MXPA99007355A - Compositions of metilen bis (fenilisocianato) stable in storage - Google Patents

Abstract

The present invention provides a liquid methylene bis (phenylisocyanate) composition, which includes a high concentration of methylene bis (phenylisocyanate) having improved storage stability. The invention further provides a method for producing the liquid methylene bis (phenylisocyanate) compositions of the present invention.

Description

COMPOSITIONS OF METILEN BIS (FENILISOCIANATO) STABLE IN STORAGE BACKGROUND OF THE INVENTION 1. Technical Field The invention relates to a liquid methylene bis (phenyl isocyanate) composition having improved storage stability. 2. Description of the Previous Technique The polyisocyanate compositions include a high concentration of methylene bis (phenyl isocyanate) ("MDI"), particularly 4, 4'-methylene bis (phenylisocyanate) ("4, 4 '-MDI"), while being useful for various applications of cellular and non-cellular polyurethanes, often have a processing problem since they are usually a solid at room temperature, ie about 25 ° C. The material therefore has to be melted and maintained in order to be useful as a liquid. Unfortunately, it is also known that bis (phenylisocyanate) compositions having relatively high levels of 4,4 '-MDI have a limited shelf life due to the formation of diphenylmethane uretdione, or otherwise referred to herein as uretdione. Uretdione tends to couple with 4,4 '-MDI molecules contained in the methylene bis (phenylisocyanate) compositions thereby forming a precipitate substantially insoluble with time. For example, the 4,4 '-MDI compositions maintained at approximately 43 ° C for 14 days have exhibited uretdione concentrations above the generally acceptable saturation concentrations of 0.5%. The formation of high concentrations of uretdione to date has made the methylene bis (phenylisocyanate) compositions substantially useless. Interestingly, the uretdione reaction is both temperature dependent and phase dependent. For example, as the temperature of a composition of 4,4 '-MDI increases by about 43 ° C, the rate of uretdione formation increases. In addition, the rate of uretdione formation is accelerated when the methylene bis (phenylisocyanate) is in the solid state as compared to the liquid composition at 43 ° C; this formation is generally attributed to the alignment of the isocyanate groups in the crystal lattice structure. In an effort to limit the formation of uretdione, methylene bis (phenylisocyanate) compositions, particularly as made 4,4 '-MDI are often frozen and stored at temperatures below about 0 ° C. While this temporarily delays the formation of the dimer uretdione, cooling the compositions for extended periods of time before use can be expensive and introduces logistical considerations that must be addressed. It is therefore an object of the present invention to provide a liquid composition of methylene bis (phenylisocyanate) which is stable in storage at temperatures above about 30 ° C. A further object of the invention is to provide a liquid composition of methylene bis (phenylisocyanate) which increases the saturation concentration of uretdione. Another object of the present invention is to provide a methylene bis (phenylisocyanate) having a reduced freezing point. Still another object of the present invention is to provide a liquid composition of methylene bis (phenylisocyanate) which can be used in the preparation of all types of polyurethanes for which pure MDI is currently employed. In view of the above, it would be highly desirable to develop a stable methylene bis (phenylisocyanate) composition in liquid storage, including a high concentration of 4,4'-MDI which can be shipped in bulk, thus reducing the high costs associated with the shipment of frozen drum compositions.

COMPENDIUM OF THE INVENTION The above objects, among others, are achieved by the methylene bis (phenylisocyanate) compositions of the present invention comprising a mixture of (a) a methylene bis (phenylisocyanate) component that includes at least about 90% by weight of 4,4 ' -MDI; and (b) an uretonimine. Under preferred embodiments, uretonimine will be present in positive amounts of less than about 5.0% by weight, based on the weight of the methylene bis (phenylisocyanate) composition. More preferably, uretonimine is present in amounts in the range of about 0.1 to less than about 5.0 parts per 100 parts of the methylene bis (phenylisocyanate) composition, with amounts in the range of about 0.25 part to about 2.5 parts by weight particularly preferred. As will be described in more detail below, a catalyst can be employed to cause the formation of uretonimine in situ. The amount of catalyst in general will be in the range of about 0.0001 to about 5.0 parts, preferably about 0.0002 to about 2.5 parts, per 100.0 of methylene bis (phenylisocyanate). The invention also provides a method for preparing liquid stable storage methylene bis (phenylisocyanate) compositions by mixing a methylene bis (phenylisocyanate) component including at least about 90.0 by weight of 4,4 'MDI with a uretonimine, to form a liquid composition of methylene bis (phenylisocyanate) which is stable in storage at temperatures as low as about 30 ° C. Another method of the present invention relates to the in situ formation of uretonimine in a liquid methylene bis (phenylisocyanate) composition, which includes at least about 90.0% by weight of 4,4'-MDI. DETAILED DESCRIPTION OF THE INVENTION The methylene bis (phenylisocyanate) composition of the present invention comprises (a) a methylene bis (phenylisocyanate) component that includes at least about 90.0 wt% of 4,4 '-MDI; and b) an uretonimine. The methylene bis (phenylisocyanate) component a) which includes at least about 90.0 wt.% Of 4,4 '-MDI, more preferably will include at least about 95.0 wt.% 4,4'-MDI and under a highly preferred embodiment, will include at least about 98.0% by weight of 4,4'-MDI. In general, in addition to 4,4 '-MDI, component a) can include 2,4' -MDI; 2,2 '-MDI and other isomers, the 2,4'-isomer is the predominant species there. The 2,4'-MDI isomer (and other MDI isomers) can constitute the remainder of component a). Preferably, however, these isomers are limited to relatively low levels, ie approximately 2% or less by weight of component a). The amount of methylene bis (phenylisocyanate) component a) in the composition of the present invention can be as low as about 80% by weight based on the total weight of the methylene bis (phenylisocyanate) composition. However, the compositions of the present invention preferably comprise at least about 90.0% by weight, more preferably at least about 95% by weight, particularly at least about 99% by weight of the methylene bis (phenylisocyanate) component. In another aspect of the present invention, the uretonimine source to the composition may contribute additional amounts of methylene bis (phenylisocyanate) isomers (predominantly 4,4'-MDI) to raise the level of methylene bis (phenylisocyanate) component in the composition , as described below. As such, the amount of methylene bis (phenylisocyanate) component a) in the composition of the present invention can be at least 97.5% by weight, based on the total weight of the methylene bis (phenylisocyanate) composition, preferably at least of about 98.75% by weight, and more preferably at least about 99.75% by weight. As described above, this component a) will predominantly comprise the 4,4'-MDI isomer, with the remainder of the methylene bis (phenylisocyanate) component (preferably 2% or less) comprising 2, 4 '-MDI and other isomers. The methylene bis (phenylisocyanate) component a) it can be produced by any of the commonly used processes including the distillation of crude isocyanate mixtures which are obtained by phosgenation of a mixture of polyamines generally obtained by the acid condensation of aniline and formaldehyde. The uretonimine b) can be introduced into the methylene bis (phenylisocyanate) composition as part of an organic isocyanate mixture or can be formed in situ in the methylene bis (phenylisocyanate) component to form the composition of the present invention. Urethtonimine b) is generally formed by reacting initially, for example 4,4 '-MDI with a convenient catalyst such as phospholene oxide with heating to give the carbodiimide MDI. The carbodiimide MDI then reacts with excess of 4,4 '-MDI to give uretonimine groups as illustrated by the following reaction: In this way, in the presence of excess 4,4 '-MDI, carbodiimide is converted (but remains in equilibrium with carbodiimide) to uretonimine. This organic isocyanate mixture, therefore, comprises uretonimine and methylene bis (phenylisocyanate), for example in proportions of 25:75, respectively. In the composition r of the present invention, the amount of methylene bis (phenylisocyanate) takes into account contributed amounts that come from the organic isocyanate mixture. The uretonimine can be formed as described above from organic isocyanates including isomers of 2,4'-MDI and 2,2'-MDI and mixtures thereof (particularly those at least about 45% by weight 4,4 '-MDI), as well as aromatic, aliphatic and cycloaliphatic polyisocyanates and combinations thereof. Representative of these types are monoisocyanates which include phenyl isocyanates, cyclohexyl isocyanate; diisocyanates such as m-phenylene diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, mixtures of 2,4- and 2,6-toluene diisocyanate, hexamethylene diisocyanate, tetramethylene diisocyanate, cyclohexan-1,4-diisocyanate , hexahydrotoluene diisocyanate (and isomers), isophorone diisocyanate, hydrogenated methylene bis (phenylisocyanate), naphthalene-1,5-diisocyanate, 1-methoxyphenyl-2,4-diisocyanate, 4,4'-biphenylene diisocyanate, 3,3'-dimethoxy -4,4 '-biphenyl diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate; the triisocyanate such as 4,4 ', 4"-triphenylmethane triisocyanate and toluene 2,4,6-triisocyanate and the tetraisocyanates such as 4,4'-dimethyldiphenylmethane-2,2', 5,5'-tetraisocyanate and polymeric polyisocyanates such as polymethylene polyphenylene polyisocyanate, by way of non-limiting example.The reaction mechanism in each case is well known to those skilled in the art and is similar to those exemplified above for the production of uretonimine from 4.4 '. The amount of uretonimine to be included in the methylene bis (phenylisocyanate) composition of the present invention is generally in the range of about 0.1 to about 5.0 parts per 100.0 parts of the methylene bis (phenylisocyanate) composition, more preferably from about 0.25 part to about 2.5 parts, and more in particular from about 0.25 to about 1.25 parts per 100.0 parts of the composition. In the alternative embodiment of the present invention, a desired amount of uretonimine is produced in situ in the methylene bis (phenylisocyanate) composition of the present invention, wherein a catalyst c) capable of reacting with 4,4 '-MDI to give carbodiimide MDI , at least some of which is then converted to uretonimine in the presence of excess 4,4'-MDI, as described above. Thus, under certain embodiments, it may be convenient to add a catalyst c) to the methylene bis (phenylisocyanate) component a) to produce the stable liquid storage methylene bis (phenylisocyanate) compositions of the present invention. Illustrative of these catalysts are: (a) phospholene-1-oxides and 1-sulfides having the formulas: wherein a, b, c and d are each selected from the group consisting of hydrogen and hydrocarbyl of 1 to 12 carbon atoms, inclusive, R is selected from the group consisting of lower alkyl and aryl and X is selected from the group consisting of oxygen and sulfur. The above phospholene compounds and methods for their preparation are described in U.S. Pat. Nos. 2,633,737, 2,663,738 and 2,853,473, which are incorporated herein by reference. The 3-phospholenes can be easily isomerized into the corresponding 2-phospholenes by thermal or reflux treatment with an aqueous base, as described by Quin et al., Journal American Chemical Society, 33, 1024, 1968. Representative compounds within the above class they are 1-phenyl-2-phospholene-1-oxide; 3-methyl-1-phenyl-2-phospholene-1-oxide; 1-phenyl-2-phospholene-1-sulfide; 1-ethyl-2-phospholene-l-oxide; l-ethyl-3-methyl-2-phospholene-l-oxide; 1-ethyl-3-methyl-2-phospholene-1-sulfide; and the isomeric phospholenes corresponding to the aforementioned compounds. Also, polymer-bound phospholene oxide can be employed, specifically those having recurring units, for example.

As described in U.S. Pat. No. 4,105,643 and those of the following structure as described in U.S. Pat. No. 4,105,642, both of which patents are expressly incorporated herein by reference. (b) diaza- and oxaza-phospholenes and -phosphorinanos wherein CnH2n represents alkylene with from 1 to 12 carbon atoms inclusive, at least one and not more than three adjacent carbon atoms and the alkylene or alkylene radical forming a chain, one end of which is connected to Y, the other end of which connects to N, thus completing the heterocyclic ring; R 'is selected from the group consisting of hydrocarbyl containing from 1 to 12 carbon atoms, inclusive; and hydrocarbyl with 1 to 12 carbon atoms substituted with halo, nitro, alkoxy, alkyl, mercapto, and cyano, inclusive; R "is hydrocarbyl containing 1 to 12 carbon atoms inclusive and Y is selected from the group consisting of -O- and -NR" - wherein R "has the meanings given above The above compounds and methods for their preparation are described in US Patent No. 3,522,303, Representative examples of these compounds are: 2-ethyl-1,3-dimethyl-1,2,3-diazaphospholane-2-oxide; 2-chloromethyl-1,3-dimethyl- 1, 3, 2-diazaphospholane-2-oxide; 2-trichloromethyl-1,3-dimethyl-1,3, 2-diazaphospholane-2-oxide; 2-phenyl-1,3-dimethyl-1,3, 2- diazaphospholane-2-oxide; 2-phenyl-1,3-dimethyl-1,3, 2-diaza-phosphorin-2-oxide; 2-benzyl-1,3-dimethyl-1,3, 2-diazaphospholane-2 Oxide; 2-allyl-1,3-dimethyl-1,3,2-diazaphospholane-2-oxide; 2-bromomethyl-1,3-dimethyl-1,3,2-diazaphospholane-2-oxide; 2-cyclohexyl -l, 3-dimethyl-1,3, 2-diazaphospholane-2-oxide; 2-cyclohexyl-1,3-dimethyl-1,3, 2-diaphospholane-2-oxide; 2- (2-ethoxyethyl) -1 , 3-dimethyl-1,2,3-diazaphospholane-2-oxide and 2-naphthyl-1 , 3-dimethyl-1,2,3-diazaphospholane-2-oxide. (c) Triaryl arsines wherein the aryl group is free of substituents containing reactive hydrogen atoms, arsine is represented by the formulas: wherein each R, Rx and R2 represent the same or different aryl portions having from 6 to 12 carbon atoms, inclusive. These compounds are described in Patent of the U.S.A. No. 3,406,198. Representative examples are: triphenylarsine, tris (p-tolyl) arsine, tris (p-methoxyphenyl) arsine, tris (p-ethoxyphenyl) arsine, tris (p-chlorophenyl) arsine, tris (p-fluorophenyl) arsine, tris (2, 5-xylyl) arsine, tris (p-cyanophenyl) arsine, tris (l-naphthyl) arsine, tris (p-methylmercaptophenyl) arsine, tris (p-biphenylyl) arsine, p-chlorophenyl bis (ptolyl) arsine and phenyl (p -chlorophenyl) (p-bromophenyl) arsine. (d) Also included are compounds of the formula: wherein each R, Rx and R2 represent the same or different alkyl or aryl compound having 6 to 12 carbon atoms inclusive. Representative examples of these are: triphenylarsine oxide, triethylarsine oxide, and arsine oxide bound with polymer as described in US Pat. No. 4,143,063: wherein Rx and R2 are hydrocarbyl with 1 to 12 carbon atoms inclusive, R3 is hydrogen, chlorine or methyl, R4 is hydrogen or methyl, and n is 0 or 1. (e) Acetylacetone metal derivatives such as beryllium, aluminum derivatives , zirconium, chromium, and iron thereof as described in the US Patent No. 3,152,131. (f) Phosphate esters of the formula: (RO) 3PO where R is hydrocarbyl with 1 to 12 carbon atoms, inclusive. These esters and methods for their preparation are described in U.S. Pat. No. 3,056,835. Representative examples are trimethylphosphate, triethylphosphate, ethylidipropylphosphate, triisopropylphosphate, triallylphosphate, triphenyl phosphate and tricresyl phosphate. (g) Phosphine oxides of the formula: R3PO wherein R is hydrocarbyl with 1 to 12 carbon atoms, inclusive. Representative examples are: triethylphosphine oxide, tributylphosphine oxide, triphenylphosphine oxide and tris (chloromethyl) phosphine oxide. (h) Metal complexes derived from a transition element of group d and a p-linking ligand selected from the group consisting of carbon monoxide, nitric oxide, hydrocarbylisocyanides, trihydrocarbylphosphine, trihydrocarbyllarsine, trihydrocarbylsilbine and dihydrocarbylsulfide, wherein hydrocarbyl in each instance contains from 1 to 12 carbon atoms inclusive provided that at least one of the binding ligands p- in the complex is carbon monoxide or hydrocarbylisocyanide . These complexes and methods for preparation are described in U.S. Pat. No. 3,406,197. Representative examples of these complexes are pentacarbonyl iron, pentacarbonyl di-iron, hexacarbonyl tungsten, hexacarbonyl molybdenum, hexacarbonyl chromium, decacarbonyl dimanganese, tetracarbonyl nickel, pentacarbonyl ruthenium and the tetracarbonyl: methylisocyanide iron complex.

The term "hydrocarbyl" of 1 to 12 carbon atoms inclusive employed herein means the monovalent radical which is obtained by removing a hydrogen atom from a main hydrocarbon having the content of carbon atoms established. Illustrative of these groups are alkyl such as methyl-, ethyl-, propyl-, butyl-, pentyl-, hexyl-, heptyl-, octyl, nonyl-, decyl-, undecyl-, undodecyl-, including their isomeric forms, alkenyl as allyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl and dodecenyl, including their isomeric forms, cycloalkyl such as cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl and the like; cycloalkenyls such as cyclopentenyl, cyclohexenyl, cycloheptenyl and the like; aralkyls such as benzyl, phenethyl, phenylpropyl, benzhydryl, naphthylmethyl and the like; and aryls such as phenyl, tolyl, xylyl, naphthyl, biphenylyl and the like. The term "lower alkyl" as used herein, means alkyl of 1 to 6 carbon atoms, inclusive, such as methyl, ethyl, propyl, butyl, pentyl, hexyl and their isomeric forms. The preferred carbodiimide catalysts for use in preparing the compounds of the present invention are the 1-phospholenes and 2-phospholenes, respectively. The preferred carbodiimide catalysts for use in preparing these compounds according to the invention are l-aryl-3-lower alkyl-2-phospholene-1-oxide and 1,3-di (lower alkyl) -2-phospholene 1- oxide, l-phenyl-3-methyl-2-phospholene-1-oxide, l-ethyl-3-methyl-2-phospholene-1-oxide and tris (chloromethyl) phosphine oxide. The most preferred phospholene oxide catalyst is 1H-phospholene-2, 5-dihydro-3-methyl-1-phenyl-1-oxide, (i) Organo tin compounds. Tin organ compounds can also be employed in the present invention. The tin organ compounds that can be employed in the present invention are both quadrivalent and divalent organo tin compounds. The quadrivalent tin organ compound can be described by the following formula: wherein Z and Z 'are individually an alkyl, aryl, alicyclic, heterocyclic, oxyalkyl or acyloxy group having from 1 to 18 carbon atoms and can be the same or different, X is an alkyl, aryl, alicyclic, heterocyclic, oxyalkyl group , acyloxy, thioalkyl or thioalkenyl acyloxy having 1 to 18 carbon atoms, Y is equal to X or oxy groups or a group represented by the following formula: provided that when Y is this group, X is an alkyl or aryl group, m is equal to 1 except when Y is an oxy group, then m equals 0 and a divalent organ tin compound which can be described by the following formula: Sn (OOCZ ") 2 wherein Z" is an alkyl, aryl, alicyclic, heterocyclic having from 1 to 18 carbon atoms. These quadrivalent tin organ compounds which can be used as described in the above formula are dibutyltin dilaurate, dibutyltin diacetate, dibutyltin di (2-ethylhexanoate), dioctyltin dilaurate, dibutyltin maleate, di (n-octyl) tin maleate, bi s ( dibut il ac e toxi est year) oxide, bis (dibutylauroyloxystane) oxide, dibutyltin dibuthoxide, dibutyltin dimethoxide, dibutyltin disalicylate, dibutyltin bis (isooctylmaleate), dibutyltin bis (isopropylmaleate), dibutyltin oxide, tributyltin acetate, tributyltin isopropyl succinate, tributyltin linoleate, tributyltin nicotinate, dimethyltin dilaurate, dimethyltin oxide, dioctyltin oxide, bis (tributyltin) oxide, diphenyltin oxide, triphenyltin acetate, tri-n-propyltin acetate, tri-n-propyltin laurate and bis (tri-n-propyltin) oxide, dibutyltin dilauril mercaptide, dibutyltin bis (isooct ilmercaptoace tato) and bis (triphenyltin) oxide. Preferred are dibutyltin diacetate, dibutyltin dilaurate, dibutyltin dilaurylmercaptide, dibutyltin bis (isooctylmercaptoacetate), dibutyltin oxide, bis (triphenyltin) oxide, bis (tri-n-butyltin) oxide. Those divalent organotin compounds which can be used as catalysts as described in the above formula are stannous oxalate, stannous oleate, stannous naphthenate, stannous acetate, stannous butyrate, stannous 2-ethylhexanoate, stannous laurate, stannous palmitate and stannous stearate. The preferred divalent tin compounds are stannous oxalate, stannous oleate and stannous 2-ethylhexanoate. The catalyst c) which helps in forming uretonimine in the methylene bis (phenylisocyanate) compositions of the present invention, as will be demonstrated in the following data, will generally be present in amounts in the range of 0.0001 part to about 5.0 parts per 100 parts. of methylene bis (phenylisocyanate) and preferably are in the range of about 0.0002 part to about 2.5 parts, depending on the catalyst employed. For example, and without limitation, the phospholene oxides in general will be in the range of about 0.0001 to about 0.1 part per 100 parts of methylene bis (phenylisocyanate), with a preferred range of 0.0002 to 0.05. Tricarbyl phosphates, however, will preferably be in the range of from about 0.1 to about 5.0 parts per 100 parts of methylene bis (phenylisocyanate) with a range from 0.2 part to about 2.5, preferred. To finish the rate of uretonimine formation, a limited amount of acid can be added to the polyisocyanate composition to deactivate the catalyst. Useful catalyst deactivators include aromatic and aliphatic acid chloride such as acetyl chloride, benzoyl m-chloride and benzenesulfonyl chloride, oxalyl chloride, adipyl chloride, sebacyl chloride, and carbonyl chloride, by way of non-limiting example. Also inorganic acids such as perchloric acid, and strong organic acids such as trifluoromethanesulfonic acid and trifluoroacetic acid, may be employed. Chloroformates can also be used such as methyl chloroformate, ethyl chloroformate, isopropyl chloroformate, n-butyl chloroformate, isopropyl chloroformate, n-butyl chloroformate, sec-butyl chloroformate and diethylene glycol bis chloroformate. A method for preparing ureonimine-modified methylene bis (phenylisocyanate) for mixed compositions will now be described using two different catalysts. Isocyanate A Modified with Uretonimine A thousand parts of a mixture of 98% of 4,4-isomers and 2,0% of 2,4-isomers of methylene bis (phenylisocyanate) and 10 parts of triethyl phosphate, are rapidly heated to 220 ° C and maintain at that temperature of 2.5 to 3 hours. The reaction contents are then rapidly cooled to 25 ° C. The product in this manner exhibits an NCO content of 29.3% by weight and a viscosity of 40 cps at 25 ° C. The same procedure can be repeated to produce compositions using the methylene bis (phenylisocyanate) compositions having up to 55% of 2,4'-isomer. Isocyanate B Modified with Uretonimine A thousand parts of a mixture of 98% of 4,4-isomers and 2.0% 2, 4'-methylene bis (phenylisocyanate) isomers are mixed with 0.004 parts of 3-methyl-1-phenyl-2 phospholene-1-oxide and heated rapidly to 105 ° C and maintained at that temperature for 3 to 4 hours. The reaction contents are then cooled to 70 ° C and 0.04 part of trifluoromethane sulphonic acid are added to deactivate the catalyst. When the product is cooled to 25 ° C it exhibits an NCO content of 29.3% by weight and a viscosity of 40 cps at 25 ° C. The same procedure can be repeated to produce compositions using methylene bis (phenylisocyanate) compositions having up to 55% 2,4'MDI isomer. In addition to the above compositions of uretonimine modified isocyanate, certain similar commercially available uretonimine products such as MONDUR® CD available from Bayer Corporation, ISONATE® 143L and 143LM available from Dow Chemical Company, RUBINATE® LF 168 available from ICI Limited and LUPRINATE® MM103, available from BASF Corporation, may be used. EXPERIMENTAL RESULTS Experiments are conducted to verify the formation of uretdione over time at various temperatures to determine formation rates, product lifetimes, and saturation concentrations of uretdione of the methylene bis (phenylisocyanate) compositions of the present invention. Comp, samples of essentially pure MDI, ie 98.0% 4,4'-MDI (the rest is pedominantly 2,4'-MDI isomers and other isomers) are mixed for various amounts of uretonimine optionally with a catalyst as described with more detail below. Example 1 A mixture of 90% by weight, essentially pure 4,4'-MDI and 10% by weight of isocyanate-modified uretonimine, which represents a calculated content of 97.5% of 4,4'MDI and 2.5% of uretonimine, is prepared by mixing at 45 ° C. The contents are then cooled to 30 ° C and stored at this temperature. The product remains as a stable liquid without any precipitation occurring for more than three months at 30 ° C, while essentially 4,4'-pure MDI frozen at 30 ° C has a shelf life of only four days. The same procedure is repeated with MDI modified with isocyanate B uretonimine to produce similar results. Example 2 A mixture of 95% by weight of essentially pure 4,4'-MDI and 5.0% of uretonimine-modified isocyanate A representing a calculated content of 98.75% 4,4'-MDI and 1.25% of uretonimine, is prepared at Mix at 45 ° C. The product is then cooled and stored at 30-35 ° C. The product remains as a stable liquid for three months without any precipitation. The same procedure is repeated with isocyanate B modified with uretonimine which leads to the same results.

EXAMPLE 3 A mixture of 99.0% by weight essentially of 4,4 '-MDI and 1.0% by weight of isocyanate A modified with uretonimine, representing 99.75% essentially of 4,4' -MDI 0.25% of uretonimine, is prepared Mix at 45 ° C. The product is stored from 43 ° C to 45 ° C. An essentially pure 4,4'-MDI sample that does not have uretonimine reaches the saturation uretdione content in 15 days and precipitation begins while no precipitation is observed in the uretonimine-containing sample for 44 days. The same procedure is repeated using isocyanate B modified with uretonimine giving similar results. A method for preparing methylene bis (phenylisocyanate) modified with uretonimine in situ will now be described using two different catalysts. Example 4 A thousand parts of a mixture of an essentially pure 4,4 '-MDI composition (containing approximately 98% of 4,4' -MDI and about 2.0% or less of 2,4'-MDI isomers) and ten parts of triethyl phosphate is quickly heated to 220 ° C and maintained at high temperature for 1 to 1.5 hours. Then it cools quickly to 30 ° C. The NCO content of products 33.0% and the calculated uretonimine content is 2.5%. Examination of the infrared spectrum of the product indicates the presence of peaks attributable to the uretonimine portion. As with the previous Examples, no significant precipitation of uretdione is noted when stored at 30 ° C for at least about 40 days Example 5 Thousand parts of a mixture of a composition of 4,4 '-MDI essentially pure and 0.002 part of oxide of phospholene are maintained at 45-50 ° C for 5 hours. Subsequently, 0.02 part of trifluoromethane sulfonic acid are added to deactivate the catalyst. The product is cooled and stored at 30 ° C. The NCO content is 33.0% by weight. Again, no significant precipitation of uretdione is expected to occur at 30 ° C for at least about 40 days. The storage stable liquid polyisocyanate composition resulting from the present invention which includes a relatively high concentration of methylene bis (phenylisocyanate), can be employed for multiple applications including those for which 4,4'-MDI is currently employed. As such, the methylene bis (phenylisocyanate) compositions can be employed for the preparation of both cellular and non-cellular polyurethanes including, by way of non-limiting example, semi-rigid and rigid, flexible foams, as well as elastomers as illustrated in Table 1 then . Properties of molded elastomers prepared from the isocyanate-based prepolymers of the present invention are compared in the following Table, with those preparations of the prepolymer based on essentially pure methylene bis (phenylisocyanate). Table 1 The comparison of the properties in the above Table indicates that the elastomers prepared from isocyanate in the present invention exhibit properties that are similar or better than those based on essentially pure 4,4'-methylene bis (phenylisocyanate) not containing uretonimine. While it will be apparent that the preferred embodiments of the invention described are well calculated to meet the stated objectives, it will be appreciated that the invention is susceptible to modification, variation and changes without departing from its spirit.

Claims (26)

1. CLAIMS 1. A methylene bis (phenylisocyanate) composition, characterized comprising on the basis of the total weight of the composition: a) at least about 90.0% of a methylene bis (phenylisocyanate) component including at least about 90.0% by weight 4 , 4 '-MDI; and b) less than about 5.0% by weight of an uretonimine; wherein the methylene bis (phenylisocyanate) composition is stable in storage as a liquid.
2. 2. The composition of methylene bis (phenylisocyanate) in accordance with the claim

   1, characterized in that the uretonimine is produced using a catalyst capable of converting an organic isocyanate to carbodiimide which in turn is converted to uretonimine in the presence of excess of 4,4 '-MDI.
3. 3. - The composition of methylene bis (phenylisocyanate) in accordance with the claim

   2, characterized in that the catalyst is used in amounts of between about 0.0001 part to about 5.0 parts per 100.0 parts of methylene bis (phenylisocyanate).
4. 4. The methylene bis (phenylisocyanate) composition according to claim 2, characterized in that the catalyst is present in an amount of between about 0.0002 part to about 2.5 parts per 100.0 parts of methylene bis (phenylisocyanate).
5. 5. The methylene bis (phenylisocyanate) composition according to claim 2, characterized in that the organic isocyanate is selected from the group consisting of phenyl isocyanates, cyclohexyl isocyanate, methylene bis (phenylisocyanate) and toluene diisocyanate.
6. 6. The composition of methylene bis (phenylisocyanate) according to claim 5, characterized in that the organic isocyanate comprises at least 45% by weight 4,4 '-MDI, the rest comprises 2,4'-MDI and other MDI isomers .
7. 7. The methylene bis (phenylisocyanate) composition according to claim 1, characterized in that the uretonimine is produced in situ using a catalyst capable of converting a portion of the methylene bis (phenylisocyanate) component into carbodiimide which in turn becomes uretonimine in the presence of excess 4,4 '-MDI.
8. 8. The methylene bis (phenylisocyanate) composition according to claim 1, characterized in that the uretonimine is present in amounts of at least 0.1 part per 100.0 parts of the methylene bis (phenylisocyanate) composition.
9. 9. The methylene bis (phenylisocyanate) composition according to claim 1, characterized in that the uretonimine is present in amounts of between about 0.25% by weight at 20% to about 2.5% by weight per 100.0 parts of methylene bis composition (phenylisocyanate).
10. 10. The composition of methylene bis (phenylisocyanate) in accordance with the claim

    2, characterized in that the catalyst is selected from the group consisting essentially of phospholene oxides, phosphates, and mixtures thereof.
11. 11. A methylene bis (phenylisocyanate) composition that is storage stable with a liquid at room temperature, characterized in that it comprises: a) a methylene bis (phenylisocyanate) component that includes at least about 90.0 wt% of 4.4 '-MDI; and b) less than about 5.0% by weight, based on the weight of the composition of an uretonimine.
12. 12. - The composition of methylene bis (phenylisocyanate) in accordance with the claim

    11, characterized in that the methylene bis (phenylisocyanate) component is present in amounts of at least about 97.5% by weight and the uretonimine is present in amounts from about 0.25 to about 2.5% by weight based on the weight of the methylene bis composition. (phenylisocyanate).
13. 13. The methylene bis (phenylisocyanate) composition according to claim 11, characterized in that the uretonimine is produced using a catalyst capable of converting an organic isocyanate to carbodiimide which in turn is converted to uretonimine in the presence of excess of 4%., 4'-MDI.
14. 14. The methylene bis (phenylisocyanate) composition according to claim 13, characterized in that the catalyst is used in amounts of between about 0.0002 part to about 2.5 parts per 100.0 parts of methylene bis (phenylisocyanate).
15. 15. The methylene bis (phenylisocyanate) composition according to claim 13, characterized in that the organic isocyanate is selected from the group consisting of phenyl isocyanates, cyclohexyl isocyanate, methylene bis (phenylisocyanate) and toluene diisocyanate. 6.
16. The methylene bis (phenylisocyanate) composition according to claim 15, characterized in that the organic isocyanate comprises at least 45% by weight 4,4'-MDI, the rest comprises 2,4 '-MDI and other MDI isomers .
17. 17. The methylene bis (phenylisocyanate) composition according to claim 11, characterized in that the uretonimine is present in amounts of at least 0.1 part per 100.0 parts of the methylene bis (phenylisocyanate) composition.
18. 18. The methylene bis (phenylisocyanate) composition according to claim 11, characterized in that the uretonimine is present in amounts of between about 0.25% by weight to about 1.25% by weight per 100.0 parts of the methylene bis (phenylisocyanate) composition ).
19. 19. The composition of methylene bis (phenylisocyanate) according to claim 13, characterized in that the catalyst is selected from the group consisting essentially of phospholene oxides, phosphates, and mixtures thereof.
20. 20. A polyisocyanate composition, which is storage stable as a liquid comprising the reaction product of: a methylene bis (phenylisocyanate) component that includes at least about 90.0% by weight of 4,4'-MDI; and b) a catalyst capable of converting a 4,4'-MDI portion to carbodiimide, the carbodiimide is converted to uretonimine in the presence of 4,4'-MDI excess, wherein the uretonimine is present in an amount less than about 5.0 % by weight, based on the weight of the composition.
21. 21. A method for preparing a storage liquid stable methylene bis (phenylisocyanate) composition comprising the steps of mixing: a) a methylene bis (phenylisocyanate) component including at least 90.00% by weight of 4.4 '-MDI with b) an uretonimine.
22. 22. The method according to claim 21, characterized in that the uretonimine is present in amounts of between about 0.25 part to about 1.25 parts per 100.0 parts of the methylene bis (phenylisocyanate) composition.
23. 23. - A method for preparing a liquid methylene bis (phenylisocyanate) composition, stable in storage by the in situ formation of uretonimine, the method is characterized in that it comprises the steps of: mixing a methylene bis (phenylisocyanate) component that includes 90.0% by weight 4,4'-MDI with a catalyst capable of reacting with 4,4'-MDI to form the carbodiimide, the carbodiimide is converted to form uretonimine in the presence of excess 4,4'-MDI in the composition, wherein the amount of the uretonimine is a positive amount less than about 5.0% by weight of the methylene bis (phenylisocyanate) composition.
24. 24. The method according to claim 23, characterized in that the uretonimine is present in amounts of between about 0.25 part to about 1.25 parts per 100.0 parts of the methylene bis (phenylisocyanate) composition.
25. 25. The method according to claim 23, characterized in that the catalyst is present in amounts of between about 0.0002 part to about 2.5 parts per 100.0 parts of methylene bis (phenylisocyanate).
26. 26. The method according to claim 23, characterized in that the catalyst is selected from the group consisting essentially of phospholene oxides, phosphates, and mixtures thereof.