Solution vinyl resins

Union Carbide Corp. (1996) Solution Vinyl Resins for Coatings, technical literature. Union Carbide Corp., Danbury, CT. 

Most solution vinyl resins are more soluble than the powder coating or dispersion grade vinyl resins. They will, therefore, require much less plasticizer to reach any specific level of "softening." The compounder has to be extremely careful that he does not over plasticize and obtain a "tacky" or "soft" film. 

When an actual "bake" is required in order to produce a high gloss or due to the treatment of some other part of the item coated, the selection of the stabilizer is very difficult. As mentioned earlier, the copolymer may depolymerize before HCl degradation takes place. This limits the selection of the stabilizer. The sulfur-containing organotin type stabilizers appear to be more effective with respect to improving the heat stability of the solution vinyl resin systems. 

All vinyl resins have a linear carbon chain with lateral substituents and exhibit a range of molecular masses. Increasing molecular mass is accompanied by improved mechanical properties, a decrease in solubility, and an increase in the viscosity of their solutions. Vinyl resins of high molecular mass can therefore only be used in the form of dispersions or powders for paint applications. Solvent-containing paints require vinyl resins of considerably lower molecular mass than plastics, since only then a sufficient binder content can be achieved in the viscosity range required for paint application. 

Ucar, Solution vinyl resins. Union Carbide Cap. 

Due to the wide range of polarities exhibited by acrylics (dependent upon molecular weight and monomer composition), it is important to thorou ly check compatibility before deciding to use a particular resin. Solution vinyl resins impart adhesion and anticorrosive properties to the acrylic binder, but at the expense of application solids and film hardness . This is shown in Figure 3-1. 

The use of thermoplastic acrylics in high build, heavy duty anti-corrosive systems is reported by Steed who describes top coat formulations based on thermoplastic acrylic resins, chlorinated rubber, solution vinyl resins as well as blends of two or more of these. 

British Plastics Federation. UK Consumption of Plastics Materials (1995). Union Carbide. UCAR Solution Vinyl Resins (1983)... 

Solution vinyl resins can be readily dissolved by slow addition to solvent at room or elevated temperature, either with a low-speed turbine mixer or with a high-speed mixer such as a Cowles dissolver. Resin feed is either manual or metered. When a solvent/diluent blend is used, the resin is often first slurried in the diluent, containing about 20 percent solvent, and then the remaining solvent is added. 

The beater additive process starts with a very dilute aqueous slurry of fibrous nitrocellulose, kraft process woodpulp, and a stabilizer such as diphenylamine in a felting tank. A solution of resin such as poly(vinyl acetate) is added to the slurry of these components. The next step, felting, involves use of a fine metal screen in the shape of the inner dimensions of the final molded part. The screen is lowered into the slurry. A vacuum is appHed which causes the fibrous materials to be deposited on the form. The form is pulled out after a required thickness of felt is deposited, and the wet, low density felt removed from the form. The felt is then molded in a matched metal mold by the appHcation of heat and pressure which serves to remove moisture, set the resin, and press the fibers into near final shape (180—182). 

The specific solvents that make up the three solvency categories depend on the solute in question. For example, an aUphatic hydrocarbon may have adequate solvency for a long oil alkyd, but would be a diluent for an acryUc or vinyl resin, which require stronger solvents such as ketones or esters. The formulator must understand the solvency requirements of the solute to know which category a particular solvent would occupy. 

Poly(vinyl acetate) and its copolymers with ethylene are available as spray-dried emulsion soHds with average particle sizes of 2—20 p.m the product can be reconstituted to an emulsion by addition of water or it can be added directly to formulations, eg, concrete. The powders may be used to raise soHds of a lower soHds latex. Solutions of resin in methyl and ethyl alcohol at 2—50 wt % soHds are also available. 

In more recent years two new types of antifouling composition have been developed, using organometallic compounds as poisons. In one type, based chiefly on vinyl resin and organotin compounds (e.g. tributyltin fluoride), the poison and resin form a solid solution. As the poison dissolves from the surface of the film, more poison diffuses from deeper in the film to... 

Uses Plasticizer for lacquers, plastics, cellulose esters, and vinyl resins heat-exchange liquid carbonless copy paper systems in aircraft hydraulic fluids solvent extraction of metal ions from solution of reactor products uranium extraction and nuclear fuel reprocessing pigment grinding assistant antifoaming agent solvent for nitrocellulose and cellulose acetate. 

The combination of vinyl resins with epoxies is useful in formulations of solution coatings. Desirable characteristics are offered by low cost and high oxidation resistance of the vinyl resin. 

TBC is used as a plasticizer that does not support fungal growth in cellulosic and vinyl resins (especially PVC), polyactic acid resins (as a biodegradable component), and furniture coatings. Also used as a solvent for nitrocellulose and lacquers intended for food contact applications. Additional applications include a defoaming agent in proteinaceous solutions. 

Diluents or organic liquids with low solvent power for the vinyl resin are frequently used to lower cost, alter evaporation rate, change rheological properties of the solution, or to achieve special characteristics such as flow out, odor, flammability, resistance to blushing, etc. A more soluble resin and a high concentration of good solvent in the system permits wider latitude in using the diluent. 

With organosols we are formulating to resist solvation of the resin by the volatile component. We are trying to take advantage of its fluid properties only. This is directly opposite to our formulating approach with solution or soluble vinyl resins, i.e., incomplete solvation of the resin by the solvent will result in erratic viscosity and lowered physical properties of the final film. 

Figure 1 shows the typical steps in the manufacture of suspension (solution type) resins. The vinyl chloride and vinyl acetate monomers are "charged" (added) to a pressure vessel. Water and suspending agent, etc., are added, the actual polymerization being carried out under conditions of controlled pressure and temperature. 

Because water is the fluid component, very low viscosities at relatively high solids (50%) are attainable. Latexes are usually cheaper than solution vinyls but similar in cost to dispersion resins. As with organosols and solution vinyls, coating thickness is limited due to the evaporation of the fluid component. Note that more heat is usually required to remove water than organic solvents, and corrosion of equipment must be considered. 

Stabilizers are not used as frequently with the solution vinyl systems as with the dispersion resin systems. The reasons for this are as follows ... 

The UV absorbers are used to a greater extent with the solution vinyls than with the general-purpose and dispersion resins. This is due to the solution vinyl systems having been used to a greater extent outdoors than any of the other systems. The high color pigment loadings used with solution vinyl often act like UV screeners and protect the vinyl resin from attack. 

Ketones are true solvents for vinyl resins with the solution resin system. The solvent power of the solvent will depend upon many properties of the volatile, including molecular weight and chemical configuration. Depending upon the solubility of the resin, various volatiles such as acetates, nitroparaffins, etc., may be considered primary solvents. 

The molecular and chemical composition of the polymer will influence its solubility characteristics. Park (A) has discussed the solvent-resin relationships in detail in "Advances in Chemistry Series 12A." They can be summarized as follows Aromatics such as toluene and xylene are primary solvents for only the most soluble of the vinyl resins. The homopolymers have very slight aromatic tolerances. Aliphatic-type solvents are not considered good solvents for vinyls. As with the aromatics, the extremely soluble resins will tolerate aliphatic solvents if a strong ketone is present. Only fair aliphatic tolerance is obtained with the low molecular weight high vinyl chloride content solution polymers. Aliphatic tolerance of the homopolymers is practically nil. The alcohol tolerance of vinyl resins is very limited. Recent studies with the high solubility type metal adhesion copolymers indicate that appreciable quantities of 2-propanol may be used, if a strong ketone solvent is used. 

Vinyl copolymers require a large amount of solvent to dissolve. Due to low sohd content in the solution, vinyl coats are applied in thin coats and require several (up to five) layers to coat the substrate. Vinyl copolymer has excellent protection against acids, alkali, and water and good protection against weather. Vinyl resins are used as primers in industrial coatings with recoating intervals of over 20 years [7]. 

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