CA1056665A - Method for rendering substrates resistant to abrasion - Google Patents

Abstract

ABSTRACT

Coating comprising the reaction product of ambifunctional silanes and organic esters of titanium, aluminum or zirconium are solvent and abrasion resistant and can be readily applied to soft surfaces as a protective coating.

Description

It is advantageous to protect soft surfaces against abrasion by applying a protective coating to the soft surface. This application relates to new and improved abras:ion resistant coatings made from ambif~mctional silanes.
Much prior art is available in the area of abrasion resistant coatings, but the most relevant art found has been ~nited States Patents 3,687,882; 3,637,416; 3,642,681; 3,708,225; 3,460,956; 3,762,981; and

2,768,909; and Japanese Patent No. 49-117529, issued November 9, 1974~ The present invention overcomes some deficiencies of the prior art and displays 10 a high degree of abrasion resistance, little lprocessing (especially no ~ :
requirement for hydrolysis of substituents), moderate curing temperatures, good corrosion and solvent resistance and exhibit low surface energy to which foreign particles do not readily adhereO
The coatings are applicable to any soft or damageable surface including plastics, natural materials, metals, ceramics and glass.
The process aspect of the present invention is the protection of a substrate by applying to said substrate a thin coating of a composition : ~;
comprising: ~
(1) an epoxy~silane, methacryloxy-silane and/or vinyl silane, and ~:
(2) a metal ester selected from the group comprising aluminum, titanium or zirconium having at least two ester groups of the formula -OR directly bounded to the metal wherein R is ;~
hydrocarbyl of 1 to 18 carbon atoms, and more preferably alkyl ` or acyl of 1 to 8 carbon atoms. The;remaining valences of . the metal may be satisfied by organic moieties, inorganic moieties, complexing agents or even repeating -O-Tl-O- groups, .~ etc~ ~Preferably, if OR groups are not used, halides or alkyl groups are used). As long as two of the ester groups are present, the metal ester.can react into the final poly-meric structure to form an abrasion resistant coating, and curing said composition :...

The present invention also provides a solvent resistant, abrasion resistant film col~rising the reclc-tion product of (a) applying to said substrate a composition consisting of:
Il) a metal ester selected from ~he group comprising titanium aluminum or zirconium; having at least two ester groups of the formula -OR
bonded to the metal and wherein R is hydrocarbyl of 1 to 18 carbon atoms; and ~ 2) a reactive silane selected from epoxy-silanes, methac~yloxy~
silanes and/or vinyl-silanes; and ~b) a reactive silane selected from epoxy-silanes, methacryloxy-silanes and/or vinyl-sil~nes.
It is generally preferred ~hat all valences of the metal are satisfied by ester groupsJ but the other groups may be present so long as at lea~st two ester groups are present. Compounds of the formula RtM~OR)m n are therefore useful, wherein R is as defined above, m is the valence of M
and n is 0, 1, or 2 such that m-n is always a~ leas~ 2; and R' is an organic or inorganic moiety bonded to M or a complexing agent satisfying the valence requirements of M. Compounds of the ~ormula M(OR~m are generally preferred because of availability and generally improved characteristics. Examples of these preferred compounds are tetraisopropyl titanate, tetrabutyl titanate, tetra-2-ethylhexyl titanate, tetraethyl titanate, aluminum isopropoxide, aluminum n-butoxide~ and tetraisopropyl titanate, It is critical that the metal ester not be hydrolyzed completely or hydrolyzed to a condition where less than two ester groups per titanium atom are present on the metal ester. If the metal ester is so hydrolyzed~

the ambifunctionalsil~ne and the metal ester will coprecipitate into A 2~

. ~

an inso:Lublt? mate~laL becallse reactive sites f`or the sllane on the ester havebeerl renlovecl.
The preserlt coat;ing compositions are prepared simply b,y the admixing or blendlrlg of the metal ester and ambi-functional silane at room temperature (e.g., 25C.) andallowing the materials to react. Other additives such as leveling agents, colorants and viscos:lty modifiers may be included by mixing ~hem with the ester and silane. Typically, ; the coating composition is filtered through a 10 micron filter before application.
It is pref'erred that the reactants in the coating compositions not be hydrolyzed. Although reactants which are partially hydrolyzed can be used, the amount of water which may be present in the compositions must not be more than one-half equivalent per equivalent of metal ester. For example, use of water over this amount in compositions con-taining titanium ester results in formation of titanium dioxide which readily precipitates out of the composition.
Another disadvantage with the use of hydrolyzed reactant is that an additional step is required in the preparation of the coating compositions. Furthermore, hydrolyzed reactants do not possess the desirable shelf stability exhibited by unhydrolyzed reactants.
Reactive silanes useful in the practice of the present invention include those represented by the following ~formula:

'' CRl ] Si - [R2 wherein R is selected from a vinyl group, ~ 3 ~

:,~. '- ' , . .

C112 = C~l -a methacryloxy gro~lp, CH2 = C - C - 0 - R3 -or an epoxy group, O~ r CH2 - CH - R m ~ or L ~ ( m) ~
wherein R3 is an alkylene group of 1 to 8 carbon atoms~ ancl R4 i5 hydrogen or hydrocarbyl radical of 1 to 8 carbon atoms (preferably alkyl) and R5 =
divalent hydrocarbon radical (aliphatic, aromatic, or aliphatic and aromatic containing) of less than 20 carbon atoms or a divalent radical of less than 20 carbon atoms composed of C, H, N, S, and 0 atoms (these atoms are the only atoms which may appear in the backbone of the divalent radicals), the last being in the form of ether linkages. No two hetero atoms may be adjacent within the backbone of the divalent hydrocarbon radical. The value of m is 1, 2 or 3 and n is 0 or 1. R2 is an oxyhydrocarbyl group, preferably alkoxy, acyl, or acetoxy, having 1 to 8 carbon atoms or a radical of formula (CH2CH20)kZ in which k is an integer of at least 1 and Z is an aliphatic hydrocarbon radical of less than 10 carbon atoms or hydrogen. An oxyhydro-carbyl group is a hydrocarbon group or hydrocarbon group having no more than one heteroatom in the backbone selected from N, S, and 0 for every two carbon atoms in the backbone, ~herein a hydrogen attached to a carbon atom has been replaced with ~,;
~.

~3~

a cllvalent oxygen atom to E`orm an external boncl.
For example, starting wlth CH3CH2OCH3, the oxyhydro-carbyl der:lvcltives itlC lude -O-CH2CH2()CH3. Exemplary hydrocarbyl groups incLude aromatic gr-oups (e.g~, phenyl, naphthyl and benzothienyl~ and aliphat:Lc groups (linear~ branched, or cyclic) lncluding cyclohexyl, tetrahydrofuryl, dioxanyl, peperidyl, pyrolidinyl, ethoxyethoxy ethyl, etc.) Preferably, this oxyhydrocarbyl group has 1 to 10 carbon atoms.
Examples of useful silanes are vinyltriethoxy silanes, vinyltris(2-methoxyethoxy) silane, vinyltriacetoxysilane, gamma-methacryloxy-propyltrimethoxy silane, beta-(3,4, epoxycyclohexyl) ethyltrimethoxy silane and gamma-glycldoxy-propyltrimethoxy silane. Other useful silanes of this type 15 are known to the art. Combinations of these silanes or ~-additions to these silanes of compounds copolymerizable with either functional group of the reactant (silane, epoxy, vinyl or methacryloxy) is anticipated in the practice of this inven-tion.
It has been found that the molar ratios of the metal ester to the reative silane may be varied depending upon the coating system chosen. For example, in the compositions con~
taining the titanium ester and an epoxy-functional silane, the molar ratio of metal ester to silane may vary rrom about 1:0.5 to about 1:7 with the most preferred ratio being 1:4.
In compositions containing the titanium ester and acryloxy-functional silane, the molar ratio may vary from ~ about 1:3 to about 1:15, while the pre~erred molar rat;io :

:;;.~: i : , ~ ........................ . .
: . ': - . ' ' -ma~/ vary ~`rom about, 1:3 t,o about, :I:7 w:lt;h the most pref'errecl rat;io belng ahout, I:ll~ W:ith the compositlons contalnln~
the tltanium ester ancl vinyl-furlcti.onal silane, the useful molar rat:io of metal ester to s.ilane ls about 1:4~ Other molar ratios of metal ester to reactive s:Llanes are given : in Table I.

, :~ . . , . - , . .

ABI,E' I

Molar Ratio _ Metal F:,ster to R active Silene Most Coating PreferredPreferred _ _O ~ tion ___ _Usef`ul Range _Ran~ atio Al-ester/epoxy- 1:1 to 1:5 ]:2 to :L:51:4 functional silane A1-ester/acryloxy- 1:1 to 1:101:2 to 1:5 1:4 10 functional silane Zr-ester/epoxy- 1:3.5 to 1:4.5 1:4 1:4 functional silane Zr-ester/acryloxy- 1:3.5 to 1:4.5 1:4 1:4 functional silane Various ingredients rnay be incorporated into the coating compositions, if desired. For example, pigments or dyes may be incorporated in order to provlded a co~ored coating. Solvents may be added to the coating cornposition in order to facilitate the addition of solid metal esters.
Solvents, or other viscosity modifiers, may also be added to ad~ust the viscosity of the uncured composition. Various conventional leveling agents may also be added to the coating composition. These may be useful in producing a high quality optical grade coating. Furthermore, various accelerators may be added to the cornpositions in order to speed the curing process. Fillers and polymeric modifiers may be added.
In order to reduce the viscosity of the coating compositions in the practice of the invention there may be added solvents such as the lower alcohols, lower carboxy1ic .. ,,:~ ,. . , , ~: .

acids, halogenated hydlocarbon solvents, and aromatlc solvents.
These inclucle ethanol, methanol, tert-butanol~ chloroform, methy:lene chlor:ide, ace~ic acld, toluene, ben~ene, xylene, trichloroethane, 1,2-dlchloroethane, etc. Other useful 801 `
vents of the type described are known to t;he art. The amount of solvent added is dependent upon the particular metal ester used and the coating viscosity desirecl.
In order to increase the v:Lscosity of the coatlng compositions there may be added oligomerized siIane in an amount ranging from 1-20% by weight of said composition. For example, gamma-methacryloxypropyl-trimethoxysilane which is prepolymerized by a Pree radical mechanism at 100C~ for about 20 minutes and diluted to a 50% solution in ethyl alcohol is .
useful in increasing the viscosity of the coating composition by addition thereto.
Leveling agents are also useful in the practice of the invention in that they level ridges formed in the coating durlng the coating process. Leveling agents which have been found useful in the practice of the present invention include "SF-1023"~, a silicon based surfactant available from General Electrlc; "FC-430'i* and "FC-431"*, fluorocarbon~
based surfactants available from Minnesota Mining and Manufacturing Co., etc. Preferably these leveling agents are present at about 0.3 weight percent of the coating solution, although more or less may be used if desired. A
preferred leveling agent is 'ISF-1023"*.
l'he coating compositions used in this invention may be applied to a wide variety of substrates to impart *trademark , abrasion resl~tance, ;olverlt resLt3tan(e, corros:lon reslstance and to irnpart -release charclcterlst;icc, to the surface. In general, the type of` subst;rates that may be coated ln accordance with -~ s inventlon include rigid and flexible substrates such as: plastlcs, glass, metal and cerarnics.
For example, soft substrates such as plastics can be rendered very mar and abrasion resistant ~y the practice of this invention. Representative examples include: lenses used in ophthalmic spectacles, sunglasses, optical instruments, illuminators, watch crystals and the like; plastic window glazing; signs and decorative surfaces. Metal surfaces can be rendered resistant to corrosion by the practice of this invention whereby the brilliance of polish may be maintained on decorative metal strips and front surface mirrors.
Further, the coating can be colored and be applied to sur~
faces as a paint.
Those substrates to which the coatings of the invention do not exhibit exce:llent na-tural adhesion may nevertheless be readily coated in accordance with this invention, with resultant excellent adhesion thereto, by first modifying the surface thereof Such modlfying ~echniques include roughening of the surface (e.g., by mechanical means, by solvent, by chemical etching, oxida-tion, etc.), and by application to such surface of a con-ventional priming agents.
The coatings of the present invention may beapplied to a substrate in any desired thickness. It has been found that coatings Gf between about 3 and 5 microns - 9 ~

of~er exceLlent l~)r~asion reslstarlce. Mowever, thicker coatlngs (e.g., up to 20 micl-ons or more) may be obtained by applying successive layers of the coatlng to the substrate.
Thls may be done by applying a layer of the coating composi-tion to the substrate and then partially curing lt, forexample, by heating it for about one minute at about 75C.
A second layer of the coating may then be applied. This procedure may be repeated until the desired coating thickness is attained. These multiple coatings offer much higher resistance to abrasion than do single coatings.
Various methods may be employed to cure the coatings of the present invention. For example, they may be cured by heat, exposure to ultraviolet light, or exposure to electron beam radiation. The particular method used is dependent upon the coating being applied, and the substrate being coated.
All of the coating compositions will cure when exposed to heat. However, the exposure conditions may vary depending upon the coating composition used. For example, ; 20 the vinyl-functional and acryloxy-functional silane~metal ester coatings require exposure to temperatures between about 130C. to 170C. and preferably, about 150C~ for periods of time between about 30 to 60 minutes. Epoxy-functional silane-metal ester coatings can be cured by 25 exposure to temperatures between 75C. to 100C. for perlods of time from between about 16 to 40 hours. As the curing temperature is increased the time necessary to cure the composition is decreased.

. ~.

:
It ~las beerl f`ound that; t;he amount Or time necessary to cure these coat;lngs at t~lese temperatures can be materlally reduced by the addition of a small amount of an accelerator to the compos:Ltion. The accelerators have been found useful in the range of from about 0.4 to about 2.5% by welght of the coating composition. Accelerators which have been found useful are the mlneral acids such as hydrochloric, nitric, ~ ~
sulfuric, etc. Other acids which have been found useful ; ~-include boron trifluoride and aluminum trichloride.
All of the coating compositions containing titanium ;~
.. ~
metal esters will cure when exposed to ultraviolet light. It is preferable that the irradiation be carried out in an inert atmosphere such as nitrogen, carbon dioxide, helium, argon, etc. since oxygen inhibits the reaction. The amount of tlme necessary to completely cure the coatings varies inversely with the intensity of the light. For example~ ~
irradiation may be effected by shining a General Eléctric -275 watt sun lamp through a quartz glass cover into a nitrogen purged chamber eontaining the coated substrate.
The quartz glass cover allows the passags of ultraviolet light in the range of about 2,000 to about 4,000 angstroms.
Curing is complete in from 5 to 20 minutes depending upon the distance from the light source to the substrate.
Vinyl-functional and acryloxy-functional silane-metal ester coatings w111 also cure when exposed to electron beam irradiation. It is desirable to carry out the irradiation in an inert atmosphere such as nitrogen, carbon dioxide, helium~ argon, etc. ~he amount o~ tlme necessary ~, ''~ .

to cornpletely cure ~le co~ltlngs varles inver-sely wlth the power Or the elec~;ron beam ;ource. IrradLation may be effected, for example, by passing the coated substrate through a chamber purged w:l~h an lnert gas into whlch a stream of electrons is directed~ The source of the electron beams may be a Model CB-150 Elec-tro-Curtain* available from Energy Sciences, Incorporated, Burlington, Massachusetts.
Typically, the coatings are cured in about 4 seconds.
The unexpected resistance to abrasion exhibited by the coatings prepared in accordance with the present inventlon is shown by the Oscillating Abrader Test. This test is performed on the oscillating abrader apparatus shown in Figure 1.
The oscillating abrader apparatus 10 comprises shaker table 14 in housing 12. Table 14 is connected to motor driven osclllating means via arm 16. Such oscillating apparatus 10 is commercially available from Eberbach ~-Corporation as Model 6000. Table 14 oscillates at a frequenoy of 1.25 cycles per second and a stroke of 3.75 cm.
A coated substrate 18 to be tested is first firmly fastened to the top of table 14 by means of double coated `':
tape. Abrasive means 20 is pressed a~ainst the coated surface 22 of substrate 18 and is anchored to the base of abrader block 24 by means of double coated tape.
Abrasive means 20 comprises 3/0 grade steel wool. The base 26 of block 24 is 2.5 cm. by 2.5 cm. and the portion ~trademark , ~ ' .

of abraslve means 20 whlc~ Ls in pressure-contact wlth surface 22 is there'ore about 2.5 cm. by 2.5 cm. The deslred abrasive force to be applied is controlled by means of weights 28 supported o~ rod 30 by means of` rinr 32. Rod 30 is connected to block 24. Weights 28 are maintained directly above block 24 by means of a suitable bushing 34 held by ~ ;
` arms 36, the bushing permittlng unrestrict;ed vertical move-ment while preventing horizontal movement of block 24.
Abrasion resistance is measured by fastening a coated substrate 18 to the top of table 14 as described above and pressing abrasive means 20 against the coated surface 22 and applying a predetermined abrasive force by ~: ;
means of weights 28. The oscillating motion of table 11~ is started. The number of complete oscillations is counted by ;
Z 15 means of counter 38. When 100-cycles (a cycle being one .~ ~.,; , .
complete forward and back movement) are completed the oscillating table is stopped and the surface 22 of the coated substrate 18 is visually inspected for scratches. Weights 28 are then either increased or decreased incrementally and khe 20 procedure is repeated on an unabraded portion of the test -'sample.
1The maximum weight (including block 24, rod 30, ~ring 32, and weights 28) which can be placed on abrasive !means 20 without producing visible scratches on the test ;~
125 sample after 100 cycles is recorded. Since the area of the ,ibase of block 24 (and, hence~ the abrasi~e means 20) is one square inch, the abrasion resistance value can also be referred to as pounds per square inch. (1 lb/ln =70.4g/cm ~` `:

:
~ .:: ~ , :- . . , :

Adi~es:lorl of` t~le cllred cocltlrlgs to the su~strate is measure~ by cllt~ing the c~ured, coated surf2ce through with a sharp edge ln a ser:les of parallel lines about 0.318 cm. apart and t~en with a s:Lmilar series of parallel ; 5 l:Lnes at right angles to the first series, also spaced ; about 0.318 cm. apart. A total of fifty squares are thereby cut through the cured~ coated substrate. A section of 'tScotch"~ Brand Magic Transparent Tape No. 810 is firmly pressed into contact with the coated surface so as to cover the entire cross-hatched area. The tape is then rapidly manually stripped from the substrate at a 90angle to it.
Adhesion is rated at 0 to 100 percent. For each square which is removed durlng the test, the recorded adhesion value is reduced by 2 percent.
The following examples are meant to illustrate, but not limit this invention. Parts and percentages are by weight unless otherwise indicated.
__ __ _ *trademark _ 14 -EXAMPL,E 1 _ ___ _ Tetralsopropyl titanate was added to ~amma-meth-acryloxypropyltrime~loxy silane at a molar ratio of' 1:10 and mLxed at room temperature. The composition was spin coated 5 onto a sheet o~ polydiallylglycolcarbonate and cured by ;
exposure to ultraviolet light for 15 minutes.
The 3 to 5 micron coating was smooth, clear, trans-parent, firmly bonded to the substrate and abrasion reslstant.
The experiment was repeated with a mola~ ratio of 1:4 with comparable results.

, Aluminum isopropoxide (0.1 mole) was heated (117 - 120C.) to melting and dissolved in 80 g. toluene heated to 80C. Dlssolution took one-half hour and the solution was filtered through No. 1 Whatman filter paper.
; The solution was then mîxed with gamma-glycidoxypropyltri-methoxy silane in the molar ratios shown in Table II, spin ~, i , coated onto 5 x 5 x 0.16 cm. sheets of polyallylglycolcar-bonate and cured for 16 hours at 85C. The cured coatings .. .
(3 to 5 microns) were clear, smooth, transparent and abrasion resistant.
. . , Table II reports the data for these examples.
:
,j TABLE II

` _ ~ 2 3 4 5 6 7 8 ." ~
25 Molar Ratio 1:11:2 1:3 1:4 1:5 1 7 1:10 `, Metal Ester:
i Reactive Silane ,1 Abrasion 10 15 20 25 20 5 0 l Resistance (PSI) `~ 3 (g/cm ) 704 1056 14081760 1l~08 352 ~, ~, .
: . . . - .

5~

_ _ _ _ _ _ Aluminum isopropoxlde was dissolved as above and added to gamma-methacryloxypropyltrlmethoxy sllane. This was again spin coated onto the carbonate squarles and cured in an oven ~or 60 m:Lnutes at 150QC. All coatings were clear, smooth and transparent. Table III shows their abrasion resistance and adhesion.
TABLE III
Example 9 10 11 12 13 14 15 16 17 18 Molar Ratio 1~ 2 1.3 1:4 1:5 1:7 1:10 1:15 1;20 1:30 Metal Ester:
Reactive Silane Abra~ion 12 3 17 25 12 15 12 10 10 7 15 Resistance (PSI~ ~
Adhesion (%) 100 100 100 100 100 100 100 100 100 100 ~ -A 5 cm. x 5 cm. x o.64 cm. sheet of polycarbonate ("Lexan"*~ commercially avallable from General Eleotric) is washed with absolute ethyl alcohol and then dried with a llnt free towel. A coating solutlon of the following formula was l;
prepared as described in Example 1.
Tetraisopropyl titanate 2 gm.

Gamma-glycidoxypropyltrimethoxy 3 gm, silane , Gamma-methacryloxypropyltrimethoxy 3 gm. ;~ -silane 1~
HCl (Goncentrated) 4 drops ;

"SF-1023"* (silicone leveling agent 1 drop commercially available from General Electric) *trademark ,.

The solutlon ~las ;~)In coat;~d ont;o the polycarbonate and placed :In an oven for l5 minutes at 150C. The cure was then completed by plac:Lng t;he partIally cured substrate into a nltrogen purged chamber and exposlng it to ultraviolet light. The cured coating (approximately 3 to 5 microns thick) was clear~ smooth~ transparent, firmly bonded to the substrate, and very abrasion resistant.
EXAMPLES__0 - 29 Coating compositions are prepared by mixing tetra-isopropyl tltanate with gamma-methacryloxypropyltrimethoxy silane in a glass beaker at room temperature at various molar ratios. The resultlng coating compositions are then spin coated onto polycarbonate and cured as described in Example 19. ;~
The cured coatings (approximately 3 to 5 microns thick) are ~ 15 clear~ smooth, transparent and firmly bonded to the substrate.
; They are also very solvent resistant and very corrosion resistant. Results of the abrasion test and adhesion test are shown in Table IV. -~
, TABLE IV

-~ 20 _E ample 20 21 22 23 24 25 26 27 28 29 `~ Mol~r Ratio 1~ 2 1:3 1:4 1:5 1:7 1:10 1:15 1:20 1:3Q
' Metal Ester:
Reactive i Silane Abrasion 2 3 15 3 25 15 lLI 10 9 3 ' Resistance ,! ~ (PSI) Adhesion t%) 100 100 100 100 100 100 100 100 100 100 :

-,: ~

~ J5~ r p EXAMPLE~ 30 - 38 Coat:Lng compositiorls are prepared by mixing tetra-isopropyl titanate wi-th gamma-glycidoxypropyltrimethoxy silane in a glass beaker at varlous molar ratios at room temperature. The resultin~ coating compositions are then spin coated onto polydiallylglycolcarbonate and partially cured by exposure to ultraviolet light as described in Example 1 for 4 minutes at a distance o~ about 7.5 cm. The cure is then completed by exposure to 85C. ~or 16 hours. The coatings were slmilar to previous coatings of this invention. Results of the abrasion test and adhesion test are shown in Table V. `-TABLR V
Example _30 _ _31 _3233 34 35 36_ 37 38 Molar Ratio1:0.5 1:1.5 1:4 1:5 1:6 1:10 1:15 1:20 1:30 15 Metal Ester:
Reactive ' ` Silanes -Abrasion 32 3235 20 18 4 6 3 2 Resistance 20 ~PSI) -Adhesion (%) 100 100 100100100 100 100 100 100 Substrates precoated with commercially available abrasion resistant coatings are obtained and tested for , abrasion resistance on the oscillating abrader. The results are shown in Table VI.
i .

:. , ;
- 18 - ~

:~ :
... 1 . . ~ . . . . . .

;~a~ tP
TAE~I.E V'[
Example _ 39 4 __~
Coating/substra~e (;eneral Electric du Pont "Abcite"*, -~
"MR-4000"*, an organic a silioon rluoro-melamine -type coatin~, carbon hard coat, on "Lexan" Polycar- on polymethyl-bonate methacrylate Pressure required 2 10 to abrade (PSI) ~
10 EXAMPLE 41 ;
A 5 cm. x 5 cm. x 0.16 cm. sheet of polydiallyl-glycolcarbonate is washed with absolute ethyl alcohol and dried with a lint free towel. A coating composition is pre-pared in a glass beaker at room temperature and spin coated onto the substrate. The coating composition comprises:~
, Tetraisopropyl titanate1.75 gm.

~amma-glycidoxypropyltri-methoxy silane 6.o gm.

Borontrifluoride ether ; ~`
complex 4.0 drops Silicone leveling agent (S~ 1023) 1.0 drop The coated substrate is partially cured by placing ~;
it into a nitrogen purged chamber and exposlng it to ultra j ~ 25 violet light as described in Example 1 for 4 minutes at a ~ : :
distance of about 7.5 cm. The cure is oompleted by exposure to 85C. for 8 hours. The cured coatings (approximately 3 to 5 microns thick) are clear, smooth, : ' transparent and firmly bonded to the substrate. The coating is also very abrasion resistant (exhibitin~ an __ _ _ ~tradernark .

abrasion resistance o~` 25 P';;r on the osclllating abrad~r),very solvent resistant and very corrosion resistant.
EXA~IPLE. ll2 Z:lrconiun1isopropoxide (33 ~rams) is dissolved in toluene (167 grams) heated to approximately 75C. The warm solution is filtered using the Buchner funnel and "No. 1 Whatman" filter paper. A 5 cm. x 5 cm. x 0.16 cm. sheet of' polydiallylglycolcarbonate is washed with absolute ethyl alcohol and dried with a lint ~ree towel. A coating composi-tion is then prepared in a glass beaker at room temperatureand spin coated onto the substrate. The coating composition comprises: ~ -Zirconium isopropoxide-toluene 12.0 gms.
solution I 15 Gamma-methacryloxypropyltri- 6.o gms.
-~ methoxy silane , Silicone leveling agent (SF 1023) 1.0 drop The coated substrate is cured by exposure to 140C.
for 60 minutes. The cured coating (approximately 3 to 5 microns thick) is clear, smooth, transparent and is ~irmly bonded to the substrate. The coating is also abrasion resistant (exhibiting an abrasion resistance of 12 PSI on the oscillatlng abrader), very solvent resistant and very corro-sion resistant.
E _ PLE 43 A 5 cm. x 5 cm. x 0.16 cm. sheet of polymethyl-methacrylate is washed with absolute ethyl alcohol and dried with a lint free towel. A coating solution is then prepared in a glass beaker at room temperature and spin `~ 30 coated onto the substrate. The coating composition . .- -,, .

~ 9 ~, .
comprises:
Tetraiso~ropyl titanate 1.75 gms.

Vlnyl-tris-(2-rnethoxy- 7.0 ~ms.
ethoxy)silane ("A-172~'*
5 commerclally a-vailable ~rom Union Carbide) The coating is cured by electron beam radiation by passing the coated substrate through a chamber purged with nitrogen into which a stream of electron beams ls directed.
The source of the electron beams is a CB-150* Electro-Curtain available from Energy Sciences, Incorporated3 ~ ~-Burlington, Massachusetts. The Electro-Curtain is operated at 10 milliamperes and 150 kilovolts. The coated substrate is exposed to electron beam radiation for 4 seconds~ The 15 cured coating (a'pproximately 3 to 5 microns thick) ls clear, ;
smooth, transparent and is firmly bonded to~the substrate.
.~ , The coating is also abrasion resistant (exhlbiting an abrasion resistance of 10 to 12 PSI on the oscillating ..
abrader), very solvent resistant and very corrosion resistant~
EXAMPLE 4'4 A coating composition is prepared utilizing partially hydrolyzed tetraisopropyl titanate. The tetra-isopropyl titanate is hydrolyzed as follows:

'' a) 4.7 gms. 37% (concentrated) HCL ~-~
is added to 67 gms. absolute ethyl alcohol.

b) Z8.4 gms. (0.1 mole) tetralso-propyl titanate is added to the above solution.
Hydrolysis takes place at room temperature in about 15 minutes. The following materlals are then *trademarks combined at room temperatures lo make the coating solu~iorl:
IIydxoIyzed tetralsopropyl 5.0 gms.
titanate solut;ion Gamma-methacryloxypropy]- 6.o gms.
5 tr:lmethoxy silane Silicone leveling agent (SF 1023) 0.26 gms.

A 5 cm. x 7 cm. x n.16 cm. sheet of aluminum was cleaned with an abrasive pad and water then washed with absolute ethanol and dried with a lint free towel. The coating composition of the previous Example was spin coated onto the surface of the alumlnum sheet and cured at 150C ;~
for 60 minutes. The cured coating (approximately 3 to 5 microns thick) was clear-~ smooth, transparent, abrasion resistant and is firmly bonded to khe substrate.
EXAMPLE 4 6 :;
Polyester sheets are etched with a dilute solution of sulfuric acid in absolute ethyl alcohol. The coating composition of the previous Example was spin coated onto ;~
20 the etched polyester sheets and cured at 150C. for 60 minutes.
The cured coatings (approximately 3 to 5 microns thick) were clear, smooth, transparent, abrasion resistant and firmly ;;~
bonded to the substrate.

Sheets of acrylic resin were pretreated by a) immersion in chloroform for 2 minutes b) submerging the substrate in dichloro-methane (e.g., 30 seconds at 25C.) c) roughening the surface of the sub-strate with fine sandpaper (410 through 600 grit polishing paper) ',... . . .

.

r~

d) rollgh(?ning the ~lrl'ace of` the substrate with alu~inllm oxide abra~;lve powder, each substrate was therl 5 coated wlth the ~olut-lon of' t~le previous Example and cured at 150C for 60 minutes.
The cured coatings (approximately 3 to 5 microns ;~
thick) are clear, smooth, transparent, abrasion and solvent and are f`irmly bonded to ~he substrate.

A 5 cm. x 5 cm. x 0.16 cm. sheet of polydlallyl-glycolcarbonate is washed with absolute ethyl alcohol and ~' dried with a lint free towel. A coating solution of the following formula is prepared as described in Example l.
., ~.
15 Tetraisopropyl titanate 2 gms ~amma-methacryloxypropyl- 6 gms.
trimethoxy silane Sllicone leveling agent l drop The coating was then flow coated onto the substrate ;~
and cured by electron beam radiation as described above. The coating cured ln about 8 seconds. The cured coatlng (approxi-mately 3 to 5 microns thick) is clear, smooth~ transparent, `~ abraslon and solvent resistant and was firmly bonded to the substrate.

- A coating compasition comprising a 1:4 molar ratio ~' of tetraisopropyl titanate to gamma-methacryloxypropyltri- ;
methoxy silane was prepared as described in Example l. The coating composition was spin coated onto "Lexan" poly-~` 30 carbonate and cured by exllosure to 150C, for 20 minutes followed by exposure to ultraviolet light as described .

in E~ample L ~ol~ l5 InirllJt;~s at; a dist;arlce of about 7.5 cm.
Th~ so:lvent res-lst,ance of` the cured coating was then checked by forillir~ four l;o f:ive small pools of' solvent on the coated surface of the substrate, allowing said pools to remain on said surface for about 20 minutes, wiping said pools dry, and visually inspecting for damage to the cured coating. When tested according to this procedure~ t,he cured coating was unaffected by the following solvents:
a) Water f) Chloroform b) Ethanol g) Dimethyl formamide c) Methanol h) HCl (concentrated) d) Acetone i) Toluene e) 2-Butanone A 10 cm. x 10 cm. x 0.013 cm. sheet of polyester film was primed with amidized and epoxidized polybutadiene -~
in methanol. A coating composition was then prepared in a glass beaker at room temperature. The coating comprised: ~ -Tetraisopropyl titanate 2.0 gms.

Gamma-glycidoxypropyl- 6.o ~ms.
trimethoxy silane Sllicone leveling agent (SF 1023) 1.0 drop The coating composition was spin coated onto the primed substrate and partially cured at 75~C. for 1 minute.
The coated substrate was cooled to room temperature (e.g., 25C.) and a second layer of the coating composition spin coated onto the partially cured coating~ The multiple coating was cured by exposure to 75C. for 16 hours.

- 2~

The c~ured c~oatirllr, (al,)prox:Lmately 8 microns thlck) is clear, smooth~ ~lex.Lble, transparent and is firmly bonded to the substrate. The coatLn~ is also very abrasion reslstant; (exhlbitlnK an abrasion resistance of 20 PSI on the oscll.latln~ abrader), very solvent resistant, and very corroslon resistant. :
-' '; ' ~ :~
,', ' ' .. . .

~ .
, ` i :
;~ ;' .
' -~ : - 25 -.. ~.
. .
.

I~.XA~!~[,[i,~S 5~_ 'r~ese examples s~o~ the general usefulnesE; of various rorms of` metaJ esters having at least two ester groups per metal atom.
Thirty-six (36.o) grams of gamma-glycidoxypropyl-trimethoxy silane was split into three portions, A~ B~ and C.
To A was added 5.0 g. Or triethanolamine chelate of bis titanium isopropoxide ~ .
[(OHC~2CH2)2N]2 Ti(OC3H7)2' ~` ~
10 to B was added 8.5 g. dichlorodialkoxytitanate ~ -Cl Ti(O(CH ) CH3)2, and to C was added 8.o g. chlorodibutoxy aluminum solution ~' Cl Al (O(CH2)3C113)2-The metal esters of B and C were added as solutions in methylene chloride comprislng 25% by weight solids. Two drops of an oligomeric fluorocarbon leveling `~
agent were added as a coating aid.
Coating solution D was made with 6.o g. gamma-gly-cidoxypropyltrimethoxy silane and 4.5 g. of a polymeric alkyl titanate having the repeating structure 0 (CH ) CH

~Ti O~

-~CHZ)3cH3 were mixed with one drop of SF1023 (leveling agent).
Sheets of polydialylglycolcarbonate (about 7.7 x ;~
7.7x.16 cm) were washed with absolute ethanol and dried with lint free tissue. The solutions were applied by spin ~oating to respective sheets and cured in an oven at 85C. for 16 hours.

~ .. . . - , . : ~
:: . : .. . ,, ., , :. ~ -; :

The cured coat;ings :Ln all cases were smooth, transparent~ solverlt; resistcln~, and ~ad ~ery good abraslon resist.ance to 3/0 steel wool.

` "".

.

~ .
. .

Claims (20)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method for rendering a surface of a substrate resistant to abrasion comprising:
(a) applying to said substrate a composition consisting of:
(1) a metal ester selected from the group comprising titanium, aluminum or zirconium; having at least two ester groups of the formula -OR bonded to the metal and wherein R is hydrocarbyl of 1 to 18 carbon atoms; and (2) a reactive silane selected from epoxy silanes, methacryloxy-silanes and/or vinyl-silanes; and (b) curing said composition to an abrasion resistant state.

2. The method of Claim 1 wherein the metal ester is of the formula:
M(OR)m or R'nM(OR)m-n wherein R is alkyl or acyl of 1 to 18 carbon atoms; R' is halide, hydrogen or alkyl or 1 to 8 carbon atoms, m is the valence of M; n is 0, 1, or 2 and m-n is at least 2; and M is Ti, Al or Zr.

3. The method of Claim 1 wherein said epoxy-silane is represented by the formulae:

and wherein, each R is independently a divalent hydro-carbon radical of less than 20 carbon atoms, or a divalent radical of less than 20 carbon atoms the backbone of which is C atoms which may be inter-rupted by individual atoms from the group of N, S and O, the O atoms in the form of ether linkages; m is 1, 2, or 3; n is 0 or 1; and R' is hydrocarbyl of 1 to 18 carbon atoms or a radical of the formula (CH2CH2O)kZ in which k is an integer of at least 1, and Z is hydrogen or an aliphatic hydrocarbon radical of less than 10 carbon atoms.

4. The method of Claim 1 wherein said methacryloxy silane is represented by the formula:

wherein R2 is an oxyhydrocarbyl group of 1 to 18 carbon atoms, R3 is an alkylene of 1 to 8 carbon atoms, R4 is hydrogen or hydrocarbyl of 1 to 8 carbon atoms, and n is 1 or 2.

5. The method of Claim 1 wherein the vinyl-silane is represented by the formula:

(CH2 = CH?nSi - (R2)4-n wherein R2 is an oxyhydrocarbyl group having 1-8 carbon atoms and n is 1 or 2.

6. The method of Claim 3 wherein said metal ester comprises Ti(OR)4 and the mole ratio of metal ester to epoxy-silane is from 2:1 to 1:7.

7. The method of Claim 3 wherein said metal ester is Al(OR)3 and the mole ratio of metal ester to silane is from 1:1 to 1:5.

8. The method of Claim 3 wherein said metal ester is Zi(OR)4 and the mole ratio of metal ester to silane is from 1:3.5 to 1:5.

9. The method of Claim 1 wherein said substrate is coated with a priming agent prior to the application of said composition.

10. The method of Claim 1, 3 or 4 where said cure is effected by exposure to sources selected from ultraviolet radiation, heating, electron-beam irradiation, or combinations thereof.

11. The method of Claim 1, 3 or 4 wherein said metal esters are selected from tetraisopropyl titanate, tetrabutyl titanate, tetra-2-ethylhexyl titanate, tetraethyl titanate, aluminum isopropoxide, aluminum n-butoxide and tetraisopropyl zirconate.

12. The method of Claim 1, 3 or 4 wherein said compositions further comprises materials copolymerizable with silanes or the epoxy of said epoxy-silane, the methacryloxy of said methacryloxy-silane, or the vinyl of the vinyl-silane.

13. A solvent resistant, abrasion resistant film comprising the reaction product of (a) applying to said substrate a composition consisting of:

(1) a metal ester selected from the group comprising titanium, aluminum or zirconium; having at least two ester groups of the formula -OR
bonded to the metal and wherein R is hydrocarbyl of 1 to 18 carbon atoms;
and (2) a reactive silane selected from epoxy-silanes, methacryloxy-silanes and/or vinyl-silanes; and (b) a reactive silane selected from epoxy-silanes, methacryloxy-silanes and/or vinyl-silanes.

14. The film of Claim 13 wherein the metal ester is of the formulae:

M(OR)m or R?M(OR)m-n wherein R is alkyl or acyl of 1 to 18 carbon atoms; R' is halide, hydrogen or alkyl of 1 to 8 carbon atoms; m is the valence of M; n is 0, 1 or 2 and m-n is at least 2; and M is Ti, Al or Zr.

15. The film of Claim 13 wherein said reactive silane is an epoxy silane of the formulae:

and wherein, each R is independently a divalent hydrocarbon radical of less than 20 carbon atoms, or a divalent radical of less than 20 carbon atoms the backbone of which is C atoms which may be interrupted by individual atoms from the group of N, S and O, the O atoms in the form of ether linkages;

m is 1, 2 or 3; n is 0 or 1; and R' is hydrocarbyl of less than 8 carbon atoms, or a radical of the formula (CH2CH2O)kZ in which k is an integer of at least 1, and Z is hydrogen or an aliphatic hydrocarbon radical of less than 10 carbon atoms.

16. The film of Claim 13 wherein said reactive silane is a methacry-loxy silane of the formula:
wherein R2 is an oxyhydrocarbyl group of 1 to 18 carbon atoms, R3 is an alkylene of 1 to 8 carbon atoms, R4 is hydrogen or an alkyl group of 1 to 8 carbon atoms, and n is 1 or 2.

17. The film of Claim 13 wherein said reactive silane is a vinyl silane of the formula:
(CH2=CH?nSi - (R2)4-n wherein R2 is an oxyhydrocarbyl group having 1-8 carbon atoms and n is 1 or 2.

18. The film of Claim 13, 15 or 16 wherein the metal ester is selected from tetraisopropyl titanate, tetrabutyl titanate, tetra-2-ethylhexyl tita-nate, tetraethyl titanate, aluminum isopropoxide, aluminum n-butoxide and tetraisopropyl zirconate.

19. The film of Claim 13, 15 or 16 wherein the metal ester is Ti(OR)4.

20. The film of Claim 13, 15 or 16 wherein said film is firmly bonded to a substrate.