US2933411A - Method of dry cleaning and rendering fabrics water repellent - Google Patents

Description

United States Patent METHOD OF DRY CLEANING AND PmENDERING FABRICS WATER REPELLENT Leo J. Novak, Dayton, Ohio, assignor to The Commonwealth Engineering Company of Ohio, Dayton, Ohio, a corporation of Ohio No Drawing. Application June 18, 1953 Serial No. 362,659

1 Claim. (Cl. 11'7-66) This invention relates to dry cleaning and more particularly to compositions and methods for simultaneously dry cleaning fibrous materials such as articles of clothing and the like and imparting water-repellency thereto.

There are a number of methods now employed for waterproofing fabrics. For example, raincoats are usually waterproofed by impregnating the cloth with a solution of an oil-soluble soap such as aluminum stearate. Different types of waxes are also used. Such treatments do impart a measure of water-resistance to the fabric but, as is known, even though the waxes and soaps may be insoluble in water or the common dry cleaning solvents, the water-resistant effect does not last for the life of. the garment because the adhesion of these substances to the fibers of the fabric is not particularly strong and the coating tends to rub off during use.

Synthetic resins have also been proposed and used, but have the disadvantage that, in order to compensate for the antipathy between the hydrophobic resins and the hydrophilic fibers of the fabric, the finishers tend to load the fabric with the resin, thereby rendering the fabric so stiff and boardy that it becomes necessary to subject it to working on flexers which break up the continuity of the resin coating to leave the resin on the fabric in the form of discrete particles. Such particles tend to peel off in use and, also, the discrete condition of the resin may lead to swelling and distortion of some of the fibers on exposure of the fabric to moisture.

Methods involving chemical alteration of the fibers of the fabric, as by treating the fabric with formaldehyde in the presence of an acid or acid-yielding catalyst, have been proposed for controlling the swelling of hydrophilic fibers in water, which is, in effect, to impart waterresistance to the fabric. Despite the extensive research which has been carried out with a view to perfecting these methods, including the use of softening agents conjointly with the formaldehyde or the like, it is known that no commercial method has been developed which does not result in some embrittlement of the fibers and fabric.

it is a fact that, regardless of the composition and method used for rendering the fabric water-repellent, the effects of the treatment do not persist for the life of the garment for one reason or another, and, in practice, the water-repellent effect has to be renewed periodically. For instance, it is a common occurrence for those who prefer raincoats made of fabric (as opposed to resin film or sheet material which does not breathe nor possess good draping quality) to instruct the dry-cleaner to water-proof the garment before returning it.

Since, invariably, it is necessary to renew the waterrepelling or water-resisting effects by periodically treating the fabric or garment with a water-repellent, the primary object of this invention is to provide a means Q 'ice and method for rendering fabrics water-resistant or waterrepellent during dry cleaning thereof without requiring special handling of the fabric or after-treatments performed on the cleaned and dried fabric.

A further object is to impregnate fabrics, for example cotton, wool and regenerated cellulose fabrics, with a Water-repelling substance which adheres tenaciously to the fabric, does not tend to peel or rub off, and prevents wetting or spotting of the fabric by water in use.

These and other objects are achieved by the present invention in accordance with which, during dry cleaning thereof, fabrics to be rendered water-resistant are impregnated or coated with certain fatty acid esters of a dextran or of a partial dextran conversion product containing, initially, some hydrophobic substitutent groups and some free hydroxyl groups dissolved or dispersed in the dry cleaning solvent or solvent mixture.

The dextrants are inherently hydrophilic high molec ular weight, branched polysaccharides comprising anhydroglucopyranosidic units joined by molecular structural repeating alpha-1,6 and non-alpha--l,6 linkages, ,at least 50% of the linkages being, apparently, alphal,6 linkages. The properties of the dextrans, including the extent of branching (number and distribution of side chains or groups), the molecular weight, the molecular structural repeating alpha-1,6 to non-alpha-1,6 linkages ratios, and the sensitivity to water vary.

It is found that esters of the dextrans with saturated fatty acids of from 8 to 18 carbon atoms and having a BS. (degree of substitution or number of fatty acid radicals per anhydroglucopyranosidic unit of the dextran) from 2.0 to 3.0 are water-repellent substances which have an affinity for hydrophilic fibrous materials and are or garment is impregnated with, or carries a protective,

water-repellent film or coating of, the ester which remains adhered to the fabric until it is again dry-cleaned, when the Water-repellent finish may be renewed.

The higher saturated fatty acid radicals may be introduced into the dextran molecule by any appropriate method. Thus, the dextran, preferably in the form of a freefiowing powder, may be reacted with an esterifying derivative of the fatty acid, and preferably a halide such as the chloride thereof, in the presence of an acid acceptor or binding agent such as an organic base, as for instance a heterocyclic tertiary amine of the type of quinoline, pyridine, N-methyl morpholine, etc., and in the presence of a substance in which the reaction product is at least partially solvated, that is dissolved or swollen, as it is formed during the reaction. This results in the reaction mass being maintained in a highly swollen or dissolved state and thus insures substantially uniform, homogeneous reaction between the dextran and the esterifying agent.

Substances which dissolve or swell the ester as it is formed are, for example, xylene, toluene, dioxane, etc.

In general, the reactionmay be carried out at temperatures between C. and C. for time periods varying inversely with the temperature between a half hour and three hours. The ester may be recovered from the crude reaction mixture by washing the latter with water to remove the hydrochloride of the organic base, removing the aqueous layer, adding a solvent for the ester to ether and dichloroisopropyl ether.

the residual mass, precipitating the solution into a nonsolvent for the ester, such as a lower aliphatic alcohol, and filtering to obtain the ester.

Also the introduction of the higher fatty acid radicals into the dextran molecule may be effected by reacting the dextran with the selected acid in the presence of an impeller which may be the anhydride of a monohalogenated monobasic organic acid, e.g., monochloro acetic anhydride, and an esterification catalyst such as magnesium perchlorate at temperatures at which the reaction mixture remains in the liquid state, in general in the range between 50 C. and 100 C. and for a time varying inversely with the temperature between one-half hour and two hours. The ester may be isolated from the crude reaction massbycooling the mass, dissolving it in a solvent therefor, precipitating it into a non-solvent for the ester, and filtering the ester.

The higher fatty acids which may be used as esterification agent, in the free acid form or in the form of their chlorides, are those saturated acids containing from 8 to 18 carbon atoms and including caprylic, pelargonic, palmitic, margaric,'and stearic acids, and the corresponding chlorides. Two or more of the substantially pure acids, or chlorides thereof, may be used, resulting in the production of mixed dextran esters. Or commercial acids, which comprise mixtures, may be used. For example, commercial or technical grade stearic acid, which comprises a mixture of stearic and palmitic acids, yields dextran stearate-palmitate.

As has been mentioned hereinabove, the esters to be used as water-repellents in the dry cleaning solvents are those having a D8. of from at least 2.0 up to 3.0. Other conditions, such as the reaction time and temperature, being appropriately controlled, such esters may be obtained by using the fatty acid or itsrchlorides in amounts varying between about 2 and 10 parts thereof by weight per part of dextran. These highly substituted dextran esters, and more particularly those derived from the saturated acids of longer chain'length, i.e., those containing between 14 and 18 carbon atoms, have a waxy consistency and, in addition to rendering the fabric waterresistant, also give it a soft, pleasing hand or feel.

The production of these dextran esters is exemplified in detail, and claimed in the pending-application of L. I. Novak et al., Serial No. 371,743, filed April 28, 1953, and now abandoned.

The dextran esters described herein are soluble in the solvents commonly used in dry cleaning, such as Stoddards solvent, gasoline and cleaners naphtha. They are also soluble in the nonfiammable chlorinated compounds which are rapidly replacing flammable solvents like naphtha in the dry cleaning trade and including carbon tetrachloride, ethylene and propylene dischloride, trichlorethane, trichloroethylene, perchlorethylene, dichloroethyl The esters are also soluble in mixtures of these solvents with each other and with neutral soaps such as the mixtures oftenused in commercial large-scale dry cleaning establishments.

The solutions may be prepared and marketed as such for home or large-scale commercial use or just prior to use they may be prepared by adding the ester to the solvents. For example, in the commercial cleaning houses the ester may be added to clarified, used solvent as his recirculated to the tumbler or washing machine. -The concentration of the dextran ester in the solution may vary depending on the type. of fabric, garment or fibrous aritcle treated, larger amounts being generally desirable for heavier fabrics.

As a general rule solutions containing from 1% to 20% by weight will be found satisfactory, the conditions of the treatment being controlled so that the amount of dextran ester deposited on the fabric is between 2% and 5% on the fabric weight.

7 The 'fabric or the like to be dry-cleaned may be introduced directly into the ester solution. When the dry cleaning procedure involves a dual-step method in which the fabric or garment is washed in the solvent and then rinsed in fresh solvent or in clarified used solvent, the dextran ester may be present in both baths but is preferably present in the rinsing bath, only. For instance, in one commercial method of dry cleaning fabrics according to the invention, a batch of 20 lbs. of soiled garments is placed in the Washing machine of conventional type and containing the usual quantity of solvent, such as carbon tetrachloride. The clothing or the like is then agitated in the solvent for approximately 10 minutes to remove loose dirt. The solvent is then re moved and clarified bypassage through a suitable filter, by centrifuging, or by allowing the dirt to settle and decanting off the clarified supernatant.

The purpose of removing and clarifying the solvent at this point is to prevent loading thereof by dirt, grease, etc. removed from the garments. Before the clarified solvent is returned to the machine for further washing of the garments, etc. it is fortified by the addition of a sulficient amount of water-resistant dextran ester, for example a dextran palmitate containing, per anhydroglucopyranosidic unit, an average of about 2.9 palmitoyl radicals,

or a dextran stearate containing, per anhydroglucopyram osidic unit, an average of;2.9 stearoyl radicals, to provide a cleaning and water-repelling solution of the required concentration.

The solution of the ester is entered into the tumbling machine and agitated with the clothing forthe predetermined length of time. The treated goods is then removed from the machine and dried in the usual way.

There is thus obtained a cleaned article carrying a renewable water-repellent finish. The articles being cleaned may be forwarded from one machine or compartment to another and treated at each stage with the dry cleaning solvent, and at least at the final stage with a composition consisting of a solution of the dextran ester in the solvent or mixed solvents.

Instead of esters of dextran there may be used esters of dextran conversion products containing, per anhydroglucopyranosidic unit, an average of at least 2.0 of the radicals derived from the saturated aliphatic acids, of from 8 to 18 carbon atoms and, in addition to those radicals, an average of about 1.0 hydrophobic substituent such as alkyl radicals of 1-5 carbons or aralkyl radicals of 7-10 carbons, total.

Preferably, the esterified dextran product does not contain more than an average of 1.0 free hydroxyl group orradical of hydrophilic character per anhydroglucopyranosidic unit and has little, if any, water attracting powen In-the specifically preferred embodiment, the

water-repellants contain, per anhydroglucopyranosidic' unit, between 2.5 and 3.0 substituent groups at least 2.0 of which are derived from the saturated fatty acids.

The dextrans to be esterified may be obtained in various ways. For example, they may be produced microbiologically, by inoculating a nutrient medium containing sucrose, particular nitrogeneous compounds and certain inorganic salts, with an appropriate microorganism, such as those of the Leuconostoc mesenteroides and L. dextranicum types, and incubating the culture at the temperature most favorable to the growth of the particular microorganism.

In one method of obtaining a dextran to be esterified to produce the water-repellents for incorporation in the dry cleaning composition of the invention, there is first prepared an aqueous nutrient medium which may have the following composition:

Percent by weight This medium is adjusted to a pH of between about 6.5 and about 7.5, preferably 7.2, and then sterilized. The material is cooled to room temperature and inoculated with a culture of the dextran-producing microorganism, for instance, Leuconosmc mesenteroides B-S 12 (Northern Regional Research Laboratory classification) and incubated at 20 to 30 C. (optimum 25 C.) until a maximum yield of dextran has been attained; normally a period of between 12 and 48 hours will be satisfactory for this procedure. The fermented product contains approximately 80-85% of water and is a thick turbid liquid.

Upon completion of the fermentation, which process renders the material somewhat acid, that is, to a pH of 3.5-5.5 (average 4.2), calcium chloride is added to the ferment to bring the pH thereof to about 7.0 to 8.0. This aids in the precipitation of phosphates. Thereafter, acetone or alcohol, which may be a water-miscible ali phatic, such as methyl, ethyl or isopropyl, is added in sufiicient quantity to precipitate the dextran and this brings down, with the dextran, occluded and adsorbed bacteria, and nitrogenous and inorganic elements. To occasion complete precipitation of the dextran it may be desirable to allow the mix to stand for a relatively long period, such as about 6 hours. The precipitated dextran may be dried in any suitable manner, for example by drum drying. Thereafter, it may be reduced to a powdered condition, if desired.

A purer dextran may be obtained by adding an aliphatic alcohol to the fermented culture at a pH between about 2.5 and 4.5. The precipitate thus obtained may be further purified by again precipitating it with the alcohol. Several precipitations may be performed.

The dextran thus produced is a so-called native dextran having a high molecular weight and being, in the particular case, soluble in water at ordinary temperatures.

The higher saturated fatty acid radicals may be introduced into the molecule of high molecular weight dextrans such as the native dextran described above, or other dextrans of equivalent or similar high molecular weight, or lower molecular weight dextrans may be used as starting material for production of the water-resistant esters containing chemically bound radicals derived from the saturated fatty acids.

Lower molecular weight dextrans may be obtained directly or by hydrolysis, in any suitable way, as by acid or enzymatically, of higher molecular weight dextrans. The hydrolyzed material may be fractionated, if desired, and the dextran may be a so-called clinical" dextran of the type useful as a blood plasma extender.

In general, the dextran may have a molecular weight between 5,000 and 150x10 as determined by light scattering measurements.

The dextran may be obtained by inoculating a culture medium of the type described with microorganisms other than that mentioned above. Thus, it may be a water-soluble dextran obtained by the use of the microorganisms bearing the following NRRL classifications; Leuconostoc mesenteroides B-l19, B1l46, Bll90, or a water-insoluble or substantially water-insoluble dextran obtained by the use of Leuconostoc mesenteroides B-742, B-1l91, B-1196, B4208, 13-1216, 13-1120, B-ll44, B-523, Streptobacterium dextranicum B-1254 and Betabactcrizmz vermiforme 13-1139.

The dextran is not limited to one prepared under any particular set of conditions, including the microorganism used. It may be produced enzymatically, in the substantial absence of bacteria, by cultivating an appropriate microorganism, for example, Leuconostoc mesenteroides B-512 to obtain a dextran-producing enzyme, separating the enzyme from the medium in which it is produced, and introducing the enzyme into a medium in which dextran is produced by the action of the enzyme. Also, the dextran may be obtained by bacterial conversion of 1,4 linkages of dextrin to 1,6 linkages of dextran. The dextran may be insoluble in water under ordinary conditions but soluble in aqueous alkali solution.

In the presently preferred embodiment of the invention, the water-resistant fatty acid esters are derived from substantially pure native unhydrolyzed microbiologically produced dextrans precipitated from culture media of the types described herein, or from dextrans of equivalent high molecular weight.

The higher saturated fatty acid esters of the dextrans are strongly water-repellent. For instance, it has been observed that if a film of dextran palmitate 0r dextran stearate containing, per anhydroglucopyranosidic unit, an average of 2.9 palrnitoyl or stearoyl groups is deposited on the hands during handling of the solutions thereof, the film is not removed by repeated washing or scrubbing with soap and water.

The strong resistance to water coupled with the effective substantivity which these esters exhibit for fibers of hydroxylated materials renders them ideally adapted to use as renewable water-repellents to be applied to garments and other articles in the course of dry cleaning the same. The esters are applied to the garments or the like while they are being cleaned, and no after-treatment or special handling is required.

No special precautions or use of elevated or baking temperatures are required such as must be performed when the water-repellent is a synthetic resin, nor are the fabrics subjected to harsh conditions leading to embrittlement or loss of strength. The dextran esters protect the fibers, tend to increase their strength and resistance to abrasion, and to improve the suppleness and drapability of the fabrics, so that, in addition to rendering the fabrics water-resistant or water-repellent the esters of the dextran or dextran conversion products exert beneficial effects on the quality of fabrics drycleaned in accordance with this invention which, therefore, provides a means and method for treating fabrics by means of which, in essentially a single-step procedure, the fabric is dry-cleaned, conditioned, and rendered strongly water-resistant. The esters do not detract from the effectiveness of the dry cleaning compounds as scouring and degreasing agents for fabrics. The dispersions or solutions of the esters in the dry cleaning solvents are stable. The term solution as used herein includes colloidal solutions or dispersions.

It will be understood that while there have been described certain specific embodiments of this invention, it is not intended thereby to limit or circumscribe it by the details given, in view of the fact that this invention is susceptible of various modifications and changes which come within the scope of this disclosure and of the appended claim.

I claim:

In amethod of dry cleaning fabrics comprising washing the fabric in a solution containing volatilizable organic solvents and then separating the solution from the fabric and drying the fabric, the improvement which consists in simultaneously cleaning and waterproofing the fabric by washing the same in a dry cleaning solvent containing from 1% to 20% by weight of a saturated fatty acid ester of dextran, said saturated fatty acid containing from 14 to 18 carbon atoms in the molecule, and the dextran having a molecular weight between 5,000 and x10 and produced by the reaction of sucrose with a dextran-producing strain of Leuconoszic mesenteroides, and separating the washed fabric from said cleaning solvent leaving a residue of said dextran fatty acid ester of from 2% to 5% based upon the weight of the fabric thus treated, said dry cleaning solvent being selected from the group consisting of carbon tetrachloride, ethylene dichloride, trichlorethylene and perchlorethylene and mixtures thereof.

(References on following page) References Cited in th file of this patent UNITED STATES PATENTS Lejeune et a1 Oct. 29, 1935 Bucy Nov. 28, 1939 Stzihly 61; 3 1. .2 Jan. 23, 194 1 Thackston et 'al. Mar. 21, 1944 Maxwell Sept. 26, 1944 Walde Oct. 16, 1945