Process for providing barrier properties to porous substrates
The invention relates to an improvement in a process for imparting barrier properties to porous substrates, such as, concrete, masonry products, and wood products. The process comprises the steps of: applying an aqueous based sealing composition comprising a polymeric resin to said porous substrate, evaporating the water and forming a water repellent coating of said polymeric resin on said porous substrate. The improvement comprises: deriving the polymeric resin from an aqueous based polymer emulsion comprising a polymer comprised of emulsion polymerized units of vinyl acetate and ethylene, preferably with a carboxylic acid monomer, the polymer containing amorphous and crystalline ethylene segments and having: (a) a crystalline melting point (T m ) ranging from 35 to 110° C., preferably 50 to 100° C.; measured at a heat rate of 20° C./minute; and, (b) a tensile storage modulus of at least 1×10 5 dynes/cm 2 at 115° C. measured at 6.28 rad/sec.
1. In a process for imparting barrier properties to porous substrates selected from the group consisting of concrete, masonry products and wood which comprises the steps: applying an aqueous based sealing composition comprising a polymeric resin to said porous substrate, evaporating the water and forming a water repellent coating of said polymeric resin on said porous substrate, the improvement which comprises:
using a polymeric resin comprised of a polymer formed by emulsion polymerization in the presence of a stabilizing system and comprising emulsion polymerized units of ethylene and vinyl acetate and having:
(a) a crystalline melting point ranging from 35 to 110° C. measured at a heat rate of 20° C. per minute;
(b) a tensile storage modulus of at least 1×10 5 dynes/cm 2 at a temperature of 115° C. and measured at 6.28 rad/sec;
(c) a crystalline heat of fusion of from about 5 to 100 joules per gram as measured at a heat rate of 20° C. per minute; and,
(d) a glass transition temperature from +25° C. to about −35° C. as measured at a heat rate of 20° C. per minute.
2. The process of claim 1 wherein the polymer is comprised of emulsion polymerized units of from 15 to 80 wt % vinyl acetate, 20 to 85 wt % ethylene, and 0 to 5 wt % of a carboxylic acid, based on the total weight of the polymer.
3. The process of claim 1 wherein the polymer is comprised of emulsion polymerized units of from 40 to 70 wt % of vinyl acetate and from about 30 to 60 wt % of ethylene, based upon the total weight of the polymer.
4. The process of claim 3 wherein the polymer is also comprised of about 0.1 to about 10 wt % of polymerized units of a monomer selected from the group consisting of a carboxylic acid and N-methylolacrylamide.
5. The process of claim 3 wherein the polymer has a tensile storage modulus of at least 2×10 5 dynes/cm 2 at 115° C. and measured at 6.28 rad/sec.
6. The process of claim 2 wherein the polymer is comprised of polymerized units of ethylene, vinyl acetate, and acrylic acid.
7. The process of claim 6 wherein the crystalline heat of fusion ranges from 10 to 50 joules per gram as measured at a heat rate of 20° C. per minute.
8. The process of claim 6 wherein the crystalline melting point ranges from 50 to 100° C. as measured at a heat rate of 20° C. per minute.
9. The process of claim 7 wherein a portion of the emulsion polymerization is carried out at a pressure of from 1000 to 2000 psig (6,996 to 13,891 kPa).
10. The process of claim 7 wherein the stabilizing system comprises hydroxyethyl cellulose in combination with a surfactant.
11. The process of claim 7 wherein the stabilizing system includes a surfactant selected from the group consisting of an anionic surfactant and a nonionic surfactant.
12. The process of claim 4 wherein the polymer comprises polymerized units of vinyl acetate, ethylene, and N-methylolacrylamide.
13. The process of claim 12 wherein the crystalline melting point ranges from 50 to 100° C. as measured at a heat rate of 20° C. per minute.