US2756160A - Colloidal dispersion of dextran for finishing textiles - Google Patents

Description

COLLOIDAL DISPERSION OF DEXTRAN FOR FINISHING TEXTILES Leo J. Novak, Walter S. Hogue, and Howard J. Homer,

Dayton, Ohio, assignors to The Commonwealth Enginearing Company of Ohio, Dayton, Ohio, a corpora tion of Ohio No Drawing. Application June 18, 1953, Serial No. 362,664

4 Claims. (Cl. 106-462) This invention relates to the sizing and finishing of nbrous materials. More particularly, it relates to a laundry treating agent adapted for use by commercial laundries and in the home as an ironing aid which imparts an attractive finish or hand to fibrous materials.

Raw starch has been, and is, the substance most widely used in the sizing and finishing of cotton textile goods. The major drawback of raw starch is that it is neither soluble nor uniformly dispersible in water at ordinary temperatures and, therefore, it must be mixed with water and pro-cooked to obtain a dispersion useful as such or after suitable dilution as a sizing medium for the cotton goods. If the raw starch is supplied to the ultimate user in the dry lump or powder form, the pre-cooking to effect adequate dispersion thereof in the water is carried out by the user, for instance by the housewife, and is not only inconvenient and time-consuming, usually requiring from to minutes at temperatures of 55 C.100 (3., but also presents a hazard in that the cooking must be controlled to avoid under-degradation or over-degradation of the starch, which conditions result in excessive penetration of the size into the fibers and yarns of the fabric with little or no protecting film of the size left on the fabric surface, or to undue sticking of the iron when the sized fabric is pressed with a hot iron. In addition, during the cooking step, the starch granules tend to swell and then rupture, so that much of the stiffnessimparting property of the substance is lost upon subsequent ironing of the fabric sized therewith.

In an attempt to avoid these diificulties it has been proposed to use partially cooked or raw starch in admixture with cold water. Since uncooked or only partially cooked starch is not readily and uniformly dispersed in water, the granules have a tendency to aggregate and the mixtures require skill in their application and continuous agitation before and during application thereof in order to avoid settling and packing of the starch. Even when great care is exercised it is found that when fabrics are treated with a mixture of cold water and a raw or partially cooked starch, the aggregates which inevitably form are non-uniformly distributed on the fabric. When the fabric carrying the aggregates is ironed, the aggregates appear as visible white streaks or blotches.

It has also been proposed to render starches soluble or dispersible in water by cooking them in the course of their preparation for marketing. During such cooking, precautions must be taken to guard against both undercooking and over-cooking of the starch. The available pre-cooked starches are only poorly dispersible in water at room temperature, tend to ball up and form clumps which must be broken up by prolonged stirring. and invariably yield weak sols. v

In another attempt to solve the problem involved in the use of starch as a laundry size or stiffener, so-called liquid starches have been marketed. These comprise a dispersion of cooked starch in water or a composition consisting essentially of cooked starch dispersed inan nited States Patent Patented July 24, 1956 aqueous medium by means of an emulsifying agent. However, as is well known, these prepared liquid starches have proved to be unsatisfactory in many instances and mostly because their stiifness-imparting properties have been greatly reduced in the cooking process.

It may be stated, then, that no wholly satisfactory starch product is at present available for use as a size and which does not involve a prolonged cooking either by the supplier of the size or by the ultimate user in laundry plants or the like or in the home.

It is an object of this invention to provide a new and improved sizing and stiffening agent for fibrous materials such as fabrics, garments, yarns, paper, etc. which has the stiffening and sizing properties of starch but which is soluble or dispersible in water at ordinary room temperatures without pre-cooking thereof.

Another object is to provide a sizing and stiffening agent which is directly soluble or dispersible in water at ordinary temperatures in a wide range of concentrations.

A further object is to provide a sizing or stiffening agent which can be shipped in dry, particulate conditions and dissolved or dispersed in water at room temperature, without pre-cooking by either the supplier or user, to obtain a sizing or stiffening bath of any suitable concentration between 0.1% and 20% by weight.

Another object is to provide a simple, relatively inexpensive method for sizing and stiffening fibrous materials including fabrics, garments, paper and the like.

These and other objects are accomplished by the present invention in accordance with which there is provided a sizing and stiffening agent comprising a water-soluble or water-dispersible dextran.

The dextrans are high molecular weight, balanced polysaccharides comprising anhydroglucopyranosidic units joined by alpha-1,6 and non-alpha-l,6 molecular structural repeating linkages and at least 50% of which linkages are, apparently, alpha-1,6 linkages. The properties of the dextrans, including the molecular structural repeating alpha-1,6 to non-alpha-1,6 linkages ratios, the molecular weight, and the sensitivity to water, vary widely and a large number of dextrans which diflier specifically with respect to these various properties are now known.

According to the present invention, it is found that fibrous materials can be sized and stifiened effectively and conveniently by the use of substantially pure dextrans having a range of molecular structural repeating alphal,6 to non-alpha-1,6 linkages ratios between 1.9:1 and 30:1, a molecular weight of from 5,000 to x10 as determined by light-scattering measurements, and a solubility or dispersibility in water such as to form colloidally stable, aqueous solutions or dispersions of from 0.5% to 50% by weight concentration at ordinary temperatures.

The present invention is not dependent on the method by which the dextran having the required combination of characteristics is obtained. It may be produced microbiologically, for example by inoculating, with suitable selected bacteria, a sucrose-bearing medium containing particular nitrogenous substances and certain inorganic salts. For instance, the dextran may be obtained by inoculating a medium containing 5-10% of sucrose, 0.5% peptone, 0.5% dipotassium phosphate, 0.1% of sodium chloride and 0.005% of manganous sulfate With Leuconostoc mesenteroides B-512 (Northern Regional Research Laboratory classification), and incubating the inoculated medium at the temperature most favorable to the selected'microorganism until the maximum amount of dextran is produced, after which the dextran may be precipitated from the culture medium by the addition of acetone or a water-miscible lower aliphatic alcohol, such as methanol, ethanol, isopropanol thereto. Or the dextran may be obtained by cultivating a selected bacterium, such as Leuconoszoc mesentcroides B-512 to obtain a dextran-producing enzyme, separating the dextran from the medium in which the bacterium is cultivated, and introducing the enzyme into a medium in which dextran is formed by the action of the enzyme. The dextran may also be produced by methods involving the bacterial conversion of 1,4 linkages of dextrins to the 1,6 bonds of dextran, or by any other feasible method.

However the dextran to be used as the sizing or stiffening agent is obtained, it is important that it be in pure or substantially pure condition to avoid staining of the sized fibrous material thereby. Dextran produced microbiologically as described above should be substantially free from nitrogenous substances, bacteria and enzyme precipitated from the fermentate with it. Such impurities may be held to a minimum by controlling the conditions of the initial precipitation. Thus, a relatively pure dextran can be precipitated from the fermentate obtained by incubation of the culture medium inoculated with Leuconostoc mesenteraides B-512 by adding alcohol to the fermentate at a pH of 2.5 to 4.5. The dextran thus precipitated may be further purified by one or more additional precipitations with the lower aliphatic alcohol or with acetone.

The dextran thus produced is a so-called native dextran which is soluble in water, has a molecular structural repeating alpha-1,6 to non-alpha-l,6 linkages ratio of 19:1 and a high molecular weight calculated to be in the millions. It may be dried, as by drum drying, to obtain a fluffy product usable as such or after reduction to a powder, in preparing the present sizing bath. Other dextrans of similar high molecular weight may also be used, or the dextran may have a lower molecular Weight in the range stated previously herein. The lower molecular weight dextrans may be obtained by hydrolysis of the higher molecular weight materials, as by means of acid or enzymatically, followed by fractionation, if desired, and such purification as may be required to obtain a substantially pure, non-staining dextran.

Very advantageously, the size may comprise low molecular weight dextran fragments obtained in the conventional production of clinica dextran and which have hitherto been discarded as waste material. Such waste products usually have an average molecular weight between 5,000 and 50,000.

The dextran may be an initially water-soluble dextran obtained using the microorganisms bearing the following NRRL classifications: Leuconostoc mesenteroides B419, B-l146 and B4190, and which may or may not be hydrolyzed to lower molecular weight. Or it may be an initially water-insoluble or substantially water-insoluble dextran obtained using the microorganisms Leucolmstoc mesenteroides B-742, B4191, B-1196, 13-1208, 13-1216, B-1120, 8-1144, B-523, StreptObacterium dextranicum B-1254 and Betabacterium vermiforme Bl139, these dextrans being used as obtained, after purification, if they are dispersible in water to the required concentration, or being hydrolyzed to lower molecular weight, more readily water-dispersible or watersoluble products.

In sharp contrast to starch, the dextrans having the combination of properties described have the important advantage that as obtained intially, or after hydrolysis, they are soluble or uniformly dispersible in water Without cooking by either the supplier or ultimate user and they may be shipped and sold in the dry condition. The advantage over raw starch is obvious. The need to precook the raw starch to effect satisfactory dispersion thereof in water always presents the problem that unless the pre-cooking is carried out under controlled conditions, the starch will be either under-degraded or over-degraded, both of which conditions result in inadequate or unsatisfactory sizing of the fibrous base. The pre-cooking is particularly hazardous when carried out in the home and improper cooking is usually the cause of the common complaint about sticking of the iron, and scorching, during ironing of the starched article. Elimination of the cooking, as is possible when these dextrans are used, eliminates both the cooking and sticking problems, and the supplier can exercise complete control over the properties of the sizing agent since, in use, the dextran is not exposed to haphazard, uncontrolled degradation by heat.

The concentration of the dextran in the aqueous sizing bath may be varied widely, within the upper and lower limits of dispersibility or solubility of the dextrans in water, and depending upon the particular dextran used. In general, aqueous baths containing 0.1% to 5.0% dextran are satisfactory when the dextran is a high molecular weight or native unhydrolyzed dextran. Aqueous baths containing up to 20% by weight dextran may be used when the dextran has a comparatively low molecular weight, i. e., when it is a hydrolyzed dextran or the by product low molecular weight fraction of clinical dextran production. Within these ranges, the dextran concentration may be selected for the type of fibrous material to be sized, higher dextran water ratios being useful for such laundry as shirts and the like, and lower ratios being generally preferred for sizing table linens, dresses, etc. The presence of the dextran on the laundered article does not interfere with smooth ironing thereof, and the stilfened, ironed article has a polished or glossy appearance and a soft or velvety touch. The dextran size or finish, which adheres firmly to the cotton or other fibers, impedes penetration of soil or dirt into the fabric.

In this regard, it may be noted that the dextrans are particularly desirable sizing or finishing agents for shirts or other articles to be laundered since these dextrans are anti-soil fixation agents which facilitate laundering of the article sized therewith. The dextran removed from the fabric during laundering thereof functions to hold soil removed in the washing operation in suspension so that the soil cannot redeposit on the article.

The following examples, in which the parts are by weight, are illustrative of specific embodiments of the invention.

Example I A sizing bath was prepared by simply dissolving one part of a particulate pure, hydrolyzed dextran having a molecular weight of about 100,000 and a molecular struc' tural repeating alpha-1,6 to n0n-alpha-1,6 linkages ratio of 10:1 in five parts of water at room temperature. The collar and cuffs of a freshly laundered white cotton shirt were immersed in the sizing bath for about one minute, removed, wrung out, and the shirt was ironed. The sized portions of the ironed shirt were stiffened and had a high, smooth polish.

Example [I A sizing bath was prepared by dissolving one part of a substantially pure, native B-512 dextran in 20 parts of water, at room temperature. A white cotton. blouse was immersed in the bath for about five minutes, removed, and wrung out. It carried a uniform film of dextran and on drying and ironing acquired a stiff but full mellow hand.

Other dextrans, such as those having structural molecular repeating alpha-1,6 to non-alpha-1,6 linkages ratios of 1.9:1, 3.521, 8:1,15:1,16:1,18:1and 22:1 and molecular weights between 5,000 and that of a native microbiologically produced dextran may be substituted in the Examples and give the same results.

As will be apparent, the molecular structural repeating alpha-1,6 to non-alpha-1,6 linkages ratios, are independent of the molecular weight and dextrans of different molecular weights may have the same linkages ratio.

As is known, textile finishers of cotton goods often obfeet to starch finishes as too stiff and harsh and prefer to utilize starch compositions comprising special plasticizing agents, generally some type of tallow which is usually sulfated and modifies the dryness and boardiness frequently imparted to cotton by starch. Instead of sulfated tallow, sulfonated oils such as castor or olive oil and sulfated cetyl and stearyl alcohols have been used. The dextrans do not require combination with these adjuvants since, under normal conditions, the fabrics sized with the dextrans in the absence of the plasticizers has sufficient soft ness and plasticity to be commercially acceptable. However, the dextran may be used in conjunction with plasticizing aids, or with wetting agents, emulsifiers, dispersants or the like, if desired.

The dextrans may be used as substitutes for laundry starch in the sizing and stiffening of cotton goods. They may also be used as sizing and finishing agents for other materials, for instance in textile finishing treatments performed in the mill, and may be used for purposes for which starch is not generally acceptable to the trade. Thus, it is well known that starch is not suitable for sizing and finishing regenerated cellulose, silk and similar luxury fabrics designed and processed to have luxurious appearance and softness of touch because starch films impair the desired handle and detract from the high quality appearance of those fabrics. The finishers have resorted to other finishes, such as finishes of protein origin, glue, and synthetic resins. The protein sizes have a tendency to yellow whites and to impart an odor to the fabrics, glue has a loading or weighting effect, and the synthetic resins must be carefully controlled both as to type, composition, and degree of polymerization to avoid rendering the fabric so stiff and boardy, that it must be put through flexers to break up the resin film or coating. In contrast to starch and the protein, glue or resin finishes, the dextrans may be used to stiffen the so-called luxury fabrics Without impairrnent and even for improvement of the feel or appearance and draping quality thereof, and thus have a much wider range of usefulness than raw or modified starch.

The substantially pure dextrans, which are odorless, non-staining, non-irritating substances may be used to size, stiffen or finish all types of fabrics, particularly cotton fabrics in concentrations between 0.1% and 20% by weight, the concentration being selected on the basis of the molecular weight and to produce the desired stiffness, bulk and body. The more highly concentrated dispersions, which may have a consistency of or approximating a paste may be applied to the goods on a pad or by means of a doctor blade, during finishing of the goods for marketing. These dextrans form smooth, uniform films or coatings on the sized fabrics, which effectively mask the reedy, irregular appearance of many types of cotton goods and that is, at best, imperfectly masked by starch finishes. After ironing or pressing, the sized fabrics have a smooth, polished appearance and are substantially free from blotches or streaks because of the homogeneity of the dextran dispersion applied thereto and the absence of aggregates or balls from the dispersion. It is found that goods sized with the dextrans disclosed herein may be dampened, prior to ironing thereof, and ironed in the damp condition, without effecting uniform distribution of dextran size or causing the iron to pick up the dextran from the fabric.

The dextrans may be used as size and finish for all types of fibrous materials. They may be used as the tub or coating size for paper, and as a warp size to coat and impregnate threads so as to strengthen them for weaving and the sizing medium for the threads may contain, in addition to the dextran, special lubricants which assist in preventing sticking of the threads to the drier rolls, as well as softeners, penetrants, preservatives and loading agents. The dextran sizing medium may be applied to the warp threads on a slasher and has the important advantage that it may be removed from the woven fabric prior to dyeing thereof, by simply passing the fabric through a plain water bath whereas when starches are used, the fabric must be subjected to special scouring treatments for removal of the size. The dextrans may also be used in the pure and backfill finishing of various types of textile fabrics. Used as a laundry starch, it may be applied to the fabrics in combination with brighteners which exhibit effects similar to blueing.

This invention provides, for the first time, a starch substitute which is soluble or uniformly dispersible in water at room temperature without pre-cooking thereof either in the course of its production or by the user, which may be shipped in dry, particulate condition for direct dispersion or dissolution in water at ordinary temperatures, which is at least as effective as starch in sizing and finishing fibrous materials and adapted to use in a wide range of concentrations which may be varied to obtain particular effects, and depending on the fabric treated. It will be understood, therefore, that while there have been described certain specific embodiments of the invention, it is not intended thereby to limit or circumscribe it by the details given, in view of the fact that the invention is susceptible of various modifications and changes within the scope of this disclosure and of the appended claims.

We claim:

1. As a finishing agent for textile materials to provide said materials, Without loss of the essential flexibility of the textile, and without the application of starch thereto, with a smooth, glossy surface finish substantially free from streaks, blotches and discoloration on hot-pressing thereof after application of a solution of the finishing agent thereto, and drying of the textile, a substantially pure, dry, particulate dextran having a molecular weight of about 5000 to about 50,000, as determined by light scattering measurements, a molecular structural repeating alpha-l,6 to non-alpha-l,6 linkages ratio of 1.9:1 to 30:1 and which forms, in water, and at ordinary temperatures, colloidally stable dispersions of from 0.5% to 50% by weight concentration.

2. An aqueous finishing bath for textile materials consisting essentially of water and, dispersed therein, for providing the textile materials, without loss of the essential flexibility thereof and without the application of starch thereto, with a smooth, glossy surface finish substantially free from streaks, blotches and discoloration on hot-pressing thereof after application of the dispersion thereto and drying of the textile, from 1% to 20% by weight of, a substantially pure dextran having a molecular weight of about 5000 to about 50,000 as determined by light scattering measurements, a molecular structural repeating alpha-1,6 to non-alpha1,6 linkages ratio between 1.9:1 and 30:1, and which forms, in water and at ordinary temperatures, colloidally stable dispersions of from 0.5 to 50% by weight concentration.

3. The method of finishing textile materials which cornprises treating said material With a finishing aqueous dispersion of 1% to 20% by weight of substantially pure dextran having a molecular weight of about 5000 to about 50,000 as determined by light scattering measurements, a molecular structural repeating alpha-1,6 to non-alpha-1,6 linkages ratio of 1.9:1 to 30:1, and which forms, in wa ter, at ordinary temperatures, colloidally stable dispersions of, by weight, 0.5 to 50% concentration, removing excess treating medium from the fibrous material, and drying and pressing the material under heating whereby the ma terial acquires a smooth, glossy surface finish substantially free from streaks, blotches and discoloration without the application of starch thereto.

4. Finished, unstarched, hot-pressed textile material carrying a finishing film of a substantially pure dextran of molecular weight about 5000 to about 50,000 as determined by light scattering measurements, a molecular structural repeating alpha-1,6 to non-alpha-1,6 linkages ratio between 1.9:1 and 30:1 and which forms, in water, at ordinary temperatures, colloidally stable aqueous disper- 7 sions of 0.5% to 50% by weight concentration, said hotpressed fabric having a smooth, glossy surface finish sub stantially free from streaks, blotches and discoloration.

References Cited in the file of this patent UNITED STATES PATENTS 8 Griinwall et a1. July 7, 1953 Deniston Apr. 6, 1954 OTHER REFERENCES

Claims (1)

1. AS A FINISHING AGENT FOR TEXTILE MATERIALS TO PROVIDE SAID MATERIALS, WITHOUT LOSS OF THE ESSENTIAL FLEXIBILITY OF THE TEXTILE, AND WITHOUT THE APPLICATION OF STARCH THERETO, WITH A SMOOTH GLOSSY SURFACE FINISH SUBSTANTIALLY FREE FROM STREAKS, BLOTCHES AND DISCOLORATION ON HOT-PRESSING THEREOF AFTER APPLICATION OF A SOLUTION OF THE FINISHING AGENT THERETO, AND DRYING OF THE TEXTILE, A SUBSTANTIALLY PURE, DRY, PARTICULATE DEXTRAN HAVING A MOLECULAR WEIGHT OF ABOUT 5000 TO ABOUT 50,000, AS DETERMINED BY LIGHT SCATTERING MEASUREMENTS, A MOLECULAR STRUCTURAL REPEATING ALPHA-1,6 TO NON-ALPHA-1,6 LINKAGES RATIO OF 1.9:1 TO 30:1 AND WHICH FORMS, IN WATER, AND AT ORDINARY TEMPERATURES, COLLOIDALLY STABLE DISPERSIONS OF FROM 0.5% TO 50% BY WEIGHT CONCENTRATION.