Asbestos floor tile manufacturing process & contents: this article describes how asphalt asbestos floor tiles & vinyl asbestos floor tiles were produced, their ingredients and the equipment used to make them.
We include data on athe estimaged production levels of asphalt-based flooring products in square feet by type and material. Our page top photograph illustrates popular and widely-installed Armstrong™ vinyl asbestos floor tiles.
This articles series about the manufacture & use of asbestos-containing products includes detailed information on the production methods, asbestos content, and the identity and use of asbestos-containing materials.
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The following text is Adapted from Rosato (1959) p. 86-93  © 2013 InspectApedia.com
In the past few decades [into the 1950's ] there has been a gradual development and increase in the use of tile. Vinyl floor tile and asphalt floor tile can use as much as 30 to 50 per cent, by weight, of asbestos shorts and floats. See Figure 4.1 below.
Shown at left, Sears vinyl-asbestos flooring. [Click to enlarge any image]
Sometimes, longer fibers are used; however, it is rare inasmuch as they are more expensive and tend to interfere with producing smoothly surfaced tiles. Asbestos is also used in the manufacture of synthetic resin tile.
Resilient floor coverings identify such organic types as asphalt tile, rubber tile, linoleum, and plastic tile. The nonresilient floor coverings pertain to stone, brick, etc. The original resilient floor coverings were developed during the latter part of the Nineteenth Century by Frederick Walton.
The mastic was troweled on the floor. In 1917, the United States Navy used the mastic as a deck covering over wood. The original mixes included asphaltic binders, with fillers of asbestos; mixing was done on a rubber mill.
Shown at left: Figure 4.1. View of asphalt tile floor with pattern. (Courtesy Armstrong Floor Div.)
It has been reported that the asphalt tile industry had its beginning in 1920 when the asphalt roofing manufacturers attempted to develop a material similar to slate shingles. The material developed was not suitable for shingles, but it started the asphalt floor tile business.
The term tile generally identifies tiles using asphalt materials as the principal binder; such organic resin binders as vinyl are used too, because they permit the manufacture of light-colored products. Vinyl asbestos tile competes with asphalt tile.
Both of these markets are expanding , however, the vinyl market is expanding faster. [That is to say, asbestos-based floor tile tile markets were still significantly expanding in 1959 - Ed.]
The first publicized installation of asphalt tile was in the Western Union office in New York City (1920). By the end of 1930 3 million sq yd was being produced annually.
By 1936 it had reached 4 1/2 million sq yd per year. Approximately five per cent of the floor covering in 1940 was of asphalt tile. After World War II, the volume increased to twelve per cent or approximately 41,000,000 sq yd of asphalt tile. In 1949 with the post-war building boom, there was an annual production of 61 million sq yd.
Annual production of vinyl plastic tile in 1952 was approximately 35 million sq yd. Reports indicate that in 1952 vinyl plastic tile production was approximately one-half of asphalt tile production. See Table 4.1 for estimated production.
Figures 4.2 and 4.3 show some of the operations involving the preparation and manufacture of tiles. The usual procedure is to combine plasticized resin with filler for the resin tile and asphalt with filler for the asphalt tile. Banbury mixers are generally used to mix the basic material. In the case of asphalt mixes, the. binder softens at moderately low temperatures. A steam-heated jacket is generally used with the mixer in order to soften the mix.
Pigments and other fillers are added during the mixing operation. After the mixes are completel blended with coloring matter, they are fed through calenders in order to produce smooth sheets of specified thickness. Then, these sheets are cut to proper size, prior to the material cooling and hardening.
Asphalt floor tile was originally manufactured with heavy asphalt solutions mixed with a very high percentage of asbestos filler. The tiles were hardened by means of solvent evaporation. Hot mixed asphalt solutions were also used.
These tiles were black or extremely dark in color. In order to obtain a different color, brown or intermediate colors, gilsonite is used.
Figure 4.2. The original doughy mass for tile is a heavy caramel-like sheet. Sheeting-mill operators pull it from the machine and lay it on a conveyor belt, which will take it to the calender rolls for thinning out. (Courtesy Kentile, Inc.)
Gilsonite is usually approximately 90 per cent soluble in carbon disulfide but its solubility in petroleum naphtha varies from 10 to 60 per cent. It is miscible in all proportions with drying oils and with the resins commonly used in making varnishes.
Unlike other asphalts, it can mix in almost any proportion with waxes to form stable compounds.
A typical formula for dark colored tile includes 40 parts by weight of asphalt or gilsonite, 60 parts of asbestos floats, 30 parts of powdered limestone, and pigment as required.
Another typical mixture includes 70 per cent asbestos fiber, 15 per cent gilsonite, 15 per cent vegetable pitch, and sufficient coloring.
The vegetable pitch provides for the proper flow of the binder.
The nomenclature of asphalt tile is misleading. The original asphalt tile contained a high percentage of asphalt; however, modern asphalt tile contains very little or no asphalt. Rather than the use of asphalt or gilsonite, most of the binders used now are synthetic organic resins.
The additives or plasticizers used with the resins are vegetable or petroleum pitches. These synthetic binders produce a brighter, lighter, and wider range of colors. Asbestos fillers however, are still the main ingredient in asphalt tile.
Figure 4.3. Continuous flow of floor tile moving from mill at rear through polished calender rolls on the production line—side view.
The coumarone-indene resins are the principal resins used 92 Asbestos Tile 93 in asphalt tile manufacture. They are readily fusible and resistant to water and the alkalies which makes them well adapted to tile manufacture.
When using coumarone-indene resins, the tile is brittle. Plasticizers are required in order to soften the tile. A general procedure is to mix vegetable and animal pitches in a dispersion of the resin in oil.
For a light-colored tile a conventional mixture is coumarone-indene resin of 22 parts, cottonseed pitch of 20 parts, asbestos of 65 parts, powdered limestone of 35 parts and pigments as required. Other mixes include a two to one ratio of coumarone-indene resin with the various pitches.
When marbleized tile is to be manufactured, the marbleizing color is added to the mixture at the end of the mixing operation. Generally this coloring matter is prepared in a mixture which has a slightly higher melting point so that it does not flow too readily when mixed with other compounds.
Summary of Typical Ingredients in Asphalt-Asbestos Floor Tile by Percent
Rosato cites another flooring material from the 1950's called asbetic flooring which was a mixture of ground mother rock and the shortest, otherwise unusable asbestos fibers.
Other sources such as the Rotterdam Convention PIC archive,  note that while vinyl-asbestos floor tile ingredient mixes varied by manufacturer, typically vinyl-asbestos floor tiles contained:
Short asbestos fibers may also be among the more hazardous if airborne. Asbestos was also used in a mixture with waterglass (a clear binder used in many chemical applications and even for cementing stove gaskets) as a hard binding compound.
Vinyl resin is the most important type of plastic floor tile. The use of vinyl resin in floor coverings started after World War II. These floor coverings can be made in many different colors (light and dark).
Similar to asphalt tile, but generally more flexible, vinyl asbestos tile has the largest volume of sales of the vinyl flooring family. The annual production rate is estimated at more than 80 million sq yd; the tile produced is usually 9 in. by 9 in. and 1/16 in. thick. Commercial installations usually use 1/8 in. tile.
Shown at left, Ever-Wear vinyl-asbestos floor tiles.
Vinyl-asbestos tile is used above or below grade on smooth wood or concrete base. As it wears, it gets smoother and takes waxing very well. Its resistance to scratching or marring and to strong detergents is excellent.
The batch type-continuous process type of flooring is made by a combination batch type and continuous process. It consists of vinyl-chloride vinyl-acetate copolymer resin mixed with plasticizers, stabilizers, asbestos, limestone and color pigments.
Varying types of intensive mixing equipment are used to fuse these ingredients into a hot mass of the base, or field color.
A thick blanket of stock is cut from this mill when the pattern is right; it is butted to the previous slab and fed into a two-roll calender which squeezes it to what is almost the required thickness. From this point, the process is continuous as the sheet passes through a second and often a third two-roll calender, cooling equipment and then a blanking press.
Shown at left, Armstrong Accoflex 1950's vintage asphalt-based floor tile advertisement.
See Armstrong Floor Tiles for a guide to identifying Armstrong asbestos floor tiles.
In the press, depending upon the width of the sheet two rows of three to five tiles are die cut from the sheet per stamping. The rest of the sheet travels back on an overhead conveyor to the mixer, for immediate reworking, while the tiles move along to be visually inspected for pattern, color and surface appearance.
An entirely different approach to the processing of vinyl resins into flooring materials is the use of vinyl plastisols or organosols. These materials are dispersions of vinyl resins in plasticizer (plastisols) or combinations of plasticizer and volatile diluent (organosols).
These dispersions are of a fluid nature; the methods for their application are based on their flow characteristic, on their ability, when heated to 350°F to fuse into the same tough resilient vinyl plastic that requires the above-described heavy processing techniques.
Another application of asbestos with vinyl tile involves the use of asphalt saturated asbestos felt applied under 1/8 in. thick tile. This felt underlay provides for smoother finished flooring.
This discussion has moved to LEAD in FLOORING PRODUCTS & POLISHES - separate article.
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