JP3047453B2 - Polyester resin compound - 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 has a low aldehyde content when melt-molded,
Another object of the present invention is to provide a polyester resin compound suitable for obtaining a molded product having high transparency, and more specifically, a polyethylene terephthalate resin compound for a biaxially stretched blow container.

Polyethylene terephthalate (hereinafter abbreviated as PET)
Due to its excellent mechanical, thermal, and electrical properties, it is widely used in commercial applications. However, with the expansion of applications and demands, the characteristics required for PET are becoming stricter in each application field. One of those required properties is a PET molded article having a low content of aldehydes and less whitening.

(Prior art) Usually, when PET is manufactured by a melt polymerization method that is industrially performed, acetaldehyde, crotonaldehyde, and other 1,3-dimethyl compounds that are considered to be reactants of aldehyde and glycol due to thermal decomposition and side reactions. Aldehydes such as dioxolane (hereinafter, various aldehyde reactants are simply referred to as aldehydes) are generated and contained in PET. Accordingly, in a field of application that requires a low content of aldehydes, a molded article having a low aldehyde content cannot be obtained by molding the molten polymer resin without dealdehyde treatment. Therefore, in an application field where the content of aldehydes is required to be low, a resin in which aldehydes are reduced to several ppm by solid-phase polycondensation or long-time drying treatment is usually used.

However, even with these resins in which aldehydes are reduced, aldehydes are generated and increased during melt molding, so that it is difficult to reduce them to such an extent that they do not adversely affect the use of molded articles thereafter. In the case of PET molded articles containing these aldehydes, for example, bottles, the aldehydes cause an unpleasant odor or an unpleasant odor, or change the flavor or aroma of the contents, thereby significantly lowering the commercial value.
Further, usually, polyester is accompanied by whitening at the time of molding, crystallizes, and becomes opaque, and the commercial value of the molded product is easily damaged. This whitening can be prevented to some extent by raising the polymer temperature at the time of molding, but increasing the temperature will also accelerate the decomposition reaction of the polymer, and even if the aldehyde content in the polymer before molding is reduced, molding Occasionally, aldehydes increase significantly.

(Problems to be Solved by the Invention) As a method for simultaneously satisfying whitening of a molded article and prevention of an increase in aldehyde during molding, a third component is copolymerized with a normal polyester to lower the melting point or to improve the crystallinity. A method is known in which the molding temperature is lowered to suppress the generation of aldehyde during molding and to suppress whitening due to crystallization by reducing the size. However, the addition of these third components is not an appropriate method because it significantly impairs the other important required properties of the molded article, such as stretch formability, mechanical strength, and barrier properties.

Aldehydes are produced by thermal decomposition from ethylene terephthalate units, and methods for chemically inhibiting this have been proposed, such as reducing the number of terminal hydroxyl groups and increasing the number of carboxyl groups (Japanese Patent Application Laid-Open No. Sho 53-53). 28649
JP-A-53-43796). However, these methods require complicated operations in polymer production and are difficult to incorporate into industrial-scale operations.

Further, as the aldehyde inhibitor, a sterically hindered phenol compound disclosed in JP-A-58-157852, and JP-B-63-10740, a method of adding 2 to 20 ppm of an alkali metal compound as a metal to a polyester having a special constitutional component. Is presented. However, even with these methods, it cannot be said that obtaining a low-aldehyde, low-haze, and high-transparency molded article in an application field requiring a small amount of aldehyde is sufficiently satisfactory.

(Means for Solving the Problems) The present inventor has noted the above points, and has suppressed the aldehyde generated by the thermal decomposition at the time of melt injection or extrusion molding of polyester, and produced a molded article having extremely excellent transparency. As a result of intensive studies on additives to obtain, it was found that a metal compound having a low primary ionization potential was effective, and this was achieved by adding and compounding a potassium salt of a specific higher fatty acid at a specific concentration after completion of melt polycondensation. Found to be.

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-mixed with the polyester (A) or another polyester resin. A compound comprising a master batch obtained by kneading, or a compound obtained by dry blending (A) with (B), wherein the compounding ratio of the potassium salt (B) in the compound is as potassium metal. It is a polyester resin compound for a biaxially stretched blow container characterized by having a concentration of 25 to 85 ppm.

The polyester (A) having ethylene terephthalate as a main repeating unit of the present invention is one in which 80 mol% or more of ethylene terephthalate is composed of ethylene terephthalate, and has important properties such as stretch moldability, mechanical strength, and barrier properties. 97 to 98 mol% or more is desirable so as not to adversely affect the characteristics. Isophthalic acid, p-β-
Oxyethoxybenzoic acid, diphenyl ether-4,4 '
Dicarboxylic acid, diphenoxyethane-4,4'-dicarboxylic acid, dicarboxylic acid components such as adipic acid, sebacic acid, propylene glycol, butanediol, neopentyl glycol, cyclohexane dimethanol, ethylene oxide adduct of bisphenol A, etc. Glycols.

The above polyester can be obtained by either a method of performing polycondensation via direct esterification or a method of performing polycondensation via a transesterification reaction.However, the polyester obtained by the melt polymerization method has a temperature of 180 to 250 ° C. It is necessary to polymerize in a solid state at reduced pressure or in an inert gas at a temperature. At this time, if necessary, one or more metal compounds such as Mn, Zn, Co, Ge, Sb, and Ti can be arbitrarily selected and used as a catalyst for the esterification, transesterification, and polycondensation reactions. Further, the polyester of the present invention can contain additives such as a colorant, an ultraviolet absorber, an antistatic agent, a thermal antioxidant, an antibacterial agent, and a lubricant in an appropriate ratio, if necessary.

The potassium salt of an aliphatic monocarboxylic acid having 10 to 32 carbon atoms includes capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, montanic acid, melicic acid, oleic acid, oleic acid, linoleic acid, and the like. It refers to the potassium compound of unsaturated fatty acids.

The amount of the potassium salt of an aliphatic monocarboxylic acid having 10 to 32 carbon atoms is shown in Examples (Table 1). The potassium metal is 40 ppm, and the aldehyde content is the lowest.
If less than 5 ppm, target aldehyde content in molded article material is 10 ppm
There can be no less. In addition, potassium metal is 85
Above ppm, the haze value is greater than 10%.

The potassium salt of an aliphatic monocarboxylic acid having 10 to 32 carbon atoms according to the present invention may be dry-blended with polyester directly before molding or melt-kneaded with polyester beforehand and kneaded with an extruder to obtain a high concentration of potassium. Re-pelletized polyester of potassium salt of aliphatic monocarboxylic acid having 10 to 32 carbon atoms, so-called masterbatch (hereinafter abbreviated as MB)
Is prepared by mixing MB with polyester before molding. The addition of the potassium salt of the aliphatic monocarboxylic acid having 10 to 32 carbon atoms during the esterification reaction of the polyester, the transesterification reaction, or the melt polycondensation reaction may result in the formation of aldehyde during molding. Not only is the suppression effect lost, but it can also color the polyester,
It has adverse effects such as increasing crystallinity.

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

(Examples) Hereinafter, the present invention will be described in more detail with reference to examples. What
The evaluation methods and measurement methods of the characteristic values listed in the examples and comparative examples are as follows.

1. Intrinsic viscosity (IV) It was determined from a value measured at 30 ° C. at a concentration of 400 mg / dl in a mixed solvent of phenol / tetrachloroethane = 60/40 weight ratio.

2. Acetaldehyde A sample is cut into 2-3 mm squares, and a sample / distilled water = 1 g / 2 ml is placed in a glass ampoule purged with nitrogen, and the upper part is sealed.
Extraction at 2 ° C for 2 hours. After cooling, the aldehyde in the extract was measured by high-sensitivity gas chromatography and the concentration was ppm.
Displayed with.

3. Haze (% haze) A plate with a thickness of 5 mm obtained by injection molding is JIS-K6
714, K6717, K7105, measured by a direct-reading haze meter manufactured by Toyo Seiki Seisaku-sho, manufactured according to ASTM D1003. The formula for calculating the haze is shown below.

Example 1 After 100 parts of terephthalic acid and an esterification reaction of ethylene glycol having twice the mole of terephthalic acid were performed under pressure, 0.014 part of germanium dioxide and 0.025 part of phosphoric acid were added, and the intrinsic viscosity was reduced to 0.600 at 285 ° C. under reduced pressure. After polycondensation, withdrawn in running water to obtain pellets, after crystallization treatment 210 ° C.
Was subjected to solid-state polycondensation in an atmosphere under a nitrogen stream until the intrinsic viscosity became 0.750. And the intrinsic viscosity obtained by this method
A PET having a thickness of 0.750 and an aldehyde content of 3.5 ppm was dry-blended with potassium stearate, and a 5 mm-thick plate was molded at a molding temperature of 285 ° C. using an injection molding machine.
%, Aldehyde = 7.0 ppm.

Examples 2 to 7 and Comparative Examples 3 to 14 The solid-state polymerized resin obtained by the method of Example 1 was subjected to a twin-screw extruder at 280 ° C. under a condition of a residence time of 1 minute at 2.0% by weight.
Knead the additives of / PET to obtain MB of potassium stearate. Next, the PET obtained by solid-phase polycondensation for MB is shown in Table-
Mix to achieve the compounding amount of 1. and mold with an injection molding machine at a molding temperature of 28.
A plate having a thickness of 5 mm was formed at 5 ° 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.

For Comparative Example 2, after the esterification reaction was completed, stearic acid K was added and melt polymerization and solid phase polymerization were performed in the same manner as in Example 1 to form a plate having a thickness of 5 mm. There was no effect of suppressing generation, and the haze value was also very high.

As is clear from the Examples and Comparative Examples (Table-1), the addition of the K salt of the specific higher fatty acid was changed to 25 as K after the melt polymerization.
Aldehyde content of molded article <10 ppm
The value of 5 mm thickness haze <10% can be satisfied at the same time. The use of a compound with an organic acid having a small number of carbon atoms, the use of an alkali metal other than K, or the K concentration outside the above range cannot simultaneously satisfy the haze and aldehyde amounts. Further, even if K stearic acid is added before melt polymerization, the effect of suppressing aldehyde during molding is lost.

(Effect of the Invention) By molding using the polyester resin composition of the present invention, it is possible to obtain a polyester molded article having low aldehyde and extremely excellent transparency. In addition, the polyester resin does not need to have a special raw material composition, and ordinary polyethylene terephthalate can achieve the object of the present invention, which is of great industrial significance.

Claims (1)

(57) [Claims] 1. The polyester of (A) or another polyester resin comprising (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. And a compound consisting of a master batch obtained by melt-kneading, or
A composition obtained by dry blending (B) with (A),
A polyester resin composition for a biaxially stretched blow container, characterized in that the content of the potassium salt (B) in the composition is 25 to 85 ppm as potassium metal.