JP4733004B2 - Method for polymerizing aliphatic vinyl ester and method for producing polyvinyl alcohol resin - Google Patents
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Description
本発明は、重合度の高いポリビニルアルコール系樹脂を工業的に有利に生産することのできる、脂肪族ビニルエステルの重合方法およびポリビニルアルコール系樹脂の製造方法に関する。 The present invention relates to a method for polymerizing an aliphatic vinyl ester and a method for producing a polyvinyl alcohol resin, which can industrially advantageously produce a polyvinyl alcohol resin having a high degree of polymerization.
ポリビニルアルコール（以下ＰＶＡと略記する場合がある）系樹脂は工業的には脂肪族ビニルエステルをアルコール溶媒中において大気圧下で重合し、得られた脂肪族ポリビニルエステルをケン化して製造されている。ポリビニルアルコール系樹脂は繊維加工、紙加工、フィルム、接着剤、各種無機材料のバインダー、乳化安定剤など多くの用途に使用されており、その用途は広がりつつある。 Polyvinyl alcohol (hereinafter sometimes abbreviated as PVA) resin is industrially produced by polymerizing an aliphatic vinyl ester in an alcohol solvent at atmospheric pressure and saponifying the resulting aliphatic polyvinyl ester. . Polyvinyl alcohol resins are used in many applications such as fiber processing, paper processing, films, adhesives, binders of various inorganic materials, and emulsion stabilizers, and their applications are expanding.
近年、ポリビニルアルコール系樹脂を水溶液にした場合に、より高い粘性を発現させることを要求する用途や、フィルムにした場合に、より高い被膜強度を要求する用途が増えてきている。これらの要求を満たすためにはポリビニルアルコール系樹脂の重合度を高くすることが一つの方法として挙げられる。 In recent years, there has been an increase in applications that require higher viscosity when a polyvinyl alcohol-based resin is used as an aqueous solution and applications that require higher coating strength when it is used as a film. In order to satisfy these requirements, one method is to increase the degree of polymerization of the polyvinyl alcohol-based resin.
一般的に、ポリビニルアルコール系樹脂の重合度を高くする方法としては、酢酸ビニル等のビニルエステルを重合してポリビニルエステルとする際に、低温下で重合することが最も効果的であることが知られている。低温で酢酸ビニルを重合する具体的な方法としては低温下での光重合や低温光乳化重合（例えば、非特許文献１参照）などがよく知られているが、重合熱の除熱をジャケットに頼る場合には、除熱量に限界があり、十分な生産性を得ることが出来ない場合がほとんどである。 In general, as a method for increasing the degree of polymerization of a polyvinyl alcohol-based resin, it is known that polymerization at a low temperature is most effective when a vinyl ester such as vinyl acetate is polymerized to form a polyvinyl ester. It has been. As specific methods for polymerizing vinyl acetate at low temperatures, photopolymerization at low temperatures and low-temperature photoemulsion polymerization (for example, see Non-Patent Document 1) are well known. When relying on, there is a limit to the amount of heat removal, and in most cases, sufficient productivity cannot be obtained.
また、減圧下において原料である単量体を沸騰させつつ、低温でビニルエステルの乳化重合を行う方法が提案されている（例えば、特許文献１参照）。また、アクリル酸エステル等を重合する方法として、減圧下で反応液から液状物質の少なくとも１種類を蒸発させつつ懸濁重合を行う方法（特許文献２参照）も提案されている。これらの方法で乳化重合ないし懸濁重合が採用されているのは、反応液の粘度が高くならない点で有利なためと考えられるが、その反面、乳化重合ないし懸濁重合で得られたポリビニルエステルを分散媒である水から取り出し、ケン化してポリビニルアルコールとするには膨大なコストがかかり、工業的には不利である。 Further, a method has been proposed in which emulsion polymerization of a vinyl ester is performed at a low temperature while boiling a monomer as a raw material under reduced pressure (see, for example, Patent Document 1). In addition, as a method for polymerizing an acrylate ester or the like, a method is also proposed in which suspension polymerization is performed while evaporating at least one liquid substance from a reaction solution under reduced pressure (see Patent Document 2). The reason why emulsion polymerization or suspension polymerization is adopted in these methods is considered to be advantageous in that the viscosity of the reaction solution does not increase, but on the other hand, the polyvinyl ester obtained by emulsion polymerization or suspension polymerization. It is very disadvantageous industrially to take out from water as a dispersion medium and to saponify it into polyvinyl alcohol.
そのため、従来の技術においては、工業的に重合度が高いポリビニルアルコールを製造することは困難であり、現在市販されている工業用ポリビニルアルコールとしては、通常は重合度が４５００程度までのものであり、近年高まりつつある高重合度ポリビニルアルコールに対する要求に十分答え切れていないのが現状である。 Therefore, in the conventional technology, it is difficult to produce polyvinyl alcohol having a high degree of polymerization industrially, and industrial polyvinyl alcohol currently on the market usually has a degree of polymerization of up to about 4500. However, the present situation is that the demand for high-polymerization polyvinyl alcohol, which has been increasing in recent years, has not been fully answered.
かかる現状に鑑み、本発明は、重合度が高いポリビニルアルコールの効率的な工業的生産を可能にするために、脂肪族ポリビニルエステルの新規な重合方法およびポリビニルアルコールの新規な製造方法を提供することを課題とする。 In view of the current situation, the present invention provides a novel polymerization method of aliphatic polyvinyl ester and a novel production method of polyvinyl alcohol in order to enable efficient industrial production of polyvinyl alcohol having a high degree of polymerization. Is an issue.
本発明者らは、上記目的を達成するために鋭意検討した結果、脂肪族ビニルエステルを重合する際、減圧下で反応液を沸騰させつつ溶液重合を行い、得られた脂肪族ポリビニルエステルをケン化することにより重合度の高いポリビニルアルコール系樹脂が効率的に製造できることを見いだし、さらに検討を重ねて、本発明を完成させるに至った。 As a result of intensive studies to achieve the above-mentioned object, the inventors of the present invention conducted solution polymerization while boiling the reaction solution under reduced pressure when polymerizing the aliphatic vinyl ester. As a result, it has been found that a polyvinyl alcohol resin having a high degree of polymerization can be efficiently produced, and further studies have been made, and the present invention has been completed.
すなわち、本発明は、
［１］ 脂肪族ビニルエステルを重合する方法であって、重合機内圧力を減圧にして、該減圧下において重合反応液を沸騰させつつ、大気圧下での重合反応液の沸騰温度よりも低い温度で溶液重合を行うことを特徴とする脂肪族ビニルエステルの重合方法、
［２］ 脂肪族ビニルエステルが酢酸ビニルであることを特徴とする前項［１］記載の脂肪族ビニルエステルの重合方法、
［３］ 重合反応液を攪拌する攪拌翼として、攪拌軸のないダブルヘリカルリボン翼を用いることを特徴とする前項［１］または［２］に記載の重合方法、および
［４］ 前項［１］〜［３］のいずれかに記載の方法により得られた脂肪族ポリビニルエステルをケン化して、１，２−グリコール結合量が１．９モル%未満のポリビニルアルコール系樹脂を製造することを特徴とするポリビニルアルコール系樹脂の製造方法
に関する。
That is, the present invention
[1] A method for polymerizing an aliphatic vinyl ester, wherein the temperature inside the polymerization machine is reduced, and the polymerization reaction liquid is boiled under the reduced pressure, while the temperature is lower than the boiling temperature of the polymerization reaction liquid at atmospheric pressure. A method of polymerizing an aliphatic vinyl ester, characterized by performing solution polymerization in
[2] The method for polymerizing an aliphatic vinyl ester according to [1] above, wherein the aliphatic vinyl ester is vinyl acetate,
[3] The polymerization method as described in [1] or [2] above, wherein a double helical ribbon blade without a stirring shaft is used as a stirring blade for stirring the polymerization reaction solution;
[4] A polyvinyl alcohol-based resin having a 1,2-glycol bond amount of less than 1.9 mol% by saponifying an aliphatic polyvinyl ester obtained by the method according to any one of [1] to [3] It is related with the manufacturing method of the polyvinyl alcohol-type resin characterized by manufacturing this.
本発明の重合方法を用いることにより、工業的に有利に重合度の高いポリビニルアルコールを製造することが可能となる。また、減圧下でビニルエステルを溶液重合することにより、最終的に得られるポリビニルアルコール系樹脂の主鎖中にある１，２−グリコール結合量が減少し、耐熱性の向上したポリビニルアルコール系樹脂が得られる。 By using the polymerization method of the present invention, polyvinyl alcohol having a high degree of polymerization can be produced industrially advantageously. Further, by subjecting the vinyl ester to solution polymerization under reduced pressure, the amount of 1,2-glycol bonds in the main chain of the finally obtained polyvinyl alcohol resin is reduced, and a polyvinyl alcohol resin having improved heat resistance is obtained. can get.
本発明の重合方法においては、溶液重合のため重合終了後の脱モノマーが容易である。この点、乳化重合による方法では、乳化剤残渣の影響により脱モノマーが困難であり、また、乳化剤が不純物となるおそれもある。したがって本発明が有利である。 In the polymerization method of the present invention, it is easy to remove the monomer after completion of polymerization because of solution polymerization. In this respect, in the method using emulsion polymerization, it is difficult to remove the monomer due to the influence of the emulsifier residue, and the emulsifier may become an impurity. The present invention is therefore advantageous.
乳化重合では重合機の内壁にスケール（汚れ）が付着しやすいが、本発明では溶液重合であるため重合溶媒の存在によりスケールが付着せず、また、重合終了時に重合溶媒をさらに加えて希釈する作業も容易に行えるので有利である。 In emulsion polymerization, scale (dirt) is likely to adhere to the inner wall of the polymerization machine. However, in the present invention, scale is not attached due to the presence of a polymerization solvent because of solution polymerization, and dilution is further performed by adding a polymerization solvent at the end of polymerization. This is advantageous because the work can be easily performed.
乳化重合は通常、回分重合で行われ、連続重合も可能であるが、高重合度のものを効率良く重合するためには複数の重合機が直列に並ぶ高度な設備が必要となり、高コストとなる。この点、本発明では溶液重合のため連続重合が容易であり、重合機１基からでも連続重合による効率的な重合ができるので有利である。 Emulsion polymerization is usually carried out by batch polymerization, and continuous polymerization is also possible, but in order to efficiently polymerize those having a high degree of polymerization, sophisticated equipment in which a plurality of polymerizers are arranged in series is required, resulting in high costs. Become. In this respect, the present invention is advantageous because continuous polymerization is easy because of solution polymerization, and efficient polymerization can be achieved by continuous polymerization even from one polymerization machine.
乳化重合では、水溶性の重合開始剤（水溶性開始剤）を使用する必要があるが、水溶性開始剤、特にノンハロゲン系の水溶性開始剤は一般的に活性の低いものが多く、十分な反応速度を得るためには光重合開始剤を用いることが必要になる。この点、本発明では溶液重合のため油溶性の重合開始剤（油溶性開始剤）を用いることができ、油溶性開始剤にはノンハロゲン系で活性の高いものが多く存在するので有利である。なお、ハロゲン系の重合開始剤においては、ハロゲンとして塩素が一般的であり、ポリビニルエステルないしＰＶＡの製造過程で塩素を反応系内に添加することは、近年では環境保全上好ましくないとされている。 In emulsion polymerization, it is necessary to use a water-soluble polymerization initiator (water-soluble initiator). However, water-soluble initiators, particularly non-halogen-based water-soluble initiators are generally low in activity and are sufficient. In order to obtain the reaction rate, it is necessary to use a photopolymerization initiator. In this respect, in the present invention, an oil-soluble polymerization initiator (oil-soluble initiator) can be used for solution polymerization, and there are many non-halogen-based and highly active oil-soluble initiators. In halogen-based polymerization initiators, chlorine is generally used as the halogen, and it has recently been considered unfavorable for environmental protection to add chlorine to the reaction system during the production of polyvinyl ester or PVA. .
以下、本発明について詳細に説明する。
本発明の重合方法は、脂肪族ビニルエステルを重合する方法であり、この重合方法により高重合度の脂肪族ポリビニルエステルが得られ、それをケン化することにより高重合度のポリビニルアルコール系樹脂が得られる。
Hereinafter, the present invention will be described in detail.
The polymerization method of the present invention is a method of polymerizing an aliphatic vinyl ester. By this polymerization method, an aliphatic polyvinyl ester having a high degree of polymerization is obtained, and by saponifying it, a polyvinyl alcohol resin having a high degree of polymerization is obtained. can get.
本発明に使用される脂肪族ビニルエステル（単量体）としては、例えば、ギ酸ビニル、酢酸ビニル、プロピオン酸ビニル、ピバリン酸ビニル、ステアリン酸ビニル等があげられるが、工業的には酢酸ビニルが望ましい。 Examples of the aliphatic vinyl ester (monomer) used in the present invention include vinyl formate, vinyl acetate, vinyl propionate, vinyl pivalate, and vinyl stearate. desirable.
また、本発明の効果を損なわない範囲で、前記脂肪族ビニルエステルと共重合可能な不飽和単量体を脂肪族ビニルエステルと共重合してもよく、そのような共重合を伴う態様もまた、本発明にいう「脂肪族ビニルエステルの重合」の範疇に含まれる。 In addition, the unsaturated monomer copolymerizable with the aliphatic vinyl ester may be copolymerized with the aliphatic vinyl ester within a range not impairing the effects of the present invention, and an embodiment involving such copolymerization is also possible. Are included in the category of “polymerization of aliphatic vinyl ester” in the present invention.
脂肪族ビニルエステルと共重合可能な不飽和単量体としては、例えば、アクリル酸等の不飽和一塩基酸またはその塩、マレイン酸、イタコン酸、フマル酸等の不飽和二塩基酸またはその塩、あるいはマレイン酸モノメチル、イタコン酸モノメチル等の不飽和二塩基酸モノアルキルエステル類、（メタ）アクリル酸エステル類、アクリルアミド、ジアセトンアクリルアミド、ジメチルアクリルアミド、Ｎ−メチロールアクリルアミド、Ｎ−ビニル−２−ピロリドン等のアミド基含有単量体、ラウリルビニルエーテル、ステアリルビニルエーテル等のアルキルビニルエーテル類、アリルアルコール、ジメチルアリルアルコール、イソプロペニルアリルアルコール等の水酸基含有単量体、アリルアセテート、ジメチルアリルアセテート、イソプロペニルアリルアセテート等のアセチル基含有単量体、ビニルスルホン酸ソーダ、アリルスルホン酸ソーダ、アクリルアミド−２−メチルプロパンスルホン酸ソーダ等のスルホン基含有単量体、塩化ビニル、塩化ビニリデン等のハロゲン含有単量体、スチレン等の芳香族系単量体を挙げることができるが、それらに限らない。 Examples of unsaturated monomers copolymerizable with aliphatic vinyl esters include unsaturated monobasic acids such as acrylic acid or salts thereof, unsaturated dibasic acids such as maleic acid, itaconic acid, fumaric acid, or salts thereof. Or unsaturated dibasic acid monoalkyl esters such as monomethyl maleate and monomethyl itaconate, (meth) acrylic esters, acrylamide, diacetone acrylamide, dimethyl acrylamide, N-methylol acrylamide, N-vinyl-2-pyrrolidone Amide group-containing monomers such as lauryl vinyl ethers, alkyl vinyl ethers such as stearyl vinyl ether, hydroxyl group-containing monomers such as allyl alcohol, dimethylallyl alcohol, isopropenyl allyl alcohol, allyl acetate, dimethylallyl acetate, isopropene Acetyl group-containing monomers such as ruaryl acetate, sulfone group-containing monomers such as sodium vinyl sulfonate, sodium allyl sulfonate, sodium acrylamide-2-methylpropane sulfonate, and halogen-containing monomers such as vinyl chloride and vinylidene chloride. Examples thereof include aromatic monomers such as styrene and styrene, but are not limited thereto.
本発明においては、脂肪族ビニルエステルの重合に際し、溶液重合を行う。本発明において、溶液重合とは、重合溶媒に脂肪族ビニルエステルが完全溶解した均一系による重合を意味する。したがって、以下においては、重合反応液のことを重合溶液ということがある。 In the present invention, solution polymerization is performed in the polymerization of the aliphatic vinyl ester. In the present invention, solution polymerization means polymerization in a homogeneous system in which an aliphatic vinyl ester is completely dissolved in a polymerization solvent. Therefore, in the following, the polymerization reaction liquid may be referred to as a polymerization solution.
重合溶媒としては、例えばメタノール、エタノール、プロパノール等のアルコール類やベンゼン、アセトン、グリセリン、ポリエチレングリコール等が使用されるが、工業的にはメタノールが好ましい。重合溶媒の使用量としては、脂肪族ビニルエステル１００質量部に対して、１〜５０質量部が好ましい。１質量部未満では、重合機の内壁にスケールが付着しやすくなり、一方、５０質量部を超えると、本発明が目的とする高重合度ポリビニルアルコール系樹脂ないし高重合度脂肪族ポリビニルエステルが得られ難くなる傾向にあるので好ましくない。 As the polymerization solvent, for example, alcohols such as methanol, ethanol, and propanol, benzene, acetone, glycerin, polyethylene glycol, and the like are used, but methanol is preferred industrially. As a usage-amount of a polymerization solvent, 1-50 mass parts is preferable with respect to 100 mass parts of aliphatic vinyl ester. When the amount is less than 1 part by mass, the scale easily adheres to the inner wall of the polymerization machine. On the other hand, when the amount exceeds 50 parts by mass, the high-polymerization degree polyvinyl alcohol resin or the high-polymerization degree aliphatic polyvinyl ester targeted by the present invention is obtained. This is not preferable because it tends to be difficult to be obtained.
本発明における溶液重合の重合開始剤としては、特に制限はなく、通常アゾ系化合物や過酸化物等が用いられる。 There is no restriction | limiting in particular as a polymerization initiator of the solution polymerization in this invention, Usually, an azo type compound, a peroxide, etc. are used.
また、溶液重合の際には、脂肪族ビニルエステルの加水分解を防止する目的で酒石酸、クエン酸、酢酸等の有機酸を添加してもよい。 In the solution polymerization, an organic acid such as tartaric acid, citric acid, and acetic acid may be added for the purpose of preventing hydrolysis of the aliphatic vinyl ester.
なお、重合度調整のために、２−メルカプトエタノールや１−ドデカンチオール、アセトアルデヒド等の連鎖移動剤を用いてもかまわないが、高重合度ポリビニルアルコール系樹脂を製造する場合にはなるべく添加しない方が好ましい。 In order to adjust the degree of polymerization, a chain transfer agent such as 2-mercaptoethanol, 1-dodecanethiol, or acetaldehyde may be used, but it should not be added as much as possible when producing a highly polymerized polyvinyl alcohol resin. Is preferred.
本発明においては、溶液重合に際し重合機内圧力を減圧にすること、すなわち重合機内の圧力を大気圧より低い圧力に保った状態で重合を行うことが重要である。その際の重合機内の圧力としては、大気圧より低い圧力であれば特に制限はないが、１０〜７０ｋＰａが好ましい。１０ｋＰａ未満では、反応液の沸騰温度が下がりすぎるため重合温度が低くなりすぎて十分な重合速度が得られ難く、一方、７０ｋＰａを超えると、本発明が目的とする高重合度ポリビニルアルコール系樹脂ないし高重合度脂肪族ポリビニルエステルが得られ難くなる傾向にあるので好ましくない。 In the present invention, it is important to carry out the polymerization in a state where the pressure in the polymerization machine is reduced, that is, the pressure in the polymerization machine is maintained at a pressure lower than the atmospheric pressure during the solution polymerization. The pressure in the polymerization machine at that time is not particularly limited as long as it is lower than atmospheric pressure, but is preferably 10 to 70 kPa. If it is less than 10 kPa, since the boiling temperature of the reaction solution is too low, it is difficult to obtain a sufficient polymerization rate because the polymerization temperature is too low. On the other hand, if it exceeds 70 kPa, Since it tends to be difficult to obtain a highly polymerized aliphatic polyvinyl ester, it is not preferred.
重合機内の圧力を大気圧より低い圧力に保つ方法としては特に制限はなく、一般的には反応熱を除去するために付設される還流凝縮器の大気解放側に、真空ポンプ等の吸引装置を設けることで実現することが出来る。 There is no particular limitation on the method for maintaining the pressure in the polymerization machine at a pressure lower than the atmospheric pressure. Generally, a suction device such as a vacuum pump is provided on the open side of the reflux condenser attached to remove reaction heat. This can be realized.
また、溶液重合の際の温度（重合反応温度）としては、大気圧下での反応液の沸騰温度よりも低い温度であることが必要である。本発明において、溶液重合の際の温度とは、具体的には重合反応中の重合溶液の温度を意味する。 Further, the temperature at the time of solution polymerization (polymerization reaction temperature) needs to be lower than the boiling temperature of the reaction solution under atmospheric pressure. In the present invention, the temperature during solution polymerization specifically means the temperature of the polymerization solution during the polymerization reaction.
なお、重合反応液の沸騰温度とは、所定の圧力下で、重合反応液の表面からの蒸発のほかに、重合反応液の内部からも気化がおこり始める温度をいい、圧力が一定のもとでは、該沸騰温度は概ね一定に保たれる。 The boiling temperature of the polymerization reaction liquid means a temperature at which vaporization starts from the inside of the polymerization reaction liquid in addition to evaporation from the surface of the polymerization reaction liquid at a predetermined pressure. In this case, the boiling temperature is kept substantially constant.
重合反応温度としては、大気圧下での反応液の沸騰温度よりも低い温度であればよく、それ以外に特に制限はなく、反応液の組成にもよるが、１０〜５６℃程度が好ましい。本発明においては、溶液重合により高い重合度を得ることから、低温下で溶液の粘度が著しく高くなると攪拌が困難になる場合もあるため、工業的には重合反応温度を０℃以上とすることが好ましい。したがって、特に好ましい重合温度は、０〜５６℃程度である。 The polymerization reaction temperature is not particularly limited as long as it is lower than the boiling temperature of the reaction solution under atmospheric pressure, and is preferably about 10 to 56 ° C. depending on the composition of the reaction solution. In the present invention, since a high degree of polymerization is obtained by solution polymerization, it may be difficult to stir when the viscosity of the solution becomes extremely high at low temperatures. Therefore, the polymerization reaction temperature should be 0 ° C. or higher industrially. Is preferred. Therefore, a particularly preferable polymerization temperature is about 0 to 56 ° C.
本発明においては、大気圧下の重合反応液の沸騰温度よりも低い温度で溶液重合を行うために、上記の減圧下において重合反応液を沸騰させつつ溶液重合を行う。減圧下で重合反応液を沸騰させつつ行うことにより、反応液の温度を大気圧下の重合反応液の沸騰温度よりも低い概ね一定の温度に保つことが容易になる。したがって、重合反応温度は、重合機内の圧力によっても調節され得る。なお、この沸騰による蒸発物は、重合機に還流凝縮器を付設して還流させればよい。 In the present invention, in order to perform solution polymerization at a temperature lower than the boiling temperature of the polymerization reaction solution under atmospheric pressure, solution polymerization is performed while boiling the polymerization reaction solution under the above-described reduced pressure. By carrying out the boiling of the polymerization reaction liquid under reduced pressure, it becomes easy to keep the temperature of the reaction liquid at a substantially constant temperature lower than the boiling temperature of the polymerization reaction liquid under atmospheric pressure. Therefore, the polymerization reaction temperature can also be adjusted by the pressure in the polymerization machine. In addition, what is necessary is just to attach the reflux condenser to a superposition | polymerization machine, and to evaporate the evaporation material by this boiling.
本発明において使用する、脂肪族ビニルエステルを溶液重合するための重合機としては、重合機内の圧力を大気圧より低い圧力に保てるものであれば特に形式を問わない。重合方式としては、回分重合、半連続重合、連続重合のいずれでもよい。生産性に優れる点では連続重合が好ましく、重合度をより高くするという観点からは回分重合が好ましい。 The polymerization machine for solution polymerization of the aliphatic vinyl ester used in the present invention is not particularly limited as long as the pressure in the polymerization machine can be maintained at a pressure lower than atmospheric pressure. The polymerization method may be any of batch polymerization, semi-continuous polymerization, and continuous polymerization. From the viewpoint of excellent productivity, continuous polymerization is preferable, and batch polymerization is preferable from the viewpoint of increasing the degree of polymerization.
攪拌装置も公知のものを用いることができ、重合反応液を攪拌する攪拌翼としては、特に限定されるものではないが、低温で重合して比較的重合収率を上げる処方においては、攪拌軸のないダブルヘリカルリボン翼が好ましい。本発明における溶液重合では、重合が進むにつれ重合反応液の粘度が上昇し、低温で重合して比較的重合収率を上げる処方においては相当な高粘度となるが、攪拌軸のないダブルヘリカルリボン翼を用いることにより、そのような場合でも支障なく攪拌することができ、本発明の目的を十分に達成することができる。 A well-known stirrer can also be used, and the stirring blade for stirring the polymerization reaction liquid is not particularly limited. A double helical ribbon wing with no blade is preferred. In the solution polymerization in the present invention, as the polymerization proceeds, the viscosity of the polymerization reaction solution increases, and in a formulation in which the polymerization yield is relatively increased by polymerization at a low temperature, the viscosity becomes considerably high, but a double helical ribbon without a stirring axis. By using a blade, even in such a case, stirring can be performed without any problem, and the object of the present invention can be sufficiently achieved.
攪拌軸のないダブルヘリカルリボン翼それ自体は公知であり（例えば、高田一貴ら、ながれ ２２（２００３）２０１−２０７「高効率攪拌翼の開発」参照）、具体的な製品としては、株式会社神鋼環境ソリューション製「ログボーン（登録商標）」等が挙げられる。なお、攪拌軸のないダブルヘリカルリボン翼を用いることにより、本発明の応用として塊状重合を行うことも可能になる。 Double helical ribbon blades without stirring shafts are known per se (see, for example, Kazutaka Takada et al., Nagare 22 (2003) 201-207 “Development of High-Efficiency Stirring Blades”). Examples include “Logbone (registered trademark)” manufactured by Shinko Environmental Solution. In addition, by using a double helical ribbon blade without a stirring shaft, bulk polymerization can be performed as an application of the present invention.
重合反応を終了した際の重合溶液には、通常、得られた脂肪族ポリビニルエステル以外に、未反応の脂肪族ビニルエステルモノマーが残存しているが、本発明では、この未反応モノマーを除去する脱モノマーを行うことが好ましい。本発明の重合方法は、溶液重合によるものであるため、脱モノマーは常法により容易に行うことができる。例えば、多段塔の上部から重合溶液を落下させ、塔下部からメタノール蒸気を吹き込むことで脱モノマーを行うことができる。 In the polymerization solution when the polymerization reaction is completed, the unreacted aliphatic vinyl ester monomer usually remains in addition to the obtained aliphatic polyvinyl ester. In the present invention, this unreacted monomer is removed. Demonomerization is preferably performed. Since the polymerization method of the present invention is based on solution polymerization, the demonomer can be easily performed by a conventional method. For example, the monomer removal can be performed by dropping the polymerization solution from the upper part of the multistage tower and blowing methanol vapor from the lower part of the tower.
上記したような本発明の重合方法により、高重合度の脂肪族ポリビニルエステルが得られ、この脂肪族ポリビニルエステルをケン化することにより、高重合度のポリビニルアルコール系樹脂を製造することができる。そのような、ポリビニルアルコール系樹脂の製造方法もまた、本発明のひとつである。 By the polymerization method of the present invention as described above, an aliphatic polyvinyl ester having a high degree of polymerization is obtained, and a polyvinyl alcohol resin having a high degree of polymerization can be produced by saponifying the aliphatic polyvinyl ester. Such a method for producing a polyvinyl alcohol-based resin is also one aspect of the present invention.
本発明において、脂肪族ポリビニルエステルをケン化する方法としては、公知の方法に準じて行えばよく、例えばメタノール等のアルコール類、酢酸メチル、酢酸エチル等のエステル類とアルコール類との混合溶媒中で、水酸化ナトリウムなどのアルカリ金属の水酸化物やナトリウムメチラートなどのアルコラート等をケン化触媒として用いる方法が採用できる。また、ケン化物の乾燥、粉砕方法も特に制限はなく、公知の方法で行えばよい。 In the present invention, the method for saponifying the aliphatic polyvinyl ester may be carried out in accordance with a known method. For example, in a mixed solvent of alcohols such as methanol, esters such as methyl acetate and ethyl acetate, and alcohols. Thus, a method of using an alkali metal hydroxide such as sodium hydroxide or an alcoholate such as sodium methylate as a saponification catalyst can be employed. Moreover, there is no restriction | limiting in particular also in the drying and grinding | pulverization method of a saponification thing, What is necessary is just to perform by a well-known method.
本発明により得られる脂肪族ポリビニルエステルないしポリビニルアルコール系樹脂の重合度としては、４５００以上が好ましく、５０００〜８０００がより好ましい。重合度が４５００未満では、本発明の目的を十分に達成できるとは言い難い。 As a polymerization degree of the aliphatic polyvinyl ester thru | or polyvinyl alcohol-type resin obtained by this invention, 4500 or more are preferable and 5000-8000 are more preferable. If the degree of polymerization is less than 4500, it is difficult to say that the object of the present invention can be sufficiently achieved.
また、本発明では、１，２−グリコール結合量の少ない耐熱性に優れたポリビニルアルコール系樹脂を製造することができる。該１，２−グリコール結合量としては、１．９モル％未満が好ましく、１．８モル％以下がより好ましい。 Moreover, in this invention, the polyvinyl alcohol-type resin excellent in heat resistance with few amounts of 1, 2- glycol bonds can be manufactured. The amount of 1,2-glycol bonds is preferably less than 1.9 mol%, more preferably 1.8 mol% or less.
以下、実施例により本発明をさらに詳しく説明するが、本発明はこれらの実施例により何ら限定されるものではない。
なお、得られたＰＶＡの特性評価は、以下の方法で行った。
（１）重合度；
ＪＩＳ Ｋ ６７２６（１９９４）に従って求めた。
（２）ケン化度；
ＪＩＳ Ｋ ６７２６（１９９４）に従って求めた。
（３）１，２−グリコール結合量；
ＮＭＲ測定装置（Ｖａｒｉａｎ社製、ＵＮＩＴＹ ＩＮＯＶＡ６００）にて、ＤＭＳＯ−ｄ６溶媒で１Ｈ−ＮＭＲスペクトル測定を行い、常法により算出した。
EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited at all by these Examples.
In addition, the characteristic evaluation of obtained PVA was performed with the following method.
(1) Degree of polymerization;
It calculated | required according to JISK6726 (1994).
(2) Saponification degree;
It calculated | required according to JISK6726 (1994).
(3) 1,2-glycol bond amount;
The 1 H-NMR spectrum was measured with a DMSO-d6 solvent using an NMR measurement apparatus (Varian, UNITY INOVA600), and calculation was performed by a conventional method.
（実施例１）
酢酸ビニル９５０質量部、メタノール５０質量部、２，２‘−アゾビス（２、４−ジメチルバレロニトリル）０．０９質量部を図１に示すような攪拌機（中〜高粘度用の平板翼を使用）、還流凝縮器、減圧機、圧力計の付属した重合機に仕込み、重合機の内圧を６１ｋＰａにまで減圧した状態で、沸騰するまで昇温し、溶液重合を開始した。重合溶液の沸騰温度は５２．２℃であった。上記の減圧および沸騰を保ったまま重合反応を行い、重合収率が３６．１％の時点で重合を終了した。
次いで、常法により脱モノマーした後、得られたポリ酢酸ビニルをアルカリケン化して、ケン化度１００モル％のポリビニルアルコールを得た。このポリビニルアルコールの重合度は５１３０であり、１，２−グリコール量は１．７モル％であった。
Example 1
A stirrer (medium to high viscosity flat blades as shown in FIG. 1) is used with 950 parts by weight of vinyl acetate, 50 parts by weight of methanol, and 0.09 parts by weight of 2,2′-azobis (2,4-dimethylvaleronitrile). ), A polymerization condenser equipped with a reflux condenser, a decompressor, and a pressure gauge, and with the internal pressure of the polymerizer reduced to 61 kPa, the temperature was raised until boiling, and solution polymerization was started. The boiling temperature of the polymerization solution was 52.2 ° C. The polymerization reaction was performed while maintaining the above reduced pressure and boiling, and the polymerization was terminated when the polymerization yield was 36.1%.
Subsequently, after demonomerization by a conventional method, the obtained polyvinyl acetate was alkali saponified to obtain polyvinyl alcohol having a saponification degree of 100 mol%. The degree of polymerization of this polyvinyl alcohol was 5130, and the amount of 1,2-glycol was 1.7 mol%.
（実施例２）
酢酸ビニル９８０質量部、メタノール２０質量部、クエン酸０．００１質量部、ジ−ｎ−プロピル パーオキシジカルボネート７．０質量部を、実施例１で使用したのと同じ重合機に仕込み、重合機の内圧を１４ｋＰａにまで減圧した状態で、沸騰するまで昇温し、溶液重合を開始した。重合溶液の沸騰温度は１６．８℃であった。上記の減圧および沸騰を保ったまま重合反応を行い、重合収率が２０％の時点で重合を終了した。
次いで、常法により脱モノマーした後、得られたポリ酢酸ビニルをアルカリケン化して、ケン化度１００モル％のポリビニルアルコールを得た。このポリビニルアルコールの重合度は７８４０であり、１，２−グリコール結合量は１．２モル％であった。
(Example 2)
980 parts by weight of vinyl acetate, 20 parts by weight of methanol, 0.001 part by weight of citric acid, and 7.0 parts by weight of di-n-propyl peroxydicarbonate were charged into the same polymerization machine used in Example 1 and polymerized. In a state where the internal pressure of the machine was reduced to 14 kPa, the temperature was raised until boiling, and solution polymerization was started. The boiling temperature of the polymerization solution was 16.8 ° C. The polymerization reaction was carried out while maintaining the above reduced pressure and boiling, and the polymerization was terminated when the polymerization yield was 20%.
Subsequently, after demonomerization by a conventional method, the obtained polyvinyl acetate was alkali saponified to obtain polyvinyl alcohol having a saponification degree of 100 mol%. The degree of polymerization of this polyvinyl alcohol was 7840, and the amount of 1,2-glycol bonds was 1.2 mol%.
（実施例３）
酢酸ビニル９９０質量部、メタノール１０質量部、２，２‘−アゾビスイソブチロニトリル０．２８質量部を、実施例１で使用したのと同じ重合機に仕込み、重合機の内圧を５１ｋＰａにまで減圧した状態で、沸騰するまで昇温し、溶液重合を開始した。重合溶液の沸騰温度は４８．９℃であった。上記の減圧および沸騰を保ったまま重合反応を行い、重合収率が２５．５％の時点で重合を終了した。
次いで、常法により脱モノマーした後、得られたポリ酢酸ビニルをアルカリケン化してケン化度１００モル％のポリビニルアルコールを得た。このポリビニルアルコールの重合度は６９００であり、１，２−グリコール結合量は１．６モル％であった。
(Example 3)
990 parts by weight of vinyl acetate, 10 parts by weight of methanol, and 0.28 parts by weight of 2,2′-azobisisobutyronitrile were charged into the same polymerization machine used in Example 1, and the internal pressure of the polymerization machine was adjusted to 51 kPa. In a state where the pressure was reduced to 0, the solution was heated to boiling and solution polymerization was started. The boiling temperature of the polymerization solution was 48.9 ° C. The polymerization reaction was carried out while maintaining the above reduced pressure and boiling, and the polymerization was terminated when the polymerization yield was 25.5%.
Subsequently, after demonomerization by a conventional method, the obtained polyvinyl acetate was alkali saponified to obtain polyvinyl alcohol having a saponification degree of 100 mol%. The degree of polymerization of this polyvinyl alcohol was 6900, and the 1,2-glycol bond amount was 1.6 mol%.
（比較例１）
重合機内を減圧せずに大気圧下で行ったこと、およびポリ酢酸ビニルの重合収率を３３．７％としたこと以外は、実施例１と同じ操作をして重合した。沸騰温度は６６．２℃であった。
次いで、常法により脱モノマーした後、得られたポリ酢酸ビニルをアルカリケン化してケン化度１００モル％のポリビニルアルコールを得た。このポリビニルアルコールの重合度は３６５０であり、１，２−グリコール結合量は１．９モル％であった。
(Comparative Example 1)
Polymerization was carried out in the same manner as in Example 1, except that the inside of the polymerization machine was carried out under atmospheric pressure without reducing the pressure, and that the polymerization yield of polyvinyl acetate was 33.7%. The boiling temperature was 66.2 ° C.
Subsequently, after demonomerization by a conventional method, the obtained polyvinyl acetate was alkali saponified to obtain polyvinyl alcohol having a saponification degree of 100 mol%. The degree of polymerization of this polyvinyl alcohol was 3650, and the amount of 1,2-glycol bonds was 1.9 mol%.
（比較例２）
重合機内を減圧せずに大気圧下で行ったこと、ジ−ｎ−プロピル パーオキシジカルボネート７．０質量部の代わりに２，２‘−アゾビス（２，４−ジメチルバレロニトリル）０．０８質量部を用いたこと、およびポリ酢酸ビニルの重合収率を３４．９％としたこと以外は、実施例２と同じ操作をして重合した。沸騰温度は７０．３℃であった。
次いで、常法により脱モノマーした後、得られたポリ酢酸ビニルをアルカリケン化してケン化度１００モル％のポリビニルアルコールを得た。このポリビニルアルコールの重合度は４１８０であり、１，２−グリコール結合量は１．９モル％であった。
(Comparative Example 2)
It was carried out under atmospheric pressure without reducing the pressure in the polymerization machine, and instead of 7.0 parts by mass of di-n-propyl peroxydicarbonate, 2,8'-azobis (2,4-dimethylvaleronitrile) 0.08 Polymerization was carried out in the same manner as in Example 2, except that parts by mass were used and that the polymerization yield of polyvinyl acetate was 34.9%. The boiling temperature was 70.3 ° C.
Subsequently, after demonomerization by a conventional method, the obtained polyvinyl acetate was alkali saponified to obtain polyvinyl alcohol having a saponification degree of 100 mol%. The degree of polymerization of this polyvinyl alcohol was 4180, and the amount of 1,2-glycol bonds was 1.9 mol%.
（比較例３）
重合機内を減圧せずに大気圧下で行ったこと、およびポリ酢酸ビニルの重合収率を２９．１％としたこと以外は、実施例３と同じ操作をして重合した。沸騰温度は７２．５℃であった。
次いで、常法により脱モノマーした後、得られたポリ酢酸ビニルをアルカリケン化してケン化度１００モル％のポリビニルアルコールを得た。このポリビニルアルコールの重合度は４２５０であり、１，２−グリコール結合量は２．０モル％であった。
(Comparative Example 3)
Polymerization was carried out in the same manner as in Example 3, except that the inside of the polymerization machine was carried out under atmospheric pressure without reducing the pressure, and that the polymerization yield of polyvinyl acetate was 29.1%. The boiling temperature was 72.5 ° C.
Subsequently, after demonomerization by a conventional method, the obtained polyvinyl acetate was alkali saponified to obtain polyvinyl alcohol having a saponification degree of 100 mol%. The degree of polymerization of this polyvinyl alcohol was 4250, and the 1,2-glycol bond amount was 2.0 mol%.
（実施例４）
酢酸ビニル９９０質量部、メタノール１０質量部、ジ−ｎ−プロピル パーオキシジカルボネート７．０質量部を、図２に示すような攪拌機（攪拌軸のないダブルヘリカルリボン翼を使用）、還流凝縮器、減圧機、圧力計の付属した重合機に仕込み、重合機の内圧を１４ｋＰａにまで減圧した状態で、沸騰するまで昇温し、溶液重合を開始した。重合溶液の沸騰温度は１８．０℃であった。上記の減圧および沸騰を保ったまま重合反応を行い、重合収率が３９％の時点で重合を終了した。
次いで、常法により脱モノマーした後、得られたポリ酢酸ビニルをアルカリケン化して、ケン化度１００モル％のポリビニルアルコールを得た。このポリビニルアルコールの重合度は７１７０であり、１，２−グリコール結合量は１．２モル％であった。
Example 4
990 parts by weight of vinyl acetate, 10 parts by weight of methanol, and 7.0 parts by weight of di-n-propyl peroxydicarbonate were mixed with a stirrer (using a double helical ribbon blade without a stirring shaft) as shown in FIG. Then, the solution was charged into a polymerization machine equipped with a pressure reducer and a pressure gauge, and the temperature was raised to boiling with the internal pressure of the polymerization machine reduced to 14 kPa, and solution polymerization was started. The boiling temperature of the polymerization solution was 18.0 ° C. The polymerization reaction was performed while maintaining the above reduced pressure and boiling, and the polymerization was terminated when the polymerization yield was 39%.
Subsequently, after demonomerization by a conventional method, the obtained polyvinyl acetate was alkali saponified to obtain polyvinyl alcohol having a saponification degree of 100 mol%. The degree of polymerization of this polyvinyl alcohol was 7170, and the amount of 1,2-glycol bonds was 1.2 mol%.
重合条件および得られたポリビニルアルコールの特性をまとめて下記表１に示す。 The polymerization conditions and the properties of the obtained polyvinyl alcohol are summarized in Table 1 below.
１ 重合機
２ 攪拌機
３ 圧力制御バルブ
４ 還流凝縮器
５ 減圧機
６ 圧力計
７ 原料仕込み口
８ 排出口
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