Polyvinyl alcohol copolymer composition
View Patent ↗A polyvinyl alcohol copolymer latex composition comprises an intimate polymer composition obtained from 10% to 60% by weight of a substantially hydrolyzed low molecular weight polyvinyl alcohol (PVOH); 2% to 80% by weight of at least one diene; 2% to 80% by weight of at least one hydrophobic monomer other than a diene and optionally either up to 10% by weight of at least one hydrophilic ethylenically unsaturated acid monomer or up to 40% by weight of a cationic monomer. The copolymer latex composition can be prepared as an emulsion from an aqueous blend of the above listed monomers which are generally added at various stages during the polymerization and a free radical initiator, surfactants, and, if desirable, chain transfer agents. Up to 80% of the PVOH may be added after the monomers have been polymerized.
1. A method for preparing a latex, the method comprising:
providing an aqueous solution of polyvinyl alcohol;
adding a free-radical forming initiator to the aqueous solution of polyvinyl alcohol; and
adding monomer to the solution of polyvinyl alcohol and initiator at least 10 minutes after said adding a free-radical forming initiator to the aqueous solution of polyvinyl alcohol;
allowing the monomer to polymerize in the presence of the initiator and polyvinyl alcoholic to form the latex.
2. The method of claim 1 , where said providing an aqueous solution of polyvinyl alcohol includes charging water and polyvinyl alcohol to a reactor and heating the resulting mixture for at least 30 minutes at a temperature of about 90° C. to about 99° C. prior to said adding monomer.
3. The method of claim 2 , further comprising allowing the aqueous solution of polyvinyl alcohol to cool prior to said adding a free-radical forming initiator.
4. The method of claim 1 , where the free-radical forming initiator is sodium persulfate.
5. The method of claim 1 , where said aqueous solution of polyvinyl alcohol includes at least 16% by weight polyvinyl alcohol.
6. The method of claim 4 , where said adding a free-radical forming initiator to the aqueous solution of polyvinyl alcohol includes adding at least 0.01 gram of sodium persulfate per gram of polyvinyl alcohol.
7. The method of claim 1 , where the monomer includes at least one conjugated diene.
8. The method of claim 7 , where the monomer further includes at least one hydrophobic monomer other than a diene.
9. The method of claim 8 , where the monomer further includes at least one cationic monomer.
10. The method of claim 1 , further comprising adding additional polyvinyl alcohol after said adding monomer.
11. A method for preparing a latex, the method comprising:
providing an aqueous solution of polyvinyl alcohol, wherein said aqueous solution of polyvinyl alcohol includes at least 16% by weight polyvinyl alcohol;
adding a free-radical forming initiator to the aqueous solution of polyvinyl alcohol, where the free-radical forming initiator is sodium persulfate and the sodium persulfate is added in an amount of at least 0.01 g of sodium persulfate per gram of polyvinyl alcohol; and
adding monomer to the solution of polyvinyl alcohol and initiator at least 10 minutes after said adding a free-radical forming initiator to the aqueous solution of polyvinyl alcohol allowing the monomer to polymerize in the presence of the initiator and polyvinyl alcohol to form the latex.
12. The method of claim 1 , where said adding monomer occurs 20 minutes after said adding a free-radical forming initiator.
13. The method of claim 11 , where said adding monomer occurs 20 minutes after said adding a free-radical forming initiator.