Stock material or miscellaneous articles – Composite – Of quartz or glass
Reexamination Certificate
2000-04-03
2002-03-26
Copenheaver, Blaine (Department: 1773)
Stock material or miscellaneous articles
Composite
Of quartz or glass
C428S328000, C428S415000, C428S447000, C524S430000, C524S437000, C524S441000, C528S010000
Reexamination Certificate
active
06361868
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to coating compositions based on epoxy group-containing hydrolysable silanes, articles coated therewith and their use.
Materials which are suitable as coatings can be prepared from alkoxides, for example aluminium propanolate or aluminium butanolate, with use of modified alkoxy silanes, using the sol-gel method. These sol-gel processes are substantially characterised in that a mixture of the starting components reacts to form a viscous liquid phase as a result of a process of hydrolysis and condensation. This synthesis procedure gives rise to an organically modified inorganic parent structure whose surface hardness is greater than that of conventional organic polymers. However, a crucial disadvantage is that the high reactivity of the aluminium-containing component is a barrier to achieving good stability in storage (pot life). The layers obtained are still relatively soft by comparison with inorganic materials. The reason is that although the inorganic constituents in the system produce a strong cross-linking effect, their very small size prevents such mechanical properties as, for example, their hardness and abrasion resistance from having an effect. So-called filled polymers offer the potential for full exploitation of the favourable mechanical properties of the inorganic constituents, because particle sizes which are present in this case are of several micrometers. Yet in this case the transparency of the materials is lost, and applications in the optical field are no longer possible. While it is possible to use small SiO
2
particles (for example Aerosils®) to produce transparent layers having increased abrasion resistance, the abrasion resistance values achievable at the low concentrations which can be used are similar to those of the above-mentioned system. The upper limit to the quantity of filler which can be used is dictated by the high surface reactivity of the small particles which results in agglomeration or unacceptably increased viscosity.
WO 95/13326 describes a process for the preparation of an organically modified inorganic system which has markedly greater hardness than that of the systems described above, and a high degree of optical transparency. It also describes organically modified inorganic systems suitable for protecting metal surfaces from corrosion as well as corresponding systems for hydrophilic coatings. The compositions are obtained by a process which comprises the addition, to at least one pre-hydrolysed silicon compound having an epoxy group-containing radical bonded directly to Si, of a particulate material which is selected from among oxides, oxide hydrates, nitrides and carbides of Si, Al and B or transition metals and has a particle size within the range 1 to 100 nm, preferably boehmite, and/or the addition of a preferably nonionic surfactant and/or of an aromatic polyol. A high scratch resistance is achieved by combining the pre-hydrolysed silicon compound with the particulate material. On the other hand, by combining the pre-hydrolysed silicon compound with a surfactant hydrophilic coatings are obtained, while, by combining the pre-hydrolysed silicon compound with an aromatic polyol, corrosion-inhibiting coatings can be obtained. The addition of fluorinated silanes may be chosen in the process, in order to prepare hydrophobic or oleophobic coatings, or the addition of Lewis bases or alcoholates as cross-linking catalysts, or the addition of further hydrolysable compounds.
DE-40 20 316-A1 describes a lacquer based on hydrolysable silanes which affords abrasion-resistant, flexible coatings after curing. It is obtainable by reacting with water one or more silicon compounds containing an epoxy group, wherein the molar ratio of water to hydrolysable groups which are present is from 1:1 to 0.4:1. Further hydrolysable compounds of, for example, aluminium, titanium, zirconium, vanadium. tin, lead and boron, may also be used in addition to the silicon compound. Tertiary amines which bring about cross-linking of the epoxy groups at temperatures above 60° C. are particularly suitable as catalysts for curing the composition.
DE-OS 30 21 018 discloses a coating composition which contains a partially hydrolysed condensation product of alkyl trialkoxysilanes, an organic carboxylic acid and an anionic fluorocarbon surface-active agent. The silanes used contain no epoxy groups. The composition affords surface coatings having an abrasion-resistant surface and good transparency, heat resistance and adhesion to the base material, as well as water-resistance.
U.S. Pat. No 5,134,191 discloses a hard coating composition which contains an epoxy group-containing organic silicon compound and inorganic submicron particles, such as silica sol, and is curable using a minimal amount of an antimony compound as the curing catalyst. It is usable as a coating film for plastics-material optical articles. The composition may optionally also contain an aluminium compound.
The object of the present invention is to provide a composition having scratch resistance, adhesion, lacquer viscosity and elasticity which are improved even further, and a lesser tendency towards gelation and clouding compared with the or art compositions.
SUMMARY OF THE INVENTION
This object is achieved by a coating composition comprising at least one silicon compound (A) which has at least one radical which is bonded directly to Si, is not able to be separated hydrolytically and contains an epoxy group, a particulate material (B) which is selected from among oxides, oxide hydrates, nitrides and carbides of Si, Al and B and of transition metals and has a particle size within the range 1 to 100 nm, an Si, Ti, Zr, B, Sn or V compound (C) and at least one hydrolysable Ti, Zr or Al compound (D), characterised in that it comprises the following ratio
1.0 mol of the silicon compound (A),
0.27 to 0.49 mol of the particulate material (B),
0.36 to 0.90 mol of the compound (C) and
0.14 to 0.22 mol of the compound (D)
DETAILED DESCRIPTION OF THE INVENTION
The compositions according to the invention characterised by certain quantitative ratios of the components used afford highly scratch-resistant coatings which have particularly good adhesion to the coated material and a markedly increased pot life. A Lewis base (E) may be used additionally as a catalyst in order to achieve a more hydrophilic character for the composition according to the invention.
A hydrolysable silicon compound (F) having at least one non-hydrolysable radical which has 5 to 30 fluorine atoms bonded directly to carbon atoms may additionally be used, wherein the latter carbon atoms are separated from the Si by at least 2 atoms. The use of such a fluorinated silane imparts hydrophobic and soil-repellent properties to the corresponding coating.
A preferably nonionic surfactant (G) may also be used additionally in order to achieve enduring hydrophilic properties, and/or an aromatic polyol (H) in order to tat achieve corrosion-inhibiting properties (increased resistance to condensation).
The compounds (A) to (H) are explained in greater detail below:
Silicon Compound (A)
The silicon compound (A) is a silicon compound which has available 2 or 3 hydrolysable radicals, preferably 3, and one or 2 non-hydrolysable radicals, preferably one. The single non-hydrolysable radical and, respectively, at least one of the two non-hydrolysable radicals, have available an epoxy group.
Examples of the hydrolysable radicals are halogen (F, Cl, Br and I, in particular Cl and Br), alkoxy (in particular C
1-4
-alkoxy, such as, for example, methoxy, ethoxy, n-propoxy, i-propoxy and n-butoxy, i-butoxy, sec-butoxy and tert-butoxy), aryloxy (in particular C
6-10
-aryloxy, for example phenoxy), acyloxy (in particular C
1-4
-acyloxy, such as, for example, acetoxy and propionyloxy) and alkylcarbonyl (for example acetyl). Alkoxy groups, in particular methoxy and ethoxy, are particularly preferred hydrolysable radicals.
Examples of non-hydrolysable radicals having no epoxy group are hydrogen, alkyl, in particular C
1-4
-alk
Bier Peter
Krug Herbert
Sepeur Stefan
Stein Sabine
Bayer Aktiengesellschaft
Copenheaver Blaine
Gil Joseph C.
Paulraj Christopher
Roy Thomas W.
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