Paint mills

Fig. 63. Production diagram of sealants (a) and compounds (b) 1, 3 - sowers 2, 4 - bins 5,7 - agitators 6, 10 - collectors 8 - paint mill 9 - pressure filter...

Solid stabilizers are encountered occasionally when they can contribute to increasing the yield or raising the viscosity of the paste, if these properties are required. Solid stabilizers are added, in most cases, after they have been effectively dispersed in plasticizer on a three-roll paint mill. 

The UV absorbers in use today are solids thus requiring dispersion via the three-roll paint mill technique. 

The dispersion of the color pigment becomes more difficult since the quantity of plasticizer required for a three-roll paint mill dispersion may be in excess of that permissible in the final coating. It is frequently desirable to add the color pigment directly to the resin itself. In the case of the nonreactive pigments, it may be possible to mill fuse the resin and add the color pigment directly to the resin upon the mill. Color "chips" are obtained in this manner. The chips can later be incorporated into the solution during mixing. 

For fine dispersion of curatives and colorants a paint mill is commonly used. This equipment consists of 3 rolls turning at slightly different surface speeds relative to each other. The adjustable nip between the rollers allows dispersion with exceptional fineness of grind. 

Paint mills are available in different sizes to meet production requirements for high viscosity. (See Table XIV) Other mixers available for high speed processing of sealants include the SIGMA blade type supplied by Hockmeyer Corp. or the high speed Meyers mixer. High speed dispersers are generally limited to compounds up to 600 poises in viscosity. 

The optimum dispersion of a fiiier is obtained on a paint mill where all filler is subjected to a grinding action, and the various agglomerates are broken down. The setting of the rolls is dependent on the viscosity of the sealant and the fineness of grind desired. 

The paint mills can turn out considerable volume when used in conjunction with a change can pre-mixer. The following table gives approximate sizes and production capabilities of various size paint mills when used in conjunction with pre-mixing equipment. 

Paint mills are available with pressure gauges for controlling film thickness one or two speed operations cold or hot water change can holding and tilting devices fixes or floating center roll, and other modifications. 

Production of polysulfide sealant basically involves mixing and dispersion. Therfore, the equipment used in coating and ink manufacture is applicable to sealant manufacture. Viscosities of up to 60,000 P are common in polysulfide sealant, and therefore heavy equipment is generally used in its manufacture. Typical useful equipment includes sigma blade mixers, kneader-extruders, and high-speed dispersators. A three-roll paint mill gives... 

Some of the most attractive solvents to dispose of in cement kilns are washings from paint mills. These contain substantial quantities of resins and pigments but, in general, have a high calorihc value (8500 kcal/kg) and are primarily composed of low-cost solvents, which makes them unattractive to recover. They tend to contain relatively high concentrations of iron and titanium, neither of which is harmful to the properties of cement. Because paint must not contain highly toxic metal compounds or solvents, it would be imhkely that paint mill washings would present toxicity problems. 

Chem. Desaip. Amide/glycol/hydrocarbon oil-based Uses Defoamer for aq. foaming systems, flat and semigloss paints, mill effluent and waste treatment systems, kraft pulp mill screening and bleaching operations, acid and alkaline papermaking systems defoamer in food-contact paper/paperboard... 

The solution is then blended until homogeneous. Natural rubber is usually premasticated. Solvation is facilitated by increasing the surface area of the elastomer (i.e., chopping or shredding the polymer). Some polymers such as Butyl or EP (ethylene propylene) rubber may be added to the mixer as a solvent solution. Where needed the blend can be sequentially processed on a paint mill or ball mill to attain sufficient dispersion/ grind of the filler. 

The lime used was Fort Adams unground lime. It was slaked to powder by the affusion of one-third its bulk of water, and allowed to stand several days. As it was about to be used, it was reduced to paste and passed through a hand paint-mill, by which it was made very fine. It should be borne in mind that this lime is slightly hydraulic. 

In making the mortars, just enough water was added to the slaked lime taken from the cask, to make a stiff paste. This paste being passed throu a hand paint mill, which ground it very fine, was mixed, By careful manipulation, with the due proportions of sand. Much care was bestowed upon the operation of filling the prism-moulds with mortar and each prism was submitted to a pressure of 600 lbs. for a few minutes, that is to say while the succeeding prism was being formed. 

Insoluble powders, which can include blowing agents for foaming adhesives, curatives, fillers ete., ean be pre-dispersed in any liquid polymer or resin present, thoroughly wetted out using a conventional two-roll paint mill and then added as an intimate dispersion to the main mix. 

Plastisols of modest viscosity are commonly filtered through stainless steel mesh to remove tramp contaminants, often from the use of low-cost fillers. For thin-film applications, organosols and low-viscosity plastisols are pressure-filtered through cartridge or bag filters. Organosols may also be refined on three-roll paint mills for improved dispersion and ejection of contaminants. 

---