MXPA00002825A - Aqueous wax dispersions as cell openers in making polyurethane flexible foams - Google Patents

Abstract

A method for preparing a flexible or semi-flexible polyurethane foam by reacting an organic polyisocyanate with a polyol in the presence of urethane catalyst, water as a blowing agent, optionally a silicone surfactant, and a cell opening additive characterized in that the cell opening additive comprises an aqueous dispersion of particles comprising a wax substance and optionally an emulsifier, at least 35%of the particles having a size of 0.2 to 5 microns and a melting point which ranges from 0 to 55ºC below the maximum foam exotherm temperature.

Description

DISPERSIONS OF AQUEOUS WAXES AS CELLULAR OPENERS IN THE PERFORMANCE OF FLEXIBLE POLYURETHANE FOAMS DESCRIPTION OF THE INVENTION The invention is related to making flexible polyurethane foams using dimensional stability / cell opening additives. The flexible molded polyurethane foam requires mechanical crushing to open foam cells and prevent shrinkage and to improve the dimensional stability of the foam pad. The current mechanical methods for cell opening consist mainly of crushing, vacuum rupture or release of time pressure. When unmolding, mechanically crushing and breaking the polyurethane foam cells allows the polyurethane foam to be more dimensionally stable. Another method of cell disruption is vacuum crushing, which involves extracting a vacuum in the final polyurethane foam, causing cellular breakdown. The total effect of these methods is to reduce shrinkage of the foam. Other mechanical attempts have been made to achieve dimensionally stable foam, such as decreased production cycle times. For example, unmolding the polyurethane foam in three minutes, as compared to four minutes will dramatically improve the dimensional stability. Another method to produce foam , ._, < _ £ '__; . dimensionally stable is the time pressure release (TPR). The TPR comprises opening the mold during the curing process to release the internal pressure and then the reconnection for the duration of the cure time. The abrupt release of internally generated pressure bursts from the cell windows, thereby obtaining an open cellular foam. Mechanical methods usually result in an incomplete or inconsistent cell opening and require a flexible molded foam produced to reverse additional machinery. A chemical method for cell opening could be preferred. All current chemical methods have setbacks such as the high levels often required as high as 1-5 parts by weight per one hundred parts of polyol (pphpp) or adversely effecting the physical properties of the foam. US 3,454,504 describes a cell opening agent for producing polyurethane foam which is a liquid polypropylene or a polybutene. US 4,431,455 discloses an organic polyisocyanate composition containing a liquid organic polyisocyanate and a mixture of a wax and a liquid ester.

The composition, which is preferably applied in the form of an aqueous emulsion, is used for the manufacture of sheets or molded bodies, such as cardboard, hardboard and plywood, by the hot pressure of a lignocellulosic material and promotes the release of the material from the press . US 4,751,253 discloses a cell opening, dimensionally stabilizing a flexible foaming agent comprising an ester reaction product of a long chain acid with polyethylene glycols or polypropylene and / or containing free acid to be provided for a desired acid value. US 4,929,646 discloses flexible polyurethane foams prepared using certain high molecular weight, poly (oxyethylene) high functionality compounds such as cellular softeners and softeners. In Example 1, the Cell Opener A, a nominally functional 6.9 random copolymer of 75% ethylene oxide and 25% propylene oxide having a molecular weight of about 35,000, was added to the polyurethane formulation as a 70 / mixture. 30 with water. US 5,614,566 discloses rigid foams which are open cells prepared by reacting the components in the presence of liquid, high molecular weight, unsaturated hydrocarbons, which are free of groups capable of reacting with isocyanates, such as polybutadiene and polyoctenylene.

WO 96/37533 discloses preparing rigid polyurethane foams using an emulsified polyol mixture comprising (a) a polyol formulation comprising a polyol having an OH value of 150 to 500, (b) a blowing agent, (c) a cell opening agent which is a divalent metal salt of a long chain fatty acid having a softening point of about 100-180 ° C and (d) a acid, the mixture has drops of the cell opening agent having an average average diameter of less than about 50 μl stable suspended in the polyol mixture. US 4,936,917 discloses a method for making a polyurethane foam using a water-based mold release composition comprising an aqueous dispersion of at least one effective substance released and a poly (siloxane-glycol) surfactant. In a book of technical advantages distributed by Dow Plastics to customers (1991 edited by Ron Herrington and Kathy Hock, page 2.31), it states that "Known additives to induce cellular opening include antifoams based on silicone, waxes, finely divided solids and certain polyether polyols made using high concentrations of ethylene oxide. " No further discussion is given in this publication regarding the types of polyurethane applications these are useful X for, or types of waxes that are necessary to achieve cell opening. In particular, a table is provided (page 3.19) of known cell opening additives and there is no list of a wax-like compound. Also, this reference does not disclose a method for introducing the wax into the foam composition. The invention provides a method for preparing flexible or semi-flexible polyurethane foams using certain additives dispersed in stabilized / cellular opening water. The method comprises reacting an organic polyisocyanate and a polyol in the presence of a catalyst composition, a blowing agent, optionally a cellular stabilizer of the silicone surfactant, and as the cell opening agent dimensionally stabilizing an aqueous dispersion of particles comprising a substance of wax and optionally an emulsifying agent for the wax substance, at least 35% of the dispersed wax substance, or wax / emulsifier substance particles, having a size of 0.2 to 5 microns (μm). The use of such aqueous dispersions of wax substances in the production of flexible polyurethane foam provides the following advantages: • polyurethane foams (flexible and semi-flexible moldings and flexible thick sheets) exhibit reduced shrinkage which provides for improved dimensional stability while a fine cellular structure is maintained especially on the foam surface. • a reduction in the force required to crush freshly demoulded foam without adversely affecting the physical properties of the foam • relatively low levels of the dispersion additive, eg, only 0.0001-2 parts by weight solids (wax substance and emulsifiers) per percent parts of polyol (pphpp) are necessary to create the cell opening • aqueous cell opening compositions are quite efficient to allow the use of strong stabilizing surfactants such as silicone polyether copolymers having lower emission properties than weak stabilizing surfactants, such as dimethylsilicone fluids which are traditionally used in molded flexible MDI foam. For purposes of this invention and as understood by many in the art, flexible and semi-flexible foams may include microcellular foams such as those used in shoe sole and steering wheels as well as flexible molded foams used in furniture, lamination and automotive fastening. including MDI flexible molded foam, TDI / MDI flexible molded foam, TDI flexible molded foam, integral skin foam, instrument panel foam and flexible thick foamed foam. The dimensional stabilizing / cellular opener additives used in the preparation of the flexible and semi-flexible foams are aqueous dispersions of wax substances optionally containing an emulsifying agent for the wax substance. Good cell opening properties are obtained by using wax substances, such as microcrystalline or paraffin waxes, with melting points with a temperature range of 55 ° C between the exothermic temperature of maximum polyurethane foam. That is to say that the maximum exothermic temperature of a particular foam formulation is above about 55 ° C before the melting point of the wax, or wax particles / emulsifier. The limiting of the melting point will vary as a function of the type of foam formulation, ie, MDI, TDI or MDI / TDI foams, since the various foam formulations will have different exothermic temperatures. (The general terms "wax" and "wax substance" are used interchangeably.) It will also be understood that "wax particle" also means, when an emulsifying agent is used, the wax particle / emulsifier.) For foam compositions of polyurethane where the organic polyisocyanate is MDI, the melting point of the dispersed particles should be 0 ° to 30 ° C lower than the maximum exothermic temperature of the foam, preferably from 2 ° to 10 ° C lower. For TDI-based foam compositions the melting point of the dispersed particles should be 0 ° to 50 ° lower than the maximum foam exothermic temperature, preferably 2 ° to 45 ° C lower. For a foam composition comprising a mixture of MDI and TDI in approximately a weight ratio of 40-60 / 60-40 MDI / TDI, the melting point of the dispersed particles should be from 0 ° to 40 ° C lower of the maximum foam exothermic temperature, preferably 2 ° to 30 ° C lower. For MDI / TDI blends comprising one of the isocyanate in the mixture the highest melting point range defined for the dispersed particle approaches set forth above for those hearth isocyanates. These ranges should be considered approximate since the polyurethane foam components can affect the melting temperature of the current wax particle and different foam formulations will vary at a maximum exothermic temperature. In addition, the particle size of the wax or wax / emulsifier dispersed in the aqueous medium should be 0.2 to 5 microns, preferably 1.5 to 3 microns. At least 35% of the dispersed wax or wax / emulsifier particles, preferably 70%, and more preferably 80% should be within the established size range of 0.2 to 5 microns. It is also desirable that at least 25% of the particles be 1.5 to 3 microns. The present cellular openers provide a much better surface than traditional cellular aperture agents and can be especially useful for integral skin formulations where good skin is desired. It is speculated that the cellular opening occurs inside the foam due to the fusion of wax particles due to the exothermic reaction foam; some openings can be achieved by a rough cell structure. It is speculated that a good foam surface is due to the remaining solid of the wax particles in about a 1 cm zone on the surface of the foam due to the relatively lower temperature of the mold surface compared to the exothermic temperature of internal foam. and cell opening does not occur in this area. Accordingly, it is also advantageous that the wax particles have a melting temperature above the mold temperature, although this is not mandatory. Aqueous wax dispersions contain wax substances, preferably ionic and / or nonionic emulsifiers, and other additives, with the total water content of the composition being in general from about 50 to 95% by weight, preferably 55 to 90% by weight. weight. Suitable cell opening and stabilization is obtained when the waxes are present in the foam formulations in concentrations ranging from 0.0001 to 2 parts by 5 weight per hundred parts by weight of polyol (pphpp), preferably from about 0.001 to 0.3 pphpp . Of course, it is required that the wax substances and any emulsifying agents comprising the particles dispersed in the aqueous dispersion have a melting point which is not higher than 55 ° C, preferably 4 to 45 ° C, lower than the maximum foam exothermic temperature and also has the established particle size. Suitable wax substances are any of these waxes, microwaxes, thickener oil fractions, and polysiloxane release agents well known in the art. The wax substances are typically microcrystalline waxes or paraffins with melting points between 85 ° and J.00 ° C. Also effective are synthetic waxes such as esters of fatty acid glyceryl and polie tilenglicoles ele high molecular weight. These high molecular weight esters of fatty acids typically contain 5-30 carbon atoms and can be used in either their unsaturated or hydrogenated forms. The polyethylene glycols have molecular weights from 4,000 to 8,000. 25 Waxes that can also be used in the ^ Is "? At ^ -S_i ^." T ^ '. ¡.ssá __-. ", A__fr-.iJSi_ compositions include vegetable waxes, for example, eera ele carnauba; modified vegetable oils, for example, hydrogenated castor oil; microcrystalline waxes, for example, Bareco and sco waxes; mineral waxes, for example, Montan wax (a mineral obtained from lignite); and animal waxes, for example, beeswaxes or lacquer waxes. Synthetic or modified animal waxes such as pentaerythritol tetrastearate, or commercially available synthetic waxes may also be used. Mixtures of waxes can also be used. Suitable emulsifying agents are any of those known in the art for preparing aqueous emulsions of waxy substances, particularly those with an HLB value of 8-15 and especially polyalkoxylated non-ionic surfactants To obtain efficient emulsification of the waxy substances in water, ionic emulsifiers are used in combination with nonionic emulsifiers Preferred emulsifying agents are fatty alcohol ethoxylates such as ethoxylates of lauryl alcohol having 3-4 ethoxy units and cetyl alcohol having about 10 ethoxy units. fatty alcohols would typically have an HLB value between 10 and 13. Other useful emulsifying agents are fatty amines such as bait amines comprising combinations of octadecyl and hexadecyl amine In addition to the amines £ * £ • Fats, fatty acids such as octadecyl acid can also be used. Typically, no emulsifying agent is sufficient to adequately emulsify the wax substances in the aqueous composition. Rather it is a combination of emulsifying agents provided for the most consistent dispersion. Fatty alcohol ethoxylates are typically used between 0.5 and 4.5% by weight based on the aqueous wax composition. Fatty amines are typically used between 0.5 and 3% by weight. The fatty acids serve as effective emulsifiers and can be used in concentrations of approximately 0.25 to 0.75 '. by weight. The aqueous wax dispersions of the invention can be prepared by mixing the components together with sufficient cutting energy and at such a temperature that the wax is in a liquid state within the described particle size range. Thus, the water, wax and emulsifier nectant, usually at different temperatures, can be vigorously stirred together at a temperature in the range of 90 ° to 150 ° C, preferably 100 ° to 140 ° C, the dispersion is then rapidly cooled to minus 50 ° C, extinguishing with cold water. The preferred used level of these aqueous dispersion cell openers is 0.0001-2 parts by weight of wax substance per one hundred parts polyol (pphpp) plus JP preferred is 0.001-0.3 pphpp, and most preferred is 0.005-0.05 pphpp. The aqueous wax dispersion is added to one of the formulation components such as the surfactant, water, amine catalyst, crosslinker or polyol, but preferably to the B side comprising the polyol composition., surfactant, blowing agent (preferably water), amine catalyst, and crosslinker. The stabilizer / cell openers according to the invention are used in the manufacture of flexible and semi-flexible polyether and polyester polyurethane foams in the manner known in the art. In the production of polyurethane foams using these cell openers, one or more polyether or polyester polyols are employed for reaction with a polyisocyanate, especially a diisocyanate, to provide the urethane linkage. Such polyols typically have an average of 2.0 to 3.5 hydroxyl groups per molecule, hydroxyl numbers (OH #) of 20 to 60, and weight average molecular weights of 2000 to 7000 daltons. The density of a flexible polyurethane foam can be 0.6-37.5 lbs / ftJ (10-600 kg / m ') and a semi-flexible foam 1-3.75 lbs / ft3 (16-60 kg / mJ). Illustrative of the polyols as a component of the polyurethane composition are the polyalkylene ether and polyester polyols. Polyalkylene ether polyols include poly (alkylene oxide) polymers such as poly (ethylene oxide) and poly (propylene oxide) polymers and copolymers with terminal hydroxyl groups derived from polyhydric compounds, including cliols and triols; for example, among others, glycolol, propylene glycol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, propylene glycol, pentaerythritol, glycerol, diglycerol, trimethylol propane and low molecular weight polyols. Similar . In the practice of this invention, a single high molecular weight polyether polyol can be used. Also, mixtures of high molecular weight polyether polyols such as mixtures of di and trifunctional materials and / or different molecular weight or materials of different chemical composition can be used. Useful polyester polyols include those products by reacting a dicarboxylic acid with an excess of a diol, for example, adipic acid with ethylene glycol or butanediol, or by reacting a lactone with an excess of a diol such as caprolactone with propylene glycol. In addition to the polyether and polyester polyols, the masterbatches, or premix compositions, often contain a polymer polyol. The polymer polyols are used in polyurethane foam to increase the foam's resistance to deformation, is to choose, to increase the load-bearing properties of the foam. Currently, two different types of polymer polyols are used to improve load support. The first type, described as a graft polyol, consists of a triol in which the vinyl monomers are copolymerized grafts. Styrene and acrylonitrile are the usual monomers of choice. The second type, a polyurea modified by polyurea, is a polyol containing a polyurea dispersion formed by the reaction of a cliamine and TDI. Since TDI is used in excess, some TDI can react with polyol and polyurea. This type sealant of the polymer polyol has a variant called PIPA polyol which is formed by the in situ polymerization of TDI and alkanolamm in the polyol. Depending on the load bearing requirements, the polymer polyols may comprise 20-80% of the polyol portion of the masterbatch. The polyurethane products are prepared using any suitable organic polyisocyanate well known in the art, including, for example, hexamethylene diisocyanate, phenylene diisocyanate, toluene diisocyanate (TDI) and, 4'-diphenylmethane (MDI) diisocyanate. Especially suitable are the 2, 4- and 2,6-TDT individually or together as their mixtures are currently available. Other suitable isocyanates are mixtures of > 46 diisocyanates known commercially as "unpurified MDI", also known as PAPI, containing about 60% MDI along with zeros isomeric higher polyisocyanates and the like. Also suitable are the "prepolymers" of these polyisocyanates comprising a partially pre-reactive mixture of a polyisocyanate and a polyether or polyester polyol. Suitable urethane catalysts useful in making flexible polyurethane foams are those well known to those skilled in the art and include tertiary amines such as triethylene diamine, N-methylimidazole, 1,2-dimethylamidazole, N-methylmorpholine, N-ethylmorpholine. , triethylamine, tributylamine, triethanolamine, dimethylethanolamine and bis (dimethylaminoethyl) ether, and organotins such as stannous octoate, stannous acetate, stannous oleate, stannous laurate, dibutyltin dilaurate, and others such as tin salts. Other typical agents found in flexible polyurethane foam formulations include chain extenders such as ethylene glycol and butanediol; crosslinkers such as diethanolamine, diisopropanolamine, triethanolamine and tripropanolamine; blowing agents such as water, liquid carbon dioxide, CFC, HCFC, HFC, pentane, acetone and the like, especially water or water and HCFC; and cell stabilizers such as silíconas. i & iÉ &_i __ ii = r: _?, ^ __, _ g € l __¡_ -3 «tífa- - The flexible diesfoliurethane foams which can be prepared using the present invention include thick sheet foams having a density of 12-100 kg / m ", such as based on polyether: conventional (12-60 kg / m" '), high elasticity (18-80 kg / m3), filled (40-100 kej / m3), semi-rigid (22-35 kg / m3), and polyester based; technical grades (20-50 kg / m3), rolling grades (20-35 kg / mJ), and semi-rigid (22-35 kg / m3) as well as molded foams that have a density of 22-300 kg / m3, such as based on polyether; conventional heat cure (22-50 kg / mJ), high elasticity and cold cure (28-55 kg / m3), semi-rigid (40-150 kg / mJ), and polyester base (50-150 kg / mJ), "repulsed" or re-bonded (60-300 kg / m). Also possible are microcellular molded foams having a core density of 400-600 kg / m "', a surface density of 600-800 kg / rrr' and a total density of 500-700 kg / m3. Flexible molding of polyurethane having a density of 1-5 pounds / ft '(16-80 kg / m3) (eg, automotive fastener) containing a dispersion of aqueous wax substance as the cellular opener will comprise the following components in parts by weight (bp): Flexible Foam Formulation pbw Polyol 20-100 Polymer 80-0 Polyol __ 5 > .á_l,.-__ &-_ B_t_ Silicone Surfactant 0.5-2.5 Cellular Opener 0.001-0.3 Water 1-6 Blowing Auxiliary Agent 0-4.5 5 Reticulator 0.5-2 Catalyst Composition 0.1-5 Isocyanate Index 70-115 * matepal Active In the present invention, the preferred blowing agent for making flexible molded foams is water of 1 to 6 parts per hundred polyol (pphp), especially 3 to 6 pphp, optionally with other blowing agents. Other additives can of course be employed to impart specific properties to flexible foams. Examples are materials such as flame retardants, colorants, fillers and hardness modifiers. The polyurethane foams of this invention can be formed in accordance with any of the processing techniques known in the art, such as, in particular, the "unique" technique. According to this method, the foamed products are provided to carry out the reaction of the polyisocyanate and polyol simultaneously with the foaming operation. ? r. In the following examples the following materials were used: Synthetic copolymer wax CP-7 (Petrolite Corporation) Brij 56 Polyoxyethylene Terethylene (ICI Americas, Inc.) Armeen 18D Octadecylamine (Akzo) Vibar 253 Hydrocarbon Copolymer Wax (Petrolite) Wybar 260 Hydrocarbon Copolymer Wax (Petrolite) Wax Epoleno E15 (Eastman) Polyol CP6001 (Dow Chemical; OH # = 28) Cell opening polyol CP1421 (Dow Chemical) DEOA (diethanolamine) TEOA (triethanolamine) DABCO ™ DEOA-LF (85% DEOA, 15% water; Air Products and Chemicals, Inc.) DABCO © DC2585 Silicone Surfactant (Air Products and Chemicals, Inc.) DABCO Amine Catalyst © BL11 (Air Products and Chemicals, Inc.) DABCO 33LV © Amine Catalyst (Air Products and Chemicals, Inc.) Amine Catalyst H2050 (Air Products and Chemicals, Inc.) Desmodur 3230 MDI (Bayer, equivalent weight = 130-08) Release agent PORC-798 (Chem-Trend, Inc.) LX1000 - registered water / wax dispersion (Petrolite; made with Polywax 1000 wax, melting temperature = 113 ° C) LX1130 - registered water / wax dispersion (Petrolite, made with wax EP-700, melting temperature = 96 ° C) LX1061 - registered water / wax dispersion (Petrolite, made with Polywax 655 wax, melting point = 99 ° C) Epoleno E15 # 3 - water dispersion / wax (Eastman) Epoleno E20 # 6 - water dispersion / wax (Eastman) Duramul 766 - water / wax dispersion (Astor Chemical Co.) Polyol voranol 232-027 (Dow Chemical, OH # = 26) Mondur MRS-5 MDI (Bayer, equivalent weight = 133) Polyetherpolyol Arcol E 648 (Chemical Arc, OH # = 35) Copolymer Polyol Arcol E519 SAN (Arco Chemical; OH # = 24.4) Silicone surfactant DABCO DC5169 (Air Products and Chemicals, Inc.) Silicone surfactant DABCO DC5164 (Air Products and Chemicals, Inc ) Silicone surfactant DABCO DC5043 (Air Products and Chemicals, Inc ) Silicone surfactant L1505A (Air Products and Chemicals, Inc.) DABCO BL 17 Amine Catalyst (Air Products and Chemicals, Inc.) TDI-80 (Bayer Corp.) MDI Rubinate M MDI (ICI Americas, Inc., 31.5% NCO; Funct. 2. 7). EXAMPLE 1 This example shows the preparation of aqueous wax dispersions (water / wax dispersions). For each water / wax dispersion (WWD) in Table 1, 150 g of wax, 22.5 g of Brij 56 emulsifier and 15 g of Armeen 18 emulsifier were combined and melted at 110 ° C. In a separate vessel, 525 g of water were heated to 93 ° C or higher. The molten wax components were added to the hot water with extreme agitation. 787.5 grams of 20 ° C water were added to stop the wax particles. The water / wax dispersions WWD1-WD3 were used "as is done" in the following examples. Table 1 a Melting point in the pure component b Published 'Max in DCS The wax dispersion WWD4 of Table 2 was made using a slightly different procedure due to the high melting point of the wax. For 1500 g of dispersion, 150 g of Epoleno E15 wax, 22.5 g of Brij 56 emulsifier and 15 g of Armeen 18D emulsifier were combined and melted at 139 ° C. In a separate vessel, 525 g of water were heated to 100 ° C. When the water reached 93 ° C, the mixing blade was submerged in the water to warm up. The wax should not be added to the water unless the water is at 100 ° C. Afterwards, the wax was added to the hot water and mixed with extreme agitation, 787.5 g of cold water was added and mixed to stop the wax particles. Table 2 Melting point in pure component h Published in Max in DCS Table 3 shows the melting point of the wax particle dispersed in commercially available water / wax dispersions (WWD) that were used in Example 2: Table 3 Melting point in pure component b Published 'Melting point in particle dispersion Max in DCS EXAMPLE 2 Flexible molded polyurethane foams MDI were prepared using the formulation of the Table 4. Table 4 The molded polyurethane samples were prepared using the following procedure. The premixed amine was prepared by mixing the water, DEOA-LF and amine catalysts, on the same day the foam was made.

~ A The polyol was measured out in a 1 gallon cup (1. u 9 1) and the DC2585 silicone surfactant and the WWD stabilizer / cell opener was added. The load factor was 3.5 which produced an overpack in the 6% mold. Using a Servodyne © disperser with a 3 inch (7.6 cm) disc mixing the blade and the fixation controller at 6000 rpm load, the liquid cup was mixed for 25 seconds. The premixed amine was added and mixed for 20 seconds. The MDI was added and the liquid was mixed for 6 seconds. The mixture was poured into a mold of 12x12x4 inches (30.5 X 30.5 X 10.2 cm), 126 ° F (52 ° C), which was sprayed with a solvent based on the release agent (PRC-798), the cup was emptied during seconds, and the mold was immediately closed. The demolding time was 355 seconds after mixing. The force to crush the measurements was taken 410 seconds after mixing. For each foam, the following data were obtained and are presented in Table 5: the force to crush (FTC), volume stability, surface quality and percent shrinkage. The premix was incubated to control the temperature.

Table 5 * pphpp - wax dispersion parts per one hundred parts of polyol ** phpp - wax parts / emulsifier per hundred parts of polyol VOLUME STABILITY is ordered from 1 to 5 with 1 being larger cells and 5 being uniform fine cells. SUPERFICIAL QUALITY is ordered from 1 to 5 with 1 being large surface cells and 5 being fine surface cells. the cellular structure is maintained in volume and surface. The CP1421 commercial cellular openers also improve foam shrinkage and force shredding, however, not to the same extent as WWDl and also to the higher used level than WWDl. CP1421 is typically used at levels of use of 1 to 2 pphpp, that is, 1 to 2 parts by weight of CP1421 per one hundred parts by weight of polyol. Aqueous wax particles that melt much less (WWD2-60.7 ° C and WWD3 42.8 ° C) result in foam clesestabilization and a lower volume stability rating. The wax particles that melt higher (LX1000 - 111 ° C and LX1130 - 90 ° C) do not provide any cell opening advantage in terms of forcing crushing or% shrinkage. The WWDl water / wax dispersion has a dispersion particle melting point of 85 ° C. Without being bound by any particular theory, a wax that melts much less during the polymerization process, destabilizes the foam more easily before the viscosity of the foam which is high enough to maintain stability. Some waxes that melt higher, retain a solid particle and do not affect the cell opening. Therefore, it is believed that the optimum waxes and emulsifiers used for cell opening in MDI foam formulations will provide an elementary particle having a melting point in a range whose upper limit is the maximum foam exothermic temperature and the lower limit is about 30 ° C lower than the maximum foam exothermic temperature. For example, the approximate maximum exothermic foam temperature of the MDI formulation of Table 4 is 9 ° C, then the range of the wax particle melting point could be from about 61 to 91 ° C, with a preferred range of 81 to 89 ° C. These ranges could be considered approximate since the polyurethane foam components can affect the current wax particle melt temperature and different foam formulations will vary at the maximum exothermic temperature. EXAMPLE 3 This example shows the effect of using the individual WWDl aqueous wax dispersion components as cellular openers in the MDI flexible molded foam formulation of Table 4. As seen in Table 6, none of the components used individually performed the same. than its combination in WWDl. safíSjs *? ' . , z x Táéía 6 Example 4 This example illustrates the effect of wax particle size on the cell opening. Without being bound by any particular theory, it is believed that the size of the wax particle in the water / wax dispersion is important for the cell opening in the polyurethane foam. Cell windows are generally thought to have a thickness of approximately 0.2 to 0.4 microns (μm). If the particle size is smaller compared to the cell window thicknesses, the water / wax dispersion can not be affected. If the particle size is larger compared to the cell window thicknesses, the deficient cellular structure may result, or the wax particle may be unable to reside in the cell window or the cell window.

The entire particle may not be able to fully melt during the optimal time for cell opening. The average particle size of wax determined by the Horiba LA-910 Laser Diffraction System for various water / wax dispersions are shown in Table 7 Table 7 k midpoint of the largest peak in the particle size distribution •• "' * major peaks Epoleno E15 # 3 dispersion was compared with WWDl because both of these materials have a similar particle melting point (86 ° C versus 85 ° C, respectively), but have very different average particle sizes (1.7 versus 0.09 microns, respectively). The WWDl water / wax dispersion was very effective at the cell opening in the MDI formulation of Table 4 as shown in Table 5, whereas, Epoleno E15 # 3 was ineffective at cell opening to use varying levels of 0.2 to 3 pphpp. Epoleno E15 # 3 had no adverse impact on surface quality or volume stability, but had no impact on the initial crushing force. The particle size of Epoleno E15 # 3 is probably smaller to have an impact on the cell opening even considering the melting point of this wax / water dispersion is in an acceptable range. Example 5 A second formulation of MDI as shown in Table 8 was used. The load factor for this formulation was 3.4 which produced a 6% overpack part in the mold. As shown in Table 9 the water-wax dispersion WWDl provides a reduced force to crush and improve shrinkage in this formulation as well. Table 8 Table 9 EXAMPLE 6 This example demonstrates another aspect of the invention wherein the cell opening materials are quite efficient to allow the use of strong stabilizing surfactants such as silicone polyether copolymers having low emission properties which weaken the stabilizing surfactants such as dimethylsilicone fluids that are traditionally used in flexible molded MDI foam. The traditional MDI stabilizing surfactant (DC2585) comprising a dimethylsilicone fluid was replaced by a strong stabilizing surfactant (L1505A) comprising a silicone polyether copolymer traditionally used in TDI formulations. It can be seen in Table 10, L1505A by itself provides overstatement in the MDI formulation of Table 4 with high values of force for crushing and shrinking. When L1550A was used together with the WWDl water / wax dispersion, a good foam resulted with low values of crushing and shrinking strength and good volume and surface properties. Table 10 also shows that WWDl in combination with L1505A also provides a lower lower crushing force than the commercially available CP1421 at 2.0 pphpp in combination with L1505A in the flexible MDI molded foam formulation of Table 8.

Table 10 * Foam formulation from Table 4 ^ Foam formulation from Table 8 Example 7 Flexible molded polyurethane foams from TDI were prepared in this example using the formulation in Table 11. Table 11 The molded polyurethane foam samples were prepared using the following procedure. The polyols were mixed in a container, and the water, DEOA- ^ z ^ _2__É ____ É_E & __- LF, and amine catalysts were mixed in another vessel. The polyol mixture was incubated at 73 ° F (? 3 ° C). The polyol was measured out in a gallon cup (1.89 1) and the silicone surfactant was added. The load factor was 2.65, which produced an overpacked part of 6 in the mold. Using the Servodyne Disperser with a 3 inch (7.6 cm) mixing blade disc and a charged 6000 rpm setting controller, the liquid cup was mixed 20 seconds. The water, DEOA-LF and the amine catalyst mixture was then added. The liquid cup was mixed 20 seconds, then the TDI was added and mixed for approximately 5 seconds. The mixture was poured into a mold of 12x12x4 inches (30.5X30.5X10.2cm), 155 ° F (68 ° C), which was sprayed with a solvent-based release agent PRC-798, and the cup was kept inverted for 5 seconds, and the mold was immediately closed. For each foam, the following data were obtained and are presented in Table 12; Extrusion time, spinning gel, weight extrusion, pad weight, and crushing force. The demolding time was 275 seconds, with the time of FTC (force to grind) being 330 seconds after mixing.

Table 12 Table 12 shows that WWDl in the TDI formulation reduces the force for grinding, but also provides a rough cell structure as evidenced by the low value for volume stability. For TDI formulations, the WWDl wax dispersion, which melts lower compared to the exothermic temperature of the foam, causes a destabilization of the foam and poor cellular structure. The exothermic temperature of the approximate foam of this TDI formulation was 134 ° C while the WWDl water / wax dispersion melting point was 85 ° C, which is the edge of the lower limit. The wax dispersion of the high melting point WWD4, which had a wax particle melting point of 91 ° C, showed a reduced force to grind with good cell structure in volume and surface. _____ £, _ .. _ * ££ g ^ a £ ___ ^ __? - ___ Example 8 Flexible molded polyurethane foams TDI / MDI were prepared in this example using the procedure of Example 7 and the formulation of Table 11 except that a 50/50 mixture of TDI-80 and Mondur MRS-5 MDI was used. Table 13 The data in Table 13 show the dispersion of WWD1 wax, whose lower particle fusions compared to the exothermic temperature of the foam, causes destabilization of the foam and poor cellular structure. The approximate exothermic foam temperature of this TDI / MDI formulation is 124 ° C while the Hf®? > fusion of the water dispersion particle / WWDl wax is 85 ° C. The dispersion of wax. Dtf $ Najt? Ul 766 highly fused, 1 furnace having a wax particle melting point of 126 ° C, was higher to be effective. The water-wax dispersions LX1130 and LX1061, have dispersion of wax particle melting points of 90 ° and 92 ° C, respectively, demonstrating a reduced force to crush with good cellular structure in the volume and surface of the foam . This demonstrates that there is an optimum range of water / wax dispersion melting points that are effective for cell opening in flexible molded polyurethane foam. Example 9 This example shows the different exothermic foam temperatures for different foam formulations. The internal temperature of the foam made in a free elevated cube of 1 gallon (3.78 1) was measured by an MDI, a TDI and an MDI / TD1 formulation and the maximum temperatures are listed in Table 14. The exothermic temperatures in the Table 14 are only to approximate the exothermic temperature of a molded foam and free high temperatures may be different than the temperatures currently measured in a molded foam. The MDI formulation of Table 4, the TDI formulation of Table 11 and the MDI / TDI formulation of Example 8 were evaluated. ? Example 10 This example shows the preparation of a foam car instrument panel using the formulation shown in Table 15 by the following procedure. The molded foam was made in a hot mold 12x12x2 inches (30.5x30.5x5.1 cm); the temperature of the mold was maintained at 115 ° F (46 ° C). The premix containing the materials for component B comprises the first seven components in Table 15 except the catalyst and the cellular opener were prepared the day before the foam made. A measured quantity of the premix of component B was poured into a half-gallon paper can (1.89 1), the appropriate amount of the catalyst and the cell opener was added to the premix and blended for 12 seconds at 4500 rpm using a doctor blade. mixed 2 inches (5.1 cm) in diameter. A calculated amount of MDI provided for an index of 100 was added into the mixing bowl, mixed for 7 seconds and the foaming mixture emptied for 15 seconds into the mold. The foam was demolded after 3.5 minutes. A load factor of 3.6 was used faith *: to produce an overpacked molded part of 20% The parts were made using the previous instrument panel formulation of Table 15 and severe shrinkage was observed until part demolding and cooling. The water dispersion / WWD wax was added to the above formulation at a level used of 0.15 parts of wax dispersion per hundred parts by weight of polyol (0.0188 solids by weight per 100 by weight polyol) and very little or no shrinkage It was observed until the part was demold and cooled. The CP1421 cellular opener was used above 1.5 pphpp, but the part had shrinkage and decomposition. The parts made without the cellular opener or CP1421 were so deficient that the physical property measurements were not made. Example 11 This example was an attempt to make a piece of flexible foam to hot water in a 14x14x14 inch cardboard box (35.6x35.6x35.6 era) This collapsed foam .. The formulation of Table 16 was used Table 16 WWD 1 was used in the previous formulation at 0.10 parts The premix (polyol, water and amine) was mixed in a container in a shaker for about half an hour and then allowed to stand still for at least 20 minutes before the foams were made . The premix was incubated at 23 ° C. The laboratory temperature was approximately 23 ° C. The relative humidity of the hood was 60-65%. The premix was measured in one gallon cup and the silicone surfactant and catalyst Dabco T-10 were added. Using the Servodyne disperser with a mixing blade disk, and fixing controller at 4500 RPM, torque lock at 25, and fixing time at 7 seconds, the liquid cup was mixed for 25 seconds. The TDI / methylene chloride mixture was added and mixed for about 5 seconds. The cup was decreased by 35.6x35.6x35.6 and emptied, and maintained for 5 seconds * V allowed to rise free. The foam collapsed. ^^ ^ * To the additional experiments in other 5 foimulations, it was understood that the wax dispersion chosen for the previous experiment, may have been the harmful choice since the exothermic foam typical in the piece of flexible foam can reach such high temperatures as 149 ° C. It is believed that if a high melting wax 10 was used to make the dispersion, a stable foam with good cellular structure could have been obtained. The invention provides a method for making porous polyurethane and semi-flexible foams with improved cellular aperture.

Claims (5)

1. CLAIMS 1. In a method for preparing a flexible and semi-flexible polyurethane foam comprising reacting an organic polyisocyanate with a polyol in the presence of a urethane catalyst, a blowing agent, optionally a cellular stabilizer of silicone surfactant, and a additive of the cell opening, the reaction generates exothermic foam, the improvement is characterized in that it comprises as the cellular opening additive an aqueous dispersion of particles comprising a wax substance and optionally an emulsifier, at least 35% of the particles having a size of 0.2 to 5 microns and a melting point with a range of 55 ° C below the maximum foam exothermic temperature.
2. 2. The method of compliance with the claim 1, characterized in that the particles are present from 0.0001 to 2 parts by weight of solids per one hundred parts of polyol (pphpp).
3. 3. The method according to claim 1, characterized in that at least 25% of the particles have a size of 1.5 to 3 microns.
4. 4. The method according to claim 1, characterized in that the aqueous dispersion is 5 to 60% by weight of solids. 5. The method according to claim 1, characterized in that the blowing agent comprises water or water and an HCFC. The method according to claim 1, characterized in that the organic polyisocyanate is MDI and the melting point of the dispersed particles is 0 to 30 ° C lower than the maximum foam exothermic temperature. The method according to claim 1, characterized in that the organic polyisocyanate is TDI and the melting point of the dispersed particles is 0 to 50 ° C lower than the maximum foam exothermic temperature. The method according to claim 1, characterized in that the organic polyisocyanate is a mixture of MDI and TDI the melting point of the dispersed particles is 0 to 40 ° C lower than the maximum foam exothermic temperature. 9. The method according to claim 1, characterized in that at least 70% of the particles are within the established size range of 0.2 to 5 microns. 10. The method of compliance with the claim 1, characterized in that the particles are present from 0.001 to 0.3 parts by weight of solids per one hundred parts of polyol (pphpp). 11. The method according to claim 1, characterized in that the wax substance is selected from the group consisting of paraffin waxes, microcrystalline waxes, synthetic waxes, vegetable waxes, mineral waxes, animal waxes, thickener oil fractions and agents of release of polysiloxane. 12. In a method for preparing a flexible polyurethane foam comprising reacting an organic isocyanate that is MDI, TDI or an MDI / TDI mixture with a polyester or polyester polyol in the presence of urethane catalyst, water, carbon dioxide liquid, CFC, HCFC, HFC, pentane, acetone and mixtures thereof as the blowing agent, optionally a cellular stability of silicone surfactant, and a cell opening additive, the improvement is characterized in that it comprises as the opening cellular present at 0.0001-2 pphpp an aqueous dispersion which is 5-60% by weight of particle comprising a wax substance and an emulsifier, at least 35% of the particles have a size of 0.2 to 5 microns and a point Fusion within the range of 30 ° C lower than the maximum foam exothermic temperature at the exothermic temperature of the MDI-based foam, 50 ° C lower than the maximum foam exothermic temperature at Exothermic temperature of the foam based on TDI or 40 ° C lower than the exothermic temperature of maximum foam at the exothermic temperature of the foam based on MDI / TDI. 13. The method according to claim 12, characterized in that cellular Xl opener is present at 0.001 to 0.3 pphpp. 14. The method according to the claim 13, characterized in that at least 25% of the particles have a size of 1.5 to 3 microns. 15. The method of compliance with the claim 14, characterized in that the aqueous dispersion is from 10 to 45% by weight of solids. The method according to claim 13, characterized in that the organic polyisocyanate is MDI and the melting point of the dispersed particles is 0 to 10 ° C lower than the maximum foam exothermic temperature. The method according to claim 13, characterized in that the organic polyisocyanate is TDI and the melting point of the dispersed particles is 0 to 45 ° C lower than the maximum foam exothermic temperature. The method according to claim 13, characterized in that the organic polyisocyanate is a mixture of MDI and TDI and the melting point of the dispersed particles is 0 to 30 ° C lower than the maximum foam exothermic temperature. 19. The method according to claim 13, characterized in that at least 70% of the particles are within the established size range. 20. A flexible polyurethane foam having a density of 0. (10-600 kg / m3) prepared by reacting a dQ? Apolacion characterized in that it comprises the following Stones in parts by weight (pbw): Polyol 20-100 80-0 Polyol Polymer Silicon Surfactant 0.5-2.5 Cell Aperture Additive 0.05-3 Water 1-8 Auxiliary Blowing Agent 0-4.
5. 5 Reticulator 0.5-2 Catalyzed Composition 0.1-5 Isocyanate Index 70-115 The additive of the cell opening comprises an aqueous dispersion of particles comprising a wax substance and optionally an emulsifier, at least 35% of the particles having a size of 0.2 to 5 microns and a melting point ranging from 0 to 55 ° C lower at the maximum foam exothermic temperature.