JPH0570569A - Production of polyester - Google Patents

Abstract

PURPOSE:To improve hue and heat resistance by allowing a specific lower alkyl ester of naphthalene-2,6-dicarboxylic acid to undergo the transesterification with ethylene glycol and polycondensing the resulting product. CONSTITUTION:A dicarboxylic acid component contg. at least 70mol% lower alkyl ester of naphthalene-2,6-dicarboxylic, of which acid value is 1mgKOH/g, weight reduction initiating temp in therogravimetric analysis is 230 deg.C or higher, and m.p. meseared with a differential scanning calorimeter is 190 deg.C, acid is allowed to undergo the transesterification with a glycol component contg. at least 70mol% ethylene glycol in the presence of a transesterification catalyst followed by the polycondensation in a vacuum in the presence of a polycondensation catalyst.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a melt polymerization method, and more particularly to a method for producing polyester by a transesterification method. More specifically, it relates to a method for producing a polyester having a good hue and excellent heat resistance.

[0002]

2. Description of the Related Art Polyester, especially polyethylene terephthalate (hereinafter sometimes abbreviated as PET)
Is widely used for fibers, films, industrial resins, bottles, cups, trays, etc. due to its excellent mechanical and chemical properties. However, in recent years, demands for quality have become more severe in various applications. Among them, polyester containers (especially biaxially stretched blow containers) are required to have improved heat resistance and gas barrier properties from the viewpoint of sterilization and storability of the filling, and polyethylene terephthalate containers are not sufficient. May be done.

On the other hand, polyethylene naphthalene dicarboxylate (hereinafter sometimes abbreviated as PEN) has been known for its excellent characteristics, and is superior to PET in terms of heat resistance and gas barrier property. It is considered.

Therefore, many studies have been reported on application to films and containers. For example, Japanese Patent Laid-Open No. 52-
The method of applying as a hollow container having excellent gas barrier property, heat resistance, and transparency to 45466 publication, PEN and PET are used in order to supplement the difficulty of molding while making the best use of the characteristics such as heat resistance of PEN. An application method as a blended biaxially oriented film for packaging or as a hollow container is disclosed in Japanese Patent Laid-Open No. SHO 50-1.
No. 22549, JP-A-2-274757, JP-A-2-276855, and the like.

However, the PEN polymer obtained from a general polyester production method is highly colored and has insufficient heat resistance, and there are few cases in which it is actually used as a hollow container for food.

[0006]

The object of the present invention is to provide P for use in bottles, for example.
It is an object of the invention to provide an EN polymer having a good hue and good heat resistance.

[0007]

The present invention relates to a method for producing this PEN polymer, and in order to make the best use of its heat resistance, PEN with little coloring.
As a result of earnest research on a method for producing a polymer, when a lower alkyl ester of naphthalene-2,6-dicarboxylic acid to be used has an acid value of a specific amount or less and physical properties limited by thermal analysis are used as a raw material, The inventors have found that a polyester having an excellent hue with an extremely small decrease in the molecular weight of can be obtained, and arrived at the present invention.

That is, the present invention is naphthalene-2,6-
When transesterifying a dicarboxylic acid component mainly composed of a lower alkyl ester of dicarboxylic acid and a glycol component mainly composed of ethylene glycol and then polycondensing it to produce a polyester, the acid as a naphthalene-2,6-dicarboxylic acid ester is used. Value is less than 0.1 mg KOH / g and TGA (thermogravimetric analysis) has a weight loss onset temperature of 23.
A method for producing a polyester, characterized in that a polyester having a melting point of 0 ° C. or higher and a melting point of 190 ° C. or higher as measured by DSC (Differential Scanning Calorimeter) is used.

The present invention will be described. The "dicarboxylic acid component" used in the present invention is a lower alkyl ester of naphthalene-2,6-dicarboxylic acid (hereinafter 2,6-DA).
Abbreviated as N), that is, naphthalene-2
The main target is methyl ester and butyl ester of 6-dicarboxylic acid. And, in the ester used in the present invention, a part thereof (30 mol% or less with respect to the total acid component,
Other dicarboxylic acids such as terephthalic acid, isophthalic acid, 4,4'-diphenyldicarboxylic acid, diphenoxyethane-4,4'-dicarboxylic acid, diphenylsulfone-4,4'-dicarboxylic acid, preferably 20 mol% or less) Aromatic dicarboxylic acids such as acids; sebacic acid; and those substituted with lower alkyl esters of aliphatic dicarboxylic acids such as adipic acid are also included.

Next, the "acid value" of the lower alkyl ester of naphthalene-2,6-dicarboxylic acid, which is the main component of "dicarboxylic acid component", means that 2,6-DAN is converted into P-xylene: ethanol (2: 1 volume). 2,6-DAN 1 when dissolved in a mixed solvent of (ratio) and neutralized and titrated with a KOH alcoholic solution.
Represents the number of mg of KOH required to neutralize g. The acid value of 2,6-DAN used in the present invention is 0.1 mg K.
OH / g or less, 0.05 mg KOH /
g or less is preferable, and 0.03 mg KOH / g or less is particularly preferable. If the acid value exceeds 0.1 mg KOH / g, the reason is not clear, but it may be due to the effect of shifting the equilibrium between the formation reaction and the decomposition reaction that undergo oligomerization from the transesterification reaction toward the decomposition reaction. The reaction rate decreases, the hue of the resulting polymer deteriorates, and the thermal stability also decreases.

Further, the "temperature reduction starting temperature by TGA (thermogravimetric analysis)" of a lower alkyl ester of naphthalene-2,6-dicarboxylic acid means a general thermal analyzer such as Thermal Analyzer 1090B manufactured by Dupont. In the measurement by the TGA measuring device, as shown in FIG.
It is the temperature represented by the intersection of the tangent lines A and B among the tangent lines A, B and C when the temperature is raised at ° C / min. Then, the weight loss starting temperature of the lower alkyl ester must be 230 ° C. or higher. If the temperature is lower than 230 ° C, the polymer is highly colored and the heat resistance is insufficient because it is likely to be decomposed during the transesterification reaction.

Further, "melting point measured by DSC (differential scanning calorimeter)" means 20 ° C./mi as shown in FIG. 2 in the DSC measurement by the same thermal analyzer as described above.
This is the point represented by the peak value when the temperature is raised at n. And its melting point must be above 190 ℃,
When it is less than the above, it is unlikely that the polymer becomes the same as when the weight loss starting temperature is less than 230 ° C.

In the present invention, the "glycol component" is intended mainly for ethylene glycol, but a part (30 mol% or less, preferably 20 mol% or less based on the total glycol component) of another glycol is used. For example, it may be replaced with tetramethylene glycol, neopentyl glycol, trimethylene glycol, hexamethylene glycol, decamethylene glycol, cyclohexane dimethylol or the like.

In the present invention, polyethylene-2,6-
Naphthalene dicarboxylate (polyester) can be produced by a conventionally known method.

For example, 2,6-DAN and ethylene glycol are heated in the presence of a transesterification catalyst (eg magnesium acetate, sodium acetate) to cause a transesterification reaction, and the obtained glycol ester is further reacted to obtain the glycol. The ester is further obtained by heating under vacuum in the presence of a polycondensation catalyst (eg germanium oxide) to cause polycondensation.

In the present invention, various stabilizers (eg, antioxidants, ultraviolet absorbers, etc.), pigments, optical brighteners, and various other additives can be used as required.

[0017]

INDUSTRIAL APPLICABILITY According to the present invention, a lower alkyl ester of naphthalene-2,6-dicarboxylic acid and a polyester containing ethylene glycol as a main component have good color tone and excellent heat resistance, and are used for packaging materials. Can be produced as a polymer suitable for.

[0018]

The present invention will be described in detail below with reference to examples. In the examples, "part" means "part by weight", and the intrinsic viscosity [η] is phenol / tetrachloroethane (3: 2).
(Parts by weight), and is obtained from the solution viscosity measured at 35 ° C.

The color tone is Minolta color difference meter CR-1.
The value of L, a, and b was determined by measuring at 00. The L value represents brightness, where L = 100 is white and L = 0 is black. The a value indicates reddish to greenish, with a greater value on the + side centering on 0, more reddishness, and a greater value on the − side, more greenishness. Further, the B value indicates yellowish to bluish, with a larger value on the + side with a center of 0 being more yellowish and a larger value on the − side being more bluish.

Further, the molding temperature is 290 ° C. and the mold temperature is 40 ° C.
The outer diameter of the cylindrical body is 25 to 26 mm, the wall thickness is 3.5 mm,
A preform having a total length of 155 mm and one end having a bottom is injection-molded, and the difference between the intrinsic viscosity of the preform after injection molding and the intrinsic viscosity of the pellet before molding is represented by Δ [η]. Use as a guide. That is, the smaller Δ [η] is, the better the melting heat stability and the better the heat resistance.

The lower alkyl ester of naphthalene-2,6-dicarboxylic acid used in the following examples is further purified by the method described in, for example, JP-A-48-14656. The heat history is shortened.

For example, naphthalene-2,6-dicarboxylic acid is heated using methanol and sulfuric acid, esterified under pressure and stirring, the reaction solution is cooled, filtered, and the precipitated crystals are crude naphthalene-2. It is obtained as a dimethyl ester of 6-dicarboxylic acid, and is further recrystallized and purified with an aromatic hydrocarbon or the like to have a short thermal history when used.

Incidentally, JP-A-48-14656 discloses that the melting point of dimethyl-2,6-naphthalenedicarboxylate is 184.5 ° C., and JP-A-62-2.
No. 90722 discloses an acid value of 0.52 to 0.69 mg KO.
An example of H / g is shown.

[0024]

Example 1 Dimethyl having an acid value of 0.02 mg KOH / g, a weight loss starting temperature of 234 ° C. and a melting point of 194 ° C.
2,6-Naphthalenedicarboxylate 97.6 parts, ethylene glycol 49.6 parts, magnesium acetate 0.0
69 parts and 0.003 parts of sodium acetate were put in a transesterification tank, methanol was distilled off, and the temperature was raised while the transesterification reaction proceeded, and the theoretical amount of methanol was 100%.
At the time of distilling, 0.049 parts of trimethyl phosphoric acid and 0.016 parts of germanium oxide as a polymerization catalyst were added, and then transferred to a polycondensation reaction tank and depressurized to a high vacuum while 290
The temperature is raised to ℃ and the high vacuum reaction time of 0.5 mmHg or less is 100
The reaction was terminated when the time reached minutes. The obtained polymer has [η] = 0.65, color tone L = 76.0, a = −1.
1, and b = -1.1, the color tone was excellent.
In addition, [η] of the preform obtained by injection molding =
It was 0.61, that is, Δ [η] = 0.04.

[0025]

Example 2, Comparative Examples 1 to 4 Similar to Example 1 except that various kinds of dimethyl-2,6-naphthalenedicarboxylate having different acid values, starting temperatures for weight reduction and melting points were used. Carried out. The results are shown in Table 1.

[0026]

[Table 1]

[Brief description of drawings]

FIG. 1 is a graph illustrating a weight loss start temperature of the present invention.

FIG. 2 is a graph showing a measurement example of the melting point of a lower ester of naphthalene-2,6-dicarboxylic acid of the present invention from DSC.

Claims (1)

[Claims] 1. A polyester is produced by transesterifying a dicarboxylic acid component mainly composed of a lower alkyl ester of naphthalene-2,6-dicarboxylic acid and a glycol component mainly composed of ethylene glycol, followed by polycondensation. Naphthalene-2,6-dicarboxylic acid lower alkyl ester having an acid value of 0.1 mg KOH / g or less, and a thermogravimetric analysis (TGA) temperature reduction starting temperature of 230 ° C.
The method for producing a polyester, wherein the polyester having a melting point of 190 ° C. or higher as measured by a differential scanning calorimeter (DSC) is used.