Polyamide polycarbonate block copolymer

Abstract: Polyamide-carbonate block copolymers are made by admixture of polyamides with carbonate polymers containing carboxyl groups or an ester groups capable of elimination to form carboxyl groups, in the presence of a polyepoxy linking agent, such as triglycidyl isocyanurate. Such block copolymers may be used as thermoplastics or as blending agents for polyamides and carbonate polymers.

Description: BACKGROUND OF THE INVENTION Field of the Invention The invention is directed to compatible blends of polyamides and aromatic carbonate polymers useful as thermoplastics, and methods for making such compatible blends. Brief Description of the Prior Art Much effort has been expended on the problem of blending polyamides (especially nylons) with aromatic carbonate polymers (especially polycarbonates). Such blends and alloys are particularly useful for achieving simultaneously the good impact strength and dimensional stability characteristic of the carbonate polymers and the good solvent resistance, toughness, ease of processing and resistance to environmental stress cracking characteristic of the polyamides. These two classes of polymers are normally not miscible, at least not without unacceptible delamination. In order to achieve miscibility and to obtain useful blends which exhibit no tendency to delaminate, various strategems have been used. One method is to utilize a relatively more compatible type of amorphous polyamide as taught by Maresca et al., U. S. Pat. 4,798,874 (Jan. 1989). Another method is to compatibilize a polyamide with a polycarbonate or polyester carbonate by use of an effective amount of a polyamide-polyester block copolymer as taught by Maresca et al. in U. S. Pats. 4,788,248-9 (Nov. 29, 1988), or by use of an effective amount of a polyetherimide, a polyurethane or certain linear segmented thermoplastic elastomers as taught by Perren et al. in U. S. Pat. 4,782,114 (Nov. 1, 1988). It has also been shown by Maresca, Eur. Pat. 227053 (July 1, 1987) that a compatibilizing agent with epoxy functional groups is useful for compatibilizing a polyamide with a carbonate polymer. However, this effect is not as complete as desired because the usual carbonate polymer lacks functional groups for chemical interaction with the epoxy compatibilizing agent. In order to make this type of polyamide/polycarbonate block copolymer required as a compatibilizing agent, it it necessary to find a means of creating a functionalized polycarbonate onto which the polyamide segment can be attached by means of the functional chain ends of the polyamide, which are normally carboxyl and amino groups. Normally, aromatic carbonate polymers lack functional end groups. It is however known that aromatic carbonate polymers can be made having carboxyl end groups or ester side groups. The present invention offers an effective and convenient means for attaching the carboxyl or ester end groups of such an aromatic carbonate polymer to the end groups of the polyamide (polyamide), thus providing a graft polyamide-polycarbonate for use as such as a thermoplastic or for use as a compatibilizing agent in blending of polyamides with aromatic carbonate polymers. SUMMARY OF THE INVENTION The present invention provides a process for preparing block copolymers of polyamides and aromatic carbonate polymers which comprises reacting for 0.1 minute to 1 hour at a temperature of 100° to 400°C. a dry blend of (a) a polyamide, (b) a thermoplastic aromatic carbonate polymer containing (i) a carboxy or ester-terminated end group, or (ii) a carboxy or ester side chain, the ester group being capable of forming a carboxyl group under the reaction conditions, and (c) 0.1 to 10%, based on the total weight of components (a) and (b), of a polyepoxy compound selected from O- or N-epoxyalkyl-substituted cyclic amides, imides and imidates. The invention further provides a method for compatibilizing polyamides and carbonate polymers by admixing them with a compatibilizing amount of the block copolymer of the invention. DETAILED DESCRIPTION OF THE INVENTION The polyamides suitable for use in practicing the invention are described in col. 6 line 53 to col. 8 line 51 of Maresca et al., U. S. Pat. 4,798,874 (Jan. 17, 1989). Preferred polyamides are those crystalline polyamides whose blends with polycarbonates will provide a beneficial balance of overall properties and amorphous polyamides that provide transparent blends with polycarbonates. Especially preferred polyamides for use in the present invention are amorphous polyamide nylon 6,I and the crystalline polyamides nylon 6 and nylon 6,6. It is generally recognized that polyamides have amino and carboxyl end groups and it is either or both of such end groups that provide the reactive sites fob the polyamide in the context of the present invention. Polymers suitable as reactant polymer (b) in the composition and process of the invention preferably contain end groups of the formula -O-R¹-O-C(=O)-O-A¹ wherein each R¹ is independently a divalent aliphatic, alicyclic or aromatic radical and A¹ is a carboxylic acid-substituted phenoxy group or a functional derivative thereof. By a functional derivative is meant a derivative which under reaction conditions of the invention, forms a carboxylic acid group as an end group; an example is the tertiary-butyl ester which eliminates isobutylene to form a carboxylic acid. Further illustration of such carboxyl-functionalized polycarbonates is provided by U. S. Patent 4,853,458. As a less preferred alternatives for component (b), the present invention can make use of carbonate polymers which have carboxyl side groups or ester side groups which can convert to carboxyl under the conditions of the invention. One such group of acid side group carbonate polymers is the class of copolyester-carbonate resins containing in the polymer chain at least one divalent moiety of the formula: wherein m and n are 0 or 1 and the sum of m plus n equals 1, or of the formula: wherein m and n are as previously defined and each R is independent and is a hydrocarbyl group. These carbonate polymers are further described in U. S. Patent 4,927,914 In component (c) the presence of more than one epoxy group per molecule is essential. At least three of such groups are preferred, by reason of the ease of preparation therefrom of branched polyesters with a minimum of crosslinking and resulting gel formation. Illustrative cyclic nuclei which may be present are the triazine, barbiturate, hydantoin, uracil, pyromellitic diimide, piperazinedione, and parabanate ring systems. The epoxy-containing functionalities are preferably present as substituents on nitrogen atoms. The most suitable compounds are triazine derivatives, including triglycidyl cyanurate and triglycidyl isocyanurate (TGIC). TGIC is particularly preferred because of its availability and particular suitability for use in the present invention. The ratio of the polyamide (a) to the carbonate polymer (b) in the compositions and process of the invention is from 1:10 to 10:1 by weight. The amount of the polyepoxy compound (c) is 0.1 to 10% of the combined weight of the components (a) plus (b). More preferred would be for the amount of the polyepoxy compound to be in the amount of from about 0.2 to about 2% of the combined weight of the components (a) plus (b). It will be evident to one skilled in the art of polymer blending that the optimum amount required will be adjusted to suit the particular choice of polyamide and carbonate polymer and the degree of carboxyl functionality on these two polymers and of amino functionality on the polyamide, so that a sufficient number of the reactive groups on each of (a) and (b) are grafted together by the polyepoxide. Thus, within the ranges taught in the foregoing, the optimum amount of polyepoxide will be readily found by the compounder making minor adjustments in the amount of (c) dependent on the number of amino and carboxyl functional groups on the polyamide and the number of carboxyl functional groups on the carbonate polymer, and on the extent of grafting that is desired for the particular application. The process of the invention consists in causing the three ingredients (a), (b) and (c) to react, specifically to cause the coupling of (a) and (b) by way of the epoxy-ring-opened moiety derived from (c). This will take place by admixing (a), (b) and (c) at temperatures in the range of 100 to 400 degrees C (preferably by melt blending in an extruder or other high torque blending device at 250 to 350 degrees C) for times from 0.1 minute to one hour (preferably for times typical of extrusion which are from 0.5 minutes to 20 minutes). The components may be first mixed by dry blending; an option in the blending is to blend one of the ingredients first with another of the ingredients to make a concentrate, and then to blend the third ingredient. In the case of the present invention, since TGIC is somewhat hazardous, it is often found best to blend it with one of the polymer ingredients (a) or (b) to make a relatively easily handled concentrate, which is then conveniently blended with the other polymer ingredient, as described in European Patent Application 89 311,681 filed Aprl 19, 1989. The completion of the reaction can be noted when an essentially stable rheology is observed, exhibiting elasticity but with enough flow to indicate the absence of gellation, such rheology being characteristic of a high molecular weight branched polymer. In addition to the use of the block copolymers of the invention by themselves as thermoplastics for molding, extruding, coating and the like, they can be used as compatibilizing agents for making delamination-resistant blends of polyamides and carbonate polymers. The polyamides are as hereinabove defined. Suitable carbonate polymers for such blends are aromatic polycarbonates. The method of preparation of aromatic polycarbonates by interfacial polymerization are well known; see for example the details provided in the U.S. Patents 3,028,365; 3,334,154; 3,275,601; 3,915,926; 3,030,331; 3,169,121; and 4,188,314, In general, the method of interfacial polymerization comprises the reaction of a dihydric phenol with a carbonyl halide (the carbonate precursor). Some of the dihydric phenols are represented by the general formula: wherein A is a divalent hydrocarbon radical containing from 1 to 15 carbon atoms; a substituted divalent hydrocarbon radical containing from 1 to 15 carbon atoms and substituent groups such as halogen; -S- ; -SS-; -S(O)- ; -S(O)₂-; -O- : or -C- ; wherein each X is independently selected from the group consisting of hydrogen, halogen, and a monovalent hydrocarbon radical such as an alkyl group of from 1 to 8 carbon atoms, an aryl group of from 6-18 carbon atoms, an aralkyl group of from 7 to 14 carbon atoms, an alkaryl group of from 7 to 14 carbon atoms, an alkoxy group of from 1 to 8 carbon atoms, or an aryloxy group of from 6 to 18 carbon atoms; and wherein m is zero or 1 and n is an integer of from 0 to 5. Typical of the dihydric phenols that can be employed in the practice of the present invention is 2,2-bis(4-hydroxyphenyl)propane (also known as bisphenol-A). Also included within the scope of the present invention are the high molecular weight thermoplastic randomly branched polycarbonates. These randomly branched polycarbonates are prepared by coreacting a polyfunctional organic compound with the aforedescribed dihydric phenols and carbonate precursor. The polyfunctional organic compounds useful in making the branched polycarbonates are set forth in U.S. Pat. Nos. 3,635,895 and 4,001,184. These polyfunctional compounds are generally aromatic and contain at least three functional groups which are carboxyl, carboxylic anhydrides, phenols, haloformyls or mixtures thereof. Some nonlimiting examples of these polyfunctional aromatic compounds include 1,1,1-tri(4-hydroxyphenyl) ethane, trimellitic anhydride, trimellitic acid, trimellitoyl trichloride, 4-chloroformyl phthalic anhydride, pyromellitic acid, pyromellitic dianhydride, mellitic acid, mellitic anhydride, trimesic acid, benzophenonetetracarboxylic acid, benzophenonetetracarboxylic anhydride, and the like. The preferred polyfunctional aromatic compounds are 1,1,1-tri(4-hydroxyphenyl)ethane, trimellitic anhydride or trimellitic acid or their haloformyl derivatives. Also included herein are blends of a linear polycarbonate and a branched polycarbonate. The preferred polycarbonates for use in the blends with polyamides in accordance with the present invention are those derived from bisphenol A and phosgene and having an intrinsic viscosity of about 0.3 to about 1.5 deciliters per gram in methylene chloride at 25°. Such blends are made compatible by admixture of an effective amount of the block copolymer made from components (a), (b) and (c) as described above; an effective amount will typically be in the range of from 2 to 90% by weight, and more preferred from 5 to 50% by weight. The blends of the invention may be further modified by the addition of other types of additives known to the art of plastics compounding. Such additives can include for example fillers (such as clay or talc), reinforcing agents (such as glass fibers), impact modifiers, other resins, antistats, plasticizers, flow promoters and other processing aids, stabilizers, colorants, mold release agents, flame retardants, ultraviolet screening agents, and the like. The invention will be better understood with reference to the following examples. Example 1 A. Preparation of carboxy-terminated polycarbonate A mixture of 29.1 g (128 mmole) of bisphenol A, 65 ml of methylene chloride, 55 ml of water, and 2.58 ml of triethylamine (added in the form of a 5% w/v solution in methylene chloride) and 3.5 mole % of a carboxylated phenol was stirred at room temperature and a 50% aqueous solution of sodium hydroxide was added to bring the pH to 11. Phosgene was then passed through the mixture for 18 minutes at 0.8 g/min, with maintenance of the pH at 11, to provide a 25% excess of phosgene. Additional methylene chloride was added as necessary to control the viscosity. When the reaction was complete, the organic phase was removed and washed once with 7% aqueous hydrochloric acid solution and three times with water. The thus-produced carboxy-functionalized polycarbonate was precipitated into methanol, filtered out, and dried in vacuum. In the case where the carboxyphenol used was p-hydroxybenzoic acid, a polycarbonate of molecular weight 56,000 and Mw/Mn of 5.6 was obtained. This polymer is designated CT-PC in the Table given below. Further descriptions of preparation of this class of carbonate polymer are provided in copending U. S. Patent Application SN 109,873, filed Oct. 14, 1987. B. Preparation of isopropyl diphenolate In a 3-l flask fitted with a Dean-Stark trap were mixed 572 g (2.0 moles) of diphenolic acid, 1500 of isopropanol, and 10 g of toluenesulfonic acid. The mixture was refluxed for 22 hours, with gradual removal of 500 ml of condensate (which, from azeotrope tables, should be 12% water). Then, 1 l of methylene chloride and 1 l of water were mixed into the reaction mixture, and the methylene chloride layer then separated and washed with water until the pH of the washings was 5. Drying over MgSO₄ and removal of solvent yielded 631 g of crystalline solid. Recrystallization of the product from 500 ml of ethyl acetate and washing with three 50 ml portions of ethyl acetate yielded 498 g of powder, mp 128-130.5 o C with nmr indicating the desired isopropyl ester had been obtained. C. Preparation of carbonate polymer with isopropyl diphenolate links in the main chain (ester-side-chain modified carbonate polymer) A 3-l four-neck flask was fitted with a mechanical stirrer, a pH measuring probe, an aqueous caustic inlet tube, and a Claisen adaptor to which was attached a dry ice condenser and a gas inlet tube. To the flask was added 560 ml of water, 680 ml of methylene chloride, 2.8 ml (0.02 mole) of triethylamine, 1.65 g (0.0175 mole, 3.5 mole %) of phenol, 114 g (0.475 mole) of bisphenol A, and 0.025 mole of isopropyl diphenolate (from procedure A. above). With stirring, the pH of the mixture was raised to 10 by addition of 25% aqueous sodium hydroxide, then phosgene was introduced into the flask at 1 g/min for 60 minutes (total of 0.6 mole of phosgene) while maintaining the pH at 9.5 to 11.5. At the end of the reaction, the pH was adjusted to 11. The resin layer was separated from the brine layer, washed with 3 wt.% hydrochloric acid until the washings remained acidic, then washed twice with distilled water. The resin was then precipitated into 3 l of methanol in a Waring blender, then washed with additional methanol and dried. The product was a polycarbonate having an intrinsic viscosity of 0.467 dl/g and a Tg of 146 o C. It contained 5 mole % of the isopropyl ester units derived from the isopropyl diphenolate. This ester-side-group modified carbonate polymer is designated as ESG-PC. Further examples of this class of carbonate polymer are available in copending U. S. Patent Application SN 280,845 filed Dec. 7, 1988. D. Preparation of block copolymers of carbonates and polyamides. Samples were prepared by charging 25 g. each of component A and component B, as well as 0.50 g. of the linking agent (except in comparison runs without the linking agent, into the mixing bowl of a Brabender apparatus. These samples were then melt blended at 300 o C and 150 rpm for 20 minutes. Copolymer analysis was then conducted on the mixtures thus prepared, by running an extraction with chloroform in a Soxhlet extraction system for 13 hours. Before placing in the extraction thimble, samples of 10 g. were ground in a Wiley mill with liquid nitrogen cooling. The copolymer content was determined by the average of the material lost from the extraction thimble and the amount of extracted material recovered from the solution abstract. Since polyamide is insoluble in chloroform, the percent copolymer is based on the percentage amount of polycarbonate in the blend. The properties of the mixed material in the Brabender were also observed as an indication of the occurrence or nonoccurrence of a reaction, and as an indication of the nature of the reaction. For instance, a normal melt means that after mixing, the mixture was of typical viscosity of the components and very sticky. This is behavior indistinguishable from the behavior of carbonate alone. The occurrence of a rubbery melt means that after mixing, the resultant material showed very high melt viscosity, and the melt showed a significant amount of elasticity when removed from the mixing chamber and was non-sticky. The occurrence of a very rubbery melt means that after mixing, the material appeared to be of extremely high melt viscosity and almost but not quite gelled. It showed a high degree of elasticity but deformed in a fluid fashion. This is characteristic of a highly branched thermoplastic. The experimental results on a series of such mixtures are shown in the following Table: Sample No. Component (a) Component (b) Linking Agent % Copolymer Character of melt 1 nylon CT-PC TGIC 43.6 very rubbery 2 nylon ESG-PC TGIC 23.5 rubbery 3 nylon PC TGIC 18.1 rubbery 4 nylon ESG-PC none 0.2 normal melt 5 nylon CT-PC none 25.6,19.1 normal melt 6 nylon CT-PC none 5.0 normal melt 7 nylon CT-PC none 7.4 normal melt 8 nylon nylon TGIC - normal melt Notes to table : CT-PC = carboxy-terminated polycarbonate made in accordance with example 1A above. ESG-PC = ester-side-chain polycarbonate made in accordance with example 1C above. nylon = Zytel 330 amorphous nylon made by DuPont. TGIC = triglycidyl isocyanurate These data show that a copolymer was formed in good yield in the cases where TGIC was present as a linking agent, and that this copolymer was of high molecular weight and branchy. By contrast, without TGIC, either little or no copolymer formed or a low molecular weight product formed, which did not exhibit the rheology of a high molecular weight branchy product. Both the carboxy-end-group functionalized polycarbonate and the ester-side-chain polycarbonate (with an eliminatable alkyl group on the ester) were effective reactants with polyamide for formation of a block copolymer in the presence of TGIC. The result of sample 3 shows that a non-carboxy containing polycarbonate in admixture with polyamide and TGIC in accordance with the teachings of Maresca, Eur. Pat. 227053 (July 1, 1987) gives less copolymer than the use of carboxyl-containing or carboxyl-forming carbonate polymers with TGIC as the linking agent.

Claims: A process for preparing block copolymers of polyamides and aromatic carbonate polymers which comprises reacting for 0.1 minute to 1 hour at a temperature of 100° to 400°C. a dry blend of (a) a polyamide, (b) a thermoplastic aromatic carbonate polymer containing (i) a carboxy or ester-terminated end group, or (ii) a carboxy or ester side chain, the ester group being capable of forming a carboxyl group under the reaction conditions, and (c) 0.1 to 10%, based on the total weight of components (a) and (b), of a polyepoxy compound selected from O- or N-epoxyalkyl-substituted cyclic amides, imides and imidates. The process defined in Claim 1 wherein said polyepoxy compound is triglycidyl isocyanurate. The process of Claim 1 or 2 wherein component (b) has at least one group in the chain of the structure : wherein m and n are 0 or 1 and the sum of m plus n equals 1. The process of Claim 1 or 2 wherein component (b) has at least one group in the chain of the structure of the formula : wherein m and n are 0 or 1 and the sum of m plus n equals 1 and where each R is independently hydrocarbyl. A process for the blending of a polyamide and a carbonate polymer which comprises admixing said polyamide and carbonate polymers with 2 to 90% by weight of the block copolymer produced by the process of any one of Claims 1 to 4.

Inventors: DERUDDER JAMES LOUIS, DERUDDER, JAMES LOUIS
Applicants: GEN ELECTRIC, GENERAL ELECTRIC COMPANY
Application year: 1990
Main classification: C08G81
IPC codes: C08L63, C08G69, C08L77, C08G59, C08G81, C08L69, C08G64