Process for plasticizing polyvinyl alcohol resin

An improved method for the production of a plasticizer-containing dry flowable polyvinyl alcohol (PVA) resin blend capable of thermoplastic processing. The method provides for the incorporation of plasticizers in intimate contact with the PVA resin without heating, cooling, or extended drying steps. Specifically, PVA resin granules having an appropriately small particle size distribution are spray-coated with a liquid plasticizer medium, and then mixed with a dry, fine powder coating medium to produce a flowable, dry plasticized PVA blend. Additional components, such as antioxidants, dyes, and antiblocking agents, may also be incorporated into the finished product.

BACKGROUND OF THE INVENTION 
Polyvinyl alcohol (PVA) decomposes at 200.degree. C., well below the 
temperatures required for thermoplastic processing. In order to process 
PVA thermoplastically, it is necessary to incorporate plasticizers into 
the PVA resin to be processed. Plasticizers act to lower the softening 
temperature of PVA below the decomposition point. 
Incorporation of plasticizer into the PVA resin has proven to be a 
challenge. The plasticizer must be in intimate contact with the PVA resin 
to assure a homogeneous melt upon processing. Granules of PVA which have 
been insufficiently permeated by plasticizer using known methods yield 
incompletely plasticized regions after thermoplastic processing. The art 
has addressed this difficulty by providing various means to absorb the 
plasticizer into the PVA resin. For example, plasticizer has been 
incorporated into PVA resin by the use of a liquid carrier which must be 
subsequently removed, requiring processing and drying steps. An alternate 
process requires heating and cooling of PVA resin in the presence of 
plasticizer. The resin particles absorb the plasticizer, swell, 
agglomerate, and are then mechanically separated prior to thermoplastic 
processing. Other processes require the presence of numerous solvents, 
substantial energy inputs, or long reaction times for the plasticization. 
Generally, currently known processes are intricate and/or require careful 
control of temperature in order to produce a homogeneous mixture of PVA 
and plasticizer. 
BRIEF DESCRIPTION OF THE INVENTION 
The present invention relates to the addition of plasticizer to polyvinyl 
alcohol (PVA) to provide a dry, granular compound which is capable of 
thermoplastic processing, e.g., it is extrudable. 
It has been surprisingly found that when PVA particles of a sufficiently 
small size distribution are plasticized, it is not necessary that the 
plasticizer be absorbed into the PVA particle to provide a homogeneous mix 
of PVA and plasticizer for thermoplastic processing. Rather, it is thought 
that the plasticizer is adsorbed onto the surface of the PVA particle, 
with only trace amounts of plasticizer absorption. It is also believed 
that the intimate contact of the plasticizer and the PVA resin which is 
afforded by the large surface to volume ratio of the particle allows the 
production of PVA/plasticizer granules which provide a homogeneous 
thermoplastic melt. To complete the process, a dry powder coating medium 
is employed for coating the PVA/plasticizer granules and producing a dry, 
flowable PVA/plasticizer blend. The process may be conducted within an 
ambient temperature range. 
In a preferred embodiment, an antioxidant is mixed with the PVA resin 
particles prior to contact with a plasticizer, providing improved 
characteristics during thermoplastic processing of the PVA/plasticizer 
blend, e.g., reduced oxidation of the PVA. It is also preferred that the 
dry coating medium comprise one or more antiblocking agents which also act 
to provide enhanced properties (e.g., reduced blocking) to sheet or film 
products made from the PVA/plasticizer blend. 
It is an object of the present invention to provide a dry, flowable mixture 
of plasticized PVA for use in thermoplastic processing and from which high 
quality films may be extruded. 
It is still another object of the invention to provide a process for 
plasticizing PVA particles which does not require heating or cooling 
steps. 
It is another object of the present invention to provide plasticized PVA 
granules which yield improved melt uniformity upon thermoplastic 
processing. 
It is another object of the present invention to provide a process for 
plasticizing PVA particles which does not require long processing times. 
It is yet another object of the present invention to provide a plasticized 
PVA blend which may be thermoplastically processed.

DETAILED DESCRIPTION OF THE INVENTION 
In accordance with the present invention, appropriately sized PVA particles 
are agitated and coated with a liquid plasticizer medium. The 
PVA/plasticizer granules are then mixed with a dry coating to produce a 
dry, flowable PVA/plasticizer blend. Other additives, as appropriate, may 
be incorporated into the dry PVA/plasticizer blend. 
Polyvinyl alcohol (PVA) resin is widely used as a film-forming material, 
and has good strength and water solubility characteristics. PVA is made by 
polymerizing vinyl acetate and subsequently hydrolyzing the resin, and PVA 
can and typically does include up to about 20 mole percent residual 
acetates, and may be considered a copolymer of vinyl alcohol and vinyl 
acetate. Other comonomers can be polymerized with the vinyl acetate, and 
are within the scope of the present invention. The term "polyvinyl 
alcohol" thus includes such copolymers. Examples of other comonomers 
include those having carboxylic acid or ester functional groups, such as 
acrylic acids, methacrylic acids, acrylates, methacrylates and maleates, 
and sulfonates. Such PVA copolymers are all included within the scope of 
the process of the invention herein. 
The use of appropriately sized PVA particles is critical to achieving the 
proper association of PVA and plasticizer necessary for successful 
thermoplastic processing of PVA. PVA resins include particles of varying 
diameters. The range of particle sizes, or particle size distribution, of 
a particular resin is critical to the practice of the subject invention. 
Resins which are appropriate for use in the subject invention will have a 
distribution of particle sizes, prior to adsorption of plasticizer, which 
provides a passage of at least 80% of the particles through a 35 mesh 
screen. This specification is satisfied by PVA resins comprised of 
granules of which at least 80 weight percent are less than about 500 
microns (0.5mm) in diameter. Preferably, the PVA particle size 
distribution provides a passage of at least 80% through a 35 mesh screen, 
at least 25% through a 60 mesh screen, and at least 15% through a 100 mesh 
screen. More preferably, the PVA resin will be sized such that at least 
95% pass through a 35 mesh screen. PVA resins which meet this more 
preferred specification will have particles in which at least 95 weight 
percent are less than about 500 microns in diameter. Most preferably, the 
PVA resin particles should have a particle size distribution such that at 
least 95% pass through a 35 mesh screen, at least 65% through a 60 mesh 
screen, and at least 25% through a 100 mesh screen. As used herein, all 
screen sizes are standard U.S. mesh. 
A PVA resin having a particle size distribution such that less than 80% of 
the granules pass through a 35 mesh screen will result in a wet and sticky 
blend which may not be fully plasticized, is not free-flowing and which is 
difficult to extrude. 
PVA resin having an appropriate particle size distribution is commercially 
available and exemplified by the products sold under the trademarks: POVAL 
(Kuraray), VINOL 205S (Air Products and Chemicals), GOHSENOL 
(Nippon-Gohsei), and GELVATOL 3000 (Monsanto). Other commercially 
available PVA resins can be mechanically conditioned, e.g., by milling, 
screening or pulverizing, to result in the appropriate size distribution. 
Air Products and Chemicals' PVA resins sold under the trademark VINOL 205 
can be milled or pulverized to yield the requisite particle size 
distribution. 
Other characteristics of the PVA resin, e.g., molecular weight and percent 
hydrolysis are determined by the end use of the resin and do not 
significantly affect the practice of the present invention. 
Generally, the PVA resin particles, together with appropriate additives, 
are coated with a liquid plasticizer medium. Plasticizers act to reduce 
the softening point of PVA to below the decomposition point, and are added 
to PVA to facilitate thermoplastic processing. The plasticizer may be a 
single compound, or a mixture of compounds. Appropriate plasticizers are 
known to the art, and include but are not limited to glycerin, 
trimethylolpropane (TMP), water, neopentyl glycol, polyethylene glycol, 
and mixtures thereof. Particularly preferred is a mixture of water, 
glycerol and TMP. Plasticizers which are liquids at ambient temperatures 
are especially appropriate for use with the subject process. Plasticizers 
which are solid or crystalline at ambient temperatures, such as 
trimethylolpropane, may be dissolved in water or another liquid 
plasticizer medium for use as a sprayable plasticizer. The plasticizer 
medium may be heated as necessary to incorporate non-liquid components; 
however, the plasticizer medium is preferably allowed to return to ambient 
temperatures to avoid heating of PVA granules during the process. 
To achieve a uniform plasticizer coating it is preferred to utilize a spray 
mechanism to coat the PVA resin. The spray pattern must be appropriate for 
the PVA batch size, and for the spray nozzle and mixing apparatus used. A 
poor spray pattern may result in poor coating, incomplete plasticization 
of the PVA resin, and ultimately, an inferior product after thermoplastic 
processing. Spray patterns will be individual to the apparatus used, 
however, some generalities may apply. In general, a less viscous spray 
will coat better and cause less clogging of the nozzle. Nozzles providing 
a fine spray are preferred as they will generally coat more evenly than 
those with a coarse spray. Nozzles should be arranged so that a maximum 
area is covered. An example of a preferred spray nozzle is that 
manufactured by Spraying Systems Company, Wheaton, Ill., and sold under 
the trademark VEEJET, especially a VEEJET Model 31655 atomizing nozzle. 
The pressure used to spray the plasticizer through this particular nozzle 
is about 30 psig. The nozzle may be employed in a single, or more 
commonly, a ganged, configuration. The PVA granules may be mixed, 
agitated, or fluidized during coating to assure a uniform plasticizer 
layer. If used, mixing should provide maximal exposure of the granules 
with a minimum of heat generated. Thus, low and medium-intensity mixers, 
such as those utilized in the art for plastic processing, are preferred if 
mixing is used. 
PVA granules should not be heated during the plasticizer coating process, 
as they may agglomerate and prevent adequate coating. Excessive shear 
forces result in excessive heat, which can increase the gross temperature 
of the PVA granules or cause degradation of the granules due to increased 
localized temperatures. Generally, the temperature should be maintained at 
less than 105.degree. F., preferably less than 90.degree. F., and mixing 
should be limited to that conducted in the low or medium-intensity mixers. 
The specific configuration of the mixer used is not critical, as long as 
sufficient mixing is achieved to effect even, homogeneous coating without 
production of excess heat. Alternatively, a fluid bed or electrostatic 
coating process may be employed. 
The quantity of plasticizer which is present in the dry, plasticized PVA 
blend will be that amount which is sufficient to plasticizer the PVA 
granules. The specific amount of plasticize will generally vary from about 
10 to about 20 weight percent, preferably from about 12 to about 18 weight 
percent, and more preferably from about 15 to about 17 weight percent. 
The length of time required for coating of the PVA resin granules with 
plasticizer will vary depending upon equipment used, materials, and batch 
size, but in general will take from about 30 seconds to about 45 minutes, 
more usually from about 1 to about 15 minutes. 
The PVA/plasticizer granules are next coated with a dry, fine powder 
coating, preferably an impalpable powder coating, producing a dry, 
flowable PVA/plasticizer blend. "Impalpable" refers to a powder which is 
so fine that the individual particles cannot be distinguished as such by 
pressing the powder between the thumb and index finger. Impalpable powders 
include, but are not limited to, powders of magnesium stearate, potassium 
stearate, sorbitol, fructose, starch, and mixtures thereof. Such powders 
are known to the art and are commercially available. More preferred for 
the thermoplastic production of sheets and films is the use of one or more 
antiblocking agents as the dry, fine powder coating. An antiblocking agent 
is a substance, e.g., finely divided solids of a mineral nature such as 
magnesium stearate, potassium stearate and the like, which is added to 
prevent adhesion of the surfaces of films to each other or to other 
surfaces. Particularly preferred is an impalpable powder/antiblocking 
agent, such as magnesium stearate available, for example, from 
Mallinckrodt, Inc., St. Louis, Missouri. An example of the most preferred 
impalpable magnesium stearate sold by Mallinckrodt is that sold under the 
registered trademark HYQUAL. This powder has a particle size distribution 
such that at least 99.8 percent is smaller than a 325 mesh screen, and has 
a bulk density of about 7-9 lbs/ft.sup.3. A less preferred, though 
acceptable, fine powder coating/antiblocking agent is a potassium 
stearate, sold by the Witco Chemical Corporation, New York, New York, and 
having a particle size distribution of at least 50% through a 100 mesh 
screen. 
A coating-effective quantity of the dry, fine powder coating medium is 
present in the dry, plasticized PVA blend, and generally will be from 
about 1.0 to about 10.0 weight percent, preferably from about 1.0 to about 
7.0 weight percent, more preferably from about 1.0 to about 5.0 weight 
percent. The dry, fine powder coating may comprise only one compound, or 
may comprise mixtures of two or more compounds. The dry, fine powder 
coating is distributed on the PVA/plasticizer granules by mixing, 
spraying, or blending, and, as with the plasticizer coating step, must be 
done in the absence of excessive shear forces or heating. FIG. 1 
demonstrates the average range of temperatures encountered during a series 
of six runs, plotted against time of the plasticizing process. The PVA was 
blended in a low-intensity mixer, and plasticizer and dry, fine powder 
coating mixtures were added. The temperature of the resin ranged from 
77.9.degree. F. to 82.1.degree. F. initially, and the average was 
79.9.degree. F. At the ten minute point, temperatures ranged from 
89.1.degree. F. to 99.1 .degree. F., averaging 96.4.degree. F. The final 
temperature of the blend ranged from 89.5.degree. F. to 104.6.degree. F., 
averaging 96.9.degree. F. In general, the highest temperature during the 
process should be below about 105.degree. F. 
The dry, flowable PVA resin blend produced when PVA resin granules have 
been coated with plasticizer and the dry, fine powder coating medium will 
have a distribution of granule sides which provides for passage of at 
least 90% of the particles through a 1/4 inch screen. This specification 
is satisfied by PVA resin blends having a particle size distribution of at 
least 90 weight percent less than about 1/4 inch in diameter. Preferably, 
the PVA resin blend particle size distribution provides a passage of at 
least 90% through a 1/4 inch screen, at least 85% through a 6 mesh screen, 
at least 70% through a 16 mesh screen, and at least 50% through a 20 mesh 
screen. More preferably, the PVA resin will be sized such that at least 
95% pass through a 1/4 inch screen. PVA resin blends which meet the more 
preferred specification will have particles in which at least 95 weight 
percent are less than about 1/4 inch in diameter. 
It may be desirable to incorporate additional components into the 
PVA/plasticizer blend. Antioxidants are an especially preferred additive 
in PVA thermoplastic processing, as they act to protect the PVA chemically 
during extrusion and melt processes. Antioxidants are generally added to 
the PVA resin granules in an amount of from about 0.0 to about 2.5%, 
preferably about 0.1 to about 1.0% by weight. 
In a preferred embodiment, one or more antioxidants are mixed with PVA 
resin granules before coating with plasticizer. The choice of antioxidant, 
if any, will depend in part upon the ultimate use of the PVA product and 
of the thermoplastic environment. For example, if the PVA is to be used in 
a water-soluble film, it is preferable that the antioxidant be 
water-solubhle. Antioxidants which are appropriate for use with the 
present invention include but are not limited to citric acid, aspartic 
acid, phosphoric acid, heavy metals, and a tetrakis (methylene [3, 
5-di-tert-butyl-4-hydroxyhydrocinnamate]) methane with the chemical 
formula of C.sub.73 H.sub.108 O.sub.12, especially that sold under the 
trademark IRGANOX 1010 by Ciba-Geigy Corp. Other appropriate antioxidants 
are well known in the art. 
Additives which facilitate the processing of the granular PVA/plasticizer 
blend may also be incorporated, especially lubricants such as stearic 
acid, waxes, fine-particle silic acid, and heat stabilizers. Additives 
such as dyes or colors may also be desired to affect characteristics of 
the product to be formed by thermoplastic processing. If the PVA is to be 
incorporated into a film which is to be in contact with a 
perborate-containing compound, such as a bleach, it may be desirable to 
include a borate scavenger, as described, e.g., in U.S. Pat. No. 4,626,372 
issued Kaufmann et al., the disclosure of which is incorporated herein by 
reference, and/or a pH control agent in the dry powder coating. 
Additives desired in the dry, flowable PVA/plasticizer blend may be 
included during the processing of the blend, and granular additives may be 
conveniently added to the PVA resin before the plasticizer coating. Liquid 
materials, and suspensions or solutions of solid materials, may be 
incorporated into the plasticizer spray. Additives which may be formed 
into a sufficiently fine or impalpable powder may be added to, or used as, 
the dry powder coating. Finally, additives may be mixed with the dry 
PVA/plasticizer blend at any time before or during thermoplastic 
processing. 
The total amount of such additives is preferably less than about 10%, more 
preferably less than about 5%. 
EXPERIMENTAL 
PVA resin blends may be formulated to have various compositions, depending 
in part upon the intended use of the blend. Generally, blends will include 
PVA resin, one or more plasticizers, and a dry powder coating medium. 
Colorizing agents, antioxidants, antiblocking agents, pH buffers, etc., 
may be included in the blend. Variations within the teachings of this 
invention will be obvious to those skilled in the art. Exemplary of such 
blends are: 
______________________________________ 
Formula Weight 
Ingredient percent 
______________________________________ 
Example 1 
Polyvinyl Alcohol Resin 
60.0- 85.0 
Plasticizer 10.0- 20.0 
Dry coating powder 
1.0- 10.0 
Other additives 0.0- 10.0 
Example 2 
Polyvinyl Alcohol Resin 
69.0- 83.0 
Glycerin (96%) 0.0- 15.0 
Water 1.0- 7.0 
Trimethylolpropane 
0.0- 14.0 
Borate Scavenger 0.0- 10.0 
Magnesium Stearate 
0.0- 2.0 
Potassium Stearate 
0.0- 2.0 
Citric Acid 0.0- 0.10 
Antioxidant 0.0- 0.25 
Other additives 0.0- 10.0 
Example 3 
Weight % 
Weight % 
PVA Resin 74.26.sup.(a) 
83.27.sup.(b) 
Borate scavenger 8.16 9.67 
Water 3.00 1.95 
Glycerin 6.64 2.69 
TMP 6.64 1.13 
Magnesium Stearate 1.02 1.02 
Antioxidant 0.27 0.27 
______________________________________ 
.sup.(a) PVA Resin as Kuraray 405S 
.sup.(b) PVA Resin as NipponGohsei KL05S 
Exemplary of a specific formulation to produce a 2.27 kilogram batch of PVA 
blend is the following: 
______________________________________ 
Ingredient Weight % Quantity (grams) 
______________________________________ 
Example 4 
PVA resin 72.75 1651 
Sorbitol 8.00 181.6 
Water 5.00 113.5 
Glycerin 6.50 147.6 
TMP 6.50 147.6 
Magnesium Stearate 
1.00 22.7 
Antioxidant 0.25 5.7 
______________________________________ 
Particle size, which is critical to the success of the process, is 
conveniently measured by "screening" the PVA resin. A series of 
progressively finer screens are weighed to determine tare weights. PVA 
resin is then passed through the series of screens. PVA granules which do 
not pass a given screen mesh are weighed, together with the screen, and 
the tare weight is subtracted, to give the amount of PVA resin which 
remains on the screen. PVA resin which passes a screen is then screened by 
the next in the series. A particle size distribution for a given PVA resin 
source or batch may thus be determined. Alternatively, methods other than 
screening may be currently available and may find use to determine 
particle size. For example, a GRANULOMETRE (a trademarked product of Micro 
Scientific) utilizes a laser to determine particle size ranges. Tables 1 
and 2 show particle size distributions for various commercially available 
resins, both as supplied and after conditioning. Note that Samples C and D 
of Table 1 do not possess the requisite particle size distribution of the 
present invention. 
TABLE 1 
______________________________________ 
Particle Size Distribution 
of Uncoated PVA Resins 
as Measured by Screening 
(Weight percent) 
Screen Sample 
Size A B C D E F 
______________________________________ 
5 0 -- 0 0 -- -- 
6 0 0 -- 0 -- -- 
8 -- 0.4 -- -- -- -- 
20 0.1 -- 76.9 15.2 0 0.05 
30 0 -- 15.6 13.3 0 0.05 
35 0.2 0 -- -- 0.1 0.2 
40 -- -- 5.1 -- -- -- 
50 -- -- 0.9 -- -- -- 
60 0.1 0.2 -- 40.0 21.2 15.2 
80 -- 24.1 -- -- -- -- 
100 12.2 4.7 -- 15.4 44.8 41.4 
170 -- 23.0 -- -- -- -- 
200 60.3 3.6 -- -- 26.0 35.3 
Tray 27.3 34.4 0.9 16.0 7.8 7.7 
Total.sup.(1) 
100.2 100 99.8 99.9 99.9 99.9 
______________________________________ 
A = GELVATOL 3000 (Monsanto) 
B = GELVATOL 3000 (Monsanto) 
C = M488 (Hoechst) 
D = VINOL V205 (Air Products) 
E = Pulverized VINOL V205 (Air Products) using a MikroPulverizer, type SH 
(a trademark of Mikropul, a division of the Slick Corporation) 
F = Twice Pulverized VINOL V205 (Air Products) using a MikroPulverizer, 
type SH 
.sup.(1) Total may not equal 100% due to rounding. 
TABLE 2 
______________________________________ 
Particle Size Distribution 
of Uncoated PVA Resins 
as Measured bv Granulometer 
(Weight percent) 
Particle Kuraray Nippon-Gohsei 
Size Screen 405-S KL-05S 
(Microns) 
Size Trial #1 Trial #2 
Trial #1 
Trial #2 
______________________________________ 
1 * 0.4% 0.7% 0.2% 0.2% 
1.0-1.5 * 0.2% 0.2% 0.2% 0.1% 
1.5-2 * 0.8% 0.5% 1.0% 1.5% 
2-3 * 0.9% 0.1% 1.2% 0.8% 
3-4 * 0.6% 0.0% 1.1% 1.1% 
4-6 * 0.6% 0.0% 1.1% 1.1% 
6-8 * 0.5% 0.2% 0.5% 0.7% 
8-12 * 0.6% 0.0% 0.2% 0.3% 
12-16 * 2.2% 0.3% 2.1% 2.7% 
16-24 * 4.4% 0.3% 5.4% 5.6% 
24-32 * 5.9% 2.3% 8.5% 7.6% 
32-48 325 12.8% 6.9% 20.8% 20.9% 
48-64 250 7.1 8.1% 10.3% 9.7% 
64-96 150-250 23.74% 35.4% 25.4% 26.3% 
96-128 120-150 29.4% 33.7% 16.4% 15.9% 
128-192 60-120 9.9% 11.3% 5.6% 5.3% 
Total.sup.(1) 100.0 100.0 100.0 99.8 
Median, 81.5 91.4 59.8 60.1 
in microns 
______________________________________ 
*= screen size smaller than 325 mesh 
.sup.(1) Total may not equal 100% due to rounding. 
EXAMPLE A 
A clean, dry medium-intensity mixer was charged with PVA resin and 
antioxidant (IRGANOX 1010) in the proportions given in Example 4. The PVA 
resin was GELVATOL 3000 having the particle size distribution of Sample A 
of Table 1. One-half of the sorbitol was added, and the mixer was run for 
30 seconds prior to addition of plasticizer. The liquid plasticizer 
mixture of TMP, water, and glycerin was sprayed onto the dry ingredients 
at a rate of 200-300 grams per minute, and the mixture was blended for 1 
minute following the complete addition of the plasticizer. Mixing 
continued for 1 minute after the magnesium stearate and the remainder of 
the sorbitol were added, and the blend was discharged. 
The maximum temperature of the blend during mixing, as measured by a probe 
within the mixer, was 80.degree. F., and the maximum blend temperature 
immediately after discharge was 105.degree. F. After discharge of the 
blend, the mixer appeared clean with only trace amounts of resin and 
plasticizer on the mixing plows and walls of the mixer. The blend was 
free-flowing upon discharge, and remained free-flowing after storage in a 
sealed bag. The particle size distribution of the PVA/plasticizer blend 
was such that at least 90% of the granules passed a 1/4 inch screen, at 
least 85% passed a 6 mesh screen, at least 70% passed a 16 mesh screen, 
and at least 50% passed a 20 mesh screen. 
EXAMPLE B 
The PVA resin of this Example was mechanically conditioned to meet the 
particle size distribution requirement. 
A clean, dry medium-intensity mixer was started and charged with pulverized 
V205 PVA from Air products, IRGANOX 1010, and TMP in the proportions given 
in Example 4. The pulverized V205 PVA had the particle size distribution 
as shown by Sample E of Table 1. The mixer was run for 30 seconds, and 
then glycerin and water were sprayed in at a uniform rate over 75 seconds. 
A mixture of sorbitol and magnesium stearate was then added, the mixer was 
run an additional 30 seconds, and the blend was discharged. No temperature 
increase was noted: the temperature remained near ambient. The mixer 
appeared clean except for some residue on the plows and walls. The blend 
was dry and flowable, and did not cake. The particle size distribution of 
the resulting PVA/plasticizer blend was such that at least 95% of the 
granules passed a 1/4 inch screen, at least 90% passed a 6 mesh screen, at 
least 75% passed a 16 mesh screen, and at least 50% passed a 20 mesh 
screen. 
EXAMPLE C 
Example C demonstrates the effect of a poor liquid plasticizer coating on 
an otherwise appropriately-sized PVa resin. 
The procedure of Example A was followed, but all the sorbitol was added to 
the liquid mixture. This caused the liquid mixture to be extremely 
viscous, and a good spray pattern was not formed. The resulting blend was 
wet and sticky. Upon drying, the blend took the shape of the container, 
and was difficult to break apart. The addition of the sorbitol to the 
spray mixture resulted in a more viscous solution, causing a poor spray 
pattern. As a result, plasticization was incomplete, the resultant 
PVA/plasticizer resin blend was not dry or free-flowing, and a particle 
size distribution of the coated PVA/plasticizer blend was unobtainable. 
EXAMPLE D 
Example D demonstrates the failure to provide a suitable dry powder 
coating. Here, the dry powder coating agents were added to the PVA resin 
before plasticization. 
The procedure of Example A was followed, but all the sorbitol and the 
magnesium stearate were initially added to the PVA and antioxidant instead 
of being used as a dry powder coating. The result was a wet, sticky blend 
which took the shape of the container upon drying and was very difficult 
to break apart. No particle size distribution was obtained for the 
resulting PVA/plasticizer blend. The use of a dry coating powder as a 
coating layer after plasticization is important to the production of a 
free-flowing PVA/plasticizer resin blend. 
EXAMPLE E 
Example E demonstrates the use of a PVA resin having an inappropriate 
particle size distribution, leading to incomplete plasticization resulting 
in a PVA/plasticizer resin blend which is not free-flowing. 
A clean, dry medium-intensity mixer was started and charged with M4-88 PVA 
from Hoechst, IRGANOX 1010, and TMP in the proportions given in Example 4. 
The M4-88 PVA had the particle distribution as shown by Sample C of Table 
1. The mixer was run for 30 seconds, then a total of 259.4 grams of 
glycerin and water were sprayed in at a uniform rate over 75 seconds. A 
mixture of sorbitol and magnesium stearate was added, the blender was run 
for 30 seconds, and the blend discharged. No temperature increase was 
noted. The mixer was extremely messy, with wet beads of resin coating the 
entire mixer. The blend was very dense and wet, and caked severely. No 
particle size distribution was obtained due to the caking. 
EXAMPLE F 
Example F demonstrates the inability to obtain a useful product due to high 
intensity mixing resulting in a blend temperature of above about 
105.degree. F. Runs were carried out with both Nippon Gohsei GL-05, and 
Kuraray 405-S resins, each having a particle size distribution satisfying 
the minimum requirements of the present invention. The formulations used 
to produce the blends were as defined in Example 1. A clean, dry 
high-intensity mixer, of the type used in the art for plastic processing, 
was filled with the dry ingredients. The mixer was started at low speed, 
then run to high speed as liquid plasticizer was sprayed in. Mixing 
continued until the blend reached a temperature of about 212 to 
220.degree. F., then mixing was stopped and the blender cooled. The mixer 
was emptied when the blend temperature dropped to about 150.degree. F. The 
GL-05 resin batch yielded a very clumped blend, having a number of 
"plastic" lumps which were difficult to break apart. The 405-S batch mixed 
well, however the walls of the mixer were gummed up with the blend and 
were difficult to scrape down. Blend particle size distributions were not 
obtained. 
Although the above description and the claims which are appended hereto 
describe methods and compositions which are useful for providing a 
PVA/plasticizer blend suitable for thermoplastic processing, in fact, 
variations and modifications thereof will be obvious to those skilled in 
the art, and obvious equivalents and alternative embodiments consistent 
with the scope and content of this application are included herein.