Note: Descriptions are shown in the official language in which they were submitted.
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B~cJ~round of the Invention
This invention relates to Si containing coating co.?esitions
and more particularly to coatin~ compositions for polymeric
substrates.
Prior Art
U. S. Patent No. 3,894,881 issued ~uly 15, 1975 to
. Suzuki et al. This patent reiates to a c02ting.composition
which comprises a mixture of separately hydrolyzed Si contai~ing.:
- materîals and a metal salt. The patent does not refer to
10 any coating co~positions of a similar type which are hydrolyze~ -
as a mixture.
Summary of the Invention
We have developed an improved type of abrasion-
resista~t coating based upon siloxane copolymers. These
coa.ings are useful for increasing the abrasion resis,ance
of plastics, especially those used for the manufacture of
eyeglass lenses, sunglasses, goggles, ana windo~ and architec~ura
glazing. Typical plastic substrates that can be used for
these applications are polycarbonate, polymethyl me.hacrylate,
20 cellulose propionate, celluiose butyrate, and polydiethylene
I ~lycol bis-allyl carbonate. Polyc2rbon2te and pol~diethylene ~.:
: glycol bis-aliyl carbonate are pre erred lens materials.
.: ~enses can be formed from thermoplastics by molding
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: . techniques, from thermosetting plastics by casting techniques,
and from both by machining and surfacing processes. Such
. .` lenses can be coated with the poiysiloxane coating to provide
- a surface that is more xesistant-to both abrasion and solvent
attack than the uncoated plastic.
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While these coatings provide good resistance to bo.h
abrasion and solvents, they introduce an additional feature
that was not possible before with earlier polysiloxane
coatings. The polysiloxane coatings of this invention can
be tinted or dyed with organic dyes so that coated lenses
can be provided with fashion or sunglass colors in a manner
simllar to the way uncoated lenses are now currently dyed in
the industry.
The principal monomers of our copolymer three dimensional
siloxane coating are tetraethyl orthosilica~e and certain
combina,ions of methyltrimethoxy silane, methyltrietnoxysil~ne,
ethyltrimethoxysilane, ethyltriethoxysilane, dimethyl-
dimethoxysilane and dimethyldiethoxysilane. ~or example,
useful abrasion resistant coatings for both polycarbonate
and diethylene glycol bis-ally carbonate are prepared by
reacting 40 to 70 weight per cent tetraethyl orthosilicate
and 60 to 20 weight per cent of methyltrimethoxysilane to
form~a highly-crosslinked polysiloxane network polymer. ~y
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allowing these monomers to hydrolyze in-si~u by addition of
water to the alcohol solution, the polymer will form a tough
abrasion -esistant coating when applied to the surface of a
lens and then allowed to crosslink and cure by the application
of heat either in the presence or absence of a catalyst.
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When the substrate to be coated is one which will absorb
water under humid conditions, e.g. poly diethylene glycol
Bis (allyl carbonate) and cellulose acetate propionate,
less tetraethyl orthosilicate is preferred. Suitable
coatings for these substrates are obtained from the reaction
of about 35 to 45 weight per cent tetraethyl orthosilicate,
about 45 to 55 weight per cent methyltrimethoxy silane and
about 5 to 15 weight per cent 3-glycidoxypropyltrimethoxy-
silane.
10In addition to the discovery of these new abrasion
resistant coatings, we have also discovered how to render
them suitable for dyeing once they have been applied to and .
cured upon the surface of a lens. Since highly crosslinked
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poiysiloxanes are rather impervious to attack by most coloring
agents, we have developed two techniques to modify their
properties so that organic dyes will penetrate the co2ting
an~ will ~e adsorbed within the molecular structure.
;The first technique involves the addition of certain
surfactants or wetting agents to the coating formulation.
For example, the addition of a non-ionic wetting agent such
as Triton X-100, a polyethylene oxide derivative of nonylphenol
made by Rohm & Haas Company, permits conventional ophthalmic
organic dyes to penetrate into the coating. Another useful
wetting agent is Fluorad FC-430, a non-ionic fluorinated
alkyl ester made by the 3M Company. Coatings prepared with
this material also permitted organic dyes to penetrate into
the co~ting.
A second approach is the use of up to 20 weight per
cent of a reactive siloxane monomers with polar sites that
; serves to attract the organic dyes. Typical reactive siloxane
monomers are:
3-chloropropyltrimethoxysilane
3-glycidylpropyltrimethoxysilane
3-methacryloxypropyltrimethoxysilane
bis~2-hydroxyethyl)aminoprop~ltrimethoxysilane
and (3,4-epoxycyclohexyl)ethyl,rimethoxysilane
These monomers are reacted with the basic tetraethyl orthos-
; ilicate~silane coating formulation as shown in the examples
to yield dyeable lens coatings. ~hen these monomers are
used and if they are considered as part of the "silane"
component of the basic tetraetyyl orthosilicate/ silane
mixture, the silane component must be present in a to~al of
at least 30 weight per cent.
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Example 1
2G8 grams of te,raethyl orthosilicate, 136 grams o~
methyltrimethoxysilane were hydrolyzed in 95 grams of
alcohol (50% isopropanol, 50% n-butanol), 130 grams of
water, 30 grams of acetic acid, and 14 drops of hydrochloric
acid using an ice bath for 10 minutes to control the iniiial
exotherm, and then at room temperature overnight.
Polycarbonate lenses were primed by dipping for one
minute in a solution containing 10~ gamma-amino propyl
triethoxysilane, 85% ethyl alcohol and 5% water, rinsed, air
dried and then dip-coated in the abrasion-resistant coating
solution and cured at 104 C for 8 hours. The resulting
coatings were on the average of 2 microns thick and resistant
to abrasion and solvent attack.
- Example 2
50 grams of methyltrimethoxysilane, 50 grams of tetraethyl ~ -
orthosilicate, were hydrolyzed in 4~ grams of 50/S0 weight %
solution of isopropanol and n-butanol by stirring constantly
while 35 grams Gf water and 10 grams of acetic acid were
added dropwise. The solution was aged for 1 day.
Polycarbonate (primed as in Example 1) and CR-39 ~hydrolized)
lenses were dip-coated with the abrasion-resistant coating
solution and cured at 104C for 8 hours. The resu~ting
coatings were on the average 2 microns thick and quite
reslstant to abrasion and solvent attaok.
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Example 3
100 grams of methyltrimethoxysilane, 100 grams o'
tetraethyl orthosilicate, and 80 grams of 50/50 isopropanol-
n-butanol were mixed while 70 grams of water and 20 grams of
acetic acid,were 510wly added.
After aging the solution overnight, it was di~-ided into
seven 50 gram batches to which 0, 0.1, 0.25, 0.50, 1.00,
2.50, and 5.00~ Triton X-100 was added, respectively.
Primed polycarbonate lenses were coated from each
solution and cured at 220 F for 8 hours. The resulting
coatings were 2-3 microns in thickness. They were dyed by
dipping organic dye (ophthalmic grey from Brain Power Inc.)
mixed with water. Visual transmission of the lenses after 5
minutes of dyeing at 200 F were 87~, 88~, 88~, 86%, 84~, 62%
and 25%, respectively.
Example 4
To 50 grams of coating solution as prepared in Example
3 above, was added 2~ ~luorad FC-430. Brimed polycarbona~e
lenses were coated and cured as above. The coating again
accepted the organic dye to give a visual transmission of
56% after 5 minutes of 200 F in the water dye mixture.
_ ample 5
24 grams of tetraethyl orthosilicate, 12 grams of
methyltrimethoxysiland, 4 grams of 3-methacryloxypropyl-
trimethoxysilane, were hydrolyzed in 19 grams of 50J50
isopropanol-n-butanol by slowly ,adding 1~.5 grams of water
and 3.75 grams of acetic acid. The solution was aged three
days.
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Primed polycarbonate lenses were coated and cured as in
previou~ examples. The coating was receptive to convention
ophthalmic organic dyes. Visual transmission equaled 7~%
aft..er 5 minutes at 200F in theaqueous/dye (BPI Grey) mixture.
Exa~lple 6
.24 grams of tetraethyl orthosilicate, 12 grams of
- methyltrime,hoxysilane, and 6.~5 grams of bis(2-
hydroxyethyl) aminopropyltriethoxysilane, were hydrolyzed in
16 grams of 50/50 alcohol by adding 12.75 grams of water and
3.75 grams of acetic acid slowly. The p~ was the adjusted , .
to 3 with hydrochloric acid.
Coated ~olycarbonate lenses again were quite receptive
to the 5 minute dye treatment at 200F in the a~ueous mixture
of BPI Grey. The lenses had a transmission of 74~.
Example 7
. 344 grams of tetratheyl orthosilicate, 430 grams of meth,yl-
: trimethoxysilane and 86 grams of 3-glycidoxypropyl-trimethoxy-
. silane were hydrolized by slowly adding 310 grams of a 50/50 ~.
. ' mixture of isopropyl alcohol and butyl alcohol, 310 grams of
water and 69 grams of acetic acid at a rate that permitted the
' r,eaction to proceed without exceeding 30C. The coating solution
'.~ should be aged about 4 days before use and has useful pot life of
approximately 4 to 6.weeks.
~ Hydrolized CR-39 ophthalmic lenses were coated by dipping in
', ~ r ,: th,e aged coating solution and withdrawing them from the solution
.,, . at à rate of about 10 inches per minute. The coating obtained
wa5 about 2 to 3 microns thick - had good adhesion to the.lenses -'
passed cycle humidity, boiling water and abrasion tests as well
a~ enhanced the impact re9istance of the lenses.
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