Cellulose ether slurries

Details Cellulose ether slurries Cellulose ether slurries

1999-03-30

2001-10-23

Sanders, Kriellion (Department: 1714)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Processes of preparing a desired or intentional composition...

C524S037000, C524S038000, C524S041000

Reexamination Certificate

active

06306933

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to slurries of water soluble polymers. More specifically, the present invention relates to slurries of water soluble cellulose ethers in oxygenated, organic carriers.
BACKGROUND OF THE INVENTION
Cellulose ethers have been used commercially in a variety of applications. Typical industrial applications for cellulose ethers include, for example, use as viscosity adjusters, suspension aids, oil field drilling and fracturing materials, adhesion promoters for siliceous substrates, e.g., glass panels and ceramics, coating materials for plastic and metal substrates, protective colloids and building materials, e.g., wallboard compound and latex grout additive. Typical personal care applications include, for example, pharmaceutical and cosmetic compositions, e.g., ointments, skin creams, lotions, soaps, shampoos, conditioners and the like.
One predominant use for cellulose ethers is in the latex industry where the cellulose ethers are utilized as thickeners. In latex paint, cellulose ethers generally provide excellent thickening efficiency and other properties while being substantially inert to the latexes, surfactants and coalescing agents commonly used in latex paints.
Cellulose ethers, such as for example, hydroxyethyl cellulose, are generally sold as dry powders. The final compositions which comprise the cellulose ethers are often liquids. The dry powdered cellulose ethers are typically incorporated into the final liquid compositions by the formulators of the liquid products. In general, solids are more difficult to measure, dissolve, transfer and store than liquids. In contrast, liquids generally dissolve more smoothly and are easier to transfer, i.e., can be pumped, than solids.
Aqueous slurries of cellulose ethers have been proposed whereby high concentrations of salt,. e.g., sodium formate, potassium carbonate or diammonium phosphate, are used to sufficiently reduce the water solubility of the cellulose ether to provide a suspension of cellulose ether particles in the carrier. However, such salt-containing slurries have not achieved widespread use in the latex industry, particularly the latex paint industry because the high salt concentration in the slurry is deleterious to the final dried paint film as the salt impairs the weatherability, adhesion and water resistance of the coating.
Accordingly, improved cellulose ether slurries are desired which do not require the use of high concentrations of salt in order to disperse the cellulose ether. In addition, it is desired that the slurries provide high concentrations, e.g., greater than 30 weight percent, of the cellulose ether. It is further desired that the other ingredients in the slurry, e.g., the carrier, be compatible and beneficial to the final composition in which the slurry is employed.
SUMMARY OF THE INVENTION
By the present invention, slurries of cellulose ethers and processes for making and using the cellulose ethers are provided. The cellulose ether slurries of the present invention comprise a cellulose ether and an oxygenated, organic carrier which is substantially a non-solvent for the cellulose ether. The cellulose ether slurries of the present invention can be prepared to be substantially free of salt and water.
Quite advantageously, the cellulose ether slurries of the present invention comprise ingredients, e.g., the oxygenated, organic carrier, thickener, surfactants and the like, which are commonly used in the preparation of latex compositions, e.g., paints. Moreover, quite surprisingly in accordance with the present invention, the use of the organic, oxygenated carrier can provide significant performance advantages in latex compositions as compared to slurries made using other carriers, such as, for example, hydrocarbons. Moreover, the cellulose ether slurries of the present invention can provide formulators greater efficiency in production and simpler hardware and manpower requirements as compared to using cellulose ethers in a dry powder form.
DETAILED DESCRIPTION OF THE INVENTION
Cellulose ethers suitable for use in accordance with the present invention include etherified derivatives of cellulose. Typical cellulose ethers include for example, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl methyl cellulose, hydroxyethyl carboxymethyl cellulose, and the like. Preferred cellulose ethers include hydroxyethyl cellulose and ethyl hydroxyethyl cellulose.
Ether substituents suitable for use in accordance with the present invention comprise ethers preferably having 2 to 4 carbon atoms per molecule. Typically, the ether substituent is derivatized onto the cellulose by reacting the cellulose with an alkylene oxide, preferably ethylene oxide. The amount of ether substitution is typically from about 1.5 to G and preferably from about 2 to 4 moles of ether substituent per mole of cellulose ether. Further details concerning the manufacture of such cellulose ethers are known to those skilled in the art.
The molecular weight of the cellulose ethers suitable for use in accordance with the present invention typically ranges from about 10,000 to 2×10
6
grams per gram mole and preferably ranges from about 70,000 to 1×10
6
grams per gram mole. As used herein, the term “molecular weight” means weight average molecular weight. Methods for determining weight average molecular weight of cellulose ethers are known to those skilled in the art. One preferred method for determining molecular weight is low angle laser light scattering. The viscosity of the cellulose ethers typically ranges from about 5 to 6000 centipoise, preferably from about 100 to 3000 centipoise. Unless otherwise indicated, as used herein the term “viscosity” refers to the viscosity of a 1.0 weight percent aqueous solution of the polymer measured at 25° C. with a Brookfield viscometer. Such viscosity measuring techniques are known in the art and are described in ASTM D 2364-89. The average particle size of the cellulose ethers is not critical, but is preferably from about 0.01 to 1000 microns and more preferably from about 50 to 400 microns.
The cellulose ethers may be substituted with one or more hydrophobic substituents. Such hydrophobic substituents are known in the art and typically comprise alkyl, alkene, aryl-alkene or aryl-alkyl groups having about 8 to 24 carbon atoms per molecule. Such hydrophobically-modified cellulose ethers are described, for example, in U.S. Pat. Nos. 4,228,277; 5,120,328 and 5,504,123 and European Patent Publication 0 384 167 B1.
The substitution level of the hydrophobic substituents on the cellulose ether is typically from about 0.001 to 0.1 and preferably from about 0.004 to about 0.05 moles of the hydrophobic substituent per mole of cellulose ether. More than one particular hydrophobic substituent can be substituted onto the cellulose ether provided that the total substitution level is within the desired range.
The ionic character of the cellulose ethers of the present invention is not critical. It is typically preferred however that the ionic charge be anionic and more preferably nonionic. Cationic cellulose ethers are often undesirable in latex compositions since they can cause agglomeration and flocculation with anionic ingredients, e.g., anionic polyacrylate dispersants, anionic maleic acid copolymer dispersants, and sodium sulfosuccinate surfactants often found in latex compositions. Further details concerning the substituents and methods for modifying the ionic character of cellulose ethers are known to those skilled in the art.
The cellulose ether derivatives of the present invention are water-soluble. As used herein, the term “water-soluble” means that at least 1 gram, and preferably at least 2 grams of the cellulose ether derivative are soluble in 100 grams of distilled water at 25° C. and 1 atmosphere. The extent of water-solubility can be varied by adjusting the extent of ether substitution on the cellulose ether and by adjusting the substitution level of the hydrophobic substituents, when pre

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