APRESTOS FOR TEXTILES OF POLYMER POLYMER MIXTURES (VINYL ALCOHOL) WITH IMPROVED CAPACITY TO BE DISAPPESTED OR DESCENDED
BACKGROUND OF THE INVENTION Field of the Invention This invention relates to compositions useful for textile sizing, based on blends of particular poly (vinyl alcohol) copolymers with other poly (vinyl alcohol) polymers, and to the processes of weaving textile fabrics that uses the compositions as sizing, and uses its ability to be desprestadas or desecolados easily. The sizes are based on copolymers having a high level of acrylic ester comonomer, mixed with other polyvinyl alcohol polymers. Desizing involves the use of caustic solutions, and is ideally suited for such compositions. BACKGROUND OF THE INVENTION Poly (vinyl alcohol) homopolymers and certain poly (vinyl alcohol) copolymers have been known to be used as textile sizing for many years. By convention, both will be generically called hereafter PVA (s) or PVA polymers. When specificity is required, they will be called PVA homopolymers or PVA homopolymers and PVA copolymers or PVA copolymers. By convention, the PVA homopolymer includes PVA derived from poly (vinyl acetate) homopolymer that has been partially hydrolyzed only, REF: 22664 as well as that which has been 'fully' (> 98%) hydrolyzed. The terms 'fully hydrolyzed PVA homopolymer' and 'partially hydrolyzed PVA homopolymer' will be used where distinction is necessary. It is also possible to have PVA copolymers fully or partially hydrolyzed, although most copolymers are fully hydrolysed. These different PVas differ very significantly in their properties as textile sizing, and in the capacity of the fabrics prepared with them to be desapressed. This difference depends primarily on the degree of hydrolysis and the comonomer content, but also on other factors, which they include molecular weight and thermal history. PVAs are commonly prepared by alcoholysis of the corresponding poly (vinyl acetate) homopolymer or copolymer. The process is frequently (though not strictly correctly) called hydrolysis; hence the term 'partially hydrolyzed' when not all acetate groups are completely converted to alcohol groups. When the poly (vinyl acetate) homopolymer is only partially hydrolyzed, the resulting pVA is actually a vinyl alcohol / vinyl acetate copolymer. However, as noted, such polymers are generally referred to as PVA homopolymers. The term copolymer in this respect is reserved for materials resulting from the hydrolysis of the corresponding vinyl acetate copolymer, i.e., a polymer that also contains units derived from a monomer other than vinyl acetate. The fully hydrolyzed PVA hourpolymer is highly crystalline, and strong, but because of its high crystallinity, it dissolves only in hot, not cold water. In addition, when subjected to elevated temperatures, it can develop even higher levels of crystallinity than when it was prepared, resulting in a polymer that is even more difficult to dissolve. Finishing machines with certain fabrics, particularly fabrics with blends, tend to use a thermoset condition to release fiber tension. The treatment is typically carried out at temperatures that develop additional crystallinity in the fully hydrolyzed pVA homopolymer, such that when such polymer is used as a sizing on a fabric, the treatment causes an increase in its crystallinity, and a decrease in the subsequent despatched facility. PVA copolymers and partially hydrolyzed PVA homopolymers are less crystalline, and dissolve at lower temperatures, or more quickly at a given temperature. As a result, they are more easily de-sensitized in water, and are less subject to change in their crystallinity and in their ability to be de-sensitized with thermofixed tissue treatments. For a given level of comonomeme-k-ro 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 the comonomer units (or units derived from them by lactonization, as discussed below) along the polymer chain is not the same as the distribution of the residual units of acetate along the chain after partial hydrolysis. One difference, for example, is that the acetate units tend to be compact, and the compaction of partially hydrolyzed pVA causes more surfactant behavior, and more foam formation when used as a sizing agent. Various PVA copolymers have been described as useful for textile finishing. The Patent of E.U.A. No. 3,689,469 (Inskip et al.) Discloses PVA copolymers with from 2 to 6.5 percent by weight of methyl methacrylate as a comonomer, which are useful as sizing agents for textiles, and compares their properties as sizing with the PVA homopolymer completely hydrolyzed and partially hydrolyzed. The description also indicates, however, that above about 6 percent by weight of methyl methacrylate, such copolymers are excessively soluble in water. PVA copolymers containing 1 to 10 mole percent of methyl acrylate or methyl methacrylate as a comonomer are described in the U.S. Patent. Do not.
4,990,335 (Bateman et al.). (For methyl acrylate, this corresponds to about 2 to 16 percent by weight of methyl acrylate in the polymer, calculated as non-lactonized vinyl alcohol copolymer). The polymers are described as being useful for certain tabletting applications. There is no suggestion of the use of such polymers as a sizing for textiles. Japanese Patent No. 75-32355 discloses sizing agents for modified polyvinyl alcohol polymer fibers containing from 0.1 to 15 mol% of lactone rings. In one example, a cotton fabric prepared with a polymer containing 4.7% by weight of lactone prepared by saponifying (hydrolyzing) a poly (vinyl acetate / methyl acrylate) copolymer with 4.5% methyl acrylate (corresponding to ponde to 4.7% in moles of lactone when the comonomer is fully lactonized, and about 8.1% by weight of methyl acrylate calculated as copolymer of non-lactonized vinyl alcohol) had a better firmness or resistance to washing with a water jet than the PVA homopolymer. Desizing or desizing usually involves washing with water. However, desizing of particular polymers with a caustic solution is sometimes used, and has been described. The Patent of E.U.A. No. 4,013,805 (COrey et al.) Discloses a poly (vinyl acetate) copolymer containing a comonomer with free carboxylic acid groups derived from a monomer such as acrylic acid, which can be desized with an aqueous base. The poly (vinyl acetate) copolymer is not hydrolyzed to the corresponding polyvinyl alcohol copolymer. The desizing of the PVA polymer free of wax or copolymer sizes, wherein the copolymer may contain up to 6 weight percent of methyl methacrylate or other comonomers, and wherein the size contains an alcohol ethoxylate surfactant, using a alkaline discharge bath, followed by hot water rinsings, is described as easy, compared to comparable wax-free surfactant-free surfactants, in US Pat. No. 4,640,946 (Vasallo et al.) The Patent of E.U.A. No. 4,172,930 (Kajitani et al.) Discloses a PVA copolymer as sizing for textiles, wherein the comonomer is 0.1-10 mole percent of a diacid such as maleic and fumaric acids, but has no monoester, diester or diacid anhydride. Copolymers containing free acid can be extremely sensitive to water. The solubility and dissolution times of various types of PVA in water and in caustic solutions are discussed in 'Polyvinyl Alcohol', John Wiley & Sons, LTD., 1992, Chapter 11, pages 365-368. It is noted that the partially hydrolyzed PVA homopolymer dissolves more slowly in caustic solutions than in water, whereas the PVA copolymers with methyl methacrylate as a comonomer dissolve more rapidly in caustic than in water. This is explained by the fact that the caustic solution additionally hydrolyses the partially hydrolyzed PVA to homopolymer, while with the copolymer, the lactone rings that are known to be present are saponified, resulting in ionic groups which are highly soluble. The methacrylate methyl copolymers discussed were designated as. T-25 and T-66. The amounts of methyl methacrylate in those copolymers were not described. Those polymers are manufactured by E. I. du Pont de Nemours. Both contain less than 6.5 weight percent methyl methacrylate, calculated on the basis of the non-lac-toned polyvinyl alcohol copolymer. The entire chapter in the above reference provides a general background to the use of PVA copolymers and other materials in sizing applications. Many other materials are known to be used as apparel for textiles. Unmodified starches are cheap, but generally do not have properties as good as PVAs, and often exfoliate the thread when used as sizing. They do not give stable solutions, and frequently the desaprestado requires the use of enzymes. Many modified almonds are known, which are improvements in several ways over simple starches, but can be considerably more expensive. Polyacrylic sizing agents are also known, and they have good properties, but they are extremely sensitive to water. It can be considered that the sizing based PVA-based have, very generally, intermediate sizing properties between starches and acrylic sizing. The mixing of different sizing materials is known and used. The mixing can provide properties of the same size, and economic, intermediate between those of the components. However, so far, PVA copolymers containing up to 6.5 percent by. Comonomer weight of the ester have not been considered as components of mixed sizing. Neither the mixing as a means of increasing the capacity to be desaprestados has been considered until here. The ease of desizing can strongly affect the economic aspect of the weaving process. While many sizing materials are known, and each has its particular position, there remains a need for sizing materials that are very readily desapressed, and that have acceptable mechanical properties, and give stable sizing solutions, and still have an insensitivity to the sizing. acceptable water. There remains also a need for a sizing material that can be used to improve various sizing properties, but particularly to improve the ability to be desized, by the use of such material in blends with known PVA sizing materials. BRIEF DESCRIPTION OF THE INVENTION The invention relates to improved sizing compositions, which are mixtures of PVA copolymers containing a very high level of an ester comonomer and other PVA sizing materials. The mixtures are effective. They are used as aqueous solutions. The fabrics prepared with these mixtures are capable of being desentated in a very effective way, compared with the other sizing materials alone. More particularly, the present invention provides a sizing composition which is an aqueous solution of a polyvinyl alcohol polymer mixture, comprising: a) from 10 to 90 parts of a polyvinyl alcohol first polymer. , which is a polyvinyl alcohol copolymer containing from about 7 to 15 weight percent of units derived from an alkyl acrylate or methacrylate, or a fumarate or dialkyl maleate, wherein the alkyl group has from 1 to 8 carbon atoms, and b) from 90 to 10 parts of a second polymer of polyvinyl alcohol, which is a polyvinyl alcohol homopolymer, or a polyvinyl alcohol copolymer containing less of 7 percent by weight of units derived from an alkyl acrylate or methacrylate, or a fumarate or maleate of-1.0-dialkyl, wherein the alkyl group contains from 1 to 8 carbon atoms, or a mixture of such second polymers of poly- (vinyl alcohol). The invention further provides a process for producing woven woven materials, wherein the yarn is sizing with the mixed sizing materials above, and then woven, the sizing is removed from the woven textile fabric with a dilute caustic solution, and, optionally , the tissue despressed with caustic solution is washed additionally with water. DETAILED DESCRIPTION OF THE INVENTION In this description, it is to be understood that the use of the term "comonomer," when referring to PVA copolymers, as used herein and as conventionally used, refers to the copolymerized comonomer in the polypropylene copolymer. (vinyl acetate), before the latter is converted to a PVA by alcoholysis. In the PVA copolymers, ester units of the comonomer are subjected to reactions with a hydroxyl of an adjacent vinyl alcohol unit to form lactones, and free alcohol of the ester unit. Thus, the original ester monomer unit can no longer exist as the same entity that was present in the poly (vinyl acetate) precursor copolymer. Nearly complete lactonization may occur, although the degree may vary with the different comonomers. The use of phrases such as PVA copolymers 'with' or 'containing' a given comonomer and the like should be understood in this context. PVA copolymers containing up to 15 mole percent lactone rings have generally been described as sizing materials. Commercially, PVA copolymers containing up to about 5 weight percent methyl methacrylate have actually been used for textile sizing compositions. It has been considered that about 6 percent by weight of methyl methacrylate is the useful upper limit, since, as noted above, it was considered that higher levels would make the polymers highly sensitive to water. Surprisingly, PVA copolymers with comonomer levels even above 7 percent by weight of certain acrylates, methacrylates and certain other comonomers are suitable as textile finishes. This is because they have a major advantage over prior sizing compositions, where it has now been found that they are particularly easy to be desensitized if dilute caustic solutions are used instead of the usual disinfectant water. In addition, presumably because such copolymers have low crystallinity and crystallize less easily, the ability to depress them using caustic solutions is much less affected by heat treatment than copolymers containing less ester comonomer.
The chemical nature and solubility characteristics in water and in caustic solutions of the PVA copolymers containing an ester comonomer have been recognized in a general quantitative manner. However, so far, it has not been recognized that a major divergence in solubility characteristics between solubility in water and in caustic solutions occurs when high levels of ester comonomer are present (ie, above about 6%). More significantly, it has not been recognized that such ditrergency presents an ideal situation for the use of such copolymers as sizing, either alone, but particularly in blends with other sizing materials, because such copolymers are treatable for easy desizing using solutions caustic. The sizing based on mixtures of such copolymers of
PVA with high ester content with most of the PVA polymers previously used as sizing materials are more readily desized than such PVA polymers alone. The use of these PVA copolymers with high ester content alone is the subject of a co-pending patent application. In general, PVA copolymers have good mechanical properties such as sizing. When added, the advantage of desizing of the copolymers with a comonomer with high ester content is taken into account, and they have a place as sizing materials and as materials for mixing, to assist in desizing. Thus, they are also useful as sizing when mixed with other PVA polymer sizing materials, or when mixed with starches. They can contribute in both, to the properties of the mixed sizing, and to the total desizing facility, whenever a caustic desizing is used. In the mixed compositions tested, it has been found that the ease of desizing or with caustic solutions is, very roughly, an in-fluenced average of the desizing capacity of the components of the mixture, rather than being limited by the component desprestado less easily . This means that if a particular quality of a sizing material - a particular property, or low cost, for example - is desired in an apres-to material that is difficult to despress, then a mixture with a PVA copolymer containing a comonomer With high ester content can offer an ideal compromise between properties and ability to be desaprestado. The PVA copolymers with acrylate and methacrylate comonomers can be prepared by well-known methods, involving the preparation of the corresponding poly (vipyl acetate) copolymer, followed by saponification, alco-holysis or 'hydrolysis'. The typical preparation of such poly (vinyl acetate) copolymers and their hydrolysis is given in the patent of E.U.A. No. 3,689,469, which describes laboratory-scale preparations, and U.S. Patent No. 4,900,335, which describes a continuous process for such polymerizations, and particularly for PVA copolymers containing a high level of ester. The amounts of monomer are adjusted for different levels required in the polymer, and for their different reactivities. These two patents are incorporated herein by reference. Methacrylates are more reactive than acrylates, but both are much more reactive than vinyl acetate, so they are fully reacted, while vinyl acetate, less reactive, has to be removed, and would be recycled in a process continuous commercial. Dialkyl maleates are considerably less reactive. Suitable comonomers in the PVA copolymers with a high ester level comonomer useful in the mixed copolymers of this invention are the unsaturated monocarboxylic acid esters and the unsaturated dicarboxylic acid diesters. Free carboxylic acids should not be present in the copolymers. Examples include acrylates and alkyl methacrylatesdialkyl fumarates and maleates having a group or alkyl groups containing from 1 to 8 carbon atoms. The comonomer level can be from 7 to 15 percent by weight, calculated on the basis of non-lactonized poly (alcohol / vinyl ester) copolymers. As it was noted, after the alcoholysis, during the neutralization of the alkaline catalyst with acid, it is believed that the ester group of the comonomer and the hydroxyl groups of the adjacent vinyl alcohol are greatly converted to lactone rings, with release of the ester alcohol . There is thus a loss of weight, due to the loss of the alcohol of the ester, but the units that are not units of vinyl alcohol are units of lactone, and will comprise a percent by greater weight of the polymer than that of the comonomer, since it is involved an adjacent alcohol unit in the lactone unit, which then has two carbon atoms in the chain. To obtain up to 15 percent by weight of ester in the polyvinyl alcohol copolymer, calculated on a non-lactonized base, a precursor of the polyvinyl acetate copolymer which is difficult to prepare is required. Alkyl acrylates are preferred, and methyl acrylate is more preferred. While it has been assumed that the decreased level of crystallinity resulting from increased levels of comonóraero, causes very high sensitivity to water (ie, tendency to absorb water and get sticky, which can result in a decreased tissue efficiency), this It is not necessarily the case. Thus, very surprisingly, it was found that a copolymer containing 9 percent by weight of methyl acrylate was actually less sensitive to water, (dissolves less quickly, determined by the ease of desaturated by water), than that of a copolymer of PVA with 5.5 percent by weight of methyl methacrylate, or a partially hydrolyzed PVA homopolymer at 88%. While we are not limiting ourselves to any particular theory, it is thought that methyl acrylate or other acrylates as as -nomers will decrease the crystallinity in the resultant copolymer less than "what methyl methacrylate or other meta-crilates do, even if if the comonomer unit becomes lactonized, because of the absence of a methyl group attached to a carbon that is within the chain that methyl methacrylate produces when it is polymerized, alternatively, the differences in the amount of lactonization Different comonomers will result in varying levels of water sensitivity in the resulting copolymer.The sensitivity will depend on the reduction in crystallinity due to the increasing number of comonomer units (or derived lactone units), but will also depend on the net decrease in polarity with increasing level of comonomer, while alkyl acrylates and methacrylates with large alkyl chain are less polar than those of short alkyl chain, the PVA copolymers of acrylates and large chain methacrylates, in the lactonization may contain the same lactone group within the chain as that of any other acrylate copolymer or methacrylate respectively. However, the lactone rings derived from methacrylate will not be the same as the lactone rings derived from acrylate. In addition, the amount of lactonization may vary. In any case, any copolymer can be expected to have a sensitivity to water which is a balance due to the amount of reduction in crystallinity caused by the comonomer or the derivatized lactone, and the total decreased polarity of the copolymer with the increasing content of comonomer or lactone. derivative All the ester comonomers and the lactone rings that they can form will be less polar and hence less sensitive to water than the vinyl alcohol units. While PVA copolymers with methacrylate comonomer are less favoredeven here, when the comonomer level is significantly increased, a reduced polarity will result in the copolymer. At very high corao-number levels, the decreased polarity will eventually neutralize the increased water sensitivity resulting from decreasing crystallinity. The main advantage of the easy desizing at high levels of ester comonomer can make the PVA copolymers of methacrylate, as well as of methyl acrylate with high comonomer level useful. Such copolymers will be particularly useful as blending components, to improve the total desizing of sizing materials that are difficult to desaturate. Sizing can be carried out using solutions of the PVA copolymer and the PVA polymer mixture having a total polymer concentration of from 1 to 20 weight percent, preferably from 4 to 12 weight percent. The sizing composition can incorporate other materials typically found in the sizing compositions of the prior art. Such materials may include waxy type lubricants, defoaming surfactants, and other surfactants. A skilled artisan will be able to judge what concentration of sizing solution to use to achieve their desired additive level of sizing, and which additives are best suited for their operations. The desizing or desizing of the prepared fabrics is commonly carried out using washes with water at variable temperatures. Surprisingly, it has been found that with the high levels of ester comonomer of the PVA copolymers of the present invention, desizing can be effectively performed with caustic solutions, and those caustic solutions can be very dilute. PVA homopolymers, and many PVA copolymers with lower comonomer levels than the high ester copolymers of this invention, are either less rapidly depleted, or require higher temperatures and / or higher concentrations of caustic for the same amount of desaprestado. The caustic solutions for desizing can be as dilute as about 0.001 percent by weight, particularly if somewhat elevated temperatures are used to depress, although more often, concentrations above 0.05 percent by weight will be required. Generally, a faster desizing is possible, at a lower temperature, or more complete when the temperature is increased. However, in mixtures containing partially hydrolyzed PVA homopolymer, more dilute caustic solutions may be favored, as the examples discussed below show. Generally, the caustic compound will have to be removed subsequently, so that larger caustic concentrations than those that are suitable should be avoided. The caustic solutions for desizing should have, at most, a concentration of 10 percent by weight. Preferably, however, they should be below 2 percent by weight, and more preferably between 0.1 and 1.5 percent by weight. For any PVA copolymer size or particular PVA polymer blend size, additive level, heat treatment of the fabric, a suitable concentration for the caustic solution for desizing and a suitable temperature for desizing can be easily determined when it has been decided that so quickly and how completely desiring is required. Thus, the emphasis may be on the faster despatching for economic reasons. Or the emphasis may be on a deskew at a temperature as low as possible, because the material is somewhat sensitive to temperature. Generally, an almost complete desizing is required. There will be not only a concentration of the caustic compound and a temperature that is adequate, but a range of alternatives. Suitable caustic materials include any of the alkali metal hydroxides or carbonates, ie, sodium, potassium or lithium, with sodium hydroxide being preferred. It has been found that carbonates depress the copolymers and copolymer blends of the invention much less efficiently, although more efficiently in general than water. However, in some spinning and weaving factories, conditions may need a softer desizing. When this is the case, carbonates can be used, and adjustments made in the concentration and time and temperature of the desalted. It is important to recognize that, while the sizes made of the high ester level PVA copolymers alone or even the blending sizes of this invention, are more rapidly and effectively de-activated in caustic solution than many PVA homopolymers or copolymer size materials of PVA with low comonomer level, or natural sizing materials such as starch, can be less effectively depleted when a normal desizing (aqueous) is employed. Thus, as noted previously, a copolymer with 9 percent by weight of methyl acrylate could not be desized as effectively as a partially hydrolyzed homopolymer at 88%, or a copolymer with 5.5 percent by weight of methyl methacrylate at 22 ° C. This can be a significant advantage, since materials that are not readily de-sensitized to water will be less sensitive to water and, in general, may have less tendency to become sticky in moist environments. Of course, this does not mean that the mixtures of the invention can not be despressed with water. However, longer times and / or higher temperatures will be necessary than with desprestado with caustic solution. The yarns that may advantageously employ the sizes of this invention are any conventional yarn, either spun fiber or filament splices, or other tractable structures, and may be hydrophilic, such as cotton, or hydrophobic, such as nylon or nylon. polyester, or hydrophilic / hydrophobic combinations. Some finishing operations on textiles (woven), or even knitted fabrics, may also advantageously employ the sizes of this invention. The PVA copolymer with high ester level itself can have a 4% solution viscosity of 1 to 60 centipoise. Preferably, it should have a viscosity between 3 and 25 centipoise. The skilled artisan will be able to determine the optimum polymer viscosity, the polymer sizing concentration, and the additive level for the particular yarn, fabric and weaving conditions that he is using. The other PVA polymer in the mixture can be any PVA homopolymer previously known for use as sizing, or other PVA copolymers previously used for sizing, but containing low (less than 7 percent by weight) comonomer levels. This includes both fully and partially hydrolyzed homopolymers, and PVA copolymers with less than 7 weight percent comonomer selected from the group consisting of alkyl methacrylates, alkyl acrylates, dialkyl fumarates and dialkyl maleates, wherein the alkyl group contains from 1 to 8 carbon atoms. The partially hydrolyzed PVA can be from 50 to 98% hydrolyzed, but preferably above 80% hydrolyzed. The mixture used to prepare the sizing solution can contain from 10 to 90 percent by weight of the high ester content PVA copolymer, and from 90 to 10 percent by weight of the other PVA polymer. Preferably, however, there must be at least about 30 percent of the high ester content PVA copolymer in the polymer blend used for sizing. The blends of this invention are ideally suited for use as dressings. However, the mixtures may also be adaptable for uses in certain gmmo film applications. Such films may include films for agricultural vegetable cover, biodegradable packaging films, and water soluble films. The blends may also be adaptable for use as hot melt adhesives, binders and the like. EXAMPLES The PVA polymers used in the various examples and in the comparative examples are listed in Table I. Sizing solutions of these polymers, or mixtures of these polymers, having a concentration of 8 percent by total weight were made. polymer, dissolving them in water at about 90 ° C, mixing for about 2 hours. The sizing solutions were clear and slightly viscous. When the sizes were tested, the mixtures contained 50 percent by weight of each component. The sizes used are listed in Table II. Tissue samples were prepared as follows. Weighs first approximately 50.8 cm (2 inches) by 50.8 cm (2 inches) of a 198.45 g (7 oz), 100% cotton, bleached, type 464 canvas fabric, obtained from Test Fabrics Inc., then it was impregnated in sizing solution for about 2 minutes, at about 35 ° C, mixing gently. The samples were then dried by placing them on an aluminum sheet, treated with Teflon lubricant to prevent sticking, at 50 ° C, in a convection oven, for 17 ± 1 hour. Then they were cooled in a calcium sulfate desiccator, and reweighed to de-finish the amount of sizing added to them. In some cases, the samples were treated with heat, placing them in a convection oven at 140 ° C for 10 minutes. The desizing tests were carried out by soaking the sample of tissue prepared in 100 grams of the test desizing medium, (either water or caustic solution) for 10 minutes, with gentle mixing. In some cases, when water was used, the sample was further de-sensitized by soaking in another 100 grams of water for 10 minutes. In all cases where caustic solution was used, the sample was subsequently soaked in 100 grams of water for 10 minutes. This subsequent water treatment removes the caustic compound, as well as provides an additional light desizing. The despressed or partially despressed samples were then dried in a convection air oven at 140 ° C for 1 hour and then allowed to cool in a calcium sulfate desiccator. The details are shown in Tables IIIA and IIIB. When examples of blending sizes of the invention are shown in the Tables, they are given. a number without a prefix C. When examples of sizes are listed that are outside the compositions of the invention, either of a single PVA polymer or of a mixture that does not include the high ester content PVA copolymer of the invention , are marked with a prefix C, indicating that they are shown by comparison. The process of the invention includes a desizing step with caustic solution. The examples illustrating the process of the invention are shown with an asterisk (*). While a complete desizing is generally considered necessary, the percentage of desizing in the examples is considered to be an indication of the ease of a complete desizing. If the displayed value is less than 100%, then longer desizing times, a different concentration of the caustic compound, or somewhat higher temperatures would be necessary to achieve complete desizing. Examples C12 and C13 show that double washes (ie, equivalent to longer desizing times) produced an increased desizing, but the despressed quantity order remains the same (compare Cl and C2). Table IIIA shows the effect of desaturating PVA polymers alone, or mixtures of the invention in water. In some examples the prepared fabrics were treated with heat, and some were subjected to a double wash with water. Examples Cl a C5 are for PVA polymers alone. C2 is for the PVA copolymer with high ester content. The copolymer with a high ester content is not particularly well desalted in water - in fact not as well as the partially hydrolyzed PVA homopolymer (C5) or the copolymer (C4) of methyl methacrylate with lower content of as-nitrate. Examples C7 to Cll are parallel to Cl to C5, but the finished fabric has been treated with heat. It is seen that all are less easily de-sensitized after heat treatment. Examples 1 to 4 show that with desizing with water, the PVA polymers blended with the PVA copolymer with high ester content show little or no improvement in their ability to desaturate. Example 3, for example, which is a mixture of copolymer with high ester content and partially hydrolyzed homopolymer is less desensitized than C5, which is sizing of the same partially hydrolyzed homopolymer by itself. Only at higher temperatures, (Example 2) a high percentage of desizing occurs. These experiments emphasize that with desizing with water, mixing is not an advantage. The advantage comes only when using a desprestado with caustic solution. The experiments also emphasize that the sensitivity to water would not increase significantly in the examples of the mixtures shown. Table IIIB shows similar samples subjected to desizing with caustic solution, followed by a wash with water. They demonstrate the complete difference in behavior between the desaturated with water and the desaprestado with caustic solution. They also demonstrate how the addition of PVA copolymer with high ester comonomer to various other PVA polymers improves the total proportion of desaturated. Still as Table IIIA demonstrated, the sensitivity to water in general is not increased, as is shown by the no-little to no improvement in desalting with water by the use of PVA copolymer blends with high ester content. Examples C14 to C19 are for PVA polymer sizing alone, including the copolymer (C15) of PVA with high ester content co-monomer, which can be seen to be completely de-sensitized by a 1% caustic compound solution . Values above 100% are an artefact due to the fact that some of the tissue is lost in the desizing process, even with water (see values above .100% in Table IIIA). For this reason, it is likely that all values are up to about 5% higher than the true level of desaprestado achieved. Examples C20 to C23 and C25 are for the same five sizes of PVA polymer alone, such as C14 to C19, except that the prepared fabrics were heat treated. It is seen that all were despressed to a lesser degree after the heat treatment, except the copolymer (C21) of PVA with comonomer of high ester content. Examples C19 and C24 are for mixtures that are outside the invention. The rest, with an asterisk, use the mixed polymers of the invention, with the passage of the desizing process with caustic solution. Comparison of Examples C14 for the fully hydrolyzed PVA homopolymer * with 5 and 6 for fully hydrolyzed hourly polymer blends and the high ester content comonomer copolymer shows the tremendous increase in the desaturated amount. The difference between * # # 5 and 6 is that 6 is a higher viscosity homopolymer (see
Table I for H99-1 and H99-2). The higher viscosity results in a less easy desizing. The most dramatic improvement seen is with the partially hydrolyzed PVA homopolymer (only in Examples C18 and C23, size I), and mixed with the PVA copolymer with high ester comonomer * * * * # * (Examples 7, 11, 12 and 13, sizing, and 14 and 15, which use a HVA-HVA-PVA partially hydrolyzed homopolymer of higher viscosity, see Table I). Note that Example 12 shows that even a very dilute caustic solution is effective in desizing. Examples 7 and 13 show that KOH and NaOH give a comparable desizing. Note the astonishing decrease in amount of desaturated from Example 14 to 15, despite a large increase in the concentration of the caustic compound. This demonstrates the phenomenon that the partially hydrolyzed PVA homopolymer is subject to further hydrolysis, causing the resin to approach the fully hydrolyzed PVA homopolymer, which is much less readily desized by any means of de-borrowing. It also shows that, in this case, the best desalting medium is a more dilute solution of the caustic compound. In general, the strength of the most suitable caustic compound will depend on the particular mixture, and can be easily determined by a few experiments.
TABLE I TESTED PVA SAMPLES Code Viscosity Percent Description of Solids Hydrolysis Composition H88-1 21-26 87-89 'partially hydrolyzed homopolymer' H88-2 44-50"" "" H99-1 12- 15 99.0-99.8 'fully' hydrolyzed homopolymer H99-2 27-33"" "" "C3M 24-32 99.0-99.8 fully hydrolyzed copolymer, 3.3-4.3% MMA C5M 12-15 98.0-99.8 fully hydrolyzed copolymer, 5.0 -6.0% MMA
C9A 15-21 98.0-99.8 fully hydrolyzed copolymer, 8.5-10.5% MA
The designations with codes of the polymers summarize the nature of the composition; H for Homopolymer, C for Copolymer, 88 for ~ 88 moles hydrolyzed, M for methyl methacrylate comonomer, and A for methyl acrylate comonomer.
The viscosity of the solutions is in Centipoises, measured in a solution at 4 percent by weight at 20 ° C, determined by the method of descending spheres of Hoeppler, based on dry adhesion. All samples have a solution pH between 5 and 7. All samples have a maximum ash level of 0.7 percent by weight, calculated as sodium oxide, dry base. The comonomer level in the copolymer is in percent by weight, calculated as the non-lactonized comonomer unit in the polyvinyl alcohol chain. Comonomer abbreviations: MMA = methyl methacrylate MA = methyl acrylate
TABLE II COMPOSITION OF PROPOSED APRESTED COMPOSITION A 8% solution of H99-1 B "C9A C 8% solution of C3M D 8% solution of 50/50 H99-1 / C3M E * 8% solution of 50/50 H99-1 / C9A F 8% solution of 50/50 C3M / C9A G 8% solution of C5M H * 8% solution of 50/50 C5M / C9A I 8% solution of H88-1 J 8% solution of 50/50 C5M / H88-1 K * 8% solution of 50/50 H88-1 / C9A L * 8% solution of 50/50 H99-2 / C9A M * 8% solution 50/50 H88-2 / C9A
# sizes used in the Examples of the Invention. Other sizes are for comparative purposes
TABLE I I IA DISASTER TESTS < N WATER Ex. # Ap res to Treatment Weight of Temperature Solution Percent Thermal Abatement Depressed from Depressed Apressed Yes (S) No (N) (grams) tado ° C Eliminated Cl AN .182 Water 22 27, .5 C2 BN .207 Water 23 36 , .6 C3 CN .223 Water 22 29 .7 C4 GN .171 Water 22 51 .9 C5 IN .260 Water 22 65 .5 C6 DN .213 Water 22 27 .0?
1 E N .203 Water 22 43 .4)
2 EN .151 Water 80 114 .0 3 KN .235 Water 22 60 .6 C7 AS .173 Water 22 17 .3 C8 BS .223 Water 23 23, .5 C9 CS .217 Water 22 15, .6 CIO G s .203 Water 22 31, .3 Cll I s .245 Water 23 58, .3 4 E s .151 Water 22 25, .0 C12 AN .164 Water / Water 22 34., 6 C13 BN .272 Water / Water 22 53.1
TABLE, IIIB TEST * - JE DISAPPEARED WITH SOLUC. "ES CAUSTICAS Ex. # Apresto Treatment Weight of Temperature Solution of Thermal Percent Apressed Deskewed Desprestado Apresto Si (S) No (N) (grams) oc Eliminated C14 AN .182 NaOH at 1% / Water 22 35.6 C15 BN .324 NaOH 1% / Water 22 105.9 C16 CN .230 1% NaOH / Water 22 57.7 C17 GN .144 1% NaOH / Water 22 92.5 C18 IN .255 1% NaOH / Water 22 55.4 C19 JN .207 NaOH at 1 % / Water 22 71.3 5 EN .176 1% NaOH / Water 22 79.6 6 LN .212 1% NaOH / Water 22 62.1 * 7 KN .181 1% NaOH / Water 22 97.6 u >
* 8 MN .236 1% NaOH / Water 22 85.4 C20 AS .143 1% NaOH / Water 22 19.1 C21 BS .249 1% NaOH / Water 22 107.3 C22 GS .177 1% NaOH / Water 22 67 C23 IS .266 1% NaOH / Water 22 48.7 9 * ES .180 1% NaOH / Water 22 63.1 * 10 HS .189 1% NaOH / Water 22 93.9 C24 JS .243 1% NaOH / Water 22 50.6 C25 CS .192 1% NaOH / Water 22 31.1 11 KS .241 1% NaOH / Water 22 90.0 * 12 KN .222 1% NaOH / Water 22 96.0
TABLE I I IB PR-'SZ'AS OF DISAPRESTED WITH CAUSTIC SOLUTIONS (Continued) Ex. # Apresto Treatment of the Temperature Percent Thermal Solution Apresto Desprestado Desprestado Apresto Si (S) No (N) (ggriaumiio? Ss), 1 < - • Eliminated 13 K N .197 1% KOH / Water 22 96.6 14 M N .206 0.1% KOH / Water 22 94.8 •? 15 M N .223 2.5% NaOH / Water 22 78.9 16 F S .221 1% NaOH / Water 22 57.8
Notes for Tables IIIA and IIIB Tissue samples were approximately 0.5 grams, ranging from about 0.45 to 0.65 grams. The desizing liquid is either water or the indicated caustic solution. The percentage is per cent by weight. NaOH and KOH are sediment and potassium hydroxide. Where two desizing liquids are shown, desizing was carried out in the two consecutively, for example caustic solution, then water.