DE2620281A1 - Oriented fibre forming melt spinnable polyesters - prepd. from aromatic hydroxy acids, divalent phenols and aromatic or cycloaliphatic dicarboxylic acids - Google Patents

Abstract

Novel polyesters contng. at least one phenolic carboxylic acid residue are claimed. The polyesters have a melting temp. >=200 degrees C and are capable of formign anisotropic melts (determined by thermo-optical test) which can be spun to oriented filaments, the strength of which can be increased by >=50% by heat-treatment. Also claimed is a process for prepg. the polyesters comprising reacting aromatic hydroxyacids, pref. p-hydroxybenzoic acid, and/or their derivs., and divalent phenols and/or their derivs. and aromatic and/or cycloaliphatic dicarboxylic acids and/or their derivs., until the polyester achieves inherent viscosity >=0.3. The use of the polyesters for producing oriented fibres by spinning at a draw ratio >=10 is also claimed.

Description

Polyesters and Processes for Making Same The invention relates to new, synthetic polyester, especially in the form of threads, produced by spinning Synthetic polyesters of this type are made from melts and are valuable Have properties, e.g. high strength, that make them suitable for use as give special value to technical threads, e.g. for reinforcement in tires, as well as for other purposes in form'formter structures. The invention is another Embodiment of the invention described in DT-OS 25 20 819.

The production of synthetic polyester threads is already getting technical carried out for many years. The basic principles of the formation of fully synthetic linear polymers are available from W.H. Carothers has been described more than 40 years ago, and this was followed by the industrial production of nylon threads by melt spinning. The production of threads from poly (ethylene terephthalate) is the first time from lfihinfield and Dickson, and the industrial production of polyesters by Melt spinning was essentially the same Publications. For certain purposes it is advantageous to have extremely high strength threads to be able to. Strength is the most important property in most technical Yarns, e.g. for use as tire cord, albeit with different properties can also be of importance.

We have succeeded in increasing the strength of threads made of poly (ethylene terephthalate) improve by stretching.

The manufacture of typical technical polyesters suitable for the Suitable for use as tire cord is from Riggert in "Modern Textiles", November 1971, pages 21-24. An important feature of this discussed by Riggert Manufacturing process is the need to use poly (ethylene terephthalate) of high To use molecular weight and the pre-orientation of the freshly spun poly (ethylene terephthalate) to keep it low, d. H. until solidification and refinement of the Thread are complete. Hence it is important to reduce the stretch on the solidifying Poly (ethylene terephthalate) thread only to act when this Stage is complete, and the solidified thread only then for orientation and increasing its strength to stretch. It is therefore spun when poly (ethylene terephthalate) threads high strength are needed, poly (ethylene terephthalate) of high molecular weight into a heated zone to retard orientation. It is also used to avoid decomposition at the high temperatures that lower the melt viscosity are necessary to enable spinning, the polyester first on one heated lower temperature and then through a leading to the spinning orifices Special filter passed to the temperature (by converting mechanical into thermal Energy) to the threads required for spinning through the openings To increase value.

The production of technical poly (ethylene terephthalate) threads with a Strength of well over 10 g / den was previously not technically feasible.

It would be desirable to have artificial polyester threads with even better ones To be able to have strength properties. It is important that the flow temperature such thread is high enough to cause a decrease in strength when used and Avoid processing, and it would be desirable if such polyesters had a flow temperature of at least 2000 C, preferably at least 2500 C (the term "flow temperature" the meaning used here is described in detail later). It it is also important to be able to produce the polyester threads by melt spinning, and therefore it is desirable that the melting point of the polyester is not so high as that melt spinning would no longer be practical.

According to DT-OS 25 20 819 it was found that by polycondensation of dihydric phenols and aromatic or cycloaliphatic dicarboxylic acids Valuable polyester can be produced, the flow temperatures of at least 2000 C, preferably at least 2500 C and have the property of a to form anisotropic melt from which oriented threads can be melt-spun) which are characterized by heat treatment according to the method of DT-OS 25 20 820 in their properties can be significantly improved, in particular their strength by at least 50 DX and preferably increases several times.

The remarkable structural feature of the polyester according to the DT-OS 25 20 819 consists in the fact that the molecular units in the polymer chains predominantly (aromatic or cycloaliphatic ) Have longitudinal structures. Homopolyesters, which consist entirely of unsubstituted ring structures, have Melting points that are too high for normal uses, e.g. for melt spinning. It is assumed that polyester, to give valuable anisotropic melts, let the stiffness of a chain have made up predominantly of aromatic or cycloaliphatic Wrestling exists while the melting point is in a controlled manner on one for the Use appropriate area must be reduced. It is believed that this feature in terms of a melting point suitable for practical use polyesters with such ring structures as they are without loss of stiffness are required for the formation of an anisotropic melt, can be achieved, inaem one wholly ring structure homopolyester by the following Features modified: (1) A limited substitution of the ring structures, e.g.

by chlorine and bromine atoms and lower alkyl groups, which is preferred and / or (2) limited copolymerization through the use of several R1 radicals and / or more R2 radicals, which is often preferred, and / or (3) introduction of more limited ones Flexibility between the rings, e.g. through ether bonds and X or aliphatic Chains of limited length.

In contrast to melt-spun threads made from technical, i.e. high-grade solid polyesters, mainly poly (ethylene terephthalate), which are spun into threads, in which the polyester molecules immediately have a random (statistically disordered) arrangement assume, i.e. are disoriented, and which require stretching in order for the Polyester molecules orient themselves, these new polyesters can become oriented Threads are melt-spun if they are subjected to sufficient elongation while they emerge from the spinning orifice, generally having a spinning elongation factor of 10 is enough. It is believed that this ability to get oriented from the melt Spinning threads on the peculiar nature of anisotropic melts from which the threads are spun; the anisotropic nature of the Melt is based, as is believed, on the fact that the polyester molecules are in extended chain form and oriented in local areas of the melt are, and that these local areas are oriented when spinning, according to what this orientation is retained.

For economic reasons, spinning and winding are generally done preferably at very high speeds, and such speeds result in practice spinning because factors above 10. It is assumed that at such spinning speeds Fluctuations in the spinning stretch factor do not lead to significant differences in the thread orientation lead (the corresponding differences in the strength of the resulting threads Would result). This is in contrast to the experience with previously known Polyesters, such as poly (ethylene terephthalate), for which, if not compensated, Fluctuations in the spinning stretch factor are significant differences in the resulting threads can bring about.

According to previous publications (e.g. Rowland Hill, "Fibers From Synthetic Polymers ", Elsevier Publishing Company, 1953) approach in practice the properties of the previously known polyester threads with increasing molecular weight a constant value, although theoretically the higher the strength of the thread should be, the higher the molecular weight of the polyester. The usage of Extremely high molecular weight polyesters for making threads were not practicable due to the high melt viscosity the same (See US Pat. No. 3,216,187) and the processing difficulties resulting therefrom in connection with the tendency of the known polyesters to decompose at the high Temperatures that were necessary to produce a spinnable melt. In practice, therefore, there was always an optimal molecular weight above that it was not possible to produce polyester threads with improved strength. It was previously not possible after spinning technical polyester threads, e.g. poly (ethylene terephthalate) threads, from a melt of suitable melt viscosity and suitable molecular weight the strength by increasing the molecular weight of the polyester in thread form to increase significantly.

Although the increase in the molecular weight of poly (ethylene terephthalate) stores after spinning was possible, the strength was not increased significantly. It is believed that the effect of such heating was to reduce the To reinforce the folding of the molecular chains of poly (ethylene terephthalate) and the To reduce orientation (as described by T4ilson in "Polymor", Volume 15, Pages 277-282, Mentioned May 1974).

In contrast, it is by using the polyester according to the DT-OS 25 20 819 possible, polyester of suitable melt viscosity to filaments spin and then increase their strength by heating. The increase strength is of an increase in molecular weight and often an increase accompanied by orientation. It is believed that with the right combination of Flexibility and stiffness in the molecular chain such that the polyester is a Anisotropic melt forms the molecular weight of the molecules by heating the Threads in the as-spun state is increased while overall order and orientation can be maintained or increased without causing folding of the molecular chains comes, as it appears with poly- (ethylene tere.phthalate) the case is. It is important that the polyester one is sufficient for such a heat treatment has a high flow temperature. It is also important to do the heat treatment, as long as further polymerization is still possible, since end-capping of the Molecules (e.g. by oxidation or decarboxylation) the possibility of such Seems to affect heat treatment. The threads are preferably open heated as high a temperature as possible, i.e. a temperature as close as possible at the flow temperature, in practice within about 200 C below the flow temperature, lies. If such a heat treatment were applied to poly (ethylene terephthalate), thus, as shown by Wilson, supra, the strength was rapidly decreased. With many the preferred polyesters according to the invention should be the heat treatment temperatures during technical work above the melting point of poly (ethylene terephthalate), e.g. in the range from 280 to 320 ° C.

An important feature is that the melt spinning of polyester filaments is possible that take on strengths of over 10 g / den during heat treatment.

It has now been found that it is possible to produce valuable polyester that also flow temperatures of at least 2000 C, preferably of at least 2500 C, and have the property of forming an anisotropic melt, from which oriented threads can be spun, the strength of which is determined by heat treatment can be increased by at least 50 D / o by copolycondensation of phenolic carboxylic acids with other, predominantly ring structure, polyester-forming compounds, such as the dihydric phenols and aromatic or cycloaliphatic dicarboxylic acids, to produce, according to DT "S 25 20 819 used for the production of polyesters will.

The invention therefore includes polyesters with a flow temperature of at least 200 ° C, which have the ability to form an anisotropic melt which can be spun oriented threads, the strength of which is determined by heat treatment can be increased by at least 50%, the recurring units being the polyester Contain residues of one or more phenolic carboxylic acids, and a method for the preparation of such copolyesters by copolycondensation of one or more phenolic carboxylic acids with other, predominantly consisting of ring structures, polyester-forming compounds, preferably with one or more divalent ones Phenols and one or more aromatic and / or cycloaliphatic dicarboxylic acids, and / or derivatives of such reactants capable of polyesters to images where the polyester achieves an inherent viscosity of at least 0.3.

The preferred phenolic carboxylic acid is p-hydroxybenzoic acid, and this acid is preferably used in the form of an acyl derivative, in particular as p-acetoxybenzoic acid, used; however, other phenolic carboxylic acids may also prove to be suitable turn out especially those in which the carboxyl group is directly attached to an aromatic Core is bound, wis in p-hydroxybenzoic acid itself or in compounds with several aromatic rings.

U.S. Patents 3,778,410 and 3,804,805 describe a method for Production of a copolyester by reacting a starting polyester with a aromatic acyloxycarboxylic acid or certain copolyesters made from poly (ethylene terephthalate) and an acyloxybenzoic acid. In this procedure, first a fragmented polyester by acidolysis of the starting polyester (which is an inherent Viscosity of at least 0.2) with the aromatic acyloxycarboxylic acid and then make the final copolyester by indening the inherent viscosity of the fragmented polyester increased (to at least 0.4). The preferred aromatic acyloxyzarboxylic acid is p-acetoxybenzoic acid; one can however, use other acids as well. The preferred starting polyester is poly (ethylene terephthalate); however, other starting polyesters can also be used.

It has been possible to produce anisotropic melts from copolyesters which are derived, for example, from 6o mol percent of p-acetoxybenzoic acid residues and 40 mol percent from poly (ethylene terephthalate) residues, as described in Example 1 of these patents, as well as from copolyesters with different proportions of the constituents, for example 67 mol percent p-hetoxybenzoic acid residues, and it has also been possible to spin oriented threads from these anisotropic melts; however, it has not been possible to significantly increase the strength of these threads by subsequent heat treatment, whereas this is possible with the threads described in the examples below. It is not clear why the strength of these known threads cannot be improved by heat treatment, as described in DT-OS 25 20 820; however, it is believed that a cause for this could be the large amount of poly (ethylene terephthalate) residues, the significant amounts of ethylene bonds in a repeating unit of the formula contain.

As you can see, this repeating unit contains a chain of 6 non-ring atoms and therefore does not consist predominantly of rings, so that it can be expected to be so flexible that it, in contrast to the repeating units in the Examples of the starting polyester described in DT-OS 25 20 819 suffers chain folding, as is typical for poly (ethylene terephthalate) and has been described by Wilson (loc. Cit.).

It should be noted that the longest chain between rings in these Structures 4 has chain atoms not belonging to a ring, and this applies to the copolyester 4A, i.

not every recurring unit contains this long, pliable bond. Preferred polyesters according to the invention contain not more than 4 not one Caught related chains of atoms. Some non-ring residues cause a lesser flexibility than others and one can expect the maximum Number of chain atoms depending on the overall combination of flexibility and chain stiffness of molecules varies. It should also be noted that the repeating units consist mainly of ring structures. It is also important that the starting polyester are able to continue to polymerize below their flow temperature, while Polyesters, which are made from poly (ethylene terephthalate) using the two-stage fragmentation and an aromatic acyloxycarboxylic acid, among such Conditions apparently do not lead to such a desired further polymerization are able to. Preferred polyesters are obtained by polycondensation of derivatives of phenolic carboxylic acids, especially those with an aromatic carboxyl group, and dihydric phenols with aromatic and / or cycloaliphatic dicarboxylic acids made and then subjected to heat treatment in the form of threads before it, e.g. by oxidation or decarboxylation, leads to end-capping. As the The example below shows, an aromatic acyloxycarboxylic acid can be divalent Phenols and aromatic and / or cycloaliphatic dicarboxylic acids to form a copolyester polycondensed, which is then processed into a molded product, which has the ability in the sense of the invention by heat treatment in to improve its strength. It may be that the special procedure which for the production of the hitherto known polyesters were used for this responsible is that the threads made from them nter the heat treatment conditions do not attain higher strength; z .. karm the fact that in the process polyeter arise that contain poly (ethylene terephthalate) units in their chains, or the fact that in the process there are residual aliphatic hydroxyl groups to be responsible for it.

The invention will first be referred to for chemical simplicity of a copolyester of 82 mol percent p-oxybenzoyl radicals and 18 mol percent oxy-bis (1,4-phenyleneoxy) radicals and terephthaloyl radicals, and then it is explained how the composition the polyester can be modified to make other copolyesters predominantly aromatic hydroxy acids and other predominantly ring structures, polyester-forming reactants, such as dihydric phenols and aromatic compounds or cycloaliphatic dicarboxylic acids, which have the same essential and have valuable characteristics; further details can be found in the DT-OS 25 20 819. The polymerization conditions are conventional, as well as according to FIG DT-OS 25 20 819; the particular importance of the invention lies in the surprising Properties of the molded products, especially the oriented threads, the can be produced from the melt of the polyester according to the invention, wherein this melt has the further characteristic property that it is anisotropic and the melting points of the polyesters are in a technically useful range. The melt spinning conditions are conventional with the exception of being oriented Threads are spun by stretching the threads emerging from the spinneret which corresponds to a spin stretch factor of more than 10. The test methods are those described below.

Heat treatment is carried out according to the following method: The yarn is wound on a perforated bobbin, previously covered with ceramic insulating wadding has been coated to provide a soft, heat-resistant surface place that yields under low tension, and the coil is placed in an oven used, through which a stream of nitrogen is constantly passed. Furnace and Samples are heated in the temperature-time cycle specified in the table, as well as in DT-OS 25 20 820.

Example copolyester with repeating units R1 R2 x 0.82 polymerization, OC / min / mm 25-305 / 15, 305/15, 320/10, 320/10 / 0.5-1 t, inh 1.6 flow temp., OC 316 spinneret temp., 0C 330 Thread properties * in spun condition T / E / Mi 2.5 / 2.2 / 149 OAO (sheet) 26 (19.9) heat treatment, ° C / h 270 / 0.5, 300 / 0.5, 310/1 , 320 / 2.5 thread properties * after heat treatment T / E / Mi 9.1 / 6.9 / 75 0A0 (sheet) 26 (19.5) * These properties refer to the individual thread (in contrast to yarn properties).

T = tensile strength, g / den E = elongation at break,% Mi = initial modulus, g / den OA = X-ray orientation angle.

It is believed that similar results were obtained with some dicarboxylic acids are obtainable if the chlorine-substituted starting material is replaced by fluorine-substituted Could replace 1,4-phenylenediacetate, although the fluorine substituent is proportionate is small. According to DT-OS 25 20 819, bromine-substituted reactants are used, and it is to be expected that it is possible for the manufacture as well the polyester of the invention to use bromine-substituted reactants; the bromine substituent can give the polyesters valuable properties, e.g. flame resistance, to lend. It is to be expected that the iodine substituent will be too large and unstable is. For the polyesters according to DT-OS 25 20 819 are organic substituents, that are larger than the methyl group, e.g. ethyl and nethoxy, for use too big with some dicarboxylic acids; however has the ethyl group proven to be suitable in certain combinations; if better hydrolysis resistance if desired, the methyl substituent is preferred to chlorine; however can Chlorine-substituted polyesters are very valuable; it is to be expected the same Considerations in the present case apply.

The large number of those mentioned in DT-OS 25 20 819 as examples Copolyester shows that many other changes are possible. Although economic considerations, the preference is likely to be relatively easier and / or ask cheaper reaction participants in relatively simple combinations It should be borne in mind that the inventions are based on the discovery of polyesters with fundamentally new properties, and accordingly special, Combinations that are not specifically mentioned here are interesting and valuable properties Offer.

The properties given above are determined as follows: Optical Anisotropy: TOT (Thermo-Optical Test) It is known to be translucent, optical anisotropic substances in optical equipped with crossed polarization prisms Systems allow polarized light to pass through while light is passing through Isotropic substances should theoretically be zero under the same conditions. This feature becomes more anisotropic in the following thermo-optic identification test Polyester melts according to the invention are used using an apparatus, essentially that of 1. Kirshenbaum, R.B. Isaacson and TS.C. Feist, "Polymer Letters ", Vol. 2, pp. 897-901 (1964), but with device use that are available in the present work, The thermo-optical Test (TOT) requires a polarizing microscope that has tension-free optics and with crossed polarization prisms (90 °) have a sufficiently strong extinction is intended to give the background permeability mentioned later. With those here described determinations a microscope of the type "Leitz Dialux-Pol" was used, equipped with a Polaroid polarizing prism, binocular and a heating table was. A photodetector was attached to the front of the microscope tube. The microscope pointed a long focal length lens (32x) and a first order red plate (the only used for visual observations with crossed polarizing prisms and is used at an angle of 45 ° with each polarizing prism). That Light from a light source is passed through the polarizing prism, through the sample the heating table d directed through the analyzer to the photodetector or eyepiece. A Slider enables the image to be transferred from the eyepiece to the photodetector. Of the Heating table, a vacuum heating table of the type MHS "Unitron" (Unitron Instrument Co., 66 Needham St., Newton Highlands, Massachusetts, V.St.A.) can be heated to 500 ° C. The photodetector signal is amplified and fed to the Y-axis of an X-Y recorder. The system should respond linearly to light intensity and a measurement error should be within - + 1 mm on the Schrelber blade. The heating table has two thermocouples one of which is used to record the heating table temperature with the X-axis of the X-Y recorder and the other connected to a temperature program controller Is.

The microscope is displayed visually (with crossed polarizing prisms) a polyester sample prepared and assembled as follows is adjusted by the sample, but not the coverslip, removed from the optical path, the Polaroid analyzer of the microscope swings out of the optical path for image transmission to the photodetector switches and adjusts the system so that a full scale deflection (18 cm on the used Recorder sheet) on the Y-axis of the X-Y recorder 36 C% o of the photometer signal is equivalent to. The background transmittance value is when the polarizing prisms are crossed (900) and recorded with the cover slip (but not the sample) in the optical path. The background permeability in the system should be independent of temperature and less than about 0.5 cm on the scribe sheet.

The sample is preferably a 5 microtome section made with a Diamond knife made from a solid, well coalesced disc of pure polyester and embedded in epoxy resin. According to a less preferred method, the but is particularly suitable for low molecular weight substances which, when cut with the Shattering the microtome is heated on a cover slip that is on a microscope slide lies, a sample of the finely divided polyester on a hot plate. The hot plate temperature (initially about 10 C above the flow temperature of the polyester) is increased until the polyester is just coalescing into a thin film, the thickness of which is essentially is equivalent to the microtome sections (i.e. about 5 µ).

The specimen section is pressed flat between cover slips, whereupon one cover slip is removed and the sample on the other cover slip (with the glass after lunten) on the heating table. The background transmission is now measured and the sample arranged such that substantially all of the photodetector collected light passes through the sample. While the rehearsal is between crossed polarizing prisms (900) and placed under nitrogen, light intensity and temperature recorded on the X-Y recorder while the temperature was programmed with Speed of about 140 C / min is increased from 25 to 4500 C. The sample temperature is derived from the recorded temperature using an appropriate calibration curve obtain.

The TOT test is described in more detail in DT-OS 25 20 819 and explained.

Adjust the intensity of the light passing through the analyzer isotropic melts located between crossed polarization prisms (900) (the sample should be completely melted) is essentially the background transmission (which is obtained when the sample - but not the cover slip - is outside the Field of view with polarization prisms crossed by 900). While the melt forms, the intensity of the light passing through is either (1) already substantially equal to or (2) it takes from the background transmittance higher value on such values.

The polyesters according to the invention are called anisotropic melts considered formative when heating a sample between crossed polarizing prisms (90 °) beyond the flow temperature, the intensity of the resulting anisotropic Melt the light shining through on you scribe sheet results in a curve whose Height is at least twice the height of the background permeability curve and at least 0.5 cm larger than that of the background transmittance curve is. As these melts form, the value (height) is the light transmission curve (1) at least 0.5 cm larger than that of the background permeability and at least equal to twice the background transmittance or (2) it is not towards such a value.

The polyesters according to the invention often show optical anisotropy in the entire tested temperature range, i.e. from the flow temperature to the Decomposition temperature of the polyester or the maximum test temperature (4500). With certain However, polyesters can be isotropic in parts of the melt when the melt begins to thermally decompose. With still others Types can be the character of the melt with increasing temperature completely change from anisotropic to isotope.

The inherent viscosity (#inh) was determined according to US Pat. No. 3,827,998, Using 1,3-dichloro-1,1,3,3-tetrafluoroacetone hydrate as a solvent, certainly.

The range of suitable inherent viscosities largely depends on the flexibility of the polyester molecules, and the inherent viscosities apply only for soluble polyesters. Polyester with an inherent viscosity of only 0.3 can e.g.

of value even as coatings. In the case of soluble polyesters, the inherent viscosity in the interest of easy processability in general 4.0 lie. It is well known that excessively high melt viscosities lead to processing difficulties. e.g. when melt spinning threads. Insoluble threads that are within the said Flow temperature ranges can prove to be technically valuable.

The flow temperature is the temperature at which the polyester flows, which, with increasing melt viscosity, is expressed by the fact that the sharp Edges of a tiny disc of polyester or a cut fiber are rounded off.

The flow temperature is determined by visual observation of the sample a cover slip, which is placed between crossed polarizing prisms (90 °) on the heating table described above for the thermo-optical test. Usually A heating speed of 140 C / min is suitable, but in some cases, in where a rapid further polymerization takes place, one works with a higher one Speed, about 50 C / min.

The flow temperature of a given sample depends on its history away. For example, the flow temperatures of molded products are sometimes from different from those of the polyester from which the product was formed; by Gradual heating will usually increase the flow temperature, and it will be possible to the heat treatment temperature progressively above the initial flow temperature addition to increase.

In the interest of processability, the polyesters should be at temperatures flow that do not yet decompose rapidly; otherwise plasticizers, solvents or other methods are required to achieve the desired, molded products to arrive. While processing some polyester with high flow temperatures of, for example, 450 ° C may be feasible, should the Flow temperature preferably below 4000 C, e.g. in the range from 200 to 3700 C, in particular from 250 to 3500 ° C.

The spinning stretch factor is the ratio of the speed of the spun thread material (measured during winding) to the speed with which the melt through the Spinneret occurs, the latter being equal to the volume of the melt spun per minute divided by the product of the cross-sectional area of each hole and the number of holes, is.

The thread properties are both for threads in the spun state as well as for heat-treated threads. The tensile strength properties are determined in accordance with US Pat. No. 3,827,998. "OAO (arch) gives the orientation angle and the specific arc (2 O) as the value in brackets and is used according to US Pat. No. 3,671,542, Method (2), determined.

Claims (19)

Claims 1. Polyesters, the residues of one or more phenolic carboxylic acids contain, characterized in that they have a melting temperature of at least Have 200 ° C and are capable, as determined by the thermo-optical test, anisotropic To form melts from which oriented threads can be spun, their strength can be increased by at least 50% by heat treatment. 2. Polyester according to claim 1, characterized in that the residues are p-hydroxybenzoic acid residues. 3. Polyester according to claim 1 or 2, characterized in that they also residues of one or more dihydric phenols and one or more contain aromatic and / or cycloaliphatic dicarboxylic acids. 4. Polyester according to claim 1 to 3, characterized in that it consist entirely of ring structures, some of which are rings by chlorine and / or Bromine atoms and / or lower alkyl groups are substituted. 5. Polyester according to claim 4, characterized in that the substitution is on an aromatic ring. 6. Polyester according to claim 5, characterized in that the substitution is on the remainder of a dihydric phenol. 7. Polyester according to claim 1 to 6, characterized in that they essentially consist of ring structures in which rings are formed by ether bonds are connected. 8. Polyester according to claim 1 to 7, characterized in that they mainly consist of ring structures, but with chains between the rings contain aliphatic groups. 9. Polyester according to claim 1 to 8, characterized in that the ring structures are substituted by chlorine. 10. Polyester according to claim 1 to 8, characterized in that the ring structures are substituted by lower alkyl groups. 11. Polyester according to claim 10, characterized in that the ring structures are substituted by methyl groups. 12. Polyester according to claim 1 to 8, characterized in that the ring structures are substituted by bromine. 13. Polyesters, the residues of one or more phenolic carboxylic acids contain, characterized in that they are able to be determined by the thermo-optical Test to form anisotropic melts from which oriented threads are spun the strength of which can be increased by at least 50% by heat treatment. Process for the production of polyesters according to claims 1 to 13, characterized characterized in that aromatic hydroxy acids and / or derivatives thereof with dihydric phenols and / or derivatives thereof and aromatic and / or cycloaliphatic Dicarboxylic acids and / or derivatives the same converts until the polyester achieved an inherent viscosity of at least 0.3. 15. Polyester according to claim 1 to 13 in the form of a molded product. 16. Polyester according to claim 15 in the form of a thread or a film. 17. Polyester according to claim 1 to 13 in the form of an anisotropic melt, determined according to the thermo-optical test. 18. Use of the polyesters according to claims 1 to 13 for the production of molded products. 19. Use of a polyester according to claim 17 for production of oriented filaments by spinning the anisotropic melt with a spinning elongation factor of at least 10.