US1961946A - Bituminized felt - Google Patents

Description

Patented June 5, 1934- PATENT OFF-l 1,961,946 BITUMINIZED FELT Milton 0. Schur and Walter L. Hear-n, Berlin,

N. H., assignors to Brown Company, Berlin, N. E, a corporation of Maine No Drawing.

Application January 12, 1933,

Serial No. 651,358

2 Claims.

- pose of covering the walls, roofs, and other parts of a building and, when properly finished, as with linseed-oil-paint ornamentation, are serviceable as floor coverings or the like. The presgoing purposes were fabricated from cheap rags as the main raw material. The rags were placed in the usual hollander or beater engine, wherein they were beaten in the presence of water until the roof, undergo flexing.

a smooth pulp or halfstufi, the fibers of'which were of sufficiently reduced length to be feltable,

was obtained, whereupon the pulp was appropriately diluted with water and delivered to the tear resistance to withstand rough handling.

during the laying of shingles cut therefrom, particularly when the shingles are interlocked bytabs 01' similar elements. Moreover, such shingles may be insufiicientlyflexible to withstand cracking when their interlocking portions are subjected to comparatively sharp bending during assembly on a roof. The fact is that the laying of such shingles must be done carefully, since, otherwise, the interlocking portions.

may be broken off, or torn awayfrom the main body. Even when such shingles are carefully handled, however, it may-be difficult to make them lie fiat or snugly against the roof particularly at the interlocking portions. When laying so-called roll roofing, the usual bituminized rag felts may give trouble over sharp comers because the felt base tends to crack or open up under sharp flexing or to. become so greatly weakened as to tear off under slight provocation.

It has been established that a bituminized felt whose felt base is made largely or entirely from refinedcellulose pulp in a substantially unhy- 6C1 drated condition represents a vast improvement over the conventional bituminized rag felt. For instance, the bituminization of a waterlaid felt whereinto substantially unhydrated refined wood pulp having an alpha cellulose content of say, at least about 93%, has entered as a principal raw material gives rise to a product of excellent moldability, pliability, and such high tear resistance as to be considered practically tearproof. Moreover, the felt itself can be folded 'on itself without cracking. We have now found that even when therefined but substantially unhydrated cellulosepulp is used as a subordinate fibrous component in the felt-making furnish, that is, in amount even less than by weight of the dry fibrous materials constituting the furnish, it is possible to arrive at felts "which, too, are practically as resistant to cracking when folded onto, themselves as felts consisting mostly of refined cellulose pulp in substantially unhydrated condition, and which, when bituminized, display remarkably better properties than the usual bituminized rag felts. Indeed, we have found that the use of as little as 20% to 30% by weight of refined but substantially unhydrated cellulose pulp in a felt-making furnish is all that is necessary to enhance the pliability and folding endurance of the bituminized felt enormously even though the tear resistance of the bituminized felt is not so markedly benefited. For many roofing purposes, however, the ultimate or best tear resistance in the bituminized felt may not be vital, but an enhanced pliability or moldability may be of tremendous advantage. The point is that by using a preponderant proportion of rags and a subordinate proportion of refined but substane tially unhydrated cellulose pulp as raw materials in the felt-making furnish, it is possible to arrive at bituminized felts which are surprisingly superior to the usual bituminized rag felts for danger of being cracked or trim at their interlocking portions, whereat they are weakest, and can be made to lie flatly against the roof more easily than the usual rag felt base shingles. It is thus seen that we accomplish the desired ends with a minimum usage of refined cellulose pulp, which is a far more expensive raw material than wool fiber, is added to the felt-making furnish,

the sharp-bend flexibility is improved, but the strength of the felt tends to drop rapidly. On the other hand, the simple addition of compar- "atively little refined cellulose pulp to the feltmaking furnish affords an inexpensive way of both realizing sharp-bend flexibility in the felt and of improving the toughnessof the bituminized felt. The interesting aspect of the results which we secure is that the effect of the refined but substantially unhydrated cellulose pulp is not largely or entirely obliterated by the larger proportion of hydrated but unrefined rag pulp entering into the felt-making furnish, which, if it were made from only rags as raw material, would yield felt tending to flake or crack open very badly on the surface when folded on itself. In

other words, it might reasonably be expected,

that the great dilution with inferior hydrated pulp which the refined but substantially unhydrated pulp undergoes would give rise to bituminized felts possessing little, if any, advantage over the usual bituminized rag felts. Apparently, the softness and other desirable qualities inhering in the refined but substantially unhydrated pulp persist in a felt containing only about 10% to 20% of such pulp and "are responsible for the qualities of good moldability, pliancy, and tear resistance in a bituminized felt. In other words, such impurities and hydrated cellulose as arise from the rag pulp in the felt-making furnish evidently remain external to the refined fibers, that is, do not exist in intimate association with the fiber wall of the refined fibers as impurities occur in an unrefined wood pulp, for

instance.

While theremay be various procedures falling within the purview ofthe present invention, we shall give typical practice such as may be advantageously adopted inpreparinga bituminized roofing felt in accordance with our invention. A beater engine may be charged with cheap rags such as are customarily employed for felt-making purposes and with suflicient water to ensure circulation of the mass. The beater roll may be put in operation with its knives or bars so clearing the bed-plate as to cut or reduce the rags sufliciently to yield a smooth .pulp or halfstuff satisfactory for felt formation. At this time, the

' the furnish even though the rags have inevitably refined pulp of wood or other origin having an alpha cellulose content of say, at least about 93%.

It is thus seen that the refined pulp is maintained in substantially unbeaten or unhydrated statein undergone considerable hydration or gelatinization wliilebeing reduced to a pulp. The mixed furnish may then be run off on a felt-making machine, the resulting felt bituminized as by passage through a bath of molten asphalt having a melting point of about 130 F. (ball and ring test) and at a temperature of about 385 to 400 F. in the bath, and the bituminized felt may be coated with blown asphalt or the like and be surfaced with ornamental, weather-resisting material, such as crushed, colored slate or its equivalent.

The refined cellulose pulp employed in the feltmaking furnish of the present invention may be prepared as by exposing the usual chemical wood pulps, e. g., kraft or sulphite pulp, to the action of alkaline liquors under conditions resulting in 'an extraction of a substantial proportion of the non-alpha cellulose components from the pulp, for instance, bringing the alpha cellulose content of the pulp to at least, say, about 93% or greater. In some instances, as when sulphite pulp is being refined, a dilute alkaline liquor and comparatively high temperature may be advantageously relied upon in bringing about this refinement. 0n the other hand, a pulp may be refined in strong alkaline liquors at comparatively low temperatures, for instance, in liquors of sumci'ent concentration to mercerize the pulp. In any case, however, the refined pulp entering into the felt-making furnish should be maintained in a substantially'unhydrated condition'in order to yield a bituminized sheet of the desired characteristics. When pulps are refined in alkaline liquors, the impurities existing in intimate asso- 5 ciation with the fiber wall are evidently leached out, leaving the fiber wall in a more or less etched condition. The softness and flexibility of the refined fibers evidently remain unimpaired even when such fibers are commingled with comp'ara- 2 tively impure hydrated rag pulp, whose impurities and hydrocellulose appear to remain as'a phase external to the refined pulp fibers.

We claim: I 1. A bituminized, waterlaid felt whose fibrous 5 base is made up essentially of at least about 60% to 85% of hydrated rag pulp and about 40% to 15% of substantially unhydrated wood pulp having an alpha cellulose content of at least about 2. A process which comprises beating unrefined rags in water to form a hydrated, feltablepulp, admixing with said pulp substantially unhydrated wood pulp 'having an alpha cellulose content of at least about 93% in amount to produce a furnish containing only about 15% to 40% of said wood pulp, making a waterlaid felt from said furnish, and bituminizing the felt.

. MILTON O. SCHUR.

WALTER L. HEARN.