CA2069980A1 - Process for the preparation of high molecular weight linear polyester - Google Patents
Process for the preparation of high molecular weight linear polyesterInfo
- Publication number
- CA2069980A1 CA2069980A1 CA002069980A CA2069980A CA2069980A1 CA 2069980 A1 CA2069980 A1 CA 2069980A1 CA 002069980 A CA002069980 A CA 002069980A CA 2069980 A CA2069980 A CA 2069980A CA 2069980 A1 CA2069980 A1 CA 2069980A1
- Authority
- CA
- Canada
- Prior art keywords
- polyester
- carbon atoms
- molecular weight
- mol
- heat transfer
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 229920000728 polyester Polymers 0.000 title claims abstract description 99
- 238000000034 method Methods 0.000 title claims abstract description 52
- 230000008569 process Effects 0.000 title claims abstract description 49
- 238000002360 preparation method Methods 0.000 title claims abstract description 15
- 238000012546 transfer Methods 0.000 claims abstract description 29
- 238000009833 condensation Methods 0.000 claims abstract description 26
- 239000000725 suspension Substances 0.000 claims abstract description 13
- 229920002545 silicone oil Polymers 0.000 claims abstract description 10
- 239000007787 solid Substances 0.000 claims abstract description 9
- 239000007788 liquid Substances 0.000 claims abstract description 5
- 125000004432 carbon atom Chemical group C* 0.000 claims description 21
- -1 polymethylene groups Polymers 0.000 claims description 15
- 239000005020 polyethylene terephthalate Substances 0.000 claims description 11
- 238000002844 melting Methods 0.000 claims description 7
- 230000008018 melting Effects 0.000 claims description 7
- 125000002947 alkylene group Chemical group 0.000 claims description 6
- 125000003118 aryl group Chemical group 0.000 claims description 6
- 238000003756 stirring Methods 0.000 claims description 6
- 125000002496 methyl group Chemical group [H]C([H])([H])* 0.000 claims description 4
- 125000001997 phenyl group Chemical group [H]C1=C([H])C([H])=C(*)C([H])=C1[H] 0.000 claims description 4
- 125000000217 alkyl group Chemical group 0.000 claims description 3
- 239000011261 inert gas Substances 0.000 claims description 3
- 125000003710 aryl alkyl group Chemical group 0.000 claims description 2
- 125000000753 cycloalkyl group Chemical group 0.000 claims description 2
- MTHSVFCYNBDYFN-UHFFFAOYSA-N diethylene glycol Chemical compound OCCOCCO MTHSVFCYNBDYFN-UHFFFAOYSA-N 0.000 claims description 2
- 229920000151 polyglycol Polymers 0.000 claims description 2
- 239000010695 polyglycol Substances 0.000 claims description 2
- ZIBGPFATKBEMQZ-UHFFFAOYSA-N triethylene glycol Chemical compound OCCOCCOCCO ZIBGPFATKBEMQZ-UHFFFAOYSA-N 0.000 claims 1
- 239000000470 constituent Substances 0.000 abstract description 2
- 239000002245 particle Substances 0.000 description 43
- 238000006068 polycondensation reaction Methods 0.000 description 35
- 230000005494 condensation Effects 0.000 description 14
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 12
- 239000000463 material Substances 0.000 description 11
- 239000000047 product Substances 0.000 description 11
- 229920000139 polyethylene terephthalate Polymers 0.000 description 8
- 239000003054 catalyst Substances 0.000 description 7
- 238000006243 chemical reaction Methods 0.000 description 7
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 description 6
- JXTHNDFMNIQAHM-UHFFFAOYSA-N dichloroacetic acid Chemical compound OC(=O)C(Cl)Cl JXTHNDFMNIQAHM-UHFFFAOYSA-N 0.000 description 6
- 238000002474 experimental method Methods 0.000 description 6
- 229910052757 nitrogen Inorganic materials 0.000 description 6
- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 description 5
- 238000005227 gel permeation chromatography Methods 0.000 description 5
- 239000007790 solid phase Substances 0.000 description 5
- HEDRZPFGACZZDS-UHFFFAOYSA-N Chloroform Chemical compound ClC(Cl)Cl HEDRZPFGACZZDS-UHFFFAOYSA-N 0.000 description 4
- 238000001035 drying Methods 0.000 description 4
- 239000007789 gas Substances 0.000 description 4
- 238000010348 incorporation Methods 0.000 description 4
- 238000005809 transesterification reaction Methods 0.000 description 4
- DTQVDTLACAAQTR-UHFFFAOYSA-N Trifluoroacetic acid Chemical compound OC(=O)C(F)(F)F DTQVDTLACAAQTR-UHFFFAOYSA-N 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- 150000001991 dicarboxylic acids Chemical class 0.000 description 3
- 229960005215 dichloroacetic acid Drugs 0.000 description 3
- 238000009826 distribution Methods 0.000 description 3
- 230000032050 esterification Effects 0.000 description 3
- 238000005886 esterification reaction Methods 0.000 description 3
- WGCNASOHLSPBMP-UHFFFAOYSA-N hydroxyacetaldehyde Natural products OCC=O WGCNASOHLSPBMP-UHFFFAOYSA-N 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 239000003921 oil Substances 0.000 description 3
- 239000012071 phase Substances 0.000 description 3
- 229920000642 polymer Polymers 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
- 239000002904 solvent Substances 0.000 description 3
- OFOBLEOULBTSOW-UHFFFAOYSA-N Malonic acid Chemical compound OC(=O)CC(O)=O OFOBLEOULBTSOW-UHFFFAOYSA-N 0.000 description 2
- 229920004482 WACKER® Polymers 0.000 description 2
- 125000001931 aliphatic group Chemical group 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- 235000010290 biphenyl Nutrition 0.000 description 2
- 125000006267 biphenyl group Chemical group 0.000 description 2
- 239000012159 carrier gas Substances 0.000 description 2
- 239000007795 chemical reaction product Substances 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 238000006731 degradation reaction Methods 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- 150000002009 diols Chemical class 0.000 description 2
- 238000001704 evaporation Methods 0.000 description 2
- 230000008020 evaporation Effects 0.000 description 2
- 239000008187 granular material Substances 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 239000003960 organic solvent Substances 0.000 description 2
- 239000007858 starting material Substances 0.000 description 2
- 125000001424 substituent group Chemical group 0.000 description 2
- 125000000020 sulfo group Chemical group O=S(=O)([*])O[H] 0.000 description 2
- JIAARYAFYJHUJI-UHFFFAOYSA-L zinc dichloride Chemical compound [Cl-].[Cl-].[Zn+2] JIAARYAFYJHUJI-UHFFFAOYSA-L 0.000 description 2
- SCYULBFZEHDVBN-UHFFFAOYSA-N 1,1-Dichloroethane Chemical compound CC(Cl)Cl SCYULBFZEHDVBN-UHFFFAOYSA-N 0.000 description 1
- YJTKZCDBKVTVBY-UHFFFAOYSA-N 1,3-Diphenylbenzene Chemical group C1=CC=CC=C1C1=CC=CC(C=2C=CC=CC=2)=C1 YJTKZCDBKVTVBY-UHFFFAOYSA-N 0.000 description 1
- 125000001989 1,3-phenylene group Chemical group [H]C1=C([H])C([*:1])=C([H])C([*:2])=C1[H] 0.000 description 1
- YZTJKOLMWJNVFH-UHFFFAOYSA-N 2-sulfobenzene-1,3-dicarboxylic acid Chemical compound OC(=O)C1=CC=CC(C(O)=O)=C1S(O)(=O)=O YZTJKOLMWJNVFH-UHFFFAOYSA-N 0.000 description 1
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 1
- 238000002441 X-ray diffraction Methods 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 150000001298 alcohols Chemical class 0.000 description 1
- 125000003545 alkoxy group Chemical group 0.000 description 1
- 125000005907 alkyl ester group Chemical group 0.000 description 1
- 150000004945 aromatic hydrocarbons Chemical class 0.000 description 1
- 125000004429 atom Chemical group 0.000 description 1
- CCDWGDHTPAJHOA-UHFFFAOYSA-N benzylsilicon Chemical compound [Si]CC1=CC=CC=C1 CCDWGDHTPAJHOA-UHFFFAOYSA-N 0.000 description 1
- 239000004305 biphenyl Substances 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 238000012512 characterization method Methods 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 239000000460 chlorine Substances 0.000 description 1
- 229910052801 chlorine Inorganic materials 0.000 description 1
- 239000012141 concentrate Substances 0.000 description 1
- 239000007859 condensation product Substances 0.000 description 1
- 238000004132 cross linking Methods 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 238000010790 dilution Methods 0.000 description 1
- 239000012895 dilution Substances 0.000 description 1
- 125000000118 dimethyl group Chemical group [H]C([H])([H])* 0.000 description 1
- 238000002845 discoloration Methods 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 150000002148 esters Chemical class 0.000 description 1
- 239000000284 extract Substances 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000000835 fiber Substances 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 150000002334 glycols Chemical class 0.000 description 1
- 239000011551 heat transfer agent Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 239000002198 insoluble material Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000000155 melt Substances 0.000 description 1
- 125000000325 methylidene group Chemical group [H]C([H])=* 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 150000004950 naphthalene Chemical class 0.000 description 1
- QQVIHTHCMHWDBS-UHFFFAOYSA-N perisophthalic acid Natural products OC(=O)C1=CC=CC(C(O)=O)=C1 QQVIHTHCMHWDBS-UHFFFAOYSA-N 0.000 description 1
- ZUOUZKKEUPVFJK-UHFFFAOYSA-N phenylbenzene Natural products C1=CC=CC=C1C1=CC=CC=C1 ZUOUZKKEUPVFJK-UHFFFAOYSA-N 0.000 description 1
- ACVYVLVWPXVTIT-UHFFFAOYSA-N phosphinic acid Chemical compound O[PH2]=O ACVYVLVWPXVTIT-UHFFFAOYSA-N 0.000 description 1
- 229920001921 poly-methyl-phenyl-siloxane Polymers 0.000 description 1
- 238000006116 polymerization reaction Methods 0.000 description 1
- 229920001296 polysiloxane Polymers 0.000 description 1
- 230000002250 progressing effect Effects 0.000 description 1
- 239000011541 reaction mixture Substances 0.000 description 1
- 230000035484 reaction time Effects 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 238000007086 side reaction Methods 0.000 description 1
- 238000009987 spinning Methods 0.000 description 1
- 230000008961 swelling Effects 0.000 description 1
- 235000012976 tarts Nutrition 0.000 description 1
- 150000003609 titanium compounds Chemical class 0.000 description 1
- YJGJRYWNNHUESM-UHFFFAOYSA-J triacetyloxystannyl acetate Chemical compound [Sn+4].CC([O-])=O.CC([O-])=O.CC([O-])=O.CC([O-])=O YJGJRYWNNHUESM-UHFFFAOYSA-J 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 238000004383 yellowing Methods 0.000 description 1
- 235000005074 zinc chloride Nutrition 0.000 description 1
- 239000011592 zinc chloride Substances 0.000 description 1
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
- C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
- C08G63/02—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds
-
- 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
- C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
- C08G63/78—Preparation processes
- C08G63/80—Solid-state polycondensation
Landscapes
- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Polyesters Or Polycarbonates (AREA)
Abstract
Abstract of the Disclosure:
Process for the preparation of high molecular weight linear polyester.
A process for the preparation of a high molecular weight polyester by post-condensation of a suspension of a solid, finely divided polyester of lower molecular weight at elevated temperature in a liquid heat transfer medium which does not penetrate into the polyester is described.
The process is preferably employed for the post-conden-sation of polyesters of structural groups of the formulae III and IV
(III) (IV) and silicone oils are used as the heat transfer medium.
The resulting products are very substantially linear and are free from insoluble constituents.
Process for the preparation of high molecular weight linear polyester.
A process for the preparation of a high molecular weight polyester by post-condensation of a suspension of a solid, finely divided polyester of lower molecular weight at elevated temperature in a liquid heat transfer medium which does not penetrate into the polyester is described.
The process is preferably employed for the post-conden-sation of polyesters of structural groups of the formulae III and IV
(III) (IV) and silicone oils are used as the heat transfer medium.
The resulting products are very substantially linear and are free from insoluble constituents.
Description
HOECHST AKTIE~GESELLSCHAFT HOE 91/F 169 Dr.VA/St Description Process for the preparation of high molecular weight linear polyester The present invention relates to a process for the preparation of high molecular weight linear polyesters by post-condensation of a suspension of a solid, finely divided polyester of lower molecular weight at elevated temperature in a liquid heat transfer medium.
High molecular weight polyesters are useful starting msterials for the production of shaped materials, in particular for the production of fibers, the strength of the materials which can be achieved under certain produc-tion conditions as a rule being higher, the higher the molecular weight of the polyester. To obtain polyester threads with maximum strength, it is thus nece~sary, for example, to employ polye~ters having very high molecular weight~ for the spinning, if appropriate in combination with the use of novel ~pinning processe~. Examples in thi~ context are to be found in Japanese Patents 61-207616 and 62-263317, Japanese Published Specification 22 33 33/1987 and European Patent Applications 251 313 and 359 692.
For a long time there has therefore been the need for polye~ter materials of the highest possible molecular weight, and the diverse attempts which have been made in this direction demonstrate the constant effort to achieve this aim.
In industry, high molecular weight polyesters are often prepared by a procedure in which polyesters of relatively lower molecular weight prepared in the melt by trans-esterification or esterification are sub~ected to a solid - 2 - ~'0~9980 phase condensation. In this process, the polyester ~ particles, as a rule granules, are heated in a ~tream of ine~t gas or in vacuo to a temperature below their melting temperature. Further conden~ation takes place during thi~ treatment, the molecular weight being increased, and volatile components which are formed in the solid phase during the condensation are removed.
However, this proce~s is impeded by the increasing crystallization of the polyester, which proceeds in parallel, and the therefore ever more ~lowly progressing diffusion of the volatile components through the poly-ester particle. Finally, at the high temperatures u~ed, degradation reaction~ also gain increasing importance, 80 that the molecular weight which can be achieved is limited. If the IV value (intrinsic viscosity) is taken as a measure of the molecular weight, only an IV value of up to about 1.0 dl/g, for example, can be achieved in practice by conventional solid pha~e condensation carried out on an industrial scale starting from customary polyethylene terephthalate chip~.
One propo~al for the preparation of high molecular weight polye~ter having higher IV values than about 1.0 dl/q by solid phase conden~ation iB to be found in European Patent Application 0 335 819. Thi~ proposes dissolving a polyester initially still of relatively low molecular weight in an organic solvent and precip~tating it again from this solution by dilution with a second organic solvent which doe~ not dis~olve the polye~ter and i8 miscible with the first solvent. The porous, fibrou~
polyester ma~s thus obtained iB filtered off, dried, and then pressed to small shaped articles, and these are then sub~ected to solid phase conden~ation in a manner which is known per se.
The large surface area of these particle~ i~ said to facilitate the diffusion of volatile component~ within the particles and accelerate their removal.
_ 3 - 2069980 However, this process is much too cumbersome for indus-trial use.
A process for the preparation of ultra-high molecular weight polyester is known from European Patent Applica-tion 207 856, in which the post-condensation of a rela-tively low molecular weight polyester is carried out in an organic heat transfer medium.
According to the statements in this patent specification (page 4, lines 27-30), a heat transfer medium which can penetrate partly into the polyester particle and cau~e it to swell is to be chosen. The polycondensation product glycol i8 said to be removed faster from the polyester particle in this ca~e, and the polycondensation i8 thus said to be facilitated. The volatile component~ are then removed from the reaction mixture, together with some of the heat transfer medium, with a stream of inert gas. A
serious disadvantage of this process, however, is that heat tran~fer medium is incorporated in the polyester particles becauee of the swelling and can no longer be removed by simply washing off. The structure of the polyester particles employed is furthermore destroyed, and a large ~uantity of dust i~ formed, which is deposited on the walls of the stirred kettle. Another dieadvantage of this known method is that a heat tran~fer medium which swelle the polyester particles as a rule leads to a yellowish discoloration of the polye~ter during the polycondensation.
Aromatic hydrocarbons and nlicyclic hydrocarbons, ~uch as, for example, diphenyl or ~ubstituted diphenyls and dicycloalkyls and polycyclonlkylene~, are employed a8 the heat transfer oil in thi~ process. The product~ prepared by this proce~s show a marked tendency to agglutinate during the condensation in the heat tran~fer medium, this tendency increasing further as the particle ~ize decreases.
Another process for the preparation of high molecular weight polyesters by melt polycondensation is described in European Patent Application 181 498. Here, long-chain, aliphatic ~ dicarboxylic acids are cocondensed into the polyester during the transesterification, with the aim that these long-chain dicarboxylic acids ~hould form cyclic oligomers with the glycol during the poly-conden~ation phase. Th~ vapor pressure of the glycol i~
said to be reduced and the polycondensation accelerated in this manner. According to the information in this patent application, IV values of up to 2.35 dl/g are achieved. A serious di~advantage of this process is that as the degree of condensation increases, i.e. as the molecular weight of the polyester increa es, the poly-e~ter melt becomes ever more highly viscous and very large amounts of energy are needed to stir the polycon-densation batch. Special reinforced stirrers andcorresponding kettles must also be employed for carrying out such a reaction. If titanium compounds are employed a~ the polycondensation catalyst in this process, marked yellowing of the polye~ter takes place.
Furthermore, a large proportion of the amounts of ~ alkanedicarboxylic acids employed is incorporated in the polyester in this process and can no longer be removed. The polyester thus obtained therefore also has a reduced melting point compared with purely aromatic polyesters of the same degree of condensation. It is also to be expected that mechanical properties relevant to the use of the polyester material will be adversely influ-enced by the incorporation of the long-chain ~,~-alkane-dicarboxylic acids.
Because of the disadvantages de6cribed in the processes known to date for the preparation of high molecular weight and ultra-high molecular weight polye~ters, there was still the need for an industrially practicable process for the preparation of such products which does not have the disadvantages of the processes known to date, or has these disadvantage6 at least to a reduced extent.
In particular, it was an object of the present invention to prepare ultra-high molecular weight polyester6 without the size and shape of the particles employed being chan~ed or having to be changed. As far as possible no S side reactions which lead to crosslinking and to insol-uble particles should proceed during this process.
The present invention thus relates to such an improved proce8s for the preparation of a hi~h molecular weight polyester by post-condensation of a suspension of a solid, finely divided polyester of lower molecular weight at elevated temperature in a liquid heat transfer medium.
In contrast to the known process, however, a heat trans-fer medium which does not penetrate into the polyester and does not swell this i6 employed in the process lS according to the invention. It has in fact been found, surprisingly, that - in contrast to the doctrine of the prior art - for solid phase condensation of the polyester it is not necessary to employ a heat transfer medium which penetrates into the polyester and in this way extracts volatile con~tituents from the polyester particle, but that, in contrast, lt is much mare advan-tageou~ to employ a heat transfer medium which does not penetrate into the polyester particles and therefore does not cau~e them to ~well.
It is of particular importance that the post-condensation according to the invention is carried out in a ~uspension of solid polyester particles. This means that the temper-ature of the polye~ter suspension in the heat transfer oil mu~t be below the melting temperature of the polye~ter particles. It has proved to be particùlarly advantageou~ to carry out the post-condensation at a temperature of 5-50C, preferably 10 to 30C, in parti-cular 15 to 20 below the melting temperature of the polyester particles.
As the polycondensation of the polyester progresses and - its melting temperature thus increases, the temperature of the polycondensation can also be increased gradually to the same extent. The most advantageous polyconden-S sation temperature can easily be determined by prelim-inary experiments. The current melting point of the polye~ter granules can likewise easily be determined by taking samples from the running batch, and the polycon-densation temperature can be ad~usted within the above-mentioned limits. Ad~ustment of the polycondensationtemperature provides the advantage that the reaction can be concluded within a shorter time.
When establishing a temperature program for the polycon-densation, however, it should also be taken into account that thermal degradation of the polye~ter may ~tart at very high temperatures. In an individual ca6e, it is advantageous for the optimum temperature program for the specific polyester to be sub~ected to po~t-conden~ation to be determined by preliminary experiments.
It i~ also of particular importance that the polyester i~
pre~ent in the ~uspension in an adequate fine division.
The smaller the polyester particle~ in the ~uspen~ion, the faster the increase in molecular weight takes place.
In the case of ~mall particles, for example in the range from about 150 to 180 ~m, low molecular weight conden-~ation products can probably escape faster than in the case of large particles, for example in the range from about 1000 to 1400 ~m. The rate of the polycondensation reaction changes accordingly. Polyester particles having dimension~ of between 0.1 mm and about 3 mm are advan-tageously employed. The most advantageous size in an individual case also depends, as well as on the desired increase in molecular weight, on the possibilities which exi~t for comminution and for the necessary separation of the polyester from the heat transfer agent after the post-condensation. It has proved particularly 7 206~980 advantageous to employ polyester chips or cut spun wires.
A favorable particle size from a cut spun wire ha~ a diameter of about 0.2 to 0.5 mm, for example 0.35 mm, and a length of between 1 and 5 mm, for example 3 mm.
Depending on the condensation temperature, particle size and other reaction conditions, a slower or faster increase in the average molecular weight of the polyester and therefore of its intrinsic viscosity takes place up to a plateau, at which practically no further increase in these values i8 achieved.
The reaction time taken to reach the viscosity plateau is between about 10 and 40 hours, depending on the tempera-ture program and the heat transfer medium chosen. For example, in the case of polyethylene terephthalate particles in silicone oil a~ the heat transfer medium at 245, the visco~ity plateau is reached after a conden-sation time of about 30 hours.
According to the invention, all the inert media which are liquid at the polycondensation temperature and which meet the condition that they do not diffuse into the polyester particle and therefore do not swell it under the condensation conditions can be employed as heat transfer media for the polycondensation of the polyester.
The choice o suitable heat tran~fer media can ea~ily be made by preliminary experiments, in which the polyester particles are heated in the heat transfer medium under the customary polycondensation conditions and are iso-lated when the condensation time ha~ elapsed. The surface of the particles i~olated is washed off with a highly volatile solvent and dried in vacuo. The amount of heat transfer medium which has diffused into the polyester particles can then be ascertained by a thermogravimetric determination, in which the decrease in weight of the particle~ on heating to temperatures of about 200 to 300C is determined.
Heat transfer media which are suitable for the process according to the invention are those which diffuse into the polyester particles to the extent of less than 5~, preferably to the extent of less than 1~, i.e. a weight 1088 of < 5%, preferably < l~, occurs during thermo-gravimetric determination on the polyester materials sub~ected to polycondensation in these heat transfer media.
Particularly suitable heat transfer media for the process according to the invention are silicone oils which can be heated to the polycondensation temperature, i.e. up to about 250C, without decomposition and without evapor-ation losses which are too high. Silicone oils which meet these conditions are built up, for example, from units of the formula I:
t ~1 3 In these formulae Rl i8 alkyl having 1 to 10, preferably 1 to 4 carbon atoms, cycloalkyl having 4 to 8, preferably 5 or 6 carbon atoms, aryl having 5 to 14, preferably 5 to 10 carbon atoms or aralkyl having 6 to 16, preferably 7 to 12 carbon atoms and Rz is R1 or another radical from the group of radicals ment~oned for R1.
A particularly advantageous group of heat transfer media comprises those which consist of units of the formulae II
and IIa ~ ~ 3 3 (IIa) ~ 5l 3 g In these R3 is phenyl and R4 is methyl, or R3 and R4 are both methyl or both phenyl.
Heat transfer media having the abov~mentioned composition are commercially available. Silicone oils having viscosities of about 50-500 mm2/6 (at 25C), viscosity-temperature coefficients of about 0.7 to 0.85, refractive indices at 25-C of about 1.4 to 1.51, densities of about 1 to 1.11 (at 25-C), a he~t ~tability in an open crucible at 250C of about 500 to 1500 hours and a volatility after 2 hours in an open crucible at 250C of about 5 to 1~ are particularly suitable heat transfer media of this ~ub~tance class.
Particularly suitable commercial products are, for example, the phenyl-methyl-silicone oils obtainable under the name Wacker Silicone Oil6 AP.
The concentration of the polyester particles in the ~uspension in the process according to the invention is advantageously 50 to 500 g/l. The particle concentration can be increaeed in individunl ca~e~; a~ a rule, however, it i~ found that if the concentration i8 lncreased above thi~ limit, ~tirring of the su~pension is made more difficult and the limit of the molecular weight achieved is reduced. If the concentratlon falls below the lower limit stated, there are no di~advantages as ~uch for the reaction, but the economy of the proces~ is reduced.
The particle concentration in the suspension iB prefer-ably 100 to 300 g/l. The value of the intrinsic viscosity of the end product which can be achived by the process according to the invention ~hows a certain dependence on the particle concentration in the suspension As the concentration increa~es, lower final viscosity value~ are in general achieved, under otherwise identlcal conditions.
2~69980 During the polycondensation in the heat transfer medium, the suspension is advantageously kept in motion such that the concentration of the polyester particles is about the - same at all points. This thorough mixing of the 6uspen-sion can in principle be carried out by all the known processes, for example by passing a ~tream of gas through the suspension or by stirring it or by combining several such known processes with one another. The particle suspension is preferably kept in motion by stirring. The stirring speed also has a certain influence on the final vi~cosity of the polyester which can be achieved in the process according to the invention. An increasing stir-ring speed as a rule leads to a certain increase in the final viscosity, under otherwise identical conditions.
The removal of the highly volatile condensation products, lower alcohols, glycols and, if appropriate, a little water, from the polycondensation mixture is of particular importance for e~tablishing equilibrium of the polycon-den~ation.
Removal of these reaction products can be facilitated by applying a vacuum. However, it i~ preferable to flush the reaction ~pace with an inert gas, which has been dried if appropriate.
In practice, the highly volatile compounds are advantage-ously removed by a ~tream of nitrogen, which is either pa~ed over the reaction batch or introduced into it.
Although the intensity of the stream of nitrogen usually has only a slight influence on the level of the molecular weight which can be achieved, it is advantageous to maintain a certain minimum flow. A ~tream of nitrogen of about 50 to 250 l/h ha~ proved u~eful for a batch of about 1 1 of su~pen~ion.
All polye~ter materials which can be sub~ected to post-condensation to high molecular weights by a solid pha~e condensation are in principle suitable as the starting polyester for the polycondensation by the process ~069980 according to the invention. Particularly suitable polyesters are those which contain aromatic radicals in the polymer chain, such as, for example, polyester~ which are built up from 0 to 100 mol% of structural groups of the formula III
O O
(III) ~
--c--x--c--o Y o----and 100 to 0 mol% of structural groups of the formula IV
_ _ (IV) ll _--c X 0- _ in which X i~, to the extent of more than 75 mol%, aromatic radical~ having 5 to 16, preferably 6 to 12 carbon atoms and, to the extent of not more than 25 mol%, aliphatic rsdical~ having 4 to 10 carbon atoms, preferably 6 to 8 carbon atom~, and Y i~, to the extent of at least 85 mol%, alkylene or polymethylene group~ having 2 to 4 carbon atoms and, to the extent of not more than 15 mol%, longer-chain poly-methylene or alkylene group~, preferably having up to 8 cnrbon atom~, and divalent radicals which are derived from diglycol, triglyGol or polyglycol.
Those ~tarting polyesters which have an intrinsic visco-~ity of 0.3 to 0.6 dl/g, mea~ured in dichloroacetic acid at 25C a~ described below, are advantageously employed.
2~69980 Polyeæters which contain structural groups of the formula IV preferably contain 70 to 100 mol%, in particular 85 to 100 mol~, of structural groups of the formula III and 0 to 30 mol~, in particular 0 to 15 mol%, of structural S groups of the formula IV.
Polyesters in which at least 95 mol% of X is aromatic and not more than 5 mol% of X is aliphatic radicals, and in particular those in which X is exclusively aromatic radicalE, are preferred.
Preferred aromatic radicals X are 1,4- and 1,3-phenylene, 1,4-, 1,5-, 1,8-, 2,6- and 2,7-naphthylene, 4,4'-bipheny-lene, furylene and radicals of the formula (V) ~z~3 in which Z is polymethylene or alkylene having 1 to 4 carbon atoms, -S02-, -C00-, -0- or -S-.
The aromatic radicals can in turn also carry one or two substi'cuents. In this case, however, it is preferable for only an amount of up 15%, in particular of up to 7%, of the aromatic radicals present to be substituted. The substituted aromatic radicals preferably in each case carry only one substituent. Particularly suitable substi-tuents are alkyl having 1 to 4 carbon atoms, alkoxy having 1 to 4 carbon atoms, chlorine and the sulfo group.
Radicals which are derived from aliphatic dicarboxylic acids, and aromatic radicals which produce angled chains, for example isophthalic acid radicals, or contain bulky aromatic nuclei, such as the naphthalene nucleus, and the lonqer-chain structural groups Y, are incorporated into the polyester chain in particular if modification of the properties of the polyester i8 desired.
Polye~ters which contain le~s 7~ of these modifying component~ are preferred.
A group of preferred polyesters corresponds to the formula VI
(VI) ~ C ~ C - 0-(C~7)- 0 k in which l is a number from 2 to 6 and k i~ a number above 10.
A psrticularly preferred polyester which can be sub~ected to polycondensation by the proce~s according to the invention to give particularly high molecular weights is pure polyethylene terephthalate and polyethylene tereph-thalate which has been modified by incorporation of up to 10 mol~ of other units from the abovementioned qroups such that certain use properties are obtained, such as, for example, polyethylene terephthalate which has acquired an affinity for bas~c dyestuffs by incorporation of units containing sulfo groups (for example sulfoiso-phthalic acid), or which has a low combustibility due tothe incorporation of radicals of phosphinic acid deriva-tives, for example those of the formulae VII ~ o~ _o 3 aDd VIII ~ R6 C
2~69~8~
in which R5 is preferably lower alkyl radicals and R6 is preferably alkylene or polymethylene having 1 to 6 carbon atoms.
The low molecular weight polyesters employed as starting materials for the process according to the invention can be obtained from the corresponding starting materials in a manner which is known per se by all the preparation processes known to date, in particular by direct esteri-fication of the dicarboxylic acids with the diols or by transesterification of dicarboxylic acid lower alkyl esters, for example the dicarboxylic acid dimethyl esters, with the corresponding diols.
The catalysts employed during conventional polyester preparation, such as esterification and transesteri-fication catalysts, can also be used for the preparationof the low molecular weight starting polyester for the process according to the invention. The same applies to the polycondensation catalysts employed in the polycon-densation. The nature of these catalysts in general has little effect on the level of the final molecular weight (final vi~cosity) which can be achieved in the process according to the invention; only if tin acetate is employed a~ the polycondensation catalyst are somewhat higher final molecular weights, i.e. also a higher final viscosity, as 8 rule reached than when other polyconden-sation catalyst~ are employed, under otherwise identical conditions.
The low molecular weight polyester materials should be dried thoroughly before the polycondensation according to the invention. Drying is advantageously carried out at 110 to 190C in a manner which is known per se, but it should be ensured that too high a crystallinity of the polyester particles does not occur during drying.
Drying temperatures outside the limit~ stated as a rule provide no advantages, but may be appropriate in specific - 15 - 2069~80 cases. In particular, drying below 110 and if appropriate in vacuo may provide advantages if it seems appropriate to avoid an increase in the crystallinity as far as possible.
If required, the crystallinity can be determined in a manner which is known per se either by X-ray analysis or by determination of the density of the polyester par-ticles, advantageously in a gradient column charged with, for example, zinc chloride solution in a concentration which decreases toward the top.
An important criterion for carrying out the process according to the invention is the use of a starting polyester having a sufficient concentration of free end carboxyl groups. Starting polyesters which contain between 10 and 40 mmol/kg, preferably 20 to 30 mmol/kg of carboxyl end groups are particularly suitable. The optimum OH/COOH ratio for the starting polyester in the solid pha~e condensation according to the invention is in the range from 1.5 to 4.5.
The proce~s according to the invention opens up a route which is also readily accessible industrially for the preparation of polyesters having very high molecular weights and corre~pondingly high intrinsic viw osities.
As is known, the intrinsic viscosity is the limiting value of the quotient of the specific viscosity and the concentration at a concentration tending toward zero:
~] z lim c I O c The specific viscosities necessary for calculation of the intrinsic viscosity according to the above equation were de~termined in dichloroacetic acid at 25C. During the measurement, it should be ensured and guaranteed that highly crystalline polyesters or highly crystalline portions of the polyesters are also dissolved completely.
The high molecular weight polyesters prepared according to the invention have a narrower molecular weight distri-bution than products prepared conventionally. In parti-cular, the products contain only very small amounts, if any, of insoluble portions. Gel chromatography can be employed to determine the molecular weight distribution.
The GPC apparatus used here consists of a pump, a W
detector and 10 ~ (R)Styragel columns (500, 103, 104, 105, 106 ~). Chloroform/HFIP (98:2% by volume) was used a6 the eluting agent. The calibration is carried out in a manner which is known per se using polyethylene terephthalate standards. (A detailed description of this process i~ to be found in the paper by K. Weisskopf, Characterization of Polyethylene Terephthalate by Gel Permeation Chromato-graphy (GPC) in Journal of Polymer Science, Part A, Chemistry, Volume 26, (1988), page 1920 et seq.).
The in~oluble portions of the high molecular weight polyester~ prepared according to the invention are determined by dissolving 6 g of the polyester to be analyzed in 100 ml of trifluoroacetic acid/dichloroethane (TFA/DE) (lsl) at 25C, the material being stirred in the solvent at 150 to 200 revolutions/minute for 6 hours. The solution is then filtered through a glass frit (20 to 30 ~). The insoluble material which remains on the frit is washed with chloroform and dried at 130C for 24 hours.
On analysis of the polyesters prepared according to the invention by the method described by K. Wei3skopf in Journal of Applied Polymer Science, Volume 39, 2141-2152 (1990) for analysis of branched polyethylene tereph-thalate, no branchings can be detected therein. This shows that these products are very substantially linear.
Other advantages of the process according to the inven-tion are the possibility of preparing polyester materials having intrinsic viscosities of up to more than 2.0 dl/g on an industrial scale, the fact that this is possible within a shorter time than by conventional processes, and the fact that the homogeneity of the polyester particles which have undergone solid phase condensation by the proce~s according to the invention is far better than that after conventional colid phase polymerization. The use of silicone oil as the heat transfer medium has the further advantage that from the commercially available examples of this clas~ of compound, tho~e which have 6uch a high boiling point that no substantial 108s of BolVent due to evaporation occurs in the course of the polycon-densation process can be chosen, and furthermore that the low molecular weight volatile products of the poly-conden~ation reaction do not concentrate in the fiiliconeoil~ and the silicone oil can therefore be used again for the next polycondensation batch - as a rule without further working up - after the polyester which has undergone polycondensation has been ~eparated off.
The proae~s according to the invention is illustrated with the aid of the following embodiment examples.
Examples 1 to 6 60 g of polyethylene terephthalate particles in 300 ml of Wacker Silicone Oil AP 500 were employed in each of the following 6 batches. The polyester particle~ were cylin-ders having a diameter of 0.35 mm and a length of 3 mm, which were prepared by cutting corresponding polye~ter monofilaments. The intrinsic visco~ity of the polyester material employed was 0.6 dl/g, the carboxyl end group content was 23 mmol/kg nnd the OH/COOH ratio was 2.87.
The polycondensations were carried out in a 2 1 four-necked flask with a stirrer (250 revolutions/minute), a contact thermometer for control of the internal temperature and a gas inlet tube. Dry nitrogen was employed as the carrier gas. The polyester suspension was - 18 - 206998~
heated to the particular polycondensation temperature (PC temperature) in the course of 0.75 hour.
The polycondensation temperature, the polyconden~ation time and the inten ity of the stream of nitrogen were varied in the experiments. ~he corresponding data are shown in the following Table 1. The last column of this table contains the IV values of the high molecular weight polyester~ obtained in the experiments. Experiment~ 1 and 2 show the good reproducibility of the process according 10 to the invention.
TABL~ 1 Experi- PC PC N2 IV(GPC) IV(DCA) ISC
ment tempera- time stream ture C h l/h dl/g dl/g g 1 240 7.25 120 1.51 1.51 0 2 240 7.25 120 1.57 - 0 3 245 7.25 250 1.66 1.69 0 4 245 7.25 120 1.66 1.59 0 245 15.25 120 1.90 1.84 0 6 245 23.25 120 2.05 2.02 0 ~ ISC = insoluble constituents The narrow molecular weight distribution which can be achieved by the process according to the invention is shown by the quotient M~/N~, which has a value of 3.42 for each of the products from Examples 1 and 2.
ComDarison Exam~le For comparison, 60 g of polyethylene terephthalate particles were sub~ected to polyconden~ation in 300 ml of hydrogenated terphenyl as the heat transfer medium. As in Examples 1-6, the polye~ter particles were cylinders having a diameter of 0.35 mm and a length of 3 mm, and con~isted of the same material which was employed in Examples 1-6.
The polycondensations were carried out in a 2 1 _ 19 --four-neckedflask with a stirrer (250 revolutions/minute), a contact thermometer for controls of the internal tempersture and gas inlet tube. Dry nitrogen in an amount of 120 l/h was employed as the carrier gas. The polyester suspension was heated to the polycondensation temperature of 240C in the course of 0.75 hour and the polycondensation time was 7.25 hours.
The product thus obtained had an IVG~ Of 1.35 and an M~/N~
value of 4.70.
High molecular weight polyesters are useful starting msterials for the production of shaped materials, in particular for the production of fibers, the strength of the materials which can be achieved under certain produc-tion conditions as a rule being higher, the higher the molecular weight of the polyester. To obtain polyester threads with maximum strength, it is thus nece~sary, for example, to employ polye~ters having very high molecular weight~ for the spinning, if appropriate in combination with the use of novel ~pinning processe~. Examples in thi~ context are to be found in Japanese Patents 61-207616 and 62-263317, Japanese Published Specification 22 33 33/1987 and European Patent Applications 251 313 and 359 692.
For a long time there has therefore been the need for polye~ter materials of the highest possible molecular weight, and the diverse attempts which have been made in this direction demonstrate the constant effort to achieve this aim.
In industry, high molecular weight polyesters are often prepared by a procedure in which polyesters of relatively lower molecular weight prepared in the melt by trans-esterification or esterification are sub~ected to a solid - 2 - ~'0~9980 phase condensation. In this process, the polyester ~ particles, as a rule granules, are heated in a ~tream of ine~t gas or in vacuo to a temperature below their melting temperature. Further conden~ation takes place during thi~ treatment, the molecular weight being increased, and volatile components which are formed in the solid phase during the condensation are removed.
However, this proce~s is impeded by the increasing crystallization of the polyester, which proceeds in parallel, and the therefore ever more ~lowly progressing diffusion of the volatile components through the poly-ester particle. Finally, at the high temperatures u~ed, degradation reaction~ also gain increasing importance, 80 that the molecular weight which can be achieved is limited. If the IV value (intrinsic viscosity) is taken as a measure of the molecular weight, only an IV value of up to about 1.0 dl/g, for example, can be achieved in practice by conventional solid pha~e condensation carried out on an industrial scale starting from customary polyethylene terephthalate chip~.
One propo~al for the preparation of high molecular weight polye~ter having higher IV values than about 1.0 dl/q by solid phase conden~ation iB to be found in European Patent Application 0 335 819. Thi~ proposes dissolving a polyester initially still of relatively low molecular weight in an organic solvent and precip~tating it again from this solution by dilution with a second organic solvent which doe~ not dis~olve the polye~ter and i8 miscible with the first solvent. The porous, fibrou~
polyester ma~s thus obtained iB filtered off, dried, and then pressed to small shaped articles, and these are then sub~ected to solid phase conden~ation in a manner which is known per se.
The large surface area of these particle~ i~ said to facilitate the diffusion of volatile component~ within the particles and accelerate their removal.
_ 3 - 2069980 However, this process is much too cumbersome for indus-trial use.
A process for the preparation of ultra-high molecular weight polyester is known from European Patent Applica-tion 207 856, in which the post-condensation of a rela-tively low molecular weight polyester is carried out in an organic heat transfer medium.
According to the statements in this patent specification (page 4, lines 27-30), a heat transfer medium which can penetrate partly into the polyester particle and cau~e it to swell is to be chosen. The polycondensation product glycol i8 said to be removed faster from the polyester particle in this ca~e, and the polycondensation i8 thus said to be facilitated. The volatile component~ are then removed from the reaction mixture, together with some of the heat transfer medium, with a stream of inert gas. A
serious disadvantage of this process, however, is that heat tran~fer medium is incorporated in the polyester particles becauee of the swelling and can no longer be removed by simply washing off. The structure of the polyester particles employed is furthermore destroyed, and a large ~uantity of dust i~ formed, which is deposited on the walls of the stirred kettle. Another dieadvantage of this known method is that a heat tran~fer medium which swelle the polyester particles as a rule leads to a yellowish discoloration of the polye~ter during the polycondensation.
Aromatic hydrocarbons and nlicyclic hydrocarbons, ~uch as, for example, diphenyl or ~ubstituted diphenyls and dicycloalkyls and polycyclonlkylene~, are employed a8 the heat transfer oil in thi~ process. The product~ prepared by this proce~s show a marked tendency to agglutinate during the condensation in the heat tran~fer medium, this tendency increasing further as the particle ~ize decreases.
Another process for the preparation of high molecular weight polyesters by melt polycondensation is described in European Patent Application 181 498. Here, long-chain, aliphatic ~ dicarboxylic acids are cocondensed into the polyester during the transesterification, with the aim that these long-chain dicarboxylic acids ~hould form cyclic oligomers with the glycol during the poly-conden~ation phase. Th~ vapor pressure of the glycol i~
said to be reduced and the polycondensation accelerated in this manner. According to the information in this patent application, IV values of up to 2.35 dl/g are achieved. A serious di~advantage of this process is that as the degree of condensation increases, i.e. as the molecular weight of the polyester increa es, the poly-e~ter melt becomes ever more highly viscous and very large amounts of energy are needed to stir the polycon-densation batch. Special reinforced stirrers andcorresponding kettles must also be employed for carrying out such a reaction. If titanium compounds are employed a~ the polycondensation catalyst in this process, marked yellowing of the polye~ter takes place.
Furthermore, a large proportion of the amounts of ~ alkanedicarboxylic acids employed is incorporated in the polyester in this process and can no longer be removed. The polyester thus obtained therefore also has a reduced melting point compared with purely aromatic polyesters of the same degree of condensation. It is also to be expected that mechanical properties relevant to the use of the polyester material will be adversely influ-enced by the incorporation of the long-chain ~,~-alkane-dicarboxylic acids.
Because of the disadvantages de6cribed in the processes known to date for the preparation of high molecular weight and ultra-high molecular weight polye~ters, there was still the need for an industrially practicable process for the preparation of such products which does not have the disadvantages of the processes known to date, or has these disadvantage6 at least to a reduced extent.
In particular, it was an object of the present invention to prepare ultra-high molecular weight polyester6 without the size and shape of the particles employed being chan~ed or having to be changed. As far as possible no S side reactions which lead to crosslinking and to insol-uble particles should proceed during this process.
The present invention thus relates to such an improved proce8s for the preparation of a hi~h molecular weight polyester by post-condensation of a suspension of a solid, finely divided polyester of lower molecular weight at elevated temperature in a liquid heat transfer medium.
In contrast to the known process, however, a heat trans-fer medium which does not penetrate into the polyester and does not swell this i6 employed in the process lS according to the invention. It has in fact been found, surprisingly, that - in contrast to the doctrine of the prior art - for solid phase condensation of the polyester it is not necessary to employ a heat transfer medium which penetrates into the polyester and in this way extracts volatile con~tituents from the polyester particle, but that, in contrast, lt is much mare advan-tageou~ to employ a heat transfer medium which does not penetrate into the polyester particles and therefore does not cau~e them to ~well.
It is of particular importance that the post-condensation according to the invention is carried out in a ~uspension of solid polyester particles. This means that the temper-ature of the polye~ter suspension in the heat transfer oil mu~t be below the melting temperature of the polye~ter particles. It has proved to be particùlarly advantageou~ to carry out the post-condensation at a temperature of 5-50C, preferably 10 to 30C, in parti-cular 15 to 20 below the melting temperature of the polyester particles.
As the polycondensation of the polyester progresses and - its melting temperature thus increases, the temperature of the polycondensation can also be increased gradually to the same extent. The most advantageous polyconden-S sation temperature can easily be determined by prelim-inary experiments. The current melting point of the polye~ter granules can likewise easily be determined by taking samples from the running batch, and the polycon-densation temperature can be ad~usted within the above-mentioned limits. Ad~ustment of the polycondensationtemperature provides the advantage that the reaction can be concluded within a shorter time.
When establishing a temperature program for the polycon-densation, however, it should also be taken into account that thermal degradation of the polye~ter may ~tart at very high temperatures. In an individual ca6e, it is advantageous for the optimum temperature program for the specific polyester to be sub~ected to po~t-conden~ation to be determined by preliminary experiments.
It i~ also of particular importance that the polyester i~
pre~ent in the ~uspension in an adequate fine division.
The smaller the polyester particle~ in the ~uspen~ion, the faster the increase in molecular weight takes place.
In the case of ~mall particles, for example in the range from about 150 to 180 ~m, low molecular weight conden-~ation products can probably escape faster than in the case of large particles, for example in the range from about 1000 to 1400 ~m. The rate of the polycondensation reaction changes accordingly. Polyester particles having dimension~ of between 0.1 mm and about 3 mm are advan-tageously employed. The most advantageous size in an individual case also depends, as well as on the desired increase in molecular weight, on the possibilities which exi~t for comminution and for the necessary separation of the polyester from the heat transfer agent after the post-condensation. It has proved particularly 7 206~980 advantageous to employ polyester chips or cut spun wires.
A favorable particle size from a cut spun wire ha~ a diameter of about 0.2 to 0.5 mm, for example 0.35 mm, and a length of between 1 and 5 mm, for example 3 mm.
Depending on the condensation temperature, particle size and other reaction conditions, a slower or faster increase in the average molecular weight of the polyester and therefore of its intrinsic viscosity takes place up to a plateau, at which practically no further increase in these values i8 achieved.
The reaction time taken to reach the viscosity plateau is between about 10 and 40 hours, depending on the tempera-ture program and the heat transfer medium chosen. For example, in the case of polyethylene terephthalate particles in silicone oil a~ the heat transfer medium at 245, the visco~ity plateau is reached after a conden-sation time of about 30 hours.
According to the invention, all the inert media which are liquid at the polycondensation temperature and which meet the condition that they do not diffuse into the polyester particle and therefore do not swell it under the condensation conditions can be employed as heat transfer media for the polycondensation of the polyester.
The choice o suitable heat tran~fer media can ea~ily be made by preliminary experiments, in which the polyester particles are heated in the heat transfer medium under the customary polycondensation conditions and are iso-lated when the condensation time ha~ elapsed. The surface of the particles i~olated is washed off with a highly volatile solvent and dried in vacuo. The amount of heat transfer medium which has diffused into the polyester particles can then be ascertained by a thermogravimetric determination, in which the decrease in weight of the particle~ on heating to temperatures of about 200 to 300C is determined.
Heat transfer media which are suitable for the process according to the invention are those which diffuse into the polyester particles to the extent of less than 5~, preferably to the extent of less than 1~, i.e. a weight 1088 of < 5%, preferably < l~, occurs during thermo-gravimetric determination on the polyester materials sub~ected to polycondensation in these heat transfer media.
Particularly suitable heat transfer media for the process according to the invention are silicone oils which can be heated to the polycondensation temperature, i.e. up to about 250C, without decomposition and without evapor-ation losses which are too high. Silicone oils which meet these conditions are built up, for example, from units of the formula I:
t ~1 3 In these formulae Rl i8 alkyl having 1 to 10, preferably 1 to 4 carbon atoms, cycloalkyl having 4 to 8, preferably 5 or 6 carbon atoms, aryl having 5 to 14, preferably 5 to 10 carbon atoms or aralkyl having 6 to 16, preferably 7 to 12 carbon atoms and Rz is R1 or another radical from the group of radicals ment~oned for R1.
A particularly advantageous group of heat transfer media comprises those which consist of units of the formulae II
and IIa ~ ~ 3 3 (IIa) ~ 5l 3 g In these R3 is phenyl and R4 is methyl, or R3 and R4 are both methyl or both phenyl.
Heat transfer media having the abov~mentioned composition are commercially available. Silicone oils having viscosities of about 50-500 mm2/6 (at 25C), viscosity-temperature coefficients of about 0.7 to 0.85, refractive indices at 25-C of about 1.4 to 1.51, densities of about 1 to 1.11 (at 25-C), a he~t ~tability in an open crucible at 250C of about 500 to 1500 hours and a volatility after 2 hours in an open crucible at 250C of about 5 to 1~ are particularly suitable heat transfer media of this ~ub~tance class.
Particularly suitable commercial products are, for example, the phenyl-methyl-silicone oils obtainable under the name Wacker Silicone Oil6 AP.
The concentration of the polyester particles in the ~uspension in the process according to the invention is advantageously 50 to 500 g/l. The particle concentration can be increaeed in individunl ca~e~; a~ a rule, however, it i~ found that if the concentration i8 lncreased above thi~ limit, ~tirring of the su~pension is made more difficult and the limit of the molecular weight achieved is reduced. If the concentratlon falls below the lower limit stated, there are no di~advantages as ~uch for the reaction, but the economy of the proces~ is reduced.
The particle concentration in the suspension iB prefer-ably 100 to 300 g/l. The value of the intrinsic viscosity of the end product which can be achived by the process according to the invention ~hows a certain dependence on the particle concentration in the suspension As the concentration increa~es, lower final viscosity value~ are in general achieved, under otherwise identlcal conditions.
2~69980 During the polycondensation in the heat transfer medium, the suspension is advantageously kept in motion such that the concentration of the polyester particles is about the - same at all points. This thorough mixing of the 6uspen-sion can in principle be carried out by all the known processes, for example by passing a ~tream of gas through the suspension or by stirring it or by combining several such known processes with one another. The particle suspension is preferably kept in motion by stirring. The stirring speed also has a certain influence on the final vi~cosity of the polyester which can be achieved in the process according to the invention. An increasing stir-ring speed as a rule leads to a certain increase in the final viscosity, under otherwise identical conditions.
The removal of the highly volatile condensation products, lower alcohols, glycols and, if appropriate, a little water, from the polycondensation mixture is of particular importance for e~tablishing equilibrium of the polycon-den~ation.
Removal of these reaction products can be facilitated by applying a vacuum. However, it i~ preferable to flush the reaction ~pace with an inert gas, which has been dried if appropriate.
In practice, the highly volatile compounds are advantage-ously removed by a ~tream of nitrogen, which is either pa~ed over the reaction batch or introduced into it.
Although the intensity of the stream of nitrogen usually has only a slight influence on the level of the molecular weight which can be achieved, it is advantageous to maintain a certain minimum flow. A ~tream of nitrogen of about 50 to 250 l/h ha~ proved u~eful for a batch of about 1 1 of su~pen~ion.
All polye~ter materials which can be sub~ected to post-condensation to high molecular weights by a solid pha~e condensation are in principle suitable as the starting polyester for the polycondensation by the process ~069980 according to the invention. Particularly suitable polyesters are those which contain aromatic radicals in the polymer chain, such as, for example, polyester~ which are built up from 0 to 100 mol% of structural groups of the formula III
O O
(III) ~
--c--x--c--o Y o----and 100 to 0 mol% of structural groups of the formula IV
_ _ (IV) ll _--c X 0- _ in which X i~, to the extent of more than 75 mol%, aromatic radical~ having 5 to 16, preferably 6 to 12 carbon atoms and, to the extent of not more than 25 mol%, aliphatic rsdical~ having 4 to 10 carbon atoms, preferably 6 to 8 carbon atom~, and Y i~, to the extent of at least 85 mol%, alkylene or polymethylene group~ having 2 to 4 carbon atoms and, to the extent of not more than 15 mol%, longer-chain poly-methylene or alkylene group~, preferably having up to 8 cnrbon atom~, and divalent radicals which are derived from diglycol, triglyGol or polyglycol.
Those ~tarting polyesters which have an intrinsic visco-~ity of 0.3 to 0.6 dl/g, mea~ured in dichloroacetic acid at 25C a~ described below, are advantageously employed.
2~69980 Polyeæters which contain structural groups of the formula IV preferably contain 70 to 100 mol%, in particular 85 to 100 mol~, of structural groups of the formula III and 0 to 30 mol~, in particular 0 to 15 mol%, of structural S groups of the formula IV.
Polyesters in which at least 95 mol% of X is aromatic and not more than 5 mol% of X is aliphatic radicals, and in particular those in which X is exclusively aromatic radicalE, are preferred.
Preferred aromatic radicals X are 1,4- and 1,3-phenylene, 1,4-, 1,5-, 1,8-, 2,6- and 2,7-naphthylene, 4,4'-bipheny-lene, furylene and radicals of the formula (V) ~z~3 in which Z is polymethylene or alkylene having 1 to 4 carbon atoms, -S02-, -C00-, -0- or -S-.
The aromatic radicals can in turn also carry one or two substi'cuents. In this case, however, it is preferable for only an amount of up 15%, in particular of up to 7%, of the aromatic radicals present to be substituted. The substituted aromatic radicals preferably in each case carry only one substituent. Particularly suitable substi-tuents are alkyl having 1 to 4 carbon atoms, alkoxy having 1 to 4 carbon atoms, chlorine and the sulfo group.
Radicals which are derived from aliphatic dicarboxylic acids, and aromatic radicals which produce angled chains, for example isophthalic acid radicals, or contain bulky aromatic nuclei, such as the naphthalene nucleus, and the lonqer-chain structural groups Y, are incorporated into the polyester chain in particular if modification of the properties of the polyester i8 desired.
Polye~ters which contain le~s 7~ of these modifying component~ are preferred.
A group of preferred polyesters corresponds to the formula VI
(VI) ~ C ~ C - 0-(C~7)- 0 k in which l is a number from 2 to 6 and k i~ a number above 10.
A psrticularly preferred polyester which can be sub~ected to polycondensation by the proce~s according to the invention to give particularly high molecular weights is pure polyethylene terephthalate and polyethylene tereph-thalate which has been modified by incorporation of up to 10 mol~ of other units from the abovementioned qroups such that certain use properties are obtained, such as, for example, polyethylene terephthalate which has acquired an affinity for bas~c dyestuffs by incorporation of units containing sulfo groups (for example sulfoiso-phthalic acid), or which has a low combustibility due tothe incorporation of radicals of phosphinic acid deriva-tives, for example those of the formulae VII ~ o~ _o 3 aDd VIII ~ R6 C
2~69~8~
in which R5 is preferably lower alkyl radicals and R6 is preferably alkylene or polymethylene having 1 to 6 carbon atoms.
The low molecular weight polyesters employed as starting materials for the process according to the invention can be obtained from the corresponding starting materials in a manner which is known per se by all the preparation processes known to date, in particular by direct esteri-fication of the dicarboxylic acids with the diols or by transesterification of dicarboxylic acid lower alkyl esters, for example the dicarboxylic acid dimethyl esters, with the corresponding diols.
The catalysts employed during conventional polyester preparation, such as esterification and transesteri-fication catalysts, can also be used for the preparationof the low molecular weight starting polyester for the process according to the invention. The same applies to the polycondensation catalysts employed in the polycon-densation. The nature of these catalysts in general has little effect on the level of the final molecular weight (final vi~cosity) which can be achieved in the process according to the invention; only if tin acetate is employed a~ the polycondensation catalyst are somewhat higher final molecular weights, i.e. also a higher final viscosity, as 8 rule reached than when other polyconden-sation catalyst~ are employed, under otherwise identical conditions.
The low molecular weight polyester materials should be dried thoroughly before the polycondensation according to the invention. Drying is advantageously carried out at 110 to 190C in a manner which is known per se, but it should be ensured that too high a crystallinity of the polyester particles does not occur during drying.
Drying temperatures outside the limit~ stated as a rule provide no advantages, but may be appropriate in specific - 15 - 2069~80 cases. In particular, drying below 110 and if appropriate in vacuo may provide advantages if it seems appropriate to avoid an increase in the crystallinity as far as possible.
If required, the crystallinity can be determined in a manner which is known per se either by X-ray analysis or by determination of the density of the polyester par-ticles, advantageously in a gradient column charged with, for example, zinc chloride solution in a concentration which decreases toward the top.
An important criterion for carrying out the process according to the invention is the use of a starting polyester having a sufficient concentration of free end carboxyl groups. Starting polyesters which contain between 10 and 40 mmol/kg, preferably 20 to 30 mmol/kg of carboxyl end groups are particularly suitable. The optimum OH/COOH ratio for the starting polyester in the solid pha~e condensation according to the invention is in the range from 1.5 to 4.5.
The proce~s according to the invention opens up a route which is also readily accessible industrially for the preparation of polyesters having very high molecular weights and corre~pondingly high intrinsic viw osities.
As is known, the intrinsic viscosity is the limiting value of the quotient of the specific viscosity and the concentration at a concentration tending toward zero:
~] z lim c I O c The specific viscosities necessary for calculation of the intrinsic viscosity according to the above equation were de~termined in dichloroacetic acid at 25C. During the measurement, it should be ensured and guaranteed that highly crystalline polyesters or highly crystalline portions of the polyesters are also dissolved completely.
The high molecular weight polyesters prepared according to the invention have a narrower molecular weight distri-bution than products prepared conventionally. In parti-cular, the products contain only very small amounts, if any, of insoluble portions. Gel chromatography can be employed to determine the molecular weight distribution.
The GPC apparatus used here consists of a pump, a W
detector and 10 ~ (R)Styragel columns (500, 103, 104, 105, 106 ~). Chloroform/HFIP (98:2% by volume) was used a6 the eluting agent. The calibration is carried out in a manner which is known per se using polyethylene terephthalate standards. (A detailed description of this process i~ to be found in the paper by K. Weisskopf, Characterization of Polyethylene Terephthalate by Gel Permeation Chromato-graphy (GPC) in Journal of Polymer Science, Part A, Chemistry, Volume 26, (1988), page 1920 et seq.).
The in~oluble portions of the high molecular weight polyester~ prepared according to the invention are determined by dissolving 6 g of the polyester to be analyzed in 100 ml of trifluoroacetic acid/dichloroethane (TFA/DE) (lsl) at 25C, the material being stirred in the solvent at 150 to 200 revolutions/minute for 6 hours. The solution is then filtered through a glass frit (20 to 30 ~). The insoluble material which remains on the frit is washed with chloroform and dried at 130C for 24 hours.
On analysis of the polyesters prepared according to the invention by the method described by K. Wei3skopf in Journal of Applied Polymer Science, Volume 39, 2141-2152 (1990) for analysis of branched polyethylene tereph-thalate, no branchings can be detected therein. This shows that these products are very substantially linear.
Other advantages of the process according to the inven-tion are the possibility of preparing polyester materials having intrinsic viscosities of up to more than 2.0 dl/g on an industrial scale, the fact that this is possible within a shorter time than by conventional processes, and the fact that the homogeneity of the polyester particles which have undergone solid phase condensation by the proce~s according to the invention is far better than that after conventional colid phase polymerization. The use of silicone oil as the heat transfer medium has the further advantage that from the commercially available examples of this clas~ of compound, tho~e which have 6uch a high boiling point that no substantial 108s of BolVent due to evaporation occurs in the course of the polycon-densation process can be chosen, and furthermore that the low molecular weight volatile products of the poly-conden~ation reaction do not concentrate in the fiiliconeoil~ and the silicone oil can therefore be used again for the next polycondensation batch - as a rule without further working up - after the polyester which has undergone polycondensation has been ~eparated off.
The proae~s according to the invention is illustrated with the aid of the following embodiment examples.
Examples 1 to 6 60 g of polyethylene terephthalate particles in 300 ml of Wacker Silicone Oil AP 500 were employed in each of the following 6 batches. The polyester particle~ were cylin-ders having a diameter of 0.35 mm and a length of 3 mm, which were prepared by cutting corresponding polye~ter monofilaments. The intrinsic visco~ity of the polyester material employed was 0.6 dl/g, the carboxyl end group content was 23 mmol/kg nnd the OH/COOH ratio was 2.87.
The polycondensations were carried out in a 2 1 four-necked flask with a stirrer (250 revolutions/minute), a contact thermometer for control of the internal temperature and a gas inlet tube. Dry nitrogen was employed as the carrier gas. The polyester suspension was - 18 - 206998~
heated to the particular polycondensation temperature (PC temperature) in the course of 0.75 hour.
The polycondensation temperature, the polyconden~ation time and the inten ity of the stream of nitrogen were varied in the experiments. ~he corresponding data are shown in the following Table 1. The last column of this table contains the IV values of the high molecular weight polyester~ obtained in the experiments. Experiment~ 1 and 2 show the good reproducibility of the process according 10 to the invention.
TABL~ 1 Experi- PC PC N2 IV(GPC) IV(DCA) ISC
ment tempera- time stream ture C h l/h dl/g dl/g g 1 240 7.25 120 1.51 1.51 0 2 240 7.25 120 1.57 - 0 3 245 7.25 250 1.66 1.69 0 4 245 7.25 120 1.66 1.59 0 245 15.25 120 1.90 1.84 0 6 245 23.25 120 2.05 2.02 0 ~ ISC = insoluble constituents The narrow molecular weight distribution which can be achieved by the process according to the invention is shown by the quotient M~/N~, which has a value of 3.42 for each of the products from Examples 1 and 2.
ComDarison Exam~le For comparison, 60 g of polyethylene terephthalate particles were sub~ected to polyconden~ation in 300 ml of hydrogenated terphenyl as the heat transfer medium. As in Examples 1-6, the polye~ter particles were cylinders having a diameter of 0.35 mm and a length of 3 mm, and con~isted of the same material which was employed in Examples 1-6.
The polycondensations were carried out in a 2 1 _ 19 --four-neckedflask with a stirrer (250 revolutions/minute), a contact thermometer for controls of the internal tempersture and gas inlet tube. Dry nitrogen in an amount of 120 l/h was employed as the carrier gas. The polyester suspension was heated to the polycondensation temperature of 240C in the course of 0.75 hour and the polycondensation time was 7.25 hours.
The product thus obtained had an IVG~ Of 1.35 and an M~/N~
value of 4.70.
Claims (9)
1. A process for the preparation of a high molecular weight polyester by post-condensation of a suspen-sion of a solid, finely divided polyester of lower molecular weight at elevated temperature in a liquid heat transfer medium, which comprises employing a heat transfer medium which does not penetrate into the polyester.
2. The process as claimed in claim 1, wherein a stream of inert gas is passed into the polyester suspension or passed over it.
3. The process as claimed in at least one of claims 1 and 2, wherein a silicone oil which is built up from units of the formula I
(I) wherein R1 is alkyl having 1 to 10, preferably 1 to
(I) wherein R1 is alkyl having 1 to 10, preferably 1 to
4 carbon atoms, cycloalkyl having 4 to 8, preferably 5 or 6 carbon atoms, aryl having
5 to 14, preferably 5 to 10 carbon atoms or aralkyl having 6 to 16, preferably 7 to 12 carbon atoms and R2 is R1 or another radical from the group of radicals mentioned for R1, is employed as the heat transfer medium.
4. The process as claimed in at least one of claims 1 to 3, wherein the silicone oil is built up from units of the formulae II and IIa (II) (IIa) wherein R3 is phenyl and R4 is methyl, or R3 and R4 are both methyl or both phenyl.
5. The process as claimed in at least one of claims 1 to 4, wherein a polyester is employed which is built up from 0 to 100 mol% of structural groups of the formula III
(III) and 100 to 0 mol% of structural groups of the formula IV
(IV) in which X is, to the extent of more than 75 mol%, aromatic radicals having 5 to 16, preferably 6 to 12 carbon atoms and, to the extent of not more than 25 mol%, aliphatic radicals having 4 to 10 carbon atoms, preferably 6 to 8 carbon atoms, and Y is, to the extent of at least 85 mol%, alkylene or polymethylene groups having 2 to 4 carbon atoms and, to the extent of not more than 15 mol%, longer-chain polymethylene or alkylene groups, preferably having up to 8 carbon atoms, and divalent radicals which are derived from diglycol, triglycol or polyglycol.
4. The process as claimed in at least one of claims 1 to 3, wherein the silicone oil is built up from units of the formulae II and IIa (II) (IIa) wherein R3 is phenyl and R4 is methyl, or R3 and R4 are both methyl or both phenyl.
5. The process as claimed in at least one of claims 1 to 4, wherein a polyester is employed which is built up from 0 to 100 mol% of structural groups of the formula III
(III) and 100 to 0 mol% of structural groups of the formula IV
(IV) in which X is, to the extent of more than 75 mol%, aromatic radicals having 5 to 16, preferably 6 to 12 carbon atoms and, to the extent of not more than 25 mol%, aliphatic radicals having 4 to 10 carbon atoms, preferably 6 to 8 carbon atoms, and Y is, to the extent of at least 85 mol%, alkylene or polymethylene groups having 2 to 4 carbon atoms and, to the extent of not more than 15 mol%, longer-chain polymethylene or alkylene groups, preferably having up to 8 carbon atoms, and divalent radicals which are derived from diglycol, triglycol or polyglycol.
6. The process as claimed in at least one of claims 1 to 5, wherein a polyester of the formula VI
(VI) in which 1 is a number from 2 to 6 and k is a number above 10, is employed.
(VI) in which 1 is a number from 2 to 6 and k is a number above 10, is employed.
7. The process as claimed in at least one of claims 1 to 6, wherein the polyester is polyethylene tereph-thalate.
8. The process as claimed in at least one of claims 1 to 7, wherein the post-condensation is carried out at a temperature which is in each case 5 to 50°C
below the particular melting point of the polyester.
below the particular melting point of the polyester.
9. The process as claimed in at least one of claims 1 to 8, wherein the post-condensation is carried out with stirring.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE4117825 | 1991-05-31 | ||
DEP4117825.4 | 1991-05-31 |
Publications (1)
Publication Number | Publication Date |
---|---|
CA2069980A1 true CA2069980A1 (en) | 1992-12-01 |
Family
ID=6432857
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
CA002069980A Abandoned CA2069980A1 (en) | 1991-05-31 | 1992-05-29 | Process for the preparation of high molecular weight linear polyester |
Country Status (5)
Country | Link |
---|---|
EP (1) | EP0516016B1 (en) |
JP (1) | JPH0656980A (en) |
CA (1) | CA2069980A1 (en) |
DE (1) | DE59208259D1 (en) |
MX (1) | MX9202558A (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5736621A (en) * | 1995-06-27 | 1998-04-07 | Hoechst Aktiengesellschaft | Process for the preparation of polyesters and copolyesters, the products prepared by this process and their use |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE69509927T2 (en) * | 1994-01-21 | 2000-01-27 | Shimadzu Corp., Kyoto | Method of producing polylactic acid |
Family Cites Families (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS60141720A (en) * | 1983-12-29 | 1985-07-26 | Mitsubishi Rayon Co Ltd | Manufacture of polyester |
JPS621724A (en) * | 1985-06-27 | 1987-01-07 | Toyobo Co Ltd | Production of polyester having ultrahigh molecular weight |
JPS6239621A (en) * | 1985-08-14 | 1987-02-20 | Mitsubishi Rayon Co Ltd | Polymerization of polyester |
JPH0739478B2 (en) * | 1985-10-31 | 1995-05-01 | 住友化学工業株式会社 | Method for producing aromatic polyester |
JPS6395224A (en) * | 1986-10-08 | 1988-04-26 | Sumitomo Chem Co Ltd | Production of crystalline aromatic polyester |
-
1992
- 1992-05-25 EP EP92108786A patent/EP0516016B1/en not_active Expired - Lifetime
- 1992-05-25 DE DE59208259T patent/DE59208259D1/en not_active Expired - Fee Related
- 1992-05-29 MX MX9202558A patent/MX9202558A/en not_active IP Right Cessation
- 1992-05-29 CA CA002069980A patent/CA2069980A1/en not_active Abandoned
- 1992-06-01 JP JP4140291A patent/JPH0656980A/en active Pending
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5736621A (en) * | 1995-06-27 | 1998-04-07 | Hoechst Aktiengesellschaft | Process for the preparation of polyesters and copolyesters, the products prepared by this process and their use |
Also Published As
Publication number | Publication date |
---|---|
EP0516016A2 (en) | 1992-12-02 |
DE59208259D1 (en) | 1997-04-30 |
EP0516016B1 (en) | 1997-03-26 |
EP0516016A3 (en) | 1993-03-03 |
JPH0656980A (en) | 1994-03-01 |
MX9202558A (en) | 1992-11-01 |
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