Laminates with improved tensile properties

Abstract

The present invention relates to a method of making an elastic laminate, the method comprising: providing a first aqueous coating composition comprising a first polymer and discrete silica nanoparticles, where the first polymer is a polyurethane; providing a second aqueous coating composition comprising a second polymer; coating a substrate with the first aqueous coating composition to form a first film on the substrate; coating the first film with the second aqueous coating composition to form a second film on the first film; and removing the base material. In another aspect, the present invention relates to an elastic laminate comprising a plurality of polymeric films and one or more interfaces wherein each pair of adjacent films define one interface wherein at least one of the plurality of polymeric films comprises a polyurethane wherein the laminate comprises silica nanoparticles, and wherein at least 60% by weight of the silica nanoparticles are present at one or more interfaces defined at least in part by the polyurethane-containing film. In both cases, the laminate may be a condom, and the invention also relates to a condom obtained or obtainable by the process of the invention.

Description

[0001] The present invention relates to a laminate having improved tensile properties and a method for making the same. The laminate is an elastic article, such as a film intended for use in contact with the human body (e.g., skin), such as during sexual activity or as a barrier during medical procedures. In one embodiment, the present invention provides a condom having improved tensile strength compared to prior art condoms while maintaining comparable softness and elasticity.

[0002] The ability of a condom to maintain its integrity throughout sexual intercourse is crucial to its role as a contraceptive measure and to prevent the spread of sexually transmitted infections. Condoms must also be highly deformable while being thin and flexible enough to allow for tactile and sensory sensitivity. Many polymeric materials have been found suitable for this purpose. Natural rubber latex ("NRL") has been used as a condom material for many years, while synthetic polyisoprene ("PI") condoms have been developed as an alternative for those allergic to latex. Polyurethane ("PU") condoms are also known. Due to the inherent strength of the PU material, PU condoms can be made with thinner walls than NRL and PI condoms, but are generally less elastic or soft. Thin condoms are desirable to some consumers, in part because they can withstand less of a reduction in feel and pleasure than condoms with thicker walls. Polyurethane condoms can also exhibit improved heat transfer properties compared to NRL, giving consumers a more pleasurable experience along with enhanced sensation.

[0003] Various attempts have been made to improve the mechanical properties of the elastic films that form condoms. However, it is often difficult to provide an improvement in one mechanical property without adversely affecting another mechanical property. Reinforcements previously used in elastomers include silica, carbon black, carbon nanotubes, and graphene. However, due to the rigidity of these materials, their addition also tends to increase the hardness and stiffness of the material (reflected in an increase in the elastic modulus) and reduce the elongation at break. This is disadvantageous for condom applications because high-modulus materials may reduce sensation or sensitivity, so their use is generally avoided.

[0004] Similar principles apply to other elastic laminate products, such as gloves, finger cots, dental dams, balloon catheters, etc. For example, these products can be made by dipping.

[0005] US 2017 / 0333602 A1 discloses the use of nanocellulose as an additive to elastomeric materials (which may include polyurethanes) for the purpose of providing enhanced tensile strength and toughness while avoiding a significant increase in elastic modulus or stiffness.

[0006] There remains a need for further methods to improve the tensile properties of laminates, such as condoms. In particular, there remains a need for further methods to improve the tensile strength of a laminate without significantly affecting its elastic modulus.

[0007] According to a first aspect, the present invention provides a method for preparing an elastic laminate, the method comprising:

[0008] (i) providing a first aqueous coating composition comprising a first polymer and discrete silica nanoparticles, wherein the first polymer is a polyurethane;

[0009] (ii) providing a second aqueous coating composition comprising a second polymer;

[0010] (iii) coating a substrate with the first aqueous coating composition to form a first film on the substrate;

[0011] (iv) coating the first film with the second aqueous coating composition to form a second film on the first film; and

[0012] (v) removing the substrate.

[0013] In one embodiment, these goods are condoms. In one embodiment, the first aqueous coating composition is applied to the substrate by immersing the substrate in the first aqueous coating composition. When the substrate is a molding model (for example, a condom model), the method can include removing the laminate from the substrate to provide the molded article (for example, a condom). In another embodiment, at first the laminated film can be removed from the substrate, then for example, formed into goods by thermoforming.

[0014] The substrate is coated with multiple films in sequence to achieve the desired thickness of the elastomer and achieve a consistent thickness along the length of the condom or other product. However, the present inventors believe that the interface between the films constitutes a structural weakness. They have found that incorporating discrete silica nanoparticles into at least the first film-forming composition (comprising polyurethane) improves the tensile strength of the condom while not significantly increasing the elastic modulus compared to an equivalent condom lacking the discrete silica nanoparticles. In particular, the present inventors have found that discrete silica nanoparticles (unlike other forms of silica) can migrate to the interface between the first coating and the ambient air, while only a limited amount remains dispersed within the bulk polymer matrix. This means that when the second film is formed on the first film, the silica nanoparticles are present at the interface between the two films. Without wishing to be bound by theory, it is believed that the silica nanoparticles present at the interface can provide reinforcement at the interface, which would otherwise constitute an inherent structural weakness, without significantly interfering with the performance of the bulk elastomer. Because the silica does not accumulate in large quantities in the bulk, the modulus of the elastomer or its ability to withstand changes when subjected to strain is not affected. Thus, the tensile strength of the condom is increased without a concomitant significant increase in the elastic modulus. It is believed that the same principle applies to other laminates, especially thin laminates.

[0015] According to a second aspect, the present invention provides an elastic laminate (preferably a condom) obtained or obtainable by the process of the first aspect.

[0016] According to a third aspect, the present invention provides an elastic laminate comprising a plurality of polymeric films and one or more interfaces, wherein each pair of adjacent films defines one said interface,

[0017] wherein at least one of the plurality of polymer films comprises polyurethane,

[0018] wherein the elastic laminate comprises silica nanoparticles, and

[0019] wherein at least 60 weight percent of the silica nanoparticles are present at one or more interfaces at least partially defined by a film comprising the polyurethane.

[0020] According to a fourth aspect, the present invention provides a condom comprising a laminate comprising a plurality of elastic films and one or more interfaces, wherein each pair of adjacent elastic films defines one said interface,

[0021] wherein at least one of the plurality of elastic films comprises polyurethane,

[0022] wherein the laminate comprises silica nanoparticles, and

[0023] wherein at least 60 weight percent of the silica nanoparticles are present at one or more interfaces at least partially defined by a film comprising the polyurethane.

[0024] According to a fifth aspect, the present invention provides a sealed package comprising the condom of the second aspect or the fourth aspect.

[0025] The present invention will now be further described. In the following paragraphs, different aspects / embodiments of the present invention are defined in more detail. Each aspect / embodiment so defined can be combined with any other aspect / embodiment or multiple aspects / embodiments, unless clearly indicated to the contrary. In particular, any feature indicated as preferred or advantageous can be combined with any other feature or features indicated as preferred or advantageous.

[0026] The present invention provides a method for preparing an elastic laminate. In one embodiment, the laminate is a dipped article. The article can be used to be worn in or on the body. In one embodiment, the article is a film for contact with the human body (e.g., contact with the skin). The article can be used for sexual activity or used during medical procedures. Examples of laminates that can be manufactured by the present invention include condoms, dental dams, finger cots, gloves, and balloon catheters. In one embodiment, the laminate is less than 1 mm thick, preferably less than 500 microns thick, and most preferably less than 100 microns thick.

[0027] In one embodiment, the article is a condom. The condom is preferably a male condom, preferably a condom intended to cover substantially the entire penis. Alternatively, in some embodiments, the condom is a female condom.

[0028] The first step of the method includes providing a first aqueous coating composition comprising a first polymer and discrete silica nanoparticles. The first polymer is a polyurethane. The nature of the polyurethane is not particularly limited, as long as it can form a film having one or more mechanical properties (such as strength or flexibility) required for the product to be formed. For example, suitable polyurethanes for use as condom materials are known in the art. The polyurethane can be a polyether-based polyurethane, i.e., a polyurethane obtained by polymerizing a diisocyanate and a polyether. Alternatively, the polyurethane can be a polyester-based polyurethane, i.e., a polyurethane obtained by polymerizing a diisocyanate and a polyester. The polyurethane can be an aliphatic polyurethane, i.e., a polyurethane that does not include an aromatic structure. Alternatively, the polyurethane can be an aromatic polyurethane. The first polymer can be provided in a mixture with one or more other polyurethanes. It can be an elastomer or a thermoplastic elastomer, but is preferably an elastomer.

[0029] Preferably, the first polymer is hydrophobic. Preferably, the first polymer has a logarithmic partition coefficient (logP) greater than 1. The term "partition coefficient" is known in the art and refers to the octanol-water partition coefficient (P), i.e., the proportion of a substance distributed when it reaches equilibrium in a mixture of 1-octanol and water. The logarithmic partition coefficient is the logarithm of the partition coefficient to the base 10. A logP greater than 1 indicates hydrophobicity. Hydrophobic polymers may be advantageous in the present invention because they have a lower tendency to bind to discrete silica nanoparticles than hydrophilic polymers and therefore do not interfere with the migration of discrete silica nanoparticles to the air interface during the coating step. As described above, it is believed that the migration of discrete silica nanoparticles to the interface ultimately enables the present invention to provide improved tensile strength without a significant increase in elastic modulus.

[0030] As mentioned above, the first aqueous coating composition comprises discrete silicon dioxide ("silica") nanoparticles. "Nanoparticles" refers to particles with a diameter of 1 nm to 1000 nm. "Discrete" means that the particles are present in the first aqueous coating composition in an individualized or loosely bound form and are not fused together to form aggregates or agglomerates. In embodiments where the particles are loosely bound in the aqueous coating composition, they are still considered to be discrete (rather than fused together to form aggregates or agglomerates) because they can be separated again by stirring or dispersion. It should be understood that discrete silica nanoparticles are amorphous, i.e., non-crystalline. Preferably, discrete silica nanoparticles are non-porous. Preferably, discrete silica nanoparticles are spherical or substantially spherical.

[0031] The discrete silica particles used in the first aqueous coating composition should be distinguished from other forms of silica. The preparation of fumed silica involves the hydrolysis of silicon tetrachloride vapor in a hydrogen-oxygen flame. During the combustion process, roughly spherical molten particles are formed. These molten fumed silica spheres (commonly referred to as primary particles) fuse with each other by colliding at their contact points to form branched three-dimensional chain aggregates. Due to the fusion, the force required to break the aggregates is considerable and is generally considered irreversible. During the cooling and collection process, the aggregates undergo further collisions, which may cause some mechanical entanglement, thereby forming agglomerates. Compared to aggregates in which primary particles are fused together, agglomerates are considered to be loosely bound together by van der Waals forces and can be reversed (i.e., disaggregated) by properly dispersing the aggregates in a suitable medium. However, these aggregates cannot be reversed to form primary particles because the primary particles are fused. Due to aggregation and agglomeration, fumed silica cannot be considered to be composed of discrete nanoparticles.

[0032] Another amorphous form of silica is precipitated silica, which is formed from solutions containing silicates. Like fumed silica, the primary particles of precipitated silica form aggregates (fused primary particles) and agglomerates during the production process and therefore cannot be considered to consist of discrete nanoparticles. Precipitated silica is a porous form of amorphous silica.

[0033] Preferably, the discrete silicon nanoparticles used in the first aqueous coating composition comprise surface silanol (Si-OH) groups. That is, the silanol groups are preferably present on the surface of the nanoparticle. Due to the hydrophobic Si-O-Si part in the hydrophilic silanol groups on the surface and the silicon dioxide nanoparticle core, this silicon dioxide nanoparticle is amphipathic. Therefore, they can be adsorbed on the surface (air-water interface) of polymer-water droplet, thereby help them to migrate to the interface of the first film and air during the coating step, rather than staying in the bulk polymer matrix.

[0034] Preferably, the average particle size of the discrete silica nanoparticles is less than 100 nm, preferably less than 90 nm, less than 80 nm, less than 70 nm, less than 60 nm, less than 50 nm, less than 40 nm, less than 30 nm, less than 20 nm or less than 10 nm. Preferably, the average particle size is from 1 nm to 100 nm, more preferably from 2 nm to 50 nm, even more preferably from 4 nm to 20 nm, most preferably from 5 nm to 10 nm. For example, the average particle size can be measured by dynamic light scattering (DLS). Preferably, the average particle size is the volume weighted average particle size (D 4,3 ). It is believed that small particle sizes are advantageous in the present invention due in part to their enhanced ability to migrate to the coating-air interface during the coating step.

[0035] Preferably, the discrete silica nanoparticles have a BET surface area of ​​at least 200 m 2 / g, more preferably at least 250m 2 / g, most preferably at least 300m 2 It is believed that silica nanoparticles with higher surface areas may provide greater improvements in tensile strength.

[0036] Preferably, the first aqueous coating composition comprises the first polymer in an amount of at least 10 wt %, more preferably at least 15 wt %, at least 20 wt % or at least 25 wt % of the first aqueous coating polymer. Preferably, the first polymer is present in an amount of at most 60 wt %, at most 50 wt % or at most 40 wt % by weight of the first aqueous coating composition. In one embodiment, the first aqueous coating composition comprises the first polymer in an amount of 10 wt % to 50 wt %, more preferably 20 wt % to 40 wt % of the first aqueous coating composition weight.

[0037] Preferably, the first aqueous coating composition comprises from 0.1 wt% to 3 wt% discrete silica nanoparticles, more preferably from 0.2 wt% to 4 wt%, still more preferably from 0.3 wt% to 2 wt%, and even more preferably from 0.5 wt% to 1 wt%, based on the weight of the first aqueous coating composition.

[0038] Preferably, the first aqueous coating composition comprises the first polymer and discrete silica nanoparticles in a weight ratio of 5:1 to 200:1, more preferably 10:1 to 200:1, even more preferably 20:1 to 150:1, and most preferably 40:1 to 80:1.

[0039] The first step of the method of the present invention preferably comprises combining a source of a first polymer with a source of discrete silica nanoparticles to form a first aqueous coating composition. The source of the first polymer can be a dispersion of the first polymer in a liquid, preferably an aqueous dispersion. Thus, the source of the first polymer is preferably an aqueous polyurethane dispersion ("PUD"). Suitable PUDs for forming condoms and other articles are commercially available, for example, from Alberdingk Boley. U228.

[0040] Preferably, the source of discrete silica nanoparticles can be a dispersion of discrete silica nanoparticles in a liquid. Such dispersions are known in the art as "colloidal silica." It is believed that the use of colloidal silica rather than solid silica facilitates the dispersion of the nanoparticles and the migration of the nanoparticles to the interface. Preferably, the dispersion is an aqueous dispersion. Preferably, the pH of the aqueous dispersion is from 7 to 11, more preferably from 8 to 10. Suitable sources of silica nanoparticles for use in the present invention are SM colloidal silica, which is an aqueous dispersion.

[0041] The first aqueous coating composition may further comprise other ingredients typically included in polyurethane-based condom-forming materials. For example, the first aqueous coating composition may further comprise a crosslinking agent, such as a carbodiimide crosslinking agent, preferably in an amount of 0.2 to 5 wt %, more preferably 0.5 to 2 wt %, based on the weight of the first aqueous coating composition.

[0042] As alternatively or additionally, the first aqueous coating composition can also include surfactant, preferably, its amount is 0.05 % by weight to 1 % by weight, more preferably 0.1 % by weight to 0.5 % by weight of the first aqueous coating composition weight. It is believed that nano-silicon dioxide particles can cause the surface tension of the first aqueous coating composition to increase, making it more difficult to form a uniform layer on substrate. The adding of surfactant helps to reduce the surface tension of the first aqueous coating composition, making it easier to form a uniform layer on substrate. Suitable surfactants for reducing the aqueous coating composition surface tension are known in the art, including for example alkoxylated surfactants, for example polyether-modified siloxane surfactants.

[0043] The first aqueous coating composition preferably comprises 40 to 90 wt% water, more preferably 50 to 80 wt%, and even more preferably 60 to 75 wt%, based on the weight of the first aqueous coating composition.

[0044] The second step of the inventive method includes providing a second aqueous coating composition comprising a second polymer. The nature of the second polymer is not particularly limited, as long as it can form a film having one or more mechanical properties (e.g., strength or flexibility) required for the desired product (e.g., condom). Many suitable polymers are known in the art, such as polyurethane, polyisoprene, polyethylene, and copolymers of acrylonitrile and butadiene ("nitrile rubber") . Preferably, the second polymer is selected from polyisoprene, polyurethane, or a mixture thereof. Polyisoprene can be synthetic cis-1,4-polyisoprene. Alternatively, polyisoprene can be provided in the form of natural rubber latex ("NRL"). Natural rubber latex typically contains cis-1,4-polyisoprene and a small amount of impurities, such as proteins, lipids, carbohydrates, and inorganic salts. Synthetic polyisoprene does not contain allergenic proteins, such as those found in natural rubber latex, and is therefore suitable for users who are sensitive to latex.

[0045] Most preferably, the second polymer is a polyurethane.In this embodiment, each of the optional or preferred features described above with respect to the first polymer also applies to the second polymer.

[0046] The second polymer and the first polymer can be the same or different. For example, the first polymer can be polyurethane and the second polymer can be polyisoprene, or vice versa. As another example, the first polymer and the second polymer can be two different polyurethanes (e.g., having different molecular weights or monomer unit compositions). However, preferably, the first polymer and the second polymer are the same (i.e., the same polyurethane).

[0047] In some embodiments, the second aqueous coating composition may further comprise discrete silica nanoparticles. As will be explained below, such embodiments are particularly preferred when the method further comprises forming a third film on the second film.

[0048] In an embodiment in which the second aqueous coating composition also includes discrete silica nanoparticles, the second step of the method preferably includes combining a source of a second polymer with a source of discrete silica nanoparticles to form a second aqueous coating composition. The source of the second polymer can be a dispersion of the second polymer in a liquid, preferably an aqueous dispersion. As described above, when the second polymer is a polyurethane, the source of the second polymer is preferably an aqueous polyurethane dispersion ("PUD"). When the second polymer is polyisoprene, the source of the second polymer is preferably an aqueous polyisoprene dispersion, such as an aqueous dispersion of synthetic cis-1,4-polyisoprene or natural rubber latex. Suitable formulations of natural rubber latex and synthetic polyisoprene are known in the art. Each optional or preferred feature described above for the "source of discrete silica nanoparticles" described for the first aqueous coating composition is equally applicable to the second aqueous coating composition.

[0049] Each optional or preferred feature described above about the first coating composition and its constituent is equally applicable to the second aqueous coating composition.Preferably, the first aqueous coating composition and the second aqueous coating composition are identical.For example, the first aqueous coating composition and the second aqueous coating composition can constitute a single composition for the coating step described below.

[0050] The third step of the method comprises coating a substrate with the first aqueous coating composition to form a first film on the substrate. The substrate is subsequently removed and does not constitute a part for the finished product. In some embodiments, the substrate is a former. The term "former" is known in the art and, in the case of a condom mold, refers to a condom-shaped mold on which a polymer coating composition is applied to form a condom. For example, the former can be made of glass, plastic, or ceramic. In other embodiments, the substrate is a casting, plate, or sheet. In one embodiment, the substrate is a glass, plastic, or ceramic plate or sheet. In these embodiments, the first film is typically flat rather than taking the shape of the product to be formed.

[0051] The term "film" refers to a thin layer of polymer material, the thickness of which is typically in the order of a few micrometers or tens of micrometers, for example 5 μm to 30 μm.

[0052] The 3rd step preferably comprises that the first aqueous coating composition layer is applied on substrate, dries this first aqueous coating composition layer to form the first film.The first aqueous coating composition layer is applied on substrate and can relate to substrate being immersed in the first aqueous coating composition or the first aqueous coating composition is sprayed, brushed, cast or roll-coated on substrate.The first aqueous coating composition layer can be directly applied on substrate, or in some embodiments, before applying the first aqueous coating composition, coagulant is applied on substrate.In some embodiments, when applying the first aqueous coating composition layer, substrate is stationary.In other embodiments, when applying this layer, substrate is in mobile state.In the embodiment in which substrate is immersed in the first aqueous coating composition, the speed of changing dipping and / or taking-up can be used for the thickness of controlled layer.The drying step can be carried out by evaporating in an open atmosphere or in a baking oven or evaporator.In some embodiments, heating substrate is to promote drying.

[0053] As mentioned above, during the coating step, a considerable portion of discrete silica nanoparticles can migrate to the interface between the coating and the air. When forming the first film, these silica nanoparticles are fixed at the interface with the air. At this stage, at least some of the silica nanoparticles present at the interface can be loosely combined or aggregated with each other. Other silica nanoparticles present at the interface or in the polymer matrix body can maintain a fully individualized form. It should be understood that, even if some of the silica nanoparticles are loosely combined, they still do not fuse together to form the aggregates or agglomerates described above about the fumed silica.

[0054] Preferably, the temperature and duration of the drying step are sufficient to reduce the water content of the first film to less than 10% by weight, more preferably less than 5% by weight. The temperature and duration of the drying step may vary depending on the composition of the first aqueous coating composition (including the nature of the first polymer) and the thickness of the layer. The layer is preferably dried at a temperature of 40° C. to 100° C., more preferably 50° C. to 70° C., and / or for a drying time of 1 to 10 minutes, more preferably 3 to 7 minutes.

[0055] In some embodiments, the first aqueous coating composition layer undergoes a chemical change during the drying step. For example, in embodiments where the first aqueous coating composition comprises a crosslinker, crosslinks between polymer chains of the first polymer can form during the drying step.

[0056] In some embodiments, the thickness of the first film is 5 μm to 30 μm. The preferred thickness of the first film will vary depending on the number of coating steps and the desired thickness of the final product, which in turn will depend to some extent on the polymer material from which it is formed. For example, due to the inherent strength of polyurethane-based films, they can be sufficiently strong for use as condom material at a lower thickness than polyisoprene-based films. The thickness of the first film comprising polyurethane is preferably 5 μm to 15 μm, more preferably 6 μm to 10 μm.

[0057] The 4th step of the inventive method comprises applying the first film with the second aqueous coating composition to form the second film on the first film.It should be understood that the second aqueous coating composition is directly applied on the first film so that the second film and the first film directly contact, i.e., without any intermediate film or layer.The 4th step preferably comprises applying the second aqueous coating composition layer on the first film, drying this second aqueous coating composition layer to form the second film.The first film preferably remains on the base material within the duration of the 4th step.Therefore, the 4th step preferably comprises immersing the base material that scribbles film in the second aqueous coating composition, or by spraying, brushing, casting or roll-coating the first aqueous coating composition on the base material that scribbles film.Except the temperature and duration of the drying step and the thickness of the gained film, each optional or preferred feature described above about the 3rd step is equally applicable to the 4th step, and just the 4th step relates to coating the first film rather than base material itself.

[0058] The temperature and duration of the step of drying the second aqueous coating composition layer to form the second film will depend on the nature of the second polymer. In embodiments where the second polymer is polyurethane, the layer is preferably dried at a temperature of 40°C to 100°C, more preferably 50°C to 70°C, and / or for a drying time of 1 to 10 minutes, more preferably 3 to 7 minutes. In embodiments where the second polymer comprises polyisoprene provided in the form of natural rubber latex, the layer is preferably dried at a temperature of 50°C to 120°C, more preferably 60°C to 90°C, and / or for a drying time of 30 seconds to 5 minutes, more preferably 1 to 4 minutes. In embodiments where the second polymer is synthetic cis-1,4-polyisoprene, the layer is preferably dried at a temperature of 70°C to 130°C, more preferably 80°C to 120°C, and / or for a drying time of 30 seconds to 5 minutes, more preferably 1 to 4 minutes.

[0059] The preferred thickness of the second film will vary depending on the number of coating steps and the desired thickness of the final condom, which in turn will depend to some extent on the polymer material from which it is formed. For example, due to the inherent strength of polyurethane-based films, they can be sufficiently strong for use as condom materials at lower thicknesses than polyisoprene-based films. When the second polymer is polyurethane, the thickness of the second film is preferably 5 μm to 15 μm, more preferably 6 μm to 10 μm. When the second polymer is polyisoprene, the thickness of the second film is preferably 15 μm to 30 μm, more preferably 20 μm to 25 μm.

[0060] In embodiments where the first aqueous coating composition and the second aqueous coating composition are the same, the conditions (e.g., temperature and duration) of the third and fourth steps are preferably the same. Preferably, in embodiments where the first aqueous coating composition and the second aqueous coating composition are the same, the thickness of the first film is substantially the same as the thickness of the second film, or is within 10% of the thickness of the second film.

[0061] In some embodiments, the method further comprises providing a third aqueous coating composition comprising a third polymer, and between the fourth step and the fifth step (discussed below) of the inventive method, coating the second film with the third aqueous coating composition to form a third film on the second film. Each optional or preferred feature described above with respect to the second aqueous coating composition, coating step, and film is equally applicable to the third aqueous coating composition, coating step, and film. Preferably, the first, second, and third polymers (and preferably, the first, second, and third aqueous coating compositions) are identical. In other embodiments, at least two of the three polymers (or at least two of the three aqueous coating compositions) are identical, and one is different. For example, the first polymer can comprise polyurethane, the second polymer can comprise polyisoprene derived from natural rubber latex, and the third polymer can comprise polyurethane. Such an embodiment will result in the formation of a laminated PU-NRL-PU product, such as a condom. In other embodiments, all three polymers (or all three aqueous coating compositions) are different.

[0062] The number of coating steps is not particularly limited, as long as goods can not become too thick and can't reach desired purpose.For example, the method can also include providing the 4th aqueous coating composition that comprises the 4th polymer, and before the 5th step, apply the 3rd film to form the 4th film on the 3rd film with the 4th aqueous coating composition.The method can include one or more further continuous steps that provide aqueous coating composition and one or more further continuous coating steps.In some embodiments, the aqueous coating composition used in each step (or the polymer used in each coating step at least) is identical.In some embodiments, the method only includes three coating steps.In some embodiments, the method only includes two coating steps.

[0063] In some embodiments, the method further comprises heating the first film, the second film, and (if present) the substrate.

[0064] The third film and any subsequent films are subjected to a heating step. This heating step, if present, is performed before the fifth step (discussed below) of the method of the present invention. One purpose of this heating step is to completely dry the film if it was not completely dried in the previous drying step. The heating step may also induce or increase the formation of crosslinks between the polymer chains present in the film. In one embodiment, the film is heated to a temperature of 60°C to 150°C, preferably a temperature of 80°C to 140°C, and / or a heating time of 5 minutes to 20 minutes, preferably 8 minutes to 15 minutes.

[0065] In one embodiment, the fifth step of the method of the present invention includes removing the substrate to provide an article; or removing the substrate to provide a laminate, and forming an article from the laminate. In an embodiment in which the substrate is in the shape of a condom (e.g., a condom mold), the fifth step provides a condom. In an embodiment in which the substrate is a casting, plate, or sheet, the fifth step provides a laminate, which is then formed to form a condom. In some such embodiments, the step of forming a condom from the laminate includes heating the laminate and contacting the heated laminate with a mandril so that the laminate takes the shape of the mandril. Examples of suitable methods for forming laminates are disclosed in US 4576156A and US 5458936 A, the contents of which are incorporated herein by reference. In some embodiments, the fifth step involves peeling the film structure from the substrate. In some embodiments, before removing the substrate to provide the laminate, the film structure is leached (e.g., in an alkaline solution at a temperature of 20°C to 40°C).

[0066] In embodiments of the present invention where the article is a condom, the condom preferably has a thickness of from 10 μm to 60 μm. "Thickness" refers to the wall thickness (i.e., the combined thickness of the films forming the condom as defined herein), excluding any bead formed at the condom opening. The preferred thickness of the condom will vary depending, in part, on the polymeric material from which it is formed. Preferably, the condom has a thickness of from 10 μm to 30 μm, or from 10 μm to 25 μm, or from 10 μm to 20 μm. The increase in tensile strength provided by the discrete silicon nanoparticles of the present invention allows for the use of relatively thicker condoms.

[0067] Preferably, the tensile strength of the article (preferably a condom) is at least 10 MPa, or at least 20 MPa, or at least 30 MPa, or at least 40 MPa. In some embodiments, the tensile strength of the article (preferably a condom) is at most 100 MPa, or at most 90 MPa, or at most 80 MPa. The term "tensile strength" refers to the maximum stress that the article can withstand before breaking.

[0068] Preferably, the elastic modulus of the article (preferably a condom) at 300% elongation is at most 5 MPa, or at most 4 MPa, or at most 3.5 MPa. In these embodiments, the elastic modulus of the article (preferably a condom) at 300% elongation may be at least 2 MPa, or at least 2.5 MPa, or at least 3 MPa. The term "elastic modulus" refers to the stress of an article at a specific elongation and is related to the hardness of the material. Articles with a lower elastic modulus are softer and are generally perceived as having a better feel.

[0069] Preferably, the elastic modulus of the article (preferably a condom) at 500% elongation is at most 8 MPa, or at most 7 MPa, or at most 6 MPa, or at most 5.5 MPa. In these embodiments, the elastic modulus of the article (preferably a condom) at 500% elongation may be at least 2.5 MPa, or at least 3 MPa.

[0070] Preferably, the tensile strength and elastic modulus are determined according to the procedure described in Example 2. Preferably, the tensile strength and elastic modulus are determined according to ISO standard ISO 4074:2015.

[0071] Preferably, the tensile strength of the article (preferably a condom) is at least 10% higher, more preferably at least 20% higher, and even more preferably at least 30% higher than the tensile strength of an article (preferably a condom) prepared by the same process but without the use of discrete silica nanoparticles.

[0072] Preferably, the elastic modulus of the article (preferably a condom) at 300% elongation is within 10%, preferably within 5%, of the elastic modulus of an article (preferably a condom) prepared by the same process but without the use of discrete silica nanoparticles.

[0073] Preferably, the elastic modulus of the article (preferably a condom) at 500% elongation is within 10%, preferably within 5%, of the elastic modulus of an article (preferably a condom) prepared by the same process but without the use of discrete silica nanoparticles.

[0074] In some embodiments, where the article is intended to be worn on the body, such as a condom, glove, or finger cot (preferably a condom), the method further comprises coating one or more surfaces of the article with a finishing powder. The one or more surfaces may be interior and / or exterior, preferably both. In the context of male condoms, "inside" refers to the side facing the penis, while "outside" refers to the side facing the wearer's partner; in the context of gloves or finger cots, "inside" refers to the side facing the fingers. In embodiments where the method further comprises coating one or more surfaces of the condom with a finishing powder, this is performed before rolling and before applying any lubricant. Coating one or more surfaces of the article with a finishing powder may comprise applying the finishing powder to the one or more surfaces as a powder or as a liquid slurry (preferably an aqueous slurry). In the latter embodiment, the water is allowed to evaporate to form a coating of the finishing powder on one or more surfaces of the article. Finishing powders are known in the art. They are typically alkaline and are often based on compounds such as silica, talc, carbonates, and corn starch. They are used to prevent the surfaces of the article from sticking to each other and to facilitate donning. In particular, the inclusion of anti-stick powder on the inner surface of the condom serves to prevent the condom from sticking to itself, while the inclusion of anti-stick powder on the outer surface also serves to prevent the condom from sticking to other condoms during the manufacturing process.

[0075] In some embodiments, the method further comprises applying a dose of lubricant to one or more surfaces of the condom to form a lubricated condom. The one or more surfaces may be the inner and / or outer surfaces of the condom. Preferably, a dose of lubricant is applied at least on the outer surface of the condom. Suitable lubricants for condoms are known in the art and are typically water-based or silicone-based. In some embodiments, the condom is rolled up before the lubricant is applied. In this embodiment, a dose of lubricant may be applied at or near the top of the rolled-up condom. The lubricant may then move along the condom roll over time (including after the condom is sealed in the package, as discussed below). In this embodiment, the condom may already be in the package or on a material that will form part of the package (e.g., a piece of foil) when the dose of lubricant is applied. In embodiments where the condom is sealed in the package (as described below), only the sealing step must be performed after the lubricant is applied.

[0076] Alternatively, a dose of lubricant can be applied to the condom prior to any rolling step. The lubricant can be applied in various known ways, for example, by spraying, rolling on a sponge soaked in lubricant, or a dose of lubricant can be applied to one or more points along the length of the condom prior to rolling. It will be appreciated that a higher viscosity lubricant can be tolerated if the lubricant is pre-applied to the condom in all or substantially all areas where it is needed, so that it does not need to migrate to the desired areas.

[0077] The method may include other steps, such as electrically testing the condom for holes, rolling up the condom, and / or sealing the condom in a package. Suitable sealed packages for condoms are known in the art and may comprise, for example, two sheets of laminated material sealed around the condom along their edges. The laminated material may, for example, comprise an aluminum layer. Another possible sealed package is a plastic pot sealed with a film lid, or a so-called "butter dish." The condom is preferably arranged in a rolled-up state in the package.

[0078] According to a second aspect, the present invention provides an article, preferably a condom, obtained or obtainable by the method of the first aspect.

[0079] According to a third aspect, the present invention provides an elastic laminate comprising a plurality of polymeric films and one or more interfaces, wherein each pair of adjacent films defines one said interface,

[0080] wherein at least one of the plurality of polymer films comprises polyurethane,

[0081] wherein the elastic laminate comprises silica nanoparticles, and

[0082] wherein at least 60 weight percent of the silica nanoparticles are present at one or more interfaces at least partially defined by a film comprising the polyurethane.

[0083] Optionally, the article is a condom.

[0084] "Laminate" refers to a composite structure composed of multiple layers, which in the present invention are preferably composed of multiple elastic films. The number of films is not particularly limited and will depend in part on the desired thickness of the article. However, preferably, the laminate contains only two or three films. In some embodiments, the laminate is composed of multiple films. It should be understood that the laminate forms the wall of the article. In the case of male condoms, the condom has an inner surface (i.e., the side facing the penis during use) and an outer surface (i.e., the side facing the user's partner during use), and the surface of the laminate defines the inner and outer surfaces.

[0085] It should be understood that each film comprises polymer, preferably elastomer (rubber-like polymer with elasticity).Elastomer character is not particularly limited, as long as it can form an elastic film with one or more mechanical properties (such as strength or flexibility) required for condom or other products to be manufactured.Suitable polymers for other films (preferably elastic films) include polyurethane, polyisoprene, polyethylene and acrylonitrile and butadiene copolymers (" nitrile rubber "), as described about first aspect.Preferably, the elastic film defining the inner surface of the condom comprises polyurethane.

[0086] The polymer in each film can be identical. For example, each film can comprise identical polyurethane. In some embodiments, the polymer in some films is identical, while the polymer in other films is different. For example, the laminate can comprise alternating films comprising polyurethane and polyisoprene respectively. As an alternative, the laminate can comprise alternating films comprising different polyurethanes (for example, having different molecular weights or monomer units). In other embodiments, the polymer in each film is different. Preferably, each layer in the multilayer comprises polyurethane, preferably identical polyurethane. The polymer present in the one or more films (preferably each film of the third aspect) of the third aspect is preferably crosslinked.

[0087] As mentioned above, laminate comprises silicon dioxide nanoparticles.Silicon dioxide nanoparticles are not necessarily " discrete " as defined above about the aqueous coating composition of the first aspect.This is because at least some of the silicon dioxide nanoparticles present in the laminate at one or more interfaces may be loosely combined or gathered with each other, and in the laminate, can't be separated again to form fully individualized particles.Other silicon dioxide nanoparticles present in one or more interfaces or in the film body can keep individualized form.It should be understood that the silicon dioxide nanoparticles in the laminate of the third aspect, even if some of them are loosely combined, still do not fuse together to form aggregates or agglomerates (as described above about fumed silica).

[0088] At least 60% by weight of the silica nanoparticles are present at one or more interfaces at least partially defined by the film containing polyurethane, more preferably at least 70% by weight, most preferably at least 80% by weight. In other words, at most 40% by weight, more preferably at most 30% by weight, most preferably at most 20% by weight of the silica nanoparticles are not present at one or more interfaces (i.e., they are present in the "body" of the film). As described above, each interface is defined by an adjacent pair of films. It should be understood that the films forming a pair must be in direct contact with each other to define the interface. The term "interface" as used herein refers to an area extending from the boundary between two adjacent films to 500nm, preferably 100nm, or 50nm, or 20nm, or 10nm from both sides of the boundary and perpendicular to the boundary. The term "body" refers to a portion of the film that does not form an interface. The ratio of the silica nanoparticles present at one or more interfaces at least partially defined by the film containing polyurethane can be determined by scanning electron microscopy. In some embodiments, at most 95% by weight, or at most 90% by weight of the silica nanoparticles are present at one or more interfaces at least partially defined by the film containing polyurethane. In other words, in some embodiments, at least 5% by weight, or at least 10% by weight, of the silica nanoparticles are not present at one or more interfaces at least partially defined by the polyurethane-containing film. The silica nanoparticles present in the bulk of the film may be dispersed within the polymer matrix and / or may be present at one or more defects within the film.

[0089] As described above, the present inventors have discovered that by concentrating silica nanoparticles at the interface between a pair of adjacent films, prior to the bulk, structural weaknesses associated with the interface can be enhanced without significantly interfering with the properties of the bulk polymer. This is possible when at least one of the films comprises polyurethane. Consequently, the tensile strength of the article can be increased without a significant increase in the elastic modulus.

[0090] Preferably, the silicon nanoparticles contain surface silanol (Si-OH) groups. That is, the silanol groups are preferably present on the surface of the nanoparticles. Due to the hydrophilic silanol groups on the surface and the hydrophobic Si-O-Si portion in the silica nanoparticle core, the silica nanoparticles are amphiphilic. This is a method for increasing the concentration of silica nanoparticles at one or more interfaces relative to the bulk. This is because, during the preparation of the laminate, the amphiphilic silica nanoparticles can be adsorbed on the surface of the polymer-water droplets (air-water interface), thereby helping them migrate to one or more interfaces, rather than remaining in the bulk polymer matrix.

[0091] Preferably, the primary particle size of the silica nanoparticles is from 1 nm to 100 nm, more preferably from 2 nm to 50 nm, even more preferably from 4 nm to 20 nm, and most preferably from 5 nm to 10 nm. "Primary particle size" refers to the diameter of a single silica nanoparticle, not the size of any association or cluster of nanoparticles.

[0092] Preferably, the silica nanoparticles have a BET surface area of ​​at least 200 m 2 / g, more preferably at least 250m 2 / g, most preferably at least 300m 2 / g.

[0093] Preferably, the laminate comprises at least 2 wt%, at least 3 wt%, at least 4 wt%, at least 5 wt%, or at least 6 wt% of silica nanoparticles, based on the weight of the laminate. Preferably, the laminate comprises up to 10 wt% of silica nanoparticles, based on the weight of the laminate.

[0094] Preferably, the thickness of the one or more membranes (preferably each membrane) is from 5 μm to 30 μm.The optional or preferred thicknesses described above in relation to the membrane of the first aspect also apply to the membrane of the third aspect.

[0095] Preferably, the thickness of the article and its mechanical properties (tensile strength, elastic modulus, etc.) are as defined in relation to the first aspect. Preferably, the tensile strength of the article is at least 10% higher, more preferably at least 20% higher, and even more preferably at least 30% higher than the tensile strength of an otherwise identical article that does not contain silica nanoparticles.

[0096] Preferably, the article has an elastic modulus at 300% elongation that is within 10%, preferably within 5%, of the elastic modulus of an otherwise identical article that does not comprise silica nanoparticles.

[0097] Preferably, the article has an elastic modulus at 500% elongation that is within 10%, preferably within 5%, of the elastic modulus of an otherwise identical article that does not comprise silica nanoparticles.

[0098] According to a fourth aspect, the present invention provides a condom comprising a laminate comprising a plurality of elastic films and one or more interfaces, wherein each pair of adjacent elastic films defines one said interface,

[0099] wherein at least one of the plurality of elastic films comprises polyurethane,

[0100] wherein the laminate comprises silica nanoparticles, and

[0101] wherein at least 60 weight percent of the silica nanoparticles are present at one or more interfaces at least partially defined by a film comprising the polyurethane.

[0102] Each optional or preferred feature described with respect to the polyurethane of the first aspect is also applicable to the polyurethane of the third and fourth aspects, unless the context requires otherwise. Each optional or preferred feature described with respect to the continuous polymer of the first aspect ("first polymer," "second polymer," etc.) is also applicable to the continuous polymer of the films of the third and fourth aspects, unless the context requires otherwise. In embodiments where the polymer present in one or more films is a polyisoprene derived from natural rubber latex, the film in which the polymer is present is considered a "natural rubber latex film."

[0103] In some embodiments (of the fourth aspect, or in the case of the third aspect where the article is a condom), the condom further comprises an anti-sticking powder on one or more surfaces thereof. The one or more surfaces may be the interior and / or exterior surfaces, preferably the interior and exterior surfaces. Suitable anti-sticking powders and methods of applying the same are disclosed in the first aspect.

[0104] In some embodiments (of the fourth aspect, or in the case of the third aspect where the article is a condom), the condom further comprises a lubricant on one or more surfaces thereof. The one or more surfaces may be the interior and / or exterior surface of the condom, preferably at least the exterior surface. Suitable lubricants are described in the first aspect.

[0105] According to a fifth aspect, the present invention provides a sealed package comprising the condom of the second, third or fourth aspect. The sealed package is preferably as described in relation to the first aspect.

[0106] A number of particularly preferred embodiments of the first and fourth aspects of the present invention will now be described.

[0107] In certain preferred embodiments, the present invention provides a method for preparing a condom, the method comprising:

[0108] (i) providing an aqueous coating composition comprising a polyurethane and discrete silica nanoparticles;

[0109] (ii) coating a substrate with the aqueous coating composition to form a first film on the substrate;

[0110] (iii) coating the first film with the aqueous coating composition to form a second film on the first film;

[0111] (iv) optionally coating the second film with an aqueous coating composition to form a third film on the second film; and

[0112] (v) removing the substrate to provide a condom; or removing the substrate to provide a laminate, and forming a condom from the laminate.

[0113] In certain preferred embodiments, the present invention provides a condom comprising a laminate comprising N elastic films and N-1 interfaces, wherein each pair of adjacent elastic films defines one interface, wherein N is at least 2, preferably 2 to 4,

[0114] wherein each elastic membrane comprises polyurethane, preferably the same polyurethane,

[0115] wherein the laminate comprises silica nanoparticles, and

[0116] At least 60 weight percent of the silica nanoparticles are present at one or more interfaces.

[0117] In certain preferred embodiments, the present invention provides a condom comprising a laminate comprising two elastic films defining an interface therebetween,

[0118] wherein each elastic membrane comprises polyurethane, preferably the same polyurethane,

[0119] wherein the laminate comprises silica nanoparticles, and

[0120] At least 60 weight percent of the silica nanoparticles are present at the interface.

[0121] In certain preferred embodiments, the present invention provides a condom comprising a laminate comprising a first elastic film, a second elastic film, and a third elastic film,

[0122] The first elastic film and the second elastic film define a first interface, and the second elastic film and the third elastic polyurethane film define a second interface.

[0123] wherein each elastic membrane comprises polyurethane, preferably the same polyurethane,

[0124] wherein the laminate comprises silica nanoparticles,

[0125] At least 60 weight % of the silica nanoparticles are present at the first interface or the second interface.

[0126] In each of the particularly preferred embodiments described above, each membrane preferably has the same chemical composition.

[0127] The invention will now be described with reference to the following non-limiting drawings.

[0128] Figure 1 shows the tensile and burst properties of condoms prepared according to Example 1, measured according to Example 2. In each graph, the data points from left to right are the control formulation (U228), 1 wt% SiO2, 2 wt% SiO2, and 3 wt% SiO2.

[0129] exist Figure 1A In the middle, the bars represent the breaking force (N, left axis) and the lines represent the thickness (μm, right axis).

[0130] exist Figure 1B In the figure, the bars represent tensile strength (MPa, left axis), and the lines represent elongation at break (%, right axis).

[0131] exist Figure 1C In the graph, the left bar represents the modulus (MPa) at 300% elongation, and the right bar represents the modulus (MPa) at 500% elongation.

[0132] exist Figure 1D In the figure, the right bar represents the burst volume (L) and the left bar represents the burst pressure (kPa).

[0133] Figure 2 shows the tensile and burst properties of condoms prepared according to Example 3, measured according to the method disclosed in Example 2, and compared to the 2 wt% SiO2 and control condoms of Example 1. In each graph, the data points from left to right are the control formulation (U228) with a wall thickness of 26.3 μm, the 2 wt% SiO2 with a wall thickness of 24.8 μm, and the 2 wt% SiO2 with a wall thickness of 20.0 μm.

[0134] exist Figure 2A In the middle, the bars represent the breaking force (N, left axis) and the lines represent the thickness (μm, right axis).

[0135] exist Figure 2B In the figure, the bars represent tensile strength (MPa, left axis), and the lines represent elongation at break (%, right axis).

[0136] exist Figure 2C In the graph, the left bar represents the modulus (MPa) at 300% elongation, and the right bar represents the modulus (MPa) at 500% elongation.

[0137] exist Figure 2D In the figure, the right bar represents the burst volume (L) and the left bar represents the burst pressure (kPa).

[0138] The invention will now be described with reference to the following non-limiting examples.

[0139] Example 1

[0140] The aliphatic polyether polyurethane aqueous dispersion ( U228 (50% solids, purchased from Alberdingk Boley) was diluted to 35% solids with deionized water and crosslinked with a water-based carbodiimide crosslinker ( SV-02 (40% solids, available from Nisshinbo Chemical Inc.) was mixed in an amount of 3% solid carbodiimide by weight based on the total solids content of the diluted polyurethane dispersion. The resulting mixture was stirred for 30 minutes. Then, a 363 m2 surface area polyurethane dispersion was added in an amount of 1%, 2%, or 3% solids based on the weight of the solid polyurethane. 2 / g SM colloidal silica (30 wt% suspension of SiO nanoparticles in H2O, purchased from Sigma-Aldrich) was added, and the resulting mixture was stirred for 30 minutes and then sonicated for 30 minutes. A liquid polyether-modified siloxane surfactant (BYK-348, purchased from BYK) was added at 0.2% w / v, and the resulting mixture was stirred for 30 minutes.

[0141] Condoms are produced by dipping a glass former into the mixture three times using a dipping robot to form a three-layer material on the former. Between each dipping step, the material is dried on the former in a circulating air oven at 60°C for 5 minutes to form a film. After the final film-forming step, the material is dried on the former in another circulating air oven at 120°C for 12 minutes. After cooling to room temperature, a starch-based finishing slurry is applied, and the condom is peeled from the glass former and then dried in a dryer. The wall thickness of the three-layer condom is 25 to 30 μm.

[0142] A control was prepared in the same manner as above, but without the addition of any colloidal silica or surfactant.

[0143] The sample formulations are summarized in the table below:

[0144]

[0145] Table 1: Formula for preparing the condom of Example 1

[0146] The addition of colloidal silicon dioxide was found to have no significant effect on the condom's appearance. After removing the starch-based anti-stick powder, all condoms appeared transparent.

[0147] Example 2

[0148] The tensile (force at break, tensile strength, elongation at break, modulus) and air burst (burst pressure and burst volume) properties of condom samples obtained from condoms prepared according to Example 1 were determined.

[0149] To determine the tensile properties, a circular sample is cut from each condom and tested using a universal tensile testing machine according to ISO 4074. The samples are tested using a 500N load cell and stretched at a rate of 500mm / min until they break. The tensile stress is calculated by finding the ratio of force to the initial cross-sectional area of ​​the sample. Strain or elongation is defined as the ratio of the elongated length of the sample to the initial length. The modulus is defined as the stress at a specific elongation, for example the modulus at an elongation of 300% (M300) and 500% (M500) is referred to as the stress at 300% and 500% elongation, respectively. Force, elongation and breaking stress are defined as breaking force, elongation at break and tensile strength, respectively. Five replicates are measured for each sample and the average value of all properties is calculated.

[0150] The thickness of each condom (ie, wall thickness, excluding flange) was measured at right angles to the length of the condom when the condom was unfolded and laid flat without any creases. Thickness measurements were taken three times for each sample condom using a thickness gauge and the average was determined.

[0151] According to ISO 23409:2011, the burst pressure and burst volume of condom samples are evaluated by inflating the condom like a balloon and measuring the air pressure and volume required to burst, respectively. The condom is unrolled and clamped onto a rod, leaving approximately 150 mm of air to be inflated. The test instrument inflates the condom at a specified rate with clean, oil-free, moisture-free air.

[0152] The results are shown in Table 2 and Figures 1A to 1D middle.

[0153] performance Control PU <![CDATA[1%SiO2-SM]]> <![CDATA[2%SiO2-SM]]> <![CDATA[3%SiO2-SM]]> Thickness (μm) 26±1 27±1 25±1 29±4 M300(MPa) 3.15±0.09 3.07±0.16 3.47±0.17 3.36±0.08 M500(MPa) 5.00±0.11 4.83±0.27 5.30±0.27 5.23±0.18 Breaking force (N) 49.25±5.61 64.9±7.9 64.8±10.7 64.2±7.3 Tensile strength (MPa) 46.93±4.88 59.62±6.86 65.42±11.02 56.47±2.4 Elongation at break (%) 447±5 462±8 462±8 453±8 Burst pressure (KPa) 4.33±0.32 4.96±1.282 5.2±1.16 5.125±1.29 Explosion volume (L) 3.13±0.25 3.20±0.91 3.70±0.75 3.00±0.816

[0154] Table 2: Tensile and burst properties of PU condoms containing 0 wt%, 1 wt%, 2 wt% and 3 wt% SM-SiO2 produced according to Example 1

[0155] The addition of SiO2 nanoparticles to the formulation was found to significantly increase the breaking force and tensile strength of the condom samples. However, the differences in modulus at 300% elongation, modulus at 500% elongation, elongation at break, burst pressure, or burst volume due to the addition of SiO2 nanoparticles were limited. Notably, the tensile strength peaked at 2% by weight SiO2. It is believed that increasing SiO2 further increases the material's ductility, ultimately reducing its tensile strength. However, it should be noted that the tensile strength of the 3% by weight SiO2 condoms was still significantly higher than the control.

[0156] Example 3

[0157] Another condom was prepared using the 2 wt% SiO2 formulation of Example 1 by the same method disclosed in Example 1, but with a lower wall thickness than the 2 wt% SiO2 condom of Example 1 (20 μm versus 25 μm). Physical properties were measured as in Example 2.

[0158] The results are shown in Table 3 and Figures 2A to 2D The thicker 2% SiO2 condoms of Examples 1 and 2 and a control condom were included for comparison.

[0159]

[0160] Table 3: Comparison of tensile and burst properties of the PU condoms made according to Example 3 and the reference condoms in Example 1

[0161] The rupture force of the 20 μm thick condom sample containing 2% SiO2 by weight was lower than both the 25 μm thick condom sample and the 26 μm thick control sample. However, this was still within the acceptable range for condoms. Furthermore, the tensile strength of the 20 μm thick condom sample containing 2% SiO2 by weight was higher than the control sample, while the modulus at 300% elongation and the modulus at 500% elongation were comparable. The burst pressure of the 20 μm thick condom sample containing 2% SiO2 by weight was slightly lower than that of the other two samples, but still within the acceptable range.

[0162] Overall, the data indicate that the incorporation of SiO2 nanoparticles into the formulation allows condom thickness to be reduced while maintaining acceptable physical properties.

[0163] Example 4

[0164] Scanning electron microscope (SEM) images were taken of samples cut from condoms prepared according to Example 1 to investigate the surface morphology of the condom samples. Each sample was cut into small pieces and immersed in liquid nitrogen for one minute, after which the sample was immediately broken to prepare cross-sectional specimens. The samples were placed on a sample stage and then gold-coated under vacuum. Finally, surface micrographs of the sample grids were analyzed using a field emission scanning electron microscope (FE-SEM).

[0165] Taken the SEM micrographs that magnification is 5000x, 10000x and 25000x.For the sample that contains SiO 2, can see SiO 2 nanoparticles at the interface between polyurethane layers.This provides SiO 2 nanoparticles during each coating step, migrates to air-water interface and when forming each continuous film, stays on the evidence of the ability at interface.At 1 % by weight SiO 2, the SiO 2 nanoparticles that are dispersed in the bulk polyurethane matrix are very low in concentration.At 2 % by weight and 3 % by weight SiO 2, the SiO 2 nanoparticles that are dispersed in the bulk polyurethane matrix are increased in concentration.

[0166] Example 5

[0167] Scanning electron microscopy (SEM) using energy dispersive X-ray analysis (EDX) was performed on the samples imaged in Example 4 to investigate the distribution of elements in the polyurethane matrix.

[0168] Condom samples without SiO2 primarily contained carbon and oxygen as the main components of the polyurethane. However, Si components were observed in the samples containing SiO2, indicating the presence of SiO2. SEM-EDX micrographs clearly showed that the Si-containing particles were primarily located at the interfaces between the polyurethane layers. The SEM-EDX micrographs provided further evidence that discrete SiO2 nanoparticles were able to migrate to the interfaces between the films produced during each impregnation step.

[0169] The foregoing detailed description has been provided by way of illustration and description and is not intended to limit the scope of the appended claims. Many variations in the presently preferred embodiments shown herein will be apparent to those skilled in the art and fall within the scope of the appended claims and their equivalents.

Claims

1. A method for preparing an elastic laminate, the method comprising: (i) providing a first aqueous coating composition comprising a first polymer and discrete silica nanoparticles, wherein the first polymer is a polyurethane; (ii) providing a second aqueous coating composition comprising a second polymer; (iii) coating a substrate with the first aqueous coating composition to form a first film on the substrate; (iv) coating the first film with the second aqueous coating composition to form a second film on the first film; as well as (v) removing the substrate.

2. The method according to claim 1, wherein: The second polymer is selected from the group consisting of polyisoprene, polyurethane, and mixtures thereof.

3. The method according to claim 1 or 2, wherein: The second polymer is a polyurethane, preferably wherein the first polymer and the second polymer are the same polyurethane, preferably wherein the first aqueous coating composition and the second aqueous coating composition are the same.

4. A method according to any one of the preceding claims, wherein: The discrete silica nanoparticles have a particle size of 1 nm to 100 nm, more preferably 2 nm to 50 nm, still more preferably 4 nm to 20 nm, and most preferably 5 nm to 10 nm.

5. A method according to any one of the preceding claims, wherein: The discrete silica nanoparticles have a BET surface area of ​​at least 200 m 2 / g, more preferably at least 250m 2 / g, most preferably at least 300m 2 / g.

6. A method according to any one of the preceding claims, wherein: The discrete silica nanoparticles include surface silanol groups.

7. A method according to any one of the preceding claims, wherein: The step of providing a first aqueous coating composition comprising a first polymer and discrete silica nanoparticles comprises combining a source of the first polymer with a source of discrete silica nanoparticles to form the first aqueous coating composition.

8. The method according to claim 7, wherein: The source of the first polymer comprises an aqueous polyurethane dispersion and / or the source of the discrete silica nanoparticles is colloidal silica.

9. A method according to any one of the preceding claims, wherein: The method further includes providing a third aqueous coating composition comprising a third polymer, and coating the second film with the third aqueous coating composition to form a third film on the second film between the step of coating the first film with the second aqueous coating composition to form a second film on the first film and the step of removing the substrate.

10. A method according to any one of the preceding claims, wherein: The elastic laminate is a condom.

11. A condom obtained or obtainable by the method of claim 10.

12. An elastic laminate comprising a plurality of polymer films and one or more interfaces, wherein each pair of adjacent films defines one said interface, wherein at least one of the plurality of polymer films comprises polyurethane, wherein the laminate comprises silica nanoparticles, and wherein at least 60 weight percent of said silica nanoparticles are present at one or more of said interfaces at least partially defined by a polyurethane-containing film.

13. A condom comprising a laminate comprising a plurality of elastic films and one or more interfaces, wherein each pair of adjacent elastic films defines one said interface, wherein at least one of the plurality of elastic films comprises polyurethane, wherein the laminate comprises silica nanoparticles, and wherein at least 60 weight percent of the silica nanoparticles are present at one or more of the interfaces at least partially defined by a film comprising the polyurethane.

14. An elastic laminate according to claim 12, or a condom according to claim 13, wherein at least 70 wt% of the silica nanoparticles are present at one or more of the interfaces, more preferably at least 80 wt%.

15. A sealed package comprising the condom of any one of claims 11, 13 or 14.

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