Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2000-07-13
2002-03-26
Sellers, Robert E. L. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S187000, C604S370000
Reexamination Certificate
active
06362277
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a water-degradable or flushable polyolefin-containing film. More particularly, the present invention relates to a water-degradable or flushable polyolefin-containing film having greater than about 55 weight percent of a modified polyolefin and less than about 45 weight percent of poly(ethylene oxide).
BACKGROUND OF THE INVENTION
Such articles typically have some portion, usually the backing layer, liner, or baffle constructed of a liquid repellent film material. This repellent material is appropriately constructed to minimize or prevent the exudation of the absorbed liquid from the article and to obtain greater utilization of the absorbent capacity of the product. The liquid repellent film commonly used includes plastic materials such as polyethylene films and the like.
Although such products are relatively inexpensive, sanitary and easy to use, disposal of a soiled product is not without its problems. With greater interest being placed in protecting the environment today, there is a need to develop materials that are more compatible with the existing and developing waste disposal technologies while still delivering performance consumers have come to expect. An ideal disposal alternative would be to use municipal sewage treatment and private residential septic systems. Products suited for disposal in sewage systems can be flushed down a convenient toilet and are termed “flushable.” While flushing such articles would be convenient, the liquid repellent material which normally does not disintegrate in water tends to plug toilets and sewer pipes. It therefore becomes necessary, although undesirable, to separate the barrier film material from the absorbent article prior to flushing.
In addition to the article itself, typically the packaging in which the disposable article is distributed is also made from a water resistant material. Water resistivity is necessary to prevent the degradation of the packaging from environmental conditions and to protect the disposable articles therein. Although this packaging may be safely stored with other refuse for commercial disposal, and especially in the case of individual packaging of the products, it is often more convenient to dispose of the packaging in the toilet with the discarded disposable article. However, in the cases where such packaging is composed of a water resistant material, plugging of the drains to the toilet typically results.
Desirably, a commercial, flushable product should be relatively responsive to water and be transportable in a sewer system. Commercially available water-soluble polymers, such as polyethylene oxide (PEO), polyvinyl alcohol (PVOH), acrylamide polymers, acrylic acid-based polymers, and cellulose derivatives, possess the desired characteristics for flushability, such as water solubility and/or water dispersibility. However, due to their in-use degradability and storage degradation, these materials function poorly as components in personal care products. Other disadvantages are that these polymers are difficult to process and are substantially more expensive than polyolefins.
The requirements for a functional and flushable product provide a substantial challenge in finding suitable materials with the desired properties. In an attempt to overcome the flushability problem of a water resistant film the prior art has modified the water resistant polymer. One of the more useful ways of modifying polymers involves blending them with other polymers of different structures and properties.
Polymer blends of polyolefins and poly(ethylene oxide) have been shown to be water modifiable at expectedly low weight % polyolefin levels. Such blends would be anticipated to be flushable when exposed to water in a toilet but do not possess the dry mechanical properties required for functionality in use. Moreover, the high content of poly(ethylene oxide) makes such materials prohibitively expensive for use in a disposable personal hygiene article such as a sanitary napkin, diaper and the like. Polymer blends of polyolefins and poly(ethylene oxide) containing greater than about weight percent of polyolefin are generally water resistant and are not water modifiable.
In view of the problems of the prior art, it remains highly desirable to provide a water modifiable film having a substantial portion of thereof composed of a polyolefin. More desirably, the water modifiable film should have greater than about 55 weight percent of a polyolefin. When dry, the film should have the mechanical properties necessary for functionality. When wet, the films should lose at least a portion of its mechanical properties which would render the film flushable and transportable in a sewer system. Such films could be used for making flushable barrier films for personal care products.
It is therefore an object of the invention to provide a polyolefin-containing film that is water modifiable or water-degradable which contains higher levels of polyolefin content. More specifically, it is an object of the invention to provide a polyolefin-containing film having greater than about 55 weight percent of a polyolefin and less than about 45 weight percent of poly(ethylene oxide) that is water-modifiable or water degradable.
SUMMARY OF THE INVENTION
In its principal embodiment, the present invention provides a water-modifiable or water-degradable film comprising at least about 55 weight percent of a modified polyolefin and no more than about 45 weight percent of poly(ethylene oxide). The polyolefin is modified by having from about 0.1 weight percent to about 30 weight percent, based on the total weight of the polyolefin and poly(ethylene oxide), of a monomer grafted onto the polyolefin backbone. Preferably the monomer is 2-hydroxyethyl methacrylate or polyethylene glycol ethyl ether methacrylate. The film of the invention has a loss of at least 10% in two or more tensile properties selected from percent strain-to-break, peak stress, energy-to-break and modulus after being immersed in water for 30 seconds.
In an alternative embodiment, the present invention provides a flushable personal care article having a backing or barrier layer comprising a water-modifiable or water-degradable film comprising greater than about 55 weight percent of a modified polyolefin and less than about 45 weight percent of poly(ethylene oxide). The polyolefin is modified by having from about 0.1 weight percent to about 30 weight percent, based on the total weight of the polyolefin and poly(ethylene oxide), of a monomer grafted onto the polyolefin backbone. Preferably the monomer is 2-hydroxy-ethyl methacrylate or polyethylene glycol ethyl ether methacrylate. The film comprising the backing or barrier layer of the invention has a loss of at least 10% in two or more tensile properties selected from percent strain-to-break, peak stress, energy-to-break and modulus after being immersed in water for 30 seconds.
DETAILED DESCRIPTION OF THE INVENTION
As used herein “water modifiable” means that a four mil thick film (one mil equals 0.001 of an inch or 0.025 mm), when immersed in water for 30 seconds, will have modified by greater than 10% two or more of the following tensile properties: percent strain-to-break, peak stress, energy-to-break and modulus. To determine the degree of modification, the “wet” values are compared to the pre-immersed or “dry” film values.
The term “personal care product” or “personal care article” means articles such as infant diapers, sanitary napkins, adult incontinence garments, and the like.
By the term “backing layer” or “barrier layer” is meant that component of an infant diaper, sanitary napkin, adult incontinence garment or the like which is worn during normal use furthest from the user's body and which serves to minimize or prevent the exudation of the absorbed liquid.
Although the present invention is described with reference to a water modifiable film and, in particular, to personal care articles having a backing layer, liner, or barrier layer comprising such films, one skilled in the art will unders
Schertz David Michael
Wang James Hongxue
Sellers Robert E. L.
Wilheim Thomas D.
Wilheim Law Service
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