MXPA01000191A - Permanent gas blown microcellular polyurethane elastomers - Google Patents

Abstract

Microcellular polyurethane elastomers having sharply reduced or virtually no urea linkages may be prepared without resort to organic physical blowing agents by frothing a frothable mixture containing isocyanate reactive polyols and chain extenders, and a frothable isocyanate component. The isocyanate component is derived by reacting a stoichiometric excess of a di- or polyisocyanate with a polyol component containing an ultra-low unsaturation polyol. The froth-produced elastomers surprisingly exhibit greatly improved tear strengths, compression set, and other physical properties as compared to all water-blown microcellular elastomers of the same density.

Description

TISSUE MICROCELLULAR POLYURE ELASTOMERS BLOWED WITH PERMANENT GAS Technical Field The present invention belongs to the microcellular polyurethane elastomers, in the form of foam. More particularly, the present invention pertains to microcellular polyurethane elastomers prepared from low unsaturation polyoxyalkylene polyethers, and foamed with permanent gases. These microcellular elastomers are very suitable for use as shoe sole components.

Description of Related Art Microcellular polyurethane elastomers have numerous uses, for example as energy absorbing buffers, automotive components such as head rests and arm rests, and in particular as shoe sole components. Prior to the Montreal Protocol, it was possible to use volatile halocarbons such as CFC-11, CFC-22, Ref: 125998 methylene chloride, and the like as blowing agents to provide the numerous very fine cells, characteristics of the microcellular elastomers. However, the severe limitations imposed on the use of halogenated hydrocarbons, and the increasing environmental problems, in relation to the use of even the most environmentally friendly organic blowing agents, have required the development of microcellular elastomers blown with water. In the microcellular polyurethane elastomers blown with water, the water present in the formulation reacts with a portion of the isocyanate component to generate an amine and carbon dioxide. The carbon dioxide serves as the blowing agent. However, the amine generated reacts with the additional isocyanate to produce urea bonds. The microcellular elastomer produced in this way is not a polyurethane elastomer, but a polyurethane / urea elastomer containing urea bonds of substantially hard segment. Such elastomers are often harder and less elastic than all their polyurethane counterparts. More importantly, however, the tear resistance of such elastomers is limited. Tear resistance is particularly important in applications such as those of the footwear industry. Flexible polyurethane foams have been air-foamed for use in carpet reinforcements and subwoofer applications. However, such foams are not microcellular. The cell size is very large, as evidenced by the much lower density of these foams, for example, from about 0.015 g / cm3 to about 0.09 g / cm3, and the systems are highly filled to increase the capacity to withstand load. The large cell sizes required of these foams, coupled with the use of doctor blades and the like to regulate the height of the foam, results in a considerable degree of cell collapse. The contribution to the large cell size, as well as the propensity for these cells to collapse is the relatively low viscosity of these systems in the form of flexible foam. The collapse can not be tolerated in molded microcellular elastomers, and the formulations employed in lower reinforcement in foam form, for carpets, are not suitable for microcellular elastomers. It may be desirable to provide microcellular elastomers containing exclusively urethane linkages, or substantially all urethane linkages with only a much smaller amount of urea linkages, without the use of organic, volatile blowing agents. It may further be desirable to provide microcellular polyurethane elastomers that exhibit improved tear strength, relative to water-blown polyurethane / urea microcellular elastomers, of similar density.

Brief Description of the Invention The present invention pertains to the microcellular elastomers in the form of foam, prepared by foaming the main reactive polyurethane-forming ingredients, with a non-organic permanent gas in the presence of a foaming surfactant; and to the polyurethane / urea microcellular elastomers, of foam having much lower urea group content than comparable microcellular polyurethane / urea blown with water elastomers. The sides A and B of the formulation can be separately foamed and the two foams combined and processed appropriately. The resulting polyurethane and the microcellular polyurethane / urea elastomers have surprisingly improved tear strengths when a substantial portion of the polyoxypropylene polyol portion of an isocyanate-terminated prepolymer used to prepare the elastomers is a low unsaturation polyoxypropylene polyol. .

Description of the Preferred Modalities The microcellular polyurethane elastomers of the present invention are prepared by foaming microcellularly foamable polyurethane reactive ingredients, generally supplied at least as two streams of reactive components: a stream of resin containing an isocyanate-reactive polyol mixture, and a isocyanate stream containing one or more foamable di- and / or polyisocyanate prepolymers, quasi-prepolymers, or mixtures thereof, optionally together with one or more di- or polyisocyanates. The resin side (side B) contains minimally one or more polyisoles reactive with isocyanate and / or polymer polyols and preferably a chain extender. Optional components include catalysts, crosslinkers, pigments, fillers and other conventional additives. A foaming surfactant should also be generally present. Suitable isocyanate-reactive polyols are low unsaturation polyoxypropylene polyols having equivalent weights in the range of 1,000 Da to 6,000 Da, preferably from 1,500 Da to 5,000 Da, and more preferably from 1,500 Da to 3,000 Da. The unsaturation of these polyols should be below 0.015 meq / g, preferably less than 0.010 meq / g, and more preferably about 0.007 meq / g or less. The molecular weights and equivalent weights present in Da (Daltones) are equivalent and molecular weights in number, unless indicated otherwise. Suitable polyols include polyoxyalkylene polyols having nominal functionalities of about 2 to about 8. "Nominal functionality" means the theoretical functionality, for example the functionality of the initiator molecule used to prepare the polyol. In general, mixtures of polyoxyalkylene polyols are used, preference being given to average functionalities in the range of 2 to about 4 and average weights greater than 1000 Da. The polyoxyalkylene polyols are preferably polyoxypropylene homopolymer polyols, or polyoxypropylene polyols containing up to about 30% by weight of oxyethylene portions, these oxyethylene portions being randomly dispersed within the polymer chain, or located at the ends of the polymer chain as a polyoxyethylene cap. Polyols with internal oxyethylene portions (random and / or in blocks) and polyols with external oxyethylene (encased) blocks are also useful. Higher alkylene oxide polyols, for example 1,2-butylene oxide or 2,3-butylene oxide, oxetane, or tetrahydrofuran are also useful, when used in conjunction with the low unsaturation polyoxypropylene polyols of the present invention. Polyester polyols are also useful as minor components in the practice of the present invention. Preferred polyoxyalkylene polyether polyols are di- and trifunctional polyols prepared by the oxyalkylation of difunctional initiators such as propylene glycol, dipropylene glycol, ethylene glycol, diethylene glycol, 1,4-butanediol, and the like, or trifunctional initiators such as glycerin and trimethylolpropane. These examples of initiators are not limiting. Polyols having low unsaturation, for example, in the range of 0.012 to 0.020 meq / g measured by ASTM D-2849-69, "TESTING OF URETH-ANE FOAM POLYOL RAW MATERIALS", can be prepared with complex metal cyanide catalysts. double such as those described in U.S. Patent Nos. 5,158,922; 5,470,813, 5,482,908; and 5,545,601. However, the most preferred ultra-low unsaturation polyoxyalkylene polyols are those which have unsaturation levels of less than about 0.010 meq / g, and generally in the range of 0.003 to 0.007 meq / g, the synthesis of which is made possible by catalysts of highly active DMC as shown in U.S. Pat. Nos. 5, 470,812, 5,482,908, 5,545,601, and 5,689,012. Batch and continuous processes employing such catalysts are described in co-pending U.S. Application Serial No. 08 / 597,781 and U.S. Patent No. 5,689,012. Such polyoxyalkylene polyether polyols are commercially available as ACCLAIMMR polyols from ARCO Chemical Company. The above patents are incorporated herein by reference. Also suitable for use in the present foams are polymeric polyols. Polymeric polyols are polyoxyalkylene polyols, polyester polyols, or other base polyols that contain a finely dispersed solid polymer phase. Polymers having solid phases derived from isocyanate reactions with a variety of reactive species such as di- and trialkanolamines ("PIPA polyols"), hydrazine ("PHD polyols") and others, including polyurea dispersions ("PUD") and polyisocyanate ("PID") can be used. However, the preferred polymer polyols are the vinyl polymer polyols which can be prepared by the in situ polymerization of one or more vinyl monomers in the presence of a suitable vinyl polymerization initiator. Preferred vinyl monomers include, but are not limited to, styrene, acrylonitrile, tyrosine, methyl methacrylate, and the like. More preferred are acrylonitrile and styrene, optionally with minor proportions of other monomers. The solids content of the polymeric polyols may be in the range of about 5 weight percent to about 70 weight percent, with solids contents in the range of 20 weight percent to 50 weight percent which are the preferred. The preparation methods of the various polymeric polyols are well known, and a wide variety of such polyols are commercially available. More preferably, the base polyols of the polymeric polyols are polyoxyalkylene polyether polyols of ultra-low unsaturation. In addition to the polymer polyols and polyols, the resin side (side B) preferably contains at least about 50 percent equivalents, based on the content of the isocyanate-free isocyanate group (side A), of one or more extenders. low molecular weight chain, preferably those having a molecular weight less than 300 Da, more preferably less than about 150 Da. Suitable chain extenders include difunctional species such as ethylene glycol, diethylene and triethylene glycols, propylene glycol, dipropylene and tripropylene glycols, 1,3-propanediol, 1,4-butanediol, 2,2,4-trimethylpentanediol, 1,4-cyclohexanediol. , 1,4-cyclohexanedimethanol, 1/6-hexanediol, and the like. More preferred is 1,4-butanediol. You can use mixtures of chain extenders. The catalyst or catalysts is / are usually included in the resin side of the formulation. Conventional urethane promoter catalysts, such as the various tin catalysts, for example dibutyltin dilaurate, dibutyltin diacetate, tin octoate, and the like, are suitable. Amine-based catalysts such as diazabicyclooctane can also be used. When preferred formulations which do not substantially contain water are employed, blowing catalysts which accelerate the reaction of isocyanate with water, and which are ordinarily necessary for the preparation of water-blown microcellular polyurethane / urea elastomers, are not required. When the formulation contains some water, as described hereinafter, a blowing catalyst such as diazabicyclo [2.2.2] octane or another catalyst that catalyzes the isocyanate / water reaction, should also be included in the formulation. The types and amounts of the catalysts can be easily selected by a person of ordinary skill in the art of microcellular polyurethane elastomers. While the preferred compositions according to the present invention do not substantially contain water, for example, water is purposely not added to the formulation to serve as a blowing agent, the resin side may contain a smaller amount of water as defined. later in the present. Polyurethane reagents often contain very small amounts of water as supplied, particularly polyols, chain extenders, and crosslinkers. However, the amounts are so low that no observable blowing occurs, and without the addition of a reagent or non-reactive blowing or foaming agent, only the non-cellular polyurethanes would result from their use. In microcellular polyurethane / urea foams, blown with water, water is added in amounts of about 0.05 to about 0.5 parts of water per 100 parts of resin / isocyanate combined. These amounts can, for example, producing microcellular foams with densities in the range of about 0.8 g / cm 3 to about 0.2 g / cm 3. In the present invention, all preferred polyurethane microcellular foams can be produced in this same density range without incorporating water as a blowing agent. The foams will not substantially contain urea groups. However, if minor amounts of urea groups can be tolerated for a specific application, then a very minimal amount of water can also be added. This amount of "very minimal" water can be defined as 50 percent by weight or less of the amount of water that might be needed to provide a microcellular elastomer of the same density without foaming. By way of illustration, if 0.1 parts of water per 100 parts of the total elastomeric system formulation could provide a microcellular elastomer having a target density of about 0.70 g / cm3 in the absence of foaming, then a "very minimal" amount of water in such a system it could be about 0.05 parts or less. Additional microcells and / or additional microcells and / or larger microcells required to produce the target density will be provided by the foaming. The elastomer produced in this way will have much less urea groups than the microcellular elastomer all blown with water, and is thus expected to show considerably different physical properties, in particular, higher elongation and tear resistance. • Such an elastomer, which has a considerable proportion of urea bonds lower than the amount contained in a water-blown polyurethane / urea elastomer of similar density, is still considered a microcellular polyurethane elastomer as this term is used herein, and not a polyurethane / urea elastomer. While the isocyanate-reactive components have been described as "B-side" or "resin side" thus far, this terminology should not be construed to imply that the isocyanate-reactive components need to be blended into a single component. While this is certainly possible, and may be preferable in some cases, it is likely that in high production manufacturing, the various components of the resin side may be distributed to a multi-inlet mixing head such as those supplied by Henneke, Kraus. -Maffei, and other manufacturers. The combined currents on the resin side can then be foamed and combined with the foam on the A side, or the A side (isocyanate components, together or separately) can be added as separate streams together with the B-side components and formed into foam . The isocyanate component used to form the isocyanate-terminated prepolymers and the quasi-prepolymers can be selected from organic and aliphatic di- and poly-isocyanates in the preparation of polyurethane polymers. Non-limiting examples of suitable isocyanates include aromatic isocyanates such as 2,4- and 2,6-toluene diisocyanate and mixtures thereof; the various methylene diphenylene diisocyanates (MDI), including 2,2'-, 2,4'- and 4,4'-MDI and various mixtures thereof; modified aromatic isocyanates such as those prepared by the reaction of isocyanates with themselves or with low molecular weight or oligomeric reactive species, particularly carbodiimide, uretdione and urethane-modified MDI; Polymeric MDI, and the various aliphatic and cycloaliphatic isocyanates such as 1,6-hexane diisocyanate, 1,8-octane diisocyanate, 2,4- and 2,6-methylcyclohexane diisocyanate, 2,2'-, 2-diisocyanate , 4'- and 4, '-dicyclohexylmethane, and isophorone diisocyanate. Aliphatic and modified cycloaliphatic isocyanates are also useful. The isocyanate-terminated prepolymers prepared by reacting an extequiometric excess of a di- or polyisocyanate with a polyoxyalkylene glycol or a mixture of one or more polyoxyalkylene glycols with oxyalkylated species of higher functionality are preferably used.

The average nominal functionality is preferably between about 2.0 and 2.2, and is more preferably about 2.0. Suitable glycols include polyoxypropylene glycols; polyoxypropylene glycols further containing up to about 30 weight percent oxyethylene portions as an internal and / or external block and / or as internal oxyethylene random portions; and polytetramethylene ether glycols (PTMEG). The polyoxyalkylene polyol component may contain minor amounts of polyester diols, polycaprolactone diols, and the like. The isocyanate reactive component preferably has a molecular weight of from about 1,000 Da to 15,000 Da, more preferably 1,000 Da to 8,000 Da, and most preferably about 2,000 Da to 4,000 Da. More preferred are polyoxypropylene homopolymer glycos with ultra-low unsaturation and polyoxypropylene / polyoxyethylene copolymer glycols with ultra-low unsaturation, containing random internal oxyethylene portions, the latter preferably prepared by DMC catalysis as previously described.

The isocyanate-terminated prepolymers should have isocyanate group contents of between about 2 weight percent and 18 weight percent, preferably 4 weight percent up to 12 weight percent, and most preferably about 6-10 percent by weight weight. Low viscosity isocyanates, for example TDI and MDI can also be used in processes according to the present invention, where the individual components or the separated sides A and B are first mixed and then formed into foam, provided of course that the mixture of polyols, the low viscosity isocyanates, the chain extenders and the like are of foamable viscosity such that a stable foam can be obtained, which does not collapse. However, for elastomers having desirable physical properties, it is generally necessary to employ isocyanate-terminated prepolymers. In the embodiment of the present invention, where side A and side B are separately foamed, the isocyanate component of side A must itself have a foamable viscosity. For this reason, the isocyanate-terminated prepolymers are particularly suitable, although isocyanates of foamable viscosity can be prepared by the addition of viscosifiers to the lower viscosity di- or polyisocyanates, quasi-prepolymers, or low viscosity prepolymers. Foaming, either as a combined stream or as separate streams, should generally take place in the presence of a suitable foaming surfactant. Such surfactants are available from OSI, Inc. A surfactant of this type is the VAX6123 surfactant. Other surfactants may also be useful. It may be possible for a particular component or a particular side to be foamed without the addition of a foaming surfactant. The term "icrocellularly foamable" with respect to a complete system, system A or side B, or component of the system, indicates that the system, side, or respective component may be foamable to a non-collapsible, stable foam of suitable density and suitable cell size for the molding of a part of microcellular elastomer. Such "foamable microcellular" components will generally include one or more foaming surfactants. It was surprising that the microcellular foams of the present invention showed less variation in physical properties, as reflected by differences in total density, and core density compared to microcellular elastomers blown with water. This is particularly unexpected in view of the tendency of conventional (non-microcellular) foams to rapidly collapse. However, more surprising was the fact that the A-side and B-side components could be separately foamed, the foams combined, and molded to form a fully cured microcellular polyurethane elastomer, which has excellent physical properties. In addition to the reactive components as described above, the formulation may contain other conventional additives and auxiliaries, for example pigments, colorants, plasticizers, fillers, and the like. These components are present in much smaller amounts, and when they are present, they should not be taken into account when calculating or when measuring the density of the microcellular foam. The foamed reactive formulation is introduced into a suitable mold, and generally heated until the elastomer has developed sufficient strength before firing to allow demolding. For example, the molds can be conveniently preheated to 50 ° C, the foamable mixture introduced, and the mold kept in an oven at 50 ° C until it is cured. The foam is generally introduced into the mold under positive pressure. Positive pressure ensures that the mold cavity is completely filled and a free part of empty spaces is produced. The term "permanent organic non-organic gas (s)" means a substance that is a gas at standard temperature and pressure, is not a hydrocarbon or halocarbon, and has been incorporated as a gas, not generated by chemical reaction. Preferred permanent gases are nitrogen, air, and carbon dioxide, or mixtures thereof. The term should not be considered to require complete absence of organic blowing agents, since smaller amounts of such blowing agents can be added without causing substantial changes in physical properties and therefore could not depart from the spirit of the invention. The amounts of the organic blowing agents should be less than 20 weight percent of the calculated amount of the blowing agent needed to prepare a blown, non-foamed foam of similar density to meet the above definition. Preferably, the organic blowing agent is not used. A substantial portion, and preferably all gases contained in the cells, must be introduced by foaming, and / or by adding water in a smaller amount. Preferably, at least 50% of the gases are air, nitrogen, carbon dioxide introduced by foaming, or their mixtures, with or without non-condensable water vapor (at 0 ° C or higher). More preferably, this gas mixture comprises 70%, and more preferably 90% or more of the total gas contained in the microcells. Having generally described this invention, further understanding can be obtained by reference to certain specific examples, which are provided herein for purposes of illustration only and are not to be construed as limiting, unless otherwise specified. .

Examples 1 and 2 Microcellular elastomers were prepared according to the following procedure: The formulations presented in Table 1 were foamed using a wire shake mixer. The resulting foam had a density of 0.67 g / cm3.

Table 1 1-Pololol A is a triol of polyoxypropylene initiated with glycerin, catalyzed with KOH, having 19% by weight of polyoxyethylene cap and a hydroxyl number of 35. 2Polol B is a polymer polyol based on polyol A, nominally containing 40% by weight. weight of acriIonitri / styrene solids.

Separately, the prepolymer compositions prepared by the previous reaction of the components shown in the Table were formed into a foam using a wire shake mixer. The resulting prepolymer foams had the densities expressed in Table la.

TABLE The foams in Tables 1 and 1 were beaten together and cast in a mold at 50 ° C, and allowed to cure. The foam and elastomer densities and other physical properties of the elastomer are reported in Table 2 below.

TABLE 2 * A small amount of moisture was trapped inside the sample due to moisture in the environment. This resulted in an elastomer of lower density than what was predicted.

Ex empl o Compare ti vo Cl A comparative polyurethane / urea elastomer was prepared from a similar formulation but containing enough water to provide a microcellular elastomer blown with water having a density of 0.49 g / cm 3 (target density 0.50 g / cm 3). One of the advantages of a free microcellular elastomer of the urea group is the improved resistance to tearing. The tear is one of the most important properties in applications in footwear. The following table compares the tear properties of water blown and air blown (foamed) microcellular elastomers: TABLE 3 As illustrated in Table 3, the microcellular polyurethane elastomers prepared by foaming showed an improvement of 46% in the tear to the break, and 30% improvement in the tear C compared to a polyurethane foam / microcellular urea, blown with water, of the same density. The polymeric polyols used on the B side of the formulations of Examples 1 and 2, contained conventionally catalyzed polyoxypropylene / polyoxyethylene base polyols.

Example 3 A foam formulation was prepared by adding to a mixing kettle 48.61 g of a 7% NCO prepolymer prepared from 4,4'-MDI and a polyoxypropylene / polyoxyethylene diol of ultra-low unsaturation, which had a weight molecular weight of approximately 4000 Da; 121.5 g of a 7% NCO prepolymer prepared from 4,4'-MDI and an ultra-low unsaturation polyoxypropylene triol of about 6,000 Da; 42.4 g of butanediol; and 6.1 g of VAX 6123 foaming surfactant. The prepolymers, prepared using the ultra-low unsaturation polyols, were added to a mixing vessel together with the chain extender and the foaming surfactant.

These were mixed for 30 seconds, after which the catalysts were added (0.19 g of BL 11, 0.16 g of NIAX® 33LV) and the mixture was continued with a shake for 60 seconds. The resulting foam was poured into a 20.3 cm x 15.2 cm x 2.5 cm (8"x 6" x 1") aluminum mold preheated to 50 ° C, and cured at 50 ° C for 5 to 10 minutes.

Example 4 A formulation was made, formed into foam, molded, and cured in an identical manner to that of Example 3, and using an identical formulation, notwithstanding the initial mixing shortened to 16 seconds and mixing after addition of the catalyst It was shortened to 30 seconds.

Examples Use Compare C3 and C4 The elastomers were prepared from the same formulation as used in Examples 3 and 4, except that water was used as a blowing agent to prepare the microcellular foams blown with water having total densities of 0.53 g / cm 3 and 0.56 g. / cm3 for comparison purposes. The physical characteristics of foamed and water blown foams are described in Table 4 below.

TABLE 4 From the table, it can be seen that the foams are more consistent, showing less difference between the total density and the density of the core. In addition, the foams were unexpectedly hard and had higher tensile strengths. The tear C and the tear to the break were both markedly improved, the elasticity was higher, and the compression strain decreased dramatically. In shoe applications, low compression deformation is highly important. The properties of the foams described in the table reveal some significant differences between the foamed and blown samples with water. It is believed that these differences may be due to differences in the composition of the hard segment. The foamed samples are 100% urethane, while the samples blown with water are a mixture of urethane and urea. In addition to the properties shown in the Table above, compression hysteresis techniques, which can be correlated with comfort factors in the shoes, were tested. The test involves 5 repeated compressions at a known rate up to 50% deformation of a sample. The following table shows the results obtained in the fifth cycle at three speeds, 12.7, 25.4 and 50.8 cm / min (5, 10 and 20 inches / minute) respectively. The materials tested are the same as those described in the previous table: TABLE 5 The foamed system shows superior hysteresis and higher capacity to support load compared to the water blow system.

Example 5 and Ex empl o Compare the volume C5 Two similar elastomeric formulations were used to prepare microcellular elastomers, and the physical properties of the elastomers were compared. The first elastomer was formed into foam. Water was added to the second formulation to produce a microcellular polyurethane / urea elastomer blown with water. Both examples employ an isocyanate-terminated prepolymer, based on diol, with ultra-low unsaturation, prepared by the reaction of 2500 g of Acclaim ™ 4201, a polyoxyalkylene diol with hydroxyl number of 28 available from ARCO Chemical Co., with 856.1 g of Mondur® M (pure MDI). Both examples also employ an isocyanate-terminated prepolymer, based on ultra-low unsaturation triol, prepared by the reaction of 2500 of Acclai MR 6300, a polyoxyalkylene triol with hydroxyl number 28 also available from ARCO Chemical Co. , with 858.1 g of Mondur® M. The formulation is given in Table 6a below.

TABLE 6a The physical properties of the elastomer are listed in Table 6b below.

TABLE 6b Example 6 and Ex empl o Compare ti vo C6 Two foamable formulations were prepared, foamed, and cured in the same manner as in Example 3. The microcellular polyurethane elastomer of Example 6 was prepared from the polyether polyol ACCLAIM® 4200, a polyoxypropylene diol having a molecular weight of 4000 Da and an unsaturation of 0.005 meq / g. The microcellular polyurethane elastomer of Comparative example C6 was prepared from a polyoxypropylene diol having a molecular weight of 4000 Da but a greater unsaturation in the conventional range of about 0.08 meq / g. The results are described in Table 7 below.

TABLE 7 By the term "unfilled density" is meant the density that the foam could have free of the filler, when it is used. The molecular weights and the equivalent weights are number-average molecular weights and the equivalent weights in Daltones (Da). The term "major" means 50% or more. The term "minor" is understood to be less than 50%, these percentages being by weight, unless indicated otherwise. Each component described herein can be used for the exclusion of components not necessary for achieving the objectives of the invention, and in particular can be used for the exclusion of components and processes not described herein. The necessary components include an isocyanate component and an isocyanate-reactive component, at least one of which is prepared from a polyol with low or ultra-low unsaturation, such that the latter comprises at least 35 weight percent, and preferably a larger part of the total polyoxyalkylene polyol component of the formulation, either present as an isocyanate-reactive polyol or incorporated in an isocyanate or quasi-prepolymer-terminated prepolymer. Having now fully described the invention, it will be apparent to a person of ordinary skill in the art that many changes and modifications may be made thereto without departing from the spirit or scope of the invention as described herein.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (25)

CLAIMS Having described the invention as above, the content of the following claims is claimed as property:

1. A microcellular polyurethane elastomer having microcells filled with one or more substances, characterized in that it is: a gas at standard temperature and pressure; neither a hydrocarbon nor a halocarbon; and incorporated directly as a gas and not generated in situ, the elastomer being preparable by foaming at least one isocyanate-terminated polyoxyalkylene prepolymer, prepared by the reaction of a stoichiometric excess of one or more di- or polyisocyanates with a polyol component of polyoxyalkylene having an average equivalent weight greater than 1,000 Da, and at least one polyoxyalkylene polyol composition, the polyoxyalkylene polyol composition has an average equivalent weight of at least 1,000 Da, an average functionality of 2.0 or more, and optionally in addition to the polyol composition, 50 percent equivalent or more based on the reactive isocyanate groups of an aliphatic glycol chain extender having a molecular weight below 300 Da to prepare a curable foam, and introducing said foam into a mold and allowing the foam to cure, wherein the polyoxyalkylene polyols having unsaturation n less than 0.015 meq / g comprise at least 35 weight percent of the total polyoxyalkylene polyol component polyoxyalkylene polyol and polyoxyalkylene polyol composition taken untamente conj.

2. The elastomer according to claim 1, characterized in that all or a portion of the isocyanate-reactive components are foamed to form a first foam, and a composition containing the isocyanate-terminated prepolymer is foamed to form a second foam, the First and second foams are combined to form the curable foam.

3. The elastomer according to claim 1 or 2, characterized in that all the reactive ingredients are intensively mixed and foamed together to form the curable foam.

4. The elastomer according to any preceding claim, characterized in that the isocyanate-terminated prepolymer comprises one or more microcellularly foamable, isocyanate-terminated prepolymers prepared from one or more polyoxyalkylene polyethers having an average functionality between 2 and 4.

5. The elastomer according to any of the preceding claims, characterized in that at least one of the isocyanate-terminated prepolymers is one prepared by reacting a stoichiometric excess of one or more di- or polyisocyanates with one or more low unsaturation polyoxypropylene polyols. , which have an unsaturation less than 0.010 meq / g.

6. The elastomer according to claim 5, characterized in that the polyoxypropylene polyol contains oxyethylene portions in an amount up to 30 weight percent.

7. The elastomer according to claim 6, characterized in that the oxyethylene portions are internal, random oxyethylene portions.

8. The elastomer according to any preceding claim, characterized in that the urea groups are present in the microcellular polyurethane elastomer, the urea groups being produced through the reaction of the free isocyanate groups with added water as an auxiliary blowing agent, said water in not more than 50 weight percent of the amount of water required to produce an identical density foam without foaming.

9. The elastomer according to any preceding claim, characterized in that one or more substances consist essentially of one or more of nitrogen, air, and carbon dioxide.

10. The elastomer according to any preceding claim, characterized in that the density of the microcellular elastomer is from 0.2 g / cm3 to 0.8 g / cm3, preferably from 0.25 g / cm 'to 0.5 g / cm3.

11. The elastomer according to any preceding claim, characterized in that it has substantially no urea bonds formed by a water / isocyanate reaction.

12. E.1 elastomer according to any preceding claim, characterized in that the major portion of the total polyoxyalkylene polyols comprises one or more polyoxypropylene polyols having an unsaturation less than 0.015 meq / g.

13. The elastomer according to any preceding claim, characterized in that the major portion of the total polyoxyalkylene polyols comprises one or more polyoxypropylene polyols having an unsaturation less than 0.010 meq / g.

14. The elastomer according to any preceding claim, characterized in that all polyoxyalkylene polyols having equivalent weights greater than 1,000 Da have unsaturation less than 0.015 meq / g.

15. A process for the preparation of a microcellular polyurethane elastomer, the process is characterized in that it comprises: a) foaming a first foamable mixture comprising one or more isocyanate-reactive components comprising one or more polyoxyalkylene polyols with one or more substances as defined in claims 1 or 9 to form a first foam; b) foaming a second foamable mixture containing one or more isocyanate-terminated prepolymers having an average isocyanate group content of 2 weight percent up to 18 weight percent, with one or more substances as defined in the claim 1 or 9 to form a second foam, the isocyanate terminated prepolymer prepared by the reaction of a stoichiometric excess of one or more di- or polyisocyanates with a polyoxyalkylene polyol component, the total polyoxyalkylene polyol in the isocyanate reactive component and the isocyanate-terminated prepolymer taken together comprises 35 weight percent or more of one or more polyols with low unsaturation having a functionality of 2 to 8, an equivalent weight of 1,000 Da or greater, and an unsaturation of less than 0.015 meq / g; c) the combination of the first foam and the second foam to form a curable foam; d) introducing the curable foam into a mold and allowing the curable foam to cure; e) removal of the microcellular polyurethane elastomer from the mold.

16. The process according to claim 15, characterized in that the first foamable mixture further comprises at least 50 equivalent percent based on the amount of free isocyanate employed in said process, of one or more aliphatic chain extenders having a molecular weight per below about 300 Da.

17. The process according to claim 15 or 16, characterized in that the polyols with low unsaturation have an average unsaturation of less than 0.010 meq / g.

18. The process according to any of claims 15 to 17, characterized in that the isocyanate-reactive components have an average unsaturation less than 0.010 meq / g.

19. A process for the preparation of a microcellular polyurethane elastomer having a low content of urea groups, the process is characterized in that it comprises: a) the selection as an isocyanate component, of an isocyanate component consisting essentially of one or more prepolymers or isocyanate-terminated quasi-prepolymers, the isocyanate-terminated prepolymer or quasi-prepolymer prepared by the reaction of a stoichiometric excess of one or more di- or polyisocyanates with a polyol component, the polyol component comprising for the most part one or more polyols with low unsaturation having a functionality of 2 to 8, an equivalent weight of 1,000 Da or greater, and an unsaturation less than 0.015 meq / g; b) the selection of an isocyanate-reactive component comprising one or more polyoxyalkylene polyols having a nominal functionality of 2 to 3 and at least 50 equivalent percent based on the isocyanate reactive groups of component (a), of one or more glycol chain extenders having a molecular weight of less than 300 Da, such that the average nominal functionality of component (b) is from 2.0 to 2.3, the isocyanate reactive component is supplied as a single component or as multiple components; c) foaming the components (a) and (b) to form a curable foam, stable at an isocyanate index of 90 to 110, by incorporating a quantity of one or more substances as defined in claims 1 or 9, in components (a) and (b); d) the introduction of the curable foam into a mold; and e) curing the foam to form a microcellular polyurethane elastomer.

20. The process according to claim 19, characterized in that the foaming takes place in the presence of an effective amount of one or more foam stabilizing surfactants.

21. The process according to claim 19 or 20, characterized in that the components (b) further comprise a smaller amount of water, said smaller amount of water is less than 50% by weight of the amount of water that could be effective to form a microcellular elastomer having the same density of the gas-foamed elastomer, not permanent, but without foaming.

22. The process according to any of claims 19 to 21, characterized in that the isocyanate component consists essentially of one or more isocyanate-terminated prepolymers, each of said prepolymers is prepared by the reaction of MDI, modified MDI, or mixtures thereof. same, with one or more low unsaturation polyoxypropylene polyols, polyoxypropylene polyols containing not more than 30 weight percent oxyethylene portions, polyoxypropylene polyols having number average molecular weights between 1,000 Da and 5,000 Da, and an average unsaturation of less than 0.015 meq / g.

23. The process according to claim 22, characterized in that the average unsaturation is less than 0.010 meq / g.

24. The process according to any of claims 15 to 17, characterized in that the major portion of the total polyoxyalkylene polyols comprises one or more polyoxypropylene polyols having an unsaturation less than 0.15 meq / g, preferably less than 0.010 meq / g.

25. The process according to any of claims 15 to 17 and 24, characterized in that all the polyoxyalkylene polyols having equivalent weights greater than 1,000 Da have unsaturation less than 0.015 meq / g.