U.S. patent application number 12/794952 was filed with the patent office on 2011-06-30 for high internal phase emulsion comprising photoinitiator.
Invention is credited to Thomas Allen Desmarais, Steven Ray Merrigan.
Application Number | 20110160689 12/794952 |
Document ID | / |
Family ID | 44187861 |
Filed Date | 2011-06-30 |
United States Patent
Application |
20110160689 |
Kind Code |
A1 |
Merrigan; Steven Ray ; et
al. |
June 30, 2011 |
HIGH INTERNAL PHASE EMULSION COMPRISING PHOTOINITIATOR
Abstract
The present invention relates to a High Internal Phase Emulsion
(HIPE) and HIPE foams produced therefrom comprising two or more
layers and having a photoinitiator.
Inventors: |
Merrigan; Steven Ray; (West
Chester, OH) ; Desmarais; Thomas Allen; (Cincinnati,
OH) |
Family ID: |
44187861 |
Appl. No.: |
12/794952 |
Filed: |
June 7, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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61290947 |
Dec 30, 2009 |
|
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Current U.S.
Class: |
604/378 ;
521/50.5; 522/12; 522/28; 522/30; 522/78; 522/79; 522/84;
522/85 |
Current CPC
Class: |
C08J 2201/028 20130101;
B29C 41/28 20130101; B29K 2105/04 20130101; B29C 2948/9298
20190201; B29C 33/68 20130101; B29C 48/269 20190201; B29C 48/355
20190201; C08F 120/10 20130101; B29C 67/202 20130101; B29C 48/08
20190201; B29C 44/60 20130101; B29C 44/28 20130101; C08F 2/50
20130101 |
Class at
Publication: |
604/378 ; 522/84;
522/85; 522/78; 522/79; 522/30; 522/12; 522/28; 521/50.5 |
International
Class: |
A61F 13/53 20060101
A61F013/53; C08F 2/46 20060101 C08F002/46; C08F 2/50 20060101
C08F002/50; C08K 5/00 20060101 C08K005/00; C08K 5/10 20060101
C08K005/10 |
Claims
1. A High Internal Phase Emulsion comprising: a) a first layer
having 1) an oil phase including i) monomer; ii) cross-linking
agent; iii) emulsifier; 2) aqueous phase; 3) photoinitiator; b) a
second layer having 1) an oil phase including i) monomer; ii)
cross-linking agent; iii) emulsifier; 2) aqueous phase; 3)
photoinitiator.
2. The High Internal Phase Emulsion of claim 1, wherein monomer
from the first or second layer is at least one of alkyl acrylate or
alkyl methacrylate.
3. The High Internal Phase Emulsion of claim 2, wherein the monomer
from the first or second layer is at least one of ethylhexyl
acrylate, butyl acrylate, hexyl acrylate, octyl acrylate, nonyl
acrylate, decyl acrylate, isodecyl acrylate, tetradecyl acrylate,
benzyl acrylate, nonyl phenyl acrylate, hexyl methacrylate,
2-ethylhexyl methacrylate, octyl methacrylate, nonyl methacrylate,
decyl methacrylate, isodecyl methacrylate, dodecyl methacrylate,
tetradecyl methacrylate, or octadecyl methacrylate.
4. The High Internal Phase Emulsion of claim 1, wherein emulsifier
from the first or second layer is at least one of sorbitan
monoesters of branched C.sub.16-C.sub.24 fatty acids; linear
unsaturated C.sub.16-C.sub.22 fatty acids; linear saturated
C.sub.12-C.sub.14 fatty acids, polyglycerol monoesters of -branched
C.sub.16-C.sub.24 fatty acids, linear unsaturated C.sub.16-C.sub.22
fatty acids, linear saturated C.sub.12-C.sub.14 fatty acids,
diglycerol monoaliphatic ethers of -branched C.sub.16-C.sub.24
alcohols, linear unsaturated C.sub.16-C.sub.22 alcohols, or linear
saturated C.sub.12-C.sub.14 alcohols.
5. The High Internal Phase Emulsion of claim 4, wherein emulsifier
from the first or second layer is at least one of sorbitan
monooleate, sorbitan monomyristate, sorbitan monoesters, sorbitan
monolaurate diglycerol monooleate, polyglycerol monoisostearate,
polyglycerol monomyristate, diglycerol monooleate, diglycerol
monomyristate, diglycerol monoisostearate, diglycerol monoesters,
or polyglycerol succinate.
6. The High Internal Phase Emulsion of claim 1, wherein the first
or second layer comprises coemulsifier that is at least one of
phosphatidyl choline, aliphatic betaines, C.sub.12-C.sub.22
dialiphatic quaternary ammonium salts, C.sub.1-C.sub.4 dialiphatic
quaternary ammonium salts, C.sub.12-C.sub.22
dialkoyl(alkenoyl)-2-hydroxyethyl, C.sub.1-C.sub.4 dialiphatic
quaternary ammonium salts, C.sub.12-C.sub.22 dialiphatic
imidazolinium quaternary ammonium salts, C.sub.1-C.sub.4
dialiphatic imidazolinium quaternary ammonium salts,
C.sub.12-C.sub.22 monoaliphatic benzyl quaternary ammonium salts,
C.sub.12-C.sub.22 dialkoyl(alkenoyl)-2-aminoethyl, C.sub.1-C.sub.4
monoaliphatic benzyl quaternary ammonium salts, or C.sub.1-C.sub.4
monohydroxyaliphatic quaternary ammonium salts.
7. The High Internal Phase Emulsion of claim 1, wherein the first
or second layer comprises between about 0.05% and about 10%
photoinitiator by weight of the oil phase.
8. The High Internal Phase Emulsion of claim 1, wherein the first
or second layer comprises photoinitiator that absorbs UV light at
wavelengths of about 200 nm to about 800 nm.
9. The High Internal Phase Emulsion of claim 1, wherein the first
or second layer comprises photoinitiator that is at least one of
benzyl ketals, .alpha.-hydroxyalkyl phenones, .alpha.-amino alkyl
phenones, or acylphospine oxides.
10. The High Internal Phase Emulsion of claim 9, wherein the first
or second layer comprises photoinitiator that is at least one of
2,4,6-[trimethylbenzoyldiphosphine]oxide in combination with
2-hydroxy-2-methyl-1-phenylpropan-1-one; benzyl dimethyl ketal;
.alpha.-,.alpha.-dimethoxy-.alpha.-hydroxy acetophenone;
2-methyl-1-[4-(methyl thio)phenyl]-2-morpholino-propan-1-one;
1-hydroxycyclohexyl-phenyl ketone;
bis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide;
diethoxyacetophenone;
4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-methylpropyl)ketone; or
Oligo[2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone].
11. The High Internal Phase Emulsion of claim 1, wherein the first
or second layer comprises electrolyte that is at least one of
chloride salts of alkaline earth metals, chloride salts of alkali
earth metals, sulfate salts of alkaline earth metals, or sulfate
salts of alkali earth metals.
12. The High Internal Phase Emulsion of claim 1, wherein the first
and second layer each have an average cell size and the average
cell size of the first layer is greater than the average cell size
of the second layer.
13. The High Internal Phase Emulsion of claim 1, wherein the first
layer allows UV light to reach the second layer.
14. The High Internal Phase Emulsion of claim 13, wherein UV light
wavelength is in the range from about 200 nm to about 800 nm.
15. The High Internal Phase Emulsion of claim 1, wherein the
average thickness of each layer of the High Internal Phase Emulsion
is from about 1 mm to about 4 mm.
16. A High Internal Phase Emulsion foam formed by polymerizing a
High Internal Phase Emulsion comprising: a) a first layer having 1)
an oil phase including i) monomer; ii) cross-linking agent; iii)
emulsifier; 2) aqueous phase; 3) photoinitiator; b) a second layer
having 1) an oil phase including i) monomer; ii) cross-linking
agent; iii) emulsifier; 2) aqueous phase; 3) photoinitiator.
17. The High Internal Phase Emulsion foam of claim 16, wherein the
first layer and second layer have pores, and the average pore size
of the first layer is greater than the average pore size of the
second layer.
18. The High Internal Phase Emulsion foam of claim 16, wherein the
Tg is less than about 40.degree. C.
19. An absorbent article comprising the High Internal Phase
Emulsion foam of claim 16.
20. The absorbent article of claim 19, wherein the absorbent
article is at least one of a feminine hygiene article, disposable
diaper, incontinence article, adult diaper, homecare article,
beauty care article, or skin care article.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 61/290,947 filed on 30 Dec. 2009, the substance of
which is incorporated herein by reference.
FIELD OF THE INVENTION
[0002] This application relates to a High Internal Phase Emulsion
(HIPE) comprising photoinitiator.
BACKGROUND OF THE INVENTION
[0003] An emulsion is a dispersion of one liquid in another liquid
and generally is in the form of a water-in-oil mixture having an
aqueous or water phase dispersed within a substantially immiscible
continuous oil phase. Water-in-oil (or oil in water) emulsions
having a high ratio of dispersed aqueous phase to continuous oil
phase are known in the art as High Internal Phase Emulsions, also
referred to as "HIPE" or HIPEs. At relatively high dispersed
aqueous phase to continuous oil phase ratios the continuous oil
phase becomes essentially a thin film separating and coating the
droplet-like structures of the internal, dispersed aqueous phase.
The continuous oil phase of a water-in-oil HIPE generally comprises
one or more polymerizable monomers. These monomers can be
polymerized, forming a cellular structure, for example a foam,
having a cell size distribution defined by the size distribution of
the dispersed, aqueous phase droplets.
[0004] Polymerization of monomers in a HIPE usually involves the
application of thermal energy or heat. The HIPE can be subjected to
heat in an enclosed area, such as an oven; and the heat source can
be varied, such as steam or direct application of heat through one
or more heating elements. However there are several significant
drawbacks to using heat alone for curing HIPEs. A HIPE usually has
a large surface area and the unequal application of heat to such a
large surface can cause defects in the resulting HIPE foam, such as
dimpling, shrinkage, and edge curls. Further, whatever form the
heat application takes such application is usually quite expensive
in energy and monetary costs, as the heat being applied to a HIPE
usually has a temperature ranging from around 50.degree. C. to
150.degree. C. An additional drawback to the use of heat alone to
polymerize HIPEs is that an enclosed area, such as an oven, is
required to keep the heat from escaping into the environment and
reducing the amount of heat applied to the HIPE. This need for an
oven further increases the cost of producing HIPE foams and takes
up a large amount of physical space on the HIPE foam production
line.
[0005] Attempts in the past to move away from the use of heat to
polymerize HIPEs have used ultraviolet (UV) light to polymerize
HIPEs into foams. However, these methods have had problems, such as
a reliance on the use of polyelectrolytes in the HIPE which can
lead to undesirable properties in the resulting HIPE foam, as
polyectrolytes are trapped in the polymer backbone, whether through
entanglements; polymerized in, via chain transfer reactions; or
simply absorbed onto the surface of the HIPE foam struts. The
polyelectrolytes thus incorporated into the HIPE foam change the
physical properties of the foam, typically decreasing the strength
and increasing friability of the resulting HIPE foam. Further,
these methods have not been usable on thicker HIPEs and
preferentially polymerize the monomers on the surface of the HIPE
exposed to the source of the UV light, leaving the bulk of the HIPE
unpolymerized. Accordingly, there is a need for a method of HIPE
polymerization using UV light that overcomes the problems in the
prior art.
SUMMARY OF THE INVENTION
[0006] A High Internal Phase Emulsion is provided that comprises a
first layer having an oil phase which includes monomer,
cross-linking agent, emulsifier; photoinitiator; and an aqueous
phase. The High Internal Phase Emulsion also includes a second
layer having an oil phase which includes monomer, cross-linking
agent, emulsifier; photoinitiator; and an aqueous phase.
[0007] A High Internal Phase Emulsion foam formed by polymerizing a
High Internal Phase Emulsion is provided that comprises a first
layer having an oil phase which includes monomer, cross-linking
agent, emulsifier; photoinitiator; and an aqueous phase. The High
Internal Phase Emulsion also includes a second layer having an oil
phase which includes monomer, cross-linking agent, emulsifier;
photoinitiator; and an aqueous phase.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a process flow diagram of the present
invention.
[0009] FIG. 2 is a process flow diagram of the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0010] The present invention relates to a high internal phase
emulsion (HIPE) comprising a photoinitiator and HIPE foams produced
therefrom. HIPEs of the present invention comprising a continuous
oil phase containing monomers and an aqueous phase are produced
using a continuous process, for example by having a HIPE deposited
on a belt, such as an endless belt. While on the belt the HIPE may
be moved to an ultraviolet (UV) light zone, where the monomers are
polymerized to form a HIPE foam. The HIPE foams of the present
invention are useful for the absorption of liquid materials and are
comprised of two or more open celled polymeric HIPE foam
layers.
[0011] A High Internal Phase Emulsion (HIPE) comprises two phases.
One phase is a continuous oil phase comprising monomers that are
polymerized to form a HIPE foam and an emulsifier to help stabilize
the HIPE. The oil phase may also include one or more
photoinitiators. The monomer component, which is capable of rapid
UV light polymerization, may be present in an amount of from about
80% to about 99%, and in certain embodiments from about 85% to
about 95% by weight of the oil phase. The emulsifier component,
which is soluble in the oil phase and suitable for forming a stable
water-in-oil emulsion may be present in the oil phase in an amount
of from about 1% to about 20% by weight of the oil phase. The
emulsion may be formed at an emulsification temperature of from
about 20.degree. C. to about 130.degree. C. and in certain
embodiments from about 20.degree. C. to about 100.degree. C.
[0012] In general, the monomers will include from about 20% to
about 97% by weight of the oil phase at least one substantially
water-insoluble monofunctional alkyl acrylate or alkyl
methacrylate. For example, monomers of this type may include
C.sub.4-C.sub.18 alkyl acrylates and C.sub.2-C.sub.18
methacrylates, such as ethylhexyl acrylate, butyl acrylate, hexyl
acrylate, octyl acrylate, nonyl acrylate, decyl acrylate, isodecyl
acrylate, tetradecyl acrylate, benzyl acrylate, nonyl phenyl
acrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, octyl
methacrylate, nonyl methacrylate, decyl methacrylate, isodecyl
methacrylate, dodecyl methacrylate, tetradecyl methacrylate, and
octadecyl methacrylate. In certain embodiments, blends of these
monomers can provide the desired glass transition temperature (Tg)
of the resulting HIPE foams.
[0013] The oil phase may also comprise from about 2% to about 40%,
and in certain embodiments from about 10% to about 30%, by weight
of the oil phase, a substantially water-insoluble, polyfunctional
crosslinking alkyl acrylate or methacrylate. This crosslinking
comonomer, or crosslinker, is added to confer strength and
resilience to the resulting HIPE foam. Examples of crosslinking
monomers of this type comprise monomers containing two or more
activated acrylate, methacrylate groups, or combinations thereof.
Nonlimiting examples of this group include
1,6-hexanedioldiacrylate, 1,4-butanedioldimethacrylate,
trimethylolpropane triacrylate, trimethylolpropane trimethacrylate,
1,12-dodecyldimethacrylate, 1,14-tetradecanedioldimethacrylate,
ethylene glycol dimethacrylate, neopentyl glycol diacrylate
(2,2-dimethylpropanediol diacrylate), hexanediol acrylate
methacrylate, glucose pentaacrylate, sorbitan pentaacrylate, and
the like. Other examples of crosslinkers contain a mixture of
acrylate and methacrylate moieties, such as ethylene glycol
acrylate-methacrylate and neopentyl glycol acrylate-methacrylate.
The ratio of methacrylate:acrylate group in the mixed crosslinker
may be varied from 50:50 to any other ratio as needed.
[0014] Any third substantially water-insoluble comonomer may be
added to the oil phase in weight percentages of from about 0% to
about 15% by weight of the oil phase, in certain embodiments from
about 2% to about 8%, to modify properties of the HIPE foams. In
certain cases, "toughening" monomers may be desired which impart
toughness to the resulting HIPE foam. These include monomers such
as styrene, vinyl chloride, vinylidene chloride, isoprene, and
chloroprene. Without being bound by theory, it is believed that
such monomers aid in stabilizing the HIPE during polymerization
(also known as "curing") to provide a more homogeneous and better
formed HIPE foam which results in better toughness, tensile
strength, abrasion resistance, and the like. Monomers may also be
added to confer flame retardancy as disclosed in U.S. Pat. No.
6,160,028 (Dyer) issued Dec. 12, 2000. Monomers may be added to
confer color, for example vinyl ferrocene, fluorescent properties,
radiation resistance, opacity to radiation, for example lead
tetraacrylate, to disperse charge, to reflect incident infrared
light, to absorb radio waves, to form a wettable surface on the
HIPE foam struts, or for any other desired property in a HIPE foam.
In some cases, these additional monomers may slow the overall
process of conversion of HIPE to HIPE foam, the tradeoff being
necessary if the desired property is to be conferred. Thus, such
monomers can be used to slow down the polymerization rate of a
HIPE. Examples of monomers of this type comprise styrene and vinyl
chloride.
[0015] The oil phase may further contain an emulsifier used for
stabilizing the HIPE. Emulsifiers used in a HIPE can include: (a)
sorbitan monoesters of branched C.sub.16-C.sub.24 fatty acids;
linear unsaturated C.sub.16-C.sub.22 fatty acids; and linear
saturated C.sub.12-C.sub.14 fatty acids, such as sorbitan
monooleate, sorbitan monomyristate, and sorbitan monoesters,
sorbitan monolaurate diglycerol monooleate (DGMO), polyglycerol
monoisostearate (PGMIS), and polyglycerol monomyristate (PGMM); (b)
polyglycerol monoesters of -branched C.sub.16-C.sub.24 fatty acids,
linear unsaturated C.sub.16-C.sub.22 fatty acids, or linear
saturated C.sub.12-C.sub.14 fatty acids, such as diglycerol
monooleate (for example diglycerol monoesters of C18:1 fatty
acids), diglycerol monomyristate, diglycerol monoisostearate, and
diglycerol monoesters; (c) diglycerol monoaliphatic ethers of
-branched C.sub.16-C.sub.24 alcohols, linear unsaturated
C.sub.16-C.sub.22 alcohols, and linear saturated C.sub.12-C.sub.14
alcohols, and mixtures of these emulsifiers. See U.S. Pat. No.
5,287,207 (Dyer et al.), issued Feb. 7, 1995 and U.S. Pat. No.
5,500,451 (Goldman et al.) issued Mar. 19, 1996. Another emulsifier
that may be used is polyglycerol succinate (PGS), which is formed
from an alkyl succinate, glycerol, and triglycerol.
[0016] Such emulsifiers, and combinations thereof, may be added to
the oil phase so that they comprise between about 1% and about 20%,
in certain embodiments from about 2% to about 15%, and in certain
other embodiments from about 3% to about 12% by weight of the oil
phase In certain embodiments, coemulsifiers may also be used to
provide additional control of cell size, cell size distribution,
and emulsion stability, particularly at higher temperatures, for
example greater than about 65.degree. C. Examples of coemulsifiers
include phosphatidyl cholines and phosphatidyl choline-containing
compositions, aliphatic betaines, long chain C.sub.12-C.sub.22
dialiphatic quaternary ammonium salts, short chain C.sub.1-C.sub.4
dialiphatic quaternary ammonium salts, long chain C.sub.12-C.sub.22
dialkoyl(alkenoyl)-2-hydroxyethyl, short chain C.sub.1-C.sub.4
dialiphatic quaternary ammonium salts, long chain C.sub.12-C.sub.22
dialiphatic imidazolinium quaternary ammonium salts, short chain
C.sub.1-C.sub.4 dialiphatic imidazolinium quaternary ammonium
salts, long chain C.sub.12-C.sub.22 monoaliphatic benzyl quaternary
ammonium salts, long chain C.sub.12-C.sub.22
dialkoyl(alkenoyl)-2-aminoethyl, short chain C.sub.1-C.sub.4
monoaliphatic benzyl quaternary ammonium salts, short chain
C.sub.1-C.sub.4 monohydroxyaliphatic quaternary ammonium salts. In
certain embodiments, ditallow dimethyl ammonium methyl sulfate
(DTDMAMS) may be used as a coemulsifier.
[0017] Photoinitiators may comprise between about 0.05% and about
10%, and in certain embodiments between about 0.2% and about 10% by
weight of the oil phase. Lower amounts of photoinitiator allow
light to better penetrate the HIPE foam, which can provide for
polymerization deeper into the HIPE foam. However, if
polymerization is done in an oxygen-containing environment, there
should be enough photoinitiator to initiate the polymerization and
overcome oxygen inhibition. Photoinitiators can respond rapidly and
efficiently to a light source with the production of radicals,
cations, and other species that are capable of initiating a
polymerization reaction. The photoinitiators used in the present
invention may absorb UV light at wavelengths of about 200
nanometers (nm) to about 800 nm, in certain embodiments about 250
nm to about 450 nm. If the photoinitiator is in the oil phase,
suitable types of oil-soluble photoinitiators include benzyl
ketals, .alpha.-hydroxyalkyl phenones, .alpha.-amino alkyl
phenones, and acylphospine oxides. Examples of photoinitiators
include 2,4,6-[trimethylbenzoyldiphosphine]oxide in combination
with 2-hydroxy-2-methyl-1-phenylpropan-1-one (50:50 blend of the
two is sold by Ciba Speciality Chemicals, Ludwigshafen, Germany as
DAROCUR.RTM. 4265); benzyl dimethyl ketal (sold by Ciba Geigy as
IRGACURE 651); .alpha.-,.alpha.-dimethoxy-.alpha.-hydroxy
acetophenone (sold by Ciba Speciality Chemicals as DAROCUR.RTM.
1173); 2-methyl-1-[4-(methyl thio)phenyl]-2-morpholino-propan-1-one
(sold by Ciba Speciality Chemicals as IRGACURE.RTM. 907);
1-hydroxycyclohexyl-phenyl ketone (sold by Ciba Speciality
Chemicals as IRGACURE.RTM. 184);
bis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide (sold by Ciba
Speciality Chemicals as IRGACURE 819); diethoxyacetophenone, and
4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-methylpropyl)ketone (sold by
Ciba Speciality Chemicals as IRGACURE.RTM. 2959); and
Oligo[2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone]
(sold by Lamberti spa, Gallarate, Italy as ESACURE.RTM. KIP EM.
[0018] The dispersed aqueous phase of a HIPE comprises water, and
may also comprise one or more components, such as initiator,
photoinitiator, or electrolyte, wherein in certain embodiments, the
one or more components are at least partially water soluble.
[0019] One component of the aqueous phase may be a water-soluble
electrolyte. The water phase may contain from about 0.2% to about
40%, in certain embodiments from about 2% to about 20%, by weight
of the aqueous phase of a water-soluble electrolyte. The
electrolyte minimizes the tendency of monomers, comonomers, and
crosslinkers that are primarily oil soluble to also dissolve in the
aqueous phase. Examples of electrolytes include chlorides or
sulfates of alkaline earth metals such as calcium or magnesium and
chlorides or sulfates of alkali earth metals such as sodium. Such
electrolyte can include a buffering agent for the control of pH
during the polymerization, including such inorganic counterions as
phosphate, borate, and carbonate, and mixtures thereof. Water
soluble monomers may also be used in the aqueous phase, examples
being acrylic acid and vinyl acetate.
[0020] Another component that may be present in the aqueous phase
is a water-soluble free-radical initiator. The initiator can be
present at up to about 20 mole percent based on the total moles of
polymerizable monomers present in the oil phase. In certain
embodiments, the initiator is present in an amount of from about
0.001 to about 10 mole percent based on the total moles of
polymerizable monomers in the oil phase. Suitable initiators
include ammonium persulfate, sodium persulfate, potassium
persulfate,
2,2'-azobis(N,N'-dimethyleneisobutyramidine)dihydrochloride, and
other suitable azo initiators. In certain embodiments, to reduce
the potential for premature polymerization which may clog the
emulsification system, addition of the initiator to the monomer
phase may be just after or near the end of emulsification.
[0021] Photoinitiators present in the aqueous phase may be at least
partially water soluble and may comprise between about 0.05% and
about 10%, and in certain embodiments between about 0.2% and about
10% by weight of the oil phase. Lower amounts of photoinitiator
allow light to better penetrate the HIPE foam, which can provide
for polymerization deeper into the HIPE foam. However, if
polymerization is done in an oxygen-containing environment, there
should be enough photoinitiator to initiate the polymerization and
overcome oxygen inhibition. Photoinitiators can respond rapidly and
efficiently to a light source with the production of radicals,
cations, and other species that are capable of initiating a
polymerization reaction. The photoinitiators used in the present
invention may absorb UV light at wavelengths of from about 200
nanometers (nm) to about 800 nm, in certain embodiments from about
200 nm to about 350 nm, and in certain embodiments from about 350
nm to about 450 nm. If the photoinitiator is in the aqueous phase,
suitable types of water-soluble photoinitiators include
benzophenones, benzils, and thioxanthones. Examples of
photoinitiators include
2,2'-Azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride;
2,2'-Azobis[2-(2-imidazolin-2-yl)propane]disulfate dehydrate;
2,2'-Azobis(1-imino-1-pyrrolidino-2-ethylpropane)dihydrochloride;
2,2'-Azobis[2-methyl-N-(2-hydroxyethyl)propionamide];
2,2'-Azobis(2-methylpropionamidine)dihydrochloride;
2,2'-dicarboxymethoxydibenzalacetone,
4,4'-dicarboxymethoxydibenzalacetone,
4,4'-dicarboxymethoxydibenzalcyclohexanone,4-dimethylamino-4'-carboxymeth-
oxydibenzalacetone; and 4,4'-disulphoxymethoxydibenzalacetone.
Other suitable photoinitiators that can be used in the present
invention are listed in U.S. Pat. No. 4,824,765 (Sperry et al.)
issued Apr. 25, 1989.
[0022] In addition to the previously described components other
components may be included in either the aqueous or oil phase of a
HIPE. Examples include antioxidants, for example hindered
phenolics, hindered amine light stabilizers; plasticizers, for
example dioctyl phthalate, dinonyl sebacate; flame retardants, for
example halogenated hydrocarbons, phosphates, borates, inorganic
salts such as antimony trioxide or ammonium phosphate or magnesium
hydroxide; dyes and pigments; fluorescers; filler particles, for
example starch, titanium dioxide, carbon black, or calcium
carbonate; fibers; chain transfer agents; odor absorbers, for
example activated carbon particulates; dissolved polymers;
dissolved oligomers; and the like.
[0023] HIPE foam is produced from the polymerization of the
monomers comprising the continuous oil phase of a HIPE. In certain
embodiments, HIPE foams may have one or more layers, and may be
either homogeneous or heterogeneous polymeric open-celled foams.
Homogeneity and heterogeneity relate to distinct layers within the
same HIPE foam, which are similar in the case of homogeneous HIPE
foams or which differ in the case of heterogeneous HIPE foams. A
heterogeneous HIPE foam may contain at least two distinct layers
that differ with regard to their chemical composition, physical
properties, or both; for example layers may differ with regard to
one or more of foam density, polymer composition, specific surface
area, or pore size (also referred to as cell size). For example,
for a HIPE foam if the difference relates to pore size, the average
pore size in each layer may differ by at least about 20%, in
certain embodiments by at least about 35%, and in still other
embodiments by at least about 50%. In another example, if the
differences in the layers of a HIPE foam relate to density, the
densities of the layers may differ by at least about 20%, in
certain embodiments by at least about 35%, and in still other
embodiments by at least about 50%. For instance, if one layer of a
HIPE foam has a density of 0.020 g/cc, another layer may have a
density of at least about 0.024 g/cc or less than about 0.016 g/cc,
in certain embodiments at least about 0.027 g/cc or less than about
0.013 g/cc, and in still other embodiments at least about 0.030
g/cc or less than about 0.010 g/cc. If the differences between the
layers are related to the chemical composition of the HIPE or HIPE
foam, the differences may reflect a relative amount difference in
at least one monomer component, for example by at least about 20%,
in certain embodiments by at least about 35%, and in still further
embodiments by at least about 50%. For instance, if one layer of a
HIPE or HIPE foam is composed of about 10% styrene in its
formulation, another layer of the HIPE or HIPE foam should be
composed of at least about 12%, and in certain embodiments of at
least about 15%.
[0024] A HIPE foam having separate layers formed from differing
HIPEs, as explained in more detail below, provides a HIPE foam with
a range of desired performance characteristics. For example, a HIPE
foam comprising a first and second foam layer, wherein the first
foam layer has a relatively larger pore or cell size, than the
second layer, when used in an absorbent article may more quickly
absorb incoming fluids than the second layer. By way of example
when used in an absorbent articled the first foam layer may be
layered over the second foam layer having relatively smaller pore
sizes, as compared to the first foam layer, which exert more
capillary pressure and drain the acquired fluid from the first foam
layer, restoring the first foam layer's ability to acquire more
fluid. HIPE foam pore sizes may range from 1 to 200 .mu.m and in
certain embodiments may be less than 100 .mu.m.
[0025] HIPE foams of the present invention having two major
parallel surfaces may be from 0.05 to 10 mm thick and in certain
embodiments 2 mm to 8 mm thick. The desired thickness of a HIPE
will depend on the materials used to form the HIPE, the speed at
which a HIPE is deposited on a belt, the intended use of the
resulting HIPE foam, the nature of the UV light used for
polymerization, photoinitiator type, and amount of photoinitiator
used. For example, decreasing the amount of photoinitiator can
decrease the light absorption of the emulsion and may increase
light penetration.
[0026] HIPEs having more than one layer can be produced that allow
the UV light to polymerize the whole HIPE to a HIPE foam. For
example, a HIPE foam of the present invention may comprise a first
layer and a second layer, wherein the first layer is the layer of
HIPE foam closest to the UV light source and the second layer the
farthest. The first layer can be made in such a manner as to allow
the UV light to both polymerize it and pass through to polymerize
the second layer. For example, the first layer can be a HIPE having
larger aqueous droplets in the aqueous phase, which after
polymerization will form the pores or cells of HIPE foam. The
larger aqueous droplet size will have less scattering and allow
more UV light to pass through the first layer and be available to
polymerize the monomers in the second HIPE layer, which has a
smaller average aqueous droplet size. The desired properties in a
HIPE layer, such as being transparent to the UV light wavelength
absorbed by the photoinitiator in the emulsion or larger aqueous
droplet size can be produced by modifying the chemical composition
of the HIPE layer or modifying the method of making the HIPE layer.
In addition, in certain embodiments, the concentration of
photoinitiator can be greater in the bottom layer as compared to
the top layer, allowing for similar levels of polymerization in
both layers, even with reduced UV light in the lower layer. In
another embodiment, using different photoinitiators with different
UV light absorbencies in the top layer as compared to the bottom
layer may also be used to increase the depth of penetration of the
UV light. In still another embodiment, a HIPE can be exposed to UV
light on both its bottom and top surfaces, which may be
accomplished by using a belt, film or both that is mostly
transparent to UV light and move the HIPE over a UV light source
while also exposing the top of the HIPE to a UV light source. In
another example, in the oil phase the type and amounts of monomer
can be adjusted or during the formation of the HIPE the shear rate
can be increased during the emulsion making process or the amount
of time the HIPE is in the emulsion making step can be increased.
This is contrasted with what is in the prior art wherein layered
foams may be made by polymerizing a sequence of layers, with each
new emulsion layer being placed on the previously polymerized
layers. This contrasts with the present invention wherein the
layers are already present in the HIPE before the HIPE is exposed
to UV light to form a HIPE foam.
[0027] The HIPE foams of the present invention are relatively
open-celled. This refers to the individual cells or pores of the
HIPE foam being in substantially unobstructed communication with
adjoining cells. The cells in such substantially open-celled HIPE
foam structures have intercellular openings or windows that are
large enough to permit ready fluid transfer from one cell to
another within the HIPE foam structure. For purpose of the present
invention, a HIPE foam is considered "open-celled" if at least
about 80% of the cells in the HIPE foam that are at least 1 .mu.m
in size are in fluid communication with at least one adjoining
cell.
[0028] In addition to being open-celled, in certain embodiments
HIPE foams are sufficiently hydrophilic to permit the HIPE foam to
absorb aqueous fluids, for example the internal surfaces of a HIPE
foam may be rendered hydrophilic by residual hydrophilizing
surfactants or salts left in the HIPE foam following
polymerization, by selected post-polymerization HIPE foam treatment
procedures (as described hereafter), or combinations of both.
[0029] In certain embodiments, for example when used in certain
absorbent articles, the HIPE foam may be flexible and exhibit an
appropriate glass transition temperature (Tg). The Tg represents
the midpoint of the transition between the glassy and rubbery
states of the polymer. In general, HIPE foams that have a higher Tg
than the temperature of use can be very strong but will also be
very rigid and potentially prone to fracture. In certain
embodiments, regions of the HIPE foams of the current invention
which exhibit either a relatively high Tg or excessive brittleness
will be discontinuous. Since these discontinuous regions will also
generally exhibit high strength, they can be prepared at lower
densities without compromising the overall strength of the HIPE
foam.
[0030] HIPE foams intended for applications requiring flexibility
should contain at least one continuous region having a Tg as low as
possible, so long as the overall HIPE foam has acceptable strength
at in-use temperatures. In certain embodiments, the Tg of this
region will be less than about 40.degree. C. for foams used at
about ambient temperature conditions, in certain other embodiments,
less than about 30.degree. C. For HIPE foams used in applications
wherein the use temperature is higher or lower than ambient, the Tg
of the continuous region may be no more that 10.degree. C. greater
than the use temperature, in certain embodiments the same as use
temperature, and in further embodiments about 10.degree. C. less
than use temperature wherein flexibility is desired. Accordingly,
monomers are selected as much as possible that provide
corresponding polymers having lower Tg's.
[0031] The HIPE foams of the present invention may be used as
absorbent core materials in absorbent articles, such as feminine
hygiene articles, for example pads, pantiliners, and tampons;
disposable diapers; incontinence articles, for example pads, adult
diapers, homecare articles, for example wipes, pads, towels; and
beauty care articles, for example pads, wipes, and skin care
articles, such as used for pore cleaning.
[0032] To produce a HIPE using the above, and shown in FIG. 1, an
aqueous phase 10 and an oil phase 20 are combined in a ratio
between about 8:1 and 140:1. In certain embodiments, the aqueous
phase to oil phase ratio is between about 10:1 and about 75:1, and
in certain other embodiments the aqueous phase to oil phase ratio
is between about 13:1 and about 65:1. This is termed the
"water-to-oil" or W:O ratio and can be used to determine the
density of the resulting HIPE foam. As discussed, the oil phase may
contain one or more of monomers, comonomers, photoinitiators,
crosslinkers, and emulsifiers, as well as optional components. The
water phase will contain water and in certain embodiments one or
more components such as electrolytes.
[0033] In certain embodiments, photoinitiator combinations can be
used that have different absorption characteristics, so as one
photoinitiator is used up the polymerization continues throughout
the depth of the HIPE, allowing increased penetration of the UV
light providing a more complete polymerization. In certain
embodiments, photoinitiator can be added to the aqueous phase, oil
phase, or both and the exposure UV light wavelengths controlled to
selectively produce different concentrations of radicals at
different points throughout the polymerization process. For
example, without being bound by theory, an aqueous phase soluble
photoinitiator can be used to provide radicals that will migrate
from the aqueous phase to the oil phase to supply a steady, but
lower concentration of radicals to the oil phase (compared to the
amount of radicals produced using a photoinitiator in the oil
phase); resulting in a slower polymerization, but a stronger HIPE
foam by reducing the number of radicals produced early in
polymerization, leading to longer polymer chain lengths yielding
stronger polymer and enabling higher water-to-oil ratios.
[0034] The HIPE can be formed from the combined aqueous 10 and oil
20 phases by subjecting these combined phases to shear agitation in
a mixing chamber or mixing zone 30. The combined aqueous 10 and oil
20 phases are subjected to shear agitation produce a stable HIPE
having aqueous droplets of the desired size. The emulsion making
process produces a HIPE where the aqueous phase droplets are
dispersed to such an extent that the resulting HIPE foam will have
the desired structural characteristics. Emulsification of the
aqueous 10 and oil 20 phase combination in the mixing zone 30 may
involve the use of a mixing or agitation device such as an
impeller, by passing the combined aqueous and oil phases through a
series of static mixers at a rate necessary to impart the requisite
shear, or combinations of both. Once formed, the HIPE can then be
withdrawn or pumped from the mixing zone 30. One method for forming
HIPEs using a continuous process is described in U.S. Pat. No.
5,149,720 (DesMarais et al), issued Sep. 22, 1992 and U.S. Pat. No.
5,827,909 (DesMarais) issued on Oct. 27, 1998.
[0035] In certain embodiments, for a continuous process the HIPE
can be withdrawn or pumped from the mixing zone 30 and transported
to a UV light zone 50 by being deposited on to a belt 40 travelling
in a substantially horizontal direction. The HIPE may be deposited
on to the belt through one or more devices such as a die, sprayer,
or caster. As shown in FIG. 2, in the present invention two or more
distinct HIPEs can be produced, which after polymerization will
form two or more distinct layers in a HIPE foam, for example a
first HIPE and a second HIPE, wherein each HIPE may have an
individual composition (aqueous and oil phases) or individual
combinations of properties, for example pore dimensions, mechanical
properties, and the like, that differs from the other HIPEs. The
individual HIPEs can be formed from one or more individual oil
phases and one or more individual aqueous phases, and combinations
thereof. For example, individual HIPEs can be formed from a single
oil phase combined with 2 or more different aqueous phases, or as
shown in FIG. 2 a single aqueous phase 11 combined with 2 or more
individual oil phases 21, 22.
[0036] The individual aqueous 11 and oil phases 21, 22 enter
separate mixing zones 31 and 32 and then are deposited the same way
as individual HIPEs. For example, in a continuous process of the
present invention a first die 71 can deposit one HIPE layer on to a
belt 40 then the same die or a second die 72, as shown in FIG. 2,
could deposit a second HIPE on top of the first HIPE. In another
embodiment using the previously described continuous method a die
could deposit HIPEs adjacently on to a belt where the individual
HIPEs may or may not overlap each other, or any other means of
moving one or more HIPEs from a mixing zone to produce a HIPE
foam.
[0037] Examples of belts may include endless belts made of one or
more metals, a resin, or combinations thereof; or sheet materials
such as films that may be positioned on the belt and moving
therewith. The average thickness of the HIPE, as measured from the
surface of the HIPE that is in contact with the belt to the
opposing HIPE surface, can be adjusted by the movement speed of the
belt, the flow of HIPE deposited on the belt, or the configuration
of one or more devices used to deposit the HIPE on the belt.
[0038] The belt can be any thickness or shape suitable for
producing a HIPE foam. Further, the surface of the belt upon which
the HIPE will be deposited, can be substantially smooth or may
comprise depressions, protuberances, or combinations thereof. The
protuberances or depressions may be arranged in any formation or
order and can be used to provide patterns, designs, markings or the
like to HIPE foam. The belt may comprise one or more materials
suitable for the polymerization conditions (various properties such
as heat resistance, weatherability, surface energy, abrasion
resistance, recycling property, tensile strength and other
mechanical strengths) and may comprise at least one material from
the group including films, non-woven materials, woven materials,
and combinations thereof. Examples of films include, fluorine
resins such as polytetrafluoroethylene,
tetrafluoroethylene-perfluoroalkylvinyl ether copolymers,
tetrafluoroethylene-hexafluoropropylene copolymers, and
tetrafluoroethylene-ethylene copolymers; silicone resins such as
dimethyl polysiloxane and dimethylsiloxane-diphenyl siloxane
copolymers; heat-resistant resins such as polyimides, polyphenylene
sulfides, polysulfones, polyether sulfones, polyether imides,
polyether ether ketones, and para type aramid resins; thermoplastic
polyester resins such as polyethylene terephthalates, polybutylene
terephthalates, polyethylene naphthalates, polybutylene
naphthalates, and polycyclohexane terephthalates, thermoplastic
polyester type elastomer resins such as block copolymers (polyether
type) formed of PBT and polytetramethylene oxide glycol and block
copolymers (polyester type) formed of PBT and polycaprolactone may
be used. These materials may be used either singly or in mixed form
of two or more materials. Further, the belt may be a laminate
comprising two or more different materials or two or more materials
of the same composition, but which differ in one or more physical
characteristics, such as quality or thickness. In certain
embodiments the belt or a film positioned on the belt and moving
therewith may be transparent to UV light; allowing the UV light
from a UV light source positioned below the belt, film or both to
polymerize the monomers in a HIPE foam.
[0039] As shown in FIG. 2, a belt 40 moves the HIPE into a UV light
zone 50 where the monomers present in the HIPE are polymerized.
Without being bound by theory, it is believed that HIPE foam
formation comprises two overlapping processes. These are the
polymerization of the monomers and the formation of crosslinks
between active sites on adjacent polymer backbones. As used herein
the term "polymerize" as in to polymerize monomers to form a HIPE
foam encompass both polymerization of monomers and formation of
crosslinks between active sites on adjacent polymer backbones.
Crosslinking provides HIPE foams with strength and integrity that
is helpful to their further handling and use. In certain
embodiments, polymerization can be initiated prior to reaching the
UV light zone 50 by, for example, preparing the HIPE at a
temperature sufficient to begin polymerization. However, the HIPE
is polymerized beyond the point of shapability or moldability in
the UV light zone 50.
[0040] The present invention relates to using ultraviolet (UV)
light to polymerize monomers in the oil phase of a HIPE. An example
of a source of UV light is a UV lamp. There may be one or more
sources of UV light used to polymerize the HIPE monomers. The
sources may be the same or differ. For example, the sources may
differ in the wavelength of the UV light they produce or in the
amount of time a HIPE is exposed to the UV light source.
Photoinitiation of monomer polymerization may be started by
subjecting the HIPE foam containing unpolymerized monomers, and one
or more photoinitiators, to UV light. The UV light wavelength in
the range from about 20 to about 800 nm, and in certain embodiments
from about 200 nm to 450 nm, overlaps to at least some degree with
the UV light absorption band of the photoinitiator and is of
sufficient intensity and exposure duration to substantially
complete the polymerization of the unpolymerized monomers.
[0041] In certain embodiments, of the present invention can be
rapidly polymerized using UV light. After being exposed to UV light
HIPEs may be polymerized in less than 20 min, less than 10 minutes,
less than 5 minutes, less than 1 min, less than 30 seconds, or less
than 15 seconds. The time of exposure of a HIPE foam to UV light in
a continuous process is measured by when a 1 cm long portion, as
measure in the machine direction, of the HIPE foam enters and then
exits the UV light zone. This rapid polymerization allows a wide
variety of HIPE compositions to be used. Because polymerization can
occur quickly with the methods of the present invention, a HIPE
need only be stable for a short period of time, for instance up to
several minutes.
[0042] Following polymerization the resulting HIPE foam is
saturated with aqueous phase that needs to be removed to obtain
substantially dry HIPE foam. In certain embodiments, HIPE foams can
be squeezed free of most of the aqueous phase by using compression,
for example by running the HIPE foam through one or more pairs of
nip rollers 90. The nip rollers 90 can be positioned such that they
squeeze the aqueous phase out of the HIPE foam. The nip rollers 90
can be porous and have a vacuum applied from the inside such that
they assist in drawing aqueous phase out of the HIPE foam. In
certain embodiments, nip rollers 90 can be positioned in pairs,
such that a first nip roller 90 is located above a liquid permeable
belt 40, such as a belt 40 having pores or composed of a mesh-like
material, and a second opposing nip roller 91 facing the first nip
roller 90 and located below the liquid permeable belt 40. One of
the pair, for example the first nip roller 90 can be pressurized
while the other, for example the second nip roller 91, can be
evacuated, so as to both blow and draw the aqueous phase out the of
the HIPE foam. The nip rollers may also be heated to assist in
removing the aqueous phase. In certain embodiments, nip rollers are
only applied to non-rigid HIPE foams, that is HIPE foams whose
walls would not be destroyed by compressing the HIPE foam. In yet a
further embodiment, the surface of the nip rollers may contain
irregularities in the form of protuberances, depressions, or both
such that a HIPE foam can be embossed as it is moving through the
nip rollers. When the HIPE has the desired dryness it may be cut or
sliced into a form suitable for the intended application.
[0043] In certain embodiments, in place of or in combination with
nip rollers, the aqueous phase may be removed by sending the HIPE
foam through a drying zone 80 where it is heated, exposed to a
vacuum, or a combination of heat and vacuum exposure. Heat can be
applied, for example, by running the foam though a forced air oven,
IR oven, microwave oven or radiowave oven. The extent to which a
HIPE foam is dried depends on the application. In certain
embodiments, greater than 50% of the aqueous phase is removed. In
certain other embodiments greater than 90%, and in still other
embodiments greater than 95% of the aqueous phase is removed during
the drying process.
EXAMPLES
[0044] Preparation of High Internal Phase Emulsions (HIPE) and
their subsequent polymerization into absorbent foams are
illustrated in the following example. The HIPE sample comprised a
single layer having an average pore size of about 30 microns.
HIPE Components:
[0045] To prepare the HIPE sample the aqueous phase, oil phase, and
initiator contained the following components as shown below in
Table 1.
TABLE-US-00001 TABLE 1 % Amount Based on Total Oil Phase Weight of
Oil Phase 2-ethylhexyl acrylate (EHA) 36.7% 2-ethylhexyl
methacrylate (EHMA) 37.61% ethyleneglycol dimethacrylate (EGDMA)
17.43% dimethyl ammonium methyl sulfate 0.93% (DTDMAMS)
Polyglycerol succinate (PGS) 6.48% Photoinitiator - Darocur 1173*
0.99% % Amount Based on Total Weight of Aqueous Aqueous Phase Phase
CaCl.sub.2 3.85% Water:oil ratio 27:1 *BASF Corporation, Florham
Park, NJ
Equipment:
[0046] The HIPE is prepared in equipment comprising static mixers
and a recirculation pump. The static mixers are manufactured by
Sulzer (Sulzer Ltd. Zurcherstrasse 14, 8401 Winterthur,
Switzerland). Forty-eight elements of SMX style mixers, sized to
fit within a standard 1.5'' diameter pipe were used as the primary
mixing loop elements. Four sets of twelve elements welded so that
each sequential segment is rotated 90.degree. are fitted into
independent sections of pipe fitted with 2'' tri-clover quick
disconnect piping flanges.
[0047] The aqueous phase is introduced into a recirculation loop
via a modified 17/8'' tubing 90.degree. elbow with 2'' tri-clover
quick disconnect piping flanges, with a 1/2'' pipe welded into the
elbow to form an annulus such that the aqueous phase is entering
the discharge end of the elbow, concurrent with the recirculation
flow, both proceeding vertically downward. The end of the annular
1/2'' pipe is internally threaded and a set screw with a 17/64''
hole drilled in it to direct the aqueous incoming flow toward the
static mixers.
[0048] Three sections of the SMX containing pipes, vertically
oriented, follow the aqueous introduction elbow. Then the flow is
directed by two elbows, both 17/8'' tubing elbows with tri-clover
fittings, first a 90.degree. and then a 45.degree.. The final
section of SMX mixers is connected upward at a convenient angle to
have its discharge at about the same elevation as the inlet
fittings to the recirculation pump.
[0049] The discharge from the final SMX mixer segment goes through
a conical reducer to a 7/8'' Tee. (Tee A). One side of the Tee is
connected to a same diameter elbow fitted with a temperature probe,
which then connects to another 7/8'' Tee (Tee B). One side of Tee B
connects to a Teflon lined hose 11/4'' in diameter and 48'' long.
The hose connects to the stem side of a 7/8'' Tee (Tee C). One side
of Tee C's cross piece is connected upwardly to the inlet of the
recirculation pump, a Waukesha Model 030 U2 lobe pump (Waukesha
Chemy-Burrell Company, Delavan, Wis.). The other side of Tee C's
cross piece in connected downwardly to a 7/8'' to 5/8'' conical
reducer. The small end of the conical reducer uses a 3/4''
tri-clover connection to a custom made section of 3/8'' stainless
steel tubing with a 3/4'' tri-clover fitting welded onto the tube
by first drilling a matching diameter hole in a 3/4'' tri-clover
end cap. This allows the tube to project into and past the
intersection of the stem side of Tee C to the cross piece of Tee C.
The end of the tube projecting inward toward the Waukesha pump is
internally threaded and fitted with a set screw into which a 7/64''
hole has been drilled. The other end of the tube is fitted with a
3/4'' tri-clover fitting facing downward fabricated in the same way
as mentioned above.
[0050] The discharge from the Waukesha pump transfers to a 13/8''
diameter by 6'' spool piece with a small port for a temperature
probe and tri-clover sanitary fittings, followed by six elements of
11/4'' Kenics helical static mixers (Chemineer Inc., Dayton, Ohio)
in a section of pipe just long enough to contain them, with ends
fitted with tri-clover fittings. Next is a 13/8'' 90.degree. tubing
elbow with tri-clover fittings, a 13/8'' diameter by 6'' spool
piece, a second 13/8'' diameter by 6'' spool piece fitted with a
means to vent gasses from this, the high spot of the total first
stage mixing assembly, and then a 13/8 to 17/8'' conical spool
piece connected to the aqueous injector elbow mentioned above. This
completes the description of the mixing stage for the small celled
emulsion.
[0051] It has been found that the supply pumps or the recirculation
pump can lead to cyclic pulsations of flow. To mitigate that
behavior, the free end of Tee A in the above description can be
connected to a surge dampener assembly containing a pressure
transducer to monitor pressures and a chamber which can be vented
to allow for different volumes of air to be maintained in the
chamber in order to dampen the pressure fluctuations.
[0052] The discharge from the mixing stage issues from Tee B
through a Teflon lined 11/4'' braided steel hose to a 1'' piping
elbow fitted with a similar injector tube arrangement to the
aqueous injector elbow described above, but with 3/8'' tubing
instead of 1/2'', and fitted with a set screw with a 3/32'' drilled
hole. The initiator solution is introduced through this
arrangement. The discharge of the HIPE and the centrally
introduced, collinear initiator stream flow are directed to a
series of three segments of twelve elements of SMX mixers sized to
fit in a 1'' pipe section with tri-clover fittings. The flow then
proceeds through a conical reducer into a custom coat hanger style
die. The die then deposits the HIPE unto an endless belt moving at
a speed of 10 meters per minute.
HIRE Formation:
[0053] To start this equipment, aqueous phase is heated to about 80
C and delivered to the aqueous injector point described above at a
flow rate of about 2 liters/minute to conveniently fill the
equipment and to pre heat the equipment to a temperature indicated
by the temperature indicating devices with the loop of about 65 C.
The Waukesha pump is started at a theoretical rate of 2 liters per
minute when aqueous phase is observed to be coming out of the die,
which is higher than the pump, so that the pump is not run dry.
[0054] When the equipment temperature is reached, the oil phase is
then delivered to the oil phase injector at a rate of 0.5
kilograms/minute. (Aqueous phases are metered in liters per minute
and the oil phase is referred to in kilograms per minute in order
to describe the theoretical density of the cured emulsion. This
also means that one can change the salt concentration or salt type
in the aqueous phase and still make the same density product
without re-calculating flow rates in kilograms to accomplish the
desired product). The water to oil ratio at this stage of startup
is then 4:1. After a period of about 5 minutes from the first
introduction of oil phase, low viscosity HIPE can be observed
issuing from the die. At that point the aqueous temperature
setpoint is adjusted to about 72 C and the flow rate is uniformly
increased from 2 liters per minute to 8.107 liters per minute over
a period of 3 minutes. Only the aqueous phase temperature is
controlled, since it is >92% of the total mass of emulsion. The
recirculation pump, starting simultaneously with the start of the
increase in aqueous phase flow, is uniformly increased in speed to
yield a pumping rate of 28 liters per minute over a period of 2
minutes. The oil phase flow, also beginning at the same time as the
increase in aqueous phase flow, is decreased uniformly to a flow
rate of 0.313 kg/minute over a period of 5 minutes. Sodium acrylate
flow at 0.031 liters/minute is comingled with the aqueous flow
prior to the introduction to the mixing loop and is generally
started during the aqueous flow rate ramp. At equilibrium, the
water to oil ratio at the discharge from the recirculation loop is
27:1. The HIPE issuing from the die at the end of the flow ramps is
very thick and very white.
[0055] A sample of the HIPE was dispensed into a 2'' long.times.2''
wide.times.4 mm deep container and placed underneath a
medium-pressure mercury vapor lamp (UV Bulb: 250 mm long, 600
Watts/inch max medium pressure mercury vapor lamp; MonoCure UV
Curing System available from UV Systems Group of Nordson
Corporation, Amherst, Ohio.). The container was completely filled
with the HIPE. The top surface of the container was at a 2''
distance from the bottom surface of the lamp housing. The lamp
power was set at 200 Watts/inch with lamp intensity and dose as
given in Table 2. The UV light measurements were taken with a Power
Puck (10 Watt, EIT, Sterling, Va.). The surface of the sample was
not covered. The lamp had been turned on and off intermittently for
certain periods of time until a total light exposure time of 5
minutes was achieved (this time does not include the time when the
lamp was off). The lamp on/off regimen was as follows: 10
seconds/10 seconds for the first 120 seconds of experiment and 20
seconds/20 seconds for the rest 480 seconds of experiment. During
and after the experiment the surface of the sample was smooth and
there were no signs of discoloration, bubbles or surface
imperfections. At this point, the sample was taken away from the
lamp and carefully observed. Observations were done during the
treatment procedure when the lamp had been off. The changes in the
sample properties had been followed visually by observations and by
touching the sample with a stainless steel spatula. Skin formation
at the surface of the sample, which provided evidence of monomer
polymerization, had been observed after 2 minutes of UV light
exposure. The entire thickness of the sample had been polymerized
in about 4 minutes of UV light exposure. Water could be easily
squeezed out of the polymerized sample by pressing on it with a
spatula.
TABLE-US-00002 TABLE 2 First UV Lamp Spectral Range Joules/cm.sup.2
Watts/cm.sup.2 UVA 48.06 0.16 UVB 86.79 0.29 UVC 15.21 0.05 UVV
22.95 0.23
[0056] The dimensions and values disclosed herein are not to be
understood as being strictly limited to the exact numerical values
recited. Instead, unless otherwise specified, each such dimension
is intended to mean both the recited value and a functionally
equivalent range surrounding that value. For example, a dimension
disclosed as "40 mm" is intended to mean "about 40 mm."
[0057] Every document cited herein, including any cross referenced
or related patent or application, is hereby incorporated herein by
reference in its entirety unless expressly excluded or otherwise
limited. The citation of any document is not an admission that it
is prior art with respect to any invention disclosed or claimed
herein or that it alone, or in any combination with any other
reference or references, teaches, suggests or discloses any such
invention. Further, to the extent that any meaning or definition of
a term in this document conflicts with any meaning or definition of
the same term in a document incorporated by reference, the meaning
or definition assigned to that term in this document shall
govern.
[0058] While particular embodiments of the present invention have
been illustrated and described, it would be obvious to those
skilled in the art that various other changes and modifications can
be made without departing from the spirit and scope of the
invention. It is therefore intended to cover in the appended claims
all such changes and modifications that are within the scope of
this invention.
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