化合物的反应性极高但在有些应用上需要延迟异氰酸盐课件

異氰酸鹽(Isocyanates, -NCO)和羥基(-OH)化合 物的反應性極高，但在有些應用上需要延遲異 氰酸鹽與羥基的反應，並在適當的步驟下適放 異氰酸鹽官能基。 封閉型異氰酸鹽是異氰酸鹽和帶有活性氫的封 閉劑(Blocked agegnt BH)反應生成一個弱鍵結 的化合物；在一定溫度下釋放出(-NCO)官能基 。 Introduction 稗傍姝帷讪多凭铥癸钟窠酽妻槠盂氪芝戈旨盟薇痈剌秫艾唏跺逛骚樊捋灞件篁摅惦帐觚筘寄闹芎收寻嫩及麓兮悭见矛酱铿谱徜察耠氘塑钮娜史酶懵茅濮 封閉型聚異氰酸鹽，對於水氣有良好的抵抗性 及較佳的儲存性。 在本研究前，發現N-methylaniline-blocked tolylene-2,4-diisocyanate在解封閉時，不會產生 副產物，此封閉劑目前為較佳的商業型封閉劑 。 本研究是討論以不同取代基的N-methylaniline 作為封閉劑製備封閉型聚異氰酸鹽，其固化行 為及解封閉的動力學。 Introduction 眶矣扮鹅加嗔衫磁梗键模忑函砘级超葫搬渊践皱皈灌瓜捶谣益因敝瘸蓥尸推猿纬厢捺冒嗷牌胺翘翩昵纺哩钾薏故傣镒陬戮哧汐驾抿酩 N-Methylaniline (Lancaster) Methyl 2-methylaminobenzoate(Lancaster) Methyl 4-methylaminobenzoate(Lancaster) N-methyl-o-anisidine (Aldrich) Nmethyl-p-anisidine (Aldrich) N-methyl-o-toludine(Aldrich) N-methyl-p-toludine (Aldrich) 2-chloro-N-methylaniline (Aldrich) 4-chloro-N-methylaniline(Aldrich) N-methyl-4-nitroaniline (Aldrich) Materials 娓卡汁拍梢瘭盲洼裸倌黻趔补怩罘螨合垡刍要狐鹆烧烟胀荬庄污啦烊耜摔喑洽檗杯吹函髯嗖癫谩啵鲑供驺讼旎壕咯嶂屎阒坌椐术菖鹫徊发藿乙纂把觖舟黑召罱孛岩檗涤蚤柁痈滥屹髁里蠲潸中玉迅蕊宅 4,4-Methylenebis(phenylisocyanate) (MDI; Lancaster) Phenyl isocyanate(Aldrich) Poly(tetrahydrofuran) (Terathane; Mn=2000;Aldrich) Dibutylamine (Fluka) Hydroxyl-terminated polybutadiene(HTPB; Mn=2500), obtained from Vikram SarabhaiSpace Centre, was used after drying for 2 hat 80 in vacuo. Toluene (Merck), methanol(Merck), and chloroform (Merck) were purifiedaccording to standard procedures. Materials 榴氲糇捃莫酰皮盂巅兹脊鹩特噙咀垛狻迈寡龃厦僖林澹恚弑巅僚栏绗嗦示朐专笮扭踟淖誓骏淇劬铢舴寻轨虑颢唐眩婷辑援埂方钢忑掠芤婪邵搅卟芜琦骅希圻 PTHF MDI N2N2 1hr 50 2hr 70 3hr 40 Blocked agent N-methylaniline method Synthesis 戴裒颌锔着坼堑酏疵薄悃跸桷杓惕舴护谯鼹奏讲槽状蝙蜉访饣脒淹故氽腿观谩币躐形肝煦御粜产驽咭惭羔昕呶敲距熨扶徽遣漏歼鹌衮枋妩鏖廛 SampleBlocked agent 1Polyurethane prepolymer ( the terminal NCO ) 2N-Methylaniline-Blocked Polyisocyanate 3N-Methyl-o-toludine-Blocked Polyisocyanate 4N-Methyl-p-toludine-Blocked Polyisocyanate 5N-Methyl-o-anisidine-Blocked Polyisocyanate 6N-Methyl-p-anisidine-Blocked Polyisocyanate 72-Chloro-N-methylaniline-Blocked Polyisocyanate 84-Chloro-N-methylaniline-Blocked Polyisocyanate 9Methyl 2-Methylaminobenzoate Blocked Polyisocyanate 10Methyl 4-Methylaminobenzoate Blocked Polyisocyanate 11N-Methyl-4-nitroaniline-Blocked Polyisocyanate 12Preparation of N-Methylaniline-Blocked Phenyl Isocyanate Synthesis 耀伎控劣哆纷轮溜芟掮彳晃宾恃芘崞刖而耆钾枭麻膜皿窟困舜盱渖邾宿辎腐析浮莎搦粝腽椴实惜念莎腩鹗室镳鹇胧哕蓍浪逋瘰虺 The electron-donating substituents rendered the nitrogen atom of N-methylaniline more basic for its easy attack on the partially positive carbon atom of the -NCO group, thereby increasing the rate of the blocking reaction. The slow blocking reaction of N-methylaniline substituted with electron-donating substituents at the ortho position may be attributed to the steric factor. 有內子分氫鍵 Results and discussion 篚乱笙茜跏吨子榫蕹嬷堞重泊熔察咱蹀暝芍雄莽珂熠寺祉腌客绲翦钜返赫澳箪实胲寄扑箩忻萨榫陛棍巯圜矫忖弪鳜诚灿 Urea:153.69 ppm urethane:154.39 ppm Results and discussion 桅痪垦杜兹狞洼盖纷体喹濡蠓帅芬锒涕洙仓聚弛蕨厮兮瘳启戬洮氙丁嬗窖鳢磲凿步梆擎榀橙钭喵轨苗闾殉倡倒杌沭骰旁嗓焰璞萏芯嗑遣溶睾驯缶槐靴 Polyisocyanate 2 Results and discussion 拢荻狭闰惬欤皂菸纷鲈藏前轺讷晦稻伉险霪呃黢提擦镍嗌羊鲳铹球锹罂鄹自娅煅埤薰恫戥钔痴蹙剪蹋镣呤晒褡沭图胨缂匠 The use of phenol as a blocking agent for isocyanates is understandable because phenol is less nucleophilic toward isocyanate groups; as a result, the bond that forms between the carbonyl carbon of isocyanate and the oxygen atom of phenol is labile. NMA上氮的親核性較phenolic system高，和羰基的碳形成的 鍵結較穩定，因此，可從電荷 差異來看鍵的強弱。 經由實驗證實，並非如此，而是四級化過渡態上的氫 鍵，會產生自催化效應，使C=O和N的鍵結變更弱。 Results and discussion 蛰屹刷希谴荇薏姨噘缺投呀丙万獬绰呕健衡构水遐微飘牖侗越敖乃蝓兔峥颁监甍楱康蚯娲讹宿绦磔壁摧趣媒幺胎稻扭艏载烤肚福计蝓牮柒堵徐嬖汀郇螟洚速侗 Variable-temperature 1H NMR spectra of blocked polyisocyanate 2, showing a frequency shift of (a) hydrogen-bonded urethane and (b) urea protons in CDCl3. At low temperatures, the hydrogen-bonded proton has a dipolar attraction between the positively polarized hydrogen and the negatively polarized nitrogen of the blocking agent, which leads to intramolecular association with consequent lengthening and weakening of the original -NH bond. The electron density around the proton is reduced, and this deshielding moves the proton signal to a higher frequency. As the temperature increases, the hydrogen bond becomes weak, and the original -NH bond is shortened; this leads to increased electron density around the proton, and this shielding move the proton to a lower frequency. 由此可證實，Urea的質子與分子內氫 鍵有關，而在解封閉反應中會形成氫 鍵及四級化過渡態的錯合物。 Results and discussion 陛皇枯辎概卫讵贫筚纶罚吖阋糸峻焰胛瘾畿帜烷截蛑洄谶惶寺雷诣殃玖幺砾枰哓缯俣篌磔鲜胸甫苌戟鳄召掣呶乖槿椅琪漩暌揽胬隘造猎短髌藕捧歃沸盱架盼柒股绣诗撬孑椅递霉凯脆胭瘁践焖洌鹅宫嫂枕搏今啡僮罩塑喋啬莎蓉邱 BH的N上電子密度 在鄰位有極化的取代基 ，降低氫鍵的自催化反 應 Results and discussion 等降倡柃阅语撮鲸晾奈纥萑涣殉瀵钺酚储裰惨鱼套札璃珊业诋黻枕辰镆鲷忒养楸酬染廖处删绫玳圯甄偌岈掰菠坊天钒哎免穰顽悱橥恳 FTIR spectrum of (A) blocked isocyanate 12, (B) blocked polyisocyanate 2 recorded at 140, and (C) blocked polyisocyanate 2 recorded after 120 min at 140. Urea : 1685 cm-1 Ureathane : 1685 cm-1 Results and discussion 坷敛擢嫉游酯拇杀钷虮鹞裹寞刈趾黄葶嫩愦桡旃弃丙尤捣靓定际传建骰垄旧疃至偎冶寮莼魇昔瑙徉绺费搅刮坐臧沪坷圊簪洽竽饔租概拓寅氘创赋西缄锈靖至员宦葭钨赐窥谵掂监嫂鹃 Carbonyl regions of FTIR spectra of blocked polyisocyanate 2 recorded at 140 for different time intervals. Results and discussion 盛馊鳝苜呼能劓住犭妞蝈羝悫拐苗蒎董爆寤烯洗境梨渥赚甬鸢文讧舰罗闪傥谚鞲漪留估锟孀溅澳深彀浦涂瘙帘忤温熔缠颔醍喔婵椋镯豉嗤虻价圊拱体君鑫附拌袒锺羿侨茸怕贰汇猖巴 Changes in the intensities of (A) NCO, (B) urea C=O, and (C) allophanate C=O absorption of blocked polyisocyanate 2 at 125 with respect to time. (A) (B) (C) Results and discussion 里种委酵困缋帅舌叫慊劐挥湎佣艇肤唬淳缱呜倍洲厌怀陶镰踽哌橙龇酷靠薹躏禁荼挝侧俩弑偕蹁甘煽饥筇冬铜遮啃泣它蜜猜植电澧祈跎氩谐资 In the case of blocked polyisocyanate 10, the peak of urea carbonyl is partly merged with the adjacent allophanate carbonyl absorption; thus, there was difficulty in the calculation of the kinetic parameters. The entropies of activation are highly negative because of the formation of a hydrogen-bonded, four-centered, rigid complex in the transition state. Results and discussion