Stock material or miscellaneous articles – Composite – Of epoxy ether
Reexamination Certificate
2001-05-22
2003-03-25
Moore, Margaret G. (Department: 1712)
Stock material or miscellaneous articles
Composite
Of epoxy ether
C428S447000, C106S287130
Reexamination Certificate
active
06537672
ABSTRACT:
The present invention relates to domestic appliances with a scratch-resistant and abrasion-resistant topcoat of a coating material comprising condensates based on hydrolysable silanes containing at least one epoxide group, on a powder-coated substrate.
The advantages of powder coating materials for the coating of surfaces, such as very good adhesion to metal surfaces, corrosion protection for metal surfaces, and ease of processability, for example, are known from the prior art. However, there is great interest in improvements to the coat morphology (increase in smoothness and uniformity, reduction in coat thickness) and in increasing the surface hardness and abrasion resistance. In the field of acrylate powder coating materials, a number of processes are known for providing the powder-coated surface with a coating based on organic-inorganic copolymers which is applied by wet chemical means.
JP-A-04318088 describes a methacryloyloxy-propyltrimethoxysilane-styrene copolymer for coating surfaces coated with an acrylate powder coating material. The transparent coatings, 20-30 &mgr;m in thickness, are said to possess good acid-resistance and scratch-resistance.
JP-A-06039349 describes a coating material based on polymerization products of hydrolysable silanes with a methacryloyloxypropyl substituent, further hydrolysable silanes, acrylate, methacrylate and epoxy methacrylate, and also the curing catalyst aluminium tris(acetylacetonate).
It is known that essentially inorganic coatings, i.e. coatings based on inorganic components, frequently have good surface hardness and abrasion resistance. Because of their high hardness, however, inorganic coatings are more brittle than essentially organic coatings, i.e. coatings based on organic components, with the result that cracking may occur. In particular, inorganic coatings are more brittle than organic powder coatings, with the result that cracking may occur on thermal curing at temperatures near the crosslinking temperature of the powder coating material and on cyclic temperature loading of the composite coating system.
The present invention is therefore based on the object of applying a thin, abrasion-resistant coat to powder-coated surfaces of domestic appliances without the occurrence of cracking or brittleness under temperature load.
This object is achieved by means of the domestic appliances of the invention, bearing on a powder-coated surface a scratch-resistant and abrasion-resistant topcoat of a coating material which comprises:
a) condensates based on hydrolysable silanes containing at least one non-hydrolysable substituent, the hydrolysable silanes having an epoxide group on at least one non-hydrolysable substituent;
b) a curing catalyst selected from Lewis bases and alkoxides of titanium, zirconium or aluminium;
c) nanoscale particulate inorganic solids having a particle size in the range from 1 to 100 nm; and
d) at least one organic monomer, oligomer or polymer containing at least one epoxide group.
In accordance with the invention, surprisingly thin, highly abrasion-resistant coatings are obtained which adhere particularly well to powder-coated surfaces, are very well adapted to the powder coating in their flexibility, and consequently possess a markedly improved cyclic temperature resistance (no cracking during preparation and application) and, moreover, exhibit very good scratch resistance or surface hardness and abrasion resistance.
In relation to the prior art, the process of the invention is easier to carry out, since it does not require complex preparation of copolymers or polymerization products of hydrolysed silanes with organic monomers or oligomers prior to the application of the coating material, so that it is possible to form substantially thinner coats having the aforementioned advantages.
The hydrolysable silanes containing at least one non-hydrolysable substituent, the hydrolysable silanes having an epoxide group on at least one non-hydrolysable substituent, comprise one or more silicon compounds possessing from 1 to 3, preferably 2 or 3, with particular preference 3, hydrolysable radicals and 1, 2 or 3, preferably one, non-hydrolysable radical. At least one of the non-hydrolysable radicals possesses at least one epoxide ring.
The silanes of component a) comprise, for example, compounds of the general formula (I):
R
n
SiX
4−n
(I)
in which n is 1, 2 or 3, preferably 1 or 2, with particular preference 1, X may be identical or different and is a halogen (F, Cl, Br and I, especially Cl and Br), alkoxy (especially C
1-4
alkoxy, such as methoxy, ethoxy, n-propoxy, isopropoxy and butoxy, for example), aryloxy (especially C
6-10
aryloxy, e.g. phenoxy), acyloxy (especially C
1-4
acyloxy, such as acetoxy and propionyloxy, for example) and alkylcarbonyl (e.g. acetyl), and R may be identical or different and is a non-hydrolysable radical, at least one radical R having an epoxide group.
Particularly preferred hydrolyzable radicals X are alkoxy groups, especially methoxy and ethoxy. Examples of non-hydrolysable radicals R without an epoxide ring are alkyl, especially C
1-4
alkyl (such as methyl, ethyl, propyl and butyl, for example), alkenyl (especially C
2-4
alkenyl, such as vinyl, 1-propenyl, 2-propenyl and butenyl, for example), alkynyl (especially C
2-4
alkynyl, such as acetylenyl and propargyl, for example) and aryl (especially C
6-10
aryl, such as phenyl and naphthyl, for example), it being possible for the groups just mentioned to carry, if desired, one or more substituents, such as halogen and alkoxy, for example. Also deserving of mention in this context of radicals R are methacrylic and methacryloxypropyl radicals.
Examples of non-hydrolysable radicals R with an epoxide ring are in particular those possessing a glycidyl or glycidyloxy group. They may be linked to the silicon atom via an alkylene group, e.g. a C
1-6
alkylene, such as methylene, ethylene, propylene, butylene. Specific examples of hydrolysable silanes which may be used in accordance with the invention may be found, for example, in EP-A-195493.
Hydrolysable silanes which are particularly preferred in accordance with the invention are those of the general formula (II):
X
3
SiR (II)
in which the radicals X, identical to or different from one another (preferably identical), are a hydrolysable group, for example one of the radicals X described above for the formula (I), preferably C
1-4
alkoxy and with particular preference methoxy and ethoxy, and R is a glycidyloxy-C
1-6
alkylene radical. Owing to its ready availability, &ggr;-glycidyloxypropyltrimethoxysilane (referred to below as GPTS for short) is used with particular preference in accordance with the invention.
In addition to the hydrolysable silanes containing at least one epoxide group, other hydrolysable compounds may also be used to construct the inorganic matrix. By other hydrolysable compounds are meant hereinbelow those not comprising hydrolysable silane containing at least one epoxide group. These other compounds likewise include an inorganic element with hydrolysable substituents attached to it.
It is possible to use one or more other hydrolysable compounds together with the hydrolysable silane or silanes containing at least one epoxide group in component a), the amount of the other hydrolysable compounds preferably not exceeding 80 mol %, and especially 60 mol %, based on the total hydrolysable compounds employed. Preferably at least 10, and with particular preference at least 20, mol % of all hydrolysable compounds employed are the other hydrolysable compounds which are different from the hydrolysable silane or silanes containing at least one epoxide group on a non-hydrolysable substituent.
Examples of suitable other hydrolysable compounds are hydrolysable compounds of elements selected from the third and fourth main groups (especially B, Al, Ga, Si, Ge and Sn) and from the third to fifth transition groups of the Periodic Table (especially Ti, Zr, Hf, V, Nb and Ta). However, other metal compounds may also lead to advantageous results, such as those o
Dittfurth Carola
Joerdens Frank
Schmidmayer Gerhard
Schmidt Helmut
Sepeur Stefan
Heller Ehrman White & McAuliffe LLP
Institut für Neue Materialien gem. GmbH
Moore Margaret G.
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