Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1999-05-21
2002-02-12
Zitomer, Fred (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S269000, C526S310000, C526S319000, C526S320000, C526S321000, C526S325000
Reexamination Certificate
active
06346591
ABSTRACT:
FIELD OF THE INVENTION
The invention concerns water-soluble and water-dispersible monomers and resins and processes for preparing aqueous resin compositions.
BACKGROUND OF THE INVENTION
Aqueous resin compositions are widely used in many different fields, including coatings, inks, detergents, additives for plastics, water treatment, papermaking, and oil field production and refining. In particular, polyacrylamide and copolymers of acrylamide have gained prominence as nonionic or cationic polymers that are water soluble. Because of industrial hygiene considerations associated with use of acrylamide monomer, a replacement for acrylamide has long been sought. Modifications such as N-substituted acrylamide monomers (e.g., N-methylol acrylamide) have been proposed. Polymers produced with the acrylamide and modified acrylamide monomers, however, have other shortcomings that make them undesirable. For example, the only reactive functional group of acrylamide is the unsaturation, so the polymerized acrylamide unit does not provide a site for crosslinking or further modification. Crosslinking or other modification of the acrylamide unit would be useful to reduce water sensitivity of the homopolymer or copolymer at an appropriate time.
Thus it would be desirable to provide a water soluble monomer that could be used in the place of acrylamide, would not have the industrial hygiene concerns associated with acrylamide, and could be modified when it would be appropriate to reduce the water sensitivity of a polymer prepared from the water soluble monomer.
SUMMARY OF THE INVENTION
We have now invented a method of preparing improved aqueous resin compositions. The resins are prepared by employing a &bgr;-hydroxy carbamate monomer. The &bgr;-hydroxy carbamate monomer is polymerized to form water-soluble homopolymers or, if polymerized as a mixture with one or more comonomers, copolymers that are soluble or dispersible in water. The &bgr;-hydroxy carbamate monomer of the invention can be used as a replacement for acrylamide, especially for preparing aqueous resin compositions. The &bgr;-hydroxy carbamate monomer offers an advantage of providing reactive sites for crosslinking or other reactions after polymerization.
When used in connection with the invention, the term “carbamate group” refers to a group having a structure
in which R
1
is H or alkyl. Preferably, R
1
is H or alkyl of from 1 to about 4 carbon atoms, and more preferably R
1
is H.
When polymerized, the monomer of the invention provides two reactive sites, a hydroxyl group and a reactive carbamate group, for crosslinking or other modification of the polymer.
DETAILED DESCRIPTION OF THE INVENTION
The &bgr;-hydroxy carbamate monomer has an ethylenically unsaturated group and a &bgr;-hydroxy carbamate group. Preferably, there are from 1 to about 4 carbons between the ethylenically unsaturated group and the &bgr;-hydroxy carbamate group. The &bgr;-hydroxy carbamate monomer of the invention can be represented by a structure:
wherein either each R
2
is hydrogen or one R
2
is hydrogen and the other R
2
is methyl; n is from 1 to about 4, preferably 1; and one of Y and Z is OH and the other of Y and Z is
wherein R
1
is H or alkyl. Preferably, R
1
is H or alkyl of from 1 to about 4 carbon atoms, and more preferably R
1
is H. In a typical synthesis of the &bgr;-hydroxy carbamate monomer, the reaction kinetics produces a product that is a mixture of the compound in which Y is hydroxyl and Z is the carbamate group and the compound in which Z is a hydroxyl and Y is the carbamate group.
Unlike acrylonitrile, the monomer of the present invention has reaction rates comparable to other acrylic monomers. The monomer can be polymerized to form a homopolymer. The polymerization can be carried out in water or in an a mixture that includes water. The monomer of the invention can also be copolymerized with other monomers, including acrylic, methacrylic, vinylic and allylic monomers, again preferably in an aqueous medium. Particular examples of suitable comonomers include, without limitation, acrylic acid, methacrylic acid, crotonic acid, esters of these acids, maleic anhydride, styrene, alpha-methylstyrene, vinyl acetate, and so on. Other functional monomers may be copolymerized along with the &bgr;-hydroxy carbamate monomer, including, without limitation, acid- and anhydride-functional monomers such as those already mentioned; hydroxyl-functional monomers such as hydroxyalkyl acrylates and methacrylates, amino-functional acrylic monomers such as t-butylaminoethyl methacrylate and t-butylamino-ethylacrylate; epoxide-functional monomers such as glycidyl acrylate, glycidyl methacrylate, and allyl glycidyl ether; other carbamate-functional monomers, and so on.
One way of preparing the &bgr;-hydroxy carbamate monomer of the invention is by reacting a glycidyl-group containing polymerizable monomer first with carbon dioxide to convert the oxirane group to a cyclic carbonate group, and then with ammonia or a primary amine to convert the cyclic carbonate group to a &bgr;-hydroxy carbamate group. Examples of suitable oxirane group-containing polymerizable monomers include, without limitation, glycidyl acrylate, glycidyl methacrylate, glycidyl crotonate, and allyl glycidyl ether. Oxirane groups can be converted to carbamate groups by first converting to a cyclic carbonate group by reaction with CO
2
. This can be done at any pressure from atmospheric up to supercritical CO
2
pressures, but is preferably under elevated pressure (e.g., 60-150 psi). The temperature for this reaction is preferably 60-150° C. Useful catalysts include any that activate an oxirane ring, such as tertiary amine or quaternary salts (e.g., tetramethyl ammonium bromide), combinations of complex organotin halides and alkyl phosphonium halides (e.g., (CH
3
)
3
Snl, Bu
4
Snl, Bu
4
Pl, and (CH
3
)
4
Pl), potassium salts (e.g., K
2
CO
3
, Kl) preferably in combination with crown ethers, tin octoate, calcium octoate, and the like.
The cyclic carbonate group is reacted with ammonia or a primary amine. The primary amine preferably has up to four carbons, e.g. methyl amine. Preferably, the cyclic carbonate is reacted with ammonia. The ammonia may be aqueous ammonia (i.e., NH
4
OH). The reaction ring-opens the cyclic carbonate to form a &bgr;-hydroxy carbamate monomer according to the invention.
The &bgr;-hydroxy carbamate monomer is water soluble. In one embodiment of the invention, the &bgr;-hydroxy carbamate monomer is polymerized to form a homopolymer. The homopolymer is water-soluble. The &bgr;-hydroxy carbamate monomer may be polymerized in the presence of free-radical initiators or with a redox initiator system. Useful initiators and redox initiator systems are well-known. The polymerization may be carried out without solvent or in an organic or aqueous medium. In a preferred embodiment, the &bgr;-hydroxy carbamate monomer is polymerized in an aqueous medium, preferably without any organic solvent or with a minor amount (up to about 10% by weight of the aqueous medium) of a polar solvent such as methanol, tetrahydrofuran, propylene glycol monomethyl ether, or other water-soluble or water-miscible solvents. The &bgr;-hydroxy carbamate monomer may be dissolved in water along with the initiating system and polymerized at a suitable temperature for the initiating system.
Alternatively, the &bgr;-hydroxy carbamate monomer may be polymerized as a mixture with one or more comonomers. Depending on the comonomers chosen, and the ratio of the &bgr;-hydroxy carbamate monomer with the other comonomers, the copolymers may be water soluble or water dispersible. As used herein, “dispersible” or “water dispersible” encompasses not only dispersible (solid) copolymers, but also emulsifiable or water emulsifiable copolymers, that is, copolymers that are liquids or above their T
g
at room temperatures and thus form emulsions. Examples of suitable comonomers include, without limitation, &agr;,&bgr;-ethylenically unsaturated monocarboxylic acids containing 3 to 5 carbon atoms such as acrylic, methacrylic,
Herrel Patricia A.
Ohrbom Walter H
BASF Corporation
Budde Anne M.
Zitomer Fred
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