US2949623A - High speed frictional glossifying medium - Google Patents

Description

Aug. 23, 1960 Filed May 16, 1958 FIG.|

24 i VARNISH SIZING 2| EXFOLIATED VERMICULITE 22 y GLUE BOND 2o I BACKING VARNISH SIZING EXFOLIATED VERMICULITE VARNISH BOND PRESIZE 'BACKING FIG.3

EXFOLIATED VERMICULITE Mime/ 1 FIG. 4

INVENTOR.

LLOYD E. DIMOND mum ATTORNEY aetaszs Patented Aug. 23, 1960 ice HIGH SPEED FRICTIONAL GLOSSIFYIN G MEDIUM Lloyd E. Dimond, New Albany,

Plywood Corporation, of Kentucky 'Ind., assignor to General Louisville, Ky., a corporation This invention relates to a high speed frictional rubbing medium, such as is used in the microseal process of the US. Alexander Patent #2,827,935, for glossifying wall panels, flush doors and other fiat-faced products.

Glossifying belts, composed of various heat-insulating materials, have heretofore been proposed and tried. These include asbestos, plain canvas, plastic-coated canvas, rubberized cloth and cork. Asbestos belts produce a highly satisfactory degree of gloss but are more expensive than any of the other belts. Thus far, while cork belts are also expensive, they have proven to be the most satisfactory from the important standpoints of the degree of gloss they produce, the average length of their useful lives and their ultimate cost per unit of area glossified.

A typically constructed cork belt comprises: a flexible, dimensionally-stable canvas backing, at making coat on said backing; a layer of cork particles distributed over and bonded to said making coat; and a sand size or size coat over said cork layer, this coat including mildly abrasive particles such as fine tripoli. The good performance of the cork belt has been attributed to the resiliency of the cork particles, which, when they are subjected to rubbing pressure, causes them to yield and thus promote uniform frictional rubbing contact and demote rapid Wear.

Exfoliated vermiculite particles have not heretofore been used as a frictional glossifying medium. This may be due to the fact that individual vermiculite particles are not resilient and tenaciously coherent like individual cork particles, but, on the contrary, are brittle and nonresilient. Consequently, instead of resiliently yielding when they are subjected to rubbing pressure, one would expect vermiculite particles to crumble and thereby demote uniform frictional rubbing contact and promote rapid wear. I have discovered, however, that when expanded vermiculite particles are substituted for cork particles in a glossifying belt, a new and substantially improved glossifying belt is unexpectedly and surprisingly produced.

Vermiculite is a hydrated magnesium-aluminum iron silicate containing approximately 39% SiO 21% MgO, 15% A1 9% Fe O 57% K 0, 1% CaO, 5-9% H 0 and small quantities of Cr, Mn, P, S, CI. The fact that it is a non-resilient, unabrasive, heat-insulating hydrated silicate, having the propertiy of expanding 6 to 20 times the volume of the unexpanded mineral when heated to about 2000 C., has led me to discover that popped perlite particles produce a similarly improved glossifying belt. Perlite is a non-resilient, unabrasive, heat-insulating hydrated silicate in the form of glossy rock similar to obsidian. It usually contains about 65- 75 SiO 10-20% A1 0 2-5% H 0 and smaller amounts of soda, potash and lime. When heated to the softening point, perlite expands up to times its original volume to form popped perlite, a light fiufiy material.

The principal object of the present invention is to provide a new and improved glosslfying medium or beltv essentially including, as its glossifying agent, non-resilient, unabrasive, heat-insulating, expanded silicate particles, such as vermiculite, perlite and the materials which are derived from hydrated unexpanded particles having the property of expanding, by exfoliation, popping or otherwise, from 6 to 20 times when suitably heated to form a light flulfy material of low density.

Another important object is to provide a novel glossifying frictional rubbing medium, which, in comparison with contemporaneous cork belts, possesses one or more of the following advantageous properties or character istics, viz: superior heat insulator; superior frictional heat generator; better glossifier under equivalent operating conditions; equivalent glossifier under easier or less strin gent operating conditions; easier to break in; longer average useful life; and somewhat smaller manufacture ing cost.

I believe that a vermiculite belt is a better heat insulator and frictional heat generator than a cork belt. My belief is based on the fact that, with all operating conditions otherwise the same, the vermiculite belt requires less rubbing pressure to produce the same degree of surface gloss. As a matter of fact, the' gloss produced by a vermiculite belt is, to the eye, very noticeably improved over that produced by the cork belt although this difference cannot be determined on a glossmeter which measures the reflected light. Vermiculite belts are easier to break in than cork belts. My experience with cork belts during the last two years, and my more limited experience with vercirnulite belts indicates that the average vermiculite belt should outlast the average cork belt by a very substantial margin. Finally, vermiculite itself is more readily available than cork and much less expensive.

The invention is illustrated in the accompanying drawing wherein:

Figs. l-4 inclusive are sections of unused belts constituting somewhat different embodiments of this invention.

The techniques employed to make a belt in accordance with the present invention are the same as those commonly employed in making coated abrasive products generally and cork belts specifically. Accordingly, a belt made in accordance with my invention comprises: a backing; a make coat, with or without an intervening presize coat; a layer of vermiculite particles bonded to the backing by the make coat; and a size coat with or Without a succeeding levelling or oversize coat. All ma terials employed, except vermiculite, are conventionally selected, conventionally composed or compounded and conventionally applied. In fact, the belts of Figs. 1-3 are used to demonstrate, among other things, that the present invention is applicable to conventional belts using different conventional combinations of make and size coats. Thus, the make and size coats are composed of animal glue in Fig. l, of animal glue and varnish respectively in Fig. 2 and of varnish in Fig. 3.

FIG. 1

The Fig. 1 embodiment comprises: a cloth backing 10; a layer of exfoliated vermiculite 11; a making coat 12 of animal glue bonding the vermiculite to the backing; and a size 14 of animal glue covering the exposed vermiculite particles.

The backing 10 may be of any suitable material heretofore employed as a backing for coated abrasive belts. Preferably a cloth backing is used such as greige or drills cloth, jeans, herringbone cloth and the like. These are conventionally prepared by washing and dyeing the cloth, filling it, drying the filled cloth and, during the drying process, prestretching it to reduce warp stretching and increase warp tensile strength.

In providing the vermiculite layer, an excess of exfoliated vermiculite'i's distributed over the making coat before the latter dries and while it remains tacky. These particles are pressed into the making coat with a roller mounted to exert light pressure directly on the particles. The coated backing is then passed around a roll to permit the excess to drop off.

The glue size coat 14 preferably contains some filler such as tripoli.

FIGS 2-3,

The rubbing medium of Fig. 2 comprises: a cloth backing 20; an animal glue making coat or bond 22; the vermiculite layer 21; and a varnish size 24 which may be an oil modified phenolic varnish containing a melamine resin.

" The vermiculite belt of Fig. 3 comprises: a cloth back ing 30; a presize coat 31; a varnish making coat 34; a vermiculite layer 32; and a varnish sizing coat 35. The presize coat 31 is used to promote a good bond between the backing and the varnish making coat. It conventionally includes latex containing a mixture of a copolymer of butadiene and acrylonitrile and a polymer of vinyl chloride. The making coat may be composed 'of an oil modified phenolic varnish prepared from chinawood oil and having an oil length of 12 to 20 gallons. The size coat 35 may be the same as the size 24 used in Fig. 2.

Waterproof rubbing mediums A glossifying belt may be of either waterproof or nonwaterproof construction. Where the finished product is to be flexible, dimensionally-stable and essentially waterproof, it can be made by conventional techniques involving first the treatment of the backing with materials rendering it waterproof or water resistent and second by using waterproof or water resistent making and size coats such as oil modified phenolic varnish coats.

Fillers These are conventionally selected and employed in accordance with conventional requirements. The use of a mild abrasive such as tripoli is recommended but it should not be used in such concentration that it will remove the surface being glossified.

Vermiculite The name vermiculite, as used herein, embraces a number of micaceous minerals, all of which are hydrated silicates characterized by considerable expansion at right angles to their basal cleavage when heated. These include: culsageeite; dudleyite; hallite; jetr'ersite; kerrite;

'lennilite; maconite; philadelphite; pyrosclerite; vaalite;

and vermiculite. All members of this group show the common physical characteristics of exfoliation. The term exfoliation, as used herein, refers to expansion perpendicular to the basal cleavage when the mineral is strongly heated. The hardness of vermiculite is approximately 1.0 to 1.5 on the moh scale. The specific gravity of the expanded or exfoliated material is about 0.9. It weighs from 4.5 to lbs. per cubic foot, depending on the size and kind.

The exfoliated vermiculite used may be and preferably is that obtainable commercially in the graded size range '20 +40 mesh on Tyler standard screens although particles ranging from 10 +180 mesh appear usable. This commercial product, which is not completely dehydrated but appears to have undergone exfoliation in substantially uniform manner throughout its mass, is very inexpensive in comparison with either cork or rubber.

Mic-rascal and superseal process One way of frictionally glossifying a flush door (e.g., 36" W. x 80" L.) by means of rnicroseal and superseal processes comprises: conveying the door (5 to 200 f.p.m.)

successively through three difierent rubbing zones; rubbing the same face of said. door, as it passes through each zone, with an endless glossifying belt, which moves rapidly (1500 to 7500 f.p.m.) toward and away from the door through a concavo-convex path with the convex side of the belt pressed intimately and firmly against said door over a transversely extending band (e.g., 36"

' L. x W.) of rubbing contact in each rubbing zone at a rubbing pressure high enough to cause said belt to effect the progressive glossification of said door face without charring it. In the first rubbing zone, the door is microsealed, which is to say that its dull sanded surface is glossified, pressure smoothed, densified, hardened, and reduced in porosity and absorbency.

Between the first and second rubbing zones, the door is prepared for the first supersealing operation by coating its microsealed surface with a plasticizable additive, such as a thin solution of melamine resin, and then drying that coating. Accordingly, in the second rubbing zone, the door is super microsealed or supersealed, which is to say, that its coated microsealed surface is once again glossified and pressure smoothed. In the third rubbing zone the glossified coated surface of the door is once again super microsealed or supersealed in order to enhance the gloss on it.

The rnicroseal and supersealing operations are also conventional.

Advantages of vermiculite to bring all portions of the door up to the same degree of gloss whereas the cork belt may be less efficient in this respect. Cork belts, when new, do not work well until they are broken in. New vermiculite belts do a fairly creditable job and require less use to bring them up to peak performance.

Three cork belts performing the rnicroseal operation wore out after microsealing 22,560, 25,263 and 29,753 door sides for a total of 77,576 door sides or a total of 38,788 doors. This averages out at 12,929 doors per cork belt. One vermiculite belt microsealed a total of 168,916 door sides or 84,458 doors and even then was not completely worn out.

Again, in performing the super microsealing or supersealing operation, one vermiculite belt wore out after glossifying 95,465 door sides whereas two cork belts Wore out upon glossifying 60,523 and 58,685 door sides respectively.

FIGURE 4 The rubbing medium of Fig. 4 comprises: a cloth backing 40; a bond 42; a vermiculite layer 41; a size 44; and an oversize or leveling coat 45. All of this assembly, except the oversize coat 45, may be assumed to be the same as any one of the belts heretofore described, particularly the belts of Figs. 1 and 2.

The leveling coat 45 is deposited from a solution of alkali lignin, such as is commonly produced by refining the black liquor from the production of paper pulp by the sulphite process, or from any other source. Sufiicient alkali lignin solution should be applied to form, upon evaporation of the solvent, a deposit of lignin on the surface of the belt. The amount of lignin required is not great. For example, a deposit of as little as /2 lb. to 2%. lbs. of lignin per ream is effective.

The primary advantage of the lignin deposit is that break-in time is decreased and the period in which optimum results are obtained is reached after a shorter break-in time. The lignin deposit can also be used advantageously for decreasing the break-in time of ordinary cork or rubber abrasive belts of the conventional type.

While it is preferred that the lignin be deposited from a solvent, it can also be applied to the belt in other ways.

Perlite The vermiculite belt appears to be somewhat better than the perlite belt but I have used a perlite belt and found that it not only produces good results but appears to be superior and longer lived than the cork belt. The perlite rubbing medium used was composed of the following elements: a resin-filled drills cloth backing; an an oil modified phenolic varnish making coat or bond; expanded perlite particles; and an oil modified phenolic varnish size including one part of cream tripoli and two parts of an aromatic solvent thinner. A concrete grade of expanded perlite was used and regraded to a 30 grit as follows: 47.3% on 28 mesh; 21.4% on 32 mesh; and 31.3% of fines.

Other fields of application While the primary field of application of the present invention appears presently to be in the field of glossifying wood, plastic and plastic coated surfaces without re moving any of the surface material, the applicability of this invention to the abrasive polishing of glass, metal and other surfaces should not be overlooked. Where abrasive polishing is in mind, the sizing should conventionally contain finely divided polishing materials such as cerium oxide, rouge of iron oxide, tripoli, tin oxide, pumice, calcium carbonate, aluminum oxide, silicon carbide, fiint, emery, garnet, corundum, wollastonite, cryolite, and various other siliceous materials.

Other forms of the invention While the invention is primarily concerned with coated sheet material, the teachings herein are also applicable to the production of wheels, butfs, sleeves, and to belts that can be used on expanding chucks. The periphery of a wheel, for example, can be dressed to match or mate with the shape of a molding for glossifying or polishing purposes. All such forms of buifing media, which are made in accordance with this invention, should normally have a much longer useful life period than the cork or rubber coated abrasive media of the prior art.

Having described my invention, I claim:

1. A frictional rubbing medium presenting a working face essentially including adherently-bonded, non-resilient, unabrasive, heat-insulating, expanded inorganic particles which are derived from hydrated unexpanded inorganic particles having the property of expanding from about six to about twenty times when suitably heated to form a relatively light material of low density.

2. The medium of claim 1 wherein: the expanded particles are derived from hydrated unexpanded silicate particles.

3. The medium of claim 2 wherein: the expanded particles are in the graded size range 10 mesh on Tyler standard screens.

4. The medium of claim 2 wherein: the expanded particles comprise exfoliated vermiculite.

5. The medium of claim 4 wherein: the expanded particles are in the graded size range -20 +40 mesh.

6. The medium of claim 4 in coated sheet form comprising: a flexible backing; a make coat thereon; a layer of said vermiculite particles adherently-bonded bythe make coat to the backing; and a size coat over the vermiculite layer.

7. The medium of claim 6 wherein the vermiculite particles are in the graded size range 20 +40 mesh on Tyler standard screens.

8. The medium of claim 2 wherein the hydrated silicate particles include popped perlite.

References Cited in the file of this patent UNITED STATES PATENTS 2,211,354 Spokes Aug. 13, 1940 2,542,058 Riedesel Feb. 20, 1951 2,720,732 Eubanks Oct. 18, 1955 2,734,812 Robie Feb. 14, 1956 OTHER REFERENCES Bureau of Mines Information Circular, August 1946, Perlite, Source of Synthetic Pumice (page 6 relied on).

United States Dept. of Commerce Report, 1951, Production and Uses of Perlite (page 1 relied on).

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