A sealing gasket for closure, made of a polyurethane elastomer obtained by reacting the following (A) and (B):
(A) a polyisocyanate component having an isocyanate group content of 5 to 38% by weight and average 2 to 3 functional groups, obtained by modifying an aliphatic isocyanate and/or an alicyclic isocyanate, and
(B) a polyol component having a hydroxyl value of 20 to 350 mgKOH/g and average 2 to 3 functional groups; and a process for producing a closure using such a sealing gasket.
The closure sealing gasket made of a polyurethane elastomer, obtained by the present invention, when used for a closure (e.g. a metal closure of food container), resists yellowing by ultraviolet light, has a strength at least equal to those of sealing gaskets produced from an aromatic isocyanate and, moreover, excellent rubber properties, is low in dissolution in liquid foods contained in the food container, and promises sufficient sealability.
The process for producing a closure according to the present invention is high in productivity and can use the production facilities for other materials such as polyvinyl chloride resin and the like.
一种用于封闭的密封垫片,由聚
氨酯弹性体制成,聚
氨酯弹性体是由以下(A)和(B)反应而成:
(A) 通过改性脂肪族
异氰酸酯和/或脂环族
异氰酸酯而获得的多
异氰酸酯组 分,其
异氰酸酯基含量为 5 至 38%(重量百分比),平均具有 2 至 3 个官能团,以及
(B) 具有 20 至 350 mgKOH/g 的羟值和平均 2 至 3 个官能团的多元醇组分;以及使用这种密封垫片生产封口的工艺。
本发明获得的由聚
氨酯弹性体制成的封口密封垫片在用于封口(例如食品容器的
金属封口)时,可防止紫外线照射变黄,其强度至少等于由芳香族
异氰酸酯制成的密封垫片的强度,而且具有优异的橡胶性能,在食品容器所含液体食品中的溶解度低,并保证足够的密封性。
根据本发明生产密封垫的工艺生产率高,可以使用其他材料(如聚
氯乙烯树脂等)的生产设备。