MXPA99009626A - Flexible, substantially open celled polyurethane foam and method of making same - Google Patents

Abstract

There is provided method of making substantially windowless open-celled polyurethane foam suitably a flexible foam which is especially desirable as a sponge material having superior wiping properties. The ingredients for a formulation for making said foam comprise:a polyol, a catalyst, a silicone stabilizer, a blowing agent, toluene diisocyanate, and cell openers and/or surfactants. In this method the ingredients are injected into a reaction chamber.

Description

FLEXIBLE POLYURETHANE FOAMS OF SUBSTANCI LENT OPEN CELL AND METHOD TO PREPARE THE SAME BACKGROUND OF THE INVENTION FIELD OF THE INVENTION The invention relates to polyurethane foam material having substantially no window cells. Some flexible foams of this type have superior properties of liquid absorption and surface cleaning.

ANALYSIS OF THE PREVIOUS TECHNIQUE Natural sponges have excellent surface cleaning and absorption qualities.

However, they are very expensive and, therefore, very little is still used in ordinary domestic and industrial cleaning. Synthetic sponges, both so-called hydrophilic plastic foams and expanded cellulose structures, have been developed with various techniques in an attempt to produce the optimal household sponge for cleaning and rubbing surfaces. While some of these materials have been successful to a greater or lesser degree, during use they have proven not to be such optimal products. The manufacture of flexible urethane foam and urethane foam sponges is well known.

Recently, foams with a viscoelastic property have already been produced for the furniture industry and in an attempt to duplicate the cushioning characteristics of the polyester wadding. These foams typically have a slower Recovery Rate than conventional foams and have a hulled characteristic. This hulosa characteristic can be reinforced by decreasing the TDI index. These foams have been developed by Arco Chemical using their hydroxyl U-1000 polyol and these properties are now well known in the industry.

SUMMARY OF THE INVENTION In view of the foregoing it is desirable to address these various problems to provide very practical and absorbent cleaning devices. It has been found that by modifying the urethane foam systems in a very unique and unexpected way, a very satisfactory, long-lasting, absorbent sponge can be produced which has very practical surfaces rubbing characteristics and which produces a product with both absorbent and of surface cleaning that to date had not been available. Unexpectedly, it has been found that slow recovery or low resilience or viscoelastic foams, when combined with surfactants and cell openers, provide a foam with excellent surface cleaning characteristics. This is due to the drag produced as the foam is rubbed through a surface providing an effect very similar to that of a rubber squeegee or water cleaner. Foams of this nature can be defined as foams having a ball rebound value of less than 25% and preferably less than 20% using the Ball Rebound Test described in the ASTM D3574 method. A method for making polyurethane foams is provided having substantially windowless cells, which are conventionally called open cell foams. The foams in this category, which are formulated to be flexible, are especially suitable as sponge materials since they not only absorb bulk liquid but also have superior surface rubbing properties. This means that at the same time they essentially dry the previously wet surface. This last property to date is not readily available. The ingredients for a formulation in the manufacture of foams of the present invention comprise: at least one polyol, at least one catalyst, a stabilizer of silicone foam, a blowing agent, toluene diisocyanate and cell openers. When flexible foams are desired for the sponges, a surfactant is present. This surfactant can by itself act as the cell opener or "cell window remover" or can be used with other cell openers of different chemical structure. The method for making the foams with these new combinations of ingredients is essentially conventional, although there are certain modifications that will be established in detail later. In this method, the ingredients are injected into a reaction chamber in at least two streams. It has been found that the surfactants, particularly the wetting agents that are incorporated in the aforementioned polyurethane foam formulation, increase the wetting ability with water in the foams. This effect is accentuated when an amount less than the theoretical amount of toluene diisocyanate is used (the theoretical amount is designated as TDI 100, that is, 60% of the theoretical amount corresponds to a TDI 60). Indexes in the range of 50 to 90 are useful, indexes in the range of 65 to 85 are suitable and indexes of 74 to 84 are preferred for sponge foams. Any surfactant may be used, but surfactants that have good wetting and reduced foaming characteristics are more profitable. Current levels of surfactants will vary depending on many variables of the formulation, such as the density of the final foam, the type or mixture of polyol, the index and compatibility of the surfactant. Not unexpectedly, the surfactants do have an effect on the structure of the cell and the degree of foam opening. Flexible foams are described as open cell foams, while foamed foams are described as closed cell foams. When a single foam cell is described as consisting of two parts, a frame and a window, an open cell foam is a foam in which practically all the windows are broken and where some or all of the windows are non-existent. A closed cell foam can be described as a frame with a window that has no cracks or broken. The closed cell flexible foam is a very unsatisfactory product when used in sponges, since the foams tend to shrink very severely during curing. When making flexible foams, it is desired that most of the cells' windows break, at least so that when the foam is flexed or compressed there is a free movement of air between the cells. The degree of openness in flexible urethane foams is controlled by the balance between tin and amine in the tin / amine catalysts conventionally used and / or in the surfactants. The reticulated foam, flexible, is a foam whose cells present a substantially complete removal of the windows. Very often, the reticulated foams are foams that receive a subsequent treatment in which the windows are removed by means of a caustic treatment or a rapid decompression. A flexible open cell foam with adequate formulation will have a combination of cells with "broken windows", particularly "windows" removed and some cells that have the windows completely removed. It has been found that by producing an improved sponge of very high absorbency with good surface rubbing properties, it is desired to have a sponge having at least 50% of the removed windows and preferably 100% of the windows have been removed. removed. Some solvents may be used for this purpose. Methylene chloride which is also used as a blowing agent (to expand the foam, decrease the density) is an example. One skilled in the art knows that a foam with a suitable formulation contains a balance between the catalysts, which are generally amine catalysts and tin catalysts, and the silicone-based cell stabilizers, and can normally produce a cell that is "open". "a little more, with the addition of 2 to 5% methylene chloride, based on the weight of the polyol. The blowing agent used at these levels decreases the density of the open foam and at the same time "opens or breaks more windows". Unfortunately, the use of methylene chloride has been censored in many states due to environmental problems. While attempts were made to develop an open and mostly reticulated sponge, it was discovered that a group of "safe" solvents, such as terpenes, were very effective at low concentrations to open and crosslink the cells. A suitably balanced foam can be opened and additionally crosslinked by adding from 0.05 to 5.0%, and more adequately from 0.1% to 2.0%. Depending on the formulation, care must be taken to use as little as possible of excessive amounts with respect to the quantities needed to open and crosslink the cells, since with these quantities the foam can be attacked and weakened until it reaches a low tensile strength. . An improved method for producing an open cross-linked foam structure was discovered. Secondary surfactants, namely surfactants that do not have hydroxyl groups that can react with TDI, and particularly those comprising silicone and siloxanes and polyalkyl siloxane and polyalkyl silicone oils, were very effective at extremely low concentrations. Particularly preferred cell openers comprise polydimethylsiloxane oil, polysiloxane emulsions, dimethylsilicon emulsion and dimethylpolysiloxanes, particularly those modified with polyalkylene oxide. These agents can be used per se or together with other surfactants such as for example fatty acid esters, phosphate-based esters as well as some highly aromatic derivatives. It was found that better results are obtained when these defoamers are dispersed extremely well in the foam system, either dispersed in the polyol or in other components such as water. In a preferred option, the cell opener is dispersed as a water / cell opener emulsion containing from about 10 to about 40% by weight of the dispersed opener, at a globule size of less than about 20 microns, preferably from about 0.1 to about 5 microns. This emulsion is then dispersed in the polyol. Similarly, the cell opener can be directly dispersed in a small amount of polyol with a high-speed mixer or with a homogenizer to a similar globule size. This component is dosed separately to fine-tune the degree of cross-linking and the degree of opening. The thinner the dispersion of the oil, the greater the degree of opening or cross-linking of the foam and the smaller the cell size of the foam. Over time (several hours) this dispersion becomes less effective and the cell size of the foam increases and becomes irregular. It is believed that this occurs due to the agglomeration of finely dispersed oil. As the size of the oil globule becomes larger, not only is the window of the cell destroyed, but also the frame structure is destroyed causing small gaps in the foam. Specifically designed emulsions of silicone oil in water and / or surfactant / polyol can be used to preserve the finely divided emulsions or high-speed continuous stirring of this component can be used to keep the oil finely dispersed. The use of these cell openers is not limited to absorbent foams, but also more conventional foams are used where a greater "breathing capacity" is desired. It is known that certain formulations become "compact". That is, they have a tendency to generate closed cells. As an example, the "Softcel" MR series of foams provided by Arco Chemical are known in the literature as compact type. The cell openers allow the use of higher levels of tin for faster curing and to facilitate handling without shrinkage. As polyols polyether polyols with a hydroxyl number of from about 50 to about 200, having a molecular weight of from about 500 to about 6500, preferably from about 750 to about 2000 can be used. The esters based on polytetramethylether glycol caprolactam are especially suitable. and polyester polyols of adipate and succinate, poly (oxypropylene) polyols with a hydroxyl number of between about 120 and 180 and an equivalent weight of between 200 and 400 are particularly preferred. The use of polyols of high molecular weight polymers with hydroxyl number of between about 20 and about 75, being suitable within a range of molecular weight of 1000 to 4000 and a range of equivalent weight of 300 to 1500. Especially preferred are polymer polyols which provide a hulose grade, in particular, graft polyols. polymer containing copolymerized styrene / acrylonitrile solids. The compositions may also contain AMENDED SHEET fillers of the type generally known for the urethane foams technique. Absorbent sponge foams with good surface rubbing and wetting characteristics can occur when, in addition to the toulendiisocyanate at a low TDI index and at least one polyol, suitably a viscoelastic polyol, at least two of the following factors are present: at least one suitable surfactant as a wetting agent and a cell opener preferably a defoaming surfactant containing siloxane or silicone. These sponges also have low resilience qualities.

DESCRIPTION OF THE PREFERRED MODALITIES The foams of the present invention are produced by any of the standard methods of producing polyurethane foams that are known in the art. These procedures are well known and are summarized below. According to the process of the present invention, each component is mixed together with the others in a mixing chamber. In one embodiment, each of the components is introduced separately into the mixing chamber. For example, each of the components can be introduced as a separate stream to the mixing chambers. In addition, any means that AMENDED SHEET has been recognized in the art, for example a variable speed pump, may be employed to separately control the flow of each of the components towards the mixing chamber, in order to provide the desired product. . In this form, the catalyst can be controlled according to the operating conditions and, more particularly, the cell opener component can be adjusted to optimally open the cells independently of the tin / amine ratio and the silicone surfactant stabilizer. In an alternative embodiment, one or more of the components may be premixed prior to their introduction into the mixing chamber. As an example, the polyols including the surfactant polyol and the surfactant can be preblended and introduced into the mixing chamber as a single component. Although it is not preferred, it is possible to combine all ingredients other than diisocyanate and introduce only two components to the mixing stream. However, in most cases, it is preferred to control the cell opener component as a separate feed stream. A less desirable method in many applications is to pre-react the diisocyanate with at least a portion of the polyol. The pre-polymer is then introduced to the mixing chamber together with the other SHEETS AMENDED components, either individually or previously mixed, to produce a foam. Because this involves an additional step, the resulting foam is usually more expensive. These described processes are not intended to limit the present invention. Another method for processing the described materials is known to those skilled in the art. As an example, by combining the above materials in a mixing chamber with liquid C02 under pressure and releasing these materials after mixing to at least partially foam the foam, or discharge the above materials into a large chamber and reduce the pressure in the chamber. camera to help the expansion of the foam, only some examples are provided.

EXAMPLES In the examples that we establish next, two suitable polyols are used, in similar proportions. A high loaded polymer polyol having a hydroxyl number of about 20 to about 55, such as for example ARCOL HS-100, as well as a low molecular weight polyether polyol with a hydroxyl number of about 50 to about 200, example ARCOL Polyol U-1000 (both manufactured by ARCO Chemical Company).

The catalysts are a tin catalyst and an amine catalyst. The surfactant is a wetting agent, for example Pluronic (manufactured by BASF). The cell opener is a polydimethylsiloxane oil. It has been found useful to disperse the polydimethylsiloxane in water, as an emulsion, this emulsion is further dispersed in the surfactant or the polyol. Water was used as the blowing agent. A variety of silicone oils, silicone emulsions and silicone anti-foaming formulations were used and all were effective in opening the cells to a greater or lesser degree. Among them were the SM2115 silicone microemulsion, Dimethylsilicon AF-60 oil, both GE Silicones; Additive 26, Additive 29, Additive 65, silicone oils of private formula from Dow Corning; SAG 30 and SAG 471, both silicone defoamers from itco Chemical Co. In the following table the selection of foams produced by the processes of the present invention is established. The ingredients such as as encoded below are as follows: ARCOL HS 100 Polyol: a polymer / polyol graft of poly (oxypropylene / oxyethylene) polyol with hydroxyl number of about 52 and equivalent weight to about 1080, containing high concentration of copolymerized styrene / acrylonitrile dispersed solids, manufactured by ARCO Chemical Company; ARCOL Polyol U-1000: a low molecular weight poly (oxypropylene) polyol (approximately 1000 g / mol.) with a hydroxyl number of about 170 and an equivalent weight of about 330, manufactured by ARCO Chemical Company; 7057: Triol Polyol 3,000 molecular weight manufactured by Bayer Corp., Pittsburgh, PA. L-5770: a silicone foam stabilizer manufactured by ISI, Division of Witco Chemical. Stabilizer L-620: a silicone foam stabilizer manufactured by ISI, Division of Witco Chemical. Niax A-1: An amine catalyst manufactured by OSI, Division of Witco Chemical. Amine # 5: A mixture of: 0.5 parts of Niax Amine # 77 manufactured by OSI, Division of Witco Chemical. 0.5 parts of Dipropylene Glycol 1.0 of Dimethylamine 4.0 of Triol Polyol of molecular weight 3,000. Tin Catalyst T-10: Tin Octoate manufactured by M & T Chemical, Inc. DEOA: Diethanolamine; TDI: toluene diisocyanate; index:% by weight of TDI used effectively compared to the theoretical amount calculated stoichiometrically; Pluronic: suitably 31R1, a block copolymer surfactant manufactured by BASF Corporation, Mount Olive, NJ; Tetronic 901: A tetrafunctional block copolymer surfactant manufactured by BASF, Mt. Olive, NJ; Surfynol: A defoaming or non-foaming, non-ionic and emulsifiable wetting agent manufactured by Air Products Corporation; AF 60: A 30% emulsion of polydimethylsiloxane, manufactured by General Electric Corporation; Production Run The # 126 foam was gently lifted to provide a sponge that sank in water in approximately 5 seconds. It had a very open cell, had a structure with virtually no windows and excellent surface rubbing qualities. Foam # 130 rose gently, was more open than # 126, had excellent surface rubbing qualities and presented small drop-like masses throughout the foam area.

Claims (26)

1. CLAIMS: 1. A method for making a polyurethane foam having virtually windowless cells, wherein the ingredients of a formulation for making the foam comprise: at least one polyol, at least one catalyst, one blowing agent, one silicone-based foam stabilizer, toluene diisocyanate and a cell opener selected from the group consisting of surfactants that do not have hydroxyl groups, wherein the ingredients are injected into a reaction chamber.
2. 2. A method for making a polyurethane foam having virtually windowless cells, wherein the ingredients of a formulation for making the foam comprise: at least one polyol, at least one catalyst, a blowing agent, a stabilizer silicone-based foam, toluene diisocyanate wherein the amount of toluene diisocyanate is between about 50 and 90% of the stoichiometrically required amount, and the cell opener is selected from the group consisting of surfactants that do not have hydroxyl groups, wherein said ingredients are they inject into a reaction chamber.
3. 3. The method according to claims 1 and 2, wherein the ingredients for a foam-making formulation further comprise surfactants. AMENDED SHEET
4. 4. The method according to claim 3, wherein the additional surfactants are wetting agents. The method according to claims 1 and 2, wherein the cell opener comprises a member of the group consisting of anti-foaming siloxane and silicone surfactants and polyalkyl siloxane and polyalkyl silicone oils. The method according to claim 5, wherein the cell opener comprises a member selected from the group consisting of polydimethyl siloxane oil, polysiloxane emulsions, dimethyl silicone emulsion and dimethylpolysiloxanes. The method according to claims 1 and 2, wherein a low molecular weight polyether polyol with a hydroxyl number of between about 50 and about 200 is used. The method according to claims 1 and 2, wherein the weight equivalent of the low molecular weight polyether polyol is in the range of about 200 to about 400. 9. The method according to claims 1 and 2, wherein a polyol grafted polymer of high molecular weight and hydroxyl number of about 20 to about 7
5. 5. 10. The method according to claims 1 and 2, wherein the equivalent weight of the polymer grafted with high molecular weight polyol is in HTIAEH EHBA ©! -the range from about 300 to about 1500. 11. The method according to claims 1 to 10, wherein the amount of toluene diisocyanate is between about 65 and 85% of the stoichiometrically required amount. The method according to claim 11, wherein the amount of toluene diisocyanate is between about 74 and 84% of the stoichiometrically required amount. The method according to claims 1 and 2, wherein the catalyst comprises a tin catalyst and an amine catalyst. The method according to claims 3 to 6, wherein the amount of surfactant is in the range of 5 to 40% by weight of the entire formulation. 15. The method according to claim 14, wherein the amount of surfactant is in the range of 10 to 20% by weight of the entire formulation. The old claim 14 is now claim 5. 1
6. 6. The method according to claims 1 to 13, further comprising a load. 1
7. 7. The method according to claims 1 to 13, wherein the blowing agent is water. The method according to claims 1 and 2, wherein the cell opener is dispersed within the water as an emulsion containing between 10 and RED AMENDED 40% by weight thereof, to a globule size less than about 20 microns and the emulsion is further dispersed within the polyol. 19. The method according to claim 18, wherein the cell opener is dispersed within the polyol with a globule size of less than about 20 microns. The method according to claim 19, wherein the globule size is in the range of about 0.1 to about 5 microns. The method according to claims 1 and 2, wherein the amount of the cell opener is between about 0.002 and 0.5% by weight of the weight of the polyol. 22. An open-cell, virtually windowless polyurethane foam material made according to the method of claim 1. 23. A flexible, virtually windowless, open cell polyurethane foam sponge material having superior properties of rubbing surfaces, made according to the method of claim 2. 24. A sponge material of polyurethane foam, open cell, virtually windowless, flexible, having superior rubbing properties is surface, made by the method of the claims 3 and 4. 25. A viscoelastic polyurethane foam, ANNOUNCED, open, virtually windowless, flexible sheet containing cell-free surfactants free of hydroxyl groups, which have a ball bounce value of less than 25% in the Ball Rebound Test of Method ASTM D3574. 26. A viscoelastic, open cell, essentially windowless, flexible polyurethane foam containing cell-opening surfactants that do not have hydroxyl groups and that are produced from an original charge of toluene diisocyanate of between 50 and 90% of the stoichiometrically required amount, which has a ball rebound value of less than 25% in the Ball Rebound Test of Method ASTM D3574. HOI ^ IH ^ HB ^^