Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Reexamination Certificate
2002-06-07
2004-04-13
Kiliman, Leszek (Department: 1773)
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
C428S036500, C428S323000, C428S324000, C428S325000, C428S328000, C428S331000, C428S423100, C428S423300
Reexamination Certificate
active
06720049
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to low-tack thin-walled articles comprising a polyurethane elastomer, for example surgical gloves, clean-room gloves, condoms, and the like. More particularly, the invention relates to such elastomeric articles containing specific amounts of molecular sieve.
2. Description of Background Art
Elastomeric gloves are known for use in sterile, surgical, and chemical environments. United States Patents U.S. Pat. No. 2,814,834 (Hess et al.), U.S. Pat. No. 3,553,308 (Kobayashi et al.), and U.S. Pat. No. 5,132,129 (Potter et al.) disclose “reaction dipping” methods for making gloves. United States Patents U.S. Pat. No. 5,391,343 (Dreibelbis et al.) and U.S. Pat. No. 5,728,340 (Dreibelbis et al.) described processes for making polyurethane thin-walled articles, such as gloves and condoms, which have superior mechanical properties, for example low set and high resistance to tear and puncture.
A problem characteristic of elastomeric thin-walled articles like gloves is surface tack, which can result in difficulty removing a glove from the mandrel during manufacture or from its package, and/or difficulty in donning a glove. United States Patent U.S. Pat. No. 6,016,570 (Vande Pol et al.) discloses the use of powder and lubricant additives and of contact-reducing textures formed by intermittent spray coating (optionally containing fillers to reduce droplet size) to control tack of vinyl gloves. However, lubricants can contaminate clean rooms and operating rooms, and surface textures can reduce tactility. Several disclosures have been made of inorganic particulates in polymers: in United States Patents U.S. Pat. No. 3,832,214 (Wang) and U.S. Pat. No. 3,622,526 (Zorn et al., directed to porous coagulated coatings for simulated leather), U.S. Pat. No. 4,521,465 (Schreor et al., directed to coated textiles as pipe liners), U.S. Pat. No. 6,203,901 (Kosinski et al., directed to clay in fibers and films), U.S. Pat. No. 6,027,803 (Jacobson et al., directed to barium sulfate in fibers), and European Patent Application EP1125978 (Roberts, directed to clay in latices). However, reduced tack polyurethane elastomeric thin-walled articles are still needed.
SUMMARY OF THE INVENTION
The present invention provides a thin-walled article comprising at least one surface layer of: a polyurethane elastomer; and about 20 to 40 weight percent, based on the weight of the layer, of a molecular sieve having a mean particle size of about 1 to 15 microns and less than 1 weight percent, based on weight of molecular sieve, of particle size greater than about 40 microns.
DETAILED DESCRIPTION
It has now been unexpectedly found that thin-walled articles containing certain amounts of molecular sieve have an unexpected combination of very low tack, low porosity, reduced set and stress, smooth hand, no particulate visible to the unaided eye, and only slightly opaque appearance. The low tack is advantageous for removing the article from a package and for donning, the low porosity for good barrier protection in clean room and medical environments, the reduced set and stress for better shape retention and improved comfort, and the tactile and visual properties for good aesthetics.
The term “thin-walled”, as used herein, refers to a thickness of no greater than about 0.18 millimeters. The article can be said to have an inner surface and an outer surface, preferably identified in the configuration in which the article is to be used. “Polyurethane” refers to a long-chain synthetic polymer comprising alternating “soft segments” comprising primarily polyester, polyether, or polycarbonate and “hard segments” derived from the reaction of a diisocyanate and a difunctional chain extender. “Elastomer” means a polymer which, free of diluents, retracts to less than 1.5 times its original length within one minute after being stretched at room temperature to twice its original length and held for one minute before release. “Molecular sieve” means a crystalline inorganic material having pores, cavities, or other interstices which are uniformly on the order of Angstroms in size and includes synthetic and natural zeolites, which can be alumino-silicates, titano-silicates, and the like.
The thin-walled article of the invention comprises at least one surface layer of a polyurethane elastomer and about 20 to 40 wt % (preferably about 25 to 35 wt %), based on the weight of the layer, of a molecular sieve having a mean particle size of about 1 to 15 microns and less than about 1 wt %, based on weight of molecular sieve, of particle size greater than about 40 microns. The article can have a stress at 100% extension of no greater than about 200 psi (1.4 megaPascals), a “calculated water vapor transmission rate” of less than about 50 g/hr/m
2
(preferably less than about 20 g/hr/m
2
), calculated for an 0.1 mm thick sample, and a percent set of less than about 25%.
Elastomeric polyurethanes useful in this invention can be prepared by reacting a polymeric glycol with a diisocyanate to form an isocyanate-terminated prepolymer (a “capped glycol”), preferably having an isocyanate (NCO) end-group concentration in the range of about 1.4 to 2.0%. The capped glycol can be dissolved in a suitable solvent, and then reacting the capped glycol with a difunctional chain extender having active hydrogen atoms. Suitable solvents for preparing solutions of such polymers are amide solvents such as dimethylacetamide (“DMAc”), dimethylformamide, and N-methylpyrrolidone, but other solvents such as dimethylsulfoxide and tetramethylurea can also be used.
Polymeric glycols used in the preparation of the elastomeric polyurethanes include polyether glycols, polyester glycols, polycarbonate glycols and copolymers thereof. Examples of such glycols include poly(ethyleneether) glycol, poly(trimethyleneether) glycol, poly(tetramethyleneether) glycol, poly(tetramethylene-co-2-methyltetramethyleneether) glycol, poly(ethylene-co-butylene adipate) glycol, poly(2,2-dimethyl-1,3-propylene dodecanedioate) glycol, poly(3-methyl-1,5-pentamethylene dodecanedioate) glycol, poly(pentane-1,5-carbonate) glycol, and poly(hexane-1,6-carbonate) glycol. Polyester glycols having a number average molecular weight of about 3,000 to 6,000 are preferred. Polyester glycols derived from the reaction of adipic acid with a mixture of ethylene glycol and 1,4-butanediol (mole ratio of 30:70 to 75:25) are more preferred.
Useful diisocyanates include 1-isocyanato-4-[(4′-isocyanatophenyl)methyl]benzene (preferred), 1-isocyanato-2-[(4′-isocyanato-phenyl)methyl]benzene, isophorone diisocyanate, 1,6-hexanediisocyanate, 2,4-tolylene diisocyanate, and mixtures thereof.
The chain extender can be a diol, an aminoalcohol, or a diamine. Useful diols include ethylene glycol, 1,3-trimethylene glycol, 1,4-butanediol, and mixtures thereof. When the chain extender is a diol, the polyurethane can be prepared using the two-step prepolymer method described hereinabove or using a one-step method in which the ingredients are mixed together at substantially the same time. Useful diamines include ethylene diamine (preferred), 1,2-propanediamine, 2-methyl-1,5-pentanediamine, 1,3-diaminopentane, 1,4-cyclohexane-diamine, 1,3-cyclohexanediamine, and mixtures thereof. When the chain extender is a diamine, the two-step, prepolymer polymerization method is generally used. Monofunctional amine chain terminators such as diethyl amine, butylamine, cyclohexylamine, and the like can be added to control the molecular weight of the polymer, and small amounts of trifunctional ingredients such as diethylenetriamine can be added for solution viscosity control.
Typically, the solution of polyurethane can have a falling ball viscosity of about 25 to 125 poise and a polyurethane concentration of about 12 to 20 wt %, based on the total weight of the solution.
The molecular sieve can be mixed directly into the polyurethane solution, or optionally prepared first as a concentrated slurry or masterbatch which can then be added to the main polyurethane sol
E. I. du Pont de Nemours and Company
Furr, Jr. Robert B.
Kiliman Leszek
LandOfFree
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