JPH023412B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a copolyester having excellent melt flowability and capable of producing molded articles having high strength and high modulus of elasticity.

In recent years, the demand for higher performance plastics has increased, and many polymers with various new performances have been developed.In the field of thermoplastic polyester, for example, copolymerization by reacting polyethylene terephthalate with acyloxy aromatic carboxylic acid has been developed. Polyester (Japanese Unexamined Patent Publication No. 49-72393)
is known to give various molded products with excellent mechanical properties.

However, although the modulus of elasticity of molded articles, such as fibers, obtained from the above-mentioned copolyester is higher than that of polyethylene terephthalate, the strength is considerably lower, and the melt flowability thereof is not necessarily satisfactory.

Therefore, the present inventors investigated with the aim of improving the drawbacks of the above-mentioned copolymerized polyester and obtaining a copolymerized polyester that does not have a very high melting point and can provide molded products with high strength and high modulus of elasticity. ′-
It has been discovered that a copolymerized polyester meeting the above purpose can be obtained by using a polyethylene terephthalate copolymer containing diphenyl dicarboxylic acid as a copolymerization component as a starting material and reacting it with p-acyloxy aromatic carboxylic acid. Ta.

That is, the present invention reacts p-acyloxybenzoic acid with a polyethylene terephthalate copolymer consisting of 40 to 80 mol% of ethylene-4,4'-diphenyl dicarboxylate units and 60 to 20 mol% of ethylene terephthalate units, When producing a copolymerized polyester by polycondensation, the total amount of ethylene-4,4'-diphenyldicarboxylate units and ethylene terephthalate units in the copolymerized polyester is 10 to 70 mol%, p-oxybenzoate The present invention provides a method for producing a copolyester, characterized in that the reaction is carried out so that the unit content is 90 to 30 mol%.

In contrast to conventional copolyesters made by reacting polyethylene terephthalate with p-acyloxybenzoic acid, the copolyesters obtained in the present invention that further contain 4,4'-diphenyldicarboxylic acid as a copolymerization component have melt fluidity. It has extremely good properties and can be easily molded into fibers, films, various molded products, etc. with excellent mechanical properties by ordinary melt molding. Here, the melting point of polyethylene terephthalate is approximately 256℃,
Since the melting point of polyethylene-4,4'-diphenyldicarboxylate is approximately 355°C, 4.
The copolyester of the present invention obtained using a polyethylene terephthalate copolymer copolymerized with 4'-diphenyldicarboxylic acid as a starting material has a higher pour point than the conventional copolyester using polyethylene terephthalate as a starting material. It is expected that the melt fluidity will be poor. However, the copolymerized polyester obtained by the present invention has a pour point that is not much different from the above-mentioned conventional copolymerized polyester, and has improved melt flowability and mechanical properties.
Such findings can be said to be completely unexpected from conventional common sense.

The polyethylene terephthalate copolymer used as a starting material in the present invention has the following structural units A and B.
Contains as an essential ingredient.

Here, A is an ethylene-4,4'-diphenyldicarboxylate unit, and B is an ethylene terephthalate unit, and the ratio of A unit/B unit is 40 to 80 mol%/60 to 20 mol%, especially 50 to 70 mol%. Mol%/50~
Selected from a range of 30 mol%. If the proportion of the A unit in this polyethylene terephthalate copolymer is less than 40 mol%, the strength and elastic modulus of the final copolymerized polyester obtained will be insufficient, and the melt fluidity will be poor, and if it exceeds 80 mol%, the final This is not preferable because the melting point and melt viscosity of the copolymerized polyester obtained will become high. This polyethylene terephthalate copolymer is obtained by polycondensing 4,4'-diphenyldicarboxylic acid, terephthalic acid, and ethylene glycol, but in addition to these components, 1,2-bis(4-carboxyphenoxy ) Ethane, 2,6-naphthalenedicarboxylic acid, 3,3'-diphenyldicarboxylic acid, 3,4'-
Aromatic and alicyclic dicarboxylic acids such as diphenyldicarboxylic acid, 2,2'-diphenyldicarboxylic acid, hexahydroterephthalic acid, or ester-forming derivatives thereof, and diethylene glycol, 1,3-propanediol, 1,4- A small amount of a glycol component such as butanediol or 1,6-hexanediol may be further included as a copolymer component.

The polyethylene terephthalate copolymer in the present invention is 0.5 g/dl in orthochlorophenol.
Concentration, logarithmic viscosity measured at 30℃ is 0.03 to 1.5 dl/
g, more preferably 0.1
~1.0dl/g.

In the present invention, the desired copolyester is produced by reacting this polyethylene terephthalate copolymer with p-acyloxybenzoic acid and polycondensing it. The total amount of ethylene-4,4'-diphenyldicarboxylate units and ethylene terephthalate units is
The reaction is carried out so that the p-oxybenzoate units derived from p-acyloxybenzoic acid account for 10 to 70 mol%, preferably 15 to 60 mol%, and 90 to 30 mol%, preferably 85 to 40 mol%.

The p-acyloxybenzoic acid mentioned here is typically p-acetoxybenzoic acid.

If the amount of p-acyloxy aromatic carboxylic acid used is less than 30 mol% of the total or exceeds 90 mol%, the strength and elastic modulus of the final copolyester obtained will be insufficient. Undesirable.

The method for producing copolyester of the present invention consists of the following two steps. First, in the first step, polyethylene terephthalate copolymer is reacted with p-acyloxy aromatic carboxylic acid to remove acetic acid to form an initial polymer, and in the second step, this initial polymer is further polycondensed to increase the intrinsic viscosity. In this way, the desired copolymerized polyester can be obtained.

The reaction conditions for the first stage are such that the reaction mixture is heated to 240 to 350°C, particularly 250 to 300°C, under an inert gas atmosphere at normal pressure, and the acetic acid that is desorbed is actively removed. If the reaction temperature in the first stage is 240°C or lower, the reaction rate is slow, and if it is 350°C or higher, thermal decomposition of the reactants may occur, which is not preferable.

The reaction conditions for the second stage are such that the molten initial polymer is heated under reduced pressure of 1 mmHg or less until it reaches the desired intrinsic viscosity.

The copolymerized polyester of the present invention obtained in this way has a low melting point of 200°C or less in most cases and has excellent melt fluidity, so it can be subjected to ordinary melt molding such as extrusion molding, injection molding, compression molding, and blow molding. can produce fibers, films, three-dimensional molded products,
It can be processed into containers, hoses, etc.

During molding, reinforcing agents such as glass fibers, carbon fibers, and asbestos, fillers, nucleating agents, pigments, antioxidants, stabilizers, plasticizers, lubricants, mold release agents, etc. may be added to the copolymerized polyester of the present invention. Agents and other thermoplastic resins can be added to impart desired properties to the molded article.

Molded articles obtained from the copolyester of the present invention have optical anisotropy and extremely excellent mechanical properties such as strength and elastic modulus.

The present invention will be further explained below with reference to Examples.
Note that the characteristics evaluation in the examples was performed according to the following regulations.

Strength of fibers…ASTM D1708 〃 Elongation…ASTM D1708 Elastic modulus of fibers…ASTM D790 Tensile strength of molded products…ASTM D1708 〃 Flexural modulus…ASTM D790 Melt viscosity…275℃ using Koka flow tester, shear rate 100sec ^-1 It was measured with

Pour point, liquid crystal onset temperature...Measured by microscopic observation on a hot stage.

Example 1 Polyethylene terephthalate copolymer (logarithmic viscosity 0.76 dl/g) 4.2 kg (ethylene-4,4' - The total amount of diphenyl dicarboxylate units and ethylene terephthalate units is equivalent to 18 moles) and p-acetoxybenzoic acid 4.9 kg (27
mol) was charged into a reactor equipped with a stirrer, a distillation column, and a nitrogen gas inlet, and 280
Stir at ℃. After about 60 minutes, most of the acetic acid was distilled off, and a copolyester initial polymer with a low melt viscosity was obtained.

Next, the reaction system was kept at 280℃ and vacuumed to 0.5mmHg, and stirring was continued for an additional 3 hours.
Approximately 6 kg of copolymerized polyester, which was pale yellow and opaque and had an increased melt viscosity, was obtained.

This copolymerized polyester was subjected to a Koka type flow tester, and the properties of the fiber (undrawn yarn) obtained by melt-extruding it at 275°C from a spinneret with a diameter of 0.3 mm were evaluated. As a result, the strength was 8.2 g/d and the elongation was 9.1. % and elastic modulus of 261 g/d.

In addition, this copolymerized polyester is manufactured by Toshiba Corporation.
Subjected to 50AM injection molding machine, cylinder temperature 240~260
When a dumbbell test piece was molded at a mold temperature of 80°C, the melt fluidity during molding was good, and the properties of the test piece were a tensile strength of 2870 Kg/cm ² and a flexural modulus of 14.2.
×10 ⁴ Kg/cm ² was excellent.

Example 2 Polyethylene terephthalate copolymer (logarithmic viscosity 0.68 dl/g) 2.24 kg (ethylene-4,4' -The total amount of diphenyldicarboxylate units and ethylene terephthalate units is 9
equivalent to moles) and p-acetoxybenzoic acid 2.4Kg
(13.5 mol) was charged into the same reactor as in Example 1,
As a result of reaction under similar conditions, 3 kg of pale yellow opaque copolymerized polyester was obtained.

This copolyester has extremely good fluidity, with a pour point of 130°C and a melt viscosity of 50 poise.
It showed optical anisotropy at temperatures above ℃.

When the properties of the undrawn yarn obtained by melt-spinning this copolyester polyester under the same conditions as in Example 1 were evaluated, the yarn had excellent strength of 9.1 g/d, elongation of 7.3%, and elastic modulus of 287 g/d.

In addition, a test piece obtained by injection molding under the same conditions as in Example 1 had a tensile strength of 2990 Kg/cm ² and a flexural modulus of 17.2 ×
It had excellent properties of 10 ⁴ Kg/cm ² .

Comparative example 1 Polyethylene terephthalate (logarithmic viscosity 0.61
dl/g) 3.5Kg (ethylene terephthalate unit 18
equivalent to mole) and p-acetoxybenzoic acid 4.9Kg
(27 mol) under the same conditions as in Example 1, approximately 5 kg of light yellow opaque copolymerized polyester was obtained.
was gotten.

This copolyester had a pour point of 180°C, a melt viscosity of 200 poise, and exhibited liquid crystallinity at temperatures above 240°C, but its melt fluidity was inferior to that of the copolyester of the present invention.

In addition, the characteristics of the undrawn yarn obtained by melt spinning this copolymerized polyester under the same conditions as in Example 1 are as follows.
Strength 3.1g/d, elongation 5% and elastic modulus
It was inferior at 150g/d.

Comparative Example 2 20 mol% of ethylene-4,4'-diphenyl dicarboxylate units and ethylene terephthalate units
80 mol% polyethylene terephthalate copolymer (logarithmic viscosity 0.52 dl/g) 1.9 kg (total amount of ethylene-4,4'-diphenyldicarboxylate units and ethylene terephthalate units corresponds to 9 mol) and p - Acetoxybenzoic acid 2.4Kg (13.5
As a result of reacting mol) under the same conditions as in Example 1,
2.5 kg of pale yellow opaque copolymerized polyester was obtained.

The properties of an undrawn yarn obtained from this copolyester under the same conditions as in Example 1 were strength: 5.8 g/d, elongation: 9.5%, and elastic modulus: 193 g/d.

From this result, if the ethylene-4,4'-diphenyldicarboxylate unit in the polyethylene terephthalate copolymer used as the starting material is less than 40 mol%,
It is clear that the strength and elastic modulus of the obtained copolymer are insufficient.

Claims (1)

[Claims] 1 A polyethylene terephthalate copolymer consisting of 40 to 80 mol% of ethylene-4,4'-diphenyl dicarboxylate units and 60 to 20 mol% of ethylene terephthalate units is reacted with p-acyloxybenzoic acid to undergo polycondensation. When producing a copolymerized polyester, the total amount of ethylene-4,4'-diphenyldicarboxylate units and ethylene terephthalate units in the copolymerized polyester is 10
~70 mol%, p-oxybenzoate units are ~90
A method for producing a copolymerized polyester, which comprises reacting the copolyester to a concentration of 30 mol%.