U.S. patent number RE31,992 [Application Number 06/556,170] was granted by the patent office on 1985-09-24 for reinforcement promoters for filled thermoplastic polymers.
This patent grant is currently assigned to Union Carbide Corporation. Invention is credited to Fred H. Ancker, Arnold C. Ashcraft, Jr., Audrey Y. Ku, Martin S. Leung.
United States Patent |
RE31,992 |
Ancker , et al. |
September 24, 1985 |
Reinforcement promoters for filled thermoplastic polymers
Abstract
A reinforced, filled thermoplastic polymer composition, having
increased strength and ductility, contains a reinforcement promoter
having at least two reactive olefinic double bonds and a positive
promoter index, based on the double bond resonance and polarity,
and the promoter adsorptivity.
Inventors: |
Ancker; Fred H. (Warren
Township, Union County, NJ), Ashcraft, Jr.; Arnold C.
(Hightstown, NJ), Leung; Martin S. (Manhattan Beach, CA),
Ku; Audrey Y. (Chesterfield, MO) |
Assignee: |
Union Carbide Corporation
(Danbury, CT)
|
Family
ID: |
26969345 |
Appl.
No.: |
06/556,170 |
Filed: |
November 29, 1983 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
295811 |
Aug 27, 1981 |
04385136 |
May 24, 1983 |
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Current U.S.
Class: |
523/202; 523/200;
523/215; 523/216; 523/351; 524/425; 524/430; 524/431; 524/432;
524/444; 524/447; 524/449; 524/451; 524/493; 524/497 |
Current CPC
Class: |
C08K
9/04 (20130101) |
Current International
Class: |
C08K
9/04 (20060101); C08K 9/00 (20060101); C08K
003/22 (); C08K 003/26 (); C08K 003/34 (); C08K
009/04 () |
Field of
Search: |
;523/201,215,216,351,200,202
;524/425,430,432,431,437,445,451,493,496,497 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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55-110138 |
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Aug 1980 |
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JP |
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55-133438 |
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Oct 1980 |
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JP |
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Other References
E M. Danenberg et al., Journal of Polymer Science, vol. 31, pp.
127-153, 195. .
E. G. Howard et al., "Ultrahigh Molecular Weight Polyethylene
Composites: A New Dimension in Filled Plastics", Preprint of
National Tech. Conference of Society of Plastic Engineers, Oct.
1976, pp. 36-38. .
Hausglein et al., Applied Polymer Symposia, No. 11, pp. 119-134,
1969. .
Hawthorne et al., Journal of Macromolecular Science, Part A,
Chemistry, vol. (3) pp. 659-671, 1974. .
"Silane Coupling Agents in Mineral Filled Composites", Brochure
F-43598A, Union Carbide Corp., Feb. 1979. .
C. D. Han et al., Polymer Engineering and Science, vol. 19, No. 11,
pp. 849-854, 1978. .
D. E. Cope, Reprint No. 24-E presented at 1979 Annual Technical
Conference of Reinforced Plastics Composites Institute (Society of
the Plastics Industry). .
de Souza et al., "Low-Cost Highly Filled Impact Resistant
Thermoplastic Composites", pp. 492-496 of Preprints from Annual
Technical Conference of the Society Plastics Engineers. .
F. H. Ancker et al., entitled "A Coated Asbestos with Better
Coupling", Plastics Engineering, pp. 32-36, Jul. 1974. .
Newman et al., "Mica Composites of Improved Strength", Polymer
Composites, vol. 1, pp. 37-43, Sep. 1980..
|
Primary Examiner: Lieberman; Allan M.
Attorney, Agent or Firm: Mauro; Jean B.
Claims
What is claimed is:
1. A polymer composition substantially free of a free radical
initiator or its residue comprising a thermoplastic polymer,
selected from the groups consisting .Iadd.of .Iaddend.normally
.[.of.]. solid hydrocarbon polymers, polyamides and polyvinyl
chlorides including the copolymers of the latter with vinyl acetate
and an inorganic filler having an average particle size <100
.mu.m wherein the improvement comprises providing about 0.1 to 5
weight % based on the weight of the total composition of a
reinforcement promoter having at least two reactive olefinic double
bonds, said promoter being characterized by having a promoter
index, P, being greater than zero, which is defined by the
formula:
wherein n is the number of olefinic double bonds in the promoter,
having .[.values .gtoreq..]. .Iadd.a value of at least .Iaddend.2,
Q and e are the Alfrey-Price resonance and polarity parameters,
respectively, of at least one of the olefinic double bonds in the
compound, wherein Q.[..gtoreq.2.]..Iadd.>0 .Iaddend.and
e.[..gtoreq.2 but <4,.]..Iadd.>0 .Iaddend.and
R.degree..sub.f, having .[.values.gtoreq.0 to .ltoreq..]. .Iadd.a
value <.Iaddend.0.5, is the relative flow ratio of the promoter
measured by thin layer chromatography on a neutral silica gel using
xylene as the eluant and di-n-butyl fumarate as the standard.
2. The composition of claim 1 wherein the thermoplastic polymer is
a hydrocarbon homopolymer or copolymer.
3. The composition of claim 2 wherein the hydrocarbon polymer is a
polyolefin homopolymer or copolymer, or a natural or synthetic
rubber.
4. The composition of claim 1 wherein the reinforcement promoter
has the structure: ##STR18## wherein R.sup.1 is an organic group
free of olefinic or acetylenic unsaturation having a valence of n;
R.sup.2, and R.sup.3 and R.sup.4 are hydrogen, carboxy or
monovalent organic groups free of olefinic or acetylenic
unsaturation; X is: ##STR19## m has a value of 0 or 1; and n has a
value of at least two.
5. The composition of claim 4 wherein the reinforcement promoter
has an .[.R'.]. .Iadd.R.sup.1 .Iaddend.or X group, for when m is 1
or 0, respectively, which contains a double or triple bond which is
in conjugation with the olefinic bond and which is electron
withdrawing.
6. The composition of claim 1 wherein the reinforcement promoter is
a condensation product of an acrylic or maleamic acid with an
aliphatic, aromatic or heterocyclic polyol; or an acrylamide,
maleimide or maleamic acid of an aliphatic, aromatic or
heterocyclic polyamine.
7. The composition of claim 6 wherein the reinforcement promoter
compound is an imide, maleate, acrylate, or acryloyl heterocyclic
compound.
8. The composition of claim 7 wherein the reinforcement promoter is
epoxidized linseed oil/acrylate,
1,3,5-triacryloylhexahydro-s-triazine, melamine triacrylate or
maleamic acid derivatives of methylene-aniline oligomers.
9. The composition of claim 1 wherein the inorganic filler is
aluminum trihydrate, clay, talc or calcium carbonate.
10. The composition of claim 1 wherein the reinforcement promoter
is present in an amount of from about 0.1 to 5.0 weight percent,
the filler is from about 10 to 90 weight percent and the
thermoplastic polymer is from about 10 to 90 weight percent, based
on the total weight of promoter, filler and polymer in the
composition.
11. A reinforced polymer composition substantially free of a free
radical initiator or its residue comprising a thermoplastic polymer
.Iadd.selected from the group consisting of normally solid
hydrocarbon polymers, polyamides and polyvinyl chlorides including
the copolymers of the latter with vinyl acetate .Iaddend.and an
inorganic filler .Iadd.having an average particle size <100
.mu.m .Iaddend.wherein the improvement comprises providing
.Iadd.about 0.1 to 5 weight % based on the weight of the total
composition of .Iaddend.a reinforcement promoter at the boundary
between the filler and polymer, for increasing the strength and
ductility of the filled thermoplastic polymer, wherein the promoter
has at least two reactive olefinic double bonds, and wherein said
promoter is characterized by having a promoter index, P, being
greater than zero, and which is defined by the formula:
wherein n is the number of olefinic bonds in the promoter,
.Iadd.having a value of at least 2, .Iaddend.Q and e are the
Alfrey-Price resonance and polarity parameters, respectively, for
at least one of the olefinic double bonds in the promoter,
.Iadd.wherein Q>0 and e>0, .Iaddend.and R.sub.f
.degree..Iadd., having a value <0.5, .Iaddend.is the relative
flow ratio of the promoter measured by thin layer chromatography on
a neutral silica gel using xylene as the eluant and di-n-butyl
fumarate as the standard.
12. A process for making a reinforced, filled polymeric composition
comprising:
(a) admixing a filler .Iadd.having an average particle size <100
.mu.m .Iaddend.with a reinforcement promoter having at least two
reactive olefinic double bonds, wherein said promoter is
characterized by having a promoter index, P, being greater than
zero, and which is defined by the formula:
wherein n is the number of olefinic double bonds in the promoter,
.Iadd.having a value of at least 2, .Iaddend.Q and e are the
Alfrey-Price resonance and polarity parameters, respectively, of at
least one of the olefinic double bonds in the promotor,
.Iadd.wherein Q>0 and e>0, .Iaddend.and R.sub.f .degree.,
.Iadd.having a value <0.5, .Iaddend.is the relative flow ratio
of the promotor measured by thin layer chromatography on a neutral
silica gel using xylene as the eluant and di-n-butyl fumarate as
the standard;
(b) compounding the filler and promoter mixture with a
thermoplastic polymer .Iadd.selected from the group consisting of
normally solid hydrocarbon polymers, polyamides and polyvinyl
chlorides including the copolymers of the latter with vinyl acetate
.Iaddend.for a time sufficient to generate a reinforced, filled
thermoplastic polymer having increased strength and ductility;
(c) wherein said admixing and compounding is carried out in the
substantial absence of any free radical initiator.
13. The process of claim 12 wherein the filler and promoter are
admixed simultaneously to the compounding with the thermoplastic
polymer.
14. The process of claim 12 wherein the reinforcement promoter is
formed in situ during mixing with the filler or during compounding
with the polymer.
15. The use of a reinforcement promoter in a filled thermoplastic
polymer.Iadd., selected from the group consisting of normally solid
hydrocarbon polymers, polyamides and polyvinyl chlorides including
the copolymers of the latter with vinyl acetate,
.Iaddend.composition substantially free of a free radical initiator
or its residue wherein the improvement comprises providing a
reinforcement promoter having at least two reactive olefinic double
bonds, said promoter being characterized by having a promoter
index, P, being greater than zero, and which is defined by the
formula:
wherein n is the number of olefinic double bonds in the promoter,
.Iadd.having a value of at least 2, .Iaddend.Q and e are the
Alfrey-Price resonance and polarity parameters, respectively, of at
least one of the olefinic double bonds in the promoter,
.Iadd.wherein Q>0 and e>0, .Iaddend.and R.sub.f
.degree..Iadd., having a value <0.5, .Iaddend.is the relative
flow ratio of the promoter measured by thin layer chromatography on
a neutral silica gel using xylene as the eluant and di-n-butyl
fumarate as the standard. .Iadd.
16. The composition of claim 1 wherein the Alfrey-Price resonance
parameter, Q, is .gtoreq.0.4..Iaddend. .Iadd.17. The composition of
claim 16 wherein the number of olefinic bonds, n, is at least 3 and
the relative flow ratio, R.degree..sub.f, is <0.05..Iaddend.
.Iadd.18. The composition of claim 11 wherein the Alfrey-Price
resonance parameter, Q, is .gtoreq.0.4..Iaddend. .Iadd.19. The
composition of claim 18 wherein the number of olefinic bonds, n, is
at least 3 and the relative flow ratio, R.degree..sub.f, is
<0.05..Iaddend. .Iadd.20. The process of claim 12 wherein the
Alfrey-Price resonance parameter, Q, is .gtoreq.0.4..Iaddend.
.Iadd.21. The process of claim 20 wherein the number of olefinic
bonds, n, is at least 3 and the relative flow ratio,
R.degree..sub.f, is <0.05..Iaddend. .Iadd.22. The process of
claim 15 wherein the Alfrey-Price resonance parameter, Q, is
.gtoreq.0.4..Iaddend. .Iadd.23. The process of claim 22 wherein the
number of olefinic bonds, n, is at least 3 and the relative flow
rate, R.degree..sub.f, is <0.05..Iaddend.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
This application is related to copending patent applications Ser.
No. .[.461,088.]. .Iadd.295,812 .Iaddend., entitled "Integral
Additives and Methods for Making Filled Thermoplastics" and Ser.
No. 295,813, .Iadd.now U.S. Pat. No. 4,409,342 .Iaddend.entitled
"Synergistic Reinforcement Promoter Systems for Filled Polymers"
both filed concurrently with this application.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a filled, thermoplastic polymer
composition containing a reinforcement promoter, and a method for
its production. The term "reinforcement promoter" refers to
chemicals which provide both improved tensile strength and
ductility when combined with a filled thermoplastic polymer.
2. Description of the Prior Art
A broad range of chemicals have been evaluated as filler treatments
or interfacial agents in filled polymers with and without the
addition of free radical initiators, such as peroxides.
Unfortunately, the literature terminology is usually ambiguous and
often erroneous. For example, the terms "coupling agent" or
"adhesion promoter", which imply that the additives increase the
adhesion or bonding between the filler particle and the surrounding
polymer matrix, are often used uncritically. Usually there is no
proof of any adhesion effect, and the particular additive may
function merely as a filler dispersing aid and, sometimes, as a
processing aid by reducing the viscosity of the molten, filled
composite. In many cases, the mechanical properties reported for
the filled polymers even imply that the additive facilitates
release of the matrix polymer from the filler particles, such that
the so-called coupling agent actually has a decoupling or debonding
effect.
The varied behavior of filler treatment additives in filled
polymers may be more clearly envisioned with the help of a
composite property chart such as that shown in the FIGURE. On this
chart, the abscissa or "x" axis represents the elongation at break
and the ordinate or "y" axis represents the maximum tensile
strength of a filled polymer. The chart presents the relative
strength and ductility of filled polymers for specific polymers
containing a specified filler loading, but which vary according to
the type of interfacial agent which is added to the composition.
The area near "A" represents these properties for a filled
composite without any interfacial agent added or where the
interfacial agent is ineffective for increasing tensile strength or
elongation at break. In general, for filler loadings in a range of
about 50 weight percent, the tensile strength and the elongation at
break will both be quite low, i.e., the filled composite is both
weak and brittle. Certain currently used interfacial agents and
filler treatments result in increases in tensile strength with
little or no increase in elongation such that although the
materials get stronger, they remain brittle. These composites are
grouped in the area from "A" to "B" and the interfacial agents
producing this effect will here be called coupling agents in the
strict sense of the word. Other commonly used additives result in
gains in elongation at break with little changes or even decreases
in tensile strength such that although such composites can become
more ductile, they remain weak, and are often best characterized as
"cheesy". These composites are grouped in the area from "A" to "C"
and the interfacial agents producing this effect will here be
termed decoupling agents. Clearly, the interfacial agents which
cause a filled polymer to become both strong and tough, i.e., which
causes improvements in both tensile strength and ductility, are by
far the commercially most attractive composites. These composites
would be grouped in the area from "A" to "D". However, not all
interfacial agents can be clearly defined as reinforcing, coupling,
decoupling or ineffective since, as can be seen from the FIGURE, no
sharp boundaries exist between the designated areas. This is
particularly evident for composites which exhibit only modest
increases in strength or elongation at break, i.e., which approach
area "A" in the FIGURE, or composites made with lower filler
loadings.
The dramatic mechanical property improvements attained in
vulcanized rubbers by melt compounding with carbon black and
certain silica and silicate fillers are well known--such that
without the use of these so-called reinforcing fillers the
commercial utility of many elastomers, especially the amorphous
rubbers, would be severly limited. Encouraged by the filler
.[.reinforcemnt.]. .Iadd.reinforcement .Iaddend.response in cured
rubbers, many attempts have been made to achieve similar effects in
other polymers, especially in thermoplastics. These efforts have to
date met with limited success and only for special filler/polymer
combinations. In particular, the polyolefins have been notably
unresponsive to reinforcement by particulate mineral fillers as
would be expected from the unreactive chemical structure of
polyolefins.
Early attempts at reinforcing polyethylene with carbon black
resulted in stiff, brittle composites of little commercial value.
However, it was found that by cross-linking a carbon
black/polyethylene blend either by ionizing radiation or by a free
radical initiator, such as peroxide, strong and tough thermoset
composites could be made. See E. M. Dannenberg et al., Journal of
Polymer Science, Volume 31, pages 127-153, 1958. Of course,,
cross-linking removes many desirable attributes of the
thermoplastic polyolefins such as the facility of using low-cost
thermoplastic molding methods, the post-forming ability, such as
vacuum and thermoforming, the ability to reprocess scrap and
rejects, and more, all of which has limited the commercial usage of
this discovery.
A second technically successful approach for reinforcing filled
thermoplastic polymers has been developed more recently and is
described in U.S. Pat. No. 4,187,210 (Howard, Jr.), issued Feb. 5,
1980. By this technique, an olefin polymerization catalyst is
deposited on the filler surface after which the polymer is formed
directly on each filler particle resulting in a filled polyolefin
composite, which is exceptionally strong and tough. This method has
proven useful in preparing filled composites from so-called
ultra-high molecular weight (UHMW) polyethylene, i.e., polyethylene
having such extreme melt viscosities that conventional melt
processing such as injection molding, extrusion, melting,
calendering, and the like, is not possible. In this case,
incorporation of a filler by melt compounding is not possible and
direct polymerization on the filler surface is thus the only
feasible alternative. The resulting filled UHMW polyethylene powder
may subsequently be formed by powder metallurgical processes such
as pressure sintering the powder, e.g., into a billet, followed by
forging, skiving, turning, etc. The properties attainable in such
composites have been discussed by E. G. Howard et al., in a talk
entitled "Ultrahigh Molecular Weight Polyethylene Composites: A New
Dimension in Filled Plastics", recorded on pages 36-38 of the
preprints of the October 1976 National Technical Conference of the
Society of Plastic Engineers. However, for reasons of logistics and
cost, it is commercially unattractive to use this technique for
polyolefins in the more conventional molecular weight ranges which
are capable of standard plastic processing. Hence, this technique
has also found limited commercial usage.
A third attempt at reinforcing filled thermoplastics related to
both of the above techniques was aimed at coating the filler
particles with a layer of cross-linked polymer as described in U.S.
Pat. No. 3,471,439 (Bixler et al.), issued Oct. 7, 1969. This was
attempted by adsorbing a broad variety of unsaturated organic
compounds onto the filler particles and then melt compounding the
treated filer with a polymer and a free radical initiator, such as
an organic peroxide, a percarbonate or an azo-compound. In contrast
to the present invention, the patent discloses that the use of a
free radical initiator is preferred and produces better results
than in the absence of a free radical initiator. Furthermore,
little distinction is made regarding the nature of possible
coupling or decoupling effects of the individual filler treatments.
This technique was subsequently replaced by an in-situ filler
coating method with direct polymerization on the filler particles
as described in U.S. Pat. No. 3,519,593 (Bolger), issued July 7,
1970. See also R. W. Hausslein and G. J. Fallick, Applied Polymer
Symposia, No. 11, pages 119-134, 1969. None of these efforts proved
commercially successful. In a similar vein, U.S. Pat. No. 3,956,230
(Gaylord), discloses the use of maleic anhydride plus a peroxide
free radical initiator as a coupling agent system for polyolefins
containing "hydroxyl containing fillers". The resulting composites
were not fully characterized in terms of possible coupling or
decoupling effects resulting from the use of the selected
additives. Some treated filler composites showed improvements in
ductility, i.e., elongation at break, and impact but no improvement
in, or actual decreases in, the tensile strength. In other cases
the reverse occurred and only in infrequent instances, such as
Examples 2, 6, 16, 17 and 29, were increases reported for both
ductility and strength.
The above techniques were further studied for kaolin-filled
polyethylene by D. G. Hawthorne and D. H. Solomon, in
"Reinforcement of Polyethylene by Surface-Modified Kaolins, "
Journal of Macromolecular Science: Part A, Chemistry, Volume 8 (3),
pages 659-671, 1974. The article lists the properties of various
polyethylene composites containing 20-40 weight percent kaolin
filler containing a variety of surface treatments, including some
based on the teachings of U.S. Pat. No. 3,471,439 (Bixler et al.).
Attempts were also made to develop more acceptable alternatives to
these polymer-encapsulated fillers. The data show no significant
increases in composite tensile strength, i.e., "breaking stress",
in the cases of treated kaolins as compared to those either
untreated or treated with nonreactive, i.e., "saturated", coatings.
Also, at the 40 weight percent filler loading, only one sample,
having a peroxy initiated pretreatment with a mixture of
2-methyl-5-vinyl-pyridine and diethylene glycol diacrylate, showed
a significant increase in elongation at break of from 13 percent to
24 percent.
A recent Japanese patent, Japan Kokai No. 55-110, 138 (Tanaka et
al.), which issued Aug. 25, 1980, describes the use of triacryloyl
hexahydro-s-triazine in combination with free radical initiators in
calcium carbonate filled polypropylene and high-density
polyethylene, and in talc filled polypropylene. Small amounts of
1,2 polybutadiene were added in two experiments. In this procedure,
the filler was first treated and heated with a mixture of the
unsaturated compound and a free radical initiator, such as
azo-bis-isobutyronitrile, and then melt compounded with the
polymer, preferably with the further addition of more initiator,
such as dicumyl peroxide. The injection molded specimens showed
generally good increases in impact strength and low to moderate
increases in tensile strength. No evaluations were reported without
the addition of the free radical initiators.
There are many disadvantages associated with the use of peroxide
initiated coupling systems in filled thermoplastics. Perhaps the
principal one is that of stability. For example, pretreatment of
the filler with the combination of a polymerizable monomer and a
free radical initiator can cause pre-polymerization on heating or
standing rendering the surface treatment ineffective at the time of
compounding the promoter with the polymer. Even when satisfactory
conditions for so-called integral blending have been established,
i.e., when the filler treatment chemicals can be dispersed directly
into the filler and the resin mixture at the time of melt
compounding, the resulting compounds often have highly variable
rheological properties during processing and highly variable
mechanical properties after molding or extrusion. This difficulty
in achieving reproducible results no doubt has contributed to the
general lack of success of peroxide initiated coupling systems in
commercial practice. Furthermore, the decomposition products of
organic peroxides are notoriously .[.odiferous.]. .Iadd.odoriferous
.Iaddend.and confer a characteristic, undesirable smell to the
final products similar to that well known from present peroxide
cured polyolefin products. Finally, the use of peroxide additives
adds to the cost and processing complexity in the manufacturing of
filled polyolefin compounds.
Organic silanes are presently the most widely used coupling agents.
These agents are used extensively as surface treatments for
fiberglass where they serve a number of diverse functions such as
protecting the glass fibers from water-induced stress corrosion,
from mechanical damage in handling and processing, by improving the
bonding of the fibers to various matrix polymers and by preserving
the composite strength upon exposure to water. The state-of-the-art
of silane treated mineral fillers in thermosetting and in
thermoplastic polymers is outlined in a brochure F-43598A by Union
Carbide Corporation published in February, 1979 and entitled,
"Silane Coupling Agents in Mineral-Filled Composites." The
principal commercial use to date of silanes in mineral-filled,
non-crosslinked polyolefins is to maintain good electrical
insulating properties after water exposure. The reinforcement
promoting effect of most silanes in polyolefins is relatively
modest for most mineral fillers. The high cost of silanes also
detracts from their use with low-cost commodity mineral
fillers.
The use of organic titanates as surface treatments for talc and
calcium carbonate in polyolefins has been reviewed by C. D. Han et
al., in Polymer Engineering and Science, Vol. 18, No. 11, pages
849-854, 1978. The titanates are reported to act as processing aids
and to increase the toughness and the elongation at break of the
composites. However, the tensile strength in the best cases is only
slightly increased and in most cases it is actually reduced. Hence,
referring to most titanates as coupling agents is a misnomer and
the disclosed compounds do not belong to the class referred to here
as reinforcement promoters.
Other materials such as fatty acids, i.e., stearic acid, fatty acid
salts, such as zinc or calcium stearate, various detergents, oils
and waxes are commonly employed as compounding ingredients or as
pretreatments for mineral fillers in polyolefins. Generally, their
effect is similar to that reported above for the titanates in that
they facilitate filler dispersion and processing and often increase
the elongation at break and sometimes the toughness. However, they
do not improve the composite strength and often they even reduce
the tensile properties relative to that of the filled polymer
without the additive. The state-of-the-art of "hydrophobic"
additives has recently been reviewed by D. E. Cope in reprint no.
24-E entitled, "Hydrophobic Filler Wetting-- A New Technique for
Improved Composite Performance and Production", from a talk
presented at the 1979 Annual Technical Conference of the Reinforced
Plastics/Composites Institute of the Society of the Plastics
Industry. Another typical example of a recently developed organic
filler treatment additive is described by de Souza et al. at pages
492-496 of the preprints from the 1979 Annual Technical Conference
of the Society of Plastics Engineers, entitled "Low-Cost Highly
Filled Impact Resistant Thermoplastics Composites". The article
discloses that the tensile strength of a CaCO.sub.3 -filled
polypropylene decreases rapidly with increasing concentration of
the filler treatment additive. Hence, these types of filler
treatment additives also are not reinforcement promoters as defined
herein.
Certain organic compounds are effective coupling agents in specific
filler/polyolefin composites. For example, 2,6-dimethylol 4-alkyl
phenols dramatically increase the tensile strength of chrysotile
asbestos/polyolefin composites up until enough coupling agent is
added corresponding to monomolecular coverage of the filler
surface. See the article by F. H. Ancker et al., entitled "A Coated
Asbestos with Better Coupling", Plastics Engineering, pages 32-36,
July 1974. However, these organic compounds are rather specific to
the brucite surface of chrysotile and they do not in general
provide significant property improvements with particulate mineral
fillers.
Certain simple organic chemicals, such as acrylic acid, have some
reinforcement promoting effect in isolated filler/polyolefin
composites such as aluminum trihydrate and CaCO.sub.3 -filled
polyethylene. However, acrylic acid has a high vapor pressure and
is quite noxious, both when used as a filler pretreatment or as an
integral blend additive during hot melt compounding, and is has
therefore not found wide-spread commercial use.
Chloroparaffins are effective coupling agents in mica-filled
polypropylene as described in S. Newman and F. J. Meyer in "Mica
Composites of Improved Strength", Polymer Composites, Volume 1,
pages 37-43, September 1980. While these compounds are true
coupling agents by the terms of this invention, they are not
reinforcement promoters because they do not simultaneously improve
tensile and impact strength. This was clearly recognized by the
authors, at page 41 of the above article, who stated: "The impact
behavior as measured by Izod impact values for the coupled systems
are generally lowered and appear to be dominated by the reduced
strain to yield and failure (ductility) of the matrix in the
coupled systems. Moreover, this effect is seen to override the
increased strength exhibited by these systems."
In summary, the state-of-the-art prior to the disclosure of the
present invention is that most so-called coupling agents for filled
thermoplastic polymers are not reinforcement promoters by the terms
of this invention, i.e., they do not at the same time improve the
strength and the ductility (elongation and toughness) of the filled
polymer. In instances where some reinforcement promotion has
occurred, it has been limited to the use of particular materials or
processes which are either costly, inefficient or noxious in use;
has been limited to highly select filler-polymer systems; has
required the simultaneous use of free-radical generating additives
with their associated problems of stability, odor generation, and
the like; or has possessed a combination of these detracting
features which have severely limited its commercial utility.
SUMMARY OF THE INVENTION
The present invention relates to a polymer composition, and process
for producing such compositions, substantially free of a free
radical initiator or its residue, which comprises a thermoplastic
polymer and an inorganic filler, wherein the improvement comprises
providing a reinforcement promoter which increases both the
strength and ductility of the filled thermoplastic polymer. The
reinforcement promoter has at least two reactive olefinic double
bonds and is characterized by having a promoter index, P, which is
greater than zero, and which is defined by the formula:
wherein n is the number of olefinic double bonds in the promoter, Q
and e are the Alfrey-Price resonance and polarity parameters,
respectively, of at least one of the olefinic double bonds in the
promoter, and R.sub.f .degree. is the relative flow ratio of the
promoter measured by thin layer chromatography on a neutral silica
gel usly xylene as the eluant and di-n-butyl fumarate as the
standard.
BRIEF DESCRIPTION OF THE DRAWING
The FIGURE is a diagram portraying the properties of an embodiment
of the present invention, as compared with properties of
embodiments as disclosed in the prior art.
DETAILED DESCRIPTION OF THE INVENTION
THERMOPLASTIC POLYMER
The invention relates to filled thermoplastic polymers whose
strength and ductility properties are improved by the addition of
certain reinforcement promoters. A preferred group of
thermoplastics responsive to the reinforcement promoters of this
invention are the normally solid hydrocarbon polymers comprising
the polyalkenes, such as the polymers and copolymers of ethylene,
propylene, butene, hexene, neohexene and 4-methyl pentene. These
polymers may further contain residual unsaturation enabling
subsequent curing or cross-linking as can be achieved, for example,
by co- or terpolymerization with diene monomers such as
norbornadiene. Included in the hydrocarbon polymers are the homo-
and copolymers of dienes such as polybutadiene and polyisoprene, as
well as the copolymers of butadiene and isoprene with styrene.
Another preferred group of thermoplastics responsive to the
reinforcement promoters of this invention is the group of
hydrocarbon polymers containing low to moderate amounts (<18
weight percent) of polar comonomers such as vinyl acetate and ethyl
acrylate. Also included among the responsive thermoplastic polymers
are the polyamides and polyvinyl chlorides, including the
copolymers of the latter with vinyl acetate.
Specifically preferred are the commercially available, normally
solid, grades of HDPE (high-density polyethylene), PP
(polypropylene), EPR and EPDM (ethylene/propylene rubbers),
polyisoprene, polybutadiene and polybutadiene/styrene polymers. A
most preferred thermoplastic polymer is high-density polyethylene
having a density of about 0.94 to about 0.96 and a melt index of
about 0.01 to about 20, preferably 0.05 to 10.
FILLER
The inorganic fillers that may be used in the compositions of the
present invention are finely divided inorganic materials of natural
or synthetic origin. The fillers may be particulates, platelets,
fibers or fibrils, they may be regular or irregular in shape, and
they may be amorphous or crystalline. Most of these fillers are
generally considered to be "inert" when used in the preferred
polymers of this invention, i.e., non-reinforcing in the sense that
although they normally increase the stiffness (modulus) and often
reduce the volume cost of a plastic composite, other properties
such as strength and ductility are adversely affected, often to a
severe degree. The reinforcement promoters of the present invention
offset these negative effects by improving specifically the
strength and ductility properties of such composites.
Illustrative of the natural silicates in Kaolinite, also known as
China Clay, which may be used either in a natural ("hydrous") form
or in a dehydrated ("calcined") form. Examples of other common clay
minerals are feldspar, nepheline, montmorillonite, bentonite and
attapulgite. Other typical natural silicates are talc, mica,
wollastonite and asbestos. Various synthetic silicates are commonly
used as fillers in elastomers such as, for example, precipitated
calcium and aluminum silicates. Special silicates such as the
natural and synthetic zeolites are sometimes used in polymer-bonded
compositions where good mechanical properties are important for
proper performance. Examples of expanded silicates are perlite and
vermiculite. Illustrative of silica fillers are pyrogenic or fumed
silica, precipitated or hydrated silica, vitreous or fused silica,
and various natural silica fillers such as quartz, novaculite,
tripoli and diatomite. Illustrative of carbonate mineral fillers
are the natural calcite, dolomite, and limestone products (calcium
and magnesium carbonates) which may be ground or provided in
precipitated ("synthetic") forms. Illustrative of metal oxides and
hydroxides are alumina, gibbsite, precipitated aluminum trihydrate,
magnesium hydroxide, manganese oxides, titanium dioxide, various
iron oxides and hydroxides, zinc oxide and zirconium oxide.
Illustrative of ceramic fillers are barium titanate, barium ferrite
and neodynium titantate. Illustrative of sulphate fillers are
baryte and gypsum. Other illustrative fillers are fibers made from
glass, basalt and other molten glasses, such as furnace slag. The
average particle size of the filler is usually up to 100 .mu.m, and
preferably less than 30 .mu.m.
REINFORCEMENT PROMOTER
The reinforcement promoters of the present invention are chemicals
which have at least two reactive olefinic double bonds and which
are further characterized by having a positive promoter index
value, P, which is defined by the following equation:
where n is the number of olefinic bonds in the promoter, Q and e
are the Alfrey-Price parameters with regards to the resonance and
polarity, respectively, for at least one of the olefinic double
bonds in the promoter, and R.sub.f .degree. is the flow rate ratio
of the promoter measured by thin layer chromatography on a neutral
silica gel using xylene as the eluant and di-n-butyl fumarate as
the standard. In Equation (A), the promoter index, P, has a value
greater than zero, preferably greater than 2.0 and most preferably
greater than 20. The promoter index formula illustrates the complex
relation between the four critical parameters which contribute to
the exceptional performance of the class of reinforcing promoters
utilized in the present invention.
Of the four parameters in Equation (A) which determine the promoter
index, n is the number of reactive olefinic double bonds in the
structure of the reinforcing promoter. The term "reactive" covers
those double bonds which exhibit Q and e-values which satisfy
Equation (A) to provide a positive reinforcement promotion index.
It is preferred that n be at least three although in special cases
where the other parameters are particularly favorable, n may be as
low as two. Equation (A) reflects the experimental finding, with
all other factors being equal, that the reinforcement performance
varies strongly with n when n is at least two. The form of the
n-term reflects the importance of localized network, i.e., bound
polymer, formation near the surface of the filler particle as is
discussed in the mechanism section below.
The next two parameters in Equation (A), Q and e, are commonly used
for characterizing the resonance and the polarity effects,
respectively, for monomers used in copolymerization. A detailed
description of the Q and e concepts is presented by T. Alfrey, Jr.
and L. J. Young in Copolymerization at Chapter 2, pages 67 to 87,
1964, and in the references listed at the end of the chapter. At
extensive tabulation of Q and e-values for monomers is given by L.
J. Young at pages II-387 to II-404 in the second edition of Polymer
Handbook, edited by J. Brandrup and E. H. Immergut, Interscience,
(New York) 1975. The promoters defined by Equation (A) cannot in
general be found in such tables, however, Q and e-values for
potential reinforcement promoters may be estimated from the values
of monomers having closely similar olefinic double bond structures.
Where the Q and e-values have not been tabulated for any closely
similar structures, the values can be determined experimentally
using the procedures set forth in the Brandrup and Immergut
handbook and the references cited therein. The Q and e terms in
Equation (A) reflect the experimental finding that Q values should
preferably be high, most preferably greater than or equal to 0.4,
and that, in general, positive e-values are preferred, and most
preferably have a value of at least 1.0.
The final parameter in Equation (A) of the relative flow ratio,
R.sub.f .degree., is a measure of the adsorptivity of a potential
reinforcement promoter onto highly polar mineral surfaces. Many
interactions between organic chemicals and solid surfaces are
highly specific, in that one mineral may result in chemical bonding
whereas another mineral may result in adsorption through
dipole/dipole interactions. However, for the purpose of the present
invention, the requirement of adsorptivity is for convenience
expressed in terms of the relative flow ratio of the promoter
measured by thin layer chromatography on a neutral silica gel using
xylene as the eluant and di-n-butyl fumarate as the standard. The
silica gel is a convenient representation of a filter (silica) in a
hydrocarbon polymer (xylene). Xylene is preferred over the simple
aliphatic hydrocarbons because it is a better solvent for polar
compounds and the compounds must be dissolved in order to perform
the chromatographic adsorptivity test. The R.sub.f .degree. term
assures that the potential reinforcement promoter molecule will
adsorb sufficiently onto the filler surface so as to effectively
contribute to the morphological change required in the polymer
layer immediately adjacent to the filler particle. The relative
flow ratio, R.sub.f .degree., which is used as the chromatographic
adsorption parameter, is defined as the ratio of advancement of the
dissolved chemical relative to the advancement of the solvent front
in a conventional thin-layer chromatography test such that the
greater the adsorptivity of the chemical, the lower the flow ratio.
The R.sub.f .degree. parameter used in Equation (A) is defined as
the ratio of the flow ratio for the chemical being tested, R.sub.f,
relative to the flow ratio of a standard compound, R.sub.fs, as
follows:
The standard selected for purposes of the present invention is
di-n-butyl fumarate. Background concerning chromatographic
techniques and concepts is provided by L. R. Synder, in Principles
of Adsorption Chromatography, Marcel Dekker Inc., (New York), 1968.
A specific reference to thin layer plate techniques using
particulate material coatings on glass plates is presented by J. G.
Kirchner, J. N. Miller, and G. J. Keller, in Analytical Chemistry,
Volume 23, at pages 420-425, March 1951.
The R.sub.f .degree. terms in Equation (A) requires that the
adsorptivity of an effective reinforcement promoter must be
appreciably greater than that of di-n-butyl fumarate under the
stated conditions. This is evident since for P to remain positive
the algebraic requirement is for R.sub.f .degree. to be less than
0.5. The R.sub.f .degree. term in Equation (A) should therefore be
as small as possible, preferably less than 0.05, and most
preferably no more than 0.01. It is not critical, although often
desirable, that a reinforcement promoter have a specific or
chemical bonding interaction with the filler surface in a given
filled polymer composition.
Equation (A) is a statement of the findings that the four critical
parameters of n, Q, e, and R.sub.f .degree. must simultaneously be
within certain ranges of values, and that some relaxation in the
requirement for one or more parameters is allowable only if one or
more of the other parameters assume particularly favorable values.
The following tables give the values for the four critical
parameters for various chemicals which either satisfy Equation (A)
(Table I chemicals), other chemicals containing olefinic double
bonds which fail to satisfy Equation (A) (Table II chemicals), or
chemicals which do not contain the reactive double bonds, some of
which are disclosed in the prior art as being used as dispersing
and processing aids in mineral-filled polymers (Table III
chemicals). The latter chemicals generally fall into the categories
of lubricants and plasticizers depending on their adsorptivity.
TABLE I
__________________________________________________________________________
Carbon-carbon Relative Promoter double bonds, Resonance, Polarity,
flow ratio, index, Chemical Designation n Q e R.degree..sub.f P
__________________________________________________________________________
Trimethylolpropane triacrylate TTA 3 0.4 1.0 0.12 3.0
Pentaerythritol triacrylate PETA 3 0.4 1.0 0.05 4.0
Polycaprolactone triacrylate PCLTA 3 0.4 1.0 0.01 4.6 m-Phenylene
bis maleimide PBM 2 3.0 1.6 0.06 16.5 Dipentaerythritol
pentaacrylate DPEPA 5 0.4 1.0 0.04 19.6 Melamine triacrylate MTA 3
1.3 1.2 0.02 21.5 Epoxidized linseed oil/acrylate ELA 5 0.4 1.0
0.01 21.0 Triacryloyl hexahydro-s-triazine TAHT 3 1.3 1.2 0.01 22.0
Maleamic acid derivatives of methylene-aniline MADMA 3 1.2 1.5 0.01
22.2 oligomers* Trimethylolpropane trimaleate TTM 3 1.2 1.5 0.01
22.2 Trimethacryloyl hexahydro-s-triazine TMHT 3 1.5 1.2 0.01 25.7
N,N--Tetraacryloyl 1,6-diaminopyridine TADAP 4 1.3 1.2 0.01 46.4
__________________________________________________________________________
*Methylene-aniline oligomers fall under the tradename "Jeffamine"
as produced by the Jefferson Chemical Company.
TABLE II
__________________________________________________________________________
Carbon-carbon Relative double bonds, Resonance Polarity, flow
ratio, Promoter index, Chemical Designation n Q e R.degree..sub.f P
__________________________________________________________________________
Diethylene glycol diacrylate DGDA 2 0.4 1.0 0.01 -0.1 Ester diol
2,4-diacrylate EDDA 2 0.4 1.0 0.03 -0.2 1,4 butylene glycol
diacrylate BGDA 2 0.4 1.0 0.21 -1.1 Diethylene glycol
dimethacrylate DGDMA 2 0.7 0.4 0.31 -1.2 1,3 butylene glycol
dimethacrylate BGDM 2 0.7 0.4 0.35 -1.5 Triallyl cyanurate TAC 3
0.02 -1.0 0.01 -2.4 Triallyl-s-triazine-2,4,6- TATZTO 3 0.02 -1.0
0.01 -2.4 (1H, 3H, 5H)trione Triallyl mellitoate TAM 3 0.02 -1.0
0.01 -2.4 Glycerol monoacrylate GMA 1 0.4 1.0 0.01 -2.5 Abietic
acid ABA 1 2.4 -1.2 0.02 -2.5 Maleic anhydride MAH 1 0.2 2.2 0.02
-2.5 Acrylamide AAM 1 1.3 1.2 0.03 -2.5 Oleic acid OA 1 0.01 -1.5
0.06 -2.5 Sorbic acid SA 1 2.0 -1.0 0.06 -2.5 Hydroxy methyl
norbornene HMNB 1 0.01 -1.0 0.29 -2.5 Di n-butyl maleate DNBM 1 1.2
1.5 0.43 -2.5 Linalool LLO 2 0.01 -0.6 0.49 -2.5 Di n-butyl
fumarate DNBF 1 1.2 1.5 1.00 -2.5 Dicyclopentadiene DCPD 2 0.02
-0.5 2.80 -2.8 Squalene SQ 6 0.01 -1.6 2.79 -3.0
__________________________________________________________________________
TABLE III
__________________________________________________________________________
Carbon-carbon Relative double bonds, Resonance Polarity, flow
ratio, Promoter index, Compound Designation n Q e R.degree..sub.f P
__________________________________________________________________________
Polyethylene glycol PEG 0 0 0 0.005 -2.5 n-Propyl acid phosphate
PAP 0 0 0 0.02 -2.5 Isopropyl tri-isostearyl titanate ITIT 0 0 0
0.02 -2.5 2-Ethyl hexyl phosphate EHP 0 0 0 0.03 -2.5 Stearic acid
STA 0 0 0 0.06 -2.5 Polydimethyl siloxane PDMS 0 0 0 0.24 -2.5
Pentane dione PD 0 0 0 0.63 -2.5 Stearyl acetate STAC 0 0 0 1.40
-2.5 Paraffin oil PO 0 0 0 2.80 -2.5 Trimethylolpropane
tripropionate TTP 0 0 0 0.14 -2.5 Isostearic acid ISTA 0 0 0 0.08
-2.5 Calcium stearate CSTA 0 0 0 0.00 -2.5
__________________________________________________________________________
As is demonstrated in the examples appearing below, the reactive
chemicals listed in Table I are greatly superior to those listed in
Table II and to the nonreactive interfacial agents listed in Table
III. The chemicals in Table I are reinforcement promoters which
satisfy Equation (A), which do not require the addition of
peroxides or other free radical initiators, and which are more
cost-effective in use than presently used interfacial agents.
In some instances it is possible or even preferable to carry out
the synthesis of certain reinforcement promoters directly on a
filler surface as illustrated in Example 12 below. It is therefore
within the spirit and intent of the present invention that the
definition of reinforcement promoters applies to those chemicals as
they actually occur on the filler surfaces, even though the
individual reagents may not satisfy the requirements under Equation
(A).
Preferred reinforcement promoters include those chemicals having
the following structure: ##STR1## wherein R.sup.1 is an organic
group free of olefinic or acetylenic unsaturation having a valence
of n; R.sup.2, R.sup.3 and R.sup.4 are hydrogen, carboxy or
monovalent organic groups free of olefinic or acetylenic
unsaturation; X is: ##STR2## m has a value of 0 or 1; and n has a
value of at least two, and preferably from 3 to 5. When m is zero,
R.sup.1 preferably has a double or triple bond which is conjugated
with the olefinic double bond, and which is electron withdrawing.
When m is one, X preferably has a similar conjugated double or
triple bond structure providing an electron withdrawing effect on
the olefinic double bond. Illustrative of the group represented by
R.sup.1 are heterocyclic groups consisting of carbon, hydrogen and
nitrogen, e.g., s-triazine and diaminopyridine where the free
valences are on nitrogen; polyvalent hydrocabon groups, such as
alkylene, phenylene, or a group derived from polyhydroxy alkanes by
the removal of the hydroxyl groups, such as contained in the
condensation products of acrylic and maleamic acids with aliphatic,
aromatic or heterocyclic polyols; or acrylamides, maleimides and
maleamic acids of aliphatic, aromatic and heterocyclic polyamines.
Particularly preferred reinforcement promoter compounds are those
compounds listed in Table I, some of which are identified by the
structures in Table IV below:
TABLE IV
__________________________________________________________________________
Designation m n R.sup.1 R.sup.2 R.sup.3 R.sup.4 X
__________________________________________________________________________
TTA 1 3 CH.sub.3 CH.sub.2 C(CH.sub.2 ) .sub.3 H H H ##STR3## PETA 1
3 (CH.sub.2).sub.3 CCH.sub.2 OH H H H ##STR4## DPEPA 1 5 ##STR5## H
H H ##STR6## MTA 1 3 ##STR7## H H H ##STR8## TAHT 1 3 ##STR9## H H
H ##STR10## MADMA 1 2 + x ##STR11## H H COOH ##STR12## TTM 1 3
CH.sub.3 CH.sub.2 C(CH.sub.2 ) .sub.3 H H COOH ##STR13## TMHT 1 3
##STR14## CH.sub.3 H H ##STR15## TADAP 1 4 ##STR16## H H H
##STR17##
__________________________________________________________________________
The most preferred compounds are ELA, TAHT, MTA, and TADAP.
The proportions of the three components in the reinforced filled
thermoplastic polymer of the present invention are from about 0.1
to 5.0 weight percent, preferably about 0.5 to 2.0 weight percent,
of the reinforcement promotor; about 10 to 90 weight percent,
preferably about 10 to 60 weight percent, of the inorganic filler;
and about 10 to 90 weight percent, preferably about 40 to 90 weight
percent, of the thermoplastic polymer. These percentages are based
on the total amount of promoter, filler and polymer in the
composition.
ADJUVANTS
Adjuvants which may be employed in the compositions of the present
invention include curing agents; flame retardant additives; blowing
agents; nucleating agents for blown systems; lubricants; UV
stabilizers; dyes and colorants; voltage stabilizers; metal
deactivators; and traditional coupling agents. These adjuvants
would be used in amounts designed to provide the intended effect in
the resulting composition. The total amount of adjuvants would
usually range from 0 to about 60 weight percent based on the total
weight of the reinforced, filled thermoplastic composition. Where
the adjuvants are compounds which may interfere with a performance
of the reinforcement promoter, they should be added subsequent to
the formation of the reinforced, filled thermoplastic composition.
If there is no significant interaction to inhibit the performance
of the reinforcement promoter, the adjuvants may be added at any
time based on the established procedures of the prior art.
FREE RADICAL INITIATOR ABSENCE
To overcome the problems involving the presence of a free radical
initiator or similar type of chemical which would inhibit the
effectiveness of the reinforcement promoter, the composition should
be substantially free of such chemicals or their residue to the
extent that the presence of such chemicals would significantly
interfere with the effectiveness of the reinforcement promoter.
Similarly, in conducting the process of the invention, the admixing
and compounding of the composition is conducted in the substantial
absence of free radical initiators or related chemicals to the
extent that the presence of such chemicals would significantly
interfere with the effectiveness of the reinforcement promoter. In
quantitative terms, the composition should generally contain less
than 0.01 weight percent of free radical initiator or its residue
with respect to the weight amount of reinforcement promoter
provided, and preferably no more than 0.005 weight percent.
PROCESS
In an embodiment of the process of the present invention, the
reinforcement promoters may be admixed with the filler by stirring
the promoter with the filler using a solution containing a solvent
which is allowed to evaporate before compounding the filler into
the thermoplastic polymer. This is done to assure uniformity of
distribution for the various reinforcement promoters onto the
fillers since the chemicals vary greatly in physical form, i.e.,
liquid vs. solid, in viscosity, melting point and the like. In
practice, less expensive methods are preferred. These methods would
include the reinforcement promoter being used as a filler
pretreatment, e.g., from an aqueous dispersion by spray-tumbling in
a ribbon blender; by mechanically mixing the promoter at high shear
as a liquid or solid which is predispersed or dissolved in other
compounding ingredients, if any; by direct addition of the promoter
to the filled thermoplastic resin prior to compounding; or as a
concentrate in the polymer.
The filler and reinforcement promoter may be dispersed in the
polymer by processes such as banburying, milling,
extrusion-including twin screw extrusion and the like. The reaction
of the reinforcement promoter with the filler and the matrix
polymer is believed to require polymer free radical formation by
the mechanochemical rupture of polymer chains, hence a minimum
intensity of compounding and a minimum length of time is required
to achieve the reinforcement promoter effect. As will be
appreciated by those skilled in the art, those threshold conditions
depend not only on the particular reinforcement promoter but also
on the actual equipment used, the operating temperatures, the
rheological properties of the polymer, the lubricity of the
compound as influenced by various additives and adjuvants, etc.
Hence, at the current state of the art it is not possible to
specify this threshold of compounding intensity and time, yet for
the purpose of this invention the conditions corresponding to good
compounding practice is generally sufficient. In any event,
reasonable experimentation by one skilled in the art would be
sufficient for determining when sufficient compounding has been
achieved.
It is desired for reasons of efficiency and cost to use
thermoplastic polymers with little or no antioxidant added prior to
compounding with the filler. The reason is that antioxidants (AH)
compete with the reinforcement promoter for the free radicals
formed on the polymer chains (.about.R.degree.) during melt
compounding usually by hydrogen transfer to the polymer radical as
follows:
As a result, the polymer radical site is terminated while being
replaced with a stable antioxidant radical, A.degree. which itself
is incapable of forming new polymer radicals by hydrogen
abstraction from the polymer. In cases where a commercial
thermoplastic polymer already contains significant amounts of
antioxidant additives, it may be desirable to reduce this effect by
shearing the polymer briefly by itself to pre-react most of the
antioxidant molecules with polymer radicals formed by shear or
oxidation. This will usually alleviate the inhibiting effect of the
antioxidant on the reinforcement promoter reaction with the
polymer. Nevertheless, a preferred route is to use thermoplastic
polymers with little or no antioxidant added, by melt compounding
the filler and reinforcement promoter under intensive shear, and
lastly, if required, add additional antioxidant. In a batch
compounding operation such as banburying or milling, this is done
by a proper sequencing of the compound ingredient addition. In
continuous compounding, utilizing twin screw extruders or similar
devices, the sequencing is most conveniently done by introducing
the ingredients at suitable feedport locations in the extruder.
The reinforced, filled thermoplastic polymers of the present
invention may be utilized in any application for which increased
strength and utility would be valuable for the filled thermoplastic
polymer such as molded parts, extruded film and sheet, pipe and
profiles, calendered film and sheet as well as thermoformed parts
and blow-molded or rotationally cast hollow parts. Other
applications include adhesives and sealants having improved
strength and stiffness.
MECHANISM
Without wishing to be bound to any particular theory or mechanism,
it is believed that the reinforcement promoters of the present
invention react chemically with the thermoplastic polymer matrix
during the hot melt compounding of the filled thermoplastic
polymer, which may include extrusion, milling or other hot melt
processing. It is believed further that the reinforcement promoter
reaction with the polymer causes the formation of a strong and
tough interphase between the individual filler particles and the
surrounding matrix polymer, enabling this layer to withstand the
local stress concentrations caused by the filler particles which
would otherwise result in matrix crack initiation and catastrophic
failure. It is believed that such increases in the toughness of the
interphase enables the simultaneous achievement of high strength
and ductility in the final composite. Filler treatments which rely
solely on increased adhesion, i.e., coupling, between the filler
surface and the matrix polymer, can increase the composite strength
but if there is no improvement in interphase toughness, the
composite will remain brittle. On the other hand, filler treatments
which reduce the bonding between the filler particle and the matrix
polymer, e.g., by introducing a weak interphase, can reduce the
tendency for crack initiation by a mechanism of microavitation
which reduces both the actual strain of the polymer matrix and the
local matrix tensile stress near the filler particle, and may
therefore result in marked improvements in composite ductility.
However, a decreased level of adhesion, i.e., decoupling, will
reduce the load-bearing contribution by the filler particles and
hence often .[.causes.]. .Iadd.cause .Iaddend.a concomitant
reduction in the strength of the composite. In summary, the effect
of the reinforcement promoter of the present invention may not
merely be to increase the adhesion between the filler particles and
the thermoplastic polymer matrix, nor may it be that the promoter
is solely a "graded seal", i.e., an interphase layer having a
modulus intermediate between that of the filler and the polymer. In
contrast, it may be that the desired effect is a much more complex
morphological change in the polymer interphase layer which must
become both stronger and tougher than the original matrix polymer
while at the same time exhibit adhesion both to the polar surface
of the filler particles and to the relatively unmodified, non-polar
bulk thermoplastic polymer matrix phase.
There are certain similarities between the behavior of carbon black
and silica in many elastomers and the behavior of mineral fillers
in polyolefins in the presence of the reinforcement promoters of
the present invention. For a review of filler reinforcement
phenomena in elastomers, see G. Kraus (editor), Reinforcement of
Elastomers, New York, 1965 (Interscience), particularly Chapter 8
by W. F. Watson entitled "Chemical Interactions of Fillers and
Rubbers During Cold Milling". It has been long known that both cold
and hot milling of carbon or silica filled rubbers lead to the
formation of so-called "bound rubber", such that even in the
uncured state, the filler becomes irreversibly bound to a portion
of the rubber which swells but does no longer dissolve in a typical
rubber solvent. Although the detailed relationship between the
formation of "bound rubber" and the extraordinary reinforcement
effect of carbon black and silica in rubber is still not fully
understood, there is a general agreement that the two phenomena are
related. Such "bound" polymer has been observed on the filler after
solvent extraction of polyolefins milled with mineral fillers in
the presence of the reinforcement promoters of the present
invention, suggesting that the utilization of the reinforcement
promoters which satisfy the Equation (A) may enable a unique
achievement in the reinforcement of general purpose, thermoplastic
polyolefins with heretofore non-reinforcing mineral fillers.
EXAMPLES
The following examples illustrate the effect of the reinforcement
promoters of the present invention, as compared with various
control chemicals. Unless otherwise indicated, the procedure for
making the treated, filled thermoplastic polymer compositions was
as follows.
The filler pretreatment procedure consisted of dissolving about 10
g of reinforcement promoter in enouth solvent, e.g., acetone, to
dissolve the promoter, but less than the amount of solvent which
would produce a paste with the wetted filler. The promoter solution
was then added to 500 g of filler, blended mechanically and air
dried overnight.
The pretreated filler was compounded with 250 g of thermoplastic
polymer on a 6" by 12" 2-roll mill at 180.degree. C. by adding 250
g of pretreated filler incrementally to the fluxed polymer. Mixing
was continued using thorough compounding procedures. A sheet of the
treated, filled polymer was then cut and rolled into a cylindrical
bar, i.e., "pig", and then passed end-wise through the compounding
mill about ten times for a total mixing time .[.for.]. .Iadd.of
.Iaddend.ten minutes after all the filler .[.has.]. .Iadd.had
.Iaddend.been added. The product composition was then sheeted off
the mill, allowed to cool to room temperature and granulated in a
granulator.
The following testing procedures were used for each product
composition. The granulated product composition was injection
molded at a melt temperature of 215.degree. C. using a 38 cm.sup.3
capacity, 30 ton reciprocating screw-injection machine with a mold
providing an ASTM dog bone test bar with dimensions of 2" by 1/2"
by 1/8" for testing tensile properties, and a rectangular bar with
dimensions of 5" by 1/2" by 1/8" for testing flexural properties.
The following tests were used for each product composite:
______________________________________ Property Tested ASTM Test
Designation ______________________________________ Tensile Strength
Tensile Modulus Elongation at Yield D638-76 Elongation at Break
Flexural Strength D790-71 Flexural Modulus Izod Impact Strength
D256-73 Heat Distortion Temperature D648-72
______________________________________
During the tension and flexural tests a cross-head speed of 0.2"
per minute was utilized.
The chemical designations used in the examples are defined as
follows:
______________________________________ Designation Description
______________________________________ AAM Acrylamide ABA Abietic
acid ATH Aluminum trihydrate having an average particle size of 0.3
to 1.0 .mu.m and a surface area of about 6 to 15 m.sup.2 g.
CaCO.sub.3 I Calcium carbonate consisting of a finely ground
limestone having 93 to 96 percent calcium carbonate in the form of
a calcite having an average particle size of 3.5 .mu.m. Clay I An
unmodified hard clay consisting of a hydrated kaolin with a mean
particle size of 0.3 .mu.m and a B.E.T. surface area of 20 to 24
m.sup.2 g. CSTA Calcium stearate DGDA Diethylene glycol diacrylate
HDPE I A high-density polyethylene having a density of 0.959 g/cc
and a melt index of 0.7. HDPE II A high-density polyethylene having
a density of 0.948 g/cc and a melt index of 0.15. GMA Glycerol
monoacrylate ISTA Isostearic acid ITIT Isopropyl tri-isostearyl
titanate MADMA Maleamic acid derivatives of methylene-aniline
oligomers MAH Maleic anhydride MTA Melamine triacrylate PCLTA
Polycaprolactone triacrylate PEG Polyethylene glycol PETA
Pentaerythritol triacrylate PP I A pre-stabilized polypropylene
homopolymer having a density of 0.905 and a melt flow of 5.0. PP II
An unstabilized polypropylene homopolymer having a density of 0.905
g/cc and a melt flow of 2.0. TAC Triallyl cyanurate TADAP
N,N--Tetraacryloyl 1,6-diaminopyridine TAHT Triacryloyl
hexahydro-s-triazine Talc I A natural, asbestos free, magnesium
silicate containing 98 percent talc with a mean particle size of
1.5 .mu.m and a B.E.T. surface area of 17 m.sup.2 /g. TAM Triallyl
mellitoate TATZTO Triallyl-s-triazine-2,4,6-(1H,3H,5H) trione TETA
Triethylene tetramine TTA Trimethylolpropane triacrylate TTM
Trimethylolpropane trimaleate TTP Trimethylolpropane tripropionate
______________________________________
EXAMPLE 1
Treated, filled thermoplastic polymer composition containing about
50 weight percent HDPE I, as thermoplastic polymer, about 49 weight
percent ATH as filler and about 1.0 weight percent reinforcement
promoter, or other control treating chemical, were prepared and
tested using the procedures described above. The ATH filler was
pretreated with the chemicals listed in Table 1 with the following
results.
TABLE 1 ______________________________________ (ATH/HDPE I)
Treating Izod Agent Impact Type Tensile Tensile Elongation Strength
(Table I, Treating Strength Modulus at Break (ft-lbs/ II or III)
Agent (psi) (ksi) (%) in.) ______________________________________
-- None 3,416 269 4.4 1.7 I TTA 5,606 338 16.3 2.2 I TTM 5,080 336
15.8 2.7 I PETA 5,180 311 35.0 5.7 II DGDA 3,710 247 12.6 1.5 II
GMA 3,610 247 10.0 1.4 II AAM 3,710 276 8.1 0.9 III ITIT 2,930 180
27.0 0.8 III PEG 3,300 217 6.8 2.6 III TTP 3,300 243 6.5 2.3
______________________________________
The samples treated with reinforcement promoter compounds listed in
Table I show an increase in tensile strength of 50-65 percent; a
noticeable increase in stiffness; a four to eight fold increase in
elongation; as well as a 30 to 330 percent increase in Izod impact
strength. In contrast, the chemicals selected from Table II produce
only very minor improvements in tensile strength, with little or no
increases in tensile modulus some increases in elongation and
actual decreases in Izod impact strength. The Table III chemicals
significantly reduce both tensile strength and modulus while
obtaining improvements in elongation or Izod impact strength.
EXAMPLE 2
The following samples were prepared and tested using the same
procedures as in Example 1 except that CaCO.sub.3 I was used as
filler in place of the ATH in Example 1.
TABLE 2
__________________________________________________________________________
(CaCO.sub.3 I/HDPE I) Treating Izod Agent Impact Type Tensile
Tensile Elongation Strength (Table I, Treating Strength Modulus at
Break (ft-lbs/ II or III) Agent (psi) (ksi) (%) in.)
__________________________________________________________________________
-- None 2,900 215-248 23-63 0.5 I TTA 5,420 296 25 1.9 II AAM 3,070
254 25 0.6 III ITIT 2,040 150 33 1.7
__________________________________________________________________________
The results illustrate, for a CaCO.sub.3 /HDPE filled polymer, that
the reinforcement promoter performance is important in
simultaneously increasing both tensile and impact strength.
EXAMPLE 3
The following samples were prepared and tested as described in
Example 1 except that the Clay I was used as the filler in place of
the ATH in Example 1.
TABLE 3 ______________________________________ (Clay I/HDPE I)
Treating A- Tensile Elonga- Izod gent Type Tensile Mod- tion Impact
(Table A, Treating Strength ulus at Break Strength II or III) Agent
(psi) (ksi) (%) (ft-lbs/in.) ______________________________________
-- None 3,610 256 3.5 0.6 I TTA 5,080 372 10.6 1.8 I PCLTA 4,600
358 10.0 1.9 II MAH 3,970 293 4.4 0.6 III ISTA 3,520 281 3.2 1.1
______________________________________
The results show that for a Clay I/HDPE I filled polymer, the
n-value in the structural formula is important for reinforcement
promoter performance.
EXAMPLE 4
Additional ATH-filled HDPE composites were prepared and tested as
in Example 1, with the following results.
TABLE 4 ______________________________________ (ATH/HDPE I)
Treating Tensile Elonga- Izod Agent Type Treat- Tensile Mod- tion
Impact (Table I, ing Strength ulus at Break Strength II or III)
agent (psi) (ksi) (%) (ft-lbs/in.)
______________________________________ -- None 3,416 269 4.4 1.7 I
TAHT 4,340 290 66.0 4.5 I PBM 5,140 314 46.0 4.6 II TAC 3,810 251
3.4 1.6 II TAM 3,760 221 5.2 N/A* III CSTA 3,340 286 68.0 2.9
______________________________________ *N/A -- data not
available
These results, along with the data in Tables I, II and III for Q, e
and n-values, show that the presence of more than one ethylene
unsaturation in itself is not sufficient to establish effective
reinforcement promoter performance. Instead, both the Q and
e-values should be sufficiently favorable to satisfy the
requirement for having a positive promoter index value. These
samples show that high Q-values and positive e-values are important
for simultaneously achieving high tensile properties as well as
high elongation and impact properties.
EXAMPLE 5
The following treated CaCO.sub.3 I/HDPE I samples were prepared and
tested as were the samples in Example 2.
TABLE 5
__________________________________________________________________________
(CaCO.sub.3 I/HDPE I) Izod Impact Treating Agent Type Treating
Tensile Tensile Elongation at Strength (Table I, II or III) Agent
Strength (psi) Modulus (ksi) Break (%) (ft-lbs/in.)
__________________________________________________________________________
-- None 2,900 215-248 23-63 0.5 I TAHT 4,330 265 23 2.5 I PBM 4,570
275 65 2.6 I MADMA 4,290 279 88 2.4 II TAC 3,900 252 22 0.7
__________________________________________________________________________
These samples for treated CaCO.sub.3 I/HDPE I filled polymers show
that, as with the treated ATH/HDPE filled polymers in Example 4,
multiple ethylenic unsaturation alone in chemicals such as TAC
without favorable Q and e-values is insufficient to provide
effective reinforcement promotion when compared with the properties
of filled polymers treated with chemicals like those listed in
Table I.
EXAMPLE 6
The following Clay I-filled HDPE I compositions were prepared and
tested as in EXAMPLE 3.
TABLE 6
__________________________________________________________________________
(Clay I/HDPE I) Izod Impact Treating Agent Type Treating Tensile
Tensile Elongation at Strength (Table I, II or III) Agent Strength
(psi) Modulus (ksi) Break (%) (ft-lbs/in.)
__________________________________________________________________________
-- None 3,610 256 3.5 0.6 I TADAP 4,650 375 9.4 1.6 I TAHT 5,060
340 28.0 3.6 II TATZTO 4,050 336 3.6 0.6
__________________________________________________________________________
The results show, as with Examples 4 and 5, that favorable Q and
e-values are necessary as well in clay filled HDPE composition to
attain superior reinforcement promoter performance.
EXAMPLE 7
The following treated, ATH-filled polypropylene compositions were
prepared and tested as in EXAMPLE 1. In the first three samples a
conventional antioxidant stabilized polypropylene, designated PP I,
was utilized. In the last four samples an antioxidant-free
polypropylene, designated PP II, was utilized.
TABLE 7 ______________________________________ (ATH/PP) Treating A-
Tensile Elonga- Izod gent Type Tensile Mod- tion Impact (Table I,
Treating Strength ulus at Break Strength II or III) Agent (psi)
(ksi) (%) (ft-lbs/in.) ______________________________________ Part
A - With Antioxidant, PP I -- None 3,330 325 2.2 0.3 I TTA 3,530
316 1.4 0.5 I PETA 3,330 260 2.7 0.5 Part B - Without Antioxidant,
PP II -- None 3,770 337 1.5 0.3 I TTA 5,150 357 6.2 0.8 I PETA
5,050 365 10.0 0.9 II DGDA 3,800 344 2.5 0.4
______________________________________
The results show that antioxidants contained in commercial grade
polyolefins can inhibit the reinforcement promotion action of the
promoters. A comparison of the data between Parts A and B reveals
that TTA and PTA have little or no beneficial effects in a highly
stabilized PP but produce substantial improvements in both tensile,
elongation and impact properties in antioxidant-free PP. In
general, therefore, and especially in a less thermally stable
polyolefin such as polypropylene, any desired antioxidant addition
should occur after the mechano-chemical effects of the
reinforcement promoter grafting to the matrix resin have had an
opportunity to take place.
EXAMPLE 8
A treated, filled thermoplastic polymer composition of about 1.5
weight percent TTA, about 58.5 weight percent ATH and about 40
weight percent HDPE I, was prepared and tested as in Example 1
yielding the following results:
TABLE 8A ______________________________________ (ATH/HDPE I)
Tensile Tensile Elongation Izod Impact Strength Modulus at Break
Strength (psi) (ksi) (%) (ft-lbs/in.)
______________________________________ 5,110 391 25 4.5
______________________________________
The mechanical properties of the composition are surprisingly good
considering the high ATH loading. No reference data could be
obtained since the untreated control sample was too dry and stiff
to achieve compounding.
A high ATH-loading is desirable if the flame retardent properties
of ATH are to be fully utilized. The effect of ATH-concentration on
the oxygen index and UL-94 flammability ratings is described in an
article by B. L. Glazar, E. G. Howard, and J. W. Collette entitled,
"The Flammability Characteristics of Highly Mineral Filled
Ultrahigh Molecular Weight Polyethylene Composites", in the Journal
of Fire and Flammability, Vol. 9, October 1978, at pages 430-444,
in which it is reported that the effect of ATH on flame retardancy
increases steeply above 50 weight percent ATH. Using the previously
referred to technique, by Housslein and Fallick, for directly
polymerizing ethylene on filler surface, polyethylenes were
prepared with ATH contents up to 80 weight percent, much higher
than has been feasible using conventional compounding of ATH into
polylethylene at molecular weight ranges suitable for normal
thermoplastic processing.
The following results illustrate the UL-94 flammability test data
for the ATH filled HDPE composition produced as described above, as
compared with unfilled HDPE I controls.
TABLE 8B ______________________________________ (ATH/HDPE I Flame
Ratings) Sample Thickness ATH Limiting UL-94 (Inches) (wt. %)
Oxygen Index.sup.1 Rating.sup.2
______________________________________ 1/8 0 18 NR 1/8 60 26 VI/VO
1/4 0 18 NR 1/4 60 26 VO ______________________________________
.sup.1 Lists the percent of oxygen required to sustain combustion.
.sup.2 Using a vertical flame test from Underwriters Laboratories
with th following designations: NR -- not rated by test since
sample continues to burn VI less than 25 seconds of burning with no
drip VO less than 5 seconds of burning with no drip.
The sample represents a successful attempt at compounding a heat
formable, highly flame-retarded polyolefin with excellent
mechanical properties which is free of noxious and corrosive
combustion gases resulting from halogen-containing, flame-retardent
additives.
EXAMPLE 9
As shown in previous examples, TAHT is a reinforcement promoter
which is highly effective for a broad range of filled resin
compositions. Unfortunately, TAHT is a crystalline solid under
normal operating conditions and has low solubility in organic
solvents or other compounding additives. To assure uniform
treatment of the fillers it may be advantageous for ease of
compounding to utilize a more soluble reinforcement promoter than
pure TAHT. To accomplish this, several mixed structure
hexahydro-s-triazines were prepared from mixtures of acrylonitrile
and methacrylonitrile using the synthetic procedure previously used
to make TAHT. This procedure involves reacting a molar amount of
trioxane equivalent to the sum of the number of moles of
acrylonitrile and methacrylonitrile, in hexane solvent using a
catalytic amount of sulfuric acid/acetic anhydride mixture. The
resulting mixed structures have depressed melting point properties
and improved solubility as compared with TAHT. Treated, filled
polymer compositions containing about 1.0 weight percent of these
triazines, about 49 weight percent Clay I, and about 50 weight
percent HDPE I exhibited the following properties. The mole
fraction of acrylonitrile refers to the ratio of moles of
acrylonitrile to the total moles of acrylonitrile and
methacrylonitrile in the reactant mixture.
TABLE 9 ______________________________________ (Clay I/HDPE I)
Tensile Tensile Elongation Izod Impact Mole Fraction Strength
Modulus at Break Strength of Acrylonitrile (psi) (ksi) (%)
(ft-lbs/in.) ______________________________________ No treatment
3,610 292 4 0.6 1.00 (TAHT) 5,040 354 40 3.4 0.80 4,900 352 46 3.5
0.75 4,870 353 38 3.6 0.67 4,700 338 50 2.8
______________________________________
The results indicate that the use of more soluble mixed triazines,
as compared with pure TAHT, produces little or no reduction in the
reinforcement promotion effect of pure TAHT.
EXAMPLE 10
This example illustrates that improvement in the stiffness, impact
strength and burst strength can be achieved simultaneously in
extruded, high density polyethylene pipe when using low-cost
hydrous clay as the filler and TAHT as the reinforcement promoter.
Hydrous clay is a non-reinforcing filler in polyolefin when used
alone.
The composition was prepared by charging 50 lbs. of Clay I to a
Henschel mixer. The mixer was operated at low speed initially while
a solution containing 0.500 lbs. of TAHT in 2.5 l of
dichloromethane was slowly added to assure uniform distribution. An
exhaust fan was then connected and the mixer was turned to
high-speed operation while the temperature of the mixture was
raised from ambient to 100.degree. C. After five minutes, the
mixing speed was reduced to low-speed operation with mixing and
drying being continued for another 10 minutes. 25 lbs. of the
resulting TAHT-treated clay was then blended with 75 lbs. of HDPE
II resin powder in a rotating drum for 10 minutes. The blend was
then fed to a twin-screw, compounding extruder with temperatures of
the rear of the barrel at about 193.degree. C., and with the middle
and front barrel at about 215.degree. C. The multi-strand die was
kept at about 215.degree. C. The treated, filled polymer
composition was extruded in strands which were diced-in-line to
standard 1/8 " by 1/8" size pellets.
These pellets were then extruded into nominal 1" diameter pipe
using a Davis-Standard extruder having a 21/2" barrel diameter and
a 24 to 1 fluted mixing screw ratio, under the following operating
conditions:
______________________________________ Barrel Temperatures Zone 1
205.degree. C. Zone 2 210.degree. C. Zone 3 207.degree. C. Zone 4
210.degree. C. Zone 5 215.degree. C. Screen Pack 20/60 mesh Die
Temperature 217.degree. C. Stock Temperature 225.degree. C. Screw
Speed 32 rpm Throughput Rate 79 lbs./hr.
______________________________________
The resulting pipe had a 1.8" O.D. with a wall thickness of 0.0074"
having a smooth surface inside and outside. No gels, die plate-out,
smoking, or odor problems were encountered during the extrusion.
The resulting pipe was tested as is for and for burst strength
using compression molded plaques made from granulated extrudate for
the other properties, and compared with unfilled HDPE II pipe with
the following results:
TABLE 10 ______________________________________ (Clay I/HDPE II
Pipe) Test Compositions Unfilled Filled (wt. %) (wt. %)
______________________________________ Composition HDPE II 100
74.75 Clay I -- 25.00 TAHT -- 0.25 Properties Tensile Modulus, ksi
120 170 Izod Impact Strength, ft-lbs/in. 1.9 3.9 Yield Strength,
psi 3270 4000 Instant Burst Strength, psi 3500 4050 Long Term Time
to Burst, hrs 36 594 (at 1975 psi Hoop Stress)
______________________________________
The results show that using a TAHT reinforcement promoter enables
improvements in both stiffness and toughness as well as burst
strength to be obtained for treated, clay-filled HDPE in contrast
to unfilled HDPE. Untreated, clay-filled HDPE exhibits a reduction
in impact and burst strength as compared with unfilled HDPE.
EXAMPLE 11
The following talc-filled HDPE I compositions were prepared and
tested as in Example 1.
TABLE 11 ______________________________________ (Talc I/HDPE I)
Treating A- Elonga- Izod gent Type Treat- Tensile Tensile tion
Impact (Table I, ing Strength Modulus at Break Strength II or III)
Agent (psi) (ksi) (%) (ft-lbs/in.)
______________________________________ -- None 4,160 339 4.1 1.6 I
MTA 5,090 401 6.6 2.5 II ABA 4,450 378 3.3 1.0 III ISTA 4,170 312
4.1 1.2 ______________________________________
The results show that talc, which is a naturally hydrophobic
mineral filler traditionally unresponsive towards many traditional
coupling agents, responds with significant improvements in all the
tested properties when treated with a reinforcement promoter, MTA,
within the present invention. In contrast, other treating agents,
such as ABA, cause only moderate improvements in tensile properties
at an expense in ductility and toughness.
EXAMPLE 12
In this example, two non-reinforcement promoters, MAH and TETA,
were reacted in situ on a calcium carbonate filler surface. The
resulting compound, however, which is considered to be a maleamic
acid adduct of TETA, meets the criteria for being a reinforcement
promoter within the present invention, having values for n of 3 to
4, for Q of about 1.2, for e of about 1.5, and for R.sub.f .degree.
of less than or equal to about 0.01.
The treatment procedure involves first dissolving MAH in diethyl
ether, mechanically stirring the solution into calcium carbonate
powder and allowing the mixture to dry overnight at room
temperature. TETA is dissolved in dichloromethane, stirred into the
MAH-treated CaCO.sub.3 powder mixture and then allowed to dry
overnight at room temperature. The total concentration of MAH/TETA
was maintained at 2 weight percent of the CaCO.sub.3 I filler while
the ratio between the MAH an TETA was varied as indicated in Table
12. Compounding and testing was done as in Example 1.
TABLE 12 ______________________________________ (CaCO.sub.3 I/HDPE
I) MAH TETA Tensile Tensile Elongation Izod Impact (wt. (wt.
Strength Modulus at Break Strength %) %) (psi) (ksi) (%)
(ft-lbs/in.) ______________________________________ 0.00 0.00 2,980
258 26 0.7 0.80 1.20 3,320 282 36 0.6 1.15 0.85 4,200 281 52 1.3
1.34 0.66 4,360 280 88 3.6 1.46 0.54 4,410 275 59 3.7 2.00 0.00
3,820 261 21 0.8 ______________________________________
The mixture producing the best results occurs at a MAH:TETA
mole-ratio of about 3:1, while the mechanical properties are lower
at both low mole-ratios of MAH to TETA and for MAH alone. These
results clearly demonstrate that although TETA and MAH by
themselves are not reinforcement promoters, their reaction products
are very effective reinforcement promoters. The reinforcement
promoters of the present invention therefore include those
chemicals which may be formed in situ during the treatment of the
filler or during compounding, using additives which by themselves
are not within the definition of reinforcement promoters within the
present invention since they do not satisfy Equation (A), as long
as the reaction products satisfy the structure and parametric
equations characterizing the claimed invention.
* * * * *