CA1081245A - Terephthalic acid ethylene glycol esters, their production and use in the production of polyester polymers - Google Patents
Terephthalic acid ethylene glycol esters, their production and use in the production of polyester polymersInfo
- Publication number
- CA1081245A CA1081245A CA245,053A CA245053A CA1081245A CA 1081245 A CA1081245 A CA 1081245A CA 245053 A CA245053 A CA 245053A CA 1081245 A CA1081245 A CA 1081245A
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- Prior art keywords
- product
- glycol
- ester
- weight
- ethylene glycol
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G65/00—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule
- C08G65/34—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule from hydroxy compounds or their metallic derivatives
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C67/00—Preparation of carboxylic acid esters
- C07C67/03—Preparation of carboxylic acid esters by reacting an ester group with a hydroxy group
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C69/00—Esters of carboxylic acids; Esters of carbonic or haloformic acids
- C07C69/76—Esters of carboxylic acids having a carboxyl group bound to a carbon atom of a six-membered aromatic ring
- C07C69/80—Phthalic acid esters
- C07C69/82—Terephthalic acid esters
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
- Polyesters Or Polycarbonates (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE:
Terephthalic acid ethylene glycol esters solid at ambient temperature are disclosed which have a solidification point in the range of from 180 to 220°C, a reduced viscosity of from 0.07 to 0.14 dl/g, a melt viscosity not higher than 250 cP,an oligomeric ester content of at least 80% by weight, a free ethylene glycol content of at most 5% by weight and an average degree of condensation of from 2.2 to 6.7. A process for the production of these esters is disclosed which requires the use of a column reactor in which transesterification of dimethyl terephthalate with ethylene glycol is carried out at elevated temperature, the reaction mixture employed passing downwardly through the column from an upper chamber in which the reactants are first provided. The transesterification product is then subjected to condensation to produce an oligomer by heating under reduced pressure in a separate chamber or chambers until a predetermined amount of glycol has been distilled off from the transesterification product. The liquid product thus obtained is allowed to impinge on a surface on which it can solidify and be obtained therefrom in for example flake or pellet form. The ester produced is particularly suitable for subsequent condensation to produce polyesters and a variety of other ester group-containing polymers.
Terephthalic acid ethylene glycol esters solid at ambient temperature are disclosed which have a solidification point in the range of from 180 to 220°C, a reduced viscosity of from 0.07 to 0.14 dl/g, a melt viscosity not higher than 250 cP,an oligomeric ester content of at least 80% by weight, a free ethylene glycol content of at most 5% by weight and an average degree of condensation of from 2.2 to 6.7. A process for the production of these esters is disclosed which requires the use of a column reactor in which transesterification of dimethyl terephthalate with ethylene glycol is carried out at elevated temperature, the reaction mixture employed passing downwardly through the column from an upper chamber in which the reactants are first provided. The transesterification product is then subjected to condensation to produce an oligomer by heating under reduced pressure in a separate chamber or chambers until a predetermined amount of glycol has been distilled off from the transesterification product. The liquid product thus obtained is allowed to impinge on a surface on which it can solidify and be obtained therefrom in for example flake or pellet form. The ester produced is particularly suitable for subsequent condensation to produce polyesters and a variety of other ester group-containing polymers.
Description
~ 5 '~hi~ inven-t~on relates -to low molecular weight terephthalic acid ethylene glycol ester~ in ~olid form and to a process for -the production thereof.
~ ow molecular weigh-t terephthalic acid eth~lene glycol esters ~re the monomeric ester, bi~-(2-hydroxyethyl)-terephthalate~
and the linear and cyclic oligo e~ters containing from 3 to 20 ethylene terephthalic units. These e~ter~ are fre~uently obtained in the form of mi~tures Of the individual compound~ in -thi3 ~`
group, only bis-(2-hydroxyethyl)-terephthalate ha~ hitherto been produced on a commercial ~cale, being obtained by reacting terephthalic acid with ethyle-ne oxideO Bis-(2-hydroxyethyl)-terephthalate melt~ at around 110C and may be polycondensed to form polyethylene terephthalate However, it is not used for this purpose in practice bec~u~e~ during its polycondensation which takes a relatively long time, a large part of its own weight accumulate~ a~ secondary product. '~hu~ the product con-tains at least 24% by weight o~ impure glycol, with -the re~ult thst the m~ximum yield of polye~ter is limited to 76%, Another, commercially significan-t reason why this compound has never been u~ed for polycondensation is its high price~
~ erephthalic acid and dimethyl terephthalate (DMT) are used almo~t exclusively in practice as the sources of terephthalate unit~ for polyethylene terephthalate, being reacted with e-thylene glycol, Since only the terephthaloyl radical of the terephthalic acid component participates in synthesis of the polyester, only 79 5% by weight of the starting terephthalic acid and only 68%
. .
by weight of starting DMT are left in the end product. ~hi~
means that 20.5~ and 32% respectively, of these starting material~
have to be tran~ported and stored and act as sources of seconaary products during processing to form the polyester. These secondary products include inflammable meth~nol, formed when using Dll~, and water containing glycol, acetaldehyde and other secondary con-~ ~ .
.,; ,,. . ~ . . . ., :~ .
:.: . .. . .. . .. .
~ ~ 8~ S
stituents when u~ing terephthalic acid, ~hese ~econdary product~ -increa~e manufacturing cost~ ~y requiring both increased sa~ety measures and effluent purification, Mixtures of low molecular weight terephthalic acid glycol esters are temporarily formed during processes for the production of polyethylene terephthalate.
The use of different process conditions also results in differences in the composition and properties of the mixtures~ ~he~e pro-ducts are further processed either immediately or after brief intermediate storage in liquid form, Intermedia-te ~torage enables various polyester~ to be produced from a ~ingle starting product in any sequence and quantity adapted to meet particular re~uire-ments, In practice, only low-melting products with a relatively high glycol content are stored in the liquid phase, and care -mu~t be taken to avoid relatively high ~torage temperatures because they give rise to troublesome and even damaging change~ in the products, An example of such a product is the mixtures melting below 160C which may be obtained by transesterifying D~ ~th at least 2 moles of ethylene glycol, ~y virtue of the low melting point which it i~parts to the product the large excess of glycol allows the liquid products to be stored for up to a few day~.
~everthele~s certain difficulties arise, ~o begin with, it in~
creases the volume of the product and hence ~he amount of ~pace required for subsequent reaction and the glycol subsequently accumulates during further processing as an impure secondary product ~hich ha~ to be worked up before i-t can be re-used, However~ the greatest disadvantage is that of time since the higher the glycol content of the starting product~ the longer the poly-condensation take 9 .
Products with a lower glycol content, for example products which contain tereph-thalic acid and glycol radical~
in a molar ratio of 1: C1,5, behave more favourably in this respect. In other words they may be polycondensed more quicldy
~ ow molecular weigh-t terephthalic acid eth~lene glycol esters ~re the monomeric ester, bi~-(2-hydroxyethyl)-terephthalate~
and the linear and cyclic oligo e~ters containing from 3 to 20 ethylene terephthalic units. These e~ter~ are fre~uently obtained in the form of mi~tures Of the individual compound~ in -thi3 ~`
group, only bis-(2-hydroxyethyl)-terephthalate ha~ hitherto been produced on a commercial ~cale, being obtained by reacting terephthalic acid with ethyle-ne oxideO Bis-(2-hydroxyethyl)-terephthalate melt~ at around 110C and may be polycondensed to form polyethylene terephthalate However, it is not used for this purpose in practice bec~u~e~ during its polycondensation which takes a relatively long time, a large part of its own weight accumulate~ a~ secondary product. '~hu~ the product con-tains at least 24% by weight o~ impure glycol, with -the re~ult thst the m~ximum yield of polye~ter is limited to 76%, Another, commercially significan-t reason why this compound has never been u~ed for polycondensation is its high price~
~ erephthalic acid and dimethyl terephthalate (DMT) are used almo~t exclusively in practice as the sources of terephthalate unit~ for polyethylene terephthalate, being reacted with e-thylene glycol, Since only the terephthaloyl radical of the terephthalic acid component participates in synthesis of the polyester, only 79 5% by weight of the starting terephthalic acid and only 68%
. .
by weight of starting DMT are left in the end product. ~hi~
means that 20.5~ and 32% respectively, of these starting material~
have to be tran~ported and stored and act as sources of seconaary products during processing to form the polyester. These secondary products include inflammable meth~nol, formed when using Dll~, and water containing glycol, acetaldehyde and other secondary con-~ ~ .
.,; ,,. . ~ . . . ., :~ .
:.: . .. . .. . .. .
~ ~ 8~ S
stituents when u~ing terephthalic acid, ~hese ~econdary product~ -increa~e manufacturing cost~ ~y requiring both increased sa~ety measures and effluent purification, Mixtures of low molecular weight terephthalic acid glycol esters are temporarily formed during processes for the production of polyethylene terephthalate.
The use of different process conditions also results in differences in the composition and properties of the mixtures~ ~he~e pro-ducts are further processed either immediately or after brief intermediate storage in liquid form, Intermedia-te ~torage enables various polyester~ to be produced from a ~ingle starting product in any sequence and quantity adapted to meet particular re~uire-ments, In practice, only low-melting products with a relatively high glycol content are stored in the liquid phase, and care -mu~t be taken to avoid relatively high ~torage temperatures because they give rise to troublesome and even damaging change~ in the products, An example of such a product is the mixtures melting below 160C which may be obtained by transesterifying D~ ~th at least 2 moles of ethylene glycol, ~y virtue of the low melting point which it i~parts to the product the large excess of glycol allows the liquid products to be stored for up to a few day~.
~everthele~s certain difficulties arise, ~o begin with, it in~
creases the volume of the product and hence ~he amount of ~pace required for subsequent reaction and the glycol subsequently accumulates during further processing as an impure secondary product ~hich ha~ to be worked up before i-t can be re-used, However~ the greatest disadvantage is that of time since the higher the glycol content of the starting product~ the longer the poly-condensation take 9 .
Products with a lower glycol content, for example products which contain tereph-thalic acid and glycol radical~
in a molar ratio of 1: C1,5, behave more favourably in this respect. In other words they may be polycondensed more quicldy
-2-- . .
~ 2'~5 with very li-ttle glycol formation These products melt at 170C
and higher and in order to keep them i:n liquid form, temperatures are re~uired which initiate unde~irable change~ and ~econdary reactions. Thus, for example, the melting polnt~ o~ product~
of low gl~col content may be so high that -the material undergoing polycondensation solidifies as the melting point rise~ or the quality of the product~ may be reduced by glycol ether formation and degradation reactions. Accordingly, the~e relatively high melting product~, unsuitable for ~torage in liquid form, have tended to be directly further processed, According to one a3pect of thi~ invention~ there i~
provided a terephthalic acid ethylene glycol ester solid at ambient temperature and having a purity such that it posses~e~
each of the following characteristic~: a solidification point in the range of from 180 to 220C; a reduced viscosity measured as herein specified of from 0,07 to 0.14 dl/g; a melt viscosity not higher than 250 cP; an oligomeric ester content of at least 80% by weight: a free ethylene glycol content of at most 5~o by weight and an average degree of condensation of from 2.2 to 6.7.
The~e products are suitable for use as starting materials in the produotion of polyethylene terephthalate and copolymers containing ethylene terephthalate units ~ince they can be ~tored and transported without ~mdergoing any change~ and can be polycondensed or co-polyco.nden~ed ~uickly and with very little formation of ~econdary products. ~ -The products are solid u~ually in the form of flake~
or pellet~ and preferably have solidification point~ from 185 to 210CD ~hey have a melt ~isco~ity in molten form below 250 cP
and a reduced ~iscosity, of from 0~07 to 0.14 dl/g. Reduced viscosities referred to herein are measured at 25~ in phenol/
tetrachlorethane 60:40, by volume The prod~lct~ preferably con~ist of 84 to 96% by weight
~ 2'~5 with very li-ttle glycol formation These products melt at 170C
and higher and in order to keep them i:n liquid form, temperatures are re~uired which initiate unde~irable change~ and ~econdary reactions. Thus, for example, the melting polnt~ o~ product~
of low gl~col content may be so high that -the material undergoing polycondensation solidifies as the melting point rise~ or the quality of the product~ may be reduced by glycol ether formation and degradation reactions. Accordingly, the~e relatively high melting product~, unsuitable for ~torage in liquid form, have tended to be directly further processed, According to one a3pect of thi~ invention~ there i~
provided a terephthalic acid ethylene glycol ester solid at ambient temperature and having a purity such that it posses~e~
each of the following characteristic~: a solidification point in the range of from 180 to 220C; a reduced viscosity measured as herein specified of from 0,07 to 0.14 dl/g; a melt viscosity not higher than 250 cP; an oligomeric ester content of at least 80% by weight: a free ethylene glycol content of at most 5~o by weight and an average degree of condensation of from 2.2 to 6.7.
The~e products are suitable for use as starting materials in the produotion of polyethylene terephthalate and copolymers containing ethylene terephthalate units ~ince they can be ~tored and transported without ~mdergoing any change~ and can be polycondensed or co-polyco.nden~ed ~uickly and with very little formation of ~econdary products. ~ -The products are solid u~ually in the form of flake~
or pellet~ and preferably have solidification point~ from 185 to 210CD ~hey have a melt ~isco~ity in molten form below 250 cP
and a reduced ~iscosity, of from 0~07 to 0.14 dl/g. Reduced viscosities referred to herein are measured at 25~ in phenol/
tetrachlorethane 60:40, by volume The prod~lct~ preferably con~ist of 84 to 96% by weight
-3- ~
:
" ' ~ ~ . , , !
: ' ' ' , ' ' , ' , , ' . .. . . . ~ i , ~ ~ 8~ 2 ~ S
of oligomeric esters, and preferably contain from 1 to 3.5% by weight, o~ free glycol. '~hey have a methoxyl group content of not more than 0.1% by weight.
The average degree of condensation of the product~
which indicate~ the average number o~ ~erephthalic acid radical~
per molecule, i9 ~rom 2.2 to 6.7 and pre~erably from 2.5 to 5.
Terephthalic acid/glycol molar ratio~ o~ from 1:1,45 to 1:1.15, and from 1:104 to 1:1.2 re~pectively corre~pond to these range~
of value 9, The advantages of the product~ according to the in-vention are not confined to the fact that they may be stored for indefinite periods and may also be quickly polyconden~ed. Another advantage is that9 by comparison with conventional ~tarti:ng materials for polyethylene terephthalate production, a larger proportion o~ -their ~eight i~ involved in polyester formation and a ~maller proportion in the formation o~ ~econdary products, The variation in the manner in which di~ferent ~tarting materials are utili~ed in polycondensations i~ illustrated by the ~ollowing Table 1:
Table 1 . . _ le~t in the polye~ter kg o~ secondary Starting ~ , - I product from100kg material o~ starting mater~
T % G c~O total %
, _ D~ 68.0 _ 68 0 33~0 methanol ~PA ~9,5 _ 7905 21.7 water ~G~ 1:2.052.0 23,6 75.6 24,4 glycol CET 1:1.46009 27.7 88,6 11.4 "
CET 1:1.362.7 28,5 91.2 8,8 "
OET 1:1.264~5 29.4 93~9 6.1 "
_ The abbreviations used in the foregoing Table have the ~ollowing meanings: T and G = terephthalic acid and glycol radical~, ~PA = terephthalic acid, DGT = diglycol terephthalate, i.e. bi~-(2-hydroxyethyl)-terephthalate, and CET = products , ...
.
S ~ , according -to the invention (in this ca~e oligoethylene tere-phthala-te) The numerical ratios indicate q':G molar ratio~
where relevant ~ he products according to the invention have further advantages over conventional s-tarting material~ for polyethylene terephthalate production. Thu~, only one ~tarting material i9 required instead o~ terephthalic acid or DM~ and ethylene glycolO
In addition, there i9 no longer any need for e~teri~ication or transesterification of the terephthalic acid component 9 thereby eliminating the entire first stage of conventional production processes, ~urthermore, after proce~sing of the product~ accord- ~ ?
ing to the invention i9 not accompanied by any sublimation or by the formation of any volatile, inflammable methanol.
A~ already mentioned, condensate~ containing low molecular weight terephthalic acid ethylene glycol ester are also formed from DM~ and glycol in conventional processes as well.
Difference~ in the molar ratio of terephthalic acid component to ethylen0 glycol of from say 1:3 to 1:1.1 yield low ~;
molecular weight intermediate products which differ greatly in their composition. A number of other proce~ condition~ al~o influence compo~ition and product propertie~ for rea~on~ that have not yet been explained. ~hu~, in this latter connection, the Example~ of German Au~lege~chrift No, 1,493~113 show there to be a distinct difference between the products obtained by the con-tinuou~ tran~esterification of DM~ with ethylene glycol in a -i molar ratio of 1:1.6 under the same conditions~ but u~ing reactors of different ~ize. The product from the ~maller apparatus con-tained 48~o by weight of monomeric ester and 49% by weight of oligomsric e~ters, whil~t the product from the larger apparatus contained 32% by weight of monomeric ester and 65% by weight of oligomeric esters. According to another Example, a product con~
taining 31% by weight of monomeric e~ter, 60~5~o by weight of ~5~
,... . . . .
; ., ~ ~ ., .;
. . . .
~ Q 8 ~
oligomeric ester~ and 5~5% by weight of free glycol was obtained using the starting monomers in a molar ratio of 1:1.7 and a-n increased initial temperature, de~pite the fac-t that a larger content of monomeric e~ter in -the product might have been expected a~ a result of the greater input of glycol, ~ either i~ there any clear relationship between the molar ratio~ and, for example, the melting or softening points of the products, as can be seen from data relating to products produced by similar processes by continuous transesterification and subsequent reduction of the glycol content in a thin layer evaporator. According to U,S, Patent SpeciPication No, 3,167,531, products ~th average degrees of condensation of from 8 to 16 had melting points of from 238 to 242C, whilst the proaucts described in German Offenlegung~schrift No, 1,495,696 had ~oftening points of from 256 to 258C despite considerably lower degree~ of con-densation, for example 2,7 (calculated from Example 1 of the Offenlegungsschrift). ~he dependence upon several proce~s con-ditions, especially the ~:G molar ratio, the reaction temperature and the reaction time, al~o means that, in the case of batch- : :
type processes, variation~ in the reaction conditions re~ult in the formation o~ products with properties that are difficult to keep constant.
Accordingly, it ha~ alway~ been difficult to produce defined, uniform products, Any proce~s for producing the terephthalic acid ethy-lene glycol e~ter~ of the firs-t aspect of the present invention must take -the following requirements into con~ideration :
1. uniform quality oP the product with strictest possible adherence to predetermined property values; 0 2. complete reaction under moderate conditions in order to obtain a highly polyconden~ible product of low diethylene glycol content;
,~ :
3 ~trict maintenance and control of the T:G molar ratio during reduction of the glycol content; and
:
" ' ~ ~ . , , !
: ' ' ' , ' ' , ' , , ' . .. . . . ~ i , ~ ~ 8~ 2 ~ S
of oligomeric esters, and preferably contain from 1 to 3.5% by weight, o~ free glycol. '~hey have a methoxyl group content of not more than 0.1% by weight.
The average degree of condensation of the product~
which indicate~ the average number o~ ~erephthalic acid radical~
per molecule, i9 ~rom 2.2 to 6.7 and pre~erably from 2.5 to 5.
Terephthalic acid/glycol molar ratio~ o~ from 1:1,45 to 1:1.15, and from 1:104 to 1:1.2 re~pectively corre~pond to these range~
of value 9, The advantages of the product~ according to the in-vention are not confined to the fact that they may be stored for indefinite periods and may also be quickly polyconden~ed. Another advantage is that9 by comparison with conventional ~tarti:ng materials for polyethylene terephthalate production, a larger proportion o~ -their ~eight i~ involved in polyester formation and a ~maller proportion in the formation o~ ~econdary products, The variation in the manner in which di~ferent ~tarting materials are utili~ed in polycondensations i~ illustrated by the ~ollowing Table 1:
Table 1 . . _ le~t in the polye~ter kg o~ secondary Starting ~ , - I product from100kg material o~ starting mater~
T % G c~O total %
, _ D~ 68.0 _ 68 0 33~0 methanol ~PA ~9,5 _ 7905 21.7 water ~G~ 1:2.052.0 23,6 75.6 24,4 glycol CET 1:1.46009 27.7 88,6 11.4 "
CET 1:1.362.7 28,5 91.2 8,8 "
OET 1:1.264~5 29.4 93~9 6.1 "
_ The abbreviations used in the foregoing Table have the ~ollowing meanings: T and G = terephthalic acid and glycol radical~, ~PA = terephthalic acid, DGT = diglycol terephthalate, i.e. bi~-(2-hydroxyethyl)-terephthalate, and CET = products , ...
.
S ~ , according -to the invention (in this ca~e oligoethylene tere-phthala-te) The numerical ratios indicate q':G molar ratio~
where relevant ~ he products according to the invention have further advantages over conventional s-tarting material~ for polyethylene terephthalate production. Thu~, only one ~tarting material i9 required instead o~ terephthalic acid or DM~ and ethylene glycolO
In addition, there i9 no longer any need for e~teri~ication or transesterification of the terephthalic acid component 9 thereby eliminating the entire first stage of conventional production processes, ~urthermore, after proce~sing of the product~ accord- ~ ?
ing to the invention i9 not accompanied by any sublimation or by the formation of any volatile, inflammable methanol.
A~ already mentioned, condensate~ containing low molecular weight terephthalic acid ethylene glycol ester are also formed from DM~ and glycol in conventional processes as well.
Difference~ in the molar ratio of terephthalic acid component to ethylen0 glycol of from say 1:3 to 1:1.1 yield low ~;
molecular weight intermediate products which differ greatly in their composition. A number of other proce~ condition~ al~o influence compo~ition and product propertie~ for rea~on~ that have not yet been explained. ~hu~, in this latter connection, the Example~ of German Au~lege~chrift No, 1,493~113 show there to be a distinct difference between the products obtained by the con-tinuou~ tran~esterification of DM~ with ethylene glycol in a -i molar ratio of 1:1.6 under the same conditions~ but u~ing reactors of different ~ize. The product from the ~maller apparatus con-tained 48~o by weight of monomeric ester and 49% by weight of oligomsric e~ters, whil~t the product from the larger apparatus contained 32% by weight of monomeric ester and 65% by weight of oligomeric esters. According to another Example, a product con~
taining 31% by weight of monomeric e~ter, 60~5~o by weight of ~5~
,... . . . .
; ., ~ ~ ., .;
. . . .
~ Q 8 ~
oligomeric ester~ and 5~5% by weight of free glycol was obtained using the starting monomers in a molar ratio of 1:1.7 and a-n increased initial temperature, de~pite the fac-t that a larger content of monomeric e~ter in -the product might have been expected a~ a result of the greater input of glycol, ~ either i~ there any clear relationship between the molar ratio~ and, for example, the melting or softening points of the products, as can be seen from data relating to products produced by similar processes by continuous transesterification and subsequent reduction of the glycol content in a thin layer evaporator. According to U,S, Patent SpeciPication No, 3,167,531, products ~th average degrees of condensation of from 8 to 16 had melting points of from 238 to 242C, whilst the proaucts described in German Offenlegung~schrift No, 1,495,696 had ~oftening points of from 256 to 258C despite considerably lower degree~ of con-densation, for example 2,7 (calculated from Example 1 of the Offenlegungsschrift). ~he dependence upon several proce~s con-ditions, especially the ~:G molar ratio, the reaction temperature and the reaction time, al~o means that, in the case of batch- : :
type processes, variation~ in the reaction conditions re~ult in the formation o~ products with properties that are difficult to keep constant.
Accordingly, it ha~ alway~ been difficult to produce defined, uniform products, Any proce~s for producing the terephthalic acid ethy-lene glycol e~ter~ of the firs-t aspect of the present invention must take -the following requirements into con~ideration :
1. uniform quality oP the product with strictest possible adherence to predetermined property values; 0 2. complete reaction under moderate conditions in order to obtain a highly polyconden~ible product of low diethylene glycol content;
,~ :
3 ~trict maintenance and control of the T:G molar ratio during reduction of the glycol content; and
4. isolation of the product in solid, size-reduced form favourable both for packaging and also for melting.
'~he ~irst two ré~uirement~ are best ~atisfied by the continuou~ transesterification of DM~ with ethylene glycol which may be carried out in the ab~ence of pre~ure at about 150 to 250C. ~hese conditions may be contrasted with those used in the esterification of terephthalic acid which is normally carrled out under pressure at 220 to 320C~ ;~
Although continuou~ transesterification proce~ses are known, they do not satisfy requirements to any significant extent.
~hus, the conversion~ quoted in the aforementioned German Auslege~chrift ~o. 1,493,113 for exa~ple amount to only between 98~6 and 99~o, which i~ not high enough ~or yielding products fqr proces~ing into high quality polye~ter~, In German Offenlegungsschrift No 1,495,696 it is propo~ed to convert the liquid products obtained therein into solid form by quenching.
However, this method cannot be worked on a commercial scale either, becau~e, when quickly cooled, the low molecular weight products initially form an amorphou~, vi~cous ma~ and -thereafter only solidify slowly in crystalline ~orm, According to a second aspect of this invention there i~
provided a process for the production o~ a terephthalic acid ethylene glycol ester solid at ambient temperature and having a purity such that it pos~es~es each of the following charac-teristics:
a solidification point in the range of ~rom 180 to 220C; a re-duced viscosity measured a~ herein speci~ied of from 0.07 to 0.14 dl/g; a melt vi~oo~ity not higher -than 250 cP; an oligomeric ester content of at lea~t 80% by weight; a ~ree ethylene glycol content of at mo~t 5~ by weight and an average degree o~ condensa-tion of from 202 to 6~7; which compri~e~ continuou~ly introducing . , .
. . . ~.
climethyl terephthalate and ethylene glycol in a molar ratio of from 1:1.6 to 1:2 into an upper chamber of a multi-chamber column reactor which comprises a plurality of chambers arranged ver-tica]ly one above the other, each communicating with the chamber or chambers thereadjacent, catalytically effecting transesterifi-cation of the dimethyl terephthalate at temperatures in the range of from 140 to 240C as the reaction mixture from said upper chamber passes through a plurality of the chambers to yield a transesterification product in a lower chamber, which product is continuously passed to a zone in which the pressure is below ambient pressure, the temperature is from 10 to 40C above the solidification point of the transesterification product and the residence time of the transesterification product is such that as much glycol is removed therefrom as is necessary for adjusting the terephthalic acid: glycol molar ratio of the product to a value of from 1:1.45 to 1:1.15, and continuously applying the liquid product thus obtained in a thin layer to a surface heated to from 40 to 100C and removin~ the product Erom said surface in said Eorm.
This process is a variant of that described and claimed in the specification of Applicant's copending Canadian application No. 244,701, filed January 2~, 1976, and may be carried out using apparatus oE the type described therein additionally provided with means for forming the liquid product into droplets or a continuous coating on a heated surface. ' ' The reduced-pressure zone may form a structural unit with the multiple stage transesterification reactor or may be arranged separately therefrom. In order to increase the surface of'the liquid, it may contain such fittings as platesj overflow plates and tubes, and mixi~ng systems, such as stirrers or nozzles deli-vering jets of inert gas. In order to reduce the glycol content ''~' of the transesterification mixture to the level required for _~_ : , . .. :,,,,` ; ., ::
~ ~ 8 ~ ~ 4 5 -the end produc-t, it i~ generally nece~ary to apply a pressure of from 50 -to ~50 mm Hg, the pressure selected being governed by the ~uantity of glycol which has to be distilled 0~9 by the temperature~ by the residence time and by the li~uid ~urface in this zone. Since the glycol is to be distilled o~f from the tran~esterification reactor together with methanol, in a certain ratio, the pressure may be adjusted and regulated by comparatively measuring the weight or ~olume of the methanol and glycol frac-tion~ of the distillate (proportional control). ~his method o~
regulation o~ pressure i~ pre~erable to that of maintainingccon-~-tant a low pressure in that the required ~:G molar ratio oP the end product dQes not change 9 even in the event of intentional or unintentional changes in the input o~ -the DMT/glycol starting mixture.
The process of the second aspect of this invention, enables new products to be obtained in a defined quality which is generally such that their solidification points deviate by no more than ~ 1.5C, their reauced vi~cosity by no more than 0 0057 their oligomeric ester content by no more than ~ 3~o and ~o their terephthalic acid/ethylene glycol molar ratio by no more then 0.03 mole of glycol from predetermined mean values as specified hereinabove.
~ he transesteri~ication reaction may be carried ou-t in the presence of commonly used catalysts for this type of reaction, for example ~inc or manganese acetate. It has been ~ound that the ~irst phase o~ the reaction may be carried out at relatively low temperatures or may be additionally accelerated at the usual temperatures by adding, in addition to the catalyst, an alkali metal alcoholate, co-catalyst, generally a ~odium alcoholate and pre~erably sodium-methylate or sodium-~2-hydroxyethylate), in a ~uantity which corresponds to at least 1 mole per equivalent weight of the catalystO ~nother advantage of this addition is _g_ , .. : -S
that it reduces the formation of glyeol ether.
To stabilise an oligomerie ester produet o~ this in-vention against decompo~ition, a ~tabili~er may be added thereto, preferably being sdded to the aforesaid ~ranse~terifica~ion product before reduction of the glycol content thereof. To simplify sub~equent operation when producing polyethylene tere-phthalate from the oligomer by melt condensation, a polyeonden~a-tion eatalyst may be added to the liquid product obtained after reduetion of the glyeol eontent of the -tran~esterification pro-duct, The low moleeular weight terephthalie acid ethylene glycol ester~ of this invention may be processed into polyethy-lene terephthalate by conventional batch-type and continuous proees~e~ The new starting material may be used in vir-tually any existing installation, because it i~ no longer necessary to take preeaution~ of the type required when starting with DMT or terephthalic acid. Sinee the new starting material doe~ not give off any readily ~olatile ~econdary produets during proees~ing, it i9 partieularly suitable for eontinuou~ proee~es.
The low moleeular weight terephthalie aeid ethylene glycol esters (OET) are also suitable for u~e as ~tarting materials for the production of copolymer~ containing ethylene terephthalate unit~. ~or this purpose, they may be reacted with the eorre~pond-ing ~urther eomponent~. Copolyrners of thi~ type are, for ex~mple, linear or cros~-linked eopolye~ter~ whieh9 in addition to tere-phthalie aeid and ethylene glyeol units, contain other diearboxylic acids and diols, including component~ with 3 or more e~ter-forming function~. ~inear or branched polyesteramide~, polye~terimide~
and polye~ter urethanes may al~o be produeed from CET. Since it is, in effeet, a relatively high molecular weight diol, CET i~
al~o suitable for use in the produetion of unsaturated polyester re~ins and polyaerylates containing ethylene terephthalate units, '.,: ' ~
.
s and in addi-tion may be incorporated by the etherifi¢ation of methylol group.s in phenol-t melamine or urea-formaldehyde resins, The following Example~ illustrate this invention: -18.5 kg/h of DM~ and 10 kg/h of ethylene glycol (molar ratio appro~imately 1:1,7) ~ere fed in the form of a mixture heated to 150C, onto the uppermost plate of a 120 litre capacity reaction column divided into 5 ~tages by intermediate plate~, which uppermost plate had been heated to 160C, A ~olution of 2,6 g of zinc acetate in 100 ml of ethylene glycol as catalyst was intro~uced into the column at the same time, ~he reaction mixture flowed from one plate to the next through o~erflow pipes and~ in doing ~o, wa~ gradually heated to 220C, 'Ihe reaction mixture was mixed in each stage wi.th ~tirrer blades which were fixed to a common stirrer ~haft guided through central tubes extending through the individual plates, The methanol/glycol vapour mixture ascending~through the control tubes wa~ pa~ed to a packed column, and separated into it~ constituent~ o~ which the : ~`
glycol flowed back onto the upper plate, The methanol distillate separated off at a rate of approximately 7,7 l/h and con-tained 98.5% of methanol and 0,5~o of glycol, ~he reaction mixture wa~
drawn from the lower.most plate of the reaction column~ through a ~`
regulating valve into an underlying two-stage low pres~ure section who~e stages were heated to 210 and 230C~ respectively, The pressure was regulated to be between 270 and 285 mm,Hg.in this section so that for every 4 litres of methanol distillate 1 litre :
of glycol distillate pas~ed over at a rate of approximately 1.9 l/h~ ~he liquid reaction product was then delivered from the vacuum compartment onto a cooling band which had been heated to 77C. ~ow molecular weight ethylene terephthalate was flaked off the band at a rate of 20,4 kg/h, The characteristi~s of the product thu~ obtained are ~ , . -8 ~ ~ ~ 5 ~hown in Table 2, EX~MP~ 2 The procedure of Example 1 wa~ repeated with the ~ole difference that a solution of sodium methylate in glycol was introduced in addition to the zinc acetate at a rate ~uch that 2.8 g of sodium methylate wa~ supplied per hour to the column.
The ratio of glycol distillate to methanol distillate wa~ i:n-crea~ed in relation to Example 1 (from 1:4 to 1:3.9). The di3--tillate containing 97.7% of glycol was continuously rectified and returned in the form of 99,8% gl~col in a quantity of 2 kg/h to the glycol container for the starting mixture. The reaction product wa~ ~laked of~ from the cooling band in a ~uantity of 20.3 kg/h at a band -temperature of 78C, The characteristics of the product obtained are al~o ~hown in Table 2~ It can be seen that the main difference be-tween this product and the product obtained in Example 1 wa~
its lo~r methoxyl conten-t. The other characteristics did not dif~er to any ~igni~ican-t extent apart from the sligh-tly modified T:G molar ratio. .
': ,' ' ' ~'' ' ' ~8~ 5 Table 2 . _ ¦Characteristics Example 1 Exarnple 2 Solidification point 189. 5 191 . oa Melt viscosity 52.5 cP ( 220C) not determined Reduced viscosity 0.090 0~092 dl/g Oligomer content 87.1 88. oo~O
Free glycol 2 . 1 1 ~ 8qo Methoxyl content 0. 085 0 . 04 2~o ~:G rnolar ratio 1:1.35 1:1,337 Average degree of condensation 2.855 2.966 Degree of transesterifica-ticn 0.9971 0.9~86 ~ efore it was drawn into the vacuum compartrnent, part of the product obtained in ~xample 2 was stabilized by the addition o~ 3.6 g/h of triphenyl phosphite.
Polycondensation tests were carried out with the. ~
stabili~ed product of Example 2 and the reduced viscosity ~.
( ~ red) of the polyesters determlned in accordance with the duration of the polycondensation reaction which was carried out at 275C/0.5 mm.Hg:
Polycondensation time Red viscosity 120 mins. 0.955 150 " 1,112 ~.-180 " 1.218 '~he diethylene glycol content of the polyester a~ounted to ~rom 0.6 to 0. 70jo by weight.
'~he ~irst two ré~uirement~ are best ~atisfied by the continuou~ transesterification of DM~ with ethylene glycol which may be carried out in the ab~ence of pre~ure at about 150 to 250C. ~hese conditions may be contrasted with those used in the esterification of terephthalic acid which is normally carrled out under pressure at 220 to 320C~ ;~
Although continuou~ transesterification proce~ses are known, they do not satisfy requirements to any significant extent.
~hus, the conversion~ quoted in the aforementioned German Auslege~chrift ~o. 1,493,113 for exa~ple amount to only between 98~6 and 99~o, which i~ not high enough ~or yielding products fqr proces~ing into high quality polye~ter~, In German Offenlegungsschrift No 1,495,696 it is propo~ed to convert the liquid products obtained therein into solid form by quenching.
However, this method cannot be worked on a commercial scale either, becau~e, when quickly cooled, the low molecular weight products initially form an amorphou~, vi~cous ma~ and -thereafter only solidify slowly in crystalline ~orm, According to a second aspect of this invention there i~
provided a process for the production o~ a terephthalic acid ethylene glycol ester solid at ambient temperature and having a purity such that it pos~es~es each of the following charac-teristics:
a solidification point in the range of ~rom 180 to 220C; a re-duced viscosity measured a~ herein speci~ied of from 0.07 to 0.14 dl/g; a melt vi~oo~ity not higher -than 250 cP; an oligomeric ester content of at lea~t 80% by weight; a ~ree ethylene glycol content of at mo~t 5~ by weight and an average degree o~ condensa-tion of from 202 to 6~7; which compri~e~ continuou~ly introducing . , .
. . . ~.
climethyl terephthalate and ethylene glycol in a molar ratio of from 1:1.6 to 1:2 into an upper chamber of a multi-chamber column reactor which comprises a plurality of chambers arranged ver-tica]ly one above the other, each communicating with the chamber or chambers thereadjacent, catalytically effecting transesterifi-cation of the dimethyl terephthalate at temperatures in the range of from 140 to 240C as the reaction mixture from said upper chamber passes through a plurality of the chambers to yield a transesterification product in a lower chamber, which product is continuously passed to a zone in which the pressure is below ambient pressure, the temperature is from 10 to 40C above the solidification point of the transesterification product and the residence time of the transesterification product is such that as much glycol is removed therefrom as is necessary for adjusting the terephthalic acid: glycol molar ratio of the product to a value of from 1:1.45 to 1:1.15, and continuously applying the liquid product thus obtained in a thin layer to a surface heated to from 40 to 100C and removin~ the product Erom said surface in said Eorm.
This process is a variant of that described and claimed in the specification of Applicant's copending Canadian application No. 244,701, filed January 2~, 1976, and may be carried out using apparatus oE the type described therein additionally provided with means for forming the liquid product into droplets or a continuous coating on a heated surface. ' ' The reduced-pressure zone may form a structural unit with the multiple stage transesterification reactor or may be arranged separately therefrom. In order to increase the surface of'the liquid, it may contain such fittings as platesj overflow plates and tubes, and mixi~ng systems, such as stirrers or nozzles deli-vering jets of inert gas. In order to reduce the glycol content ''~' of the transesterification mixture to the level required for _~_ : , . .. :,,,,` ; ., ::
~ ~ 8 ~ ~ 4 5 -the end produc-t, it i~ generally nece~ary to apply a pressure of from 50 -to ~50 mm Hg, the pressure selected being governed by the ~uantity of glycol which has to be distilled 0~9 by the temperature~ by the residence time and by the li~uid ~urface in this zone. Since the glycol is to be distilled o~f from the tran~esterification reactor together with methanol, in a certain ratio, the pressure may be adjusted and regulated by comparatively measuring the weight or ~olume of the methanol and glycol frac-tion~ of the distillate (proportional control). ~his method o~
regulation o~ pressure i~ pre~erable to that of maintainingccon-~-tant a low pressure in that the required ~:G molar ratio oP the end product dQes not change 9 even in the event of intentional or unintentional changes in the input o~ -the DMT/glycol starting mixture.
The process of the second aspect of this invention, enables new products to be obtained in a defined quality which is generally such that their solidification points deviate by no more than ~ 1.5C, their reauced vi~cosity by no more than 0 0057 their oligomeric ester content by no more than ~ 3~o and ~o their terephthalic acid/ethylene glycol molar ratio by no more then 0.03 mole of glycol from predetermined mean values as specified hereinabove.
~ he transesteri~ication reaction may be carried ou-t in the presence of commonly used catalysts for this type of reaction, for example ~inc or manganese acetate. It has been ~ound that the ~irst phase o~ the reaction may be carried out at relatively low temperatures or may be additionally accelerated at the usual temperatures by adding, in addition to the catalyst, an alkali metal alcoholate, co-catalyst, generally a ~odium alcoholate and pre~erably sodium-methylate or sodium-~2-hydroxyethylate), in a ~uantity which corresponds to at least 1 mole per equivalent weight of the catalystO ~nother advantage of this addition is _g_ , .. : -S
that it reduces the formation of glyeol ether.
To stabilise an oligomerie ester produet o~ this in-vention against decompo~ition, a ~tabili~er may be added thereto, preferably being sdded to the aforesaid ~ranse~terifica~ion product before reduction of the glycol content thereof. To simplify sub~equent operation when producing polyethylene tere-phthalate from the oligomer by melt condensation, a polyeonden~a-tion eatalyst may be added to the liquid product obtained after reduetion of the glyeol eontent of the -tran~esterification pro-duct, The low moleeular weight terephthalie acid ethylene glycol ester~ of this invention may be processed into polyethy-lene terephthalate by conventional batch-type and continuous proees~e~ The new starting material may be used in vir-tually any existing installation, because it i~ no longer necessary to take preeaution~ of the type required when starting with DMT or terephthalic acid. Sinee the new starting material doe~ not give off any readily ~olatile ~econdary produets during proees~ing, it i9 partieularly suitable for eontinuou~ proee~es.
The low moleeular weight terephthalie aeid ethylene glycol esters (OET) are also suitable for u~e as ~tarting materials for the production of copolymer~ containing ethylene terephthalate unit~. ~or this purpose, they may be reacted with the eorre~pond-ing ~urther eomponent~. Copolyrners of thi~ type are, for ex~mple, linear or cros~-linked eopolye~ter~ whieh9 in addition to tere-phthalie aeid and ethylene glyeol units, contain other diearboxylic acids and diols, including component~ with 3 or more e~ter-forming function~. ~inear or branched polyesteramide~, polye~terimide~
and polye~ter urethanes may al~o be produeed from CET. Since it is, in effeet, a relatively high molecular weight diol, CET i~
al~o suitable for use in the produetion of unsaturated polyester re~ins and polyaerylates containing ethylene terephthalate units, '.,: ' ~
.
s and in addi-tion may be incorporated by the etherifi¢ation of methylol group.s in phenol-t melamine or urea-formaldehyde resins, The following Example~ illustrate this invention: -18.5 kg/h of DM~ and 10 kg/h of ethylene glycol (molar ratio appro~imately 1:1,7) ~ere fed in the form of a mixture heated to 150C, onto the uppermost plate of a 120 litre capacity reaction column divided into 5 ~tages by intermediate plate~, which uppermost plate had been heated to 160C, A ~olution of 2,6 g of zinc acetate in 100 ml of ethylene glycol as catalyst was intro~uced into the column at the same time, ~he reaction mixture flowed from one plate to the next through o~erflow pipes and~ in doing ~o, wa~ gradually heated to 220C, 'Ihe reaction mixture was mixed in each stage wi.th ~tirrer blades which were fixed to a common stirrer ~haft guided through central tubes extending through the individual plates, The methanol/glycol vapour mixture ascending~through the control tubes wa~ pa~ed to a packed column, and separated into it~ constituent~ o~ which the : ~`
glycol flowed back onto the upper plate, The methanol distillate separated off at a rate of approximately 7,7 l/h and con-tained 98.5% of methanol and 0,5~o of glycol, ~he reaction mixture wa~
drawn from the lower.most plate of the reaction column~ through a ~`
regulating valve into an underlying two-stage low pres~ure section who~e stages were heated to 210 and 230C~ respectively, The pressure was regulated to be between 270 and 285 mm,Hg.in this section so that for every 4 litres of methanol distillate 1 litre :
of glycol distillate pas~ed over at a rate of approximately 1.9 l/h~ ~he liquid reaction product was then delivered from the vacuum compartment onto a cooling band which had been heated to 77C. ~ow molecular weight ethylene terephthalate was flaked off the band at a rate of 20,4 kg/h, The characteristi~s of the product thu~ obtained are ~ , . -8 ~ ~ ~ 5 ~hown in Table 2, EX~MP~ 2 The procedure of Example 1 wa~ repeated with the ~ole difference that a solution of sodium methylate in glycol was introduced in addition to the zinc acetate at a rate ~uch that 2.8 g of sodium methylate wa~ supplied per hour to the column.
The ratio of glycol distillate to methanol distillate wa~ i:n-crea~ed in relation to Example 1 (from 1:4 to 1:3.9). The di3--tillate containing 97.7% of glycol was continuously rectified and returned in the form of 99,8% gl~col in a quantity of 2 kg/h to the glycol container for the starting mixture. The reaction product wa~ ~laked of~ from the cooling band in a ~uantity of 20.3 kg/h at a band -temperature of 78C, The characteristics of the product obtained are al~o ~hown in Table 2~ It can be seen that the main difference be-tween this product and the product obtained in Example 1 wa~
its lo~r methoxyl conten-t. The other characteristics did not dif~er to any ~igni~ican-t extent apart from the sligh-tly modified T:G molar ratio. .
': ,' ' ' ~'' ' ' ~8~ 5 Table 2 . _ ¦Characteristics Example 1 Exarnple 2 Solidification point 189. 5 191 . oa Melt viscosity 52.5 cP ( 220C) not determined Reduced viscosity 0.090 0~092 dl/g Oligomer content 87.1 88. oo~O
Free glycol 2 . 1 1 ~ 8qo Methoxyl content 0. 085 0 . 04 2~o ~:G rnolar ratio 1:1.35 1:1,337 Average degree of condensation 2.855 2.966 Degree of transesterifica-ticn 0.9971 0.9~86 ~ efore it was drawn into the vacuum compartrnent, part of the product obtained in ~xample 2 was stabilized by the addition o~ 3.6 g/h of triphenyl phosphite.
Polycondensation tests were carried out with the. ~
stabili~ed product of Example 2 and the reduced viscosity ~.
( ~ red) of the polyesters determlned in accordance with the duration of the polycondensation reaction which was carried out at 275C/0.5 mm.Hg:
Polycondensation time Red viscosity 120 mins. 0.955 150 " 1,112 ~.-180 " 1.218 '~he diethylene glycol content of the polyester a~ounted to ~rom 0.6 to 0. 70jo by weight.
Claims (22)
1. A terephthalic acid ethylene glycol ester solid at ambient temperature and having a purity such that it possesses each of the following characteristics: a solidifica-tion point in the range of from 180 to 220°C; a reduced viscosity of from 0.07 to 0.14 dl/g; a melt viscosity not higher than 250 cP; an oligomeric ester content of at least 80% by weight; a free ethylene glycol content of at most 5%
by weight and an average degree of condensation of from 2.2 to 6.7.
by weight and an average degree of condensation of from 2.2 to 6.7.
2. An ester as claimed in Claim 1, which has a solidification point of from 185 to 210°C.
3. An ester as claimed in Claim 1 or 2, which has an oligomeric ester content of from 84 to 96% by weight.
4. An ester as claimed in Claim 1, which has an ethylene glycol content of from 1 to 3.5% by weight.
5. An ester as claimed in Claim 1, which has an average degree of condensation of from 2.5 to 5.
6. An ester as claimed in Claim 1, which contains not more than 0.1% by weight of methoxyl groups.
7. An ester as claimed in Claim 1, which is in the form of flakes or pellets.
8. An ester as claimed in Claim 1, which contains a stabiliser.
9. An ester as claimed in Claim 1, which contains a polycondensation catalyst.
10. A process for the production of a terephthalic acid ethylene glycol ester solid at ambient temperature and having a purity such that it possesses each of the following characteristics: a solidification point in the range of from 180 to 220°C; a reduced viscosity of from 0.07 to 0.14 dl/g;
a melt viscosity not higher than 250 cP; an oligomeric ester content of at least 80% by weight; a free ethylene glycol content of at most 5% by weight and an average degree of condensation of from 2.2 to 6.7; which comprises continuously introducing dimethyl terephthalate and ethylene glycol in a molar ratio of from 1:1.6 to 1:2 into an upper chamber of a multi-chamber column reactor which comprises a plurality of chambers arranged vertically one above the other, each communicating with the chamber or chambers thereadjacent, catalytically effecting transesterification of the dimethyl terephthalate at temperatures in the range of from 140 to 240°C as the reaction mixture from said upper chamber passes through a plurality of the chambers to yield a transesterification product in a lower chamber, which product is continuously passed to a zone in which the pressure is below ambient pressure, the temperature is from 10 to 40°C above the solidification point of the transesterifica-tion product and the residence time of the transesterification product is such that as much glycol is removed therefrom as is necessary for adjusting the terephthalic acid: glycol molar ratio of the product to a value of from 1:1.45 to 1:1.15, and continuous-ly applying the liquid product thus obtained in a thin layer to a surface heated to from 40 to 100°C and removing the product from said surface in solid form.
a melt viscosity not higher than 250 cP; an oligomeric ester content of at least 80% by weight; a free ethylene glycol content of at most 5% by weight and an average degree of condensation of from 2.2 to 6.7; which comprises continuously introducing dimethyl terephthalate and ethylene glycol in a molar ratio of from 1:1.6 to 1:2 into an upper chamber of a multi-chamber column reactor which comprises a plurality of chambers arranged vertically one above the other, each communicating with the chamber or chambers thereadjacent, catalytically effecting transesterification of the dimethyl terephthalate at temperatures in the range of from 140 to 240°C as the reaction mixture from said upper chamber passes through a plurality of the chambers to yield a transesterification product in a lower chamber, which product is continuously passed to a zone in which the pressure is below ambient pressure, the temperature is from 10 to 40°C above the solidification point of the transesterifica-tion product and the residence time of the transesterification product is such that as much glycol is removed therefrom as is necessary for adjusting the terephthalic acid: glycol molar ratio of the product to a value of from 1:1.45 to 1:1.15, and continuous-ly applying the liquid product thus obtained in a thin layer to a surface heated to from 40 to 100°C and removing the product from said surface in solid form.
11. A process as claimed in Claim 10, in which said below ambiant pressure is from 50 to 350 mm.Hg.
12. A process as claimed in Claim 10, in which the pressure is reduced in said zone to a value at which sufficient glycol is removed from the transesterification product as is necessary for adjusting the terephthalic acid: glycol molar ratio of the product to a value in the range of from 1:1,4 to 1:1.2.
13. A process as claimed in Claim 10, 11 or 12, in which said liquid product is applied in the form of a continuous coating or in the form of droplets to said surface and is removed from the surface in the form of solid flakes or pellets respectively.
14. A process as claimed in Claim 10, in which said surface is heated to from 60 to 90°C.
15. A process as claimed in claim 10, which is carried out so that the solidification point of said solid product deviates by no more than ? 1.5°C, the reduced viscosity by no more than ? 0.005 dl/g, the oligomeric ester content by no more than ? 3% and the terephthalic acid/ethylene glycol molar ratio by no more than 0.03 mole of glycol from predeter-mined values set for the solid product.
16. A process as claimed in Claim 10, wherein the pressure in the said zone is regulated in accordance with the weight or volumetric ratio of methanol to glycol in distillate obtained from said zone.
17. A process as claimed in Claim 10, wherein an alkali metal alcoholate is employed in the transesterification as co-catalyst used in an amount of at least 2 moles per mole of catalyst employed in the transesterification.
18. A process as claimed in Claim 17, in which the alkali metal alcoholate is a sodium alcoholate.
19. A process as claimed in claim 18, in which the co-catalyst is sodium methylate or sodium-2-hydroxy ethylate.
20. A process as claimed in claim 10, in which a stabilizer is added to the transesterification product before its glycol content is reduced.
21. A process as claimed in claim 10, in which a polycondensation catalyst is added to said liquid product obtained after reduction of the glycol content of the transesterification product.
22. A process as claimed in claim 10, in which glycol distilled from said reactor and from said zone is returned to said upper chamber after purification by distillation in a continuously operating distillation unit.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19752504156 DE2504156A1 (en) | 1975-02-01 | 1975-02-01 | LOW MOLECULAR MOLECULAR TEREPHTHAL ACID AETHYLENE GLYCOLESTER, THEIR PREPARATION AND USE |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1081245A true CA1081245A (en) | 1980-07-08 |
Family
ID=5937840
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA245,053A Expired CA1081245A (en) | 1975-02-01 | 1976-02-02 | Terephthalic acid ethylene glycol esters, their production and use in the production of polyester polymers |
Country Status (16)
| Country | Link |
|---|---|
| JP (1) | JPS51101946A (en) |
| BE (1) | BE838080A (en) |
| BR (1) | BR7600251A (en) |
| CA (1) | CA1081245A (en) |
| DD (1) | DD123738A5 (en) |
| DE (1) | DE2504156A1 (en) |
| FR (1) | FR2299310A1 (en) |
| GB (1) | GB1511412A (en) |
| IN (1) | IN145144B (en) |
| IT (1) | IT1053475B (en) |
| MX (1) | MX3016E (en) |
| NL (1) | NL7600984A (en) |
| PL (1) | PL103014B1 (en) |
| RO (1) | RO69845A (en) |
| SU (1) | SU625598A3 (en) |
| TR (1) | TR18730A (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1986001200A1 (en) * | 1984-08-14 | 1986-02-27 | Mitsubishi Chemical Industries Limited | Process for preparaing tetramethyl biphenyltetracarboxylate |
| CN1195727C (en) * | 1999-08-04 | 2005-04-06 | 株式会社爱伊斯 | Methods for the preparation or purification of bis-beta-hydroxyethyl terephthalate |
| US6380352B1 (en) * | 2000-08-29 | 2002-04-30 | Eastman Chemical Company | Polyester precursor purification process |
-
1975
- 1975-02-01 DE DE19752504156 patent/DE2504156A1/en not_active Withdrawn
- 1975-11-24 MX MX100139U patent/MX3016E/en unknown
- 1975-12-15 DD DD190149A patent/DD123738A5/xx unknown
-
1976
- 1976-01-16 BR BR7600251A patent/BR7600251A/en unknown
- 1976-01-27 TR TR18730A patent/TR18730A/en unknown
- 1976-01-29 SU SU762317700A patent/SU625598A3/en active
- 1976-01-29 GB GB3648/76A patent/GB1511412A/en not_active Expired
- 1976-01-30 FR FR7602570A patent/FR2299310A1/en active Granted
- 1976-01-30 BE BE163933A patent/BE838080A/en unknown
- 1976-01-30 NL NL7600984A patent/NL7600984A/en not_active Application Discontinuation
- 1976-01-30 IT IT7647875A patent/IT1053475B/en active
- 1976-01-31 RO RO7684665A patent/RO69845A/en unknown
- 1976-01-31 PL PL1976186951A patent/PL103014B1/en unknown
- 1976-02-02 CA CA245,053A patent/CA1081245A/en not_active Expired
- 1976-02-02 JP JP51010222A patent/JPS51101946A/en active Pending
- 1976-02-13 IN IN262/CAL/1976A patent/IN145144B/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| FR2299310A1 (en) | 1976-08-27 |
| PL103014B1 (en) | 1979-05-31 |
| TR18730A (en) | 1977-07-27 |
| FR2299310B1 (en) | 1979-05-18 |
| DD123738A5 (en) | 1977-01-12 |
| DE2504156A1 (en) | 1976-08-05 |
| BE838080A (en) | 1976-05-14 |
| BR7600251A (en) | 1976-08-31 |
| RO69845A (en) | 1981-07-30 |
| SU625598A3 (en) | 1978-09-25 |
| MX3016E (en) | 1980-02-04 |
| JPS51101946A (en) | 1976-09-08 |
| GB1511412A (en) | 1978-05-17 |
| IT1053475B (en) | 1981-08-31 |
| IN145144B (en) | 1978-09-02 |
| NL7600984A (en) | 1976-08-03 |
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