JP4041534B2

JP4041534B2 - Ethylene-vinyl acetate copolymer emulsion, method for producing the same, and adhesive composition

Info

Publication number: JP4041534B2
Application number: JP2003172880A
Authority: JP
Inventors: 学八箇; 広記山本
Original assignee: Denki Kagaku Kogyo KK
Current assignee: Denka Co Ltd
Priority date: 2003-06-18
Filing date: 2003-06-18
Publication date: 2008-01-30
Anticipated expiration: 2023-06-18
Also published as: JP2005008718A

Description

【０００１】
【発明の属する技術分野】
本願発明は、エチレン−酢酸ビニル系共重合体エマルジョン、及びその製造に関するものであり、更に詳しくは平均粒子径が３μｍ以上と大きく、不揮発分が７０質量％以上であることを特徴とする初期接着性や耐熱クリープ性、耐寒性のバランスに優れた塩ビオーバーレイ用接着剤やオレフィンフィルム用接着剤などに好適に使用できるエチレン−酢酸ビニル系共重合体エマルジョン、およびその製造方法に関するものである。
【０００２】
【従来の技術】
エチレン−酢酸ビニル系共重合体エマルジョン（以後ＥＶＡ系エマルジョンと称す）は接着剤として、また土木建材分野、塗料分野、製紙分野、繊維分野においても広く利用されている。また、他の水系エマルジョンと異なり、ＥＶＡ系エマルジョンは比較的容易に６０質量％程度の高不揮発分にすることが可能であり、初期接着性能に優れた高不揮発分ＥＶＡ系エマルジョンが各社から製品化されている。
従来は、界面活性剤にポリオキシエチレン−ポリオキシプロピレンブロック共重合体を用いて７０重量％までの不揮発分を含有する酢酸ビニル−エチレン共重合体エマルジョンを製造する方法や（例えば、特許文献１参照）、低重合度のポリビニルアルコール（以後ＰＶＡと称す）と特定のＨＬＢを持った界面活性剤を併用して平均粒子径が０．９μｍ以下で不揮発分が６５〜７０重量％の酢酸ビニル−エチレン共重合体エマルジョンを製造する方法（例えば、特許文献２参照）、また、低重合度のポリビニルアルコールと界面活性剤を併用することによって不揮発分６５％以上の安定な酢酸ビニル−エチレン共重合体エマルジョンを製造する方法（例えば、特許文献３参照）がある。ところがこれまでの技術では、高不揮発分のＥＶＡ系エマルジョンを重合するにあたって、乳化剤として界面活性剤を多量に使用して高不揮発分化していたものが殆どであり、使用した界面活性剤は被着体との間で接着阻害を生じ、十分な接着性能を発現していなかった。その為、市場からは接着性能に優れ、且つこれまで以上の高不揮発分なＥＶＡ系エマルジョンの要求が非常に強くなってきている。
【０００３】
【特許文献１】
特公昭４２−２２６９２号公報（第１頁）
【特許文献２】
特公平６−５５８７４号公報（第１〜２頁、請求項１〜６）
【特許文献３】
特許番号第２６２４７４１号公報（第１頁、請求項１）
【０００４】
【発明が解決しようとする課題】
本願発明の目的は、不揮発分が７０％以上でも粘度が低く十分な作業性を持っており、且つ初期接着性に優れ、耐熱特性と低温特性のバランスに優れたＥＶＡ系エマルジョン、及びその製造方法を提供することにある。
【０００５】
【課題を解決するための手段】
本願発明は、かかる目的を達成すべく鋭意検討した結果、ＥＶＡ系エマルジョンを重合する際に特殊な乳化剤を組み合わせる事によって、平均粒子径が３μｍ以上あり、不揮発分が７０質量％以上で、初期接着性に優れ、且つ耐熱特性と低温特性のバランスに優れたＥＶＡ系エマルジョンを製造できることを見出したものである。また、本願発明のＥＶＡ系エマルジョンは機械安定性や化学的安定性にも優れていることから、各種溶剤やイソシアネート等を混和し特徴のある接着剤組成物を得られることを見出したものである。
【０００６】
【発明の実施の形態】
本願発明で重合されるＥＶＡ系エマルジョンのエチレンと酢酸ビニルとその他共重合可能な単量体の割合は質量比で５〜４０：９５〜４０：０〜２０、好ましくは１０〜３５：９０〜５０：０〜１５である。その他共重合可能な単量体としては、例えば塩化ビニル、プロピオン酸ビニル、バーサチック酸ビニル、アクリル酸、メタアクリル酸、マレイン酸、イタコン酸、エチルアクリレート、プロピルアクリレート、ブチルアクリレート、２−エチルヘキシルアクリレート、エチルメタアクリレート、プロピルメタアクリレート、ブチルメタアクリレート、２−エチルヘキシルメタアクリレート、２−ヒドロキシエチル（メタ）アクリレート、Ｎ−ビニルピロリドン、スチレン、アクリロニトリル、（メタ）アクリルアミドがあるが、これらの成分のうち一種類以上を共重合させることが可能である。また、トリアリルシアヌレート、トリアリルイソシアヌレートを併用することもでき、接着剤として使用した場合は耐熱性の向上が、モルタル用途に使用した場合は耐アルカリ性を向上させる効果がある。その添加量は１質量％以下、好ましくは０．５質量％以下である。
【０００７】
本願発明におけるＥＶＡ系エマルジョンを接着剤に使用する場合、エチレンの割合が５〜４０質量％の範囲から外れると、低温接着性、初期接着性、耐熱性の少なくとも１つの特性が損なわれる。また酢酸ビニルの割合が９５質量％を超えると低温接着性が低下し、逆に酢酸ビニルの割合が４０質量％未満になると乳化重合時のエマルジョンの安定性もしくは常態接着強度が低下する傾向にある。その他共重合可能な単量体の割合が２０質量％を超えると、低温接着性もしくは常態接着強度が低下する傾向にある。特に、低温接着性を重視する用途には、エチレンの割合が２１〜４０質量％のＥＶＡ系エマルジョン、耐熱性が重視される用途にはエチレンの割合が５〜２１質量％のＥＶＡ系エマルジョンが好ましい。
【０００８】
本願発明で使用する乳化剤は、次の２つの成分から成り立っており、これらのうち１つでも無い場合は十分な性能を発現するＥＶＡ系エマルジョンが得られない。１つは鹸化度が低く重合度も小さいＰＶＡ（以後「低鹸化低重合度ＰＶＡ」と称す）で、１つは分子内にアリル基を有する反応性の界面活性剤である。
【０００９】
本願発明で使用する低鹸化低重合度ＰＶＡの鹸化度範囲は、６０〜８６ｍｏｌｅ％で、好ましくは６５〜８４ｍｏｌｅ％、更に好ましくは７０〜８２ｍｏｌｅ％の範囲である。鹸化度が６０ｍｏｌｅ％未満の場合、極端に水への溶解性が低下し、特殊な溶解方法を用いなければ溶解できず、工業的には使用し難い。また、出来上がったＥＶＡ系エマルジョンの構造粘性が極端に上昇してしまい、高速で貼り合わせを行うと、糊飛び（ロールから糊が剥がれ飛ぶ現象）等の問題も生じてくる。鹸化度が８６ｍｏｌｅ％を超えると、出来上がったＥＶＡエマルジョンの構造粘性が上がらず、ロール適性やハケでの作業性が極端に落ちてしまう。
【００１０】
本願発明で使用する低鹸化低重合度ＰＶＡの重合度は、１００〜５００、好ましくは１５０〜４５０、更に好ましくは２００〜４００である。重合度が１００より小さいと出来上がったＥＶＡ系エマルジョンの不揮発分は高くできるが、エマルジョン中に多量の糊アカ（ＪＩＳＫ６８２８でいう粗粒子）が生じてしまう。重合度が５００を超えると、出来上がったＥＶＡ系エマルジョンに生じる糊アカの量は少ないものの、重合中に粘度が上昇し、不揮発分を７０質量％まで上げることが不可能となる。
【００１１】
本願発明で使用する低鹸化低重合度ＰＶＡの使用量は、重合する酢酸ビニルモノマー単位１００質量部に対して０．５〜４．０質量部、好ましくは１．０〜３．５質量部、更に好ましくは１．２〜３．０質量部である。低鹸化低重合度ＰＶＡの量が０．５質量部よりも少ない場合は、出来上がったＥＶＡ系エマルジョンに
多量の糊アカが含まれることになり、４．０質量部よりも多い場合は重合中にエマルジョンの粘度が上昇し、不揮発分を７０質量％まで上げることが不可能となる。
【００１２】
本願発明で使用する反応性の界面活性剤とは、下記の（式１）、(式２）に示した様に分子内にアリル基を有しており、酢酸ビニルモノマーもしくはエチレンモノマーと反応するものであれば、特に限定されるものではない。
【化２】

【００１３】
本願発明で使用する反応性の界面活性剤の量は、酢酸ビニルモノマー１００質量部当たり０．２〜３．０質量部、好ましくは０．４〜２．０質量部、更に好ましくは０．６〜１．５質量部である。反応性の界面活性剤の量が０．２質量部よりも少ないと、出来上がったエマルジョンの粒子径が十分に大きくならず、粘度が高くなりすぎてしまう。反応性の界面活性剤の量が３．０質量部よりも多いと、粒子径は十分に大きくなるが、粒子間の架橋が進みすぎてしまい、その結果、粘度が高くなり過ぎてしまう。
【００１４】
本願発明で使用する重合用の乳化剤には低鹸化低重合度ＰＶＡと反応性の界面活性剤が必須成分ではあるが、得られるエマルジョンの物性に大きな影響を与えない範囲で、その他の水溶性高分子などの保護コロイドや界面活性剤などを使用しても良い。具体的には、ヒドロキシエチルセルロース、メチルセルロースといった水溶性高分子、ポリオキシエチレンアルキルエーテル、ポリオキシエチレンアルキルフェニルエーテル、ポリオキシエチレンポリオキシプロピレンブロックコポリマー等のノニオン界面活性剤、ラウリル硫酸エステル、アルキルベンゼンスルホン酸塩、アルキルフェニルエーテル硫酸エステル塩やメチルタウリン酸塩、スルホコハク酸塩、エーテルスルホン酸塩、リン酸エステル塩などのアニオン界面活性剤、ノニルフェニル系、ポリアルキレングリコール系、脂肪酸エステル系等のノニオン界面活性剤、第４級アンモニウム塩やアミン塩類などのカチオン界面活性剤、その他の両性界面活性剤を使用しても良い。但し、これらの各種界面活性剤は添加量を増やすことによって得られるＥＶＡ系エマルジョンのトルエン不溶分が低下し、接着剤として使用する場合、耐熱性が低下することが懸念されるので、可能な限り少量であることにこしたことはない。そのため、トルエン不溶解分が４０質量％以上のＥＶＡ系エマルジョンが得られるように、ＰＶＡ成分は全乳化剤成分の３０％質量以上であることが好ましい。
【００１５】
なお、ＥＶＡ系エマルジョンにおけるトルエン不溶解分の測定は、合成樹脂エマルジョンの乾燥皮膜を細かく裁断したもので行い、例えば、０．５ｇの皮膜を５０ｍｌのトルエンに浸漬し、５０℃で５時間振盪した後、２００メッシュの金網で濾過回収される不溶解分の重量を測定することにより求められる。
【００１６】
本願発明におけるＥＶＡ系エマルジョンの重合方法はとしては、通常用いられている乳化重合方法を使用することができ、例えば、還元剤と酸化剤からラジカルを生成させるレドックス重合法や、熱分解でラジカルを生成させる熱重合法などが適用できる。レドックス重合法において使用する還元剤も公知なものを使用でき、例えばロンガリット、ソジウムホルムアルデヒド、Ｌ−アスコルビン酸、酒石酸などである。その際には硫酸第一鉄などの水溶性金属化合物も併用できる。また、開始剤として使用する酸化剤としては過酸化水素、過硫酸カリウム、過硫酸アンモニウム等の水溶性無機過酸化物または過硫酸塩や、ｔ−ブチルハイドロパーオキサイド、クメンハイドロパーオキサイド等の有機過酸化物、アゾビスイソブチロニトリル等のアゾ化合物が使用できる。また、エチレンジアミン四酢酸四ナトリウム等のキレート剤もラジカル開始効率を上げるために併用できる。重合に使用する酢酸ビニルモノマーに関しては、初期に全量を重合缶内に投入してもかまわないし、一部を重合途中に継続的に重合缶内に添加してもかまわない。重合温度に関してはラジカルが十分な速度で生成する条件であれば特に規定はないが、通常は４０〜８０℃の範囲が好ましい。
【００１７】
本願発明によって製造されるＥＶＡ
系エマルジョンは、平均粒子径が３μｍ以上と大きく、更には不揮発分が７０質量％以上であるのにもかかわらず、粘度が１００〜５０００ｍＰａ・ｓと低く、十分な作業性を有している。また、乳化剤に特殊なＰＶＡと反応性の界面活性剤を使用することによって、トルエン不溶解分も４０質量％以上と高く、且つ従来接着阻害を引き起こしていた界面活性剤成分が少ないため、接着剤として使用した際には各種被着体との接着性に優れ、水分が蒸発した後にはその高いトルエン不溶解分のために高い耐熱性を発現する。また、粒子径が３μｍ以上で且つ粒子径分布がブロードであるため、水が蒸発して粒子が融着する際に粒子間に存在する空隙部の体積が小さくなり、結果として水が早く蒸発することとなり、初期接着性が大幅に向上する。特に被着体に木材や紙などの吸水性基材を使用した場合はその傾向が顕著に現れ、これまでには発現できなかったほどの初期接着力を発現しうる。
【００１８】
「実施例」
以下に更に詳細に実施例をもって説明する。なお、本願発明記載の部及び％は特に記載がなければいずれも質量基準で示したものである。
【００１９】
＜実施例１＞
ＰＩＤ自動温度制御の冷却ジャケット及び攪拌機付の高圧重合缶に鹸化度８０ｍｏｌｅ％、重合度４００のＰＶＡであるユニチカレジンＵＭＲ−１０Ｈ（ユニチカ株式会社製）を３部、アルキルスルホコハク酸ナトリウムの構造を有する反応性界面活性剤エレミノールＪＳ−２（三洋化成株式会社製）を１部、ノニオン系界面活性剤であるエマルゲン９１３を０．２部、エマルゲン９５０を０．２部（いずれも花王株式会社製）を予め９０℃以上に調整した蒸留水４５部に溶解し、これに酢酸ソーダ０．２部、ロンガリット（住友精化製）０．２部、硫酸第一鉄・七水和物０．００５部、エチレンジアミン四酢酸四ナトリウム０．０１部を５部の蒸留水に溶解してから仕込み、更に攪拌下酢酸ビニルモノマー７０部を仕込み、窒素で重合缶内部を置換した後、エチレン２５部を充填した。温度を５５℃とした後、１％の過硫酸アンモニウム水溶液を７時間、連続添加し重合を行った。酢酸ビニルの残りの３０部は過硫酸アンモニウム水溶液を添加してから１時間後から計３時間に渡って連続添加した。未反応の酢酸ビニルモノマー量が１％未満になるまで重合を継続し、残存するエチレンをパージしＥＶＡエマルジョンを得た。
【００２０】
＜実施例２＞
実施例１においてユニチカレジンＵＭＲ−１０Ｈの使用量を４部、エレミノールＪＳ−２の使用量を０．３部とした以外は実施例１と同様にして重合を行った。
【００２１】
＜実施例３＞
実施例１においてユニチカレジンＵＭＲ−１０Ｈの使用量を１部、エレミノールＪＳ−２の使用量を３部とした以外は実施例１と同様にして重合を行った。
【００２２】
＜実施例４＞
実施例１においてエレミノールＪＳ−２に替わって、（式２）の構造を持つアデカリアソープＳＥ−１０Ｎ（旭電化株式会社製）を１部使用する以外は実施例１と同様にして重合を行った。
【００２３】
本発明において実施した各物性値の測定・評価方法を以下に説明する。
（不揮発分、粗粒子、ｐＨ、粘度、機械安定性、残存モノマー）
ＪＩＳＫ６８２８に準じて評価した。なお、残存モノマーは臭素／臭化カリウム水溶液による直接滴定法によって測定した。
（構造粘性指数）
単一円筒回転粘度計にて測定した６ｒｐｍの値と６０ｒｐｍの値を以下の式に代入し構造粘性指数として算出した。
構造粘性指数＝Ｌｏｇ１０｛（６ｒｐｍの測定値）／（６０ｒｐｍの測定値）｝
（平均粒子径）
透過型電子顕微鏡（ＳＥＭ）にて撮影した写真からエマルジョン粒子個々の粒子径を実測し、その平均値を算出した。
（トルエン不溶解分）
エマルジョンをテフロン（登録商標）板上に薄く引き延ばし、室温にて３日間以上乾燥してフィルム化した後、ハサミで細かく１ｍｍ四方以下に裁断する。これを蓋付き５０ｍｌ試験管に０．５ｇ程度計り取り、トルエンを４５ｍｌ程度加え、５０℃で５時間振とうする。冷却した後、重量を測定した２００メッシュ金網で内容物をろ過し、ろ過残分を室温で２４時間、１０５℃で１時間乾燥させて、その重量を測定し、以下の式からトルエン不溶解分を算出した。
（式）トルエン不溶解分（％）＝（ろ過残分）／（フィルム重量）×１００
【００２４】
（塩ビ合板接着試験／試験体作製方法）
半硬質塩ビシートに接着剤をウェットで９０ｇ／ｍ^２となる様にバーコーターを用いて塗布し、これを５．５ｍｍ厚の耐水Ｉ類合板に載せ、０．１ｋｇ／ｃｍ^２の圧締を３時間実施し、解圧後室温で６日間養生する。グラインダーで幅２５ｍｍ、長さ１５０ｍｍに切り分け試験体とする。
（塩ビ合板接着試験／常態剥離強度）
試験体の塩ビシートと合板を１８０°方向に引張り速度２００ｍｍ／分で引張り、その時の剥離強度を測定する。
（耐寒性）
上記の試験体を−２０℃雰囲気下、３時間放置後、その雰囲気下で手により半硬質塩ビシート側を引張って強制剥離し、剥離面を以下の規準で判定した。
○：塩ビシート側に木の大部分（７０％以上）が剥がれて、付着している状態
△：塩ビシート側に木の一部部分が付着している状態
×：塩ビシートと木とが界面剥離している状態
（耐熱クリープ性）
上記試験体を半硬質塩化ビニルシートを下側にして両端を固定した状態で水平に置き、６０℃のギヤーオーブン中に１時間放置した。雰囲気温度６０℃、９０°剥離の状態で５００ｇの静荷重でをかけ、３０分後の剥離長さを測定した。
（低温接着性）
２℃雰囲気下に試験に供する接着剤、合板、半硬質塩ビシートを２４時間養生し、この雰囲気下、半硬質塩ビシートに接着剤をウェットで９０ｇ／ｍ^２となる様にバーコーターを用いて塗布し、これを５．５ｍｍ厚の耐水Ｉ類合板に載せてマングルロールにて０．１ｋｇ／ｃｍ^２の圧力で圧着する。２℃の雰囲気下で２４時間養生した後、同雰囲気下、半硬質塩ビシート面にカッターで切り目を入れ、手で強制剥離して破壊状態を判定した。評価結果は合板表面が破壊した（木破）割合を示すが、この数値が大きいほど低温接着性が良好である。
【００２５】
（初期接着性）
温度２３℃、湿度６５ＲＨ％の雰囲気下に試験に供する接着剤、コピー用上質紙を２４時間養生し、この雰囲気下、塗膜厚０．２ｍｍ（ウェット）のアプリケーターを用いてコピー用上質紙側に接着剤を塗布する。直ちにこの塗布面にコピー上質紙を重ねてロールテスターにて圧着した後、テーブル上にて約５ｃｍ／分の速度で１３０°方向に圧着したコピー用上質紙を引き剥がしてゆき、何秒後に紙破壊を生じるかを測定する。圧着してから紙破壊状態が生じるまでの時間が短いほど初期接着性が良好と見なす。
【００２６】
上記試験結果を、表１に示す。
【表１】

【００２７】
表１から、本願発明の製造方法で得られるＥＶＡ系エマルジョンは不揮発分が７０質量％以上と高いわりに、粘度が３０℃、３０ｒｐｍ値で５０００ｍＰａ・ｓ以下と低く、平均粒子径も３μｍ以上と大きく、トルエン不溶解分も４０質量％以上であった。このＥＶＡ系エマルジョン９２質量部にトルエンを２質量部、キシレンを５質量部添加したものを接着剤として評価した。表２に接着剤としての性能の評価結果を示したが、本願発明の製造方法で得られたＥＶＡ系エマルジョンを使用した接着剤では、初期接着性能に優れ、且つ耐熱クリープ性、耐寒性、低温接着性の何れの評価項目でも優れた性能を発現した。
【００２８】
「比較例」
＜比較例１＞
実施例１で使用したユニチカレジンＵＭＲ−１０Ｈ（鹸化度８０ｍｏｌｅ％，重合度４４０、ユニチカ株式会社製ＰＶＡ）に替わってユニチカレジンＵＭＲ−３０Ｈ（鹸化度８０ｍｏｌｅ％，重合度６６０，ユニチカ株式会社製ＰＶＡ）を同量使用したが、得られたエマルジョンの粘度が著しく増大し、且つ構造粘性指数も０．６２と著しく増大した。構造粘性指数が０．６を超えてしまうと、ライン塗工の設備にて貼り合わせスピードを上げた際に見かけのエマルジョン粘度の低下が大きくなり、糊飛びなどの不具合を生じてしまう。また、このエマルジョンに溶剤を加えて接着剤としたものは、更に粘度が増大してしまい、試験に供するものにはならなかった。
【００２９】
＜比較例２＞
実施例１で使用したユニチカレジンＵＭＲ−１０Ｈ（鹸化度８０ｍｏｌｅ％，重合度４４０、ユニチカ株式会社製ＰＶＡ）に替わってデンカポバールＢ−０４（鹸化度８８ｍｏｌｅ％，重合度４００，電気化学工業株式会社製ＰＶＡ）を同量使用したが、重合途中で重合缶内のエマルジョンの粘度が著しく上昇してしまい、滴下した触媒の酸化剤の混合不良が生じてしまい、重合が制御不可能となってしまい、エマルジョンが得られなかった。
【００３０】
＜比較例３＞
実施例１で使用したユニチカレジンＵＭＲ−１０Ｈ（鹸化度８０ｍｏｌｅ％，重合度４４０、ユニチカ株式会社製ＰＶＡ）の量を３質量部から０．３質量部まで減らし、それ以外は実施例１に準じて重合を行った。その結果、エマルジョンの粗粒子の量が２３００００ｍｇ／１００ｇと著しく増加した。また、このエマルジョンに溶剤を加えて接着剤としたものは、耐熱クリープ性の剥離長が１５０ｍｍと十分ではなかった。
【００３１】
＜比較例４＞
実施例１で使用したユニチカレジンＵＭＲ−１０Ｈ（鹸化度８０ｍｏｌｅ％，重合度４４０、ユニチカ株式会社製ＰＶＡ）の量を３質量部から５質量部に増やし、それ以外は実施例１に準じて重合を行った。その結果、エマルジョンの粘度が１８０００ｍＰａ・ｓと著しく増大した。また、このエマルジョンに溶剤を加えて接着剤としたものは、更に粘度が増大してしまい、試験に供するものにはならなかった。
【００３２】
＜比較例５＞
実施例１で使用した反応性の界面活性剤エレミノールＪＳ−２（三洋化成株式会社製）の量を１質量部から０．１質量部まで減じ、それ以外は実施例１に準じて重合を行った。その結果、得られたエマルジョンの不揮発分が７０質量％で粘度が６０００ｍＰａ・ｓと高く、平均粒子径が１．９μｍと小さかった。このエマルジョンに溶剤を加えて接着剤としたものは、表３より塩ビ合板接着試験は良好な値を示したが、初期接着性が２２秒と改善されず目的とした物性が発現できなかった。
【００３３】
＜比較例６＞
実施例１で使用した反応性界面活性剤エレミノールＪＳ−２（アルキルアリルルスルホコハク酸ナトリウム、三洋化成株式会社製）の量を１質量部から５質量部まで増やし、それ以外は実施例１に準じて重合を行った。その結果、得られたエマルジョンの平均粒子径は６．５μｍと大きくなったが、不揮発分が７０質量％で粘度が３００００ｍＰａ・ｓと著しく増大した。このことから、過剰量の反応性界面活性剤による粘度低下は不可能である。
【００３４】
＜比較例７＞
実施例１で使用したノニオン系界面活性剤エマルゲン９１３，９５０（ポリオキシエチレンノニルフェニルエーテル、花王株式会社製）の量をそれぞれ０．２質量部から１質量部まで増やし、それ以外は実施例１に準じて重合を行った。結果、得られたエマルジョンの平均粒子径は５．８μｍと大きくなり、不揮発分が７０質量％で粘度が５００ｍＰａ・ｓまで低下した。また、粗粒子の量も８００ｍｇ／１００ｇと低く、エマルジョンの状態は良好であったが、トルエン不溶解分は１５％と著しく低下し、これに溶剤を添加した接着剤の塩ビ合板物性では耐熱クリープ性の剥離長が２００ｍｍと著しく低下した。
【００３５】
比較例１〜７の試験結果を表２と表３に示す。
【表２】

【表３】

【発明の効果】
【００３６】
本願発明の製造方法で得られるＥＶＡ系エマルジョンは、平均粒子径が３μｍ以上と大きく、不揮発分が７０質量％以上と高く、且つ粘度が１００〜５０００ｍＰａ・ｓと低く、更にはトルエン不溶解分が４０質量％以上と高いことから、紙や木といった多孔性被着体に対しては良好な初期接着性を持ち、塩ビオーバーレイ用接着剤としては十分な耐熱クリープ性能と耐寒性、及び低温接着性を同時に発現するため、各種接着剤に幅広く使用可能なエマルジョンである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ethylene-vinyl acetate copolymer emulsion and its production. More specifically, the initial adhesion is characterized in that the average particle size is as large as 3 μm or more and the non-volatile content is 70% by mass or more. The present invention relates to an ethylene-vinyl acetate copolymer emulsion that can be suitably used for a vinyl chloride overlay adhesive, an olefin film adhesive, and the like, which have an excellent balance of heat resistance, heat creep resistance, and cold resistance, and a method for producing the same.
[0002]
[Prior art]
Ethylene-vinyl acetate copolymer emulsions (hereinafter referred to as EVA emulsions) are widely used as adhesives and also in the fields of civil engineering and building materials, paints, papermaking and textiles. Also, unlike other water-based emulsions, EVA-based emulsions can be easily made into a high non-volatile content of about 60% by mass, and high non-volatile content EVA-based emulsions with excellent initial adhesion performance are commercialized by various companies. Has been.
Conventionally, a method for producing a vinyl acetate-ethylene copolymer emulsion containing a nonvolatile content of up to 70% by weight using a polyoxyethylene-polyoxypropylene block copolymer as a surfactant (for example, Patent Document 1) A vinyl acetate having an average particle size of 0.9 μm or less and a non-volatile content of 65 to 70% by weight in combination with a polyvinyl alcohol having a low polymerization degree (hereinafter referred to as PVA) and a surfactant having a specific HLB. A method for producing an ethylene copolymer emulsion (for example, see Patent Document 2), and a stable vinyl acetate-ethylene copolymer having a nonvolatile content of 65% or more by using polyvinyl alcohol having a low polymerization degree and a surfactant in combination. There is a method for producing an emulsion (for example, see Patent Document 3). However, in the conventional technology, in the polymerization of EVA emulsion having a high non-volatile content, most of them are highly non-volatile differentiated by using a large amount of a surfactant as an emulsifier. Adhesion was inhibited with the body, and sufficient adhesion performance was not expressed. For this reason, there is a strong demand from the market for EVA-based emulsions that are excellent in adhesive performance and have a higher nonvolatile content than ever before.
[0003]
[Patent Document 1]
Japanese Patent Publication No.42-22692 (first page)
[Patent Document 2]
Japanese Patent Publication No. 6-55874 (pages 1 and 2, claims 1 to 6)
[Patent Document 3]
Japanese Patent No. 2624741 (first page, claim 1)
[0004]
[Problems to be solved by the invention]
An object of the present invention is an EVA emulsion having a low viscosity and sufficient workability even when the non-volatile content is 70% or more, excellent initial adhesion, and excellent balance between heat resistance and low temperature characteristics, and a method for producing the same Is to provide.
[0005]
[Means for Solving the Problems]
As a result of intensive studies to achieve the above object, the present invention has an average particle size of 3 μm or more, a nonvolatile content of 70% by mass or more, and an initial adhesion by combining a special emulsifier when polymerizing an EVA emulsion. The present inventors have found that an EVA-based emulsion having excellent properties and a good balance between heat resistance and low temperature properties can be produced. The EVA emulsion of the present invention is also excellent in mechanical stability and chemical stability. Therefore, it has been found that a characteristic adhesive composition can be obtained by mixing various solvents and isocyanates. .
[0006]
DETAILED DESCRIPTION OF THE INVENTION
The ratio of ethylene, vinyl acetate and other copolymerizable monomers in the EVA emulsion polymerized in the present invention is 5 to 40:95 to 40: 0 to 20, preferably 10 to 35:90 to 50 in terms of mass ratio. : 0-15. Other copolymerizable monomers include, for example, vinyl chloride, vinyl propionate, vinyl versatate, acrylic acid, methacrylic acid, maleic acid, itaconic acid, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, There are ethyl methacrylate, propyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl (meth) acrylate, N-vinylpyrrolidone, styrene, acrylonitrile, (meth) acrylamide, one of these components More than one type can be copolymerized. Further, triallyl cyanurate and triallyl isocyanurate can be used in combination. When used as an adhesive, heat resistance is improved, and when used for mortar, alkali resistance is improved. The amount added is 1% by mass or less, preferably 0.5% by mass or less.
[0007]
When the EVA emulsion in the present invention is used for the adhesive, if the proportion of ethylene is out of the range of 5 to 40% by mass, at least one characteristic of low temperature adhesiveness, initial adhesiveness, and heat resistance is impaired. Further, when the proportion of vinyl acetate exceeds 95% by mass, the low-temperature adhesiveness decreases, and conversely, when the proportion of vinyl acetate is less than 40% by mass, the stability of emulsion during emulsion polymerization or normal adhesive strength tends to decrease. . When the proportion of other copolymerizable monomers exceeds 20% by mass, the low-temperature adhesiveness or the normal state adhesive strength tends to decrease. In particular, EVA-based emulsions with an ethylene ratio of 21 to 40% by mass are preferred for uses where low-temperature adhesiveness is important, and EVA-based emulsions with an ethylene ratio of 5 to 21% by mass are preferred for uses where heat resistance is important. .
[0008]
The emulsifier used in the present invention is composed of the following two components, and when none of these components is present, an EVA emulsion exhibiting sufficient performance cannot be obtained. One is a PVA having a low saponification degree and a low polymerization degree (hereinafter referred to as “low saponification low polymerization degree PVA”), and one is a reactive surfactant having an allyl group in the molecule.
[0009]
The saponification degree range of the low saponification low polymerization degree PVA used in the present invention is 60 to 86 mole%, preferably 65 to 84 mole%, more preferably 70 to 82 mole%. When the degree of saponification is less than 60 mole%, the solubility in water is extremely lowered, and it cannot be dissolved unless a special dissolution method is used, and is difficult to use industrially. In addition, the structural viscosity of the finished EVA emulsion is extremely increased, and when bonding is performed at a high speed, problems such as glue skipping (a phenomenon in which glue peels off from the roll) occur. When the saponification degree exceeds 86 mole%, the structural viscosity of the finished EVA emulsion does not increase, and roll suitability and workability with a brush are extremely lowered.
[0010]
The degree of polymerization of the low saponification low polymerization degree PVA used in the present invention is 100 to 500, preferably 150 to 450, more preferably 200 to 400. If the degree of polymerization is less than 100, the non-volatile content of the finished EVA emulsion can be increased, but a large amount of glue red (coarse particles referred to in JIS K 6828) is produced in the emulsion. If the degree of polymerization exceeds 500, the amount of glue residue generated in the finished EVA emulsion is small, but the viscosity increases during the polymerization, and the nonvolatile content cannot be increased to 70% by mass.
[0011]
The amount of the low saponification low polymerization degree PVA used in the present invention is 0.5 to 4.0 parts by mass, preferably 1.0 to 3.5 parts by mass with respect to 100 parts by mass of the vinyl acetate monomer unit to be polymerized. More preferably, it is 1.2-3.0 mass parts. When the amount of low saponification and low polymerization PVA is less than 0.5 parts by mass, the resulting EVA emulsion contains a large amount of glue red, and when the amount is more than 4.0 parts by mass, polymerization is in progress. The viscosity of the emulsion increases and it becomes impossible to increase the nonvolatile content to 70% by mass.
[0012]
The reactive surfactant used in the present invention has an allyl group in the molecule as shown in the following (formula 1) and (formula 2 ), and reacts with vinyl acetate monomer or ethylene monomer. If it is a thing, it will not specifically limit.
[Chemical 2]

[0013]
The amount of the reactive surfactant used in the present invention is 0.2 to 3.0 parts by mass, preferably 0.4 to 2.0 parts by mass, more preferably 0.6 per 100 parts by mass of the vinyl acetate monomer. -1.5 parts by mass. When the amount of the reactive surfactant is less than 0.2 parts by mass, the particle diameter of the finished emulsion is not sufficiently increased, and the viscosity becomes too high. When the amount of the reactive surfactant is more than 3.0 parts by mass, the particle diameter becomes sufficiently large, but the crosslinking between the particles proceeds too much, and as a result, the viscosity becomes too high.
[0014]
The emulsifier for polymerization used in the present invention has a low saponification low polymerization degree PVA and a reactive surfactant as essential components. However, other water-soluble high-performance emulsions are used as long as they do not significantly affect the properties of the resulting emulsion. Protective colloids such as molecules and surfactants may be used. Specifically, water-soluble polymers such as hydroxyethyl cellulose and methyl cellulose, nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene polyoxypropylene block copolymer, lauryl sulfate, alkylbenzene sulfonic acid Anionic surfactants such as salts, alkylphenyl ether sulfates, methyl taurates, sulfosuccinates, ether sulfonates, phosphate esters, and nonionic interfaces such as nonylphenyl, polyalkylene glycol, and fatty acid esters Activators, cationic surfactants such as quaternary ammonium salts and amine salts, and other amphoteric surfactants may be used. However, since these various surfactants are reduced in toluene-insoluble content of the EVA emulsion obtained by increasing the amount added, and when used as an adhesive, there is a concern that the heat resistance may decrease, so as much as possible. I've never been a small person. Therefore, the PVA component is preferably 30% by mass or more of the total emulsifier component so that an EVA-based emulsion having a toluene insoluble content of 40% by mass or more can be obtained.
[0015]
The toluene-insoluble matter in the EVA emulsion was measured by finely cutting a dry film of the synthetic resin emulsion. For example, 0.5 g of the film was immersed in 50 ml of toluene and shaken at 50 ° C. for 5 hours. Then, it is calculated | required by measuring the weight of the insoluble part collected by filtration with a 200 mesh metal-mesh.
[0016]
As the polymerization method of the EVA emulsion in the present invention, a commonly used emulsion polymerization method can be used. For example, a redox polymerization method for generating radicals from a reducing agent and an oxidizing agent, or radicals by thermal decomposition. A thermal polymerization method to be generated can be applied. As the reducing agent used in the redox polymerization method, a known reducing agent can be used, and examples thereof include Rongalite, sodium formaldehyde, L-ascorbic acid, tartaric acid and the like. In that case, water-soluble metal compounds such as ferrous sulfate can be used in combination. As the oxidant used as the initiator, water-soluble inorganic peroxides or persulfates such as hydrogen peroxide, potassium persulfate and ammonium persulfate, and organic peroxides such as t-butyl hydroperoxide and cumene hydroperoxide are used. An azo compound such as an oxide or azobisisobutyronitrile can be used. A chelating agent such as tetrasodium ethylenediaminetetraacetate can also be used in combination to increase the radical initiation efficiency. Regarding the vinyl acetate monomer used for the polymerization, the whole amount may be initially charged into the polymerization can, or a part of the vinyl acetate monomer may be continuously added to the polymerization can during the polymerization. The polymerization temperature is not particularly limited as long as radicals are generated at a sufficient rate, but a range of 40 to 80 ° C. is usually preferable.
[0017]
EVA manufactured by the present invention
The system emulsion has a large average particle diameter of 3 μm or more, and further has a low workability of 100 to 5000 mPa · s and a sufficient workability despite the non-volatile content of 70% by mass or more. In addition, by using a special PVA and reactive surfactant as an emulsifier, the toluene insoluble content is as high as 40% by mass or more, and there are few surfactant components that have conventionally caused adhesion inhibition. When used as, it has excellent adhesion to various adherends, and exhibits high heat resistance due to its high toluene insoluble content after moisture has evaporated. Further, since the particle size is 3 μm or more and the particle size distribution is broad, the volume of voids existing between the particles is reduced when the water evaporates and the particles are fused, and as a result, the water evaporates quickly. As a result, the initial adhesiveness is greatly improved. In particular, when a water-absorbing substrate such as wood or paper is used for the adherend, the tendency appears remarkably, and an initial adhesive force that could not be developed so far can be expressed.
[0018]
"Example"
This will be described in more detail with reference to examples. In addition, unless otherwise indicated, all the parts and% described in the present invention are based on mass.
[0019]
<Example 1>
A PID automatic temperature control cooling jacket and a high pressure polymerization vessel equipped with a stirrer have 3 parts of Unitika Resin UMR-10H (manufactured by Unitika Co., Ltd.) PVA having a saponification degree of 80 mole% and a polymerization degree of 400, and has a structure of sodium alkylsulfosuccinate 1 part of the reactive surfactant Eleminol JS-2 (manufactured by Sanyo Chemical Co., Ltd.), 0.2 part of Emulgen 913, which is a nonionic surfactant, and 0.2 part of Emulgen 950 (both manufactured by Kao Corporation) Is dissolved in 45 parts of distilled water previously adjusted to 90 ° C. or higher, and 0.2 parts of sodium acetate, 0.2 parts of Rongalite (manufactured by Sumitomo Seika), 0.005 parts of ferrous sulfate and heptahydrate Then, 0.01 part of ethylenediaminetetraacetic acid tetrasodium was dissolved in 5 parts of distilled water and charged, and then 70 parts of vinyl acetate monomer was added with stirring, and the inside of the polymerization vessel was filled with nitrogen. After replacing the, it was charged with 25 parts of ethylene. After the temperature was adjusted to 55 ° C., 1% ammonium persulfate aqueous solution was continuously added for 7 hours for polymerization. The remaining 30 parts of vinyl acetate were continuously added over a total of 3 hours from 1 hour after addition of the ammonium persulfate aqueous solution. Polymerization was continued until the amount of unreacted vinyl acetate monomer was less than 1%, and the remaining ethylene was purged to obtain an EVA emulsion.
[0020]
<Example 2>
Polymerization was carried out in the same manner as in Example 1 except that the amount of Unitika Resin UMR-10H used in Example 1 was 4 parts and that of Eleminor JS-2 was 0.3 parts.
[0021]
<Example 3>
Polymerization was carried out in the same manner as in Example 1 except that the amount of Unitika Resin UMR-10H used in Example 1 was 1 part and that of Eleminol JS-2 was 3 parts.
[0022]
<Example 4>
Polymerization was carried out in the same manner as in Example 1 except that 1 part of Adekaria soap SE-10N (Asahi Denka Co., Ltd.) having the structure of (Formula 2) was used instead of Eleminol JS-2 in Example 1. It was.
[0023]
The measurement / evaluation method of each physical property value carried out in the present invention will be described below.
(Non-volatile content, coarse particles, pH, viscosity, mechanical stability, residual monomer)
Evaluation was performed according to JIS K 6828. The residual monomer was measured by a direct titration method using a bromine / potassium bromide aqueous solution.
(Structural viscosity index)
The value of 6 rpm and the value of 60 rpm measured with a single cylinder rotational viscometer were substituted into the following formula to calculate the structural viscosity index.
Structural viscosity index = Log 10 {(measured value at 6 rpm) / (measured value at 60 rpm)}
(Average particle size)
The particle diameter of each emulsion particle was measured from a photograph taken with a transmission electron microscope (SEM), and the average value was calculated.
(Toluene insoluble matter)
The emulsion is thinly stretched on a Teflon (registered trademark) plate, dried at room temperature for 3 days or more to form a film, and then finely cut to 1 mm square or less with scissors. About 0.5 g of this is weighed into a 50-ml test tube with a lid, added with about 45 ml of toluene, and shaken at 50 ° C. for 5 hours. After cooling, the contents were filtered through a 200 mesh wire mesh whose weight was measured, and the residue was dried at room temperature for 24 hours and at 105 ° C. for 1 hour, and its weight was measured. Was calculated.
(Formula) Toluene insoluble matter (%) = (Filtering residue) / (Film weight) × 100
[0024]
(PVC plywood adhesion test / specimen preparation method)
Adhesive was applied to the semi-rigid PVC sheet with a bar coater so that the wet weight would be 90 g / m ^2, and this was placed on a 5.5 mm thick water-resistant type I plywood and pressed to 0.1 kg / cm ² . Carry out for 3 hours and cure for 6 days at room temperature after decompression. A specimen is cut into a width of 25 mm and a length of 150 mm with a grinder.
(PVC plywood adhesion test / normal peel strength)
The test piece of PVC sheet and plywood are pulled in a 180 ° direction at a pulling speed of 200 mm / min, and the peel strength at that time is measured.
(Cold resistance)
The test specimen was allowed to stand for 3 hours in an atmosphere at −20 ° C., and then the semi-rigid PVC sheet side was pulled by hand in the atmosphere to forcibly peel off, and the peeled surface was judged according to the following criteria.
○: Most of the tree (70% or more) is peeled off and attached to the PVC sheet side △: A part of the tree is attached to the PVC sheet side ×: Interface between the PVC sheet and the tree Peeled (heat-resistant creep resistance)
The test specimen was placed horizontally with both ends fixed with the semi-rigid vinyl chloride sheet facing down and left in a gear oven at 60 ° C. for 1 hour. A 500 g static load was applied at an atmospheric temperature of 60 ° C. and 90 ° peeling, and the peeling length after 30 minutes was measured.
(Low temperature adhesion)
Adhesives, plywood and semi-rigid PVC sheets to be tested in an atmosphere at 2 ° C. are cured for 24 hours, and a bar coater is used in this atmosphere so that the adhesive is 90 g / m ² wet with the semi-rigid PVC sheets. It is applied and placed on a water-resistant type I plywood having a thickness of 5.5 mm and pressure-bonded with a mangle roll at a pressure of 0.1 kg / cm ² . After curing for 24 hours in an atmosphere of 2 ° C., a cut was made on the semi-rigid PVC sheet surface with a cutter in the same atmosphere. The evaluation results indicate the ratio of broken (wood break) on the plywood surface. The larger this value, the better the low-temperature adhesiveness.
[0025]
(Initial adhesion)
Adhesive for test and high-quality paper for copying are cured for 24 hours in an atmosphere of temperature 23 ° C and humidity 65RH%, and the high-quality paper for copying is used in this atmosphere using an applicator with a coating thickness of 0.2 mm (wet) Apply adhesive to Immediately after copying the quality paper on the coated surface and pressing with a roll tester, the quality paper for copying, which was pressure-bonded in the direction of 130 ° at a speed of about 5 cm / min, was peeled off. Measure whether destruction occurs. The shorter the time from the press bonding to the occurrence of the paper breaking state, the better the initial adhesiveness.
[0026]
The test results are shown in Table 1.
[Table 1]

[0027]
From Table 1, the EVA emulsion obtained by the production method of the present invention has a high non-volatile content of 70% by mass or more, but the viscosity is as low as 5000 mPa · s at 30 ° C. and 30 rpm, and the average particle size is as large as 3 μm or more. The toluene insoluble matter was 40% by mass or more. An adhesive obtained by adding 2 parts by mass of toluene and 5 parts by mass of xylene to 92 parts by mass of this EVA emulsion was evaluated. Table 2 shows the results of evaluation of the performance as an adhesive. The adhesive using the EVA emulsion obtained by the production method of the present invention is excellent in initial adhesive performance, heat resistant creep resistance, cold resistance, and low temperature. Excellent performance was exhibited in all evaluation items of adhesiveness.
[0028]
"Comparative example"
<Comparative Example 1>
Unitika resin UMR-30H (degree of saponification 80 mole%, degree of polymerization 660, unit of PVA manufactured by Unitika Co., Ltd.) instead of unitika resin UMR-10H (degree of saponification 80 mole%, degree of polymerization 440, unit PVA manufactured by Unitika Co., Ltd.) used in Example 1 ) Was used in the same amount, but the viscosity of the resulting emulsion was significantly increased and the structural viscosity index was also significantly increased to 0.62. When the structural viscosity index exceeds 0.6, when the bonding speed is increased in the line coating equipment, the apparent emulsion viscosity is greatly reduced, resulting in problems such as glue skipping. In addition, the adhesive obtained by adding a solvent to this emulsion further increased the viscosity and did not serve for the test.
[0029]
<Comparative example 2>
Instead of Unitika Resin UMR-10H (degree of saponification 80 mole%, degree of polymerization 440, PVA manufactured by Unitika Ltd.) used in Example 1, Denkapoval B-04 (degree of saponification 88 mole%, degree of polymerization 400, Denki Kagaku Kogyo Co., Ltd.) Although the same amount of PVA) was used, the viscosity of the emulsion in the polymerization can significantly increased during the polymerization, resulting in poor mixing of the oxidizer of the dropped catalyst, and the polymerization could not be controlled. An emulsion was not obtained.
[0030]
<Comparative Example 3>
The amount of Unitika Resin UMR-10H (degree of saponification 80 mole%, degree of polymerization 440, PVA manufactured by Unitika Co., Ltd.) used in Example 1 was reduced from 3 parts by weight to 0.3 parts by weight. Polymerization was performed. As a result, the amount of coarse particles in the emulsion was remarkably increased to 230000 mg / 100 g. In addition, the adhesive obtained by adding a solvent to this emulsion had a heat-resistant creep-resistant peel length of 150 mm, which was not sufficient.
[0031]
<Comparative Example 4>
The amount of Unitika Resin UMR-10H (degree of saponification 80 mole%, degree of polymerization 440, PVA manufactured by Unitika Co., Ltd.) used in Example 1 was increased from 3 parts by mass to 5 parts by mass. Went. As a result, the viscosity of the emulsion was remarkably increased to 18000 mPa · s. In addition, the adhesive obtained by adding a solvent to this emulsion further increased the viscosity and did not serve for the test.
[0032]
<Comparative Example 5>
The amount of the reactive surfactant Eleminol JS-2 (manufactured by Sanyo Chemical Co., Ltd.) used in Example 1 was reduced from 1 part by mass to 0.1 part by mass, and other than that, polymerization was performed according to Example 1. It was. As a result, the non-volatile content of the obtained emulsion was 70% by mass, the viscosity was as high as 6000 mPa · s, and the average particle size was as small as 1.9 μm. As a result of adding a solvent to this emulsion to make an adhesive, the PVC plywood adhesion test showed good values from Table 3, but the initial adhesion was not improved to 22 seconds, and the intended physical properties could not be expressed.
[0033]
<Comparative Example 6>
The amount of the reactive surfactant Eleminol JS-2 (sodium alkylallylsulfosuccinate, manufactured by Sanyo Chemical Co., Ltd.) used in Example 1 was increased from 1 part by mass to 5 parts by mass, and otherwise the same as in Example 1 Polymerization was performed. As a result, the average particle size of the obtained emulsion increased to 6.5 μm, but the non-volatile content was 70% by mass and the viscosity was significantly increased to 30000 mPa · s. For this reason, it is impossible to reduce the viscosity by an excessive amount of the reactive surfactant.
[0034]
<Comparative Example 7>
The amount of the nonionic surfactant Emulgen 913,950 (polyoxyethylene nonylphenyl ether, manufactured by Kao Corporation) used in Example 1 was increased from 0.2 parts by mass to 1 part by mass, and other than that, Example 1 Polymerization was carried out according to the above. As a result, the average particle size of the obtained emulsion was as large as 5.8 μm, the non-volatile content was 70% by mass, and the viscosity was reduced to 500 mPa · s. In addition, the amount of coarse particles was as low as 800 mg / 100 g, and the emulsion state was good, but the toluene insoluble content was remarkably reduced to 15%. The peel-off length was significantly reduced to 200 mm.
[0035]
The test results of Comparative Examples 1 to 7 are shown in Table 2 and Table 3.
[Table 2]

[Table 3]

【The invention's effect】
[0036]
The EVA emulsion obtained by the production method of the present invention has a large average particle size of 3 μm or more, a high non-volatile content of 70% by mass or more, a low viscosity of 100 to 5000 mPa · s, and a toluene insoluble content. Since it is as high as 40% by mass or more, it has good initial adhesiveness for porous adherends such as paper and wood, and it has sufficient heat-resistant creep performance, cold resistance, and low-temperature adhesiveness as an adhesive for PVC overlays. Is an emulsion that can be used widely in various adhesives.

Claims

The reactive surfactant having the structure shown in the following (formula 1) or (formula 2) as an emulsifier is 0.2 to 3.0 parts by mass per 100 parts by mass of vinyl acetate monomer, and the saponification degree is 60 to 85 mole%. Polyvinyl alcohol having an average degree of polymerization of 100 to 500 is used in an amount of 0.5 to 4.0 parts by weight per 100 parts by weight of vinyl acetate monomer, and a nonionic surfactant is used in an amount of 0 to less than 2 parts by weight per 100 parts by weight of vinyl acetate monomer. The ethylene-vinyl acetate copolymer is characterized in that the average particle diameter measured by the following is 3 μm or more and the nonvolatile content measured according to JIS K 6828 is 70% by mass or more. A method for producing a polymer emulsion.
Measurement of average particle diameter: The particle diameter of each emulsion particle was measured from a photograph taken with a transmission electron microscope (SEM), and the average value was measured.

2. The method for producing an ethylene-vinyl acetate copolymer emulsion according to claim 1, wherein the viscosity at 30 [deg.] C. and 30 rpm measured with a single cylinder rotational viscometer is 100 to 5000 mPa.s.

The logarithmic value of the ratio of the viscosity value at 30 ° C. and 6 rpm and the viscosity value at 30 ° C. and 60 rpm measured by a single cylindrical rotational viscometer is 0.2 to 0.6. A process for producing the ethylene-vinyl acetate copolymer emulsion as described.

An ethylene-vinyl acetate copolymer emulsion obtained by the production method according to any one of claims 1 to 3.

Ethylene according to 請 Motomeko 4 you, wherein the toluene insoluble content was measured as follows is 40 mass% or more - vinyl acetate copolymer emulsion.
Toluene insoluble matter measurement: drying the emulsion to form a film, measuring its weight, immersing in toluene, shaking, collecting the insoluble matter by filtration, and measuring the weight of the filtered residue after drying Was calculated from the following equation.
Toluene insoluble matter (%) = (filtering residue) / (film weight) × 100

6. The ethylene-vinyl acetate copolymer according to claim 5, wherein the toluene-insoluble content is 40% by mass or more, and the heat-resistant creep resistance of the PVC plywood measured by the following is 20 mm or less. Polymer emulsion .
Measurement of heat-resistant creep resistance: Using a test specimen in which the ethylene-vinyl acetate copolymer emulsion was applied to a semi-rigid vinyl chloride sheet and a water-resistant plywood was bonded, both ends were fixed with the semi-rigid vinyl chloride sheet facing down. The sample was left horizontally at 60 ° C. for 1 hour, and a static load of 500 g was applied with the atmospheric temperature at 60 ° C. and 90 ° peeled, and the peel length after 30 minutes was measured.

The composition for adhesive agents formed by containing the ethylene-vinyl acetate type copolymer emulsion of any one of Claims 4-6.