BRANCHED POLYCARBONATES CONTAINING METHYLENE-BIS-NAPHTALENE COMPOUNDS AND PROCESS FOR THEIR PREPARATION

Abstract: Branched, thermoplastic polycarbonates, suitable for being processed by means of the blow-moulding technique, are prepared by means of copolymerization with methylene-bis-naphthalene compounds.

Description: The present invention relates to branched, thermoplastic, polycarbonates, suitable for being transformed by means of the blow-moulding technique (blow moulding of hollow bodies). Linear polycarbonates have been long known in the art. Such polymers are widely used in different applicative sectors, but, contrarily to most thermoplastic polymers, they are not suitable for being processed by means of extrusion or blow-moulding techniques, which are the techniques suitable for supplying particular transformation products (cellular sheets, bottles, hollow containers, and so forth). This difficulty in processability of linear polycarbonate is due to its exclusively Newtonian behaviour, according to which the apparent viscosity (η) is substantially independent from the shear rate (γ). The transformation of a material according to the techniques of extrusion or of blow-moulding requires, on the contrary, that it has a decreasing apparent viscosity with increasing shear rate, a typical aspect of non-Newtonian behaviour, so that the state of the molten polymer can be differentiated into two successive moments: a first moment, when it is inside the transformation machine (e.g., an extruder), and a second moment, when the product leaves it (e.g., from the die of the same extruder). In the first step, the shear rates the fluid is subject to, are high, and its apparent viscosity is, vice-versa, low, so that the processability thereof results facilitated; when the fluid leaves the extruder, on the contrary, low values of γ, and high viscosity values appear, and this prevents the product from collapsing, and makes it possible a good dimensional stability of the manufactured article to be achieved. The non-Newtonian behaviour of the molten polymer has a considerable influence on two properties, i.e., the melt elasticity, or pseudo-elasticity, and the melt strength, thereof, which are equally very important for the transformation techniques of extrusion and blow-moulding. The melt elasticity consists essentially in the capability of the non-Newtonian fluid of swelling to a greater extent, when exiting the die, than a Newtonian fluid, as a consequence. of a higher recovery of elastic energy inside its interior, thanks to a greater molecular deflection and orientation under the action of a shear stress. That results in an increase in the processability of the product, due to the effect of a greater flexibility and ductility of the material. The second property indicated, viz., the melt tenacity, becomes vice-versa meaningful when the molten polymer exits the transformation machine. It can be considered as the tenacity of the polymer in the molten state, i.e., the stress-supporting capacity shown by the polymer. If, in fact, the molten mass is not capable of supporting its own weight, the collapse occurs of the extrudate, and, as a consequence, obtaining the desired shape of the manufactured article is not possible. It is apparent from the foregoing that the polymers which display a non-Newtonian behaviour are endowed with two basic characteristics, which enable them to be transformed by extrusion and/or blow-moulding techniques: a very easy processability inside the machine (low apparent viscosity for high values of "gamma" and high melt elasticity), and very good shape retention when exiting said machine (high apparent viscosity for low values of "gamma" and considerable melt tenacity). In the art, banched polycarbonates are known, which have non-Newtonian rheological properties, suitable for being processed according to to techniques of extrusion and blow-moulding. Such polycarbonates can be obtained by means of the copolymerization with polyfunctional comonomers containing three or more -OH and/or -COCl and/or COOH groups. Thus, for example, DE-A-1 595 762 discloses branched polycarbonates which are obtained by using, as the branching agent, a benzene compound, or a biphenyl compound carrying three groups selected from hydroxyl and carboxyl. US-A-4 562 242 discloses blow-mouldable branched polycarbonates which are prepared by using a carboxybiphenol compound as the branching agent. Finally, EP-A- 227 177 teaches to prepare branched polycarbonates using a naphthalene compound, carrying chlorocarbonyl groups and/or chlorosulphonic groups as the branching agents. The main technical problem which can be met in the preparation of the branched polycarbonates consists essentially in the reactivity of the polyfunctional comonomer used, and in the characteristics of the branched polycarbonate obtained with such a comonomer. In particular, the comonomer should show so high a reactivity, as to make it possible to achieve the desired branching degree (such as to give the polymer a shear sensitivity greater than 15), when used in small amounts. The branched polycarbonate, besides showing a shear sensitivity greater than 15, should maintain,unchanged, the other characteristics which are typical of the linear polycarbonates. The polyfunctional comonomers of the prior art have not proven to be completely satisfactory from all of these viewpoints. It has been found, now, that it is possible to overcome the drawbacks stemming from the prior art, and to obtain branched, thermoplastic, blow-mouldable polycarbonates by copolymerization with a polyfunctional, highly reactive comonomer used in small amounts. Such polycarbonates, thanks to the branchings due to the presence of the polyfunctional comonomer in the macromolecule, show a shear sensitivity (which is the ratio of the flow rates of the molten polymer at two different shear rates) greater than 15, while maintaining, unchanged, the other characteristics which are typical of the linear polycarbonates. This invention,therefore, provides blow-mouldable branched polycarbonates produced from an aromatic dihydroxy compound, phosgene or a dialkyl-, diaryl-, or alkylaryl carbonate, and a compound having the formula: wherein R₁ and R₂ are equal to, or different from one another, and represent -COOH or -COCl. Another aspect of this invention is a process for preparing the blow-mouldable branched polycarbonates as defined above, comprising the steps of: a) Preparing a chloroformyl-capped oligomer, by reacting phosgene and a dihydroxyaromatic compound having the formula: wherein R, if present, is selected from: a substituted or unsubstituted alkyl containing up to 5 carbon atoms; or -O-, or -S-, or SO₂-; x and y , equal to, or different from one another, are -H, -CH₃ or a halogen atom, and m and n , equal to, or different from one another, are within the range of 1 to 4; b) Condensing the thus obtained oligomer with the compound of formula (I) of Claim 1; c) Adding the dihydroxyaromatic compound of formula (II) and carrying out the polycondensation reaction, and d) Recovering the blow-mouldable branched polycarbonate from the reaction mixture. The necessary chloroformyl-capped oligomers are prepared by interfacial reaction of phosgene with a dihydroxyaromatic compond (II) dissolved in an aqueous alkaline solution, in the presence of a water-immiscible organic solvent, and of a molecular weight regulator, such as p-tert.butyl phenol or p-isopropyl phenol. Examples of suitable dihydroxyaromatic compounds are: 4,4'-dihydroxybiphenyl; 2,2-bis(4-hydroxyphenyl)propane; 2,2-bis(3,5-dichloro-4-hydroxyphenyl)propane; 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane, and bis(4-hydroxyphenyl)methane. Also single-aromatic ring bivalent compounds can be used, such as resorcinol, hydroquinone and pyrocatechol. The process is carried out at a temperature of from 15°C to 35°C, room temperature (20°C-25°C) being preferred. The thus obtained oligomers have a mol wt of from 400 to 2000. Upon separation of the two phases, to the organic phase, containing the chloroformyl-capped oligomers, the polyfunctional comonomer (I), dissolved in a water-immiscible organic solvent, preferably methylene chloride, is added, so to obtain in the end polycarbonate from 0.01 to 1.5 mol of comonomer per each 100 mol of aromatic dihydroxy-compound. Some examples of polyfunctional comonomers used are: 4,4'-methylene-3,3'-hydroxy-2,2'-carboxy-bis-naphthalene; 4,4'-methylene-3,3'-hydroxy-2-carboxy-2'-chlorocarbonyl--bis-naphthalene, and 4,4'-methylene-3,3'-hydroxy-2,2'-chlorocarbonyl-bis-naphthalene An aqueous-alkaline solution is then added, which contains a reducing agent, preferably sodium dithionite, for the purpose of preventing the formation of coloured byproducts, and an aqueous solution is added, which contains the phase-transfer catalyst, e.g, a tertiary amine, preferably triethylamine. The temperature at which the condensation is carried out ranges from 15°C to 35°C and is preferably kept around room values (20-25°C). After a time period ranging from 30 to 60 minutes, preferably 40 minutes, the biphasic system coming from the condensation with the polyfunctional comonomer is treated with an alkaline solution of the aromatic dihydroxy-derivative. An aqueous-alkaline solution of sodium hydroxide at 40% by weight is then added. After a time period of from 2 to 3 hours, the so obtained branched polycarbonate is isolated by washing the organic phase according to the methods of the known art, and distillation of the solvent, or precipitation by means of a non-solvent. The preparation of such branched polycarbonates can be carried out also by means of other processes, such as, e.g., the process which provides the condensation between aromatic dihydroxy-derivatives, phosgene and polyfunctional comonomer, by means of an interfacial reaction, or of a reaction in solution, in one single reaction step. Such polycarbonates can be also obtained by transesterification in the molten state, by reacting the dihydroxyaromatic compound with diaryl-, dialkyl- or alkylaryl-carbonates at temperatures of from 100 to 300°C, in the presence of transesterification catalysts. The branched polycarbonates of the present invention have a molecular weight ranging from 20,000 to 30,000, and are characterized in that they are completely soluble in the usual solvents of the linear polycarbonate, and show a high dependence of the melt viscosity from the shear rate. Such polycarbonates are hence well suitable for being processed both by the injection-moulding technique, typical of the linear polycarbonates, and by, e.g., extrusion. Due to the excellent stability of the molten mass, such polycarbonates are particularly well suitable for being transformed by the blow-moulding method, for the production of hollow bodies. The reactivity of the polyfunctional comonomer used as the branching agents is such that an amount of from 0.01 to 1.5 mol of such comonomer per each 100 mol of aromatic dihydroxy-compound are enough for reaching such a crosslinking degree that the shear-sensitivity has values always higher than 15. For the characterization of the branched polycarbonates according to the present invention, the following methods were used: Intrinsic Viscosity - the intrinsic viscosity is determined in methylene chloride at 20°C by means of an Ubbelhode viscometer and is expressed as dl/g. Shear Sensitivity - the evaluation of this quantity is carried out on the melt-indexer, under loads of from 2.16 to 21.6 kg, at 260°C, according to ASTM D 1238. Impact Resistance (120D). - The impact resistance is measured on specimens with notch, at 0°C, according to ASTM D 256. The following examples are illustrative and not limitative of the same invention. Example 1 Preparation of 4,4'-Methylene-3,3'-hydroxy-2,2'-chlorocarbonyl-bis-naphthalene) To a flask of 250 ml of capacity, 20.0 g (51 mmol) of 4,4'-methylene-3,3'-hydroxy-2,2'-carboxy-bis-naphthalene (pamoic acid), 21.2 g (102 mmol) of phosphorus pentachloride and 145 ml of thionyl chloride are charged: the mixture is refluxed, with stirring, for 5 hours. The reaction kinetics can be monitored by I.R. spectroscopy, by observing the disappearance of the absorption band around 1,660 cm⁻¹, and the contextual appearance of a wider band at 1,760:1,780 cm⁻¹. When the reaction has subsided, the precipitated product is recovered by filtration, and is then thoroughly washed with ethyl ether and is dried. Said product us a solid of white colour. The yield is of 40%. Elemental Analysis : Cl = 17.2% (C₁₃H₁₄O₄Cl₂ requires: Cl = 16.7% The equivalent weight and molecular weight values (chloride titration) are in good agreement with the proposed formula. The other hemichlorinated methylene-bis-naphthalene derivatives corresponding to formula (I) are prepared by modalities analogous to those as above disclosed. Example 2 To a glass reactor of 3 l of capacity, kept at the controlled temperature of 25°C, 84 g of bisphenol A, 115 mg of pamoic acid (branching agent, equivalent to 0.08% by mol, relatively to bisphenol), 65.2 g of sodium hydroxide dissolved in 650 ml of water, 20 mg of sodium dithionite (as a reducing agent) and 6.3 ml of an 0.5 N aqueous solution of triethylamine are charged under nitrogen. Then, 2.7 g of p-tert.butyl-phenol dissolved in 1,300 ml of methylene chloride is added, and through the mixture 44 g of phosgene gas is bubbled, within a 30-minute time, with vigorous stirring. The reaction is continued for 2 hours, with aqueous sodium hydroxide (at 20% by weight) being added for the purpose of maintaining a pH value higher than 11. At the end, the reaction mixture is diluted with 500 ml of methylene chloride, and the organic phase is separated and successively washed with 300 ml of water (twice), 800 ml of 0.15 N aqueous sodium hydroxide (three times), 600 ml of water (twice), 800 ml of 0.1 N hydrochloric acid and, finally, with portions of 600 ml of water until neutrality. At the end, the polymer is recovered by distilling of the organic solvent, is dried and ground until a powder is obtained. The branched polycarbonate displays the following characteristics: Intrinsic Viscosity = 0.571 dl/g; Shear Sensitivity = 20.0; IZOD Impact Resistance = 821 j/m. Example 3 An amount of 243 g of chloroformyl-capped polycarbonate oligomers (number average molecular weight = 826, chloroformyl end groups = 2,300 meq/kg; hydroxy end groups = 121 meq/kg), prepared from bisphenol A, phosgene and p-tert.butyl-phenol and dissolved in 900 ml of methylene chloride, is charged, under nitrogen, to a glass reactor of 2.5 l of capacity, kept at the controlled temperature of 25°C. With the above solution bein kept mechanically stirred, by means of a magnetic-anchor stirrer (300 rpm), to it 50 ml of water containing 490 mg of pamoic acid (branching agent, equivalent to 0.12% by mol relatively to total bisphenol A), 1.0 g of sodium hydroxide, 31mg of sodium dithionite and 5 ml of an 0.05 N aqueous solution of triethylamine are added in the order shown. Forty minutes later, 300 ml of water is added, containing 54.0 g of bisphenol A and 20 g of sodium hydroxide and, then, 92 ml of an aqueous solution of sodium hydroxide at 20% (by weight) is charged over a 10-minute time, by using a metering pump. After 140 minutes, the mixture is poured into 2,200 ml of methylene chloride; the organic phase is subsequently separated and washed, in the order, with 450 ml of water (twice), 1,300 ml of 0.15 N aqueous sodium hydroxide (3 times), 900 ml of water (twice), 1,300 ml of 0.1 N hydrochloric acid, and, finally, with portions of 900 ml of water, until neutrality. The branched polycarbonate, isolated by means of the usual methodology, shows the following characteristics: Intrinsic Viscosity = 0.563 dl/g; Shear Sensitivity = 18.6; IZOD Impact Resistance = 806 j/m. Example 4 The process is carried out by the same operative modalities and amounts of reactants as of Example 3, except that 980 mg of pamoic acid (0.24% by mol relatively to total bisphenol A) is added. The branched polycarbonate obtained has the following characteristics: Intrinsic Viscosity = 0.589 dl/g; Shear Sensitivity = 22.7; IZOD Impact Resistance = 830 j/m. Example 5 The process is carried out by the same operative modalities as of Example 3, except that 540 mg of 4,4'-methylene-3,3'-hydroxy-2,2'-chlorocarbonyl-bis-naphthalene) (0.12% by mol relatively to total bisphenol A) is added. The branched polycarbonate obtained has the following characteristics: Intrinsic Viscosity = 0.542 dl/g; Shear Sensitivity = 18.8; IZOD Impact Resistance = 810 j/m. Example 6 The process is carried out by the same operative modalities as of Example 3, except that 1.08 g of 4,4'-methylene-3,3'-hydroxy-2,2'-chlorocarbonyl-bis-naphthalene) (0.24% by mol relatively to total bisphenol A) is added. The branched polycarbonate obtained has the following characteristics: Intrinsic Viscosity = 0.549 dl/g; Shear Sensitivity = 20.0; IZOD Impact Resistance = 830 j/m.

Claims: Claims for the following Contracting States : BE, CH, DE, FR, GB, GR, LI, LU, NL, SE Blow-mouldable branched polycarbonates produced from an aromatic dihydroxy compound, phosgene or a dialkyl-, diaryl-, or alkylaryl carbonate, and a compound having the formula: wherein R₁ and R₂ are equal to, or different from one another, and represent -COOH or -COCl. Blow-mouldable branched polycarbonates according to Claim 1, wherein the compound of formula (I) is selected from: 4,4'-methylene-3,3'-hydroxy-2,2'-carboxy-bis-naphthalene; 4,4'-methylene-3,3'-hydroxy-2-carboxy-2'-chlorocarbonyl-bis-naphthalene, and 4,4'-methylene-3,3'-hydroxy-2,2'-chlorocarbonyl-bis-naphthalene Blow-mouldable branched polycarbonates according to Claim 1, wherein the compound of formula (I) is present in an amount of from 0,01 mol to 1,5 mol per 100 mol of the aromatic dihydroxy compound. Process for preparing the blow-mouldable branched polycarbonates as defined in Claim 1, comprising the steps of: a) Preparing a chloroformyl-capped oligomer, by reacting phosgene and a dihydroxyaromatic compound having the formula: wherein R, if present, is selected from: a substituted or unsubstituted alkyl containing up to 5 carbon atoms; or -O-, or -S-, or SO₂-; x and y , equal to, or different from one another, are -H, -CH₃ or a halogen atom, and m and n , equal to, or different from one another, are within the range of 1 to 4; b) Condensing the thus obtained oligomer with the compound of formula (I) of Claim 1; c) Adding the dihydroxyaromatic compound of formula (II) and carrying out the polycondensation reaction, and d) Recovering the blow-mouldable branched polycarbonate from the reaction mixture. Process according to Claim 4, wherein the dihydroxyaromatic compound of formula (II) is selected from: 4,4'-dihydroxybiphenyl; 2,2-bis(4-hydroxyphenyl)propane; 2,2-bis(3,5-dichloro-4-hydroxyphenyl)propane; 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane, and bis(4-hydroxyphenyl)methane. Process according to Claim 4, wherein step (a) is carried out in a biphasic water/organic solvent medium and in the presence of a monofunctional phenol as a molecular-weight controlling agent, the thus produced oligomers having a molecular weight of from 400 to 2.000. Process according to Claim 6, wherein the organic solvent is methylene chloride and the monofunctional phenol is selected from phenol, p-isopropyl phenol and p-tert.butyl phenol. Process according to Claim 4, wherein step (b) is carried out in a biphasic water/organic solvent medium and in the presence of a phase-transfer catalyst, and the compound of formula (I) of Claim 1 is selected from: 4,4'-methylene-3,3'-hydroxy-2,2'-carboxy-bis-naphthalene; 4,4'-methylene-3,3'-hydroxy-2-carboxy-2'-chlorocarbonyl-bis-naphthalene, and 4,4'-methylene-3,3'-hydroxy-2,2'-chlorocarbonyl-bis-naphthalene Process according to Claim 8, wherein step (b) is carried out with methylene chloride as the organic solvent, and a tertiary amine as the phase-transfer catalyst. Claims for the following Contracting States : AT, ES Process for preparing blow-mouldable branched polycarbonates from an aromatic dihydroxy compound, phosgene or a dialkyl-, diaryl-, or alkylaryl carbonate, and a compound having the formula: wherein R₁ and R₂ are equal to, or different from one another, and represent -COOH or -COCl , characterized in that it comprises the steps of: a) Preparing a chloroformyl-capped oligomer, by reacting phosgene and a dihydroxyaromatic compound having the formula: wherein R, if present, is selected from: a substituted or unsubstituted alkyl containing up to 5 carbon atoms; or -O-, or -S-, or -SO₂-; x and y , equal to, or different from one another, are -H, -CH₃ or a halogen atom, and m and n , equal to, or different from one another, are within the range of 1 to 4; b) Condensing the thus obtained oligomer with the compound of formula (I) of Claim 1; c) Adding the dihydroxyaromatic compound of formula (II) and carrying out the polycondensation reaction, and d) Recovering the blow-mouldable branched polycarbonate from the reaction mixture. Process according to Claim 1, characterized in that the dihydroxyaromatic compound of formula (II) is selected from: 4,4'-dihydroxybiphenyl; 2,2-bis(4-hydroxyphenyl)propane; 2,2-bis(3,5-dichloro-4-hydroxyphenyl)propane; 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane, and bis(4-hydroxyphenyl)methane. Process according to Claim 1, characterized in that step (a) is carried out in a biphasic water/organic solvent medium and in the presence of a monofunctional phenol as a molecular-weight controlling agent, the thus produced oligomers having a molecular weight of from 400 to 2.000. Process according to Claim 3, characterized in that the organic solvent is methylene chloride and the monofunctional phenol is selected from phenol, p-isopropyl phenol and p-tert.butyl phenol. Process according to Claim 1, characterized in that step (b) is carried out in a biphasic water/organic solvent medium and in the presence of a phase-transfer catalyst, and the compound of formula (I) of Claim 1 is selected from: 4,4'-methylene-3,3'-hydroxy-2,2'-carboxy-bis-naphthalene; 4,4'-methylene-3,3'-hydroxy-2-carboxy-2'-chlorocarbonyl-bis-naphthalene, and 4,4'-methylene-3,3'-hydroxy-2,2'-chlorocarbonyl-bis-naphthalene Process according to Claim 5, characterized in that step (b) is carried out with methylene chloride as the organic solvent, and a tertiary amine as the phase-transfer catalyst.

Inventors: PETRI, ALBERTO
Applicants: ECP ENICHEM POLIMERI S.R.L.
Application year: 1987
Main classification: C08G64
IPC codes: C08G64