U.S. patent application number 11/346129 was filed with the patent office on 2006-06-15 for merchandisers having anti-fog coatings and methods for making the same.
This patent application is currently assigned to Hussmann Corporation. Invention is credited to Edward A. Bernheim, Sesha C. Madireddi, Benjamin W. Raglin, John R. Roche.
Application Number | 20060127586 11/346129 |
Document ID | / |
Family ID | 29272948 |
Filed Date | 2006-06-15 |
United States Patent
Application |
20060127586 |
Kind Code |
A1 |
Roche; John R. ; et
al. |
June 15, 2006 |
Merchandisers having anti-fog coatings and methods for making the
same
Abstract
A variety of refrigerators and merchandisers having glass or
plastic substrates that are substantially fog-resistant are
provided. For example, refrigerator doors having a substantially
transparent substrate including an anti-fog coating on at least a
portion thereof are provided. The portion of the substrate may
substantially not fog when the portion has an initial surface
temperature and is then exposed to a moist air ambient with a
dewpoint temperature equal to or greater than the surface
temperature for a period of time. The surface temperature may be
less than about 0.degree. C. and the period of time may be greater
than about 6 seconds.
Inventors: |
Roche; John R.; (Ballwin,
MO) ; Madireddi; Sesha C.; (Maryland Heights, MO)
; Bernheim; Edward A.; (Corpus Christi, TX) ;
Raglin; Benjamin W.; (Mathis, TX) |
Correspondence
Address: |
MICHAEL BEST & FRIEDRICH, LLP
100 E WISCONSIN AVENUE
MILWAUKEE
WI
53202
US
|
Assignee: |
Hussmann Corporation
Bridgeton
MO
|
Family ID: |
29272948 |
Appl. No.: |
11/346129 |
Filed: |
February 2, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10341525 |
Jan 13, 2003 |
|
|
|
11346129 |
Feb 2, 2006 |
|
|
|
60377334 |
May 2, 2002 |
|
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|
Current U.S.
Class: |
427/372.2 |
Current CPC
Class: |
C08G 18/8074 20130101;
C08G 18/283 20130101; C08G 18/8093 20130101; C08G 18/4277 20130101;
C09D 175/04 20130101; C03C 17/322 20130101; A47F 3/0434 20130101;
C08G 18/4833 20130101; C08G 2290/00 20130101 |
Class at
Publication: |
427/372.2 |
International
Class: |
B05D 3/02 20060101
B05D003/02 |
Claims
1. A method of manufacturing a refrigerator door having a
substantially transparent substrate, the method comprising the acts
of: mixing a blocked hexamethylene diisocyanate and a polyol to
form a mixture; applying the mixture to at least a portion of the
substantially transparent substrate; and curing the mixture,
wherein the substrate is part of a refrigerator door or is used to
manufacture a refrigerator door.
2. The method of claim 1, wherein the diisocyanate is blocked by
3,5-dimethylpyrazole.
3. The method of claim 1, wherein the polyol comprises polyalkylene
glycols.
4. The method of claim 1, wherein the blocked hexamethylene
diisocyanate comprises 3,5-dimethylpyrazole blocked biuret of
hexamethylene diisocyanante.
5. The method of claim 1, wherein the blocked hexamethylene
diisocyanate comprises 3,5-dimethylpyrazole blocked biuret of
hexamethylene diisocyanante and the polyol comprises a block
polymer of polyethylene glycol and polypropylene glycol.
6. The method of claim 5, wherein the mixture comprises about 15%
to about 90% by weight 3,5-dimethylpyrazole blocked biuret of
hexamethylene diisocyanate and about 10.0% to about 85.0% by weight
block polymer of polyethylene glycol and polypropylene glycol.
7. The mixture of claim 6 further comprising dibutyl tin dilaurate
in an amount not greater than about 2% by weight.
8. The method of claim 1, wherein the mixture further comprises
dibutyl tin dilaurate.
9. The method of claim 8, wherein the mixture further comprises
diacetone alcohol.
10. The method of claim 1, wherein the mixture comprises about 15%
to about 90% by weight blocked hexamethylene diisocyanate and about
10.0% to about 85.0% by weight polyol.
11. The method of claim 10 further comprising dibutyl tin dilaurate
in an amount not greater than about 2% by weight.
12. The method of claim 1, wherein the mixture is applied to a
transparent substrate having a low-emissivity surface or a
low-emissivity coating thereon.
13. The method of claim 12, wherein the low-emissivity surface or
coating does not emit radiation between about 0.7 microns and about
2.7 microns.
14. The method of claim 1, wherein the cured mixture forms a
coating comprising a hydrophobic surface having a surface
tension.
15. The method of claim 14, wherein the surface tension of the
hydrophobic surface is less than about 58 dynes/cm.
16. The method of claim 14, wherein the surface tension of the
hydrophobic surface is less than about 39 dynes/cm.
17. The method of claim 14, wherein the surface tension of the
hydrophobic surface is less than about 26 dynes/cm.
18. The method of claim 1, wherein the portion of the substrate
does not substantially fog when the portion has an initial surface
temperature and is then exposed to a moist air ambient with a
dewpoint temperature equal to or greater than the surface
temperature for a period of time, wherein the surface temperature
is less than about 0.degree. C. and the period of time is greater
than about 6 seconds.
19. The method of claim 18, wherein the period of time is greater
than about five minutes.
20. The method of claim 1, wherein the portion of the substrate
does not substantially fog when the portion has an initial surface
temperature and is then exposed to a moist air ambient with a
dewpoint temperature equal to or greater than the surface
temperature for a period of time, wherein the surface temperature
is less than about -18.degree. C. and the period of time is greater
than about 6 seconds.
21. The method of claim 20, wherein the period of time is greater
than about five minutes.
Description
[0001] CROSS-REFERENCE TO RELATED APPLICATIONS
[0002] This application is a continuation of U.S. application Ser.
No. 10/341,525 filed Jan. 13, 2003, which claims the benefit of
priority under 35 U.S.C. .sctn. 119(e) of U.S. provisional
application no. 60/377,334 filed on May 2, 2002. The subject matter
of these prior applications is hereby fully incorporated by
reference.
BACKGROUND OF THE INVENTION
[0003] Low temperature merchandisers for frozen foods are designed
to maintain product temperatures in the display area less than
about 0.degree. C., and more particularly, less than or equal to
about -15.degree. C. for frozen food and below about -24.degree. C.
for ice cream, which in the past have required cooling coil
temperatures in the range of about -24.degree. C. down to about
-37.degree. C. Low temperature merchandisers are generally kept at
temperatures less than about 0.degree. C., and more particularly
below -21.degree. C. Medium temperature merchandisers maintain
non-frozen food items, at temperatures generally in the range of
about -1.degree. C. to about 5.degree. C.
[0004] Multi-shelf reach-in merchandisers for the storage and
display of fresh and frozen food products (including ice cream)
provide a generally vertical display of the product for greater
visibility and product accessibility to shoppers. In order to
prevent the escape of cold air into the shopping arena, a
transparent glass or plastic front door typically closes the
display area of the merchandisers. Glass and plastic are poor
thermal insulators. As a result, the doors are conventionally
formed by two or three spaced apart panes of glass, defining one or
two air spaces to increase the thermal insulation of the door. The
air spaces must be sealed for maximum insulating effect, and to
prevent entry of moisture into these air spaces. Moisture in the
air space condenses on the cold glass (or fogs) and obscures
viewing of the product in the merchandiser. In the past, sealing of
the air space has been accomplished by forming an "insulating glass
unit" or "IG unit" (sometimes called a "glass pack") which consists
of opposing glass panes (called "lights" or "lites") separated by a
metallic spacer secured by a suitable polymer (e.g., polysulfide,
polyisobutylene, etc.). The glass pack is placed in a metal frame
to complete the door. Thus, the door assembly process usually has
involved two separate steps of forming the sealed air spacers
because it has a good strength-to-weight ratio. In addition, metal
is an excellent moisture barrier and when used as a spacer seals
the air space from moisture for many years. However, metal has two
important drawbacks when used in reach-in-doors. The first is that
metal is a poor thermal insulator, and the second is that metal is
an excellent electrical conductor.
[0005] Conventional attempts to attenuate thermal conduction
through the metal in the door generally involve placing barriers in
the path of thermal conduction. Others have attempted to partially
or entirely replace the metal frame with a polymeric material
having a substantially lower thermal conductivity. However, it will
be noted that these attempts to reduce the metal used in the doors
have not eliminated the metallic spacers, nor have they replaced
the need for sealing glass lites before forming the frame.
[0006] The electrical conductivity of metal has also been a
hindrance because in the past electrical power was commonly used to
heat one or more surfaces of the glass lites in the door in order
to prevent condensation from collecting and obscuring vision
through the glass or plastic panes. For instance, the moisture in
the relatively warm ambient air of the store readily condenses on
the outside of the door if it was not heated. Also, when the door
is opened, moisture condenses on the cold inside glass surface.
Without heating, this condensation would not clear quickly and so
the view of the product in the merchandiser would be obscured.
Typically, two types of heaters have been used: (1) an anti-sweat
heater wire is applied to the perimeter of the metal frame; and (2)
a semi-conductive coating or film (e.g., fluorine-doped tin-oxide)
on the inner surface of the outer glass lite in the door is powered
by bus bars along opposing edges of the lite to provide an
electrical potential causing a current to flow through the
electrically-conductive film and produce heat. It has been
necessary to keep wiring and bus bars supplying the electric power
carefully insulated and isolated from the outer metal door frame
and the inner metal spacer. This means that a portion of the
heating film had to be eliminated at the edge margin where there
would be contact with metal. Avoiding electrical wiring and heating
is desired.
[0007] Therefore, new ways are sought of preventing or inhibiting
fogging of glass or plastic substrates when a door is exposed to a
cool environment (as discussed above and in more detail below), and
is then exposed to moist air ambient conditions upon being opened.
The cool inside surface of a refrigerator door may be exposed to an
ambient environment for a few seconds, thirty seconds, or longer,
depending on how long the customers or employees keep the door
open. In other words, new ways to optimize visibility for the
marketing of frozen food products are sought.
SUMMARY OF THE INVENTION
[0008] The invention provides a variety of fog-resistant coatings
that can be used in a variety of applications. More particularly,
the invention provides a variety of refrigerators and merchandisers
including glass or plastic substrates having coatings thereon,
rendering the substrates substantially fog-resistant.
[0009] In one aspect, for example, the invention provides a
refrigerator door comprising a substantially transparent substrate
having an anti-fog coating on at least a portion thereof. The
portion of the substrate may not substantially fog when the portion
has an initial surface temperature and is then exposed to a moist
air ambient with a dewpoint temperature equal to or greater than
the surface temperature for a period of time. The surface
temperature may be less than about 0.degree. C. and the period of
time may be greater than about 6 seconds.
[0010] In another aspect, the invention provides a refrigerator
door comprising a substantially transparent substrate having a
polyurethane coating thereon. The coating may have a surface
tension of less than about 60 dynes/cm.
[0011] In yet another aspect, the invention provides a method of
manufacturing a refrigerator door having a substantially
transparent substrate. The method includes mixing an isocyanate
with a polyol to form a mixture, applying the mixture to at least a
portion of the substantially transparent substrate, and then curing
the mixture. The substrate may be part of a refrigerator door or
the substrate may be used to manufacture a refrigerator door.
DESCRIPTION OF THE DRAWINGS
[0012] In the accompanying drawings that form a part of this
specification and wherein like numerals refer to like parts
wherever they occur:
[0013] FIG. 1 is a perspective view of a refrigerated reach-in
merchandiser;
[0014] FIG. 2 is a fragmentary perspective view of reach-in doors
and associated door casing of the merchandiser;
[0015] FIG. 3 is a greatly-enlarged fragmentary sectional view of a
three lite reach-in door taken in the plane of line 3-3 of FIG. 2,
and illustrating a preferred embodiment of a no-heat door having
both a hydrophilic film and low-E glass;
[0016] FIG. 4 is a fragmentary edge-on elevational view of a spacer
member for the reach-in doors, laid out flat and showing a metal
moisture sealing tape exploded above the spacer;
[0017] FIG. 5 is a fragmentary perspective view from a comer of the
spacer as installed on the glass lites, and partially exploded to
illustrate the assembly of the spacer ends by a spacer locking key
for the door;
[0018] FIG. 5A is a fragmentary perspective view from the opposite
side from FIG. 5;
[0019] FIG. 6 is a side elevation of the spacer locking key for the
spacer;
[0020] FIG. 6A is a greatly enlarged fragmentary view of the spacer
locking key taken from the right side of FIG. 6;
[0021] FIG. 7 is a fragmentary elevational view of the upper comer
of the reach-in door and door casing, with parts broken away to
show details of construction;
[0022] FIG. 7A is a fragmentary elevational view of the lower comer
of the reach-in door and door casing, with parts broken away to
show details of a torsion rod and lower hinge construction;
[0023] FIG. 8 is an exploded view showing a torsion rod adjustment
feature of the door;
[0024] FIG. 8A is cross-sectional view of FIG. 8, taken along line
8A-8A;
[0025] FIG. 9 is a view of the spacer as assembled around the glass
lites, and is broken away to illustrate the no-heat coating applied
to the exposed surface of the inner lite; and
[0026] FIG. 10 is a view of the spacer and glass lites from the
side opposite to FIG. 9 to show the outer lite exposed to the
ambient environment, and is broken away to illustrate a low-E
coating applied to the inner surface thereof.
DETAILED DESCRIPTION OF THE INVENTION
[0027] A wide variety of refrigerators, refrigerator doors, and
merchandisers may be used in conjunction with the present
invention. More particularly, the coatings disclosed below may be
used in conjunction with existing merchandisers using heaters (as
described above), or with merchandisers having no heaters. Examples
may include, but are not to be limited to, the refrigerated
merchandisers disclosed in U.S. Pat. Nos. 6,148,563 and 6,401,399,
each of which issued to Roche, and each of which is hereby fully
incorporated by reference. The following is a description of one
particular embodiment of a merchandiser or refrigerator, upon which
the coatings may be used. As used herein, "merchandisers" and
"refrigerators" may be used interchangeably. Again, the coatings
may be used with any refrigerators or merchandisers, and should not
be limited in application to the following example.
[0028] FIG. 1 shows one example of a low temperature reach-in
merchandiser, which is indicated generally at M for disclosure
purposes. The merchandiser has an outer insulated cabinet having a
front opening 11 (FIG. 2) defined by a cabinet casing C and closed
by doors D hingedly mounted on the casing C. More particularly, the
reach-in door D is mounted on the door casing C of the refrigerated
merchandiser M for swinging motion between a closed position in
which the door covers the encased front opening 11 in the cabinet
10 (center door in FIG. 2), and an open position for access to the
refrigerated display zone 13 within the cabinet (left door in FIG.
2). Multiple shelves 12 are selectively provided in the cabinet to
hold and display product in the refrigerated interior product zone
13. As shown in FIG. 2, the doors D are opened by handles H to
access the refrigerated zone 13 inside the merchandiser where
product is held for display. The refrigerated zone 13 may be
illuminated by lighting L mounted on mullions 14 of the door casing
C. These lights L are covered by diffusers 15 which spread the
light within the merchandiser display area 13, as will be described
more fully hereinafter.
[0029] FIG. 3 shows in more detail the low temperature door
including three panes, lites or substrates G of glass, namely an
inner lite 17, a middle lite 18 and an outer lite 19 that are
assembled and held together by the molded frame F. In a typical
three lite panel, the glass surfaces are generally sequentially
numbered from 1 to 6 starting from the outermost ambient store or
customer side. These correlate to the three lites 19, 18 and 17 as
surfaces 19a, 19b, 18a, 18b, 17a and 17b, respectively (FIG. 3).
The precise number of lites may differ, but typically at least one,
and more typically, at least two lites may be used in the door. The
anti-fog coatings described herein may be applied using application
techniques discussed in more detail below on any portion of any of
the three lites. Typically, however, the anti-fog coatings
described herein are applied on the exposed inner surface 17b of
the inner lite 17 next to the low temperature product area 13
(FIGS. 2, 3 and 9).
[0030] The refrigerators used herein may also selectively utilize
low-emissivity (Low-E) glass in combination with the inner glass 17
having an anti-fogging film 80. Use of low-E is not limited to this
particular embodiment. One or more of the lites (17, 18, or 19) may
comprise low-E glass or have low-E coatings thereon (as described
in more detail below), and in the three-lite door D of FIG. 3 both
lites 18 and 19 may be provided with low-E coatings 85. Although
any of the substrates 19a, 19b, 18a, 18b, 17a, 17b may comprise
low-E glass or be coated with a low-E coating (i.e. have low-E
properties), most typically at least one of substrates 19b, 18a,
18b, and 17a will have low-E properties. In one example, substrates
19b and 18b may have low-E properties, while in another example,
substrate 18a and 17a may possess low-E properties. Alternatively,
substrates 19b and 17a may comprise low-E glass or have a low-E
coating thereon. The lites may or may not be heated. Accordingly,
the efficacy of the door to resist fogging and/or to maintain high
transparency may depend on the character and application of the
surface coating described above (together with the no-metal door
frame now to be described).
[0031] The glass or plastic lites are held in parallel spaced
apart, generally face-to-face positions relative to each other by a
spacer S to form a basic glass panel subassembly preliminary to
molding the frame F. Referring to FIGS. 3 and 4, the spacer may be
made of polypropylene, or other suitable material, which has low
thermal and electrical conductivity in a three lite door, two
separator or spacer body portions 21 of the spacer S are inwardly
disposed between adjacent pairs of the glass lites (i.e. 17,18 and
18,19), and these portions 21 are joined together by an integral,
unitary outer wall portion 22. The number of separator portions
depends upon the number of glass lites to be spaced by the
separator portions. Each separator or spacer body portion 21 has a
generally D shaped or rectangular configuration with spaced side
walls 21a connected by a free inner wall 21b opposite to the outer
wall member 22. The side walls 21a are engaged in surface contact
with respective glass lites (17,18 or 18,19) adjacent to the free
edge margins 23 thereof. In addition, a sealing lip 23a may be
provided along the juncture of the outward side wall and free wall
(21 a, 21b) of each spacer body 21 as an additional assurance of
continuous sealing engagement of the spacer bodies 21 with the
respective inner surfaces 17a,19b of the outermost glass lites
17,19. Continuous sealing contact of the spacer around the lites
prevents molded material from encroaching the sealed air spaces 23b
between adjacent lites during formation of the door frame F.
[0032] The planar-outer wall 22 forms one wall of each spacer body
21 and has a connecting web 22a between the spacer bodies and also
projects laterally outwardly to form flanges 22h at the outer
longitudinal edges of the spacer. The laterally projecting flange
portions 22b abut against the outer peripheral edge margins 23 of
the inner and outer lites 17,19 in the door for additional sealing
and also to maintain the spacer in position under frame molding
pressure. Still referring to FIG. 3, the spacer bodies 21 are
typically hollow (24), but filled with a suitable desiccant
material 24a (e.g., molecular sieve) for trapping moisture.
[0033] Referring to FIG. 4, the spacer S is a flat extruded strip
with four angle-cut or chamfered notches 25 being formed in the
spacer body 21 corresponding to the four corners of the basic glass
panel for the door D. The spacer S forms an outer peripheral
covering for the three lites 17, 18, 19 by coming together at the
corners (in the fashion of a miter joint) when the spacer is
assembled around the lites so that the spacer segments extend
continuously along the sides and mate together through the comers.
The spacer S is constructed with five sequential segments
identified in FIG. 4 as 26a-26e, and being interconnected at the
angle cuts 25 by the continuous outer wall 22. Clearly, when the
spacer S is folded or bent during assembly with the glass lites,
the two alternate short segments 26b and 26d will be in opposed
relation and form the short horizontal top and bottom walls of the
panel. The long segment 26c will define the long vertical wall
margin of the panel that will become the outer free (unhinged)
handle margin of the door, and the two remaining segments 26a and
26e at the free ends 25a of the strip will close the inner hinged
vertical margin of the panel and may be joined together by a spacer
locking key 30.
[0034] As shown best in FIGS. 5, 5A, 6, 6A and 9, the locking key
30 has a main assembly or locking body section 31 (and originally
included an electrical connector section 32 for conventional
electrical heating of the inner lite 17). The main locking body
section 31 is constructed and arranged to mate with and join the
free ends 25a of the spacer S, and it is configured with spaced
separator body portions 31a and a connecting wall 31b with outer
flanges to match the configuration of the spacer 21. Connector
blocks or keys 31c project longitudinally from both ends of the
separator bodies 31 a, and these are sized to fit into the hollow
cavities 24 of the spacer bodies 21 (FIGS. 5, 5A and 6A). In
addition, the inner wall 21b of the spacer bodies 21 have an
orifice 31d adjacent to their free edge 25a, and each key 31c has a
chamfered locking detent 31c to snap lock into these holes 3 id and
form a secure interlock therewith. The reach-in door D incorporated
a heated glass lite (17) requiring an electrical hook-up that was
accommodated through an electrical connector section 32 and leads
50, 50a to connectors and bus bars constructed and arranged on the
door to provide the electrical heating field across the inner lite
17. However, since a non-heated door that still has excellent
anti-fogging or rapid clearing action may be provided, it is
possible to eliminate the electrical hook-up for heating the inner
panel 17 including the protruding electrical connector section
32.
[0035] The preferred reach-in door embodiment includes moisture
barrier tape 33 which is applied to the outer surface of the outer
wall 22 and flange 22b. This tape 33 may be an aluminum foil tape
or, may be a thin substantially non-metallic tape of
moisture-impervious metalized-polyester/polyethylene film that is
electrically non-conductive. Referring to FIGS. 3, 4 and 5, the
tape 33 has a main body 33a that covers the entire outer wall 22 of
the spacer S and has an edge wrap that extends around the outer
flange segments 22b and, preferably, onto the adjacent outer
surfaces of the inner and outer lites 17,19. Thus, as shown in FIG.
4, the tape 33 may be provided as a unitary one-piece main body
sheet 33a with integral edge wrap portions (33b) or as a series of
main body sheets or segments corresponding to the five sections
26a-26e of the spacer strip 21. The foil or film sheets 33a may be
applied to cover the outer wall 22 throughout its length so that
the outer spacer wall surface is covered before it is assembled
with the glass lites 17-19. In that event, the width of the tape or
film would be only slightly greater than the width of the outer
wall 22. The tape may wrap around and under the flanges 22b and
would be in contact with the peripheral edge of the outer lites
17,19 when installed. The locking key 30 is also covered with the
same film or tape 33c. The tape 33 provides a non-structural
moisture barrier to inhibit significant transfer or migration of
water vapor into the spaces 23b between the lites.
[0036] As indicated, the basic glass panel with assembled lites,
spacer and moisture barrier tape is encased in the outer molded
door frame F. As shown in FIG. 3, this frame F has a main body
portion 35 that surrounds the periphery of the glass panel
subassembly, and has an outer wall margin 35a and side walls 35b
that extend inwardly and capture the outer glass surface margins
(35c) of the inner and outer lites 17,19.
[0037] In use, the reach-in door D is mounted on the door casing C
of the refrigerated merchandiser M for swinging motion between a
closed position in which the door covers the encased front opening
11 in the cabinet 10 (center door in FIG. 2), and an open position
for access to the refrigerated display zone 13 within the cabinet
(left door in FIG. 2).
[0038] Referring to FIGS. 7 and 7A, the hinge for mounting the door
D are accommodated during the frame molding process by forming an
upper cylindrical opening 38 receiving a metal sleeve or bushing
38a and a lower cylindrical opening 39 receiving a sleeve or
bushing 39a. After completion of molding the frame F around the
glass lite subassembly, the upper bushing 38a preferably receives a
plastic sleeve 38b (FIG. 9) in which an upper hinge pin 40 is
slidably received for free turning movement so that this hinge pin
is free of any fixed connection to the molded frame F. The bushing
38a contains a compression spring 40a which biases the pin 40 for
vertical outward movement relative to the frame F so that the pin
projects upwardly to be received into an opening in an upper
mounting plate 40b attached by bolts 40c to the door casing C of
the merchandiser M. The bolts 40c are received through elongate
slots 40e. Located at offset positions in the upper mounting plate
40b to permit the upper mounting plate 40b to be moved laterally on
the door casing. In this way the pivot axis of the door D can be
adjusted for optimum alignment within the casing opening.
[0039] The upper bushing sleeve 38a for the upper hinge pin 40 may
be part of an upper reinforcing member 40g molded into the door
frame to rigidify and strengthen the frame E in the region of the
upper door mounting connection. The member 40g also provides a
hearing portion (41a) to receive a pivot pin 41b to connect one end
of a hold open bar 41 to the door. The hold open bar 41 limits the
maximum angle of opening of the door relative to the merchandiser,
and functions to hold the door fully open when needed (e.g., as for
stocking the merchandiser).
[0040] As shown in FIG. 7A, the lower hinge pin 43 is provided for
during the frame molding process by forming the lower cylindrical
opening 39 for the bushing 39a, and after the molding process a
plastic sleeve 39h is received in the metal bushing as a bearing
for the lower hinge pin 43 which is free of an fixed connection to
the molded frame F. The lower bushing 39a may be secured to a lower
reinforcing member 43a for reinforcing the frame F in the door
mounting area where the major weight of the door I) is translated
to the casing C. The lower end 43b of the hinge pin projects
outwardly below the frame F and is hexagonal (or otherwise shaped)
to have a non-rotational fit into a complementary opening 43c in a
casing bearing plate 43d bolted at 43e to the casing C, see FIG.
9A. Thus, the door D will turn on the lower hinge pin 43 as it is
opened and closed while the lower hinge pin is stationary relative
to the cabinet casing C.
[0041] FIGS. 8 and 8A show torsion rod assembly 144 for
self-closing of the door. The assembly 144 is accommodated in the
vertical opening 39 in the molded door frame F. The assembly 144
includes an upper torsion housing member 146 molded into the frame
F, a torsion rod 145 having an upper hook-end 145b received in the
housing member 146 and a lower end secured on a torque control
member 148, and a lower bearing plate 143d having a toothed ratchet
opening 143c therein. In this embodiment the vertical opening 139
is created with the sheath 139a at the time of molding the door
frame, as before. However, the upper housing member 146 is
constructed and arranged to receive the upper hook-end 145b of the
torsion rod with a sliding fit in the final assembly 144. Thus, the
housing member 146 is configured to provide a tubular section 146d
with a vertical opening 146a having an end section 146b to
accommodate the sleeve 139a and an extended opening 146c of
rectangular cross-section in which the hook-end 145b is received in
a fixed (relatively non-rotational) relationship with the door D
per se. The housing member 146 is also formed with an integral
rigid side section 146e extending laterally from the tubular
section 146d to act as an anchor in the molded frame F.
[0042] The hook-end 145b is bent over to facilitate holding the
torsion rod 145 from turning about its axis at the upper end within
the frame F. By bending the rod 145 back upon itself, the effective
width of the rod is doubled at the hook-end 145b. The two contact
points of the hook-end 145b which engage the walls of the housing
member 146 within the extended opening 146c are spaced apart for
additional mechanical advantage in resisting turning about the axis
of the torsion rod 145. Although bending of the torsion rod 145 to
form the hook-end 145b is shown, the same effect could be achieved
by initially forming the rod with a flat or wider upper (not
shown). For example, the upper end of the rod 145 (at least the
portion received in the extended opening 146c) could be
flattened.
[0043] The housing member 146 is designed for universal use with
right-hand or left-hand doors and is double-ended with a center web
146f extending across the side section 146e and through the center
of the tubular section 146d intermediate of the ends (146b). Thus,
the anchoring housing member 146 can be oriented for the side
section 146e to extend in either direction. The side section 146e
is constructed with a series of pockets or recesses 146g defined by
spaced webs or ribs 146h to receive a mass of mold material and
work with the forces on the housing member to prevent weakening or
destruction of the molded frame, as exerted by the torsion rod 145
during opening and closing of the door D through continuous use
over long time spans.
[0044] The torque control member 148 on the lower end of the
torsion rod 145 has a saw-toothed ratchet 148a with typical
vertical lock edges 148b and sloping cam surfaces 148c. A hexagonal
or like nut 148d is integral or locked to the ratchet 148a for
selective pre-tensionsing of the self-closing torque applied to the
door. More specifically, prior to insertion of the ratchet 148a
into the opening 143c in the lower bearing plate 143d, the nut 148d
is turned to twist the torsion rod 145 within the bushing 39a. The
ratchet 148a is then inserted into the opening 143c, with the teeth
of the ratchet engaging the teeth of the opening to hold the
torsion rod 145 in a pre-tensioned configuration.
[0045] It will thus be seen that the molded door D may eliminate
metal framing and provides better insulation and thermal properties
in closure of the low temperature product zone 13. In order to keep
the door lites clear of exterior condensation and/or to clear
interior condensation after the door has been opened, one of the
door lites and the inner surface of the outer Tile 19 may be heated
by applying an electrical potential across a transparent,
electrically conducting film on that inner surface. Alternatively,
only the inner surface 17a of the inner lite 17 would be heated and
thus the electrically conductive film would be applied to that
surface (17a). In addition, the space between adjacent lites may be
filled with a dry gas, such as argon or krypton, having low thermal
conductivity. The increased thermal resistance of that arrangement
may reduce concern over external condensation. Thus, the heated
surface was shifted to the inside lite where it was still needed
for door clearing. It was also believed that that embodiment was
more energy efficient since only about half the power was required
to clear the door in a commercially acceptable time.
[0046] The reach-in door D of this embodiment may or may not have
electrical heat applied thereto, but achieves commercially
acceptable performance levels utilizing an anti-fogging coating
(described in more detail below). The coating may be applied to any
portion of the lites 17, 18, 19, and may be applied to other
interior portions of the refrigerator, e.g., shelves or mirrors.
Typically, the coating is applied on the innermost surface 17b of
the inner lite 17 facing the product zone 13. The anti-fog coatings
may be used in conjunction with low-emissivity (low-E) glass or
coatings. Use of low-E glass or coatings on the lites is not
required, however. A variety of application techniques that are
well-known in the art, some of which are discussed below, may be
used on the doors.
[0047] Again, the anti-fog coatings described herein are compatible
with any refrigeration units having glass, plastic or similar
substrates, especially when those substrates are substantially
transparent. The anti-fog coatings work particularly well, however,
when used in conjunction with one or more other lites (e.g. 18 and
19) at least partially made from or comprising low-E glass or
coated with a low-E coating. The low-E glass may be selected to
meet two primary criteria: 1) high reflective capability as to the
infrared spectrum (thereby rejecting invisible radiant heat); and
2) high visibility transmittance (so that it does not obscure or
cloud visibility through it). Low-E coatings typically are
"interference" coatings of about one-fourth wave length with a
emissivity rating from "zero" identifying a perfect infrared
reflector to "one" which would be the least reflective and
undesirable material. There are a large number of such glass
coating materials having varying low-emissivity properties. Clear
window glass transmits radiation between 0.3 to 2.7 micron
wavelength. 95% of the energy in blackbody radiation is contained
within this spectrum. The visible spectrum is 0.4-0.7 microns.
Infrared radiation is 0.7 to 1000 microns. Thus, to reduce radiant
heat gain in a refrigerator, it is desirable to reflect the
non-visible 0.7 to 2.7 micron infrared radiation. Emissivity is the
inverse of reflectivity. Thus, a perfect emitter has an emissivity
of 1 and reflects nothing. Low-E glass and low-E coated glass or
plastic as used herein are meant to refer to glasses or plastics
that are designed not to emit (thus reflect) radiation above 0.7
microns. This may be achieved by applying a thin coating (typically
1/4 the desired wavelength) to the surface of the glass or plastic.
More specifically, the low-E glasses and plastics tend to possess a
hemispherical spectral emissivity over 0.7, and more particularly
from 0.7 to 2.7. Typically, several layers are used to reflect
greater percentage in the 0.7 to 2.7 micron range. The low-E
surfaces or coatings may have a visible transmittance of about 70%
to about 90%.
[0048] Low temperature and normal temperature merchandisers are
typically used in the storage and display of food products
merchandised in a supermarket or other food store having a
temperature and humidity controlled ambient atmosphere. The ASHRAE
design ambient for the best shopper comfort zone is about
24.degree. C. DB (dry bulb) with 55% RH (relative humidity). A low
temperature merchandiser (M) with a product zone (13) temperature
of -21.degree. C. will result in a surface temperature of
-18.degree. C. on the inner surface 17b of the inner door lite 17.
The resulting gradient across the door to the outer lite 19
depends, in part, on the use of low-E glass and store environment,
but in the above example of 24.degree. C. DB and 55% RH, the
resultant outer lite surface (19a) will have a temperature of about
15.degree. C. to 18.degree. C. Thus, it will be seen that there is
some transference of heat across the door D between the store
ambient and the cold product zone 13 even when the door is closed
and the zone 13 is shielded from the store. It is also clear that
the ambient heat and humidity will impinge on the cold inner lite
surface 17b when the door is opened by a customer, the immediate
effect being to tend to cause water condensation (and fogging) on
the inner cold surfaces of the door (and adjacent casing and into
the product zone).
[0049] Generally, the door D has an anti-fog coating applied to the
exposed inwardly facing surface 17b of the inner glass lite 17,
which may obviate the need for any electrical heating of any glass
lite. Hydrophilic coatings or films may act to increase the surface
energy of the substrate, thereby causing water condensate to sheet
out on the surface (as opposed to beading up). Thus, the moisture
condensation that occurs on this exposed cold inner lite surface
17b when the door D is opened, presents a transparent see-through
phenomenon as distinguished from a vision obscuring fog, and
rapidly clears. Typical examples of anti-fog hydrophilic coatings
(which may differ from the coatings having a hydrophobic surface
and hydrophilic interior described below) are hydrophilic polyester
films and hydrophilic titanium dioxide pyrolic coatings for glass
that are compounded and applied to meet certain favorable
performance criteria as compared with typical heated doors.
[0050] As indicated, it is desirable that coatings set forth herein
produce a substantially-no-fog result on the inner glass surface
17b during the door opening periods of most shoppers, and this
efficacy is enhanced by the use of low-E glass 85, particularly,
for the middle and outer lites 18 and 19. The door opening periods
may range from a second or two to several minutes or much longer.
Although the use of two low-E coatings is disclosed on surface 19b
(#2) of the outer lite and surface 18b (#4) of the middle lite, it
will be understood that the two low-E coatings may be applied to
surfaces 2 and 5 or surfaces 3 and 5 with equal effectiveness.
Further, in instances where the merchandiser M is placed in higher
humidity ambient environments, there will be a greater moisture
condensation on the film surface, in the case of the hydrophilic
coatings, which will sheet or spread out evenly and become a
no-fog, transparent layer of moisture due to the high affinity of
hydrophilic materials for water vapor. Such a moisture layer will
be attracted to the colder interior of the merchandiser and rapidly
and evenly absorbed or evaporated therein.
[0051] Typically, the hydrophilic materials of the invention
produce a hard, smooth impervious coating as through molecular
bonding at its interface with the glass lite 17. A hardness of
about 2 to 8 H (pencil hardness) is desirable. The hydrophilic
films depress the freezing point of that surface to prevent
freezing.
[0052] In addition to the hydrophilic coatings, a wide variety of
highly scratch-resistant coatings having a hydrophobic surface and
hydrophilic interior may also be used to inhibit fogging on the
substrate of the refrigerator or merchandiser. These coatings may
be applied in a similar fashion as discussed above to inhibit
fogging, thereby optimizing visibility for the marketing of frozen
foods. For example, polyurethane compositions may be used.
Polyurethane compositions of the present invention may be
non-fogging and water repellent, and may maintain excellent
abrasion resistance, clarity, and adhesive properties on most
plastics and glass. A hydrophilic layer of the composition
possesses a water-repellent surface due to the unique material
combinations put forth in the invention. Hydrophilic and
water-repellent properties are generally achieved without the
addition of fog-preventing surfactants or need for chain extenders.
This makes the anti-fog composition superior to other materials in
anti-fog properties. The composition system may comprise one or
more of the following: an isocyanate prepolymer having reactive or
blocked isocyanate groups or a blocked isocyanate, a water-soluble
or water dispersible polyol, any compatible organic solvents or
water (and emulsifier, if water-based), any required catalysts, and
rheological additives. The invention can be also cast in a
solvent-free state in order to produce a film, or casting molding
composition.
[0053] The coatings, which are the result of curing mixtures that
have been applied to a substrate, tend to possess permanent,
non-fogging properties and remain hard enough to be used in the
everyday situations required in applications such as refrigerator
doors, shelves and mirrors within a refrigerator, other interior
portions of a refrigerator, optical lenses, goggles, shields,
sunglasses, windshields, sunroofs, shelves, mirrors etc. These
coatings work particularly well when used in conjunction with the
low-E glass described above, particularly, in a merchandiser
application. By combining a porous, hydrophobic surface with a
hydrophilic base polymer, it is possible to obtain a composition
possessing excellent anti-fog characteristics and surface
hardness.
[0054] Composition hardness and adhesive properties may also be
significantly improved in order to adapt the coatings to especially
difficult substrates. Hydrophilic (anti-fog) properties can also be
varied to suit the end product's intended use. Solvent-free, liquid
compositions that can be used as coatings or in the casting of
molded elements, are also within the scope of the invention. The
desired properties of the coatings are discussed in more detail
below.
[0055] The polymeric composition exhibits excellent surface
hardness and water repellent properties without the need for chain
extenders or surfactant materials to provide the desired balance of
physical and non-fogging properties. Although most of the mixtures
do not employ surfactants or chain extenders, surfactants and chain
extenders may be used in some instances. Accordingly, many of the
coatings described herein are "substantially free" of chain
extenders or surfactant materials. In this instance, "substantially
free" means having less than about 3%, more particularly less than
about 1%, and more typically, 0.5% to 0% of chain extender or
surfactant. The hydrophobic nature of the surface reduces the
presence of water deposited on the surface. Any water that is
deposited thereon may be at least partially absorbed through the
porous surface layers and absorbed into the coating's hydrophilic
interior. This combination of hydrophilic and hydrophobic
properties provides a very effective non-fogging and scratch
resistant surface.
[0056] The composition system typically comprises an isocyanate
prepolymer with reactive isocyanate groups or a blocked isocyanate,
and a water-soluble or water dispersible polyol. The system may
further comprise, although it need not, appropriate organic
solvents or water, emulsifiers, and coalescent, catalysts, and
paint additives (typically at levels below 1% by weight). The
reaction of the isocyanate and the polyol forms a part hydrophilic
and part hydrophobic polyurethane composition when reacted and
cured under particular conditions. By varying the type of
isocyanate, the type and molecular weight of the polyol, the
percent solids of the material and the catalyst, the hardness, fog
resistance, efficacy, and other physical and chemical properties
can be varied.
[0057] More specifically, the coating may be the product of the
reaction, usually under heat, of an isocyanate prepolymer and a
polyalkylene glycol. Isocyanate adducts and prepolymers
particularly effective in the invention include blocked and
unblocked cyclic or aliphatic diisocyanates. Polyalkylene glycol
polymers that may be used include diols, multi-functional variants
such as tri- and tetrahydroxy glycols, branched ethylene
oxide/propylene glycol copolymers and block polymers of the above.
Catalysts may include the common organometallic materials normally
used to produce polyurethane substances. Specifically, dibutyl tin
dilaurate may be used as an acceptable catalyst. Other additions
include solvents, and rheological additives. The inclusion of
catalytic substances is pendent on the choice of polymeric
functionality and the intended cure schedule. Thus, some materials
function well without the usual polyurethane initiators.
[0058] These materials are described in more detail below.
[0059] Isocyanates Typically, the isocyanate prepolymers used to
prepare the coatings contain 2 or 3 isocyanate groups, although
more groups are certainly acceptable. Examples of isocyanate
systems include a biuret or an isocyanurate of a diisocyanate,
triisocyanate or polyisocyanate. The following are typical
diisocyanates prepolymers that may be used: hexamethylene
diisocyanate, diisophorone diisocyanate, and toluene diisocyanate.
Blocked isocyanates may also be used in order to address ingredient
limitations and stability problems.
[0060] Mixtures having the blocked polyisocyanates may be applied
using any of the application techniques discussed herein.
Typically, mixtures having the blocked polyisocyanates are cured or
heated after having been applied to a plastic or glass substrate.
During heating, the blocked polyisocyanates dissociate so that the
isocyanate groups become available to react with the active groups
of the polyols (discussed in more detail below), thereby leading to
substantial crosslinking and hardening of the coating. Blocked
isocyanates are isocyanates in which at least one isocyanate group
has reacted with a protecting or blocking agent to form a
derivative which will dissociate on heating to remove the
protecting or blocking agent and release the reactive isocyanate
group.
[0061] Examples of blocking agents for polyisocyanates include
aliphatic, cyclo-aliphatic or aralkyl monobydric alcohols,
hydroxylamines and ketoximes. Other examples of applicable blocking
agent functionalities include the following: oximes (compounds
containing the radical --CH(:N.OH)), pyrazoles, phenols and
caprolactams. Typical pyrazoles are 4 membered rings having the
following formula: ##STR1## Blocked isocyanates and combinations of
the above also produce effective formulations.
[0062] Most of these blocked polyisocyanates tend to dissociate at
temperatures of about 90.degree. C. to about 180.degree. C.
(160.degree. C.). Other blocked polyisocyanates, however, may
dissociate at lower temperatures, especially when used in the
company of a catalyst. For example, the temperature to which the
coated article must be heated may generally fall to about 100 to
140.degree. C. when using the polyisocyanates discussed below. The
presence of a catalyst may increase the rate of reaction between
the liberated polyisocyanate and the active hydroxyl group of the
polyol. Examples of blocked polyisocyanates having a lower
dissociation temperature include compounds having the following
formulas: R--Y.sub.m FORMULA A wherein R is a cycloaliphatic,
heterocyclic, m valent aliphatic, or aromatic residue and each Y,
which may be the same or different, is ##STR2##
[0063] Where R.sub.1 is, or, when n is more than 1, each R.sub.1,
which may be the same or different, is an alkyl, alkenyl, aralkyl,
N-substituted carbamyl, phenyl, NO.sub.2, halogen or ##STR3## group
where R.sub.2 is a C.sub.1-C.sub.4 alkyl group,
[0064] n is 0, 1, 2, or 3
[0065] and m is an integer >1, preferably 2-6.
[0066] When R.sub.1 represents an alkyl or alkenyl group it may
contain up to 4 carbon atoms. R.sub.1 may also be an aralkyl group,
wherein the aryl portion may be phenyl and that the alkyl portion
may contain 1 to 4 carbon atoms. When R.sub.1 is a halogen, it may
typically be chlorine or bromine.
[0067] The blocked polyisocyanate of the formula A is formed by
admixing the polyisocyanate R(NCO).sub.m with a sufficient quantity
of a pyrazole of the formula: ##STR4## such that the reaction
product contains substantially no free isocyanate groups and is a
urea of formula I. This reaction is exothermic and since the
reaction product will dissociate if the temperature is raised
sufficiently, cooling may be required to keep the temperature of
the reaction mixture down, preferably to 80.degree. C. or less.
[0068] Other blocking agents used in the present invention may be
pyrazoles of the formula: ##STR5## where R.sub.1 and n are as
defined above. Examples of the pyrazoles include, but are not
limited to, 3,5-dimethylpyrazole, 3-methylpyrazole,
4-nitro-3,5-dimethylpyrazole and 4-bromo-3,5-dimethylpyrazole.
[0069] Some of these pyrazoles can be made by converting
acetylacetone (AA) into a derivative that will react with hydrazine
to give the desired pyrazole as shown below:
AA+N.sub.a+CH.sub.2.dbd.CH
CH.sub.2Cl.fwdarw.Ac.sub.2CHCH.sub.2CH.dbd.CH.sub.2
AA+N.sub.a+PhCH.sub.2Cl.fwdarw.Ac.sub.2CHCH.sub.2Ph
AA+PhNCO.fwdarw.Ac.sub.2CHCONHPh
[0070] The polyisocyanate which is to be blocked may be any organic
polyisocyanate suitable for crosslinking compounds containing
active hydrogen, e.g., those listed above as well as aliphatics
including cycloaliphatic, aromatic, heterocyclic, and mixed
aliphatic aromatic polyisocyanates containing 2, 3 or more
isocyanate groups. The group R will normally be a hydrocarbon group
but substitution, e.g., by alkoxy groups is possible.
[0071] Other blocked isocyanates may include, but should not be
limited to, hexamethylene diisocyanate, toluene diisocyanate,
diphenylmethane diisocyanate, bis(methylcyclohexyl) diisocyanate,
oxime blocked hexamethylene diisocyanate, diethyl malonate blocked
toluene diisocyanate. The isocyanate may also be a biurate, e.g.,
defined as the partial reaction of a polyisocyanate with hydroxyl
or amine components to increase terminal isocyanate groups. All
isocyanates listed as Desmodur tradenames may also be used,
including, Desmodur 75, which is a hexamethylene diisocyanate.
[0072] Other isocyanate compounds may be, for example, ethylene
diisocyanate, propylene diisocyanate, tetramethylene diisocyanate,
decamethylene diisocyanate, dodecamethylene diisocyanate,
2,4,4-trimethylhexamethylene-1,6 diisocyanate, phenylene
diisocyanate, tolylene or naphthylene diisocyanate,
4,4'-methylene-bis (phenyl isocyanate), 4,4'-ethylene-bis (phenyl
isocyanate), .omega., {acute over
(.omega.)}-diisocyanato-1,3-dimethyl benzene, .omega., {acute over
(107 )}-diisocyanato-1,3-dimethylcyclohexane,
1-methyl-2,4-diisocyanato cyclohexane, 4,4'-methylene-bis
(cyclohexyl isocyanate), 3-isocyanato-methyl-3,5,5-trimethyl
cyclohexyl isocyanate, dimer acid-diisocyanate, .omega., {acute
over (.omega.)}-diisocyanato-diethyl benzene, .omega., {acute over
(.omega.)}-diisocyanatodimethyl cyclohexyl benzene, .omega., {acute
over (.omega.)}-diisocyanatodimethyl toluene, .omega., {acute over
(.omega.)}-diisocyanato-diethyl toluene, fumaric acid-bis
(2-isocyanato ethyl) ester or triphenyl-methane-triisocyanate,
1,4-bis-(2-isocyanato prop-2yl) benzene, 1,3-bis-(2-isocyanato
prop-2yl benzene.
[0073] These isocyanates are commercially available from
manufacturers and distributors such as DuPont, Dow, Cytec, PPG,
Crompton, Bayer, and Baxenden. Typically, the isocyanates that are
used have low molecular weights, e.g., hexamethylene diisocyanate
and toluene diisocyanate, in order to maximize the available
anti-fog effect.
[0074] Use can also be made of polyisocyanates obtained by reaction
of an excess amount of the isocyanate with a) water, b) a lower
molecular weight polyol (e.g. m.w.<300) or c) a medium molecular
weight polyol, e.g. a polyol of greater than 300 and less than 8000
m.w., e.g., sucrose, or by the reaction of the isocyanate with
itself to give an isocyanurate. The lower molecular weight polyol
comprises, for example, ethylene glycol, propylene glycol,
1,3-butylene glycol, neopentyl glycol, 2,2,4-trimethyl-1,3-pentane
diol, hexamethylene glycol, cyclohexane dimethanol, hydrogenated
bisphenol-A, trimethylol propane, trimethylol ethane, 1,2,6-hexane
triol, glycerine, sorbitol or pentaerythritol, and combinations
thereof.
Polyols
[0075] Typical polyols used in conjunction with the invention have
a molecular weight of at least about 90, and more particularly at
least about 600, and most typically at least about 800. The
molecular weight of the polyols will generally be less than about
30,000, more particularly less than about 12,000, even more
particularly less than about 4000, and typically below 1500. The
polyols used in conjunction with the invention may be straight,
branched, or cyclic.
[0076] Examples of some of the many possible polyols include
polyalkylene glycols such as polyethylene glycols (PEGs), and
polypropylene glycols (PPGs). A general formula for polyalkylene
glycols follows: H(OR).sub.nOH, wherein R is an alkyl group and
n>10. A general formula for polyethylene glycols is
H(OCH.sub.2CH.sub.2).sub.nOH, wherein n is >2. A general formula
for polypropylene glycol is H(OCH.sub.2CH.sub.2CH.sub.2).sub.nOH,
wherein n is >2. Typically, the polyols are water soluble or
dispersible. Block polymers of polyalkylene glycols, and more
particularly, block polymers of polyethylene glycol and
polypropylene glycols may be used. Even more particularly,
polyethylene-90 or polyethylene-180 may commonly be used.
Polyoxyethylene glycols can also be employed.
[0077] While a very wide variety of polyols may be used, the
typical system will employ at least one of polyalkylene glycols,
water soluble triols, tetrahydroxy-functional branched ethylene
oxide/propylene glycol copolymers, block polymers thereof, and
combinations thereof. Other variations include water soluble triols
or glycerin polymers and other multi-functional, branched
polyhydroxyl compounds such as tetrahydroxy functional copolymer of
ethylene oxide and propylene glycol, and/or block polymer
combinations of any of the above. Tetrahydoxy
functional-branched/ethylene oxide/propylene glycol co-polymers may
also be used.
Catalysts
[0078] Catalysts may or may not be employed in conjunction with the
mixtures and coatings of the present invention. When used, a wide
variety of catalysts that are known in the art may be employed. For
example, catalysts such as dibutyl tin dilaurate or triethylene
diamine may be used. In addition, other catalysts that may be used
include, but are not limited to, the following: amines such as
tetramethylbutanediamine; azines such as 1,4
diaza(2,2,2)bicyclooctane; and other organotin compounds such as
tinoctoate. These catalysts may facilitate the reaction and may be
used to complete the cure of the mixture. More particularly,
catalysts may be effective, during heating, to facilitate the
dissociation of the blocked polyisocyanates so that the isocyanate
groups become available to react with the active groups of the
polyols, thereby leading to substantial crosslinking and hardening
of the coating.
Solvents
[0079] The mixtures of the present invention may or may not
comprise at least one solvent. A wide variety of solvents may be
used and will be understood by those of ordinary skill in the art.
For example, tertiary butyl alcohol, as shown below, may be used:
##STR6## Other solvents that may be used include diacetone alcohol,
primary and secondary alcohol. A non-polar solvent that may be used
is xylene, although polar solvents tend to work better.
[0080] In the case of coatings using reactive isocyanates,
non-reactive solvents such as tertiary butyl alcohol, diacetone
alcohol, isophorone, glycol ether EB (2-butoxy ethanol), and the
like are used. In these systems, the greater part of the solvent
mixture is composed of polar solvents without primary or secondary
alcohols. Smaller amounts of aliphatics, aromatics and other
non-polar solvents may then make up the remainder, if so
desired.
[0081] The systems can be prepared solvent free. This form of the
invention may be used to produce film, cast/molded objects, and
co-extruded materials. Using methods well known to the industry,
the production of thin films, solids sheets, and monolithic shapes,
(i.e., lenses, 3-dimensional objects, etc.) is thus possible.
[0082] In systems using blocked isocyanates, most solvents are
applicable. Any of various solvents including alcohols, ketones,
aromatics, and aliphatics may be used depending upon the specific
substrate and/or application and curing environments.
Rheological Agents
[0083] The mixtures and coatings of the present invention may also
comprise rheological additives. Rheological agents may be added to
increase film thickness without increasing solids, to stabilize the
coatings, control slip, flow and/or leveling difficulties. Examples
of rheological agents include, but are not limited to, ethyl
cellulose, methyl cellulose, associative PUR thickeners, anti-mar
agents, and combinations thereof. Examples may include DC 28
distributed by Dow Corning, or L-7602 and L-7608 obtained from
Crompton of Pittsburg, Pa., some of which are polyether silicone
flow/level agents.
The Mixture
[0084] Typically, the mixtures of the present invention comprise
the following:
[0085] Polyol About 10.0% to about 85.0% by weight;
[0086] Isocyanate About 15.0% to about 90.0% by weight;
[0087] Catalyst About 0.0% to about 2.0% by weight;
[0088] Solvent About 0.0% to about 95.0% by weight; and
[0089] Rheological Agent About 0.0% to about 2.0% by weight.
[0090] These components are weighed out using techniques that are
generally known in the art. Some or all of the components are then
mixed using simple mixing, admixing, homogenization, or a
combination thereof in order to form the mixture. This initial
mixing is typically performed at ambient conditions, namely,
ambient temperatures and pressures. Each of these mixing techniques
is well-known in the art.
[0091] The mixtures may then be applied to a variety of substrates
using a variety of techniques that are well-known in the art. For
example, the mixtures discussed herein may be applied directly or
indirectly to glass and plastic. In other words, one or more
substrates, coatings, layers, or other substances may exist between
the mixture (and subsequently, the coating) and the glass or
plastic substrate. As used herein, "applying a mixture to a
substrate," "a substrate having a coating" thereon or a "substrate
having a coating or at least a portion thereof" may mean that one
or more substrates, coatings, layers or other substances exist
therebetween unless otherwise specified. For example, the mixtures
or coatings described herein may be applied to a plastic film (e.g.
an acrylic adhesive), wherein the plastic film bonds to the glass
or plastic substrate. In addition the mixtures or coatings might be
applied to a low-E plastic film or a substrate. Regarding glass,
the hardness, tintability, water repellency, and hydrophilicity are
properties to consider when choosing the glass. On plastics, the
properties to consider are hardness, tintability using hot dye at
90.degree. C., water repellency, hydrophilicity, flexibility,
thermoformability using heat and/or pressure, and adhesion.
Examples of possible plastic substrates include, but are not
limited to, polycarbonate, allyl diglycol carbonates or copolymers
thereof, acrylic, acrylics, urethanes, polysulfone, polyarylate,
PETG, PET, polyolefins, and combinations thereof. The selection of
the base components may be as important. For example, the selection
of an aliphatic polyurethane base contributes to good resistance to
adverse weather conditions and solar aging/ultraviolet rays. Again,
using the low-E surfaces and coatings discussed above produces
superior results.
[0092] The mixtures may be applied to these substrates using a
variety of techniques that are well-known in the art. For example,
the mixtures may be sprayed onto the substrate using high pressure
spray applications. Additionally, the substrate may be dipped into
the mixture. Flow, spin, curtain, and blade techniques may also be
used.
[0093] Subsequently, after the mixture is applied to the substrate,
the mixture is exposed to ambient conditions. Typically, the
exposure will be for greater than about one minute, and more
particularly greater than about 10 minutes. The exposure to ambient
conditions after application is generally less than about 60
minutes, and more particularly less than about 40 minutes. The
mixtures are generally exposed to ambient conditions in order to
let any solvents in the mixture evaporate.
[0094] The mixture is then cured. Typically, the mixture is at
least briefly cured at a temperature that is greater than
80.degree. C., more particularly greater than 100.degree. C., and
even more particularly greater than 125.degree. C. Curing is
usually performed at temperatures that are less than about
180.degree. C., more particularly less than about 135.degree. C.,
and even more particularly less than about 125.degree. C. Curing
times may vary. Typically, the mixture is cured for at least about
10 minutes, more particularly at least about 20 minutes, and even
more particularly at least about 40 minutes. Curing times are
generally less than about 60 minutes, and more particularly less
than about 40 minutes. Overall, the curing temperature and time
will depend on the substrate's melting point, as well as the types
and molecular weights of the isocyanate, polyol, blocking agent
being used. The intended use of the part may also dictate the
curing time and temperature. Again, when using a blocked
isocyanate, the curing time and temperature must be sufficient to
enable the blocker to dissociate, thereby allowing the isocyanate
group to react with the hydroxyl groups and cross-link. Generally,
the mixtures that are applied to the substrates are the result of
at least one of the pre-polymers isocyanates at least partially
reacting with at least one of the polyols. The resultant mixture,
accordingly, typically comprises a cross-linked polyurethane.
[0095] Alteration of the amount of the individual components, i.e.
ratios of solvent, polyols, isocyanates, etc. results in products
having variable functional properties. The coatings and
compositions of the present invention may possess a variety of
chemical and physical properties and functionalities.
[0096] The resulting cured coating is part hydrophilic and part
hydrophobic. More particularly, the surface is substantially
hydrophobic, while the interior is substantially hydrophilic. By
combining a porous, hydrophobic surface with a hydrophilic base
polymer, it is possible to obtain a composition possessing
excellent anti-fog characteristics and surface hardness. The
absorbent polymer coating of the invention possesses a
water-repellant surface due to the unique material combinations set
forth in the application. This hydrophobic surface may be achieved,
while maintaining a hydrophilic core layer, by substantially
excluding surfactants and using higher molecular weight polyols as
discussed herein. Increasing the molecular weight of the polyols
tends to produce increasingly more non-polar polyurethanes after
reaction with the isocyanates discussed above. These higher
molecular weight polyurethanes contribute to the water-repellancy
of the coatings.
[0097] In terms of hydrophobicity, water may run off part of the
coating when applied to a substrate. Part of the water is actually
repelled. The surfaces of these particular coatings generally do
not tend to sheet and generally do not tend to be wet by water.
This is due to the surface tension of the coating, which
substantiates the water-repellancy or hydrophobicity of the
coatings. Typically, the surface tension of the surface of the
coatings will be greater than about 15 dynes/cm, more particularly,
greater than about 20 dynes/cm, and even more particularly, greater
than about 25 dynes/cm. The surface tension is typically less than
about 60 dynes/cm, although the surface tension may be less than
about 50 dynes/cm, or even less than about 45 dynes/cm. The surface
tension of the coatings was tested according to the Wilhelmy Plate
Method, which is well-known or readily ascertainable by those
having ordinary skill in the art.
[0098] Cured coatings of the present invention that are products of
the reaction of polyols having molecular weights of less than about
600 (see Example 1 below) may tend to have a surface tension of
about 56 to about 61 dynes/cm. Polyurethanes made from polyols
having molecular weights of about 600-800 (see Example 6), about
800-1500 (see Example 4), about 1500-4600 (see Example 3), and even
about 12,000 tend to have surface tensions of about 50-57 dynes/cm,
about 27-38 dynes/cm, about 23-25 dynes/cm and about 21 dynes/cm,
respectively. The lower the measurement in terms of dynes/cm, the
more hydrophobic the surface. In other words, the low surface
tension means that water is actually repelled (i.e. it beads off),
rather than being sheeted or absorbed. Accordingly, by using
polyols having higher molecular weights, the resulting
polyurethanes exhibit more hydrophobic tendencies, at least at the
surface.
[0099] As discussed above, however, the coatings described herein
also have a hydrophilic interior portion. Hydrophilicity may be
measured according to weight gain the coatings experience upon
aqueous immersion. More specifically, "hydrophilicity" is a measure
of the percent weight gain experienced by a coating that has been
fully immersed in an aqueous medium for 96 hours at about 20 to
25.degree. C. In other words, during this period, the coating will
tend to attract a certain amount of water. The difference between
the weight of the coating after being immersed and the weight of
the coating before immersion, as expressed as a percent weight gain
(as compared to the weight of the non-immersed coating) measures
the hydrophilicity of the coating. In other words, the difference
between the mass of the soaked coating and the dry coating measures
the hydrophilicity of the coatings. Typically, the coatings
described herein tend to gain greater than about 20% weight, more
particularly greater than about 30% weight, and often times greater
than about 35% weight. Weight gain is generally less than about
150%, and typically the weight gain is less than about 140%, and
more particularly less than about 110%.
[0100] As shown in more detail below in the Examples, polyurethanes
made from polyols having a molecular weight around 400 (see Example
1) may experience a weight gain of about 140% when exposed to the
conditions discussed above. Polyurethanes made from polyols having
molecular weights of about 800-1500 (see Example 2) experience a
weight gain of somewhere between about 75 and about 105%, while
polyurethanes made from polyols having molecular weights of about
4600 may exhibit a weight gain of around 35%. Typically, the higher
the molecular weight of the polyol being used to form the coating,
the less hydrophilic the hydrophilic portion of the coating will
be. For the most part, general interpolation may be used to roughly
determine the hydrophilicity of coatings discussed herein based on
these numbers.
[0101] In addition, the coatings possess excellent anti-fogging
characteristics after being cured. Accordingly, the coatings are
suitable for a variety of applications including, but not limited
to, eyewear, optics, automotive and residential glass surfaces, and
flat, sheet stock. Again, the cured anti-fog coatings have the
ability to both repel and absorb water, rather than just sheet
water. More particularly, many of the coatings of the present
invention have the ability to pass EN-166, EN-168, and ENE-2205
(analogous to the ASTM D 4060 abrasion test described herein)
tests, each of which is a standardized test, the specifications for
which can be obtained from the European Union. More particularly,
the coatings described herein may be able to pass the EN-166 test
for over a minute, and often times for over five minutes.
[0102] Glass or plastic (that is usually transparent) coated with
the coatings described herein tends not to fog when first exposed
to a "cool environment," in which the temperature is between about
10.degree. C. to about -25.degree. C., for greater than about
thirty seconds and then subsequently exposed to humid ambient
conditions. At these temperatures, the relative humidity, of
course, will be very low. Even after being exposed to the cool
environment as set forth above for more than one minute, many of
the glass or plastic substrates will not fog regardless of the
amount of time they are exposed to ambient conditions. In more
detail, the substrates will not fog after being exposed to the cool
environment for a minute or more, and then being exposed to ambient
conditions for ten seconds, thirty seconds, and even three minutes
or more of exposure. Again, many of the coated substrates will not
fog after humid ambient exposure for more than five minutes, more
than ten minutes, and even indefinitely after being removed from
the cool environment, after having been there for a minute or
longer.
[0103] More particularly, in one set of experiments, transparent
glass and plastic substrates coated with the coatings set forth
herein were exposed to a variety of temperatures falling with the
cool environment for about one minute, and then were exposed to
ambient conditions. Many of the substrates did not fog after being
exposed to the ambient conditions for 10 seconds, thirty seconds,
and even three minutes and longer. Many of the coatings never
fogged at all under these conditions. In another set of
experiments, different coated transparent glass and plastic
substrates were exposed to different temperatures within the cool
environment for about five minutes and longer. The substrates were
then removed and exposed to different ambient conditions. The
substrates did not fog after 10 seconds. Many of the substrates did
not fog after thirty seconds, after three minutes, after five
minutes, after ten minutes and longer. Again, many of the
substrates never fogged.
[0104] In addition, portions of substrates that are coated with the
anti-fog coatings may not substantially fog when the coated portion
has an initial surface temperature and is then exposed to a moist
air ambient with a dewpoint temperature equal to or greater than
the surface temperature for a period of time. More particularly,
the substrates may not fog when the initial surface temperature is
less than one or more of the following: 20.degree. C., 10.degree.
C., 5.degree. C., 0.degree. C., -5.degree. C., -0.degree. C.,
-15.degree. C., -18.degree. C., -20.degree. C. and -25.degree. C.
The period of time of exposure to the dewpoint temperature equal to
or greater than the surface temperature may be greater than one or
more of the following: 0 seconds, about 1 second, about 3 seconds,
about 5 seconds, about 6 seconds, about 10 seconds, about 30
seconds, about 1 minute, about 2 minutes, about 15 minutes, about
30 minutes and about 1 hour. In other words, when coated substrates
are first exposed to any of the temperatures or below the
temperatures set forth above, and then exposed to a dewpoint
temperature equal to or greater than the surface temperature for
any of the periods of time set forth above, the substrate may not
substantially fog. Not every coating described herein will prevent
fog at each and every one of these parameters, although some of the
coatings will. The dewpoint temperature that is equal to or greater
than the surface temperature may encompass ambient conditions.
[0105] Typically, ambient conditions include any temperature or
humidity that falls with the ambient temperatures and humidities
discussed below. Ambient temperatures include temperatures that are
typically greater than 10.degree. C., and generally greater than
15.degree. C. Ambient temperatures are usually less than about
60.degree. C., typically less than about 55.degree. C., and more
particularly less than about 50.degree. C. Ambient relative
humidities mean some moisture was present in the air. The relative
humidities are generally greater than about 20%, typically greater
than about 30%, and more typically greater than about 35%. The
relative humidity is typically less than about 100%, more typically
less than about 95%, and more particularly, less than about 90%.
Most typical of the ambient conditions is about 18.degree. C. to
about 30.degree. C. and a relative humidity about 40 to about 70%.
As used herein, "moist ambient conditions" and "moist air ambient"
are meant to refer to temperatures and relative humidities, falling
within the ranges of this paragraph, that are most typically
associated with the humid ambient conditions in a grocery store,
convenience store, or supermarket, or the conditions immediately
adjacent a beverage cooler. Moisture is typically present in these
conditions. Substrates first exposed to the cool environment may
not fog when exposed to some or all of the ambient conditions.
[0106] Curing the mixtures also results in coatings that have
excellent hardness characteristics as demonstrated by testing as
specified by ASTM D 4060. More particularly, the coatings tend to
have a taber haze of less than about 10% at 100 cycles with 500
gram load and a CS-10F load, and more specifically less than about
5%. Some of the coatings described herein may have a taber haze of
less than about 3% or even about 1%. Typically, known anti-fog
coatings exhibit a taber haze of greater than 15%. Most
polysiloxane hardcoats typically exhibit a taber haze of 3 or
greater.
[0107] When testing the coatings according to ASTM 3363 described
in more detail below, the coatings tend to exhibit a hardness of
greater than about 2H, and typically greater than about 4H.
Generally, the hardness is less than about 8H, and less than about
6H. In this test, the pencil's lower 10-15 mm is trimmed of wood,
leaving only the central lead core extending out of the body of the
pencil. Then the lead is held perpendicular to a flat surface upon
which a piece of fine sandpaper is mounted. The protruding section
of lead then is abraded at 90.degree., so as to render the tip of
the lead perfectly flat and perpendicular to the pencil's length.
The hardness test is performed by applying a pencil hardness tester
consisting of a rolling tester weighing 200g and fixing the pencil
at a 45.degree. angle through the body of the tester and extending
onto the test surface below. The device is moved across the sample
(laid flat, horizontally on a hard, level surface) for a distance
of about 24 mm. As it moves, the pencil's lead (at a 45.degree.
angle) will incise/etch a scratch/line into the sample surface if
the pencil's graphite/hardness rating is harder than the sample's
coated surface. Hardness is rated as the hardest lead that does not
leave a visible score.
[0108] The coatings of the present invention may also have
excellent adhesion properties as indicated by the coatings' ability
to pass the ASTM B 3359 Method B discussed herein. For example,
many of the coatings can withstand at least one, three and even
five pulls with standard Scotch tape 3M 160 on 100 square hatch
with no pull up. Moreover, some of the coatings can even withstand
boiling water exposure, and pass 120 minute adhesion tests.
[0109] The coatings also tend to be substantially clear. This
property makes the coatings ideal for substrates that are
transparent. In other words, the coatings do not blur or obstruct
vision through transparent substrates. When applied to transparent
substrates, the coatings may exhibit less than 0.5% detectable haze
by hazemeter, more particularly less than 0.3% detectable haze by
hazemeter, and even more particularly less than 0.2% detectable
haze by hazemeter.
[0110] The life of the coating, when applied to a substrate, is
typically greater than about 2 years, but may be greater than about
5 years, and may even be longer than about 10 years. The shelf-life
of the mixtures is also excellent. Compositions may be formulated
into single- or dual-component (2K) forms. This allows the
selection of unique reactive materials to suit the various needs of
the end product. Typically, the shelf life of the mixtures is at
least about 6 months, sometimes at least about 1 year, and at times
at least about 2 years.
[0111] The coatings also exhibit exceptional thermoformability.
More particularly, the coatings have been applied to substrates and
then bent between two pieces of curve metal under high heat, more
particularly, temperatures greater than about 150.degree. C., and
even greater than about 180.degree. C. for about 1 to about 2
minutes. The coatings did not crack or lose adhesion properties
during this test.
[0112] The coatings after being cured tend to have a thickness of
at least about one-half micron, more particularly greater than
about one micron, more particularly greater than about 3 microns,
and typically greater than about 5 microns. The thicknesses also
tend to be less than about 30 microns, more particularly less than
about 20 microns, and typically less that about 15 microns.
[0113] Resulting urethanes also accept commercially-available color
tints and functional solution treatments (i.e. non-fogging,
uv-filtration, anti-static) utilized by the retail optical
industry.
[0114] The present invention is further explained by the following
examples that should not be construed by way of limiting the scope
of the present invention.
EXAMPLES
Example 1
[0115] To illustrate the preparation of an abrasion resistant
anti-fog coating with a hydrophilic surface. Part A was mixed using
simple mixing, namely, a magnetic stir bar and plate with Part B.
Part A comprised about 28.1 grams Desmodur N-75 (Bayer) well mixed
with about 21.9 grams of diacetone alcohol. Part B comprised about
37.8 grams of diacetone well mixed with about 11.0 grams PEG-90,
0.2 grams dibutyltin dilaurate, and DC-57 additive (Dow Coming).
The mixture was immediately applied to a 4'' square of Lexan
polycarbonate, via an airbrush. The mixture was then allowed to
stand at ambient conditions for about 10 minutes. It was then baked
for one hour at 125.degree. C. The sample had excellent anti-fog
properties when blown on. A 100-cycle taber abrasion test resulted
in a haze of less than 5% using a dual, 500-gram load and a CS-10F
abraser wheel. Note that the light transmittance of the coated
sample exceeded the uncoated polycarbonate (approx. 92% before
coating application). Separately, each part exhibited a shelf life
of over 6 months with no loss of performance properties after
mixing appropriately. The pot life of the prepared/mixed
composition was about 24 to 36 hours. See Table I for summarized
performance properties.
Example 2
[0116] Part A was mixed with Part B using simple stirring, namely,
a magnetic stir bar and plate to form the mixture. Part A comprised
28.1 grams of Desmodur N-75 (Bayer) well mixed with 21.9 grams of
diacetone alcohol. Part B comprised 35.8 grams of diacetone well
mixed with 13.9 grams of polyethylene glycol-180, 0.2 grams of
dibutyl tin dilaurate, and 0.05 grams of DC-57 manufactured by Dow
Coming. The mixture was immediately applied by flow-coating to a
4'' square of Teflon coated metal, and allowed to stand at ambient
conditions for about 5-10 minutes. The cooled, cured film was
peeled from the teflon surface and wrapped around a 0.5'' steel rod
to observe the flexibility of the film. No crazing or marring was
observed even after wrapping the cured film around itself multiple
times. The film shows excellent anti-fog properties when blown on
or exposed to changes in humidity and temperatures. Condensed water
vapor reduces clarity after a few minutes of exposure. The film
exhibited excellent anti-fog properties when blown on, it fills
light scratches produced by 6H pencil, and had exceptional
flexibility. These coatings resist cracking when rolled into a
circular shape.
See Table I for summarized performance properties.
Example 3
[0117] Example 3 illustrates the preparation of a water-repellant,
anti-fog coating for low-temperature usage. In a 1-L beaker
equipped with a magnetic stirrer and a beating mantle, about 200
grams Baxenden 7683 obtained by Baxenden was stirred with about 281
grams of diacetone alcohol to produce a solution of blocked
polyisocyante in solvent. The solution was then heated to
60.degree. C. To the heated, stirring solution was added a solution
of 179g of PEG-4600 in about 179 grams of diacetone alcohol. The
solution was stirred and maintained at 60.degree. C for about 10
minutes. Then 1.6 grams each of dibutylyin dilaurated, and DC-57
additive (Dow Corning) were stirred in to produce a coating
composition. The heated mixture was then applied to glass panels
via flowcoating, and allowed to hang vertically at ambient
conditions for 5 minutes. Samples were then baked for about 25
minutes at 150.degree. C. Subsequently, the cooled, cured samples
were exposed to -25.degree. C. for 10 minutes, and then exposed to
ambient conditions (25.degree. C., 70 to 75% relative humidity) for
about 15 minutes. This was repeated 20 times. The coated glass was
found to maintain clarity and did not collect excessive moisture on
its coated surfaces. The surface tension was found to be about 23
dynes/sq cm compared to the untreated glass having a surface
tension of about 76-78 dynes/sq cm (this quantifies the hydrophobic
nature of the surface of the invention when prepared with higher
molecular weight polyols). See Table I for summarized performance
properties.
Example 4
[0118] To illustrate the preparation of a water repellant, anti-fog
coating, about 396 grams Desmodur N-75 (Bayer) was stirred with
about 193 grams of diacetone alcohol in a 1-L beaker equipped with
a magnetic stirrer, in order to produce a solution of blocked
polyisocyante in solvent. To the stirring solution was added a
solution of about 147 grams of PEG-1500 in about 147 grams of
diacetone alcohol. Subsequently, about 2.2 grams of dibutylyin
dilaurate, about 0.5 grams of FC-4430 (3M of Minnesota) -
flow/leveling aid, and about 1.0 grams of Silwet
L-7602--slip/anti-mar agent (Crompton) were added, with stirring,
to produce a low-viscosity coating composition. Commercial ADC
(allyl diglycol carbonate, CR-39) panels, 4 inch by 4 inch, were
etched, cleaned, and then dipped into the filtered coating solution
using a 4.5 inch/minute withdrawal rate. Coated samples were then
baked for 90 minutes at 105.degree. C. The cured samples were found
to perform very well. Surface tension measured after conditioning
at about 20-22.degree. C.; 70 to 75% relative humidity for about 24
hours: 27-29 dynes/sq cm. See Table I for summarized performance
properties.
Example 5
[0119] To illustrate another preparation of a water-repellant,
anti-fog coating, a solution of 115 grams of a DEM (diethyl
malonate)-blocked hexamethylene diisocyante prepolymer containing
70% solids (Baxenden 7963), by weight in methoxypropanol (glycol
ether PM) was added to 100 grams of 2-butoxethanol (glycol ether
EB). To this stirring solution was added: 1.1 grams of DBTDL
(dibutyl tin dilaurate), 10% in EB. Then, 38.5 grams of a
monohydroxy,-monobutoxy-functional polypropelene polyglycol
(B01/120 form Clariant Germany) and 20.0 grams of a
polycaprolactone (CAPA 3091 from Solvay UK) were added. Finally, a
solution of 0.8 grams of DC-57, and 1.5 g. of Silwet
L-7608--leveling & air release aid in 150 grams of DA were
added to complete the coating formulation. Polyamide lenses
(trogamid brand) were cleaned, flow-coated with the solution at
20.degree. C. and then suspended vertically for 15 minutes to allow
solvents to partially evaporate. Coated samples were cured in a
convention oven. After 120 minutes at about 109.degree. C., the
samples were removed and cooled. Anti-fog properties were
excellent, and accelerated weathering (QUV test cabinet from
Q-Panel Corp) tests indicated excellent resistance to UV and
moisture. See Table I for summarized performance properties.
Example 6
[0120] To illustrate the production of a 3-dimensional shape
(monolith) exhibiting permanent, intrinsic anti-fog properties. A
mixture of about 5500 grams of caprolactam-blocked, 100% solids TDI
prepolymer product (Baxenden BI 7773), about 1200 grams of PEG-800,
and 2220 grams of a polyethylene glycol monomethyl ether having a
molecular weight of 720-780 (M750 from Clariant) were stirred
together at room temperature. To the well-mixed liquid was added
about 5.4 g of DBTDL and about 0.5 g of tin diocctoate. The liquid
molding composition was cast into a rectangular solid measuring 100
cm.times.100 cm.times.1 cm thick. The sample was cast between two
glass plates that were sealed with a silicone elastomeric gasket,
and cured at 165.degree. C. for 2 hours. After cooling and removal
from the mold, the solidified sample exhibited excellent optical
properties and good hardness. Non-fogging properties were excellent
on all surfaces. The lenses were also tinted and treated to block
UV using a hot (90-92 C.) aqueous solution of Electron Beam Gray
and UV-Shield (BPI of Miami Fla.). After 10 minutes of exposure,
the lenses were rinsed and dried. Luminous transmittance of the
gray lenses was less than 40%; UV transmittance was <2%. See
Table I for summarized performance properties. TABLE-US-00001 TABLE
I Taber Test % Adhesion Pencil Chemical Impact Water Soak - ID LT
%.sup.1 Haze %.sup.2 Haze.sup.3 %.sup.4 hardness.sup.5
Resistance.sup.6 Resist.sup.7 Anti-fog.sup.8 AF.sup.9 1 >97.4
<0.5% 4.7 100 6H Fail Acetone PASS Pass 40 s Fall 20 s Pass
Others 2 >99.1 <0.1 3.9 100 -na- Pass all -na- -na- -na- 3
>98.0 <0.3 1.8 90/100* 8H Pass all -na- Pass 5 min Pass 5 min
4 >96.8 <0.2 2.2 100 4H Fail Acetone PASS Pass 3 min Pass 2
min Fail Xlene Pass others 5 >92.5 <0.5 1.1 100 4H Fail PASS
Pass 2 min Pass 2 min isopropanol** Pass others 6 >94.3 <0.5
0.78 -na- 5H Pass all PASS Pass Infinite Pass Infinite *Example #3,
when repeated using an air-dry primer prepared from 0.5% Silquest
A-1100 in isobutanol. The primer was stirred and sprayed onto the
glass substrate. After 30 minutes of air-drying, the composition
from Example #3 was applied and cured as before. Adhesion was
excellent. **Isopropanol exposure resulted in the appearance of
visible haze - polyamide substrates are attacked by alcohols.
.sup.1ASTM (American Society for Testing and Materials) E 1348:
Test Method for Transmittance by Spectrophotometry using
Hemispherical Geometry .sup.2ASTM E 284: Reflection Haze .sup.3ASTM
D 4060: Method of Abrasion Resistance of Organic Coatings - 100
cycles under a dual, 500 gram load using a standard Taber Apraser
device [CS-10F Calibrase Abraser wheel] .sup.4ASTM D 3359 Method B:
Standard Test Methods of Measuring Adhesion by Tape Test .sup.5ASTM
D 3363: Test Method for Film Hardness .sup.6ASTM D 1308: Test
Method for Effects of Household Chemicals on Clear Organic
Finishes. Chemicals include: isopropanol 70%, acetone, petroleum
ether/hexane, xylene, ammonia, acetic acid, hydrochloric acid,
Windex, cola/coffee/tea, sweat/saline, and water. .sup.7ASTM D
2794: Test for Method of Resistance of Organic Coatings to the
Effects of Rapid Deformation (Impact). .sup.8EN 166 European
Anti-Fog standard - continuous photometric measurement of luminous
transmittance of sample exposed to fog-conducive environment.
Measures point of loss of 20% of clarity. .sup.9ASTM D 870:
Practice for Testing Water Resistance of Coatings Using Water
Immersion. Measure of Anti-fog performance (w/EN 166) after 96
hours of continual aqueous exposure followed by conditioning at
25.degree. C./70-75% relative humidity for 24 hours before
testing.
Example 7
[0121] Example 7 illustrates the preparation of another
water-repellant, anti-fog coating for low-temperature usage. The
prepolymer solution follows: In a 10-L polyethylene tank equipped
with a gear-driven stirrer and an immersion heater, 1948 grams of
caprolactam-blocked TDI prepolymer with an equivalent weight of
1395 was stirred with 400 grams of 4-hydroxy-4-methyl-2-pentanone
and 200 grams of 2-butoxy ethanol to produce a solution of blocked
polyisocyante in solvent.
[0122] A 3-L dual-necked round-bottomed flask was equipped with a
magnetic stirrer, reflux condenser, and a heating mantle. A mixture
of 855 grams of powdered PEG-4600 and 200 grams of PEG-1000 was
poured into the flask and 400 grams of tert-butanol was added. Heat
was then applied, and the solution was brought to reflux for 10
minutes to dissolve the PEG solids. The solution was cooled to
60.degree. C., and then added to the prepolymer solution, with
stirring. 2.8 grams of dibutyltin dilaurate (DBTDL) was stirred in
for 15 minutes, and then 0.4 g each of L-7602 and L-7608 was
added.
[0123] The solution was maintained at 50-55.degree. C. via the
immersion heater and filtered through a 0.5 micron cartridge
filter. Glass panels were sprayed with a 0.25% of an
amino-functional silicone adhesion-promoter (Silquest A-1106) in a
50/50 aqueous solution ethanol. After drying for 5 minutes at
20.degree. C., the primed glass was exposed to IR lamps for 15
minutes to cure the primed surface, and then allowed to cool to
room temperature.
[0124] The filtered, hot coating solution was applied to the primed
glass panels and allowed to hang vertically at ambient conditions
for 25 minutes. Samples were cured for 45 minutes at 150.degree. C.
via a forced-air convection oven. After curing, the samples were
cooled to room temperature. The surface tension was found to be
about 29 dynes/sq. cm, and the samples possessed excellent surface
hardness.
[0125] The prepared samples were exposed to -10.degree. C. for 5
minutes, and then exposed to a humidity test cabinet maintained at
20.degree. C. and 80% relative humidity. The coated glass was found
to maintain clarity indefinitely, and did not collect excessive
moisture on its coated surfaces, i.e., the surface did not fog.
Samples were also saturated in deionized water via immersion for 96
hours. After removal from the water, samples were subjected to
low-temperature testing as above. The samples collected excessive
moisture on their surfaces after 5 minutes of humidity cabinet
exposure but did not fog. However, after allowing 30 minutes at
20.degree. C. and 75% relative humidity for the saturated samples
to equilibrate/dry out samples performed analogously to the initial
test set. See Table II for summarized performance properties.
Example 8
[0126] Similar to Example 7, 2782 grams of a pyrazole-blocked
toluene diisocyanate prepolymer with an equivalent weight of 560
was stirred with 400 grams of 4-hydroxy-4methyl-2-pentanone and 250
grams of 2-butoxy ethanol to produce a solution of blocked
polyisocyante in solvent.
[0127] A 3-L dual-necked round-bottomed flask was equipped with a
magnetic stirrer, reflux condenser, and a heating machine. Powdered
PEG-4600, 1060 g, was poured in and 400 g of
4-hydroxy-4-methyl-2-pentanone was added. Heat was then applied,
and the solution was brought to reflux for 2 minutes to dissolve
the PEG solids. The solution was cooled to 60.degree. C., and then
added to the prepolymer solution, with stirring. DBTDL 175 g, was
stirred in for 60 minutes, and then 0.4 g each of L-7602 &
L-7608 was added.
[0128] The solution was maintained at 50-55.degree. C. via the
immersion heater and filtered through a 1.0 micron cartridge
filter. Glass panels were sprayed with a 0.25% of an
amino-functional silicone adhesion-promoter (Silquest A-1106) in a
50/50 aqueous solution ethanol. After drying for 5 minutes at
20.degree. C., the primed glass was cured for 15 minutes in a
thermal convection oven at 60.degree. C., and then allowed to cool
to room temperature. The filtered, hot coating solution was applied
to the primed glass panels and allowed to hang vertically at
ambient conditions for 15 minutes. Samples were cured for 30
minutes at 125.degree. C. via a convection oven. Samples were
cooled to room temperature.
[0129] The samples were then exposed to -20.degree. C. for 10
minutes, and then exposed to a humidity test cabinet maintained at
20.degree. C. and 78% relative humidity. The coated glass was found
to maintain clarity indefinitely, and did not collect excessive
moisture on its coated surfaces. Samples were also saturated in
deionized water for 96 hours. After removal from the water, samples
were subjected to low-temperature testing as above. The samples
were clear after 5 minutes of humidity cabinet exposure and
maintained clarity indefinitely. See Table II for summarized
performance properties.
Example 9
[0130] Example 9 was conducted as set forth above with respect to
Example 7, except that 2-butoxyethanol was replaced with diacetone
alcohol (DAA), using the same amount. Example 9 exhibited similar
properties to Example 7, except Example 9 exhibited superior
hardness. This Example shows the effect solvents have on the final
surface hardness. See Table II for summarized performance
properties.
Example 10
[0131] Example 10 was conducted as set forth above with respect to
Example 9, except the mixture was applied with a spray appliance,
which produces a much thinner coating--about 2-3 microns. The
anti-fog results were similar to Example 7, however, the coating
fogged only after saturation and repetition of low-temperature
exposure to test chamber. It did not fog if allowed to
equilibrate/dry out. See Table II for summarized performance
properties.
Example 11
[0132] This Example was the same as Example 8, except it was
sprayed. The results were essentially identical to Example 8. It
was a more hydrophilic/anti-fog due to the reduced molecular weight
of the polyol(s), despite thickness variance. See Table II for
summarized performance properties.
Example 12
[0133] This Example was the same as Example 8, except that PEG-1000
in the same amount was substituted for the PEG of Example 8. In
addition, 2-butoxyethanol was replaced with 200 g of isophorone,
and 2 grams of DC-57 was added. The coating fogged in 25 seconds
upon removal from low low-temperature (-12.degree. C. for 5
minutes) and exposure to humidity cabinet. After saturation and
soak, the substrate fogged immediately when brought from freezer to
test chamber. This shows the effect of using a lower molecular
weight polyol. See Table II for summarized performance
properties.
Example 13
[0134] This Example was the same as Example 8, except Baxenden BI
7986 (an HDI biuret blocked with dimethylpyrazole) was substituted
for the blocked isocyanate of Example 8. In addition, 1250 grams of
PEG 4000 was substituted for the PEG of Example 8. This is an
example of an alternated polyisocyante. See Table II for summarized
performance properties. TABLE-US-00002 TABLE II Taber Test Pencil
Water Soak - ID LT %.sup.1 Haze %.sup.2 % Haze.sup.3 Adhesion
%.sup.4 hardness.sup.5 Chemical Resistance.sup.6 Anti-fog.sup.8
AF.sup.9 7 >97 <0.5 6.9 100 6H Pass all Pass 5 min Pass 3 min
8 >96 <0.5 1.2 100 10H Pass all Pass 5 min Pass 5 min 9
>99 <0.5 2.1 100 8H Pass all Pass 5 min Pass 3 min 10 >99
<0.2 8.3 100 4H Fail Acetone Pass 3 min Pass 1 min Fail Xlene
Pass others 11 >97 <0.5 6.0 100 6H Fail Acetone Pass 3 min
Pass 2 min Fail Xlene Pass others 12 >93 <0.5 12.8 100 -
tacky 3H Fail acetone Pass 40 s Fail Pass others 13 >93 <0.3
5.5 100 6H Pass all Not Not available available
Example 14
[0135] Part A was mixed with Part B using simple stirring, namely,
a magnetic stir bar and plate to form the mixture. Part A comprised
51.45 grams of trixene 7683 (commercially available from Baxenden
of Lancashire, England) well mixed with 20.67 grams of diacetone
alcohol. Part B comprised 20.67 grams of diacetone alcohol well
mixed with 27.79 grams of polyethylene glycol 4600 (i.e. PEG having
a molecular weight of 4600), 0.053 grams of dibutyl tin dilaurate
(obtained from Gelest of PA, USA) and 0.037 grams of DC-28
(obtained from Dow Coming). The mixture was immediately applied
using flow-coating to a 4'' square of Teflon coated metal, and
allowed to stand at ambient conditions for about 10 minutes. The
mixture was then baked for about 1 hour at about 125.degree. C. to
produce the coating.
Example 15
[0136] Part A was mixed with Part B using simple stirring, namely,
a magnetic stir bar and plate to form the mixture. Part A comprised
51.45 grams of trixene 7683 (commercially available from Baxenden
of Lancashire, England) well mixed with 20.68 grams of diacetone
alcohol. Part B comprised 20.68 grams of diacetone alcohol well
mixed with 27.79 grams of polyethylene glycol 4600, 0.053 grams of
dibutyl tin dilaurate (obtained from Gelest of PA, USA), and 0.018
grams of L-7602 (obtained from Crompton of Pittsburg, Pa., USA) and
0.018 grams of L-7608 (obtained from Crompton). These last two
components are flow/leveling aids and slip-aids, respectively. The
mixture was immediately applied using flow-coating to a 4'' square
of Teflon coated metal, and allowed to stand at ambient conditions
for about 10 minutes. The mixture was then baked for about I hour
at about 125.degree. C. to produce the coating.
Example 16
[0137] Part A was mixed with Part B using simple stirring, namely,
a magnetic stir bar and plate to form the mixture. Part A comprised
42.88 grams of trixene 7683 (commercially available from Baxenden
of Lancashire, England) well mixed with 33.85 grams of diacetone
alcohol. Part B comprised 33.85 grams of diacetone alcohol well
mixed with 23.18 grams of polyethylene glycol 3000 (i.e. having a
molecular weight of 3000), 0.053 grams of dibutyl tin dilaurate
(obtained from Gelest of PA, USA) and 0.037 grams of DC-28
(obtained from Dow Coming). The mixture was immediately applied
using flow-coating to a 4'' square of Teflon coated metal, and
allowed to stand at ambient conditions for about 10 minutes. The
mixture was then baked for about 1 hour at about 125.degree. C. to
produce the coating.
Example 17
[0138] Part A was mixed with Part B using simple stirring, namely,
a magnetic stir bar and plate to form the mixture. Part A comprised
42.67 grams of trixene 7683 (commercially available from Baxenden
of Lancashire, England) well mixed with 33.75 grams of diacetone
alcohol. Part B comprised 33.75 grams of diacetone alcohol well
mixed with 23.49 grams of polyethylene glycol 3000, 0.053 grams of
dibutyl tin dilaurate (obtained from Gelest of PA, USA) and 0.037
grams of DC-28 (obtained from Dow Corning). The mixture was
immediately applied using flow-coating to a 4'' square of Teflon
coated metal, and allowed to stand at ambient conditions for about
0 minutes. The mixture was then baked for about 1 hour at about
125.degree. C. to produce the coating.
Example 18
[0139] Part A was mixed with Part B using simple stirring, namely,
a magnetic stir bar and plate to form the mixture. Part A comprised
42.88 grams of trixene 7683 (commercially available from Baxenden
of Lancashire, England) well mixed with 33.91 grams of diacetone
alcohol. Part B comprised 33.91 grams of diacetone alcohol well
mixed with 11.56 grams of polyethylene glycol 3000, 0.053 grams of
dibutyl tin dilaurate (obtained from Gelest of PA, USA) and 0.037
grams of DC-28 (obtained from Dow Corning). The mixture was
immediately applied using flow-coating to a 4'' square of Teflon
coated metal, and allowed to stand at ambient conditions for about
10 minutes. The mixture was then baked for about I hour at about
125.degree. C. to produce the coating.
Example 19
[0140] Part A was mixed with Part B using simple stirring, namely,
a magnetic stir bar and plate to form the mixture. Part A comprised
42.88 grams of trixene 7683 (commercially available from Baxenden
of Lancashire, England) well mixed with 33.91 grams of diacetone
alcohol. Part B comprised 33.91 grams of diacetone well mixed with
11.56 grams of polyethylene glycol 12000 (i.e. molecular weight
12000), 11.56 grams of polyethylene glycol 1000, 0.053 grams of
dibutyl tin dilaurate (obtained by Gelest of PA, USA) and 0.037
grams of DC-28 (obtained from Dow Corning). The mixture was
immediately applied using flow coating to a 4'' square of Teflon
coated metal, and allowed to stand at ambient conditions for about
10 minutes. The mixture was then baked for about I hour at about
125.degree. C. to produce the coating.
Example 20
[0141] Part A was mixed with Part B using simple stirring, namely,
a magnetic stir bar and plate to form the mixture. Part A comprised
35.75 grams of trixene 7683 (commercially available from Baxenden
of Lancashire, England) well mixed with 42.98 grams of diacetone
alcohol. Part B comprised 42.98 grams of diacetone alcohol well
mixed with 21.22 grams of polyethylene glycol 1000, 0.028 grams of
dibutyl tin dilaurate (obtained by Gelest of PA, USA), 0.011 grams
of L-7602 (obtained from Crompton of Pittsburgh, Pa., USA) and
0.011 grams of L-7608 (obtained from Crompton). The mixture was
immediately applied using flow-coating to a 4'' square of Teflon
coated metal, and allowed to stand at ambient conditions for about
10 minutes. The mixture was then baked for about I hour at about
125.degree. C. to produce the coating.
Example 21
[0142] Part A was mixed with Part B using simple stirring, namely,
a magnetic stir bar and plate to form the mixture. Part A comprised
35.75 grams of trixene 7683 (commercially available from Baxenden
of Lancashire, England) well mixed with 42.98 grams of diacetone
alcohol. Part B comprised 42.98 grams of diacetone well mixed with
21.22 grams of polyethylene glycol 1500, 0.028 grams of dibutyl tin
dilaurate (obtained by Gelest of PA, USA), and 0.011 grams of
L-7602 (obtained from Crompton of Pittsburgh, Pa., USA) and 0.011
grams of L-7608 (obtained from Crompton). The mixture was
immediately applied using flow-coating to a 4'' square of Teflon
coated metal, and allowed to stand at ambient conditions for about
10 minutes. The mixture was then baked for about I hour at about
125.degree. C. to produce the coating.
Example 22
[0143] Anti-fog testing was performed on refrigerator doors having,
among others, the coating set forth in Example 14. More
particularly, testing was performed on refrigerators having a
plurality of adjacent doors with the coatings thereon. Testing was
conducted on both no-heat doors and heated doors. The test
conditions for the no-heat doors follow: dry bulb temperature
75.degree. F.; relative humidity 55%, discharge air temperature -1
2.degree. F.; door surface temperature on the product side
-3.degree. F.; and door surface temperature on the customer side of
64.degree. F. The test conditions for the heated door follow: dry
bulb temperature 75.degree. F.; relative humidity 55%, discharge
air temperature -12.degree. F.; door surface temperature on the
product side 9.degree. F.; and door surface temperature on the
customer side of 74.degree. F.
[0144] When the samples were tested, the coated surface was dry and
had substantially no dust accumulation. Visible trans. was about 40
to about 50%. Anti-fogging properties were tested at certain time
intervals. More particularly, the following time intervals were
tested: 6 seconds, 15 seconds, 30 seconds, 1 minute, 2 minutes, 2
minutes and 30 seconds, 3 minutes, 4 minutes and 5-15 minutes. When
coated doors having the surface temperatures set forth above were
opened, and then exposed to the ambient conditions discussed above,
substantially no fogging occurred at any of these time intervals.
Similarly, the doors in the refrigerator adjacent the open door
also did not fog during any of these time intervals. In other
words, when one door was opened, allowing ambient air to flood the
refrigerator, the closed doors adjacent the opened door exhibited
substantially no fogging.
* * * * *