DE1938315B2 - Solid bleaching and reducing agent made from a mixture of a dithionite with a stabilizer - Google Patents

Description

O (CH ₂ -CH ₂ O) ₁ H.

Il /

C ₁₇ H ₃₅ -CN

\ (CH ₂ -CH ₂ O) ₁ H

in which (x + y) has a value between 2 and 50, or an amphoteric surface-active compound of the general formula

R ₂

R ₁ -N ⁺ -R ₃

IR ₄ -COO-

in which Ri is an alkyl or alkenyl group with 1 to 8 carbon atoms or a dodecyl group, R ₂ and R _{3 are} alkyl or alkenyl groups with 1 to 6 carbon atoms and R «denotes an alkylene group with 1 to 6 carbon atoms

2. Means according to claim 1, characterized in that the surfactant in one Concentration of 0.5 to 40% by weight, based on the weight of the dithionite present, present is

3. Composition according to claims 1 and 2, characterized in that as the free flowability regenerative agent urea is present.

4. Process for the preparation of the agent according to claims I to 3, characterized in that the Dithionite is added to a melt of the surfactant, and the paste thus formed solidified by cooling and then crushed.

The invention relates to a solid bleaching and reducing agent made from a mixture of a dithionite, especially sodium dithionite, with a stabilizer.

Aqueous solutions of sodium dithionite are widely used in the textile, pulp and paper industries Used extensively as a bleaching agent, also as a reducing agent for vat dyes and as an agent for Decomposition of dyes that contain azo groups.

The commercially available storable powdery, Anhydrous sodium dithionite is stable for a long time in dry air, but suffers in the presence of water or water vapor decomposition, the action of water initially forms the dihydrate of dithionite formed with the development of heat and this is particularly easy due to atmospheric oxygen oxidized, also with an exothermic reaction. Will the heat generated in these two reactions

ίο is developed, not discharged quickly enough, so can a third exothermic reaction can occur, namely the spontaneous decomposition of the salt with liberation of Sulfur dioxide and formation of thiosulphate, bisulphite and Sulfur. The one exposed during these reactions Heat can be so great that the temperature of the itself decomposing agent rises above the ignition point of the sulfur, so that the agent ultimately to starts to burn High humidity, such as B. under normal atmospheric conditions in a dye works or in a bleaching plant, accelerates the Decomposition of the dithionite, if one does not take precautions, this before contact with the atmosphere look. There is therefore an urgent need that Technique of making anhydrous sodium dithionite available, which is especially under unfavorable and adverse conditions of use and storage has a longer service life than common, commercially available products.

Stabilization methods have already been proposed in which the dithionite is mixed with certain Additives. According to US Pat. No. 3,287,276, such an additive is water-soluble, macromolecular Polyacrylic acid, its salt or amide, polyvinyl alcohol or polyvinylpyrrolidones, which means if present small amounts of water form highly viscous solutions which, as it were, envelop the oithionite but not are surface-active.

Other methods only prevent the initial stages

decomposition and prevent the final stage of self-ignition or only take effect in the final stage by preventing spontaneous combustion. The known stabilization methods are with the Disadvantage connected that a foreign material, which in

v, the subsequent processing operations is devoid of any value in which dithionite is incorporated. In addition, in many cases the additive contributes to contamination of the material which has been treated with the dithionite.

V) It has now been found that effective stabilizers for sodium dithionite in particular are certain known nonionic or amphoteric surface-active agents or agents which lower the surface tension, as they are often in common with anyway

v, dithionites used in many applications are, in which one works with aqueous solutions of the latter means, z. B. at Stripping and lightening of dyes as well as bleaching paper, protein fibers and wool. About that-

ho in addition, the new stabilizers inhibit immediately the initial stages of decomposition described above and they prevent one from occurring Heating leading to the final stage of self-ignition.

hi The solid lead and reducing agent according to the invention from a mixture of a uithionite with a Stabilizer and, if necessary, a compound that improves free flowability is characterized by this.

shows that it is a non-ionic, surface-active compound of the general formula

RO (CHR'CHRO), H

where R is an alkyl, araikyl, cycloalkyl, aryi-acyl group, R 'is hydrogen or a lower alkyl group and χ is a number between 3 and 100, or of the general formula

C ₁₇ H ₃₅ -CN

(CH ₂ -CH ₂ O) _x H.

in which (x + y) has a value between 2 and 50 or an amphoteric surface-active compound of the general formula

R ₁ -N ⁺ -R ₃

R ₄ -COO-

in which Ri is an alkyl or alkenyl group with 1 to 8 carbon atoms or a dodecyl group. R ₂ and R _{3 are} alkyl or alkenyl groups with 1 to 6 carbon atoms and R _{4 is} an alkylene group with 1 to 6 carbon atoms

The preferred dithionite is sodium dithionite, but others can also Dithionites such as kavurn, calcium and zinc dithionite, be stabilized. It is true that surface-active agents, along with dithionites and ceresin, are made from the paste as a paste GB-PS 11 17 930 known However, it is here a non-aqueous bleaching paste that is supposed to release sulfur dioxide in the presence of water, the Surfactants are said to merely emulsify the waxy carrier and promote dithionite decomposition. On the other hand, the stabilizer effect that is bound up is in the case of solid ones, in particular in the case of flowable ones Dithionites surprising. It is best of all if the surfactants are non-ionic in nature are. According to the invention it is particularly advantageous that the agents are free-flowing.

The nonionic surface-active agents which are preferably suitable in the agents according to the invention Substances can be both biodegradable and non-degradable polyoxyethylene compounds of the general formula

RO (CHR '■ CHR'0), H

in which the group R has a high molecular weight and χ is a number between 6 and 50. Such compounds are e.g. B .:

I. polyoxyethylene alkyl esters, the general formula

like stearic acid ester

and oleic acid esters of the general formula III-, C ₇ CO ₂ (CHjCH ₂ O) ₁ II,

in which χ can fluctuate within wide limits. z. B. between the values 15 and 40.

% Polyoxyethylene-alkaryl and -cycloalkylaryl-ethers, z, B, Nonylphenylärher, those of the general formula

H ₁₉ C ₁₉ C ₆ O (CH ₂ CH ₂ O ^ H

in which χ can vary within wide limits, for example between the values 1 to 70. 3. Polyoxyethylene alkyl ethers, for example the hexadecyl ethers, of the general formula

H ₃₃ C ₁₆ O (CH ₂ CH ₂ O) ₁ H,

in which χ can in turn fluctuate within wide limits, which depend on the nature of the fatty alcohol base and are generally between 1 and 70.

Polyoxypropylene-polyoxyethylene condensation products can also be used.

The most suitable non-ionic surfactants are those made by reacting a long aliphatic alcohol with 10 up to 20 carbon atoms in the molecule, especially cetyl and stearyl alcohol with ethylene oxide in one

Ethylene oxide to alcohol molar ratio of 15 to 25: 1 are formed. Mixtures of 2 or more types of mutually compatible stabilizing nonionic surfactants can also be used. If necessary, the means can

jo also with other compatible, non-stabilizing additives the various functions meet, be mixed. So it can be B. may occasionally be desirable to use anionic surfactants the agents according to the invention with non-ionic

r, and / or amphoteric surfactants are stabilized to mix.

To the amphoteric surface-active compounds of the general formula

I '

R ₁ -N ⁺ -R ₃

R ₄ -COO "

used in the means according to the invention include, in particular, long-chain substituted betaines. If a single surfactant is used

-, o det, this should as a rule be water-soluble. It however, it can sometimes be advantageous to use a mixture of surfactants, of Ίεηεη one is insoluble in water, however by the presence of the other, water-soluble

-, -> surface-active substance is made water-soluble.

Amount of surfactant used The material can vary within wide limits. the The minimum amount depends on the stabilizing Effectiveness of the material and of the active

Mi lifespan that one wishes to give to the means and the maximum amount of the amount of surfactant which, as such, together with the Dithionite is required for the intended use. In general, the invention

h) according to new agents contain between 0.5 and 40 percent by weight of the surfactant, based on the dithionite, and preferably the amount is 20 to 25 percent by weight.

The compositions of the invention can be mixed together by any conventional method, e.g., by directly mixing and grinding the ingredients. However, best results are obtained when the dithionite is added to a melt of the surfactant to form a paste, which on cooling results in a solid mixture of the intimately mixed components dithionite and stabilizer. B. methanol, are mixed so as to form a slurry from which the stabilized agents according to the invention can be obtained by evaporation of the solvent.

Normally, during the mixing together, there is very little decomposition of the Dithionhs, which by working in a vacuum or in an inert atmosphere to prevent entry Stopping moisture and oxygen can be prevented.

The agents according to the invention are normally required in powdered or granulated form Grinding or comminuting has become a device of the type in which the agitator blade against a fixed one Rotate surface, proven to be most suitable.

The property of the dithionite to flow freely is not affected by the addition of the surfactant, provided that the latter is a relatively brittle solid or that Less brittle, waxy or liquid surface-active substances can then be used in smaller quantities. However, where these conditions are not to be met, the flowability properties and the grindability of the agent can deteriorate Incorporation of a compound, such as urea in particular, can be improved.

Other free-flow improvers are sodium phosphates and sodium salts of condensed phosphoric acids, sodium carbonate ^, sodium bicarbonate, sodium benzoate and ethylenediaminetetraacetic acid (EDTA). The solidifying agent can be in any Step of the mixing operation should be added, and it should be as intimately as possible in the invention Funds can be engaged.

The amount of solidifying agent needed can vary within wide limits, depending on both the properties of the agent itself and those of the depending on the surfactant. The flow properties of the latter materials often vary considerably within different batches of the same material. In general, a level of 60 to 100% solidifying agent, based on the Surfactant weight, not unusual. For example, both Polyoxyethylene ester reaction product of 16 moles of ethylene oxide with a mixture of unsaturated Fatty acids and heterocyclic resin acids, as sold as a liquid with 100% active ingredient, as also the polyoxyethylene ether reaction product of 12 moles of ethylene oxide with a tridecyl alcohol, as it is called Liquid with 100% active substance is distributed, 'calibrated in free-flowing powder thereby converted are to incorporate 100% urea based on the weight of the 100% active surfactants.

The means according to the invention can generally

can replace the non-stabilized dithionites in all applications in which they are currently used, ζ, Β, when peeling off stains "on Textiles for the reductive lightening of dyed Fibers and in the bleaching of textile materials and Paper. Due to the presence of surface-active substances in the agents according to the invention, the Need for a separate addition of detergents, wetting, emulsifying, saponifying, leveling or

ι ο dispersants for all of these purposes omitted. They are of particular use value Agents according to the invention for reductive lightening of dyed polyester fibers.

The invention is illustrated by the following examples

explained in which all parts indicated are parts by weight.

example 1

100 parts of a commercially available sodium hydrosuction (sodium dithionite content 90 percent by weight) were mixed with 20 parts of a powdered stearyl alcohol ethoxylate with an ethyleneoxy to alcohol ratio of 25: 1. 25 g of this mixture were exposed to an atmosphere in a container , which had a temperature of 20 ⁰ C and a relative humidity of 75%. The dithionite content of the sample exposed to the atmosphere was determined daily by quantitative iodometric analysis

jo 25 g of the same but unmixed dithionite were treated analogously The results, which are summarized in Table I below, demonstrate that the surfactant has a high degree of stability towards the initial stage of the Decomposition in which dithionite has conferred

Table I. Storage time dithionite alone

Dithionite / ethoxylate mixture

(in days) (remaining dithionite (remaining dithionite as% of the initial as% of the originally available borrowed Dithionites) dithionites)

0 100 100 Example 2 1 87 94 2 77 84 3 60 76 4th 37 63 7th 7th 33

100 parts of a commercially available sodium hydrosulfite (sodium dithioiyt content 90 percent by weight) were with 20 parts of a powdered stearyl alcohol ethoxylate, which has an ethyleneoxy-to-alcohol molar ratio of 25: 1, mixed. The stability of a sample of this mixture against decomposition was determined according to the in Example 1 was determined and the results were compared to that Decomposition of an equal amount by weight of a mixture of 100 parts of the hydrosulfite with 20 parts anhydrous sodium sulfate (which was added as an inert diluent), the latter being the latter Mixture was tested in the same way under the same conditions.

The results are summarized in Table II. Again, the significantly better stability is the Mixture containing the surfactant clearly visible against decomposition.

Table Il

1 term

(in days)

Dithionite / Sull'ate mixture

(Dithionite content in '■ ·)

73
59
51
39
28
I.

Example 3

Dithionite /
Athoxylate mixture

Dithionite in "..)

73
68
61
\ S
46
24

l-agerdjuer
ι ^: n deeds *

riilhionit alone

(remaining dithionite
than that initially
existing)

Dithionite / Atho \ ylate mixture

(Remaining dithionite as' ■> of the original existing

100

8 ⁷

60

37 7th 3

100
93
86
81
74
58
50
40

The melt was allowed to cool in an oxygen-free atmosphere and it was then powdered using a grinder. The stability of the mixture against atmospheric oxidation was tested comparatively against that of an unmixed hydrosulphite, in the same way and under the same conditions as in the previous examples.
The results are shown in Table IV.

Table IV
l. storage period
(in days)

10 parts of cetyl stearyl alcohol ethoxylate, in which the ethylene oxide to alcohol molar ratio was 20: 1, were dissolved in 40 parts of technical-grade ethyl alcohol at room temperature, and 100 parts of a commercially available sodium hydrosulfite containing 90 percent by weight of sodium dithionite were added to this solution to form a slurry. The slurry was then dried in vacuo to obtain a friable mass that could easily be powdered. The stability against atmospheric oxidation was tested comparatively against that of the unmixed dithionite at 20 ^° C. and a relative humidity of 75% using the method used in the preceding examples. The results compiled in Table II clearly illustrate the stabilizing effect of the surfactant.

Table IH Example 4

100 parts of a commercially available sodium hydrosulfite (Sodium dithionite content 90 percent by weight) were added to 20 parts of a melt of the cetyl stearyl alcohol ethoxylate added, which has an ethylene oxide-to-alcohol molar ratio of 20: I and was kept at a temperature just sufficient to urn to keep the ethoxylate in the molten state during the addition sprout. After mixing Dithionil alone

Dithionil / Ethoxylal mixture

(remaining dithionite (remaining dithionite as ". · of the originally as" v. of the originally present) borrowed existing)

100

84

66

23

10

KX)
98
94
73
62
49
40
28.5

Example 5

A mixture of a dithionite and the surfactant was prepared and this opposite an unmixed dithioni; tested in the same way as in Example 4 with the only one Difference that 30 parts of the cetyl stearyl ethoxylate to 100 parts of the sodium hydrosulfite were added. The results are shown in Table V.

Table V

Laaer duration

(in days I

Dithionite alone

Dithionite / ethoxylate mixture

(remaining dithionite (remaining dithionite as \ of the originally as% of the originally present) borrowed existing)

100 Example 6 100 87 96 77 90 60 83 37 79 7th 59 3 46 - 35

A mixture of 100 parts of a NatriumhydrosulFits commercially available (Natriumdithionitgehalt 90 weight percent) and 20 parts of a powdered Stearylalkoholäthoxylats that a Äthylenoxydzu-alcohol molar ratio of 25: 1 showed, was determined by means of an ordinary physical mixing process zusammengemischL The stability of the sample against atmospheric oxidation wherein 20 ⁰ C and a relative humidity of 90% was - as in the preceding examples - tested comparatively against that of an unmixed hydrosulfite. The results are shown in Table VI.

Table VI

Storage time dithionite alone

Üithionite / Älhoxylat-Ciemisch

(in days) (remaining I mhionite (remaining dithionite

as X of what was originally borrowed as% of the original)

0 100 100 1 83 90 2 73 86 4th 24 64 Ί 0 23

Example 7

A mixture was prepared as in Example 4 and at 20 ° C. and a relative humidity of

Chen, commercially available hydrosulfite using the method used in Example 6. the Results are shown in Table VII.

Table VII

Storage time
(in days)

Dithionite alone dilhionite / ethoxy-

lat-Ciemisch

(remaining dithionite (remaining dithionite as% of the originally present as "/» of the originally present) borrowed existing)

100
83

73

24

100 97 91

78 57

Table VIII Dithionite alone Dithionite / ethoxy Storage time lal-Uemish (remaining dithionite (remaining dithionite (in days) as% of the original as "Ir of the orig existing) available) 100 100 0 91.4 97 3 85.4 94.6 10 75.7 93.2 17th 70.0 88.8 23 64.8 85.7 38

Example 9

It was made by mixing in a non-ionic Surfactant tested for improved stability of sodium hydrosulfite against spontaneous combustion.

8 3 parts of a commercially available sodium hydrosulfite (sodium dithionite content 90 percent by weight) were made with 17 parts of a non-ionic surfactant Substance as used in Example 4, mixed with that described in Example 4 Method was used. 70 g of this mixture were placed in a glass tube with an internal diameter of 3.5 cm and 16.5 cm in length. The tube was kept at 133 ° ± 3 ° C in a salt bath, and after 15 For minutes, 0.5 ml of water was pipetted onto the surface of the sample. At certain time intervals were read the temperatures using a thermometer. Hessen ball just under the The surface of the pattern was sufficient. The maximum temperature that was observed and the length of time after Added water that had passed before the measurement. were noted and compared with the results of an analog, compared tests performed using neat hydrosulfite. The results are compiled in Table IX.

Table IX Example 8

100 parts of a commercially available sodium hydrosulfite (sodium dithionite content 90 percent by weight) were mixed by means of an ordinary physical mixing process with 20 parts of a powdery stearyl alcohol ethoxylate having an ethylene oxide to alcohol molar ratio of 25: 1. The stability against atmospheric oxidation was ^{tested at 20 °} C. and a relative humidity of 54% according to the method used in the preceding examples, comparing it with that of conventional, commercially available hydrosulfite. The results are shown in Table VIII.

template

Achieved

Period of time

Maximum temperature / between Rrrci-

the maximum temperature and

(Ο

(Starting temperature
133 C ± 3 C)

Water / usat /
(Minutes)

Unmixed

commercially available

Hydrosulfite

Mixture of
Hydrosuint
and surfactant

301-311

262-286

28

Example 10

100 parts of a commercially available sodium hydrosulfite (sodium dithionite content 90 percent by weight) were added to 20 parts of a melt of a Nonylphenoläthoxylats, with an Äthylenoxya-to-phenol molar ratio of not less than 45: 1, and the ethoxylate was kept at a temperature which was just sufficient to To keep ethoxylate in a molten state during the addition process. After mixing, the melt was allowed to cool in an oxygen-free atmosphere and it was then powdered. The stability of the mixture against atmospheric oxidation was then tested comparatively with that of an unmixed hydrosulfite, in the same way and under the same conditions as in the example 6 are described (20 ⁰ C; relative humidity 90%). The results are shown in Table X below.

it

Table X
Storage time
(in days)

Dithionite alone Dithionite / Atho \ y-

lat mixture

(remaining dithionite (remaining dithionite air% of what was originally available as% of the original) borrowed existing)

100
83

73
24

100 95 92 81

The results clearly illustrate that the π surfactant has a high degree of stability towards the first stages of decomposition in the Dithionite has conferred.

Example ii

100 parts of a commercially available sodium hydrosulfite (sodium dithionite content 90 percent by weight) were added to 20 parts of a melt of a sorbitan stearate ethoxylate having an ethylene oxide to ester molar ratio of 20: 1, and the ethoxylate was kept at a temperature just sufficient to to keep the ethoxylate in a molten state during the addition process. After mixing, d ^; . ·; Cool the melt in an oxygen-free atmosphere, and it was then pulverized. The stability of the mixture against atmospheric oxidation was then tested comparatively with that of an unmixed hydrosulfite, in the same way and under the same conditions as are described in Example 6 (20 ° C.; 90% relative humidity). The results are compiled in Table XI, and they again demonstrate that the mixture which contains the surfactant had a significantly better stability against decomposition.

Table XI

Storage time

Dithionite alone

Dithionite / athoxylal mixture

(ICMIIlIlC ^ 1./1IMUHIII (t IMI Il I tt-Λ 1 1 1 Il IU * ι ti ι

as% of what was originally borrowed as% of what was originally available)

100
83
73
24

100 98 95 90

example

20 parts of a commercially available long-chain substituted betaine, in which the alkyl group Ri in the general formula

/ \
R, R ₄ COO

at least 90% consists of a dodecyl radical, were in an excess of a technical ethyl alcohol at room temperature, and there were 100 parts of a commercially available sodium hydrosulfite, the 90 Weight percent sodium dithionite was added to this solution to form a slurry. the Slurry was then evaporated in vacuo and dried to obtain a friable mass, which could easily be powdered. The stability against atmospheric oxidation was compared compared to that of the unmixed dithionite at 20 ° C and a relative humidity of 90% tested as described in the previous examples. The results are in Table XI! compiled; they illustrate the stabilizing effect of the surfactant.

Table XIl

l. storage period

(in days)

Dithionite alone

Dithionite / Bülain-Ciemisch

0 100 I. 83 2 73 4th 24

(remaining dithionite (remaining dithionite as "ή of the originally as% of the originally available) borrowed existing)

100 97 86

82

Claims (1)

Patent claims: U Solid bleaching and reducing agent made from a mixture of a dithionite with a stabilizer and optionally a compound which improves the free flowability, characterized in that it is a nonionic stabilizer surface-active compound of the general formula RO (CH ^ CHRO) ₁ H where R is an alkyl, aralkyl, cycloalkyl, aryl, acyl group, R 'is hydrogen or a lower alkyl group and χ is a number between 3 and 100 or of the general formula