U.S. patent application number 10/611132 was filed with the patent office on 2004-07-01 for advanced polymer wood composite.
This patent application is currently assigned to Andersen Corporation. Invention is credited to Deaner, Michael J., Heikkila, Kurt E., Puppin, Giuseppe.
Application Number | 20040126568 10/611132 |
Document ID | / |
Family ID | 27558692 |
Filed Date | 2004-07-01 |
United States Patent
Application |
20040126568 |
Kind Code |
A1 |
Deaner, Michael J. ; et
al. |
July 1, 2004 |
Advanced polymer wood composite
Abstract
The invention relates to a composition comprising a polymer and
wood fiber composite that can be used in the form of a linear
extrudate or thermoplastic pellet to manufacture structural
members. The polymer and wood fiber composite structural members
can be manufactured in an extrusion process or an injection molding
process. The linear extrudate or pellet can have a cross-section of
any arbitrary shape, or can be a regular geometric. The pellet can
have a cross-section shape having a volume of at least about 12
mm.sup.3. Preferably the pellet is a right cylindrical pellet
having a minimum radius of about 1.5 mm and a minimum length of 1
mm weighing at least 14 mg. The invention also relates to an
environmentally sensitive recycle of waste streams. The polymer and
wood fiber composite contains an intentional recycle of a waste
stream comprising polymer flakes or particles or wood fiber. The
waste stream can comprises, in addition to polymer such as
polyvinyl chloride or wood fiber, adhesive, paint, preservative, or
other chemical stream common in the wood-window or door
manufacturing process, or mixtures thereof. The initial mixing step
before extrusion of the composite material insures substantial
mixing and melt contact between molten polymer and wood fiber. The
extruded pellet comprises a consistent proportion of polymer, wood
fiber and water. During the extrusion, water is removed
intentionally to dry the material to a maximum water content of
less than about 10 wt-% based on the pellet weight. To make a
structural unit, the pellet is introduced into an extruder or
injection molding apparatus wherein, under conditions of
temperature and pressure, the composite pellet material is shaped
into a useful cross-section. Alternatively, the extruded
thermoplastic mass, in the form of a elongated linear extrudate
without a pelletizing step, can be immediately directed after
formation into an extruder or injection molding apparatus.
Inventors: |
Deaner, Michael J.;
(Osceola, WI) ; Puppin, Giuseppe; (Bayport,
MN) ; Heikkila, Kurt E.; (Circle Pines, MN) |
Correspondence
Address: |
MERCHANT & GOULD PC
P.O. BOX 2903
MINNEAPOLIS
MN
55402-0903
US
|
Assignee: |
Andersen Corporation
Bayport
MN
|
Family ID: |
27558692 |
Appl. No.: |
10/611132 |
Filed: |
July 1, 2003 |
Related U.S. Patent Documents
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Application
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Filing Date |
Patent Number |
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10611132 |
Jul 1, 2003 |
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09957596 |
Sep 19, 2001 |
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09957596 |
Sep 19, 2001 |
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09484622 |
Jan 18, 2000 |
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09484622 |
Jan 18, 2000 |
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09304351 |
May 4, 1999 |
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6015612 |
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09304351 |
May 4, 1999 |
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09178953 |
Oct 26, 1998 |
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6004668 |
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09178953 |
Oct 26, 1998 |
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08543959 |
Oct 17, 1995 |
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5827607 |
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08543959 |
Oct 17, 1995 |
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08224396 |
Apr 7, 1994 |
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08224396 |
Apr 7, 1994 |
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07938364 |
Aug 31, 1992 |
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Current U.S.
Class: |
428/326 ;
428/292.4; 428/359; 428/361 |
Current CPC
Class: |
B29K 2311/14 20130101;
C08L 97/02 20130101; Y10T 428/253 20150115; C08L 97/02 20130101;
C08L 97/02 20130101; C08L 2666/04 20130101; C08L 2666/26 20130101;
C08L 2666/08 20130101; C08L 2666/06 20130101; C08L 2666/02
20130101; C08L 97/02 20130101; Y10T 428/249925 20150401; C08J 5/06
20130101; C08L 97/02 20130101; Y10T 428/2904 20150115; B29B 9/14
20130101; B27N 3/28 20130101; C08K 7/02 20130101; Y10T 428/2907
20150115; C08L 2205/03 20130101; C08J 5/04 20130101; C08J 5/045
20130101; C08J 2327/06 20130101; C08L 27/06 20130101; B27N 3/007
20130101; C08L 27/06 20130101; C08L 101/00 20130101 |
Class at
Publication: |
428/326 ;
428/292.4; 428/359; 428/361 |
International
Class: |
D21J 001/00 |
Claims
We claim:
1. A composite pellet, capable of formation into a structural
member, which pellet comprises a cylindrical extrudate having a
radius of about 1 to 5 mm, a length of about 1 to 10 mm; the pellet
composition comprising: (a) about 45 to 70 wt-% of a polymer
comprising vinyl chloride; (b) about 30 to 50 wt-% of wood fiber
having a minimum thickness of 1 .mu.m and a minimum length of 3
.mu.m and a minimum aspect ratio of about 1.8; and (c) less than
about 8 wt-% water; and wherein the wood fiber is dispersed
throughout a continuous polymer phase.
2. The composition of claim 1 wherein the polymer comprises a
polyvinyl chloride homopolymer.
3. The composition of claim 1 wherein the polymer comprises a
polyvinyl chloride copolymer.
4. The composition of claim 1 wherein the wood fiber comprises a
by-product of milling or sawing wooden members.
5. The composition of claim 4 wherein the wood fiber comprises
sawdust.
6. The composition of claim 1 wherein the composition additionally
comprises a compatiblizing agent.
7. The composition of claim 2 wherein the polymer has a molecular
weight of about 90,000.+-.50,000.
8. The composition of claim 3 wherein the copolymer has a molecular
weight of about 88,000.+-.10,000.
9. The composition of claim 1 wherein the wood fiber has a fiber
width of about 0.3 to 1.5 mm, a fiber length of about 1 to 10 mm
and a aspect ratio of about 2 to 7.
10. The composition of claim 1 wherein the water comprises
about.0.01 to 5 wt-% of the pellet.
11. The composition of claim 1 wherein the intentionally recycled
impurity comprises about 0 to 5 wt-% of a hot melt adhesive
composition, about 0 to 5 wt-% of a paint and about 0.01 to 15 wt-%
of recycled polyvinyl chloride cladding, wherein the cladding
comprises about 9.0 to 99.9 wt-% polyvinyl chloride and about 0.01
to 2 wt-% of a pigment.
12. A polymer and wood fiber composite capable of formation into a
structural member, which composite comprises a cylindrical linear
extrudate having a radius of about 1 to 5 mm; the linear extrudate
composition comprising: (a) about 45 to 70 wt-% of a polymer
comprising vinyl chloride; (b) about 30 to 50 wt-% of wood fiber
having a minimum thickness of 1 mm and a minimum length of 3 mm and
an aspect ratio of about 1.8; (c) less than about 8 wt-% water; and
wherein the wood fiber is dispersed throughout a continuous polymer
phase.
13. The composition of claim 12 wherein the polymer comprises a
polyvinyl chloride homopolymer.
14. The composition of claim 12 wherein the polymer comprises a
polyvinyl chloride copolymer.
15. The composition of claim 12 wherein the wood fiber comprises a
by-product of milling or sawing wooden members.
16. The composition of claim 15 wherein the wood fiber comprises
sawdust.
17. The composition of claim 12 wherein the composition
additionally comprises a compatiblizing agents.
18. The composition of claim 15 wherein the polymer has a molecular
weight of about 95,000.+-.50,000.
19. The composition of claim 14 wherein the copolymer has a
molecular weight of about 88,000.+-.10,000.
20. The composition of claim 12 wherein the wood fiber has a fiber
width of about 0.3 to 1.5 mm, a fiber length of about 1 to 10 mm
and a aspect ratio of about 2 to 7.
21. The composition of claim 12 wherein the water comprises about
0.01 to 5 wt-% of the pellet.
22. A composite composition, capable of extrusion into a
dimensionally stable structural member, which composition
comprises: (a) about 40 to 70 wt-% of a polymer comprising vinyl
chloride; (b) about 30 to 50 wt-% of wood fiber having a minimum
width of 0.3 mm and a minimum length of 1 mm and An aspect ratio of
greater than about 1.8; (c) about 0.01 to 25 wt-% of an
intentionally recycled impurity comprising thermoplastic polymer,
an adhesive, a paint, a thermoplastic resin or mixtures thereof;
and (d) less than about 10 wt-% water; wherein the wood fiber is
dispersed throughout a continuous polymer phase.
23. The composition of claim 22 wherein the polymer comprises a
polyvinyl chloride homopolymer.
24. The composition of claim 22 wherein the polymer comprises a
polyvinyl chloride copolymer.
25. The composition of claim 22 wherein the wood fiber comprises a
by-product of milling or sawing wooden members.
26. The composition of claim 22 wherein the wood fiber comprises
sawdust.
27. The composition of claim 23 wherein the polymer has a molecular
weight of about 95,000.+-.50,000.
28. The composition of claim 24 wherein the copolymer has a
molecular weight of about 88,000.+-.10,000.
29. The composition of claim 22 wherein the wood fiber has a fiber
width of about 0.3 to 1.5 mm, a fiber length of about 1 to 10 mm
and a aspect ratio of about 2 to 7.
30. The composition of claim 22 wherein the concentration of water
comprises about 0.01 to 3.5 wt-% of the composition.
Description
FILED OF THE INVENTION
[0001] This invention relates to composite thermoplastic materials
used for the fabrication of structural members. Such members an be
any structural unit, preferably they are for use in windows and
doors for residential and commercial architecture. These composite
materials include an optional, intentional recycle of by-product
streams, from window and door manufacture, of polymer, adhesive,
paint, etc. More particularly, the invention relates to an improved
composite material adapted to extrusion or injection molding
processes for forming structural members that have improved
properties when used in windows and doors. The composite materials
of the invention can be made to manufacture structural components
such as rails, jambs, stiles, sills, tracks, stop and sash,
nonstructural trim elements such as grid, cove, bead, quarter
round, etc.
BACKGROUND OF THE INVENTION
[0002] Conventional window and door manufacture has commonly used
wood and metal components in forming structural members. Commonly,
residential windows are manufactured from milled wood products that
are assembled with glass to form typically double hung or casement
units. Wood windows while structurally sound, useful and well
adapted for use in many residential installations, can deteriorate
under certain circumstances. Wood windows also require painting and
other periodic maintenance. Wooden windows also suffer from cost
problems related to the availability of suitable wood for
construction. Clear wood products are slowly becoming more scarce
and are becoming more expensive as demand increases. Metal
components are often combined with glass and formed into single
unit sliding windows. Metal windows typically suffer from
substantial energy loss during winter months.
[0003] Extruded thermoplastic materials have been used in window
and door manufacture. Filled and unfilled thermoplastics have been
extruded into useful seals, trim, weatherstripping, coatings and
other window construction components. Thermoplastic materials such
as polyvinyl chloride have been combined with wood members in
manufacturing PERMASHIELD.RTM. brand windows manufactured by
Andersen Corporation for many years. The technology disclosed in
Zanini, U.S. Pat. Nos. 2,926,729 and 3,432,883, have been utilized
in the manufacturing of plastic coatings or envelopes on wooden or
other structural members. Generally, the cladding or coating
technology used in making PERMASHIELD.RTM. windows involves
extruding a thin polyvinyl chloride coating or envelope surrounding
a wooden structural member.
[0004] Polyvinyl chloride has been combined with wood to make
extruded materials. However, such materials have not successfully
been used in the form of a structural member that is a direct
replacement for wood. Common thermoplastic composite materials
cannot provide similar thermal and structural properties to wood.
These extruded materials fail to have sufficient modulus,
compressive strength, coefficient of thermal expansion that matches
wood to produce a direct replacement material. Further, many prior
art extruded composites must be milled after extrusion to a final
useful shape. Typical commodity plastics have achieved a modulus no
greater than about 500,000. One class of composite, a polyvinyl
chloride/wood flour material, poses the added problem that wood
dust, which can accumulate during manufacture, tends to be
explosive at certain concentrations of wood flour in the air. Most
commonly, poly vinyl chloride, polystyrene and polyethylene
thermoplastics have been used in such products.
[0005] Accordingly, a substantial need exists for a composite
material that can be made of polymer and wood fiber with an
optional, intentional recycle of a waste stream. A further need
exists for a composite material that can be extruded into a shape
that is a direct substitute for the equivalent milled shape in a
wooden or metal structural member. This need requires a coefficient
of thermal expansion that approximates wood, a material that can be
extruded into reproducible stable dimensions, a high compressive
strength, a low thermal transmission rate, an improved resistance
to insect attack and rot while in use and a hardness and rigidity
that permits sawing, milling, and fastening retention comparable to
wood members. Further, companies manufacturing window and door
products have become significantly sensitive to waste streams
produced in the manufacture of such products. Substantial
quantities of wood waste including wood trim pieces, sawdust, wood
milling by-products; recycled thermoplastic including recycled
polyvinyl chloride, has caused significant expense to window
manufacturers. Commonly, these materials are either burned for
their heat value in electrical generation or are shipped to
qualified landfills for disposal. Such waste streams are
contaminated with substantial proportions of hot melt and
solvent-based adhesives, waste thermoplastic such as polyvinyl
chloride, paint, preservatives, and other organic materials. A
substantial need exists to find a productive environmentally
compatible use for such waste streams to avoid returning the
materials into the environment in an environmentally harmful
way.
BRIEF DISCUSSION OF THE INVENTION
[0006] We have found that the problems relating to forming a
substitute for wood and metal structural members and the problems
relating to the recycle of waste streams in window manufacture can
be solved by forming a polymer/wood fiber composite material into
window and door structural members. The polyvinyl chloride can be
combined with wood fiber and waste materials to form a polyvinyl
chloride/wood fiber composite, preferably in the form of a pellet.
The wood fiber comprises the sawdust or milling byproduct waste
stream from milling wooden members in window manufacture and can be
contaminated with substantial proportions of hot melt adhesive,
paint, solvent or adhesive components, preservatives, polyvinyl
chloride recycle pigment, plasticizers, etc. We have found that the
PVC and wood fiber composite can be manufactured into acceptable
substitutes for wooden members if the PVC and wood material
contains less than about 10 wt-%, preferably less than 3.5% water
based on pellet weight. The compositions can achieve in a final
product high modulus, high compressive strength, reproducible,
stable dimensions and a superior modulus of elasticity. We have
also found that the successful manufacture of structural members
for windows and doors requires the preliminary manufacture of the
polyvinyl chloride wood fiber composite in the form of a pellet
wherein the materials are intimately mixed and contacted in forming
the pellet prior to the extrusion of the members from the pellet
material. We have found that the intimate mixing of the polyvinyl
chloride, wood fiber, and waste in the manufacture of the pellet
process with associated control of moisture content produces a
pelletized product that is uniquely adapted to the extrusion
manufacture of PVC/wood fiber components and achieves the
manufacture of a useful wood replacement product.
DETAILED DESCRIPTION OF THE INVENTION
[0007] The invention relates to the use of polyvinyl chloride and
wood fiber composite materials with a controlled water content in
the form of a pelletized material wherein the wood fiber is
intimately contacted and wetted by the organic materials. The
intimate contact and wetting between the components in the
pelletizing process ensures high quality physical properties in the
extruded composite materials after manufacture.
Pellet
[0008] The polyvinyl chloride and wood fiber can be combined and
formed into a pellet using a thermoplastic extrusion processes.
Wood fiber can be introduced into pellet making process in a number
of sizes. We believe that the wood fiber should have a minimum size
of length and width of at least 1 mm because wood flour tends to be
explosive at certain wood to air ratios. Further, wood fiber of
appropriate size of a aspect ratio greater than 1 tends to increase
the physical properties of the extruded structural member. However,
useful structural members can be made with a fiber of very large
size. Fibers that are up to 3 cm in length and 0.5 cm in thickness
can be used as input to the pellet or linear extrudate
manufacturing process. However, particles of this size do not
produce highest quality structural members or maximized structural
strength. The best appearing product with maximized structural
properties are manufactured within a range of particle size as set
forth below. Further, large particle wood fiber an be reduced in
size by grinding or other similar processes that produce a fiber
similar to sawdust having the stated dimensions and aspect ratio.
One further advantage of manufacturing sawdust of the desired size
is that the material can be pre-dried before introduction into the
pellet or linear extrudate manufacturing process. Further, the wood
fiber can be pre-pelletized into pellets of wood fiber with small
amounts of binder if necessary.
[0009] During the pelletizing process for the composite pellet, the
polyvinyl chloride and wood fiber are intimately contacted at high
temperatures and pressures to insure that the wood fiber and
polymeric material are wetted, mixed and extruded in a form such
that the polymer material, on a microscopic basis, coats and flows
into the pores, cavity, etc., of the fibers. The fibers are
preferably substantially oriented by the extrusion process in the
extrusion direction. Such substantial orientation causes
overlapping of adjacent parallel fibers and polymeric coating of
the oriented fibers resulting a material useful for manufacture of
improved structural members with improved physical properties. The
degree of orientation is about 20%, preferably 30% above random
orientation which is about 45 to 50%. The structural members have
substantially increased strength and tensile modulus with a
coefficient of thermal expansion and a modulus of elasticity that
is optimized for window and doors. The properties are a useful
compromise between wood, aluminum and neat polymer.
[0010] Moisture control is an important element of manufacturing a
useful linear extrudate or pellet. Depending on the equipment used
and processing conditions, control of the water content of the
linear extrudate or pellet can be important in forming a successful
structural member substantially free of internal voids or surface
blemishes. The concentration of water present in the sawdust during
the formation of pellet or linear extrudate when heated can flash
from the surface of the newly extruded structural member and can
come as a result of a rapid volatilization, form a steam bubble
deep in the interior of the extruded member which can pass from the
interior through the hot thermoplastic extrudate leaving a
substantial flaw. In a similar fashion, surface water can bubble
and leave cracks, bubbles or other surface flaws in the extruded
member.
[0011] Trees when cut depending on relative humidity and season can
contain from 30 to 300 wt-% water based on fiber content. After
rough cutting and finishing into sized lumber, seasoned wood can
have a water content of from 20 to 30 wt-% based on fiber content.
Kiln dried sized lumber cut to length can have a water content
typically in the range of 8 to 12%, commonly 8 to 10 wt-% based on
fiber. Some wood source, such as poplar or aspen, can have
increased moisture content while some hard woods can have reduced
water content.
[0012] Because of the variation in water content of wood fiber
source and the sensitivity of extrudate to water content control of
water to a level-of less than 8 wt-% in the pellet based on pellet
weight is important. Structural members extruded in non-vented
extrusion process, the pellet should be as dry as possible and have
a water content between 0.01 and 5%, preferably less than 3.5 wt-%
When using vented equipment in manufacturing the extruded linear
member, a water content of less than 8 wt-% can be tolerated if
processing conditions are such that vented extrusion equipment can
dry the thermoplastic material prior to the final formation of the
structural member of the extrusion head.
[0013] The pellets or linear extrudate of the invention are made by
extrusion of the polyvinyl chloride and wood fiber composite
through an extrusion die resulting in a linear extrudate that can
be cut into a pellet shape. The pellet cross-section can be any
arbitrary shape depending on the extrusion die geometry. However,
we have found that a regular geometric cross-sectional shape can be
useful. Such regular cross-sectional shapes include a triangle, a
square, a rectangle, a hexagonal, an oval, a circle, etc. The
preferred shape of the pellet is a regular cylinder having a
roughly circular or somewhat oval cross-section. The pellet volume
is preferably greater than about 12 mm.sup.3. The preferred pellet
is a right circular cylinder, the preferred radius of the cylinder
is at least 1.5 mm with a length of at least 1 mm. Preferably, the
pellet has a radius of 1 to 5 mm and a length of 1 to 10 mm. Most
preferably, the cylinder has a radius of 2.3 to 2.6 mm, a length of
2.4 to 4.7 mm, a volume of 40 to 100 mm.sup.3, a weight of 40 to
130 mg and a bulk density of about 0.2 to 0.8 gm/mm.sup.3.
[0014] We have found that the interaction, on a microscopic level,
between the polymer mass and the wood fiber is an important element
of the invention. We have found that the physical properties of an
extruded member are improved when the polymer melt during extrusion
of the pellet or linear member thoroughly wets and penetrates the
wood fiber particles. The thermoplastic material comprises an
exterior continuous organic polymer phase with the wood particle
dispersed as a discontinuous phase in the continuous polymer phase.
The material during mixing and extrusion obtains an aspect ratio of
at least 1.1 and preferably between 2 and 4, optimizes orientation
such as at least 20 wt-%, preferably 30% of the fibers are oriented
in an extruder direction and are thoroughly mixed and wetted by the
polymer such that all exterior surfaces of the wood fiber are in
contact with the polymer material. This means, that any pore,
crevice, crack, passage way, indentation, etc., is fully filled by
thermoplastic material. Such penetration as attained by ensuring
that the viscosity of the polymer melt is reduced by operations at
elevated temperature and the use of sufficient pressure to force
the polymer into the available internal pores, cracks and crevices
in and on the surface of the wood fiber.
[0015] During the pellet or linear extrudate manufacture,
substantial work is done in providing a uniform dispersion of the
wood into the polymer material. Such work produces substantial
orientation which when extruded into a final structural member,
permits the orientation of the fibers in the structural member to
be increased in the extruder direction resulting in improved
structural properties.
[0016] The pellet dimensions are selected for both convenience in
manufacturing and in optimizing the final properties of the
extruded materials. A pellet is with dimensions substantially less
than the dimensions set forth above are difficult to extrude,
pelletize and handle in storage. Pellets larger than the range
recited are difficult to introduce into extrusion or injection
molding equipment, and are different to melt and form into a
finished structural member.
Polyvinyl Chloride Homopolymer, Copolymers and Polymeric Alloys
[0017] Polyvinyl chloride is a common commodity thermoplastic
polymer. Vinyl chloride monomer is made from a variety of different
processes such as the reaction of acetylene and hydrogen chloride
and the direct chlorination of ethylene. Polyvinyl chloride is
typically manufactured by the free radical polymerization of vinyl
chloride resulting in a useful thermoplastic polymer. After
polymerization, polyvinyl chloride is commonly combined with
thermal stabilizers, lubricants, plasticizers, organic and
inorganic pigments, fillers, biocides, processing aids, flame
retardants and other commonly available additive materials.
Polyvinyl chloride can also be combined with other vinyl monomers
in the manufacture of polyvinyl chloride copolymers. Such
copolymers can be linear copolymers, branched copolymers, graft
copolymers, random copolymers, regular repeating copolymers, block
copolymers, etc. Monomers that can be combined with vinyl chloride
to form vinyl chloride copolymers include a acrylonitrile;
alpha-olefins such as ethylene, propylene, etc.; chlorinated
monomers such as vinylidene dichloride, acrylate momoners such as
acrylic acid, methylacrylate, methylmethacrylate, acrylamide,
hydroxyethyl acrylate, and others; styrenic monomers such as
styrene, alphamethyl styrene, vinyl toluene, etc.; vinyl acetate;
and other commonly available ethylenically unsaturated monomer
compositions.
[0018] Such monomers can be used in an amount of up to about 50
mol-%, the balance being vinyl chloride. Polymer blends or polymer
alloys can be useful in manufacturing the pellet or linear
extrudate of the invention. Such alloys typically comprise two
miscible polymers blended to form a uniform composition. Scientific
and commercial progress in the area of polymer blends has lead to
the realization that important physical property improvements can
be made not by developing new polymer material but by forming
miscible polymer blends or alloys. A polymer alloy at equilibrium
comprises a mixture of two amorphous polymers existing as a single
phase of intimately mixed segments of the two macro molecular
components. Miscible amorphous polymers form glasses upon
sufficient cooling and a homogeneous or miscible polymer blend
exhibits a single, composition dependent glass transition
temperature (T.sub.g). Immiscible or non-alloyed blend of polymers
typically displays two or more glass transition temperatures
associated with immiscible polymer phases. In the simplest cases,
the properties of polymer alloys reflect a composition weighted
average of properties possessed by the components. In general,
however, the property dependence on composition varies in a complex
way with a particular property, the nature of the components
(glassy, rubbery or semi-crystalline), the thermodynamic state of
the blend, and its mechanical state whether molecules and phases
are oriented. Polyvinyl chloride forms a number of known polymer
alloys including, for example, polyvinyl chloride/nitrile rubber;
polyvinyl chloride and related chlorinated copolymers and
terpolymers of polyvinyl chloride or vinylidine dichloride;
polyvinyl chloride/alphamethyl styrene-acrylonitrile copolymer
blends; polyvinyl chloride/polyethylene; polyvinyl
chloride/chlorinated polyethylene and others.
[0019] The primary requirement for the substantially thermoplastic
polymeric material is that it retain sufficient thermoplastic
properties to permit melt blending with wood fiber, permit
formation of linear extrudate pellets, and to permit the
composition material or pellet to be extruded or injection molded
in a thermoplastic process forming the rigid structural member.
Polyvinyl chloride homopolymers copolymers and polymer alloys are
available from a number of manufacturers including B.F. Goodrich,
Vista, Air Products, Occidental Chemicals, etc. Preferred polyvinyl
chloride materials are polyvinyl chloride homopolymer having a
molecular weight of about 90,000.+-.50,000, most preferably about
88,000.+-.10,000.
Wood Fiber
[0020] Wood fiber, in terms of abundance and suitability can be
derived from either soft woods or evergreens or from hard woods
commonly known as broad leaf deciduous trees. Soft woods are
generally preferred for fiber manufacture because the resulting
fibers are longer, contain high percentages of lignin and lower
percentages of hemicellulose than hard woods. While soft wood is
the primary source of fiber for the invention, additional fiber
make-up can be derived from a number of secondary or fiber reclaim
sources including bamboo, rice, sugar cane, and recycled fibers
from newspapers, boxes, computer printouts, etc.
[0021] However, the primary source for wood fiber of this invention
comprises the wood fiber by-product of sawing or milling soft woods
commonly known as sawdust or milling tailings. Such wood fiber has
a regular reproducible shape and aspect ratio. The fibers based on
a random selection of about 100 fibers are commonly at least 3 mm
in length, 1 mm in thickness and commonly have an aspect ratio of
at least 1.8. Preferably, the fibers are 1 to 10 mm in length, 0.3
to 1.5 mm in thickness with an aspect ratio between 2 and 7,
preferably 2.5 to 6.0. The preferred fiber for use in this
invention are fibers derived from processes common in the
manufacture of windows and doors. Wooden members are commonly
ripped or sawed to size in a cross grain direction to form
appropriate lengths and widths of wood materials. The by-product of
such sawing operations is a substantial quantity of sawdust. In
shaping a regular shaped piece of wood into a useful milled shape,
wood is commonly passed through machines which selectively removes
wood from the piece leaving the useful shape. Such milling
operations produces substantial quantities of sawdust or mill
tailing by-products. Lastly, when shaped materials are cut to size
and mitered joints, butt joints, overlapping joints, mortise and
tenon joints are manufactured from pre-shaped wooden members,
substantial waste trim is produced. Such large trim pieces are
commonly cut and machined to convert the larger objects into wood
fiber having dimensions approximating sawdust or mill tailing
dimensions. The wood fiber sources of the invention can be blended
regardless of particle size and used to make the composite. The
fiber stream can be pre-sized to a preferred range or can be sized
after blending. Further, the fiber can be pre-pelletized before use
in composite manufacture.
[0022] Such sawdust material can contain substantial proportions of
waste stream by-products. Such by-products include waste polyvinyl
chloride or other polymer materials that have been used as coating,
cladding or envelope on wooden members; recycled structural members
made from thermoplastic materials; polymeric materials from
coatings; adhesive components in the form of hot melt adhesives,
solvent based adhesives, powdered adhesives, etc.; paints including
water based paints, alkyd paints, epoxy paints, etc.;
preservatives, anti-fungal agents, anti-bacterial agents,
insecticides, etc., and other waste streams common in the
manufacture of wooden doors and windows. The total waste stream
content of the wood fiber materials is commonly less than 25 wt-%
of the total wood fiber input into the polyvinyl chloride wood
fiber product. Of the total waste recycle, approximately 10 wt-% of
that can comprise a vinyl polymer commonly polyvinyl chloride.
Commonly, the intentional recycle ranges from about 1 to about 25
wt-%, preferably about 2 to about 20 wt-%, most commonly from about
3 to about 15 wt-% of contaminants based on the sawdust.
Composition and Pellet Manufacture
[0023] In the manufacture of the composition and pellet of the
invention, the manufacture and procedure requires two important
steps. A first blending step and a second pelletizing step.
[0024] During the blending step, the polymer and wood fiber are
intimately mixed by high shear mixing components with recycled
material to form a polymer wood composite wherein the polymer
mixture comprises a continuous organic phase and the wood fiber
with the recycled materials forms a discontinuous phase suspended
or dispersed throughout the polymer phase. The manufacture of the
dispersed fiber phase within a continuous polymer phase requires
substantial mechanical input. Such input can be achieved using a
variety of mixing means including preferably extruder mechanisms
wherein the materials are mixed under conditions of high shear
until the appropriate degree of wetting and intimate contact is
achieved. After the materials are fully mixed, the moisture content
can be controlled at a moisture removal station. The heated
composite is exposed to atmospheric pressure or reduced pressure at
elevated temperature for a sufficient period of time to remove
moisture resulting in a final moisture content of about 8 wt-% or
less. Lastly, the polymer fiber is aligned and extruded into a
useful form.
[0025] The preferred equipment for mixing and extruding the
composition and wood pellet of the invention is an industrial
extruder device. Such extruders can be obtained from a variety of
manufacturers including Cincinnati Millicron, etc.
[0026] The materials feed to the extruder can comprise from about
30 to 50 wt-% of sawdust including recycled impurity along with
from about 50 to 70 wt-% of polyvinyl chloride polymer
compositions. Preferably, about 35 to 45 wt-% wood fiber or sawdust
is combined with 65 to 55 wt-% polyvinyl chloride homopolymer. The
polyvinyl chloride feed is commonly in a small particulate size
which can take the form of flake, pellet, powder, etc. Any polymer
form can be used such that the polymer can be dry mixed with the
sawdust to result in a substantially uniform pre-mix. The wood
fiber or sawdust input can be derived from a number of plant
locations including the sawdust resulting from rip or cross grain
sawing, milling of wood products or the intentional commuting or
fiber manufacture from waste wood scrap. Such materials can be used
directly from the operations resulting in the wood fiber by-product
or the by-products can be blended to form a blended product.
Further, any wood fiber material alone, or in combination with
other wood fiber materials, can be blended with waste stream
by-product from the manufacturer of wood windows as discussed
above. The wood fiber or sawdust can be combined with other fibers
and recycled in commonly available particulate handling
equipment.
[0027] Polymer and wood fiber are then dry blended in appropriate
proportions prior to introduction into blending equipment. Such
blending steps can occur in separate powder handling equipment or
the polymer fiber streams can be simultaneously introduced into the
mixing station at appropriate feed ratios to ensure appropriate
product composition.
[0028] In a preferred mode, the wood fiber is placed in a hopper,
controlled by weight or by volume, to meter the sawdust at a
desired volume while the polymer is introduced into a similar
hopper have a volumetric metering input system. The volumes are
adjusted to ensure that the composite material contains appropriate
proportions on a weight basis of polymer and wood fiber. The fibers
are introduced into a twin screw extrusion device. The extrusion
device has a mixing section, a transport section and melt section.
Each section has a desired heat profile resulting in a useful
product. The materials are introduced into the extruder at a rate
of about 600 to about 1000 pounds of material per hour and are
initially heated to a temperature of about 215-225.degree. C. In
the intake section, the stage is maintained at about 215.degree. C.
to 225.degree. C. In the mixing section, the temperature of the
twin screw mixing stage is staged beginning at a temperature of
about 205-215.degree. C. leading to a final temperature in the melt
section of about 195-205.degree. C. at spaced stages. Once the
material leaves the blending stage, it is introduced into a three
stage extruder with a temperature in the initial section of
185-195.degree. C. wherein the mixed thermoplastic stream is
divided into a number of cylindrical streams through a head section
and extruded in a final zone of 195-200.degree. C. Such head
sections can contain a circular distribution (6-8" diameter) of 10
to 500 or more, preferably 20 to 250 orifices having a
cross-sectional shape leading to the production of a regular
cylindrical pellet. As the material is extruded from the head it is
cut with a double-ended knife blade at a rotational speed of about
100 to 400 rpm resulting in the desired pellet length.
[0029] The following examples were performed to further illustrate
the invention that is explained in detail above. The following
information illustrates the typical production conditions and
compositions and the tensile modulus of a structural member made
from the pellet. The following examples and data contain a best
mode.
EXAMPLE 1
[0030] A Cincinnati millicron extruder with an HP barrel,
Cincinnati pelletizer screws, an AEG K-20 pelletizing head with 260
holes, each hole having a diameter of about 0.0200 inches was used
to make the pellet. The input to the pelletizer comprised
approximately 60 wt-% polymer and 40 wt-% sawdust. The polymer
material comprises a thermoplastic mixture of approximately 100
parts of polyvinyl chloride homopolymer (in. weight of
88,000.+-.2000), about 15 parts titanium dioxide, about 2 parts
ethylene bis-stearamide wax lubricant, about 1.5 parts calcium
stearate, about 7.5 parts Rohm & Haas 820-T acrylic resin
impact modifier/process aid and about 2 parts of dimethyl tin
thioglycolate. The sawdust comprises a wood fiber particle
containing about 5 wt-% recycled polyvinyl chloride having a
composition substantially identical to that recited above.
[0031] The initial melt temperature in the extruder was maintained
between 350.degree. C. and 400.degree. C. The pelletizer was
operated at a polar vinyl chloride-sawdust composite combined
through put of 800 pounds per hour. In the initial extruder feed
zone, the barrel temperature was maintained between 215-225.degree.
C. In the intake zone, the barrel was maintained at 215-225.degree.
C., in the compression zone the temperature was maintained at
between 205-215.degree. C. and in the melt zone the temperature was
maintained at 195-205.degree. C. The die was divided into three
zones, the first zone at 185-195.degree. C., the second die zone at
185-195.degree. C. and in the final die zone at 195-205.degree. C.
The pelletizing head was operated at a setting providing 100 to 300
rpm resulting in a pellet with a diameter of 5 mm and a length as
shown in the following Table.
1TABLE I PELLETIZER RESULTS Pelletizer Pellet Profile Sawdust
Pellet Pellet Bulk Profile Tensile PVC/Wood Melt Length Melt
Profile Moisture Moisture Density Density Modulus Fiber (Temp.
.degree. F.) (in.) (Temp. .degree. F.) Visc. (%) (%) (g/cc) (g/cc)
(psi) 60/40 0.233 366 2580 4.71, 4.83 0.96 0.546 (.006) 1.426
990600 365 2755 1 60/40 0.233 362 2452 4.71, 4.83 0.96 0.546 (.006)
70/30 375 0.080 375 2274 5.28 1.54 0.454 (.007) 1.43 733300 70/30
375 0.080 376 2299 5.28 1.54 0.454 (.007) 1.435 820100 50/50 372
0.084 382 2327 4.94 1.95 0.347 (.002) 1.367 697600 70/30 374 0.195
385 2431 0.93 0.595 (.005) 1.427 752900 70/30 374 0.195 378 2559
0.93 0.595 (.005) 1.433 787600 60/40 375 0.089 377 1985 5.36 1.33
0.418 (.003) 1.423 1103000 60/40 375 0.089 374 2699 5.36 1.33 0.418
(.003) 1.408 815800 50/50 374 0.201 367 2541 5.33 2.09 0.462 (.004)
50/50 364 0.201 366 2670 5.33 2.09 0.462 (.004) 1.397 724300 60/40
351 0.247 374 1948 4.62 1.03 0.466 (.009) 1.426 860000 60/40 351
0.247 370 2326 4.62 1.03 0.466 (.009) 1.433 996700 60/40 361 0.103
373 1605 5.53 1.57 0.387 (.005) 1.431 985400 60/40 361 0.103 381
2221 5.53 1.57 0.387 (.005) 1.435 855800 70/30 364 0.202 376 1837
5.25 1.50 0.429 (.010) 1.433 868300 70/30 364 0.202 378 2376 5.25
1.50 0.429 (.010) 1.434 798100 70/30 367 0.085 374 1593 1.48 0.378
(.002) 1.438 744200 70/30 367 0.085 375 2145 1.48 0.378 (.002)
1.439 765000 50/50 367 0.177 371 2393 5.08, 5.51 1.61 0.434 (.007)
1.408 889200 50/50 367 0.177 371 3008 5.08, 5.51 1.61 0.434 (.007)
1.528 1029000 50/50 366 0.085 370 2666 2.01 0.438 (.003) 1.405
922100 50/50 366 0.085 369 2257 2.01 0.438 (.003) 1.383 922600
[0032] In Table I, the composite material is made from a polyvinyl
chloride known as GEON 427 obtained from B.F. Goodrich Company. The
wood fiber is sawdust by-product of milling soft woods in the
manufacture of wood windows at Andersen Corporation, Bayport, Minn.
The modulus for neat polyvinyl chloride measured similarly to the
composite materials is about 430,000. The Youngs modulus is
measured using an Instron Model 450S (Series 9 software) automated
materials testing system and uses an ASTM method D-638. Specimens
are milled to specifications of the test and are measured at 50%
relative humidity, 73.degree. F. with a cross set speed of 0.200
in./min.
[0033] Table II contains tensile modulus results from composite
materials made using injection molding technology. The Table shows
a substantial increase in tensile modulus when compared to
non-composite PVC.
[0034] We have found that the preferred pellet of the invention
displays, in a formed structural member, a Youngs modulus of at
least 500,000 and commonly falls in the range greater than about
800,000, preferably between 800,000 and 2.0.times.10.sup.6.
Further, the coefficient of thermal expansion of the material is
well matched to a compromising between aluminum, PVC and wood
products and ranges from about 1.6 to 1.8.times.10.sup.-5 inches
per inch-fahrenheit degree. We believe that the superior properties
of the structural members made from the composite or pellet of the
invention are in large part due to the nature of the pellet set
forth in the Table above. We believe the Table clearly shows that
the polyvinyl chloride and wood fiber can be combined at various
proportions under a variety of temperature conditions to produce a
regular pellet. The pellet then can be used in further extrusion
processes to form a useful extruded structural member useful in the
manufacture of environmentally sensitive windows and doors. The
composite is a superior replacement for wood because it has similar
mechanical properties but attains a dimensional stability and
resistance to rot, and insect damage not attainable by wood
products.
2TABLE II Injection Molded Samples Tensile Modulus Standard
Deviation Description psi psi High Melt/ 1,205,000 242,400 Large
Pellet/40% PVC 488,800 28,370 High Melt/ 1,232,000 133,300 Small
Pellet/40%
[0035]
3 Small 1 Large 1 Small 3 Large 3 Lg. Pellet Lg. Pellet Small 2
Large 2 Sm. Pellet Sm. Pellet Pellet 40% 40% PVC PVC 40% 40% STD.
CYCLE.sub.1 30.0 30.0 30.0 sec. 30.0 sec. 30.0 sec. 30.0 sec. Inj.
Fast Time -- -- -- -- -- -- Inj. Boost Time 2.5 3.0 2.5 3.0 3.0 3.0
Fill Time 1.0 to 1.2 to 1.2 1.6 1.2 1.6 1.2 1.5 Inj. Mold Time 12.0
12.0 12.0 12.0 12.0 12.0 Mold Closed Time 25.0 25.0 25.0 25.0 25.0
25.0 Mold Open Time 0.5 0.5 0.5 0.5 0.5 0.5 Inj. Fast Pressure --
-- -- -- -- -- Inj. Boost Pressures 1800 psi 1850 psi 1300 psi 1350
psi 1600 psi 1700 psi Inj. Mold Pressure 800 psi 800 psi 1000 psi
1000 psi 1000 psi 1000 psi Back Pressure 30 lbs. 30 lbs. 30 lbs. 30
lbs. 30 lbs. 30 lbs. Inj. Speed w/o w/o w/o w/o w/o w/o Fast Fast
Fast Fast Fast Fast Screw Speed Slow Slow Slow Slow Slow Slow Feed
1 1/2" 2" 1 1/2" 2" 1 1/2" 2" Cushion 1/2" 1/2" 1/2" 1/2" 1/2" 1/2"
Decompress Off Off Off Off Off Off Front Zone 340.degree. F.
340.degree. F. 340.degree. F. 340.degree. F. 340.degree. F.
340.degree. F. Rear Zone 330 330 330 330 330 330 Melt Temp. 360 to
360 to 360 to 360 to 360 to 360 to 370 370 370 370 370 370 Nozzle
Radius 1/2" Nozzle Orifice Same as Mold Core Seq. None -- -- -- --
-- E. J. Stroke Max. -- -- -- -- -- K. O. Bar Length The Backs Std.
-- -- -- -- -- K. O. Stud Length 5/8" -- -- -- -- -- Mold Open
Stroke 16" -- -- -- -- -- Multi Stroke 2 -- -- -- -- -- Die Slow To
Fast --Med. -- -- -- -- -- A-Side Water Tower Tower Tower Tower
Tower Tower Tower Water B-Side Water Tower Tower Tower Tower Tower
Tower Average 76* Pot Settings Full Open Auto Auto Auto Auto Auto
Auto
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