U.S. patent application number 09/801009 was filed with the patent office on 2001-08-09 for emulsion polymerization process.
This patent application is currently assigned to General Electric Co.. Invention is credited to Dong, Stephen, Traver, Frank J., Warrenchak, James F..
Application Number | 20010012872 09/801009 |
Document ID | / |
Family ID | 23419023 |
Filed Date | 2001-08-09 |
United States Patent
Application |
20010012872 |
Kind Code |
A1 |
Dong, Stephen ; et
al. |
August 9, 2001 |
Emulsion polymerization process
Abstract
A method for preparing a silicone emulsion, more particularly a
method for preparing a silicone emulsion with a low cyclic siloxane
level and particle size control.
Inventors: |
Dong, Stephen; (Clifton
Park, NY) ; Traver, Frank J.; (Troy, NY) ;
Warrenchak, James F.; (Albany, NY) |
Correspondence
Address: |
Kenneth S. Wheelock
GE Plastics
One Plastics Avenue
Pittsfield
MA
01201
US
|
Assignee: |
General Electric Co.
|
Family ID: |
23419023 |
Appl. No.: |
09/801009 |
Filed: |
March 7, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09801009 |
Mar 7, 2001 |
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09360684 |
Jul 26, 1999 |
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6232396 |
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Current U.S.
Class: |
524/837 |
Current CPC
Class: |
C08J 2383/04 20130101;
C08G 77/06 20130101; C08J 3/03 20130101 |
Class at
Publication: |
524/837 |
International
Class: |
C08J 003/00 |
Claims
1. A process for making a silicone emulsion comprising: a)
preparing a neutral aqueous surfactant by adding to water an
anionic surfactant and a base, and mixing to form a uniform neutral
aqueous surfactant having a pH of about 7; b) forming a mixture of
approximately equal portions of the surfactant and a polysiloxane;
c) homogenizing the mixture to form an emulsion, wherein the
emulsion is homogenized until a desired particle size is achieved;
d) cooling the homogenized emulsion; e) adding an acid to the
cooled emulsion and condensing the emulsion to form a polymer,
wherein the polymer is condensed until the viscosity reaches the
desired level; and f) neutralizing the condensed emulsion with an
effective amount of a neutralizing agent wherein the level of
cyclic siloxanes in the emulsion is less than one percent by
weight.
2. The process of claim 1, comprising: i) from about 0.3 to about 5
pbw of an anionic surfactant, from about 0.06 to about 1.1 pbw of a
base and from about 30 to about 90 pbw water; ii) from about 8 to
about 65 pbw of a polysiloxane; iii) from about 0.09 to about 1.5
pbw of an acid; iv) an effective amount of a neutralizing agent to
neutralize the emulsion to a pH of from about 6 to 8.5.
3. The process of claim 1, wherein the mixture is homogenized at a
pressure of from about 4,000 to about 12,000 psig.
4. The process of claim 1, wherein the emulsion is cooled after
homogenization to from about 15 to about 50.degree. C.
5. The process of claim 1, wherein the polymer viscosity is from
about 100,000 to about 6,000,000 cps.
6. The process of claim 2, wherein the anionic surfactant is
alkylbenzenesulfonic acid.
7. The process of claim 6, wherein the anionic surfactant is
dodecylbenzenesulfonic acid.
8. The process of claim 1, wherein the polysiloxane is a low
viscosity silanol-stopped polymer of the formula:
OH--(R.sub.2SiO).sub.x--H wherein each R is independently a
monovalent hydrocarbon radical; and x is an integer, wherein x is
chosen such that the viscosity is from about 15 to about 1000
centistokes.
9. The process of claim 8, wherein each R is methyl.
10. The process of claim 1, wherein the neutralizing agent is an
alkanolamine of the formula: (R.sup.1OH).sub.3N wherein R.sup.1 is
(C.sub.1-C.sub.8)alkyl.
11. The process of claim 10, wherein the neutralizing agent is
triethanolamine.
12. The process of claim 1, wherein the particle size of the
emulsion is from about 0.1 to about 2.0 microns.
13. An emulsion formed the process of claim 1.
14. A personal care composition comprising the emulsion formed by
the process of claim 1.
15. A silicone emulsion, comprising: a) water; b) a polysiloxane
formed from a low viscosity silanol-stopped siloxane of the
formula: OH--(R.sub.2SiO).sub.x--H wherein each R is independently
a monovalent hydrocarbon radical; and x is an integer, wherein x is
chosen such that the viscosity is from about 15 to about 1000
centistokes, wherein the polysiloxane has a particle size of from
about 0.1 to about 2.0 microns and a polymer viscosity of from
about 100,000 to about 6,000,000 centipoise, wherein the emulsion
contains less than one percent by weight cyclic siloxanes.
16. A personal care composition, comprising the emulsion of claim
15, a surfactant, a thickening agent, a colorant, a fragrance and
water.
Description
TECHNICAL FIELD
[0001] The present invention is directed to an emulsion
polymerization process, more particularly, to an emulsion
polymerization process that allows for control of the level of
cyclic siloxanes and the particle size.
BACKGROUND
[0002] Current emulsion polymerization processes have cyclic
siloxane levels greater than one percent in the final emulsion.
With a lower cyclic siloxane level, final product formulations can
be better controlled.
[0003] Cyclic siloxane contaminants are undesirable from the
perspective of health and safety, and there are regulations on the
allowed levels in products. Additionally, cyclic siloxanes have a
tendency to lower the viscosity of shampoos.
[0004] Emulsion polymerization processes have been previously
reported, but prior art processes utilized either cyclic siloxanes
or mixtures of cyclic and linear siloxanes, and these processes
cannot produce emulsions with low cyclic siloxane levels. See, for
example, U.S. Pat. No. 5,504,149, which utilizes cyclic siloxanes,
surfactant and an initiator that is a silanolate or an
organosilanolate; U.S. Pat. No. 4,066,594, which uses cyclic
siloxanes and benzene sulfonic acid and optionally a platinum
catalyst; EPA 874017, which uses a metal containing catalyst for a
chain extension reaction; and JP 9278626, which uses a catalyst and
heat for the emulsion polymerization. When cyclic siloxanes are
used, the emulsion must be heated to allow polymerization and then
cooled for condensation, and the final polymer viscosity is a
function of the condensation temperature.
[0005] A process is needed in which the particle size of the
emulsion can be controlled, as well as the viscosity and the level
of cyclic siloxanes in the emulsion. It has been discovered that by
using a neutral surfactant system instead of an acid catalyst
surfactant during homogenization, particle size, viscosity and
cyclic siloxanes can be controlled. A benefit is that with the
lower cyclic siloxane level, a safer product can be produced.
SUMMARY OF THE INVENTION
[0006] In a first aspect, the present invention is directed to a
process for making a silicone emulsion comprising:
[0007] a) preparing a neutral aqueous surfactant by adding to water
an anionic surfactant and a base, and mixing to form a uniform
neutral aqueous surfactant having a pH of about 7;
[0008] b) forming a mixture of approximately equal portions of the
surfactant and a polysiloxane;
[0009] c) homogenizing the mixture to form an emulsion, wherein the
emulsion is homogenized until a desired particle size is
achieved;
[0010] d) cooling the homogenized emulsion;
[0011] e) adding an acid to the cooled emulsion and condensing the
emulsion to form a polymer, wherein the polymer is condensed until
the viscosity reaches the desired level; and
[0012] f) neutralizing the condensed emulsion with an effective
amount of a neutralizing agent wherein the level of cyclic
siloxanes in the emulsion is less than one percent by weight.
[0013] In a second aspect, the present invention is directed to an
emulsion that is used in personal care applications comprising the
silicone produced by the process of the present invention.
[0014] The process of the present invention is effective in
controlling the particle size and the viscosity of the emulsion as
well as controlling the level of cyclic siloxanes at a level of
less than one percent. Another advantage of the present invention
is that the emulsion does not need to be heated for polymerization
to take place.
DETAILED DESCRIPTION OF THE INVENTION
[0015] In a preferred embodiment, from about 0.3 to 5.0, more
preferably from about 0.8 to about 3.0, even more preferably from
about 0.9 to about 1.8 parts by weight ("pbw"), of an anionic
surfactant and from about 0.06 to about 1.1, more preferably from
about 0.2 to about 0.7, even more preferably from about 0.2 to
about 0.35 pbw of a base are added to a vessel containing from
about 30 to about 90, more preferably from about 35 to about 70,
even more preferably from about 40 to about 55 pbw deionized water
to form a mixture. In a preferred embodiment, this mixture is then
metered with approximately from 8 to about 65, more preferably from
about 25 to about 65, even more preferably from about 45 to about
55 pbw of a polysiloxane. In a preferred embodiment, the mixture is
then blended by passing the mixture through a paste disperser, such
as for example, Premier, and then by milling the mixture, by for
example, a colloid mill such as IKA or Gaulin. After blending, the
mixture is then fed to a homogenizer, such as a Gaulin, Bran &
Lubbe, or a microfluidizer by Microfluidics, to form an emulsion.
In a preferred embodiment, the mixture is homogenized, preferably
without the addition of heat, at a pressure of from about 4,000 to
12,000 psig, more preferably at a pressure of from about 5,000 to
about 8,000, even more preferably at a pressure of about 6000 psig,
and a recycle loop is utilized to set the desired particle size and
to ensure stability of the emulsion. In a preferred embodiment, the
particle size ranges from about 0.1 to about 2.0, more preferably
from about 0.2 to about 1.0, even more preferably from about 0.3 to
about 0.6 microns, as measured by a Malvern Mastercizer or a Nicomp
170. Once homogenized, the emulsion is fed to a condensation vessel
where it is cooled to about 15 to 50.degree. C., more preferably,
from about 20 to 35.degree. C., even more preferably to about 20 to
25.degree. C., and from about 0.09 to about 1.5, more preferably
from about 0.25 to about 0.9, even more preferably from about 0.29
to about 0.45 pbw of a strong acid is added to bring the pH of the
emulsion to about 2, more preferably less than 2. Once the emulsion
is acidified, a controlled condensation begins. Once the
condensation is complete and the desired polymer viscosity has been
achieved, preferably between 100,000 centipoise (cps) and 6,000,000
cps, more preferably between 500,000 and 3,000,000 cps, even more
preferably between 1,000,000 and 2,000,000 cps, the emulsion is
neutralized to prevent further condensation. In a preferred
embodiment, the pH is from about 6 to about 8.5, more preferably
from about 6.5 to about 8, even more preferably from about 7 to
about 7.5 with a neutralizing agent.
[0016] Anionic surfactants suitable for use in the present
invention are those that emulsify and provide good condensation.
Examples of suitable surfactants include alkylbenzenesulfonic acids
and salts such as hexylbenzenesulfonic acid, octylbenzenesulfonic
acid, decylbenzenesulfonic acid, dodecylbenzenesulfonic acid,
cetylbenzenesulfonic acid and myristylbenzenesulfonic acid, more
preferably dodecylbenzenesulfonic acid. Additionally,
co-surfactants, such as sodium lauryl sulfate, may also be
used.
[0017] In a preferred embodiment, the base of the present invention
is one that will neutralize the anionic surfactant. Examples of
bases suitable for use in the present include, but are not limited
to, sodium carbonate, sodium hydroxide, potassium hydroxide,
calcium carbonate. Preferably, the base is sodium carbonate.
[0018] Compounds suitable as the polysiloxane intermediate of the
present invention are those that are hydrolyzates. Examples of
polysiloxane intermediates that may be used in the present
invention include, but are not limited to, linear silanol-stopped
polyorganosiloxanes. Preferably, the polysiloxane intermediate of
the present invention is a low viscosity silanol-stopped polymer of
the formula:
OH--(R.sub.2SiO).sub.x--H
[0019] wherein each R is independently a monovalent hydrocarbon
radical;
[0020] and x is an integer, wherein x is chosen such that the
viscosity is from about 15 to about 1000 centistokes, more
preferably from about 50 to about 500 centistokes, and even more
preferably from about 70 to about 150 centistokes.
[0021] Suitable monovalent hydrocarbon groups include acyclic
hydrocarbon radicals, monovalent alicyclic hydrocarbon radicals,
monovalent and aromatic hvdrocarbon radicals. Preferred monovalent
hydrocarbon radicals are monovalent (C.sub.1-C.sub.6)alkyl
radicals, monovalent aryl radicals and monovalent aralkyl
radicals.
[0022] As used herein, the term "(C.sub.1-C.sub.6)alkyl" means a
linear or branched alkyl group containing from 1 to 6 carbons per
group, such as, for example, methyl, ethyl, propyl, iso-propyl,
n-butyl, iso-butyl, sec-butyl, tert-butyl, pentyl, and hexyl,
preferably methyl.
[0023] In a preferred embodiment, the monovalent hydrocarbon
radical is a monovalent (C.sub.1-C.sub.6)alkyl radical, most
preferably, methyl.
[0024] As used herein, the term "aryl" means a monovalent
unsaturated hydrocarbon ring system containing one or more aromatic
rings per group, which may optionally be substituted on the one or
more aromatic rings, preferably with one or more
(C.sub.1-C.sub.6)alkyl groups and which, in the case of two or more
rings, may be fused rings, including, for example, phenyl,
2,4,6-trimethylphenyl, 2-isopropylmethylphenyl, 1-pentalenyl,
naphthyl, and anthryl, preferably phenyl.
[0025] As used herein, the term "aralkyl" means an aryl derivative
of an alkyl group, preferably a (C.sub.2-C.sub.6)alkyl group,
wherein the alkyl portion of the aryl derivative may, optionally,
be interrupted by an oxygen atom, such as, for example,
phenylethyl, phenylpropyl, 2-(1-naphthyl)ethyl, preferably
phenylpropyl, phenyoxypropyl, and biphenyloxypropyl.
[0026] Suitable intermediate polysiloxanes are made by known
methods, such as, for example, hydrolysis, and are commercially
available.
[0027] In a preferred embodiment, the acid of the present invention
is one that is a strong acid that will neutralize the base to form
a salt and free up the alkylbenzenesulfonic acid. Examples of acids
suitable for use in the present invention include, but are not
limited to, nitric acid, hydrochloric acid, formic acid, phosphoric
acid and sulfuric acid. Preferably the acid is sulfuric acid.
[0028] In a preferred embodiment, the neutralizing agent of the
present invention is any base that will raise the final pH to about
6 to about 8.5, preferably from about 6.5 to about 8, more
preferably from about 7 to about 7.5. Examples of neutralizing
agents suitable for use in the present invention include, but are
not limited to, alkanolamines of the formula:
(R.sup.1OH).sub.3N
[0029] wherein R.sup.1 is (C.sub.1-C.sub.8)alkyl. Preferably, the
neutralizing agent is triethanolamine.
[0030] The process of the present invention may optionally contain
additional components, such as, for example, biocides, antifoam
agents, fragrances, colorants, preservatives and any other
additives known in the art.
[0031] In a preferred embodiment, the process of the present
invention further comprises adding minor amount, preferably, less
than 1% by weight of the composition, and, more preferably, less
than 0.5% by weight of the composition, a biocide. Suitable
biocides include microbiocides such as Proxel GXL microbiocide,
commercial available from Zeneca, and Kathon CG+IP II microbiocide,
commercially available from Rohm & Haas. Preferably, the
biocide is Kathon CG+IP II.
[0032] The emulsions are useful in personal care applications such
as shampoos, conditioners, lotions, cosmetics, etc. The emulsion is
generally incorporated into a personal care product in an amount of
about 0.01 to about 50 weight percent, more preferably 0.1 to 20
weight percent, of the total personal care composition. The
personal care composition of the present invention may, optionally,
further contain such known components as, for example, emollients,
moisturizers, humectants, pigments, colorants, fragrances,
biocides, preservatives, exfoliants, hormones, enzymes, medicinal
compounds, anti-microbial agents, anti-fungal agents, vitamins,
electrolytes, alcohols, polyols, surfactants, emulsifiers, silicone
oils, organic oils, waxes, suspending agents, thickening agents and
water.
[0033] The following example illustrates the process of the present
invention. It is illustrative and the claims are not to be
construed as limited to the example.
EXAMPLE
[0034] Four batches of emulsion were prepared using the process of
the present invention. Results of the batches are shown in the
tables below. The batches were produced as follows:
[0035] To a suitable vessel, 44.87 parts by weight of deionized
water were charged, and an agitator started at moderate speed. To
the water, about 1.2 parts by weight of dodecylbenzenesulfonic acid
was added to make an aqueous solution. Approximately 0.26 parts by
weight of sodium carbonate were added to neutralize the acid. The
mixture was blended until the solution pH was approximately 7
(about 20 minutes). This solution was then proportionately metered
into another vessel (in about equal parts) with about 52 parts by
weight of a polysiloxane (silanol-stopped low viscosity polymer,
approximately 100 cps). The mixture was then passed through a
Premier paste disperser and milled through a Bran and Lubbe colloid
mill. The emulsion stream was then fed to a surge tank to feed the
homogenizer.
[0036] The emulsion was fed to the homogenizer (about 6000 psig) at
a rate equivalent to about two passes to set the particle size of
the emulsion and to ensure product stability. Homogenized emulsion
was then transferred to a condensation tank. Once filled, the
condensation tank is cooled in line to an appropriate temperature
between 20 and 35.degree. C. To the cooled emulsion, about 0.35
parts by weight of concentrated sulfuric acid was added, bringing
the pH of the emulsion to less than 2. The condensation proceeded
until the viscosity of the polymer was about 1,500,000 to 1,600,000
cps.
[0037] Once the condensation was completed, the emulsion was
neutralized with about 1.2 parts of 85% aqueous triethanolamine. A
biocide (Kathon II) was added (0.1% by weight). Optionally, an
antifoam agent may be added to control foaming during the
operation. If necessary, the completed emulsion is adjusted with
water to control the solids content. The emulsion is then filtered
into a final container.
1TABLE 1 Physical Properties Batch 1 Batch 2 Batch 3 Batch 4 Comp.
1 Comp. 2 Gradient - Dilute % 1.05 1.05 1.44 1.13 -- -- Gradient -
Straight % 4 0.4 2.83 3.51 .78 .83 Polymer Visc. (cps) 1641000
1639000 1620000 1550000 1790000 1700000 % Cyclic Siloxanes 0.34
0.31 0.30 0.35 0.98 2.47 Particle Size D50 (microns) 0.36 0.41 0.42
0.42 0.48 0.35 Particle Size D90 (microns) 0.70 0.77 0.80 0.80 0.93
0.71 Emulsion Visc. (cps) 30 30 40 40 -- 120 % Solids 50.6 50.5
50.5 50.4 -- 50.5 pH 7.62 7.35 7.14 7.16 -- -- Comparative Example
1 - existing technology of prior art using acid; Comparative
Example 2 - competitive emulsion
[0038]
2TABLE 2 Polymer Viscosity vs. Time during Condensation Batch 1
Batch 2 Batch 3 Batch 4 Viscosity Viscosity Viscosity Viscosity
Time (Hours) (cps) (cps) (cps) (cps) 1 692 1,416 889 -- 2 2,045
4,876 -- 9,751 3 7,471 26,895 33,737 -- 4 35,545 83,044 -- 103,000
5 95,941 189,260 -- 117,803 6 227,663 455,488 255,837 251,648 7
511,964 651,139 710,000 718,000 8 780,109 1,130,843 1,140,000
1,110,000 9 1,228,357 1,639,644 1,620,000 1,550,000 10 1,640,657 --
-- --
[0039]
3TABLE 3 Cyclic Siloxane Levels at Various Condensation
Temperatures after about 11 hours Temperature .degree. C. % Cyclic
Siloxane 6 0.11 18 0.25 25 0.33 30 0.51 35 0.58 40 0.79 45 1.05 53
1.69
[0040]
4TABLE 4 % Cyclic Siloxane and Viscosity vs. Condensation Temp.
& Time Temp. .degree. C. Time (hours) % Cyclic Siloxane
Viscosity (cps) 6 11.5 0.11 87,605 6 20.7 0.15 1,727,459 18 10.9
0.22 -- 18 16.9 0.27 2,830,000 25 7 0.2 -- 25 9.5 0.26 817,856 30
7.6 0.38 -- 30 12 0.54 1,118,000 35 8.9 0.47 -- 35 12.4 0.58
801,000 40 6.5 0.54 -- 40 11.3 0.79 458,471 45 13.5 1.05
334,220
* * * * *