Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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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
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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
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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
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; 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
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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
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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
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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
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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.
