Compositions: coating or plastic – Coating or plastic compositions – Carbohydrate or derivative containing
Reexamination Certificate
1999-02-05
2001-06-05
Brunsman, David (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Carbohydrate or derivative containing
C106S162200, C106S162800
Reexamination Certificate
active
06241812
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to acid-stable and cationic-compatible high surface area cellulose compositions that provide enhanced rheology and stability to suspensions, emulsions and foams, and their methods of preparation.
2. Background of the Invention
Sanitizers and disinfectants are a group of cleaning products used in hospital and institutional care, first aid facilities, and in food and agricultural hygiene. In general terms, sanitizers and disinfectants have some bacteriostatic or bacteriocidal properties. Sanitizers are used to reduce the number of living bacteria or viable viral particles on inanimate surfaces, or in water or air. Disinfectants destroy, or irreversibly inactivate bacteria, microbial fungi or viruses. Many of the compounds used as sanitizing and disinfecting agents are cationic surfactants, and many of the formulations used for cleaners, sanitizers and disinfectants are acidic. Typical cleaning additives, including cationic surfactants, form stable compositions, having good flow properties, when formulated in acidic or neutral media.
Cationic surfactants are used in a variety of other applications, for example, as emulsifiers, dispersants, or anti-caking agents. Cationic surfactants have also been used as de-bonding agents and have been added to cellulose pulps before drying to reduce the energy required to separate the dry pulp fibers for use as absorbants, U.S. Pat. No. 4,144,122.
Rheological modifiers or thickeners, such as xanthan and hydroxyethyl cellulose are often used in formulating sanitizers or disinfectants to enhance the aesthetic properties and to improve the ease of application and coating properties, for example, of hard surface cleaners. However, use of these modifiers or thickeners in stabilized sprayable foams and liquids, which remain on the surface upon application, is limited.
Cellulose, particularly reticulated bacterial cellulose has been used to prepare a variety of rheologically modified compositions. For example, U.S. Pat. No. 5,009,797 discloses a mixture of reticulated bacterial cellulose and a gellant, such as guar, hydroxypropyl guar, xanthan, hydroxyethyl cellulose, etc., for use in a high viscosity hydraulic fracturing fluid. U.S. Pat. No. 5,350,528 describes cross-linked fracturing fluids prepared using reticulated bacterial cellulose, a gellant and a cross-linking agent.
Water soluble polymers, such as cellulose derivatives, polyacrylamides or other polysaccharides have been used in combination with reticulated bacterial cellulose to prepare well bore drilling muds, useful for drilling subterranean formations, as disclosed in U.S. Pat. No. 5,362,713.
Non-aqueous, edible compositions of ultrahigh surface area cellulose have been disclosed in U.S. Pat. No. 5,366,750. These compositions were prepared by shearing co-dried mixtures of the cellulose and a chaotropic agent, particularly corn syrup, in a non-aqueous solvent.
However, the formation of stable, aqueous cellulose dispersions is pH dependent. Changing the pH of some of the cellulose compositions, described above, to either acidic or basic compositions, may result in flocculation and separation of the cellulose. The use of cellulose as a rheological modifier or stabilizer for suspensions, emulsions and foams requires the cellulose to form stable compositions, having high viscosity and good flow properties in the presence of cationic components and/or media having acidic or alkaline (basic) pH.
Accordingly, acid-stable and cationic-compatible cellulose compositions that are useful as rheological modifiers for cationic formulations, and particularly as rheological modifiers for sanitizer and disinfectant compositions, would be highly desirable.
SUMMARY OF THE INVENTION
The present invention relates to acid-stable and cationic-compatible high surface area cellulose compositions, and their methods of preparation. Preferably, high surface area cellulose used in the acid-stable and cationic compatible cellulose compositions of this invention is reticulated bacterial cellulose. High surface area cellulose, in combination with at least one cationic co-agent, water, and optionally an acid, provides an acid-stable rheologically modified aqueous composition. In addition, this acid-stable composition may be dried to form dry cellulose compositions that may be effectively re-dispersed in acidic or neutral media. Optionally, the dried acid-stable composition also contains sucrose. Other agents, such as cationic surfactants may be combined with the high surface area cellulose to produce stable rheologically modified suspension, emulsion or foam compositions. Cationic surfactants useful in the present invention include fatty amines, fatty amine salts, or quaternary ammonium compounds. Optionally, at least one cationic-compatible co-agent is combined with the high surface area cellulose and cationic surfactants to produce rheologically modified compositions that are stable in acidic, neutral and/or basic media. The acid-stable and cationic-compatible compositions of this invention may be used as thickeners for cleaners, sanitizers, or disinfectants and may be used in other applications where viscosity and extreme pH stability are required.
DETAILED DESCRIPTION OF THE INVENTION
The acid-stable compositions of this invention are rheologically modified compositions, having an acid pH (pH<7.0), that possess and retain a homogeneous texture and appearance, even on long term storage. The cationic-compatible rheologically modified compositions of this invention possess these features when used in media, or in combination with other elements, having an acid, neutral or basic pH. Generally, the cationic-compatible compositions will be used in an acidic medium.
High surface area cellulose may be used as an effective rheological modifier in the compositions of this invention, which when dispersed in fluids, produces highly viscous, thixotropic mixtures possessing high yield stress. Yield stress is a measure of the force required to initiate flow in a gel-like system. It is indicative of the suspension ability of a fluid, as well as indicative of the ability of the fluid to remain in situ after application to a vertical surface.
The high surface area cellulose useful in this invention may be produced from insoluble cellulose fiber material, by chemical and/or mechanical processes. Typically high surface area cellulose is produced in the form of an dispersion from insoluble cellulose material by successive high energy processing of a mixture of the cellulose in a hydrophilic solvent, such as water, polyhydroxy fluids (e.g., ethylene glycol, glycerin, polyethylene glycol, etc.), or mixtures thereof. This high energy processing is called “activation” and comprises high pressure homogenization and/or high shear mixing. Activation is a process in which the 3-dimensional structure of the cellulose is modified such that the cellulose imparts functionality to the base solvent or solvent mixture in which the activation occurs, or to a composition to which the activated cellulose is added. Functionality includes providing such properties as thickening, imparting yield stress, heat stability, suspension properties, freeze-thaw stability, flow control, foam stabilization, coating and film formation, and the like. The high energy processing that is typically used in the activation process does significantly more than to just disperse the cellulose in base solvent. The high energy processing “teases apart” the cellulose fibers to expand the cellulose fibers. Apparatus that may be useful for activating the high surface area cellulose in water include a Gaulin homogenizer at high pressure, e.g., 8000 psi, Waring blender, Silverson high-shear mixer, Greaves high-shear mixer, a Heidolph propeller mixer, or colloidal mills. Although a single pass homogenization produces activated high surface area cellulose dispersions, preferably, the compositions of this invention may be prepared by passing the cellulose, or a mixture of cellulose and any added agents, throug
Colegrove George T.
Rakitsky Walter G.
Smith Barbara A.
Brunsman David
Fitzpatrick ,Cella, Harper & Scinto
Pharmacia Corporation
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