U.S. patent application number 11/051784 was filed with the patent office on 2005-06-23 for low gloss free radical powder coatings.
This patent application is currently assigned to E.I. DU PONT DE NEMOURS AND COMPANY. Invention is credited to Bailey, Frederick L., Decker, Owen H., Flosbach, Carmen, Polu, Rajendra Kumar.
Application Number | 20050137279 11/051784 |
Document ID | / |
Family ID | 23144856 |
Filed Date | 2005-06-23 |
United States Patent
Application |
20050137279 |
Kind Code |
A1 |
Decker, Owen H. ; et
al. |
June 23, 2005 |
Low gloss free radical powder coatings
Abstract
The present invention is directed to a powder coating
composition that produces a low gloss coating upon cure. The powder
coating composition includes one or more crosslinkable base
polymer, a crosslinkable acrylic polymer and one or more free
radical initiators. By adding spheroidal particles to the powder
coating composition further reduction in gloss can be obtained
while improving smoothness. These compositions are well suited to
produce coatings on metallic substrates, such as automotive bodies
and non-metallic substrates, such as reconstituted wood substrates,
used for desk or table tops.
Inventors: |
Decker, Owen H.; (Houston,
TX) ; Bailey, Frederick L.; (Houston, TX) ;
Polu, Rajendra Kumar; (Houston, TX) ; Flosbach,
Carmen; (Wuppertal, DE) |
Correspondence
Address: |
E I DU PONT DE NEMOURS AND COMPANY
LEGAL PATENT RECORDS CENTER
BARLEY MILL PLAZA 25/1128
4417 LANCASTER PIKE
WILMINGTON
DE
19805
US
|
Assignee: |
E.I. DU PONT DE NEMOURS AND
COMPANY
|
Family ID: |
23144856 |
Appl. No.: |
11/051784 |
Filed: |
February 4, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11051784 |
Feb 4, 2005 |
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10165652 |
Jun 7, 2002 |
|
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6852765 |
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60297100 |
Jun 8, 2001 |
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Current U.S.
Class: |
522/107 |
Current CPC
Class: |
C08L 33/062 20130101;
C09D 5/032 20130101; C08K 9/06 20130101; C08K 7/16 20130101; C09D
7/42 20180101; C09D 171/02 20130101; C09D 175/16 20130101; C08K
9/02 20130101; C08L 71/02 20130101; C09D 167/06 20130101; C08K 9/02
20130101; C08L 63/00 20130101; C08K 9/06 20130101; C08L 63/00
20130101; C08L 71/02 20130101; C08L 2666/04 20130101; C09D 167/06
20130101; C08L 2666/04 20130101; C09D 171/02 20130101; C08L 2666/04
20130101 |
Class at
Publication: |
522/107 |
International
Class: |
C08G 002/00 |
Claims
1. (canceled)
2. (canceled)
3. (canceled)
4. (canceled)
5. (canceled)
6. (canceled)
7. (canceled)
8. (canceled)
9. A process for producing a coating having low gloss, said process
comprising the steps of: applying over a substrate a layer of low
gloss powder coating composition comprising a base polymer selected
from the group consisting of a crosslinkable polyester,
crosslinkable polyurethane, crosslinkable acrylated polyether and a
combination thereof; about 5 percent to about 60 percent of
crosslinkable acrylic polymer; and about 0.1 to 10 percent of one
or more free radical initiators, all percentages in weight percent
based on total weight of said crosslinkable base and acrylic
polymer solids; heating said layer into a film; and curing said
film into said coating having low gloss.
10. The process of claim 9 wherein said coating composition further
comprises about 5 percent to 50 percent of spheroidal particles,
all percentages being in weight percent based on the total weight
of the coating composition and wherein said spheroidal particles
have a median particle diameter ranging from about 10 microns to
about 50 microns.
11. The process of claim 9 or 10 wherein said curing step comprises
exposing said layer to actinic radiation.
12. The process of claim 9 or 10 wherein said curing step comprises
exposing said layer to an elevated temperature ranging from
90.degree. C. to 220.degree. C.
13. The process of claim 9 or 10 wherein said curing step comprises
simultaneously exposing said layer to actinic radiation and
elevated temperature ranging from 90.degree. C. to 220.degree.
C.
14. The process of claim 13 wherein said curing step further
comprising continuing exposure for about 5 minutes to about 30
minutes of said layer to said elevated temperature after cessation
of exposure to said actinic radiation.
15. The process of claim 9 or 10 wherein said curing step comprises
exposing said layer to actinic radiation followed by exposure to an
elevated temperature ranging from 90.degree. C. to 220.degree. C.,
or by exposure to an elevated temperature ranging from 90.degree.
C. to 220.degree. C. followed by exposure to actinic radiation.
16. The process of claim 9 or 10 wherein said coating is
smooth.
17. The process of claim 9 or 10 wherein said substrate is an
automotive body or a reconstituted wood substrate.
18. A process for producing a low gloss powder coating composition
comprising the steps of: mixing a base polymer selected from the
group consisting of a crosslinkable polyester, crosslinkable
polyurethane, crosslinkable acrylated polyether and a combination
thereof with about 5 percent to about 60 percent of a crosslinkable
acrylic polymer and about 0.1 to 10 percent of one or more free
radical initiators to form a blend, all percentages in weight
percent based on total weight of said crosslinkable base and
acrylic polymer solids; heating said blend into a molten blend;
melt extruding said molten blend into a molten extrudate;
solidifying said molten extrudate into a solid extrudate;
fracturing said solid extrudate into fragments; and grinding said
fragments.
19. The process of 18 wherein said blend further comprises about 5
percent to 50 percent of spheroidal particles, all percentages
being in weight percent based on the total weight of the coating
composition and wherein said spheroidal particles have a median
particle diameter ranging from about 10 microns to about 50
microns.
20. The process of claim 18 or 19 further comprising straining
ground fragments through a 180-micrometer screen to remove coarse
fragments.
21. The process of claim 18 or 19 further comprising adding water
to said fragments to form aqueous slurry.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a non-provisional claiming priority from
a provisional application having Ser. No. 60/297,100 filed on Jun.
8, 2001.
FIELD OF THE INVENTION
[0002] The present invention is directed powder coating
compositions and more particularly directed to a class of powder
coating compositions that upon cure result in low-gloss coatings
preferably having smooth finish.
BACKGROUND OF THE INVENTION
[0003] Powder coatings are widely used to provide a decorative
and/or protective coating on substrates. They are becoming
increasingly popular because they are applied in a solid state or
slurry. Unlike conventional liquid coating compositions, the powder
coating compositions use little or no solvents. In addition, solid
state application permits the powder to be collected, purified and
re-used.
[0004] UV curable powders have been used in powder coating
compositions. Typically, UV curable powders are formulated from
solid crosslinkable base resins with low Tg, such as crosslinkable
polyesters; crosslinkable co-polymerizable crosslinker resins, such
as vinyl ethers; photoinitiators; flow and leveling agents; and, if
necessary, pigments and fillers.
[0005] During coating operations, UV curable powders are applied to
a substrate in the usual fashion, using electrostatic spray
techniques. The coated substrate is then heated for as long as it
takes to drive out substrate volatiles and fuse the powders into a
smooth molten film. Immediately following fusion, the molten film
is exposed to UV light, which, in an instant, cures and hardens the
film into a durable, smooth, attractive coating.
[0006] In certain applications, it is necessary or desirable for
the powder coating to have a surface that is preferably smooth in
appearance, but has a low gloss or shine. Such applications are
those where low gloss is aesthetically desired, or where glare from
the coating surface can interfere with the safe or proper use of
the coated article, such as desks, tables, counter tops or other
horizontal work surfaces, optical devices, motor vehicles, aircraft
and ships.
[0007] One drawback of UV curable powders is that it is very hard
to produce a low gloss (i.e., matte) coating from such powders
since the coatings resulting therefrom tend to be glossy. Gloss
reduction can normally be obtained in traditional powder coatings
through the introduction of matting agents, such as fillers or
waxes, which rise to the surface during curing and cause matting
through disruption of the surface of the coating. However, due to
the fast cure rate of UV curable powders, conventional fillers or
waxes cannot flocculate to the surface fast enough to produce the
low gloss and they remain trapped within the coating. Higher
amounts of fillers or waxes, which can be employed to overcome this
problem, tend to cause the powders to block or cake during normal
storage and/or produce coatings with severe orange peel, limiting
the amount of gloss reduction that could be attained.
[0008] One approach to tackle the foregoing problem associated with
obtaining low gloss coatings from UV curable powder coating
compositions was presented in U.S. Pat. No. 6,017,593. In U.S. Pat.
No. 6,017,593, low gloss was obtained by the use of a mixture of
crystalline and amorphous resins and by adding a cooling step after
the melting step but before, the photoinitiated curing step during
which the crystalline resin recrystallizes. However, the process in
U.S. Pat. No. 6,017,593 is limited in practical applications to
only those substrates having a uniform heating and cooling profile.
Thus, the process of U.S. Pat. No. 6,017,593 gives rise to
differential crystallization, differing gloss, and a mottled
appearance when used with substrates having variable heating and
cooling profiles, such as non-metallic substrates or those having
varying thicknesses, sharp edges and corners.
[0009] Therefore, it would be desirable to provide a method for
producing coatings with a low gloss appearance from UV curable
powder coating compositions on substrates having variable heating
and cooling profiles, such as non-metallic substrates.
STATEMENT OF THE INVENTION
[0010] The present invention is directed to a powder coating
composition that produces a low gloss coating upon cure, said
composition comprising:
[0011] a base polymer selected from the group consisting of a
crosslinkable polyester, crosslinkable polyurethane, crosslinkable
acrylated polyether and a combination thereof;
[0012] about 5 percent to about 60 percent of crosslinkable acrylic
polymer; and
[0013] about 0.1 to 10 percent of one or more free radical
initiators, all percentages in weight percent based on total weight
of said crosslinkable base and acrylic polymer solids.
[0014] The present invention is also directed to a process for
producing a coating having low gloss, said process comprising the
steps of:
[0015] applying over a substrate a layer of low gloss powder
coating composition comprising a base polymer selected from the
group consisting of a crosslinkable polyester, crosslinkable
polyurethane, crosslinkable acrylated polyether and a combination
thereof; about 5 percent to about 60 percent of crosslinkable
acrylic polymer; and about 0.1 to 10 percent of one or more free
radical initiators, all percentages in weight percent based on
total weight of said crosslinkable base and acrylic polymer
solids;
[0016] heating said layer into a film; and
[0017] curing said film into said coating having low gloss.
[0018] The present invention is further directed to a process for
producing a low gloss powder coating composition comprising the
steps of:
[0019] mixing a base polymer selected from the group consisting of
a crosslinkable polyester, crosslinkable polyurethane,
crosslinkable acrylated polyether and a combination thereof with
about 5 percent to about 60 percent of a crosslinkable acrylic
polymer and about 0.1 to 10 percent of one or more free radical
initiators to form a blend, all percentages in weight percent based
on total weight of said crosslinkable base and acrylic polymer
solids;
[0020] heating said blend into a molten blend;
[0021] melt extruding said molten blend into a molten
extrudate;
[0022] solidifying said molten extrudate into a solid
extrudate;
[0023] fracturing said solid extrudate into fragments; and
[0024] grinding said fragments.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0025] As defined herein:
[0026] "Low gloss coatings" means coatings having a gloss ranging
from 0.1 to 80, preferably ranging from 1 to 50, more preferably 10
to 30 when measured at a reflectance angle of 60.degree. by
Micro-Tri-Gloss Glossimeter supplied by BYK Gardner, Pomano Beach,
Fla.
[0027] "Smooth Coatings" means coatings having a writable and
appearance smoothness. A coating is considered to be writably
smooth if a line drawn manually using a fine ball point pen on a
standard photocopy quality paper placed directly over the coated
surface appears visually to be continuous (uninterrupted) and
regular (non-wiggly). The appearance smoothness of the coating is
determined on a scale of 1 to 10 by using PCI (Powder Coating
Institute, Alexandria, Va.) smoothness standards, 1 representing
heavy orange peel and 10 representing highest degree of
smoothness.
[0028] "Crosslinkable polymer" means a polymer having one or more
carbon-carbon double bonds positioned in the backbone of the
polymer, pendant from the backbone of the polymer, terminally
positioned on the backbone of the polymer, or a combination
thereof.
[0029] The term "spheroidal" as used herein means generally
spherical in shape. More specifically, the term means filler
materials that contain less than 25% particle agglomerates or
fractured particles containing sharp or rough edges. The spheroidal
particles should be non-reactive or inert so as not to interfere
with the other properties of the composition.
[0030] "Reconstituted wood substrate" (RWS) means, substrates
produced from wood particles, fibers, flakes or chips, such as, a
hardboard, a medium density fiberboard, an oriented strand board
also known as wafer board, a flake board, a chipboard and a
particleboard. Such a RWS is typically fabricated under heat and
pressure from particles, fibers, flakes or chips. RWS is produced
by treating particles, flakes, chips or fibers with a binder and
then arranging these treated particles, flakes, chips or fibers in
the form of a mat under dry or wet conditions. The mat is then
compressed into a dense substrate, typically in a sheet form, by
the application of heat and pressure. The binder binds particles,
flakes, chips or fibers and enhances the structural strength and
integrity of the RWS and its water resistance. The RWS, if desired,
may be molded into desired shape or provided with a textured
surface, such as, wood grain texture. Some examples of the RWS,
which include medium density fiberboard, oriented strand board,
particle board, flake board and underlayment are further defined
below.
[0031] "Medium density fiberboard" means a board manufactured from
lignocellulosic fibers bonded under heat and pressure by means of a
well dispersed synthetic resin or a similar binder. Such a board is
manufactured to a specific gravity of 0.50 to 0.88.
[0032] "Oriented strand board (OSB)" means a board manufactured
from lignocellulosic strand-type flakes purposefully aligned in a
direction that makes the resultant board stronger, stiffer and
having improved dimensional properties in the direction of
alignment when compared to a board having random flake orientation.
OSB is also known as wafer board.
[0033] "Particle board" means a board manufactured from wood
particles bonded under heat and pressure by means of a well
dispersed synthetic resin or similar binder. Such a board includes
conventional extruded and mat-formed particle boards.
[0034] "Flake board" means a board manufactured from wood flakes
bonded under heat and pressure by means of a well dispersed
synthetic resin or similar binder.
[0035] "Underlayment" means a smooth flat RWS used as a floor panel
upon which resilient floor covering may be glued.
[0036] "Plywood" means a glued wood panel made up of relatively
thin layers of veneer with the grain of adjacent layers at right
angles or a panel made up of veneer in combination with a core of
lumber or of RWS.
[0037] The powder coating compositions of this invention provide
the formulator with an opportunity to control the gloss of the
final coating while minimizing or eliminating the negative effects
of the prior art attempts at controlling gloss; i.e., loss of
coating flow and creation of "orange peel" surface effects.
[0038] The applicants have unexpectedly discovered that the gloss
of a coating resulting from a UV curable powder coating composition
can be controlled by utilizing a blend of one or more free
radically-curable base polymers and one or more free
radically-curable acrylic polymers to provide coatings with low
gloss, presumably through a differential-cure mechanism. This
effect can be further enhanced by the use of spheroidal
particles.
[0039] The powder coating composition that produces a low gloss
coating upon cure includes a base polymer selected from the group
consisting of a crosslinkable polyester, crosslinkable
polyurethane, crosslinkable acrylated polyether, and a combination
thereof; about 5 percent to about 60 percent, preferably about 10
weight percent to about 50 weight percent, more preferably about 20
to about 40 weight percent of crosslinkable acrylic polymer; and
about 0.1 to about 10 percent, more preferably about 0.1 percent to
about 4 percent of one or more free radical initiators, all
percentages in weight percent based on total weight of the
crosslinkable base and acrylic polymer solids.
[0040] The base polymer can have a concentration of crosslinkable
groups ranging from about 0.3 percent to about 10 percent,
preferably from about 0.5 percent to about 5 percent, more from
about 0.7 percent to about 3 percent based on the weight of the
crosslinkable base polymer. The GPC weight average molecular
weight, using polystyrene as a standard, of the base polymer can
range from 500 to 20,000, preferably from 1500 to 10,000.
[0041] Some of the crosslinkable groups that are suitable for the
crosslinkable polyester include acrylate, methacrylate, maleate,
fumarate and a combination thereof.
[0042] If desired, the crosslinkable polyesters can be blended with
other suitable crosslinkable polymers.
[0043] The crosslinkable polyesters are generally made by
condensing carboxylic acid or polycarboxylic acids (or their
anhydrides) with hydroxy or polyhydroxy-functional monomers.
Suitable acids include 1,2,4-benzenetricarboxylic acid,
1,2-benzenedioic acid, 1,3-benzenedioic acid, 1,4-benzenedioc acid,
cyclohexanedicarboxylic acid; C2 to C12 linear aliphatic diacids,
such as adipic acid and dodecanedioc acid; adipic anhydride,
succinic anhydride, dodecanedioc anhydride, maleic acid, maleic
anhydride, fumaric acid, itaconic acid, C1-C20 aromatic and
aliphatic monoacids such as acetic acid, benzoic acid; and
ethylenically-unsaturated acids such as acrylic acid and
methacrylic acid. Suitable hydroxy-functional monomers include
polyols, such as 2-hydroxymethyl-2-methyl-1,3-propanediol;
2,2-bis-(2-hydroxymethyl)-1,3-p- ropanediol; C2 to C12 linear
diols, for example 1,2-ethanediol, 1,3-propanediol, 1,4-butanediol
and 1,6-hexanediol; branched C2-C12 diols, for example
2-methyl-1,3-propane diol, 2,2-dimethyl-1,3-propane diol and
2-ethyl-2-butyl-1,3-propanediol; alicyclic diols, for example
1,2-cyclohexanediol, 1,4-cyclohexanediol and
1,4-cyclohexanedimethanol.
[0044] Some of the suitable commercial crosslinkable polyesters
include those supplied by:
[0045] I. UCB Chemicals of Smyrna, Ga. under the trademark
Uvecoat.RTM. 1000 Unsaturated polyester resin with methacrylate end
groups, Uvecoat.RTM. 1100 Unsaturated polyester resin with
methacrylate end groups, Uvecoat.RTM. 2000 Unsaturated polyester
resin with methacrylate end groups, Uvecoat.RTM. 2100 unsaturated
polyester resin with methacrylate end groups, Uvecoat.RTM. 2101
Unsaturated polyester resin, Uvecoat.RTM. 2200 Unsaturated
polyester resin with methacrylate end groups, Uvecoat.RTM. 2300
Unsaturated polyester resin with methacrylate end groups,
Uvecoat.RTM. 9000 crystalline unsaturated polyester resin with
methacrylate end groups, Uvecoat.RTM. 9010 crystalline unsaturated
polyester resin with methacrylate end groups and Uvecoat.RTM. D
8337 unsaturated polyester resin and Uvecoat.RTM. 3101 unsaturated
polyester resin.
[0046] II. DSM Coating Resins, Zwolle, The Netherlands under the
trademark Uracross.RTM. ZW 4892 P Unsaturated polyester,
Uracross.RTM. ZW 4557 P Unsaturated polyester resin, Uracross.RTM.
ZW 4989 P Unsaturated polyester resin with methacrylate end groups,
Uracross.RTM. ZW 5125 P unsaturated polyester resin, Uracross 5026
P unsaturated polyester resin with GMA functional groups,
Uracross.RTM. ZW 4901 P unsaturated polyester resin with maleate
end groups, and Uracross.RTM. P 3125 unsaturated polyester resin
with maleate end groups.
[0047] III. Solutia Inc, St. Louis, Mo. under the trademark
Viaktin.RTM. VAN 1743 Unsaturated polyester resin, Viaktin.RTM.
03490 Unsaturated polyester resin with methacrylate end groups,
Viaktin.RTM. 03890 Unsaturated polyester resin with methacrylate
end groups, Viaktin.RTM. 03929 Unsaturated polyester resin with
methacrylate end groups, Viaktin.RTM. 03732 Unsaturated polyester
resin with methacrylate end groups, and Viaktin.RTM. 03729
Semi-crystalline unsaturated polyester resin with methacrylate end
groups.
[0048] IV. Cray Valley, Saint Celani, Spain under the trademark
Reafree.RTM. ND-1291 Unsaturated polyester resin, Reafree.RTM.
ND-1530 Saturated polyester resin with acrylate groups and
Reafree.RTM. ND-1446 Saturated polyester resin.
[0049] V. Panolam, Auburn, Me. under the trademark Pioester.RTM.
1937 Unsaturated polyester resin, Pioester.RTM. 275 Unsaturated
polyester resin and Pioester.RTM. 202 HV Unsaturated polyester
resin.
[0050] Suitable blends of crosslinkable polyesters and other
crosslinkable polymers include Uvecoat.RTM. 3000 mixture of
unsaturated polyester and epoxy acrylate resin, Uvecoat.RTM. 3001
mixture of unsaturated polyester and epoxy acrylate resin,
Uvecoat.RTM. 3002 mixture of unsaturated polyester and epoxy
acrylate resin and Uvecoat.RTM. 3003 mixture of unsaturated
polyester and epoxy acrylate resin, all supplied by UCB Chemicals
of Smyrna, Ga.
[0051] Some of the crosslinkable groups that are suitable for the
crosslinkable polyurethane include acrylate, methacrylate, maleate,
fumarate, itaconate, alkenoxy and a combination thereof.
[0052] If desired, the crosslinkable polyurethane can be blended
with other suitable crosslinkable polymers.
[0053] The crosslinkable polyurethanes are generally made by
condensing polyisocyanates with polyols, which are described above,
and with monomers bearing the crosslinkable groups described above.
Suitable polyisocyanates include aliphatic or cycloaliphatic di-,
tri- or tetra-isocyanates, which may or may not be ethylenically
unsaturated. Some specific examples of aliphatic polyisocyanates
include 1,2-propylene diisocyanate, trimethylene diisocyanate,
tetramethylene diisocyanate, 2,3-butylene diisocyanate,
hexamethylene diisocyanate, octamethylene diisocyanate,
2,2,4-trimethyl hexamethylene diisocyanate, 2,4,4-trimethyl
hexamethylene diisocyanate, dodecamethylene diisocyanate,
omega-dipropyl ether diisocyanate, 1,3-cyclopentane diisocyanate,
1,2-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate,
isophorone diisocyanate, 4-methyl-l,3-di isocyanatocyclohexane,
trans-vinylidene diisocyanate,
dicyclohexylmethane-4,4'-diisocyanate,
3,3'-dimethyl-dicyclohexylmethane 4,4'-diisocyanate and
meta-tetramethylxylylene diisocyanate; polyisocyanates having
isocyanurate structural units, such as the isocyanurate of
hexamethylene diisocyanate and isocyanurate of isophorone
diisocyanate; the adduct of 2 molecules of a diisocyanate, such as
hexamethylene diisocyanate; uretidiones of hexamethylene
diisocyanate; uretidiones of isophorone diisocyanate or isophorone
diisocyanate; the adduct of 3 molecules of hexamethylene
diisocyanate and 1 molecule of water (available under the trademark
Desmodur.RTM. N of Bayer Corporation, Pittsburgh, Pa.). Examples of
suitable aromatic polyisocyanates include toluene diisocyanate and
diphenylmethane diisocyanate.
[0054] Suitable monomers bearing the aforedescribed crosslinkable
groups include vinyl ethers, such as 2-hydroxyethyl vinyl ether and
4-hydroxybutyl vinyl ether, and esters such as 2-hydroxyethyl
acrylate, 2-hydroxyethyl methacrylate, 4-hydroxybutyl acrylate and
4-hydroxybutyl methacrylate.
[0055] Some of the suitable commercial crosslinkable polyurethanes
include those supplied by:
[0056] I. Cray Valley, Saint Celani, Spain under the trademark
Reafree.RTM. ND-1605 Acrylated aromatic polyurethane resin and
Reafree.RTM. ND-1605/2 Acrylated aliphatic polyurethane resin.
[0057] II. DSM Coating Resins, Zwolle, The Netherlands under the
trademark Uracross.RTM. P 3898 Vinylether urethane polyester,
Uracross.RTM. ZW 5150 P epoxy acrylate resin with maleate end
groups and Uracross.RTM. ZW 5151 P epoxy acrylate resin with
maleate end groups.
[0058] III. Solutia Inc, St. Louis, Mo. under the trademark
Viaktin.RTM. 03546 unsaturated urethane acrylic resin.
[0059] IV. Bayer Corp, Pittsburgh, Pa. under the trademark FAC.RTM.
314 Urethane acrylate resin and FAC.RTM. 320 B Urethane acrylate
resin.
[0060] V. Bomar Specialty Company, Winstead, Conn. under the
trademark XJH1-148 A urethane acrylate and STC3-130 A urethane
acrylate resin.
[0061] VI. DuPont Company, Wuppartal, Germany under the trademark
Dekatol.RTM. SK 1866 Urethane acrylate resin and Dekatol.RTM. SK
2092 Urethane acrylate resin.
[0062] VII. Estron, Calvert City, Ky. under the trademark U-810
Epoxy acrylate resin.
[0063] IX. Dow Chemical, Freeport, Tex., under the trademark
XZ92478.00 Epoxy acrylate.
[0064] The crosslinkable acrylated polyethers are generally made by
the reaction of epoxy-functional polyethers with ethylenically
unsaturated carboxylic acids. Some of the suitable epoxy functional
polyethers include polymers of bisphenol A and epichlorohydrin; and
polymers of bisphenol F and epichlorohydrin. Some of the suitable
ethylenically unsaturated carboxylic acids include acrylic acid,
methacrylic acid, maleic acid, itaconic acid and fumaric acid.
[0065] The crosslinkable acrylic polymer suitable for use in the
present invention can have a glass transition temperature ranging
from about 40.degree. C. to about 100.degree. C., preferably from
about 45.degree. C. to about 65.degree. C.; a GPC weight average
molecular weight, using polystyrene as the standard, ranging from
about 1000 to about 30,000, preferably from about 2000 to about
20,000. The crosslinkable acrylic polymer can have a concentration
of crosslinkable groups ranging from about 0.3 percent to about 10
percent, preferably 0.5 percent to about 3 percent of the weight of
the crosslinkable acrylic polymer. Some of the suitable
crosslinkable groups include acrylate, methacrylate, maleate,
fumarate, itaconate and a combination thereof.
[0066] The crosslinkable acrylic polymer can be prepared by the
reaction at elevated temperatures ranging from 50.degree. C. to
220.degree. C. of epoxy-functional acrylic polymer with
(meth)acrylic acid, fumaric acid, itaconic acid and maleic acid;
hydroxy-functional acrylic polymers with (meth)acrylic acid,
fumaric acid, itaconic acid and maleic acid and anhydrides thereof;
or anhydride-functional polymer with hydroxy-functional
ethylenically unsaturated monomers.
[0067] Suitable epoxy functional acrylic polymers can be
conventional polymers having a GPC weight average molecular weight
ranging from 1,000 to 30,000. Commercial epoxy-functional acrylic
polymers, among others, are supplied by Anderson Acrylic Company,
Adrian, Mich. under the trademark of Almatex.RTM. PD 7610 and
Almatex.RTM. PD 7690.
[0068] Suitable hydroxy functional acrylic polymers are
conventional polymers having a GPC weight average molecular weight
ranging from 1,000 to 30,000. Commercial hydroxy-functional acrylic
polymers, among others, are supplied by S. C. Johnson Company,
Racine, Wis., under the trademark of Joncryl.RTM. 802 and
Joncryl.RTM. 804.
[0069] The free radical initiators suitable for use in the present
invention include one or more free radical photoinitiators, one or
more free radical thermal initiators or a combination thereof. The
free radical photoinitiators are initiated photolytically, and the
free radical thermal initiators are initiated upon exposure to
elevated temperatures. A combination of UV photoinitiation and
thermal initiation (dual cure) can be also employed. When used as a
combination, the proportion by weight of the thermal initiator to
photoinitiator ranges from 10:90::90:10, preferably
25:75::75:25.
[0070] Some of the suitable free radical photoinitiators include
bis-acyl phosphine oxides, such as 2,4,6-trimethylbenzoyl
diphenylphosphine oxide; .alpha.-hydroxy ketones. Some of the other
suitable free radical photoinitiators initiators include:
[0071] I. .alpha.-cleavage free radical photoinitiators, include
benzoin and its derivatives, for example, benzoin ethers, such as
isobutyl benzoin ether and benzyl ketals, such as benzyl dimethyl
ketal, 2-hydroxy-2-methyl-1-phenylpropan-1-one and
4-(2-hydroxyethoxy)phenyl-2-h- ydroxy-2-propyl ketone.
[0072] II. Aryl ketones, such as 1-hydroxycyclohexyl phenyl ketone,
2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one,
2,2-dimethoxy-2-phenylaceto-phenone, mixture of benzophenone and
1-hydroxycyclohexyl phenyl ketone, perfluorinated diphenyl
titanocene, and
2-methyl-1-(4-(methylthiophenyl)-2-(4-morpholinyl))-1
-propanone.
[0073] Hydrogen abstraction free radical type photoinitiators can
be used in combination with the above or alone such as Michler's
ketone (4,4'-bisdimethylamino benzophenone), Michler's ethyl ketone
(4,4'-bisdiethylamino benzophenone ethyl ketone), benzophenone,
thioxanthone, anthroquinone, d,l-camphorquinone, ethyl
d,l-camphorquinone, ketocoumarin, anthracene, or derivatives
thereof.
[0074] Some of the suitable commercial suitable photoinitiators are
supplied by Ciba Specialty Chemicals, Basel, Switzerland under the
trademark Irgacure.RTM. 819 Bis acyl phosphine oxide photoinitiator
and Irgacure.RTM. 2959 a-hydroxy ketone photoinitiator.
[0075] Some of the suitable free radical thermal initiators include
organic peroxides, such as benzoyl peroxide; diacyl peroxides, such
as 2-4-diclorobenzyl peroxide, diisononanoyl peroxide, decanoyl
peroxide, lauroyl peroxide, succinic acid peroxide, acetyl
peroxide, benzoyl peroxide, and diisobutyryl peroxide; acetyl
alkylsulfonyl peroxides, such as acetyl cyclohexylsulfonyl
peroxide; dialkyl peroxydicarbonates, such as di(n-propyl)peroxy
dicarbonate, di(sec-butyl)peroxy dicarbonate,
di(2-ethylhexyl)peroxy dicarbonate, diisopropylperoxy dicarbonate,
and dicyclohexylperoxy dicarbonate; peroxy esters, such as
.alpha.-cumylperoxy neodecanoate, .alpha.-cumylperoxy pivalate,
t-amyl neodecanoate, t-amylperoxy neodecanoate, t-butylperoxy
neodecanoate, t-amylperoxy pivalate, t-butylperoxy pivalate,
2,5-dimethyl-2,5-di(2-ethy- lhexanoylperoxy)hexane,
t-amylperoxy-2-ethyl hexanoate, t-butylperoxy-2-ethyl hexanoate,
and t-butylperoxy isobutyrate; azobis (alkyl nitrile) peroxy
compounds, such as 2,2'-azobis-(2,4-dimethylvalero- nitrile),
azobisisobutyronitrile, and 2,2'-azobis-(2-methylbutyronitrile);
t-butyl-peroxymaleic acid, 1,1'-azobis-(1-cyclohexanecarbonitrile);
peroxy ketals, such as
1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane; peroxy esters,
such as o,o'-t-butyl-o-isopropyl monoperoxy carbonate,
2,5-dimethyl-2,5-di(benzoylperoxy)carbonate,
o,o'-t-butyl-o-(2-ethylhexyl- )-monoperoxy carbonate, t-butylperoxy
acetate, t-butylperoxy benzoate, di-t-butyldiperoxy azelate, and
di-t-butyidiperoxy phthalate; dialkylperoxides, such as dicumyl
peroxide, 2,5-dimethyl-2,5-di(t-butylpe- roxy)hexane, t-butyl cumyl
peroxide, di-t-butyl peroxide, and 2,5-dimethyl,
2,5-di(t-butylperoxy)hexyne-3; hydroperoxides, such as
2,5-dihydroperoxy-2,5-dimethyl hexane, cumene hydroperoxide,
t-butyl hydroperoxide and t-amyl hydroperoxide, ketone peroxides;
such as n-butyl-4,4-bis-(t-butylperoxy)valerate,
1,1-di(t-butylperoxy)-3,3,5-trim- ethyl cyclohexane,
1,1'-di-t-amyl-peroxy cyclohexane, 2,2-di(t-butylperoxy)butane,
ethyl-3,3-di(t-butylperoxy)butyrate, and blend of t-butyl
peroctoate, and 1,1-di(t-butylperoxy)cyclohexane; and diazo
compounds, such as
1,1'-azobis(cyclohexanecarbonitrile)peroxide.
[0076] Additional thermal and photoinitiators are disclosed in U.S.
Pat. No. 5,922,473; U.S. Pat. No. 6,005,017; and U.S. Pat. No.
6,017,640, all of which are incorporated herein by reference.
[0077] In addition to the foregoing, the powder coating
compositions of this invention can contain other additives that are
conventionally used in powder coating compositions. Examples of
such additives include fillers, extenders, flow additives,
catalysts, light stabilizers, hardeners and pigments. Compounds
having anti-microbial activity can also be added. Such compounds
are disclosed in U.S. Pat. No. 6,093,407, which is incorporated
herein by reference.
[0078] The gloss of a coating from the powder coating composition
of the present invention can be further reduced by including about
5 percent to about 60 percent, preferably about 10 percent to about
50 percent and more preferably about 20 percent to about 40 percent
of spheroidal particles, all percentages being in weight percent
based on the total weight of the coating composition and wherein
said spheroidal particles have a median particle diameter ranging
from about 10 micrometers to about 50 micrometers, preferably from
15 micrometers to 50 micrometers. As the mean particle diameter
decreases, the surface per unit weight increases. The increase in
surface area results in a tendency of the filler to dry the
coating, reduce flow, and induce roughness in the coating.
Spheroidal particles having a mean diameter of less than 10
micrometers had less effect in further reducing gloss, whereas at
mean diameters greater than 10 micrometers, particularly of greater
than 15 micrometers, the presence of spheroidal particles resulted
in further gloss reduction.
[0079] The upper limit of the diameter of the spheroidal particles
is dependent on the intended thickness of the final coating in that
the particles must have a diameter less than the coating thickness.
Most powder coatings, especially "decorative" powder coatings, are
designed to be applied at a dry film thickness of about 50 microns.
Thus, in most applications, the spheroidal particles should have a
maximum diameter of less than about 50 microns, preferably 40
microns.
[0080] The spheroidal particles suitable for use in the present
invention include glass microspheres, ceramic microspheres,
spheroidal minerals, polymer microspheres, metal microspheres or a
combination thereof.
[0081] Some of suitable commercially available spheroidal particles
are listed below:
1TABLE 1 Spheroidal Gloss Control Agents Max. Dia. Median Dia.
Gloss Grade (.mu.M) (.mu.M) Reduction Glass Microspheres (Potters
Industries, Inc, Valley Forge, Pennsylvania) Spheriglass .TM. 3000E
90% .ltoreq. 60 .mu.m 35 High.sup.1 Spheriglass .TM. 3000E 45 23
High screened at 45 .mu.m Spheriglass .TM. 10000E 6 3 Low (too
fine) Ceramic Microspheres (3M Corporation, Minneapolis, Minnesota)
G200 Zeeospheres .TM. 12 4 Low (too fine) G400 Zeeospheres .TM. 24
5 Low (too fine) G600 Zeeospheres .TM. 40 6 Low (too fine) W610
Zeeospheres .TM. 40 10 Marginal (too fine) G800 Zeeospheres .TM.
200 18 High.sup.1 G850 Zeeospheres .TM. 200 40 High.sup.1 G850
Zeeospheres .TM. 45 20 High screened at 45 .mu.m Cristobalite
(C.E.D. Process Minerals, Inc., Akron, Ohio) Goresil .TM. C-400 100
9 Low (too fine).sup.1 Goresil .TM. 1045 45 10 Marginal (too fine)
Goresil .TM. 835 35 8 Low (too fine) Goresil .TM. 525 25 5 Low (too
fine) Goresil .TM. 215 15 2 Low (too fine)
[0082] The low gloss powder coating composition can be prepared by
utilizing the following steps of:
[0083] A base polymer selected from the group consisting of a
crosslinkable polyester, crosslinkable polyurethane, crosslinkable
acrylated polyether and a combination thereof; about 5 percent to
about 60 percent of a crosslinkable acrylic polymer and about 0.1
to 10 percent of one or more free radical initiators are mixed in a
conventional mixer to form a blend. All the aforedescribed
percentages are in weight percent based on total weight of the
crosslinkable base and acrylic polymer solids. Then, the blend is
heated, typically in a conventional extruder, into a molten blend.
The melt temperature, depending upon the chemical make-up of the
composition, generally ranges from 80.degree. C. to 150.degree. C.
The molten blend is then melt extruded into a molten extrudate.
Typically, the melt extruding step takes place under sufficient
pressure to produce a molten extrudate, which is then solidified
into a solid extrudate, typically by passing it through chilled
rolls. The solidified extrudate is then fractured by conventional
means, such as by passing though toothed or grooved rollers, into
fragments, which are then conventionally ground into ground
fragments of size ranging from 5 to 200, preferably 10 to 100
micrometers. If desired, uniformity of the particle size can be
improved by straining the ground fragments through screen, such as
a 180-micrometer screen, to remove coarse fragments. If desired,
water or an aqueous medium can be added to ground fragments to form
aqueous slurry.
[0084] If desired, the blend described above can include the
aforedescribed spheroidal particles in the aforestated
percentages.
[0085] A smooth coating having low gloss can be produced in
accordance with the following steps:
[0086] A layer of the aforedescribed low gloss powder coating
composition is applied over a substrate by conventional means, such
as by electrostatic spray, thermal or flame spray, or by submersing
in a fluidized bed containing the powder coating composition. If
desired, the powder coating composition can contain the
aforedescribed spheroidal particles in the aforedescribed
quantities. The coatings can be applied over metallic or
non-metallic substrates. The layer thickness is adjusted to produce
a coating thickness ranging from 10 micrometers to 500 micrometers.
It should be understood that the coating thickness is dependent
upon its intended use. Thus, for example when applied over a
reconstituted wood substrate, it can range from 25 to 300
micrometers (1 to 12 mils), when applied over metal substrate, it
can range from 10 to 500 micrometers (0.5 to 20 mils).
[0087] Following deposition of the layer of the powder coating
composition on the substrate, the substrate is typically heated to
melt the composition and cause it to flow and form a film over the
substrate surface. In certain applications, the substrate or a
portion thereof to be coated may be pre-heated before the
application of the powder, and then, if desired, heated again after
the application of the powder. Gas or electrical furnaces are
commonly used for these various heating steps, but other methods
(e.g., microwave) are also known. Typically, depending upon the
chemical make up of the coating composition, the layer is heated to
a temperature raging from about 80.degree. C. to about 200.degree.
C., preferably about 80.degree. C. to about 150.degree. C., and
more preferably about 80.degree. C. to about 120.degree. C.
Typically, depending upon the chemical make up of the coating
composition, the layer is exposed to the aforedescribed
temperatures for about 0.5 to 10 minutes, preferably about 1 to
about 5 minutes. The higher the temperature, the shorter will be
the time of exposure and vice versa.
[0088] Once the film is formed on the substrate, it is cured into a
low gloss coating, which can be smooth. The film can be cured
through several alternative means. For example, the film can be
cured by exposing it to actinic radiation, by exposing it to
elevated temperatures, by sequentially exposing it to elevated
temperatures followed by exposure to actinic radiation, by
sequentially exposing it to actinic radiation followed by exposure
to elevated temperatures, preferably for about 5 to about 30
minutes; or by simultaneously exposing it to actinic radiation and
elevated temperatures.
[0089] Depending upon the chemical make-up of the coating
composition, typical elevated temperatures range from 90.degree. C.
to 220.degree. C., preferably from 100.degree. C. to 200.degree. C.
and more preferably from 100.degree. C. to 170.degree. C. Thermal
curing can be effected by conventional ovens, which employ heat
conduction, convection, radiation or any combination thereof.
[0090] Depending upon the chemical make-up of the coating
composition, typical actinic radiation includes UV radiation,
electron beam radiation, or a combination thereof at a dose of
about 0.25 to about 5.0, preferably of about 0.5 to about 3 joules
per square centimeters.
EXAMPLES
[0091] The following components are listed in the Examples
described below:
[0092] Polymer 1 (Preparation of Crosslinkable Acrylic Polymer)
[0093] In a three-necked glass reactor equipped with a stirrer,
thermocouple and funnel, 700 weight parts (wt-parts) of
butylacetate were heated to 120.degree. C. Then, a mixture of 1302
wt-parts glycidyl methacrylate, 348 wt-parts styrene and 747
wt-parts of methyl methacrylate were added over 6.5-hour period.
Simultaneously, a solution of 215 wt-parts of tertiary butyl
peroctoate in 250 wt-parts of butylacetate was also added. At the
end of 6.5 hours, additional solution of 34 wt-parts of tertiary
butyl peroctoate in 34 wt-parts of butylacetate was added to the
batch. Then, 50 wt-parts of butylacetate were used for the rinsing
of the monomer and initiator pipes. The batch is kept at
120.degree. C. for additional 4-hour period. Thereafter, 6.4
wt-parts of 4-Methoxyphenole were added to the batch followed by
the addition of 103 wt-parts of acrylic acid and 210 wt-parts of
butylacetate. The batch was kept at 120.degree. C. till the acid
number was below 1 mgKOH/g resin solids. Afterwards vacuum was
applied and the solvent was removed until a solids content of
>99% was reached. The viscous resulting acryloyl functional
acrylic polymer was poured onto a flat container and was broken and
crushed after solidification. The polymer had a Tg of 57-62.degree.
C. (measured via DSC), a melt viscosity at 150.degree. C. of 1800
cP and a content of double bonds of 1.4% (calculated as C.dbd.C
equals 24 D).
[0094] Uvecoat.RTM. 3002 unsaturated polyester resin from UCB
Chemicals, Smyrna, Ga.
[0095] Uvecoat.RTM. 3001 mixture of unsaturated polyester resin and
epoxy acrylate resin from UCB Chemicals, Smyrna, Ga.
[0096] Uvecoat.RTM. 3101 unsaturated polyester resin from UCB
Chemicals, Smyrna, Ga.
[0097] Uralac.RTM. 3125 unsaturated polyester resin from DSM
Coating Resins, Zwolle, The Netherlands.
[0098] Uracross.RTM. 3307 divinyl ether crosslinking agent from DSM
Coating Resins, Zwolle, The Netherlands.
[0099] Uvecoat.RTM. 2100 unsaturated polyester resin from UCB
Chemicals, Smyrna, Ga.
[0100] Uvecoat.RTM. 9010 crystalline unsaturated polyester resin
with methacrylate end groups from UCB Chemicals, Smyrna, Ga.
[0101] Irgacure.RTM. 819 photoinitiator from Ciba Specialty
Chemicals, Basel, Switzerland.
[0102] Irgacure.RTM. 2959 photoinitiator from Ciba Specialty
Chemicals, Basel, Switzerland.
[0103] R-706.RTM. titanium dioxide pigment from E. I. DuPont de
Nemours, Wilmington, Del.
[0104] Spheriglass.RTM. 3000E glass bead filler from P.Q.
Corporation, Valley Forge, Pa. (sieved at 325 mesh to remove
particles larger than 45 micrometers)
[0105] Modaflow.RTM. III flow aid from Solutia, St. Louis, Mo.
[0106] Luperox.RTM. ACP35 benzoyl peroxide thermal free radical
curing agent from Atofina Specialty Chemicals, Philadelphia,
Pa.
[0107] Powder coating compositions listed in Tables 2, 3 and 4 are
prepared by the standard method. Components are combined and
bag-blended, then melt-extruded. The extrudate is solidified
between chilled rolls, then broken up and ground to powder. Powders
are strained through an 80 mesh (180 microns) screen to remove
coarse particles.
[0108] Coatings are prepared by applying the powdered compositions
listed in Tables 2 and 4 to mild steel panels of 0.032" thickness,
melting the coating for 4 minutes at 121.degree. C.-177.degree. C.
(250-350.degree. F.), followed by exposure for 15 seconds to
ultraviolet radiation from two lamps, a Fusion "V" lamp and a
Fusion "H" lamp, for a total dose of approximately 2.5
J/cm.sup.2.
[0109] The coatings in Table 3 are prepared by preheating a 1"
thick sample of medium density fiberboard to a surface temperature
of 65.degree. C. (150.degree. F.), applying powder by electrostatic
spray, melting the coating for 4 minutes at 93.degree.
C.-127.degree. C. (200-260.degree. F.), followed by exposure for 15
seconds to ultraviolet radiation from two lamps, a Fusion "V" lamp
and a Fusion "H" lamp for a total dose of approximately 2.5
J/cm.sup.2.
[0110] After cooling, the coated substrates are evaluated for
gloss, smoothness and chemical resistance. The ASTM test for
60.degree. Gloss is ASTM D523-89. The following process is used to
determine chemical resistance:
MEK Chemical Resistance Test
[0111] (1) With a cotton swab saturated with methyl ethyl ketone
(MEK), a one-inch length of a coated part is rubbed with fifty
double-rubs. A double rub consisted of once up the coated surface
and once back, as if erasing a pencil mark. Use Approximately the
same force is used as that when erasing with a pencil eraser.
[0112] (2) After the double rubs, the MEK is allowed to evaporate
and the coating is rated as follows:
[0113] I. Rub through, i.e., the substrate is exposed.
[0114] II. Heavy rub-off, i.e., a large percentage, greater than
25% of the coating thickness as visually determined, is removed,
but the substrate is not exposed. With a non-white pigmented
coating, a large quantity of pigment is observable on the cotton
swab.
[0115] III. Moderate rub-off, i.e., a moderate percentage, 10-25%
of the coating thickness, is removed. With a non-white, pigmented
coating, a moderate quantity of pigment is observable on the cotton
swab.
[0116] VI. Light rub-off, i.e., a small amount, less than 10% of
the coating, is removed. A small amount of pigment is observable on
the swab. Loss of gloss as noted.
[0117] V. No effect, i.e., a rub off is observed. No loss of gloss
is observed.
[0118] (3) Although the standard rating is 1, 2, 3, 4 or 5,
intermediate values (for example 1.5, 2.5 etc.) can be also used
when ranking coatings
2TABLE 2 Component.sup.1 Ctl 1 Ctl 2 Ctl 3 Ctl 4 5 6 7 8 9 10 11 12
13 14 Coating Formulations (Parts by Weight) Polymer 1 100 -- -- --
50 30 20 10 50 50 30 50 30 50 Uvecoat .RTM. 2100 -- 100 -- -- 50 70
80 90 50 -- -- -- -- -- Uvecoat .RTM. 3002 -- -- 100 -- -- -- -- --
-- 50 70 -- -- -- Uralac .RTM. 3125 -- -- -- 85 -- -- -- -- -- --
-- 35 35 35 Uracross .RTM. 3307 -- -- -- 15 -- -- -- -- -- -- -- 15
15 15 Spheriglass .RTM. 3000E -- -- -- -- -- -- -- -- 40 -- -- --
-- 40 Coating Properties Gloss (60.degree. 86 97 97 96 73 31 46 51
47 64 57 61 41 27 Reflectance) Smoothness.sup.3 6 4 7 4 1 6 3 2 5 6
8 5 3 7 Chemical Resistance.sup.4 3.5 4 3 5 3.5 2.5 2.5 4 4.5 4 2.5
3 4 3 Notes .sup.1Ctl1, Ctl2, Ctl3 and Ctl4 are comparative
examples. 2. All coatings also contained Modaflow .RTM. III, 1.3
parts; Irgacure .RTM. 819, 2.5 parts; Irgacure .RTM. 2959, 0.5
parts; and R-706 .RTM., 40 parts. .sup.3PCI Smoothness: By
comparison to standards from 1 (heavy orange peel) to 10 (smooth).
.sup.4Determined by subjecting the coating to 50 double rubs with a
methyl ethyl ketone-soaked cotton swab, rating from 1 (rub through)
to 5 (no effect). 5. All the foregoing coatings had writable
smoothness.
[0119]
3 TABLE 3 Component.sup.1 Ctl5 15 16 Coating Formulations (Parts by
Weight) 046X021-42 -- 30 30 Uvecoat 3001 34.3 24 24 Uvecoat 3101
51.4 36 36 Uvecoat 9010 14.3 10 10 Spheriglass 3000E 40 (sieved at
45 microns) Coating Properties Gloss (60.degree. 58 36 26
Reflectance) Smoothness.sup.2 8 9 9 Chemical 4 4 4 Resistance.sup.3
Notes .sup.1Ctl5 is a comparative example. .sup.2All coatings also
contained Modaflow .RTM. 6000, 1.3 parts; Irgacure 819, 1.5 parts;
Irgacure 2959, 1.0 parts; and R-706, 30 parts. .sup.3PCI
Smoothness: By comparison to standards from 1 (heavy orange peel)
to 10 (smooth). .sup.4Determined by subjecting the coating to 50
double rubs with a methyl ethyl ketone-soaked cotton swab, rating
from 1 (rub through) to 5 (no effect). .sup.5All the foregoing
coatings had writable smoothness.
[0120]
4TABLE 4 Component.sup.1 Ctl 6 Ctl 7 Ctl 8 Ctl 9 Ctl 10 Ctl 11 Ex.
17 Ex. 18 Ex. 19 Coating Formulations (Parts by Weight) Polymer 1
100 -- 100 -- 100 -- 30 30 30 Uvecoat .RTM. 3002 -- 100 -- 100 --
100 70 70 70 Irgacure .RTM. 819 2.5 2.5 -- -- 2.5 2.5 2.5 -- 2.5
Irgacure .RTM. 2959 0.5 0.5 -- -- 0.5 0.5 0.5 -- 0.5 Luperox .RTM.
ACP35 1.0 1.0 0.5 0.5 -- 1.0 0.5 Coating Properties Gloss
(60.degree. 87 97 82 85 82 86 9 8 8 Reflectance) Smoothness.sup.2 7
7 1 1 2 1 5 6 4 Chemical Resistance.sup.3 1.5 3 1.5 1 1.5 4.5 3 2
4.5 Notes .sup.1All coatings also contained Modaflow .RTM. III, 1.3
parts; and R-706 .RTM., 40 parts. .sup.2PCI Smoothness: By
comparison to standards from 1 (heavy orange peel) to 10 (smooth).
.sup.3Determined by subjecting the coating to 50 double rubs with a
methyl ethyl ketone-soaked cotton swab, rating from 1 (rub through)
to 5 (no effect). 4. All the foregoing coatings had writable
smoothness.
Discussion of Results
Controls (Comparative Examples) 1-4
[0121] These comparative examples, which are outside the scope of
the invention show the high gloss typical of commercial UV resin
systems. Coatings show light to moderate orange peel, and good to
excellent chemical resistance.
Controls (Comparative Example) 5
[0122] This example, outside the scope of the invention, shows the
lowest gloss smooth coating currently available where low gloss
comes from combinations of resins, and where crosslinkable acrylic
polymer is not included.
Examples 5-8
[0123] These examples show the effect of varied amounts of the
crosslinkable acrylic polymer blended with the crosslinkable
polyester (Uvecoat.RTM. 2100). Lowest gloss and optimum smoothness
are seen when the blend includes 30 Wt. % of Polymer 1. Gloss is
desirably reduced from 86 and 97 (Ctl. 1 and Ctl. 2) to 31 (Ex. 6),
while smoothness is desirably maintained or increased from 6 and 4
(Ctl. 1 and Ctl. 2) to 6 (Ex. 6). Minimal reduction in chemical
resistance is observed (from 3.5 and 4 (Ctl. 1 and Ctl. 2)) to 2.5
(Ex. 6).
Examples 10 and 11
[0124] These examples show that that the trend observed in Examples
5-8 is also observed for other acrylic/polyester combinations.
Gloss is desirably reduced from 86 and 97 (Ctl. 1 and Ctl. 3) to 64
and 57 (Ex. 10 and Ex. 11), and while smoothness is desirably
increased from 6 and 7 (Ctl. 1 and Ctl. 3) to 6 and 8 (Ex. 10 and
Ex. 11). Minimal reduction in chemical resistance is observed, from
3.5 and 3 (Ctl. 1 and Ctl. 3) to 2.5 (Ex. 11).
Examples 12 and 13
[0125] These examples show that the trend observed in Examples 5-8
and 10-11 is also observed for combinations of crosslinkable
acrylic polymer with blends of crosslinkable polyester and
crosslinkable polyurethane. Gloss is desirably reduced from 86 and
96 (Ctl. 1 and Ctl. 4) to 41 (Ex. 13). Minimal reduction in
smoothness is observed, from 6 and 4 (Ctl. 1 and Ctl. 4) to 3 (Ex.
13). Minimal reduction in chemical resistance is observed, from 3.5
and 5 (Ctl. 1 and Ctl. 4) to 4 (Ex. 13).
Example Pair 5 and 9, Example Pair 12 and 14, and Example Pair 15
and 16
[0126] These example pairs show that a significant reduction in
gloss and increase in smoothness is observed upon the addition of
spheroidal glass fillers. Addition of 40 parts spheroidal filler
reduced gloss from 73 (Ex. 5) to 47 (Ex. 9) while improving the
smoothness from 1 to 5. Addition of 40 parts spheroidal filler
reduced gloss from 61 (Ex. 12) to 27 (Ex. 14) while improving
smoothness from 5 to 7. Addition of 40 parts spheroidal filler
reduced gloss from 36 (Ex. 15) to 26 (Ex. 16) without affecting
smoothness.
Examples 15 and 16
[0127] These examples show that low gloss coatings can be obtained
at powder melt-out temperatures of 90-120.degree. C. typically used
for heat-sensitive substrates such as medium density fiberboard.
The presence of crosslinkable acrylic polymer when compared to
Control 5 not only reduced gloss, but also improved smoothness.
* * * * *