Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1999-10-28
2001-05-08
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S385000, C524S391000, C524S405000, C524S437000, C528S014000, C528S020000
Reexamination Certificate
active
06228921
ABSTRACT:
The present invention relates to a process for the production of compositions based on hydrolyzable silanes having epoxy groups, the compositions obtainable thereby, and the use of said compositions. Particularly, the present invention relates to a process for the production of such compositions for coatings and molded bodies having variable properties.
The prior art shows that it is possible to produce materials suitable for coating purposes via the sol-gel process from alkoxides such as, e.g., aluminum propylate or butylate, additionally using modified alkoxysilanes. Said processes are essentially characterized in that a mixture of the starting components can react to form a viscous liquid phase via a hydrolysis and condensation process. In said synthesis methods an organically modified inorganic basic skeleton is formed, which skeleton, in comparison to conventional polymers, is characterized by an increased surface hardness (scratch hardnesses using a Vickers diamond of 4 to 5 as compared to scratch hardnesses of conventional polymers of a magnitude of 1). However, a decisive disadvantage of said process is that due to the high reactivity of the aluminum-containing component no stable intermediate phases (“living system”) can be achieved. Thus, the so-called pot life is limited (depending on the application purpose, between several hours and several days). The longer pot lives are not a consequence of the stability of the system but are to be considered merely a consequence of the application. This means that for different applications in the field of coatings, a relatively wide range of the varying property of the material (viscosity) may be tolerated. As already mentioned, in comparison to organic polymers, said layers have a relatively high hardness but are still relatively soft in comparison to inorganic materials. The reason therefor is that although the inorganic components in the system act strongly crosslinking, due to their very low size (in molecular dimensions, i.e., <1 nm), the mechanical properties such as, e.g., hardness and abrasion resistance, do not manifest themselves. The last mentioned properties are very pronounced in so-called filled polymers since in that case the particles have sizes of several &mgr;m. However, the transparency of corresponding materials is lost and applications in the field of optics are not possible anymore. Although small particles of SiO
2
(e.g., Aerosil®, DEGUSSA) have successfully been employed for producing transparent layers having increased abrasion resistance, the abrasion resistances achieved with the employable low concentrations are similar to those of the systems mentioned above. The upper limit of the amount of filler is determined by the high surface reactivity of said small particles which results in agglomeration and intolerable increases in viscosity, respectively.
Thus, a first object of the present invention is to provide an organically modified inorganic system which shows a hardness significantly higher than that of the materials described in the prior art and which has a high optical transparency. Moreover, said system should also allow the preparation of stable intermediates which may be applied onto substrates and show properties constant with time as well as the adjustment of variable surface-physical and surface-chemical properties such as hydrophilic property or hydrophobic property in combination with oleophobic property.
In order to protect metallic surfaces against corrosion there are usually employed systems which develop passivating layers and are characterized in that they bond strongly to the surface, e.g., formation of mixed esters or oxides (Pb
3
O
4
on surfaces of iron, Cr
2
O
3
on surfaces of aluminum, etc.). By means of said surface compounds the reaction of water in combination with oxygen with the substrate material is prevented, said reaction resulting in a permanent oxidation of the surface layer of the substrate (metal). The protective oxide layers (passivating layers) generally show the further property of not reacting further even in the presence of moisture, but forming passivated surfaces (basic carbonates, hydroxides, oxides). For that reason it is not possible to protect metals such as iron or aluminum against corrosion without prior passivation merely by coating said metals with organic polymer paints. Purely organic paints show the property of being permeable to moisture and oxygen and thus, do not offer any protection against the attack by moisture and oxygen on the metallic surfaces.
The organically modified inorganic coating materials mentioned above on principle show the same disadvantages since due to the presence of organic groups they also allow the diffusion of water and moisture, respectively as well as oxygen through the corresponding layers. Although an improved protection against corrosion may be achieved by certain specific process measures, the corresponding materials are brittle and tend to form microcracks (particularly with variable load bending stress). Said formation of microcracks may damage the surface and corrosion may take place.
Thus, a second object of the present invention is the provision of an organically modified inorganic system suitable for the protection of metallic surfaces against corrosion without concomitantly showing the known disadvantages of corresponding systems such as brittleness, microcracking and poor adhesion to the substrate (metal).
The two objects mentioned above are achieved generically by a process for the production of compositions based on hydrolyzable silanes having epoxy groups, which process is characterized in that it comprises the addition of
i) at least one particulate material B, selected from the group of oxides, oxohydrates, nitrides, and carbides of Si, Al and B, as well as of transition metals, preferably Ti and Zr, and having a particle size ranging from 1 to 100 nm, particularly from 2 to 50 nm; and/or
ii) a preferably non-ionic surfactant C; and/or
iii) an aromatic polyol D having an average molecular weight not exceeding 1000;
to at least one pre-hydrolyzed silicon compound A having at least one hydrolytically unremovable radical directly bonded to Si, which radical includes an epoxide ring, provided that the hydrolysis of compound A may also be conducted in the presence of said material B.
By suitably selecting and optionally suitably combining the above components (i) to (iii) the coatings and molded bodies of the corresponding compositions may be provided with the properties mentioned above alternatively or cumulatively.
Particularly, the combination of the particulate material B with the hydrolyzable silicon compound A results in a composition for highly scratch-resistant coatings and molded bodies. If a composition for coatings and molded bodies of (long-term) hydrophilic property is desired the pre-hydrolyzed silicon compound A is preferably combined with a cationic, anionic or non-ionic surfactant, particularly preferred a non-ionic surfactant.
Finally, the combination of pre-hydrolyzed silicon compound A and aromatic polyol D results in a composition for corrosion-inhibiting coatings.
Obviously, one or both of the remaining components (i) to (iii) may be incorporated in each of the three basic types of compositions mentioned above, only provided that the composition for the corrosion-inhibiting coatings should not contain any surfactant C.
Thus, for example, in the composition for hydrophilic coatings and molded bodies, said particulate material B and/or said aromatic polyol D may additionally be incorporated in order to provide the corresponding coatings and molded bodies with a still better scratch resistance (particulate material B) or additionally an improved condensation water resistance (polyol D).
In the case of the composition for the corrosion-inhibiting coatings the additional incorporation of the particulate material B results in a higher scratch resistance of the corresponding coat. Furthermore, a hydrolyzable silicon compound having at least one non-hydrolyzable radical which has 5 to 3
Arpac Ertugrul
Geiter Elisabeth
Gerhard Volker
Kasemann Reiner
Schmidt Helmut
Aylward D.
Dawson Robert
Institut fur Neue Materialien gemeinnutzige GmbH
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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