Initially erasable ink composition for a ball point writing instrument

Claim 1

The method of making an ink composition which is characterized by initial erasability by ordinary pencil erasers of a trace thereof when applied by a ball-point writing instrument to an absorbent paper-like writing surface and which trace thereafter develops permanence, said method comprising the steps of: (a) providing a pre-pigmented elastomer component in which pigment is substantially homogeneously distributed throughout and aggregated onto molecular chains of elastomer component; (b) dispersing the pre-pigmented elastomer component in a solvent system, the solvent system being present in amount sufficient to provide an ink composition having a viscosity in the range of 1 - 4 X 10 6 cps and comprising a volatile component having a boiling point less than about l80°C and which contributes to initial erasability of an applied trace of the ink composition and an essentially non-volatile component which contributes to development of permanence of the applied trace; and (c) controlling initial erasability of the ink composition and capability of subsequently developing permanence when applied as a trace to the absorbent writing surface with the ball-point writing instrument by selecting, for the elastomer component of step (a), elastomeric materials which exhibit predetermined molecular weight distribution over a wide molecular weight range and by milling the pigment into the elastomer component in the absence of the solvent system to provide the pre-pigmented elastomer component of step (a), and by selecting, for the essentially non-volatile component of step (b), a liquid having a boiling point in the range of 180-300°C and a viscosity in the range of 1-l5cps.

Claim 2

The method of making an ink composition which is characterized by initial erasability by ordinary pencil erasers of a trace thereof when applied by a ball-point writing instrument to an absorbent paper-like writing surface and which trace thereafter develops permanence, said method comprising the steps of: (a) providing a pre-pigmented elastomer component in which pigment is substantially homogeneously distributed throughout and aggregated onto molecular chains of elastomer component; (b) dispersing the pre-pigmented elastomer component in a solvent system, the solvent system being present in amount sufficient to provide an ink composition having a viscosity in the range of 1 - 4 X 10 6 cps and comprising a volatile component having a boiling point less than about l80°C and which contributes to initial erasability of an applied trace of the ink composition and an essentially non-volatile component which contributes to development of permanence of the applied trace; and (c) controlling initial erasability of the ink composition and capability of subsequently developing permanence when applied as a trace to the absorbent writing surface with the ball-point writing instrument by selecting, for the elastomer component of step (a), elastomeric materials which exhibit predetermined molecular weight distribution over a wide molecular weight range and by milling the pigment into the elastomer component in the absence of the solvent system to provide the pre-pigmented elastomer component of step (a), and by selecting, for the essentially non-volatile component of step (b), a liquid having a boiling point in the range of 180-300°C and a viscosity in the range of 1-l5cps.

Claim 7

The method of making an ink composition which is characterized by its initial erasability by ordinary pencil erasers when applied by a ball-point writing instrument to an absorbent paper-like writing surface and which thereafter develops permanence, said method comprising the steps of: (a) selecting elastomeric material from the group consisting of natural rubbers, synthetic rubbers and mixtures thereof, said elastomeric material having a low level of hard resinous gel particles and an extremely low level of retained dirt which is no more than .05% by weight; (b) masticating said selected elastomeric material by subjecting same to high shear stresses within the range of about 2.0 X 10 6 to 2.0 X 10 7 KG. Metre sec - 2 (Newtons) to soften said elastomeric material to a Mooney viscosity within the range of about 17 to 27; (c) coloring said masticated elastomeric material by introducing colored pigment into said masticated elastomeric material while subjecting same to further shear stresses so as to forcibly impregnate said material with pigment, said color pigment being selected from the group consisting of dry pigment, flushed pigment and a paste consisting of pigment dispersed in a rubber compatible vehicle, said forced impregnation thereby distributing color uniformly among the various chain lengths of said elastomeric material; and (d) mixing said pigmented elastomeric material with a solvent system to form an erasable ink composition having a viscosity in the range 1 X 10 6 - 4 X 10 6 cps, said solvent system comprising a volatile component and an essentially non-volatile component in which the volatile component has a boiling point less than about 180°C and said essentially non-volatile component is at least predominantly a low viscosity hydrocarbon oil having a viscosity in the range l-15cps and a boiling point less than about 300°C and greater than about l80°C, and which includes less than 15% by weight of the erasable ink composition of a high viscosity material having a boiling point greater than 300°C.

Claim 8

The method of making an ink composition which is characterized by its initial erasability by ordinary pencil erasers when applied by a ball-point writing instrument to an absorbent paper-like writing surface and which thereafter develops permanence, said method comprising the steps of: (a) selecting elastomeric material from the group consisting of natural rubbers, synthetic rubbers and mixtures thereof, said elastomeric material having a low level of hard resinous gel particles and an extremely low level of retained dirt which is no more than .05% by weight; (b) masticating said selected elastomeric material by subjecting same to high shear stresses within the range of about 2.0 X 10 6 to 2.0 X 10 7 KG. Metre sec - 2 (Newtons) to soften said elastomeric material to a Mooney viscosity within the range of about 17 to 27; (c) coloring said masticated elastomeric material by introducing colored pigment into said masticated elastomeric material while subjecting same to further shear stresses so as to forcibly impregnate said material with pigment, said color pigment being selected from the group consisting of dry pigment, flushed pigment and a paste consisting of pigment dispersed in a rubber compatible vehicle, said forced impregnation thereby distributing color uniformly among the various chain lengths of said elastomeric material; and (d) mixing said pigmented elastomeric material with a solvent system to form an erasable ink composition having a viscosity in the range 1 X 10 6 - 4 X 10 6 cps, said solvent system comprising a volatile component and an essentially non-volatile component in which the volatile component has a boiling point less than about 180°C and said essentially non-volatile component is at least predominantly a low viscosity hydrocarbon oil having a viscosity in the range l-15cps and a boiling point less than about 300°C and greater than about l80°C, and which includes less than 15% by weight of the erasable ink composition of a high viscosity material having a boiling point greater than 300°C.

Claim 9

The method of making an ink composition which is characterized by initial erasability by ordinary pencil erasers of a trace thereof when applied by a ball point writing instrument to an absorbent paper-like writing surface and which trace thereafter develops permanance, said method comprising the steps of: (a) milling a pigment into elastomer to provide a pre-pigmented elastomer component in which pigment is substantially homogeneously distributed throughout and aggregated onto molecular chains of elastomer; (b) dispersing the pre-pigmented elastomer in a solvent system, the solvent system being present in amount sufficient to provide an ink composition having a viscosity in the range of 1 X 10 6 - 4 X 10 6 cps and comprising a volatile component having a boiling point less than about 180°C and which contributes to initial erasability of an applied trace of the ink composition and an essentially non-volatile component which contributes to development of permanence of the applied trace and to increased writing smoothness of the ink composition when applied as a trace, said volatile and essentially non-volatile components being solvents for the elastomer component and said essentially non-volatile component having a sufficiently low viscosity as to result in ink composition having a viscosity in said range thereof.

Claim 10

The method of making an ink composition which is characterized by initial erasability by ordinary pencil erasers of a trace thereof when applied by a ball point writing instrument to an absorbent paper-like writing surface and which trace thereafter develops permanance, said method comprising the steps of: (a) milling a pigment into elastomer to provide a pre-pigmented elastomer component in which pigment is substantially homogeneously distributed throughout and aggregated onto molecular chains of elastomer; (b) dispersing the pre-pigmented elastomer in a solvent system, the solvent system being present in amount sufficient to provide an ink composition having a viscosity in the range of 1 X 10 6 - 4 X 10 6 cps and comprising a volatile component having a boiling point less than about 180°C and which contributes to initial erasability of an applied trace of the ink composition and an essentially non-volatile component which contributes to development of permanence of the applied trace and to increased writing smoothness of the ink composition when applied as a trace, said volatile and essentially non-volatile components being solvents for the elastomer component and said essentially non-volatile component having a sufficiently low viscosity as to result in ink composition having a viscosity in said range thereof.

Claim 17

The method of making an ink composition which is characterized by initial erasability by ordinary pencil erasers of a trace thereof when applied by a ball point writing instrument to an absorbent paper-like writing surface and which trace thereafter develops permanence, said method comprising the steps of: (a) masticating elastomer component having a molecular weight distributed over the range of 100,000-900,000 until it is softened to a Mooney viscosity range of 17-27; (b) force impregnating pigment paste into a softened elastomer component until the pigment is distributed uniformly among all the molecular chain lengths of elastomer component, the paste comprising about 50% pigment dispersed in an elastomer-compatible vehicle; (c) dispersing the pre-pigmented elastomer in a solvent system, the solvent system being present in amount sufficient to provide an ink composition having a viscosity in the range of 1 X 10 6 - 4 X 10 6 cps and comprising a volatile component having a boiling point less than about 180°C and which contributes to initial erasability of an applied trace of the ink composition and an essentially non-volatile component which contributes to development of permanence of the applied trace, said volatile and essentially non-volatile components being solvents for the elastomer component and said essentially non-volatile component having a sufficiently low viscosity as to result in a final ink viscosity within said range of 1 - 4 X 10 6 cps.

Claim 18

The method of making an ink composition which is characterized by initial erasability by ordinary pencil erasers of a trace thereof when applied by a ball point writing instrument to an absorbent paper-like writing surface and which trace thereafter develops permanence, said method comprising the steps of: (a) masticating elastomer component having a molecular weight distributed over the range of 100,000-900,000 until it is softened to a Mooney viscosity range of 17-27; (b) force impregnating pigment paste into a softened elastomer component until the pigment is distributed uniformly among all the molecular chain lengths of elastomer component, the paste comprising about 50% pigment dispersed in an elastomer-compatible vehicle; (c) dispersing the pre-pigmented elastomer in a solvent system, the solvent system being present in amount sufficient to provide an ink composition having a viscosity in the range of 1 X 10 6 - 4 X 10 6 cps and comprising a volatile component having a boiling point less than about 180°C and which contributes to initial erasability of an applied trace of the ink composition and an essentially non-volatile component which contributes to development of permanence of the applied trace, said volatile and essentially non-volatile components being solvents for the elastomer component and said essentially non-volatile component having a sufficiently low viscosity as to result in a final ink viscosity within said range of 1 - 4 X 10 6 cps.