Method for applying and curing by UV radiation a sealant system onto natural stone tiles to provide permanent sealing, protection, abrasion resistance, stain and mold resistance, and natural stone tiles produced by the method
The invention relates to a process for applying a liquid UV-curable primer sealant to natural stone tiles and related articles followed immediately by the exposure to a requisite amount of low intensity UVA-type UV radiation to partially cure the primer sealant. The partial curing, or pre-setting, of the primer sealant enables control of the ultimate depth of penetration of the primer sealer into the natural stone tiles and natural stone articles of which many examples are quite porous. Because the low level UV irradiation is instantaneous after the primer sealant application the level of primer sealant penetration into the natural stone surface is regulated. The pre-curing of the primer sealant is conducted to intentionally solidify or immobilize the sealant that has actually penetrated into the natural stone surface. The uppermost layers of the primer sealant are left in a semi-liquid or uncured state to allow for wetting and intermingling by the top sealant once it is applied. Thus, the prior art problem of uncontrolled wicking is solved by the present invention.
1. A natural stone or tile article sealed according to a method comprising:
a) cleaning the natural stone tile or article;
b) conditioning the natural stone tile or article to a specified surface temperature of about 30° C. to about 40° C. by exposing the natural stone tile or article to a regulated amount of heat from one or more heat sources selected from the group consisting of infrared (IR) heating and convection heating;
c) conditioning liquid UV-curable solventless primer comprising an acid functional reagent selected from the group consisting of 2% to 4% of beta-carboxyethyl acrylate (β-CEA) and 1% to 6% of 2-hydroxy ethyl methacrylate phosphate, and UV-curable solventless top sealant by heating to a temperature of about 25° C. to about 40° C.;
d) applying the conditioned UV-curable solventless primer, and exposing the primer to UV radiation sufficient to partially cure the applied primer;
e) applying the UV-curable solventless top sealant; and,
f) exposing the primer and sealant to UV radiation sufficient to cure the primer and top sealant.
2. The stone or tile of claim 1 , wherein said sealed natural stone or tile article shows improved hot water and steam resistance.
3. The stone or tile of claim 2 , wherein the improved hot water and steam resistance of the sealant is determined by ASTM D 3359-Method B.