BRANCHED POLYCARBONATES CONTAINING 2,4,6-TRIS(4'-HYDROXYARYL)-AMINO-S-TRIAZINES

Abstract: Branched, soluble, high-molecular-weight, thermoplas­ tic polycarbonates having improved properties, and, in particular, suitable to the fabrication by blow-moulding, characterized by the presence in their structure of units deriving from the use in the synthesis of tris(4'-hydrox­ yaryl)-amino-S-triazines having the formula: wherein R₁ and R₂, equal to, or different from each other, indicate hydrogen, linear or branched C 1-5 alkyl, or halogen (in particular, chlorine and bromine).

Description: Polycarbonates are thermoplastic materials which are widely used in several application fields. They are usually prepared by the reaction of a precursor of the carbonate group with a difunctional phenol, and have a linear structure. To the contrary of the most of thermoplastic polymers, linear polycarbonate (PC) has an exclusively Newtonian behaviour, at least for not excessively high values of time rate of strain, and, however, its departures from such a behaviour, at high γ ˙, are not so considerable as it happens for other products. The Newtonian behaviour occurs, as known, whenever η (apparent viscosity) is substantially independent from γ ˙ (time rate of strain). This rheological behaviour can represent a disadvantage when ductility is required to the product, by it being suitable to be fabricated by different technologies. Normally, linear PC is fabricated by injectionmoulding, whilst obtaining a high-quality product by extrusion, or blow-moulding procedures, which are techniques suitable to supply particular fabricated products (alveolar plates, bottles, hollow containers, and so forth) is not practically possible. In the above mentioned techniques, it is in fact necessary that the fluid has an apparent viscosity decreasing with increasing time rate of shear, typical outcome of the non-Newtonian behaviour, so to be able to differentiate the status of molten polymer at two sequential times: at a first time, when the molten polymer is inside the fabrication machine (e.g., inside the extruder), and at a subsequent time, at which the product leaves it (e.g., through the die of the same extruder). During the first step, the time rates of strain the fluid is submitted to, are high, and vice-versa, its apparent viscosity is low, so that the processing thereof results made easier; at the moment of the outlet thereof from the extruder, to the contrary, low γ ˙'s and high viscosities prevail, this occurrence preventing the product from collapsing, and allowing the manufactured item to display a good dimensional stability. The non-Newtonian behaviour of the molten polymer has a considerable influence on two further properties thereof, the elasticity of the molten polymer, viz. the melt elasticity, and the melt strength, which too are very important from the viewpoint of the extrusion and blow-moulding techniques of fabrication. The melt elasticity consists substantially in the capability of the non-Newtonian fluid of swelling, when emerging from the die, to a greater extent than a non-Newtonian fluid, as a consequence of a greater recovery of elastic energy in its interior, thanks to a greater distortion and molecular orientation under the action of a shear stress. The above results in an increase in product fabricability, due to a higher flexibility and ductility of the material. The second property indicated, i.e., the melt strength, becomes vice-versa significant at the moment at which the molten product comes out from the fabrication machine. It can be considered as the toughness of the polymer in the molten state, i.e., the capability shown by this to stand the stress. If, indeed, the molten mass is not able to support its own weight, the extrudate collapses and, as a consequence, obtaining the desired shapes of the manufactured item is not possible. From the above, it results clear that the polymers which are characterized by a non-Newtonian behaviour, display two basic properties, which allow them to be fabricated by extrusion and/or blow-moulding processes: high easiness of processing inside the machine (low apparent viscosity for high γ ˙'s and high melt elasticity) and very good performance when leaving the same (high apparent viscosity for low γ ˙ and considerable melt tenacity). Polycarbonates having rheological non-Newtonian properties can be easily prepared by the use of polyfunctional comonomers containing three or more reactive groups, so to obtain a structure characterized by the presence of branchings of random type. For example, in U.S.-A-2,950,266, the synthesis is disclosed of products of this type, carried out by using phloroglucinol as the polyfunctional comonomer. According to the finding illustrated in the present invention, preparing branched polycarbonates, characterized by excellent rheological properties which allow them to be fabricated by blow-moulding techniques is possible as well, by using, as the branching agents, 2,4,6-tris(4'-hydroxyaryl)-amino-S-triazines. In FR-A-2 200 308 branching groups are introduced into polycarbonates by using trihalogeno-S-triazines. These compounds show the advantage of having a reactivity at all comparable to that of the aromatic dihydroxyderivatives and they allow hence considerably branched polycarbonates to be obtained, even if they are used in amounts relatively minor, and considerably lower than those necessary in case of phloroglucinol. An object of the present invention is hence a method for the production of branched, soluble, high-molecular-weight polycarbonates, particularly suitable to be fabricated by blow-moulding. Such a method consists either in the condensation between possibly halogenated aromatic dihydroxyderivatives, or mixtures thereof, and phosgene, or precursors of carbonate group, or oligomers of polycarbonate containing chloroformyl groups, by interfacial reaction, or by reaction in solution, at temperatures comprised within the range of from 15 to 80°C, in the presence of a monovalent aromatic hydroxy compound; or in the transesterification between the same aromatic dihydroxyderivatives and alkyl, aryl or alkylaryl diesters of carbonic acid in the molten state, at temperatures comprised within the range of from 100 to 300°C; each of these methods being carried out in the presence of 0.05-5 mol% (relative to the aromatic dihydroxyderivative) of 2,4,6-tris(4'-hydroxyaryl)-amino-S-triazines, as the branching agents, corresponding to the following formula: wherein R₁ and R₂, equal to, or different from each other, indicate hydrogen, linear or branched C 1-5 -alkyl, or halogen (in particular, chlorine and bromine). Also the polycarbonates obtained according the method as herein disclosed are an object of the present invention. 2,4,6-Tris(4-hydroxyaryl)-amino-S-triazines can be prepared, for example, by the reaction between cyanuryl chloride and aminophenols (and derivatives thereof) according to known processes, typical of the inorganic chemistry. Examples of such compounds are described in Chemical Abstract 81 79232f and in US-A-2 393 755. Examples of these compounds are: 2,4,6-tris(4'-hydroxyphenyl)-amino-S-triazine (R₁ = R₂ = H); 2,4,6-tris(3'-methyl-4'-hydroxyphenyl)-amino-S-triazine (R₁ = CH₃, R₂ = H); 2,4,6-tris(3',5'-dimethyl-4'-hydroxyphenyl)-amino-S-triazine (R₁ = R₂ = CH₃); 2,4,6-tris(3'-chloro-4'-hydroxyphenyl)-amino-S-triazine (R₁ = Cl, R₂ = H); 2,4,6-tris(3',5'-dichloro-4'-hydroxyphenyl)-amino-S-triazine (R₁ = R₂ = Cl); 2,4,6-tris(3'-bromo-4'-hydroxyphenyl)-amino-S-triazine (R₁ = Br, R₂ = H); 2,4,6-tris(3',5'-dibromo-4'-hydroxyphenyl)-amino-S-triazine (R₁ = R₂ = Br); 2,4,6-tris(3'-chloro-4'-hydroxy-5'-methylphenyl)-amino-S-triazine (R₁ = Cl,R₂ = CH₃); 2,4,6-tris(3'-bromo-4'-hydroxy-5'-methylphenyl)-amino-S-triazine (R₁ = Br,R₂ = CH₃); The aromatic dihydroxycompounds which can be used in the practical embodiment of the present invention are represented by the following formula: wherein R is a substituted or not-substituted alkyl group containing from 0 to 5 carbon atoms, -O-, -S-, -SO2, -CO-; X and Y are equal to or different from each other, and equivalent to H, CH₃ or halogens, m and n are integers, equal to or different from each other, ranging from 1 to 4. Typical examples of such compounds are: 4,4'-dihydroxy diphenyl; 2,2-bis-(4-hydroxyphenyl)-propane (bisphenol A); 2,2-bis-(4-hydroxyphenyl)-methane; 2,2-bis-(3,5-dichloro-4-hydroxyphenyl)-propane; 2,2-bis-(3,5-dimethyl-4-hydroxyphenyl)-propane; and so forth. Divalent compounds with one aromatic ring only, such as resorcinol, hydroquinone and pyrocatechol, as well as mixtures of all the compounds mentioned can be used as well. To the purpose of regulating the molecular weight of the resulting polycarbonate, such monohydroxy compounds as, for example, phenol, p-isopropylphenol, p-tert.butylphenol, etc., can be used. The branched polycarbonates of the present invention can be prepared according to one of the polycondensation methods reported in the prior art. For example, the polyfunctional comonomer (branching agent), together with the dihydroxyaryl derivative, is dissolved in an aqueous solution of sodium hydroxide, and to such a mixture an organic solvent immiscible with water, such as, e.g., dichloromethane, is added. Through the mixture, gaseous phosgene is bubbled, in the presence of a regulator of molecular weight, such as, e.g., a monofunctional phenol, and of a phase transfer catalyst, for example, a tertiary amine, and the reaction mixture is maintained at a temperature comprised within the range of from 15 to 25°C for a time ranging from 1 to 6 hours. The branched polycarbonate so obtained is isolated, with high yields, after washing of the organic phase, by known techniques and distillation of the solvent, or precipitation by a non-solvent. An alternative route for carrying out the method consists in first preparing chloroformyl-terminated oligomers of polycarbonates, by interfacial reaction between phosgene and the dihydroxyaryl compounds dissolved in aqueous-alkaline solution, in the presence of an organic solvent. The average molecular weight of the oligomers, preferably comprised within the range of from 400 to 2000, can be determined a priori by the use of monofunctional phenols. After the separation of the two phases, the organic solution containing the chloroformyl-terminated oligomers is submitted to interfacial condensation in the presence of the branching agent. The branched polycarbonate to obtained is purified as indicated in the hereinabove reported methodology. Introducing into the aqueous phase such reducing agents as, for example, sodium hyposulphite is recommended, to the purpose of preventing the formation of coloured byproducts. A further possibility for achieving the branched polycarbonates consists in resorting to the known methodology of polycondensation in solution: in this case, phosgene is bubbled through a solution of methylene chloride and pyridine containing the molecular weight regulator (monofunctional phenol), the dihydroxyaryl derivative and the polyfunctional compound as the branching agent of the present invention. The polycarbonate so obtained is then directly isolated, with high yields, by distillation of the solvent, or by precipitation by a non-solvent. The mixture of diphenolic and triphenolic compounds (branching agents) can be converted into a high-molecular-weight/branched polycarbonate also by the method of transesterification in the molten state, by reaction with dialkyl-, diaryl- or alkylaryl carbonates, at temperatures comprised within the range of from 100 to 300°C, and in the presence of transesterification catalysts as alkali metals and their oxides, alkoxides of transition metals, or the like. In this case, the polymerization degree is controlled not by the presence of regulators of molecular weight, but by the efficiency of the removal of the byproducts and by the stirring of the molten mass. The high-molecular-weight branched polycarbonates obtained, according to the scope of the present invention, by any of the methods as disclosed, are characterized by the complete solubility in the usual solvents of the linear polymer, and by a strong dependence of the melt viscosity from the time rate of strain. In fact, the shear sensitivity, which is the ratio of the flow rates of the molten polymer at two different values of shear stresses and, hence, an indirect measurement of the non-Newtonian behaviour of the polymer, has values always higher than 15, whilst the linear polycarbonate has values around 12-13. The polycarbonates prepared according to the present invention are suitable to be fabricated both by extrusion and injection-moulding processes. Furthermore, due to the effect of the excellent dimensional stability of the molten mass, they can be processed also by the blow-moulding method for the production of hollow bodies. Finally, thanks to their rheological characteristics, from them extruded sheets having good mechanical properties and with higher resistance to streses can be easily obtained. For the characterization of the branched polycarbonates prepared according to the present invention, the following procedures have been used: Intrinsic Viscosity . It is measured in methylene chloride at 20°C by the Ubbelhode viscometer, and is expressed as dl/g; Shear Sensitivity . The evaluation 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 Test; Impact Strength (IZOD) . This characteristic is evaluated on notched bars at 0°C, according to ASTM D 256. Example 1 Preparation of 2,4,6-tris(4'-hydroxyphenyl)-amino-S-triazine To a solution of 62.1 g (570 mmol) of p-aminophenol in 550 ml of acetone, 150 ml of the same solvent, containing 17.5 g (95 mmol) of cyanuryl chloride is added dropwise over a 1-hour time. The reaction mixture is kept boiling (at about 56°C) for a further three hours. 36.8 g of product, 2,4,6-tris-(4'-hydroxyphenyl)-amino-S-triazine, is then obtained by precipitation with water and subsequent washings with the same non-solvent (yield = 96.3%). The values of equivalent weight (titration of aromatic hydroxy groups), molecular weight (V.P.O. and M5) and the molecular structure (N.M.R.) are in compliance with the proposed formula. The compound melts at 301°C (D.S.C.). The other derivatives of the class of 2,4,6-tris(4-hydroxyaryl)-amino-S-triazine are prepared by modalities analogous to those as described above. Example 2 Into a 3-l glass reactor, kept at the controlled temperature of 25°C, 84 g of bisphenol A, 370 mg of 2,4,6-tris(4'-hydroxyphenyl)-amino-S-triazine (0.25% by mol relatively to bisphenol), 65.2 g of sodium hydroxide dissolved in 650 ml of water, 20 mg of sodium hyposulphite (as the reducing agent) and 6.3 ml of an aqueous solution of 0.5 N triethylamine are charged under nitrogen. Then, 2.7 g of p-tert.butylphenol dissolved in 1300 ml of methylene chloride is added and into the mixture, kept under vigorous stirring, 44 g of gaseous phosgene is bubbled over 30 minutes. The reaction is made proceed 2 hours, with aqueous sodium hydroxide (at 20% by weight) being added as needed to maintain the pH value above 11. At the end, the reacted mass is diluted with 500 ml of methylene chloride, and the organic phase is separated and subsequently washed with 300 ml of water (twice), 800 ml of 0.15 N aqueous sodium hydroxide (3 times), 600 ml of water (twice), 800 ml of 0.1 N hydrochloric acid, and finally with portions of 600 ml of water up to neutrality. At the end, the polymer is recovered by distillation of the organic solvent, is dried and milled up to obtain a powder. The branched polycarbonate has the following characteristics: intrinsic viscosity = 0.521 dl/g; shear sensitivity = 22.3 IZOD impact strength = 829 J/m. Example 3 212g of chloroformyl-terminated polycarbonate oligomers (numerical molecular weight = 590, chloroformyl terminal groups = 2780 meq/kg, terminal hydroxy groups = 490 meq/kg), prepared from bisphenol A, phosgene and p-tert.butylphenol and dissolved in 900 ml of methylene chloride, are charged, under nitrogen, into a 2.5-l glass reactor kept at the controlled temperature of 25°C. Under mechanical stirring by a magnetic-anchor stirrer (300 rpm), to them 50 ml of water containing 720 mg of 2,4,6-tris(4'-hydroxyphenyl)-amino-S-triazine (0.2% by mol relatively to total bisphenol A), 4.5 of NaOH and 31 mg of sodium hyposulphite and 5 ml of 0.05 N aqueous solution of triethylamine are then added in the order as listed. Thereafter, 97 ml of an aqueous solution of NaOH at 20% (by weight) is then added over a 10-minutes time, by using a metering pump, and, 30 minutes later, 300 ml of water containing 48.1 g of bisphenol A and 17 g of NaOH are then added. Three hours later, the mixture is poured into 2200 ml of methylene chloride. The organic phase is then separated and washed, in the order, with 450 ml of water (twice), 1300 ml of 0.15 N aqueous sodium hydroxide (3 times), 900 ml of water (twice), 1300 ml of 0.1N hydrochloric acid and, finally, with portions of 900 ml of water up to neutrality. The branched polycarbonate, isolated by the usual methodology, has the following characteristics: intrinsic viscosity = 0.483 dl/g; shear sensitivity = 16.0 IZOD impact strength = 821 J/m. Example 4 Example 3 is repeated with the same operating modalities and amounts of reactants, with the exception that added is 1.45 g of 2,4,6-tris(4'-hydroxyphenyl)-amino-S-triazine (0.4% by mol relatively to total bisphenol A). The branched polycarbonate obtained has the following characteristics: intrinsic viscosity = 0:599 dl/g; shear sensitivity = 21.4 IZOD impact strength = 826 J/m. Example 5 Example 3 is repeated with the same operating modalities and amounts of reactants, with the exception that added is 2.90 g of 2,4,6-tris(4'-hydroxyphenyl)-amino-S-triazine (0.8% by mol relatively to total bisphenol A). The branched polycarbonate obtained has the following characteristics: intrinsic viscosity = 0.510 dl/g; shear sensitivity = 22.9 IZOD impact strength = 828 J/m.

Claims: Claims for the following Contracting States : BE, CH, DE, FR, GB, LI, LU, NL, SE Branched polycarbonate characterized by the presence in its structure of units deriving from tris(4'-hydroxyaryl)-amino-S-triazines having the general formula (I): wherein R₁ and R₂, equal to, or different from each other, indicate hydrogen, linear or branched alkyl containing from 1 to 5 carbon atoms, or halogen. Branched polycarbonate according to claim 1, characterized in that the compound having general formula (I) is present in an amount comprised within the range of from 0.05 to 5 mol% relatively to the aromatic dihydroxy derivative. Branched polycarbonate according to claim 1, characterized in that the compound having general formula (I) is preferably selected among: 2,4,6-tris(4'-hydroxyphenyl)-amino-S-triazine (R₁ = R₂ = H); 2,4,6-tris(3'-methyl-4'-hydroxyphenyl)-amino-S-triazine (R₁ = CH₃, R₂ = H); 2,4,6-tris(3',5'-dimethyl-4'-hydroxyphenyl)-amino-S-triazine (R₁ = R₂ = CH₃); 2,4,6-tris(3'-chloro-4'-hydroxyphenyl)-amino-S-triazine (R₁ = Cl, R₂ = H); 2,4,6-tris(3',5'-dichloro-4'-hydroxyphenyl)-amino-S-triazine (R₁ = R₂ = Cl); 2,4,6-tris(3'-bromo-4'-hydroxyphenyl)-amino-S-triazine (R₁ = Br, R₂ = H); 2,4,6-tris(3',5'-dibromo-4'-hydroxyphenyl)-amino-S-triazine (R₁ = R₂ = Br); 2,4,6-tris(3'-chloro-4'-hydroxy-5'-methylphenyl)-amino-S-triazine (R₁ = Cl,R₂ = CH₃); 2,4,6-tris(3'-bromo-4'-hydroxy-5'-methylphenyl)-amino-S-triazine (R₁ = Br,R₂ = CH₃); Process for the preparation of branched polycarbonate characterized in that in it, as the branching agent, a compound is used, having the general formula (I): wherein R₁ and R₂, equal to, or different from each other, indicate hydrogen, linear or branched alkyl containing from 1 to 5 carbon atoms, or halogen. Claims for the following Contracting State : AT Process for preparing Branched polycarbonate characterized in that in it, as the branching agent, a compound is used, deriving from tris(4'-hydroxyaryl)-amino-S-triazines, having the general formula (I): wherein R₁ and R₂, equal to, or different from each other, indicate hydrogen, linear or branched alkyl containing from 1 to 5 carbon atoms, or halogen. Process according to claim 1, characterized in that the compound having general formula (I) is present in an amount comprised within the range of from 0.05 to 5 mol% relatively to the aromatic dihydroxy derivative. Process according to claim 1, characterized in that the compound having general formula (I) is preferably selected among: 2,4,6-tris(4'-hydroxyphenyl)-amino-S-triazine (R₁ = R₂ = H); 2,4,6-tris(3'-methyl-4'-hydroxyphenyl)-amino-S-triazine (R₁ = CH₃, R₂ = H); 2,4,6-tris(3',5'-dimethyl-4'-hydroxyphenyl)-amino-S-triazine (R₁ = R₂ = CH₃); 2,4,6-tris(3'-chloro-4'-hydroxyphenyl)-amino-S-triazine (R₁ = Cl, R₂ = H); 2,4,6-tris(3',5'-dichloro-4'-hydroxyphenyl)-amino-S-triazine (R₁ = R₂ = Cl); 2,4,6-tris(3'-bromo-4'-hydroxyphenyl)-amino-S-triazine (R₁ = Br, R₂ = H); 2,4,6-tris(3',5'-dibromo-4'-hydroxyphenyl)-amino-S-triazine (R₁ = R₂ = Br); 2,4,6-tris(3'-chloro-4'-hydroxy-5'-methylphenyl)-amino-S-triazine (R₁ = Cl,R₂ = CH₃); 2,4,6-tris(3'-bromo-4'-hydroxy-5'-methylphenyl)-amino-S-triazine (R₁ = Br,R₂ = CH₃).

Inventors: PETRI, ALBERTO
Applicants: ENICHEM TECNORESINE S.P.A.
Application year: 1986
Main classification: C08G64
IPC codes: C08G63, C08G64