U.S. patent application number 09/970486 was filed with the patent office on 2003-04-17 for dry-peelable temporary protective coatings.
This patent application is currently assigned to 3M Innovative Properties Company. Invention is credited to Johnson, Stephen A., Krepski, Larry R., Lewandowski, Kevin M., Mickus, Daniel E., Rowen, Susan K..
Application Number | 20030072948 09/970486 |
Document ID | / |
Family ID | 25517017 |
Filed Date | 2003-04-17 |
United States Patent
Application |
20030072948 |
Kind Code |
A1 |
Krepski, Larry R. ; et
al. |
April 17, 2003 |
Dry-peelable temporary protective coatings
Abstract
A dry-strippable coating composition can be incorporated into a
composite article and comprises a dried water-borne polyurethane
dispersion including a release additive comprising a releasing
co-solvent or other selected release material. When water is
removed from the polyurethane dispersion of the composite article
and when the article comprises a thermoformable substrate, the
article can be thermoformed to provide a shaped article.
Dry-stripping the coating composition from the substrate provides a
thermoformed substrate and a thermoformed protective layer. The
dry-strippable coatings provide temporary protection for the
surface of various products and components during manufacture,
assembly, shipping, installation, painting, and refinishing
operations.
Inventors: |
Krepski, Larry R.; (White
Bear Lake, MN) ; Lewandowski, Kevin M.; (Inver Grove
Heights, MN) ; Mickus, Daniel E.; (Mahtomedi, MN)
; Rowen, Susan K.; (Hudson, WI) ; Johnson, Stephen
A.; (Woodbury, MN) |
Correspondence
Address: |
3M INNOVATIVE PROPERTIES COMPANY
PO BOX 33427
ST. PAUL
MN
55133-3427
US
|
Assignee: |
3M Innovative Properties
Company
|
Family ID: |
25517017 |
Appl. No.: |
09/970486 |
Filed: |
October 3, 2001 |
Current U.S.
Class: |
428/423.1 ;
524/763 |
Current CPC
Class: |
C09D 175/04 20130101;
Y10T 428/31565 20150401; C09D 175/04 20130101; Y10T 428/31576
20150401; Y10T 428/31583 20150401; Y10T 428/31605 20150401; Y10T
428/31591 20150401; Y10T 428/3158 20150401; Y10T 428/31601
20150401; Y10T 428/31551 20150401; Y10T 428/31587 20150401; C08L
91/06 20130101 |
Class at
Publication: |
428/423.1 ;
524/763 |
International
Class: |
B32B 027/00 |
Claims
It is claimed:
1. A process comprising the step of: providing a composite article
comprising 1) a nonporous substrate having on at least one surface
thereof 2) a strippable protective dried water-borne polyurethane
coating composition, said polyurethane being free of polymerizable
acrylate functionality, said composition comprising a release
additive including one or both of (a) a releasing co-solvent having
a boiling point greater than 100.degree. C., and (b) a dispersion
of a metal salt of stearic acid or a dispersion of a wax.
2. The process according to claim 1 further comprising the step of
removing said protective layer by stripping it from said substrate
in the absence of a stripping solvent.
3. The process according to claim 1 wherein said polyurethane
comprises one or both of a polyurethane-urea and a
sulfopoly(ester-urethane) all of which optionally are terminated
with one or more silyl groups.
4. The process according to claim 1 wherein said polyurethane
comprises a carboxylate or sulfonate functional polyurethane
urea.
5. The process according to claim 1 wherein said release additive
comprises a hydrophilic polyol.
6. The process according to claim 5 wherein said hydrophilic polyol
comprises glycerol or an oligomer of glycerol.
7. The process according to claim 5 wherein said hydrophilic polyol
is selected from the group consisting of ethers and esters of
ethylene glycol, polyethylene glycol, ethers and esters of
polyethylene glycol, and pentaerythritol ethoxylate.
8. The process according to claim 1 wherein said releasing
co-solvent is selected from the group consisting of castor oil,
sulfonated castor oil, and ethoxylated polydimethylsiloxanes.
9. The process according to claim 1 wherein said release additive
is present in said coating composition in an amount in the range of
0.5 to 20 weight percent relative to the weight of solids in said
polyurethane dispersion.
10. The process according to claim 9 wherein the amount of release
additive is present in the range of 5 to 10 weight percent relative
to the weight of solids in said polyurethane dispersion.
11. The process according to claim 1 wherein said substrate is
selected from the group consisting of plastic, metal, glass, and
ceramic.
12. The process according to claim 1 wherein said substrate
comprises a thermoplastic film.
13. The process according to claim 1 wherein said substrate
comprises a thermoformable material.
14. The process according to claim 13 wherein said thermoformable
material comprises a plastic material.
15. The process according to claim 12 wherein said thermoplastic
film comprises one or more of acrylonitrile butadiene styrene
polymer, high impact polystyrene, polyethylene, polypropylene,
poly(ethylene terephthalate) and copolymers thereof,
polymethylmethacrylate, poly(ethylene naphthalenedicarboxylate),
polycarbonate, polycarbonate-polyetherimide, and polyvinyl
chloride.
16. The process according to claim 13 further comprising the step
of thermoforming said composite article into a desired shape.
17. The process according to claim 16 further comprising the step
of dry-stripping said protective layer from said substrate to
produce a thermoformed substrate.
18. A coating composition comprising an aqueous polyurethane
dispersion, said polyurethane being free of acrylate functionality,
said polyurethane including a release additive comprising one or
both of (a) a releasing co-solvent having a boiling point greater
than 100.degree. C., and (b) a dispersion of a metal salt or a
dispersion of a wax.
19. The coating composition according to claim 18 wherein said
release additive is selected from the group consisting of glycerol,
oligomers of glycerol, ethers and esters of ethylene glycol,
polyethylene glycol, ethers and esters of polyethylene glycol,
pentaerythritol ethoxylate, castor oil, sulfonated castor oil,
dispersions of metal salts of stearic acid, ethoxylated
polydimethylsiloxanes, and dispersed waxes.
20. The coating composition according to claim 18 from which water
has been removed to provide a dry-strippable polyurethane
coating.
21. The polyurethane coating according to claim 18 wherein said
polyurethane is selected from the group consisting of a) a
polyurethane-urea or a sulfopoly(ester-urethane) all of which
optionally are terminated with one or more silyl groups, and b) a
carboxylate or sulfonate functional polyurethane urea.
22. The polyurethane coating according to claim 19 wherein said
release additive comprises glycerol or an oligomer of glycerol.
23. A composite article comprising a) a nonporous substrate having
on at least one surface thereof b) a strippable protective dried
water-borne polyurethane coating composition, said polyurethane
being free of acrylate functionality, said composition comprising a
release additive including one or both of (a) a releasing
co-solvent having a boiling point greater than 100.degree. C., and
(b) a dispersion of a metal salt of stearic acid or a dispersion of
a wax.
24. The composite article according to claim 23 wherein said
substrate comprises a thermoformable material.
25. The composite article according to claim 24 which has been
thermoformed to produce a shaped article.
26. The composite article according to claim 25 wherein said
thermoforming comprises one or more of heating, pressing,
stretching, and application of vacuum.
27. The composite article according to claim 23 wherein said
polyurethane is selected from the group consisting of a) a
polyurethane-urea or a sulfopoly(ester-urethane) all of which
optionally are terminated with one or more silyl groups, and b) a
carboxylate or sulfonate functional polyurethane-urea.
28. The composite article according to claim 23 wherein said
release additive is selected from the group consisting of glycerol
or an oligomer thereof, ethers and esters of ethylene glycol,
polyethylene glycol, ethers and esters of polyethylene glycol,
pentaerythritol ethoxylate, castor oil, sulfonated castor oil,
metal salts of stearic acid, ethoxylated polydimethylsiloxanes, and
dispersed waxes.
29. The composite article according to claim 23 wherein said
substrate is selected from the group consisting of plastic, metal,
glass, sealed wood, and ceramic.
30. The composite article according to claim 25 wherein said
substrate comprises a plastic material.
31. A process comprising the step of: a) providing a composite
article comprising 1) a nonporous substrate having on at least one
surface thereof 2) a strippable protective dried water-borne
polyurethane coating composition comprising a release additive
including one or both of (a) a releasing co-solvent having a
boiling point greater than 100.degree. C., and (b) a dispersion of
a metal salt of stearic acid or a dispersion of a wax, and b)
thermoforming said composite article into a desired shape.
32. A coating composition comprising an aqueous polyurethane
dispersion including a release additive comprising one or both of
(a) a releasing co-solvent having a boiling point greater than
100.degree. C., and (b) a dispersion of a metal salt or a
dispersion of a wax, wherein said polyurethane comprises a
sulfopoly(ester-urethane) which optionally is terminated with one
or more silyl groups.
Description
FIELD OF THE INVENTION
[0001] This invention relates to coatings that are effective for
protecting the surfaces of various substrates and are removable by
stripping or peeling from the substrate. The removable coatings are
also useful for the temporary protection of plastic parts prior to,
during, and after thermoforming operations.
BACKGROUND OF THE INVENTION
[0002] Temporary protective coatings are widely used to protect the
surfaces of various products, parts, or components during
manufacture, assembly, shipping, installation, or refinishing
operations. The temporary protective coatings are used to prevent
damage from scratching, nicking, pitting, staining, corrosion,
sticking, or discoloration. The protective coatings are also used
to simplify or enhance cleaning operations whereby surface
contamination is eliminated by removal of the temporary coating.
Temporary coatings or "maskings" are also used during painting or
refinishing operations of automobiles, for example, to prevent
application of paint to areas not intended to be painted, and to
prevent damage from paint overspray. Temporary protective coatings
are also used during the transportation of various articles from a
manufacturing site to a retail location. The surface finishes of
new vehicles such as automobiles or boats must often be protected
from abrasive particles or other deleterious conditions in the
environment during shipment by road, rail, or sea.
[0003] Other products or articles that may be protected by
temporary removable coatings include those with precision or high
gloss surfaces such as mirrors, windows, optical lenses, plastics
such as Plexiglas.TM., plastic laminates such as Formica.TM.,
composites such as Corian.TM. countertops, appliances, metal tools,
parts, and machinery, and kitchen and bathroom fixtures such as
sinks, bathtubs, and plumbing fixtures.
[0004] Temporary removable coatings may also be applied to various
surfaces such as floors, countertops, showerstalls, appliances, and
the like which tend to become contaminated with dirt, oil, or
grease through normal use. In these applications, the temporary
protective coating on the surface will become contaminated or
dirty, and removal of the temporary protective coating eliminates
the contamination, thereby greatly simplifying cleaning of the
surface.
[0005] A number of approaches that utilize the application of a
liquid solution or dispersion temporary protective coating
composition have been described.
[0006] U.S. Pat. No. 4,341,687 describes a peelable, film forming
paint comprising a mixture of an isocyanate functional prepolymer,
a polyurethane resin, and ethylene glycol monoalkyl ether in a
volatile organic solvent. The paint is useful for removing
contamination from and protecting surfaces subject to
contamination. No aqueous dispersions are disclosed.
[0007] There has been a move in recent years to avoid the use of
volatile organic solvents (VOCs). Volatile organic solvents are
often flammable and hazardous from a health and safety perspective.
They are subject to increasingly stringent environmental
regulations due to emission and disposal concerns. For these
reasons, much effort has been expended in replacing organic solvent
based adhesives, coatings, and sealers, for example, with water
based systems.
[0008] U.S. Pat. No. 6,124,044 describes the use of aqueous
emulsions of vinyl-acrylic copolymers and vinyl acetate ethylene
emulsions to form barrier films on applied surfaces, the film being
removable by peeling from the surface. The emulsion is said to be
useful for protecting the exterior surfaces of automobiles and
other products from damage.
[0009] U.S. Pat. No. 5,494,702 describes solvent-free aqueous based
compositions for protecting surfaces from paint in painting
operations. The compositions comprise polyvinyl alcohol, a
plasticizer, and a surfactant in water. After the painting
operation, the protective composition is removed by washing with a
pressurized stream of water or by scrubbing.
[0010] Other compositions for protecting surfaces during painting
operations and that are removed by washing with water have been
described. U.S. Pat. No. 5,308,647 describes compositions
comprising film forming thickeners, surfactants, and polyglycerols
in water. U.S. Pat. No. 6,117,485 describes the use of compositions
comprising dextrin, a plasticizer, and water for temporary masking
operations. No peelable coatings are disclosed.
[0011] U.S. Pat. Nos. 5,081,174, 5,639,814 and 6,187,849 B1
describe weldable, protective coatings for use on metal. The
coatings comprise neutralized acrylic polymers and wax lubricants.
The coatings are removed by washing with an aqueous acid or
alkaline cleaning solution.
[0012] U.S. Pat. No. 5,945,462 describes the use of aqueous based
compositions comprising polymerizable acrylic functional urethane
prepolymer resins containing a photoinitiator and a release agent
which are irradiated with UV radiation to photocrosslink the
prepolymer resins to form strippable, protective coatings. The
release agents include lecithin, polyethylene glycols, and fatty
acids.
[0013] Canadian Patent Application CA 2,314,523 describes
strippable coating compositions for temporary protection purposes.
The compositions comprise at least two different aqueous anionic
dispersions of polyurethane polyureas wherein the films resulting
from drying the dispersions have glass transition temperatures in
the range of -30.degree. C. to -45.degree. C. The coating
composition is stated to be co-solvent free.
[0014] U.S. Pat. Nos. 5,965,195 and 6,172,126 B1 describe
strippable coating compositions comprising organic solvent-free
aqueous, anionic dispersions of polyurethane polyureas derived from
a prepolymer prepared from diisocyanates, polyols, a
2,2-bis(hydroxymethyl)alkane monocarboxylic acid, a monofunctional
chain terminating agent, water, and a neutralizing agent, with the
specific provisions that the NCO content of the prepolymer is up to
25% lower than the theoretical value. The entire synthesis is
performed in the homogeneous phase, and no solvent having a boiling
range of greater than 100.degree. C. is used during the preparation
of the dispersion. The coating composition is stated to be
co-solvent free.
SUMMARY OF THE INVENTION
[0015] Briefly, the present invention provides a process comprising
the step of providing a composite article comprising 1) a nonporous
substrate having on at least one surface thereof, 2) a strippable
protective dried water-borne polyurethane coating composition, said
polyurethane being free of polymerizable acrylate functionality,
said composition comprising one or both of (a) a releasing
co-solvent having a boiling point greater than 100 degrees C., and
(b) a dispersion of a metal salt of stearic acid or a dispersion of
a wax. The coating can be removed from the substrate by stripping
it from the substrate in the absence of a stripping solvent.
Preferably, the releasing co-solvent has a boiling point greater
than 110.degree. C. and more preferably greater than 150.degree.
C., and most preferably greater than 200.degree. C.
[0016] It has now been found that the addition of releasing
co-solvents having a boiling point greater than 100.degree. C. or
certain other release additives to aqueous polyurethane dispersions
provides a coating composition effective for the temporary
protection of the surfaces of various products or components. The
coatings are applied in liquid form in water dispersion without
substantial amounts, i.e., no more than 25 weight percent, of
organic solvents and form a protective coating when the water
evaporates or is removed. The resulting protective coatings can be
removed by stripping or peeling from the surface without the need
for the application of an aqueous or non-aqueous stripping or
washing solution. The removable coatings are also useful for the
temporary protection of sheets of metal or plastic parts, after
which the coatings may be removed by peeling.
[0017] In another aspect, the present invention provides an
additional process step when the substrate is a plastic part
wherein the composite article is thermoformed prior to stripping
the protective layer from the substrate. The coating of the
invention provides temporary protection for the substrate during
the thermoforming step after which the coating may be removed by
peeling.
[0018] In a further aspect the present invention provides a
dry-strippable coating composition comprising a dried water-borne
polyurethane composition, said polyurethane being free of
polymerizable acrylate functionality, including a release additive
comprising a releasing co-solvent having a boiling point greater
than 100 degrees C. or certain other release additives, all
preferably being selected from the group consisting of hydrophilic
polyols such as glycerol, oligomers of glycerol, ethers and esters
of ethylene glycol, polyethylene glycol, ethers and esters of
polyethylene glycol, pentaerythritol ethoxylate, as well as other
release additives such as castor oil, sulfonated caster oil,
dispersions of metal salts of stearic acid, ethoxylated
polydimethylsiloxane, and dispersed waxes, the dispersions
preferably being aqueous dispersions.
[0019] In a yet another aspect, the present invention provides a
composite article comprising 1) a nonporous substrate having on at
least one surface thereof 2) a dry-strippable protective layer
comprising a dried water-borne polyurethane composition comprising
a releasing co-solvent having a boiling point greater than 100
degrees C. or other release additive, all being selected from the
group consisting of glycerol, oligomers of glycerol, ethers and
esters of ethylene glycol, ethers and esters of polyethylene
glycol, pentaerythritol ethoxylate, caster oil, sulfonated castor
oil, metal salts of stearic acid, ethoxylated polydimethylsiloxane,
and dispersed waxes.
[0020] Aqueous polyurethane dispersions that are useful in the
present invention include the well-known carboxylate or sulfonate
functional polyurethane-ureas that are prepared from diisocyanates,
polyols, and carboxylic acid or sulfonic acid containing diols.
[0021] Cationic polyurethane-ureas, which contain quaternary
ammonium groups in their backbone, are also useful in the present
invention. Other types of aqueous polyurethane dispersions useful
in the present invention are the non-ionic polyurethane-ureas that
contain no ionic groups but contain hydrophilic groups such as
polyethylene oxide chains in their structure.
[0022] Releasing co-solvents having a boiling point greater than
100.degree. C. include hydrophilic polyols, preferably glycerol and
oligomers of glycerol, as well as certain other release additives,
that may be added to the aqueous polyurethane dispersions to render
the coating removable.
[0023] The releasing co-solvent or other release additive is added
to the aqueous polyurethane dispersion in an amount of about 0.5 to
20 weight percent, preferably 5 to 10 weight percent, relative to
the weight of the solids in the polyurethane dispersions.
[0024] Particularly preferred types of aqueous polyurethane
dispersions useful in the present invention include polyurethanes
terminated with one or more silyl groups such as the silyl
terminated sulfopoly(ester-urethan- es) described in U.S. Pat. Nos.
5,747,626, 5,756,633, and 5,929,160.
[0025] In general, the aqueous polyurethane dispersions described
above form films or coatings that characteristically demonstrate
excellent clarity, toughness, strength, abrasion resistance, and
weatherability. Preferably, the coatings are colorless. They also
usually exhibit excellent adhesion to a variety of substrates, and
therefore it is surprising that the addition of releasing
co-solvents or certain other release additives to the dispersion
provides a coating that can be peeled from the substrate without
tearing.
[0026] Glycerol and oligomers of glycerol are preferred releasing
co-solvents. In this application:
[0027] "glycerol" and "oligomers of glycerol" mean glycerol,
diglycerol, and other polyglycerols;
[0028] "group" or "compound" or "polymer" means a chemical species
that allows for substitution or which may be substituted by
conventional substituents which do not interfere with the desired
product; e.g., substituents can be alkyl, alkoxy, aryl, phenyl,
cyano, etc.;
[0029] "molecular weight" means the sum of the atomic weights of
all atoms in a group of atoms or in a segment of a polymer and
under circumstances where the group or segment may be a mixture of
two or more groups or segments is the number average of molecular
weights of the groups or segments;
[0030] "nonporous" means a material not allowing components of the
polyurethane composition to migrate into the substrate;
[0031] "peelable," "strippable," or "dry-strippable" coating means
one that may be removed from the surface it coats simply by
mechanical peeling. A "peel able" coating possesses sufficient
flexibility, tensile and tear strength so that it does not fracture
during peeling. In a preferred embodiment, the adhesive ability of
the coating is sufficient to keep it completely bound to the
underlying substrate throughout the period of protection and yet
remains fully peelable at the time of removal. It is particularly
preferred that the peelable coating strip without trouble or
without being torn in pieces. A useful coating when peeled should
not remain partially unpeeled, leaving portions adhering to the
substrate;
[0032] "plastic" means any of various organic compounds produced by
polymerization, capable of being molded, cast into various shapes
and films, or drawn into filaments used as textile fibers;
materials that are thermoplastic are included;
[0033] "polymer" includes oligomers;
[0034] "releasing co-solvent" means a substance that controls or
minimizes the adhesion between two surfaces; it imparts the
property of strippability to a coating (film) and has a boiling
point greater than 100 degrees C., preferably greater than 110
degrees C., and more preferably greater than 150 degrees C., and
preferably a melting point of at most 60 degrees C.;
[0035] "silyl group" means Si(Q).sub.p(OQ).sub.3-p where p=0, 1, or
2 wherein each Q independently can be hydrogen or a lower alkyl
group having 1 to 4 carbon atoms such that an OQ group in which Q
is a lower alkyl group is the hydrolyzable unit;
[0036] "sulfo group" or "sulfonate group" or "sulfonic acid group
or salt thereof" means a --SO.sub.3M group where M can be H or a
cation, preferably an alkali metal ion;
[0037] "sulfopolyol" means a symmetric or asymmetric compound or
polymer or a random polymer comprising at least one sulfo group, at
least two hydroxyl groups, optionally containing other functional
groups such as ester, ether, urea, urethane, and thiocarbamate;
[0038] "sulfopolyester polyol" or "sulfoester polyol" means a
symmetric or asymmetric polymer or a random polymer comprising at
least one sulfo group, at least two ester groups, at least two
hydroxyl groups, optionally containing other functional groups such
as ester, ether, urea, urethane, and thiocarbamate; and
[0039] "sulfopoly(ester-urethane)" means a symmetric or asymmetric
polymer or a random polymer comprising at least one sulfo group, at
least two ester groups and at least one urethane group, optionally
containing other functional groups such as ether, carbonate, urea,
and thiocarbamate.
[0040] The present invention provides water-borne polyurethane
compositions that can be used as temporary protective coatings.
Preferably, the polyurethane compositions are water dispersible
poly(ester-urethane) or sulfopoly(ester-urethane) compositions all
of which optionally are functionalized with silyl groups. The
addition of releasing co-solvents or certain release additives to
aqueous polyurethane dispersions provides peelable coatings that
are dry strippable from a substrate without the need for any type
of aqueous or non-aqueous stripping or washing solution. The
coating is applied to a substrate in water dispersion without
substantial amounts of organic solvents (i.e., using no more than
25 weight percent organic solvents based on the total composition
weight) and forms a protective coating when the water is removed.
The coating compositions of the present invention can be applied
using conventional coating techniques such as dipping, knife
coating, pouring, spraying, atomization, brushing, or roller
application. The dry-strippable coatings are also useful for the
temporary protection of plastic parts or articles, preferably in
sheet form, prior to thermoforming operations, after which the
coating can be removed by peeling. Useful dry coating thicknesses
are in the range of 2.0 to 1500 micrometers, preferably 2.0 to 500
micrometers, more preferably 5.0 to 250 micrometers. It is to be
appreciated that for specific uses such as small electronics, e.g.
cell phone covers, pagers, and transmitters, thickness of 2.0 to 20
micrometers can be preferred. Major appliances such as
refrigerators, cars, and dishwashers, and sporting goods such as
helmets, goggles, skis, golf clubs, and the like, preferably can
have coatings of thicknesses in the range of 50 to 300
micrometers.
[0041] High gloss plastic durable sheet goods can be produced by
thermoforming and are subject to damage of the plastic surface
caused by contact with the thermoforming mold. Slight imperfections
in the mold can result in nicks, gouges, bubbles, deformations,
scratches, or reduction of gloss of the plastic surface of the
thermoformed part. One way to prevent this damage during
thermoforming is to protect the surface of the plastic to be
thermoformed by coating it with a temporary protective coating that
will survive the thermoforming operation and be removable from the
thermoformed article after the thermoforming operation. The
protective coating is in intimate contact with the substrate to
provide a uniform, defect-free thermoformed surface on the
substrate.
[0042] The polyurethane coating compositions of the present
invention are effective for the temporary protection of surfaces of
various products, parts, or components during manufacture,
assembly, shipping, installation or refinishing operations. These
coating compositions, when used on thermoformable substrates, such
as sheets of plastic, and subjected to thermoforming conditions,
can produce shaped thermoformed articles. Dry-stripping of the
protective coating composition produces a shaped substrate and a
protective layer.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT OF THE INVENTION
[0043] The present invention provides coatings and a process
therefore that are effective in protecting the surfaces of various
products or components and are removable by stripping or peeling
from the surface without the need for any type of aqueous or
non-aqueous stripping or washing solution. The coatings are derived
from aqueous polyurethane solutions or dispersions to which an
effective amount of a release additive has been added. The coatings
are applied in liquid form in water solution or dispersion and form
the removable protective coating when the water evaporates or is
removed. The removable coatings are also useful for protecting the
surfaces of plastic substrates prior to thermoforming operations.
After thermoforming, the temporary protective coating may be
removed from the substrate by dry-peeling or stripping from the
surface of the thermoformed article.
[0044] One plastic that is widely used for thermoforming into
useful articles is high impact polystyrene (HIPS). Articles
produced by thermoforming HIPS include, for example, disposable
food service containers, lunch trays, drinking cups, domes, lids,
and covers. A plastic that is especially useful for thermoforming
is acrylonitrile-butadiene-styrene (ABS) polymer. The physical
properties of ABS are superior to HIPS and most other thermforming
materials. Because of its excellent chemical resistance, good low
temperature impact strength, high gloss, and ability to accept
electroplating, ABS is widely used for manufacturing durable goods
and large appliance parts such as refrigerator door liners,
automobile, boat, and recreational vehicle parts, and luggage
exteriors. Other plastics that are useful for thermoforming include
high density polyethylene, polypropylene, crystallized
poly(ethylene terephthalate) (CPET), poly(ethylene terephthalate)
copolymer (PETG), polycarbonate, polycarbonate-polyetherim- ide,
poly(methyl methacrylate) (PMMA), poly(vinyl chloride) (PVC),
poly(ethylene naphthalenedicarboxylate), and cellulosics such as
cellulose acetate, cellulose acetate butyrate, and cellulose
propionate.
[0045] The aqueous polyurethane dispersions that are useful in the
present invention include the well known carboxylate or sulfonate
functional polyurethanes-ureas that are prepared from
diisocyanates, polyols, and carboxylic acid or sulfonic acid
containing diols. Cationic polyurethane-ureas, which contain
quaternary ammonium groups in their backbone, are also useful in
the present invention. Other types of aqueous polyurethane
dispersions useful in the present invention are the non-ionic
polyurethane-ureas that contain no ionic groups but contain
hydrophilic groups such as polyethylene oxide chains in their
structure. The preparation and description of these aqueous
polyurethane dispersions is well known and is described in a number
of reviews, for example, D. Dieterich, Prog. Org. Coat., 9, 281-340
(1981); J. W. Rosthauser and K. Nachtkamp, J. Coated Fabrics, 16,
39-79 (1986); D. Dieterich and K. Uhlig, in Ullmann 's Encyclopedia
of Industrial Chemistry, Volume A21, 665-716 (1992); S. Ramesh, K.
Tharanikkarasu, G. N. Mahesh, and G. Radhakrishnan, J. Macro. Sci.,
Rev. Macromol. Chem. Phys., C38, 481-509 (1998). The polyurethane
dispersions useful in the invention do not contain polymerizable
acrylate functionality.
[0046] More particularly, the polyurethanes or polyurethane
prepolymers are prepared by methods well known in the art and
involve the reaction of polyisocyanates, especially diisocyanates,
with polyols, especially diols, wherein a portion of the diol
charge may consist of diols which contain ionic or potentially
ionic groups, optionally in the presence of other isocyanate
reactive monomers such as diamines or bismercaptans. The reaction
is generally carried out in a water soluble organic solvent
unreactive with an isocyanate such as acetone, methyl ethyl ketone
(MEK), tetrahydrofuran, and N-methyl pyrrolidinone, wherein the
solubility in water is at least 10 weight percent. The total
concentration of polyisocyanates and polyols (optionally any of
other different polyamines, or polythiols) is generally desirable
to be quite high such as at least 30 weight percent, preferably
greater than at least 50 weight percent. High monomer
concentrations and elevated reaction temperatures of from
50.degree. to 110.degree. C. are desirable so that high conversions
of monomers to polymer can occur in a reasonable time, e.g., less
than eight hours, preferably less than three hours. Catalysts may
be employed such as metal salts including dibutyltin dilaurate and
dibutyltin diacetate, and amines, such as triethylamine, DBU
(1,8-diazabicyclo[5.4.0]undec-7-ene) and DABCO
(1,4-diazabicyclo[2.2.2]oc- tane), in useful concentrations of from
0.01 to 1.0 mole percent (relative to the isocyanate reagent).
[0047] Representative polyisocyanates that can be used to react
with the polyols are any of the well-known aliphatic and aromatic
polyisocyanates. Useful polyisocyanates include hexamethylene
diisocyanate, toluene diisocyanate, isophorone diisocyanate
(3,5,5-trimethyl-1-isocyanato-3-iso- cyanatomethylcyclohexane),
bis(4-isocyanatocyclohexyl)methane,
1,3-bis(isocyanatomethyl)cyclohexane,
1,3-bis(1-isocyanato-1-methylethyl)- benzene, 4,4'-diphenylmethane
diisocyanate (MDI), tetramethylxylylenediiso- cyanate,
4,4',4"-triisocyanatotriphenylmethane, and the
polymethylenepolyphenylisocyanates. Other polyisocyanates are well
known and include those described in U.S. Pat. Nos. 3,700,643 and
3,600,359, among many others, which are incorporated herein by
reference. Mixtures of polyisocyanates can also be used such as
Isonate.TM. 2143L, available from Dow Chemical Company (Midland,
Mich.). The aliphatic polyisocyanates are preferred.
[0048] Polyols containing ionic or potentially ionic groups include
sulfonated polyester diols such as those described in U.S. Pat.
Nos. 5,747,626, 5,756,633, 5,929,160, and the sulfonated polyester
Rucoflex.TM. polyols, such as Rucoflex XS-5483 and XS-5536,
available from the Ruco Polymer Corporation (Hicksville, N.Y.), N,
N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid, and
3-hydroxy-2-hydroxymethylpropanesufonic acid. Other useful
sulfonated polyols include those derived from the addition of
bisulfite to ethylenically unsaturated polymeric precursors as
described in U.S. Pat. Nos. 5,698,626 and 5,753,774. Examples of
polyols containing carboxylate ionic groups include
dihydroxypropionic acid, dimethylolpropionic acid,
dimethylolbutyric acid, dihydroxysuccinic acid, and
dihydroxybenzoic acid. The sulfo and carboxyl groups in these
monomers may also be present in the form of their alkalai metal
salts such as lithium, sodium, or potassium salts, or amine salts.
Other examples of suitable monomers containing potentially ionic
groups include amino alcohols containing tertiary amine nitrogens
which may be converted at least partly into quaternary ammonium
groups by reaction with, for example, methyl iodide or dimethyl
sulfate such as N-methyl diethanolamine and
1,4-bis(2-hydroxyethyl)piperazine.
[0049] The exact nature and relative amounts of the other polyols
which may be incorporated can be varied to change the properties of
the final films. Suitable diols include ethylene glycol, propylene
glycol, neopentyl glycol, 2-butyl, 2-ethyl-1,3-propanediol,
polypropylene glycol, polyethylene glycol, polyester diols such as
polycaprolactone diol, and polyether diols such as
polytetramethylenediol and polycarbonate diols such as PC-1122.TM.
PC-1667.TM., and PC-1733.TM., available from Stahl USA, Peabody,
Mass. Properties that can be varied include ductility, water
uptake, tensile strength, modulus, abrasion resistance, minimum
film formation temperature, and glass transition temperature.
Longer chain polyols tend to provide materials which are more
ductile and having lower Tg, whereas shorter chain polyols tend to
contribute to high modulus, greater tensile strength, and having
high Tg materials. Aliphatic polyols tend to provide materials with
decreased water uptake whereas diols containing heteroatoms in the
backbone tend to have increased water uptake.
[0050] Useful optional polyamines include: ethylenediamine,
1,6-diaminohexane, piperazine, tris(2-aminoethyl)amine, and amine
terminated polyethers such as those marketed under the Jeffamine
trademark by the Huntsman Corporation (Salt Lake City, Utah).
Useful polythiols include 1,2-ethanedithiol, 1,4-butanedithiol,
2,2'-oxytris(ethane thiol), and di- and trimercapto propionate
esters of poly(oxyethylene) diols and triols.
[0051] Aqueous polyurethane dispersions are available from a number
of suppliers and include, for example the Bayhydrol.TM. products
such as Bayhydrol 110, Bayhydrol 121, Bayhydrol 123, Bayhydrol
140AQ, Bayhydrol DLN, and Bayhydrol PU-402A (available from Bayer
Corporation, Pittsburgh, Pa.), the NeoReZ.TM. polyurethane
dispersions such as NeoRez R-960, NeoRez R-972, NeoRez R-9649,
NeoRez R-9637, and NeoRez R-9679 (available from NeoResins,
Wilmington, Mass.), and the Witcobond.TM. polyurethane dispersions
such as Witcobond W-232, Witcobond W-505, and Witcobond W-507
(available from Crompton Corporation, Greenwich, Conn.).
[0052] The general preparation of the silyl terminated
polyurethanes is similar to that described above for the non-silyl
terminated polyurethanes with regard to reaction conditions, useful
monomers, and catalysts. In the preparation of a silyl terminated
polyurethane, the polyisocyanates can be reacted in greater than
stoiochiometric amount relative to the polyols (including
polyamines and polythiols). This results in a isocyanate functional
polymer that can be reacted with an nucleophilic, hydrolyzable
silane reagent such as 3-aminopropyltriethoxys- ilane,
3-N-methylaminopropyltrimethoxysilane,
3-mercaptopropyltrimethoxysi- lane, 3-hydroxypropyltriethoxysilane,
and bis(3-triethoxysilyl propyl)amine. Alternatively, the
polyisocyanates can be reacted in less than stoiochiometric amount
relative to the polyols (including polyamines and polythiols). This
results in a hydroxy, amino, or mercapto functional polymer which
can be reacted with an electrophilic, hydrolyzable silane reagent
such as 3-isocyanatopropyltriethoxysilane,
3-glycidoxypropyltrimethoxysilane, and
3-chloropropyltriethoxysilane.
[0053] Other types of aqueous polyurethane dispersions that are
useful in the present invention include the polyurethanes
terminated with one or more silyl groups such as the silyl
terminated polyurethanes described in U.S. Pat. Nos. 5,554,686 and
3,941,733. Additional silyl functional polyurethanes are described
in U.S. Pat. Nos. 4,567,228, 5,041,494, 5,919,860, and
6,111,010.
[0054] It has now been found that the addition of glycerol or
certain other releasing co-solvents or release additives to aqueous
polyurethane dispersions provides a coating composition effective
for the temporary protection of surfaces of various products or
components. The coatings are applied in liquid form in water
dispersion without substantial amounts of organic solvents and form
the protective coating when the water is removed or evaporates. The
protective coatings can be removed by stripping or peeling from the
surface without the need for any type of aqueous or non-aqueous
stripping or washing solution. The removable coatings are also
useful for the temporary protection of plastic parts prior to,
during, and after thermoforming operations, after which the
coatings may be removed by peeling.
[0055] In addition to glycerol, other releasing co-solvents
including hydrophilic polyols that have boiling points greater than
100.degree. C. may be added to the aqueous polyurethane dispersions
to render the coatings removable. These include higher oligomers of
glycerol such as diglycerol, triglycerol, and hexaglycerol, ethers
and esters of ethylene glycol such as ethylene glycol monobutyl
ether, polyethylene glycol of molecular weights about 150 to 8000,
ethers and esters of polyethylene glycol such as polyethylene
glycol methyl ether of molecular weights about 150 to 8000, and
pentaerythritol ethoxylate of molecular weights about 250 to 1000.
In addition to these hydrophilic polyols, other useful release
additives include mold release additives that are soluble or
dispersible in water such as castor oil, sulfonated castor oil,
metal salts of stearic acid, ethoxylated polydimethylsiloxanes, and
dispersed waxes.
[0056] Glycerol and oligomers of glycerol are preferred releasing
co-solvents. Triglycerol and hexaglycerol are available from
Hexagon Enterprises, Inc., Mountain Lakes, N.J., under the
tradenames Hexapol.TM. G-3 and Hexapol G-6, respectively. Hexapol
G-3 has the following approximate composition: glycerol, 13%;
diglycerol, 17%, triglycerol, 51%, tetraglycerol, 11%;
pentaglycerol, 5%; other glycerols, remainder. Hexapol G-6 has the
following approximate composition: diglycerol, 6%, triglycerol,
28%, hexaglycerol, 64%; other glycerols, remainder. Advantages of
these release additives are that they dissolve or disperse readily
in the aqueous polyurethane dispersion and generally result in
clear, defect free coatings.
[0057] The releasing co-solvents or other release additives are
added to the aqueous polyurethane dispersion in about 0.5 to 20
weight percent, preferably 5 to 10 weight percent, relative to the
weight of the solids in the polyurethane dispersions.
[0058] The releasing co-solvent or other release additive may be
added to the preformed aqueous polyurethane dispersion.
Alternatively, the release additive may be added to a solution of
the polyurethane before the polyurethane is dispersed in water. For
example, if a polyurethane is prepared by the acetone process,
wherein the polyurethane is prepared in acetone solution, water is
added, and finally acetone is removed to leave the polyurethane
dispersed in water, the release additive may be added to the
acetone solution of the polyurethane. Water may then be added and
acetone removed from the mixture to leave the aqueous dispersion of
the polyurethane and the release additive. When a polyurethane is
prepared by first preparing a prepolymer, and then chain extending
this polyurethane prepolymer in water containing diamines, for
example, the release additive may be added to the mixture of water
and chain extender agent used to chain extend the prepolymer and
form the polyurethane dispersion.
[0059] The coating compositions of the present invention are
applied using conventional coating techniques by dipping, knife
coating, pouring, spraying, atomization, brushing, or roller
application.
[0060] Temporary protective coatings are also useful for various
aspects of polymer processing, for example, in thermoforming of
plastic sheets into useful articles. Thermoforming is the process
of manufacturing products from thermoplastic sheets, whereby the
plastic sheet is heated to its softening point, formed in a mold by
the action of pressure or vacuum into the desired shape, and can
then be separated from the mold.
[0061] Substrates useful as carriers for the protective coatings of
the present invention include plastics, metals, glass, and
ceramics. If the articles are to be thermoformed, plastic
substrates are useful.
[0062] The temporary protective coatings of the invention are
useful to protect the surfaces of various products, parts, or
components during manufacture, assembly, shipping, installation,
refinishing or painting operations. The temporary protective
coatings are used to prevent damage from scratching, nicking,
pitting, staining, corrosion, or discoloration or to simplify or
enhance cleaning operations whereby surface contamination is
removed by stripping the temporary coating. Temporary coatings or
"maskings" are also used during painting or refinishing operations
of automobiles, for example, to prevent application of paint to
areas not intended to be painted, and to prevent damage from paint
overspray.
[0063] Other products or articles that may be protected by
temporary coatings of the present invention include products with
high gloss surfaces such as sealed wood, mirrors, windows, optical
lenses, plastics such as Plexiglas, plastic laminates such as
Formica, composites such as Corian countertops, appliances, metal
tools, stamped or formed metal parts, and machinery, and kitchen
and bathroom fixtures such as sinks, bathtubs, and plumbing
fixtures.
[0064] Thermoformed parts or articles can be protected from slight
imperfections in a mold that can result in nicks, gouges, scratches
or reduction of gloss of plastic surfaces of the thermoformed
product by use of the temporary protective thermoformable coatings
of the present invention. Stripping of the coating provides two
articles, the shaped thermoformed substrate and the thermoformed
self-supporting coating.
[0065] The present invention also allows for artwork, intricate
designs, decals or special appearance promoters such as metallic
chips, paint, or glitter to be adhered to the surface, topcoated
with the protective coating and further thermoformed. It is to be
appreciated that metal parts can be protected with the peelable
coating of the invention prior to stamping, bending, or forming
operations.
[0066] Polymeric films, whether single- or multi-layer, are widely
used in a broad range of industrial and consumer applications and
may benefit from the temporary protective coatings of the present
invention. Such films, for example, can be employed as transparent
or tinted barrier films to protect myriad underlying substrates.
Among other properties, they exhibit clarity, durability,
toughness, pliability, formability and affordability. Depending on
the desired properties of the polymeric film, it may be desirable
to orient the film by stretching. Typically, a polymeric film is
oriented in either or both the lengthwise (sometimes referred to as
machine) direction and the transverse (or cross-machine) direction.
Although the degree of orientation in either direction can vary
greatly (and are not necessarily the same), typically the oriented
film dimensions in both directions vary between 2.0 and 5.0 times
the films original dimensions.
[0067] Often times these polymeric films require a temporary
protective layer which prevents damage to the surface of one or
both faces of the film. These temporary protective layers typically
consist of some form of polyethylene liner of about 50 micrometer
(2 mil) thickness which is applied just prior to winding the film
into stockroll form. Besides being somewhat cumbersome to work
with, which can limit the caliper and/or length of a given
stockroll, liners have also been known to cause static issues, web
handling difficulties, and/or create unwanted patterns in the film.
Finally, these liners can add substantial cost to the price of the
film.
[0068] The present invention provides a method for eliminating the
need for these liners by the application of a temporary protective
coating to the film. These coatings can be applied in-line or
off-line. These coatings can also be applied to the film before or
after orientation. In some instances, these coatings can be
subjected to the high temperature conditions associated with
heat-setting films and continue to exhibit the ability to be peeled
from the film.
[0069] Objects and advantages of this invention are further
illustrated by the following examples, but the particular materials
and amounts thereof recited in these examples, as well as other
conditions and details, should not be construed to unduly limit
this invention.
[0070] In the Examples, the glass transition temperatures are
reported as the midpoint of the change in specific heat over the
transition range using an average sample heating rate of 5.degree.
C./min. The tensile properties were obtained from sample specimens
with gauge lengths of 1.43 cm (0.562 inches) and strain rates of
2.54 cm/min. (1 in./min.).
[0071] Preparation A--Preparation of Sulfopolyester diol
Precursor
[0072] A mixture of dimethyl 5-sodiosulfoisophthalate (DMSSIP,
337.3 g, 1.14 mol, available from E. I. DuPont de Nemours,
Wilmington, Del.), diethylene glycol (DEG, 483 g, 4.55 mol,
available from Aldrich Chemical Co., Milwaukee, Wis.), and zinc
acetate, (0.82 g, available from Aldrich) was heated to 180.degree.
C. and the methanol by-product was distilled from the reaction
mixture. After 4.5 hours NMR analysis of the reaction product
showed that less than 1% residual methyl ester was present in the
product.
[0073] Dibutyltin dilaurate (1.51 g, 2.4 mmol, available from
available from Alfa Chemical Co., Ward Hill, Mass.) was added to
the above reaction product, the temperature held at 180.degree. C.,
and epsilon-caprolactone (1753 g, 15.36 mol, available from Union
Carbide Corp., Danbury, Conn.)) was added portionwise over about a
30 minute period. When addition was complete, the reaction mixture
was held at 180.degree. C. for 4 hours, then cooled to afford the
desired product.
[0074] Determination of the hydroxyl equivalent weight of the
reaction product was as follows. A 4.81 g sample of the product
mixture was dissolved in 20 mL of methyl ethyl ketone, isophorone
diisocyanate (2.08 g, 9.36 mmol, available from Aldrich), and
dibutyltin dilaurate (0.02 g) added, and the solution heated 4
hours at 80.degree. C. The solution was cooled to room temperature,
a solution of dibutyl amine (4 mL of a 1.71 molar solution in
methyl ethyl ketone) was added, and the solution was stirred for 15
minutes. Then 20 mL of methanol and 4-5 drops of Bromophenol Blue
indicator were added, and the solution was titrated to a yellow
endpoint with 1.87 mL of a 1.0 molar hydrochloric acid solution in
water. This corresponded to a hydroxyl equivalent weight of
349.
[0075] Preparation B--Preparation of Silyl Terminated
Sulfo(Polyester-Urethane) with Tg of 30.degree. C.
[0076] The sulfopolyester diol of Preparation A with a hydroxyl
equivalent weight of 349 (425.8 g, 0.61 mol), polycaprolactonediol
(157.2 g, 0.30 mol, PCP 0201.TM., average molecular weight 524,
available from Union Carbide Corp., Danbury, Conn.), ethylene
glycol (74.5 g, 1.20 mol), and isophorone diisocyanate (505.7 g,
2.28 mol, available from Huls America, Inc., Piscataway, N.J.),
dibutyltin dilaurate (0.80 g, 1.2 mmol, available from Alfa
Chemical Co., Ward Hill, Mass.) were dissolved in methyl ethyl
ketone (626 g). The solution was stirred at 80.degree. C. for 3.5
hours, then an aliquot was removed for titration as described in
Preparation A. The isocyanate equivalent weight of the product was
determined to be 3245. Methyl ethyl ketone (610 g) and
3-aminopropyltriethoxysilane (76.7 g, 0.35 mol, available from
Aldrich) were added and the solution was stirred 15 minutes at
80.degree. C. Water (1240 g) was then added to the reaction mixture
over about a 5 minute period and methyl ethyl ketone was distilled
from the mixture under reduced pressure to produce a dispersion
(48% solids) of silyl terminated sulfo(polyester-urethane) in
water. Modulated Differential Scanning Calorimetry (MDSC) and
tensile property analyses made of a spun cast film produced from
the dispersion indicated that the polymer had a Tg of 30.degree. C.
and a tensile strength of 31.3 MPa (4549 psi) at 345%
elongation.
[0077] Preparation C--Preparation of Silyl Terminated
Sulfo(Polyester-Urethane) with Tg of 12.degree. C.
[0078] A silyl terminated sulfo(polyester-urethane) was prepared
substantially according to the procedure of Preparation B except
that the reagents were charged as follows:
[0079] The sulfopolyester diol of Preparation A with a hydroxyl
equivalent weight of 333 (370.6 g, 0.56 mol), polycaprolactonediol
(PCP 0201.TM., 170.3 g, 0.32 mol), ethylene glycol (44.9 g, 0.72
mol), isophorone diisocyanate (395.6 g, 1.78 mol), and
3-aminopropyltriethoxysilane (78.6 g, 0.36 mol) were allowed to
react. Modulated Differential Scanning Calorimetry (MDSC) and
tensile property analyses made of a spun cast film produced from
the dispersion indicated that the polymer had a Tg of 12.degree. C.
and a tensile strength of 20.3 MPa (2945 psi) at 418%
elongation.
[0080] Preparation D--Preparation of Silyl Terminated
Sulfo(Polyester-Urethane) with Tg of 22.degree. C.
[0081] A silyl terminated sulfo(polyester-urethane) was prepared
substantially according to the procedure of Preparation B except
that the reagents were charged as follows:
[0082] The sulfopolyester diol of Preparation A with a hydroxyl
equivalent weight of 335 (368.5 g, 0.55 mol), polycaprolactonediol
(PCP 0201.TM., 167.7 g, 0.31 mol), ethylene glycol (49.7 g, 0.80
mol), isophorone diisocyanate (401.8 g, 1.81 mol), and
3-aminopropyltriethoxysilane (56.7 g, 0.26 mol) were allowed to
react. Modulated Differential Scanning Calorimetry (MDSC) and
tensile property analyses made of a spun cast film produced from
the dispersion indicated that the polymer had a Tg of 22.degree. C.
and a tensile strength of 27.9 MPa (4045 psi) at 395%
elongation.
[0083] Preparation E--Preparation of Silyl Terminated
Sulfo(Polyester-Urethane) with Tg of -15.degree. C.
[0084] A silyl terminated sulfo(polyester-urethane) was prepared
substantially according to the procedure of Preparation B except
that the reagents were charged as follows:
[0085] The sulfopolyester diol of Preparation A with a hydroxyl
equivalent weight of 370 (555 g, 0.75 mol), polycaprolactonediol
(PCP 020.TM., 393 g, 0.75 mol), isophorone diisocyanate (375.1 g,
1.69 mol), and 3-aminopropyltriethoxysilane (80.5 g, 0.36 mol) were
allowed to react. Modulated Differential Scanning Calorimetry
(MDSC) and tensile property analyses made of a spun cast film
produced from the dispersion indicated that the polymer had a Tg of
-15.degree. C. and a tensile strength of 6.3 MPa (917 psi) at 462%
elongation.
[0086] Preparation F--Preparation of Silyl Terminated
Sulfo(Polyester-Urethane) with Tg of 47.degree. C.
[0087] A silyl terminated sulfo(polyester-urethane) was prepared
substantially according to the procedure of Preparation B except
that the reagents were charged as follows:
[0088] The sulfopolyester diol of Preparation A with a hydroxyl
equivalent weight of 370 (388.5 g, 0.53 mol), polycaprolactonediol
(PCP 0201.TM., 52.4 g, 0.10 mol), ethylene glycol (74.5 g, 1.2
mol), diethylene glycol (31.8g 0.30 mol), isophorone diisocyanate
(503.9 g, 2.27 mol), and 3-aminopropyltriethoxysilane (66.0 g, 0.30
mol) were allowed to react. Modulated Differential Scanning
Calorimetry (MDSC) and tensile property analyses made of a spun
cast film produced from the dispersion indicated that the polymer
had a Tg of 47.degree. C. and a tensile strength of 34.0 MPa (4927
psi) at 40% elongation.
[0089] Preparation G--Preparation of a Silyl Terminated
Sulfo(Polyester-Urethane) with Tg of 28.degree. C.
[0090] A sulfopolyester diol was prepared by heating 1 mole of
DMSSIP with 4 moles of polyethylene glycol of molecular weight 400
substantially according to the procedure of Preparation A except
that the reagents were charged as follows. A mixture of DMSSIP
(277.7 g, 0.94 mol), polyethylene gylcol (1500 g, 3.75 mol,
available from Union Carbide Corp.) was heated at 150.degree. C.
under vacuum for 1 hour, then nitrogen was admitted to the system
and tetrabutyl titanate (1.33 g, available from Aldrich) was added.
After heating at 220.degree. C. for 4 hours and distilling methanol
from the reaction mixture, the temperature was reduced to
175.degree. C. and vacuum was applied for 30 minutes. The hydroxyl
equivalent weight of the product sulfopolyester diol was determined
to be 284 by the method of Preparation A.
[0091] A silyl terminated sulfo(polyester-urethane) was prepared
from this sulfopolyester diol substantially according to the
procedure of Preparation B except that the reagents were charged as
follows:
[0092] The sulfopolyester diol described above (81.8 g, 0.14 mol),
polycaprolactonediol (PCP 0201.TM., 47.2 g, 0.09 mol), ethylene
glycol (14.9 g, 0.24 mol), isophorone diisocyanate (113.4 g, 0.51
mol), and 3-aminopropyltriethoxysilane (8.9 g, 0.04 mol) were
allowed to react. Modulated Differential Scanning Calorimetry
(MDSC) and tensile property analyses made of a spun cast film
produced from the dispersion indicated that the polymer had a Tg of
28.degree. C. and a tensile strength of 18.6 MPa (27.04 psi) at
702% elongation.
[0093] Preparation H--Preparation of a Silyl Terminated
(Polyester-Urethane) Substituted with Carboxy (CO.sub.2.sup.-)
Groups Instead of Sulfo (SO.sub.3.sup.-) groups.
[0094] A mixture of Tone.TM. A249 (163.4 g, 0.075 mol; Tone A249 is
available from Union Carbide and is a monoacid functional diol with
hydroxyl equivalent weight of 1079 that is prepared by chain
extending dimethylolpropionic acid with epsilon-caprolactone),
polycaprolactonediol (PCP.TM. 0201, 58.9 g, 0.11 mol), ethylene
glycol (14.9 g, 0.24 mol), isophorone diisocyanate (105.9 g, 0.48
mol), and dibutyltin dilaurate (0.20 g, 0.3 mmol) were allowed to
react in acetone until the isocyanate equivalent weight of the
product reached 3179. Then a mixture of
3-aminopropyltriethoxysilane (18.0 g, 0.081 mol) and triethylamine
(7.8 g, 0.077 mol) were added, followed by water (675 mL).
Distillation of acetone and some water from the mixture left a
dispersion (42% solids) of the carboxy substituted silanol
terminated (polyester-urethane) in water. Modulated Differential
Scanning Calorimetry (MDSC) and tensile property analyses made of a
spun cast film produced from the dispersion indicated that the
polymer had a Tg of 38.degree. C. and a tensile strength of 5.1 MPa
(742 psi) at 454% elongation.
[0095] Preparation I--Preparation of a Silyl Terminated
Sulfo(Polyester-Urethane) from a Sulfopolyester diol Different from
the Sulfopolyester diols Described in Preparation A and Preparation
G.
[0096] The sulfopolyester diol used in this trial was Witco.TM. UCX
SSTG-112-30, available from Crompton Corporation.
[0097] A mixture of Witco sulfo diol UCX SSTG-112-30 (146.7 g, 0.15
mol) polycaprolactonediol (PCP 0201.TM., 13.1 g, 0.025 mol),
ethylene glycol (10.9 g, 0.18 mol), isophorone diisocyanate (86.1
g, 0.39 mol), and dibutyltin dilaurate (0.15 g, 0.2 mmol) were
allowed to react in acetone until the isocyanate equivalent weight
of the product reached 4558. Then 3-aminopropyltriethoxysilane
(11.0 g, 0.05 mol) was added, followed by water (300 mL).
Distillation of acetone and some water from the mixture left a
dispersion (44% solids) of the silyl terminated
sulfo(polyester-urethane) in water. Modulated Differential Scanning
Calorimetry (MDSC) and tensile property analyses made of a spun
cast film produced from the dispersion indicated that the polymer
had a Tg of 6.degree. C. and a tensile strength of 12.3 MPa (1785
psi) at 440% elongation.
[0098] In the Examples, weight % is relative to weight of solids in
the dispersion.
EXAMPLE 1 (COMPARATIVE)
[0099] This example shows that the silyl terminated
(polyester-urethane)s of Preparations B through I, and two
commercially available non-silyl terminated waterbome polyurethane
dispersions, Bayhydrol.TM. 123 (available from Bayer Corporation),
and NeoReZ.TM. R-9679 (available from NeoResins, Wilmington, Mass.)
produced clear coatings on glass that were not peelable from the
glass.
[0100] In separate trials, approximately 15 mL of the dispersion of
the silyl terminated (polyester-urethane) of Preparations B through
I or the polyurethane dispersions Bayhydrol.TM. 123 and NeoReZ.TM.
R-9679 were applied to an eight-path wet film applicator device,
available from the Paul N. Gardner Co., Inc., Pompano Beach, Fla.,
and coated onto glass plates (10 cm by 20 cm by 0.48 cm; 4 inches
by 8 inches by {fraction (3/16)} inches thick) at wet thicknesses
of about 0.05 to 0.5 mm (2 to 20 mil) and widths of about 9 cm (3.5
in). When dry, the clear, tough coatings could be scrapped off the
glass in small sections with a razor blade, but they could not be
peeled from the glass.
EXAMPLE2
[0101] This example shows that when glycerol was added to the
dispersions of the silyl terminated (polyester-urethane)s of
Preparations B through I, and to two commercially available
non-silyl terminated waterbome polyurethane dispersions, Bayhydrol
123 and NeoRez R9679, the dispersions produced clear coatings on
glass that were easily removed in a sheet by peeling from the
glass.
[0102] To 100 g of the silyl terminated sulfo(polyester-urethane)
of Preparation B were added 2.4 g (5 weight percent) of glycerol.
The mixture was agitated briefly by shaking, then allowed to stand
at room temperature for 1 hour. The dispersion was coated onto
glass plates at wet thicknesses of about 0.05 to 0.5 mm (2 to 20
mil) and allowed to dry to form clear, tough coatings which could
be easily removed in a sheet by peeling from the glass plate. These
examples were repeated except that 10 weight percent glycerol was
added to the silyl terminated sulfo(polyester-urethane) of
Preparation B. The dispersions were coated on glass plates as
before and allowed to dry. The coatings could be easily peeled from
the glass plate. The experiments were repeated with the silyl
terminated sulfo(polyester-urethane)s of Preparations C through I
and with the commercially available waterborne polyurethane
dispersions. All coatings were easily peeled from the glass
plates.
EXAMPLE 3
[0103] This example shows that the amount of force required to
remove the dry, peelable coating varies with the amount of glycerol
that was added to the dispersion. Peel adhesion (ASTM D 3330-78;
PSTC-1 (11/75)) is the force required to remove a coated test
specimen from a test panel measured at a specific angle and rate of
removal. Peel adhesion was measured with an IMASS SP-2000 peel
testing instrument, available from Instrumentor's, Inc.,
Strongsville, Ohio. In the trials, this force was expressed in
Newtons per decimeter width (N/dm) of coated sheet and is the
average of four determinations. The procedure followed was:
[0104] 1) The polyurethane dispersion was coated onto a clean glass
test plate (or other substrate) and completely dried. The coating
was cut into 26 mm wide strips, and the end of the strip was peeled
from the substrate.
[0105] 2) The free end of the specimen was doubled back nearly
touching itself so the angle of removal was 180.degree.. The free
end was attached to the adhesion tester scale.
[0106] 3) The glass test plate was clamped in the jaws of the
tensile testing machine which moved the plate away from the scale
at a constant rate of 0.3 meters per minute.
[0107] 4) The scale reading in Newtons ("Peel Value") was recorded
as the coating was peeled from the glass surface.
1 Wt % Peel Release Release avg, Trial Additive Additive Dry Film
Thickness N/dm 3-1 glycerol.sup.a 1 0.2 mm (8 mil) 147.5 3-2
glycerol.sup.a 3 0.2 mm (8 mil) 82.9 3-3 glycerol.sup.a 7 0.2 mm (8
mil) 4.8 3-4 glycerol.sup.a 9 0.2 mm (8 mil) 2.8 3-5 glycerol.sup.b
5 0.13 mm (5 mil) 1.4 3-6 glycerol.sup.b 10 0.2 mm (8 mil) 1.3 3-7
glycerol.sup.b 20 0.13 mm (5 mil) 1.6 3-8 glycerol.sup.c 5 0.05 mm
(2 mil) 2.8 .sup.asilyl terminated sulfo(polyester-urethane) of
Preparation C with a Tg of 12.degree. C. was used in this Example.
.sup.bsilyl terminated sulfo(polyester-urethane) of Preparation B
with a Tg of 30.degree. C. was used in this Example. .sup.csilyl
terminated sulfo(polyester-urethane) of Preparation I with a Tg of
6.degree. C. was used in this Example.
EXAMPLE 4
[0108] This example shows the amount of force required to peel the
coating of the silyl terminated sulfo(polyester-urethane) of
Preparation C with a Tg of 12.degree. C. containing 5 weight
percent glycerol from various substrates at various film
thicknesses.
2 Peel avg, Trial Substrate Dry film thickness N/dm 4-1 glass 0.05
mm (2 mil) 3.7 4-2 glass 0.10 mm (4 mil) 3.9 4-3 glass 0.20 mm (8
mil) 3.4 4-4 glass 0.30 mm (12 mil) 4.8 4-5 aluminum 0.10 mm (4
mil) 25.6 4-6 polyester 0.10 mm (4 mil) 6.0 4-7 ceramic tile 0.10
mm (4 mil) 2.8
EXAMPLE 5
[0109] This example shows the amount of force required to peel the
coating of the silyl terminated sulfo(polyester-urethane) of
Preparation C with a Tg of 12.degree. C. containing other release
additives than glycerol from a glass substrate. In all trials, film
thickness was 0.20 mm (8 mil).
3 Wt % Peel Release avg, Trial Release Additive Additive N/dm 5-1
SC-PDMS-EO.sup.a 5 24.1 5-2 SC-PDMS-EO.sup.a 4 62.7 5-3
SC-PDMS-EO.sup.a 6 77.4 5-4 SC-PDMS-EO.sup.a 7 81.8 5-5
SC-PDMS-EO.sup.a 8 88.3 5-6 SC-PDMS-EO.sup.a 10 50.6 5-7
Block-PDMS-EO.sup.b (1) 5 33.0 5-8 Block-PDMS-EO.sup.c (2) 5 63.0
5-9 PEG 600.sup.d 5 94.0 5-10 PEG 2000.sup.e 5 43.1 5-11
triethylene glycol.sup.f 5 153.3 5-12 PEG 2000 monomethyl 5 64.1
ether.sup.f 5-13 PEG 5000 mono 5 32.3 methyl ether.sup.f 5-14
pentaerythritol 5 92.3 ethoxylate (1:3).sup.g 5-15 pentaerythritol
5 62.1 ethoxylate (1:5).sup.h 5-16 pentaerythritol 5 60.0
ethoxylate (1:15).sup.i 5-17 ethylene glycol.sup.f 5 j 5-18
Diethylene glycol.sup.f 5 j 5-19 Jonwax .TM. 26.sup.k 5 121.2 5-20
Jonwax 26.sup.k 10 108.2 5-21 Actrasol .TM. C75.sup.l 5 146.8 5-22
Actrasol C75.sup.l,m 5 47.5 .sup.aSC-PDMS-EO is
poly[dimethylsiloxane-co-methyl(3-hydroxypropyl)siloxane]-graft-poly(ethy-
lene/propylene glycol); Aldrich catalog number 45,798-1
.sup.bBlock-PDMS-EO (1) is poly(dimethylsiloxane) ethoxylated,
hydroxypropoxylate end-capped; Aldrich catalog number 48,271-4
.sup.cBlock-PDMS-EO (2) is poly(dimethylsiloxane) ethoxylated,
dihydroxy terminated; Aldrich catalog number 48,322-2 .sup.dPEG
.TM. 600 is poly(ethylene glycol) of 600 number average molecular
weight, available from Aldrich. .sup.ePEG 2000 is poly(ethylene
glycol) of 2000 number average molecular weight, available from
Aldrich. .sup.favailable from Aldrich. .sup.gpentaerythritol
ethoxylate (1:3) is pentaerythritol ethoxylated with 3 moles of
ethylene oxide, number average molecular weight 270, available from
Aldrich. .sup.hpentaerythritol ethoxylate (1:5) is pentaerythritol
ethoxylated with 5 moles of ethylene oxide, number average
molecular weight 355, available from Perstorp Polyols, Inc.,
Toledo, OH. .sup.ipentaerythritol ethoxylate (1:15) is
pentaerythritol ethoxylated with 15 moles of ethylene oxide, number
average molecular weight 797, available from Perstorp Polyols,
Inc., Toledo, OH. .sup.jadhesion was too great for films to be
peeled from the substrate. .sup.kJonwax 26 is a 26% solids
polyethylene/paraffin wax emulsion, available from S.C. Johnson
Company, Racine, WI; weight percent of the Jonwax 26 used with the
silyl terminated sulfo(polyester-urethane) refers to weight of
Jonwax 26 solids relative to urethane dispersion solids.
.sup.lActrasol C75 is a sulfated castor oil available from
Actrachem, Bedford Park, IL. .sup.msilyl terminated
sulfo(polyester-urethane- ) of Preparation B with a Tg of
30.degree. C. was used in this example.
EXAMPLE 6
[0110] This example shows the amount of force required to peel the
coating of some commercially available non-silyl terminated
waterbome polyurethane dispersions containing 5 weight percent
glycerol from a glass substrate. In all trials, film thickness was
0.13 mm (5 mil).
4 Trial Polyurethane Dispersion Peel avg, N/dm 6-1 Bayhydrol 110
7.2 6-2 Bayhydrol 123 4.3 6-3 Bayhydrol PR 240 4.2 6-4 Bayhydrol
140 AQ 4.0 6-5 Witcobond W-232 1.9 6-6 Witeobond W-505 6.0 6-7
Witcobond W-507 0.5 6-8 NeoRez R-972 2.0 6-9 NeoRez R-960 1.4 6-10
NeoRez R-9367 1.7 6-11 NeoRez R-9649 0.6 6-12 NeoRez R-9679 0.9
EXAMPLE 7
[0111] This example shows the preparation of a rheologically
modified (thickened) formulation with good wetting characteristics
that was useful for producing thick coatings or for coating
surfaces with low surface energy or for coating objects by
dipping.
[0112] To 12.1 kg of the silyl terminated sulfo(polyester-urethane)
dispersion of Preparation B (46% solids, viscosity of 52 centipoise
as measured with a Brookfield Model DV-II+viscometer, available
from Brookfield Engineering Laboratories, Inc., Middleboro, Mass.
with an LV-3 spindle at 50 rpm) in a 19 liter (5 gallon) carboy
were added glycerol (275 g), ethanol (1240 g), and Rheolate.TM. 278
(162 g; Rheolate 278 is a rheological modifier available from
Rheox, Inc., Hightstown, N.J.). The mixture was agitated for one
hour by tumbling and then allowed to stand overnight at room
temperature. Viscosity of the formulated dispersion was determined
to be 1812 centipoise as measured with the Brookfield LV-3 spindle
at 50 rpm.
[0113] A hemispherically shaped stainless steel stirring blade,
approximate measurements 18 cm by 3.8 cm by 0.15 cm thick (7 inches
by 1.5 inches by 0.0625 inches thick) and a 5 iron golf club head
were separately coated with the formulated dispersion by dipping.
The coatings were dried by placing the objects in an oven at a
temperature of 80.degree. C. for 1 hour. The objects were removed
from the oven and allowed to cool to room temperature. The coatings
(approximate film thickness 0.40-0.48 mm; 15-19 mil) were easily
removed by peeling from the objects.
EXAMPLE 8
[0114] This example shows the use of higher boiling oligomers of
glycerol to provide peelable coatings that remain removable when
the coatings have been heated for extended periods of time.
[0115] Dispersions with 5 weight percent of the specified release
additive were prepared from the silyl terminated
sulfo(polyester-urethane) dispersion of Preparation C and either
glycerol, triglycerol, or hexaglycerol. Triglycerol and
hexaglycerol are available from Hexagon Enterprises, Inc., under
the tradenames Hexapol G-3.TM. and Hexapol G-6.TM., respectively.
Hexapol G-3 has the following approximate composition: glycerol,
13%; diglycerol, 17%, triglycerol, 51%, tetraglycerol, 11%;
pentaglycerol, 5%; other glycerols, remainder. Hexapol G-6 has the
following approximate composition: diglycerol, 6%, triglycerol,
28%, hexaglycerol, 64%; other glycerols, remainder. The Hexapol G-3
and Hexapol G-6 materials were dissolved in a small amount of water
before mixing with the silyl terminated sulfo(polyester-urethane)
dispersion.
[0116] The dispersions were coated onto glass plates at wet
thicknesses of approximately 0.13 mm (5 mil), allowed to dry at
room temperature, and then the coated plates were placed in an oven
at 60.degree. C. Removability of the dried films was investigated
by periodically removing the coated plates from the oven, allowing
to cool to room temperature, slicing a 10 cm (0.4 inch) wide strip
of the film with a razor blade, and peeling the film from the
glass. If the films were peelable, the coated plates were then
returned to the oven for longer aging. It was found that the film
from the glycerol containing dispersion was still peelable up to
about 4 days in the 60.degree. C. oven. The film from the
dispersion containing Hexapol G-3 was peelable up to about 140 days
in 60.degree. C. oven, and the film from the dispersion containing
Hexapol G-6 remained peelable after 180 days in the 60.degree. C.
oven.
EXAMPLE 9
[0117] This example shows the use of the temporary protective
coatings of the present invention for the protection of plastic
sheeting during a thermoforming operation.
[0118] After the thermoforming operation, the protective coatings
were peeled from the thermoformed plastic sheeting. The
thermoforming device utilized was a Formech.TM. 450 vacuum
thermoforming machine, available from Formech, Inc., Kings Park,
N.Y. The plastic sheeting, approximately 20 cm by 20 cm (8 inches
by 8 inches), was coated with the dispersion at wet thicknesses of
approximately 0.25-0.30 mm (10-12 mil). Temperature controls of the
three heating zones of the Formech 450 were set to high. The mold
objects used were either a wooden wedge of approximate dimensions
7.6 cm by 3.8 cm by 3.8 cm (3 inches by 1.5 inches by 1.5 inches)
or a Teflon.TM. dome, 7.6 cm diameter by 2.5 cm high (3 inch by 1
inch). The coated pieces of plastic sheet were clamped into the
forming area of the thermoforming machine, either with the coated
side of the sheet up (towards the heating element, and away from
the mold object), or with the coated side of the sheet down
(towards the mold object). The heating element was moved into place
and the plastic sheeting was heated until it visibly started to
soften, as observed from the viewing port. The heating element was
then removed, the mold object was raised into the plastic sheet,
and vacuum was applied until the plastic sheeting conformed to the
mold object. Vacuum was released, and the coated, thermoformed
sheet was removed. After cooling to room temperature, the temporary
protective film could be peeled from the plastic sheeting. When the
plastic sheeting was thermoformed with the protective coating
towards the mold object, it was seen upon removal of the protective
coating film that the film had protected the surface of the plastic
sheeting from abrasion or loss of gloss.
[0119] The types of plastic sheeting (available from McMaster-Carr
Supply Co., Elmhurst, Ill.), used in these trials were
acrylonitrile-butadiene-s- tyrene (ABS, 0.60 mm (23 mil)
thickness), high impact polystyrene (HIPS, 0.80 mm (31 mil)
thickness), polypropylene (1.6 mm (63 mil) thickness), polyethylene
terephthalate co-polymer (PETG, 1.6 mm (63 mil) thickness),
polycarbonate (1.6 mm (63 mil) thickness), polymethyl methacrylate
(PMMA, 0.80 mm (31 mil) thickness), and polyvinyl chloride, type 1
(PVC, 1.6 mm (63 mil) thickness).
[0120] The following table indicates the types of plastic
substrates that were coated with the temporary protective coatings
of the present invention and then thermoformed. The protective
coating films were easily peeled from the plastic substrates.
5 Trial Substrate Coating formulation Dry film thickness 9-1 ABS AA
0.05 mm, 2 mil.sup.a 9-2 ABS AA 0.15 mm, 6 mil.sup.b 9-3 ABS AA
0.15 mm, 6 mil.sup.c 9-4 ABS BB 0.15 mm, 6 mil.sup.c 9-5 ABS CC
0.15 mm, 6 mil.sup.c 9-6 ABS DD 0.15 mm, 6 mil.sup.c 9-7 ABS EE
0.15 mm, 6 mil.sup.c 9-8 ABS FF 0.15 mm, 6 mil.sup.c 9-9 ABS
GG.sup.e 0.15 mm, 6 mil.sup.c,d 9-10 ABS HH.sup.e 0.15 mm, 6
mil.sup.c 9-11 ABS II.sup.e 0.15 mm, 6 mil.sup.c 9-12 ABS JJ.sup.e
0.15 mm, 6 mil.sup.c 9-13 ABS KK.sup.e 0.15 mm, 6 mil.sup.c 9-14
ABS LL.sup.e 0.15 mm, 6 mil.sup.c 9-15 ABS MM.sup.e 0.15 mm, 6
mil.sup.c 9-16 ABS NN.sup.e 0.15 mm, 6 mil.sup.c 9-17 ABS OO.sup.e
0.15 mm, 6 mil.sup.c 9-18 ABS PP.sup.e 0.15 mm, 6 mil.sup.c,d 9-19
ABS QQ.sup.e 0.15 mm, 6 mil.sup.c,d 9-20 ABS RR.sup.e 0.15 mm, 6
mil.sup.c,d 9-21 HIPS FF 0.15 mm, 6 mil.sup.c 9-22 PETG EE 0.20 mm,
8 mil.sup.c 9-23 polycarbonate EE 0.20 mm, 8 mil.sup.c 9-24 PMMA EE
0.20 mm, 8 mil.sup.c 9-25 polypropylene DD 0.20 mm, 8 mil.sup.c AA
= coating formulation was prepared by mixing the silyl terminated
sulfo(polyester-urethane) of Preparation C with a Tg of 12.degree.
C. (420 g of a 45% solids dispersion) with glycerol (19 g), ethanol
(42 g), and Rheolate .TM. 278 (5.7 g). BB = coating formulation was
prepared by mixing the silyl terminated sulfo(polyester-urethane)
of Preparation C with a Tg of 12.degree. C. (420 g of a 45% solids
dispersion) with glycerol (9 g), Hexapol G-3 (9 g), ethanol (42 g),
and Rheolate 278 (5.7 g). CC = coating formulation was prepared by
mixing the silyl terminated sulfo(polyester-urethane) of
Preparation C with a Tg of 12.degree. C. (420 g of a 45% solids
dispersion) with Hexapol G-3 .TM. (19 g), ethanol (42 g), and
Rheolate 278 (5.7 g). DD = coating formulation was prepared by
mixing the silyl terminated sulfo(polyester-urethane) of
Preparation C with a Tg of 12.degree. C. (420 g of a 45% solids
dispersion) with glycerol (9 g), Hexapol G-6 .TM. (9 g), ethanol
(42 g), and Rheolate 278 (5.7 g). EE = coating formulation was that
of Example 7. FF = coating formulation was prepared by mixing the
silyl terminated sulfo(polyester-urethane) of Preparation B with a
Tg of 30.degree. C. with 5 weight percent (relative to percent
solids) of glycerol. GG = coating formulation was prepared by
mixing Bayhydrol 123 (100 g) with glycerol (4.0 g), ethanol (10 g),
and Rheolate 278 (1.2 g). HH = coating formulation was prepared by
mixing Bayhydrol 110 (50 g) with glycerol (2.0 g), ethanol (5 g),
and Rheolate 278 (0.6 g). II = coating formulation was prepared by
mixing Bayhydrol PR240 (50 g) with glycerol (2.0 g), ethanol (5 g),
and Rheolate 278 (0.6 g). JJ = coating formulation was prepared by
mixing Bayhydrol 140AQ (50 g) with glycerol (2.0 g), ethanol (5 g),
and Rheolate 278 (0.6 g). KK = coating formulation was prepared by
mixing NeoRez R-9679 (75 g) with glycerol (3 g), ethanol (7.5 g),
and Rheolate 278 (0.9 g). LL = coating formulation was prepared by
mixing NeoRez R-960 (50 g) with glycerol (1.6 g), ethanol (5 g),
and Rheolate 278 (0.5 g). MM = coating formulation was prepared by
mixing NeoRez R-972 (50 g) with glycerol (1.7 g), ethanol (5 g),
and Rheolate 278 (0.5 g). NN = coating formulation was prepared by
mixing NeoRez R-9649 (50 g) with glycerol (1.8 g), ethanol (5 g),
and Rheolate 278 (0.5 g). OO = coating formulation was prepared by
mixing NeoRez R-9637 (50 g) with glycerol (1.8 g), ethanol (5 g),
and Rheolate 278 (0.5 g). PP = coating formulation was prepared by
mixing Witcobond W-232 (50 g) with glycerol (1.6 g), ethanol (5 g),
and Rheolate 278 (0.5 g). QQ = coating formulation was prepared by
mixing Witcobond W-505 (50 g) with glycerol (1.6 g), ethanol (5 g),
and Rheolate 278 (0.6 g). RR = coating formulation was prepared by
mixing Witcobond W-507 (50 g) with glycerol (3.0 g), ethanol (5 g),
and Rheolate 278 (0.9 g).
[0121] a coated side was away from mold object (wooden wedge).
[0122] b coated side was towards the mold object (wooden
wedge).
[0123] c coated side was towards the mold object (Teflon dome).
[0124] d film could only be removed in small sections, it was too
elongatable to be easily peeled in a large section from the
ABS.
[0125] e non-silyl terminated polyurethane dispersion.
EXAMPLE 10
[0126] This example shows the use of a silyl terminated
sulfo(polyester-urethane) dispersion including glycerol to provide
removable coatings on thermoplastic films.
[0127] A silyl terminated sulfo(polyester-urethane) dispersion was
prepared essentially as described in Preparation B except as
follows:
[0128] A mixture of the sulfopolyesterdiol of Preparation A with a
hydroxyl equivalent weight of 323 (34.1 kg, 52.8 mol), PCP 0201
(15.2 kg, 28.7 mol), ethylene glycol (4.1 kg, 66 mol), isophorone
diisocyanate (36.5 kg, 164.2 mol), and acetone (96 kg) was heated
to 85.degree. C. and held at this temperature under 377 KPa of
pressure. The temperature and pressure were then reduced to
60.degree. C. and 115 KPa, respectively, and
3-aminopropyltriethoxysilane (5.4 kg, 24.6 mol) was added to the
resulting mixture and allowed to react with the mixture for 15
minutes. The resulting acetone solution and deionized water were
metered at 5.8 kg/min and 2.9 kg/min, respectively, into a
high-shear mixing cavity of a Silverson 275 LS rotor stator mixer
(Silverson Machines, Inc. of East Longmeadow, Mass.), forming a
dispersion. The acetone was then distilled from the mixture under
reduced pressure to produce a dispersion (48% solids) of silyl
terminated sulfo(polyester-urethane) in water.
[0129] Dispersions with approximately 2.5 and 5 weight percent
glycerol in the above silyl terminated sulfo(polyester-urethane)
dispersion were prepared. These were coated out on 3M Radiant
Mirror Film.TM. (66 micrometer poly(ethylene
naphthalenedicarboxylate) multilayer film available from 3M, St.
Paul, Minn.) (PEN) and 3M Scotchpar.TM. (50.8 micrometer
poly(ethylene terephthalate) film available from 3M, St. Paul,
Minn.) (PET) using a number 36 wire-wound coating rod (available
from RD Specialties, Webster, N.Y.). The resulting coated films
were placed in a 121.degree. C. oven for one minute. After allowing
the coated films to return to room temperature, all of the
resulting dry coatings were found to be relatively easy to remove
by peeling the coating from the film. Dry coating thickness was
found to be about 34 micrometers when one pass with the coating rod
was used. Thicker coatings were also made using two and three
passes with the coating rod (approximately 68 micrometers and 102
micrometers, respectively) with oven drying as above after each
pass. In general, it was found that the thicker the coating, the
easier it was to peel from the film. All coatings were peelable by
hand.
EXAMPLE 11
[0130] This example shows the use of the temporary protective
coatings of the present invention for the protection of
thermoplastic films before, during, and after biaxial orientation.
After biaxial orientation the protective coatings were stripped
from the oriented film using an adhesive tape to grip the film
because of the thinness of the resulting protective coating.
[0131] Dispersions with 1.25, 2.5, 3.75, and 5 weight percent
glycerol in the silyl terminated sulfo(polyester-urethane)
dispersion of Example 10 were prepared. The resulting
glycerol-containing dispersions were coated onto 1.02 mm thick
poly(ethylene terephthalate) cast web prepared by extruding the
poly(ethylene terephthalate) onto a cooled roll and collecting the
resulting film on a roll. The dispersions were coated on the film
with a coating rod and dried as above in Example 10. The resulting
coated films were then stretched in a laboratory biaxial stretching
device to a total film stretch ratio of 6:1, (2:1 in the transverse
direction and 3:1 in the machine direction). Final thicknesses of
the resulting coatings were approximately 5 to 8 micrometers. The
coatings were contacted with Scotch.RTM. 351 tape (available from
3M, St. Paul, Minn.) and then peeled from the films by pulling the
tape. All of the coatings were easily peeled from the films.
EXAMPLE 12
[0132] Dispersions with 2.5 weight percent of the specified release
additive were prepared from the silyl terminated
sulfo(polyester-urethane- ) dispersion of Example 10 and either
glycerol, poly(ethylene glycol) of 400 number average molecular
weight, poly(ethylene glycol) methyl ether of 350 number average
molecular weight, pentaerythritol ethoxylated with 3 moles of
ethylene oxide of 270 number average molecular weight, or
hexaglycerol.
[0133] The resulting dispersions were coated onto PEN film and
dried at either 143.degree. C. for 3 minutes or 221.degree. C. for
20 seconds. Various dry coating thicknesses were utilized, ranging
from 6 to 51 micrometers. All of the coatings were peeled from the
films.
[0134] Various modifications and alterations that do not depart
from the scope band intent of this invention will become apparent
to those skilled in the art. This invention is not to be unduly
limited to the illustrative embodiments set forth herein.
* * * * *