Dispersible vinylidene chloride polymer microgel powders as additives for urethane polymer foam

A crosslinked vinylidene chloride polymer microgel powder is recovered from a latex and dispersed with moderate shear in a nonsolvent for vinylidene chloride polymers, such as a polyol used in the preparation of polyurethane materials. A dispersion of the powder and a polyol is eminently suited for use in the preparation of polyurethane foams to impart enhanced flame-retardancy and load-bearing properties thereto.

BACKGROUND OF THE INVENTION 
The present invention relates to vinylidene chloride polymers and, more 
particularly to vinylidene chloride polymers which are dispersible in 
nonsolvents for such polymers. 
Halogenated compounds, such as chlorinated polyethylenes, crosslinked 
copolymers of vinyl halides, bromophenols, vinylidene chloride polymers, 
and the like, have long been used as additives for polymeric materials to 
provide enhanced flame-retardancy. Typically, the object in this art has 
been to achieve such flame-retardancy without significantly decreasing 
other beneficial properties of the base polymeric material. 
On the other hand, a great deal of art has also been developed on the 
incorporation of high molecular weight polymer additives in polymeric 
materials to enhance properties other than flame-retardancy. With respect 
to polyurethane foam materials in particular, it is known that the 
load-bearing properties can be improved by using additives such as aqueous 
elastomer latices, vinyl aromatic polymers, and film-forming polymers 
having radicals reactive with the isocyanate component of the foam. 
Generally, this art has required the use of a further additive to provide 
enhanced flame-retardancy. 
It would be highly desirable to have a polymer additive which could be 
incorporated in polyurethane foam materials to provide both improved 
flame-retardancy and enhanced load-bearing properties. 
Accordingly, it is a primary object of the present invention to provide 
such polymer additive. More specifically, it is an object of the present 
invention to provide such an additive in the form of a vinylidene chloride 
polymer powder that can be dispersed in a polyol used to prepare the 
polyurethane foam materials. 
A more general object of the present invention is to provide a vinylidene 
chloride polymer powder which can be dispersed in a nonsolvent for 
vinylidene chloride polymers and thereafter used to prepare polymeric 
materials having enhanced physical properties. 
SUMMARY OF THE INVENTION 
In one aspect, the present invention resides in a composition of matter for 
use in the preparation of polymeric materials having enhanced physical 
properties comprising (A) a nonsolvent for vinylidene chloride polymers, 
such as a polyol used in the preparation of polyurethane materials, and 
(B) a crosslinked vinylidene chloride polymer microgel powder which is 
dispersible in the nonsolvent. The powder employed is obtained by a method 
comprising the steps of (I) preparing a microgel latex by emulsion 
polymerizing (a) about 50 to about 90 parts by weight of vinylidene 
chloride, (b) about 10 to about 50 parts by weight of a copolymerizable 
ethylenically unsaturated comonomer, and (c) a minor amount of a 
copolymerizable crosslinking polyfunctional comonomer, wherein the 
microgels in the resulting latex have a gel content of about 25 to 99 
percent and a second order transition temperature of at least about 
30.degree. C., and (II) recovering the microgel powder from the latex. The 
microgels prior to recovery have a diameter less than about 1 micron. 
In another aspect, the present invention resides in such a composition of 
matter wherein the method for obtaining the powder further comprises, 
between steps (I) and (II), the steps of adding to the latex an effective 
degradation-reducing amount up to about 20 weight percent of a 
sequentially polymerizable monomer mixture comprising an ethylenically 
unsaturated non-vinylidene chloride monomer, and polymerizing the monomer 
mixture. 
In a further aspect, the present invention resides in a polyurethane 
material prepared from such a composition of matter, e.g., wherein the 
nonsolvent comprises a polyol. 
In a still further aspect, the present invention resides in an improvement 
in a method of forming a polyurethane material by reacting a 
polyfunctional isocyanate with an active-hydrogen-containing material, 
wherein the improvement is characterized by including in the reactant 
mixture a crosslinked vinylidene chloride polymer microgel powder obtained 
by the method hereinbefore described. 
DETAILED DESCRIPTION OF THE INVENTION 
The crosslinked vinylidene chloride polymer microgel powders of the present 
invention are recovered from latices which have been prepared by 
polymerization in an aqueous emulsion according to processes well known in 
the art. Preferably, the polymerization is carried out by essentially 
continuous, carefully controlled addition of the requisite polymerization 
constituents (including polymerization initiator systems if desired) to 
the aqueous medium. 
Generally, it is preferred to start the polymerization by adding a small 
amount of monomeric material to the aqueous medium and then adding the 
desired polymerization initiator to form a polymeric seed latex to aid in 
the control of particle size. The aqueous medium in which the seed latex 
is formed will contain the necessary surfactants to form the emulsion and 
will generally be adjusted to the desired pH value, as is well known in 
the art. Following the formation of the seed latex, the remaining amount 
of monomeric material is continuously added under carefully controlled 
conditions to the aqueous medium. 
In accordance with the present invention, the microgel latices are prepared 
by emulsion polymerizing about 50 to about 90, preferably about 50 to 
about 80, parts by weight of vinylidene chloride; about 10 to about 50, 
preferably about 20 to about 50, parts by weight of a copolymerizable 
ethylenically unsaturated comonomer; and from about 1 to about 10, 
preferably about 2 to about 6, parts by weight of a copolymerizable 
crosslinking polyfunctional comonomer. The resulting microgels should have 
a second order transition temperature of at least about 30.degree. C., 
preferably at least about 35.degree. C. 
Exemplary copolymerizable ethylenically unsaturated comonomers which can be 
utilized in the present invention include the alkyl esters of acrylic and 
methacrylic acids such as methyl acrylate and methyl methacrylate; 
nitriles of ethylenically unsaturated carboxylic acids such as 
acrylonitrile and methacrylonitrile; ethylenically unsaturated carboxylic 
acids such as acrylic acid and methacrylic acid; and other ethylenically 
unsaturated monomers known to polymerize with vinylidene chloride. 
Exemplary copolymerizable crosslinking polyfunctional comonomers which can 
be employed include 1,3-butylene glycol diacrylate, 1,4-butane diol 
diacrylate, allyl acrylate, vinyl acrylate, 1,3-butylene glycol 
dimethacrylate, 1,4-butane diol dimethacrylate, allyl methacrylate, vinyl 
methacrylate, and the like. The actual amount of polyfunctional comonomer 
needed for dispersibility will depend upon the crosslinking efficiency of 
the particular polyfunctional comonomer used, as well as the particular 
polyfunctional comonomer used, as well as the ethylenically unsaturated 
comonomer which is polymerized therewith. Generally, it can be stated that 
sufficient polyfunctional comonomer should be used to provide a gel 
content of about 25 to about 95, preferably about 50 to about 99, percent 
in the resulting vinylidene chloride polymer microgel. Typically, the 
amount of crosslinking monomer needed to obtain such gel contents will 
range from about 1 to about 10, preferably from about 2 to about 6, parts 
by weight. 
As used herein, "percent gel" is determined by the following technique: Add 
36.6 ml tetrahydrofuran (THF) and a predetermined amount (W.sub.S), 
usually about 0.7-1.2 g, of the desired microgel to a 50 ml centrifuge 
tube. Cap the tube and then agitate it overnight (usually about 12 hours) 
on a horizontal agitator. Thereafter, centrifuge the tube at 19,000 rpm 
for about 1 hour at 5.degree. C. Extract 10 ml of the resulting 
supernatant liquid and place it into an evaporating dish. Evaporate most 
of the THF over low heat and then complete the drying by placing the dish 
in a oven for about 1 hour at 40.degree. C. Finally, determine the weight 
(W.sub.F) of resin in the dish and calculate gel content by the following 
formula: 
##EQU1## 
In view of the fact that amine catalysts are typically used in the 
preparation of polyurethane foam materials to control the rate of urea and 
urethane reactions and that the urethane reactions are significantly 
exothermic, it will be appreciated by workers in the art that the 
crosslinked vinylidene chloride polymer microgel powders recovered from 
the latices described hereinbefore could have a tendency to degrade and 
produce hydrogen chloride when used in such applications. The accelerated 
evolution of hydrogen chloride caused by such degradation could not only 
result in discoloration of the vinylidene chloride polymer and the 
resultant polyurethane foam material, but could also alter the kinetics of 
the urethane reaction. 
It has been found that a moderate decrease in the propensity of the 
microgel powders to discolor when exposed to the conditions of the 
polyurethane foam reaction and similar deleterious environments can be 
achieved by sequentially polymerizing such microgels with a monomer 
mixture comprising an ethylenically unsaturated non-vinylidene chloride 
monomer. Without intending to be bound by such theory, it is believed that 
the sequential polymerization provides a thin cap on the microgels which 
protects them from the amine catalyst, thereby reducing the rate of 
decomposition. 
The sequential polymerization can be carried out in a conventional manner 
by adding an effective degradation-reducing amount up to about 20 percent 
by weight of the microgels, preferably from about 5 to about 10 percent by 
weight, of the desired monomer mixture (including emulsifiers and 
initiators as needed) to the microgel latex and subjecting the monomer 
mixture to polymerization conditions. In a preferred mode, the desired 
monomer mixture for sequential polymerization is not added to the microgel 
latex until it is certain that essentially all of the residual vinylidene 
chloride monomer has been depleted. Depletion of residual vinylidene 
chloride monomer can be accomplished, for example, by adding an additional 
amount of initiator or a minor amount of methyl acrylate to the 
polymerization vessel subsequent to the apparent completion of the 
microgel reaction, but prior to the addition of the sequentially 
polymerizable monomer mixture. In this manner, the possibility of 
including vinylidene chloride in the resultant non-vinylidene chloride 
polymer "cap" (which term will be occasionally used herein for convenience 
only) will be reduced. 
In order to provide adequate dispersibility for purposes of this invention, 
the non-vinylidene chloride polymer "cap" which results from this 
sequential polymerization should either be uncrosslinked and have a second 
order transition temperature greater than about 60.degree. C., preferably 
greater than about 65.degree. C., or it should be cross-linked. If the 
"cap" is crosslinked, i.e., by copolymerizing a minor amount of a 
crosslinking polyfunctional comonomer with the desired ethylenically 
unsaturated non-vinylidene chloride monomer or monomers, the second order 
transition temperature requirement is not as critical, though values 
within the aforementioned range are preferred. 
Exemplary ethylenically unsaturated non-vinylidene chloride monomers which 
can be used in the sequential polymerization reaction to prepare the "cap" 
polymer include the alkyl esters of methacrylic acid such as methyl 
methacrylate; the vinyl aromatic monomers such as styrene and vinyl 
toluene; and other sequentially polymerizable monomers, i.e., those which 
are compatible with the vinylidene chloride microgels and which are 
capable of producing a "cap" satisfying the aforementioned criteria. 
Exemplary copolymerizable crosslinking polyfunctional comonomers which can 
be sequentially polymerized with the ethylenically unsaturated 
non-vinylidene chloride monomers include 1,3-butylene glycol diacrylate, 
1,4-butane diol diacrylate, allyl acrylate, vinyl acrylate, 1,3-butylene 
glycol dimethacrylate, 1,4-butane diol dimethacrylate, allyl methacrylate, 
vinyl methacrylate, and the like. In a manner like that described for the 
microgels, the amount of crosslinking monomer required for dispersibility 
will depend upon the efficiency of the particular crosslinking monomer 
chosen, as well as the ethylenically unsaturated non-vinylidene chloride 
monomer or monomers with which it is polymerized. Generally the amount of 
crosslinking monomer used, if any, will be less than about 6 percent of 
the weight of the sequentially polymerizable monomer mixture. 
The diameter of the microgels in the resulting latex, which includes those 
microgels which have been "capped" by sequential polymerization as well as 
those which have not been "capped", should be less than about 1 micron. 
Preferably, the mean microgel diameter is in the range of about 0.05 to 
0.5 micron, most preferably in the range of about 0.1 to 0.3 micron, with 
substantially all of the microgels having a diameter within that range. 
The preferred ranges are especially applicable if the powders obtained 
therefrom are to be used in the preparation of polyurethane foam 
materials. The larger latex particles will produce less discoloration in 
polyurethane foam materials, but smaller particles have longer dispersion 
stability in the polyol starting material and also provide better 
load-bearing properties in the foam material. Accordingly, the 
aforementioned preferred range represents those sizes which will give the 
best overall balance of properties when used in the preparation of 
polyurethane foam material. 
The crosslinked vinylidene chloride polymer microgel powders of the present 
invention are recovered from the microgel latices by conventional 
techniques, preferably by coagulating the latex and then washing and 
drying the coagulum or by spray drying the latex to produce a fine powder. 
The optimum temperature for coagulation will vary depending upon the type 
and amount of comonomer employed in preparing the microgels and 
particularly upon the second order transition temperature of the so-formed 
microgels. Generally, the coagulation temperature will be in the range of 
about 50.degree. to 95.degree. C., preferably from about 50.degree. to 
70.degree. C. 
It is necessary that the vinylidene chloride polymer powders of the present 
invention be dispersible in nonsolvents for vinylidene chloride polymers. 
For purposes of the present invention, "dispersibility" is measured under 
the following conditions: 20 weight percent of the desired powder is mixed 
with a polyol having a room temperature viscosity of about 900-1000 cps, 
(such as the polyol obtainable from The Dow Chemical Company under the 
trademark VORANOL.RTM. 4701) and the mixture is passed once through a 
Gifford-Wood colloid mill operating at 10,000 rpm with a gap setting 0.004 
in and then twice through a Gaulin homogenizer operating at 5000 psi. 
Under such conditions, substantially all of a powder suitable for use in 
the present invention will break down in the polyol and regenerate the 
original latex particles. Essentially all of the powder particles which do 
not break down to the latex particle size, if any, should be of a size 
less than about 100 microns. 
As used herein, "nonsolvents for vinylidene chloride polymers" is intended 
to be descriptive of liquid organic reactants which are used in the 
preparation of polymeric materials. In particular, it is intended to 
include polyols, which are used in the preparation of polyurethane 
materials; dihydroxy alcohols, which are used in the preparation of 
polyester resins; and the like. In all cases, the crosslinked vinylidene 
chloride polymer microgel powders of the present invention are suitably 
employed to render the resulting polymeric materials more resistant to 
ignition and burning while generally retaining and/or improving other 
beneficial physical properties. 
Conventional vinylidene chloride polymers can, in some instances, be 
blended directly with a suitable thermoplastic polymer to produce a 
satisfactory product. However, the microgel powders according the present 
invention are advantageously incorporated into polymeric materials by 
dispersing the powder in the desired nonsolvent liquid reactant with 
moderate shear and thereafter carrying out the contemplated polymerization 
reaction. It will be appreciated that the latter method is critically 
employed in the preparation of many foamed polymeric materials, 
particularly in the preparation of foamed polyurethane materials. 
In accordance with the present invention, the use of the microgel powders 
in the preparation of polymeric materials having enhanced physical 
properties will now be described by way of example with respect to the 
preparation of polyurethane materials--which may or may not be foamed. 
Polyurethane materials are prepared by the methods well known in the art 
by reacting a polyfunctional isocyanate with a polyfunctional chemical 
compound having an active hydrogen in its structure such as a polyester, 
polyesteramide or polyether or mixture of two or more of such materials. 
The latter component is generally referred to as the 
"active-hydrogen-containing material" and is typically sufficiently liquid 
to permit mixing and reaction with the polyfunctional isocyanate in 
producing the polyurethane. The active-hydrogen-containing materials 
conventionally used contain hydroxyl groups as the radicals having the 
active hydrogen and thus are generally termed "polyols". The preparation 
of such materials is shown, for example, in U.S. Pat. No. 2,888,409 and in 
the patents referred to therein. In addition, other hydroxyl-capped 
polymers useful as the polyol in preparing polyurethane resins include 
polyformals as described, for example, in U.S. Pat. No. 3,055,871 to 
Heffler, et al.; the hydroxyl-terminated lactone polyesters described in 
U.S. Pat. No. 3,051,687 to Young et al.; the alkylene oxide adducts of the 
alkyl alcohol-styrene polymers as described in U.S. Pat. No. 2,965,615 to 
Tess, et cetera. For reasons of commercial availability and cost, it is 
conventional to use polyethers having hydroxyl-terminated chains in the 
preparation of polyurethane foams and either such polyethers or 
hydroxyl-terminated polyesters in preparing vulcanizable gum, adhesive, 
films, et cetera. The polyurethane end products may occasionally be 
cross-linked to some extent by including with the polyol (which is 
generally di- or polyfunctional) a small amount of polyfunctional 
crosslinking agent. 
The active-hydrogen-containing materials suitable for use in the 
preparation of polyurethane materials of the present invention are any of 
those known in the art and (1) which form stable and uniform dispersions 
with the crosslinked vinylidene chloride polymer microgel powders, which 
dispersions are preferably dilutable without the formation of undesirable 
precipitates with other components used to form the polyurethane; (2) 
which are liquids, at least at the temperatures used for preparing the 
dispersions and for the reaction with the polyisocyanate; and (3) which 
have at least two radicals reactive with the isocyanato radicals of the 
polyisocyanate so as to form a polymeric reaction product. The preferred 
active-hydrogen-containing materials are the polyols having the 
aforementioned properties. 
The polyols employed can have hydroxyl numbers which vary over a wide 
range. The exact polyol employed depends, among other things, upon the end 
use of the polyurethane product to be produced. For example, in the case 
of foamed reaction products, the molecular weight of the hydroxyl number 
is selected preferably to result in flexible, semiflexible, or rigid 
foams. In such applications, the polyols preferably possess a hydroxyl 
number of from about 200 to about 1000 when employed in rigid foam 
formulations, from about 50 to about 150 for semiflexible foams, and from 
about 20 to about 70 or more when employed in flexible foam formations. 
Such limits are not intended to be restrictive, but are merely 
illustrative of the large number of combinations possible. 
As referred to earlier, the vinylidene chloride polymer microgel powders 
are advantageously incorporated into polyurethanes by first forming a 
dispersion of the powder in the desired polyol. Generally, the resulting 
dispersions should have a viscosity low enough to permit ready mixing with 
additional quantities of polyol used, if any, and with the other 
components of the polyurethane reaction. Furthermore, the resulting 
dispersions should be at least sufficiently stable to prevent 
sedimentation during the period required to carry out the polyurethane 
reaction. If the dispersions are to be prepared and then stored prior to 
use, it will be appreciated that they should be stable for a much longer 
period of time, e.g., usually at least about 3 months. Generally, the 
dispersions of the present invention demonstrate such long-term stability 
requirements, particularly those dispersions containing vinylidene 
chloride polymer microgel powder particles having a size within the 
preferred range described hereinbefore. 
The polymer powder/polyol dispersions of the present invention may be used 
in place of the polyols of the prior art in any of the processes used in 
preparing polyurethanes. Thus, the dispersions may be used in the 
prepolymer process, the quasi-prepolymer process, or the one-shot process. 
The polyurethanes may be further reacted with epoxy resins, cured with 
sulfur, peroxides or other curing agents, or otherwise reacted or modified 
as known to those skilled in the art. 
Referring now to the use of the present vinylidene chloride polymer 
microgel powders in the preparation of polymeric materials in general, the 
amount of powder which will be incorporated into a desired polymeric 
material will depend upon the particular vinylidene chloride polymer 
microgel powder used and upon the degree to which it is desired to enhance 
flame-retardancy and/or other beneficial physical properties in the 
resulting polymeric material, as well as other technical and economic 
considerations known and understood by those skilled in the art. In 
accordance with the present invention, the resulting polymeric materials 
will contain an amount of the microgel powder which effectively enhances 
the physical properties thereof. This amount generally ranges from about 2 
to about 50 percent, preferably from about 3 to about 30 percent of the 
weight of the polymeric material. Accordingly, the amount of microgel 
powder dispersed in the nonsolvent will be adjusted to produce such 
results. 
It will be understood that the resulting polymeric materials may be 
prepared so at to contain further modifying ingredients such as heat and 
light stabilizers, pigments, conventional flame-retardant synergists, and 
so forth, as necessary or desired for particular applications, without 
departing from the scope of the present invention. 
With respect to polyurethane foam materials in particular, surfactants or 
emulsifiers are frequently used to provide the necessary cell formation 
and growth for optimum processability. However, polyurethane foam 
materials prepared from polyols containing crosslinked vinylidene chloride 
polymer microgel powders in accordance with the present invention do not 
generally require the use of such surfactants or emulsifiers, as will be 
readily appreciated and understood by those familiar with the performance 
of polymer/polyol systems which have heretofore been used in the art. 
Nevertheless, such surfactants or emulsifiers may be advantageously 
employed, especially when using powders prepared from the larger-sized 
microgels inasmuch as such microgels have a reduced tendency to improve 
cell size in the polyurethane foam material. A user can, with only minimal 
experimentation, determine when such a surfactant or emulsifier will 
provide improved results in the practice of this invention. 
As referred to earlier, the microgel powders of the present invention can 
be moderately stabilized in an environment of high temperature and/or 
basic compounds, e.g., that environment encountered in preparing 
polyurethane foam materials, by sequential polymerization with 
non-vinylidene chloride monomers. Alternatively, or in addition thereto, 
conventional stabilizers for vinylidene chloride polymers, such as the 
hindered phenolic antioxidants and the like, may also be employed. It has 
been found that only marginal improvement in the color of a polyurethane 
foam material is achieved by using certain epoxy stabilizers, such as 
DER.RTM. 331 epoxy resin obtained from The Dow Chemical Company. 
Accordingly, it may be necessary for a user to determine by simple 
preliminary experimentation those stabilizers which will be suitably 
employed with the vinylidene chloride polymer microgel powders used in the 
present invention. Suitable stabilizers are preferably used by adding them 
to the aqueous medium prior to or during the emulsion polymerization of 
the vinylidene chloride polymer microgels, according to methods which are 
generally known in the art.

The following specific examples illustrate the invention but are not to be 
taken as limiting its scope. Parts and percentages are by weight unless 
otherwise indicated. 
EXAMPLE 1 
In accordance with the present invention, the following recipe and 
technique were used to prepare a crosslinked vinylidene chloride polymer 
microgel powder which is dispersible in polyols and other nonsolvents for 
vinylidene chloride polymers: 
INITIAL WATER PHASE 
1800 g water 
15 g AEROSOL MA emulsifier 
pH adjusted to 3.5 with glacial acetic acid 
REDUCING AGENT STREAM 
9.75 g HYDROSULFITE AWC reducing agent in 1000 g aqueous solution 
Feed rate=10 g/hr 
INITIATOR STREAM 
5.0 g of 83% t-butyl hydroperoxide (TBHP) in 1000 g aqueous solution 
Feed rate=10 g/hr 
MONOMER FOR SEED LATEX REACTION 
450 g vinylidene chloride (VDC) 
50 g methyl methacrylate (MMA) 
10 g 1,3-butylene glycol dimethacrylate (BGDM) 
Used 150 g in seed latex reaction 
AQUEOUS EMULSIFIER STREAM 
236 g of 45% DOWFAX 2Al emulsifier in 1600 g of aqueous solution 
Used 800 g in 20 hours (Feed rate=40 g/hr) 
MONOMER MIX 
800 g MMA (20 parts by weight) 
3200 g VDC (80 parts by weight) 
80 g BGDM (2 parts by weight) 
Used 2500 g in 20 hours (Feed rate=125 g/hr) 
FINISHING 
Fed Reducing Agent and Initiator Streams at 10 g/hr for one hour 
The initial water phase was poured into a two-gallon Pfaudler reactor and 
the reactor pressure tested for leaks at 35 psi with nitrogen. The 
nitrogen was then released. The reactor was placed under a vacuum of 25 
inches Hg and the reactor was heated to a temperature of 40.degree. C. The 
vacuum was then shut off and 150 g of the seed latex monomer was added to 
the reactor while agitating the contents thereof. Immediately thereafter, 
pumping of the reducing agent and initiator streams were begun at 10 g/hr 
each. The seed latex reaction was completed in approximately one hour as 
indicated by a drop in pressure of 2 psi from the maximum pressure 
attained during the seed latex reaction. When the pressure reached such 
point, introduction of the monomer mix at 125 g/hr and the aqueous 
emulsifier stream at 40 g/hr were begun and continued for 20 hours, while 
maintaining the flow of the reducing agent and initiator streams at 10 
g/hr each. After the monomer and emulsifier streams were shut off, the 
reducing agent and initiator streams were pumped at 10 g/hr for one 
additional hour to complete the reaction. The resulting microgels had a 
gel content above 25% and a second order transition temperature of about 
35.degree. C. 
The microgel powder was recovered from the latex by conventional alum 
coagulation techniques and then air dried. 200 g of the dry microgel 
powder was mixed into 800 g of polyol with a spatula and then passed 
through a colloid mill to break up the powder particles. When adequately 
mixed, microscopy revealed that many of the original microgel particles 
were present. Some aggregates of particles were observed, but it was not 
apparent that the particles in the aggregates were sintered together, but 
may have just gathered together during microscopy. All of the aggregates 
were less than 100 microns in cross section. 
By way of comparison, a conventionally prepared non-crosslinked copolymer 
containing essentially the same amount of MMA and VDC and coagulated in 
the same procedure had many solid particles of a size greater than 1000 
microns following the same degree of shearing in the polyol, and was 
further characterized by a gel content of 0% and a second order transition 
temperature of about 35.degree. C. (hereinafter referred to as Comparative 
Sample No. 3). 
EXAMPLE 2 
Various polyurethane foam samples were prepared by first mixing the desired 
polymeric additive with the following ingredients: 
______________________________________ 
Ingredient Amount (grams) 
______________________________________ 
VORANOL.RTM. 4701 polyol 
200 
Silicone surfactant 2 
70% solution of bis(N,N-dimethylaminoethyl)- 
ether in dipropylene glycol 
0.15 
50% solution of stannous octoate in 
di(2-ethylhexyl)phthalate 
0.6 
33% solution of triethylenediamine 
in dipropylene glycol 0.8 
Diethanolamine 2.4 
Water 5.2 
______________________________________ 
To the above, 70.4 g of toluene diisocyanate (TDI) were added, with 
blending. As soon as foaming had started, the mixture was poured into a 
container and permitted to foam over a period of 5 minutes. The resulting 
foamed polyurethane material was then heated in a 120.degree. C. oven for 
a period of 10 minutes, compressed to open the cells, and reheated for a 
period of 15 additional minutes at 120.degree. C. 
The following Table I sets forth the physical properties of such foam 
samples containing varying amounts and types of polymeric additives: 
TABLE I 
__________________________________________________________________________ 
Sample Wt. % 
Tear Strength 
25% Compression 
65% Compression 
Identification 
Used* 
lb/in lb/4 in.sup.2 
lb/4 in.sup.2 
__________________________________________________________________________ 
For Comparison 
1. Control (no additive) 
0.0 1.0 1.0 2.0 
2. Styrene/acrylonitrile 
copolymer (Niax-34-28) 
10 1.8 1.3 3.0 
3. Non-crosslinked Emulsion 
Copolymer of 80 wt % VDC 
and 20 wt % MMA 
15 1.23 1.03 2.93 
The Invention 
4. Microgel powder 
of Example 1 15 1.96 1.47 4.83 
__________________________________________________________________________ 
*Based on the weight of the initial ingredients, i.e., prior to the 
addition of TDI. 
The data set forth in Table I illustrate the enhanced load-bearing 
properties of the polyurethane material obtained by utilizing the microgel 
powder/polyol dispersion of the present invention. In addition, that 
polyurethane foam material passed the Department of Transportation Motor 
Vehicle Safety Standard No. 302, thereby demonstrating the 
flame-retardancy of that material. 
Similar good results are obtained utilizing any of the crosslinked 
vinylidene chloride polymer microgel powder dispersions of the present 
invention.