Process for making PVC resin having improved initial color and clarity

This invention discloses methods of polymerization in the field of PVC dispersion resins, in particular, dispersion PVC, made by the emulsion or microsuspension process with or without monomer metering. The invention achieves improved initial plastisol color without destroying blush resistance by employing techniques which entail at least two air evacuation steps. In the preferred embodiment a specified amount of a metabisulfite reducing agent is incorporated into the polymerization medium and/or monomer mixture followed by polymerization initiaton and further processing. Another disclosure of the invention is a simple method for reducing the haze of dispersion resin plastisol films thereby improving their clarity by the addition of a small amount of non-copolymerizable polybasic carboxylic acid to the dispersion resin or monomer dispersion prior to isolating the resin. The preferred poly basic acids are non-ethylenic unsaturated, di- or tri-carboxylic acids like citric acid and tartaric acid.

FIELD OF THE INVENTION 
This invention pertains to methods of polymerization in the field of PVC 
resins, in particular, dispersion PVC made by the emulsion or 
microsuspension process. The art area encompasses plastisols derived from 
dispersion PVC, and articles formed using plastisols. 
BACKGROUND OF THE INVENTION 
PVC compounds are susceptible to discoloration absent proper stabilization. 
Also, while good stabilization features may be obtained by proper 
compounding, there still may be inherent deficiencies in the clarity, 
color and heat stability of the resin polymer which present limitations 
for commercial applications. With regard to dispersion PVC, these resins 
may be more specifically referred to as emulsion type or micro-suspension 
type dispersion PVC. These terms correspond to different methods of 
polymerization. Dispersion PVC is typically used in plastisol and 
organosol formulations, and there are limitations in inherent initial 
color after fusion, and color stability evidenced by premature yellowing 
of films either for unsupported films or film coatings on articles. 
Initial color is particularly noticeable when a clear film is applied to a 
light colored, opaque substrate like white flooring sheets. One important 
aspect not dependent on the resistance to discoloration after heat aging, 
is the initial color obtained only after sufficient heat for fusion. This 
color is also referred to the water-whiteness initially obtained. In 
addition to yellowing tendencies, in many applications, an article 
containing a plastisol coating can be susceptible to blushing on contact 
with water. Compounding formulation may limit to some extent the blushing 
of film or coatings, however it has been observed that the dispersion 
resin preparation method plays the most important part in determining the 
initial color and the blushing characteristics of the fused compound. 
U.S. Pat. No. 4,076,920 discloses a method of preparing dispersion PVC 
which yields dispersion resins having improved heat stability, color and 
resistance to blushing on contact with water. These resins are made by 
polymerization using a colloidal dispersant system free of alkali metal 
soaps, and including the use of ammonium salt of a fatty acid and a long 
chain alcohol, with polymerization in basic medium which reduces polymer 
coagulum. The resins, when formulated into plastisols, fused into finished 
films, and subjected to elevated humidity showed improved blush resistance 
characterized by rapid recovery of film clarity. There are however 
limitations in the initial color of this type of resin when formulated as 
clear layers over white or light colored substrates. 
Studies with other dispersion resins of the current state of the art, as 
clear plastisol films, still evidence some haze and coloration 
limitations. It would be desirable therefore to improve the initial color 
while also, preferably not sacrificing blush resistance in a dispersion 
PVC resin adaptable to plastisol applications. It would also be desirable 
to provide an effective method for improvement in clarity or haze of the 
articles derived from dispersion resins. 
A method has been devised for manufacturing a dispersion PVC polymer which 
exhibits improved retention of water-white color, good resistance to 
blushing and improved clarity. 
SUMMARY OF THE INVENTION 
One object of the invention is to provide dispersion PVC resins with 
improved initial color and without destroying color blush resistance. The 
method of polymerization can be applied with emulsion polymerization and 
micro-suspension polymerization techniques which entail at least two air 
removal steps. In the preferred embodiment a specified amount of a 
metabisulfite salt reducing agent is incorporated into the polymerization 
medium and/or monomer mixture followed by polymerization initiator and 
further processing. The resin product when formulated into plastisols 
evidences improved initial color, without adversely affecting the 
resistance to blushing on contact with moisture. 
It is another aspect of the invention to provide a simple method for 
reducing the haze of dispersion resin films thereby improving the clarity. 
The method entails the addition of a small amount of non-copolymerizable 
polybasic carboxylic acid to the resin or monomer dispersion. The 
preferred poly basic acids are di- or tri-carboxylic acids like citric 
acid and tartaric acid. 
DETAILED DISCLOSURE OF THE INVENTION 
This invention is directed to PVC dispersion resins useful in plastisols, 
organosols and the like. By virtue of the flowability of plastisol 
compounds, these can be processed into various useful products. For 
example, the plastisols can be used in making molded products, films, 
coatings, and the like. Accordingly, the vinyl dispersion resins mixed 
with the plasticizers to form liquid plastisols are capable of producing 
films, and like products, of good clarity, on fusing at elevated 
temperatures. 
Dispersion PVC refers to particles of PVC polymer having a typical mean 
particle size diameter measured prior to drying of from 0.05 microns to 
about 10 microns, preferably the average diameter ranges from about 0.5 to 
about 3 microns. 
In general, the preparation of dispersion PVC is effected by the emulsion 
or micro-suspension polymerization processes, where the latex obtained 
contains colloidally stable particles prior to removal of water. The use 
of various different emulsifiers and catalysts are known. Also, varying 
the conditions of polymerization has been suggested. The preferred method 
for preparing the dispersion PVC herein using emulsion process is referred 
to as a low soap recipe and is made in a batch-wise process. The preferred 
method for making dispersion PVC using the microsuspension method is the 
pre-mix monomer method. The methods of the present invention are also 
applicable to monomer metering methods which are known in the art. For the 
sake of brevity, a batch-wise, low soap, emulsion polymerization method 
and a micro suspension method using a pre-mix recipe will be described in 
sufficient detail so as to provide a method of practicing the invention. 
When preparing dispersion vinyl homopolymers or copolymers by means of an 
emulsion or micro suspension polymerization technique, an aqueous medium 
is employed. When using these polymerization procedures, the aqueous 
reaction medium will contain one or more emulsifiers, or an emulsifier 
system. Anionic emulsifiers, such as the alkali metal or ammonium 
sulfonate or sulfate salts having from 8 to 18 carbon atoms can be used. 
Examples of such emulsifiers are sodium sulfate, ethanolamine lauryl 
sulfate, ethylamine lauryl sulfate, and the like; alkali metal and 
ammonium salts of sulfonated petroleum and paraffin oils; sodium salts of 
hydrocarbon sulfonic acids, such as dodecane-1-sulfonic acid and 
octadiene-1-sulfonic acid; sodium salts of alpha-olefin sulfonates, 
aralkyl sulfonates, such as sodium isopropyl benzene sulfonate, sodium 
dodecyl benzene sulfonate, sodium isobutyl naphthalene sulfonate, and the 
like; alkali metal and ammonium salts of sulfonate, and the like; alkali 
metal and ammonium salts of sulfonate dicarboxylic acid esters, such as 
sodium dioctyl sulfosuccinate, disodium-n-octadecyl sulfosuccinate, and 
the like; alkali metal and ammonium salts of the free acid of complex 
organic mono- and di-phosphate esters and the like. Nonionic emulsifiers, 
such as octyl- or nonylphenyl polyethoxyethanol, may also be used. 
Dispersion vinyl copolymer lattices having an excellent colloidal 
stability are obtained when using the alkali metal and ammonium salts of 
long chain sulfonates. 
Fatty acid derivatives can be used as an emulsifier. Preferable versions 
are ammonium salts of long chain saturated fatty acids. Significant 
amounts of alkali metal salts of the fatty acids are preferably avoided. 
The fatty acids useful herein may be either natural or synthetic and 
preferably contain from 8 to 30 carbon atoms, more preferably 8 to 20 
carbons. As examples of such acids there may be named lauric, myristic, 
palmitic, margaric, stearic, and the like. The sources of these include 
beef tallow, coconut oil, and the like including mixtures. Commercial 
sources are listed in Chemical Week Buyers Guide. The emulsifier is 
generally employed in an amount in the range of about 0.5% to about 4.0% 
by weight based on the total weight of the monomer or monomers being 
introduced for polymerizing. It is also possible to use mixtures of 
ammonium salts of the fatty acids in the emulsifier system. 
The ammonium salt can be made beforehand by mixing the fatty acid and 
ammonium hydroxide. However, it can be prepared in situ, that is, an 
unneutralized fatty acid and ammonium hydroxide are added to the 
polymerization medium wherein they form the water soluble salt. It is 
preferred to use an excess molar amount of ammonium hydroxide over the 
amount of fatty acid employed. 
In addition to the ammonium salt of a long chain fatty acid, a nonionic 
emulsifier is preferred. These include long chain saturated alcohols 
containing 8 to 30 carbons, preferably from 12 to 24 carbon atoms. 
Examples of such preferred alcohols are dodecanol, tridecanol, 
tetradecanol, pentadecanol, hexadecanol, heptadecanol, octadecanol, 
nonadecanol, eicosanol, heneicosanol, docosanol, tricosanol, and 
tetracosanol. Mixtures of alcohol and another nonionic sufactant can also 
be employed, for example, a 14 carbon alcohol and an 18 carbon alcohol. 
The polymerization reaction is preferably carried out in basic medium, that 
is in a pH range of from about 7.0 to about 12.0. It is more preferred to 
polymerize at a pH range of about 8.0 to about 10.5. If the pH is too low, 
for example below 7.0, then more base is needed. The amount of base, for 
example, NH.sub.4 0H needed to properly adjust the pH will depend in part 
on the particular emulsifier system being used in the reaction mixture. 
Free radical yielding initiators, normally used for polymerizing 
olefinically unsaturated monomers, are satisfactory for use herein. Alkali 
metal, initiators such as containing sodium and potassium, and the like 
are preferably avoided. The useful initiators include, for example, the 
various peroxygen compounds, such as lauryl peroxide, isopropyl 
peroxydicarbonate, benzoyl peroxide, t-butyl hydroperoxide, t-butyl 
peroxypivalate, cumene hydroperoxide, t-butyl diperphthalate, pelargonyl 
peroxide, 1-hydroxycyclohexyl hydroperoxide, and the like; azo compounds, 
such as azodiisobutyronitrile, dimethylazodiisobutyrate, and the like. 
Other exemplary initiators are the water-soluble peroxygen compounds, such 
as hydrogen peroxide, persulfates, such as potassium persulfate, ammonium 
persulfate, and the like. The amount of initiator used will generally be 
in the range between about 0.01% to about 0.5% by weight, based on the 
weight of 100 parts of monomer or monomers being polymerized, and 
preferably between about 0.02% and about 0.1% by weight. The most 
preferred initiators for emulsion polymerization are ammonium peroxygen 
compounds. For microsuspension polymerization, in general, any monomer 
soluble initiator may be used such as the percarbonates and peroxyesters. 
The general method for a batch-wise process is distinguished from the 
premix method discussed below. Initiators may be charged completely at the 
outset of a batch-wise polymerization. In a premixed monomer recipe, 
initiator may be added to the monomer premix with the other ingredients of 
the reaction mixture. This is particularly true if the premix is 
homogenized prior to introduction into the reactor, and is preferred. Upon 
introduction of the homogenized mixture into the polymerization reactor 
(poly), the temperature is then raised to that at which initiation will 
take place. 
Prior to initiation, the present invention involves a combination of steps 
to be taken in order to provide the aforementioned improvements in film 
color. The first step involves removal of substantially all of the air in 
the pre-mix or polymerization vessel at least twice followed by a 
introduction into the vessel(s) of an inert gas such as nitrogen. The 
preferred method of air removal is by evacuation means. This is referred 
to as gas inerting. In the present method of the invention it was found 
that performing the evacuation at least twice, and gas inerting at least 
once before polymerization, resulted in substantial improvement in film 
color. In practice, when evacuation is conducted only once, the result is 
poorer film color. Under somewhat less extensive evacuation, there can be 
three or four successive evacuations prior to initiation which will result 
in notable color improvements. 
Evacuation followed by introduction of monomer instead of gas is referred 
to as monomer inerting. It was found in one small scale experiment that 
after four gas inerting steps, followed by monomer inerting, and the 
introduction of a reducing agent, prior to initiation, substantial 
improvements in initial plastisol color resulted. Also, when the resin was 
used in a plastisol and fused, the film exhibited desirable low blushing 
characteristics in a high humidity environment. Thus, a distinct color 
advantage was obtained while the amount of reducing agent additive used 
was not destructive of the water blushing performance. If substantially 
more reducing agent is employed, film color noticeably worsens. 
Measurement of oxygen levels from the head space of the polymerizer is 
helpful. The level of oxygen in the head space of the polymerizer found to 
exceed about 350 ppm results in undesirable film color. Preferably, oxygen 
levels should be below about 250 ppm in the head space. These measurements 
can be made with the use of an electrochemical fuel cell type or 
para-magnetic types which are commercially available. An in-line sampling 
device may be installed, for example, in a vent line. 
It is a general practice to initially check for air leaks in all pressure 
vessels and handling lines. This is routinely achieved when maximum vacuum 
is applied and the vessel and/or lines are closed for a time sufficient 
for monitoring any rise in pressure. At altitudes near sea level, for all 
practical purposes, it is sufficient to evacuate a vessel to at least 
about 26 inches of mercury in any evacuation step, preferably 27 inches of 
mercury (Hg), and most preferably at least about 28 inches Hg. 
The temperature of reaction in the instant polymerization process is 
considered since the molecular weight hence, intrinsic viscosity (I.V.) of 
PVC is a direct function of the temperature of reaction. Accordingly, the 
end use considerations for the resin to be produced will normally dictate 
the reaction temperature. For example, when producing dispersion resins to 
be used in coatings or casting flexible films, a relatively lower 
temperature may be suggested in order to attain a relatively higher I.V. 
resin desirable for coating applications. Generally, dispersion resins are 
polymerized at temperatures in the range of about 30.degree. C. to about 
70.degree. C. It is preferred, however, to employ a temperature of 
polymerization in the range of about 40.degree. C. to about 60.degree. C. 
In another preferred embodiment, a small amount of polybasic carboxylic 
acid or its derivative is added to the aqueous dispersion, preferably 
after polymerization has proceeded substantially to completion. It is 
preferred to neutralize this acid prior to introducing into the 
polymerization. Preferred polybasic acids are the saturated di-, tri-, or 
tetra- carboxylic acids. The polybasic carboxylic acids are not polymeric 
and preferably are not ethylenically unsaturated. Aminocarboxylic acids 
are preferably avoided and do not achieve effective improvements in 
clarity and haze by this method. The polybasic carboxylic acids which are 
most preferred include tartaric acid and citric acid. Citric acid 
derivatives include, for example, acetonedicarboxylic acid, citraconic 
acid, mesaconic acid, aconitic acid, methylsuccinic acid, and oxalic acid. 
Generally, the amount of polybasic acid which can be used ranges from 
about 0.01 to about 1.0 weight parts, more preferably 0.05 to 0.5 weight 
parts and 
most preferably 0.08 to 0.2 weight parts per 100 parts of monomer (phm) 
charged, that is the amount of monomer initially employed before monomer 
conversion to resin. 
Upon completion of the polymerization reaction, the dispersion resin is 
typically isolated in powder form from the latex by means of spray drying 
or other methods such as coagulation and fluid energy mill drying. Spray 
drying involves producing a fine spray of the polymer latex which is 
injected into a heated air chamber thereby removing the water and 
recovering the dried resin in powder form. 
Plastisols are typically made with the dispersion resins of the present 
invention by uniformly blending or intimately mixing, by conventional 
mixing or blending means, with for example, 100 parts by weight of the 
dispersion resin in powder form, from about 30 to about 100 parts by 
weight of one or more plasticizers and any stabilizer and other optional 
ingredients. Exemplary plasticizers are the alkyl and alkoxy alkyl esters 
of dicarboxylic acids or the esters of a polyhydric alcohol and monobasic 
acid. As examples of such materials are dibutyl phthalate, dioctyl 
phthalate, diethylhexyl phthalate, dibutyl sebacate, dinonyl phthalate, 
di(2-ethyl hexyl)phthalate, di(2-ethyl hexyl)adipate, dilauryl phthalate, 
dimethyl tetrachlorophthalate, butyl phthalyl butyl glycollate, glyceryl 
stearate, and the like. 
EMULSION RESIN EXAMPLES 
The invention was carried out with an emulsion batchwise process to prepare 
the dispersion resins. The following recipe was used: 
______________________________________ 
weight parts 
______________________________________ 
Vinyl chloride 100 
Water 163 
Amm. persulfate 0.04 
Amm. hydroxide 0.03 
Hydrogen peroxide 0.0008 
Seed latex (32% solids)** 
16 
Amm. laurate* 0.8 
CuSO.sub.4 0.0003 
______________________________________ 
** 0.5.mu. average particle size PVC 
*proportioned 
The reactor was evacuated 3 times and broken with N.sub.2. Preceding the 
charging of water into the polymerizer, nitrogen was bubbled through the 
water for about 15 minutes. Seed latex, which is a polyvinyl chloride 
emulsion polymer having an average particle diameter of about 0.5 microns, 
water and CuSO.sub.4 are drawn into the reactor. It is advisable to pull a 
vacuum again on the poly, recording the pressure, waiting about 15 minutes 
and noting the pressure to check for any leaks. In this instance vacuum 
was pulled to 28 inches Hg for leak testing, then the vacuum was broken to 
0 psig with nitrogen. Maximum vacuum in this instance, under the 
prevailing ambient atmospheric pressure, using the particular equipment 
was about 28 inches Hg. A second evacuation was drawn again. At this time 
agitation was started and vinyl chloride monomer charged to the poly. The 
poly was heated and when the reactor contents reached approximately 
42.degree. C., initiator solution of ammonium persulfate and ammonium 
hydroxide in 0.5 lb. water was introduced. When the contents reached 
45.degree. C., hydrogen peroxide in 0.5 lb. water was added. Surfactant 
solution was proportioned into the reactor at a rate of 450 cc/hour. The 
proportioning was completed after the third hour of polymerization. The 
reaction was allowed to proceed until pressure dropped 15 psig. The 
reactor was heated to 80.degree. C. while venting. The dispersion was 
filtered through a muslin sock and spray dried. 
This resin, when formulated into a plastisol and drawn into a film on a 
standard substrate followed by fusing, gave a color rating of 3 compared 
to the control resin which had a color rating of 5. Under this rating 
system a rating of 1 is the best and 5 is the worst. The color rating is a 
qualitative visual comparison between the film exhibiting the best 
water-whiteness and one made by introducing a substantial amount of air 
prior to polymerization. 
It is preferred to pre-treat the water and sope solution before 
proportioning by evacuation, bubbling nitrogen and keeping any pre-mixed 
components under a nitrogen blanket until used. It is also preferred to 
store the components under a positive nitrogen pressure. There are a 
variety of alternative mechanical means for pretreating water which may be 
employed, such as by the use of deaerators, or by commercial chemical 
treatments. 
In another preferred embodiment, a small amount of ammonia neutralized 
tartaric or citric acid is added to the aqueous dispersion resin prior to 
spray drying. Generally, the amount which can be used ranges from 0.01 to 
1.0 phr, more preferably 0.05 to 0.5 phr, and most preferably 0.08 to 0.2 
phr on a weight solids basis. The surprising effect was a substantial 
reduction in film haze and improved clarity. 
DISPERSION PASTE RESINS 
The pre-mixed monomer polymerization procedure for preparing 
microsuspension resins referred to as paste resins will be described. The 
microsuspension process differs substantially from the emulsion process. 
Instead of a water soluble initiator which provides an aqueous phase 
polymerization in the emulsion process, an oil soluble initiator system is 
used in micro-suspension processes which provides a monomer phase 
polymerization site. The ultimate plastisol properties of dispersion 
resins are different between these two sub-classes of dispersion resin 
primarily in the differences of rheology exhibited, and foamability 
characteristics, which are beyond the scope of the invention. 
Dispersion paste PVC resins having the aforementioned improvements can be 
made using the semi-batch process, also referred to as the premix monomer 
method. In the premix method the polymerization components are charged 
initially to a premix vessel followed by homogenization and transfer to 
the polymerization vessel for heating to initiate the reaction. In 
contrast to the emulsion process which employs a water soluble initiator, 
the paste resin process is a microsuspension method using oil soluble 
initiators. Suitable oil soluble initiators are peroxyesters and 
peroxydicarbonates. 
In the practice of the invention applied in preparing paste resins, the 
polymerizer and the pre-mix vessel are evacuated and broken with nitrogen 
at least twice. Any vessel used for holding ingredients such as surfactant 
solutions are advantageously kept under a nitrogen blanket. It is also 
preferable to bubble nitrogen through any water prior to use. In the most 
preferred method, the reactor is evacuated three times and broken with 
inert gas, followed by evacuation twice, broken with vinyl chloride 
monomer to a pressure of about 5-10 psig. Generally, it is desirable to 
assess the level of oxygen in the monomer used. The concentration of 
oxygen the head space over any monomer, for example vinyl chloride 
monomer, contained in a vessel should be kept below about 250 ppm. Venting 
of the monomer head space as well as other methods previously mentioned 
can be effected to reduce the oxygen level. Vinyl chloride monomer 
handling systems in practice are designed for closed loop recycling, thus, 
where monomer venting is undertaken, it is presumed to be venting to the 
closed recovery system. 
The preferred microsuspension pre-mixed monomer method described herein 
includes the steps of combining water, monomer(s) and surfactant in a 
pre-mix vessel followed by homogenization, transfer to the poly and 
initiation of polymerization. A preferred water insoluble C.sub.8 
-C.sub.24 nonionic surfactant, is combined with a long chain carboxylic 
acid ammonium salt as the surfactant system. More preferred are C.sub.8 to 
C.sub.20 nonionic surfactants, and most preferred are C.sub.10 to C.sub.18 
nonionic surfactants. The nonionic surfactant is first emulsified in hot 
water which contains a portion of the total long chain carboxylic acid 
salt surfactant to be used. This emulsion of nonionic surfactant is then 
combined with the other ingredients in the premix and the pre-mix is then 
homogenized. 
During the preparation of the pre-mix, the contents of the pre-mix vessel 
should be kept under a nitrogen or vinyl chloride blanket until 
transferred. Water is first charged to the pre-mix vessel. Nitrogen is 
bubbled for at least about 15 minutes. In addition, evacuation is 
preferably commenced during the charging of water. A quantitative amount 
of prepared surfactant emulsion is charged to the premix vessel, and 
agitation is commenced. Initiator, vinyl chloride monomer and reducing 
agent are charged to the pre-mix vessel. The pre-mix is homogenized by 
recirculating through a homogenizer for a time sufficient to provide a 
uniform, fine dispersion of monomer in water. A suitable commercially 
available rotor-stator homogenizer can be used. A variety of other 
homogenizer types may also be used. After homogenization, the pre-mixture 
is transferred to the poly which has been evacuated at least twice 
followed by breaking with inert gas, and optionally evacuated followed by 
breaking the vacuum with monomer. The poly is then heated to the desired 
initiation temperature wherein polymerization commences. Upon completion 
of the polymerization reaction, as noted typically by a pressure drop, the 
dispersion resin is preferably treated with an effective amount of 
polybasic carboxylic acid, followed by isolation of the resin in powder 
form from the aqueous dispersion by means of spray drying.

PASTE RESIN EXAMPLES 1-5 
Dispersion paste resins were prepared using the premix paste method and 
visual comparisons were made between the initial color of cast clear films 
coated on black/white standard plaques, with those resins made without 
following the method of the invention. 
The polymerization ingredients are listed in table A. All parts are 
expressed as weight parts per 100 weight parts of monomer (phm). In these 
examples, homopolymers were made, thus parts are expressed as parts per 
100 parts vinyl chloride monomer. In example 1, resin was prepared by 
charging water, ammonium hydroxide, and ammonium laurate to the pre-mix 
vessel. The nonionic surfactant was emulsified with 0.2 phm of the 
ammonium laurate in 25 phm of water. This emulsion along with plasticizer 
was added to the premix vessel under agitation. The initiator and 0.007 
parts of the BHT were then added. The premix vessel was evacuated 3 times 
followed each time with breaks using nitrogen. Vinyl chloride was charged 
and the mixture was further agitated. The premix was homogenized and then 
transferred through inerted lines to the polymerizer which had been 
evacuated 2 times followed each time with nitrogen breaks. The 
polymerization ingredients were heated to the initiation temperature, 
which in this case was 45.degree. C. The reaction was allowed to proceed 
14 hours or until the pressure dropped 15 psig. At this time the 
remainder of the BHT was added. The poly was then vented while heating to 
70.degree. C. for 2 hours. The dispersion was cooled and spray dried. 
TABLE A 
______________________________________ 
component 
1 2 3 4 5 
______________________________________ 
Vinyl 100 100 100 100 100 
Chloride 
Water 175 175 175 175 175 
Ammonium 1.63 1.63 1.63 1.63 1.63 
Laurate 
Ammonium 0.01 0.01 0.01 0.01 0.01 
Hydroxide 
Nonionic 0.4 0.4 0.4 0.4 0.4 
Surfactant 
Plasticizer 
0.25 0.25 0.25 0.25 0.25 
BHT 0.207 0.207 0.207 0.207 0.207 
Organic 0.068 0.068 0.068 0.04 0.04 
Peroxide 
Initiator 
Sodium 0 0 0 0.03 0.02 
Metabisulfite 
______________________________________ 
By the method described above, the control example 1 was made wherein prior 
to commencing initiation of polymerization, a vacuum was twice drawn to 
about 28 inches of mercury and broken each with nitrogen. There was no 
monomer inerting step. The color rating of the cast film plaques was 2 on 
a scale of 1 to 5, wherein 5 was the worst and 1 was the best color 
rating. 
Control example 2 comprised a film made from a dispersion resin prepared in 
the same manner as example 1 except after the second poly evacuation, 
oxygen was bled into the reactor to a pressure rise of 2.0 inches of 
mercury. The color rating of the film plaques was 5 which is the worst 
rating. 
Control example 3 was prepared as in example 1 except four successive 
evacuations followed by nitrogen breaks were performed on both the poly 
and the premix vessel. The color rating of film plaques using this resin 
was 2. 
Inventive example 4 illustrates the effect of 4 vacuum cycles, however in 
the last 2 cycles in both the premix vessel and polymerizer, the vacuum 
was broken by bleeding vinyl chloride instead of nitrogen, and 0.03 parts 
of sodium metabisulfite was added after the evacuation steps in the 
premix. The initial color was 1. 
Inventive example 5 was prepared as in example 4, except that 0.02 parts of 
reducing agent was introduced. The initial color rating was 1. 
In the preparation of the dispersion resins used in the above examples 4 
and 5, the amount of reducing agent employed was effective in improving 
color but not in an amount which interfered with initiation, nor the rate 
of polymerization to any appreciable extent. While the effective amount of 
the reducing agent did have a positive effect on initial color, the 
effective amount did not cause an increase in blushing on contact with 
water. Suitable reducing agents are metal salts of metabisulfite such as 
sodium metabisulfite. 
IMPROVED CLARITY AND HAZE 
The following examples illustrate the effect of the addition of a small 
amount of polybasic acid to the dispersion resin before drying. The 
following examples employed plastisol films made with dispersion resin 
following the above microsuspension method but with post-added neutralized 
polybasic carboxylic acid prior to drying. The control film was made with 
a resin which did not contain any post-added polybasic acid. 
______________________________________ 
EXAMPLE 
6 7 8 
______________________________________ 
Tartaric Acid 
0 0.1 phr -- 
Citric Acid 0 -- 0.1 phr 
Viscosity, cp 
1 Day V2* 2050 2500 2100 
1 Day V20* 1895 2420 1840 
Severs Effulux 
26.7 25.8 22.5 
(1 Day, 95 psi) 
Initial Color 
1 1 1 
(1 = best, 5 = worst) 
Clarity % 28.1 77.1 87.1 
(% Transmission) 
Haze, % 65.0 17.1 8.3 
______________________________________ 
*Brookfield viscosity at 2 and 20 rpm after 1 day aging. 
As is seen from the table above there is a significant effect on the 
resulting plastisol film clarity and percent haze upon the addition of an 
effective amount of polybasic acid, in this case either tartaric acid or 
citric acid. 
While the present invention has been described in terms of its specific 
embodiments, certain modifications and equivalents will be apparent to 
those skilled in the art and are intended to be included within the scope 
of the present invention, which is to be limited only by the reasonable 
scope of the appended claims.