JP4439670B2 - Method for producing polyvinyl acetal resin - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、ポリビニルアセタール樹脂の製造方法に関し、さらに詳しくは透明性及び溶剤溶解性に優れた微粉末状のポリビニルアセタール樹脂を工業的に有利に製造する方法に関する。
【０００２】
【従来の技術】
ポリビニルアセタール樹脂は、合わせガラス用中間膜、塗料、印刷、接着剤等の用途に幅広く用いられている樹脂であり、ポリビニルアルコールを原料として、これをアセタール化することにより得られる。その製造方法としては、例えば、溶解法、沈殿法等が知られている。
【０００３】
このうち、沈殿法は単一工程で水溶液から粉末状製品を得ることができるため、反応後に溶液中からポリビニルアセタール化物を析出させて分離する必要がある溶解法に比べて工程が簡単で生産コストも安く、工業的生産に好適である。
【０００４】
しかしながら、沈殿法においては、一般に反応温度が高いと沈殿析出に要する時間は短くなるが、得られるポリビニルアセタールの粒子が粗大化し、場合によっては沈殿した粒子同士が凝集するので、比較的低い温度でポリビニルアルコール溶液中にカルボニル化合物を添加することにより、微小な粉末状の化合物を沈殿させる必要があった。
【０００５】
特に、重合度の低いポリビニルアルコールによるアセタール化は、粒子が粗大化を防ぐために、より低い温度にて沈殿させる必要があり、時には反応温度を０℃より低い温度に保たなければ微小な粉末状の樹脂が得られないため、このような低温に保持するための特別な冷却設備を必要とするという欠点がある。
【０００６】
また、低温に冷却することによって、ポリビニルアルコール水溶液のゲル化や、沈殿析出直後のアセタール化物の凍結等によりポリビニルアセタール樹脂の物性に悪影響を及ぼすこともあり、特に、平均重合度１００〜５００のポリビニルアルコールのアセタール化によって微小な粒子を得ることは困難である。
【０００７】
【発明が解決しようとする課題】
本発明の目的は、上述の問題点を解消し、特に、低重合度のポリビニルアルコールとアルデヒドとを縮合反応させる際に、反応系を０℃より低い温度まで冷却させずに、透明性及び溶剤溶解性に優れ、しかも酸触媒やその中和剤に由来する不純物の含有量が少なく、微小粉末状のポリビニルアセタール樹脂を製造する方法を提供することにある。
【０００８】
【課題を解決するための手段】
上記の目的を達成するために、請求項１の発明では、酸触媒の存在下に水相中でポリビニルアルコールとアルデヒドとを縮合反応させてポリビニルアセタール樹脂を製造する方法であって、反応系を２０℃以下に保ってポリビニルアルコール全添加量の７０〜８５重量％にアルデヒド全添加量の一部を添加して縮合反応を行った後、反応系の温度を１０〜１５℃に降下させ、ポリビニルアルコール全添加量の１０〜２０重量％に相当するポリビニルアルコールを添加した後、ポリビニルアセタール化物の沈殿析出しない量のアルデヒドを添加して縮合反応を行い、しかる後、反応系の温度を２〜１０℃とした上で、ポリビニルアルコールの残量を添加した後、反応系の温度を０〜５℃にしてアルデヒドの残量を添加して縮合反応を行ってポリビニルアセタール化物の沈殿を析出させることを特徴とする。
【００１０】
本発明において、ポリビニルアルコールとしては、平均重合度は、一般に１００〜２０００、水酸基の含有割合が２０モル％以上のものが用いられ、特に平均重合度１００〜５００、水酸基の含有割合が２０〜４０モル％のものに適用するのが好ましい。そして、ポリビニルアルコールは、一般に３〜１５重量％の水溶液として用いられる。
【００１１】
ポリビニルアルコールの水溶液には、酸触媒が添加される。酸触媒としては、塩酸、燐酸、硫酸、パラトルエンスルホン酸などの単独或いは二種以上の混合物が用いられる。これ等の酸触媒は、一般に、反応液のｐＨが０．２〜２になるように適量が添加される。酸触媒は所定量を一度に添加してもよいが、分割して添加するのが、微小な粒子を得る点で好ましい。
【００１２】
アルデヒドとしては、（パラ）ホルムアルデヒド、（パラ）アセトアルデヒド、プロピオンアルデヒド、ブチルアルデヒド、ヘキシルアルデヒドなどの単独或いは二種以上の混合物が、得られるポリビニルアセタール樹脂の用途に応じて選定される。これ等のアルデヒドの使用量は、製造するポリビニルアセタール樹脂のアセタール化度に応じて適宜決定されるが、一般に目的のアセタール化度を得るのに必要な理論量の２〜１０重量％増しの過剰に用いられる。
【００１３】
本発明の製造方法では、先ず、ポリビニルアルコール全添加量の７０〜８５重量％に相当するポリビニルアルコール水溶液に上記のような酸触媒を適量添加した後、反応系を２０℃以下に保ってアルデヒド全添加量の一部を添加して縮合反応を行う。
【００１４】
次いで、反応系の温度を１０〜１５℃に降下させ、ポリビニルアルコールの残量３０〜１５重量％のうち、２０〜１０重量％に相当するポリビニルアルコール水溶液を添加し、その後、反応生成物であるポリビニルアセタール化物の沈殿が析出しない量のアルデヒドを添加して縮合反応を行う。
【００１５】
さらに、反応系の温度を２〜１０℃にした後、ポリビニルアルコールの残量を添加し、さらに反応系の温度を０〜５℃にして、アルデヒドの残量を添加し、縮合反応を行って反応生成物であるポリビニルアセタール化物の沈殿を析出させる。
【００１６】
このように、ポリビニルアルコールの残量３０〜１５重量％は、反応生成物であるポリビニルアセタール化物の沈殿が析出するまでの間に２回に分割して添加される。なお、最終のアルデヒドの添加以外は、アルデヒドの１回の添加量が、ポリビニルアセタール化物を沈殿させるに至らないような量である。
【００１７】
その後、従来法と同様に熟成反応が行われる。この熟成反応は、酸触媒を適量追加した後、反応系の温度を、例えば２０℃以上に上げ、数時間保持することにより行われる。
【００１８】
こうしてポリビニルアセタール化物のスラリーが形成される。このスラリーは、酸触媒により酸性を呈しており、これを中和するためにスラリーに水酸化ナトリウムや重炭酸ナトリウムのような中和剤が添加される。その後、脱水、洗水、乾燥を行って、微粉末状のポリビニルアセタール樹脂が製造される。
【００１９】
（作用）
本発明によれば、ポリビニルアルコールを分割添加することにより、ポリビニルアルコールの界面活性効果と、反応系で生成されるポリビニルアセタール化物のアセタール化度の分布が広くなり、沈殿析出するする分子に時間差が与えられることによる効果とが相まって、透明性及び溶剤溶解性に優れた微粉末状のポリビニルアセタール樹脂が得られる。
【００２０】
しかも、反応生成物であるポリビニルアセタール化物の沈殿が析出するまでの間に、ポリビニルアルコールの残量を２回に分割して添加することにより、上記の作用がさらに効果的に行われ、透明性及び溶剤溶解性に優れた微粉末状のポリビニルアセタール樹脂が確実に得られる。さらに、ナトリウムや塩素などの酸触媒やその中和剤に由来する不純物の含有量を少なくすることができる。
【００２１】
【発明の実施の形態】
以下、本発明の実施例及び比較例を説明することにより、本発明をより詳細に説明する。
【００２２】
（実施例１）
平均重合度２３０のポリビニルアルコール２３６ｇ（全添加量の８０重量％）を純水２３００ｇに加熱溶解した後、４０℃まで冷却して酸触媒（３５％塩酸）５５ｇを加え、反応系の温度を１５℃まで降下させて、ブチルアルデヒド３８．５ｇを添加して縮合反応を行った。
【００２３】
次いで、反応系の温度を１０℃まで降下させてポリビニルアルコール全添加量の１５重量％に相当するポリビニルアルコール水溶液を添加し、さらに、反応系の温度を２℃まで降下させて、ブチルアルデヒド３８．５ｇを添加して縮合反応を行った。さらに、反応系の温度を２℃まで降下させて、ブチルアルデヒド３８．５ｇを添加し、ポリビニルアルコール全添加量の５重量％に相当するポリビニルアルコール水溶液を添加し、しかる後、反応系の温度を１℃まで降下させて、ブチルアルデヒド１０１．３ｇを添加し縮合反応を行って、反応生成物であるポリビニルアセタール化物の白色の沈殿物を析出させた。
【００２４】
その後、３０分後に酸触媒（３５％塩酸）３００ｇを添加し、さらに９０分後に反応系の温度を２０℃へ昇温して５時間保って熟成反応を行った後、常法によりｐＨが８となるように水酸化ナトリウムで中和し、脱水、洗水、乾燥を行って、微粉末状ポリビニルブチラール化物を得た。
【００２５】
得られたポリビニルブチラール樹脂は、ブチラール化度約７０モル％、平均粒径６５μｍで微小な粉末状であり、樹脂中のナトリムは６０ｐｐｍ、塩素は６５ｐｐｍであり、不純物は少なかった。また、このポリビニルブチラール樹脂の透明性及びメチルエチルケトンによる溶剤溶解性は共に良好であった。
【００２６】
（実施例２）
平均重合度４９０のポリビニルアルコール２５６ｇ（全添加量の８０重量％）を純水２４００ｇに加熱溶解した後、４０℃まで冷却して酸触媒（３５％塩酸）６２ｇを加え、反応系の温度を１５℃まで降下させて、ブチルアルデヒド４７．８ｇを添加して縮合反応を行った。
【００２７】
次いで、反応系の温度を１０℃まで降下させて、ポリビニルアルコール全添加量の１５重量％に相当するポリビニルアルコール水溶液を添加し、さらに、反応系の温度を５℃まで降下させて、ブチルアルデヒド４２．８ｇを添加して縮合反応を行った。さらに、反応系の温度を２℃まで降下させて、ポリビニルアルコール全添加量の５重量％に相当するポリビニルアルコール水溶液を添加し、しかる後、反応系の温度を１℃まで降下させて、ブチルアルデヒド１５０．９ｇを添加し縮合反応を行って、反応生成物であるポリビニルアセタール化物の白色の沈殿物を析出させた。
【００２８】
その後、３０分後に酸触媒（３５％塩酸）３５４ｇを添加し、さらに９０分後に反応系の温度を３８℃へ昇温して６時間保った後、常法によりｐＨが８となるように水酸化ナトリウムで中和し、脱水、洗水、乾燥を行って、微粉末状ポリビニルブチラール化物を得た。
【００２９】
得られたポリビニルブチラール樹脂は、ブチラール化度約７８モル％、平均粒径７０μｍで微小な粉末状であり、樹脂中のナトリムは７０ｐｐｍ、塩素は７８ｐｐｍであり、不純物は少なかった。また、このポリビニルブチラール樹脂の透明性及びメチルエチルケトンによる溶剤溶解性は共に良好であった。
【００３０】
（比較例１）
平均重合度２３０のポリビニルアルコール２８０ｇを純水２７００ｇに加熱溶解した後、４０℃まで冷却して酸触媒（３５％塩酸）５５ｇを加え、次いで、反応系の温度を１７℃まで降下させてブチルアルデヒド４２ｇを添加して縮合反応を行った。さらに、反応系の温度を１℃まで降下させて、ブチルアルデヒド１４４．３ｇを添加し縮合反応を行って、反応生成物であるポリビニルアセタール化物の白色の沈殿物を析出させた。
【００３１】
その後、３０分後に酸触媒（３５％塩酸）３００ｇを添加し、さらに９０分後に反応系の温度を２０℃へ昇温して５時間保った後、常法によりｐＨが８となるように水酸化ナトリウムで中和し、脱水、洗水、乾燥を行って、粉末状ポリビニルブチラール化物を得た。
【００３２】
得られたポリビニルブチラール樹脂は、ブチラール化度約７０モル％、平均粒径１４０μｍで粗大な粒子のため、酸触媒の洗浄除去が充分に行われず、このポリビニルブチラール樹脂は微白濁がみられた。また、メチルエチルケトンによる溶剤溶解性では微量の未溶解物が確認された。
【００３３】
（比較例２）
平均重合度２３０のポリビニルアルコール２８０ｇ（全添加量の９５重量％）を純水２７００ｇに加熱溶解した後、４０℃まで冷却して酸触媒（３５％塩酸）５５ｇを加え、反応系の温度を１５℃まで降下させて、ブチルアルデヒド３８．５ｇを添加して縮合反応を行った。
【００３４】
次いで、反応系の温度を３℃まで降下させてポリビニルアルコール全添加量の５重量％に相当するポリビニルアルコール水溶液を添加し、さらに、反応系の温度を２℃まで降下させて、ブチルアルデヒド３８．５ｇを添加して縮合反応を行った。さらに、反応系の温度を１℃まで降下させて、ブチルアルデヒド１０１．３ｇを添加し縮合反応を行って、反応生成物であるポリビニルアセタール化物の白色の沈殿物を析出させた。
【００３５】
その後、３０分後に酸触媒（３５％塩酸）３００ｇを添加し、さらに９０分後に反応系の温度を２０℃へ昇温して５時間保って熟成反応を行った後、常法によりｐＨが８となるように水酸化ナトリウムで中和し、脱水、洗水、乾燥を行って、微粉末状ポリビニルブチラール化物を得た。
【００３６】
得られたポリビニルブチラール樹脂は、ブチラール化度約７０モル％、平均粒径８０μｍで微小な粉末状であり、樹脂中のナトリムは９０ｐｐｍ、塩素は９５ｐｐｍであり、実施例１に比べて、平均粒径、ナトリム量及び塩素量は大きな値であった。なお、このポリビニルブチラール樹脂の透明性及びメチルエチルケトンによる溶剤溶解性は共に良好であった。
【００４１】
【発明の効果】
本発明のポリビニルアセタール樹脂の製造方法は、上述の構成であり、特に低重合度ポリビニルアルコールとカルボニル化合物との縮合反応を０℃よりも低い温度まで冷却せずに行うことができるので、従来法に比べて、特別な冷却設備を必要とせず、工業的に極めて有利である。ポリビニルアルコール水溶液のゲル化や、沈殿析出直後のアセタール化物の凍結等によりポリビニルアセタール樹脂の物性に悪影響を及ぼすこともない。
【００４２】
また、得られるポリビニルアセタール樹脂は、微小な粉末状であり、透明性及び溶剤溶解性に優れており、しかもナトリムや塩素などの酸触媒やその中和剤に由来する不純物の含有量が少なく、合わせガラス用中間膜、塗料、印刷、接着剤などの用途に好適に使用され得る。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a polyvinyl acetal resin, and more particularly to a method for industrially advantageously producing a finely divided polyvinyl acetal resin excellent in transparency and solvent solubility.
[0002]
[Prior art]
The polyvinyl acetal resin is a resin that is widely used in applications such as an interlayer film for laminated glass, paint, printing, and adhesive, and can be obtained by acetalizing this from polyvinyl alcohol. As its production method, for example, a dissolution method, a precipitation method and the like are known.
[0003]
Among these, the precipitation method can obtain a powdered product from an aqueous solution in a single step, so the process is simpler and the production cost is lower than the dissolution method that requires the polyvinyl acetalized product to be precipitated and separated from the solution after the reaction. It is cheap and suitable for industrial production.
[0004]
However, in the precipitation method, generally, when the reaction temperature is high, the time required for precipitation is shortened. However, the obtained polyvinyl acetal particles are coarsened, and in some cases, the precipitated particles are aggregated. It was necessary to precipitate a fine powdery compound by adding a carbonyl compound into the polyvinyl alcohol solution.
[0005]
In particular, acetalization with polyvinyl alcohol having a low degree of polymerization requires precipitation at a lower temperature in order to prevent the particles from becoming coarse, and sometimes fine powdery form unless the reaction temperature is kept below 0 ° C. Therefore, there is a disadvantage that a special cooling facility for maintaining such a low temperature is required.
[0006]
Moreover, by cooling to low temperature, the physical properties of the polyvinyl acetal resin may be adversely affected by gelation of the polyvinyl alcohol aqueous solution, freezing of the acetalized product immediately after precipitation, and the like. It is difficult to obtain fine particles by acetalization of alcohol.
[0007]
[Problems to be solved by the invention]
The object of the present invention is to solve the above-mentioned problems, and in particular, when a polycondensation reaction between polyvinyl alcohol and an aldehyde having a low polymerization degree is carried out, the reaction system is not cooled to a temperature lower than 0 ° C. An object of the present invention is to provide a method for producing a finely divided polyvinyl acetal resin which is excellent in solubility and has a small content of impurities derived from an acid catalyst or a neutralizing agent thereof.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the invention of claim 1 is a method for producing a polyvinyl acetal resin by a condensation reaction of polyvinyl alcohol and an aldehyde in an aqueous phase in the presence of an acid catalyst, the reaction system comprising: After carrying out the condensation reaction by adding a part of the total amount of aldehyde added to 70 to 85% by weight of the total amount of polyvinyl alcohol added at 20 ° C. or lower, the temperature of the reaction system is lowered to 10 to 15 ° C. After adding polyvinyl alcohol corresponding to 10 to 20% by weight of the total amount of alcohol added, an aldehyde is added in such an amount that the polyvinyl acetalized product does not precipitate, and the condensation reaction is carried out. After adding the remaining amount of polyvinyl alcohol, the reaction system temperature was changed to 0 to 5 ° C. Wherein the deposit precipitation of acetal compound.
[0010]
In the present invention, as the polyvinyl alcohol, those having an average degree of polymerization of generally from 100 to 2,000 and a hydroxyl group content of 20 mol% or more are used, and particularly, an average degree of polymerization of from 100 to 500 and a hydroxyl group content of from 20 to 40. It is preferable to apply to mol%. Polyvinyl alcohol is generally used as a 3 to 15% by weight aqueous solution.
[0011]
An acid catalyst is added to the aqueous solution of polyvinyl alcohol. As the acid catalyst, hydrochloric acid, phosphoric acid, sulfuric acid, p-toluenesulfonic acid or the like may be used alone or in combination of two or more. In general, an appropriate amount of these acid catalysts is added so that the pH of the reaction solution is 0.2-2. The acid catalyst may be added in a predetermined amount at a time, but it is preferable to add it in divided portions from the viewpoint of obtaining fine particles.
[0012]
As the aldehyde, (para) formaldehyde, (para) acetaldehyde, propionaldehyde, butyraldehyde, hexylaldehyde or the like alone or a mixture of two or more thereof is selected according to the use of the obtained polyvinyl acetal resin. The amount of these aldehydes to be used is appropriately determined according to the degree of acetalization of the polyvinyl acetal resin to be produced, but in general, an excess of 2 to 10% by weight of the theoretical amount necessary to obtain the desired degree of acetalization. Used for.
[0013]
In the production method of the present invention, first, an appropriate amount of the above acid catalyst is added to a polyvinyl alcohol aqueous solution corresponding to 70 to 85% by weight of the total addition amount of polyvinyl alcohol, and then the reaction system is kept at 20 ° C. or lower to reduce the total amount of aldehyde. A condensation reaction is performed by adding a part of the added amount.
[0014]
Next, the temperature of the reaction system is lowered to 10 to 15 ° C., and a polyvinyl alcohol aqueous solution corresponding to 20 to 10% by weight is added out of the remaining amount of polyvinyl alcohol of 30 to 15% by weight. The condensation reaction is carried out by adding an amount of aldehyde that does not cause precipitation of the polyvinyl acetalized product.
[0015]
Furthermore, after the temperature of the reaction system is set to 2 to 10 ° C. , the remaining amount of polyvinyl alcohol is added, the temperature of the reaction system is further set to 0 to 5 ° C. , the remaining amount of aldehyde is added, and a condensation reaction is performed. A precipitate of polyvinyl acetalized product, which is a reaction product, is deposited.
[0016]
In this way, the remaining amount of 30 to 15% by weight of polyvinyl alcohol is added in two portions until the precipitation of the polyvinyl acetalized product as the reaction product is precipitated. Except for the addition of the final aldehyde, the amount of aldehyde added once is such an amount that the polyvinyl acetalized product is not precipitated.
[0017]
Thereafter, an aging reaction is performed as in the conventional method. This aging reaction is performed by adding an appropriate amount of an acid catalyst, and then raising the temperature of the reaction system to, for example, 20 ° C. or higher and holding it for several hours.
[0018]
Thus, a slurry of the polyvinyl acetalized product is formed. This slurry is acidic due to the acid catalyst, and a neutralizing agent such as sodium hydroxide or sodium bicarbonate is added to the slurry to neutralize the slurry. Thereafter, dehydration, washing with water, and drying are performed to produce a finely divided polyvinyl acetal resin.
[0019]
(Function)
According to the present invention, by adding polyvinyl alcohol in a divided manner, the surface-active effect of polyvinyl alcohol and the distribution of the degree of acetalization of the polyvinyl acetal product produced in the reaction system are widened, and there is a time difference between molecules that precipitate. Combined with the effects given, a finely divided polyvinyl acetal resin excellent in transparency and solvent solubility can be obtained.
[0020]
Moreover, by adding the remaining amount of polyvinyl alcohol in two portions until the precipitation of the polyvinyl acetalization product, which is a reaction product, precipitates, the above-described action is more effectively performed, and transparency is achieved. In addition, a finely divided polyvinyl acetal resin excellent in solvent solubility can be obtained with certainty. Furthermore, it is possible to reduce the content of impurities derived from acid catalysts such as sodium and chlorine and neutralizers thereof.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in more detail by describing examples and comparative examples of the present invention.
[0022]
Example 1
After 236 g of polyvinyl alcohol having an average degree of polymerization of 230 (80% by weight of the total amount added) was dissolved in 2300 g of pure water by heating, it was cooled to 40 ° C. and 55 g of acid catalyst (35% hydrochloric acid) was added, and the temperature of the reaction system was 15 The temperature was lowered to 0 ° C., and 38.5 g of butyraldehyde was added to conduct a condensation reaction.
[0023]
Subsequently, the temperature of the reaction system is lowered to 10 ° C., an aqueous polyvinyl alcohol solution corresponding to 15% by weight of the total amount of added polyvinyl alcohol is added, the temperature of the reaction system is further lowered to 2 ° C., and butyraldehyde 38. 5 g was added to conduct a condensation reaction. Further, the temperature of the reaction system was lowered to 2 ° C., 38.5 g of butyraldehyde was added, an aqueous polyvinyl alcohol solution corresponding to 5% by weight of the total amount of polyvinyl alcohol was added, and then the temperature of the reaction system was changed. The temperature was lowered to 1 ° C., 101.3 g of butyraldehyde was added, and a condensation reaction was performed to precipitate a white precipitate of a polyvinyl acetalization product as a reaction product.
[0024]
Then, after 30 minutes, 300 g of an acid catalyst (35% hydrochloric acid) was added, and after 90 minutes, the temperature of the reaction system was raised to 20 ° C. and maintained for 5 hours, and then the aging reaction was carried out. The mixture was neutralized with sodium hydroxide, dehydrated, washed with water and dried to obtain a finely powdered polyvinyl butyral product.
[0025]
The obtained polyvinyl butyral resin was a fine powder with a degree of butyralization of about 70 mol% and an average particle size of 65 μm. The resin contained 60 ppm sodium and 65 ppm chlorine, and contained few impurities. Moreover, both the transparency of this polyvinyl butyral resin and the solvent solubility with methyl ethyl ketone were good.
[0026]
(Example 2)
After 256 g of polyvinyl alcohol having an average degree of polymerization of 490 (80 wt% of the total amount added) was dissolved in 2400 g of pure water by heating, the mixture was cooled to 40 ° C. and 62 g of acid catalyst (35% hydrochloric acid) was added, and the temperature of the reaction system was 15 The temperature was lowered to 0 ° C., and 47.8 g of butyraldehyde was added to conduct a condensation reaction.
[0027]
Next, the temperature of the reaction system is lowered to 10 ° C., an aqueous polyvinyl alcohol solution corresponding to 15% by weight of the total amount of added polyvinyl alcohol is added, and the temperature of the reaction system is further lowered to 5 ° C. .8 g was added to conduct a condensation reaction. Further, the temperature of the reaction system is lowered to 2 ° C., an aqueous polyvinyl alcohol solution corresponding to 5% by weight of the total amount of added polyvinyl alcohol is added, and then the temperature of the reaction system is lowered to 1 ° C. 150.9g was added and the condensation reaction was performed, and the white deposit of the polyvinyl acetalization product which is a reaction product was deposited.
[0028]
Thereafter, 354 g of an acid catalyst (35% hydrochloric acid) was added after 30 minutes, and after 90 minutes, the temperature of the reaction system was raised to 38 ° C. and maintained for 6 hours, and then water was added so that the pH became 8 by a conventional method. The mixture was neutralized with sodium oxide, dehydrated, washed with water, and dried to obtain a finely powdered polyvinyl butyral product.
[0029]
The obtained polyvinyl butyral resin had a degree of butyralization of about 78 mol%, an average particle size of 70 μm, and was in the form of a fine powder. Sodium in the resin was 70 ppm, chlorine was 78 ppm, and there were few impurities. Moreover, both the transparency of this polyvinyl butyral resin and the solvent solubility with methyl ethyl ketone were good.
[0030]
(Comparative Example 1)
After 280 g of polyvinyl alcohol having an average degree of polymerization of 230 is dissolved in 2700 g of pure water by heating, it is cooled to 40 ° C., 55 g of acid catalyst (35% hydrochloric acid) is added, and then the temperature of the reaction system is lowered to 17 ° C. 42g was added and the condensation reaction was performed. Further, the temperature of the reaction system was lowered to 1 ° C., 144.3 g of butyraldehyde was added, and a condensation reaction was performed to precipitate a white precipitate of a polyvinyl acetalization product as a reaction product.
[0031]
Thereafter, after 30 minutes, 300 g of an acid catalyst (35% hydrochloric acid) was added, and after 90 minutes, the temperature of the reaction system was raised to 20 ° C. and maintained for 5 hours, and then water was added so that the pH became 8 by a conventional method. The mixture was neutralized with sodium oxide, dehydrated, washed with water, and dried to obtain a powdered polyvinyl butyral product.
[0032]
The obtained polyvinyl butyral resin was coarse particles having a degree of butyralization of about 70 mol% and an average particle size of 140 μm, so that the acid catalyst was not sufficiently washed and removed, and the polyvinyl butyral resin was slightly clouded. In addition, a trace amount of undissolved material was confirmed in the solvent solubility with methyl ethyl ketone.
[0033]
(Comparative Example 2)
After 280 g of polyvinyl alcohol having an average degree of polymerization of 230 (95% by weight of the total amount added) was dissolved in 2700 g of pure water by heating, it was cooled to 40 ° C., 55 g of acid catalyst (35% hydrochloric acid) was added, and the temperature of the reaction system was 15 The temperature was lowered to 0 ° C., and 38.5 g of butyraldehyde was added to conduct a condensation reaction.
[0034]
Subsequently, the temperature of the reaction system is lowered to 3 ° C., an aqueous polyvinyl alcohol solution corresponding to 5% by weight of the total amount of added polyvinyl alcohol is added, the temperature of the reaction system is further lowered to 2 ° C., and butyraldehyde 38. 5 g was added to conduct a condensation reaction. Further, the temperature of the reaction system was lowered to 1 ° C., 101.3 g of butyraldehyde was added, and a condensation reaction was performed to precipitate a white precipitate of a polyvinyl acetalized product as a reaction product.
[0035]
Then, after 30 minutes, 300 g of an acid catalyst (35% hydrochloric acid) was added, and after 90 minutes, the temperature of the reaction system was raised to 20 ° C. and maintained for 5 hours, and then the aging reaction was carried out. The mixture was neutralized with sodium hydroxide, dehydrated, washed with water and dried to obtain a finely powdered polyvinyl butyral product.
[0036]
The obtained polyvinyl butyral resin is a fine powder with a degree of butyralization of about 70 mol% and an average particle size of 80 μm, and the sodium in the resin is 90 ppm and the chlorine is 95 ppm. The diameter, the amount of sodium and the amount of chlorine were large. The polyvinyl butyral resin had good transparency and solvent solubility with methyl ethyl ketone.
[0041]
【The invention's effect】
The method for producing the polyvinyl acetal resin of the present invention has the above-described configuration, and in particular, since the condensation reaction between the polyvinyl alcohol having a low polymerization degree and the carbonyl compound can be performed without cooling to a temperature lower than 0 ° C., the conventional method Compared to the above, no special cooling equipment is required, which is extremely advantageous industrially. The physical properties of the polyvinyl acetal resin are not adversely affected by gelation of the aqueous polyvinyl alcohol solution, freezing of the acetalized product immediately after precipitation, or the like.
[0042]
Moreover, the obtained polyvinyl acetal resin is in a fine powder form, excellent in transparency and solvent solubility, and has a low content of impurities derived from an acid catalyst such as sodium or chlorine and its neutralizing agent, It can be suitably used for applications such as an interlayer film for laminated glass, paint, printing, and adhesive.
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| DE102004054569A1 (en) | 2004-11-11 | 2006-05-24 | Wacker Polymer Systems Gmbh & Co. Kg | Low shear thinning polyvinyl acetals |
| JP5079299B2 (en) * | 2005-11-30 | 2012-11-21 | 株式会社クラレ | Polyvinyl acetal powder and powder coating |
| JP4865403B2 (en) | 2006-05-15 | 2012-02-01 | 株式会社クラレ | Polyvinyl acetal powder coating |
| EP2185602B1 (en) * | 2007-09-05 | 2011-06-08 | Kuraray Europe GmbH | Method for the production of polyvinyl acetals having low residual aldehyde content in waste water |
| US11374222B2 (en) * | 2015-03-20 | 2022-06-28 | Sekisui Chemical Co., Ltd. | Composition for lithium secondary battery electrodes |
| CN109293803A (en) * | 2018-10-14 | 2019-02-01 | 营口天元高分子树脂有限公司 | A kind of method of production of low-temperature polyethylene butyral composition |
| CN113845609B (en) * | 2021-08-26 | 2022-04-08 | 忠信（清远）光伏材料科技有限公司 | Preparation method of polyvinyl butyral |
| CN116199807A (en) * | 2022-12-30 | 2023-06-02 | 安徽皖维先进功能膜材料研究院有限公司 | Polyvinyl acetal molecular sequence distribution regulation and control method and polyvinyl acetal resin |
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