Bleaching acrylics

As an alternative to oxidative bleaching with sodium chlorite, acrylic fibres may be given a reductive bleach using sodium bisulphite in the presence of oxalic acid. This method is... 

Epoxy acrylate, DIBFe,f TMPTA 5% 40 30 % pickoff 10 10 500g Few to medium no. 2 blisters A little rust around the edges Bleaching... 

INCOMPATIBILITY DS2 is a corrosive material and because of its content, it is incompatible with some metals (e.g., cadmium, tin and zinc) some plastics (e.g., Lexan, cellulose acetate, polyvinyl chloride, Mylar, and acrylic) some paints wool leather oxidizing materials (e.g., Super Tropical Bleach or High Test Hypochlorite) and acids. 

Cationic FBAs are used to brighten polyacrylonitrile fibres. The brightening of acrylic fibres is carried by the exhaust method at an acid pH, usually in the presence of sodium chlorite or bisulfite bleach. Pyrazolines produce very high whites but are unstable to bleach and therefore the quaternary benzimidazoles are the preferred class, e.g. (3.65) and (3.66). 

Benzoyl peroxide is used as an initiator for polymerization of acrylates (including dental cements and restoratives) and other polymers as a bleaching agent for flour, fats, oils, waxes and milk used in the preparation of certain cheeses in pharmaceuticals for the topical treatment of acne in rubber curing and as a finishing agent for some acetate yams (Anon., 1984 Lewis, 1993 Medical Economics Co., 1996 United States Food and Dmg Administration, 1997). 

Our use of bleachable photoinitiators to carry out polymerization at depth opens the possibility of controlling the vertical dimension photochemically rather than mechanically. We have used the photoreduction of Eosin by triethanolamine to sensitize the polymerization of multifunctional acrylates to demonstrate the principle. Irradiation is carried out at 514 nm with an Ar+ laser having a beam diameter of 1.4 mm. The volume of sample irradiated is a small fraction of the total, simulating the conditions found in stereolithography. Because of bleaching of the photoinitiator, the irradiation generates... 

Good resistance to bleaches, dry-cleaning Fluids, and most common solvents. Dissolves in warm acetone and acrylic-type solvents. 

Uses. The most important commercial use for benzonitrile is the synthesis of benzoguanamine, which is a derivative of melamine and is used in protective coatings and molding resins (see Amino RESINS Cyanamides). Other uses for benzonitrile are as an additive in nickel-plating baths, for separating naphthalene and alkylnaphthalenes from nonaromatics by azeotropic distillation (qv), as a jet-fuel additive, in cotton bleaching baths, as a drying additive for acrylic fibers, and in the removal of titanium tetrachloride and vanadium oxychloride from silicon tetrachloride. 

In other oxygen applications, metal fabrication involves cutting and welding with an oxygen-acetylene torch. Chemical manufacture use includes the formation of ethylene oxide, acrylic acid, propylene oxide, and vinyl acetate. Miscellaneous uses include sewage treatment, aeration, pulp and paper bleaching, and missile fuel. 

Chemistry, Physics, and Biology Laboratories. As a rule, before any artifact is subjected to treatment, the chemistry laboratory determines the causes of any alterations or deterioration. The nature and structure of the artifact, its pigments and inks, are identified to avoid negative reactions to prescribed treatment. Fixatives are recommended if required these may be cellulose acetate dissolved in acetone, soluble nylon, or acrylic resin sprays. Once stains are identified, several possible solvents are selected. For deacidification, either magnesium bicarbonate or barium hydroxide usually is recommended, depending on whether an aqueous or nonaqueous solution is called for. Bleaching is discouraged, but when necessary, hypochlorites are used with suitable antichlors. 

Another similar example, also used in polymerization initiation, is the case of the iodonium salts of Rose Bengal (RB2-) [224, 225]. Methylene chloride solutions of these salts bleach in a few seconds in room light through an electron transfer photoinduced from the excited RB2- to the iodonium cation the resulting phenyl radicals were reported to initiate polymerization of acrylate. 

Rau [2] prepared terpolymers of ethyl ot-acetoxyacrylate, acrylic acid, and vinyl acetate that were used as bleach stabilizers in phosphate-free laundry detergent formulations. 

The strong oxidizing agent dinitrogen tetroxide is used for many applications. It is employed as a catalyst in oxidation reactions and as an inhibitor in the distillation of acrylates. It is also used in the manufacture of explosives and as bleach. In rocket propellants, it is used in a hypergolic mixture with hydrazine derivatives. The command module of the Apollo mission used a 1 1 mixture of hydrazine and N,N -dimethylhydrazine with N2O4 as the oxidant. 

Optical brightener for polyacrylonitrile fibers. Because of the high brilliance of the brightening effect, most acrylic fibers do not require a sodium chlorite bleach. 

CNC SOFT XXX is exceptionally versatile as it is compatible with anionic, cationic or nonionic substances. It is compatible with resins, catalysts and optical bleaches also acrylic resins, polyvinyl acetate emulsions and starches. The product may be applied by padding or exhaust methods. 

Non-yellowing softener for bleached white and pastel dyed cotton, polyester/cotton and acrylic/cotton knit goods. 

Cationic OBA for acrylic fibers. Stable in sodium chlorite bleach baths. Reddish cast. 

Cationic OBA for acrylics. Produces brilliant whites without bleaching. Reddish cast. 

Certain acrylic fibres should not be chlorite bleached because of their tendency to yellow/or loose stability to light. Many fluorescent brighteners added to the chlorite bath are also not stable and such materials may exhibit an accelerated fade when... 

If the cellulosic portion is cotton, bleaching is invariably required for this fibre. If the acrylic portion does not require bleaehing, then a peroxide treatment can be done at pH 9.5. The alkaline eondition should not be high as otherwise it would cause degradation of the fibre. The fabric is treated with a solution containing 7.5-10.0 g/1 H,Oj (35%), 3 g/1 sodium silicate (79°Tw) and 1 g/1 sodium carbonate at 90 C for 45-60 min. After bleaching the bath is cooled slowly to 50°C, rinsed and neutralised. 

When acrylic fibre also requires bleaching, then mild chlorite treatment will act on both the fibres in the blend. The bath is prepared at 35°C with 1.5 g/1 sodium... 

Hydrogen peroxide is not suitable for acrylic fibre at highly alkaline condition and moreover acrylic fibre turns yellowish on alkaline peroxide treatment. The discolouration can be improved by after-treatment with formic acid in presence of detergent. Acrylic/wool blends can also be bleached by a reduction bleach or by combination of peroxide and reduction bleaching process. 

The one bath two stage bleaching and brightening of acrylic fibres is quite popular. In this procedure, the material is boiled with chlorite, using oxalic acid as an accelerator for about 30 min, the bath is cooled to 80 C and excess chlorine is eliminated with sodium hydrosulphite. In the second phase, the optical brightening agent is added and the bath is again heated to the boil in 30 min and the material is treated at this temperature for further 30 min. The material is then worked up in the usual manner. 

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