U.S. patent application number 10/123757 was filed with the patent office on 2003-05-29 for composite compositions.
Invention is credited to Garft, James E., Heath, Richard B., Koller, Levante E..
Application Number | 20030100634 10/123757 |
Document ID | / |
Family ID | 23088963 |
Filed Date | 2003-05-29 |
United States Patent
Application |
20030100634 |
Kind Code |
A1 |
Heath, Richard B. ; et
al. |
May 29, 2003 |
Composite compositions
Abstract
Disclosed are composite compositions well suited for forming
shaped articles which comprise thermoplastic polymer, cellulose, a
coupling agent comprising anhydride moities, and a lubricant
comprising an alkyl ester of carboxylic acid. Preferably the
lubricant is substantially free of zinc stearate.
Inventors: |
Heath, Richard B.;
(Morristown, NJ) ; Garft, James E.; (Yardley,
PA) ; Koller, Levante E.; (Andover, NJ) |
Correspondence
Address: |
Synnestvedt & Lechner LLP
2600 Aramark Tower
1101 Market Street
Philadelphia
PA
19107-2950
US
|
Family ID: |
23088963 |
Appl. No.: |
10/123757 |
Filed: |
April 16, 2002 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60284131 |
Apr 16, 2001 |
|
|
|
Current U.S.
Class: |
524/35 |
Current CPC
Class: |
C08L 23/06 20130101;
C10M 111/02 20130101; C08L 2205/16 20130101; C10M 105/34 20130101;
C08L 101/00 20130101; C08L 51/06 20130101; C08L 97/02 20130101;
C08J 5/10 20130101; C10M 105/38 20130101; C08L 23/06 20130101; C08L
2666/24 20130101; C08L 101/00 20130101; C08L 2666/26 20130101 |
Class at
Publication: |
524/35 |
International
Class: |
C08J 003/00; C08L
001/00 |
Claims
What is claimed is:
1. A composition for forming shaped articles comprising: cellulosic
fiber; thermoplastic binder; a coupling agent containing maleic
anhydride or malieic anhydride functionality; and a lubricant
comprising alkyl ester of carboxylic acid.
2. The composition of claim 1 wherein said lubricant further
comprises carboxyamide wax.
3. The composition of claim 1 wherein said lubricant is
substantially free of free of zinc stearate.
4. The composition of claim 1 wherein said lubricant is
substantially free of free of metal stearate.
5. The composition of claim 1 wherein said lubricant is
substantially free of free of metal carboxylate.
6. A lubricant composition for a cellulose containing composite
comprising an alkyl ester and an amide wax in a weight ratio of
alkyl ester to amide wax of from about 30:1 to about 1:1.
7. The lubricant composition of claim 6 wherein said alkyl ester
and an amide wax are present in a weight ratio of from about 20:1
to about 2:1.
8. The lubricant composition of claim 6 wherein said alkyl ester
comprises a mixture of alkyl esters of the formula 1 below,
2wherein: R is independently hydrogen, or --C(O)R' and wherein at
least on of R is --C(O)R'; R' is hydrogen, an unsaturated or
saturated alkyl chain having from about 3 to about 18 carbon atoms,
or --C(O)--X--COOH; and X is a unsaturated or saturated alkyl chain
having from about 3 to about 18 carbon atoms.
9. A method of manufacturing an article comprising: providng a
composition for forming shaped articles comprising: cellulosic
fiber; thermoplastic binder; a coupling agent containing maleic
anhydride or malieic anhydride functionality; and a lubricant
comprising alkyl ester of carboxylic acid; and forming said
composition into a shaped article.
10. A composition for forming shaped articles comprising:
cellulose; thermoplastic binder; a coupling agent comprising an
organic polymer electrophilic functionality; and a lubricant.
11. The composition of claim 10 wherein said lubricant is
substantially free of free of metal carboxylate.
12. The composition of claim 10 wherein said lubricant does not
contain an antagonistic amount of metal carboxylate.
13. The composition of claim 12 wherein said lubricant comprises
alkyl ester of carboxylic acid.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is related to and claims the priority of
U.S. Provisional Application No. 60/284131, filed Apr. 16, 2001,
which is incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to composite compositions
comprising thermoplastic polymer and cellulosic fibers, to
lubricant/coupling agents for such composite compositions, and to
structural members and structures formed from such compositions.
The composites of the present invention are well-suited for use as
wood substitutes when formed into structural members.
BACKGROUND
[0003] Composite materials which comprise an organic resin and a
filler have been known and used for a number of years. For example,
there has been a need to find materials that exhibit the look and
feel of natural wood. One reason for this need relates to efforts
to conserve the limited supply of natural wood for construction
purposes from the world's forest. Another reason is that certain
composite materials can exhibit properties that are superior to
natural wood in certain respects. For example, it is possible to
formulate composite materials into synthetic wood that has enhanced
moisture resistance.
[0004] In addition to the general cost and difficulty associated
with wholesale use of wood products in construction, much of the
wood in general board fabrication is wasted material. A substantial
amount of sawdust is created together with pulp materials such as
branches or the like as the lumber producers endeavor to transform
a harvested tree into a collection of elongated boards and planks
for use in fabrication of structures. Attempts have thus been made
to manufacture products as substitutes for virgin wood utilizing
wood fiber or particles together with various binder materials.
Such products have become available and are generally known as
"fiber board" or "particle board." In addition, the use of wood
particles or fibers together with plastic binders have created
so-called plastic wood. As a result, cellulose and related
materials are highly desirable material for use in composites in
general, and in composites intended for use as wood substitutes in
particular.
[0005] One problem associated with manufacture and effectiveness of
such composite materials is the ability to strongly bind the
cellulosic fibers and the thermoplastic binder. Adhesion stability
between the filler and the resinous mixture has been recognized as
a source of degradation and failure of these materials for nearly
as long as such materials have been known. As reported in U.S. Pat.
No. 5,981,067, one solution to this problem involves enhancing
polymer-fiber compatibility, that is, the tendency of the polymer
and fiber to mix and/or adhere to one another. U.S. Pat. No.
5,120,776, which is incorporated herein by reference, teaches
cellulosic fibers pretreated with maleic or phthalic anhydride to
improve the bonding and dispersibility of the fiber in the polymer
matrix. Also of relevance in this regard is Maldas and Kokta,
"Surface modification of wood fibers using maleic anhydride and
isocyanate as coating components and their performance in
polystyrene composites", Journal Adhesion Science Technology, 1991,
pp. 1-14.
[0006] While maleic anhydride-based coupling agents have been
suggested for use in making composite materials, there has been a
decided absence of success in the use of such materials in
commercial applications.
[0007] Commercial applications of composite compositions frequently
involves the shaping of such compositions by molding, extrusion or
the like. In order for such operations to be practically effective
in a commercially competitive environment, it is necessary that
such processes be carried out at a relative high rate and with a
minimum of operational problems. Toward this end, the use of
additives in the composite composition to aid in the processing
thereof are practically essential. One commonly used processing aid
is a lubricant or release agent, which allows the effective
processing of such composites at commercially acceptable speeds.
Metal stearates, and in particular zinc stearate, are frequently
used in lubricant packages for composites involving thermoplastic
polymers and cellulosic filler. See for example U.S. Pat.
No.6,180,257 B1 (col., 2,11. 26-28).
SUMMARY OF THE INVENTION
[0008] The present invention has several aspects, including novel
lubricant compositions, novel composite compositions, novel
structural members and novel methods of manufacture. Each of these
aspects flows, at least in part, from the recognition by the
present inventors that certain lubricants, and in particular metal
carboxylate lubricants, such as metal stearates, can negatively
affect the performance of certain desirable coupling agents, and
the discovery that certain lubricants operate in a synergistic
manner with such coupling agents to produce unexpectedly superior
performance.
[0009] Applicants have discovered composite compositions well
suited for forming shaped articles, such composition comprising
polymer (preferably thermoplastic polymer), cellulose, a coupling
agent comprising carboxylic functionality (for example, anhydride
moieties), and a lubricant comprising electrophilic functionality
(for example alkyl ester of a carboxylic acid or a functional
derivative thereof). According to highly preferred embodiments, the
lubricant is free of an antagonistic amount of metal carboxylate,
such as metal stearate, and is even more preferably is
substantially free of metal carboxylate, such as metal stearate. As
used herein, the term antagonistic amount refers to an amount of
metal carboxylate which has a more than nominal negative impact on
the properties of the composite (especially the processing
properties, such as extrudeability) as compared to the same
composite without any such metal carboxylate.
[0010] The present invention also provides lubricant compositions
comprising an alkyl ester and an amide ester.
[0011] The methods of the present invention comprise forming a
composite of the present invention into a shaped article,
preferably by extruding the composite.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a cross-sectional, semi-schematic view of one
structural member in accordance with one embodiment of the present
invention.
[0013] FIG. 2 is a cross-sectional, semi-schematic view of one
structural member in accordance with another embodiment of the
present invention.
[0014] FIG. 3 is a cross-sectional, semi-schematic view of one
structural member in accordance with another embodiment of the
present invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0015] The invention is directed to composite compositions which
may be fabricated at high rates into shaped articles, and in
particular structural members, exhibiting desirable strength
properties. Generally, the composition preferably comprises from
about 10 to about 50 parts by weight of thermoplastic polymer, from
about 50 to about 90 parts by weight of cellulosic fiber, effective
amounts of a coupling agent and effective amounts of lubricant in
accordance with the present invention. As used herein, the term
effective amount refers to any amount which produces a noticeable,
and preferably a substantial, improvement in the corresponding
performance of the composition. With respect to coupling agents,
therefore, an effective amount of a coupling agent produces a
noticeable improvement in the compatibility of and/or adherence
between the thermoplastic an the cellulosic fiber, which will
typically although not exclusively be manifested in an improvement
in the tensile strength of the shaped article. With respect to
lubricant, an effective amount produces a noticeable improvement in
the processability of the composition, which will typically
although not exclusively be manifested in an improvement in the
speed and/or efficiency with which the composition can be
effectively formed, and preferably extruded, into a shaped
article.
[0016] According to certain preferred embodiments, the composite
composition preferably comprises from about 20 to about 40 parts by
weight, and even more preferably from about 25 to about 35 parts by
weight of thermoplastic polymer, from about 50 to about 80 parts by
weight, and even more preferably from about 50 to about 65 parts by
weight, of cellulosic fiber, from about 1 to about 5 parts by
weight of coupling agent, and from about 1 to about 5 parts by
weight of lubricant.
[0017] Preferred embodiments of the present compositions produce
shaped articles with unexpectedly improved performance properties
relative to prior art compositions. More particularly, preferred
composite compositions which include maleic anhydride-based
coupling agents and lubricating agent in accordance with the
present invention produce shaped articles with tensile strength
properties that exhibit a tensile strength which is at least about
25 relative percent, and even more preferably at least about 50
relative percent, greater than the same compositions containing
substantial amounts of the commonly used prior art lubricant zinc
stearate. The preferred composite compositions of the present
invention exhibit a tensile strength of at least about 2000 psi,
more preferably at least about 2500 psi, and even more preferably
3000 psi.
[0018] Another substantial and unexpected advantage of the present
invention, and particularly the present lubricant compositions, is
a cost advantage which derives from the improved processing
performance of the present lubricants. More particularly, the
present lubricants are more effective in enhancing the formability,
and particularly the extrudeability, of the composite compositions.
This improvement is illustrated by the fact that the present
compositions can be formed at substantially the same rate as those
compositions using prior art zinc stearate lubricants with a
lubricant loading that is no greater than about 90 relative
percent, and even more preferably no greater than about 75 relative
percent, of the loading required by the prior art to achieve the
same processing speed.
[0019] The Thermoplastic Polymer
[0020] It is contemplated that any substantially thermoplastic
polymer is adaptable for use in accordance with the present
invention. For example, it is contemplated that thermoplastic
polymer useful in the present compositions may include polyamides,
polyvinyl halides, polyesters, polyolefins, polyphenylene sulfides,
polyoxymethylenes, styrene polymers, and polycarbonates. Particular
preferred is polyolefin polymer.
[0021] The primary requirement for the substantially thermoplastic
polymeric material is that it retain sufficient thermoplastic
properties to permit melt blending with cellulosic fiber and permit
effective formation into shaped articles by extrusion or molding in
a thermoplastic process. It is thus contemplated that minor amounts
of thermosetting resins may be included in the present compositions
without sacrificing these essential properties. Both virgin and
recycled (waste) polymers can be used.
[0022] As used herein, the term polyolefin refers to homopolymers,
copolymers and modified polymers of unsaturated aliphatic
hydrocarbons. Among the preferred polyolefins, polyethylene and
polypropylene are most preferred. Especially preferred is high
density polyethylene (HDPE). For economic and environmental
reasons, regrinds of HDPE from bottles and film are preferred.
[0023] The Cellulose Fibers
[0024] The present compositions include filler that comprises
cellulose. The filler component may be comprised of reinforcing
(high aspect ratio) filler, non-reinforcing (low aspect ratio)
filler, and combinations of both reinforcing and non-reinforcing
filler. Aspect ratio is defined as the ratio of the length to the
effective diameter of the filler particle. High aspect ratio offers
an advantage, i.e., higher strength and modulus for the same level
of filler content. Inorganic fillers, such as glass fibres, carbon
fibres, talc, mica, kaolin, calcium carbonate and the like, may be
included as an optional supplement to the cellulose. In addition,
other organic fillers, including polymeric fiber, may also be
used.
[0025] The cellulose filler in accordance with the present
invention is particularly important and preferred because of its
low cost and for other reasons, such as light weight, ability to
maintain high aspect ratio after processing in high intensity
thermokinetic mixer and low abrasive properties (thus, extending
machine life). The cellulose may be derived from any source,
including wood/forest and agricultural by-products. The cellulose
fiber may include hard wood fiber, soft wood fiber, hemp, jute,
rice hulls, wheat straw, and combinations of two or more of these.
In ceratin embodiments, the cellulose preferably comprises high
aspect ratio fiber, such as are present in hard woods, in a
substantial proportion. However, such high aspect ration fibers are
generally more difficult to process and therefore may be less
desirable in embodiments in which processing speed and efficiency
are particularly important considerations.
[0026] The Coupling Agent
[0027] As used herein, the term coupling agent refers to a compound
or composition which tends to promote dispersion and/or
compatibilization of the cellulose particles and the thermoplastic
polymer. In general, compounds, including organic polymers, with
electrophilic functionality, and in particular carboxylic
functionality, have been found to be potentially effective for this
purpose, and it is contemplated that all such compounds are
adaptable for use in accordance with the present invention.
Preferred organic compounds include polymers with maleic anhydride
functionality.
[0028] It is contemplated that numerous compounds having maleic
anhydride functionality can be used in accordance with the present
invention in view of the teachings contained herein, and all such
compounds or combinations of compounds are within the scope of this
invention. In certain embodiments, functionalized polymers are
preferred, particularly maleated polyolefin polymers.
[0029] As those skilled in the art will appreciate from the
disclosure contained in the present application, the particular
properties and characteristics of functionalized polymers used in
accordance with the present invention can be varied widely to
accommodate the particular needs of numerous applications. In
general, however, applicants have found that it is frequently
desirable to select functionalized polymers which have a backbone
that corresponds generally to at least a portion of the
thermoplastic polymer of the composite. For example, in embodiments
of the present invention in which the thermoplastic polymer is
polyethylene, it may be preferred to utilize functionalized
polyethylene as the coupling agent. Similarly, for embodiments in
which the thermoplastic polymer comprises polypropylene, it may be
preferred to utilize functionalized polypropylene as the coupling
agent. Applicants have surprisingly discovered, however, a coupling
agent which is highly effective for use in connection with both
different polyolefin polymers, more preferably C.sub.2-C.sub.4
polyolefins, and even more preferably polyethylene and
polypropylene. For the embodiments of the present invention in
which it is desirable to have a coupling agent which can be used
with a high degree of effectiveness in a wide variety of composite
compositions, applicants have discovered that is preferred to
utilize a maleated polypropylene polymer, and particular
polypropylene having a molecular weight of from about 10,000 to
about 15,000 and about 1.5 to about 2.5 maleic anhydride
functionalities, on average, per polymer chain. More generally for
embodiments in which the thermoplastic polymer comprises
polyolefin, it is preferred that the coupling agent comprise
functionalized polyolefin, and preferably functionalized
polyethylene, functionalized polypropylene, and/or combinations of
functionalized polyethylene and functionailzed polypropylene having
a molecular weight of from about 10,000 to about 25,000 (and even
more preferably from about 10,000 to about 20,000) and about 0.6 to
about 3 maleic anhydride functionalites (and even more preferably
from about 0.8 to about 2.5), on average, per polymer chain. Such
functionalized polyolefins are available, for example, from
Honeywell International under trade designations A-C 1221, 597, 596
and 575. In additional, functionalized polyethylene and
polypropylene are disclosed in U.S. Pat. Nos. 3,882,1945, 4,404,312
and 5,001,197, each of which is incorporated herein by
reference.
[0030] It is contemplated that in certain embodiments it may be
preferred to use silane coupling agent(s) alone or in combination
with other preferred coupling agents. Of course other effective
coupling compounds not specifically mentioned herein, but which are
now known or become known to those skilled in the art, may also be
used in addition to, or in certain cases as substitutes for, the
preferred coupling agents described herein.
[0031] The Lubricant
[0032] The present compositions include an effective amount of a
lubricant or a lubricant package. In one embodiment, the lubricant
comprises alkyl ester. Particularly preferred are polyol esters
formed by the reaction of polyol (that is, polyhydroxyl compounds)
with one or more mono- or poly-basic carboxylic acid or carboxylic
acid functional groups.
[0033] Among the polyols are those represented by the general
formula R(OH).sub.n wherein R is any aliphatic or cyclo-aliphatic
hydrocarbyl group (preferably an alkyl) and n is at least 2. The
hydrocarbyl group may contain from about 2 to about 20 or more
carbon atoms, and the hydrocarbyl group may also contain
substituents such as chlorine, nitrogen and/or oxygen atoms. The
polyhydroxyl compounds generally may contain one or more
oxyalkylene groups and, thus, the polyhydroxyl compounds include
compounds such as polyetherpolyols. The number of carbon atoms
(i.e., carbon number, wherein the term carbon number as used
throughout this application refers to the total number of carbon
atoms in either the acid or alcohol as the case may be) and number
of hydroxy groups (i.e., hydroxyl number) contained in the
polyhydroxyl compound used to form the carboxylic esters may vary
over a wide range.
[0034] The following alcohols are particularly useful as polyols:
neopentyl glycol, trimethylolethane, trimethylolpropane,
trimethylolbutane, mono-pentaerythritol, technical grade
pentaerythritol, and di-pentaerythritol. The most preferred
alcohols are technical grade (e.g., approximately 88% mono-, 10%
di- and 1-2% tri-pentaerythritol) pentaerythritol,
monopentaerythritol, and di-pentaerythritol.
[0035] Preferred carboxylic acids include any C.sub.2 to C.sub.20
mono- and di-acids, including preferably adipic and stearic
acid.
[0036] Functional derivatives of carboxylic acids may also be used
to form the lubricating agent. For example, anhydrides of polybasic
acids can be used in place of the polybasic acids, when esters are
being formed. These include, for example, succinic anhydride,
glutaric anhydride, adipic anhydride, maleic anhydride, phthalic
anhydride, trimellitic anhydride, nadic anhydride, methyl nadic
anhydride, hexahydrophthalic anhydride, stearic anhydride and mixed
anhydrides of polybasic acids. Particularly preferred lubricating
compounds in accordance with the present invention are the complex
esters described in U.S. Pat. Nos, 4,487,874 and 5 6,069,195, each
of which is incorporated herein by reference.
[0037] The preferred alkyl ester of the present invention comprises
a mixture of alkyl esters of the formula 1 below, 1
[0038] wherein:
[0039] R is independently hydrogen, or --C(O)R' and wherein at
least on of R is --C(O)R';
[0040] R' is hydrogen, an unsaturated or saturated alkyl chain
having from about 3 to about 18 carbon atoms, or --C(O)--X--COOH;
and
[0041] X is a unsaturated or saturated alkyl chain, which may be
mono- or poly-valent, having from about 3 to about 18 carbon
atoms.
[0042] The alkyl ester preferably comprises pentaerythritol
adipate-stearate, which is a mixture of alkyl esters of formula 1
wherein about 14% of the organic moieties are --C(O)--X--COOH
moieties derived from adipic acid and about 71% of the organic
moieties are --C(O)R' moieties derived from stearic acid and its
associated acids (chiefly palmitic acid). Such material is sold
under the trade designation RL 710 by Honeywell International
Inc.
[0043] The lubricant packages in accordance with the present
invention also preferably include carboxyamide wax, and even more
preferably stearamide wax, as disclosed in U.S. Pat. No. 3,578,621,
which is incorporated herein by reference. Especially preferred is
ethylenebis stearamide ("EBS").
[0044] Although it is contemplated that the alkyl ester and the
amide wax may be used over a wide range of relative concentrations
in the lubricant package, it is preferred that the weight ratio
alkyl ester to amide wax is from about 30:1 to about 1:1, with 20:1
to about 2:1 being more preferred.
[0045] According to preferred embodiments, the lubricating package
contains no more than about 25% by weight of metal carboxylate,
even more preferably no more than 10% by weigh of metal
carboxylate, and most preferably is substantially free of metal
carboxylate. According to highly preferred embodiments, the
lubricating package contains no more than about 25% by weight of
zinc stearate, even more preferably no more than 10% by weigh of
zinc stearate, and most preferably is substantially free of zinc
stearate.
[0046] With respect to the composite composition, it is generally
preferred that the composite contains no more than 0.5% by weight
of metal carboxylate, and more preferably no more than 0.25% by
weigh of metal carboxylate. It is especially preferred that the
composite contains no more than 0.5% by weight of zinc stearate,
and more preferably no more than 0.25% by weigh of zinc
stearate.
[0047] According to certain embodiments, the lubricant comprises
hydrogenated castor oil.
[0048] Additive Packages
[0049] One aspect of the present invention involves additive
compositions useful in connection with the formation of composite
compositions having advantageous processing and end-use properties.
More particularly, the additive packages comprise a unique
combination of lubricating agents and/or coupling agents which are
effective at improving the processing characteristics of the
composite without detracting from, and in some cases enhancing, the
strength characteristics of the finished product.
[0050] In certain preferred embodiments, the additive is a
lubricating agent which contains less than an antagonistic amount
of metal carboxylate. Particularly preferred lubricants in
accordance with the present invention are substantially free of
metal carboxylate and comprises a major proportion by weight of
alkyl ester and/or hyrdrogenated Castor Oil, and a minor proportion
by weight of carboxyamide wax. In ceratin embodiments, the
lubricating package further comprises a minor proportion by weight
of polyolefin, preferably a polyethylene or polypropylend, and even
more preferably substantially linear polyethylene or polypropylene.
In certain preferred embodiments, the lubricating composition
comprises from about 80 parts by weight to about 97 parts by weight
of a compound selected from the group of alkyl esters, hydrogenated
castor oils, and combinations of two or more of these, from about 1
part to about 10 parts by weight of carboxyamide wax and from about
1 part to about 10 parts by weight of polyolefin.
[0051] Although it is contemplated that the lubricating packages of
the present invention can beneficially be used alone in certain
embodiments, it is generally preferred to provide an additive
package which includes a lubricant agent/package according to the
present invention in combination with a coupling agent/package in
accordance with the present invention. Furthermore, while it is
contemplated that these packages can be combined in a wide range of
relative proportions in accordance with the present invention, it
is generally preferred to provide an additive package having a
lubricant:coupling agent weight ratio of from about 1:1 to about
4:1, and even more preferably in certain embodiments of about
3:2.
[0052] The Structural Members
[0053] As indicated previously, the present compositions can be
used to form a wide variety of structural members, and all such
structural members are within the broad scope of the present
invention. Applicants have found, however, that the present methods
and compositions can be utilized to form structural members, and
particularly extruded structural members, that would otherwise be
exceptionally difficult to form and/or practically unfeasible from
an economic stand point because of high processing costs. More
specifically with respect to FIGS. 1-3, it can be seen that the
present invention includes structural members that are at once both
strong and lightweight. It will be appreciated by those skilled in
the art that such lightweight structural members would not have
been practically possible to manufacture by extrusion from prior
composite compositions because of the high cross-sectional area of
the structures. More particularly, the present composite
compositions have a unique combination of high-strength and high
lubricity that permit the extrusion of such high surface area
configurations under relatively higher rate, economical extrusion
conditions. Applicants believe that such structural members could
not have been produced in a commercially efficient and
cost-effective manner in accordance with prior art techniques.
[0054] The Methods
[0055] The present methods involve forming a shaped article
comprising the steps providing a composite composition in
accordance with the invention as described herein and forming said
composition into the desired shaped article. The composition can be
provided by combing the components in accordance with any of the
techniques well known in the art for combing components to form
homogeneous composite compositions, as disclosed in U.S. Pat.
Nos.3,943,079; 4,338,228; 5,886,066; and 5,997,784 each of which is
incorporated herein by reference.
[0056] The forming step can also comprise any of the techniques
well known in the art for forming homogeneous composites into
shaped articles, including injection molding and extruding, as
disclosed in the aforementioned patents. Forming by extrusion is
preferred.
COMPARATIVE EXAMPLE 1
[0057] The present comparative example does not necessarily
represent an item of prior art and may in fact be closer to the
present invention than the closest item of prior art. Nevertheless,
this example serves as a basis for illustrating the superior
performance of the present invention.
[0058] A composite composition is prepared by extrusion compounding
62 parts by weight ("pbw") of wood fiber, 33 pbw of HDPE, 2 pbw of
maleated polyethylene coupling agent, and 3 pbw of a lubricant
consisting essentially of EBS and zinc stearate in a 1:2 weight
ratio.
[0059] The composite composition is formed into a shaped article by
known methods under known conditions. The resultant article
exhibits a tensile strength of approximately 2000 psi.
EXAMPLE 1
[0060] A composite composition is prepared by extrusion compounding
62.8 parts by weight ("pbw") of wood fiber, 33 pbw of HDPE, 2 pbw
of maleated polyethylene coupling agent, and 2.2 pbw of a lubricant
consisting essentially of EBS, zinc stearate and pentaerythritol
adipate-stearate in a 1:1:20 weight ratio.
[0061] The composite composition is formed into a shaped article by
the same methods under the same conditions as in the comparative
example. The resultant article exhibits a tensile strength of
approximately 2900 psi, representing an improvement of 45% over the
comparative example.
EXAMPLE 2
[0062] A composite composition is prepared by extrusion compounding
62.75 parts by weight ("pbw") of wood fiber, 33 pbw of HDPE, 2 pbw
of maleated polyethylene coupling agent, and 2.25 pbw of a
lubricant consisting essentially of EBS and pentaerythritol
adipate-stearate in a 2.5:20 weight ratio.
[0063] The composite composition is formed into a shaped article by
the same methods under the same conditions as in the comparative
example. The resultant article exhibits a tensile strength of
approximately 3500 psi, representing an improvement of 75% over the
comparative example.
EXAMPLE 3
[0064] A composite composition is prepared by extrusion compounding
62.5 parts by weight ("pbw") of wood fiber, 33 pbw of HDPE, 2 pbw
of maleated polyethylene coupling agent, and 2.5 pbw of a lubricant
consisting essentially of pentaerythritol adipate-stearate.
[0065] The composite composition is formed into a shaped article by
the same methods under the same conditions as in the comparative
example. The resultant article exhibits a tensile strength of
approximately 3200 psi, representing an improvement of 60% over the
comparative example.
COMPARATIVE EXAMPLE 2
[0066] The present comparative example does not necessarily
represent an item of prior art and may in fact be closer to the
present invention than the closest item of prior art. Nevertheless,
this example serves as a basis for illustrating the superior
performance of the present invention.
[0067] A composite composition is prepared by extrusion compounding
60.5 parts by weight ("pbw") of wood fiber, 33 pbw of HDPE, 2 pbw
of maleated polyethylene coupling agent, and 4.5 pbw of a lubricant
consisting essentially of EBS and zinc stearate in a 1:2 weight
ratio.
[0068] The composite composition is formed into a shaped article by
known extrusion methods under known conditions.
EXAMPLE 4
[0069] A composite composition is prepared by extrusion compounding
62 parts by weight ("pbw") of wood fiber, 33 pbw of HDPE, 2 pbw of
maleated polyethylene coupling agent, and 3 pbw of a lubricant
consisting essentially of EBS and pentaerythritol adipate-stearate
in a 2.5:20 weight ratio.
[0070] The composite composition is formed into a shaped article by
the same methods under the same conditions as in the comparative
example 2. Despite using approximately 50 percent less on both a
weight and cost basis of lubricant than comparative example 2, the
forming operation proceeds at least as efficiently as and at at
least about the same production rate as in comparative example
2.
* * * * *