Glass Compositions and Fibers Therefrom

This invention relates to sodium barium borosilicate glass compositions. Fibers from these compositions make glass fiber insulation.

Glass fiber insulation is well known and has been a commercial product for a long period of time. The insulation is made from intertwined soda lime alumina borosilicate glass fiber which a binder holds together. The binder may be any suitable material but quite commonly is a phenolformaldehyde resin or a ureaformaldehyde resin. These binders are well known and a spray nozzle generally applies them to the glass fibers as hot gases attenuate the fibers from a rotating device, commonly called a spinner. A conveyer collects the binder-coated fibers in the form of a blanket, and heat cures the blanket to produce the final insulation. The process produces various densities by varying the conveyor speed and the thickness of the cured insulation.

The German government has proposed regulations for glass fibers. Glass fiber compositions meeting the regulations are considered to be free of suspicion. The problem, however, for the manufacturer is to produce glass fibers which meet the regulations and standard criteria. These glasses must meet the proposed regulations, be fiberizable in standard wool processes, have sufficient durability and have acceptable insulating properties.

We have developed glass compositions which meet all the criteria. Our glasses have a high BaO content, a high soda content and contain small amounts of alumina. The glass compositions meet the proposed German regulations. They have a numerical index (KI) greater than or equal to 40. Standard wool processes easily produce fibers from these compositions. The difference (delta T) between the temperature where the glass has a viscosity of 1,000 poise and the liquidus temperature generally is 50.degree. F. and is often 200.degree. F. or greater. Durability as shown by fiber weight loss is good and is often less than 5% fiber weight loss after 24 hours in water at 205.degree. F.

We made measurements of viscosity, liquidus and durability for a number of glasses with KI.gtoreq.40. The measurements indicated a compositional region of glasses which are useful for production of glass fiber insulation. This range is as follows for the major components:

and less than about 10% of any or all of ZnO, TiO.sub.2, Fe.sub.2 O.sub.3, ZrO.sub.2, SrO or Li.sub.2 O, the total being 100% by weight, wherein each glass composition has a KI value equal to or greater than 40.

More preferably, the glass compositions consist essentially of:

and less than about 5% of any or all of ZnO, TiO.sub.2, Fe.sub.2 O.sub.3, ZrO.sub.2, SrO or Li.sub.2 O, the total being 100% by weight, and wherein each glass composition has a KI value equal to or greater than 40.

Even more preferably, the glass compositions have a BaO content of 5 to 30 weight percent and less than about 2% of any or all of ZnO, TiO.sub.2, Fe.sub.2 O.sub.3, ZrO.sub.2, SrO or Li.sub.2 O. Even more preferably the glass compositions have a a BaO combat of 12 to 25 weight percent, and less than 2% of any or all of ZnO, TiO.sub.2, Fe.sub.2 O.sub.3, ZrO.sub.2, SrO or Li.sub.2 O.

Insulation products of these glass fibers can be produced from a conventional fiber forming process.

The German regulation requires a numerical index (KI) greater than or equal to 40 to be considered free of suspicion. The index is calculated by KI=.SIGMA.(Na.sub.2 O, K.sub.2 O, CaO, MgO, BaO, B.sub.2 O.sub.3)--2Al.sub.2 O.sub.3. This places severe restrictions on alumina levels and anything not included in the index, such as silica. The obvious choice is to lower alumina to very low levels. These glasses, however, have poor durabilities and most could not be fiberized by a standard wool process. We discovered that high BaO levels yielded glasses with significantly improved durability and fiberizability by standard processes.

We designed an array of glasses to show the effect of glass composition in this narrow field on select properties. All glasses are shown together with measured properties in the following table.

Examples of the compositions are given in the following table. All the glass compositions have KI index of 40 or higher.

Glass fibers of the present invention have the following compositions. Most of the compositions have measured forming temperatures (the temperature where the viscosity of the glass is about 1,000 poise) and liquidus temperatures.