Microfibrillated articles comprising hydrophillic component

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Reexamination Certificate

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C428S304400, C428S332000, C428S359000, C428S364000

Reexamination Certificate

active

06692823

ABSTRACT:

The invention relates to hydrophilic microfibrillated articles; hydrophilic microfibers and microflakes; and methods of preparing each. The microfibrillated articles exhibit hydrophilic properties and wettability, and can be incorporated into or used as a large variety of useful products, such as water-absorbing wipes, mops, mats, tape backings, filters, fabrics, fabric replacements, and nearly any variety of other useful industrial and commercial products where hydrophilicity is desired.
BACKGROUND
Materials that can be processed to form microfiber-bearing surfaces have been identified, including oriented polypropylene. See, e.g., U.S. Pat. No. 6,110,588. Microfibrillatable materials of U.S. Pat. No. 6,110,588 can be prepared from certain materials and processed using various techniques to produce oriented films capable of being microfibrillated. Microfibrillation of these oriented films results in, e.g., a microfiber-bearing surface, the microfiber being a specific size and shape.
Fibrillated (e.g., microfibrillated) surfaces and articles exhibit a variety of uses, by themselves or in combination with other materials that may or may not include a fibrillated surface. For example, certain fibrillated articles can be used as a wipe, a wrap, a backing, a fabric, a filter, etc. In some of these applications, it can be desirable to select a fibrillated surface that exhibits a physical or chemical property suited for a particular application. For instance, it can be useful in certain applications to select a fibrillated surface that includes any one or more of hydrophilic, hydrophobic, oleophilic, oleophobic, inert or stain resistant, electrostatically chargeable material, etc.
Certain melt-processable polymers that can be used to prepare microfibrillatable and microfibrillated materials are not especially hydrophilic. Polyolefins such as polypropylene, for example, and other similar polymeric materials useful in forming microfibrillated surfaces, are generally not hydrophilic due to their non-polar nature. Thus, it would be desirable to identify methods or materials that could be used to improve the hydrophilicity of such melt-processable polymers useful in forming microfibrillated surfaces. It can be unpredictable, however, whether or not the chemistry of melt-processable materials and hydrophilic materials will allow the hydrophilic material to be incorporated into and retained within a melt-processable polymer, through processing of the melt-processable polymer en route to a microfibrillated surface. As a single example, certain water-soluble hydrophilic surfactants or hydrophilic polymers may be expected to be washed away or dissolved during hydroentanglement or other microfibrillation processes, and therefore may not be expected to remain with a microfibrillated article to improve hydrophilicity.
Furthermore, in preparing a microfibrillated article, selection of ingredients can be important to succeed in producing a fibrillated surface. A typical method of preparing a microfibrillated article includes: selecting a polymer that is capable of being melt-processed to form a fibrillated surface such as a film; melt-processing the film so that the film is capable of being fibrillated, such as by stretching, orienting, lengthening, etc.; and microfibrillating, e.g., hydroentangling, the film to disrupt the surface of the film in a manner to form a microfibrillated surface. Each of the steps must be performed, and the materials of the film must be selected, with the design of providing an extruded, oriented film that has a morphology and mechanical and chemical makeup to allow the film to be processed to a microfibrillated surface.
While various additives might be thought to be generally useful if added to a melt-processable or microfibrillatable polymer useful to prepare a microfibrillated article, a balance of morphology, e.g., crystallinity, and other properties such as the presence and concentration of voids, molecular orientation, polymeric strength, etc., is required to extract a microfibrillated surface from a melt-processable polymeric material. Any additive material included in a polymer or polymeric film being processed to form a microfibrillated article has the potential to detrimentally affect the ability of the film material to be processed to a microfibrillated surface. For example, an additive may frustrate the ability of a polymer to be melt-processed (e.g., extruded), calendered and/or length oriented, or microfibrillated. The additive may, for example, prevent a useful mixture from being formed by melt-processing; weaken the composition of a melt-processed polymeric material, preventing processing such as orientation, stretching, or calendering, etc.; or may allow melt-processing and orienting, but may have the effect of frustrating microfibrillation, e.g., by not allowing the formation of voids, or by otherwise disturbing the morphology, crystallinity, or other physical features necessary in a film to allow microfibrillation.
New and different microfibrillated articles and methods for their preparation are always desirable. In particular, there continues to be a need for microfibrillated articles that exhibit improved properties such as improved wettability or hydrophilicity.
SUMMARY OF THE INVENTION
The invention relates to hydrophilic microfibrillated microflake or microfiber articles and their preparation. The microflakes or microfibers can be prepared by including a hydrophilic component with a melt-processable polymer, in appropriate amounts, so that the melt-processable mixture of melt-processable polymer and hydrophilic material may be processed to be microfibrillated to form microflakes or microfibers.
According to the invention, a hydrophilic component can be included in a melt-processable polymer in an amount that will improve the hydrophilicity of the material, but will at the same time not prevent the material from being melt-processed to form a film, followed by other necessary processing to form a microfibrillated microfiber or microflake surface.
The invention can be accomplished using any of a variety of melt-processable polymers capable of being processed to form microflakes or microfibers. Certain important examples include polyolefins such as polyethylene, polypropylene, polyester, and their mixtures, but many others as well, with or without additional ingredients such as a void initiating agent or blowing agent.
The invention can be accomplished using any of a variety of hydrophilic components combined with the melt-processable polymer in an amount that will still allow a variety of processing steps that result in a microfibrillated surface. Important examples include certain hydrophilic polymers and certain hydrophilic surfactants, particularly nonionic hydrophilic surfactants.
As used herein, “hydrophilic,” “hydrophilicity,” and similar terms are used to describe materials that can be wet by water, by aqueous solutions of acids and bases (e.g., aqueous potassium hydroxide), by polar liquids (e.g. sulfuric acid and ethylene glycol), or combinations thereof. (See, U.S. Pat. No. 5,804,625). In certain preferred embodiments of the invention, microfibrillated microflake or microfiber articles can be sufficiently hydrophilic to about 5 or 10 grams of water per gram of microfibrillated article. Other embodiments of microfibrillated articles of the invention can be sufficiently hydrophilic to have the ability to increase the amount of absorbed water at least 30% and up to 1000% or more, e.g., 200%, compared with the same article without the hydrophilic component.
Thus, an aspect of the invention relates to a hydrophilic microfibrillated article that includes an oriented melt-processed polymeric material, wherein the polymeric material includes a melt-processed polymer that is a polypropylene, a polyethylene, or a mixture thereof, and hydrophilic component preferably in an amount effective to improve the hydrophilicity of the microfibrillated article.
Another aspect of the invention relates to a hydrophilic article that includes an oriented melt-pro

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