U.S. patent application number 09/790093 was filed with the patent office on 2002-10-24 for mold release and anti-blocking coating for powder-free natural or synthetic rubber articles.
Invention is credited to Gardner, Joseph B., Li, Zhixin, Petrash, Stanislaw, Thomaides, John S., Tokimori, Yasuo, Xiao, Chaodong.
Application Number | 20020155309 09/790093 |
Document ID | / |
Family ID | 25149625 |
Filed Date | 2002-10-24 |
United States Patent
Application |
20020155309 |
Kind Code |
A1 |
Li, Zhixin ; et al. |
October 24, 2002 |
Mold release and anti-blocking coating for powder-free natural or
synthetic rubber articles
Abstract
The present invention is directed to a release composition for
molds and formers used in the production of natural and synthetic
latex articles. The release coating contains a water-borne, high Tg
polymer formed from at least one hydrophobic monomer and at least
one hydrophilic monomer, where the Tg of the polymer is at least
-10.degree. C. One advantage of the release composition is that it
is compatible with a coagulant solution used in the formation of
latex gloves. Articles formed using the release coating have good
anti-blocking properties
Inventors: |
Li, Zhixin; (Bridgewater,
NJ) ; Gardner, Joseph B.; (Somerville, NJ) ;
Xiao, Chaodong; (East Hanover, NJ) ; Thomaides, John
S.; (Berkeley Heights, NJ) ; Tokimori, Yasuo;
(Osaka, JP) ; Petrash, Stanislaw; (Whippany,
NJ) |
Correspondence
Address: |
Thomas F. Roland
National Starch and Chemical Company
P.O. Box 6500
Bridgewater
NJ
08807-0500
US
|
Family ID: |
25149625 |
Appl. No.: |
09/790093 |
Filed: |
February 21, 2001 |
Current U.S.
Class: |
428/494 ;
427/413; 427/430.1; 428/519; 428/520 |
Current CPC
Class: |
B29C 41/14 20130101;
Y10T 428/31917 20150401; Y10T 428/31833 20150401; B29C 33/62
20130101; A41D 19/0062 20130101; Y10T 428/31924 20150401; C08J 5/02
20130101; B29C 41/38 20130101; Y10T 428/31909 20150401; Y10T
428/31928 20150401 |
Class at
Publication: |
428/494 ;
428/519; 428/520; 427/430.1; 427/413 |
International
Class: |
B32B 025/08; B32B
025/12; B05D 001/18; B05D 001/36 |
Claims
What is claimed is:
1. A mold or former for producing a natural or synthetic rubber
article having on its surface a release composition comprising a
water-borne high Tg polymer formed from: (1) at least one
hydrophobic monomer; and (2) at least one hydrophilic monomer,
wherein said water-borne polymer has a Tg of at least -10.degree.
C.
2. The mold or former of claim 1 wherein said water-borne polymer
comprises an emulsion polymer.
3. The mold or former of claim 1 wherein said hydrophobic monomer
comprises styrene.
4. The mold or former of claim 1 wherein said hydrophilic monomer
is an acid monomer.
5. The mold or former of claim 1 wherein said mold release
composition further comprises a surfactant.
6. The mold or former of claim 1 wherein said release composition
further comprises microspheres.
7. The mold or former of claim 1 wherein said release composition
further comprises a dispersant.
8. The mold or former of claim 1 wherein said water-borne polymer
further comprises a cross-linker.
9. The mold or former of claim 1 wherein said release composition
further comprises a rheology modifier.
10. The mold or former of claim 1 wherein said release composition
further comprising a coagulant.
11. The mold or former of claim 1 wherein said high Tg polymer
comprises: a) from 20 to 35 percent by weight of methyacrylic acid;
b) from 65 to 80 percent by weight of styrene; and c) from 0.5 to
1.5 percent by weight of a crosslinker.
12. The mold or former of claim 1 wherein said release composition
is free of silicon compounds.
13. An article comprising a formed natural or synthetic rubber
article having thereon a coating composition comprising a
water-borne high Tg polymer formed from: (1) at least one
hydrophobic monomer; and (2) at least one hydrophilic monomer,
wherein said water-borne polymer has a Tg of at least -10.degree.
C.
14. The article of claim 12 wherein said article is
powder-free.
15. A process for making a glove comprising: (a) immersing a glove
former in a coagulant solution containing a release composition
comprising a water-borne polymer with Tg of at least -10.degree. C.
formed from at least one hydrophobic monomer, and at least one
hydrophilic monomer, producing a coated former; (b) immersing said
coated mold into a natural rubber latex to coat the former with
said latex; (c) immersing the latex coated former into a inner
surface coating composition; (d) curing the latex in an oven; and
(e) removing the finished glove from the former.
16. The process of claim 14 wherein step (a) comprises two separate
steps comprising: a.1) immersing said ceramic former into said
water-borne polymer release composition; and a.2) immersing said
release coated ceramic former into a coagulant solution.
17. The process of claim 14 wherein said the latex coated former of
step (b) is leached in water prior to step (c).
18. A release composition comprising: a) a water-borne high Tg
polymer formed from at least one hydrophobic monomer; and at least
one hydrophilic monomer, wherein said water-borne polymer has a Tg
of at least -10.degree. C.; b) a coagulant.
19. The composition of claim 17 wherein said coagulant is a calcium
salt.
20. The composition of claim 17 further comprising
microspheres.
21. The composition of claim 17 further comprising a rheology
modifier.
22. The composition of claim 17 further comprising a surfactant.
Description
[0001] The present invention relates to the use of a polymeric
release composition for molds and formers used in the production of
natural and synthetic rubber articles. In particular the polymeric
release composition is useful for the formation of latex gloves,
and also for preventing blocking on the outer surface of such
gloves. The release composition of the present invention has the
advantage of being easily cleaned from molds and formers, and is
compatible with coagulant currently used in many manufacturing
processes, eliminating the need for an extra step to coat the mold
or former with a release coating.
BACKGROUND OF THE INVENTION
[0002] As used herein, the terms latex glove or latex article refer
to a glove or article made of natural or synthetic rubber. Articles
made from natural or synthetic rubber are elastic materials having
low glass transition temperatures. The surfaces of these materials
are tacky and tend to adhere to each other. For example, latex
gloves are difficult to strip from glove formers at the end of the
manufacturing process, and they tend to stick together, or block,
when packaged for distribution and sale.
[0003] There are currently several approaches to solving the
problem. One method involves the use of a particulate or powder
material, such as starch, talc, or calcium carbonate. The
particulate can be blended into a coagulant solution to form a
barrier between the latex rubber and the surface of the former. The
powder facilitates the stripping of gloves from the formers, and
also prevents blocking. Unfortunately, the powder coating is a
known nuisance, as loose powder can become airborne. Starch powder
tends to adsorb proteins found in natural rubber latex and the
powder is easily dislodged during use, contaminating the
surrounding environment and causing allergies and other negative
effects. Further, the protein/powder complex serves as a food
source for bacteria, allowing them to proliferate. Recently, there
has been a growing demand for powder-free natural and synthetic
rubber gloves, which do not use loose powder.
[0004] Another approach is the use of a chlorination process to
provide the necessary anti-blocking properties, as described in
U.S. Pat. No. 4,851,266. In this case, calcium carbonate is used as
a mold release agent and washed away prior to chlorination.
Although this reduces the tack and friction of the rubber, this
process makes the rubber less pliant and reduces the shelf life of
the rubber article. Also, chlorination leaves the article quite
slippery, which makes it difficult to handle objects with
chlorinated gloves. To address this problem, chlorinated gloves are
often textured.
[0005] Yet another approach is the use of silicone materials. These
materials facilitate removal of gloves from the formers, and also
reduce blocking. Unfortunately, the residue of this material is
rather hard to clean from the former in preparation for the next
dipping cycle.
[0006] Talc-free mold release agents using surfactants are
described in U.S. Pat. No. 4,310,928.
[0007] Polymeric mold release agents have also been disclosed in
the art. Formulated polychloroprenes are described in EP 0 640623,
Urethane dispersions in U.S. Pat. No. 5,534,350, and
Styrene/acrylates containing silicone in U.S. Pat. Nos. 5,993,923;
5,691,069; 5,700,585; and 5,712,346. Copending U.S. patent
application Ser. No. 09/400,488, and copending U.S. patent
application, submitted Sep. 15, 2000 describe the use of star
polymers as inner coatings for latex gloves.
[0008] Surprisingly it has been found that a release composition
containing a water-borne high Tg polymer formed from at least one
hydrophobic monomer and at least one hydrophilic monomer provides a
powder-free mold release agent, provides anti-blocking in the
finished article, and also aids in providing a smooth latex
deposition on the formers. Additionally, the release composition is
dispersible in high electrolyte coagulant, making it compatible
with current manufacturing processes.
SUMMARY OF THE INVENTION
[0009] The present invention is directed to a mold or former for
natural or synthetic rubber articles having on its surface a
release composition comprising a water-borne polymer formed from at
least one hydrophobic monomer and at least one hydrophilic monomer,
where the polymer has a Tg of at least -10.degree. C.
[0010] Other embodiments of the invention are methods of making a
latex glove in which a release composition, containing a
water-borne polymer, having a Tg of at least -10.degree. C., and
formed from at least one hydrophobic monomer and at least one
hydrophilic monomer, is applied to a former as a release
coating.
[0011] Still another embodiment of the invention is a natural or
synthetic rubber article having on its surface a coating comprising
a polymer having a Tg of at least -10.degree. C., and formed from a
hydrophobic monomer and a hydrophilic monomer.
[0012] Still another embodiment of the invention is a latex
coagulant, comprising a release composition, comprising a polymer
having a Tg of at least -10.degree. C., and formed from a
hydrophobic monomer and a hydrophilic monomer, which is used in
manufacturing powder-free rubber articles.
[0013] While not wishing to be bound to any particular theory, it
is believed that the key performance characteristics desirable for
a release coating are: a high Tg polymer, which provides
anti-blocking; ease of cleaning from a former; wettability of the
film, for smooth latex deposition; an affinity to the latex
surface; the ability to impart an anti-blocking character to the
article formed from a mold or former.
DETAILED DESCRIPTION OF THE INVENTION
[0014] The present invention is directed to a mold or former for
the production of natural and synthetic rubber articles, having on
its surface a release composition comprising a water-borne high Tg
polymer formed from at least one hydrophobic monomer and at least
one hydrophilic monomer.
[0015] Natural and synthetic rubber articles, as used herein, refer
to articles made from low-Tg, tacky polymeric materials. Examples
of such materials include, but are not limited to, butyl rubber,
natural latex rubber, polyvinyl chloride, neoprene, nitrile, viton,
styrene butadiene copolymers, polyurethanes, or interpenetrating
polymer network emulsion polymers, or combinations of these.
[0016] The water-borne polymer of the present invention is one
which is water-borne, and formed by means known in the art, such as
emulsion polymerization and suspension polymerization.
[0017] By high Tg polymer is meant a polymer having a Tg of at
least -10.degree. C., preferably from 25 to 200.degree. C., and
most preferably from 40 to 150.degree. C. Monomers useful in
forming the polymer of the present invention are ethylenically
unsaturated monomers or mixtures thereof. Particularly useful
hydrophobic monomers include (meth)acrylates, vinyl acetate,
ethylene, and styrene. A preferred hydrophobic monomer is
styrene.
[0018] The polymer of the present invention is also formed from a
hydrophilic monomer. The hydrophilic monomer is present in the
polymer at from 10-90 percent, based on the weight of the polymer.
Suitable hydrophilic monomers include those monomers that are
ionic, e.g. anionic, cationic, or zwitterionic, or have sufficient
nonionic polar functionality, e.g. hydroxyl or amido groups to
render them hydrophilic. Examples of such monomer include, but are
not limited to hydroxyethyl acrylate, acrylonitrile,
2-(dimethylamino)ethyl (meth)acrylate,
[3-(methacryloylamino)propyl]trimethylammonium chloride,
2-acrylamido-2-methyl-1-propanesulfonic acid sodium salt (a.k.a.
AMPS), [2-(acryloyloxy)ethyl]trimethylammonium chloride. Preferred
hydrophilic monomers are acrylic acid and methacrylic acid.
[0019] The polymer may optionally contain a cross-linker. The
cross-linker is present at from 0 to 10 percent, and preferably
from 0.5 to 5 percent by weight, based on the weight of the
polymer. The cross-linker is preferably a di-functional
cross-linker, such as divinylbenzene, diallyl maleate, ethylene
glycol dimethacrylate, vinyl crotonate and diallyl phthalate.
Multi-functional cross-linkers, such as allyl and vinyl sucrose
ethers, pentaerythritol tetra(meth)acrylate, trimethylolpropane
tri(meth)acrylate, and the like, can also be used.
[0020] The release composition may optionally contain other
ingredients, such as dispersants, surfactants, microspheres, and
rheology modifiers.
[0021] Surfactants useful in the present invention include, but are
not limited to: anionic, cationic, nonionic, and amphoteric
surfactants; and polymeric surfactants including but not limited to
linear and star copolymers. The surfactant improves the uniformity
of the latex deposition, improves the ease of stripping and
improves the wettability of the coated former by the latex.
[0022] Preferably the release coating contains no silicones,
however the addition of a silicone to the composition can also be
advantageous. A problem with having silicon compounds in the
release composition is that they can remain on a mold or former,
making the mold or former more difficult to clean.
[0023] The release composition may also contain microspheres.
Microspheres are useful in reducing the surface contact area, and
thus the adhesion between the coated rubber article and the mold,
former, or other object. This improves both the release and
anti-blocking characteristics. The microspheres have diameters
below 60 microns, preferably from 5 to 40 microns, and most
preferably from 10 to 30 microns. The microsphere may be made of
any material that is harder than the article being coated. Examples
of microspheres useful in the present invention are those made of
polyamides such as nylons, polymethylmethacrylate, polystyrene,
polyethylene, polypropylene, polytetrafluoroethylene, polyesters,
polyethers, polysulfones, polycarbonates, polyether ether ketones,
and other polymers and copolymers, silica, and microcrystalline
cellulose. Preferably the microspheres are present in the release
composition at from 0.05 to 5 percent by weight, and most
preferably at from 0.1 to 1 percent by weight.
[0024] A dispersant may optionally be added to aid in dispersion of
the microspheres into the aqueous release composition. Dispersants
useful in the present invention include, but are not limited to,
surfactants and polymeric dispersants including amphiphilic linear
and star copolymers.
[0025] A rheology modifier is optionally present in the release
composition. The rheology modifier is used to control the viscosity
of the composition for ease of use in different manufacturing
processes and equipment, and to control the uniformity and
thickness of the coating. Rheology modifiers useful in the present
invention include, but are not limited to cellulosics such as
hydroxyethylcellulose, cationic hydroxyethylcellulose, such as
polyquaternium-4 and polyquaternium-10, hydrophobically modified
hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, and
hydroxypropylcellulose; dispersed or soluble starches or modified
starches; and polysaccharide gums such as xanthan gum, guar gum,
cationic guar gum such as guar hydroxypropyltrimonium chloride, and
locust bean gum. Other suitable rheology modifiers include but are
not limited to acid soluble copolymers, surfactants, etc. The
rheology modifier is typically added at from 0.01 to 10 percent by
weight, and preferably from 0.02 to 3 percent by weight, based on
the release composition.
[0026] The release composition may also contain other additives
known in the art, such as adhesion promoters, crosslinking agents,
biocides, low surface energy compounds, fillers, and anti-foaming
agents.
[0027] The release composition of the present invention is made by
combining each of the ingredients to form an aqueous dispersion, by
means known in the art.
[0028] The polymeric release coating may be used to coat a variety
of materials used as molds and formers of natural and synthetic
rubber articles. The molds and formers may be of any material known
in the art, including but not limited to ceramics, glass, and
stainless steel. Items produced in the molds or formers include
gloves, prophylactics, catheters, tires, swimming caps, balloons,
tubing, and sheeting. A particularly suitable end use application
is as a release composition in the production of latex gloves,
including surgeons' gloves, physicians' examining gloves, and
workers' gloves, more particularly powder-free latex gloves.
[0029] When used to coat the molds or formers in the preparation of
gloves, the polymeric coating composition may be applied using
several different methods. For example, in one method for coating
the glove mold or former, a former or mold in the shape of a hand
is dipped into a solution or dispersion containing the release
composition, then dipped into a coagulant mixture containing a
latex coagulant. Useful coagulants include, but are not limited to,
calcium nitrate and calcium chloride. In another method, a clean
former or mold in the shape of a hand is dipped into a coagulant
containing a release composition. After drying, the mold coated
with the release coating and coagulant can be used to prepare a
glove by methods known in the art. For example, the coated mold is
immersed in a natural or synthetic rubber latex for a time
sufficient for the rubber to coagulate and form a rubber coating of
the desired thickness. Optionally, the glove then may be water
leached to remove impurities from the rubber. The formed glove is
then oven cured, cooled, and dipped into a coating composition,
which will become the inner glove coating. Alternatively, the
formed glove can be dipped into a coating composition prior to the
oven cure and cooling. The inner surface treatments include, but
are not limited to those known in the art, including polymers such
as that described in U.S. patent application Ser. 09/663,468
incorporated herein by reference, other polymer coatings,
chlorination, and starch or clay powders. After cooling, the glove
is simultaneously stripped from the mold and inverted. Some, or all
of the release coating on the glove mold or former is transferred
to the what has become the outer surface of the glove.
[0030] The release composition and the coagulant can be combined
into the same solution or dispersion. The release composition of
the present invention is compatible with coagulants currently used
in the production of rubber articles. The combination of the
coagulant and release composition into the same processing step,
allows manufacturers to use the release composition in current
processes without the need for costly modifications or the need for
additional processing steps.
[0031] In addition to being useful as an outside coating on a
glove, the polymer composition of the present invention is useful
as a release agent in other industries, including but not limited
to: injection molding, C-V joints, and in the manufacture of tires,
synthetic gloves, and other rubber articles.
[0032] Articles formed using the release composition of the present
invention possess good anti-blocking properties. This property
prevents adhesion between articles, such as latex gloves, which are
packed together, but must be easily separated from each other for
use.
[0033] The following examples are presented to further illustrate
and explain the present invention and should not be taken as
limiting in any regard.
[0034] Method A--Making a Latex Glove with a Pre-treated Former
[0035] A latex glove can be made by:
[0036] (a) Immersing a glove former in a solution or dispersion
comprising a release composition comprising a water-borne polymer
with Tg higher than -10.degree. C. formed from at least one
hydrophobic monomer, and at least one hydrophilic monomer,
producing a coated former;
[0037] (b) after drying, immersing the coated former into a
conventional coagulant solution;
[0038] (c) immersing said coated mold into a natural rubber latex
to coat the former with said latex;
[0039] (d) optionally, leaching the latex coated former in water to
remove impurities from the rubber;
[0040] (e) immersing the latex coated former into a inner surface
coating composition;
[0041] (f) curing the latex in an oven; and
[0042] (g) removing the finished glove from the former.
[0043] Method B--Making a Latex Glove with a Formulated
Coagulant
[0044] A latex glove can be made by:
[0045] (a) immersing a glove former in a coagulant solution
containing a release composition comprising a water-borne polymer
with Tg higher than -10.degree. C. formed from at least one
hydrophobic monomer, and at least one hydrophilic monomer,
producing a coated former;
[0046] (b) immersing said coated mold into a natural rubber latex
to coat the former with said latex;
[0047] (c) optionally, leaching the latex coated former in water to
remove impurities from the rubber;
[0048] (d) immersing the latex coated former into a inner surface
coating composition;
[0049] (e) curing the latex in an oven; and
[0050] (f) removing the finished glove from the former.
[0051] EXAMPLE 1
[0052] Preparation of an Emulsion Polymer
[0053] A resin kettle equipped with a mechanical stirrer, nitrogen
inlet, thermometer, and two slow addition feeds was charged with
LUBRHOPHOS LB-400 (8.6 g), TOMADOL 1-3 (13.8 g) and water (391 g).
This stirred mixture was warmed to 65.degree. C. while flushing
with nitrogen. To this mixture was added 5% of a well mixed
pre-emulsion prepared from the slow addition of premixed styrene
(83.5 g), methacrylic acid (MAA) (177.5 g), and ethylene glycol
dimethacrylate (2.4 g) to a stirred premixed solution of LUBRHOPHOS
LB-400 (8.6 g), TOMADOL 1-3 (13.8 g), and water (216 g). After this
addition was complete, the reaction vessel was charged with an
initial catalyst of sodium persulfate (0.2 g in 16.8 g water) and
the reaction mixture was allowed to warm to 80.degree. C. over the
next 30 minutes. Once the reaction temperature of 80.degree. C. was
obtained, the reaction mixture was simultaneously charged with the
pre-emulsion over 180 minutes and a sodium persulfate solution
(0.27 g in 60 g water) over 210 minutes. Immediately after the
addition of the catalyst was complete, the remaining monomer was
scavenged by the addition of tert-butyl hydroperoxide (1.2 g in 2 g
water), followed by the addition of ferrous ammonium sulfate (0.3 g
of a 2% solution dissolved in 5 g water) 30 minutes later, then the
slow addition of erythorbic acid (1.2 g in 10 g water) over the
next 30 minutes. The reaction mixture was then cooled, filtered
through an 80 mesh filter, and used for the formulation without
additional purification. The emulsion product contains 30% solids
with 68 parts MAA, 32 parts styrene and 1 part cross-linker. The Tg
of the polymer was estimated to be 115.degree. C. using MSI
simulation software.
EXAMPLE 2
[0054] Preparation of Polymer Containing Coagulant
[0055] 500 g of polymer solution from example 1 was added to a
2-gallon container. 4500 g of coagulant solution (containing 10%
calcium nitrate or 5% calcium chloride) were then slowly introduced
while stirring. The polymer was stable in the coagulant dispersion,
but mild flocculation was observed. Slight sedimentation was found
over time but this can be easily redispersed. The polymer
containing coagulant can last several weeks without changing the
properties.
EXAMPLE 3
[0056] Making a Powder Free Glove using Method B
[0057] A clean ceramic mold was rinsed and dried at 70.degree. C.
It was then immediately immersed for 10-20 seconds into the polymer
containing coagulant from Example 2. The coated mold was then
partially dried and immersed into natural rubber latex at room
temperature for 20-30 seconds. After a brief cure (120.degree. C.
for 2 minutes), the latex deposit was leached in water at
60.degree. C. to remove impurities from the natural rubber. The
leached latex deposit was then dried and dipped into a polymeric
inner surface treatment solution to coat the inner surface. The
polymer treated glove was then vulcanized at 90-130.degree. C. for
15-30 minutes.
[0058] The latex glove was easily stripped from the mold. The
2-side polymer treated latex glove was powder free, with the inside
surface exhibiting good donnability and the outside surface
exhibiting anti-blocking and non-slippery grip.
[0059] The mold was then immersed into a 1 molar KOH alkaline
solution and rinsed with water to remove residual polymer. The
cleaned mold was used for new latex depositions.
EXAMPLE 4
[0060] Making a Powder Free Glove Using Method A
[0061] A clean ceramic mold was rinsed and dried at 70.degree. C.
It was then immediately immersed for 10-20 seconds into a 3% solids
dispersion of the polymer from example 1 in water. The mold was
then dried at 70.degree. C. for 1-4 minutes and immersed for 10-20
seconds into a regular coagulant (10% calcium nitrate aqueous
solution or 5% calcium chloride). The coated mold was then
partially dried and immersed into natural rubber latex at room
temperature for 20-30 seconds. After a brief cure (120.degree. C.
for 2 minutes), the latex deposit was leached in water at
60.degree. C. to remove impurities from the natural rubber. The
leached latex deposit was then dried and dipped into a polymeric
inner surface treatment solution to coat the inner surface. The
polymer treated glove was then vulcanized at 90-130.degree. C. for
15-30 minutes.
[0062] The latex glove was easily stripped from the mold. The
2-sided polymer treated latex glove is powder free, with the inside
surface exhibiting good donnability and the outside surface
exhibiting anti-blocking and non-slippery grip.
[0063] The mold was cleaned by immersing into a 1 molar KOH
alkaline solution and rinsing with water to remove remaining
polymer. The clean mold was used for new latex depositions, with no
degradation in glove quality.
EXAMPLE 5
[0064] Making Powder Free Latex Gloves with Emulsion Polymers with
Different Tg's
[0065] Emulsion polymers were made as in example 1 with different
Tg's by varying the monomer compositions. All polymers contained 1
part per hundred monomer (pphm) of a difunctional cross-linker.
1 TABLE 1 MAA Styrene Butyl Acrylate Estimated* Tg Sample 5A 68%
32% 115.degree. C. Sample 5B 35% 40% 25% 74.degree. C. Sample 5C
35% 25% 40% 53.degree. C. *All Tg were estimated using MSI
simulation software.
[0066] These polymers were used as release agents in the
preparation of powder free latex gloves, using Method B at 3%
polymer concentration. For all polymers, the latex deposits were
uniform and the stripped molds were easy to clean. The
anti-blocking of polymer 5A was very good, polymer 5B was good, and
polymer 5C was fair.
EXAMPLE 6
[0067] Making Powder Free Latex Gloves with Emulsion Polymers of
Different Cross-linking Density
[0068] Emulsion polymers were made as in example 1 with different
cross-linker (ethylene glycol dimethacrylate) amounts. The
cross-linker, parts per hundred monomer (pphm), varied from 0 pphm,
0.5 pphm, 1 pphm, 2 pphm, 3 pphm, 4 pphm to 5 pphm. Gelling was
noted at 5 pphm cross-linker. These polymers, with the exception of
the one containing 5 pphm cross-linker, were used as release agents
in the preparation of powder free latex gloves, using Method B at
3% polymer concentration. All polymers produced uniform latex
deposition and the stripped molds were easy to clean. Zero pphm
cross-linker showed reduced mold release and anti-blocking. All
other polymers showed very good anti-blocking and mold release.
Four pphm cross-linker showed exceptional ease of stripping.
EXAMPLE 7
[0069] Making Powder Free Latex Gloves with Emulsion Polymers of
Different Acid Level
[0070] Emulsion polymers were made as in example 1 with different
acid levels. All polymers contained 1 pphm ethylene glycol
dimethacrylate cross-linker.
2 TABLE 2 MAA, % Styrene, % Sample 7A 0 100 Sample 7B 5 95 Sample
7C 20 80 Sample 7D 25 75 Sample 7E 35 65 Sample 7F 38 62 Sample 7G
48 52 Sample 7H 50 50 Sample 7I 68 32 Sample 7J 74 26 Sample 7K 80
20
[0071] The 80% MM reaction gelled. These polymers, with the
exception of the one containing 80% MM, were used as release agents
in the preparation of powder free latex gloves, using Method B at
3% polymer concentration. Zero and 5% MM showed good anti-blocking
and mold release. All others showed very good anti-blocking and
mold release. Polymer 7D exhibited long time stability in the
coagulant mixture.
EXAMPLE 8
[0072] Making Powder Free Latex Gloves with Emulsion Polymers
Containing Methyl Methacrylate (MMA)
[0073] Polymer emulsions were prepared according to example 1 using
methyl methacrylate (MMA) in place of styrene. All polymers
contained 1 pphm ethylene glycol dimethacrylate cross-linker.
3 TABLE 3 MMA MAA Sample 8A 32% 68% Sample 8B 50% 50% Sample 8C 75%
25%
[0074] These polymers were used as release agents in the
preparation of powder free latex gloves, using Method B at 3%
polymer concentration. The results showed that the higher the
percent of methyl methacrylate, the better the mold release and
anti-blocking. All gave acceptable mold release and anti-blocking
properties.
EXAMPLE 9
[0075] Polymer emulsions were prepared according to example 1 using
other hydrophobic monomers in place of styrene (table 4).
4 TABLE 4 Hydrophobic Monomer MAA Sample 9A CHM 32% 68% Sample 9B
IBXM 75% 25% Sample 9C DPA 75% 25%
[0076] Monomers for polymers 9A-C include cyclohexyl methacrylate
(CHM), isobornyl methacrylate (IBXM), and dicyclopentanyl acrylate
(DPA). All polymers contained 1 pphm of a difunctional
cross-linker. These polymers were used as release agents in the
preparation of powder free latex gloves, using Method B at 3%
polymer concentration. All samples gave acceptable anti-blocking
and mold release.
EXAMPLE 10
[0077] Making Powder Free Latex Gloves with Surfactants
[0078] A series of non-ionic surfactants, including BRIJ and TWEEN
from ICI, and SURFYNOL from Air Products, were used as release
agents in the preparation of powder free latex gloves, using Method
B. The concentration of the surfactants was 2% in the release
coatings. The latex deposit was uniform and the stripped formers
were very easy to clean. The latex glove was easily stripped off
the mold, but exhibited poor anti-blocking.
EXAMPLE 11
[0079] Making a Powder Free Latex Glove with Beads
[0080] Poly(methyl methacrylate) (PMMA) beads with particle size
around 20 .mu.m were dispersed in a regular coagulant solution
(containing 10% calcium nitrate or 5% calcium chloride). The weight
percentage of beads was 3% in the total solution. This dispersion
was used as a release agent in the preparation of powder free latex
gloves, using Method B. The latex glove was hard to strip off the
former.
EXAMPLE 12
[0081] Making Powder Free Latex Gloves with a Thickener
[0082] Xanthan gum was dissolved in a regular coagulant solution,
containing 10% calcium nitrate or 5% calcium chloride. The
concentration of xanthan gum in the formulated coagulant was 0.04%.
This dispersion was used as a release agent in the preparation of
powder free latex gloves, using Method B. The latex gloves were
hard to strip off the formers and showed poor anti-blocking.
EXAMPLE 13
[0083] Making Powder Free Latex Gloves with a Polymer and a
Thickener
[0084] A formulated coagulant containing 0.04% xanthan gum and 3%
polymer from example 1 was prepared. This dispersion was used as a
release agent in the preparation of powder free latex gloves, using
Method B. The outside polymer coating was more uniform than in
example 3.
EXAMPLE 14
[0085] Making Powder Free Latex Gloves with Beads, a Surfactant,
and a Thickener
[0086] A formulated coagulant containing 0.3% Beads, 0.1%
SURFYNOL-465 and 4% CaCl.sub.2 was prepared. This dispersion was
used as a release agent in the preparation of powder free latex
gloves, using Method B. The outside coating was uniform, but the
latex gloves were hard to strip off the formers and showed poor
anti-blocking.
EXAMPLE 15
[0087] Making Powder Free Latex Gloves with a Polymer
Formulation
[0088] A formulated coagulant containing, 4% calcium chloride, 2%
polymer from example 1, 0.25% PMMA beads, and 0.1% SURFYNOL-465
surfactant was prepared. This dispersion was used as a release
agent in the preparation of powder free latex gloves, using Method
B. Compared to examples 3 & 4, the glove is more uniform, and
easier to strip off the former. The glove also exhibited excellent
anti-blocking.
* * * * *