Plastic and nonmetallic article shaping or treating: processes – Mechanical shaping or molding to form or reform shaped article – Shaping against forming surface
Reexamination Certificate
1996-12-23
2003-02-18
Heitbrink, Jill L. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Mechanical shaping or molding to form or reform shaped article
Shaping against forming surface
C264S331190
Reexamination Certificate
active
06521164
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates broadly to thermoplastic polyurethane elastomers, and more specifically to a p-phenylene diisocyanate (PPDI)-based composition therefor having a unique chain extender combination for improved injection moldability.
Polyurethane elastomers are often specified for applications wherein a material is specified as having exceptional resistance to abrasion, solvents, and oxygen aging, in addition to superior toughness, tear strength, elongation, shock absorption, hardness, flexibility, elasticity, and dynamic properties. Interest in these materials has continued to increase with the introduction of injection-moldable grades which may be economically processed for use in a wide variety of industrial and consumer products including: gears, bearings, and joints for precision machines; parts for electronic instruments; soles and uppers for atheletic shoes and ski boots; automotive parts; and seals, gaskets, and packings for hydraulic fluid systems and other applications.
Thermoplastic polyurethane materials, and particularly the injection-moldable TPUs of the type herein involved may be prepared by reacting diols or polymeric polyols, diisocyanate compounds, and polyfunctional chain extender compounds having, for example, hydroxyl or amino functional groups. Different combinations of these reactants have been processed by various methods to yield TPUs having a diverse range of properties. For example, U.S. Pat. Nos. 4,371,684 and 4,245,081 discloses a continuous process for the production of TPUs involving the steps of reacting in an extruder a linear polyol, a diisocyanate, and a chain extender which is a mixture of at least two different glycols. Preferred linear polyols include polyester, polycaprolactone, polyether, polythioether, polyesteramide, polycarbonate, and polyacetal polyols, with preferred diisocyanates including aliphatic, cycloaliphatic, aromatic, araliphatic and heterocyclic diisocyanates generally known in the art such as diphenyl methane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, lysine ester diisocyanates, and tolylene, diphenyl methane, and xylene diisocyanates and hydrogenation products thereof. The preferred glycols include ethylene glycol, di- and tri-ethylene glycol, 1,2-propane diol, 1,3- and 1,4-butane diol, 1,6-hexane diol, 2-ethyl-1,3-hexane diol, 2,2-dimethyl propane diol, 1,4-bis-hydroxylmethyl cyclohexane, and hydroquinone dihydroxy ethyl ether. The chain extender mixture is stated to improve the processing of the composition in a twin- or other multi-screw extruder. The reference is silent, however, as to whether the chain extenders improve the injection molding properties of the resulting TPU.
U.S. Pat. No. 5,066,762 discloses a TPU resin having improved hydrolysis and heat deterioration resistance, temperature dependency, and compression set. The TPU is prepared by the reaction of p-phenylene diisocyanate, a hydroxyl terminated poly(hexamethylene carbonate) polyol, and a short chain polyol, such as ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, p-xylene glycol, 1,4-bis-(&bgr;-hydroxyethoxy)benzene, 1,3-bis-(&bgr;-hydroxyethoxy)benzene, cyclohexane 1,4-dimethanol, octane-1,8-diol, and decane-1,10-diol, as a chain extending agent.
Castro, Hentschel, Brodowski, and Plummer, “Influence of Processing Conditions on Mechanical Properties of High Performance CHDI Based TPUs,” J. Elast. and Plast., Vol. 17 (October 1985), pp. 238-248, discloses that mixed chain extenders may be employed to facilitate the injection molding of a trans-1,4-cyclohexane diisocyanate (CHDI)-based TPU. The chain extenders employed were bis (2-hydroxyethyl) bisphenol A, i.e., Dianol 22, and cyclohexane dimethanol (CHDM). A p-phenylene diisocyanate (PPDI)-based formulation additionally is referenced as illustrative of another high performance TPU.
Hepburn, “Polyurethane Elastomers,” 2d ed., pp. 249-280, Elsevier Applied Science (London and New York, 1992), discloses the use of mixed chain extender systems in CHDI- and PPDI-based TPUs formulated with polycaprolactone (Capa 225) as the polyol. Bi-component combinations of 1,4-butane diol, 1,4cyclohexane dimethanol, 1,6-hexane diol, 1,1′-isopropylidene-bis-(p-phenylene-oxy)-di-&bgr;-ethanol (Dianol 22), 1,1′-isopropylidene-bis-(p-phenylene-oxy)-di-&ohgr;-propanol (Dianol 33) are employed for the chain extender system. Additionally disclosed is a PPDI-based TPU formulated with polytetramethylene glycol as the polyol which uses as a single-component chain extender such as hydroquinone dihydroxy ethyl ether.
U.S. Pat. No. 4,980,445 discloses a TPU exhibiting high resistance to abrasion forces while retaining a good impact resistance and creep behavior. The TPU is formed from the reaction product of a mixture of a polyester and a polyether diol, a difunctional chain extender, and a diisocyanate. The polyester diol may be a poly(oxycaproyl) diol or a poly(alkylene alkanedioate)diol, such as a poly(ethylene adipate), poly(propylene adipate), poly(butylene adipate), poly(ethylene/butylene adipate) diol, while the polyether diol may be a poly(alkylene oxide) glycol such as poly(ethylene oxide) diol, poly(propylene oxide) diol, poly(tetramethylene oxide) diol, or a block or random polyoxypropylene/polyoxyethylene or polyoxytetramethylene/polyoxyethylene copolymeric glycol. Preferred difunctional chain extenders include ethylene and propylene glycol, 1,4-butane diol, 1,3-butane diol, 1,5-pentanediol, 1,6-hexanediol, 1,10-decanediol, 1,12-dodecanediol, ethoxylated hydroquinone, 1,4-cyclohexane diol, N-methylethanolamine, N-methylisopropanolamine, 4-aminocyclo-hexanol, 1,2-diaminoethane, 2,4-toluenediamine, and the like. Preferred diisocyanates include aromatic, aliphatic, and cycloaliphatic diisocyanates such as m- and p-phenylene diisocyanates, 2,4- and 2,6-toluene diisocyanate, 4,4′-methylenebis(cyclohexyl isocyanate), and mixtures thereof The TPU may be prepared in a single-step process wherein the diols, diisocyanate, and chain extender are simultaneously mixed and reacted at an elevated temperature, or in a two-step process wherein the mixture comprising the diols is first reacted with the diisocyanate to form a diisocyanate-terminated prepolymer, which prepolymer is further reacted with the difunctional chain extender. Alternatively, the diisocyanate may first be reacted with the chain extender to form a product which is then reacted with the polyester and polyether diol mixture.
U.S. Pat. No. 5,013,811 discloses a linear TPU elastomer of a polyol, a first and second chain extender, and a diisocyanate component. The polyol may be a polyether polyol, polycarbonate polyol, polycaprolactone polyol, polyester polyol, polybutadiene polyol, or a mixture thereof The diisocyanate preferably is a diphenylmethane diisocyanate (MDI). The first and second chain extenders may be selected as different polyol or amine compounds having a molecular weight of less than about 500. Preferred first and second chain extends include 1,4-butane diol, tripropylene glycol, dipropylene glycol, propylene glycol, ethylene glycol, 1,6-hexane diol, 1,3-butane diol, neopentyl glycol, ethylene diamine, and mixtures thereof The TPU is formed at a relatively low processing temperature by initially reacting the diisocyanate with the first chain extender to form a modified diisocyanate, which diisocyanate is then reacted with the polyol and second chain extender.
U.S. Pat. No. 3,929,732 discloses a TPU elastomer formulation having enhanced exposure resistance to low temperatures. The TPU is derived from the reaction of 4,4′-methylenebis(phenyl isocyanate), a poly(1,4-butylene azelate), and a chain extender such as an aliphatic diol or bis(2-hydroxyethylether). The elastomer is described as particularly useful in fabrication parts for automobiles and the like which are exposed to severe temperature extremes.
U.S. Pat. No. 4,532,316 discloses polyurethane prepolymers which phase-separate into hard and soft segments. The prepol
Comes Val C.
Plummer Thomas L.
Wallace George R.
Heitbrink Jill L.
Molnar, Jr. John A.
Parker-Hannifin Corporation
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