Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B82—NANOTECHNOLOGY
  • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
  • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
  • B29D22/00—Producing hollow articles
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
  • C08J5/005—Reinforced macromolecular compounds with nanosized materials, e.g. nanoparticles, nanofibres, nanotubes, nanowires, nanorods or nanolayered materials
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/34—Silicon-containing compounds
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K9/00—Use of pretreated ingredients
  • C08K9/08—Ingredients agglomerated by treatment with a binding agent
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2377/00—Characterised by the use of polyamides obtained by reactions forming a carboxylic amide link in the main chain; Derivatives of such polymers

Definitions

• This invention relates to a process to prepare a nanocomposite material comprising a polymer matrix having dispersed therein a silicate. More particularly, this invention relates to a process to prepare a nanocomposite material comprising forming a flowable mixture of a polyamide and a silicate material, dissociating the silicate, and subjecting the dissociated flowable mixture to a solid state polymerization step to produce the nanocomposite material.
• International Application WO 93/041 17 discloses a process of preparing a polymer nanocomposite having platelet particles dispersed therein, where the polymer and the swellable and polymer-compatible intercalated layered material are melt-processed;
• the layered material is compatibilized with one or more "effective swelling/compatibilizing agents" selected from primary ammonium, secondary ammonium and quaternary phosphonium ions.
• the selected swelling/compatibilizing agents "...render their surfaces more organophilic than those compatibilized by tertiary and quaternary ammonium ion complexes../', facilitate exfoliation, resulting in less shear in mixing and less decomposition of the polymer, and heat stabilize the composite more than other cations (such as quaternary ammonium cation) swelling/compatibilizing agents. - 2
• WO 94/22430 discloses a nanocomposite composition having a polymer matrix comprising at least one gamma phase polyamide, and dispersed in the polyamide is a matrix of a nanometer-scale particulate material.
• the addition of the particulate material to nylon 6 resulted in an improvement of flexural modulus and flexural strength (from 7 to 35%), when compared to unfilled nylon 6.
• the addition of the particulate material to nylon 6,6 resulted in very little improvement (1 to 3%) of flexural modulus and flexural strength when compared to unfilled nylon 6,6.
• International Patent Application WO 95/14733 discloses a method of producing a polymer composite that does not demonstrate melting or glass transition by melt-processing a polymer with a layered gallery-containing crystalline silicate.
• the examples include intercalated sodium silicate and a crystalline poly(ethylene oxide), montmorillonite intercalated with a quaternary ammonium and polystyrene, and montmorillonite intercalated with a quaternary ammonium and nylon 6.
• U.S. Patent No. 5,514,734 (issued May 7, 1996) describes polymer composites containing layered or fibrillar particles derivatized with organosilanes, organotitanates, or organozirconates. Composite materials are characterized by thickness, diameter, and interlayer distances.
• EPO application 0 358 415 Al describes a polyamide resin containing a dispersed layered silicate which has been treated with an organic cation of a lactam as a swelling agent.
• Japanese Kokai Patent No. SHO 62[1987]-252426 describes polymerization of a nylon 6 monomer in the presence of a silicate. The cooling rate of the polymer is controlled to achieve particular crystalline structures in the resulting composite.
• This invention relates to a process to prepare a polymer nanocomposite composition suitable for automotive, electronic, film and fiber applications, where a combination of tensile strength, tensile modulus and flexural modulus are required. Additionally, the claimed polymer nanocomposite composition has a desirable surface appearance, toughness, ductility and dimensional stability. The composition processes well and tolerates a wide range of molding conditions.
• the present invention relates to a process to prepare the above polymer nanocomposite composition
• a process to prepare the above polymer nanocomposite composition comprising forming a flowable mixture of a polyamide and a silicate material and dissociating (as that term is described in more detail below) at least about 50% but not all of the silicate, and subjecting the polyamide in the dissociated flowable mixture to a solid state polymerization step.
• the silicate is a silicate material treated with at least one ammonium ion of the formula:
• R] R 2 , R 3 and R 4 are independently selected from a group consisting of a saturated or unsaturated C] to C 22 hydrocarbon, substituted hydrocarbon and branched hydrocarbon, or where R] and R 2 form a N,N-cyclic ether.
• Examples include saturated or unsaturated alkyls, including alkylenes; substituted alkyls such as hydroxyalkyls, alkoxyalkyls, alkoxys, amino alkyls, acid alkyls, halogenated alkyls, sulfonated alkyls, nitrated alkyls and the like; branched alkyls; aryls and substituted aryls, such as alkylaryls, alkyoxyaryls, alkylhydroxyaryls, alkylalkoxyaryls and the like.
• one of R b R 2 , R 3 and R 4 is hydrogen.
• the milligrams of treatment per 100 grams of silicate (MER) of the treated silicate is preferably from about 10 milliequivalents/100 g below the cation exchange capacity of the untreated silicate to about 30 milliequivalents/100 g above the cation exchange capacity of the untreated silicate.
• An additional embodiment of the invention relates to nanocomposite compositions comprising a polyamide and a silicate.
• the polyamide may have a concentration of amine groups at least 10 mole % greater than the concentration of the carboxylic acid end groups.
• the polyamide has a weight average molecular weight in the range of about 30,000 D to about 40,000 D.
• the polyamide may have a weight average molecular weight of at least 40,000 D.
• a further embodiment is directed towards a nanocomposite composition
• a nanocomposite composition comprising a polyamide and a silicate, wherein the silicate is treated with an ammonium ion of the formula: + NR a R b R c R d ; wherein R a , R b and R c is hydrogen (H) and and R d includes a carboxylic acid moiety.
• the composite polymer matrix material of the present invention demonstrates, when tested, an improvement in tensile modulus and flexural modulus, without a substantial decrease in tensile strength or toughness when compared to that of the polymer without the silicate.
• Polyamides of the present invention are synthetic linear polycarbonamides characterized by the presence of recurring carbonamide groups as an integral part of the polymer chain which are separated from one another by at least two carbon atoms.
• Polyamides of this type include polymers, generally known in the art as nylons, which can be obtained from diamines and dibasic acids having the recurring unit represented by the general formula:
• R 5 is an alkylene group of at least 2 carbon atoms, preferably from about 2 to about 11 or arylene having at least about 6 carbon atoms, preferably about 6 to about 17 carbon atoms; and Rg is selected from R 5 and aryl groups.
• copolyamides, terpolyamides and the like obtained by known methods, for example, by condensation of hexamethylene diamine and a mixture of dibasic acids consisting of terephthalic acid and adipic acid.
• Polyamides of the above description are well-known in the art and include, for example, poly(hexamethylene adipamide) (nylon 6,6), poly(hexamethylene sebacamide) (nylon 6J0), poly(hexamethylene isophthalamide), poly(hexamethylene terephthalamide), poly(heptamethylene pimelamide) (nylon 7,7), poly(octamethylene suberamide) (nylon 8,8), poly(nonamethylene azelamide) (nylon 9,9), poly (decamethylene sebacamide) (nylon 10,9), poly(decamethylene sebacamide) (nylon 10J0), poly[bis(4-amino cyclohexyl)methane-lJO-decanecarboxamide)], poly(m-xylene adipamide), poly(p-xylene sebacamide), poly(2JJ-trimethyl hexamethylene terephthalamide), poly(piperazine sebacamide), poly(p-phenylene terephthalamide),
• isophthalamide and copolymers and terpolymers of the above polymers.
• Additional polyamides include nylon 4,6, nylon 6,9, nylon 6J0, nylon 6J2, nylon 11, nylon 12, amorphous nylons, aromatic nylons and their copolymers.
• useful polyamides are those formed by polymerization of amino acids and derivatives thereof, as for example, lactams.
• Illustrative of these useful polyamides are poly(caprolactam) (nylon 6), poly(4-aminobutyric acid) (nylon 4), poly(7-aminoheptanoic acid) (nylon 7), poly(8-aminooctanoic acid) (nylon 8), poly(9-aminononanoic acid) (nylon 9), poly(10-aminodecanoic acid) (nylon 10), poly(l 1 -aminoundecanoic acid) (nylon 11), poly(12- aminodocecanoic acid) (nylon 12) and the like.
• the preferred polyamide is Vydyne nylon, which is poly(hexamethylene adipamide)
• nylon 6 which gives a composite with the desired combination of tensile strength, tensile modulus and flexural modulus for the applications contemplated herein (Vydyne ® is a registered trademark of Solutia Inc.).
• the preferred molecular weight of the polyamide is in the range of about 30,000 to about 80,000 D (weight average) with a more preferred molecular weight in the range of about 30,000 to about 40,000 D.
• the most preferred molecular weight of the polyamide is at least about 40,000 D (weight average).
• Increasing the weight average molecular weight of the polyamide from about 35,000 to about 55,000 D results in an unexpected increase in toughness as indicated by the notched Izod impact test. Whereas an increase in the weight average molecular weight of from about 35,000 to about 55,000 D in the polyamide neat results in a small increase in toughness, the same increase in molecular weight in the nanocomposite results about twice the increase in toughness. Therefore, the increase in toughness is enhanced in the nanocomposite when compared to that of the polyamide neat.
• the polyamide has an amine end group/acid end group ratio greater than one (1). More preferably, the concentration of amine end groups is at least 10 mole % greater than the concentration of the carboxylic acid end groups. In an even more preferred embodiment, the polyamide has a concentration of amine end groups at least 20 mole % greater than the concentration of the carboxylic acid end groups, and in a most preferred embodiment, the polyamide has a concentration of amine end groups at least 30 mole % greater than the concentration of the carboxylic acid end groups. In another embodiment, the concentration of amine end groups is essentially equal to the concentration of carboxylic acid end groups.
• nylon 6, nylon 6,6, blends thereof and copolymers thereof is nylon 6, nylon 6,6, blends thereof and copolymers thereof.
• the range of ratios of the nylon 6/nylon 6,6 in the blends is from about 1/100 to 100/1.
• the range is from about 1/10 to 10/1.
• the range of ratios of the nylon 6/nylon 6,6 in the copolymers is about 1/100 to 100/1.
• the range is from about 1/10 to 10/1.
• the nanocomposite composition comprises at least one additional polymer.
• suitable polymers include polyethyleneoxide, polycarbonate, polyethylene, polypropylene, ⁇ oly(styrene-acrylonitrile), poly(acrylonitrile-butadiene-styrene), poly(ethylene terephthalate), poly(butylene terephthalate), poly(trimethylene terephthalate), poly(ethylene naphthalate), poly(ethylene terephthalate-co-cyclohexane dimethanol terephthalate), polysulphone, poly(phenylene oxide) or poly(phenylene ether), poly(hydroxybenzoic acid-co- ethylene terephthalate), poly(hydroxybenzoic acid-co-hydroxynaphthenic acid), poly(esteramide), poly(etherimide), poly(phenylene sulfide), poly(phenylene terephthalamide).
• the mixture may include various optional components which are additives commonly employed with polymers.
• optional components include surfactants, nucleating agents, coupling agents, fillers, impact modifiers, chain extenders, plasticizers, compatibilizers, colorants, mold release lubricants, antistatic agents, pigments, fire retardants, and the like.
• Suitable examples of fillers include carbon fiber, glass fiber, kaolin clay, wollastonite, mica and talc.
• Suitable examples of compatibilizers include acid-modified hydrocarbon polymer, such as maleic anhydride-grafted propylethylene, maleic anhydride-grafted polypropylene, maleic anhydride-grafted ethylenebutylene-styrene block copolymer.
• Suitable examples of mold release lubricant includes alkyl amine, stearamide, and di-or tri- aluminum stearate.
• Suitable examples of impact modifiers include ethylene-propylene rubber, ethylene- propylene diene rubber, methacrylate-butadiene-styrene (with core-shell morphology), poly(butylacrylate) with or without carboxyl modification, poly(ethylene acrylate), poly(ethylene methylacrylate), poly(ethylene acrylic acid), poly(ethylene acrylate) ionomers, poly(ethylene methacrylate acrylic acid) terpolymer, poly(styrene-butadiene)block copolymers, - 8 -
• Suitable coupling agents include silane, titanate and zirconate coupling agents. Silane coupling agents are well-known in the art and are useful in the present invention. Examples of
• suitable coupling agents include octadecyltrimethoxysilane, gamma-aminopropyltriethoxysilane, garnma-aminopropyltrimethoxysilane, gamma-aminopropylphenyldimethoxysilane, gamma- glycidoxypropyl tripropoxysilane, 3,3-epoxycyclohexylethyl trimethoxysilane, gamma- proprionamido trithoxysilane, N-trimethoxysilylpropyl-N(beta-aminoethyl) amine, trimethoxysilylundecylamine, trimethoxysilyl-2-chloromethylphenylethane, l o trimethoxysilylethylphenylsulfonylazide, N-trimethoxysilylpropyl-N,N,N-trimethylammoni
• the preferred concentration range of silane coupling agent is about 1 to about 3 weight % of the layered silicate in the composite.
• the nanocomposite composition further comprises a composition wherein an end group of the polyamide is bonded to a surface of the treated silicate by a silane
• the silicate materials of the present invention are selected from the group consisting of layered silicates and fibrous, chain-like silicates, and include phyllosilicates.
• fibrous, chain-like silicates include chain-like minerals, for example sepiolite and attapulgite, with sepiolite being preferred.
• Such silicates are described, for example, in Japanese Patent
• layered silicates include layered smectite clay minerals such as montmorillonite, nontronite, beidellite, volkonskoite, Laponite ® synthetic hectorite, natural hectorite, saponite, sauconite, magadiite, and kenyaite; vermiculite; and the like.
• Other useful materials include layered illite minerals such as ledikite and admixtures of illites with one or 9 -
• the preferred layered silicates are the smectite clay minerals such as montmorillonite, nontronite, beidellite, volkonskoite, Laponite ® synthetic hectorite, natural hectorite, saponite, sauconite, magadite, and kenyaite.
• the layered silicate materials suitable for use in the present invention are well-known in the art, and are sometimes referred to as "swellable layered material". A further description of the claimed layered silicates and the platelets formed when melt processed with the polyamide is found in International Patent Application WO 93/04117, which is hereby incorporated by reference.
• the layered silicate materials typically have planar layers arrayed in a coherent, coplanar structure, where the bonding within the layers is stronger than the bonding between the layers such that the materials exhibit increased interlayer spacing when treated.
• the layered silicate materials may be treated as described in more detail below with the subject ammonium ion to enhance the interlayer swelling and/or spacing useful for the performance of the treated silicate of the present invention.
• inter layer spacing refers to the distance between the faces of the layers as they are assembled in the treated material before any delamination (or exfoliation) takes place.
• the preferred clay materials generally include interlayer or exchangeable cations such as Li + , Na + , Ca + , K + , Mg + and the like. In this state, these materials have interlayer spacings usually equal to or less than about 4 A and only delaminate to a low extent in host polymer melts regardless of mixing.
• the cationic treatment is a ammonium species which is capable of exchanging with the interlayer cations such as Li + , Na + , Ca + , K + , Mg + and the like in order to improve delamination of the layered silicate.
• the treated silicate of the present invention is a silicate material as described above which is treated with at least one ammonium ion of the formula
• R ] , R 2 , R 3 and R 4 are independently selected from a group consisting of a saturated or unsaturated C, to C 22 hydrocarbon, substituted hydrocarbon and branched hydrocarbon, or where R, and R 2 form a N,N-cyclic ether.
• saturated or unsaturated alkyls including alkylenes; substituted alkyls such as hydroxyalkyls, alkoxyalkyls, alkoxys, amino alkyls, acid 10
• alkyls halogenated alkyls, sulfonated alkyls, nitrated alkyls and the like; branched alkyls; aryls and substituted aryls, such as alkylaryls, alkyoxyaryls, alkylhydroxyaryls, alkylalkoxyaryls and the like.
• one of R R 2 , R 3 and R 4 is hydrogen.
• a mixture of two or more ammonium ions is contemplated by the present invention.
• R j is selected from the group consisting of hydrogenated tallow, unsaturated tallow or a hydrocarbon having at least 6 carbons, and R 2 , R 3 and R 4 independently have from one to eighteen carbons.
• Tallow is composed predominantly of octadecyl chains with small amounts of lower homologues, with an average of from 1 to 2 degrees of unsaturation.
• the approximate composition is 70% C ]8 , 25% C 16 , 4% C 14 and 1% C 12 .
• R] and R 2 are independently selected from the group consisting of hydrogenated tallow, unsaturated tallow or a hydrocarbon having at least 6 carbons and R 3 and R 4 independently have from one to twelve carbons.
• R R 2 , R 3 and R 4 groups are alkyl such as methyl, ethyl, octyl, nonyl, tert-butyl, ethylhexyl, neopentyl, isopropyl, sec-butyl, dodecyl and the like; alkenyl such as 1-propenyl, 1-butenyl, 1-pentenyl, 1-hexenyl, 1-heptenyl, 1-octenyl and the like; cycloalkyl such as cyclohexyl, cyclopentyl, cyclooctyl, cycloheptyl and the like; alkoxy such as ethoxy; hydroxyalkyl; alkoxy alkyl such as methoxymethyl, ethoxymethyl, butoxymethyl, propoxy ethyl, pentoxybutyl and the like; aryloxyalkyl and aryloxyaryl such as phenoxyphen
• Suitable ammoniums used in treating the silicate materials include oniums such as dimethyldi(hydrogenated tallow) ammonium, dimethylbenzyl hydrogenated tallow ammonium, dimethyl(ethylhexyl) hydrogenated tallow ammonium, trimethyl hydrogenated tallow ammonium, methylbenzyldi(hydrogenated tallow) ammonium, N,N-2- cyclobutoxydi(hydrogenated tallow) ammonium, trimethyl tallow ammonium, methyldihydroxyethyl tallow ammonium, octadecylmethyldihydroxyethyl ammonium, dimethyl(ethylhexyl) hydrogenated tallow ammonium and mixtures thereof.
• Particularly preferred ammoniums include quaternary ammoniums, for example, dimethyldi(hydrogenated - 11
• the treatment with the ammonium ion(s), also called “cationic treatments”, includes introduction of the ions into the silicate material by ion exchange.
• the cationic treatments may be introduced into the spaces between every layer, nearly every layer, or a large fraction of the layers of the layered material such that the resulting platelet layers comprise less than about 20 particles in thickness.
• the platelet layers are preferably less than about 8 particles in thickness, more preferably less than about 5 particles in thickness, and most preferably, about 1 or about 2 particles in thickness.
• the treated silicate has a MER of from about 10 milliequivalents/100 g below the cation exchange capacity of the untreated silicate to about 30 milliequivalents/100 g above the cation exchange capacity of the untreated silicate.
• the MER is the milliequivalents of treatment per 100 g of silicate.
• Each untreated silicate has a cation exchange capacity, which is the milliequivalents of cations available for exchange per 100 g of silicate.
• the cation exchange capacity of the layered silicate montmorillonite can be about 95, and the exchange capacity of sepiolite is in the range of about 10 to about 20.
• a first nanocomposite sample may have a higher concentration of treated silicate but a lower concentration of silicate, than a second nanocomposite sample, because the first sample has a higher MER than the second sample.
• the MER value of the treated silicate is substantially less than its exchange capacity, for example about 85 MER for the preferred montmorillonite, there is too little of the cationic treatment to have a beneficial effect. If the MER exceeds about 125, the excess ammonium may be detrimental to the properties of the nylon.
• the treated layered silicate has an exchange capacity of about 95, the treated layered silicate has a cation exchange capacity of from about 85 to about 125.
• the amount of silicate included in the composition is in the range of about 0J to about 12 weight % of the composite.
• the concentration is adjusted to provide a composite polymer matrix material which demonstrates, when tested, an increase in tensile modulus and flexural modulus, without a substantial decrease in tensile strength.
• the increase in tensile modulus and flexural modulus is at least about 10%. More preferably, the increase in tensile modulus and flexural modulus is at least about 20%. Too little silicate fails to provide the desired increase in tensile modulus and flexural modulus. Too much silicate provides a polyamide composite with a decreased tensile strength. Further, it may be desirable to have the crystalline regions of the polyamide in the nanocomposite composition be less than about 1.0 ⁇ m.
• the particle size of the silicate is such that optimal contact between the polymer and the silicate is facilitated.
• the range of particle size can vary from about 10 microns to about 100 microns.
• the particle size is in the range of from about 20 to about 80 microns.
• the particle size is below about 30 microns, such as those that pass through 450 mesh screens, in that the resulting polymer nanocomposite has improved performance properties.
• the silicate can be treated with one or more ammonium ions of the formula NR a R b R c R d wherein at least one of R a , R b and R c is hydrogen (H) and R d is selected from a group consisting of a saturated or unsaturated Cj to C 22 hydrocarbon, substituted hydrocarbon and branched hydrocarbon.
• Examples include saturated or unsaturated alkyls, including alkylenes; substituted alkyls such as hydroxyalkyls, alkoxyalkyls, alkoxys, amino alkyls, acid alkyls, halogenated alkyls, sulfonated alkyls, nitrated alkyls and the like; branched alkyls; aryls and substituted aryls, such as alkylaryls, alkyoxyaryls, alkylhydroxyaryls, alkylalkoxyaryls and the like.
• R d group for the ammonium ion is generally the same as the definition for the R 4 group in the ammonium ion, the Examples set forth above for the R 4 group are also exemplary of the R d group. - 13 -
• R a , R b and R c are hydrogen (H), and the R d group contains a carboxylic acid moiety such that the ammonium ion
• NR a R b R c R d is an amino acid, for example 12-aminolauric acid ammonium.
• the amine end groups/acid end groups ratio of the polyamide is greater than one (1) .
• the above ammonium ions may be mixed with at least one quaternary ammonium ion, said mixture used to treat the silicate.
• the quaternary ammonium ion preferably has a hydrocarbon chain.
• the hydrocarbon chain may be saturated or unsaturated.
• the hydrocarbon chain may be obtained from a natural source such as tallow, or from a synthetic source such as a synthesized or purified C 12 , C 14 , C 16 , or C 18 chain.
• a preferred mixture includes at least one of dimethyldi(hydrogenated tallow) ammonium, methyl dihydroxyethyl tallow ammonium, dimethylbenzyl hydrogenated tallow ammonium and/or dimethyl(ethylhexyl) hydrogenated tallow ammonium, either alone or in combination with 12-aminolauric acid ammonium.
• the silicate can be further treated with azine cationic dyes, such as nigrosines or anthracines.
• azine cationic dyes such as nigrosines or anthracines.
• Said cationic dyes would impart color-fastness and uniformity of color in addition to increasing the intercalation of the polymer molecules.
• the preferred nanocomposite contains a concentration of silicate of from about 0J to about 12.0 weight % of the composite.
• the most preferred nanocomposite contains a concentration of silicate of from about 0.5 to about 6.0 weight % of the composite.
• the nanocomposite composition is prepared using a three step process.
• One step includes forming a flowable mixture of the polyamide as a polymer melt and the silicate material.
• the second step includes dissociating at least 50% but not all of the silicate material.
• dissociating means delaminating or separating the silicate material into submicron-scale structures comprising individual or small multiple units. For the embodiment wherein layered silicates are utilized this 14 -
• dissociating step includes delaminating the silicate material into submicron scale platelets comprising individual or small multiple layers.
• this dissociating step includes separating the silicate material into submicron scale fibrous structures comprising individual or small multiple units.
• a flowable mixture is a mixture which is capable of dispersing dissociated silicate material at the submicron scale.
• a polymer melt is a melt processable polymer or mixture of polymers which has been heated to a temperature sufficiently high to produce a viscosity low enough for submicron scale mixing to occur.
• the process temperature should be at least as high as the melting point of the polyamide employed and below the degradation temperature of the polyamide and of the organic treatment of the silicate.
• the actual extruder temperature may be below the melting point of the polyamide employed, because heat is generated by the flow.
• the process temperature is high enough that the polymer will remain in the polymer melt during the conduct of the process. In the case of a crystalline polyamide, that temperature is above the polymer's melting temperature.
• a typical nylon 6, having a melting point of about 225°C can be melted in an extruder at any temperature equal to or greater than about 225°C, as for example between about 225°C and about 260°C.
• nylon 6,6 a temperature of preferably from about 260°C to about 320°C is normally employed.
• the flowable mixture can be prepared through use of conventional polymer and additive blending means, in which the polymer is heated to a temperature sufficient to form a polymer melt and combined with the desired amount of the silicate material in a granulated or powdered form in a suitable mixer, as for example an extruder, a Banbury type mixer, a Brabender type mixer, Farrell continuous mixers, and the like.
• a suitable mixer as for example an extruder, a Banbury type mixer, a Brabender type mixer, Farrell continuous mixers, and the like.
• the flowable mixture may be formed by mixing the polyamide with a previously formed silicate-containing concentrate.
• the concentrate includes the silicate and a polymer carrier.
• concentration of the silicate material in the concentrate, and the amount of concentrate are selected to provide the desired silicate concentration for the final nanocomposite composition.
• suitable polymers for the carrier polymer of the concentrate include - 15 -
• polyamide polyamide, ethylene propylene rubber, ethylene propylene diene rubber, ethylene-ethylacrylate, ethylene-ethylmethacrylate or ethylene methacrylate.
• examples include Iotek ionomer and Escor" ATX acid terpolymer, both available from Exxon.
• the polyamide polymers suitable for the carrier polymer include nylons such as nylon 6, nylon 6,6, nylon 4,6, nylon 6,9, nylon 6J0, nylon 6J2, nylon 11, nylon 12, amorphous nylons, aromatic nylons and their copolymers.
• the polymer of the carrier may be the same as or different from the polyamide of the flowable mixture.
• both polymers may be a polyamide, particularly nylon 6,6, but may have the same or different molecular weight.
• the preferred weight average molecular weight of the carrier polymer of the concentrate is in the range of about 5,000 D to about 60,000 D.
• the most preferred range of the weight average molecular weight for the carrier polymer is in the range of about 10,000 to about 40,000 D.
• the dissociation step of the present process may occur at least in part via the forming of the concentrate such that the dissociation step may precede the step of forming the flowable mixture. It is therefore understood that the process steps (e.g., forming and dissociating) may occur sequentially without regard to order, simultaneously or a combination thereof.
• the flowable mixture is sufficiently mixed to form the dispersed nanocomposite structure of dissociated silicate in the polymer melt, and it is thereafter cooled.
• the silicate can be dissociated by being subjected to a shear having an effective shear rate.
• an effective shear rate is a shear rate which is effective to aid in dissociation of the silicate and provide a composition comprising a polyamide matrix having silicate substantially homogeneously dispersed therein without substantially breaking the individual units (e.g., platelets or fibrous chains).
• any method which can be used to apply a shear to a flowable mixture or any polymer melt can be used.
• the shearing action can be provided by any appropriate method, such as by mechanical means, by thermal shock, by pressure alteration, or by ultrasonics.
• the flowable polymer mixture is sheared by mechanical methods in which portions of the melt are caused to flow past other portions of the mixture by use of mechanical means such as stirrers,
• Banbury type mixers Brabender type mixers, Farrel continuous mixers, and extruders.
• the mixture is subjected to multiple shearings.
• increased residence time is also provided, which results in - 16
• shearing is achieved by alternatively raising or lowering the temperature of the mixture causing thermal expansions and resulting in internal stresses which cause the shear.
• shear is achieved by sudden pressure changes in pressure alteration methods; by ultrasonic techniques in which cavitation or resonant vibrations which cause portions of the mixture to vibrate or to be excited at different phases and thus subjected to shear.
• twin screw single or twin screw
• a preferred twin screw extruder is a co-rotating fully intermeshing type, such as the ZSK series manufactured by Werner and Pfleiderer Company.
• the silicate can be fed into the twin screw extruder at the feed throat or at the downstream vent.
• the preferred method is to feed the silicate at the downstream vent, which produces a composite polymer with improved performance properties.
• FCM Farrel Continuous Mixer
• the preferred temperature of the melt is in the range from about 275 to 315°C, with the most preferred range being from about 275 to 295°C.
• the polymer melt containing nano-dispersed dissociated silicate material may also be formed by reactive extrusion in which the silicate material is initially dispersed as aggregates or at the nanoscale in a liquid or solid monomer and this monomer is subsequently polymerized in an extruder or the like.
• the polymer may be granulated and dry mixed with the treated silicate material, and thereafter, the composition may be heated in a mixer until the polymer is melted forming the flowable mixture.
• the third process step is a solid state polymerization step, wherein the compounded pellets are held for several hours at a high temperature at least about 20°C below the melting or softening point of the polymer.
• a high temperature at least about 20°C below the melting or softening point of the polymer.
• typical solid state polymerization conditions are heating the solid polymer in the range of about 200°C to about 17 -
• the solid state polymerization step can be further effected with a catalyst that increases the molecular weight of the polyamide, e.g., a phosphorous-containing catalyst such as monosodium phosphate.
• a catalyst that increases the molecular weight of the polyamide e.g., a phosphorous-containing catalyst such as monosodium phosphate.
• phosphorous-containing catalysts are disclosed in U.S. Patent No. 4,966,949.
• milder treatment conditions are needed to effect the desired polymerization.
• the treatment temperature can be below the temperature used in solid state polymerization absent the catalyst using the same polyamide, i.e., more than 20°C below the melting or softening point of the polyamide.
• the treatment time can be lowered to the range of about 0.5 hours to about 5 hours.
• An optional processing step is a heat treatment step, where the composition is heated to improve intercalation of the nylon molecules into the silicate structure.
• Said heat treatment step is performed by heating the composition at a temperature in the range of about 200°C to about 240°C for a period of about 2 to about 5 hours.
• the heat treatment step can optionally be incorporated into the dissociating step by increasing the residence time of the mixture in the mixer or extruder, thereby heat treating under melt conditions.
• the process to form the nanocomposite is preferably carried out in the absence of air, as for example in the presence of an inert gas, such as argon, neon or nitrogen.
• the process can be carried out in a batchwise or discontinuous fashion, as for example, carrying out the process in a sealed container.
• the process can be carried out in a continuous fashion in a single processing zone, as for example, by use of an extruder, from which air is largely excluded, or in a plurality of such reaction zones in series or in parallel.
• the process to prepare a polymer nanocomposite composition comprises forming a first flowable mixture of a polyamide, at least one monomer and a silicate material; dissociating at least 50% but not all of the silicate material; polymerizing the monomer; and subjecting the polyamide in the mixture to solid state polymerization. It is to be understood that the polymerization of the monomer step can occur - 18
• At least one monomer of the this embodiment includes monomers such as ⁇ - caprolactam, lauryllactam, and their corresponding lactones.
• the process to prepare a polymer nanocomposite composition comprises forming a flowable mixture of a polyamide and a treated silicate material; dissociating the at least about 50% but not all of the treated silicate material; adding an additional amount of said polyamide, most preferably during said dissociating step; and subjecting the polyamide in the mixture to solid state polymerization.
• Each of the above embodiments of the process to prepare the polymer nanocomposite composition can be followed by additional steps or treatments, or additional melt polymerization of the composition by increasing the residence time in the mixer with the removal of water condensation product.
• the increased residence time can also improve the intercalation of the polyamide into the silicate, as discussed above.
• composition of the present invention may be made into, but is not limited to, the form of a fiber, film or a molded article.
• Solid state polymerization increases toughness, strength, and ductility of the produced polymer, while generally maintaining processability and modulus. Solid-state polymerization may improve properties such as elongation at yield, tensile elongation at break, flexural modulus, elastic modulus and both notched and unnotched Izod impact strength. Additional catalysts may be added, but are not required. Acid-functional clay treatments are particularly amenable to SSP (e.g., SCPX 1016 and SCPX 1255). They may serve to build polymer-clay linkages by tethering nylon molecules to the adsorbed acid moieties. The stoichiometric balance of amine and acid groups can impact the properties of the resulting polymer.
• SSP e.g., SCPX 1016 and SCPX 1255
• a higher amine:acid ratio in the nylon is desirable, especially in the case of aminoacid-treated silicates.
• the use of solid state polymerization to finish the nanocomposite would allow starting with a lower RV nylon that would enhance intercalation, leading to greater exfoliation of the clay layers.
• the inherent brittleness of nanocomposites compounded on the FCM may be overcome with SSP finishing, to make the FCM a viable low cost process alternative.
• nylon 6,6 polymers The following types of nylon 6,6 polymers have been employed in nanocomposites described herein.
• the montmorillonite clay used has an exchange capacity of about 95 millieqivalents per 100 g of silicate.
• Example 1 Conventional compounding without SSP
• a high molecular weight in the nylon matrix of nanocomposites has been found to be even more beneficial for the ductility and toughness of the nanocomposites than for the neat nylon polymer.
• the smectic silicates reduce nylon molecular weight during the compounding operation, especially in the first pass, resulting in a loss of ductility and toughness.
• the molecular weight of nylon b was observed to drop from 36,500 to 31,500 D in a single pass of 7% montmorillonite treated with dimethyl di (hydrogenated tallow) ammonium cation (2M2HT-montmorillonite) through a 40 mm ZSK twin screw extruder manufactured by Krup Werner & Pfleiderer Company.
• a second pass reduced the MW further to only 21,000 D.
• Solid state polymerization can be implemented in compounded nanocomposites under similar conditions used for the neat polymer as a more efficient method for building molecular weight. Improvements are obtained in tensile strength and elongation, as well as notched and un-notched Izod impact strength. Slight losses in modulus sometimes occur, perhaps due to breakage of the thin delaminated platelets during flow of the higher viscosity nylon matrix.
• RV on mechanical properties
• the nylon RV is that of the raw material fed to the extruder.
• PI and P2 in Figure 2 refer to the first and second passes through the compounder.
• a higher amine/ carboxyl end group ratio on the nylon is preferable for nanocomposites, including those that are later subjected to SSP.
• the inherent Lewis acidity of the clay surface in combination with any acidity introduced from clay treatment, either in the form of an aminoacid cation or the polyacrylate peptizer used on some clay grades, could alter the end group balance of the nylon, resulting in some degree of depolymerization.
• an acidity of 40 ⁇ equiv/g (4.0 mequiv/lOOg clay) -COOH was measured for both acrylate-coated Na- montmorillonite and the 2M2HT-montmorillonite.
• Amino acid exchanged grades would have higher acid levels according to the degree of substitution, as measured by the milliequivalenet exchange ratio (MER) in milliequivalents of cation per 100 g of silicate.
• MER milliequivalenet exchange ratio
• nylons a, and c are preferred to nylon b.
• the higher amine end group concentration of nylon d would be especially important in the case of silicates treated with amino acid cations, which can react with the amine end groups of the nylon.
• These treated silicates show a stronger response to the effects of SSP, resulting in larger increases in the above properties than nanocomposites containing pristine silicates or those treated with unreactive moieties.
• the molecular weight changes to the high amine nylon d due to compounding with 4% montmorillonite exchanged with 12-aminolauric acid (ALA-montmorillonite) and subsequent solid state polymerized have been analyzed via GPC.
• Mn number-average molecular weight IV: intrinsic viscosity measured in formic acid
• the extrusion process is seen in the above table to not change the molecular weight or its distribution in the nylon significantly. While a large increase in molecular weight of the nanocomposite does occur during SSP, it is reduced from that of the neat resin (which gels) by the presence of the acid moieties on the clay. There is, furthermore, evidence that the nylon matrix is being bound to the clay even during the compounding operation. During solid state polymerization, the nylon either branches or couples further with the organosilicate to form very high molecular weight species that become insoluble.
• Solid state polymerization was practiced by heating the plastic pellets to 200-240°C (typically 220°C) with a dry nitrogen sweep to remove the water of condensation for a period of 2-4 hours (typically 4 hours). It was not necessary to add additional catalysts above those present from the initial melt polymerization, although mono- or di- sodium phosphate could have been added at 100-500 ppm. In one instance, adding 1,000 ppm monosodium phosphate resulted in an increase of compounded molecular weight from 27,400 to 30,600 D (SSP was not performed). 22-
• the SSP dryer is set to 470°F (243 °C) oil temperature and the nylon nanocomposite is heated for four hours at 220°C (230°C shell temperature) following an approximately 2-hour heat-up period.
• the resulting time-temperature profiles are shown below for representative nanocomposite solid state polymerization runs.
• Example 4 Increase in molecular weight Increasing molecular weight of the nylon matrix is indicated by the intrinsic viscosity measurements shown in the table below.
• Intrinsic viscosity builds linearly with time in the SSP dryer, as for example shown by the following data and graph ( Figure 5).
• Example: 5 Injection molding of solid state polymerized nanocomposites
• Solid-state polymerized nanocomposites based on nylons c and d mold easier with higher temperature setpoints than at lower temperature.
• the nylon d-based nanocomposites mold more easily than those based on the nylon c, perhaps because the nylon c matrix reaches a higher viscosity level than the nylon d.
• Lower pack and hold pressures can also be used.
• Example 6 Mechanical properties for concentrate route using high amine nylon matrix
• a high amine nylon concentrate comprising 17% ALA-montmorillonite in nylon d was then let down into three different resins having a range in molecular weight and amine/acid end group concentration, with and without subsequent solid-state polymerization prior to molding.
• a fairly intense screw design was used in the ZSK 40mm twin screw extruder with a feed rate of 100 lbs/hr (43.5 kg/hr) and screw speed of 250 rpm. The barrel zone temperatures were set at 270°C.
• the polymerization dryer was set to 470°F (243 °C) oil temperature from start to finish, giving a residence time of up to four hours at a 220°C resin temperature and 230°C shell temperature. Sample descriptions and mechanical properties are given in the table below.
• montmorillonite compensates any molecular weight degradation of the nylon that might have occurred during compounding.
• the effects of the parameters can be analyzed more quantitatively by use of the neural network CAD/Chem software (AlWare, Cleveland, OH).
• the nylons are described by their nominal weight-average molecular weight and the nominal ratio of amine/acid end groups.
• the mineral content of the nanocomposite is retained as a correlating variable to account for the minor differences between samples.
• the following linear correlation coefficients are obtained.
• SSP refers to the solid state polymerization time, in hours.
• Figure 7 shows increasing tensile strength with SSP time when nanoclay is present, but not in the neat nylon.
• the ductility and toughness of nanocomposites are increased significantly by solid state polymerization and to a lesser extent by higher amine/acid ratio and initial molecular weight of the nylon ( Figures 8, 9 and 10).
• the ALA-montmorillonite concentration in the last two figures is 4.9%.
• Stiffness tensile modulus
• Solid state polymerization perhaps through network formation between the high MW nylon and the clay by reactive tethering of the nylon polymer molecules to the ammonium ions adsorbed on the clay surface ( Figure 11).
• compositions, SSP time and mechanical property data is given in the table below for all of the ALA-montmorillonite, 2M2HT-montmorillonite, 2MBHT- montmorillonite and sepiolite nanocomposite preparations involving solid state polymerization.
• Aminoacid organoclay is seen to provide the most favorable combination of nanocomposite properties following SSP. However, it may cause more embrittlement than other clay types if SSP is not practiced.
• the acid functionalization is believed to compete for the amine end groups on the nylon chains, thus upsetting the end group balance and degrading nylon molecular weight during compounding. Higher initial molecular weight or amine/acid end group ratio in the selected nylon would help to counteract this effect, but SSP preferably would be performed following compounding to restore or even further increase the nylon molecular weight.
• Pristine sepiolite is observed to be less destructive to ductility and toughness than is the montmorillonite. Nanocomposite material compounded with a single pass through the Farrell Continuous

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