Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1999-08-16
2003-03-18
Short, Patricia A. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S328600, C525S366000, C525S370000, C525S471000, C525S521000
Reexamination Certificate
active
06534602
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process for reducing copolymers containing keto groups (C═O) to polyalcohols using a metal alkoxide compound and novel compositions related thereto.
BACKGROUND OF THE INVENTION
Copolymers containing keto groups as functional groups, also referred to as polyketones, are well-known molding resins and blending resins, e.g., copolymers of ethylene and carbon monoxide commonly used as plasticizers for solid organic polymers such as polyvinyl chloride. It is known that by chemical reaction, the keto groups in polyketones can at least be partly converted into a variety of other functional groups. The chemical modification, changing the keto groups into other functional groups, changes the properties of the polyketones and renders them eligible for uses for which the original polymers were not or not very suitable. Reduction of polyketones produces polyalcohols, which can be used as adhesives or coatings in a number of applications.
Various methods have been used for the reduction of these polyketones to polyalcohols. U.S. Pat. No. 4,929,701 describes the use of copper chromite or nickel catalysts to reduce polyketones to polyalcohols by hydrogenation using a transition metal catalyst. The starting materials are linear alternating polymers of carbon dioxide and at least one ethylenically unsaturated monomer. Terpolymers of carbon monoxide, ethylene, and propylene can also be employed. U.S. Pat. No. 4,868,254 teaches the hydrogenation of polyketones using nickel salts reacted with borohydrides as a catalyst in an alcoholic media. U.S. Pat. No. 5,300,596 discloses an improved process for reducing polyketones containing from 1 to 50% keto group to polyalcohols using borohydride salts where water was used instead of alcohols. In the prior art teaching, the reaction is conducted in a solution or suspension for an extended period of a few hours at least. This type of reaction necessitates the costly process of removing the solvent. Furthermore, the use of borohydrides releases hydrogen gas, potentially a safety hazard due to the inherent flammability of hydrogen.
It would be desirable to conduct the reaction converting the keto group to polyalcohols in such a way that does not require the solvent recovery step. It would also be beneficial to use a reducing agent that does not pose a fire and explosion problem associated with hydride reducing agents. The reduction of keto groups in ketones using such a reducing agent, i.e., a metal alkoxide such as an aluminum alkoxide, lithium alkoxide, sodium alkoxide, or magnesium alkoxide, is well-known in the literature as the Meewein-Pondorff-Verley reaction. The alkoxide attacks only the keto compound and transfers hydride reversibly to the keto acceptor.
However, it has been reported that the reaction will not take place with high polymers. Journal of Polymer Science Vol. XLIV, pages 383-389 (1960) reports that an attempted reaction with polyketones as hydride acceptors and aluminum isopropoxide (AIP) catalyst failed, showing no change in the starting polyketone material. The polymer was combined with AIP and butanol-2 or 1,2-diphenylethanol, or isopropanol in a dry flask and heated under reflux. There was no evidence of acetone formation. The polyketones, both linear and crosslinked, did not at all participate in the Meewein-Pondorff-Verley reaction even under forcing conditions. These reagents worked with small molecules and not with polymers. In fact, the authors concluded that the failure of reaction must be primarily due to the steric hindrance that is presented by the long chains of the high molecular weight polymer groups.
It has been surprisingly found that contrary to the prior belief, copolymers containing keto groups can be reduced to polyalcohols by using aluminum alkoxides.
SUMMARY OF THE INVENTION
The invention provides a novel polyalcohol composition comprising:
a) one or more carbonyl (C═O) groups;
b) one or more secondary alcohol (CHOH) groups; and
c) a by-product aluminum trihydrate.
The polyalcohol composition is obtained by reduction of carbonyl groups in polyketones having between 0.1-50 mole % carbonyl (C═O) using metal alkoxides as the reagents, producing aluminum trihydrate as a by-product.
Further, the invention provides a process for the reduction of polyketones to produce polyalcohols comprising:
a) mixing a carbon monoxide vinyl-based copolymer with a metal alkoxide in molten condition to form a metal salt of the copolymer;
b) hydrolyzing said metal salt to form a polyalcohol; and
c) recovering said polyalcohol product.
The invention also provides a process for the reduction of polyketones to produce polyalcohols comprising:
a) mixing a carbonyl containing copolymer in molten condition with a metal alkoxide to form a metal salt as a side product in the presence of an excess amount of:
i) an isopropyl alcohol; or
ii) an alcohol substituted with a bulky alkyl group; or
iii) a ketone which is substituted with a bulky alkyl group,
b) hydrolyzing said metal salt to form a polyalcohol; and
c) removing said side-product acetone and recovering said polyalcohol product.
DETAILED DESCRIPTION OF THE INVENTION
A process has now been found for the reduction of keto groups in polyketones having between 1-50 mole % keto groups using metal alkoxides as the reagents, producing polyalcohols. Accordingly, the present invention provides a continuous process for the reduction of a polyketone polymer, the process comprising: reacting the polymer in molten condition with a metal alkoxide (preferably aluminum alkoxide) as a reagent, liberating acetone and thus forming a metal alkoxide salt of the polymer; hydrolyzing said metal salt forming a polyalcohol; and recovering said polyalcohol product.
According to another aspect of the invention, the reduction reaction of the polyketone polymer in molten condition with a metal alkoxide (preferably aluminum alkoxide) is carried out in the presence of a stoichiometric or excess amount of: i) isopropyl alcohol, ii) an alcohol which is substituted with a bulky alkyl group; or iii) a ketone which is substituted with a bulky alkyl group, which reacts with the metal alkoxide salt of the polymer to re-generate metal alkoxide forming a polyalcohol.
There is also provided a novel polyalcohol composition from the reduction reaction, comprising un-reacted keto groups and hydroxyl function groups, and the by-product aluminum trihydrate resulting from aqueous hydrolysis.
Polyketones. One class of polyketones capable of reacting with metal, e.g. aluminum, alkoxides to form polyalcohol compositions include homo and copolymers of alkyl vinyl ketones. Comonomers used in conjunction with these keto group-containing vinyl monomers can include other vinyl monomers, including ethylene, propylene, styrene, acrylates, methacrylates, vinyl chloride and vinyl flouride.
Another class of polyketones in the reduction reaction according to the present invention includes ethylene/carbon monoxide copolymers, carbon monoxide/alpha olefin copolymers, carbon monoxide/ethylene/alpha olefin copolymers, and ethylene terpolymers of the general formula E/X/CO. In the E/X/CO formula, E is the ethylene, X is a “softening” monomer such as, for example, vinyl acetate or an acrylic ester, and CO is the carbon monoxide. An example is an ethylene/carbon monoxide/acrylate copolymer where X is a C
1
-C
10
n-alkyl acrylate, such as E
BA/CO terpolymers where nBA stands for n-butyl-acrylate.
Reagents Metal Alkoxides. The metal alkoxides include alkoxides bearing aluminum cations such as aluminum-t-butoxide, aluminum cyclohexoxide, aluminum ethoxide, aluminum isopropoxide. However, alkoxides exhibiting good hydride-donating tendencies such as lithium isopropoxide, sodium alkoxide, and magnesium alkoxide may also be used for the reduction. Reagent aluminum alkoxides are commercially available from common scientific and chemical supplies sources. The most preferred aluminum alkoxide is aluminum isopropoxide (AIP).
Product Polyalcohols. The novel polyalcohol produced according to th
Hofmann George Henry
Lee Sampson Chun Fai
E. I. du Pont de Nemours and Company
Short Patricia A.
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