JP2008050412A - Method for producing polyvinyl acetal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a polyvinyl acetal having unsaturated double bonds derived from a specific monomer in the intramolecular main chain. <P>SOLUTION: The method for producing the polyvinyl acetal comprises the following process. A closed reaction vessel is continuously fed with a modified polyvinyl alcohol containing in the main chain bond units having a specific unsaturated double bond each, an aldehyde and an acid catalyst to make an acetalization reaction proceed, and following reaching at least 10 mol% in the degree of acetalization of the resulting polyvinyl acetal, the polyvinyl acetal is continuously unloaded from the reaction vessel. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a method for producing a polyvinyl acetal having a double bond derived from a specific monomer in the main chain, and a polyvinyl acetal obtained by the production method.

Polyvinyl acetal is used in various applications such as paints, adhesives, binders and molded articles. This polyvinyl acetal is obtained by reacting polyvinyl alcohol and aldehyde in an aqueous solution in the presence of an acid catalyst, neutralizing the resulting polyvinyl acetal resin slurry with alkali, dehydrating, washing, and drying to obtain a powdery granular form. For example, a method of performing acetalization reaction and precipitation under high stirring mixing (for example, see Patent Document 1), a method using a loop reactor (for example, see Patent Document 2), and slurry into a powder A method of precipitation and purification by electrodialysis (for example, see Patent Document 3) is known.
JP-A-11-349629 JP 05-059117 A Japanese Patent Laid-Open No. 12-038456

This invention makes it a subject to provide the manufacturing method of the polyvinyl acetal which has the unsaturated double bond derived from a specific monomer in the principal chain in a molecule | numerator.

The above-mentioned problem can be solved by acetalizing a specific modified polyvinyl alcohol.

（式中、Ｘ１とＸ２は、炭素数１〜１２の低級アルキル基、水素原子または金属塩を表す。ｇは、０〜３の整数を表す。ｈは、０〜１２の整数を表す。Ｙ１は、カルボン酸、カルボン酸エステル、カルボン酸金属塩または水素原子を表す。） That is, in the present invention, a modified polyvinyl alcohol containing a bond unit represented by the general formula (Chemical Formula 2), an aldehyde, and an acid catalyst are continuously fed into a closed reactor in a molecular main chain. A step of continuously advancing the acetalization reaction and discharging the polyvinyl acetal from the inside of the sealed reactor after the degree of acetalization of the produced polyvinyl acetal reaches at least 10 mol%. It is a manufacturing method. The polyvinyl acetal continuously discharged from the closed reactor was further aged in another reactor, and after the polyvinyl acetal degree of acetalization reached at least 60 mol%, the polyvinyl acetal was neutralized, washed with water, It is preferable to have the process of dehydrating and drying, and it is preferable that the reaction temperature in a closed reactor is the range of 20-50 degreeC. The content of unmodified polyvinyl alcohol in the modified polyvinyl alcohol is preferably 25 mol% or less, and the modified polyvinyl alcohol contains a monomer having an ethylenically unsaturated double bond and a monomer having a vinyl ester unit. It is preferably obtained by polymerization and saponification, and the modified polyvinyl alcohol preferably further contains a bond unit having an anionic group, and the content of the bond unit having an anionic group is modified. It is preferable that it is the range of 0.05-10 mol% in polyvinyl alcohol.

(In formula, X1 and X2 represent a C1-C12 lower alkyl group, a hydrogen atom, or a metal salt. G represents the integer of 0-3. H represents the integer of 0-12. Y1. Represents a carboxylic acid, a carboxylic acid ester, a carboxylic acid metal salt or a hydrogen atom.)

A polyvinyl acetal having an unsaturated double bond derived from a specific monomer in the main chain in the molecule is obtained.

The modified polyvinyl alcohol is obtained by copolymerizing a monomer having an ethylenically unsaturated double bond and a monomer having a vinyl ester unit, followed by saponification to obtain a carbonyl group-containing polyvinyl alcohol, washing and drying. In this case, an unsaturated double bond starting from a carboxyl group is randomly introduced into the main chain.

The monomer having an ethylenically unsaturated double bond is not particularly limited. For example, dimethyl maleate, diethyl maleate, dimethyl fumarate, monoethyl fumarate, diethyl fumarate, dimethyl citraconic acid, maleic anhydride And citraconic anhydride.

The content (copolymerization amount) of these monomers is not particularly limited, but in the range of 0.1 to 50 mol% in the modified polyvinyl alcohol, more preferably 0.1 to 10 mol%, The resulting modified polyvinyl alcohol is preferred because the balance between the amount of unsaturated double bonds in the molecule and the water solubility is improved.

The monomer having a vinyl ester unit is not particularly limited. For example, vinyl formate, vinyl acetate, vinyl propionate, vinyl valelate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, and pivalin. Examples include vinyl acid vinyl and versatic acid vinyl. Among these, it is preferable to use vinyl acetate because polymerization of the modified polyvinyl alcohol can be performed stably.

The content of unmodified polyvinyl alcohol in the modified polyvinyl alcohol is not particularly limited, but if it is in the range of 25 mol% or less, the content ratio of unsaturated double bonds is improved and the properties derived from double bonds are improved. It is preferable because it improves. The content of unmodified polyvinyl alcohol may be 0 mol%. The content of unmodified polyvinyl alcohol can be adjusted by changing the ratio of the monomer having an ethylenically unsaturated double bond to be polymerized and the monomer having a vinyl ester unit. To reduce the content of unmodified polyvinyl alcohol, the proportion of monomers having vinyl ester units should be increased. To increase the content of unmodified polyvinyl alcohol, the proportion of monomers having ethylenically unsaturated double bonds Should be reduced.

Modified polyvinyl alcohol is preferable because the activity of the resulting dispersant is improved by including a binding unit having an anionic group in the molecule.

In order to contain a bond unit having an anionic group in the molecule, it is not particularly limited, but a method of copolymerizing a monomer having an anionic group when polymerizing a modified polyvinyl alcohol, or a hydroxyl group in polyvinyl alcohol. There is a method of post-denaturation utilizing the reactivity with.

When the content of the binding unit having an anionic group in the molecule is in the range of 0.05 to 10 mol% in the modified polyvinyl alcohol, the dispersibility of the resulting dispersant itself in a solvent is improved, A range of 0.1 to 3 mol% is more preferable.

Although it does not specifically limit as a monomer which has an anionic group, For example, there exist a carboxylic acid group containing vinyl monomer, a sulfonic acid group containing vinyl monomer, etc., and a carboxylic acid group containing vinyl monomer is used. It is preferable because it is easy to handle.
Examples of the carboxylic acid group-containing vinyl monomer include polymerizable monocarboxylic acids such as (meth) acrylic acid, crotonic acid and isocrotonic acid and esters thereof, polymerizable dicarboxylic acids such as maleic acid, fumaric acid and itaconic acid, Examples thereof include polymerizable dicarboxylic acid anhydrides such as maleic anhydride, and aliphatic vinyl esters. Among these, itaconic acid is preferable because the dispersibility of the resulting dispersant itself in a solvent is further improved.
Examples of the sulfonic acid group-containing vinyl monomer include olefin sulfonic acids such as ethylene sulfonic acid and allyl sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, 2-acrylamido-1-methylsulfonic acid, and 2-methacrylic acid. Amido-2-methylpropanesulfonic acid and the like.

If necessary, the modified polyvinyl alcohol may be copolymerized with a monomer copolymerizable with these monomers. The copolymerizable monomer is not particularly limited, but examples thereof include olefins such as ethylene, propylene, 1-butene and isobutene, acrylic acid, methacrylic acid, crotonic acid, phthalic acid, maleic acid, itaconic acid and the like. Unsaturated acids, or salts thereof, monoalkyl esters or dialkyl esters having 1 to 18 carbon atoms, acrylamide, N-alkyl acrylamides having 1 to 18 carbon atoms, N, N-dialkyl acrylamides, diacetone acrylamides, 2 Acrylamides such as acrylamidopropanesulfonic acid and its salts, acrylamidopropyldimethylamine and its salts or quaternary salts thereof, methacrylamide, N-alkylmethacrylamide having 1 to 18 carbon atoms, N, N-dialkylmethacrylamide, di Methacrylamides such as seton methacrylamide, 2-methacrylamide propanesulfonic acid and salts thereof, methacrylamide propyldimethylamine and salts thereof or quaternary salts thereof, alkyl vinyl ethers having an alkyl chain length of 1 to 18 carbon atoms, hydroxyalkyl Vinyl ethers such as vinyl ether and alkoxyalkyl vinyl ether, N-vinyl amides such as N-vinyl pyrrolidone, N-vinyl formamide and N-vinyl acetamide, vinyl cyanides such as acrylonitrile and methacrylonitrile, vinyl chloride, vinylidene chloride, fluorine Vinyl halides such as vinyl chloride, vinylidene fluoride, vinyl bromide, vinylidene bromide, vinyl silanes such as trimethoxyvinyl silane, allyl acetate, allyl chloride, allyl alcohol Allyl compounds such as dimethyl allyl alcohol, vinyl silyl compounds such as vinyltrimethoxysilane, there is isopropenyl acetate and the like, may be used in combination of two or more.
Although the usage-amount of these copolymerizable monomers is not specifically limited, 0.001-20 mol% is preferable with respect to all the monomers to be used.

The number average molecular weight (hereinafter abbreviated as Mn) of the modified polyvinyl alcohol is not particularly limited, but is generally in the range of 1900 to 66500, and in the range of 3800 to 28500, it is water-soluble and protective colloid. This is preferable because the balance of properties is improved.

As the monomer polymerization method, known polymerization methods such as bulk polymerization, emulsion polymerization, suspension polymerization, and solution polymerization are used, and are not particularly limited, but a solution using an alcohol such as methanol, ethanol, or isopropyl alcohol as a solvent. It is preferable to employ polymerization because the polymerization can be easily controlled. The solution polymerization may be continuous polymerization or batch polymerization, and the monomer to be polymerized may be charged separately, may be charged all at once, or any means such as adding continuously or intermittently can be used. .

The polymerization initiator used in the solution polymerization may be a known radical polymerization initiator, and is not particularly limited. For example, azobisisobutyronitrile, azobis-2,4-dimethylpareronitrile Azo compounds such as azobis (4-methoxy-2,4-dimethylpareronitrile), acetyl peroxide, benzoyl peroxide, lauroyl peroxide, acetylcyclohexylsulfonyl peroxide, 2,4,4-trimethylpentyl-2- Peroxides such as peroxyphenoxyacetate, diisopropyl ether peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, percarbonate compounds such as diethoxyethyl peroxydicarbonate, t-butyl peroxyneodecanate, α-cumylpao Shineodekaneto, perester compounds such as t- butyl peroxyneodecanoate, azobisdimethylvaleronitrile, and the like azo-bis-methoxy valeronitrile. The polymerization reaction temperature is usually selected from the range of about 30 ° C to 90 ° C.

In saponification, a copolymer obtained by copolymerizing monomers is dissolved in alcohol, and an ester in the molecule is hydrolyzed in the presence of an alkali catalyst or an acid catalyst. Examples of the alcohol include methanol, ethanol, butanol and the like. The concentration of the copolymer in the alcohol is not particularly limited, but is selected from a range of 10 to 80% by weight.
As the alkali catalyst, for example, an alkali catalyst such as an alkali metal hydroxide or alcoholate such as sodium hydroxide, potassium hydroxide, sodium methylate, sodium ethylate, potassium methylate or the like can be used.
As the acid catalyst, for example, an inorganic acid aqueous solution such as hydrochloric acid or sulfuric acid, or an organic acid such as p-toluenesulfonic acid can be used.
These catalysts are preferably used in an amount of 1 to 100 mmol equivalents relative to the copolymer. The saponification temperature is not particularly limited, but is in the range of 10 to 70 ° C, preferably 30 to 40 ° C. Although reaction time is not specifically limited, It is performed over 30 minutes-3 hours.

The degree of saponification of the modified polyvinyl alcohol is not particularly limited, but a range of 30 to 99.9 mol% is preferable because a sufficient amount of unsaturated double bonds are generated in the molecule.

  As the aldehyde, an aldehyde used for the synthesis of ordinary polyvinyl acetal can be used, and is not particularly limited. For example, formaldehyde, acetaldehyde, propionaldehyde, n-butyraldehyde, t-butyraldehyde, amylaldehyde, hexyl Examples thereof include aliphatic aldehydes such as aldehyde and 2-ethylhexyl aldehyde, alicyclic aldehydes such as cyclohexyl aldehyde and furfural, aromatic aldehydes such as benzaldehyde, alkyl-substituted benzaldehyde, halogen-substituted benzaldehyde, and phenyl-substituted alkyl aldehyde. Among these, acetaldehyde and butyraldehyde are preferably used because they are easy to handle. These aldehydes may be used alone or in combination of two or more.

  The acid catalyst is not particularly limited, and examples thereof include hydrochloric acid, phosphoric acid, sulfuric acid, citric acid, and paratoluenesulfonic acid. These acid catalysts may be used alone or in combination of two or more. May be used in combination. In general, it is preferable to add these acid catalysts after adjusting the pH of the reaction solution to be 0.3 to 2.0.

Polyvinyl acetal is continuously supplied with modified polyvinyl alcohol, aldehyde and acid catalyst in a closed reactor to advance the acetalization reaction, and after the degree of acetalization reaches at least 10%, the polyvinyl acetal is continuously discharged. Then, after aging reaction in another reactor, it is obtained by neutralization, washing with water, dehydration and drying.

The reason why the reaction liquid is continuously discharged from the closed reactor in which the degree of acetalization has reached at least 10 mol% is to make the polyvinyl acetal obtained by aging porous. By making the polyvinyl acetal porous, it is possible to obtain a polyvinyl acetal having excellent metal component cleaning and removing properties.

  The raw material supply method is not particularly limited, but a method of supplying three types from separate supply ports, a modified polyvinyl alcohol and an acid catalyst are mixed in advance, a mixture of the modified polyvinyl alcohol and the acid catalyst, an aldehyde, A method of separately supplying from a supply port, a method of previously mixing a modified polyvinyl alcohol and an aldehyde, and supplying a mixture of the modified polyvinyl alcohol and aldehyde and an acid catalyst separately from the supply port can be employed. Among these supply methods, a method in which three types are supplied from separate supply ports, a modified polyvinyl alcohol and an acid catalyst are mixed in advance, and a mixture of modified polyvinyl alcohol and an acid catalyst and an aldehyde are separately supplied from the supply port. The method is preferable because the reaction control becomes easy.

  The method for discharging the polyvinyl acetal from the closed reactor is not particularly limited as long as it is continuously performed, but the method of introducing the raw material from the upper part of the reactor and continuously discharging from the lower part of the reactor, the reactor Feeding raw material from the upper part to the lower lower part of the reactor using an insertion tube and continuously discharging from the upper part of the reactor, supplying raw material from the lower part of the reactor, and continuously discharging from the upper part of the reactor, etc. Is a preferred method. Further, the method of filling the reactor with water in advance and then supplying the raw material is effective as a method for preventing air accumulation in the reactor. In these cases, the pipe part and the welded part of the reactor and the inner wall of the pipe should have a smooth surface finish so that the reaction product does not stagnate locally or macroscopically in the vicinity of the reactor outlet or in the discharge pipe. It is preferable to use it.

The closed reactor is preferably a tank reactor with a stirring mechanism or a tubular reactor because three kinds of raw materials can be reacted uniformly. As a stirring condition, it is preferable that the stirring power per unit volume is 0.4 kW / m ³ or more from the viewpoint of developing sufficient mixing and stirring.

  As the stirring blade used for stirring the reaction liquid in the closed reactor, a known blade can be used, and is not particularly limited. For example, three blades, paddle blades, anchor blades, Max blend blades, full zone There are wings. Among these, it is preferable to use a so-called large blade such as a Max blend blade or a full zone blade because the reaction solution can be sufficiently mixed.

  The reaction temperature of the acetalization reaction is not particularly limited, but it is preferable to carry out the reaction in the range of 10 to 60 ° C., preferably 20 to 50 ° C., because the obtained polyvinyl acetal becomes more porous.

  The reaction time of the acetalization reaction is selected for each reaction temperature condition so that the degree of acetalization is at least 10 mol% or more, preferably 15 mol% or more, more preferably 20 mol% or more. Although the time to reach the desired degree of acetalization varies depending on the reaction temperature, a range of 10 seconds to 7 minutes may be selected as a guide.

  The polyvinyl acetal discharged from the closed reactor is then transferred to another reactor for aging reaction. The reaction temperature for aging is not particularly limited, but is preferably in the range of room temperature to 90 ° C, preferably 30 to 70 ° C. The reaction time for aging is not particularly limited, but it is usually set within a range of 1 to 24 hours, preferably 1 to 10 hours until the acetalization reaction reaches a desired degree of acetalization. By this aging reaction, the degree of acetalization of polyvinyl acetal can be 60 mol% or more, preferably 65 mol% or more.

  The polyvinyl acetal thus obtained is acidic due to the use of an acid catalyst during the acetalization reaction. In order to neutralize this polyvinyl acetal, it is preferable to adjust the pH to 7 to 11 by adding an alkali neutralizing agent such as sodium hydroxide or sodium bicarbonate.

  Next, dehydration and water washing are repeated to remove metal components remaining in the voids and the surface of the granular material. In addition, the remaining acid catalyst and reaction residues such as aldehyde are also removed.

  Washing with water is performed at room temperature to 60 ° C. In general, the temperature is preferably 40 ° C. or higher. However, since the polyvinyl acetal obtained by the present invention has a large specific surface area, it has sufficient detergency even with water washing at room temperature.

  The drying method is not particularly limited, and for example, a known method such as a vacuum drying method or a hot air fluidized drying method can be employed.

  The obtained polyvinyl acetal can be appropriately selected and added with a plasticizer, a lubricant, a filler, a stabilizer and the like. As a method of blending the compounding agent, any method usually used in the resin processing field can be adopted. For example, a closed mixer such as a mixing roll or a kneader, an extruder having a kneading function, or the like can be used.

Hereinafter, the present invention will be described in more detail with reference to examples.
Unless otherwise specified, “parts” and “%” mean “parts by mass” and “mass%”.

Example 1
<Production of modified polyvinyl alcohol>
17 parts of vinyl acetate, 14 parts of methanol, 0.023 part of dimethyl maleate and 0.10% azobisisobutyronitrile with respect to vinyl acetate are charged into the polymerization vessel, heated after nitrogen substitution and heated to the boiling point. Furthermore, a mixed solution of 6 parts of vinyl acetate, 5 parts of methanol and 0.207 parts of dimethyl maleate was continuously added until a polymerization rate of 75% was reached, and the polymerization was carried out when the polymerization rate reached 90%. Stopped. Subsequently, unpolymerized vinyl acetate was removed by a conventional method, and the resulting polymer was saponified with sodium hydroxide by a conventional method. Thereafter, it was dried with hot air at 90 ° C. for 90 minutes, molecular weight (Mn) 11000, saponification degree 88.0 mol%, dimethyl maleate 0.6 mol%, 0.2% abs. A modified polyvinyl alcohol having a modified polyvinyl alcohol content of 13% was obtained.

<Analysis method>
The degree of saponification of the modified polyvinyl alcohol is measured according to JIS K 6276 “3.5 degree of saponification”. The molecular weight of the modified polyvinyl alcohol is GPC and the sample concentration is 0.25 w / v% aqueous solution. Is measured at 40 ° C., and Mn is calculated in terms of standard polyethylene glycol. The content of the unmodified polyvinyl alcohol was determined by completely saponifying the modified polyvinyl alcohol with an alkali catalyst in methanol, adjusting the Soxhlet-extracted sample to an aqueous solution of 0.01 w / v%, using ion exclusion HPLC, IR It is calculated by the area ratio of the detector. The absorbance at 270 nm is obtained by adjusting the absorbance of ultraviolet rays at 270 nm by adjusting the modified polyvinyl alcohol to a 0.2% by mass aqueous solution. The content of dimethyl maleate is measured by NMR.

  A 2 L cylindrical glass sealed reactor having three supply ports at the bottom and one discharge port at the top was filled with pure water, and the internal temperature was kept at 30 ° C. while stirring at 400 rpm with an anchor blade. .

In a closed reactor, 10% aqueous solution of modified polyvinyl alcohol, hydrochloric acid with a concentration of 35% as an acid catalyst, and butyraldehyde (purity 99.5%) as an aldehyde were prepared, and their supply rates were 60 kg / hr, 1.9 kg. / Hr and 4.5 kg / hr were fed from the bottom of the reactor, and the acetalization reaction was allowed to proceed while stirring. When the degree of acetalization of the produced polyvinyl acetal reaches 10 mol%, while adding a modified polyvinyl alcohol aqueous solution, hydrochloric acid, and butyraldehyde from the lower part of the reactor, a reaction liquid containing the polyvinyl acetal is simultaneously added from the upper part of the reactor. It was discharged.

  The discharged reaction liquid containing polyvinyl acetal (hereinafter often referred to as “slurry”) was sent to a separately prepared 10 L aging tank (transfer amount 5 kg), and then aged at 50 ° C. for 2 hours.

  The aging tank had a stirring blade with three retreating blades, and was aged while stirring the slurry at a stirring rotation speed of 250 rpm. At this time, the average residence time of the reactor was 2 minutes, the effluent from the closed reactor was sampled, the measured butyralization degree at the reactor outlet was 41 mol%, and after aging at 50 ° C. for 2 hours The degree of butyralization was 68 mol%.

  Next, an aqueous sodium hydroxide solution was added to the slurry to adjust the pH to 8.

  After the slurry was cooled to room temperature, the slurry was dehydrated to 45% by weight with a centrifuge, diluted by adding 10 times the amount of water to the resin, stirred for 30 minutes and washed with water.

  This dehydration and water washing operations were repeated three times, and the resulting slurry was dehydrated again and dried to obtain a white powdery polyvinyl butyral resin. The temperature of water used for washing was 25 ° C.

  The degree of butyralization of the obtained polyvinyl butyral resin was 68 mol%.

  The specific surface area per unit weight of the resin particle body measured using Shimadzu Corporation automatic porosimeter Autopore IV9500 was 2.6 m2 / g.

  The sodium element content in the resin measured by ICP luminescent element analysis was 20 ppm.

  The degree of butyralization of the reactant sampled at the reactor outlet, the degree of butyralization of the finally obtained polyvinyl butyral resin, the specific surface area, bulk density, particle size, and ICP of the resin particles measured with a porosimeter The results of the amount of sodium in the resin are summarized in Table 1.

(Example 2)
In Example 1, the temperature of the reactor was 20 ° C., and the other conditions were the same as in Example 1.

  The degree of butyralization of the slurry sampled at the reactor outlet was 19 mol%.

(Example 3)
In Example 1, the feed rate of the three raw materials to the reactor was doubled (that is, the average residence time was 1 minute), and the other conditions were the same as in Example 1.

  The degree of butyralization of the slurry sampled at the reactor outlet was 25 mol%.

Example 4
In Example 1, the method of feeding the three raw materials to the reactor was as follows, and the other conditions were the same as in Example 1.
A 10% aqueous solution of denatured polyvinyl alcohol and hydrochloric acid having a concentration of 35% were mixed in advance so as to obtain a predetermined ratio. This mixed solution and butyraldehyde were fed from two supply ports at the bottom of the reactor so that the amounts were 61.9 kg / hr and 4.5 kg / hr, respectively, and the degree of acetalization of the produced polyvinyl acetal was 10 mol%. After reaching, the slurry was discharged from the upper part of the reactor in parallel while adding the modified polyvinyl alcohol aqueous solution, hydrochloric acid and butyraldehyde from the lower part of the reactor.

  The degree of butyralization of the slurry sampled at the reactor outlet was 39 mol%.

(Example 5)
In Example 4, a mixed solution composed of a 10% aqueous solution of modified polyvinyl alcohol and hydrochloric acid having a concentration of 35% was passed through a nozzle inserted from the upper part of the reactor, and the lower part in the reactor (when the actual height of the reactor was H, The nozzle tip was set at a position of H / 5 from the bottom, and the slurry was discharged from the discharge port at the top of the reactor. The other conditions were the same as in Example 4.

  The degree of butyralization of the slurry sampled at the reactor outlet was 35 mol%.

(Example 6)
In Example 4, a mixture of 10% aqueous solution of modified polyvinyl alcohol and 35% hydrochloric acid and butyraldehyde were fed from two supply ports at the top of the reactor, and the slurry was discharged from the bottom of the reactor. The conditions were the same as in Example 4.

  The degree of butyralization of the slurry sampled at the reactor outlet was 37 mol%.

(Example 7)
In Example 4, a Max Blend blade (manufactured by Sumitomo Heavy Industries, Ltd., the ratio of the blade width to the reactor inner diameter is 0.55) was used as the stirring blade of the reactor, and other conditions were the same as in Example 4. Carried out.

  The degree of butyralization of the slurry sampled at the reactor outlet was 43 mol%.

(Example 8)
In Example 4, two paddle blades (the ratio of the blade width to the inner diameter of the reactor is 0.6) were used as the stirring blades of the reactor, the stirring rate was 120 rpm, and the other conditions were the same as in Example 4. Carried out.

  The degree of butyralization of the slurry sampled at the reactor outlet was 35 mol%.

(Comparative Example 1)
Although similar to Example 1, a glass reactor having an internal volume of 2 L without a supply port at the bottom of the reactor was prepared. A 10% aqueous solution of modified polyvinyl alcohol, hydrochloric acid and butyraldehyde having a concentration of 35% were prepared under conditions where the feed amount per unit time was the same ratio as in Example 1. With the stirring blades of the reactor rotated, the above three raw materials were added simultaneously from separate supply ports at the top of the reactor. After 2 minutes, it was quickly transferred to a separately prepared aging tank and then aged.

  The degree of butyralization of the slurry sampled immediately after the lapse of 2 minutes was 49 mol%. The polyvinyl butyral resin powder was finally obtained in accordance with the procedure of Example 1.

(Comparative Example 2)
In Comparative Example 1, a liquid mixture composed of a 10% aqueous solution of modified polyvinyl alcohol and hydrochloric acid having a concentration of 35% was prepared in advance, and 619 g of this liquid mixture and 45 g of butyraldehyde were added.

Polyvinyl acetal obtained by the present invention includes ceramic binder, ceramic capacitor, paint binder, ink binder, paper phenol resin substrate copper foil adhesive, thermal transfer recording agent binder, wash primer, retroreflective sheet, glass interlayer In general, it can be effectively used in applications where polyvinyl acetal is used.

Claims (8)

Acetalization reaction proceeds by continuously supplying a modified polyvinyl alcohol containing a bond unit represented by the general formula (Chemical Formula 1), an aldehyde, and an acid catalyst into the sealed reactor in the molecular main chain. And a step of continuously discharging the polyvinyl acetal from the sealed reactor after the degree of acetalization of the produced polyvinyl acetal reaches at least 10 mol%.

(In formula, X1 and X2 represent a C1-C12 lower alkyl group, a hydrogen atom, or a metal salt. G represents the integer of 0-3. H represents the integer of 0-12. Y1. Represents a carboxylic acid, a carboxylic acid ester, a carboxylic acid metal salt or a hydrogen atom.) The polyvinyl acetal continuously discharged from the closed reactor is further aged in another reactor, and after the polyvinyl acetal degree of acetalization reaches at least 60 mol%, the polyvinyl acetal is neutralized, washed with water, The method for producing a polyvinyl acetal according to claim 1, comprising steps of dehydration and drying. The method for producing a polyvinyl acetal according to claim 1 or 2, wherein the reaction temperature in the sealed reactor is in the range of 20 to 50 ° C. Content of unmodified polyvinyl alcohol in modified polyvinyl alcohol is 25 mol% or less, The manufacturing method of the polyvinyl acetal as described in any one of Claims 1-3 characterized by the above-mentioned. The modified polyvinyl alcohol is obtained by copolymerization of a monomer having an ethylenically unsaturated double bond and a monomer having a vinyl ester unit and then saponification. The method for producing polyvinyl acetal according to any one of 4. The method for producing polyvinyl acetal according to any one of claims 1 to 5, wherein the modified polyvinyl alcohol further contains a binding unit having an anionic group. The method for producing a polyvinyl acetal according to claim 6, wherein the content of the binding unit having an anionic group is in the range of 0.05 to 10 mol% in the modified polyvinyl alcohol. The polyvinyl acetal obtained by the manufacturing method as described in any one of Claims 1-7.