JPH0543782A - Polyester resin composition for container and container made thereof - Google Patents

Abstract

PURPOSE:To provide a polyester resin composition for container, composed of polyethylene terephthalate and a higher alcohol and giving a container having low acetaldehyde content and suitable as a container for drink. CONSTITUTION:The objective polyester resin composition for container is produced by compounding (A) 100 pts.wt. of a polyester resin containing ethylene terephthalate unit as main recurring unit and having an intrinsic viscosity of preferably 0.6-0.9dl/g with (B) 0.02-3 pts.wt. (preferably 0.1-2 pts.wt) of a higher alcohol, preferably a 10-35C saturated chain aliphatic alcohol (e.g. stearyl alcohol and cetyl alcohol) and, as necessary, a colorant, a filler, a lubricant, an ultraviolet absorber, etc. The addition of the component B is carried out e.g. by adding to a reaction system during the production of the component A or adding in the melt-molding of the component A. The obtained composition is molded to form a hollow vessel by extrusion blow-molding or injection blow-molding process, etc., or is extrusion molded to obtain a sheet, which is formed to a container such as tray.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polyester resin composition for a container and a container made of the resin composition. More specifically, the present invention relates to a polyester resin composition for containers, which gives a polyester container having a low content of acetaldehyde, and the container.

[0002]

2. Description of the Related Art In recent years, containers obtained by melt-molding polyester resins such as polyethylene terephthalate are excellent in transparency, mechanical properties, hygiene and economy, and are suitable for use in carbonated beverages such as cola and mineral water. It is widely available on the market as a beverage container. However, a polyester resin whose main repeating unit is ethylene terephthalate, typified by polyethylene terephthalate, usually undergoes thermal decomposition during melt polymerization and melt molding to generate acetaldehyde. When acetaldehyde is present in the container material, it elutes after filling the contents and adversely affects the taste and odor of the contents.Therefore, the amount of acetaldehyde present in the polyester container material is small. Has become. In particular, cola and mineral water are extremely susceptible to acetaldehyde, and the elution of acetaldehyde can even significantly impair the commercial value of these beverages, so there is a strong need for polyester containers with a lower acetaldehyde content. Is the reality.

As one method for reducing the amount of acetaldehyde in a container material made of a polyester resin whose main repeating unit is ethylene terephthalate, a polyester resin having a low acetaldehyde content is used as a polyester resin used for melt-molding the container. There is a way. For that purpose, it is known that it is effective to use a polyester resin obtained by solid phase polymerization. That is, by subjecting the polyester prepolymer obtained by the melt polymerization method to solid-phase polymerization under reduced pressure or under the flow of an inert gas, the degree of polymerization is increased while reducing the acetaldehyde content in the polyester prepolymer. Can be made However, even if the container obtained by subjecting the polyester resin obtained by such a solid-state polymerization method to melt molding, it is difficult to say that the content of acetaldehyde is necessarily at a sufficiently low level depending on the application, and the content of acetaldehyde is not included. It would be desirable to have a container polyester material that would provide even lower volume containers.

[0004]

One of the objects of the present invention is to provide a polyester material for containers which provides a polyester container having a further reduced content of acetaldehyde. Another object of the present invention is to provide a polyester material. The object is to provide a polyester container having a smaller quantity.

[0005]

According to the present invention, one of the above objects is to provide a polyester resin whose main repeating unit is ethylene terephthalate and the polyester resin 1.
This is achieved by providing a polyester resin composition for a container, which comprises 0.02 to 3 parts by weight of higher alcohol relative to 00 parts by weight. Further, according to the present invention, the above-mentioned other object is achieved by providing a container made of the polyester resin composition.

The polyester resin in the present invention contains ethylene glycol as a main component of the glycol component, preferably 70 mol% or more. Here, ethylene glycol as one of the glycol components also includes an ester-forming derivative thereof, and the ester-forming derivative is exemplified by ethylene oxide. As the polyester resin, a polyethylene terephthalate resin or a copolymerized polyester resin containing ethylene terephthalate as a main repeating unit is preferable because it gives a container having excellent mechanical properties and transparency. From this viewpoint, as the copolymerization component, dicarboxylic acids such as phthalic acid, isophthalic acid, hexahydrophthalic acid, naphthalenedicarboxylic acid, adipic acid and sebacic acid are preferably used in an amount of 10 mol% or less of the total acid component; p-oxybenzoic acid. Carboxylic acids such as oxy acids such as acids and preferably 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol in an amount of up to 10 mol% of the total alcohol component. Examples include diols such as 1,9-nonanediol, neopentyl glycol, diethylene glycol, triethylene glycol, and cyclohexanedimethanol; and alcohols such as trivalent or higher alcohols such as trimethylolpropane and pentaerythritol.

The polyester resin used in the present invention can be produced by a conventional method. That is, a glycol raw material mainly composed of ethylene glycol; a monomer such as a dicarboxylic acid raw material mainly composed of a terephthalic acid lower alkyl ester such as terephthalic acid or dimethyl terephthalate is subjected to an esterification reaction or a transesterification reaction, and the obtained low polymer is melted. The polyester resin according to the present invention can be obtained by solidifying the prepolymer obtained by polymerization to obtain a chip having an arbitrary shape such as a die shape or a column shape, and then solid-phase polymerizing the chip. Melt polymerization is preferably carried out in the presence of an ester polymerization catalyst such as germanium dioxide under reduced pressure at 250 to 290 ° C. The intrinsic viscosity of the prepolymer produced by melt polymerization is preferably in the range of 0.35 to 0.70 dl / g. In the esterification reaction, transesterification reaction, or melt polymerization, a tetraalkylammonium hydroxide such as tetraethylammonium hydroxide, a triethyleneamine, or a diethylene glycol by-product inhibitor such as an organic amine such as triethylamine may be added to the reaction system. Good. The amount of acetaldehyde in the container may be further reduced by adding the diethylene glycol byproduct inhibitor. 1 prepolymer chip
It is preferable to carry out solid-state polymerization after preliminary drying at a temperature of 90 ° C. or lower. The solid phase polymerization is preferably carried out by flowing the prepolymer chips at a temperature of 190 to 240 ° C. under reduced pressure or under the flow of an inert gas such as nitrogen gas. For the purpose of obtaining a container having good mechanical properties, the intrinsic viscosity of the polyester resin obtained by solid phase polymerization is 0.6 to
It is preferably within the range of 0.9 dl / g.

The polyester resin composition of the present invention contains a higher alcohol in addition to the above polyester resin. The higher alcohol has 10 to 3 carbon atoms such as stearyl alcohol, cetyl alcohol and melysyl alcohol.
A chain saturated aliphatic alcohol of 5 is preferred. The content ratio of the higher alcohol in the polyester resin composition of the present invention is 0.02 with respect to 100 parts by weight of the polyester resin.
-3 parts by weight, preferably 0.1-2 parts by weight. If the amount of the higher alcohol is less than 0.02 part by weight based on 100 parts by weight of the polyester resin, the acetaldehyde content of the obtained container cannot be sufficiently reduced. On the other hand, if it exceeds 3 parts by weight, the effect of reducing the acetaldehyde content of the obtained container is lowered, and the transparency of the container is lowered. As a method for blending the higher alcohol into the polyester resin, any method such as (1) addition to the reaction system during the production of the polyester resin and (2) addition during melt molding of the polyester resin are adopted. .. The polyester resin composition of the present invention includes known additives such as colorants, fillers, lubricants, ultraviolet absorbers, antioxidants and surfactants, and / or polyethylene,
Different polymers such as polycarbonate and ethylene / vinyl alcohol copolymer may be contained.

The container of the present invention can be produced by using the above polyester resin composition by a melt molding method which is generally used for ordinary polyester resins. For example, the polyester resin composition can be used to prepare carbonated drinks, juices, mineral water, etc. by a blow molding method such as a usual extrusion blow method, an injection blow method, and a method of blow molding after reheating a preform (cold parison method). It can be a hollow container suitable for filling beverages. Further, after being formed into a sheet by extrusion molding, a container such as a cup or tray can be formed by vacuum or pressure air thermoforming. In addition, in such melt molding, a molding temperature of not less than the melting point of the polyester resin and usually not more than 320 ° C. is generally adopted, but in order to suppress the production of acetaldehyde at the time of melt molding, a temperature as low as possible and It is preferable to mold with a short residence time.

[0010]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

The measuring methods adopted in the following Reference Examples, Examples and Comparative Examples are as follows.

(1) Intrinsic Viscosity It was determined based on the result of measuring viscosity at 30 ° C. using a solution of a sample (prepolymer or polyester resin) in a mixed solvent of phenol / tetrachloroethane and the like.

(2) Acetoaldehyde content in hollow container Barrel temperature 290 using dry polyester resin chips
C, cycle time 36 seconds, mold temperature 12 ° C. to form a preform by injection molding, then this preform is heated and preform temperature 100 ° C. immediately before blowing,
A round-bottomed hollow container having an internal volume of 1.5 liter was produced by blow molding under a blow pressure of 20 Kg / cm ² . A Nissei ASB50 was used as the injection molding machine, and Corpoplast LB01 was used as the blow molding machine. The round-bottomed hollow container thus obtained was tightly closed immediately after molding, and 2
After left at 1 ° C. and 65% relative humidity for 1 hour, the air in the container was replaced with nitrogen gas, which was then sealed and left at 21 ° C. and 65% relative humidity for 24 hours. The nitrogen gas in the container was recovered and quantitatively analyzed by a gas chromatograph GC-9A manufactured by Shimadzu Corporation, and the acetaldehyde concentration (μg /
dl) was determined.

Reference Example 100 ppm of tetraethylammonium hydroxide was added to a slurry consisting of 100 parts by weight of terephthalic acid and 45 parts by weight of ethylene glycol, and this was added under pressure to 25
Esterified at 0 ° C, bis-β- with an esterification rate of 95%
A mixture of hydroxyethyl terephthalate and its low polymer was prepared. Then, 0.016 parts by weight of germanium dioxide as a catalyst was added to 124 parts by weight of the mixture, and polycondensation reaction was carried out at 280 ° C. under a reduced pressure of 1 Torr absolute pressure to prepare a prepolymer having an intrinsic viscosity of 0.60 dl / g. Then, it was extruded in a strand form from a nozzle and cut into a cylindrical chip. The obtained prepolymer chips are put in 150
After drying at ℃ 5 hours, under nitrogen flow at 205 ℃ 15
Solid-state polymerization was carried out for a period of time. The intrinsic viscosity of the obtained polyester resin chip was 0.75 dl / g.

Examples 1 and 2 The polyester resin chips obtained in Reference Examples were fed to a melt extruder, and the polyester resin in the molten state was used.
After kneading with the amount of stearyl alcohol shown in (1), injection molding was carried out into a preform. Then, the preform was blow-molded to obtain a round-bottom hollow container having an internal volume of 1.5 liter and good transparency. Table 1 shows the amount of acetaldehyde in the round bottom hollow container.

Comparative Example The polyester resin chips obtained in the Reference Example were supplied to a melt extruder, injection molding was performed without blending stearyl alcohol, and then blow molding was performed to obtain an internal volume of 1.
A round bottom hollow container having a good transparency of 5 liters was obtained. Table 1 shows the amount of acetaldehyde in the round bottom hollow container.

[0017]

[Table 1]

[0018]

Industrial Applicability According to the present invention, as is apparent from the above examples, there is provided a polyester resin composition for containers which gives a container having a reduced acetaldehyde content.
Moreover, since the container provided by the present invention has a low content of acetaldehyde, it is particularly suitable as a container for filling a beverage such as cola or mineral water whose taste or odor is likely to be reduced by acetaldehyde.

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Claims (2)

[Claims] 1. A polyester resin whose main repeating unit is ethylene terephthalate and the polyester resin 1.
A polyester resin composition for a container, which comprises 0.02 to 3 parts by weight of higher alcohol relative to 00 parts by weight. 2. A container made of the polyester resin composition according to claim 1.