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.

A composition is provided for making a polyurethane that may be incorporated in various products, such as a sealant, a coating, a caulk, an electric potting compound, a membrane, a sponge, a foam, an adhesives, and a propellant binder. The composition includes one or more polyols, one or more isocyanate-group containing compounds having an isocyanate group functionality of at least two, and optionally one or more chain extenders. At least one of the polyols is a farnesene-based polyol having a number average molecular weight less than or equal to 100,000 g/mol and a viscosity at 25? C. less than 10,000 cP. The farnesene-based polyol may be a homopolymer or a copolymer of farnesene. The composition may also comprise additional polyols, such as a polyol of a homopolymer or copolymer of a polydiene. Methods of preparing a polyurethane are also provided.

A composition is provided for making a polyurethane that may be incorporated in various products, such as a sealant, a coating, a caulk, an electric potting compound, a membrane, a sponge, a foam, an adhesives, and a propellant binder. The composition includes one or more polyols, one or more isocyanate-group containing compounds having an isocyanate group functionality of at least two, and optionally one or more chain extenders. At least one of the polyols is a farnesene-based polyol having a number average molecular weight less than or equal to 100,000 g/mol and a viscosity at 25? C. less than 10,000 cP. The farnesene-based polyol may be a homopolymer or a copolymer of farnesene. The composition may also comprise additional polyols, such as a polyol of a homopolymer or copolymer of a polydiene. Methods of preparing a polyurethane are also provided.

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.

A non-baked pencil lead containing a water-soluble polymer, a crosslinking agent, and a powder, in which the water-soluble polymer is selected from a group consisting of a carboxymethyl cellulose salt, starch, polyvinyl alcohol, and xanthan gum, and the crosslinking agent is selected from a group consisting of an acid, polyamide epoxy, polyacrylamide, titanium alkoxide, and glyoxal.

A non-baked pencil lead containing a water-soluble polymer, a crosslinking agent, and a powder, in which the water-soluble polymer is selected from a group consisting of a carboxymethyl cellulose salt, starch, polyvinyl alcohol, and xanthan gum, and the crosslinking agent is selected from a group consisting of an acid, polyamide epoxy, polyacrylamide, titanium alkoxide, and glyoxal.