MELT-PROCESSABLE LIQUID CRYSTALLINE POLYESTER, PROCESS FOR THE PREPARATION THEREOF AND PRODUCTS PREPARED FROM THE POLYESTER

Abstract: The invention concerns a liquid crystalline polymer which is optically anisotropic in the melt state and which, as far as its molecular weight is concerned, is suitable for melt processing, a process for preparing such a polyester, and products prepared from the polyester. According to the invention a liquid crystalline polymer is provided, containing a structural unit of formula (I), wherein R1, R2, R3 and R4 each independently represent hydrogen, halogen, lower alkyl, lower alkoxy, phenyl, which optionally is substituted with one or more halogens or lower alkyls, or benzyl, which optionally is substituted with one or more halogens or lower alkyls, and R5 and R6 represent hydrogen, lower alkyl, phenyl, or benzyl, with the proviso that if one of them is something else than hydrogen then the other one is hydrogen, n is an integer from 0 to 5. The glass transition temperature of the polyester according to the invention is higher than 90 DEG C and its forms an anisotropic mesophase at temperatures below 300 DEG C, which makes it possible to use the polyester for preparing polymer blends with conventional matrix polymers, in particular with polyolefins. High-strength constructional parts can be manufactured from the polyester.

Description: Melt-processable liquid crystalline polyester, process for the preparation thereof and products prepared from the polyester The present invention relates to a liquid crystalline polyester, which is optically aniso¬ tropic in the melt phase and which has a molecular weight which makes it suitable for melt processing. The invention also relates to a process for preparing such a polyester as well as to products prepared from the polyester. Liquid crystalline polyesters, i.e. polyesters which in the melt state are optically anisotropic, are well known in the art. Liquid crystalline polyesters are described in numerous patent publications and some of them are mentioned in, for instance, the following articles: Jackson, W.J. Jr. , Liquid Crystal polymers. XI. Liquid Crystal Aromatic Polyesters: Early History and Future Trends. Mol. Crvst. Liq. Crvst, 169 (1989) 23-49, and Noel, C. and Navard, P. , Liquid Crystal Polymers, Prog. Polvm. Sci. 16 (1991) 55-110. The prior art is also represented by U.S. Patent Specifications Nos. 4,600,764, 4,599,395 and 4,083,829. The strength and stiffness of many thermoplastics can be considerably improved by mixing them with liquid crystalline polymers. The liquid crystalline polymer forms fibres which align in the direction of the melt flow of the thermoplastic polymer matrix, thus improving the mechanical properties, such as tensile strength and modulus of elasticy, in this direction. By adding liquid crystalline polymers it is often also possible to improve the heat resistance and the dimensional stability of thermoplastics and to make the processing of them easier. The known liquid crystalline aromatic polyesters are. however, hampered by the problem that their melt and processing temperatures are often too high for them to be processed together with thermoplastics and to be used in blends with these polymers. This is true for the aromatic polyesters disclosed by the above-mentioned U.S. Patent Specifications as well as for the commercially available thermotropic polyesters marketed under the product names "Vectra" (supplied by Hoechst-Celanese) and "Xydar" (supplied by Amoco). Polymers prepared by the transesterification method are discussed in the U.S. Patent Specification No. 3,804,805 and in the article by Jackson, W.J., Jr. and Kuhfuss, EL F. in J. Polvm. Sci. Polvm. Chem. Ed. 14 (1976) 2043. The polymers form an anisotropic mesophase at temperatures above 220 °C. The disadvantage of these known polymers resides in their low glass transition temperatures. Since the glass transition temperature limits the highest temperature at which the polymers can be used, said temperature being about 30 to 40 °C below the glass transition point, a low glass transition temperature is not advantageous as far as the use of the polymer and its compounds and blends are concerned. It is an aim of the present invention to eliminate the problems associated with the prior art and to provide an entirely novel liquid crystalline polyester, which can be used in injection and blow moulded products which require extremely high strength, stiffness and toughness as well as dimensional stability. The present invention is based on the concept of providing a liquid crystalline polymer containing a repeating unit of the formula (I) wherein R,. R 2 , R 3 and R« each independently represent hydrogen, halogen, lower alkyl. lower al oxy, phenyl, which optionally is substituted with one or more halogens or lower alkyls, or benzyl, which optionally is substituted with one or more halogens or lower alkyls: and R 5 and Rg represent hydrogen, lower alkyl, phenyl, or benzyl, with the provisio that if one of them is something else than hydrogen then the other one is hydrogen, and n is an integer 0 to 5. Preferably, the polyester according to the invention contains a structural unit with the formula (II) wherein R,, R 2 , R 3 , R 4 , R s and -f^ have the same meaning as above. Preferably, in formula (I), Rj, R 2 , R 3 and R. each independently stand for hydrogen, phenyl. benzyl, 1,1-dimethylethyl, methyl, metoxy. chloro, bromo or ethylphenyl. and R 5 and R^ are hydrogen or a phenyl, benzyl or alkyl group. Preferably, R, is a lower alkyl and R 2 , R 3 , R 4 , R 5 and R^ are hydrogens and n is 0. The polyester according to the invention is then copolymerized with monomers having formula (III) OH-R 7 -OH (HI) and formula (IN) HOOC-R 8 -COOH (IV) and/or formula (N) Thus, the polymer contains repeating units of formulas (Ilia) -O-R 7 -O- (πia) and (TVa) -OOC-R 8 -COO- (INa) and/or (Na) -OOC-R^O- (Na) whereat, in formulas (IE), (ma), (IV), (INa), (V) and (Na) R 7 , R g , Re, are the same or different and represent an unsubstituted or substituted arylene or naphthenylene radical or an unsubstituted or substituted biphenyl radical having the formula R 10 -A-R 10 . wherein R 10 is a phenyl radical and A is -CH,-, -C(CH 3 ) 2 , -O-, -S(O) 2 - or -S-. Alternatively, instead of strucmral units (III) and (IN), the polymers according to the invention can contain poly(ethylene terephthalate) (PET), poly(butylene terephthalate) (PBT), poly(ethylene naphthenate) (PEN), poly(butylene naphthenate) (PBN) or poly- ((dimethylol)cycIohexyl) terephthalate (PCT). According to a particularly preferred embodiment, the polyester contains in addition to the structural unit of formula (I) 0 to 49.5 % of strucmral unit -O-R 7 -O- (ffla) and 0 to 49.5 % of structural unit -OOC-Rg-COO- (INa) or 0 to 99.9 % of strucmral unit -OOC-R^O- (Na)- According to another particularly preferred embodiment, the polyester contains instead of structural units (Ilia) and (IVa) 0 - 99,9 % of poly(ethylene terephthalate) (PET), poly(butylene terephthalate) (PBT), poly(ethylene naphthenate) (PEN), poly(butylene naphthenate) (PBN) or poly((dimethylol)cyclohexyl) terephthalate (PCT). In particular, the polyester according to the invention contains 2 to 60 % of a structural unit of formula (I), 10 to 49 % of a monomer of formula (III), 10 to 49 % of a mono¬ mer of formula (IV) and 20 to 70 % of a monomer of formula (V). The preferred relative amounts of the structural units are: 5 to 40 % of (I), 20 to 40 % of (III), 20 to 40 % of (IV) and 30 to 60 % of (V). Alternatively, strucmral units (ill) and (IV) can be replaced by 10 to 80 %, preferably 20 to 60 % of poly(ethylene terephthalate) (PET), poly(butylene terephthalate) (PBT), polyethylene naphthenate) (PEN), poly(bu- tylene naphthenate) (PBN) or poly((dimethylol)cyclohexyl) terephthalate (PCT). Within the scope of the present invention, the term "halogen" means fluoro, chloro, bromo or jodo, preferably chloro or bromo. "Lower alkyl" is a straight or branched chain saturated hydrocarbon group, which contains 1 to 6, preferably 1 to 4 carbon atoms. The following examples may be mentioned: methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl (1,1-dimethylethyl) and 2-methylbutyl. "Lower alkoxy" means an alkoxy containing 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms, such as methoxy, ethoxy, propoxy and tert-butoxy. "Arylene" is a bivalent aromatic group such as phenylene or biphenylene. The arylene, naphthenylene or biphenylene group can be substituted with halogen, lower alkyl, or phenyl. The last-mentioned can be substituted with halogen or lower alkyl. Preferably the substituent comprises a phenyl group or a 1,1-dimethylethyl-, methyl-, chloro-, bromo- or ethyl-substituted phenyl group. In this invention, the terms "strucmral units" and "monomer" are used to designate the repeating units of the polymer, which are linked to each other via ester bonds. The polymers according to the invention, which contain groups of formulas I and II and optionally groups of formulas -QTa and IVa and/or Va or, alternatively, instead of structural units (ϋla) and (TVa), poly(ethylene terephthalate) (PET), poly(butylene terephthalate) (PBT), poly(ethylene naphthenate) (PEN), poly(butylene naphthenate) (PBN) or poly((dimethylol) cyclohexy) terephthalate (PCT), are formed by reacting polyester-forming precursors containing said groups at polyester-forming conditions. Thus, according to the invention, a hydroxyphenylalkanoic acid of the formula (VI) R wherein R l3 R 2 , R 3 , R 4 , R 5 , Rg and n have the same meaning as above, or a reactive derivative thereof, is subjected to a esterification reaction with a hydroxyphenylalkanoic acid of the formula (VI) or monomers of formula (III) OH-R 7 -OH OH) and formula (IN) HOOC-R g -COOH (IN) and/or of formula (N) HOOC-R -OH (N) wherein R 7 , R 8 and Ro have the same meaning as above, or a reactive derivative there- of. Alternatively, instead of being reacted with monomers of formulas (III) and (IN), the hydroxyphenylalkanoic acid of the formula (VI) is reacted with poly(ethylene terephthalate), poly(butylene terephthalate), poly(ethylene naphthalate), poly(butylene naphthenate) or poly((dimethylol)cyclohexyl) terephthalate. The reactive derivatives of the above acids are, e.g. , selected from the group comprising acid anhydrides, acid chlorides and esters. The esterification reaction can be based on methods known per se, such as the acetate method, the "in situ" acetylation method and the transesterification method. The reactants used for these reactions include a) diacids and acetylated hydroxyl compounds, b) diacids, diols and acetylation agents and c) diacid esters and diols or polyesters. The polyesters can also be prepared by the known esterification reaction between an aromatic acid chloride and a diol. Only low-molecular weight polyesters are, however, produced by this reaction. Furthermore, the acid chlorides are expensive and the solvent removal from the polymer is complicated. Postpolymerization of the product is needed. According to a preferred embodiment of the invention, when groups of formulas (I) or (II) and (III) and (IV) and/or (V) are used in the preparation process, the molar ratios are selected such that the molar amounts of terminal hydroxyl groups (-OH) and terminal carboxylic groups (-COOH) are equivalent. Then, polymers will be produced having stoichiometrically equal amounts of repeating units of formulas (Ilia) and (IVa). In the "in situ" acetylation method is its preferred to use an excess of acetanhydride, the suitable excess being 1.1 to 1.5 molar equivalents in relation to the amount of hydroxyl groups. According to another preferred embodiment of the invention, the molar amounts of the terminal hydroxyl groups and terminal carboxylic groups are not equivalent, which makes it possible to provide the polyester with desired terminal groups. Thus, by employing more terminal carboxylic groups than there are terminal hydroxylic groups, polyester can be produced, whose terminal groups essentially are carboxylic groups. The products can be produced by solution or emulsion polymerization, melt poly¬ merization, which is a preferred method for preparing polyesters which are suitable for melt processing, and in solid state. Polyester production by the melt polymerization method is hampered by the high viscosity of the polymer and the tack of the polymer to the reaction equipment. The tack can be reduced by carrying out the polymerization in solution, slurry or solid state. The problem with solution polymerization resides in the difficult removal of the high-boiling organic solvent and the reaction of the solvent with the reactants and the product formed. In solid state, polymerization is slow. The product often forms a network and its mechanical properties are poor. According to a preferred embodiment of the invention, the polymers are synthetized by using a two-stage melt polymerization based on the acetate method. The advantage of the two-stage melt polymerization resides in its low processing costs, relatively short polymerization time and the good mechanical and rheological properties of the product formed. The reactants used can be selected from the group comprising aromatic dicarboxylic acids, diols and hydroxy acids. The hydroxylic groups are generally esterified by using acetic acid anhydride. The esterification can be carried out before polymerization or in connection therewith, an excess of the acid anhydride being used in the reaction mixture. The polymerization is carried out in the melt phase, usually at a temperamre in the range from 250 to 350 °C in nitrogen or argon atmosphere. The reaction between the monomers is a condensation reaction which splits off a small molecular product, gene¬ rally acetic acid. The condensation products must be removed from the reaction mixture. In the first stage of the reaction, the temperamre is gradually raised. Raising the temperamre makes the distillation of the condensation product easier and accelerates the progress of the reaction. The second stage of the polymerization is carried out at high-vacuum and standard temperamre. The reaction time is generally 3 to 6 hours. Sometimes a postpolymerization is further carried out in high-vacuum at a temperature slightly below the melting point of the polymer during a time period of a couple of days. As far as the reaction is concerned, it is preferred to use a catalyst for accelerating the reaction. The catalysts suited to catalyzing transesterifications include catalysts commonly used in condensation, transesterification and polycondensation reactions. These catalysts are, as generally known, represented by Lewis acids and hydrohalides; oxides, hydrides, hydroxides, halides, alcoholates, phenolates, salts and organic and inorganic salts (in particular carboxylic acid salts), salt complexes of alkali metals or salts mixtures, for instance of magnesium ja calcium salts. Other examples are tin, lead, and antimony, alkali metals and alkaline earth metals as such, in particular sodium, sodium hydroxide, litium, sodium, potassium, calcium, magnesium, cobalt, and zink acetate, calcium benzoate, magnesium and zinc acetylacetonate, titanium alkoxy Is, such as titanium tetrabutyrate, titanium tetrapropylate, alkoxytitanium silicates, zirkonium propylate and zirkonium butylate, antimony trioxide, dialkyl and diaryl stannic oxides, dibutyl stannic diacetate and i-butyldimetoxyl tin. Particularly suitable catalysts are magnesium, manganese, sodium, potassium and zinc acetate and dibutyl stannic oxide, tetra-n-butyl titanate and titanium(IV) isopropylate. If desired, the reaction can, however, also be carried out without any catalyst. By means of the invention, considerable benefits are obtained. Thus, the glass transition temperamre of the polyester according to the invention is essentially higher that that of known polymers prepared by the transesterification process. Typically the glass transition temperamre is over 90 °C. The polyester is optically amsotropic in melt phase, its phase transition temperamre being less than 300 °C, typically about 200 to 300 °C. The polymer according to the invention is well suited to use in blends with thermo¬ plastics, in particular polylefins and copolymers thereof, and with polyesters. The following examples of suitable polyolefins may be mentioned: polyethylene, polypropylene, polybutylene, polyisobutylene, poly(4-methyl-l-pentylene), including copolymers of ethene and propene (EPM, EPDM), and chlorinated and chloro- sulphonated polyethylene. Also corresponding polyalkanes are possible as matrix polymers provided that they contain styrene, acryl, vinyl and fluoroethyl groups. The matrix polymers can, further, be comprised of various polyesters, such as poIy(ethylene terephthalate), poly(butylene terephthalate) and polycarbonate. In addition to the above mentioned polymers, the polyester according to the invention can also be blended with polyamides and polyethers. The theremoplastic/liquid crystalline polymer blends according to the invention can be prepared by methods known per se. The mixing methods are either batch or continuous processes. As examples of typical batch mixers, the Banbury mixer and the heated roll mill may be mentioned. Continuous mixers are exemplified by, for instance, the Farrel mixer, and single- and double-screw extruders. Preferably single- or double-screw extruders are used for blending the liquid crystalline polymer with the thermoplastic. The liquid crystalline polymers are blended with the thermoplastics either by first premixing the liquid crystalline polymers with the thermoplastics in a double-screw extruder and then processing them in an injection moulding machine or, alternatively, by processing them by injection moulding or extrusion without premixing. The present polyesters can be used for preparing reinforcements for polymer materials. By blending the polyesters according to the invention with polymer matrices, it is possible to produce thermoplastic reinforced plastics, whose particularly benefit is the possibility of reuse (since they do not contain reinforcement fibres made of a different materials, such as glass). At the same time process equipment wear is diminished. The fibrous polyester can be used in industrial products and in consumer goods, which require great strength and light weight, as well as recycling of the product. The poly¬ mer and blends thereof can be used, in particular, in injection moulded, blow moulded, extruded, and deep drawn products. These products are exemplified by threads, films, pipes, tubes, sheats and formed and deep drawn products. Further applications are constructional parts and sheaths of cables. The polyesters can also be used in manufacturing processes as processing agents which reduce the viscosity of polymer melt. In the following the invention is described in greater detail with the help of the attached drawings and the non-limiting examples given below. The figures indicate the results of thermal analysis of the polyesters according to examples 1, 1A, 2, 3, 4, 5 and 6: Figure 1 shows the DSC thermogram of a polyester prepared according to Example 1 , Figure 2 shows the TGA thermogram of the same example, Figure 3 shows the DSC thermogram of the copolymer prepared in comparative Example 1A and Figure 4 shows the TGA thermogram of the same compound, Figure 5 shows the DSC thermogram of the polyester prepared in Example 2 and Figure 6 shows the corresponding TGA thermogram, Figures 7 and 8 show the DSC and TGA thermograms of the polyester according to Example 3, Figures 9 and 10 show the DSC and TGA thermograms of the polyester according to Example 4, Figures 11 and 12 show the DSC and TGA thermograms of the polyester according to Example 5, and Figures 13 and 14 show the DSC and TGA thermograms of the polyester according to Example 6. EXAMPLE 1 Preparation of a copolymer comprising terephthalic acid, 3-tert- butylhydroquinone, 4-hydroxybenzoic acid and 3-(4-hydroxy-3-tert-butylphenyl) propanoic acid by the acetate method 0.25 moles of terephthalic acid, 0.25 moles of 3-tert-butyl-l ,4-diacetoxyphenyl. 0.30 moles of 4-acetoxybenzoic acid and 0.20 moles of 3-(4-acetoxy-3-tert-butylphenyl)- propanoic acid and 0.003 moles of Na-acetate were metered into a reactor, which was equipped with a stirrer, a distillation system and an N 2 -inlet. The reactants were dried at +110 °C by repeating three times a cycle comprising nitrogen feed - pressure reduction. The first step of the reaction was carried out in N 2 -atmosphere, the temperature of the heating bath being raised within 10 minutes to 210 °C, furtheron during 60 minutes to 275 °C, the reaction time at said temperamre being 60 minutes. Finally, the temperature was raised within 30 minutes to 300 °C, at which temperamre the reaction time was 90 minutes. The second stage of the reaction was performed at reduced pressure, the pressure first being reduced to 560 mbar, and then halved each 10 minutes until a pressure of 0.5 mbar was obtained. The reaction time at this pressure was 90 min. The amorphous polyester prepared by this method was fibrous and formed an anisotropic mesphase at temperatures above 260 °C. Based on differential scanning calorimetry, the glass transition temperamre of the polymer was 146 °C (cf. Fig. 1) and the thermogravimetrically detemiined decomposition temperature was 390 °C (Fig. 2). The logaritmic viscosity number of the polymer, determined at 45 °C in a solution of 4-chlorophenol/l,l,2,2-tetrachloroethane at a concentration of 0.5 g / 100 ml was 1.25 dl/g. EXAMPLE 1A (comparative) Preparation of a copolymer comprising terephthalic acid, 3-tert-butyl- hydroquinone, and 4-hydroxybenzoic acid by the acetate method 0.20 moles of terephthalic acid, 0.20 moles of 3-tert-butvl-l ,4-diacetoxybenzene. 0.60 moles 4-acetoxybenzenoic acid and 0.003 moles of Na-acetate were metered into a similiar reactor as the one described in Example 1. The reactants were dried and the reaction was carried out as described in Example 1, with the exception that the final temperamre of the first reaction step was 340 °C, at which temperamre the reaction time was 60 minutes. This was necessary because the melting temperamre of the formed polyester was considerably much higher than the melting temperamre of the polymer prepared in Example 1. which contained 3-(4-acetoxy-3-tert-butylphenyl)- propanoic acid. The polyester prepared by the method described was fibrous and it formed an anisotropic mesophase at temperatures above 311 °C. Based on differential scanning calorimetry, the glass transition temperature of the polymer was 185.2 °C (Fig. 3) and its themogravimetrically measured decomposition temperamre was 440 °C (Fig. 4). The logaritmic viscosity number of the polymer, determined at 45 °C in a solution of 4-chlorophenol/l,l,2,2-tetrachloroethane at a concentration of 0.5 g / 100 ml was 1.25 dl/g. The melting temperamre of the polymer was, however, to high for use in blends with thermoplastics. EXAMPLE 2 Preparation of a copolymer comprising terephthalic acid, 3-tert- butylhydroquinone, 4-hydroxybenzoic acid and 3-(4-hydroxy-3-tert-butylphenyl)- propanoic acid by the "in situ" -method 0.290 moles of terephthalic acid, 0.290 moles of 3-tert-butylhydroquinone, 0.520 moles of 4-hydroxybenzoic acid, 0.058 moles of 3-(4-hydroxy-3-tert-butylphenyl)-propanoic acid, 1.04 moles of acetic acid anhydride and 0.003 moles of Na-acetate were metered into a similar reactor as the one described in Example 1. The temperamre of the reaction mixture was raised to 170 °C in an N 2 atmosphere. At the end of acetic acid distillation (after about 1 hour) the temperamre was raised during 60 minutes to 275 °- C, the reaction time at that temperamre being 60 min and, finally, the temperamre was raised to 300 °C within 30 minutes and kept at that temperamre for further 90 min. The second stage of the reaction was carried out as described in Example 1. The polyester prepared by the process was fibrous and it formed an amsotropic mesophase at temperatures above 280 °C. The glass transition temperamre of the polymer was 159 °C and its thermal decomposition temperamre was 420 °C (Figures 5 and 6). The logaritmic viscosity number of the polymer was 1.08 dl/g. EXAMPLE 3 Preparation of a copolymer comprising polyethylene terephthalate, 4-hydroxy¬ benzoic acid and 3-(4-hydroxy-3-tert-butylphenyI)-propanoicacid by the transesterification method 0.180 moles of poly(ethylene terephthalate, 0.090 moles of 4-acetoxybenzoic acid and 0.03 moles of 3-(4-acetoxy-3-tert-butylphenyl)-propanoic acid were metered into a reactor similiar to the one described in Example 1. The reactants were dried as described in Example 1. The first stage of the reaction was carried out in N 2 atmosphere, the temperamre of the heating bath being raised to 275 °C, at which temperamre the reaction time was 180 minutes or the reaction was continued until distillation of acetic acid ended. The second stage of the reaction was carried out at reduced pressure, the pressure first being reduced to 560 mbar, and then halved each 10 minutes until a pressure of about 0.5 mbar was reached. The reaction time at this pressure was 180 minutes at 275 °C and 30 minutes at 295 °C. The amorphous polymer prepared by the described method was light-coloured and fibrous. Analyzed by the methods described in Examples 1 and 2; it formed an aniso¬ tropic mesophase at temperamres above 280 °C. The glass transition temperamre of the polymer was 92.6 °C (Fig. 1) and the thermal decomposition temperamre 390 °C (Fig. 8). The logaritmic viscosity number of the polymer was 1.13 dl/g. EXAMPLE 3A (comparative) Preparation of a copolymer comprising poly(ethylene terephthalate) and 4- hydroxybenzoic acid by the transesterification method A polymer was prepared according to the article Jackson. W.J., Jr. and Kuhfuss, H. F. J. Polvm. Sci. Polvm. Chem. Ed. 14 (1976) 2043 and the US Patent Specification No. 3,804,805. 0.073 moles of poly(ethylene terephthalate), 0.109 moles of 4-acetoxybenzoic acid was metered into a reactor similar to that described in Example 1. The reactants were dried according to Example 1. The first stage of the reaction was carried out in N 2 atmosphere, the temperamre of the heating bath being raised to 275 °C, the reaction time at that temperamre being 180 min or the raction was continued until the distillation of acetic acid ended. The second stage of the reaction was performed at reduced pressure, the pressure first being reduced to 560 mbar, and then halved each 10 minutes until a pressure of about 0.5 mbar was reached. The reaction time at this pressure was 240 minutes at 275 °C. The polymer prepared by the described method was light-coloured and fibrous. Analyzed by the methods described in Examples 1 and 2, it formed an anisotropic mesophase at temperamres above 220 °C, but the glass transition temperamre of the polymer was low, i.e. 61 °C. The logaritmic viscosity number of the polymer was 0.71 dl/g. The low glass transition temperamre of the polymer limits the highest temperamre of use, which means that a low glass transition point of the polymer is not preferred. The following Examples 4 to 10 illustrate the preparation of copolymers of formula (I) starting from different derivatives of hydroxyphenylalkanoic acid. EXAMPLE 4 0.25 moles of terephthalic acid, 0.25 moles of 3-tert-butyl-l ,4-diacetoxybenzene, 0.30 moles of 4-acetoxybenzoic acid and 0.20 moles of 3-(4-acetoxyphenyl)-propanoic acid and 0.003 moles of Na-acetate were metered into a similiar reactor as the one described in Example 1. The polymer was prepared according to Example 1. The polymer prepared by the described method was light-coloured and fibrous. Analyzed by the methods described in Examples 1 and 2. it formed an amsotropic mesophase at temperatures above 225 °C. The glass transition temperamre of the polymer was 129 °C and the thermal decoposϊtion temperamre 400 °C (Figs. 9 and 10). The logaritmic viscosity number of the polymer was 0.58 dl/g. EXAMPLE 5 0.25 moles of terephthalic acid, 0.25 moles of 3-tert-butyl-l ,4-diacetoxybenzene . 0.30 moles of 4-acetoxybenzoϊc acid and 0.20 moles of 3-(4-acetoxy-3-metoxyphenyl)- propanoic acid and 0.003 moles of Na-acetate were metered into a similiar reactor as the one described in Example 1. The polymer was prepared according to Example 1. The polyester prepared by the method was light-coloured and fibrous and it formed an anisotropic mesophase at temperatures above 240 °C. Based on differential scanning calorimetry, the glass transition point of the polymer was 122 °C and its thermogra- vimetrically determined decomposition temperature was 390 °C (Figs. 11 and 12). The logaritmic viscosity number of the polymer, determined at 45 °C in a solution of 4- chlorophenol/l,l,2,2-tetrachIoroethane at a concentration of 0.5 g / 100 ml was 1.16 dl/g. EXAMPLE 6 0.25 moles of terephthalic acid, 0.25 moles of 3-tert-butyl-l ,4-diacetoxybenzene. 0.30 moles of 4-acetoxy benzoic acid and 0.20 moles of 3-(4-acetoxy-3-chlorophenyl)- propanoic acid and 0.003 moles of Na-acetate were metered into a similiar reactor as the one described in Example 1. The polymer was prepared according to Example 1. The polymer prepared by the described method was light-coloured and fibrous. Analyzed by the methods described in Examples 1 and 2, it formed an anisotropic mesophase at temperamres above 220 °C. The glass transition temperamre of the polymer was 126 °C and the thermal decoposition temperamre 380 °C (Figs. 13 and 14). The logaritmic viscosity number of the polymer was 0.65 dl/g. EXAMPLE 7 0.25 moles of terephthalic acid, 0.25 moles of 3-tert-butyl-l , 4-diacetoxybenzene. 0.30 moles of 4-acetoxy benzoic acid and 0.20 moles of 3-(4-acetoxy-3-benzylphenyl)- propanoic acid and 0.003 moles of Na-acetate were metered into a similiar reactor as the one described in Example 1. The polymer was prepared according to Example 1 or according to Example 2, acetates being used as precursors of the polymer instead of hydroxylic compounds. EXAMPLE 8 0.25 moles of terephthalic acid, 0.25 moles of 3-tert-butyl-l, 4-diacetoxybenzene, 0.30 moles of 4-acetoxybenzoic acid and 0.20 moles of 3-(4-acetoxy-3-butylphenyl)- pentanoic acid and 0.003 moles of Na-acetate were metered into a similiar reactor as the one described in Example 1. The polymer was prepared according to Example 1 or according to Example 2, acetates being used as precursors of the polymer instead of hydroxylic compounds. EXAMPLE 9 0.25 moles of terephthalic acid, 0.25 moles of 3-tert-butyl-l ,4-diacetoxybenzene, 0.30 moles of 4-acetoxybenzoic acid and 0.20 moles of 3-(4-acetoxy-3-tert- butylphenyl)-3-methylpropanoic acid and 0.003 moles of Na-acetate were metered into a similiar reactor as the one described in Example 1. The polymer was prepared according to Example 1 or accordmg to Example 2, acetates being used as precursors of the polymer instead of hydroxylic compounds. EXAMPLE 10 0.25 moles of terephthalic acid, 0.25 moles of 3-tert-butyl-l, 4-diacetoxybenzene, 0.30 moles of 4-acetoxybenzoic acid and 0.20 moles of 3-(4-acetoxy-3-tert-butylphenyl)-3- phenylpropanoic acid and 0.003 moles of Na-acetate were metered into a similiar reactor as the one described in Example 1. The polymer was prepared according to Example 1 or according to Example 2, acetates being used as precursors of the polymer instead of hydroxylic compounds.

Claims: Claims: 1. A liquid crystalline polymer, c h a r a c t e r i z e d in that it contains a strucmral unit of formula (I) wherein Rι, R 2 , R 3 and R, each independently represent hydrogen, halogen, lower alkyl, lower alkoxy, phenyl, which optionally is substimted with one or more halogens or lower alkyls, or benzyl, which optionally is substimted with one or more halogens or lower alkyls, and R 5 and )% represent hydrogen, lower alkyl, phenyl, or benzyl, with the provisio that if one of them is something else than hydrogen the other one is hydrogen, n is an integer 0 to 5, and structural units of formulas (Ilia) -O-R 7 -O- (Illa), (IVa) -OOC-R R -COO- (IVa), and/or of formula (Va) wherein R 7 , R 8 , Rg are the same or different and represent an unsubstimted or substimted ary- lene- or naphthenylene radical or an unsubstimted or substimted biphenyl radical which has the formula R 10 -A-R 10 , wherein R, 0 is a phenyl radical and A is -CH 2 -, -C(CH 3 ) 2 , - O-, -S(O) 2 - or -S-. 2. The polyester according to claim 1, wherein, in formula (I), R,, R 2 , R 3 and R* independently stand for hydrogen, phenyl, benzyl, 1,1-dimethylethyl, methyl, metoxy, chloro, bromo or ethylphenyl, and R 5 and R 6 are hydrogen or a phenyl, benzyl or alkyl group. 3. The polyester according to claim 1 or 2, wherein n is 0. 4. The polyester according to claim 1, wherein ι% and ^ both represent hydrog 5. The polyester according to claim 4, wherein the strucmral units (D3a) and (INa), respectively, are replaced by poly(ethylene terephthalate) (PET), poIy(butylene terepht- halate) (PBT), poly (ethy lene naphthenate) (PEN), poly utylene naphthenate) (PBN) or poly((dimetylol)cyclohexyl) terephthalate (PCT). 6. The polyester according to any one of the previous claims, wherein the polyester contains - 0,1 to 99 % of a monomer of formula (I), 0 to 49,5 % of a structural unit -O-R^-O- of formula (Ilia), and 0 to 49,5 % of a strucmral unit -OOC-R 7 -COO- of formula (IVa) and/or 0 to 99,9 % of a strucmral unit -OOC-Rg-O- of formula (Va). 7. The polyester according to claim 6, wherein the polymer contains instead of strucmral units (Ilia) and (INa) 0 to 99,9 % of poly(ethylene terephthalate) (PET), poly(butylene terephthalate) (PBT), poly(ethylene naphthenate) (PEN), poly(butylene naphthenate) (PBN) or poly((dimethylol)cyclohexyl) terephthalate (PCT). 8. The polyester according to claim 6, wherein the polymer contains 2 to 60 % of a strucmral unit of formula (I), 10 to 49 % of a monomer of formula (HI), 10 to 49 % of a monomer of formula (IN) and 20 to 70 % of a monomer of formula (N), in particular 5 to 40 % of a monomer of formula (I), 20 to 40 % of a monomer of formula (III), 20 to 40 % of a monomer of formula (IV) and 30 to 60 % of a monomer of formula (V). 9. The polyester according to claim 7, wherein the polymer contains 10 to 80 %, preferably 20 to 60 % of poly(ethylene terephthalate) (PET), poly(butylene terephthala¬ te) (PBT), polyethylene naphthenate) (PEN), poly (buty lene naphthenate) (PBN) or poly((dimethylol)cyclohexyl) terephthalate (PCT). 10. The polyester according to any one of the previous claims, wherein the glass transition temperature of said polyester is at least about 90 °C and it forms an anisotropic mesophase at a temperamre below 300 °C. 11. Process for preparing a liquid crystalline polyester, c h a r a c t e r i z e d by subjecting hydroxyphenylalkanoic acid of the formula (VI) wherein Rι, R 2 , R 3 and R 4 each independently represent hydrogen, halogen, lower alkyl. lower alkoxy, phenyl, which optionally is substituted with one or more halogens or lower alkyls, or benzyl, which optionally is substituted with one or more halogens or lower alkyls, and Rs and Rs represent hydrogen, lower alkyl, phenyl, or benzyl, with the provisio that if one of them is something else than hydrogen then the other one is hydrogen, n is an integer 0 to 5, or its reactive derivative, to an esterification reaction with a hydroxyphenylalkanoic acid of the formula (VI) or a monomer of formula (Hi.) OH-R 7 -OH (HI) and of formula (IN) HOOC-R 8 -COOH (TV) and/or of formula (V) wherein R 7 , R g , % are the same or different and represent an unsubstimted or substituted arylene- or naphthenylene radical or an unsubstituted or substituted biphenyl radical which has the formula R 10 -A-R 10 , wherein R 10 is a phenyl radical and A is -CH , -C(CH 3 ) 2 , -O-, -S(O) 2 - or -S-, or, alternatively, instead of being reacted with monomers of formulas (Tfl) and (IN), the hydroxyphenylalkanoic acid of the formula (VI) is reacted with poly(ethylene terephthalate), poly(butylene terephthalate), ρoly(ethylene naftelate), poly(butylene naphthenate) or poly((dimethylol) cyclohexyl) terephthalate. 12. The process according to claim 11, wherein the polyester is prepared from monomers of formulas (1), (HI) and (TV) and/or (V), c h a r a t e r i z e d in that the molar ratios of the preparation are selected such that the molar amounts of the hydroxylic terminal groups (-OH) and terminal carboxylic groups (-COOH) are equivalent. 13. The process according to claim 11, wherein the polyester is prepared from monomers of formulas (I), (III) and (IV) and/or (V), c h a r a t e r i z e d in that the molar ratios of the preparation are selected such that the molar amounts of the hydroxylic terminal groups (-OH) and the terminal carboxylic termical groups (-COOH) are not equivalent. 14. The process according to claim 11, wherein the polyesters are prepared according to the acetate method. 15. The process accordmg to claim 14, wherein the hydroxyl groups of the monomers are at least partially acetylated before esterification. 16. The process according to claims 14 or 15, wherein the polyesters are prepared by two-phase melt processing. 17. The process according to any one of claims 11 to 13. wherein the polyesters are prepared by the transesterification method. 18. The process according to claim 17, wherein the reaction is carried out in the presence of a catalyst. 19. The process according to any one of claims 11 to 13, wherein the polyesters are prepared by the "in situ" -acetylation method, in which the acetylation is performed in connection with the reaction. 20. Polymer blend, which includes a polymer matrix containing thermoplastics blended with liquid crystalline plastics, c h a r a c t e r i z e d in that the liquid crystalline comprises a polymer according to one of claims 1 to 10. 21. The polymer according to claim 20, wherein the polymer matrix comprises a poly- olefine or a copolymer of polylefines, of a polyester, a polyamid or a polyether. 22. A polymer product, characterized in that it contains a polyester according to any one of claims 1 to 10, possibly blended with a polymer matrix and shaped into a product by methods known per se in polymer technology. 23. The polymer product according to claim 22, characterized in that it is prepared by injection moulding, blow moulding, extrusion, melt spinning or deep drawing. 24. The polymer product accordmg to claims 22 or 23, characterized in that it is in the form of a fibre, filament or a film. 25. The polymer product according to claim 22 or 23, characterized in that it is in the form of a tube or a sheath. 26. The polymer product according to claim 22 or 23, characterized in that it is shaped into strucmral parts of a cable or into a sheath of a cable. 27. The use of a polyester according to one of claims 1 to 10 as a polymer melt viscosity reducing adjuvent of manufacturing processes.

Inventors: ALANKO HELI, HAERKOENEN MIKA, LAHTINEN LEILA, PAJUNEN ESKO, ALANKO, HELI, HAERKOENEN, MIKA, LAHTINEN, LEILA, PAJUNEN, ESKO
Applicants: ALANKO HELI, HAERKOENEN MIKA, LAHTINEN LEILA, NESTE OY, PAJUNEN ESKO
Application year: 1993
Main classification: C08G63
IPC codes: C08G63, C08J5, C08L23, C08L67, C08L71, C08L77, C09K19, H01B7