CA2063115C

CA2063115C - Rigid fiberboard

Info

Publication number: CA2063115C
Application number: CA002063115A
Authority: CA
Inventors: Richard L. Maine; Joseph W. Cook
Original assignee: Lydall Inc
Current assignee: Gilles Lussier v-P Of Bennett Fleet (chambly) Inc
Priority date: 1991-06-13
Filing date: 1992-03-16
Publication date: 1998-01-06
Anticipated expiration: 2012-03-16
Also published as: EP0518018A1; KR930000220A; BR9202205A; JPH0596899A; KR100209070B1; CA2063115A1

Abstract

A rigid fiberboard suitable as a replacement for the natural woods presently used for the manufacture of pencils is provided. The fiberboard essentially comprises a fiber network together with a filler and binder. A lubricant is added to improve the sharpening characteristics of the fiberboard, and dimensional stability is preserved by incorporating a water proofing agent to minimize the absorption of water by the fiber network.

Description

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RIGID FIBERBOARD
BACKGROUND OF THE INVENTION
The present invention relates to a rigid fiherboard material. More particularly, the present invention relates to ~ rigid fiberboard useful in the manufacture o~ penc:ils.
The familiar wooden sh~ft which forms a part of almost all standard lead pencils, colored lead pencils, cosmetic pencils and other ~uch marking implements has traditionally been formed from two kinds of wood.
Approximately 85~ of such pencils axe manufa~tured from incense cedar, which grows from central Oregon to lower California. The remaining 15% are made from jelutong which is a tropical rain forest hardwood found in Malaysia and Indonesia.
Incense cedar typically grows amo~g large stands of fir trees and, in the past, has been obtained through the "clear-cutting'l of such trees. However, ~evere restrictions are about to be placed on the "clear cutting" operations commonly practiced by the timber industry. Thus, incense cedar will have to be selectively harvested from the fir forests in which it grows. This will, of course, result in a substantial rise in the cost of cedar to pencil manufactur-ers. Cedar costs will be further increased by restrictions 2~3~

on the supply of this wood. App~oximately one-third of the incense cedar harvest area will~shortly be ta~en ouk of production to protect endangered species of wildlife such as the "Spotted" Owl.
~elutong has, to this point, been a low cost substitute ~or incense cedar; however, this is likely to change in the very near $uture. The fragile rain forest ecosystem in which this wood grows is easily damaged by harvesting operations. Thus~ access to much o~ the growing area has already been restricted by the Indonesian and Malaysian governments in an ef~ort to protect their nations' rain forests from degradation. Déspite these efforts, illegal harvesting of jelutong from restricted areas is widespread. In view of these activities and the ecological damage they cause, several environmental groups have called for a boycott of those pencil manufact~rers who employ jelutong in the manufacture of their pencils. Further, the increased demand for jelutong as a substitute for cedar in ~he manufacture of pencils has pro~pted some environmental organizations to designate jelutong as an endangered tree species.
Accordingly, it is an object of the present invention to provide a rigid fiberboard material which is useful as a substitute for the natural woods currently employed in the manufacture of pencils.
It is a further object of the invention to provide 20~e31 ~

a rigid fiberboard which pencil man~facturer~ can substitute directly into their manu~actur~ng process without the need to significantly alter existing machinery or methods.
It is a still further object of the invention to provide a rigid fiberboard which comprises recycled materials.
SUMMARY OF THE INVENTION
The present invention meets the above-stated objects and other objects which will be readily apparent by providing a rigid fiberboard and a pencil formed there~rom.
The fiberboard comprises fibers, filler, binder, lubricant and water proofing agent. The fiberboard may further comprise at least one processing aid.
A rigid fiberboard made according to the invention is useful as a substitute for the incense cedar and jelutong currently used to make pencil shafts~ Moreover, the fiberboard is substituted directly into the currently employed pencil manufacturing process. The rigid fiberboard is formed in a wet laid process on conventional papermaking equipment. Initially, the fiberboard is formed in large sheets, each having a length of about 132 inches, a width of about 110 inches and a thickness of from about 0.15 to 0.18 inches, or in rolls. Each sheet or roll is then cut, in an automated cutting process, into slabs measuring approxi~ately 2.75 inches by 7.25 inches; slabs of this size closely ~ 2~3~

; approximate the natural wood slabs c~lrrently sllpplied to pencil manufacturers.
As is -the case with the natural wood slabs currently being used, each pencil is formed from a portion of two fiberboard slabs, a top slab and a bottom slab, adhered together. Prior to adhering the slabs together, each slab is grooved under grooving wheels, and the bottom slab has polyvinyl acetate glue or other suitable wood glues applied into its grooves through an appropriate dispenser. Once the glue ~as been applied, fired graphite lead is laid into the grooves of the bottom slab and lightly pressed into place under a roller. The top slab is then adhesively treated to apply adhesive into its grooves and onto the flats between the grooves. The top slab is then attached to the bottom slab and held in place under pressure until the adhesive dries~
~ he dried slabs are squared with a diamond-tipped rotating blade and then passed to a ~haping machine with top and bottom knives and shaped into the f~ r hexagon by first cutting the bottom slab and then the top. After three or four coats of paint have been applied, the pencils are printed. The pencils are then pressed into an end constrictor to reduce the diameter at one end so that the ferrule and eraser can be applied.
As will be further discussed below, not only does the invention provide a rigid fiberboard that eliminates the need to ~se natural woods from ecologlcally sensitive area~
in the manufacture of pencils, but also the fiberboard itself can be made largely from recycled materials such as recycled newspaper and pulp by-products. Moreover, because the fiherboard is made in a wet-laid process on pap~rmaking equipment it is far more uniform than the natural woods presently being used which evidence a good deal of variation among individual trees and among the parts of a single tree.
DETAILED DESCRIPTION OF THE INVENTION
The rigid fiberboard taught by the present invention comprises from about 3~ to about 75% by weight of fibers. The fi~ers form the basic structural network for the fiberboard and, when properly combined with other constituents, provide the fiberboard with a wood like quality. A wide ~ariety o~ both natural and man-made fibers may be utilized: preferably, however, cellulose fibers are used. It has been found that cellulose fibers derived from recycled materials produce excelle~t results. Accordingly, in the preferred embodiment of the invention the fiberboard comprises secondary cellulose fibers derived from, for example, one or more of the following sources: recycled newspapers, kraft bags, corrugated boxes, cotton linters, denim fi~ers, bleached papers, kraft papers and cotton rags.

The use of these recycled, biodegradable fibers not only :

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results in reduced costs but also provides an enviromnentally attractive product.
It should ~e understood, however, that the invention is in no way limited in this regard. Virgin cellulose ~ibers from, for example, wood pulp may also be used, either alone or in combination with other types of fibers. As noted above, the fiberboard may also comprise man-made fibers. Suitable man-made fibers include, for example, polyester fibers, acrylic fibers, aramid fibers, rayon fibers, nylon fibers and glass fibers.
To provide the fiberboard with sufficient bulk, the material further comprises from about 10 to about 30% by weight of filler. A large number of ~o~h organic and inorganic particulates have been found useful for this purpose such as, for example, perlite, vermiculite, glass microbubbles, corn cob flour, rice hull flour, nut shell flour, fruit pit flour, wood flour, cork dust, ground rubber~
phenolic resin microbubbles, carbon microbubbles and saran microbubbles. Certain fibers, commonly referred to by those skilled in the art as bulking fibers, may also be used together with ~he particulate fillers. Sui~able bulking fibers are, for example, "HBA" fibers available from Weyerhaeuser Paper Co., Tacoma, Washington and "INTERFIsE"
fibers available from Interfibe, Inc., Portage, Mich.
Preferably, the filler comprises one or more organic particulates formed as by-products in various 3 1 ~ 3' industries such as the lumber, agriculture and food industries. In this regard, wood flour ~rom Wilner Wood Products Co., Norway, Maine, cork dust available from Maryland Cork Co., Elkton, Maryland, corn cob flour supplied by Composite Materials, Inc., Montgomery, Alabama, corn starch and mixtures thereof have been found to be particularly suitable. By employing filler materials which are recycled, biodegradable by-products ~rom other industries a more economical and environmentally safe product can be achieved.
To provide rigidity, the fiberboard further comprises from about 10 to about 35% by weight of binder.
Any binder recognized by those skilled in the art as suitable for the fiber~particulate formulation described above may be used. ~owever, the binder preferably is a thermoset resin, a water soluble gum or a combination of the two. Suitable thermoset resin binders, used either alone or in combination, are phenolic resins, melamine resins, urea-formaldehyde resins, latex resins and epoxy resins. Water soluble ~ums which have been found to be particularly useful are guar gum, carboxymethyl cellulose and hydroxyethyl cellulose. In the most preferred embodiments of the invention the binder is a phenolic resin binder such as the resins sold under the trademark "PLYOPHEN" by BTL Speciality Resins, Malvern, Ark., Reichhold Chemicals, Inc., Warren, NJ, "CASCOPHEN" by Borden 2~3~1 ~

Packaging and Industrial Products, Vancouver, B.C., "VARCUM
~ND DUREZ" from Oxychem, Tonowanda, NY or a combination of these resins and carboxymethyl cellulose.
An important consideration when supplying a S material intended as a replacement for the natural woods currently used in pencil makiny is that the material exhibits satisfactory sharpening characteristics. That is, the substitute material mus~ sharpen smoothly without burrs or chips, as is the case with cedar and jelutong. Accordingly, the fiberboard further comprises from about 2 to about 15% by weight o~ a lubricating agent to help insure that it will sharpen correctlyO A number of lubricants have been found to be suitable for this purpose including, for example, polyethylene powder, emulsified wax, powdered wax, talcs, stearates, fatty acids and mixtures of these material~. In the most preferred embodiment of the invention the lubricant is either polyethylene powder, such as that available from USI Chemicals Co., Cincinnati, OH u~der the trademark 'IMICROTHENE" or 'IPARACOL" wax emulsion from Hercules, Inc.
Wilmington, DE, stearic acid or mixtures thereof.
As noted above, formulating the fiberboard with secondary cellulose fib~rs provides both economic and ecologic advantages. However, such fibers also present a disadvantage: they tend to absorb water during the paper making process and ambient moisture after the fiberboard has been formed and dried. If the fiber network absorbs too much 2 ~ 1 J

wa~er, then the dimension~l stabi~ity o~ t~le fiberboard cannot be preserved. Therefore, to reduce this tendency, the fiberboard further includes from about 0.4 to about 1.5% by weight of a water proofing agent. Preferably, the water proofing agent is wood rozin size, a by-product of the pulp industry, or a silicone-based wat~er repellant. In the most preferred embodiment of the invention, the water proofing agent is wood ro~in size available from Hercules, Inc., Wilmington, DE under the trademark ''PEXOL" 243.
The fiberboard further comprises O to about 3~ by weight of processing aids. Any number of a wide variety of processing aids commonly used by those skilled in the art may be employed including, for example, one or more of the following: retention aids, anti-foaming agents, coagulants, lS floculents and pH modifiers. The use of polyamide resin-type retention aids, such as "KYMENE" 557H from Hercules, Inc., Wilmington, DE or "AMRES" 8855 from Georgia Pacific, Crossett, Ark., have been found to be particularly advantageous. A retention aid of this type not only provides better retention of fines but also enhances the wet strength of the fiberboard.
Finally, the fiberboard may further include one or more dyes to provide the familiar reddish color of pencils made from cedar. In this regard, chrysoidine and paper red are particularly suitable.
The present invention will be further understood from the following specific examples:

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Example I
component 'wt. %
newspaper 19.6 kraft bags 9.8 S corrugated cardboard 9.8 wood flour ~1.6 phenolic resin 31.4 polyamide resin .80 wood rosin size ~49 wax emulsion 1.6 stearic acid 2.9 Example II
component ~ _~
newspaper . 27.1 corrugated cardboard 24~6 wood flour 7~4 cork dust 9.9 phenolic resin 27~1 wood rozin size 0.62 polyamide resin 1.1 2 ~ g 3 1 ~ ~ j Example III
component ~ wt. %
newspaper 25.9 kra~t bags 11.8 corrugated cardboard 11.8 wood flour 7.1 cork 14.1 wax emulsion 1.9 phenolic resin 25.8 wood rozin size 0.59 polyamide resin 1.1 Example IV
component wt %
newspaper 24.3 corrugated cardboard 22.1 wood flour 6~6 cork dust 13.2 phenolic resin 24.3 wood rozin size 0.55 wax emulsion 3.5 polyethylene powder 4.4 polyamide resin 1.0 ~Q~3~

Ex~mple v component ~ w-t. %
newspaper 21.6 corrugated cardboard 21.6 wood flour 10.8 corX dust 12~9 phenolic resin 23.7 wood rozin si~e 0.54 wax emulsion 3.4 stearic acid 4.3 polyamide resin 1.0 While preferred embodiments have been shown and described, various modifications and substitutions may be made without departing from the spirit and scope of the lS invention. Accordingly, it is to be understood that the present invention has been described by way of example and not by limitation.

Claims

1. A rigid fiberboard for use as a pencil shaft, said fiberboard comprising fibers, binder, filler, lubricant and a water proofing agent.

2. The fiberboard of claim 1 wherein the fibers are selected from the group consisting of natural fibers, man-made fibers and mixtures thereof.

3. The fiberboard of claim 2 wherein the natural fibers are cellulose fibers derived from a source selected from the group consisting of wood pulp, cotton linters, denim fibers, newspapers, corrugated boxes, kraft bags, bleached papers, kraft papers, cotton rags and mixtures thereof.

4. The fiberboard of claim 2 wherein the man-made fibers are selected from the group consisting of polyester fibers, acrylic fibers, aramid fibers, rayon fibers, nylon fibers, glass fibers and mixtures thereof.

5. The fiberboard of claim 1 wherein the binder is selected from the group consisting of thermoset resin binders and water soluble gums and mixtures thereof.

6. The fiberboard of claim 5 wherein the binder is a thermoset resin binder selected from the group consisting of phenolic resins, melamine resins, urea-formaldehyde resins, latex resins, epoxy resins and mixtures thereof.

7. The fiberboard of claim 5 wherein the binder is a water soluble gum selected from the group consisting of guar gum, carboxymethyl cellulose and hydroxyethyl cellulose and mixtures thereof.

8. The fiberboard of claim 1 wherein the filler is selected from the group consisting of organic particulate materials, inorganic particulate materials, bulking fibers and mixtures thereof.

9. The fiberboard of claim 8 wherein the filler is an inorganic particulate material selected from the group consisting of perlite, vermiculite, glass microbubbles and mixtures thereof.

10. The fiberboard of claim 8 wherein the filler is an organic particulate material selected from the group consisting of corn cob flour, rice hull flour, nut shell flour, fruit pit flour, wood flour, ground cork, ground rubber, phenolic resin microbubbles, carbon microbubbles, saran microbubbles and mixtures thereof.

11. The fiberboard of claim 1 wherein the lubricant is selected from the group consisting of polyethylene powder, emulsified wax, powdered wax, talc, stearates, fatty acids and mixtures thereof.

12. The fiberboard of claim 1 wherein the water proofing agent is selected from the group consisting of rosin size, silicone-based water repellants and mixtures thereof.

13. The fiberboard of claim 1 further comprising at least one processing aid selected from the group consisting of retention aids, anti-foaming agents, coagulants, floculents, pH modifiers and mixtures thereof.

14. The fiberboard of claim 13 wherein the retention aid is a polyamide resin.

15. The fiberboard of claim 1 further comprising at least one dye.

16. The rigid fiberboard of claim 1 comprising by weight:
from about 38 to 75% fibers;
from about 10 to about 35% binder;
from about 10 to about 30% filler;
from about 2 to about 15% lubricant;
from about 0.4 to about 1.5% water proofing agent, and 0 to about 3% processing aids.

17. A pencil comprising a marking core and a shaft surrounding the core, said shaft formed from a fiberboard comprising fibers, binder, filler, lubricant and water proofing agent.

18. The pencil of claim 17 wherein said fiberboard comprises about 38-75% fibers, about 10-35% binder, about 10-30% filler, about 2-15% lubricant, about 0.4-1.5% water proofing agent and 0-3% processing aids.