HK1038238B - Erasable colored pencil lead - Google Patents

Description

Erasable colour pencil lead

Cross reference to related applications

The present invention is a continuation of part of pending U.S. patent application No. 09/197283, filed on day 11 and 20 of 1998, which is pending U.S. patent application No. 09/105704, filed on day 26 of 1998, and a continuation of part of the present U.S. patent No. 6011084. The disclosures of the '283 and' 704 applications are hereby incorporated by reference in their entirety.

Technical Field

The present invention relates generally to lead compositions for colored pencils, and more particularly to erasable colored pencil lead compositions and methods of making and using the same.

Background

Although colored pencils have long provided pleasure to children and others, attempts have been made to improve the performance of these pencils. The properties required to make the coloring a pleasant and do-worthy task should include smooth spreading of the lead composition, good color strength of the mark, good burst strength, and sufficient lead flexural strength. Further, colored pencils are desirable to produce marks on paper that do not smear or smear and that can be erased with a conventional pencil eraser.

Common colored pencils are made from a blend of pigments, binding resins and fillers. Although these colored pencils have excellent writing properties, their marks are not easily erased with a common pencil eraser. Attempts have been made to improve the lead properties, especially the erasability of the lead mark. For example, attempts have been made to improve erasability by reducing the pigment content of the pencil. Although this method reduces the color contrast between the erased mark and the paper, the color intensity of the original mark is not satisfactory.

In another method of improving erasability of a marking, a colored pencil is made by blending a mixture of a pigment, one or more fillers, and a wax, such as a low melting wax. Although this method can improve the erasability of the mark, it has not been possible to completely remove the mark. In addition, the wiped areas leave a stained appearance. It is believed that the wax contributes to the erasability on the one hand, but also causes incomplete and soiling wiping on the other hand.

It is believed that the shear force generated when marking paper with a colored pencil is sufficient to warm the wax. This warming action imparts a degree of fluidity to the wax and lead composition so that the pencil material can significantly penetrate into the open spaces between the paper fibers. Thus, a significant amount of colored pencil lead material is trapped below the surface of the paper, and the pencil lead material thus penetrated into the paper fiber matrix is not wiped and therefore cannot be removed with an eraser.

In addition, the wiping action also provides friction and also warms the wax component of the colored pencil lead marking. Thus, the wiping action can impart a degree of fluidity to pencil marks already on the paper surface. This results in further penetration of the wax into the open spaces in the paper matrix, thereby rendering further amounts of the pigment contained within the pencil mark unavailable for mechanical abrasion by the eraser.

In addition, the fluid nature of the wax can cause most pencil marks to move from one location to another under the wiping action without being removed from the paper surface. This relocation of material is commonly referred to as contamination. Repeated use of the eraser over the colored pencil marks can continuously contaminate and drive the pencil marks into the fibrous substrate until substantially all of the colored pencil material is deposited in the open spaces of the paper substrate. At this point, the colored pencil mark is not substantially changed by further wiping.

Attempts have been made to produce colored pencils that eliminate contamination and wiping residue. For example, one approach is to reduce the wax content of the lead. Unfortunately, this method makes the lead very hard, and the deposition characteristics of the lead are affected, resulting in poor writing of the lead. In another approach, attempts have been made to use low melting point materials, such as oils. Colored pencil leads are made by blending pigments, binding resins, fillers and oils. This approach is not easily implemented industrially, as it both increases the manufacturing cost and affects some other qualities of the lead. For example, if the lead is made in a wet forming process, the wet lead should be dried at a temperature below the melting point or flow temperature of the oil. This increases the drying time of the lead, thus reducing productivity. The oil also tends to bleed or migrate away from the lead, which results in a loss of lead strength and failure to obtain a mark with the proper color strength. In addition, the oil tends to bleed through the paper, further affecting the quality of the coloration. To alleviate some of the drawbacks associated with the use of oil, complex manufacturing processes have been proposed, but unfortunately increase the manufacturing steps and cost of the pencil. The resulting marks of ordinary colored pencil leads containing low melting waxes or oils are prone to contamination when contacting objects such as fingers, paper and toning nibs (b1ending stubs).

Therefore, there is a need for a colored pencil lead having improved erasability, and which requires that the colored pencil lead not be contaminated when erased with a conventional pencil eraser. It is also desirable that colored pencil leads do not contaminate when rubbed against fingers, mixed nibs, or other objects. There is also a need for a colored pencil lead having a smooth laydown, good color strength, suitable flexural strength, and suitable breaking strength.

These and other objects and advantages of the invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.

Summary of the invention

The foregoing needs are met, to a great extent, by the present invention, which provides an erasable colored pencil lead composition capable of forming a mark comprised of a cohesive layer of the composition on a surface to be marked. The lead composition includes a colorant, one or more binder resins, a fibrillatable or fibrillated material, and a filler. In a preferred embodiment, the colored pencil lead composition of the present invention is free or substantially free of low melting waxes, derivatives of such waxes, waxy materials, and other materials that prevent its removal from paper fibers. The lead composition may optionally contain a lubricant, such as a particulate lubricant, e.g., PTFE, or a non-particulate lubricant, e.g., a polar material.

The invention also provides a method of using an erasable colored pencil lead composition on a surface to be marked comprising applying the lead to the surface to produce a mark which forms a tie layer of the colored pencil lead composition. The invention also provides a method of wiping a mark obtained from the colored pencil lead composition of the invention.

Although the invention is disclosed below in terms of certain preferred embodiments and process steps, it is not intended that the invention be limited to these specific embodiments. Rather, it is intended to embrace all such other embodiments and modifications that fall within the spirit and broad scope of the present invention.

In particular, the invention relates to:

1) an erasable colored pencil lead composition comprising a colorant, one or more binder resins, a fibrillatable or fibrillated polymer, and a filler, wherein said composition is substantially free of wax or waxy materials having a melting or softening point of 90 ℃ or less.

2) The erasable colored pencil lead composition according to 1) above, wherein the low melting wax or wax-like material has a penetration hardness value of 5 units or more.

3) The erasable colored pencil lead composition according to 1) or 2) above, wherein the binder resin is a polyolefin.

4) The erasable colored pencil lead composition according to 3) above, wherein the polyolefin is selected from the group consisting of polypropylene, high density polyethylene, low density polyethylene, high melting polyolefin wax, and mixtures thereof.

5) The erasable colored pencil lead composition according to 4) above, wherein the polyolefin is a mixture of polypropylene, low density polyethylene and high melting point polyethylene wax.

6) The erasable colored pencil lead composition according to 1) above, wherein the fibrillatable or fibrillated polymer is a fibrillatable or fibrillated copolymer.

7) The erasable colored pencil lead composition according to 6) above, wherein the fibrillatable or fibrillated copolymer is a fibrillatable or fibrillated ethylene vinyl acetate copolymer.

8) The erasable colored pencil lead composition according to 1) above, further comprising a lubricant.

9) The erasable colored pencil lead composition according to 8) above, wherein the lubricant is a non-particulate lubricant.

10) The erasable colored pencil lead composition according to the above 9), wherein the lubricant forms a region separated from the binder resin.

11) The erasable colored pencil lead composition according to 10) above, wherein the lubricant is a polar material.

12) The erasable colored pencil lead composition according to 11) above, wherein the polar material comprises an alkoxylated material.

13) The erasable colored pencil lead composition according to 12) above, wherein said alkoxylated material is selected from the group consisting of polyalkylene glycols, alkoxylated ethers, alkoxylated lanolin alcohols, alkoxylates of mono-and polyhydric alcohols, alkoxylated fatty acids, alkoxylated vegetable oils, alkoxylated hydrogenated vegetable oils, and mixtures thereof.

14) The erasable colored pencil lead composition according to 12) above, wherein the alkoxylated material is an ethoxylated material.

15) The erasable colored pencil lead composition according to 14) above, wherein said ethoxylated material is selected from the group consisting of polyethylene glycols, ethoxylated ethers, ethoxylated lanolin alcohols, ethoxylates of mono-and polyhydric alcohols, ethoxylated fatty acids, ethoxylated vegetable oils, ethoxylated hydrogenated vegetable oils, and mixtures thereof.

16) The erasable colored pencil lead composition according to 14) above, wherein the ethoxylated material is polyethylene glycol.

17) An erasable colored pencil lead composition according to any one of 1) -2) and 4) -16) above, wherein the composition comprises an antioxidant.

18) A method of using an erasable colored pencil lead composition on a surface to be marked comprising:

(a) providing an erasable colored pencil lead composition of any one of 1) -2) and 4) -16) above;

(b) providing the surface; then the

(c) The pencil lead is applied to the surface to draw a mark to form a coherent layer of the colored pencil lead composition.

19) The method according to 18) above, further comprising erasing the mark with a normal pencil eraser.

20) The method according to 18) above, wherein the surface is a porous surface.

21) The method according to 20) above, wherein the porous surface is paper.

22) A method of erasing a mark created on a surface by an erasable colored pencil lead composition, the method comprising applying a conventional pencil eraser to the mark, wherein the mark forms a tie layer of the colored pencil lead composition comprising a colorant, one or more binder resins, a fibrillatable or fibrillated polymer, and a filler; wherein the colored pencil lead composition is free of wax or waxy materials having a melting or softening point of 90 ℃ or less.

23) An erasable colored pencil lead composition according to 1) above, further comprising a non-fibrillatable particulate lubricant.

24) The erasable colored pencil lead composition according to 23) above, wherein the non-fibrillatable particulate lubricant is a non-fibrillatable particulate polymer.

25) The erasable colored pencil lead composition according to 24) above, wherein the non-fibrillatable particulate polymer is polytetrafluoroethylene.

26) The erasable colored pencil lead composition according to 23) above, wherein the colorant is a pigment.

27) The erasable colored pencil lead composition according to 26) above, wherein said fibrillatable or fibrillated polymer is polytetrafluoroethylene.

28) The erasable colored pencil lead composition according to 23) above, wherein at least one of said binder resins is selected from the group consisting of thermoplastic polymers, thermosetting polymers, and latex polymers.

29) The erasable colored pencil lead composition according to 28) above, wherein the binder resin is a thermoplastic polymer.

30) The erasable colored pencil lead composition according to 29) above, wherein the thermoplastic polymer is a polyolefin.

31) The erasable colored pencil lead composition according to 30) above, wherein the composition comprises an olefin homopolymer and an olefin copolymer as binder resin.

32) The erasable colored pencil lead composition according to 31) above, wherein the olefin homopolymer is selected from the group consisting of polypropylene and high density polyethylene, and the olefin copolymer is an ethylene-acrylic acid copolymer.

33) The erasable colored pencil lead composition according to 23) above, wherein the ratio of the non-fibrillatable particulate lubricant and the fibrillatable or fibrillated polymer is from 1: 0.01 to 1: 1.

34) The erasable colored pencil lead composition according to 31) above, wherein said filler is selected from the group consisting of mica, silica, clay and calcium carbonate.

35) The erasable colored pencil lead composition according to 24) above, wherein the amount of said colorant is 10-30% by volume of said composition, the amount of said one or more binder resins is 30-50% by volume of said composition, the amount of said fibrillatable or fibrillated polymer is 2-10% by volume of said composition, the amount of said non-fibrillatable particulate polymer is 10-30% by volume of said composition, and the amount of said filler is 10-30% by volume of said composition.

36) A process for preparing an erasable colored pencil lead composition comprising a colorant, one or more binder resins, a fibrillatable or fibrillated polymer, a non-fibrillatable particulate lubricant, and a filler, the process comprising mixing said colorant, said one or more binder resins, said fibrillatable or fibrillated polymer, said non-fibrillatable particulate lubricant, and said filler to give a blend, and then forming said pencil lead from said blend; wherein the colored pencil lead composition is free of wax or waxy materials having a melting or softening point of 90 ℃ or less.

37) The method according to 36) above, wherein the blending is performed by a dry mixing process, a semi-dry mixing process, or a wet mixing process.

38) The method according to 36) above, wherein the pencil lead is shaped by processing the blend in a melt process, a wet process, or a reactive process.

39) The method according to 36) above, wherein the non-fibrillatable particulate lubricant is a non-fibrillatable particulate polymer.

40) The method according to 39) above, wherein the non-fibrillatable particulate polymer is polytetrafluoroethylene.

41) A process for preparing an erasable colored pencil lead composition comprising a colorant, one or more binder resins, a fibrillatable or fibrillated polymer, a non-fibrillatable particulate lubricant, a filler and an antioxidant according to 1) above, which process comprises mixing said colorant, said one or more binder resins, said fibrillatable or fibrillated polymer, said non-fibrillatable particulate lubricant, said filler and said antioxidant to give a blend and then forming said pencil lead composition from said blend.

42) The colored pencil lead composition according to 23) above, wherein the lead composition is used to draw a first mark on a white security paper and erase the first mark to form a second mark, the second mark having an indelibility of 15% or less, wherein the first mark is produced on the paper under a constant applied force of 300 and 600 grams, and the first mark is erased under a constant applied force of 600 grams using a normal pencil eraser.

43) The colored pencil lead composition according to 42) above, wherein the first mark is contaminated by wiping to produce a third mark, the third mark having an eraser contamination rate of 20% or less, wherein the eraser extends beyond the first mark on the paper by a distance equal to the spacing at which wiping of the eraser over the first mark produces the third mark.

44) The colored pencil lead composition according to 42) or 43) above, wherein the first mark has a shading rate of the toned nib of 20% or less, wherein the nib rubs the first mark under a constant applied force of 1200 g, and the nib extends beyond the first mark on the paper by a distance equal to the distance at which it rubs on the mark.

45) An erasable colored pencil lead composition according to any one of 1) -2), 4) -16), 23) -25) and 42) -43) above, wherein the composition is capable of producing a mark when applied to a surface, forming a tie layer of the composition.

46) The erasable colored pencil lead composition of 1) above, which is capable of producing a second mark having an unerased rate of 15% or less on a white security paper, wherein said second mark is formed by wiping said first mark with a normal pencil eraser applying a constant force of 600 grams to said first mark, said first mark being produced on said paper under a constant force of 300-600 grams.

47) The erasable colored pencil lead composition according to 46) above, wherein said third mark is formed by wiping said second mark, said third mark having an eraser smear rating of 30% or less, wherein said eraser extends beyond the first mark on the paper a distance equal to the spacing at which its wiping over said first mark produces said third mark.

48) The erasable colored pencil lead composition according to 46) above, wherein the first mark has a toned nib blurring ratio of 20% or less, wherein the nib rubs the first mark under a constant applied force of 1200 grams, and the nib extends beyond the first mark on the paper by a distance equal to the distance it rubs on the mark.

49) The colored pencil lead composition according to 42) above, wherein the first mark is contaminated by wiping to obtain a third mark, the third mark having a contamination rate of an eraser of 30% or less, wherein the eraser extends beyond the first mark on the paper by a distance equal to a pitch at which it erases the third mark on the first mark.

50) A process for preparing the erasable colored pencil lead composition of 8) above, comprising mixing the colorant, the one or more binder resins, the fibrillatable or fibrillated polymer, the non-particulate lubricant, and the filler to provide a blend, and then forming the pencil lead composition from the blend.

51) A process for preparing the erasable colored pencil lead composition of 1) above, comprising mixing the colorant, the one or more binder resins, the fibrillatable or fibrillated polymer, and the filler to provide a blend, and then forming the pencil lead composition from the blend.

52) The process of 51) above, wherein the erasable colored pencil lead composition further comprises an antioxidant, the process comprising mixing the colorant, the one or more binder resins, the fibrillatable or fibrillated polymer, the filler, and the antioxidant to provide a blend, and then forming the pencil lead composition from the blend.

53) The erasable colored pencil lead composition of 3) above, wherein the composition comprises an antioxidant.

54) A method of using an erasable colored pencil lead composition on a surface to be marked, the method comprising:

(a) providing the erasable colored pencil lead composition of 3) above;

(b) providing the surface; and

(c) applying said pencil lead composition to the surface to draw a mark to form a coherent layer of said colored pencil lead composition.

55) The erasable colored pencil lead composition of 3) above, wherein the composition is capable of drawing a mark to form a tie layer of the colored pencil lead composition when the composition is applied to a surface.

56) The erasable colored pencil lead composition of 44) above, wherein the composition is capable of drawing a mark when the composition is applied to a surface, forming a tie layer of the colored pencil lead composition.

Brief description of the drawings

FIG. 1 depicts a Scanning Electron Micrograph (SEM) of a mark obtained from one embodiment of a colored pencil lead composition of the present invention on a 20 pound basis weight security paper at 1500X magnification with additional details given in example 15.

Fig. 2 depicts the SEM of the indicia shown in fig. 1 at a higher magnification, 10000 times.

Fig. 3 depicts the SEM of the indicia shown in fig. 2 at a higher magnification, 30000 times.

Fig. 4 depicts an SEM of a mark obtained from another embodiment of the colored pencil lead composition of the present invention on a 20 pound basis weight security paper at 2000 x magnification, for additional details see example 16.

Fig. 5 depicts the SEM of the marks shown in fig. 4 at a higher magnification, 10000 times.

Fig. 6 depicts an SEM of a mark obtained from another embodiment of the colored pencil lead composition of the present invention on a 20 pound basis weight security paper at 2000 x magnification, for additional details see example 17.

Fig. 7 depicts the SEM of the marks shown in fig. 6 at a higher magnification, 10000 times.

Detailed description of the embodiments

The present invention relates to an erasable colored pencil lead composition having high erasability and low staining and smearing problems. The colored pencil lead composition also has improved laydown characteristics. The colored pencil lead composition of the present invention is capable of forming a coherent layer of the composition on a marking surface. The lead composition includes a colorant, one or more binder resins, a fibrillatable or fibrillated material, and a filler. In a preferred embodiment, the colored pencil lead composition of the present invention is free or substantially free of low melting waxes, derivatives of such waxes, waxy materials, and other materials that prevent its removal from paper fibers. In a preferred embodiment of the invention, the composition further comprises a lubricant, such as a particulate lubricant or a non-particulate lubricant. The non-particulate lubricant is preferably one that is capable of undergoing a phase change and is immiscible with the binder material under processing conditions, for example, under melt processing conditions.

The lead composition is free or substantially free of waxes, wax derivatives, waxy materials such as stearates, and other materials capable of adhering to and preventing removal of paper fibers therefrom. A wax, wax derivative, waxy material, or other material is defined herein as a natural or synthetic, aliphatic or other relatively non-polar compound having a molecular weight of less than about 500, a melting point of less than about 90 ℃, and a penetration hardness value of greater than about 5 units (or 0.5 millimeters) @100 g/5 seconds/25 ℃.

It is believed that the excellent properties of the colored pencil lead composition are obtained by the following mechanism. The composition is carefully formulated so that when marked with a colored pencil on a writing surface, the shear forces generated are capable of producing a strongly colored mark; but this force does not cause significant fluidization of the pencil material. Thus, the possibility of forming a fluidized pencil material and its penetration into a substrate, such as a paper fiber substrate, is reduced or eliminated. During the process of marking on the surface of a substrate, a coating of colored pencil material is deposited on the surface with little penetration into the substrate, such as a paper fiber matrix.

The colored pencil lead composition of the present invention can produce highly cohesive marks. The cohesive nature of the pencil material helps resist contamination when subjected to wiping mechanical shear forces and improves the effectiveness of the wipe by breaking off from the paper surface in small pieces or film-like pieces rather than in discrete pieces or chips. The colored pencil lead composition also has low flow characteristics which resist penetration into the paper fibrous matrix during marking and wiping.

In addition, the colored pencil lead composition as a surface coating resists deformation or stretching when subjected to abrasion, such as wiping. Thus, the layer of pencil lead material is less soiled when wiped and can be completely or almost completely removed by abrasion with an eraser.

The cohesive nature of the colored pencil lead composition of the present invention results from the inclusion of one or more substances capable of imparting film-forming or sheeting properties to the pencil material. Thus, the included material is capable of forming a fibrillar network structure within the layer deposited on the marking surface. Thus, fibrillatable or fibrillated materials, such as fibrillatable or fibrillated polymers, may be included in the composition. Fibrillatable Polytetrafluoroethylene (PTFE) and ethylene vinyl acetate copolymer (EVA) are examples of polymers that can produce the desired fibril network in a colored pencil lead composition when the composition is deposited on paper under normal marking forces. Fibrillatable polymers are therefore preferred.

It has been found that mark erasability increases with the proportion of fibrillatable material in the colored pencil lead composition. But it is preferred to adjust the content of the fibrillated material so that the cohesiveness is not so high as to affect the laydown characteristics.

The present invention also provides a method of using an erasable colored pencil lead composition on a surface to be marked comprising:

(a) providing an erasable colored pencil lead composition;

(b) providing the surface; then the

(c) The lead is applied to the surface to create a mark, forming a tie layer of the colored pencil lead composition.

The marks produced by the leads can be easily erased using a conventional pencil eraser without leaving a significant residue or stain, and the marks do not substantially smear when rubbed against other objects with which they come into contact. The colored pencil lead of the present invention has improved erasability without compromising other desirable properties such as smooth laydown, good color strength, less tip fraying, and good burst strength.

The colored pencil lead composition comprises a suitable colorant-pigment, dye, or mixture thereof. The pigments may be organic or inorganic. Pigments capable of producing special visual effects, such as pearlescent pigments, may be used. The pigment may be a dry pigment or may be dispersed in water, optionally stabilised with a surfactant or resin or encapsulated in an organic binder such as a melamine/formaldehyde resin. Examples of pigments stabilized with surfactants include SUNSPERSE^TMBrand Dispersion, available from Sun Chemical colors group (Amelia, Ohio)]. Examples of resin-stable pigment dispersions include FLEXIYERSE^TMDispersions, which are water-based, alkali-stable acrylic dispersions, are also available from the solar chemical colorant group. Examples of pigments encapsulated in organic binders include RENOL^TMPigments, which are polyvinyl butyral coated pigments, are available from clariant corp.

In certain embodiments, it is preferred to make the lead of the present invention with pigments dispersed in water and stabilized with surfactants. Predispersed pigments are easier to add with other ingredients, and surfactant-stabilized dispersions generally produce better quality extrudates than resin-stabilized dispersions. It is believed that when the latter is used to mark paper, the resin penetrates into the paper and occupies the space between the fibers, thus making it difficult to wipe the mark.

The pigment can be present in the lead in any suitable amount. The preferred pigment amount on a dry volume basis is from about 10% to about 30% of the lead composition, and more preferably the pigment amount on a dry volume basis is from about 15% to about 20% of the lead composition.

The binder material imparts integrity to the colored pencil lead by binding the components of the lead together. The binder material generally forms a continuous phase. Any suitable binder material known to those of ordinary skill in the art may be used. The binder material may be a thermoplastic polymer such as polyolefins, acrylics, styrenics, PVC, and plasticized PVC, with polyolefins being a preferred binder material. Polyolefin example bagIncluding polyethylene and polypropylene. High Density Polyethylene (HDPE) and low density polyethylene are preferred polyethylene binder resins. The preferred HDPE resin is MICROTHENE^TMFA 70000, a spherical powder available from Equistar chemicals inc (Houston, Texas). Polyethylene in powder form is particularly preferred. A preferred LDPE resin is MICROTHENE FN 51000 also available from Equistar Chemicals Inc. A preferred polypropylene binder resin is microthen FP 80000, also available from Equistar Chemicals inc. Other examples of binder materials include waxes, especially polyolefin waxes, having melting or softening points in excess of about 90 deg.C and preferably having penetration hardness values below about 5 units. The preferred polyolefin wax is polyethylene wax. An example of a suitable polyethylene wax is EPOLENE^TME-10, available from Eastman Chemical Corp, (Kingsport, TN). EPOLENE^TMThe pin penetration hardness value of E-10 is 3 units, the ring and ball softening point is 106 ℃, and the molecular weight is about 3000.

The binder material may be in the form of a dry resin, latex or dispersion, or a solution. Examples of latexes or dispersions include acrylic dispersions, copolymers of Ethylene and Acrylic Acid (EAA), and copolymers of styrene and butadiene. The ratio of ethylene to acrylic acid can vary from about 1: 10 to about 10: 1, preferably 1: 1. Examples of the polymer solution include polystyrene dissolved in a solvent such as methyl ethyl ketone, and polyvinyl alcohol dissolved in water.

The binder resin may also be thermosetting. Examples of thermosetting polymers include unsaturated polyesters, vinyl esters, and epoxy resins.

The binder material can be used in any suitable amount. For example, the binder material may be present in an amount of about 10-60% of the lead composition on a dry volume basis, with a preferred amount being about 40-50% of the lead composition on a dry volume basis.

It is particularly preferred that in certain embodiments, HDPE and EAA are used in combination as the binder material. This combination results in good spreading and therefore excellent colour strength of the marking. Examples of suitable EAAsThe seed is POLYEMULSION available from Chemcor (Chester, New York)^TM540N30, which contains 95% of ethylene and 5% of acrylic acid. The ratio of polyethylene to EAA may be from about 1: 0 to about 0: 1, preferably from about 1: 0.3 to about 1: 0.05.

In certain other embodiments, it is preferred to use polypropylene, LDPE, and high melting polyethylene waxes in combination as the binder material. Such combinations may include any suitable ratio of the three components, preferably in a volume ratio of about 5 to 20: about 0.5 to 2: about 2 to 8, more preferably in a volume ratio of about 10: about 1: about 4, and even more preferably in a volume ratio of 10: 1: 4, respectively.

The colored pencil lead of the present invention can include any suitable filler. The filler acts to provide stiffness and strength to the lead. Examples of suitable fillers include talc, silica, calcium carbonate, mica, wollastonite, and clay. The filler may have any suitable geometry. Platy fillers such as talc and mica are particularly preferred because they have a soft consistency and the edges of the particles promote abrasion of the lead to produce a smooth spreading action. The filler may optionally be surface treated to improve dispersibility and/or adhesion to the bonding material. The filler has a particle size of less than about 1 μm to about 50 μm, preferably about 10-30 μm. The lead composition may contain any suitable amount of filler, for example in an amount of from about 10 to 60%, preferably from about 20 to 40% of the lead composition on a dry volume basis.

The lead compositions of the present invention include a fibrillatable or fibrillated material. Preferably the material is fibrillatable. Fibrillatable polymers are capable of forming fibers when subjected to shear forces, such as when writing. In some cases, fibrillation may occur during the lead manufacturing process. Any suitable fibrillatable or fibrillated material can be used to prepare the present compositions. It has been found that small diameter fibrils, particularly fibrils having a diameter of about 0.1 to 5 μm, especially about 0.05 to 0.5 μm, can impart excellent erasability to the lead. Preferably, a fibrillatable polymer is used. The fibrillatable polymer can be a homopolymer or a copolymer. Examples of fibrillatable polymers include polyolefins, preferably PTFE, polyethylene, and polypropylene. PTFE is a particularly preferred fibrillatable polymer. Examples of fibrillatable copolymers include ethylene-vinyl acetate copolymers. Examples of ethylene-vinyl acetate copolymers include MICROTHENE MU 7600, available from Equistar Chemcals Inc.

Examples of other fibrillatable or fibrillated polymers include aliphatic and aromatic polyamides, such as nylon and KEVLAR^TMPolyimide, and polyester. The fibrils may be added as follows: starting from materials already in fibrillar form, dispersing them with other ingredients; or formed in situ starting from a fibrillatable polymer in latex, suspension or dry powder form. An example of a preferred fibrillatable PTFE is FLUON^TMAD-1 emulsion from ICI fluorinated polymers (Wilmington, Delaware). The emulsion is made of 0.25 μm PTFE particles and contains 59-62% solid matter. This emulsion form allows for easy mixing of the PTFE with the other ingredients of the lead composition.

The fibrillatable or fibrillated material can be used in any suitable amount. For example, in certain embodiments of the invention, if a polyolefin resin such as PTFE is used, it can be present in an amount of from about 0.4 to about 10% (on a dry volume basis) of the lead composition, preferably in an amount of from about 1.5 to about 3% (on a dry volume basis) of the lead composition.

While, for example, in certain other embodiments, if a copolymer such as ethylene vinyl acetate is used as the fibrillatable or fibrillated material, it can be present in an amount of from about 1 to about 15% (on a dry volume basis) of the lead composition, preferably in an amount of from about 2 to about 12% (on a dry volume basis) of the lead composition, and more preferably in an amount of from about 4 to about 10% (on a dry volume basis) of the lead composition.

The colored pencil lead of the present invention may contain a lubricant. In certain embodiments, the lubricant is a non-fibrillatable particulate lubricant. The material remains in the form of pellets during the melt extrusion or wet processing steps.

In addition, the lubricant is believed to improve the spreading properties of the lead. The lubricant also improves erasability because it does not stick or is minimalAdhering to the paper fibers. Any suitable lubricant may be used. The preferred lubricant is micronized PTFE powder, which can be made by grinding sintered PTFE to a particle size of about 1 to about 20 μm. An example of a suitable micronized PTFE powder is SST-2SP5^TM. From Shamrock scientific (Newark, New Jersey). Micronized PTFE is particularly advantageous because it does not adhere to the paper fibers. Furthermore, micronized PTFE is white and therefore does not impair the color quality of colored pencil leads.

The non-fibrillated particulate lubricant may be used in any suitable amount, for example, it may be used in an amount of about 5 to about 50% (on a dry volume basis) of the lead composition, and preferably in an amount of about 10 to about 30% (on a dry volume basis) of the lead composition. If the amount of lubricant is less than 5% by volume of the lead composition, the lead tends to be too soft and the tip tends to wear excessively.

In certain other embodiments, the lead compositions of the present invention may comprise a non-fibrillatable, non-particulate lubricant. The lubricant undergoes a phase change, such as melting, during lead manufacture. The lubricant preferably forms a discontinuous phase when the binder material forms a continuous phase. The lubricant forms domains distributed within the continuous phase. Further, the lubricant also forms a region separated from the binder resin. Any suitable non-fibrillatable non-particulate lubricant may be used. Preferably the non-fibrillatable non-particulate lubricant is a polar material, especially when a non-polar binder material such as polypropylene or polyethylene is used. The polar material is preferably a polar polymer.

Examples of polar materials that may be used as non-particulate lubricants include alkoxylated materials. The alkoxylated material may include one or more alkoxy groups, or as a polymer may have any suitable degree of polymerization of the alkoxy repeat units, such as up to 100000, preferably from about 1 to about 1000, more preferably from about 1 to about 500. Examples of alkoxylated materials include alkoxylated ethers, alkoxylated lanolin alcohols, alkoxylates of mono-and polyhydric alcohols, alkoxylated fatty acids, alkoxylated vegetable oils, and alkoxylated hydrogenated vegetable oils. The alkoxy group or repeating unit may have any suitable number of carbon atoms, such as 1 to about 6 carbon atoms, preferably 1 to about 3 carbon atoms, and more preferably 2 carbon atoms.

Thus, ethoxylated materials are particularly preferred. Examples of ethoxylated materials include ethoxylated ethers, ethoxylated lanolin alcohols, ethoxylates of mono-and polyhydric alcohols, ethoxylated fatty acids, ethoxylated vegetable oils, and ethoxylated hydrogenated vegetable oils.

Other examples of alkoxylated materials include polyalkylene glycols, especially polyethylene glycols. A suitable polyethylene glycol is PEG 20M, available from Union carbide (Danbury, CT). The molecular weight of the polymer is about 20000 and is crystalline.

The amount of non-particulate lubricant may be up to about 30%, preferably from about 2 to about 20%, more preferably from about 5 to about 15%, based on the dry volume of the lead composition.

The volume ratio of non-fibrillatable particulate lubricant to fibrillated or fibrillatable material can be from about 1: 0.01 to about 1: 1, preferably from about 1: 0.1 to 1: 0.4. The volume ratio of non-fibrillatable non-particulate lubricant to fibrillated or fibrillatable material can be from about 1: 1 to about 4: 1, preferably about 3: 2.

The colored pencil lead composition of the present invention may further comprise an antioxidant. Antioxidants inhibit the discoloration, oxidation, or degradation of the colored pencil lead, particularly during its production or manufacture. Any suitable antioxidant may be used. For example, phenolic antioxidants may be used. Examples of phenolic antioxidants include IRGAFOS * 168 (tris (2, 4-di-tert-butylphenyl) phosphite) and IRGANOX * 1010 (tetrakis (3, 5-di-tert-butyl-4-hydroxycinnamic acid) methylene ester methane), both from Ciba specialty agents. In a preferred embodiment, a mixture of two antioxidants, such as IRGAFOS 168 and IRGANOS 1010, may be used, preferably in equal amounts.

The antioxidant may be present in the lead composition in any suitable amount, for example, in an amount of about 0.01% or more, preferably in an amount of about 0.05 to about 2.0%, more preferably in an amount of about 0.05 to about 0.2% of the lead composition on a dry volume basis.

It has been found that the properties of lead tend to be related to the volume fraction of each component. For this reason, the amount of each component is expressed herein as a volume fraction. If one or more of the components is to be replaced by a material of different density, the volume fraction of that component (and all other components) should remain substantially the same as the original formulation so that a lead of comparable performance is produced.

The volume fraction can be converted to a weight fraction using the following formula:

W_fn＝(V_fn).(V_T)(D_n/W_T)

wherein is W_fnIs a weight fraction, V_fnIs a volume fraction, and D_nIs the density of component n. W_TIs the total dry weight of the lead composition and V_TIs the total dry volume.

As described above, the colored pencil lead composition of the present invention has excellent spreading effect and erasability. The lead markings do not smear when in normal contact with objects, nor when erased with a conventional pencil eraser. The erasability, smudging, and haziness of the mark are further described below. The percentage of color mark left unremoved on the substrate after the drawn mark was rubbed a given number of times with a common pencil eraser was expressed as the percentage of unerased mark. The amount of marking that extends to adjacent unmarked areas when the marking is rubbed with a conventional pencil eraser is related to the soiling of the marking. The amount of extension to adjacent unmarked areas when the mark is rubbed against an object such as a wand or pen head is related to the obscuration of the mark.

The erasability, haziness and staining of lead can be quantitatively determined by methods known to those skilled in the art, for example, using a spectrophotometer. The color applied to the surface is known to be defined in terms of the color in the color sphere. The color sphere is determined by a luminance ("L") value, a red/green ("a") value, and a blue/yellow ("b") value. See, for example, the following examples,color measuring instrument manualX-Rite * No. 948-968 (1990). Thus, these three values in combination define the color of the object as seen by the human eye. Any given color can therefore be measured in terms of the "l.a.b." value and expressed as a relative value to a known reference standard such as white paper l.a.b. The difference in l.a.b. value between the substrate and the standard is expressed as l.a.b.de (or Δ E) value. This process is generally referred to in the industry as the ellipsoidal tolerance process.

The ambiguity can be determined as follows: obtaining newly-applied indicia₀A value which is then set equal to 100% color intensity. The mark is then rubbed with a stylus under constant applied pressure. The rubbing is extended in a controlled manner to areas of the substrate outside the marks. The amount of label transferred to the extension region is determined.

The amount of mark left unremoved after rubbing the mark with an eraser can be determined as follows. The mark was rubbed a given number of times with a constant applied pressure of rubber. The eraser is extended to the adjacent unmarked area. The l.a.b.de value left to remove the mark was determined. The erasability of the mark is then expressed as the percentage of color left after abrasion with an eraser. The l.a.b.de value of the extension zone was also determined, which value is related to rubber staining. The examples herein further illustrate the determination of eraser smear, percent unerased, and tip smudge rating.

Thus, the colored pencil marks of the present invention have an eraser unerased rating (percent unerased) of about 15% or less; an eraser smear rating of about 30% or less; and/or a nib blurriness of about 20% or less. The indicia preferably have a degree of eraser smear of less than about 20%, more preferably less than about 15%, and even more preferably less than about 10%.

The marking preferably has a nib haze of less than about 15%, more preferably less than about 10%, even more preferably less than about 6%, even more preferably less than about 3%, and even more preferably less than about 2%. The mark preferably has an unerased rating of less than about 12%, more preferably less than about 10%, and even more preferably less than about 6%.

As discussed hereinThe marks of (a) are formed under conditions that are common when a colored pencil is normally used. Thus, the force applied to generate the mark (described herein in mass units for ease of understanding) is 300-600 grams. The marks are produced at a rate of about 20-36 feet per minute with an average rate of about 29 feet per minute. The wiping is performed by using an EberhardFaber, PINK PEARL common pencil eraser^TMThe sample No. 100 was run under a force of 600 g; and the tip smudging was performed at an applied force of 1200 grams. The substrate is white paper, such as white security paper or white tablet paper, which is a paper having a basis weight of 56.4 g/m²15Sub paper having a TAPPI brightness standard rating of 82.0, a Sheffield smoothness standard rating of 300, and an opacity standard rating of 78.

The invention also provides a process for preparing the colored pencil lead composition of the invention comprising compounding a colorant, one or more binder resins, a fibrillatable or fibrillated material, optionally a lubricant, an antioxidant, and a filler to provide a blend and forming a pencil lead from the blend.

The blend of ingredients can be prepared by any method known to one of ordinary skill in the art. Thus, compounding can be carried out by dry, semi-dry, or wet mixing the ingredients. Prior to blending, the ingredients are ground to the appropriate particle size for ease of handling or feeding through various processing equipment.

When dry blended, all ingredients are in a dry state, preferably in powder form. All ingredients are charged to a powder mixing device, such as a V-blender or any other suitable mixer. The powders were mixed together and the ingredients were mixed thoroughly. The mixed powder is then used for lead production.

In semi-dry mixing, a small amount of water is used in the blending step, so that the blend can be produced in the form of a thick paste. Water may be added to the dry blend of powders or may be added with one or more ingredients. For example, the binder resin may be in the form of an aqueous dispersion, such as an ethylene-acrylic acid dispersion having a solids content of 30% by weight, a pigment dispersion having a solids content of 55% by weight, or an aqueous dispersion of a fibrillatable polymer, such as an aqueous dispersion of fibrillatable PTFE having a solids content of 60% by volume.

Thus, in semi-dry mixing, all dry ingredients are mixed to give a homogeneous mixture, and then the required amount of water is added to give a thick paste. The paste is extruded into lead or extruded into strands and subsequently pelletized. The pellets are then dried to remove water, preferably at elevated temperatures to speed up the drying process. The pellets are then used for extrusion into lead.

Upon wet mixing, the blend is in the form of a viscous liquid having the consistency of a paint. Wet mixing is carried out on dispersing equipment commonly used for dispersing solid materials in liquids, such as those used for preparing paints, for example vertical or horizontal mixers and ball or pebble mills.

The wet mixing may be carried out as follows: the pigment dispersion is charged into a suitable vessel and then mixed at high speed with a high speed disperser. Water is added to reduce the viscosity of the dispersion if necessary. The binder resin, filler, and non-fibrillatable lubricant, which may be in powder or dispersion form, are added and stirring is continued for about 20 minutes. The fibrillatable material, preferably in the form of a dispersion, is then added. Mixing was continued until a well-mixed blend was obtained. Drying is then carried out by any known drying method, for example preferably in an open pan at elevated temperature or by spray drying.

The blends prepared above can be formed into lead using methods known to those of ordinary skill in the art, for example, by melt processing, wet processing, or reactive processing. For methods of plastic processing, see generallyKirk-Othmer encyclopedia of chemical technology， 19290, page 316, 4 th edition (1996). In melt processing, the blend is dry, while wet processing requires the blend to be a thick paste. Reactive processing is carried out using a reactive binder, such as an epoxy resin, or an unsaturated curable resin, such as an unsaturated polyester resin.

For example, during melt processing, the lead may be formed by extrusion, compression molding, or calendering. In extrusion, the blend is fed in dry form to an extruder, such as a single or twin screw extruder, and extruded through a die to form strands. The die may have a suitable cross-section, circular, square or any desired cross-section. The strand was cooled to room temperature and then cut into suitable lengths to give colored pencil leads.

If the extruder feed is in powder form, the extruder should be equipped with a device to facilitate the powder feed, such as a screw feeder. Extrusion is carried out in one or two steps. If performed in two steps, a preliminary extrusion is first performed to achieve good mixing and produce the material in pellet form. A second extrusion is performed on the pellets, thereby producing the lead.

Compression molding uses a hydraulically operated press with a platen to form the desired part (lead herein) in conjunction with a metal mold and to hold the dense molding material in the desired shape until the system is sufficiently solidified or cooled and the part is removed. Thus, the dry blend is loaded into a compression mold and then heated to soften or melt the binder. The molten material is extruded into a recess having the shape of a pencil lead. After cooling, the lead was removed.

Calendering is a process for producing plastic sheets. See, for exampleKirk-Othmer methylation Encyclopedia of science and technology， 19Page 309, 4 th edition (1996). Calenders typically have four heavy large steel rolls that are typically assembled in an inverted L configuration. The dry blend was fed to rolls and calendered to give sheets. The sheet is then slit into rectangular or square cross sections.

Blends made by wet mixing can be processed into lead using extrusion, compression molding or calendering. In extrusion, the wet mixture is fed to an extruder and then extruded through suitable orifices at room temperature or elevated temperature (but preferably below the boiling point of water). The lead formed by this method is cut into a suitable length and dried. After drying is complete, the temperature of the lead may be raised to melt the binder and increase the strength of the lead.

In compression molding, the wet mixture is charged into a compression mold having a matching groove representing the shape of the lead. The press table was closed and the mixture was compressed into the desired lead shape. The platen was opened and the lead was removed and dried. After drying is complete, the temperature of the lead may be raised to melt the binder and increase the strength of the lead.

In calendering, the wet mixture is calendered between a set of rolls to form a sheet. The sheet is then slit into lead having a rectangular or square cross-section.

In reactive processing the blend, the blend is processed in a manner similar to wet processing except that the lead must be heated during or after extrusion to cure the reactive binder.

The colored pencil of the present invention can be manufactured using methods known to those of ordinary skill in the art. For example, colored lead and pencil lead casings can be co-extruded; or the colored lead, sleeve and any other outer coating can be co-extruded to provide a colored pencil. Further, the colored pencil can be assembled by combining and assembling the lead and the preformed sleeve, for example, two halves of the preformed sleeve can be pressed together with the lead to obtain the colored pencil. The sleeve may be made of any material known to those skilled in the art, including wood and plastic.

The following illustrative examples further illustrate the invention and, of course, should not be construed as in any way limiting its scope.

Example 1

This example illustrates one embodiment of the preparation of colored pencil leads. The ingredients used, lead, were produced as follows.

The desired amount of pigment dispersion was weighed into the mixing vessel and mixing was then initiated. Polyethylene powder was added with stirring. The desired amount of talc is then added. A small amount of water was added to reduce the viscosity of the mixture. Subsequently micronized PTFE with an average particle size of 4 μm was added. The fibrillatable PTFE emulsion and the ethylene acrylic acid emulsion are then added. The resulting paste was poured into a drying tray and dried in an oven at 110 ℃ overnight. The pan was removed from the oven and cooled to room temperature. The material was removed from the pan and then pulverized into a powder in a blender. The crushed material was sorted through a #10 mesh screen. The powder was then extruded in an 3/4 inch, L/D24/1 extruder (1.5: 1 compression ratio) with the following conditions: the diameter of the die head is 3 mm; temperature distribution: 160 ℃ (zone 1, feed side), 180 ℃ (zone 2), 180 ℃ (zone 3, die side) and 180 ℃ (die). The screw was operated at 60 rpm.

% by weight % by volume

Composition (I)

SUNSPERSE RHD 6011 (organic Red pigment) 13.216.5

FLUO HT (micronized PTFE, Micro 20.816.8)

Powders, Inc., Tarrytown, New York, Inc.)

FLUON AD-1 (fibrillatable PTFE) 3.63.0

HDPE FA 700 (high Density polyethylene powder) 17.933.5

POLYEMULSION 540N30 (ETHYLENE-ACRYLIC COPOLYMER) 1.52.9

MICROTUFF AG 609 (surface treated Talc, 43.027.3)

Barretts Minerals Inc., Southof Dillon, Montana, Inc.)

Total 100.0100.0

The colored pencil thus produced provides a marking having good color strength and good erasability.

Example 2

This example illustrates another embodiment of the preparation of colored pencil leads according to the present invention. Colored pencil leads were produced following the procedure described in example 1 except that the relative amounts of micronized PTFE and fibrillatable PTFE were varied. The amounts of the ingredients are given below.

Composition (I) % by weight % by volume

SUNSPERSE RHD 6011 (organic Red pigment) 13.216.5

FLUO HT (micronized PTFE) 12.29.9

FLUON AD-1 (fibrillatable PTFE) 12.29.9

HDPE FA 700 (high Density polyethylene powder) 17.933.5

POLYEMULSION 540N30 (ETHYLENE-ACRYLIC COPOLYMER) 1.52.9

MICROTUFF AG 609 (surface treated talc)43.0 27.3

Total of100.0 100.0

The lead produced a mark with medium color strength and good erasability.

Example 3

This example illustrates another embodiment of the preparation of colored pencil leads according to the present invention. Colored pencil leads were produced following the procedure described in example 1, except that the micronized PTFE particles had a particle size of 12-20 μm. The composition has a low level of surface treated talc. The amounts of the ingredients are given below.

Composition (I) % by weight % by volume

SUNSPERSE RHD 6011 (organic Red pigment) 13.216.5

FLU0 HT (micronized PTFE) 20.816.8

FLUON AD-1 (fibrillatable PTFE) 3.63.0

HDPE FA 700 (high Density polyethylene powder) 17.933.5

POLYEMULSION 540N30 (ETHYLENE-ACRYLIC COPOLYMER) 1.52.9

MICROTUFF AG 609 (surface treated talc)43.0 27.3

Total of100.0 100.0

The lead produces a mark with higher color strength and erasability.

Example 4

This example illustrates another embodiment of the preparation of colored pencil leads according to the present invention. Colored pencil leads were produced according to the procedure described in example 1 except that red iron oxide pigment was used instead of the organic red pigment and surface treated mica was used instead of the surface treated talc. The ethylene acrylic acid emulsion was omitted. The amounts of the components used are given below.

Composition (I) % by weight % by volume

C888-1045F (Red iron oxide pigment, 53.519.8)

Creanova, Inc., Somerset, New Jersey products)

FLUO HT (micronized PTFE) 24.020.2

FLUON AD-1 (fibrillatable PTFE) 4.23.5

HDPE FA 700 (high Density polyethylene powder)22.3 43.5

Total of100.0 100.0

The lead produced a mark with good color strength and erasability.

Example 5

This example illustrates another embodiment of the preparation of colored pencil leads according to the present invention. Colored pencil leads were produced according to the procedure described in example 1, except that the composition included low density polyethylene, Ethylene Vinyl Acetate (EVA) copolymer, and ethylene acrylic acid copolymer. The amounts of the ingredients are given below.

Composition (I) % by weight % by volume

SUNSPERSE RHD 6011 (organic Red pigment) 10.913.5

FLUO HT (micronized PTFE) 21.016.8

FLUON AD-1 (fibrillatable PTFE) 3.83.0

MICROTHENE FN 51000 (Low Density polyethylene powder, 12.323.5)

Manufactured by Equistar Chemicals)

MICROTHENE FE 53200 (ethylene-vinyl acetate copolymer 5.410.0 article)

POLYEMULSION 540N30 (ETHYLENE-ACRYLIC COPOLYMER) 1.52.9

SILWAX WS (polydimethylsiloxane copolymer, Siltech 1.73.0)

Corp, Toronto, Canada)

MICROTUFF AG 609 (surface treated Talc) 43.427.3

Total 100.0100.0

The lead produced a mark with good color strength and erasability.

Example 6

This example illustrates another embodiment of the preparation of colored pencil leads according to the present invention. Colored pencil leads were produced according to the procedure described in example 1, except that the composition included polypropylene and an EVA copolymer. The amounts of the ingredients are given below.

Composition (I) % by weight % by volume

SUNSPERSE RHD 6011 (organic Red pigment) 13.815.2

FLUO HT (micronized PTFE) 21.715.4

FLUON AD-1 (fibrillatable PTFE) 1.41.0

MICROTHENE FP 80000 (polyethylene) 19.533.5

MICROTHENE MU 76000(EVA) 5.1 8.4

PEG 20M (polyethylene glycol 20000Mw, Union 3.85.3)

Carbide Corp, Danbury, Connecticut, Inc.)

SILWAX WD-F (polydimethylsiloxane wax, 1.82.9)

Siltech corp. production)

MICROTUFF AG 609 (surface treated talc)32.9 18.4

Total of100.0 100.0

The lead produced a mark with good color strength and erasability.

Example 7

This example illustrates another embodiment of the preparation of colored pencil leads according to the present invention. Colored pencil leads were produced according to the procedure described in example 1, except that the composition included polypropylene and EVA copolymer, and silica as filler. The amounts of the ingredients are given below.

Composition (I) % by weight % by volume

SUNSPERSE RHD 6011 (organic Red pigment) 13.615.4

FLUO HT (micronized PTFE) 21.515.7

FLUON AD-1 (fibrillatable PTFE) 1.91.4

MICROTHENE FP 80000 (Polypropylene) 16.729.6

MICROTHENE MU 76000(EVA) 5.0 8.6

PEG 20M (polyethylene glycol 20000Mw) 3.75.4

SILWAX WD-F (polydimethylsiloxane wax, 1.82.9)

Siltech products)

SYLOID 74 (silica from Grace-Davison) 3.12.5

MICROTUFF AG 609 (surface treated talc)32.5 18.6

Total of100.0 100.0

The lead produced a mark with good color strength and erasability.

Example 8

This example illustrates another embodiment of the preparation of colored pencil leads according to the present invention. The amounts of the ingredients are given below. The ingredients were combined and then extruded in a twin screw extruder to give pencil leads.

Composition (I) % by weight % by volume

Pigment Red 210 (organic Red pigment) 13.915.0

MICROTHENE FP 80000 (polyethylene) 15.426.1

MICROTHENE MU 76000(EVA) 4.8 7.8

MICROTHENE FN 51000(LDPE) 1.6 2.6

MICROTUFF AG 609 (surface treated Talc) 50.327.6

PEG 20M 7.6 10.5

EPOLENE E-10 (high melting point wax)6.4 10.4

Total of100.0 100.0

The lead produced a mark with good color strength and erasability.

Example 9

This example illustrates another embodiment of the preparation of colored pencil leads according to the present invention. The amounts of the ingredients are given below. Lead was produced as in example 8.

Composition (I) % by weight % by volume

Pigment Red 210 (organic Red pigment) 13.615.0

MICROTHENE FP 80000 (polyethylene) 15.026.0

MICROTHENE MU 76000(EVA) 3.6 6.0

MICROTHENE FN 51000(LDPE) 1.5 2.6

MICROTUFF AG 609 (surface treated Talc) 52.629.5

PEG 20M 7.5 10.5

EPOLENE E-10 (high melting point wax)6.2 10.4

Total of100.0 100.0

The lead produced a mark with good color strength and erasability.

Example 10

This example illustrates another embodiment of the preparation of colored pencil leads according to the present invention. The amounts of the ingredients are given below. Lead was produced as in example 8.

Composition (I) % by weight % by volume

SUNRITE RED 235-7511 (organic RED pigment) 14.816.0

MICROTHENE FP 80000 (polyethylene) 15.626.1

MICROTHENE MU 76000(EVA) 4.8 7.8

MICROTHENE FN 51000(LDPE) 1.6 2.6

MICROTUFF AG 609 (surface treated Talc) 49.126.7

PEG 20M 7.7 10.4

EPOLENE E-10 (high melting point wax)6.4 10.4

Total of100.0 100.0

The lead produced a mark with good color strength and erasability.

Example 11

This example illustrates a method of measuring the pressure or force used to mark a test subject (including children and adults) with a colored pencil in normal use. This example also illustrates the determination of writing angle and writing speed.

The means for measuring the marking pressure include a desk, load cell, strip chart recorder, and the necessary load cell control electronics. Therefore, a desk needs to be modified, and an opening is arranged above the desk. A 25 pound capacity load cell from Omega Engineering was placed under the desk opening so that the pressure sensitive surface of the load cell was flush with the top surface of the desk. Load cells were connected to a strip chart recorder and fitted with appropriate power and control electronics. The device is constructed so that the load cell is hidden from view of the test subject to eliminate any bias.

An object to be marked, such as a hot air balloon, is removably fixed to the load cell face, and the test subject is allowed to color the object. The average and maximum forces at marking are recorded by a strip chart recorder. As a result, the average applied force was found to be 300 grams, while the maximum applied force was found to be 600 grams.

The writing angle is determined using a protractor (e.g. model 180-. The average writing angle was 53 degrees. It can be seen that the writing angle does not significantly affect the application of the mark. In addition, a stopwatch was used to measure writing speed. The writing speed is calculated from the time required to span a known distance between given points of the object, such as the distance between lines of a hot air balloon. As a result, it was found that the writing speed was about 20 to 36 feet/minute, with an average of 28 feet/minute.

Example 12

This example illustrates a method of drawing colored pencil marks under controlled conditions that simulates the marks actually made by a test subject under normal marking conditions. Such simulated markings can be used to repeatedly evaluate various properties of colored pencil leads, including the laydown, smudging, and erasability of the markings.

The markings of colored pencil leads were made using a Contecma writer 611 type (Contecma precision writer, Contecma SA, P.O. Box/Viaagli Orti 20, Viganello-Lugano, Switzerland) which is commonly used to evaluate writing instruments such as touch tip markers and ball point pens. ANGLE FINDER from Dasco Pro Inc. (Rockford, Illinois) was used^TMThe protractor is used for measuring and adjusting the writing angle.

Before each writing or erasing, the pencil is sharpened using an electronic pencil sharpener of the Hunt Boston type (available from Hunt manufacturing, Inc., located in Statesville, North Carolina) or Panasonic KP-33 type (available from Matsushita electronics industries, Japan). The pencil was sharpened to a tip angle of about 10-12 (about 5-6 relative to the longitudinal axis of the pencil) and then the cross-section of the tip was flattened using a dust-separating plate and a file. The dust plate is a rectangular stainless steel plate with a thickness of 0.118 inch and a hole diameter of 0.078 inch. The sharpened pencil stub was placed in the hole, and then the portion of the pencil stub extending out of the hole was removed using a metal file to obtain a pencil having a flat cross-sectional tip. This ensures that any variability in pencil sharpening is reduced or eliminated and provides a uniform tip diameter at the start of each erasure test.

The colored pencil was placed in the writing instrument sample holder of the writing machine. The pencil was held in a vertical position, the verticality was ensured by a protractor, with the writing tip pointing to the paper. A weight block of 300-. The total weight of the weight block used corresponds to the force exerted during wiping.

The writing instrument uses a roll paper, but other kinds, such as paper, can be used by sticking the paper with tape. The machine was programmed with a "zig-zag" pattern that was written at a rate of 36 feet/minute in a zig-zag manner to produce a uniform colored solid pattern 30 mm wide. At these selected feed and writing speeds, the colored pencil written in a zigzag manner to obtain a solid pattern without leaving blank dots. For a given colored pencil, 6 wipes were made, each 25 feet long. Before beginning each erasing operation, the pencil was sharpened and the tip was flattened as described above.

Example 13

This example illustrates a method of assessing the soiling, smudging and erasability of colored pencil lead markings.

In X-RITE SP68 available from X-Rite Inc. (Granyille, Michigan)^TMOn Sphere spectrophotometer, QA MASTER was used^TMThe software determines the l.a.b. value of the wipe. The spectrophotometer employed a 10 mm reading head. The DE value of the wipe relative to the white area is obtained from the l.a.b. value measurement. The DE value of the non-erased piece was obtained by measuring the l.a.b. value at three points along the width, the measurement being made over the first 10 mm length of the wipe. These three readings were made on each of the six wipes and the average of the 18 DE values obtained was taken as the DE₀This is a measure of the laydown performance of colored pencil leads.

The piece to be wiped was rubbed with an eraser to determine the soiling characteristics. The sample was wiped with PINK PEARL No. 100 pencil eraser. A constant force of 600 grams (measured with a load cell as discussed in example 11) was applied to wipe the sample. The wiper wipes only half the distance across its width. According to said, the width of the wiper is 30 mm, so that the wiper is wiped to a width of 15 mm. The erased area is a rectangular area, 15 mm long in one direction and 10-20 mm long in the other direction. The eraser operating stroke from the midpoint of the wipe was measured in width and extended beyond 15 mm past the edge to an unmarked white region. The eraser was moved in a saw tooth fashion and for each wiping trial, 24-36 manual wipes were used, each wipe comprising one forward and one backward run. Eraser crumb was removed after every 6-12 wipes. In addition, the l.a.b. values of the wiped and extended regions were measured against the white region, and then the DE value was calculated. An average DE value was obtained for at least two wiping tests. The amount of unerased material and the amount of erasures contaminating the white area were calculated as follows:

erasing with eraser not removedPercent of substance (DE)₁/DE₀) X 100, wherein DE₁Is the DE value of the wipe region.

Percent rubber contamination rate (DE)₂/DE₀) X 100, wherein DE₂Is the DE value of the extension.

The wipes prepared according to example 12 were subjected to the nib smudge test. The wipe was gelatinized using a toned tip (#8) supplied by Art & drawing Connection (bethlehm, Pennsylvania), the end of product No. 894 (similar to the tip of a pen head used with toned color crayons and crayon-type media commonly used by the artist). The tip of the nib is at an angle of 15 deg. with respect to the longitudinal axis. A constant pressure of 1200 grams (measured by loading a load cell) was applied, pushing from the midpoint of the wipe across the width of 15 mm and extending into the white region. If the formulation of the colored pencil was changed, the end was flattened with 320 sandpaper.

The l.a.b. values of the force and extension regions were measured against the white region and the DE value was calculated. The average DE values of at least three fuzzification tests were obtained. The fuzzification is expressed as follows:

percent fuzzification rate (DE)₃/DE₀) X 100, wherein DE₃Is the DE value of the extension.

Example 14

This example illustrates certain properties of the colored pencil. The eraser smear, percent unerased, and percent tip smudge properties shown in example 13 are given below, along with corresponding data for a commercially available non-erasable colored pencil. The advantages of the colored pencil of the present invention are evident from the data given below.

EXAMPLES Wipe percent applied percent un-percent

Erase rate paste rate of load (gram) skin pollution rate for formula number

1 600 18.9 10.0 2.5

1 300 18.7 10.4 5.6

6 600 9.2 7.7 2.1

6 300 16.1 6.0 2.2

5 600 12.9 9.1 0.8

5 300 20.4 6.6 2.4

7 600 11.0 12.0 2.0

8 600 4.2 6.4 11.7

9 600 2.4 11.0 8.8

Non-erasable color 600455923

Colored pencil

The data given above illustrates the excellent properties of the colored pencil lead composition of the present invention. The effect of a fibrillatable material such as EVA can be seen by comparing the performance of the compositions of examples 8 and 9. The EVA content of the example 8 composition was higher than the example 9 composition. The data show that by increasing the EVA content, the percent unerased can be decreased.

In addition to being useful in the manufacture of colored pencil leads, the compositions of the present invention can be formed into other useful articles such as refill for mechanical pencils, free standing pencils, crayons, and the like, as well as paints, and marking systems, including those having a marking delivery device.

Example 15

This example illustrates the cohesive nature of a mark formed by the colored pencil lead of the present invention. Thus, the marking was performed manually on standard 20 pound white security paper (photocopy paper) using a pencil containing the lead obtained in example 10 under normal writing pressure. The markers were studied with a scanning electron microscope. Fig. 1 depicts a photomicrograph at 1500 x magnification and shows paper cylindrical fibers and lead composition distributed between and adjacent to or on the fibers. Fibrils are particularly visible in the middle zone of the fiber photograph. It can be seen that these fibrils interconnect the various portions of the indicia. These fibrils are more readily seen in fig. 2-3, which depict photomicrographs of fig. 1 at higher magnifications, i.e., 10000 x and 30000 x, respectively. It is believed that the EVA fibrils are formed during writing due to shear forces applied to the composition. If a force is applied to the mark with an eraser, the material with interconnected fibrils will leave the surface as sheet-like or film-like segments.

Example 16

This example illustrates the cohesive nature of a mark formed by the colored pencil lead of the present invention. Thus, the marking was performed manually on standard 20 pound white security paper (photocopy paper) using a pencil containing the lead obtained in example 8 under normal writing pressure. The markers were studied with a scanning electron microscope. Fig. 4 depicts a micrograph at 2000 x magnification and shows the adhesive properties of the lead composition. The fibrils which impart cohesiveness to the composition can be seen throughout the micrograph, particularly in the upper middle region. It can be seen that these fibrils interconnect the various portions of the indicia. These interconnected fibrils are more readily seen in fig. 5, which depicts the microstructure at a higher magnification (10000 ×), particularly concentrated in the upper middle region of fig. 4.

Example 17

This example further illustrates the cohesive nature of the marking formed by the colored pencil lead of the present invention. A pencil was made from a lead having the following composition.

Composition (I) % by weight % by volume

SUNSPERSE RHD 6011 (organic Red pigment) 13.414.8

MICROTHENE FP 80000 (Polypropylene) 16.428.4

FLUON AD-1 (fibrillatable PTFE) 1.00.7

MICROTHENE MU 76000(EVA) 4.5 7.5

PEG 20M 7.0 9.8

MICHEM 66930 (high melting point wax, melting point 106 ℃, 5.89.7)

Michelman Inc.，Cincinnati，OH)

MICROTUFF AG 609 (surface treated Talc) 51.929.1

Total 100.0100.0

The lead produced a mark with good color strength and erasability. The marking was performed manually using a pencil containing the above lead on standard 20 pound white security paper (photocopy paper) under normal writing pressure. The markers were studied with a scanning electron microscope. Fig. 6 depicts a micrograph at 2000 x magnification and shows the adhesive properties of the lead composition. The interconnected fibrils can be seen from the entire micrograph. These interconnected fibrils are more readily seen in fig. 7, which depicts the microstructure at a higher magnification (10000 ×), particularly concentrated in the upper middle region of fig. 6.

Example 18

This example illustrates another embodiment of the preparation of colored pencil leads according to the present invention. A colored pencil lead was manufactured from the following ingredients.

Composition (I) % by weight % by volume

MONASTRAL RED Y RT-759-D (PIGMENT) 8.08.54

IRGAZIN RED DPP BO (pigment) 4.03.86

MICROTHENE FP 80000 (Polypropylene) 15.926.97

MICROTHENE MU 76000(EVA) 4.6 7.54

MICROTHENE FN 51000(LDPE) 1.6 2.68

MICROTUFF AG 609 (surface treated Talc) 51.428.32

PEG 20M 7.3 10.39

EPOLENE E-10 (high melting wax) 7.011.49

IRGAFOS 168 (antioxidant) 0.10.15

IRGANOX 1010 (antioxidant)0.1 0.15

100.0 100.0

The lead produced a mark with good color strength and erasability.

All references, including patents, patent applications, and publications, cited herein are hereby incorporated by reference in their entirety.

While the invention has been described with emphasis on several embodiments, it will be obvious to those skilled in the art that variations of the embodiments may be employed and that the invention may be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications encompassed within the spirit and scope of the invention as defined by the following claims.

Claims (46)

1. An erasable colored pencil lead composition comprising a colorant, one or more binder resins, a fibrillatable or fibrillated polymer, and a filler, wherein said composition is free of wax or waxy materials having a melting or softening point of 90 ℃ or less.

2. An erasable colored pencil lead composition according to claim 1, wherein said low melting wax or wax-like material has a penetration hardness value of 5 units or more.

3. An erasable colored pencil lead composition according to claim 1 or 2, wherein said binder resin is a polyolefin.

4. An erasable colored pencil lead composition according to claim 3, wherein said polyolefin is selected from the group consisting of polypropylene, high density polyethylene, low density polyethylene, high melting polyolefin waxes, and mixtures thereof.

5. The erasable colored pencil lead composition of claim 4, wherein said polyolefin is a mixture of polypropylene, low density polyethylene and high melting point polyethylene wax.

6. An erasable colored pencil lead composition according to claim 1, wherein said fibrillatable or fibrillated polymer is a fibrillatable or fibrillated copolymer.

7. An erasable colored pencil lead composition according to claim 6, wherein said fibrillatable or fibrillated copolymer is a fibrillatable or fibrillated ethylene vinyl acetate copolymer.

8. The erasable colored pencil lead composition of claim 1, further comprising a lubricant.

9. An erasable colored pencil lead composition according to claim 8, wherein said lubricant is a non-particulate lubricant.

10. The erasable colored pencil lead composition of claim 9, wherein said lubricant forms a separate region from the binder resin.

11. The erasable colored pencil lead composition of claim 10, wherein said lubricant is a polar material.

12. The erasable colored pencil lead composition of claim 11, wherein said polar material comprises an alkoxylated material.

13. The erasable colored pencil lead composition of claim 12, wherein said alkoxylated material is selected from the group consisting of polyalkylene glycols, alkoxylated ethers, alkoxylated lanolin alcohols, alkoxylates of mono-and polyhydric alcohols, alkoxylated fatty acids, alkoxylated vegetable oils, alkoxylated hydrogenated vegetable oils, and mixtures thereof.

14. The erasable colored pencil lead composition of claim 12, wherein said alkoxylated material is an ethoxylated material.

15. The erasable colored pencil lead composition of claim 14, wherein said ethoxylated material is selected from the group consisting of polyethylene glycols, ethoxylated ethers, ethoxylated lanolin alcohols, ethoxylates of mono-and polyhydric alcohols, ethoxylated fatty acids, ethoxylated vegetable oils, ethoxylated hydrogenated vegetable oils, and mixtures thereof.

16. The erasable colored pencil lead composition of claim 14, wherein said ethoxylated material is polyethylene glycol.

17. An erasable colored pencil lead composition according to any one of claims 1-2 and 4-16, wherein said composition comprises an antioxidant.

18. An erasable colored pencil lead composition according to claim 1, further comprising a non-fibrillatable particulate lubricant.

19. An erasable colored pencil lead composition according to claim 18, wherein said non-fibrillatable particulate lubricant is a non-fibrillatable particulate polymer.

20. The erasable colored pencil lead composition of claim 19, wherein said non-fibrillatable particulate polymer is polytetrafluoroethylene.

21. The erasable colored pencil lead composition of claim 18, wherein said colorant is a pigment.

22. An erasable colored pencil lead composition according to claim 21, wherein said fibrillatable or fibrillated polymer is polytetrafluoroethylene.

23. The erasable colored pencil lead composition of claim 18, wherein at least one of said binder resins is selected from the group consisting of thermoplastic polymers, thermosetting polymers, and latex polymers.

24. The erasable colored pencil lead composition of claim 23, wherein said binder resin is a thermoplastic polymer.

25. The erasable colored pencil lead composition of claim 24, wherein said thermoplastic polymer is a polyolefin.

26. The erasable colored pencil lead composition of claim 25, wherein said composition comprises an olefin homopolymer and an olefin copolymer as binder resins.

27. The erasable colored pencil lead composition of claim 26, wherein said olefin homopolymer is selected from the group consisting of polypropylene and high density polyethylene, and said olefin copolymer is an ethylene-acrylic acid copolymer.

28. An erasable colored pencil lead composition according to claim 18, wherein the ratio of said non-fibrillatable particulate lubricant to said fibrillatable or fibrillated polymer is from 1: 0.01 to 1: 1.

29. The erasable colored pencil lead composition of claim 26, wherein said filler is selected from the group consisting of mica, silica, clay, and calcium carbonate.

30. The erasable colored pencil lead composition of claim 19, wherein the amount of said colorant is from 10 to 30 volume percent of said composition, the amount of said one or more binder resins is from 30 to 50 volume percent of said composition, the amount of said fibrillatable or fibrillated polymer is from 2 to 10 volume percent of said composition, the amount of said non-fibrillatable particulate polymer is from 10 to 30 volume percent of said composition, and the amount of said filler is from 10 to 30 volume percent of said composition.

31. The erasable colored pencil lead composition of claim 3, wherein said composition comprises an antioxidant.

32. The erasable colored pencil lead composition of claim 3, wherein said composition is capable of drawing a mark when said composition is applied to a surface, forming a tie layer of said colored pencil lead composition.

33. A method of using an erasable colored pencil lead composition on a surface to be marked comprising:

(a) providing an erasable colored pencil lead composition of any one of claims 1-2, 4-16, and 18-30;

(b) providing the surface; then the

(c) The pencil lead is applied to the surface to draw a mark to form a coherent layer of the colored pencil lead composition.

34. The method of claim 33, wherein the surface is a porous surface.

35. The method according to claim 34, wherein the porous surface is paper.

36. A method of erasing a mark created on a surface by an erasable colored pencil lead composition, the method comprising applying a conventional pencil eraser to the mark, wherein the mark forms a tie layer of the colored pencil lead composition comprising a colorant, one or more binder resins, a fibrillatable or fibrillated polymer, and a filler; wherein the colored pencil lead composition is free of wax or waxy materials having a melting or softening point of 90 ℃ or less.

37. A process for preparing an erasable colored pencil lead composition comprising a colorant, one or more binder resins, a fibrillatable or fibrillated polymer, a non-fibrillatable particulate lubricant, and a filler, the process comprising mixing said colorant, said one or more binder resins, said fibrillatable or fibrillated polymer, said non-fibrillatable particulate lubricant, and said filler to provide a blend, and then forming said pencil lead from said blend; wherein the colored pencil lead composition is free of wax or waxy materials having a melting or softening point of 90 ℃ or less.

38. The method of claim 37, wherein the blending is performed by a dry blending process, a semi-dry blending process, or a wet blending process.

39. A method according to claim 37, wherein the pencil lead is shaped by processing the blend in a melt process, a wet process, or a reactive process.

40. The method according to claim 37, wherein the non-fibrillatable particulate lubricant is a non-fibrillatable particulate polymer.

41. The method according to claim 40 wherein said non-fibrillatable particulate polymer is polytetrafluoroethylene.

42. A method of making an erasable colored pencil lead composition comprising a colorant, one or more binder resins, a fibrillatable or fibrillated polymer, a non-fibrillatable particulate lubricant, a filler, and an antioxidant according to claim 1 comprising mixing said colorant, said one or more binder resins, said fibrillatable or fibrillated polymer, said non-fibrillatable particulate lubricant, said filler, and said antioxidant to provide a blend and then forming said pencil lead composition from said blend.

43. A process for preparing an erasable colored pencil lead composition of claim 8 comprising mixing said colorant, said one or more binder resins, said fibrillatable or fibrillated polymer, said non-particulate lubricant, and said filler to provide a blend and then forming said pencil lead composition from said blend.

44. A process for preparing an erasable colored pencil lead composition of claim 1 comprising mixing said colorant, said one or more binder resins, said fibrillatable or fibrillated polymer, and said filler to provide a blend, and then forming said pencil lead composition from said blend.

45. The method of claim 44 wherein said erasable colored pencil lead composition further comprises an antioxidant, the method comprising mixing said colorant, said one or more binder resins, said fibrillatable or fibrillated polymer, said filler, and said antioxidant to provide a blend, and then forming said pencil lead composition from said blend.

46. A method of using an erasable colored pencil lead composition on a surface to be marked, the method comprising:

(a) providing an erasable colored pencil lead composition of claim 3;

(b) providing the surface; and

(c) applying said pencil lead composition to the surface to draw a mark to form a coherent layer of said colored pencil lead composition.