JPS5856588B2 - Coating composition containing ultraviolet absorber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to novel ultraviolet light absorbers containing organosilane ester groups, novel coating solutions and methods of manufacturing therefrom which are particularly useful for providing light- and scratch-resistant coatings to plastics. The present invention relates to the coatings produced and the moldings produced from the coated articles, in particular the polycarbonates obtained by the coatings.

Many polymers, especially polycarbonates, have deficiencies in climate compatibility due to the negative effects of ultraviolet (UV) radiation, which induces yellowing and surface degradation and lack of abrasion resistance.

Comparable coatings containing polysilicic acids, such as those described in U.S. Pat. No. 3,429,845, are useful for increasing scratch resistance, especially when exposed, but lack adhesion to certain resins. I found out that

In addition, the mixing of ultraviolet absorbers may cause the coating to harden and/or
or migration during exposure.
on), were not effective due to losses due to evaporation and leaching.

Polymeric UV absorbers have been proposed in US Pat. Nos. 3,340,231 and 3,341,493.

According to these studies, resistance to light can be improved by reacting an epoxy monomer such as unsaturated glycidyl ester with 2,4-dihydroxybenzophenone and using the resulting monomer in copolymerization with vinyl halide. be done.

However, it is generally incompatible with useful solvents and polymer surfaces.

The polycarbonate or acrylate surface may be 2-hydroxy-4 as shown in U.S. Pat. No. 3,451,838.
It is also known to improve the process by using -methoxy-benzophenone with a mixture of aliphatic and aromatic silanes.

However, further improvements are expected with respect to abrasion resistance, compatibility, potability, stability and ease of application.

In accordance with the present invention, we now provide novel silicon-containing compounds useful as UV absorbers and methods for their preparation; Novel coating solutions and coating methods using the same; and novel coatings and coated products made when preformed objects are coated from the solutions, particularly products made from polycarbonate, are provided.

The novel silicon-containing compound useful as a UV absorber, which is the basis of the present invention, has the formula [wherein R is a divalent hydrocarbon group which may contain an ether bond; R1 is a lower hydrocarbon group or (CH2CH20)nz, where n is an integer from 1 to 8 and 2 is lower alkyl; R2 is bonded to oxygen through an aromatic carbon and is from 2500 to
It is a stable aromatic group that absorbs light in the range of 4,000 people;
and a is O or 1].

Details of these novel compounds as well as other features of the invention will become apparent from the description below.

A novel silicon-containing compound having a UV-absorbing residue represented by the above formula is a compound that converts epoxysilane into a hydroxyaromatic UV-absorbing compound.
It can be prepared by reacting with the hydroxyl groups of an absorbent, and is herein referred to as 'adduct'.
It will be called.

Epoxy silicon compounds or epoxy silanes used in reaction with hydroxyaromatic UV absorbers are described in U.S. Pat.
No. 45701.

They have the formula [wherein R is a divalent hydrocarbon group having less than 10 carbon atoms, or a divalent group having less than 10 carbon atoms consisting of C, H and O atoms, i.e. in the form of an ether bond. (and preferably R is CH20CH2CH2CH2-); R1 is an aliphatic hydrocarbon group having less than 5 carbon atoms, an acyl group having less than 5 carbon atoms, or a group of the formula (CH2CH20)Z , where n is an integer of at least 1 and Z is an aliphatic hydrocarbon group having less than 5 carbon atoms; and a is 0 or 1.

A method for producing the above compound is disclosed in the above-mentioned US Pat. No. 2,946,701.
No.

A particularly suitable compound is union carbide (Unio carbide).
γ-glycidoxypropyltrimethoxysilane and α-(3.4
-epoxycyclohexyl)ethyltrimethoxysilane.

The precursor hydroxyaromatic UV absorbers include a basic class of commercially available UV screening agents (UVScreeni
ng agents), ie, benzophenones, benzotriazoles, succinates, substituted quinazolines, and phenyltriazines.

All of these typically absorb light in the 2500-4000 range and dissipate UV radiation into harmless energy.

The requirements for effective absorption are described in Advances in Chemis, edited by the American Chemical Society, District of Columbia.
try, 5eries 85, p. 284 (1968
)°' 5tabilization of Poly
mer and 5tebilizer Processes
ses” and British Pergamon (Pergamon)
) Published by European Polymer Journa
l-5upp 11969, No. 105-132J HlJ, Heler,
Protection of Polymersag
ainst Light Radiation”.

The molecular formula of the above precursor is [where b is 1 or 2 depending on the number of reacted hydroxyls, and R2 is a hydroxyaromatic group that absorbs the aforementioned light and contains 2 to 4 aromatic rings. It can be written as

This generally has a molecular weight of at least 1510 (Structure 2 below,
p-1) and typically have a molecular weight (unsubstituted: structure 13) of less than 325.

In the following structural formula 8 shown in Reference Examples 2 and 3, R2 is 2
silane groups (i.e. R2 with b=2
(OH)b).

The fi group present on the ring may increase the molecular weight up to about 400.

A particularly useful UV absorption structure as a typical example of R2 can be shown by the following formula.

Any of these structures may optionally contain up to two inert substituents on the core carbon, such as halogen, alkyl, phenyl,
It may contain alkoxy.

It is generally preferred for the group of the above formula that the bond is in the para position.

Particularly useful precursor hydroxy compounds are those described above.
2,4-hydroxybenzophenone.

Particularly useful hydroxyaromatic compounds in addition to those in Reference Examples 1 and 2 below include 2,4-dihydroxybenzoate, 2-(2'-hydroxyphenyl)-4-phenyl 6
-hydroxyquinazoline and 2-(2'.4'dihydroxyphenyl)benzotriazole.

The reaction conditions between the precursor silane and the hydroxy compound are simple.

These compounds may be simply brought into contact under anhydrous conditions in the presence of an alkali quaternary ammonium salt, generally at 50 to 150°C for 4 to 10 hours.

A diluting solvent is not required, but can be used if desired.

The novel adducts prepared are generally soluble in polar organic solvents such as lower aliphatic alcohols, lower aliphatic ketones, acetonitrile, lower aliphatic esters such as ethyl acetate, dioxane, furan, dimethyl sulfoxide and dimethyl formamide. It is a viscous liquid.

This adduct is particularly suitable for use in coating solutions and coatings that are mixed with polysilicic acids and copolymers as taught in US Pat. No. 3,429,845.

For this purpose, the silicic acid present may be present in a percentage calculated as silica in each case from about 10 to
It can range from about 90%, preferably from about 20 to about 50%.

The polysilicic acid is a mixture of ethyl alcohol and water, or preferably 0.5%. IN in hydrochloric acid about 5:1 to 2:1
, preferably by hydrolyzing tetraethyl silicate in a ratio of about 3 to 4:1.

The copolymer used in the coating solution is a hydroxylated fluoropolymer, preferably in which the hydroxyl is
It is a copolymer of tetrafluoroethylene and ω-hydroxyalkyl vinyl ether, which is of the same class and whose alkyl group has 2 to 6 carbon atoms.

These copolymers consist of alternating units, thus 1:1
has a molar ratio of

Copolymers in which at least some of the tetrafluoroethylene is replaced with chlorotrifluoroethylene or in which the hydroxyl is secondary, such as in hydrolyzed copolymers of fluoroolefins and vinyl esters. , less preferred than those mentioned above.

These further include U.S. Pat. Nos. 3,429,845 and 34
It is described in No. 29846.

The silicic acid agents of the present invention are preferred as imparting good scratch resistance, but include hydroxylated fluoropolymers and hexa(alkoxyalkyl)melamines of the type taught in U.S. Pat. No. 3,651,003. (However, “alkoxy” is 8
Coating mixtures of hexa(methoxymethyl)melamine, for example hexa(methoxymethyl)melamine, can also be used.

In this variant, up to 45% by weight of fluoropolymer can be replaced by melamine.

Of course, silica itself may be used with these ingredients as taught in US Pat. No. 3,651,003.

In order for the improvement of the coating obtained by the present invention to be effective, approximately 0.5 to 35 % by weight of one of the above-mentioned novel adducts is simply included in the coating solution.

Of course, more than one adduct can also be used, which is sometimes advantageous.

Solvents for the above-mentioned components and possibly other minor components are miscible in wide ranges of proportions and are generally used when there is an acceptable vapor pressure at about 100°C.

Useful are lower alkanols, mixtures of alkanols and lower alkanoic acids and/or lower aliphatic ketones.

A small amount of ether alcohol [Cellosolf@(Ce1lo)]
solve■)], esters, aromatic hydrocarbons and water may be present.

Generally, sufficient solvent is used to provide the desired solution viscosity (see below), but the amount is not critical.

A long shelf life of the coating solution is achieved.

If a compound that reacts with any remaining epoxy groups, such as an alcohol such as n-butanol, is added to the epoxy-containing silane/UV absorber mixture, the reaction between the latter components must first be substantially completed. (see Example 3B below) to prevent reaction of the epoxy groups present with the polymer of the coating solution.

Since these compounds are good solvents, they can be easily used as such and at the same time can stabilize the solution.

In addition to those mentioned above, the following substances can optionally and in small quantities be included in the solution: (1) in an amount of 0.05 to 5%, based on the weight of polysilicic acid (calculated as SiO2) present; The organosilicon compound used is a block copolymer of lower alkylene (2 to 4 carbon atoms) oxide and lower dialkylsiloxane.

These are further described in U.S. Pat. No. 3,476,827;
Salts such as potassium and sodium thiocyanate and sodium or potassium carboxylates used in amounts of ~2%.

and (3) have a macrocyclic ring of at least 14 atoms containing at least 4 ring oxygens as described in U.S. Pat. No. 3,546,318. Polyether.

They can be used in amounts of 0.01 to 5%, based on the total weight of polysilicic acid (as SiO2) and copolymer.

The coating solution has a solids content of 2 to 25% (polysilicic acid or equivalent and fluoropolymer and possibly small amounts of the substantially non-volatile components of (1), (2) and (3) above).
has.

Hydroxyl and fluorine containing polymer polysilicic acid (S102
(as) can be 10-90:90-10, but is usually present at 80-50:20-50.

The coating solution is generally about 10-50 cps (
room temperature) or even up to 300 cps.

In this case, low viscosity materials are used to give a thin coating.
High viscosities (30 or higher) are also used to provide thick coatings.

For storage or transport, high viscosities, e.g. 100-30
0cp3 is preferred.

The total composition percentages of coating solutions useful in the present invention are shown in the table below in weight percent: 10-300 cps of solvent (preferably used 10-50 cps)
The coating solution is useful for providing light- and scratch-resistant coatings on surfaces such as metals, polymers, and wood, and can be applied by flowing, spraying, dipping, etc. It can be applied to the substrate by conventional solution coating methods such as.

The contact time of the coating solution with the substrate, such as the rate of extrusion from the bath, is of course a factor that influences the thickness of the resulting coating.

The composition is then finally dried and preferably baked.

In this case the maximum baking temperature is maintained below about 200°C.

Generally the time and temperature are interrelated, i.e. from 170 to
1 hour at 180℃, 5-16 hours at 120-130℃
Time is used.

This baking or curing provides a hard surface and highly adhesive coating.

Although very thin coatings of the invention (0.1 micron) may be used, generally a coating of 3 to 20 microns (usually preferably 3. to 7 micron) provides excellent UV protection to the substrate.

Particularly excellent adhesion is obtained when the polymer is used with polysilicic acid to provide an abrasion resistant coating.

Additionally, UV absorption is generally retained during baking operations, which tend to remove low molecular weight protectants by evaporation or transpiration.

It should be noted that the solid materials of the invention (produced by evaporation of the solvent) are self-supporting and can be used alone, for example for producing shaped articles.

The trialkoxysilane groups 5i(OR1)3 of the present adducts probably hydrolyze and condense in the coating solution during application and condense with the polysilicic acid and/or hydroxyl-containing polymeric substrates such as TFE/HBVE copolymers or Forms a complex.

During this hydrolysis, aging and curing process, the UV screening residues later become an integral part of the wear-resistant coating material, which has superior properties due to its non-volatility and lack of capacity for migration.

The ultimate structure of these polymer coatings or complexes is
The silanol groups are probably coextensive and compatible in a strong linear polymer chemically bonded, hydrogen bonded and/or mechanically entangled with a rigid three-dimensional network with some residual silanol groups. It consists of a hollow structure.

The following examples illustrate various aspects of the invention and are not intended to limit the scope of the invention.

Reference Examples 1-3 show novel adducts, Examples 1 and 2 show coatings on quartz and poly(methyl methacrylate), respectively.

Example 3 illustrates an adduct in a coating solution used to coat a suitable polycarbonate.

In these Examples and Reference Examples, parts and percentages of materials are by weight unless otherwise specified.

The abbreviations used are: TFE for tetrafluoroethylene; HBVE for 4-hydroxybutyl vinyl ether; and PMMA for poly(methyl methacrylate).

Reference example ■ 1:1 adduct of 2.4-dihydroxybenzophenone/γ-glycidoxyprobyltrimethoxysilane The above compound (adduct 1) was prepared by adding 2.・4 dihydroxybenzophenone 10.1 (0.05 mol) and γ-
Glycidoxypropyltrimethoxysilane 12.04P
(0,051 mol) by heating a mixture of

This mixture was stirred and gradually heated to 75-80°C,
This temperature was then maintained for 8 hours.

During this period the mixture turned into a homogeneous viscous oil.

The reaction was heated to 80°C for 4 hours [phase]. An equivalent product was obtained when heated for 0 hours.

A coating prepared as in Example 1 but applied to polycarbonate and cured for 60 minutes at 130°C could not be removed from this substrate by adhesive tape tensile testing.

Reference example 2 2,2',4,4'-tetrahydroxybenzophenone/γ-glycidoxyprobyltrimethoxysilane 1:2
Using the general method of adduct reference example 1, 2, 2', 4, 4'
-Tetrahydroxybenzophenone 4.29P (0,0
2 mol) of the epoxysilane of Reference Example 1 (9.44'i? (
The above adduct ① was prepared by reacting with 0.04 mol).

After adding 0.1 S' of tetramethylammonium chloride, the mixture was heated at 75-80<0>C for 6 hours.

This resulted in a clear, slightly reddish yellow oil.

27/73-8i0 on PMMA without further purification.
2/TFE = evaluated in HBVE.

A coating applied to polycarbonate and cured for 60 minutes at 130° C. did not scrape off this substrate in the adhesive tape 9 test.

Reference example 3 2,2',4,4'-tetrahydroxybenzophenone/β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane 1:2 adduct The above adduct (■) is 2,2',4,4 '-Tetrahydroxybenzophenone (4,92P10.02 mol) was converted into β-
9.84 ft (0.04 mol) of (3,4-epoxycyclohexyl)ethyltrimethoxysilane and 0.0 ft (0.04 mol) of tetramethylammonium chloride. It was produced by heating to 80°C with IP.

This resulted in a pale, reddish-brown oil.

Example 1 Optical density of coatings on quartz 5i0 in n-butanol/1-butanol as solvent
2/approximately 10% polysilicic acid with a copolymer weight ratio of 27/73 (
A coating solution containing approximately 10% by weight (solids basis) of the new silanes of Reference Examples 1-3 together with SiO2)TFE-EBvE was coated onto quartz (transparent to UV radiation) and the solvent was removed by evaporation.

Place a PMMA sheet directly on this layer and heat to 170°C for 60 minutes.
Heated for minutes.

The following table shows the percent loss in optical density of the coating on quartz over 2800-3500 years due to evaporation and migration to the PMMA sheet.

Example 2 Coating on poly(methyl methacrylate) Compounds ■ and ■ in a solution of about 10% polysilicic acid/TFE-HBVE in a mixed solvent of n- and jet-butyl alcohol.
No. 3,429,845 containing 10 and 15% by weight (based on total solids in the coating solution) of
It was applied to a PMMA surface as described in No. 2003 and the Examples above and cured at 170° C. for 1 hour.

The following table shows the results obtained in comparison to a copolymer coating without UV absorber.

Of particular note is the improvement in adhesion retention.

Example 3 2,4-dihydroxybenzophenone and gamma-glycidoxypropyltrimethoxysilane 1:1 adduct and coating on polycarbonate containing the same Part A Essentially according to the method of Reference Example 1, using a stirrer, thermometer, reflux In a 12J three-tube dry round bottom flask equipped with a condenser and nitrogen inlet, γ-glycidoxypropyl trimethoxysilane 1796S' (7,6 mol), 2,4-dihydroxybenzophenone 1628P (7, 6 mol) and 151 mol of tetramethylammonium chloride were charged.

2,4-dihydroxybenzophenone was dissolved at a pot temperature of 60 to 80°C without heating or stirring.

Heating and stirring was then continued at an initial temperature of 110-116°C.

After 1 hour the mixture became viscous and gradually began to reflux.

Heating was continued for a total of 5 hours, and the pot temperature at the end was 110°C.

n-Butanol (5136f) and tetramethylammonium chloride (15S') were added and the mixture was heated under reflux for a further 2 hours.

After cooling overnight, the clear brown solution was placed in a dry container under nitrogen and sealed.

This solution (8538t) contained approximately 40% adduct ■.

Part B 1. The first coating solution was prepared as follows: Polysilicic acid solution in ethanol (prepared by mixing 65 parts of an approximately 70% solution of tetraethyl orthosilicate in ethanol and 20 parts of 0.IN aqueous hydrochloric acid.

This mixture was aged for 17 hours before adding the remaining portion.

) 85 parts TFE/HBVE copolymer [approximately 1:1 solution in mixed tert-butanol/n-butanol (approximately 11% solids);
1315 parts glacial acetic acid 100 parts "L-520" organosilicon (copolymer of lower alkyleneoxycyto and dimethylsiloxane, manufactured by Union Carbide Co.) 125P KSCN 10% solution in methanol 1.6 parts n- 40 of 2, 5, 8, 18, 21 hexaoxatricyclo[20, 4, 0, 09° 14] hexacosane in butanol
% solution 1.6 parts n-butanol 65 parts The Brookfield viscosity of the cono coating solution is 25
It was 30.8 cps at ℃.

Coating solution prepared above 38.7 P of a 40% n-butanol solution of the adduct as prepared in Part A
Combined with 7P.

After 24 hours at room temperature, this mixture had 31.45 cp at 25°C.
It had a Fultzfield viscosity of s.

Two weeks after this initial preparation, the mixture was still liquid and had a Brookfield viscosity of 41.5 cps at 25°C.

2. A second, somewhat less stable coating solution containing no excess n-butanol was prepared as follows: A solution of polysilicic acid in ethanol [9 parts of tetraethyl orthosilicate, 4 parts of ethyl alcohol and 0.2 parts of ethyl alcohol. Prepared by mixing 4 parts of IN aqueous hydrochloric acid (as above) J
460 TFE/HBVE copolymer solution in gubutanol (as above) 170P Glacial acetic acid 5401 "L-520" silicon (as above) 1.6f Solution of KSCNlo, 2P dissolved in 100 Ttl of methanol 8.5 ml A 40% solution of hexaoxatricyclohexacosane (as described above) in n-butanol 8.641 This coating solution was added to the following addition product 21
Added to: 2,4-dihydroxybenzophenone 10.7P (0,
05 mol), γ-glycidoxypropyltrimethoxysilane 1o, 7P (0,0453 mol) and tetraethylammonium chloride 0.11** into a dry 200 m/round bottom flask, and the bath temperature was 90 to 100. Stirred under 'C and dry nitrogen for 63/4 hours.

A viscous brown oil was obtained which was ready to use upon cooling overnight.

This coating solution gelled when left for 4 days, but the solution treated with alcohol as shown in Part 1B (1) was stable because there was no residual epoxy group.

Part C elf x1// in the coating solution of part B(1)
×1//1 part of the plate was immersed.

After 2 minutes, the quartz plate was pulled out at a speed of 15 inches/minute.

The board was dried under nitrogen, the coating removed from one side with a razor blade, and then Cary 1
4 Using a spectrophotometer, measure the ultraviolet spectrum of a quartz plate coated on only one side from 2500~
It swept over 4,000 people.

This plate was cured in a circulating oven at 135°C for 16 hours, and then
V spectrum was measured.

Table 3 shows the maximum absorbance (A
max).

In a comparative experiment, 21 lbs of 2,4-dihydroxybenzophenone was added to 200 ft of Part B (1) coating solution that did not contain the Part A adduct.

A quartz plate was coated and the UV spectra were measured before and after curing as described above.

"Amax" of the dihydroxybenzophenone-containing coating before and after curing is shown in Table 3.

The percentage of ΔAmax directly gives the percentage loss in optical density upon curing.

As described in Part A, 2,4-dihydroxybenzophenone 42.8 (0.4 mol), γ-glycidoxyprobyltrimethoxysilane 47.2 P (0.4 mol), tetramethylammonium chloride 0 .2 parts each of 4P,
and n-butanol 1351 to prepare a 40% solution of adduct (1) in n-butanol.

The total amount of the resulting 40% solution 67.5S' of the addition product was added to Coating Solution 2 prepared as described in Part B(2).
71M'.

A 16" x 12" x 1/8" extruded polycarbonate sheet was immersed in this solution for 2 minutes and withdrawn at a rate of 15 inches/minute.

After drying for 45 minutes, the coated polycarbonate sheet was cured at 135° C. for 16 hours.

The coating thickness is J, Opt, Soc,
Am. 37.873 (1947).

Similarly, a non-UV stabilized coating was applied to polycarbonate from the same coating solution without the addition of adducts.

The thickness of this coating was 4.5μ.

Acceleration weathering (aeeelera) that follows this sheet
tedweathering) was used as a comparative example for irradiation.

Both the polycarbonate plates with the UV stabilized coating and the non-stabilized comparison were tested on an Atlas Weather Meter.
The specimens were exposed to accelerated weathering in a er-Ameter (1) XW model.

The adhesion of the coating to the polycarbonate on the exposed surface was then determined by the adhesive tape pull test described in US Pat. No. 3,546,318.

Furthermore, the point at which cracks or blisters first appear was observed regularly, and this is shown in Table 4 as ``peeling''.
** Indicated as '''.

The UV stabilized coated polycarbonate and the comparison were exposed to outdoor accelerated weathering in Arzona.

EMMA is an equatorial follow-the 5u mirrored equatorial follow-the-sun irradiation shelf.
nexposurerack).

This solar irradiation increases by almost a factor of 10 compared to a stationary table tilted 45° to the south.

EMMAQUA combines EMMA irradiation with water spray for 8 minutes every hour during the day.

The 12 hour results of EMMA and EMMAQUA irradiation are summarized in Table 5.

In addition to the adhesive tape tensile test and visual observation for "peeling," the degree of yellowing (yellowness index, Y
l) Measured.

The aspects and related matters of the present invention are summarized as follows.2. In the presence of an alkyl quaternary ammonium salt in an anhydrous liquid state, the formula [wherein R has up to 10 carbon atoms] is a divalent hydrocarbon group or a hydrocarbon group with an intervening oxygen; R1 is an aliphatic hydrocarbon group having less than 5 carbon atoms, an acyl group having less than 5 carbon atoms, or a group of the formula (CH2CH20)nz; , where n is an integer of at least 1, and Z is an aliphatic hydrocarbon group having less than 5 carbon atoms: and a is 0 or 1] At least one epoxysilane of the formula [ In the formula, R2 is bonded to oxygen via an aromatic carbon and 2
is a stable aromatic group that absorbs light in the range of 500 to 4000: and b is 1 or 2] and [where R, R1, R2 and a has the above meaning] A method for producing a compound.

2. Polysilicic acid and/or hexa(alkoxyalkyl)
Polysilicic acid and/or hexa(alkoxyalkyl)melamine and copolymers, calculated as silica, in coating compositions prepared from melamine and copolymers of chlorotrifluoroethylene or bathydrafluoroethylene and ω-hydroxyalkyl vinyl ethers. 0.5 to 35% by weight based on the total weight of the formula [wherein R is a divalent hydrocarbon having up to 10 carbon atoms or a hydrocarbon group with intervening oxygen; R1 is the number of carbon atoms an aliphatic hydrocarbon group having less than 5 carbon atoms, an acyl group having less than 5 carbon atoms, or a group of the formula (CH2CH20)nz, where n is an integer of less than 1 and Z is a group having less than 5 carbon atoms. is an aliphatic hydrocarbon group of less than 2,500 to
a stable aromatic group that absorbs light in the range of 4,000 people; and a is O or 1] is added to the composition to increase resistance to ultraviolet light coating composition.

3. Products manufactured from synthetic plastics having the coating composition of 2 above.

Claims (1)

[Claims] 1. Polysilicic acid and/or hexa(alkoxyalkyl)
Coating compositions prepared from melamine and copolymers of chlorotrifluoroethylene or hydrafluoroethylene and ω-hydroxyalkyl vinyl ethers, comprising polysilicic acid and/or hexa(alkoxyalkyl)melamine, calculated as silica. and 0.5 to 35% by weight based on the total weight of the copolymer of the formula [wherein R is a divalent hydrocarbon having up to 10 carbon atoms or a hydrocarbon group with intervening oxygen; is an aliphatic hydrocarbon group having less than 5 carbon atoms, an acyl group having less than 5 carbon atoms, or a group of the formula (CH2CH20)nZ, where n is an integer of at least 1 and 2 is a carbon atom less than 5 aliphatic hydrocarbon groups; R2 is bonded to oxygen via an aromatic carbon and has 2500 to
A stable aromatic group that absorbs light in the region of 4000 A; and a is O or 1] is added to the composition to increase its resistance to ultraviolet light. coating composition.