Note: Descriptions are shown in the official language in which they were submitted.
CA 02435129 2003-07-11
1
CELLULOSE FILLED THERMOPLASTIC COMPOSITES
Field of the Invention
The present invention relates to cellulose filled thermoplastic composites,
for use
in structural and non-structural applications.
Background of the Invention
Composite materials comprising a mixture of a cellulose filler and a granular
olefin series thermoplastic material are molded by compression molding,
rotational
molding, extrusion molding or injection molding, anÃi such a composite
material
products are widely used in a variety of structural applications, such as in
parts, panels,
beams, boards and sheets. Mechanical properties, such as flexural properties,
tensile
properties and impact strength, of such composite materials are important
considerations for their use in structural applications. There is a
coritinuing need in the
art to improve the mechanical properties of such composites. Additionally,
there is a
continuing need in the art to improve the service ternperature, fire
resistance and
biological resistance of such composites.
United States Patent 6,066,278 discloses a composite material composed of a
wood cellulose filler and an olefin series plastic having a rigidity improving
agent
consisting of propylene modified by maleic anhydride and a carefully
calculated amount
of calcium oxide so that the water of the wood cellulose filler becomes
finally 2-5% by
weight. Since humidity varies from one location to another, the niethod
disclosed in
this patent is difficult as the correct humidity of the wood is not always
easy to
determine. This patent also teaches that the use of CaO requires surface
treatment of
the CaO.
CA 02435129 2003-07-11
2
Summary of the Invention
According to an aspect of the invention, there is provided a thermoplastic
composite comprising: a polyolefin; a cellulosic filler; a carboxylic acid
and/or carboxylic
acid anhydride graft polyolefin having an acid number greater than 15 mgKOH/g;
and, a
basic reactive filler present in an amount of 5-25 wt%,, based on the weight
of the
composite.
According to another aspect of the invention, there is provided an article of
manufacture comprising a thermoplastic composite of the present invention.
According to yet another aspect of the invention, there is provided a method
for
producing a thermoplastic composite, the method comprising: blending a
polyolefin, a
cellulosic filler, a carboxylic acid and/or carboxylic acid ainhydride graft
polyolefin having
an acid number greater than 15 mgKOH/g and 5-25 wt% based on the weight of the
composite of a basic reactive filler to form a blend; and, nnolding the blend.
It has been surprisingly found that the combination of about 5-25 wt% basic
reactive filler with a carboxylic acid and/or carboxylic ;acid anhydride graft
polyolefin
having an acid number greater than about 15 mgKOH/g in cellulose filled
thermoplastic
composites of the present invention leads to enhanced performance of the
composite in
comparison to cellulose filled thermoplastic composites of the prior art, for
example, the
composites described in US Patent 6,066,278. The composites of the present
invention
also lead to enhanced heat deflection temperature, fire resistance, and/or
resistance to
biological degradation (e.g. insects, decay, termites, etc.). Furthermore, it
has been
surprisingly found that the amount of basic reactive filler usable in
composites of the
present invention is less dependent on humidity levels in the cellulosic
filler, unlike in
prior art composites such as those disclosed in Uniteci States Patent
6,066,278. In
addition, composites of the present invention exhibit improved flexural,
strength and/or
impact properties over composites of the prior art. Also, a wider variety of
basic
CA 02435129 2003-07-11
3
reactive fillers may be used in composites of the present invention than are
usable in
composites of the prior art. Also, the basic reactive filler does not require
surface
treatment before use.
Further features of the invention will be described or will become apparent in
the
course of the following detailed description.
Detailed Description
As used in the specification and the appended claims, the singular forms "a,"
itan"
and "the" include plural referents unless the context clearly dictates
otherwise.
Ranges may be expressed herein as from "about" or "approximately" one
particular value and/or to "about" or "approximately" another particular
value. When
such a range is expressed, another embodiment includes from the one particular
value
and/or to the other particular value. Similarly, when values are expressed as
approximations, by use of the antecedent "about," it will be understood that
the
particular value forms another embodiment.
The thermoplastic composite of the present invention comprises a polyolefin.
The polyolefin may be a singie polyolefin or a mixture of two or more
polyolefins. The
polyolefin may also be mixed with other types of thermoplastics and
elastomers. The
polyolefin acts as the matrix binder for the composite within which other
components
are dispersed. Polyolefins include, for example, polyethylenes (e.g., LDPE,
HDPE,
LLDPE, UHMWPE, XLPE, copolymers of ethylene with another monomer (e.g.,
ethylene-propylene copolymer)), polypropylene, polybutylene,
polymethylpentene, or
mixtures thereof. Polypropylene and high density polyethylene (HDPE) are of
particular
note. It is particularly noteworthy that recycled polyolefins may be used in
this
invention. The polyolefin component may be present in the composite in any
suitable
amount. For example, the polyolefin may be present iin an amount of about 20-
90%,
CA 02435129 2003-07-11
4
30-70% or 40-60%, all by weight based on the weight of the composite. There
should
be sufficient polyolefin present to act as an effective matrix binder for the
other
components of the composite.
The thermoplastic composite of the present invention comprises a cellulosic
filler.
The cellulosic filler acts as a reinforcement in the composite. Cellulosic
filler may be
obtained from any suitable source of cellulose. SomE: suitable sources of
cellulose
include, for example, wood sources (e.g, pulp, wood flour such as sawdust,
wood
shavings, etc. from softwood and/or hardwood), agricultural sources (e.g.
fruits, grain
crops, vegetables, hemp, grass, rice straw, etc.) and recycled paper,
cardboard, etc. Of
particular note are cellulosic fibers. The cellulosic filler may be of any
suitable size
distribution depending on the end use of the composite and the desired
properties of the
composite. A cellulosic filler can be used alone or mixed with different
cellulose
sources. Cellulosic filler having an average particle size of from about 0.1-
20 mm, more
particularly from about 0.1-5 mm are suitable. When the cellulosic filler is
fibrous, the
average particle size refers to the average length of the fiber. The
cellulosic filler may
be present in the composite in any suitable reinforcing amount. For example,
the
cellulosic filler may be present in an amount of about 30-80%, 30-60% or 35-
50%, all by
weight based on the weight of the composite.
The thermoplastic composite of the present invention comprises a carboxylic
acid
and/or carboxylic acid anhydride graft polyolefin having an acid number
greater than
about 15 mgKOH/g. The carboxylic acid and/or carboxylic acid anhydride graft
polyolefin is thought to act as a coupling agent to improve interaction
between the non-
polar hydrophobic polyolefin component and the hydrophilic cellulosic filler
component
to thereby improve the performance of the composite.
The polyolefin part of the graft polyolefin may be any suitable polyolefin as
discussed above for the polyolefin matrix component of' the composite. It is
generally
CA 02435129 2003-07-11
preferable that the polyolefin part of the graft polyolefin is as compatible
as possible with
the polyolefin matrix component of the composite. For example, when the
polyolefin
used in the graft polyolefin is the same as the polyolefin matrix component,
excellent
compatibility can be achieved.
5 Any suitable carboxylic acid and/or carboxylic acid anhydride may be
employed
in the graft polyolefin. Some suitable carboxylic acids include, for example,
acrylic acid,
maleic acid, tetrahydrophthaiic acid, fumaric acid, itaconic acid, nadic acid,
and
methylnadic acid. Some suitable anhydrides include, for example, maleic
anhydride,
tetrahydrophthalic anhydride, itaconic anhydride, nadic anhydride, and
methylnadic
anhydride. Maleic anhydride is of particular note.
As indicated previously, the graft polyolefin has an acid number greater than
about 15 mgKOH/g. Of particular note are graft polyolefins having an acid
number
greater than about 35 mgKOH/g or greater than about 40 mgKOH/g, more
particularly
from about 40-50 mgKOH/g. The graft polyolefin preferably has a molecular
weight
(Mn) of less than about 50,000 g/mol. Of particular note is a molecular weight
of less
than about 20,000 g/mol, or from about 1000-10,000 g/mol. Graft polyolefins
used in
the present invention have a low molecular weight and high grafting amount of
the
carboxylic acid and/or carboxylic acid anhydride, which is thought to improve
penetration of the graft polyolefin into the surface and pores of the
cellulosic filler
leading to improved interaction between the polyolefin matrix and the
cellulosic filler. A
single type of graft polyolefin or a mixture of two or more types of graft
polyolefin may
be used. Other coupling agents may be used in conjunction with the graft
polyolefin.
The graft polyolefin is present in the composite in any suitable amount to
impart
improved interaction between the polyolefin matrix and the cellulosic filler.
For example,
the graft polyolefin may be present in an amount up to about 5%, by weight
based on
CA 02435129 2003-07-11
6
the weight of the composite. Amounts of about 0.54 / or 1-3% by weight may be
mentioned in particular.
The thermoplastic composite of the present invenltion comprises a basic
reactive
filler present in an amount of about 5-25% by weight, based on the weight of
the
composite. The basic reactive filler may be used alone or mixed with other
types of
reactive or non-reactive fillers. More than one type of basic reactive filler
may be used
together. Any suitable basic reactive filler may be used in the composite. For
example,
some suitable basic reactive fillers are CaO, MgO, AI2 3, BaO, ZnO or mixtures
thereof.
It is thought that the basic reactive filler reacts with both the acid part of
the graft
polyolefin and acid-like components in the cellulosic filler to improve the
over all
properties of the composite without loss in impact strength. In addition, it
is thought that
the basic reactive filler reduces humidity in the cellulosic ifiller to
minimize degradation of
the composite. Unlike the prior art, surface treatment of the basic reactive
filler is not
required in order to use the basic reactive filler in fabrication of
composites of the
present invention. As indicated above, the basic reactive filler is present in
the
composite in an amount of about 5-25% by weight. An amount of about 8-20% by
weight may be particularly mentioned.
The thermoplastic composite of the present invention may further comprise
additional additives. Some examples of additives include secondary
reinforcements
(e.g. glass fibers, glass fiber/polyolefin composites, carbon nanotubes,
carbon whiskers,
layered clays, metal oxide nanotubes, etc.), lubricarits (e.g. stearic acid,
PTFE,
molybdenum disulphide, etc.), impact modifiers (e.g. eth)(iene-propylene
rubber (EPR)),
fillers (e.g. calcium carbonate, talc, carbon black, etc.), colorants,
pigments,
antioxidants, stabilizers, flame retardants, reheat aids, crystallization
aids, acetaidehyde
reducing compounds, recycling release aids, oxygen scavengers, plasticizers,
flexibilizers, nucleating agents, foaming agents, mold release agents, and the
like, or
their combinations.
CA 02435129 2007-11-30
. . ,
7
Secondary reinforcements, particularly synthetic reinforcements, are of
particular note since they improve mechanical properties, especially strength
and
impact resistance. Additives may be used in any suitable amount for the
purpose for which they are intended. Secondary reinforcements are typicaily
added in an amount of up to about 20% by weight. Lubricants are typicaily
added in an amount of up to about 4% by weight. Impact modifiers are typically
added in an amount of up to about 10% by weight. Filters are typically added
in
an amount of up to about 20% by weight.
The thermoplastic composite of the present invention may be produced by
any suitable compounding and molding techniques known in the art. A
discussion of such techniques may be found in the following three references:
Polymer Mixing, by C. Rauwendaat, (Carl Hanser Verlag, 1998); Mixing and
Compoundina of Polymers, by I. Manas-Zloczower and Z. Tadmor (Carl Hanser
Verlag, 1994); and Polymeric Materials Processing: Piastics. Elastomers and
Composites, by Jean-Michel Charrier (Carl Hanser Verlag, 1991). Such
techniques are well known to one skilled in the art and do not require
elaboration.
Outlined below are some examples of suitable techniques for forming
thermoplastic composites.
In extrusion/injection molding, the components of the thermoplastic
composite are dry-blended and extruded through a twin-screw extruder at an
elevated temperature to compound the components. The extruded blend is
injected at eievated temperature by an injection machine into a mold where the
composite is formed Into a desired article. In dry-blend injection, the
components of the thermoplastic composite are
dry-blended and fed directly into an injection machine which injects the dry
blend at elevated temperature into a mold where it is formed into a desired
article.
CA 02435129 2003-07-11
8
In compression molding, the components of the thermoplastic composite are dry-
blended and fed directly into a molding machine and molded at an elevated
temperature
under pressure to form a desired article.
The thermoplastic composite of the present invention may be used in a variety
of
applications, particularly in structural applications. For example, parts,
boards, panels,
hollow profiles, lumber and sheets of thermoplastic composite are usable in
the
construction industry for houses, office buildings and the like, in the
automotive industry
for car parts especially interior parts, etc.
Examples
Materials:
Table 1A provides information about the nature and source cof materials. Table
1 B provides the size distributions of fine spruce sawdust, spruce sawdust and
fir
sawdust. The designation MAgPP refers to maleic anhydride grafted
polypropylene.
The term CF refers to cellulosic filler.
Table 1A
Designation Description Source Notes
Polyolefins (PO):
PP reground and recycled Novoplas Injection grade; MI = 5
polypropylene (Quebec, Canada) g/min
PP1 recycled polypropylene Novoplas Injection grade; MI = 8
(Quebec, Canada) g/min
HDPE recycled high density Novoplas Extrusion grade; MI =
polyethylene (Quebec, Canada) 0.2 g/min
PP 6100 SM virgin polypropylene Montel Injection grade; MI =
1.2 g/rnin
CA 02435129 2007-11-30
9
Table 1A - continued
PP HMI virgin BASEL Injection grade; Mi =
homopolypropylene 35 g/min
Cellulosic fillers (CF):
CF1 fine spruce sawdust JER EnvironTech <2% relative humidity;
average particle size
of 0.5 mm
CF2 spruce sawdust JER EnvironTech <2% relative humidity;
average particle size
of 0.82 mm
CF3 spruce-fir saw dust JER EnvironTech <2% relative humidity;
average particle size
of 0.41 mm
CF4 spruce macro fiber JER EnvironTech <2% relative humidity;
-10 mm in length
CF5 fir shavings JER EnvironTech <2% relative humidity;
- 5 mm in length
CF6 spruce sawdust and fiber JER EnvironTech <2% relative humidity
and shavings
CF7 spruce fiber JER EnvironTech <2% relative humidity;
-0.5 mm in length
CF8 banana fiber JER EnvironTech Phillipines banana
CF9 spruce sawdust JER EnvironTech <2% relative humidity
CF10 wet spruce sawdust of JER EnvironTech 19% relative humidity
CF9
Graft polyolefin:
EpoleneT""- maleic anhydride (MA) Eastman AN=45; Mn=9,100;
43 (E43) grafted polypropylene Chemicals -3.81 wt% of MA
EpoleneTm- maleic anhydride (MA) Eastman AN=15; Mn=47,000;
3015 grafted polypropylene Chemicals -1.31 wt !o of MA
(E3015)
EpoleneTM- maleic anhydride (MA) Eastman AN=8; Mn=52,000;
3003 grafted polypropylene Chemicals -0.71 wt% of MA
(E3003)
CA 02435129 2003-07-11
Table 1A - continued
Basic reactive filler:
CaO(1) calcium oxide Labaratoire Mat 98% purity
CaO(2) Calcium oxide The C.P. Hall Max 92% CaO
Company
AI2 3 aluminum oxide Malakoff Industries -0.4-0.5 m in size
Other additives:
GF/PP long glass fiber-PP BayComp 50 wt% glass fiber;
pellet (10 mm long) secondary
reinforcement
CaCO3 calcium carbonate Genstar Camel cal; filler
SA stearic acid JT Baker Inc. lubricant
EPR ethylene-propylene DSM Sarlink 4190 impact modifier
rubber
5 Table 1 B
Type Average Particle Size (mm)
0.15 0.25 0.4 0.7 1.1 1.9
Fine spruce sawdust 7% 25% 26% 33% 9% 0%
Spruce sawdust 6% 9% 27% 42% 16% 0%
Spruce-fir sawdust 6% 3% 12% 23% 38% 18%
CA 02435129 2003-07-11
11
Compounding/Processing:
Cellulose filled thermoplastic composites were prepared by extrusion-
injection,
dry-blend injection or compression techniques. For dry-blend injection and
compression
techniques, a blend of polyolefin and graft polyoiefin may be made by
extrusion prior to
dry blending with the other components.
For extrusion-injection, extrusion was performed in a twin-screw extruder
Extrusion Spec W&P 30mm having L/D=40; speed='150-175 rprn; TmeX=1$5 C and
injection was performed using a BOYT"" 30A injection machine at T=200 C. In a
typical
extrusion/injection process, cellulose filler (e.g. spruce sawdust), basic
reactive filler
(e.g. CaO), polypropylene, maleic anhydride grafted polypropylene, and any
other
desired reinforcements or fillers were first dry-blended together before
extrusion through
the twin-screw extruder. The extrudate was then injected into a mold by the
injection
machine.
For dry-blend injection, injection was performed using a BOYT"" 30A injection
machine at T=200 C. In a typical dry-blend injection process, cellulose
filler (e.g.
spruce sawdust), basic reactive filler (e.g. CaO), polypropylene, maleic
anhydride
grafted polypropylene, and any other desired reinforcements or fillers were
first dry-
blended together before being injected into a mold by the injection machine.
For compression, molding was performed using a WabaschT"" machine at T=200
C, P=100 psi, t=5 min and then cooled to room temperature using air for 6
minutes and
water for 10 minutes. In a typical compression molding process, cellulose
filler (e.g.
spruce sawdust), basic reactive filler (e.g. CaO), polypropylene, maleic
anhydride
grafted polypropylene, and any other desired reinforcements or fillers were
first dry-
blended together before compression molding.
CA 02435129 2003-07-11
12
Characterization:
Tensile properties (ASTM D638) were measured using the dog bone type I test
at a test speed of 5 mm/min.
Flexural properties (ASTM D790) were measured using a bending test where
length was 12.5 mm, test speed was 1.3 mm/min and span was 48 mm.
Impact resistance (ASTM D256) was measure using an un-notched IZOD impact
test.
Samples were tested at ambient temperatures before and after conditioning in
water for different periods of time between 1 and 7 days.
Microstructural observations of the composites were made using a JEOL JSM-
61OOT"' scanning electron microscope (SEM). Observations of the dispersion
between
the cellulosic fiiler and the poiyoiefin matrix were made using a Leitz
DialuxTM 20 optical
polarised microscope (OM) and their interface using scanning electron
microscopy
(SEM).
Density measurements were made with a pycnometer AccuPycTM 1330. Water
absorption was determined by measuring the weight gain or loss after immersing
the
sample in water for I to 4 days. Interaction between the basic reactive filler
and the
graft polyolefin were studied by transmission infrared spectroscopy at room
temperature
(-25 C) on a Nicolet MagnaTM 860 Fourier transform instrument at a resolution
of 4 cm'.
Interaction between the basic reactive filler and the graft polyolefin were
studied
by transmission infrared spectroscopy at room temperature (-25 C) on a Nicolet
MagnaTM 860 Fourier transform instrument at a resolution of 4 cm-'.
CA 02435129 2003-07-11
13
Mechanical properties of the materials at high temperature were determined by
dynamical mechanical thermal analysis (DMTA) Lising a Rheometric Scientific
instrument. Samples were subjected under torsion mode at a frequency of 1 Hz
from -50
to 120 C.
Thermal stability of the composites was evaluated by SetaramTM TG 96 thermal
analysis system of Scientific & Industrial Equipment. Samples were heated
under argon
from 25 to 500 C at a heating rate of 10 C/min.
For estimating the flame retardency, samples were placed horizontally and one
edge of the sample was just exactly above the butane gas nozzle and the
distance from
the lower face of the sample was 20 mm from the nozzle head. Samples were
burned
from one end in ambient atmosphere and the burning length was determined at
each
time interval.
Results:
Table 2 provides the formulation for various composites studied. Amounts are
given in percentage by weight, based on the weight of the composite. Example
numbers
starting with the letter 'C' are comparative examples.
CA 02435129 2003-07-11
14
Table 2
Ex. Cellulosic Polyolefin Graft Basic Other
filler polyolefin reactive fiiler additive
C1 40% CF1 58% PP 2% E43
2 40% CF1 53% PP 2% E43 5% CaO
3 40% CF1 48% PP 2% E43 10% CaO
C4 40% CF1 53% PP 2% E43 5% EPR
C5 40% CF1 48% PP 2% E43 10% EPR
C6 40% CF1 53% PP 2% E43 5% CaCO3
7 40% CF3 53% PP 2% E43 5% AI203
8 40% CF3 48% PP 2% E43 10% A1203
9 40% CF3 48% PP 2% E43 5% CaO
40% CF3 43% PP 2% E43 10% CaO
C11 40% CF3 58% PP 2% E3015
C12 40% CF3 53% PP 2% E3015 5% CaO
C13 40% CF3 48% PP 2% E3015 10% CaO
C14 40% CF1 58% PP 2% E3003
C15 40% CFI 43% PP 2% E3003 10% CaO 5% EPR
16 40% CF9 58% PP1 2% E43
17 40 lo CF9 48% PP1 2% E43 10% CaO
18 40% CF9 48 l PP1 2% E43 5% CaO 5% GF/PP
C19 30 fo CF8 68% PP 6100 SM 2% E43
40% CF9 48% PP 6100 SM 2% E43 10% CaO
C21 40% CF9 48% PP HMI 2% E43
22 40% CF9 48% PP HMI 2% E43 10% CaO
23 40% CF10 48% PP HMI 2% E43 10% CaO
CA 02435129 2003-07-11
Table 3 provides the results of various parameters characterized for each
composite.
Table 3
Ex. Tensile Properties Flexural Properties Impact
Young Stress Strain at Elastic Stress Strain Impact
Modulus (MPa) Break Modulus (MPa) (%) Resistance
(MPa) (%) (MPa) (kJlm2)
C 1 4180 34 2.2 2036 50 4.8 8.9
2 5100 34 1.9 2420 52.1 4.1 9.8
3 5511 37.8 1.7 4243 68.3 2.7 10.6
C4 4297 30.5 2.6 1921 46.5 5 10.2
C5 3662 28.5 3.3 1834 44.5 5.4 11.2
C6 4654 35.2 2.1 2368 54.5 4.3 10.1
7 4275 33.2 3.4 3460 58.1 3.2 11.2
8 4220 33.3 3.6 3397 57.9 3.2 11.1
9 4933 35.6 3.1 3914 61.2 2.8 10.2
10 5157 35.6 2.6 4252 62.5 2.6 10.4
C 11 3476 35.2 7.7 2482 62 5.4 15.67
C12 4164 33.9 4.1 3210 59.3 3.6 13.0
C13 4611 32.7 2.6 3752 58.1 2.9 10.1
C14 3591 30.4 4.2 2664 57.7 4.4 11.03
C15 4027 27.8 2.8 2967 51.4 3.4 8.85
16 3288 24.1 3.5 2580 44.3 3.5 7.6
17 4305 28.8 2.2 3432 52.0 2.7 4.5
18 4361 30.6 2.8 3657 54.3 2.9 10.0
C19 3372 23.9 3.7 2202 41.7 6.1
4627 34.2 2.3 3806 61.6 2.7 5.9
CA 02435129 2003-07-11
16
Table 3 - continued
C21 2619 24.9 3.0 2021 45.9
22 2923 25.2 2.3 2635 45.4
23 2903 23.5 3.1 2161 43.1
With reference to Tables 2 and 3, comparing example Cl to examples 2 and 3
illustrates that cellulose filled thermoplastic composites of the present
invention (ex. 2
and 3) have significantly improved mechanical properties over a similar
comparative
composite (ex. Cl), the comparative composite not having a basic reactive
filler (e.g.
CaO). Furthermore, the level of improvement provided by composites of the
present
invention is superior when compared with the results reported in U.S. patent
6,066,278.
Comparing examples 2 and 3 to comparative examples C4, C5 and C6, it is also
evident that the use of a basic reactive filler (e.g. CaO) provides
significant improvement
in tensile and flexural properties than the use of an impact modifier (e.g.
EPR) or a
simple filler (e.g. CaCO3) in a similar composite.
As evidenced by examples 7 and 8, the use of A1203 as the basic reactive
filler
provides significant improvement in flexural properties and impact resistance
of the
composite. Although the level of improvement to flexural properties and impact
resistance is not as high as with CaO, the use of A1203 provides more
improvement in
tensile strain at break than CaO. Thus, the use of CaO or A1203 will depend on
the
specific application to which the composite will be put.
Similar results have been obtained using different cellulosic fillers and
recycled
polypropylenes, for example, as evidenced by examples 3, 9, C13, C15, 17 and
19.
CA 02435129 2003-07-11
17
Referring to examples 9 and 10, it is evident that increasing the amount of
CaO
from 5 wt% to 10 wt% results in no reduction in mechanical properties (except
for
tensile strain at break), but rather results in a great improvement in
mechanical
properties. Additionally, even when the amount of CaO is 15 wt%, there is no
reduction
in such mechanical properties. This is in contradiction to the teachings of
U.S.
6,066,278, which teaches that the amount of CaO needs to be controlled
carefully and
kept small or there will be a reduction in the mechanical properties of the
composite.
Comparative examples C11, C12 and C13 illustrate that the presence of CaO in
a composite comprising E3015 (acid number < 35 mgKOH/g) provides significant
improvement to mechanicai properties when CaO is 5 wt%, but that the
improvement
becomes negligible as the amount of CaO is increased beyond 5 wt%. This
illustrates
that the balance between the amount of basic reactive filler in the composite
and the
acid number of the graft polyolefin is an important consideration in respect
of
improvements to the mechanicai properties of the cellulose filled
thermoplastic
composite.
The importance of balance between the amount of basic reactive filler and acid
number of the graft polyolefin is further illustrated by examples C14 and C15
in which
E3003 was used. E3003 has an even smaller acid number than E3015. While there
is
a small improvement in modulus with the addition of CaO, there is a
significant
reduction in both strength and impact resistance at all levels of CaO in the
composite.
Example 17 illustrates that similar improvements to mechanical properties in
accordance with the present invention can be obtained using another type of
recycled
polypropylene. In addition, exampie 18 ifiustrates that the addition of glass
fiber can
further increase the mechanical properties, especially the strength and impact
resistance.
CA 02435129 2003-07-11
18
The effect of the type of polypropylene used was also considered. Virgin
polypropylene leads to higher mechanical properties compared to recycled
polypropylene as illustrated by examples 17 and 20.
For a virgin PP with very high melt index and low performance, similar
improvement in the mechanical properties when CaO is used have also been
obtained
(example C21 as compared to example 22). Example 23 had the same type of
components and formulation as example 22, except that example 22 was made
using
dried wood (<2% relative humidity) while the example 23 used wet wood (about
19%
relative humidity). As indicated in Table 3, the mechanical properties of
example 23 are
poorer compared than those of example 22. Thus, while the composites of the
present
invention are less dependent on the humidity of the cellulose filler than
prior art
composites, extreme amounts of humidity in the cellulose filler can lead to
some
degradation in mechanical properties of the composite.
Table 4 demonstrates that the composites of the present invention also have
improved mechanical properties at higher temperatures, allowing for a higher
service
temperature for the composites.
Table 4
Example -20 C 0 C 20 C 50 C 100 C
22 G' (Pa) 2.65e+09 1.88e+09 1.42e+09 8.34e+08 3.36e+08
G" (Pa) 9.40e+07 1.03e+08 5.94e+07 5.70e+07 2.76e+07
23 G' (Pa) 2.18e+09 1.45e+09 1.05e+-09 6.12e+08 2.59e+08
G" (Pa) 8.25e+07 9.41 e+07 5.23e+07 4.42e+07 1.94e+07
Table 5 demonstrates that the composites of the present invention are more
resistant to thermal degradation, as reflected by the higher temperatures at a
weight
CA 02435129 2003-07-11
19
loss of 10 wt !o (T1ooio) and 20 wt% (T20%) and the weight loss at 500 C as
measured by
TGA.
Table 5
Example Thermal properties
Tjo% ( C) Tlo%( C) Weight loss at 500 C (wt%)
C21 334 364 91
22 346 398 73
Table 6 demonstrates that the composites of the present invention are more
resistant to burning. The burning rate of example 22 at 1 min (LI) and 5 min
(L5) is
smaller than that of example C21. Even though the burning test used is not a
standard
test, it qualitatively demonstrates the flame retardancy of the composites.
Table 6
Example L, (mm) L5 (mm)
C21 12 65
22 7 36
Table 7 provides the results of water absorption tests on various cellulose
filled
thermoplastic composites. Amounts in the composition are given in weight
percent
based on the weight of the composite. Example numbers starting with the letter
`C' are
comparative examples. The designation 'clay' refers to a layered clay
reinforcement
while `clayexf' refers to the same clay exfoliated. The clay used was
CloisiteTM 15A
from Southern Clay Products.
CA 02435129 2003-07-11
Table 7
Ex. Composition Water Absorption ( !o)
24 h in water 24 h in water, 24 h in air 7 days in water
C100 40% CF1 0.6 0.35 1.85
60% PP
C101 40% CF1 0.4 0.25 0.95
56% PP
2% E43
2% SA
C102 40% CF1 0.35 0.2 0.9
58% PP
2% E43
103 40% CFI 0.55 0.25 1.25
53% PP
2% E43
5% CaO
104 40% CF1 0.55 0.3 1.45
48% PP
2% E43
10% CaO
C105 40% CFI 0.45 0.2 1.0
53% PP
2% E43
5% clay
C106 40% CF1 0.4 0.25 0.95
53% PP
2% E43
5% clayexf
CA 02435129 2003-07-11
21
It is evident from Table 7 that even though a basic reactive filler such as
CaO is
present in the composite in amounts as high as 10 wt%, the extent of water
absorption
can be kept low, which is in contradiction to the teachings of U.S. patent
6,066,278.
Furthermore, the mechanical properties of the composite of examples 103 and
104
remained unchanged even after conditioning in water up to 7 days.
FTIR studies confirmed that a chemical reaction had taken place between the
maleic anhydride group of E43 and the basic reactive filler (CaO or A1203)
during
extrusion of the cellulose filled thermoplastic composites.
Other advantages which are inherent to the invention are obvious to one
skilled
in the art.
It will be understood that certain features and sub-combinations are of
utility and
may be employed without reference to other features and sub-combinations. This
is
contemplated by and is within the scope of the claims.
Since many possible embodiments may be rriade of the invention without
departing from the scope thereof, it is to be understood that all matter
herein set forth or
shown in the accompanying drawings is to be interpreted as illustrative and
not in a
limiting sense.
Having described the invention, what is claimed is:
