Lead refill for writing, drawing and/or painting devices and method for the production thereof

Abstract

A polymer-bound lead refill for writing, drawing and/or painting devices, in particular for pencils or colored pencils, including at least one binding agent, at least one wax, at least one coloring agent and at least one filling agent. The lead refill including at least one surfactant.

Claims

1. A polymer-bonded colored pencil refill for writing, drawing and/or painting tools, comprising: at least one polymeric binder, wherein the at least one polymeric binder is formed from at least one polymer from the group consisting of: polystyrene (PS); styrene/acrylonitrile (SAN); polylactide (PLA); styrene/butadiene (SB); polyolefins (PO); and acrylonitrile/butadiene/styrene (ABS); at least one wax and/or oil fraction; at least one colorant; at least one filler; and at least one cationic surfactant which is quaternary ammonium, wherein the quantity of the at least one surfactant is 0.2 to 3% by weight, wherein the refill comprises TABLE-US-00009 12% to 30% by weight polymeric binder 2% to 20% by weight wax and/or oil remainder graphite or graphite and carbon black as the colorant and filler.

2. The refill as claimed in claim 1, further comprising an anionic surfactant which is sodium alkyl sulphonate.

3. A method for manufacturing a polymer-bonded refill according to claim 1, comprising the steps of extruding the refill.

Description

SUMMARY AND DESCRIPTION OF THE INVENTION

(1) Thus, the object of the invention is to provide a refill for writing, drawing and/or painting which does not exhibit the disadvantages mentioned above and which in particular has a high specific strength in the presence of waxes.

(2) A further object of the invention is constituted by the provision of a method for the manufacture of refills of this type.

(3) This object is accomplished by adding surfactants to the refill compound. In this manner, a polymer-bonded refill for writing, drawing and/or painting devices, in particular for lead and/or colored pencils is provided, which comprises at least one polymeric binder, at least one wax, at least one colorant, at least one filler and at least one surfactant as a wetting agent.

(4) The surfactant, being a wetting agent or surface-active substance, improves wetting of the fillers by the molten polymer, whereby the differences in polarity between the individual components of the mixture are reduced, whereupon a stable structure is formed and thus the specific strength increases.

(5) It has surprisingly been shown that by adding at least one surfactant to the refill compound, the strength of the refills produced therefrom increases by up to 15%.

(6) In addition, it has surprisingly been shown that the marks that are produced with the refill in accordance with the invention have good gliding properties as well as good erasability.

(7) These surprising effects have been observed with both lead and colored refills.

(8) The proportion of the at least one surfactant in the refill composition is in the range from more than zero to 6% by weight, preferably in the range 0.2% to 3% by weight.

(9) The surfactant may be a cationic, anionic and/or non-ionic surfactant.

(10) Examples of non-ionic surfactants are surfactants from the fatty acid ester group.

(11) Examples of cationic surfactants are ammonium compounds.

(12) An example of an anionic surfactant is sodium alkyl sulphonate.

(13) Preferably, the at least one surfactant comprises at least one compound from the group formed by fatty acid esters and/or quaternary ammonium compounds.

(14) Advantageously, the polymer-bonded refill comprises:

(15) TABLE-US-00001 10% to 40% by weight polymeric binder more than zero to 6% by weight surfactant 2% to 25% by weight wax and/or oils 0 to 30% by weight colorant remainder fillers

(16) Particularly preferably, the polymer-bonded refill comprises:

(17) TABLE-US-00002 12% to 30% by weight polymeric binder 0.2% to 3% by weight surfactant 4% to 20% by weight wax and/or oils remainder fillers

(18) The polymer-bonded refill may be either a lead refill and/or a colored pencil refill.

(19) Advantageously, the at least one filler is selected from at least one filler from the groups comprising graphite, hexagonal boronitride, phyllosilicates, chalk, barite, colored pigments and/or achromatic pigments.

(20) Preferably, for pencil lead refills, in particular, graphite or graphite in combination with carbon black is used as the colouring filler.

(21) For colored pencil refills, combinations of white or achromatic fillers such as hexagonal boronitride, phyllosilicates etc., with colouring pigments such as azo pigments, phthalocyanines, dioxazines, quinacridones, iron oxides, carbon black, graphite, ultramarine, iron-cyano complexes have proved to be advantageous.

(22) A preferred composition for a pencil lead refill comprises the following:

(23) TABLE-US-00003 12% to 30% by weight polymeric binder 0.2% to 3% by weight surfactant 2% to 20% by weight wax and/or oil remainder graphite or graphite and carbon black

(24) Formulation example 1 for a pencil lead refill comprises:

(25) TABLE-US-00004 styrene acrylonitrile (SAN) 20% by weight POE fatty ammonium ethosulphate 1% by weight calcium stearate 8% by weight palm oil 1% by weight graphite 66% by weight carbon black 4% by weight

(26) Formulation example 2 for a pencil lead refill comprises:

(27) TABLE-US-00005 Polystyrene (PS) 18% by weight POE fatty ammonium ethosulphate 1% by weight fatty alcohol polyglycol ether 1% by weight graphite 69% by weight aluminium stearate 11% by weight

(28) The graphite listed in the examples may act as the colorant for pencil lead refills. Similarly, however, combinations of graphite and carbon black may also be employed.

(29) A composition for a colored pencil refill comprises the following:

(30) TABLE-US-00006 10% to 30% by weight binder 5% to 20% by weight wax and/or oil fraction greater than zero to 6% by weight surfactant remainder phyllosilicate(s) and/or hexagonal boronitride as well as at least one colored pigment and/or at least one achromatic pigment

(31) Formulation example 3 for a colored pencil refill:

(32) TABLE-US-00007 polystyrene (PS) 16% by weight ethylene bis-stearamide 13% by weight perylene 2.0% by weight fatty acid ester 4% by weight phthalocyanine 8% by weight phyllosilicate 62% by weight

(33) Colored and/or achromatic pigments may be employed as the colouring agent in colored pencil refills. Examples of pigments of this type are azo pigments, phthalocyanines, dioxazines, quinacridones, iron oxides, carbon black, graphite, ultramarine and iron-cyano complexes.

(34) The at least one polymeric binder is formed from at least one polymer from the group comprising polystyrene (PS), styrene/acrylonitrile (SAN), polylactide (PLA), styrene/butadiene (SB), polyolefins (PO) and acrylonitrile/butadiene/styrene (ABS).

(35) At least one wax from the group comprising fatty acids, stearates, montan waxes, amide waxes and paraffins may be used as the at least one wax.

(36) The table below compares the bending strengths of refills with and without a surfactant content. The refill compound used was a mass in accordance with formulation example 2 (pencil lead refill), whereas for the comparison, the surfactant or the surfactant mixture was omitted from the compound of formulation example 2.

(37) TABLE-US-00008 Refill with Refill without surfactant surfactant Bending strength 52.8 45.3 (MPa)

(38) It can clearly be seen from the table that a refill which comprises at least one surfactant has a measured increase in strength of approximately 15% compared with refills without surfactants.

(39) The measurement was carried out by means of a 3-point bending test complying with DIN 52186, in which cylindrical test pieces/refills with a diameter of 3 mm and a length of 170 mm were tested. The test pieces in this case were mounted on movable rollers with a span of 50 mm. the force was applied by means of a test head. The rollers and test stamps had a radius of 2 mm.

(40) An extrusion method has been shown to constitute an advantageous method for the manufacture of a polymer-bonded refill in accordance with the invention.

(41) In particular, the refill in accordance with the invention is manufactured by carrying out the following steps: mixing and granulating all of the components for the formulation of the refill in order to form a refill granulate extruding the refill granulate at a temperature in the range 120? C. to 200? C. in an extruder through a suitable die in order to form continuous refill rods cooling and solidifying the continuous refill rod, and cutting the continuous refill rod to final length, in particular to the required length of the pencil lead.

(42) Depending on the extrusion head, the cross-section of the refill may have any formround, square or combinations thereof. Furthermore, it is possible to carry out multiple co-extrusion of various refill formulations in one extrusion head in order to bond a multi-component refill.

(43) Furthermore, a suitable co-extrusion method may be employed in order to extrude the refill granulate with other polymer-bonded materials so as to form a complete pencil lead.