DE2932178C2 - polyester - Google Patents

Description

The invention relates to fiber-forming and anisotropic melt-forming, melt-spinnable aromatic Polyester and high modulus fibers or filaments same.

A class of aromatic polyesters that are optically anisotropic Form melts that make up oriented filaments melt spinning is described in US 4,118,372. Other aromatic polyesters with this property are in US 4,066,620. The in the above Patents described polyester are derived primarily of p-oriented dihydric phenols and p-oriented aromatic dicarboxylic acid. Made of such polyesters melt-spun filaments can be used on high strength and modulus values are heat treated.

Aromatic polyesters obtained by the condensation of 4,4'- Dihydroxybenzophenones with isophthalic and terephthalic acid are prepared, are known from GB 9 07 647. aromatic Polyesters derived from m-substituted aromatics, for example, resorcinol are described in US 40 83 829.

The present invention makes various anisotropic ones Melt-forming polyesters are available which are too Filaments melt-melt, in the spun state a high modulus (eg greater than 177 dN / tex respectively. The new filaments can also be heat treated in order to increase their strength values, preferably to a level above 8.84 dN / tex, while module values of over 177 dN / tex were obtained stay.

The present invention is directed to fiber-forming poly or Copolyester directed, which in the melt the property show the optical anisotropy and the out Units of Recurring Formulas

in equimolar amounts, wherein R₁ at at least 85 mole percent of the O-R₁-O units

is (X is methyl or chlorine and n is 0, 1 or 2) and up to 15 mol% from the group m-phenylene, p-phenylene, Chloro-p-phenylene, methyl-p-phenylene, p, p'-biphenylene, Tetramethyl-p, p'-biphenylene, 2,6-naphthylene and 2,7-naphthylene may be selected and R₂ at least 85 mole% of the units

the group p-phenylene, 2,6-naphthylene and p, p'-biphenylene belongs and up to 15 mol% m-phenylene may be, with the proviso that in the case of n equal to 1 or 2 R₂ 2,6-naphthylene or p, p'-biphenylene.

A preferred radical R₁ is

In these preferred compounds R₂ is preferably p-phenylene or 2,6-naphthylene.

R₂ is preferably 2,6-naphthylene or p, p'-biphenylene.  

Another preferred radical R₁ is

In these preferred compounds R₂ is preferably p-phenylene.

The present invention further fiber and Anisotropic melting forming poly or Copolyester consisting of units of the structural formulas

wherein

is (X is methyl or chlorine and n is 0, 1 or 2) and R₂ of the group p-phenylene, 2,6-naphthylene and p, p'-biphenylene belongs with the proviso that in the case of n is 1 or 2 R₂ is 2,6-naphthylene or p, p'-biphenylene is.  

Alternatively exist the polyesters or copolyesters according to the invention from units

is (X is methyl or chlorine and n is 0, 1 or 2), R₂ p-phenylene, 2,6-naphthylene or p, p'-biphenylene and R₃ m- or p-phenylene, wherein the unit III up to 15 mol% represents the total amount of units I and III.

The invention also includes high modulus filaments of these Polyesters.

The invention is described in detail below.

The polyesters or copolyesters according to the invention are made from units -O-R₁-O-, which are of bivalent Derive phenols, and units

derived from aromatic dicarboxylic acids, in equimolar  Amounts. At least 85 mol% of the units -O-R₁-O-, preferably all of these are

where X Chlorine or methyl and n is 0, 1 or 2. Preferably n is 0, d. H. the unit is not substituted. The remaining units -O-R₁-O-, d. H. up to 15 mole% u. a. the group

on. At least 85 mol% of the units

preferably all of these belong to the group

on. The remaining units

d. H. up to 15 mol%, are

When n is 1 or 2, R₂ must at least 85 mole% of the units

2,6-naphthylene or p, p'-biphenylene. Alternatively, they exist Poly or copolyester

(X = methyl or chlorine and n is 0, 1 or 2),
B) terephthaloyl, 2,6-naphthoyl or p, p'-bibenzoyl and
C) m- or p-oxybenzoyl units in proportions as above.

The polyesters or copolyesters according to the invention are able to optically to form anisotropic melts and have a to Melt spinning to filaments sufficient molecular weight. The term poly- or copolyester encompasses both homo- as well as copolyesters.

polymerization

The preparation of the polyesters or copolyesters can be carried out according to standard techniques the melt polymerization or condensation from one or more aromatic dicarboxylic acids of the formula

wherein R₂ has the above meaning, and a or more diphenols of the formula HO-R₁-OH, where R₁ has the above meaning. Often one uses the diphenols in its diester form (eg diacetate). The diphenols and Diacids are normally in equimolar  Quantities combined and placed in a reaction vessel under nitrogen and heated with stirring for about 1 to 3 hours. The for the polymerization applied temperatures are above the melting points of the reactants and generally in the region of 200 up to 350 ° C. The reaction vessel is equipped with means by-product removal during the polymerization process allow. Normally you put to the end of the polymerization apply a vacuum to the removal of residual by-products to facilitate and complete the polymerization to lead. Polymerization conditions such as temperature, heating time, Pressures, etc. can be used in accordance with z. B. the used Reactants and the desired degree of polymerization be varied.

filament production

The polyesters and copolyesters may be prepared by conventional melt spinning techniques to be spun into filaments. One extrudes a melt of the polymer through a spinneret in a quenching atmosphere (For example, air or nitrogen on Room temperature are kept) and wound the Filamentgut on. General spinning conditions are described in US 4 066 620 called.

As used herein, the term refers to of the fiber in the "spun state" on a fiber that after Extrusion and normal winding not stretched or has been heat treated.

Heat treatment and utility

The as-spun fibers according to the Invention can while in a relaxed state be subjected to a heat treatment in an oven, to obtain high-strength fibers that are suitable for a variety technical purposes, as for plastic and rubber or rubber reinforcement. In the heat treatment process Become the fiber samples or items, such as strands or on  (preferably collapsible) coils located fiber material, usually heated in an inert atmosphere, which is continuous flushed through the furnace by flowing inert gas is to remove by-products from the environment of the fiber. You work with temperatures that are at the merger point approach, but are low enough to To avoid filament-filament fusion. Preferably you drive gradually to the maximum temperature.

Measurements and tests

The inherent viscosity (η _inh ) is given by the equation

wherein (η _rel ) means the relative viscosity and C means a concentration of 0.5 g of the polymer in 100 ml of solvent. The relative viscosity (η _rel ) is determined by dividing the flow time of the dilute solution in a capillary viscometer by the flow time of the pure solvent. Unless stated otherwise, the flow times are determined at 30 ° C. and work with p-chlorophenol as solvent.

The fiber tensile properties are subsequently in SI units

Denier dtex Strength (T) dN / tex Elongation (E) % (the length in the unstretched state) Module (Mi) dN / tex

The measurement is carried out according to those described in US Pat. No. 3,827,998 Working on fibers that conditions for at least 1 h have been. One wins the mean of at least three Fractures.  

The thermo-optical test (TOT) is described in US 4 066 620. Polymers satisfying this test are considered to be optical considered anisotropic.

The following examples serve to further explain the Invention.

example 1 Synthesis of 3,4'-diacetoxybenzophenone

The 3,4'-diacetoxybenzophenone used in the following polymerizations was started in stages from m-anisic acid manufactured. First, a conversion into m-anisoyl chloride, then in 3,4'-dimethoxybenzophenone, then in 3,4'- Dihydroxybenzophenone and finally in 3,4'-diacetoxybenzophenone. The present example gives the details of such Transfer and provides, with the exception of changes to the Working standard the general working method for all such Preparations.

Preparation of m-anisoyl chloride

A mixture of 100 g (0.658 mol) of m-anisic acid, 250 g (2.10 mol) of thionyl chloride and 5 ml of dimethylformamide heated in a round bottom flask under reflux, with for holding atmospheric humidity in the radiator head Desiccant was. By means of a rotary film evaporator was from the product excess thionyl chloride at about Distilled off 26.6 kPa. Then, the m-anisoyl chloride became by fractional distillation through a 25 cm. Vigreux column isolated at 109 ° C / 1.6 kPa. The Yield was 90 g (0.528 mol), d. H. about 80%.

Preparation of 3,4'-dimethoxybenzophenone

A round bottom flask was equipped with a stirrer, dropping funnel,  Nitrogen inlet and thermometer equipped and in one Ice / water bath cooled. The initial batch in the form of a mixture of 69.0 g (0.638 mol) of anisole, 90 g (0.675 mol) nonaqueous aluminum trichloride and 108 g tetrachloroethane was cooled with stirring to below 15 ° C, while over it a slow stream of nitrogen was passed. On the Dropping funnel was a solution of 90 g (0.528 mol) m Anisoyl chloride in 108 ml tetrachloroethane with such Speed added that a temperature increase the stirred mixture was avoided above 15 ° C (Addition time 1 to 2 h). After mixing, the flask became allowed to stand for two days at room temperature before decomposition of the AlCl₃ complex carefully added ice (about 250 g) has been. The tetrachloroethane was purified by steam distillation away. The organic products were made the aqueous mixture by extraction in 500 ml of methylene chloride separated, whereupon the aqueous layer withdrawn and was discarded. This was followed by two washing treatments the methylene chloride solution with about 200 ml of 5% aqueous Sodium hydroxide solution and a washing treatment with about 200 ml of water, each time removing and discarding the aqueous layer has been. After distilling off the methylene chloride under Use of a rotary film evaporator remained 102 g (0.42 mol) of 3,4'-dimethoxybenzophenone, which upon cooling to Room temperature crystallized. The material was out Recrystallized ethanol, with 87 g (0.36 mol) of crystals incurred, which melted at 53 to 55 ° C. This material is together with its production also in J. Am. Chem. Soc., 54 (1932), p. 1449.

Preparation of 3,4'-dihydroxybenzophenone

By heating a mixture of 87 g (0.36 mol) for 15 hours. 3,4'-dimethoxybenzophenone and a previously prepared mixture of 240 ml of 48% aqueous hydrobromic acid, 120 ml of acetic anhydride and 120 ml of acetic acid under reflux the demethylation was effected. To isolate the  Dihydroxy product became the cooled reaction mixture poured into about 400 ml of water, filtered, washed with water and dried in an oven at 80 ° C. The melting point was 193 to 194 ° C and the yield was 77 g (0.36 mol), d. H. about 100%.

Preparation of 3,4'-diacetoxybenzophenone

A slurry of 73 g (0.34 mol) of 3,4'-dihydroxybenzophenone in 225 ml of acetic anhydride in a beaker was added with 8 drops of concentrated sulfuric acid and the mixture heated for 30 min on a steam bath. The resulting clear solution was cooled and then added to Precipitate the product poured into about 600 ml of water. The Product was filtered off, washed with water and in a Oven dried at about 80 ° C. The recrystallization from Methanol gave 80 g (0.268 mol) of diacetoxybenzophenone, m.p. 81 up to 83 ° C.

Example 2 Polyterephthalate of 3,4'-dihydroxybenzophenone

The polymerization apparatus used was a 250 ml three-necked flask, the one with a in a pressure-tight synthetic resin bushing sitting glass stirrer, 2. a nitrogen inlet, 3. a short Vigreux column leading to a water-cooled Cooler with a piston for the collection of acetic acid, and 4. an electrically heated, the vertical height adjustable arranged Bad Wood's metal was provided. In the distillation adapter was a means for vacuum application intended.

The flask was charged with 9.57 g (0.032 mole) of diacetoxybenzophenone and 4.98 g (0.03 mole) of terephthalic acid and heated from 238 to 310 ° C with stirring under nitrogen at atmospheric pressure in 48 minutes. During this period most of the acetic acid by-product was released. Heating at 310 ° C was continued for a further 22 minutes. Then, a vacuum of 0.0266 kPa was applied and the temperature was raised to 325 ° C in 8 minutes and maintained at this value for 17 minutes. The cooled polymer had an inherent viscosity, η _inh , of 0.78. Its melt proved above its flow temperature of 296 ° C as anisotropic (determined by the TOT test).

The shredded solid polymer became a cylindrical one Grafted and grafted using this a press-spinning device through a spinneret hole of 0.23 mm diameter at 325 ° C and 4830 kPa pressure spun. The winding speed was 914 m / min. As filament properties averaged a D / T / E / Mi of 3.92 / 4.45 / 1.77 / 318th The filament was loosely wound on a soft spool and in an oven heated in slow nitrogen stream according to the following program: 220 ° C / 1 h + 240 ° C / 1 h + 260 ° C / 1 h + 280 ° C / 1 h + 300 ° C / 1 h. After this heating, the average filament properties were as follows before (the titre being essentially unchanged was): T / E / Mi = 10.28 / 3.76 / 320. The were the best tensile properties individual values after heating T / E / Mi = 17.66 / 6.02 / 376.5.

Example 3 Poly-2,6-naphthalenedicarboxylate of 3,4'-dihydroxybenzophenone

By the procedure of Example 2, 9.84 g (0.033 mol) of 3,4'-diacetoxybenzophenone was polymerized with 6.48 g (0.030 mol) of 2,6-naphthalenedicarboxylic acid. The polymerization temperature was increased from 235 to 345 ° C at atmospheric pressure in 87 minutes and from 345 to 365 ° C under vacuum in 40 minutes. The inherent viscosity, η _inh , was 0.78. In the TOT test, the melt above the flow temperature of 298 ° C proved to be anisotropic.

As in Example 2 except that the extrusion temperature 360 ° C and the extruding 2760 kPa amounted to, from the crushed, solid product Grafting molded and spun. As average Filament properties were found to be D / T / E / Mi = 10.12 / 4.18 / 1.37 / 338. Heating under nitrogen (as in Example 2 at 225 ° C / 24 h + 300 ° C / 19 h improved the average tensile properties to T / E / Mi = 14.04 / 4.67 / 308.

Example 4 Copoly-2,6-naphthalenedicarboxylate from 3,4'-dihydroxybenzophenone (90 mol%) and hydroquinone (10 mol%)

The copolyester was prepared by the procedure of Example 2 from 14.35 g (0.048 mol) of 3,4'-diacetoxybenzophenone, 1.04 g (0.0054 mol) of 1,4-diacetoxybenzene and 10.80 g (0.050 mol) 2 , 6-Naphthalenedicarboxylic acid. The polymerization temperature was increased from 310 to 352 ° C at atmospheric pressure in 50 minutes and kept at 352 ° C under vacuum for 34 min. The crushed solid polymer was thoroughly washed with acetone to extract low molecular weight substances. The inherent viscosity, η _inh , was 0.59. In the TOT test, the melt above the flow temperature of 323 ° C proved to be anisotropic.

As in Example 2, a more molded from the copolyester Graft spun. The features of 549 m / min wound filaments averaged D / T / E / Mi = 4.78 / 4.30 / 1.67 / 279th By heating like in Example 2 at 225 ° C / 24 h + 280 ° C / 21 h + 300 ° C / 16 h were used as tensile properties T / E / Mi = 12.40 / 4.90 / 304 receive.  

Example 5 Copolyesters of 3,4'-dihydroxybenzophenone with 2,6-naphthalenedicarboxylic acid (90 mol%) and isophthalic acid (10 mol%)

In the manner described in Example 2, a mixture of 15.95 g (0.0535 mol) of 3,4'-diacetoxybenzophenone, 0.83 g (0.005 mol) of isophthalic acid and 9.7 g (0.045 mol) of 2,6- Naphthalene dicarboxylic acid polymerized. The polymerization temperature was increased from 305 to 358 ° C at atmospheric pressure in 53 minutes and kept at 358 ° C under vacuum for 17 minutes. The inherent viscosity, η _inh , was 0.92, and the TOT test showed melt anisotropy above the flow temperature of 303 ° C.

As in Example 2, one of the crushed, solid Copolyester molded plugs spun into a filament, with the plug at 380 ° C and the spinneret at 385 ° C and the spinning pressure was 4140 kPa and the winding speed was 549 m / min. The Filament had in the spun state on average D / T / E / Mi = 6.26 / 4.22 / 2.63 / 250th To Heating as in Example 2 at 200 ° C / 24 h + 225 ° C / 3 h + 250 ° C / 20 h were the average tensile properties T / E / Mi = 7,37 / 4,14 / 238 ago.

Example 6 Preparation of 3,4'-dimethoxy-3'-methylbenzophenone

The operation and setup of this monomer representation corresponded to Example 1. A solution of 94.5 g (0.554 mol) of m-anisoyl chloride in 113 ml of tetrachloroethane dropwise with stirring to a cooled mixture of 80.7 g (0.661 mol) of o-methylanisole, 94.5 g of non-aqueous Added aluminum chloride and 113 ml of tetrachloroethane, the temperature being maintained at about 15 ° C. The  Mixture was allowed to stand at room temperature for 24 hours. To Add ice and extract with methylene chloride (as in the preparation of 3,4'-methoxybenzophenone in Example 1) an impure liquid was obtained from which the 3,4'- Dimethoxy-3'-methylbenzophenone by fractionated Destilla tion in a 25 cm Vigreux column at 198 ° C and 0.27 kPa Pressure was gained. The yield was 114 g (0.445 mol).

Preparation of 3,4'-dihydroxy-3'-methylbenzophenone

By 15-hour reflux treatment with a previously ange set mixture of 313.5 ml of 48% aqueous bromine water acid, 148 ml of acetic anhydride and 148 ml of acetic acid the demethylation of 114 g (0.445 mol) of 3,4'-di methoxy-3'-methylbenzophenone causes. The isolated product melted at 173 to 174 ° C. The recrystallization from Ethanol / water gave 79 g (0.346 mol) of 3,4'-dihydroxy- 4-methylbenzophenone, mp 174-175 ° C.

Preparation of 3,4'-diacetoxy-3'-methylbenzophenone

The 3,4'-dihydroxy-3'-methylbenzophenone was in the hehal amount of 79 g (0.346 mol) using 237 ml Acetic anhydride and 8 drops of concentrated sulfur acid and acetylated for 30 min heating on a steam bath. The product was precipitated in water, filtered, washed and dried at about 80 ° C. After crystallization of the From methanol, the melting point was 60-64 ° C. The yield was 87 g (0.279 mol). Before the polymerization this product was again extracted from methanol crystallizes.

Polyester of bibenzoic acid and 3,4'-diacetoxy-3'-methyl benzophenone

With the apparatus and procedure of Example 2, 10.89 g (0.045 mol) of bibenzoic acid and 14.36 g (0.046 mol) of 3,4'-diacetoxy-3'-methylbenzophenone were polymerized. The heating was carried out at atmospheric pressure in 80 minutes from 290 to 357 ° C and under vacuum for 19 min at 357 ° C. The inherent viscosity, η _inh , of the product was 1.09. The TOT test showed melt anisotropy above the flow temperature of 311 ° C.

As in Example 2, one of the crushed product molded cylindrical plug at 378 ° C and Spun 1380 kPa, the take-up speed 366 m / min. As the average properties of Filaments in the as-spun state gave D / T / E / Mi = 8.9 / 3.67 / 1.15 / 338th After heating the Filaments as in Example 2 at 200 ° C / 2 h + 250 ° C / 2 h + 260 ° C / 1 h + 280 ° C / 1 h + 305 ° C / 20 h were average tensile properties T / E / Mi = 7.34 / 2.90 / 268 in front.

example 7 Synthesis of 3-hydroxy-4 '- (4-hydroxyphenyl) benzophenone (and its diacetate)

A 1 liter autoclave was charged with 85.0 g (0.5 mol) of 4-phenylphenol, 69.0 g (0.5 mol) of 3-hydroxybenzoic acid and 500 ml of HF (on Cooled to 0 ° C). After closing the autoclave Air was removed by rinsing with BF₃. Under 6 hours Maintaining an autoclave temperature of 0 ° C was on the autoclave contents with shaking BF₃ at a pressure of 207 kPa.  

At the end of this period, the reaction mixture was in poured an excess of water (about 2 l) to the crude one To precipitate the product, which is filtered off, washed well with water wash and dried. The yield of the crude Product was 136 g (94%), mp 213-219 ° C.

The above crude product was refluxed for 2 hours about 400 ml of acetic anhydride and 0.15 g of sulfuric acid hitzt. By precipitating the Ac₂O solution in about 2 liters of water isolated the product and then filtered off, washed and dried. The yield of the crude product was 183 g (Theory 187), mp 95 to 99 ° C. The recrystallization from Ethanol gave mp 119-121 ° C.

example 8 Polyterephthalate of 3-hydroxy-4 '- (4-hydroxyphenyl) benzo phenone

The polymerization apparatus was similar to that used in Example 2. The flask was charged with 15.56 g (0.042 mole, 4% excess) of the diacetate of 3-hydroxy-4 '- (4-hydroxyphenyl) -benzophenone and 6.64 g (0.040 mole) of terephthalic acid and stirred Stick at atmospheric pressure in 35 minutes from 280 to 346 ° C heated. Then a high vacuum was applied and the heating continued for 7 minutes at 346 ° C. The cooled polymer had an inherent viscosity, η _inh , of 0.76 (determined in 7.5% trifluoroacetic acid, 17.5% methylene chloride, 12.5% dichlorotetrafluoroacetone hydrate, 12.5% tetrachlorethylene (Perclene®), and 50% 4- chlorophenol).

The polymer was spun at 300 ° C as in Example 2 and the filament wound at 549 m / min. The accruing Filament had a mean titer of 8.6 dtex and average tensile properties in the form of T / E / Mi =  2.21 / 0.76 / 448th After heat-setting as in Example 2 at 230 ° C / 2h + 250 ° C / 2h + 270 ° C / 1h + 280 ° C / 18h lay as average tensile properties T / E / Mi = 5.85 / 2.95 / 226 ago.

example 9 Polyester from 3-hydroxy-4 '- (4-hydroxyphenyl) benzophenone and 2,6-naphthalenedicarboxylic acid

The polymerization corresponded to the modification of that of Example 8, that instead of the terephthalic acid here 8.64 g (0.040 mol) of 2,6-naphthalenedicarboxylic acid were used. The initial heating from 268 to 340 ° C was carried out in 31 minutes under nitrogen at atmospheric pressure and heating under vacuum for 2 min at 340 to 344 ° C. The polymer had an inherent viscosity, η _inh , of 0.73 (determined using the solvent used for this purpose in Example 8).

The polymer was melted as in Example 2 at 276 ° C spun and the filament wound at 366 m / min. The Meltspun filaments had an average Titer of 7.6 dtex and average tensile properties in the form of T / E / Mi = 1.41 / 0.54 / 234. After the heat-resistant as in Example 2 at 220 ° C / 2 h + 240 ° C / 2 h + 260 ° C / 2 h + 280 ° C / 2 h + 304 ° C / 18 h were average tensile properties:

T / E / Mi = 4.79 / 2.3 / 231

in front.

Claims (13)

1. fiber-forming, anisotropic melts forming poly or copoly ester, consisting of units of the structural formulas O-R₁-O and in equivalent amounts, in which R₁ contains at least 85 mol% of the units O-R₁-O-] is (X is methyl or chlorine and n is 0, 1 or 2) and up to 15 mol% of the group m-phenylene, p-phenylene, chloro-p-phenylene, methyl-p-phenylene, p, p ' -Bi phenylene, tetramethyl-p, p'-biphenylene, 2,6-naphthylene and 2,7-naphthylene may be selected and R₂ at least 85 mol% of the units belongs to the group p-phenylene, 2,6-naphthylene and p, p'-biphenylene and may be up to 15 mol% m-phenylene with the proviso that in the case of n is 1 or 2 R₂ 2,6-naphthylene or p, p'-biphenylene. 2. poly- or copolyester according to claim 1, characterized in that R₁ is. 3. poly- or copolyester according to claim 2, characterized characterized in that R₂ is p-phenylene.   4. poly- or copolyester according to claim 2, characterized ge indicates that R₂ is 2,6-naphthylene. 5. poly- or copolyester according to claim 1, characterized ge indicates that R₂ is 2,6-naphthylene. 6. poly- or copolyester according to claim 1, characterized ge indicates that R₂ is p, p'-biphenylene. 7. Poly- or copolyester according to one of the preceding Claims in the form of a filament. 8. poly- or copolyester according to claim 7 in the form of a heat treated filament with a modulus of over 177 dN / tex and a strength of over 8.84 dN / tex. 9. poly- or copolyester according to claim 1, characterized in that R₁ is. 10. poly- or copolyester according to claim 9, characterized ge indicates that R₂ is p-phenylene. 11. Fiber-forming, anisotropic melts forming poly or copolyester, consisting of units of the structural formulas wherein R₁ is (X is methyl or chlorine and n is 0, 1 or 2) and R₂ of the group p-phenylene, 2,6-naphthylene and p, p'- biphenylene belongs with the proviso that in the case of n is 1 or 2 R₂ is 2,6-naphthylene or p, p'-biphenylene. 12. Fiber-forming, anisotropic melts forming poly or copolyester, consisting of units of the structural formulas is (X is methyl or chlorine and n is 0, 1 or 2), R₂ p-phenylene, 2,6-naphthylene or p, p'-biphenylene and R₃ m- or p-phenylene, wherein the unit III up to 15 Represents mole% of the total amount of units I and III. 13. Poly- or copolyester according to one of the preceding Claims in the form of a filament.