Polyurea elastomers made using polyoxyalkylene tetra- or higher functional amine chain extenders

Abstract: Polyurea elastomers, suitable as foams with improved strength, and spray coatings with improved modulus, are prepared by reacting a polyisocyanate with a polyoxyalkylene polyamine and a chain extender which is a low molecular weight, polyoxyalkylene polyamine having at least four functional groups, including two or more amino groups. Preferably the chain extender has the formula: wherein: Q is the polyvalent residue of an active hydrogen-containing compound such as α-methyl glucoside; each R is independently hydrogen or alkyl; each x is independently at least 0.5; and y is at least 4; and each group z is independently an amino or other active hydrogen-containing functional group, provided that two or more of the groups are amino.

Description: This invention concerns polyurea elastomers, useful as foams and in solventless spray coatings, and more particularly relates to the production of polyurea elastomers using low molecular weight, polyoxyalkylene tetra- or higher functional amines, such as aminated propoxylated α-methyl, glucoside, as chain extenders. Polyurea elastomers have found widespread utility, e.g. as coatings, such as for spray applications, and as foams. When used in coatings, these materials provide a desirable balance of properties including: light stability; fast cure; relative water insensitivity; the ability to be used as solventless systems; excellent physical properties, including tensile strength, elongation and abrasion resistance; pigmentation capability; ease of application, such as by using commercially available spray application equipment; and, since no catalyst is needed, consistent reactivity and long term storage stability. These and other well known properties are discussed in the literature, such as by D.J. Primeaux II, in "Spray Polyurea, Versatile High Performance Elastomer for the Polyurethane Industry", Proceedings of the SPI 32nd Annual Technical/Marketing Conference, pages 126-130, October 1989; and by D.J. Primeaux II, in "Sprayed Polyurea Elastomers Offer Superior performance", UTECH'90. pages 189-194, April 1990. Polyureas are useful in a variety of foam applications including, among others: moulded foams, such as in automobile interiors, e.g. for seating and so on; slabstock foams, frequently used as carpet underlays or in furniture; and various other padding or cushioning uses. Foams having rigid, closed-cell structure are useful as insulation; simulated wood parts like speaker cabinets, picture frames, doors and the like; packaging foams; shock absorbing foams; and so on. Such foams should have good tensile strength, elongation, compressive strength, dimensional stability and other desired properties in order to perform well in these or other applications. Polyureas can be made by reacting amines with isocyanates. For example, US-A-4732919 discloses polyurea elastomer made from high molecular weight polyol or polyoxyalkylene polyamine, a chain extender and a quasi-prepolymer of polyoxyalkylene polyamine and aromatic isocyanate. Polyoxyalkylene polyamines made from polyoxyalkylene polyols obtained by oxyalkylene addition to polyhydric aliphatic alcohols, including methyl glucoside among others, are disclosed in US-A-3654370 as intermediates for polyurea preparation. EP-A-367 478 describes a tetrafunctional polyoxyalkyleneamine component reacted with a polyisocyanate which may be ISONATE 143 L, a quasi-prepolymer made from JEFFAMINE T-5000 and ISONATE 143 L, a quasi-prepolymer of ISONATE 143 L and PPG-2000 or a prepolymer of THANOL SF-5505. This single component polyurea is non-reactive when the polyoxyalkyleneamine component and the polyisocyanate are mixed at room temperature (30°C). It is stated that the component must be heated in order to achieve polymer formation and cure (100°C-150°C). EP-A-434 348 describes a reactive injection molding resinous composition comprising a very specific polyamine component and a very specific polyisocyanate component. The polyoxyalkylene polyamine components of the compositions of this document are different from the polyoxyalkylene polyamine chain extenders of the present application. This invention concerns polyurea elastomers obtained by reacting a polyisocyanate with a polyoxyalkylene polyamine and a low molecular weight, polyoxyalkylene polyamine chain extender having at least 4 functional groups, including two or more amino groups. Foams comprising gas and the polyurea are also provided by carrying out the reaction in the presence of water or a blowing agent. It has been discovered that polyurea elastomer can be made using polyoxyalkylene polyamine chain extenders having high functionality. The resulting polyureas provide superior foams and spray coatings with improved physical properties. The polyisocyanate starting material may be any, including known, compound, or mixtures thereof, falling under the definition of claim 1 having two or more isocyanate groups bonded to an organic radical. The polyisocyanate may be a monomeric polyisocyanate or, preferably, the reaction product of a monomeric polyisocyanate with polyoxyalkylene polyamine, such as a polyurea polyisocyanate quasi-prepolymer. The term "quasi-prepolymer" means a mixture of monomers and oligomers, essentially dimers, made using a stoichiometric excess of one type of monomer, in this case polyisocyanate, as compared with the other monomer, i.e. polyamine. Polyisocyanates include compounds shown by Formula 1. R"(-NCO) z Polyisocyanate In Formula 1, R" is an organic radical having a valence z and can be: straight or branch chain; acyclic, cyclic or heterocyclic; saturated, and unsaturated, unsubstituted or halo-substituted; hydrocarbylene having at least 1, preferably from 6 to 25, and most preferably from 6 to 12 carbon atoms. The number of isocyanate groups, defined by z , is at least 2, preferably from 2 to 4, and most preferably 2. Typical polyisocyanates include, among others, one or more of the following: alkylene polyisocyanates with 4 to 12 carbon atoms in the alkylene radical, such as 1,12-dodecane diisocyanate, 1,4-tetramethylene diisocyanate and 1,6-hexamethylene diisocyanate; cycloaliphatic diisocyanates such as 1,3-and 1,4-cyclohexane diisocyanate, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate), 4,4'-, 2,2'- and 2,4'-dicyclohexylmethane diisocyanate; and other isocyanates, such as described in US-A-2683730, US-A-2950263, US-A-3012008, US-A-3344162, US-A-3362979 and US-A-3394164. Preferred polyisocyanates include isophorone diisocyanate, hexamethylene diisocyanate, and cyclohexane diisocyanate. The polyoxyalkylene polyamine, such as used to make either polyisocyanate quasi-prepolymer or as component (B) and other than the low molecular weight, polyoxyalkylene polyamine chain extender is of Formula 2. The variables in Formula 2 have the following meanings. Q' is the polyvalent residue of an active hydrogen-containing compound used as an initiator. The valence of Q' is given by y' , where y' is 2 to 3. Each R' is independently hydrogen or alkyl, preferably lower alkyl, such as methyl or ethyl. The R' groups are preferably hydrogen and/or methyl, including their mixtures. The average number of oxyalkylene repeating units per amine, given by x' , is at least 1, preferably from 1 to 40, and most preferably from 1 to 10. Typical initiators include, among others, one or more of the following: polyhydroxy compounds, including diols such as ethylene glycol, propylene glycol, 1,2- or 1,4-butanediols, and triols such as trimethylolpropane and glycerol. Preferred initiators include ethylene glycol, propylene glycol, trimethylolpropane, and glycerol. Typical oxyalkylene repeating units include oxyethylene, oxypropylene, oxybutylene, and so on, including mixtures thereof. When two or more oxyalkylenes are used, they may be present in any form such as randomly or in blocks. Preferred polyoxyalkylene polyamines include JEFFAMINE® polyoxyalkylene amines from Texaco Chemical Co. Inc., such as diamines D-230, D-400, D-2000 and D-4000, and triamines T-403, T-3000 and T-5000. The ratio of monomeric polyisocyanate to polyoxyalkylene polyamine for quasi-prepolymer production is at least a stoichiometric excess of monomeric polyisocyanate to polyoxyalkylene polyamine. Generally more than 1, preferably from 1.5 to 25, and most preferably from 10 to 25, moles of isocyanate are used per mole of amine. Although no additional ingredients, such as solvent or catalyst, are needed or preferred to conduct the quasi-prepolymer synthesis reaction, any other suitable materials may be present, if desired. The reaction between the monomeric polyisocyanate and the polyoxyalkylene polyamine may be conducted under any effective, including known, conditions for reacting isocyanates and amines. Typically, reactions are conducted under ambient temperature and pressure. Since the reaction proceeds rapidly, the ingredients are preferably thoroughly mixed, such as using a high speed mixer. The polyoxyalkylene polyamine chain extenders are preferably compounds shown in Formula 3 and are of a molecular weight of lower than 500. The variables in Formula 3 have the following meanings. Q is a saccharide residue. The valence of Q, given by y is from 4 to 8, and most preferably 4. Each R is independently hydrogen or alkyl, preferably lower alkyl, such as methyl or ethyl. The R groups are preferably hydrogen and/or methyl, including their mixtures. The average number of oxyalkylene repeating units per functional group, given by x , is at least 1, preferably from 1 to 3, and most preferably from 1 to 2. Z is a functional group, generally amino (H 2 N-) or hydroxyl (HO-), providing polyamine functionality, by which is meant a compound having a plurality of amino or other groups which react with isocyanate to form polyureas. Accordingly, two or more Z are amino groups, with any remaining Z groups being hydroxyl or other active hydrogen groups, such as thiol or the like. At least half, and most preferably an average of about 60% of Z are amino groups, including mixtures of compounds having a distribution of different functional groups for Z. Mixtures of chain extender may contain minor portions of compounds having less than two amino groups, provided the average number of amino groups per molecule in the mixture is two or more. Typical initiators for the polyoxyalkylene polyamine chain extenders include, among others, one or mixtures of the following: saccharides such as α-methyl glucoside, sucrose, sorbitol, xylitol, inositol, mannitol and pentaerythritol; A preferred initiator is α-methyl glucoside. The polyoxyalkylene polyols used to make chain extender have a small amount of oxyalkylene units. Typically an average of 1 to 10, oxyalkylene units are present per molecule. Typical oxyalkylene repeating units include oxyethylene, oxypropylene, oxybutylene, and so on, including mixtures thereof. When two or more oxyalkylenes are used, they may be present in any form such as randomly or in blocks. Preferred polyoxyalkylene polyamine chain extenders include α-methyl glucoside having an average of about 4 oxypropylene repeating units. The chain extenders can be made by alkoxylating active hydrogen-containing compounds by any effective, process. For example, alkylene oxide can be reacted with active hydrogen-containing compound in the presence of a basic catalyst at elevated temperature and pressure under an inert atmosphere for several hours. The alkaline product can then be neutralized and isolated, such as by vacuum stripping and filtration. The polyoxyalkylene polyols can be partially or completely aminated to produce the polyoxyalkylene polyamine chain extenders by any effective, including known, procedure. Generally, the polyol reacts with any aminating material, preferably ammonia and hydrogen or the like, which results in amino group substitution in the place of hydroxyl or other active hydrogen on the polyol. The relative amounts of polyoxyalkylene polyol and aminating material can be any amounts sufficient to make aminated product. Typically, the molar ratio of hydroxy to aminating group is from 1:2 to 1:40, preferably from 1:5 to 1:30, and most preferably from 1:10 to 1:20. The polyoxyalkylene polyol may be aminated using any effective catalyst and under any effective conditions. Typically, the temperature during the amination reaction is from 180 to 240°C, preferably from 190 to 220°C, and most preferably from 200 to 215°C. The pressure may be at least 0.8 MPa (100 psig), preferably from 3.55 to 20.8 MPa (500 to 3,000 psig), and preferably from 10.4 to 17.35 MPa (1,500 to 2,500 psig). The amination reaction is generally conducted as a continuous process. The rate at which product passes through the reactor is generally from 0.05 to 3, preferably from 0.1 to 2, and most preferably from 0.2 to 1, grams of product per cubic centimetre of catalyst per hour (gm/cm 3 /h). Any effective amination catalyst can be used. Typical amination catalysts include, among others, one or more mixtures of the following: nickel-chromium-copper metal or metal oxides, such as described in US-A-3152998; or other effective catalyst. Preferred amination catalysts include those prepared by reducing nickel, copper and chromium oxides in the presence of hydrogen, generally at a temperature of 250 to 400°C and at any effective pressure, following established procedures. The catalyst generally has from 60 to 85, preferably from 70 to 80, mole percent of nickel; from 14 to 37, preferably from 20 to 25, mole percent of copper; and from 1 to 5 mole percent chromium. The chain extender has a molecular weight of less than 500, based on the presence of a small number of oxyalkylene units, preferably from 50 to 400. The relative amount of polyisocyanate to polyoxyalkylene polyamine and chain extender is any amount sufficient to make polyurea elastomer. Typically, from 0.7 to 1.6, preferably from 0.8 to 1.3, and most preferably from 0.85 to 1.15, moles of amine are provided per mole of isocyanate. The relative proportion of polyoxyalkylene polyamine to chain extender is not critical so long as an effective amount, i.e. an amount sufficient to make polyurea elastomer having improved properties, of chain extender is provided. Typically, from 10 to 60, preferably from 20 to 50, and most preferably from 30 to 50, weight percent of chain extender is provided, based on the amount of polyoxyalkylene polyamine. Other materials may be added, if desired to the reaction mixture. These optional ingredients include, among others, one or more of the following: other chain extenders, such as aromatic diamines, e.g. 1-methyl-3,5-diethyl-2,4- or 2,6-diaminobenzene (also called diethyltoluene diamine), 1,3,5-triethyl-2,6-diaminobenzene, 3,5,3',5'-tetraethyl-4,4'-diaminodiphenylmethane, di-(methylthio)-toluene diamines including 3,5-di(methylthio)-2,4- and -2,6-toluene diamine, N,N'-bis-(t-butyl) ethylene diamine, or low molecular weight polyoxyalkylene polyamines e.g. polyoxypropylene diamines or triamines, including JEFFAMINE® D-230 and T-403, respectively; foam stabilizers, such as silicone oil, silicon emulsifier, organic silanes or siloxanes e.g. cyanalkyl-polysiloxanes, hydrolyzable or non-hydrolyzable, polysiloxanepolyoxyalkylene block copolymers, including L-5340, L-5421, Y-10184 and Y-10197 from Union Carbide Chemicals and Plastics Co., Inc.; pigments or colouring agents, such as titanium dioxide; reinforcing materials, such as chopped or milled glass fibres, carbon fibres and/or other mineral fibres; blowing agents e.g. water, carbon dioxide, (hydro)chlorofluorocarbons, methylene chloride and acetone; catalysts, such as tertiary amines e.g. one or more mixtures of 2,2'-dimorpholinodiethyl ether, N,N'-dimethylpiperazine, N-butylmorpholine, N-methylmorpholine, N-ethylmorpholine, bis-(2,2'-dimethylamino)ethyl ether, 2-(2-dimethylaminoethyoxyl)ethanol, N,N,N'-trimethyl-N'-hydroxyethylbisaminoethyl ether, 4-(2-methoxyethyl) morpholine, or organic tin compounds; fillers; surfactants; mould release agents such as zinc stearate, sodium oleate and silicones; and any other suitable materials. The polyisocyanate, polyoxyalkylene polyamine and chain extender, along with any other optional ingredients, are reacted under any effective conditions for reacting polyamines with polyisocyanate. Typically, the temperature during the reaction may be from 0 to 80°C, preferably from 15 to 80°C, and most preferably from 25 to 75°C. The components can be combined under ambient or higher pressures of up to 20.8 MPa (3,000 psig), preferably from 3.55 to 17.35 MPa (500 to 2,500 psig), and most preferably from 7.0 to 13.9 MPa (1,000 to 2,000 psig). When used in spray applications, the components can be impingement-mixed directly, using high pressure spray equipment, such as a GUSMER® VR-H-2000 proportioner fitted with a GUSMER® Model GX-7 spray gun, where open mould work or coating is desired or, where closed mould work is desired, such as in reaction-injection-moulding (RIM) or reinforced-reaction-injection-moulding (RRIM), the proportioner can be fitted with suitable RIM or RRIM equipment. In particular, first and second pressurized streams of components (a) and (B), respectively, are delivered from two separate chambers of a proportioner and impacted or impinged upon each other at high velocity for intimate mixing of the two components, producing the elastomer which is then delivered onto or into desired substrate using the spray gun or RIM equipment. The volumetric ratio of components (A) to (B) may be any suitable amount, typically from 3:7 to 7:3. The components are typically applied at a rate of at least 0.225 Kg/min (0.5 pounds per minute), and preferably from 0.45 to 13.6 Kg per minute (1 to 30 pounds per minute), and most preferably at about 9.1 Kg per minute (20 pounds per minute). The polyurea elastomer may, optionally, undergo post curing by heating, such as following established procedures. Post curing is typically employed where flexible, open cell foams are produced, to improve elastomeric properties, such as heat sag. In contrast, rigid, closed cell polyurea foams of this invention generally do not undergo post curing. The low molecular weight, polyoxyalkylene polyamine acts as a chain extender for the reaction between the polyisocyanate and polyoxyalkylene polyamine. The chain extender reacts with the polyisocyanate, providing hard-segment segregation in the elastomeric polyurea product, resulting in increased polymer modulus and glass transition temperature as well as thermal stability. The polyurea may have a small amount of urethane or other bonds, formed from isocyanate reaction with hydroxyl or other active hydrogen groups in the chain extender. These may also be some unreacted functional groups, such as hydroxyl which is less reactive than amine with isocyanate. It has been discovered that polyurea made using low molecular weight, polyoxyalkylene polyamine chain extender having at least 4 functional groups provides foams with improved strength, and spray coatings with improved modulus properties. Foams with greater compressive strength withstand increased loads without collapsing. Coatings with higher modulus or stiffness provide increased support to materials to which the coating is applied. The following Example present an illustrative embodiment for a chain extender preparation useful in the process of the present invention. All percentages given in the disclosure and claims are by weight, unless otherwise stated. Example : Chain Extender Preparation This example shows how to make low molecular weight, polyoxyalkylene polyamine chain extender by aminating polyoxyalkylene polyol. Propoxylated α-methyl glucoside is first made by adding methyl glucoside (4.5 kg) and flaked potassium hydroxide (50.4g) to a 20 litre reactor. The reactor is then heated to 100°C while maintaining a nitrogen purge. Propylene oxide (5.4 kg) is then slowly added at 105 to 110°C at 445 kPa over a period of 6.5 hours. The reaction mixture is then maintained at an equilibrium pressure 110°C and purged with nitrogen for one-half hour. The alkaline product is then neutralized at 95°C by stirring for two hours with an aqueous slurry of 550 g MAGNESOL® 30/40 absorbent. The neutralized product is then vacuum stripped to a minimum pressure, nitrogen stripped and filtered. Properties of the alkoxylated product are as follows: Hydroxyl no. (mg KOH/g) 504 Water (wt%) 0.15 pH (in 10:6 isopropanol-water) 7.3 Sodium (ppm) 23 Potassium (ppm) 0.7 The amination is then carried out by continuously feeding the α-methyl glucoside propoxylate, ammonia and hydrogen to a tubular reactor containing 600 cm 3 of a nickel-copper-chromium catalyst as described in US-A-3152998 (Moss), at rates of 160 and 236 grams per hour and 25 litres per hour, respectively. The reaction is conducted at a temperature of 205°C and a pressure of 13890 KPa. The aminated product is stripped at a temperature of 100°C under 6.67 KPa pressure for one hour. Using the previously described procedures, the product is analyzed to have a total acetylatables content of 9.06 milliequivalents per gram (meq/g), a total amine content of 6.24 meq/g, and a primary amine content of 6.02 meq/g. The product is an aminated α-methyl glucoside propoxylate having a structure: wherein an average of at least about 60% of the Z groups are amine and the rest are hydroxyl, and the sum of w , x , y and z is an average of about 4.

Claims: A process for making a polyurea elastomer by reacting a monomeric aliphatic or cycloaliphatic polyisocyanate or a quasi-prepolymer made by reacting polyoxyalkylene polyamine with a stoichiometric excess of a monomeric aliphatic or cycloaliphatic polyisocyanate, with a polyoxyalkylene polyamine and a chain extender, characterised in that the chain extender has the formula: wherein: Q is a saccharide residue; each R is hydrogen and/or methyl; each x is at least 1; y is from 4 to 8; at least half the Z groups are amino; the remaining Z groups being hydroxyl or other active hydrogen-containing groups; and wherein the chain extender molecular weight is less than 500; and that the polyoxyalkylene polyamine has the formula: wherein Q' is the polyvalent residue of an active hydrogen-containing compound; each R' is independently hydrogen or alkyl; each x' is at least 1; and y' is 2 or 3. A process according to Claim 1 characterised in that Q is an α-methyl glucoside residue such that y is 4, all groups R are methyl, and x averages about 1, and an average of about 60 % of all Z groups are amino. A process according to any one of Claims 1 and 2 characterised in that a foam is obtained by carrying out the process in the presence of water or a blowing agent. Use of the process according to any of the preceding claims in spray applications.

Inventors: PRIMEAUX II DUDLEY JOSEPH, ZIMMERMAN ROBERT LEROY, PRIMEAUX II, DUDLEY JOSEPH, ZIMMERMAN, ROBERT LEROY
Applicants: HUNTSMAN CORP, HUNTSMAN CORPORATION
Application year: 1993
Main classification: C08G18
IPC codes: C08G18