Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-10-28
2001-05-22
Szekely, Peter (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
Reexamination Certificate
active
06235814
ABSTRACT:
This invention relates to the use of polymers as modifiers or coatings in masonry applications.
Masonry refers to bound aggregates such as clay or bricks, cinder blocks, slag blocks, concrete blocks, blocks made from other aggregates, concrete, cement or stone walls, glazed bricks, glazed ceramic tile, marble, limestone, buildings of masonry construction, masonry curbs, blocks made from small stones, stucco, mortar, concrete roof tiles, slurry coats for concrete roof tiles, cement blocks, or masonry walls or ceilings. Masonry is made from solid particles (aggregate), water, and air. One requirement of masonry is that it has flexural strength. By flexural strength is meant that the masonry does not break or crack too readily when stressed. Another requirement of masonry is that it be water resistant. This is because a high amount of water absorption will weaken the masonry and lead to cracking.
It is known to admix polymers with masonry in order to improve permanence and reduce water absorption. U.S. Pat. No. 4,762,867 discloses the use of a copolymer containing from 1 to 15% of a hydrophobic monomer in cement mortar and concrete applications, where stearyl methacrylate is the preferred hydrophobic monomer. Copolymers containing 5% of a hydrophobic monomer are exemplified being admixed with the cement mortar. The use of the copolymer is taught to provide mortar or concrete with reduced water absorption and improved permanence.
Polymers have also been used to protect masonry surfaces from graffiti. U.S. Pat. No. 4,141,755 discloses the use of copolymers containing from 50 to 98% hydroxyalkyl (meth)acrylate and from 2 to 50% stearyl (meth)acrylate for sealing and coating building materials. The copolymer coating is taught to be useful for dirt pick up resistance and enabling the clean up of graffiti. The coating prevents the graffiti from penetrating the pores of the masonry. Instead, the graffiti is applied to the coating, which can be cleaned with a solvent. The copolymer coating however, is also taught to be moisture vapor permeable. Moisture vapor permeability may lead to the building material taking up water, which may weaken the building material.
Despite these disclosures, we have found that the use of a polymer containing from 20 to 100% by weight of a hydrophobic monomer as a masonry modifier provides increased flexural strength and water resistance to the masonry. We have also found that the use of a polymer containing from 20 to 100% by weight of a hydrophobic monomer as a masonry coating provides improved water resistance to the masonry. The hydrophobic monomer is present as polymerized units within the polymer. This polymer which provides flexural strength and improved water resistance when admixed with masonry and water resistance when applied as a coating on masonry has the added benefit of requiring only one polymer to modify the masonry in the place of two polymers.
The present invention provides a method of modifying a masonry composition comprising: treating the masonry composition with a polymer wherein the polymer comprises as polymerized units: a) from 20 to 100 parts by weight of at least one C
12
to C
40
alkyl ester of (meth)acrylic acid, b) from 0 to 80 parts by weight of at least one ethylenically unsaturated monomer, and c) from 0 to 80 parts by weight of at least one ethylenically unsaturated acid containing monomer or salts thereof, provided that when the at least one ethylenically unsaturated monomer is selected from hydroxyethyl (meth)acrylate and hydroxypropyl (meth)acrylate, the combined total level of hydroxyethyl (meth)acrylate and hydroxypropyl (meth)acrylate ranges from 0 to 40 parts by weight.
The present invention also provides a composition containing masonry and the polymer described above. The polymer may be dispersed throughout the masonry, dispersed throughout a slurry coating on the masonry, coated on the surface of the masonry or any combination thereof.
As used throughout this specification, by (meth)acrylic is meant either acrylic or methacrylic and by (meth)acrylate is meant either acrylate or methacrylate.
The polymer used in this invention may be prepared by a single stage or multi-stage process. The process may be an emulsion polymerization. See U.S. Pat. No. 5,521,266 for a detailed description of emulsion polymerization processes. The process may also be solution polymerization followed by emulsification. See U.S. Pat. No. 5,539,021 for detailed descriptions of a solution polymerization followed by mini-emulsion polymerization or micro-emulsion polymerizations. The emulsion polymerization process of U.S. Pat. No. 5,521,266 is preferred. In the process utilized for preparing the samples within this application, a first stage was prepared by adding a monomer emulsion and sodium persulfate to a solution containing methyl-p-cyclodextrin (“CD”), deionized water, and surfactant. The first stage was reacted at 85° C. A second stage was prepared by making a second monomer emulsion and feeding the second monomer emulsion and a sodium persulfate solution to the reacted first stage. The second stage was reacted at 85° C.
The polymer used in this invention is a composition which contains as polymerized units from 20 to 100 parts by weight, preferably from 30 to 100 parts by weight, more preferably 40 to 100 parts by weight of at least one C
12
to C
40
alkyl ester of (meth)acrylic acid (also referred to as a hydrophobic monomer). It is further preferred that the polymer used in this invention contains as polymerized units from 30 to 96 parts by weight, more preferably 40 to 93 parts by weight of at least one C
12
to C
40
alkyl ester of (meth)acrylic acid. It is preferred that the alkyl ester of (meth)acrylic acid be a C
16
to C
30
alkyl ester of (meth)acrylic acid. It is more preferred that the alkyl ester of (meth)acrylic acid be a C
16
to C
18
alkyl ester of (meth)acrylic acid. Suitable alkyl esters of (meth)acrylic acid include cetyl (meth)acrylate, stearyl (meth)acrylate, behenyl (meth)acrylate, and eicosyl (meth)acrylate. Beneficial properties may be obtained by utilizing more than one C
12
to C
40
alkyl ester of (meth)acrylic acid.
The polymer used in this invention may also contain as polymerized units from 0 to 80 parts by weight, preferably 0 to 50 parts by weight, more preferably 1 to 20 parts by weight of at least one ethylenically unsaturated monomer. Suitable ethylenically unsaturated monomers for use in the preparation of the polymer compositions of this invention include, but are not limited to (meth)acrylic ester monomers including methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, decyl acrylate, methyl methacrylate, and butyl methacrylate; acrylamide or substituted acrylamides; styrene or substituted styrene; vinyl acetate or other vinyl esters; vinyl monomers such as vinyl chloride, vinylidene chloride, N-vinyl pyrolidone; and acrylonitrile or methacrylonitrile. Butyl acrylate, methyl methacrylate, and styrene are preferred. More preferred are butyl acrylate and methyl methacrylate.
The ethylenically unsaturated monomer may be selected from hydroxyethyl (meth)acrylate and hydroxypropyl (meth)acrylate. When hydroxyethyl (meth)acrylate and hydroxypropyl (meth)acrylate are present in the polymer used in this invention, they are present as polymerized units at combined total levels ranging from 0 to 40 parts by weight, preferably 0 to 20 parts by weight, more preferably 0 to 10 parts by weight.
The polymer used in this invention may also contain as polymerized units from 0 to 80 parts by weight, preferably 0 to 50 parts by weight, more preferably 1 to 15 parts by weight ethylenically unsaturated acid containing monomer or salts thereof. Suitable ethylenically unsaturated acid containing monomers include, but are not limited to acrylic acid, methacrylic acid, crotonic acid, phosphoethyl methacrylate, 2-acrylamido-2-methyl-1-propanesulfonic acid, sodium vinyl sulfonate, itaconic acid, fumaric acid, maleic acid, monomethyl itaconate, monomethyl fumarate, monobutyl fumarate, and maleic anhydride
Greenblatt Gary D.
Rohm and Haas Company
Szekely Peter
LandOfFree
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