KR920009687B1 - Process for preparing low carboxyl content polyester - Google Patents

Abstract

Polyester having a low amt. of the terminating carboxyl gp. is prepd. by adding and reacting a mono-functional epoxy cpd. in the process of melt-spinning of the polyester having above 0.60 dl/g of intrinsic viscosity which comprises as main repeating unit of more than 85 mol.% of ethylene terephthalate. In the polymerization step of the preparing process, 0.01-0.1 mol.% of the alkali metal halogen cpd. able to dissolve in the polyester is added. Pref. the halogen cpd. of alkali metal is selected from sodium iodide, potassium iodide, sodium chloride, potassium bromide, lithium chloride, or potassium chloride.

Description

Method for producing polyester with low terminal carboxyl group content

The present invention relates to a method for producing a polyester having a low content of terminal carboxyl groups. More specifically, prior to the addition of the monofunctional epoxy compound in the process of melt spinning the polyester, the invention is to significantly reduce the content of the terminal carboxyl group by adding a halogen compound of the alkali metal in the polymerization process.

Polyester, which is represented by polyethylene terephthalate, is a material widely used for fibers, films, and other molded products because of its physical and chemical properties, but has a disadvantage in that strength and elongation are decreased due to hydrolysis at high temperatures in the presence of moisture. . Therefore, when the polyester is used as an industrial fiber, for example, tire cords, such hydrolysis is a major obstacle.

As a result, it is an object of the present invention to provide an industrial fiber such as a tire cord that can continuously maintain strength even under conditions where hydrolysis occurs, under rubber or at high temperature by removing such obstacles.

When polyester is used for tires, belts and the like for reinforcement purposes, it is a standard that is generally suggested in the art that the terminal carboxyl concentration of polyester should be less than 15EQ / 10 ⁶ g in order to maintain a predetermined strength.

The present inventors have made this proposal in order to meet such criteria and to provide a polyester having a significantly lower carboxyl group concentration compared to other proposals.

First of all, by looking at some of the preceding proposals having a similar purpose as the present invention, we will try to solve the problem.

As a proposal to reduce the terminal carboxyl group concentration of polyester, a method using a combination of melt polymerization and solid phase polymerization is described in Japanese Patent Publication No. 46-41034, and in the same 48-41713, a carbonate such as ethylene carbonate is added and reacted. I suggest a way to make it. In addition, U. S. Patent No. 4016142 claims that the desired polyester can be obtained by adding a monofunctional epoxy compound in the polymerization process.

Among these methods, the method of using solid phase polymerization in combination has less thermal decomposition during polymerization, and the esterification reaction between the carboxyl end group and the hydroxyl end group easily proceeds, and the polyester having a carboxyl end group concentration of 10eq / 10 ⁶ g or less is easily progressed. It is possible to prepare. However, the solid phase polymerization has a low reaction temperature, so the reaction rate is very slow. Therefore, a very long reaction time is required, and the concentration of terminal carboxyl groups is increased again due to thermal decomposition during melt spinning of the obtained polymer. We come to the conclusion that we do not achieve this.

On the other hand, the method of adding a carbonate or an epoxy compound at the end of the polycondensation also has a very low concentration of the terminal carboxyl group, but the concentration increases again during the melt spinning process, as in the case of solid phase polymerization.

In order to improve this point, a method of introducing a monofunctional epoxy compound in the melt spinning process is proposed, but in this case, since the reaction efficiency is very low, there is a drawback that the desired effect cannot be obtained.

Therefore, the present inventors have reached the present invention as a result of earnestly examining a method for producing a polyester having extremely high hydrolysis resistance by solving the above problems and solving the problems.

Referring to the configuration of the present invention in detail. In the present invention, at least 85 mole% of the main repeating unit is ethylene terephthalate and the monofunctional epoxy compound is added and reacted during the melt spinning process of the polyester having an intrinsic viscosity of 0.60 dl / g or more. The halogen compound of the present invention relates to a method for producing a polyester having a low content of terminal carboxyl groups, characterized in that the addition step.

Monofunctional epoxy compounds that can be used in practicing the present invention are styrene oxide, 1,2-hexadecyl oxide, 1,2-octadecyl oxide, butane-1,2-oxide, phenylglycidyl ether, allyl glycy Dyl ether, n-butylglycidyl ether, cyclohexyl glycidyl ether, and the like are particularly preferred among these, phenylglycidyl ether having good affinity with polyester.

Although the degree to which the monofunctional epoxy compound is added depends on the concentration of the terminal carboxyl group contained in the polyester before the melt spinning, it is generally appropriate to add it in the range of 0.1 to 2.0% by weight. This is because when it is less than this range, it is difficult to demonstrate the effects of the present invention, and on the contrary, when it exceeds this, no reaction can be caused.

In the present invention, the addition of the halogen compound of the alkali metal, which is a structural feature of the present invention, may be performed at any time after the start of the polymerization. Examples of the halogen compound of the alkali metal used in the present invention include sodium iodide, potassium iodide, sodium chloride, potassium bromide, lithium chloride, potassium chloride, and the like, and any of these can sufficiently exhibit the effects of the present invention.

In addition, it is preferable that these alkali metal halide compounds are added in an amount of 0.01 to 0.1 mole%. If the amount is less than 0.01 mole%, the reaction promoting effect is insignificant. If the alkali metal halide compound is more than 0.1 mole%, problems such as aliphasis or side reactions occur in the polyester. to be.

In carrying out the present invention, if an extruder equipped with a static mixer or the like is used, the agitation effect can be increased and the bar is also revealed. The polyester obtained according to the above-described configuration is very useful for use as a cord of tires, belts, etc. because the content of the terminal carboxyl group is significantly lowered up to 10 eq / 10 ⁶ g or less and the hydrolysis resistance is greatly improved.

Meanwhile, the present invention is based on the premise that more than 85 mol% of the repeating unit is an ethylene terephthalate and an intrinsic viscosity of 0.60 dl / g or more for the purpose of using as an industrial fiber. A part of the glycol may be a copolymer composed of other third components. As with ordinary polyesters, small amounts of pigments such as titanium dioxide and carbon black, thermal stabilizers, antioxidants, colorants and the like may be added.

Hereinafter, the results of the present invention will be shown. As already noted, however, this is a prerequisite for the general fact that several methods are presented to enable the verification of the effects of the present invention in the same industry, and are not intended to cover the entire contents of the present invention.

For reference, each compound listed as an alkali metal halide may be included in the category of equivalents depending on the example, but includes examples for each of them for a more detailed explanation effect, the contents before and after the limits of the range of addition amount, and It is made up of examples of the preceding limitations.

Intrinsic viscosity determined as a measuring element in the present embodiment was measured by using a Uberode viscometer at 25 ° C. dissolving polyester in a solvent mixture of phenol / 1,1,2,2-tetrachloroethane (weight ratio of 3/2), The concentration of carboxyl end groups was measured by Phol's method described in Analytic Chemicals, Volume 26, page 1614 (194).

[Examples 1-10 and Comparative Examples 1-4]

Bis- (2-hydroxyethyl) terephthalate obtained by esterification of 166 parts of terephthalic acid, 69 parts of ethylene glycol, and 0.07 parts of antimony trioxide into an reactor equipped with a reflux tower for 3 hours 40 minutes at 250 ° C. and a nitrogen stream. Transfer the mixture of oligomers to a polymerization apparatus, add 0.03 part of trimethyl phosphate and an alkali metal halide compound, and slowly increase the temperature of the reaction system and depressurize the mixture to allow 285 ° C and 0.5 mmHg after 40 minutes, and continue condensation under these conditions for 120 minutes. . After polycondensation is carried out, it is pressurized with nitrogen gas and granulated by discharging and sintering polyester in water.

The granules of the polyester thus obtained were dried under a rotary dryer for 3 hours under conditions of 175 DEG C and 0.5 mmHg, and then added and mixed with a monofunctional epoxy compound while maintaining the inside of the dryer at atmospheric pressure using a nitrogen gas. This was fed to an extruder type spinning machine and spun at a temperature of 292 ° C. The physical properties of the polyester thus obtained were measured and listed in the table collectively.

The specific names and addition amounts of the halogen compound and the monoluminescent epoxy compound of the alkali metal are also shown in the table.

[Comparative Example 5]

In this Comparative Example, a polyester granulated product having an intrinsic viscosity of 0.55 and a carboxyl end group concentration of 20 eq / 106 g was obtained with a polycondensation time of 75 minutes without the addition of lithium chloride. Solid phase polymerization was carried out using a tumble dryer at 220 ° C. under a condition of 0.5 mmHg for 5 hours to obtain a polymer having an intrinsic viscosity of 0.76 carboxyl end group concentration of 10 eq / 106 g. As a result of spinning the polymer at a temperature of 292 ° C, the polyester obtained had an intrinsic viscosity of 0.73 and a carboxyl terminal group concentration of 18 eq / 106 g.

Therefore, it was confirmed that the concentration of carboxyl end groups cannot be lowered when solid phase polymerization is used in combination.

Comparative Example 6

After polycondensation for 100 minutes in the same manner as in Example 1, the reaction system was brought to atmospheric pressure using nitrogen, 0.4% by weight of phenylglycidyl ether was added, and the resultant polycondensation was continued for 25 minutes. A polyester having a carboxyl end group concentration of 8 eq / 10 ⁶ g was obtained. As a result of drying and spinning in the same manner as in Example 1, the intrinsic viscosity of the polyester was 0.75 and the carboxyl end group concentration was 17eq / 10 ⁶ g. Therefore, it was confirmed that the intended purpose cannot be achieved even by the method of adding and reacting a monofunctional epoxy compound during the polymerization reaction. This is of course because the concentration of carboxyl end groups increases again during the melt spinning process, as mentioned at the outset.

[table]

Claims (2)

85 mol% or more of the main repeating unit is ethylene terephthalate and the halogen compound of alkali metal soluble in polyester in the addition and reaction of monofunctional epoxy compound in the melt spinning process of polyester having an intrinsic viscosity of 0.60 dl / g or more. Method for producing a polyester with a low content of terminal carboxyl groups, characterized in that the addition of 0.01 to 0.1 mol% in the polymerization step. The method of claim 1, wherein the halogen compound of the alkali metal is selected from sodium iodide, potassium iodide, sodium chloride, potassium bromide, lithium chloride and potassium chloride.