JPH0541500B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a biaxially stretched blow container made of polyester having a pearl-like surface luster. Biaxially stretched blow containers made of polyester, especially polyethylene terephthalate, have come to be widely used as containers for seasonings, cosmetics, carbonated drinks, etc. due to their excellent mechanical properties, transparency, chemical resistance, gas barrier properties, etc. . However, when looking at the appearance of containers, most containers are colorless and transparent or transparent and colored. However, in the field of cosmetic containers, where importance is placed on the appearance and decorative aspect of the container, containers with pearl-like surface luster are desired. Conventional techniques for obtaining pearl-like surface luster include adding pearl pigments and molding a mixture of specific thermoplastic resin compositions, as described in Japanese Patent Publication No. 46-31467 and Japanese Patent Application Laid-open No. 56-27328. There is a way to do it, but
There were drawbacks such as the toxicity of additives, cracks at the gate during injection molding, crystallization of the parison, peeling between layers, and the complexity of blending. The present inventor has arrived at the present invention as a result of studies aimed at improving the drawbacks of the above-mentioned conventional methods. That is, the present invention provides a container made of polyester containing polyethylene terephthalate as a main component, in which the transparency of the outer surface is better than the transparency of the inner surface over substantially the entire surface of the container body, and the haze value of the outer surface is lower than that of the inner surface. is 5% or less, and the haze value of the inner surface is
The present invention relates to a polyester biaxially stretched blow container having a pearl-like surface gloss of 30% or more. The polyester in the present invention includes a homopolymer consisting of terephthalic acid and ethylene glycol, and a copolymer obtained by copolymerizing terephthalic acid and ethylene glycol with another third component. Such copolymers are known and the third component is usually an aromatic dicarboxylic acid such as isophthalic acid or naphthalene dicarboxylic acid;
Oxycarboxylic acids such as p-hydroxybenzoic acid, alkylene glycols such as propylene glycol, tetramethylene glycol, and neopentyl glycol, and polyalkylene glycols such as polyethylene glycol are used. Preferably, the proportion of the third component in the copolymer is 30 mol% or less. Alternatively, it may be a blend of polyethylene terephthalate and another polyester resin having the above-mentioned copolymer component. Furthermore, commonly used additives such as stabilizers, color tone improvers, and colorants may also be included. In particular, the addition of coloring agents such as pigments and dyes that can maintain the transparency of the parison is useful when the colored parison is biaxially stretched and blown using the method described above. is obtained, and the decorative effect is increased, which is preferable. The polyester used in the present invention has an intrinsic viscosity of
0.6 or more, and the intrinsic viscosity of the resulting container is 0.57
It is preferable to set it as above. If the intrinsic viscosity is too low, mechanical strength problems will occur. The container having a pearl-like surface luster according to the present invention can be obtained by changing the transparency of the outer surface and the inner surface of the container so that the transparency of the outer surface is better than the transparency of the inner surface. Such a container having different transparency inside and outside can be manufactured as follows. In the process of heating and stretch-blowing the parison, the temperature of the inner surface of the parison is intentionally lowered by 10°C to 20°C than the normal stretching temperature, and the temperature of the outer surface of the parison is lowered to the normal drawing temperature, e.g. 85°C to 105°C. After heating to
A method in which biaxial stretch blowing is performed, and during stretch blowing, only the inside of the parison becomes white and stretched, while the outer surface remains transparent. To simplify this method, in the method of heating the parison from the outside, it is preferable to shorten the heating time compared to the normal heating time. In the hot parison method, a method in which cold air is blown onto the inner surface of the parison is preferable. Alternatively, heat the parison to 110°C from the inside.
The inner surface of the parison is heated to ~130°C to cause crystallization due to high temperature on the inner surface of the parison, and the outer surface of the parison is heated to a normal stretching temperature of 85°C to 105°C for biaxial stretching blowing, so that the inner surface becomes white. , a method for obtaining a container with a transparent outer surface, and the like. In the container of the present invention, it is necessary that the outer surface has better transparency than the inner surface over substantially the entire body, and the haze of the outer surface is 5% or less, more preferably 1% or less, and the haze of the inner surface is is more than 30%,
More preferably, it is 60% or more. Most preferably, the inner surface undergoes a whitening phenomenon while the outer surface maintains transparency. The container having a pearl-like luster obtained by the above method is an excellent container which is preferable in terms of food hygiene and has no peeling property between the front and back. The present invention will be explained in more detail below using Examples. Examples 1 to 2 and Comparative Examples 1 to 2 A colored masterbatch containing copper phthalocyanine blue and monoazo yellow pigments based on this polyethylene terephthalate was added to chips of polyethylene terephthalate having an intrinsic viscosity of 0.78 in a ratio of 15:1. The mixture was blended and vacuum dried at 160°C for 12 hours. From this resin, using Toshiba Machine's injection molding machine IS60B model, 25mmφ x 150mm
A transparent green parison measuring L x 4 mm was molded. This parison was heated from the outside with an infrared heater for the time shown in Table 1, and then stretched and blown to form a container with a body diameter of 110φ and a capacity of 2. However, the heating time value varies depending on the heater voltage, installation position, etc., and is not absolute. Table 1 shows the values of the haze of the container body measured using a haze meter manufactured by Nippon Denshoku Kogyo Co., Ltd. The haze on the outer surface of the container can be represented by the haze of Comparative Example 1 under normal stretch blowing conditions. Since the haze obtained in Comparative Example 1 is an extremely small value, it is considered that the haze values obtained in other examples are approximately equal to the haze value of the inner surface of the container.

[Table] The outer layer of the container obtained in Example 1 was transparent green, the inner layer was less transparent, and the container was green in color, almost silvery overall, and had pearly surface luster as a whole. The outer layer and inner layer of this container were extremely difficult to peel off. In Example 2, it is more translucent than in Example 1,
A container with a pearly surface luster was obtained. Comparative Example 1 is under conditions for molding a normal transparent stretch-blown container, and pearl-like surface gloss cannot be obtained. Comparative Example 2 has a slightly inferior transparency compared to Comparative Example 1, and no pearl-like surface luster is observed. Comparative Examples 3 to 4 After stretch blowing, while keeping the mold cooled at 10℃, the outer surface was rapidly cooled and
A container with a capacity of 2 was prepared in the same manner as in Comparative Example 1, except that air whose temperature was controlled to 0.degree. C. was blown into the container and the inner surface was slowly cooled for the time shown in Table 2. The test results for this container are shown in Table 2.

[Table] In Comparative Examples 3 and 4, transparent containers were obtained with no whitening of the inner surface, and no pearl-like surface luster was observed.

Claims (1)

[Claims] 1 A container made of polyester containing polyethylene terephthalate as a main component, in which the transparency of the outer surface is better than the transparency of the inner surface over substantially the entire surface of the container body, and the haze value of the outer surface is 5.
% or less, and a polyester biaxially stretched blow container having a pearl-like surface luster with a haze value of 30% or more on the outer and inner surfaces.