Microemulsions of gel-free polymers

Described is a method of preparing microemulsions of organopolysiloxanes, by copolymerizing a cyclic siloxane and a polyfunctional silane, in an aqueous medium containing a nonionic surfactant, an anionic or cationic surfactant, and a catalyst, until the desired increase in molecular weight is obtained. The invention resides in controlling the gel content of the organopolysiloxanes in the microemulsion by control of the concentration of silane and concentration of silanol in the resulting organopolysiloxane, such that a functionality ratio .phi. results in formation of a gel-free polymer molecular weight distribution of finite organopolysiloxane species in the microemulsion.

BACKGROUND OF THE INVENTION 
This invention is directed to microemulsions of gel-free polymers, and to a 
method for making polysiloxane emulsions using what is commonly known as 
emulsion polymerization. Microemulsions are produced from a mixture of a 
siloxane oligomer, a hydrolyzable water-soluble alkoxysilane, a cationic 
or anionic surfactant, a nonionic surfactant, a catalyst, and water. 
Silicon containing reactants react in the presence of water and 
surfactants to form polysiloxane emulsions. By using our method, it is 
feasible to produce microemulsions of gel-free polymers. 
Our invention is an improvement on methods described in European Patent 
Application 0 459 500 (EP 459500), published Dec. 4, 1991, assigned to the 
assignee of our invention. While EP 459500 teaches similar techniques for 
making microemulsions, it does not teach how to avoid gelation of 
non-linear siloxane polymers. 
Polysiloxane emulsions are categorized by the size of the polysiloxane 
particles and the appearance of the emulsion. The art recognizes three 
categories of silicone emulsions, (i) standard emulsions, (ii) fine 
emulsions, and (iii) microemulsions. Silicone standard emulsions have a 
large particle size greater than 300 nanometers and appear to the human 
eye to be opaque and impenetrable to light. Silicone standard emulsions 
have an intense white appearance. Silicone fine emulsions have a smaller 
particle size from 140-300 nanometers and visually are slightly opaque to 
very slightly translucent. Fine emulsions transmit light but with 
distortion. Silicone microemulsions have a particle size less than 140 
nanometers and visually appear translucent to transparent and transmit 
light without distortion. Microemulsions are most desired due to smaller 
particle size, higher stability, and translucent to transparent 
appearance. 
Emulsions of polysiloxanes in water can be made by mechanically or by 
emulsion polymerization. Mechanically means taking the preformed 
polysiloxane and using mechanical apparatus such as a homogenizer or 
vigorous agitator to emulsify the siloxanes in water. A surfactant can be 
added to the polysiloxane or water to aid the emulsification process. 
Emulsion polymerization to which our invention pertains entails combining 
silicon containing reactants, surfactants, polymerization catalyst, and 
water. The mixture is stirred and the silicon containing reactants are 
allowed to polymerize until a microemulsion is formed. Alkoxysilanes, 
cyclic siloxanes, and combinations of alkoxysilanes and cyclic siloxanes 
can be used as reactants to form the microemulsion. 
While techniques in EP 459500 have been largely successful in producing 
suitable microemulsions of linear siloxane polymers, they do not provide 
for avoidance of polymer gelation when production of a non-linear siloxane 
polymer microemulsion is the desired product, which is the essence and 
contribution of our invention. 
SUMMARY OF THE INVENTION 
This invention relates to a composition and a process for producing 
polysiloxane microemulsions containing a gel-free polymer molecular weight 
distribution. According to our process, polyfunctional alkoxysilanes and 
permethylcyclic siloxanes are copolymerized in the presence of nonionic, 
and an anionic or cationic surfactant. A gel-free polymer molecular weight 
distribution is observed within a specific range of the functionality 
ratio provided the polyfunctional monomer is dispersed throughout the 
polymer in a nearly random manners. The functionality ratio .phi. is the 
molar ratio of initial polyfunctional silane to remaining total silanol. 
Our process may be illustrated by reference to the following three 
scenarios where DBSA is dodecylbenzene sulfonic acid: 
##STR1## 
The concentration of polyfunctional monomer (alkoxysilane) is controlled by 
the initial charge of ingredients to the reactor (recipe), whereas the 
concentration of silanol is controlled by prevailing reaction temperatures 
and particle sizes. The specific functionality range which results in a 
gel-free polymer molecular weight distribution of "finite" polymeric 
species is theoretically defined in relation to a gel point, or the point 
of incipient heterogeneity in the polymer molecular weight distribution. 
The functionality ratio at the gel point .phi..sub.g is theoretically 
defined as: 
EQU .phi..sub.g theoretical=.rho./(1-p.sub.g). 
.rho. and p.sub.g are in turn defined by the following equation where 
.alpha..sub.g has the value 0.5. Thus: 
##EQU1## 
where; .alpha..sub.g is the branching coefficient relating to 
polyfunctional monomer structure, 
.rho. is the ratio of initial polyfunctional silane (i.e. complete 
hydrolysis of all alkoxysilane groups present in the formulation) to 
initial total silanol (i.e. complete hydrolysis of all alkoxysilane groups 
present in the formulation plus complete hydrolysis of all cyclosiloxane 
species), and 
p.sub.g is the molar conversion of silanol at the gel point or the moles of 
total .tbd.SiOH consumed at the gel point divided by the initial total 
silanol. 
It is understood that the simplest theoretical prediction of the gel point 
requires that all condensation reactions are intermolecular and the 
reactivities of HO(Me.sub.2 SiO)H and MeSi(OH).sub.3 are equal. Since both 
of these requirements are unlikely to apply to the emulsion 
copolymerization of a permethylcyclic siloxane and a polyfunctional 
silane, .phi. can be empirically determined from the following equation: 
##EQU2## 
where; f is silane functionality, i.e. 3 for MeSi(OMe).sub.3 and 4 for 
Si(OEt).sub.4, 
brackets [ ] are units of concentration (w/w) for R.sub.n SiO.sub.(4-n)/2 
and SiOH, 
MWSiOH is molecular weight of silanol, 
MWR.sub.n SiO.sub.(4-n)/2 is molecular weight of branched site, 
n is 0 or 1, and 
R is CH.sub.3 --, CH.sub.3 (CH.sub.2).sub.2 --, CH.sub.3 (CH.sub.2).sub.7 
--, or CH.sub.3 (CH.sub.2).sub.11 --, for example. 
If the functionality ratio .phi. is less than the functionality ratio at 
the gel point .phi..sub.g, the polymer molecular weight distribution will 
be gel-free (unimodal) and contain only "finite" species. If the 
functionality ratio .phi. is at the functionality ratio at the gel point 
.phi..sub.g, the polymer molecular weight will not be gel-free (unimodal), 
but will contain a soluble polymer fraction and a gel fraction (bimodal). 
As the functionality ratio .phi. increases beyond the functionality ratio 
at the gel point .phi..sub.g, the gel fraction will become more 
predominant until a complete network forms. The average size of network 
will be bounded by the average diameter of the polymer particles. 
It is not believed that the functionality ratio .phi. has been previously 
used to control the gel content, i.e. molecular weight distribution, of 
nonlinear silicone emulsion polymers. According to our invention, the 
relative rate at which the two monomers (alkoxysilane and cyclic siloxane) 
are introduced into the reactor is not critical, as long as irreversible 
homopolymerization of the polyfunctional monomer (alkoxysilane) does not 
occur. The functionality ratio, .phi., of a highly nonrandom copolymer 
would have no predictive value. It is believed that the extremely high 
surface area unique to microemulsions facilitates mass transfer of water 
soluble siloxane species between particles, thereby providing a mechanism 
for rapid siloxane redistribution within the entire system. Thus, if 
reversible homopolymerization of the polyfunctional monomer occurs, 
rearrangement reactions will ensure a random distribution of branching 
within the polymer. 
Due to the reversible nature of ionic siloxane polymerizations, a lightly 
crosslinked siloxane gel in microemulsion form can be rearranged to form 
100% sol. For purposes of this application, the term "sol" is used in the 
sense of denoting a finite polymeric species, i.e. "gel-free". This is 
accomplished by manipulation of the polymerization temperature. In 
emulsion systems of this type, the equilibrium concentration of silanol in 
the polymer is directly proportional to the reaction temperature. Thus, 
.phi. is inversely proportional to the reaction temperature. If a given 
set of processing conditions result in .phi. being larger than 
.phi..sub.g, then .phi. can be decreased to a value less than .phi..sub.g 
by simply increasing the reaction temperature after all of the 
microemulsion particles have been formed. The ability to recover sol 
would, of course, be dependent upon the physical constraints of the 
system. For example, a reaction temperature of 200.degree. C. would be 
quite impractical. 
The viscous dissipation factor of gel-free nonlinear emulsion polymers is 
higher than that of polymers of similar viscosity which contain a gel 
fraction. Therefore emulsions of gel-free polymers are useful in 
applications which require lubrication properties without excessive 
tackiness. For example, anionic or cationic emulsions of gel-free but 
branched silicone polymers of high viscosity are useful as hair 
conditioning agents. 
While not being bound by metes and bounds, generally, our method entails 
making microemulsion containing particles with a size of about 25-70 
nanometers (0.025-0.070 microns), using a nonionic, and a cationic or 
anionic surfactant, cyclic siloxane monomers such as 
octamethylcyclotetrasiloxane, and C.sub.1 -C.sub.12 alkyltrialkoxysilanes 
or tetraalkoxysilanes. With a molar ratio of silane to cyclic siloxane of 
0.0001-0.02, a polymer viscosity of 1000-5,000,000 centistokes (mm.sup.2 
/s) can be produced. .phi. should range from 0.0001 to the experimentally 
determined gel point .phi..sub.g. 
These and other features and objects of the invention will become apparent 
from a consideration of the detailed description. 
DETAILED DESCRIPTION OF THE INVENTION 
The emulsions of this invention are made from a siloxane oligomer, a 
hydrolyzable water,soluble alkoxysilane, either a cationic or anionic 
surfactant, a nonionic surfactant, a catalyst, and water. In some cases, 
an anionic surfactant can also act as catalyst thereby eliminating the 
need for a catalyst. In other cases, some cationic surfactants have 
nonionic characteristics, eliminating the need for a nonionic surfactant. 
Polymerization according to the method of our invention involves the 
opening of a cyclic siloxane ring using an acid or base catalyst in the 
presence of water. Upon opening of the ring, polysiloxanes oligomers with 
terminal hydroxy groups are formed. These polysiloxane oligomers then 
react with each other or with other silicon containing reactants in the 
reaction medium, through a condensation reaction to form polysiloxane 
polymers or copolymers. 
The siloxane oligomers are cyclic siloxanes of formula: 
##STR2## 
where each R is a saturated or unsaturated alkyl group of 1-6 carbon 
atoms, an aryl group of 6-10 carbon atoms, and x is 3-7. R can optionally 
contain a functional group which is unreactive in the ring opening and 
polymerization reaction. 
Suitable R groups are methyl, ethyl, propyl, phenyl, allyl, vinyl, and 
--R.sup.1 F. R.sup.1 is an alkylene group of 1-6 carbon atoms or an 
arylene group of 6-10 carbon atoms, and F is a functional group such as an 
amine, diamine, halogen, carboxy, or mercapto. R can also be --R.sup.1 
F.sup.1 R where R.sup.1 and R are described above and F.sup.1 is a 
non-carbon atom such as oxygen, nitrogen, or sulfur. 
Cyclic siloxanes useful in our invention include compounds such as 
hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, 
decamethylcyclopentasiloxane, tetramethyltetravinylcyclotetrasiloxane, 
tetramethyltetraphenylcyclotetrasiloxane, and mixtures thereof. 
We make copolymers in the emulsion polymerization reaction by having 
present in the reaction medium a small portion of other silicon containing 
reactants. These reactants may be any compound that contains a 
hydrolyzable or silanol group and is capable of polymerization using 
emulsion polymerization. The other reactant should be water-soluble, and 
included at a level less than 2 mole percent of the total silicone 
content. 
Examples of other silicon containing reactants include organofunctional 
siloxanes such as hydroxy endblocked polysiloxanes, exemplified by silanol 
terminated polydimethysiloxanes with a degree of polymerization between 
1-7. 
Most preferred, however, are hydrolyzable water-soluble alkoxysilanes 
RSi(OR').sub.3 or (R'O).sub.4 Si where R is an organic group, preferably 
containing 1-12 carbon atoms, such as an unsubstituted alkyl group C.sub.n 
H.sub.2n+1, or an aryl group. R' in hydrolyzable group --(OR') is an alkyl 
group containing 1-6 carbon atoms. Silanes RSi(OR').sub.3 are therefore 
alkoxysilanes with neutral organic groups R. 
Tetraalkoxysilanes (R'O).sub.4 Si are best exemplified by 
tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and 
tetrabutoxysilane. 
Hydrolyzable water-soluble alkoxysilanes RSi(OR').sub.3 with neutral 
organic groups R are exemplified by methyltrimethoxysilane, 
ethyltrimethoxysilane, propyltrimethoxysilane, n-butyltrimethoxysilane, 
hexyltrimethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, 
dodecyltrimethoxysilane, dodecyltriethoxysilane, and 
phenyltrimethoxysilane. 
Hydrolyzable water-soluble alkoxysilanes RSi(OR').sub.3 with cationic 
organofunctional groups R exemplified by amino functional silanes are not 
included in our invention. 
Our emulsions-contain a silicone concentration of 10-70% by weight of the 
total emulsion solution, preferably 25-60%. While emulsions with less than 
10% silicone content can be made, such emulsions hold little or no 
economic value. 
The reaction to polymerize the silicon containing reactants and form 
emulsions is carried out in a reactor containing a reaction medium of 
water, at least one cationic or anionic (ionic) surfactant, at least one 
nonionic surfactant, and a catalyst. Any catalyst capable of polymerizing 
cyclic siloxanes in the presence of water is useful in our method. 
Catalysts include condensation polymerization catalysts capable of 
cleaving siloxane bonds, for example strong acids such as substituted 
benzene sulfonic acids, aliphatic sulfonic acids, hydrochloric acid, and 
sulfuric acid; and strong bases such as quaternary ammonium hydroxides and 
metal hydroxides. Anionic surfactants such as dodecylbenzene sulfonic acid 
(DBSA) can additionally function as catalyst. Other useful catalytic 
systems include phase transfer catalysts such as tetrabutyl ammonium 
hydroxide or ion exchange resins where catalysts are formed in situ. 
The catalyst is present in the reaction medium at levels of 0.01-30% by 
weight of total silicone. Strong acids and basic metal hydroxides can be 
used within the lower end of this range, while surfactants which also 
function as catalyst will be present at concentrations on the higher end 
of the range. 
It is important that the reaction medium contain both an ionic and nonionic 
surfactant to stabilize the polysiloxane in the emulsion. Ionic 
surfactants can be cationic or anionic but surfactants known in the art as 
useful in emulsion polymerization. 
Suitable anionic surfactants include but are not limited to sulfonic acids 
and their salt derivatives. Useful anionic surfactants are alkali metal 
sulfosuccinates; sulfonated glyceryl esters of fatty acids such as 
sulfonated monoglycerides of coconut oil acids; salts of sulfonated 
monovalent alcohol esters such as sodium oleyl isothionate; amides of 
amino sulfonic acids such as the sodium salt of oleyl methyl tauride; 
sulfonated products of fatty acid nitriles such as palmitonitrile 
sulfonate; sulfonated aromatic hydrocarbons such as sodium 
alpha-naphthalene monosulfonate; condensation products of naphthalene 
sulfonic acids with formaldehyde; sodium octahydro anthracene sulfonate; 
alkali metal alkyl sulfates; ether sulfates having alkyl groups of eight 
or more carbon atoms; and alkylaryl sulfonates having one or more alkyl 
groups of eight or more carbon atoms. Commercial anionic surfactants 
useful in our invention include dodecylbenzene sulfonic acid (DBSA) sold 
under the tradename BIOSOFT S-100 by Stepan Company, Northfield, Ill.; and 
the sodium salt of dodecylbenzene sulfonic acid sold under the tradename 
SIPONATE DS-10 by Alcolac Inc., Baltimore, Md. 
Useful cationic surfactants are the various fatty acid amines, amides, and 
derivatives, and salts of fatty acid amines and amides. Cationic 
surfactants can be exemplified by aliphatic fatty amines and derivatives 
such as dodecyl amine acetate, octadecyl amine acetate, and acetates of 
amines of tallow fatty acids; homologues of aromatic amines having fatty 
chains such as dodecyl aniline; fatty amides derived from aliphatic 
diamines such as undecyl imidazoline; fatty amides derived from 
di-substituted amines such as oleylamino diethylamine; derivatives of 
ethylene diamine; quaternary ammonium compounds such as tallow 
trimethylammonium chloride, dioctadecyldimethyl ammonium chloride, 
didodecyldimethyl ammonium chloride, and dihexadecyldimethyl ammonium 
chloride; amide derivatives of amino alcohols such as beta-hydroxyethyl 
stearyl amide; amine salts of long chain fatty acids; quaternary ammonium 
bases derived from fatty amides of di-substituted diamines such as 
oleylbenzylamino ethylene diethylamine hydrochloride; quaternary ammonium 
bases of benzimidazolines such as methylheptadecyl benzimidazole 
hydrobromide; basic compounds of pyridinium and derivatives such as 
cetylpyridinium chloride; sulfonium compounds such as octadecyl sulfonium 
methyl sulfate; quaternary ammonium compounds of betaine such as betaine 
compounds of diethylamino acetic acid, and octadecylchloromethyl ether; 
urethanes of ethylene diamine such as condensation products of stearic 
acid and diethylene triamine; polyethylene diamines; and polypropanol 
polyethanol amines. Commercial cationic surfactants include products sold 
under the tradenames ARQUAD T-27W, 16-29, C-33, T-50; and ETHOQUAD T/13 
and T/13 ACETATE; by Akzo Chemicals Inc., Chicago, Ill. The anionic or 
cationic surfactant is present at 0.05-30% by weight of total emulsion, 
preferably 0.5-20%. 
Useful nonionic surfactants have a hydrophilic-lipophilic balance (HLB) of 
10-20. Nonionic surfactants with HLB of less than 10 may be used but hazy 
solutions may result due to limited solubility of the nonionic surfactant 
in water. When using a nonionic surfactant with HLB less than 10, a 
nonionic surfactant with HLB greater than 10 should be added during or 
after polymerization. Commercial nonionic surfactants can be exemplified 
by 2,6,8-trimethyl-4-nonyloxy polyethylene oxyethanols (6EO) and (10EO) 
sold under the trademarks TERGITOL.RTM. TMN-6 and TERGITOL.RTM. TMN-10; 
alkyleneoxy polyethylene oxyethanol (C.sub.11-15 secondary alcohol 
ethoxylates 7EO, 9EO, and 15E0) sold under the trademarks TERGITOL.RTM. 
15-S-7, TERGITOL.RTM. 15-S-9, TERGITOL.RTM. 15-S-15; other C.sub.11-15 
secondary alcohol ethoxylates sold under the trademarks TERGITOL.RTM. 
15-S-12, 15-S-20, 15-S-30, 15-S-40; and octylphenoxy polyethoxy ethanol 
(40EO) sold under the trademark TRITON.RTM. X-405. All of these 
surfactants are sold by Union Carbide Corporation, Danbury, Conn. Other 
commercial nonionic surfactants are nonylphenoxy polyethoxy ethanol (10EO) 
sold under the tradename MAKON 10 by Stepan Company, Northfield, Ill. One 
especially useful nonionic surfactant is polyoxyethylene 23 lauryl ether 
(Laureth-23) sold commercially under the tradename BRIJ 35 by ICI 
Surfactants, Wilmington, Del. The level of nonionic surfactant should be 
0.1-40% by weight based on total weight of emulsion, preferably 0.5-30%. 
Some commercially available ionic surfactants have characteristics of both 
ionic and nonionic surfactants combined, such as methyl polyoxyethylene 
(15) octadecyl ammonium chloride sold under the tradename ETHOQUAD 18/25 
by Akzo Chemicals Inc., Chicago, Ill. It is a cationic quaternary ammonium 
salt with polyethylene oxide tails. When this type of ionic surfactant is 
used in our invention it is not necessary to have both ionic and nonionic 
surfactants in the reaction medium. Only the ionic surfactant having the 
nonionic characteristics is needed. If the ionic surfactant does not have 
characteristics of both ionic and nonionic surfactants, it is necessary to 
use both types of surfactants in the method of our invention. Surfactants 
such as ETHOQUAD 18/25 are typically used in the emulsion at levels equal 
to the level of ionic surfactants used. 
Our method is preferably carried out by creating a mixture comprising a 
cyclic siloxane, hydrolyzable water-soluble alkoxysilane, ionic (cationic 
or anionic) surfactant, nonionic surfactant, water, and catalyst. The 
mixture is then heated with agitation at a polymerization reaction 
temperature until essentially all of the cyclic siloxane and silane are 
reacted and a stable, oil-free emulsion of gel-free polymer is formed. The 
time required for formation of the stable, oil-free emulsion of gel-free 
polymer will vary depending on the reactants and the reaction conditions. 
The mixture of cyclic siloxane, silane, ionic surfactant, nonionic 
surfactant, water, and catalyst is not stable and will separate without 
some means of agitation. It is not necessary to have all of the cyclic 
siloxane and silane fully dispersed into the mixture during the reaction, 
however some means of agitation must be provided throughout the course of 
the reaction. 
Combining the cyclic siloxane, silane, ionic surfactant, nonionic 
surfactant, water, and catalyst, and then reacting the cyclic siloxane and 
silane to form the emulsion can take place in several ways. The first to 
combine all ingredients with agitation, in any given order, and heat to 
the desired polymerization temperature with agitation, allowing the cyclic 
siloxane and silane to react and form an emulsion. Another way is to 
combine all ingredients with agitation, except for the catalyst, heat to 
the desired polymerization temperature, add the catalyst, and thereafter 
heat and agitate at the desired polymerization temperature, thereby 
allowing the cyclic siloxane and silane to react and form an emulsion. A 
third way is to combine all ingredients with agitation, except for the 
cyclic siloxane and silane, heat to the desired polymerization 
temperature, add or feed in the cyclic siloxane and silane, and thereafter 
heat and agitate at the desired polymerization temperature, thereby 
allowing the cyclic siloxane and silane to react and form an emulsion. It 
is not essential that the ingredients be combined in any given order. 
However, it is essential to have agitation during and following the 
addition of the ingredients, and to have achieved or to heat to the 
polymerization temperature when all of the ingredients have been combined. 
The preferred method for forming emulsions is to create a mixture by 
combining the cyclic siloxane, mixture of cyclic siloxanes, silane, at 
least one nonionic surfactant, at least one ionic (cationic or anionic) 
surfactant, and water; providing agitation such that the cyclic siloxane 
and silane are fully dispersed in the mixture; heating to the 
polymerization temperature; and adding the catalyst. The mixture is then 
held at the polymerization temperature with agitation until a stable 
oil-free emulsion of gel-free polymer is formed. 
The method may also be carried out by combining and mechanically 
emulsifying at least the cyclic siloxane and silane reactants, nonionic 
surfactant, and part of the water. Additional water, the ionic surfactant, 
and catalyst, can be added to the pre-emulsion with agitation. The mixture 
is then heated to the polymerization reaction temperature and held 
optionally with agitation until the monomers are consumed in forming the 
emulsion. Because of the formation and stability of the pre-emulsion, it 
is not necessary to have agitation during the course of the polymerization 
reaction. 
Polymerization reaction temperatures are typically above the freezing point 
but below the boiling point of water. Pressures above or below atmospheric 
pressure allow operation outside of this range. At lower temperatures 
below room temperature, the polymerization reaction may proceed more 
slowly. The preferred temperature range is 50.degree.-95.degree. C. 
The polymerization reaction can be stopped at the desired level of 
conversion of cyclic siloxane/silane and/or particle size by using known 
methods. It is preferred to stop the reaction when the largest amount of 
cyclic siloxane and silane have been reacted or when ring/chain 
equilibrium for the system and the desired particle size have been 
obtained. Reaction times of less than 24 hours, typically less than 5 
hours, are sufficient to achieve the desired particle size and/or level of 
conversion. The methods for stopping the reaction encompass neutralization 
of the catalyst by addition of equal or slightly greater stoichiometric 
amounts of acid or base depending upon the type of catalyst. Either a 
strong or weak acid/base may be used to neutralize the reaction. Care must 
be taken when using a strong acid/base not to over neutralize, as it is 
possible to re-catalyze the reaction. It is preferred to neutralize with 
sufficient quantities of acid or base such that the resulting emulsion has 
a pH of less than 7 when a cationic surfactant is present, and a pH of 
greater than 7 when an anionic surfactant is present. 
The equilibrium molecular weight of emulsion polymers is inversely 
proportional to temperature. Therefore, if a higher degree of 
polymerization (DP) is desired, a reduction of reaction temperature 
pursuant to particle formation will result in a higher molecular weight 
polymer. A useful range of temperature for this procedure is 
10.degree.-50.degree. C. 
A small quantity of alcohol can be added to the reaction medium before or 
after catalysis to increase the particle size of the emulsion. Alcohols 
useful in the method include methanol, ethanol and isopropanol. Since 
alcohols are typically used to break emulsions, it is preferred to keep 
the concentration of the alcohol at low levels, preferably below 5% by 
weight. To have the greatest effect on particle size, it is preferred to 
have the alcohol present throughout the course of the polymerization 
reaction.

In order to show how our invention is an improvement over EP 459500, the 
following example is set forth for purposes of comparison. 
COMISON EXAMPLE I 
This example shows the use of cyclic siloxanes and an organo silane such 
that there is copolymerization between the cyclic siloxanes and the 
silane. This example is, in principle, comparable to Example 11 of EP 
459500, in that cyclic siloxanes and an organic trialkoxysilane are 
copolymerized in the presence of an ionic surfactant, a nonionic 
surfactant, and water. In Example 11 of EP 459500, cyclic siloxanes and a 
silane with cationic functionality 
N-(2-aminoethyl)-3-aminopropyltrimethoxysilane are copolymerized in the 
presence of a cationic surfactant (ARQUAD T-27W), a nonionic surfactant 
(MAKON 10), and water. In this comparison example, cyclic siloxanes and a 
silane with a neutral non-functional organic groups, i.e. 
methyltrimethoxysilane, are copolymerized in the presence of an anionic 
surfactant (dodecylbenzene sulfonic acid), a nonionic surfactant (BRIJ 
35L), and water. This comparison example does not teach how to avoid 
gelation of the resulting siloxane polymer, nor is it taught in EP 459500. 
644.0 grams of water, 131.6 grams of dodecylbenzene sulfonic acid (DBSA), 
and 10.5 grams of BRIJ 35L, were added to a reaction flask and,the 
contents heated to 80.degree. C. 350.00 grams of cyclic siloxanes having 
an average of four silicon atoms per molecule were added with stirring to 
the mixture in the reaction flask at a rate of 1.94 grams per minute. 
About 30 minutes after the start of the cyclic siloxane feed, 7.0 grams of 
methyltrimethoxysilane MeSi(OMe).sub.3 were added to the mixture in the 
reaction flask at a rate of 0.467 grams per minute. The reaction was held 
at 80.degree. C. for an additional three hours after the completion of the 
cyclic siloxane feed in order to reach equilibrium. 79.9 grams of an 85% 
aqueous solution of triethanolamine were added to neutralize the catalyst, 
which in this case was DBSA functioning as both catalyst and anionic 
surfactant. The resulting product was an oil-free microemulsion with a 
particle size of 36 nanometers (nm) as measured by a Nicomp Model 370 
Submicron Particle Sizer. The conversion of monomer was approximately 
96.0% by weight. The polymer was extracted from the emulsion by adding 10 
grams of emulsion, 1.5 grams of anhydrous CaCl.sub.2, 20 ml of methanol, 
and 25 ml of pentane to an appropriate container. The mixture was shaken 
vigorously, added to a plastic centrifuge tube, and centrifuged at 3000 
rpm (314 rad/s) for 15 minutes. The top layer was removed from the tube, 
and stripped to yield only siloxane polymer. The shear viscosity of the 
extracted polymer was approximately 53,000 cp (mm.sup.2 /s) at a shear 
rate of 20.0 l/s (reciprocal seconds) using a Brookfield Model HBDV-III 
Viscometer. The molecular weight distribution of the polymer as measured 
by Gel Permeation Chromatography was comprised of one broad low molecular 
weight peak corresponding to sol (finite polymeric species) and one narrow 
high molecular weight peak corresponding to gel. 
Our invention in contrast is represented by the following examples. 
EXAMPLES WITHIN THE SCOPE OF OUR INVENTION 
Example 1--Procedure--A 
The following procedure illustrates the method used to collect data set 
forth below separately for each of our individual Examples 1-6 and 8. This 
procedure while being specific to Example 1, was used in Examples 2-6, 8, 
and Comparison Example II. A separate procedure is set forth below for 
Example 7. Thus, 644.0 grams of water, 131.6 grams of dodecylbenzene 
sulfonic acid and 10.5 grams of Brij 35L were added to a reaction flask, 
and the contents heated to 80.degree. C. Once the temperature reached 
80.degree. C., 343.14 grams of cyclic siloxanes having an average of four 
silicon atoms per molecule, were added with stirring to the mixture in the 
reaction flask at a rate of 1.906 grams/minute. Approximately 30 minutes 
after the start of the cyclic siloxane feed, 7.0 grams of a mixture of 
methyltrimethoxysilane MeSi(OMe).sub.3 in cyclic siloxane (2.0% silane by 
weight) were added to the mixture in the reaction flask at a rate of 0.467 
grams/minute. The reaction was held at 80.degree. C. for an additional 3 
hours after the completion of the cyclic siloxane feed to reach 
equilibrium. Subsequently, the temperature of the reaction flask was 
reduced to 10.degree. C. to increase the molecular weight of the polymer. 
The flask contents were held at 10.degree. C. for approximately 4 hours to 
reach the equilibrium concentration of silanol, then 79.9 grams of an 85% 
aqueous solution of triethanolamine was added to neutralize the catalyst. 
The resulting product was an oil-free microemulsion with a particle size 
of 37 nanometers (nm) measured by a Nicomp Model 370 Submicron Particle 
Sizer. The conversion of monomer was approximately 93.5% by weight. The 
polymer was extracted from the emulsion by adding 10 g of emulsion, 1.5 g 
of anhydrous CaCl.sub.2, 20 ml of methanol, and 25 ml of pentane to an 
appropriate container. The mixture was shaken vigorously, added to a 
plastic centrifuge tube, and centrifuged at 3000 rpm for 15 minutes. The 
top layer was removed from the tube and stripped to yield only siloxane 
polymer. The shear viscosity of the extracted polymer was approximately 
250,000 mm.sup.2 /s at a shear rate of 6.0 s.sup.-1 (reciprocal seconds 
1/s), using a Brookfield Model HBDV-III Viscometer. The concentration of 
silanol in the polymer was approximately 454 ppm as measured by a 
Fourier-Transform Infrared Spectroscopy (FTIR)-deuteration technique. The 
FTIR-deuteration method was accomplished by subtraction of FTIR spectrum 
of a deuterated dilute solution of polydimethylsiloxane in CCl.sub.14 from 
a spectrum of the same solution without deuteration. After correcting the 
spectrum for the presence of water, the absorbance at 3693 cm.sup.-1 was 
correlated to the .tbd.SiOH concentration. The concentration of 
MeSiO.sub.3/2 in the polymer was approximately 256 ppm as measured by 
equilibration of polymer sample with a large excess of 
hexamethyldisiloxane in the presence of trifluoromethane sulfonic acid 
catalyst to yield the corresponding triorganosiloxy derivatives. The 
resultant solution was analyzed by internal standard gas chromatography to 
allow determination of the concentration of minor silicon substituents. 
The molecular weight distribution of the polymer measured by Gel 
Permeation Chromatography (GPC) was comprised of only one broad peak, and 
therefore this polymer contained only sol, denoting a finite polymeric 
species, i.e. "gel-free". 
Example 1--Procedure--B 
To experimentally determine the gel point, the reaction temperature is 
decreased if the polymer is known to contain only sol (finite polymeric 
species), or increased if the polymer is known to contain sol and gel. It 
is then held until a static concentration of silanol is achieved. The 
polymer is extracted from a sample of the emulsion, and a chromatogram is 
obtained of the molecular weight distribution. The reaction temperature is 
systematically adjusted until the molecular weight distribution is only 
slightly bimodal containing a soluble polymer fraction and a gel 
fraction), and this transition is defined as the gel point. This procedure 
was used to identify the gel point in Examples 2-7 and Comparison Example 
II. 
Example 1 
______________________________________ 
Silane functionality f = 3 (i.e. methylsilsesquioxane CH.sub.3 SiO.sub.3/2 
______________________________________ 
Wt % Water 56.68* 
Wt % Dodecylbenzene sulfonic acid (Anionic) 
11.58* 
Wt % Polyoxyethylene (23) lauryl ether (Nonionic) 
0.92* 
Wt % Octamethylcyclotetrasiloxane 
30.80* 
ppm Methyltrimethoxysilane 123* 
Reaction temperature (.degree.C.) to form particles 
80 
Reaction temp. (.degree.C.) to increase polymer molecular 
9-10ht 
Reaction temp. (.degree.C.) at neutralization 
9-10 
Reaction temp. (.degree.C.) at gelation of polymer, for 
&lt;9ference 
Particle size, Gaussian intensity weighted mean (nm) 
36.5 
Polymer characterization Tables 1 & 2 
______________________________________ 
*= amounts added to the reaction flask. 
In Example 1, value 1.1 of .phi. was determined by: 
##EQU3## 
where f is the silane functionality 3 for MeSi(OMe).sub.3, [R.sub.n 
SiO.sub.(4-n)/2 ] is CH.sub.3 SiO.sub.3/2 concentration measured on the 
resulting polymer as 256 ppm, [SiOH] is silanol concentration measured on 
the resulting polymer as 454 ppm, MWSiOH is the molecular weight of 
silanol SiOH (28+16+1), MWR.sub.n SiO.sub.(4-n)/2 is the molecular weight 
of a branched site as CH.sub.3 SiO.sub.3/2 [12+3+28+(3.times.16)/2], n is 
1, and R is CH.sub.3. This same type of computation was used in 
determining the .phi. value in Examples2-8, but is not shown in such 
detail. 
Example 2 
______________________________________ 
Silane functionality f = 3 (i.e. methylsilsesquioxane CH.sub.3 SiO.sub.3/2 
______________________________________ 
Wt % Water 56.61 
Wt % Dodecylbenzene sulfonic acid 
11.57 
Wt % Polyoxyethylene (23) lauryl ether 
0.92 
Wt % Octamethylcyclotetrasiloxane 
30.77 
ppm Methyltrimethoxysilane 1230 
Reaction temperature (.degree.C.) to form particles 
81 
Reaction temp. (.degree.C.) to increase polymer molecular 
N/Aght 
Reaction temp. (.degree.C.) at neutralization 
81 
Reaction temp. (.degree.C.) at gelation of polymer, for 
23ference 
Particle size (nm) 32.5 
Polymer characterization Tables 1 & 2 
______________________________________ 
Example 3 
______________________________________ 
Silane functionality f = 3 (i.e. propylsilsequioxane C.sub.3 H.sub.7 
SiO.sub.3/2) 
______________________________________ 
Wt % Water 56.61 
Wt % Dodecylbenzene sulfonic acid 
11.57 
Wt % Polyoxyethylene (23) lauryl ether 
0.92 
Wt % Octamethylcyclotetrasiloxane 
30.76 
ppm Propyltrimethoxysilane 1485 
Reaction temperature (.degree.C.) to form particles 
80 
Reaction temp. (.degree.C.) to increase polymer molecular 
N/Aght 
Reaction temp. (.degree.C.) at neutralization 
80 
Reaction temp. (.degree.C.) at gelation of polymer, for 
49ference 
Particle size (nm) 33.4 
Polymer characterization Tables 1 & 2 
______________________________________ 
Example 4 
______________________________________ 
Silane functionality f = 3 (i.e. octylsilsesquioxane C.sub.8 H.sub.17 
SiO.sub.3/2) 
______________________________________ 
Wt % Water 56.53 
Wt % Dodecylbenzene sulfonic acid 
11.57 
Wt % Polyoxyethylene (23) lauryl ether 
0.94 
Wt % Octamethylcyclotetrasiloxane 
30.72 
ppm Octyltriethoxysilane 2500 
Reaction temperature (.degree.C.) to form particles 
80 
Reaction temp. (.degree.C.) to increase polymer molecular 
N/Aght 
Reaction temp. (.degree.C.) at neutralization 
80 
Reaction temp. (.degree.C.) at gelation of polymer, for 
50-80ence 
Particle size (nm) 40.6 
Polymer characterization Tables 1 & 2 
______________________________________ 
Example 5 
______________________________________ 
Silane functionality f = 3 (i.e. dodecylsilsesquioxane C.sub.12 H.sub.25 
SiO.sub.3/2) 
______________________________________ 
Wt % Water 56.50 
Wt % Dodecylbenzene sulfonic acid 
11.55 
Wt % Polyoxyethylene (23) lauryl ether 
0.92 
Wt % Octamethylcyclotetrasiloxane 
30.73 
ppm Dodecyltriethoxysilane 3010 
Reaction temperature (.degree.C.) to form particles 
80 
Reaction temp. (.degree.C.) to increase polymer molecular 
N/Aght 
Reaction temp. (.degree.C.) at neutralization 
80 
Reaction temp. (.degree.C.) at gelation of polymer, for 
50ference 
Particle size (nm) 36.3 
Polymer characterization Tables 1 & 2 
______________________________________ 
Example 6 
______________________________________ 
Silane functionality f = 4 (i.e. silicate SiO.sub.2) 
______________________________________ 
Wt % Water 56.65 
Wt % Dodecylbenzene sulfonic acid 
11.58 
Wt % Polyoxyethylene (23) lauryl ether 
0.93 
Wt % Octamethylcyclotetrasiloxane 
30.78 
ppm Tetraethoxysilane 703 
Reaction temperature (.degree.C.) to form particles 
80 
Reaction temp. (.degree.C.) to increase polymer molecular 
51ight 
Reaction temp. (.degree.C.) at neutralization 
51 
Reaction temp. (.degree.C.) at gelation of polymer, for 
23ference 
Particle size (nm) 35 
Polymer characterization Tables 1 & 2 
______________________________________ 
Example 7--Procedure 
In this example, cationic surfactant is used, and the procedure in this 
example differs from the procedure in Examples 1-6 and 8 where an anionic 
surfactant is employed. 
630.0 grams of water, 144.2 grams of ETHOQUAD T/13 cationic surfactant, 
65.8 grams of TERGITOL.RTM. 15-S-12 nonionic surfactant, and 399.0 grams 
of cyclic siloxanes having an average of four silicon atoms per molecule, 
were added to a reaction flask and the contents heated to 85.degree. C. 
4.9 grams of a 50% aqueous catalyst solution of NaOH were added to the 
mixture in the reaction flask. About 8 hours after the addition of the 
NaOH catalyst, 22.2 grams of a mixture of methyltrimethoxysilane 
MeSi(OMe).sub.3 in cyclic siloxanes (11.3% silane by weight) were added to 
the mixture in the reaction flask at a rate of 0.37 grams per minute. The 
reaction was held at 85.degree. C. for an additional four hours after the 
completion of the silane feed in order to reach equilibrium. Subsequently, 
the temperature of the reaction flask was reduced to 23.degree. C. for 
approximately four hours, then 3.8 grams of glacial acetic acid were added 
to neutralize the catalyst. The resulting product was an oil-free 
microemulsion with a particle size of 61 nanometers (nm) as measured by a 
Nicomp Model 370 Submicron Particle Sizer. The conversion of monomer was 
not determined. The methods used to extract the polymer, measure the 
silanol concentration of the polymer, measure the methylsilsesquioxane 
concentration of the polymer, and obtain the molecular weight distribution 
of the polymer, were identical to the procedure described for Example 1. 
Example 7 
______________________________________ 
Silane functionality f = 3 (i.e. methylsilsesquioxane CH.sub.3 SiO.sub.3/2 
______________________________________ 
Wt % Water 50.54 
Wt % Ethoquad T/13 (Cationic) 
11.57 
Wt % Tergitol .RTM. 15-S-12 (Nonionic) 
5.28 
Wt % Octamethylcyclotetrasiloxane 
32.01 
Wt % NaOH (50% aqueous solution) 
0.39 
ppm Methyltrimethoxysilane 2000 
Reaction temperature (.degree.C.) to form particles 
85 
Reaction temp. (.degree.C.) to increase polymer molecular 
23ight 
Reaction temp. (.degree.C.) at neutralization 
23 
Reaction temp. (.degree.C.) at gelation of polymer, for 
6ference 
Particle size (nm) 61 
Polymer characterization Tables 1 & 2 
______________________________________ 
Example 8 
______________________________________ 
Silane functionality f = 3 (i.e. methylsilsesquioxane CH.sub.3 SiO.sub.3/2 
______________________________________ 
Wt % Water 56.64 
Wt % Dodecylbenzene sulfonic acid (Anionic) 
11.57 
Wt % Polyoxyethylene (23) lauryl ether (Nonionic) 
0.92 
Wt % Octamethylcyclotetrasiloxane 
30.80 
ppm Methyltrimethoxysiloxane 
615 
Reaction temperature (.degree.C.) to form particles 
80 
Reaction temp. (.degree.C.) to increase polymer molecular 
15ight 
Reaction temp. (.degree.C.) at neutralization 
15 
Reaction temp. (.degree.C.) at gelation of polymer, for 
&lt;15 ence 
Particle size (nm) 36 
Polymer characterization Tables 1 & 2 
______________________________________ 
Example 8 demonstrates the preparation of a high polymer viscosity of about 
I million mm.sup.2 /s without the presence of a gel fraction. 
In each of Examples 1-8 representing methods of our invention, the 
functionality ratio .phi. had a value less than the functionality ratio at 
the gel point .phi..sub.g. This is shown in Table 1. 
EXAMPLE OUTSIDE THE SCOPE OF OUR INVENTION 
Example II--COMISON 
______________________________________ 
Silane functionality f = 3 (i.e. methylsilsesquioxane CH.sub.3 SiO.sub.3/2 
______________________________________ 
Wt % Water 56.6 
Wt % Dodecylbenzene sulfonic acid 
11.6 
Wt % Polyoxyethylene (23) lauryl ether 
0.92 
Wt % Octamethylcyclotetrasiloxane 
30.8 
ppm Methyltrimethoxysilane 1230 
Reaction temperature (.degree.C.) to form particles 
81 
Reaction temp. (.degree.C.) to increase polymer molecular 
10-11t 
Reaction temp. (.degree.C.) at neutralization 
10-11 
Reaction temp. (.degree.C.) at gelation of polymer, for 
23ference 
Particle size (nm) 34.9 
Polymer characterization Tables 1 & 2 
______________________________________ 
In Comparison Example II representing a method not according to our 
invention, functionality ratio .phi. (4.26) did not have a value less than 
the functionality ratio at the gel point .phi..sub.g (4.13). Therefore, 
the microemulsion polymer in Comparison Example II contained a soluble 
polymer fraction and a gel fraction. Tables 1 and 2 referred to above are 
shown below. 
TABLE 1 
__________________________________________________________________________ 
Features of Polymer Molecular Weight Distribution 
ppm R.sub.n SiO.sub.(4-n)/2 
ppm SiOH in 
Gel Peak 
Sol Peak 
ppm R.sub.n SiO.sub.(4-n)/2 in 
ppm SiOH in 
in Polymer at 
Polymer at 
Example 
Present (.dagger.) 
Present (.dagger.) 
Example Polymer 
Example Polymer 
.phi. 
Gel Point (*) 
Gel Point (*) 
.phi.g 
__________________________________________________________________________ 
1 No Yes 256 .sup. 
454 1.1 
not available 
not available 
&gt;1.1 
2 No Yes 1077 .sup. 
1274 1.7 
1124 .sup. 
548 4.1 
3 No Yes 2820 (.dagger-dbl.) 
1114 3.6 
2820 (.dagger-dbl.) 
825 4.9 
4 No Yes 4940 (.dagger-dbl.) 
1238 3.3 
4940 (.dagger-dbl.) 
792-1238 
3.3-5.1 
5 No Yes 6600 (.dagger-dbl.) 
1302 3.1 
6600 (.dagger-dbl.) 
911 4.4 
6 No Yes 677 (.dagger-dbl.) 
838 2.4 
677 (.dagger-dbl.) 
554 3.7 
7 No Yes 2580 .sup. 
1056 4.9 
2580 .sup. 
749 6.9 
8 No Yes 980 .sup. 
487 4.0 
not available 
not available 
&gt;4.0 
II Yes Yes 1044 .sup. 
494 4.3 
1124 .sup. 
548 4.1 
__________________________________________________________________________ 
.dagger. = determined by Gel Permeation Chromatography 
.dagger-dbl. = estimated value assuming 100% incorporation of silane 
* The gel point corresponds to the incipient heterogeneity of the polymer 
molecular weight distribution 
TABLE 2 
______________________________________ 
Additional Characterization Data 
Equilibrium Viscosity 
Equilibrium Viscosity 
Ex- Wt % Cyclics 
of Example Polymer 
of Polymer at Gel- 
ample Conversion (cs) Point (cs) 
______________________________________ 
1 93.4 250,000 at shear rate = 
not available 
6.0 1/s 
2 97.4 4,500 (shear rate not 
128,000 at shear rate = 
noted) 6.0 1/s 
3 98.9 14,000 at shear rate = 
112,000 at shear rate = 
80.0 1/s 8.0 1/s 
4 97.9 16,000 at shear rate = 
not available 
80.0 1/s 
5 97.8 6,300 at shear rate = 
68,000 at shear rate = 
200 1/s 16 1/s 
6 97.3 not available not available 
7 not determined 
5,500 at shear rate = 
not available 
200 1/s 
8 92.6 1,300,000 at shear 
not available 
rate = 0.4 1/s 
II 100 2,100,000 at shear 
128,000 at shear rate = 
rate = 0.4 1/s 
6.0 1/s 
______________________________________ 
cs = centistokes = mm.sup.2 /sec 
1/s = s-.sup.1 = reciprocal seconds