Reduced melt viscosity CPVC blends containing sulfur and various metal carbonate stabilizers

Chlorinated polyvinyl chloride when blended with sulfur is often miscible and has reduced melt flow viscosity. Various metal carbonates impart improved stability and optionally various fibers can be utilized to increase the tensile strength of the composition.

FIELD OF THE INVENTION 
Chlorinated polyvinyl chloride when blended with sulfur and various metal 
carbonates have reduced melt flow viscosity and improved stability with 
regard to dehydrohalogenation. 
BACKGROUND ART 
Heretofore, various tin compounds such as dibutylin-S,S'-bis-isooctyl 
mercaptoacetate, have been utilized to improve the stability of 
chlorinated polyvinyl chloride. 
The article Sulfur-Containing, Smoke-Inhibited Polymer Compositions, 
Research Disclosure, October 1979, pp 556-57, relates to reduced smoke 
generation of polymers such as polyvinyl chloride obtained by the addition 
of sulfur or sulfur-containing compounds. 
U.S. Pat. No. 4,394,325 to Bresser et al relates to an inorganic antimony 
compound composition comprising at least one organic antimony compound 
having at least 1 antimony-sulfur-carbon linkage and as a stabilizer 
therefore, elemental sulfur. 
U.S. Pat. No. 4,711,921 to Lehr relates to the use of BaCO.sub.3 with 
various organotin compounds, such as dibutyltin-S,S'-bis-isooctyl 
mercaptoacetate, in chlorinated polyvinyl chloride polymers to improve the 
heat stability thereof. 
Soviet Pat. No. 717,118 to Nizhnik et al relates to improved cohesive 
strength of an adhesive and its adhesion to asphaltic concrete wherein the 
adhesive contains a chlorinated polyvinyl chloride, a plasticizer, rosin, 
and sulfur. 
French Pat. No. 2,519,995 to Du Saint Heveny, relates to a laminate applied 
to a ship hull to reduce cracking. The topcoat of the laminate contains 
polyvinyl chloride having copper oxide and flowers of sulfur therein. 
Russian Pat. No. 1,151,565 to Vyborov et al relates to an adhesive 
composition containing chlorinated polyvinyl chloride, sulfur, and 
diethanolamine-formaldehyde-tri(p-aminophenyl)methane which increases the 
binding strength of the compound to vulcanizates containing unsaturated 
rubbers. 
SUMMARY OF THE INVENTION 
Utilization of sulfur blended with chlorinated polyvinyl chloride results 
in improved melt flow characteristics, that is a reduced melt flow 
viscosity of at least 10 percent, desirably at least 25 percent, and often 
in excess of 50 percent. Every 100 parts by weight of chlorinated 
polyvinyl chloride (57 or 58 percent to about 72 percent by weight of 
chlorine therein) contains from about 3 parts to about 42 parts by weight 
of sulfur which often is miscible therewith and is stabilized with from 
about 1 to about 10 parts by weight of a stabilizing compound such as a 
metal carbonate. Optionally, various fibers are incorporated into the 
blend to yield an improved flex modulus. The fibers can be inorganic or 
organic such as fiberglass, polyester, graphite, polyaramid, and the like.

DETAILED DESCRIPTION OF THE INVENTION 
The chlorinated polyvinyl chloride (CPVC) of the present invention contains 
from about 57 or 58 percent to about 72 percent by weight and preferably 
from about 63 percent to about 70 percent by weight of chlorine therein 
based upon the total weight of the polymer. The preparation of CPVC is 
well known to the art and to the literature. CPVC however is generally 
unstable at high processing temperatures such as at least 200.degree. C. 
and must be stabilized. Conventional stabilizers often promote undesired 
crosslinking of the polymer and, when organotin sulfide stabilizers are 
utilized in the presence of sulfur, they result in an accelerated 
blackening of the resin. The stabilizers of the present invention, 
however, have been found to stabilize the resin better than when 
conventional stabilizers are used. 
The utilization of sulfur has been found to generally improve fusion and 
melt flow of the CPVC resin as well as reduce the tendency thereof to 
crystallize. Generally, an amount of from about 3 to about 42 parts by 
weight and preferably from about 5 to about 20 parts by weight of sulfur 
is utilized for every 100 parts by weight of the CPVC resin. 
The stabilizers which are utilized in the present invention are metal 
carbonates. Examples of metal carbonates include barium carbonate, cadmium 
carbonate, and lead carbonate with barium carbonate being preferred. The 
amount of stabilizer is generally from about 1 to about 13 parts by weight 
and preferably from about 3 to about 7 parts by weight per 100 parts by 
weight of the CPVC resin. 
In order to improve the flex modulus of the blend, various organic and 
inorganic fibers are optionally utilized so long as the blend has 
adherence to the fibers. Examples of suitable inorganic fibers include 
fiberglass, and the like, whereas examples of organic fibers include 
graphite, polyester, polyaramid, and the like. The amount of fibers is 
from about 5 to about 75 parts by weight and preferably from about 10 to 
about 40 parts by weight per 100 parts by weight of the total CPVC blend 
or composition, that is based upon the total weight of the CPVC resin, the 
sulfur, the stabilizers, as well as any other additives. When fiberglass 
is utilized as a fiber, it desirably has a coupling agent thereon. 
Generally, any conventional coupling agent can be utilized such as various 
amino silane compounds as set forth in U.S. Pat. No. 4,536,360 to Rahrig 
which is hereby fully incorporated by reference. 
The CPVC blend can contain various conventional compounding aids in desired 
amounts as known in the art as well as to the literature. For example, 
various conventional lubricants such as oxidized polyethylene, paraffin 
wax, and the like can be utilized. Various impact modifiers can be 
utilized but must be saturated to avoid reaction with sulfur. These 
include the various acrylates such as polymethylmethacrylate grafted onto 
polybutylacrylate, and the like. Examples of suitable fillers include 
titanium dioxide, mica, wollastonite, and the like. Other additives 
include various conventional antioxidants, and processing aids including 
those known to the art and to the literature. 
The above blends are prepared by powder blending the various ingredients 
followed by fusion in a heated mixer such as a mill, a Banbury, an 
extruder, or the like. The order of addition is generally not important. 
An important benefit of the use of sulfur is the improved melt flow of the 
CPVC resin. As noted above, CPVC compounds generally do not possess good 
melt flow or processability. Utilization of the sulfur not only improves 
the flow characteristics as well as wetting properties of the resin, but 
improves adhesion with the fibers as well. 
The CPVC blends of the present invention generally exhibit improved melt 
flow as measured by reduced melt flow viscosity of at least 10 percent, 
desirably at least 25 percent, and preferably at least 50 percent in 
comparison to non-blended CPVC resins. Such blends additionally have 
improved stability as noted hereinabove. Moreover, the sulfur is often 
miscible with the CPVC resin, that is is partially soluble therein. By the 
term "miscible," it is meant that a single phase system is formed which is 
generally clear to the naked eye and has a single glass transition 
temperature. Miscible systems which are produced will vary depending upon 
the amount of sulfur, the temperature, and pressure. 
The CPVC blends of the present invention can be utilized as protective 
coatings for metal, concrete, wood products, and the like. 
The invention will be better understood by reference to the following 
examples. 
The following formulations were prepared: 
TABLE I 
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INGREDIENTS 
1 2 3 4 
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Nippon Carbide 
100 80 80 80 
T-382 
(CPVC 68% Cl) 
Thermolite 31 
2.0 2.0 -- -- 
a tin stabilizer 
TiO.sub.2 5.0 5.0 5.0 5.0 
BaCO.sub.3 -- -- -- 5.0 
S -- 20 20 20 
Oxidized PE 
1.25 1.25 1.25 1.25 
lubricant 
DTS* (min) 26 21 20 29 
Torque Minimum 
38.5 18.5 16.5 18.5 
Newton-Meters 
crumb crumb no crumb 
slight 
State at 30' at 26' at 24' crumb at 50' 
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*Dynamic thermal stability -- the time at which the torque rises 1 
newtonmeter above its minimum point. Usually this indicates the onset of 
decomposition, that is, dehydrohalogenation and crosslinking. 
As apparent from the above table, the addition of the sulfur resulted in a 
drastic reduction in processing torque. Hence, improved melt flow and 
fusion was imparted by the addition of the sulfur. The addition of a metal 
carbonate stabilizer such as barium carbonate as in Formula 4 resulted in 
improved stability as measured by DTS. 
Sulfur was found to be partially miscible in CPVC as indicated by the 
results in Table II. Both differential scanning calorimetery (DSC) and 
optical tests help to estimate the solubility limits as a function of 
temperature. In the DSC analysis, both the CPVC glass transition 
temperature (Tg) and the sulfur melting peak at about 120.degree. C. were 
sought. However, because the DSC tests do not clearly define the 
solubility of the sulfur in CPVC owing to the effect of melt viscosity on 
the rate of sulfur crystallization, visual observation of the hot and cold 
blends were also included. The preparation and thermal treatment of these 
blends are described after the table. 
TABLE II 
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A B C D E 
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CPVC 100 95 90 80 70 
Nippon Carbide 
T-382 --68% Cl 
Sulfur -- 5 10 20 30 
BaCO.sub.3 
5 5 5 5 5 
PE 0.5 0.5 0.5 0.5 0.5 
Tg (.degree.C.) 
132 121 112 109 --* 
Tm (.degree.C.) 
-- -- -- -- 118 
eta (kPa .multidot. s) 
2.89 2.39 1.95 0.85 0.59 
% Viscosity 
0 17 33 71 80 
Reduction 
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*Tg obscured by sulfur melting peak. 
After powder blending the ingredients and heating in an oven at 150.degree. 
C. for 15 min to allow the resin to soak up the sulfur, the above 
formulations were fluxed on a 2-roll mill at 190.degree. C. for 2-3.5 min. 
The Tg and Tm results were recorded on a Perkin Elmer DSC-2 differential 
scanning calorimeter after heating the samples first to 170.degree. C. In 
the first heat scan, only composition E showed a sulfur melting peak at 
118.degree. C., which was still present in the second heat scan. This 
clearly indicated a separate sulfur phase in which the sulfur molecules 
had sufficient mobility to crystallize on cooling. The melt flow 
improvement data set forth in kilopascals seconds and percent reduction 
was obtained utilizing an Instron rheometer at 210.degree. C. at a shear 
rate of 297 s.sup.-1, using a die with a 0.13 centimeter diameter and a 
length/diameter ratio of 10. As apparent from the data, good melt 
viscosity reductions were obtained as the amount of sulfur utilized was 
increased. 
The CPVC/S partially miscible system exhibits an upper critical solution 
temperature, as apparent from Table III. That is to say, the solubility of 
the CPVC/S blend increases with temperature. This was shown by the 
following experiments in which the optical properties of different 
compositions were observed while the stock was hot on the mill and after 
it had cooled to room temperature. Owing to the presence of BaCO.sub.3 
stabilizer, which was insoluble in the polymer blend, the mixtures were 
translucent instead of transparent. These experiments show that the limit 
of solubility of sulfur in a 68 weight percent chlorine CPVC resin at 
190.degree. C. is between 12.5 and 15 percent. One skilled in the 
technology of polymer alloying would expect that the solubility of sulfur 
in CPVC to depend on the weight percent of chlorine in the resin as well 
as on the molecular weight of the polymer. Indeed, similar experiments 
with PVC, which contains 56.5 weight percent chlorine, showed that at 
190.degree. C. the limit of solubility of sulfur was between 5-10 percent. 
TABLE III 
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F G H I 
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CPVC 90 87.5 85 82.5 
same as above 
S 10 12.5 15 17.5 
BaCO.sub.3 5 5 5 5 
PE 0.5 0.5 0.5 0.5 
190.degree. C. 
T T SO O 
25.degree. C. 
T T* O O 
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T = Translucent 
SO = Slightly Opaque 
O = Opaque 
* = Thicker edges of sheet slightly opaque 
Table IV relates to the utilization of glass fibers. 
TABLE IV 
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J K L M 
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TempRite CPVC 
100 95 90 80 
687 .times. 563 (67% Cl) 
Sulfur -- 5 10 20 
BaCO.sub.3 
PE (Allied 0.5 0.5 0.5 0.5 
AC-629A) 
Glass fibers 40 40 40 40 
(Owens Corning CRX) 
Tensile (psi) 
15,500 12,660 18,010 17,120 
S.D.* .+-. 1,860 430 220 220 
no. samples 6 5 4 3 
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*Standard deviation 
Powder ingredients without glass fibers were mixed for 2 min. in a blender, 
then heated at 150.degree. C. for 15 min. to enable the resin to absorb 
the sulfur. The mixture was fluxed on a 2-roll mill at 190.degree. C. 
while adding the glass fibers. 
Without glass fibers the tensile strength of a 67 weight percent chlorine 
CPVC is about 10,000 psi. As expected, the addition of 40 weight percent 
glass fibers increased the tensile strength, but as indicated by the 
standard deviation (12 percent), the values were quite variable. This 
suggests possibly poor uniformity in adhesion between the matrix polymer 
and the glass fibers. However, unexpectedly when 10-20 percent sulfur 
(based on CPVC+S=100) was added, the variability dropped to less than 2 
percent and the tensile value increased slightly. This improvement in 
tensile properties suggests improved adhesion between the glass and 
matrix. 
While in accordance with the Patent Statutes, the best mode and preferred 
embodiment have been set forth, the scope of the invention is not limited 
thereto, but rather by the scope of the attached claims.