JPH04272920A - Production of polyester - Google Patents

Abstract

PURPOSE:To produce a moisture-resistant polyester having a decreased melt viscosity or an increased flowability, i.e., an excellent moldability, by solid-state polymn. CONSTITUTION:A polyfunctional compd. having at least 3 functional groups, such as trimellitic anhydride (provided that the number of functional groups is f) in an amt. of 0.1-3mol% based on the total amt. of reactants for producing a polyester and a monofunctional compd. such as an o-methylbenzoyl benzoate in an amt. of f-2 to f mol per mol of the polyfunctional compd. are added to the reactants, which are polymerized in melt and then in solid state.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing polyester, and more particularly to a method for producing polyester having excellent heat and humidity resistance and fluidity.

0002

[Prior art] Polyethylene terephthalate (hereinafter referred to as PE)
(abbreviated as T) and polybutylene terephthalate (hereinafter referred to as PBT)
Because of their excellent chemical and mechanical properties, polyesters such as polyesters are widely used in fibers, films, bottles, molding resins, etc. Particularly in recent years, these polyesters have come to be used in fields where they are used under harsh conditions, such as electrical and electronic parts. In such applications, conventional polyesters are susceptible to hydrolysis at high temperatures and high humidity, and white powder stains and scum may occur during molding. To solve these problems, we reduced the concentration of carboxyl groups at the end of the polymer to prevent hydrolysis, especially under high temperature and high humidity conditions, and also reduced the content of oligomers that cause white powder stains and scum during molding. Therefore, solid phase polymerization is performed after melt polymerization.

0003

However, polyester produced by solid phase polymerization has a lower oligomer content and narrower molecular weight distribution than polyester of the same molecular weight produced by melt polymerization, and therefore has a high melt viscosity. Therefore, when melt-molded, it decomposes, resulting in a decrease in the degree of polymerization and an increase in volatile gas. If conditions are chosen to suppress decomposition, it will be difficult to obtain thin molded products due to the high melt viscosity. There is a method of adding a plasticizer to lower the melt viscosity, but this is not preferable because it causes scum and gas to be generated due to oozing during molding. An object of the present invention is to provide a method for producing a polyester having excellent moist heat resistance and moldability by lowering the melt viscosity in a solid phase polymerization method.

0004

[Means for Solving the Problems] The present invention provides a method for producing a polyester containing an aromatic dicarboxylic acid as a main acid component and an aliphatic diol as a main glycol component by a solid phase polymerization method. (the number of functional groups is f) is 0.1 to 3 mol% of the total acid components constituting the polyester, and the monofunctional compound is added in an amount of (f- 2) A method for producing polyester, which is characterized in that the amount is added in an amount of not less than f times and not more than f times, and melt polymerization is performed, followed by solid phase polymerization.

[0005] In the present invention, the term "polyester" refers to a polyester containing an aromatic dicarboxylic acid as the main acid component and an aliphatic diol as the main glycol component. Examples of the "aromatic dicarboxylic acid" include terephthalic acid, naphthalene dicarboxylic acid, isophthalic acid, diphenyl dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenyl ketone dicarboxylic acid, and the like. Examples of the "aliphatic diol" include ethylene glycol, trimethylene glycol, tetramethylene glycol, hexamethylene glycol, and the like.

[0006] The term "mainly" used herein refers to approximately 80 mol% or more, although it is not particularly limited. Other acid components, hydroxy compounds, etc. may be copolymerized within a range of less than 20 mol%. As the copolymerizable third component, aromatic dicarboxylic acids other than the aromatic dicarboxylic acids and aliphatic diols constituting the main component of the polyester; aliphatic diols;
Sodium-sulfoisophthalic acid; dibromoterephthalic acid; diethylene glycol (DEG), polyethylene glycol, etc.; alicyclic dicarboxylic acids, such as decalin dicarboxylic acid, hexahydroterephthalic acid, etc.; aliphatic dicarboxylic acids, such as malonic acid, succinic acid, adipic acid etc.; aromatic diols such as hydroquinone, catechol, naphthalenediol, resorcinol, 4,4'-dihydroxydiphenylsulfone, bisphenol A [2,2
-bis(4-hydroxyphenyl)propane], tetrabromobisphenol A, bishydroxyethoxybisphenol A, etc.; alicyclic diols, such as cyclohexanediol; aliphatic oxycarboxylic acids, such as glycolic acid, hydroacrylic acid, 3-oxy propionic acid, etc.; alicyclic oxycarboxylic acids, such as asiatic acid, quinobic acid, etc.; aromatic oxycarboxylic acids, such as salicylic acid, m-oxybenzoic acid, p-oxybenzoic acid, mandelic acid, atrolactic acid, etc. Can be done.

“Polyfunctional compound” used in the present invention
Examples include glycerin, trimethylolpropane, pentaerythritol, trimellitic acid, trimesic acid, pyromellitic acid, tricarballylic acid, and gallic acid. The amount of the polyfunctional compound added is 0.1 to 3 mol % based on the total acid components constituting the polyester, and if it is out of this range, the viscosity-reducing effect will be reduced.

[0008] Furthermore, in the present invention, "monofunctional compound"
Examples include benzoic acid, o-benzoylbenzoic acid, naphthoic acid, stearic acid, and amyl alcohol. The number of moles of the monofunctional compound needs to be at least (f-2) times and at most f times the number of moles of the polyfunctional (where f is the number of functional groups) compound. The number of moles of the monofunctional compound is (f-2)
If it is less than twice that, there is a risk of gelation during melt polymerization, and f
If the amount exceeds twice that, the polymerization reaction may be delayed. Preferably it is in the range of (f-2) times to (f-1) times. By combining a polyfunctional compound and a monofunctional compound in the above amounts, it is possible to reduce the radius of inertia of the molecule without causing gelation, and increase the fluidity of the polymer.

[0009] For melt polymerization, conventionally known methods such as direct polymerization method and transesterification method are employed. In the case of direct polymerization, acid and glycol are esterified without a catalyst or in the presence of a by-product inhibitor such as DEG or THF, and then polycondensed. As the polymerization catalyst, antimony, germanium, titanium compounds, etc. are preferably used. In the case of transesterification, a dialkyl ester of an acid and a glycol are transesterified in the presence of a transesterification catalyst, such as a calcium, magnesium, manganese, or cobalt compound, and then polycondensed. During melt polymerization, other additives such as colorants, antioxidants, ultraviolet absorbers, antistatic agents, flame retardants, etc. may be used as necessary.

In the present invention, the prepolymer produced by melt polymerization is further subjected to solid phase polymerization in order to make it less carboxylated, less oligomerized, and the like. Solid state polymerization is carried out at a temperature below the melting point of the polymer, in an inert gas stream or under vacuum, and is allowed to react to the desired degree of polymerization.

[0011]

[Examples] The present invention will be explained in more detail with reference to the following examples. In addition, "parts" and "%" in the examples are parts by weight and weight %.
means. Furthermore, the methods for measuring characteristics used in the examples are shown below. Intrinsic viscosity; [η] Phenol/tetrachloroethane (weight ratio 60/40)
Calculated from the solution viscosity measured at 35°C using a mixed solvent of

Terminal carboxyl group concentration; [COOH]A
．． Conix method (Makromol. Chem
．． , vol. 26, p. 226, 1958). Grind and dry the melt viscosity polymer and use a flow tester to measure the nozzle diameter at 280°C for PET and 260°C for PBT with a nozzle diameter of 0.5.
mm, extruded from a die with a land length of 2.0 mm, and the viscosity at a shear rate of 103 cm-1 was measured.

Oligomer content: 15 mg of polymer was accurately weighed and dissolved in 0.4 ml of hexafluoroisopropanol/0.4 ml of chloroform.
Dilute the total volume to 10 ml with chloroform. This was injected into a fluid chromatography system equipped with Nippon Analytical Industries AJ-2H and AJ-1H columns, and the eluent was chloroform, which was run at a flow rate of 3.5 ml/min. In the case of , quantify the cyclic dimer + cyclic tetramer.

Example 1 40 parts of dimethyl terephthalate, 2 parts of ethylene glycol
5.5 parts, 0.4 parts of trimellitic anhydride (f=3) (1 mol% relative to dimethyl terephthalate), 0.5 parts of o-methylbenzoylbenzoate [equimolar as trimellitic anhydride (f-2 ) times], manganese acetate tetrahydrate 0.01
5 parts were charged into a reactor equipped with a stirrer, and transesterification reaction was carried out at 200 to 240°C. When almost the theoretical amount of methanol has been distilled off, a solution of monomethyl/dimethyl phosphate mixture in ethylene glycol (5.6% solution as P)0
．． 039 parts, and 0.016 parts of antimony trioxide were added.
The reaction was carried out under reduced pressure at 285°C. When [η] reached 0.61, the polymer was taken out and pelletized.
Solid phase polymerization was performed at 0°C under a nitrogen stream, and [η] was 0.7.
The degree of polymerization was increased until it reached 1. [C
OOH] is 20 eq/T (ton), oligomer content is 0
．． 7%, and the melt viscosity was 4,500 poise.

Comparative Example 1 In Example 1, only melt polymerization was performed without solid phase polymerization (
η) was increased to 0.71. The obtained polymer had a low melt viscosity of 4,000 poise, but had a [COOH] of 47 eq/T and an oligomer content of 1.3%, causing trouble during molding and having low moist heat resistance.

Comparative Example 2 Example 1 was repeated except that trimellitic anhydride and o-methylbenzoyl benzoate were not added.
In the same manner as above, a solid phase polymerized polymer having [η] of 0.71 was obtained. [COOH] of the obtained polymer is 20 eq/T
The oligomer content was 0.7%, both at a good level, but the melt viscosity was very high at 5,000 poise, and the fluidity was poor.

Comparative Example 3 In Example 1, the amount of o-methylbenzoylbenzoate added was 0.25 parts (based on trimellitic anhydride).
f-2.5) times], the polymer almost gelled and was partially insoluble in the measurement solvent [η], making it impossible to measure.

Comparative Example 4 In Example 1, the amount of o-methylbenzoylbenzoate added was 1.75 parts [based on trimellitic anhydride].
f + 0.5) times] in the same manner as in Example 1, [η] reached a ceiling of 0.62, and the degree of polymerization could not be increased any further.

Example 2, Comparative Example 5 In Example 1, 0.45 parts of pyromellitic anhydride (f=4) (1 mol % based on dimethyl terephthalate) was used instead of 0.4 parts of trimellitic anhydride. Solid phase polymerization was carried out in the same manner as in Example 1 except that o-methylbenzoylbenzoate was used in an amount of 0.99 parts [(f-2) times the amount of pyromellitic anhydride], and [η] was increased to 0.74. (Example 2). The melt viscosity of this polymer was 4,900 poise. The melt viscosity of a product in which [η] was increased to 0.74 by solid phase polymerization without adding pyromellitic anhydride or o-methylbenzoylbenzoate (Comparative Example 5) was 5,700 poise.

[0020]

According to the present invention, it is possible to obtain a polyester having low carboxyl group concentration, low oligomer content, low melt viscosity, moist heat resistance, low scum, and high fluidity.

Claims (1)

[Claims] Claim 1: When producing a polyester containing an aromatic dicarboxylic acid as the main acid component and an aliphatic diol as the main glycol component by solid phase polymerization, a polyfunctional compound of trifunctional or higher functionality (the number of functional groups is f) 0.1 to 3 mol% of the total acid components constituting the polyester, and a monofunctional compound, where the number of moles of the monofunctional compound is at least (f-2) times and no more than f times the number of moles of the polyfunctional compound. 1. A method for producing polyester, which comprises adding a polyester in such a manner as to cause melt polymerization, followed by solid phase polymerization.