WO1981002313A1

WO1981002313A1 - Low temperature bleaching

Info

Publication number: WO1981002313A1
Application number: PCT/US1980/000133
Authority: WO
Inventors: T Davis; T Girard
Original assignee: Glyco Chemicals Inc; T Davis; T Girard
Priority date: 1978-05-30
Filing date: 1980-02-11
Publication date: 1981-08-20
Also published as: EP0046767A4; WO1981002314A1; EP0046767A1; EP0045740A1; EP0046767B1; AR221639A1

Abstract

Improved bleaching agent composition composed of a mixture of an organo-N-chlorinated compound, e.g., N, N-dichloro-substituted hydantoin compound with a material capable of forming bromonium ions, such as an inorganic bromide salt, e.g., sodium bromide, which has enhanced bleaching effectiveness for textile materials, particularly in laundry systems, when used at lower-than-normal washing temperatures, e.g., in the range of about 60 to 140 F.

Description

LOW TEMPERATURE BLEACHING

This application is a continuation-in- part of co-pending application Serial No. 911,190, filed May 30, 1978. This invention relates to an improved bleaching agent composition for use in low temperature aqueous systems, such as in laundry operations or in the commercial processing of textile materials, e.g., cotton grey goods.

The use of halogen-releasing agents for bleaching as well as disinfecting purposes in the processing or laundering of textile materials is, of course, well known, and has a long history. Various inorganic halogen-based bleaching agents are known including not only elemental chlorine gas, but also sodium hypochlorite, sodium hypobromite, etc. In addition, a number of halogen-releasing organic agents have been disclosed as bleaching agents. These include, for instance, halogenated glycourils described in U.S. Patent 3,071,591 and a number of other N-halogenated derivatives of amines, amides, imides and various N-heterocyclic compounds, such as those mentioned in U.S. Patent 3,412,021.

Included in such known N-halogenated organic compounds are of course organo-N-chlorinated compounds such as the

N,N-dihalo-substituted hydantoin compounds. It is with respect to this class of organo N-chlorinated materials in combination with a potential source of bromonium (Br⁺) ion, e.g., an inorganic bromide, that the present invention is particularly concerned.

Characteristically, in previous years, bleaching agents for use in the laundering or processing of textile materials were employed in practice at relatively elevated temperatures of, for instance, above 160°F. (approx. 70ºC). For some years, however, there has been an interest in the processing of textiles in a bleaching environment at lower temperatures — dictated in part from the standpoint of energy conservation measures, and in part from the standpoint of protecting the textile material against chemical damage. At such lower temperatures, however, many of the most commonly used and hitherto satisfactory bleaching agents lose a substantial amount of their activity.

There has consequently existed for some time a need for improved bleaching agents which can be effectively used at the desired lower processing temperatures. It is a principal object of this invention to provide such improved bleaching compositions, and which also offers a decrease in the amount of organic bleaching additive required for the purpose (thereby decreasing effluent contaminant problems), and with cost saving advantages.

According to the present invention, there is provided an effective method for the bleaching of textile goods at low temperatures in the range of from 60° to 140ºF by exposing the textile goods to an aqueous solution at said temperatures, which solution consists essentially of a mixture by weight of:

(a) 25 to 75 parts of an organo-N-chloro compound selected from the group consisting of: i) N-chlorinated-5,5-cialkyl- hydantoins; ii) N-chlorinated isccyanurates; iii) N-chlorinated rcelamines; and iv) N-chlorinated giycolurils; and (b) from 75 to 25 parts of an alkali metal, alkaline earth metal or ammonium bromide salt. The bromide salt serves as a potential source of bromonium ions for the mixture under bleaching conditions (i.e., in aqueous solution also containing the organo-N-chloro compound). The alkyl group contains up to 8 carbons.

According to one embodiment of the present invention, an improved bleaching composition is provided which, in its preferred form, consists essentially of the combination of a 5 ,5-di-substituted-N,N-dichloro hydantoin component together with sodium bromide. The present invention is based on the unexpected discovery that such combination of the organo-N-chlorinated compound and source of bromonium ion, (e.g., inorganic bromide - such as chlorinated hydantoin compound with sodium bromide) leads to an unexpected potentiation of the bleaching activity than would otherwise be expected from use of the organo-N-chlorinated compound alone.

It will be recognized by those skilled in the art, of course, that the bleaching action of N-halogenated organic compounds is thought to be due to the release of positive halogen ions which are themselves powerful oxidizing agents and act as the effective bleaching agent. It is also generally considered that positive bromine ions are more powerful and effective bleaching agents than positive chlorine ions. However, N-bromo- substituted organic compounds are characteristically more expensive than N-chloro- substituted organic compounds. Thus, the use of such brominated compounds has not been and is not as attractive as using the corresponding chlorinated compound from a cost consideration point of view, provided that adequate bleaching effectiveness could be realized from the chlorinated material. It has been observed, as in the tests described hereinafter, that N,N-dichloro hydantoin compounds are themselves relatively ineffective as bleaching agents particularly at the lower temperatures of, for instance, 120ºF. (approx. 50ºC.) desired for today's bleaching operations, and not even very effective as a bleaching agent at higher temperatures of, for instance, 160ºF. and above (particularly at reasonable concentration levels). This is in marked contrast to the behavior of N,N-dibromo-substituted hydantoins which are nearly as effective at 160°F. as they are at 120°F., on a weight-for-weight basis. Indeed, relatively speaking, the activity of the N,N-dichloro substituted hydantoins declines even more severely, with a lower temperature, than is experienced with the presently used sodium dichloroisocyanurate.

The present method and compositions used therein provide for a safe, clean and economical means for achieving effective bleaching with positive bromonium ions of textile materials at temperatures significantly lower than conventionally employed heretofor.

It is also not to have been expected that at the desired lower temperatures the

N,N-dichloro-substituted hydantoins would function as effective bleaching agents, even in combination with the sodium bromide component because the lower temperatures appear to be below the required level for oxidizing effectiveness of the dichloro hydantoin material.

It is believed that in the practice of the present invention, and the use of the compositions herein described and provided, the organo-N-chlorinated compound component interacts with the bromide component to form positive bromonium (Br⁺) ions. Such positive bromonium ions then act as oxidizing agents for the organic, or inorganic, stain, or other discolorations to be removed from the textile. In such a process the positive bromonium ions are themselves chemically reduced back to the bromide ions. Such re-formed bromide ions are thus susceptible again to oxidation to new bromonium ions, as a result of interaction with additional molecules of the organo-N-chlorinated compound. The entire process thus repeatedly occurs until the organic-N-chloro component is itself completely consumed.

Assuming the above explanation is accurate for the operation of the present invention, it was thus not known heretofore that in the complex heterogenous systems of, for instance, a conventional load of laundry, that the desired course of the reaction would occur in substantial preference to the multitude of possible competing reactions which might take place. As noted above, the organo-N-chloro compound may be selected from a number of sources. Especially preferred are the N-chlorinated -5 ,5-alkylhydantoins and the N-chlorinated isocyanurates. One may also use N-chlorinated melamines or glycolurils as described in the aforementioned U.S. Patents Nos. 3,071,591 and 3,412,021. Particularly preferred organo-N-chlorinated compounds are sodium dichloroisocyanurate (NaDCC), N,N-dichloro-5,5-dimethylhydantoin (DCDMH) and N-bromo-N-chloro-5,5-dimethylhydantoin (BCDMH) .

Of course, this invention is not limited to the use of N,N-dichloro-5,5-dimethyl hydantoin. In general, other alkyl groups may be present in place of the methyl groups, as desired, up to, for instance, lower alkyl groups of 8 carbon atoms. The N,N-dichloro hydantoin parent compound may also be used. No significant advantage is, however, seen from using alkyl groups larger than the methyl group because the resulting increased molecular weight v/ould simply require the addition of more organic material to the system for an equivalent bleaching activity. The dimethyl-substituted hydantoin is also the presently preferred material from a standpoint of cost and availability.

A preferred source of the potential source of bromonium ions is an inorganic bromide salt, preferably sodium bromide due to its relatively low cost and availability. However, other potential sources of the bromonium icn besides sodium bromide may also be employed, for instance, other alkali or alkaline earth metal or ammonium bromide salts (e.g., KBr, MgBr2 Ca3r2, etc). In general, it is not a cation associated with the bromide ion that is of significance to the invention; rather, the bromide ion may be derived from any desired non-interfering source. For example, N,N-dibromo-5,5-dimethylhydentoin (DBDMH) in combination with N,N-dichloro-5,5- dimethyl-hydantoin (DCDMH) may be employed, the DBDMH serving as a source of bromonium ion when the composition is placed in an aqueous environment for the bleaching of textile materials.

The data generally shows that equivalent bleaching is obtained with DCDMH and NaBr with substantially lesser amounts of DCDMH if potentiated with NaBr. Since the present invention preferably utilizes the relatively inexpensive sodium bromide salt as a substantial amount of the bleaching composition provided herein (even above 50% by weight), cost advantages can be readily realized. Moreover, since the relative amount of organic material is also reduced, effluent polluting problems can also be minimized.

The term "available halogen" as used herein, is a term established for comparing a potential bleaching or disinfecting power of halogen atoms with that of the elemental halogen on a weight basis. Elemental halogen is defined as containing 100% "available" halogen. When elemental chlorine is dissolved in water, hydrochloric acid and hypcchlorous acid are generated. The hypochlorous acid is the active bleaching component. Therefore, one half of the original weight of the elemental chlorine is useless. The chlorine contained in the N-halogenated compounds is in the positive

(equivalent to hypochlorous acid) state, and is therefore totally useful for bleaching. It is conventional in the industry to multiply the active (Cl⁺) components by two and express it as available chlorine. At the same time, the compositions of the present invention would appear to leave substantially intact the optical brighteners, typically in a detergent composition, for their desired effect on the appearance of the finished laundry, and it is also not seen that there is a deteriorative effective on the fabric itself.

These latter beneficial effects may be realized because the reaction of the organo-N-chloro compound with the bromide has a finite kinetic rate such that the actual release of the oxidizing positive bromide ions into the system takes place over a period of time during the bleaching operation. This effect might be expected to lead to milder bleaching effects; however, even though that may be the case, the results as hereinafter described demonstrate that the desired bleaching effects are still in fact obtained. The practice and effectiveness of the present invention is illustrated by the following tests wherein unbleached cotton muslin was washed with a control detergent, AATCC Standard 124. The machine used was a Terg-O-Tometer (60cpm) with distilled water and a washing time of 10 minutes, followed by a 5 minute rinse cycle and two cold water hand rinses. To measure the bleaching effectiveness, the light reflectance of the fabric was measured before and after each wash with a Photovolt reflectometer equipped with a blue filter. The results are recorded as an increase in the light reflectance of the dry samples. The test procedure was as follows. The standard detergent (2.5 grams/liter of water) was used with varying concentrations (per liter) of the bleaching agents, as listed hereinbelow. In Tables 1, 2, 3 and 4 sodium dichloroisocyanurate (NaDCC) was used as a standard for comparison purposes; N,N-dichloro5,5-dimethylhydantoin (DCDMH) and N,N-dibromo5 ,5-dimethylhydantoin (DBDMH) were also used for comparison purposes. A mixture, representative of the invention of DCDMH and sodium bromide (DCDMH/NaBr) was also used, in which the weight percent of DCDMH was 48.8%. Each component was employed at three concentration levels, the same having been calculated so that at each respective level an equivalent amount of "available" halogen was present in the organic component.

The washing cycle was conducted, as indicated above, at a water temperature of 120°F. (48.9°C.), at a pH of 7 (adjusted by the use of dilute sulfuric acid and sodium carbonate). The results of the reflectance readings, measured as described above, are tabulated below.

The "Control" represents the results when the standard detergent alone was used.

Another test was also conducted by the same procedure described above, again with the water temperature at 120ºF., but the pH of the washing solution having been adjusted to 10. Again, the results of the tests for the respective concentrations are listed below in Table 2.

Still another test was conducted using the procedure described again but this time with a water temperature of 160ºF. (71°C.), and at a pH of 7. The results of this test for the respective concentrations of the materials employed are listed in Table 3.

TABLE 3

( 1600^ºF. ; pH=7]

A fourth test was conducted, again following the above procedure, but using water adjusted to a pH of 10 and a temperature of 160^ºF. The reflectance reading increase results obtained are listed in Table 4.

TABLE 4 (160°F.; pH=10)

From these data it will be seen that the dichloro hydantoin/sodium bromide combination exhibits a far greater relative bleaching effectiveness than the dichloro hydantoin used alone. To interpret these data it should also be appreciated that each of the respective concentrations of the DCDMH used alone and of the NaDCC provides an equivalent "available" chlorine concentration. That is, e.g., 227 mg of the DCDMH provides the same number of chlorine atoms as 273 mg of the NaDCC (calculated as the dihydrate). This is also true for the DCDMH concentrations, used in the admixture with NaBr, with respect to the amounts of DBDMH employed (e.g., the three DCDMH concentrations thus used, 66 mg, 99 mg, 132 mg, respectively provide the same number of halogen atoms as do 96, 144 and 192 mg of DBDMH). To further illustrate the advantage of the invention, these data for a pH of 7 are graphically portrayed in the attached Figure wherein the solid curves connect data points measured at 120°F. and the dashed curves connect data points at 160 °F. in the above tests. The data is plotted on the basis of the concentration of the organic bleaching agent present.

It is readily seen therefrom that used by itself DCDMH (the triangular points) is, comparatively speaking, a rather ineffective bleach used at 120^ºC. However, when used in combination with sodium bromide, it is even more effective than the dibromo dimethyl hydntoin, on a weight-for-weight basis. For instance, to obtain a reflectance reading increase of 5 , a concentration of approximately 115 mg per liter of DCDMH, in combination with sodium bromide, is sufficient, whereas for the same increase in reflectance reading a concentration approximately 145 mg of DBDMH is necessary, i.e., 26 weight percent more. As noted above, even when these relative amounts are considered on an equivalent "available" halogen basis, the bleaching effectiveness of the DCDMH is some 80% of that of the DBDMH, when the former is used in combination with sodium bromide. In absence of sodium bromide, at 120^°F. and a pH of 7, the DCDMH is only about 30% as effective as DBDMH, on the same basis.

For the data at pH of 10 in the above Tables, it can also be seen that the combination with NaBr greatly potentiates the bleaching effect of DCDMH, however, the bleaching effectiveness of all materials is depressed under these alkaline conditions.

Yet another test was conducted by the same procedure described above, but at several different temperatures, 160º, 110º and 60ºF at a pH of 10. In each instance the amount of ingredient was adjusted to give 200 ppm total halogen expressed as chlorine. In addition to the materials tested above, comparisons were made with sodium hypochlorite (NaOCl) and N-bromo-N-chloro- 5,5-dimethyl hydantoin (BCDMH) . The results are set forth in Table 5.

A further procedure was carried out as reported in Table 5, but in this instance, where there was chlorine present in the ingredient, an equivalent amount of NaBr was added (i.e. Br=Cl), to give a total available chlorine at 200 ppm. The results are set forth in Table 6.

While NaOCl/NaBr is effective throughout the temperatures tested, the potentially hazardous effects of forming elemental bromine render the composition unsuitable from a practical standpont. The use of organo-N-chlorinated compounds herein rather than sodium hypochlorite (NaHOCl) a known bleaching agent, avoids harsh and detrimental treatment of the textile material. Thus, a bleach composition formed from a mixture of sodium hypochlorite and sodium bromide when placed in water reacts to evolve elemental bromine which not only is harsh on fabrics, but is highly corrosive to people and equipment which may come in contact therewith. Further, the invention is not limited to the use of approximately 50:50 weight mixtures of the organo-N-chloro and bromide components in the composition. Considering, for example, the N,N-dichloro dimethylhydantoin and sodium bromide combination, weight ratios in the range of at least 25:75 up to 75:25,, preferably 40:60 up to 60:40, may be employed. Similar proportions may also be used, calculated on a basis of available chlorine on the one hand and bromide ion on the other hand when other organo-N-chloro compounds and bromide salts are employed.

As a result, one is able to achieve effective bleaching at low temperatures with a corresponding decrease in the amount of effluent and cost due to the potentiated bleaching effect attributable to the compositions employed according to the present invention.

Furthermore, significantly less organic material will then be present in the effluent from a laundry or bleaching system when using the composition of the present invention as compared to the amount which would be introduced if NaDCC were used at an equivalent level of bleaching effectiveness. While the foregoing examples illustrate the particular advantages of the invention at washing temperatures of about 120ºF., it will also be appreciated that similar efects will be realized at other temperatures, ranging from about 60°F. up to about 140ºF., the precise level thereof depending upon the particular composition and conditions employed. Of course, the technological effectiveness of the invention is also demonstrated at even higher temperatures, such as at 160°F., although from a cost-effective standpoint the present compositions are not, at present, competitive with other existing bleaching systems.

Claims

WHAT IS CLAIMED IS:

1. A method for the effective bleaching of textile goods at temperatures in the range of 60° to 140ºF. which consists essentially in exposing the same to an aqueous solution, at said temperatures, containing a mixture consisting essentially of 25 to 75 parts by weight of an organo-N-chloro compound selected from the group consisting of N-chlorinated-5, 5-dialkylhydantoins; N-chlorinated isocyanurates, N-chlorinated melamines and N-chlorinated glycolurils, and from 75 to 25 parts by weight of an alkali metal, alkaline earth metal or ammonium bromide salt, said alkyl containing up to 8 carbons.

2. The method of claim 1, wherein said salt is an alkali metal bromide.

3. The method according to claim 1 or 2, wherein said organo-N-chloro compound is present in an amount from 40 to 60 parts by weight and wherein said salt is present in said solution in an amount of from 60 to 40 parts by weight.

4. The method of claim 1, wherein said temperature is in the range of 80º to 120ºF.

5. The method of claim 1 or 2, wherein said organo-N-chloro compound is a N-chlorinated 5,5-dialkylhydantoin selected from the group consisting of:

N,N-dichloro-5,5-dimethylhydantoin and N-chloro-N-bromo-5,5-dimethylhydantoin.

6. The method of claim 1 or 2, wherein said organo-N-chloro compound is sodium dichloroisocyanurate.

7. A method for the effective bleaching of textile goods at temperatures in the range of

100º to 140ºF. which consists essentially in exposing the same to an aqueous solution, at said temperatures, containing mixture consisting essentially of 25 to 75 parts by weight of N,N-dichloro-5,5-dialkylhydantoin and from 75 to 25 parts by weight of an alkali metal, alkaline earth metal or ammonium bromide salt, said alkyl containing up to 8 carbons.

8. The method of claim 7, wherein said salt is an alkli metal bromide.

9. The method of claim 7, wherein said hydantoin is present in an amount of from 40 to 60 parts by weight and wherein said salt is present in an amount of from 60 to 40 parts by weight.

10. The method of claim 7, wherein said bromide salt is sodium bromide.

11. The method of claim 10, wherein said hydantoin is N,N-dichloro-5, 5-dimethyl hydantoin.

12. The method of claim 7, wherein said bromide salt is selected from the group consisting of KBr, MgBr₂ and CaBr₂.

13. A method for the effective bleaching of textile goods at temperatures in the range of 60° to 140ºF. which consists essentially in exposing the same to an aqueous solution, at said temperatures, containing a mixture consisting essentially of 25 to 75 parts by weight of an organo-N-chloro compound selected from the group consisting of N-chlorinated-5,5-dialkylhydantoins; N-chlorinated isocyanurates, N-chlorinated melamines and N-chlorinated glycolurils, and from 75 to 25 parts by weight a material capable of generating bromonium (Br⁺) ions during the bleaching of said textile goods.

14. The method of claim 13 wherein said mixture consists essentially of N,N-dichloro-5,5- dimethylhydantoin and N,N-dibromo-5,5-dimethylhydantoin.