Gypsum boards with glass fiber reinforcements having a titanate or zirconate coupling coating

Abstract

A bond is created between a gypsum matrix and titanium or zirconium based coupling coating applied onto a glass fiber during gypsum board cure. The commercially available titanium or zirconium based coupling has a generic formula of the type [RO-}-nTi—[—OXR′Y]4-n or [RO-}-nZr—[—OXR′Y]4-n. These coupling compositions chemically bond to glass fibers by replacing the —OH groups present on the glass fibers in aqueous solutions with Ti—O or Zr—O bonds. In order to bond with calcium ions in hydrated gypsum crystals, the X functionality is selected to be a phosphate or pyrophosphato group. The bond between the glass fiber and the titanium or zirconium based coupling composition is due to the formation of a monolayer, while the bond between the hydrated gypsum crystal and the coupling composition is intermittent due the acicular structure of gypsum crystals. The titanium or zirconium based coupling composition coating on glass fibers bonded to the gypsum matrix results in load transfer between the gypsum matrix and the glass fibers, resulting in improved flexure strength and nail pullout resistance. The Titanate / Zirconate can also be used as a board mechanical properties enhancing agent without addition of glass fiber.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to glass fibers used in products for building construction; and more particularly, to a titanium or zirconium containing sizing or coupling composition and a glass fiber coupling coating process that bonds to a gypsum matrix in a gypsum board, thereby providing superior flexure strength and nail pullout resistance. [0003] 2. Description of the Prior Art [0004] Glass fibers are commonly used in the production of a wide variety of articles, notably including many building products including gypsum boards. The fibers are employed in many forms, including individual fibers, strands containing plural fibers, and rovings. These fiber products, in turn, may be used in discrete form or they may be assembled into woven and non-woven fabric or mats and incorporated into a gypsum matrix. [0005] Glass fiber filaments or strands that are to be incorporated in a gypsum matrix, either as individual fi...

AI Technical Summary

Benefits of technology

[0030] The present invention provides a high strength, improved flexure resistant and improved nail pull out resistant gypsum board with glass fiber reinforcement that is bonded to the gypsum matrix through the incorporation of a coupling agent. The coupling agent chemically bonds to the glass fibers and to the gypsum matrix. The coupling agent provides a thin layer of coating on the glass fibers, with the hydroxyl group present on glass fibers replaced by a Ti—O or Zr—O group; while phosphate or pyrophosphate functionality potentially creates a chemical bond with calcium ions of hydrated gypsum crystal when the gypsum board is dried. The composition is suitable for use in aqueous mediums wherein different functionality of the coupling agent disassociates forming these chemical bonds.

[0035] The quantity of coupling agent is selected to be in the range of 0.01 to 3 weight percent of the glass fiber weight, providing a thin layer of coating on the glass fiber's external surface, sufficient to provide a bond. Excessive amounts of coupling agents do not provide the gypsum board strength improvement since multiple layers interfere with each other. During the gypsum cure cycle, the excess water is evaporated and the coupling layer coated glass fiber comes into intimate contact with acicular gypsum crystals, forming a localized and intermittent chemical bond. When the board is flexed or subjected to stress during nail pullout, the glass fiber—gypsum matrix interface is stressed. Instead of the glass fiber separating from the gypsum matrix the structure is retained by the chemical nature of the bond between the gypsum matrix and the glass fiber's external surface. The bond also provides energy absorption due to crack deflection and the board absorbs significant energy prior to breakage, thereby providing increased flexure strength.

Problems solved by technology

However, actual mat properties are generally found to be unpredictable.

As a result, formulation of sizing has generally been carried out by trial and error.

Moreover, the multiple constituents used in sizing, and their interacting roles, make it especially difficult to predict or achieve fully satisfactory properties in glass fibers dispersed into a gypsum matrix, either as fibers or as finished products like non-woven mats.

However, replacement of asbestos fibers with glass is said not to have the expected benefit, in that the glass fibers tend to adhere together and thereby inhibit the removal of water during mat or board production.

The '136 patent does not disclose a sizing that contains titanium or zirconium compositions

Significantly, the '538 patent does not disclose or suggest any sizing composition that includes a titanium or zirconium composition.

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