MXPA96002180A - Procedure of molding by injection dereaction using demetilendipenyl diisocianate liquid - Google Patents

Abstract

The present invention relates to a process for the production of an article molded through the technique of injection molding of reaction (MIR) introducing a reaction mixture in a closed mold, where said reaction mixture has an isocyanate index of about 80 to 120 and said reaction mixture consists of: A) an isocyanate-reactive material, B) a chain extender, and C) a stable and liquid diphenylmethane-diphenyl diisocyanate prepared by: 1) (a) the reaction of i) an equivalent of a diisocyanate with ii) an equivalent of an aliphatic alcohol or an aromatic alcohol 2) (a) the reaction of i) an equivalent of a diisocyanate with ii) an equivalent of an aliphatic alcohol or an aromatic alcohol, leaving that said reaction mixture reacts completely and separating the molded article from the mole

Description

MIR PROCEDURE USING LIQUID METILENDIPHENYL DIISOCIANATE BACKGROUND OF THE INVENTION The present invention relates to a process for producing molded articles from a reaction mixture consisting of a new isocyanate through the technique of reaction injection molding. More specifically, the reaction mixtures suitable for the present invention contain dialiphanate-modified DIM prepolymers. The liquid methylene diphenyl diisocyanates are generally known in the art. U.S. Pat. No. 3,644,457 describes liquid isocyanates stable at room temperature, derived from one mole of diphenylmethane diisocyanate and 0.1 to 0.3 moles of poly-1,2-propylene ether glycol. U.S. Pat. No. 4,055,548 describes liquid isocyanate prepolymer compositions obtained by reacting polymethylene polyphenylisocyanate containing from about 65 to about 85 percent by weight of methylene bis (phenyl) isocyanate with a polyoxyethylene glycol having a molecular weight of 200 to 600 in an equivalent ratio of 0.0185 to 0.15: 1. The US Patents 4,115,429 and 4,118,411 disclose liquid diphenylmethane diisocyanates stable to low temperature storage (as low as -5 degrees Centigrade) which are produced by reaction of diphenylmethane diisocyanates having a specified content of 2,4'-isomer with propylene glycol or poly-1, 2-propylene ether glycol. U.S. Pat. No. 4,261,852 describes liquid polyisocyanate compositions consisting of (A) the reaction product of 90 to 50% by weight of a reaction product of diphenylmethane diisocyanate and a polyoxypropylene diol or triol having an equivalent hydroxyl weight of 750 to 3000, said reaction product having an NCO content of 8 to 26% by weight and (B) of about 10 to 50% by weight of a diphenylmethane diisocyanate containing from 30 to 65% by weight of diphenylmethane diisocyanate, the remainder being polymethylene polyphenyl polyisocyanate. U.S. Pat. No. 4,490,300 discloses liquid isocyanates stable at room temperature which are derived from the reaction of diphenylmethane diisocyanate with an aliphatic diol having a pendant aromatic group, for example 2-methyl-2-phenyl-1,3-propanediol or phenyl-1, 2-ethanediol. U.S. Pat. No. 4,490,301 describes liquid isocyanates which are stable at room temperature and which are derived from the reaction of diphenylmethane diisocyanate with monoallyl ether or trimethylolpropane. In U.S. Pat. No. 4,490,302 also describes liquid compositions of diphenylmethane diisocyanate. These are prepared by reaction of diphenylmethane diisocyanate with a mixture of (i) a monohydroxy alcohol, (ii) a poly-1,2-propylene ether glycol having a molecular weight of 134 to 700 and (iii) an alcohol trihydroxylic selected from the group consisting of trimethylolpropane, triethylolpropane, glycerin and 1,3,6-hexanetriol. U.S. Pat. No. 4,910,333 describes a process for the preparation of modified liquid isocyanate consisting of the reaction of (i) diphenylmethane diisocyanate, (ii) an organic material containing two or more hydroxyl groups and forming a solid product at 25 ° C when it reacts with DIM in an amount such that the solid product has an isocyanate group content of 10 to 30% by weight and (iii) of 1 to 6% by weight, based on the weight of (i), (ii) ) and (iii), tripropylene glycol. The amount of (i), (ii) and (iii) is such that the resulting product is both stable and liquid at 25 ° C and has an isocyanate group content of about 10 to 30% by weight. U.S. Pat. No. 4,738,991 discloses organic polyisocyanates characterized by allophanate linkages that are prepared by reaction of an organic polyisocyanate, including 2,4'- and 4,4'-methylenediphenyl diisocyanate, with poly- or monohydric alcohol in the presence of an organometallic catalyst. The catalyst is then deactivated using a compound such as an inorganic acid, an organic acid, an organic chloroformate or an organic acid chloride. U.S. Pat. No. 4,866,103 discloses a polyisocyanate composition for use in the production of elastomers in a MIR process, said composition being the product of the reaction of an alcohol and / or thiol having an average functionality of about 1.5 to about 4 and a average equivalent weight of at least 500 with at least 2 equivalents per equivalent hydroxyl and / or thiol of an organic polyisocyanate, including the 4,4'- and 2,4 'isomers of the diphenylmethane diisocyanate, under conditions such that at least about 20% of the initially formed urethane and / or thiourethane groups are converted to allophanate and / or thioalophonate groups. Other patents related to the preparation of allophanates containing isocyanates are British Patent 994,890, which relates to the reaction of urethane isocyanates with an excess of diisocyanate either only by heat or in the presence of a catalyst such as a metal carboxylate, a metal chelate or a tertiary amine, until the isocyanate content is reduced to that theoretically obtained when the complete reaction of the urethane groups is achieved. U.S. Pat. No. 4,160,080 describes a process for producing allophanate containing aliphatic and / or cycloaliphatically bound isocyanate groups, wherein the compounds containing urethane groups react with polyisocyanates having aliphatic and / or cycloaliphatic isocyanate groups in the presence of a strong acid. The process is generally carried out at a temperature of 90 ° C to 140 ° C for about 4 to 20 hours. Japanese Patent Application No. 1971-99176 describes a method of preparing liquid diphenylmethane diisocyanate by reaction of diphenylmethane diisocyanate with monovalent aliphatic alcohol. In U.S. Pat. 5,319,054. A process for the production of modified DIP is described which is stable to storage at 25 ° C. Although this patent broadly discloses that these allophanate-modified DIM prepolymers are suitable for use in a MIR process, it is not suggested that products prepared by a MIR process using these allophanate-modified DIMs exhibit better mechanical properties. U.S. Pat. No. 5,319,053 is directed to a stable liquid DIM prepolymer. This liquid prepolymer consists of an alcohol-based allophanate-modified DIM prepolymer having an isocyanate content of about 12 to 32.5% and characterized in that the allophanate is a reaction product of an aliphatic alcohol and an isomeric composition. specified DIM containing from 2 to 60% of the 2,4 'isomer, less than 6% of the 2,2' isomer and the remainder is the 4,4 'isomer. It is also possible according to another embodiment in U.S. Pat. No. 5,319,053 that this stable liquid DIM prepolymer has an isocyanate content of 5 to 30%. In this embodiment, the prepolymer consists of the reaction product of the allophanate described above and an organic material containing at least two active hydrogen groups and / or a low molecular weight diol. The organic material containing active hydrogen groups can be one in which these groups are hydroxyl groups, primary amino groups, secondary amino groups or combinations thereof. Copending Application Serial No. 08 / 116,141, filed September 2, 1993, commonly assigned, discloses that the MIR processing of the stable liquid DIM prepolymers described in US Pat. 5,319,053 results in molded products exhibiting a high flexion coefficient. These stable liquid DIM prepolymers contain allophanate groups and possibly urethane groups.

By the present invention, an MIR process is available for the production of molded articles from a reaction mixture consisting of a new liquid isocyanate. The molded parts produced by this process exhibit a better flexural coefficient. Because these prepolymers give elastomers with a better bending coefficient, lower levels of fast reaction chain extenders are required to achieve a given rigidity. This allows the filling of larger instruments at a given performance of the machine due to the longer gel time. This is important, since the MIR instruments become larger and require a larger unit of measurement if the reactivity of the system can not be reduced. DESCRIPTION OF THE INVENTION The present invention relates to polyurethane moldings produced by the reaction injection molding (MIR) process. This process consists of the steps of introducing a reaction mixture into a closed mold, allowing said reaction mixture to fully react and separating molded article from the mold. The reaction mixture has an isocyanate index of about 80 to 120 and consists of an isocyanate-reactive material, a chain extender and a liquid dialofanate-modified diphenylmethane diisocyanate. These diphenylmethane-dialphanate-modified diisocyanates can be prepared by two different methods. The first method consists of 1) (a) reacting: (i) an equivalent of a diisocyanate with (ii) an equivalent of an aliphatic alcohol containing from 1 to 36 carbon atoms, preferably 2 to 16 carbon atoms, or an aromatic alcohol containing from 6 to 18 carbon atoms, preferably from 6 to 12 carbon atoms, wherein the hydroxyl group is directly attached to the aromatic ring to form a diurethane of the diisocyanate; (b) reacting the diurethane formed in (a) with an isomeric composition of diphenylmethane diisocyanate containing from 0 to 60% (preferably 0 to 30% and, more preferably, 1 to 10%). %) by weight of 2,3,4'-diphenylmethane diisocyanate and less than 6% (preferably less than 3% and, more preferably, less than 1%) by weight of diisocyanate of 2,2'- diphenyl methane and the remainder being 4,4 '-diphenylmethane diisocyanate, in the presence of an allophanate catalyst to obtain the liquid and stable diphenylmethane diphenylmethane diisocyanate, followed by addition of an agent to stop the catalyst. The stable liquid diphenylmethane-modified diphenylmethane diisocyanate prepared according to this method has an isocyanate group content of 12.0 to a .0%, preferably from 17 to 28% and, more preferably, from 17 to 24%.

It is also possible to prepare these dialhenate-modified diphenylmethane diisocyanates by the alternative method of 2) (a) reacting: (i) one equivalent of a diisocyanate with (ii) one equivalent of an aliphatic alcohol containing from 1 to 36 carbon atoms , preferably 2 to 16 carbon atoms, or an aromatic alcohol containing from 6 to 18 carbon atoms, preferably from 6 to 12 carbon atoms, wherein the hydroxyl group is directly attached to the aromatic ring to form a diurethane of the diisocyanate; (b) reacting the diurethane formed in step 2) (a) with an isomeric composition of diphenyl diisocyanate containing from 0 to 60% (preferably 0 to 30% and, more preferably, 1 at 10%) by weight of 2,4,4'-diphenylmethane diisocyanate and less than 6% (preferably less than 3% and, more preferably, less than 1%) by weight diisocyanate of 2, 2 '-diphenylmethane, the remainder being 4,4'-diphenylmethane diisocyanate, in the presence of an allophanate catalyst to obtain a diphenyl diisocyanate methano-dialphanate-modified diisocyanate having an isocyanate group content of 12%., 0 to 30%, followed by addition of an agent to stop the catalyst, and (c) reacting the diphenylmethane-dialphanate-modified diisocyanate having an isocyanate group content of 12.0 to 30.0% with a compound selected from the group consisting of: (i) an organic material having -20 has about 1.8 or more hydroxy groups, primary amino or secondary amino or any combination thereof, which has a molecular weight of 400 to 6000, preferably from 500 to 5200 and, more preferably, from 1000 to 4800, (ii) a diol having a molecular weight of from 60 to 200, preferably from 76 to 192 and, more preferably, from 76 to 150 and (iii) ) mixtures of (i) and (ii). This method forms a stable liquid dialofanate-modified isocyanate having an isocyanate group content of 5 to 29%, preferably 9 to 27% and, more preferably, 12 to 21%. According to the above, the present invention, in the first embodiment, encompasses a process for the production of molded parts through a MIR process from a reaction system consisting of an isocyanate-reactive material, a chain extender and a DIM dialofanato-modified that is a liquid stable to storage at 25 ° C. The dialhanoate-modified DIM is prepared by (a) reaction of (i) one equivalent of a diisocyanate selected from the group consisting of hexamethylene diisocyanate (DIH), isophorone diisocyanate (DIIF), toluene diisocyanate (DIT), diisocyanate, diphenylmethylene diene (DIM) and DIM hydrogenated with (ii) an equivalent of an aliphatic alcohol containing from 1 to about 36 carbon atoms or an aromatic alcohol containing from 6 to 18 carbon atoms to form a diurethane of the diisocyanate, ( b) reacting the product of (a) with a specified isomeric composition of diphenylmethane diisocyanate in an amount sufficient to obtain a liquid dialofanate-modified DIM having an NCO content of about 12.0 to 30.0%. Typically, the isomeric composition of diphenylmethane diisocyanate contains 4,4'-diphenylmethane diisocyanate, from 0 to 60% and, preferably, from 1 to 60%, by weight of 2,4'-DIM and less than 6% by weight of 2, 2 '-DIM. In the second embodiment, the present invention encompasses the MIR procedure indicated above, wherein the dialhanoate-modified DIM has been further modified. Specifically, a dialphoanate-modified DIM having an isocyanate group content of from 12.0 to 30.0% is reacted with at least one compound selected from the group consisting of (i) an organic material containing about 1, 8 or more hydroxy groups, primary amino or secondary amino or any combination thereof having a molecular weight of 400 to 6000, (ii) a diol having a molecular weight of 60 to 200 and (iii) mixtures thereof, wherein the resulting liquid prepolymer has an isocyanate group content of 5 to 29% by weight. It is a distinctive feature that the resultant dialofanato-modified DIM prepolymers that are suitable for use in the present process are stable and liquid at 25 ° C. By the term "stable" is meant here that the isocyanate has no more than one percent absolute change in NCO content and no more than ten percent change in viscosity when stored at 25 ° C for 3 hours. months By the term "liquid" it is meant here that the modified isocyanate does not precipitate solids when stored at 25 ° C for 3 months. Particularly useful applications for the molded products produced by this method include, for example, reaction injection molding (MIR) of automobiles, shoe sole applications and rigid foam.

In the first method of preparing dialphanate compounds suitable for use in the present invention, the dialofanate-modified DIM-containing prepolymer is characterized to be stable and liquid at 25 ° C and has an isocyanate content of about 12 to 30%. %, preferably 17 to 28% and, more preferably, 17 to 24% by weight. In the second method of preparing dialphanate compounds suitable for use in the present invention, the dialofanato-modified DIM is characterized in that it has an isocyanate group content of about 5 to 29%, preferably 9 to 27%, and , more preferably, 12 to 21% by weight. The dialhanoate-modified DIM may be prepared by reaction of a diisocyanate with an aliphatic or aromatic alcohol in order to produce a diurethane, followed by reaction of the diurethane with the specified DIM isomer composition to form a dialphanate. More specifically, the diurethane of the diisocyanate can be obtained by reaction of one equivalent of a diisocyanate with one equivalent of an aliphatic alcohol containing from 1 to about 36, preferably about 2 to 16 carbon atoms, or with an aromatic alcohol containing about 6 to 18, preferably about 6 to 12 carbon atoms, where the hydroxyl group is directly attached to the aromatic ring. Suitable diisocyanates according to the present invention include all known diisocyanates. It is preferred that the diisocyanate be selected from the group consisting of hexamethylene diisocyanate (DIH), isophorone diisocyanate (DIIF), toluene diisocyanate (DIT), diphenylmethylene diisocyanate (DIM) and hydrogenated DIM. Aliphatic alcohols useful herein include those which can react with the diisocyanate to form the diurethane, which can then be converted to an allophanate according to the invention. Useful aliphatic alcohols may contain about 1 to 36 and, preferably, 2 to 16 carbon atoms. Illustrative, but not limiting, examples of the aliphatic alcohols can be selected from the group consisting of cycloaliphatic alcohols, aliphatic alcohols containing aromatic groups and aliphatic alcohols containing groups that do not react with isocyanates, for example ether and halogen groups such as bromine and chlorine. Suitable compounds include, for example, aliphatic alcohols such as 1-butanol, cetyl alcohol, 2-methoxyethanol and 2-bromoethanol. Ethanol, isomeric butanols and isomeric pentanols are preferred aliphatic alcohols. Suitable examples of the aromatic alcohols include phenol, 1-naphthol and substituted phenols, such as cresol, and substituted naphthols, such as 2-methyl-1-naphthol. Preferred aromatic alcohols are phenol and substituted phenols. In the reaction of the aliphatic or aromatic alcohol with the diisocyanate, the equivalent ratio of NCO to OH is about 1: 1, the reaction being monitored up to preferably 80%, more preferably 90% and, more preferably, 95% of the NCO groups have reacted and have become the urethane groups. Solvents which are typically inert to the isocyanate may be employed, such as, for example, toluene, tetrahydrofuran, o-dichlorobenzene or the like. According to the invention, the process consists in reacting the resulting diurethane with the specified isomeric composition of diphenylmethane diisocyanate in an amount sufficient to obtain a dialphanate having an isocyanate group content of about 12.0 to 30.0%. As stated above, the isomeric composition of diphenylmethane diisocyanate consists of from about 0 to 60%, preferably from 0 to 30% and, more preferably, from 1 to 10% by weight of 2,4,4-diisocyanate. -diphenylmethane and less than 6%, preferably less than 3%, and more preferably less than 1, 0% by weight of the 2,2'-diphenylmethane diisocyanate and the remainder being 4,4'-diphenylmethane diisocyanate. The reaction of dialhanate formation is usually carried out in the presence of a catalyst. Suitable catalysts are those which can be neutralized or prevented from subsequently catalyzing subsequent reactions. Illustratively, a catalyst such as zinc acetylacetonate can be employed and an agent for stopping the catalyst can be used, such as acidic materials, such as, for example, anhydrous hydrochloric acid, sulfuric acid, benzoyl chloride, bis (2-) phosphate. ethylhexyl), Lewis acids and the like in the ratio of 2 equivalents of the acid per mole of the zinc acetylacetonate. Other allophanate catalysts may be employed such as zinc 2-ethylhexanoate, cobalt 2-ethylhexanoate, cobalt naphthanate, lead lino-resin, stannous octoate or the like. In a preferred embodiment of the process of the invention, the dialophosate can be prepared by reaction of the diisocyanate, as described above, with an aliphatic or aromatic alcohol, at about 20 ° C to about 115 ° C. The resulting diurethane is dissolved in the specified DIM isomer composition and converted to a dialofanato-modified DIM of 90 to 110 ° C, using zinc acetylacetonate as a catalyst and benzoyl chloride as a stopping agent for the catalyst in a ratio of 2: 1 weight of benzoyl chloride to zinc acetylacetonate. In the second embodiment of the invention, the method includes, in addition to the process steps described above, the reaction of the diaphoanate-modified DIM as described above with a high and / or low molecular weight organic material containing approximately 1 , 8 or more and, preferably, from 2 to 3 active hydrogen groups such as hydroxyl, primary or secondary amino groups or the like. The high molecular weight organic material may have a molecular weight of 400 to 6000, preferably 500 to 5200 and, more preferably, 1000 to 4800. The weight range of the low molecular weight material may be 60 to 200, preferably 76 to 192 and, more preferably, 76 to 150. The object reaction of urethane, urea or biuret is carried out in a well known manner, for example by heating the reactants at a temperature of about 40 to 150 ° C, preferably 50 at 100 ° C, to form urethane or urea and heating at a temperature of 100 to 150 ° C, preferably 110 to 120 ° C, to form the biuret. Useful organic materials containing about 1.8 or more hydroxyl groups and having a molecular weight of 400 to 6000 may be a polyol selected from the group consisting of polyester polyols, polyether polyols, polyhydroxypolycarbonates, polyhydroxy-polyacetals, polyhydroxy polyacrylates, polyhydroxypolyester-ter amides and polyhydroxypolythioethers. Polyester polyols, polyether polyols and polyhydroxypolycarbonates are preferred. Suitable polyester polyols include the reaction products of polyhydric alcohols, preferably dihydric alcohols, to which polyhydric alcohols and polybasic, preferably dibasic, carboxylic acids can be added. Instead of these polycarboxylic acids, the corresponding carboxylic acid anhydrides or polycarboxylic acid esters of lower alcohols or mixtures thereof can be used to prepare the polyesters. The polycarboxylic acids can be aliphatic, cycloaliphatic, aromatic and / or heterocyclic and can be substituted, for example by halogen atoms, and / or unsaturated. The following are mentioned as examples: succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, italic acid, isophthalic acid, trimellitic acid, italic acid anhydride, tetrahydrophthalic anhydride, hexahydrophthalic acid anhydride, tetrachlorophthalic anhydride, endomethylenetetrahydrophthalic acid anhydride, glutaric acid anhydride, maleic acid, maleic acid anhydride, fumaric acid, dimeric and trimeric fatty acids such as oleic acid, which can be mixed with monomeric fatty acids, dimethyl terephthalates and bisglycol terephthalate . Suitable polyhydric alcohols include, for example, ethylene glycol, propylene glycol- (1, 2) and - (1,3), butylene glycol- (1,) and - (1,3), hexanediol- (1, 6) , octanediol- (1, 8), neopentylglycol, cyclohexanedimethanol (1,4-bishydroxymethylcyclohexane), 2-methyl-1,3-propanediol, 2,2,4-trimethyl-1,3-pentanediol, triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol, dibutylene glycol and polybutylene glycol, glycerin and trimethylolpropane. The polyesters may also contain a portion of carboxyl end groups. It is also possible to use lactone polyesters, for example e-caprolactone or hydroxylcarboxylic acids, for example γ-hydroxycaproic acid. Polycarbonates containing hydroxyl groups include those which are known per se, such as the products obtained from the reaction of diols such as propanediol- (1, 3), butanediol- (1, 4) and / or hexanediol- (1, 6), diethylene glycol, triethylene glycol or tetraethylene glycol with phosgene, diaryl carbonates such as diphenyl carbonate or with cyclic carbonates such as ethylene or propylene carbonate. Also suitable are polyester carbonates obtained from the aforementioned polyesters or polylactones with phosgene, diaryl carbonates or cyclic carbonates. Suitable polyether polyols are obtained in a known manner by the reaction of starting compounds containing hydrogen atoms reactive with alkylene oxides such as ethylene oxide, propylene oxide, butylene oxide, styrene oxide, tetrahydrofuran, epichlorohydrin or mixtures thereof. these alkylene oxides. It is preferred that the polyesters contain no more than about 10% by weight of ethylene oxide units. More preferably, the polyethers obtained without the addition of ethylene oxide are used. Suitable starting compounds containing reactive hydrogen atoms include the polyhydric alcohols indicated for the preparation of the polyester polyols and, in addition, water, methanol, ethanol, 1, 2, 6-hexanetriol, 1,2,4-butane- triol, trimethylolethane, pentaerythritol, mannitol, sorbitol, methyl glycoside, sucrose, phenol, isononylphenol, resorcinol, hydroquinone and 1,1,1- or 1,1,1-tris (hydroxylphene-nyl) ethane. The polyethers modified by vinyl polymers are also suitable for the process according to the invention. Products of this type can be obtained by polymerization, for example, of styrene and acrylonitrile in the presence of polyethers (US Patent Nos. 3,383,351, 3,304,273, 3,523,095, 3,110,695 and German Patent No. 1,152,536). Among the polythioethers that should be particularly mentioned are the condensation products obtained from thiodiglycol by itself and / or with other glycols, dicarboxylic acids, formaldehyde, aminocarboxylic acids or aminoalcohols. The products obtained are polythio-mixed esters, polythioether esters or polythioether ester amides, depending on the co-components. The amine-terminated polyethers useful herein may be prepared by reacting a primary amine with polyether containing terminal leaving groups such as halides, or mesylates, as described in US Patent Application Ser commonly assigned Serial Number 07 / 957,929, filed October 7, 1992, or as described in U.S. Pat. 3,666,726, 3,691,112 and 5,066,824. Useful polyacetals include compounds which can be prepared from aldehydes, for example formaldehyde, and glycols such as diethylene glycol, triethylene glycol, 4,4'-dihydroxydifenyldimethylmethane ethoxylated and hexanediol- (1, 6). Polyacetals suitable for the purposes of the invention can also be prepared by polymerization of cyclic acetals. Suitable polyhydroxypolyester amides and polyamines include the predominantly linear condensates obtained from polybasic saturated and unsaturated carboxylic acids or their polyvalent saturated or unsaturated anhydrides and aminoalcohols., diamines, polyamines and their mixtures. Suitable monomers for producing hydroxy-functional polyacrylates include acrylic acid, methacrylic acid, crotonic acid, maleic anhydride, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate. , 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, glycidyl acrylate, glycidyl methacrylate, 2-isocyanatoethyl acrylate and 2-isocyanatoethyl methacrylate. The low molecular weight material which preferably contains two hydroxyl groups and which has an average molecular weight of 60 to 200 can be used in combination with or instead of the high molecular weight material containing two or more hydroxyl groups. Useful low molecular weight materials include the polyhydric alcohols that have been previously described for the preparation of the polyester polyols and polyether polyols. Dihydric alcohols are preferred. The weight ratio of the low molecular weight material to the high molecular weight material containing about 1.8 or more hydroxyl groups may be from 0.001 to 2 and, preferably, from 0.01 to 0.40. In addition to the aforementioned components, small amounts of monofunctional compounds can also be used. In the process of the invention, the hydroxyl functional material (s) can (n) react with the dialophonate in the temperature range of 40 to 150 and, preferably, 50 to 100 ° C, over a period of time sufficient to complete the reaction. Catalysts and solvents can be used to help the reaction. Examples of catalysts useful for promoting urethane reactions can be selected from the group consisting of di-n-butyltin dichloride, di-n-butyltin diacetate, di-n-butyltin dilaurate, triethylene diamine, bismuth nitrate and Similar. Examples of the useful solvents can be selected from the group consisting of toluene, tetrahydrofuran and chlorobenzene. The product resulting from the first embodiment is a liquid isocyanate prepolymer having an isocyanate group content of 12 to 30%, preferably 17 to 28% and, more preferably, 17 to 24%. The product resulting from the second embodiment is a liquid isocyanate prepolymer having an isocyanate group content of 5 to 29%, preferably 9 to 27% and, more preferably, 12 to 21%. These liquid isocyanate prepolymers have proved to be particularly useful for the preparation of molded polyurethane articles through the MIR process which exhibit unique properties. More specifically, the molded parts have a better bending coefficient. The liquid isocyanate prepolymer compositions of the present invention can be further combined with one or more isocyanate-reactive compounds, a catalyst and any other known additives and process aids known to be useful in MIR procedures. This reactive mixture can then be molded according to known reaction injection molding techniques. The isocyanate-reactive compounds useful to produce the reactive mixture to be molded include those described above as useful for the production of the liquid isocyanate prepolymers previously described. These suitable isocyanate-reactive materials include, for example, polyethers, polyesters, polythioethers, polyacetals, polycarbonates, amine-terminated polyethers, aminopolyethers, polymeric polyols, PHD-polyols or so-called filled polyols. These compounds may have molecular weights of about 500 to 10,000 and contain from 1 to 4 isocyanate-reactive groups of the type known for the production of polyurethanes. Other isocyanate-reactive compounds useful for the production of the reactive mixture to be molded include, for example, low molecular weight chain extenders. These compounds generally have molecular weights of about 60 to 500, preferably 61 to 400, and may contain hydroxyl groups or amino groups that are reactive with the isocyanate. Suitable compounds include, for example, organic diols and triols, primary amines and secondary organic amines, aminoalcohols, etc. Some suitable amine chain extenders include l-methyl-3,5-diethyl-2, phenyldiamine, l-methyl-3,5-diethyl-2,6-phenyldiamine and mixtures thereof. Catalysts that can be used to produce MIR articles according to the present invention include, for example, tertiary amines, silylamines having carbon-silicon bonds, basic nitrogen compounds and organic metal compounds such as, for example, organic tin compounds . Some suitable examples of these include those described in, for example, US Pat. 5,198,522, the description of which is hereby incorporated by reference. Other additives that can be used in the MIR process according to the present invention include surfactant additives such as emulsifiers and foam stabilizers. Examples include N-stearyl-N ', N'-bishydroxyethylurea, oleyl polyoxyethyleneamide, stea-ryldiethanolamide, isostearyldiethanolamide, polyoxyethylene glycol monooleate, an ester of pentaerythritol / adipic acid / oleic acid, a hydroxyethylimidazole derivative of oleic acid, N-stearylpropylenediamine and the sodium salts of sulfonates of castor oil or of fatty acids. Alkali metal or ammonium salts of sulphonic acid, such as dodecylbenzenesulfonic acid or dinaphthylmethanesulfonic acid and also fatty acids as surfactant additives may also be used. Suitable foam stabilizers include water-soluble polyether siloxanes. The structure of these compounds is generally such that a copolymer of ethylene oxide and propylene oxide is attached to a polydimethylsiloxane radical. Such foam stabilizers are described, for example, in US Pat. 2,764,565. In addition to the catalysts and surfactants, other additives that can be used in the molding compositions of the present invention include known blowing agents, including nitrogen, cellular regulators, flame retardants, plasticizers, antioxidants, stabilizers. UV, adhesion promoters, dyes, fillers and reinforcing agents such as glass in the form of fibers or flakes or carbon fibers. It is also possible to use the known internal mold release agents, such as, for example, zinc stearate, in the MIR process of the invention. As is known to one of ordinary skill in the art, an isocyanate and compounds containing active hydrogen are mixed in the MIR process and injected into molds, where the reactants are allowed to react completely. The molded products of the present invention are prepared by reaction of the components in a closed mold through the MIR process. The compositions according to the present invention can be molded using conventional processing techniques at isocyanate rates ranging from about 80 to 120. (preferably, from 90 to 110). The term "isocyanate index" (which is also commonly referred to as the NCO index) is defined here as the isocyanate equivalents, divided by the total isocyanate equivalents-materials containing reactive hydrogen, multiplied by 100. The term " "molecular weight" as used herein refers to the number-average molecular weight of a material. A numerical average molecular weight definition is given in "Principles of Polymer Chemistry" by Paul J.

Flory, 1953, Cornell University, p. 35. In general, in a MIR procedure, two independent currents are intimately mixed and then injected into a suitable mold, although it is possible to use more than two currents. The first stream contains the polyisocyanate component, while the second stream contains the isocyanate-reactive components and any other additives that are to be included. The following examples further illustrate the details for the process of this invention. The invention, which has been established in the foregoing description, is not to be limited in spirit or scope by these examples. Those skilled in the art will readily understand that known variations of the conditions of the following procedures can be used. Unless stated otherwise, all temperatures are degrees Celsius and all percentages are percentages by weight. EXAMPLES DIM-x: diphenylmethane diisocyanate containing less than 6% by weight of 2,2'-isomer of diphenylmethane diisocyanate and where x represents the weight percentage of 2,4'-isomer of diphenylmethane diisocyanate, the remainder being 4,4 'and 2,2' isomers. * Polyol A: an adduct of propylene glycol / propylene oxide having a molecular weight of 2000 and a hydroxyl value of 56. Polyol B: a polyether initiated in glycerol of propylene oxide and ethylene oxide (83% by weight of OP and 17% by weight of OE) having an OH number of 35 and a primary OH content of approximately 90% based on the total OH content of the polyether polyol. Isocyanate A 321 parts of DIM-2 at 60 ° C were added 226 parts of 1-pentanol. The reaction mixture produced an exotherm to 95 ° C and the temperature was maintained between 95 and 120 ° C for about 1 hour. To the thick liquid at 110 ° C, 1926 parts of DIM-20 were added. 0.25 parts of zinc acetylacetonate were added to the reaction mixture at 110 ° C and this temperature was maintained at 110 ° C for 2 hours, giving a material with 21.9% NCO content. The reaction mixture was cooled to 60 ° C and 0.75 part of benzoyl chloride was added. After stirring at 60 ° C for 15 minutes, 963 parts of Polyol A and 333 parts of Polyol B were added and the reaction mixture was maintained at 60 ° C for 2 hours. The reaction mixture was then cooled to 25 ° C to give a material with 13.0% NCO and a viscosity at 25 ° C of 6260 mPa-s. Isocyanate B To a stirred reactor containing 658 parts of 2,4-toluene diisocyanate (DIT) was added 1679 parts of 1-butanol at a rate such that the reaction temperature was maintained at 90 ° C with cooling. Within 30 minutes of completion of the addition, no isocyanate peaks remained in the IR (infrared) spectrum. Excess 1-butanol was removed by vacuum distillation to give 1218 parts of DIT diurethane. To this were added 6062 parts of DIM-2 and 1.1 parts of zinc acetylacetonate. The reaction mixture was heated at 90 ° C for 1 hour, cooled to 60 ° C and 3.3 parts of benzoyl chloride added. The transparent light yellow liquid had an NCO content of 23.6%. To this were added 3409 parts of Polyol A and 1183 parts of Polyol B. The reaction mixture was kept at 60 ° C for 2 hours and then cooled to 25 ° C. The resulting prepolymer had an NCO content of 12.9% and a viscosity at 25 ° C of 3710 mPa-s. Isocyanate C (not according to the invention) 654 parts of DIM-2 and 32 parts of 1-butanol in a stirred reactor and heated to 60 ° C. 0.034 part of zinc acetylacetonate was added and the stirred reaction mixture was heated to 90 ° C. After one hour at 90 ° C, the NCO content was 26.8%. The reaction mixture was cooled to 60 ° C and 0.069 parts of benzoyl chloride was added. After stirring at 60 ° C for 15 minutes, 144 parts of Polyol B and 420 parts of Polyol A were added and the reaction mixture was maintained at 60 ° C for 2 hours. The reaction mixture was then cooled to 25 ° C to give a material containing 12.9% NCO and a viscosity at 25 ° C of 2640 mPa-s. Isocyanate D (not according to the invention) 702 parts of DIM-2 and 40.7 parts of 1-butanol were charged in a stirred reactor and heated to 60 ° C. 0.037 part of zinc acetylacetonate was added and the stirred reaction mixture was heated to 90 ° C. After one hour at 90 ° C, the NCO content was 25.7%. The reaction mixture was cooled to 60 ° C and 0.087 part of benzoyl chloride was added. After stirring at 60 ° C for 15 minutes, 142 parts of Polyol B and 415 parts of Polyol A were added and the reaction mixture was maintained at 60 ° C for 2 hours. The reaction mixture was then cooled to 25 ° C to obtain a material containing a 13.0% NCO and a viscosity at 25 ° C of 2760 mPa-s. Examples MIR Liquid isocyanate prepolymers prepared according to the above examples (1-4) were used to produce molded articles by reaction injection. The specific materials and the quantities used of these materials appear in the following Tables. Below is a description of the materials. The polyurethane forming system was injected using a MIR RIMDOMAT Hennec e machine. The isocyanate-reactive materials and various additives were placed on the B-side of the machine and the appropriate quantities of isocyanate-specific to achieve an isocyanate index of 105 were loaded on the A side. The RIMDOMAT was equipped with a Hennecke mixing head mq8 . Side B was preheated to 45 ° C and side A was heated to 45 ° C. The materials were injected at an isocyanate index of 105 at an injection pressure of 200 bar and an injection speed of 200 grams / sec. The material was injected into a flat plate mold of 3x200x300 mm heated to 65 ° C and pulverized with Chemtrend 2006 mold release spray. After a dwell time of 30 seconds, the part was demolded. The physical properties were determined according to the ASTM standards. Other MIR examples were made in the same way, except for the parts by weight of several components. The following components were used in the MIR examples. All the MIR examples were performed at an NCO index of 105. Isocyanate A: see the previous description. Isocyanate B: see the previous description. Isocyanate C: see the previous description.

Isocyanate D: see the previous description. Polyol C: a polyether initiated in glycerol of propylene oxide and ethylene oxide (83% by weight of OP and 17% by weight of OE) with an OH number of 35 and an OH primary content of approximately 90% based on the total OH content of the polyether polyol. Amine A: a propoxylated ethylenediamine with an OH number of 630. Polyol D: a polyester having an OH number of 51 and which is based on oleic acid, adipic acid and pentaerythritol in a molar ratio of about 6: 2: 3. IMR A: a mixture of zinc stearate and amine A in a weight ratio of 2: 3 and having an OH number of 378. DETDA: an 80:20 mixture of l-methyl-3,5-diethyl-2 , 4- and 2, 6-phenyldiamine. L-5304: a silicone surfactant available from Union Carbide Corp. UL-28: dimethyltin dilaurate.

Dabco 33-LV: 33% by weight of triethylenediamine in dipropylene glycol with an OH # of 559. Isocyanates A and B show the advantages of the dialofanato modification and isocyanates C and D are comparative examples of monoalphanate. In the examples according to the invention, there is a marked increase in the flexion coefficient at a given level of DETDA. This is true despite the fact that the comparative isocyanates have the highest moles of allophanate modification per 100 g of isocyanate. The other properties are essentially similar. However, fragility is not a problem with any of these elastomers, since all impacts are well above the level of 3 to 5 feet. pound / inch The ability to greatly increase hardness with a good balance of elastomeric properties has two key advantages. The first is the cost. The DETDA is the most expensive of all the raw materials in these formulations. This approach allows us to achieve higher bending coefficients with less DETDA through an appropriate formulation of the prepolymer. This translates directly into savings in terms of cost. The second is the reduction of reactivity. Lower levels of DETDA mean lower concentrations of rapidly reacting amines that result in slower systems, even at high flexion coefficients. This allows the filling of larger molds in a given MIR machine and the reduction of density gradients and other production problems related to reactivity.

TABLE. 1 TABLE 2 TABLE 3 ASTM tests Although the invention has been described in detail in the foregoing for illustrative purposes, it should be understood that said detail has only that purpose and that those skilled in the art can make variations therein that constitute other embodiments without departing from the spirit and scope of the invention. invention, except as may be limited by the claims.

Claims (13)

1. CLAIMS 1. A process for the production of an article molded through the injection molding technique of reaction (MIR) by introducing a reaction mixture into a closed mold, wherein said reaction mixture has an isocyanate index of about 80 to 120 and said reaction mixture consists of: A) an isocyanate-reactive material, B) a chain extender and C) a liquid and stable diphenylmethane di-to-methane diisocyanate prepared by: 1) (a) the reaction of (i) ) an equivalent of a diisocyanate with (ii) an equivalent of an aliphatic alcohol containing from 1 to 36 carbon atoms or an aromatic alcohol containing from 6 to 18 carbon atoms, where the hydroxyl group is directly attached to the ring aromatic to form a diurethane of the born diisocyanate; (b) the reaction of said urethane with an isomeric composition of diphenylmethane diisocyanate consisting of from about 0 to 60% by weight of 2,4'-diphenylmethane diisocyanate and less than 6% by weight of diisocyanate of 2%. , 2'- 10 diphenylmethane, the remainder being diisocyanate of 4, '-diphenylmethane, in the presence of an allophanate catalyst to obtain said liquid and stable modified diphenylmethane diisocyanate 15 dialofanate, followed by the addition of an agent to stop the catalyst , wherein said diphenylmethane diisocyanate dialofanate-modifies liquid and stable has an isocyanate group content of from 12.0 to 30.0%; or 2) (a) the reaction of (i) an equivalent of a diisocyate with (ii) an equivalent of an aliphatic alcohol containing from 1 to 36 carbon atoms or an aromatic alcohol containing from 6 to 18 carbon atoms; carbon to form a diurethane of the diisocyanate; (B) the reaction of said diurethane with an isomeric composition of diphenylmethane diisocyanate consisting of about 0 to 60% by weight diisocyanate of 2,4,4'-diphenylmethane and less than 6% by weight diisocyanate of 2,2'-diphenylmethane, the remainder being 4,4 '-diphenylmethane diisocyanate, in the presence of an allophanate catalyst to obtain a diisocyanate-diphenylmethane-dialphanate-modified diisocyanate having an isocyanate group content of 12.0 to 30%, followed by addition of an agent to stop the catalyst, and 5 (c) the reaction of said diphenylmethane diisocyanate-dialphanate-modified diisocyanate having an isocyanate group content of 12.0 to 30.0%, with minus one compound selected from the group consisting of: (i) an organic material containing about 1.8 or more hydroxy groups, primary amino or secondary amino or any combination thereof, having a molecular weight of 4; 00 to 6000; (ii) a diol having a molecular weight of 60 to 200, and (iii) mixtures of (i) and (ii), to form said stable and liquid dialofanate-modified isocyanate wherein said dialophthalate-modified isocyanate has a content of isocyanate groups of 5 to 29%; letting said reaction mixture react completely and separating the molded article from the mold.
2. 2. The method of Claim 1, wherein said aliphatic alcohol contains from 2 to 16 carbon atoms.
3. 3. The process according to claim 1, wherein said aromatic alcohol is a phenol or a substituted phenol.
4. 4. The process of Claim 1, wherein said diisocyanate is selected from the group consisting of toluene diisocyanate, methylene bis (phenylisocyanate) and 1,6-hexamethylene diisocyanate.
5. The process of Claim 1, wherein said diol is selected from the group consisting of 1,2-propanediol, 1,3-butanediol, diethylene glycol, triethylene glycol, tripropylene glycol and dipropylene glycol.
6. The method of Claim 1, wherein said organic material containing about 1.8 or more hydroxy groups, primary amino or secondary amino or mixtures thereof has a molecular weight of 1000 to 4800 and a functionality of about 2 to 3.
7. 7 The procedure of Claim 1, wherein said isocyanate index is from 90 to 110.
8. 8. The process of Claim 1, wherein said liquid and stable diphenylmethane-modified diphenylmethane diisocyanate prepared by method 1) has an isocyanate group content of from 17 to 28. %.
9. The process of Claim 8, wherein said liquid and stable diphenylmethane-diphenylmethane diisocyanate has an isocyanate group content of 17 to 24%.
10. The process of claim 1, wherein said liquid and stable diphenylmethane-modified diphenylmethane diisocyanate prepared by method 2) has an isocyanate group content of 9 to 27%.
11. The process of Claim 10, wherein said liquid and stable diphenylmethane-diphenylmethane diisocyanate has an isocyanate group content of 12 to 21%.
12. 12. The method of Claim 1, wherein said isomeric composition of diphenylmethane diisocyanate consists of about 0 to 30% by weight of 2,4,4'-diphenylmethane diisocyanate and less than 3% by weight of 2,2'-diisocyanate. -diphenylmethane, the remainder being 4,4'-diphenylmethane diisocyanate. The process of Claim 12, wherein said isomeric composition of diphenylmethane diisocyanate consists of about 0 to 10% by weight of 2,4,4'-diphenylmethane diisocyanate and less than 1% by weight diisocyanate of 2, 2'-diphenylmethane, the remainder being 4,4'-diphenylmethane diisocyanate.