JPH0859809A - Method for producing high degree of polymerization polyester - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a method of significantly increasing the degree of polymerization of a copolyester having low crystallinity and not capable of solid-state polymerization in a short time by melt polymerization. [Structure] A copolymerized polyester having terephthalic acid or naphthalene-2,6-dicarboxylic acid and ethylene glycol as main constituents and having a heat of crystal fusion of less than 45 J / g and an intrinsic viscosity of 0.7 or more is produced. At that time, at any stage when the intrinsic viscosity of the polyester reached 0.3 or more, at least one of the compounds represented by the following general formula (I) or (II) was added to the polyester in an amount of 0.05 A method for producing a polyester having a high degree of polymerization, which comprises adding 5 mol% to polycondensation. Embedded image (In the above formula, R ₁ , R ₃ , R ₄ and R ₅ are each independently a monovalent aryl group or substituted aryl group having 20 or less carbon atoms, or at least one secondary or tertiary group. (A group having a carbon atom, which is an organic residue other than an aryl group and a substituted aryl group, R ₂ is a divalent organic residue, and n is an integer of 0 or 1)

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a polyester having a high degree of polymerization. More specifically, the present invention relates to a method of significantly increasing the degree of polymerization of a copolyester that has low crystallinity and cannot be solid-phase polymerized in a short time by melt polymerization.

[0002]

BACKGROUND OF THE INVENTION Polyester, especially polyethylene terephthalate, is widely used as a material for fibers, films and bottles, and its industrial value is extremely high. Further, in recent years, a molded body obtained by thermoforming an unstretched sheet made of polyethylene terephthalate (hereinafter abbreviated as A-PET) has begun to be widely used in containers for foods, medicines and the like due to environmental problems and the like.

However, when the degree of polymerization of the raw material polyester is low and the crystallization rate is high, the sheet itself draws down in the process of heating the A-PET sheet to form a container, or the sheet becomes white and loses transparency. It's easy to do. Further, when the container is punched out from the sheet after molding, if the degree of polymerization is low and the degree of crystallinity is high, the product container will crack. Further, if the intrinsic viscosity of polyester is low, the recycling rate cannot be sufficiently increased.

In order to solve such problems, it has been earnestly desired to establish a method for producing a polyester having a large amount of copolymerization and a high degree of polymerization. Generally, in the production of polyethylene terephthalate, bis (β-hydroxyethyl) terephthalate which is an intermediate thereof and / or a low polymer thereof is produced in advance, a condensation reaction is performed in the presence of a polymerization catalyst, and ethylene glycol produced as a by-product is used as a system. It is done by distilling outside. When producing a high degree of polymerization polyester by such a method, it is necessary to perform heating at a high temperature and high vacuum for a long time, and a thermal decomposition reaction occurs at the same time in the reaction process to obtain a desired high degree of polymerization. Obtaining polyester is difficult. In addition, an increase in terminal carboxyl groups and coloring occur, which is not preferable.

For this reason, a high-polymerization degree polymer is generally produced by a solid-state polymerization method at a temperature (200 ° C. to 240 ° C.) below the melting point of the polymer so that a thermal decomposition reaction hardly occurs. That is, the solid-phase polymerization method is a method in which a prepolymer having a relatively low degree of polymerization produced by a melt polymerization method is made into chips, and then this polymer is held at a temperature 10 to 50 ° C. lower than its melting point while stirring and heated. This is a method of advancing the polymerization reaction by flowing an inert gas or drawing a high vacuum.

However, such a solid-state polymerization method has serious drawbacks. That is, since the polymerization temperature is relatively low, the reaction rate is smaller than that in the melt polymerization method, it takes a long time to obtain a polymer having a sufficiently high degree of polymerization, and the productivity is low. In the case of solid-state polymerization of a copolyester obtained by copolymerizing dicarboxylic acid such as isophthalic acid or 1,4-cyclohexanedimethanol and / or glycol with polyethylene terephthalate, the melting point is low. Even if it tries, the reaction rate is extremely slow and a polymer having a substantially high degree of polymerization cannot be obtained. Furthermore, if the amount of copolymerization is large, chips are fused to each other, so that solid-state polymerization is extremely impossible.

Therefore, a method for producing a copolyester having a high degree of polymerization in a short time without using the solid phase polymerization method has been desired.

[0008]

[Means for Solving the Problems] The inventors of the present invention have paid attention to the above circumstances, and have been keen to establish a method for producing a polyester having a high degree of polymerization by a melt polymerization method without using a solid phase polymerization method. As a result of repeated studies, the present invention has been completed. That is, the gist of the present invention is that terephthalic acid or naphthalene-2,6-dicarboxylic acid and ethylene glycol are the main constituents, and the heat of crystal fusion is 45 J /
When producing a copolyester having an intrinsic viscosity of less than g and an intrinsic viscosity of 0.7 or more, it is represented by the following general formula (I) or (II) at any stage when the intrinsic viscosity of the polyester reaches 0.3 or more. At least one of the compounds is added in an amount of 0.05 to 5 mol% with respect to the acid component of the polyester, and polycondensed, which is a method for producing a high-polymerization degree polyester.

[0009]

Embedded image

(In the above formula, R ₁ , R ₃ , R ₄ and R ₅
Are each independently a monovalent aryl group having 20 or less carbon atoms or a substituted aryl group, or a group having at least one secondary or tertiary carbon atom, other than the aryl group and the substituted aryl group. Organic residue, R ₂ is 2
Valent organic residue, n represents an integer of 0 or 1) The present invention will be described in more detail below.

The polyester used in the present invention refers to a polyester obtained by using terephthalic acid or naphthalene-2,6-dicarboxylic acid and ethylene glycol as main starting materials. The polymer is once melted and then cooled.
The heat of crystal fusion when heated at a rate of 10 ° C / min is 45 J /
It is a copolyester containing another third component so as to be less than g. In this case, as the dicarboxylic acid component, for example, one or more of isophthalic acid, naphthalene-2,6-dicarboxylic acid, terephthalic acid, adipic acid and sebacic acid can be used in combination. As the glycol component, diethylene glycol, triethylene glycol, propylene glycol, butanediol,
One or more of 1,4-cyclohexanedimethanol and neopentyl glycol can be used in combination.

In any case, the polyester of the present invention is a polyester whose main repeating structural unit has an ethylene terephthalate unit or an ethylene-2,6-naphthalate unit and has a heat of crystal fusion of less than 45 J / g, preferably. Less than 35 J / g, more preferably 25
It refers to a copolyester containing a plurality of dicarboxylic acid components and / or a plurality of glycol components so as to be less than J / g. At this time, the copolymerization component is usually 5 to 95 mol% with respect to the acid component or glycol component of the polyester.
When it is contained, the polyester of the present invention has a heat of fusion of crystal of less than 45 J / g. Suitable polyesters for A-PET sheet and the like include isophthalic acid and / or 1,4 in the case of polyethylene terephthalate polymer.
-Examples in which cyclohexanedimethanol is copolymerized at 5 to 10 mol% are mentioned. When the heat of crystal fusion is 45 J / g or more, when the A-PET sheet is heated to be molded into a container, the crystallization rate of the raw material polyester is high, so that the sheet itself is whitened and easily broken, and the transparency is lost. I will be destroyed.

The copolymerized polyester referred to here contains conventionally known catalysts, heat-resistant agents, anti-coloring agents, flame retardants, inert fine particles, etc., if the heat of crystal fusion is less than 45 J / g. But of course it doesn't matter. The following are specific examples of the compounds represented by the general formulas (I) and (II) used as a reaction accelerator in the present invention. That is, in the general formulas (I) and (II), R ₁ , R ₃ , R ₄ and R ₅ are phenyl groups which may be substituted with chloro, tolyl groups, diphenyl groups, naphthyl groups, isopropyl groups, Examples of the divalent organic residue represented by R ₂ include a phenylene group, a naphthylene group, and a t-butyl group.
An alkylene group and the like. The specific chemical formula is as follows. (I) Compound represented by general formula (I)

[0014]

[Chemical 3]

[0015]

[Chemical 4] (Ii) Compound represented by general formula (II)

[0016]

[Chemical 5]

Of these, diphenyl carbonate, diphenyl terephthalate, diphenyl naphthalate, di-t-butyl terephthalate and the like are particularly preferably used. The intrinsic viscosity of the polyester when the compounds represented by the general formulas (I) and (II) are added is 0.3 or more, but when the intrinsic viscosity is 0.7 or more, the melt viscosity of the polyester is Since it is difficult to uniformly mix the added reaction accelerator, the intrinsic viscosity of the polyester is preferably 0.3 or more and less than 0.7, more preferably 0.4 or more and less than 0.7. It is less than 7, and particularly preferably 0.5 or more and less than 0.7. When the intrinsic viscosity is less than 0.3, the general formulas (I) and (II) of the present invention are used.
Even if the compound represented by is added, a remarkable effect of promoting polymerization cannot be obtained.

In the present invention, the general formulas (I) and (I
The addition amount of the compound represented by I) is 0.05 to 5 mol% with respect to the acid component of the polyester, preferably 0.05 to
It is 3 mol%. If the amount of the compounds (I) and (II) added is less than 0.05 mol%, the effect of the present invention is not exhibited, and if the amount added exceeds 5 mol%, the polycondensation reaction is rather inhibited, which is not preferable. . The addition amount of the compounds (I) and (II) is more preferably in the range shown in the following equation, which is a relational expression with the intrinsic viscosity of the polyester at the time of addition.

[0019]

## EQU1 ## − [η ₀ ] + 0.8 ≦ M ≦ −4 [η ₀ ] +4.2

(In the above formula, M is the mol% of the acid component of the polyester of compounds (I) and (II), and [η ₀ ] is the intrinsic viscosity of the polyester at the time of adding compounds (I) and (II). The method of adding the compounds (I) and (II) may be any method. For example, once the reaction system is returned to normal pressure, the powder of the compound is directly added and added, and A method of performing melt polycondensation under a high vacuum may be adopted, but in order to sufficiently bring out the effect of the present invention, 1 mm after addition
It is desirable to hold the mixture at a vacuum of Hg or higher for 30 minutes or more with stirring.

The compounds (I) and (II) may be added in two or more divided portions, or two or more of them may be added in combination, as long as they fall within the above-mentioned addition amounts. The effect of the present invention is exhibited irrespective of the purpose when producing a polymer having an intrinsic viscosity of 0.7 or more, particularly 0.8 or more. That is, even if the compounds (I) and (II) are added, if the intrinsic viscosity of the final polyester is less than 0.7, A-
When the PET sheet is heated and molded into a container, the sheet itself draws down, so that the molding process cannot be performed well.

[0022]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist. Incidentally, the measuring methods of various physical properties and characteristics in Examples,
The definition is as follows. In Examples and Comparative Examples, “part” means “part by weight”. (1) dissolving the polymer composition the polymer in trifluoroacetic acid -d _1, ¹ H-
It was analyzed by the NMR method. (2) Heat of Crystal Melting Polymer was heated at 10 ° C./min, melted at 285 ° C. for 5 minutes, cooled in liquid nitrogen, and again heated at 10 ° C./min by the DSC method (differential scanning calorimetry Method) to perform thermal analysis. (3) Intrinsic viscosity 1 g of polymer is phenol / tetrachloroethane = 50
Dissolve in 100 ml of 50/50 (weight ratio) mixed solvent and
It was measured at 0.0 ° C. (4) Terminal carboxyl group concentration A. The method of Conix (makromol. Chem.
26, 226 (1958)). (5) Drawdown resistance A square sheet 200 mm long × 200 mm wide × 0.3 mm thick is held in the air at 140 ° C for 10 seconds, and the maximum hanging width of the center of the sheet is measured. The drawdown resistance of the raw material polyester was judged according to the following criteria.

[0023]

[Equation 2]

Evaluation Criteria Drawdown Rate ≦ 7% ・ ・ ・ ○ (Good) 7% <Drawdown Rate ≦ 14% ・ ・ ・ △ (Normal) 14% <Drawdown Rate ≦ 21% ・ ・ ・ × (Poor) 21% <Drawdown rate ... XX (extremely bad) (6) Whitening resistance A square sheet 200 mm long × 200 mm wide × 0.3 mm thick is held in air at 140 ° C for 10 seconds to The whitening state was visually judged according to the following criteria. ○ ・ ・ ・ Transparent, △ ・ ・ ・ Light whitening, × ・ ・ ・ Whitening

Example 1 [Production of polyester] Dimethyl terephthalate 78
Parts, 22 parts of dimethyl isophthalate, 66 parts of ethylene glycol and 0.094 parts of calcium acetate 1 / hydrate are heated in a reactor, heated and heated to distill off methanol to carry out an ester exchange reaction, and 4 hours from the start of the reaction. The temperature was raised to 240 ° C., and a polyester oligomer was obtained. Next, 0.037 part of orthophosphoric acid was added, and 0.04 part of antimony trioxide was further added, and the temperature was adjusted to 250 ° C from 285
While raising the temperature to ℃ in 1 hour, the vacuum degree is 760mm at the same time.
Reduce the pressure from Hg to 1 mmHg and continue at 285 ° C for 1 m
Polycondensation was carried out under the condition of mHg.

When the intrinsic viscosity of the polyester reached 0.53, the reaction system was returned to normal pressure with nitrogen, and 0.836 parts of diphenyl carbonate was added as a reaction accelerator,
The reaction was continued at 285 ° C. under a high vacuum of 1 mmHg for 40 minutes. The intrinsic viscosity of the obtained polyester is 0.8.
7, the terminal carboxyl group concentration is 18.5 equivalents / ton,
The heat of fusion of crystal was 12.5 J / g.

[Production of Polyester Sheet] The obtained polyester was vacuum-dried at 60 ° C. for a whole day and night and then 280 using a 65 mmφ single screw extruder equipped with a T-die.
Melt extruded at ℃, 0.3mm thick amorphous sheet (A-
A PET sheet) was obtained. The obtained polyester sheet was good in terms of drawdown resistance and whitening resistance. The obtained results are summarized in Table 1 below together with other examples and comparative examples.

Example 2 A polyester and a sheet were obtained in the same manner as in Example 1 except that the raw material acid component of the polyester to be produced was changed to 67 parts of dimethyl terephthalate and 33 parts of dimethyl isophthalate.

Example 3 90 parts of dimethyl terephthalate as raw material acid component of the polyester to be produced and ethylene glycol 4 as glycol component
A polyester and a sheet were obtained in the same manner as in Example 1 except that 7 parts, 23 parts of 1,4-cyclohexanedimethanol and the reaction accelerator added during the polycondensation reaction were changed to diphenyl terephthalate.

Example 4 85 parts of dimethyl terephthalate, 15 parts of dimethyl terephthalate as raw material acid component of polyester to be produced, 58 parts of ethylene glycol as glycol component, 13 parts of 1,4-cyclohexane dimethanol and diphenyl terephthalate as reaction accelerator. A polyester and a sheet were obtained in the same manner as in Example 1 except for the changes.

Example 5 78 parts of dimethyl terephthalate, 19 parts of dimethyl isophthalate, 58 parts of ethylene glycol, 8 parts of 1,4-cyclohexanedimethanol and 8 parts of dimethyl terephthalate as raw material acid components of the polyester to be produced were added during the polycondensation reaction. A polyester and a sheet were obtained in the same manner as in Example 1 except that the reaction accelerator was changed to di-t-butyl terephthalate.

Example 6 In Example 1, the raw material acid component of the polyester produced was 82 parts of dimethyl naphthalene-2,6-dicarboxylate,
A polyester and a sheet were obtained in the same manner as in Example 1 except that 18 parts of dimethyl terephthalate, 54 parts of a glycol component and 54 parts of ethylene glycol and the reaction accelerator added during the polycondensation reaction were changed to diphenyl naphthalate.

Comparative Example 1 A polyester and a sheet were obtained in the same manner as in Example 1 except that the raw material acid component of the polyester to be produced was changed to 100 parts of dimethyl terephthalate and the glycol component was changed to 66 parts of ethylene glycol.

Comparative Example 2 A polyester and a sheet were obtained in the same manner as in Example 2 except that the addition amount of diphenyl carbonate as a polymerization accelerator was changed to 0.005 mol%.

Comparative Example 3 A polyester and a sheet were obtained in the same manner as in Example 3 except that the polymerization accelerator, diphenyl terephthalate, was added at the time when the intrinsic viscosity reached 0.21. .

Comparative Example 4 A polyester and a sheet were obtained in the same manner as in Example 5, except that the addition amount of di-t-butyl terephthalate, which is a polymerization accelerator, was changed to 7.5 mol%.

Comparative Example 5 In Example 6, the raw material acid component of the polyester to be produced was the naphthalene-2,6-dicarboxylic acid dimethyl 101.
Parts and a glycol component were changed to 51 parts of ethylene glycol to obtain polyester and a sheet in the same manner as in Example 6. As shown in Table 1, the sheet properties of Examples 1 to 6, which are in the category of the present invention, are improved in drawdown resistance and whitening resistance at the same time, and the method for producing the raw material polyester is extremely useful.

[0038]

[Table 1]

[0039]

INDUSTRIAL APPLICABILITY The polyester obtained by the method of the present invention has low crystallinity and a high degree of polymerization, and is industrially very useful as a polyester raw material for obtaining a sheet or the like.

Claims (1)

[Claims] 1. Terephthalic acid or naphthalene-2,6
-When producing a copolyester having a dicarboxylic acid and ethylene glycol as main constituents and having a heat of crystal fusion of less than 45 J / g and an intrinsic viscosity of 0.7 or more, the intrinsic viscosity of the polyester is 0.3. At any stage that has reached the above, at least one of the compounds represented by the following general formula (I) or (II) is added in an amount of 0.05 to 5 mol% with respect to the acid component of the polyester, and polycondensed. A method for producing a polyester having a high degree of polymerization. Embedded image (In the above formula, R ₁ , R ₃ , R ₄ and R ₅ are each independently a monovalent aryl group or substituted aryl group having 20 or less carbon atoms, or at least one secondary or tertiary group. (A group having a carbon atom, which is an organic residue other than an aryl group and a substituted aryl group, R ₂ is a divalent organic residue, and n is an integer of 0 or 1)