JPH04170464A - Polyester resin composition - Google Patents

Abstract

PURPOSE:To obtain a polyester resin composition prevented from forming an aldehyde during molding and improved in the transparency of a molding by mixing a polyester comprising repeating ethylene terephthalate units with a specified potassium salt of an aliphatic monocarboxylic acid. CONSTITUTION:A polyester obtained by melt polymerization is polymerized at 180-250 deg.C in a solid state in a vacuum or an inert gas to obtain a polyester mainly consisting of repeating ethylene terephthalate units and having an ethylene terephthalate content of 80mol% or above, desirably 98mol% or above. The title composition is obtained by dry-blending the polyester with a potassium salt of a 10-32C aliphatic monocarboxylic acid in an amount to give 25-85ppm of potassium atoms or by mixing a masterbatch prepared by previously melt- kneading the above salt or another polyester with the above polyester.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention provides a polyester resin compound suitable for obtaining a molded article having a low aldehyde content and high transparency when melt-molded, and more specifically, The present invention provides a polyethylene terephthalate resin composition for biaxially stretched blow containers.

Polyethylene terephthalate (hereinafter abbreviated as PET) is
It is widely used in commercial applications due to its excellent mechanical, thermal, and electrical properties. However, with the expansion of applications and demand, the properties required of PET are also becoming stricter in each application field. One of these required properties is a PET molded product with a low content of aldehydes and little whitening.

(Prior art) When PET is produced by the industrial melt polymerization method, 1,3-dimethyl, which is thought to be a reaction product of acetaldehyde, crotonaldehyde, and other aldehydes and glycol, is produced through thermal decomposition and side reactions. Aldehydes such as dioxolane (hereinafter, reaction products of various aldehydes are simply referred to as aldehydes) are generated and contained in PET.

Therefore, in fields of application where a low content of aldehydes is required, molded products with a low aldehyde content cannot be obtained if the molten polymer resin is molded as is without being subjected to dealdehyde treatment. Therefore, in application fields that require a low content of aldehydes, aldehydes are usually reduced to several ppm by solid-phase polycondensation or long-term drying.
A resin with a reduced amount is used.

However, even in resins with reduced aldehydes, since aldehydes are generated and increased during melt molding, it is difficult to reduce the content to a level that does not adversely affect the subsequent use of molded products. In PET molded products, such as bottles, containing these aldehydes, the aldehydes cause foul odors and foreign odors, change the flavor and aroma of the contents, and significantly reduce the commercial value. Furthermore, polyester usually undergoes whitening during molding, crystallization occurs, and becomes opaque, which tends to impair the commercial value of the molded product.

This whitening can be prevented to some extent by increasing the temperature of the polymer during molding, but increasing the temperature also accelerates the decomposition reaction of the polymer. Sometimes aldehydes increase significantly.

(Problems to be Solved by the Invention) As a method to simultaneously prevent the whitening of molded products and the increase in aldehyde during molding, it is possible to copolymerize ordinary polyester with a third component to lower the melting point or to improve crystallinity. A known method is to reduce the molding temperature by reducing the molding temperature to suppress the generation of aldehyde during molding, and to suppress whitening due to crystallization. However, adding these third components is not an appropriate method because it significantly impairs other important properties required for the molded product, such as stretch formability, mechanical strength, and barrier properties.

Aldehydes are generated from ethylene terephthalate units through thermal decomposition, and methods such as decreasing the terminal hydroxyl group and increasing the carboxyl group have been proposed as methods for chemically inhibiting this (Japanese Patent Application Laid-Open No. 1983-1973-1). 286
49, JP-A-53-437913). However, these methods require complicated operations for polymer production and are difficult to incorporate into industrial scale operations.

In addition, as an aldehyde inhibitor, JP-A-58-15785
Sterically hindered phenol compound of Publication No. 2, Japanese Patent Publication No. 1983-1
Publication No. 0740 proposes a method in which 2 to 20 ppm of an alkali metal compound is added as a metal to polyester as a special component. However, these methods cannot be said to be fully satisfactory in terms of obtaining molded products with low aldehyde content, low haze, and high transparency in application fields that require low aldehyde content.

(Means for Solving the Problems) With the above points in mind, the present inventor has created a molded product that suppresses aldehyde generated by thermal decomposition during melt injection and extrusion molding of polyester, and has extremely excellent transparency. As a result of extensive research into additives for the production of polycondensates, we found that metal compounds with a low secondary ionization potential were effective, and by adding potassium salts of specific higher fatty acids at specific concentrations after the completion of melt polycondensation. found that it can be achieved.

That is, (A) a polyester having ethylene terephthalate as a main repeating unit and (B) a potassium salt of an aliphatic monocarboxylic acid having 10 to 32 carbon atoms are melt-blended with the polyester of (A) or another polyester resin. A compound consisting of a masterbatch obtained by kneading, or (A)
(B) is dry breaded, the blending ratio of the potassium salt (B) in the blend is 25 to 85 ppm as potassium metal, and
This polyester resin compound has a haze of 10% or less and an aldehyde content of 10 ppm or less when melt-molded into a plate of 1.0 mm in diameter.

The polyester (A) containing ethylene terephthalate as a main repeating unit of the present invention is one in which 30 mo1% or more is ethylene terephthalate, but it has important characteristics such as stretch formability, mechanical strength, barrier properties, etc. of molded products. In order not to adversely affect the characteristics, it is desirable that the content be 97 to 98 mo1% or more. Its copolymerization components include isophthalic acid,
Dicarboxylic acid components such as p-β-,1-1-jethoxybenzoic acid, diphenyl ether-4゜4'-dicarboxylic acid, diphenoxyethane-4゜4'-dicarboxylic acid, adipic acid, sebacic acid, propylene glycol, butane These are glycols such as diol, neopentyl glycol hexane dimetatool, and ethylene oxide adduct of bisphenol A.

The above polyester can be obtained by either direct esterification followed by polycondensation or transesterification followed by polycondensation, but the polyester obtained by the melt polymerization method is It is necessary to polymerize in a solid phase at a reduced pressure or in an inert gas at a temperature. At this time, one or more metal compounds such as Mn1Zn1CO)Ge1Sbv Ti can be arbitrarily selected and used as a catalyst for esterification, transesterification and polycondensation reactions, if necessary. Furthermore, the polyester of the present invention may contain additives such as colorants, ultraviolet absorbers, antistatic agents, thermal antioxidants, antibacterial agents, and lubricants in appropriate proportions, if necessary.

Potassium salts of aliphatic monocarboxylic acids having 10 to 32 carbon atoms include saturated and A potassium compound of unsaturated fatty acids.

The amount of potassium salt of aliphatic monocarboxylic acid having 10 to 32 carbon atoms is shown in Examples (Table 1), and the amount of aldehyde shows the lowest value at 40 ppm as potassium metal, which is less than 25 ppm of potassium metal. Therefore, it is impossible to reduce the amount of aldehyde in the target material of the molded product to less than 10 ppm. Moreover, when potassium metal is 85 ppm+ or more, the haze value becomes larger than 10%.

The method of blending and adding the potassium salt of an aliphatic monocarboxylic acid having 10 to 32 carbon atoms according to the present invention is to dry-bread the potassium salt of an aliphatic monocarboxylic acid having 10 to 32 carbon atoms directly with the polyester before molding, or to melt and knead it into the polyester in advance using an extruder. Carbon number 10-3
The polyester of the potassium salt of aliphatic monocarboxylic acid No. 2 was re-pelletized, and the so-called masterbatch (hereinafter referred to as MB) was re-pelletized.
MB is mixed with polyester before molding. If the potassium salt of an aliphatic monocarboxylic acid having 10 to 32 carbon atoms is added during the esterification reaction or transesterification reaction of polyester, or during the melt polycondensation reaction, it may be difficult to form aldehydes during molding. Not only is the inhibitory effect lost, but there are also negative effects such as coloring the polyester and increasing crystallinity.

According to the present invention, not only the transparency of the molded product is not impaired even when a compound having a melting point higher than that of polyester, such as potassium palmitate and potassium stearate, is blended, but also the thickness of the molded product is 5 mm. It is quite surprising that transparency can be maintained even under harsh conditions.

(Example) Hereinafter, the present invention will be explained in detail with reference to Examples.

The methods for evaluating and measuring the characteristic values listed in Examples and Comparative Examples are as follows.

1. Viscosity (IV) It was determined from the value measured at 30° C. at a concentration of 400 μ/dl in a mixed solvent of phenol/tetrachloroethane:EiO/40 weight ratio.

2 Cut the acetaldehyde sample into 2-3 pieces, sample/distilled water = 1g/2d
Place it in a nitrogen-substituted glass ampoule and melt-seal the top.
Extraction treatment was carried out at 160°C for 2 hours, and after cooling, the aldehyde in the extract was measured using high-sensitivity gas chromatography, and the concentration was expressed in ppm.

3. Haze (haze %) A plate with a wall thickness of 511 m obtained by injection molding is JI
S-6714, K6717, K7105, ASTM
D 1003! : Measured using a direct reading haze meter manufactured by Toyo Seiki Seisakusho. The haze calculation formula is shown below.

Total light transmittance (Tt): Tt=T2/TIX
100(%)ll Haze% (11) :H=Td/TtX100(
%) Example 1 After esterifying 100 parts of terephthalic acid and 2 times the mole of ethylene glycol as terephthalic acid under pressure, 0.014 parts of germanium dioxide and 0.025 parts of phosphoric acid were added, and the mixture was evaporated at 285°C under reduced pressure. Polycondensation is carried out until the viscosity becomes o, eoo, and pellets are obtained by extraction into running water. After crystallization, solid phase polycondensation is carried out in an atmosphere under a nitrogen stream at 210°C until the intrinsic viscosity becomes 0.750. Did. Then, the PET with an intrinsic viscosity of 0.750 and an aldehyde content of 3.5 ppm obtained by this method was dry-blended with potassium stearate and molded into a plate with a thickness of 51 cm at a molding temperature of 285°C using an injection molding machine. , Haze = 7%
, a molded article containing aldehyde = 7.0 ppm was obtained.

Examples 2-7, Comparative Examples 3-14 Example 1. The solid-phase polymerized resin obtained by the above method was heated to 2°0 by using a twin-screw extruder at 280°C for a residence time of 1 minute.
Additives of weight %/PET are kneaded to obtain MB of potassium stearate. Next, PET obtained by solid phase polycondensation was mixed with MB in a blending amount of -1°, and a plate having a thickness of 5 mm was molded using an injection molding machine at a molding temperature of 285°C.

The results are shown in Table 1.

In Comparative Example 1, the solid phase polymerized resin obtained by the method of Example 1 was molded without any additives.

Regarding Comparative Example 2, K stearate was added after the esterification reaction was completed, and Example 1. Melt polymerization and solid phase polymerization were carried out in the same manner as above to form a plate with a wall thickness of 5 cm, but there was no effect of suppressing aldehyde formation during molding, and the haze value was very high.

As is clear from the Examples and Comparative Examples (Table 1), the addition of salt to specific higher fatty acids after melt polymerization was
By controlling the amount of aldehyde to 5 to 85 ppm, the values of aldehyde content <10 ppm and 15 dragon thickness haze <10% can be satisfied at the same time. Compounds with organic acids with a small number of carbon atoms, use of alkali metals other than K, or K outside the above range
At 211 degrees, haze and aldehyde content cannot be satisfied at the same time. Furthermore, even if stearic acid is added before melt polymerization, the effect of suppressing aldehyde during molding will be lost.

(Effects of the Invention) By molding using the polyester resin composition of the present invention, it is possible to obtain a polyester molded article with low aldehyde content and extremely excellent transparency. Moreover, the polyester resin does not need to have a special raw material composition, and the purpose of the present invention can be achieved with ordinary polyethylene terephthalate, which has great industrial significance.

Claims (1)

[Claims] (A) A polyester having ethylene terephthalate as a main repeating unit and (B) a potassium salt of an aliphatic monocarboxylic acid having 10 to 32 carbon atoms are melt-kneaded with the polyester of (A) or another polyester resin. or a blend consisting of a masterbatch obtained by adding (A) to (B
), wherein the blending ratio of the potassium salt (B) in the blend is 2 as potassium metal.
5 to 85 ppm, and when melt-molded into a plate with a thickness of 5 mm at 285°C, the haze of the plate is 10% or less and the aldehyde content is 10 ppm or less.