Ziegler-natta catalyzed polyisoprene articles

Abstract

To provide prophylactic devices, such as condoms, finger cots and polymeric gloves that are thin, strong and non-allergenic.SOLUTION: A method for producing a polymeric article comprises: disposing on a former an elastomeric coating of a Ziegler-Natta catalyzed polyisoprene material; and curing the elastomeric coating to form an elastomeric layer of the polymeric article. A polymeric article comprises an elastomeric layer comprising cured synthetic polyisoprene particles that comprise a Ziegler-Natta catalyzed polyisoprene material.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to personal protection articles, and more particularly to condoms comprising Ziegler-Natta catalyzed polyisoprene. [Background technology]

[0002] Prophylactic devices, such as condoms, finger cots, and gloves, such as examination and surgical gloves, are typically made from polymeric materials to provide protection against chemicals, abrasions, pathogens, viruses, and microorganisms among many other uses. Polymeric materials include natural rubber latex (natural polyisoprene), synthetic polyisoprene, or various polyurethanes. Prophylactic devices made from natural rubber are strong. Natural rubber, derived from Hevea brasiliensis and / or guayule, has a high level of stereoregularity, meaning that the polymer molecules that make it up are composed almost exclusively of cis-1,4 isoprene units. Natural rubber latex is also a highly branched polymer with a high molecular weight and a broad molecular weight distribution. These properties of natural rubber result in vulcanized rubber products with a unique combination of strength and elasticity. However, natural rubber also contains proteins that can produce allergic skin reactions in some susceptible individuals.

[0003] Synthetic polyisoprene resins have been developed to offer the benefits of natural rubber while eliminating the potential for protein allergies. However, some synthetic polyisoprenes, such as those produced by anionic addition polymerization by Kraton Inc., typically have lower levels of tacticity (i.e., less than 90% cis 1,4 isoprene) and reduced molecular weight. As a result, articles produced from such synthetic polyisoprenes have inferior properties compared to natural rubber articles. In addition, synthetic polyisoprene latexes with lower levels of tacticity tend to aggregate and clump in suspension, resulting in defects in the dipped articles. The usable processing window for dipping such synthetic polyisoprene latex dip tanks is accordingly limited. Furthermore, the addition of anti-agglomerating agents interferes with crosslinking, resulting in anisotropic cure properties, such as poor strength and elongation properties, and voids and cracks due to the formation of fractures within interparticle and intraparticle regions.

[0004] There is a continuing need to produce prophylactic devices, such as condoms, finger cots, and polymer gloves, that are thin, strong, and non-allergenic. Summary of the Invention

[0005] Embodiments according to the present disclosure include polymeric articles and methods for producing polymeric articles comprising Ziegler-Natta catalyzed synthetic polyisoprene materials, as substantially shown in and / or described in connection with at least one of the drawings, and as more fully set forth in the claims. Various advantages, aspects, and novel features of the present disclosure will become more fully understood from the following description and drawings.

[0006] The above summary is not intended, and should not be construed, to describe each embodiment or every implementation of the present disclosure. Other and further embodiments are described below.

[0007] Thus, in a manner in which the above-recited features of the present disclosure may be understood in detail, a more particular description of the disclosure briefly outlined above may be understood by reference to embodiments, some of which are illustrated in the accompanying drawings. It should be noted, however, that the accompanying drawings illustrate only typical embodiments of this disclosure and therefore should not be considered to limit its scope, as the disclosure may admit of other equally effective embodiments. It should be understood that elements and features of one embodiment may be present in other embodiments without further recitation. It is further understood that, where possible, the same reference numerals have been used to indicate corresponding elements common to the figures. [Brief explanation of the drawings]

[0008] [Figure 1] 1 shows a first transmission electron microscope (TEM) image according to an embodiment of the present disclosure. [Figure 2] 1 shows a second TEM image according to an embodiment of the present disclosure. [Figure 3] 10 shows a third TEM image according to an embodiment of the present disclosure. [Figure 4] 10 shows a fourth TEM image according to an embodiment of the present disclosure. [Figure 5] 1 is a perspective schematic view of a condom according to one embodiment. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] The embodiments described in this disclosure, briefly summarized above and described in more detail below, include polymeric articles, such as condoms, including thin-walled condoms, and gloves. The embodiments may include condoms or gloves formed using a coagulant. The embodiments may include condoms and gloves formed using a Ziegler-Natta catalyzed synthetic polyisoprene material. The embodiments may include condoms and gloves made using a Ziegler-Natta catalyzed synthetic polyisoprene material and a coagulant.

[0010] The inventors have unexpectedly observed that condoms made from the Ziegler-Natta catalyzed polyisoprene resins described herein have enhanced tensile strength, allowing for the production of thinner condoms. Thinner condoms can provide greater sensitivity to the wearer. Thinner gloves are more flexible yet unexpectedly retain puncture and abrasion resistance. Any, all, or some of the embodiments according to the present disclosure include condoms and / or polymeric gloves having a cross-sectional thickness of, for example, 0.030-0.065 mm. Exemplary embodiments according to the present disclosure include condoms or polymeric gloves having a cross-sectional thickness of 0.040-0.055 mm.

[0011]

[0010] Embodiments of the present disclosure further include gloves, such as examination gloves, surgical gloves, and household gloves, as well as finger cots. Embodiments further include gloves formed with a coagulant. Embodiments include polymeric gloves including a thumb having a front and back surface; multiple fingers; a palm region; and a back region.

[0012] Embodiments of the present disclosure further include condoms. Embodiments further include condoms formed using a coagulant. Embodiments include condoms including an open end, a closed end, and a tubular sheath extending from the closed end to the open end. FIG. 5 is a perspective schematic diagram of a condom according to one embodiment. A ZN-catalyzed PI condom 100 disclosed herein includes a closed end 104 and an open end 108. A hollow shaft 106 extends from the closed end 104 to the open end 108, with the open end having an opening 110 opposite the nipple end 102 of the closed end 104. Optionally, the condom further includes beads 114. The hollow shaft of the condom includes ZN-catalyzed PI particles, which may be provided by a ZN-catalyzed aqueous PI latex composition. The aqueous latex composition may have a solids content ranging from 60% to 65% by weight. The composition may further include additional water, preferably deionized water, resulting in a composition with a solids content ranging from 55% to 60% by weight. Optionally, the aqueous latex composition may further comprise one or more thickeners and / or stabilizers / surfactants. Colorants and / or pigments may optionally be added to the aqueous latex composition.

[0013] In describing the embodiments of the present disclosure in detail, the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. The embodiments described herein should not necessarily be limited to specific compositions, materials, designs, or devices, which may vary as such. All technical and scientific terms used herein have the ordinary meanings conventionally understood by those skilled in the art to which this disclosure belongs, unless otherwise specified by context. Also, as used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0014] The terms "flexion" or "bending" refer to finger movements such as bending, fisting, grasping, gripping, clenching or otherwise folding the fingers.

[0015] The terms "emulsion," "dispersion," "latex," and "suspension" are generally similar and refer to a system in which small particles of a substance, such as rubber particles, are mixed with a fluid solvent (e.g., water and / or alcohol and / or other organic fluids) but remain at least partially insoluble and dispersed by agitation (mechanical suspension) and / or by molecular forces in the surrounding medium (colloidal suspension). Emulsions contemplated herein may further include typical and suitable ingredients for rubber or elastomer formulations and compounds, such as accelerators, such as guanidines, thiazoles, thiurams, sulfenamides, thioureas, dithiocarbamates, and xanthanates. The emulsions contemplated herein may further include activators, such as zinc oxide; crosslinkers and curing agents, such as elemental sulfur, monosulfide donors, disulfide donors, such as tetramethylthiuram disulfide and tetraethylthiuram disulfide; and / or polysulfide donors, such as xanthogen polysulfide and dipentamethylenethiuram tetrasulfide. The emulsions contemplated herein may further include antioxidants and / or antiozonants. At least one suitable antioxidant is Wingstay L. The emulsions contemplated herein may further include surfactants, such as sodium dodecyl sulfate and polyvinyl alcohol. The emulsions contemplated herein may further include rheology modifiers, such as various clays and aluminosilicates, pH adjusters, such as hydroxides, e.g., potassium hydroxide, pigments, treating agents, and / or fillers known to those skilled in the art.

[0016] The term "polymer" generally includes, but is not limited to, homopolymers, copolymers, such as, by way of example, block, graft, random and alternating copolymers, terpolymers, etc. Furthermore, unless otherwise specifically limited, the term "polymer" includes all possible geometric configurations of the molecules. These configurations include, but are not limited to, isotactic, syndiotactic, and random symmetries.

[0017] The term "thermoplastic" generally includes polymeric materials that are reversibly flexible, moldable, and can be heated above a certain temperature and solidify upon cooling. The term "thermoset" generally includes polymeric materials that become tough after heating and solidifying, and cannot be reheated and remolded after initial molding. The term "thermoplastic elastomer" (TPE) refers to a class of copolymers that contain both thermoplastic and thermoset segments, resulting in materials with properties of both segments. The term "rubber" generally refers to elastomers made from natural rubber latex or synthetic elastomers.

[0018] A method for producing synthetic polyisoprene articles involves using an emulsion of synthetic polyisoprene resin catalyzed with a Ziegler-Natta catalyst. Typically, the synthetic polyisoprene particles of the Ziegler-Natta-catalyzed polyisoprene material contain 96% or more cis-1,4-polyisoprene. The synthetic polyisoprene particles may have a median particle size ranging from approximately 0.2 to 2 micrometers, preferably 0.2 to 1.5 micrometers. An exemplary synthetic polyisoprene material is supplied by BST Elastomer Co., Ltd., Thailand. The method may further include pre-vulcanization and post-vulcanization compositions along with conventional emulsion additives, such as stabilizers, pH control agents, antioxidants, and preservatives. A typical synthetic polyisoprene latex composition is provided in terms of 100 parts by weight of dry rubber (PHR). During compounding, the components of the latex composition may be suspended in aqueous and / or organic solvents.

[0019] Typically, the pre-vulcanizing composition contains sulfur in the range of 0.6 to 1.8 PHR. The accelerator package includes zinc diethyldithiocarbamate (ZDEC) and / or zinc dibutyldithiocarbamate (ZDBC) accelerators, and / or sodium dibutyldithiocarbamate (SDBC) accelerators, diisopropyl xanthogen polysulfide (DIXP) accelerators, and / or dipentamethylenethiuram tetrasulfide (DPTT) accelerators. The pre-vulcanizing composition may contain a total accelerator content in the range of 0.6 to 2.5 PHR. The pre-vulcanizing composition may contain a zinc oxide activator. The pre-vulcanizing composition may contain a surfactant, i.e., a wetting agent. The surfactant may be a salt of a fatty acid, such as sodium stearate, sodium oleate, or potassium caprylate. Some embodiments contain more than one surfactant, such as potassium caprylate, also known as the potassium salt of octanic acid, and sodium dodecylbenzenesulfonate (SDBS). An exemplary embodiment includes a surfactant package having potassium caprylate, sodium dodecylbenzene sulfonate (SDBS), and polyoxyethylene cetyl / stearyl ether in the range of 0.3 to approximately 1.5 PHR. An antioxidant and preservative package includes a butylated reaction product of p-cresol and, optionally, dicyclopentadiene in the range of 0.3 to approximately 1.0 PHR.

[0020] The sulfur in the pre-vulcanization package is, for example, elemental sulfur, typically having a high soluble sulfur content of the S8 ring structure. The pre-vulcanization composition further includes an accelerator. For example, an accelerator capable of destroying or splitting the S8 sulfur ring structure is zinc dithiocarbamate. Reference to a "high soluble sulfur content" means that sufficient soluble sulfur is present in the aqueous latex emulsion to penetrate into the latex particles present and crosslink during curing, achieving commercially acceptable articles, such as condoms and / or gloves. Pre-vulcanization of the synthetic latex particles in the latex generally occurs over a period of time, e.g., 9 hours to 2 days, depending on the temperature of the latex, which is in the range of 20°C to 30°C. The degree of pre-vulcanization at different points after initial compounding of the synthetic latex particles can be monitored by at least one of four tests. The equilibrium swelling test uses any suitable solvent and measures the equilibrium swelling of a film dried from the synthetic latex. The Relaxation Modulus Test evaluates the relaxation modulus at 100% elongation (MR100) of films dried from melted latex vulcanization. Similarly, the Pre-vulcanization Relaxation Modulus Test (PRM) measures the relaxation modulus at 100% elongation of pre-vulcanized films.

[0021] The Toluene Swell Index (TSI) test can be used to measure the level of crosslinking by immersing a dried cast film sample in toluene and calculating the swelling ratio. The TSI can be substituted for the isopropanol index test. A film of the formulated latex is cast to produce a film thickness of 0.10-0.15 mm, and the film is dried at 50 + / - 3 degrees Celsius for 10 minutes and / or the film is allowed to stand at ambient temperature until it is completely dry. A powder such as cornstarch or CaCO3 is used to release the film to prevent the film surface from sticking to itself. Disk samples are cut with a die cutter. The film disks are submerged in toluene for 60 minutes. The diameter of the swollen film is measured. The % swelling is calculated by subtracting the original disk diameter from the swollen film diameter and dividing by the original film diameter. The latex particles progress from an uncrosslinked stage (index > 220%), to a partially crosslinked stage (index < 220%), then to a semi-crosslinked stage (index < 180%), and finally to a fully crosslinked stage (index < 100%) as pre-vulcanization sulfur is incorporated into the particles.

[0022] A compounding method according to an embodiment of the present disclosure involves dissolving the latex composition in an aqueous solvent and periodically stirring, and examining the penetration of the pre-vulcanizing agent into the synthetic polyisoprene particles, for example, by using the isopropanol index test. Polyisoprene latex has an inherent tendency to aggregate and "surface harden" due to peripheral reactions with sulfur catalyzed by ZDBC or ZDEC, i.e., the outer surface hardens, preventing internal molecular crosslinking. The presence of surfactants and the creation of sulfur S8 chain openings allow sulfur to diffuse into the particles. In other words, sulfur diffusion into the particles, i.e., "core hardening," can occur, allowing internal molecular crosslinking. Latex articles or products containing core-hardened structures are stronger than otherwise similar latex articles or products with surface-hardened structures.

[0023] The pre-vulcanization composition provides sulfur to synthetic polyisoprene latex particles in an aqueous synthetic polyisoprene emulsion to pre-vulcanize the intra-particle regions. During pre-vulcanization, the sulfur ring structure is broken by the catalytic action of an accelerator, e.g., zinc dithiocarbamate, and penetrates the polyisoprene particles, first interacting with the isoprene double bonds therein.

[0024] Without intending to be bound by theory, it is believed that the penetration of the components of the pre-vulcanization composition into the polyisoprene particles is a function of a diffusion process, which may be a linear function of time. The component penetration involves an exponential function of temperature, reflecting a heat-activated process. Therefore, increasing the temperature by a few degrees during the pre-vulcanization step increases the pre-vulcanization rate. For example, pre-vulcanization at room temperature may take about 3-5 days or about 9 days, while pre-vulcanization at, for example, about 50-70°C may take about 3-7 hours. Without pre-vulcanization of the synthetic polyisoprene particles, crosslinking occurs primarily at the periphery of the synthetic polyisoprene particles (i.e., surface hardening), resulting in weak particles. Attempts to crosslink the inter-particle regions within the particle clusters only during post-vulcanization, as described below, result in over-crosslinking of the intra-particle regions, which in turn results in a latex product with poor elastic properties.

[0025] The post-vulcanization composition contains amorphous or polysulfur, which is insoluble at latex emulsion temperatures (e.g., 20-40°C) but becomes soluble at vulcanization or cure temperatures (e.g., 110-150°C). Generally, the post-vulcanization composition contains an accelerator, such as, but not limited to, zinc diethyldithiocarbamate (ZDEC), zinc dibutyldithiocarbamate (ZDBC), sodium diethyldithiocarbamate (SDEC), sodium dibutyldithiocarbamate (SDBC), a thiuram compound, and a xanthogen. Examples of suitable xanthogens include, but are not limited to, diisopropyl xanthogen polysulfide (DIXP), diisopropyl xanthogen, tetraethylthiuram disulfide, and xanthogen sulfide. DIXP is a preferred xanthogen due to its polysulfide-donating properties. The post-vulcanization composition may further contain a thiuram accelerator. An example of a polysulfide thiuram accelerator is dipentamethylene thiuram tetrasulfide (DPTT). Another example of a thiuram compound is tetrabenzyl thiuram disulfide. Zinc oxide may also be added as an activator.

[0026] The post-vulcanization composition provides the ability to crosslink the inter- or inter-particle regions of the synthetic polyisoprene, thereby ensuring a high quality, substantially uniformly cured synthetic polyisoprene product.

[0027] The post-vulcanization composition activates interparticle crosslinking at temperatures of, for example, 100-150°C. In addition, the post-vulcanization process also crosslinks the synthetic polyisoprene particles with sulfur. Such post-vulcanization results in a more homogeneous latex coating with greater strength and elongation properties. The resulting composition is stable at 20-25°C for up to approximately five days, making it useful for production lines.

[0028] Table 1 shows at least one exemplary embodiment of a Ziegler-Natta (ZN) catalyzed synthetic polyisoprene resin latex composition for producing polymeric articles. The latex composition is preferably water-based. [Table 1]

[0029] Table 2 below shows a comparison of the pre-vulcanization behavior of an exemplary anionic polyisoprene and an exemplary Ziegler-Natta catalyzed synthetic polyisoprene resin. [Table 2]

[0030] The present disclosure also provides a method for forming a synthetic polyisoprene polymer article. The method includes depositing an elastomeric coating of Ziegler-Natta catalyzed polyisoprene material on a former and curing the elastomeric coating to form an elastomeric layer of the polymer article. The depositing step can include dipping the coagulant-free or coagulant-coated former at least once into an emulsion of Ziegler-Natta catalyzed polyisoprene material (which may be an aqueous latex composition according to Table 1 having pre-vulcanized particles), forming a thin layer of latex or elastomeric coating having individual particles of pre-vulcanized synthetic polyisoprene on the surface of the former. The former can be any suitable former known in the art. The inventive composition is particularly useful for laminating onto formers for condoms and gloves.

[0031] The Ziegler-Natta catalyzed formulation embodiments disclosed in Table 1 (the ZN PI resins in Table 2 can be used), as well as other Ziegler-Natta catalyzed formulations, can produce condoms with lighter colors than natural rubber condoms, allowing for the production of a wider range of colored condoms while maintaining similar hardness and tensile strength properties. Furthermore, the residual solvent content in the condoms produced therefrom is lower, contributing to lower allergenicity. Furthermore, the allergenicity of condoms produced from Ziegler-Natta catalyzed formulations is lower compared to natural rubber and anionic formulations due to the lower amounts of accelerators and sulfur. The branched molecular structure of Ziegler-Natta catalyzed synthetic polyisoprene provides greater strength than the linear molecular structure of latex produced by anionic catalysts. Ziegler-Natta catalyzed synthetic polyisoprene also contains a greater amount of cis character, e.g., cis-1,4 isomer, of the polyisoprene molecule than anionically catalyzed polyisoprene, resulting in improved strength properties for products made with Ziegler-Natta catalyzed synthetic polyisoprene.

[0032] Additionally, the exemplary Ziegler-Natta catalyzed formulations of Table 1 potentially have a lower total solids content, allowing for the production of thinner condoms. Additionally, the exemplary Ziegler-Natta catalyzed formulations of Table 1 potentially have a lower viscosity during the dipping process, allowing for thinner condoms to be produced therefrom. Lower viscosity also allows for faster line speeds during production. In at least some embodiments, unlike other condom manufactures, a coagulant can be placed on the condom former prior to the placement of the Ziegler-Natta catalyzed polymer coating on the former, allowing for stronger condoms to be produced at similar thicknesses compared to anionically polymerized condom formulations.

[0033] Additionally, the Ziegler-Natta catalyzed formulations in Table 1 produce smaller particle sizes, which allow for thinner films and improved user sensitivity during intercourse and / or glove use. Smaller particles also exhibit improved cross-linking, which improves the processability of thinner products. For example, this prevents condoms or gloves from collapsing during the washing process and allows the powder to coat evenly both inside and outside, thereby reducing defects.

[0034] Table 3 lists a typical dipping method for producing condoms using pre-vulcanized Ziegler-Natta catalyzed polyisoprene resin as described above. A similar method can be created for synthetic polyisoprene surgical gloves. [Table 3]

[0035] The dipping process for condoms using surfactant-stabilized, pre-vulcanized synthetic polyisoprene latex compositions is typically a five-day period, e.g., within the average lifespan of a synthetic polyisoprene latex emulsion tank. The condom former is dipped into the composition in the first dip. The wall thickness of the latex coating is controlled by the viscosity of the latex, which is a function of the total solids content of the composition in the dip tank. The speed at which the former moves during dipping also affects the wall thickness. The latex coating that coats the former is dried at approximately 60-100°C for approximately 1-3 minutes. The latex coating on the former is optionally dipped again into the composition to apply a second dip coat. The latex coating after the second dip is dried at approximately 60-80°C for approximately 1-3 minutes. The open end of the condom is rolled to create a bead ring distal to the tip of the closed end of the condom.

[0036] The coating can be post-vulcanized by heating the coating, for example, to about 110-150°C for approximately 8-15 minutes to form the elastomeric layer of the condom. An exemplary embodiment includes post-vulcanization, which is achieved by heating in an oven at approximately 120°C for approximately 12 minutes. During this period, the interparticle regions are crosslinked. The intraparticle regions also undergo further crosslinking, producing a more homogeneous latex product. The condom is optionally leached in water at approximately 70-80°C for approximately 1-2 minutes to remove residual surfactants and crosslinking agents from the condom. The condom is then stripped from the former. The resulting latex article, e.g., a condom, exhibits higher strength and improved stretchability, even when synthetic polyisoprene with low stereoregularity is used. Synthetic polyisoprene articles do not contain irritating proteins that contribute to latex sensitivity issues.

[0037] Embodiments according to the present disclosure include the use of a coagulant solution to wet the former, an exemplary solution being 5% calcium nitrate in water, although other concentrations are possible as known to those skilled in the art, such as aqueous solutions ranging in concentration from 6-40% calcium nitrate. Other salts, such as calcium chloride, calcium citrate, aluminum sulfate, etc., and / or mixtures thereof, may be used. Additionally, the coagulant solution may be aqueous, alcoholic, or a mixture of aqueous and alcoholic solutions / solvents. Weak acid solutions, such as formic acid, acetic acid, and other low-pKa acids known to those skilled in the art, may also be used as coagulants.

[0038] Embodiments according to the present disclosure include the use of pre-vulcanization and post-vulcanization techniques, which are disclosed in commonly assigned U.S. Patent Nos. 8,087,412; 8,464,719; 9,074,027; and 9,074,029, which are incorporated by reference in their entireties. c Methods for determining .alpha. are disclosed in U.S. Patent Nos. 8,087,412; 8,464,719; 9,074,027; and 9,074,029.

[0039] Embodiment Embodiment 1. A polymeric article comprising an elastomeric layer comprising cured synthetic polyisoprene particles comprising a Ziegler-Natta catalyzed polyisoprene material.

[0040] Embodiment 2. The polymeric article of any preceding embodiment, wherein the synthetic polyisoprene particles are pre-vulcanized.

[0041] Embodiment 3. The polymeric article of any preceding embodiment, wherein the Ziegler-Natta catalyzed polyisoprene material comprises a branched macrostructure.

[0042] Embodiment 4. The polymeric article of any preceding embodiment, wherein the Ziegler-Natta catalyzed polyisoprene material comprises a cis-1,4 isomer content of 95% by weight or greater.

[0043] Embodiment 5. The polymeric article of any preceding embodiment, wherein the Ziegler-Natta catalyzed polyisoprene material comprises about 96% to 97% by weight of a cis-1,4 isomer content.

[0044] Embodiment 6. The polymeric article of any preceding embodiment, wherein the Ziegler-Natta catalyzed polyisoprene material comprises a trans-1,4 isomer content of 1 wt.% or less.

[0045] Embodiment 7. The polymeric article of any preceding embodiment, wherein the Ziegler-Natta catalyzed polyisoprene material comprises a 3,4 isomer content of 5% by weight or less.

[0046] Embodiment 8. The polymeric article of any preceding embodiment, wherein the article has a thickness in the range of 0.030 to 0.065 mm.

[0047] Embodiment 9. The polymeric article of any preceding embodiment, wherein the elastomeric layer comprises a post-vulcanized structure having a crosslink molecular weight (Mc) of less than 11,000 g / mol.

[0048] Embodiment 10. The polymeric article of any preceding embodiment, wherein the synthetic polyisoprene particles have a median particle size in the range of approximately 0.2 to 2 micrometers, or wherein the synthetic polyisoprene particles have a median particle size in the range of approximately 0.2 to 1.5 micrometers.

[0049] Embodiment 11. The polymeric article of any preceding embodiment, wherein the synthetic polyisoprene particles are bonded to one another by polyisoprene intra-particle and polyisoprene inter-particle crosslinks.

[0050] Embodiment 12. The polymeric article of any preceding embodiment in the form of a condom.

[0051] Embodiment 13. A condom comprising an elastomeric layer comprising pre-vulcanized cured synthetic polyisoprene particles, the synthetic polyisoprene particles comprising a Ziegler-Natta catalyzed polyisoprene material having a cis-1,4 isomer content of 95% or more by weight; a trans-1,4 isomer content of 1% or less by weight; and a 3,4 isomer content of 5% or less by weight.

[0052] Embodiment 14. The condom of any preceding embodiment, wherein the elastomeric layer forms an open end, a closed end, and a tubular sheath extending from the closed end to the open end.

[0053] Embodiment 15. The condom of any of embodiments 13 through the preceding embodiments, wherein the Ziegler-Natta catalyzed polyisoprene material comprises a branched macrostructure.

[0054] Embodiment 16. A condom of any of embodiments 13 to the preceding embodiments, wherein the elastomeric layer comprises a post-vulcanized structure having a molecular weight between crosslinks (Mc) of less than 11,000 g / mol.

[0055] Embodiment 17. The condom of embodiment 13 to any of the preceding embodiments, wherein the synthetic polyisoprene particles have a median particle size in the range of approximately 0.2 to 1.5 micrometers.

[0056] Embodiment 18. The polymeric article of any of embodiments 13 through the preceding embodiments, wherein the synthetic polyisoprene particles are bonded to one another by polyisoprene intra-particle and polyisoprene inter-particle crosslinks.

[0057] Embodiment 19. A method for producing a polymeric article, comprising: disposing an elastomeric coating of Ziegler-Natta catalyzed polyisoprene material on a former; and curing the elastomeric coating to form an elastomeric layer of the polymeric article.

[0058] Embodiment 20. The method of the previous embodiment, wherein disposing the elastomeric coating on the former comprises dipping the former into an emulsion of Ziegler-Natta catalyzed polyisoprene material.

[0059] Embodiment 21. The method of any of embodiments 19 through the preceding embodiments, wherein the emulsion of Ziegler-Natta catalyzed polyisoprene material is pre-vulcanized before immersing the former.

[0060] Embodiment 22. The method of any of embodiments 19 through the preceding embodiments, wherein the polymeric article comprises a condom, and the elastomeric layer forms an open end, a closed end, and a tubular sheath extending from the closed end to the open end.

[0061] Embodiment 23. The method of any of embodiments 19 through the preceding embodiments, wherein the synthetic polyisoprene particles are bonded to one another by polyisoprene intra-particle and polyisoprene inter-particle crosslinks.

[0062] Example Condoms were produced with the formulations in Table 1.

[0063] The method for measuring molecular weight distribution and calculating crosslink density involves cutting disks from condom samples and swelling the disk samples to equilibrium in toluene. The disks were initially weighed, and after swelling, they were weighed again. The equilibrium volume fraction of the swollen rubber was calculated using the equation shown below, where Pr is the density of rubber (0.92 g / cm 3 ), P s is the density of toluene (0.862 g / cm 3 ), W r is the weight of the rubber before swelling, and W s is the weight of the swollen rubber.

[0064] WrPrWrPr+Ws-WrPs

[0065] The volume fraction was used to calculate the crosslink density in the Florey-Rehner equation shown below, where n is the crosslink density and V s is the molar volume of the swelling solvent, toluene, which is 106.3 cm3 / mol, and V r is the volume fraction of the rubber phase in the swollen gel, and χ is the toluene-cis-polyisoprene interaction parameter, which is 0.39.

[0066] n=-1 / Vs(multiply)[ln (1-Vr)+Vr+χ Vr2][Vr13-0.5 Vr]

[0067] The molecular weight between crosslinking points was calculated using the following formula: Mc=Prn

[0068] Example 1 Table 4, shown below, reports the measured crosslink molecular weight and corresponding crosslink density for some of the synthetic polyisoprene condoms produced according to embodiments of the subject disclosure. The higher the crosslink molecular weight, the lower the crosslink density.

[0069] The data presented demonstrate that the process of the present disclosure results in synthetic polyisoprene condoms with highly consistent molecular weights between crosslinks, providing condoms with satisfactory mechanical properties. c ) is 0.0000845 mol / cm 3 , which is 0.0000159 mol / cm 3 This is comparable to that of natural rubber, which has a crosslink density of 1000 kJ / g. [Table 4]

[0070] FIG. 1 shows a first transmission electron microscope (TEM) image of the surface of a condom according to an embodiment of the present disclosure.

[0071] FIG. 2 shows a second TEM image of the surface of a condom according to an embodiment of the present disclosure.

[0072] FIG. 3 shows a third TEM image of the surface of a condom according to an embodiment of the present disclosure.

[0073] FIG. 4 shows a fourth TEM image of the surface of a condom according to an embodiment of the present disclosure.

[0074] The condoms studied in the first, second, third, and fourth TEM images were prepared as follows: Each condom was washed in propan-2-ol to remove lubricant and then immersed in propan-2-ol containing a small amount of talc to prevent adhesion and facilitate handling. The condoms were then allowed to air dry. A number of rings were cut from the condoms using a parallel twin-blade cutter with blades nominally 10 mm apart. These rings were used for two analytical methods: network visualization by TEM and Vr measurement by equilibrium swelling.

[0075] Network visualization. After extraction in acetone overnight, condom samples were swollen and equilibrated in styrene. The samples were then transferred to gelatin capsules and polymerized by heating. Ultrathin sections were then prepared at room temperature using a glass knife by ultrathin sectioning. Sections were collected on water-filled plates, relaxed in xylene vapor, and then collected on TEM grids. The sections were then stained with osmium tetroxide vapor for 1 hour. Osmium tetroxide reacts with carbon-carbon double bonds, thus making the rubber network appear darker than polystyrene. Representative TEM micrographs are provided in Figures 1-4 (see TEM 16803-6).

[0076] The latex particles were fairly tightly bound together, although the boundaries between particles were often visible. The sample also contained many voids, i.e., areas where the styrene had infiltrated and formed large, thin regions. Some of these voids contained small, dark particles, so it is possible that most or all of them were caused by styrene forming pools around these particles that were not bound to the rubber. Voids that appeared empty may actually contain invisible particles because they were located above or below the section.

[0077] There are also some small dark patches inside some of the rubber particles: these do not look like particles, but are thought to be small regions of the rubber network that have some electron-dense (i.e., high atomic number) material attached to them.

[0078] The uncertainty for the scale bar dimensions is ±10% for all TEM micrographs.

[0079] Latex particles, i.e., synthetic polyisoprene particles catalyzed with a Ziegler-Natta catalyst, showed tight binding.

[0080] All numerical values ​​listed herein are exemplary and should not be considered limiting, and include ranges therebetween, with or without endpoints. Optionally included ranges can be from the integer value to the recited digit or the next lower digit. For example, if the lower range value is 0.1, optional included endpoints can be 0.2, 0.3, 0.4...1.1, 1.2, etc., as well as 1, 2, 3, etc.; if the upper range value is 10, optional included endpoints can be 7, 6, etc., as well as 7.9, 7.8, etc.

[0081] For ease of understanding, the same reference numerals have been used, where possible, to designate equivalent elements common to the figures. The figures are not drawn to scale and may be simplified for clarity. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.

[0082] It should be understood that various changes and modifications to the embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present disclosure and without diminishing its attendant advantages. Therefore, it is intended that such changes and modifications be covered by the appended claims.

[0083] All references, including publications, patent applications, and patents, cited in this specification are hereby incorporated by reference to the same extent as if each reference was individually and specifically indicated to be incorporated by reference and was set forth herein in its entirety.

Claims

1. A condom comprising an elastomer layer containing pre-vulcanized cured synthetic polyisoprene particles, The aforementioned synthetic polyisoprene particles contain sulfur crosslinks within the particles, The aforementioned synthetic polyisoprene particles are 95% by weight or more of cis-1,4 isomer content; trans-1,4 isomer content of 1% by weight or less; and Content of 3,4 isomers of 5% by weight or less Includes a polyisoprene material catalyzed by Ziegler-Natta, A condom comprising a post-vulcanization structure in which the elastomer layer has an inter-crosslinking molecular weight (Mc) of less than 11,000 g / mol.

2. The condom according to claim 1, wherein the elastomer layer forms an open end, a closed end, and a tubular sheath extending from the closed end to the open end.

3. The condom according to claim 1, wherein the polyisoprene material catalyzed by Ziegler-Natta includes a branched macrostructure.

4. The condom according to claim 1, wherein the synthetic polyisoprene particles have a particle median diameter in the range of 0.2 to 1.5 micrometers.

5. The condom according to any one of claims 1 to 4, wherein the synthetic polyisoprene particles are bonded to each other by inter-polyisoprene crosslinking and inter-polyisoprene crosslinking.

6. A method for producing a condom, Pre-vulcanizing an emulsion containing polyisoprene material catalyzed by Ziegler-Natta, sulfur, and one or more surfactants; Post-vulcanization of polyisoprene material catalyzed by Ziegler-Natta with a post-vulcanization composition containing sulfur; Placing an elastomer coating of polyisoprene material catalyzed by Ziegler-Natta onto a former; and The elastomer coating is cured to form the elastomer layer of the condom. Includes, The method wherein the elastomer layer comprises a post-vulcanization structure having an inter-crosslinking molecular weight (Mc) of less than 11,000 g / mol.

7. The method according to claim 6, wherein the arrangement of the elastomer coating on the former includes immersing the former in an emulsion of polyisoprene material catalyzed by the Ziegler-Natta.

8. The method according to claim 6 or 7, wherein the elastomer layer forms an open end, a closed end, and a tubular sheath extending from the closed end to the open end.

9. The method according to claim 6, wherein the cured synthetic polyisoprene particles include both intra-polyisoprene sulfur crosslinking and inter-polyisoprene sulfur crosslinking.

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