PRESSURE-RESISTANT POLYESTER CONTAINER AND PROCESS FOR PRODUCING THE SAME
A pressure-resistant polyester container having a multilayer structure comprising inner and outer layers of a polyester resin and at least one intermediate layer of a functional resin, wherein in the container body portion, the inner layer of the polyester resin has a crystallinity of not less than 23%, the outer layer thereof has a crystallinity of not less than 18%, the average value of the crystallinity of the inner layer and the crystallinity of the outer layer is not less than 24%. The pressure-resistant polyester container effectively prevents whitening even after the passage of time and features excellent transparency despite of using, as an intermediate layer, a functional resin composition obtained by blending a functional resin with a clay. The invention, further, provides a process for producing the same.
1 . A pressure-resistant polyester container having a multilayer structure comprising inner and outer layers of a polyester resin and at least one intermediate layer of a functional resin, wherein in the container body portion, the inner layer of the polyester resin has a crystallinity of not less than 23%, the outer layer thereof has a crystallinity of not less than 18%, the average value of the crystallinity of the inner layer and the crystallinity of the outer layer is not less than 24%, and a clay is dispersed in the functional resin.
2 . The pressure-resistant polyester container according to claim 1 , wherein said functional resin contains a polymetaxyleneadipamide or an ethylene/vinyl alcohol copolymer as abase material resin.
3 . A process for producing a pressure-resistant polyester container by biaxially stretch-blow-molding a multilayer preform which comprises inner and outer layers of a polyester resin and at least one intermediate layer of a functional resin in which a clay is dispersed, wherein said multilayer preform is biaxially stretch-blow-molded being heated at a temperature of 110 to 120° C. so as to mold a multilayer container in which in the container body portion, the inner layer of the polyester resin has a crystallinity of not less than 23%, the outer layer thereof has a crystallinity of not less than 18%, and the average value of the crystallinity of the inner layer and the crystallinity of the outer layer is not less than 24%.