| PATENT NUMBER | This data is not available for free |
| PATENT GRANT DATE | March 2, 1993 |
| PATENT TITLE |
Macrocyclic filled compositions convertible to polyester composites |
| PATENT ABSTRACT |
Thermoplastic polyester composites are prepared from compositions comprising a filler, at least one macrocyclic poly(alkylene dicarboxylate) oligomer and a polymerization catalyst therefor. The use of polyester oligomer mixtures is preferred, and they may be present in liquid or solid form. The polyester composites prepared therefrom are characterized by excellent properties including solvent resistance. |
| PATENT INVENTORS | This data is not available for free |
| PATENT ASSIGNEE | This data is not available for free |
| PATENT FILE DATE | May 16, 1991 |
| PATENT REFERENCES CITED | Evans et al., U.S. patent application Ser. No. 07/702,577, filed May 20, 1991 |
| PATENT CLAIMS |
What is claimed is: 1. A composition comprising a filler; at least one macrocyclic polyester oligomer comprising structural units of the formula ##STR4## wherein R is an alkylene or mono- or polyoxyalkylene radical containing a straight chain of about 2-8 atoms and A is an m- or p-linked monocyclic aromatic or alicyclic radical; and a catalytically effective amount of a macrocyclic polyester oligomer polymerization catalyst. 2. A composition according to claim 1 wherein a mixture of polyester oligomers is employed. 3. A composition according to claim 2 wherein the catalyst is a basic reagent, tin alkoxide, organotin compound, titanate ester or metal acetylacetonate. 4. A composition according to claim 3 wherein the catalyst is present in the amount of about 0.01-2.0 mole percent based on structural units in the oligomers. 5. A composition according to claim 4 wherein R is ethylene or tetramethylene and A is m- or p-phenylene. 6. A composition according to claim 5 wherein the catalyst is an alkali metal salicylate, alkali metal alkoxide or phosphine. 7. A composition according to claim 5 wherein the catalyst is a stannous alkoxide containing C.sub.1-4 alkyl groups. 8. A composition according to claim 5 wherein the catalyst is a dialkyltin(IV) oxide, a dialkyltin(IV) dialkoxide or a heterocyclic analog thereof. 9. A composition according to claim 8 wherein the catalyst is 2,2-di-n-butyl-2-stanna-1,3-dioxacycloheptane. 10. A composition according to claim 5 wherein the catalyst is a titanate ester. 11. A composition according to claim 5 wherein the catalyst is a metal acetylacetonate or a combination thereof with an aliphatic alcohol. 12. A composition according to claim 11 wherein the catalyst is an equimolar mixture of ferric acetylacetonate and 1,12-dodecanediol. 13. A composition according to claim 5 wherein the filler comprises continuous or chopped fibers. 14. A composition according to claim 13 wherein the proportion of filler is in the range of about 5-80% by weight. 15. A composition according to claim 5 wherein A is p-phenylene. 16. A composition according to claim 15 wherein R is tetramethylene. 17. A composition according to claim 16 wherein the catalyst is employed in the amount of about 0.05-1.0 mole percent based on structural units in the oligomers. 18. A composition according to claim 17 wherein A is p-phenylene. 19. A composition according to claim 18 wherein R is tetramethylene. 20. A composition according to claim 5 wherein the oligomers are in liquid form. 21. A composition according to claim 5 wherein the oligomers are in solid unconsolidated form. 22. A composition according to claim 5 wherein the oligomers are in solid consolidated form. -------------------------------------------------------------------------------- |
| PATENT DESCRIPTION |
This invention relates to the formation of thermoplastic composites. More particularly, it relates to compositions convertible to thermoplastic polyester composites. Resinous composites containing thermoplastic resins in combination with fillers, most often of a fibrous nature, have become of increasing interest in recent years. Several problems have been encountered in the preparation of such composites. In the first place, most thermoplastic resins have relatively high melt viscosities which make fiber wetting difficult. In the second place, such resins can be melted only at relatively high temperatures, requiring substantial and expensive energy input for fabrication. Composite formation therefore typically requires providing an extremely short path that the resin must traverse to reach the fiber surface. This is typically achieved by grinding the resin into very fine powder which is intermingled with the fibers, or by employing solution impregnation followed by evaporation of the solvent. Thermoset composites, on the other hand, are often much easier to prepare. The thermosetting materials are typically of much lower viscosity when liquid than are thermoplastic resins. Moreover, it is easy to demold a thermoset material after a molding operation, since melting does not occur at or above the curing temperature. Methods and materials for forming thermoplastic composites which offer similar advantages to those encountered in thermoset composite systems are very desirable. A step in this direction was made by the development of the cyclic polycarbonate oligomer "prepregs" described in U.S. Pat. No. 4,740,583. Such prepregs, comprising cyclic polycarbonate oligomers in combination with filler materials, are easy to process because of the relatively low melt viscosity of the cyclic polycarbonate compositions. It is relatively easy to polymerize the cyclic polycarbonates to linear polycarbonates, forming thermoplastic composites with many valuable properties. Nevertheless, polycarbonate composites prepared from cyclic polycarbonate oligomers have some disadvantages which warrant further investigation in the thermoplastic composite area. One such disadvantage is that the melt viscosities of the cyclic polycarbonate oligomers, while substantially lower than those of essentially all thermoplastic resins (e.g., about 5.7 poise at 250.degree. C. for bisphenol A polycarbonate cyclics), are still too high for convenient employment in certain types of composite-forming operations. Another is that polycarbonate is inherently not a solvent-resistant material, with the result that the composites are easily degraded by organic solvents. Still another is the necessity for a large thermal cycle (typically 100.degree.-150.degree. C.), since the mold must be cooled to solidify the polycarbonate before the composite part is removed. The present invention provides composite precursor compositions of extremely low melt viscosity, convertible by polymerization to polyester composites of high crystallinity and solvent resistance. Said compositions are capable of polymerization at temperatures between the melting point of the resin precursor and the crystalline melting temperature of the product polyester. Thus, it is possible to employ an essentially isothermal molding cycle for the preparation (e.g., by molding) of composite parts from such precursors. In one of its aspects, therefore, the invention includes compositions comprising a filler; at least one macrocyclic polyester oligomer comprising structural units of the formula ##STR1## wherein R is an alkylene or mono- or polyoxyalkylene radical containing a straight chain of about 2-8 atoms and A is an m- or p-linked monocyclic aromatic or alicyclic radical; and a catalytically effective amount of a macrocyclic polyester oligomer polymerization catalyst. Suitable fillers for the compositions of this invention include particulate materials such as clay, talc, quartz, wood flour, finely divided carbon and silica. Fillers comprising continuous or chopped fibers, including fibrous carbon, glass, boron and fibrous polymers such as poly(butylene terephthalate) and highly oriented polyamide, are particularly useful. Carbon and glass fibers are frequently preferred, with carbon fibers being advantageous when a particularly stiff composite article is desired. Continuous fillers may be in unidirectional form, either as yarns or as random fibers, or may be woven into fabric batts or tapes. The macrocyclic polyester oligomers may be employed as single compounds or, preferably, as mixtures of oligomers of various degrees of polymerization. Such oligomer mixtures may be prepared by contacting at least one diol of the formula HO-R-OH and at least one diacid chloride of the formula ##STR2## under substantially anhydrous conditions and in the presence of a substantially water-immiscible organic solvent, with at least one unhindered tertiary amine; said contact being conducted at a temperature from about -25.degree. to about +25.degree. C. This method of preparation is disclosed and claimed in copending, commonly owned application Ser. No. 07/608,767 now U.S. Pat. No. 5,039,783. Useful diols include alkylene glycols and polyalkylene glycols, provided the straight chain connecting the hydroxy groups contains about 2-8 atoms. Suitable alkylene glycols include ethylene glycol, propylene glycol, tetramethylene glycol, hexamethylene glycol and neopentylene glycol. Suitable polyalkylene glycols include diethylene glycol and triethylene glycol. Ethylene glycol and tetramethylene glycol are preferred. The other reagent used to form the macrocyclic polyester oligomers is a diacid chloride containing an A value which may be an m- or p-linked monocyclic aromatic or alicyclic radical. Included are m- and p-phenylene, substituted derivatives thereof, and similarly structured cyclohexylene and cyclopentylene radicals. The m- and p-phenylene radicals, and especially p-phenylene, are preferred. Also employed is at least one unhindered tertiary amine and a substantially water-immiscible organic solvent. The essential feature of the amine is the lack of a substantial amount of steric hindrance around the basic nitrogen atom. Preferred amines of this type are polycyclic compounds with a tertiary nitrogen in the bridgehead position, as illustrated by quinuclidine and 1,4-diazabicyclo[2.2.2]octane (DABCO), which have the following formulas, respectively: ##STR3## Also suitable, though less preferred because they produce the macrocyclic oligomers in lower yield, are N-methyl heterocyclic monoamines such as N-methylpyrrolidine and N-methylpiperidine, especially the former. As organic solvents, various water-immiscible non-polar organic liquids may be employed. Illustrative liquids of this type are aromatic hydrocarbons such as toluene and xylene; substituted aromatic hydrocarbons such as chlorobenzene, o-dichlorobenzene and nitrobenzene; and chlorinated aliphatic hydrocarbons such as chloroform, methylene chloride, trichloroethane and tetrachloroethane. Chlorinated aliphatic hydrocarbons are preferred, with methylene chloride frequently being most preferred because of its availability and particular suitability. It is frequently advantageous to employ, in combination with the water-immiscible solvent, a more polar combined oxygen-containing solvent such as tetrahydrofuran in which the diol is soluble to facilitate dissolution thereof. The molar ratio of diol to diacid chloride is preferably about 1:1, although some variation (generally no more than about 5%) is permissible. Unlike the method for preparation of cyclic polyarylates described in the aforementioned U.S. Pat. No. 4,829,144, the present method requires that the amine be employed in amounts approximating those of the diol and diacid chloride combined, rather than in catalytic amounts. Formation of an acylammonium salt by reaction of the amine with the diacid chloride is apparently a step in the process. Typical molar ratios of amine to combination of diol and diacid chloride are in the range of about 1.0-1.5:1, with 1.25:1 frequently being preferred. The proportion of solvent employed in the reaction is not critical. In general, highest yields are obtained at concentrations of diol and diacid chloride in the range of about 0.1-0.5M. The precise order of addition of reagents is not critical, except that the amine and diacid chloride should be prevented from coming into contact with each other prior to contact with the diol. This is necessary because the acylammonium salt which is thus formed undergoes nearly immediate decomposition by nucleophilic displacement of nitrogen from a carbon atom by the chloride ion also present in said salt. Thus, it is possible to introduce the diol, diacid chloride and amine simultaneously into the reaction vessel, with the amine being introduced either separately or in admixture with the diol. It is also possible to introduce the diol and diacid chloride into the reaction vessel which already contains the amine, in which case the diol and diacid chloride may be introduced separately or in admixture. It is essential that the reaction conditions be substantially anhydrous. The presence of an appreciable amount of water will cause hydrolysis of the diacid chloride or the acylammonium salt, to produce carboxylic acid which may then undergo dehydration to an anhydride. Such hydrolysis will naturally decrease the yield of macrocyclic polyester oligomer. It is also essential to conduct the reaction at a temperature from about -25.degree. to about +25.degree. C., preferably from about -25.degree. to about 5.degree. C. and most preferably from about -10.degree. to 0.degree. C. At temperatures below about -25.degree. C., the process becomes impractical by reason of an extremely low reaction rate. At temperatures above about +25.degree. C., side reactions predominate; they may include decomposition of the acylammonium salt and reaction of the amine with chlorinated aliphatic hydrocarbon used as solvent, to form quaternary ammonium salts. Yields are maximized at temperatures no higher than about 5.degree. C. When the solvent is a chlorinated aliphatic hydrocarbon or similar material containing highly nucleophilic substituents, reaction with the amine may be relatively rapid at temperatures above about 5.degree. C. Under such conditions, it will generally be advisable to introduce the diol, diacid chloride and amine simultaneously as previously described, so as to ensure contact between the amine and diacid chloride before the former comes into possible reactive contact with the solvent. Following the reaction between the diacid chloride and diol, it is generally necessary to remove linear polyester in the form of oligomers and high polymer. The high polymer portion of the linears is insoluble in the solvents employed, and may be removed by filtration. Linear oligomers are most conveniently removed by column chromatography through silica gel or the like. Following the removal of high polymer and linear oligomers, the solvent may be removed and the macrocyclic oligomers recovered in substantially pure form. The compositions prepared by the above-described method are mixtures of macrocyclic polyester oligomers, usually having degrees of polymerization from 2 to about 12. They usually comprise predominantly dimer, trimer, tetramer and pentamer. Structural identification of the macrocyclic polyester oligomers was made by comparison with authenic samples isolated from commercially availabe linear polyesters. Thus, extraction of a commercial sample of poly(butylene terephthalate) with hot dioxane yielded about 1% by weight of a pale yellow semi-solid, from which linear oligomers were removed by flash chromatography over silica gel. Medium pressure liquid chromatography was then employed to isolate the macrocyclic dimer, trimer, tetramer, pentamer and hexamer from the remaining mixture |
| PATENT EXAMPLES | Available on request |
| PATENT PHOTOCOPY | Available on request |
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