Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G18/00—Polymeric products of isocyanates or isothiocyanates
  • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
  • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
  • C08G18/40—High-molecular-weight compounds
  • C08G18/48—Polyethers
  • C08G18/4854—Polyethers containing oxyalkylene groups having four carbon atoms in the alkylene group
• • A—HUMAN NECESSITIES
  • A63—SPORTS; GAMES; AMUSEMENTS
  • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
  • A63B37/00—Solid balls; Rigid hollow balls; Marbles
  • A63B37/0003—Golf balls
  • A63B37/0023—Covers
  • A63B37/0024—Materials other than ionomers or polyurethane
• • A—HUMAN NECESSITIES
  • A63—SPORTS; GAMES; AMUSEMENTS
  • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
  • A63B37/00—Solid balls; Rigid hollow balls; Marbles
  • A63B37/0003—Golf balls
  • A63B37/007—Characteristics of the ball as a whole
  • A63B37/0072—Characteristics of the ball as a whole with a specified number of layers
  • A63B37/0074—Two piece balls, i.e. cover and core
• • A—HUMAN NECESSITIES
  • A63—SPORTS; GAMES; AMUSEMENTS
  • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
  • A63B37/00—Solid balls; Rigid hollow balls; Marbles
  • A63B37/0003—Golf balls
  • A63B37/007—Characteristics of the ball as a whole
  • A63B37/0077—Physical properties
  • A63B37/0094—Rebound resilience
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G18/00—Polymeric products of isocyanates or isothiocyanates
  • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
  • C08G18/08—Processes
  • C08G18/10—Prepolymer processes involving reaction of isocyanates or isothiocyanates with compounds having active hydrogen in a first reaction step
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G18/00—Polymeric products of isocyanates or isothiocyanates
  • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
  • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
  • C08G18/40—High-molecular-weight compounds
  • C08G18/42—Polycondensates having carboxylic or carbonic ester groups in the main chain
  • C08G18/4236—Polycondensates having carboxylic or carbonic ester groups in the main chain containing only aliphatic groups
  • C08G18/4238—Polycondensates having carboxylic or carbonic ester groups in the main chain containing only aliphatic groups derived from dicarboxylic acids and dialcohols
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G18/00—Polymeric products of isocyanates or isothiocyanates
  • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
  • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
  • C08G18/40—High-molecular-weight compounds
  • C08G18/42—Polycondensates having carboxylic or carbonic ester groups in the main chain
  • C08G18/44—Polycarbonates
• • A—HUMAN NECESSITIES
  • A63—SPORTS; GAMES; AMUSEMENTS
  • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
  • A63B37/00—Solid balls; Rigid hollow balls; Marbles
  • A63B37/0003—Golf balls

Definitions

• This invention generally relates to preparing castable polyurethane prepolymers containing reduced levels of unreacted hexamethylene 1,6-diisocyanate (HDI) monomer. More particularly, this invention is directed to producing high performance HDI-based cast polyurethane elastomer chains extended with diols and/or diamines. These systems provide improved industrial hygiene, easier casting, and improved mechanical properties. Golf ball covers produced from such systems exhibit a surprising combination of resilience, durability (groove shear resistance) and colorfastness. Rolls, tires and wheels with low hysteresis can also be produced from such systems.
• HDI hexamethylene 1,6-diisocyanate
• Castable polyurethane elastomers are well known and can be formed from a polyurethane prepolymer based on a reaction of a molar excess of diisocyanate monomer(s), e.g., aromatic diisocyanates such as diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI), or para-phenylene diisocyanate (PPDI) or aliphatic diisocyanates such as dicyclohexylmethane diisocyanate (H 12 MDI), isophorone diisocyanate (IPDI) or trans-1,4-cyclohexanediisocyanate (CHDI), with an organic polyol, e.g., polytetramethylene ether glycol (PTMEG), polyester or polycaprolactone glycol (PE), homopolymers and copolymers of ethylene oxide and propylene oxide (E/PO) and a chain extend
• 4,385,171 discloses a method for the removal of unreacted diisocyanate monomer (TDI) from prepolymers by codistilling the prepolymer reaction product with a compound that boils at a temperature greater than the boiling point of the diisocyanate.
• U.S. Pat. No. 5,703,193 discloses a process for reducing the amount of residual organic diisocyanate monomer (PPDI) in prepolymers by codistilling the reaction product in the presence of a combination of two inert solvents, with the first inert solvent having boiling point below the boiling point of the diisocyanate monomer and the second inert solvent having temperature boiling point above the boiling point of the diisocyanate monomer.
• PPDI residual organic diisocyanate monomer
• 4,061,662 discloses a process for the removal of unreacted toluene diisocyanate from prepolymers by passing the prepolymer reaction product through a column containing molecular sieves.
• U.S. Pat. No. 4,288,577 discloses the removal of unreacted methylene bis(4-phenyl isocyanate) (MDI) via solvent extraction with hexane.
• distillation is much simpler and more economical than solvent extraction or molecular sieve adsorption. There is no need to subsequently separate the monomer from either (flammable) hexane solvent or molecular sieves.
• high temperatures must be avoided to prevent decomposition reactions in the prepolymer. Distillation without use of solvents is simpler still.
• HDI monomer 1,6-hexamethylene diisocyanate
• TDI and MDI are used more widely.
• HDI finds widespread commercial use in polyurethane coatings, it is rarely used in cast elastomers as the health hazards of unreacted HDI monomer are well known.
• HDI has a low boiling point and high vapor pressure similar to TDI, PPDI, and IPDI, it is generally converted to a higher molecular weight adduct before sale. These adducts typically have a high functionality, e.g., about 3. They are not polyurethane adducts, as they contain no urethane linkages.
• the volatile HDI monomer is typically removed from the much less volatile adduct by agitated film vacuum distillation. See, e.g., U.S. Pat. No. 4,888,442 which discloses such adducts, with functionality greater than about 2.5.
• Prepolymers of both aromatic and aliphatic diisocyanates are heat-sensitive. However, prepolymers based on aromatic diisocyanates are much more thermally unstable than prepolymers based on aliphatic diisocyanates. Polyurethane prepolymers made from aliphatic diisocyanates are more resistant to thermal degradation than those made from aromatic diisocyanates, making removal of aliphatic monomeric diisocyanate by distillation less difficult. However, polyurethanes based on aliphatic diisocyanates are generally accompanied by a decrease in the mechanical properties. The presence of an aromatic diisocyanate in the hard segment typically produces a stiffer polymer chain with a higher melting point. For example, U.S. Pat. No. 6,046,297 discloses the inferiority of prepolymers based on H 12 MDI to those from TDI or mixtures of TDI and H 12 MDI.
• polyurethane prepolymers based on an aliphatic diisocyanate which is suitable for producing cast polyurethane elastomers having excellent mechanical properties.
• Applications directed to golf ball covers would be particularly desirable, as existing cast polyurethane covers from aromatic diisocyanates exhibit an unwelcome tendency to yellow over time.
• TDI-based solid polyurethane elastomers are most commonly made by reacting the liquid prepolymers with aromatic diamines, e.g., 4,4′-methylene-bis(3-chloroaniline) (MBCA) to give satisfactory properties.
• aromatic diamines e.g., 4,4′-methylene-bis(3-chloroaniline) (MBCA)
• Diol curatives give generally inferior properties with TDI prepolymers.
• MBCA is a suspect carcinogen that requires careful attention to industrial hygiene during casting For industrial safety, it would be particularly desirable to have prepolymers that are both (a) low in monomeric diisocyanate level and (b) capable of being used with diol chain extenders or aromatic diamine chain extenders that are not cancer suspect.
• Methylene dianiline derivatives that are fully alkylated at the four positions ortho to the amine groups are reported as a class to be Ames negative and of reduced suspicion as potential carcinogens.
• aromatic diamines include 4,4′-methylene-bis(3-chloro-2,6-diethylaniline) and 4,4′-methylene-bis(2,6-diethylaniline), available from Lonza, Inc. (Basel, Switzerland) as Lonzacure MCDEA and Lonzacure MDEA respectively.
• aromatic amine chain extenders are preferred to diol (glycol) chain extenders—“Glycol extended polyurethanes are more flexible and less strong than the amine-extended analogs” as disclosed in Lamba et al., page 17, in “Polyurethanes in Biomedical Applications”, CRC Press LLC, page 17, (1998), and give generally higher hysteresis. Consequently, amine-extended polyurethanes are generally used in applications such as, for example, tires and rolls, which arc subject to failure from overheating by hysteresis. Thus, it would be desirable to provide an aliphatic diisocyanate-based prepolymer that is capable of being chain-extended by a diamine curative to yield cast elastomers with low hysteresis.
• a diamine curative e.g., trimethylene glycol di-p-aminobenzoate, or a diol curative.
• Another object of the present invention is to provide castable polyurethane elastomer systems that are hygienically safe, that cast without difficulty, and provide elastomers with excellent mechanical properties.
• a further object is to provide golf ball covers with excellent mechanical properties, e.g., resilience and shear resistance, and with colorfastness on aging, thereby permitting elimination of a paint coating on the covers obtained from such prepolymers and their elastomers.
• Yet a further object of the present invention is to provide wheels, e.g., those used on forklifts, tires and rollers with excellent mechanical performance obtained from such prepolymers and their elastomers.
• the present invention relates to the preparation of low free HDI polyurethane prepolymers from difunctional polyols and their ready conversion to cast elastomers from hydroxy or amine curatives, e.g., aliphatic diols or aromatic diamines.
• hydroxy or amine curatives e.g., aliphatic diols or aromatic diamines.
• the resulting elastomers possess surprisingly good dynamic mechanical properties in golf ball covers, e.g., resisting mechanical damage from the shearing action of grooves in golf clubs, while providing high resilience for long flight.
• the present invention also relates to reducing the content of unreacted HDI monomer in a difunctional prepolymer reaction product by distilling the reaction product under vacuum in an agitated film evaporator.
• the molar ratio of the HDI diisocyanate monomer to the one or more polyols i.e., the ratio of NCO groups to OH groups
• the OH functionality of the polyol or polyol blend is about 1.9 to about 2.3, preferably about 1.98 to about 2.1 and most preferably about 2.0.
• two or more distillation stages are employed in series with successively more powerful vacuum to successively reduce the content of monomer in the prepolymer to below about 2% by weight and most preferably below about 0.1% by weight.
• the present invention further relates to polyurethane elastomers obtained by chain extending the low monomeric HDI containing prepolymers containing low concentrations of monomeric HDI.
• the chain extenders can be hydroxy or amine functional such as aliphatic diols or aromatic diamines.
• the extender/prepolymer stoichiometry i.e., the molar ratio of hydroxyl or amine groups to isocyanate groups
• the present invention is directed to a process for reducing the amount of residual 1,6-hexamethylene diisocyanate (HDI) monomer in a polyurethane prepolymer reaction product comprising the step of distilling the reaction product in one or more agitated film evaporators in series under vacuum to reduce the level of unreacted HDI monomer to below about 2 wt. %.
• HDI 1,6-hexamethylene diisocyanate
• a polyurethane prepolymer which comprises the reaction product of one or more polyols and a stoichiometric excess of HDI diisocyanate monomer at an NCO:OH ratio in the range of from about 2:1 to about 30:1, wherein the unreacted HDI diisocyanate monomer is removed by a process comprising distilling the reaction product in one or more agitated film evaporators in series under vacuum.
• a polyurethane prepolymer comprising the reaction product of one or more polyols and a stoichiometric excess of HDI diisocyanate monomer at an NCO:OH ratio in the range of from about 2:1 to about 30:1, wherein the unreacted HDI diisocyanate monomer is removed by a process comprising distilling the reaction product in one or more agitated film evaporators in series under vacuum.
• a polyurethane elastomer comprising the reaction product of (a) a prepolymer terminated with HDI, said prepolymer comprising no more than about 2 wt. % free HDI and at least 70% of theoretical NCO content for pure ABA structure with (b) a hydroxy or amine-functional chain extender, wherein the equivalent ratio of chain extender to prepolymer is in the range of from about 0.7:1 to about 1.2:1.
• a preferred embodiment of the present invention is a polyurethane elastomer comprising the reaction product of (a) a HDI-terminated prepolymer comprising the reaction product of one or more polyols having an overall functionality of about 1.9 to about 2.3 with a stoichiometric excess of HDI diisocyanate monomer at an NCO:OH ratio in the range of from about 2:1 to about 30:1; wherein unreacted HDI diisocyanate monomer is removed from the reaction product by a process comprising distilling the reaction product in one or more agitated film evaporators in series under vacuum; with (b) a chain extender selected from the group consisting of aliphatic diols, aromatic diamines or combinations thereof; wherein the equivalent ratio of prepolymer to chain extender is in the range of from about 0.7:1 to about 1.2:1.
• a golf ball cover comprising a core and a cover, the cover comprising a polyurethane elastomer, the polyurethane elastomer comprising the reaction product of (a) a HDI-terminated prepolymer comprising the reaction product of one or more polyols with a stoichiometric excess of HDI diisocyanate monomer wherein unreacted HDI diisocyanate monomer is removed to less than about 2 wt. % and (b) at least one hydroxy or amine functional chain extender.
• Yet another preferred embodiment of the present invention is a wheel or roll comprising a core and a polyurethane cover wherein the cover comprises a polyurethane elastomer comprising the reaction product of (a) a HDI-terminated prepolymer comprising the reaction product of one or more polyols with a stoichiometric excess of HDI diisocyanate monomer wherein unreacted HDI diisocyanate monomer is removed to less than about 2 wt. % and (b) at least one hydroxy or amine functional chain extender.
• the present invention is directed to the removal of the monomeric diisocyanate HDI from prepolymer reaction products.
• prepolymer reaction product as used herein shall be understood to mean the product from the reaction of one or more polyols and one or more diisocyanates.
• the polyurethane prepolymers herein can be obtained by reacting one or more polyols with a diisocyanate monomer by procedures known in the art.
• a prepolymer is formed by the reaction of one or more polyols, e.g., polyethers and/or polyesters, with a large excess of diisocyanate monomer, such as HDI.
• U.S. Pat. No. 4,888,442 disclosed the removal of low boiling, aliphatic monomers 4,4′-methylene bis (cyclohexyldiisocyanate) and 1,6-diisocyanatohexane from polyisocyanate adduct mixtures and solvents of lower boiling point by distillation. According to the process, the polyisocyanate adduct was prepared without solvent. Unreacted diisocyanate level was first reduced by distilling the reaction product without solvent once, and further reduced by distilling the treated reaction product in the presence of 2 to 30% of an inert solvent.
• the adducts of HDI were isocyanurate and biuret types, but not polyurethane prepolymer type; they contained no urethane bonds and did not derive from polyols.
• the prepolymer is passed through two or more agitated film vacuum distillation stages in series with progressively deeper vacuum to reduce the HDI content to below 0. 1% by weight.
• the polyurethane prepolymers of the present invention can be prepared by reacting a stoichiometric excess of the HDI diisocyanate monomers with one or more polyols.
• other diisocyanate monomers can be employed herein in minor amounts, e.g., amounts up to about 15 weight percent, preferably up to about 5 weight percent and most preferably about 0 weight percent.
• other diisocyanates include aromatic diisocyanates such as TDI and MDI.
• MDI is commercially available as the pure isomer 4,4′-diphenyl methane diisocyanate from such sources as Mondur MP and Bayer and as mixtures of isomers from such sources as Mondur Ml, Bayer, Lupranate MI and BASF.
• aromatic diisocyanate monomers include PPDI, tolidene diisocyanate (TODI), naphthalene-1,5-diisocyanate (NDI), diphenyl-4,4′-diisocyanate, stilbene-4,4′-diisocyanate, benzophenone-4,4′-diisocyanate, and mixtures thereof.
• Aliphatic diisocyanate monomers include dibenzyl-4,4′-diisocyanate, isophorone diisocyanate (IPDI), 1,3 and 1,4-xylene diisocyanates, 1,3-cyclohexyl diisocyanate, 1,4-cyclohexyl diisocyanate (CHDI), the three geometric isomers of 1,1′-methylene-bis(4-isocyanatocyclohexane) (H 12 MDI), and mixtures thereof.
• Suitable polyols for use herein are typically high molecular weight polyols including, but not limited to, polyethers, polyesters such as, for example, polycaprolactones, polycarbonates, or hydrocarbon polyols having a molecular weight ranging from about 100 to about 12,000 to prepare prepolymers for cast elastomers. It is to be understood herein that molecular weights and equivalent weights are number average. If desired, low molecular weight glycols or triols, those glycols or triols having a molecular weight from 62 to 400, can be included. I prepolymer with a polyol or combination of polyols having an overall functionality of from about 1.9 to about 2.3, preferably from about 1.95 to about 2.2, and most preferably from about 1.98 to about 2.1.
• Suitable high molecular weight polyols having a number average molecular weight of at least about 250 are used to prepare the prepolymer of the instant invention.
• the polyols Preferably have a molecular weight of about 400 to about 6000 and most preferably a molecular weight of from about 500 to about 4000.
• the molecular weight of the high molecular weight polyols may be as high as 12,000 or as low as 100.
• the preferred polyether polyols are polyalkyleneether polyols represented by the general formula HO(RO) n H, wherein R is an alkylene radical and n is an integer large enough that the polyether polyol has a number average molecular weight of at least 250.
• These polyalkyleneether polyols are well-known components of polyurethane products and can be prepared by the polymerization of cyclic ethers, e.g., alkylene oxides, and glycols, dihydroxyethers, and the like by methods known in the art. Examples include those polyether polyols available as Terathane PTMEG polyols from Dupont and Poly G polyols of propylene oxide and ethylene oxide from Arch Chemical.
• the polyester polyols are prepared by reaction of dibasic acids, e.g., adipic acid, glutaric, sebacic, or phthalic acid, with diols such as, for example, ethylene glycol, 1,2-propylene glycol, 1,4-butanediol, 1,6-hexanediol and the like, where linear polymer segments are required. Minor amounts of units of higher functionality, such as glycerol or trimethylolpropane, may be employed. Polyester polyols are available as Fomrez polyester polyols from Crompton and as Rucoflex polyester polyols from Bayer.
• dibasic acids e.g., adipic acid, glutaric, sebacic, or phthalic acid
• diols such as, for example, ethylene glycol, 1,2-propylene glycol, 1,4-butanediol, 1,6-hexanediol and the like, where linear polymer segments are required. Minor amounts
• polyester polyols employ caprolactone or dimerized unsaturated fatty acids in their manufacture.
• Polycaprolactone polyols are available as TONE polyols from Dow.
• Polycarbonate polyols are available as Desmophen 2020E from Bayer.
• Other suppliers include Daicel (Japan) and Ube (Japan).
• Suitable hydrocarbon polyols include those produced from butadiene available as Poly-Bd from Sartomer and Krasol from Kaucuk (Czech Republic).
• Preferred polyols of the current invention include polytetramethylene ether glycols (PTMEG), ), polycaprolactones, polycarbonates, and polyesters from adipic acid.
• PTMEG polytetramethylene ether glycols
• polycaprolactones polycaprolactones
• polycarbonates polycarbonates
• polyesters from adipic acid polyesters from adipic acid.
• the total polyol blend portion of the instant invention can be a combination of high molecular weight polyol, as previously described, and low molecular weight polyol.
• An aliphatic glycol is the preferred low molecular weight polyol.
• Suitable aliphatic polyols are ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol, and the like.
• the weight of the low molecular weight polyol should be no more than 20% of the combination of high molecular weight polyol and low molecular weight polyol.
• the preferred range is 0 to 15% of the combination; more preferred is 0-8%.
• a mole ratio ordinarily ranging from about 2:1 to about 30:1 HDI/polyol and preferably about 8:1 to about 20:1 HDI/polyol is recommended.
• the reaction is typically carried out at a reaction temperature ranging from about 50° C. to about 120° C.
• the reaction is carried out by maintaining the reaction temperature at about 70 to about 110° C. with agitation.
• the reaction product can be of low viscosity and primarily comprises the urethane-linked adduct of HDI-polyol-HDI structure (termed herein as an “ABA” structure, where A denotes HDI and B denotes a polyol).
• ABA urethane-linked adduct of HDI-polyol-HDI structure
• A denotes HDI
• B denotes a polyol
• oligomers of urethane-linkcd structure
• ABABA urethane-linkcd structure
• An HDI:polyol mole ratio of at least about 8:1 or greater favors formation of a final prepolymer (after removal of free HDI monomer) with NCO content of at least 70% of the theoretical NCO content for a pure ABA structure and preferably at least 80% of the theoretical NCO content for a pure ABA structure.
• each ABA and ABABA adduct has two unreacted NCO groups, one on each of the terminal A moieties.
• the internal A moiety in the ABABA adduct has no remaining unreacted NCO group. Therefore, the ABABA adduct has a lower NCO content than the ABA adduct. Accordingly, in a prepolymer reaction product mixture substantially free of unreacted A, the relative content of ABA to higher molecular weight adducts can be determined by the NCO content of the mixture. By employing a large molar excess of HDI over polyol, oligomer formation is minimized.
• Polyol number average equivalent weight (“ew”) can be obtained by titration of hydroxyl (OH) groups as described in ASTM methods E222, E326, and D4274. This quantity gives the number of grams (or other mass unit) required for one Avogadro's number of OH groups. The number average molecular weight is taken by multiplying the Ew by the functionality of the polyol. Thus, for a polyol having a functionality of 2 (i.e., 2 OH groups per polyol molecule), the number average molecular weight (mw) is twice the ew.
• NCO content of prepolymers can be obtained by titration methods as described in ASTM method D2572.
• the crude reaction product prepared in accordance with the present invention contains a large amount of unreacted HDI which is removed by distillation.
• Any distillation equipment that can be efficiently operated at deep vacuum, moderate temperature, and short residence time can be used in this step.
• an agitated film distillation system commercialized by such sources as Pope Scientific, Inc.; Artisan Industries, Inc.; GEA Canzler GmbH & Co.; Pfaudler-U.S., Inc.; InCon Technologies, L.L.C.; Luwa Corp.; UIC Inc.; or Buss-SMS GmbH for this purpose.
• Continuous units with internal condensers are preferred because they can reach lower operating vacuums of from about 0.001 to about 1 torr.
• the condenser temperature for the distillate be at least about 100° C. below the evaporative temperature.
• the condenser must also be cold enough to efficiently condense substantially all HDI vapor.
• a condenser temperature of about 20° C. or below is preferred.
• the residue can contain less than about 2% by weight free HDI, preferably less than about 0.5% free HDI and most preferably less than about 0.1% by weight free HDI, and the distillate can come out clean and remain transparent at room temperature.
• the distillate can then be reused to produce more prepolymer.
• the resulting prepolymers can have low viscosity, low monomeric HDI level and high NCO content (preferably 80% or more of the theoretical NCO content for ABA structure).
• the prepolymer can be easily chain-extended by various chain extenders at moderate processing temperatures.
• the chain extenders can be, for example, water, aliphatic diols, aromatic diamines, or their mixtures.
• Suitable aliphatic diols for use herein include, but are not limited to, 1,4-butanediol (BDO), di (beta-hydroxyethyl) ether (HER), di (beta-hydroxypropyl) ether (HPR), hydroquinione-bis-hydroxyethyl ether (HQEE), 1,3-propanediol, ethylene glycol, 1,6-hexanediol, 1,4-cyclohexane dimethanol (CHDM) and the like and combinations thereof.
• BDO 1,4-butanediol
• HER beta-hydroxyethyl
• HPR di (beta-hydroxypropyl) ether
• HQEE hydroquinione-bis-hydroxyethyl ether
• CHDM 1,3-propanediol
• Suitable aromatic diamines for use herein include, but are not limited to, 4,4′-methylene-bis(3-chloroaniline) (MBCA), 4,4′-methylene-bis(3-chloro-2,6-diethylaniline) (MCDEA), 4,4′-methylene-bis(2,6-diethylaniline) (MDEA), diethyl toluene diamine (DETDA, EthacureTM 100 from Albemarle Corporation), tertiary butyl toluene diamine (TBTDA), dimethylthio-toluene diamine (EthacureTM 300 from Albemarle Corporation), trimethylene glycol di-p-amino-benzoate (Vibracure® A157 from Uniroyal Chemical Company, Inc.
• aliphatic triols and tetrols e.g., trimethylol propane, and adducts of propylene oxide, and/or ethylene oxide having molecular weight 190 to 500, such as various grades of Voranol (Dow Chemical), Pluracol (BASF Corp.) and Quadrol (BASF Corp.) can also be used.
• the most preferred chain extenders are BDO, HQEE, MBCA, MDEA, trimethylene glycol di-p-amino-benzoate, MCDEA, and DETDA.
• the polyurethane clastomers of the present invention can be made by chain-extending the foregoing prepolymers of low monomeric HDI content with the foregoing chain extenders by methods known in the art.
• the amine or diol chain extender and the prepolymer are mixed together to polymerize.
• the chain extension temperature for the polymerization will ordinarily range from about 20° C. to about 150° C.
• the specimens so obtained are preferably aged for about 4 weeks at room temperature before undergoing their intended use or standard testing for mechanical properties.
• a working life (pour life) of at least sixty seconds is typically required to mix prepolymer and chain extender and to pour the mixture into molds without bubbles. In many cases, a working life of about 5 to about 10 minutes is preferred.
• a working life shall be understood herein to mean the time for the mixture of prepolymer and chain extender to reach a Brookfield viscometer viscosity of about 200 poise when each component is “preheated” to a temperature at which viscosity is about 15 poise or lower and preferably about 10 poise or lower.
• H 12 MDI Dicyclohexyl methane diisocyanate
• Adiprene® LW 90 Crompton Corp., Prepolymer consisting essentially of PTMEG and TDI with below 0.1% monomeric TDI, approx. 3.8% NCO.
• Adiprene® LF 95 Crompton Corp., Prepolymer consisting essentially of PTMEG and TDI with below 0.1% monomeric TDI, approx. 6.1% NCO.
• Adiprene® LW 570 Crompton Corp., Prepolymer consisting essentially of PTMEG and H 12 MDI without a monomer removal step for unreacted H 12 MDI monomer (10% by weight).
• Lonzacure® MCDEA Lonza, 4,4 ′-methylene-bis(3-chloro-2,6-diethylaniline)
• MBCA 4,4′-methylene-bis(3-chloroaniline)
• Vibracure® A250 Crompton Corp., Blend of 1,4-butanediol and trace mixing aid;
• HQEE hydroquinone-bis-hydroxyethyl ether (Arch Chemical)
• EthacureTM100 Albemarle Corporation, Diethyl toluene diamine (“DETDA”)
• TMGDAB Trimethylene glycol di-p-amino-benzoate
• Trimethylolpropane (Celanese Chemical Corporation)
• Comparative Examples A through E are taken from Examples 0, P, R, S and 9 from U.S. Pat. No. 6,046,297, the teachings of which are incorporated herein by reference. These examples were directed to the preparation of industrial rolls such as paper mill rolls, industrial wheels, and industrial tires with low hysteresis.
• Cured elastomers were prepared from Lonzacure MCDEA curative and the following prepolymers:
• Comparative Example A Adiprene® LF 90: Prepolymer consisting essentially of PTMEG and TDI with below 0.1% monomeric TDI due to removal of free TDI by vacuum distillation; approx. 3.8% NCO.
• Comparative Example B AdipreneTM LF 95: Prepolymer consisting essentially of PTMEG and TDI with below 0.1% monomeric TDI due to removal of free TDI by vacuum distillation; approx. 6.1% NCO.
• Comparative Example C Adiprene®LW 570: Prepolymer consisting essentially of PTMEG and H 12 MDI without a monomer removal step for unreacted H 12 MDI monomer (10%); approx. 7.4% NCO.
• Comparative Example D Low free H 12 MDI prepolymer. Reaction product of 10 moles H 12 MDI with one mole of PTMEG, 650 mw, then freed of unreacted H 12 MDI monomer by vacuum distillation on a wiped film evaporator. 6.7% NCO content.
• Comparative Example E Physical blend of 86 parts by weight Adiprene LF 90 (the LFTDI prepolymer of Comp. A) with 14 parts by weight unreacted H 12 MDI monomer. 7.8% NCO content.
• the low monomeric HDI content prepolymers of the present invention were prepared according to the following general prepolymer synthesis procedure.
• a prepolymer was prepared by charging first 1680 parts HDI, then 952 parts PTMEG 1000 (952 mw) to a batch reaction flask equipped with nitrogen sweep, an agitator, a thermometer, a heating mantle, and a vacuum source.
• the molar ratio of HDI to PTMEG (hence the equivalent ratio of NCO groups to OH groups) was 10:1.
• the reaction mixture was cooked for 6 hours at a temperature of 80° C. with vacuum of 1-10 torr the last hour to remove entrained gases.
• the NCO content of this crude reaction mixture reached 28.4% at 3 hours and remained there at 6 hours.
• the crude reaction mixture was then processed through a wiped film evaporator to remove unreacted HID monomer. Vacuum was 0.04 torr or less. Jacket temperature was 140° C. and the condenser temperature was 5° C.
• the stripped prepolymer contained less than 0.1% fire HDI. It had 6.12% NCO content, 94% of the theoretical value of 6.53% for prepolymer of pure ABA structure (1288 mw when B is 952 mw). The distillate had 50% NCO content, as expected for substantially pure HDI monomer.
• a prepolymer was prepared by the procedures of Example 1, using 1000 mw polyhexamethylene adipate glycol as the polyol in place of PTMEG 1000.
• This polyester polyol is commercally available as Fomrez 66-112 (Crompton Corp.). The specific lot had 499 ew, hence 998 mw as functionality is 2.0. Phosphoric acid was added at 15 ppm.
• the resulting prepolymer had 5.80% NCO content, 92% of the theoretical value of 6.30% for prepolymer of pure ABA structure (1166 mw when B is 998 mw). Also, the resulting prepolymer contained a free HDI content of 0.14%.
• a prepolymer was prepared by the procedures of Example 1, using 2000 mw polyhexamethylene carbonate glycol as the polyol. This polycarbonate polyol is available as Desmophen 2020E (Bayer Corp.). The specific lot had 1002 ew, hence 2004 mw as functionality is 2.0. Phosphoric acid was added at 15 ppm. The resulting prepolymer had 3.84% NCO content and contained 0.08% free HDI content.
• polyurethane elastomers formed from the low monomeric HDI content prepolymers of the present invention were prepared according to the following general synthesis procedure.
• Example 4 An Elastomer from HDI/PTMEG Prepolymer And MCDEA
• An elastomer was prepared by mixing the HDI prepolymer of Example 1 with Lonzacure MCDEA by the procedures used in Comparative Examples A-E. Thus, 100 parts by weight prepolymer was mixed with 27 parts by weight MCDEA (98% of the MCDEA needed to provide one amine group per isocyanate group in the prepolymer).
• Dynamic mechanical properties were determined on a Rheometrics dynamic mechanical spectrometer under conditions of 1% strain and 10 Hz frequency. Properties measured included storage modulus, loss modulus, and tangent delta. From these properties, a comparative power loss also may be calculated.
• G′ in Table I is given in units of dynes/cm 2 .
• G′ storage Modulus
• Tangent Delta is a dimensionless number indicating hysteresis. Lower values are typically desired throughout the temperature range from 30° C. to 200° C., and especially from 30° C. to 150° C.
• a polyurethane elastomer was prepared by mixing the HDI prepolymer of Example 2 with Lonzacure MCDEA by the procedures used in Comparative Examples A-E. Thus, 100 parts by weight prepolymer was mixed with 26 parts by weight MCDEA (98% of the MCDEA needed to provide one amine group per isocyanate group in the prepolymer).
• a polyurethane elastomer was prepared by mixing the HDI prepolymer of Example 3 with Lonzacure® MCDEA by the procedures used in Comparative Examples A-E. Thus, 100 parts by weight prepolymer was mixed with 17 parts by weight MCDEA (98% of the MCDEA needed to provide one amine group per isocyanate group in the prepolymer).
• Elastomers were prepared by mixing the HDI prepolymer of Example 1 with various diamine and diol curatives.
• the diamines were used at 98% of the weight needed to provide one amine group per isocyanate group in the prepolymer.
• the diols were used at 95% of the weight needed to provide one hydroxyl group per isocyanate group in the prepolymer. In all cased the elastomers were allowed to cure 24 hours at 127° C.
• polyurethanes are advantageous in the production of golf ball covers because they have the feel and click of balata covered balls with much greater cut resistance.
• the polyurethanes are generally more resilient than balata, allowing balls to be made with both good feel and good distance. Resilience can be measured as percent rebound of a steel ball bouncing on a flat elastomer sample from a height of one meter, where the sample is at least 0.5 inches thick and is firmly mounted so as to prevent movement.
• Ionomer covers such as SURLYN® have good resilience, but are harder and do not give the click and feel of the polyurethane and balata covers.
• Shear resistance measures the damage to a cover from the impact of club with sharp grooves, which can tear away bits of the cover.
• cut resistance measures the resistance to damage of the cover from a miss hit shot, where the leading edge of the iron cuts directly into the cover.
• Shear resistance of polyurethane formulations can vary. One such method that can be used to improve the shear resistance of a polyurethane formulation is disclosed in U.S. Pat. No. 5,908,358.
• U.S. Pat. No. 6,309,313 discloses convenient methods for assessing the resilience and groove shear resistance of polyurethane formulations as golf ball covers, the contents of which are incorporated herein by reference.
• a prepolymer was prepared by the procedures of Example 1, substituting the HDI distillate from Example 1 for the fresh HDI. In addition, a different batch of PTMEG 1000 was used. This batch had 988 mw.
• the stripped prepolymer had 5.70% NCO content, 90% of the theoretical value of 6.35% for prepolymer of pure ABA structure (1324 mw when B is 988 mw).
• the HDI prepolymer of Example 13 was mixed with 1,4-butanediol in a weight ratio 100/6.0, providing 98/100 ratio of hydroxyl groups to isocyanate groups.
• a commercially available white pigment paste was also included in the mixture at 2 parts per 100 parts prepolymer.
• the resultant mixture was de-aerated and cast into a mold cavity containing a golf hall core to form a standard sized golf ball.
• the golf ball was cured at 70° C. for 16 hours.
• a golf ball was prepared by the procedures of Example 14, substituting an 80/20 blend by weight of 1,4-butanediol and trimethylolpropane for the pure 1,4-butanediol and mixing the blend with the HDI prepolymer of Example 13. (Each of the two components t is particularly advantageous when forming the cast polyurethane elastomers, to form the
• [0112] of the blend had ew 45).
• the prepolymer/curative weight ratio was 100/6.0, providing 98/100 ratio of hydroxyl groups to isocyanate groups.
• the resultant mixture was de-aerated and cast into a mold cavity containing a golf ball core to form a standard sized golf ball.
• the golf ball was cured at 70° C. for 16 hours.
• the golf balls of Examples 14 and 15 were tested side by side with three commercially available golf balls: (1) the Nike Tour Accuracy, which has a thermoplastic polyurethane cover; (2) the Strata Professional Balata, which has a balata cover; and (3) the Nike Precision Distance, which has an ionomer cover. All balls were hit by a golf professional with a pitching wedge having sharp grooves and the contact points were marked. Damage to the balls was rated on a 1 to 10 scale, where 10 indicated no marks at the point of contact and the ball is indistinguishable from a new ball. A 5 indicated a ball with substantial damage to the cover at the point of contact, but no loss of material. A 1 indicated a ball with cover material loss at the point of contact. Three different observers rated the balls and the ratings were averaged as follows: Example 14: 7.3 Example 15: 6.7 Nike Tour Accuracy 5.0 Strata Professional Balata 4.9 Nike Precision Distance 1.0
• the golf balls of Examples 14 and 15 containing the polyurethane elastomers of this invention were also tested for their colorfastness by exposing the golf balls in a Weather-o-Meter under a UV exposure of 5500 watts for 36 hours. The results of this test indicated no change in color or fading to the polyurethane elastomer covers of the golf balls.
• the golf balls of Examples 14 and 15 containing the polyurethane elastomers of this invention were also tested for resilience by dropping a steel ball on the elastomer and measuring the height of rebound. In this test, recovery of at least 50% of the drop height is considered good. The two elastomers each exhibited 70% resilience.

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