Note: Descriptions are shown in the official language in which they were submitted.
82
60SI-3gl
ABRASION RESISTANT ULTRi~VIOLET LIGHT
CUR:i~B:I,E HAR~ COATING CO~?OSITIONS
Field of the Invention
This invention reIates to photocurable hard
coating compositions,;and articles coated with such
compositions. These coatings are comprised of the
; photoreaction products of certain multifunctional
acrylate ester monomers or mixtures thereof which are
~' catalyzed with a blend of photoinitiators comprised of
photosensitive ketones and certain hindered amines,
which are effective for crosslinking the acrylate ester
monomers upon exposure'to ultraviolet~radiation. The
process of the present invention specifically does not
' require an inert atmosphere such as nitrogen and may in
' 15 fact be carried out in air.
More particularly, this invention relates to an
~' article having a photocured coating thereon which is mar,
``~ abrasion, and solvent resistant, has good adhesion to the
substrate, and is compatible with'the substrate i.e., does
not adversely affect thè substrate by stress cracking and
crazing it, by causing crack propagation into the substrate
as a result of brittleness of the coating itse~If,~ and/or
- by adversely affecting the' properties of the substrate
generally such as, for example, lmpact resistance,
elongation, and tensile'strength.
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60SI-391
Background of the Invention
Recently, the substitution of glass glazing with
transparent materials which'do not shatter or are more
resistant to shattering than glass, has become widespread.
For example, transparent glazing made from synthetic organic
polymers is now utilized in public transportation vehicles,
such as trains, buses, taxis and airplanes. ~enses, such
as for eye glasses and other optical instruments, as well
as glazing for large buildings, also employ shatter-
resistant transparent plastics. The lighter weight ofthese plastics in comparison to glass is a further
advantage,' especially in the transportation industry where
the weight of the vehicle is a major factor in its fuel
economy.
While txansparent plastics provide the major
~' advantage Qf being more resistant to shattering and lighter
' than glass, a serious drawback lies in the ease with which
'~ these plastics mar and scratch, due to everyday'contact
~'~ with abrasives, such as dust, cleaning equipment and
~` 20 ordinary weathering. Continuous scratching and marring
results in impaired~visibility and poor aesthetics, and
often requires replacement of the glazing or lens or the
like.
~' One of the most promising and widely used
transparent plastics for glazing is polycarbonate, such
as that known as Lexan , sold by Gene~al Electric Company.'
It is a tough~ material, having high impact strength,
high heat deflection temperature,~ good dimensional
stability, as well as being se~lf-extinguishing, and is
easily fabricated. Acrylics, such as polymethylmethacrylate,
are also widel'y used transparent plastics for glazing.
Attempts have been made'to improve~the abrasion-
resistance`of transparent pla~stics.~ For example, scratch-
resistant coatings formea from mixtures of silica, ~such`as
colloidal silica or silica gel, and hydrolyzable silanes
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60SI-391
--3--
in a hydrolysi5 medium, such as alcohol and water, are
known. U.S. Patents 3,708,225, Robert D. Misch et al,
issued January 2, 1973, 3,986,997, Clark, issued October
19, 1976 and 3,976,497, Clark, issued August 24, 1976.
In Canadian Application Serial No. 339,539 ,
November 9, 1979, coating compositions havin~ improved
resistance to moisture`and humidity and ultraviolet light
are disclosed. It was discovered therein that, in direct
contrast to the teachings of U.S. Patent 3,986,997
compositions having a basic pH, i.e., 7.1-7.8, do not
immediately gel but in fact provide excellent abrasion-
resistant coatings on solid substrates.
The present~ invention offers a significant
~; advantaye over many of the heretofore known coating
compositions in that it does not require heat in order to
initiate the cure reaction. The radiation cure system of
~` the present invention expends considerably less thermal
energy than conventional heat cure systems.
In copending Canadian Application Serial No.
376,679, May 1, 1981, the present applicant has disclosed
a radiation curable hardcoating composition which requires
the use of the acid hydrolysis product of an alkoxy
functional silane. In another copending application,
Serial No. 380,250, June 19, lg81, the present applicant
has provided a different radiation curable hardcoating
composition which requires the combination of colloidal
silica, acryloxy or glycidoxy functional silanes and non-
silyl acrylates. Applicant's present invention, however,
provides highIy abrasion resistant coatings which require
neither alkoxy functional silanes of Serial No. 376,679
nor the acryloxy or glycidoxy functional silanes of Serial
No. 380,250.
In fact, the coating compositions of the present
invention are specific improvements over the coatings and
articles disclosed in U.S. Patent No. 4,13&,465, Moore et
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- 4 - 60SI 391
al, April 15, 1~80. The Moore et al disclosure teaches
that certain very useful coatings and coated articles can
be provided through the photoreaction of certain poly-
functional acrylate monomers and resorcinol monobenzoate.
The Moore et al coatings use any of several well known
;; W radiation photosensitizers including ketones such as
benzophenone. The Moore et al disclosure, however,
failed to recognize that the improved coatings of the
present invention could be provided by combining the
ketone-type photoinitiator with a hindered amine-type
compound whereupon the photosensitized acrylate coating
composition could be cured without the necessity of using
resorcinol monobenzoate and without the necessity of an
inert atmosphere (both of which are required by the
Moore et al disclosure~, in order to provide suitable and
` sometimes improved hard coatings. The savings provided
by the use of a non-inert atmosphere such as air can be
substantial, and these savings can be provided by the
-~ present invention without derogating from the quality of
the hard coating composition or coated product.
Since ultraviolet light is one of the most widely
; used types of radiation because of its relatively low
cost, ease of maintenance, and low potential harzard to
industrial users, rapid photo-induced polymerizations
utilizing UV light rather than thermal energy for the
curing of hard coatings offer several other significant
advantages. First, faster curing coatings offer
substantial economic benefits. Furthermore, heat
sensitive materials can be safely coated and cured with
UV light without the use of thermal energy which could
damage the substrate. Additionally, the essentially
solvent free media reduce the necessity for expensive
; and time consuming pollution abatement procedures.
Thus, the advantages provided by the
35 materials of the present invention are particularly ~ c~~
for a number of purposes. For e~ample,
., ".. ...
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~2Z4~2
60SI-391
polycarbonates are commercially important materials
possessing exceIlent physical and chemical properties
which are useful in a wide range of applications from
non-opaque impact resistant sheets to shaped articles.
Generally, however, polycarbonates have rathex low scratch
resistance and are somewhat susceptible to attac~ by many
common solvents and chemicals.
; Previous efforts to overcome this low scratch
resistance and susceptibility to attack by solvents have
included lamination procedures and applications onto the
polycarbonate of a surface coating. Many of these prior
; art remedial efforts have been unsuccessful due to the
incompatibility of the laminae and coating materials with
the polycarbonate substrate. This incompatibility has
resulted in stress cracking and crazing of the polycarbonate,
crack propagation into the polycarbonate as a result of
the brittleness of the coating, and a reduction of the
advantageous properties of the polycarbonate such as,
for example, impact resistance, tensile strength, non-
opacity and elongation.
The prior art coatings for polycarbonates have
included organopolysiloxanes, U.S. Patent No. 3,707,397,
Gagnon, issued ~ecember 26, 1972; polyester-melamines
or acrylic-melamines, U.S. Patent No. 3,343,390, Hudson
et al, issued October 22, 1974; and allyl resins, U.S.
Patent No. 2,332,461. These types of prior art coatings
are generally applied from solutions of inert solvents
and are cured to ~inal properties by baking at elevated
- temperatures. The disadvantages of such systems are
obvious. The heat curing requires a supply of thermal
energy thereby adding to the cost of the system. Further,
the thermal curing step is somewhat limited by the hea~
distortion temperature of the polycarbonate which is to be
coated. Thus, in coating of polycarbonates, sheets of 30
mils and Iess generally cannot be coated and cured
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60SI-391
economically because of excessive warpage of the sheets
during the thermal curing process.
U.S. Patent No. 3,968,305, Oshima et al, issued
~uly 6, 1976, describes a synthetic shaped article having
a mar-resistant polymer surface layer inegrated with the
polymer surface body, said polymer surface layer consisting
essentially of, in polymerized form, (a) 20 to 100 weight
percent of a compound having a total of at least three
acryloxy and/or methacryloxy groups linked with a straight
chain aliphatic hydrocarbon residue having not more than
20 caxbon atoms, and (b) 0 to 80 weight percent of at least
one copolymerizable mono- or diethylenically unsaturated
compound. This type of a surface layer suffers from the
fact that it generally has poor durability of adhesion after
prolonged exposure to weathering.
U.S. Patent`No. 3,968,309, Matsuo et al, issued
July 6, 1976, describes a molded article of plastic having
on its surface a cured film of a coating material comprising
at least 30% by weight of at least one polyfunctional
compound selected from the group consisting of polymeth-
acryloxy compounds having a molecular weight of 250 to 800
and containing at least three methacryloyloxy groups in
the molecule and polyacryloyloxy compounds having a
molecular weight of 250 to 800 and containing at least
three acryloyloxy groups in the molecule. This patent,
however, also teaches that this coating must contain from
0.01 to 5% by weight of a fluorine-containing surfactant
in order for the coated article to be acceptable. This
patent teaches that when the coating material contains
less than 0.01% by weight of the fluorine-containing
surfactant, it is impossible to obtain a coated article
having the requisite degree`of surface hardness, surface
smoothness, abrasion resistance and optical clarity. If
the coating material contains more than 5~ by weight of
said fluorine-containing surfa~tant, the adhesion between
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60SI-391
--7--
a cured film of the coating material and a molded substrate
of plastic is unsatisfactory.
It has now been found that a coating composition
containing certain specific polyfunctional aGrylic
monomers in combination with a blend of ketone and
hindered amine photoinitiators providés excellent and
durable UV cured coatings, especially for high strength
plastic substrates such as polycarbonate, polyester,
polymethylmethacrylate, and other polyacrylates, as well as
polyamides, nylon and metalized plastic surfaces. These
materials may be in films or sheets as well as in the form
of molded parts. Thus, the present invention provides certain
acrylate ester monomer based UV-cured coatings which adhere
tenaciously and durably to the substrate, are compatible
with the substrate, are mar, abrasion and solvent resistant,
and maintain properties after prolon~ed exposure to
weathering.
It is therefore an object of the present invention
to provide ultraviolet light curable coating compositions
` 20 providing improved mar and abrasion resistance which are
curable under a non-inert atmosphere such as air.
It is another abject to provide a UV curable
coating comprising the photoreaction products of certain
polyfunctional acrylate monomers and a bIend of ketone-
type and hindered amine-type photoinitiators.
~` It is anothe`r object to provide a process for
providing abrasion resistant ultraviolet light curable
coating compositions which are curable on rigid and
flexible substrates, and which do not require an inert
atmosphere for proper curing thereon.
It is still another object to provide articles of
manufacture which are highIy mar and abrasion resistant by
virtue of ha`ving been coated with the coatings of the
present invention which have been cur~d thereon.
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~Z4~512
60SI-391
Summary of the Invention
The present inven-tion provides an abrasion
resistant, durably adhered, ultraviolet light curable
hardcoating composition which is curable in a non-inert
-~ 5 atmosphere, and which comprises:
(A) at least one ultraviolet light curable
(i.e. cross-linkable) polyfunctional acrylate monomer
represented by the general formula
(H2C=CR' -COO) n~~R
lQ
wherein n is an integer having a value of from 1 to 4,
and R is selected from the group consisting of n valent
aliphatic hydrocarbon residue, n valent aliphatic
hydrocarbon residue containing at least one ether
linkage, and n valent substituted hydrocarbon residue
of either type, and R' is hydrogen or a lower alkyl radical
s`uch as methyl.
~ . ~ cor~Pos; tlor~,
The coating aompoistion is completed by adding to
ingredient (A) a blend of photoinitiators which have been
discovered e'ffective for crosslinking (A) to form the hard
coatings of the present invention, upon exposure to ultra-
violet radiation and without the necessity of an inert
(e.g. N2) blanketing atmosphere.
Description of the Invention
In accordance with the present invention, there
may be provided a non-opaque, more specifically, a
transparent, article having deposited on thè surface
thèreof an adherent, mar, abrasion and chemical resistant
non-opaque coating, said coating containing the photoreaction
3Q products of at least one W curabIe polyfunctional
acrylate monomer, and a blend of ketone and amine type
^' photoinitiators as will be described beIow. The coating
is obtained through the UV cure of a UV curable'coating
'~ composition comprised of (i) at least one'UV curable
polyfunctional acrylate monomer, and (ii) the seIected
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- 9 - 60SI 391
photoinitiator blend, under a non-inert atmosphere. An
anti-weathering agent such as resorcinol monobenzoate,
resorcinol dibenzoate, methyl rescorcinol monobenzoate, and
methyl resorcinol dibenzoate, and may be included if
optionally desired.
To exemplify the practice of this invention, any
of the aromatic polycarbonates can be employed. These are
homopolymers and copolymers and mixtures thereof that are
prepared by reactin~ a dihydric phenol with a carbonate
precursor. Typical of some of the dihydric phenols that
may be employed in the practice of this invention are
bisphenol-A (2r2-bis(4-hydroxyphenyl)propane), bis(4-hydroxy-
phenyl)methane, 2,2-bis(4-hydroxy-3-methylphenyl)propane,
3,3-bis(4-hydroxyphenyl~pentane, 2,2-bis(3,5-dichloro-4-
` 15 hydroxyphenyl~propane, 2,2-bis(4,3,5-dibromo-4-hydroxyphenyl)-
propane, and bis(3-chloro-4-hydroxyphenyl) methane. Other
dihydric phenols of the bisphenol type are also available
and are disclosed in U.S. Patent Nos.2,999,835, issued
September 12, 1961 to Goldberg; 3,02~,365, issued April 3,
20 1962 to Schnell et al; and 3,334,154, issued August 1,
1967 to Kim.
It is, of course, possible to employ two or more
different dihydric phenols or a copolymer of a dihydric
phenol with a glycol or with hydroxy or acid terminated
polyester, or with a dibasic acid in the event a carbonate
copolymer or interpolymer rather than a homopolymer is
desired fox use in the preparation of the aromatic carbonate
polymers of this invention. Also employed in the practice
of this invention may be blends of any of the above
materials to provide the aromatic carbonate polymer.
To carbonate precursor may be either a carbonyl
halide, a carbonate ester or a haloformate. The
-~arbonyl halides which can be employed herein are carbonyl
bromide, carbonyl chloride and mixtures thereof. Typical
`~ 35 of the carbonate esters which may be employed herein are
diphenyl carbonate, di-(halophenyl) carbonates such as
di-(chlorophenyl) carbonate, di-(bromophenyl) carbonate,
.
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60SI-391
--10--
di-(trichlorophenyl) carbonate, di-(tribromophenyl) carbonate,
etc., di-~alkylphenyl) carbonate such as di(tolyl) carbonate,
etc., di-(naphthyl) carbonate, di-(chIoronaphthyl) carbonate,
phenyl tolyl carbonate, chIorophenyl chIoronaphthyl carbonate,
etc., or mixtures thereof. The haloformates suitable for
~ use herein include bis-haloformates of dihydric phenols
- ~bischloroformates of hydroquinone, etc.) or glycols
(bishaloformates of ethylene glycol, neopentyl glycol,
polyethylene glycol, etc.). While other carbonate
precursors will occur to those skilled in the art, carbonyl
chloride, also known as phosgene, is preferred.
Also included are the polymeric derivatives of a
dihydric phenol, a dicarboxylic acid and carbonic acid.
These are disclosed in U.S. Patent No. 3,169,121, Goldberg,
issued February 9, 1965.
The aromatic carbonate polymers of this invention
may be prepared by employing a molecular weight regulator,
an acid acceptor and a catalyst. The molecular weight
regulators which`can be employed in carrying out the
process of this invention include monohydric phenols such
as phenol, chroman-I, para-tertiarybutyl-phenol,
para-bromophenol, primary and secondary amines, etc.
Preferably phenol is employed as the molecular weight
regulator.
A suitable acid acceptor may be either an organic
or an inorganic acid acceptor. A suitable organic acid
acceptor is a tertiary amine and includes such materials
as pydridine, triethylamine, dimethylaniline, tributylamine,
etc. The inorganic acid acceptor may be one which can be
either a hydroxide, a carbonate, a bicarbonate, or a
; phosphate of an alkaki or alkaline earth metal.
The catalysts which are employed here can be
any of the`suitable catalysts that aid the polymerization
of bisphenol-A with`phosgene.` SuitabIe catalysts include
tertiary amines such as, for example, triethylamine,
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~:2~2
ÇOSI-391
tripropylamine, N,N-dimethylaniline, quaternary ammonium
compounds such as, for example, tetraethylammonium bromide,
cetyl triethyl ammonium bromide, tetra-n-heptyl-
ammonium iodide, tetra-n-propyl ammonium bromide,
tetramethyl ammonium chIoride, tetramethyl-ammonium
hydroxide, tetra-n-butyl-ammonium iodide, benzyltrime-
` thylammonium chloride and quaternary phosphonium compounds
such as, for example, n-butyltriphenyl phosphonium bromide
and methyltriphenyl phosphonium bromide.
Also included therein are branched polycarbonates
wherein a polyfunctional aromatic compound is reacted with
the dihydric phenol and carbonate precursor to provide a
thermplastic randomly branched polycarbonate.
These polyfunctional aromatic compounds contain
at least three functional groups which are carboxyl,
carboxylic anhydride, or haloformyl groups or mixtures
thereof. Examples of these polyfunctional aromatic
compounds which may be employed in the practice of this
invention include: trimellitic anhydride, trimellitic
acid, trimellityl trichloride, ~-chloroformyl phthalic
anhydride, pyromellitic acid, pyromellitic dianhydride,
. mellitic acid, mellitic anhydride, trimesic acid,
~; ~ b,~ ,p/~ "~r~c~l, b~.Yy/~c
'~,' -be ~ e ~ _ ~ acld, benzophenonetetracarboxyllc
anhydride and the like. The preferred polyfunctional
aromatic compounds are trimellitic anhydride or trimellitic
acid, or their haloformyl deri~atives.
Also included herein are blends of a linear
polycarbonate and a branched polycarbonate.
It is to be understood that the utility of the
coating composition of the present inventio~ is not
limited to the polycarbonates described abo~e. There are
numerous other classes of substrates which may be
suitably rendered mar and abrasion resistant by the
coatings and processes disclosed herein. Among these
other substrates are such sheet, film and molded substrates
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- 12 - 60SI 391
as polyester and polymethylmethacrylate and other high
- strength films such as polyacrylates, polyamides, nylon
and plastic surfaces which have been metalized by such
techniques as sputtering, electroplating and vapor
deposition. Metal surfaces such as aluminum may also be
~ coated.
:~ The polyfunctional acrylate ester monomers of the
present invention are represented by the general formula
O
( I ) 2 C ~C - C - - ~ --- R
R J n
wherein n is an integer from l to 8, preferably from l
to 6, and more preferably from l to 4; and R is a
n functional hydrocarbon residue, a n functional
substituted hydrocarbon residue, a n functional
hydrocarbon residue containing at least one ether
linkage, and a n functional substituted hydrocarbon residue
containing at least one ether linkage, and R' is hydrogen
or a lower alkyl radical such as methyl.
Preferred n functional hydrocarbon residues
are the n functional aliphatic, preferably saturated
aliphatic, hydrocarbon residues containing from l to
about 20 carbon atoms and the n functional aromatic
hydrocarbon residues containing from 6 to about lO carbon
atoms.
Preferred n functional hydrocarbon residues
: 25 containing at least one ether linkage are the n functional
aliphatic hydrocarbon residues, preferably saturated
: aliphatic hydrocarbon residues, containing from l to
about 5 ether linkages and from 2 to about 20 carbon
atoms.
~:~ 30 Preferred n functional substituted hydrocarbon
:~ residues are the n functional aliphatic hydrocarbon
residues, preferably the saturated aliphatic hydrocarbon
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60SI-3gl
-13-
residues, containin~ from 1 to about 20 carbon atoms,
; and the n functional aromatic hydrocarbon residues
containing from 6 to about 10 carbon atoms which contain
substituent groups such as the halogens, i.e., fluorine,
chIorine, bromine and iodine, hydroxyl, --COOH, and --COOR'
groups wherein R~ represents alkyl groups containing from
1 to about 6 carbon atoms.
Preferred n functional substituted hydrocarbon
residues containing at least one ether linkage are the n
functional aliphatic, preferably saturated aliphatic,
hydrocarbon residues containing from 2 to about 20 carbon
atoms and from 1 to about 5 ether linkages which contain
substituent groups such as the halogen hydroxyl, --COOH,
and --COOR' groups wherein R' is as defined above.
It is to be understood that where substituent
groups are present, they should be such that they do not
unduly hinder or interfere with the photocure of the
polyfunctional acrylic monomers.
The more preferred polyfunctional acrylic
monomers are those represented by formula I wherein R is
selected from the group consisting of an n functional
saturated aliphatic hydrocarbon residue containing from
1 to about 20 carbon atoms, a hydroxyl substituted n
fuhctional saturated aliphatic hydrocarbon residue
containing from 1 to about 20 carbon atoms, an n
functional saturated aliphatic hydrocarbon residue
containing from about 2 to about 20 carbon atoms and from
about 1 to about 5 ether linkages, and a hydroxyl
substituted n functional saturated aliphatic hydrocarbon
residue containing from 2 to about 20 carbo~ atoms and
from 1 to about 5 ethe`r linkages.
The preferred polyfunctional acrylate ester
monomers are those wherein R is an n funct~ional saturated
aliphatic hydrocarbon, ether, or polyether radical, with
those monomers wherein ~ is an n valent saturated
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60SI-391
-14-
aliphatic hydrocarbon radical being more preferred.
More particularly, the difunctional acrylic
monomers, or diacrylates, are represented by formula I
wherein n is 2; the trifunctional acrylic monomers, or
triacrylates, are represented by formula I wherein n
is 3; and the tetra-functional acrylic monomers, or
: tetraacrylates, are represented by formula I wherein n
is 4. Illustrative of suitable polyfunctional acrylate
ester ~onomers of formula I are those listed below in
TABLE I.
TABLE I
2 CHCO2 - CH2 - OCOCH = CEI
CH2 = CCH3CO2 - CH - OCOCCH3 = CH2
2 = CHC2 ~ CH2CH2 ~ OCOCH = CH2
CH2 = CCEI3C2 ~ CH2CH2 - OCOCCH3 = CH2
CH2 = CH - CO2 - CH2CHOHCH2 - OCOCH =CH2
CH2 = CCH3CO2 - CH2CHOHCH2 - OCOCCH3 = CH2
2 2 CH2CH2 o - CH2CH2 - OCOCH = CH
2 3 2 CH2CH2 - 0 - CH2CH - OCOCCH CH
CH2 = CH2C2 ~ CH2CH2 ~ - CH2cH2 _ OCOCH = CH2
CH2CCH3 2 2 2 2 2 2 2 3 2
2 2 2 CH2CH~ -- O -- CH2CH -- Q ~' CFI CH
~-~
`. 2 3 2 2 2 2 2 2 2 2 2 3 2
~,
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60SI-391
-15-
` CH2 = CHco2-cH2cH2cH2 - OCOCH = CH2
CH2 = CCH3CO2 - CH2CH2CH2 - OCOCCH3 = CH2
: 2 2 2 2 2 2 2
CH = CCH3C2 - CH2CH2CH2CH2 - OCOCCH3 = CH2
2 2 CH2CH2CH2CH2CH2 - OCOCH = CH
2 3C2 CH2CH2CH2CH2CH2 - OCOccH3 = CH2
CH2 CHCO2 CH2CH2CH2c 2C 2 2 2
`;; CH2 = CCH3C2 - CH2CH2CH2CH2CH2CH2 _ OCOCCH3 = CH2
CH2 CHCO2 CH2CH2 CHCH3 2
CH - CCH CO - CH CH - CHCH - OCOCCH3 = CH2
` CH2 = CHCO2 - CH2C(CH3)2 CH2 2
CH2 = CCH3C2 - CH2C(CH3)2CH2 - 0 - COCCH3 = CH2
CH3
CH2 = CHCO2 - CH2 - C - OCOCH = CH2
~, C~I2Br
CH3
: CH2 = CCH3CO2 - CH2 - C - OCOCCH3 = CH2
CH2Br
CH
CH2 = CHC2 - CH2 - C - OCOCH = CH2
CH2O~
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- 16 - 6OSI 391
CH3
C 2 CC 3C2 C 2 ~ 3 2
:~ CH20H
20H
CH2 = CHCO2 - CH2 - C - OCOCH = CH2
CE12 OH
CH2H
`;: CH2 = CCH3CO2 - CH2 - C~ - OCOCCH3 ' CH2
CH2H
: CH20H
:: CH2 = CH - C2 - CH2 - C - OCO - CH = CH2
CH2Br
CH20H
~ 5 CH2 = CCH3C02 - CH2 - ~C - OCOCCH3 = CH2
`'';`' CH2Br
;~ CEI2 = CHCO2 - CH2 - CH = CH - CH2 - CH2 - OCOCH = CH2
~ CH2 = CCH3CO2 - CH2 - CH = CH - CH2CH2 - OCOCH = CH2
:~` CH2 = CH2CO2 - CH2 - CH = CH - CH ~ OCOCH = CH2
CH20H
," CH2 = CCH3C02 - CH2 - CH = CH - CH - OCOCH = CH2
.;, CH20H
` 10 CH2 = CHCO2 - CH2CHOCH3CH2 - OCOCH = CH2
' `:
:~`.`.~
CH2 = CCH3CO2 - CH2CHOCH3CH2 - COCCH3 = CH2
: ,
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60SI-391
-17-
CH2 = CHCO2 - ~ ~ OCOCH = CH2
CE~2 = CCH3C02 - ~ - ococH3 -- ,CEI2
CH2 = CHC02 - ~ - OCOCH = CH2
CH3
CH2 = CCH3CO2 - ~ - OCOCCH3 = CEI2
CH3
CH = CHCO2 - ~ - 0 - COCH = CE12
B
CH2 = CCH3C02 6 ~ _ OCOCCH3 = CH2
Br
CH2 = CHCO2 - ~ - OCOCH = CH2
CH2 = CCH3CO2 - ~ - OCOCCH3 = CEI2
CH2 = CHCO2 - ~ - CH2CH2 - oCOCH = CH2
.~ ~ .
`' 10 CH2 = CCH3C02 -~ ~ ~- CH2CH2 - 0COCCH3 CH2
~'
~ .
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~Z~82
- 18 - 60SI 391
OCOCH = CH2
CH = CHCO2 - CH CH - CH - CH - OCOCH = CH
OCOCCH3 = CH2
2 C 3 2 C 2C 2 ~C
;; CH2 - OCOCCH3 = CH2
CH2 - OCOCH = CH2
` C 2 CHCO2 CH2 ~C CH2CH3
CH - OCOCH = CH2
: CH2 - OCOCCH3 = CH2
2 CCH3CO2 - CH2 - C - CH CH
~: CH2 - OCOCCH3 = CH2
.'' CH20COCH = CH2
~ 5 CH2 = CHCO2 - CH2 - C - CH2OH
:~ CH20cOCH = CH2
CH2OCOCCH3 C 2
2 CCH3CO2 - CH2 - C - CH OH
CH20COCCH3 CH2
;~
OCOCH = CH2
CH2 = CHCo2~3--OCOCH = CH2
:,:
~ OCOCCH3 = CH2
~., I
~` CH2 = CCH3CO2 ~ 3 2
.~
~ CH20COCH = CH2
`-. CH2 = CH - C2 - CH2 - ~C - CH2OCOCH = CH2
CH20COCH = CH2
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3L2~4~2
60SI-391
--19--
7H2OCOCCH3 = CH2
H2 CC~13C2 ~ CH2 - 7 - CH20COCCH3 = CH2
CH20COCCH3 = ,CH2
CH2 - OCOCH = CH2
CH2 = CHC02 - CH2 - CIH - CH - CH20COCH = CH2
CH2 = HCC02 CH2
CIH2 - OCOCCH3 = CH2
2 3 2 - CH2CIH - CH - CH2 - OCOCCH3 = CH2
CH2 CCH3 2 2
CH2 = CHC02CIH2 Cl 120COCH = CH2
~: CH~ = CHC02 - CH2 - CH - CIH - CH2CH - CH2 - OCOCH = CH
: OH
~: CH2 = CCH3C02CH2 OIH20COCCH3 H2
5CH2 = CCH3C02 - CH2 - CH - CIH - CH2CH - CH2 - OCOCCH3 = CH2
OH
CH2 = CHC02CH2CHCH3 - OCH2CHCH30CH2 - CHCH30CO - CH = CH2
CH2 = CH - C02 - CH2CH2 - O - phenyl
CH = CCH - CO - CH CH O - phenyl
CH2 = CHC02 - CH2 ~Q
CH2 = CCH3C02 CH2
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~L2~411~;~
- 20 - 60SI 391
These polyacry]ate esters and their production
are well known to those skilled in the art. One method
of producing the di-, tri-, and tetraacrylate esters
; involves reacting acrylic acid with a di-, tri-, or
tetrahydroxyl compound to produce the diester, triester or
tetraester. Thus, for example, acrylic acid can be
reacted with ethylene glycol to produce ethylene glycol
diacrylate.
Although the coating compositions may contain
only one of said polyfunctional acrylate monomers,
preferred coating compositions contain a mixture of two
polyfunctional monomers, preferably a diacrylate and a
triacrylate. When the coating compositions contain a
mixture of acrylate monomers, it is preferred that the
ratio, by weight, of the diacrylate to the triacrylate
be from about 30/70 to about 70/30. Exemplary mixtures
of diacrylates and triacrylates include mixtures of
hexanediol diacrylate with pentaerythritol triacrylate,
hexanediol diacarylate with trimethylolpropane triacrylate,
`~ 20 diethyleneglycol diacrylate with pentaerythritol
triacrylate, and diethyleneglycol diacrylate with
~ trlmethylolpropane triacrylate.
;~ While the corresponding coatings may likewise
contain the ultra~iolet light reaction product of a single
polyfunctional acrylate monomer, coatings containing the
photoreaction product of two polyfunctional acrylate
monomers, preferably a diacrylate and a triacrylate,
are preferred.
Generally, the coating composition contains from
about 70 to about 99 percent of the polyfunctional acrylate
or acrylates. The UV cured coating contains from about 70
to about 99 weight percent of the photoreaction products
of the polyfunctional acrylate monomer or mixture of
acrylate monomers present in the coating composition.
qhe photocurable coating compositions also contain
a photosensitizing amount of photosensitizer, i.e., an
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60SI-391
-21-
amount effective to effect the photocure of the coating
composition. Generally, this amount is from about 0.1~
to about 10% by weight and preferably from about 0.1% to
about 5~ by weight of the photocurable coating composition.
It has been discovered through the present
invention that certain blends of ketone-type and
hindered amine type materials are photoinitiators which
are effective for crosslinking the above described
polyfunctional acrylates to form suitable hard coatings
upon exposure to UV radiation. It is preferred that the
ratio, by weight, of the ketone compound to the hindered
amine compound be from, approximately, 80/20 to 20/80.
Ordinarilly, 50/50 or 60/40 mixtures are quite satisfactory.
Among the particularly preferred ketone-type
compounds are those selected from the group consisting of:
benzophenone, and other acetophenones,
benzil, benzaldehyde and o-chlorobenzaldehyde,
xanthone,
thioxanthone,
2-chlorothioxanthone,
9,10-phenanthrenequinone,
9,10-anthraquinone,
ethylbenzoin ether,
isopropyl benzoin ether,
a, a-diethoxyacetophenone,
l-phenyl-l 2-propanediol-2-o-benzoyl oxime, and
a,a - dimethoxy-a-phenylacetophenone,
In the above formulas, lower case a represents
configurations of radicals in the alpha position.
Among the particularly preferred hindered amine-
type compounds are`those selected from the ~roup consisting
of:
methyldiethanol amine,
ethyldiethanol amine,
dimethylethanol amine,
.
~ZZ4182
60SI-391
-22-
diethyl ethanol amine,
; triethanol amine,
dimethyl amino ethylbenzoate,
ethyl-3-dimethyl amino benzoate,
~ 5 4~dimethyl amino benzophenone,
; 4-diethyl amino benzophenone,
4,4' -bis (diethylamino) benzophenone,
4,4' -bis (dimethylamino) benzophenone,
N, N-diethyl aniline,
phenyl methyl ethanol amine,
phenyl ethyl ethanol amine,
phenyl diethanol amine, and
N,N,N',N' -tetramethyl - 1,3 -butanediamine.
The coating compositions of the instant invention
may also optionally contain resorcinol monobenzoate. The
resorcinol monobenzoate is present in an amount, based upon
` the weight of the coating composition, exclusive of any
additional solvent which may optionally be present, of
.:~,
` from about 1 to about 20 weight percent, preferably from
about 3 to about 15 weight percent. The UV cured coating
~; contains from about 1 to about 20% by weight of the
photoreaction products of resorcinol monobenzoate, which
products are formed during the UV cure of the UV curable
` coating composition if the resorcinol monobenzoate is
utilized.
The coating compositions of the instant invention
may also optionally contain various flatting agents,
surface active agents, thi~otropic agentsj UV light
- absorbers and dyes. All of thèse additives and the use
thereof are weIl known in the art and do not require
e~tensive discussions. Therefore, only a limited number
will be referred to, it being understood that any
compounds possessing the ability to function in such a
manner, i.e., as a flatting agent, sur~ace active agent,
W light absorber, and the likèj can be used so long as
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60SI 391
'
-23-
they do not deleteriously affect the photocuring of the
coating compositions and do not adversely affect the non-
opaque character of the coating.
The various surface-active agents, including
anionic, cationic and nonionic surface-active agents
are described inKirk-Othmer Encyclopedia of Chémical
Technology, Vol. 19, Interscience Publisher, New York,
1969, pp. 507-593, and Encyclopedia of Polymer Seience
and Technology, Vol. 13, Interseience Publishers, New
York, 1970, pp. 477-486.
In the practice of the present invention, the
photocurable coating compositions are first compounded
by adding together the polyfunctional acrylic monomer
or mixtures thereof, the W photosensitizer blend, and,
optionally, any of the other a-forementioned additives.
Additionally, if so desired to reduce the viscosity of
the coating formulation, an organic solvent, such as an
alcohol, may optionally be incorporated into the
formulation. Generally, the amount of solvent, if any,
present shouLd be sueh that evaporation of the solvent
~' occurs before any deleterious effect on the substrate.
The various components are thoroughIy mixed so as to
form a generally homogeneous coating compositions. A
thin, uniform coating of the coating solution is then
applied onto the substrate by any of the known means sueh
; as dipping, spraying, rolleoating and the like. The
eoating is then cured in a non-inert, e.g., air, atmosphere,
by W irradiàtion which ean have a wavelength of from
1849 A. to 4000A. The lamp systems used to generate such
radiation can consist of ultraviolet lamps which can
eonsist of diseharge lamps, as for example, xenon,
metallic halide, metallic arc, such as low or high pressure
mercury vapor diseharge lamp, ete., having operating
pressures of from as low as a few milli-torr up to about
10 atmospheres. By curing is means bbth polymerization
. . .
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60SI-391
-24-
of the polyfunctional acrylic monomers and cross-
linking of the polymers to form hard, non-tacky coatings.
PREFERRED EMBODIMENT OF THE' INVENTI'ON
In order to more fully and clearly describe the
invention, it is-intended that the examples be considered
as illustra~ive rather than limiting the invention disclosed
and claimed herein. All parts are by weight.
EXAMPLE 1
An aromatic polycarbonate is prepared by reacting
2,2-bis(4-hydroxyphenyl) propane and phosgene in the
presence of an acid acceptor and a molecular weight
regulator. The product is then fedto an extruder, which
~; extruder is operated at about 265C and the extrudate is
comminuted into pellets.
' 15The pellets are then injection molded at about
~"315C into test panels of about 4 in. by 4 in. by about
1/8fin. thick. The test panels are sub~ected to an
abrasion test, Gardner Impact Test and an adhesion test.
The abrasion, test in one wherein test panels
having a 17/64th inch diameter hole cut in the center
are subjected to a Taber Abraser. The Taber Abraser is
equipped with CS-lOF wheels which are resurfaced every
500 cycles by abrading for 25 cycles on a S-lll refacing
disc. The weights used in combination with the CS-lOF
wheels are 500 gm weights. Initial measurements of % Haze
are made at four places around the future wear track of the
sample using a Gardner Hazemeter. The sample is abraded
;for 500 cycles, cleaned with warm soap and water and dried
by blowing compressed air across the sample, and the %
Haze is remeasured at the same four places. The four
differences in % Haze are'calculated are averaged to give
the % Haze.' The ~ % Haze of this uncoated sample is
generally between 45 to 50.
~he scribed adhesion tes~ consists of using a
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60SI-391
-25-
multiple blade tool to cut parallel grooves through the
; coating and into the substrate. The test panel is then
rotated 90 and the cutting process is repeated,,thereby
leaving a grid pattern consisting of 1 mm squares cut into
i ~ 5 the coating. An adhesive tape such as 3M's Scotch'71~ is
applied over the cross hatched area and quickly pulled off.
A sample fails the adhesion test if any of the squares are
pulled off by the tape. This test is repeated three times.
Examples 2,3, and 4 are comparative examples of
unsuccessful hardcoating compositions utilizing poly-
functional acrylate monomers as basic ingredients.
EXAMPLE 2
A coating composition was prepared by combining
150 parts of hexanedioldiacrylate (HDDA), 150 parts of
trimethylolpropanetriacrylate (TMPTA), 2 parts of
'', benzophenone, 2 parts of dimethylethanol amine, and one
' part of a surface active agent BYK-300 produced by
Mallincrodt Chemical Co. of New Jersey. A film of about
0.15 mil of this mixture was coated on a polycarbonate
panel produced in accordance with example 1. The coated
panel was passed thorugh a PPG Model QC 1202 UV-processor
under an air atmosphere, where the conveyer speed was
20 feet/minute. Two passes through the system resulted in
a coating which'was tacky and undercured.
EXAMPLE 3
_ _ .
; A coating composition was formulated by combining
200 parts diethylene glycol diacrylate, 200 parts
trimethylolpropanetriacrylate, 2 parts benzophenone,
~ 1.5 parts methyldiethanolamine, and one part B~K-300.
'~ 30 This mixture was-coated on a polycarbonate test paneI which
was then twice passed through the PPG UV-processor under
an air atmosphere. The resulting coating was-tacky and
not fully cured.
~-
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~LZ;i:4~32
60SI-391
-26-
EXAMPLE 4
A coating mixture was formulated by combining
200 grams hexanedioldiacrylate, 200 grams ~rimethylol-
propanetriacrylate, 4 grams diethoxyacetophenone, 20
grams resorcinol monobenzoate, and 2 grams BYK-300. A
~ film of about 0.2 mils was applied to a Lexan polycarbonate
`~` panel and passed 5 times through the PPG 1202 UV-
Processor under a nitrogen blanket of 15 psi and at a
conveyor speed of 20 ft./min. The resulting coating was
tacky, had cracks and was hazy.
The remaining examples demonstrate the successful
hard coating compositions of the present invention.
EXAMPLE 5-
,:~
A coating mixture was prepared by combining 100
~' 15 parts of hexanedioldiacrylate, 100 parts of trimethylol-
propanetriacrylate, 4 parts by weight of benzophenone,
', 4 parts by weight of methyldiethanolamine, and 1 part
by weight of surface active agent BYK-300. This coating
composition was applied to a polycarbonate panel and was
,~ 20 then passed through a PPG 1202 W-processor in an air
atmosphere where the conveyer speed was 20,ft/min. One pass
through this system resulted in a coating which was hard
and tack-free.
EXAMPLE 6
A coating mixture was prepared by combining 100g
of hexanedioldiacrylate, 100g of trimethylolpropanetriacrylate,
4g of benæophenone, 4g of methyldiethanolamine, lg of
BYK-300 and 10g of resorcinol monobenzoate. This mixture
was coated on LexanR and passed through a UV-Processor as
in Example 2. The coated LexanR was subj~ected to the afore-
described abrasion and scribed adhèsion tests and the
results are set forth in Table II.
EXAMPL~ 7
A coating composition was made by combining
200 g of diethylene glycol diacrylate, 4g of benzophenone,
4g of methyldiethanol amine, and 1 g of BYK-300. This
::. .: .
lZ24~2
60SI-391
-27-
coating was applied to a LexanR panel and passed through
a W-Processor as in Example 2. The coated Lexan panel
; was also subjected to the afore-described abrasion and
scribed-adhesion tests and the results are set forth in
Table II.
EXAMPLE 8
-~ A coating composition was formulated by combining
100 g of trimethylolpropanetriacylate, 2 g of benzophenone,
2 g of methyldiethanolamine, and 0.5 g o BYK-300. A film
.~ 10 of about 0.2 mils thickness was applied to a LexanR sheet
and passed through a W-Processor as in Example 2. The
coated LexanR panel was subjected to the afore-described
abrasion and scribed adhesion tests an'd the results are
set forth in Table II.
EXAMPLE 9
A coating composition was formulated by
combining 250 g of diethylene glycol diacrylate, 250 g
: of trimethylolpropane triacylate, lOg of benzophenone,
lOg of methyldiethanolamine, and 2.5 g of BYK-300. This
:~ 20 material was coated on a LexanR panel and passed through
a UV-Processor as in Example 2. The results are set forth
in Table II.
: TABLE II
Example No. Adhesion Test~%H500
pass 24.6
6 pass 28.5
7 pass 23.3
8 pass 21.2
9 pass 19.2
Those skilled in the art will recognize that the
~' ~ % H500 haze'data given in Table II represents coated
articles having excellent abrasion resistance.
The'foregoing example'demonstrate'that it is
possible to pxovide~air curable coating composition through
the part.icular combination of polyfunctional acrylates and
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~2Z9L~L~32
60SI-391
-28-
blended photoinitiators described above. These coatings
and coated articles also possess such other desirable
properties as optical clarity~ durability of adhesion,
~;~ non-degradation of the properties of the substrate, and
protection of the substrate from the ~e~cr~5 effects
of prolonged exposure to W.
Although specific embodiments of the invention
~: have been described, it should not be limited to the
- particular compositions and articles described herein,
but is intended to include all modifications that may be
made which, pursuant to the patent statutes and laws, do
not depart from the spirit and scope of the invention.
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