in step (2) is 80° C., the remaining steps and conditions are the same as those in Example 1.

[0057] Comparative Example 5

[0058] Except that the heating rate in step (2) is 10°C / h, the remaining steps and conditions are the same as those in Example 1.

[0059] The properties of the samples obtained in the above embodiments and comparative examples are shown in Table 1.

[0060] Table 1 Test results of acetal degree, hydroxyl value and hydroxyl block degree of polyvinyl acetal resin

[0061]

[0062]

[0063] The above description is only an exemplary embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for regulating the molecular sequence distribution of polyvinyl acetal, characterized in that: The steps include: (1) adding an acidic catalyst, an aldehyde and a penetrant into a polyvinyl alcohol aqueous solution within 5 minutes to 2 hours at a temperature range of 5 to 30°C; the penetrant is a multi-arm structure having multiple hydrophilic and lipophilic segments, the amount of the penetrant added is 0.01 to 0.2 wt% of the mass of the polyvinyl alcohol, and the penetrant is added by dissolving in the aldehyde and then adding together with the aldehyde; (2) Raise the temperature of the reaction system to 40-60°C and keep warm for maturation; (3) Adding alkali solution to the matured reaction system, stirring for 5 to 30 minutes, and filtering to obtain a solid resin product; (4) washing the solid resin product 1 to 10 times with a mixture of water and alcohol having an alcohol volume percentage of 1 to 50%, and filtering to obtain a washed product; (5) Drying the washed product at 40-60° C. to obtain polyvinyl acetal resin.

2. The method for controlling the molecular sequence distribution of polyvinyl acetal according to claim 1, characterized in that: In step (1), the penetrant includes at least one of a sulfonate penetrant, a sulfate ester penetrant, a phosphate ester penetrant, polyethylene glycol octylphenyl ether and nonylphenol polyoxyethylene ether.

3. The method for controlling the molecular sequence distribution of polyvinyl acetal according to claim 1, characterized in that: In step (2), the heating rate of the reaction system is not less than 20° C. / h, thereby achieving the purpose of accelerating the acetal reaction kinetics.

4. The method for controlling the molecular sequence distribution of polyvinyl acetal according to claim 1, characterized in that: In step (2), the heat preservation and aging is to continue the constant temperature reaction for 0.5 to 2 hours after the reaction system reaches the target temperature.

5. The method for controlling the molecular sequence distribution of polyvinyl acetal according to claim 1, characterized in that: In step (4), the alcohol includes at least one of methanol, ethanol, propanol, butanol, isobutanol, propylene glycol, n-butanol and n-octanol.

6. A polyvinyl acetal resin prepared by the method according to any one of claims 1 to 5.

7. The polyvinyl acetal resin according to claim 6, characterized in that: The hydroxyl value of the polyvinyl acetal resin is 17-20 wt %, the c / i ratio of the VA structural unit is in the range of 0.6-1.1, and the initial degradation temperature of the polyvinyl acetal resin is greater than 300° C.

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