HIGH CHAR YIELD BENZOXAZINE COMPOSITIONS

Abstract: A polybenzoxazine comprised of the reaction product of a mixture comprised of (i) a benzoxazine compound, (ii) a furan compound, (iii) a benzoxazine-furan compound or (iv) combinations thereof, wherein the mixture has a furan ring to benzoxazine ring ratio of at least 0.001 to at most 10. Said mixture forming a polybenzoxazine by heating the mixture for a sufficient time to form the polybenzoxazine.

Description: HIGH CHAR YIELD BENZOXAZINE COMPOSITIONS The invention relates to benzoxazines, high char yield polybenzoxazines formed therefrom and method of forming said polybenzoxazines. Benzoxazines are a class of phenolic resins that are generally formed by the 5 reaction of a phenol, primary amine and formaldehyde or paraformaldehyde. The benzoxazine may be polymerized by simple heating to open the oxazine ring. This leads to the formation of a chemical bond between the phenolic groups. Cross-linked (that is, thermoset) polybenzoxazines generally require multi-functional benzoxazine monomers (that is, they contain more than two reactive sites). Generally, cross-linked o polybenzoxazines are formed from benzoxazine monomers having more than one benzoxazine rings. Benzoxazines exhibit several advantages for forming thermally stable polymers compared to resole phenolics and novolacs. For example, benzoxazines do not form any volatile reaction products upon polymerization, which is, for example, an 5 advantage for forming composite parts (that is, no out-gassing). In addition, they do not require the use of strong acid polymerization catalysts; such as used to cure resoles, which can cause corrosion of a mold. One of the desirable traits of the cured benzoxazines is their potential to achieve high char yields, which are indicative of their thermal stability. However, many of o the benzoxazine monomers that give cured products with high char yields often have limited processability because of their high viscosity below their reaction temperature. This makes them more suitable for processing methods, such as compression molding, rather than high speed processing methods, such as pultrusion. That is to say, they do not achieve desirable processing viscosities (that is, sufficient to easily impregnate fiber matrices) without the aid 5 of a solvent or substantial heating. Unfortunately, the use of a solvent adds processing steps to remove it. The disadvantage of applying heat to the neat resin (benzoxazine) is that at the temperatures (for example, 160°C) needed to achieve a reasonable processing viscosity (for example, <1000 centipoise) the benzoxazines autopolymerize resulting in a very short processing time. As a o result, the viscosity builds faster than the ability to efficiently impregnate the fiber mat because of polymerization. Consequently, a method of obtaining both high char yields and good processability, without the use of solvents, is desirable for extending the utility of benzoxazines into applications, such as structural composites. A recent attempt to increase the char yield of polybenzoxazines has been described by Ishida in WO 99/18092. Ishida describes incorporating a pendant reactive 5 group, either to the phenolic or amine reactants, to create the benzoxazine monomer. The pendant reactive group is a group that is reactive with itself (for example, acetylene group) or is a first reactive pendant group that is reactive with a second pendant reactive group, neither being reactive with itself. Unfortunately, even though these benzoxazines are reported to increase the char yield, they fail to address the processing problems described 0 above. Accordingly, it would be desirable to provide a polybenzoxazine that overcomes one or more of the problems of the prior art, such as one of those described above. It would be particularly desirable to provide an easily processed benzoxazine composition that still forms a high char yield polybenzoxazine. 5 A first aspect of the present invention is a polybenzoxazine comprised of the reaction product of a mixture comprised of (i) a benzoxazine compound, (ii) a furan compound, (iii) a benzoxazine-furan compound or (iv) combinations thereof, wherein the mixture has a furan ring to benzoxazine ring ratio of at least 0.001 to at most 10. A second aspect of the invention is a method of forming a polybenzoxazine o comprised of: mixing (i) a benzoxazine compound, (ii) a furan compound, (iii) a benzoxazine-furan compound or (iv) combinations thereof, wherein the mixture has a furan ring to benzoxazine ring ratio of at least 0.001 to at most 10 and heating the mixture for a sufficient time to form the polybenzoxazine. 5 A third aspect is a mixture useful for preparing a polybenzoxazine comprised of (i) a benzoxazine compound, (ii) a furan compound, (iii) a benzoxazine-furan compound or (iv) combinations thereof, wherein the mixture has a furan ring to benzoxazine ring ratio of at least 0.001 to at most 10. In the broadest sense, the benzoxazine compound is a compound that o contains at least one benzoxazine ring, but fails to have a furan ring. Similarly, the furan compound is a compound that contains at least one furan ring but fails to have a benzoxazine ring. Finally, the benzoxazine-furan compound contains at least one furan ring and at least one benzoxazine ring. Practically, each of the compounds, generally, has at most 100 carbon atoms. 5 Surprisingly and unknown until the present invention, it has been discovered that a furan group, which does not react with itself, can be combined with a benzoxazine to give polymers with improved char yields after curing. Furthermore, it is unnecessary and may even be detrimental to add a compound containing a group that is reactive with the furan (i.e, maleimide) to the benzoxazine compound or benzoxazine-furan compound to i o obtain increased char yield. That is to say, the mixture preferably fails to have a benzoxazine compound that contains a maleimide group when the benzoxazine-furan compound is present in the mixture. It is even more preferable to have the mixture devoid of any maleimide. In addition, the invention allows, for example, the use of certain 15 benzoxazine-furan compounds that have only one benzoxazine ring and one furan group to unexpectedly form a thermoset polymer by itself. This type of compound also has been found to reduce the viscosity of a benzoxazine compound or benzoxazine-furan compound containing more than one benzoxazine ring without being detrimental to the final properties, such as char of the resultant polybenzoxazine. o These new polybenzoxazines may be used in the same applications as polymers, such as polyimide, phenolics, epoxies and other thermally stable polymers. In particular, they may be used in applications that take advantage of properties, such as fire resistance and low water absorption. Examples of applications include brake pads or composite applications, such as interiors and structural components of an aircraft, piping, 5 ladders, ship masts, gratings, table trays, ducts, beams, ship housings, and printed wiring boards. The polybenzoxazine is comprised of the reaction product of a mixture comprised of (i) a benzoxazine compound, (ii) a furan compound, (iii) a benzoxazine-furan compound or (iv) combinations thereof, wherein the mixture has a furan ring to benzoxazine o ring ratio of at least 0.001 to at most 10. Because of the furan ring to benzoxazine ring ratio limitation, it is understood that the mixture must contain at least some amount of either the furan compound or benzoxazine-furan compound. That is to say, one of these has to be present in the mixture to provide the furan ring required by the furan/benzoxazine ring ratio. The mixture preferably contains the benzoxazine compound and the furan compound. In addition, it is preferred to have a benzoxazine compound or benzoxazine-furan compound that has more than one benzoxazine ring in the mixture. More preferably, the mixture contains a benzoxazine-furan compound that has at least two benzoxazine rings and at least one furan ring. Even more preferably, the mixture contains a benzoxazine-furan compound having at least two benzoxazine rings, in combination with a benzoxazine-furan compound that has one benzoxazine ring and one or more furan rings. To reiterate, the ratio of furan to benzoxazine rings in the mixture is at least 0.001 to at most 10. Preferably, the ratio is at least .1, more preferably at least 0.2, even more preferably at least 0.4 and most preferably at least 0.5 to preferably at most 8, more preferably at most 7, even more preferably at most 5 and most preferably at most 4. The benzoxazine compound may be any suitable benzoxazine, such as those known in the art. The benzoxazine may be, for example, those described by U.S. Patent No. 5,543,516; WO 99/18092 and Japanese Patent Application HEI 9-59333. Preferred benzoxazine compounds include those of the formula: where R. is a divalent radical that is (a) an aliphatic, aromatic or combination thereof and composed of 1-35 carbon atoms, together with up to five atoms selected from oxygen, nitrogen, sulfur, phosphorous, halogen and combinations thereof; (b) a single bond or (c) S, S 2 , SO, SO 2 , O or CO and R 5 is one or more H, substituted or unsubstituted alkyl of 1 to 24 carbon atoms, or aromatic or substituted aromatic or aromatic substituted alkyl of 6 to 24 carbon atoms. Preferably, P is a single carbon that has bonded to it one or more groups, such as H, CH 3 , C 2 H 5 , C 3 H 7 , n-C 3 H 7 , i-C 3 H 7 , cyclohexyl, bicyclohexyl(2.2.1)heptyl, phenyl, CF 2 , CF 3 , CC1 3 , CF 2 C1, CN, (CH 2 ) 2 COOH 3 or PO(OCH 3 ) 2 . More preferably, R* is one carbon directly bonded to two CH 3 groups or two hydrogens. Preferably, R 5 is an unsubstituted alkyl of 1 to 24 carbon atoms or unsubstituted aryl of 6 to 24 carbon atoms. More preferably, R 5 is a 6 to 12 unsubstituted aryl. Most preferably, R5 is a phenyl. R 5 may also contain at least one reactive group described previously. The reactive group may be, other than a furan group, a group such as an alkene (that is, C=C), alkyne (that is, C≡C), nitrile (i.e, C≡N), oxazole, oxazoline, phenol, epoxy, anhydride or imide. Examples of preferred R 5 structures are: — C≡CR., -C— C≡N, where Ri is one or more H, halogen, substituted or unsubstituted alkyl of 1 to 6 carbon atoms, or aromatic or substituted aromatic (for example, a benzoxazine, but not a furan) or aromatic substituted alkyl of 6 to 24 carbon atoms and R 2 is an alkyl of 1 to 5 carbon atoms, a halogen, a phenyl or combinations thereof. Ri may be a cyclic, linear or branched alkyl. Ri may be substituted with a group containing 1-3 atoms of O, N, P, S, halogen or combinations thereof. Preferably, R \ is H, OH, a substituted aromatic or aromatic substituted alkyl of 6 to 18 carbon atoms, more preferably of 6 to 12 carbon atoms. More preferably, Ri is H, OH, unsubstituted or substituted alkyl having 1 to 6 carbons. Most preferably, Ri is H or OH. Generally, the furan compound is given by the formula: wherein X is composed of a total of 1-50 carbon atoms and up to 10 atoms selected from oxygen, nitrogen, sulfur, phosphorous, halogen and combinations thereof. Preferably, X is composed of at most 30, more preferably at most 25, even more preferably at most 20, and most preferably at most 18 carbon atoms. Preferably, X contains at most 9, more preferably at most 8, even more preferably at most 7 and most preferably at most 6 atoms selected from oxygen, nitrogen, sulfur, phosphorous, halogen and combinations thereof. Preferably, X contains a reactive group. The reactive group is a group that reacts with either another reactive group (for example, an alkene reacting with another alkene) other than the furan or with the benzoxazine of the benzoxazine compound. Thus, a furan ring is believed to be a reactive group and is treated as such herein because of the belief that it reacts with the benzoxazine ring. The other reactive group may be another furan group or may be a group, such as an alkene (that is, C=C), alkyne (that is, C≡C), nitrile (that is, C≡N), oxazole, oxazoline, phenol, epoxy, anhydride and imide. Reactive group examples, besides the furan, include: — C≡CR -C— C≡N, where Ri and R 2 are the same as described above. Preferred furan compounds include (1) compounds of a reaction between an aldehyde or ketone-containing furan group with a primary amine (that is, Schiff base), such as those described by Hui, et al., Eur. Polvm. J., Vol., 28, No. 12, 1461-1469 (1992); (2) hydrogenated Schiff bases described by (1); (3) compounds of a reaction between a polyol (for example, diol and triol) and an aldehyde containing a furan (for example, furfural) to form, for example, an acetal, such as those described by Gousse, et al., Polymer International. Vol. 48, 723-741 (1999); (4) a polymer containing a furan described by Laita, et al., Eur. Polvm. J.. Vol. 8, 1203-1211 (1997) and (5) Gousse, et al., Macromolecule. Vol. 31, 314-321 (1998). To reiterate, the benzoxazine-furan compound has at least one benzoxazine ring and at least one furan, such as those shown in the formula: wherein X is as described previously, Ar is a benzene ring or 2 to 4 fused benzene rings, j is 5 an integer from 4-10 and Y is independently a monovalent radical that is H; OH; halogen (for example, fluorine, bromine, chlorine) or an alkyl, aryl, alkenyl, alkynyl or combination thereof composed of 1-35 carbon atoms containing up to 5 atoms selected from oxygen, nitrogen, sulfur, phosphorous, halogen and combinations thereof. Although Ar may be a benzene ring, or 2 to 4 fused benzene rings, Ar is l o preferably the benzene ring or 2 fused benzene rings (that is, naphthalene-type structure). Most preferably, Ar is a benzene ring. When Y is an alkyl, aryl, alkenyl and alkynyl or combination thereof, Y preferably contains at most 24, more preferably at most 18 and most preferably at most 12 carbon atoms. It is also understood that this monovalent radical may have combinations of 15 alkyl, aryl, alkenyl and alkynyl (that is, saturated, unsaturated and aromatic double bonds). Y may also be cyclic, linear or branched. When Y has an aryl constituent, the aryl may be heteroaromatic, such as aromatic compounds containing, for example, O, S, N or combinations thereof. That is to say, Y may contain a benzoxazine and furan group. Preferred benzoxazine-furan compounds include those with the formulas: 0 where R 3 is a single bond or substituted or unsubstituted alkyl group having from 1-6 carbon atoms and R 7 is one or more H, halogen, substituted or unsubstituted alkyl of 1 to 24 carbon atoms, or aromatic or substituted aromatic (for example, contains a benzoxazine or furan group) or aromatic substituted alkyl of 6 to 24 carbon atoms. R 7 may be a cyclic, linear or branched alkyl. R 7 may be a group containing 1-12 atoms of O, N, P, S, halogen or combinations thereof. Preferably, R is H, a substituted aromatic or aromatic substituted alkyl of 6 to 24 carbon atoms, more preferably of 6 to 12 carbon atoms. More preferably, R is H, an unsubstituted or substituted alkyl having 1 to 6 carbons. Most preferably, R 7 is H or an unsubstituted alkyl having 1 to 6 carbons. Preferably, R 3 is a Ci to C 6 unsubstituted alkyl. More preferably, R 3 is CH 2 or C 2 H . Most preferably, R is CH 2 . More preferred benzoxazine-furan compounds include compounds having the following formulas: where R 3 and R are as described previously and R 7 is as described previously, with the proviso that it is devoid of a benzoxazine and furan group. Preferred benzoxazine-furan compounds containing one benzoxazine and one furan (that is, R 7 lacks a benzoxazine and furan group and the benzoxazine-furan compound is not of an unsubstituted phenol) have surprisingly been found to not only form a thermoset cross-linked polymer, but also reduce the viscosity, particularly at temperatures below the temperature of polymerization, of a benzoxazine or benzoxazine-furan compound having at least two benzoxazine rings without being detrimental to properties, such as char yield. Even more surprising is that the addition of these to a benzoxazine or benzoxazine-furan compound containing more than one benzoxazine ring improves properties, such as char yield (that is, increase char yield) of the resultant polybenzoxazine. These improvements are more readily observed when the addition is to the benzoxazine compound having more than one benzoxazine ring. Generally, the benzoxazine or benzoxazine-furan compound is made by reacting a phenol, primary amine and formaldehyde or paraformaldehyde. Examples of phenols suitable in making the benzoxazine include those having the formula: wherein Ar is a benzene ring or 2 to 4 fused benzene rings and 1 is an integer from 6-12 and Y is independently a monovalent radical that is H; OH; halogen (for example, fluorine, bromine, chlorine) or an alkyl, aryl, alkenyl, alkynyl, or combination thereof, composed of 1-35 carbon atoms containing up to 5 atoms selected from oxygen, nitrogen, sulfur, phosphorous, halogen and combinations thereof, with the proviso that at least one Y is OH that has an H ortho thereto. Although Ar may be a benzene ring or 2 to 4 fused benzene rings, Ar is preferably the benzene ring or 2 fused benzene rings (that is, naphthalene type structure). Most preferably, the Ar is a benzene ring. When Y is an alkyl, aryl, alkenyl and alkynyl or combination thereof, the radical preferably contains at most 24, more preferably at most 18 and most preferably at most 12 carbon atoms. It is also understood that this monovalent radical may have combinations of alkyl, aryl, alkenyl and alkynyl (that is, saturated, unsaturated and aromatic double bonds). Y may also be cyclic, linear or branched. When Y has an aryl constituent, the aryl may be heteroaromatic, such as aromatic compounds containing, for example, O, S, N or combinations thereof. Examples of monovalent Y radicals include reactive groups described previously. Preferably, Y is H, OH or an alkyl of at most 6 carbons. More preferably, Y, other than the one required OH, is H. Preferred phenolic compounds have the formulas: where * and R5 are the same as previously defined. Examples of phenols include phenol; cresol; 2-bromo-4-methylphenol; 2 allylphenol; 1,4-aminophenol; phenolphthalein; 2,2'- biphenol; 4,4'-methylene-diphenol; 4,4'-dihydroxybenzophenone; bisphenol A; 1,8- dihydroxyanthraquinone; 1 ,6-dihydroxnaphthalene; 2,2'-dihydroxyazobenzene; resorcinol; fluorene bisphenol; 1,3,5-trihydroxy benzene; novolac resin and polyvinyl phenol. The primary amine may be any suitable amine to react with the phenolic compound, such as those known in the art. It is preferred that a reactive group, such as those described above, is bonded to the nitrogen. More preferably, the primary amine has the formula: where R^ is a single bond or a divalent alkyl radical having from 1 to 6 carbon atoms. Preferably, the primary amine is furfurylamine. Other examples of amines include monofunctional amines (that is, one amine) and include those with up to 40 carbon atoms, such as ammonia; methylamine; 5- methylfurfurylamine; ethylamine; propylamine; butylamine; isopropylamine; octadecylamine; cyclohexylamine; alkylamine; 1 aminoanthracene; 4-aminobenzaldehyde; 4-aminobenzophenone; aminobiphenyl; 2-amino-5-bromopyridine; 3-amino-ε-caprolactam; 2-amino-2,6-dimethylpiperidine; 3-amino-9-ethylcarbazole; 4-(2-aminoethyl)morpholine; 2- aminofluorenone; 2-aminofluorene; 1-aminohomopiperidine; 9-aminophenanthrene; 1- aminopyrene; 4-bromoaniline and aniline. Examples of multifunctional amines (that is, more than one amine) include those having up to 40 carbon atoms, such as 2-aminobenzylamine; 1,3-diaminopropane; 1,4- diaminobutane; 1,10-diaminodecane, 2,7-diaminofluorene; 1 ,4-diaminocyclohexane; 9,10- diaminophenanthrene; 1 ,4-diaminopiperizine; 4,4'-methylenedianiline; 4,4'- diaminobenzophenone; diaminodiphenylsulfone; diaminodiphenylsulfide; 4,4'-oxydianiline; melamine; fluorene-tetraamine and tetraaminediphenylether. 5 The benzoxazine or benzoxazine-furan compound may be made by any suitable method, such as those known in the art. Exemplary methods include those described by U.S. Patent Nos. 5,543,516 and 5,152,939; WO 99/18092; Japanese Patent Application Nos. Hei 9-59333 and Hei 8-74896 and Swiss Patent A5 11 606169. Generally, the benzoxazine is made by reacting a phenolic compound, such as those described above o with a primary amine and formaldehyde, paraformaldehyde or combination thereof in an equivalent ratio of phenol, amine and aldehyde of 1 :1 :2. Variations from this equivalent ratio may be used such as those described by Swiss Patent A5 11 606169. In making the benzoxazine, a phenol, primary amine and formaldehyde or paraformaldehyde are combined with or without a solvent. This mixture is then heated to a 5 temperature sufficient to form the benzoxazine. Generally, the temperature is from 70°C to 100°C. Preferably, the temperature is at least 80°C. After cooling, if a solvent is used, it may be removed by any suitable method, such as those known in the art. Examples of suitable solvents are dioxane, toluene, n-butyl acetate and methylisobutyl ketone. The polybenzoxazine is generally made by heating the mixture compound to 0 a temperature for a time sufficient to form the polybenzoxazine. The temperature is desirably at least 70°C to at most 300°C. Preferably, the temperature is at least 100°C and more preferably at least 150°C to preferably at most 250°C and more preferably at most 225°C. Generally, the time at temperature to form the polybenzoxazine is from 1 minute to 20 hours. 5 Polymerization of the benzoxazines is usually done without the use of a solvent, however, a solvent may be used, for example, to facilitate application of the monomer to a substrate. Examples of solvents that may be used include dioxane, tetrahydrofuran, acetone, dimethylformamide, toluene, n-butyl acetate and methylisobutyl ketone. o Even though a catalyst is not necessary, one may be used. Typical catalysts are described in J. Appl. Polvm. Sci.. 1995, 58, 1751-1760; J. Polvm. Sci. Part A: Polvm. Chem.. 1999, 37, 1913-1921; Polymer, 1999, 40, 4563-4570; Poly. Mat. Sci. Ens.. 1999, 81, 114-115 and GB 1 437 814 and include compounds, such as acids, phenols, novolacs, Lewis acids and bases. When a catalyst or initiator is used, it is employed in small quantities, such as 0.01 percent to 5 percent by weight of the mixture. 5 When forming the polybenzoxazine, another additive may also be added for reasons, such as color, fire retardancy, mechanical properties, processing properties and electrical properties. An example of an additive is an epoxy resin, such as those known in the art. EXAMPLES o Analytical Measurement Techniques : Viscosity Measurements Viscosities were measured on a TA Instrument Model CSL 500 Cari-Med Rheometer. A cone and plate method with a 2 cm, 1 degree geometry was used. Thermal Measurements 5 Char yields at 600°C were measured from a thermo-gravimetric analysis run on a TA Instrument Model Number 2050 Thermal Gravimetric Analyzer (TGA). The thermo-gravimetric analysis was under nitrogen to 600°C at 10°C per minute. The temperature at 5 percent weight loss was also measured from the thermo-gravimetric analysis. o Example 1 (a) : Bis A/Furfurylamine Benzoxazine-Furan Compound To begin, about 260 grams of dioxane (Aldrich Chemical Co., Milwaukee, WI), about 2.1 moles of paraformaldehyde (Aldrich Chemical Co., Milwaukee, WI), about 1 mole of furfurylamine (Aldrich Chemical Co., Milwaukee, WI), and about 0.5 mole of bisphenol A "Bis A" (PARABIS, The Dow Chemical Company, Midland, MI) were 5 combined in a reaction flask fitted with a mechanical stirrer, condenser and thermometer. Then, additional dioxane (about 150 grams) was added to wash all of the reactants to the bottom of the reactor. The mixture was then heated to 90°C and maintained at this temperature for about 25 hours. The homogeneous mixture was then cooled to room temperature and the solvent removed at reduced pressure on a rotary evaporator. The final o solvent stripping was done at about 1 mbar at 125°C until no more bubbling was observed. The product was poured into a glass dish containing an aluminum foil insert and allowed to cool to room temperature. Example 1(b): Bis A/Furfuryl amine Polybenzoxazine The benzoxazine-furan compound of Example 1(a) was sealed in a glass 5 bottle, then heated in an oven as follows. The sealed bottle containing the compound was placed in an oven maintained at 150°C, which was then heated to 210°C at 1°C per minute. The sample was maintained at 210°C for about 3 hours to form a polybenzoxazine. The polybenzoxazine had a char yield of 56 percent and a 5 percent loss temperature of 355°C, which is also shown in Table 1. 0 Examples 2-4: Bis A Furfurylamine-Furoin Polybenzoxazine Polybenzoxazines of the benzoxazine-furan compound of Example 1(a) and furoin, a furan compound, (Aldrich Chemical Co., Milwaukee, WI) were prepared by mixing them for about 15 seconds using a WIG-L BUG mixer (Wilmad Glass Co., Buena, NJ). Each mixture was then cured by the same method of Example 1(b). The amount of 5 each component, furan rings/benzoxazine ring ratio, char yield and the loss temperature are shown for each of these Examples in Table 1. Examples 5-7: Bis A Furfurylamine-Furil Polybenzoxazine Polybenzoxazines of the benzoxazine-furan compound of Example 1(a) and furil, a furan compound, (Aldrich Chemical Co., Milwaukee, WI) were prepared by mixing o them for about 15 seconds using a WIG-L BUG mixer. Each mixture was then cured by the same method of Example 1(b). The amount of each component, furan rings/benzoxazine ring ratio, char yield and the loss temperature are shown for each of these Examples in Table 1. Comparative Example 1(a): Bis A/ Aniline Benzoxazine Compound 5 To begin, about 260 grams of dioxane (Aldrich Chemical Co., Milwaukee, WI), about 2.1 moles of paraformaldehyde (Aldrich Chemical Co., Milwaukee, WI), about 1 mole of aniline (Aldrich Chemical Co., Milwaukee, WI), and about 0.5 mole of bisphenol A (PARABIS, The Dow Chemical Company, Midland MI) were combined in a reaction flask fitted with a mechanical stirrer, condenser and thermometer. Then, additional dioxane o (about 150 grams) was added to wash all of the reactants to the bottom of the reactor. The mixture was then heated to 90°C and maintained at this temperature for about 25 hours. The homogeneous mixture was then cooled to room temperature and the solvent removed at reduced pressure on a rotary evaporator. The final solvent stripping was done at about 1 mbar at 125°C until no more bubbling was observed. The product was poured into a glass dish containing an aluminum foil insert and allowed to cool to room temperature. Comparative Example 1(b): Bis A Aniline Polybenzoxazine The benzoxazine monomer of Comparative Example 1(a) was sealed in a glass bottle, then heated in an oven as follows. The sealed bottle containing the monomer was placed in an oven maintained at 150°C, which was then heated to 210°C at 1°C per minute. The sample was maintained at 210°C for about 3 hours to form a polybenzoxazine. The polybenzoxazine had a char yield of 32 percent and a 5 percent loss temperature of 329°C, which is also shown in Table 1. Examples 8-10: Bis A Aniline-Bis A/Furfurylamine Polybenzoxazine Polybenzoxazines of the benzoxazine-furan compound of Example 1(a) and benzoxazine compound of Comparative Example 1(a) were prepared as follows. The components were first mixed by placing the desired amounts of each in a pan and then adding a sufficient amount of tetrahydrofuran (THF), while agitating, to dissolve all of the components. Once all of the components had been dissolved, the THF was removed by first warming slightly and then applying a vacuum at 90°C to 100°C until no bubbling was observed. The mixtures, after removing the THF, were checked by gas chromatography to ensure no residual solvent remained. The mixture was then cured in the same manner as described by Example 1(b) to form a polybenzoxazine. The amount of each component, furan rings/benzoxazine ring ratio, char yield and the loss temperature is shown for each of these Examples in Table 1. Examples 11-13: Bis A/Aniline-Furoin Polybenzoxazine Polybenzoxazines of the benzoxazine of Comparative Example 1(a) and furoin were prepared by the same method described by Examples 2-4. The amount of each component, furan rings/benzoxazine ring ratio, char yield and the loss temperature is shown for each of these Examples in Table 1. Examples 14-16: Bis A Aniline-Furil Polybenzoxazine Polybenzoxazines of the benzoxazine of Comparative Example 1(a) and furil were prepared by the same method described by Examples 5-7. The amount of each component, furan rings/benzoxazine ring ratio, char yield and the loss temperature is shown 5 for each of these Examples in Table 1. From the results shown in Table 1 , it is readily apparent that the char yield increases substantially with increasing furan ring/benzoxazine ring ratio. Also, the increase in char yield does not significantly change the 5 percent loss temperature. The improved char yield is clearly exemplified by comparing Example 1(b) to Comparative Example 1(b). l o These polybenzoxazines are made from a starting benzoxazine monomer with the same structure, except that Example 1(b) has a furan pendant off each benzoxazine ring (that is, benzoxazine-furan compound compared to benzoxazine-aniline compound, respectively). The results show that the furan ring presence results in almost doubling the char yield and an increase in 5 percent loss temperature of Example 1(b) compared to Comparative 15 Example 1(b). The results of Table 1 also show that the inclusion of a furan compound (for example, furil or furoin) also improves the char yield of a polybenzoxazine of a benzoxazine compound (see Examples 11-14). The results also show that a furan compound improves the char yield of a polybenzoxazine of a benzoxazine-furan compound (see Examples 2-7). Table 1 Bis A = bisphenol A FA = furfurylamine Examples 17-19: Bis A/ Aniline- Dimethyl 3,4-Furandicarboxylate(DMFDC) Polybenzoxazine Polybenzoxazines of the benzoxazine compound of Comparative Example 1(a) and DMFDC (Aldrich Chemical Co., Milwaukee, WI) were prepared by weighing out the desired amount of each into a common container and then melting the components by heating to less than 100°C to form a homogeneous liquid. This mixture was then cured by the same method described by Example 1(b) to form a polybenzoxazine. The amount of each component, furan rings/benzoxazine ring ratio, char yield and the loss temperature is shown for each of these Examples in Table 2. Examples 20 & 21: Bis A/Furfurylamine- DMFDC Polybenzoxazine Polybenzoxazines of the benzoxazine-furan compound of Example 1(a) and DMFDC (Aldrich Chemical Co., Milwaukee, WI) were prepared by weighing out the desired amount of each into a common container and then melting the components by heating to less than 100°C to form a homogeneous liquid. This mixture was then cured by the same method described by Example 1(b) to form a polybenzoxazine. The amount of each component, furan rings/benzoxazine ring ratio, char yield and the loss temperature is shown for each of these Examples in Table 2. The results in Table 2 show that even a furan compound with only one furan ring and no other reactive group will improve the char yield of a polybenzoxazine of a benzoxazine compound (see Examples 17-19 and Comparative Example 1 of Table 1). This is so even though DMFDC, when cured by itself using the same method described herein, has a char yield of zero (nothing remained after 180°C) and a 5 percent loss temperature of 111 °C. The results in Table 2 also show that the DMFDC may not be as effective when mixed with a benzoxazine-furan compound (see Examples 20 and 21 and Example 1 of Table 1 ). That is to say, the DMFDC appears to have reduced the char yield of the polybenzoxazine of Bis A/furfurylamine. Table 2 Bis A = bisphenol A FA = furfurylamine DMFDC = dimethyl 3,4-furandicarboxylate Example 22: Bis A/Furfurylamine-4-t-Butylphenol (TBP /Furfurylamine Polybenzoxazine 70 Parts by weight of Bis A/furfurylamine of Example 1(a) were mixed with 30 parts by weight of a benzoxazine-furan compound of TBP/furfurylamine. The TBP/furfurylamine was made using the same method described by Example 1(a). The TBP was obtained from Aldrich Chemical, described previously. The viscosity of the mixture at various temperatures was determined. The char yield and 5 percent loss temperature of the polybenzoxazine of this mixture was also determined. The curing method used to form the polybenzoxazine was the same as described by Example 1(b). The results are shown in Table 3. Example 23: Bis A/Furfurylamine- 2,4-Dimethylphenol (DMP urfurylamine Polybenzoxazine 70 Parts by weight of Bis A furfurylamine of Example 1(a) was mixed with 30 parts by weight of a benzoxazine-furan compound of 2,4-dimethylphenol (DMPyfurfurylamine. The DMP/furfurylamine was made using the same method described by Example 1(a). The DMP was obtained from Aldrich Chemical, described previously. The viscosity of the mixture at various temperatures was determined. The char yield and 5 percent loss temperature of the polybenzoxazine of this mixture was also determined. The curing method used to form the polybenzoxazine was the same as described by Example 1 (b). The results are shown in Table 3. Example 24: Bisphenol F (Bis F)/Furfurylamine Polybenzoxazine A benzoxazine-furan compound and polybenzoxazine made therefrom were made by the same methods described in Example 1 (a and b), except that the phenol was Bisphenol F (Mitsui Toatsu Toyko, Japan) instead of Bis A. The viscosity of the benzoxazine-furan compound prior to curing and the char yield and 5 percent loss temperature of the polybenzoxazine are shown in Table 3. Example 25: (Bis F)/Furfurylamine-TBP/Furfurylamine Polybenzoxazine 70 Parts by weight of Bis F/furfurylamine of Example 24 were mixed with 30 parts by weight of a benzoxazine-furan compound of TBP/furfurylamine. The TBP/furfurylamine was made by the same method described in Example 22. The curing method used to form the polybenzoxazine was the same as described by Example 1(b). The viscosity of the mixture, prior to curing, the char yield and 5 percent loss temperature of the polybenzoxazine are shown in Table 3. Example 26: (Bis F)/Furfurylamine-DMP/Furfurylamine Polybenzoxazine 70 Parts by weight of Bis F/furfurylamine of Example 24 were mixed with 30 parts by weight of a benzoxazine-furan compound of dimethylphenol (DMPyft-rfurylamine. The DMP/furfurylamine was made using the same method described by Example 23. The curing method used to form the polybenzoxazine was the same as described by Example 1 (b). The viscosity of the mixture, prior to curing, the char yield and 5 percent loss temperature of the polybenzoxazine are shown in Table 3. Example 27: Biphenol/Furfurylamine Polybenzoxazine A benzoxazine-furan compound and polybenzoxazine made therefrom were made by the same methods described in Example 1 (a and b), except that the phenol was 2,2'-Biphenol (Aldrich Chemical Company) instead of Bis A. The viscosity of the benzoxazine- furan compound, prior to curing, the char yield and 5 percent loss temperature of the polybenzoxazine are shown in Table 3. Example 28: Biphenol/Furfurylamine-TBP/Furfurylamine Polybenzoxazine 70 Parts by weight of biphenol/furfurylamine of Example 27 was mixed with 30 parts by weight of a benzoxazine-furan compound of TBP/furfurylamine. The TBP/furfurylamine was made by the same method described in Example 22. The curing method used to form the polybenzoxazine was the same as described by Example 1(b). The viscosity of the mixture, prior to curing, the char yield and 5 percent loss temperature of the polybenzoxazine are shown in Table 3. Example 29: Biphenol/Furfurylamine-DMP/Furfurylamine Polybenzoxazine 70 Parts by weight of biphenol/furfurylamine of Example 27 was mixed with 30 parts by weight of a benzoxazine-furan compound of DMP/furfurylamine. The DBP/furfurylamine was made by the same method described in Example 23. The curing method used to form the polybenzoxazine was the same as described by Example 1(b). The viscosity of the mixture, prior to curing, the char yield and 5 percent loss temperature of the polybenzoxazine are shown in Table 3. Comparative Example 2: Bisphenol F (Bis FV Aniline Polybenzoxazine A benzoxazine compound and polybenzoxazine made therefrom were made by the same methods described in Comparative Example 1 (a and b), except that the phenol was Bisphenol F (Aldrich Chemical Company) instead of Bis A. The viscosity of the benzoxazine compound, prior to curing, the char yield and 5 percent loss temperature of the polybenzoxazine are shown in Table 3. Comparative Example 3: Biphenol/ Aniline Polybenzoxazine A benzoxazine compound and polybenzoxazine made therefrom were made by the same methods described in Comparative Example 1 (a and b), except that the phenol was 2,2 -Biphenol (Aldrich Chemical Company) instead of Bis A. The viscosity of the benzoxazine compound, prior to curing, the char yield and 5 percent loss temperature of the polybenzoxazine are shown in Table 3. From Table 3, it is readily apparent that the polybenzoxazine of a benzoxazine-furan compound (Examples 24 and 27) have substantially increased 5 percent loss temperature compared to a polybenzoxazine of a benzoxazine having the same structure, except for the absence of a furan group (Comparative Examples 2 and 3). Further, the results shown in Table 3 show that the use of benzoxazine-furan compound containing only 1 benzoxazine ring and one furan ring reduces the viscosity of the benzoxazine mixture of a benzoxazine-furan compound containing two benzoxazine and f ran rings (see Examples 22, 23, 25, 26, 28 and 29). However, this reduced viscosity does not result in a substantial (that is, hardly any) reduction in char yield or 5 percent loss temperature, while the viscosity is reduced by an order of magnitude (see previously described examples compared to Examples 1, 24 and 27). Table 3 I 5 I

Claims: CLAIMS: 1. A polybenzoxazine comprised of the reaction product of a mixture comprised of (i) a benzoxazine-compound, (ii) a furan compound, (iii) a benzoxazine-furan compound or (iv) combinations thereof, wherein the mixture has a furan ring to 5 benzoxazine ring ratio of at least 0.001 to at most 10. 2. The polybenzoxazine of Claim 1 wherein the mixture fails to have a benzoxazine compound that contains a maleimide group when the benzoxazine-furan compound is present in the mixture. 3. The polybenzoxazine of Claim 1 wherein the mixture is devoid of any l o compound containing a maleimide. 4. A polybenzoxazine comprised of the reaction product of a mixture comprised of a benzoxazine compound having at least two benzoxazine rings and a benzoxazine-furan compound of the formula: wherein R 7 is H, C C 6 unsubstituted alkyl or Cι-C 6 substituted alkyl and R 3 is a single bond 15 or substituted or unsubstituted alkyl group having from 1-6 carbon atoms and the mixture fails to contain a benzoxazine compound that has a maleimide group. 5. The polybenzoxazine of Claim 4 wherein Ri is H. 6. The polybenzoxazine of Claim 4 wherein R 3 is methylene or ethylene. 7. The polybenzoxazine of Claim 4 wherein the benzoxazine compound is 0 of the formula: where R is a divalent radical that is aliphatic, aromatic or combination thereof and composed of 1-35 carbon atoms, together with up to five atoms selected from oxygen, nitrogen, sulfur, phosphorous, halogen and combinations thereof, (b) a single bond or (c) S, S 2 , SO, SO 2 , O or CO and R 5 is one or more H, halogen, alkyl of 1 to 6 carbon atoms, or aromatic or substituted aromatic or aromatic substituted alkyl of 6 to 24 carbon atoms. 8. The polybenzoxazine of Claim 4 wherein R 5 is: — C≡CR,, -C— C≡N, where Ri is H, OH, Cι-C 6 unsubstituted alkyl or Cι-C 6 substituted alkyl and R 2 is an alkyl of 1 to 5 carbon atoms, a halogen, a phenyl or combinations thereof. 9. The polybenzoxazine of Claim 7 wherein Rt is a single carbon that has bonded to it one or more groups selected from H, CH 3 , C 2 H 5 , C 3 H , n-C 3 H , i-C 3 H 7 , cyclohexyl, bicycyclohexyl(2.2.1)heptyl, phenyl, CF 2 , CF 3 , CC1 3 , CF 2 C1, CN, (CH 2 ) 2 COOH 3 and PO(OCH 3 ) 2 . 10. The polybenzoxazine of Claim 9 wherein the single carbon is bonded to two methyl groups. 11. A polybenzoxazine comprised of the reaction product of a mixture of a benzoxazine-furan compound of the formula: or combinations thereof, where R 3 is a single bond or a substituted or unsubstituted Ci to C alkylene and t is a divalent radical that is aliphatic, aromatic or combination thereof and composed of 1-35 carbon atoms, together with up to five atoms selected from oxygen, 0 nitrogen, sulfur, phosphorous, halogen and combinations thereof, (b) a single bond or (c) S, S 2 , SO, SO 2 , O or CO and R 7 is H, Cι-C 6 unsubstituted alkyl or Cι-C 6 substituted alkyl and the mixture is devoid of a benzoxazine compound that contains a maleimide group. 12. The polybenzoxazine of Claim 11 wherein the benzoxazine-furan compound is of the formula: 5 13. The polybenzoxazine of Claim 12 wherein R 3 is methylene or ethylene. 14. The polybenzoxazine of Claim 11 wherein R) is a single carbon that has bonded to it one or more groups selected from H, CH 3 , C 2 H 5 , C 3 H 7 , n-C H 7 , i-C 3 H 7 , cyclohexyl, bicycyclohexyl(2.2.1)heptyl, phenyl, CF , CF 3 , CC1 3 , CF 2 C1, CN, o (CH 2 ) 2 COOH 3 and PO(OCH 3 ) 2 . 15. The polybenzoxazine of Claim 14 wherein R is a carbon directly bonded to two CH 3 groups. 16. A polybenzoxazine comprised of the reaction product of a benzoxazine compound that has at least two benzoxazine rings and fails to have a reactive group and a benzoxazine-furan compound of the formula: or combination thereof, wherein R 7 is H, Cj-C unsubstituted alkyl or C C 6 substituted alkyl and R 3 is a single bond, or substituted or unsubstituted alkyl group, having from 1-6 carbon atoms. 17. The polybenzoxazine of Claim 16 wherein the benzoxazine compound is of the formula: where t is (a) a divalent radical that is aliphatic, aromatic or combination thereof and composed of 1-35 carbon atoms, together with up to five atoms selected from oxygen, nitrogen, sulfur, phosphorous, halogen and combinations thereof, (b) a single bond or (c) S, S 2 , SO, SO 2 , O or CO and R 5 is an unsubstituted alkyl of 1 to 24 carbon atoms or an unsubstituted aryl of 6 to 24 carbon atoms. 18. The polybenzoxazine of Claim 17 wherein R 5 is a 6 to 12 unsubstituted aryl. 19. The polybenzoxazine of Claim 17 wherein R 5 is phenyl. 20. A mixture useful for preparing a polybenzoxazine comprised of (i) a benzoxazine compound, (ii) a furan compound, (iii) a benzoxazine-furan compound or (iv) combinations thereof, wherein the mixture has a furan ring to benzoxazine ring ratio of at least 0.001 to at most 10. 21. The mixture of Claim 20 wherein the mixture is devoid of a benzoxazine-containing compound that has a maleimide. 5 22. The mixture of Claim 20 wherein the ratio is at least 0.01. 23. The mixture of Claim 22 wherein the ratio is at least 0.1. 24. The mixture of Claim 23 wherein the ratio is at most 4. 25. A process for preparing a polybenzoxazine comprising: mixing (i) a benzoxazine compound, (ii) a furan-compound, (iii) a l o benzoxazine-furan compound or (iv) combinations thereof, wherein the mixture has a furan ring to benzoxazine ring ratio of at least 0.001 to at most 10. heating the mixture for a sufficient time to form the polybenzoxazine. 26. A benzoxazine monomer useful for preparing high char yield polybenzoxazines, the benzoxazine monomer having the formula: 15 where R 3 is a single bond or a substituted or unsubstituted Ci to C 6 alkylene and Rt is a divalent radical that is aliphatic, aromatic or combination thereof and composed of 1-35 carbon atoms, together with up to five atoms selected from oxygen, nitrogen, sulfur, 0 phosphorous, halogen and combinations thereof, (b) a single bond or (c) S, S 2 , SO, SO 2 , O or CO and R 7 is H, Cι-C 6 unsubstituted alkyl or Cι-C 6 substituted alkyl.

Inventors: DETTLOFF MARVIN L, NULL MARTY J, WHITE JERRY E, DETTLOFF, MARVIN, L., NULL, MARTY, J., WHITE, JERRY, E.
Applicants: DOW CHEMICAL CO, THE DOW CHEMICAL COMPANY
Application year: 2000
Main classification: C07D265
IPC codes: C07D265, C07D413, C08G73