Stabilising baths

Formaldehyde and formaldehyde releasers are used as preservatives in process solutions and for gelatine, and in stabilising baths for colour film and colour paper prints. Kathon CG and i,2-benzisothiazolin-3-one (BIT) may also be used as slimicides in process solutions and in stabilisers for colour paper prints (Ericson, personal communication). They may be undeclared. 

Formaldehyde 1% aq Biocide in process solutions for gelatine in stabilising baths for colour film and colour paper prints... 

Succinic acid has also been proposed for the stabilisation of a selfregulating bath, a recommended bath composition consisting of 375 g/1 of CrOj, 8 g/1 of SrS04, and 40 g/1 of succinic anhydride the bath is... 

Surface cleaning as a preparation for coatings is discussed in Sections 11.1 and 11.2. It is important to control degreasing baths to prevent accumulation of water and formation of corrosive products which will contaminate the atmosphere as well as the objects being degreased. In the case of tri-chlorethylene, stabilisers are added to prevent formation of hydrochloric acid Exclusion of dust is beneficial, and may necessitate filtering the air or use of a temporary protective. 

The process offered by the service provider allows to achieve a similar quality of the finished pieces with advantages in several aspects as compared to the conventional nickel plate process, as long as the bath is stabilised, operating under optimal conditions and using the polishers developed by the service provider. 

The selection of alkali to be used in peroxide bleaching is dependent on the fibres or blends being bleached. Sodium hydroxide, sodium carbonate are generally used on cellulosic fibres whilst ammonia and various phosphates are used when bleaching protein fibres. Of the various phosphates only tetrasodium pyrophosphate, Na P,0 and hexametaphosphates are of interest as stabilisers in alkaline bleach bath. 

Peracetic acid can also be used for bleaching polyester/cotton blended fabrics with a solution containing 4 g/1 peracetic acid, 1 g/1 tetrasodium pyrophosphate (stabiliser) and 1 g/1 wetting agent with a liquor ratio of 5 1. Peracetic acid has a pH of about 1.5 and the bleaching bath solution is adjusted to pH 5.5 with the help of dilute alkali. The material is entered cold and run for 10 min. Then the temperature is raised to 65-70 C in 15 min and bleaching is continued at this temperature till the concentration of peracetic acid drops to 0.09 g/1. The fabric is then washed thoroughly... 

As peroxide-bleached goods tend to show reversion to a creamy colour, it is usual to follow with a treatment in reducing agent to stabilise the bleach in a bath containing 3-4 g/1 stabilised hydrosulphite and 1 g/1 synthetic detergent at 50 C for 30-40 min, rinsed and dried. 

The goods are entered into a bath containing 2-3 volume H O, 1 g/1 sodium hydroxide flake, 0.2 g/1 peroxide stabiliser, 0.25 g/1 sequestering agent and 0.002 to 0.05 g/1 free radical suppressor at 40 C, the temperature is raised to 85 C and then the treatment continued for 1 h. The treated goods are then cooled and rinsed thoroughly. When appropriate, selected optical brighteners may be incorporated in the peroxide bleach bath. 

For acrylic/wool blends, the acrylic portion is brightened in the normal way and then the wool is bleached with hydrogen peroxide and subsequent reduction bleaching is done in a bath containing suitable brightener (1-2%) and stabilised sodium hydrosulphite (3-5 g/1) at 85 C for 30 min. The fabric is then rinsed and dried. 

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