Modified blends of polyphenylene ether resin and a polyamide

Abstract: Thermoplastic blends of a polyphenylene ether and a polyamide are described in which the two resins are blended over a broad range of amounts in the presence of an organic phosphate. The compositions can be formulated to be flame retardancy enhanced, and in optional embodiments they con­ tain a stable, relatively non-volatile bromine material for further improvements in the flame retardancy.

Description: The polyphenylene ether resins (also sometimes referred to as polyphenylene oxide resins) are a well known family of engineering thermoplastics which are characterized by good thermal, mechanical and electrical properties and which can be prepared into articles of various shapes and sizes by extrusion, molding and other procedures. Despite the many commercial applications possible for polyphenylene ether resins, their use has been somewhat restricted because of relatively poor flow properties which can cause difficulties during extrusion operations. A further drawback is that they are poor in solvent resistance after molding, and therefore, their use for certain applications has been further limited. Proposals have been made for upgrading the properties of polyphenylene ethers by combining them with other polymers. U.S.-A-3,379,792, teaches that the addition of a polyamide improves the flow properties of a polyphenylene oxide. The blends are limited to up to only about 20% by weight of the polyamide, however. The patentee states that when the polyamide concentration exceeds this amount, appreciable losses in other physical properties occur. Apart from these teachings, it is also known elsewhere in the art that polyphenylene oxide (ether) resins and polyamide resins are not completely compatible with each other over the full range of relative proportions, and that poor mechanical properties and phase separation occur if attempts are made to add too large an amount of the polyamide. U.S.-A-4,338,421 discloses that compositions containing 70 to 5% by weight of a polyphenylene oxide and 30 to 95% by weight of a polyamide can be formed by melt blending the two, and the resultant blend is characterized by improvement in both the solvent resistance and the impact strength. The patent states the belief that some graft interaction takes place between the polyphenylene oxide and the polyamide under those conditions, thus resulting in good interfacial adhesion and non-phase separation between the two resins. EP-A-46040 describes a highly heat-resistant thermoplastic resin composition having high oil resistance which comprises (1) a polyphenylene ether resin, (2) a copolymer comprising a vinyl aromatic compound and an α,β-unsaturated dicarboxylic acid anhydride or a copolymer comprising a vinyl aromatic compound and an imide compound of an α,β-unsaturated dicarboxylic acid, and (3) a polyamide resin and, additionally,- if desired - (4) an impact resistant reinforcing agent. Additionally, the composition may include a phosphoric acid ester as flame retardant. It has been found that compatibility between a polyphenylene ether resin, an elastomeric material and a relatively large amount of polyamide resin is achieved if just a minor amount of an organic phosphate is added. As an additional benefit, the flame retardancy of the compositions can easily be enhanced by selecting the organic phosphate from among those materials known to provide this function. As a further aspect of the invention, the flame retardancy can be improved even further by use of an optional feature, comprising the presence in the compositions of a stable, brominated flame retardant material, for example, a relatively non-volatile bis-bromophenoxy alkane or bromine containing polycarbonate resin. The compositions can be prepared without the need for melt blending, as is required with US-A-4,338,421 compositions referred to above. Good compatibility between the polyphenylene ether, the elastomeric material and the polyamide is achievable using a variety of preparation methods. According to the invention there is provided a thermoplastic composition comprising an admixture of (a) 99 to 30 parts by weight of a polyamide resin based on 100 parts of (a) and (b) together; (b) a polyphenylene resin; (c) an elastomeric material selected from polystyrene-polybutadiene block copolymers, polystyrene-polyisoprene block copolymers, polystyrene-polybutadiene-polystyrene block copolymers, polystyrene-polyisoprene-polystryene block copolymers, and polystyrene-polyethylene/polybutylene-polystyrene block copolymers; (d) 1 to 20 parts by weight of an organic phosphate per 100 parts by weight of (a) and (b), and optionally (e) a stable flame retardant brominated material with or without a synergistic agent, (f) a filler, and (g) one or more additives selected from plasticizers, antioxidants, stabilizers, reinforcing agents, pigments, dyes and other impact modifiers. Within the invention summarized above, there are certain composition components which are preferred for the practice of this invention. The polyphenylene ether resin is desirably a homo- or copolymer having units of the formula wherein Q, Q', Q'' and Q''', are independently selected from the group consisting of hydrogen, halogen, hydrocarbon radicals, halohydrocarbon radicals, hydrocarbonoxy radicals, and halohydrocarbonoxy radicals; and n represents the total number of monomer units and is an integer at least about 20, and preferably at least 50. In general, the polyphenylene ether resins are self-condensation products of monohydric monocyclic phenols with oxygen in the presence of complex metal catalysts, with molecular weight being controlled by reaction time, longer times providing a higher average number of repeating units. Particular procedures are known to those skilled in the art and are described in the patent literature, including U.S.-A-3,306,874; 3,306,875; 3,257,357 and 3,257,358. Illustrative polymers which can be produced by such procedures and which are within the above general formula are: poly(2,6-dilauryl-1,4-phenylene)ether: poly(2,6-diphenyl-1,4-phenylene)ether; poly(2,6-dimethoxy-1,4-phenylene)ether: poly(2,6-diethoxy-1,4-phenylene)ether; poly(2-methoxy-6-ethoxy-1,4-phenylene)ether; poly(2-ethyl-6-stearyloxy-1,4-phenylene)ether; poly(2,6-dichloro-1,4-phenylene)ether; poly(2-methyl-6-phenyl-1,4-phenylene) ether; poly(2,6-dibenzyl-1,4-phenylene)ether; poly(2-ethoxy-1,4-phenylene)ether; poly(2-chloro-1,4-phenylene) ether; poly(2,6-dibromo-1,4-phenylene)ether; and the like. Examples of polyphenylene ethers corresponding to the above formula can be found in the above referenced patents. Also included are polyphenylene ether copolymers, such as copolymers of 2,6-dimethylphenol with other phenols, for example, with 2,3,6-trimethylphenol or 2-methyl-6-butylphenol, etc. For purposes of the present invention, an especially preferred family of polyphenylene ethers include those having alkyl substitution in the two positions ortho to the oxygen ether atom, i.e., those of the above formula wherein Q and Q' are alkyl, most preferably having from 1 to 4 carbon atoms. Illustrative members of this class are: poly(2,6-dimethyl-1,4-phenylene)ether: poly(2,6-diethyl-1,4-phenylene)ether; poly(2-methyl-6-ethyl-1,4-phenylene)ether; poly(2-methyl-6-propyl-1,4-phenylene) ether; poly(2,6-dipropyl-1,4-phenylene)ether; poly(2-ethyl-6-propyl-1,4-phenylene)ether; and the like. The most preferred polyphenylene ether resin for purposes of the present invention is poly(2,6-dimethyl-1,4-phenylene)ether. The compositions also contain, as indicated, a polyamide. The term "polyamide" is used throughout this disclosure in its conventional sense to denote a polymeric condensation product which contains recurring aromatic and/or aliphatic amide groups as integral parts of the main polymer chain, such products being known generically as "nylons". In general, the polyamides useful in this invention are those having linkages of the formula in the main chain. These include polymers formed from the condensation of diamines and dibasic acids, from the self-condensation of amino acids, and by the polymerization of lactams. Procedures for preparing polyamides are well known in the art. Details of their formation can be found in "Polyamides", Encyclopedia of Polymer Science and Technology; John Wiley & Sons, Inc., Vol. 10, pages 487 to 491 (1969). Usually, the polyamides useful in the practice of this invention can be obtained by polymerizing a monoaminocarboxylic acid or internal lactam thereof having at least two carbon atoms between the amino and carboxylic acid groups; or by polymerizing substantially equimolar proportions of a diamine which contains at least two carbon atoms between the amino groups and a dicarboxylic acid; or by polymerizing a monoamino carboxylic acid or an internal lactam thereof together with substantially equimolar proportions of a diamine and a dicarboxylic acid. These are not the only means which can be used, however. Examples of the monoaminocarboxylic acid or lactam include compounds containing from 2 to 16 carbon atoms between the amino and carboxylic acid groups (the carbon atoms forming a ring with the amide group in the case of a lactam). As particular examples, mention is made of ε-aminocaproic acid, butyrolactam, picalolactam, caprolactam, caprylactam, enantholactam, undecanolactam, dodecanolactam and 3- and 4-amino benzoic acids. Examples of the diamine are those of the general formula H₂N(CH₂) n NH₂, in which n is an integer of from 2 to 16, such as trimethylenediamine, tetramethylenediamine, pentamethylenediamine, octamethylenediamine, decamethylenediamine, dodecamethylenediamine, hexadecamethylenediamine, and especially hexamethylenediamine. C-alkylated diamines, e.g., 2,2-dimethylpentamethylenediamine and 2,2,4- and 2,4,4-trimethylhexamethylenediamine, are further examples. Other diamines which may be mentioned as examples are aromatic diamines, e.g., p-phenylenediamine, 4,4'-diaminodiphenyl sulphone, 4,4'-diaminodiphenyl ether and 4,4'-diaminodiphenylmethane; and cycloaliphatic diamines, for example, diaminodicyclohexylmethane. The dicarboxylic acids may be aromatic, for example, isophthalic and terephthalic acids. Preferred dicarboxylic acids are of the formula HOOC-Y-COOH wherein Y represents a divalent aliphatic radical containing at least 2 carbon atoms, and examples of such acids are sebacic acid, octadecanedioic acid, suberic acid, azelaic acid, undecanedioic acid, glutaric acid, pimelic acid, and especially adipic acid. Illustratively, the following polyamides may be incorporated in the thermoplastic polymer blends of the invention: Homopolymers polyhexamethylene adipamide (nylon 6:6) polypyrrolidone (nylon 4) polycaprolactam (nylon 6) polyheptolactam (nylon 7) polycaprylactam (nylon 8) polynonanolactam (nylon 9) polyundecanolactam (nylon 11) polydodecanolactam (nylon 12) polyhexamethylene azelaiamide (nylon 6:9) polyhexamethylene sebacamide (nylon 6:10) polyhexamethylene isophthalamide (nylon 6:ip) polymetaxylylene adipamide (nylon MSD:6) polyamide of hexamethylenediamine and n-dodecanedioic acid (nylon 6:12) polyamide of dodecamethylenediamine and n-dodecanedioic acid (nylon 12:12) Copolymers hexamethylene adipamide/caprolactam (nylon 6:6/6) hexamethylene adipamide/hexamethylene-isophthalimide (nylon 6:6/6ip) hexamethylene adipamide/hexamethylene-terephthalamide (nylon 6:6/6T) trimethylhexamethylene oxamide/hexamethylene oxamide (nylon trimethyl-6:2/6:2) hexamethylene adipamide/hexamethylene-azelaiamide (nylon 6:6/6:9) hexamethylene adipamide/hexamethylene-azelaiamide caprolactam (nylon 6:6/6:9/6). The average molecular weight of the polyamide used in the compositions of this invention can range from 1.000 to 20,000 or higher (number average). Special mention is made herein of the polyamides known as nylon 6 (a polycaprolactam), nylon 11 (a polyundecanolactam), and nylon 6:6 (a polyhexamethylene adipamide). The polyphenylene ether homopolymer or copolymer and the polyamide resin can be present in virtually any desired proportions, between 1 and 70 parts of polyphenylene ether resin, and correspondingly, between 99 parts and 30 parts of polyamide, based on 100 parts by weight of the two. Compatible admixture of these resins with this broad range of amounts is enabled by the co-presence of a minor amount of an organic phosphate compound, as explained. Preferred for use as the organic phosphate compound in the compositions of this invention are aromatic compounds having the formula wherein R is the same or different and can be alkyl, cycloalkyl, aryl, alkyl substituted aryl, halogen substituted aryl, aryl substituted alkyl, halogen, and combinations of any of the foregoing, provided that at least one R is aryl. Typical examples include phenylbisdodecyl phosphate, phenylbisneopentyl phosphate, phenyl-bis (3,5,5'-trimethylhexyl phosphate), ethyldiphenyl phosphate, 2-ethyl-hexyldi(p-tolyl)phosphate, bis-(2-ethylhexyl)p-tolylphosphate, tritolyl phosphate, bis-(2-ethylhexyl)phenyl phosphate, tri-(nonylphenyl)phosphate, di(dodecyl)p-tolyl phosphate, tricresyl phosphate, triphenyl phosphate, dibutylphenyl phosphate, 2-chloro-ethyldiphenyl phosphate, p-tolyl bis-(2,5,5'-trimethylhexyl)phosphate, 2-ethylhexyldiphenyl phosphate, and the like. The preferred phosphates are those where each R is aryl. Especially preferred is triphenyl phosphate, either unsubstituted or substituted, e.g., isopropylated triphenyl phosphate. Alternatively, the aromatic phosphate can be a di- or polyfunctional compound or polymer having the formula and mixtures thereof, wherein R₁, R₃ and R₅ are, independently, hydrocarbon; R₂, R₄, R₆ and R₇ are, independently, hydrocarbon or hydrocarbonoxy; X¹, X² and X³ are halogen, m and r are 0 or integers from 1 to 4, and n and p are from 1 to 30. Examples include the bis diphenyl phosphates of resorcinol, hydroquinone or bisphenol-A, respectively, or their polymeric higher molecular weight counterparts. These phosphates and methods of their preparation are described in British Patent No. 2,043,083. Minor amounts of the organic phosphate, ranging from 1 to 20 parts by weight per 100 parts of polyphenylene ether and polyamide combined, will in most cases be sufficient to achieve the desired compatibilizing effect. In instances where a degree of flame retardancy enhancement is desired, the organic phosphate can be selected from among normally flame retardant materials, e.g., triphenyl phosphate. This can be used alone or in conjunction with other materials which function as flame retardant agents. Of particular interest are stable brominated compounds having a low volatility in the temperature range 100-150°C., e.g., brominated bis-phenoxy alkanes of the formula where R' is alkylene, straight or branched, having from 1 to 10 carbon atoms, and q and s represent the total number of bromine atoms on each ring and are, independently, integers from 1 to 5. Examples of the above are 1,2-bis(2,4,6-tribromophenoxy)ethane; 1,3-bis(2,4,6-tribromophenoxy)propane; 1,4-bis(2,4,6-tribromophenoxy)butane; 2,2-bis(4-bromophenoxy)propane; and 1,2-bis(2,3,4,5,6-pentabromophenoxy) ethane. These are available commercially or can be prepared by use of procedures described in the patent literature, including U.S-A-4,016,138. Also useful are flame retardant brominated polymers, including those which are described in U.S-A-3,334,154 and 3,833,685. Preferably, these are aromatic carbonate copolymers having units of the formula: in which R¹ and R² are hydrogen, (lower) alkyl or phenyl, X¹ and X² are bromo or chloro, and m and r are from 1 to 4, and units of the formula: in which R¹ and R² are as defined above. Especially preferred are oligomeric tetrabromobisphenol-A polycarbonates chain stopped with tribromophenol. Amounts of between 1 and 20 parts by weight of this optional additional component, based on 100 parts of total resin, are preferred. The compositions of the present invention also include an elastomeric material selected from polystyrene-polybutadiene block copolymers, polystyrene-polyisoprene block copolymers, polystyrene-polybutadiene-polystyrene block copolymers, polystyrene-polyisoprene-polystyrene block copolymers, and polystyrene-polyethylene/polybutylene-polystyrene block copolymers. The compositions of the invention can also include one or more additives conventionally employed with polyphenylene ether resins to improve the chemical and physical properties of the molded articles. The additives can be selected from among placticizers, antioxidants, stabilizers, fillers e.g. mineral fillers, (e.g., clay), reinforcing agents (e.g., glass fibers), pigments, dyes, and other impact modifiers, and so forth. In the typical case, the additive or additives are included in minor but effective amounts varying between 1 and 50% by weight, or more, of the total composition. Preparation of the compositions may be accomplished by milling the ingredients on a roll mill at a temperature of 380 (193°C) to 450°F (232°C) and molding at 440 (227°C) to 460°F (238°C). Other procedures are possible, however, as shown in some of the examples The following examples illustrate the invention. They are intended to show preferred or best embodiments only and not as a limitation on the scope. All parts are by weight. EXAMPLES 1- 3 The compositions were prepared by milling the ingredients at 380-390°F (193-199°C) and molding the milled material for ten minutes at 460°F (238°C). EXAMPLES 4- 6 The compositions noted below were prepared by blending the ingredients for thirty seconds on a Henschel mixer and extruding the blend at 500°F (260°C) on a single screw extruder. Ingredients 4 5 6 Polyamide resin (nylon 6:6) 50 50 50 Poly(2,6-dimethyl-1,4-phenylene ether) resin 40 40 40 Styrene-ethylene/butylene-styrene block copolymer 10 10 10 Tetrabromobisphenol-A oligomeric polycarbonate 10 10 10 Bis diphenyl phosphate of resorcinol -- 10 10 Antimony oxide -- -- 5 Properties Horizontal propagation, in inches (mm), after 30 seconds ½ inch (6.35) ¼ inch (6.35) NP Horizontal Burn Test, 1/8 inch (3.175mm) specimen ND ND ND ND = No Drip NP = No Propagation EXAMPLES 7-9 The compositions noted below were prepared by milling the ingredients at 440-450°F (227-232°C) in the case of Example and at 400-410°F (204-210°C) in the case of Examples and , and molding the milled material at 460°F (238°C) for ten minutes in each case. Ingredients 7 8 9 Polyamide resin (nylon 11) 50 50 50 Poly (2,6-dimethyl-1,4-phenylene ether) resin 50 50 50 Styrene-ethylene/butylene-styrene block copolymer 20 20 20 Tetrabromobisphenol-A oligomeric polycarbonate -- -- 30 Bis diphenyl phosphate of resorcinol 10 10 10 Antimony oxide -- 5 5 Properties Horizontal propagation, in inches (mm), after 30 seconds ¼ inch (6.35) ¼ inch (6.35) ¼ inch (6.35) Horizontal Burn Test, 1/8 inch (3.175mm) specimen ND ND ND ND = No Drip EXAMPLE 10 The ingredients were extruded at 480-510°F (249-266°C) and molded for ten minutes at 500°F (260°C). Ingredients Polyamide resin (nylon 11) 50 Poly(2,6-dimethyl-1,4-phenylene ether) resin 50 Styrene-ethylene/butylene-styrene block copolymer 20 Tetrabromobisphenol-A oligomeric polycarbonate 30 Bis diphenyl phosphate of resorcinol 10 Antimony oxide 5 Properties Horizontal propagation, in inches (mm) after 30 seconds NP Horizontal Burn Test, 1/8 inch (3.175mm) specimen ND NP = No Propagation ND = No Drip Obviously, other modifications and variations are possible in light of the above disclosure. For instance, instead of poly(2,6-dimethyl-1,4-phenylene ether)resin, copolymers such as poly(2,6-dimethyl- co -2,3,6-trimethyl-1,4-phenylene ether) can be substituted. Instead of 1,2-bis(2,4,6-tribromophenoxy) ethane, other brominated compounds such as 1,2-bis(2,3,4,5,6-pentabromophenoxy) ethane can be used. Optionally, the compositions can and often do also contain an additional compound selected from among those known to synergistically enhance the effect of brominated flame retardant agents, such as compounds based on antimony or molybdenum. Particular mention is made of antimony oxide, as shown. Small amounts, for example, less than 10% by weight, are usually sufficient to even further enhance the flame retardancy of the present compositions. In addition these compositions may incorporate antioxidants, other stabilizers, plasticizers, mineral fillers and glass fibers and spheres.

Claims: A thermoplastic composition consisting of an admixture of (a) 99 to 30 parts by weight of a polyamide resin based on 100 parts of (a) and (b) together; (b) a polyphenylene ether resin; (c) an elastomeric material selected from polystyrene-polybutadiene block copolymers, polystyrene-polyisoprene block copolymers, polystyrene-polybutadiene-polystyrene block copolymers, polystyrene-polyisoprene-polystyrene block copolymers, and polystyrene-polyethylene/polybutylene-polystyrene block copolymers; (d) 1 to 20 parts by weight of an organic phosphate per 100 parts by weight of (a) and (b), and optionally (e) a stable flame retardant brominated material with or without a synergistic agent, (f) a filler, and (g) one or more additives selected from plasticizers, antioxidants, stabilizers, reinforcing agents, pigments, dyes and other impact modifiers. A composition according to Claim 1, in which (a) and (b) are present in a weight ratio in the range between 30:70 and 70:30. A composition according to Claim 1, in which polyamide (a) contains linkages of the formula in the main polymer chain. A composition according to Claim 1, in which polyamide (a) is selected from among polycaprolactam, polyundecanolactam and polyhexamethylene adipamide. A composition according to Claim 1, in which polyphenylene ether (b) is a homo- or copolymer having units of the formula wherein Q, Q', Q'', Q''' are independently selected from the group consisting of hydrogen, halogen, hydrocarbon radicals, halohydrocarbon radicals, hydrocarbonoxy radicals, and halohydrocarbonoxy radicals; and n represents the total number of monomer units and is an integer at least about 20. A composition according to Claim 1, in which component (b) is poly(2,6-dimethyl-1,4-phenylene) ether. A composition according to Claim 1, in which component (d) has the formula wherein R is the same or different and can be alkyl, cycloalkyl, aryl, alkyl substituted aryl, halogen substituted aryl, aryl substituted alkyl, halogen, and combinations or any of the foregoing, provided at least one R is aryl. A composition according to Claim 1, in which (d) is triphenyl phosphate. A composition according to Claim 8, in which the triphenyl phosphate is isopropylated. A composition according to Claim 1, in which component (d) is a di- or polyfunctional compound or polymer having the formula and mixtures thereof, wherein R₁, R₃ and R₅ are, independently, hydrocarbon; R₂, R₄,R₆ and R₇ are, independently, hydrocarbon or hydrocarbonoxy; X¹, X² and X³ are halogen; m and r are 0 or integers from 1 to 4, and n and p are from 1 to 30. A composition according to Claim 10, in which component (d) is bis diphenyl phosphate of resorcinol. A composition according to Claim 10, in which component (d) is bis diphenyl phosphate of hydroquinone. A composition according to Claim 10, in which component (d) is bis diphenyl phosphate of bisphenol-A. A composition according to Claim 1, in which the brominated material, (e) is a bisphenoxy alkane of the formula where R' is alkylene, straight or branched, having from 1 to about 10 carbon atoms, and q and s represent the total number of bromine atoms on each ring and are, independently, integers from 1 to 5. A composition according to Claim 14, in which (e) is 1,2-bis(2,4,6-tribromophenoxy) ethane or 1,2-bis(2,3,4,5,6-pentabromophenoxy) ethane. A composition according to Claim 1, in which component (e) is an aromatic polycarbonate having units of the formula in which R¹ and R² are hydrogen, (lower) alkyl or phenyl, X¹ and X² are bromo or chloro, and m and r are from 1 to 4, and units of the formula in which R¹ and R² are as defined above. A composition according to claim 1, in which (e) is a tetrabisphenol-A oligomeric polycarbonate. A composition according to claim 1, in which the synergistic agent is an antimony compound. A composition according to claim 18, in which the antimony compound is antimony oxide.

Inventors: ABOLINS VISVALDIS, BETTS JOSEPH ELWOOD, HOLUB FRED FRANK, ABOLINS, VISVALDIS, BETTS, JOSEPH ELWOOD, HOLUB, FRED FRANK
Applicants: GEN ELECTRIC, GENERAL ELECTRIC COMPANY
Application year: 1984
Main classification: C08L71
IPC codes: C08L77, C08K5, C08L69, C08L71, C08K3, C08K13