Abstract: A multi-layer polyester container comprising inner and outer layers of a polyester resin and at least one intermediate layer of a functional resin or a functional resin composition, wherein a difference of tan ? of the inner polyester layer at 80° C. and 60° C. is 0.035 or less in the measurement of the dynamic viscoelasticity (DMS) thereof at 0.5 Hz. Even when the functional resin or the functional resin composition having a large draw stress is used as an intermediate layer, therefore, excellent transparency is obtained while effectively exhibiting the function such as barrier property possessed by the functional resin or the functional resin composition.

Abstract: [Problems] To provide a package excellent in barrier property, transparency and appearance, and having a layer forming an island-in-the-sea structure of a small domain diameter and a high domain density without impairing the formability into containers. [Means for Solution] A package having a mixed layer of a mixture of a base resin and a functional resin composition containing inorganic fine particles, wherein the mixed layer forms an island-in-the-sea structure in which the base resin is forming a continuous phase and the functional resin composition is forming discontinuous phases, and the area percentage of the functional resin composition in cross section is 25 to 55%.

Abstract: A multilayer polyester container comprising inner and outer layers of a polyester resin and at least one intermediate layer of a polyamide resin, wherein in the container body portion, the intermediate layer of the polyamide resin has an exothermic peak starting temperature due to crystallization of not lower than 96° C. as measured by a differential scanning calorimetry, and a clay is dispersed in the polyamide resin, effectively preventing whitening of the intermediate layer even after the passage of time and featuring excellent transparency despite of using, as an intermediate layer, a polyamide resin composition obtained by blending the polyamide resin with the clay.

Abstract: A multi-layer polyester container comprising inner and outer layers of a polyester resin and at least one intermediate layer of a functional resin or a functional resin composition, wherein a difference of tan ? of the inner polyester layer at 80° C. and 60° C. is 0.035 or less in the measurement of the dynamic viscoelasticity (DMS) thereof at 0.5 Hz. Even when the functional resin or the functional resin composition having a large draw stress is used as an intermediate layer, therefore, excellent transparency is obtained while effectively exhibiting the function such as barrier property possessed by the functional resin or the functional resin composition.

Abstract: 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.