COLOUR PENCIL LEAD

Abstract

The present invention concerns an extrudable, unexpanded colour pencil lead, comprising, by weight relative to the total weight of the lead: between 25 and 45%, and advantageously between 30 and 40%, of a polyolefin; between 25 and 50%, and advantageously between 30 and 40%, of a colourless mineral filler; between 4 and 20%, and advantageously between 5 and 15%, of a pigment coated with or mixed with a polyolefin wax; between 0 and 10%, and advantageously between 2 and 10%, of an additive, and between 10 and 30%, and advantageously between 15 and 25%, of stearate chosen from magnesium stearate, calcium stearate and the mixture of same. It further concerns the colour pencil comprising a lead according to the invention.

Claims

1. A non-expanded, extrudable color pencil lead, comprising, on a weight basis relative to the total weight of the lead: between 25 and 45% of a polyolefin; between 25 and 50% of a colorless mineral filler; between 4 and 20% of a pigment coated or mixed with a polyolefin wax; between 0 and 10% an additive and between 10 and 30% of stearate chosen in the group consisting of magnesium stearate, calcium stearate and a mixture thereof.

2. The color pencil lead as claimed in claim 1, wherein the polyolefin is polypropylene.

3. The color pencil lead as claimed in claim 1, wherein the colorless mineral filler is chosen in the group consisting of a clay, talc, boron nitride, silica, calcium carbonate, mica, steatite powder, and mixtures thereof.

4. The color pencil lead as claimed in claim 3, wherein the colorless mineral filler is a lamellar mineral filler.

5. The color pencil lead as claimed in claim 1, wherein the pigment content of the pigment coated with or mixed with a polyolefin wax is between 25 and 65% relative to the total weight of the pigment coated with or mixed with a polyolefin wax.

6. The color pencil lead as claimed in claim 1, wherein the pigment is coated with a polyolefin wax.

7. The color pencil lead as claimed in claim 1, wherein the polyolefin wax is a polyethylene wax.

8. The color pencil lead as claimed in claim 1, wherein the additive is chosen in the group consisting of glidants, processing agents, coupling agents, dispersants, lubricants, other pigments, and mixtures thereof.

9. The color pencil lead as claimed in claim 1, which does not comprise any plasticizer.

10. The color pencil lead as claimed in claim 1, which is extruded.

11. A color pencil comprising a lead as claimed in claim 1.

12. The color pencil lead as claimed in claim 1 which comprises, on a weight basis relative to the total weight of the lead: between 30 and 40% of a polyolefin; between 30 and 40% of a colorless mineral filler; between 5 and 15% of a pigment coated or mixed with a polyolefin wax; between 2 and 10% of an additive and between 15 and 25% of stearate chosen in the group consisting of magnesium stearate, calcium stearate and a mixture thereof.

13. The color pencil lead as claimed in claim 3, wherein the colorless mineral filler is a clay.

14. The color pencil lead as claimed in claim 13, wherein the clay is chosen in the group consisting of montmorillonite, bentonite and kaolin.

15. The color pencil lead as claimed in claim 14, wherein the clay is kaolin.

16. The color pencil lead as claimed in claim 5, wherein the pigment content of the pigment coated with or mixed with a polyolefin wax is between 30 and 60% by weight relative to the total weight of the pigment coated with or mixed with a polyolefin wax.

17. The color pencil lead as claimed in claim 6, wherein the pigment content of the pigment coated with a polyolefin wax is between 40 and 65% by weight relative to the total weight of the pigment coated with a polyolefin wax.

18. The color pencil lead as claimed in claim 8, wherein the additive is chosen in the group consisting of zinc stearate, an amide, waxes, fatty acids, glycerols and derivatives thereof, siloxane grafted onto polypropylene, rutile titanium, maleic anhydride-grafted polypropylene, and mixtures thereof.

Description

EXAMPLE 1

[0053] The table below collates examples of lead compositions according to the present invention for obtaining the characteristics of improving the erasability, good color intensity and sufficient mechanical properties to be used in color pencils.

TABLE-US-00001 TABLE 1 No. 5 Composition No. 1 No. 2 No. 3 No. 4 Saint-Michael (weight %)/example bistre Red Yellow black green Polypropylene 34.4 34.4 33.4 33.3 33.4 Kaolin 35.3 35.3 34.1 34.3 34.1 Calcium stearate 19.3 19.3 18.7 18.6 18.7 Pigment coated with 5.5 7 10 10 6 polyethylene wax Additive 5.5 4 3.8 3.8 7.8 Total 100 100 100 100 100