Electrically conductive compositions and methods for their preparation

Compositions and methods are described that relate to the use of reaction products of metal compounds and protonic acids for plasticizing and neutralizing acidic, protonated compositions comprising substituted and unsubstituted polyanilines and co-polymers and or mixtures thereof; and for reducing the percolation threshold for conductivity in blends with insulating bulk polymers.

FIELD OF INVENTION 
This invention relates generally to conducting polymer compositions, and 
more particularly relates to electrically conductive compositions and 
shaped articles, such as parts, containers, fibers, tapes, films and 
coatings and the like, from polyanilines and blends thereof; and to 
methods of forming and use of the same compositions and conductive 
articles. More specifically, this invention relates to the use of reaction 
products of metal compounds and protonic acids as plasticizers; and for 
reducing the percolation threshold for the onset of conductivity in blends 
comprising polyanilines and insulating bulk polymers; and for neutralizing 
acidic, protonated polyaniline compositions. 
BACKGROUND OF THE INVENTION 
Electrically conductive, thermoplastic polymer compounds are of increased 
practical interest, for instance, for packaging electronic instruments and 
parts, and to solve a wide range of static discharge, electrostatic 
dissipation and electromagnetic shielding problems. Often, such compounds 
are made by mixing, for example, carbon black, stainless steel fibers, 
silver or aluminum flakes or Nickelcoated fibers with insulating bulk 
thermoplastics such as polystyrene, polyolefins, nylons, polycarbonate, 
acrylonitrile butadiene styrene co-polymers (ABS), and the like. These 
filled compounds are subsequently processed into desired shapes and 
articles by common plastics processing methods such as extrusion, 
injection or blow molding and the like. Major problems related to the 
above filled thermoplastic compounds are that processing of these 
materials is not trivial and is often associated with excessive machine 
wear, and that the final compounds frequently exhibit undesirable 
mechanical properties such as brittleness and a reduced elongation to 
break in comparison with the corresponding properties of the untilled 
matrix polymer. 
More recently, there has been an increased interest in replacing such 
carbon black or metal-filled compounds with intrinsically electrically 
conductive polymers and their blends with common insulating polymers. The 
latter systems are believed to be more cost competitive, easier to process 
and to exhibit desirable mechanical properties. Among the various 
conductive polymers, the polyanilines in particular have attracted 
attention because of their excellent environmental stability and their low 
production costs. 
Polyaniline is well known in the art, and the preparation of the 
electrically conductive form of this polymer based on, for example, 
contacting polyanilines with protonic acids has been described. Green, A. 
G., and Woodhead, A. E., "Aniline-black and Allied Compounds, Part 1," J. 
Chem. Soc., Vol. 101, pp. 1117 (1912); Kobayashi, et al., Electrochemical 
Reactions . . . of Polyaniline Film-Coated Electrodes, "J. Electroanl. 
Chem., Vol. 177, pp. 281-91 (1984); U.S. Pat. Nos. 3,963,498, 4,025,463 
and 4,983,322. Typical examples of such described protonic acids are HCl, 
H.sub.2 SO.sub.4, sulfonic acids of the type R.sub.1 --SO.sub.3 H, 
phosphoric acids, etc. Chiang, J.-C. and MacDiarmid, A. G., "Polyaniline: 
Protonic Acid Doping of the Emeraldine Form to the Metallic Regime", 
Synthetic Metals, Vol. 13, p. 196 (1986); Salaneck, W .R. et al., 37 A 
Two-Dimensional-Surface "State" Diagram for Polyaniline", Synthetic 
Metals, Vol. 13, p. 297 (1986). Such acids form complexes with 
polyaniline, which, generally, exhibit electrical conductivities of 
10.sup.-3 S/cm or more. Their electrical properties make these so-called 
"doped" polyanilines and their blends and compounds with common insulating 
bulk polymers suitable for a variety of the antistatic and shielding 
applications that are currently served by metal or carbon black filled 
systems. 
Processing of polyanilines has been described in several patents and patent 
applications. In U.S. Pat. No. 5,006,278 a conductive product is described 
which has been made by mixing a solvent, a doping agent and a polyaniline, 
whereafter the solvent has been removed by evaporation. In POT Publication 
No. WO 9013601 a polymer mixture is prepared by mixing a suitable solvent 
with a mixture of polyaniline and a multi-sulphonic acid, used as a doping 
agent, whereafter the solvent is evaporated. According to this 
specification, the doping is generally carried out at 
20.degree.-25.degree. C. It is described that the doping can be carried 
out as a heterogeneous reaction, followed by dissolution of the mixture in 
a suitable solvent. The processing into a final shape is carried out in 
the presence of a solvent. (p. 15, 1.23). 
PCT Publication No. WO 9010297, U.S. Pat. No. 5,002,700 and European Patent 
Publication No. EP 152 632 describe the use of dodecylbenzene sulphonic 
acid as a doping agent for polyaniline. PCT Publication No. WO 9001775 
describes a multi-sulphonic acid as a doping agent for polyaniline with 
the advantage of better thermal stability compared with other sulphonic 
acids. In the examples of this specification, the doping of polyaniline 
has been carried out in a suspension of polyaniline and the sulphonic acid 
in an aqueous solution of formic acid. In none of the examples of the 
above mentioned patent specifications, however, have adequate methods been 
described for melt processing of polyaniline compositions. 
Melt processing of compounds comprising conductive polyanilines, has 
typically been executed by mechanically mixing the components, where the 
conductive polyaniline is in the solid form and the matrix polymer in its 
molten form before shaping the blend into the desired article. Generally, 
the blends obtained exhibit varying conductivity, are of non-homogeneous 
quality and of poor mechanical properties and, generally show a high 
percolation threshold for the onset of electrical conductivity. 
It has indeed been suggested, that certain polyaniline-based systems and 
blends may be processed using standard polymer processing techniques. For 
example, in Plastics Technology 37 (1991):9 pp. 19-20 is described the use 
of protonated, conductive polyanilines to impart conductivity to mixtures 
with common insulating thermoplastic polymers such as nylons and 
poly(vinylchloride). In this application, however, the conductive 
polyaniline is in the form of solid, intractable particles, which, much 
like carbon black, are dispersed in the non-conducting matrix, which is in 
its molten form. Melt-processing of these compounds requires special melt 
dispersion techniques; European Patent Publication Nos. EP 168 620 and 168 
621. A relatively high content of conductive polyaniline is required to 
reach desirable levels of conductivity in the blends with insulating 
polymers; or, in other words, the percolation threshold for the onset of 
conductivity is relatively high. Thus, in the aforementioned blends of 
solid polyaniline particles dispersed in poly(vinylchloride) a percolation 
threshold existed of about at least 13% w/w of the conductive polyaniline. 
Such a high content of conductive polyaniline particles is not desirable, 
because it is not economical and, in addition, may substantially alter the 
mechanical properties of the blend in comparison with those of the pure 
matrix polymer. 
An improved method of making conductive polyaniline compositions has been 
described in Finnish Patent Application 915 760. According to this 
application, polyaniline, or derivatives thereof, and an excess of an 
organic protonic acid are mechanically mixed. The liquid-like mixture or 
suspension is subsequently thermally solidified between 
40.degree.-250.degree. C. in a mixer. As a result, a dry, solid 
composition, in the form of a granulate comprising protonic acid-doped 
polyaniline is obtained. The solid polyaniline-protonic acid complex can 
subsequently be mixed with insulting thermoplastic polymers and formed 
into parts of desired shapes using standard polymer melt-processing 
techniques. Improved visual surface characteristics and lower percolation 
thresholds for the conductivity were observed for parts made according to 
this method. However, as stated above, an excess of acid is used in the 
technique. The latter generally is unacceptable from a processing, 
application and environmental point of view. The excess acid, of course, 
can be removed, but this process is tedious and uneconomical, and limits 
the scope of the products that can be manufactured. 
In a publication in Synthetic Metals (Vol. 48 (1992) pp. 91-97) are 
described blends that exhibit much lower percolation thresholds, sometimes 
even below 1% w/w, of conductive polyaniline and a wide variety of 
non-conducting matrix polymers, such as polyethylenes, 
poly(vinylchloride), polystyrene, nylons, and the like; 
poly(methylmethacrylate), polycarbonate, acrylonitrile butadiene styrene 
copolymers (ABS), and the like. However, invariably, the compositions that 
exhibit such low percolation thresholds are made from solutions of the 
conductive polyaniline and the matrix polymers, which is uneconomical, and 
limits the use to fabrication of products such as film, coatings and 
fibers. 
Thus, clearly, a need exists for electrically conductive polyaniline 
compositions that can be processed from the melt, and for polyaniline 
blends with, for example, insulating bulk polymers that exhibit a low 
percolation threshold, and do not contain an excess of protonic acid, i.e. 
are neutral or only slightly acidic, and for economical methods to 
fabricate articles from the melt of such compositions. 
SUMMARY OF THE INVENTION 
It is accordingly an object of the present invention to provide 
electrically conductive compositions containing polyaniline and the 
reaction products of metal compounds and protonic acids, that can be 
processed from the melt and that are approximately neutral or only 
slightly acidic. 
It is additionally an object of the present invention to provide 
electrically conductive blends and articles that comprise polyaniline and 
further comprise the reaction products of metal compounds and protonic 
acids, that can be processed from the melt and that display a low 
percolation threshold for the onset of electrical conductivity. 
Another object of the present invention is to provide a method to make, 
from the melt, electrically conductive compounds and articles comprising 
polyaniline that are neutral or only slightly acidic by the addition of 
the reaction products of metal compounds and protonic acids. 
It is still another object of the present invention to provide a method to 
make, from the melt, electrically conductive compounds and articles 
comprising polyaniline that display a low percolation threshold by the 
addition of the reaction products of metal compounds and protonic acids to 
blends of said polyaniline and insulating matrix polymers. 
Still another object of the present invention is to provide a method to 
make, from the melt, electrically conductive compounds and articles 
comprising polyaniline that display a low percolation threshold by the 
addition of metal compounds, that form a fluid composition with protonic 
acids, to blends of acidic polyaniline compositions and insulating matrix 
polymers. 
It is still yet another object of the present invention to provide shaped 
articles, fibers, coatings, films, tapes and the like from electrically 
conductive polyaniline and blends of electrically conductive polyaniline 
with insulating bulk polymers and pre-polymers. 
Additional objects, advantages and novel features of the invention will be 
set forth, in part, in the description which follows, and, in part, will 
become apparent to those skilled in the art on examination of the 
following, or may be learned by practice of the invention. The objects and 
advantages of the invention may be realized and attained by means of the 
instrumentalities and combinations particularly pointed out in the 
appended claims. 
In one aspect of the invention, neutral, or only slightly acid, 
meltprocessable polyaniline compositions are fabricated; for example, an 
amount of the metal oxide ZnO is contacted at 150.degree. C. with 2 moles 
of dodecylbenzene sulfonic acid to yield a fluid reaction product. This 
fluid reaction product is mixed at 180.degree. C. with the conductive salt 
complex of polyaniline and dodecylbenzene sulfonic acid, and an 
essentially neutral, plasticized melt is formed, which is processed into 
useful shapes such as, for example, films, fibers and parts, and the like. 
In another aspect of this invention, the above described melt of the 
conductive polyaniline-dodecylbenzene sulfonic acid complex and the 
reaction product of the ZnO and the dodecylbenzene sulfonic acid is 
blended at elevated temperatures with molten insulating matrix polymers, 
such as, for example polyethylene. Surprisingly, the inventors have found 
that compositions are obtained that can be processed from the melt and 
that display unexpectedly low percolation thresholds for electrical 
conductivity.

DETAILED DESCRIPTION OF THE INVENTION 
DEFINITIONS 
It must be noted that, as used in the specifications and the appended 
claims, the singular forms "a", "an" and "the" include plural referents 
unless the context clearly dictates otherwise. Thus, for example, 
reference to "a polyaniline" includes mixtures of polyanilines, reference 
to "a reaction product" includes mixtures of two or more reaction 
products, reference to "a metal compound" includes mixtures of two or more 
metal compounds, reference to "an acid" includes mixtures of two or more 
acids, and the like. 
When the term "polyaniline" is used in this application, it is used 
generically to include substituted and unsubstituted polyanilines and 
polyaniline copolymers, and mixtures thereof, unless the context is clear 
that only the specific nonsubstituted form is intended. 
As used hereinafter, the "percolation threshold" is defined as the weight 
fraction of conductive compound needed to impart a conductivity of 
10.sup.-8 S/cm or more to a blend with an insulating matrix substrate. 
The term "insulating" or "substantially non-conducting material" refers to 
materials that have an electrical conductivity of less than about 
10.sup.-10 S/cm. 
The specification "approximately neutral or slightly acidic" compositions 
refer to compositions that impart to water after 24 hrs exposure a pH of 
between about 4 and 8. 
The compositions of this invention typically include three or four types of 
components. 
(i) A substituted or unsubstituted polyaniline or co-polymers, or mixtures 
thereof; 
(ii) A protonic acid solute that forms salt complexes with the substituted 
or unsubstituted polyanilines or co-polymers or mixtures thereof and that 
have a conductivity greater than about 10.sup.-6 S/cm; 
(iii) A metal compound that neutralizes protonic acids and forms a reaction 
product with certain acids, having a softening temperature of below about 
300.degree. C. The addition of this component effectuates the special 
eventuality described in this invention of neutralization, plasticization 
and/or percolation-threshold reduction in the aforementioned polyaniline 
compositions. 
(iv) One or more optional organic substrate phases. This phase is an 
insulating material, and can be one or more polymers or pre-polymers, or 
mixtures thereof, which is fluid during compounding or mixing with (i), 
(ii) and (iii) and/or during shaping into the conductive article. 
Surprisingly, it has been discovered that, unlike the electrically 
conductive compositions described in the prior art, materials can be 
prepared from the melt comprising polyaniline, substituted polyanilines or 
co-polymers, or mixtures thereof, that are approximately neutral or only 
slightly acidic; and that display a percolation threshold for the onset of 
conductivity in blends with insulating substrates as low as below 1% w/w. 
THE POLYANILINE 
One component in the present materials is substituted or unsubstituted 
polyaniline or a polyaniline copolymer as described in U.S. Pat. No. 
4,983,322, which by reference is incorporated herein in its entirety. 
Particularly preferred for the use in the practice of this invention, is 
the polyaniline that is derived from unsubstituted aniline. 
In general, the polyanilines useful in the practice of this invention are 
those which are of sufficiently high molecular weight to exhibit high 
electrical conductivity, i.e. having a weight average molecular weight of 
more than 5,000 daltons. In general substituted and unsubstituted 
polyanilines and polyaniline copolymers will be of at least 20 repeat 
units. In the preferred embodiments of the invention, the number of repeat 
units is at least about 25, and in the most preferred embodiments, the 
number of repeat units is at least about 50. 
The polyaniline can be conveniently used in the practice of this invention 
in any of its physical forms. Illustrative of useful forms are those 
described in U.S. Pat. No. 4,983,322, which by reference is incorporated 
herein in its entirety. For unsubstituted polyaniline, useful forms 
include leucoemeraldine, protoemeraldine, emeraldine, nigraniline and 
tolu-protoemeraldine forms. Useful polyanilines can be prepared through 
the use of chemical and electrochemical synthetic procedures referred to, 
for example, in the above references. 
THE PROTONIC ACID 
A second component of the compositions of the present invention is a 
protonic acid that imparts a conductivity to the composition. 
As used herein, a "protonic acid" is an acid that protonates the 
polyaniline to form a salt complex with said polyaniline, which has a 
conductivity greater than about 10.sup.-6 S/cm. Preferred protonic acids 
are those that protonate the polyaniline to form a salt complex, said 
complex having an electrical conductivity of greater than about 10.sup.-3 
S/cm, and particularly preferred protonic acids are those that impart a 
conductivity of greater than about 0.1 S/cm to the salt complex with 
polyaniline. Amongst these particularly preferred embodiments, most 
preferred are those embodiments in which said polyaniline salt complex has 
a conductivity of greater than 10 S/cm. 
Protonic acids are well known as dopants in the conductive polymer art as 
shown by the references to J.-C. Chiang and A. G. MacDiarmid; W. R. 
Salaneck et al.; U.S. Pat. No. 5,006,278; PCT Publication No. WO 
9013601;Synthetic Metals Vol. 48 (1992) pp. 91-97, noted above. 
METAL COMPOUND 
The third component of the compositions of the present invention is a metal 
compound that generally neutralizes protonic acids and forms a reaction 
product with certain acids having a softening temperature of below about 
300.degree. C. 
Surprisingly, it was discovered that 
mixtures of certain metal compounds, such as, and in particular, the 
amphoteric metal oxide ZnO, and certain protonic acids, such as, for 
example, dodecylbenzene sulfonic acid, form a fluid especially after 
heating at elevated temperatures, e.g. above about 100.degree. C.; and 
that 
when the resulting fluid was mixed with an approximately neutral conductive 
salt complex of polyaniline and a protonic acid, an essentially neutral, 
plasticized melt was formed that could be directly formed into useful 
conductive articles, such as fibers, films, pans and the like; and that 
when this melt was blended with molten insulating substrates, compositions 
were obtained that displayed unexpectedly low percolation thresholds for 
electrical conductivity. 
Thus, in this instant the reaction product of the metal compound and the 
protonic acid fulfils a special role of plasticizer and, in blends, a 
percolation-threshold reducing agent. It will become apparent from the 
examples attached hereto that the latter effect is unusual, and cannot 
simply be effected by the addition of most commonly available 
plasticizers. 
The metal compounds for use in the practice of this invention generally are 
compounds that form condensation products with protonic acids and can be 
oxides, hydroxides, halides, stearates, carbonates, palmitates, octoates, 
laurates, phenolates, maleates, octylthioglycolates, and the like. 
Particularly preferred metal compounds for use in the present invention 
consist of the group of metal compounds comprising the elements Zn, Cu, 
Mg, Ba, Al, Ca, Ti, Fe, Zr, Cd, Pb and Sn. Amongst the particularly 
preferred metal compounds for use in the present invention, the especially 
preferred compounds are the metal compounds comprising the elements Zn, 
Cu, Ca or Mg. Amongst the particularly preferred metal compounds for use 
in the present invention, the most preferred compounds are the metal 
compounds comprising the element Zn. In the preferred embodiment of the 
present invention, the metal compounds are selected from the group 
consisting of oxides and hydroxides. In the particularly preferred 
embodiment of the present invention the metal compounds are oxides. 
Amongst the particularly preferred metal oxides for use in the present 
invention is ZnO. 
In the embodiments of the present invention, the certain protonic acid that 
reacts with the aforementioned metal compound and is neutralized by the 
above metal compound to form a reaction product having a softening 
temperature of below about 300.degree. C., is selected from the group 
consisting of those of Formulas I and II: 
##STR1## 
wherein: "A" is sulphonic acid, selenic acid, phosphonic acid, boric acid 
or a carboxylic acid group; or hydrogen sulphate, hydrogen selenate or 
hydrogen phosphate; 
"n" is an integer in the range of 0-5 inclusive; 
"m" is an integer in the range of 0-4 inclusive, with the proviso that the 
sum of n+m is 5; 
"R.sub.1 " is an alkyl, alkenyl, alkoxy, alkanoyl, alkylthio, 
alkylthioalkyl containing 1-20 carbon atoms; or alkylaryl, arylalkyl, 
alkylsulphinyl, alkoxyalkyl, alkylsulphonyl, alkoxycarbonyl, carboxylic 
acid, where the alkyl or alkoxy has from 0 to about 20 carbon atoms; or 
alkyl having from 3-20 carbon atoms substituted with one or more sulphonic 
acid, carboxylic acid, halogen, nitro, cyano, diazo or epoxy moieties; or 
a substituted or unsubstituted 3, 4, 5, 6, or 7 membered aromatic or 
alicyclic carbon ring, which ring may include one or more divalent 
heteroatoms of nitrogen, sulfur, sulfinyl, sulfonyl or oxygen such as 
thiophenyl, pyrolyl, furanyl, pyridinyl. 
In addition to these monomeric acid forms, R.sub.1 can be a polymeric 
backbone from which depend a plurality of acid functions "A". Examples of 
polymeric acids include sulfonated polystyrene, sulfonated polyethylene 
and the like. 
R is the same or different at each occurrence and is an alkyl, alkenyl, 
alkoxy, cycloalkyl, cycloalkenyl, alkanoyl, alkylthio, aryloxy, 
alkylthioalkyl, alkylaryl, arylalkyl, alkylsulphinyl, alkoxyalkyl, 
alkylsulphonyl, aryl, arylthio, arylsulphinyl, alkoxycarbonyl, 
arylsulphonyl, carboxylic acid, halogen, cyano, or alkyl which has been 
substituted with one or more sulfonic acid, carboxylic acid, halogen, 
nitro, cyano, diazo or epoxy moieties; or any two R substitutent taken 
together are an alkylene or alkenylene group completing a 3, 4, 5, 6 or 7 
membered aromatic or alicyclic carbon ring or multiples thereof which ring 
or rings may include one or more divalent heteroatoms of nitrogen, sulfur, 
sulfinyl, sulfonyl or oxygen. R typically has from about 1 to about 20 
carbons, especially 3 to 20 and more especially from about 8 to 20 
carbons. 
Particularly preferred for use in the practice of this invention are the 
protonic acids of formulae I and II wherein: 
A is sulphonic acid; 
n is the integer 1 or 2; 
m is the integer 3 or 4, with the proviso that the sum n+m is 5; 
R.sub.1 is alkyl or alkoxy, having from 2 to about 14 carbon atoms, or an 
alkyl having from 3 to about12 carbon atoms substituted with one or more 
halogen moieties; 
R is alkyl or alkoxy, having from 4 to about 14, especially 12 carbon 
atoms, or alkyl substituted with one or more halogen moieties. 
In the most preferred embodiments, the protonic acid that according to the 
present invention is reacted with the metal compound is dodecylbenzene 
sulphonic acid. 
Those skilled in the art of chemistry will be readily able to select the 
particular combination of metal compounds and protonic acids that yield a 
reaction product with a softening temperature of below about 300.degree. 
C. 
It should be noted that the protonic acid that is used to form the 
conductive complex with the polyaniline can be different from, or the same 
as the certain protonic acid that is used to form the reaction product 
with the metal compound. 
In the event that an excess of a protonic acid of the component (ii) is 
used to form the electrically conductive complex with the polyaniline (i), 
the reaction product (iii) of the metal compound and the protonic acid may 
simply be formed by adding the metal compound to the acidic, protonated 
polyaniline composition. In this instant, the protonic acid of components 
(ii) and (iii) of the present invention are identical, and the metal 
compound additionally fulfils a role as neutralizer. 
THE SUBSTRATE PHASE 
A fourth, optional, component of the compositions of this invention is the 
substrate. This can be bulk oligomeric or polymeric or pre-polymeric 
materials which can be transformed into a fluid (liquid or semisolid) form 
during processing so as to achieve the required intimate mixing with the 
polyaniline, the protonic acids and the metal compound-acid reaction 
product. Illustrative of useful polymeric substrates are polyethylenes, 
isotactic polypropylene, elastomers, styrene-butadiene-styrene (SBS) 
copolymers, polybutadiene, and the like, poly(vinylchloride), polystyrene, 
poly(vinylalcohol), poly(ethylene terephthalate), nylons, such as nylon 6, 
nylon 6.6, nylon 12 and the like; poly(methylmethacrylate), polycarbonate, 
acrylonitrile butadiene styrene copolymers (ABS), and the like. Generally, 
the substrate is a substantially nonconductive material. 
OVERALL COMPOSITIONS 
The proportions of materials of the present invention can vary widely, 
depending on the desired level of electrical conductivity and the 
application. However, the relative amounts of the polyaniline, protonic 
acid and metal compound is such that approximate neutrality or only slight 
acidity is achieved in the final composition; i.e. that when the materials 
of the present inventions are exposed to water, the pH is between 3 and 8; 
more preferably between 4 and 8; and most preferably between 5 and 8. 
Typically, the compositions of this invention include polyaniline, 
substituted polyaniline, copolymers and/or mixtures thereof, a protonic 
acid, the reaction product of a protonic acid and a metal compound, and an 
optional insulating substrate. The relative weight or volume proportions 
of these materials strongly depend not only on the desired conductivity, 
but also on the density, molecular weight and the number of acid protons 
or functionality of the various components involved. Therefore, below are 
given general practical guidelines in the form of molar fractions and 
ratios for one of the preferred polyaniline/acid/metal compound systems, 
namely that comprised of unsubstituted polyaniline, dodecylbenzene 
sulfonic acid and ZnO. 
In one embodiment of the present invention directed for use with the 
preferred polyaniline/dodecylbenzene sulfonic acid/ZnO system, an 
approximately neutral, or slightly acidic polyaniline-dodecylbenzene 
sulfonic acid salt complex is formed, wherein the molar ratio between acid 
protons and the aniline repeat unit is from about 0.2 to about 0.5, more 
preferably from about 0.3 to about 0.5. When mixed with this neutral, or 
slightly acidic salt complex, the added reaction products of the metal 
compound and the protonic acid also are neutral or slightly acidic. The 
molar ratio of said metal compound reaction products, based on the element 
Zn, relative to said polyaniline-dodecylbenzene sulfonic acid complex, 
based on the aniline repeat unit, according to this embodiment of the 
present invention ranges from about 0.2 to about 20, preferably from about 
0.25 to 15, and most preferably from about 0.3 to about 10. 
In another embodiment of the present invention compositions can be prepared 
using highly acidic polyaniline-salt complexes, i.e. those complexes 
containing an amount of acid or acids in excess of 0.5 moles of acid 
protons per aniline repeat unit. In this embodiment, the composition of 
the metal compound-protonic acid reaction mixture needs to be altered and 
adjusted so that approximate neutrality or slight acidity of the final 
mixture is achieved after mixing with the acidic polyaniline-salt complex. 
Thus, in this embodiment of the present invention, the amount of protonic 
acid that is reacted with the metal compound is reduced by an amount of 
acid protons that is approximately the same as the excess amount used in 
the preparation of the acidic polyaniline-salt complex. In a particular 
embodiment of the present invention, the excess amount of acid or acids 
used in the preparation of the polyaniline-salt complex is such that only 
the pure metal compound without any additional acid is added to the 
mixture, and is reacted with the excess acid to yield the plasticizing 
compound and, in blends with insulating substrates, the percolation 
threshold reducing agent. Conversely, if in another embodiment of the 
present invention the polyaniline-salt complex is prepared with a 
deficiency in acidic protons, i.e. less than 0.3 mole per aniline repeat 
unit, the metal compound-acid reaction mixture will contain an excess of 
acid, so that after mixing of the final blend approximate neutrality or 
only slight acidity is achieved. 
In the above preferred embodiments the protonic acid is dodecylbenzene 
sulfonic acid and the metal compound is ZnO, which have normal equivalents 
of protons of 1 and 2, respectively. In other embodiments of the present 
invention acids and metal compounds may be used that have different normal 
equivalents of protons. It will be appreciated to those skilled in the art 
of acid-base chemistry that the relative proportions of the different 
acids and metal compounds need to be varied according to the normal 
equivalent of protons of the components to ensure neutrality or only 
slight acidity of the final mixture. 
The amount of conductive polyaniline-salt complex in blend compositions 
comprising insulating substrates may vary widely, and is dependent on the 
desired level of conductivity. Hence, the content of the polyaniline-salt 
complex according to this invention ranges from at least about 0.05% by 
weight to about 90% by weight, preferably from about 0.1% by weight to 
about 40% by weight, and most preferably from about 0.5% by weight to 
about 20% by weight. 
In addition to the polyaniline homopolymer or substituted aniline 
homopolymers, copolymers, or mixtures thereof, a protonic acid, a metal 
compound and a substrate, the compositions used in the present invention 
can include other optional components which either dissolve or do not 
dissolve in said compositions. The nature of such optional components can 
vary widely, and include those materials such as flame retardants, 
anti-oxidants, heat stabilizers, inorganic fillers, dyes and the like; 
which are known to those of skill in the art for inclusion in polymer 
articles. The total of other materials that can be present is as much as 
98% of the total mixture, and being optional can be omitted altogether. 
Usually, for commercially attractive products these added components may 
make up 2% to 50% by weight of the total final product. 
The method of forming the electrically conductive compositions of this 
invention is not very critical and can vary widely. It is important, 
however, that at some stage the substrate be processed with the 
polyaniline, protonic acid and metal compound in a fluid (liquid, 
semi-solid, or molten form) to assure proper intimate mixing. Otherwise, 
no special requirements are needed and common melt-processing techniques 
known to those ordinarily skilled in the art of polymer processing can be 
applied, such as extrusion, kneading and the like. 
Also, the sequence in which the different components are mixed together is 
not critical and may be varied widely. For example, the polyanilines may 
be first mixed with an excess of protonic acid to ensure homogeneous 
doping. Subsequently, the metal compound may be added to neutralize the 
complex, and simultaneously form the reaction product with the excess 
amount of protonic acid, which fulfils the special role of plasticizer and 
the percolation-threshold reducing agent. The resulting mixture can be 
directly processed from the melt in desirable shapes or be blended with 
the optional insulating substrate phase to yield the final blend of the 
present invention. Alternatively, the metal compound-protonic acid product 
is first prepared by common mixing methods, to yield the plasticizing and 
percolation-threshold reducing agent. This product, subsequently may be 
added to a separately prepared conductive polyaniline-protonic acid 
complex; and the resulting mixture can be directly processed from the melt 
in desirable shapes or be blended with the optional insulating substrate 
phase. Other mixing methods and sequences may be practiced within the 
scope of the present invention, if so desired. 
Typically, mixing and preparation of the metal compound-acid reaction 
product and blending with the polyaniline-salt complex is carried out at 
elevated temperatures, but below temperatures where thermal degradation 
commences. Preferably, processing temperatures range from at least about 
40.degree. C. to below about 300.degree. C., and most preferably from a 
least about 50.degree. C. to below about 250.degree. C. 
Common manufacturing methods may be used to fabricate useful electrically 
conductive articles from the compositions of the present invention. It 
will be appreciated by those skilled in the art of polymer product 
manufacturing that a variety of technologies may be utilized, depending on 
the nature and shape of the desired article or product, such as 
melt-spinning, melt-blowing, injection molding, film casting, and the 
like. 
The following specific examples are presented to illustrate the invention 
and are not to be construed as limitations thereon. 
EXAMPLE 1 
0.2 g zinc oxide (ZnO, Aldrich) powder and 0.6 g liquid dodecylbenzene 
sulphonic acid (DBSA, Tokyo Kasei), (ZnO:DBSA=1:3 w/w), were mixed in a 
dispersing mixer, whereafter the mixture was thermally solidified at 
150.degree. C. using a screw-mixer. A white reaction product was obtained 
that exhibited a melting temperature of about 115.degree. C. The reaction 
product was further transferred into a powder or a granulate using a 
grinder or a granulator, respectively. 
A solid, acidic complex comprising polyaniline (PANI) and DBSA, PANI-DBSA, 
with a weight ratio (w/w) of PANI:DBSA=1:4, was prepared in a screw mixer 
at 180.degree. C. as described in FI Patent Application 915 760 and herein 
included as a reference. 
0.8 g of the ZnO-DBSA reaction product, 0.8 g of the PANI-DBSA complex and 
10.4 g polystyrene (PS, Neste Chemicals, Finland, SB 735) resin were mixed 
in an injection molding apparatus at 180.degree. C. The obtained shaped 
article had a surface resistance of 500 k.OMEGA. and a surface pH of 7. 
The total amount of the electrically active component, polyaniline, was 
only 1.5 wt.-% of the total composition. 
EXAMPLE 2 
A 1:1 (w/w) mixture comprising acidic, solid PANI-DBSA complex and the 
reaction product of ZnO and DBSA, both prepared according to Example 1, 
was made by mechanical mixing. The resulting mixture was further 
melt-processed at 130.degree. C. using a screw-mixer. The obtained 
composition had a surface resistance of 100 k.OMEGA., exhibited excellent 
plasticizing properties and was neutral. 
EXAMPLE 3 
1105 g acidic PANI-DBSA complex (1:2.5 w/w) and 1606 g of a dispersion of 
ZnO in DBSA (1:2.7, w/w) were mechanically mixed. During mixing evolution 
of heat was observed and the mixture solidified completely in about 30-50 
minutes. The as-formed solid, neutral composition had a dark green color, 
a surface resistance of 500 .OMEGA. and exhibited good melting 
characteristics. 
EXAMPLE 4 
400 g ZnO and 2880 g DBSA (1:7.2 w/w) were mixed in a blender. To this 
mixture, 720 g of the emeraldine base (EB) form of PANI was added and 
mixed. The resulting dark grey liquid mixture was solidified according to 
a process described in FI Patent Application 915 760 at 185.degree. C. The 
resulting solid was neutral, had a surface resistance of 500 k.OMEGA. and 
exhibited good melting characteristics. 
EXAMPLE 5 
A 1:2.5 (w/w) complex of PANI-DBSA was prepared according to a process 
described in FI Patent Application 915 760. A reaction product was 
prepared by reacting 27 wt-% ZnO with 73 wt-% DBSA at 130.degree. C. A 
blend was prepared by mixing 2.4 g of a mixture containing 2.4 parts 
ZnO-DBSA reaction product and 3.5 parts of the PANI-DBSA complex and 9.6 g 
polystyrene (Neste, SB 735). The mixture was injection molded at 
170.degree. C. The resulting injection molded article had a surface 
resistance of 30 M.OMEGA. and excellent surface appearance. 
EXAMPLE 6 
15 g of a 1:1.2 (w/w) PANI-DBSA complex was mechanically mixed with 15 g of 
the reaction product of ZnO and DBSA of Example 1. The resulting mixture 
was mixed at 130.degree. C. using an apparatus as described in FI Patent 
Application 915 760. The resulting composition was neutral, had good 
plasticizing characteristics and had a surface resistance of 30 k.OMEGA.. 
EXAMPLE 7 
5 g PANI-EB and 15 g of the reaction product of ZnO and DBSA of Example 1 
was mixed according to Example 6. The resulting composition was neutral 
and had a surface resistance of 5 M.OMEGA.. 
EXAMPLE 8 
25 wt-% of ZnO-DBSA (1:3, w/w) and 75 wt-% PANI-DBSA (1:4, w/w) were mixed 
at 150.degree. C. The surface resistance of the resulting composition was 
3 k.OMEGA.. 
EXAMPLE 9 
20 wt-% of ZnO-DBSA (1:3, w/w) and 80 wt-5 PANI-DBSA (1:2.5, w/w) were 
mixed at 150.degree. C. The surface resistance of the resulting 
composition was 200 .OMEGA.. 
EXAMPLE 10 
20 wt-% of the composition of Example 9 and 80 wt-% polystyrene (Neste, SB 
735) were mixed at 160.degree. C. The surface resistance of the resulting 
blend was 500 k.OMEGA.. 
EXAMPLE 11 
25 wt-% of the composition of Example 9 and 75 wt-% of polyethylene (Neste, 
NCPE 2220) were mixed at 160.degree. C. The surface resistance of the 
resulting blend was 2 M.OMEGA.. 
EXAMPLE 12 
50 wt-% of ZnO-DBSA (1:4, w/w) and 50 wt-% PANI-DBSA (1:4, w/w) were mixed 
at 150.degree. C. The surface resistance of the resulting composition was 
2 M.OMEGA.. 
EXAMPLE 13 
13 wt-% of the composition of Example 12 and 87 wt-% of polyethylene 
(Neste, NCPE 2220) were mixed at 150.degree. C. The surface resistance of 
the resulting blend was 2 M.OMEGA.. 
EXAMPLE 14 
20 wt-% of the composition of Example 12 and 80 wt-% of polyethylene 
(Neste, NCPE 2220) were mixed at 150.degree. C. The surface resistance of 
the resulting blend was 1 M.OMEGA.. 
EXAMPLE 15 
50 wt-% ZnO-DBSA (1:4, w/w) and 50 wt-% PANI-DBSA (mole ratio 1:0.5) were 
mixed at 150.degree. C. The surface resistance of the composition was 500 
.OMEGA.. 
EXAMPLE 16 
25 wt-% ZnO-DBSA (1:3, w/w) and 75 wt-% PANI-DBSA (1:2.5, w/w) were mixed 
at 150.degree. C. The surface resistance of the composition was 1 
k.OMEGA.. 
EXAMPLE 17 
20 wt-% of the composition of Example 16 and 80 wt-% polystyrene (Neste, SB 
735) were mixed at 150.degree. C. The surface resistance of the resulting 
blend was 5 M.OMEGA.. 
EXAMPLE 18 
20 wt-% of the composition of Example 16 and 80 wt-% polyethylene (Neste, 
NCPE 2220) were mixed at 150.degree. C. The surface resistance of the 
resulting blend was 10 M.OMEGA.. 
From the blends according to Example 7-18 testing pieces were prepared in 
an injection moulding machine. The blends prepared in these experiments 
had by the injection moulding good plasticising properties, the working 
trace was good, and the mechanical properties of the products closely 
resembled those of the matrix plastics. 
EXAMPLES 1-18 are summarized in Table 1. 
TABLE 1 
______________________________________ 
ZnO/ PANI/ 
DBSA DBSA Matrix 
Example 
(w/w) (w/w) T/.degree.C. 
polymer 
pH R 
______________________________________ 
1 1:3 1:4 180 PS 7 500k.OMEGA. 
0.8 g 0.8 g 10.4 g 
2 1:3 1:4 130 No 6-7 100k.OMEGA. 
0.8 g 0.8 g Matrix 
3 1:2.7 1:2.5 RT No 6-7 500k.OMEGA. 
1606 g 1105 g Matrix 
4 1:7.2 185 No 6-7 500k.OMEGA. 
2880 g 720 g Matrix 
5 1:2.7 1:2.5 170 PS 6-7 30M.OMEGA. 
0.98 g 1.425 g 9.6 g 
6 1:3 1:1.2 130 No 6-7 30M.OMEGA. 
15 g 15 g Matrix 
7 1:3 130 No 6-7 5M.OMEGA. 
15 g 5 g Matrix 
8 1:3 1:4 150 No 6-7 3k.OMEGA. 
2.5 g 7.5 g Matrix 
9 1:3 1:2.5 150 No 6-7 200k.OMEGA. 
2.0 g 8.0 g Matrix 
10 1:3 1:2.5 160 PS 6-7 500k.OMEGA. 
2.0 g 8.0 g 40 g 
11 1:3 1:2.5 160 PE 6-7 200k.OMEGA. 
2.0 g 8.0 g 30 g 
12 1:4 1:4 150 No 5-6 200k.OMEGA. 
2.0 g 2.0 g Matrix 
13 1:4 1:4 150 PS 5-6 2M.OMEGA. 
2.0 g 2.0 g 27 g 
14 1:4 1:4 150 PE 5-6 1M.OMEGA. 
2.0 g 2.0 g 16 g 
15 1:4 1:0.5 150 No 5-6 500.OMEGA. 
2.0 g 2.0 g Matrix 
16 1:3 1:2.5 150 No 6-7 1k.OMEGA. 
2.0 g 6.0 g Matrix 
17 1:3 1:2.5 150 PS 6-7 5M.OMEGA. 
2.0 g 6.0 g 54 g 
18 1:3 1:2.5 150 PE 6-7 10M.OMEGA. 
______________________________________ 
COMATIVE EXAMPLES A-C (OUTSIDE THIS INVENTION) 
Comparative Example A 
An amount of 0.6 g of polyaniline (PANI) (of an inherent viscosity in 97% 
sulfuric acid, at room temperature, in a 0.1% w/w solution of 1.2 dl/g), 
in its conductive salt form with dodecylbenzene sulphonic acid (DBSA), 
having a molar ratio of PANI(DBSA)0.5, was mixed with 2.4 g of finely 
divided powder of isotactic polypropylene (Neste, VB 80 12 B, MFR=8 g/10 
min @230.degree. C.) using a laboratory-scale twin-screw extruder at 
170.degree. C., at 100 rpm for 5 minutes. The resulting polypropylene 
blend contained 20wt-% of the PANI(DBSA).sub.0.5 complex and had an 
electrical conductivity of 10.sup.-8 S/cm, as measured by the usual four 
probe technique. Small samples of the blend were immersed in water and the 
pH was monitored. After 24 hrs the pH of the water was 5.6. 
This example illustrates that conductive PANI(DBSA).sub.0.5 salt could be 
melt-blended with thermoplastics to produce an electrically conducting 
polymer blend which was only slightly acidic after immersion in water for 
24 hours. However, the required amount of the PANI salt was high to 
achieve desirable levels of conductivity, i.e. the percolation threshold 
was higher than 20 wt-%. 
Comparative Example B 
A total of 3 g of a mixture containing 2.4 g of low density polyethylene 
(LDPE, Neste, NCE 1804, MI 1.8) and 0.6 grams of PANI(DBSA).sub.1.1, i.e. 
a PANI(DBSA)-complex containing an excess amount of DBSA (wt-ratio 
PANI/DBSA=1/4), was mixed in a laboratory-scale twin-screw extruder at 
180.degree. C. at 100 rpm for 3.5 minutes. The resulting blend of LDPE 
contained 20 wt-% of PANI(DBSA).sub.1.1 and had a conductivity of 
2.times.10.sup.-4 S/cm. Pieces of the blend were immersed in water and 
the pH was monitored. After 24 hrs the pH of the water was pH.about.1. 
Comparative Example C 
A polymer blend was made according to Example B with the exception that 
only 10 wt-% of PANI(DBSA).sub.1.1 was used instead of 20%. The 
conductivity of the resulting blend was 3.times.10.sup.-7 S/cm. Pieces of 
the blend were immersed in water and the pH was monitored. After 24 hrs 
the pH of the water was pH.about.1. 
Comparative Examples B and C demonstrate that electrically conducting 
polymer blends could be produced using thermoplastics and 
PANI(DBSA).sub.1.1 utilizing conventional melt processing techniques. The 
examples further demonstrate, however, that addition of an excess amount 
of DBSA to the PANI-salt was required in order to lower the percolation 
threshold of the conductivity. However, due to the large amount of free 
acid in the blend, the acidity of the final product was unacceptably high. 
EXAMPLE 19 
ZnO powder and liquid DBSA, using different molar ratios ranging from 
1:1-1:8, were mixed between 130.degree.-180.degree. C. During the 
reaction, water was liberated under the formation of a complex between ZnO 
and DBSA, suggesting the formation of the structure denoted Zn(DBS).sub.2. 
This solid complex had a melting temperature of ca. 115.degree. C., was 
observed to be liquid crystalline and of fiber forming characteristics, in 
addition of being non-conducting. For simplicity, in subsequent examples, 
this reaction product will be referred to as Zn(DBS).sub.2. 
EXAMPLE 20 
An amount of 2.7 g of LDPE, 0.3 g of PANI(DBSA).sub.0.5 and 0.86 g of the 
Zn(DBS).sub.2 material prepared according to the method of Example 19 such 
that the molar ratio Zn(DBS).sub.2 /PANI(DBSA).sub.0.5 =1.0, were mixed in 
a twin-screw extruder for 3.5 minutes at 180.degree. C. at 100 rpm. The 
conductivity of the resulting polymer blend, containing 7.8 wt-% of 
PANI(DBSA), had a four probe conductivity of 8.times.10.sup.-2 S/cm. 
Pieces of the blend were immersed in water and the pH was monitored. After 
24 hrs the pH of the water was pH.about.4. 
EXAMPLES 21-25 
Blends were made according to Example 20 but with different amounts of 
PANI(DBSA).sub.0.5. The ratio of Zn(DBS).sub.2 /PANI(DBSA).sub.0.5 was 
maintained at 1.0. The conductivities of the resulting polymer blends were 
measured and are listed in Table 2 below. 
TABLE 2 
______________________________________ 
wt % Conductivity 
Example PANI(DBSA).sub.0.5 
(S/cm) 
______________________________________ 
21 2.3 4 .times. 10.sup.-5 
22 3.2 2 .times. 10.sup.-3 
23 4.4 3 .times. 10.sup.-2 
24 7.8 8 .times. 10.sup.-2 
25 12.8 2 .times. 10.sup.-1 
______________________________________ 
EXAMPLE 26 
An amount of 2.7 g of isotactic polypropylene (i-PP, Neste, VB 80 12 B), 
0.3 g of PANI(DBSA).sub.0.5 and 0.86 g of Zn(DBS).sub.2, prepared 
according to Example 19, were mixed in a twin-screw extruder at 
170.degree. C., at 100 rpm for 5 minutes. The resulting polymer blend, 
containing 7.8 wt-% PANI(DBSA)0.5 of the total composition of the blend, 
had a four probe conductivity of 2.times.10.sup.-2 S/cm. Pieces of the 
blend were immersed in water and the pH was monitored. After 24 hrs the pH 
of the water was pH.about.4. 
EXAMPLES 27-31 
Blends were made according to Example 26 but with different the amounts of 
PANI(DBSA).sub.0.5. The ratio of Zn(DBS).sub.2 /PANI(DBSA).sub.0.5 was 
varied. The conductivities of the resulting polymer blends were measured 
and are listed in Table 3 below. 
TABLE 3 
______________________________________ 
wt % Conductivity 
Example PANI(DBSA).sub.0.5 
(S/cm) 
______________________________________ 
27 3.2 4 .times. 10.sup.-6 
28 4.4 2 .times. 10.sup.-3 
29 7.8 2 .times. 10.sup.-2 
30 12.8 6 .times. 10.sup.-2 
31 21.0 2 .times. 10.sup.-1 
______________________________________ 
EXAMPLE 32 
An amount of 2.7 g polystyrene (Neste, SB 735), 0.3 g PANI(DBSA).sub.0.5 
and 0.86 g of Zn(DBS).sub.2, prepared according to example 1, were mixed 
in a twin-screw extruder at 190.degree. C. at 100 rpm for 5 minutes. The 
resulting polymer blend, containing 7.8 wt-% of PANI(DBSA).sub.0.5 of the 
total composition of the blend, had a four probe conductivity of 
2.times.10.sup.-2 S/cm. Pieces of the blend were immersed in water and the 
pH was monitored. After 24 hrs the pH of the water was pH.about.5. 
EXAMPLE 33-37 
Blends were prepared according to Example 14 but with different the amounts 
of PANI(DBSA).sub.0.5. The ratio of Zn(DBS).sub.2 /PANI(DBSA).sub.0.5 was 
maintained at 1.0. The conductivities of the resulting polymer blends were 
measured and are listed in Table 4 below. 
TABLE 4 
______________________________________ 
wt % Conductivity 
Example PANI(DBSA) (S/cm) 
______________________________________ 
33 2.3 8 .times. 10.sup.-7 
34 3.2 5 .times. 10.sup.-6 
35 4.4 8 .times. 10.sup.-4 
36 7.8 2 .times. 10.sup.-3 
37 12.8 2 .times. 10.sup.-2 
______________________________________ 
Examples 20-37 and Tables 2-4 demonstrate that by the addition of 
Zn(DBS).sub.2 to a mixture of a common thermoplastic commodity polymer and 
PANI(DBSA).sub.0.5, polymer blends could be produced, using ordinary melt 
processing techniques, that exhibited surprisingly lower percolation 
thresholds for electrical conductivity (1-3 wt-% of the conducting 
polyaniline complex) than observed in blends produced without the addition 
of the Zn(DBS).sub.2. 
EXAMPLE 38 
A polymer blend was made according to example 2 with the exception that 
instead of ZnO, CuO (Aldrich) was used as the metal compound. The 
resulting blend was electrically conducting, the four point conductivity 
being 10.sup.-5 S/cm. 
Example 20 demonstrate that also other metal compounds than ZnO could be 
used to form a condensation product with a protonic acid that acted as a 
percolation-threshold reducing agent. 
EXAMPLE 39 
A polymer blend was made according to example 2 with the exception that 
instead of DBSA, ethylsulfonic acid (ESA, Aldrich) was used as the 
protonic acid. The resulting blend was electrically conducting and the 
four point conductivity was measured to be 10.sup.-4 S/cm. 
EXAMPLE 40 
7.17 g of Zn(DBS).sub.2 was mixed with 1.7 g of conducting polyaniline 
compound (Versicon.TM., Allied-Signal) for 5 minutes at 130.degree. C. in 
a conical twin-screw extruder. 0.355 g of the obtained mixture, 0.717 g of 
additional Zn(DBS).sub.2 and 2.328 of acrylonitrile-butadiene-styrene 
(ABS) were mixed in the same extruder at 160.degree. C. for 5 minutes. The 
conductivity of films of the above blend, pressed at 180.degree. C., was 
8.3.times.10.sup.-2 S/cm, containing only 2 wt-% of the conducting 
component Versicon.TM.. 
Comparative Example D (Outside This Invention) 
Example 1 was repeated, but instead of DBSA, p-toluene sulphonic acid (TSA, 
Aldrich) was used. Mixing of ZnO and TSA resulted in the formation of a 
white powder that did not display an melting point below 300.degree. C. A 
polymer blend was made according to Example 2 with the exception that 
instead of Zn(DBS).sub.2, the above condensation product of ZnO and TSA 
was used. The resulting blend was non-conducting and optical microscopy 
showed that the blend comprised of dispersed particles of the condensation 
product. 
Comparative Example E (Outside This Invention) 
A polymer blend was made according to Example 20 with the exception that 
instead of Zn(DBS).sub.2, the common, commercial plasticizers, pentadecyl 
phenol and dodecylphenol (Aldrich) were used. The blends, although well 
plasticized, were non-conducting. 
This example illustrates that the use of the aforementioned condensation 
products of metal compounds, preferably ZnO, and protonic acids indeed 
were unusually effective in functioning as a neutralization, 
plasticization and percolation-threshold reducing agents, which was not 
observed in the use of the common plasticizers as those employed in 
Example 39.