Glass Compositions

This invention relates to improved glass compositions for fiberizable glass production.

In one of its more specific aspects, this invention relates to a fiberizable glass composition which provides improved dry strength of the fiber/binder matrix combination and water durability of the fiber itself.

In the production of glass fibers usable in the form of "wool" batts for insulation purposes, one of the more widely used processes is a centrifugal process in which glass, at temperatures above its liquidus, is emitted through the apertures of a rapidly rotating spinner. The glass is further attenuated by contact with blasts of hot gases, such as steam or combustion gases. The attenuated fibers are contacted with a binder, frequently of a phenol-formaldehyde or phenol-urea type, and are collected on a moving conveyor in the form of batts which are subsequently dried and packaged for shipment as insulation.

The composition of the chemicals which are combined to form the "batch", which is subsequently melted to form the glass, is important for many reasons, one of which is cost and a second of which includes the general properties of the batt itself, particularly as evidenced by the dry strength and water durability of the fibers contained therein.

There now has been discovered a glass composition which is less expensive than conventional batches and which, more importantly, in the form of fibers, reacts with phenol-based binders to facilitate the adherence of the pack as a unit and, hence, improves dry strength. These fibers also possess improved water durability.

The composition of this invention, in its preferred embodiment, comprises a glass batch consisting essentially by weight of:

The invention will be more easily understood by referring to the attached drawings in which:

FIG. 1 depicts the method of producing the fibers of this composition;

FIG. 2 is a graph of water durability for fibers for several glass compositions; and,

FIG. 3 is a graph showing the relative strength of certain glass fiber-binder matrix for several glass compositions.

Referring now to FIG. 1, there is shown a simplified fiber formation process, in elevation, in which glass is introduced into rotary spinner 1 through conduit 2, and glass fibers are ejected through apertures 3 as fibers 4. These fibers are further attenuated by hot gases originating in burners 5 and form a veil-like blanket 6 which falls towards movable belt 8. As the veil-like blanket moves past nozzles 7, it is sprayed with binder, after which it falls and forms a blanket 9 on movable belt 8.

In general, the composition of this invention can comprise a glass or a glass batch consisting essentially by weight of:

Also according to this invention there is provided a method of improving the adherence between a phenol-based binder composition and glass fibers which comprises forming glass fibers from a batch composition and introducing the phenol-based binder composition into contact with the glass fibers, the batch composition consisting essentially of one of the compositions given above.

Various comparisons were made between the glass of this invention, B2, that is, the glass containing 2 weight percent B.sub.2 O.sub.3 and other glasses containing greater, or lesser, amounts of B.sub.2 O.sub.3. The analyses of these glasses were as follows:

Fibers were made from all of the above glasses. In a water durability test, which was a modification of ASTM C225-73, all specimens were subjected under comparable conditions to water at 96.degree. C. for 24 hours. The results are shown in FIG. 2. This figure indicates that the glass of this invention, B2, had a weight loss of about 1.3 weight percent, that is, a better water durability than any of the other glasses tested. In FIG. 2, the abscissa, "Bulk Boron Concentration," refers to the total boron concentration in the glass fiber and not merely to the boron concentration on the surface of the fiber.

In separate determinations, the glass fiber surface concentration of B.sub.2 O.sub.3 of the various glasses was determined as follows:

These glasses were subjected to comparable treatments and strength determinations made. In these treatments, a like number of strands of glass were coated with a binder comprising a phenol-urea reaction product (75.9 g phenol/36.4 g of 50% urea). This product was comparable to those well known and conventionally employed in the industry. The glass bundles were formed into relatively uniform, circular bundles of equal length. These bundles were then subjected to breaking tests until failure occurred. The results are shown on FIG. 3 which indicates that the inventive composition, B2 which had the highest surface concentration of boron, exhibited the greatest strength.

It will be evident from the foregoing that the inventive glass of the defined composition exhibits both improved dry strength and water durability.

It will be evident from the foregoing that various modifications can be made to this invention. Such, however, are considered within the scope of the invention.