| Production of gloves and other articles of flexible polymer material -> Monitor Keywords |
|
|
 
Production of gloves and other articles of flexible polymer materialRelated Patent Categories: Apparel, Body Garments, Gloves, Work Glove, Medical GloveProduction of gloves and other articles of flexible polymer material description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060179541, Production of gloves and other articles of flexible polymer material. Brief Patent Description - Full Patent Description - Patent Application Claims
STATEMENT OF RELATED CASES [0001] This application is a continuation of U.S. application Ser. No. 10/203,267 filed Feb. 8, 2001, the content of which is herein incorporated by reference. FIELD OF THE INVENTION [0002] This invention relates generally to the manufacture of articles in a flexible foamed polymer material. The invention is particularly useful in the production of articles such as gloves in foamlined natural or synthetic latex, and in one aspect further relates to a novel latex foam glove. BACKGROUND [0003] A variety of latex compositions including natural and synthetic rubbers are disclosed in U.S. Pat. Nos. 3,968,285, 4,373,033, 5,332,621 and 5,084,514. U.S. Pat. No. 4,373,033 discloses a blend of high styrene resin, natural rubber and latex. U.S. Pat. No. 5,332,621 discloses a latex comprising 20-100% by weight of SBR latex, with a minimum proportion of more than 15% by weight of styrene, and 80-0% by weight of natural rubber latex or other synthetic latexes. U.S. Pat. No. 5,084,514 relates to the manufacture of gloves. For the purpose of obtaining what the reference describes as excellent donning and doffing characteristics, the latex includes a carboxylated latex terpolymer of butadiene/acrylonitrile methacrylate, and preferably another component selected from a wide range of synthetic and natural rubbers. [0004] It is a general objective of the present invention to provide a new process of making a glove and to provide a new glove to achieve improvements in the process itself and/or in the end product. SUMMARY [0005] In a first aspect of the invention, it has been discovered that if the latex polymer components of the latex foam mixture include a natural latex polymer as a primary component and a synthetic latex such as an acrylic terpolymer or polyurethane polymer as a secondary component, significant benefits can be obtained in the open cell structure of the final latex foam layer. [0006] In accordance with the first aspect of the invention, therefore, there is provided a process for producing an article in a flexible foamed polymer material, including: treating a former with a coagulant; dipping the treated former in a latex foam mixture to form a layer of the mixture on the former that includes air cells; curing the layer to gel the foam mixture to a cross-linked open cell structure; and stripping the layer from the former; where the latex foam mixture includes a natural latex polymer as a primary polymer component, and a synthetic latex polymer as a secondary polymer component, which synthetic latex polymer is selected to enhance the evenness and/or fineness of said open cell structure. [0007] With optimum choice of the synthetic latex polymer, a very even open cell structure can be achieved that offers good insulation against both heat and cold and excellent sweat absorption. Advantageously, it is possible to achieve air content in the cured layer in the range 30-60%, more preferably in the range 45-55%. In this way, a higher than conventional air content can be achieved with optimal performance, thereby reducing the material cost of providing protection by way of the cured layer. [0008] The synthetic polymer used is preferably a proprietary acrylic copolymer, a polyurethane polymer or a blend of both. The acrylic copolymer is advantageously an acrylic terpolymer. Preferably, the synthetic polymer is present in a proportion of the total of the primary and secondary polymer components in the range 2-10%, more preferably about 5-6%. [0009] A second aspect of the invention concerns the surfactant package employed in the latex foam mixture. Typically, the latex foam mixture includes one or more latex polymers, for example the mix of primary and secondary polymer components of the first aspect of the invention, air bubbles injected into the mixture, and selected dispersion components. Such dispersion components may typically include a cure package such as zinc oxide/sulfur/selected dithiocarbamates or thiurams etc. for cross-linking, antioxidants for reduction of ageing, pigments and viscosity modifiers. A typical latex foam mixture further includes surfactant packages that, among other roles, are useful in stabilizing and sustaining the combination of latex polymer(s), air bubbles and dispersion components. It has been found, in accordance with a second aspect of the invention, that a particularly effective surfactant package for this purpose includes a pair of foam stabilizer sub-packages including a salt of a fatty acid soap and a protonated amine oxide. [0010] Accordingly, the invention provides, in a second aspect, a process for producing an article in a flexible foamed polymer material, including: treating a former with a coagulant; dipping the treated former in a latex foam mixture to form a layer of the mixture on the former that includes air cells; curing the layer to gel the foam mixture to a cross-linked open cell structure; and stripping the cured layer from the former; wherein the latex foam mixture includes in combination one or more latex polymers, air bubbles and dispersion components, and further includes a surfactant package having a salt of a fatty acid soap and a protonated amine oxide for stabilizing and sustaining said combination. Preferably, the salt of a fatty acid soap is associated with a fatty alcohol, and the protonated amine oxide is associated with an anionic surfactant. It is thought that interaction occurs between the protonated amine oxide cation and the anion of the salt, where the cation and anion are very strongly hydrogen bonded via the H.sup.+ of the cation. The same occurs for the fatty acid alcohol containing OH.sup.- groups to form hydrogen bonding with the anionic surfactant. Hence the nature of the polar group is significant in facilitating the formation of hydrogen bonding to increase the foam stability. [0011] The surfactant package is found to be useful in optimizing air dispersion in the latex foam mixture. Preferably, in the latex foam mixture, and relative to a latex polymer content of 100 parts, the primary surfactant, e.g. a salt of a fatty acid soap, is present in the range of 1-2 parts, most preferably about 1.5 parts, and the secondary surfactant, the protonated amine oxide, is present in the range 0.5 to 1.5 parts, preferably about 1 part. The fatty alcohol and anionic surfactant are each preferably present in the range 0.5 to 1.5 parts, most preferably about 1 part. [0012] By way of example, the salt may be the sulfated alkali metal salt of a long chain fatty acid such as lauryl acid or oleic acid, e.g. sodium or potassium lauryl sulphate. A suitable protonated amine oxide is lauryl dimethylamine oxide. The fatty alcohol may usefully then be lauryl myristyl alcohol, and the anionic surfactant may conveniently be sodium dodecylbenzene sulfonate. [0013] The latex foam mixture will typically include one or more cross-linking activators, accelerators and/or agents to facilitate the gelation process. For maintaining the dispersion of these components, the surfactant package preferably further includes appropriate anionic stabilizers. [0014] A third aspect of the invention relates to the dipping step and its effect on the subsequent curing process. In the aforementioned known process, the former is typically treated with a coagulant by first dipping the former into a tank containing the coagulant, most commonly an aqueous solution of calcium nitrate and allowing it to dry on the former just prior to a first latex dip. Following this dip, the former, with a first layer of the latex mixture thereon, is leached in water tanks to extract excess calcium nitrate, leaving just enough present to coagulate the second latex layer in a following second latex dip. In accordance with a third aspect of the invention, it has been found advantageous to treat the former with the first latex layer already thereon with a strong coagulant solution immediately prior to the second dip. [0015] It has also been found advantageous to incorporate into the foam latex a thixotropic agent which functions to allow easy flow during stirring and dipping but which increases the viscosity of the latex rapidly as soon as shearing (stirring in the tank and dipping) ceases, thereby allowing the foam latex to remain as a thick, even layer on the former until the former passes into the oven. [0016] Accordingly, in the third aspect of the invention, there is provided a process for producing an article in a flexible foamed polymer material, including: treating a former with a coagulant; dipping the treated former in a latex foam mixture to form the layer of the mixture on the former that includes air cells; curing the layer to gel the foam mixture to a cross-linked open cell structure; and stripping the cured layer from the former; wherein said dipping is effected by dipping the treated former twice so as to form successive layers of an unfoamed latex and said latex foam mixture thereon, and wherein, after the first dip, the former with said unfoamed latex layer thereon is leached to remove excess coagulant and then treated with a relatively stronger coagulant to accelerate said gelation and to enhance bonding between said layers. [0017] It is thought that the first layer should be unfoamed for greater tensile strength and durability. Said coagulant is conveniently calcium nitrate, and said leaching is preferably in water. The coagulant employed for the second treatment is preferably stronger by virtue of being more concentrated. The latex foam mixture is preferably rendered thixotropic by utilizing as a thixotropic agent a proprietary modified bentonite. If necessary, said cured layer is leached, preferably in water, to extract excess coagulant. [0018] A fourth aspect of the invention concerns the control of the curing step. Essentially, the primary facet of the curing is a cross-linking reaction that converts the latex into a truly elastic film. During this process, several other changes must take place in correct sequence. As the cross-linking proceeds, the viscosity of the polymer increases rapidly and water evaporates. The walls of the air cells must rupture so that the open cell structure is formed, a desirable feature for sweat absorption and flexibility. However, it is preferred that the cell walls do not rupture too early or polymer viscosity will be still too low and the foam will collapse. In accordance with the fourth aspect of the invention, it is preferred that some of the air cells at the surface do collapse so that a thin film, preferably a very thin film of substantially solid latex, apart from perforations where the air bubbles were located, is formed. This film provides a suitable substantially continuous surface which may subsequently be treated, e.g. by chlorination and optionally leaching to reduce its permeability and/or friction and/or allergenicity. More particularly, in the fourth aspect of the invention, there is provided a process for producing an article in a flexible foamed polymer material, including: treating a former with a coagulant; dipping the treated former in a latex foam mixture to form a layer of the mixture on the former that includes air cells; curing the layer to gel the foam mixture to a cross-linked open cell structure; and stripping the cured layer from the former; wherein said curing is controlled whereby said cured layer with an open cell structure includes one or more surface films of substantially solid perforated latex. Preferably, said film(s) is treated to reduce its permeability and/or friction and/or allergenicity. [0019] Preferably, the fourth aspect further includes controlling the dipping step to further facilitate the recited outcome. Advantageous control factors include the dip speed, and the air drying and heating profile, of ovens employed in the curing step. The said treatment of the film is advantageously by chlorination, e.g. by subjecting the cured and cooled layer while still on its former to an aqueous solution containing dissolved chlorine or a dissolved source of chlorine. Chlorine reacts with the latex film to form a surface of low permeability and low friction, and also denatures proteins by reacting with them and reducing their allergenicity. The treatment preferably further includes multiple subsequent leaching steps, e.g., with water at temperatures varying from 90-40.degree. C. In this way, where the article is a glove or other item of apparel, it is possible to produce a chlorinated film surface which is adapted to easy donning (i.e., putting the gloves on and off). [0020] Accordingly, in the fourth aspect of the invention, there is also provided a latex foam glove in which the interior contact surface of the glove is provided by a surface film of substantially solid perforated latex on an underlying layer of a cross-linked open cell structure, which surface film is unlined but treated to enhance its donnability and whereby the extractable protein level of the glove as measured by EN test method 455-33 is below 50 micrograms per gram of rubber preferably below 30 micrograms per gram of rubber. The extractable protein level is a recognized measure of allergenicity. Continue reading about Production of gloves and other articles of flexible polymer material... Full patent description for Production of gloves and other articles of flexible polymer material Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Production of gloves and other articles of flexible polymer material patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Production of gloves and other articles of flexible polymer material or other areas of interest. ### Previous Patent Application: Breast binder gown Next Patent Application: Breastfeeding indicator bracelet with time indicator and method of use Industry Class: Apparel ### FreshPatents.com Support Thank you for viewing the Production of gloves and other articles of flexible polymer material patent info. IP-related news and info Results in 0.26114 seconds Other interesting Feshpatents.com categories: Medical: Surgery , Surgery(2) , Surgery(3) , Drug , Drug(2) , Prosthesis , Dentistry 174 |
 * Protect your Inventions * US Patent Office filing 
PATENT INFO |
|
