JP3699225B2 - Porous water-absorbing crosslinked polymer and process for producing the same - Google Patents
Porous water-absorbing crosslinked polymer and process for producing the same Download PDFInfo
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- JP3699225B2 JP3699225B2 JP34492196A JP34492196A JP3699225B2 JP 3699225 B2 JP3699225 B2 JP 3699225B2 JP 34492196 A JP34492196 A JP 34492196A JP 34492196 A JP34492196 A JP 34492196A JP 3699225 B2 JP3699225 B2 JP 3699225B2
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- Prior art keywords
- water
- crosslinked polymer
- porous
- group
- absorbing
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- 229920006037 cross link polymer Polymers 0.000 title claims description 80
- 238000000034 method Methods 0.000 title claims description 22
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- 238000010521 absorption reaction Methods 0.000 claims description 66
- 230000002209 hydrophobic effect Effects 0.000 claims description 27
- 239000000178 monomer Substances 0.000 claims description 25
- 238000006460 hydrolysis reaction Methods 0.000 claims description 10
- 230000007062 hydrolysis Effects 0.000 claims description 9
- 125000004432 carbon atom Chemical group C* 0.000 claims description 7
- 239000000839 emulsion Substances 0.000 claims description 7
- 239000002250 absorbent Substances 0.000 claims description 6
- 239000007864 aqueous solution Substances 0.000 claims description 6
- 238000004519 manufacturing process Methods 0.000 claims description 6
- 125000003262 carboxylic acid ester group Chemical group [H]C([H])([*:2])OC(=O)C([H])([H])[*:1] 0.000 claims description 5
- 239000002504 physiological saline solution Substances 0.000 claims description 5
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- 229910001854 alkali hydroxide Inorganic materials 0.000 claims description 3
- 150000008044 alkali metal hydroxides Chemical class 0.000 claims description 3
- 125000001183 hydrocarbyl group Chemical group 0.000 claims 2
- -1 2-ethylhexyl Chemical group 0.000 description 28
- NIXOWILDQLNWCW-UHFFFAOYSA-M Acrylate Chemical compound [O-]C(=O)C=C NIXOWILDQLNWCW-UHFFFAOYSA-M 0.000 description 23
- 239000012071 phase Substances 0.000 description 23
- 239000004094 surface-active agent Substances 0.000 description 19
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- SNRUBQQJIBEYMU-UHFFFAOYSA-N Dodecane Natural products CCCCCCCCCCCC SNRUBQQJIBEYMU-UHFFFAOYSA-N 0.000 description 4
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- DLBIZQBMDGOEFK-UHFFFAOYSA-N didodecyl 2-methylidenebutanedioate Chemical compound CCCCCCCCCCCCOC(=O)CC(=C)C(=O)OCCCCCCCCCCCC DLBIZQBMDGOEFK-UHFFFAOYSA-N 0.000 description 4
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- VBICKXHEKHSIBG-UHFFFAOYSA-N 1-monostearoylglycerol Chemical compound CCCCCCCCCCCCCCCCCC(=O)OCC(O)CO VBICKXHEKHSIBG-UHFFFAOYSA-N 0.000 description 2
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- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 2
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- 125000001931 aliphatic group Chemical group 0.000 description 2
- 125000000484 butyl group Chemical group [H]C([*])([H])C([H])([H])C([H])([H])C([H])([H])[H] 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- FJKIXWOMBXYWOQ-UHFFFAOYSA-N ethenoxyethane Chemical compound CCOC=C FJKIXWOMBXYWOQ-UHFFFAOYSA-N 0.000 description 2
- 125000001495 ethyl group Chemical group [H]C([H])([H])C([H])([H])* 0.000 description 2
- 239000000835 fiber Substances 0.000 description 2
- 125000004051 hexyl group Chemical group [H]C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])* 0.000 description 2
- 239000004620 low density foam Substances 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 125000002496 methyl group Chemical group [H]C([H])([H])* 0.000 description 2
- 125000004108 n-butyl group Chemical group [H]C([H])([H])C([H])([H])C([H])([H])C([H])([H])* 0.000 description 2
- 125000002347 octyl group Chemical group [H]C([*])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])[H] 0.000 description 2
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- 239000011591 potassium Substances 0.000 description 2
- 229910052700 potassium Inorganic materials 0.000 description 2
- 239000012966 redox initiator Substances 0.000 description 2
- 235000010267 sodium hydrogen sulphite Nutrition 0.000 description 2
- CHQMHPLRPQMAMX-UHFFFAOYSA-L sodium persulfate Substances [Na+].[Na+].[O-]S(=O)(=O)OOS([O-])(=O)=O CHQMHPLRPQMAMX-UHFFFAOYSA-L 0.000 description 2
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- VPTNWGPGDXUKCY-KHPPLWFESA-N (z)-4-decoxy-4-oxobut-2-enoic acid Chemical compound CCCCCCCCCCOC(=O)\C=C/C(O)=O VPTNWGPGDXUKCY-KHPPLWFESA-N 0.000 description 1
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- FGRVOLIFQGXPCT-UHFFFAOYSA-L dipotassium;dioxido-oxo-sulfanylidene-$l^{6}-sulfane Chemical compound [K+].[K+].[O-]S([O-])(=O)=S FGRVOLIFQGXPCT-UHFFFAOYSA-L 0.000 description 1
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- SVUQHVRAGMNPLW-UHFFFAOYSA-N glycerol monostearate Natural products CCCCCCCCCCCCCCCCC(=O)OCC(O)CO SVUQHVRAGMNPLW-UHFFFAOYSA-N 0.000 description 1
- 150000002314 glycerols Chemical class 0.000 description 1
- 125000005843 halogen group Chemical group 0.000 description 1
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- 125000001165 hydrophobic group Chemical group 0.000 description 1
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- 125000000959 isobutyl group Chemical group [H]C([H])([H])C([H])(C([H])([H])[H])C([H])([H])* 0.000 description 1
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- Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
Description
【０００１】
【発明の属する技術分野】
本発明は、親水化により著しく吸水速度および吸水倍率の改善された、多孔質吸水性架橋重合体に関する。
【０００２】
【従来の技術】
水性液体を多量に含有する多孔質架橋ポリマー材料として、９０％までの内部水相を含む油中水滴型エマルジョンの硬化物が知られている（英国特許第１４５８２０３号公報）。そしてこのような油中水滴型エマルジョンの応用として、特開昭６２−２５０００２号公報には弾性を有する低密度多孔質架橋ポリマー材料が開示され、特開平６−５１００７６号公報には高吸収容量の低密度フォームが開示されている。
【０００３】
一般的に、これらの高吸収容量の低密度フォームは、界面活性剤の存在下で9：1を越える水相対油相の重量比の高分散相油中水滴型エマルジョンを形成させた後重合させることによって製造される。しかしながら、高分散相油中水滴型エマルジョン形成後に得られる重合体は実質的に疎水性のもので、吸水剤として使用するためにはその親水化が必須である。
【０００４】
例えば、特開平６−５０９８３４号公報には、界面活性剤をその内部に含有するフォームの表面に塩化カルシウムなどの無機残査を残す方法が開示されている。なるほどこの方法により得られる重合体の初期の水への濡れ性は改善されるものの、その吸水速度、吸水倍率は満足できるものではなく、特に長期間保存した後の吸水特性が低下するという問題があった。
【０００５】
【発明が解決しようとする課題】
本発明の目的は、改良された吸水速度および吸水倍率を長期間保存後も発揮する多孔質吸水性架橋重合体を提供することである。
【０００６】
【課題を解決するための手段】
本願発明者らは、改良された吸水速度を有する多孔質吸水性架橋重合体を得る方法について鋭意検討した結果、油中水滴型高分散相エマルジョンを用いて製造された多孔質疎水性架橋重合体そのものを親水化することにより、著しく吸水速度および吸水倍率に優れた多孔質吸水性架橋重合体が得られることを見いだし、本発明に到達した。
【０００７】
すなわち本発明は、
（１）一般式−ＣＯＯＲ（但し、Ｒは炭素原子数が１〜３０の置換または非置換の１価の炭化水素基である。）で表されるカルボン酸エステル基を含む多孔質疎水性架橋重合体を、加水分解することにより親水化する多孔質吸水性架橋重合体の製法；
（２）多孔質吸水性架橋重合体の加水分解を、水酸化アルカリの水溶液を用いて行う、上記（１）に記載の多孔質吸水性架橋重合体の製法；
（３）一般式−ＣＯＯＲ（但し、Ｒは炭素原子数が１〜３０の置換または非置換の１価の炭化水素基である。）で表されるカルボン酸エステル基を含む前記多孔質疎水性架橋重合体が、溶解度パラメーター（ＳＰ値）が９以下の単量体および分子中に少なくとも２個の重合性不飽和基を有する架橋性単量体を主成分とする単量体成分を含む油中水滴型エマルジョンを６０℃未満の温度で硬化させて得られたものである、上記（１）または（２）に記載の多孔質吸水性架橋重合体の製法；
（４） 上記（１）〜（３）のいずれかに記載の製法で得られた多孔質吸水性架橋重合体であって、生理食塩水（０．９％ 食塩水）の吸水速度が５秒〜２１秒である多孔質吸水性架橋重合体；
（５） 上記（４）の多孔質吸水性架橋重合体を含んでなる吸水物品；
を提供するものである。
【０００８】
以下に本発明を詳しく説明する。
【０００９】
本発明で使用される多孔質疎水性架橋重合体は、例えば疎水性のビニルモノマーと分子中に少なくとも2個の重合性不飽和基を有する架橋性単量体を使用して、油中水滴型高分散相エマルジョンを形成後、重合することで得ることができる。好ましい疎水性の単量体は、溶解度パラメーター（ＳＰ値）が９以下の単量体を主成分とする単量体である。
【００１０】
本発明で用いられる溶解度パラメーター（ＳＰ値）が９以下の単量体としては、例えば、スチレン、α一メチルスチレン、クロロメチルスチレン、ビニルエチルベンゼン、オクチルスチレン及びビニルトルエンのような、モノアルケニルアレンモノマー：メチル（メタ）アクリレート、エチル（メタ）アクリレート、2ーエチルヘキシル（メタ）アクリレート、n一ブチル（メタ）アクリレート、イソブチル（メタ）アクリレート、ｔ−ブチル（メタ）アクリレート、ヘキシル（メタ）アクリレート、フェニル（メタ）アクリレート、オクチル（メタ）アクリレート、ノニルフェニル（メタ）アクリレート、ジノニルフェニル（メタ）アクリレート、ラウリル（メタ）アクリレート、イソデシル（メタ）アクリレート、ジブチルマレエート、ジドデシルマレエート、ドデシルクロトネート、ジドデシルイタコネートのような不飽和カルボン酸エステル：（ジ）ブチル（メタ）アクリルアミド、（ジ）ステアリル（メタ）アクリルアミド、（ジ）ドデシル（メタ）アクリルアミド、（ジ）ブチルフェニル（メタ）アクリルアミド、（ジ）オクチルフェニル（メタ）アクリルアミドなどの炭化水素基を有する（メタ）アクリルアミド：ブタジエン、イソプレン、１−ヘキセン、１−オクテン、イソオクテン、１−ノネン、１−デセン、１−ドデセンなどのα−オレフィン：ビニルシクロヘキセンなどの脂環式ビニル化合物：ドデシルアリルエーテルなどの脂肪族炭化水素基を有するアリルエーテル：カプロン酸ビニル、ラウリン酸ビニル、ステアリン酸ビニル、パルミチン酸ビニルなどの脂肪族炭化水素基を有するビニルエステル：エチルビニルエーテル、ブチルビニルエーテル、ドデシルビニルエーテルなどのビニルエーテル：およびこれらの混合物を挙げることができる。
【００１１】
本発明で用いられる分子中に少なくとも2個の重合性不飽和基を有する架橋性単量体としては、例えばエチレングリコールジ（メタ）アクリレート、ジエチレングリコールジ（メタ）アクリレート、ポリエチレングリコールジ（メタ）アクリレート、ポリエチレングリコールーポリプロピレングリコールジ（メタ）アクリレート、プロピレングリコールジメタアクリレート、ポリプロピレングリコールジ（メタ）アクリレート、１，３−ブチレングリコールジ（メタ）アクリレート、ネオペンチルグリコールジ（メタ）アクリレート、１，６−ヘキサンジオールジ（メタ）アクリレート、トリメチロールプロパントリ（メタ）アクリレート、テトラメチロールメタンテトラ（メタ）アクリレートなどの多官能（メタ）アクリレートやジビニルベンゼンなどを挙げることができる。
【００１２】
また、本発明において使用される分子中に少なくとも2個の重合性不飽和基を有する架橋性単量体の全単量体成分に対する割合は、全単量体成分中の1〜50重量％、好ましくは5〜45重量％、より好ましくは10〜40重量％の範囲である。架橋性単量体の使用量が1重量％未満では、得られる多孔質架橋重合体の強度が不足し、５０重量％よりも多い場合には得られる多孔質架橋重合体が硬くなりすぎることがある。
【００１３】
本発明において油中水滴型エマルジョンを形成するために使用される界面活性剤としては、例えばソルビタンモノラウレート、ソルビタンモノパルミテート、ソルビタンモノステアレート、ソルビタンジステアレート、ソルビタントリステアレート、ソルビタンモノオレエート等のソルビタン誘導体：グリセロールモノステアレート、グリセロールモノオレエートなどのグリセリン誘導体：ポリオキシエチレンラウリルエーテル等のポリオキシエチレン脂肪酸エステル類などを例示できる。これら油溶性界面活性剤は単独でもしくは２種以上を混合して使用され、その使用量は単量体成分１００重量部に対し１〜４０重量部の範囲、好ましくは５〜３０重量部の範囲である。１重量部よりも少ない場合には油中水滴型エマルジョンが不安定となり、４０重量部よりも多い場合には得られる多孔質架橋重合体が脆くなりすぎることがある。
【００１４】
更に本発明では、重合時の油中水滴型エマルジョンを安定化せしめる目的で、各種の安定化剤を上記界面活性剤に加えて添加することもできる。安定化剤として好適なものは水溶性の無機塩であり、このものを水相中に添加しておくことが好ましい。このような水溶性無機塩としては、例えばカリウム、ナトリウム、カルシウム、マグネシウム、アルミニウム等の水溶性塩が挙げられ、特に多価金属塩が好ましい。水溶性無機塩の添加量は水１００重量部に対し０．１〜２０重量部、特に０．５〜１５重量部の範囲が好ましい。
【００１５】
本発明において、疎水性多孔質架橋重合体を親水化するための方法としては、重合体自体を親水化させることができるのであれば特に限定されない。好ましい親水化方法は、重合体中にカルボン酸（塩）などの陰イオン基を共有結合で導入する方法である。より好ましくは、一般式−ＣＯＯＲ（但し、Ｒは炭素原子数が１〜３０の置換または非置換の１価の炭化水素基である。）で表されるカルボン酸エステル基を含む多孔質疎水性架橋重合体を予め形成しておき、その後該重合体を加水分解することによりカルボン酸（塩）を重合体中に生成せしめ親水化する方法である。
【００１６】
本発明において、一般式−ＣＯＯＲで表されるカルボン酸エステル中のＲは、炭素原子数１〜３０の置換又は非置換の１価の炭化水素基であり、該置換基は、反応を阻害しないものであれば特に限定されるものではない。Ｒの具体例としては、メチル基、エチル基、ｎ−プロピル基、ｉ−プロピル基、ｎ−ブチル基、ｓｅｃ−ブチル基、ｔ−ブチル基、ｎ−ペンチル基、ヘキシル基、オクチル基、ノニル基、デシル基等のアルキル基などの飽和脂肪族炭化水素基；シクロペンチル基、シクロヘキシル基、４−メチルシクロヘキシル基等のシクロアルキル基などの脂環式炭化水素基；ビニル基、アリル基、２−ブテニル基、３−ブテニル基等のアルケニル基などの脂肪族不飽和炭化水素基；フェニル基、２−メチルフェニル基、３−メチルフェニル基、４−メチルフェニル基、キシリル基、ナフチル基等のアリール基、あるいは２−ブロモフェニル基、２−メトキシフェニル基、３−エトキシフェニル基、４−メトキシフェニル基、３−ブロモフェニル基、４−ブロモフェニル基、２−クロロフェニル基、３−クロロフェニル基、４−クロロフェニル基、２−フルオロフェニル基、３−フルオロフェニル基、４−フルオロフェニル基、２−ヨードフェニル基、３−ヨードフェニル基、４−ヨードフェニル基、２，４−ジブロモフェニル基、２，５−ジブロモフェニル基、２，６−ジブロモフェニル基、２，３−ジクロロフェニル基、２，４−ジクロロフェニル基、２，５−ジクロロフェニル基、２，６−ジクロロフェニル基、３，４−ジクロロフェニル基、３，５−ジクロロフェニル基、２，４−ジフルオロフェニル基、２，５−ジフルオロフェニル基、２，６−ジフルオロフェニル基、３，４−ジフルオロフェニル基、２，４，６−トリブロモフェニル基、２，３，４−トリクロロフェニル基、２，４，５−トリクロロフェニル基、２，４，６−トリクロロフェニル基等のフッ素、塩素、臭素、ヨウ素等のハロゲン原子や低級アルコキシ基で置換されたアリール基などの置換又は非置換のアリール基；並びにベンジル基、２−フェニルエチル基、４−メチルベンジル基等のアラルキル基などが挙げられる。
【００１７】
本発明の多孔質疎水性架橋重合体を得るためには、まず疎水性のビニルモノマーと、分子中に少なくとも2個の重合性不飽和基を有する架橋性単量体からなる油相成分1〜10重量％と水99〜90重量％とを単量体100重量部に対し1〜40重量部の界面活性剤の存在下に混合し、多量の水を内部不連続相として有する油中水滴型エマルジョンを形成せしめる。油相成分と水の混合割合は油相成分1〜10重量％に対し水99〜90重量％の範囲が好ましく、さらに好ましくは油相成分1〜5重量部に対し水99〜95重量％の範囲である。油相成分の量が1重量％未満では、得られた多孔質疎水性架橋重合体の強度が低下して取扱い性に問題が生じる場合がある。また油相成分の量が10重量％よりも多い場合には、得られる多孔質吸水性架橋重合体の吸水速度が不十分となる場合がある。
【００１８】
本発明において、油相成分を油溶性界面活性剤の存在下に水と混合し油中水滴型エマルジョンを形成する方法としては、多量の水を内部不連続相として有する油中水滴型エマルションを形成できるのであれば特にこだわらない。例えば、１）油溶性界面活性剤を溶解した油相を攪拌下に水中に添加する方法、2）油溶性界面活性剤を溶解した油相に水を攪拌下に添加する方法、3）油溶性界面活性剤を溶解した油相に水を加え攪拌する方法、4）水に油溶性界面活性剤を溶解した油相を加え攪拌する方法、5）油溶性界面活性剤を溶解した油相と水とをそれぞれ連続的にフィードしながら混合する方法などを挙げることができる。またそれぞれの方法において、油溶性界面活性剤は前記のように油相に予め溶解していてもよいが、水に予め分散させておいたり、油相成分と水と油溶性界面活性剤を別々に供給混合することもできる。経済的観点から好ましい方法は予め油溶性界面活性剤を油相成分に溶解させておく方法である。油中水滴型エマルジョンを形成するために使用できる混合あるいは攪拌装置としては、従来公知のものを使用でき、例えば、各種攪拌翼を装備した槽型攪拌装置、スタティックミキサー、二一ダー、ホモジナイザー、マグネットスターラー等を例示できる。
【００１９】
本発明で使用できる多孔質疎水性架橋重合体は、例えば前記手法により形成された油中水滴型エマルジョンをレドックス開始剤存在下で好ましくは６０℃未満の温度に加熟重合され得ることができる。重合に際し、油中水滴型エマルジョンは、その内部水相が破壊されない条件下で静置重合するのが好ましく、例えば油中水型エマルジョンをバッチ毎にあるいは連続的にフィードしながら、キャスト重合することができる。重合にあたり、重合容器を任意の形状とすることで、重合により得られる多孔質疎水性架橋重合体を任意形状、例えば粒子状、繊維状、マット状、シート状、ブロック状等に成形重合することも可能である。もちろん重合法として連続重合法を採用することも可能である。硬化温度は好ましくは６０℃未満の範囲、より好ましくは20〜50℃の範囲である。硬化を20〜50℃の温度範囲で行ない、硬化後に重合を50〜90℃の温度範囲で完結することが最も好ましい。重合硬化時間は1〜30時間程度が適切である。重合温度が15℃未満では、重合に長時間を要し工業的に好ましくない、硬化温度が６０℃を越える場合、得られる多孔質疎水性架橋重合体の孔径が不均一となることがあり、また最終的に得られる本発明の多孔質吸水性架橋重合体の吸水倍率が低下する。
【００２０】
レドックス重合開始剤として使用される水溶性酸化剤としては、例えば過酸化水素のような水溶性過酸化物：過硫酸カリウム、過硫酸ナトリウム、過硫酸アンモニウム等の水溶性過硫酸塩：過酢酸ナトリウム、過酢酸カリウム等の水溶性過酢酸塩：過炭酸ナトリウム、過炭酸カリウムなどの水溶性過炭酸塩などを挙げることができる。水溶性酸化剤の使用量は総単量体成分の総モル数に対し、0.001モル％〜８０モル％の範囲が好ましい。
【００２１】
重合の際、酸化剤と共に使用される還元剤としては、亜硫酸水素ナトリウム、亜硫酸水素カリウムなどの亜硫酸水素塩：チオ硫酸ナトリウム、チオ硫酸カリウムなどのチオ硫酸塩：トリエタノールアミン、ジエタノールアミン、ジメチルアニリンなどのアミン類：などの多価金属塩：Ｌ−アスコルビン酸などを挙げることができる。より好ましくは、水溶性酸化剤／還元剤のモル比が１以下となるような量の還元剤を使用することがより好ましい。
【００２２】
本発明において最も好ましい形態は、一般式−ＣＯＯＲ（但し、Ｒは炭素原子数が１〜３０の置換または非置換の１価の炭化水素基である。）で表されるカルボン酸エステル基を含む疎水性単量体を必須成分として含む単量体成分を、油中水滴型エマルジョン形態で重合することにより得られる多孔質疎水性架橋重合体を、加水分解することにより該重合体中にカルボン酸（塩）を生成せしめ、該重合体を親水化する方法である。
【００２３】
加水分解は、例えば、水酸化アルカリ（例えばＮａＯＨまたはＫＯＨ）の水溶液、好ましくは０．５％〜飽和濃度までの水溶液を用いて行うことができる。本発明において、加水分解は５０〜１５０℃の温度範囲で行われ、加水分解反応中に生じるカルボキシル基の中和の程度は適当な量の鉱酸、例えばＨＣｌを加えることにより変えることができる。必要な反応時間は反応温度および所望の加水分解の程度により任意に選択可能である。また、加水分解後の本発明の多孔質吸水性架橋重合体は必要により水洗の後、圧縮処理されて乾燥される。
【００２４】
このようにして得られる本発明の多孔質吸水性架橋重合体は重合体そのものが親水化処理されているため、従来の界面活性剤や無機塩添加処理品に比べ、以下の優れた点を有する。
【００２５】
１）著しく吸水速度および吸水倍率が向上される。
【００２６】
２）残留界面活性剤、無機塩などがなく安全である。
【００２７】
３）界面活性剤の変質などに起因する長期間保存後での吸水特性の変質がない。
【００２８】
４）架橋重合体そのものが親水化されるため、架橋重合体の一部も水による膨潤が可能で、そのため加圧状態での吸水・保水能力が格段にアップする等。
【００２９】
本発明の多孔質吸水性架橋重合体は、必要によりさらに裁断するなどして任意の形状、例えばシート状、ブロック状、繊維状、フィルム状、粉末状などの目的に応じた形態とすることができ、しかも、水性液体と接触した際に液体が成形体内部へ浸透してゆく連続した多数の孔を有している。本発明の多孔質吸水性架橋重合体をそのまま吸水材として用いてもよいが、多孔質吸水性架橋重合体を少なくとも一部が液透過性を有するフィルムで挟持したり、多孔質吸水性架橋重合体を液透過性材料からなる容器に充填したりして、吸水物品として使用することも可能である。
【００３０】
【実施例】
次に、本発明について実施例をあげて詳細に説明するが、本発明はこれだけに限定されるものではない。なお、例中特にことわりのない限り、部は重量部を表すものとする。
【００３１】
本発明における多孔質架橋重合体の吸水倍率および吸水速度は以下の方法で測定した。
【００３２】
（吸水倍率）
１ｃｍ角の大きさに裁断した予め秤量した試料を用い、温度１０℃の生理食塩水（0.9%食塩水）にこの試料を浸した。生理食塩水を吸収し膨張した試料を、直径120mm高さ5mmのガラスフィルター（＃0：Duran社製）の上に30秒間放置して液切りを行なった後、吸水した試料の重量を測定し、以下の式で吸水倍率（g／g）を求めた。
【００３３】
吸水倍率＝（吸水後の試料重量−吸水前の試料重量）／吸水前の試料重量
（吸水速度）
吸水倍率測定時に、試料が生理食塩水を吸収し終えるまでの時間を測定し、吸収に要する時間を吸水速度とした。
【００３４】
参考例
１０００mlの円筒形ポリプロピレン製容器に、水相として塩化カルシウム５０部、過硫酸ナトリウム０．７部および純水４５０部を仕込んだ。ついで、油相としてスチレン１．７３部、２−エチルヘキシルアクリレート５．２１部、55%ジビニルベンゼン１．７３部、およびソルビタンモノラウレート（商品名レオドールスーパーＳＰ−Ｌ１０、花王株式会社製）１．３１部からなる溶液を室温で攪拌下に容器中へ添加した。混合物がヨーグルト状になり良好なエマルジョンが得られたのを確認して、亜硫酸水素ナトリウム０．７部を純水１０部に溶かした溶液を加え、再びエマルジョンが均一になるまで攪拌した。攪拌終了後、容器を４０℃に保って３時問重合硬化を行ない重合を完結させ、多孔質疎水性架橋重合体（ａ）を得た。
【００３５】
実施例１
厚さ１０ｍｍにスライスした多孔質疎水性架橋重合体（ａ）を６０℃の純水で膨潤、圧縮脱水を２回行い洗浄せしめた。次いで、この洗浄した多孔質架橋重合体１０部を、４８％水酸化ナトリウム水溶液１００部に浸漬し、還流冷却器を備えた５００ｍＬのセパラブルフラスコ中で１時間１３０℃で加熱処理した。処理終了後、フラスコより親水化処理された多孔質架橋重合体を取り出し、アルカリを純水で洗浄して除去し、６０℃の熱風乾燥器中で１時間乾燥して、本発明の多孔質吸水性架橋重合体（１）を得た。本発明の多孔質吸水性架橋重合体（１）の吸水倍率は６７ｇ／ｇで吸水速度は５秒であった。またこのものは、６０℃の熱風乾燥器中で２週間エージングした後もその吸水速度・吸水倍率は変わらなかった。
【００３６】
実施例２
厚さ１０ｍｍにスライスした多孔質疎水性架橋重合体（ａ）を６０℃の純水で膨潤、圧縮脱水を２回行い洗浄せしめた。次いで、この洗浄した多孔質架橋重合体１０部を、４８％水酸化ナトリウム水溶液１００部に浸漬し、還流冷却器を備えた５００ｍＬのセパラブルフラスコ中で３０分間１２０℃で加熱処理した。処理終了後、フラスコより親水化処理された多孔質架橋重合体を取り出し、アルカリを純水で洗浄して除去し、６０℃の熱風乾燥器中で１時間乾燥して、本発明の多孔質吸水性架橋重合体（２）を得た。本発明の多孔質吸水性架橋重合体（２）の吸水倍率は６０ｇ／ｇで吸水速度は７秒であった。またこのものは、６０℃の熱風乾燥器中で２週間エージングした後もその吸水速度・吸水倍率は変わらなかった。
【００３７】
実施例３
厚さ１０ｍｍにスライスした多孔質疎水性架橋重合体（ａ）を６０℃の純水で膨潤、圧縮脱水を２回行い洗浄せしめた。次いで、この洗浄した多孔質架橋重合体１０部を、４８％水酸化ナトリウム水溶液１００部に浸漬し、還流冷却器を備えた５００ｍＬのセパラブルフラスコ中で２時間１３０℃で加熱処理した。処理終了後、フラスコより親水化処理された多孔質架橋重合体を取り出し、アルカリを純水で洗浄して除去し、６０℃の熱風乾燥器中で１時間乾燥して、本発明の多孔質吸水性架橋重合体（３）を得た。本発明の多孔質吸水性架橋重合体（３）の吸水倍率は７５ｇ／ｇで吸水速度は５秒であった。またこのものは、６０℃の熱風乾燥器中で２週間エージングした後もその吸水速度・吸水倍率は変わらなかった。
【００３８】
実施例４
厚さ１０ｍｍにスライスした多孔質疎水性架橋重合体（ａ）を６０℃の純水で膨潤、圧縮脱水を２回行い洗浄せしめた。次いで、この洗浄した多孔質架橋重合体１０部を、４０％水酸化ナトリウム水溶液１００部に浸漬し、還流冷却器を備えた５００ｍＬのセパラブルフラスコ中で５時間１３０℃で加熱処理した。処理終了後、フラスコより親水化処理された多孔質架橋重合体を取り出し、アルカリを純水で洗浄して除去し、６０℃の熱風乾燥器中で１時間乾燥して、本発明の多孔質吸水性架橋重合体（４）を得た。本発明の多孔質吸水性架橋重合体（４）の吸水倍率は５７ｇ／ｇで吸水速度は１３秒であった。またこのものは、６０℃の熱風乾燥器中で２週間エージングした後もその吸水速度・吸水倍率は変わらなかった。
【００３９】
実施例５
厚さ１０ｍｍにスライスした多孔質疎水性架橋重合体（ａ）を６０℃の純水で膨潤、圧縮脱水を２回行い洗浄せしめた。次いで、この洗浄した多孔質架橋重合体１０部を、２０％水酸化ナトリウム水溶液１００部に浸漬し、還流冷却器を備えた５００ｍＬのセパラブルフラスコ中で５時間１３０℃で加熱処理した。処理終了後、フラスコより親水化処理された多孔質架橋重合体を取り出し、アルカリを純水で洗浄して除去し、６０℃の熱風乾燥器中で１時間乾燥して、本発明の多孔質吸水性架橋重合体（５）を得た。本発明の多孔質吸水性架橋重合体（５）の吸水倍率は４７ｇ／ｇで吸水速度は２１秒であった。またこのものは、６０℃の熱風乾燥器中で２週間エージングした後もその吸水速度・吸水倍率は変わらなかった。
【００４０】
比較例１
厚さ１０ｍｍにスライスした多孔質疎水性架橋重合体（ａ）を６０℃の純水で膨潤、圧縮脱水を４回行い洗浄せしめた。次いで、６０℃の熱風乾燥器中で１時間乾燥して、比較多孔質吸水性架橋重合体（１）を得た。比較多孔質吸水性架橋重合体（１）の吸水倍率は４２ｇ／ｇで吸水速度は１２０秒であった。
【００４１】
比較例２
厚さ１０ｍｍにスライスした多孔質疎水性架橋重合体（ａ）を６０℃の１％塩化カルシウム水溶液で膨潤、圧縮脱水を２回行い洗浄せしめた。次いで、６０℃の熱風乾燥器中で１時間乾燥して、比較多孔質吸水性架橋重合体（２）を得た。比較多孔質吸水性架橋重合体（２）の吸水倍率は３４ｇ／ｇで吸水速度は１時間であった。
【００４２】
比較例３
厚さ１０ｍｍにスライスした多孔質疎水性架橋重合体（ａ）を６０℃の純水で膨潤、圧縮脱水を２回行い洗浄せしめた。次いで、０．５％ソルビタンモノラウレート水溶液で更に膨潤、圧縮脱水を２回行い、６０℃の熱風乾燥器中で１時間乾燥して、比較多孔質吸水性架橋重合体（３）を得た。比較多孔質吸水性架橋重合体（３）の吸水倍率は４２ｇ／ｇで吸水速度は２０分であった。
【００４３】
【発明の効果】
本発明により、著しく吸水速度、吸水倍率などの吸水特性が向上し、長時間保存後もその吸水特性を維持できる新規な多孔質吸水性架橋重合体を提供することが可能である。
【図面の簡単な説明】
【図１】多孔質疎水性架橋重合体（ａ）のＩＲである。
【図２】加水分解後の本発明の多孔質吸水性架橋重合体（１）のＩＲである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a porous water-absorbing crosslinked polymer whose water absorption speed and water absorption ratio are remarkably improved by hydrophilization.
[0002]
[Prior art]
As a porous cross-linked polymer material containing a large amount of an aqueous liquid, a cured product of a water-in-oil emulsion containing up to 90% of an internal aqueous phase is known (UK Patent No. 1458203). As applications of such a water-in-oil emulsion, Japanese Patent Application Laid-Open No. 62-250002 discloses a low density porous crosslinked polymer material having elasticity, and Japanese Patent Application Laid-Open No. 6-510076 discloses a high absorption capacity. A low density foam is disclosed.
[0003]
In general, these high-absorption capacity low-density foams are polymerized after forming a water-in-oil emulsion in a highly dispersed phase with a weight ratio of water relative oil phase exceeding 9: 1 in the presence of a surfactant. Manufactured by. However, the polymer obtained after the formation of the highly dispersed phase water-in-oil emulsion is substantially hydrophobic, and its hydrophilicity is essential for use as a water-absorbing agent.
[0004]
For example, JP-A-6-509834 discloses a method of leaving an inorganic residue such as calcium chloride on the surface of a foam containing a surfactant therein. Although the wettability of the polymer obtained by this method to the initial water is improved, the water absorption rate and the water absorption ratio are not satisfactory, and there is a problem that the water absorption characteristics after storage for a long period of time are deteriorated. there were.
[0005]
[Problems to be solved by the invention]
An object of the present invention is to provide a porous water-absorbing crosslinked polymer that exhibits improved water absorption rate and water absorption capacity even after long-term storage.
[0006]
[Means for Solving the Problems]
As a result of intensive studies on a method for obtaining a porous water-absorbing crosslinked polymer having an improved water absorption rate, the present inventors have determined that a porous hydrophobic crosslinked polymer produced using a water-in-oil type highly dispersed phase emulsion It has been found that a porous water-absorbing crosslinked polymer having a remarkably excellent water absorption rate and water absorption ratio can be obtained by hydrophilizing itself, and the present invention has been achieved.
[0007]
That is, the present invention
( 1 ) Porous hydrophobic bridge containing a carboxylic acid ester group represented by the general formula -COOR (wherein R is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 30 carbon atoms) A method for producing a porous water-absorbing crosslinked polymer, wherein the polymer is hydrophilized by hydrolysis;
( 2 ) The method for producing a porous water-absorbing crosslinked polymer according to ( 1 ) above, wherein the hydrolysis of the porous water-absorbing crosslinked polymer is performed using an aqueous solution of an alkali hydroxide;
( 3 ) The porous hydrophobic group containing a carboxylic acid ester group represented by the general formula —COOR (wherein R is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 30 carbon atoms). An oil in which the cross-linked polymer contains a monomer having a solubility parameter (SP value) of 9 or less and a monomer component mainly composed of a cross-linkable monomer having at least two polymerizable unsaturated groups in the molecule. The method for producing a porous water-absorbent crosslinked polymer according to the above ( 1 ) or ( 2 ), which is obtained by curing a water-in-water emulsion at a temperature of less than 60 ° C;
(4) A porous water-absorbing crosslinked polymer obtained by the method according to any one of (1) to (3) above, wherein the water absorption rate of physiological saline (0.9% saline) is 5 seconds. A porous water-absorbing crosslinked polymer that is ˜21 seconds;
(5) A water-absorbing article comprising the porous water-absorbing crosslinked polymer of (4) above;
Is to provide.
[0008]
The present invention is described in detail below.
[0009]
The porous hydrophobic cross-linked polymer used in the present invention is, for example, a water-in-oil type using a hydrophobic vinyl monomer and a cross-linkable monomer having at least two polymerizable unsaturated groups in the molecule. It can be obtained by polymerizing after forming a highly dispersed phase emulsion. A preferred hydrophobic monomer is a monomer whose main component is a monomer having a solubility parameter (SP value) of 9 or less.
[0010]
Examples of monomers having a solubility parameter (SP value) of 9 or less used in the present invention include monoalkenyl allene monomers such as styrene, α-methyl styrene, chloromethyl styrene, vinyl ethyl benzene, octyl styrene and vinyl toluene. : Methyl (meth) acrylate, ethyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, hexyl (meth) acrylate, phenyl (Meth) acrylate, octyl (meth) acrylate, nonylphenyl (meth) acrylate, dinonylphenyl (meth) acrylate, lauryl (meth) acrylate, isodecyl (meth) acrylate, dibutyl maleate, zido Unsaturated carboxylic esters such as decyl maleate, dodecyl rotonate, didodecyl itaconate: (di) butyl (meth) acrylamide, (di) stearyl (meth) acrylamide, (di) dodecyl (meth) acrylamide, (di) butyl (Meth) acrylamide having a hydrocarbon group such as phenyl (meth) acrylamide and (di) octylphenyl (meth) acrylamide: butadiene, isoprene, 1-hexene, 1-octene, isooctene, 1-nonene, 1-decene, 1 Α-olefin such as dodecene: alicyclic vinyl compound such as vinylcyclohexene: allyl ether having an aliphatic hydrocarbon group such as dodecyl allyl ether: vinyl caproate, vinyl laurate, vinyl stearate, vinyl palmitate, etc. Fat Vinyl esters having a family hydrocarbon group: ethyl vinyl ether, butyl vinyl ether, vinyl ether and dodecyl vinyl ether: and the like, and mixtures thereof.
[0011]
Examples of the crosslinkable monomer having at least two polymerizable unsaturated groups in the molecule used in the present invention include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, and polyethylene glycol di (meth) acrylate. , Polyethylene glycol-polypropylene glycol di (meth) acrylate, propylene glycol dimethacrylate, polypropylene glycol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1,6 -Polyfunctional (meth) acrylates such as hexanediol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethane tetra (meth) acrylate, Can be mentioned.
[0012]
The ratio of the crosslinkable monomer having at least two polymerizable unsaturated groups in the molecule used in the present invention to the total monomer component is 1 to 50% by weight in the total monomer component, Preferably it is 5-45 weight%, More preferably, it is the range of 10-40 weight%. When the amount of the crosslinkable monomer used is less than 1% by weight, the strength of the obtained porous crosslinked polymer is insufficient, and when it is more than 50% by weight, the resulting porous crosslinked polymer may be too hard. is there.
[0013]
Examples of the surfactant used for forming the water-in-oil emulsion in the present invention include sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan distearate, sorbitan tristearate, sorbitan monostearate. Examples include sorbitan derivatives such as oleate: glycerin derivatives such as glycerol monostearate and glycerol monooleate: polyoxyethylene fatty acid esters such as polyoxyethylene lauryl ether. These oil-soluble surfactants are used alone or in admixture of two or more, and the amount used is in the range of 1 to 40 parts by weight, preferably in the range of 5 to 30 parts by weight with respect to 100 parts by weight of the monomer component. It is. When the amount is less than 1 part by weight, the water-in-oil emulsion becomes unstable, and when the amount is more than 40 parts by weight, the resulting porous crosslinked polymer may become too brittle.
[0014]
Further, in the present invention, various stabilizers can be added in addition to the above surfactant for the purpose of stabilizing the water-in-oil emulsion during polymerization. A suitable stabilizer is a water-soluble inorganic salt, which is preferably added to the aqueous phase. Examples of such water-soluble inorganic salts include water-soluble salts such as potassium, sodium, calcium, magnesium, and aluminum, and polyvalent metal salts are particularly preferable. The addition amount of the water-soluble inorganic salt is preferably in the range of 0.1 to 20 parts by weight, particularly 0.5 to 15 parts by weight with respect to 100 parts by weight of water.
[0015]
In the present invention, the method for hydrophilizing the hydrophobic porous crosslinked polymer is not particularly limited as long as the polymer itself can be hydrophilized. A preferred hydrophilization method is a method of introducing an anionic group such as a carboxylic acid (salt) into the polymer by a covalent bond. More preferably, the porous hydrophobicity includes a carboxylic acid ester group represented by the general formula —COOR (wherein R is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 30 carbon atoms). In this method, a crosslinked polymer is formed in advance, and then the polymer is hydrolyzed to produce a carboxylic acid (salt) in the polymer to make it hydrophilic.
[0016]
In the present invention, R in the carboxylic acid ester represented by the general formula —COOR is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 30 carbon atoms, and the substituent does not inhibit the reaction. If it is a thing, it will not specifically limit. Specific examples of R include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, sec-butyl group, t-butyl group, n-pentyl group, hexyl group, octyl group and nonyl. Group, saturated aliphatic hydrocarbon group such as alkyl group such as decyl group; alicyclic hydrocarbon group such as cycloalkyl group such as cyclopentyl group, cyclohexyl group, 4-methylcyclohexyl group; vinyl group, allyl group, 2- Aliphatic unsaturated hydrocarbon group such as alkenyl group such as butenyl group and 3-butenyl group; aryl such as phenyl group, 2-methylphenyl group, 3-methylphenyl group, 4-methylphenyl group, xylyl group and naphthyl group Group, 2-bromophenyl group, 2-methoxyphenyl group, 3-ethoxyphenyl group, 4-methoxyphenyl group, 3-bromophenyl group, 4-butyl group, Mophenyl group, 2-chlorophenyl group, 3-chlorophenyl group, 4-chlorophenyl group, 2-fluorophenyl group, 3-fluorophenyl group, 4-fluorophenyl group, 2-iodophenyl group, 3-iodophenyl group, 4- Iodophenyl group, 2,4-dibromophenyl group, 2,5-dibromophenyl group, 2,6-dibromophenyl group, 2,3-dichlorophenyl group, 2,4-dichlorophenyl group, 2,5-dichlorophenyl group, 2 , 6-dichlorophenyl group, 3,4-dichlorophenyl group, 3,5-dichlorophenyl group, 2,4-difluorophenyl group, 2,5-difluorophenyl group, 2,6-difluorophenyl group, 3,4-difluorophenyl Group, 2,4,6-tribromophenyl group, 2,3,4-trichlorophenyl group, 2,4 A substituted or unsubstituted aryl group such as an aryl group substituted with a halogen atom such as fluorine, chlorine, bromine or iodine such as 5-trichlorophenyl group or 2,4,6-trichlorophenyl group or a lower alkoxy group; and benzyl Groups, aralkyl groups such as 2-phenylethyl group, 4-methylbenzyl group and the like.
[0017]
In order to obtain the porous hydrophobic crosslinked polymer of the present invention, an oil phase component 1 to 1 comprising a hydrophobic vinyl monomer and a crosslinkable monomer having at least two polymerizable unsaturated groups in the molecule. 10% by weight and 99 to 90% by weight of water are mixed in the presence of 1 to 40 parts by weight of surfactant with respect to 100 parts by weight of monomer, and a water-in-oil type having a large amount of water as an internal discontinuous phase. An emulsion is formed. The mixing ratio of the oil phase component and water is preferably in the range of 99 to 90% by weight of water with respect to 1 to 10% by weight of the oil phase component, more preferably 99 to 95% by weight of water with respect to 1 to 5 parts by weight of the oil phase component. It is a range. When the amount of the oil phase component is less than 1% by weight, the strength of the obtained porous hydrophobic crosslinked polymer may be lowered, causing a problem in handling. When the amount of the oil phase component is more than 10% by weight, the water absorption rate of the obtained porous water-absorbing crosslinked polymer may be insufficient.
[0018]
In the present invention, as a method of mixing an oil phase component with water in the presence of an oil-soluble surfactant to form a water-in-oil emulsion, a water-in-oil emulsion having a large amount of water as an internal discontinuous phase is formed. If you can, don't worry. For example, 1) a method in which an oil phase in which an oil-soluble surfactant is dissolved is added to water with stirring, 2) a method in which water is added to an oil phase in which an oil-soluble surfactant is dissolved, and 3) oil solubility. Method of adding water to the oil phase in which the surfactant is dissolved and stirring, 4) Method of adding and stirring the oil phase in which the oil-soluble surfactant is dissolved in water, 5) Oil phase and water in which the oil-soluble surfactant is dissolved And a method of mixing them while continuously feeding them. In each method, the oil-soluble surfactant may be preliminarily dissolved in the oil phase as described above. Alternatively, the oil-soluble surfactant may be preliminarily dispersed in water, or the oil phase component, water, and the oil-soluble surfactant may be separated. It is also possible to feed and mix. A preferable method from an economical viewpoint is a method in which an oil-soluble surfactant is previously dissolved in the oil phase component. As a mixing or stirring device that can be used to form a water-in-oil emulsion, a conventionally known device can be used, for example, a tank-type stirring device equipped with various stirring blades, a static mixer, a mixer, a homogenizer, a magnet. A stirrer etc. can be illustrated.
[0019]
The porous hydrophobic crosslinked polymer that can be used in the present invention can be subjected to ripening polymerization, for example, in the presence of a redox initiator, preferably at a temperature of less than 60 ° C., in the presence of a redox initiator. In the polymerization, it is preferable that the water-in-oil emulsion is allowed to stand and polymerize under the condition that the internal aqueous phase is not destroyed. For example, the water-in-oil emulsion is cast-polymerized by feeding batchwise or continuously. Can do. In polymerization, by forming the polymerization vessel into an arbitrary shape, the porous hydrophobic crosslinked polymer obtained by polymerization is molded and polymerized into an arbitrary shape, for example, a particle shape, a fiber shape, a mat shape, a sheet shape, a block shape, etc. Is also possible. Of course, a continuous polymerization method can also be adopted as the polymerization method. The curing temperature is preferably in the range of less than 60 ° C, more preferably in the range of 20-50 ° C. Most preferably, the curing is performed in a temperature range of 20 to 50 ° C., and the polymerization is completed in the temperature range of 50 to 90 ° C. after curing. The polymerization curing time is suitably about 1 to 30 hours. When the polymerization temperature is less than 15 ° C., it takes a long time for the polymerization and is not industrially preferable. When the curing temperature exceeds 60 ° C., the pore size of the resulting porous hydrophobic crosslinked polymer may be uneven, Moreover, the water absorption magnification of the porous water-absorbing crosslinked polymer of the present invention finally obtained is lowered.
[0020]
Examples of the water-soluble oxidant used as the redox polymerization initiator include water-soluble peroxides such as hydrogen peroxide: water-soluble persulfates such as potassium persulfate, sodium persulfate, and ammonium persulfate: sodium peracetate, Water-soluble peracetates such as potassium peracetate: water-soluble percarbonates such as sodium percarbonate and potassium percarbonate. The amount of the water-soluble oxidizing agent used is preferably in the range of 0.001 mol% to 80 mol% with respect to the total number of moles of the total monomer components.
[0021]
In the polymerization, the reducing agent used together with the oxidizing agent includes bisulfites such as sodium bisulfite and potassium bisulfite: thiosulfates such as sodium thiosulfate and potassium thiosulfate: triethanolamine, diethanolamine, dimethylaniline, etc. Examples of amines: Multivalent metal salts such as: L-ascorbic acid and the like. More preferably, it is more preferable to use an amount of reducing agent such that the water-soluble oxidizing agent / reducing agent molar ratio is 1 or less.
[0022]
The most preferable form in the present invention includes a carboxylic ester group represented by the general formula -COOR (wherein R is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 30 carbon atoms). Carboxylic acid is contained in the polymer by hydrolyzing a porous hydrophobic crosslinked polymer obtained by polymerizing a monomer component containing a hydrophobic monomer as an essential component in the form of a water-in-oil emulsion. (Salt) is produced to hydrophilize the polymer.
[0023]
The hydrolysis can be performed using, for example, an aqueous solution of alkali hydroxide (for example, NaOH or KOH), preferably an aqueous solution of 0.5% to a saturated concentration. In the present invention, the hydrolysis is carried out in the temperature range of 50 to 150 ° C., and the degree of neutralization of the carboxyl group generated during the hydrolysis reaction can be changed by adding an appropriate amount of a mineral acid such as HCl. The required reaction time can be arbitrarily selected depending on the reaction temperature and the desired degree of hydrolysis. Moreover, the porous water-absorbent crosslinked polymer of the present invention after hydrolysis is subjected to a compression treatment and dried after washing with water as necessary.
[0024]
The porous water-absorbing crosslinked polymer of the present invention thus obtained has the following excellent points as compared with conventional surfactants and inorganic salt-added products because the polymer itself is hydrophilized. .
[0025]
1) The water absorption speed and the water absorption magnification are remarkably improved.
[0026]
2) There is no residual surfactant and inorganic salt, and it is safe.
[0027]
3) No change in water absorption characteristics after long-term storage due to alteration of the surfactant.
[0028]
4) Since the crosslinked polymer itself is hydrophilized, a part of the crosslinked polymer can be swollen with water, so that the water absorption / retention ability in a pressurized state is remarkably improved.
[0029]
The porous water-absorbing cross-linked polymer of the present invention may be formed into an arbitrary shape, for example, a sheet shape, a block shape, a fiber shape, a film shape, a powder shape, or the like by further cutting if necessary. Moreover, it has a large number of continuous holes through which the liquid permeates into the molded body when it comes into contact with the aqueous liquid. Although the porous water-absorbing crosslinked polymer of the present invention may be used as a water-absorbing material as it is, at least a part of the porous water-absorbing crosslinked polymer is sandwiched between films having liquid permeability, It is also possible to fill the container with a liquid-permeable material and use it as a water-absorbing article.
[0030]
【Example】
Next, although an Example is given and this invention is demonstrated in detail, this invention is not limited only to this. In the examples, unless otherwise specified, parts represent parts by weight.
[0031]
The water absorption rate and water absorption rate of the porous crosslinked polymer in the present invention were measured by the following methods.
[0032]
(Water absorption ratio)
Using a pre-weighed sample cut to a size of 1 cm square, this sample was immersed in physiological saline (0.9% saline) at a temperature of 10 ° C. After the sample that had absorbed physiological saline and expanded was left on a glass filter (# 0: Duran) with a diameter of 120 mm and a height of 5 mm for 30 seconds to drain the liquid, the weight of the absorbed sample was measured. The water absorption capacity (g / g) was determined by the following formula.
[0033]
Water absorption ratio = (sample weight after water absorption−sample weight before water absorption) / sample weight before water absorption (water absorption speed)
At the time of measuring the water absorption magnification, the time until the sample finished absorbing the physiological saline was measured, and the time required for absorption was taken as the water absorption rate.
[0034]
[0035]
Example 1
The porous hydrophobic cross-linked polymer (a) sliced to a thickness of 10 mm was swollen with pure water at 60 ° C. and subjected to compression dehydration twice to be washed. Next, 10 parts of the washed porous crosslinked polymer was immersed in 100 parts of a 48% aqueous sodium hydroxide solution and heat-treated at 130 ° C. for 1 hour in a 500 mL separable flask equipped with a reflux condenser. After completion of the treatment, the porous crosslinked polymer hydrophilized from the flask is taken out, the alkali is removed by washing with pure water, dried in a hot air drier at 60 ° C. for 1 hour, and the porous water absorption of the present invention. Crosslinkable polymer (1) was obtained. The porous water-absorbing crosslinked polymer (1) of the present invention had a water absorption rate of 67 g / g and a water absorption rate of 5 seconds. Further, the water absorption rate and the water absorption magnification of this product did not change even after aging for 2 weeks in a hot air dryer at 60 ° C.
[0036]
Example 2
The porous hydrophobic cross-linked polymer (a) sliced to a thickness of 10 mm was swollen with pure water at 60 ° C. and subjected to compression dehydration twice to be washed. Next, 10 parts of the washed porous crosslinked polymer was immersed in 100 parts of a 48% aqueous sodium hydroxide solution and heat-treated at 120 ° C. for 30 minutes in a 500 mL separable flask equipped with a reflux condenser. After completion of the treatment, the porous crosslinked polymer hydrophilized from the flask is taken out, the alkali is removed by washing with pure water, dried in a hot air drier at 60 ° C. for 1 hour, and the porous water absorption of the present invention. Crosslinkable polymer (2) was obtained. The porous water-absorbing crosslinked polymer (2) of the present invention had a water absorption rate of 60 g / g and a water absorption rate of 7 seconds. Further, the water absorption rate and the water absorption magnification of this product did not change even after aging for 2 weeks in a hot air dryer at 60 ° C.
[0037]
Example 3
The porous hydrophobic cross-linked polymer (a) sliced to a thickness of 10 mm was swollen with pure water at 60 ° C. and subjected to compression dehydration twice to be washed. Next, 10 parts of the washed porous crosslinked polymer was immersed in 100 parts of a 48% aqueous sodium hydroxide solution and heat-treated at 130 ° C. for 2 hours in a 500 mL separable flask equipped with a reflux condenser. After completion of the treatment, the porous crosslinked polymer hydrophilized from the flask is taken out, the alkali is removed by washing with pure water, dried in a hot air drier at 60 ° C. for 1 hour, and the porous water absorption of the present invention. Crosslinkable polymer (3) was obtained. The porous water-absorbing crosslinked polymer (3) of the present invention had a water absorption rate of 75 g / g and a water absorption rate of 5 seconds. Further, the water absorption rate and the water absorption magnification of this product did not change even after aging for 2 weeks in a hot air dryer at 60 ° C.
[0038]
Example 4
The porous hydrophobic cross-linked polymer (a) sliced to a thickness of 10 mm was swollen with pure water at 60 ° C. and subjected to compression dehydration twice to be washed. Next, 10 parts of this washed porous crosslinked polymer was immersed in 100 parts of a 40% aqueous sodium hydroxide solution, and heat-treated at 130 ° C. for 5 hours in a 500 mL separable flask equipped with a reflux condenser. After completion of the treatment, the porous crosslinked polymer hydrophilized from the flask is taken out, the alkali is removed by washing with pure water, dried in a hot air drier at 60 ° C. for 1 hour, and the porous water absorption of the present invention. Crosslinkable polymer (4) was obtained. The porous water-absorbing crosslinked polymer (4) of the present invention had a water absorption rate of 57 g / g and a water absorption rate of 13 seconds. Further, the water absorption rate and the water absorption magnification of this product did not change even after aging for 2 weeks in a hot air dryer at 60 ° C.
[0039]
Example 5
The porous hydrophobic cross-linked polymer (a) sliced to a thickness of 10 mm was swollen with pure water at 60 ° C. and subjected to compression dehydration twice to be washed. Next, 10 parts of the washed porous crosslinked polymer was immersed in 100 parts of a 20% aqueous sodium hydroxide solution and heat-treated at 130 ° C. for 5 hours in a 500 mL separable flask equipped with a reflux condenser. After completion of the treatment, the porous crosslinked polymer hydrophilized from the flask is taken out, the alkali is removed by washing with pure water, dried in a hot air drier at 60 ° C. for 1 hour, and the porous water absorption of the present invention. Crosslinkable polymer (5) was obtained. The porous water-absorbing crosslinked polymer (5) of the present invention had a water absorption rate of 47 g / g and a water absorption rate of 21 seconds. Further, the water absorption rate and the water absorption magnification of this product did not change even after aging for 2 weeks in a hot air dryer at 60 ° C.
[0040]
Comparative Example 1
The porous hydrophobic crosslinked polymer (a) sliced to a thickness of 10 mm was swollen with pure water at 60 ° C. and subjected to compression dehydration four times and washed. Subsequently, it dried for 1 hour in a 60 degreeC hot-air dryer, and the comparative porous water-absorbing crosslinked polymer (1) was obtained. The comparative porous water-absorbing crosslinked polymer (1) had a water absorption rate of 42 g / g and a water absorption rate of 120 seconds.
[0041]
Comparative Example 2
The porous hydrophobic crosslinked polymer (a) sliced to a thickness of 10 mm was swollen with a 1% calcium chloride aqueous solution at 60 ° C. and subjected to compression dehydration twice and washed. Subsequently, it dried for 1 hour in a 60 degreeC hot air dryer, and the comparative porous water-absorbing crosslinked polymer (2) was obtained. The comparative porous water-absorbing crosslinked polymer (2) had a water absorption rate of 34 g / g and a water absorption rate of 1 hour.
[0042]
Comparative Example 3
The porous hydrophobic cross-linked polymer (a) sliced to a thickness of 10 mm was swollen with pure water at 60 ° C. and subjected to compression dehydration twice to be washed. Subsequently, it was further swelled with a 0.5% sorbitan monolaurate aqueous solution and subjected to compression dehydration twice and dried in a hot air dryer at 60 ° C. for 1 hour to obtain a comparative porous water-absorbing crosslinked polymer (3). . The comparative porous water-absorbing crosslinked polymer (3) had a water absorption rate of 42 g / g and a water absorption rate of 20 minutes.
[0043]
【The invention's effect】
According to the present invention, it is possible to provide a novel porous water-absorbing crosslinked polymer that can significantly improve the water absorption characteristics such as the water absorption rate and the water absorption ratio and can maintain the water absorption characteristics even after long-term storage.
[Brief description of the drawings]
FIG. 1 is an IR of a porous hydrophobic crosslinked polymer (a).
FIG. 2 is an IR of the porous water-absorbing crosslinked polymer (1) of the present invention after hydrolysis.
Claims (5)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP34492196A JP3699225B2 (en) | 1996-12-25 | 1996-12-25 | Porous water-absorbing crosslinked polymer and process for producing the same |
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| Application Number | Priority Date | Filing Date | Title |
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| JP34492196A JP3699225B2 (en) | 1996-12-25 | 1996-12-25 | Porous water-absorbing crosslinked polymer and process for producing the same |
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| Publication Number | Publication Date |
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| JPH10182708A JPH10182708A (en) | 1998-07-07 |
| JP3699225B2 true JP3699225B2 (en) | 2005-09-28 |
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| JP2021106648A (en) * | 2019-12-27 | 2021-07-29 | ユニ・チャーム株式会社 | Absorbent article |
| JP7657890B2 (en) | 2023-11-09 | 2025-04-07 | ユニ・チャーム株式会社 | Absorbent articles |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US6573305B1 (en) * | 1999-09-17 | 2003-06-03 | 3M Innovative Properties Company | Foams made by photopolymerization of emulsions |
| WO2001027165A1 (en) * | 1999-10-08 | 2001-04-19 | The Procter & Gamble Company | APPARATUS AND PROCESS FOR IN-LINE PREPARATION OF HIPEs |
| JP4601812B2 (en) * | 1999-12-13 | 2010-12-22 | 株式会社日本触媒 | Method for producing porous crosslinked polymer |
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| JP2021106648A (en) * | 2019-12-27 | 2021-07-29 | ユニ・チャーム株式会社 | Absorbent article |
| JP7467115B2 (en) | 2019-12-27 | 2024-04-15 | ユニ・チャーム株式会社 | Absorbent articles |
| JP7657890B2 (en) | 2023-11-09 | 2025-04-07 | ユニ・チャーム株式会社 | Absorbent articles |
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| JPH10182708A (en) | 1998-07-07 |
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