Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
1999-10-13
2002-05-21
Cooney, Jr., John M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C521S155000, C521S170000, C521S172000, C521S174000
Reexamination Certificate
active
06391933
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
Polyurethane foam material having substantially windowless.cells. Certain flexible foams of this type have superior liquid absorbent and wiping properties.
2. Discussion of the Prior Art
Natural sponges have excellent wiping and absorbing qualities. They are however very expensive and are therefore seldom still used for ordinary domestic and industrial cleaning. Synthetic sponges both the so-called hydrophilic plastic foams and the expanded cellulosic structures, have been made by various techniques in an attempt to produce the optimum household cleaning and wiping sponge. While some of these materials have succeeded to a greater or lesser degree, they have proven in use, to be less than optimal products.
The manufacturing of flexible urethane foam and for that matter urethane foam sponges, is well known. Recently, foams with a viscoelastic property have been produced for the furniture industry in an attempt to duplicate the cushioning characteristics of polyester batting. These foams typically have a slower recovery rate than conventional foams and have a rubbery characteristic. This rubbery characteristic can be enhanced by lowering the TDI index. These foams were developed by Arco Chemical using their hydroxyl U-1000 polyol and these properties are now well known to the industry.
SUMMARY OF THE INVENTION
It was therefore found desirable to address these various shortcomings, to yield very practical, absorbent, cleaning devices. It has been found that by modifying urethane foam systems in quite a unique and unexpected manner, a highly satisfactory, absorbent and long lasting sponge can be produced having very practical wiping characteristics and yielding a product that has both absorbent and wiping properties heretofore not available.
Unexpectedly, it was found that slow recovery or low resilience or viscoelastic foams, when combined with cell openers and surfactants, yield a foam with excellent wiping characteristics. This is due to the drag produced as the foam is wiped across a surface yielding almost squeegee-like effect. Foams of this nature can be defined as those foams having a ball rebound value of less than 25% and preferably less than 20% using the Ball Rebound Test described in ASTM D3574.
There is provided a method of making polyurethane foams having substantially windowless cells, conventionally called open celled foams. The foams in this category which are formulated to be flexible are especially suitable as a sponge material because the are not only absorbent of the bulk liquid but also have superior wiping properties. This means that it essentially drys the previously wet surface as well. This latter property has heretofore not been readily available.
The ingredients for a formulation for making the foams of the present invention comprise: at least one polyol, at least one catalyst, a silicone foam stabilizer, a blowing agent, toluene diisocyanate, and a cell openers. Where flexible foams for sponges are desired a surfactant is also present. This surfactant may be itself act as the cell opener or “cell window remover” or may be used with cell openers of different chemistry. The method of making the foams with these novel combinations of ingredients is essentially conventional although there are certain modifications which will be set forth in detail below. In this method the ingredients are injected into a reaction chamber in at least two streams.
It has been found that surfactants, particularly wetting agents, incorporated into the aforementioned rubbery polyurethane foam formulation, increases the foams ability to wet out in water. This effect is heightened when less than the theoretical amount of toluene diisocyanate is used (theoretical amount is designated as TDI 100, i.e., 60% theory is TDI 60). Indexes in range of 50-90 are useful, suitably 65-85, 74-84 being preferred for sponge foams. Any surfactant could be used but surfactants that have good wetting and low foaming are advantageous. Actual surfactant levels will vary depending on many formulation variables such as density of final foam, polyol type or blend, the index and surfactant compatibility.
Not unexpectedly, surfactants do effect cell structure and degree of openness of the foam. Flexible foams are described as open cell foams, while ridged foam is described as closed cell foams. If a single cell of foam is described as having two parts, a frame and a window, an open cell foam is foam in which substantially all the windows are broken with some or all of the window missing. A closed cell foam can be described as a frame with a window that has no crack and is not broken. Closed cell flexible foam is a very unsatisfactory product for use as sponges, as the foam tends to shrink severely when cured. It is desirable when manufacturing flexible foam that most of the cell windows are at least broken so that when the foam is flexed or compressed, there is free movement of air between the cells. The degree of openness in flexible urethane foam is controlled by the balance of tin to amine in the conventionally used tin/amine catalyst and/or of the surfactants. A flexible reticulated foam is a foam whose cells have the windows substantially completely removed. Most often, reticulated foams are post treated foams, which remove the window by caustic treatment or rapid decompression. A properly formulated open cell flexible foam will have a combination of cells with “broken windows”, partially removed “windows” and some cells with windows completely removed. It has been found that when producing an improved, highly absorbent sponge with good wiping properties, it is desirable to have a foam with at least 50% of the windows removed and preferably 100% of the windows removed.
Certain solvents can be used for this purpose. Methylene chloride also used as a blowing agent (to expand the foam, lowering density) is an example. It is known by anyone skilled in the art, that a properly formulated foam containing a balance of catalysts generally amine catalysts and tin catalysts and silicone cell stabilizers can often be “opened” a little further with the addition of 2-5%, based on polyol weight, of methylene chloride. This blowing agent used at these levels lowers the density of the open foam and at the same time, “breaks open more windows”. Unfortunately, the use of methylene chloride has been banned in many states for environmental reasons.
As attempts were made to develop an open mostly reticulated sponge, it was discovered that a group of “safe” solvents, the terpenes, are very effective at low concentrations for opening and reticulating cells. A properly balanced foam can be further opened and reticulated with the addition of 0.05 to 5.0% suitably 0.1% to 2.0%. Care must be taken to use as little as possible depending on the formulation as excess amounts over that needed to open and reticulate cells can attack the foam leaving it weak with reduced tensile strength.
An improved method of producing an open reticulated foam structure was discovered. Secondary surfactants, namely surfactants which do not have hydroxyl groups reactable with TDI, and particularly those comprising silicone and siloxanes and polyalkyl -siloxanes and -silicone oils, were found to be very effective at extremely low concentrations. Particularly preferred cell openers comprise polydimethyl siloxane oil, polysiloxane emulsions, dimethyl silicone emulsion, and dimethylpolysiloxanes, particularly those modified with polyalkylene oxide. These may be used per se or in conjunction with other surfactant agents such as fatty acid esters, phosphate based esters as well as certain highly aromatic derivatives.
It was found that the best results are obtained when these anti-foams are extremely well dispersed in the foam system either dispersed in polyol or other components such as water. In one preferred option the cell opener is dispersed as a water/cell opener emulsion containing from about 10-about 40% by weight of opener dispersed to a globule size of less than about 20 microns, preferably ab
Cooney Jr. John M.
Magla World Wide, L.L.C.
Selitto Behr & Kim
LandOfFree
Flexible, substantially open celled polyurethane foam and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Flexible, substantially open celled polyurethane foam and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Flexible, substantially open celled polyurethane foam and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2842554