Water repellent finishes

Water Repellency and Water Resistance. Water repeUency is defined as the abihty of a textile fiber, yam, or fabric to resist wetting, whereas water resistance is a general term appHed to a fabric s abiUty to resist wetting and penetration by water (2). A third term, waterproof, is appHed to those fabrics that do not allow any water penetration at all. Waterproof fabrics are generally coated with an impermeable surface layer that does not allow air permeabihty. Water-repellent finishes are hydrophobic compounds that are appHed to fabrics to inhibit water penetration while still allowing air permeabihty. 

The principle of blending a conduction fiber with a static-prone fiber has been known for years. A mixture of a substantial quantity (30—40%) of a hydrophilic fiber such as cotton or rayon with a hydrophobic static-prone fiber such as a polyester can produce a static-free blend under ordinary conditions. However, blocking the hydrophilic groups by cross-linking of the cotton with biflinctional reagents such as dimethylolethylene urea or addition of a water-repellent finish such as a sUicone resin increases the static propensity of such a blend. 

A/-substituted, long-chain alkyl monomethylol cycHc ureas have also been used to waterproof cotton through etherification. Other water repellent finishes for cotton are produced by cross-linked siHcone films (56). In addition to the polymeri2ation of the phosphoms-containing polymers on cotton to impart flame retardancy and of siHcone to impart water repeUency, polyduorinated polymers have been successfuUy appHed to cotton to impart oil repeUency. Chemical attachment to the cotton is not necessary for durabUity oU repeUency occurs because of the low surface energy of the duorinated surface (57). 

The silicones have established their value as water-repellent finishes for a range of natural and synthetic textiles. A number of techniques have been devised which result in the pick-up of 1-3% of silicone resin on the cloth. The polymer may be added as a solution, an emulsion or by spraying a fine mist alternatively, intermediates may be added which either polymerise in situ or attach themselves to the fibre molecules. 

There are reactive softeners, some of which are N-methylol derivatives of long-chain fatty amides (10.241) while others are triazinyl compounds (10.242). The N-methylol compounds require baking with a latent acid catalyst to effect reaction, whereas dichloro-triazines require mildly alkaline fixation conditions. The N-methylol compounds are sometimes useful for combination with crease-resist, durable-press, soil-release and water-repellent finishes. In this context, the feasibility of using silane monomers such as methyltri-ethoxysilane (10.243), vinyltriethoxysilane (10.244), vinyl triace tylsilane (10.245) and epoxypropyltrimethoxysilane (10.246) in crosslinking reactions to give crease-resist properties and softness simultaneously has been investigated [492]. 

Polyfluorinated chemicals now dominate in the fields of oil-repellent and water-repellent finishes. The earlier so-called conventional polyfluorinated products were of the type represented by poly(N-methylperfluoro-octanesulphonamidoethyl acrylate) (10.248) [499]. Such products presented a shield of closely packed fluoroalkyl groups at the fibre-air interface, thus giving low-energy surfaces with excellent oleophobicity. These showed excellent resistance to oil-based stains but were less satisfactory as soil-release agents during... 

These copolymers have been mentioned already in section 10.10.4 as versatile and highly effective stain-resist, oil- and water-repellent finishing agents. 

The application of water-repellent finishes to fabrics actually involves a chemical reaction between the material and the finish. Cellulose-based fibers such as cotton possess hydroxyl (-OH) groups that exist on the surface of fabrics spun and woven from the fiber. The basic structure of cellulose portrayed in Fig. 7.6.1 reveals... 

Fluoro group containing aliphatic carbodiimides are used to impart oil and water repellent finishes to nylon and polyester fabrics and to leather materials. " ... 

CONDENSOL I New is a special metal salt catalyst for water-repellent finishing with the silicone product PERSISTOL SIN. 

CONDENSOL II protects coloured goods from any loss of rub fastness caused by water-repellent finishing. CONDENSOL II is affected by metal salt. If fairly large quantities of cross-linking agent and catalyst are to be used, preliminary trials should always be carried out to test whether the bath stability is adequate. 

The PERSISTOL types are supplied in the form of aqueous emulsions. They are wash-resistant water-repelling agents derived from paraffin wax or silicone and are used mainly for the water-repellent finishing of outerwear. 

PERSISTOL HP is a metal salt-free, reactive product for the wash-resistant water-repellent finishing of textiles composed of cellulosic fibres, alone and in blends with synthetics. It can be applied in one bath together with the KAURIT and FIXAPRET types in resin finishing. In oleophobic finishing it is used as an extender to promote the finishing effect. 

PERSISTOL SIN is a sillcone-type impregnating agent for the water-repellent finishing of fabrics of all types. According to the type of substrate, it is necessary to use CONDENSOL I New or CONDENSOL II. 

Fluorochemical Stain Repellent Water Repellent Finish for Outerwear,... 

CNC AQUAFILM PA is a new aqueous fluorochemical finish designed to impart lasting high oil and water repellent finishes on outerwear fabrics. Application of this fluorochemical is especially easy because it is completely miscible with cold or warm water. CNC AQUAFILM PA is a one component system which is cationic. Generally, it may be used with any nonionic or cationic additive. Anionic and basic materials have limited compatibility. 

A resinous/amide durable type water repellent requiring satisfactory curing either alone or in the presence of additional thermosetting resin finishes. This material is highly recommended as an extender for the fluorocarbon type oil/water repellent finishes currently being used. 

Efficient polymeric softener formulated for polyester and polyester/cotton blends. Especially recommended when transfer printing operations follow or a semidurable water repellent finish is required. 

Activated catalyst for use on goods to be over-printed or with water repellent finishes for fast curing—modified magnesium chloride solution. 

Non-rewetting scouring agent. Use to prepare goods prior to a water repellent finish--non-ionic. 

At low concentration it can be used in water repellent finishes without causing rewetting of the fabric after drying. SULFANOLE 634 can also be used to stabilize latex finishes and can be used in standard resin finishes. 

Helps in eliminating pad roll build-up of water repellent finishes... 

SEQUAFOAM LC surfactant is a blowing agent that can be used with fluorochemical and water repellent finishes. It is also very effective in the foam finishing of yarn striped fabric. SEQUAFOAM LC surfactant can also be used as a dyed stabilizer... 

Surfactant combination based on alkyl aryl sulfonate, mainly for the finishing of wool- and wool-blend fabrics advantageous for fabrics receiving water-repellent finish. 

Twisting lubricant, anionic, can be washed off easily, especially for textiles to receive water-repellent finish later. 

Silicone resin emulsion for water-repellent finishes. 

Fluorocarbon extender additive for water-repellent finishes. PROTE-SOIL 397 ... 

VIPLEX SR is a vinyl acetate homopolymer emulsion which is an excellent hand builder for textile water repellent finishes because it has a film of high water resistance. It also forms dilute dispersions in water which are stable to substantial concentrations of electrolytes such as borax, multivalent metallic ions and quaternary compounds which coagulate many types of vinyl acetate emulsion polymers. 

VIKON FGT is also a good hand builder for silicone water repellent finishes because it has essentially no effect on the spray rating and it is fully compatible with the silicone repellents and their catalysts. 

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