An Anti-tack composition and a method for producing a non-tacky elastomeric article

Abstract

The present invention discloses a composition for producing a non-tacky elastomeric article comprising an elastomer; characterized by 0.5 to 50 parts of polyacrylic polymer or derivative thereof per hundred of part of the elastomer, incorporated in the composition; wherein the polyacrylic polymer or derivative thereof has a glass transition temperature from 5 °C to 120 °C. The method for producing a non-tacky elastomeric article is also disclosed herein. The method for producing a non-tacky elastomeric article is also disclosed herein.

Description

[0001] AN ANTI-TACK COMPOSITION AND A METHOD FOR PRODUCING A NON-TACKY ELASTOMERIC ARTICLE FIELD OF THE INVENTION

[0002] The present invention relates to incorporating polyacrylic polymer or its derivatives in the main polymeric chain of the elastomer of an elastomeric article to enable tack free condition both inside and outside, particularly an anti-tack composition and a method for producing a non-tacky powder-free elastomeric article.

[0003] BACKGROUND OF THE INVENTION

[0004] In the process of making an elastomeric article more specifically hand gloves there are some basic steps to keep the continuous dipping line in operation. In brief the continuous chain carrying formers (moulds) passes through washing series, drying, coagulant dipping, drying, dipping into latex batch, drying, pre-leaching, polymer coating (optional), beading, vulcanization, post-leaching, chlorination (optional in combination with other surface coating), neutralization (optional), slurry coating (optional), drying and stripping. In this process to enable stripping of the article (glove) from the former the elastomeric article requires an anti-tack agent to be incorporated in the coagulant solution for ease of stripping, along with the salt solution which enables the deposition of latex. The common anti-tack agent used in the coagulant for powderless or powder free glove is metallic stearates, laurates and oleates either alone or in combination. The salts of fatty acids are effective anti-tack agents in the making of powderless elastomeric article by coating on the surface of the article, as functional and proven material over a period of time. However, in the continuous production line the metallic stearates deposit on the formers and will be difficult to remove even with the strong acids and alkali. The prolonged deposits alter the surface characteristics of the former and hence the film formation is affected resulting in weakness or unevenness of film and which in turn results in barrier defects and making the product unsuitable for the ultimate intended usage. To fulfil the ultimate intended use of barrier defect free article, the cleaning cycle has to be robust and multi staged involving acid tank, alkali tanks, multiple brush stations bothhorizontal and vertical and circular brushes and multiple hot water rinsing tanks. Whenever the output of glove production is to be increased, the cleaning efficiency has to be increased in such cases the number of stations cannot be increased physically due to design restrictions. Under such conditions the concentrations of cleaning agents namely the acids and the alkali-based cleaners has to be increased to compensate the extra deposition of metallic soaps on formers. This cycle of cleaning of formers increases the concentration of cleaning chemicals with increasing speed of the continuous line is an on-going activity, in this process another disadvantage is inevitable, namely the erosion of the former surface. The erosion of former surface results in poor film formation due to micro spikes (since the adjoining surface is removed by mechanical and chemical influences) which will in turn affect the product quality viz., the final elastomeric article like hand gloves. The continuous erosion of the formers results in localized and spot porous structures on the former surface and hence the intended former design providing smooth surface for film formation is compromised.

[0005] The elastomeric article is known for its medium or high elasticity and that is the intended purpose for making the hand gloves, condoms or related applications in view of obtaining necessary comfort in wearing. The main polymers used in the making of elastomeric articles are natural rubber, man-made nitrile butadiene rubber, polychloroprene rubber and synthetic polyisoprene. The main reason for such elastomeric rubber to have high elasticity is the unsaturated double bonds present in the butadiene monomer and the disadvantage is that it has a sticking tendency to the adjoining surfaces, in the first place it starts with the formers where the film formation is enabled. To avoid such sticking tendency the double bond has to be neutralized at surface level to single bond like chlorination or hindering or masking the double bond by applying powder or polymer coating. Such secondary treatment costs more in terms of money and efforts. In some cases, the surface treatment process associates with environment damage like release of chlorine to the atmosphere during chlorination operation. The polymer coating involves additional cost and maintaining process station in the continuous dipping lines and inconsistency of quality during changes in the coating process. In the case of powderapplication to avoid sticking, the powder hinders the double bond and thereby deactivating the sticking tendency, will result in messy spread of powder material when the article is in use, by sticking to the hands, dresses and the objects in touch with the glove.

[0006] Hence any attempt to incorporate a component in the formulation and compounding stage which will reduce or eliminate sticking tendency will help the industry in a big way. The stickiness varies, it starts from the former by sticking to the surface of the former, after stripping and stacking the gloves may stick together at outside (glove to glove). Stickiness may also happen at the inside of the glove and thereby blocking the donning (wearing) of the glove.

[0007] SUMMARY OF THE INVENTION

[0008] The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the invention. Its sole purpose is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that is presented later.

[0009] BRIEF DESCRIPTIONS OF THE DRAWINGS

[0010] Figure 1 is a schematic diagram of the blended emulsion state of the compounded formulation at compounding stage according to an embodiment of the invention; Figure 2 is a schematic diagram of the wet gel at the dipping stage on the former according to an embodiment of the invention;

[0011] Figure 3 is a schematic diagram of the film formed on the former at almost dried condition according to an embodiment of the invention;

[0012] Figure 4 is a schematic diagram of the final film after dried and cured condition according to an embodiment of the invention;

[0013] Figure 5 is a flow chart of the glove manufacturing process using the current invention from compounding stage and continuous stripping stage including stripping stage;Figure 6 is a chart showing the physical property trend of PAP added NBR film (Unaged condition) at the dosage level of 0-5 phr;

[0014] Figure 7 is a chart showing the physical property trend of PAP added NBR film (Aged condition) at the dosage level of 0-5 phr;

[0015] Figure 8 is a chart showing the physical property trend of PAP added NBR film (Unaged condition) at the dosage level of 10-40 phr; and

[0016] Figure 9 is a chart showing the physical property trend of PAP added NBR film (Aged condition) at the dosage level of 10-40 phr.

[0017] DETAILED DESCRIPTION

[0018] As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting but merely as a basis for claims. It should be understood that the drawings and detailed description thereto are not intended to limit the invention to the particular form disclosed, but on the contrary, the invention is to cover all modifications, equivalents and alternatives falling within the scope of the present invention as defined by the appended claims. As used throughout this application, the word "may" is used in a permissive sense (i.e., meaning having the potential to), rather than the mandatory sense (i.e., meaning must). Similarly, the words "include," "including," and "includes" mean including, but not limited to. Further, the words "a" or "an" mean "at least one" and the word "plurality" means one or more, unless otherwise mentioned. Where the abbreviations or technical terms are used, these indicate the commonly accepted meanings as known in the technical field.

[0019] Compared to regular elastomeric materials of natural or synthetic polymers, the polyacrylic polymer or its derivative does not have sticking tendency once dried and cured. Usage of polyacrylic polymer or its derivative is known in the industry for a long period of time however it is applied as a coating once the film of the elastomer is formed either in the wet gel state or in the dry film state. The coating isdone in a separate station as dipping process and sufficient length of chain track is kept open for the dripping of excess polymer solution.

[0020] The concept of this invention is to add polyacrylic polymer or its derivative to the main elastomeric film forming material at compounding stage along with other crosslinking agents, curatives, antioxidants, colorants, pigments, surfactants, pH modifiers and fillers. This compounded polymer blend is processed in the same way as the regular compound with due maturation normally 6 to 48 hours depending on the base elastomer and the curative content. After due deaeration and stabilization the compound is released to the dipping line. The various aspects of the invention will be discussed hereafter.

[0021] The present invention is described hereinafter by various embodiments with reference to the accompanying drawings, wherein reference numerals used in the accompanying drawings correspond to the like elements throughout the description. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiment set forth herein. Rather, the embodiment is provided so that this disclosure will be thorough and complete and will fully convey the scope of the invention to those skilled in the art. In the following detailed description, numeric values and ranges are provided for various aspects of the implementations described. These values and ranges are to be treated as examples only and are not intended to limit the scope of the claims. In addition, a number of materials are identified as suitable for various facets of the implementations. These materials are to be treated as exemplary and are not intended to limit the scope of the invention

[0022] The present invention proposes a composition for producing a non-tacky elastomeric article comprising an elastomer characterized by 0.5 to 50 parts of polyacrylic polymer or derivative thereof per hundred of part of the elastomer incorporated within the elastomer matrix wherein the polyacrylic polymer or derivative thereof has a glass transition temperature from 5 °C to 120 °C.In accordance with an embodiment of the present invention, the elastomer is a synthetic elastomer, a natural elastomer, or a combination thereof.

[0023] In accordance with an embodiment of the present invention, the elastomer is selected from any one or combination of acrylo nitrile butadiene rubber, styrene butadiene rubber, polychloroprene rubber, polyisoprene rubber, or their derivatives.

[0024] In accordance with an embodiment of the present invention, the elastomer is carboxylated acrylo nitrile butadiene rubber.

[0025] In accordance with an embodiment of the present invention, the polyacrylic polymer or derivative thereof having a structure represented by Formula (I)

[0026] [ - CH2- CR1(COOR2)-]n...(I)

[0027] where

[0028] Ri is hydrogen or methyl,

[0029] R2is hydrogen, methyl, ethyl or sodium.

[0030] It is contemplated that Formula (I) may combine with other alkyl or aryl groups, thereby creating copolymers or modified polymers with varied properties.

[0031] The present invention proposes a method for producing a non-tacky elastomeric article comprising of providing an elastomer; blending 0.5 to 50 parts of polyacrylic polymer or derivative thereof per hundreds of parts of the elastomer with the elastomer to form a composition at a compounding stage and forming the composition into the elastomeric article.

[0032] In accordance with an embodiment of the present invention, the compounding stage further comprising blending into the composition any one or combination of cross-linking agents, curative chemicals, antioxidants, stabilizers, wax, opaqueness providers, fillers, colorants, surfactants, or pH modifiers.

[0033] In accordance with an embodiment of the present invention, the composition is subjected to maturation for a duration of 6 hours to 3 days.

[0034] In accordance with an embodiment of the present invention, the elastomeric is a glove.In accordance with an embodiment of the present, forming the composition into the elastomeric article comprises dipping a former with a coagulant, dipping the former with the composition, wherein the coagulant does not contain anti-tack material.

[0035] Polyacrylic Polymer (PAP)

[0036] Compared to the base elastomer, more specifically to the carboxylated nitrile butadiene rubber the molecular structures of polyacrylic polymer are simple and different, this is due to the chemical composition and arrangement of molecules. Polyacrylic polymers are generally made by the polymerization of acrylic acid and its derivatives. The Carbon-Carbon (C-C) chain obtained from polymerized acrylic acid monomers form the backbone for polyacrylic polymers. Based on this backbone the side groups consist of repeating carboxylic acid group (-COOH) or its salt (-COO ) depending on the pH.

[0037] The general chemical structure is [ - CH2- CH(COOH)-]n

[0038] The polyacrylic polymers are basically hydrophilic due to -COOH / -COO~ groups. However, the solubility depends on crosslinking and molecular weight.

[0039] Carboxylated Nitrile Butadiene Rubber

[0040] Carboxylated Nitrile Butadiene Rubber is produced by copolymerizing butadiene, acrylonitrile and carboxylic acid monomer. The main hydrocarbon chain of the nitrile latex chain is formed by the polymerized butadiene monomers which are basically hydrophobic. The acrylonitrile (-C=N) and carboxylic acid (-COOH) functional groups are randomly distributed throughout the main chain of butadiene. The variation is the functional groups determines the types of nitrile latex commercially available in the market. The percentage of acrylonitrile functional group determines the strength and chemical resistance property of the nitrile latex.

[0041] The general chemical formula for the carboxylated nitrile butadiene rubber (NBR) is

[0042] [-CH2-CH=CH-CH2-]x[-CH2-C(CN)-]y[-CH2-C(COOH)-]zx, y and z represent the molar ratios of butadiene, acrylonitrile and carboxylic acid respectively. The elasticity and flexibility are provided by the butadiene backbone. The oil resistance, chemical resistance and mechanical strength are imparted by the acrylonitrile functional side groups. The polarity, chemical reactivity and adhesion is provided by the carboxylic acid functional groups.

[0043] Comparison of PAP and NBR

[0044] Based on the comparison between the structures of the polyacrylic polymer and nitrile it can be understood that the mechanism in which the polyacrylic polymer (PAP) addition serves the purpose

[0045] 1. The backbone of PAP is formed by linear carbon chain whereas NBR consists of hydrocarbon chain comprising double bond in each butadiene monomer 2. The side functional groups of PAP consist of carboxylic acid (-COOH) or salts of (-COO ) whereas NBR consists of acrylonitrile (-C N) and carboxylic acid (- COOH)

[0046] 3. The PAP is highly polar whereas NBR is moderately polar (due to -C N and - COOH groups) however presence of butadiene will offset to an extent 4. The hydrophilicity of PAP is high in fact water soluble, whereas NBR is not soluble but dispersible this restriction is due to hydrophobic backbone of butadiene chain which will always be more than 50% of the total weight and volume wise much higher percentage in NBR latex.

[0047] 5. The PAP selected for this invention is hydrophilic whereas NBR is hydrophobic which is a key aspect deciding the intended application of reducing tackiness.

[0048] 6. The PAP selected for this invention has a typical molecular weight of 10k - 100k g / mol whereas for NBR it varies from 50k - 500k g / mol. The higher molecular weight PAP is not suitable for this invention. The higher molecular weight PAP is used for making thickeners and absorbents.

[0049] Glass Transition Temperature

[0050] The glass transition temperature (Tg) of NBR varies with respect to the acrylonitrile content (ACN). At low ACN content of 18-20% the Tg is approximately -55 °C to -60 °C, at medium range of 25-35% the Tg is approximately - 40 °C to - 50 °C at high level of 40-50% the Tg is approximately -30 °C to -40 °C

[0051] For PAP of molecular weight range of 10k to 50k the Tg varies from 50 to 80 °C for higher molecular weight it varies from 500k 1500k the Tg varies from 100 to 120 °. For crosslinked PA polymer: Tg > 120°C, depending on crosslinking density.

[0052] Effect of Adding polyacrylic polymers to nitrile compounds

[0053] The addition of polyacrylic polymers to nitrile compounds reduces tackiness through a combination of physical, chemical, and mechanical mechanisms.

[0054] Polyacrylic polymers typically have a higher glass transition temperature (Tg) compared to nitrile rubber, contributing to the formation of a harder, non-tacky surface upon drying or curing or drying and curing. When blended with nitrile latex, the polyacrylic polymer creates a film that increases the overall hardness and reduces surface stickiness. Tackiness, which arises from the soft, sticky nature of nitrile rubber at room temperature, is mitigated as the harder acrylic polymer dominates the surface characteristics.

[0055] Due to differences in surface energy, polyacrylic polymers may migrate to the surface of the nitrile compound during curing or drying. This forms a protective layer that shields the underlying rubber, reducing direct contact and adhesion to other surfaces. The surface becomes smoother and less prone to sticking.

[0056] Polyacrylics, especially those with carboxyl groups (e.g., carboxylated polyacrylics), can chemically interact with the nitrile rubber through ionic or covalent bonds during crosslinking. For example, zinc oxide used in nitrile formulations can act as a crosslinking agent for carboxylated acrylics, increasing crosslink density. Higher crosslink density enhances the rigidity and cohesiveness of the polymer matrix, reducing surface tack. Blending polyacrylic polymers with nitrile reduces the mobility of the nitrile polymer chains due to the rigid structure of the acrylic components. This limits the ability of the material to deform or flow under minor stress, a primary contributor to tackiness. The material exhibits reduced surface stickiness and improves dimensional stability.Polyacrylics have inherently different surface energy properties compared to nitrile rubber. The incorporation of polyacrylics increases the overall surface energy of the compound, making it less sticky. The compound exhibits reduced wetting and sticking tendencies.

[0057] Polyacrylic polymers generally exhibit better thermal resistance. When blended with nitrile, they help the compound to maintain a stable structure under elevated temperatures, reducing tackiness that might otherwise increase with heat. Tackiness is controlled even during processing or in high-temperature applications. Carboxylated polyacrylates are known for chemical interaction. Styrene-acrylic copolymers are known for increased hardness. Zinc oxide or other metal salts enhance interactions between the nitrile and acrylic components, since all the nitrile compounds have metallic oxides especially zinc oxide in the formulation the simple addition of polyacrylic with nitrile compound will be sufficient.

[0058] Conceptually hard polyacrylic polymers with high glass transition temperature preferably above 10 deg.C help increase film hardness. Some of the common polyacrylic polymers are methyl methacrylate and styrene acrylic copolymers like styrene butyl acrylate. However crosslinked acrylics provide a harder and non-tacky surface due to increased crosslinking structure for example carboxylic and or epoxy functional acrylates.

[0059] The curing mechanisms of the polyacrylic polymers depend on the polymer composition, the curing agents used and the intended applications. The primary curing mechanisms for polyacrylic polymers are thermal curing, ionic crosslinking, covalent crosslinking, hydrogen bonding, mechanical interlocking and interfacial compatibility (phase mixing).

[0060] In thermal curing process, as the name indicates heat activates crosslinking agents for example peroxides, isocyanates or melamine formaldehyde resins, that react with functional groups in the polyacrylic polymer. For carboxylated polyacrylics heat can facilitate ionic or covalent bonding between carboxyl groups and metal ions specifically multivalent metal ions like zinc oxide, magnesium oxide or aluminum oxide either alone or in combination and end product obtained from such reactioncould be used in coatings, adhesives and films. Depending on the film thickness the temperature could be 100 °C to 180 °C, and the duration could be 5 - 30 minutes, In the case of ionic crosslinking the carboxylic acid groups (-COOH) in the XNBR and polyacrylic polymers react with multivalent cations such as Zinc (Zn2+), Magnesium (Mg2+), Calcium (Ca2+), Aluminum (Al3+) etc., to form ionic bonds. Zinc Oxide (ZnO), is commonly used in carboxylated NBR (XNBR) formulations, acts as a crosslinking agent by coordinating with carboxyl groups from both XNBR and the polyacrylic polymer.

[0061] In case the polyacrylic polymer contains reactive functional groups such as epoxy, hydroxyl (-OH), or glycidyl groups, they can react covalently with carboxylic groups in XNBR through condensation or nucleophilic addition reactions. The covalent bonding is typically induced by heat, curing agents and or catalysts.

[0062] Esterification (condensation reaction):

[0063] R-COOH + R"-OH -^R-COO-R"+H20

[0064] Amide Formation (with amine-functionalized acrylics):

[0065] R-COOH + R"-NH2 -^R-CONH-R"+ H20

[0066] Covalent crosslinking produces a chemically bonded, durable network that improves resistance to wear and chemical degradation.

[0067] In the case of hydrogen bonds Carboxylic acid groups (-COOH) in both XNBR and polyacrylic polymers form hydrogen bonds. These interactions are non-covalent and reversible, but they contribute to improved compatibility and reduced tackiness. Hydrogen bonding enhances the miscibility of the two polymers, improving processability and surface properties without permanent crosslinking.

[0068] In the case of mechanical interlocking, during blending, the polyacrylic polymer disperses into the XNBR matrix. The long polymer chains of both components become physically entangled. Crosslinking agents like ZnO or sulfur may stabilize these physical networks by creating additional random ionic or covalent bonds especially at the surface level of the film during vulcanization of theelastomeric film. Mechanical interlocking results in a uniform polymer blend with improved flexibility and reduced tack.

[0069] In the case of interfacial compatibility (Phase mixing), the carboxylic acid groups on both XNBR and polyacrylic polymers increase polar compatibility between the two polymers, reducing phase separation, the enhanced interfacial adhesion improves the overall mechanical properties and creates a homogeneous material with improved abrasion resistance and lower tack.

[0070] Polyacrylic Polymers and its derivatives.

[0071] The chemical structures of polyacrylic and polyacrylate polymers are based on the polymerization of acrylic acid and its derivatives. Below is an overview of their structures:

[0072] 1. Polyacrylic Acid (PAA)

[0073] • Chemical Structure: [-CH2- CH(COOH)-]n

[0074] The backbone is a linear chain of repeating methylene (-CH2-) and substituted methine (-CH-) groups. The side group contains a carboxylic acid group (-COOH) on each repeating unit. This is highly hydrophilic due to the -COOH group. It can form hydrogen bonds or ionic interactions and soluble in water and forms gels at high concentrations, higher molecular weight can be made to super-absorbent polymers (e.g., in diapers) and also thickening agents in cosmetics and pharmaceuticals and ion-exchange resins.

[0075] 2. Polyacrylate Polymers

[0076] • General Structure: [-CH2- CH(COOR)-]n

[0077] Polyacrylates are esters of polyacrylic acid, where the hydrogen in the -COOH group is replaced by an alkyl or other functional group. R: Represents the alkyl or functional group, such as methyl (CH3), ethyl (CH2CH3), or other variations.

[0078] a. Polymethyl Acrylate (PMA)

[0079] • Structure: [-CH2- CH(COOCH3)-]nProperties: Hydrophobic, flexible and transparent. Application involves, coatings, adhesives, and optical films.

[0080] b. Polyethyl Acrylate (PEA)

[0081] • Structure: [-CH2- CH(COOCH2CH3)-]n

[0082] Properties: Slightly more flexible than PMA due to the longer ethyl group. Applications involves making of impact modifiers and adhesives.

[0083] c. Polymethacrylic Acid (PMAA)

[0084] • Structure: Similar to polyacrylic acid, but with a methyl group on the backbone:

[0085] [-CH2- C(CH3)(COOH)-]n

[0086] Properties: More hydrophobic than PAA. Applications involves making of pharmaceuticals related products and specialty coatings.

[0087] 3. Crosslinked Polyacrylates

[0088] • Structure: [-CH2- C(COONa)-]n

[0089] Crosslinked versions of polyacrylic or polyacrylate polymers include additional crosslinking agents (e.g., divinyl compounds like divinylbenzene or ethylene glycol dimethacrylate) to create a three-dimensional network. Examples: Super-absorbent Polyacrylate, crosslinked sodium polyacrylate. Highly water-absorbing due to the sodium salt form of the carboxyl groups.

[0090] Properties: Insoluble in water but can swell significantly.

[0091] Applications: Water-absorbing gels in hygiene products.

[0092] The plausible molecular rearrangement of PAP and NBR

[0093] In this invention the PAP is added as aqueous dispersion to the NBR emulsion. The addition is done during compounding stage.

[0094] At first the nitrile compound is prepared as per the standard operating procedure.The NBR compound is prepared by adding surfactant, water, curatives like sulfur, accelerator, zinc oxide, antioxidants, titanium oxide, colorants and pH modifiers like KOH. The dilution is done according to the end product film thickness. Once compound is made with the targeted total solid content (TSC) and pH the polyacrylic polymer is added with due dilution and pH adjustment to avoid micro flocking. The compound thus made is left for maturation for stipulated time may be from 12 - 40 hours depending on the curative level and process-ability at the dipping line.

[0095] Referring to Figures 1 to 4, the molecular arrangement of NBR and PAP in different stages will now be described in more detail.

[0096]

[0097] Both NBR and PA polymers are in aqueous media

[0098] In this stage (Figure 1) of compounding the NBR molecular chain and polyacrylic polymer or its derivative are randomly and homogeneously mixed in the aqueous media with suitable surfactants and other chemical additives as stated above. All the polymer molecules either NBR or PAP are free to move around in the entire bath of the compound. Since the PAP is hydrophilic and relatively of low molecular weight, it has more freedom to move around the aqueous dispersion rather than that of NBR chains.

[0099] At dipped state before drying

[0100] Both NBR and PA polymers are in aqueous media

[0101] In this stage (Figure 2), once the maturation is complete the compound is fed to the dipping line to the latex dip tank. The latex dip tank is kept in a controlled temperature (25-40 °C) by cooling of the excess heat received from the continuously dipping formers at the temperature approximately 50 - 70 °C. The latex compound inside the tank is circulated by separate stirrers and the moving formers also keeps the compound in a state of suspension.

[0102] The metallic salt (more specifically divalent calcium nitrate or calcium chloride or like) coated former will be dipped into the latex compound, due to thecationic nature of the salt the latex will be deposited / coated on the former. At this wet gel state, as shown Figure 2, the water content is getting reduced and this makes the NBR molecular chains comes closer and becoming more hydrophobic and PAP associated itself more with water media. Due to compressive state inside the wet gel the PAP molecules tend to migrate to the outer surface of gel through the water as media of transport, the same mechanism is indicated by tiny arrows pointing towards the film surface.

[0103] The film formation in almost dried condition

[0104] When the film formation nearing a completion and reaching towards the drying condition the film will be in a state as illustrated in Figure 3.

[0105] There are two main reasons for such film formation as per Figure 3

[0106] a. The coalescence of NBR molecules becomes more and more hydrophobic and squeeze out the water molecules which is a continuous media of the emulsion.

[0107] b. The PAP molecules are hydrophilic and attached more to the water in the emulsion once the water is getting expelled in the drying process the PAP molecules follow the same path of the water and migrates to the surface of the film where the water gets evaporated.

[0108] c. The PAP molecules get concentrated on the surface of the film and forms a continuous array.

[0109] Final film formation after drying and curing

[0110] After final curing in Figure 4 i.e., after completion of vulcanization either in partial or complete the main core is left with NBR and the surfaces are left with PAP. The film this formed by PAP shows no tackiness and sticking tendency due to the nature of the molecular structure of the PAP.

[0111] The hydrophilic nature of PAP and the higher Tg helps to avoid tackiness or stickiness caused by the NBR film (obviously due to the double bond)Thus, the PAP film formed partially reacts with carboxylic bonds of NBR and double bonds of NBR during vulcanization and to an extent physically hinder the double bonds of NBR rendering the outside surface tack-free.

[0112] Possible reactions between the Nitrile butadiene Rubber and Polyacrylic acid The carboxylic groups in the NBR latex and the PAP participates in the reaction with ZnO added in the formulation and forms an ionic bond between themselves which is the basis that the PAP adheres to the surface of the NBR and thereby reducing the surface tackiness or the stickiness.

[0113]

[0114] In this invention, the polyacrylic polymer and or its derivative is blended with base elastomeric latex and compounded together along with other chemicals and processed in the standard way the normal elastomeric articles are processed as per process flow chart illustrated in Figure 5.

[0115] The glove without anti-tack will be a breakthrough in case of elastomer like nitrile butadiene rubber which is further processed for clean room application where the particle count has to be the minimum depending upon the class of applicable clean room standards.

[0116] However, in case of regular disposable applications either medical or nonmedical purposes the gloves will be stacked together in a dispenser where there could be a mild sticky between the gloves due to less amount of PAP addition or residual stickiness in such case very little amount of soluble or easily washable antitack could be added in the coagulant which may result in savings in the washing chemicals and complication in the cleaning series. Which will in turn results in betterquality of the elastomeric article in terms of barrier property. In the competitive glove market with ever reducing price savings in terms of operational expenditure and at the same time with required quality meeting the standards of medical devices will be a great advantage.

[0117] The added PAP in the NBR at compounding stage along with the other curative chemicals, migrates to the surface of the article due to the hydrophilic nature of the PAP and hydrophobic nature of the NBR, the higher Tg of the PAP renders non sticking property which invariably incorporated to the main NBR elastomer.

[0118] Compounding

[0119] The compounding is done in the normal way. The NBR latex is stabilized with mechanical stabilizer and chemical stabilizer and partially diluted. The preconditioned NBR latex is added with curative, anti-oxidant, other additives like opaqueness provider and colorants. Then the PAP is diluted, pH adjusted and added with surfactant to avoid any micro flocking, thus conditioned PAP is added to the pre compounded NBR and allowed to mature as per the respective standard operating procedure of the company. The other controls like TSC, pH and viscosity are adjusted in line with the end product thickness and weight.

[0120] Continuous dipping line configuration and its functions in the making of a glove Cleaning Series

[0121] Depending on the output of the continuous dip line, chain length of the machine the cleaning series components varies. However, the cleaning series contain an acid cleaning station, single or multiple alkali cleaning station / s, single or multiple brush station / s and hot rinsing tanks. The chemical concentration of cleaning station is periodically monitored for effective cleaning process. However, the concentrations of the cleaning solutions will be increased with increasing line speed for effective cleaning of the formers. With the increasing chemical concentration of alkali-based cleaners the former surface erodes faster and the former surface characteristics changes affecting the film formation resulting in more barrier defectives. The cost forcleaning depends on the amount of chemicals used, usage of consumables like brushes and others, and power consumed by motors, heat energy spent on heating the cleaning solutions and rinsing water. The purpose of the cleaning series is to remove the excess deposit of anti-tack to enable the proper film formation. The antitack coated on the former partly adheres to the former and partly transferred to the product, it is a fine balance between the coating and sharing between the former and dipped article. Excess coating will exhibit as powder mark on the product, if the product is dark colored it leaves a white mark and identified as powder mark. Another important point for raising the anti-tack level is the severity of the sticking tendency of the film this could be due to the type of elastomer, level of curatives in the formulation cross linking density and the curing level of the film after passing through the vulcanization ovens of appropriate temperatures in various zones. Any measure to reduce the stickiness of the article will reduce the anti-tack load on the cleaning system and hence reduce the cost on the cleaning and in turn increase the life of the formers used for dipping.

[0122] Normally any type of inorganic acids is used for the cleaning, like hydrochloric acid, sulfuric acid more specifically nitric acid and like. The alkali commonly used is potassium hydroxide and at times sodium hydroxide however mixture of anionic surfactants is used to give better cleaning of the formers.

[0123] Former drying

[0124] After drying, the former goes through a drying oven to remove excess water adhering to the former. If the last rinsing temperature is high the former will dry on its own before reaching the coagulant oven.

[0125]

[0126] This is a critical stage in determining the glove quality with respect to the film thickness and uniformity of the film formed. Here salt is used to deposit compounded anionic emulsion. The preferred salt is of multivalent nature more preferably calcium nitrate, in some cases calcium chloride is also used. To get the uniform spread of salt bath non ionic surfactant / s is / are used specifically block copolymer surfactant, having hydrophilic polyethylene glycol and hydrophobicpolypropylene glycol block-based surfactants which is a proven surfactant in the industry any combination of anionic and or non-ionic surfactant could be used.

[0127] Another key component is an anti-tack material selected from various groups depending on the end product applications. Earlier calcium carbonate was used as powder dispersion in the coagulant, still for making clean room products and offline wash products precipitated calcium carbonate is being used. Later metallic stearate is being used for making powder free products, more specifically potassium and calcium stearate are the important ones. Potassium stearate is used for some specific applications where the cleaning series is less effective. However, the most used metallic stearate is calcium stearate which is more effective at less dosage but cleaning of the same poses lot of challenges due to high melting point and its tough against acid and alkaline cleaners.

[0128] As per the current invention the addition of anti-tack in the coagulant could be totally removed, and the stripping of the glove from the formers will not be affected. However, depending on the dosage of PAP to the latex formulation there will be mild sticky between glove to glove. However, if the gloves are taken for offline wash with chlorine or polymer, the PAP addition in the latex will work even without anti-tack in the coagulant.

[0129] For improving the cleaning efficiency and avoiding mild sticky between gloves water soluble anti-tack material like high molecular weight polyethylene glycols could be used.

[0130] The percentage of calcium nitrate is the key in deciding the film thickness and product weight.

[0131]

[0132] The formers dipped in coagulant solution is dried up to remove the excess water and at the same time to increase the former temperature for an effective pick up of latex compound on the former. The ineffective drying can affect the film formation and coagulum formation in the latex dip tank (since the undried nitrate will diffuse into the latex resulting in localized coagulation of the rubber particles.)Latex di

[0133] The dried coagulant dipped former will be dipped into the latex bath maintained at particular temperature and pH condition enabling the formation of the film on the former. The former temperature could also play a role in the film formation. The TSC of the latex is a key aspect in deciding the film thickness and weight of the article. Along with the pH, the amount of surfactant determines the stability of the compounded latex in a continuous run. The latex dipping could be in multiple to improve the product quality with respect to barrier defects. In the case of multiple dipping there should be a drying oven in between dips to enable the proper pick up of latex. In some cases to increase the latex pick up calcium nitrate could be coated by spraying or dripping, on the latex gel formed in the previous dipping.

[0134] Latex Gelling oven

[0135] The film formed on the former either by single dip or multiple dips should be dried partially to enable better film formation and avoid washing off in the preleaching operation.

[0136]

[0137] The gelled latex film will be pre-leached to remove the soluble material in the gel which may cause allergic reaction to the wearer. The soluble material may consist of surfactant added to stabilize the compound, the residual nitrate and other water- soluble material present in the latex emulsion.

[0138]

[0139] For some powder free product polymer coating is done after pre-leaching operation. The polymer used in the coating could be polyacrylic and its derivatives or polyurethane. The polymer bath could be maintained at the TSC of 0.5% to 3.5%. For prolonged shelf life of the polymer, the tank could be kept at low temperature in view of controlling bacterial growth and anti-bacterial material should be added to avoid bacterial contamination.

[0140] BeadingBeading is done to enable better donning of the glove providing better strength to the cuff area by rolling off the thin edges of the cuff thereby avoiding ripping off while donning.

[0141] Vulcanization

[0142] The beaded glove is then vulcanized at higher temperature to enable proper crosslinking of elastomer and as well bonding of the PAP with the base film.

[0143] Chlorination (Optional)

[0144] In case of surface treatment by chlorination, after vulcanization the glove dipped former is cooled down by passing through a series of cooling water tanks and then passing through the tanks containing chlorine water. The chlorine ppm could be from 150 until 1200 depending on the final product requirement. After chlorination the gloves is passed through a neutralizer to remove residual chlorine on the glove.

[0145] Post Leaching

[0146] Post leaching is carried out to remove any excretion of surfactant and other impurities after vulcanization process which squeezes out the impurities while strengthening the film.

[0147]

[0148] After post leaching the inside of the glove could be slurry coated to enhance the donning by providing a slip, mainly by silicone or other polymeric material which enables extra smoothness to the inner surface of the dipping product.

[0149] ing

[0150] After slurry coating the formers are passed through slurry oven to remove excess water and the article is stripped off.

[0151] EXAMPLE

[0152] Hereinafter, examples of the present invention will be provided for more detailed explanation by referring to Figures 5 to 9. These examples aim to illustrates the key principles and advantages of the present invention that may be more readily understood and put into practical effect from these examples. However, it is to beunderstood that the following examples are not intended to limit the scope of the present invention in any ways.

[0153] EXPERIMENTAL SET UP

[0154] To understand the practical implication of the concept of reduction in tackiness, the following main set of experiments is designed.

[0155] General information:

[0156] The formulation followed in the following experiments is a tentative one, which are designed to evaluate the effect of PAP addition to the synthetic nitrile butadiene rubber. However, the alterations to the given formulation could be very well done to meet the specific need of the end product. The NBR latex used in these experiments had acrylonitrile content of approximately low to medium and hence the Tg could be around -55 °C to -45 °C

[0157] The Polyacrylic Polymer used in these following trials from Experiments 2 to 10 has a Tg value of 63 °C

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[0162]

[0163] Table 1

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[0167] Table 2

[0168]

[0169] Table 3

[0170]

[0171] Table 4

[0172]

[0173] Table 5

[0174] Nitrile Latex - Carboxylated Acrylo Nitrile Butadiene rubber latex with Tg of -55 to -45 °C

[0175] KOH - Potassium hydroxide, pH modifier, chemical stabilizer

[0176] ZnO - Zinc Oxide in milled form

[0177] ZDBC - Zinc Dibutyl Dithiocarbamate in milled formSulfur - Sulfur as crosslinking agent in milled form

[0178] Antioxidant - Hindered phenols as anti-oxidant to retard the oxidation of the end product

[0179] TiO2 - Titanium oxide as opaqueness provider

[0180] SDBS - Sodium dodecyl benzene sulphonate - surfactant, stabilizer

[0181] PA Polymer-Tg63 - Polyacrylic polymer having a Tg of 63 °C

[0182] Natural latex - Natural polyisoprene latex derived from rubber tree / could also be replaced with synthetic polyisoprene

[0183] ZDEC - Zinc diethyl dithiocarbamate

[0184] Filler CC - Calcium carbonate filler from grinding or precipitation

[0185] Filler Clay - Silicon based finely ground filler obtained from mining

[0186] PA Polymer -Tg24 - Polyacrylic polymer having a Tg of 24 °C

[0187] Fleximix - Proprietary curative composite supplied by Crestage Industries, Malaysia

[0188] Polychloroprene - Polychloroprene latex emulsion

[0189] SLES - Sodium lauryl ether sulphate

[0190] Note: Except experiment 1 all other experiments were dipped without anti-tack in the coagulant solution.

[0191] Inference and discussion on the results of experimental set up

[0192] For blend ratio of PAP from 0 to 5 (Experiment 1 to 6)

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[0198] Table 1A

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[0201]

[0202] Table 6B

[0203] The PAP added gloves from 1 phr to 5 phr could be stripped off from the former without any anti-tack addition in the coagulant solution. The ease of stripping increased with increase in phr of PAP

[0204] Based on the analysis on the physical property (Figure 6) of the films formed using PAP there is no appreciable changes in the physical properties. In experiment 4 the unaged tensile is dropped to 23 compared to 33 in experiments in 3 and 5. However after aging tensile result (Figure 7) of experiment 4 is comparable with the nearby experiments. Compared to the control experiment 1 where the PAP addition is nil the elongation (unaged) results of PAP added experiments of 2, 3 and 4 are high which is not expected considering the hard nature of PAP. In the case of aged elongation results experiments 5 and 6 showed drop compared to control and the previous experiments 2, 3 and 4 which is in line with theoretical predictions.

[0205] Hence up to the phr level of 5 of PAP there is no significant changes in the properties. But the gloves could be stripped off without any difficulty.

[0206] For blend ratio of PAP from 10 to 40 (Experiment 7 to 10) <>

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[0210] Table IB

[0211]

[0212] Table 7 A

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[0214] Table 7B

[0215] The PAP added gloves from 10 phr to 40 phr could be stripped off easily from the former without any anti-tack addition in the coagulant solution. The ease of stripping increased with increase in phr of PAP

[0216] Based on the analysis of the unaged physical property of PAP addition from 10-40 phr (Figure 8) of the films, there is a gradual change or degradation in the intended physical property. The unaged tensile drops from 32 to 28, the modulus at 300% elongation increases from 3.2 to 10.5 MPa, the modulus as 500% increases from 9.2 to 26.8 MPa and the elongation at break drops from 700% to 500%.

[0217] Based on the analysis of the aged physical property of PAP addition from 10- 40 phr (Figure 9) of the films, there is a gradual change or degradation in the intended physical property. The aged tensile drops from 35 to 22, the modulus at 300% elongation increases from 5.8 to 10 MPa, the modulus at 500% increases from1

[0218] 19.9 to 23.3 MPa where as, the experiment 10 with 40 phr PAP does not even meet 500% elongation and the elongation at break drops from 620% to 420%.

[0219] Obviously at higher level of PAP the influence of PAP in the final article is substantial and significant with respect to the physical properties. However, there is no issues in the stripping of the article from the former. Due to the increased level of PAP the article loses its elastic property and gets hardened. It is clear that this change in property enables the reduction of sticking tendency of the final article. Like case hardening of steel blades especially in the making of knifes more specifically the longer knives, where the outer surface used to cut the items is hardened to withstand the wear and tear and inside is relatively soft to absorb the shock during handling namely the cutting.

[0220] Experiment involving Natural rubber latex (Experiment 11)

[0221]

[0222] Table 2

[0223]

[0224] Table 8 A

[0225]

[0226] Table 8B

[0227] The addition of PAP at the tune of 10 phr in natural rubber showed some ease of stripping without anti-tack in the coagulant solution. However, there is a severesticking tendency with glove to glove and within the glove, the fingers get stuck within the same glove. Hence the addition is not much helpful like in the case of NBR latex. Combined with excessive filler addition the glove is getting hardened with increased modulus and reducing elongation at break.

[0228] Experiment involving NBR and lower Tg PAP (24 °C) (Experiment 12)

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[0234] Table 3

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[0237] Table 9B

[0238] This experiment is designed to assess the effect of relatively lower Tg (24 °C), PAP material against the one used in experiments 2 - 10, where the Tg of PAP is 63 °C.

[0239] This experimental set up is similar to Experiment 3 with PAP of 2 phr. Comparing the properties of experiment 3 the properties of experiment 12 is very close and comparable. However, the ease of stripping using lower Tg PAP in the case of experiment 12 is not same as of experiment 3. Even though the glove made from experiment 12 is strippable without anti-tack in the coagulant there is a difference inthe feel while stripping - less ease, which is obvious since the Tg is low in the case of experiment 12 compared to experiment 3.

[0240] Experiment involving different Cure set (Experiment 13)

[0241]

[0242] Table 4

[0243]

[0244] Table 10A

[0245]

[0246] Table 10B

[0247] This experiment 13 is designed to test the variation in the cure set of NBR compound which is the main elastomer in the making of the article. As for as the PAP content is concerned it is similar to experiment 3 and experiment 12.

[0248] A proprietary curing compound produced by Crestage Industries of Malaysia is used in this experiment with minor addition of other curatives like ZnO and Sulphur.

[0249] The glove is much easier to strip off from the former without any anti-tack in the coagulant. As per the physical properties, the film formed by the cure set of experiment 13 is much stronger. This implies the PAP addition works better with higher film strength.

[0250] Experiment involving Polychloroprene Blend and PAP (Experiment 14)

[0251]

[0252] Table 5

[0253]

[0254] Table 11A

[0255]

[0256] Table 11B

[0257] The addition of PAP at the tune of 10 phr in polychloroprene blend with nitrile showed some, very little ease of stripping without anti-tack in the coagulant solution. However, there is a severe sticking tendency with glove to glove and within the glove, the fingers get stuck within the same glove. Hence the addition is not much helpful like in the case of NBR latex. By chemical nature at molecular level polychloroprene and polyisoprene are similar, the methyl group in the side chain of polyisoprene is replaced with chlorine in the case of polychloroprene, obviously the effect on stickiness is same and in fact it is inferior in the case of polychloroprene due to the presence of chlorine molecules which may entangle PAP and restrict the migration to the surface of the article.

[0258] Various modifications to these embodiments are apparent to those skilled in the art from the description and the accompanying drawings. The principles associated with the various embodiments described herein may be applied to other embodiments. Therefore, the description is not intended to be limited to the embodiments shown along with the accompanying drawings but is to be providingbroadest scope of consistent with the principles and the novel and inventive features disclosed or suggested herein. Accordingly, the invention is anticipated to hold on to all other such alternatives, modifications, and variations that fall within the scope of the present invention and appended claims.

[0259] In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

Claims

CLAIMS1. A composition for producing a non-tacky elastomeric article comprising:an elastomer;characterized by0.5 to 50 parts of polyacrylic polymer or derivative thereof per hundred of part of the elastomer, incorporated in the composition;wherein the polyacrylic polymer or derivative thereof has a glass transition temperature from 5 °C to 120 °C.

2. The composition of claim 1, wherein the elastomer is a synthetic elastomer, a natural elastomer, or a combination thereof.

3. The composition of claim 1, wherein the elastomer is selected from any one or combination of acrylo nitrile butadiene rubber, styrene butadiene rubber, polychloroprene rubber, polyisoprene rubber, or their derivatives.

4. The composition of claim 1, wherein the elastomer is carboxylated acrylo nitrile butadiene rubber.

5. The composition of claim 1, wherein the polyacrylic polymer or derivative thereof having a structure represented by Formula (I)[ - CH2- CR1(COOR2)-]n...(I)whereRi is hydrogen or alkyl,R2is hydrogen or alkyl or sodiumwhereby Formula (I) may combine with other alkyl or aryl groups.

6. A method for producing a non-tacky elastomeric article comprising of: providing an elastomer;blending 0.5 to 50 parts of polyacrylic polymer or derivative thereof per hundreds of parts of the elastomer with the elastomer to form a composition, at a compounding stage; andforming the composition into the elastomeric article.

7. The method of claim 6, wherein the compounding stage further comprising blending into the composition any one or combination of cross-linking agents, curative chemicals, antioxidants, stabilizers, wax, opaqueness providers, fillers, colorants, surfactants, or pH modifiers.

8. The method of claim 6, wherein the composition is subjected to maturation for a duration of 6 hours to 3 days.

9. The method of claim 6, wherein the elastomeric article is a glove.

10. The method of claim 9, wherein forming the composition into the elastomeric article comprises dipping a former with a coagulant, dipping the former with the composition, wherein the coagulant does not contain anti-tack or less anti-tack material.

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