Ozone-Friendly Correction Fluid

The invention relates to correction fluids.

Correction fluids for correcting handwritten, typewritten or photocopy markings on paper are well known and their performance characteristics are well defined. Essential performance characteristics include the ability to provide a film or coalesced residue on drying which can both effectively cover erroneous markings on a paper surface and receive a corrected marking. Preferably, the film covering the marking should be strongly bonded to the paper surface and should also be sufficiently flexible so that the film will not be removed under normal conditions of handling. Additionally, the correction fluid should not interact with the marking to cause excessive discoloration of the resulting film (bleeding). Another important performance characteristic involves the drying rate of the composition which should be as rapid as possible so that corrections can be made relatively quickly. Normally, commercial correction fluids form films which are sufficiently dry to receive a corrected marking in about 30-40 seconds.

Correction fluids typically are a dispersion, i.e., a suspension of solid particles in a liquid. When a correction fluid sits around for some length of time the solid particles begin to settle, causing the fluid near the bottom of the container to become more compact. Compact settling is undesirable because it is no longer easily redispersed thereby reducing coverage or the ability of the fluid to cover markings.

Correction fluids typically include some standard ingredients, including an opacifying agent, a film-forming polymeric material, a volatile solvent, and a dispersing agent. The opacifying agent is the solid that is dispersed in the fluid and provides the basic white color which can be toned with other pigments to provide a correction fluid closely corresponding to the color of the paper to which the fluid is to be applied. The film-forming polymeric material is substantially soluble in the selected solvent and binds pigment to paper and helps to form the flexible but solid covering that remains once the solvent evaporates. The volatile solvent is a carrier for all ingredients mentioned herein. The dispersing agent is included to stabilize the dispersion, i.e., to help ensure that the opacifying agent remains uniformly dispersed in the solvent.

Historically, halogenated hydrocarbons have been the solvents of choice for correction fluid compositions. Halogenated hydrocarbon solvents present special advantages primarily because they have evaporation rates which provide correction fluids that dry rapidly and completely. Additionally, they do not interact with typewritten markings to cause unacceptable bleeding. Also, they can effectively dissolve those film-forming polymeric materials which provide durable but flexible films without causing excessive cockling or distortion of paper surfaces. Despite their recognized advantages when used as correction fluid solvents, the use of halogenated hydrocarbon solvents has become a matter of increased concern primarily because of their adverse effect on the environment (stratospheric ozone depletion). Accordingly, providing an "ozone-friendly" correction fluid by eliminating the use of halogenated hydrocarbon solvents from correction fluids has become a primary objective for the art and significant efforts have been directed to the development of correction fluids free of halogenated hydrocarbon solvents. By ozone-friendly correction fluid, we mean a correction fluid which either does not contain a material that migrates to the stratosphere or, if it contains such a material, the material does not cause a reduction in the ozone concentrations.

The invention features, in one aspect, a correction fluid that includes a volatile, non-halogenated solvent; a vinyl toluene-butadiene copolymer as a film-forming material; a dispersing agent; and an opacifying agent such as titanium dioxide. By volatile, it is meant that the solvent has a boiling point of less than 155.degree. C.

The invention features, in another aspect, a correction fluid that includes a volatile, non-halogenated cyclohexane or alkylated cyclohexane containing 10 or fewer carbon atoms as a solvent; a film-forming polymeric material; an alkyl sodium sulfosuccinate as a dispersing agent; and an opacifying agent.

The invention features, in yet another aspect, a correction fluid that includes a volatile, non-halogenated cyclohexane or alkylated cyclohexane containing 10 or fewer carbon atoms as a solvent; a film-forming polymeric material; a polymeric fatty ester as a dispersing agent; a plasticizer for the polymeric material; and an opacifying agent.

The preferred dispersing agents include dialkyl sodium sulfosuccinates. Examples of preferred agents include dioctyl sodium sulfosuccinate and bistridecyl sodium sulfosuccinate.

Preferred solvents include methylcyclohexane, ethylcyclohexane, and dimethylcyclohexane; the most preferred solvent is methylcyclohexane. The solvent can also be a blend of cyclohexane or an alkylated cyclohexane and other hydrocarbons; preferably, such blends include at least 50% of the cyclohexane or alkylated cyclohexane by weight.

The preferred correction fluid includes between 35% and 55% by weight solvent; between 4% and 12% by weight copolymer; between 1% and 3.5% by weight dispersing agent; and between 35% and 55% by weight opacifying agent.

The correction fluid provides excellent coverage without bleeding typed originals, writing inks, and copies. Importantly, the fluid exhibits excellent pigment redispersibility after long term storage. Also, because a non-halogenated solvent is employed in the fluid, it is ozone-friendly.

Other features and advantages of the invention will be apparent from the description of the preferred embodiment thereof, and from the claims.

The preferred correction fluid includes methylcyclohexane as the solvent; vinyl toluene-butadiene copolymer as the film-forming material; dioctyl sodium sulfosuccinate as the dispersing agent; titanium dioxide as the opacifying agent; lampblack as a pigment to color match paper; mustard oil as a deterrent; and a fragrance.

A sufficient amount of methylcyclohexane should be included to make the fluid thin enough to be easily spread. So much should not be used so that the hiding power of the fluid diminishes. Preferably, the correction fluid should include 35%-55% by weight methylcyclohexane.

The preferred vinyl toluene-butadiene copolymer has a weight-average molecular weight of between 78,000 and 152,000, and is available from Goodyear Chemicals. A sufficient amount of the material should be included to provide good flexibility to the covering, but not so much that the viscosity of the fluid becomes too high, which can lead to reduced coverage and difficult brushing. The present correction fluid can also contain an effective amount of a plasticizer to improve flexibility of the cured copolymer. Preferred plasticizers are dialkyl phthalate compounds and a most preferred plasticizer is Jayflex.RTM. (DTDP) brand ditridecyl phthalate plasticizer distributed by Exxon Chemical. Preferably, the correction fluid includes between 4% and 12% of the copolymer.

The preferred dialkyl sodium sulfosuccinate, dioctyl sodium sulfosuccinate, is sold under the tradename AEROSOL OTS by American Cyanamid Co. The preferred polymeric fatty ester is sold under the tradename HYPERMER LP1 by ICI Specialty Chemicals. A sufficient amount of the agent should be included to achieve complete dispersion of the titanium dioxide, but not so much should be included that the hiding power is reduced. The preferred fluid includes between 1% and 3.5% dioctyl sodium sulfosuccinate by weight. Bistridecyl sodium sulfosuccinate (sold under the tradename AEROSOL TR70 by American Cyanamid Co.) can also be used.

Suitable titanium dioxide pigments include commercially available rutile titanium dioxides and anatase titanium dioxides or blends or mixtures of these which preferably have an average particle size between about 0.2 to about 0.4 microns and an average oil absorption of about 14 lbs. oil/100 lbs. pigment to about 36 lbs./100 lbs. The amount of titanium dioxide included in the composition can vary depending on the degree of coverage desired. However, amounts between about 30 to about 60 percent by weight titanium dioxide based on total weight of composition are generally suitable. Other opacifying pigments may be used either alone but preferably in combination with the titanium dioxide. Such pigments include zinc sulfide and zinc oxide. Preferably the fluid includes between 35% and 55% of the opacifying agent by weight.

Lamp black is included as a coloring pigment to match the color of fluid to standard white paper. Other pigments such as raw umber or yellow oxide can also be included to match the tone of colored paper.

A small amount (0.2-0.2%) of mustard oil is included as a deterrent.

A small amount of a fragrance is included in the preferred formula to help mask the odor of the methylcyclohexane. Preferred is Fragrance 759292/D60218 S, which is available from Haarmann & Reimer.

Examples of preferred correction fluids are the following:

Correction fluids containing the above ingredients are prepared by first dissolving the vinyl toluene-butadiene polymer in methylcyclohexane. Next, the dioctyl sodium sulfosuccinate or polymeric fatty ester dispersant and titanium dioxide opacifying agent are added and the mixture dispersed for 3 hours in a bead mill, after which colorants, mustard oil, fragrance, and other ingredients are added to obtain final fluid composition.

Other embodiments are within the claims. For example, in addition to the most preferred ingredients the composition may also include various additives known to those skilled in the art. These additives are incorporated to improved specific properties. These include plasticizers to improved dry film adhesion and flexibility, flattening agents to control film gloss, flow additives and thickeners to control brushing, leveling and settling and pigment extenders to reduce cost. Moreover, other dialkyl sodium sulfosuccinates, in particular those with alkyl groups having less than 5 or 20 carbon atoms, can be used in place of dioctyl sodium sulfosuccinate.