MXPA98000137A - Use of polydyene dioles in polyurethane foams, resilien - Google Patents

Abstract

The present invention relates to thermoplastic polyurethanes which are formed from a polydiene diol, preferably a hydrogenated polybutadiene diol, having from 1.6 to 2 terminal hydroxyl groups per molecule, and a number average molecular weight of between 500 and 20,000 , an isocyanate having two isocyanate groups per molecule, and optionally a chain extender having two hydroxyl groups per molecule. The thermoplastic polyurethane composition is prepared by a prepolymer method, preferably a prepolymer method, without solvents, using the branched chain extender

Description

USE OF POLYDYENE DIOLES IN THERMOPLASTIC POLYURETHANES FIELD OF THE INVENTION This invention relates to elastomeric compositions of thermoplastic polyurethane which contain a polymeric diol, especially to polyurethane compositions containing an anionic polymerized diol, having hydroxyl groups.

BACKGROUND OF THE INVENTION The thermoplastic polyurethane compositions and the cast polyurethane compositions, based on the reaction of polyisocyanates with polymeric diols, are known for their use as elastomers, adhesives, sealants, elastomeric surface coatings, and coatings for metals and plastics. KURARAY markets a hydrogenated polyisoprene diol that is described in product brochures as being useful in the manufacture of polyurethanes when reacted with isocyanates and various chain extenders. The diol has a weight REF: 26551 average molecular number in 3,800, a broad molecular weight distribution and a hydroxyl content of approximately 2.2 terminal hydroxyl groups per molecule. Typically the hydrogenation of this product is about 80%. The isocyanate described by KURARAY includes MDI, IPDI, and TDI. The chain extenders described by KURARAY include 1,4-butanediol, 2-ethyl-1, hexanediol, 3-methyl-1,5-pentanediol and 1-α-nano-diol. The polyurethanes have properties consistent with the addition of a hydrogenated polyisoprene, with a molecular weight of 3,800, to the polyurethane structure, properties that include good resistance to hydrolysis. The average functionality of KURARAY materials, which is above 2, makes these products unsuitable for thermoplastic polyurethane application. Thermoplastic polyurethanes (PTP) allow the production of elastomeric materials, by means of thermoplastic processing techniques. TPUs may not thermally degrade when plasticized by the influence of temperature and pressure. Therefore, the TPU molecules have to be linear and unbranched molecules, which can not be thermoformed repeatedly. Only bifunctional isocyanates, chain extenders and long chain diols can be used to make the thermoplastic polyurethanes.

DESCRIPTION OF THE INVENTION An object of the present invention is to provide thermoplastic polyurethane compositions, which have improved physical properties. and resistance to hydrolysis. The present invention relates to polyurethane compositions comprising polydiene diols having from 1.6 to 2, more preferably from 1.8 to 2, and most preferably from 1.9 to 2, terminal hydroxyl groups per molecule, and a weight molecular average in number between 500 and 20,000, more preferably between 1,000 and 10,000, an isocyanate having two isocyanate groups per molecule, and a low molecular weight chain extender, having two hydroxyl groups per molecule. Polyurethane compositions containing polydiene diols, have improved physical properties compared to polyurethane compositions containing hydrogenated polyisoprene polyols, and are suitable for thermoplastic polyurethane applications.

The present invention relates to compositions for manufacturing thermoplastic polyurethanes comprising polydiene diols having from 1.6 to 2, more preferably from 1.8 to 2, and most preferably from 1.9 to 2, terminal hydroxyl groups per molecule, and a number average molecular weight of between 500 and 20,000, more preferably between 1,000 and 10,000, an isocyanate having two isocyanate groups per molecule, and optionally low molecular weight chain extender, qu < _-has two hydroxyl groups per molecule. The thermoplastic polyurethane compositions, made from polydiene diols, have good physical properties and excellent weathering properties, and, in comparison with the known polyurethane compositions containing hydrogenated polyisoprene polyols, are suitable for applications in thermoplastic polyurethanes. The polydiene diols used in this invention are prepared anionically, as described in U.S. Patent Nos. 5,376,745, 5,391,663, 5,393,843, 5,405,911, and 5,416,168, which are incorporated herein by reference. The polydiene diols have from 1.6 to 2, more preferably from 1.8 to 2, and most preferably from 1.9 to 2 terminal hydroxyl groups per molecule, and a number average molecular weight of from 500 to 20,000, in the form most preferred between 1,000 and 10,000. Hydrogenated polybutadiene diols are preferred and have an addition of 1.4, of between 30% and 70%, to minimize viscosity. Polymerization of the polydiene diols begins with a monolithium or dilithium initiator, which constructs a living polymer skeleton at each lithium site. The conjugated diene is typically 1,3-butadiene or isoprene. The anionic polymerization can also be used in an organic solvent, typically a hydrocarbon such as hexane, cyclohexane or benzene, although polar solvents such as tetrahydrofuran can also be used. When the conjugated diene is 1, 3-butadiene and when the resulting polymer will be hydrogenated, the anionic polymerization of butadiene, in a hydrocarbon solvent, such as cyclohexane, is typically controlled with structure modifiers such as diethyl ether or glyme (1,2-diethoxyethane) to obtain the desired amount of addition in 1.4. The optimum balance between low viscosity and high solubility in a hydrogenated polybutadiene polymer occurs at a ratio of 60/40 of 1,4-butadiene / 1,2-butadiene. This microstructure of the butadiene is achieved during the polymerization at 50 C in cyclohexane containing about 6% e * -. volume of diethyl ether or about 1,000 ppm of glyme. The anionic polymerization is terminated by the addition of a functionalizing agent such as those described in U.S. Patent Nos. 5,391,637, 5,393,843, and 5,418,296, which are also incorporated by reference, but preferably ethylene oxide, before termination. The preferred dilithium initiator is formed by the reaction of two moles of secbutylthio with one mole of diisopropylbenzene. This di-initiator is used to polymerize butadiene in a solvent composed of 90% by weight of cyclohexane and 10% by weight of diethyl ether-The molar ratio of the di-initiator to the monomer determines the molecular weight of the polymer. The living polymer is then capped with two moles of ethylene oxide and terminated with two moles of methanol to produce the desired polydiene diol. The polydiene diol can also be made using a monolithium initiator containing a hydroxyl group that has been blocked, such as silyl ether (as in U.S. Patent Nos. 5,376,745 and 5,416,168 which are also incorporated by reference). A suitable initiator is hydroxypropylthio in which the hydroxyl group is blocked as the trimethylsilyl ether. This monolithium initiator can be used to polymerize butadiene, in hydrocarbons or in a polar solvent. The molar ratio of the initiator to the monomer determines the molecular weight of the polymer. The living polymer is then capped with one mole of ethylene oxide and terminated with one mole of ethanol to produce the at-polymer. monohydroxy polydiene. The silyl ether is then removed by acid catalyzed cleavage, in the presence of water, to produce the desired dihydroxy polydiene diol. The polybutadiene diols are hydrogenated, so that at least 90%, preferably at least 95%, of the carbon-to-carbon double bonds in the diols are saturated. The hydrogenation of these polymers and copolymers can be carried out through a variety of well-established processes that include hydrogenation in the presence of catalysts such as Ñique. Raney, noble metals such as platinum and the like, transition metal catalysts, soluble catalysts, and titanium catalysts, as in US Patent No. 5,039,755 which is also incorporated by reference. A particularly preferred catalyst is a mixture of nickel 2-ethexanoate and triethylaluminium. The polybutadiene polymer has no less than about 40% addition of 1, butadiene, because, after hydrogenation, the polymer will be a waxy solid at room temperature if it contains less than about 40% addition of 1-2. butadiene. To minimize the viscosity of the diol, the 1,2-butadiene content should be between about 40 and 60%. The isoprene polymers have not less than 80% addition of 1,4-isoprene, to reduce the vitreous transition temperature (Tg) and the viscosity. The diene microstructures are typically determined by nuclear magnetic resonance (NMR) with C13, in chloroform. Do the polydiene diols have weight? hydroxyl equivalents which are between about 250 and about 10,000, preferably between 500 and 5,000. Thus, for the dihydroxy polydiene polymers, the maximum molecular weights, suitable, will be between 500 and 20,000, preferably between 1,000 and 10,000. The maximum molecular weights referred to are molecular weights measured by permeation chromatography in gel (CPG) calibrated with polybutadiene standards, which have known maximum molecular weights. The solvent for the CPG analysis is tetrahydrofuran. The isocyanate used in this invention is a diisocyanate having a functionality of two isocyanate groups per molecule, since these produce thermoplastic polyurethane compositions, when combined with a true diol. Examples of suitable diisocyanates are the diisocyanate of 4'-di-phenylmethane, isomer mixtures of diphenylmethane diisocyanate, toluene diisocyanate, isodocyanate, hexamethylene diisocyanate and ethylene diisocyanate, etc. The chain extender used to make the polyurethane compositions are low molecular weight diols having hydroxyl groups per molecule. Preferred chain extenders have methyl, ethyl, or higher hydrocarbon side chains, which make these diols more apolar and therefore more compatible with the apolar hydrogenated polydienes. Examples of these chain extenders are 2-yl-l, 3-hexanediol, 2-yl-2-butyl 1,3-propanediol and 2,2,4-t-rimethyl-1,3-pentanediol. Linear chain extenders, without carbon side chains, such as 1,4-butanediol, ethylenediamine, 1,6-hexanediol, and the like, also result in polyurethane compositions if a prepolymer method in solvent is used, to avoid incompatibility.

A preferred way to manufacture the thermoplastic polyurethanes is by the prepolymer method, wherein the isocyanate component is first reacted with the polydiene diol to form an isocyanate-terminated prepolymer, which can then be further reacted with The chain extender of choice. The polyurethane compositions can be formulated to make elastomers using a solvent-free prepolymer method, or a solvent / prepolymer method, as described in more detail below. In the prepolymer method, without solvents, the polydiene diol is heated to at least 70 ° C and not more than 100 ° C, and then mixed with the desired amount of isocyanate for at least 2 hours, under nitrogen flow. The amount of the chain extender is added and mixed thoroughly before rapidly degassing the mixture under vacuum. The mixture is then poured into a heated mold, treated with a compound for mold release. The polyurethane composition is formed by curing, in the mold, for several hours and then post-curing the thermoplastic polyurethane above 110 ° C for at least 2 hours. In the solvent / prepolymer method, the polydiene diol is dissolved in a solvent, preferably in dry toluene, heated to at least 70 ° C and not more than 100 ° C, and then mixed with an isocyanate having two groups isocyanate per molecule, for at least two hours, under nitrogen flow. The type and quantity, desired, of the chain extender is added and mixed thoroughly until the reaction ends.

The mixture is then poured into an aluminum container to evaporate the solvent and then set for at least 2 hours at 110 ° C while keeping it empty. The thermoplastic polyurethane composition can then be thermally pressed, above the melting point of the elastomer, to form an elastomeric polyurethane article. A composition of the present invention may contain plasticizers, such as oils used in conventional rubber compounds. These oils can be used in the thermoplastic polyurethanes herein, because the polydiene diol is a rubber or rubber. Oils that form compositions with rubber are well known in the art and include both oils with a high content of saturated compounds, and oils with a high content of aromatics. Preferred plasticizers are highly saturated oils (such as Tufflo oil 6056 and 6204 manufactured by Arco) and process oils (such as Shellflex 371 oil manufactured by Shell), amounts of the oil that forms C compositions? The rubber used in the composition of the invention can vary from 0 to about 500 phr, preferably from about 0 to about 100 phr, and most preferably from about 0 to about 60 phr. A wide variety of fillers can be used in the formulations of the present invention. Suitable fillers include calcium carbonate, clays, talcs, zinc oxide, titanium dioxide, silica and the like. The amount of filler material is usually in the range of 0 to about 800 phr, depending on the type of filler material used and the intended application of the formulation. Preferred fillers are silica and titanium dioxide. The filler material should be thoroughly dried so that the adsorbed moisture does not interfere with the reaction between the polyisocyanate and the saturated polyhydroxylated polydiene polymer. Stabilizers known in the art can also be incorporated into the composition. These can be used for protection during the life of the sealant or adhesive, against, for example, oxygen, ozone and against ultraviolet radiation. These can also be used for stabilization against thermooxidative degradation during high temperature processing. Antioxidants and UV inhibitors that interfere with the curing reaction of urethane should be avoided. Preferred antioxidants are sterically hindered phenolic compounds, such as butylated hydroxytoluene. The UV radiation inhibitors are the UV radiation absorbers, such as the benzotriazole compounds. The amount of the stabilizer in the formulation will depend greatly on the application that is intended to give the product. If the durability and processing requirements are modest, the amount of stabilizer in the formulation will be less than about 1 phr. If the adhesive is to be mixed at high temperature or if the product must survive many years in service, the concentration of the stabilizer should be as much as approximately 10 phr. The preferred embodiment of the present invention relates to compositions for manufacturing thermoplastic polyurethanes comprising 80 to 100 parts of a hydrogenated polybutadiene diol, having from 1.9 to 2.0 terminal hydroxyl groups, per molecule, an addition in 1.4 of between 40% and 60%, and a number average molecular weight of between 1,000 and 10,000, an Index amount of 90 to 100 of an isocyanate having two isocyanate groups per molecule, and 0 to 20 parts of a branched chain extender, selected from a group consisting of 2-yl-l, 3-hexanediol and 2, 2, 4- trimet i 1-1, 3-pentanediol. Polyurethane compositions made from polybutadiene diols have improved physical properties, compared to polyurethane compositions containing hydrogenated polyisoprene polyols, and are thermoplastic polyurethanes. The following examples show that thermoplastic polyurethane compositions are produced using the prepolymer method without solvents, with branched chain extenders such as 2-yl-l, 3-hexanediol.

Example 1 A hydrogenated butadiene diol polymer having 1.95 terminal hydroxyl groups per molecule, a number average molecular weight of 3.650, and a butadiene 1.2 addition of 43% was obtained from Shell Chemical, labeled as HPVM 2201. This polymer is a viscous liquid at 25 ° C but flows easily at slightly elevated temperatures (viscosity of 20 poises at 60 ° C). A thermoplastic polyurethane elastomer was produced by dissolving 95 parts of the hydrogenated polybutadiene diol in 285 parts of dry toluene and heating the mixture to 80 ° C. Then, 15.0 parts of RUBINATO 44, a 4, 4 '-difenilmetandiisocianato pure, of functionality 2.0 were added. The components were mixed for 3 hours at 80 ° C under nitrogen flow. Then 5 parts of 2-ethyl-1,3-hexanediol were added, and the mixture was stirred at 80 ° C until it started to form a gel. The mixture was then poured into an aluminum container and the solvent evaporated overnight. Then the mixture was postcured for 2 hours at 110 ° C under vacuum. The resultant polyurethane elastomeric composition was passed through a heated press to form an elastomeric sheet. The sheet had a total hard phase content of 17.4% and a Shore A hardness of 60. KURARAY reports an elastomer made with 92.2 parts of its polyisoprene polyol, TH-1, 7.8 parts of 2-ethyl 1, 3- hexandiol and 20.3 parts of 4,4'-diphenylmethane diisocyanate. For a hard phase content of 23.3%, the Shor A hardness reported is only 59 (the larger the content of the hard phase, the greater the hardness).

Example 2 The diol of Example 1 was used to make a thermoplastic elastomer. The elastomer was produced by dissolving 90 parts of the hydrogenated polybutadiene diol in 285 parts of dry toluene and heating the mixture to 80 ° C. Then, 23.3 parts of RUBINATE 44, a 4,4'-diphenylmethane diisocyanate, of functionality 2.0, were added. The components are mixed for 3 hours at 80 ° C under nitrogen flow. Then 10 parts of 2-ethyl-1,3-hexanediol were added, and the mixture was stirred at 80 ° C until it started to gel. The mixture was then poured into an aluminum container and the solvent evaporated overnight. Then the mixture was postcured for 2 hours at 110 ° C under vacuum. The resultant polyurethane elastomeric composition was passed through a hot press to form an elastomeric sheet. The sheet had a Shore A hardness of 72 for a hard phase content of 27%. This elastomer was also tested for its resistance to hydrolysis. Samples were immersed for 5 weeks in distilled water at 95 ° C. The weight increase after the immersion period was only 0.8% and the Shore A hardness was reduced by 2.1%. (A normal test for urethane elastomers is 2 weeks of immersion at 70 ° C, and a weight gain of 2% is considered good).

Example 3 The diol of Example 1 was used to make the thermoplastic elastomer. The elastomer was produced by dissolving 85 parts of the hydrogenated polybutadiene diol in 285 parts of dry toluene and heating the mixture to 80 ° C. Then 31.6 parts of RUBINATE 44, a 2,4,4'-diphenylmethane diisocyanate, of functionality 2.0, were added. The components were mixed for 3 hours at 80 ° C, under nitrogen flow. Then 15 parts of 2-ethyl-1,3-hexanediol were added, and the mixture was stirred at 80 ° C until gel formation began. The mixture was then poured into an aluminum container and the solvent evaporated overnight. Then the mixture was postcured for 2 hours at 110 ° C under vacuum. The resulting elastomeric polyurethane composition was passed through a hot press to form an elastomeric sheet. The sheet had a Shore A hardness of 80 for a hard phase content of 35.4%.

Example 4 The diol of Example 1 was used to make a thermoplastic elastomer. The elastomer was produced by dissolving 25 parts of the hydrogenated polybutadiene diol, in 75 parts of dry toluene, and heating the mixture to 80 ° C. Then, 3.4 parts of RUBINATE 44, a pure, functionality-specific 2,4,4'-di-phenylmethane diisocyanate, were added. The components were mixed for 3 hours at 80 ° C, under nitrogen flow. Then 0.6 parts of 1,4-butanediol were added, and the mixture was stirred at 80 ° C until gel formation began. The mixture was then poured into an aluminum container and the solvent evaporated overnight. Then the mixture was postcured for 2 hours at 110 ° C, under vacuum. The resulting elastomeric polyurethane composition was passed through a hot press to form an elastomeric sheet. The sheet had a Shore A hardness of 60 and a solid phase content of 13.8%.

It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects to which it relates.

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

Claims (10)

1. A composition for manufacturing thermoplastic polyurethanes, characterized in that: a polydiene diol having from 1.6 to 2 terminal hydroxyl groups per molecule and a number average molecular weight between 500 and 20,000; an isocyanate having two isocyanate groups per molecule; and optionally a low molecular weight chain extender, having two hydroxyl groups per molecule.

2. The composition according to claim 1, characterized in that the polydiene diol has from 1.9 to 2 hydroxyl groups by molecule.

3. The composition according to claim 1, characterized in that the polydiene diol has a number average molecular weight between 1,000 and 10,000.

4. The composition according to claim 1, characterized in that the polydiene diol is a diol of hydrogenated polybutadiene.

5. The composition according to claim 1, characterized in that isocyanate is the diisocyanate of 4, diphenylmethane.

6. The composition according to claim 1, characterized in that it comprises the chain extender that is selected from a group consisting of 2-yl-l, 3-hexanediol and 2, 2,4-trimethyl-l, 3-pentanediol. .

7. The composition according to claim 6, characterized in that the chain extender is 2-ethyl-1,3-hexanediol.

8. A composition for manufacturing thermoplastic polyurethanes, characterized in that it comprises: from 80 to 100 parts of a hydrogenated polybutadiene diol, having from 1.9 to 2.0 terminal hydroxyl groups per molecule, an addition in 1.4 of 40% and 60%, and a number average molecular weight between 1,000 and 10,000; an index amount of 90 to 100 of an isocyanate having two isocyanate groups per molecule; and from 0 to 20 parts of a branched chain extender, selected from a group consisting of 2-yl-l, 3-hexanediol and 2,2,4-trimethyl-l, 3-pentanediol.

9. The composition according to claim 8, characterized in that the isocyanate is the 4,4'-diphenylmethane diisocyanate.

10. The composition according to claim 9, characterized in that the chain extender is 2-ethyl-l, 3-hexanediol.