DE1905188C3 - Process for the production of polyalkylene terephthalates and modified polyesters - Google Patents

Description

A general method for making polyalkylene terephthalates is that one Terephthalic acid or its lower aliphatic ester with an alkylene glycol of the general formula

HO- (CHA-OH

40

in which η means 2 or an integer greater than 2, converts to bis (hydroxyalkyl) terephthalate and then produces polyalkylene terephthalate therefrom. The reaction is thus carried out in two stages, the bis (hydroxyalkyl) terephthalate in the first and the polyalkylene terephthalate being produced in the second by polycondensation of the bis (hydroxyalkyl) terephthalate. Different catalysts are used in both stages.

There are already many publications with regard to the catalyst for the polycondensation. So for example, British Patent 740,381 describes antimony compounds used in the reaction system are soluble. Dutch patent specification 97 835 describes cobalt compounds. The japatusche Patent specification 288 887 and British patent specification 793 1Π name titanium compounds. The known However, catalysts are physical in terms of color tone and various Properties of the polyesters obtained are unsatisfactory.

The object of the invention is therefore to provide a method which uses a suitable catalyst provides colorless polyesters with excellent physical properties.

Up to now, organic titanium compounds have mainly been used as catalysts for polycondensation used. These compounds are usually soluble and possess in the reaction mixture high catalytic activity. However, the polymers obtained are colored yellow or brown, so that these compounds can only be used with difficulty in practice.

It has now surprisingly been found that metallic titanium is catalytically active, the Activity very high and the polymer obtained is not colored at all. With the verve Antimoutrioxyd shows that when using the known catalyst, the polymers obtained are discolored yellow-green, while titanium is a completely colorless and transparent polymer supplies. It has also been shown that with regard to the other physical properties, i.e. the number of carboxyl groups, the melting point, which with Polymers obtained from titanium are far superior.

The invention therefore relates to a process for the preparation of polyalkylene terephthalates and modified polyesters comprised of at least 75 mole percent of a polyalkylene terephthalate and up to 25 mol percent consist of units that are formed from at least one further ester-forming component, namely an aliphatic diol, a polyethylene glycol, an aromatic diol, an acyclic diol, an aliphatic dicarboxylic acid. an aromatic dicarboxylic acid or an alicyclic acid Derive dicarboxylic acid by polycondensation of bis (hydroxyalkyl) terephthalate. possibly in a mixture with less than 25 mol percent of the other component, in the presence of a metal catalyst, which is characterized by it. that titanium is used as the metal catalyst.

From the French patent 1 509 306 it is already known that in the production of Polyethylene terephthalate can use titanium dioxide gel hydrate as a catalyst for the polycondensation, however, the use of metallic titanium is not mentioned or suggested in this document.

According to the method of French patent 1 410481, polyethylene terephthalate is used made of antimony powder as a catalyst. Notes on the use of metallic However, titanium is not found in this publication either

In the Belgian patent specification 636 944 metallic titanium is used in connection with the production described by polyesters, but metallic titanium is just like certain metal oxides, z. B. zinc oxide. Titanium oxide is only used as an esterification catalyst when using terephthalic acid with ethylene glycol to bis (/ i-hydroxyethyl) terephthalate After this reaction, the metallic titanium is filtered off and the polycondensation takes place in Presence of another catalyst. Thus, only the conclusion can be drawn from this publication that metallic titanium is suitable as an esterification catalyst.

Investigations were carried out with metallic titanium, which in the form of finely divided particles, coarser particles and other small moldings such as blocks, flakes, chips, chips, Ribbons, nets composed of fine wires, small balls or fine granules were present. As a result, it has been found that all of these forms are useful as a catalyst.

Furthermore, various experiments were carried out in which the Reakt'onsgefäß or at least one

IO

for the accessories that came into contact with the reaction mixture, made of metallic titanium or a Legiejjiag consisting mainly of this metal was made. The polycondensation takes place through the catalytic action of the reaction capsules or the accessories which have been found to be permanent and uniform polycondensation took place.

First, the use of fine titanium powder, which is one of the most favorable embodiments of the invention, will be explained in more detail.

When using metallic titanium as a catalyst, it is useful to increase the titanium to increase the Contact area for more uniform dispersion in the reaction system in the form of finely divided powder is to use. The results of various tests show that the ability of the catalyst to accelerate polycondensation varies with the particle size of the powder. The one in polycondensation The catalyst used generally remains in the polymer and is used in the subsequent Process steps not removed so that it remains in the threads after spinning. Consequently there are certain limitations on the shape, the particle size and the amount of catalyst that can be used Powder.

It has been found that with an average particle size of the metallic titanium of less than 100u the desired results can be obtained and that the use of powders with a maximum of 30 μ is preferable. Furthermore, when the average particle size is at most 3 μ can be set, which can be achieved by suitable selection of the manufacturing conditions of the powder, these particle sizes can be done by sieving and, if necessary, by further auxiliary measures with regard to the catalytic ability and the quality of the polymer and filament obtained especially preferable.

In addition, the finely divided powder has a very high dispersion stability in glycol.

As already stated, cause! the metallic titanium used according to the invention in the polymer no undesirable yellow or brown discoloration, so that the amount added does not must be limited as critically as when using antimony compounds and the other known ones Catalysts. However, if the amount exceeds a certain amount of titanium, a greenish black occurs Color, as it has the catalyst itself on. It is therefore appropriate to add an addition of more than 1 percent by weight and especially when a white appearance is required limit the amount to 0.1 percent by weight.

The aim is now to use a relatively coarser titanium according to a further embodiment of the invention Procedure are explained

The reaction leading to the formation of the polyester is an equilibrium reaction, so that in addition to the formation reaction always has the reverse reaction, d. H. the depolymerization can take place. Since the catalyst which accelerates the formation reaction, also catalyzes the reverse reaction at the same time, it is advisable to to remove the catalyst quickly from the polymer after the polycondensation has ended, in order to avoid decomposition reactions of the polymer to avoid.

As conventional catalysts for manufacture

55

Sixty of polyesters have used soluble substances in the reaction system. In some cases, insoluble fine particles can also be used. However, in each of these cases, the separation of the catalysts from the polymer is difficult, so that the catalysts remain in the polymer. Thus, when the polymer is melted again during the subsequent spinning, the viscosity of the polymer is lowered due to the decomposition which takes place. In addition, undesirable discoloration occurs. These disadvantages pose great problems in the production of polyesters. Furthermore, when fine metal particles are used as catalysts, these are often incorporated into the spun thread, so that button formation and breakage of the yarn can disadvantageously occur. When using relatively coarse metallic titanium, for example blocks, flakes. Chips, shavings, ribbons, nets composed of fine wires, small spheres, fine or coarser granules, the catalyst can, however, be separated quickly from the polymer by simple filtration. In this way, polymers can be produced which contain little or no catalyst at all. If the titanium catalyst is in the form of coarse granules with a longitudinal diameter of more than 100 μ, then most of the granules are filtered out by a filter used in the spinning, so that the disadvantages described above can be reduced considerably. In view of the filtration efficiency, larger particle sizes are more desirable, but in this case the useful surface area for the catalytic efficiency is reduced and the catalytic ability is reduced as compared with the same amount of finer particles. In this connection, various studies have been made, and it has been found that since the catalyst effect can be increased by stronger agitation and by a larger proportion, it is quite useful in view of the filtration efficiency. To use powders with a particle size greater than 200μ if the quality of the polymer and the yarn are considered more important. With particle sizes above 500 μ, the filtration efficiency is sufficiently high

The catalytic activity of metallic titanium is actually so high that even coarse powders or Blocks are catalytically effective.

Metallic titanium is usually very stable and is not harmful to the human body.

It is of course advisable to use metallic titanium with high purity, but it does The presence of small amounts of impurities and additives does not have any significant disadvantages When starting materials for synthetic fibers, however, it is preferable if, because of the discoloration of the There are strict restrictions on polymers, metallic titanium with a purity of more than 90% to use. If metallic titanium with lower purity is used, unexpected Appearances are expected. Recently, a method for cleaning titanium has been so developed It has been found that high-purity titanium with a purity of more than 99% can easily be supplied can. The use of such a metallic titanium is particularly recommended.

The metallic titanium catalyst can be separated from the polymer after use

Lind remains in the reaction vessel. There was no significant decrease in the catalytic Activity observed so that the catalyst can be used several times.

When using metallic titanium in piece form or the catalyst can be removed as granules after the polycondensation during extrusion. As a result, the polymer obtained is never discolored. The other various properties are also those using the conventional catalysts, e.g. B. Antimony trioxide produced Superior to polymers.

When using the titanium catalyst in relatively coarse form, such as coarse granules, flakes, chips, Chips, ribbons or fine wires are deposited so quickly on the bottom of the catalyst Reaction vessel that the dispersion of the catalyst is likely to be insufficient. Therefore good mechanical agitation must be ensured.

It has also been found that a steady and uniform reaction takes place even if one «In the part of the reaction vessel that comes into contact with the reaction mixture, or at least part of the accessories, for example the stirrer, made of metallic titanium or one mainly Titanium manufactures existing alloy. However, the reaction can already take place sufficiently if the part of the system that is in contact with the reaction mixture is wholly or partially is coated with titanium or an alloy containing titanium. This can be done, for example, by dressing up. Plating or gluing can be achieved. This also applies to projections, grooves, folds or protrusions to that on the inner wall of the vessel and the inner parts, such as pipes, grids, perforated plates. Nets, partitions or multi-level panels are provided. The term "accessories" fall under the heading z. B. stirrers, small plates, chains, rings, fine wires and nets provided on the stirrer to rotate therewith. The same applies Screws or washers used in devices for continuous polycondensation. This embodiment is particularly suitable for a continuous polycondensation process.

Lately there has been an increasing interest in a continuous polycondensation process, and a large number of studies have already been carried out on this. One of the most important Problems are posed by the difficulty of uniform addition and distribution of the catalyst represents. In the embodiment of the invention described above, the reaction vessel is now effective itself as a catalyst, so that the separate addition of a catalyst is unnecessary. The liquid one The reaction mixture is used during the entire reaction in which the polycondensation is completed is, circulated uniformly, standing with the inner surface of the reaction vessel, which acts as a catalyst acts, in touch. Thus, the disadvantages described above do not occur, so that a polymer with high uniformity can be obtained. The catalytic effect of the titanium alloy varies accordingly the conditions during the polycondensation, for example according to the contact area and the stirring speed. The higher the titanium content, the greater it is catalytic effect, so that in general alloys containing more than 75 percent by weight of titanium preferred

According to the method of the invention are polyalkylene terephthalate ^ such as polyethylene terephthalate, polypropylene terephthalate, polytetrameth> len terephthalate, polyhexamethylene terephthalate can be produced. The modified polyesters are obtained by using less than 25 mol percent of the other

ίο component.

The modified polyesters which can be prepared according to the invention consist of up to 25 mol percent of units which is different from an aliphatic diol (excluding the alkylene glycol a main component of polyalkylene terephthalate), such as ethylene glycol, propylene glycol, tetramethylene glycol, pentamethylene glycol, Hexamethylene glycol, polyethylene glycol, such as diethylene glycol, triethylene glycol; aromatic Diol such as catechol, resorcinol, hydroquinone; alicyclic diol, such as cyclohexanedimethanoJ. Cyclohecandiol an aliphatic dicarboxylic acid. such as adipic acid, sebacic acid, decanedicarboxylic acid; aromatic Dicarboxylic acids such as phthalic acid. Isophthalic acid, sodium sulfoisophthalic acid. Sodium sulfoterephthalic acid, Naphthalenedicarboxylic acid: alicyclic dicarboxylic acids, such as hexahydroisophthalic acid, Derive hexahydroterephthalic acid.

The presence of titanium oxide as a matting agent, pigment, dye, fluorescent luster and of other additives generally used in polyester has to the process of Invention no influence.

The invention is illustrated in the examples. In these examples mean "parts" if nothing else indicated, parts by weight.

Example I.

Into a reaction vessel equipped with a stirrer, an inlet for nitrogen gas and an outlet for nitrogen gas and by-products were provided, 100 parts of dimethyl terephthalate, 70 parts of ethylene glycol, Entered 0.015 part of zinc formate and 0.017 part of triethyl phosphate. The resulting mixture became Heated rapidly to 170 ° C. while passing in gaseous nitrogen. 30 minutes after the temperature When 170 ° C. had been reached, the stirrer was switched on at a stirring speed of 60 rpm. On that the temperature of the jacket of the reaction vessel was increased by 10 C every hour. The ester interchange reaction was stopped after 7 hours at 240 ° C. The course of the reaction was determined by determination of the distilled methanol determined. At the end of the reaction, the ester interchange was reached 98%.

To prepare the catalyst for the polycondensation, metallic titanium with a purity of 99.9% for 72 hours with 4 times the amount of ethylene glycol in a porcelain ball mill.

It was then diluted with ethylene glycol to such an extent that a 5% dispersion was obtained. These was left to stand in a cylindrical jar for 24 hours. The one at the bottom of the cylindrical The coarse particles deposited in the vessel were carefully removed from the dispersion containing fine particles separated and determined the concentration of titanium in the dispersion. Then the dispersion was using Ethylene glycol diluted to 1 percent by weight titanium.

The size distribution in the dispersion was determined after starting phases. The average particle size was 2.4 μ.

A certain amount of the titanium dispersion thus prepared became that described above Ester interchange reaction product given. The temperature of the jacket of the reaction vessel was then increased to 280 ° C. over the course of one hour. The mixture was stirred and nitrogen gas was introduced. Then the gases were in the reaction vessel Aspirated by means of a vacuum pump in order to reduce the pressure in the reaction vessel to 0.3 mm Hg. In this state, the polycondensation reaction was continued. As the reaction progresses the viscosity of the reaction product increased and the electrical required to operate the stirrer increased Energy on. The electrical energy was of both the size and shape of the vessel and the Depending on the stirrer, as well as the viscosity. The relationship between the operation of the stirrer required electrical energy and the viscosity of the content was determined beforehand. If the electric power reached a predetermined value, then the stirring was stopped and the operation of the vacuum pump ceased. Nitrogen gas was introduced to terminate the reaction. (The time required to reach the 0.3 mm Hg vacuum before the reaction stops will be referred to as "polycondensation time in vacuo.") The reaction product was from the bottom of the vessel removed and cut into small pieces.

A series of experiments was carried out by changing the amount of titanium dispersion added. The polycondensation time was measured. Furthermore, the properties were obtained Polymers determined and with those obtained when using antimony trioxide as a catalyst Products compared. These results are shown in Table I.

The viscosity of the polymer is (40/60 by weight) at 25 ⁰ C specified as the intrinsic viscosity in a solvent mixture of Äthantetrachlorid and phenol. This results from the following formula:

'/ r-1

C-Q

in which>, _{r means} the relative viscosity at a polymer concentration of C (g) / 100 cm ³ .

The number of carboxyl groups is given as carboxyl group equivalents / 10 ⁶ g of the polymer. This quantity was determined by titrating the polymer in benzyl alcohol with potassium hydroxide.

The melting point was determined on a hot bench. It indicates the temperature at which the Half of the sample has melted.

Tabel

catalyst catalyst
lot Polycondens
sation time in
vacuum Intrinsic
Viscosity Carboxyl
group number Melting point Color of the polymer (Weight Equival.'lO'g percent) (Hours.) CC) Metallic titanium 0.0025 4th 0.65 20.2 261.5 colorless 0.005 2V2 0.63 13.4 263.0 colorless 0.03 0.66 19.3 262.5 low Gray coloring 0.1 1 0.73 25.6 262.5 easy Gray coloring 1.0 1 0.82 20.0 261.0 Gray coloring Antimony trioxide 0.03 3 0.69 29.7 259.5 light yellow-gray coloring

It can be seen from Table 1 that the catalyst used according to the invention has a very good catalytic activity compared to the conventional catalysts. The polymers obtained therewith have excellent physical properties and do not show any disadvantageous yellowing.

The catalyst showed even when the titanium dispersion was added to the mixture of starting materials was added before the ester interchange reaction started, the same activity. Here, too, polymers were found with the same properties as in Table 1 obtain.

Example 2

Spongy metallic titanium (with a purity of 99.2%) was roughly crushed and then in a PorzeUankugdmühle with 4 times the weight of ethylene glycol. Grind for the times given in the table below. It was then diluted with ethylene glycol to form dispersions with a titanium content of 1 percent by weight. The average particle size in the dispersions was determined after starting phases. 0.5 parts of the individual dispersions (which corresponds to an amount of titanium of 0.005 percent by weight, based on the polymer) were weighed out and added to the ester interchange reaction product obtained according to Example 1. DA after the polycondensation was carried out according to Example. 1

It was found that the smaller the particle size, the shorter the time required for the polycondensation. so that side reactions and thermal mixed decomposition practically does not occur and polymers with better physical properties could be obtained.

At an average particle size of 121 microns , the catalyst precipitated in the reaction mixture , so that it was necessary to increase the speed of rotation of the stirrer to three times the normal value. The results of these experiments are summarized in Table II.

509 619 Ί 01

Table II

Grinding time (hours)

Average particle size (μ)

Polycondensation time in
Vacuum (hours)

Stirring speed (rpm) ..

Intrinsic viscosity

Number of carboxyl groups, equivalents / 10 ⁶ g

Melting point (° C)

Color of the polymer

12th

121.4

180 0.53

28.6 260.0 light yellow

24

60 0.61

20.4 261.5 very light yellow 48

38.7

60
0.60

25.1
260.5
very light yellow

22.5

47 *
60
0.70

18.7

262.5

colorless

72
(sifted)

2.4

60
0.63

13.4

263.0

colorless

Example 3

In the reaction vessel according to Example 1, 85 parts of dimethyl terephthalate, 15 parts of dimethyl isophthalate, 70TeUe of ethylene glycol, 0.015 parts of zinc acetate, 0.02 part triphenyl phosphite and 0.4 part titanium oxide introduced as a matting agent. Then an ester interchange reaction was carried out according to Example 1. The percentage ester exchange, calculated from the amount of distilled methanol was 85%.

The catalyst was prepared by leaving crushed titanium in a ball mill for 72 hours was ground with ethylene glycol. The milled titanium was then mixed with ethylene glycol to form a dispersion diluted with 5 weight percent titanium. After allowing the coarse particles to sit for 24 hours separated and removed from the dispersion of fine particles.

The titanium dispersion thus obtained became the above in the amounts shown in Table III Ester interchange reaction product added. The polycondensation was then carried out as in Example 1 performed. The required reaction time and the characteristic properties of the obtained Polymers were produced with the corresponding values when using antimony trioxide as a catalyst compared. As a result, it was found that even if the amount of the catalyst used was less than that conventional catalyst, the reaction in the use of the catalyst according to the invention was completed in less time. It was also found that the polymer produced according to the invention with regard to its physical properties and its color shade compared to conventionally produced polymers was superior. The results are shown in Table II1.

Table III

catalyst

Metallic titanium

Antimony trioxide

Catalyst quantity,
Weight percent /
Polymer

0.005
0.025
0.04
0.04

Polycondensation

tion time in

vacuum

(Hours.)

IV ₄ 3

Intrinsic viscosity

0.61

0.65 0.71 0.72 carboxyl

group number.

Equivalents

10 "ρ

15.6
18.2
27.2
24.8

Melting point
(C)

221.0
221.0
220.5
220.5

Hue of the poh meren

White
White

light gray
light yellow

Example 4

1 η a stainless steel autoclave, which is equipped with a Stirrer, an inlet for nitrogen gas and an outlet for nitrogen gas and by-products, the was in turn connected to a fractionating column, 100 parts of dimethyl tere were added phthalate. 70 parts of ethylene glycol. 0.015 parts zinc formate and 0.017 part of triethyl phosphate entered. The whole thing was done while bubbling nitrogen gas heated 30 minutes after the temperature reached 170 C, the stirrer was turned on at a stirring speed of 60rpm started up. Then the temperature of the autoclave jacket increased by 10 C every hour. The ester interchange reaction was stopped after 7 hours at 240.degree The ester interchange, calculated from the amount distilled off, was Methanol amount c. 97.5%.

Furthermore, the polycondensation catalyst was produced that sponge-shaped Titanme Tall blocks with a purity of 99.5% were roughly crushed and the crushed titanium was sieved was to obtain coarse particles having a particle size of 100 µ 3 mm.

The ester interchange reaction product became the amounts given in Table IV were added. The temperature of the autoclave jacket was then added increased to 280 ° C. within one hour. In doing so, nitrogen gas was introduced. In this case de Stirrer with a stirring speed of 1501 ^ put into operation to prevent the deposition of titar particles after the Temperau When the temperature reached 280 ° C, the autoclave pressure returned to mid-atmospheric pressure within one hour a vacuum pump lowered to 0.3 mm Hg. Nad

the viscosity had risen so much that the When the catalyst was prevented from separating, the stirring speed was reduced to 60 rpm and the polycondensation reaction stopped when the viscosity almost reached the desired value would have. The viscosity of the reaction product was determined from the electric consumed in the stirring motor Energy appreciated. The operation of the vacuum pump and the rotation of the stirrer were

broke. Nitrogen gas was introduced into the autoclave and the reaction product from the bottom of the Autoclave extruded in the form of a string under nitrogen gas pressure. The extruded string became shavings cut up. When extruding the polymer, the titanium particles were through a at the bottom of the Reaction vessel provided filter removed.

The results obtained are summarized in Table IV.

Table IV

Catalyst- Polycondensation Intrinsic
viscosity catalyst Weight tion line in
vacuum percent/ Polymer (Hours) 0.65 Metallic titanium 0.5 6th 0.61 1.0 0.60 3.0 ? U 0.60 5.0 ι ¹ / * 0.63 10.0 _^5/6 0.65 Antimony trioxide 0.03 4th

Carboxyl

group number,

Equivalents /

10 "g

29.3
22.5
16.1
13.4
12.0

27.3

Melting point
CO

260.5
260.0
260.5
262.5
262.0

260.0

Color of the polymer

light yellow

colorless

colorless

colorless

colorless

light yellow green

From Table IV it can be seen that the catalyst of the invention gives polymers with very good properties. In particular, the polymers obtained are excellent in terms of color, which can be attributed to the absence of the polycondensation catalyst is. In addition, the separated from the polymer and remaining in the reaction vessel can Catalyst can be used repeatedly.

Example 5

A titanium plate made of high-purity titanium with a purity of over 99.5% was made by means of an electrical Drill cut into strips of metallic titanium. The tapes were average Width of 4 mm and a thickness of 0.3 to 0.5 mm. They have been cut to make their longest section was not larger than 5 mm. To the ester interchange reaction product obtained in Example 4 the amounts of this catalyst indicated in Table V below were added and then the polycondensation reaction carried out. In this case, in the primary polycondensation stage the stirring speed 150rpm until the viscosity of the reaction product became that high that the deposition of the catalyst was avoided. After the viscosity reaches this value the agitation speed was decreased to 60 rpm. When extruding the polymer the catalyst was removed therefrom through a filter provided on the bottom of the reaction vessel.

The results obtained are summarized in Table V. set

Table V Catalyst amount, Weight ^ ρτοζεπί

Pol> meres

1.0

3.0

5.0

10.0

Polycondensation in vacuo

(Hours.)

4%

I ntrinsic viscosity

0.67

0.65
0.69
0.68 number of carboxyl groups.
Equivalents 10 "g

26.3
18.8
14.1

Melting point
<C)

259.5

261.0
260.5
260.0

Color of the polymer

very light

Yellowing

colorless

colorless

colorless

Example 6

The autoclave according to Example 1 was charged with 90 parts of dimethyl terephthalate, 0 parts of dimethyl isophthalate, 70 parts of ethylene glycol, 0.015 part of zinc acetate and 0.02 part of triphenyl phosphite. An ester exchange reaction was then carried out under the same conditions as in Example 4. In this case, the ester exchange, calculated from the amount of methanol distilled off, was 97%.

The band pieces of metallic titanium that ii Example? 5 had been used were added to the esters in the amounts given in Table VI exchange reaction product added. Under the conditions of glc 6s as in example 4, a PnI condensation reaction carried out. In table> are the analytical data for the obtained Pol Merschnitzel delivered

Table VI

catalyst catalyst
lot,
Weight
percent/
Polymer Polycondensation
tion time in
vacuum
(Hours.) lnlrinsic
Viscosity Carboxyl
group number,
Equivalents'
10 "g Melting point
(C) Color of the polymer Metallic titanium
Antimony trioxide 1.0
5.0
10.0
0.03 5V ₆
WU
4th 0.64
0.62
0.65
0.66 28.8
19.0
12.1
25.3 240.5
241.0
241.0
240.5 light yellow
colorless
colorless
light yellow green

Example 7

Sponge-shaped titanium blocks were crushed into a powder. This was sifted and put in 4 particle size classes divided: Less than 100 μ; 100 to 200 µ; 200 to 500 μ and larger than 500 μ. The ester interchange reaction product prepared according to Example 4 each powder of the classes described above was added. Then the Polycondensation reaction carried out. The polymer obtained was shaped into chips and dried and spun into threads with 60 den. These became four times the original length stretched and wound on a weft spool. The drawn thread was made in the manner described below Device examined for the number of yarn knots.

Two small lightweight rollers made of stainless steel were previously run through one pre-selected contact pressure brought into contact so that they formed a gap. The one of Rolling was rotated at a fixed position. The other could while moving along the vertical turned to the surface of the nip of the two rollers, can be shifted slightly. When passing through of a thread between the two rollers would be the position of the second roller if the thread was irregular Buttons had moved. This shift is due to the variation in the diameter of the thread when the buttons run through the nip. This variation was measured by a voltmeter recorded. This allowed the number of buttons to graze in the thread determined.

It was found that when using titanium particles with less than 100 μ the 2 ^ number of the irregular ones The buttons of the polyester thread were 135/1000 Ω. The corresponding number was at particle size from 100 to 200 µ 28; at 200 to 500 μ Π and for particle sizes above 500 μ 3.

Example 8

100 parts of dimethyl terephthalate, 64 parts of ethylene glycol, 0.015 part calcium acetate and 0.035 part triphenyl phosphite were placed in a reaction vessel given. The resulting mixture was heated to 170 ° C. The temperature increased from 170 increased to 230C. The reaction was at this Temperature continued for 2 hours with stirring to carry out the ester interchange reaction. The ester exchange was, calculated from the amount of methanol distilled off, 97.8%.

This ester interchange reaction product was transferred to a second reaction vessel passed through a Tube was connected to the first reaction vessel. The polycondensation was then carried out.

In the polycondensation reaction vessel was the

! S stainless steel inner surface of the autoclave connected by explosion welding to a plate made of pure metallic titanium. The stirrer was made of a round bar and a plate of pure metallic titanium.

In this case, the calculated ratio of the polymer to the titanium surface area was 1.14 g of polymer cm ^{2 of} titanium surface area.

The reaction temperature was 280 ° C. and the stirring speed was 60 rpm. The pressure was reduced to 0.3 mm Hg in 2 hours. Under these conditions, the reaction was continued for 4V for ₂ hours and then stopped. The extruded polymer had an intrinsic viscosity [i /] of 0.64, a carboxyl group number of 23.5 and a melting point of 262.5 ° C. The polymer obtained was completely colorless.

This is done by polycondensation in a stainless steel autoclave in the presence of 0.04% antimony trioxide Control polymer obtained was colored dark yellow green.

The hue of the polymer obtained in this example was very close to that of the control polymer strongly superior. In particular, this variation, in which both polymers are broken up into chips, should

thoroughly dried and then transferred to test tubes and under nitrogen gas for 2 hours Atmospheric pressure were heated to 280 ° C, must be observed. That when using antimony trioxide obtained polymers was after heating

has been discolored considerably to yellow. The intrinsic viscosity was decreased from 0.66 to 0.54. The number of carboxyl groups was increased from 19.8 to 32.4 been. In contrast, the polymer obtained according to the invention had the intrinsic viscosity

only slightly decreased from 0.64 to 0.61. The number of carboxyl groups varied from 23.5 to 25.8 Finally, the polymer obtained was practical

colorless. ... ,

Example 9

In a device for continuous polycon densation. which consisted of a horizontal cylindrical reaction vessel made of metallic titanium unc which was fitted with a set of screws for stirring and circulating the polymer, became the ester

Exchange reaction product of Example 8 given. The reaction vessel was heated to 290 ° C. This in Gas in the reaction vessel was withdrawn to create a vacuum and the screws ii Offset. The feed speed de

6s ester interchange reaction product and the decrease The speed of the polymer was adjusted so that the residence time was 8 hours. Received that Polymers were turned into one by a metering pump

The string is deformed, cooled and then turned into chips blended.

The polymer had an intrinsic viscosity of 0.60 and a carboxyl group number of 19.2. It was colorless. The polymer had a viscosity of 0.57 and a viscosity of 0.57 according to the heat test according to Example 8 Carboxyl group number of 23.4. It was colorless and had excellent heat resistance.

Example 10

100 parts of dimethyl terephthalate, 65 parts of ethylene glycol, 0.02 part of zinc acetate and 0.03 part of triphenyl phosphite were placed in a glass reactor equipped with a stirrer. The resulting mixture was heated under a nitrogen gas atmosphere to carry out the ester interchange reaction. The temperature was raised within 7 hours from 17O ⁰ C to 230 ° C to distill off the methanol, and stopped Esteraustauschreaktion. The ester exchange reaction was calculated from the amount of methanol distilled off to be 98.0%. Then, a certain amount of the obtained ester exchange reaction product was placed in a cylindrical glass reaction vessel equipped with a stirrer. The blade of the stirrer was made from a titanium alloy plate. The ratio of titanium to nickel in the alloy was 80:20. A large number of pores with a diameter of 4 mm were drilled into the plate. The whole was melted under nitrogen gas at 230 ⁰ C, and the temperature was raised with stirring to 280 ° C. The pressure was then reduced to 0.35 mm Hg over one hour. In this state, the reaction was continued in vacuo. After 3 _^3/4 hours, the polycondensation reaction was completed. The obtained polymer was extruded from a lower part of the reaction vessel under nitrogen pressure to obtain samples. The polymer was practically colorless and transparent and had an intrinsic viscosity [> /] of 0.71 and a number of carboxyl groups of 25.7 and a melting point of 260.5 ° C.

Comparative example

Into an autoclave equipped with a stirrer and a fractionating column, 580 g of dimethyl terephthalate (hereinafter abbreviated as DMT), 300 cm ^{3 of} ethylene glycol and 0.6 g of potassium acetate were placed. The resulting mixture was heated under Einleileitung of gaseous nitrogen at 170 ° C and then in the course of 7 hours at a rate of 10 ^c C per hour to 240 ° C is further heated. After the temperature reached 240 ° C, the heating was stopped. During the heating, the methanol released from the reaction system was distilled off by the fractionating column

200 mg of antimony trioxide were then added to the ester interchange reaction product obtained. This amount corresponds to that of example 3 of French patent 1 509 306, as well as with metallic titanium in various shapes and amounts. The individual amounts are shown in Table VII. Then, the polycondensation reaction was carried out at an internal temperature of the autoclave of 275 ° C and under a pressure of 0.2 mm Hg over a period of 3 ^ ¹ hour, thereby obtaining the illustrated results in Table VII. In experiments No. 3 and 4, after the end of the polycondensation reaction, metallic titanium was removed by passing the polymer through a filter arranged at the bottom of the autoclave.

Table VIl

attempt No.

Metallic titanium

Fine particles (average particle size: 2.7 μ) the same.

Coarse particles (mean particle size: 100 μ - 3 mm) Beads (thickness: 0.3-0.5mm, width: 4mm, length: no longer than 5mm)

Amount of titanium added, weight percent DMT

2.9 mg (0.0005%)

1.5 mg (0.00026%) 0.58 g (0.1%) 1.74 g (0.3%)

Properties of the polymer

Intrinsic viscosity

0.71
0.64
0.67
0.66

number of Hydroxyl groups (Equiv. ΊΟ "g)

23.5
20.3
19.2
19.7

Melting point CC)

260 261 260 259

Color tint

colorless colorless colorless colorless

For comparison, the same procedure was followed using the following polymerization catalysts A and B carried out.

Catalyst A

Only 200 mg of antimony trioxide was used.

Catalyst B

There were 200 mg of antimony trioxide and titanium hydroxide in an amount of 1.5 mg, calculated as metallic titanium is used.

The properties of the polymers obtained are summarized in Table VIII:

Table VIII

Intrinsic number of Enamel hue Kata viscosity Carboxyl Point lyser groups (Equiv. / (C) easy 0.59 10 "g) 261 easy A. 0.61 18.3 262 B. 18.7

From the above experiments it can be seen that by using the procedure according to the invention Polymers with significantly better properties can be obtained.

509 619/101

Claims (3)

Patent claims: 1. Process for the preparation of polyalkylene terephthalates and modified polyesters made from at least 75 mole percent of a polyalkylene terephthalate and up to 25 mole percent consists of units differing from at least one further ester-forming component, namely an aliphatic diol, a polyethylene glycol, an aromatic diol, an alicyclic diol, an aliphatic dicarboxylic acid, derive an aromatic dicarboxylic acid or an alicyclic dicarboxylic acid by polycondensation of bis (hydroxyalkyl) terephthalate,> 5 optionally in a mixture with less than 25 mol percent of the further component, in the presence a metal catalyst, characterized in that that titanium is used as the metal catalyst. 2. The method according to claim I, characterized in that the metallic titanium in finely divided Form used with average particle sizes less than 100 μ. 3. The method according to claim 1 or 2, characterized in that at least part of the The reaction vessel or the accessories that come into contact with the reaction mixture are made of metal Titanium or an alloy consisting mainly of metallic titanium are.