Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1996-10-21
2001-12-18
Jagannathan, Vasu (Department: 1511)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S430000, C524S445000, C524S556000, 26, C106S031230, C106S031600, C106S031640
Reexamination Certificate
active
06331579
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to aqueous correction fluids.
Correction fluids are used for obscuring handwritten, typewritten, photocopied, or laser printed markings on paper. Generally, a correction fluid is applied, in liquid form, to a marking on a paper surface, and then allowed to dry to form a film which effectively covers the underlying marking and is capable of receiving a corrective marking.
Water-based correction fluids typically include a pigment, e.g., titanium dioxide, and a latex binder which is usually an aqueous polymer emulsion, e.g., an acrylic copolymer or ethylene vinyl acetate (EVA) emulsion. While water-based fluids are better for the environment than solvent based systems, the water and/or any organic solvents formulated into aqueous based correction fluids have a tendency to dissolve or solubilize the dyes present in the underlying marking, causing “bleeding” or “smudging” of the underlying ink marking into the liquid correction fluid, which results in a discoloration of the dried film. The latex binder can, in some formulations, reduce the dissolution of underlying markings to which the fluid is applied, but they often do not prevent the problem of bleeding or smudging entirely. “Non-water-fast” inks, e.g., porous or rollerball pen inks, are especially difficult to cover with aqueous correction fluids without bleeding of the marking into the correction fluid.
SUMMARY OF THE INVENTION
The correction fluids of the invention have improved bleed resistance, particularly when used to correct non-water-fast inks, and have excellent hiding power, allowing the correction fluid to completely obscure most or all markings.
The improved correction fluids avoid the problem of bleeding by including a cationic stain blocking agent. The correction fluids also include an opacifying agent which is formulated to provide excellent hiding power. Preferably, the opacifying agent includes a blend of a titanium dioxide and a clay which have particular physical properties and which are provided in a specific ratio, so that the blend acts in combination with the selected stain blocking agent to provide the correction fluid with good hiding power.
In one aspect, the invention features a correction fluid which includes, as a cationic stain blocking agent, ABCO Experimental Size E-700; water; and an opacifying agent. Preferably, the opacifying agent includes a blend of a titanium dioxide that is amphoteric over a pH range of 2-12 with an acid activated clay. More preferably, the acid activated clay is anionic over a pH range of 2-12 and has a Zeta-potential that is substantially constant over a pH range of 2-12, and the titanium dioxide has an isoelectric point (Zeta-potential=0) at a pH between 7 and 9. The titanium dioxide and clay are preferably provided in a ratio of from about 0.5:1 to 0.9:1, more preferably 0.6:1 to 0.8:1. Preferably, the correction fluid includes between 41 and 56%, and more preferably between 45 and 53%, of the opacifying pigment by weight. Preferably, the correction fluid thus includes between 25 and 33%, and more preferably between 27 and 31% of a rutile TiO
2
by weight, and between 16 and 23%, and more preferably between 18 and 21%, of an acid activated clay by weight. The preferred fluid further includes at least 40%, more preferably between 41 and 53% of the stain blocking agent by weight, and between 0 and 10%, more preferably between 0 and 9% water by weight, based on the total weight of the correction fluid.
In another aspect, the invention features a correction fluid which includes, as a cationic stain blocking agent, a polymer selected from WORLEECRYL 7712, WORLEECRYL 7712E and WORLEECRYL 7712W; water; and an opacifying agent that includes a blend of a titanium dioxide that is amphoteric over a pH range of 2-12 with an acid activated clay. Preferably, the clay is anionic over a pH range of 2-12 and has a Zeta-potential that is substantially constant over a pH range of 2-12, and the titanium dioxide has an isoelectric point (Zeta-potential=0) at a pH between 7 and 9. The titanium dioxide and clay are preferably provided in a ratio of from about 0.7:1 to 1.2:1, more preferably 0.8:1 to 1.1:1. Preferably, the correction fluid includes between 42 and 58%, and preferably between 45 and 55%, of the opacifying pigment by weight. Preferably, the correction fluid thus contains between 22 and 30%, and more preferably between 24 and 28% of a rutile TiO
2
by weight, and between 20 and 28%, and more preferably between 22 and 26%, of an acid activated clay by weight. The fluid further includes between 21 and 29%, more preferably between 22 and 28% of WORLEECRYL 7712 by weight, and between 22 and 28%, more preferably between 23 and 27% water by weight, based on the total weight of the correction fluid. The correction fluid can further include between 1 and 2% of a wetting agent.
In both aspects, it is preferred that the opacifying pigment include a blend of rutile titanium dioxide and an acid activated clay composition. The titanium dioxide preferably has an average particle diameter of less than 0.8 micrometer and a hydrophilic surface. The hydrophilic surface can result from surface treatment of the titanium dioxide particles with alumina or a combination of alumina and silica. A preferred clay is an acid activated bentonite clay. In some preferred embodiments, the correction fluid further includes a nonionic, cationic and/or amphoteric wetting agent.
The invention also features methods of covering a non-water-fast ink marking on paper by applying to the non-water-fast ink marking on the paper a correction fluid of the invention, and allowing the correction fluid to dry.
In another aspect, the invention features a method of making a correction fluid, including: (a) selecting a suitable quantity of a cationic polymer capable of inhibiting bleed of anionic dyes found in aqueous inks; (b) determining a ratio of an acid activated clay to an alumina and/or silica treated TiO
2
, so that the ratio, when used in conjunction with said quantity of cationic polymer, will fully obscure, without observable bleed, markings made with a Papermate metal roller ball blue ink pen on notepad paper (TOPS “The Legal Pad” Wide Rule Gum 10 No. 7525, Tops Business Forms, St. Charles, Ill.), when the pen is used to form a line of circles on the paper, and the correction fluid is applied at a uniform wet film thickness of 1.5-2.0 mils over the circles using a drawdown bar, and (c) combining the cationic polymer, the clay and the titanium dioxide with a sufficient quantity of water to provide an aqueous correction fluid. Preferably, the method also includes the step of selecting an acid activated clay that is anionic over a pH range of 2-12 and has a Zeta-potential that is substantially constant over a pH range of 2-12.
As used herein, the term “non-water-fast ink” refers to an ink that contains one or more dyes that are soluble in or resolubilized by the water and/or organic solvents present in an aqueous based correction fluid that is applied to a marking made with the ink.
As used herein, a “stain blocking agent” is a cationic polymer that has the ability to bind anionic dye and prevent the dye from moving through the correction fluid, and unacceptably discoloring the dried corrective film.
As used herein, the term “Zeta-potential” refers to the potential difference produced at a solid-liquid interface due to ions absorbed from the moving solution. Zeta-potential is generally measured by electrophoresis.
Other features and advantages of the invention will be apparent from the Description of the Preferred Embodiments thereof, and from the claims.
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patent: 3926890 (1975-12-01), Huang et al.
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patent: 3997498 (1976-12-01), Reese e
Fish & Richardson P.C.
Guarriello John J.
Jagannathan Vasu
The Gillette Company
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