Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-08-09
2002-05-14
Reddick, Judy M. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S047000, C524S053000, C524S503000
Reexamination Certificate
active
06387991
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to compositions which are particular poly(vinyl alcohol) copolymer ionomers, a process to prepare those compositions, and textile sizes based on those compositions. It also relates to sizes based on blends of those ionomers with other poly(vinyl alcohol) polymers or starches. The compositions are poly(vinyl alcohol) copolymers which have carboxylate salt ionomer comonomer units. Desizing sizes of these ionomers or blend sizes containing these ionomers, in either water or caustic solutions is easier than desizing sizes based on polymers or polymer blends which contain no poly(vinyl alcohol) copolymer ionomer.
2. Discussion of Related Art
Poly(vinyl alcohol) homopolymers, and certain poly(vinyl alcohol) copolymers, with comonomers such as alkyl acrylates, have been known for use as textile sizes for many years. For convenience, both will be generically referred to hereinafter as PVA polymers. When specificity requires they will be referred to as PVA homopolymers and PVA copolymers. By convention, PVA homopolymer includes PVA polymer derived from homopolymer poly(vinyl acetate) which has been only partially ‘hydrolysed’ or ‘saponified’, as well as that which has been ‘fully’ (>98%) hydrolysed. The terms ‘fully hydrolysed PVA homopolymer’ and ‘partially hydrolysed PVA homopolymer’ will be used if distinction is necessary. It is also possible to have fully or partially hydrolysed PVA copolymers. Indeed, certain partially hydrolysed copolymers have found specific use as sizes for hydrophobic fibers, as noted below.
Different PVA polymers differ quite significantly in properties as textile sizes and in the ability of fabrics sized with them to be desized. This difference primarily depends on the degree of saponification or hydrolysis, the particular comonomer and the comonomer content. Other factors including molecular weight and thermal history can also be important in size characteristics.
PVA polymers are generally prepared by alcoholysis or hydrolysis of the corresponding poly(vinyl acetate) homopolymer or copolymer. Strictly, alcoholysis, carried out with a basic catalyst, leads to the corresponding alkyl acetate and the poly(vinyl alcohol) unit, and is conducted in alcohol as reaction medium. Hydrolysis, in water, generally uses larger amounts of metallic caustic base, leading to the corresponding metal acetate rather than alkyl acetate, and the poly(vinyl alcohol) unit. Formation of metal salts, i.e. acetates, has led to use of the term ‘saponification’ for the process, akin to formation of metal salts of fatty acids with caustic, in forming soaps. When aqueous alcohol is used as the reaction medium both hydrolysis and alcoholysis may occur. However. U.S. Pat. No. 2,940,948 discloses that under specific circumstances, even with aqueous alcohol, alcoholysis rather than hydrolysis occurs. While the distinction strictly depends on reaction products, the terms have tended to be used non-rigorously. The product are typically referred to as ‘hydrolysed’ or ‘saponified’.
It is common to use the term ‘partially hydrolyzed’ or ‘partially saponified’ when not all the acetate groups are completely converted to alcohol groups. When homopolymer poly(vinyl acetate) is only partially hydrolysed, the resulting PVA is strictly a vinyl alcohol/vinyl acetate copolymer. However, as noted, such polymers are generally referred to as PVA homopolymers. The term copolymer in this regard is usually reserved for materials which result from hydrolysis of the corresponding vinyl acetate copolymer, i.e. polymer also containing units derived from a monomer other than vinyl acetate, such as an alkyl acrylate.
Fully hydrolysed PVA homopolymer is highly crystalline and strong, but because of its high crystallinity it dissolves only in hot, not cold water. Furthermore, when it is subjected to high temperatures, it can develop even higher levels of crystallinity than as prepared, resulting in polymer which is even more difficult to dissolve. Finishing mills with certain fabrics, particularly blend fabrics, tend to use a heat setting condition to relieve fiber stress. The treatment is typically carried out at temperatures which develop further crystallinity in fully hydrolysed PVA homopolymer, so that when such polymer is used as size on fabric, the treatment causes an increase in its crystallinity and a decrease in ease of subsequent desizing.
PVA copolymers and partially hydrolysed PVA homopolymers are less crystalline, and dissolve at lower temperatures, or more rapidly at a given temperature. As a result they desize in water more readily, and are less subject to change in crystallinity and ability to be desized with fabric heat-setting treatments. For a given level of comonomer or residual non-hydrolyzed acetate units however, the two types of PVAs are not identical in several respects. This is partly because the distribution of comonomer units (or units derived from them by lactonization, as discussed below) along the polymer chain is not the same as the distribution of residual acetate units along the chain after partial hydrolysis. One difference, for instance, is that acetate units tend to be blocky, and blockiness of partially hydrolysed PVA causes more surfactant behavior and more foaming when used as size. Furthermore, differences in the conditions used for hydrolysis/saponfication of a given copolymer, particularly physical differences such as degree of agitation and kneading of precipitating product, have also been disclosed as producing differences in partially hydrolysed products.
Various PVA copolymers have been disclosed as being useful for textile sizes. In 1972, U.S. Pat. No. 3,689,469 (Inskip et al.) disclosed PVA copolymers with 2 to 6.5 weight percent methyl methacrylate as comonomer which are useful as textile sizes, and compared their properties as sizes with fully hydrolysed and partially hydrolysed PVA homopolymer. The disclosure indicated however, that above about 6 weight percent methyl methacrylate such copolymers are excessively water soluble.
PVA copolymers containing 1 to 10 mole percent methyl acrylate or methyl methacrylate as comonomer are disclosed in U.S. Pat. No. 4,990,335 (Bateman et al.). (For methyl acrylate this corresponds to about 2 to 16 weight percent methyl acrylate in the polymer, calculated as non-lactonized vinyl alcohol copolymer). The polymers were not disclosed as being useful for sizes.
However, in a recent U.S. Pat. No. 5,362,515 (Hayes et al, issued Nov. 8, 1994) polymers with high acrylic or methacrylic ester comonomer levels (above Inskip's comonomer levels and in the top range of Bateman's comonomer levels, such as from 7 to 15 weight percent of methyl (meth)acrylate), were disclosed as useful in a process to produce textiles which used these polymers for sizes. The polymers are disclosed as being very readily desized, particularly with caustic solutions.
Poly(vinyl alcohol) copolymers where the comonomer directly provides an acid functionality are known. The acid functionality may derive from a copolymerized monocarboxylic, dicarboxylic acid, or a dicarboxylic acid half ester. Acid functionality, however, can result from hydrolysis of ester comonomer units, such as an alkyl acrylate or methacrylate. Depending on the precise conditions, such as the catalyst, its concentration, and the solvent medium used to hydrolyze/saponify the vinyl acetate ester units in the vinyl acetate copolymer, the other ester units, i.e., the comonomer ester units may or may not also be hydrolysed to the corresponding acid. Generally, the vinyl acetate ester units are far more readily hydrolysed than alkyl ester units. If the alkyl ester units are also hydrolysed, and if enough base is present, the resulting acid units may also be neutralized to become ionomer units.
Under some conditions, internal trans-esterification can take place between the vinyl alcohol units resulting from hydrolysis, and the alkyl ester units, resulting in in-chain lactone units. Because both the vinyl acetate este
E. I. du Pont de Nemours & Company
Reddick Judy M.
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