Controlled time-release algae resistant roofing system

Abstract

Time-release algae-resistant roofing granules have a base particle including an algaecide and an outer coating layer including another algaecide. The at least two algaecides are released over different predetermined periods. The outer layer protects the base particle from exposure to the environment for a predetermined period, then fails catastrophically so that the interior algaecide can be released.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]The present application claims the priority of U.S. Provisional Patent Application 60 / 597,903 filed Dec. 23, 2005.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to asphalt roofing shingles, protective granules for such shingles, and processes for making such granules and shingles.[0004]2. Brief Description of the Prior Art[0005]Pigment-coated mineral rocks are commonly used as color granules in roofing applications to provide aesthetic as well as protective functions to the asphalt shingles. Dark blotches or streaks sometimes appear on the surfaces of asphalt shingles, especially in warmer humid climates, because of the growth of algae and other microorganisms. The predominant species responsible is Gloeocapsa sp, a blue-green algae. Other microbial growth, including fungi, moss and lichen, can also occur under proper conditions, for example, in a shady and / or persistently damp environment. In...

AI Technical Summary

Benefits of technology

[0017]The present invention provides a process for producing time-release algae-resistant roofing granules. This process comprises providing base particles comprising at least one first algaecidal material. As disclosed below, the base particles can be prepared in a number of different ways. The base particles are in turn encapsulated with an outer coating composition including at least one second algaecidal material to form an outer layer. The at least one second algaecidal material preferably differs from the at least one first algaecidal material. The encapsulating outer layer protects the base particles from exposure to the environment. The outer coating composition is preferably selected such that the outer layer fails catastrophically after a predetermined period thereby exposing the base particles to the environment. In the interim, during the predetermined period, the at least one second algaecidal material is releasable from the outer layer, thereby providing algae resistance. After the outer layer fails, the base particle is exposed to the environment, and the at least one first algaecidal material thereafter provides algae resistance.

[0036]In a presently preferred embodiment of the algae-resistant roofing granules of the present invention, the granules further comprise an interlayer between the base particle and the outer layer. The interlayer preferably enhances the release of the at least one second algaecidal material under predetermined conditions. In one aspect of the present invention, the interlayer preferably includes a water-swellable resin. Preferably, the water-swellable resin is selected from the group consisting of natural or synthetic water-swellable resins, starch, cellulose, and gums. In another aspect of the process of the present invention, the interlayer preferably includes a UV degradable material, and may optionally include a photocatalytic material. Preferably, the UV degradable polymeric material is selected from the group consisting of virgin and recycled polyolefins and polyolefin copolymers, and combinations thereof.

[0043]It is an object of the present invention to provide a process for preparing roofing shingles to have algae-resistance that can be customized to the specific geographic region in which the shingles are intended to be used.

[0045]It is a further object of the present invention to provide asphalt roofing shingles resistant to algae over extended periods.

Problems solved by technology

In addition to being aesthetically unpleasant, the discoloration can lead to heat buildup and accelerate premature roofing failure.

Eventually, severe discoloration of the entire roof can occur.

However, frequent washing and cleaning with cleaning solutions is required, since the effective duration of such treatments is rather short.

However, such topical treatments are also usually effective only for short term, typically one to two years.

However, these biocides typically persist for around ten years, and in some limited cases, for periods approaching fifteen years.

One drawback is these compounds are effective against only one microbe, Gloeocapsa sp.

Images