Method for producing a wet-laid fiber mat

Abstract

A method is provided for forming a wet-laid nonwoven glass fiber mat comprised of a plurality of bundles of fibers. The method includes the steps of adding chopped fibers to an aqueous slurry containing a sufficient amount of a suitable hydrophobic agent to cause the fibers to form a plurality of bundles. The fibers are then formed into a mat which may be used in a number of reinforcement applications. A method is also provided for modifying the components in the water slurry to produce mats comprising either bundles of fibers or dispersed fibers.

Description

TECHNICAL FIELD AND INDUSTRIAL APPLICABILITY [0001] The present invention relates to a process for producing a non-woven fiber mat, and more particularly, to a wet-laid process for forming a glass fiber mat comprised of small bundles of glass fibers. BACKGROUND OF THE INVENTION [0002] Two main techniques utilized for producing glass fiber mats are wet-laid processing and dry-laid processing. Typically, in a wet-laid process, an aqueous slurry containing dispersed fibers and a variety of other components such as surfactants, viscosity modifiers, defoaming agents, or other chemical agents is prepared and sufficiently agitated to disperse the fibers throughout the slurry composition. The aqueous slurry is then deposited onto a moving screen, chain or fabric that retains the majority of the fibers while allowing a substantial portion of the water to be removed and thereby form a fiber web supported by the upper surfaces of the screen. [0003] A binder composition may then be applied to t...

AI Technical Summary

Benefits of technology

The present invention provides a process for producing lightweight glass fiber mats that are uniform in weight and have a porous structure. This process involves using a modified size composition that promotes the formation of fiber bundles within the slurry without adding a hydrophobic agent directly to the slurry. The resulting mat comprises bundles of chopped fibers that can be small or large. The process also allows for the production of mats with dispersed fibers by modifying the size composition or adding a surfactant. The resulting mats have a basis weight of about 40 to 550 g / m2 and a thickness of about 0.25 to 0.50 inches. The process is economically competitive and promotes the use of wet-laid glass fiber mats.

Problems solved by technology

However, conventional dry-laid processes tend to produce mats are of a less uniform weight when compared with mats produced by a wet-laid process, i.e., different areas of the mats have different weights and / or fiber densities.

At lower basis weights below about 300 g / m2, the relatively poor small-scale weight uniformity of the air-laid process mat becomes increasingly apparent in terms of uneven distribution of the fibers.

As a result, machine productivity is also sacrificed because the conveyor speed cannot be increased in proportion to the reduction in bias weight of the mat without further degrading the uniformity.

In addition, processes utilizing dry-chopped input fibers tend to be more expensive than those utilizing wet-chopped input fibers because the fibers in a dry-laid process are dried and packaged in separate steps before being chopped offline, while size can be applied directly to the manufactured fibers shortly before they are chopped to form the chopped fibers that will be added to the aqueous slurry.

However, because such mats still include a number of dispersed fibers in addition to the fiber bundles, they have proven generally unsuitable for applications in which higher porosities are desired or necessary.

This result is particularly undesirable in reinforcement applications because the longer fibers tend to be visible in the final molded product and detract from the product's appearance.

Although this method improved the uniformity and porosity of the resulting fiber mat, it was difficult to control on a commercial scale and the addition of the hydrophobic agent was associated with certain negative effects on subsequent products.

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