Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2000-12-01
2002-09-24
Sergent, Rabon (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C428S413000, C428S423100, C428S447000, C428S473500, C428S474400, C428S500000, C428S524000, C523S400000, C523S402000, C523S414000, C523S415000, C524S845000, C524S502000, C524S507000, C524S555000, C524S588000, C524S589000, C524S590000, C524S600000, C524S606000, C524S608000, C524S612000, C524S831000, C524S838000, C524S839000, C524S840000, C524S843000, C524S869000, C524S501000, C524S596000, C524S593000, C524S816000, C524S858000, C524S860000, C524S864000, C524S871000, C524S877000, C524S879000, C525S523000, C525S
Reexamination Certificate
active
06455631
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to aqueous polyurethane dispersions containing modified hydrazide groups; to aqueous, one-component, thermoset compositions containing these dispersions and a cross-linking component; and to coatings, sealants and adhesives prepared from these compositions.
2. Description of the Prior Art
The production of linear or cross-linked aqueous polyurethane-urea dispersions is known as shown by U.S. Pat. Nos. 3,479,310; 4,066,591; 4,092,286; 4,108,814; 4,237,264; and 4,238,378 which disclose linear polyurethane-ureas and U.S. Pat. Nos. 3,870,684, 4,203,883 and 4,408,008, which disclose cross-linked polyurethane-ureas. The aqueous polyurethane-urea dispersions may be used for a wide range of commercial applications such as adhesives or coatings for various substrates including textile fabrics, plastic, wood, glass fibers and metals. Chemical resistance, abrasion resistance, toughness, tensile strength, elasticity and durability are among the many desirable properties of these coatings. In some cases these properties of coatings prepared from aqueous polyurethane-urea dispersions have equaled or even surpassed the performance levels of coatings obtained from solvent-based polyurethane lacquers.
One of the disadvantages of these resins is that when they are formulated with aminoplasts resins, in particular with melamine/formaldehyde resins, the resulting coatings have low gloss and poor distinctness of image (DOI).
It is an object of the present invention to provide aqueous polyurethane dispersions which can be used to prepare one-component, thermoset coatings which have good gloss and DOI and still retain the other valuable properties of aqueous polyurethane dispersions.
This object may be achieved in accordance with the present invention by incorporating modified hydrazide groups into the aqueous polyurethane dispersions as described in more detail hereinafter.
Solvent-based polyurethanes containing modified hydrazide groups are disclosed in U.S. Pat. No. 6,127,514, and in copending application, U.S. Ser. No. 09/197,912, which can be cured with crosslinking agents, such as melamine formaldehyde resins. Because polyisocyanates blocked with volatile, monofunctional blocking agents are not used as crosslinking agents, the one-component compositions of the copending applications do not release blocking agents during cure. When these coating compositions are cured, the only compounds released are water or monoalcohols, which are much less toxic than conventional blocking agents. The preceding patent and application do not disclose that it would be possible to improve the gloss and DOI of coatings prepared from aqueous, one-component, thermoset, coating compositions.
SUMMARY OF THE INVENTION
The present invention relates to aqueous polyurethane dispersions wherein the polyurethanes contain terminal, modified hydrazide groups and correspond to the formula
wherein the terminal, modified hydrazide groups are present in an amount of 1 to 25% by weight (calculated as C(O)—NH—NH—C(O), MW 86), based on the weight of the polyurethanes and wherein
x represents OR′ or NHR′,
R represents the residue obtained by removing the isocyanate groups from an NCO prepolymer,
R′ represents a group which is inert to isocyanate groups under the conditions used to form the polyurethane of in formula I,
R″ represents a divalent, linear or branched aliphatic group containing 2 to 10 carbon atoms, provided that there are at least two carbons between the oxygen atoms, wherein the aliphatic group may optionally be substituted by heteroatoms to form ether or ester groups,
m is 0 or 1 and
n is 2 to 4.
The present invention also relates to aqueous, one-component, thermoset compositions containing the polyurethanes containing modified hydrazide groups and a cross-linking component that is reactive with these groups. Finally, the present invention relates coatings, sealants and adhesives prepared from these aqueous, one-component, thermoset compositions.
DETAILED DESCRIPTION OF THE INVENTION
In accordance with the present invention the term “polyurethane” means polymers containing urethane and/or urea groups.
The aqueous polyurethane dispersions according to the invention may be prepared by either a one-step or a two-step process, preferably by a two-step process. In the one-step process all of the components are mixed together and reacted in one step. In the two-step process an NCO prepolymer is formed in the first step and is subsequently reacted with a compound corresponding to formula II
and optionally a low molecular weight, isocyanate-reactive chain extender in the second step to form the polyurethane either before, during or after being mixed with an aqueous medium. The NCO prepolymer is prepared by reacting an organic polyisocyanate with an isocyanate-reactive compound containing hydrophilic groups and optionally a high molecular weight polyol and/or a low molecular weight polyol.
The polyurethanes may be dispersed in water by either the inverse process or the direct process. In the direct process water is added to the polymer to initially form a water-in-oil emulsion, which after passing through a viscosity maximum, is converted into an oil-in-water emulsion. In the inverse process the polymer is added to water, which avoids the need to pass through the viscosity maximum.
Even though more energy is required for preparing a dispersion by the direct process, it may be necessary to use this process if the viscosity of the polymer is too high to add it to water. A high viscosity polymer is often obtained when a fully reacted polyurethane is prepared in the organic phase, especially when large amounts of solvent are not used to reduce the viscosity.
To obtain a suitable viscosity for using the inverse process without the use of large amounts of solvent, the NCO prepolymer can be dispersed in water and then reacted with the compounds corresponding to formula 11 and optionally with an amine chain extender.
In addition to the one-step process in which all of the components are reacted to form the polyurethane in one step and the preferred two-step process previously set forth, it is also possible to incorporate the compounds corresponding to formula II into the NCO prepolymers, which are then chain extended with polyamine chain extenders or crosslinking agents in known manner.
Any of the known starting materials for preparing polyurethane dispersions may be used for preparing the dispersions according to the invention, provided that sufficient isocyanate groups are reacted with the compounds corresponding to formula 11 to obtain the required modified hydrazide content.
The groups set forth in formula I can be prepared by reacting the compounds of formula II with isocyanate groups. Suitable compounds corresponding to formula II may be prepared as described in U.S. Pat. No. 6,127,514 (m=0) and in copending applications, U.S. Ser. No. 09/197,912 (m=0), and Attorney's Docket No. MD-99-20-LS (m=1).
The compounds of formula II, wherein m=1, may be prepared by reacting a compound corresponding to formula III
with a cyclic carbonate as described in U.S. Pat. No. 4,369,301. Suitable cyclic carbonates include ethylene carbonate, 1,2-propylene carbonate, 1,3-propylene carbonate and neopentyl carbonate. Ethylene carbonate and 1,2-propylene carbonate are preferred, and 1,2-propylene carbonate is especially preferred.
It is also possible to prepare the compounds of formula II, wherein m=1, by reacting the compounds of formula III with chloroformate hydroxyesters corresponding to formula IV
This method is suitable for preparing the compounds of formula II, wherein m=1, from compounds which cannot be converted into cyclic carbonates.
To prepare the polyurethanes of formula 1, wherein m=0, the compounds of formula III are reacted with isocyanate groups without further modification.
In formulas I, II, III and IV
X represents OR′ or NHR′, preferably OR′,
R&prime
Blum Harald
Gindin Lyubov K.
Henderson Karen M.
Jacobs Patricia B.
Lee Sze-Ming
Bayer Corporation
Gil Joseph C.
Roy Thomas W.
Sergent Rabon
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