JP4754112B2 - Dispersion stabilizer for suspension polymerization of vinyl compounds - Google Patents
Dispersion stabilizer for suspension polymerization of vinyl compounds Download PDFInfo
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- JP4754112B2 JP4754112B2 JP2001220097A JP2001220097A JP4754112B2 JP 4754112 B2 JP4754112 B2 JP 4754112B2 JP 2001220097 A JP2001220097 A JP 2001220097A JP 2001220097 A JP2001220097 A JP 2001220097A JP 4754112 B2 JP4754112 B2 JP 4754112B2
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Description
【0001】
【発明の属する技術分野】
本発明はビニル系化合物の懸濁重合用分散安定剤に関する。さらに詳しくは、本発明は、少量の使用で重合槽内壁に付着する重合体スケールが少ないなどの効果を奏して懸濁重合安定性に顕著に優れ、さらにビニル系化合物の懸濁重合によって、可塑剤の吸収性能が高く、粒径分布がシャープでかつ多孔性であり、かさ比重が大きいビニル系重合体粒子を製造することができるビニル系化合物の懸濁重合用分散安定剤に関する。
【0002】
【従来の技術】
塩化ビニル系樹脂などのビニル系重合体の製造は、工業的には、水性媒体中で分散安定剤の存在下で塩化ビニルなどのビニル系化合物を分散させ、油溶性開始剤を用いて重合を行う懸濁重合により広く行われている。一般に、ビニル系重合体の品質を支配する因子としては、重合率、水−モノマー比、重合温度、開始剤の種類および量、重合槽の型式、攪拌速度あるいは分散安定剤の種類などが挙げられるが、この中でも分散安定剤の種類による影響が非常に大きい。
【0003】
ビニル系化合物の懸濁重合用分散安定剤に要求される性能としては、(1)少量の使用で懸濁重合安定性に顕著に優れ、得られるビニル系重合体粒子の粒径分布をできるだけシャープにする働きがあること、(2)可塑剤の吸収速度を大きくして加工性を容易にし、重合体粒子中に残存する塩化ビニルなどのモノマーの除去を容易にし、かつ成形品中のフィッシュアイなどの生成を防止するために、重合体粒子をできるだけ均一にし、さらに多孔性にする働きがあること、(3)かさ比重の大きい重合体粒子を形成する働きがあること、(4)重合槽などにスケールの付着がないことなどが挙げられる。
従来、ビニル系化合物の懸濁重合用分散安定剤としては、メチルセルロース、カルボキシメチルセルロースなどのセルロース誘導体のほか、部分けん化ポリビニルアルコールなどが単独でまたは適当に組み合わされて使用されている。しかしながら、従来の分散安定剤は上記の要求性能を必ずしも十分には満たしていない。
【0004】
さらには、特開昭54−127490号公報、特開平1−95104号公報、特開平3−140303号公報、特開平6−80709号公報、特開平8−259609号公報などにおいて、エチレン単位を含有する変性ポリビニルアルコールからなるビニル系化合物の懸濁重合用分散安定剤が提案されている。特開昭54−127490号公報で提案されたエチレン変性ポリビニルアルコールからなる分散安定剤については、エチレン単位の含有量が大きい変性ポリビニルアルコールを用いた場合には、分散安定剤の水溶性が悪いために作業性が悪化したり、分散安定剤の溶解性を向上させるために水−有機溶媒系の媒体を使用しなければならず、有機溶媒を使用すると懸濁重合後の排水が環境に悪影響を与える要因となる、などの問題があった。特開平1−95104号公報および特開平3−140303号公報で提案された側鎖にイオン性基を有するエチレン変性ポリビニルアルコールからなる分散安定剤においては、水溶性は改善されるものの、塩化ビニルを懸濁重合するときに泡立ちやすく重合槽にスケールが付着しやすいという問題があった。特開平6−80709号公報で提案されたエチレン変性ポリビニルアルコールからなる分散安定剤は、比較的バランスのとれた塩化ビニル樹脂を与えるものの、その塩化ビニル樹脂の可塑剤吸収性や粒子径分布のシャープさは必ずしも十分に満足できるレベルには達していない。さらに、特開平8−259609号公報で提案されたエチレン変性ポリビニルアルコールとポリビニルアルコール系重合体とを併用する分散安定剤は、重合槽内の消泡効果に優れているために、塩化ビニルを懸濁重合する際に泡立ちにより重合槽にスケールが付着するといった問題は改善されるものの、得られる塩化ビニル樹脂の可塑剤吸収性や粒子径分布のシャープさは必ずしも十分に満足できるレベルには達していない。
【0005】
【発明が解決しようとする課題】
本発明は、このような事情のもとで、少量の使用で懸濁重合安定性に顕著に優れ、さらにビニル系化合物の懸濁重合によって、可塑剤の吸収性能が高く、粒径分布がシャープでかつ多孔性であり、かさ比重が大きいビニル系重合体粒子を製造することができるビニル系化合物の懸濁重合用分散安定剤を提供することを目的とする。さらに、本発明の他の目的は、ビニル系重合体粒子中に残存するビニル系化合物の除去が容易であり、取り扱い時の粉の飛散が少なく、また、成型機へのくい込み性がよいという特性を有するビニル系重合体粒子を製造することができるビニル系化合物の懸濁重合用分散安定剤を提供することにある。
【0006】
【課題を解決するための手段】
本発明者らは鋭意検討を重ねた結果、エチレン単位の含有量が0.5〜20モル%、けん化度が60モル%以上、かつ重合度が600以上のビニルアルコール系重合体(A)、ならびにけん化度が20〜55モル%、重合度が100〜550のビニルアルコール系重合体(B)からなるビニル系化合物の懸濁重合用分散安定剤が上記課題を達成するのに有効であることを見出し、本発明を完成するに至った。
【0007】
【発明の実施の形態】
以下、本発明を詳細に説明する。
本発明において用いられるビニルアルコール系重合体(A)のエチレン単位の含有量は0.5〜20モル%であり、好ましくは0.5〜10モル%であり、より好ましくは1〜10モル%であり、さらに好ましくは1.5〜8モル%である。エチレン単位の含有量が0.5モル%未満の場合には、ビニル系化合物を懸濁重合する際に重合槽へのスケールの付着が多くなり、20モル%を越える場合には、ビニルアルコール系重合体の水溶性が低下して取り扱い性が悪化する。
ビニルアルコール系重合体(A)のけん化度は60モル%以上であり、好ましくは65〜95モル%であり、さらに好ましくは70〜90モル%である。けん化度が60モル%未満の場合には、ビニルアルコール系重合体の水溶性が低下して取り扱い性が悪化する。
また、ビニルアルコール系重合体(A)の重合度は600以上であり、好ましくは600〜8000、さらに好ましくは650〜3500である。ビニルアルコール系重合体の重合度が600未満の場合には、ビニル系化合物を懸濁重合する際に重合安定性が低下する。
【0008】
本発明において用いられるビニルアルコール系重合体(B)のけん化度は20〜55モル%であり、好ましくは25〜55モル%であり、さらに好ましくは30〜55モル%である。けん化度が20〜55モル%の範囲を外れた場合には、ビニル化合物の懸濁重合によって得られるビニル系重合体粒子の粒径分布が広くなる。ビニルアルコール系重合体(B)の重合度は100〜550であり、好ましくは150〜550であり、さらに好ましくは200〜550である。重合度が100未満の場合には、ビニル系化合物を懸濁重合する際に重合安定性が悪化し、550を越える場合には、ビニル系化合物の懸濁重合によって得られるビニル系重合体の可塑剤吸収性が悪化する。
【0009】
また、ビニルアルコール系重合体(A)とビニルアルコール系重合体(B)は、そのけん化度の差が15モル%以上および/またはその重合度の差が200以上であることが好ましい。
【0010】
本発明の懸濁重合用分散安定剤において、ビニルアルコール系重合体(A)およびビニルアルコール系重合体(B)の使用比率について厳密な意味での制限はとくにないが、通常(A)成分/(B)成分の重量比で95/5〜20/80であり、好ましくは95/5〜30/70であり、さらに好ましくは95/5〜50/50である。(A)成分/(B)成分の重量比が95/5を越える場合には、ビニル系化合物の懸濁重合によって得られるビニル系重合体の可塑剤吸収性能が悪化したり、粒径分布が広くなる傾向があり、20/80未満の場合には、ビニル系化合物を懸濁重合する際に重合安定性が低下することがある。
【0011】
本発明において、懸濁重合用分散安定剤の使用量について特に制限はないが、ビニル系化合物100重量部に対して0.01〜5重量部が好ましく、0.02〜2重量部がより好ましく、0.02〜1重量部がさらに好ましい。0.01重量部未満の場合には、ビニル系化合物を懸濁重合する際に重合安定性が低下する傾向があり、5重量部を越える場合には、懸濁重合後の廃液が白濁し、化学的酸素要求量(COD)が高くなる傾向がみられる。
【0012】
本発明において用いられるビニルアルコール系重合体(B)は水不溶性または水分散性であり、これにスルホン酸基、アミノ基、アンモニウム基、カルボキシル基、カチオン基などのイオン性基を導入することにより、自己乳化性を付与することができる。イオン性基を導入しない場合には、ビニルアルコール系重合体(B)の水溶性または水分散性が低下して、取り扱い性が悪化することがある。
【0013】
また、本発明において用いられるビニルアルコール系重合体(A)は、アンモニウム基、カルボキシル基、スルホン酸基、アミノ基などのイオン性基を導入することにより水溶性を高めることができ、あるいはノニオン基または(長鎖)アルキル基などを導入してもよい。ビニルアルコール系重合体(A)は、5〜100℃、好ましくは10〜90℃の水に対して水溶性であることが好ましい。
【0014】
ここで、イオン性基、ノニオン基または(長鎖)アルキル基などを導入されたビニルアルコール系重合体のけん化度はビニルエステル基とビニルアルコール基の比から求められ、導入されたイオン性基、ノニオン基または(長鎖)アルキル基などのけん化度は含まれない。
【0015】
本発明において、ビニルアルコール系重合体(A)の製造方法について特に制限はなく、従来公知の方法、例えば特開平8−259609号公報に記載されている方法にしたがって、ビニルエステル系単量体、エチレンおよび必要に応じてイオン性基を有する単量体を共重合し、得られた共重合体を常法によりけん化したり、あるいはチオール酢酸、メルカプトプロピオン酸などのチオール化合物の存在下でビニルエステル系単量体とエチレンを共重合し、それをけん化する末端変性法によっても得ることができる。
【0016】
また、ビニルアルコール系重合体(B)の製造方法についても特に制限はなく、従来公知の方法にしたがって、ビニルエステル系単量体および必要に応じてイオン性基を有する単量体を共重合し、得られた共重合体を常法によりけん化したり、あるいはチオール酢酸、メルカプトプロピオン酸などのチオール化合物の存在下でビニルエステル系単量体を重合し、それをけん化する末端変性法によっても得ることができる。
【0017】
ビニルエステル系単量体とエチレンを共重合する方法としては、溶液重合法、塊状重合法、懸濁重合法、乳化重合法など、従来公知の方法が適用できる。重合開始剤としては、重合方法に応じて、アゾ系開始剤、過酸化物系開始剤、レドックス系開始剤などが適宜選ばれる。けん化反応は、従来公知のアルカリ触媒または酸触媒を用いる加アルコール分解、加水分解などが適用でき、この中でもメタノールを溶剤としNaOH触媒を用いるけん化反応が簡便であり最も好ましい。
【0018】
ここで、ビニルエステル系単量体としては、例えばギ酸ビニル、酢酸ビニル、プロピオン酸ビニル、酪酸ビニル、イソ酪酸ビニル、ピバリン酸ビニル、バーサチック酸ビニル、カプロン酸ビニル、カプリル酸ビニル、ラウリル酸ビニル、パルミチン酸ビニル、ステアリン酸ビニル、オレイン酸ビニル、安息香酸ビニルなどが挙げられるが、なかでも酢酸ビニルが最も好ましい。
【0019】
本発明において、ビニルアルコール系重合体に必要に応じてイオン性基を導入するために用いられるイオン性基を有する単量体としては、特に制限はないが、例えば、エチレンスルホン酸、(メタ)アリルスルホン酸、スルホアルキルマレート、スルホアルキル(メタ)アクリレート、アクリルアミド−2−メチルプロパンスルホン酸などのスルホン酸含有単量体およびその塩;N−(1,1−ジメチル−3−ジメチルアミノプロピル)(メタ)アクリルアミド、N−(1,1−ジメチル−3−ジメチルアミノブチル)(メタ)アクリルアミド、N−ビニルイミダゾール、2−メチル−N−ビニルイミダゾール、ビニル−3−ジメチルアミノプロピルエーテル、ビニル−2−ジメチルアミノエチルエーテル、アリル−3−ジメチルアミノプロピルエーテル、アリルジメチルアミン、メタアリルジメチルアミンなどのアミノ基またはアンモニウム基含有単量体;クロトン酸、マレイン酸、フマル酸、イタコン酸、(メタ)アクリル酸などのカルボキシル基含有単量体などが挙げられる。
【0020】
本発明において、ビニルアルコール系重合体(A)およびビニルアルコール系重合体(B)は、本発明の主旨を損なわない範囲で他の単量体単位を含有しても差し支えない。使用しうるコモノマーとして、例えば、プロピレン、n−ブテン、イソブチレンなどのα−オレフィン;アクリル酸およびその塩;アクリル酸メチル、アクリル酸エチル、アクリル酸n−プロピル、アクリル酸i−プロピル、アクリル酸n−ブチル、アクリル酸i−ブチル、アクリル酸t−ブチル、アクリル酸2−エチルヘキシル、アクリル酸ドデシル、アクリル酸オクタデシルなどのアクリル酸エステル類;メタクリル酸およびその塩;メタクリル酸メチル、メタクリル酸エチル、メタクリル酸n−プロピル、メタクリル酸i−プロピル、メタクリル酸n−ブチル、メタクリル酸i−ブチル、メタクリル酸t−ブチル、メタクリル酸2−エチルヘキシル、メタクリル酸ドデシル、メタクリル酸オクタデシルなどのメタクリル酸エステル類;アクリルアミド;N−メチルアクリルアミド、N−エチルアクリルアミド、N,N−ジメチルアクリルアミド、ジアセトンアクリルアミド、アクリルアミドプロパンスルホン酸およびその塩、アクリルアミドプロピルジメチルアミンおよびその塩またはその4級塩、N−メチロールアクリルアミドおよびその誘導体などのアクリルアミド誘導体;メタクリルアミド;N−メチルメタクリルアミド、N−エチルメタクリルアミド、メタクリルアミドプロパンスルホン酸およびその塩、メタクリルアミドプロピルジメチルアミンおよびその塩またはその4級塩、N−メチロールメタクリルアミドおよびその誘導体などのメタクリルアミド誘導体;メチルビニルエーテル、エチルビニルエーテル、n−プロピルビニルエーテル、i−プロピルビニルエーテル、n−ブチルビニルエーテル、i−ブチルビニルエーテル、t−ブチルビニルエーテル、ドデシルビニルエーテル、ステアリルビニルエーテルなどのビニルエーテル類;アクリロニトリル、メタクリロニトリルなどのニトリル類;塩化ビニル、フッ化ビニルなどのハロゲン化ビニル類;塩化ビニリデン、フッ化ビニリデンなどのハロゲン化ビニリデン類;酢酸アリル、塩化アリルなどのアリル化合物;マレイン酸、イタコン酸、フマル酸などの不飽和ジカルボン酸およびその塩またはそのエステル;ビニルトリメトキシシランなどのビニルシリル化合物;酢酸イソプロペニルなどがある。
【0021】
本発明において、ビニルアルコール系重合体(A)およびビニルアルコール系重合体(B)は、通常、それぞれ別々に、もしくは混合して、水性媒体に溶解または分散され、ビニル系化合物の懸濁重合に供される。
【0022】
本発明の懸濁重合用分散安定剤は、ビニルアルコール系重合体(A)として熱処理されたものを用いることで、懸濁重合時の安定性がさらに向上する。熱処理の条件は特に制限されないが、通常、酸素、空気または窒素雰囲気下、100〜200℃の温度で0.5〜20時間加熱することが好ましい。熱処理時の温度が100℃未満では熱処理による懸濁重合時の安定性向上効果が十分発現しなくなる場合があり、200℃を越えると懸濁重合用分散安定剤が着色するおそれがある。
その際、熱処理による懸濁重合用分散安定剤の着色を抑制するために、熱処理前にビニルアルコール系重合体(A)をメタノール等の溶媒によって洗浄することが好ましい。
【0023】
本発明の懸濁重合用分散安定剤において、ビニルアルコール系重合体(A)として熱処理されたものを用いる場合、少量の使用で懸濁重合安定性に顕著に優れ、また懸濁重合で得られた重合体を加工する際に着色を抑制することができることから、ビニルアルコール系重合体(A)は、25℃におけるpKaが3.5〜5.5の酸および/またはその金属塩(C)を含有していることが好ましい。使用しうる酸の種類についてとくに制限はなく、その具体例として、酢酸(pKa4.76)、プロピオン酸(pKa4.87)、酪酸(pKa4.63)、オクタン酸(pKa4.89)、アジピン酸(pKa5.03)、安息香酸(pKa4.00)、ギ酸(pKa3.55)、吉草酸(pKa4.63)、ヘプタン酸(pKa4.66)、乳酸(pKa3.66)、フェニル酢酸(pKa4.10)、イソ酪酸(pKa4.63)、シクロヘキサンカルボン酸(pKa4.70)などを挙げることができる。奏される効果の点でとくに好ましく用いることができる酸は、酢酸、プロピオン酸、および乳酸である。
また、上記の酸の金属塩としては特に制限はないが、通常、上記の酸とナトリウム、カリウムなどのアルカリ金属からなる金属塩が用いられ、とりわけ酢酸ナトリウムが好適に用いられる。
【0024】
上記の酸および/またはその金属塩(C)の含有量は、ビニルアルコール系重合体(A)100重量部に対して、好ましくは0.05〜2重量部、より好ましくは0.1〜1.7重量部、さらに好ましくは0.2〜1.5重量部の割合である。ビニルアルコール系重合体(A)に対する酸および/またはその金属塩(C)の含有量が0.05重量部未満の場合、熱処理による懸濁重合時の安定性向上効果が低下し、2重量部を越えると、熱処理時に懸濁重合用分散安定剤が着色したり、懸濁重合で得られた重合体を加工する際に重合体が着色するため、好ましくない。
【0025】
次に、本発明の懸濁重合用分散安定剤を用いたビニル系化合物の懸濁重合方法について説明する。
【0026】
本発明の懸濁重合用分散安定剤を用いてビニル系化合物を水性媒体中で懸濁重合するに際し、水性媒体の温度には特に制限はなく、20℃程度の冷水はもとより、90℃以上の温水でも好適に用いられる。この水性媒体は、純粋な水のほか、各種の添加成分を含有する水溶液または他の有機溶剤を含む水性媒体からなることができる。水性媒体を重合反応系に仕込む際に、その供給量は重合反応系を充分に加熱できる量であればよい。また、除熱効率を高めるためにリフラックスコンデンサー付重合器も好適に用いられる。
【0027】
本発明の懸濁重合用分散安定剤は単独で使用してもよいが、ビニル系化合物を水性媒体中で懸濁重合する際に通常使用されるポリビニルアルコール、メチルセルロース、ヒドロキシエチルセルロース、ヒドロキシプロピルセルロース、ヒドロキシプロピルメチルセルロースなどの水溶性セルロースエーテル、ゼラチンなどの水溶性ポリマー;ソルビタンモノラウレート、ソルビタントリオレート、グリセリントリステアレート、エチレンオキシドプロピレンオキシドブロックコポリマーなどの油溶性乳化剤;ポリオキシエチレンソルビタンモノラウレート、ポリオキシエチレングリセリンオレート、ラウリン酸ナトリウムなどの水溶性乳化剤などを併用してもよい。その添加量については特に制限はないが、ビニル系化合物100重量部あたり0.01〜1.0重量部が好ましい。
【0028】
その他の各種添加剤も必要に応じて加えることができる。添加剤としては、例えば、アセトアルデヒド、ブチルアルデヒド、トリクロロエチレン、パークロロエチレン、メルカプタン類などの重合調節剤、フェノール化合物、イオウ化合物、N−オキシド化合物などの重合禁止剤などが挙げられる。また、pH調整剤、スケール防止剤、架橋剤などを加えることも任意であり、上記の添加剤を複数併用しても差し支えない。一方、重合開始剤としても、塩化ビニルなどのビニル系化合物の重合に従来使用されているものを用いることができ、例えば、ジイソプロピルパーオキシジカーボネート、ジ−2−エチルヘキシルパーオキシジカーボネート、ジエトキシエチルパーオキシジカーボネートなどのパーカーボネート化合物;t−ブチルパーオキシネオデカネート、α―クミルパーオキシネオデカネート、t−ブチルパーオキシデカネートなどのパーエステル化合物;アセチルシクロヘキシルスルホニルパーオキシド、2,4,4―トリメチルペンチル−2−パーオキシフェノキシアセテートなどの過酸化物;2,2’―アゾビスイソブチロニトリル、2,2’―アゾビス(2,4−ジメチルバレロニトリル)、2,2’―アゾビス(4−メトキシ−2,4−ジメチルバレロニトリル)などのアゾ化合物などが挙げられ、さらにはこれらに過硫酸カリウム、過硫酸アンモニウム、過酸化水素などを組み合わせて使用することができる。
【0029】
本発明の懸濁重合用分散安定剤を適用することができるビニル系化合物としては、例えば、塩化ビニル、塩化ビニリデン、アルキルビニルエーテル、無水マレイン酸、アクリロニトリル、イタコン酸、スチレンなどのほか、酢酸ビニル、プロピオン酸ビニルなどのビニルエステル類、(メタ)アクリル酸メチル、(メタ)アクリル酸エチルなどの(メタ)アクリル酸エステル類、エチレン、プロピレン、イソブテン、イソプレンなどのα−オレフィン類を挙げることができる。これらのビニル系化合物のうちでも代表的なものは塩化ビニルであり、塩化ビニルは単独で、あるいは塩化ビニルを主体としこれに他の単量体を混合(塩化ビニル50重量%以上)して使用することができる。この塩化ビニルと共重合されるコモノマーとしては、酢酸ビニル、プロピオン酸ビニルなどのビニルエステル類、(メタ)アクリル酸メチル、(メタ)アクリル酸エチルなどの(メタ)アクリル酸エステル類、エチレン、プロピレンなどのα−オレフィン類、無水マレイン酸、アクリロニトリル、イタコン酸、スチレン、塩化ビニリデン、ビニルエーテルなどが例示される。
【0030】
本発明の懸濁重合用分散安定剤を用いてビニル系化合物を懸濁重合するに当たって、各成分の仕込み割合、重合温度などは、従来塩化ビニルなどのビニル系化合物の懸濁重合で採用されている条件に準じて定めればよい。また、ビニル系化合物、重合開始剤、分散安定剤、水性媒体およびその他添加物の仕込み順序や比率について何ら制限はない。また、水性媒体として温水を用いると同時に、ビニル系化合物を重合器に仕込む前にビニル系化合物を加熱しておく方法も好適に用いられる。
【0031】
【実施例】
以下に実施例を挙げて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ってなんら限定されるものではない。なお、以下の実施例において「%」および「部」は特に断りのない限り、「重量%」および「重量部」を意味する。また、以下においてポリビニルアルコールをPVA、ポリ酢酸ビニルをPVAc、ビニルアルコール系重合体をPVA系重合体と略記することがある。
【0032】
(PVA系重合体の分析)
(1)重合度の測定
JIS K6726に従ってPVA系重合体の重合度を測定した。
(2)けん化度の測定
JIS K6726に従ってPVA系重合体のけん化度を測定した。
(3)酸金属塩の定量
(株)島津製作所製の細管式等速電気泳動分析装置(IP−3A)を用い、PVA系重合体中に含有される酢酸ナトリウムを電気泳動分析により定量した。
(4)熱処理時の着色性
PVA系重合体を空気雰囲気下で150℃、2時間熱処理した後、PVA系重合体の着色の程度を目視観察し、以下の基準で評価した。
○:変化なし
△:微黄色に着色
×:赤茶色に着色
【0033】
(塩化ビニル系単量体の重合性および得られた塩化ビニル系重合体の特性評価)
(1)粒径分布
タイラーメッシュ基準の金網を使用して乾式篩分析により粒径分布を測定した。
(2)かさ比重
JIS K6721に従って塩化ビニル系重合体のかさ比重を測定した。
(3)CPA(Cold Plasticizer Absorption:冷可塑剤吸収)
ASTM−D3367−75に記載された方法より、23℃におけるジオクチルフタレートの吸収量を測定した。
(4)スケール付着性
重合体スラリーを重合槽外に取り出した後、重合槽内におけるスケール付着の状態を目視観察し、以下の基準で評価した。
○:重合体スケールの付着がほとんどない
△:重合槽内壁に白色の重合体スケールが確認できる
×:重合槽内壁に白色の重合体スケールが多く確認できる
(5)熱処理時の着色性
塩化ビニル系重合体を空気雰囲気下で140℃、10分間熱処理した後、塩化ビニル系重合体の着色の程度を目視観察し、以下の基準で評価した。
○:変化なし
△:微黄色に着色
×:黄色に着色
【0034】
実施例1
(PVA系重合体の製造)
撹拌機、窒素導入口、エチレン導入口および開始剤添加口を備えた100L加圧反応槽に酢酸ビニル38.1kg、メタノール21.8kgを仕込み、60℃に昇温した後30分間窒素バブリングにより系中を窒素置換した。次いで反応槽圧力が0.10MPaとなるようにエチレンを導入仕込みした。開始剤として2,2’−アゾビス(4−メトキシ−2,4−ジメチルバレロニトリル)をメタノールに溶解した濃度2.8g/L溶液を調製し、窒素ガスによるバブリングを行って窒素置換した。上記の反応槽内温を60℃に調整した後、上記の開始剤溶液32mLを注入し、重合を開始した。重合中はエチレンを導入して反応槽圧力を0.10MPaに、重合温度を60℃に維持し、上記の開始剤溶液を102mL/hrで連続添加した。5時間後に重合率が50%に達したところで冷却して重合を停止した。反応槽を開放して脱エチレンした後、窒素ガスをバブリングして脱エチレンを完全に行った。次いで減圧下に未反応酢酸ビニル単量体を除去し、PVAc系重合体のメタノール溶液を得た。30%に調整した該溶液にアルカリモル比(NaOHのモル数/PVAc系重合体中のビニルエステル単位のモル数)が0.006となるようにNaOHメタノール溶液(10%濃度)を添加してけん化した。けん化反応後、反応溶液中の固形分を粉砕してから遠心脱液を行い、60℃で減圧乾燥してPVA系重合体を得た。該PVA系重合体のけん化度を常法のJIS K6726に準じて測定したところ85モル%であった。
【0035】
重合後に未反応酢酸ビニル単量体を除去して得られたPVAc系重合体のメタノール溶液をn−ヘキサンに投入してPVAc系重合体を沈殿させ、回収したPVAc系重合体をアセトンで溶解する再沈精製を3回行った後、60℃で減圧乾燥してPVAc系重合体の精製物を得た。該PVAc系重合体のプロトンNMR測定から求めたエチレン単位の含有量は2モル%であった。また、上記のPVAc系重合体のメタノール溶液をアルカリモル比0.2でけん化した後、メタノールによるソックスレー抽出を3日間実施し、次いで乾燥してPVA系重合体の精製物を得た。該PVA系重合体の平均重合度を常法のJIS K6726に準じて測定したところ1000であった。
上記操作により重合度1000、けん化度85モル%、エチレン含有量2モル%のPVA系重合体(A)を得た。以下、これをPVA系重合体(A−1)と称する。
【0036】
上記操作により得られる重合体は、その重合操作において酢酸ビニルなどの単量体に対するメタノールの重量比を変えることで該重合体の重合度を、反応槽内のエチレンの圧力を変えることで該重合体のエチレン含有量を変えることができ、そのけん化操作においてアルカリモル比を変えることで該重合体のけん化度を変えることができる。上記操作において、重合時にエチレンを使用せず、単量体/メタノールの重量比を変更し、けん化時にアルカリモル比を変更して重合度250、けん化度40モル%のPVA系重合体(B)を得た。以下、これをPVA系重合体(B−1)と称する。
【0037】
(塩化ビニルの重合)
グラスライニング製オートクレーブに、表1に示した分散安定剤を溶かした脱イオン水40部およびジイソプロピルパーオキシジカーボネートの70%トルエン溶液0.04部を仕込み、オートクレーブ内を0.0067MPaとなるまで脱気して酸素を除いた後、塩化ビニル単量体30部を仕込み、攪拌下に57℃に昇温して重合を行った。重合開始時、オートクレーブ内の圧力は0.83MPaであったが、重合開始6時間後に0.49MPaとなった時点で重合を停止し、未反応の塩化ビニル単量体をパージし、内容物を取り出し脱水乾燥した。塩化ビニル重合体の重合収率は85%であり、平均重合度は1050であった。重合性および塩化ビニル重合体の特性を上記の方法により評価した。評価結果を表2に示す。
【0038】
実施例2および3
(塩化ビニルの重合)
実施例1において、PVA系重合体(A)としてPVA系重合体(A−1)、PVA系重合体(B)としてPVA系重合体(B−1)を分散安定剤に用い、表1に示したようにPVA系重合体(A)の使用量、およびPVA系重合体(A)とPVA系重合体(B)の重量比(A)/(B)を変えた以外は実施例1と同様に操作して塩化ビニルの懸濁重合を行い、重合性の評価および塩化ビニル重合体の特性の評価を行った。評価結果を表2に示す。
【0039】
実施例4および5
(PVA系重合体の製造)
実施例1において、重合時に単量体/メタノールの重量比および反応槽内のエチレンの圧力を変更し、けん化時にアルカリモル比を変更して重合度1700、けん化度88モル%、エチレン含有量5モル%のPVA系重合体(A)を得た。
以下、これをPVA系重合体(A−2)と称する。
【0040】
(塩化ビニルの重合)
実施例1において、PVA系重合体(A)としてPVA系重合体(A−2)、PVA系重合体(B)としてPVA系重合体(B−1)を分散安定剤に用い、表1に示したようにPVA系重合体(A)の使用量、およびPVA系重合体(A)とPVA系重合体(B)の重量比(A)/(B)を変えた以外は実施例1と同様に操作して塩化ビニルの懸濁重合を行い、重合性の評価および塩化ビニル重合体の特性の評価を行った。評価結果を表2に示す。
【0041】
実施例6
(PVA系重合体の製造)
実施例1において、重合時に単量体/メタノールの重量比および反応槽内のエチレンの圧力を変更し、けん化時にアルカリモル比を変更して重合度700、けん化度70モル%、エチレン含有量1.5モル%のPVA系重合体(A)を得た。以下、これをPVA系重合体(A−3)と称する。
また、重合時にエチレンを使用せず、単量体/メタノールの重量比を変更し、けん化時にアルカリモル比を変更して重合度500、けん化度55モル%のPVA系重合体(B)を得た。以下、これをPVA系重合体(B−2)と称する。
【0042】
(塩化ビニルの重合)
実施例1において、PVA系重合体(A)としてPVA系重合体(A−3)、PVA系重合体(B)としてPVA系重合体(B−2)を分散安定剤に用い、表1に示したようにPVA系重合体(A)とPVA系重合体(B)の重量比(A)/(B)を変えた以外は実施例1と同様に操作して塩化ビニルの懸濁重合を行い、重合性の評価および塩化ビニル重合体の特性の評価を行った。評価結果を表2に示す。
【0043】
実施例7
(側鎖にカルボキシル基を含有するPVA系重合体の製造)
撹拌機、窒素導入口、還流冷却器および添加剤導入口を備えた100L反応槽に酢酸ビニル21.0kg、メタノール38.9kgを仕込み、60℃に昇温した後30分間窒素バブリングにより系中を窒素置換した。コモノマーとしてイタコン酸をメタノールに溶解した濃度10%溶液を調製し、窒素ガスによるバブリングを行って窒素置換した。上記の反応槽内温を60℃に調整し、イタコン酸9.4gを添加した後に、2,2’−アゾビス(イソブチロニトリル)50gを加えて重合を開始した。重合中は重合温度を60℃に維持し、イタコン酸の10%メタノール溶液を600mL/hrで連続添加し、5時間後に重合率が65%に達したところで冷却して重合を停止した。次いで減圧下に未反応酢酸ビニル単量体を除去し、PVAc系重合体のメタノール溶液を得た。30%に調整した該溶液にアルカリモル比(NaOHのモル数/PVAc系重合体中のビニルエステル単位のモル数)が0.002となるようにNaOHメタノール溶液(10%濃度)を添加してけん化した。けん化反応後、反応溶液中の固形分を粉砕してから遠心脱液を行い、60℃で減圧乾燥してPVA系重合体を得た。該PVA系重合体のけん化度を常法のJIS K6726に準じて測定したところ40モル%であった。
【0044】
重合後に未反応酢酸ビニル単量体を除去して得られたPVAc系重合体のメタノール溶液をn−ヘキサンに投入してPVAc系重合体を沈殿させ、回収したPVAc系重合体をアセトンで溶解する再沈精製を3回行った後、60℃で減圧乾燥してPVAc系重合体の精製物を得た。該PVAc系重合体のプロトンNMR測定から求めたイタコン酸単位の含有量は1モル%であった。また、上記のPVAc系重合体のメタノール溶液をアルカリモル比0.2でけん化した後、メタノールによるソックスレー抽出を3日間実施し、次いで乾燥してPVA系重合体の精製物を得た。該PVA系重合体の平均重合度を常法のJIS K6726に準じて測定したところ400であった。
【0045】
上記操作により重合度400、けん化度40モル%で、側鎖にイオン性基としてカルボキシル基を含有するPVA系重合体(B)を得た。以下、これをイオン変性PVA系重合体(B−3)と称する。
【0046】
(塩化ビニルの重合)
実施例1において、PVA系重合体(A)としてPVA系重合体(A−2)、PVA系重合体(B)としてイオン変性PVA系重合体(B−3)を分散安定剤に用い、表1に示したように重量比(A)/(B)を変えた以外は実施例1と同様に操作して塩化ビニルの懸濁重合を行い、重合性の評価および塩化ビニル重合体の特性の評価を行った。評価結果を表2に示す。
【0047】
実施例8
(末端にカルボキシル基を含有するPVA系重合体の製造)
撹拌機、窒素導入口、添加剤導入口および開始剤添加口を備えた100L反応槽に酢酸ビニル49.7kg、メタノール12.3kgを仕込み、60℃に昇温した後30分間窒素バブリングにより系中を窒素置換した。連鎖移動剤として3−メルカプトプロピオン酸(以下、3−MPAと記載する)をメタノールに溶解した濃度10%溶液を調製し、窒素ガスによるバブリングを行って窒素置換した。上記の反応槽内温を60℃に調整し、3−MPA4.2gを添加した後に、2,2’−アゾビス(4−メトキシ−2,4−ジメチルバレロニトリル)20gを加えて重合を開始した。重合中は重合温度を60℃に維持し、3−MPAの10%メタノール溶液を230mL/hrで連続添加した。4時間後に重合率が65%に達したところで冷却して重合を停止した。次いで減圧下に未反応酢酸ビニル単量体を除去し、PVAc系重合体のメタノール溶液を得た。30%に調整した該溶液にアルカリモル比(NaOHのモル数/PVAc系重合体中のビニルエステル単位のモル数)が0.002となるようにNaOHメタノール溶液(10%濃度)を添加してけん化した。けん化反応後、反応溶液中の固形分を粉砕してから遠心脱液を行い、60℃で減圧乾燥してPVA系重合体を得た。該PVA系重合体のけん化度を常法のJIS K6726に準じて測定したところ40モル%であった。
【0048】
重合後に未反応酢酸ビニル単量体を除去して得られたPVAc系重合体のメタノール溶液をn−ヘキサンに投入してPVAc系重合体を沈殿させ、回収したPVAc系重合体をアセトンで溶解する再沈精製を3回行った後、60℃で減圧乾燥してPVAc系重合体の精製物を得た。また、上記のPVAc系重合体のメタノール溶液をアルカリモル比0.2でけん化した後、メタノールによるソックスレー抽出を3日間実施し、次いで乾燥してPVA系重合体の精製物を得た。該PVA系重合体の平均重合度を常法のJIS K6726に準じて測定したところ350であった。
【0049】
上記操作により重合度350、けん化度40モル%で、末端にイオン性基としてカルボキシル基を含有するPVA系重合体(B)を得た。以下、これを末端イオン変性PVA系重合体(B−4)と称する。
【0050】
(塩化ビニルの重合)
実施例1において、PVA系重合体(A)としてPVA系重合体(A−3)、PVA系重合体(B)として末端イオン変性PVA系重合体(B−4)を分散安定剤に用い、表1に示したように重量比(A)/(B)を変えた以外は実施例1と同様に操作して塩化ビニルの懸濁重合を行い、重合性の評価および塩化ビニル重合体の特性の評価を行った。評価結果を表2に示す。
【0051】
比較例1
(PVA系重合体の製造)
実施例1において、重合時にエチレンを用いないように変更し、重合度1000、けん化度85モル%のPVA系重合体を得た。以下、これをPVA系重合体(a−1)と称する。
【0052】
(塩化ビニルの重合)
実施例1において、PVA系重合体(A)の代わりにPVA系重合体(a−1)、PVA系重合体(B)としてPVA系重合体(B−1)を分散安定剤に用いた以外は実施例1と同様に操作して塩化ビニルの懸濁重合を行い、重合性の評価を行った。得られた塩化ビニル重合体は反応槽内でブロック化したため、その特性の評価は行わなかった。評価結果を表2に示す。
【0053】
比較例2
(塩化ビニルの重合)
実施例1において、PVA系重合体(A)としてPVA系重合体(A−1)を分散安定剤に用い、PVA系重合体(B)を用いずに、それ以外は実施例1と同様に操作して塩化ビニルの懸濁重合を行い、重合性の評価および塩化ビニル重合体の特性の評価を行った。評価結果を表2に示す。
【0054】
比較例3
(PVA系重合体の製造)
実施例1において、重合時にエチレンを使用せず、単量体/メタノールの重量比を変更し、けん化時にアルカリモル比を変更して重合度1700、けん化度88モル%のPVA系重合体を得た。以下、これをPVA系重合体(a−2)と称する。
【0055】
(塩化ビニルの重合)
実施例1において、PVA系重合体(A)の代わりにPVA系重合体(a−2)、PVA系重合体(B)としてPVA系重合体(B−1)を分散安定剤に用い、表1に示したように重量比(A)/(B){ここでは重量比(a−2)/(B−1)}を変えた以外は実施例1と同様に操作して塩化ビニルの懸濁重合を行い、重合性の評価および塩化ビニル重合体の特性の評価を行った。評価結果を表2に示す。
【0056】
比較例4
(PVA系重合体の製造)
実施例1において、重合時にエチレンを使用せず、単量体/メタノールの重量比を変更し、けん化時にアルカリモル比を変更して重合度700、けん化度70モル%のPVA系重合体を得た。以下、これをPVA系重合体(a−3)と称する。
【0057】
(塩化ビニルの重合)
実施例1において、PVA系重合体(A)の代わりにPVA系重合体(a−3)、PVA系重合体(B)としてPVA系重合体(B−2)を分散安定剤に用い、表1に示したように重量比(A)/(B){ここでは重量比(a−3)/(B−2)}を変えた以外は実施例1と同様に操作して塩化ビニルの懸濁重合を行い、重合性の評価を行った。得られた塩化ビニル重合体は反応槽内でブロック化したため、その特性の評価は行わなかった。評価結果を表2に示す。
【0058】
【表1】
【0059】
【表2】
【0060】
実施例9
(PVA系重合体の製造)
実施例1において、PVAc系重合体のけん化反応後、得られたPVA系重合体を、重量基準でPVA系重合体の30倍量のメタノールを用いて25℃で洗浄し、60℃で減圧乾燥した後、空気中で150℃、2時間熱処理した以外は実施例1と同様に操作して、重合度1000、けん化度85モル%、エチレン含有量2モル%のPVA系重合体(A)を得た。以下、これをPVA系重合体(A−4)と称する。PVA系重合体(A−4)を電気泳動法により分析したところ、該PVA系重合体100重量部当たりの酢酸ナトリウムの含有量は0.7重量部であった。また、上記の熱処理されたPVA系重合体(A−4)に着色は見られなかった。
【0061】
(塩化ビニルの重合)
グラスライニング製オートクレーブに、表3に示したPVA系重合体を溶かした脱イオン水40部およびジイソプロピルパーオキシジカーボネートの70%トルエン溶液0.016部を仕込み、オートクレーブ内を0.0067MPaとなるまで脱気して酸素を除いた後、塩化ビニル単量体30部を仕込み、攪拌下に65℃に昇温して重合を行った。重合開始時、オートクレーブ内の圧力は1.08MPaであったが、重合開始6時間後に0.44MPaとなった時点で重合を停止し、未反応の塩化ビニル単量体をパージし、内容物を取り出し脱水乾燥した。
スケール付着性および塩化ビニル重合体の熱処理時の着色性を上記の方法により評価した。評価結果を表3に示す。
【0062】
比較例5
(PVA系重合体の製造)
実施例1において、PVAc系重合体のけん化反応後、得られたPVA系重合体を、電気泳動法により分析して該PVA系重合体100重量部当たりの酢酸ナトリウムの含有量が0.02重量部になるまで、重量基準でPVA系重合体の30倍量のメタノールを用いて25℃で洗浄する操作を繰り返し、60℃で減圧乾燥した後、空気中で150℃、2時間熱処理した以外は実施例1と同様に操作して、重合度1000、けん化度85モル%、エチレン含有量2モル%のPVA系重合体(A)を得た。以下、これをPVA系重合体(A−5)と称する。PVA系重合体(A−5)を電気泳動法により分析したところ、該PVA系重合体100重量部当たりの酢酸ナトリウムの含有量は0.02重量部であった。また、上記の熱処理されたPVA系重合体(A−5)に着色は見られなかった。
【0063】
(塩化ビニルの重合)
実施例9において、PVA系重合体(A−4)の代わりにPVA系重合体(A−5)を使用した以外は実施例9と同様に操作して塩化ビニルの懸濁重合を行い、スケール付着性および塩化ビニル重合体の熱処理時の着色性を評価した。評価結果を表3に示す。
【0064】
比較例6
(PVA系重合体の製造)
実施例1において、PVAc系重合体のけん化反応時に、30%に調整したPVAc系重合体のメタノール溶液に、アルカリモル比(NaOHのモル数/PVAc系重合体中のビニルエステル単位のモル数)が0.006となるようにNaOHメタノール溶液(10%濃度)を添加し、さらに酢酸ナトリウム0.3kgを添加してけん化し、60℃で減圧乾燥した後、得られたPVA系重合体を空気中で150℃、2時間熱処理した以外は実施例1と同様に操作して、重合度1000、けん化度85モル%、エチレン含有量2モル%のPVA系重合体(A)を得た。以下、これをPVA系重合体(A−6)と称する。PVA系重合体(A−6)を電気泳動法により分析したところ、該PVA系重合体100重量部当たりの酢酸ナトリウムの含有量は2.5重量部であった。また、上記の熱処理されたPVA系重合体(A−6)は赤茶色に着色していた。
【0065】
(塩化ビニルの重合)
実施例9において、PVA系重合体(A−4)の代わりにPVA系重合体(A−6)を使用した以外は実施例9と同様に操作して塩化ビニルの懸濁重合を行い、スケール付着性および塩化ビニル重合体の熱処理時の着色性を評価した。評価結果を表3に示す。
【0066】
【表3】
【0067】
【発明の効果】
本発明のビニル系化合物の懸濁重合用分散安定剤は、少量の使用で懸濁重合安定性に顕著に優れ、さらにこのものを使用してビニル系化合物を懸濁重合することにより、重合体粒子の粒径分布がシャープである、取り扱い時の飛散が少ない、成型機などへのくい込み性が良好である、可塑剤の吸収速度が大きくて加工性に優れる、重合体粒子中に残存するモノマーの除去が容易である、重合体粒子が多孔性であることから成形品中のフィッシュアイが少ない、かさ比重が高いなどの特性を具えたビニル系重合体を製造することができることから、その工業的な評価はきわめて高い。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a dispersion stabilizer for suspension polymerization of vinyl compounds. More specifically, the present invention has an effect that the polymer scale adhering to the inner wall of the polymerization tank is small when used in a small amount and is remarkably excellent in suspension polymerization stability. The present invention relates to a dispersion stabilizer for suspension polymerization of a vinyl compound that can produce vinyl polymer particles having high absorption performance of the agent, sharp particle size distribution, porosity, and large bulk specific gravity.
[0002]
[Prior art]
In the industrial production of vinyl polymers such as vinyl chloride resins, vinyl compounds such as vinyl chloride are dispersed in an aqueous medium in the presence of a dispersion stabilizer and polymerized using an oil-soluble initiator. Widely performed by suspension polymerization. In general, factors governing the quality of vinyl polymers include polymerization rate, water-monomer ratio, polymerization temperature, type and amount of initiator, type of polymerization tank, stirring speed or type of dispersion stabilizer. However, among these, the influence of the type of dispersion stabilizer is very large.
[0003]
The performance required for the dispersion stabilizer for suspension polymerization of vinyl compounds is as follows: (1) The suspension polymerization stability is remarkably excellent with a small amount of use, and the particle size distribution of the resulting vinyl polymer particles is as sharp as possible. (2) Increase the plasticizer absorption rate to facilitate processability, facilitate removal of monomers such as vinyl chloride remaining in polymer particles, and fish eyes in molded articles In order to prevent the formation of polymer particles, etc., to make the polymer particles as uniform and porous as possible, (3) to function to form polymer particles having a large bulk specific gravity, and (4) a polymerization tank For example, there is no scale adhesion.
Conventionally, as dispersion stabilizers for suspension polymerization of vinyl compounds, in addition to cellulose derivatives such as methyl cellulose and carboxymethyl cellulose, partially saponified polyvinyl alcohol and the like have been used alone or in appropriate combination. However, conventional dispersion stabilizers do not always satisfy the above required performance.
[0004]
Further, in JP 54-127490 A, JP 1-95104 A, JP 3-140303 A, JP 6-80709 A, JP 8-259609 A and the like, an ethylene unit is contained. Dispersion stabilizers for suspension polymerization of vinyl compounds comprising modified polyvinyl alcohol have been proposed. Regarding the dispersion stabilizer composed of ethylene-modified polyvinyl alcohol proposed in JP-A No. 54-127490, when the modified polyvinyl alcohol having a large ethylene unit content is used, the water-solubility of the dispersion stabilizer is poor. In order to improve workability or to improve the solubility of the dispersion stabilizer, a water-organic solvent system medium must be used. If an organic solvent is used, the waste water after suspension polymerization will adversely affect the environment. There was a problem such as becoming a factor to give. In the dispersion stabilizer composed of ethylene-modified polyvinyl alcohol having an ionic group in the side chain proposed in JP-A-1-95104 and JP-A-3-140303, although water solubility is improved, vinyl chloride is used. There was a problem that the suspension tank was easily foamed and the scale was likely to adhere to the polymerization tank. Although the dispersion stabilizer composed of ethylene-modified polyvinyl alcohol proposed in JP-A-6-80709 gives a relatively balanced vinyl chloride resin, the plasticizer absorbability and particle size distribution of the vinyl chloride resin are sharp. This is not always fully satisfactory. Furthermore, the dispersion stabilizer proposed by using JP-A-8-259609 in combination with an ethylene-modified polyvinyl alcohol and a polyvinyl alcohol polymer is excellent in the defoaming effect in the polymerization tank. Although the problem of scales adhering to the polymerization tank due to foaming during turbid polymerization is improved, the plasticizer absorbability and sharpness of the particle size distribution of the obtained vinyl chloride resin have not yet reached satisfactory levels. Absent.
[0005]
[Problems to be solved by the invention]
Under such circumstances, the present invention is remarkably excellent in suspension polymerization stability with a small amount of use, and further, by suspension polymerization of vinyl compounds, the plasticizer has high absorption performance and sharp particle size distribution. Another object of the present invention is to provide a dispersion stabilizer for suspension polymerization of a vinyl compound that can produce vinyl polymer particles that are porous and have a large bulk specific gravity. Furthermore, another object of the present invention is that the vinyl compound remaining in the vinyl polymer particles can be easily removed, the powder is less scattered during handling, and the bite into the molding machine is good. Another object of the present invention is to provide a dispersion stabilizer for suspension polymerization of a vinyl compound, which can produce vinyl polymer particles having the following.
[0006]
[Means for Solving the Problems]
As a result of intensive studies, the present inventors have found that a vinyl alcohol polymer (A) having an ethylene unit content of 0.5 to 20 mol%, a saponification degree of 60 mol% or more, and a polymerization degree of 600 or more, And saponification degree is 20 ~ 55 Mol%, degree of polymerization 100 ~ 550 A dispersion stabilizer for suspension polymerization of a vinyl compound comprising the vinyl alcohol polymer (B) was found to be effective in achieving the above-mentioned problems, and the present invention was completed.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
The ethylene unit content of the vinyl alcohol polymer (A) used in the present invention is 0.5 to 20 mol%, preferably 0.5 to 10 mol%, more preferably 1 to 10 mol%. More preferably, it is 1.5 to 8 mol%. When the ethylene unit content is less than 0.5 mol%, the scale is attached to the polymerization tank during suspension polymerization of the vinyl compound, and when it exceeds 20 mol%, the vinyl alcohol type is used. The water-solubility of the polymer is lowered and the handleability is deteriorated.
The saponification degree of the vinyl alcohol polymer (A) is 60 mol% or more, preferably 65 to 95 mol%, and more preferably 70 to 90 mol%. When the degree of saponification is less than 60 mol%, the water solubility of the vinyl alcohol polymer is lowered and the handleability is deteriorated.
Moreover, the polymerization degree of a vinyl alcohol-type polymer (A) is 600 or more, Preferably it is 600-8000, More preferably, it is 650-3500. When the degree of polymerization of the vinyl alcohol polymer is less than 600, the polymerization stability is lowered when the vinyl compound is subjected to suspension polymerization.
[0008]
The saponification degree of the vinyl alcohol polymer (B) used in the present invention is 20 to 55 Mol%, preferably 25- 55 It is mol%, More preferably, it is 30-55 mol%. Saponification degree is 20 ~ 55 When out of the mol% range, the particle size distribution of the vinyl polymer particles obtained by suspension polymerization of the vinyl compound becomes wide. The degree of polymerization of the vinyl alcohol polymer (B) is 100- 550 Preferably, it is 150-550, More preferably, it is 200-550. When the degree of polymerization is less than 100, the polymerization stability deteriorates when the vinyl compound is subjected to suspension polymerization, 550 In the case of exceeding the above, the plasticizer absorbability of the vinyl polymer obtained by suspension polymerization of the vinyl compound deteriorates.
[0009]
Further, the vinyl alcohol polymer (A) and the vinyl alcohol polymer (B) preferably have a difference in saponification degree of 15 mol% or more and / or a difference in polymerization degree of 200 or more.
[0010]
In the dispersion stabilizer for suspension polymerization of the present invention, the use ratio of the vinyl alcohol polymer (A) and the vinyl alcohol polymer (B) is not particularly limited in the strict sense. The weight ratio of the component (B) is 95/5 to 20/80, preferably 95/5 to 30/70, and more preferably 95/5 to 50/50. When the weight ratio of the component (A) / component (B) exceeds 95/5, the plasticizer absorption performance of the vinyl polymer obtained by suspension polymerization of the vinyl compound is deteriorated, or the particle size distribution is When it is less than 20/80, the polymerization stability may be lowered when the vinyl compound is subjected to suspension polymerization.
[0011]
In the present invention, the amount of the dispersion stabilizer for suspension polymerization is not particularly limited, but is preferably 0.01 to 5 parts by weight, more preferably 0.02 to 2 parts by weight with respect to 100 parts by weight of the vinyl compound. 0.02 to 1 part by weight is more preferable. When the amount is less than 0.01 part by weight, the polymerization stability tends to decrease when the vinyl compound is subjected to suspension polymerization. When the amount exceeds 5 parts by weight, the waste liquid after suspension polymerization becomes cloudy. There is a trend towards higher chemical oxygen demand (COD).
[0012]
The vinyl alcohol polymer (B) used in the present invention is water-insoluble or water-dispersible. By introducing an ionic group such as a sulfonic acid group, an amino group, an ammonium group, a carboxyl group, or a cationic group into the vinyl alcohol polymer (B). Self-emulsifying property can be imparted. When an ionic group is not introduced, the water solubility or water dispersibility of the vinyl alcohol polymer (B) is lowered, and the handleability may be deteriorated.
[0013]
The vinyl alcohol polymer (A) used in the present invention can be improved in water solubility by introducing an ionic group such as an ammonium group, a carboxyl group, a sulfonic acid group, an amino group, or a nonionic group. Alternatively, a (long chain) alkyl group or the like may be introduced. The vinyl alcohol polymer (A) is preferably water-soluble in water at 5 to 100 ° C., preferably 10 to 90 ° C.
[0014]
Here, the saponification degree of the vinyl alcohol polymer into which an ionic group, a nonionic group, or a (long chain) alkyl group is introduced is determined from the ratio of the vinyl ester group to the vinyl alcohol group, and the introduced ionic group, It does not include the degree of saponification such as nonionic groups or (long chain) alkyl groups.
[0015]
In the present invention, the production method of the vinyl alcohol polymer (A) is not particularly limited, and according to a conventionally known method, for example, a method described in JP-A-8-259609, a vinyl ester monomer, Copolymerize ethylene and a monomer having an ionic group as necessary, and saponify the resulting copolymer by a conventional method, or vinyl ester in the presence of a thiol compound such as thiolacetic acid or mercaptopropionic acid. It can also be obtained by a terminal modification method in which a monomer and ethylene are copolymerized and saponified.
[0016]
Further, the production method of the vinyl alcohol polymer (B) is not particularly limited, and a vinyl ester monomer and, if necessary, a monomer having an ionic group are copolymerized according to a conventionally known method. The obtained copolymer is saponified by a conventional method, or a vinyl ester monomer is polymerized in the presence of a thiol compound such as thiolacetic acid or mercaptopropionic acid, and obtained by a terminal modification method for saponifying it. be able to.
[0017]
As a method for copolymerizing the vinyl ester monomer and ethylene, conventionally known methods such as solution polymerization, bulk polymerization, suspension polymerization, and emulsion polymerization can be applied. As the polymerization initiator, an azo initiator, a peroxide initiator, a redox initiator, or the like is appropriately selected depending on the polymerization method. As the saponification reaction, conventionally known alcoholysis or hydrolysis using an alkali catalyst or an acid catalyst can be applied. Among them, a saponification reaction using methanol as a solvent and an NaOH catalyst is simple and most preferred.
[0018]
Here, as the vinyl ester monomer, for example, vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl versatate, vinyl caproate, vinyl caprylate, vinyl laurate, Examples thereof include vinyl palmitate, vinyl stearate, vinyl oleate, vinyl benzoate, etc. Among them, vinyl acetate is most preferable.
[0019]
In the present invention, the monomer having an ionic group used for introducing an ionic group as needed into the vinyl alcohol polymer is not particularly limited, and examples thereof include ethylene sulfonic acid, (meth) Sulfonic acid-containing monomers such as allyl sulfonic acid, sulfoalkyl malate, sulfoalkyl (meth) acrylate, acrylamide-2-methylpropane sulfonic acid, and salts thereof; N- (1,1-dimethyl-3-dimethylaminopropyl); ) (Meth) acrylamide, N- (1,1-dimethyl-3-dimethylaminobutyl) (meth) acrylamide, N-vinylimidazole, 2-methyl-N-vinylimidazole, vinyl-3-dimethylaminopropyl ether, vinyl 2-dimethylaminoethyl ether, allyl-3-dimethylaminopro Examples include amino group or ammonium group-containing monomers such as ether, allyldimethylamine, and methallyldimethylamine; carboxyl group-containing monomers such as crotonic acid, maleic acid, fumaric acid, itaconic acid, and (meth) acrylic acid. It is done.
[0020]
In the present invention, the vinyl alcohol polymer (A) and the vinyl alcohol polymer (B) may contain other monomer units as long as the gist of the present invention is not impaired. Examples of comonomers that can be used include α-olefins such as propylene, n-butene, and isobutylene; acrylic acid and salts thereof; methyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acrylate, and n-acrylate. -Acrylic esters such as butyl, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate; methacrylic acid and salts thereof; methyl methacrylate, ethyl methacrylate, methacryl Methacrylic acid esters such as n-propyl acid, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, octadecyl methacrylate; N-methyl acrylamide, N-ethyl acrylamide, N, N-dimethyl acrylamide, diacetone acrylamide, acrylamide propane sulfonic acid and its salt, acrylamide propyl dimethylamine and its salt or its quaternary salt, N-methylol acrylamide and its Acrylamide derivatives such as derivatives; methacrylamide; N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamidepropanesulfonic acid and salts thereof, methacrylamidepropyldimethylamine and salts thereof or quaternary salts thereof, N-methylolmethacrylamide and Methacrylamide derivatives such as derivatives thereof; methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether Vinyl ethers such as ether, n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether and stearyl vinyl ether; nitriles such as acrylonitrile and methacrylonitrile; vinyl halides such as vinyl chloride and vinyl fluoride; Vinylidene halides such as vinylidene chloride and vinylidene fluoride; allyl compounds such as allyl acetate and allyl chloride; unsaturated dicarboxylic acids such as maleic acid, itaconic acid and fumaric acid, and salts or esters thereof; vinyltrimethoxysilane, etc. Vinylsilyl compounds; isopropenyl acetate and the like.
[0021]
In the present invention, the vinyl alcohol polymer (A) and the vinyl alcohol polymer (B) are usually separately or mixed, and dissolved or dispersed in an aqueous medium to effect suspension polymerization of the vinyl compound. Provided.
[0022]
The dispersion stabilizer for suspension polymerization of the present invention is further improved in stability during suspension polymerization by using a heat-treated vinyl alcohol polymer (A). Although the heat treatment conditions are not particularly limited, it is usually preferable to heat at a temperature of 100 to 200 ° C. for 0.5 to 20 hours in an oxygen, air or nitrogen atmosphere. If the temperature during the heat treatment is less than 100 ° C., the effect of improving the stability during suspension polymerization due to the heat treatment may not be sufficiently exhibited, and if it exceeds 200 ° C., the dispersion stabilizer for suspension polymerization may be colored.
At that time, in order to suppress coloring of the dispersion stabilizer for suspension polymerization due to heat treatment, it is preferable to wash the vinyl alcohol polymer (A) with a solvent such as methanol before the heat treatment.
[0023]
In the dispersion stabilizer for suspension polymerization of the present invention, when a heat-treated vinyl alcohol polymer (A) is used, the suspension polymerization stability is remarkably excellent with a small amount of use, and it is obtained by suspension polymerization. Since the coloration can be suppressed when the polymer is processed, the vinyl alcohol polymer (A) is an acid having a pKa of 3.5 to 5.5 at 25 ° C. and / or a metal salt thereof (C). It is preferable to contain. There is no restriction | limiting in particular about the kind of acid which can be used, As an example, acetic acid (pKa4.76), propionic acid (pKa4.87), butyric acid (pKa4.63), octanoic acid (pKa4.89), adipic acid ( pKa 5.03), benzoic acid (pKa 4.00), formic acid (pKa 3.55), valeric acid (pKa 4.63), heptanoic acid (pKa 4.66), lactic acid (pKa 3.66), phenylacetic acid (pKa 4.10) , Isobutyric acid (pKa 4.63), cyclohexanecarboxylic acid (pKa 4.70), and the like. Acids that can be particularly preferably used in view of the effect exerted are acetic acid, propionic acid, and lactic acid.
The metal salt of the acid is not particularly limited, but usually a metal salt composed of the acid and an alkali metal such as sodium or potassium is used, and sodium acetate is particularly preferably used.
[0024]
The content of the acid and / or metal salt (C) is preferably 0.05 to 2 parts by weight, more preferably 0.1 to 1 part with respect to 100 parts by weight of the vinyl alcohol polymer (A). 0.7 parts by weight, more preferably 0.2 to 1.5 parts by weight. When the content of the acid and / or metal salt (C) thereof with respect to the vinyl alcohol polymer (A) is less than 0.05 parts by weight, the effect of improving the stability during suspension polymerization by heat treatment is reduced, and 2 parts by weight Exceeding the above range is not preferred because the dispersion stabilizer for suspension polymerization is colored during heat treatment or the polymer is colored when processing the polymer obtained by suspension polymerization.
[0025]
Next, a suspension polymerization method of a vinyl compound using the dispersion stabilizer for suspension polymerization of the present invention will be described.
[0026]
In suspension polymerization of a vinyl compound in an aqueous medium using the dispersion stabilizer for suspension polymerization of the present invention, the temperature of the aqueous medium is not particularly limited, and it is not less than about 20 ° C. cold water and 90 ° C. or higher. Hot water is also preferably used. This aqueous medium can be composed of an aqueous medium containing pure water, an aqueous solution containing various additive components, or other organic solvents. When the aqueous medium is charged into the polymerization reaction system, the supply amount may be an amount that can sufficiently heat the polymerization reaction system. In order to increase the heat removal efficiency, a polymerizer with a reflux condenser is also preferably used.
[0027]
Although the dispersion stabilizer for suspension polymerization of the present invention may be used alone, polyvinyl alcohol, methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, which are usually used in suspension polymerization of vinyl compounds in an aqueous medium, Water-soluble cellulose ethers such as hydroxypropylmethylcellulose, water-soluble polymers such as gelatin; oil-soluble emulsifiers such as sorbitan monolaurate, sorbitan trioleate, glycerin tristearate, ethylene oxide propylene oxide block copolymer; polyoxyethylene sorbitan monolaurate, You may use together water-soluble emulsifiers, such as polyoxyethylene glycerol oleate and sodium laurate. Although there is no restriction | limiting in particular about the addition amount, 0.01-1.0 weight part is preferable per 100 weight part of vinyl-type compounds.
[0028]
Various other additives can also be added as necessary. Examples of the additive include polymerization regulators such as acetaldehyde, butyraldehyde, trichloroethylene, perchloroethylene, and mercaptans, and polymerization inhibitors such as phenol compounds, sulfur compounds, and N-oxide compounds. Further, it is optional to add a pH adjuster, a scale inhibitor, a crosslinking agent, etc., and a plurality of the above additives may be used in combination. On the other hand, as the polymerization initiator, those conventionally used for the polymerization of vinyl compounds such as vinyl chloride can be used, for example, diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, diethoxy. Percarbonate compounds such as ethyl peroxydicarbonate; perester compounds such as t-butyl peroxyneodecane, α-cumyl peroxyneodecanate, t-butyl peroxydecane; acetylcyclohexylsulfonyl peroxide, 2, Peroxides such as 4,4-trimethylpentyl-2-peroxyphenoxyacetate; 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2 '-Azobis (4-methoxy-2,4-dimethyl Reronitoriru) include azo compounds such as, further, be used in combination of potassium persulfate thereto, ammonium persulfate, hydrogen peroxide and the like.
[0029]
Examples of the vinyl compound to which the dispersion stabilizer for suspension polymerization of the present invention can be applied include vinyl chloride, vinylidene chloride, alkyl vinyl ether, maleic anhydride, acrylonitrile, itaconic acid, styrene, vinyl acetate, Examples include vinyl esters such as vinyl propionate, (meth) acrylates such as methyl (meth) acrylate and ethyl (meth) acrylate, and α-olefins such as ethylene, propylene, isobutene, and isoprene. . Among these vinyl compounds, a representative one is vinyl chloride. Vinyl chloride is used alone or in combination with vinyl chloride as a main component and other monomers (vinyl chloride 50% by weight or more). can do. Comonomers copolymerized with vinyl chloride include vinyl esters such as vinyl acetate and vinyl propionate, (meth) acrylic esters such as methyl (meth) acrylate and ethyl (meth) acrylate, ethylene, propylene And α-olefins such as maleic anhydride, acrylonitrile, itaconic acid, styrene, vinylidene chloride, vinyl ether and the like.
[0030]
In suspension polymerization of a vinyl compound using the dispersion stabilizer for suspension polymerization of the present invention, the charging ratio of each component, polymerization temperature, etc. are conventionally employed in suspension polymerization of vinyl compounds such as vinyl chloride. It may be determined according to the conditions. Moreover, there is no restriction | limiting about the preparation order and ratio of a vinyl type compound, a polymerization initiator, a dispersion stabilizer, an aqueous medium, and other additives. In addition, a method of heating the vinyl compound before charging the vinyl compound into the polymerization vessel at the same time as using an aqueous medium is also suitably used.
[0031]
【Example】
The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to these examples. In the following examples, “%” and “part” mean “% by weight” and “part by weight” unless otherwise specified. In the following, polyvinyl alcohol may be abbreviated as PVA, polyvinyl acetate as PVAc, and vinyl alcohol polymer as PVA polymer.
[0032]
(Analysis of PVA polymer)
(1) Measurement of degree of polymerization
The degree of polymerization of the PVA polymer was measured according to JIS K6726.
(2) Measurement of saponification degree
The degree of saponification of the PVA polymer was measured according to JIS K6726.
(3) Determination of acid metal salt
Sodium acetate contained in the PVA polymer was quantified by electrophoresis analysis using a capillary type isotachophoresis analyzer (IP-3A) manufactured by Shimadzu Corporation.
(4) Colorability during heat treatment
After the PVA polymer was heat-treated at 150 ° C. for 2 hours in an air atmosphere, the degree of coloring of the PVA polymer was visually observed and evaluated according to the following criteria.
Y: No change
Δ: Colored slightly yellow
×: Reddish brown
[0033]
(Polymerizability of vinyl chloride monomer and characterization of the obtained vinyl chloride polymer)
(1) Particle size distribution
The particle size distribution was measured by dry sieve analysis using a Tyler mesh standard wire mesh.
(2) Bulk specific gravity
The bulk specific gravity of the vinyl chloride polymer was measured according to JIS K6721.
(3) CPA (Cold Plasticizer Absorption)
The amount of dioctyl phthalate absorbed at 23 ° C. was measured by the method described in ASTM-D3367-75.
(4) Scale adhesion
After the polymer slurry was taken out of the polymerization tank, the state of scale adhesion in the polymerization tank was visually observed and evaluated according to the following criteria.
○: There is almost no adhesion of polymer scale.
Δ: A white polymer scale can be confirmed on the inner wall of the polymerization tank.
×: Many white polymer scales can be confirmed on the inner wall of the polymerization tank
(5) Colorability during heat treatment
After the vinyl chloride polymer was heat-treated at 140 ° C. for 10 minutes in an air atmosphere, the degree of coloring of the vinyl chloride polymer was visually observed and evaluated according to the following criteria.
Y: No change
Δ: Colored slightly yellow
×: Colored yellow
[0034]
Example 1
(Production of PVA polymer)
A 100 L pressure reactor equipped with a stirrer, nitrogen inlet, ethylene inlet and initiator addition port was charged with 38.1 kg of vinyl acetate and 21.8 kg of methanol, heated to 60 ° C., and then nitrogen bubbling for 30 minutes. The inside was replaced with nitrogen. Next, ethylene was introduced and charged so that the reactor pressure was 0.10 MPa. A 2.8 g / L solution having 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile) dissolved in methanol as an initiator was prepared, and nitrogen substitution was performed by bubbling with nitrogen gas. After adjusting the temperature inside the reaction vessel to 60 ° C., 32 mL of the initiator solution was injected to start polymerization. During the polymerization, ethylene was introduced to maintain the reactor pressure at 0.10 MPa, the polymerization temperature at 60 ° C., and the above initiator solution was continuously added at 102 mL / hr. After 5 hours, when the polymerization rate reached 50%, the polymerization was stopped by cooling. After the reaction vessel was opened to remove ethylene, nitrogen gas was bubbled to completely remove ethylene. Subsequently, the unreacted vinyl acetate monomer was removed under reduced pressure to obtain a methanol solution of the PVAc polymer. An NaOH methanol solution (10% concentration) was added to the solution adjusted to 30% so that the alkali molar ratio (number of moles of NaOH / number of moles of vinyl ester units in the PVAc polymer) was 0.006. Saponified. After the saponification reaction, the solid content in the reaction solution was pulverized and then centrifuged to remove liquid, and dried under reduced pressure at 60 ° C. to obtain a PVA polymer. When the degree of saponification of the PVA polymer was measured according to JIS K6726 of a conventional method, it was 85 mol%.
[0035]
A methanol solution of the PVAc polymer obtained by removing the unreacted vinyl acetate monomer after the polymerization is poured into n-hexane to precipitate the PVAc polymer, and the recovered PVAc polymer is dissolved with acetone. After performing reprecipitation purification three times, it was dried under reduced pressure at 60 ° C. to obtain a purified product of PVAc polymer. The content of ethylene units determined from proton NMR measurement of the PVAc polymer was 2 mol%. Moreover, after saponifying the methanol solution of said PVAc type polymer by the alkali molar ratio 0.2, Soxhlet extraction with methanol was implemented for 3 days, and it dried and the purified product of the PVA type polymer was obtained. When the average degree of polymerization of the PVA polymer was measured according to JIS K6726 of a conventional method, it was 1000.
By the above operation, a PVA polymer (A) having a polymerization degree of 1000, a saponification degree of 85 mol% and an ethylene content of 2 mol% was obtained. Hereinafter, this is referred to as a PVA polymer (A-1).
[0036]
The polymer obtained by the above operation is obtained by changing the weight ratio of methanol with respect to a monomer such as vinyl acetate in the polymerization operation, and changing the polymerization degree of the polymer by changing the pressure of ethylene in the reaction vessel. The ethylene content of the polymer can be changed, and the saponification degree of the polymer can be changed by changing the alkali molar ratio in the saponification operation. In the above operation, ethylene is not used at the time of polymerization, the weight ratio of monomer / methanol is changed, and the alkali molar ratio is changed at the time of saponification to obtain a polymerization degree of 250 and a saponification degree of 40 mol% PVA polymer (B) Got. Hereinafter, this is referred to as a PVA polymer (B-1).
[0037]
(Polyvinyl chloride polymerization)
A glass-lined autoclave is charged with 40 parts of deionized water in which the dispersion stabilizer shown in Table 1 is dissolved and 0.04 part of a 70% toluene solution of diisopropyl peroxydicarbonate, and the autoclave is degassed to 0.0067 MPa. After removing oxygen by oxygen, 30 parts of vinyl chloride monomer was charged, and the temperature was raised to 57 ° C. with stirring to carry out polymerization. At the start of polymerization, the pressure in the autoclave was 0.83 MPa, but when 6 hours after the start of polymerization, the pressure reached 0.49 MPa, the polymerization was stopped, the unreacted vinyl chloride monomer was purged, and the contents were The product was taken out and dehydrated and dried. The polymerization yield of the vinyl chloride polymer was 85%, and the average degree of polymerization was 1050. Polymerizability and characteristics of the vinyl chloride polymer were evaluated by the above methods. The evaluation results are shown in Table 2.
[0038]
Examples 2 and 3
(Polyvinyl chloride polymerization)
In Example 1, PVA polymer (A-1) was used as the PVA polymer (A), and PVA polymer (B-1) was used as the dispersion stabilizer as PVA polymer (B). As shown in Example 1, except that the amount of the PVA polymer (A) used and the weight ratio (A) / (B) of the PVA polymer (A) to the PVA polymer (B) were changed. In the same manner, suspension polymerization of vinyl chloride was carried out to evaluate the polymerizability and the characteristics of the vinyl chloride polymer. The evaluation results are shown in Table 2.
[0039]
Examples 4 and 5
(Production of PVA polymer)
In Example 1, the monomer / methanol weight ratio and the ethylene pressure in the reaction vessel were changed during polymerization, and the alkali molar ratio was changed during saponification to obtain a polymerization degree of 1700, a saponification degree of 88 mol%, and an ethylene content of 5 A mol% PVA polymer (A) was obtained.
Hereinafter, this is referred to as a PVA polymer (A-2).
[0040]
(Polyvinyl chloride polymerization)
In Example 1, PVA polymer (A-2) was used as the PVA polymer (A), and PVA polymer (B-1) was used as the dispersion stabilizer as PVA polymer (B). As shown in Example 1, except that the amount of the PVA polymer (A) used and the weight ratio (A) / (B) of the PVA polymer (A) to the PVA polymer (B) were changed. In the same manner, suspension polymerization of vinyl chloride was carried out to evaluate the polymerizability and the characteristics of the vinyl chloride polymer. The evaluation results are shown in Table 2.
[0041]
Example 6
(Production of PVA polymer)
In Example 1, the monomer / methanol weight ratio and the ethylene pressure in the reaction vessel were changed during polymerization, and the alkali molar ratio was changed during saponification to obtain a polymerization degree of 700, a saponification degree of 70 mol%, and an ethylene content of 1 .5 mol% of a PVA polymer (A) was obtained. Hereinafter, this is referred to as a PVA polymer (A-3).
Further, ethylene is not used during polymerization, the weight ratio of monomer / methanol is changed, and the alkali molar ratio is changed during saponification to obtain a PVA polymer (B) having a polymerization degree of 500 and a saponification degree of 55 mol%. It was. Hereinafter, this is referred to as a PVA polymer (B-2).
[0042]
(Polyvinyl chloride polymerization)
In Example 1, the PVA polymer (A-3) was used as the PVA polymer (A), and the PVA polymer (B-2) was used as the dispersion stabilizer as the PVA polymer (B). As shown, the vinyl chloride suspension polymerization was carried out in the same manner as in Example 1 except that the weight ratio (A) / (B) of the PVA polymer (A) and the PVA polymer (B) was changed. The evaluation of the polymerizability and the characteristics of the vinyl chloride polymer were carried out. The evaluation results are shown in Table 2.
[0043]
Example 7
(Production of PVA polymer containing carboxyl group in side chain)
A 100 L reactor equipped with a stirrer, nitrogen inlet, reflux condenser and additive inlet was charged with 21.0 kg of vinyl acetate and 38.9 kg of methanol, heated to 60 ° C., and then the system was purged with nitrogen for 30 minutes. Replaced with nitrogen. A 10% concentration solution in which itaconic acid was dissolved in methanol as a comonomer was prepared, and nitrogen substitution was performed to perform bubbling with nitrogen gas. The temperature inside the reaction vessel was adjusted to 60 ° C., 9.4 g of itaconic acid was added, and 50 g of 2,2′-azobis (isobutyronitrile) was added to initiate polymerization. During the polymerization, the polymerization temperature was maintained at 60 ° C., a 10% methanol solution of itaconic acid was continuously added at 600 mL / hr, and after 5 hours, the polymerization was stopped when the polymerization rate reached 65%. Subsequently, the unreacted vinyl acetate monomer was removed under reduced pressure to obtain a methanol solution of the PVAc polymer. An NaOH methanol solution (10% concentration) was added to the solution adjusted to 30% so that the alkali molar ratio (number of moles of NaOH / number of moles of vinyl ester units in the PVAc polymer) was 0.002. Saponified. After the saponification reaction, the solid content in the reaction solution was pulverized and then centrifuged to remove liquid, and dried under reduced pressure at 60 ° C. to obtain a PVA polymer. When the degree of saponification of the PVA polymer was measured according to JIS K6726 of a conventional method, it was 40 mol%.
[0044]
A methanol solution of the PVAc polymer obtained by removing the unreacted vinyl acetate monomer after the polymerization is poured into n-hexane to precipitate the PVAc polymer, and the recovered PVAc polymer is dissolved with acetone. After performing reprecipitation purification three times, it was dried under reduced pressure at 60 ° C. to obtain a purified product of PVAc polymer. The content of the itaconic acid unit determined from proton NMR measurement of the PVAc polymer was 1 mol%. Moreover, after saponifying the methanol solution of said PVAc type polymer by the alkali molar ratio 0.2, Soxhlet extraction with methanol was implemented for 3 days, and it dried and the purified product of the PVA type polymer was obtained. The average degree of polymerization of the PVA polymer was measured according to a conventional method JIS K6726 and found to be 400.
[0045]
By the above operation, a PVA polymer (B) having a polymerization degree of 400 and a saponification degree of 40 mol% and containing a carboxyl group as an ionic group in the side chain was obtained. Hereinafter, this is referred to as an ion-modified PVA polymer (B-3).
[0046]
(Polyvinyl chloride polymerization)
In Example 1, a PVA polymer (A-2) was used as the PVA polymer (A), and an ion-modified PVA polymer (B-3) was used as the dispersion stabilizer as the PVA polymer (B). 1 except that the weight ratio (A) / (B) was changed, and the suspension polymerization of vinyl chloride was carried out in the same manner as in Example 1 to evaluate the polymerizability and the characteristics of the vinyl chloride polymer. Evaluation was performed. The evaluation results are shown in Table 2.
[0047]
Example 8
(Production of PVA polymer containing a carboxyl group at the end)
A 100 L reactor equipped with a stirrer, nitrogen inlet, additive inlet and initiator inlet was charged with 49.7 kg of vinyl acetate and 12.3 kg of methanol, heated to 60 ° C., and then bubbled with nitrogen for 30 minutes. Was replaced with nitrogen. A 10% strength solution in which 3-mercaptopropionic acid (hereinafter referred to as 3-MPA) was dissolved in methanol as a chain transfer agent was prepared, and nitrogen substitution was performed to perform bubbling with nitrogen gas. The temperature inside the reaction vessel was adjusted to 60 ° C. and 4.2 g of 3-MPA was added, and then 20 g of 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile) was added to initiate polymerization. . During the polymerization, the polymerization temperature was maintained at 60 ° C., and a 10% methanol solution of 3-MPA was continuously added at 230 mL / hr. After 4 hours, when the polymerization rate reached 65%, the polymerization was stopped by cooling. Subsequently, the unreacted vinyl acetate monomer was removed under reduced pressure to obtain a methanol solution of the PVAc polymer. An NaOH methanol solution (10% concentration) was added to the solution adjusted to 30% so that the alkali molar ratio (number of moles of NaOH / number of moles of vinyl ester units in the PVAc polymer) was 0.002. Saponified. After the saponification reaction, the solid content in the reaction solution was pulverized and then centrifuged to remove liquid, and dried under reduced pressure at 60 ° C. to obtain a PVA polymer. When the degree of saponification of the PVA polymer was measured according to JIS K6726 of a conventional method, it was 40 mol%.
[0048]
A methanol solution of the PVAc polymer obtained by removing the unreacted vinyl acetate monomer after the polymerization is poured into n-hexane to precipitate the PVAc polymer, and the recovered PVAc polymer is dissolved with acetone. After performing reprecipitation purification three times, it was dried under reduced pressure at 60 ° C. to obtain a purified product of PVAc polymer. Moreover, after saponifying the methanol solution of said PVAc type polymer by the alkali molar ratio 0.2, Soxhlet extraction with methanol was implemented for 3 days, and it dried and the purified product of the PVA type polymer was obtained. It was 350 when the average degree of polymerization of this PVA-type polymer was measured according to JIS K6726 of the conventional method.
[0049]
By the above operation, a PVA polymer (B) having a polymerization degree of 350 and a saponification degree of 40 mol% and containing a carboxyl group as an ionic group at the terminal was obtained. Hereinafter, this is referred to as a terminal ion-modified PVA polymer (B-4).
[0050]
(Polyvinyl chloride polymerization)
In Example 1, a PVA polymer (A-3) was used as the PVA polymer (A), and a terminal ion-modified PVA polymer (B-4) was used as the dispersion stabilizer as the PVA polymer (B). As shown in Table 1, except that the weight ratio (A) / (B) was changed, the vinyl chloride suspension polymerization was carried out in the same manner as in Example 1 to evaluate the polymerizability and the characteristics of the vinyl chloride polymer. Was evaluated. The evaluation results are shown in Table 2.
[0051]
Comparative Example 1
(Production of PVA polymer)
In Example 1, it changed so that ethylene might not be used at the time of superposition | polymerization, and obtained the PVA-type polymer with a polymerization degree of 1000 and a saponification degree of 85 mol%. Hereinafter, this is referred to as a PVA polymer (a-1).
[0052]
(Polyvinyl chloride polymerization)
In Example 1, instead of the PVA polymer (A), the PVA polymer (a-1), except that the PVA polymer (B-1) was used as the dispersion stabilizer as the PVA polymer (B). Was suspension-polymerized with vinyl chloride in the same manner as in Example 1 to evaluate the polymerizability. Since the obtained vinyl chloride polymer was blocked in the reaction vessel, the characteristics were not evaluated. The evaluation results are shown in Table 2.
[0053]
Comparative Example 2
(Polyvinyl chloride polymerization)
In Example 1, the PVA polymer (A-1) was used as the dispersion stabilizer as the PVA polymer (A), and the PVA polymer (B) was not used. The vinyl chloride suspension polymerization was carried out to evaluate the polymerizability and the characteristics of the vinyl chloride polymer. The evaluation results are shown in Table 2.
[0054]
Comparative Example 3
(Production of PVA polymer)
In Example 1, ethylene was not used during polymerization, the monomer / methanol weight ratio was changed, and the alkali molar ratio was changed during saponification to obtain a PVA polymer having a polymerization degree of 1700 and a saponification degree of 88 mol%. It was. Hereinafter, this is referred to as a PVA polymer (a-2).
[0055]
(Polyvinyl chloride polymerization)
In Example 1, instead of the PVA polymer (A), the PVA polymer (a-2) and the PVA polymer (B-1) were used as the dispersion stabilizer as the PVA polymer (B). As shown in FIG. 1, the same procedure as in Example 1 was performed except that the weight ratio (A) / (B) {here, the weight ratio (a-2) / (B-1)} was changed. Suspension polymerization was performed to evaluate the polymerizability and the characteristics of the vinyl chloride polymer. The evaluation results are shown in Table 2.
[0056]
Comparative Example 4
(Production of PVA polymer)
In Example 1, ethylene was not used during polymerization, the monomer / methanol weight ratio was changed, and the alkali molar ratio was changed during saponification to obtain a PVA polymer having a polymerization degree of 700 and a saponification degree of 70 mol%. It was. Hereinafter, this is referred to as a PVA polymer (a-3).
[0057]
(Polyvinyl chloride polymerization)
In Example 1, instead of the PVA polymer (A), the PVA polymer (a-3) and the PVA polymer (B-2) were used as the dispersion stabilizer as the PVA polymer (B). As shown in FIG. 1, the same procedure as in Example 1 was performed except that the weight ratio (A) / (B) {here, the weight ratio (a-3) / (B-2)} was changed. Suspension polymerization was performed to evaluate the polymerizability. Since the obtained vinyl chloride polymer was blocked in the reaction vessel, the characteristics were not evaluated. The evaluation results are shown in Table 2.
[0058]
[Table 1]
[0059]
[Table 2]
[0060]
Example 9
(Production of PVA polymer)
In Example 1, after the saponification reaction of the PVAc polymer, the obtained PVA polymer was washed at 25 ° C. with 30 times the amount of methanol of the PVA polymer on a weight basis, and dried at 60 ° C. under reduced pressure. After that, the PVA polymer (A) having a polymerization degree of 1000, a saponification degree of 85 mol%, and an ethylene content of 2 mol% was obtained in the same manner as in Example 1 except that it was heat treated in air at 150 ° C. for 2 hours. Obtained. Hereinafter, this is referred to as a PVA polymer (A-4). When the PVA polymer (A-4) was analyzed by electrophoresis, the content of sodium acetate per 100 parts by weight of the PVA polymer was 0.7 parts by weight. In addition, the heat-treated PVA polymer (A-4) was not colored.
[0061]
(Polyvinyl chloride polymerization)
A glass-lined autoclave was charged with 40 parts of deionized water in which the PVA polymer shown in Table 3 was dissolved and 0.016 part of a 70% toluene solution of diisopropyl peroxydicarbonate until the inside of the autoclave reached 0.0067 MPa. After deaeration to remove oxygen, 30 parts of vinyl chloride monomer was added, and the temperature was raised to 65 ° C. with stirring to perform polymerization. At the start of polymerization, the pressure in the autoclave was 1.08 MPa, but when 6 hours after the start of polymerization, the pressure reached 0.44 MPa, the polymerization was stopped, the unreacted vinyl chloride monomer was purged, and the contents were The product was taken out and dehydrated and dried.
Scale adhesion and colorability of the vinyl chloride polymer during heat treatment were evaluated by the above methods. The evaluation results are shown in Table 3.
[0062]
Comparative Example 5
(Production of PVA polymer)
In Example 1, after the saponification reaction of the PVAc polymer, the obtained PVA polymer was analyzed by electrophoresis, and the content of sodium acetate per 100 parts by weight of the PVA polymer was 0.02 wt. Unless it was heat-treated in air at 150 ° C. for 2 hours, after repeating the operation of washing at 25 ° C. with 30 times the amount of PVA-based methanol on a weight basis until it became parts, By operating in the same manner as in Example 1, a PVA polymer (A) having a polymerization degree of 1000, a saponification degree of 85 mol%, and an ethylene content of 2 mol% was obtained. Hereinafter, this is referred to as a PVA polymer (A-5). When the PVA polymer (A-5) was analyzed by electrophoresis, the content of sodium acetate per 100 parts by weight of the PVA polymer was 0.02 parts by weight. In addition, the heat-treated PVA polymer (A-5) was not colored.
[0063]
(Polyvinyl chloride polymerization)
In Example 9, except that the PVA polymer (A-5) was used in place of the PVA polymer (A-4), the suspension polymerization of vinyl chloride was performed in the same manner as in Example 9, and the scale was changed. The adhesion and the colorability of the vinyl chloride polymer during heat treatment were evaluated. The evaluation results are shown in Table 3.
[0064]
Comparative Example 6
(Production of PVA polymer)
In Example 1, during the saponification reaction of the PVAc polymer, an alkali molar ratio (molar number of NaOH / molar number of vinyl ester units in the PVAc polymer) was adjusted to a methanol solution of the PVAc polymer adjusted to 30%. NaOH methanol solution (10% concentration) was added so as to be 0.006, and 0.3 kg of sodium acetate was further added to saponify, and dried under reduced pressure at 60 ° C., and then the obtained PVA polymer was air-cooled. A PVA polymer (A) having a polymerization degree of 1000, a saponification degree of 85 mol%, and an ethylene content of 2 mol% was obtained in the same manner as in Example 1 except that the heat treatment was performed at 150 ° C for 2 hours. Hereinafter, this is referred to as a PVA polymer (A-6). When the PVA polymer (A-6) was analyzed by electrophoresis, the content of sodium acetate per 100 parts by weight of the PVA polymer was 2.5 parts by weight. The heat-treated PVA polymer (A-6) was colored reddish brown.
[0065]
(Polyvinyl chloride polymerization)
In Example 9, except that the PVA polymer (A-6) was used in place of the PVA polymer (A-4), suspension polymerization of vinyl chloride was performed in the same manner as in Example 9, and the scale was changed. The adhesion and the colorability of the vinyl chloride polymer during heat treatment were evaluated. The evaluation results are shown in Table 3.
[0066]
[Table 3]
[0067]
【The invention's effect】
The dispersion stabilizer for suspension polymerization of the vinyl compound of the present invention is remarkably excellent in suspension polymerization stability when used in a small amount, and further, the polymer is obtained by suspension polymerization of the vinyl compound using this. Monomer remaining in polymer particles with sharp particle size distribution, low scattering during handling, good penetration into molding machines, high plasticizer absorption rate and excellent processability Since the polymer particles are porous, the polymer particles are porous, so that it is possible to produce vinyl polymers with characteristics such as low fish eyes in molded products and high bulk specific gravity. Evaluation is very high.
Claims (9)
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DE60205836T2 (en) | 2001-10-05 | 2006-05-18 | Kuraray Co., Ltd., Kurashiki | Dispersion stabilizer for the suspension polymerization of a vinyl compound |
DE102007033971A1 (en) * | 2007-07-19 | 2009-01-22 | Kuraray Europe Gmbh | Use of carboxyl-containing polyvinyl alcohols as stabilizer additive of PVC |
JP5356313B2 (en) * | 2010-05-25 | 2013-12-04 | 株式会社クラレ | Polyvinyl chloride resin composition and method for producing the same |
WO2014104160A1 (en) * | 2012-12-28 | 2014-07-03 | 株式会社クラレ | Dispersion stabilizer for suspension polymerization and vinyl resin production method |
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JPS582962B2 (en) * | 1974-10-16 | 1983-01-19 | 株式会社クラレ | Manufacturing method of vinyl chloride resin |
JPS54127490A (en) * | 1978-03-28 | 1979-10-03 | Nippon Synthetic Chem Ind Co Ltd:The | Dispersion stabilizer for suspension polymerization of vinyl compounds |
JPS61108602A (en) * | 1984-11-02 | 1986-05-27 | Nippon Synthetic Chem Ind Co Ltd:The | Dispersion stabilizer for suspension polymerization of vinyl compound |
JPS6195053A (en) * | 1985-09-26 | 1986-05-13 | Kuraray Co Ltd | Production of polyvinyl alcohol polymer with high thermal stability |
JPH03134003A (en) * | 1989-10-19 | 1991-06-07 | Kuraray Co Ltd | Dispersion assistant and dispersion stabilizer for suspension polymerization of vinyl compound |
JP3474304B2 (en) * | 1995-03-27 | 2003-12-08 | 株式会社クラレ | Dispersion stabilizer for suspension polymerization of vinyl compounds |
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