Vinyl thickening

Precaution Combustible Hazardous Decomp. Prods. Heated to decomp., emits acrid smoke and irritating fumes Uses Stabilizer, lubricant for vinyls thickener for plastisols stabilizer for food-grade polymers stabilizer migrating from food pkg. drier in food-contact coatings Regulatory FDA 21 CFR 175.300, 178.2010, 181.29... 

Suitable protective coUoids for the preparation of acryhc suspension polymers include ceUulose derivatives, polyacrylate salts, starch, poly(vinyl alcohol), gelatin, talc, clay, and clay derivatives (95). These materials are added to prevent the monomer droplets from coalescing during polymerisation (110). Thickeners such as glycerol, glycols, polyglycols, and inorganic salts ate also often added to improve the quahty of acryhc suspension polymers (95). 

Cellulosics. CeUulosic adhesives are obtained by modification of cellulose [9004-34-6] (qv) which comes from cotton linters and wood pulp. Cellulose can be nitrated to provide cellulose nitrate [9004-70-0] which is soluble in organic solvents. When cellulose nitrate is dissolved in amyl acetate [628-63-7] for example, a general purpose solvent-based adhesive which is both waterproof and flexible is formed. Cellulose esterification leads to materials such as cellulose acetate [9004-35-7], which has been used as a pressure-sensitive adhesive tape backing. Cellulose can also be ethoxylated, providing hydroxyethylceUulose which is useful as a thickening agent for poly(vinyl acetate) emulsion adhesives. Etherification leads to materials such as methylceUulose [9004-67-5] which are soluble in water and can be modified with glyceral [56-81-5] to produce adhesives used as wallpaper paste (see Cellulose esters Cellulose ethers). 

Other thickeners used include derivatives of ceUulose such as methylceUulose, hydroxypropylmethylceUulose, and ceUulose gum natural gums such as tragacanth and xanthan (see Cellulose ethers Gums) the carboxyvinyl polymers and the poly(vinyl alcohol)s. The magnesium aluminum siHcates, glycol stearates, and fatty alcohols in shampoos also can affect viscosity. 

The viscosity of the latex can also be dependent on pH. In the case of some latices, lowering the pH with a weak acid such as glycine is an effective method for raising the viscosity without destabilising the system. Latices made with poly(vinyl alcohol) as the primary emulsifier can be thickened by increasing the pH with a strong alkaU. 

Functional derivatives of polyethylene, particularly poly(vinyl alcohol) and poly(acryLic acid) and derivatives, have received attention because of their water-solubility and disposal iato the aqueous environment. Poly(vinyl alcohol) is used ia a wide variety of appHcations, including textiles, paper, plastic films, etc, and poly(acryLic acid) is widely used ia detergents as a builder, a super-absorbent for diapers and feminine hygiene products, for water treatment, ia thickeners, as pigment dispersant, etc (see Vinyl polymers, vinyl alcohol polymers). 

The viscosity of an adhesive directly influences its penetration into a substrate as the viscosity increases, the penetrating power decreases. It also determines the amount of mileage or spread that can be obtained. An optimum viscosity exists for each substrate and each set of machine conditions and must be achieved in order to manufacture an efficient adhesive. Poly(vinyl acetate) emulsions are frequently too low in viscosity to be metered efficiently or to perform well as adhesives by themselves. They must be bodied to working viscosities, eg, by adding thickeners. 

Partially hydrolyzed grades are used in many cosmetic appHcations for their emulsifying, thickening, and film-forming properties. Poly(vinyl alcohol) is also used as a viscosity builder for aqueous solutions and dispersions. 

Poly(vinyl alcohol) will function as a non-ionic surface active agent and is used in suspension polymerisation as a protective colloid. In many applications it serves as a binder and thickener is addition to an emulsifying agent. The polymer is also employed in adhesives, binders, paper sizing, paper coatings, textile sizing, ceramics, cosmetics and as a steel quenchant. 

The polymers are of interest as water-soluble packaging films for a wide variety of domestic and industrial materials. (Additional advantages of the poly(ethylene oxide)s are that they remain dry to the feel at high humidities and may be heat sealed.) The materials are also of use in a number of solution application such as textile sizes and thickening agents. As a water-soluble film they are competitive with poly(vinyl alcohol) whereas in their solution applications they meet competition from many longer established natural and synthetic water-soluble polymers. 

Thickening agents. When pseudoplasticity is necessary in NBR adhesives (spread coating operations, sprayed cements), carboxylic vinyl polymers can be added. 

Figure 17-8. Monomers for synthetic thickeners vinyl phosphonic acid, N-vinyl-2-pyrrolidone, vinyl sulfonic acid.

Fluid loss additives such as solid particles and water-thickening polymers may be added to the drilling mud to reduce fluid loss from the well bore to the formation. Insoluble and partially soluble fluid loss additives include bentonite and other clays, starch from various sources, crushed walnut hulls, lignite treated with caustic or amines, resins of various types, gilsonite, benzoic acid flakes, and carefully sized particles of calcium borate, sodium borate, and mica. Soluble fluid loss additives include carboxymethyl cellulose (CMC), low molecular weight hydroxyethyl cellulose (HEC), carboxy-methYlhydroxyethyl cellulose (CMHEC), and sodium acrylate. A large number of water-soluble vinyl copolymers and terpolymers have been described as fluid loss additives for drilling and completion fluids in the patent literature. However, relatively few appear to be used in field operations. 

Early soil-release agents, applied particularly to resin-finished cellulosic goods, were water-soluble polymers, many being related to thickeners (section 10.8) such as starch, hydroxypropyl starch, sodium carboxymethylcellulose, methylcellulose, hydroxyethyl-cellulose, alginates, poly(vinyl alcohol) and poly(vinylpyrrolidone). These functioned essentially as temporary barriers and preferential reservoirs for soil, which was thus easily removed along with the finish in subsequent washing, when they then helped to minimise... 

Conversely, vesicants have also been thickened with various substances to enhance deployment, increase their persistency, and increase the risk of percutaneous exposure. Thickeners include polyalkyl methacrylates (methyl, ethyl, butyl, isobutyl), poly(vinyl acetate), polystyrene, plexiglas, alloprene, polychlorinated isoprene, nitrocellulose, as well as bleached montan and lignite waxes. Military thickener K125 is a mixture of methyl, ethyl, and butyl polymethacrylates. When thickened, agents become sticky with a consistency similar to honey. Typically, not enough thickener is added to affect either the color or odor of the agent. 

CA 65, 568(1966) [Fluid nitric esters, nitro aromatic compds or their mixes can be thickened and made plastic by addn of soluble polymers that contain neither nitro nor perchloro groups. The gelled compds are useful in the manuf of expls and propints. Polymers used include poly(Me-methacrylate), poly(vinyl acetate), EtOAc-vinyl chloride, phenol-HCHO, poly-(vinylpyrrolidinone) and poly(vinylpyrrolidi-none)-poly(vlnylacetate)]... 

Hydrazine gel compns contg fuel metals (such as Al, Mg, Be, etc), microdimensional fibers (such as glass, asbestos, cellulose or synthetic) and thickeners, such as polyacrylamide, Na CM-cellulose, hydroxyethyl-cellulose, poly(vinyl)aIc, poly(Me methacrylate). Thus a soft gel was prepd. It contained hydrazine 65.20, polyacrylamide 0.67, microglass fibers 0.80 Al powder 33 33%... 

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