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Description  |
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BACKGROUND OF THE INVENTION
This invention is directed to coating compositions containing a particulate
fluorocarbon resin as a texturing agent. More particularly, this invention
is directed to fluorocarbon resin-based coating compositions containing
large particle size particulate fluorocarbon resin as a texturing agent.
Fluorocarbon resins are known for their outstanding durability, that is,
their provision of a tough finish which is not readily disposed to crazing
or chalking with fluctuations in weather conditions. Fluorocarbon resins
are especially applicable in the building panel industry for use in
preparing durable surfaces for exterior use.
Textured surface are not new in the art and several methods are available
for producing them. U.S. Pat. No. 3,389,013 outlines several methods. A
first method employs "wrinkle materials". These contain drying oils,
which, upon curing, drying, or aging, form irregular films resembling
wrinkles. A second method involves the use of what is called a spatter
coat. This is generally sprayed over the surface to be coated in the form
of discrete particles which then coalesce and cover only part of the
surface. A third method involves first forming a smooth finish with a
film-forming material and then applying thereover a so-called texturing
agent such as an organic solvent to change the smooth finish to a textured
finish. A fourth method for obtaining textured finishes involves first
applying a base coat, allowing this base coat to dry, and then applying a
dissimilar top coat which contains a dispersion resin. The textured finish
resulting from this method is thought to be caused by the contraction of
the top coat, leaving part of the base exposed. Another method, the method
claimed in U.S. Pat. No. 3,389,013, involves applying a composition
comprising resinous film-forming material in particulate and in dissolved
form, the resin in particulate form being present in sufficient amount and
appropriate particle size to produce texturing. The textured coatings
produced in this manner, however, are not homogeneous, that is, the final
coating retains the original discrete particles without the intervening
formation of a fused coating with the texturing agent. Although effective
for use with many types of coatings, the aforedescribed texturing methods
have a severely limited ability to successfully texture fluorocarbon
resins. While fluorocarbon resins have many unique chemical
characteristics, conventional texturing materials used therewith, such as
polypropylene, typically change color, chalk or release from the coating
composition upon exposure to external climatic conditions or exhibit
marked yellowing upon baking for a short period. Because fluorocarbon
resins exhibit such outstanding durability and provide excellent
properties for exterior use, a method is needed to successfully texture
these resins without detracting from the excellent properties of the
fluorocarbon resin.
SUMMARY OF THE INVENTION
In accordance with the present invention, a coating composition useful for
providing a substrate with a coating having a textured appearance is
disclosed which contains a particulate fluorocarbon resin as texturing
agent. The coating composition comprises, on a resin solids basis, a
resinous mixture of:
(a) from about 40 percent to about 85 percent by weight of a film-forming
fluorocarbon resin having a particle size of from about 0.1 microns to
about 5 microns;
(b) from 0 percent to about 50 percent by weight of an acrylic resin
selected from thermoplastic homopolymers and copolymers of acrylic acid
esters or methacrylic acid esters and thermosetting copolymers of acrylic
monomers containing hydroxyl or amide groups; and
(c) from about 3 percent to about 50 percent by weight of a particulate
fluorocarbon resin having a particle size ranging from about 20 microns to
about 3500 microns, said particulate fluorocarbon resin being fused with
the film-forming fluorocarbon resin upon curing to provide said textured
appearance.
Upon heating the particulate fluorocarbon used as texturing agent fuses
into the film-forming resin to produce a textured coating for exterior use
which exhibits excellent durability, mar resistance, water resistance,
thermal stability, i.e., does not yellow upon heating, and is non-abrasive
to application equipment.
DETAILED DESCRIPTION OF THE INVENTION
The coating compositions of the present invention comprise a resinous
mixture of a film-forming fluorocarbon resin and a particulate
fluorocarbon resin. In one embodiment, an acrylic resin is used in
combination with the film-forming fluorocarbon resin. A detailed
description of the components found in the compositions of the invention
and the composition's use are given in subsequent paragraphs.
Several different film-forming fluorocarbon resins are useful in the
present invention. Such resins include the polyvinyl fluorides,
polyvinylidene fluorides, vinyl fluoride copolymers, and vinylidene
fluoride copolymers. The preferred film-forming fluorocarbon resin is
polyvinylidene fluoride. The copolymers include at least 75 percent by
weight, preferably 90 percent or more of vinyl or vinylidene fluoride
units. Examples of monomers to be copolymerized with vinyl fluoride or
vinylidene fluoride are ethylene, propylene, isobutylene, styrene, vinyl
chloride, vinylidene chloride, difluorochloroethylene,
trifluorochloroethylene, tetrafluoroethylene, trifluoropropylene,
hexafluoropropylene, vinyl formate, vinyl acetate, vinyl propionate, vinyl
butyrate, acrylic acid and its salts, methyl methacrylate, allyl
methacrylate, acrylonitrile, N-butoxymethyl acrylamide, allyl acetate,
isopropenyl acetate, etc. In a preferred embodiment, the film-forming
fluorocarbon resin is 100 percent polyvinylidene fluoride. The
film-forming fluorocarbon resin is used in the form of a powder having a
particle size of from about 0.1 microns to about 5 microns, preferably
from about 0.2 microns to about 0.4 microns. The concentration of the
film-forming fluorocarbon resin in the coating composition can be from
about 40 percent to about 85 percent by weight, preferably from about 55
to about 75 percent by weight, on a resin solids basis.
The acrylic resin optionally used in combination with the film-forming
fluorocarbon resin can be a thermoplastic or thermosetting acrylic resin,
however, the thermoplastic resins are especially useful herein. The
thermoplastic acrylic resins are the polymerized ester derivatives of
acrylic acid and methacrylic acid. The esters are formed by the reaction
of the acrylic or methacrylic acid with suitable alcohols, for example,
methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol and
2-ethylhexyl alcohol. Generally, the larger the alcohol portion of the
ester, the softer and more flexible the resultant resin. Also, generally,
the methacrylic esters form harder film than the corresponding acrylic
esters. Monomers, such as styrene, vinyl toluene, vinyl chloride, and
vinylidene chloride can be reacted with the acrylic and methacrylic esters
so as to produce resins with excellent properties.. An especially
satisfactory resin is a copolymer of methyl methacrylate and ethyl
acrylate, having a weight average molecular weight of between about 50,000
and about 150,000 as determined by gel permeation chromatography using a
polystyrene standard. Typically, the concentration of the acrylic resin in
the coating composition can be from 0 percent to about 50 percent by
weight, preferably from about 20 percent to about 40 percent by weight, on
a resin solids basis.
Thermosetting acrylic resins are normally low molecular weight copolymers
made from two, three and sometimes more monomers. Usually three monomers
are present. Many such resins are known and can be used herein. One of the
monomers is an acrylic compound containing pendant reactive groups such as
hydroxyl or amide. Another is an acrylic acid. A third monomer is usually
a styrene-type monomer such as styrene itself, vinyl toluene, methyl
styrene or ethyl styrene. The proportions of the three components in the
polymerization procedure are varied depending on the products in which the
copolymer will be used.
It should be understood that the aforesaid acrylic resins can be in a latex
form also. The acrylic particles typically have a particle size of less
than about 1 micron, preferably from about 0.05 microns to about 0.5
microns and are suspended in water.
Except, of course, for a difference in particle size, the aforedescribed
fluorocarbon resins useful as the film-forming fluorocarbon in the present
invention can also be used as the particulate fluorocarbon texturing
agent. In a preferred embodiment, polyvinylidine fluoride is used as the
texturing agent. The particulate fluorocarbon has a particle size
sufficient to provide the textured appearance of the final coating but not
so large that light abrasion will cause the texturing particles to release
from the final coating. Broadly speaking, the particles range from about
20 microns to about 3500 microns, more usually from about 20 microns to
about 500 microns. Preferably, the particles range from about 25 microns
to about 250 microns, more preferably from about 50 microns to about 150
microns. In the event that particles of substantially smaller or larger
size than specified are used, disadvantageous results are obtained. That
is, if smaller particle sizes are utilized a smoother, substantially
untextured surface will be produced; and if larger particle sizes are used
an exceptionally rough surface will be produced which may result in the
particles releasing from the final coating upon light abrasion. Moreover,
such a coating may be aesthetically objectionable and difficult to apply
with conventional application equipment. The concentration of the particle
fluorocarbon resin used as texturing agent in the coating composition can
be from about 3 percent to about 50 percent by weight, preferably from
about 3 percent to about 25 percent, more preferably from about 5 percent
to about 16 percent by weight.
The solvent used to form a film of the composition is one which cannot
dissolve the particulate flourocarbon resin at room temperature. The
film-forming resin and particulate fluorocarbon resin are dispersed in the
solvent such that the mixture has a fluid consistency. Suitable solvents
include water, the aromatic petroleum distillates, methyl ethyl ketone,
methyl isobutyl ketone, alcohols such as ethyl alcohol, propyl alcohol and
diacetone alcohol, dimethyl phthalate, and mono- and dialkyl ethers of
ethylene and diethylene glycol, such as ethylene glycol monoethyl ether,
ethylene glycol monobutyl ether, ethylene glycol monoethyl ether acetate,
diethylene glycol monobutyl ether and diethylene glycol diethyl ether. The
solvent is used at a level such that the amount of resin solids in the
composition varies generally from about 20 percent by weight to about 70
percent by weight. However, it should be understood that the amount of
resin solids can be lesser or greater than these amounts without
detracting from the properties of the final composition.
In one preferred embodiment, the film-forming resin of the claimed
composition is present as a mixture of from about 40 percent to about 85
percent by weight of a fluorocarbon resin having a particle size of from
about 0.1 microns to about 5 microns and from about 10 percent to about 50
percent by weight of an acrylic resin; while the particulate fluorocarbon
is present in an amount of from about 3 percent to about 25 percent by
weight and has a particle size of from about 25 microns to about 250
microns. More preferably, the fluorocarbon resin is present in amounts of
from about 55 percent to about 75 percent by weight and has a particle
size of from about 0.2 microns to about 0.4 microns; the acrylic resin is
present in amounts of from about 20 percent to about 40 percent by weight;
and the particulate fluorocarbon is present in an amount of from about 5
percent to about 16 percent by weight and has a particle size of from
about 50 microns to about 150 microns.
Although in a preferred embodiment, a clear, textured coating is produced,
one can also produce a pigmented textured coating. Several different
pigments can be used in the coating compositions of the present invention.
Inorganic pigments which are useful include titanium dioxide, silica, iron
oxides, talc, mica, clay, zinc oxide, zinc sulphide, zirconium oxide,
carbon black, lead chromate, metallic pigments, molybdate orange, calcium
carbonate, and barium sulfate. Organic pigments can also be used herein.
In addition to pigment, the coating compositions of the present invention
can also contain other components to enhance various properties of the
composition or final coating, such as pigment stabilizers, rheology
control agents, dispersants, adhesion promoting agents, colorants, and the
like. It should be further understood that other types of resins can be
blended into the claim coating composition so long as the properties of
the final coating are not substantially affected.
The claimed textured coating compositions are preferably applied to a
primed aluminum substrate in any conventional manner, such as by brush,
dip, roller, or spray. Typically, the thickness of the applied coating is
between about 20 and 200 microns. After being coated, the substrate is
dryed either by air drying or baking. If baked a baking temperature of up
to 275.degree. C. preferably 200.degree. C. to 275.degree. C. can be used.
The drying process results in the texturing agent fusing into the
film-forming resin thereby resulting in the exceptional qualities of
durability, mar resistance, and thermal stability. The aforedescribed
textured coatings do not yellow upon exposure to heat nor does the
texturing agent release from the coating upon exposure to exterior
climatic conditions.
The following examples are submitted for the purpose of further
illustrating the nature of the present invention and should not be
construed as a limitation on the scope thereof. All parts and percentages
in the examples and throughout the specification are by weight unless
otherwise indicated.
EXAMPLE I
A clear textured coating composition of this invention has the following
formulation:
______________________________________
Parts by
Percent of
Weight Resin Solids
______________________________________
Thermoplastic acrylic resin dispersion
259 27
(40% solids) (1)
Film-forming fluorocarbon resin (2)
242 64
Polyvinylidine fluoride used as
35 9
texturing agent (3)
Cellosolve acetate 110
Dimethyl phthalate 86
Butyl cellosolve 91
Xylene 105
Toluene 15
______________________________________
(1) Methyl methacrylateethyl acrylate copolymer dispersion available from
Rohm & Haas Co. as Acryloid B44.
(2) Polyvinylidine fluoride resin having a particle size of from 0.2 to
0.4 microns, available from Pennwalt Corp. as Kynar 500.
(3) Polyvinylidine fluoride resin having a particle size of from 50 to 15
microns, available from Pennwalt Corp. as Kynar 931.
Into a mixing tank were added to following ingredients, in order: 172 parts
of acrylic resin, 78 parts of cellosolve acetate, and 80 parts of dimethyl
phthalate. After mixing these materials, 242 parts of film-forming
fluorocarbon resin was added as quickly as possible while maintaining the
temperature below 38.degree. C. The entire disperse mixture was then
ground to a paste having a 51/2 Hegman grind. The milling apparatus was
washed with 105 parts of xylene and the wash then added to the paste. The
paste was ground into a clean, dry mixing tank and the following
ingredients were added with agitation to yield a clear liquid textured
coating composition: 87 parts of acrylic resin, 91 parts of butyl
cellosolve, 15 parts of toluene, 6 parts of dimethyl phthalate, 32 parts
of cellosolve acetate and 35 parts of polyvinylidine fluoride used as
texturing agent.
EXAMPLE II
A pigmented textured coating composition of this invention has the
following formulation:
______________________________________
Parts by
Percent of
Weight Resin Solids
______________________________________
Thermoplastic acrylic resin dispersion
172 11
(40% solids) (1)
Film-forming fluorocarbon resin (2)
541 84
Polyvinylidine fluoride used as
35 5
texturing agent (3)
Cellosolve acetate 24
Dimethyl phthalate 23
Bentonite clay (4) 3
Ethyl alcohol 3
Xylene 52
Butyl cellosolve 44
Toluene 19
Lamp black pigment 20
______________________________________
(1) Methyl methacrylateethylacrylate copolymer dispersion available from
Rohm & Haas Co. as Acryloid B44.
(2) Polyvinylidine fluoride resin having a particle size of 0.2 to 0.4
microns, available from Pennwalt Corp. as Kynar 500.
(3) Polyvinylidine fluoride resin having a particle size of from 50 to 15
microns, available from Pennwalt Corp. as Kynar 931.
(4) Available from National Lead Co. as Bentone 38.
Into a mixing tank were placed 57 parts of acrylic resin, 27 parts of
xylene, 31 parts of butyl cellosolve and 23 parts of dimethyl phthalate.
While agitating these ingredients, 3 parts of bentonite clay were sifted
in. The entire mixture was agitated at high speed for 5 minutes followed
by the addition of 3 parts of ethyl alcohol. The mixture was again
agitated at high speed for 5 minutes and 20 parts of lamp black pigment
were added. The resulting paste was thoroughly mixed, placed in a
sandmill, and ground to a 61/2 Hegman grind. The sandmill was rinsed with
23 parts of acrylic resin and 19 parts of toluene and this wash was added
to the ground paste. To this mixture were then added 92 parts of acrylic
resin, 541 parts of film-forming fluorocarbon resin, 12 parts of butyl
cellosolve, 24 parts of cellosolve acetate, 25 parts of xylene and 35
parts of polyvinylidine fluoride used as texturing agent. The mixture was
thoroughly mixed to yield a pigmented liquid textured coating composition.
EXAMPLE III
This example is a comparative example showing the difference in properties
of coating compositions textured with the particulate fluorocarbon resins
of the present invention as compared to the same coating compositions
textured with conventional texturing agents. All of the following coating
compositions were applied over the indicated primed aluminum substrate and
then baked at 246.degree. C. for 10 minutes.
______________________________________
Applied over
Applied over a
Applied over a
a Substrate
Primed Substrate
Primed Substrate
Coated with
Coating
Coated with Coated with Dark
a Primer
Com- White Coating
Brown Coating
Coating
position
Composition (1)
Composition (2)
Composition
______________________________________
(1) X
(2) X
(3) X X X
(4) X
(5) X
(6) X
(7) X
(8) X X X
(9) X X X
______________________________________
Coating composition (1) is a white pigmented coating composition without
texturing agent having the following formulation:
______________________________________
Parts by
Percent of
Weight Resin Solids
______________________________________
Thermoplastic acrylic resin dispersion
134 21
(40% solids) (1)
Film-forming fluorocarbon resin (2)
209 79
Butyl cellosolve 101
Dimethyl phthalate 77
Cellosolve acetate 102
Toluene 106
Xylene 116
Pigment 183
______________________________________
(1) Methyl methacrylateethyl acrylate copolymer dispersion available from
Rohm & Haas Co. as Acryloid B44.
(2) Polyvinylidine fluoride resin having a particle size of 0.2 to 0.4
microns, available as Kynar 500 from Pennwalt Corp.
Coating composition (2) is a dark brown, pigmented coating composition
without texturing agent having the following formulation:
______________________________________
Parts by
Percent of
Weight Resin Solids
______________________________________
Thermoplastic acrylic resin dispersion
134 21
(40% solids) (1)
Film-forming fluorocarbon resin (2)
209 79
Butyl cellosolve 107
Dimethyl phthalate 75
Bentonite clay 3
Ethyl alcohol 1
Cellosolve acetate 105
Toluene 101
Xylene 125
Pigment 129
______________________________________
(1) Methyl methacrylateethyl acrylate copolymer dispersion available from
Rohm & Haas Co. as Acryloid B44.
(2) Polyvinylidine fluoride resin having a particle size of 0.2 to 0.4
microns, available as Kynar 500 from Pennwalt Corp.
Coating composition (3) is a clear coating composition without texturing
agent having the following formulation:
______________________________________
Parts by
Percent of
Weight Resin Solids
______________________________________
Thermoplastic acrylic resin dispersion
259 30
(40% solids) (1)
Film-forming fluorocarbon resin (2)
242 70
Cellosolve acetate 110
Dimethyl phthalate 86
Butyl cellosolve 91
Xylene 105
Toluene 15
______________________________________
(1) Methyl methacrylateethyl acrylate copolymer dispersion available from
Rohm & Haas Co. as Acryloid B44.
(2) Polyvinylidine fluoride resin having a particle size of 0.2 to 0.4
microns, available as Kynar 500 from Pennwalt Corp.
Coating composition (4) is the white pigmented coating composition (1)
having a polypropylene texturing agent present as a mixture of 20 parts of
Hercoflat 135 (7% of resin solids) and 20 parts of Hercoflat 1150 (7% of
resin solids) both available from Pennwalt Corp.
Coating composition (5) is the white pigmented coating composition (1)
containing 50 parts of 50-150 microns particle size, polyvinylidine
fluoride used as texturing agent (16% of resin solids) available as Kynar
931 from Pennwalt Corp.
Coating composition (6) is the dark brown, pigmented coating composition
(2) having a polypropylene texturing agent present as a mixture of 20
parts of Hercoflat 135 (7% of resin solids) and 20 parts of Hercoflat 1150
(7% of resin solids) both available from Pennwalt Corp.
Coating composition (7) is the dark brown, pigmented coating composition
(2) containing 35 parts of 50-150 microns particle size polyvinylidine
fluoride used as texturing agent (12% of resin solids) available as Kynar
931 from Pennwalt Corp.
Coating composition (8) is the clear coating composition (3) having a
polypropylene texturing agent present as a mixture of 20 parts of
Hercoflat 135 (5% of resin solids) and 20 parts of Hercoflat 1150 (5% of
resin solids) both available from Pennwalt Corp.
Coating composition (9) is the clear coating composition (3) containing 35
parts of 50-150 microns particle size, polyvinylidine fluoride used as
texturing agent (9% of resin solids) available as Kynar 931 from Pennwalt
Corp.
OBSERVATIONS
Coatings (1), (2), and (3) contained no texturing agent and thus were
controls.
The microscopic examination of panels coated with coating compositions (5),
(7), and (9), containing polyvinylidine fluoride used as texturing agent
of 50 to 150 microns particle size, revealed that the texturing agent
fused into the clear and pigmented coating compositions after baking and
did not yellow. Upon prolonged exposure to ultraviolet light the coated
panels retained their textured appearance and color.
In comparison, the microscopic examination of panels coated with coating
compositions (4), (6), and (8), containing a conventional polypropylene
texturing agent, revealed that the texturing agent did not fuse into the
coating compositions after baking and exhibited yellowing. Upon prolonged
exposure to ultraviolet light the coatings of these panels began to
decompose and chalking was observed.
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