Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2000-11-06
2003-07-22
Harlan, Robert D. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C526S081000, C526S089000, C526S911000, C526S915000
Reexamination Certificate
active
06596804
ABSTRACT:
This invention relates to emulsion polymers and a method for preparing emulsion polymers. More particularly this invention relates to emulsion polymers capable of contributing useful rheological properties to aqueous coating compositions containing the emulsion polymers. The emulsion polymers are prepared by the post-polymerization treatment of a first emulsion polymer with colloidal stabilizer, monomer, and a redox system at 20-85° C.
U.S. Pat. No. 5,665,816 discloses aqueous dispersions prepared by the polymerization of vinyl acetate, ethylene, and various ethylenically unsaturated comonomers in the presence of unsaturated carboxylic acid and 1.5-20% by weight of cellulose ether, to form a copolymer having a glass transition temperature of −40° C. to 0° C. and comprising a cellulose ether in at least partly grafted form. The unsaturated carboxylic acid and cellulose ether are present throughout the polymerization reaction.
The problem faced by the inventors is the provision of modified emulsion polymers. The inventors found that treatment of a first emulsion polymer with colloidal stabilizer, monomer, and redox system at 20-85° C. after the formation of the first emulsion polymer was effective in modifying the emulsion polymer and offered freedom from concern over gelation of the reaction mixture during the polymerization reaction. Further, the post-polymerization process may be effected at a different time and place and at a lower temperature than the original polymerization reaction, for example, beneficially freeing up the reaction kettle for subsequent polymerization reactions.
In a first aspect of the present invention there is provided an emulsion polymer formed by the free radical polymerization of at least one first ethylenically unsaturated monomer until at least 95% of the first monomer by weight has been converted to a first emulsion polymer and subsequent treatment of the first emulsion polymer with 0.01-6%, by weight, based on the weight of the first emulsion polymer, of a colloidal stabilizer, 0.01-10%, by weight, based on the weight of the first emulsion polymer, of at least one second ethylenically unsaturated monomer, and 0.05-0.35%, by weight, based on the weight of the first emulsion polymer, of a redox system at 20-85° C. until at least 90% of the sum of the residual monomer of the first emulsion polymer and the second monomer has been converted to polymer.
In a second aspect of the present invention there is provided a method for preparing an emulsion polymer including forming a first emulsion polymer by the free radical polymerization of at least one first ethylenically unsaturated monomer until at least 95% of the first monomer by weight has been converted to the first emulsion polymer; and subsequently treating the first emulsion polymer with 0.01-6%, by weight, based on the weight of the first emulsion polymer, of a colloidal stabilizer, 0.01-10%, by weight, based on the weight of the first emulsion polymer, of at least one second ethylenically unsaturated monomer, and 0.05-0.35%, by weight, based on the weight of the first emulsion polymer, of a redox system at 20-85° C. until at least 90% of the sum of the residual monomer of the first emulsion polymer and the second monomer has been converted to polymer.
This invention relates to an emulsion polymer formed by the free radical polymerization of at least one first ethylenically unsaturated monomer until at least 95% of the first monomer by weight has been converted to a first emulsion polymer and subsequent treatment according to the method of this invention. The first emulsion polymer contains at least one copolymerized ethylenically unsaturated monomer. Ethylenically unsaturated monomers include, for example, (meth)acrylic ester monomers including methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, decyl acrylate, lauryl acrylate, methyl methacrylate, butyl methacrylate, isodecyl methacrylate, lauryl methacrylate; hydroxyethyl (meth)acrylate and hydroxypropyl (meth)acrylate; (meth)acrylamide; (meth)acrylonitrile; styrene and substituted styrenes; butadiene; vinyl acetate, vinyl butyrate and other vinyl esters; and vinyl monomers such as ethylene, vinyl chloride, vinylidene chloride. The use of the term “(meth)” followed by another term such as acrylate or acrylamide, as used throughout the disclosure, refers to both acrylates or acrylamides and methacrylates and methacrylamides, respectively.
The first emulsion polymer may contain from 0 to 5%, preferably from 0.5 to 2%, by weight based on polymer weight, of a copolymerized monoethylenically-unsaturated acid-group containing monomer, based on the weight of the polymer, such as, for example, acrylic acid, methacrylic acid, crotonic acid, itaconic acid, fumaric acid, maleic acid, monomethyl itaconate, monomethyl fumarate, monobutyl fumarate, maleic anhydride, sulfoethyl methacrylate, and phosphoethyl methacrylate. The first emulsion polymer may contain from 0 to 5%, preferably from 0 to 2%, by weight based on polymer weight, of a copolymerized monoethylenically-unsaturated amino-group containing monomer, based on the weight of the polymer, such as, for example, diethylaminoethyl (meth)acrylate and t-butylaminoethyl (meth)acrylate. The first emulsion polymer may contain from 0% to 1%, by weight based on polymer weight, copolymerized multi-ethylenically unsaturated monomers such as, for example, allyl methacrylate, diallyl phthalate, 1,4-butylene glycol dimethacrylate, 1,2-ethylene glycol dimethacrylate, 1,6-hexanediol diacrylate, and divinyl benzene. Preferred first emulsion polymers contain predominant amounts of copolymerized acrylic, styrene+acrylic, or vinyl acetate+acrylic monomers. More preferred first emulsion polymers contain copolymerized ethyl acrylate or butyl acrylate. Most preferred first emulsion polymers contain predominant amounts of methyl methacrylate and ethyl acrylate or methyl methacrylate and butyl acrylate.
The glass transition temperature (“Tg”) of the first emulsion polymer is preferably from −40° C. to 85° C., more preferably from −10° C. to 40° C., as measured by differential scanning calorimetry (DSC) taking the mid-point in the heat flow versus temperature transition as the Tg value, the monomers and amounts of the monomers being selected to achieve the desired polymer Tg range as is well known in the art.
The polymerization techniques used to prepare the first emulsion polymer are well known in the art. In the emulsion polymerization process conventional surfactants may be used such as, for example, anionic and/or nonionic emulsifiers such as, for example, alkali metal or ammonium salts of alkyl, aryl, or alkylaryl sulfates, sulfonates or phosphates; alkyl sulfonic acids; sulfosuccinate salts; fatty acids; ethylenically unsaturated surfactant monomers; and ethoxylated alcohols or phenols. The amount of surfactant used is typically 0.1% to 6% by weight, based on the weight of monomer. The monomer may be added neat or as an emulsion in water. The monomer may be added in one or more additions or continuously, linearly or not, over the reaction period , or combinations thereof.
Either thermal or redox initiation processes may be used in the preparation of the first emulsion polymer. Conventional thermal free radical initiators may be used such as, for example, hydrogen peroxide, sodium peroxide, potassium peroxide, t-butyl hydroperoxide, cumene hydroperoxide, ammonium and/or alkali metal persulfates, sodium perborate, perphosphoric acid and salts thereof, potassium permanganate, and ammonium or alkali metal salts of peroxydisulfuric acid, typically at a level of 0.01% to 3.0% by weight, based on the weight of total monomer. “Redox systems” herein are oxidant+reducing agent combinations effective to generate free radicals, including the same free radical initiators listed hereinabove as oxidant and a suitable reductant such as, for example, sodium sulfoxylate formaldehyde, ascorbic acid, isoascorbic acid, alkali metal and ammonium salts of sulfur-containing acids, such as
Edwards Steven Scott
Even Ralph Craig
Kowalski Alexander
Wieckowski Loretta Ann
Bakule Ronald D.
Harlan Robert D.
Rohm and Haas Company
LandOfFree
Emulsion polymers does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Emulsion polymers, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Emulsion polymers will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3090754