Fiber cement composite materials using cellulose fibers loaded with inorganic and/or organic substances

Abstract

This invention discloses a new technology related to cellulose fiber reinforced cement composite materials using the loaded cellulose fibers. This invention discloses four aspects of the technology: fiber treatment, formulation, method and final product. This technology advantageously provides fiber cement building materials with the desirable characteristics of reduced water absorption, reduced rate of water absorption, lower water migration, and lower water permeability. This invention also impart the final products improved freeze-thaw resistance, reduced efflorescence, reduced chemical dissolution and re-deposition, and improved rot and fire resistances, compared to conventional fiber cement products. These improved attributes are gained without loss in dimensional stability, strength, strain or toughness.

Description

RELATED APPLICATIONS [0001] This application is a continuation of U.S. patent application Ser. No. 10 / 754,137 filed Jan. 9, 2004 entitled “FIBER CEMENT COMPOSITE MATERIALS USING CELLULOSE FIBERS LOADED WITH INORGANIC AND / OR ORGANIC SUBSTANCE” which is a divisional of U.S. patent application Ser. No. 09 / 969,957 filed on Oct. 2, 2001 entitled “FIBER CEMENT COMPOSITE MATERIALS USING CELLULOSE FIBERS LOADED WITH INORGANIC AND / OR ORGANIC SUBSTANCES”, now U.S. Pat. No. 6,676,744. This application also claims the benefit of U.S. Provisional Application No. 60 / 237,850, filed on Oct. 4, 2000, which is hereby incorporated by reference in its entirety.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] This invention relates to cellulose fiber reinforced cement composite materials using loaded cellulose fibers, including formulations, methods of manufacture and final products with improved material properties relating to the same. [0004] 2. Description of the Related Art [0005]...

AI Technical Summary

Benefits of technology

[0022] The preferred embodiments of the present invention disclose a new technology, namely cellulose fiber reinforced cement composite materials using loaded cellulose fibers. The cellulose fibers are preferably individualized fibers, wherein at least a portion of the lignin has been removed from the cellulose. Aspects of the technology disclosed include formulations, methods of making the composite materials, and final materials and their properties. This technology advantageously provides fiber cement building materials with the desirable characteristics of reduced water absorption, reduced rate of water absorption, lower water migration, and lower water permeability.

[0023] Final products made from these materials have improved freeze-thaw resistance, reduced efflorescence, reduced dissolution and re-deposition of water-soluble matrix components in natural weathering. It is possible, with the proper fiber loading, to improve other product properties, for example, rot and fire resistances, compared to conventional fiber cement products. It has been found, surprisingly, that these improved attributes are gained without loss in dimensional stability, strength, strain or toughness. Even more surprisingly, strength, strain and toughness may even be improved with less cellulose being used than conventional cellulose fiber cement composite materials.

[0024] More particularly, Applicant has found that by filling, or partially filling the internal hollow spaces of cellulose fibers with insoluble inorganic and / or organic materials, an engineered cellulose fiber can be produced that, when used in cement composites, still has the advantages of regular cellulose fibers of refining, autoclaving, and manufacture without pressing, but the resultant fiber cement material also approaches or exceeds the performance advantages of artificial fibers such as PVA, in terms of the rate and amount of water absorption when used in fiber reinforced cement composite materials. What is more surprising is that smaller quantities of fibers may be used, so that the cost of loading or partially loading the fiber can be offset by the lower usage of the fiber in products, without a reduction in the important physical properties of the material, such as strength and toughness.

Problems solved by technology

The disadvantage of these products was that the high-density matrix did not allow nailing, and methods of fixing involved pre-drilled holes.

Since silica, even when ground, is much cheaper than cement, and since the autoclave curing time is much less than the air cured curing time, this became a common, but by no means universal manufacturing method.

However, cellulose reinforced cement products are more susceptible to water induced changes, compared to asbestos cement composite materials.

Hence, asbestos reinforced fiber cement products are themselves strong, stiff (also brittle), and could be used in many hostile environments, except highly acidic environments where the cement itself is rapidly attacked chemically.

The wet / dry cycling that asbestos roofing products were subjected to, often caused a few problems, primarily efflorescence, caused by the dissolution of chemicals inside the products when wet, followed by the deposition of these chemicals on the surfaces of the products when dried.

Efflorescence caused aesthetic degradation of roofing products in particular, and many attempts were made to reduce it.

This product is air-cured, since PVA fibers are, in general, not autoclave stable.

The great disadvantage of these products is a very large increase in material and manufacturing process costs.

Thick organic coatings are also expensive, and hydraulic presses are a high cost manufacture step.

However, cellulose fiber cement materials can have performance drawbacks such as lower resistance to water induced damages, higher water permeability, and higher water migration ability (also known as wicking) compared to asbestos cement composite materials.

These drawbacks are largely due to the presence of water conducting channels and voids in the cellulose fiber lumens and cell walls.

As such, conventional cellulose fibers can cause the material to have a higher saturated mass, poor wet to dry dimensional stability, lower saturated strength, and decreased resistance to water damage.

Because the materials are easier to saturate with water, the products also are far more susceptible to freeze / thaw damage.

However, for vertical products, or eaves and soffit linings, and for internal linings, none of these water-induced disadvantages are very relevant.

The primary problem with this technology is increased material and manufacturing cost.

The primary problem with this technology is increased rate, and quantity of water absorption into the product when wet.

However, most of these references are directed to increasing the bond strength of the fibrous material to the cement, rather than addressing the water and moisture related issues of cellulose and / or other fibers.

However, the teachings of the patents above are not specifically directed to the use of partially delignified and individualized fibers, which generally bond well with cement and therefore would not require such treatment methods.

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