Number

376-EN

Section

General Section

Use

Abstract

Decroline is a chemical compound used in textile industry in applications that require a reducing agent (bleach agents, reduction stage in vat-dying process, rongeant print and others). The main hazard issue associated with the use of the substance is that when it is used as a reducing agent, formaldehyde is formed. This case story describes the substitution process of a company to find safer alternatives to decroline for textile industry. This process identified sodium dithionite as a feasible alternative, and sodium borohydrate as a promising candidate .

Substituted substances

Alternative Substances

Reliability of information

Evidence of implementation: there is evidence that the solution was implemented and in use at time of publication

Reason substitution

skin/respiratory sensitizing
CMR

Hazard Assessment

Substance to be substituted: The main issue with decroline is that in its use in the described textile processes, formaldehyde is released. Formaldehyde is on the hazardous Substance Database according to SUBSPORTplus Screening Criteria (SDSC) for being a carcinogen and sensitiser. Alternative substances: The alternative substances are not in the SDSC. But natriumdithionit is self-heating and may catch fire and is harmful if swallowed.

Description of Substitution

Inditex describes below their step-wise approach to substitute decroline: 1. Definition of the problem Decroline [Zinc formaldehyde sulfoxylate, Decolin, Safolin, Colour Index Reducing Agent 6, CAS no. 24887-06-7, chemical formula Zn(HOCH2SO2)2] is a chemical compound used in textile industry as a source of dithionite (hydrosulphite) in applications which require a reducing agent (bleach agents, reduction stage in vat-dying process, rongeant print and others). Decroline is obtained by reaction of Zinc dithionite and formaldehyde. Decroline formation reaction is reversible; therefore, regeneration of dithionite from decroline under controlled conditions is simple. 2 ZnS2O4 + 4 CH2O + 2 H2O---> Zn(HOCH2SO2)2 + Zn(HOCH2SO3)2 The main reason for employing decroline in industrial processes requiring the use of dithionite is that this latter is unstable in the presence of water or oxygen, therefore the storage of dithionite is not convenient (it is flammable under certain conditions); on the other hand, decroline is a stable compound during storage in standard conditions, which allows to regenerate dithionite under controlled and mild conditions (acidic pH). The main risk factor associated to decroline originates from the fact that during the reaction to regenerate dithionite (carried out during the relevant textile process), formaldehyde is released. Risks associated to this generation of formaldehyde are: - Formaldehyde is a carcinogenic substance regulated under all environmental and consumer products regulations. - Formaldehyde is generated in presence of the textile item being processed, therefore, it must be removed from the item through washing. - There is a risk that residual formaldehyde may remain in the finished products. - There is a risk of formaldehyde release in the effluents from the manufacturing process or from the washing of the garments. 2. Substitution criteria Two potential substitution systems are considered: a. Substituting decroline by dithionite sources which do not release formaldehyde b. Replacing decroline by reducing agents not based on dithionite. 3. Possible alternatives: a. Other sulfoxylated formaldehydes (sodium formaldehyde sulfoxylate, rongalite, CAS No. 149-44-0, Colour Index Reducing Agent 2; calcium formaldehyde sulfoxylate, CAS No. 29401-90-9, Colour Index Reducing Agent 12). b. Sodium hydrosulfite (sodium dithionite, sodium sulfoxylate, CAS No. 7775-14-6). c. Sodium borohydride (CAS No. 16940-66-2). 4. Assessment of the alternatives a. Other sulfoxylated formaldehydes (sodium formaldehyde sulfoxylate, rongalite, CAS No. 149-44-0, Colour Index Reducing Agent 2; calcium formaldehyde sulfoxylate, CAS No. 29401-90-9, Colour Index Reducing Agent 12): These substances are similar to decroline and they share the inconvenience of producing formaldehyde upon regeneration of dithionite. These are therefore not considered as suitable alternatives. b. Sodium dithionite (sodium hydrosulfite, sodium sulfoxyilate, CAS No. 7775-14-6): All uses of sodium dithionite are based upon its reducing properties. In the textile industry, sodium dithionite is mainly used as a reducing agent for dyeing with sulphur dyes and vat dyeing, and for the removal of pigments in fabrics. It is also used as a bleaching agent in reducing bleaching processes, such as paper pulp, cotton and wool bleaching. It is also a bleaching agent in non-textile applications, such as in the manufacture of soap, hay and sugar. The main problems linked to sodium dithionite are related to the hazards associated to its storage, since it can decompose with the liberation of sulphur dioxide and other sulphur compounds if exposed to heat or moisture. Pros: - No formaldehyde is used in its preparation. - No formaldehyde is created as a result of its use. - It creates sulphate, an innocuous substance, easily removed, as a result of its use. - The conditions and safety requirements involved in its industrial use are widely known as its use is widespread in the textile industry. A large number of reputed suppliers of dithionite are active in the market, which can supply high quality and contaminant or toxic-free products; therefore, it is not hard to ensure a supply of this product with the appropriate quality. This is a good alternative to the use of decroline, although certain inconveniences related to the stability of the substance (e.g., storage and handling in rongeant printing conditions) need to be resolved. c. Sodium borohydride (NaBH4, CAS No. 16940-66-2) Sodium borohydride is a strong reducing agent, able, for instance, of reducing bisulphate into dithionite, which, in turn, is able to reduce the azo groups of azo dyes, which is at the basis of the application of the latter (and of decroline) in the rongeant process. At present, borohydride is not widely used in bleaching processes, therefore, the implementation of a pilot R+D project is deemed necessary to assess whether it can be used as an alternative to decroline, especially because of the fact that it may decompose to produce hydrogen, a highly flammable gas, under certain conditions 5. Pilot test a. For the direct use of sodium dithionite as a substitute for decroline. To be defined together with Technical Advice, SL (technological consulting specialised in textile sector), ASUTEX, SL (manufacture of auxiliary chemicals for the textile sector) and PULCRA CHEMICALS (manufacture of auxiliary chemicals for the textile sector and pilot productions) and the University of Santiago de Compostela (scientific consultant and development of R+D programs). Scope: - Application of stabilised formulae of sodium dithionite to rongeant printing of different textiles. - Extending the use of stabilised formulae of sodium dithionite to other uses within the textile production line. b. To define terms of use of sodium borohydride as a reducing agent of azo dyes, and by extension, the usefulness thereof in rongeant applications. Defined together with the University of Santiago de Compostela (scientific consultant and development of R+D programs), Technical Advice, SL (technological consulting specialised in textile sector) and PULCRA CHEMICALS (manufacture of auxiliary chemicals for the textile sector and pilot productions). Scope: - Studying the possibility of the use of sodium borohydride in bleaching processes (rongeant printing), either alone or together with sodium dithionite. 6. Implementation and improvement - Substitution of decroline with dithionite: The implementation process is deemed simple, as this last substance is already used in the textile industry. - Substitution of decroline with sodium borohydride: The implementation process is deemed feasible, pending the assessment of the security measures required by the handling of sodium borohydride, namely as regards its potential breakdown to generate hydrogen gas. Nowadays Inditex is using both of the substances presented as decroline substitutes, the alternatives are used depending on fashion trends, quality desired and other requirements. Final versions available in production meet all production and customer requirements.

Case/substitution evaluation

This case story describes a stepwise procedure to identify a safer alternative to a problematic substance. There are however for both suggested alternatives possible hazards related to storage and handling that should be considered with appropriate safety measures.

State of implementation

In use

Enterprise using the alternative

www.inditex.com

Availability ofAlternative

On the market

Type of information supplier

User

Contact

www.inditex.com

Date, reviewed

November 26, 2021