JP4731676B2

JP4731676B2 - Aqueous emulsion and process for producing the same

Info

Publication number: JP4731676B2
Application number: JP2000362851A
Authority: JP
Inventors: 征司谷本; 尚清猪俣; 直樹藤原
Original assignee: Kuraray Co Ltd
Current assignee: Kuraray Co Ltd
Priority date: 1999-12-03
Filing date: 2000-11-29
Publication date: 2011-07-27
Anticipated expiration: 2020-11-29
Also published as: JP2001220484A

Description

【０００１】
【発明の属する技術分野】
本発明は、耐水性の改善された、しかも温度依存性の小さい水性エマルジョンおよび重合安定性に優れる水性エマルジョンの製法に関する。
【０００２】
【従来の技術】
従来、ポリビニルアルコール（以下、ＰＶＡと略記することがある）はエチレン性不飽和単量体、特に酢酸ビニルに代表されるビニルエステル系単量体の乳化重合用保護コロイドとして広く用いられており、これを保護コロイドとして用いて乳化重合して得られるビニルエステル系水性エマルジョンは紙用、木工用およびプラスチック用などの各種接着剤、含浸紙用および不織製品用などの各種バインダー、混和剤、打継ぎ材、塗料、紙加工および繊維加工などの分野で広く用いられている。
このような水性エマルジョンは、ＰＶＡ系重合体のけん化度を調整することにより、一般的に粘度が低く、ニュートニアン流動に近い粘性を有し、比較的耐水性の良好なものから、一般的に粘度が高く、比較的エマルジョン粘度の温度依存性が小さいものが得られることから、種々の用途に賞用されてきた。
しかしながら、該水性エマルジョンのあるものは、耐水性が悪く、エマルジョン粘度の温度依存性が大きいなどの欠点を有している。
【０００３】
すなわち、乳化重合用分散剤としてのＰＶＡ系重合体は、一般的には鹸化度９８モル％程度のいわゆる“完全鹸化ＰＶＡ”と鹸化度８８モル％程度の“部分鹸化ＰＶＡ”があり、前者を使用した場合、比較的耐水性は良好なものの、いまだ十分とはいえず、さらにエマルジョン粘度の温度依存性が大きいという欠点がある。他方、後者のＰＶＡ系重合体を使用した場合、エマルジョン粘度の温度依存性は余り大きくないものの、いまだ十分とはいえず、さらに耐水性に劣る欠点を有している。このような欠点を改良するために、両者のＰＶＡ系重合体の併用、両者の中間的な鹸化度のＰＶＡ系重合体の使用等が行われているが、耐水性、エマルジョン粘度の温度依存性を同時に改善することはできなかった。そこで、エチレン単位を含有するビニルアルコール系重合体が提案（特開平１１−８１６６６）され、耐水性と低温放置安定性が改善された。しかしながら耐水性はいまだ十分とはいえず、また温度依存性も十分とはいえない（後述の比較例７参照）。また後述する比較例６に示すような末端にメルカプト基を有するPVAを乳化重合用分散安定剤として使用することも知られている（特開平３−２４４８１）が、比較例６に示すとおり、耐水性の点で十分満足すべきものではないし、温度依存性も小さいとはいえない。
【０００４】
【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、耐水性の改善された、しかも温度依存性の小さい水性エマルジョンを提供すること、および重合安定性に優れる水性エマルジョンの製法を提供することを目的とするものである。
【０００５】
【課題を解決するための手段】
上記目的は、ビニルエステル系単量体単位を有する重合体を分散質とし、１，２−グリコール結合を１．９モル％以上有するビニルアルコール系重合体を分散剤とする水性エマルジョンであって、該水性エマルジョンの６０℃における粘度をＴ₆₀ _℃、３０℃における粘度をＴ₃₀ _℃、０℃における粘度をＴ₀ _℃とするとき、Ｔ₀ _℃／Ｔ₃₀ _℃が５以下であり、Ｔ₆₀ _℃／Ｔ₃₀ _℃が１．５以下である水性エマルジョンを提供することによって達成される。
【０００６】
【発明の実施の形態】
本発明の水性エマルジョンの分散剤として用いられる１，２−グリコール結合を１．９モル％以上有するビニルアルコール系重合体の製造方法としては特に制限はなく、公知の方法が使用可能である。一例としてビニレンカーボネートを上記の１，２−グリコール結合量になるようにビニルエステルと共重合する方法、ビニルエステルの重合温度を通常の条件より高い温度、例えば７５〜２００℃で、加圧下に重合する方法などが挙げられる。後者の方法においては、重合温度は９５〜１９０℃であることが好ましく、１００〜１８０℃であることが特に好ましい。また加圧条件としては、重合系が沸点以下になるように選択することが重要であり、好適には０．２MPa以上、さらに好適には０．３MPa以上である。また上限は５Mpa以下が好適であり、さらに３Mpa以下がより好適である。重合はラジカル重合開始剤の存在下、塊状重合法、溶液重合法、懸濁重合法、乳化重合法などいずれの方法でも行うことができるが、溶液重合、とくにメタノールを溶媒とする溶液重合法が好適である。このようにして得られたビニルエステル重合体を通常の方法によりけん化することによりビニルアルコール系重合体が得られる。ビニルアルコール系重合体の１，２−グリコール結合の含有量は１．９モル％以上であることが必要であり、より好ましくは１．９５モル％以上、さらには２．０モル％以上、最適には２．１モル％以上である。１，２−グリコール結合の含有量が１．９モル％未満の場合、耐水性が低下し、粘度の温度依存性も大きくなり、さらには重合安定性も低下する懸念が生じる。また、１，２−グリコール結合の含有量は４モル％以下であることが好ましく、さらに好ましくは３．５モル％以下、最適には３.２モル％以下である。ここで、１，２−グリコール結合の含有量はＮＭＲスペクトルの解析から求められる。
【０００７】
また、ここで、ビニルエステルとしては、蟻酸ビニル、酢酸ビニル、プロピオン酸ビニル、ピバリン酸ビニルなどが挙げられるが、一般に酢酸ビニルが好ましく用いられる。
【０００８】
また、該分散剤は上記した酢酸ビニルなどのビニルエステルの重合体をけん化したものが好適であるが、本発明の効果を損なわない範囲で共重合可能なエチレン性不飽和単量体を共重合したものでも良い。このようなエチレン性不飽和単量体としては、例えば、アクリル酸、メタクリル酸、フマル酸、（無水）マレイン酸、イタコン酸、アクリロニトリル、メタクリロニトリル、アクリルアミド、メタクリルアミド、トリメチル−（３−アクリルアミド−３−ジメチルプロピル）−アンモニウムクロリド、アクリルアミド−２−メチルプロパンスルホン酸およびそのナトリウム塩、エチルビニルエーテル、ブチルビニルエーテル、Ｎ−ビニルピロリドン、塩化ビニル、臭化ビニル、フッ化ビニル、塩化ビニリデン、フッ化ビニリデン、テトラフルオロエチレン、ビニルスルホン酸ナトリウム、アリルスルホン酸ナトリウム、Ｎ−ビニルピロリドン、Ｎ−ビニルホルムアミド、Ｎ−ビニルアセトアミド等のＮ−ビニルアミド類が挙げられる。また、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、酢酸ビニルなどのビニルエステル系単量体を重合し、それをけん化することによって得られる末端にメルカプト基またはカルボキシル基を有する変性物も用いることができる。
【０００９】
本発明の水性エマルジョンの分散剤として用いる１，２−グリコール結合を１．９モル％以上有するビニルアルコール系重合体のけん化度は、特に制限されないが、通常６０モル％以上のものが用いられ、より好ましくは、７０モル％以上、さらに好ましくは７５モル％以上である。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本来の性質である水溶性が低下する懸念が生じる。また本発明の目的とする水性エマルジョンを得るためには該ビニルアルコール系重合体の重合度（粘度平均重合度）は１００〜８０００であることが好ましく、３００〜３０００がより好ましい。
【００１０】
本発明の水性エマルジョンにおける分散質を構成するビニルエステル系単量体としては、蟻酸ビニル、酢酸ビニル、プロピオン酸ビニル、ピバリン酸ビニルなどが挙げられるが、酢酸ビニルが経済的にみて好ましい。ビニルエステル系単量体単位を有する重合体（分散質）とはビニルエステル系（共）重合体であり、ポリビニルエステル、ビニルエステルとビニルエステルと共重合しうる他の単量体との共重合体が挙げられる。ビニルエステルと共重合しうる他の単量体としては、
エチレン、プロピレン、イソブチレンなどのオレフィン；塩化ビニル、フッ化ビニル、ビニリデンクロリド、ビニリデンフルオリドなどのハロゲン化オレフィン；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、バーサチック酸ビニルなどのビニルエステル；アクリル酸、メタクリル酸、アクリル酸メチル、アクリル酸エチル、アクリル酸ブチル、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２−ヒドロキシエチルなどのアクリル酸エステル；メタクリル酸メチル、メタクリル酸エチル、メタクリル酸ブチル、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２−ヒドロキシエチルなどのメタクリル酸エステル；アクリル酸ジメチルアミノエチル、メタクリル酸ジメチルアミノエチルおよびこれらの四級化物；さらには、アクリルアミド、メタクリルアミド、Ｎ−メチロールアクリルアミド、Ｎ，Ｎ−ジメチルアクリルアミド、アクリルアミド−２−メチルプロパンスルホン酸およびそのナトリウム塩などのアクリルアミド系単量体；スチレン、α−メチルスチレン、ｐ−スチレンスルホン酸およびナトリウム、カリウム塩などのスチレン系単量体；その他Ｎ−ビニルピロリドンなど；また、ブタジエン、イソプレン、クロロプレンなどのジエン系単量体が挙げられ、これらは単独あるいは二種以上混合して用いられる。ビニルエステルと共重合しうるエチレンなどの他の単量体の使用量は使用する全単量体に対し５０重量％以下が好適であり、さらには４０重量％以下がより好適である。上記したビニルエステル系単量体単位を有する重合体のうち、ポリビニルエステル、ビニルエステル−エチレン共重合体が最良である。
【００１１】
また本発明の水性エマルジョンは、３０℃におけるエマルジョン粘度Ｔ₃₀ _℃と０℃における粘度Ｔ₀ _℃の比、Ｔ₀ _℃／Ｔ₃₀ _℃が５以下であることが重要である。ここでＴ₀ _℃／Ｔ₃₀ _℃とは後述する方法で測定される値であるが、Ｔ₀ _℃／Ｔ₃₀ _℃が５以下を示すことは、０℃近辺で粘度の上昇を抑えることができること、すなわち温度依存性が小さいことを意味している。Ｔ₀ _℃／Ｔ₃₀ _℃は４以下、さらには３以下であることがより好適である。
また本発明の水性エマルジョンは、３０℃におけるエマルジョン粘度Ｔ₃₀ _℃と６０℃における粘度Ｔ₆₀ _℃の比、Ｔ₆₀ _℃／Ｔ₃₀ _℃が１．５以下であることも重要である。ここでＴ₆₀ _℃／Ｔ₃₀ _℃とは後述する方法で測定される値であるが、Ｔ₆₀ _℃／Ｔ₃₀ _℃が１．５以下を示すことは、６０℃近辺では高い粘度を示すビニルエステル系重合体水性エマルジョンが多いが、本発明では、６０℃近辺で粘度の上昇を抑えることができること、すなわち温度依存性が小さいことを意味している。Ｔ₆₀ _℃／Ｔ₃₀ _℃は１．３以下、さらには１．２以下であることがより好適である。このように低温下においても高温下においても、温度依存性が小さいことにより作業性、取り扱い性は格段と向上することになる。
【００１２】
本発明の水性エマルジョンの製造方法としては、ビニルエステル系単量体を乳化重合するに際し、（１）分散剤として１，２−グリコール結合を１．９モル％以上有するビニルアルコール系重合体を用い、（２）過酸化水素、過硫酸アンモニウムおよび過硫酸カリウムから選ばれる少なくとも一種の重合開始剤をビニルエステル系単量体に対してモル比で０．００１〜０．０３使用し、さらに（３）重合初期にビニルエステル系単量体を単量体全量（ビニルエステル系単量体の全量）の５〜２０重量％仕込み、かつ上記重合開始剤を初期仕込みのビニルエステル系単量体に対してモル比で０．００１〜０．０５一括添加する重合操作を行う方法があげられる。
【００１３】
本発明の目的を達成するためには、１，２−グリコール結合を１．９モル％以上有するビニルアルコール系重合体の使用量はビニルエステル系単量体（ビニルエステルと共重合しうる単量体と併用する場合はその合計量）１００重量部に対して１〜２０重量部であることが好適であり、より好ましくは３〜２０重量部、さらに好ましくは５〜１５重量部の範囲である。さらに本発明においては、１，２−グリコール結合を１．９モル％以上有するビニルアルコール系重合体の使用量は、少量であっても、たとえば１〜５重量部であっても本発明の目的を充分達成することができることもひとつの特長である。
【００１４】
このような方法を採用することによって、前記したＴ₀ _℃／Ｔ₃₀ _℃が５以下で、Ｔ₆₀ _℃／Ｔ₃₀ _℃が１．５以下を満足する水性エマルジョンを得ることができる。
また本発明の製法は、後述する実施例からも明らかなように、乳化重合後のろ過残が少ないなど、重合安定性が優れていることも大きな特長である。
【００１５】
本発明の水性エマルジョンを製造するにあたっては、過酸化水素、過硫酸アンモニウムおよび過硫酸カリウムから選ばれる少なくとも一種の重合開始剤を用いることは重要であり、この中でも特に過酸化水素が好ましい。また、本発明においては、重合開始剤を、使用するビニルエステル系単量体に対してモル比で０．００１〜０．０３使用して乳化重合することも重要であり、好ましくは０．００１５〜０．０２５であり、さらに好ましくは０．００１８〜０．０２３である。
【００１６】
また、前記重合開始剤は還元剤と併用し、レドックス系で用いられる場合もある。その場合、通常、過酸化水素は酒石酸、Ｌ−アスコルビン酸、ロンガリットなどとともに用いられる。また、過硫酸アンモニウム、過硫酸カリウムは亜硫酸水素ナトリウム、炭酸水素ナトリウムなどとともに用いられる。還元剤の使用量も特に限定されないが、通常、重合開始剤に対して、０．０５〜３当量用い、好ましくは０．１〜２当量、より好ましくは０．３〜１．５当量用いる。
【００１７】
前記重合開始剤の添加方法としては、重合開始初期に重合開始剤を一括添加する方法（ショットで添加する方法）を用いることが好適である。すなわちビニルエステル系単量体を、単量体全量の５〜２０％を重合初期に仕込み、重合開始剤を初期仕込みのビニルエステル系単量体に対してモル比で０．００１〜０．０５一括添加することが必要となり、好ましくは０．００１２〜０．０４５であり、より好ましくは０．００１３〜０．０４である。
初期重合は、重合開始剤を上記したとおり所定の量一括添加することにより耐水性のより改善された、しかも温度依存性のより小さい水性エマルジョンが得られ、重合安定性もさらに良好となり、重合後のろ過残量も少なくなる。
【００１８】
初期重合は、分散剤の水溶液に単量体、重合開始剤を加え、重合温度５０〜７０℃、好適には５５〜６５℃、重合時間５〜６０分、好適には１０〜５０分の条件下で行われる。初期重合において単量体は一括添加することが好適である。
初期重合は、ビニルエステルの残存濃度（生成ポリマーに対する重量％）が１０％以下、好適には５％以下、さらに好適には１％以下になった時点で終了する。初期重合後は、後期重合に入る。後期重合では重合開始剤は一括添加（ショット添加）でも良いし、連続添加あるいは断続添加でも良い。また、後期重合では、重合温度は初期重合温度よりも５〜３０℃高くすることが好適であり、５５〜１００℃、好適には６０〜９５℃、さらに好適には７０〜９０℃の範囲内で行われる。
重合圧力は初期重合、後期重合とも常圧で良いが、必要に応じ加圧する必要がある。とくにビニルエステルと他の単量体、たとえばエチレンとの共重合体エマルジョンを製造する場合は、圧力下で行うことが必要である。
このようにして得られた本発明の水性エマルジョンは耐水性がより改善されているため、耐水性の要求される各種用途に好適に使用され、また本発明の水性エマルジョンは、温度依存性が小さく、低温、高温下での保存、運搬、使用においても粘度上昇を防ぐことができるので、作業性、取り扱い性に極めて優れている。
【００１９】
本発明の水性エマルジョンは、上記の方法で得られる水性エマルジョンをそのまま用いることができるが、必要があれば、本発明の効果を損なわない範囲で、従来公知の各種エマルジョンを添加して用いることができる。
なお、本発明の水性エマルジョンにおける分散剤としては、前述の１，２−グリコール結合を１．９モル％以上有するＰＶＡ系重合体が用いられるが、必要に応じて、従来公知のアニオン性、ノニオン性あるいはカチオン性の界面活性剤や、ヒドロキシエチルセルロースを併用することができるし、また本発明の目的を損なわない範囲で１，２−グリコール結合量が１．９モル％より少ないビニルアルコール系重合体を併用することもできる。
【００２０】
本発明の水性エマルジョンは、耐水性に優れており、さらに温度依存性が小さいため、紙管、製袋、合紙、段ボール用等の紙、パルプなどの紙加工用接着剤、フラッシュパネル、集成材、ツキ板、合板加工用、合板二次加工用（練り合わせ）、一般木工等の木工用接着剤および各種プラスチック用の接着剤、含浸紙用、不織製品用のバインダー、混和剤、打継ぎ材、塗料、紙加工および繊維加工などの分野で好適に用いられる。
【００２１】
【実施例】
次に、実施例および比較例により本発明をさらに詳細に説明する。なお、以下の実施例および比較例において「部」および「％」は、特に断らない限り重量基準を意味する。また、得られたエマルジョンの耐水性（耐水接着力）、温度依存性を、下記の要領で評価した。
【００２２】
（エマルジョンの評価）
（１）耐水接着力（木の接着）
得られた水性エマルジョンをツガ材（柾目）に１５０ｇ／ｍ²塗布し、はりあわせて７ｋｇ／ｍ²の荷重で１６時間圧締した。その後、解圧し、２０℃６５％ＲＨ下で５日間養生した後、２０℃の冷水に４日間浸漬し、ぬれたままの状態で圧縮せん断強度を測定した。
（２）温度依存性
・Ｔ₀ _℃／Ｔ₃₀ _℃
・Ｔ₆₀ _℃／Ｔ₃₀ _℃
Ｔ₀ _℃：０℃に調整後測定した粘度
Ｔ₃₀ _℃：３０℃に調整後測定した粘度
Ｔ₆₀ _℃：６０℃に調整後測定した粘度
粘度はＢ型粘度計（20rpm）を用いて測定。
（３）重合安定性
重合後、得られた水性エマルジョンを６０メッシュのステンレス製金網を用いてろ過し、ろ過残量（％）（対エマルジョン）を測定した。ろ過残量が少ないほど重合安定性が優れていることを示す。
【００２３】
製造例１
攪拌機、窒素導入口、開始剤導入口を備えた５L加圧反応槽に酢酸ビニル２９４０ｇ、メタノール６０gおよび酒石酸０．０８８ｇを仕込み、室温下に窒素ガスによるバブリングをしながら反応槽圧力を２．０ＭＰａまで昇圧して１０分間放置した後、放圧するという操作を３回繰り返して系中を窒素置換した。開始剤として２,２'−アゾビス（シクロヘキサン−１−カルボニトリル）（Ｖ−４０）をメタノールに溶解した濃度０．２ｇ／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。次いで上記の重合槽内温を１２０℃に昇温した。このときの反応槽圧力は０．５ＭＰａであった。次いで、上記の開始剤溶液２．５ｍｌを注入し重合を開始した。重合中は重合温度を１２０℃に維持し、上記の開始剤溶液を用いて１０．０ｍｌ／ｈｒでＶ−４０を連続添加して重合を実施した。重合中の反応槽圧力は０．５ＭＰａであった。３時間後に冷却して重合を停止した。このときの固形分濃度は２４％であった。次いで、３０℃減圧下にメタノールを時々添加しながら未反応酢酸ビニルモノマーの除去を行い、ポリ酢酸ビニルのメタノール溶液（濃度３３％）を得た。得られた該ポリ酢酸ビニル溶液にメタノールを加えて濃度が２５％となるように調整したポリ酢酸ビニルのメタノール溶液４００ｇ（溶液中のポリ酢酸ビニル１００ｇ）に、４０℃で１１．６ｇ（ポリ酢酸ビニル中の酢酸ビニル単位に対してモル比（ＭＲ）０．０２５）のアルカリ溶液（ＮａＯＨの１０％メタノール溶液）を添加してけん化を行った。アルカリ添加後約２分で系がゲル化したものを粉砕器にて粉砕し、１時間放置してけん化を進行させた後、酢酸メチル１０００ｇを加えて残存するアルカリを中和した。フェノールフタレイン指示薬を用いて中和の終了を確認後、濾別して得られた白色固体のＰＶＡにメタノール１０００ｇを加えて室温で３時間放置洗浄した。上記洗浄操作を３回繰り返した後、遠心脱液して得られたＰＶＡを乾燥機中７０℃で２日間放置して乾燥ＰＶＡ（ＰＶＡ−１）を得た。得られたＰＶＡ（ＰＶＡ −１）のけん化度は９８モル％であった。また、重合後未反応酢酸ビニルモノマーを除去して得られたポリ酢酸ビニルのメタノール溶液をアルカリモル比０．５でけん化して、粉砕したものを６０℃で５時間放置してけん化を進行させた後、メタノールによるソックスレー洗浄を3日間実施し、次いで８０℃で３日間減圧乾燥を行って精製ＰＶＡを得た。該ＰＶＡの平均重合度を常法のＪＩＳＫ６７２６に準じて測定したところ１７００であった。ＰＶＡの１，２−グリコール結合含有量はＮＭＲのピークから求めることができる。けん化度９９．９モル％以上にけん化後（けん化度はＪＩＳＫ６７２６に準じて測定）、十分にメタノール洗浄を行い、次いで９０℃減圧乾燥を２日間したＰＶＡをＤＭＳＯ−Ｄ6に溶解し、トリフルオロ酢酸を数滴加えた試料を５００ＭＨｚのプロトンＮＭＲ（ＪＥＯＬＧＸ-５００）を用いて８０℃で測定する。
ビニルアルコール単位のメチン由来のピークは３．２〜４．０ｐｐｍ（積分値Ａ）、１，２−グリコール結合の１つのメチン由来のピークは３．２５ｐｐｍ（積分値Ｂ）に帰属され、次式で１，２−グリコール結合含有量を算出できる。
１，２−グリコール結合含有量（モル％）＝Ｂ／Ａ×100
該精製ＰＶＡの１,２−グリコール結合量を５００ＭＨｚプロトンＮＭＲ（ＪＥＯＬＧＸ−５００）装置による測定から前述のとおり求めたところ、２．２モル％であった。
【００２４】
製造例２
攪拌機、窒素導入口、開始剤導入口を備えた５L加圧反応槽に酢酸ビニル２９４０ｇ、メタノール６０gおよび酒石酸０．０８８ｇを仕込み、室温下に窒素ガスによるバブリングをしながら反応槽圧力を２．０MPaまで昇圧して１０分間放置した後、放圧するという操作を３回繰り返して系中を窒素置換した。開始剤として２,２'−アゾビス（シクロヘキサン−１−カルボニトリル）（Ｖ−４０）をメタノールに溶解した濃度０．２ｇ／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。次いで上記の重合槽内温を１２０℃に昇温した。このときの反応槽圧力は０．５ＭＰａであった。次いで、上記の開始剤溶液２．５ｍｌを注入し重合を開始した。重合中は重合温度を１２０℃に維持し、上記の開始剤溶液を用いて１０．０ｍｌ／ｈｒでＶ−４０を連続添加して重合を実施した。重合中の反応槽圧力は０．５ＭＰａであった。３時間後に冷却して重合を停止した。このときの固形分濃度は２４％であった。次いで、３０℃減圧下にメタノールを時々添加しながら未反応酢酸ビニルモノマーの除去を行い、ポリ酢酸ビニルのメタノール溶液（濃度３３％）を得た。得られた該ポリ酢酸ビニル溶液にメタノールを加えて濃度が２５％となるように調整したポリ酢酸ビニルのメタノール溶液４００ｇ（溶液中のポリ酢酸ビニル１００ｇ）に、４０℃で２．３ｇ（ポリ酢酸ビニル中の酢酸ビニル単位に対してモル比（ＭＲ）０．００５）のアルカリ溶液（ＮａＯＨの１０％メタノール溶液）と水１．４ｇを添加してけん化を行った。アルカリ添加後約２０分で系がゲル化したものを粉砕器にて粉砕し、１時間放置してけん化を進行させた後、酢酸メチル１０００ｇを加えて残存するアルカリを中和した。フェノールフタレイン指示薬を用いて中和の終了を確認後、濾別して得られた白色固体のＰＶＡにメタノール１０００ｇを加えて室温で３時間放置洗浄した。上記洗浄操作を３回繰り返した後、遠心脱液して得られたＰＶＡを乾燥機中７０℃で２日間放置して乾燥ＰＶＡ（ＰＶＡ−２）を得た。得られたＰＶＡ（ＰＶＡ−２）のけん化度は８８モル％であった。また、重合後未反応酢酸ビニルモノマーを除去して得られたポリ酢酸ビニルのメタノール溶液をアルカリモル比０．５でけん化して、粉砕したものを６０℃で５時間放置してけん化を進行させた後、メタノールによるソックスレー洗浄を３日間実施し、次いで８０℃で３日間減圧乾燥を行って精製ＰＶＡを得た。該ＰＶＡの平均重合度を常法のＪＩＳＫ６７２６に準じて測定したところ１７００であった。該精製ＰＶＡの１,２−グリコール結合量を５００ＭＨｚプロトンＮＭＲ（ＪＥＯＬＧＸ−５００）装置による測定から前述のとおり求めたところ、２．２モル％であった。
【００２５】
製造例３
攪拌機、窒素導入口、開始剤導入口を備えた５L加圧反応槽に酢酸ビニル２８５０ｇ、メタノール１５０ｇおよび酒石酸０．０８６ｇを仕込み、室温下に窒素ガスによるバブリングをしながら反応槽圧力を２．０ＭＰａまで昇圧して１０分間放置した後、放圧するという操作を３回繰り返して系中を窒素置換した。開始剤として２,２'−アゾビス（Ｎ-ブチル−２−メチルプロピオンアミド）をメタノールに溶解した濃度０．１ｇ／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。次いで上記の重合槽内温を１５０℃に昇温した。このときの反応槽圧力は１．０ＭＰａであった。次いで、上記の開始剤溶液１５．０ｍｌを注入し重合を開始した。重合中は重合温度を１５０℃に維持し、上記の開始剤溶液を用いて１５．８ｍｌ／ｈｒで２,２'−アゾビス（Ｎ-ブチル−２−メチルプロピオンアミド）を連続添加して重合を実施した。重合中の反応槽圧力は１．０ＭＰａであった。４時間後に冷却して重合を停止した。このときの固形分濃度は３５％であった。次いで、３０℃減圧下にメタノールを時々添加しながら未反応酢酸ビニルモノマーの除去を行い、ポリ酢酸ビニルのメタノール溶液（濃度３３％）を得た。得られた該ポリ酢酸ビニル溶液にメタノールを加えて濃度が２５％となるように調整したポリ酢酸ビニルのメタノール溶液４００ｇ（溶液中のポリ酢酸ビニル１００ｇ）に、４０℃で１１．６ｇ（ポリ酢酸ビニル中の酢酸ビニル単位に対してモル比（ＭＲ）０．０２５）のアルカリ溶液（ＮａＯＨの１０％メタノール溶液）を添加してけん化を行った。アルカリ添加後約３分でゲル化したものを粉砕器にて粉砕し、１時間放置してけん化を進行させた後、酢酸メチル１０００ｇを加えて残存するアルカリを中和した。フェノールフタレイン指示薬を用いて中和の終了を確認後、濾別して得られた白色固体のＰＶＡにメタノール１０００ｇを加えて室温で３時間放置洗浄した。上記洗浄操作を３回繰り返した後、遠心脱液して得られたＰＶＡを乾燥機中７０℃で２日間放置して乾燥ＰＶＡ（ＰＶＡ−3）を得た。得られたＰＶＡ（ＰＶＡ−３）のけん化度は９８モル％であった。また、重合後未反応酢酸ビニルモノマーを除去して得られたポリ酢酸ビニルのメタノール溶液をアルカリモル比０．５でけん化した後、粉砕したものを６０℃で５時間放置してけん化を進行させた後、メタノールによるソックスレー洗浄を３日間実施し、次いで８０℃で３日間減圧乾燥を行って精製ＰＶＡを得た。該ＰＶＡの平均重合度を常法のＪＩＳＫ６７２６に準じて測定したところ１０００であった。該精製PVAの１,２−グリコール結合量を５００ＭＨｚプロトンＮＭＲ（ＪＥＯＬＧＸ−５００）装置による測定から前述のとおり求めたところ、２．５モル％であった。
【００２６】
製造例４
攪拌機、窒素導入口、開始剤導入口を備えた５Ｌ加圧反応槽に酢酸ビニル２７００ｇ、メタノール３００ｇおよび酒石酸０．０８１ｇを仕込み、室温下に窒素ガスによるバブリングをしながら反応槽圧力を２．０ＭＰａまで昇圧して１０分間放置した後、放圧するという操作を３回繰り返して系中を窒素置換した。開始剤として２,２'−アゾビス（Ｎ−ブチル−２−メチルプロピオンアミド）をメタノールに溶解した濃度０．０５ｇ／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。次いで上記の重合槽内温を１８０℃に昇温した。このときの反応槽圧力は１．６MPaであった。次いで、上記の開始剤溶液０．４ｍｌを注入し重合を開始した。重合中は重合温度を１８０℃に維持し、上記の開始剤溶液を用いて１０．６ｍｌ／ｈｒで２,２'−アゾビス（Ｎ−ブチル−２−メチルプロピオンアミド）を連続添加して重合を実施した。重合中の反応槽圧力は１．６ＭＰａであった。４時間後に冷却して重合を停止した。このときの固形分濃度は２７％であった。次いで、３０℃減圧下にメタノールを時々添加しながら未反応酢酸ビニルモノマーの除去を行い、ポリ酢酸ビニルのメタノール溶液（濃度３３％）を得た。得られた該ポリ酢酸ビニル溶液にメタノールを加えて濃度が３０％となるように調整したポリ酢酸ビニルのメタノール溶液３３３g（溶液中のポリ酢酸ビニル１００ｇ）に、４０℃で１１．６ｇ（ポリ酢酸ビニル中の酢酸ビニル単位に対してモル比（ＭＲ）０．０２５）のアルカリ溶液（ＮａＯＨの１０％メタノール溶液）を添加してけん化を行った。アルカリ添加後約３分でゲル化したものを粉砕器にて粉砕し、１時間放置してけん化を進行させた後、酢酸メチル１０００ｇを加えて残存するアルカリを中和した。フェノールフタレイン指示薬を用いて中和の終了を確認後、濾別して得られた白色固体のＰＶＡにメタノール１０００ｇを加えて室温で３時間放置洗浄した。上記洗浄操作を３回繰り返した後、遠心脱液して得られたＰＶＡを乾燥機中７０℃で２日間放置して乾燥ＰＶＡ（ PVA−４）を得た。得られたＰＶＡ（ＰＶＡ−４）のけん化度は９８モル％であった。また、重合後未反応酢酸ビニルモノマーを除去して得られたポリ酢酸ビニルのメタノール溶液をアルカリモル比０．５でけん化した後、粉砕したものを６０℃で５時間放置してけん化を進行させた後、メタノールによるソックスレー洗浄を３日間実施し、次いで８０℃で３日間減圧乾燥を行って精製ＰＶＡを得た。該ＰＶＡの平均重合度を常法のＪＩＳＫ６７２６に準じて測定したところ５００であった。該精製ＰＶＡの１,２−グリコール結合量を５００ＭＨｚプロトンＮＭＲ（ＪＥＯＬＧＸ−５００）装置による測定から前述のとおり求めたところ、２．９モル％であった。
【００２７】
製造例５
攪拌機、窒素導入口、開始剤導入口を備えた５Ｌ加圧反応槽に酢酸ビニル２４００ｇ、メタノール６００ｇおよびビニレンカーボネート４９．３ｇを仕込み、室温下に窒素ガスによるバブリングをしながら反応槽圧力を２．０ＭＰａまで昇圧して１０分間放置した後、放圧するという操作を３回繰り返して系中を窒素置換した。開始剤としてα,α'−アゾビスイソブチロニトリルをメタノールに溶解した濃度１．０ｇ／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。次いで重合槽内温を９０℃に昇温した。このときの反応槽圧力は０．４ＭＰａであった。上記の重合槽内温を９０℃に調整した後、上記の開始剤溶液３．０ｍｌを注入し重合を開始した。重合中は重合温度を９０℃に維持し、上記の開始剤溶液を用いて４．９ｍｌ／ｈｒでα,α'−アゾビスイソブチロニトリルを連続添加して重合を実施した。重合中の反応槽圧力は０．４ＭＰａであった。４時間後に冷却して重合を停止した。このときの固形分濃度は３８％であった。次いで３０℃減圧下にメタノールを時々添加しながら未反応酢酸ビニルモノマーの除去を行い、ポリ酢酸ビニルのメタノール溶液（濃度３３％）を得た。得られた該ポリ酢酸ビニル溶液にメタノールを加えて濃度が２５％となるように調整したポリ酢酸ビニルのメタノール溶液４００ｇ（溶液中のポリ酢酸ビニル１００ｇ）に、４０℃で４６．４ｇ（ポリ酢酸ビニル中の酢酸ビニルユニットに対してモル比（ＭＲ）０．１０）のアルカリ溶液（ＮａＯＨの１０％メタノール溶液）を添加してけん化を行った。アルカリ添加後約１分でゲル化したものを粉砕器にて粉砕し、１時間放置してけん化を進行させた後、酢酸メチル１０００ｇを加えて残存するアルカリを中和した。フェノールフタレイン指示薬を用いて中和の終了を確認後、濾別して得られた白色固体のPVAにメタノール１０００ｇを加えて室温で３時間放置洗浄した。上記洗浄操作を３回繰り返した後、遠心脱液して得られたＰＶＡを乾燥機中７０℃で２日間放置して乾燥ＰＶＡ（ＰＶＡ−５）を得た。
得られたＰＶＡ（ＰＶＡ−５）のけん化度は９９．５モル％であった。
また、重合後未反応酢酸ビニルモノマーを除去して得られたポリ酢酸ビニルのメタノール溶液をアルカリモル比０．５でけん化した後、粉砕したものを６０℃で５時間放置してけん化を進行させた後、メタノールによるソックスレー洗浄を３日間実施し、次いで８０℃で３日間減圧乾燥を行って精製ＰＶＡを得た。該ＰＶＡの重合度を常法のＪＩＳＫ６７２６に準じて測定したところ１２００であった。該精製ＰＶＡの１,２−グリコール結合量を５００ＭＨｚプロトンＮＭＲ（ＪＥＯＬＧＸ−５００）装置による測定から前述のとおり求めたところ、２．５モル％であった。
【００２８】
製造例６
攪拌機、窒素導入口、開始剤導入口および還流冷却管を備えた５L四つ口セパラブルフラスコに酢酸ビニル２０００ｇ、メタノール４００ｇ、ビニレンカーボネート７８．８ｇを仕込み、室温下に３０分間窒素バブリングしながら系中を窒素置換した。上記の重合槽内温を６０℃に調整した後、開始剤としてα,α'−アゾビスイソブチロニトリル０．９ｇを添加して重合を開始した。重合中は重合温度を６０℃に維持し、４時間後に冷却して重合を停止した。この時の固形分濃度は５５％であった。次いで３０℃減圧下にメタノールを時々添加しながら未反応酢酸ビニルモノマーの除去を行い、ポリ酢酸ビニルのメタノール溶液（濃度３３％）を得た。得られた該ポリ酢酸ビニル溶液にメタノールを加えて濃度が２５％となるように調整したポリ酢酸ビニルのメタノール溶液４００ｇ（溶液中のポリ酢酸ビニル１００ｇ）に、４０℃で４６．４ｇ（ポリ酢酸ビニル中の酢酸ビニルユニットに対してモル比（ＭＲ）０．１０）のアルカリ溶液（ＮａＯＨの１０％メタノール溶液）を添加してけん化を行った。アルカリ添加後約１分でゲル化したものを粉砕器にて粉砕し、１時間放置してけん化を進行させた後、酢酸メチル１０００ｇを加えて残存するアルカリを中和した。フェノールフタレイン指示薬を用いて中和の終了を確認後、濾別して得られた白色固体のPVAにメタノール１０００ｇを加えて室温で３時間放置洗浄した。上記洗浄操作を３回繰り返した後、遠心脱液して得られたＰＶＡを乾燥機中７０℃で２日間放置して乾燥ＰＶＡ（ＰＶＡ−６）を得た。
得られたＰＶＡ（ＰＶＡ−６）のけん化度は９９．５モル％であった。
また、重合後未反応酢酸ビニルモノマーを除去して得られたポリ酢酸ビニルのメタノール溶液をアルカリモル比０．５でけん化した後、粉砕したものを６０℃で５時間放置してけん化を進行させた後、メタノールによるソックスレー洗浄を３日間実施し、次いで８０℃で３日間減圧乾燥を行って精製ＰＶＡを得た。該ＰＶＡの重合度を常法のＪＩＳＫ６７２６に準じて測定したところ１７００であった。該精製ＰＶＡの１,２−グリコール結合量を５００ＭＨｚプロトンＮＭＲ（ＪＥＯＬＧＸ−５００）装置による測定から前述のとおり求めたところ、３．０モル％であった。
【００２９】
製造例７
酢酸ビニル２４００ｇ、メタノール５８０ｇおよびチオール酢酸０．９３ｇを反応容器にとり、内部を十分に窒素置換した後外温を６５℃にあげ、内温が６０℃に達したところで、２，２−アゾビスイソブチロニトリル０．８６８ｇを含むメタノール２０ｇを加えた。直ちにチオール酢酸１７．４ｇを含むメタノール溶液６０ｇを５時間にわたって均一に加えた。５時間後の重合率は５０．４％であった。５時間後に容器を冷却し、減圧下に残留する酢酸ビニル(ＶＡｃ)をメタノールとともに系外へ追い出す操作をメタノールを追加しながら行い、ポリ酢酸ビニルのメタノール溶液を得た。（濃度５４．５％）このメタノール溶液の一部をとり、ポリ酢酸ビニル濃度５０％[NaOH]／[VAc]＝０．０５（モル比）となるようにNaOHのメタノール溶液を加え、４０℃でけん化した。アルカリ添加後約１分でゲル化したものを粉砕器にて粉砕し、１時間放置してけん化を進行させた後、酢酸メチル１０００ｇを加えて残存するアルカリを中和した。フェノールフタレイン指示薬を用いて中和の終了を確認後、濾別して得られた白色固体のPVAにメタノール１０００ｇを加えて室温で３時間放置洗浄した。上記洗浄操作を３回繰り返した後、遠心脱液して得られたＰＶＡを乾燥機中７０℃で２日間放置して乾燥ＰＶＡ（ＰＶＡ−１１）を得た。
得られたＰＶＡ（ＰＶＡ−１１）のけん化度は９８．６モル％であった。
また、重合後未反応酢酸ビニルモノマーを除去して得られたポリ酢酸ビニルのメタノール溶液をアルカリモル比０．５でけん化した後、粉砕したものを６０℃で５時間放置してけん化を進行させた後、メタノールによるソックスレー洗浄を３日間実施し、次いで８０℃で３日間減圧乾燥を行って精製ＰＶＡを得た。該ＰＶＡの重合度を常法のＪＩＳＫ６７２６に準じて測定したところ１３０であった。該精製ＰＶＡの１,２−グリコール結合量を５００ＭＨｚプロトンＮＭＲ（ＪＥＯＬＧＸ−５００）装置による測定から前述のとおり求めたところ、１．６モル％であった。
【００３０】
実施例１
還流冷却器、滴下ロート、温度計、窒素吹込口を備えた１リットルガラス製重合容器に、イオン交換水３００ｇ、製造例１により得られたＰＶＡ−１（重合度１７００、けん化度９８．０モル％、１，２−グリコール含有量２．２モル％）２６ｇを仕込み９５℃で完全に溶解した。次に、このＰＶＡ水溶液を冷却、窒素置換後、２００ｒｐｍで撹拌しながら、６０℃に昇温した後、酒石酸の１０％水溶液を４．４ｇおよび５％過酸化水素水３ｇをショット添加後、酢酸ビニル２６ｇを仕込み重合を開始した。重合開始３０分後に初期重合終了（酢酸ビニルの残存量１重量％未満）を確認した。次に酒石酸の１０％水溶液を０．９ｇおよび５％過酸化水素水３ｇをショット添加後、酢酸ビニル２３４ｇを２時間にわたって連続的に添加し、重合温度８０℃に維持して重合を完結させた。冷却後、６０メッシュのステンレス製金網を用いてろ過した。以上の結果、固形分濃度４７．３％のポリ酢酸ビニル系エマルジョン（Ｅｍ−１）が得られた。結果を表１〜２に示す。
【００３１】
比較例１
実施例１で用いたＰＶＡ−１を用いる代わりに従来の方法により製造されたＰＶＡ−７（（株）クラレ製PVA-117;重合度１７００、けん化度９８．０％、１，２−グリコール含有量1.6mol%）を用いた他は実施例１と同様にして固形分濃度４７．１％の（Ｅｍ−２）を得た。このエマルジョンの評価を前述の方法により行った。結果をあわせて表１〜２に示す。
【００３２】
実施例２
還流冷却器、滴下ロート、温度計、窒素吹込口を備えた１リットルガラス製重合容器に、イオン交換水３００ｇ、製造例２により得られたＰＶＡ−２（重合度１７００、けん化度８８．０モル％、１，２−グリコール含有量２．２モル％）１３ｇを仕込み９５℃で完全に溶解した。次に、このＰＶＡ水溶液を冷却、窒素置換後、２００ｒｐｍで撹拌しながら、６０℃に昇温した後、酒石酸の１０％水溶液１８ｇおよび酢酸ビニル２６ｇを仕込み、１％過酸化水素水８５ｇを２．５時間にわたって連続的に添加し、重合を開始した。重合開始３０分後に初期重合終了（酢酸ビニルの残存量１重量％未満）を確認し、さらに酢酸ビニル２３４ｇを２時間にわたって連続的に添加した。酢酸ビニル添加終了後、１％過酸化水素水４．８ｇをショットで添加し、重合温度８０℃に維持して重合を完結させた。冷却後、６０メッシュのステンレス製金網を用いてろ過した。ろ過後のろ過残量により、実施例１と同様の方法で重合安定性を評価した。以上の結果、固形分濃度４７．６％のポリ酢酸ビニル系エマルジョン（Ｅｍ−３）が得られた。このエマルジョンの評価を前述の方法により行った。結果をあわせて表１〜２に示す。
【００３３】
比較例２
実施例２において用いたＰＶＡ−２を用いる代わりに従来の方法により製造されたＰＶＡ−８（（株）クラレ製PVA-217;重合度１７００、けん化度８８．０モル％、１，２−グリコール含有量１．６モル％）を用いた他は実施例２と同様にして固形分濃度４７．４％の（Ｅｍ−４）が得られた。このエマルジョンの評価を前述の方法により行った。結果をあわせて表１〜２に示す。
【００３４】
実施例３
還流冷却器、滴下ロート、温度計、窒素吹込口を備えた１リットルガラス製重合容器に、イオン交換水３００ｇ、製造例３により得られたＰＶＡ−３（重合度１０００、けん化度９８．０モル％、１，２−グリコール含有量２．５モル％）７．８ｇを仕込み９５℃で完全に溶解した。次に、このＰＶＡ水溶液を冷却、窒素置換後、２００ｒｐｍで撹拌しながら、６０℃に昇温した後、酒石酸の１０％水溶液を４．４ｇおよび５％過酸化水素水３ｇをショット添加後、酢酸ビニル２６ｇを仕込み重合を開始した。重合開始３０分後に初期重合終了（酢酸ビニルの残存量１重量％未満）を確認した。次に酒石酸の１０％水溶液を０．９ｇおよび５％過酸化水素水３ｇをショット添加後、酢酸ビニル２３４ｇを２時間にわたって連続的に添加し、重合温度８０℃に維持して重合を完結させた。冷却後、６０メッシュのステンレス製金網を用いてろ過した。以上の結果、固形分濃度４７．７％のポリ酢酸ビニル系エマルジョン（Ｅｍ−５）が得られた。このエマルジョンの評価を前述の方法により行った。結果をあわせて表１〜２に示す。
【００３５】
比較例３
実施例３において用いたＰＶＡ−３を用いる代わりに従来の方法により製造されたＰＶＡ−９（（株）クラレ製PVA-110;重合度１０００、けん化度９８．５モル％、１，２−グリコール含有量１．６モル％）を用いた他は実施例３と同様にして乳化重合を試みたが、重合途中にブロック化がおこり安定なエマルジョンが得られなかった。
【００３６】
実施例４
実施例１において用いたＰＶＡ−１を用いる代わりに製造例４により得られたＰＶＡ−４（重合度５００、けん化度９８モル％、１，２−グリコール含有量２．９モル％）を用いた他は実施例１と同様にして固形分濃度４７．８％の（Ｅｍ−７）が得られた。このエマルジョンの評価を前述の方法により行った。結果をあわせて表１〜２に示す。
【００３７】
比較例４
実施例１において用いたＰＶＡ−１を用いる代わりに従来の方法により製造されたＰＶＡ−１０（重合度４２０、けん化度８０．０モル％、１，２−グリコール含有量１．６モル％）を用いた他は実施例１と同様にして乳化重合を試みたが、重合途中でブロック化がおこり安定にエマルジョンを得ることができなかった。
【００３８】
実施例５
実施例１において用いたＰＶＡ−１を用いる代わりに製造例５により得られたＰＶＡ−５（重合度１２００、けん化度９９．５モル％、１，２−グリコール含有量２．５モル％）を用いた他は実施例１と同様にして固形分濃度４７．８％の（Ｅｍ−８）が得られた。このエマルジョンの評価を前述の方法により行った。
結果をあわせて表１〜２に示す。
【００３９】
実施例６
実施例１において用いたＰＶＡ−１を用いる代わりに製造例６により得られたＰＶＡ−６（重合度１７００、けん化度９９．５モル％、１，２−グリコール含有量３．０モル％）を用いた他は実施例１と同様にして固形分濃度４７．８％の（Ｅｍ−９）が得られた。このエマルジョンの評価を前述の方法により行った。結果をあわせて表１〜２に示す。
【００４０】
実施例７
窒素吹き込み口、温度計、攪拌機を備えた耐圧オートクレーブにＰＶＡ−１の７．５％水溶液１００ｇを仕込み、６０℃に昇温してから、窒素置換を行った。酢酸ビニル８ｇを仕込んだ後、エチレンを４５ｋｇ／ｃｍ²まで加圧し、２．５％過酸化水素水溶液０．９ｇおよび２％ロンガリット水溶液１．３５ｇを圧入し、重合を開始した。３０分後に初期重合終了（酢酸ビニルの残存量１重量％未満）を確認した。次に、８０℃に昇温後、酢酸ビニル７２ｇ、１％過酸化水素水溶液４．５ｇおよび２％ロンガリット水溶液１．３５ｇを２時間にわたって圧入し、重合温度８０℃に維持しながら、重合を完結させた。冷却後、実施例１と同様にろ過し、固形分濃度５０．１％、エチレン含量１５重量％のエチレン−酢酸ビニル共重合体エマルジョン（Ｅｍ−１０）が得られた。評価を前述の方法により行った。結果を表１に示す。
【００４１】
比較例５
実施例７において用いたＰＶＡ−１を用いる代わりにＰＶＡ−７を用いた他は実施例７と同様にして固形分濃度４９．５％、エチレン含量１０重量％のエチレン−酢酸ビニル共重合体エマルジョン（Ｅｍ−１１）が得られた。評価を前述の方法により行った。結果を表１〜２に示す。
【００４２】
比較例６
実施例１においてＰＶＡ−１の代わりにＰＶＡ−１１（重合度１３０，けん化度９８．６モル％、１，２−グリコール含有量１．６モル％、メルカプト基を末端に含有）を用いる以外は実施例１と同様にして固形分濃度４７．１％の（Ｅｍ−１２）を得た。このエマルジョンの評価を前述の方法により行った。結果を表１〜２に示す。
【００４３】
比較例７
攪拌機、還流冷却器、滴下ロート、温度計、窒素導入口を備えた５リットルのガラス製容器に、イオン交換水１４００ｇ、エチレン変性PVA（重合度１４００、けん化度９８．０モル％、エチレン含有量５．５モル％、１，２−グリコール結合量１．６モル％）（PVA−１２）２２５ｇを仕込み９５℃で完全に溶解した。次に、変性PVA水溶液を冷却後ｐＨを４に調製し、塩化第一鉄０．０５ｇを添加し、窒素置換した後、１４０ｒｐｍで攪拌しながら酢酸ビニル３５０ｇを仕込み、６０℃に昇温した。次に０．７％の過酸化水素水を１５ｍｌ／ｈｒで、６％のロンガリット水溶液を１０ｍｌ／ｈｒで連続添加しながら、７０℃で重合を行い、３０分後に初期重合終了（酢酸ビニルの残存量１重量％未満）を確認した。次に酢酸ビニル１４００ｇを３時間にわたって連続的に添加した。添加終了後、内温を８０℃に１時間保持し重合を完結させ、固形分濃度５０．４％のポリ酢酸ビニル水性エマルジョン（Ｅｍ−１３）が得られた。
【００４４】
【表１】

【００４５】
【表２】

【００４６】
PVA-1；重合度1700，けん化度98.0モル％、1,2-グリコール結合含有量2.2モル％
PVA-2；重合度1700，けん化度88.0モル％、1,2-グリコール結合含有量2.2モル％
PVA-3；重合度1000，けん化度98.0モル％、1,2-グリコール結合含有量2.5モル％
PVA-4；重合度500，けん化度98モル％、1,2-グリコール結合含有量2.9モル％
PVA-5；重合度1200，けん化度99.5モル％、1,2-グリコール結合含有量2.5モル％
PVA-6；重合度1700，けん化度99.5モル％、1,2-グリコール結合含有量3.0モル％
PVA-7；重合度1700，けん化度98.0モル％、1,2-グリコール結合含有量1.6モル％
｛（株）クラレ製PVA-117｝
PVA-8；重合度1700，けん化度88.0モル％、1,2-グリコール結合含有量1.6モル％
｛（株）クラレ製PVA-217｝
PVA-9；重合度1000，けん化度98.5モル％、1,2-グリコール結合含有量1.6モル％
｛（株）クラレ製PVA-110｝
PVA-10；重合度420，けん化度80.0モル％、1,2-グリコール結合含有量1.6モル％
（従来PVA）
PVA-11；重合度130，けん化度98.6モル％、1,2-グリコール結合含有量1.6モル％、
メルカプト基を末端に含有
PVA-12；重合度1400，けん化度98モル％、1,2-グリコール結合含有量1.6モル％、
エチレン含量5.5モル％
【００４７】
【発明の効果】
本発明の水性エマルジョンは、耐水性に優れており、さらに温度依存性が小さく、またその製法は、重合安定性に優れている。また、得られるエマルジョンは、紙用、木工用およびプラスチック用の接着剤、含浸紙用、不織製品用のバインダー、混和剤、打継ぎ材、塗料、紙加工および繊維加工などの分野で好適に用いられる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an aqueous emulsion having improved water resistance and low temperature dependence, and a method for producing an aqueous emulsion excellent in polymerization stability.
[0002]
[Prior art]
Conventionally, polyvinyl alcohol (hereinafter sometimes abbreviated as PVA) has been widely used as a protective colloid for emulsion polymerization of ethylenically unsaturated monomers, particularly vinyl ester monomers represented by vinyl acetate, Vinyl ester aqueous emulsions obtained by emulsion polymerization using this as a protective colloid are various adhesives for paper, woodworking and plastics, various binders, admixtures and punches for impregnated paper and non-woven products. Widely used in fields such as seams, paints, paper processing and textile processing.
Such an aqueous emulsion generally has a low viscosity by adjusting the degree of saponification of the PVA polymer, has a viscosity close to Newtonian flow, and has a relatively good water resistance. Since it has a high viscosity and relatively low temperature dependence of emulsion viscosity, it has been awarded for various uses.
However, some of the aqueous emulsions have drawbacks such as poor water resistance and large temperature dependence of emulsion viscosity.
[0003]
That is, PVA-based polymers as dispersants for emulsion polymerization generally include so-called “fully saponified PVA” having a saponification degree of about 98 mol% and “partially saponified PVA” having a saponification degree of about 88 mol%. When used, the water resistance is relatively good, but it is still not sufficient, and the temperature dependence of the emulsion viscosity is large. On the other hand, when the latter PVA polymer is used, although the temperature dependence of the emulsion viscosity is not so large, it is still not sufficient, and further has a drawback of poor water resistance. In order to improve such drawbacks, the combined use of both PVA polymers and the use of PVA polymers having an intermediate saponification degree between the two have been carried out. Could not be improved at the same time. Therefore, a vinyl alcohol polymer containing an ethylene unit has been proposed (Japanese Patent Laid-Open No. 11-81666) to improve water resistance and low-temperature storage stability. However, the water resistance is still not sufficient, and the temperature dependency is not sufficient (see Comparative Example 7 described later). It is also known to use a PVA having a mercapto group at the end as shown in Comparative Example 6 described later as a dispersion stabilizer for emulsion polymerization (JP-A-3-24481). It is not satisfactory in terms of the characteristics, and the temperature dependence is not small.
[0004]
[Problems to be solved by the invention]
Under such circumstances, an object of the present invention is to provide an aqueous emulsion having improved water resistance and low temperature dependence, and a method for producing an aqueous emulsion excellent in polymerization stability. To do.
[0005]
[Means for Solving the Problems]
The above object is an aqueous emulsion having a polymer having a vinyl ester monomer unit as a dispersoid and a vinyl alcohol polymer having a 1,2-glycol bond of 1.9 mol% or more as a dispersant, The viscosity of the aqueous emulsion at 60 ° C. is expressed as T₆₀ _℃, The viscosity at 30 ° C. is T₃₀ _℃, The viscosity at 0 ° C. is T₀ _℃When T₀ _℃/ T₃₀ _℃Is 5 or less, T₆₀ _℃/ T₃₀ _℃Is achieved by providing an aqueous emulsion that is 1.5 or less.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
There is no restriction | limiting in particular as a manufacturing method of the vinyl alcohol-type polymer which has 1.9 mol% or more of 1, 2- glycol bonds used as a dispersing agent of the aqueous emulsion of this invention, A well-known method can be used. As an example, a method in which vinylene carbonate is copolymerized with a vinyl ester so as to have the above 1,2-glycol bond amount, and the polymerization temperature of the vinyl ester is polymerized under pressure at a temperature higher than normal conditions, for example, 75 to 200 ° C. The method of doing is mentioned. In the latter method, the polymerization temperature is preferably 95 to 190 ° C, particularly preferably 100 to 180 ° C. Further, it is important to select the pressurizing condition such that the polymerization system is below the boiling point, preferably 0.2 MPa or more, and more preferably 0.3 MPa or more. The upper limit is preferably 5 Mpa or less, and more preferably 3 Mpa or less. The polymerization can be carried out by any method such as bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization in the presence of a radical polymerization initiator, but solution polymerization, particularly solution polymerization using methanol as a solvent, Is preferred. A vinyl alcohol polymer is obtained by saponifying the vinyl ester polymer thus obtained by a usual method. The 1,2-glycol bond content of the vinyl alcohol polymer needs to be 1.9 mol% or more, more preferably 1.95 mol% or more, and further 2.0 mol% or more, optimal. Is 2.1 mol% or more. When the content of 1,2-glycol bond is less than 1.9 mol%, water resistance is lowered, temperature dependency of viscosity is increased, and further, there is a concern that polymerization stability is also lowered. The 1,2-glycol bond content is preferably 4 mol% or less, more preferably 3.5 mol% or less, and most preferably 3.2 mol% or less. Here, the content of 1,2-glycol bonds is determined from analysis of NMR spectra.
[0007]
Here, examples of the vinyl ester include vinyl formate, vinyl acetate, vinyl propionate, vinyl pivalate and the like, and generally vinyl acetate is preferably used.
[0008]
The dispersant is preferably a saponified polymer of vinyl ester such as vinyl acetate as described above, but is copolymerized with an ethylenically unsaturated monomer that can be copolymerized within a range that does not impair the effects of the present invention. What you did is fine. Examples of such ethylenically unsaturated monomers include acrylic acid, methacrylic acid, fumaric acid, (anhydrous) maleic acid, itaconic acid, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, trimethyl- (3-acrylamide). -3-dimethylpropyl) -ammonium chloride, acrylamido-2-methylpropanesulfonic acid and its sodium salt, ethyl vinyl ether, butyl vinyl ether, N-vinyl pyrrolidone, vinyl chloride, vinyl bromide, vinyl fluoride, vinylidene chloride, fluoride N-vinylamides such as vinylidene, tetrafluoroethylene, sodium vinylsulfonate, sodium allylsulfonate, N-vinylpyrrolidone, N-vinylformamide, N-vinylacetamide and the like can be mentioned. In addition, a modified product having a mercapto group or a carboxyl group at the terminal obtained by polymerizing a vinyl ester monomer such as vinyl acetate in the presence of a thiol compound such as thiol acetic acid or mercaptopropionic acid and saponifying it. Can also be used.
[0009]
The saponification degree of the vinyl alcohol polymer having 1.9 mol% or more of 1,2-glycol bonds used as a dispersant for the aqueous emulsion of the present invention is not particularly limited, but usually 60 mol% or more is used. More preferably, it is 70 mol% or more, More preferably, it is 75 mol% or more. When the saponification degree is less than 60 mol%, there is a concern that the water solubility, which is the original property of the vinyl alcohol polymer, is lowered. In order to obtain an aqueous emulsion as the object of the present invention, the degree of polymerization (viscosity average degree of polymerization) of the vinyl alcohol polymer is preferably 100 to 8000, more preferably 300 to 3000.
[0010]
Examples of the vinyl ester monomer constituting the dispersoid in the aqueous emulsion of the present invention include vinyl formate, vinyl acetate, vinyl propionate, vinyl pivalate, etc., but vinyl acetate is preferred from the economical viewpoint. A polymer (dispersoid) having a vinyl ester monomer unit is a vinyl ester (co) polymer, and is a copolymer of polyvinyl ester, vinyl ester and other monomers copolymerizable with vinyl ester. Coalescence is mentioned. Other monomers that can be copolymerized with vinyl esters include:
Olefins such as ethylene, propylene and isobutylene; halogenated olefins such as vinyl chloride, vinyl fluoride, vinylidene chloride and vinylidene fluoride; vinyl esters such as vinyl formate, vinyl acetate, vinyl propionate, vinyl pivalate and vinyl versatate; Acrylic acid esters such as acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, 2-hydroxyethyl acrylate; methyl methacrylate, ethyl methacrylate, methacrylic acid Methacrylic acid esters such as butyl, 2-ethylhexyl methacrylate, dodecyl methacrylate, 2-hydroxyethyl methacrylate; dimethylaminoethyl acrylate, dimethylamino methacrylate Ethyl and quaternized compounds thereof; and acrylamide monomers such as acrylamide, methacrylamide, N-methylolacrylamide, N, N-dimethylacrylamide, acrylamide-2-methylpropanesulfonic acid and sodium salt thereof; styrene, α-methylstyrene, p-styrenesulfonic acid and styrene monomers such as sodium and potassium salts; other N-vinylpyrrolidone and the like; and diene monomers such as butadiene, isoprene and chloroprene, It is used alone or in combination of two or more. The amount of other monomers such as ethylene that can be copolymerized with the vinyl ester is preferably 50% by weight or less, more preferably 40% by weight or less, based on the total monomers used. Of the polymers having the vinyl ester monomer units described above, polyvinyl esters and vinyl ester-ethylene copolymers are the best.
[0011]
The aqueous emulsion of the present invention has an emulsion viscosity T at 30 ° C.₃₀ _℃And viscosity T at 0 ° C₀ _℃Ratio of T₀ _℃/ T₃₀ _℃It is important that is 5 or less. Where T₀ _℃/ T₃₀ _℃Is a value measured by the method described later,₀ _℃/ T₃₀ _℃The value of 5 or less means that the increase in viscosity can be suppressed around 0 ° C., that is, the temperature dependency is small. T₀ _℃/ T₃₀ _℃Is more preferably 4 or less, and even more preferably 3 or less.
The aqueous emulsion of the present invention has an emulsion viscosity T at 30 ° C.₃₀ _℃And viscosity T at 60 ° C₆₀ _℃Ratio of T₆₀ _℃/ T₃₀ _℃It is also important that is 1.5 or less. Where T₆₀ _℃/ T₃₀ _℃Is a value measured by the method described later,₆₀ _℃/ T₃₀ _℃Is 1.5 or less, there are many vinyl ester polymer aqueous emulsions having a high viscosity around 60 ° C., but in the present invention, an increase in viscosity can be suppressed around 60 ° C., that is, temperature dependence. Means small. T₆₀ _℃/ T₃₀ _℃Is more preferably 1.3 or less, and even more preferably 1.2 or less. Thus, the workability and the handleability are remarkably improved due to the small temperature dependence at both low and high temperatures.
[0012]
As the method for producing the aqueous emulsion of the present invention, when the vinyl ester monomer is emulsion polymerized, (1) a vinyl alcohol polymer having 1.9 mol% or more of 1,2-glycol bonds is used as a dispersant. (2) at least one polymerization initiator selected from hydrogen peroxide, ammonium persulfate and potassium persulfate is used in a molar ratio of 0.001 to 0.03 with respect to the vinyl ester monomer, and (3) In the initial stage of the polymerization, the vinyl ester monomer is charged in an amount of 5 to 20% by weight of the total amount of the monomer (the total amount of the vinyl ester monomer), and the polymerization initiator is added to the initially charged vinyl ester monomer. An example is a method of performing a polymerization operation in which 0.001 to 0.05 is added at a molar ratio.
[0013]
In order to achieve the object of the present invention, the amount of vinyl alcohol polymer having 1.9 mol% or more of 1,2-glycol bond is used as a vinyl ester monomer (a single amount copolymerizable with vinyl ester) When combined with the body, the total amount) is preferably 1 to 20 parts by weight, more preferably 3 to 20 parts by weight, still more preferably 5 to 15 parts by weight per 100 parts by weight. . Furthermore, in the present invention, the amount of the vinyl alcohol polymer having 1,2-glycol bond of 1.9 mol% or more may be used in a small amount, for example, 1 to 5 parts by weight. One of the features is that it is possible to achieve this sufficiently.
[0014]
By adopting such a method, the above-described T₀ _℃/ T₃₀ _℃Is 5 or less, T₆₀ _℃/ T₃₀ _℃Can obtain an aqueous emulsion satisfying 1.5 or less.
Moreover, the production method of the present invention is also characterized by excellent polymerization stability, such as little filtration residue after emulsion polymerization, as will be apparent from the examples described later.
[0015]
In producing the aqueous emulsion of the present invention, it is important to use at least one polymerization initiator selected from hydrogen peroxide, ammonium persulfate and potassium persulfate, and among these, hydrogen peroxide is particularly preferred. In the present invention, it is also important to carry out emulsion polymerization using a polymerization initiator in a molar ratio of 0.001 to 0.03 with respect to the vinyl ester monomer used, preferably 0.0015. It is -0.025, More preferably, it is 0.0018-0.023.
[0016]
Further, the polymerization initiator may be used in combination with a reducing agent and used in a redox system. In that case, hydrogen peroxide is usually used together with tartaric acid, L-ascorbic acid, Rongalite and the like. Ammonium persulfate and potassium persulfate are used together with sodium hydrogen sulfite, sodium hydrogen carbonate and the like. The amount of the reducing agent used is not particularly limited, but is usually 0.05 to 3 equivalents, preferably 0.1 to 2 equivalents, more preferably 0.3 to 1.5 equivalents, relative to the polymerization initiator.
[0017]
As a method for adding the polymerization initiator, it is preferable to use a method in which polymerization initiators are added all at once at the beginning of polymerization (a method of adding by shot). That is, 5 to 20% of the total amount of the vinyl ester monomer is charged at the initial stage of polymerization, and the polymerization initiator is added in a molar ratio of 0.001 to 0.05 with respect to the initially charged vinyl ester monomer. It is necessary to add all at once, preferably 0.0012 to 0.045, and more preferably 0.0013 to 0.04.
In the initial polymerization, by adding a predetermined amount of the polymerization initiator as described above, an aqueous emulsion having improved water resistance and less temperature dependence is obtained, and the polymerization stability is further improved. The remaining amount of filtration is also reduced.
[0018]
In the initial polymerization, a monomer and a polymerization initiator are added to an aqueous solution of a dispersant, and the polymerization temperature is 50 to 70 ° C., preferably 55 to 65 ° C., the polymerization time is 5 to 60 minutes, preferably 10 to 50 minutes. Done below. In the initial polymerization, it is preferable to add the monomers all at once.
The initial polymerization is terminated when the residual concentration of vinyl ester (% by weight with respect to the produced polymer) is 10% or less, preferably 5% or less, and more preferably 1% or less. After the initial polymerization, the latter polymerization is started. In the latter polymerization, the polymerization initiator may be added all at once (shot addition), or may be added continuously or intermittently. In the latter polymerization, the polymerization temperature is preferably 5 to 30 ° C. higher than the initial polymerization temperature, 55 to 100 ° C., preferably 60 to 95 ° C., more preferably 70 to 90 ° C. Done in
The polymerization pressure may be normal pressure for both initial polymerization and late polymerization, but it is necessary to increase the pressure as necessary. In particular, when a copolymer emulsion of vinyl ester and another monomer such as ethylene is produced, it is necessary to carry out under pressure.
Since the water-based emulsion of the present invention thus obtained has improved water resistance, it is suitably used for various applications requiring water resistance, and the water-based emulsion of the present invention has low temperature dependence. In addition, it is extremely excellent in workability and handling because it can prevent the increase in viscosity even during storage, transportation and use at low and high temperatures.
[0019]
As the aqueous emulsion of the present invention, the aqueous emulsion obtained by the above method can be used as it is, but if necessary, various conventionally known emulsions may be added and used within a range not impairing the effects of the present invention. it can.
In addition, as the dispersant in the aqueous emulsion of the present invention, the PVA polymer having 1.9 mol% or more of the 1,2-glycol bond described above is used. If necessary, a conventionally known anionic or nonionic polymer is used. Vinyl alcohol polymers having a 1,2-glycol bond content of less than 1.9 mol% within a range that does not impair the purpose of the present invention. Can also be used together.
[0020]
The water-based emulsion of the present invention is excellent in water resistance and has a small temperature dependency, so that it can be used for paper tube, bag making, interleaf, paper for corrugated cardboard, paper processing adhesive such as pulp, flash panel, assembly Wood, wood board, plywood processing, plywood secondary processing (kneading), woodworking adhesives for general woodworking and various plastics, impregnating paper, binders for non-woven products, admixtures, splicing It is suitably used in fields such as materials, paints, paper processing and fiber processing.
[0021]
【Example】
Next, the present invention will be described in more detail with reference to examples and comparative examples. In the following examples and comparative examples, “parts” and “%” mean weight basis unless otherwise specified. Moreover, the water resistance (water-resistant adhesive force) and temperature dependency of the obtained emulsion were evaluated in the following manner.
[0022]
(Emulsion evaluation)
(1) Water-resistant adhesive strength (adhesion of wood)
150 g / m of the obtained aqueous emulsion is applied to a timber material.²Apply and paste 7kg / m²Was pressed for 16 hours. Thereafter, the pressure was released, and after curing at 20 ° C. and 65% RH for 5 days, it was immersed in cold water at 20 ° C. for 4 days, and the compressive shear strength was measured in the wet state.
(2) Temperature dependence
・ T₀ _℃/ T₃₀ _℃
・ T₆₀ _℃/ T₃₀ _℃
T₀ _℃: Viscosity measured after adjusting to 0 ° C
T₃₀ _℃: Viscosity measured after adjustment to 30 ° C
T₆₀ _℃: Viscosity measured after adjustment to 60 ° C
Viscosity was measured using a B-type viscometer (20 rpm).
(3) Polymerization stability
After the polymerization, the resulting aqueous emulsion was filtered using a 60 mesh stainless steel wire mesh, and the remaining amount of filtration (%) (vs. emulsion) was measured. The smaller the remaining amount of filtration, the better the polymerization stability.
[0023]
Production Example 1
A 5 L pressure reactor equipped with a stirrer, nitrogen inlet and initiator inlet was charged with 2940 g of vinyl acetate, 60 g of methanol and 0.088 g of tartaric acid, and the reactor pressure was 2.0 MPa while bubbling with nitrogen gas at room temperature. The system was increased to 1, left for 10 minutes, and then the operation of releasing the pressure was repeated three times to purge the system with nitrogen. A concentration of 0.2 g / L solution in which 2,2′-azobis (cyclohexane-1-carbonitrile) (V-40) was dissolved in methanol as an initiator was prepared, and nitrogen substitution was performed to perform bubbling with nitrogen gas. Next, the temperature inside the polymerization tank was raised to 120 ° C. The reaction vessel pressure at this time was 0.5 MPa. Then, 2.5 ml of the above initiator solution was injected to initiate polymerization. During the polymerization, the polymerization temperature was maintained at 120 ° C., and the polymerization was carried out by continuously adding V-40 at 10.0 ml / hr using the above initiator solution. The reactor pressure during the polymerization was 0.5 MPa. After 3 hours, the polymerization was stopped by cooling. The solid concentration at this time was 24%. Subsequently, unreacted vinyl acetate monomer was removed while adding methanol occasionally under reduced pressure at 30 ° C. to obtain a methanol solution of polyvinyl acetate (concentration 33%). 11.6 g (polyacetic acid) at 40 ° C. was added to 400 g of a methanol solution of polyvinyl acetate prepared by adding methanol to the obtained polyvinyl acetate solution to a concentration of 25% (100 g of polyvinyl acetate in the solution). Saponification was performed by adding an alkaline solution (NaOH in 10% methanol) having a molar ratio (MR) of 0.025) to vinyl acetate units in vinyl. About 2 minutes after the addition of the alkali, the gelled system was pulverized with a pulverizer and allowed to stand for 1 hour to allow saponification to proceed, and then 1000 g of methyl acetate was added to neutralize the remaining alkali. After confirming the end of neutralization using a phenolphthalein indicator, 1000 g of methanol was added to the white solid PVA obtained by filtration, and the mixture was left to wash at room temperature for 3 hours. After the above washing operation was repeated three times, the PVA obtained by centrifugal drainage was left in a dryer at 70 ° C. for 2 days to obtain dry PVA (PVA-1). The degree of saponification of the obtained PVA (PVA-1) was 98 mol%. In addition, a methanol solution of polyvinyl acetate obtained by removing unreacted vinyl acetate monomer after polymerization was saponified at an alkali molar ratio of 0.5, and the pulverized product was allowed to stand at 60 ° C. for 5 hours to promote saponification. After that, Soxhlet washing with methanol was carried out for 3 days, followed by drying under reduced pressure at 80 ° C. for 3 days to obtain purified PVA. It was 1700 when the average degree of polymerization of this PVA was measured according to JISK6726 of the usual method. The 1,2-glycol bond content of PVA can be determined from the NMR peak. After saponification to a saponification degree of 99.9 mol% or more (the saponification degree is measured according to JIS K6726), it is thoroughly washed with methanol, and then dried at 90 ° C. under reduced pressure for 2 days is dissolved in DMSO-D6 and trifluoro A sample with a few drops of acetic acid added to a 500 MHz proton NMR (JEOL Measured at 80 ° C. using GX-500).
The peak derived from methine of the vinyl alcohol unit is attributed to 3.2 to 4.0 ppm (integrated value A), and the peak derived from one methine of the 1,2-glycol bond is attributed to 3.25 ppm (integrated value B). The 1,2-glycol bond content can be calculated.
1,2-glycol bond content (mol%) = B / A × 100
The amount of 1,2-glycol bonds in the purified PVA was determined as described above from measurement with a 500 MHz proton NMR (JEOL GX-500) apparatus, and found to be 2.2 mol%.
[0024]
Production Example 2
A 5 L pressure reactor equipped with a stirrer, nitrogen inlet and initiator inlet was charged with 2940 g of vinyl acetate, 60 g of methanol and 0.088 g of tartaric acid, and the reactor pressure was 2.0 MPa while bubbling with nitrogen gas at room temperature. The system was increased to 1, left for 10 minutes, and then the operation of releasing the pressure was repeated three times to purge the system with nitrogen. A concentration of 0.2 g / L solution in which 2,2′-azobis (cyclohexane-1-carbonitrile) (V-40) was dissolved in methanol as an initiator was prepared, and nitrogen substitution was performed to perform bubbling with nitrogen gas. Next, the temperature inside the polymerization tank was raised to 120 ° C. The reaction vessel pressure at this time was 0.5 MPa. Then, 2.5 ml of the above initiator solution was injected to initiate polymerization. During the polymerization, the polymerization temperature was maintained at 120 ° C., and the polymerization was carried out by continuously adding V-40 at 10.0 ml / hr using the above initiator solution. The reactor pressure during the polymerization was 0.5 MPa. After 3 hours, the polymerization was stopped by cooling. The solid concentration at this time was 24%. Subsequently, unreacted vinyl acetate monomer was removed while adding methanol occasionally under reduced pressure at 30 ° C. to obtain a methanol solution of polyvinyl acetate (concentration 33%). To 400 g of polyvinyl acetate methanol solution (100 g of polyvinyl acetate in the solution) adjusted to a concentration of 25% by adding methanol to the obtained polyvinyl acetate solution, 2.3 g (polyacetic acid at 40 ° C.). Saponification was carried out by adding an alkaline solution (NaOH 10% methanol solution) in a molar ratio (MR) of 0.005) to vinyl acetate units in vinyl and water (1.4 g). About 20 minutes after the addition of the alkali, the gelled system was pulverized by a pulverizer and allowed to stand for 1 hour to allow saponification to proceed, and then 1000 g of methyl acetate was added to neutralize the remaining alkali. After confirming the end of neutralization using a phenolphthalein indicator, 1000 g of methanol was added to the white solid PVA obtained by filtration, and the mixture was left to wash at room temperature for 3 hours. After the above washing operation was repeated three times, the PVA obtained by centrifugal drainage was left in a dryer at 70 ° C. for 2 days to obtain dry PVA (PVA-2). The degree of saponification of the obtained PVA (PVA-2) was 88 mol%. In addition, a methanol solution of polyvinyl acetate obtained by removing unreacted vinyl acetate monomer after polymerization was saponified at an alkali molar ratio of 0.5, and the pulverized product was allowed to stand at 60 ° C. for 5 hours to promote saponification. After that, Soxhlet washing with methanol was carried out for 3 days, followed by drying under reduced pressure at 80 ° C. for 3 days to obtain purified PVA. It was 1700 when the average degree of polymerization of this PVA was measured according to JIS K6726 of the usual method. When the amount of 1,2-glycol bonds in the purified PVA was determined as described above from measurement with a 500 MHz proton NMR (JEOL GX-500) apparatus, it was 2.2 mol%.
[0025]
Production Example 3
A 5 L pressure reactor equipped with a stirrer, nitrogen inlet and initiator inlet was charged with 2850 g of vinyl acetate, 150 g of methanol and 0.086 g of tartaric acid, and the reactor pressure was 2.0 MPa while bubbling with nitrogen gas at room temperature. The system was increased to 1, left for 10 minutes, and then the operation of releasing the pressure was repeated three times to purge the system with nitrogen. A 0.1 g / L solution having 2,2′-azobis (N-butyl-2-methylpropionamide) dissolved in methanol as an initiator was prepared, and nitrogen substitution was performed by bubbling with nitrogen gas. Next, the temperature inside the polymerization tank was raised to 150 ° C. The reactor pressure at this time was 1.0 MPa. Next, 15.0 ml of the above initiator solution was injected to initiate polymerization. During the polymerization, the polymerization temperature was maintained at 150 ° C., and 2,2′-azobis (N-butyl-2-methylpropionamide) was continuously added at 15.8 ml / hr using the above initiator solution. Carried out. The reactor pressure during the polymerization was 1.0 MPa. After 4 hours, the polymerization was stopped by cooling. The solid concentration at this time was 35%. Subsequently, unreacted vinyl acetate monomer was removed while adding methanol occasionally under reduced pressure at 30 ° C. to obtain a methanol solution of polyvinyl acetate (concentration 33%). 11.6 g (polyacetic acid) at 40 ° C. was added to 400 g of a methanol solution of polyvinyl acetate prepared by adding methanol to the obtained polyvinyl acetate solution to a concentration of 25% (100 g of polyvinyl acetate in the solution). Saponification was performed by adding an alkaline solution (NaOH in 10% methanol) having a molar ratio (MR) of 0.025) to vinyl acetate units in vinyl. After about 3 minutes after the addition of the alkali, the gelled material was pulverized with a pulverizer and allowed to stand for 1 hour to allow saponification to proceed, and then 1000 g of methyl acetate was added to neutralize the remaining alkali. After confirming the end of neutralization using a phenolphthalein indicator, 1000 g of methanol was added to the white solid PVA obtained by filtration, and the mixture was left to wash at room temperature for 3 hours. After the above washing operation was repeated three times, the PVA obtained by centrifugal drainage was left in a dryer at 70 ° C. for 2 days to obtain dry PVA (PVA-3). The degree of saponification of the obtained PVA (PVA-3) was 98 mol%. Further, after saponification of a methanol solution of polyvinyl acetate obtained by removing unreacted vinyl acetate monomer after polymerization at an alkali molar ratio of 0.5, the pulverized product was allowed to stand at 60 ° C. for 5 hours to promote saponification. After that, Soxhlet washing with methanol was carried out for 3 days, followed by drying under reduced pressure at 80 ° C. for 3 days to obtain purified PVA. It was 1000 when the average degree of polymerization of this PVA was measured according to JIS K6726 of the usual method. The amount of 1,2-glycol bonds in the purified PVA was determined as described above from measurement with a 500 MHz proton NMR (JEOL GX-500) apparatus, and was 2.5 mol%.
[0026]
Production Example 4
A 5 L pressure reactor equipped with a stirrer, nitrogen inlet and initiator inlet was charged with 2700 g of vinyl acetate, 300 g of methanol and 0.081 g of tartaric acid, and the reactor pressure was 2.0 MPa while bubbling with nitrogen gas at room temperature. The system was increased to 1, left for 10 minutes, and then the operation of releasing the pressure was repeated three times to purge the system with nitrogen. A 0.05 g / L solution in which 2,2′-azobis (N-butyl-2-methylpropionamide) was dissolved in methanol as an initiator was prepared, and nitrogen substitution was performed by bubbling with nitrogen gas. Next, the temperature inside the polymerization tank was raised to 180 ° C. The reaction vessel pressure at this time was 1.6 MPa. Next, 0.4 ml of the above initiator solution was injected to initiate polymerization. During the polymerization, the polymerization temperature was maintained at 180 ° C., and 2,2′-azobis (N-butyl-2-methylpropionamide) was continuously added at 10.6 ml / hr using the above initiator solution. Carried out. The reactor pressure during the polymerization was 1.6 MPa. After 4 hours, the polymerization was stopped by cooling. The solid concentration at this time was 27%. Subsequently, unreacted vinyl acetate monomer was removed while adding methanol occasionally under reduced pressure at 30 ° C. to obtain a methanol solution of polyvinyl acetate (concentration 33%). 11.6 g (polyacetic acid) at 40 ° C. was added to 333 g of a polyvinyl acetate methanol solution (100 g of polyvinyl acetate in the solution) adjusted to a concentration of 30% by adding methanol to the obtained polyvinyl acetate solution. Saponification was performed by adding an alkaline solution (NaOH in 10% methanol) having a molar ratio (MR) of 0.025) to vinyl acetate units in vinyl. After about 3 minutes after the addition of the alkali, the gelled material was pulverized with a pulverizer and allowed to stand for 1 hour to allow saponification to proceed, and then 1000 g of methyl acetate was added to neutralize the remaining alkali. After confirming the end of neutralization using a phenolphthalein indicator, 1000 g of methanol was added to the white solid PVA obtained by filtration, and the mixture was left to wash at room temperature for 3 hours. After the washing operation was repeated three times, the PVA obtained by centrifugal drainage was left in a dryer at 70 ° C. for 2 days to obtain dry PVA (PVA-4). The degree of saponification of the obtained PVA (PVA-4) was 98 mol%. Further, after saponification of a methanol solution of polyvinyl acetate obtained by removing unreacted vinyl acetate monomer after polymerization at an alkali molar ratio of 0.5, the pulverized product was allowed to stand at 60 ° C. for 5 hours to promote saponification. After that, Soxhlet washing with methanol was carried out for 3 days, followed by drying under reduced pressure at 80 ° C. for 3 days to obtain purified PVA. When the average degree of polymerization of the PVA was measured according to JIS K6726 of a conventional method, it was 500. When the amount of 1,2-glycol bonds in the purified PVA was determined as described above from measurement with a 500 MHz proton NMR (JEOL GX-500) apparatus, it was 2.9 mol%.
[0027]
Production Example 5
A 5 L pressure reaction tank equipped with a stirrer, a nitrogen inlet, and an initiator inlet was charged with 2400 g of vinyl acetate, 600 g of methanol, and 49.3 g of vinylene carbonate, and the reaction tank pressure was adjusted while bubbling with nitrogen gas at room temperature. The operation of raising the pressure to 0 MPa and allowing it to stand for 10 minutes and then releasing the pressure was repeated three times to purge the system with nitrogen. A 1.0 g / L solution in which α, α′-azobisisobutyronitrile was dissolved in methanol as an initiator was prepared, and nitrogen substitution was performed by bubbling with nitrogen gas. Next, the temperature inside the polymerization tank was raised to 90 ° C. The reaction vessel pressure at this time was 0.4 MPa. After adjusting the polymerization tank internal temperature to 90 ° C., 3.0 ml of the initiator solution was injected to initiate polymerization. During the polymerization, the polymerization temperature was maintained at 90 ° C., and α, α′-azobisisobutyronitrile was continuously added at 4.9 ml / hr using the above initiator solution. The reactor pressure during the polymerization was 0.4 MPa. After 4 hours, the polymerization was stopped by cooling. The solid concentration at this time was 38%. Subsequently, unreacted vinyl acetate monomer was removed while adding methanol occasionally under reduced pressure at 30 ° C. to obtain a methanol solution of polyvinyl acetate (concentration: 33%). 46.4 g (polyacetic acid) at 40 ° C. was added to 400 g of a polyvinyl acetate methanol solution adjusted to a concentration of 25% by adding methanol to the obtained polyvinyl acetate solution (100 g of polyvinyl acetate in the solution). Saponification was carried out by adding an alkaline solution (NaOH in 10% methanol) having a molar ratio (MR) of 0.10 to the vinyl acetate unit in vinyl. After about 1 minute after addition of the alkali, the gelled product was pulverized with a pulverizer and allowed to stand for 1 hour to allow saponification to proceed, and then 1000 g of methyl acetate was added to neutralize the remaining alkali. After confirming the end of neutralization using a phenolphthalein indicator, 1000 g of methanol was added to white solid PVA obtained by filtration, and the mixture was allowed to stand and washed at room temperature for 3 hours. After the above washing operation was repeated three times, the PVA obtained by centrifugal drainage was left in a dryer at 70 ° C. for 2 days to obtain dry PVA (PVA-5).
The degree of saponification of the obtained PVA (PVA-5) was 99.5 mol%.
Further, after saponification of a methanol solution of polyvinyl acetate obtained by removing unreacted vinyl acetate monomer after polymerization at an alkali molar ratio of 0.5, the pulverized product was allowed to stand at 60 ° C. for 5 hours to promote saponification. After that, Soxhlet washing with methanol was carried out for 3 days, followed by drying under reduced pressure at 80 ° C. for 3 days to obtain purified PVA. When the degree of polymerization of the PVA was measured according to a conventional method JIS K6726, it was 1200. When the amount of 1,2-glycol bonds in the purified PVA was determined as described above from measurement with a 500 MHz proton NMR (JEOL GX-500) apparatus, it was 2.5 mol%.
[0028]
Production Example 6
A 5 L four-necked separable flask equipped with a stirrer, nitrogen inlet, initiator inlet and reflux condenser was charged with 2000 g of vinyl acetate, 400 g of methanol, and 78.8 g of vinylene carbonate, and the system was bubbled with nitrogen for 30 minutes at room temperature. The inside was replaced with nitrogen. After adjusting the polymerization tank internal temperature to 60 ° C., 0.9 g of α, α′-azobisisobutyronitrile was added as an initiator to initiate polymerization. During the polymerization, the polymerization temperature was maintained at 60 ° C., and after 4 hours, the polymerization was stopped by cooling. The solid concentration at this time was 55%. Subsequently, unreacted vinyl acetate monomer was removed while adding methanol occasionally under reduced pressure at 30 ° C. to obtain a methanol solution of polyvinyl acetate (concentration: 33%). 46.4 g (polyacetic acid) at 40 ° C. was added to 400 g of a polyvinyl acetate methanol solution adjusted to a concentration of 25% by adding methanol to the obtained polyvinyl acetate solution (100 g of polyvinyl acetate in the solution). Saponification was carried out by adding an alkaline solution (NaOH in 10% methanol) having a molar ratio (MR) of 0.10 to the vinyl acetate unit in vinyl. After about 1 minute after addition of the alkali, the gelled product was pulverized with a pulverizer and allowed to stand for 1 hour to allow saponification to proceed, and then 1000 g of methyl acetate was added to neutralize the remaining alkali. After confirming the end of neutralization using a phenolphthalein indicator, 1000 g of methanol was added to white solid PVA obtained by filtration, and the mixture was allowed to stand and washed at room temperature for 3 hours. After the above washing operation was repeated three times, the PVA obtained by centrifugal drainage was left in a dryer at 70 ° C. for 2 days to obtain dry PVA (PVA-6).
The degree of saponification of the obtained PVA (PVA-6) was 99.5 mol%.
Further, after saponification of a methanol solution of polyvinyl acetate obtained by removing unreacted vinyl acetate monomer after polymerization at an alkali molar ratio of 0.5, the pulverized product was allowed to stand at 60 ° C. for 5 hours to promote saponification. After that, Soxhlet washing with methanol was carried out for 3 days, followed by drying under reduced pressure at 80 ° C. for 3 days to obtain purified PVA. When the degree of polymerization of the PVA was measured according to a conventional method JIS K6726, it was 1700. The amount of 1,2-glycol bonds in the purified PVA was determined from measurement with a 500 MHz proton NMR (JEOL GX-500) apparatus as described above, and was found to be 3.0 mol%.
[0029]
Production Example 7
2400 g of vinyl acetate, 580 g of methanol and 0.93 g of thiol acetic acid were placed in a reaction vessel, the interior was sufficiently purged with nitrogen, the external temperature was raised to 65 ° C., and when the internal temperature reached 60 ° C., 2,2-azobisiso 20 g of methanol containing 0.868 g of butyronitrile was added. Immediately, 60 g of a methanol solution containing 17.4 g of thiolacetic acid was uniformly added over 5 hours. The polymerization rate after 5 hours was 50.4%. After 5 hours, the vessel was cooled, and the operation of expelling vinyl acetate (VAc) remaining under reduced pressure out of the system together with methanol was performed while adding methanol to obtain a methanol solution of polyvinyl acetate. (Concentration 54.5%) A part of this methanol solution was taken, and a methanol solution of NaOH was added so that the polyvinyl acetate concentration was 50% [NaOH] / [VAc] = 0.05 (molar ratio). Saponified. After about 1 minute after addition of the alkali, the gelled product was pulverized with a pulverizer and allowed to stand for 1 hour to allow saponification to proceed, and then 1000 g of methyl acetate was added to neutralize the remaining alkali. After confirming the end of neutralization using a phenolphthalein indicator, 1000 g of methanol was added to white solid PVA obtained by filtration, and the mixture was allowed to stand and washed at room temperature for 3 hours. After the above washing operation was repeated three times, the PVA obtained by centrifugal drainage was left in a dryer at 70 ° C. for 2 days to obtain dry PVA (PVA-11).
The degree of saponification of the obtained PVA (PVA-11) was 98.6 mol%.
Further, after saponification of a methanol solution of polyvinyl acetate obtained by removing unreacted vinyl acetate monomer after polymerization at an alkali molar ratio of 0.5, the pulverized product was allowed to stand at 60 ° C. for 5 hours to promote saponification. After that, Soxhlet washing with methanol was carried out for 3 days, followed by drying under reduced pressure at 80 ° C. for 3 days to obtain purified PVA. When the degree of polymerization of the PVA was measured according to JIS K6726 of a conventional method, it was 130. When the amount of 1,2-glycol bonds in the purified PVA was determined as described above from measurement with a 500 MHz proton NMR (JEOL GX-500) apparatus, it was 1.6 mol%.
[0030]
Example 1
In a 1-liter glass polymerization vessel equipped with a reflux condenser, a dropping funnel, a thermometer, and a nitrogen inlet, 300 g of ion-exchanged water and PVA-1 obtained by Production Example 1 (degree of polymerization 1700, degree of saponification 98.0 mol) %, 1,2-glycol content 2.2 mol%) was charged and completely dissolved at 95 ° C. Next, this PVA aqueous solution was cooled, purged with nitrogen, heated to 60 ° C. while stirring at 200 rpm, 4.4 g of a 10% aqueous solution of tartaric acid and 3 g of 5% aqueous hydrogen peroxide were added in a shot, and acetic acid was then added. 26 g of vinyl was charged and polymerization was started. After 30 minutes from the start of polymerization, the completion of the initial polymerization (remaining amount of vinyl acetate less than 1 wt%) was confirmed. Next, 0.9 g of a 10% aqueous solution of tartaric acid and 3 g of 5% hydrogen peroxide water were shot and then 234 g of vinyl acetate was continuously added over 2 hours, and the polymerization temperature was maintained at 80 ° C. to complete the polymerization. . After cooling, it was filtered using a 60 mesh stainless steel wire mesh. As a result, a polyvinyl acetate emulsion (Em-1) having a solid content concentration of 47.3% was obtained. The results are shown in Tables 1-2.
[0031]
Comparative Example 1
PVA-7 produced by a conventional method instead of using PVA-1 used in Example 1 (PVA-117 manufactured by Kuraray Co., Ltd .; polymerization degree 1700, saponification degree 98.0%, containing 1,2-glycol) (Em-2) having a solid content concentration of 47.1% was obtained in the same manner as in Example 1 except that the amount was 1.6 mol%. This emulsion was evaluated by the method described above. The results are shown in Tables 1-2.
[0032]
Example 2
In a 1 liter glass polymerization vessel equipped with a reflux condenser, a dropping funnel, a thermometer, and a nitrogen inlet, 300 g of ion-exchanged water and PVA-2 obtained by Production Example 2 (degree of polymerization 1700, degree of saponification 88.0 mol) %, 1,2-glycol content 2.2 mol%) was charged and completely dissolved at 95 ° C. Next, this PVA aqueous solution was cooled, purged with nitrogen, heated to 60 ° C. while stirring at 200 rpm, and then charged with 18 g of a 10% aqueous solution of tartaric acid and 26 g of vinyl acetate, and 2. The polymerization was started by adding continuously over 5 hours. 30 minutes after the start of the polymerization, the completion of the initial polymerization (remaining amount of vinyl acetate less than 1% by weight) was confirmed, and further 234 g of vinyl acetate was continuously added over 2 hours. After completion of the addition of vinyl acetate, 4.8 g of 1% hydrogen peroxide water was added by shot, and the polymerization temperature was maintained at 80 ° C. to complete the polymerization. After cooling, it was filtered using a 60 mesh stainless steel wire mesh. Polymerization stability was evaluated by the same method as in Example 1 based on the remaining amount after filtration. As a result, a polyvinyl acetate emulsion (Em-3) having a solid content concentration of 47.6% was obtained. This emulsion was evaluated by the method described above. The results are shown in Tables 1-2.
[0033]
Comparative Example 2
PVA-8 produced by a conventional method instead of using PVA-2 used in Example 2 (PVA-217 manufactured by Kuraray Co., Ltd .; polymerization degree 1700, saponification degree 88.0 mol%, 1,2-glycol) (Em-4) having a solid content concentration of 47.4% was obtained in the same manner as in Example 2 except that the content was 1.6 mol%. This emulsion was evaluated by the method described above. The results are shown in Tables 1-2.
[0034]
Example 3
In a 1 liter glass polymerization vessel equipped with a reflux condenser, a dropping funnel, a thermometer, and a nitrogen inlet, 300 g of ion-exchanged water, production example3PVA-3 (polymerization degree 1000, saponification degree 98.0 mol%, 1,2-glycol content 2.5 mol%) 7.8 g obtained by the above was charged and completely dissolved at 95 ° C. Next, this PVA aqueous solution was cooled, purged with nitrogen, heated to 60 ° C. while stirring at 200 rpm, 4.4 g of a 10% aqueous solution of tartaric acid and 3 g of 5% aqueous hydrogen peroxide were added in a shot, and acetic acid was then added. 26 g of vinyl was charged and polymerization was started. After 30 minutes from the start of polymerization, the completion of the initial polymerization (remaining amount of vinyl acetate less than 1 wt%) was confirmed. Next, 0.9 g of a 10% aqueous solution of tartaric acid and 3 g of 5% hydrogen peroxide water were shot and then 234 g of vinyl acetate was continuously added over 2 hours, and the polymerization temperature was maintained at 80 ° C. to complete the polymerization. . After cooling, it was filtered using a 60 mesh stainless steel wire mesh. As a result, a polyvinyl acetate emulsion (Em-5) having a solid content concentration of 47.7% was obtained. This emulsion was evaluated by the method described above. The results are shown in Tables 1-2.
[0035]
Comparative Example 3
PVA-9 produced by a conventional method instead of using PVA-3 used in Example 3 (PVA-110 manufactured by Kuraray Co., Ltd .; polymerization degree 1000, saponification degree 98.5 mol%, 1,2-glycol) Emulsion polymerization was attempted in the same manner as in Example 3 except that the content was 1.6 mol%. However, a stable emulsion could not be obtained due to blocking during polymerization.
[0036]
Example 4
Instead of using PVA-1 used in Example 1, PVA-4 obtained by Production Example 4 (degree of polymerization: 500, degree of saponification)98(Em-7) having a solid content concentration of 47.8% was obtained in the same manner as in Example 1 except that 1 mol-% and a 1,2-glycol content of 2.9 mol% were used. This emulsion was evaluated by the method described above. The results are shown in Tables 1-2.
[0037]
Comparative Example 4
Instead of using PVA-1 used in Example 1, PVA-10 produced by a conventional method (polymerization degree 420, saponification degree 80.0 mol%, 1,2-glycol content 1.6 mol%) was used. Emulsion polymerization was attempted in the same manner as in Example 1 except that it was used. However, block formation occurred during the polymerization, and an emulsion could not be obtained stably.
[0038]
Example 5
Instead of using PVA-1 used in Example 1, PVA-5 obtained by Production Example 5 (polymerization degree 1200, saponification degree 99.5 mol%, 1,2-glycol content 2.5 mol%) was used. (Em-8) having a solid content concentration of 47.8% was obtained in the same manner as in Example 1 except that it was used. This emulsion was evaluated by the method described above.
The results are shown in Tables 1-2.
[0039]
Example 6
Instead of using PVA-1 used in Example 1, PVA-6 obtained by Production Example 6 (degree of polymerization 1)7(Em-9) having a solid content concentration of 47.8% was obtained in the same manner as in Example 1, except that 00, saponification degree 99.5 mol%, and 1,2-glycol content 3.0 mol% were used. It was. This emulsion was evaluated by the method described above. The results are shown in Tables 1-2.
[0040]
Example 7
A pressure-resistant autoclave equipped with a nitrogen inlet, a thermometer, and a stirrer was charged with 100 g of a 7.5% aqueous solution of PVA-1, heated to 60 ° C., and then purged with nitrogen. After charging 8g of vinyl acetate, 45kg / cm of ethylene²Then, 0.9 g of a 2.5% hydrogen peroxide aqueous solution and 1.35 g of a 2% Rongalite aqueous solution were injected and polymerization was started. After 30 minutes, the completion of initial polymerization (remaining amount of vinyl acetate less than 1% by weight) was confirmed. Next, after the temperature was raised to 80 ° C., 72 g of vinyl acetate, 4.5 g of 1% hydrogen peroxide aqueous solution and 1.35 g of 2% Rongalite aqueous solution were injected over 2 hours, and the polymerization was completed while maintaining the polymerization temperature at 80 ° C. I let you. After cooling, the mixture was filtered in the same manner as in Example 1 to obtain an ethylene-vinyl acetate copolymer emulsion (Em-10) having a solid content concentration of 50.1% and an ethylene content of 15% by weight. Evaluation was carried out by the method described above. The results are shown in Table 1.
[0041]
Comparative Example 5
An ethylene-vinyl acetate copolymer emulsion having a solid content of 49.5% and an ethylene content of 10% by weight was the same as in Example 7 except that PVA-7 was used instead of PVA-1 used in Example 7. (Em-11) was obtained. Evaluation was carried out by the method described above. The results are shown in Tables 1-2.
[0042]
Comparative Example 6
Except for using PVA-11 (polymerization degree 130, saponification degree 98.6 mol%, 1,2-glycol content 1.6 mol%, containing a mercapto group at the terminal) instead of PVA-1 in Example 1. In the same manner as in Example 1, (Em-12) having a solid content concentration of 47.1% was obtained. This emulsion was evaluated by the method described above. The results are shown in Tables 1-2.
[0043]
Comparative Example 7
In a 5 liter glass container equipped with a stirrer, reflux condenser, dropping funnel, thermometer, nitrogen inlet, 1400 g of ion-exchanged water, ethylene-modified PVA (polymerization degree 1400, saponification degree 98.0 mol%, ethylene content) 5.5 mol%, 1,2-glycol bond amount 1.6 mol%) (PVA-12) (225 g) was charged and completely dissolved at 95 ° C. Next, after the modified PVA aqueous solution was cooled, the pH was adjusted to 4, 0.05 g of ferrous chloride was added, the atmosphere was replaced with nitrogen, 350 g of vinyl acetate was charged while stirring at 140 rpm, and the temperature was raised to 60 ° C. Next, polymerization was carried out at 70 ° C. while continuously adding 0.7% hydrogen peroxide solution at 15 ml / hr and 6% Rongalite aqueous solution at 10 ml / hr, and after 30 minutes, the initial polymerization was completed (residual vinyl acetate remaining). Amount less than 1% by weight). Next, 1400 g of vinyl acetate was added continuously over 3 hours. After completion of the addition, the internal temperature was maintained at 80 ° C. for 1 hour to complete the polymerization, and a polyvinyl acetate aqueous emulsion (Em-13) having a solid content concentration of 50.4% was obtained.
[0044]
[Table 1]

[0045]
[Table 2]

[0046]
PVA-1: polymerization degree 1700, saponification degree 98.0 mol%, 1,2-glycol bond content 2.2 mol%
PVA-2: Degree of polymerization 1700, degree of saponification 88.0 mol%, 1,2-glycol bond content 2.2 mol%
PVA-3: Degree of polymerization 1000, degree of saponification 98.0 mol%, 1,2-glycol bond content 2.5 mol%
PVA-4; polymerization degree 500, saponification degree98Mol%, 1,2-glycol bond content 2.9 mol%
PVA-5: polymerization degree 1200, saponification degree 99.5 mol%, 1,2-glycol bond content 2.5 mol%
PVA-6; Degree of polymerization 1700, degree of saponification 99.5 mol%, 1,2-glycol bond content 3.0 mol%
PVA-7: polymerization degree 1700, saponification degree 98.0 mol%, 1,2-glycol bond content 1.6 mol%
{PVA-117 manufactured by Kuraray Co., Ltd.}
PVA-8: Degree of polymerization 1700, degree of saponification 88.0 mol%, 1,2-glycol bond content 1.6 mol%
{PVA-217 made by Kuraray Co., Ltd.}
PVA-9: polymerization degree 1000, saponification degree 98.5 mol%, 1,2-glycol bond content 1.6 mol%
{PVA-110 manufactured by Kuraray Co., Ltd.}
PVA-10: Degree of polymerization 420, degree of saponification 80.0 mol%, 1,2-glycol bond content 1.6 mol%
(Conventional PVA)
PVA-11: polymerization degree 130, saponification degree 98.6 mol%, 1,2-glycol bond content 1.6 mol%,
Contains a mercapto group at the end
PVA-12; polymerization degree 1400, saponification degree 98 mol%, 1,2-glycol bond content 1.6 mol%,
Ethylene content 5.5 mol%
[0047]
【The invention's effect】
The aqueous emulsion of the present invention is excellent in water resistance, and further has little temperature dependency, and its production method is excellent in polymerization stability. The resulting emulsion is also suitable in fields such as adhesives for paper, woodworking and plastics, binders for impregnated paper and nonwoven products, admixtures, jointing materials, paints, paper processing and fiber processing. Used.

Claims

An aqueous emulsion comprising a polymer having a vinyl ester monomer unit as a dispersoid and a vinyl alcohol polymer having a 1,2-glycol bond of 1.9 mol% or more as a dispersant, viscosity T ₆₀ _{° C.} at 60 ° C., viscosity T ₃₀ _{° C.} at 30 ° C., when the viscosity at 0 ℃ and _{_{_{_{T 0 ℃, T 0 ℃ /}}}} T 30 ℃ is 5 or less, T ₆₀ _{_℃} / T ₃₀ _℃ Is an aqueous emulsion having a viscosity of 1.5 or less.

The aqueous emulsion according to claim 1, wherein the polymer having a vinyl ester monomer unit is a polyvinyl ester.

The aqueous emulsion according to claim 1, wherein the polymer having a vinyl ester monomer is an ethylene-vinyl ester copolymer.

In emulsion polymerization of vinyl ester monomer units, (1) a vinyl alcohol polymer having 1.9 mol% or more of 1,2-glycol bonds is used as a dispersant, and (2) hydrogen peroxide, ammonium persulfate. And at least one polymerization initiator selected from potassium persulfate in a molar ratio of 0.001 to 0.03 with respect to the vinyl ester monomer, and (3) vinyl ester monomer at the initial stage of polymerization. A polymerization operation is performed in which 5 to 20% by weight of the total amount of monomers is charged, and the polymerization initiator is collectively added in a molar ratio of 0.001 to 0.05 with respect to the vinyl ester monomer initially charged. 2. A method for producing an aqueous emulsion according to 1.