JPH0421704B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a polyester resin composition suitable as a raw material for polyester biaxially stretched blow containers. Specifically, the present invention relates to a polyester resin composition that exhibits less oligomer adhesion to a molded product during injection molding into a polyester biaxially stretched blow container. Containers made of polyester, especially biaxially stretched blow containers made of polyethylene terephthalate, have been praised for their excellent mechanical properties, transparency, and gas barrier properties, and are being used in a wide range of applications as containers for seasonings, cosmetics, carbonated drinks, etc. ing. To produce this polyester biaxially stretched blow container, a preform (hereinafter referred to as a preform) is usually formed by injection molding, and then biaxially stretched and blown by heating. At the stage of manufacturing a preform by injection molding, if molding continues for a long time, oligomers in the polyester resin will adhere to the mold and the preform. Biaxially stretched blown containers obtained from preforms to which oligomers are attached will suffer from loss of transparency and commercial value as containers. Continuous molding is possible by wiping the mold with acetone, but wiping the mold at regular intervals greatly reduces productivity. The inventors of the present invention have focused on such problems, and have arrived at the present invention as a result of intensive studies aimed at obtaining a polyester composition that reduces the amount of oligomers attached to preforms and, ultimately, to containers. That is, the present invention uses one or more compounds selected from aliphatic monocarboxylic acids having 8 to 32 carbon atoms, esters thereof, metal salts thereof, and liquid paraffin.
The present invention relates to a polyester resin composition for biaxially oriented blow containers that contains 10 to 1000 ppm and is subjected to solid phase polymerization so that the oligomer content is 1% or less. Hereinafter, to explain the present invention in more detail, the polyester referred to in the present invention means a polyester having ethylene terephthalate as a main repeating unit, and preferably 5 mol% or less of the total acid component.
In amounts of 3 mol% or less, phthalic acid, isophthalic acid,
Dicarboxylic acids such as hexahydrophthalic acid, naphthalene dicarboxylic acid, adipic acid, and sebacic acid, polycarboxylic acids such as trimellitic acid and pyromellitic acid, or oxybenzoic acids such as p-oxybenzoic acid are used as acid components. It is possible to use In addition, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol in an amount of 5 mol% or less, preferably 4 mol% or less of the total alcohol component. It is also possible to use glycols such as , diethylene glycol, triethylene glycol, cyclohexanedimethanol, polyhydric alcohols such as trimethylolpropane, triethylolpropane, pentaerythritol. The polyester is generally produced by a known method. For example, by performing a transesterification reaction,
Either a two-step method in which a polyester oligomer is obtained and then a polycondensation reaction is performed, or a direct esterification reaction may be used, and any known catalyst system may be used. In addition, additives such as stabilizers, color tone improvers, and colorants that are commonly used in the production thereof may also be included as necessary. The polymerization degree of polyester is phenol and 1,
The intrinsic viscosity when measured at 30℃ in a solvent with a polymerization ratio of 1:1 with 1,2,2-tetrachloroethane is
It is desirable that it is 0.5 or more. The solid phase polymerization referred to in the present invention is also carried out by a known method, and typically polyester resin chips produced by melt polymerization are heated at a high temperature, e.g., 170°C, under reduced pressure or under an inert gas such as nitrogen. This is carried out by maintaining the temperature above the melting point and below the melting point, preferably between 190°C and 240°C for several hours to several tens of hours. By performing solid phase polymerization in this manner, it is possible to increase the intrinsic viscosity and reduce the amount of acetaldehyde and oligomers in the chips. The amount of oligomer in chips obtained by melt polymerization is usually about 1.5 wt%, but by performing solid phase polymerization it can be reduced to 1 wt% or less, preferably 0.5 wt%.
The content can be further preferably set to 0.3 wt% or less. A polyester containing 0.5 wt% or more of oligomers has a poor effect of preventing the adhesion of oligomers even when used as a composition containing an aliphatic monocarboxylic acid or the like according to the present invention. In the present invention, the above polyester has 8 to 8 carbon atoms.
One or more selected from 32 aliphatic monocarboxylic acids, their esters, their metal salts, and liquid paraffin must be added. Examples of aliphatic monocarboxylic acids having 8 to 32 carbon atoms include capric acid, palmitic acid, stearic acid, behenic acid, and monothanic acid. Examples of the ester include glycerol stearate, butanediol-1,3-montanate, and ethylene glycol mono- or diester montanate. Further, examples of the metal salt include calcium stearate, magnesium stearate, sodium stearate, zinc stearate, calcium palmitate, and the like. Particularly preferred are alkali metal salts and alkaline earth metal salts. As the liquid paraffin, commercially available paraffin that is liquid at room temperature can be used. The amount of these compounds added is 10 to 1000 ppm, preferably 10 to 500 ppm, based on the polyester resin.
More preferably, it is 10 to 100 ppm. If the amount added is less than 10 ppm, no effect will be obtained in preventing oligomer adhesion, and if it exceeds 1000 ppm, no further effect will be obtained, and conversely, the intrinsic viscosity of the molded product will be reduced. There is a decrease in transparency and a decrease in transparency. Generally, it is desirable to add as little amount of such compounds as possible. These compounds can be added at any stage before molding the polyester resin. For example, during melt polymerization of polyester resin,
It can be added to the polymerization pot, or added and mixed to the chips before or after solid-phase polymerization to adhere to the surface of the chips, and the chips and the compound can be passed together through an extruder. It is also possible to produce a so-called masterbatch containing a high concentration of the compound and use it by blending it with chips that do not contain the compound. In this case, the value after blending is used as the amount of the compound added. The resin obtained in the present invention is molded into a biaxially stretched blow container. The molding process is a known method in which resin is melted at 280°C to 300°C by an injection molding machine and injected into a mold to form a preform. This preform is heated at 90° to 100°C and longitudinally stretched using a stretching rod in a blow mold at the same time.
A biaxially stretched blown container is formed by blowing at a pressure of cm ² to several kg/cm ² . EXAMPLES The present invention will be described in more detail with reference to Examples below, but the present invention is not limited to the following Examples unless the gist thereof is exceeded. Example 1 100 ppm of behenic acid was added to a polyethylene terephthalate resin with an intrinsic viscosity [η] of 0.78 and an oligomer content of 0.2 wt% by solid phase polymerization.
After dry blending, vacuum drying was performed at 160°C for 6 hours. Using an injection molding machine IS60B manufactured by Toshiba Machine Co., Ltd., a preform with a basis weight of 52 g and a wall thickness of 4 mm was molded, and the effect of preventing oligomer adhesion was evaluated by the number of injections until oligomers started to adhere to the molded product.
Even after continuous injection molding 400 times, no oligomers were observed to adhere to the molded product. The results are shown in Table-1. Examples 2 to 6 Evaluations were conducted in the same manner as in Example 1, with the additives changed to calcium stearate, magnesium stearate, Hoechstwax E (manufactured by Hoechst, trade name), and liquid paraffin. 400 consecutive
No oligomers were observed to adhere to the molded product even after injection molding, indicating that the molded product was effective in preventing oligomer adhesion. The results are shown in Table-1. Comparative Example 1 A polyethylene terephthalate resin produced by melt polymerization and having an intrinsic viscosity [η] of 0.73 and an oligomer content in the chip of 1.5 wt% was evaluated in the same manner as in Example 1. The results are shown in Table-1. Comparative Example 2 Calcium stearate was added to the chips of Comparative Example 1, and evaluation was performed in the same manner as in Example 1. Although some effect was observed, it was insufficient for use in bottles. The results are shown in Table-1. Comparative Example 3 The chips of Example 1 were evaluated in the same manner as in Example 1 without any additives. The number of injections is increased compared to Comparative Example 1. The results are shown in Table-1. Comparative Examples 4 to 6 Compounds shown in Table 1 were added to the chips of Example 1, and evaluation was performed in the same manner as in Example 1. The results are shown in Table-1.

【table】

[Table] (Example of manufacturing biaxially stretched blow container) The preform of the 400th shot obtained in the example and the oligomer attached
A biaxially stretched blow container was manufactured from the 200th shot preform. The biaxial stretching blow machine is self-made and uses a far-infrared heater to heat the preform. After heating the preform for 80 to 90 seconds, the body diameter is 80φ and the capacity is
The preform was longitudinally stretched and simultaneously blown at a blowing pressure of 20 Kg/m ² in a 1 liter bottle blow mold. Observation of the obtained bottles reveals that the bottles using the preforms obtained in the examples have good transparency, but the bottles using the preforms obtained in the comparative examples have cloudy areas where oligomers are attached, and the transparency is poor. It was damaged.

Claims (1)

[Claims] 1 Contains 10 to 1000 ppm of one or more compounds selected from aliphatic monocarboxylic acids having 8 to 32 carbon atoms, esters thereof, metal salts thereof, and liquid paraffin, and the content of oligomers is 1% or less. A polyester resin composition for biaxially stretched blow containers that has been subjected to solid phase polymerization.