Colloidally stabilized emulsions

Details Colloidally stabilized emulsions Colloidally stabilized emulsions

2000-09-08

2003-07-29

Dawson, Robert (Department: 1712)

Stock material or miscellaneous articles

Composite

Of polyamide

C428S479300, C428S479600, C524S503000, C524S459000, C526S202000

Reexamination Certificate

active

06599638

ABSTRACT:

FIELD AND BACKGROUND OF THE INVENTION
The present invention relates to colloidally stabilized emulsions, and particularly colloidally stabilized emulsions having reduced or no phenolics.
Phenolics (e.g., phenol-formaldehyde resins), have been used as adhesives, laminates, molding materials, paints and the like. Of particular interest is the use of phenolics as adhesives or binders in non-woven substrates and papers. More specifically, phenolics are used in bonding of refractory shapes; fiber bonding such as in filters; felt bonding; binding of friction products such as brake pads; in papermaking; in insulation; in roofing products; and in the binding of foundry sands such as abrasives. Of particular interest is the use of phenolics in filters. Typically, the filter is provided by impregnating a continuous roll of paper with a phenolic resole in the form of an alcohol solution of a condensate of phenol with formaldehyde. The impregnated and saturated paper is heated to remove the solvent (alcohol) and corrugated to increase surface area. The resin is then cured in an oven and the paper is rolled again. The rolls of the impregnated paper are provided to the filter manufacturer for completion of the process which includes pleating and final curing. Such filters are used in the both air and oil filtering systems in stationary and mobile internal combustion engines.
Phenolics, however, have disadvantages such as high phenol and formaldehyde levels, brittleness when fully cured, slow curing characteristics, instability and poor shelf life. Moreover, phenolics, particularly water-based phenolics, are difficult to use to impregnate fiber substrates. In such impregnation, co-solvents such as alcohols, must be used and then removed.
To this end, it would be desirable to substantially eliminate, or in the alternative, substantially reduce the amount of phenolics used in products and with substrates wherein phenolics have traditionally been used as binders or adhesives.
SUMMARY OF THE INVENTION
The present invention provides compositions wherein phenolics are substantially eliminated, substantially reduced or replaced by the use of a colloidally stabilized emulsion polymer. By using the colloidally stabilized polymer of the invention and eliminating or replacing the use of phenolics, a wide variety of polymers having crosslinkable functionality such as provided by crosslinkers such as epoxies, polyisocyanates, polyurethanes, N-methylol acrylamide, melaminelformaldehyde and the like, can be used or blended together while providing properties comparable to those of polymers having phenolics or of phenolics alone.
Alternatively, the colloidally stabilized emulsion polymers, when blended with phenolics, are more stable and compatible with phenolics as compared to surfactant stabilized emulsions. By compatibility, it is meant that the emulsion polymers, when blended with phenolics, remain stable without coagulating or gelling or becoming a paste over longer periods of time. Thus, the blended product can be used over extended periods of time without concern for instability or degradation of performance. Moreover, the need to use undesirable solvents is eliminated.
DETAILED DESCRIPTION OF THE INVENTION
The present invention will now be described more fully hereinafter, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
It is believed that a wide variety of polymers in emulsion form can be colloidally stabilized, particularly with polyvinyl alcohol, and optionally blended with phenolics. Specific polymers in emulsion form include polyvinylacetate, vinylacetate-ethylene(VAE), vinyl acrylics, epoxies, urethanes, acrylics, styrene acrylics, butadiene copolymers, and hybrid emulsions of combinations of the foregoing. The present invention can be used in systems to replace phenolics wherein phenolics are used alone, or can be used in systems wherein phenolics are used with other polymers. In the latter, the phenolics can be substantially eliminated or can be substantially reduced.
Of particular interest are emulsion polymers that have high levels (i.e., greater than about 15 percent by weight) of nitrogen-containing monomers such as acrylonitrile. By being able to increase the level of acrylonitrile, properties such as oil and grease resistance can be improved without adversely affecting the physical properties contributed to by the phenolics.
As stated above, it is desirable to substantially eliminate the use of phenolics; however, phenolics may still be used at a reduced level. The phenols employed in the formation of the phenolic resins generally include any phenol which as heretofore been employed in the formation of phenolic resins and which are not substituted at either the two ortho positions or at the one ortho and the para position. Such unsubstituted positions are necessary for the polymerization reaction to occur. Substituted phenols employed in the formation of the phenolic resins include: alkyl substituted phenols, aryl-substituted phenols, cycloalkyl-substituted phenols, alkenyl-substituted phenols, alkoxy substituted phenols, aryloxy substituted phenols, and halogen-substituted phenols. Specific examples of suitable phenols include: phenol, o-cresol, m-cresol, p-cresol, 3,5-xylenol, 3-4-xylenol, 3,4,5-trimethylphenol, 3-ethyl phenol, 3,5-diethyl phenol, p-butyl phenol, 3,5-dibutyl phenol, p-amyl phenol, p-cyclohexyl phenol, p-octyl phenol, 3,5-dicyclohexyl phenol, p-phenyl phenol, p-crotyl phenol, 3,5-dimethoxy phenol, 3,4,5-trimethoxy phenol, p-ethoxy phenol, p-butoxy phenol, 3-methyl-4-methyoxy phenol, and p-phenoxy phenol.
The aldehydes reacted with the phenol component can include any of the aldehydes heretofore employed in the formation of phenolic resins and include, for example, formaldehyde, and benzaldehyde. In general, the aldehydes employed have the formula R′CHO wherein R′ is a hydrogen or hydrocarbon radical of 1-8 carbon atoms. A particularly preferred phenolic is Resafen 8121 available from Resana, Sao Paulo, Brazil.
With respect to the polymers, of particular interest are the ones with aliphatic conjugated dienes. Suitable aliphatic conjugated dienes are C
4
to C
9
dienes and include, for example, butadiene monomers such as 1,3-butadiene, 2-methyl-1,3-butadiene, 2-chloro-1,3-butadiene, and the like, such as described in U.S. Pat. No. 5,900,451 to Krishnan et al., the disclosure of which is incorporated herein by reference in its entirety. Blends or copolymers of the diene monomers can also be used. The aliphatic conjugated diene is used in an amount, based on total weight of the starting monomers, from about to 1 to about 99 percent by weight, preferably from about 5 to about 30 percent by weight, and most preferably from about 5 to about 15 percent by weight. A particularly preferred aliphatic conjugated diene is 1,3-butadiene.
Suitable non-aromatic unsaturated monocarboxylic ester monomers include acrylates and methacrylates. The acrylates and methacrylates may include functional groups such as amino groups, hydroxy groups, epoxy groups and the like. Exemplary acrylates and methacrylates include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, glycidyl acrylate, glycidyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, isobutyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, 3-chloro-2-hydroxybutyl methacrylate, n-propyl methacrylate and the like. Exemplary amino-functional methacrylates include t-butylamino ethyl methacrylate and dimethylamino ethyl methacrylate. Suitable non-aromatic dicarboxylic ester monomers are dialkyl fumarates, itaconates and maleates, with the alkyl group

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