PAINT AND COATING MANUFACTURE

PAINT AND COATING MANUFACTURE Michael McCann*  * Adapted from NIOSH 1984. Paints and coatings include paints, varnishes, lacquers, stains, printing inks and more. Traditional paints consist of a dispersion of pigment particles in a vehicle consisting of a film-former or binder (usually an oil or resin) and a thinner  (usually a volatile solvent). In addition, there can be a wide variety of fillers and other additives. A varnish is a solution of oil and natural resin in an organic solvent. Synthetic resins may also be used. Lacquers are coatings in which the film dries or hardens entirely by evaporation of the solvent. Traditional paints were under 70% solids with the remainder being mostly solvents. Air pollution regulations limiting the amount of solvents that can be emitted into the atmosphere have resulted in the development of a wide variety of  substitute paints with low or no organic solvents. These include: water-based latex paints; two-part catalysed paints (e.g., epoxy and urethane systems); high solids paints (over 70% solids), including plastisol paints consisting primarily of pigments and plasticizers; radiation-cured paints; and powder coatings. According According to the US National Institute Institute for Occupatio Occupational nal Safety and Health Health (NIOSH (NIOSH 1984), about 60% of paint manufacturers employed fewer than 20 workers, and only about 3% had more than 250 workers. These statistics would be expected to be representative of paint manufacturers worldwide. This indicates a predominance of small shops, most of which would not have in-house health and safety expertise. Manufacturing Processes In general, the manufacture of paints and other coatings is a series of unit operations using batch processes. There are few or no chemical reactions; the operations are mostly mechanical. The manufacture involves the assembling of  raw materials, mixing, dispersing, thinning and adjusting, filling of containers and warehousing. Paints Raw materials used to manufacture paints come as liquids, solids, powders, pastes and slurries. These are manually weighed weighed out and premixed. premixed. Agglomerate Agglomerated d pigment pigment particles must be reduced reduced to the original original pigment size, and the particles must be wet with the binder to ensure dispersion in the liquid matrix. This dispersion process, called grinding, is done with a variety of types of equipment, including high-speed shaft-impeller dispersers, dough mixers, ball mills, sand mills, triple roll mills, pug mills and so forth. After an initial run, which might take as long as 48 hours, resin is added to the paste and the grinding process is repeated for a shorter period. The dispersed material is then transferred by gravity to a let-down tank where additional material such as tinting compounds can be added. For  water-based paints, the binder is usually added at this stage. The paste is then thinned with resin or solvent, filtered and then transferred again by gravity to the can filling area. The filling can be done manually or mechanically. After the dispersion process, it may be necessary to clean the tanks and mills before introducing a new batch. This can involve hand and power tools, as well as alkali cleaners and solvents. Lacquers Lacquer production usually is carried out in enclosed equipment such as tanks or mixers in order to minimize evaporation of the solvent, which would result in deposits of a dry lacquer film on processing equipment. Otherwise, lacquer production occurs in the same manner as paint production. Varnishes The manufacture of oleoresinous varnishes involves cooking the oil and resin to render them more compatible, to develop high molecular weight molecules or polymers and to increase solubility in the solvent. Older plants may use portable, open kettles for the heating. The resin and oil or resin alone are added to the kettle and then heated to about 316°C. Natural resins must be heated prior to adding the oils. The materials are poured in over the top of the kettle. During cooking, the kettles are covered with refractory exhaust hoods. After cooking, the kettles are moved to rooms where they are cooled quickly, often by water spray, and then thinner and driers are added. Modern plants use large closed reactors with capacities of 500 to 8,000 gallons. These reactors are similar to those used in the chemical process industry. They are fitted with agitators, sight-glasses, lines to fill and empty the reactors, condensers, temperature measuring devices, heat sources and so forth. In both older and modern plants, the thinned resin is filtered as the final step before packaging. This is normally done while the resin is still hot, usually using a filter press. Powder coatings

Powder coatings are solventless systems based on the melting and fusion of resin and other additive particles onto surfaces of heated objects. The powder coatings may be either thermosetting or thermoplastic, and include such resins as epoxies, polyethylene, polyesters, polyvinyl chloride and acrylics. The most common method of manufacture involves dry blending of the powdered ingredients and extrusion meltmixing (see figure 77.5). The dry resin or binder, pigment, filler and additives are weighed and transferred to a premixer. This process is similar to dry blending operations in rubber manufacture. After mixing, the material is placed in an extruder and heated until molten. The molten material is extruded onto a cooling conveyor belt and then transferred to a coarse granulator. The granulated material is passed through a fine grinder and then sieved to achieve the desired particle size. The powder coating is then packaged.  ______________________________________________________________________________  Figure 77.5.

Flow chart for the manufacture of powder coatings by extrusion melt-mixing method 

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Hazards and Their Prevention In general, the major hazards associated with the paint and coatings manufacture involve materials handling; toxic, flammable or explosive substances; and physical agents such as electrical shock, noise, heat and cold. The manual handling of boxes, barrels, containers and so forth which contain the raw materials and finished products are major sources of injury due to improper lifting, slips, falls, dropping containers and so on. Precautions include engineering/ergonomic controls such as materials handling aids (rollers, jacks and platforms) and mechanical

equipment (conveyors, hoists and fork-lift trucks), non-skid floors, personal protective equipment (PPE) such as safety shoes and proper training in manual lifting and other materials handling techniques. Chemical hazards include exposure to toxic dusts such as lead chromate pigment, which can occur during weighing, filling of mixer and mill hoppers, operations of unenclosed equipment, filling of powdered paint containers, cleaning of  equipment and from spills of containers. The manufacture of powder coatings can result in high dust exposures. Precautions include substitution of pastes or slurries for powders; local exhaust ventilation (LEV) for opening bags of  powders (see figure 77.6) and for processing equipment, enclosure of equipment, spill cleanup procedures and respiratory protection when needed.  _______________________________________________________________________  Figure 77.6.

Bag and dust control system

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A wide variety of volatile solvents are used in paint and coating manufacture, including aliphatic and aromatic hydrocarbons, alcohols, ketones and so forth. The most volatile solvents are usually found in lacquers and varnishes.

Exposure to solvent vapours can occur during thinning in solvent-based paint manufacture; while charging reaction vessels (especially older kettle types) in varnish manufacture; during can filling in all solvent-based coatings; and during manual cleaning of process equipment with solvents. Enclosure of equipment such as varnish reactors and lacquer mixers usually involves lower solvent exposures, except in the case of leaks. Precautions include enclosure of process equipment, LEV for thinning and can filling operations and respiratory protection and confined-space procedures for cleaning vessels. Other health hazards include inhalation and/or skin contact with isocyanates used in manufacturing polyurethane paints and coatings; with acrylates, other monomers and photoinitiators used in the manufacture of radiation-curing coatings; with acrolein and other gaseous emissions from varnish cooking; and with curing agents and other additives in powder coatings. Precautions include enclosure, LEV, gloves and other personal protective clothing and equipment, hazardous material training and good work practices. Flammable solvents, combustible powders (especially nitrocellulose used in lacquer production) and oi ls are all fire or  explosion risks if ignited by a spark or high temperatures. Sources of ignition can include faulty electrical equipment, smoking, friction, open flames, static electricity and so forth. Oil-soaked rags can be a source of spontaneous combustion. Precautions include bonding and grounding containers while transferring flammable liquids, grounding of  equipment such as ball mills containing combustible dusts, ventilation to keep vapour concentrations below the lower  explosive limit, covering containers when not in use, removal of sources of ignition, using spark-resistant tools of nonferrous metals around flammable or combustible materials and good housekeeping practices. Noise hazards can be associated with the use of ball and pebble mills, high speed dispersers, vibrating screens used for filtering and so forth. Precautions include vibration isolators and other engineering controls, replacing noisy equipment, good equipment maintenance, isolation of noise source and a hearing conservation programme where excessive noise is present. Other hazards include inadequate machine guarding, a common source of injuries around machinery. Electrical hazards are a particular problem if there is not a proper lockout/tagout programme for equipment maintenance and repair. Burns can result from hot varnish cooking vessels and spattering materials and from hot melt glues used for  packages and labels. On site Lost Formula you will find various information on the following topics: Chemistry, Cookery, Medicine. Forgotten recipes on www.lformula.com. Attention! Site is translated on English with Etranslator! Manufacturing, recipes and methods of manufacture: soap and washing powder, Perfumes and cosmetics, different materials, Artisans varnishes and colors, Stationery, Food Additives and dyes, Pyrotechnics; Chemistry and petrochemistry, Construction and Repair, Chemical Industry, Chemistry and Manufacture, Manufactured home and more... Chemistry Laundry and cleaning Perfumes and cosmetics Processing fabrics Materials processing Stationery Food Weights and cements Metal Pyrotechnics Miscellaneous manufacturing Cookery Medicine

Chemistry and manufacture

Processing of tissues Water (saponification) creams General instructions on preparing water creams Preparation of aqueous cream is based on obtaining strong wax soap emulsion with alkaline solutions. Before talking about the technical side, making water creams, I must say that these products are compared with turpentine cream many disadvantages: they are not resistant to cold, do not save your skin, do not protect it from moisture and are often covered with mold. These drawbacks can be eliminated in part by the fact that 10% of water replaced the same amount of turpentine. The addition of paraffin increases within certain limits, waterproof cream, but you can not take more than 5% by weight of paraffin wax and fat. The most suitable are water-creams colored shoes, but they need to keep in glass jars, as in metal boxes aqueous cream colored changing its color, in addition, rusting metal boxes, which also affects the color of water colored creams. As regards the methods of cooking water creams, then it requires more knowledge and skill than the production of  turpentine cream. Getting the best, from the qualitative side, and well connected product depends on the proper  formation of emulsions, and for this it is necessary to study the processes emulsirovaniya and to practice applying

them. Aqueous cream can not be called saponification in the chemical sense, since they contain only a small amount of soap needed for emulsirovaniya waxes. Soap is either added to the mass in a completed form, or formed in the process of working on the action of alkali carbonate to free fatty acids, which are in the wax. The entire mass of socks and not neutral saponify. Consequently, water cream is hardened emulsion stability (strength) which depends or  soap, or the weak alkaline solutions, or, finally, from these two factors simultaneously. During the practical work is very important the best possible distribution of fat and wax in aqueous alkali and soap solution, which is achieved by uniform stirring it at a temperature not too high, because high temperature is easily distinguished, and wax fat on the surface of the solution. The correct amount of alkali necessary for water creams, should establish a preliminary pilot tests of the raw materials, and to start a pilot practice easier and better to just add to the weight of solution equal parts soap and potash. If the water creams 10% water, turpentine substitute, it is possible to reduce by half the required amount of potash and soap, and the replacement of 20% water, turpentine amount of soap and potash reduced even more, bringing it up to one third. To protect the water cream mold is added for every kilogram of cream 3 g customary corrupt formalin. Apply the same for the preservation of salicylic acid should not be, because it binds alkali. To protect the tin boxes of rust can smear  the inside of the solution of asphalt in the heavy gasoline. The cooking process water creams are as follows: In the pot or pan with a mixture of waxes and loaded melt with stirring, trying to avoid high temperatures. Then in the case of preparation of mixed creams add a thin stream to the amount of turpentine, which want to replace a certain part of vod1, and then added in small portions of boiling hot A solution of potash. While the addition of potassium carbonate solution to closely monitor to stand out with the foam did not go over the edge, when necessary, resorting to the deposition of her vsprysnuv water. If you use soap in finished form, then you must first dissolve it in a solution of potash, which usually is prepared by ten percent. The rest of the amount of water  added to the solution kras and, with self heating continues until. Those holes until they are washed free acids and will not stop release of carbon dioxide. Unnecessarily lengthy heating should be avoided, and stirring should be done continually in the same direction. The exact amount of water is established empirically, since it depends on the hardness of waxes used. If the manufacture of creams evaporate a significant amount of water, then it should be added, but always in a heated form. At the end add the dye solution and carefully stir until until a uniform mylopodobnaya mass. Then remove from heat and continue stirring until the mass starts to get thick, which usually occurs during the cooling mass to 50-60 °. Then poured into cans or bottles, and we must try to quickly cool the cream to avoid decomposition of the emulsion. Using the information above, as well as the presence, in connection with local conditions, or that type of stuff, you can modify recipes and cooking at its discretion, and the experimental practice, which gives the production process of  manufacturing water shoe creams.

Cream Black Water  Carnauba wax 500 g Beeswax 2 kg Potash 400 l Waters 1250 cm 3 Aniline black dye, soluble in water 500 g Work is in progress following the instructions given above. The amount of water can be increased or  decreased depending on the different kinds of wax. The more accurately and completely washed the wax, the more it can hold water. When packed in glass jars of cream may contain more water than the flood in the tins.

Boot polish in all colors Carnauba wax 50 g Beeswax 25 g Ugleammonievoy salt 6 g Sound Soap 6.5 g Hot water 550 Formalin 10 g Aniline Dyes, water-soluble 2% of the weight of all components Dissolve in hot water ugleammonievuyu salt, soap and paint, then pour this solution a thin stream of molten wax, stirring it all the time. When cooled add formalin. From the paint can take any of aniline dyes, soluble in water. For example, for the black color can take Nigrosine for yellow - hrizanidin to brown - bismarkbraun, and so pour in cream cans to warm.

Cheap cream yellow shoes Soda 30 g Japan wax 150 g White paraffin 80 g Waters 750 g Dissolve baking soda when heated to 400 g of water and add small portions of beeswax and paraffin. Boil until a homogeneous mass, then at a constant boiling and constantly stirring, pour the remaining water until smooth emulsion. Embellish with paint of any shade and poured into tins.

Black shoe polish Ozokerite 230 g Rosin 200 g Japan wax 50 g Potash 120 g Nigrosine, soluble in water 40 g Waters 1.5 liter  Melt over low heat rosin and wax. In another vessel dissolve by heating potash, in half the water and pour in small portions with constant stirring to the molten mixture of resin and waxes. The mixture is heated until a homogeneous mass. Then pour the hot solution with stirring Nigrosine to the rest of the water. Give by slow stirring to cool to 45-50 ° and poured into tins. If you pour the cream in cans at a higher temperature, it turns matte. Once the cream begins to harden, it is necessary to close the box. To increase the brightness of  cream can be any amount of water to replace the same amount of turpentine.

Black Cream better quality Japan wax 50 g Rosin 100 g Mountain wax 320 g Soda 80 g Nigrosine 40 grams Waters 1400 g Prepare the above method.

Paraffin cream shoes Paraffin 400 g Lanolin seed 200 g Potash 150 g Carnauba wax 400 g Nigrosine, soluble in water 150 g Formalin 1 g Hot water 4 L Melted paraffin and lanolin, heating them to 100 °. Then slowly add a solution of sodium hydroxide and heated in a continuation of 25-30 minutes, to form a uniform mass, and then add carnauba wax and heated until complete mixing of the entire mass, adding with stirring Nigrosine. By the end, I add hot water to ward off mold - formalin.

Saponification shoe cream of different colors Carnauba wax 200 g Beeswax 400 g Solution of potassium hydroxide 40 ° Bome 80 g Hot water 3 l Melt the wax at a temperature of 100 °. Treated with a solution of potassium hydroxide and water, then with constant stirring, add a strong dye solution to obtain the desired shade of cream. So, for example, yellow can take 15 g tserotinovoy yellow paint for the Orange - a mixture of 12 g tserotinovoy yellow paint and 6 g tserotinovoy orange dye for brown - 12 g tserotinovoy orange and 8 g tserotinovoy brown paint for the black - 20 Mr. Nigrosine. Tserotinovye paint and Nigrosine need to take soluble in water.