A colored lead for writing, drawing and coloring implements, more particularly erasable, sintered colored lead, or to a colored chalk, more particularly erasable, sintered colored chalk, having a sintered lead or chalk base body which is formed from a lead or chalk base material containing at least one binder with a proportion of from 1 to 25% by weight and at least one filler with a proportion of from 25 to 99% by weight. The sintered lead or chalk base body is impregnated with at least one colorant and at least one lubricant.

A pencil lead and a pencil containing the pencil lead wherein the pencil lead is polymer-based, extrudable, non-expanded, non-calcined and comprises graphite, of which 25% to 100% by weight or 50% to 100% by weight of the graphite, in relation to the total weight of the graphite, is expanded graphite.

The present invention relates to a multifunctional clay composition which can be used as a clay capable of performing various functions before drying and which can be used as writing instruments similar to crayons, pastels or colored pencils after drying, and to a process for preparing the same. The multifunctional clay composition may comprise an extender material; a binder; a multifunctional crosslinking agent including a compound having a hydroxyl group of two or more functionality, or forming an ion having a hydroxyl group of two or more functionality in a water solvent; a wax and a pigment.

The present invention relates to a multifunctional clay composition which can be used as a clay capable of performing various functions before drying and which can be used as writing instruments similar to crayons, pastels or colored pencils after drying, and to a process for preparing the same. The multifunctional clay composition may comprise an extender material; a binder; a multifunctional crosslinking agent including a compound having a hydroxyl group of two or more functionality, or forming an ion having a hydroxyl group of two or more functionality in a water solvent; a wax and a pigment.

In a pencil lead manufactured through a baking step regardless of being a black lead or a colored lead, the mechanical strength of the pencil lead is further increased by coating a surface thereof with a resin. A pencil lead includes a baked lead body whose surface is covered by a covering layer made of resin that has a scratch hardness of HB or greater. The scratch hardness of the resin as a subject resin is defined as a lowest hardness index of a tester pencil that is able to form an indentation on a surface of a horizontal flat plate coated with a 5-m thick film of the subject resin, when the surface is scratched by the tester pencil being pressed onto the surface at an angle of 45 with a load of 7.355 N.

In a pencil lead manufactured through a baking step regardless of being a black lead or a colored lead, the mechanical strength of the pencil lead is further increased by coating a surface thereof with a resin. A pencil lead includes a baked lead body whose surface is covered by a covering layer made of resin that has a scratch hardness of HB or greater. The scratch hardness of the resin as a subject resin is defined as a lowest hardness index of a tester pencil that is able to form an indentation on a surface of a horizontal flat plate coated with a 5-m thick film of the subject resin, when the surface is scratched by the tester pencil being pressed onto the surface at an angle of 45 with a load of 7.355 N.

The present invention thus relates to a writing or color pencil comprising the following 3 layers obtained by coextrusion a polyolefin-based non-expanded lead, a non-expanded protective intermediate layer surrounding the lead and comprising a mixture of polystyrene and EVA, and an expanded synthetic wood material based on a styrene polymer surrounding the protective intermediate layer, the protective intermediate layer thickness/lead radius ratio being between 0.05 and 0.17, advantageously between 0.07 and 0.15.

The present invention thus relates to a writing or color pencil comprising the following 3 layers obtained by coextrusion a polyolefin-based non-expanded lead, a non-expanded protective intermediate layer surrounding the lead and comprising a mixture of polystyrene and EVA, and an expanded synthetic wood material based on a styrene polymer surrounding the protective intermediate layer, the protective intermediate layer thickness/lead radius ratio being between 0.05 and 0.17, advantageously between 0.07 and 0.15.

The present invention concerns an extrudable, unexpanded paper pencil lead, comprising, by weight relative to the total weight of the lead, between 40 and 60%, and advantageously between 44 and 50%, of graphite; between 15 and 40%, and advantageously between 20 and 35%, of a polyolefin; between 5 and 15%, and advantageously between 6 and 10%, of a colorless mineral filler; between 5 and 20%, and advantageously between 5 and 15%, of carbon black coated with or mixed with a polyolefin wax or a polyolefin; between 0 and 16%, and advantageously between 5 and 15%, of an additive. It further concerns the paper pencil comprising a lead according to the invention.

The present invention concerns an extrudable, unexpanded paper pencil lead, comprising, by weight relative to the total weight of the lead, between 40 and 60%, and advantageously between 44 and 50%, of graphite; between 15 and 40%, and advantageously between 20 and 35%, of a polyolefin; between 5 and 15%, and advantageously between 6 and 10%, of a colorless mineral filler; between 5 and 20%, and advantageously between 5 and 15%, of carbon black coated with or mixed with a polyolefin wax or a polyolefin; between 0 and 16%, and advantageously between 5 and 15%, of an additive. It further concerns the paper pencil comprising a lead according to the invention.