Vinylpyrrolidone (co)polymer

#A. Technical Field

#The present invention relates to a vinylpyrrolidone (co)polymer. More particularly, the present invention relates to a novel vinylpyrrolidone (co)polymer excellent in the color tone and the thermal yellowing resistance despite its low molecular weight.

#B. Background Art

#An amount of 65 parts of ion-exchanged water was added into a reaction vessel, and then its temperature was raised to a reflux temperature (100° C.) while blowing nitrogen thereinto. Under stirred conditions, 30 parts of N-vinylpyrrolidone and a solution (as prepared by dissolving 1.5 parts of dimethyl 2,2′-azobis(2-methylpropionate) (V-601, made by Wako Pure Chemical Industries, Ltd.) into 5 parts of ethanol) were dropwise added thereinto at the same time for 2 hours each. After the dropwise addition had been completed, the reaction was further continued for 2 hours with the reflux state still kept, thus obtaining a poly(vinylpyrrolidone) (PI) having a K value of 30.

#Incidentally used as the above N-vinylpyrrolidone was N-vinylpyrrolidone (1) as obtained by a process including the steps of: carrying out a reaction of γ-butyrolactone with monoethanolamine to thus form N-hydroxyethylpyrrolidone wherein the γ-butyrolactone was a derivative from maleic anhydride; and then carrying out a gas phase dehydration reaction of the resultant N-hydroxyethylpyrrolidone.

#Specifically, the N-vinylpyrrolidone (1) was synthesized in the following way. That is to say, maleic anhydride and hydrogen were supplied at the rates of 0.01 mol and 1 mol respectively per hour into a reaction tube as packed with a copper chromite catalyst, and then they were caused to react together at 265° C. to obtain γ-butyrolactone. An equimolar amount of monoethanolamine was added to the resultant γ-butyrolactone, and then their reaction was carried out at 250° C. in an autoclave to prepare N-hydroxyethylpyrrolidone. Next, a reaction tube was packed with a catalyst as prepared from lithium nitrate and silicon oxide, and then a raw gas (as prepared by diluting the N-hydroxyethylpyrrolidone with nitrogen to such an extent that the partial pressure of the N-hydroxyethylpyrrolidone would be 1.01×104 kPa (76 mmHg)) was supplied thereinto at a space velocity of the N-hydroxyethylpyrrolidone of 200 h−1 to make the N-hydroxyethylpyrrolidone react at a reaction temperature of 400° C. under an ordinary pressure. Thus the N-vinylpyrrolidone (1) was synthesized.