ES2649972T3 - Method for manufacturing an ester composition and a resin composition - Google Patents

Abstract

A method for preparing an ester composition, comprising the following steps: obtaining an ester composition comprising alkyl group substituted terephthalate compounds of the hybrid branched type, the unbranched and the hybrid type and the hybrid unbranched type by an esterification reaction, where the hybrid branched type alkyl substituted terephthalate compound is present in an amount of between 1% and 70% by weight in the ester composition, where the esterification reaction encompasses reacting terephthalic acid, an unbranched alcohol and a branched alcohol at between 130 ° C and 250 ° C for between 1 and 10 hours, in the presence of between 0.1 and 15 parts by weight of an acid catalyst relative to 100 parts by weight of terephthalic acid, where the acid catalyst comprises at least one compound selected from the group consisting of paratoluenesulfonic acid, methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, and sulfuric acid ico.

Description

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DESCRIPTION

Method for manufacturing an ester composition and a resin composition Technical field

The present invention relates to a method for preparing an ester composition and a resin composition. More specifically, the present invention is related to a method for properly preparing a plasticizer composition that has improved processability due to its high absorption rate and its short melting period in resin making, so it has superior physical properties when it is Process with resins.

Technical background

In general, a plasticizer is composed of an ester produced by a reaction between an alcohol and a polycarboxylic acid, such as phthalic acid or adipic acid. Examples of commercially essential plasticizers include C8, C9 or C10 alcohol adipates, for example, di (2-ethylhexyl) adipate, diisononyl adipate or diisodecyl adipate, and C8, C9 or C10 alcohol phthalates, for example, phthalates of di (2-ethylhexyl), diisononyl phthalate or diisodecyl phthalate.

Specifically, di (2-ethylhexyl) phthalate is incorporated into toys, films, shoes, coatings, flooring materials, gloves, wallpaper, artificial leather, sealants, tarpaulins, automotive floor coverings, furniture, foam mats or Sound insulation panels using plastisol and a dry mix. It is also used to produce exterior materials, insulators for PVC cables or other PVC products with calendered plastic.

Di (2-ethylhexyl) adipate is mainly used in films and to a lesser extent in other products, for example, wallpaper, artificial leather, coatings for car floors, gloves or sealants. In particular, di (2-ethylhexyl) adipate is usually used when the products are to be used at a low temperature and / or when plastisol is used as an intermediate.

In addition to di (2-ethylhexyl) adipate, extensive research is being carried out on ecological plasticizers due to environmental problems associated with phthalate-based plasticizers. In KR 10-2013-0035493 a method for preparing an ester composition comprising 50% by weight of 1-butyl 4- (2- ethylhexyl) terephthalate, 10% by weight of dibutyl terephthalate and 40% by weight is described. of di- (2-ethylhexyl) terephthalate by esterification of terephthalic acid with butanol and 2-ethylhexanol.

Technical problem

During the recurrent investigation of ecological plasticizers, the present inventors discovered that an ester composition having a specific content of a terephthalate compound substituted with a branched hybrid alkyl selected from terephthalate compounds substituted with branched hybrid type alkyl groups, type unbranched or hybrid and unbranched type hybrid has improved processability due to its high absorption rate and its short melting period in resin making, and also provides superior physical properties during sheet formulation and wire composite formulation, car interior materials, films, sheets, tubes, wallpaper, toys, flooring materials or similar items. The present invention was completed thanks to this discovery.

In this context, an objective of the present invention was to provide a method for preparing an ester composition comprising terephthalate compounds substituted with alkyl groups of branched hybrid type, unbranched or hybrid type and unbranched hybrid type as ecological plasticizer, where the Terephthalate compound substituted with a hybrid branched alkyl was present in a specific amount in the ester composition.

Another objective of the present invention was to provide a resin composition comprising this ester composition.

Technical solution

According to one aspect of the present invention, the foregoing and other objects can be met with a method for preparing an ester composition comprising terephthalate compounds substituted with alkyl groups of branched hybrid type, unbranched or hybrid type and unbranched hybrid type by a esterification reaction, where the terephthalate compound substituted with a hybrid branched alkyl is present in an amount of between 1% and 70% and where the esterification reaction comprises reacting terephthalic acid, an alcohol not

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branched and a branched alcohol at between 130 ° C and 250 ° C for between 1 and 10 hours, in the presence of between 0.1 and 15 parts by weight of an acid catalyst in relation to 100 parts by weight of terephthalic acid, where the Acid catalyst comprises at least one compound selected from the group consisting of paratoluenesulfonic acid, methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid and sulfuric acid. The invention will be described in detail later.

In the present invention, an ester composition is prepared comprising terephthalate compounds substituted with alkyl groups of the branched hybrid type, unbranched or hybrid type and unbranched hybrid type, where the terephthalate compound substituted with a branched hybrid type is present in a specific amount in the ester composition.

As used herein, the term "branched hybrid type" applies to a compound where the alkyl groups substituted at the symmetrical positions of a phenyl group are different and there is a branched chain type, unless otherwise specified. .

In addition, as used herein, the term "unbranched or hybrid type" applies to a compound where the alkyl groups substituted at the symmetrical positions of a phenyl group are identical and there are two types of linear hydrocarbons without branched chains, unless otherwise specified.

In addition, as used herein, the term "unbranched hybrid type" applies to a compound where the alkyl groups substituted at the symmetrical positions of a phenyl group are identical and there are two types of branched chains, unless Specify otherwise.

According to the present invention, for example, among the terephthalate compounds substituted with alkyl groups of the branched hybrid type, unbranched or hybrid type and unbranched hybrid type obtained by esterification with an acid catalyst, the terephthalate compound substituted with an alkyl of Branched hybrid type is present in an amount of between 1% and 70% by weight, between 5% and 50% by weight, between 10% and 50% by weight, between 20% and 50% by weight or between 25% and 50 % in weigh. The contents in these ranges can be obtained by controlling the conditions of the esterification reaction.

The substituted alkyl is, for example, an alkyl group with between 3 and 10 carbon atoms. In another example, the substituted alkyl comprises at least one group independently selected from an alkyl group with between 3 and 4 carbon atoms or an alkyl group with between 8 and 10 carbon atoms, because these are easier to process (for provide more efficient plasticization) because of the high absorption rate of the resins and the level of loss due to migration.

In another example, the terephthalate compound substituted with a hybrid branched alkyl may be represented by formula 1.

Formula 1

image 1

In another example, the terephthalate compound substituted with an unbranched or hybrid type alkyl can be represented by formula 2.

Formula 2

image2

In another example, the terephthalate compound substituted with a hybrid unbranched alkyl type can be represented by formula 3.

5 Formula 3

image3

In another example, the weight ratio in a mixture between a terephthalate compound substituted with an unbranched or hybrid alkyl and a terephthalate compound substituted with a hybrid unbranched alkyl is between 1:99 and 40:60 , between 1:99 and 15:85, between 1:99 and 9.9: 90.1 or between 1:99 and 9.6: 90.4. With these ranges, processability can be improved, that is, absorption rate, melting period or other physical properties.

The esterification conditions that satisfy these requirements have been obtained by combining an unbranched alcohol with a branched alcohol.

In a specific example, the unbranched alcohol is an unbranched aliphatic alcohol comprising a C3-C4 alkyl group and is present in an amount of between 1% and 80% by weight or between 15% and 50% by weight, in relation to 15 to 100% by weight of alcohol. In another example, the unbranched alcohol can be n-butyl alcohol.

In addition, in a specific example, the branched alcohol may be a branched aliphatic alcohol with a C8-C10 alkyl group, which may be present in an amount of between 99% and 20% by weight or between 80% and 20% by weight, in relation to 100% by weight of alcohol. In another example, the branched alcohol is 2-ethyl hexanol.

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The conditions of the esterification reaction that satisfy these requirements also include, for example, the use of terephthalic acid in the form of particles with an average diameter of between 30 and 100 pm or between 39 and 91 pm. With these ranges, the reaction duration is decreased and production efficiency can be improved.

In a specific example, the terephthalic acid can be mixed with an alcohol after crushing it to obtain particles with the previously defined diameter, or it can be crushed to obtain particles with the desired diameter after mixing it with the alcohol.

The crushing may include a dry crushing or a wet crushing, if necessary. In a specific example, a wet mill with a high rotation speed, such as a Cavitron device or a homogenizer, can be used.

In another example, the high rotation speed can be between 3,000 and 50,000 rpm or between 10,000 and 50,000 rpm, so as to obtain the desired distribution of the average diameter of the particles in a short period.

The terephthalic acid and alcohol content can be between 10% and 40% molar and between 90% and 60% molar, between 20% and 30% molar and between 80% and 70% molar or between 21% and 29% molar and between 79% and 71% molar, respectively, in relation to the total moles of the reagents. As a reference, with these ranges the concentration of the esterification reagents, which is a reversible reaction, is increased, and the inverse reaction is inhibited, whereby the reaction rate can be increased.

If necessary, carboxylic acids, polycarboxylic acids or anhydrides thereof can be added.

The conditions of the esterification reaction that satisfy these requirements include the use of an acid catalyst as a reaction catalyst, at a temperature between 130 ° C and 250 ° C, between 130 ° C and 220 ° C or between 180 ° C and 220 ° C, for a period of between 1 and 10 hours or between 5 and 7 hours.

The acid catalyst comprises at least one catalyst selected from paratoluenesulfonic acid, methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid or sulfuric acid.

The reaction catalyst is present in an amount of between 0.1 and 15 parts by weight, between 0.1 and 10 parts by weight, between 0.1 and 7 parts by weight or between 0.1 and 5.0 parts by weight, relative to 100 parts by weight of terephthalic acid as the raw material for the reaction. As a reference, the efficiency of the reaction can be reduced when the content of the reaction catalyst is lower than these ranges, and the products can be discolored when the content of the reaction catalyst is greater than these ranges.

The esterification reaction can be carried out under a nitrogen atmosphere to block the entry of air from outside the reaction system, and nitrogen can be bubbled into the reaction solution to remove the water produced during the reaction due to the condensation of the esterification. . To meet these objectives, the esterification reaction can be carried out at an increased or decreased pressure.

The plasticizer composition, that is, the ester composition, can be obtained with a purity of between 96% and 99.99% or between 96.1% and 99.1% by usual post-treatment processes, for example, neutralization, washing with water and desalcoholización.

The ester composition comprises a mixture of terephthalate compounds substituted with alkyl groups of the branched hybrid type, unbranched or hybrid type and hybrid unbranched type, where the terephthalate compound substituted with a hybrid branched alkyl is present in an amount of between 1% and 20% by weight, between 1% and 19.5% by weight, between 1% and 19% by weight or between 5% and 12% by weight. With these ranges, superior processability is obtained.

A resin composition can be provided by mixing the ester composition with a resin. The resin is, for example, a thermoplastic resin, and in another example, it comprises at least one compound selected from ethylene vinyl acetate, polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyurethane, thermoplastic elastomers or polylactic acid.

For example, the plasticizer is absorbed from the resin composition in between 1 and 10 minutes, between 3 and 8 minutes or 4 minutes. With these ranges, superior viability and processability are obtained.

Here, the absorption rate is evaluated by determining the time that elapses until the resin is mixed with the plasticizer, under mixing conditions with a temperature of 77 ° C, stirring at 66 rpm, 400 g of PVC (product name : LS100, LG Chem. Ltd.) and 200 g of a plasticizer, using a mixer (product name: Brabender P600) with a stabilized torque.

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A stabilized torque is one that remains even as it increases when the resin is added for the first time, and then gradually reduced while adding the plasticizer to determine the rate of absorption. This state can be determined from a graph on a monitor.

In addition, the resin composition has a solution viscosity between 4000 and 15000 cp, between 5000 and 11000 cp or between 6000 and 9000 cp. With these ranges, stable processability is ensured.

Here, the viscosity in solution is determined with a Brookfield viscosity meter (LV type), with a spindle No. 4 and stirring at between 6 rpm and 12 rpm. 100 phr of PVC were mixed as a sample (PB900, LG Chem. Ltd.), 75 phr of a plasticizer, 4 phr of a stabilizing agent (KSZ111XF), 3 phr of a foaming agent (W1039), 13 phr of TiÜ2 (TMCA100 ), 130 phr of CaCÜ3 (OMYA10), 10 phr of a viscosity reducing agent (Exa-sol) and 1 phr of a dispersant (BYK3160) to prepare a plastisol, which was stored at 25 ° C for 1 hour to Determine the viscosity in solution.

The resin composition may have a low viscosity reducing agent content, as compared to conventional products, or it may not contain it at all, that is, it may be a resin composition without viscosity reducing agents.

Hereby, a composition without viscosity reducing agents is a composition that does not contain viscosity reducing agents at all to control its viscosity.

The ester composition may be mixed in an amount of between 5 and 150 parts by weight or between 5 and 100 parts by weight, relative to 100 parts by weight of the resin. In addition, at least one plasticizer composition selected from dioctyl phthalate (DÜP), dibutyl phthalate (DBP), dioctyl terephthalate (DOTP), diisononyl phthalate (DINP) or diisodecyl phthalate (DIDP) may be added in an amount of 5 and 150 parts by weight or between 5 and 100 parts by weight, relative to 100 parts by weight of the resin.

In addition, the resin composition may comprise between 0.5 and 7 parts by weight of a stabilizing agent and between 0.5 and 3 parts by weight of a lubricant or a similar component, and optionally also comprises at least one common additive.

In addition, the resin composition may comprise, for example, a filler.

Any filler commonly used in the technical field associated with the resin composition of the present invention can be employed, without limitations.

The filler can be added, for example, in an amount of between 10 and 300 parts by weight, between 50 and 200 parts by weight or between 100 and 200 parts by weight, relative to 100 parts by weight of the resin.

In addition, the resin composition may comprise, for example, at least one component selected from the group consisting of a pigment, a dye, a processing aid, a dispersant, a foaming agent, an antifoaming agent and a reducing agent. viscosity.

Each pigment, colorant, processing aid, dispersant, foaming agent, antifoaming agent or viscosity reducing agent is present, for example, in an amount of between 0.1 and 20 parts by weight or between 1 and 15 parts by weight , in relation to 100 parts by weight of the resin.

The resin composition can be used, for example, to manufacture sheet formulations and composite formulation products such as cables, automotive interior materials, films, sheets, tubes, wallpaper, toys or flooring materials.

Advantageous effects

In the present invention there is provided a method for properly preparing a plasticizer composition having a high absorption rate, a short melting period in resin making and an improved processability.

Brief description of the drawings

An image taken with an optical microscope (x50) of example 1 according to the present invention, comparative examples 1 and 2, dioctyl phthalate (DÜP) alone and diisononyl phthalate (DINP) alone is provided, where, from From top to bottom, the DÜP alone, the DINP alone, the comparative example 2, the comparative example 1 and the example 1 according to the present invention are represented in order.

An image taken with an optical microscope (x50) of example 2 according to the present invention, comparative examples 1 and 2, dioctyl phthalate (PDO) alone and diisononyl phthalate (DINP) alone, where, from From top to bottom, the PDO alone, the DINP alone, the comparative example 2, the comparative example 1 and the example 2 according to the present invention are represented in order.

5 Best mode

The present invention will be described in greater detail in the following examples. These examples are only provided to illustrate the present invention.

Example 1

Terephthalic acid was triturated using a Cavitron device to prepare particulate ground terephthalic acid with a mean diameter (measured with a Nicomp 380 laser dispersion analyzer) between 30 and 100 pm. 440 g of ground terephthalic acid, 302 g of n-butanol and 530 g of 2-ethyl hexanol were subjected to an esterification reaction in the presence of 32 g of 70% methanesulfonic acid at 130 ° C for 7 hours. The reaction product was neutralized with Na2CO3, washed with water once and de-alcoholized by heating under reduced pressure to obtain a plasticizing composition.

15 As a result of the analysis of the plasticizer composition obtained using a GC-mass spectrometry (product name: Agilent 7890 GC, column: HP-5, carrier gas: helium maintained at an initial temperature of 70 ° C for 3 minutes, which it was increased to 280 ° C at a rate of 10 ° C / minute, where it was maintained for 5 minutes), it was determined that it comprised substances with the following formulas 1, 2 and 3.

Formula 1

image4

image5

image6

The weight ratio between formulas 1, 2 and 3 was 50:10:40.

5 Example 2

A plasticizer composition was prepared by repeating the process of example 1, except that 440 g of crushed terephthalic acid was reacted in the same manner as in example 1, 98 g of n-butanol and 823 g of 2-ethyl hexanol in the presence of 32 g of 70% methanesulfonic acid at 140 ° C for 6 hours. Using a GC-mass spectrometry, a weight ratio between formulas 1,2 and 3 of 25: 3: 72 was determined.

10 Example 3

A plasticizer composition was prepared by repeating the process of example 1, except that 440 g of crushed terephthalic acid was reacted in the same manner as in example 1.49 g of n-butanol and 909 g of 2-ethyl hexanol in the presence of 32 g of 70% methanesulfonic acid at 140 ° C for 6 hours. Through a GC-mass spectrometry, a weight ratio between formulas 1,2 and 3 of 12: 2: 86 was determined.

15 Example 4

A plasticizer composition was prepared by repeating the process of example 1, except that 440 g of crushed terephthalic acid was reacted in the same manner as in example 1.25 g of n-butanol and 951 g of 2-ethyl hexanol in the presence of 32 g of 70% methanesulfonic acid at 140 ° C for 6 hours. Using a GC-mass spectrometry, a weight ratio between formulas 1,2 and 3 of 5: 1: 94 was determined.

Comparative Example 1

A plasticizer composition was prepared by repeating the process of Example 1, except that 440 g of terephthalic acid was reacted with 890 g of n-butanol at 130 ° C for 13 hours. Using a GC mass spectrometry, it was determined that the plasticizer obtained contained a compound of formula 2.

5 Formula 2

image7

A plasticizer composition was prepared by repeating the process of Example 1, except that 440 g of terephthalic acid was reacted with 1060 g of 2-ethylhexanol using 1.6 g of tetraisopropyl titanate as catalyst at 10 220 ° C for 5 hours.

Using a GC mass spectrometry, it was determined that the plasticizer obtained contained a compound of formula 3.

Formula 3

image8

Between 5 and 100 parts by weight of the plasticizers obtained in examples 1 to 4 and comparative examples 1 and 2, DOP alone or DINP alone were combined with 100 parts by weight of a vinyl chloride resin, a

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stabilizing agent, a lubricant and a foaming agent and an extrusion was performed. Physical properties such as absorption rate and processability were evaluated.

The product of Example 1 was absorbed in 244 seconds, which was determined (with a melt analysis) with a mixture at 77 ° C and 60 rpm, with 400 g of PVC (product name: LS 100) and 200 g of plasticizer: it was a faster absorption than that obtained with dioctyl phthalate (PDO) alone (306 seconds) and much faster than that obtained with dioctyl terephthalate (DOTP) alone (428 seconds) (example comparative 2). By melting analysis of the product of example 1, a melting period of 32 seconds was determined.

In addition, to assess the migration resistance of the product of Example 1, the loss due to migration was determined based on the level of plasticizer lost due to migration after heating at 80 ° C for 72 hours, which was of 3.75%.

Wallpaper processing properties were also evaluated. In Figure 1 it can be seen that the wallpaper processed with the product of Example 1 foamed uniformly, depending on the size, shape and arrangement of the cells observed under an optical microscope once the foam was formed, compared to what was obtained with dioctyl phthalate (DOP) alone, diisononyl phthalate (DINP) alone or dioctyl terephthalate (DOTP).

The product of Example 1 was absorbed in 280 seconds, which was determined (with a melt analysis) with a mixture at 77 ° C and 60 rpm, with 400 g of PVC (product name: LS 100) and 200 g of plasticizer: it was a faster absorption than that obtained with dioctyl phthalate (PDO) alone (306 seconds), and like the product of example 1, it was much faster than that obtained with terephthalate of dioctyl (DOTP) alone (comparative example 2). By melting analysis of the product of example 2, a melting period of 38 seconds was determined. The resistance to migration was 3.46%.

Wallpaper processing properties were also evaluated. In Figure 2 it can be seen that the wallpaper processed with the product of Example 2 foamed uniformly, depending on the size, shape and arrangement of the cells observed under an optical microscope once the foam was formed, compared to what was obtained with dioctyl phthalate (DOP) alone, diisononyl phthalate (DINP) alone or dioctyl terephthalate (DOTP).

The product of comparative example 1 was absorbed in 100 seconds, which was determined (with a fusion analysis) with a mixture at 77 ° C and 60 rpm, with 400 g of PVC (product name: LS 100) and 200 g plasticizer: it was a considerably slow absorption, compared to that obtained with dioctyl phthalate (PDO) alone (306 seconds).

In addition, to assess the migration resistance of the product of comparative example 1, the loss due to migration was determined based on the level of plasticizer lost due to migration after heating at 80 ° C for 72 hours, which was 10.56%, that is, greater than that obtained with PDO alone (3.95%). This is an indication that the product of comparative example 1 migrated more due to its low molecular weight and its disadvantageous structure compared to PDO. The loss due to the migration of the product of comparative example 2 was 3.54%.

In Figures 1 and 2 it can be seen that the wallpaper processed with the product of comparative example 1 foamed uniformly, depending on the size, shape and arrangement of the cells observed under an optical microscope once the foam was formed, compared to what was obtained with DOP, DINP or DOTP alone. It was also determined that the melting period of comparative example 2 was 138 seconds, and that its migration, a reflection of its resistance to migration, was 3.54%.

The determined values are summarized in table 1 below.

Table 1

 Articles

 PDO only DINP only Comp. 2 Comp. 1 Ex. 1 Ex. 2 Ex. 3 Ex. 4

 Absorption period (minutes and seconds)

 5:06 6:20 7:08 1:40 4:04 4:40 5:21 6:35

 Fusion Period (seconds)

 32 45 138 22 32 38 68 95

 Migration (%)

 3.95 3.29 3.54 10.56 3.75 3.46 3.40 3.41

When comparing the results obtained with the products of examples 1 to 4 and the products of comparative examples 1 and 2, it was determined that examples 1 to 4, where ester plasticizers comprising all the components in one component were used appropriate mixing ratio, they presented 5 preferable physical properties.

It was also determined that the product of comparative example 1, which only comprised the compound of formula 2, presented shorter absorption and melting periods (which facilitated gelation but compromised manageability and foaming) but migrated to a greater extent .

On the other hand, the product of comparative example 1, which comprised the compound of formula 3, practically did not migrate but exhibited prolonged absorption and fusion periods.

Claims (9)

1. A method for preparing an ester composition, comprising the following steps: obtaining an ester composition comprising terephthalate compounds substituted with alkyl groups of the branched hybrid type, unbranched or hybrid type and unbranched hybrid type by an esterification reaction, 5 wherein the terephthalate compound substituted with a hybrid branched alkyl is present in an amount of between 1% and 70% by weight in the ester composition, where the esterification reaction comprises reacting terephthalic acid, an unbranched alcohol and a branched alcohol at between 130 ° C and 250 ° C for between 1 and 10 hours, in the presence of between 0.1 and 15 parts by weight of a catalyst acid relative to 100 parts by weight of terephthalic acid, wherein the acid catalyst comprises at least one compound selected from the group consisting of paratoluenesulfonic acid, methanesulfonic acid, ethanesulfonic acid, propanosulfonic acid and sulfuric acid. 2. The method according to claim 1, wherein the terephthalate compound substituted with a hybrid branched alkyl is present in an amount of between 1% and 20% by weight. 3. The method according to claim 1, wherein the terephthalate compound substituted with a branched alkyl type hybrid is represented by formula 1. Formula 1 image 1 4. The method according to claim 1, wherein the terephthalate compound substituted with an unbranched or hybrid type alkyl is represented by formula 1. 20 Formula 2 image2 5. The method according to claim 1, wherein the terephthalate compound substituted with an unbranched hybrid type alkyl is represented by formula 3. Formula 3 5 image3 6. The method according to claim 1, wherein the weight ratio between the terephthalate compound substituted with an unbranched or hybrid type alkyl and the terephthalate compound substituted with a hybrid unbranched type alkyl is between 1:99 and 40:60 7. The method according to claim 1, wherein the unbranched alcohol comprises between 1% and 80% by weight of an unbranched aliphatic alcohol having a C3-C4 alkyl group, with a ratio of 100% by weight of the alcohol. 8. The method according to claim 1, wherein the branched alcohol comprises between 99% and 20% by weight of a branched aliphatic alcohol having a C8-C10 alkyl group, relative to 100% by weight of the alcohol. 9. The method according to claim 1, wherein in relation to terephthalic acid, unbranched alcohol and branched alcohol, the amount of terephthalic acid used is between 10% and 40% molar and the sum of the amount used of 15 unbranched alcohol and branched alcohol is between 90% and 60% molar, relative to the sum of the moles of the reagents.