DE1520989A1 - Process for the production of polyethylene terephthalate - Google Patents

Description

DR. E. WEGAND DIPL-ING.W. NOBODY * C) 4 U98 $ DR. M. KOHLER DIPL-ING. C. GERNHARDT MÖNCHEN HAMBURG

phone = 55547 «8000 MONKS 15.4. July 1969

TELEGRAMS. KARPATENT NUSSBAUMSTRASSE 10

W.10 941/62 13 / Nie P 15 20 989.9

Toyo Rayon Kabushiki Kaisha Tokyo (Japan)

Process for the production of polyethylene terephthalate

The invention relates to a method for the advantageous and efficient production of polyethylene terephthalate of high degree of polymerization with good color tone and of of uniform quality on an industrial scale through direct esterification of terephthalic acid and ethylene glycol. in particular sioh the invention relates to a process for the production of polyethylene terephthalate with a high degree of polymerization, which is characterized in that the direct esterification of terephthalic acid and ethylene glycol with subsequent polymerization executes, with a Tere-

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phthalic acid with a light transmission of 90-98 %, measured according to the determination method explained below, is used.

The presently widely used process for the industrial production of polyethylene terephthalate includes the transesterification of the dimethyl ester of terephthalic acid with ethylene glycol with subsequent heating of the obtained bis-2-hydroxyäthylterephthalats under reduced Pressure. There is also a method known in which ethylene glycol with either terephthalic acid or the low aliphatic esters of terephthalic acid is reacted and then the reaction product is heated to produce the polyethylene terephthalate with a high degree of polymerization.

In the latter case, ie at. the process of direct "esterification, however, while the purification of ethylene glycol, one of the main starting materials, can be carried out relatively easily, for example by distillation, the purification of terephthalic acid, the other main starting material, is due to the properties of terephthalic acid, such as insolubility and tendency to sublime, difficult to achieve. Thus, no method is available to polyethylene terephthalate, u & a ge to Faeerbildung is is "au produce. B is therefore praJcfciaoh impossible

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the process of direct esterification to obtain polyethylene terephthalate, which can be used in particular for fibers and films, a practical use in technical Scale.

So far, numerous processes for purifying terephthalic acid itself have been proposed and described, but they have not shown the desired success. This is because too much importance is attached to the purity determined for terephthalic acid according to the usual evaluation methods, which in all cases depend on the turbidity value (Hazen No.), the optical density or the acid number of an alkaline solution of terephthalic acid became. Namely, although terephthalic acid may contain impurities such as isophthalic acid, benzoic acid, p-toluic acid, etc. as long as there was no coloring impurities, it was considered to be high-purity terephthalic acid according to the above method. However, if such terephthalic acid is used and production is carried out on an industrial scale, polyethylene terephthalate of good and uniform quality cannot be obtained, with lowering of the polymer

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sation speed, a reduction in quality of the polymer, etc. occurs. Therefore, contrary to expectations, good quality polyethylene terephthalate often cannot be obtained merely by using terephthalic acid having a high degree of whiteness or a high acid number. This leads to an undesirable situation that terephthalic acid, which is obtained by carrying out the same synthesis and purification and is of identical appearance, is sometimes obtained excellent polyethylene terephthalate, while on other occasions polyethylene terephthalate is obtained of very poor quality. Since this is often the case for terephthalic acid, which has been produced in particular by the Henkel process, this has long been a general problem. Even when the various cleaning procedures for terephthalic acid, for example the oxidizing treatment of an aqueous solution of potassium terephthalate or the decolorization treatment with charcoal , have been carried out completely and a high degree of whiteness and a high acid number have been obtained, however, the polymerization reaction could often not be carried out in a satisfactory manner *

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When checking diooor above mentioned case it was found that if Honooorbonoüuron, as BonzooGUure, ala residue in the polymerized terephthalic acid, no polyethylene terephthalate of high polyraerionagradoe can be obtained and that with a three-dimensional sfture, such as trimollithollure, the criotallinity deo Polyraerisata boeintrfiohtigt was.

As a result of the tests it was found that it was impossible, according to (lon biohor carried out Tirbeitowoioen to the purity of the torophthalic acid, to underooheiden terephthalic acids ₉ (The only production of PolyUthyleneterephthalat in high and of good quality polynorion Voioo in toohnl-Bohem Maßotab geo ^ gnet or unsuitable bind, and that ee not nüglioh wnr _r in conatanter V / eioo Polyäthylontorephthalat high polymorisationograddo gloiohförnißor quality / it to get

Ho was ebonfallo found that the nittoXe in naohfolgenden booohriobonon "LiohtdurohlHooiekoitomöthodo" a Tarophthalßtturo, di · to vortoilhnfton and wirkoataon HoroteXXung In teohnieohom HaSntab of Polyiithylentore h hm PeXyatriofttionsgrßdto ®iUv yftrbtönon "and

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0Q98 20 / .17S2

Bass.

Glololifilrnger quality is sooeißnot, selected before could that for the necessary Srziolung boi auoroiohen-. dor Polynorioationageachwindigkoit of polyethylene terephthalate high degree of polyacrylation, good color tint and ßloiohförraigor quality through direct esterification of torophthalic acid and xthylons glycol, the light-durohläeoisskGit, like sio duroh the "Liohtdurohliiooißkoitaaothode" gemoGOon, 90 bio 90 5 »must be; and that hiordtiToh a method for teohniochen horotolling of Polyethylene terephthalate high polynorioatlonossradoo, good Color tint and absolute quality thanks to direct .Pre-announcement of TorophthalsKure and Ethylonglykol go-

οο might have hoped οο.

One purpose of the invention is therefore the acquisition of a person Verfahrono zur teohnieohon Hearing of Polyathylonterophthalat.duroh direct esterification of TerophthaloHuro and ethylene glycol, at wolohom oto.is polyethylene torophthalate hohon polymerizationosradss of auoßozoiohneter Color shade and gloiohföroigör quality orhalton v; ira, wolohoo for Faotrn and Pilmo vtrwondot may have been.

Another Zwook dor Brfindmg iot dio Sohendung • #inoo VorJTfthranu ssur Hooounß dor Boinheit von Torophthal- • Hur Otäio »ur Her ο division of Pöl ^ Mvlontorophthalat high I> ulym °« ^: \ a &% imz $ iraa <iQ with auagi ^ iolmotov »work

009820/1782

tion and of uniform quality in advantageous and is effectively useful on an industrial scale.

According to the invention, a process for the preparation of polyethylene terephthalate by direct esterification of terephthalic acid and ethylene glycol and subsequent polymerization of the esterified product to high molecular weight polyethylene terephthalate is provided, which is characterized in that a terephthalic acid which has a light transmission of 90 to 98 % is used , the light transmittance with reference to an aqueous 2N-K0H solution as a standard solution of a solution prepared by dissolving 7 * 5 g of terephthalic acid in 50 ml of aqueous 2N-K0H solution at a wavelength of 340 m / rev and a cell length of 10 mm is measured.

The pre-eastering reaction of ierephthalic acid and ethylene glycol is carried out by initially mixing terephthalic acid and ethylene glycol in a molar reserve of 1x1 to 1.5 and subsequent heating to a temperature above 200 °. C at atmospheric pressure or suppressed, preferably at an overpressure of less than 10 fc / om ² in the presence of decomposition catalysts, lyoators.

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Polymer is made using polymerization catalysts carried out under reduced pressure) to obtain polyethylene terephthalate. In servants Case been βία catalyst, cobalt chloride, titanium oxide, Antiinonoxide, phosphoric acid, sodium carbonate or the like used.

Other than terephthalic acid / könnon and thylenglykol zuoätsslioh one or more compounds from the group of Zuoatzotoffon "as tPitanoxyd, carbon black and phoophorollure, the catalysts _f as Calciunaoetat, Manßanacetat, Kobaltohlorid and antimony oxide and the Hioohpolyiaerieatkonponenten" as Adipinsliure, KatrluneulfoißophthaleHureι p, p ^f -loopropylidendiphonol ( Biaphonol A) and diethylene glycol have been added

The "LiohtdurohläBoißkeitoEiothode'V duroh which the coinhoit of the terephthalo whore according to the invention is boetiffliat _t is carried out in the following Weioe ... <

7 * 5 g of terephthalic acid are obtained by adding 50 ml dissolved in an aqueous 2N potassium hydroxide solution. Under use Using the same aqueous solution of potassium hydroxide as the standard solution is used to measure the light resistance using a. Spectrophotomic

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tero toi oinor wavelength of 340 mu-wiü a cuvette length of 10 ram aungofUhrt · In the present description and in the claims, alo light permeability is denoted by the word dor light permeability, which was carried out by the execution of deo vorotohond boene or halting. Un Poly "iithylenterephthfllet good Parbtönunc au.erholten, QB lot nütig, © ine Terophthnloilure to use their Liohtdurchlüßßißkeit 90 - £ 90 cheating. The use of terephthalic acid with low translucency is generally acceptable. There is no mention of the pail, in which the light permeability at 340 cu ^ by the addition of a fluorescent substance is changed in the future can obtained ihror low Liohtdurohiaaeißkoit Polymeriflatο whose fiußerea AuoßGhon is oohoinbar good · Jodo'oh otellt for Torephthalsäure, dio geraUß the gowcJhnliohon Roinisungsarbeitsweißen was prepared, the ^v of LiohtdurohlHesigkait place a euogezeichnoten standard for assessment of their quality is · / us Torephthaloäuro "whose Liohtdiirohläasiglcoit low lot »cannot do good

78 2

lymerioate can be obtained. It also has a polymer ioat, which is a fluorescent substance like toning mentioned contains, although eo a particularly good one Color tint has "only an apparent good appearance" Diecea polymer actually has koine "guto" ! Color tint and when measuring its color using a photoelectric photometer «shows that the luminosity is low and eo shows that the polymer is not pure white

In the fluorescent substances v introduced during the manufacture / ground differ "SiOH the properties of the type in AbhnJigigJcoit dernier- ·. · Position; there verochiedene species _t v / ie those which decompose during the polymerization, since Their curvature is low, which even confer the polyinerionic pluorescence uow.Thus, one must not be fooled by the apparently fluoreozeno of terephthalic acid in order to obtain polyraerioates which have uniformity takes place, from terephthalic acids, which have high permeability to Idohtdura, polymers of good color can be obtained · In particular, from Tea? @ p1atkal0äurön with Liohtdurohias »igis © ät @ n from 93 _N to 97 ^

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made without exception good polyethylene torephthalate will.

To the Roinigungsverfahren but obtaining terephthalic acid with high light transmission those listed in the examples below are. However, in all cases, treatment with a poraanganate is particularly effective.

Although numerous processes for the production of terephthalic acid are known and the impurities contained are different depending on the production process, the present invention can be effectively applied to any of these processes. Although the examples relate to the Henkel process and the California Research Corporation - Process (CRC) bociohon, lot the ancestor according to the invention, also applicable to the terephthalic acid, which according to the Soientifio Design process in which p-Xjtol was air-oxidized with a liquid acid solvent, the Großkinsky process, which the chloromethylation comprises toluene old subsequent oxidation, or the Diatillers method, wherein terephthalic acid boi by way of fferephthaleUurenitril is obtained was prepared _f "The reasons why a tfellenlHnge 340

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If 1 I

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The following was selected: As the result of a comparison of curves of the light transmittance values verochiedonor terephthalic acids extending from the ultraviolet region to the outer region, it was found that the region was suitable for determining the lower region of the moiotite and that this difference had a good relationship with the If the light duration in the Eoroioh of 340 mu in Bozug, underlined the various types of impurities whose admixture could be assumed, there was none among them whose tips would drop off here / dignity would be particularly detrimental to the Boatiia expression ·.

According to the invention, polyethylene terephthalate, because it is suitable for the preparation of facers, with excellent Shade and a normal softening point can be obtained at low cost. So can it Vorfohron according to the invention in effective Veiao for Manufacture of polyethylene terephthalate are used, dao used as auogong material for pasers and films can be

The invention is explained in more detail below with the aid of examples ^:

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Example 1 .

Ealiuinterophthalet, the au »JCaliumphthalat according to The Henkel process was dissolved in Yasser and then filtered. Then it was treated with potassium pomangannt (0.4 wt. #, based on the terephthalic acid) treated, anoohlieOend further a Üohandlung with activated charcoal (2 55) and followed by the addition of Hydrochloric acid filled in · The terephthalic acid obtained was centrifuged and washed grtindlioh with hot water. The light duration of the terephthalic acid obtained in this way was $ 94ι2 ♦ /

100 parts of the terephthalic acid obtained v / io above were in the presence of 0.6 parts of titanium oxide and another catalyst with 50 Tollen Xthylonglykol esterified und.dajs product thus obtained was under vorringertora Pressure heated, whereby polyethylene terephthalate was obtained *

The end product obtained was pure white and the Paoer spun from it had an excellent color shade

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Boleniel 2

wet $ 9jä & Q den die Sohwofölamnoniiikcxyda + -

ÖKO vor fehr ea received f

sJiuroderivat was veraeift and nit Kaliuraperrconganat gut sequentially (3 #) and activated carbon (4? £) and on duroh addition of hydrochloric acid aungofällt · The raw Torophthals & ure was auo Vaseer at 220 ° C in Geßcnv / art $ 10 Hatriumhydroxyd umkriotallioier't. The tenacity of the terophthalic acid was 93%. When polymerized according to Example 1, pure white polymers were obtained.

control '■

13c ^ '/ urdβn the same work as in, example 1 except that the treatment with Kaliutnporcianganat weggelaoaen vmrdo »

The Liohtdurohllisaigkoit dor preserved Torephthalnäuro botrug 81,3, ^ and dio d «out through polymorionation The polymers obtained were slightly brown in color.

In ßraphinchor application of the IdchtdurohlRooigkoiton of the examples 1 and Z and the control. ^ erephthalic acids, bark Yer_Q.ohiedaßon WjjllenlHngön the curves shown in the figure resulted.

009 82 QiUf Sr

Claims (2)

Claims 1. A process for the production of polyethylene terephthalate by direct esterification of terephthalic acid and ethylene glycol and subsequent polymerization of the esterified product to high molecular weight polyethylene terephthalate, characterized in that a terephthalic acid which has a light transmission of 90 to 98 % , is used, the light transmission with reference on an aqueous 2N-KOH solution as a standard solution of a solution prepared by dissolving 7.5 g of terephthalic acid in 50 ml of aqueous 2N-KOH solution at the wavelength of JkQ m / U and a cell length of 10 mm. 2. The method according to claim 1, characterized in that the direct esterification at elevated pressure in the presence an esterification catalyst and then the polymerization at reduced pressure in the presence of a polymer tion catalyst executes under heating. New bases (Art741 from & 2 .009820 / 1782 4 k Blank page