JP5677794B2 - Production method of polyvinyl acetal and polyvinyl acetal - Google Patents

Description

The present invention relates to a method for producing a polyvinyl acetal that can produce a polyvinyl acetal having a low polymerization degree with little reaction inhibition and particle coarsening. Moreover, this invention relates to the polyvinyl acetal manufactured using the manufacturing method of this polyvinyl acetal.

Polyvinyl acetal typified by polyvinyl butyral is used for various purposes in interlayer films for laminated glass, wash primer for metal treatment, various paints, adhesives, resin processing agents, ceramic binders, etc. Is expanding. The reason why polyvinyl acetal is used in various ways is that the characteristics of the resin can be adjusted by controlling the degree of polymerization and the degree of acetalization.

Generally, as disclosed in Patent Document 1, polyvinyl acetal is produced by dehydrating and condensing polyvinyl alcohol and an aldehyde compound in the presence of an acid catalyst such as hydrochloric acid. The degree of polymerization of the polyvinyl acetal thus produced is substantially determined by the degree of polymerization of the starting polyvinyl alcohol. Therefore, in order to control the properties of the polyvinyl acetal, it is necessary to prepare a raw material polyvinyl alcohol that has been accurately adjusted so as to have the same degree of polymerization with respect to the target polyvinyl acetal.

In general, polyvinyl alcohol is produced by saponifying polyvinyl acetate solution polymerized in methanol. However, polyvinyl alcohol produced by a known method is low-polymerization having a degree of polymerization of 300 or less, because of the problem of productivity and quality, those that can be produced industrially are limited to those having a degree of polymerization exceeding 300. It is difficult to obtain a degree of polyvinyl acetal. As a method for obtaining polyvinyl alcohol having a low degree of polymerization, Patent Document 2 discloses a method using a solvent having a high chain transfer constant for the polymerization of vinyl acetate, and Patent Document 3 discloses a method in which a chain transfer agent is used before and after polymerization. A method of polymerizing vinyl acetate while being fed into is disclosed. However, these methods have problems in production such that it is necessary to replace the solvent at the time of saponification and it is necessary to recover the remaining chain transfer agent. Patent Document 4 discloses a method in which polyvinyl alcohol is subjected to main chain cleavage using an oxidizing agent such as hydrogen peroxide and reduced to reduce the degree of polymerization. However, in the polyvinyl alcohol whose degree of polymerization has been reduced by the method disclosed in Patent Document 4, the polyvinyl acetal obtained after acetalization has a low degree of acetalization due to reaction inhibition, or the polyvinyl acetal particles are coarsened. There was a problem to do.

Japanese Patent Laid-Open No. 6-1853 JP 63-278911 A JP-A-57-28121 JP 2007-269881 A

An object of this invention is to provide the manufacturing method of the polyvinyl acetal which can manufacture the polyvinyl acetal with a low polymerization degree, hardly causing reaction inhibition and particle coarsening. Moreover, an object of this invention is to provide the polyvinyl acetal manufactured using the manufacturing method of this polyvinyl acetal.

The present invention includes a step 1 in which polyvinyl alcohol is brought into contact with hydrogen peroxide in an acidic solution containing a transition metal ion to lower the degree of polymerization, and the polyvinyl alcohol having a lower degree of polymerization in step 1 above is converted into an acid catalyst. by reaction aldehyde in the presence have a step 2 of acetalization, the transition metal ion concentration of the acidic solution containing the transition metal ions is 0.01 to 10 mmol / L, containing the transition metal ions It is a manufacturing method of the polyvinyl acetal whose pH of an acidic solution is 0.3-4 .
The present invention is described in detail below.

In the production method of polyvinyl acetal in which polyvinyl alcohol is reacted with aldehyde in the presence of an acid catalyst in the presence of an acid catalyst, the present inventors peroxidize in an acidic solution containing transition metal ions as polyvinyl alcohol to be reacted with aldehyde. By using polyvinyl alcohol having a reduced degree of polymerization by contacting with hydrogen, it was found that a polyvinyl acetal having a low degree of polymerization could be produced with little reaction inhibition and particle coarsening, and the present invention was completed. I came to let you.

The manufacturing method of the polyvinyl acetal of this invention has the process 1 which makes polyvinyl alcohol contact with hydrogen peroxide in the acidic solution containing a transition metal ion, and reduces a polymerization degree.

The polyvinyl alcohol is not particularly limited, for example, vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl laurate, vinyl stearate, vinyl benzoate, etc. Conventionally known polyvinyl alcohol such as a resin produced by alkali or acid saponification of a polyvinyl ester obtained by polymerization by a bulk polymerization method, a suspension polymerization method, an emulsion polymerization method or the like can be used.
The polyvinyl alcohol may be completely saponified, but it need not be completely saponified if at least one unit having a double hydroxyl group with respect to the meso and racemic positions in at least one position of the main chain, Partially saponified polyvinyl alcohol may be used. Further, as the polyvinyl alcohol, a saponified product of a copolymer of a vinyl ester and a monomer copolymerizable with a vinyl ester such as an ethylene-vinyl alcohol copolymer or a partially saponified ethylene-vinyl alcohol copolymer may be used. it can.
In addition, the minimum with a preferable polymerization degree of the said polyvinyl alcohol is 200, a preferable upper limit is 4000, a more preferable minimum is 300, and a more preferable upper limit is 3000.

In the above step 1, the preferable lower limit of the concentration of polyvinyl alcohol in the acidic solution when the polyvinyl alcohol is brought into contact with hydrogen peroxide is 1% by weight, and the preferable upper limit is 25% by weight. When the concentration of the polyvinyl alcohol in the acidic solution in Step 1 is less than 1% by weight, the reaction efficiency when the obtained polyvinyl alcohol is acetalized in Step 2 may deteriorate. If the concentration of the polyvinyl alcohol in the acidic solution in Step 1 exceeds 25% by weight, the viscosity of the solution becomes so high that it is difficult to stir and the degree of polymerization cannot be uniformly reduced. The more preferable lower limit of the concentration of polyvinyl alcohol in the acidic solution in Step 1 is 3% by weight, the more preferable upper limit is 20% by weight, the still more preferable lower limit is 5% by weight, and the more preferable upper limit is 17% by weight.

In the step 1, the acidic substance used in the acidic solution is not particularly limited. For example, hydrogen halides such as hydrochloric acid, mineral acids such as nitric acid and sulfuric acid, carboxylic acids such as formic acid, acetic acid and propionic acid, and methane Examples thereof include sulfonic acids such as sulfonic acid, ethanesulfonic acid, benzenesulfonic acid, and paratoluenesulfonic acid, and phosphoric acid. These acid substances may be used alone or in combination of two or more compounds. Of these, hydrochloric acid, nitric acid, and sulfuric acid are preferable, and hydrochloric acid is more preferable.

The preferable lower limit of the pH of the acidic solution is 0.3, and the preferable upper limit is 4. If the pH of the acidic solution is less than 0.3, the polyvinyl acetal obtained in Step 2 contains a large amount of ionic components, which may adversely affect the solubility in a solvent. Moreover, in order to adjust pH in the process 2, it may be necessary to neutralize using an alkali neutralizer, which may lead to an increase in cost. When the pH of the acidic solution exceeds 4, the degree of polymerization of polyvinyl alcohol does not progress and the desired degree of polymerization of polyvinyl acetal may not be obtained. The more preferable lower limit of the pH of the acidic solution is 1, and the more preferable upper limit is 3.

The transition metal ion functions as a catalyst for efficiently advancing the degree of polymerization of polyvinyl alcohol, and exhibits an effect only by adding a trace amount.
The transition metal ion is not particularly limited, but is preferably an iron ion and / or a copper ion, selected from the group consisting of a divalent iron ion, a trivalent iron ion, a monovalent copper ion, and a divalent copper ion. It is more preferable that it is at least one kind.

The preferable lower limit of the transition metal ion concentration in the acidic solution is 0.01 mmol / L, and the preferable upper limit is 10 mmol / L. When the transition metal ion concentration is less than 0.01 mmol / L, the degree of polymerization of polyvinyl alcohol does not progress and the desired degree of polymerization of polyvinyl acetal may not be obtained. When the transition metal ion concentration exceeds 10 mmol / L, the polyvinyl acetal obtained in Step 2 contains a large amount of ionic components, which may adversely affect the solubility in a solvent. The more preferable lower limit of the transition metal ion concentration is 0.03 mmol / L, the more preferable upper limit is 5 mmol / L, the still more preferable lower limit is 0.05 mmol / L, and the still more preferable upper limit is 2 mmol / L.

The solvent contained in the acidic solution is not particularly limited as long as it dissolves polyvinyl alcohol. However, in order to eliminate the need for solvent substitution when acetalizing the resulting reduced-polymerized polyvinyl alcohol in step 2, the acetal is used. It is preferable to use the same solvent as the solvent for the chemical conversion. Specifically, an aqueous solvent is preferably used.

The amount of hydrogen peroxide added can be changed according to the polyvinyl acetal raw material to be used and the degree of polymerization of the target polyvinyl acetal, and the degree of polymerization of the polyvinyl alcohol obtained thereby can be arbitrarily changed. Moreover, the addition method of hydrogen peroxide may be added all at once at the initial stage of the reaction, may be dividedly added as the reaction proceeds, or may be added while continuously dropping.

In the step 1, a preferable lower limit of the temperature when the polyvinyl alcohol is brought into contact with the hydrogen peroxide is 30 ° C., and a preferable upper limit is 100 ° C. If the temperature at which the polyvinyl alcohol is brought into contact with the hydrogen peroxide is less than 30 ° C., it may take a long time to reduce the degree of polymerization of the polyvinyl alcohol. When the temperature at which the polyvinyl alcohol is brought into contact with the hydrogen peroxide exceeds 100 ° C., the solvent volatilizes and undissolved polyvinyl acetal is generated in Step 2, and the solubility of the resulting polyvinyl acetal in the solvent is adversely affected. May appear. A more preferable lower limit of the temperature at which the polyvinyl alcohol is brought into contact with the hydrogen peroxide is 40 ° C., and a more preferable upper limit is 95 ° C.

In Step 1, the time for which the polyvinyl alcohol is brought into contact with hydrogen peroxide can be changed according to the degree of polymerization of the target polyvinyl acetal. Polyvinyl alcohol having a degree of polymerization can be obtained.

The method for producing a polyvinyl acetal of the present invention includes a step 2 in which the polyvinyl alcohol having a reduced degree of polymerization in the step 1 is reacted with an aldehyde in the presence of an acid catalyst to acetalize.

In the above step 2, a conventionally known method can be used as a method for obtaining polyvinyl acetal by reacting the polyvinyl alcohol having a reduced degree of polymerization with an aldehyde in the presence of an acid catalyst to acetalize. For example, when polyvinyl butyral is obtained, an aqueous solution containing 1 to 25% by weight of polyvinyl alcohol having a degree of polymerization reduced by hydrogen peroxide is prepared, and an acid catalyst and butyraldehyde are contacted at a temperature range of -5 to 30 ° C. The reaction is allowed to proceed for 20 minutes to 6 hours, after which the temperature is raised by 10 to 50 ° C. and further aged for 30 minutes to 5 hours to complete the reaction, and preferably after passing through a cooling step, the precipitated polyvinyl butyral The method of washing | cleaning is mentioned.

In step 2, the hydrogen peroxide concentration of the system when the polyvinyl alcohol having a reduced polymerization degree is reacted with an aldehyde is preferably 0.1 mol / L or less. When the hydrogen peroxide concentration exceeds 0.1 mol / L, the acetalization is inhibited by the aldehyde forming an adduct with hydrogen peroxide before the polyvinyl alcohol reacts with the aldehyde, and the resulting polyvinyl is obtained. The degree of acetalization of the acetal may be low, or the shape of the generated polyvinyl acetal may not be obtained in a powder form and become coarse particles, which may not be sufficiently washed and dried, which may adversely affect quality.

As a method of setting the hydrogen peroxide concentration of the system when reacting the low-polymerization degree polyvinyl alcohol with an aldehyde to 0.1 mol / L or less, the amount of hydrogen peroxide added in the above step 1, By adjusting the time and the temperature of step 1 as appropriate, the conditions of step 1 may be set so that hydrogen peroxide is consumed by lowering the degree of polymerization of polyvinyl alcohol and the above concentration range is reached. If the hydrogen peroxide concentration exceeds 0.1 mol / L at the stage of transition from step 1 to step 2, a compound that promotes the decomposition of hydrogen peroxide is added to adjust the hydrogen peroxide concentration. The hydrogen peroxide concentration can be adjusted within the above range also by the method of adjusting the hydrogen peroxide concentration by adding a compound that causes a redox reaction with hydrogen peroxide.
Examples of the compound that promotes the decomposition of hydrogen peroxide include manganese dioxide and catalase. Examples of the compound that causes an oxidation-reduction reaction with hydrogen peroxide include potassium permanganate and potassium dichromate.

The acid catalyst is not particularly limited, hydrogen halide such as hydrochloric acid, mineral acid such as nitric acid and sulfuric acid, carboxylic acid such as formic acid, acetic acid and propionic acid, methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, Examples thereof include sulfonic acids such as paratoluenesulfonic acid, phosphoric acid and the like. These acid catalysts may be used alone or in combination of two or more compounds. Of these, hydrochloric acid, nitric acid, and sulfuric acid are preferable, and hydrochloric acid is more preferable.

Examples of the aldehyde include linear, branched, cyclic saturated, cyclic unsaturated, or aromatic aldehydes having 1 to 19 carbon atoms. Specific examples include formaldehyde, acetaldehyde, propionyl aldehyde, n-butyraldehyde, isobutyraldehyde, tert-butyraldehyde, benzaldehyde, cyclohexyl aldehyde and the like. The aldehyde may be used alone or in combination of two or more. The aldehyde may be one obtained by substituting one or more hydrogen atoms with halogen or the like except formaldehyde.

The degree of acetalization of the polyvinyl acetal obtained in the step 2 can be adjusted by appropriately changing the blending amount of the aldehyde with respect to the polyvinyl alcohol.

By using the method for producing polyvinyl acetal of the present invention, a polyvinyl acetal having a low degree of polymerization and a high degree of acetalization can be obtained without coarsening the particles. Polyvinyl acetal thus produced is also one aspect of the present invention.

ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the polyvinyl acetal which can manufacture the polyvinyl acetal with a low polymerization degree hardly causes reaction inhibition and particle coarsening can be provided. Moreover, according to this invention, the polyvinyl acetal manufactured using the manufacturing method of this polyvinyl acetal can be provided.

Hereinafter, embodiments of the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

Example 1
Polyvinyl alcohol A (saponification degree 99%, polymerization degree 2000) 100 g and ion exchange water 860 g were heated and stirred at 150 rpm in a 2 L separable flask at 95 ° C. for 1 hour to obtain a polyvinyl alcohol aqueous solution. Next, the temperature was adjusted to 60 ° C. with stirring, hydrochloric acid was added to adjust the pH to 1.3, and iron (II) chloride was added so that the divalent iron ion concentration was 0.2 mmol / L. Next, 25 g of 35% by weight hydrogen peroxide water was added and reacted for 1 hour to obtain a polyvinyl alcohol having a reduced degree of polymerization.
After cooling the obtained polyvinyl alcohol aqueous solution to 5 ° C. over 60 minutes, 110 g of 25 wt% hydrochloric acid and 62 g of butyraldehyde were added and acetalized for 180 minutes. Thereafter, the temperature was raised to 40 ° C. over 60 minutes, and the reaction was further continued at that temperature for 120 minutes. After cooling to room temperature, the precipitated resin was collected by filtration, and the resin content was washed with ion-exchanged water. Next, the obtained resin was washed with an aqueous sodium carbonate solution, then washed again with water and dried to obtain polyvinyl butyral. Table 1 shows the hydrogen peroxide concentration in the solution when the aldehyde was added.

(Example 2)
Polyvinyl butyral was obtained in the same manner as in Example 1 except that polyvinyl alcohol B (degree of saponification 99%, degree of polymerization 3000) was used instead of polyvinyl alcohol A. Table 1 shows the hydrogen peroxide concentration in the solution when the aldehyde was added.

Example 3
Polyvinyl butyral was obtained in the same manner as in Example 1 except that copper (I) chloride was added instead of iron (II) chloride so that the monovalent copper ion concentration was 0.2 mmol / L. Table 1 shows the hydrogen peroxide concentration in the solution when the aldehyde was added.

Example 4
Polyvinyl butyral was obtained in the same manner as in Example 1 except that the divalent iron ion concentration in the solution for reducing the degree of polymerization of polyvinyl alcohol was changed to 10 mmol / L. Table 1 shows the hydrogen peroxide concentration in the solution when the aldehyde was added.

(Example 5)
Example except that the divalent iron ion concentration in the solution when reducing the degree of polymerization of polyvinyl alcohol was changed to 0.01 mmol / L, and the reaction time after adding hydrogen peroxide was 3 hours In the same manner as in 1, polyvinyl butyral was obtained. Table 1 shows the hydrogen peroxide concentration in the solution when the aldehyde was added.

(Example 6)
The pH of the solution for reducing the degree of polymerization of polyvinyl alcohol was changed to 0.3, the divalent iron ion concentration was changed to 10 mmol / L, and the reaction time after adding hydrogen peroxide was 3 hours. Except that, polyvinyl butyral was obtained in the same manner as in Example 1. Table 1 shows the hydrogen peroxide concentration in the solution when the aldehyde was added.

(Example 7)
The pH of the solution for reducing the degree of polymerization of polyvinyl alcohol was changed to 3, the divalent iron ion concentration was changed to 10 mmol / L, and the reaction time after adding hydrogen peroxide was 3 hours. Except for the above, polyvinyl butyral was obtained in the same manner as in Example 1. Table 1 shows the hydrogen peroxide concentration in the solution when the aldehyde was added.

(Example 8)
The pH of the solution for reducing the degree of polymerization of polyvinyl alcohol was changed to 3.5, the divalent iron ion concentration was changed to 15 mmol / L, and the reaction time after adding hydrogen peroxide was 3 hours. Except that, polyvinyl butyral was obtained in the same manner as in Example 1. Table 1 shows the hydrogen peroxide concentration in the solution when the aldehyde was added.

Example 9
Example except that the divalent iron ion concentration in the solution when reducing the degree of polymerization of polyvinyl alcohol was changed to 0.005 mmol / L, and the reaction time after addition of hydrogen peroxide was 3 hours In the same manner as in 1, polyvinyl butyral was obtained. Table 1 shows the hydrogen peroxide concentration in the solution when the aldehyde was added.

(Example 10)
The pH of the solution for reducing the degree of polymerization of polyvinyl alcohol was changed to 0.2, the divalent iron ion concentration was changed to 10 mmol / L, and the reaction time after adding hydrogen peroxide was 3 hours. Except that, polyvinyl butyral was obtained in the same manner as in Example 1. Table 1 shows the hydrogen peroxide concentration in the solution when the aldehyde was added.

(Comparative Example 1)
Polyvinyl butyral was obtained in the same manner as in Example 1 except that hydrogen peroxide was not added. Table 1 shows the hydrogen peroxide concentration in the solution when the aldehyde was added.

(Comparative Example 2)
Polyvinyl butyral was obtained in the same manner as in Example 1 except that hydrochloric acid was not added to lower the degree of polymerization of polyvinyl alcohol and the acidic condition was not used (pH 7). Table 1 shows the hydrogen peroxide concentration in the solution when the aldehyde was added.

(Comparative Example 3)
Polyvinyl butyral was obtained in the same manner as in Example 1 except that iron (II) chloride was not added when reducing the degree of polymerization of polyvinyl alcohol. Table 1 shows the hydrogen peroxide concentration in the solution when the aldehyde was added.

<Evaluation>
The following evaluation was performed about the polyvinyl butyral manufactured by the Example and the comparative example. The results are shown in Table 1.

(1) Degree of polymerization 2 g of polyvinyl butyral obtained in 25 g of ethanol was added, then 10 ml of a solution of 15 g of hydroxylamine hydrochloride dissolved in 100 g of ion-exchanged water and 5 ml of hydrochloric acid were added and heated in a boiling water bath for 3 hours. After cooling, neutralized with ammonia water, methanol was added to precipitate the resin, and the resin washed with methanol and then dried was dissolved in 100 g of water by heating. The degree of polymerization of the obtained solution was measured according to JIS K6726. Moreover, it evaluated also about the numerical value (polymerization degree fall rate) which remove | divided the polymerization degree of the obtained polyvinyl butyral by the polymerization degree of the polyvinyl alcohol before low polymerization degree.

(2) Degree of butyralization The obtained polyvinyl butyral was dissolved in deuterated dimethyl sulfoxide, and the degree of butyralization was measured by ¹ H-NMR measurement.

(3) Resin Particle Shape The obtained polyvinyl butyral particle shape was evaluated through a sieve having an opening of 1 mm. The case where almost all the resin dropped from the sieve was evaluated as “◯”, the case where it dropped about half was “Δ”, and the case where almost no resin was dropped was evaluated as “×”.

ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the polyvinyl acetal which can manufacture the polyvinyl acetal with a low polymerization degree hardly causes reaction inhibition and particle coarsening can be provided. Moreover, according to this invention, the polyvinyl acetal manufactured using the manufacturing method of this polyvinyl acetal can be provided.

Claims (6)

Step 1 for reducing the degree of polymerization by contacting polyvinyl alcohol with hydrogen peroxide in an acidic solution containing a transition metal ion, and
The step 2 comprises reacting the polyvinyl alcohol having a reduced degree of polymerization in the step 1 with an aldehyde in the presence of an acid catalyst to form an acetal;
The transition metal ion concentration of the acidic solution containing the transition metal ion is 0.01 to 10 mmol / L,
The method for producing polyvinyl acetal, wherein the acidic solution containing the transition metal ion has a pH of 0.3 to 4. The method for producing a polyvinyl acetal according to claim 1, wherein the transition metal ion contains an iron ion and / or a copper ion. The transition metal ion includes at least one selected from the group consisting of a divalent iron ion, a trivalent iron ion, a monovalent copper ion, and a divalent copper ion. 2. The method for producing polyvinyl acetal according to 2. The method for producing a polyvinyl acetal according to claim 1, 2, or 3, wherein the acidic solution containing the transition metal ion has a pH of 0.3 to 3. The process for producing a polyvinyl acetal according to claim 1, 2, 3 or 4, wherein in step 1, the degree of polymerization of polyvinyl alcohol is reduced together with the dissolution of polyvinyl alcohol. 6. The polyvinyl acetal according to claim 1, wherein the concentration of hydrogen peroxide in the system when the polyvinyl alcohol and the aldehyde are contacted in Step 2 is 0.1 mol / L or less. Production method.