Note: Descriptions are shown in the official language in which they were submitted.
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LOW GLOSS POWDER COATING
The present invention relates to a powder coating composition and use
thereof on heat-sensitive substrates, such as wood products, which provides a
low gloss finish having a significantly harder surface texture for improved
weather resistance. It is surprising to combine these features into a coating
powder which must cure rapidly at lower than normal temperatures so as to not
adversely affect the structural integrity of the heat sensitive substrate onto
which the coating is applied.
BACKGROUND
In the surface coating industry, powder coatings are becoming
increasingly more popular than traditional liquid based coatings for a number
of
reasons. Foremost of which is that fact that powder coatings are virtually
free of
the potentially harmful volatile organic solvents which act as carriers in
liquid
surface finishes. The positive result is that little if any vapors escape
during the
application and curing processes. The reduction in solvent emissions benefits
the health of the workers employed in the coating operations as well as
minimizing the negative impact on the environment in general. Furthermore, in
the event of handling mishaps, powder is much easier to clean up. Another
advantage is that "oversprayed" material is easily recyclable. This aids in
manufacturing productivity and significantly reduces non-recyclable waste
material.
Notwithstanding the above identified advantages, powder coating
compositions and their application processes come with certain disadvantages.
The application of coatings onto heat sensitive substrates, such as wood, wood-
based and plastic materials is difficult because of the sensitivity that these
materials have to exposure to high heat for short durations of time or lower
temperatures for much longer periods of time. Traditional powder coating
formulations require high cure temperatures, making them unsuitable for use on
heat sensitive substrates. Much focus today is on the formulation of powder
coatings which will readily provide a thermoset cure without damaging the
sensitive substrates. The difficulty is in incorporating into the finish
coating
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various desirable properties while at the same time having to work within the
boundaries necessitated by the sensitivities of formulating, applying (in
order to
provide the required surface flow) and curing a powder coating onto heat
sensitive substrates.
Recently, low temperature curable powder coatings have been developed
using epoxy resins. However, the traditional curing agents used with epoxy
resins are derived from aliphatic or aromatic amines which tend to yellow with
the addition of heat. Further, epoxy coatings alone generally do not provide
adequate surface durability and weatherability.
Another resin which has been employed with powder coatings is based
upon unsaturated polyesters. These materials provide good weatherability and
are extremely reactive at low temperatures, making them suitable for use on
heat sensitive substrates. However, the free-radical polymerization system
used
to cure unsaturated polyesters is easily inhibited along the surface of the
coating
which is in contact with air. Oxygen in the atmosphere interferes with the
free-
radical process of cross-linking the unsaturated polyester chains leaving the
surface of the coating uncured. The surface, therefore, exhibits poor solvent
resistance, stain resistance and poor surface hardness.
Attempts to combine these two chemistries has met with limited success.
U. S. Patent no. 5,639,821 teaches the combination of a synthetic epoxy resin,
a
carboxy functional compound and a second unsaturated resin (such as a
polyester) in order to obtain a coating which exhibits high flexibility and
high
hardness. The surface finish also possesses a very high gloss. The epoxy used
in
this patent consists of the molecular weight in the range of 1000 to 15,000.
The
functionality of the epoxy used in this patent is in the range of 1.5-5.0
milliequivalents of epoxy per gram of polymer. These elements contribute to
the
high gloss coating desired for their applications. Because of the dual resin
system, the patentees teach that either thermal initiators or LTV radiation
may
be optionally used to obtain a proper cure.
The problem addressed by the present invention, which has heretofore
been unresolved by the known art, is the creation of a low gloss powder
coating
for use with heat sensitive substrates which exhibits very high surface
hardness.
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It has been recently discovered that the combination of a specific type of
epoxy
resin along with a specific type of polyester resin along with a unique
catalyzing
system leads to a powder coating exhibit the desired combination of properties
identified above.
STATEMENT OF THE INVENTION
In accordance with the present invention, a melt extrudable low
temperature curable powder coating composition suited for application onto
heat
sensitive substrates is provided which comprises a film-forming particulate
blend
of (a) an unsaturated polyester resin containing, on a weight percent basis,
from
2 to 10 wt. % ethylenically unsaturated double bonds per molecule (b) a
glycidyl
functional acrylic resin having a molecular weight of from 5,000 to 100,000,
(c) a
crystalline or semi-crystalline polycarboxylic acid or polyanhydride, and,
optionally, (d) a free-radical initiator and (d) a catalyst selected from the
group
consisting of a photoinitiator and a redox catalyst. Also provided in
accordance
with the invention are a coating comprising the inventive composition and
articles coated therewith. It has been advantageously discovered that this
composition provides an effective coating exhibiting the combined properties
of
low gloss and a hard, weather-resistant finish.
DETAILED DESCRIPTION
Throughout this specification, the measurement of the quantities used in
the various formulations will be stated in parts per hundred of the resin
component (phr). The amount of resin will consist of the total amount of both
resins in the formulation, that is, (a) plus (b).
The unsaturated polyester resin (a) of the present invention contains from
2 to 10 wt. % ethylenically unsaturated double bonds per molecule and at least
one active hydrogen site per molecule. The term "active hydrogen" used herein
means a hydrogen atom that is readily abstracted by free radicals in the
curing
reaction. Unsaturated polyester resins may be prepared via conventional means
such as by the condensation of one or more ethylenically unsaturated
polyfunctional carboxylic acids (or their anhydrides) having carboxyl
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functionalities of 2 or more with one or more active hydrogen containing
polyols
having hydroxyl functionalities of 2 or more. Although the active hydrogen in
the unsaturated polyester resin (a) is typically supplied by the polyol, it
may also
come from active hydrogen containing acids employed in conjunction with the
unsaturated acid.
Further, while the ethylenic unsaturation is typically supplied by the
acid, it may also be provided by the polyol. The ethylenic unsaturation may be
provided in the polymer backbone or at the end of the chain. The unsaturated
polyesters may be carboxyl- or hydroxyl-terminated depending upon the
monomer mixture ratio.
Examples of ethylenically unsaturated polyfunctional carboxylic acids (or
their anhydrides) include malefic acid, fumaric acid, itaconic acid,
tetrahydrophthalic acid, nadic acid and dimeric methacrylic acid. Malefic
anhydride, fumaric acid, and mixtures thereof, are preferred because of
economic
considerations.
Examples of monofunctional acids for chain end unsaturation include
acrylic acid and methacrylic acid.
The polyols with active hydrogens include polyols that contain at least one
active methylene group or active methine group per molecule. If the active
hydrogens are supplied by active methylene groups, the polyols may contain an
active hydrogen atom attached to an allylic carbon or benzylic carbon. If the
active hydrogens are supplied by active methine groups, the polyols may
contain
an active hydrogen atom attached to a cyclohexyl or tertiary alkyl carbon.
Allylic, benzylic, cyclohexyl and tertiary alkyl hydrogen atoms are readily
abstracted during free radical-induced curing to from the corresponding stable
allylic, benzylic, cyclohexly or tertiary alkyl free radicals, all of which
promote
curing at the surface of the coating film.
Exemplary polyols having an allylic hydrogen include trimethylol propane
monoallyl ether, trimethylol propane diallyl ether, vinyl cylohexanediol, etc.
Examples of polyols having a benzylic hydrogen include benzene dimethanol.
Polyols having a cyclohexyl hydrogen include cyclohexane dimethanol,
cyclohexane diol, etc.
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In addition, it is possible to supply the active hydrogen through the
carboxylic acid. Examples of polyfunctional carboxylic acids with active
hydrogens (i.e. active methylene groups) include carboxylic acids that include
a
malonyl hydrogen, such as malonic acid, or an allylic hydrogen, such as nadic
anhydride, tetrahydrophthalic anhydride or dimer acid.
Often, polyols without active hydrogens are employed in the condensation
reaction in conjunction with the active hydrogen containing polyols to provide
various desired chemical and mechanical properties. Examples of such polyols
without active hydrogens include ethylene glycol, diethylene glycol,
triethylene
glycol, propylene glycol, neopentyl glycol, butanediol, dodecanediol,
hydrogenated bisphenol A, bisphenol A/propylene oxide adducts, gylcerol,
trimethylolpropane and trimethylolethane.
In accordance with this invention, it is preferred that between 10 and 100
mole percent, and more preferably between 50 and 100 mole percent of the
hydroxyl functionality relative to the total hydroxyl functionality of
monomers
used to form the unsaturated polyester resin (a) is provided by active
hydrogen
containing polyol monomers.
The unsaturated polyester resins of the invention are solid materials at
room temperature, so that they can easily be formulated into non-blocking
powders. Their Tg, or glass transition temperature, is in the range of
30° to
70°C, preferably 40° to 60°C and most preferably
45° to 55°C.
The preferred unsaturated polyester resins contain, on a weight percent
basis, from 2 to 10 wt. %, preferably from 2 to 6 wt. %, ethylenically
unsaturated
bonds per molecule. The unsaturated polyester resins are used in the
compositions of the invention in an amount of from 40 to 80 phr, preferably
from
50 to 70 phr and more preferably from 55 to 65 phr.
The acrylic resin employed herein contains glycidyl functional groups.
Exemplary is glycidyl methacrylate (GMA) resin. It is in the form of a
(co)polymer which is produced by (co)polymerizing between 20 and 100 wt.
glycidyl acrylate or glycidyl methacrylate and between 0 and 80 wt. % other a,
(3-
ethylenically unsaturated monomers, such as methyl methacrylate, butyl
methacrylate and styrene. These resins have a weight average molecular weight
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of from 5,000 to 200,000, preferably from 5,000 to 100,000 and more preferably
from 5,000 to 50,000. The weight average molecular weight is determined by gel
permeation chromatography. The viscosity of the GMA resin is in the range of
to 500 poise, and preferably between 30 and 300 poise at 150°C, as
5 determined by ICI Cone and Plate Viscometer.
GMA resin is prepared under traditional reaction conditions well known
in the art. For example, the monomers can be added to an organic solvent such
as xylene with the reaction conducted under reflux conditions in the presence
of
an initiator such as azobisisobutyronitrile or benzoyl peroxide. Such resins
are
10 commercially available under the trademark Isocryl EP-550 from Estron
Chemical, Inc. of Calvert City, Kentucky. The amount of GMA resin present in
the composition of the invention is in the range of 5 to 40 phr, preferably,
10 to
30 phr and most preferably, 10 to 20 phr.
The crystalline or semi-crystalline polycarboxylic acid or polyanhydride
has an acid number of from 50 to 400, preferably from 60 to 150. Exemplary
compounds in this group are sebacic acid, dodencanedicarboxylic acid, adipic
acid
and acid-functional polyesters. In the practice of this invention, such
compound
is added in an amount of from 5 to 40 phr, preferably from 10 to 30 phr and,
most preferably, from 15 to 25 phr.
Free radical initiators (d) are used to generate the free radicals at the
active hydrogen sites in order to initiate curing (via homopolymerization) of
the
unsaturated polyester resins. Examples of free radical initiators useful in
the
practice of this invention include peroxide and azo compounds. Examples of
peroxide initiators include diacyl peroxides, such as benzoyl peroxide, peroxy
esters, peroxy ketals, such as 1,1-bis(t-butylperoxy)-3,3,5-
trimethylcyclohexane,
peroxy esters, dialkylperoxides and ketone peroxides. Examples of azo
compounds include azobis (alkyl nitrite) peroxy compounds. The free radical
initiators of the inventive powder coating composition are present in amounts
ranging from 0.1 to 10 phr, preferably 0.5 to 5 phr and most preferably, from
0.5
to 2 phr.
The photoinitiator catalysts which may be used in the present invention
are employed to impart a rapid, radiation activated low temperature cure to
the
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powder coating formulation. Examples of such initiators include benzoin and
its
derivatives, such as benzoin ethers, and benzoin ketals, for example, benzyl
dimethyl ketal. Aryl ketones can also be used, such as 1-hydroxycyclohexyl
phenyl ketone and perffuorinated diphenyl titanocene. Hydrogen abstraction
free radical type photoinitiators can be used in combination with the above or
alone. Examples include 4,4'-bisdimethylamino benzophenone, thioxanthone
and benzophenone.
The amount of photoinitiators which may be used herein range from 0.1
and 10 phr, preferably 0.5 to 6 phr and most preferably 1 to 5 phr.
Redox catalysts may also be employed in place of the photoinitiators.
These compounds induce the generation of free radicals from the intitiators
through an oxidation-reduction reaction. As redox catalysts, transition metal
compounds based on fatty acids or oils may be employed. Some examples include
cobalt, manganese, lead, copper, vanadium and iron+2. Cobalt containing
compounds, such as cobalt salts of monocarboxylic (i.e. fatty) acids, for
example,
cobalt octoate, cobalt neodencanoate, cobalt naphthenate, polymer bound cobalt
and cobalt octadecanoate are most preferred. During curing, at the surface of
the coating, even the free radicals formed at the active hydrogen sites tend
to
react with atmospheric oxygen to form hydroperoxides (i.e. inactivated
peroxide
initiators) which halt the curing reaction. However, these hydroperoxides so
formed, due to their location, are now readily decomposed in the presence of
the
cobalt salts to re-initiate the free radical cure, thus allowing the cure to
proceed
to completion at the surface. This provides for the hard surface cure which
was
heretofore unavailable with low-gloss producing powder coatings. The redox
catalysts are used in the powder coating formulation of this invention in
amounts of from 0.1 to 2.0 phr, preferably from 0.1 to 1.0 phr and most
preferably from 0.1 to 0.5 phr.
The powder coating composition of the invention may include additives
customarily added to provide or enhance various functional or aesthetic
properties. For instance, the coating formulation may be clear, possessing no
pigment, or colored, containing in such case, up to 200 phr, or more
customarily
about 120 phr or less, of fillers or pigments. Examples of fillers include
calcium
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carbonate, barium sulfate, wollastonite, mica, china clay and diatomaceous
earth. Exemplary pigments include titanium dioxide and organic materials, such
as carbon black.
Other common additives may be included, such as, flow control agents, dry
flow additives, anticratering agents, texturing agents, light stabilizers,
each of
which may be present, as desired, in amounts up to 15 phr. Examples of flow
control agents include acrylic resins and silicone resins. Examples of dry
flow
additives include fumed silica and alumina oxide. Examples of anticratering
agents include benzoin, benzoin derivatives and phthalate plasticizers.
Examples of texturing agents include organophilic clay and cross-linked rubber
particles. Examples of light stabilizers include hindered amines and hindered
phenols.
The powder coating of the present invention is produced by first dry
blending all the components together and then melt blending them in a single
or
twin screw extruder at a temperature range above the melting point of the
resin
system. However, if the formulation includes a redox catalyst, this component
is
added to the post extrudate formulation. The extruded formulation is then
cooled and broken into chips, ground in a mill with the particulates passed
through a screen to produce powder particles of any desired size. The average
particle size desired for electrostatic application is between 20 and 60
microns.
Once the dry, free flowing powders are produced, they are ready for
application
onto the substrate to be coated.
The heat sensitive substrates for which the inventive powder coating was
developed include wood products, in general. More specifically, these products
include hardwood, hard board, laminates, composites, such as particle boards,
low, medium or high density fiber-boards, masonite board and other materials
which contain a significant amount of wood. Other heat sensitive substrates
include plastics, polyolefins, polycarbonates, acrylics and nylons. The powder
coatings of this invention may also be applied to various heat resistant
substrates, such as metal, steel, aluminum, glass, and ceramics. The most
preferred substrate, or article, for covering with the powder coating
composition
of the invention is medium density fiberboard (MDF), as this is the substrate
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most commonly used in the production of kitchen cabinet doors and panels, as
well as various ready to assemble furniture.
The powder coatings of the invention are applied in the customary
manner, that is, electrostatically, onto the target substrate. Electrostatic
spray
booths are employed which contain a number of corona discharge or
triboelectric
spray guns along with recirculation means for collecting oversprayed paint.
Once the powder is applied to the surface of the target substrate it is
exposed to
a sufficient amount of heat to cause the powder to melt and flow out into a
continuous film over the surface of the sprayed article. The powders of this
invention are formulated to cure at low enough temperatures or for short
enough
times so as to not damage the heat sensitive coated articles. When
photoinitiators are used to catalyze part of the resin formulation, an
ultraviolet(U~ energy source is also employed in addition to a thermal source
of
energy. The UV energy source is preferably a UV lamp. An example of such an
energy source is a fusion H lamp, having a 600 watt light source at a belt
speed
of 10 to 20 feet per minute.
The thermal cure temperatures of the powder coating composition of the
invention are less than 300° F, and preferably at or below 250°
F. Since curing
the resins of the powder coating composition is a function of time versus
temperature, longer oven residence times will be needed at lower temperatures
and less residence time will be needed at higher temperatures. Preferably,
full
cure can be effected at a surface temperature of no more than 300° F
for a period
of time no more than 5 minutes.
The invention will now be described in greater detail by way of specific
examples.
EXAMPLES
Synthesis of unsaturated polyester resin containing active hydrogen:
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FORMULATION
A B
cyclohexane dimethanol (CHDM) 1.7 moles 1.6 moles
hydrogenated bisphenol-A (HBPA) 0.3 moles 0.4 moles
phthalic anhydride (PA) 1.2 moles 1.4 moles
fumaric acid (FA) 1.0 moles 0.8 moles
4-methoxy phenol (MEHQ) 50 ppm 50 ppm
SYNTHESIS:
Charge CHDM and HBPA in a resin kettle fitted with a partial condenser,
total condenser, stirrer, nitrogen inlet and temperature controller. Start
heating
the glycols in the kettle while stirring and maintaining nitrogen flow of
about
25-30 ml per minute. When the glycols have melted at about 110-120°C,
add the
remaining ingredients into the kettle (PA, FA and MEHfI) and continue heating.
When the temperature has reached about 155°C, water of esterification
starts
condensing and gets collected in the receiver. The temperature of the
reactants
in the kettle will rise slowly to the set temperature of 180°C, as
esterification
continues. When 85-90% of the theoretical distillate has been collected,
vacuum
is applied to remove the remainder of the water. The resin is then discharged
into a pan, cooled, and ground into flakes to be used in the formulations.
The polyester resins produced exhibited the following characteristics:
A B
Acid number 45 mg KOH/gm 44 mg KOH/gm
ICI Viscosity @ 175°C 40P 47.5P
Glass Transition Temp. (Tg°C) 47°C 51°C
Example 1:
The polyester resin thus produced was then formulated into a powder
coating composition. All of the ingredients shown below were weighed out in a
polyethylene bag, blended together, and extruded through a single screw
extruder, with chilled water circulating through the screw and barrel. The
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extruded chips were then broken into smaller pieces, ground in a Brinkman
grinder and then screened through a Vertisiv C-7 200 mesh to produce very fine
powder particles.
AMOUNTS (phr)
INGREDIENTS SAMPLE 1-1 SAMPLE 1-2
Polyester A 60.0 60.0
EP 550 20.0 35.0
MORFLEX 1000 10.0 10.0
Daiso ISO DAP 10.0 10.0
Spheriglass 3000E 50.0 50.0
Irgacure 2959 2.4 2.4
Irgacure 651 0.6 0.6
Vanox 231XL 1.0 1.0
Modaffow 2000 1.0 1.0
Pigments 0.535 0.535
Lanco 1900 1.5 1.5
Legend:
EP 550: glycidyl functional acrylic resin available from Estron Chemical Co.
MORFLEX 1000: semi-crystalline polyester resin, Rohm and Haas Co.
Daiso ISO DAP: diallylisophthalate pre-polymer, Osaka Soda Co. Ltd.
Spheriglass 3000E: borosilicate solid glass spheres, Potters Industries
Irgacure 2959: an alpha-hydroxy ketone photoinitiator, Ciba
Irgacure 651: a dimethyl ketal photoinitiator, Ciba
Vanox 231XL: organic peroxide catalyst, Elf Atochem
Modaflow 2000: acrylic flow modifier, Solutia, Inc.
Pigments
Lanco 1900: micronized polymeric surface modifier, Lubrizol Corp.
COATING EVALUATION
The functional performance of powder coating formulations 1-1 and 1-2
were evaluated on 1 inch thick 6" x 6" MDF panels after being applied and
cured
under the following conditions:
Spray: Nordson Corona Discharge Gun, 100KV
Application: Preheat panels at 375°F for 10 minutes. Allow surface
temperature
to rise to 225°F. Spray powder coating and wait until surface
temperature reaches 180°F.
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Cure: 375°F for 5 minutes followed by exposure to fusion H
lamp, 600 watt at 20 ft/min. speed
PROPERTIES:
1-1 1-2
Hot plate melt flow @300°F, in mm 65 68
Gel time @300°F, in sec 95 85
60° Gloss, in units 22 9
MEK Rub Resistance, 50 double rubs 5 5
(5= no rub off)
Appearance Moderate Moderate
Orange Peel Orange Peel
EXAMPLE 2:
AMOUNTS (phr)
INGREDIENTS SAMPLE 2-1 SAMPLE 2-2
Polyester B 60.0 60.0
EP-550 20.0 25
GMA 300 ----- 2.5
MORFLEX 1000 10.0 10.0
Modaffow 2000 1.0 1.0
ISO-Dap 10.0 10.0
Luperco 231XL 1.0 1.0
Irgacure 651 0.64 0.64
Irgacure 2959 2.36 2.36
Pigments 0.535 0.535
The above ingredients were then processed as in Example 1 to produce a powder
coating formulation. And, as with Example l, they were similarly coated onto
MDF sample panels and evaluated. The results follow:
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Coating Properties: 2-1 2-2
Hot plate melt flow G'~300°F, in mm 65 58
Gel time X300°F, in seconds 81 99
ONLY Thermal cure:
<60°Gloss, in units 27 19
MEK Rub Resistance, 50 double rubs 3 3
Thermal AND UV Fusion H bulb-15 Ft/min:
<60°Gloss, in units 36 23
MEK Rub Resistance, 50 double rubs 5 5
Appearance Moderate Moderate
orange peel orange peel
Standards:
MEK Rub Resistance: 3=moderate rub off 5=no rub off
The above results demonstrate that the dual cure system produced a
coating with low gloss and high surface hardness.
EXAMPLE 3:
This example was prepared to show the benefit exhibited using an
unsaturated polyester resin containing an active hydrogen compound versus a
more conventional polyester resin utilized in the powder coating art.
AMOUNTS (phr)
INGREDIENTS SAMPLE 3-1 Comparative
Polyester A 60 --
Comparative PE resin -- 60
EP 550 20.0 20.0
Daiso-ISO DAP 10.0 10.0
Irgacure 651 0.64 0.64
Irgacure 2959 2.36 2.36
Vanox 231XL 1.0 1.0
Lanco 1900 Wax 1.5 1.5
Spheriglass 3000E 50.0 50.0
MORFLEX 1000 10.0 10.0
Pigments 0.54 0.54
Modaflow 2000 1.0 1.0
Legend:
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Comparative PE resin: formulated similar to Example A polyester except that
neopentyl glycol was substituted for the CHDM
EP 550: glycidyl functional acrylic resin, Estron Chemicals
Diaso-ISO DAP: diallylisophthalate prepolymer, Osaka Soda Co.
Irgacure 651: dimethyl ketal photoinitiator, Ciba
Irgacure 2959: alpha hydroxy ketone photoinitiator, Ciba
Vanox 231XL: organic peroxide catalyst, Elf Atochem
Lanco 1900: micronized polymeric surface modifier, Lubrizol
Spheriglass 3000E: borosilicate solid glass spheres, Potters Ind.
MORFLEX 1000: semi-crystalline polyester, Rohm and Haas Corp.
Pigments
Modaflow 2000: acrylic flow modifier, Solutia, Inc.
These resins were then formulated into powder coating compositions
under the same process parameters as described for Examples 1 and 2.
COATING PROPERTIES: 3-1 Comparative
Gel time @300°F, in seconds 78 148
Hot plate melt flow @300°F, in mm 55 40
MEK Rub Resistance, 50 double rubs 5 3-4
60° gloss, in units 14-18 19-20
Appearance Slight Orange Severe
Peel Outgassing
From the foregoing examples, it is readily apparent that the combination
of the specific resins employed with the combined thermal/photoinitiator
catalyst
cure system provides a novel powder coating for use on heat sensitive
substrates.
EXAMPLE 4:
This example was prepared to show that a fairly good cure can be obtained
by using the specific polyester/epoxy/catalyst system of the invention with
the
addition of a redox catalyst. The desired low gloss surface finish was
obtained,
but there was a reduction in the durability of the final coating. For certain
applications, such as non-horizontal surfaces like cabinet doors or vertical
panels, surface wear resistance is not as important. What is surprising about
this formulation is that a low gloss surface finish is obtained due to the
unique
interaction of the glycidyl containing resin and the semi-crystalline
polyester.
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Amounts in phr (unless .
otherwise noted)
INGREDIENTS 4-1 4-2
Polyester A 60 60
EP550 30 30
MORFLEX 1000 20 20
Daiso ISO-DAP 10 10
Resiflow P67 1 1
Vanox 231XL 1 1
Pigment 20 20
Dryblended additives:
Cobalt Salt -- 1.5%
Process additive .2% .2%
,
Legend:
EP 550: glycidyl functional acrylic resin from Estron Chemical.
MORFLEX 1000: semi-crystalline polyester, Rohm and Haas
Daiso ISO-DAP: diallylisophthalate prepolymer, Osaka Soda Co.
Resiffow P67: commercially available flow modifier
Vanox 231XL: organic peroxide catalyst, Elf Atochem
Pigment: Titanium dioxide
Cobalt Salt: commercially available as Intelomer 6054
Process additive: Aluminum oxide
The resulting formulation was processed and then applied to MDF test
panels as described above. The results are as follows:
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Coating Properties' 4-1 4-2
Hot Plate Melt Flow @ 300°F 85mm 85mm
Gel time @ 300°F 90 sec 83 sec
Gloss 15 31
MEK Resistance 4 5
Appearance Very Smooth Very Smooth
