MXPA00000686A - Coloured pencil leads. - Google Patents

Abstract

The present invention discloses coloured pencil leads comprising, in addition to pigments, from about 60% to about 80% by weight of a metal stearate, from about 15% to about 25% by weight of a cellulose polymer, and from about 1% to about 6% by weight of colloidal silica. In another embodiment, the present invention relates to a coloured pencil having a coloured lead as a core, which comprises the composition as defined above.

Description

MINES FOR COLORED PENCIL.

Field of Invention: The present invention relates to a new colored mine for use in the production of colored pencils which allows it to be erased by the use of a conventional pencil gum.

Background of the Invention: Studies have been developed with the purpose of obtaining a composition of a colorful mine that can be used in pencils of conventional color but that allows its removal through the use of a simple eraser rubber of the school type.

The colorful mines conventionally used in colored pencils use waxes, which do not allow their removal, total or partial, through the simple mechanical action of a rubber. In this sense, some attempts to improve the erasing characteristics of mines containing waxes have already been proposed.

US 5,595,700, for example, describes REF. : 32562 a colorful pencil quarry, not calcined, obtained by a process comprising stages of a mixture containing at least one water-oil-repellent substance, a binder, a dye and a filler, squeezing and drying the resulting kneaded mixture and, then, impregnate it with oil, grease or wax.

Another document that foresees the use of waxes is JP 7126568 which describes colorful mines for pencils, not calcined, containing pigments, filler, water-soluble binder, esters of higher fatty acids of fatty and / or basic amino acids of chain N-acyla long and having open pores impregnated with fats and oils and / or waxes.

Other studies proposed alternatives for the production of mines for wax-free erasable pencils. This is the case, for example, of JP 8120208 which presents a color pencil lead consisting of organic binder, coloring materials and N-e-lauryl lysine as filler. Meanwhile, the processes "described in the documents known from the state of the art involve the preparation of porous materials and their subsequent impregnation treatment having as a vehicle the combination of waxy materials and dyes, thus requiring a too long time.

Other diverse materials have been studied, being that some have already become conventionally used to perfect some important characteristics of the mines for color pencils, such as greater resistance, better color printing to the substrate, and others, but without any of them get the desired erasing effect.

It is, therefore, the object of the present invention to provide mines for colored pencils having an improved erasure feature that allows their removal through the use of a conventional pencil gum.

Brief Description of the Invention The present invention relates to colorful mines for pencils comprising, apart from pigments, from 60 to 80%, by weight, of a metal stearate, from 15 to 25%, by weight, of a cellulose polymer and 1 to 6% by weight, of colloidal silica.

In another aspect the invention relates to a color pencil containing, as a core, a colorful mine containing the composition defined above.

Detailed description of the invention The term "pencil" used here should be understood as encompassing all types of pencils, pens, or the like, which use, as a core, colorful mines to transfer color to a particular substrate such as paper.

After detailed studies, the inventors verify that the joint use of metal stearate, a cellulose polymer and colloidal silica allows obtaining a colorful pencil lead that has an unexpectedly improved ability to be erased with a simple conventional pencil gum , just like the school tires.

The colorful mine of the invention contains a 60 to 80% by weight, of a metal stearate, of 15 to 25%, by weight, of a cellulose polymer and of 1 to 6%, by weight, of colloidal silica. In a preferred way, the colored pencil lead comprises 66 to 75%, by weight, of a metal stearate, from 19 to 21%, by weight, of a cellulose polymer and from 2.5 to 3.3%, by weight, of colloidal silica.

According to one aspect of the invention, stearates of alkali metals, alkaline-earth metals or zinc stearate are advantageously used. More preferably, sodium, calcium or magnesium stearates are used.

The cellulose polymers which can be used according to the invention are, for example, methylhydroxypropylcellulose and hydroxyethylcellulose. These cellulose polymers promote the mechanical strength of the mines and, together with the action of the stearate compounds responsible for the deposition of color on the substrate, and the colloidal silica that favors the erasure, make the mines obtained with this composition have a capacity of erasure far superior to the corresponding products already known from the state of the art. The color pencil mine of the invention allows its total removal from the substrate using only a rubber of the "school" type.

The mine described here may still contain other ingredients normally used in this type of mine. Like a colorful mine, it contains organic and / or inorganic pigments usually in proportions of 2 to 15%, by weight, preferably 2 to 11, by weight, depending on the color and intensity desired in the application of the final product, part of solvents and other charges.

The mines of the present invention can be obtained by conventional processes of preparation of mines for colored pencils. The process, generically, comprises the weight, mixture and homogenization of the raw materials in mixers, for example, of the sigma type, and, next, the processing in a 3-cylinder mill for a better homogeneity and opening of the pigments. Then, a squeezing step is carried out according to the conventional method and, finally, the drying in stoves, normally at a temperature between 60 and 70 ° C for approximately 48 hours. The mines thus produced can then be used in the usual production processes of color pencils.

The illustrated example presented below serves to better describe the present invention. Meanwhile, the illustrated data refers merely to some aspects of the present invention and should not be taken as limiting the purpose thereof.

Example 1 A colorful mine was prepared according to the present invention, presenting the following composition It is obtained, therefore, that a colorful mine according to the invention provides excellent erasability, expressed by the percentage of color removed from the substrate with a conventional school gum. The removal of the mine described above was practically total (> 90%) Example 2 A colorful mine analogous to that of the present invention was prepared, therefore, not including colloidal silica: Raw Materials% (by weight) calcium stearate 73 hydroxypropylmethylcellulose 25 colloidal silica 0 organic pigment-Yellow 12 2 water 40 Erase (% area removed) 70% As it can be verified the absence of one of the components already reduced the erasing capacity of the mine that remained around 70%. In any case, the mines of the previous examples provide a substantially improved erase capacity in comparison with the already known colorful mines which have a wiper capability < 10% It is noted that in relation to this date, the best method known to the applicant, to implement said invention is that which is clear from the manufacture of the objects to which it refers.

Having described the invention as above, the content of the following is claimed as property.

Claims (5)

1. Mine for color pencil characterized in that it comprises, apart from pigments, from 60 to 80%, by weight, of a metal stearate, from 15 to 25%, by weight, of a cellulose polymer and from 1 to 6%, by weight , of colloidal silica.

2. Mine according to claim 1, characterized in that the metal stearate is selected from the group comprising sodium stearate, calcium stearate, magnesium stearate and zinc stearate.

3. Mine according to claim 1 or 2, characterized in that the cellulose polymer is selected from hydroxypropylcellulose and hydroxyethylcellulose.

Four . Mine according to any of claims 1 to 3, characterized in that it comprises 66 to 75%, by weight, of metal stearate, from 19 to 21%, by weight, of the cellulose polymer and 2.5 to 3.3%, in weight, of colloidal silica.

5. Colored pencil characterized by the fact that it comprises, as a core, a colorful mine as defined in any of claims 1 to 4.