Coating processes – With post-treatment of coating or coating material – Heating or drying
Patent
1996-05-09
1999-08-03
Fortuna, Ana
Coating processes
With post-treatment of coating or coating material
Heating or drying
2105001, 21050025, 4273899, 427412, 427209, 428242, B05D 302
Patent
active
059322918
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to phase separation apparatus for use in phase separation processes, including papermaking and filtration.
When carrying out a phase separation process it is generally important to use phase separation media that exhibit good abrasion resistance, cleanliness and stability.
It is an object of the present invention to provide phase separation apparatus which exhibit such properties.
According to the present invention there is provided the use of at least one ormocer in phase separation apparatus.
The ormocer preferably acts as a phase separation medium such as a filter or papermachine clothing.
The phase separation apparatus of the invention may comprise papermachine clothing possibly including a fabric in combination with the ormocer.
Alternatively the phase separation apparatus may comprise a filter comprising a filter element including the ormocer.
Ormocers (organically-modified ceramics) are inorganic/organic composites combining the properties of ceramics with those of organic components. For the avoidance of doubt the term ormocer used herein includes organically-modified silicates. One example of an ormocer is an organosilane-impregnated silica gel which can be pyrolysed to form SiC-reinforced silica which is two to three times harder than the silica matrix alone.
An ormocer typically comprises a polar component, a hydrophobic component and micro-ceramic particles. The polar component provides good adhesion of the ormocer to the substrate. This is particularly important for papermachine clothing where adhesion of coatings to conventional polyethylene terephthalate (PET) clothing material is difficult to achieve. The hydrophobic component, which may be a fluorinated material, is preferably orientated to the air-coating interface so as to impart non-stick properties at the coating surface. The micro-ceramic particles impart abrasion resistance and anti-scratch properties.
The ormocers can be made by a typical sol-gel process. Gels are useful in that they have a good capacity to incorporate both organic and inorganic components and they allow very fine ormocer particles to be produced. Generally, sol-gel derived materials can be cast to shape at room temperature. Therefore they are excellent low-temperature hosts for organic molecules, polymers and fibres.
An additional method of preparing an ormocer coating is by impregnating porous xerogels with organic monomers and then curing the coating in situ.
Ormosils can be made by combining tetraalkoxysilanes with alkyl substituted and organofunctional alkoxysilanes, namely Si(OR).sub.4 +R.sub.2 Si(OR).sub.2 +YR.sup.1 Si(OR).sub.3 where R is alkyl, R.sup.1 is alkylenyl and Y is an organofunctional group such as --R.sup.1 --NH.sub.2, --R.sup.1 NHCOONH.sub.2 or --R.sup.1 --S--R.sup.1 --CHO. The choice of precursors depends on the solubility or thermal stability of the organofunctional substituents.
Typically ormocers are based on alumina, zirconia, titanium dioxide or silica-based organic network formers containing epoxy or methacrylate groups bonded to silicon atoms via a Si--C bond.
Either the network formers or work modifiers can be tailored for specific applications. For example, epoxysilanes may be used to impart scratch resistance. Thermoplastic or photocurable groups based on diphenylsilanes or photocurable ligands, such as methacryl vinyl or allyl groups, in combination with a variety of polymerisable monomers may be used for coatings and adhesiveness.
The ormocer may be coated on a surface of a substrate. The substrate may comprise ceramic, glass, metal or plastics, but is preferably a fabric. Any suitable coating method may be employed for coating the substrate with the ormocer, such as immersion, spraying or roller or lick coating. The ormocer is then heated to a temperature in the order of 90.degree. C. to 140.degree. C. depending on the ormocer concerned, or is cured by ultra-violet radiation (eg wave lengths of 365 nm or 254 nm) to fix the ormocer onto the substrate. Adherence of the coating to a PET substrate may be im
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Saunders Thomas
Sayers Ian Christison
Fortuna Ana
Scapa Group PLC
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