Organic compounds -- part of the class 532-570 series – Organic compounds – Amino nitrogen containing
Reexamination Certificate
2001-12-19
2002-08-27
Barts, Samuel (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Amino nitrogen containing
C528S422000
Reexamination Certificate
active
06441238
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to aminopropylated aromatic amines, more particularly to N-(aminopropyl)-ortho-toluenediamine, N-(aminopropyl)-meta-toluenediamine and their use as epoxy curing agents.
It is known to use amines, such as aliphatic or aromatic amines, for the curing of epoxy resins. See, e.g., “Handbook of Epoxy Resins” by H. Lee and K. Neville, McGraw Hill Book Co., 1967. The epoxy industry, particularly the adhesive, composite and syntactic foam markets of the industry, is in need of a low viscosity aromatic amine curing agent fairly rapid in reactivity and heat generation while providing high Tg, good fracture toughness and chemical resistance after full cure. Additionally, the civil engineering epoxy market has particular interest in finding new amine curatives that combine the rapid curing rate of aliphatic amines with the good chemical resistance typically found in aromatic amine curatives, such as MDA and DETDA.
Low viscosity amine curing agents are typically aliphatic amines, cycloaliphatic amines or amidoamines. These amine curatives provide the appropriate viscosity and in some cases adequate fracture toughness for adhesive, composite and syntactic foam applications, but are not suitable for many applications in that they are too reactive and do not provide high Tg and good chemical resistance. For civil engineering applications, these amine curatives sometimes have the appropriate reactivity and viscosity, but do not provide adequate chemical resistance. Aromatic amines, on the other hand, provide high Tg, good fracture toughness and excellent chemical resistance for adhesive, composite and syntactic foam applications but are less than ideal in that they are usually high viscosity liquids or solids, have extremely long potlifes and high toxicity. For civil engineering applications aromatic amine curatives provide good chemical resistance but are slow in reactivity and present toxicity issues as well.
The epoxy industry has employed many types of curative blends in an attempt to maximize the desired application properties, but in most cases at the expense of other properties. Additives such as accelerators, tougheners, reactive diluents and non-reactive diluents are employed to maximize a desired property but again to the deterioration of other properties. A number of good references are available on this subject including: Lee and Neville's, “Handbook of Epoxy Resins,” cited above, and W. R. Ashcroft, “Curing Agents for Epoxy Resins,” in B. Ellis (ed.). “Chemistry and Technology of Epoxy Resins,” Blackie Academic and Professional, London (1993), pp. 37-73.
Others in the epoxy industry have developed novel amines in attempting to optimize curative properties. For example, Japanese Patent 2963739 (1999) describes the use of substituted-N-phenyl-1,3-propanediamines as liquid epoxy curatives which do not B-stage during cure and thus yield a fully cured epoxy resin. The substituted-N-phenyl-1,3-propanediamines described therein are represented by the following chemical formula:
where R is hydrogen, lower alkyl group, lower alkoxyl group or halogen. Although the method of synthesis of these curatives is not disclosed, other references teach methods for synthesizing aromatic amines.
For example, European Patent 0 067 593 (1982) describes the cyanoethylation of para, meta, and ortho phenylenediamine to generate 3,3′-(p,m or o-phenylenedi-imino)-dipropanenitrile:
EP 0 067 593 teaches the use of water as the solvent and concentrated hydrochloric acid as the catalyst to obtain the dicyanoethylated product.
Elderfield et al., 68 J. Amer. Chem. Soc. 1262 (1949), describes the synthesis of &bgr;-p-anisidinopropionitrile by boiling p-anisidine and acrylonitrile in acetic acid.
Cookson et al., “The Cyanoethylation of Amines and Arsines,” J. Chem. Soc. 1949, pp. 67-72, describes the cyanoethylation of aniline by heating to 150° C. a mixture of aniline and acrylonitrile in the presence of excess acetic acid in an autoclave to generate 2-cyanoethylaniline and bis-2-cyanoethylaniline. The reference further describes the reaction of diphenylamine and acrylonitrile in an excess of acetic acid using a catalytic amount of fine copper powder to generate diphenyl-2-cyanoethylamine.
Braunholtz et al., “The Preparation of Bis(2-cyanoethyl) Derivatives of Aromatic Primary Amines, and Their Conversion into 1:6-Diketojulolidines,” J. Chem. Soc., 1952, pp. 3046-3051, describes the cyanoethylation of aniline, m-toluidine, p-toluidine, p-anisidine and p-chloroaniline in an excess of acetic acid.
Braunholtz et al., “The Preparation of Bis(2-cyanoethyl) Derivatives of Aromatic Primary Amines, and Their Conversion into 1:6-Diketojulolidines. Part II,” J. Chem. Soc., 1953, pp. 1817-1824, describes the cyanoethylation of several different aromatic primary monoamines in an excess of acetic acid using various metal catalysts to selectively generate mono and di-cyanoethylated derivatives.
All references cited herein are incorporated herein by reference in their entireties.
BRIEF SUMMARY OF THE INVENTION
The invention provides aminopropylated toluenediamines, processes for synthesizing them, compositions containing them and methods for using them to cure epoxy resins. In preferred embodiments, the aminopropylated toluenediamines are represented by the following formula:
where the nitrogen atoms are ortho or meta to each other on the aromatic ring.
With regard to the present invention and throughout the specification and claims the terms “aminopropyl toluenediamine(s)”, “aminopropylated toluenediamine(s)”, “N-(aminopropyl) toluenediamine(s)” and “N-(aminopropylated) toluenediamine(s)” are used interchangeably.
DETAILED DESCRIPTION OF THE INVENTION
The most preferred aminopropylated toluenediamines of the invention are suitable for use as epoxy resin curing agents. Aminopropylated toluenediamines where the nitrogen atoms are ortho or meta to each other on the aromatic ring have been found to be particularly suitable for this purpose. Thus, the most preferred aminopropylated toluenediamines of the invention are aminopropylated products of ortho-toluenediamine represented by the following Formulas I-IV:
and aminopropylated products of meta-toluenediamine represented by the following Formulas V-VII:
Formulas I-IV above are the aminopropylated products of ortho-toluenediamine (OTD). Formulas I-II are based on 2,3-toluenediamine (TDA) and the Formulas III-IV are based on 3,4-TDA. A commercial isomer mix of OTD is typically 60/40 2,3-TDA/3,4-TDA. Using commercial grade OTD therefore leads to aminopropylated isomer mixtures.
Formulas V-VII above are the aminopropylated products of meta-toluenediamine (MTD). Formula V is based on 2,6-TDA and Formulas VI and VII are based on 2,4-TDA.
Preparation of Aminopropylated TDA
Aminopropylated products of OTD are prepared by two reaction steps. As shown in Equations I and II (below), OTD is initially cyanoethylated by reaction with acrylonitrile (ACN) at elevated temperature in the presence of an acid and a protic solvent (e.g., water) for a period of time adequate for reaching the desired extent of conversion to the cyanoethylated product. The resulting cyanoethylated TDA is then hydrogenated under pressure (e.g., 900 psi or 6.21 Mpa) and temperature using a hydrogenation catalyst (e.g., Raney cobalt or nickel). The resulting aminopropylated TDA is then purified by reduced pressure fractional distillation.
Cyanoethylation of Orthotoluenediamine (Eq. I)
Hydrogenation of Cyanoethylated Orthotoluenediamine (Eq. II)
Aminopropylated products of MTD are prepared by two reaction steps. As shown in Equations III and IV, MTD is initially cyanoethylated by reaction with ACN at elevated temperature in the presence of an acid and a protic solvent (e.g., water) for a period of time adequate for reaching the desired extent of conversion to the cyanoethylated product. The resulting cyanoethylated TDA is then hydrogenated under pressure (e.g., 900 psi or 6.21 Mpa) and temperature using a hydrogenation catalyst (e.g., Raney cobalt or nickel).
Cush Tammy Lynn
Starner William Edward
Air Products and Chemicals Inc.
Barts Samuel
Leach Michael
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