MXPA98008948A - A method for obtaining a polyurethane foam with integral molded, low density - Google Patents

Abstract

It has been found that non-chlorinated pentafluoropropane blowing agents can be used alone or in combination with water, in a method to obtain integral, flexible skin foams. For example, foams prepared using 1,1,1, 3,3-pentafluoropropane (HFA-245fa) alone or in combination with water, exhibit physical characteristics, such as abrasion resistance and flexural fissure formation, comparable to blown foams with conventional chlorinated fluorocarbons. The method of the present invention produces foams which are suitable for use in many applications including, for example, the soles of zapat

Description

A METHOD TO OBTAIN A POLYURETHANE FOAM OF MOLDED INTEGRAL LEATHER. LOW DENSITY FIELD OF THE INVENTION The present invention relates to integral skin foams and to a process for preparing these foams. More particularly, the invention relates to a method for obtaining integral skin foams employing penta fluoropropane as the sole blowing agent or with water as a co-blowing agent.

BACKGROUND OF THE INVENTION Integral skin foams are well known to those skilled in the art of polyurethane foams. These foams have a cellular interior and a micro-cellular or non-cellular skin of greater density. In general, to prepare these foams, an organic isocyanate is reacted with a substance, which has at least one isocyanate reactive group, in the presence of a catalyst, a blowing agent and a variety of optional additives. The reaction is carried out in a molding, where the higher density skin is formed at the interface of the reaction mixture and the relatively cold internal surface of the foam.

Historically, the most common types of blowing agents, used in integral skin polyurethane foams, have been chlorofluorocarbons (CFCs) or combinations of these CFCs and other blowing agents. However, in view of the recent mandates that seek to reduce and eventually eliminate the use of CFCs, alternatives to this are considered necessary. Past methods for preparing integral skin polyurethanes with CFCs as blowing agents include Great Britain Patent No. 1,209,297, which teaches the use of a combination of a blowing agent, consisting of a CFC, and a hydrate of an organic compound, which separates water at temperatures higher than 402C. This blowing agent or combination of agents is used in a formulation with a suitable polyisocyanate, a hydroxyl group containing a polyol and a catalyst. This patent discloses that the release of water in the system leads to a skin, which is permeated with fine cells, which is inconvenient. Attempts have been made to evaluate the performance of alternative blowing agents to CFCs. In an article by JLR Clatty and SJ Haasin, entitled: Performance of Blowing Agents Alternative to Fluorocarbon Chlorine in Structural RIM and Elastomeric Polyurethane Foams, presented at the Polyurethane Technical / Marketing Annual Conference, October 1989, the authors direct the use of water as a blowing agent for the injection molded systems (RIM) of the integral skin polyurethane reaction. In this application, the concentration of water in the system is controlled by the concentration and type of the molecular sieves used. As in the Great Britain patent, discussed previously, water is not in free form, but united in some way. In this case, the authors note that this process is limited to use in rigid foam systems, and flexible integral skin formulations can provide better service using HCFC or HCFC-22 as substitutes for CFCs. An integral foam formulation, recently used, is described in U.S. Patent No. 5,100,922, to Ada et al., Which relates to a method for producing a molded product of an integral skin polyurethane foam. The method comprises reacting and curing (1) a high molecular weight polyol, comprising, as a main component, a polyoxyalkylene polyol having, as the main constituent, oxyalkylene groups of at least 3 carbon atoms and oxyethylene groups in their molecular terminals, with the general content of the oxyethylene group not being more than 15% by weight and having a hydroxyl value not greater than 80, (2) an interlacing agent, containing a compound having an aromatic nucleus and at least two groups containing active hydrogen, selected from the group consisting of hydroxyl groups, primary amino groups and secondary amino groups, and (3) a polyisocyanate, in a mold, in the presence of a catalyst and a halogenated hydrocarbon skimming agent, containing a hydrogen atom. While an extensive list of blowing agents is provided, the only pentafluoro compounds described are chlorinated compounds, such as 3,3-dichloro-l, 1,1,2,2-pentafluoropropane and 1,3-dichloro-l , 1,2,2, 3-pentafluoro-propane, which are considered undesirable. More recently, U.S. Patent No. 5,506,275, issued to Valoppi, the present inventor, which refers to the use of 1,1-tetrafluoroethane, as an alternative to chlorinated fluorocarbon blowing agents, in Comprehensive skin foam formulations While this patent offers an alternative to halogenated hydrocarbon blowing agents per se, 1,1,2-tetrafluoroethane (HFC-134a) with boiling point of -26.52C and thus requires special gas delivery systems to introduce and keeping the blowing agent in solution, especially in hot climatic conditions, that is, above 322c. Thus, further improvements in the technique are still considered necessary. It has been found that foams using the blowing agents of pentafluoropropane and, in particular, 1,1,1,3,3-pentafluoropropane, as the blowing agent alone or in combination with small amounts of water, can be prepared , which meet the strict requirements inherent in integral skin foam applications, such as an acceptable appearance and must exhibit increased resistance to abrasion and crack formation upon bending. In addition, the pentafluoropropane blowing agents, used in association with the present invention, are generally soluble in resinous solutions, thus eliminating or greatly reducing the need for specialized gas delivery systems to maintain the pressure in the system.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a flexible, low density, integral skin polyurethane foam, capable of being used in various applications, comprising the reaction product of: a) a polyisocyanate component; and b) an active hydroxy functional polyol composition; in the presence of c) a blowing agent, which includes the non-chlorinated pentafluoropropane and optionally water; d) a catalyst; and e) optionally, one or more compounds, selected from the group consisting essentially of chain extension agents, a surfactant, an alcohol having from 10 to 20 carbon atoms, fillers, pigments, antioxidants, and mixtures thereof. The general process comprises reacting a polyisocyanate component with an isocyanate reactive compound, in the presence of a catalyst of a type known to those skilled in the art, and a non-chlorinated pentafluoropropane blowing agent, optionally in association with the water as a co-blowing agent. A catalyst that helps control foam formation can also be used as a surfactant to regulate cell size and structure.

DETAILED DESCRIPTION OF A PREFERRED MODALITY OF THE INVENTION Organic polyisocyanates, used in the present process, contain aromatically bound isocyanate groups. Representative of the types of organic polyisocyanates, considered here, include, for example, 1,4-diisocyanatobenzene, 1,3-diisocyanate-o-xylene, 1,3-diisocyanate-p-xylene, 1,3-diisocyanate-m -xylene, 2,4-diisocyanato-l-nitrobenzene, 2,5-diisocyanato-l-nitro-benzene, m-phenylene-diisostanoate, 2,4-toluene-diisocyanate, 2,6-toluene-diisocyanate, mixtures of , 4- and 2,6-toluene-diisocyanate, 4,4'-biphenyl ethane-diisocyanate, 4,4'-diphenylmethane-diisocyanate, 3,3'- or 4,4'-diphenylmethane-diisocyanate and 3, 3'-dimethyldiphenylmetan-4,4'-diisocyanate; triisocyanates, such as 4,4 ', 4"-triphenylmethane-triisocyanate, polyethylene-polyphenylene-polyisocyanate and 2,4,6-toluene-triisocyanate; and tetraisocyanates, such as 4,4-dimethylcyanate; 2, 2'-5'-diphenylmethane-tetraisocyanate Especially useful, due to their availability and properties are 2,4'-diphenylmethane-diisocyanate, 4,4'-diphenylmethane-diisocyanate, polymethylene-polyphenylene-polysiocyanate and mixtures thereof. These polyisocyanates are prepared by conventional methods known in the art, such as the phosgenation of the corresponding organic amine. Within the isocyanates, modifications of the above isocyanates containing carbodiimide, allophanate, alkylene or Isocyanurate The quasi-polymers can be used in the process of the present invention These quasi-polymers are prepared by reacting an excess of the organic polyisocyanate, or mixtures thereof, with a minor amount of a compound which It has active hydrogen, determined by the well-known Zerewitinoff Test, as described by Kohler in Journal of the American Chemical Society, 49, 3181 (1927). These compounds and their methods of preparation are well known in the art. The use of any specific compound of active hydrogen is not critical here; rather, any compound can be used here. In general, quasi-polymers have a free isocyanate content of 20 to 40 weight percent. Mixtures of polymeric diphenylmethane diisocyanate (polymeric MDI) and carbodiimide or urethane-modified MDI are preferred. The isocyanate reactive composition, otherwise referred to herein as an active hydroxy functional polyol composition, can include any suitable polyoxyalkylene polyether polyol, such as those resulting from the polymerization of a polyhydric alcohol and an alkylene oxide. Representative of such alcohols may include ethylene glycol, propylene glycol, trimethylene glycol, 1,2-butanediol, 1,3-butanediol., 1,4-butanediol, 1,2-pentanediol, 1,4-pentanediols, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, glycerol, 1,1-trimethylolpropane, 1,1 , 1-trimethylolethane or 1,2,6-hexanetriol. Any suitable alkylene oxide can be used, such as ethylene oxide, propylene oxide, butylene oxide, amylene oxide and mixtures of these oxides. The polyoxyalkylene polyether polyols can be prepared from other starting materials, such as tetrahydrofuran and mixtures of alkylene oxide and tetrahydrofuran, epihalohydrins such as epichlorohydrin, as well as aralkylene oxides, such as styrene oxide. The polyoxyalkylene polyether polyols may have primary or secondary hydroxyl groups. Polyether polyols include polyoxyethylene glycol, polyoxypropylene glycol, polyoxybutylene glycol, polytetramethylene glycol, block copolymers, for example combinations of polyoxypropylene and polyoxyethylene glycols, poly-1,2-oxybutylene and polyoxyethylene. -glycols, and copolymers of prepared glycols or the sequential addition of two or more alkylene oxides. The polyoxyalkylene polyether polyols can be prepared by any known process, such as the processes described by Wurtz in 1859 and in Encyclopedia of Chemical Technology, Vol. 7, pages 257-262, published by Interscience Publishers, Inc. (1951) or in U.S. Patent No. 1,922,459. Other polyoxyalkylene polyether polyols that can be used are those containing grafted vinylic monomers. The polyols having the vinyl polymers incorporated can be prepared (1) by free radical polymerization in situ of an ethylenically unsaturated monomer or a mixture of monomers in a polyol or (2) by dispersion in a polyol of a graft polymer. preformed, prepared by the polymerization of free radical in a solvent, such as described in US Pat. Nos. 3,931,092, 4,014,846, 4,093,573 and 4,122,056; whose descriptions are incorporated herein by reference, or (3) by polymerization at low temperature, in the presence of chain transfer agents. These polymerizations can be carried out at a temperature between 65 and 1702C, preferably between 75 and 135sc. The amount of the ethylenically unsaturated monomer employed in the polymerization reaction is generally from 1 to 60 percent, preferably from 10 to 40 percent, based on the total weight of the product. The polymerization occurs at a temperature between 80 and 170SC, preferably 75 to 135SC. Polyols that can be used in the preparation of graft polymer disproportions are well known in the art. Both conventional polyoles, essentially free of ethylenic unsaturation, such as those described in US Pat. No. RE 28,715 and unsaturated polyols, such as those described in US Pat. No. 3,652,659 and RE 29,014, can be used in the preparation of the graft polymer dispersions used in the present invention, the descriptions of which are incorporated herein by reference. Reprsentative polyols essentially free of ethylenic unsaturation, which may be employed, are well known in the art. They are often prepared by the catalytic condensation of an alkylene oxide or a mixture of alkylene oxides or simultaneously or in sequence, with an organic compound having at least two active hydrogen atoms, as is evident from the patenets. of US, Nos. 1,922,459, 3,190,927 and 3,346,557, the descriptions of which are incorporated by reference. The unsaturated polyols that can be used for the preparation of the graft copolymer dispersions can be prepared by the reaction of any conventional polyol, such as those described above, with an organic compound, having both an ethylenic unsaturation, and a group of hydroxyl, carboxyl, anhydride, isocyanate or epoxy; or they can be prepared using an organic compound having both an ethylenic unsaturation and a hydroxyl, carboxyl, anhydride or epoxy group, as a reagent in the preparation of the conventional polyol. Representatives of such organic compounds include mono- and polycarboxylic unsaturated acids and anhydrides, such as maleic acid and anhydride,. fumaric acid, crotonic acid and anhydride, propenylsuccinic anhydride and halogenated maleic acids and anhydrides, unsaturated polyhydric alcohols such as 2-buten-1,4-diol, glycerol-allyl ether, trimethylolpropane-allyl ether, pentaerythritol-allyl -teter, pentaerythritol vinyl ether, pentaerythritol diallyl ether and l-buten-3,4-diol, unsaturated epoxides, such as 1-vinylcyclohexene monoxide, butadiene monoxide, vinyl glycidyl ether, glycidyl methacrylate and 3-allyloxypropylene oxide. As anets were mentioned, the graft polymer dispersions, used in the invention, are prepared by the in situ polymerization of an ethylenically unsaturated monomer or a mixture of ethylenically unsaturated monomers or a mixture of ethylenically unsaturated monomers in a solvent or in the polyols previously described. Ethylenically representative unsaturated monomers, which may be employed in the present invention include butadiene, isoprene, 1,4-pentadiene, 1,5-hexadiene, 1,7-octadiene, styrene, α-methylstyrene, methylstyrene, 2,4-dimethyl. styrene, ethylstyrene, isopropylstyrene, butyl styrene, phenylstyrene, cyclohexylstyrene, benzylstyrene and the like; substituted styrenes, such as chlorostyrene, 2,5-dichlorostyrene, bromostyrene, fluorostyrene, trifluoromethylstyrene, iodostyrene, cyanostyrene, nitrostyrene, N, N-dimethylaminostyrene, acetoxystyrene, methyl-4-vinylbenzoate, phenoxystyrene, p-vinyl-diphenyl sulfide , p-vinylphenyl phenyloxide, and the like; the acrylic and substituted acrylic monomers, such as acrylonitrile, acrylic acid, methacrylic acid, methyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, methyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, isopropyl methacrylate, octyl methacrylate, methacrylonitrile, methyl a-chloro-acrylate, a-ethoxyacrylate of ethyl, methyl α-acetam, inocrylate, butyl acrylate, 2-ethylhexyl acrylate, phenyl acrylate, phenyl methacrylate, α-chloroacrylonitrile, methacrylonitrile, N, N-dimethylacrylamide, N, N-dibenzylacrylamide, N-butylacrylamide , methacryl formamide and the like; vinyl esters, vinyl ethers, vinyl ketones, etc., such as vinyl acetate, vinyl chloroacetate, vinyl alcohol, vinyl butyrate, isopropenyl acetate, vinyl format, vinyl butyrate, isopropenyl acetate, vinyl methacrylate, vinyl methoxyacetate, vinyl benzoate, vinyl iodide, vinyltoluene, vinylnaphthalene, vinyl bromide, vinyl fluoride, vinylidene bromide, 1-chloro-1-fluoroethylene, vinylidene fluoride, vinyl- methyl ether, vinyl ether, vinyl propyl ether, vinyl butyl ether, vinyl 2-ethylhexyl ether, vinyl phenyl ether, vinyl 2-butoxyethyl ether, 2,4-dihydroyl, 2-pyran, 2-butoxy-2 '-vinyloxy-diethyl ether, vinyl-2-ethylthioethyl ether, vinyl methyl ketone, vinyl ethyl ketone, vinyl phenyl ketone, vinyl phosphonates, such as phosphonate bis (ß-chloroethyl) vinyl, vinyl-ethyl sulphide, vinyl-ethyl-sulfone, N-methyl-N-vinyl-acetamide, N-vinyl-pyrrolidene, vinyl-imidazole, divinyl sulfide, divini sulfoxide it, divinyl sulfone, sodium vinyl sulfonate, methyl vinyl sulfonate, N-vinyl pyrrole, and the like; Dimethyl fumarate, dimethyl maleate, maleic acid, crotonic acid, fumaric acid, itaconic acid, monomethyl itaconate, butylaminoethyl methacrylate, dimethylaminoethyl methacrylate, glycidyl acrylate, allyl alcohol, glycol monoesters of itaconic acid, dichlorobutadiene, vinyl- pyridine, and simians. Any of the known polymerizable monomers can be used and the compounds listed above are illustrative and not restrictive of the monomers suitable for use in this invention. Preferably, the monomer is selected from the group consisting of acrylonitrile, styrene, methyl methacrylate and mixtures thereof. The total amount of the active hydroxy functional polyol composition, employed in accordance with the teachings of the present invention, include approximately 60 to 100 parts by weight, based on a total of 110 parts by weight for the resin and an index of foam between about 96 and 104. More preferably, the total amount of the active hydroxy functional polyol composition will be about 65 to 95 parts by weight, based on the total parts by weight of the resin of 110. Initiators Illustrative examples which can be used for the polymerization of vinyl monomers are the well-known types of free radicals of vinyl polymerization initiators, for example peroxides, persulfates, percarbonates, azo compounds, etc. which include hydrogen peroxide, dibenzoyl peroxide, acetyl peroxide, benzoyl hydroperoxide, t-butyl hydroperoxide, di-t-butyl peroxide, lauroyl peroxide, butyryl peroxide, diisopropylbenzene hydroperoxide, eumeno hydroperoxide, hydroperoxide of paramentane, di-a-cumyl peroxide, dipropyl peroxide, diisopropyl peroxide, difuroyl peroxide, ditriphenylmethyl peroxide, bi (p-methoxybenzoyl) peroxide, p-monoethoxybenzoyl peroxide, rubenoperoxide, ascaridol, peroxybenzoate, t-butyl, diethyl peroxyterephthalate, propyl hydroperoxide, isopropyl hydroperoxide, n-butyl hydroperoxide, cyclohexyl hydroperoxide, trans-decalin hydroperoxide, a-methyl-a-ethyl-benzyl hydroperoxide, tetralin hydroperoxide, trifenylmethyl hydroperoxide, diphenylmethyl hydroperoxide, a, a'-azobis (2-methyl) heptonitrile, 1, 1-azo-bis (2-cyclohexan) carbo-nitrile, a, a »-azobis (isobutyronite rilo), 4,4'-azobis (cyanopentanoic acid and azobis (isobutyronitrile), 1-t-amylazo-1-cyanocyclohexane, 2-t-butylazo-2-cyano-4-methoxy-4-methylpentane, 2-t- butylazo-2-cyano-4-methylpentane, 2- (t-butylazo) isobutyronitrile, 2-t-butylazo-2-cyanobutane, 2-cyano-2- (t-butylazo) cyclohexane, peroxy-2-ethylhexanoate of t- butyl, t-butyl perpivalate 2,5-dimethylhexan-2,5-diper-2-ethylhexanoate, t-butylperneo decanoate, t-butyl perbenzoate, t-butyl percrotoate, persuccinic acid, diisopropyl peroxydiarbonate, and the like; a mixture of initiators may also be present. Photochemically sensitive radio generators can also be used. In general from about 0.5 to 10 percent, preferably from about 1 to 4 percent, by weight of the initiator, based on the weight of the monomer, will be employed in the final polymerization. Stabilizers may be employed during the process of obtaining graft polymer dispersions. One example is the stabilizer disclosed in US Patent No. 4,148,840, which comprises a copolymer that dyes a first portion composed of an ethylenically unsaturated monomer or mixture. of these monomers and a second portion which is a propylene oxide polymer. Other stabilizers that may be employed are the alkylene oxide adducts of copolymers of styrene and allyl alcohol. Preferred polyols are polyethers having an average functional range of about 1.75 to 3.0 and a molecular weight range of about 3500 to 5100. Most preferred polyols are polyethers which are copolymers of ethylene oxide and propylene, glycol glycerin or trimethylolpropane . Included in this group are the dispersions of graft polymers previously excised. Any suitable catalyst can be used, which include the tertiary amines, such as triethylene diamine, N-methylmorpholine, N-ethylmorpholine, diethylethanolamine, N-co-morpholine, l-methyl-4-dimethylaminoethylpiperazine, methoxy-propyldimethylamine, N, N, N ' -trimethylisopropylpropylene diamine, 3-diethylaminopropyldimethylamine, dimethylbenzamine and the like. Other suitable catalysts are, for example, dibutyltin dilaurate, dibutyltin diacetate, stannous chloro, di-2-ethyl-dibutyltin hexanoate, stannous oxide, available under the trademark FOMREZ®, as well as other compounds organometallics disclosed in U.S. Patent No. 2,846,408. An alcohol having approximately 10 to 20 carbon atoms or mixtures thereof, can be used in the present invention. Alcohols of this type are known to those skilled in the art. The types of alcohols considered are those commonly produced by the oxo process and are named as oxo-alcohols. Examples of coemrcially available products include the LIAL 125 from Chemica Augusta Spa or NEODOL® 25, produced by Shell. These alcohols are known to increase entanglement, thereby improving tear resistance.

While the surfactants are not generally necessary to solubilize the blowing agent of the present invention, you found other known blowing agents, the surfactants, ie the surfactants, can be employed, for example to regulate the cell size and the structure of the resulting foams. Typical examples of such surfactants include the siloxane-oxyalkylene heterol polymers and other organic polysiloxanes, oxyethylated alkylphenol, oxyethylated fatty alcohols, fluoroaliphatic polymeric esters, paraffin oils, castor oil ester. , esters of phthalic acid, ricindolic acid ester and turkey red oil, as well as cell regulators, such as paraffins. Chain extension agents that can be employed in the present invention include those that have two functional groups that carry active hydrogen atoms. A preferred group of chain extension agents include ethylene glycol, propylene glycol, dipropylene glycol or 1,4-butanediol and mixtures thereof. Additives that may be used in the process of the present invention include antioxidants, known pigments, such as carbon black, dyes and flame retardants (eg, tris-chloro-ethyl phosphates or ammonium phosphate and polyphosphate) ), stabilizers against aging and weathering, plasticizers, such as gamma-butylactone, fungistatic and bacteriostatic substances, and fillers. The blowing agent of the present invention includes a non-chlorinated pentafluoropropane compound and particularly 1,1,1,3,3-pentafluoropropane, otherwise known as HFA-245a. The penta-fluoropropane blowing agent is used either alone or together with water, in amounts sufficient to supply the desired foam density. Depending on the amount of water used as a co-blowing agent and the packing factor of the molded component, the amount of the non-chlorinated pentafluoropropane blowing agent employed will generally vary from about 0.5 to 10 parts by weight and more preferably around from 1.0 to 8.0 parts by weight, based on a total of 110 parts by weight of the resin, for foams having molded densities of 32 to 640 kg / m3. In a non-limiting example, the amount of the pentafluoropropane used as a single blowing agent for a shoe sole or the like, will generally vary from 1.5 to 5.0 parts by weight for foams having molded densities of 400 to 560 kg / m3 with a molded crest factor from 1.5 to 3.0. In the form of a further example, the amount of the petafluoropropane used as the sole blowing agent for a steering wheel, will generally vary from about 2.0 to 8.0 parts by weight for foams having molded densities of 400 to 560 kg / m3, with a packing factor of 2.0 to 6.0. As the water is added as a co-blowing agent, the amount of the non-chlorinated pentafluor blowing agent is reduced proportionally. In general, up to 0.25 parts by weight of water can be employed as a co-blowing agent and more preferably between about 0.05 to 0.17 parts by weight, based on a total of 110 parts by weight of the resin. The mechanical parameters of the present process are flexible and depend on the final application of the integral skin polyurethane foam. The reaction system is sufficiently versatile and can be obtained in a variety of densities and hardnesses. The system can be introduced into a mold in a variety of ways known to those skilled in the art. It can be loaded into a closed mold previously heated by means of a high-pressure injection technique. In this way, the process operates well enough to fill complex molds at low mold densities (from 304 to 400 kg / m3). It can also operate using a conventional open mold technique, wherein the reaction mixture or system is emptied or injected relatively at low pressure or at atmospheric pressure into an open mold previously heated. In the present process, the system can be operated at mold temperatures from about room temperature to 49ac, with room temperature being preferred. Having thus described the invention, the following examples are provided in the form of illustration, with the amounts being given in parts by weight, unless otherwise indicated.

Density ASTM D-1622 Split Tear ASTM D-1938 Tensile Strength ASTM D-412 Severe Tear ASTM D-42 Die C Stretch Lengthening ASTM Shore Hardness ASTM 2240 D-412 Die-Casting Ross ASTM 1052 Abrasion Tabler ASTM 1044 Poiiol A - is a polyoxypropylene-polyoxyethylene block copolymer, initiated with propylene glycol, having a hydroxyl number of about 25 and a molecular weight of about 3850 Polyol B - is a 31 percent solids-dispersed acrylonitrile-styrene graft copolymer in a polyoxypropylene-polyoxyethylene block copolymer initiated with trimethylolpropane, which has a molecular weight of about 4120. The dispersion of the graft polymer has a hydroxyl number of about 25.

Polyol C - is a polyoxypropylene-polyoxyethylene block copolymer initiated with glycerin, having a hydroxyl number of about 27 and a molecular weight of about 5050.

XFE-1028 - is an amine catalyst comprising a patented mixture, available from Air Products.

T-12 - is dibutyl tin dilaurate.

S-25 - is an amine catalyst comprising the patented mixture available from Air Products. WB-3092 - is a prepolymer, prepared from isocyanate modified with uretonimine and propylene glycol, having a free NCO content of 24% by weight and a viscosity of 120 cps at 25 ° C. CFC-11 - is 1-f luoro-1,1,1-trichloromethane.

HFA-245fa - is 1,1,1,3,3-pentafluoropropane.

HFC-134a - is 1,1,1,1-tetrafluoroethane.

Iso-A - is a 50/50 percent by weight, solvent-free mixture of diphenylmethane diisocyanate and a polymethylene polyphenyl polyisocyanate prepolymer, in which the mixture has an isocyanate content of 23 weight percent TABLE I Foam formulations pep = parts by weight Initially, it should be noted that the blowing agent was added in amounts to produce similar densities of free lift for all solvent blowing foams, to ensure similar packing factors, so the thickness of Skin is caused only by the blowing agent that condenses on the surface of the mold. As those skilled in the art should understand, the phrase "packaging factor" is the ratio of the free-rise density to the molded density of the resultant foam. The resin systems were foamed with the blowing agents being added so as to produce a master batch of resin, combining all the components, except the blowing agent. The Karl Fischer method for water determination was carried out and the residual water was determined to be 0.20%. This value was used to determine all the resin / prepolymer ratios. The liquid blowing agents (CFC-11 and HFA-245fa) were added to the resin system and then mixed. The blowing agent was added until a constant amount of the blowing agent was obtained after mixing. The gaseous blowing agent (HFC-134a) was added to 2000 g of resin by means of a gas dispersion tube (Pyrex 20c) from a pressurized cylinder (supplied by DuPont) equipped with a gas regulator. The resin was charged to a 3-necked, round bottom flask. The resin was kept cool by placing the flask in an ice water bath, while the addition took place, so that higher levels of HFC-134a could be added before saturation. A motor agitation shaft, connected to an engine, maintained the agitation of the resin at approximately 500 rpm. The third arm of the round bottom was connected to a cold finger with a mixture of dry ice / isopropyl alcohol for the reflux of the blowing agent. The cold finger was equipped with a bubbling apparatus, to regulate the gas flow. The addition was synchronized and the final weight of the blowing agent was obtained by measuring the change in the weight of the flask. A total percentage of the blowing agent in the resin was then calculated. The water was also tested as a blowing agent, adding it directly to the resin and Karl Fischer determination of the water was carried out. Each resin blowing agent composition was added directly into a one liter Lily cup for foaming. Sufficient resin / blowing agent composition was added to produce foam, which flowed over the lip of the one liter cup, so that free elevation densities could be measured. The appropriate amount of the prepolymer was weighed directly into the Lily cup. The mixture was then stirred for 7 seconds, with a Vorath mixing blade of 8.9 cm at 2000 r.p.m. The foam cream, gel, top of the cup, lifting time and viscosity-free scored. The net weight of the foam produced was taken and the density of the foam was calculated: g x 0.059 = lb / ft3 (0.945 kg / m3). The resulting free elevation densities and the reactivity profiles are given in Table II. Table II Free Elevation Reactivities and Densities The components of the foam were weighed, so that the final total weight is equal to the weight needed in the mold plus about 50 g of hanging in the Lily cup. The density of the desired molded plate was 0.48 g / cc. After shaking, the foam was emptied into an aluminum mold of 30.5 x 15.25 x 0.9525 cm, heated to 492C, which had been lightly sprayed with a silicone mold release. After 4 minutes, the plate was demolded and trimmed. The net weight of the plate was taken and the density of the foam was calculated (g / 442 ce = g / ml). After a one-week healing time, the physical properties were tested as presented in the following Table III. As shown in Table III, the cream time of HFA-245fa is slightly faster than that of CFC-11, but not as fast as that of HFC-134a. This is likely because the boiling point of HFA-245fa is between that of CFC-11 and that of HFC-134a. Due to the volatility, the HFA-245fa (boiling point of 15.32C) escapes from the resin faster than in CFC-11 (boiling point = 23.82C) but not as fast as in HFC-134a (time of boiling = 26.5SC). It can be deduced that HFA-245fa is, therefore, more soluble in the resin matrix than HFC-134a, but not as soluble as CFC-11. Solubility studies were not carried out due to the limited availability of HFA-245fa. The cream time presented of HFC-134a is not the actual cream time, since a foaming of the resin, caused by the blowing agent, evaporated. It is believed that the slightly longer cream time of HFA-245fa compared to CFC-11 is due to the same evaporation effect, but to a much lesser extent than in HFC-134a.

On a molar basis, HFA-245fa appears to be a more efficient blowing agent than CFC-11. At the lower free lift density (144 kg / m3), HFA-245fa is not as efficient blowing agent as HFC-134a, but is equally efficient as a blowing agent such as HFC-134a at a free lift density greater than 200 kg / m3. When comparing the parts of the blowing agent needed to produce a desired free lift density, HFA-245fa is a more efficient blowing agent than CFC-11, at both densities of 144 and 200 kg / m3. When comparing the blowing efficiency with the HFC-l34a, it can be seen that more blowing agent is required for both densities of 144 and 200 kg / m3. However, the cost associated with the added volume is believed to be greater than the displacement due to the elimination of the need for specialized transfer and storage equipment, particularly at higher temperatures. At the higher free lift density, ie 200 kg / m 3, the HFA-245fa produced foam with superior tensile strength and tear strength to the foams blown with HFC-134a (see Table III). The properties of the foam blown with HFA-245fa are only slightly lower than those foams blown with CFC-11, with the exception of lower elongations and resistance to abrasion. The abrasion resistance for HFA-245fa foam (loss of 104 mg) is still within the industry standard of a loss of 200 mg. It is believed that the Ross flexural modulus, slightly smaller, at this free lift density, is not indicative of the poorer bending properties, and instead is due to sinking in the manual mixing foam. At a free lift density of 144 kg / m3, the tensile and elongation forces are greater than those of the foams blown with CFC-11 and all other physical properties are equal. Again, the properties of foam blown with HFA-245fa are superior to those of foam blown with HFC-134a. The hardness of the foams soaked with the HFA-245fa is similar to that of the foams blown with CFC-11. Foams blown with HFC-134a tend to be softer. As expected, all the solvent blowing agents produced foams with physical properties superior to those of the foams blown with water. This is especially evident in tear resistance. The water-blown foams, used for comparison, have free elevation densities of 264 and 200 kg / m3, respectively. The higher free lift density (264 kg / m3) was used due to ease of handling and does not evaporate from the mold or produce flow lines in the final parts. The lower free lift density (200 kg / m3) was used as a comparison, since the largest crest factor can be obtained in a water-blown formulation. The foams blown with HFC-245fa produce a thick, well-defined skin, as determined by Scanning Electron Microscopy (SEM). Skin thicknesses were not measured quantitatively due to the high variability in the skin formation of mixed manual plates. It can be seen in comparison that both densities of free elevation of 144 and 200 kg / m3, the foams blown with HFC-245fa exhibited skin thicknesses approximately equal to those of foams blown with CFC-11. The skins produced with HFC-245fa were much superior to those foams blown with HFC-134a. Due to its high volatility, HFC-134a does not produce a foam with thick skin. As expected, the water exhibited very little true skin, since condensation does not take place on the surface of the mold. When used in an integral skin system, HFC-245fa produces foam with superior physical properties, and skin thicknesses to foams blown with HFC-134a. When comparing blown foams with HFC-245fa with foams blown with CFC-11, HFC-245fa produced foams with foams blown with CFC-11 in both physical properties and skin thickness. In practice, the use of HFC-245fa is believed to be an improvement over HFC-134a, since it is easier to handle, does not require special gas handling equipment and produces foams with excellent physical properties and skin thicknesses. In addition, foams employing HFC-245fa as the blowing agent and particularly integral skin foams, can be used to form articles having a relatively broad molded density, i.e. from about 32 to 640 kg / m 3. While it will be evident that the described preferred embodiments of the invention were calculated to comply with the objects indicated, it will be appreciated that the invention is susceptible to modifications, variations and changes, without departing from its true spirit.

Claims (9)

1. CLAIMS 1. A method for obtaining molded integral low density polyurethane foam articles, this method comprises the steps of: a) supplying an organic polyisocyanate; b) supplying a resin, which comprises: i) an active hydroxy functional polyol composition; ii) a blowing agent, including a non-chlorinated pentafluoropropane and, optionally, water; iii) a catalyst; and iv) optionally, one or more compounds selected from the group consisting essentially of chain extension agents, a surfactant, an alcohol having from 10 to 20 carbon atoms, fillers, pigments, antioxidants, stabilizers and their mixtures; c) introducing components a) and b) into a mold and reacting these components for a sufficient period of time to produce a molded integral skin polyurethane article.
2. 2. A method, as defined in claim 1, wherein the non-chlorinated pentafluoropropane is present in an amount of about 0.5 to 10.0 parts by weight, based on 110 parts by weight of b) i) to b) iv).
3. 3. A method, as defined in claim 1, wherein the blowing agent of the non-chlorinated pentafluoropropane is 1,1,1,3,3-pentafluoropropane.
4. 4. A method, as defined in claim 1, wherein the blowing agent includes water in an amount of about 0.05 to 0.17 parts by weight, based on 110 parts by weight of b) i) to b) iv.
5. 5. A method, as defined in claim 1, wherein the active hydroxy functional polyol composition is selected from the group consisting of polyoxyalkylene polyether polyols, polyoxyalkylene polyether dispersions grafted with a vinyl polymer, and mixtures thereof .
6. 6. A method, as defined in claim 1, wherein the active hydroxy functional polyol composition is present in an amount of about 50.0 to 95.0 parts by weight, based on 110 parts by weight of b) i) through b) iv).
7. 7. A method, as defined in claim 1, wherein the chain extension agent is selected from the group consisting of ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, butanediol, and mixtures thereof.
8. 8. A method, as defined in claim 1, wherein the alcohol containing 10 to 20 carbon atoms is an aliphatic alcohol.
9. 9. An article, according to the method of claim 1.