Silica products and UV curable systems

Details Silica products and UV curable systems Silica products and UV curable systems

1999-02-12

2000-03-21

Berman, Susan W.

Compositions: coating or plastic

Coating or plastic compositions

Wax containing

10628734, 522 83, 522 96, 522103, 523209, 523300, C08L 9106, C09D 102, C08K 900, C08J 328

Patent

active

060397985

DESCRIPTION:

BRIEF SUMMARY
FIELD OF INVENTION

The invention relates to wax coated silica matting agents used in the matting of UV curable systems and to UV curable systems containing the same.


BACKGROUND TO THE INVENTION

UV curing is based on photoinitiated polymerisation of functional oligomers and monomers into a crosslinked polymer network. When an ultraviolet curable coating is exposed to UV energy in this way a relatively hard film, having an extremely smooth surface, and hence one of high gloss, is produced. With the increasing popularity of radiation cured coatings for a wide variety of applications, the ability to control and reduce gloss is becoming more important. It is well known that matt surfaces provide the finished article with a more elegant appearance and hide imperfections at the surface, particularly in wood, furniture and PVC flooring applications, and several different methods of reducing the gloss of UV curable coatings have been reported, for example the use of "dual cure" or "gradient intensity cure" techniques, specific photoinitiators and non-silica type matting agents.
Traditional silica matting agents are conveniently used to reduce the gloss of solvent and water based finishes and in the UV industry synthetic silicas are used to provide a semi-gloss or matt effect, although as a rule high concentrations are generally required by the formulator. The high solids nature of UV systems and the absence of adequate film shrinkage, required to ensure optimal levels of particles are present in the surface of the cured film, makes efficient matting difficult. Accordingly, high concentrations of conventional silicas are required to achieve an acceptable degree of gloss reduction. Such high levels of silica can frequently cause changes in the rheological properties of the lacquer which can be detrimental to the coating and curing process and, can impair the optical properties of the cured film.
In an attempt to overcome this problem, the use of large particle size silicas has been promoted in the past for both thin and thick film applications. Such materials may produce an unacceptable level of roughness particularly in thin coatings and, depending on the viscosity of the system, can result in a greater tendency to settle on prolonged storage. It would be desirable therefore to provide a synthetic silica matting agent for UV systems, having good efficiency and minimal effect on formulation viscosity and film properties.
There is therefore a need for a new matting agent which overcomes these problems.


Definitions and Test Procedures
of Brunauer, Emmett and Teller (BET) using a multi point method with an ASAP 2400 apparatus supplied by Micromeritics of the U.S.A. The samples are outgassed under vacuum at 270.degree. C. for at least one hour before measurement. Surface area is calculated from the volume of nitrogen gas adsorbed at p/po 0.98. This apparatus also provides the pore size distribution from which it is possible to get the pore size (D.sub.10) for which 10% of the pores are below this pore size. In the same manner, it is possible to get the pore size for which 50% (D.sub.50) and 90% (D.sub.90) of the pores are below this pore size. Additionally the pore volume (cm.sup.3 /g) for a given range of pore size can be obtained from the desorption curve. have been chosen for the study, one is a urethane acrylate formulation (Formulation 2) and one is representative of an epoxy acrylate formulation (Formulation 1), details of which are given in the following Table.


______________________________________ Formulation 2 % Formulation 1 % ______________________________________ EBECRYL 294 62.1 EBECRYL 608 44.7 N-vinyl 9.5 OTA 480 22.2 pyrrolidone 2-ethyl hexyl 19.2 TPGDA 22.2 acrylate Benzophenone 2.85 Benzophenone 3.3 DAROCUR 1173 0.95 IRGACURE 651 2.2 Silica 5.4 Silica 5.4 matting agent matting agent ______________________________________ adopted. The binder and diluent were added to a 60 ml amber glass jar and stirred at 8000 rpm for 1 minute using an I

REFERENCES:
patent: 4097302 (1978-06-01), Cohen et al.
patent: 4206025 (1980-06-01), Vrancken et al.
patent: 5318808 (1994-06-01), Crivello et al.
patent: 5585415 (1996-12-01), Gorzalski et al.
patent: 5637636 (1997-06-01), Cartwright et al.

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