U.S. patent application number 11/936039 was filed with the patent office on 2008-05-15 for coating having macroscopic texture and process for making same.
Invention is credited to Loyd J. Burcham, Donald C. Ferguson, Donald B. Henry, Richard C. MacQueen, Anthony A. Parker, Deborah A. Sciangola.
Application Number | 20080113182 11/936039 |
Document ID | / |
Family ID | 23943778 |
Filed Date | 2008-05-15 |
United States Patent
Application |
20080113182 |
Kind Code |
A1 |
MacQueen; Richard C. ; et
al. |
May 15, 2008 |
Coating Having Macroscopic Texture and Process for Making Same
Abstract
In one embodiment the present invention provides a coated
substrate comprising a substrate, a radiation-cured coating or a
thermally-cured on at least a portion of the substrate, wherein the
coating comprises an inherent macroscopic texture. In another
embodiment, the present invention provides a pre-cured coating
mixture comprising a radiation-curable resin and an initiator, or a
thermally-curable resin and thermal initiator, wherein the
radiation- or thermally-curable resin and the respective initiator
form a pre-cured coating mixture capable of forming a macroscopic
texture upon application of the mixture on a substrate. In another
embodiment the present invention provides a pre-cured coating
mixture comprising a radiation- or thermally-curable resin, an
initiator, and texture-producing particles having an effective size
to provide a macroscopic texture upon application of the mixture on
a substrate. In another embodiment, the present invention provides
a coated substrate comprising a substrate and a radiation- or
thermally-cured coating oil at least a portion of the substrate,
wherein the coating comprises an inherent macroscopic texture. In
addition, the present invention provides a process for making a
coating on a substrate, comprising the steps of distributing a
pre-cured coating mixture comprising a radiation-curable resin and
an initiator or a thermally-curable resin and thermal initiator
over at least a portion of a substrate to form a pre-cured coating
having a macroscopic texture, and radiation-curing or thermally
curing, respectively, the pre-cured coating to form a
radiation-cured or thermally-cured coating having the macroscopic
texture.
Inventors: |
MacQueen; Richard C.;
(Phillipsburg, NJ) ; Burcham; Loyd J.; (Horsham,
PA) ; Parker; Anthony A.; (Newtown, PA) ;
Sciangola; Deborah A.; (Glenmoore, PA) ; Henry;
Donald B.; (Warminster, PA) ; Ferguson; Donald
C.; (Bordentown, NJ) |
Correspondence
Address: |
MORGAN, LEWIS & BOCKIUS, LLP.
2 PALO ALTO SQUARE, 3000 EL CAMINO REAL
PALO ALTO
CA
94306
US
|
Family ID: |
23943778 |
Appl. No.: |
11/936039 |
Filed: |
November 6, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10900789 |
Jul 27, 2004 |
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11936039 |
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10256271 |
Sep 26, 2002 |
6790512 |
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10900789 |
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09765713 |
Jan 19, 2001 |
6730388 |
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10256271 |
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09489420 |
Jan 21, 2000 |
6399670 |
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09765713 |
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Current U.S.
Class: |
428/323 |
Current CPC
Class: |
E04F 15/02 20130101;
Y10T 428/2438 20150115; C08J 3/244 20130101; Y10T 428/25 20150115;
Y10T 428/257 20150115; B44C 3/00 20130101; Y10T 428/254 20150115;
C09D 7/67 20180101; Y10T 428/24421 20150115; Y10T 428/24372
20150115; Y10T 428/3158 20150401; Y10T 428/31786 20150401; Y10T
428/24736 20150115; Y10T 428/24355 20150115; Y10T 428/24388
20150115; C08K 3/22 20130101; C09D 7/69 20180101; Y10T 428/31855
20150401; B05D 5/02 20130101; Y10T 428/3192 20150401; C09D 133/14
20130101; Y10T 428/31725 20150401; Y10T 428/2457 20150115; C09D
7/44 20180101; Y10T 428/24405 20150115; C08L 77/00 20130101; E04F
15/00 20130101; Y10T 428/24579 20150115; B05D 3/067 20130101; Y10T
428/24364 20150115; E04F 15/02172 20130101; C08L 2312/06 20130101;
C09D 5/28 20130101; C09D 7/65 20180101; D06N 3/08 20130101; Y10T
428/269 20150115 |
Class at
Publication: |
428/323 |
International
Class: |
B32B 27/18 20060101
B32B027/18; B32B 5/16 20060101 B32B005/16 |
Claims
1-56. (canceled)
57. A coated flooring substrate, comprising: a substrate having a
top surface, and a cured resin coating having a predetermined
thickness disposed on said top surface, wherein said cured resin
coating comprises a plurality of particles, each having a
predetermined size that is greater than said predetermined
thickness of said cured resin coating, and a visible texture
provided by said plurality of particles.
Description
[0001] This application is a continuation-in-part of U.S.
application Ser. No. 09/489,420 filed Jan. 21, 2000.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates generally to a coating composition and
process for making and applying the coating. More specifically, the
invention relates to radiation-cured and thermally-cured coatings
having a macroscopic texture that provides superior abrasion
resistance and unique aesthetic qualities.
[0004] 2. Description of Related Art
[0005] Radiation-curable coatings are used in many applications
throughout the coatings industry, such as protective coatings for
various substrates, including plastic, metal, wood, ceramic, and
others, and the advantages of radiation-curing compared to thermal
curing are well known in the art. These coatings are typically
resin-based mixtures that are usually cured using ultraviolet (UV)
radiation. The resins are typically mixtures of oligomers and
monomers that polymerize upon exposure to UV radiation resulting in
a cured coating.
[0006] Various other components may be added to the resin mixture.
A photosensitizer or photoinitiator may be added to cause
cross-linkage of the polymers upon exposure to UV radiation.
Flatting agents, such as silica, may be added to reduce or control
the level of gloss in the cured coating; however, U.S. Pat. No.
4,358,476 discloses that excessive concentrations of flatting
agents may result in undesirably high viscosities impeding proper
application of the coating to a substrate, potential separation of
the resin into separate phases, and a deleterious effect on the
efficacy of the UV radiation. U.S. Pat. No. 5,585,415 describes the
use of a pigmented composition and various photoinitiators that
produce a uniform microscopic surface wrinkling that provides a low
gloss surface without the use of flatting agents. Various other
components, such as fillers, plasticizers, antioxidants, optical
brighteners, defoamers, stabilizers, wetting agents, mildewcides
and fungicides, surfactants, adhesion promoters, colorants, dyes,
pigments, slip agents, fire and flame retardants, and release
agents, may also be added to the resin mixture to provide
additional functionality.
[0007] An important aspect of these coatings is their level of
scratch or abrasion resistance. Good abrasion resistance is
desirable so that the integrity and appearance of the coating is
maintained. For example, a superior abrasion-resistant coating
would be desirable for a flooring substrate, since flooring is
typically exposed to a variety of abrasives. Improvements in the
abrasion-resistance of coatings has been accomplished through
various techniques. U.S. Pat. No. 4,478,876 describes the addition
of colloidal silica to hydrolyzable silanes and polymers derived
from a combination of acryloxy functional silanes and
polyfunctional acrylate monomers. Another technique is the use of
compositions containing acrylate or methacrylate functionalities on
a monomer, oligomer, or resin. U.S. Pat. No. 5,104,929 describes
the use of colloidal silica dispersions in certain acrylate or
methacrylate ester monomers or mixtures thereof U.S. Pat. No.
5,316,855 describes the use of a cohydrolyzed metal alkoxide sol
with a trialkoxysilane-containing organic component having the
trialkoxysilane.
[0008] These radiation-cured coatings generally have a
substantially smooth, exposed surface such that there is no
macroscopic texture or texture visible to the naked eye. This type
of smooth surface provides for ease of cleaning. Some
radiation-cured coatings have a microscopic texture as described in
U.S. Pat. No. 5,585,415. The individual features of this texture
are not visible to the naked eye, but the combined effect of the
microscopic texture results in the scattering of visible light,
that results in a matte or low gloss appearance. This texture is
provided by the coating curing process which results in microscopic
wrinkles on the surface of the coating. While the microscopic
dimensions of this texture provide a matte finish, these dimensions
also make the coating susceptible to particle entrapment within the
microscopic wrinkles. This particle entrapment results in a visibly
dirty surface that is difficult to clean. Another microscopic
texture found in radiation-curable coatings results from the
addition of flatting agents to the uncured coating mixture. During
the curing process these flatting agents, which are small inorganic
or organic particles, concentrate at the coating surface to form a
microscopically rough surface that scatters visible light resulting
in a matte finish. The size of the particle used is typically such
that it is no larger in diameter than the average thickness of the
cured coating. Particles much larger than the coating thickness do
not result in a matte finish and are not desired. Since most
radiation-cured coatings are no more than 75-100 .mu.m thick, and
since UV radiation can not typically penetrate any deeper, typical
flatting agent particles for UV-cured coatings range in size from
0.1-100 .mu.m, depending upon average coating thickness. Flatting
agents are well known in the art as described, for example, in F.
D. C. Gallouedec et al., "Optimization of Ultrafine Microporous
Powders to Obtain Low-Gloss UV Curable Coatings," Radtech Report,
September/October 1995, pp 18-24.
[0009] To produce such macroscopically smooth surfaces requires the
application of a coating mixture that can be easily distributed
across the substrate to be coated. if the coating mixture has a
high viscosity, for example, the coating will not distribute
smoothly. Therefore, it is preferable to use a lower viscosity
coating to produce such a macroscopically smooth coating
surface.
[0010] Thermally-cured coatings are also used in many applications
throughout the coatings industry for various substrates such as
plastic, metal, wood, ceramic, and others. Thermally-cured coatings
are similar to radiation-cured coatings in that they typically
comprise resin-based mixtures of oligomers and monomers that
polymerize upon curing. Instead of using radiation to cure or
polymerize the resin, however, heat is used to affect
polymerization. As such, a thermally-activated initiator is used to
initiate polymerization, rather than a photosensitizer or
photoinitiator. However, various other components may be added to
the thermally-curable resin mixture, including the same components
that are added to radiation-curable resin mixture, such as flatting
agents, fillers, plasticizers, antioxidants, optical brighteners,
defoamers, stabilizers, wetting agents, mildewcides and fungicides,
surfactants, adhesion promoters, colorants, dyes, pigments, slip
agents, fire and flame retardants, and release agents.
[0011] Similar to the radiation-cured coatings, however,
thermally-cured coatings are also substantially smooth from a
macroscopic perspective. Also, to produce such macroscopically
smooth surfaces requires the application of a coating mixture that
can be easily distributed across the substrate to be coated. If the
coating mixture has a high viscosity, for example, the coating will
not distribute smoothly. Therefore, as with radiation-cured
coatings, it is preferable to use a lower viscosity coating to
produce such a macroscopically smooth coating surface.
[0012] Other coatings provide a macroscopically textured surface
but by methods other than radiation-curing or thermal-curing. In
chemical embossing, for example, a macroscopic texture is formed
based upon the use of various chemicals added to the substrate. In
mechanical embossing, the substrate itself is imprinted with the
desired textural pattern. In both types of embossing, the
subsequently applied coating naturally conforms to the shape of the
substrate textural pattern. However, any desired change to the
textural pattern requires changes in the amount and type of
chemicals added to the substrate and/or the replacement of the
roller used to mechanically imprint the pattern on the substrate,
which can be significantly expensive and time consuming.
Furthermore, neither the coating itself or its application are
inherently providing the desired. texture. In another form of
mechanical embossing, texture may be achieved by impressing a given
pattern on the cured coating itself. Similarly, however, the
texture is not produced inherently by the coating itself or its
application.
[0013] Based on the foregoing, there is a need for a superior
abrasion-resistant, radiation-cured and thermally-cured coatings
for various substrates including plastic, metal, wood, and ceramic,
among others, having a macroscopic texture. In addition. there is a
need for a coating having a macroscopic texture that is easily
cleanable and that provides certain aesthetic properties. Further,
there is a need for a method to produce such a superior
abrasion-resistant, radiation-cured coating having a macroscopic
texture using a high viscosity pre-cured coating mixture and/or
texture-producing particles.
SUMMARY OF THE INVENTION
[0014] In one embodiment the present invention provides a coated
substrate comprising a substrate, a radiation-cured coating on at
least a portion of the substrate, wherein the coating comprises an
inherent macroscopic texture. In another embodiment, the present
invention provides a pre-cured coating mixture comprising a
radiation-curable resin and an initiator, wherein the
radiation-curable resin and the initiator form a pre-cured coating
mixture capable of formming a macroscopic texture upon application
of the mixture on a substrate. In another embodiment the present
invention provides a pre-cured coating mixture comprising a
radiation-curable resin, an initiator, and texture-producing
particles having an effective size to provide a macroscopic texture
upon application of the mixture on a substrate.
[0015] In yet another embodiment, the present invention provides a
coated substrate comprising a substrate, a thermally-cured coating
on at least a portion of the substrate, wherein the coating
comprises an inherent macroscopic texture. In another embodiment,
the present invention provides a pre-cured coating mixture
comprising a thermally-curable resin and a thermal initiator,
wherein the thermally-curable resin and the thermal initiator form
a pre-cured coating mixture capable of forming a macroscopic
texture upon application of the mixture on a substrate. In another
embodiment the present invention provides a pre-cured coating
mixture comprising a thermally-curable resin, a thermal initiator,
and texture-producing particles having an effective size to provide
a macroscopic texture upon application of the mixture on a
substrate.
[0016] In addition, the present invention provides a process for
making a coating on a substrate, comprising the steps of
distributing a pre-cured coating mixture comprising a
radiation-curable resin and an initiator or a thermally-curable
resin and thermal initiator over at least a portion of a substrate
to form a pre-cured coating having a macroscopic texture, and
radiation-curing or thermally curing, respectively, the pre-cured
coating to form a radiation-cured or thermally-cured coating having
the macroscopic texture.
[0017] The coating of the present invention provides a top coat or
protective coating having a macroscopic texture to substrates
containing plastic such as polyvinyl chloride, metal, cellulose,
fiberglass, wood, and ceramic, among others. In a preferred
embodiment the coating of the present invention is used in
connection with sheet flooring. In an additionally preferred
embodiment, the coating of the present invention is used in
connection with floor tiles. The coating of the present invention
provides superior scratch or abrasion resistance and good
transparency. In addition, the coating of the present invention is
easily cleanable, and the macroscopic texture provides an aesthetic
aspect to the coating.
[0018] Other embodiments and features of the present invention will
appear from the following description in which the preferred
embodiments are set forth in detail in conjunction with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 illustrates a perspective view of a coated substrate
10 according to one embodiment of the present invention;
[0020] FIG. 2 illustrates a cross-sectional view of a coated
substrate according to another embodiment of the present
invention;
[0021] FIG. 3 illustrates a cross-sectional view of a coated
substrate according to yet another embodiment of the present
invention;
[0022] FIG. 4 is a process flow diagram of a process for making a
coating according to one embodiment of the present invention;
[0023] FIG. 4B illustrates a cross-sectional. view of a coated
substrate according to yet another embodiment of the present
invention;
[0024] FIG. 4C is a cross-sectional view of a vinyl tile according
to one embodiment of the present invention;
[0025] FIG. 4D is a process flow diagram of a process for applying
a coating of the present invention to a tile substrate according to
one embodiment of the present invention;
[0026] FIG. 4E illustrates a cross-sectional view of a coated
substrate according to yet another embodiment of the present
invention;
[0027] FIG. 5 is a graph of the viscosity as a function of the
shear rate for a pre-cured coating mixture made according to one
embodiment of the present invention;
[0028] FIG. 6 is a graph of the viscosity as a function of the
shear rate for a pre-cured coating mixture made, according to
another embodiment of the present invention;
[0029] FIG. 7 is a graph of the viscosity as a function of time for
a pre-cured coating mixture made according to one embodiment of the
present invention;
[0030] FIG. 8 is a graph of the viscosity as a function of the
silane concentration in a pre-cured coating mixture made according
to one embodiment of the present invention;
[0031] FIG. 9 is a photograph of the top of a portion of the coated
substrate produced according to one embodiment of the present
invention;
[0032] FIG. 10 is a photograph of the top of a portion of the
coated substrate produced according to another embodiment of the
present invention;
[0033] FIG. 11 is an illustration of the coated texture of FIG.
9;
[0034] FIG. 12 is an illustration of the coated texture of FIG.
10;
[0035] FIG. 13 is an illustration of the general type of
macroscopic texture according to one embodiment of the present
invention;
[0036] FIG. 14 is a photograph of the top of a portion of the
coated substrate produced according to another embodiment of the
present invention;
[0037] FIG. 15 is a photograph of the top of a portion of the
coated substrate produced according to another embodiment of the
present invention;
[0038] FIG. 16 is a photograph of the top of a portion of the
coated substrate produced according to another embodiment of the
present invention;
[0039] FIG. 17 is a photograph of the top of a portion of the
coated substrate produced according to another embodiment of the
present invention;
[0040] FIG. 18 is a photograph of the top of a portion of the
coated substrate produced according to another embodiment of the
present invention;
[0041] FIG. 19 is an illustration of the coated texture of FIG.
14;
[0042] FIG. 20 is an illustration of the coated texture of FIG.
15;
[0043] FIG. 21 is an illustration of the coated texture of FIG.
16;
[0044] FIG. 22 is an illustration of the coated texture of FIG.
17;
[0045] FIG. 23 is an illustration of the coated texture of FIG.
18;
[0046] FIG. 24 is an illustration of the general type of
macroscopic texture according to another embodiment of the present
invention;
[0047] FIG. 25 is an enlarged view of a portion of FIG. 24;
[0048] FIG. 26 is a photograph of the top of a portion of the
coated substrate produced according to another embodiment of the
present invention;
[0049] FIG. 27 is a photograph of the top of a portion of the
coated substrate produced according to another embodiment of the
present invention;
[0050] FIG. 28 is a photograph of the top of a portion of the
coated substrate produced according to another embodiment of the
present invention;
[0051] FIG. 29 is an illustration of the coated texture of FIG.
26;
[0052] FIG. 30 is an illustration of the coated texture of FIG.
27;
[0053] FIG. 31 is an illustration of the coated texture of FIG.
28;
[0054] FIG. 32 is an illustration of the general type of
macroscopic texture according to another embodiment of the present
invention; and
[0055] FIG. 33 is a graph of the results of scratch resistance
tests for several coatings made according to various embodiments of
the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0056] The present invention provides a coating having a
macroscopic texture that exhibits superior abrasion-resistance,
aesthetic value, and ease of cleaning. It should be appreciated
that an important aspect of the present invention is that the
macroscopic texture is provided inherently by the coating itself.
In addition, the present invention provides a pre-cured coating
mixture and a process for using the pre-cured coating mixture to
generate the coating of the present invention on a substrate.
[0057] It should be appreciated that the term "coating" refers to
the cured coating that typically would reside as an outer or
exposed layer on a substrate after it has been cured or finally
processed. The terms "radiation-cured" and "thermally-cured" mean
after curing has occurred; therefore, the coating of the present
invention, for example, may also be referred to as a
"radiation-cured coating" or a "thermally-cured coating." The terms
"radiation-curable" and "thermally-curable" mean prior to curing or
capable of being cured, and the term "pre-cured" means prior to
curing.
[0058] In one embodiment of the present invention, the pre-cured
coating mixture generally comprises a radiation-curable resin and
an initiator. The radiation-curable resin may be any resin capable
of being cured using radiant energy. Radiant energy can be
transferred through wave phenomenon and subatomic particle
movement. Most preferred forms of radiant energy are ultraviolet
(UV) and electron beam energy. Preferably, the radiation-curable
resin comprises organic monomers, oligomers, or both. U.S. Pat.
Nos. 4,169,167, 4,358,476, 4,522,958, 5,104,929, 5,585,415,
5,648,40, and 5,858,809, incorporated herein by reference, describe
various resins, including crosslinkable (thermosetting) resins,
that may be used in the present invention.
[0059] More preferably, the radiation-curable, resin comprises a
mixture of crosslinkable monomers and oligomers that contain on
average from 1-20 reactive groups per molecule of monomer or
oligomer, where the reactive group provides the functionality for
polymerization upon exposure to radiation. More preferably, the
number of reactive groups per molecular is from 1-6. Preferred
reactive groups include acrylate, vinyl, lactone, oxirane, vinyl
ether, and hydroxyl. More preferred reactive groups include
acrylate, oxirane, vinyl ether, and hydroxyl. The most preferred
monomers and oligomers, however, are acrylates. Acrylates have the
following structure:
CH.sub.2.dbd.CR--CO--
where R can be hydrogen, or alkyl including, but not limited to
methyl, ethyl, propyl, butyl, etc. These radiation-curable resins
are readily available or may be synthesized by procedures well
known to one of skill in the art. It is noted that the term
"radiation-cured groups" refers to these reactive groups after they
have been cured.
[0060] The oligomers and monomers can also have 1-100
non-radiation-curable functional groups per molecule of monomer or
oligomer. Preferred non-radiation-curable functional groups include
urethane, melamine, triazine, ester, amide, ethylene oxide,
propylene oxide, and siloxane. More preferred non-reactive groups
are urethane ester, ethylene oxide, and propylene oxide.
[0061] As will be further described below in connection with the
process for making the coating of the present invention, the
concentration of the radiation-curable resin is dependent upon
several factors. In one preferred embodiment, the concentration of
the radiation-curable resin is selected to provide an effective or
desired viscosity of the pre-cured coating mixture. The effective
viscosity of the pre-cured coating mixture is that viscosity
capable of producing a macroscopic texture, described below, upon
application of the pre-cured coating mixture to a substrate and
subsequent curing. Preferably, the viscosity of the pre-cured
coating mixture is approximately 100,000-1,000,000 cPs at a shear
rate of 0.150 s.sup.-1 at the application temperature. Therefore,
the radiation-cured resin may comprise approximately 50-99%, by
weight of the pre-cured coating mixture to provide the desired
viscosity. Preferably, the radiation-cured resin comprises
approximately 70-99%, by weight, of the pre-cured coating mixture.
Of course, the viscosity of the pre-cured coating mixture, and,
therefore, the concentration of the radiation-curable resin, will
be affected by the use of additional components in the pre-cured
coating mixture such as rheological control agents, which will be
described below. Other factors that affect the concentration of the
radiation-curable resin are well known to one of skill in the
art.
[0062] The initiator may be any chemical capable of assisting or
catalyzing the polymerization and crosslinking of the
radiation-curable resin upon exposure to radiation. The initiator
may generally be a photoinitiator or photosensitizer. Such
initiators are well known in the art and may be selected based upon
the curing conditions used (e.g., curing in an inert environment or
in air). Specifically, the initiator may be a free radical
photoinitiator, a cationic photoinitiator, and mixtures of both of
these. Preferred free radical photoinitiators include acyl
phosphine oxide derivatives, benzophenone derivatives, and mixtures
thereof. Preferred cationic photoinitiators include
triarylsulphonium salts, diaryliodonium salts, ferrocenium salts,
and mixtures thereof. It should be appreciated that the initiator
refers to the initiator both before and after curing. Therefore,
the initiator may have a different chemical structure or
composition in the radiation-cured coating after exposure to
radiation.
[0063] The concentration of a particular initiator is that amount
necessary to provide satisfactory curing for a given proved resin
based upon the properties of that particular initiator. Such
concentrations can be readily identified by one of skill in the
art. A preferred concentration of the initiator is 0.01-10 parts
per hundred resin (phr), and a more preferred concentration is
0.1-4 phr.
[0064] The pre-cured coating mixture may also comprise a
rheological control agent (RCA), particularly if the pre-cured
coating mixture does not have an inherent viscosity that is high
enough to form a macroscopic texture upon application of the
pre-cured coating mixture to a substrate. The RCA may be inorganic
particles, organic solids, and mixtures of both.
[0065] The inorganic particles may be any inorganic solid having a
size that is small enough to be included in the pre-cured coating
mixture without deleteriously affecting the pre-cured coating
mixture's ability to cure and adhere to a substrate. The particle
should also be sufficiently small and/or closely match the
refractive index of the cured coating such that the opacity of the
cured coating is minimized. The particle should also not
deleteriously affect the cured coating's abrasion resistance and in
some cases it can improve that property. Additionally, the particle
should not deleteriously affect the resistance of the cured coating
to chemical attack by strongly basic aqueous media (i.e., the
alkali resistance of the coating), since such alkali resistance is
important in flooring materials. It should be appreciated that the
size of these particles is such that they do not directly provide
or contribute to the macroscopic texture. Preferred sizes of the
inorganic particles are 1-100 nm, where 10-60 nm are most
preferred.
[0066] Preferably, the inorganic particles are metal oxides,
metals, or carbonates, where metal oxides are preferred. More
preferably, the inorganic particles are alumina, aluminosilicates,
alumina coated on silica, silica, fumed alumina, fumed silica,
calcium carbonate, and clays. Still more preferred is alumina due
to its superior hardness (for abrasion resistance) and for its
greater alkali resistance relative to silica. Most preferred is
nanometer-sized alumina with a particle size range of 27-56 nm due
to the enhanced cured coating transparency afforded by such small
particles when they are well-dispersed (e.g., through the use of an
appropriate amount and type of coupling agent). However, since
alumina has a higher refractive index (i.e., .about.1.7) than most
organic coatings and silica (both .about.1.5), it may be envisioned
that a nanometer-sized aluminosilicate material will give the
optimal combination of transparency, abrasion resistance, and
alkali resistance.
[0067] The inorganic particles may comprise approximately 1-80%, by
weight, of the pre-cured coating mixture, more preferably 1-50%, by
weight, and most preferably 1-25%, by weight. Even more preferably,
if nanometer-sized alumina is used, its concentration is
approximately 1-40%, by weight, of the pry coating mixture. If
fumed silica is used, its concentration is approximately 1-10%, by
weight, of the pre-cured coating mixture. If nanometer-sized chine
silica is used, its concentration is approximately 10-30%, by
weight, of the procured coating mixture. If exfoliated clay is
used, its concentration is approximately 10-30%, by weight, of the
pre-cured coating mixture.
[0068] Similarly, the organic solids may be any organic solid
having a size that is small enough to be included in the pre-cured
coating mixture without deleteriously affecting the pre-cured
coating mixture's ability to cure and adhere to a substrate. As
with the inorganic particles, the organic particles should also not
deleteriously affect the cured coating's transparency or abrasion
resistance. Unlike the inorganic particles, the organic particles
may dissolve or partially dissolve into the pre-cured resin at
elevated temperature and thicken the pre-cured coating mixture upon
cooling. The organic solids may be low molecular weight waxes
containing functionality such as acid, amine, amide, hydroxyl,
urea; polymers of ethylene glycol; polymers of propylene glycol;
natural polymers such as guar, gelatin, and corn starch;
polyamides; polypropylene; and mixtures of any of these. Most
preferred are functional waxes. The organic solids may comprise
approximately 1-50%, by weight, of the pre-cured coating mixture.
More preferably, the organic solids comprise between approximately
1-20%, by weight. Most preferably, if functional waxes are used,
their concentration is approximately 1-10%, by weight, of the
pre-cured coating mixture. As will be described below in connection
with the process for making the coating of the present invention,
the RCA may added for several purposes.
[0069] A coupling agent or dispersing agent may also be added for
purpose of aiding the dispersion of the RCA in the pre-cured
coating mixture. The coupling agent may be any material that
provides surfactant-like properties and is capable of enhancing the
dispersion of the RCA in the pre-cured coating mixture, in
particular, the dispersion of inorganic particles. The coupling
agent ideally forms a chemical and/or physical bond with the
pre-cured coating mixture and the inorganic particle, which
improves the adhesion of the particle to the pre-cured coating
mixture. Generally, the coupling agent is a organo-silicon or
organo-fluorine containing molecule or polymer. Preferred
organo-silicon materials are organosilanes and more preferably a
prehydrolyzed organosilane. The coupling agent may also be vinyl
phosphonic acid or mixtures of phosphonic acid with the
prehydrolyzed organosilane. The concentration of the dispersing
agent may be approximately 0.1-20%, by weight in the pre-cured
coating mixture, and more preferably approximately 0.1-15%, by
weight.
[0070] A flatting agent may also be added to the procured coating
mixture of the present invention. Flatting agents are well known in
the art. Preferred flatting agents include organic particles having
a size of approximately 0.1-100 microns, inorganic particles having
a size of approximately 0.1-100 microns, and mixes of both. When
flatting agents art used, a coupling agent may be needed to obtain
good dispersion in the pre-cured coating mixture and good adhesion
between the particle and the cured coating. For inorganic flatting
agents, preferred coupling agents are organosilanes, mixtures of
organosilanes, and low surface tension monomers and oligomers. For
organic flatting agents, preferred coupling agent include
organosilanes, mixtures of organosilanes, and low surface tension
monomers and oligomers. The particle size selected is such that it
is about the same size as the coating thickness or smaller. More
preferred flatting agents include silica, alumina, polypropylene,
polyethylene, waxes, ethylene copolymers, polyamide,
polytetrafluoroethylene, urea-formaldehyde and combinations
thereof. The concentration of the flatting agent may be
approximately 2-25%, by weight, of the pre-cured coating mixtures
and more preferably is 5-20%, by weight.
[0071] In addition to the foregoing components of the pre-cured
coating mixture, texture-producing particles may also be added.
Such texture-producing particles have an effective size or an
average diameter that is larger than the pre-cured coating
thickness after it has been applied to a substrate. These
texture-producing particles, therefore, may act to provide the
macroscopic texture of the coating of the present invention. It
should be appreciated that these texture-producing particles may be
added to a pre-cured coating mixture that has an effective
viscosity for macroscopic texture or to a pre-cured coating mixture
that does not have an effective viscosity for macroscopic texture.
In the latter case, the macroscopic texture would be produced only
by the texture-producing particles.
[0072] The degree of texture provided by the texture-producing
particles is controlled by the ratio of the particle size to the
thickness of the cured coating. As this ratio increases from 1, the
texture becomes macroscopic and can be made more aggressive,
(visibly more rough) as the ratio is increased. The degree of
aggressiveness of the texture is determined by the desired end use
properties such as abrasion resistance and cleanability. It is
important that the particles selected have good adhesion to the
cured coating. These particles can be inorganic or organic
materials. A coupling agent may be necessary to obtain good
dispersion in the pre-cured coating mixture and good adhesion
between the particle and the cured coating. Preferred inorganic
particles are glass, ceramic, alumina, silica, aluminosilicates,
and alumina coated on silica. Preferred coupling agents for
inorganic texture-producing particles are organosilanes. Preferred
organic particles are thermoplastic and thermosetting polymers. For
inorganic flatting agents, preferred coupling agents are
organosilanes, mixtures of organosilanes, and low surface tension
monomers and oligomers. For organic flatting agents, preferred
coupling agents include organosilanes, mixtures of organosilanes,
and low surface tension monomers and oligomers. Most preferred
organic particles are polyamide, including nylons, specifically,
nylon 6 and nylon 12 (although one of skill in the art will
recognize that other nylons may be used in the present invention),
polypropylene, polyethylene, polytetrafluoroethylene, ethylene
copolymers, waxes, epoxy, and urea-formaldehyde. Preferred average
particle size of both organic and inorganic particles is 30-350
.mu.m. Most preferred is 30-150 .mu.m. Preferred concentration of
particles in the pre-cured coating mixture is 1-30%, by weight. The
most preferred concentration is 5-15% by weight.
[0073] A preferred embodiment of a pre-cured coating mixture of the
present invention comprises, by weight, 79.44% of a resin mixture
comprising, by weight, 53.40%, urethane acrylate (Alua 1001,
available from Congoleum Corporation, Mercerville, N.J.), 8.8%
ethoxylated diacrylate (SR 259 available from Sartomer, Exton,
Pa.), 24.3% propoxylated diacrylate (SR 306 available from
Sartomer, Exton, Pa.), 13.4% ethoxylated trimethlyolpropane
triacrylate (SR 454 available from Sartomer, Exton, Pa.), and 0.1%
acylphosphine oxide (Luceirin TPO available from BASF, Charlotte
N.C.), 12.00% flatting agent comprising 5 micron nylon particles
(Orgasol 2001 UD available from Atofina, Philadelphia, Pa.); 6.25%
texture-producing particles comprising 60 micron nylon 12 particles
(Orgasol 2002 ES 6 available from Atofina, Philadelphia, Pa.);
2.00% alumina RCA having a particle size distribution in the range
of 27-56 nm (Nanotek Alumina #0100 available from Nanophase
Technologies Corp. Burr Ridge, Ill.); and 0.31% prehydrolyzed
silane as an RCA coupling agent comprising 0.21%
3-methacryloxypropyltrimethoxysilane (Z-6030 available from Dow
Corning, Midland, Mich.), 0.015% glacial acetic acid, 0.015%
deionized water, and 0.07% ethanol, prehydrolyzed as described in
Example 1 below. As such, a preferred cured coating according to
the present invention is that coating produced using the above
preferred pre-cured coating mixture. In particular, this pre-cured
coating mixture and the resulting cured coating are preferred for
use on sheet flooring as a substrate.
[0074] An even more preferred embodiment of a pre-cured coating
mixture of the present invention comprises, by weight, 84.59% of a
resin mixture comprising, by weight, 53.4% urethane acrylate (Alua
1001, available from Congoleum Corporation, Mercerville, N.J.),
8.8% ethoxylated diacrylate (SR 259 available from Sartomer, Exton,
Pa.), 24.3%. propoxylated diacrylate (SR 306 available from
Sartomer, Exton, Pa.), 13.3% ethoxylated trimethlyolpropane
triacrylate (SR 454 available from Sartomer, Exton, Pa.), and 0.2%
acylphosphine oxide (Luceirin TPO available from BASF, Charlotte,
N.C.); 8.0% flatting agent comprising 5 micron nylon particles
(Orgasol 2001 UD available from Atofina, Philadelphia, Pa.); 6.25%
texture-producing particles comprising 60 micron nylon 12 particles
(Orgasol 2002 ES 6 available from Atofina, Philadelphia, Pa.); 1.0%
alumina RCA having a particle size distribution in the range of
27-56 nm (Nanotek Alumina #0100 available from Nanophase
Technologies Corp. Burr Ridge, Ill.); and 0.16% prehydrolyzed
silane as an RCA coupling agent composing 0.21%
3-methacryloxypropyltrimethoxysilane (Z-6030 available from Dow
Corning, Midland, Mich.), 0.015% glacial acetic acid, 0.015%
deionized water, and 0.07% ethanol prehydrolyzed as described in
Example 1 below. As such, a preferred cured coating according to
the present invention is that coating produced using the above
preferred pre-cured coating mixture. In particular, this pre-cured
coating mixture and the resulting cured coating are preferred for
use on sheet flooring as a substrate.
[0075] In another preferred embodiment, a pre-cured coating mixture
for use with tile as the substrate comprises, by weight, 35.303%
ethoxylated trimethylolpropane triacrylate (SR 454, available from
Sartomer, Exton, Pa.), 41.050% polyester acrylate (Laromer PE56F,
available from BASF, Charlotte, N.C.), 5.747% urethane acrylate
(Alua 1001, available from Congoleum Corporation, Mercerville,
N.J.), 0.330% acylphosphine oxide (Luceirin TPO, available from
BASF, Charlotte, N.C.), 8.000% 3 micron inorganic flatting agent
(Acematte OK 412, available from Degussa Corp., Ridgefield Park,
N.J.), 2.323% prehydrolyzed silane as an RCA coupling agent
comprising 0.21% 3-methacryloxypropyltrimethoxysilane (Z-6030
available from Dow Corning, Midland, Mich.), 0.015% glacial acetic
acid, 0.015% deionized water, and 0.07% ethanol, prehydrolyzed as
described in Example 1 below, 1.000% inorganic RCA (Nanotek Alumina
#0100, available from Nanophase Technologies, Burr Ridge, Ill.),
and 6.250% 60 micron texture-producing particle (Orgasol 2002 ES6,
available from Atofina, Philadelphia, Pa.). As such, a preferred
cured coating according to the present invention is that coating
produced using the above preferred pre-cured coating mixture.
[0076] In another embodiment of the present invention, the
pre-cured coating mixture comprises a thermally-curable resin and a
thermal initiator. The thermally-curable resin may be any resin
capable of being cured using thermal energy. The thermally-curable
resins preferably include organic monomers, oligomers, or both.
U.S. Pat. Nos. 4,169,167, 4,358,476, 4,522,958, 5,104,929,
5,585,415, 5,648,40, and 5,858,809, incorporated herein by
reference, describe various resins, including crosslinkable
(thermosetting) resins, that may be used in the present invention.
The thermal initiator used for thermally-curable coatings of the
present invention is any thermal initiator known in the art.
Preferably, the free radical thermal initiator is an organic
peroxide, such as tertiary-butyl peroxybenzoate.
[0077] More preferably, the thermally-curable resin comprises a
mixture of crosslinkable monomers and oligomers that contain on
average from 1-20 reactive groups per molecule of monomer or
oligomer, where the reactive group provides the functionality for
polymerization upon exposure to heat. More preferably, the number
of reactive groups per molecular is from 1-6. Preferred reactive
groups include acrylate, vinyl, lactone, oxirane, vinyl ether, and
hydroxyl. More preferred reactive groups include acrylate, oxirane,
vinyl ether, and hydroxyl. The most preferred monomers and
oligomers, however, are acrylates. Acrylates have the following
structure:
CH.sub.2.dbd.CR--CO--
where R can be hydrogen, or alkyl, including, but not limited to,
methyl, ethyl, propyl, butyl, etc. These thermally-curable resins
are readily available or may be synthesized by procedures well
known to one of skill in the art. It is noted that the term
"thermally-cured groups" refers to these reactive groups after they
have been cured.
[0078] The oligomers and monomers can also have 1-100
non-thermally-curable functional groups per molecule of ester,
amide, ethylene oxide, propylene oxide, and siloxane. More
preferred non-reactive groups are urethane, ethylene oxide, and
propylene oxide.
[0079] As will be further described below in connection with the
process for making the coating of the present invention, the
concentration of the thermally-curable resin is dependent upon
several factors. In one preferred embodiment, the concentration of
the thermally-curable resin is selected to provide an effective or
desired viscosity of the pre-cured coating mixture. The effective
viscosity of the pre-cured coating mixture is that viscosity
capable of producing a macroscopic texture, described below, upon
application of the pre-cured coating mixture to a substrate and
subsequent curing. Preferably, the viscosity of the pre-cured
coating mixture is approximately 100,000-1,000,000 cPs at a shear
rate of 0.150 s.sup.-1 at the application temperature. Therefore,
the thermally-cured resin may comprise approximately 50-99%, by
weight of the pre-cured coating mixture to provide the desired
viscosity. Preferably, the thermally-cured resin comprises
approximately 70-99%, by weight, of the pre-cured coating mixture.
Of course, the viscosity of the pre-cured coating mixture, and,
therefore, the concentration of the thermally-curable resin, will
be affected by the use of additional components in the pre-cured
coating mixture such as rheological control agents, which will be
described below. Other factors that affect the concentration of the
thermally-curable resin are well known to one of skill in the
art.
[0080] As with the radiation-curable coatings of the present
invention, the thermally-cured coatings of the present invention
also provide a macroscopic texture. A such, the same rheological
control agents, coupling agents, flatting agents, and
texture-producing particles previously described may be used with
the thermally-curable coatings of the present invention. The manner
of use of these agents with the thermally-curable coatings of the
present invention is the same as previously described for the
radiation-curable coatings.
[0081] A preferred embodiment of a thermally pre-cured coating
mixture of the present invention comprises, by weight, 44.83%
urethane acrylate (Alua 1001, available from Congoleum Corporation,
Mercerville, N.J.), 6.92% ethoxylated diacrylate (SR 259 available
from Sartomer, Exton, Pa.), 20.53% propoxylated diacrylate (SR 306
available from Sartomer, Exton, Pa.), 11.25% ethoxylated
trimethylolpropane triacrylate (SR 454 available from Sartomer,
Exton, Pa.), 1.06% tertiary-butyl peroxybenzoate (P-20 available
from Norac, Azusa, Calif.) 8% flatting agent comprising 5 micron
nylon 12 particles (Orgasol 2001 UD available from Atofina,
Philadelphia, Pa.), 6.25% texture-producing particles comprising 60
micron nylon 12 particles (Orgasol 2002 ES6 available from Atofina,
Philadelphia, Pa.), 1% alumina RCA having a particle size
distribution in the range of 27-56 nm, and nominally 35 nm,
(Nanotek Alumina #0100 available from Nanophase Technologies Corp.
Burr Ridge, Ill.), and 0.16% prehydrolyzed silane as an RCA
coupling agent comprising 0.21%
3-methacryloxypropyltrimethoxysilane (Z-6030 available from Dow
Corning, Midland, Mich.), 0.015% glacial acetic acid, 0.015%
deionized water, and 0.07% ethanol, prehydrolyzed as described in
Example 1 below. As such, a preferred cured coating according to
the present invention is that coating produced using the above
preferred pre-cured coating mixture. Another preferred embodiment
is the use of the foregoing pre-cured coating mixture and resulting
cured coating with sheet flooring as the substrate.
[0082] It should be appreciated that many additional components
known in the art may be added to the coatings of the present
invention. These additional components may include fillers,
plasticizers, antioxidants, optical brighteners, defoamers,
stabilizers, wetting agents, mildewcides and fungicides,
surfactants, adhesion promoters, colorants, dyes, pigments, slip
agents, fire and flame retardants, and release agents.
[0083] FIG. 1 illustrates a perspective view of a coated substrate
10 according to one embodiment of the present invention. In FIG. 1
a coating 12 is adhered to a substrate 14, where the coating 12 is
produced by curing the pressured coating mixture made according to
the present invention either being a radiation-curable coating
mixture or a thermally-curable coating mixture. It should be
appreciated that the coating of the present invention may be used
in conjunction with any substrate that is capable of remaining
attached to the coating after curing. Substrates that may be used
include those containing plastic such as polyvinyl chloride, metal,
cellulose, fiberglass, wood, and ceramic, among others. Preferably,
the substrate is a flooring material, such as a floor tile or
flexible sheet, where the surface of the coating having the
macroscopic texture is the exposed surface of the flooring or that
surface upon which one would walk. The superior scratch resistance
of the coating of the present invention, and the ease of cleaning,
make the coating particularly suitable for flooring
applications.
[0084] As noted, the coating of the present invention has an
inherent macroscopic texture. The term "macroscopic texure" is
intended to encompass any textural features, regular or irregular,
produced on the surface of a coating that are visible to the naked
eye at close range, as opposed to microscopic texture that would
require the use of a microscope to view the texture. The
macroscopic texture of the present invention may also provide a
non-smooth surface such that the texture is apparent to the touch.
Additionally, the macroscopic texture when produced by the use of
texture-producing particles may be visible to the naked or unaided
eye at a close range. The macroscopic texture may have any design,
shape, or pattern on the surface of the coating. This macroscopic
texture (not shown in FIG. 1) is provided by the coating 12 and is
visible to the naked eye when viewing the coating 12 on the coated
substrate 10.
[0085] As described above in connection with the pre-cured coating
mixture, the macroscopic texture may be provided by different
components in the pre-cured coating mixture. In one embodiment of
the invention, the macroscopic texture is provided by a pre-cured
coating mixture having an effective viscosity capable of providing
a macroscopic texture. In another embodiment, the macroscopic
texture is provided by a pre-cured coating mixture that comprises
texture-producing particles having an effective size to produce a
cured coating with the macroscopic texture. In yet another
embodiment, the macroscopic, texture may be provided by a pre-cured
coating mixture having both an effective viscosity and
texture-producing particles. Several examples of various coatings
made according, to various embodiments of the present invention are
described below, which provide examples of the various macroscopic
textures. These examples are intended to provide examples of how a
macroscopic texture may be achieved, but are not intended to be
limiting as to the types, shapes, or patterns of macroscopic
texture that may be obtained.
[0086] In addition, it was surprisingly found that the coatings of
the present invention with macroscopic texture have superior
scratch and abrasion resistance as measured by a Taber scratch test
and traffic were panels. Scratch test results for various coatings
made according to the present invention are described in the
examples below.
[0087] It should be appreciated that the concentrations of the
various non-reactive groups and components in the cured coating are
assumed to be the same in the pre-cured coating mixture. As will be
described below, the coating of the present invention is made by
applying the pre-cured coating mixture to a substrate followed by
either radiation-curing or thermal curing. Therefore, it is assumed
that the concentrations of the various non-reactive groups and
components in the pre-cured coating mixture will not change
substantially during curing and will remain substantially the same.
However, those skilled in the art will recognize that other
factors, such as coating application processing conditions, may
induce some degree of variability in these concentrations.
[0088] FIG. 2 illustrates a cross-sectional view of a coated
substrate according to another embodiment of the present invention.
FIG. 2 shows a coated substrate 20 having a coating 22 on a coated
substrate layer 24 and additional substrate layers 26 attached to
the coated substrate layer 22 on the side opposite the coating 22.
The coating 22 illustrates the macroscopic texture provided by the
coating 22. As shown in FIG. 2, it should be appreciated that the
macroscopic texture of the coatings made according to the present
invention is inherent in, or provided by, the coating itself and is
independent of the substrate to which the coating is adhered.
Therefore, it should be appreciated that this coating is
significantly different from coatings that naturally conform to a
substrate having a texture or for cured coatings that are impressed
with a pattern.
[0089] FIG. 3 illustrates a cross-sectional view of a coated
substrate according to yet another embodiment of the present
invention. FIG. 3 shows a coated substrate 30 having a coating 32
on a coated substrate layer 34 and additional substrate layers 36
attached to the coated substrate layer 32 on the side opposite the
coating 32. FIG. 3 illustrates that the coatings of the present
invention may also be applied to substrates that already have
macroscopic texture themselves due to embossing or some other
method. Thus, two or more textures can exist on a given coated
substrate, i.e., texture from the coating and texture from the
substrate. As illustrated in FIG. 3, the macroscopic texture of the
coating 32 may be such that it conforms to the texture of the
underlying substrate 34. Alternatively, the macroscopic texture may
be applied so that it does not conform to the texture of the
underlying substrate.
[0090] FIG. 4 is a process flow diagram of a process for making a
coating according to one embodiment of the present invention. In
the step 40, the initiator is dissolved in the radiation-curable
resin. The initiator and the resin may be mixed in any manner
typically used in the art such that the initiator is dissolved into
the resin phase.
[0091] In the step 42, any RCA, coupling agent, flatting agent, or
texture-producing particles are added to the mixture produced in
the step 40. It should be appreciated that for the RCA, flatting
agent, and/or texture-producing particles, a coupling agent may
also be used. In this case, the particles and the coupling agent
may simply be added to the mixture either simultaneously or
sequentially, without the need to pre-treat the particles with the
coupling agent before adding these components to the mixture. This
avoids the use of a solvent that may create diffusion pathways for
staining materials to diffuse through and stain the coating. In
some cases, it is desirable to make a concentrated mixture of RCA,
coupling agent, flatting agent, and/or texture-producing particles
in a liquid medium and dilute it down into the pre-cured coating
mixture. This concentrate is called a master batch and is well
known in the art.
[0092] In the step 44, all of the components are mixed to produce
the pre-cured coating mixture. The step 44 may be accomplished
using a Cowles blade mixer, ultrasonic probe, or other high shear
mixer. It should be appreciated that during mixing the temperature
of the mixture should not be allowed to increase significantly. For
example, increases in temperature to approximately 100.degree. C.
may result in thermal reaction of the resin causing gelation. In
cases where an organic solid is used as a RCA, the temperature
during mixing should be allowed to increase to a temperature that
is adequate to dissolve the organic solid, for example, 70.degree.
C. The temperature should then be reduced to ambient temperature,
thereby producing a highly viscous pre-cured coating mixture.
[0093] In one embodiment of the invention, the pre-cured coating
mixture produced in the step 44 must have the necessary viscosity
to produce a macroscopic texture upon application and subsequent
curing of the pre-cured coating mixture on a substrate. Preferably,
the viscosity of the pre-cured coating mixture should be
approximately 100,000-1,000,000 cPs at a shear rate of 0.150
s.sup.-1 at the application temperature. As will be further
discussed below a viscosity that is too low does not provide a
macroscopic texture, and a viscosity that is too high results in
poor distribution of the pre-cured coating mixture over the
substrate surface.
[0094] To obtain the requisite, viscosity in the pre-cured coating
mixture requires the use of the appropriate concentration of the
radiation-curable resin. It should be appreciated that the
radiation-curable, resin may alone be used to provide the requisite
viscosity, but that it may be desirable to use a RCA in conjunction
with the radiation-curable resin to provide the requisite
viscosity. If a RCA is used, then the requisite viscosity will be
determined by using the appropriate concentration of both the
radiation-curable resin and the RCA. It should be appreciated that
in either case, the concentration of these components will be
dependent upon the intrinsic properties of each. It should also be
appreciated that the addition of other components, such as coupling
agents and flatting agents, may also affect the viscosity of the
pre-cured coating mixture. Therefore, these other components may
also need to be considered in determining the appropriate
concentrations of the radiation-curable resin and the RCA, if
used.
[0095] In the step 46, the pre-cured coating mixture is distributed
across the surface of a substrate. The step 46 requires that the
pre-cured coating mixture is initially applied to the substrate
surface and then distributed across the surface. Application of the
pre-cured coating mixture to the surface of the substrate may be
accomplished by any means known in the art for placing a high
viscosity material onto a substrate. For example, the pre-cured
coating mixture may be pumped to the substrate and placed on the
substrate using a slot die. It should be appreciated that it may be
necessary to heat the pre-cured coating mixture to reduce the
viscosity to allow for its placement on the substrate surface;
however, it is important that the premed coating mixture be allowed
to cool prior to actually distributing it across the substrate
surface, so that it has the required viscosity necessary to
generate macroscopic texture.
[0096] Distributing the pre-cured coating mixture across the
substrate surface may be accomplished using any means known in the
art; however, it is important that such means are capable of moving
a high viscosity material across the surface in a manner that
leaves the pre-cured coating mixture in the form of the desired
macroscopic texture that will become fixed upon curing. It should
be appreciated that it is preferred to uniformly distribute the
pre-cured coating across the substrate surface, but such uniform
distribution should not be confused with a completely smooth
distribution of the pre-cured coating mixture across the substrate
surface. After the pre-cured coating mixture has been distributed,
the macroscopic texture should be apparent, as it is this texture
that will be fixed on the substrate after curing. Therefore, it
should be appreciated that, in addition to the use of an effective
viscosity and/or texture-producing particles, the macroscopic
texture can be altered using different techniques for applying the
pre-cured coating mixture to a substrate.
[0097] Before discussing specific pre-cured coating application
methods, it should be noted that the pre-cured coatings in this
embodiment can have a viscosity that is dependent on both the
amount of shear applied to the pre-cured coating mixture, as well
as the amount of time during and after the application of the
shear. This type of behavior is referred to in the art as
thixotropic. Thus, the production of texture is dependent on the
viscosity of the pre-cured coating under the shear of the
application equipment.
[0098] One method for distributing the pre-cured coating mixture
uniformly across the substrate surface in a manner that produces a
desired macroscopic texture is by use of an air knife. The use of
an air knife requires that the pre-cured coating mixture has been
properly and uniformly applied to the substrate surface to allow
the air knife to uniformly distribute the pre-cured coating mixture
over the substrate surface. It should be appreciated that the
relatively high viscosity of the pre-cured coating mixture at low
shear rates allows the air knife to produce a macroscopic texture
and prohibits a macroscopically smooth distribution of the
pre-cured coating mixture. Thus, the pre-cured coating in this
embodiment of the present invention has a high enough viscosity
under the shear of the air knife to produce a macroscopic texture
and not level into a macroscopically smooth surface. More
specifically, the air knife actually generates a wave of pre-cured
coating mixture that flows over the substrate surface as it passes
by the air knife. This wave leaves behind a metered pre-cured
coating with ripples that are the macroscopic texture.
[0099] It should be appreciated that the operating parameters of
the air knife can be changed to produce varying macroscopic
textures. These parameters include the line speed (dwell time under
the air knife), air pressure, angle of attack, and the gap between
the substrate and the air knife. Therefore, different macroscopic
textures providing a variety of aesthetic looks may be
produced.
[0100] It can now be appreciated that one method for determining
whether the pre-cured coating mixture has the appropriate viscosity
is by distributing the pre-cured coating mixture on the desired
substrate using an air knife. If the viscosity of the pre-cured
coating under the shear of the air knife is too low, the coating
will level and produce a macroscopically smooth surface. If the
viscosity under shear is too high, the pre-cured coating mixture
will be blown off the substrate resulting in an incompletely or
uncoated substrate.
[0101] Another method for distributing the pre-cured coating
mixture uniformly across the substrate surface in a manner that
produces a desired macroscopic texture is by use of a roll coater.
The roll coater both applies and coats the pre-cured coating
mixture to the substrate. The texture is generated by the roller
being in direct contact with the coating on the substrate. As the
substrate passes under the roller, the roller passes away from the
substrate pulling or splitting some of the pre-cured coating from
the substrate. This splitting results in macroscopic texture that
can be varied with the roll coater operating parameters including
line speed, gap between the roller and the substrate, roller
material type (roller covering), engraving pattern on the roller,
roller speed relative to the line speed and roller diameter.
[0102] In the step 48 the pre-cured coating mixture that has been
distributed over the substrate surface and is in the form of the
desired macroscopic texture is cured using radiation. This curing
step acts to polymerize the pre-cured coating mixture to fix the
macroscopic texture in place and adhere it to the substrate
surface, thereby producing a radiation-cured coating on the
substrate. The step 48 may be conducted under conditions typical of
radiation-curing processes depending upon the particular
radiation-curable resin and initiator used. For example, the step
48 may be conducted using radiation lamps in an inert atmosphere.
It should be appreciated that if a matte finish is desired, the
radiation lamps can be used in an ambient atmosphere followed by an
inert atmosphere. Thus, a matte finish can be superimposed on the
macroscopic texture if a flatting agent is used.
[0103] It should be appreciated that process steps described in
connection with FIG. 4 are equally applicable to the use of a
thermally-curable coating mixture made according to the present
invention. In this case, the step 40 would be directed to a
thermally-curable resin and a thermal initiator, and the step 48
would be directed to thermal curing and the formation of a
thermally-cured coating.
[0104] In another embodiment of the invention, the pre-cured
coating mixture utilizes texture-producing particles to produce the
macroscopic texture of the coating. These texture-producing
particles may be added to the pre-cured coating mixture in the step
42. These are mixed in the same manner as the previous embodiment,
but the effective viscosity of the pre-cured coating can be much
lower, typically 50-5000 cPs at a shear rate of 0.150 s.sup.-1 at
the application temperature, as the macroscopic texture is provided
by the texture-producing particles and not necessarily by the
viscosity of the pre-cured coating mixture. It should be
appreciated, however, that these texture-producing particles can be
used in combination with a pre-cured coating mixture that does have
an effective viscosity as well. The pre-cured coating mixture
containing these texture-producing particles is then processed in a
similar manner using the steps 44, 46, and 48. Specifically, this
pre-cured coating mixture can be mixed in a similar manner as
described above in the step 44. This pre-cured coating mixture may
be applied and coated on a substrate in the step 46 using methods
known in the art, including the use of an air knife, roll coater,
spray coating, curtain coating, and other coating application
methods. Lastly, this pre-cured coating mixture may be cured in a
similar manner as described above in the step 48.
[0105] It should be appreciated that the foregoing description of
the methods used to generate the coatings of the present invention
in the context of a radiation-cured coating is equally applicable
to the generation of the thermally-cured coatings of the present
invention.
[0106] FIG. 4B illustrates a cross-sectional view of a coated
substrate according to yet another embodiment of the present
invention. In this embodiment, the coated substrate 400 is a
sheet-style flooring material. This sheet flooring 400 comprises a
bottom layer 401 made of felt or cellulose paper. On top of the
bottom layer 401 is a gel layer 403, typically comprising a
polyvinyl chloride plastisol, and on top of this gel layer 403 is a
print layer 405 that may or may not comprise ink to provide a
decorative pattern (not shown). On top of the print layer 405 is a
clear wear layer 407 that is typically made of a polyvinyl chloride
plastisol. On top of the wear layer 407 is a top coat 409, which
may be any of the coatings of the present invention. A preferred
construction of this sheet flooring comprises a felt layer of
approximately 23.5 mils, a gel layer of approximately 57 mils, a
print layer of nominal or relatively small thickness, a wear layer
of approximately 20 mils, and a top coat of approximately 1-1.3
mils.
[0107] The basic sheet floor manufacturing process is well known in
the industry. Generally, a felt backing is coated with a gel layer,
typically a plastisol. This gel layer is then gelled to solidify
it. A decorative print may then be applied to the top of this gel
layer. The inks used in printing may be used in cooperation with
the gel layer to inhibit a blowing agent that may be used in the
gel layer to subsequently enable chemical embossing of the gel
layer to provide additional aesthetics. Additionally, another
plastisol-type layer may be applied on top of the print layer to
provide protection for the decorative print or chemically embossed
effects. This layer is typically referred to as a wear layer,
however, a topcoat may also be used on top of the wear layer to
protect it from scuffing or marring. This topcoat may be a thermal
or radiation-curable coating according to any of the embodiments of
the present invention.
[0108] In a preferred embodiment of the sheet floor manufacturing
process, a 6 to 16 feet wide felt is coated with a liquid polyvinyl
chloride (PVC) plastisol (e.g., PVC resin particles dispersed in
plastisizers (e.g., phthalates)). Mixed into this liquid plastisol,
which is called a gel layer, is a blowing agent (e.g.,
azodicarbonamide) and a catalyst (e.g., zinc oxide). The catalyst
lowers the decomposition temperature of the azodicarbonamide and
increases the amount of nitrogen gas produced by the
azodicarbonamide decomposition. The liquid gel layer on felt is
then gelled at a temperature below the decomposition temperature of
the blowing agent (approximately 300.degree. F.) to provide a solid
non-foamed and smooth surface for printing. After the gel layer is
solidified, it is printed with the desired design using water-based
inks, thereby creating the print layer. In some of the inks, a
compound that inhibits the decomposition of the blowing agent is
present. After the ink is printed, the PVC-coated felt is wound up
and allowed to age about 24 hours. This aging allows the inhibitor
in the ink to diffuse into the gel layer, where it is believed that
the inhibitor reduces the effectiveness of the catalyst.
[0109] The gel coated felt is then unwound on another production
line where it is coated with another PVC plastisol that is
formulated to be a clear layer when solidified. This liquid layer,
called the wear layer since it protects the print from wearing, is
then solidified (referred to as fused) at 385.degree. F. for about
1.5 minutes. At this temperature, the azodicarbonamide blowing
agent is activated in the gel layer resulting in the foaming of
this layer which increases its thickness by forming a cell
structure due to the gas formation. The ratio of the gel thickness
before and after foaming is called the blow ratio, which is
typically 2:1 to 4:1. In the areas of the gel directly below the
ink containing inhibitor, less foaming occurs giving less of an
increase in gel layer thickness. This process results in an
embossing effect (i.e., chemical embossing). After the warm fused
sheet leaves the oven it can be mechanically embossed for
additional aesthetics.
[0110] While these PVC wear layers provide protection to the
underlying print, they are susceptible to scuffing and marring due
to the softness of the thermoplastic. To reduce the scuffing, these
PVC surfaces can be either waxed or coated with a thermosetting
coating (known as a "no wax coating") such as a radiation-curable
coating (e.g., urethane acrylate) or thermally-curable coating made
according to the present invention. If the flooring is to have a no
wax finish, a radiation-curable or thermally-curable coating is
then applied after the wear layer is cleaned with an acetic acid
solution to remove dirt and oils. Excess coating is applied to the
wear layer using a roller, where the roller transfers the coating
from a trough to the wear layer surface. An air knife immediately
meters the excess coating, where the excess is recycled back into
the trough. As partially described in Example 19, the process
conditions of the coating application and metering such as line
speed (dwell time under the air knife), air knife pressure, angle
of air knife relative to the web, gap between air knife and web,
and the speed of the application roll relative to the line speed
affect the coating texture. The uncured metered coating is then
cured thermally or under UV lamps where both air and nitrogen
atmospheres may be used for UV curing depending on the gloss of the
coating desired.
[0111] The degree of texture of the radiation-curable or
thermally-curable coating or top coat is dependent on the ratio of
wet coating thickness to particle diameter. In using an air knife,
the air knife pressure and the web (lined) speed are the critical
parameters for achieving texture. For example, low line speed and
high air knife pressure result in a very thin coating due to
increased metering. When the coating contains texture-producing
particles, if the coating is too thin it can not hold the particles
and a smooth non-textured coating results. If the line speed is
high and the air knife pressure is low, the coating will be less
metered and apply thick. If the coating is thicker than the
texture-producing particles, the coating will be smooth. Thus,
there is an optimum set of process conditions to get texture in
production that can be determined based upon the particular
pre-cured coating mixture used.
[0112] Referring back to FIG. 3 wherein the macroscopic texture may
be provided by an underlying layer in the flooring material, one
embodiment of the present invention is the use of texture producing
particles in the wear layer of a flooring composition, such as that
described in connection with FIG. 4B. In this embodiment, the
texture is provided by the wear layer which may then be coated with
a top coating that conforms to the underlying texture. By
conforming to the underlying texture, the flooring composition will
exhibit a macroscopic texture, such as a ceramic-like texture where
the inherently textured coating layer is the PVC wear layer in this
case. Alternatively, the top coating may be made according to the
present invention to provide additional macroscopic texture to the
flooring composition.
[0113] As noted above, the wear layer is constructed by applying
PVC plastisols (dispersion of PVC particles in plastisizers) that
have a viscosity of approximately 500-1600 cP to a printed surface
(e.g., using knife over roll coating) at 10-30 mils in thickness.
The plastisol is then gelled at high temperature (e.g.,
300-400.degree. F.) to form the solid, clear thermoplastic wear
layer. In generating macroscopic texture with texture-producing
particles in the wear layer, the following variables are important:
(1) the type of application methods used (e.g., knife over roll
coater), (2) the high viscosity of the plastisol (typically
500-1600 cP at room temperature), and (3) the thickness of the
applied wear layer (10-30 mils). By comparison, using an air knife
with the lower viscosity coating containing texture-producing
particles as discussed in previous embodiments of the present
invention allows the liquid coating to be metered around the
texture-producing particles to generate the macroscopic texture. In
addition, a radiation-curable or thermally-curable top coating with
a lower viscosity (e.g., 50-250 cP) facilitates this metering,
while the low application gauge (1-2 mils) allows fairly small
particles (30-100 .mu.m) to be used to provide texture in the
coating. Therefore, to achieve texture with particles in a wear
layer, specific application methods are needed to address each of
these variables.
[0114] In using a knife over roll coater to apply PVC plastisols,
the knife over roll coater mechanically sets the wet coating
thickness, thus the texture-producing particles in the plastisol
must be smaller than the wet film thickness or streaks will be
generated. Thus, to use a knife over roll coater, texture-producing
particles have to be added to the plastisol that are smaller than
the wet film thickness, or the particles have to be added after the
plastisol is coated. If the texture-producing particles are added
to the plastisol before coating, these particles must either
increase in size or change aspect ratio during gelation such that
they protrude from the gelled wear layer to provide the macroscopic
texture, or the wear layer must shrink during gelling to expose the
particles.
[0115] With regard to swelling particles, U.S. Pat. No. 5,627,231
describes a process of adding particles to a wear layer that swell
during gelation to give the wear layer a ceramic-like texture. The
particles added to the plastisol absorb plasticizer during the
gelling process and swell to give texture. However, the particles
continue to absorb plasticizer and eventually become sticky. These
sticky particles then attract dirt which quickly makes the floor
dirty and hard to clean. As such, an alternative would be to
utilize shrinking wear layer. Example 22 provides an example of a
wear layer composition that shrinks thereby allowing for greater
exposure of the texture-producing particles and providing the
macroscopic texture.
[0116] If the particles are to be added after knife over roll
coating, the particles can simply be wet flocked on to the surface
of the coated, wet plastisol, and then gelled. This ensures that
(1) the particles are on the surface of the plastisol and,
therefore, can be much smaller than the thickness of the wet
plastisol, and (2) the particles do not interfere with the coating
application method since they are sprinkled on the wet plastisol
and then the excess particles removed (i.e., wet flocking) after
the plastisol is applied. Example 23 demonstrates the use wet
flocking.
[0117] To avoid the problem of mechanically setting the wet film
thickness, a coating method such as air knife application can be
used. However, in the present invention it is preferred to use
plastisol viscosities that are much greater (500-1600 cP) than what
is recommended for the air knife (<500 cP). When high viscosity
plastisols containing texture-producing particles arm applied by an
air knife, the plastisol entraps the particles such that they are
blown off the substrate leaving a smooth coating with no particles
or texture. Thus, a standard plastisol must be modified to have a
lower viscosity so that it can be metered around particles. An
example of a plastisol with a low viscosity (200 cP) comprises by
weight, 30.8% PVC resin (75HC available from Oxychem, Dallas,
Tex.), 30.8% PVC resin (567 available from Oxychem, Dallas, Tex.),
28.4% plasticizer (N-6000 available from Velsicol, Rosemont, Ill.),
4.7% plasticizer (S4375 available from Solutia, St. Louis, Mo.),
2.0% plasticizer (A-150 available from Exxon, Houston, Tex.), and
3.3% stabilizer (2347 available from OMG, Cleveland, Ohio).
[0118] As described above, the coatings of the present invention
may also be utilized in connection with floor tiles. The vinyl tile
manufacturing process and tile construction for high-end "no wax"
residential tiles are different from those of vinyl sheet floor and
require specialized process and formulation changes to achieve
macroscopically textured, radiation-cured or thermally-cured
surface topcoats.
[0119] In general, tiles are manufactured by calendering and/or
lamination processes. For example, a tile base comprising, for
example, limestone, is made into a continuous sheet to which a
printed design and a cap film, which is positioned on top of the
printed design for protection, may be laminated. Optionally, a
topcoat may then be applied to the cap film for additional wear
protection. This topcoat may be a thermal or radiation-curable
coating according to any of the embodiments of the present
invention. It should be appreciated that the general process for
constructing tiles can be used to make tiles of any thickness or
size.
[0120] In a preferred tile manufacturing process, 9'' by 9'', 12''
by 12'', 14'' by 14'', 16'' by 16'', and 18'' by 18'' vinyl tiles
are made by first mixing PVC resin, plasticizer, pigments, and a
high level (.about.80%) of limestone (calcium carbonate) filler in
a blender held at 115-135.degree. F. The blended powder effluent is
then transferred to a continuous mixer held at 320-340.degree. F.
for fusion (i.e. chain entanglement) of the limestone-filled resin
into thermoplastic pieces of various sizes. The thermoplastic
pieces are next sent to calendering roll operations for partial
softening and re-fusion of the limestone-filled resin into the
shape of a continuous sheet having an exiting temperature of
250-270.degree. F. and a thickness of 50-200 mils. The continuous
sheet of tile base is then carried via conveyor belt to a nip
station for lamination of a printed design using either 2 mil thick
printed PVC film or 0.5 mil thick printed transfer paper. The
latter case involves transferring the ink of a printed design,
originally on a paper roll, to the tile base at the lamination nip
(the paper is subsequently removed with a re-wind operation
immediately following the lamination nip).
[0121] Next, the continuous sheet of tile base and laminated print
layer is conveyed to another nip for lamination of "cap film,"
which is an .about.3 mil thick PVC film designed to protect the
print layer. Both the cap film and print layer applications rely
upon the nip pressure and incoming substrate temperature for
lamination; the laminating rolls themselves are not heated. For
floors requiring periodic waxing, the PVC cap film forms the
uppermost layer of the manufactured tile construction (an end-user
applied, sacrificial wax layer being the uppermost layer in
practice). However, for "no-wax" floors, a thermosetting topcoat is
applied to the top of the PVC cap film during manufacture and forms
a surface with sufficient durability that the need for a
sacrificial wax layer is eliminated. Nevertheless, and regardless
of its final designation as a waxed or no-wax floor tile, the
continuous sheet of laminated tile base, print layer, and cap film
is then optionally mechanically embossed and finally punched into
9'' by 9'', 12'' by 12'', 14'' by 14'', 16'' by 16'', or 18'' by
18'' tiles using a metal die. The edge material not punched out of
the continuous sheet by the die is recycled back into the tile base
mixing process. The cut tiles themselves are conveyed to either a
final processing and packaging station (for tiles requiring waxing
in practice) or to the topcoat application operation (for no-wax
tiles).
[0122] The traditional topcoat application process for no-wax tiles
involves the deposition and metering of a liquid film of
thermally-curable or radiation-curable resin onto the tile,
followed by subsequent curing of the resin to form a durable
thermoset topcoat. The traditionally preferred (but not exclusive)
coating application method involves the use of a curtain coater to
apply and meter .about.3 mil of uncured UV-curable resin to the cap
film surface of the tile. The coated, but uncured, tiles are then
sent through a series of UV-processors containing UV lamps to
induce cross-linking of the thermosetting resin, in the case where
the coating is a radiation-curable coating. (Alternatively, the
tiles would be heated to induce the cross-linking in the case where
the coating is a thermally-curable coating.) Final processing of
most no wax tile products involves an annealing process at
110-125.degree. F. for up to two days to remove processing stresses
and to ensure dimensional stability, as well as an edge grinding
process to ensure that smooth edges are present for proper field
installation. A thermosetting urethane backcoat is also applied
with a roll-coater to balance the curling stresses imparted on the
tile by the topcoat. The physical location of the backcoater and
backcoat UV-processor is usually just prior to the topcoat
operation (i.e., the backcoat is applied and cured first).
[0123] FIG. 4C is a cross-sectional view of a vinyl tile according
to one embodiment of the present invention. The tile 410 generally
comprises a backcoat 412, a tile base 414, a print film or
alternatively a transfer print ink (not shown), a cap film 418, and
a topcoat 420 having macroscopic texture (not shown). In a
preferred embodiment, the backcoat 412 comprises a urethane
backcoat of approximately 0.5-2 mils in thickness. The tile base
414 is approximately 50-200 mils in thickness, and the print film
416 is approximately 0.5 mils in thickness. The cap film 418
comprises a PVC cap film of approximately 2.8 mils in thickness,
and the topcoat 420 comprises a urethane topcoat of approximately
1-3 mils in thickness having macroscopic texture.
[0124] The urethane topcoat 420 may alternatively be any of the
coatings according to the present invention. As discussed generally
above, the topcoat resin formulation generally contains mixtures of
monomers and oligomers with acrylate functional groups to serve as
the cross-linking centers, a photoinitiator or photoinitiator
package to activate the cross-linking process under the UV-lamps,
flatting agents for low-gloss finishes, and various mixtures of
polyurethane, polyester, and polyether functional groups for
imparting desired end-use performance into the cured topcoat.
Moreover, the precise formulation of these ingredients is tailored
to maximize performance on vinyl tile, where the rigidity of the
tile substrate relative to vinyl sheet flooring makes scratch
resistance more difficult to achieve and places less emphasis on
flexibility. UV-coatings for the preferred tile topcoat process
must also be formulated to adhere to the PVC cap film, which can
require different ingredients than those used for adhesion of
UV-topcoats to the PVC wearlayer in sheet floor, and the coating
formulation may need to form a stable curtain in the curtain
coater, since curtain coating is commonly used to apply
non-textured coatings to floor tile. Lastly, the UV-processor
conditions must be adjusted to produce the desired topcoat gloss
(inert nitrogen atmospheres being preferred for high gloss, while a
dual air, then nitrogen, curing environment is generally required
for low gloss).
[0125] A preferred UV-curable coating formulation for use with tile
substrates contains texture-generating nylon particles and
alumina/silane rheological control agents. A more preferred
pre-cured coating mixture comprises, by weight, 35.303% ethoxylated
trimethylolpropane triacrylate (SR 454, available from Sartomer,
Exton, Pa.), 41.050% polyester acrylate (Laromer PE56F, available
from BASF, Charlotte, N.C.), 5.747% urethane acrylate (Alua 1001,
available from Congoleum Corporation, Mercerville, N.J.), 0.330%
acylphosphine oxide (Luceirin TPO, available from BASF, Charlotte,
N.C.), 8.000% 3 micron inorganic flatting agent (Acematte OK 412,
available from Degussa Corp.), 2.323% prehydrolyzed silane as an
RCA coupling agent comprising 0.21%
3-methacryloxypropyltrimethoxysilane (Z-6030 available from Dow
Corning, Midland, Mich.), 0.015% glacial acetic acid, 0.015%
deionized water, and 0.07% ethanol, prehydrolyzed as described in
Example 1 below, 1.000% inorganic RCA Nanotek Alumina #0100,
available from Nanophase Technologies, Burr Ridge, Ill.), and
6.250% 60 micron texture-producing particle (Orgasol 2002 ES6,
available from Atofina, Philadelphia, Pa.). As such, a preferred
cured coating according to the present invention is that coating
produced using the above preferred pre-cured coating mixture.
[0126] FIG. 4D is a process flow diagram of a process for applying
a coating of the present invention to a tile substrate according to
one embodiment of the present invention. In this embodiment, a
radiation-curable thermosetting topcoat that providse macroscopic
texture is applied to a vinyl tile substrate using a novel
application method. This application method is called the Roll-coat
and Air-Station (RAS) process, and is used in a preferred
embodiment for application of pre-cured coating mixture to the cap
film surface of a vinyl tile. The RAS process 430 first involves
the use of a roll-coater 432 for application and metering of the
uncured coating onto the tile substrate 431 in the form of a thin
film having macroscopic, particle-generated texture. As described
previously, the aggressiveness of the macroscopic texture is
dependent upon the ratio of wet film thickness to particle
diameter, and this ratio is determined primarily (although not
necessarily exclusively) by this roll-coating step in the RAS
process of the present invention. For a preferred three-roll
coater, the horizontal metering and transfer gaps (nips) and the
vertical application gap must be carefully optimized to apply the
proper amount of coating for the generation of macroscopic
particle-generated texture. If either or both of the gaps are too
small, then the texture-generating particles cannot pass through
the nips and are not applied to the tile substrate, which results
in a smooth, non-textured coating. Conversely, if the gaps are too
large, then the coating gauge is thicker than the particle diameter
and a smooth, non-textured coating is again created (i.e., the
particles are buried). Macroscopically textured coatings are
generated in the present invention when the gaps are optimized for
deposition of coatings having about the same or slightly less film
thickness than the particle; diameter (e.g., .about.1-2 mils of wet
coatings containing 60 micron texture-generating particles).
[0127] However, the roll-coat process also imparts a directional
distribution to the particle-generated textural features due to
film-splitting between the roller and tile (see the Examples that
describe film-splitting). This directionality is generally
undesirable for field installation. Thus, subsequent passage of the
textured, but directional, coated tiles 434 under an air knife 436
is then required to remove the roll-coat directionality and
generate more desirable uniform and random macroscopic texture.
Unlike traditional air knife coaters, the present invention uses
air knife parameters of lip gap, gap to tile, line speed (dwell
time under the air knife), and air pressure that are optimized
primarily for the random redistribution of the roll-coat
directionality in the uncured coating and not for metering of the
coating off of the tile. Moreover, a vacuum conveyor is required to
hold the tile on the conveyor belt during passage under the air
knife. The assemblage of vacuum conveyor and air knife is hereafter
termed the "air-station."
[0128] It was also found that the orientation of the roll-coat
directionality relative to the airstream direction under the air
knife greatly impacts the ability of the airstation to remove the
roll-coat directionality. For example, if the tiles with uncured
coating are sent under the air knife with the roll-coat
directionality lines 435 parallel to the conveyor line direction
(i.e., normal to the air knife slit direction and parallel to the
airstream), then very little texture randomization occurs. However,
if the tile 430 is rotated 90.degree. relative to its orientation
upon exiting the roll-coater (i.e., the roll-coat directionality
lines 435 are parallel to the air knife slit 437 and normal to both
the conveyor line direction and the air knife airstream 438), then
the airstation can much more easily randomize the
particle-generated texture. By readjusting the airstation
parameters it was also possible to randomize the texture with a
45.degree. tile rotation 439, which implies that simply mounting
the air knife at 45.degree. relative to the airstation conveyor
will eliminate the need for actual rotation of the tiles in a
continuous production process.
[0129] It should be appreciated that in the use of a roll-coating
process, particularly with multiple rolls, it is desirable that the
roll in contact with the substrate is a soft durometer roll to
meter the coating mixture into the embossed areas or regions of the
substrate, such as an embossed tile or sheet flooring or other
embossed substrate. An example of this is described in Example
25.
[0130] It should be appreciated that the roll coating process and
the air knife process may also be used separately for coating
tiles. In addition, it should be appreciated that although the
foregoing methods described for use in the manufacture of coated
tiles, these methods may also be used in applying the pre-cured
coating compositions of the present invention to sheet flooring as
well. Specifically, the RAS process may be used for sheet flooring,
other flooring substrates, and non-flooring substrates. Further,
the roll coating process alone and spray coating alone may be used
to coat tiles, sheet flooring, other flooring substrates, and
non-flooring substrates.
[0131] FIG. 4E shows a cross-sectional view of another embodiment
of the present invention. The tile 440 generally comprises a
backcoat 442, a tile base 444, a print film 446 or alternatively a
transfer print ink (not shown), a cap film 448, an undercoat 450,
and a topcoat 452 having macroscopic texture 454. It should be
appreciated that the diagrammatic representation of the macroscopic
texture 454 should not be deemed limiting and is simply used to
represent the macroscopic texture. In a preferred embodiment, the
backcoat 442 comprises a urethane backcoat of approximately 0.5-2
mils in thickness. The tile base 444 is approximately 50-200 mils
in thickness, and the print film 446 is approximately 0.5 mils in
thickness. The cap film 448 comprises a PVC cap film of
approximately 2.8 mils in thickness, and the undercoat 450
comprises a radiation or thermally cured undercoat of approximately
1-3 mils in thickness. The topcoat 452 comprises a radiation or
thermally cured topcoat of approximately 0.1-3 mils in thickness
having macroscopic texture.
[0132] In this particular embodiment, there is a double layer of
radiation-cured top coats, which provides improved scratch
resistance. Such double-layer topcoats require a partial cure of
the undercoat to give the undercoat sufficient structural integrity
to withstand the RAS process used in application of the textured
upper coat. However, if the undercoat approaches a fully cured
state prior to application of the second, textured coating, then
the textured upper coat will not properly adhere to the undercoat.
Careful control of cure conditions during the partial cure of the
undercoat is, therefore, required. After the textured upper coating
has been applied on top of the partially cured undercoat via the
RAS process, normal low or high gloss curing is then used to fully
cure the entire double-layer topcoat system.
[0133] The invention having been described, the following examples
illustrate various embodiments and features of the present
invention. It should be appreciated that the following examples are
presented to illustrate, rather than to limit, the scope of the
invention.
Example 1
[0134] This example describes a microscopic, texture with good
abrasion resistance, but poor cleanability. 60 g of alumina
(available as Nanotek.RTM. alumina 0100 from Nanophase Technologies
Corp., Burr Ridge, Ill.) having an average particle diameter range.
of 27-56 nm, 7.92 g of prehydrolyzed
3-methacryloxypropyltrimethoxysilane (available as Z-6030 from Dow
Corning, Midland, Mich.), 240 g of a UV-curable resin (see Table 1
below for the resin composition), and about 200 g of 0.5 in.
diameter porcelain balls were added to a porcelain media mill.
[0135] The mixture was ball milled for about 6 hours at room
temperature. The pre-cured coating mixture, after removal of the
grinding media, was applied using a 1.5 mil draw bar to rigid
polyvinyl chloride floor tile substrates at room temperature. The
tile substrates were then UV-cured in a two step process. First,
the tile substrates were UV-cured in air using a line speed of 100
feet per minute (fpm) under two H-bulb (mercury) lamps on high.
Then the tile substrates were UV-cured in nitrogen (<500 ppm
oxygen) using two H-bulbs set on low and a line speed of 20 fpm.
The coated tiles were subjected to this latter inert UV-curing step
a second time. The resulting coatings were transparent with an
extremely low gloss of 6% (at 60.degree.). Scanning Electron
Microscopy (SEM) images of this coating indicate that microscopic
wrinkling was present, i.e., micro-wrinkling. A Taber scratch test
consisting of scribing 5 concentric circles on the coated samples
with a metal stylus weighted from 300 to 500 g in 50 g increments
yielded no visible scratches on the coating surface. A qualitative
scratch rating system was used to evaluate the scratches from the
test (i.e., a 0-7 scale was used, where 7 is the best in that there
are no visible scratches), and this coating was rated 7. When this
coating was exposed to heavy traffic areas, it picked up dirt
particles quite easily and was very difficult to clean.
TABLE-US-00001 TABLE 1 UV-Curable Resin Composition Component
Manufacturer Wt % Urethane acrylate (Alua 1001) Congoleum
(Mercerville, NJ) 53.4 Ethoxylated diacrylate (SR 259) Sartomer
(Exton, PA) 8.8 Propoxylated diacrylate (SR 306) Sartomer (Exton,
PA) 24.3 Ethoxylated trimethylolpropane Sartomer (Exton, PA) 13.4
triacrylate (SR 454) Acylphosphine oxide (Luceirin BASF (Charlotte,
NC) 0.1 TPO)
[0136] As noted above, prehydrolyzed silane was used. The silane
(Z-6030) was to prehydrolyzed to make it more reactive with the
surface of the nanometer-sized alumina. The prehydrolysis was
conducted by first mixing at room temperature 5 g of glacial acetic
acid, 5 g of deionized water, and 25 g of ethyl alcohol. Then, 75 g
of Z-6030 were added to the mixture. The mixture was gently
agitated for about 24 hours. The mixture was allowed to stand
several days before use.
Example 2
[0137] This example shows a coating with macroscopic texture having
good cleanability and scratch resistance. 31.17 g of silica
(available as Nanotek.RTM. silica 2000 from Nanophase Technologies
Corp., Burr Ridge, Ill.) having an average particle diameter range
of 15-33 nm, 10.51 g of prehydrolyzed
3-methacryloxypropyltrimethoxysilane (available as Z-6030 from Dow
Corning, Midland, Mich.) prepared as described in Example 1, 100 g
of a UV-curable resin (see Table 2 below for resin composition).
The mixture was hand stirred with a wooden spatula and then mixed
with an ultrasonic probe for about 20 minutes. The pre-cured
coating mixture was applied to flexible polyvinyl chloride floor
substrates at room temperature with a spatula and distributed on
the substrate with an air knife. These sheet vinyl substrates were
then UV-cured under nitrogen (<500 ppm oxygen) using two H-bulbs
set on high and a line speed of 100 fpm. Two passes under the lamps
were made under these conditions. The resulting coating was
transparent with a gloss value (at 60.degree.) of about 11%. The
coating also had a macroscopic wave-like texture and was found to
be cleanable. A Taber scratch test consisting of scribing 5
concentric circles on the coated samples with a metal stylus
weighted from 300 to 500 g in 50 g increments yielded no visible
scratches on the coating surface. Using the qualitative scratch
rating system, this coating was rated a 7.
TABLE-US-00002 TABLE 2 UV-Curable Resin Composition Component
Manufacturer Wt % Urethane acrylate (Alua 1001) Congoleum
(Mercerville, NJ) 53.4 Ethoxylated diacrylate (SR 259) Sartomer
(Exton, PA) 8.8 Propoxylated diacrylate (SR 306) Sartomer (Exton,
PA) 24.2 Ethoxylated trimethylolpropane Sartomer (Exton, PA) 13.3
triacrylate (SR 454) Surfactant (DC 193) DOW Corning (Midland, MI)
0.1 Acylphosphine oxide (Luceirin BASF (Charlotte, NC) 0.2 TPO)
Example 3
[0138] To show the benefits of using nanometer-sized alumina in a
coating according to the present invention, a coating was made
using larger alumina particles. 60 g of alumina (available as
A152-SG from Alcoa, Pittsburgh, Pa.) having an average particle
diameter of 1.5 .mu.m, 0.48 g prehydrolyzed silane (Z-6030), 240 g
of the resin used in Example 1, and about 200 g of 0.5 in.
porcelain balls were added to a ball mill and milled as in Example
1. This pre-cured coating mixture was applied, cured, and tested
for scratch resistance as given in Example 1. The resulting coating
was visually not as transparent as the coating in Example 1 and was
given a scratch rating of 2 indicating visual scratches were
present.
Example 4
[0139] Tests were conducted to determine the effects of silane as a
coupling agent on the dispersion of nanometer-sized alumina 2 g of
Nanotek.RTM. alumina 0100 having an average particle diameter range
of 27-56 nm was added to 10 g of each of the following liquids:
ethoxylated diacrylate (available as SR 259 from Sartomer, Exton,
Pa.), propoxylated diacrylate (available as SR 306 from Sartomer,
Exton, Pa.), ethoxylated trimethlolpropane triacrylate (available
as SR 454 from Sartomer, Exton, Pa.), and urethane acrylate
(available as Alua 1001 from Congoleum, Mercerville, N.J.). The
mixtures were stirred, shaken, and then placed into an ultrasonic
bath for 30 minutes. To some of these mixtures 0.24 g prehydrolyzed
silane, as prepared in Example 1, was added, and the mixture was
stirred. The consistencies of each of these mixtures are described
in the Table 3 below.
TABLE-US-00003 TABLE 3 Effects of Prehydrolyzed Silane Liquid
Dispersing Agent Observations SR 306 none thixotropic paste silane
low viscosity liquid SR 259 none low viscosity liquid silane low
viscosity liquid SR 454 none thixotropic paste silane low viscosity
liquid Alua 1001 none non-thixotropic cream silane low viscosity
liquid
[0140] The observations show that the urethane acrylate and the
Ethoxylated diacrylate disperse the nanometer-sized alumina better
than the propoxylated diacrylate and the Ethoxylated
trimethlolpropane triacrylate. These observations also show that
the addition of the prehydrolyzed silane dispersing agent improves
the dispersion of the nanometer-sized alumina.
Example 5
[0141] This example shows the effects of alumina size and coupling
agent on the clarity of the cured coating. The pre-cured coating
mixture in Example 1 was prepared in the identical manner described
with the following exception: the prehydrolyzed silane was prepared
using 75 g of ethanol instead of 75 g of Z-6030 silane. Thus, this
pre-cured coating mixture contained no coupling agent. This
pre-cured coating mixture (referred to as Example 5), the pre-cured
coating mixture in Example 1, and the pre-cured coating mixture in
Example 3 were applied at room temperature using a 3 mil draw-down
bar to glass substrates. The drawn down pre-cured coating mixtures
were then cured using two curing conditions as described in Table
4.
TABLE-US-00004 TABLE 4 UV-Curing Conditions Condition Parameters 1
atmosphere = air line speed = 100 feet per minute (fpm) lamp = 2
H-bulb (mercury) lamps on high passes = 1 atmosphere = nitrogen
(<500 ppm oxygen) line speed = 20 fpm lamp = 2 H-bulb lamps on
low passes = 2 2 atmosphere = nitrogen line speed = 20 fpm lamp = 2
H-bulb lamps on low passes = 2
[0142] The percent haze is defined as follows:
% haze=(100-% specular transmission)/% total transmission
and was determined for these cured coatings using a CHROMA SENSOR
CS-5 from Applied Color Systems, Inc. and a method similar to ASTM
D 1003-92. The thicknesses of the detached coatings were determined
with a MADAKE micrometer. The haze and thickness values are given
in Table 5 below.
TABLE-US-00005 TABLE 5 Coating Thickness and Haze Results % Coating
Cure Conditions Thickness (mil) Haze Example 1 1 2.6 59.3 (20%
nano-sized alumina) Example 1 2 2.6 67.3 (20% nano-sized alumina)
Example 3 1 3.2 99.4 (20% micron-sized alumina) Example 3 2 3.2
99.4 (20% micron-sized alumina) Example 5 1 1.7 82.0 (20%
nano-sized alumina, no silane) Example 5 2 6.3 97.8 (20% nano-sized
alumina, no silane)
[0143] The percent haze values show that the coating with
nanometer-sized alumina was much less hazy than the coating
containing micron-sized alumina regardless of cure conditions. The
data also show that the silane coupling agent improves the clarity
of the coatings containing nanometer-sized alumina.
Example 6
[0144] This example shows the effects of inorganic particle type
and loading on the cured coating texture. Six pre-cured coating
mixtures were prepared where the inorganic nano-particles and the
prehydrolyzed silane (as described in Example 1) were added to the
UV-curable organic phase used in Example 2. Each pre-cured coating
mixture was mixed with a Cowles blade and then an ultrasonic probe.
The composition of these pre-cured coating mixtures is shown in
Table 6.
TABLE-US-00006 TABLE 6 Pre-Cured Coating Mixture Compositions
Pre-Cured Wt % Photo- Coating Nanometer- Prehydrolyzed initiator
Mixture Sized Particle Wt %/Vol % Silane (%) 1 None 0/0 0 0.1 2
Al.sub.2O.sub.3 19.5/6.0 1.8 0.1 3 Al.sub.2O.sub.3 28.9/10 2.6 0.1
4 Al.sub.2O.sub.3 40/15.4 3.6 0.2 5 SiO.sub.2 11/5.5 2.5 0.1 6
SiO.sub.2 16/8.3 3.7 0.2 7 SiO.sub.2 22/11.8 5.1 0.2
[0145] These pre-cured coating mixtures were then applied to
flexible vinyl flooring substrates which were cleaned with a
solution of acetic acid, soap, and water. The pre-cured coating
mixtures were applied at room temperature using a pipette or a
spatula depending on the viscosity, and then the samples were
passed through an air knife to distribute the pre-cured coating
mixture over the substrate and to remove any excess. The resultant
films were then cured under UV lamps using different lamp
intensities and atmospheres as described in Table 7 below. Scanning
electron microscopy (SEM) images of the coatings were taken along
with gloss measurements at 60.degree..
TABLE-US-00007 TABLE 7 Gloss and Texture Measurements Gloss Texture
Coating Cure Conditions (%) (SEM/visual) 1 N.sub.2 - 100 fpm, 2
lamps high, 2 passes 80 smooth Air - 100 fpm, 2 lamps high 6 long
micro- N.sub.2 - 100 fpm, 2 lamps high, 2 passes wrinkles 2 N.sub.2
- 100 fpm, 2 lamps high, 2 passes 80 smooth Air - 100 fpm, 2 lamps
high 4 short micro- N.sub.2 - 100 fpm, 2 lamps high, 2 passes
wrinkles 3 N.sub.2 - 100 fpm, 2 lamps high, 2 passes 60 some macro
texture Air - 100 fpm, 2 lamps high 30 very short micro- N.sub.2 -
100 fpm, 2 lamps high, 2 passes wrinkles 4 N.sub.2 - 100 fpm, 2
lamp high, 2 passes 30 macro texture Air - 100 fpm, 2 lamps high 30
macro texture N.sub.2 - 100 fpm, 2 lamps high, 2 passes 5 N.sub.2 -
100 fpm, 2 lamp high, 2 passes 20 macro texture Air - 100 fpm, 2
lamps high 5 macro texture and N.sub.2 - 100 fpm, 2 lamps high, 2
passes micro-wrinkles 6 N.sub.2 - 100 fpm, 2 lamp high, 2 passes 17
macro texture Air - 100 fpm, 2 lamps high 16 macro texture N.sub.2
- 100 fpm, 2 lamps high, 2 passes 7 N.sub.2 - 100 fpm, 2 lamp high,
2 passes 6 macro texture Air - 100 fpm, 2 lamps high 6 macro
texture N.sub.2 - 100 fpm, 2 lamp2 high, 2 passes
[0146] Coatings cured under both air and inert atmospheres having
30% or less nanometer-sized alumina showed micro-sized wrinkles,
which looked like spaghetti in the SEM images (200.times.). As the
concentration of alumina is increased from 0 to 20%, the length of
the wrinkles decreases under inert (N.sub.2) curing conditions. At
30% alumina, the wrinkle length is quite small resulting in a
surface resembling a golf ball surface in the SEM images. At 40%
alumina, the micro-wrinkling is not observed in the SEM (surface is
smooth), but a macro wave-like texture is observed with the naked
eye. Wave-like macro texture is also observed with the coatings
having 16% and 22% silica. In the cases where micro-wrinkling is
not observed, the macro texture observed is independent of the cure
conditions (two zone versus one zone) used.
Example 7
[0147] This example demonstrates that wave-like macroscopic texture
is generated by the coating application method. Pre-cured coating
mixture 5 in Example 6 above was applied to a substrate with an air
knife as in Example 6. The same pre-cured coating mixture was also
applied to a second substrate with a 1.5 mil draw down bar. Both
samples were cured in the inert atmosphere as described in Example
6. The sample coated with a draw bar had a visibly smooth surface
and a gloss of 74% compared to a wave-like visible texture with a
gloss of 20% for the sample coated with an air knife.
Example 8
[0148] This example shows the effect of shear rate and temperature,
on the pre-cured coating viscosity. The viscosities of pre-cured
coating mixtures 3 (28.9% alumina) and 4 (40% alumina) from:
Example 6 were measured using a Brookfield viscometer (model DV-II,
RV) with spindles 21 and 29 as a function of spindle rotation rate
(related to shear rate) and temperature. FIG. 5 shows the results
of these measurements for pre-cured coating mixture 3 and FIG. 6
shows the results for pre-cured coating mixture 4. The data show
that the pre-cured coating mixture viscosity decreases with
temperature and shear rate. The viscosity dependence with shear
rate indicates that the actual viscosity of the pre-cured coating
during application with an air knife is probably less than when
measured at low shear (0.150 s.sup.-1) by the Brookfield, since the
shear rate under the air knife is assumed to be greater than 0.150
s.sup.-1. The viscosity dependence on temperature demonstrates the
importance of keeping the pre-cured coating at the required
temperature during application, since too high of a temperature may
result in a coating that does not produce macroscopic texture
because the viscosity is too low. The difference in the curves
between FIGS. 5 and 6 show that the amount of RCA in the pre-cured
coating influences the coating rheology, which could control the
type and degree of texture in the cured coating.
Example 9
[0149] This example shows the effects of pressured coating
viscosity on cured coating texture. Using the pre-cured UV resin
described in Table 2, 20%, 22.5%, 25%, 27.5%, and 30% nanometer
sized alumina (as described in Example 1) was added and mixed with
a Cowles blade mixer. Additionally 45% of nanometer-sized calcium
carbonate was added to the resin described in Table 2 and mixed
with a Cowles blade mixer. The viscosities of these pre-cured
coatings were measured as described in Example 8 and are given in
Table 8. These pre-cured coatings were then applied to flexible
sheet vinyl substrates and coated with an air knife at room
temperature. In the case of the coating with 45% calcium carbonate,
the pre-cured coating simply blew off the substrate when the air
knife was used. The samples were cured under inert conditions and
tested for scratch resistance (Taber) and the gloss was determined.
These data are also given in Table 8.
TABLE-US-00008 TABLE 8 Pre-Cured Coating Viscosity Effects on Cured
Coating Properties Viscosity (cPs) at 0.150 s.sup.-1 at Room Gloss
Macroscopic Scratch Coating Temperature (%) Texture (Taber) 20%
alumina 30,000 46 none some visible 22.5% 56,667 37 very slight
some visible 25% 110,000 25 yes some visible 27% 173,000 19 yes
some visible 30% 408,000 9 yes, most none visible aggressive 45%
calcium 1,230,000 n/a n/a n/a carbonate
[0150] These data indicate that for the air knife conditions
presently used, the viscosity of the coating needs to be
approximately in the range of 100,000-1,000,000 cPs measured at
room temperature (at a shear rate of 0.150 s.sup.-1) in order to
generate macroscopic texture. The data also indicate that more
aggressive texture yields better scratch resistance.
Example 10
[0151] This example shows the effect of aging and prehydrolyzed
silane concentration on the pre-cured coating viscosity. The
viscosity of pre-cured coating mixture 4 in Example 6 (40% alumina)
was determined as a function of time. These results are shown in
FIG. 7. The pre-cured coating mixture viscosity was found to have
an aging effect in which fresh samples change viscosity over a
period of about one week before leveling at a new viscosity.
Specifically, pre-cured coating mixtures prepared with the optimal
prehydrolyzed silane concentration (10 .mu.mol/m.sup.2) decrease
about 25% in viscosity after 10 days and change color from a dark
gray to a lighter gray, whereas pre-cured coating mixtures with 20
.mu.mol/m.sup.2 increase in viscosity by more than 4 times (i.e.,
the initial value was 75% lower than final value) in the same time
period. This behavior suggests that at and below the optimal
prehydrolyzed silane concentration the prehydrolyzed silane is
continuing to further disperse the alumina particles as the
prehydrolyzed silane molecules diffuse slowly to their final
equilibrium locations on the particle surfaces and react with
Al--OH groups. Conversely, when excess prehydrolyzed silane is
present the equilibrium favors reagglomeration and crosslinking by
prehydrolyzed silane condensation but is apparently kinetically
limited prior to equilibration. Both processes scan to involve
rather slow kinetic and/or diffusive steps and arm unlikely to be
affected much by additional mechanical mixing.
Example 11
[0152] The effect on pre-cured coating viscosity of the
concentration of prehydrolyzed silane coupling agent (as prepared
in Example 1) was determined by measuring the viscosity as in
Example 8 of a pre-cured coating mixture containing 40%
nanometer-sized alumina (e.g., the pre-cured coating mixture 4 in
Example 6 except the silane level was varied). The amount of
prehydrolyzed silane used in all the examples was calculated using
the following equation:
M.sub.ps=(10.sup.-6MW.sub.psas.sub.npm.sub.np)/C.sub.ps
where M.sub.ps is the mass of prehydrolyzed Z-6030 (in g), a is the
number of active sites on the nano-particle (in .mu.mole/m.sup.2),
MW.sub.ps is the molecular weight of the prehydrolyzed Z-6030 (234
g/mol), s.sub.np is the nanometer-sized particle surface area (in
M.sup.2/g), m.sub.np is the mass of nanometer-sized particles used
in the formulation (in g), and C.sub.ps is the weight fraction of
prehydrolyzed silane in the solution (from Example 1, typically
0.6818). Based on Parker et al., Mat. Res. Symp. Proc. 249 (1992)
273, 10 .mu.m of active sites/m.sup.2 of inorganic in all of the
samples was used, because it should give the lowest pre-cured
coating mixture viscosity and, hence, the best dispersion of the
nanometer-sized particles. However, it should be appreciated that
by controlling the amount of prehydrolyzed silane (more or less
than 10 .mu.mole/m.sup.2) can result in different shear dependent
rheology, which in turn could lead to different textures.
[0153] The pre-cured coating mixture viscosity was measured as a
function of prehydrolyzed silane level (represented by the "a"
value as described above) and the results are shown in FIG. 8.
These data show that at a given strain rate, the pre-cured coating
mixture equilibrium viscosity was found to initially decrease as
the silane concentration was increased, presumably due to enhanced
dispersion of the nanometer-sized particles in the resin phase. A
viscosity minimum was reached at approximately 10 .mu.mol
silane/m.sup.2 Al.sub.2O.sub.3 and serves as a measure of optimal
dispersion for this surfactant-inorganic-resin mixture (in
agreement with sedimentation results obtained by Parker et al. for
the n-octyltriethoxysilane-toluene-5 .mu.m Al.sub.2O.sub.3 system).
The increase in viscosity observed at slightly higher silane
concentrations corresponds, to some reagglomeration of alumina
particles as the excess silane forms larger organo-phobic phase
domains (domains that include both the alumina particles and the
hydrophilic ends of the silane molecules) that minimize surface
energies between phases. Finally, viscosity again decreases at much
higher silane concentrations due to simple mixing-rule
behavior.
Example 12
[0154] This example demonstrates the use of an organic RCA. 20 g of
an organic (castor wax derivative) RCA Thixcin R (Rheox Inc.,
Hightstown, N.J.) was added to 480 g of the pre-cured UV resin
described in Table 2 and mixed with a Cowles blade mixer. The
mixture was then heated at 70.degree. C. until the Thixcin R
dissolved. The mixture was then allowed to cool to room
temperature. The viscosity of this mixture at a shear rate of 0.150
s.sup.-1 at room temperature was 243,000 cPs. This mixture was then
coated on flexible sheet vinyl using an air knife and cured under
inert conditions. The resulting cured coating was transparent and
had a wave-like macroscopic texture. When scratched using the Taber
scratch test, no visible scratches were observed.
Example 13
[0155] This example demonstrates the use of both an organic RCA and
an inorganic flatting agent. 12 g of Thixcin R organic RCA and
19.14 g of Acematte OK 412 (Degussa Corp.) silica flatting agent
were added to 288 g of the pre-cured UV resin described in Table 2
and mixed as in Example 12. This mixture was coated on a flexible
vinyl sheet floor with an air knife and cured under both
atmospheric and inert conditions. The resulting coating had a matte
finish and wave-like texture.
Example 14
[0156] This example shows that wave-like macroscopic texture can be
generated without the use of an RCA. 85.25 g of Alua 2302 and 21.31
g Alua 1001 urethane acrylate oligomers (Congoleum Corp.,
Mercerville, N.J.), 66.14 g of Actilane 424 and 26.64 g of Actilane
430 acrylate monomers (Akcros Chemicals, New Brunswick, N.J.), 0.2
g DC 193 surfactant, and 0.394 g of Luceirin TPO photoinitiator
were added to a container at room temperature. This mixture was
heated to 70.degree. C. and mixed with a Cowles blade mixer. After
cooling to room temperature, the pre-cured coating mixture was
applied to flexible vinyl substrates, coated with an air knife, and
UV-cured under inert conditions. The resulting coating was
transparent and had macroscopic wave-like texture.
Example 15
[0157] This example demonstrates the use of organic
texture-producing particles and an inorganic flatting agent. 6.25 g
of Orgasol 2002 ES 6 NAT (Atofina, Philadelphia, Pa.) polyamide 12
texture-producing particle (60 .mu.m in diameter) and 5.625 g of
Acematte OK 412 flatting agent (3 .mu.m diameter) were added to
88.125 g of the preset UV-resin described in Table 2 and mixed with
a Cowles blade mixer. This mixture was heated to 70.degree. C. and
coated on a flexible sheet vinyl floor using an air knife. The
pre-cured coating was cured at a line speed of 100 fpm using
atmospheric and then inert conditions. The resulting coating was
transparent coating with a matte finish and sandpaper-like
texture.
Example 16
[0158] This example shows the effects of the size of the
texture-producing particles on the cured coating texture. Four
pre-cured coating mixtures were prepared as in Example 15 where
6.25% of Orgasol 2002 polyamide 12 texture-producing particles was
added to the pre-cured UV-resin described in Table 2. The four
mixtures differed in that each contained a different sized particle
of Orgasol 2002: 30 .mu.m (grade ES 3), 40 .mu.m (grade ES 4), 50
.mu.m (grade ES 5), and 60 .mu.m (grade ES 6). Each mixture was
applied at 70.degree. C. to sheet vinyl and coated with an air
knife. All coatings were UV-cured under inert conditions. The cured
coating containing the 30 .mu.m particles had a visibly fairly
smooth surface with a matte finish. The coatings with the larger
particles had progressively more visible texture as the particle
size increased, where the 60 .mu.m particles gave the most visible
and aggressive (largest textural features) texture. The scratch
resistance of the coatings improved with increasing particle size,
where 60 .mu.m showed almost no visible scratches after the Taber
scratch test. FIG. 9 is a photograph of the top of a portion of the
coated substrate produced using the 60 .mu.m particles, and FIG. 10
is a photograph of the top of a portion of the coated substrate
produced using the 40 .mu.m particles. The difference in the
aggressiveness of the texture is evident. It should be appreciated,
however, that the concentration of particles used would also be
expected to have an influence on textural aggressiveness.
[0159] For illustrative purposes, "traces" of the surface textures
of these samples were obtained by rubbing a soft graphite pencil
over translucent tracing paper that was itself placed on top of the
textured surfaces. The traces were then digitally scanned. FIG. 11
shows the texture of the coating producing using the 60 .mu.m
particles, and FIG. 12 shows the texture of the coating produced
using the 40 .mu.m particles. The traces clearly show the decrease
in textural aggressiveness as nylon particle size is decreased from
60 .mu.m as shown in FIG. 11 to 40 .mu.m in FIG. 12.
[0160] These traces also allow for estimation of certain features
of the texture. FIG. 13 is an illustration of the general type of
macroscopic texture produced by the coatings in this Example 16. As
shown, three parameters, a, b and c, are defined to describe
certain planar features of the texture. These parameters are
defined as follows: "a" represents the distance between peaks of
the texture, "b" represents the width of each textural feature, and
"c" represents the length of each textural feature. These
parameters were measured manually from the corresponding traces
and, therefore, may have substantial inherent error associated with
them; however, they can be used to distinguish gross differences
between the textures. Regardless, these parameters should not be
viewed or used as limiting the type, shape, or size of the
macroscopic texture. The ranges for these parameters for the
coatings produced in this Example 16 are as follows: for the
coating made with 60 .mu.m particles a ranges from 10-50 mils, b
ranges from 5-30 mils, and c ranges from 100-350 mils, for the
coating made with 40 .mu.m particles a ranges from 5-30 mils, b
ranges from 1-20 mils, and c ranges from 10-150 mils, and for the
coating made with 30 .mu.m particles a ranges from 5-20 mils, b
ranges from 1-10 mils and c ranges from 1-50 mils.
[0161] The average gloss values (60.degree.) and the textural
relief values (defined as maximum coating thickness minus minimum
coating thickness) were also measured for the coatings produced by
this Example 16. The gloss values are 10.8, 16.9, and 35.3 for the
coatings made with 60 .mu.m, 40 .mu.m, and 30 .mu.m particles,
respectively. The textural relief values are 1.99 mils, 0.52 mils,
and 0.29 mils for the coatings made with 60 .mu.m, 40 .mu.m, and 30
.mu.m particles, respectively.
Example 17
[0162] This example describes textured coatings. containing organic
texture-producing particles, an inorganic RCA with a coupling
agent, and both organic and inorganic flatting agents. Per-cured
coating mixtures having the composition shown in Table 9 were mixed
with a Cowles blade mixer.
TABLE-US-00009 TABLE 9 Pre-Cured Coating Mixture Compositions in
Weight Percent Component Coating A Coating B UV-Curable Resin from
Table 2 85.62 85.95 Orgasol 2002 ES 6 (60 .mu.m texture-producing
6.12 6.25 particle) Orgasol 2001 UD (5 .mu.m organic flatting
agent) 6.0 0 Acematte OK 412 (3 .mu.m inorganic flatting agent) 0
5.49 Nanotek Alumina (inorganic RCA) 1.96 2 Prehydrolyzed Z-6030
(coupling agent from 0.30 0.31 Example 1)
Both coatings were applied to flexible sheet vinyl at 70.degree. C.
and coated with an air knife. These coated substrates were UV-cured
under atmospheric and then inert environments. The resulting cured
coatings were transparent and had sandpaper-like macroscopic
texture and matte finishes.
Example 18
[0163] This example demonstrates the use of a roll coater
application method for generating and controlling macroscopic
texture similar to that of wood-grain. Three pre-cured coating
mixtures were used, including the coating of Example 9 (30%
nano-alumina inorganic RCA), the coating of Example 12 (organic
RCA), and the coating of Example 16 (60 .mu.m texture-generating
nylon particles). These pre-cured coating mixtures were then
applied to cleaned, semi-rigid vinyl tile flooring. substrates
using a pipette or spatula as described in Example 6. Distribution
of the pre-cured coating mixture to a macroscopically textured
state and removal of excess coating was then achieved by passing
the samples under a contacting roller using the process conditions
listed in Table 10. Specifically, Table 10 gives the conditions for
the contacting, roll, which actually makes contact with and the
pre-cured coating to provide macroscopic texture. More
specifically, the contacting roll acts to split the pre-cured
coating mixture that has been applied to the substrate between the
contacting roll and the substrate and is referred to as
"film-splitting," where "film" refers to the pre-cured coating
mixture as applied to the substrate. This film-splitting phenomenon
acts to form the macroscopic texture of the coating on the
substrate. The gap indicated is between the contacting roll and the
uncoated substrate surface when the uncoated substrate is between
the rolls (i.e., total gap minus substrate thickness). Also, in the
case where the contacting roll is rotating, the rotation is away
from the surface of the sample. In all cases, the lower roll
carried the samples between the rolls at 100 fpm and, upon exiting
the roll coater, the pre-cured coated samples were cured under an
inert (N.sub.2) environment at 100 fpm.
TABLE-US-00010 TABLE 10 Roll Coated Sample Compositions and Process
Conditions Sample and Figure Process Identification Coating
Conditions 1 Organic RCA Coating Hard rubber roll (stationary)
(FIGS. 15 and 19) of Example 12 Gap = 4.0 mils 2 Inorganic RCA Hard
rubber roll (stationary) (FIGS. 14 and 20) Coating of Gap = 4.0
mils Example 9 3 Organic RCA Coating Hard rubber roll (stationary)
(FIGS. 16 and 21) of Example 12 Gap = -10 mils (compressed) 4
Inorganic RCA Soft rubber roll (FIGS. 17 and 22) Coating of
(rotating 100 fpm) Example 9 Gap = 0.0 mils 5 Texture-Generating
Hard rubber roll (stationary) (FIGS. 18 and 23) Particles Coating
Gap = 18 mils of Example 16
[0164] FIGS. 14-18 are photographs of the top of a portion of each
coated substrate made using coatings 1-5 listed in Table 10. FIGS.
19-23 are traces, made as described in Example 16, of the surface
textures of these coated substrates having coatings 1-5 listed in
Table 10. Gloss (60.degree.) and gauge (thickness) measurements are
given in Table 11, where textural relief is calculated as the
maximum gauge minus the minimum gauge (in mils). Note that the
gloss is reported for both the in-line direction (i.e., the
direction that the sample traveled while passing through the roll
coater) and for the transverse direction. Gauge measurements were
made using a light microscope equipped with a microscale and
involved viewing cross-sections of the cured samples cut in the
transverse direction.
[0165] FIG. 24 illustrates the general type of macroscopic texture
produced by the coatings in this Example 18, and FIG. 25 is an
enlarged view of a portion of FIG. 24. As shown, the texture
produced in this Example 18 can be described as "branched". FIGS.
24 and 25 show three parameters, a, b and c, that are defined to
describe certain planar features of the texture. These parameters
are defined as follows: "a" represents the distance between
branches of the texture, "b" represents the width of each branch,
and "c" represents the length of each branch. These parameters were
measured manually from the traces for each of the coatings shown in
FIGS. 19-23 and, therefore, may have substantial inherent error
associated with them; however, they can be used to distinguish
gross differences between the textures. Regardless, these
parameters should not be viewed or used as limiting the type,
shape, or size of the macroscopic texture. The ranges for these
parameters for the coatings produced in this Example 18 are
provided in Table 11.
TABLE-US-00011 TABLE 11 Gloss and Texture Measurements of Roll
Coated Samples Range of Planar Gloss (60.degree.) Gauge (mils)
Dimensions (mils) Sample In-line Trans. Min Max Relief (mils) a b c
1 50.2 15.5 1.20 2.44 1.24 40-100 10-20 100-1500 2 69.3 21.2 1.35
2.34 0.99 40-100 10-20 100-1700 3 65.8 29.2 0.69 1.11 0.42 20-30
5-10 100-1000 4 32.1 16.4 1.08 2.69 1.61 40-70 10-20 100-200 5 27.6
17.4 0.79 1.71 0.92 40-70 20-40 300-500
[0166] These results show that a range of texture similar to that
of wood-grain may be achieved by adjustment of process conditions
during the roll coating application of the pre-cured coating
mixtures. Key parameters appear to be the rotational speed of the
contacting roll that directly contacts the pre-cured coating, the
gap between the contacting roll and the sample, and the hardness of
the contacting roll.
[0167] If the contacting roll is moving in the line direction, then
the pre-cured coating film is split quickly as the moving roll
pulls a fraction of the coating away from the coated substrate.
This results in very short textural branches (sees for example,
FIG. 18). Conversely, a stationary contacting roll does not split
the film as rapidly, allowing the branches to extend to much longer
lengths before a fraction of the branching film detaches from the
substrate and ends the branch. This macroscopic texture is best
described as "wood-grain" in nature. Moreover, the wood-grain
texture may be further controlled by adjusting the gap. A smaller
gap yields a more finely scaled wood-grain texture (e.g., compare
FIGS. 19 and 21). The use of texture-producing particles in a
roll-coated pre-cured coating mixture produces a hybrid macroscopic
texture that contains both wood-grain and "sandpaper-like" textural
elements (see, for example, FIGS. 18 and 23). The hardness of the
contacting roll is also expected to affect the film splitting
behavior of the roll-coating application method, as are intrinsic
pre-cured coating properties such as viscosity and particle
density.
Example 19
[0168] This example illustrates how the manipulation of process
conditions may be used to control the aggressiveness of macroscopic
texture generated by an air knife coating application method. Two
pre-cured coating mixtures were used, the first being the coating
of Example 9 (30% nano-alumina inorganic RCA). The second pre-cured
coating consisted of the coating composition given in Example 15,
with the exception that the organic text generating particles were
40 .mu.m polypropylene particles added at 5 wt % (Propyltex 200S
available from Micro Powders, Inc., Tarrytown, N.Y.) instead of the
625 wt % nylon particles. These pre-cured coating mixtures were
applied to flexible sheet vinyl floor with an air knife using the
process conditions indicated in Table 12. The pre-cured coated
samples were then cured under an inert (N.sub.2) environment at 100
fpm.
TABLE-US-00012 TABLE 12 Air Knife Coater Sample Compositions and
Process Conditions Sample and Figure Identification Line Speed Air
Knife Pressure Inorganic RCA Coating 1 (FIGS. 26 and 29) 100 4.0 2
(FIGS. 27 and 30) 50 4.0 3 (FIGS. 28 and 31) 10 4.0 Particle
Coating 4 100 4.0 5 10 4.0 6 100 1.5 7 10 1.5
[0169] FIGS. 26-28 are photographs of the top of a portion of each
coated substrate, made using coatings 1-3 listed in Table 12,
respectively. FIGS. 29-31 are traces, made as described in Example
16, of the surface textures of these coated substrates having
coatings 1-3 listed in Table 12, respectively. These figures show
that the macroscopic texture produced using the inorganic RCA are
wave-like. Traces of the particle textures for samples 4-7 in Table
12 were not made, but traces of similar particle-generated
"sandpaper" macroscopic texture can be found in Example 16.
[0170] FIG. 32 is an illustration of the general type of wave-like
macroscopic texture produced by the coatings in this Example 19. As
shown, three parameters, a, b and c, are defined to describe
certain planar features of the texture. These parameters are
defined as follows: "a" represents the distance between peaks of
the texture, "b" represents the width of each textural feature, and
"c" represents the length of each textural feature. These
parameters were measured manually from the corresponding traces
and, therefore, may have substantial inherent error associated with
them; however, they can be used to distinguish gross differences
between the textures. Regardless, these parameters should not be
viewed or used as limiting the type, shape, or size of the
macroscopic texture. The ranges for these parameters for the
coatings produced in this Example 19 are provided in Table 13.
Gloss (60.degree.) and gauge (thickness) measurements arm also
given in Table 13 and follow the same conventions as the gloss and
gauge data presented in Example 18.
TABLE-US-00013 TABLE 13 Gloss and Texture Measurements for Air
Knife Coated Samples Gloss Gauge Re- Ranges of Planar Sam-
(60.degree.) (mils) lief Dimensions (mils) ple In-line Trans. Min
Max (mils) a b c 1 20.0 29.6 2.62 4.24 1.62 50-100 20-50 20-350 2
17.6 21.6 1.68 3.31 1.63 20-70 10-20 10-400 3 23.3 30.5 0.66 1.06
0.40 10-20 5-10 20-100 4 62.4 58.0 0.97 1.44 0.47 5 37.4 36.0 0.45
0.85 0.40 6 74.9 75.3 2.62 2.62 0.00 7 16.9 17.1 0.61 1.61 1.00
[0171] These results show that it is possible to control the
aggressiveness of macroscopic textures generated with an air knife
by adjusting the process conditions. For the high viscosity coating
that employs an RCA as part of its composition, the wave-like
macroscopic textures progress from relatively large and broad
features at fast line speeds to texture with a very fine, satin
finish at low line speeds. Note that even in the latter case (FIGS.
28 and 31) the fine wave-like features can still be distinguished
with the unaided eye. Also note that the same pre-cured coating
composition was used in samples 1-3, illustrating the appreciable
textural control that may be attained from the coating application
method alone.
[0172] Similar textural control is achieved using a coating with
texture-producing particles ("sandpaper" texture), as indicated by
the large variations in gloss and relief shown in Table 13 for
samples 4-7 (similarly, a single pre-cured coating composition was
used in samples 4-7). In general, lower gloss and higher relief
correspond to more aggressive textures. However, variations in the
planar dimensions and in the average gauge (average of the minimum
and maximum gauges) are also important for the overall perceived
aggressiveness of the textures (and may also influence gloss
readings).
Example 20
[0173] This example shows the scratch resistance properties of
cured coating having macroscopic texture. The pre-cured coating
mixtures 4 (40% nano-alumina) and 7 (22% nano-silica) in Example 6
and the coating Example 12 (4% wax) were coated as described in
Example 6 on flexible vinyl sheet flooring and UV cured under inert
conditions as described in Example 6. These cured coatings had
macroscopic wave-like texture. Pieces measuring 9 in.sup.2 were
mounted on plywood and placed on the floor in a high traffic area
(a cafeteria). After a given amount of time the floor panels were
pulled up, cleaned, and evaluated for scratch resistance. The
scratch resistance was measured by counting the total number of
scratches on a given coating and dividing by the total area in
square feet. As controls, a standard high gloss (80-90%)
macroscopically smooth urethane containing no inorganics and a wood
laminate floor were also evaluated. The results of these tests are
shown in FIG. 33. The scratch data clearly show that the textured
urethane coatings have fewer scratches per square foot of exposed
surface than the standard smooth urethane and the wood
laminate.
Example 21
[0174] This example demonstrates a thermally-cured top coating that
provides macroscopic texture. The pre-cured coating composition
described in Table 14 was mixed using a Cowles blade mixer at room
temperature. This composition is nearly identical to the
radiation-curable coating mixture described in Examples 16 and 17
except that a thermally activated initiator (an organic peroxide)
was used instead of a UV activated initiator to initiate the
curing. This coating mixture was then applied to flexible sheet
vinyl at 70.degree. C. using an air knife. The resulting coated
substrate (1-1.5 mils thick) was cured at 360.degree. C. for 2
minutes. The resulting solid coating had a ceramic-like
macro-texture, which as nearly identical in appearance to those
coatings in Example 17.
TABLE-US-00014 TABLE 14 Thermally-Curable Coating Composition
Coating Component Manufacturer (Wt %) Urethane acrylate (Alua 1001)
Congoleum 44.83 Propoxylated diacrylate (SR 306) Sartomer 20.53
Ethoxylated trimethylolpropane triacrylate Sartomer 11.25 (SR 454)
Ethoxylated diacrylate (SR 259) Sartomer 6.92 Tertiary-butyl
peroxybenzoate (P-20) Norac 1.06 60 .mu.m Nylon 12 (Orgasol 2002
ES6) Atochem 6.25 5 .mu.m Nylon 12 (Orgaso 2001 UD) Atofina 8 35 nm
Alumina (Nanotek alumina) Nanophase 1 Prehydrolyzed silane (as
described in Congoleum 0.16 Example 1)
Example 22
[0175] This example demonstrates the use of a shrinking wear layer
to provide texture from the use of texture-producing particles. A
wear layer formulation was made comprising, by weight, 57.8% PVC
resin (75HC available from Oxychem, Dallas, Tex.), 6.4% PVC resin
(567 available from Oxychem, Dallas, Tex.), 26.6% plasticizer
(N-6000 available from Velsicol, Rosemont, Ill.), 2.9% plasticizer
(S-375 available from Solutia, St. Louis, Mo.), 1.9% plasticizer
(A-150 available from Exxon, Houston, Tex.), and 4.4% stabilizer
(2347 available from OMG, Cleveland, Ohio). To this mixture is
added 25% solid glass beads (no plasticizer absorption or melting)
having a mean diameter of 203 .mu.m (Spheriglass A-1922 available
from Potters Industries, Valley Forge, Pa.). The resulting wear
layer mixture was coated with a draw bar at 10 mils on a flexible
vinyl gel. The resulting sample was then fused at 385.degree. F.
for 1.5 minutes. As a control, this same wear layer formulation
without the glass beads was coated and gelled. The control
plastisol had a visibly smooth surface and a gloss value of 38%.
The sample containing glass beads had macroscopic texture and a
gloss of 23%, which indicates that the wear layer decreased in
thickness during gelation to expose the glass beads.
Example 23
[0176] To demonstrate wet flocking, a standard PVC plastisol
(Ultima Wear Layer WB4 available from Congoleum Corporation,
Mercerville, N.J.) was drawn down on flexible gelled PVC at 10
mils. Several types of particles, as described in Table 15, were
each wet flocked on the wet plastisol. These samples were then
fused at 385.degree. F. for 1.5 minutes. The visual observations as
well as the gloss values for each sample are given in Table 16. The
data in Table 16 indicate that wet flocking gives ceramic-like
texture as long as the plastisol is fused at a temperature lower
than the melting point of the particle. When the fusion temperature
is higher than the melting temperature of the particle, the
particle melts to form a semi-continuous film on the surface of the
plastisol. This phenomenon occurred when Nylon 12 and polypropylene
particles were used.
TABLE-US-00015 TABLE 15 Particles Used in Wet Flocking Diameter
Melting pt Type Tradename Manuf. (.mu.m) (.degree. F.) Solid glass
Sheriglass Potters 203 1300 A1922 Industries Nylon 12 Oragsol 2002
Atofina 60 352 ES6 Nylon 66 Ashley 70 513 Polymers Nylon 11 Ashley
100 388 Polymers polypropylene Propyltex 100 Micropowders 90 330
polypropylene Propyltex 140 Micropowders 50 330
TABLE-US-00016 TABLE 16 Ultima Wear Layer Wet Flocked With Various
Particles Particle Texture Gloss (%) Comments None Smooth 50
Propyltex 100 Smooth 13 Particles melted Propyltex 140 Smooth 12
Particles melted Nylon 12 Smooth 11 Particles melted Nylon 11
Ceramic 3 Nylon 66 Ceramic 3.4 Glass Ceramic 3
Example 24
[0177] This example illustrates the use of spray coating as a
method for applying a radiation-curable coating having macroscopic
texture onto a tile substrate. A pre-cured coating mixture having
the composition described in Table 17 was applied to a vinyl tile
substrate using an air-gun sprayer (Campbell Hausfeld Standard Duty
Air-Driven Spray Gun Model DH5300). The spray gun was operated in
pressure-feed mode using 45 psig of air pressure, and the nozzle
configuration employed was designed for external atomization of the
coating droplets by the high-pressure air stream. The tile
substrate was sprayed by multiple passes with the handheld spray
gun at a height of about 12'' from the tile surface until complete
coverage of the tile surface by the pre-cured coating mixture was
achieved. The sprayed-on, pre-cured coating mixture on the tile
substrate was then cured as in Example 2. Both the sprayed-on,
pre-cured coating mixture on the tile substrate and the cured
coating on the tile substrate exhibited macroscopic texture due to
the texture-generating particles present in the pre-cured and cured
topcoat.
TABLE-US-00017 TABLE 17 UV-Curable Coating Composition Component
Wt. % UV-curable Resin from Table 1 84.59 Orgasol 2001 UD (5 micron
organic flatting agent) 8.00 Orgasol 2002 ES6 (60 micron
texture-producing 6.25 particle) Nanotek Alumina (inorganic RCA)
1.00 Prehydrolyzed Z-6030 (coupling agent from 0.16 Example 1)
Example 25
[0178] This example shows the use of a roll-coat and air-station
combination process (termed a RAS process, as described previously)
for application of a radiation-curable, macroscopically textured
coating onto a tile substrate. Tile substrates were coated with the
pre-cured coating mixture described in Table 18 using a three-roll
coater comprised of a hard rubber roll as the upper metering roll
(about 90 Shore A Durometer hardness), an engraved steel roll (72
tri-helical) as the transfer roll, and a soft rubber roll as the
applicator roll. An especially soft durometer (35 Shore A
Durometer) for the applicator roll was chosen to promote coating
application in deeply embossed grout lines and in other deeply
embossed substrate regions. Line speed through the roll-coater was
about 70 fpm (feet per minute), and the compression of the
applicator roll upon the tile substrate was about 115 mils. The
roll-coated tiles exhibited directional lines of texture due to
"film-splitting" in the machine direction. Subsequent passage of
the roll-coated tiles through an airstation removed this
roll-coater directionality. The air-station comprised a vacuum
conveyor to hold down the moving tiles, as well as an airknife
operating at up to 3.7 psig at angles between +20.degree. and
-20.degree. from vertical (vertical referring to the airknife slit
pointing down directly upon the tile, and positive angles referring
to the slit being angled toward the incoming tile). The airstation
line speed was 40 fpm with a knife-to-tile gap of 50 mils, and
tiles were passed through with a planar rotation of 45.degree.
between the roll-coater directionality lines and the airstation
machine direction. Moreover, two passes under the airknife were
made, with 90.degree. planar rotation of the tile between passes
(i.e., on the second pass there is -45.degree. planar tile rotation
between the roll-coater directionality lines and the airstation
machine direction). Finally, the pre-cured textured coating was
subjected to a low-gloss cure cycle as follows: a) two H-bulb
(mercury) lamps on high at 125 fpm in air, then b) six H-bulb
(mercury) lamps on high in nitrogen (.about.3000 ppm residual O2)
at 100 fpm. The final, UV-cured coating exhibits a low-gloss,
macroscopically textured surface topcoat with textural features
characteristic of the 60 micron texture-generating particles
present in the coating composition.
TABLE-US-00018 TABLE 18 UV-Curable Coating Composition Component
Manufacturer Wt. % Ethoxylated trimethylolpropane triacrylate (SR
Sartomer (Exton, PA) 35.303 454) Polyester acrylate (Laromer PE56F)
BASF (Charlotte, NC) 41.050 Urethane acrylate (Alua 1001) Congoleum
(Mercerville, NJ) 5.747 Acylphosphine oxide (Luceirin TPO) BASF
(Charlotte, NC) 0.330 Acematte OK 412 (3 micron inorganic flatting
Degussa Corp. 8.000 agent) Prehydrolyzed Z-6030 (coupling agent
from See Example 1 2.320 Example 1) Nanotek Alumina (inorganic RCA)
Nanophase Technologies 1.000 (Burr Ridge, IL) Orgasol 2002 ES6 (60
micron texture- Atofina 6.250 producing particle) (Philadelphia,
PA)
Example 26
[0179] The application of a radiation-curable coating having
macroscopic texture onto a tile already pre-coated with a
non-textured radiation-curable coating is demonstrated in this
example. Approximately 5 g of a commercial, non-textured UV-curable
urethane coating (AMT-475, available from Congoleum Corp.,
Mercerville, N.J.) was applied to a 12'' square tile using a
curtain coater. This undercoat was then partially cured in an air
environment using four H-bulb (mercury) lamps on high with a line
speed of 100 fpm (feet per minute). Next, a second and final
topcoat containing macroscopic texture-producing particles and
having the composition of Table 17 was applied with a roll-coater
and air-station (RAS) process similar to that described in Example
25 (an exception being the use of a two-roll coater instead of the
three-roll coater described in Example 25). The double-coated tile
was then subjected to the following low gloss cure cycle for curing
of the two topcoat layers: a) two H-bulb (mercury) lamps on high at
100 fpm in air, then b) six H-bulb (mercury) lamps on high in
nitrogen (.about.3000 ppm residual O2) at 100 fpm. The partial cure
of the non-textured, UV-curable undercoat instills sufficient
mechanical strength into the undercoat to withstand the subsequent
roll-coating of the textured topcoat. At the same time, the partial
undercoat cure also promotes adhesion of the textured topcoat to
the undercoat via unreacted acrylate crosslinking units that remain
in the undercoat after partial cure and can crosslink with similar
reactive groups in the textured topcoat. The final, UV-cured
coating exhibits a low-gloss, macroscopically textured surface
topcoat adhered to an underlying non-textured; UV-cured
basecoat.
[0180] While the foregoing description and drawings represent the
preferred embodiments of the present invention, it will be
understood that various additions, modifications and substitutions
may be made therein without departing from the spirit and scope of
the present invention as defined in the accompanying claims. In
particular, it will be clear to those skilled in the art that the
present invention may be embodied in other specific forms,
structures, arrangements, proportions, and with other elements,
materials, and components, without departing from the spirit or
essential characteristics thereof. The presently disclosed
embodiments are therefore to be considered in all respects as
illustrative and not restrictive, the scope of the invention being
indicated by the appended claims, and not limited to the foregoing
description.
* * * * *