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Патент USA US2404426

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Patented July 23, 1946 v
‘
um'rao STATE s - PATENT _~ onucs
2,404,420
,
CHARACTERISTICS or soup
summonoaomo
ronmaas
Max Fredrick Bechtold and Paul Swithin Pinkney,
Wilmington, Del., assignors to E. 1. du Pont de
Nemours & Company, Wilmington, Del., a cor-
poration of Delaware
No Drawing. Application July 15,1944,
erial No. 545,196
11 Claims.‘ (01117-121) A
'
1
"\
This invention relates to an improvement in
the surface characteristics of solid organic poly
mers and, more particularly, to increasing the
scratch resistance and decreasing‘ the tackiness ' '
of the surface of solid organic polymers by de
prising an acid polysilicic acid ester and a volatile
organic solvent therefor. The term “acid poly
silicic acid ester" is used herein in its normal
meaning to denote an ester of a polymeric silicic
acid, which ester contains -OH groups attached
to- S1.
positing a ?lm thereon from polysilicic acid ester ‘
Polysilicic acid and esters thereof are . .
characterized by containing
solutions. This application is a continuation-in
part of application Serial No. 484,062, ?led April
22, 1943, and now abandoned.
-
‘
Application Serial No. 507,591, ?led October
25, 1943, in the name of M. F. Bechtold and en
10
titled “Coated methyl methacrylate polymer” is
‘ -0-+-o-§%1
groups.
I
‘
,- More particularly the invention is carried out
by applying to the surfaces of the solid organic
polymer the solution of ‘an acid polysilicic acid
also a continuation-in-part of application Serial
No. 484,062 and relates more speci?cally to
scratch resistant and weather resistant coatings ll ester in a volatile organic solvent, in a thin uni
form ?lm, allowing the solvent to evaporate, and
for methyl methacrylate polymer. '
_
then baking the. coated surface at an elevated
Heretofore methods have been proposed for im-'
temperature usually not exceeding the softening’
proving the surface characteristics such‘ as the
point of the organic polymer, temperatures of
scratch resistance, of solid organic polymers, par
about 75° C. to 100° C. generally being satisfac
ticularly transparent polymeric materials. One
tory; by the use of certain expedients consid
method has involved the vaporization of silica at
erably higher temperatures may be used with suc
low pressures followed by condensation on the
cess. The. coating composition may advanta
polymer surface to form a coating said to have
geously contain. an organic liquid which is a sol
improved resistance to‘ scratching. A second
- vent ‘for the organic polymer being treated, in‘
method has depended on the incorporation of a
addition to the volatile organic solvent for, the‘
solid, insoluble material such as amorphous. di
ods requires elaborate equipment and the process
polysilicic acid ester, and from 5% to 25%, by
weight of the combined S102, of an organic poly
mer which is compatible with the polysilicic acid
tory for use with transparent polymers because
resin and relative proportions of the components
atomaceous silicaon the surface‘ of the'polymer '
to render it less tacky.
The ?rst of these meth
.
is costly and inconvenient to operate on a com 80~ ester in the solvent-free ?lm.
The speci?c choice of solvent, ?lm-modifying
mercial scale. The‘ second method is unsatisfac- '
the insoluble material detracts from the clarity,
gloss, and brilliance of the surface.
,
An object of the present invention is to provide
a convenient, economical method of treating the ,
surfaces of solid organic polymers to improve
their scratch resistance, decrease their tackiness, -
ofvthe coating-composition, as well as the con
ditions of application, depend, as explained here
inafter, on the degree of esteri?cation and poly
merization of the acid polysilicic acid ester, the
nature of the esterifying alcohol, the resin being
coated, and the e?ects desired. When the in
vention is properly carried out, a uniform, clear,
and reduce their tendency to collectdust, all
?lm is obtained '
without detracting from their gloss, brilliance, 40 transparent, glossy polysilica‘te
glossy,
colored ?lm is
or,
if
a
dye
is
included,
a
and clarity. A more particular object is to pro
vide such a method suitable for treatment of
obtained.
'
_
invention given hereinafter.
To the resulting solution, 196 parts of tributyl
Speci?c embodiments of the invention are il
transparent, solid organic polymers.‘ A further
lustrated in the following examples wherein all
object is to provide‘ solid organic polymers with 45 parts
are by weight unless otherwise speci?ed.
improved scratch resistance and non-tacky sur
Example I
faces. A still further and more speci?c object
is to provide transparent methyl methacrylate
A predominantly n-butanol solution, of poly
polymer with an improved surface characterized
silicic acid partially esteri?ed- with n-butanol is
by its scratch resistance and yet at least equal 50 prepared as follows. An aqueous solution of
polysilicic acid is prepared by adding 900 parts
to the uncoated polymer with respect to clarity
of a 15.5% solution of sodium silicate
and brilliance. A further object is to provide on '
solid organic polymers and the like. glossy, col- '
(SiOa:NasO=3.25:1 by weight)
cred coatings which are highly resistant to chip
ping or cracking with rough usage. Other ob 55 tov860 parts. of'a vigorously stirred solution of
1% sulfuric acid over a period of ten minutes.
jects will be apparent from the description of the
-
The above objects are accomplished according
to the present invention by coating the surface
of a solid organic polymer with a solution com
phosphate and 460 parts of sodium chloride are
added, Stirring is continued for one hour and
60 then the mixture is allowed to stand for one
hour." 'Thefupper,
.3
tributy'l' phosphate layer
2,404,42c
is
silicate.
' separated, centrifuged. and .dried over anhydrous
-_resulting_ clear, tributyl
sulfate.
Heat
' is used-to
.4‘accelerate'
the harden- _ _
‘ing ofthe coating.
.
7
~ .
A portion. of oneside of‘ a. sample ‘of cast _
phosphate solution contains 116.5% $102 as n
' butyl acid polysilicate of a relatively low degree
methyl methacrylate polymer shooting is coated
of esteri?cationr To 1 volume of this solution
are added rapidly and with stirring 1 volume of
methanol and 2.5 volumes of benzene. The
methanol solution of partially esteri?ed P01!
silicic acid ‘which separates as a lower layer when
.the mixture is allowed to stand for ?fteen ‘min
utes contains 50% to 60% combined $102. It
as butyl acid polysilicate. 'I‘his'solution is p'ré
with a butanol solutionrcontaining 10.5% SiO:
pared by the procedure described in Example 1.‘ V
The coating is allowed to 'dry for twenty minutes. 7 v -
Then the sample is baked for ?fteen minutes at
75° C. ‘The resulting coating is clear and much
more resistant to scratching with dryvBon Ami
than is the uncoated surface. However, it is ‘_
isseparated and dissolved-in n-butanol.‘ The
' ?nal solution contains 10.4%810: as n-butyl acid .
polysillcate'oi a relatively low degree of eateri 15
?cation (0.15 to 0.25 butyl ester group per silicon
atom).
_
,
A coating solution is prepared by mixing 25
parts or the n-butyl acid polysilicate solution
tendency to lose 7 -
amoopzc a
This example shows the coating ‘of ‘a methyl’
methacrylate polymer with a tert.-butyl
polysilicate.
' ' prepared as described above with 2.6. parts of a 20
15%’ solution of polyvinyl butyral resin (10% by
~ droxyl) in butanol.
slightly crazed and shows some
adhesion when wet.
The resulting solution con
'
A tert.-butyl alcohol solution: of tert._-butyl° acid .
polysilicate is prepared as follows: An aqueous
solution of polysilicic acidis prepared by adding "
tains combined S10: and'polyvinyl butyral resin
900 parts of a 15.5% solution of sodium silicate . .
in a ratio of 87:13. It is ?owed on a portion
(SiOo:Na-.~O=3.25:1 by weight) to- 860 partsof
of one surface of a sample of each of the poly 25 a vigorously stirred solution of 7% sinfuric acid
meric materials listed below. The sample is held
.over a period of ten minutes.
with the coated surface in a vertical position‘ to
To the resulting ~
solution 200 parts of'tert.~butyl alcohol and 450
permit the excess solution to run oil. The coat
parts of sodium chloride are added and the mix
ing is allowed to dry at room temperature and
ture is stirreduntil the sodium-chloride is dis
is examined after twenty-four hours. The rel 30 solved (about ?ve minutes). The upper, tert.
ative scratch resistance of the coated portion of
butyl alcohol layer, which separates when the
a surface is determined by wiping the whole - mixture is allowed to stand for forty-?ve minutes,
surface several times with cheesecloth on which
is centrifuged to remove occluded water and im
dry Bon Ami, (a cleansing powder commonly used
purities. The resulting clear, tert.-butyl alcohol ..
for cleaning glasssurfaces) , hasmbeen placed, and
solution of tert.-butyl acid polysilicate is dried
comparing qualitatively the numbers and depth
over anhydrous sodium sulfate. Further esteri
of scratches in the coated and uncoated portions
~?cation is effected by azeotropic distillation of
of the surface.
water from the solution, ?rst with tert.-butyl
It was round that the coating on each of the
alcohol at a pressure of 75 mm. of mercury’ and
polymeric materials listed below gave a surface 40 then for about twelve hours with benzene at a
which was markedly superior to the uncoated
pressure of 135 mm. of mercury. Duringthe
surface in resistance to‘ scratching and. in some
distillation the solution is. not heated above
instances, possessed improved slip character
istics;
Cast methyl methacrylate polymer sheeting.
35° C. The ?nal product, ?ltered to remove
sodium chloride which separates on removal of
45 water from the solution, contains 10.3% SiO: as
Viny1 chloride/vinyl acetate interpolyiner ?lm
(95:5).
'
tert.-butyl acid polysilicate.
one side of a sample of cast methyl methacrylate
Vinyl chloride/diethyl fumarate interpolymer
?lm (86:14).
polymer sheeting and allowed to dry for twenty
50 minutes at room temperature._
' Polyvinyl chloride ?lm.
The resulting
clear coating is much more resistant to scratch
Ethylene polymer ?lm.
ing with dry Bon Ami than is the uncoatcd
- Ethylene/vinyl acetate interpolym'er ?lm (8:1).
Polystyrene injection molded bar.
,
.
surface.
Polyvinyl butyrate resin ?lm (10% hydroxyl).
Polyvinyl alcohol ?lm plasticized with 15% 55
glycerol.
Neoprene sheeting.
.
Y
'
v
-
.
Example 4
This example shows the coating of a methyl
methacrylate polymer with a tertgbutyl acid
F
Coated fabric with a topcoat- of unvulcanized
rubber.
.
' The solution is spread thinly on a portion of
>
'
polysilicate prepared from silicon tetrachloride
'
and'tert.-butyl alcohol.
A tert.-butyl alcohol solution of tert.-butyl acid
60
Rubber hydrochloride ?lm
polysilicate is prepared in the following manner.
Av ?lm of an interpolymer obtained by inter» _
To 296 parts of tert.-butyl alcohol 42.5 parts of
polymerization of hexamethylene diammonium .
adipate, hexamethylene diammonium sebacate,
and caprolactam-
'
-
A ?lm of N-methoxymethylpolyhexamethylen
adipamide (10.67% N, 5.85% CHaO).
Cellophane.
‘
‘
.
Ethyle cellulose ?lm plasticized with 11% dibutyl
Dhthalate.
'
'
Cellulose acetate ?lm.
Nitrocellulose?lm.
‘Example 2
This example shows v‘the coating of a methyl
‘ _ methacrylate polymer with a n-butyl acid poly
silicon tetrachloride is added‘over a period of
' ten minutes with stirring and cooling to keep the
65 temperature of the reaction mixture below 30° C.
The mixture is warmed slowly to 65° C.,' where a
vigorous reaction sets in. The tert.-butyl chlo-.
ride, formed in quantitative yield, is distilled from
the reaction mixture together with su?icient tert.
70 butyl alcohol to leave a solution which, after
_ ?ltration, contains 12.0% 81% as tert.-butyl aci
polysilicate.
_
,
-
-
'
A portion of one side of a sample of cast methyl
methacrylate polymer sheeting is wet with the
75 solution, dried, and baked at 100° C. for ?fteen _
,
2,404,428
,
minutes. The resulting clear coating is more
‘
resistant to scratching with dry Bon Ami than
' is the uncoated surface.
This example shows the coating of a methyl
_.
methacrylate polymer with a butyl- polysilicate
?lmirom asolution containing a polymerizable V
Example 5 _
carboxylic acid.
A coating composition is prepared by mixing 10
parts of the n-butyl‘ acid polysilicate solution
described in Example '6 with 1 part of methacrylic
acid, 0.0015 part of lauroyl peroxide, and 0.0015
This example shows the coating of a methyl
methacrylate polymer with an ethyl acid poly
silicate prepared by partial hydrolysis of tetra- ,
ethyl silicate.
,
6
Example 8
i
_
A coating composition is prepared by mixing
10 parts or tetraethyl silicate,‘ 2 parts of water,
part 01' benzoin. The resulting solution is spread
thinly on a portion or one side of a sample of cast
2 parts or ethanol, 15 parts of butanol and a trace
methyl methacrylate polymer sheeting and dried
' or concentrated hydrochloric acid and allowing
for three hours at 75° C. The resulting'clear,
the solution to stand at room temperature for
craze-tree coating is much more scratch resistant
twenty-four hours.
The resulting solution is 15 than isthe uncoated surface. On the other hand,
spread thinly on a portion 01 one side of a sample
a coating prepared from a similar solution con
taining no lauroyl peroxide or benzoin is crazed
of cast methyl methacrylate polymer sheeting.
It is dried in thr‘ee minutes at 75° C. to a clear
and shows less improvement in scratch resistance.
coating which is much more resistant to scratch
Example 9 '
ing with dry Bon Ami than is the uncoated 20
surface.
'
_
.
.
v
Example 6
This example shows the coating 01' a methyl
.
methacrylate polymer with a polyvinyl butyral '
~ resin-modi?ed butyl polysilicate ?lm hardened
,
This example shows the coating of a methyl
under pressure at'a relatively high temperature.
methacrylate polymer with a butylacid poly 25 A coating composition is prepared by mixing
10 parts oi the n-butyl acid polysilicate solution
silicate from a solution containing toluene in
addition to butanol.
_
>
'
described in Example 6 with 1 part of a 15%
A coating composition is prepared by adding 2
solution of a polyvinyl butyral resin (10% hy
parts of toluene to 10 partsof n-butanol solution
droxyl) in ethanol, 1 part of methacrylic acid, and
containing 9.9% 510: as nl-butyl acid polysilicate .80 5 parts of butanol. The ratio of polyvinyl butyral
prepared by the procedure described in Exam
resin to combined SiOa in the resulting solution is
ple l. The resulting solution is spread thinly on
13:87. The solution is spread thinly on a portion
a portion of one side or a sample of cast methyl
of one side of a sample of cast methyl meth
methacrylate polymer sheeting, dried, and baked
acrylate polymer sheeting. After the‘ coating has
. for sixteen hours at 75° C. The clear coating is 35 dried for ?fteen minutes at room temperature,
free of craze and is much more resistant to
it is covered with a smooth glass plate and heated ,
scratching with dry Bon Ami than is the uncoated
for ?ve minutes at 150° C. to 165° C. under a pres
sure of 1000 - lbs/sq. in, The resulting clear,
craze-‘free coating shows unusually good adhesion '
surface.
Example 7
to the methyl methacrylate polymer surface and
‘This example shows the coating of a methyl
methacrylate polymer with a butyl polysilicate
?lm containing a polyvinyl butyral resin and, in
some cases, a carboxylic acid.
,
is much more scratch resistant than is the un
coated surface.
,
Example 10
-
A coating composition is prepared by mixing 45 This example shows the coating of a methyl»
10 parts of the n-butyl acid polysilicate solution
methacrylate polymer with a polyvinyl butyral
described in Example 6, 6.67 parts of a 15% solu
resin modi?ed polysilicate ?lm prepared from
tion of apolyvinyl-butyral resin -(10% hydroxyl)
ethyl silicate.
in ethanol, and 8.1 parts of n-butanol. The ratio A coating composition is prepared by mixing
of polyvinyl butyral resin to combined ‘S10: in the
10 parts of the partially hydrolyzed ethyl silicate
solution is 1:1. A portion of one side of a sample
solution described in Example 5 with 2'parts of a
or cast methyl methacrylate polymer sheeting is
coated with this solution. After forty-three hours
at 75° C., the clear, craze-tree coating shows im
proved resistance to scratching with dry Bon Ami
in comparison with the uncoated surface. When
the ratio of polyvinyl'butyral resin to combined
15% solution of apolyvinyl butyral resin (10%
hydroxyl) in ethanol and'5 parts of butanol.
The ratio of polyvinyl butyral resin to combined'
S102 in the resulting solution is 23:77. A portion
of a sample of cast methyl methacrylate polymer
sheeting is dipped in this solution for one min
810: in the coating solution is lowered to 1 :3 and
ute and'dried at room temperature for ten min
utes. The sample is baked, ?rst at 75° C. for
‘75° C., a clear, craze-free coating is obtained 00 ?ve hours, and then at 100° C. for sixteen hours.
the baking period ‘is reduced to sixteen hours at
which shows a greater improvement in scratch '
The resulting coating is clear and shows improved
resistance. When the ratio or these ingredients
is lowered further to 12.5:87.5 and glacial acetic
acid equivalent to 16.7% of the ?nal coating com
position is added and the baking period is reduced
to one hour at 75° C., a clear, craze-tree coating
is obtained which shows an even greater improve
scratch resistance in comparison with the un
ment in scratch resistance. when the acetic acid '
hyde resin-modi?ed alkyl polysilicate ?lm pre- ,
coated surface.
*
-
.
Example 11
This example shows the coating of a methyl
methacrylate polymer with a phenol-formalde
in the above coating composition is replaceduby
pared from ethyl silicate. '
isobutyric acid and the sheeting is baked for 70 A coating composition is prepared by mixing
10 parts of the partially hydrolyzed ethyl silicate
sixteen hours at ‘70° C., a clear coating is obtained
which shows a still greater improvement in
scratch resistance. However, in the last instance
the coating and the polymer surface are both
a slightly cracked.
solution described in Example 5 with 1 part of a
50% solution '01 a diphenyl-olpropane-formalde
hyde resin in ethanol. ‘The ratio of phenol
78 iormaldehyde resin to combined $10: in the
' 2,404,426
10
‘scratch resistant coatings having more-satisfac
any form including sheet, rod, tube, supported
?lm, unsupported film, .molded article, cast ar
ticle, powder, and the like. 'The clarity and
scratch resistance of the coatings ‘obtainable by
tory weather resistance are ,obtained- when the
coating composition contains partially hydro
lyzed polyvinyl acetate or a hydrolyzed ethyl
ene/vinyl acetate (1:3) inixerpolymer in a ratio of
1 part to from 2 to'6 parts of silica.
the process of this invention are of great advan
tage when the polymers to which the coating are
applied are transparent. ,However, as shown'in
Optimum ,
coating thickness is obtained most conveniently
by use of coating solutions containing from 4%
to 8% solids (silicaplus modifying resin). The
Example 14, excellent glossy colored coatings may
be produced in which case transparency of the
pressing step, when coating polyméthyl meth
base polymer-is not necessarily of especial bene
‘ acrylate, is carried out preferably at from 125° C.
?t. The colored coatings are‘obtained by adding
to 180° C. under a pressure of at least 150 lbs/sq.
a dye to the coating composition. The dye should
in. between highly polished rigid surfaces which
preferably be soluble in the coating solution em
may be of metal or glass.
,
I
ployed, for example, a mixture of alcohol, water
In general the surface characteristics of any or 15 and acetic acid. Du Pont fuchsine, concentrated
ganic"-'polymer can be improved by application
powder, Colour Index 677 is a suitable dye for
thereto of a coating'comprising an organic poly
this purpose.
'
l
silicate from a solution comprising any acid poly
silicic acid ester and a volatile solvent. '
,
I
A solution of an acid polysilicic acid ester in ‘a
solvent may also be advantageously applied to
The term “organic polymer” is used herein to 20 glass. In this instance, the hardness of the sur
include both natural and synthetic polymeric ma
face is not improved but the coating deposited
terials. ‘Organic polymers adapted to be ‘coated
tends to reduce the re?ection of light by the glass
by the Process of this invention include; cuma;
which, in turn, tends to make the glass less visible.
rone resins; indene resins; acetylene polymers,
The application of the colored solutions to glass
including their halogenated derivatives; ole?n 25 is particularly advantageous.
hydrocarbon polymers, including polymers of _
In addition to the acid polysilicic acid esters
ethylene and butadiene and their homologs, and
prepared as described in the examples, acid poly~
halogen substituted derivatives thereof; ole?n
silicic acid esters prepared by any other processes
sulfur dioxide resins; petroleum resins, including
are suitable for use in this invention. These in
resins formed by oxidation of petroleum and 30 clude acid polysilicic acid esters prepared as de
resins formed by reaction of petroleum constitu
scribed in the following references: U. S. Applica
ents with such materials as formaldehyde,
tion Serial N0. 439,549, ?led April 18, 1942, by
methylal, metallic halides, sulfur. and sulfur chlo
Joseph S. Kirk; U. 8. application Serial No.
ride; ‘resinousv halogenated ‘petroleum hydrocar
439,548, filed April 18, 1942, by Ralph K. Iler and
bons; resins from halogenated petroleum hydro 35 Joseph S. Kirk, also assigned to the assignee of
carbons; resins from cracked hydrocarbons; poly
styrene and polymers from styrene derivatives;
the present application; U. S. Patent 1,809,755;
German Patent 568,545 and German, Patent
659,814. Suitable solutions can also be made by
controlled hydrolysis of ethyl silicate.
phenol-aldehyde resins; aldehyde resins; furufral
resins; ketone’ resins; urea-formaldehyde type
resins, including thioureai’ormaldehyde, mel 40 The formation of a hard, adherent polysilicate
amine-formaldehyde, and dicyandiamide-formal
?lm appears to depend in large part on the ability
dehyde resins; amine-aldehyde resins; sulfonaé
of acid polysilicic acid esters to polymerize fur
mide-aldehyde resins; nitro, resins; resins from
ther until a highly polymeric structure results.
such nitrogen-containing materials as hydrazine '
Therefore it is preferable that the polysilicic acid
and related substances, pyrazoles, pyridine, quin 45 ester contain free silicic acid hydroxyl groups,
oline. pyrrole, indole, and carbazole; resins from
‘wood and from carbohydrates; natural resins and
which make possible the formation of high poly
mers through condensation. It may be desirable
their esters, including rosin, shellac, and ester
in some cases to prepare the acid polysilicic acid‘
gum; condensation polyester resins, including
ester from a neutral polysilicic acid ester in situ
resins obtained from polyhydric alcohols and 60 by adding a suitable amount of water and a hy
polybasic acids, and from hydroxy-acids; poly
drolysis catalyst such as a strong mineral acid to
amide resins and derivatives thereof; mixed
the ester solution just beforev application.
polyester-polyamide resins; polyether resins;
The acid polysilicic acid esters may vary in
polyvinyl ethers; polyvinyl alcohols; polyvinyl
molecular weight from esters containing only two
esters, including esters of inorganic‘ acids; poly 55 silicon atoms per molecule to those whose mole
vinyl acetals; polyacrylic acids, anhydrides, esters, '
cules are of colloidal dimensions and whose sols
amides, and homologs thereof; rubber and its de
are approaching the gel state. In general, esters
rivatives, including rubber hydrochloride and hal
of relatively low molecular weight are preferred
ogenated. rubber; condensation resins from halo
since they areimore soluble and more compatible
genated compounds; olefin-sul?de resins such as 60 with organic materials than are the relatively
the reaction product of ethylene dichloride and
high molecular weight esters.
alkali polysul?de; phenol-sulfur and phenol-sul
The acid polysilicic acid esters may vary also
fur chloride resins; sulfur-aromatic amine resins;
in the ratio of silicic acid ester groups to silicon
»
factice; drying oil'resins; cellulose and its deriva- - atoms from 0.01:1 or less to 2:1. Although the
‘ tives, including ‘Cellophane, cellulose esters, and 65 solubility of the ester inorganicsolvents and its .
cellulose ethers; and proteins such as casein, zein,
soybean protein, and leather. These may be mod
i?ed with any of the usual modifying agents in- '
compatibility with organic polymers increase with
increase in degree of esteri?cation of the poly
silicic acid, the ester tends to polymerize more
eluding plasticizers, pigments, ?llers, dyes, and , readily‘at lower temperatures and in a shorter
materials which combine chemically with the 70 time (i. e., it forms a tack-free, hard film under .
polymer ingredients either during formation of
the polymeror during an after treatment. Thus,
copolymers, interpolymers, and mixtures of poly
milder conditions) as the degree of esteri?cation
,is' decreased. In general, the hardness of the
coating obtained from an acid polysilicic~acid
mers can advantageously be coated by the process
ester solution decreases with increase in the de
of this invention. The organic polymer may be in 75 gree of esteri?cation of the polysilicic acid. As
2,404,420
11
12
illustrated by the, above‘ examples, a butyl acid
polysilicate in which the ratio of butyl groups to
silicon atoms is 0.2:1 forms a hard, scratch re
sistant coating merely on drying at room tem
.
in the acid polysilicic acid ester solution a liquid
which will soften, or even better, dissolve the sur
face polymer. Improved anchorage of the highly
perature. As the ratio of butyl silicate groups to '
polymeric silicic acid ester coating to the polymer
surface is-bften obtained in this way. Organic
silicon atoms increases to 05:1 the ?lm obtained
polymers vary widely, of course, in their solubili
becomes softer; when the ratio reaches 0.821, the
filmiwithout modi?cation) remains tacky; and
‘ing agents are well known to those who are at all"
ties, but in most cases suitable solvents or swell-.
when it is 1:1 or greater, the ?lm obtained re
familiar with the resin ?eld. In many cases a
mains oily‘unless suitably modi?ed. The pre
mixture of solvents including both a relatively
volatile liquid and a less volatile solvent for the
organic polymer is preferable. Acid polysilicic,
acid ester and organic polymer solvents useful in
ferred ratio of silicic acid ester groups to silicon
" atoms, depends, of course, on the nature of the‘
ester group, the nature of the polymer surface to
be coated, and the characteristics desired in the
this application includealcohols, ketones, esters
coating. Acid polysilicic acid esters in which the 15 of organic or inorganic acids, ethers, amides, and
ratio of silicic acid ester groups to silicon atoms
acids. In ~general, it is preferable to include in
‘ varies from 0.1:1 to 1:1 include those useful in.
the solvent composition at least 20% of an alco
most polymer-coating applications. -Butyl acid
hol of they group consisting of ethyl, propyl, and
polysilicates containing from 0.1. to.0.3 butyl sili
butyl alcohols. In the coating of methyl meth
cate groups per silicon atom and ethyl acid poly 20 acrylate polymer good adhesion of the polysilicate
‘ silicates containing from 0.1 to 0.7 ethyl silicate
?lm to the polymer, particularly'lon immersion
‘ groups per silicon atom are among the preferred
in water, is promoted by including in the solvent
polysilicic acid esters for use in improving the
composition 1 to 50% of a carboxylic acid con
scratch resistance of polymeric materials. The
taining 2, 3, 4, or 5 carbon atoms per molecule.
optimum degree of esteri?cation for each partic
Amines are not ordinarily suitable as constituents
ular application can readily be determined by a
of the coating composition since they cause rapid
few preliminary tests.
.
gelation of acid polysilicicacid esters.
The alcohol from which the acid polysilicicvacid
In many cases the desired change in surface
characteristics can be obtained more satisfac
tertiary, aliphatic or aromatic, cyclic or alicyclic, 80 torily if a suitable organic polymer is included in
‘ ester is derived may be primary, secondary, or
‘ mono- or polyhydric, saturated or unsaturated,
and straight chain or branched chain. It may
contain additional functional groups provided
such groups do not a?ect the stability of the ester.
the coating composition. In general, the hard- '
ness and scratchresistance ofthe resulting coat
ing are intermediate between those of the modi
fying polymer and. an unmodified polysilicate'
I Suitable fimctional groups include ether, halide, 35 coating. The modifying polymer must be soluble
‘ ‘mercaptan, sul?de, ketone, ester, amide, nitro,
in the solvent composition used and is preferably
compatible with the acid polysilicic acid ester
both in the coating solution and in the solvent
‘ perior to unsubstituted esters in solubility in cer
free ?lm. The compatibility of a particular or
tain organic solvents and compatibility with cer 40 ganic polymer with an acid polysilicic acid ester
1 tain polymers. The alcohol from which the acid
depends, as indicated'above, on the ratio of silicic
‘
In some cases acid polysilicic
acid esters containing such groups may be‘ su
and nitrile groups.
‘ polysilicic acid ester is derived may vary in chain
length from 1 to 12 or more carbon atoms.
‘ In general the solubility of acid polysilicic acid
acid ester groups to silicon atoms, the nature of '
the esterifying group, and the molecular weight
of the acid polysilicic acid ester. The choice of
esters in solvents in which the ratio of carbon to 45 modifying polymer and ratio of modifying poly
oxygen is high (e. g., long-chain alcohols and
mer to acid polysilicic acid ester in the coating
esters, hydrocarbons, and halogenated hydrocar
composition depends in each case on the polymer
. bons), the compatibility of acid polysilicic acid
which is being coated, the acid polysilicic acid
1 esters with polymeric materials in which the ratio
ester being used, and the characteristics desired
‘ of carbon to omgen is high, and the softness of 50 in the coating. The modifying polymer content
coatings obtained from these esters appear to in
. crease with increase in the ratio of carbon to
silicon in the acid polysilicic acid ester. Thus,
of the coating composition solids may vary from
5% or less to 90% or more. In order to take fuller
advantage‘ of the effect of the polysilicate, the
modifying polymer content of the coating com-_
to silicon atoms, the preference as to which par-' 65 position ‘solids is- usually limited to 50% ‘and in
ticular acid polysilicic acid ester to use in a given
many cases the best results are obtained by- using"
‘ given a de?nite ratio of silicic acid ester groups
7 ‘
application depends on the polymer to be coated ' 30% or less.
‘
and the characteristics desired in the coating.
A polymer which is insoluble in the preferred
‘ In the coating of methyl methacrylate polymer
acid polysilicic acid ester solvents when com
to improve its 'scratch resistance, acid polysilicic 60 pletely polymerized may often advantageously be
. acid esters derived from alcohols containing less
than six carbon atoms per molecule are preferred.
Coatings with improved scratch resistance can be
I obtained from longer chain esters of very low de
, gree of esteri?cation.' However, the lower stabil
. ity of such esters detracts from their utility.
The choice of the solvent from which the acid ' polysilicic acid ester is applied depends on a
1 number of variables.
One is the solubility of the
acid polysilicic acid ester, which varies, as pointed _
out above, with degree of esteri?cation, nature of
esterifying group, and molecular weight. The
‘ ester should, of course, be soluble in the solvent
added to the coating composition while it is in- '
completely polymerized and still soluble, and then
polymerized further after application of the coat
ing composition. Examples ofv polymers which
are preferably used in this manner are urea
formaldehyde and phenol-aldehyde type poly- '
mers. In some cases it is preferable to add the
ingredients of the modifying polymer and a suit
able polymerization catalyst to the coating com
position and carry out the polymerization either
in the coating composition before application,
during the evaporation of the solvent from the .
?lm, or in the solvent-free ?lm. For example,
used. Another variable is the solubility of the ‘ ‘monomeric or partially polymerized methyl
polymer being coated. It is preferable to include 75 methacrylate can be used in this manner. It is V
2,404,426
I
13
.
probable that in some cases copolymer-s involving
both the acid polysilicic acid ester and the modi
fying polymer are formed.
Some of the advantages of including an organic
polymer in the coating composition are brought
out in the above examples which illustrate the
application of polysilicate coatings containing
organic polymers to methyl methacrylate poly
mer sheeting to form a more scratch resistant
14 'i
give cracked surfaces when high temperature cur-'
ing of the coatings is ‘attempted. It has now
been discovered that high temperature curing of
acid polysilicic acid ester containing coatings can
be performed successfully on the vinyl polymers
if the polymer is modified by copolymerization
with a relatively small amount of bifunctional or
p'olyfunctional cross linking agent.’ For example,
the addition of '7 parts of methacrylic anhydride
surface. \In this application a polyvinyl butyral 10 to 93 parts of methyl methacrylate in a casting
resin is particularly useful. This resin decreases
syrup will yield a high softening Point cast sheet
the tendency of the coating to crack or craze
resistant to cracking during the curing of coat- .
and improves its ?exibility, adhesion to the poly
ings at unusually high temperatures around 150°
mer surface, resistance to deterioration on im
C. In the case of styrene, a copolymer with
mersion in water, and outdoor durability.
15 2%-4%, by weight of the copolymer, of meth-'
It may in some cases be desirable to pretreat
acrylic anhydride is more'suitable than unmodi
the polymer surface which is to be coated. Thus
fled polystyrene as a base material for the high"
it may be softened or even made tacky by use
temperature curing of the coatings.
of a solvent or swelling agent before the coating
In some cases improved adhesion of me poly
composition is applied. Such pretreatment assists 20 silicate coating to the surface of the organic
penetration of the acid polysilicic acid ester into
polymer can be obtained by placing a smooth
the polymer surface and leads to formation of a
more [adherent coating.
The acid polysilicic acid ester coating compo
' plate, such. as a piece of plate glass. over the
coating after evaporation of the volatile solvent
and pressing the plate-against the surface dur
sition may be applied in any suitable manner, 25 ing the heating step. This technique permits
use‘ of higher baking'temperatures (up to 200° C.
or using a doctor knife or applicator roll. Its
or 250° C.) without deformation of the polyme
viscosity can be adjusted to suit the method of
surface.
'
application by varying the solids content of the
There is evidence indicating that when the
solution. The thickness of the film of ester, modi 30 modifying organic polymer in the coating solu
fying polymer, and non-volatile solvent for the
tition contains free alcohol hydroxyl groups, re
such as by spraying, dipping, brushing, ?owing,
polymer being coated‘ can be varied by varying
action takes place ‘during baking between the,
the proportion of volatile solvent and by varying
the thickness of the ?lm of coating solution ap
polymer and the acid polysilicic acid ester. The
‘ness. It may vary from 0.5% or less to 60% or
orester interchange _(reaction between an alco
hol hydroxyl group of the polymer and a silicic
reaction probably involves either direct esteri?
plied. Thus the solids content of the coating solu 35 cation (reaction between an alcoh'ol hydroxyl
tion is governed by the method of application to
group of the polymer and a silicic acid hydroxyl
the polymer surface and the desired film thick
group with formation of_ a molecule of water)
more.
After application of the coating solution to the 40 acid ester group with formation of a molecule
polymer surface, the volatile solvent is allowed to
of the alcohol from which the silicic acid ester
evaporate. The time required for the evaporation
is derived). A crossllnking reaction of this type
depends, of course, on several factors including
could conceivably take place between an acid
the volatility of the solvent, temperature, the cir
polysilicic acid ester and any organic polymers
culation of air over the polymer surface, the
which ordinarily contain free alcohol-hydroxyl
thiclmess oi’ the coating applied, and the nature
groups, such as polyvinyl alcohols, polyvinyl ace
of the modifying polymer in the solution. The
tals, cellulose ethers and esters, nitrocellulose,
‘rate of polymerization of acid polysilicic acid
condensation polyesters, and any other types
of polymers prepared from ingredients contain
esters increases as the concentration of ester in
creases. Accordingly, as solvent evaporates from 60 ing free alcohol hydroxyl groups not involved in
the coating the acid polysilicic acid ester poly
formation of ‘the polymer. The e?ect of this
reaction is to reduce the solubility of the modify
merizes more and more rapidly. The rate of
ing polymer and increase the hardness of the
polymerization increases also with‘ risev in tem
?lm obtained. Usually, particularly when the
perature. Thus, while it may take several hours
for. an acid polysilicicacid ester in which the 55 degree of esteri?cation of the acidpolysilicic acid
ester is relatively high and the alcohol from
ratio of silicic acid ester groups to silicon atoms
which the ester is derived has a boiling point
is low (0.25 or less to 1) to polymerize to a hard,
above about 80° 0., it is necessary to bake the
scratch resistant ?lm at room temperature, poly
film at temperatures of 80° C. to 200° C.‘ for ?f
merization is usually relatively complete within
a few minutes at higher temperatures (100° C. 60 teen minutes to two hours-to promote the cross
linking reaction to the fullest extent. It is pos
to 150° (3.). A curing period of one minute to
sible that a reaction of this type is involved ‘in
twenty-four hours at temperatures varying from
25° C. to 150°‘ C. is normally 'su?icient to produce _'the formation of a strong bond between a poly;
silicate coating and, the surface of a polymer
the desired e?ect.
'
,
\
In addition to increasing the rate of polymer 65 which contains alcoh‘ol hydroxyl groups.
The extent to which an acid polysilicic acid
ization, it has been found that the scratch re-.
ester polymerizes on heating depends on the ex
sistance and exposure resistance of acid polysilicic
tent to which it is esterifled (the ratio of silicic
acid esters-hydroxylated organic polymer coat
acid ester groups to silicon atoms). If, as pointed
ings baked on plastics increases appreciably with
increasing curing temperatures. However, the 70 out above, the degree of esteri?cation is low, the
?lm obtained is usually very hard and the hard
temperature at wl'iichthe coatings canbe baked
is limited by the softening temperature .of the ' ness decreases as the degree of esteriflcation in-‘
polymer being coated. This is‘ especially true of
creases. The silicic acid esters of lower alcohols,v
the thermoplastic resins such as methyl'methi
such as methanol or ethanol, are more easily
acrylate polymer and polystyrene which tend to 76 hydrolyzed by moisture in the atmosphere than
1's
2,404,426
16
‘ are the esters of high'er alcohols, such as butanol
ing from‘ 1 to 12 carbon atoms, inclusive, said
‘ or octanol. Therefore, the extent of polymeriza
. tion during drying, baking, or subsequent aging
‘ increases more in the cases of the methyl and
ester having from .01 to 2.0 silicic acid ester
groups per silicon atom, and an organic solvent -'
for said polymer whose surface is being coated.
5. A solid organic polymer having, a surface
ethyl esters than with the higher esters wh'en
?lm thereon obtained by coating a surface of
the polymer with a, coating solution comprising.
an acid polysilicic acid ester of an alcohol'con-v
‘ these operations are carried out in an atmos
phere containing appreciable amounts of mois
ture. , Since amines accelerate both hydrolysis of
taining from 1 to 12 carbon atoms, inclusive, said
ester having, from .01 to 2.0 silicic acid ester
groups per silicon atom, an organic polymeric
polysilicate coating may be promoted by carrying
material compatible with said ester in the sol
out the drying, baking, or aging operations in a
vent-free ?lm, and'an organic solvent for said
moist atmosphere containing an amine such as
polymer whose surface is being coated.
‘ ammonia or by ?ushing the dry, coated surface
6. A solid organic polymer having a surface
, with an aqueous solution of an amine.
15
?lm thereon obtained by coating a surface of the
Through use of this invention the surface
polymer with a coating solution comprising an
characteristics of solid organic polymeric ma
acid polysilicic acid ester of an alcohol contain~
terials are changed to enhance the utility of the '
polymeric materials in a given application- The
ing from 1 to 12 carbon atoms, inclusive, said
invention is particularly useful‘ for improving 20 ester having from .01 to 2.0 silicic acid ester
silicicacid esters and polymerization of silicic
acid, rapid formation of a 1118b]! polymerized
‘ th'e serviceability of transparent plastic mate- -
groups per silicon atom, and a polymer contain
" rials through application to the surface of the - - ing hydroxyl groups, dissolved in a volatile or
ganic solvent.
, plastic a clear, transparent coating which is more
7. A' transparent, solid organic polymer from
‘ resistant to marring and scratching than is the
‘ uncoated surface. .The invention is also useful .25 the group consisting of poiyacrylic esters and
:polymethylacrylic’ esters, having a surface ?lm
for decreasing the tackiness of polymer surfaces, .
, thereon obtained by coating a surface of the
polymer with an acid polysilicic acid ester of an
the tendency of polymer surfaces to collect dust,
alcoholcontaining from 1 to 12 carbon atoms,
I and decreasing the re?ection, of light from the
surfaces of transparent plastic materials. Fur 80 inclusive, said ester containing from 0.1 to 1.0
ther, the invention is adapted to provide glossy.
silicic‘ acid ester groups per silicon atom, dis
solved in a volatile organic solvent.
'
colored coatings, both scratch resistant and ex
8. Process of providing a solid organic polymer
posure ' sistant, on organic polymeric materials
1 and on glass.
with’ improved‘ surface characteristics which
comprises coating a surface of the polymer with
Plastics coated in accordance with this inven
‘ particularly at elevated temperatures, decreasing
tion show a reduced tendency to acquire a static
charge and, therefore, are highly useful in en
closing and panelling instruments subject to stat
an acid polysilicic acid ester of an alcohol con
taining from 1 to 12 carbon atoms, inclusive, said
ester having from .01 to 2.0 silicic acid ester
ic aberration, for example, galvanometers, volt
groups per silicon atom, dissolved in a volatile
.
meters, aircraft instruments, and the like.
40 organic solvent and drying said coating.
As many apparently widely different embodi
-9. Process of providing a solid organic polymer
I ments of this invention may be made without de- . with improved surface characteristics which
‘ parting from the spirit and scope thereof, it is
comprises coating 9. surface of the polymer with
to be understood that the invention is not limited
an acid polysilicic acid ester of an alcohol con
to the speci?c embodiments thereof except as
taining from 1 to 12 carbon atoms, inclusive,
defined in the appended claims.
,
said ester having from .01 to 2.0 silicic acid ester
' .
groups per silicon atom, dissolved in a volatile
1. A solid organic poLvmer having a surface
organic solvent, drying said coating at approxi- ..
?lm thereon obtained by coating 0. surface of the
mately room temperature and, thereafter, bak
polymer with an acid polysilicic acid ester of an 60 ing said coating at an elevated temperature.
alcohol containing from 1 to 12 carbon atoms,
10. Process of providing a solid organic poly‘- .
inclusive, said ester having from .01 to 2.0 silicic
me'r with‘ improved surface characteristics which
acid ester groups per silicon atom, dissolved in
comprises coating a surface of the polymerv with '
a volatile organic solvent.
a butyl acid polysilicate containing from 0.1 to
2. A transparent, solid organic polymer hav 55 0.3 butyl silicate groups per silicon atom, dis
We claim:
‘ ing a. surface ?lm thereon obtained by coating
solved in a volatile organic solvent, drying said .
a, surface of the polymer with a butyl acid poly
silicate containing from 0.1 to 0.3 butyl silicate
groups per silicon atom, dissolved in a volatile
‘
organic solvent.
-
-
.
_ 3. A transparent, solid organic polymerhav
ing a surface iilm thereon obtained by coating a
surface of the polymer with a coating solution
coating at approximately room temperature and,
thereafter, baking said coating at an elevated
temperature not\in excess of the softening point
60 of said polymer.. '
comprising an acid‘ polysilicic acid ester of an a
11. Process of providing a solid organic polymer with improved surface characteristics which
comprises coating a surface of the polymer, with
a coating solution comprising an acid polysilicic
0 alcohol containing from 1 to 12 carbon atoms, 65 acid ester of an alcohol containing from 1 to 12
inclusive, said ester having from .01 to 2.0 silicic
, acid ester groups per- silicon atom, and an or-,
‘ ganic polymeric materialcompatible with said
‘ ester in the solvent-free ?lm, dissolved in a vola
carbon atoms, inclusive, said ester having from
, .01 to 2.0 silicic acid ester groups per silicon
atom, a polymer containing hydroxyl groups, and
a volatile organic solvent, drying said coating at
tile organic solvent. ' '
‘
70 approximately room temperature and, there
4. Asolid organic polymer having a surface
after, baking said coating at an elevated tempera
‘ ?lm thereon obtained by coating a surface of the
polymer with a coating solution comprising an
acid polysilicic acid ester of an alcohol contain
ture.
-
MAX FY'REDRICK BECH'I'OLD.
PAUL SWITHIN PINKNEY.
17
I
c
'18
v Certi?cate of Correction
Patent No. 2,404,426.
,
MAX FREDRIOK BEOHTOLD
v
July 23, 1946.
‘It is hereby certi?ed that errors appear in the printed speci?cation of the above
numbered patent requiring correction as follows: Column 8, line 43, after “hydro—
lyzed” insert high; column 9, line 38, for “furufral” read furfaml; column '14, line 31,
for the syllable “tition" read tion; and that the said Letters Patent should be read with
these corrections therein that same may conform to the record of the case in the
Patent O?‘ice.
Signed and sealed this 8th day of October, A. D. 1946.
[mm]
' LESLIE FRAZER.
.
First Assistant Commissioner of Pateiits.
Certi?cate of Correction
Patent No. 2,404,426.
,
_
'
July 23, 1946.
MAX FREDRICK BEOHTOLD ET AL.
It is hereby certi?ed that error appears in the printed speci?cation of the above
numbered patent requiring correction'as follows: Column 7, line 24, Example 12,
for “alkyl” read alkyd; and that the said Letters Patent should be read with this
cogection therein that the same may conform to the record of the case in the Patent
ce.
'
Signed and sealed this 13th day bf May, A. D. 1947.
[mm]
LESLIE FRAZER.
, First Assistant Commissioner of Patents.
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