A non-baked pencil lead contains a colorant, a filler, a resin, and cellulose nanofibers.

A polymer having a hydrophobic polymer chain derived from monomers of farnesene and other optional monomers, such as dienes and vinyl aromatics. The polymer also includes one or more terminal functional groups, such as an amino group, a glycidyl group, a carboxylic acid group, a (meth)acrylate group, a silane group, an isocyanate group, an acetoacetate group, a phenolic group, and a hydroxyl group. Functional groups, such as carboxylic acids, may also be grafted along the hydrophobic polymer chain. The polymer may be incorporated in curable compositions that optionally include one or more polymer resins having similar functional groups. Methods for preparing the curable polymer compositions are also provided. The curable or cured form of the polymer composition may be used in various products, such as a sealant, a coating, a caulk, an electric potting compound, a membrane, a sponge, a foam, an adhesive, or a propellant binder.

A calcined solid drawing material may be capable of drawing a line excellent in color development and transparent while having a high strength regardless of a black core or a colored core. The calcined solid drawing material may include a skeleton core including at least an extender and a binder component, and a drawn line permeability T of the drawn line is 0.8 or more, as calculated by Equation (I):

T=(L*w−L*b)/(L*b−L*p)  (I),

wherein L*w is brightness of a drawn line written on white paper, L*b is brightness of a drawn line written on a black paper, and L*p is brightness of the black paper.

A calcined solid drawing material may be capable of drawing a line excellent in color development and transparent while having a high strength regardless of a black core or a colored core. The calcined solid drawing material may include a skeleton core including at least an extender and a binder component, and a drawn line permeability T of the drawn line is 0.8 or more, as calculated by Equation (I):

T=(L*w−L*b)/(L*b−L*p)  (I),

wherein L*w is brightness of a drawn line written on white paper, L*b is brightness of a drawn line written on a black paper, and L*p is brightness of the black paper.

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-μm 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-μm 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 method of manufacturing colored chalk. The method for manufacturing colored chalk includes preparing a colorant, combining the colorant with a volume of water, adding magnesium carbonate to the combination of water and colorant until a paste is formed, mixing the paste until the paste is homogenous, heating the paste in a kiln until the water is removed, and grinding a mass of colored magnesium carbonate into a powder having a desired fineness. In some embodiments, the colorant includes iron oxide, charcoal, or Camellia sinensis leaves.

A method of manufacturing colored chalk. The method for manufacturing colored chalk includes preparing a colorant, combining the colorant with a volume of water, adding magnesium carbonate to the combination of water and colorant until a paste is formed, mixing the paste until the paste is homogenous, heating the paste in a kiln until the water is removed, and grinding a mass of colored magnesium carbonate into a powder having a desired fineness. In some embodiments, the colorant includes iron oxide, charcoal, or Camellia sinensis leaves.

The present invention relates to a polymer-based extendable lead or refill for writing, drawing and/or painting tools comprising a binder comprising a mixture of polylactide with at least one polymer having a flexural modulus inferior to the flexural modulus of polylactide and at least one filler. It also relates to writing, drawing and/or painting tool, advantageously a pencil, comprising lead or a refill according to the invention and to the use of a binder comprising a mixture of polylactide with at least one polymer having a flexural modulus inferior to the flexural modulus of polylactide according to the invention to improve the vividness of polymer-based extrudable lead or refill for writing, drawing and/or painting tools.

The present invention relates to a polymer-based extendable lead or refill for writing, drawing and/or painting tools comprising a binder comprising a mixture of polylactide with at least one polymer having a flexural modulus inferior to the flexural modulus of polylactide and at least one filler. It also relates to writing, drawing and/or painting tool, advantageously a pencil, comprising lead or a refill according to the invention and to the use of a binder comprising a mixture of polylactide with at least one polymer having a flexural modulus inferior to the flexural modulus of polylactide according to the invention to improve the vividness of polymer-based extrudable lead or refill for writing, drawing and/or painting tools.