Polymeric matrices reinforced with highly dispersed synthetic zeolitic particulates

High impact strength, improved bending modulus composites are comprised of a polymeric matrix, e.g., elastomer or synthetic polymer of polypropylene or polyamide type, said matrix having highly dispersed therein a reinforcing amount of relatively small synthetic zeolitic filler particulates, e.g., of types A, 4A and Na-P, and the mean size of the elementary particles thereof advantageously closely approximating those of the secondary particles.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to novel synthetic zeolitic fillers having a 
high degree of dispersibility, and, more especially, to the use of such 
zeolites as reinforcing fillers for polymeric matrices. 
2. Description of the Prior Art 
It has long been known to utilize mineral fillers to improve or enhance 
certain properties of elastomeric polymer matrices in particular, and the 
plastics in general. 
Unfortunately, the incorporation of, and reinforcement with, such fillers 
may suffer from two types of disadvantage, one being an economic 
disadvantage, if the cost of the filler is excessively high, and the other 
being a technical disadvantage, if the improvement made in the properties 
by reason of the filler is at the expense of other properties, which is 
often the case. 
In addition, the behavior of the filler is also often characteristic of the 
filler/elastomer or filler/plastic pair, for reasons which are related to 
the morphology of the filler, and the polymer matrix, and surface 
chemistry. Thus, certain generally accepted laws have been more or less 
properly verified. However, with the conventional fillers, in certain 
instances it has been found that a coarser filler displays better 
dispersion than a finer filler. 
Accordingly, considerable studies were conducted by the present applicants 
as to those factors likely to result in good dispersion, and in an effort 
to provide a filler which satisfies the requirement of good 
dispersibility; also to verify the benefit thereof in regard to improving 
certain behaviour in specific cases, albeit it will of course be 
appreciated that such specific instances are not to be construed as in any 
way limiting the present invention. 
In particular, applicants' such efforts have been oriented as regards the 
zeolites. Indeed, it is known that the natural zeolites have already been 
incorporated in polypropylene; see Natural Zeolites by L. B. Sand and F. 
A. Mumpton, Pergamon Press, page 447. The results set forth in the noted 
publication reveal, for example, that polypropylene reinforced with a 
clinoptilolite filler suffers from a reduction in its impact strength. 
It has also been proposed that the impact or shock properties of 
polypropylene might be improved with calcium carbonate-based fillers. 
However, any improvement achieved in regard to shock properties is quite 
often insufficient in relation to the requirements necessary for the 
particular uses intended. 
SUMMARY OF THE INVENTION 
It has now surprisingly been found, and which is a major object of the 
present invention, that the aforesaid disadvantages and drawbacks can be 
avoided by utilizing as the reinforcing filler, a synthetic zeolite having 
a small particle size. 
More preferably according to the invention, the reinforcing zeolitic filler 
is characterized in that the mean particle size of the elementary 
particles closely approximates that of the secondary structure particles.

DETAILED DESCRIPTION OF THE INVENTION 
More particularly according to this invention, the mean particle sizes of 
the synthetic reinforcing zeolitic fillers is advantageously less than 10 
.mu.. And in an especially preferred embodiment of the invention, the 
granulometric distribution of said particles is over but a very narrow 
range. 
The synthetic zeolites consistent with the invention are notably of type A, 
and more advantageously are of type 4A, and of type Na-P. 
Also consistent with this invention, the size of the elementary particles 
is the apparent diameter of the particle; namely, is the diagonal of the 
face of a cube, or the diameter of a sphere if the particle is spherical. 
The size of the secondary particles is determined by measurement with an 
apparatus of Coulter type, under those conditions hereinafter specified. 
As hereinbefore mentioned, the difference between the two types of 
particles must be as small as possible. However, it should be appreciated 
that in accordance with the invention, in the event of reinforcement with 
a filler having relatively small particle sizes, namely, on the order of 
one micron or but a few microns, the latter may be larger in relative 
value, but must remain small insofar as absolute value is concerned, and 
most advantageously must not exceed one micron. 
It too will be appreciated that those limits set forth immediately above 
are not absolutely critical. Indeed, same depend on the strict necessity 
for obtaining any particular effect or property. Accordingly, it would not 
be a departure from the scope of the present invention to lower the 
particular tolerances associated with such desired result, effect or 
property. 
Advantageously, the filler particulates according to the invention are of a 
regular shape, without having sharp angles. Thus, a substantially 
spherical shape in the case of a zeolite 4A is a markedly desirable shape. 
Also as hereinbefore mentioned, the fillers according to the invention have 
the property of exhibiting remarkable dispersion in polymers and in 
elastomers, enabling them to be widely used on a general level. 
More particularly, this high level or degree of dispersibility is 
advantageous in the case of plastic materials such as the various 
polyamides. 
However, a spectacular improvement in the impact strengths and properties 
of polypropylene was unexpectedly observed, while at the same time 
retaining the improvement in the bending modulus, which is due to the 
addition of the filler. 
It too will be appreciated that the various ways of carrying out the 
invention and the advantages thereof are not limited to those described 
above. 
Nonetheless, in order to further illustrate the present invention and the 
advantages thereof, the following specific examples are given, it too 
being understood that same are intended only as illustrative and in nowise 
limitative. 
In said examples which follow, the various measurements were made in the 
following ways: 
[1] Characterization of the zeolite 
(i) Determining the size of the elementary particles 
A double-faced adhesive strip was placed on the specimen carrier of a 
scanning microscope. The appropriate amount of specimen was properly 
placed thereon, in powder form. The specimen carrier was turned over to 
remove any excess powder. A carbon lacquer was coated around the powder, 
to provide a good contact; metalization was thus effected, and the 
observations were made. 
An enlargement on the order of 2000 to 9000 was used to facilitate 
observation of the particles on a specimen having dimensions of at least 
20.mu..times.20.mu., and the size of the elementary particles was 
determined, by considering the apparent diameter of ten particles, which 
were considered as being representative of the specimen. 
(ii) Determining the size of the secondary particles 
This measurement was performed by means of a Coulter counter, using the 
following solution, by weight, as the electrolyte. 
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Water 78% 
Glycerine 20% 
NaCl 1% 
Na hexametaphosphate 0.5% 
Formol 0.5% 
Dispersion, 10 min (ultrasonics) 
40000 Hertz 
100 Watts 
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[2] Characterization of the composite 
The composites were prepared in the following manner 
(i) In the case of polypropylene, by cold mixing the polymer in powder form 
and the filler on an external Henschel mixer for a period of 15 minutes, 
followed by malaxation at a temperature of 80.degree. C. for 15 minutes, 
in a Banbury mixer or extrusion in a single-screw or double-screw 
extruder. 
The product, after granulation, was then injected at a temperature of 
230.degree. C. into a Monomat injection press, in order to produce small 
test plates. 
In the case of polyamide, the mixture of granulated polyamide and filler, 
in powder form, was extruded in a Buss rotary and reciprocating 
single-screw extruder, at a temperature of 270.degree. C., granulated and 
then injected at a temperature of 270.degree. C., to also produce small 
test plates. 
The state of dispersion in the polymer was determined using the test pieces 
which were molded in the above-described manner. The presence of any 
conglomerates of filler which may have formed was in particular, detected 
visually using an optical and/or electronic microscope. 
(ii) In the case of polypropylene/filler systems, molded test pieces were 
used to evaluate the modulus of bending strength NF T 51001 and cold 
impact strength using the non-notched Charpy method, at a temperature of 
-20.degree. C. (Standard NF.T 51 035). 
[3] The base polymers used were 
(i) Polypropylene Napryl 61200 AQ (Naphtachimie powder having a viscosity 
index of 110, in accordance with standards NF T 51620); and 
(ii) Rhone-Poulenc polyamide A 216 (Polyhexamethylene adipamide Nylon 66). 
The following zeolites were used in the examples which follow. 
Zeolite No. 1 
The apparatus depicted in FIG. 1 of the accompanying drawings was used for 
the preparation thereof, thus: 
A solution of sodium aluminate titrating at 110 g/l, calculated as Na.sub.2 
O, and 150 g/l, calculated as Al.sub.2 O.sub.3, was cooled to 0.degree. C. 
in the tubular exchanger 1, at a rate of flow of 10 l/h. The cooled stream 
was continuously mixed with a flow 3 of 4 l/h of a sodium silicate 
solution, which was at a temperature of 20.degree. C. and which titrated 
at 25% of SiO.sub.2 and 11.6% of Na.sub.2 O by weight, in a stirred 
reaction vessel 2. 
The homogenous mixture, the temperature of which was in the vicinity of 
12.degree. C., was fed by means of a peristaltic pump 4 to an injector 5 
having capillaries which were 0.5 mm in diameter, to continuously form 
drops which fall by gravity into the upper section of a reaction vessel 6 
filled with petroleum maintained at a temperature of 85.degree. C. by 
circulation of heated brine introduced via line 7 into the jacket. 
The specific gravity of the bath was adjusted such that the mean time taken 
for the drops formed by the capillaries to fall through the bath was 3 
seconds. At the end of that period of time, the spherical particles were 
gelled and were gradually converted into a fluid aluminosilicate which 
collected in the conical section 9 of the reaction vessel 6. The 
suspension was continuously drawn off by means of a suction pipe 8 at the 
rate of 14 l/h, after 2 hours of continuous supply of the reactants, in 
order to circumscribe a mean residence time for the reactants in the 
reaction vessel of 2 hours. 
In this example, the concentration in respect of crystalline sodium 
aluminosilicate in the suspension of microcrystals was approximately 340 
g/l, with the liquid phase which was virtually free of SiO.sub.2 titrating 
76 g/l of Na.sub.2 O and 12 g/l of Al.sub.2 O.sub.3. The resulting 
suspension of microcrystals was drained and washed on a filter having a 
mean orifice size of 1.mu.. The washed cake was then dried to constant 
weight in drying oven at a temperature of 100.degree. C., before analysis. 
The resulting particulate product had a uniform mean granulometry of 3.mu. 
and the following grain size distribution: 
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% of particles &lt;1.mu. 2% 
&lt;2.mu. 20% 
&lt;5.mu. 92% 
&lt;10.mu. 98% 
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Zeolite No. 2 
A solution of sodium aluminate, containing 219.5 g of aluminate, was 
dissolved in 757.3 g of a 10 g/l NaOH solution and was cooled to a 
temperature of -5.degree. C. in a tubular reactor 1, at a flow rate of 10 
l/h. The cooled flow was continuously mixed with a flow 3 of 4 l/h of 
solution of sodium silicate, which was at a temperature of 20.degree. C. 
and which titrated 26.9% of SiO.sub.2 and 39.46% of Na.sub.2 O by weight, 
in a stirred reaction vessel 2. 
Operation was as in Example 1, but the temperature of the mixture was 
15.degree. C. and the mean residence time of the reactants was 2 hours, 15 
minutes. 
The conditions of this Example reflect an initial system as follows: 
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SiO.sub.2 /Al.sub.2 O.sub.3 
= 2.00 
Na.sub.2 O/SiO.sub.2 
= 1.19 
H.sub.2 O/Na.sub.2 O 
= 26.00 
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Upon completion of the reaction, it was found that the mother liquor 
contained 70 g/l of Na.sub.2 O, 2.6 g/l of SiO.sub.2 and 3.0 g/l of 
Al.sub.2 O.sub.3. 
The theoretical yield: 
##EQU1## 
was 19%. 
The chemical formula of the resulting product was 1.06 Na.sub.2 O, Al.sub.2 
O.sub.3, 2.04 SiO.sub.2. 
The X-ray spectrum thereof was characteristic of a zeolite type of 4A. 
The granulometry, measured with the Coulter counter, evidenced a mean 
diameter for the crystalline of 3.6.mu.. 
The grain size distribution was as follows: 
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Diameter &gt; % by weight 
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15.mu. 2.5 
10.mu. 4 
5.mu. 22 
3.mu. 68 
2.mu. 93 
1.mu. 98 
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Zeolite No. 3 
The operating procedure was the same as for zeolite No. 1. 
A solution of sodium aluminate, which titrated 200 g/l calculated as 
Na.sub.2 O and 200 g/l calculated as Al.sub.2 O.sub.3, was cooled to a 
temperature of -4.degree. C. in a tubular exchanger 1 at a rate of flow of 
10 l/h. The cooled flow was continuously mixed with a flow 3 of 4 l/h of a 
solution of sodium silicate, which was at a temperature of 20.degree. C. 
and which titrated 25.4% of SiO.sub.2 and 7.4% of Na.sub.2 O by weight, in 
the stirred reaction vessel 2. 
The other conditions were otherwise identical, except for the temperature 
of the mixture which was 15.degree. C. and the residence time in the 
reaction vessel which was 1 hour. 
The suspension which was drawn off was then drained and washed. 
The resulting product had a uniform mean granulometry of 1.5.mu., with the 
following distribution: 
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% of particles &lt;1.mu. 20% 
&lt;2.mu. 68% 
&lt;5.mu. 95% 
&lt;10.mu. 98% 
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Zeolite No. 4 
This zeolite was prepared in accodance with the technique described in U.S. 
Pat. No. 4,263,266. 
The apparatus used, as depicted in FIG. 2, comprised a reaction vessel 10 
and a venturi tube 11, by means of which the reactants were brought into 
contact with each other. 
The silicate solution was introduced by means of a pipe inlet 12 while the 
aluminate solution or the recycled liquor was introduced by way of a pipe 
arrangement 13 which was associated with a circulating pump 14 when 
employs a recycle of the liquor from the reaction vessel 1, in which all 
or a portion of the aluminate was charged at the beginning of the 
operation. 
The cylindrical portion of the ventiru tube had an inside diameter of 14 
mm. The solution and the operating conditions, in particular the 
conditions of the rates of flow, were determined such as to give high 
Reynolds numbers, on the order of 100000, in the cylindrical portion of 
the apparatus. 
Utilizing a decomposed Bayer process liquor, having a specific gravity of 
1.27, containing 100 g/l of Al.sub.2 O.sub.3 and 182 g/l of Na.sub.2 O in 
total, 2 m.sup.3 of dilute solution were prepared, which were added to a 3 
m.sup.3 reaction vessel which was stirred (by a screw), in a concentration 
of 64 g/l of Al.sub.2 O.sub.3 and 111 g/l of Na.sub.2 O in total, 
including 15.4 g/l of Na.sub.2 O in carbonate form. 
500 l of silicate, with 92 g/l of Na.sub.2 O and 199 g/l of SiO.sub.2, were 
added at a temperature of 75.degree. C., over a period of 45 minutes, in a 
venturi, while recycling 10 m.sup.3 of the aluminate solution. The 
resulting gel had a loss upon firing of 84.4%. Crystallization was then 
carried out at a temperature of 81.degree. C., for a period of 2 hours. 
The mean diameter of the resultant zeolite was 3.6.mu.. 
Zeolite No. 5 
The method of producing this zeolite was the same as the method of 
producing the zeolite No. 2, except that the medium reflected the 
following molar ratios: 
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SiO.sub.2 /Al.sub.2 O.sub.3 
= 2.0 
Na.sub.2 O/SiO.sub.2 
= 1.30 
H.sub.2 O/Na.sub.2 O 
= 25 
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and same was dried without preliminary draining or filtering, resulting in 
a mean grain size of 11.mu.. 
EXAMPLE 1 
In this Example, the test measurements were carried out on polypropylene 
matrix, one being a test without any filler, and one utilizing a filler 
comprising a natural calcium carbonate having a mean diameter of 1.mu., 
and the remaining tests employing the five zeolites referred to above. 
The table set forth below also reports, in microns, the sizes of the 
primary and secondary particles of the various zeolites used, and also 
provides an evaluation of the degree of dispersion thereof in the 
polypropylene matrix. 
FIG. 3 of the drawings also illustrates the different granulometric curves, 
curves 1, 2, 3, 4 and 5, respectively corresponding to the granulometries 
ofthe zeolites Nos. 1, 2, 3, 4 and 5, while Figures 4 to 13 reflect the 
appearance of the zeolites and the dispersion thereof in the polypropylene 
matrix, under an electronic scanning microscope, i.e.: 
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FIG. 4 zeolite 1 
FIG. 5 zeolite 2 
FIG. 6 zeolite 3 
FIG. 7 zeolite 4 
FIG. 8 zeolite 5 
FIG. 9 zeolite 1 in polypropylene 
FIG. 10 zeolite 2 in polypropylene 
FIG. 11 zeolite 3 in polypropylene 
FIG. 12 zeolite 4 in polypropylene 
FIG. 13 zeolite 5 in polypropylene 
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TABLE 
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GRANULO- Bend- 
METRY OF ing 
(in .mu.) modu- 
Pri- Secon- Cold lus, in 
Nature of 
mary dary Dis- Parts impact mega 
the parti- parti- per- by strength, 
pascal 
filler cles cles sion weight 
kj/m.sup.2 
MPa 
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Ca Carbonate D 30 16 1950 
Zeolite 1 
2.9 2.8 D 30 28 2020 
Zeolite 2 
3.5 3.6 D 30 28 2025 
Zeolite 3 
1.1 1.5 D 10 18 1600 
Zeolite 4 
2.9 3.5 D 30 28 2050 
Zeolite 5 
&lt;3 11 ND 30 7 1980 
Reference polypropylene, without filler 
11 1350 
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D = good filler dispersion 
ND = filler not dispersed 
EXAMPLE 2 
This Example did not employ a zeolite of type 4A, but rather a zeolite of 
type Na-P, which was produced under the following conditions: 
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Reaction medium: 
SiO.sub.2 /Al.sub.2 O.sub.3 
= 5 
Na.sub.2 O/SiO.sub.2 
= 0.7 
Na.sub.2 O/Al.sub.2 O.sub.3 
= 3.5 
H.sub.2 O/SiO.sub.2 
= 21 
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Temperature 92.degree. C. 
Time: 4 hours 
The results of this Example are illustrated in FIG. 14 with respect to 
granulometry; FIG. 15 shows the zeolite, per se, and FIG. 16 shows the 
zeolite dispersed in a polypropylene matrix. 
EXAMPLE 3 
Recognizing that effecting an advanced state of dispersion in polyamide 66 
is the first step for attaining improved mechanical properties by surface 
treatment of the fillers, it was found that the zeolites according to the 
invention (zeolite No. 1), when reinforcing a polyamide 66 (A 216 of 
Rhone-Poulenc Technyl), in a proportion of 30%, displays this property, 
unlike the zeolite No. 5 which, as regards a polypropylene matrix, does 
not have such capacity for dispersion, under the noted conditions of 
transformation (with FIGS. 17 and 18 reflecting the dispersion of the 
zeolite No. 1 in a polyamide matrix, and the FIGS. 19 and 20 reflecting 
the dispersion of the zeolite No. 5 in polyamide 66). 
While the invention has been described in terms of various preferred 
embodiments, the skilled artisan will appreciate that various 
modifications, substitutions, omission s, and changes may be made without 
departing from the spirit thereof. Accordingly, it is intended that the 
scope of the present invention be limited solely by the scope of the 
following claims.