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
2002-05-22
2004-08-17
Sanders, Kriellion A. (Department: 1714)
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...
C524S845000
Reexamination Certificate
active
06777489
ABSTRACT:
This invention relates to the production and use of aqueous dispersions of water insoluble heteropolymeric particles. In particular it relates to the incorporation of reactive amphiphilic moieties into such polymeric particles to provide aqueous dispersions exhibiting a temperature dependent viscosity. The invention also relates to the use of these aqueous dispersions as binders or thickeners for paints, adhesives, textile coatings, carpet backings and construction materials. The aqueous dispersions are particularly useful in the preparation of paints and accordingly it will be convenient to hereinafter describe the invention with reference to this application, however it is to be understood that the aqueous dispersions have other applications.
U.S. Pat. No. 4,468,498 (Kowalski) describes a sequential emulsion polymerisation process for making an aqueous dispersion of water insoluble heteropolymeric particles having a core/sheath (or shell) structure. The core, which contains acid monomers, is alkali swellable such that addition of base to the polymerised particles to neutralise the acid monomers results in hydration of the core and swelling of the particles. The swelling allows the aqueous dispersion to be used as a thickener for water based coating compositions. It is also suggested that the dispersion could be used as a binder or part thereof in a water based coating composition.
It has now been found that the incorporation of a reactive amphiphile into a water insoluble heteropolymer during polymerisation and under particular conditions can enhance the thickening of an aqueous dispersion of the heteropolymer and provide an aqueous dispersion exhibiting a temperature dependent viscosity.
Accordingly in a first aspect the present invention provides a process for preparing an aqueous dispersion of water insoluble polymer particles comprising:
a) preparing by polymerisation an aqueous dispersion of water insoluble particles of a heteropolymer including monomeric units of a reactive amphiphile having a cloud point and monomeric units of a hydrophilic monomer, said polymerisation being conducted in the presence of a stabilising agent and the reactive amphiphile and at a temperature above the cloud point of said amphiphile,
b) cooling said aqueous dispersion to a temperature below the cloud point of the reactive amphiphile such that the viscosity of the aqueous dispersion increases.
As used herein the term “cloud point” refers to the temperature at which the molecules of reactive amphiphile disassociate from the water molecules with which they are hydrated to the extent that they form a separate phase. In the absence of monomers this event results in a separation of an aqueous solution of the amphiphile into two phases, one being a phase rich in surfactant and the other being an aqueous equilibrium mixture in which relatively little surfactant is present. This phase separation causes a clear solution of the amphiphile to become cloudy, hence the term “cloud point”. In the emulsion polymerisation process of the present invention it is believed that this event results in the amphiphile becoming associated with and embedded in the oil phase of the emulsion.
Many factors effect the cloud point of an amphiphile. Several of these factors are described in Chapter 11 of Nonionic Surfactants Chemical Analysis Vol. 19 Surfactant Science series, edited John Cross, published by Marcel Dekker, Inc. 1987 which is incorporated herein by reference.
While the exact temperature at which the amphiphile dissociates from its water of hydration in the emulsion polymerisation medium is difficult to measure, it can be approximated by measuring the cloud point of the amphiphile in an aqueous composition similar to the aqueous phase of the emulsion. As indicated in Chapter 11 of the reference above it is possible to lower the cloud point of an amphiphile by changing the composition of the aqueous phase. For example it is possible to change the cloud point of an amphiphile by addition of electrolytes, such as those based on alkali metal ions. Addition of such electrolytes generally causes a depression of the cloud point which can be quite marked.
The term “cloud point” is normally only applicable to nonionic amphiphiles, however some ionic surfactants also have a cloud point at a pH at which the surfactants are uncharged. For example anionic surfactants, such as phosphates, sulfonates or carboxylates, may have a cloud point at a pH below the pKa of the phosphate or carboxylate. Similarly cationic surfactants, such as primary and secondary amine surfactants, may have a cloud point at a pH above the pKb of the amine group.
The reactive amphiphile may be any amphiphilic compound having a cloud point and being capable of being incorporated into the heteropolymer. The amphiphile may be incorporated into the “backbone” of the heteropolymer or the amphiphile may become incorporated into the heteropolymer by reacting with functional groups present on the “backbone” monomers.
Examples of reactive amphiphiles capable of being incorporated into the backbone of the heteropolymer include surfactants having one or more polymerisable double or triple bonds, such as the unsaturated fatty acid and fatty alcohol alkoxylates and surfactants containing reactive double bonds derived from (meth)acryl or vinyl groups. Examples of reactive amphiphiles derived from unsaturated fatty acids and alcohols include undecylenic acid ethoxylate, undecylenol ethoxylate, linoleyl acid ethoxylate, linoleyl alcohol ethoxylate and octenol ethoxylate. Examples of commercially available materials which contain unsaturation derived from (meth)acryl or vinyl groups, and which have suitable cloud point characteristics are Blemmer 70PEP-350B (NOF Corp.) and Emulsogen R109 (Clariant). The reactive amphiphile may include block copolymers of propoxylate, ethoxylate and/or butoxylate with a reactive group or may be an ethoxylated alcohol or acid with propylate or butoxylate attached. These amphiphiles generally become incorporated into the heteropolymer by free radical mechanisms.
Examples of reactive amphiphiles capable of reacting with a functional group of a backbone monomer include those unsaturated amphiphiles described above, as well as amphiphiles having reactive groups, such as carboxylates, sulfonates, phosphates, primary or secondary amino and other groups known to those skilled in the art as being capable of reacting with the backbone monomers (whether before or after incorporation into the heteropolymer) under the polymerisation conditions employed. The amphiphile used in a particular polymerisation will depend on the nature of the functional groups present on the backbone monomers.
Examples of reactive amphiphiles capable of reacting with a functional group of a backbone monomer include phosphates, such as stearyl ethoxylate phosphate or carboxylates, such as alkylsuccinic anhydride ethoxylate, and polyether amines, such as Jeffamine M2070. Any of these amphiphiles may be employed provided the polymerisation medium is such that the amphiphile has a cloud point.
Examples of backbone monomers which include functional groups capable of reacting with such reactive amphiphiles include glycidyl methacrylate or acrylate, acetyl acetoethylmethacrylate, or isocyanate containing monomers such as 2-isocyantoethyl methacrylate. A person skilled in the art would be able to readily determine combinations of reactive groups on amphiphiles and reactive groups on backbone monomers which would allow incorporation of the reactive amphiphile into the heteropolymer.
The reactive group of the amphiphile may be present in either the hydrophobic or the hydrophilic region of the amphiphile.
The exact nature of the amphiphile employed will depend on several factors, the most important of which is the cloud point. Accordingly the degree of alkoxylation, the width of the alkoxylate distribution or other structural features of a given amphiphile are less critical than the cloud point of the resulting amphiphile in the polymerisation medium employed.
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Carey Michelle Jocelyn
Carr Matthew William
Houlihan Patrick William
Leary Bruce
Such Christopher Henry
Orica Australia PTY Ltd.
Pillsbury & Winthrop LLP
Sanders Kriellion A.
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