Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
1~249~:~0
This invention relates to silicate filled resin
composites made with additives which comprise chlorinated
aliphatic compounds. Inclusion of these additives can
enhance mechanical properties of the composites.
Coupling additives for certain inorganic filled
resin composites are known. For example, silane compounds
are employed in various silicate filled resin composites
for improving resin reinforcement by the silicate. Moreover,
certain chlorinated aliphatic compounds have been utilized in
resin systems to aid in fire retardancy.
It has been now discovered that certain chlorinated
aliphatic compounds act to improve silicate and polyolefin
resin adhesion especially when select melt times and
temperatures are used during processing.
Briefly, this invention concerns composites made
by a method which comprises melting a blend comprising
silane-free silicate filler, polyolefin resin and a minor
amount by weight of the combined weight of the silicate
filler and resin of an additive which comprises one or
more chlorinated aliphatic compounds with a molecular
weight in the range of about 250 to 10,000 and containing
from about 5 to 80~ chlorine by weight and maintaining
the blend as a melt for a time and at a temperature
sufficient to improve the strength of the composite.
A level of 1 to 36 parts by weight silicate filler
for each 9 parts by weight polyolefin resin provides com-
posites of particularly useful properties, whereas a weight
ratio of the filler to resin of about 2:5 - 5:2 normally
provides an optimum balance for silicates as mica flakes
and a weight ratio of about 1:10 - 4:10 being advantageous
for silicate as glass fibers. Preferred silicate is mica,
especially mica flakes.
-- 2
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Polyolefin resins suitable for this invention include
well known, commercially available materials designed for use in
moulding (as by injection, compression, etc.) and other melt
forming processes (as extrusion, stamping, etc.~. Of these
commercial resins, those made from monomers comprising olefinic
hydrocarbons such as ethylene, propylene and butene-l can provide
composites with excellent properties as well as economic advantage.
Particularly suitable in this regard are resins comprising
polyethylene or polypropylene or copolymers of ethylene and/or
propylene as well as blends of any of these. As used herein,
polyolefin resin means any of the above identified resins that
are typically melt formed and are made from monomers comprising
olefinic monomers, particularly monomers that are alphatic hydro-
carbon monomers and preferably predominantly by weight l-olefins
hydrocarbons such as ethylene, propylene, butene-l and 4-methyl-
pentene-l. Such polyolefin resins preferably comprise a major
portion of the resins in the composite (e.g., 60% by weight or
more).
Upon melting, the polyolefin resin wets the surfaces
of the silicate filler in the blends. Through some as yet undefined
mechanism it is believed that the wetting and bonding is
enhanced when the additives of this invention are included in
the blends.
Propylene resins are especially benefited by this
invention, particularly those with intrinsic viscosities of
above 1.5 and preferably about 2.0 - 2.6 for processing expedience,
although those with higher intrinsic viscosities may also be
suitably employed. The propylene resins may comprise propylene
homopolymer or propylene copolymer or mixtures thereof, such
copolymers normally comprising at least about 75 mole percent
propylene and up to 25 mole percent of other monomers
such as ethylene and butene-l. The preferred propylene resins
~12~3~
comprise propylene homopolymer or copolymer normally made
with stereospecific catalysts. Desirably, these propylene
resins are in flake or powder form and pass through a 20
mesh screen, more preferably a 60 mesh screen, and, although
currently available propylene resins are substantially re-
tained on a 325 mesh screen, even smaller sizes may be used
in this invention. Ethylene resins such as polyethylene
homopolymer or ethylene copolymers made with other aliphatic
olefin hydrocarbons as propylene, butene-l and hexene-l are
also particularly desirable.
Silicate fillers are commercially available. Among
the commonly used silicate fillers, especially suitable here-
in, are synthetic glass fibers and natural mica as well as
other naturally occurring minerals as talc. These silicate
fillers generally comprise silicon, oxygen and one or more
metals, e.g., Mg, Al, Na. Fillers having certain shapes
as glass flakes, fibers and mica flakes offer advantage in
providing increased structural integrity to polyolefin resin
composites and such composites can receive particular benefits
in accordance with this invention. For example, glass fibers
with high length to diameter ratios, e.g. 30:1 or higher
as well as flakes with at least such aspect ratios are
desirable for highest strength composites. Other silicate
fillers include magnesium silicate, calcium silicates,
wollastonite, attapulgite, silicate clays as well as others
as are disclosed in U.S. patent 3,951,680. Silicate
fillers are preferred which do not contain forms of asbestos.
It is advantageous that the silicate filler as mica
may be free of substantial chemical surface treatment for use in
this invention. For one reason, the additives of this invention
~l~4s~a
typically have low cost and can eliminate or reduce the need for
more expensive surface treatments as with silane compounds.
Moreover, it is desirable that there is minimum interference with
the operation of the additive on the silicate surface and the
polyolefin resin.
Mica fillers can be generally characterized as being
derived from aluminum silicate minerals which can be cleaved into
thin sheets. Commercially available fillers which comprise
principally muscovite, biotite and/or phlogopite micas (e.g.,
Suzorite Mica marketed by Marietta Resources International) are
preferred with mica fillers comprising principally phlogopite
mica being currently more preferred. Mixtures of micas as wel~l
as with other silicate fillers can also be employed.
Mica flakes, especially those comprising principally
phlogopite mica, having an aspect ratio (mean diameter to thick-
ness) of at least about 30 (more preferably at least about 60
so as to minimize breakage effects during processing) and up to
200 or higher are preferably employed. Mica flakes which are
retained on a 100 mesh screen, more preferably on a 60 mesh
screen, are normally more desirable, but mica which passes
through a 325 mesh can also be employed. Mica flakes which
substantially pass through a 20 mesh screen are advantageous
for processing expedience. Generally, glass flakes and fibers
of such dimensions are especially useful herein. Although various
means of preparing highly delaminated mica flakes are employed
in the mineral industry, those not employing wet grinding are
preferred. Especially preferred are those dry delamination
processes in which ore containing in part the various forms of
mica is excavated and crushed into lumps for transportation ease.
These lumps are further reduced in size by hammer milling in order
to free the boxes (or single crystals of mica) from other mineral
impurities.
11;i~4930
In such preferred dry processes, the crystals are
typically delaminated between counter rotating drums which exert
high shearing forces. The degree of delamination, hence the
aspect ratio of the resulting mica flakes, is dependent upon
the clearances set between the counter rotating drums. The
delaminated flakes are then separated from other mineral
impurities by vibration and/or air classification techniques
with the purified mica still further classified according to
particle size via conventional screening processes.
When prepared in this manner the mica surfaces are
r~latively free from large amounts of adsorbed species (such as
moisture from water grinding) which may cause interference to
the additives described in this invention.
The additive which strengthens the silicate filler as
mica and polyolefin resin adhesion is employed in minor amounts
(e.g., 0.05 - 10%, but preferably between about 0.5-5%) by weight
of the combined weight of silicate filler and polyolefin resin,
sufficient to strengthen the composite. Often a sufficient amount
of the additive also is less than the amount of silicate filler
as measured by weight. For example, resinous chlorinated waxes are
normally used at less than about 3% by weight of the total weight
of silicate filler and polyolefin resin. ASTM (D-790) Flexural-
Yield Strength is a convenient measure of the strengthening of the
composite. Other evidence of the strengthening may be seen in,
for example, enhanced tensile strength, fluxural modulus and heat
deflection temperature as well as reduction of mold shrinkage.
The chlorinated aliphatic compounds preferred in this
invention have a molecular weight (number average) in a range
of about 500 - 10,000 (more preferably about 800 - 5,000) and
a chlorine content of from about 5 - 80% by weight.
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High levels (e.g., about 60 - 80%~ be weight chlorine
are desirable for chlorinated saturated hydrocarbons such as
chlorinated paraffin waxes. Lower levels (e.g., about 5 - 50~)
of chlorine by weight are especially suitable, if there is
additional polarity (e.g., carboxyl groups) or unsaturation in
the chlorinated aliphatic compounds. Lower molecular weight
e.g. 250 can be used especially when there is a high level of
chlorine by weight.
Examples of additives comprising chlorinated aliphatic
compounds include chlorinated hydrocarbons such as resinous
chlorinated paraffin waxes (e.g. those marketed as Chlorowax
Diamond Shamrock , Kloro-chek [Keil Chemical, a division of
Ferro Chemical3 and Chlorez [Dover Chemical, a division of ICC]).
Resinous chlorinated waxes with molecular weights of about 800 -
1200 are preferred, as, for example, Chlorowax 70.
In one preferred method of making composites of thisinvention, particulate tpowder, flake) polyolefin resin, silicate
flakes (e.g. mica) or fibers and a powdered additive comprising
chlorinated aliphatic compounds are admixed by tumbling (preferably
non-intensive) followed by extrusion compounding of the blend with
vacuum venting. The extrusion compounder is fitted at the end
with a heated pipe which lengthens the time the passing melt is
exposed to a high temperature. For propylene resin, silicate
filler comprising, for example, phlogopite mica, and resinous
chlorinated paraffin waxes, a total time elapsed after melting
(i.e., melt residence time) of about 5 - 10 minutes at about
190 - 210C is preferred before melt is cooled. Subsequent
heating, as by annealing and drying may also be used to
contribute to this residence time. The melt can be shaped
thereafter by molding but other fabrication techniques can be
employed.
1124~930
In another preferred method of making, the silicate
(e.g., mica) itself is first blended with the additive comprising
one or more chlorinated aliphatic compounds to preferably provide
a coating on the silicate particles (e.g. flakes as mica flakes
or fibers). Resinous chlorinated aliphatic hydrocarbons as, for
example, chlorinated paraffin wax is desirably melted (at up to
about 15% by weight, more preferably up to about 2% by weight
of the silicate) onto the silicate preferably at high temperature
(e.g. 150C) but desirably below that temperature which would
cause severe decomposition and deterioration of the strengthening
effect attributed to the additive. This melt coating is normally
conducted during gentle mixing of the silicate particles and the
additive to achieve uniformity of the coating and minimize breakage
of shaped particles. Preferably, the silicate filler as mica is
dried prior to melt coating with additive. Advantageously, the
melt coating can be accomplished in less than one hour, normally
less than 15 minutes depending on such factors as equipment
mixing, conditions and temperature. The coating of the silicate
has the advantage of providing potentially greater uniformity
for the blends as compared to mixing the ingredients separately.
The coated silicate is further compounded preferably by admixture
with the polyolefin resin to form a dry powder blend for furthe~
processing.
Temperatures between about 170-300C are typically
suitable during such above described preferred compoundings
with the polyolefin resin. Higher temperatures with this range,
e.g, 220C or higher, usually require shorter times for optimum
development of properties while lower temperature require longer
periods. Advantageously, the additives of this invention provide
stable subsequently produced mechanical properties at usual melt
~i24930
temperatures for long periods, e.g., 30 minutes or longer.
Normally it is desirable to allow a period between about one (1)
and 30 minutes at melt temperature, more desirably between about
5-15 minutes. Subsequent operations as shaping at melt conditions
can contribute to this melt residence time.
After compounding, the melt, preferably having resided
for an extended period at melt temperature, can be passed to
a cooling zone and thereafter cut (e.g., diced) into particles
suitable for shaping processes. Alternatively, the melt may be
passed directly into a shaping operation. Shaping, if done by
injection molding, is preferably preformed at about 3,000 - 9,000
psi at temperatures of about 190 - 210C into molds held at
about 30 - 70C.
Other shaping operations such as extrusion, compression
or blow molding or stamping and the like may be employed. Further,
shaping operations can be used to maintain a time and
temperature sufficient to strengthen the composite. Moreover,
rods, sheets, tubes and films also can be fabricated and receive
the benefits of this invention.
It is to be understood that blends of this invention may
include combinations of fillers such as mica with glass fibers or
talc as well as minor amounts of additives (e.g., stabil ze_s,
pigments, lubricants and the like) which are conventionaliy in-
cluded during processing of composites. For example, alkaline
earth oxides (e.g., MgO, CaO) may be included at up to about 5~
by weight of the composite weight and are advantageous to absorb
gases resulting from entrapped moisture or decomposition of the
additive generated during high temperature compounding or melt
forming processes.
The following examples are intended to illustrate this
invention and are not intended as limitingthereof as those
1124930
skilled in the art will appreciate that many modifications of
these examples can be made within the scope of this invention.
All parts are parts by weight, all temperatures are in degrees
centigrade and all tests are ASTM standards as noted, unless
specifically indicated otherwise.
Example 1
In this example, composites are formed into standard
ASTM specimens from formulations having varying levels and types
of polyolefin resin, silicate fillers, and chlorinated aliphatic
compounds.
The composites are prepared by dry blending (non-
intensive mixing) the resin (powder form), silicate filler and
additives comprising the chlorinated aliphatic compounds. There-
after, the powdery mixture is added to a reciprocating screw injec-
tion molding machine (Arburg 200U, 42 ton, 2 oz.), held at 200C
for times indicated by Talbe 2 and injected into the mold having
a temperature of 30C. Shot size setting is at 6.3.
The formulation of the composites prepared appear in
Table l.
Properties that are obtained from a first set of com-
posites appear in Table 2. The composites for ASTM testing in
this first set are made after first purging the molding machine
with lO shots of the individual formulations spaced one minute
apart followed by shots ta~en at intervals spaced by the time
as indicated in Table 2.
--10--
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1~243;~0
In Table 3, the effect of the additive is seen by
comparison of properties of composites made with and without
the additive of this invention. The formulation used in making
composites A and B in Table 3, below, corresponds to formula-
tion 4 of Table 1, except that the formulation of B does notinclude the additive of this invention. Chlorowax(R)70-LP is used
as the additive in A. The ASTM specimens having properties as
set forth in Table 3 are made as those above except that the
molding cycle is set for 10 minutes and the first ten specimens
are discarded to approximate a steady state condition. Sufficient
specimens are thereafter collected to perform the ASTM tests
in Table 3.
TABLE 3 - PHYSICAL PROPERTIES
Composite A B
- With Without
15 Physical Property UnitsAdditive Additive
TENSILE STRENGTH psi 5,600 4,100
ASTM-D638
FLEXURAL STRENGTH psi 10,250 7,200
ASTM-D790
FLEXURAL MODULUS psi1,127,000 850,000
ASTM-D790
IZOD IMPACT ft-lbs1.25 1.30
ASTM-D256
20 HEAT DEFL. TEMP F
ASTM-D648 @66 psi301 266
@264 psi272 210
MOLD SHRINKAGE in/in
ASTM-D955 length.002 .010
width.010 .007
thickness .020 .023
Example 2
In this example, composites are made from formulations
containing 30 parts by weight Hercules Pro-Fax 6523-PM propylene
'''b~
~124930
resin and 70 parts by weight muscovite mica flakes (K-100 English
Mica Co.) with and without 1 part by weight Chlorowax 70-LP
powder. The procedure of Example 1 is followed and ASTM speci-
mens are obtained at the time intervals indicated by Table 2.
The composites made with the additive of this invention
show an ASTM-D790 Flexural Yield Strength that is higher than
composites made without the additive.
Example 3
In this example, the formulations 3-8 of Example 1
are modified by the inclusion of 1 additional part by weight of
the individual chlorinated aliphatic compounds. Composites are
made and tested by a method similar to that described in Example
1 and likewise show the desirable strengths attained by inclus-
ion of the additive of this invention as compared to composites
without the additive.
Example 4
The formulation of number 4, Table 1 is compounded in an
extrusion compounder (2 inch Transfermix, manufactured by Sterling
Extruder Corp.) having a heated pipe extension (length 50 inches,
inner diameter 2.25 inches) fitted at the end. The compounder is
operated so that the passing melt has a residenoe of about 9
minutes at 200C during extrusion and passage through the heated
pipe. The melt is cooled and then diced into pellets. The
pellets are fed into an injection molder and molded into ASTM
specimens. These specimens are tested and show advantageous
properties as compared to ones which do not have the additive
of this invention and which are made in the same manner.
_xample 5
The formulation of number 4, Table 1 is modified by
14
the addition of 5 parts by weight of commercial glass fiber
(Owens-Corning, Fiberglass 885, 1/4 inch chopped strand, aspect
ratio of about 500 to 1). Processing is done as in Example 1
above. Higher Yield Strength values (ASTM D-790) are seen in
these composites which are molded into ASTM specimens as compared
to composites made in the same manner for like periods but with-
out the additive of this invention. At 20 minutes as in Table 2,
the composite of this invention has a Flexural Yield Strength of
11,000 whereas the one without additive has a value of 8,000.
Example 6
Two parts by weight of a resinous chlorinated paraffin
(Chlore 700 of Dover Chemical) is combined 98 parts by weight
Suzorite GPA mica (Marietta Resources) by gently mixing in a V-
shaped blender at room temperature for about 3 minutes. There
after, this admixture is heated up to about 150 with gentle mixing
continued whereupon a coating of the surface of the mica occurs
and the brassy color of the mica begins to turn to a dark
red gold. Small portions of the mica mixture are taken to see
if the coating is complete by seeing if the surface is still wetted
with water.
Mica coated in this manner with additive is used in
place of the mica and additive of Example 4 and compared with a
formulation containing no additive using the conditions of
Example 4. Improved properties are seen in composites made in
accordance with this invention.
Example 7
One part by weight of Chlorowax 70 (Diamond Shamrock) is
used to coat 40 parts by weight of mica (Suzorite GPA, Marietta
~12~193~
Resources) in two ways. In Sample (A), the mica is preheated to
200C for several minutes prior to addition of the Chlorowax
at that temperature. In Sample (B), the Chlorowax 70 is added at
room temperature prior to heating at 200C. The coated mica samples
are each allowed to cool, then separately blended with 60 parts
by weight of Hercules Profax 6501 PM polypropylene and injected
molded at 200C with an extended molding cycle. The following
properties are obtained with ASTM testing.
A B
Flexural 8500 psi (mean of 5) 7778 (mean of 5)
Strength 280 psi (std. deviation) 395 (std. deviation)
Flexural 1,013,346 psi (mean of 5) 1,087,952 (mean of 5)
Modulus 61,612 psi (std. devia- 57,271 (std. devia-
tion 57,271) tion)
Example 8
The procedure of example 6 is followed using glass
flakes (aspect ratio greater than 30) rather than mica. Composites
formed show desirable properties.
_ ample 9
The procedure of example l is repeated using specially
prepared "nascent" glass fibers having no surface treatment with
silane coupling agents. Composites are made according to pro-
cedure and ormula 11 of example l. Composites made with
the additive show improvement in mechanical strength over
similar composites made without the additive of this invention.
As previously mentioned, a preferred compounding technique
in accordance with this invention utilizes an extruder that prov-
ides extended periods at melt temperatures for development of
optimum mechanical properties of the composites. Basically, this
may be accomplished, if desired, by including a melt holding chamber
-16-
11~4930
between the gate and the die (or nozzle~ of an extruder or the
extruder portion of a more complex (i.e. injection, blow molding,
foam, sheet, etc.) system. Inclusion of this melt holding chamber
enables desired production rates to be maintained. The actual
dimensions, of course, of the chamber will be determined by the
relative output rate desired as well as physical space available.
In certain specialized instances, however, usual equipment such as
large shot size injection molding devices may be used to mold small
parts whereby the melt exists for longer than usual times so
that optimum properties develop.
Example 10
The procedure of example 6 is repeated using talc (Beaver
White 200 - United Sierra) in place of mica. The coated talc,
however, does not exhibit the color changes as does mica unless
the coating process is conducted at temperatures exceeding the
onset of thermal decomposition of the chlorinated hydrocarbon
coupling agent.
Increased Heat Deflection Temperature (ASTM-D648) is
noted in composites containing 40 parts of the above described
coated talc and 60 parts polypropylene homopolymer when the
composite is prepared with the compounding techniques in accordance
with example 4.
Example 11
Fiberized blast furnace slag (Mineral Fibers - Jim
Walter Corporation), a silicate fiber filler typically containing
over 40% SiO2, is washed with xylene to remove the noramally
present antidusting oils and is subsequently dried. Dry powdery
blends are formed of a composition of 40 parts mineral fiber, 60
parts polypropylene resin (Profax 6523-PM - Mercules, Inc.) and
2 parts of chlorinated hydrocarbon additive (Chlorez 700 - Dover
Chemical).
17-
9~0
When these powdery blends are directly injection molded
in accordance with example 1 as to increase the melt residence
time to 10 minutes, the resultant molded parts exhibit improved
flexural strength at yield when tested in accordance wi~h ASTM-
D790 (Flexural Properties of Plastics).
-17a-
.~s.
