Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-04-05
2002-09-03
Szekely, Peter (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S247000, C524S249000, C524S424000, C524S436000, C524S724000, C524S839000, C564S002000, C564S252000, C564S503000, C252S182290, C252S403000, C252S405000
Reexamination Certificate
active
06444737
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to stabilizers for water-dispersed polymers, and more particularly to stabilizers for water-dispersed polymers that have a propensity to release acids and/or have groups that hydrolyze over time such as polychloroprenes and polyester urethanes.
BACKGROUND OF THE INVENTION
Water dispersed polymers and polymer systems are widely available and are used, for example, as coatings and adhesives. Many of the known water-dispersed adhesive compositions contain polychloroprene. It is known that polychloroprenes and other similar halogenated compounds are not stable over time. Such compounds have a propensity to release acids over time in the form of halogens such as chlorides. This acid release lowers the pH of the system which can destabilize the polymer dispersion, detrimentally affect open time of an adhesive, and accelerate thermal degradation of the aqueous composition and the resulting waterless solid.
To solve the above problems, zinc oxide or a combination of zinc oxide and magnesium oxide have been used in compositions containing polychloroprene. These compounds are reported to function as acid scavengers and or crosslinkers. However, the use of these compounds in compositions containing polychloroprene has produced less than satisfactory results. For example, zinc oxide cannot be used with carboxylated polychloroprene dispersions because zinc ion will react with the organic acid groups and cause the polychloroprene dispersion to coagulate prematurely. It has also been reported that the presence of zinc oxide decreases the thermal stability of polychloroprene by lowering the temperature required for the polychloroprene to release labile chlorine. Additionally, compounds such as polyester urethanes may be prone to reaction with zinc oxide and are susceptible to acid induced hydrolysis of the polyester group if the free acid is not adequately scavenged. Thus, in some instances, the use of zinc oxide as an acid scavenger may limit the types of polymers which may be used in combination with polychloroprene. The addition of magnesium oxide to the above water dispersions containing zinc oxide does not solve the problem of premature coagulation of the dispersed polymers.
SUMMARY OF THE INVENTION
In one aspect, the invention provides a stabilizer system for polymers susceptible to hydrolysis and/or acid release comprising a combination selected from the group consisting of: branched primary amino alcohol and carbodiimide; branched primary amino alcohol and dihydroxy metal compound; carbodiimide and dihydroxy metal compound; carbodiimide, branched primary amino alcohol, and magnesium oxide; branched primary amino alcohol and magnesium oxide; carbodiimide and magnesium oxide; and a combination of branched primary amino alcohol, carbodiimide, and dihydroxy metal compound.
The stabilizing systems of the invention are free from zinc oxide, that is, do not contain zinc oxide. The stabilizing systems of the invention also do not contain aziridines and can also be used in dispersed polymers or solventless polymers without the need for external plasticizers. The term “plasticizer”, as used herein, means compounds from the following classes: phthalates including alkyl benzyl phthalates; adipates including dialkyl adipates; phosphates including alkyl aryl phosphates and triaryl phosphates; alkyl and aryl sulfonamides; and hydrogenated terphenyls.
The term “acid scavenger” means acid acceptor or acid neutralizer.
The term “dispersion” encompasses any form of solid dispersed in a liquid medium including, for example, latexes, emulsions, colloidal suspensions, and the like.
The stabilizer systems of the invention can be used in aqueous polymer dispersions and the resulting polymer after water has been removed to minimize a decrease in pH over time and/or minimize the hydrolysis of susceptible groups, for example, ester groups.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The stabilizer systems of the invention are useful for stabilizing polymers or polymer systems which contain ester groups or ester functionality or release acids upon aging. The polymers or polymer systems may be in the form of a water dispersion or may be the resulting solidified or dried adhesive after the water has been removed. Depending upon the mixture of components, the stabilizer systems of the invention protect the ester groups from hydrolysis and/or scavenge or neutralize free acid without the use of zinc oxide or plasticizers. The stabilizer systems of the invention comprise combinations of two or more components that may be used in polymers or polymer systems in an effective amount to minimize hydrolysis and/or free acid. As used herein, an “effective amount” means a sufficient amount of a stabilizer system so to prevent either coagulation of the base polymer or hydrolysis of any ester moieties of the base polymer. A “base polymer” is a polymer or combination of polymers that either coagulate or have ester moieties that hydrolyze, or both, in the presence of acid.
The stabilizer systems of the invention are typically useful in water-dispersed polymers or water-dispersed polymer systems containing halogenated species and/or ionic functionality, for example, carboxylation and/or sulfonation. The term “water dispersed” means that the carrier is primarily water. However, incidental organic solvents, such as those present in additives and commercially available components, may be present. Preferably, however, “water-dispersed” refers to a 100% water carrier. Examples of water-dispersed polymers that may require stabilization from hydrolysis or acid release include acrylics, acrylates, polyesters, polyurethanes, rosin esters, polychloroprenes, chlorinated polyolefins, polyvinyl chlorides, and combinations thereof. The stabilizer systems are also useful in the resulting adhesives that are formed from removing water from the above described polymers and polymer systems.
The stabilizer systems of the invention are generally used in compositions containing water-dispersed polymers which require stabilization in an effective amount. An “effective amount” of a stabilizer system means an amount of stabilizer system so to prevent either coagulation of the polymer composition or hydrolysis of any ester moieties of the polymers or other resins containing ester moieties. Hydrolysis of ester moieties of the susceptible polymer will cause the adhesive performance of the adhesive prepared therefrom to decline. Such hydrolysis may be detected by a major shift in pH of the polymer system, for example, an adhesive composition, and by using analytical techniques such as Fourier Transform Infrared Spectroscopy (FTIR), Gas Chromatography (GC), and mass spectrometry.
The stabilizer systems of the invention may comprise one or more branched primary amino alcohols. The branched primary amino alcohols act primarily as an acid scavenger. The branched primary amino alcohols are derived from nitroparaffins by way of nitro alcohols. Useful branched primary amino alcohols are those which are miscible in water. Preferred primary amine alcohols include 2-amino-1-butanol; 2-amino-2-methyl-1,3-propanediol; 2-amino-2-methyl-1-propanol; 2-amino-2-ethyl-1,3-propanediol; and tris(hydroxymethyl)aminomethane.
The stabilizer systems of the invention may comprise one or more carbodiimides. A carbodiimide, as used herein, is a compound containing the functional group: —N═C═N—. The carbodiimides are useful for preventing hydrolysis of functional groups such as ester groups. The carbodiimides may be aliphatic or aromatic. Useful carbodiimides are either miscible or dispersible in water. Preferred carbodiimides are those that are sterically hindered, water miscible, and contain little or no organic solvent. Preferred commercially available carbodiimides include Stabaxol® P 200 (reaction product of tetramethylxylene diisocyanate; water-dispersed), Stabaxol® P (poly(nitrilomethanetetraylnitrilo (2,4,6-tris(1-methylethyl)-1,3-phenylene)), and Stabaxol® I (tetraisopropyldiphenylcarbodiimide) (RheinChemie) and Uca
3M Innovative Properties Company
Bardell Scott A.
Szekely Peter
LandOfFree
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