Epoxy resins and stable aqueous dispersions thereof
AssigneeThe Dow Chemical Company
InventorsChristian Piechocki, James E. Pate
Life of this patent
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Abstract
An epoxy resin containing a low temperature nonionic surfactant having a molecular weight of less than 7,000 Daltons, a high temperature nonionic surfactant having a molecular weight of greater than 7,000 Daltons, and an anionic surfactant, can be used to prepare an aqueous dispersion of the epoxy resin that has unusually low particle size and unusually long shelf-stability. The dispersion is preferably prepared by way of a high internal phase ratio emulsion.
Claims8
A composition comprising a mixture of an epoxy resin and a low temperature nonionic surfactant, a high temperature nonionic surfactant, and an anionic surfactant which, in combination with the low temperature surfactant and the high temperature surfactant, reduces the interfacial tension value of the epoxy resin as compared to the interfacial tension value of the epoxy resin in the absence of the anionic surfactant;
- wherein the low temperature nonionic surfactant is characterized by having a molecular weight of not less than 1,000 and not more than 7,000, the high temperature nonionic surfactant is characterized by having a molecular weight of greater than 7,000 and not more than 20,000, and each of the following criteria is met:
- i) the weight-to-weight ratio of the high temperature nonionic surfactant to the anionic surfactant is greater than 3:1;
- ii) the weight-to-weight ratio of the sum of the low temperature nonionic surfactant and the high temperature nonionic surfactant to the anionic surfactant is greater than 4.5:1;
- iii) the total surfactant concentration is 5 to 20 weight percent, based on the weight of the total surfactants and the epoxy resin.
A composition comprising a stable aqueous dispersion of an epoxy resin stabilized by a low temperature nonionic surfactant, a high temperature nonionic surfactant, and an anionic surfactant which, in combination with the low temperature surfactant and the high temperature surfactant, reduces the interfacial tension value of the epoxy resin as compared to the interfacial tension value of the epoxy resin in the absence of the anionic surfactant;
- wherein the low temperature nonionic surfactant is characterized by having a molecular weight of not less than 1,000 and not more than 7,000, the high temperature nonionic surfactant is characterized by having a molecular weight of greater than 7,000 and not more than 20,000, and each of the following criteria is met:
- i) the weight-to-weight ratio of the high temperature nonionic surfactant to the anionic surfactant is greater than 3:1;
- ii) the weight-to-weight ratio of the sum of the low temperature nonionic surfactant and the high temperature nonionic surfactant to the anionic surfactant is greater than 4.5:1;
- iii) the total surfactant concentration is 5 to 20 weight percent, based on the weight of the total surfactants and the epoxy resin.
A method of preparing a stable aqueous dispersion of an epoxy resin comprising the steps of:
- a) continuously merging into a disperser, and in the presence of an emulsifying and stabilizing amount of a surfactant mixture, a flowing stream of water flowing at a rate r1, and a flowing stream containing an epoxy resin flowing at a rate r2;
- b) mixing the streams with a sufficient amount of shear to form a high internal phase ratio emulsion;
- and
- c) diluting the high internal phase ratio emulsion with water to form the stable aqueous dispersion;
- wherein the surfactant mixture includes a low temperature nonionic surfactant and a high temperature nonionic surfactant, wherein the low temperature nonionic surfactant characterized by having a molecular weight of not less than 1,000 and not more than 7,000, the high temperature nonionic surfactant is characterized by having a molecular weight of greater than 7,000 and not more than 20,000;
- and where r2:r1 is in such a range that the volume average particle size of the dispersion is not greater than 2 microns.
Dependencies are inferred from the claim text.