ERASABLE WRITING COMPOSITIONS

Abstract

A thermoplastic writing composition includes at least one particulate filler including one or more of days, silicates, or carbonates, at least one thermoplastic binder material including one or more of high density polyethylene, polypropylene, and styrene, one or more waxes chosen from soy wax, paraffin wax, and beeswax, at least one colorant, and optionally, at least one surfactant.

Claims

1. A thermoplastic writing composition comprising: at least one particulate filler including one or more of clays, silicates, or carbonates, at least one thermoplastic binder material including one or more of high density polyethylene, polypropylene, and styrene, one or more waxes chosen from a group consisting of soy wax, paraffin wax, and beeswax, at least one colorant, and optionally, at least one surfactant.

2. The composition of claim 1, wherein the composition is configured to be applied to a substrate.

3. The composition of claim 2, wherein the composition is further configured to be erasable with a standard eraser after application to the substrate.

4. The composition of claim 1, wherein the at least one particulate filler is a clay.

5. The composition of claim 4, wherein the clay is kaolin clay.

6. The composition of claim 1, wherein the at least one thermoplastic binder material is high density polyethylene.

7. The composition of claim 1, wherein: the at least one particulate filler is present in an amount between about 20% and about 80% by weight; the at least one thermoplastic binder material is present in an amount between about 10% and about 36% by weight; the one or more waxes are present in an amount between about 2% and about 35% by weight; and the at least one colorant is present in an amount between about 1% and about 30% by weight.

8. The composition of claim 7, wherein the optional at least one surfactant is present in an amount between about 1% and about 10% by weight.

9. The composition of claim 1, wherein the at least one colorant is dry pigment.

10. The composition of claim 1, wherein the at least one colorant is a pigment predispersed in a thermoplastic material.

11. A writing instrument comprising the thermoplastic writing composition according to claim 1.

12. The writing instrument of claim 11, wherein the writing instrument was produced via an extrusion process.

13. The writing instrument of claim 11, wherein the writing instrument was produced via an injection molding process.

14. The writing instrument of claim 11, wherein a coating layer of a thermoplastic material is applied to a surface of the writing instrument.

15. The writing instrument of claim 11, wherein the writing instrument is in a pencil core shape.

16. The writing instrument of claim 11, wherein the pencil core is encased within a sheath.

17. The writing instrument of claim 16, wherein the sheath is rigid.

18. The writing instrument of claim 17, wherein the sheath is wood or plastic.

19. The writing instrument of claim 11, wherein the writing instrument is in a crayon shape.

20. The writing instrument of claim 19, wherein the writing instrument is encased within a paper sheath.

21. The composition of claim 1, wherein: the at least one thermoplastic binder material is present in an amount between about 10% and about 36% by weight; the one or more waxes are present in an amount between about 2% and about 35% by weight; the at least one colorant is present in an amount between about 1% and about 30% by weight, and the at least one particulate filler is present in an amount between about 20% and 50% by weight, and the at least one particulate filler includes one or more clays and one or more silicates.

22. The composition of claim 21, wherein the one or more clays include kaolin clay.

23. The composition of claim 21, wherein the one or more silicates include mica.

24. The composition of claim 21, wherein the one or more clays are present in an amount between about 15% and 35% by weight.

25. The composition of claim 24, wherein the one or more clays are present in an amount between about 20% and 30% by weight.

26. The composition of claim 21, wherein the one or more silicates are present in an amount between about 5% and 15% by weight.

27. The composition of claim 26, wherein the one or more silicates are present in an amount of 10% by weight.

28. A writing instrument comprising the thermoplastic writing composition according to claim 21.

29. The writing instrument of claim 28, wherein the writing instrument is in a pencil core shape.

30. The writing instrument of claim 29, wherein the writing instrument has a cross-section between about 1 mm and 10 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention relates to colored writing compositions and colored writing instruments made from the compositions. It has been surprisingly found that the writing instruments resulting from the compositions according to the present invention are capable of being produced by versatile processes, such as via extrusion and/or injection molding. The writing instruments may be injection molded or extruded into any shape, including into shapes of crayons, mechanical pencil cores, or pencil cores. Additionally, the colored writing compositions exhibit high strength characteristics and are break resistant such that writing instruments prepared from the compositions can be used without being sheathed in support materials, e.g., wood, plastic, or paper, or can be formed into very narrow mechanical pencil cores. The breaking strength and bending strength of the writing compositions are therefore highly improved. Such qualities decrease production time and production costs of writing instruments prepared from the compositions.

[0015] It has also been surprisingly found that the compositions display improved laydown qualities, which result in increased color vibrancy and opacity when the compositions are applied to dark substrates. This also results in resistance to self-erasure when marks from the compositions are layered, or built, upon one another during use. Thus, the compositions allow for building of layers of colored marks during use.

[0016] The writing compositions comprise at least one particulate filler, at least one thermoplastic material, one or more waxes, at least one colorant, and, optionally, at least one surfactant. It has also been surprisingly found that the marks made by the colored writing compositions are easily erasable with standard, ordinary pencil erasers without leaving behind substantial residue or smears, despite their wax content and lack of fibrous materials.

[0017] The writing compositions of the present invention include at least one binder material to provide integrity to the compositions by holding the components of the compositions together. Preferably, the binder is an extrudable, thermoplastic material (e.g., high density polyethylene, polypropylene, styrene), such that the colored pencil compositions are capable of being extruded when exposed to heat in an extrusion process, but are solid at room temperature. Most preferably, the binder material is a high density polyethylene (HDPE).

[0018] The binder material (e.g., HDPE) may be present in any suitable amount in the compositions. Preferably, the binder material is present in an amount between about 10% and about 36% by weight of the composition. More preferably, the binder material is present in an amount between about 11% and about 21% by weight. Even more preferably, the binder material is present in an amount of about 16% by weight.

[0019] The writing compositions include at least one suitable colorant, such as a dry pigment. The pigment may be organic or inorganic. Colorants (e.g., pigments) producing specific visual effects, such as pearlescent pigments, may be used. Pigments predispersed in thermoplastic materials, such as pigment predispersed in HDPE, may optionally be used.

[0020] The colorant can be present in the compositions in any suitable amount. Preferably, the colorant is present from about 1% to about 30% by weight of the composition. More preferably, the colorant is present from about 5% to about 15% by weight of the composition. Even more preferably, the colorant is present in an amount of about 10% by weight of the composition.

[0021] The compositions according to embodiments of the present invention also include at least one suitable particulate filler. The filler may provide stiffness and strength to the writing compositions to resist bending and breaking when formed into various shapes. The filler may also aid in reducing the amount of colorant required in the composition by more efficiently distributing colorant throughout the composition. Suitable fillers may include clays, carbonates, and silicates. Preferably, the fillers comprise clays, due to low cost and desirable absorbance qualities; i.e., it is believed the clays absorb and disperse colorant efficiently to reduce the amount of colorant necessary in the composition. Preferably, the filler is a clay chosen from a group including China clay, T-clay, and kaolin clay. Most preferably, the filler comprises kaolin clay. Additionally, preferable fillers include silicates (e.g., mica) due to their ability to impart strength and rigidity to the composition. The compositions of the present invention may include one or more fillers in any suitable amount. Preferably, the one or more fillers (e.g., kaolin clay, mica) are present in an amount between about 20% and 80% by weight of the composition. More preferably, the one or more fillers are present in an amount between about 50% and 64% by weight. Even more preferably, the one or more fillers are present in an amount of about 58% by weight.

[0022] The writing compositions of the present invention also include at least one wax (e.g., soy wax, paraffin wax, beeswax). The wax may contribute to improved color intensity of the compositions and smooth laydown properties. The waxes preferably have amorphous characteristics and lower melting temperatures to provide fluid writing properties when the compositions are used to make colored marks.

[0023] The wax may be present in any suitable amount. A wax or a combination of waxes is preferably included in an amount between 2% and about 35% by weight of the composition. Preferably, the compositions include both soy wax and paraffin wax. Preferably, soy wax is included in an amount of between about 1% and about 27% by weight of the composition. More preferably, the soy wax is present in an amount of between about 2% and about 12% by weight. Even more preferably, the soy wax is present in an amount of about 7% by weight. Preferably, paraffin wax is present in an amount between about 1% and about 26% by weight. More preferably, paraffin wax is present in an amount between about 1% and about 11% by weight. Even more preferably, paraffin wax is present in an amount of about 6% by weight of the composition.

[0024] Surfactants for stabilizing the compositions and the colorants in the compositions of the present invention and improving processing of the compositions may optionally be included. Examples of surfactants that may be used include colorant dispersants and process aids. Dispersants may prevent colorant, such as pigment, from adhering to itself such that the dispersant aids in mixing the colorant adequately into the composition. Other surfactants include process aids that improve flow properties for processing, such that the composition can easily move through mechanical processing such as extrusion or injection molding.

[0025] Surfactants may be present in any suitable amount in the compositions. The compositions may not include surfactants at all, as surfactants are optional. Preferably, surfactants are present in an amount between about 1% and about 10% by weight of the composition. More preferably, surfactants are present in an amount between about 1% and about 6% by weight. Even more preferably, surfactants are present in an amount of about 3% by weight.

[0026] The compositions produced according to embodiments of the invention set forth herein may also be formed into different shapes, including into colored pencil core shapes or into crayon shapes, by a variety of processes; that is, the compositions are versatile with respect to their processing capability. For example, the compositions may be injection molded into colored pencil cores, mechanical pencil cores, or crayons. The compositions may also be processed into, for example, colored pencil cores or mechanical pencil cores via profile extrusion, which is more efficient in terms of time and cost than injection molding. The compositions may be formed into any shape suitable for a writing instrument via injection molding and/or extrusion. The compositions may also be formed into cores having any cross-sectional thickness suitable for use with a mechanical pencil (e.g., between approximately 1 mm and 10 mm). Despite the differences in these processing techniques, the compositions according to embodiments of the invention herein are suitable for either technique and produce writing instruments having the same desirable properties.

[0027] Pencil cores and/or crayons produced from the compositions according to embodiments of the invention herein are resistant to breakage and do not require supportive sheathing to prevent breakage during use, unlike typical crayons and pencil cores. The cores/crayons may therefore be used to produce colored marks on substrates without any supportive cover. Optionally, a very thin coating layer of thermoplastic material (e.g., HDPE or the thermoplastic filler material used in the composition) may be added to the outside of the cores/crayons to “lock” the surface, such a layer being too thin to provide significant structural support. This thin coating layer of thermoplastic material on the surface of the cores prevents “blooming,” wherein waxes and colorants leach through to the surface of the cores/crayons. The thin coating layer of thermoplastic material may also add an aesthetic “shine” to the cores, without impeding ability to sharpen the core for use.

[0028] Mechanical pencil cores produced from the compositions according to embodiments of the invention herein are also resistant to breakage and can assume very narrow cross-sectional thicknesses suitable for use with mechanical pencils (e.g., between approximately 1 mm and 10 mm). The compositions of the present invention for producing mechanical pencil cores may include one or more fillers in any suitable amount. Preferably, the one or more fillers (e.g., kaolin clay and/or mica) are present in an amount between about 20% and 50% by weight of the composition. More preferably, the one or more fillers are present in an amount between about 30% and 40% by weight. Even more preferably, the one or more fillers are present in an amount of about 35% by weight. Preferably, compositions of the present invention for producing mechanical pencil cores include both clays (e.g., kaolin clay) and silicates (e.g., mica). Even more preferably, the clays are present in an amount between about 15% and 35% by weight; and the silicates are present in an amount between about 5% and 15% by weight.

[0029] While preferred embodiments of the invention have been shown and described herein, it will be understood that such embodiments are provided by way of example only. Numerous variations, changes and substitutions will occur to those skilled in the art without departing from the spirit of the invention. Accordingly, it is intended that the appended claims cover all such variations as fall within the spirit and scope of the invention.