Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1998-09-18
2002-05-21
Reddick, Judy M. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S222000, C526S271000, C526S286000, C526S287000, C526S295000, C526S310000, C526S317100, C526S319000, C526S330000
Reexamination Certificate
active
06391992
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to vinyl ester oligomers which carry a terminal sulfonate group and their hydroxyl containing derivatives. In another aspect it relates to a process for making such polymers. In still another aspect it relates to a method of using bisulfite chain transfer agents in the polymerization of vinyl esters in order to form low molecular weight, sulfonate-terminated oligomers that can be used as is or converted to oligomers containing vinyl alcohol groups and having a terminal sulfonate group.
It has become increasingly difficult to find suitable surfactants and surface-active agents to meet the vast variety of needs found in industry today. These materials are required in products such as soaps, detergents, emulsifiers, dispersion and suspension stabilizers, paper coatings, inks, pigment dispersants and grinding aids, papermaking additives, flocculents, and the like. Each of these uses has special requirements to satisfy its particular application. It would be highly desirable to be able to meet these needs by preparing low molecular weight polymers or oligomers from available monomers that polymerize readily in aqueous systems with free radical initiation. In such systems, however, molecular weight control is a problem because the polymer molecules tend to grow too large to be useful, for instance, as a surfactant. Although molecular weight can be kept lower by the use of chain transfer agents, there remains the problem of including within the polymer both the polar and nonpolar components that are required in surface-active materials. This is especially true in view of the economic constraints that limit the chemistry and number of process steps required for making a suitable product.
Poly(vinyl acetate) and its hydrolyzed derivative, poly(vinyl alcohol), are two well known polymers that are available commercially in quantity, but it has been difficult to modify these materials to include acidic groups desirable for surfactant properties. The most common route attempted to date is through copolymerization of vinyl acetate with monomers containing acidic functionality. For example, in “Functional Modification of Poly(vinyl alcohol) by Copolymerization: 1. Modification with Carboxylic Monomers.”
Polymer
, Vol. 38, No. 12, p.2933, (1997), Moritani and Kajitani suggest that multifunctional polymers useful as sizing in the paper and textile industries can be made by copolymerizing vinyl acetate and carboxyl-containing monomers and then hydrolyzing the acetate groups to alcohol as in the manufacture of poly(vinyl alcohol). The initiator used was AIBN. The copolymerization route to incorporate acidic groups in these polymers results in random distribution of the acidic groups along the polymer chain rather than in a terminal position in the molecule where acidic functionality would be more effective in enabling the polymer to serve as a surfactant.
Another way of incorporating acidic groups into a low molecular weight polymer molecule is described in U.S. Pat. No. 3,646,099, Dannals, (1972). This patent discloses making oligomers containing sodium sulfonate-terminated polymers by polymerizing a hydrophilic monomer, such as acrylic acid, by reductive polymerization using a relatively high proportion of sodium bisulfite as the reducing chemical. The monomer containing the hydrophilic group can be copolymerized with limited amounts of comonomer containing a hydrophobic group provided that the proportion of the hydrophobic comonomer does not exceed 60 mol percent and is preferably less than 30 mol percent of the polymerized monomeric units. The utility suggested for these polymers is as conductive agents. Although vinyl acetate is listed among a large group of suggested monomers containing hydrophobic groups, it is clear from the context of this disclosure that such monomers are to be used only as a minor comonomer, if at all. This is understandable since it has been found that vinyl acetate tends to react with bisulfite to form 1:1 adducts rather that polymerized products. For example, Mukherjee, et al. in “Bisulfite-Initiated Vinyl Polymerization in Aqueous Media”,
Makromolekulare Chemie
, 80, p.208 (1964), investigated the use of bisulfites in the aqueous polymerization of certain vinyl monomers such as methyl methacrylate, ethyl methacrylate, methyl acrylate and styrene. These successful products were said to contain, on average, two sulfonate end groups per polymer chain. The reactions failed, however, in the case of vinyl acetate, acrylonitrile, methacrylate and acrylic acid. It was concluded that the reaction is monomer specific. Furthermore, standard industrial practice for preparing poly(vinyl alcohol) requires polymerization of vinyl acetate in methanol solvent, in which bisulfite is insoluble. Also, Schmitt,
J. Org. Chem
., 60, p.5474 (1995), described reaction of bisulfite with allyl groups but obtained only mixtures of sulfonate and sulfite groups in 1:1 adducts.
On the other hand, U.S. Pat. No. 4,360,632, Pinschmidt et al. (1982) discloses that vinyl acetate high polymers can be made in emulsion polymerization using a ketone bisulfite as a formaldehyde-free reducing agent in the initiator system. The products are high molecular weight polymers useful in latex form in the manufacture of non-woven goods. Two runs in which sodium bisulfite was used instead of ketone bisulfite are disclosed as control runs which gave poor results. It has remained, therefore, an unsolved problem of how one might incorporate sulfonate groups into oligomers of vinyl acetate and vinyl alcohol in such a way that these polymers are provided with enhanced surface active properties.
Two papers, P. Ghoshy, S. C. Chadha, A. R. Mukherjee, and S. R. Palit,
J. Polym. Sci
., Pt. A, 2, 4433-4440 (1964) and W. D. Hergeth, W. Lebek, R. Kakuschke, K. Schmutzler,
Makromol. Chem
. 192, 2265-2275 (1991), describe highly impractical syntheses of anionically terminated polymers or oligomers using persulfate and vinyl acetate by operating at very low monomer concentration (1% in the former, giving polymers of 475,000 Mn and, in the latter, a very dilute delay feed summing to 0.05 to 0.8% polymerized vinyl acetate on water at the end of the reaction to give 3000 Mn oligomer). In both papers, the authors describe the products as made by termination (instead of transfer as in our process) and, although the latter believe their chains contain one sulfate end group, the former authors measure 1.3 to 1.8 sulfate endgroups per chain. The sulfate endgroups are described by Ghoshy, et al. as hydrolytically unstable (p.4434) relative to sulfonate endgroups and would not survive hydrolysis to prepare a vinyl alcohol oligomer. The surfactant properties of the unhydrolyzed oligomer in the second article appear significantly different than what we have measured.
A. B. Moustafa, A. A. Abd El Hakim, G. A. Mohamed,
J. Appl. Poly. Sci
. 63, 239-246 (1997) reported emulsion polymerization of vinyl acetate at low solids (only 10% VAc on water) using a 1:1 molar ratio of persulfate and bisulfite without surfactant or cosolvent. They obtained poor conversions with 2.8 wt % persulfate on monomer, but could exceed 90% conversion with an exceedingly high 5.6 wt % persulfate on monomer. Their product was a stable, presumably high molecular weight emulsion polymer, rather than a dispersible oligomer.
BRIEF SUMMARY OF THE INVENTION
According to our invention, a product is provided which is an oligomer of a vinyl ester of an organic acid having 2 to 18 carbon atoms, the molecules of the oligomer being terminated at one end by a sulfonate group. Our invention also provides a vinyl alcohol oligomer having a terminal sulfonate group. Such an oligomer is a derivative of a vinyl ester oligomer in which at least a portion of the ester moieties of the vinyl ester have been hydrolyzed to hydroxy groups. Our invention also provides a vinyl acetate or vinyl alcohol cooligomer with acid or quaternary amine containing monomers and having a terminal sulfonate group. These oligomers are unique in having one
Pinschmidt, Jr. Robert Krantz
Yacoub Khalil
Celanese International Corporation
Ferrell Michael W.
Reddick Judy M.
Rodgers Mark L.
Spiering M. Susan
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