JPS6134458B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to polyester compositions. More specifically, the present invention relates to a polyester composition containing a low acetaldehyde content, which is made by blending a compound having a carboxylic acid anhydride group with a polyester containing ethylene glycol as the main glycol component. Polyesters containing ethylene glycol as the main glycol component, such as polyethylene terephthalate, are widely used in fibers, films, etc., but in recent years they have been used for food and drink products in the form of bottles, pots, etc. However, when this polyester is molded into a bottle, for example,
If the container is left in a tightly closed state, the odor of acetaldehyde will accumulate inside the container, causing problems such as the odor being transferred to the food and drinks inside, and the taste changing. In order to manufacture a bottle free of such problems, the inventor of the present invention has conducted extensive research to improve the material polyester, and as a result, has developed a polyester that is made by blending a specific amount of carboxylic acid anhydride with polyester whose main glycol component is ethylene glycol. The composition is
The present invention was achieved based on the discovery that a polyester molded article with a sufficiently low acetaldehyde content can be obtained by producing less acetaldehyde during molding. That is, in the present invention, a compound having carboxylic acid anhydride groups and no halogen atoms in a polyester having ethylene glycol as the main glycol component is added in an amount such that the acid anhydride groups have a concentration of 1 to 500 g equivalent/10 ⁶ g polymer. This invention relates to a polyester composition containing less than 20 ppm of acetaldehyde. In the present invention, polyester containing ethylene glycol as the main glycol component refers to polyester of aromatic dicarboxylic acid and ethylene glycol,
In particular, polyethylene terephthalate is the main target, but some or all of terephthalic acid can be used, for example, isophthalic acid, naphthalene dicarboxylic acid, diphenyl dicarboxylic acid, diphenoxyethane dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid. Other aromatic dicarboxylic acids and or some of the ethylene glycols such as trimethylene glycol, tetramethylene glycol, hexamethylene glycol, decamethylene glycol, neopentylene glycol, etc.
1,1-cyclohexane dimethylol, 1,4-
Cyclohexane dimethylol, 2,2-bis(4
-β-hydroxyethoxyphenyl)propane,
It may also be a polyester substituted with other glycols such as bis(4-β-hydroxyethoxyphenyl) sulfone, and a portion of the aromatic dicarboxylic acid component of the polyester may be substituted with, for example, hexahydroterephthalic acid or hexahydroisophthalic acid. Alicyclic dicarboxylic acids such as acids, aliphatic dicarboxylic acids such as adipic acid, zeltic acid, azelaic acid, etc., p-β-hydroxyethoxybenzoic acid, ε-
It may also be a polyester substituted with other difunctional carboxylic acids such as oxyacids such as oxycaproic acid. The polyester may also contain one or more polyfunctional compounds such as pentaerythritol, trimethylolpropane, trimellitic acid, trimesic acid and functional derivatives thereof and/or o-benzoylbenzoic acid, to the extent that the polyester is substantially linear.
It may be a copolymer of one or more monofunctional compounds such as methoxypolyethylene glycol and functional derivatives thereof. Polyester has stabilizers (e.g. heat, UV,
Although additives such as oxygen stabilizers), pigments, mold release agents, and nucleating agents may be added, it is preferable to use highly stable additives if possible. Such polyesters can be produced by a production method that normally uses a melt polymerization method or a melt polymerization method followed by a solid phase polymerization method. The polyester preferably has an intrinsic viscosity of 0.5 to 1.0, preferably 0.6 to 0.9. The composition of the present invention can be obtained by blending a compound having a carboxylic acid anhydride group with such polyester, and the blending ratio of the compound is 1 to 500 g equivalent of acid anhydride group per 10 ⁶ g of polyester, preferably is the ratio of 10 to 100 g equivalent. With this blending ratio, a polyester composition with an acetaldehyde content of less than 20 ppm can be obtained. If the ratio is higher than this, the effect of reducing the acetaldehyde content is saturated, and not only is the effect less increased than the amount added, but the resulting polyester composition is undesirably reduced in delivery strength and impact strength. If the ratio is less than this, the effect of reducing the acetaldehyde content will not be sufficient, making it difficult to achieve the object of the present invention. Examples of the compound having a carboxylic acid anhydride group and no halogen atom used in the present invention include aromatic monocarboxylic acids such as benzoic acid, toluic acid, and naphthoic acid, and aliphatic monocarboxylic acids having 2 to 40 carbon atoms. acids, aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, naphthalene dicarboxylic acids, diphenoxyethane dicarboxylic acids, etc., carbon number 2
Intermolecular anhydrides of carboxylic acids or polymers thereof obtained from ~20 aliphatic dicarboxylic acids, etc., intramolecular anhydrides of carboxylic acids such as phthalic anhydride, succinic anhydride, maleic anhydride, trimellitic anhydride, pyromellitic anhydride, etc. Things can be given. Among these, intermolecular anhydrides are particularly preferred. Specifically, polyacid anhydrides obtained from dicarboxylic acids such as benzoic anhydride, toluic anhydride, naphthoic anhydride, and dicarboxylic acids such as terephthalic acid, isophthalic acid, adipic acid, sebacic acid, azelaic acid, and decanedicarboxylic acid. etc. can be mentioned. These carboxylic acid anhydride group-containing compounds can be mixed with polyester by adding them at the final stage of the polyester melt polymerization reaction, by attaching them to polyester chips and molding them, or by melt-mixing the two using an extruder. is used as a simple method, but any other method can be used as long as it has the effect of incorporating a compound having a carboxylic acid anhydride group into the polyester. To reduce the acetaldehyde content to less than 20 ppm, for example, heat treatment at a temperature of 170°C or higher and lower than the melting point for 30 minutes to 5 minutes.
This can be achieved by placing it under an inert gas or vacuum for a period of time. The polyester composition thus obtained has an acetaldehyde content of less than 20 ppm, and when molded into containers, cups, packaging films, etc., molded products with a low acetaldehyde content are obtained. These have no odor, and furthermore, they do not change the taste or add odor to the contents during use, making them useful for foods and drinks. The present invention will be explained in detail with reference to Examples below. In the examples, "part" indicates "part by weight", and the intrinsic viscosity "η" was measured in orthochlorophenol at 35°C. Example 1 Chips of polyethylene terephthalate with [η] = 0.75 obtained by esterifying terephthalic acid and ethylene glycol without a catalyst and polymerizing under high vacuum using germanium oxide as a polycondensation catalyst were heated at 160°C.
Dry in a nitrogen stream for 2 hours, then dry the chips at 100%
1.1 parts per part of benzoic anhydride were mixed. The resulting mixture was heated further to Ruder (cylinder temperature 220
It was extruded into chips at ℃). The acetaldehyde content of this chip is 65ppm
It was hot. After drying this extruded chip at 220°C for 1 hour, [η] and acetaldehyde content were measured; [η] was 0.65, and the acetaldehyde content was
It was 8ppm. This extruded chip was molded into a bottle using an injection blow molding machine at an injection cylinder temperature of 280°C. The acetaldehyde content determined by crushing this bottle is
It was 8ppm. The acetaldehyde content of the bottle formed by drying at 160°C for 2 hours instead of 1 hour at 220°C is
It was 57ppm. On the other hand, a polyethylene terephthalate bottle obtained by carrying out the same procedure as above except that benzoic anhydride was not used contained 28 ppm of acetaldehyde. The acetaldehyde content can be determined by pulverizing the polymer chip or its molded product into particles smaller than 4 meshes, heating it at 200°C for 2 hours in a helium stream, adding acetaldehyde, trapping the acetaldehyde with liquid nitrogen, and measuring it by gas chromatography. This is the value of the amount of acetaldehyde measured with E based on the weight of the polymer. Comparative Example 1 Extruded chips were obtained in the same manner as in Example 1 except that benzoic anhydride was changed to 3.0 parts. This product was dried in the same manner as in Example 1, and an attempt was made to mold it into a bottle by injection blow molding, but it broke and molding could not be completed. Example 2 A bottle was obtained in the same manner as in Example 1 except that the acid anhydrides shown in the following table were added in place of benzoic anhydride. The acetaldehyde content of this bottle is shown in the table below. 【table】

Claims (1)

[Claims] 1 A polyester containing ethylene glycol as the main glycol component is blended with a compound having a carboxylic acid anhydride group and no halogen atom in an amount such that the acid anhydride group has a concentration of 1 to 500 g equivalent/10 ⁶ g polymer. A polyester composition for forming food/beverage or cosmetic containers with an acetaldehyde content of less than 20 ppm.