WO2001045809A1

WO2001045809A1 - A balanced bladder for inflatable balls

Info

Publication number: WO2001045809A1
Application number: PCT/IN1999/000074
Authority: WO
Inventors: Satish Jain; Naresh Jain; Anil Jain; Jinesh Jain; Vipin Jain
Original assignee: Satish Jain; Naresh Jain; Anil Jain; Jinesh Jain; Vipin Jain
Priority date: 1999-12-21
Filing date: 1999-12-21
Publication date: 2001-06-28
Also published as: GB0213254D0; AU2687100A; JP3823054B2; GB2373193B; JP2003517905A; GB2373193A

Abstract

A balanced bladder for inflatable balls having the characteristics to follow the desired trajectory along with the property to rebounce along the path of forward motion. The subject bladder comprises a shell and a valve fitted at the open end of the said shell. The said shell comprises at least a layer or at least a pair of layers of compounded synthetic latex and/or compounded natural rubber latex and a partial additional layer of synthetic latex and/or natural rubber latex provided diametrically opposite to the open end of the said shell characterized in that the said partial additional layer is superimposed on 2-20 % of the circumference of the said shell, having the weight conforming to the weight of the said valve. The invention also resides in the process for the preparation of the balanced bladder wherein the shell comprising at least a layer of compounded natural rubber latex and/or compounded synthetic latex and a partial additional layer of compounded natural rubber latex and/or compounded synthetic latex each is prepared by dipping the former in not only compounded natural rubber latex bath but also in the compounded synthetic latex bath. In an another embodiment, the process comprises dipping the former in the bath comprising blended compounded natural rubber latex and compounded synthetic latex. Finally, a valve is fixed at the open end of the resultant shell to obtain a balanced bladder.

Description

TITLE OF THE INVENTION

A BALANCED BLADDER FOR INFLATABLE BALLS

FIELD OF THE INVENTION The subject invention relates to a balanced bladder for inflatable balls having the characteristics to follow the desired trajectory along with the property to rebounce along the path of forward motion.

More specifically, the subject invention relates to a balanced bladder for inflatable balls comprising a shell and a valve fitted at the open end of the said shell wherein said shell comprises at least a layer of compounded synthetic latex and/or compounded natural rubber latex and a partial additional layer of synthetic compounded latex and/or compounded natural rubber latex provided diametrically opposite to the open end of the said shell. The said partial additional layer is superimposed on 2-20% of the circumference of the said shell and is having its weight conforming to the weight of the said valve so as to obtain a balanced bladder for inflatable balls having the characteristics to follow the desired trajectory along with the property to rebounce along the path of forward motion.

The present invention also provides a bladder shell for inflatable balls comprising at least a pair of layers of compounded synthetic latex and compounded natural rubber latex and a partial additional layer of compounded synthetic latex and /or compounded natural rubber latex.

The object of the invention is to provide a balanced bladder for inflatable balls having the characteristics to follow the desired trajectory along with the property to rebounce along the path of forward motion.

The embodiment of the invention relates to a bladder for inflatable balls comprising a bladder shell and a valve fitted at the open end of the said bladder shell wherein the said bladder shell is provided with at least a layer of compounded synthetic latex followed by at least a layer of compounded natural rubber latex and an additional partial layer, laminated together and crosslinked integrally to each other by vulcanization.

Another embodiment of the invention relates to an improved process for the manufacture of a balanced bladder for inflatable balls comprising at least a layer of natural rubber latex and synthetic latex each and an additional partial layer superimposed on the partial circumference of the bladder shell.

PRIOR ART

The conventionally available bladders in the market either faces problems in having balance due to the weight of the valve . The balanced bladder for inflatable balls do not have the property to follow the desired trajectory along with the property to rebounce along the path of forward motion.

In the rubber bladders as known conventionally, rubber compounds such as butyl rubber are compounded on a rubber mill or banbury mixer. This compound is then calendered to the desired thickness in sheet form. From the rubber sheet, quarter sections of the bladder are die cut and pieced together by hand with adhesive and end patches. A valve is inserted and adhered to the construction. The total construction is then heat cured to produce a bladder. The adhesive application results in the imperfect seals and poor weight balancing. This conventional process often results in high amounts of defective bladders and excess scrap.

The bladders made up of thermoplastic materials such as polyethylene powders and vinyl plastisols are also known conventionally. However, these materials are found to have no bounce but have good air retention and hence found not suitable for inflatable bladders.

The inflatable bladders made up of natural rubber are also available conventionally. The latex rubber bladder shell made from natural rubber latex as available in the market are found to have very good bounce property but have high air permeability properties. Due to high air permeability, the air leaks out frequently leading to frequent refilling of the bladder within short durations.

The bladders made up of butyl rubber are also known conventionally. The bladder composition containing low unsaturated butyl rubber has been disclosed in U.S. Patent No. 4,022,848. This Patent teaches the use of butyl rubber composition in tire curing bladders, air bags and curing tubes.

Butyl rubber is well known in the art and is disclosed in U.S. Patent No. 3,031 ,423, column 1 , lines 15 to 24. The problems faced with the butyl rubber bladder is that while it has a good air retention, but it lacks in good bounce properties.

The present invention provides a bladder shell for inflatable ball with true balance and true re-bounce properties besides having low air permeability and high bounce characteristics. The invention also defines process for preparation of such balanced bladders.

The co-pending Indian Patent application No.1341/DEL/99 dated 08.10.1999 , relates to a bladder shell for inflatable balls comprising at least a pair of layers of compounded synthetic latex and compounded natural rubber latex laminated together and crosslinked integrally to each other by vulcanization to form a low air permeability and high bounce bladder shell.

In an another co-pending Indian Patent application No. 1342/DEL/92 dated 8.10.1999, a process for the manufacture of a bladder shell has been claimed, where a layer of compounded natural rubber latex and a layer of compounded synthetic latex is formed on the former. The sequence of deposition of two layers on the former is not material. Another co-pending Indian Patent application No. 1342/DEL/92 dated 8.10.1999, claims a process for the manufacture of a bladder shell, where a layer of compounded natuial rubber latex and a layer of compounded synthetic latex is formed on the former. The sequence of deposition of two layers on the former is not material.

In yet another co-pending Indian Patent application No. 1343/DEL/92 dated 8.10.1999, a process for the manufacture of a bladder shell has been claimed, where a compounded natural rubber latex and compounded synthetic latex blended in the ratio of 80:20 to 20:80 is formed on the former.

The corresponding co-pending U.S. Patent application No. 09/422,197 dated 08.10.1999 and E.P. Patent application No. 99308570-3 dated 8.10.1999 , corresponding to the above mentioned Indian Patent applications relates to a bladder shell having a layer of compounded synthetic latex and natural rubber latex layer blended in the ratio of 80:20, wherein the thickness of the resultant layer is from 0.25mm to 3.0mm

In co-pending application No. 1511/DEL/99 dated 29.11.1999 and in a corresponding co-pending PCT application (Number awaited) dated 8.12.1999 , a bladder shell for inflatable balls comprising at least a layer each of compounded synthetic latex and compounded natural rubber latex laminated together and crosslinked integrally to each other by vulcanization to form a low air permeability and high bounce bladder shell wherein the ratio of the said compounded synthetic latex to said compounded natural rubber latex is 80:20 to 20:80 and the total thickness of the resultant compounded laminated layers is from 0.25mm to 3.0mm., has been claimed.

The bladder shell for inflatable balls comprises at least a pair of layers of compounded synthetic latex and compounded natural rubber latex laminated together and crosslinked integrally to each other by vulcanization wherein the total thickness of the resultant laminated layers varies from 0.25mm to 3.0mm.

The bladder shell for inflatable balls may comprises at least a layer of blended synthetic latex and natural rubber latex blended in the ratio of 80:20 to 20:80 compounded with anti-oxidant, activators, accelerators, thickening and wetting agents, stabilizers etc., wherein the total thickness of the compounded laminated layers is from 0.25mm to 3.0mm.

Latex dipping processes appeared as natural rubber lattices became commercially available in an adequately stable form in the period around 1930s. The latex dipping process was a development over the rubber solution dipping as latex dipping processes were found to be less hazardous, more economic and technically more versatile with its high rubber content. Latex dipping process consists of using an inert former, which is in the shape of the ultimately desired product, and this former is coated with one or more dips of the latex compound. The coating is set by a coagulant and/or heat dried into a integral /one film which can then be stripped from the former.

The conventionally known processes have used natural rubber latex for the preparation of the bladder shell and the former is dipped into a natural rubber latex where coating is set with one or more coagulant dips.

As aforementioned , the bladders shell has been manufactured from natural rubbers like latex, butyl rubber, polyvinyl chloride and other forms of synthetic rubbers or elastomeric materials.

The bladder shell is provided with an air inlet valve through which the air is pumped into the bladder. The air inlet valve of the bladder is not visible to the naked eye as the same is covered by the other body. The bladder is placed inside the ball and the outer body either consists of panels which are stitched together or it is a molded body.

The surface of the outer body is provide with an aperture or opening to enable inflating the bladder and a s a consequence the ball.

When the bladder is inserted inside the outer body of the ball, though the valve is not visible but because of the weight of the valve being concentrated on one side of the ball it does not follow the desired path on being hit, This effect is especially visible when the ball on being hit is also spinning on its own axis. This results in a wobbling effect thereby resulting in the ball not taking the desired path and not reaching the desired destination.

There have been attempts to remove this wobbling effect by placing counterbalancing weight between the bladders and the panels to offset the weight of the lacing and the associated components thereon. However, the desired effect has still not been achieved.

To avoid wobbling effect created due to placement of the valve there have been various methods used and various modifications made in the manufacture of the bladder and the ball. The US Patent 5709622 and 5470060 define a football with odd number of panels. To avoid kicking the football at a diametrically opposite position to the location of laces of the football, the football in this invention is provided with an odd number of panels, thereby enabling the kicking of the football at a location where no seam is located to enhance the effectiveness and accuracy of kicking. US Patent 5577724 defines use of an additional lacing in order to provide balance to the weight and structure of the football.

Further US Patent 5098097 relates to a football comprising an inflatable, bladder formed in a generally elliptical shape and fabricated of an elastomeric material; where four panels are secured together over the bladder, each panel being of a similar, generally oval shape with inturned edges secured together by stitching to form four seams.

Another U.S. Patent No. 5342043, relates to a inflatable bladder wherein an essentially inextensible liner formed of four liner components, where each liner component being of a similar, generally oval shape with inturned edges are secured together and associated to a panel by stitching to form four seams. The closure means comprises two patches and a tongue between the bladder and line component and at least a pair of spaced apart counterweights of an elastomeric material , each of a weight substantially equal to half that of the said lacing and closure means and are molded to the bladder internally so that there is no abatement of kicking efficiency . However, even this patent has not been able to claim the complete elimination of wobbling effect.

The present invention relates to a process for the preparation of a balanced bladder for inflatable balls having the characteristics to follow the desired trajectory along with the property to rebounce along the path of forward motion.

The main embodiment of the present invention resides in the formation of at least a layer of natural rubber latex and a synthetic latex each acting as base layer and a partial layer on the circumference of the said base layer. The process of the present invention comprises dipping the former in not only a compounded natural rubber latex bath but also in compounded synthetic latex bath. The former is dipped in compounded natural rubber latex bath and compounded synthetic rubber latex alternatively, in any order, thereby forming two different layers of the latex on the former. A portion of the said former is again dipped into a bath having compounded synthetic latex and /or natural rubber latex partially to get a partial additional layer superimposed on the circumference of the said base layer. The end product when stripped thereof has either a combination of layers or single layer present which not only exhibits the desired true re-bounce characteristic but also the required balanced properties. More than one layer of the natural rubber latex and the synthetic rubber latex may also be deposited depending upon the characteristics of the end product required.

The various ingredients added to the latex i.e. natural rubber latex and/or synthetic rubber latex are selected from the antioxidants, accelerators, activators, stabilizers, softening agents, fillers, waxes, colours, de-webbing agents and non-foaming surfactants.

These ingredients are added into the latex in the form of solutions, dispersions, or emulsions. The ingredients in the form of dispersions and emulsions are added to lattices to form a compound. After preparing the synthetic and natural rubber compounds, the same are transferred to their respective dipping tanks.

To make a blend of natural rubber latex and synthetic rubber latex, the same are mixed in the ratio of 80:20 to 20:80 with the help of stirrer at the rate of 10-15 RPM and passed through a homogenizer to form a homogeneous mixture.

The bladder shell comprising at least a pair of layers of natural rubber latex and /or synthetic latex and an additional layer are compounded with antioxidant from 0.01 to 3 PHR accelerators from 1 to 3 PHR activators from 0.01 to 5 PHR thickening and wetting agents from 0.5-1 PHR stabilizers from 0.1-2 PHR and optionally softeners from 0.1-2 PHR and fillers from 5-20 PHR The natural rubber lattices are selected from Epoxidised NR latex, Cream latex, Centrifuge latex or double centrifuged latex.

The accelerators are selected from Dithiocarbamate, Vulkacit LDA, Vulkacit LDB, Setsit 9, Setsit 5, Butyl namate, Guanidine, Vulkacit DOTG, Vulkacit D, Mecapto or Thiuram accelerators and the like.

The antioxidants used are non-discolouring type of antioxidant and slight discolouring type of antioxidants. The Non-discolouring type of antioxidants are selected from Antioxidant BKF, Antioxidant NKF, Antioxidant MB, Antioxidant ZMB, Antioxidant NONOX SP, Antioxidant NONOX WSP, Antioxidant NONOX BROD, Antioxidant 2246, Wingstay L or Agerite White and the like.

The slight discolouring type of antioxidants are selected from Antioxidant HS or Antioxidant Nonex BROD and the like.

The optional components as softeners and fillers may also added in the subject composition, where the softeners are selected from the group comprising paraffin, paraffin wax or Stearic acid. The fillers are selected from China Clay, Mica Powder, Whiting, Lithopone, Blancfixe, Carbon Blacks or Titanium Oxide.

All the above referenced ingredients are added into the latex in the form of dispersions, emulsions or solutions in the predetermined ratio.

The inflatable bladder shell is manufactured by dipping the cleaned former into first coagulant bath containing the components selected from the Calcium Nitrate, Calcium Chloride, Acetic acid, parting agents or carriers, water and optionally alcohol, wetting agents and defoaming agents to obtain a uniform film on the former. The former having a layer of coagulant on it is then dried. The coagulant coated dried former is then dipped into the bath or a pair of baths having either a blend of compounded lattices into it or having the synthetic latex compound or natural rubber latex compound. The former is then dipped into a coagulant bath and dried. The dried former is then dipped into a bath having compounded synthetic latex and/ or compounded natural rubber latex to get a partial additional layer superimposed on the circumference of the said former.

The former is then dried in an oven and dipped into water bath for cooling and thereafter bladder shell thus formed is stripped. The bladder shell is then washed and dried and subjected to post curing treatment. The valve is then fitted on the neck of the bladder shell to form the balanced bladder for the inflatable ball.

Accordingly, the subject invention relates to a balanced bladder for inflatable balls comprising a shell and a valve fitted at the open end of the said shell wherein said shell comprises at least a layer of compounded synthetic latex and/or compounded natural rubber latex and a partial additional layer of synthetic latex and/or natural rubber latex provided diametrically opposite to the open end of the said shell characterized in that the said partial additional layer is superimposed on 2-20% of the circumference of the said shell, having the weight of the said superimposed layer conforming to the weight of the said valve.

The embodiment of the invention relates to a balanced bladder for inflatable balls comprising a shell and a valve fitted at the open end of the said shell wherein said shell comprises at least a pair of layers of compounded synthetic latex and/or compounded natural rubber latex and a partial additional layer of synthetic latex and/or natural rubber latex provided diametrically opposite to the open end of the said shell characterized in that the said partial additional layer is superimposed on 2-20% of the circumference of the said shell, having the weight of the said superimposed layer conforming to the weight of the said valve.

Further, the invention relates to an improved process for the manufacture of a balanced bladder for inflatable balls comprising a shell and a valve fitted at the open end of the said shell wherein said shell comprises at least a layer of compounded synthetic latex and/or compounded natural rubber latex and a partial additional layer of compounded synthetic latex and/or compounded natural rubber latex , comprising the steps of: a) cleaning the former; b) dipping the said cleaned former into a first coagulant bath at a temperature of 20°C -95°C to obtain a first coagulant coated former; c) drying the said first coagulant coated former; d) dipping the said dried coagulant coated former into a compounded synthetic latex and /or compounded natural rubber latex bath having 40-65% by weight water based solution for a period of 1 to 4 minutes depending upon the thickness required, at a temperature of 20°C -45° C to obtain a resulting layer of compounded synthetic latex and /or compounded natural rubber latex on said first coagulant coated former; e) dipping 2-20% of the said former having a layer of compounded synthetic latex and/or compounded natural rubber latex, into a compounded natural rubber latex and/ or compounded synthetic latex bath to form an additional layer having thickness of 0.1mm to 2.0mm f) drying the said former having layers of compounded synthetic latex and/or compounded natural rubber latex and said additional layer on 2-20% of the circumference of the said former ; g) leaching the said former having layers of said compounded synthetic latex and/or compounded natural rubber latex and said partial additional layer of compounded synthetic latex and/or compounded natural rubber latex, in hot water for 8 to 10 minutes to remove excess compounded material from the surface and drying the said former in an oven at a temperature of 55°C -115° C; h) vulcanising the said leached and dried former resulting in the said former having layers of said compounded natural rubber latex and/or said compounded synthetic latex and said partial additional layer at a temperature of 100°C -140° C; i) cooling the said resultant former; j) stripping the layers of compounded natural rubber latex, synthetic latex along with said additional superimposed layer from the said cooled resultant former to obtain a shell; k) washing the said stripped shell with water to remove any extraneous material, drying the washed shell in hot air room and post curing the said washed shell at 60°C -90 ° C for 8 to 12 hours, to obtain a resultant shell for bladder for an inflatable ball.

I) fixing a valve at the open end of the said cured resultant shell to obtain a balanced bladder with true re-bounce properties.

The embodiment of the invention also relates to an improved process for the manufacture of a balanced bladder for inflatable balls comprising a shell and a valve fitted at the open end of the said shell wherein said shell comprises at least a pair of layers of compounded synthetic latex and compounded natural rubber latex and a partial additional layer of compounded synthetic latex and/or compounded natural rubber latex , comprising the steps of: a) cleaning the former; b) dipping the said cleaned former into a first coagulant bath at a temperature of 20-95° C to obtain a first coagulant coated former; c) drying the said first coagulant coated former; d) dipping the said dried coagulant coated former into a compounded synthetic latex bath having 40-65% by weight water based solution for a period of 1 to 4 minutes depending upon the thickness required, at a temperature of 20°C - 45°C to obtain a resulting layer of compounded synthetic latex on said first coagulant coated former; e) drying the said former having layer of compounded synthetic latex; f) dipping the said dried former having layer of compounded latex into a second coagulant bath at a temperature of 20°C -95°C to obtain a coating of second coagulant on the layer of compounded synthetic latex on the former; g) drying the said second coagulant coated former; h) dipping the said dried second coagulant coated former into a compounded natural rubber latex bath having 40-65% by weight water based solution for a period of 1 to 4 minutes depending upon the thickness required, at a temperature of 20°C -45° C to obtain a layer of compounded natural rubber latex on second coagulant coated former; i) drying the said former having layers of compounded synthetic latex and compounded natural rubber latex; j) dipping the 2-20% of the said dried former having layers of compounded synthetic latex and compounded natural rubber latex in a bath having compounded natural rubber latex bath and /or compounded synthetic rubber latex to form an additional layer having thickness of from 0.1mm to 2.0mm k) drying the said former having layers of said compounded synthetic latex and said compounded natural rubber latex and said additional layer on 2-20% of the circumference of the said former ; I) leaching the said former having layers of said compounded synthetic latex, said compounded natural rubber latex and said additional layer, in hot water for 8 to 10 minutes to remove excess compounded material from the surface and drying the said former in an oven at a temperature of 55°C - 115°C; m) vulcanising the said leached and dried former resulting in the said former having layers of said compounded natural rubber latex, said compounded synthetic latex and said partial additional layer at a temperature of 100°C -140° C; n) cooling the said resultant former; o) stripping the layers of compounded natural rubber latex, synthetic latex along with said partial additional layer from the said cooled resultant former to obtain a shell; p) washing the said stripped shell with water to remove any extraneous material, drying the washed shell in hot air room and post curing the said washed shell at 60°C -90 ° C for 8 to 12 hours, to obtain a resultant shell for bladder for an inflatable ball; wherein the said step of dipping the coagulant coated former in synthetic latex bath as defined in step (d) or natural rubber latex bath as defined in step (h) is reversible. q) fixing a valve at the open end of the said cured resultant shell to obtain a balanced bladder with true re-bounce properties.

The thickness of the said partial additional layer is from 0.1 mm to 2.0 in the said balanced bladder and the weight of the said partial additional layer is from 2 gms. to 14 gms.

The subject invention is described in detail hereinafter. However, the same is for illustrative purposes and any improvements thereof shall be within the scope of the subject application and the same should not be construed to restrict the scope of the invention.

DETAILED DESCRIPTION OF THE INVENTION

For the manufacture of the bladders, the formers formed of porcelain, plastic or metals, are first cleaned to remove all dust and all extraneous material. The surface of all formers is preferably cleaned by dipping formers into acids- alkali and/or water. The effective cleaning of the formers may also be ensured by using an ultrasonic cleaning bath. The cleaned formers may also be subjected to washing and conditioning where the formers are dipped into a conditioning bath so that a uniform wetting in the next bath is obtained.

The washed, cleaned and conditioned former is then dipped into a coagulant bath, termed as first coagulant bath to form a uniform film of first coagulant on the former. The coagulant bath comprises a solution of components selected from calcium nitrate, calcium chloride and acetic acid along with the wetting agents, defoaming agents, parting agents or carriers. The calcium chloride and/or calcium nitrate are present in an amount of 10-75% of the total composition. Acetic acid is added in the solution to maintain the acidic pH between 2.2 to 6.8. The wetting agents in the coagulant bath are added in an amount of 0.01 to 10% by weight of the total composition. The wetting agents are basically surface active agents chosen from anionic, non-ionic or cationic surfactants. Alcohol may optionally be used as wetting agent. Parting agents are inert powders added to facilitate the removal of the end product. The viscosity of the coagulant is low which is increased by the addition of an inert powder, thereby enabling formation of a viscous layer of the coagulant on the former. The parting agents, i.e., the inert powders are selected from talcum powder, calcium carbonate, magnesium oxide, bentonite clay and the like inert material. The parting agents are added in an amount of 0.01 to 20%. A uniform coagulant layer is formed on the former where uniformity is ensured due to presence of the wetting agents in the coagulant bath. The thickness of the layer deposited on the former depends on the required thickness of the resultant film required to form the bladder and also on the specifications of the bladder. The temperatures of the first coagulant dip is maintained at between 20-95° C . The first coagulant coated former is then dried at room temperature or by blowing air or by heating. The defoaming agents are also surface active agents.

This dried first coagulant coated former is then dipped in a latex bath which is selected from the natural rubber bath or the synthetic latex bath. At this stage either synthetic latex bath or natural rubber latex bath may be used. If synthetic latex bath is used first, in the next stage, natural rubber latex bath is used.

Synthetic latex bath comprises of synthetic latex compounded with compounding ingredients. The synthetic lattice is selected from the group consisting of Styrene-butadiene latex, Acrylonitrile- butadiene latex,

Polychloroprene latex, Butyl latex, and EPDM latex. The synthetic latex is compounded with compounding ingredients selected from vulcanising agent; antioxidants; activators; thickening and/or wetting agents; and optionally softeners and fillers.

In the synthetic latex bath, the latex is added as an aqueous solution whereas the other compounds, i.e., vulcanising agent, antioxidants, activators, thickening and/or wetting agents, softeners and fillers are added to the tank in a solution, dispersion or emulsion form. The temperature of the synthetic latex bath is maintained between 20 to 45°C . The compounded latex bath is having a 40-65% by weight water based solution.

The dried first coagulant coated former is dipped in the synthetic latex bath for a time period sufficient to obtain a layer of synthetic latex on the first coagulant film on the former. The thickness of the layer of synthetic latex deposited depends directly on the thickness desired of the end product. The former is dipped in the synthetic latex bath preferably for a period of 0.5 to 15 minutes.

Pursuant to such synthetic latex layer formation on the former , the former with a layer of synthetic latex is dried either in open or closed chambers. Drying in open chambers is carried out by leaving the former in open while drying in closed chambers comprises blowing air or heat. The drying in closed chambers avoid deposition of any extraneous material on the layer of synthetic latex on the former.

The dried former having a layer of synthetic latex is thereafter dipped into a second coagulant bath which comprises a solution of calcium nitrate, calcium chloride and acetic acid to form a film of second coagulant on the layer of synthetic latex on the former. Besides, these components the bath also comprises wetting agents, defoaming agents. The calcium chloride, calcium nitrate and acetic acid are present in an amount of 10-75% of the total composition. The wetting agents in the coagulant bath are added in an amount of 0.01 to 10% by weight of the total composition. The wetting agents are basically surface active agents chosen from anionic, non-ionic or cationic surfactants. Alcohol may also be used as wetting agent. A uniform coagulant layer is formed on the former where uniformity is ensured due to presence of the wetting agents in the coagulant bath. The thickness of the layer deposited on the former depends on the required thickness of the resultant film required to form the bladder and also on the specifications of the bladder. The temperatures of the second coagulant bath is maintained at between 20- 95°C.

Pursuant to second coagulant dip the second coagulant coated former is dried in open or closed chambers.

The dried former is thereafter dipped in a natural rubber latex bath where the bath contains the natural rubber latex compounded with vulcanising agent, antioxidants, activators, thickening and/or wetting agents, and optionally softeners and/or fillers. The compounding ingredients are added to the tank in a solution, dispersion or emulsion form. A layer of the natural rubber latex is formed on the second coagulant. The temperature of the natural rubber latex bath is maintained between 20 to 45°C. The compounded latex bath is having a 40-65% by weight water based solution.

The former is dipped in the natural rubber latex bath for a time period sufficient to provide the required thickness of the film. The thickness of the film deposited depends directly on the thickness desired of the end product. The former is dipped in the natural rubber latex bath preferably for a period of 0.5 to 15 minutes.

The former having a layer of natural rubber latex is thereafter dried at room temperature. Thus the former here has two layers, one of the synthetic latex and the other of the natural rubber latex The 2-20% of the said former having layers of compounded synthetic latex and compounded natural rubber latex is then dipped into a bath having compounded natural rubber latex and/or compounded synthetic latex to get a partial additional layer superimposed on the circumference of the said shell having a thickness of 0.1mm to 2.0mm.

The said former having a partial additional layer is leached by washing in hot water. The films on the former are dipped in hot water for 2-20 minutes to remove the excess compounding ingredients present on the surface. By leaching process the surplus ingredients get washed into hot water.

The washed surfaces of the former are then dried in a drying oven which operate at a temperature 40-110°C. In the drying oven the water present is completely evaporated from the surface of the former.

The former are thereafter passed on for vulcanising in an oven where the temperature is the range of 100-140°C. The hot air is present with no inert medium being present. The surplus ingredients from the surface of the film on the former are completely evaporated at this stage.

The former are then cooled to room temperature preferably in open air or by using flowing water.

The film formed on the former is then stripped. The stripping is either done manually or mechanically and then this film/bladder shell is washed in water at room temperature to remove any extraneous material that might be present on/in film/bladder shell thus formed.

The stripped and washed film is thereafter subjected to post stripping curing through tumblers and hot air room chambers. The post curing is done at a temperature of 60-90°C for 8-12 hours in a hot air room. Dipping of the natural rubber bath may be done either before of after dipping in the synthetic latex bath. The film formed on the former may have the layer of either synthetic latex over natural rubber latex or vice versa.

The film thus formed is the seamless body of bladder which is converted to bladder by fixing valve(s) at the end of the bladder shell. Thus a bladder having the property to follow the desired trajectory along with the property to rebounce/retum along the path of forward motion when hit perpendicularly.

The synthetic latex and natural rubber latex compounds are transferred to their respective tanks at a particular temperature, having baffles or agitators into it to avoid the skimming and settling of the various ingredients in the compound.

The present invention can be understood explicitly and clearly from the following examples:

EXAMPLES Example 1 : A former made of metal is washed to remove all dust and all extraneous material. The surface of the aluminum former is cleaned by dipping it into acids-alkali followed by washing with water. The washed and cleaned former is then dipped in a first coagulant bath. The first coagulant bath comprises a solution of calcium nitrate and calcium chloride in an amount of 55% and 0.05% by weight of the total composition of wetting agent; 0.07% talcum powder and the rest being water. The temperatures of the first coagulant dip is maintained at about 50° C. After the former is removed from the coagulant bath, it is dried at room temperature and dipped in a synthetic latex bath comprising 45% aqueous nitrile latex; 1.5% sulfur and dithiocarbamates; 2% by weight of Antioxidant BKF; 4% by weight of zinc oxide; 1.5% of thickening and/or wetting agents; 1% liquid paraffin and upto 1% china clay. The temperature of the synthetic latex dip is maintained at 30°C. The former is dipped in the synthetic latex bath for a period of 1 minute. Pursuant to such synthetic latex film formation on the former , it is dried at room temperature. The dried former is thereafter dipped in a second coagulant bath comprising 60% solution of calcium chloride, 5% anionic surfactants, defoaming agents and alcohol at a temperature of 50° C . The former is thereafter dried and dipped in the natural rubber latex bath. The natural rubber latex bath contains the natural rubber latex along with sulfur and zinc oxide active, and Antioxidant, wetting agent, softeners and fillers. The temperature of the natural rubber latex bath is 55° C. The former is dipped in the natural rubber latex bath preferably for a period of 2 minutes. The former is thereafter dried at room temperature. The dried former is then dipped into the coagulant bath and dried. The dried coagulant coated former is then dipped upto 5% of its circumference into a bath having compounded synthetic latex to get a partial additional layer superimposed on the circumference of the said former having thickness of 1mm . The former is then dried. The dried former is washed in hot water. The films on the former are dipped in hot water for 10 minutes to remove extraneous chemicals present on the surface. The washed former is then dried in a drying oven which operates at a temperature 55° C. The former is thereafter passed on to oven where the temperature is maintained at about 110° C where hot air is present with no inert medium being present. The former are then cooled to room temperature in open air. The film formed on the former is then manually stripped and water is added into the stripped film at room temperature to remove any extraneous material that might be present on the sides of the film thus formed. The stripped and washed film is thereafter subjected to post stripping curing through tumblers and hot air room chambers. The post curing is done at a temperature of 70° C for about 8 hours in a hot air room. The valve is fitted on the open end of the bladder shell to obtain a balanced bladder for inflatable balls.

Example 2

A former made of metal is washed to remove all dust and all extraneous material. The surface of the aluminum former is cleaned by dipping it into acids-alkali followed by washing with water. The washed and cleaned former is then dipped in a first coagulant bath. The first coagulant bath comprises a solution of calcium nitrate and calcium chloride in an amount of 54.5% and 0.05% by weight of the total composition of wetting agent; 0.06% talcum powder and the balance being water. The temperatures of the first coagulant dip is maintained at about 49.5° C. The coagulant coated former is dried at room temperature and dipped in a synthetic latex bath comprising 44.5% aqueous synthetic latex; 1.4% sulfur and dithiocarbamates; 1.8% by weight of Antioxidant BKF; 4% by weight of zinc oxide; 1.6% of thickening and/or wetting agents; 1% liquid paraffin and upto 1 % china clay at temperature of 30° C for a period of 1 minute. The former is dried at room temperature. The dried former is thereafter dipped in a second coagulant bath comprising 60% solution of calcium chloride, 5% anionic surfactants, defoaming agents and alcohol at a temperature of 50° C. The former is thereafter dried and dipped in the natural rubber latex bath. The natural rubber latex bath contains the natural rubber latex along with sulfur and zinc oxide active and Antioxidant, wetting agent, softeners and fillers. The temperature of the natural rubber latex bath is 55° C. The former is dipped in the natural rubber latex bath preferably for a period of 3 minutes. The 10% of the circumference of the said former is again dipped in the same bath to get a partial additional layer on the circumference of the said former. The former is thereafter dried at room temperature. The dried former is then leached by washing in hot water. The films on the former are dipped in hot water for 12 minutes to remove excess chemicals present on the surface. The leached former is then dried in a drying oven which operates at a temperature 55° C. The former is thereafter passed on to oven where the temperature is maintained at about 110° C where hot air is present with no inert medium being present. The former are then cooled to room temperature in open air. The film formed on the former is then manually stripped and water is added into the stripped film at room temperature to remove any extraneous material that might be present on the sides of the film thus formed. The stripped and washed film is thereafter subjected to post stripping curing through tumblers and hot air room chambers. The post curing is done at a temperature of 70° C for about 8 hours in a hot air room. The valve is fitted on the open end of the bladder shell to obtain a balanced bladder for inflatable balls.

Example 3

A former made of aluminum is washed and cleaned by dipping it into acids- alkali followed by washing with water. The washed and cleaned former is then dipped in a first coagulant bath. The temperatures of the first coagulant dip is maintained at about 49° C. After the former is removed from the coagulant bath, it is dried. The dried coagulant coated former is dipped into a bath having a synthetic latex and natural rubber latex blended in a ratio of 72:28, compounded with compounding ingredients to obtain a layer of blended natural rubber latex and synthetic latex on the said former. The said former is then dipped upto 15% of the circumference in a bath having blend of compounded natural rubber latex and compounded synthetic rubber latex to form a partial additional layer superimposed on the circumference of the said shell. The said former having a layer of said blended natural rubber latex and synthetic latex and said partial additional layer is dried at room temperatures and leached in hot water for 9 minutes to remove excess compounded material from the surface followed by drying the said former in an oven at a temperature of 65° C.The said leached former is then vulcanized in an oven resulting in the said former having a blended layer of compounded natural rubber latex and synthetic latex at temperature of 115 degrees C in hot air. The said resultant former is then cooled and stripped to obtain a shell for a bladder for an inflatable ball. The stripped bladder shell is then washed with water to remove the extraneous material. The valve is fitted on the open end of the washed bladder shell to obtain a balanced bladder for inflatable balls.

Example 4

The former having layers of compounded synthetic latex and compounded natural rubber latex blended in the ratio of 72:28, is dipped upto 12% of the circumference in a bath having compounded natural rubber latex to form a partial additional layer superimposed on the circumference of the said shell. The said former having a layer of said blended natural rubber latex and synthetic latex and said partial additional layer is dried at room temperatures and leached in hot water for 9 minutes to remove excess compounded material from the surface followed by drying the said former in an oven at a temperature of 65° C.The said leached former is then vulcanized in an oven resulting in the said former having a blended layer of compounded natural rubber latex and synthetic latex at temperature of 115 degrees C in hot air. The said resultant former is then cooled and stripped to obtain a shell for a bladder for an inflatable ball. The stripped bladder shell is then washed with water to remove the extraneous material. The valve is fitted on the open end of the bladder shell to obtain a balanced bladder for inflatable balls.

Example 5

A former having layers of compounded synthetic latex and compounded natural rubber latex blended in the ratio of 72:28, is dipped upto 18% of the circumference in a bath having compounded synthetic rubber latex to form a partial additional layer superimposed on the circumference of the said shell.The said former having a layer of said blended natural rubber latex and synthetic latex and said partial additional layer is dried at room temperatures and leached in hot water for 9 minutes to remove excess compounded material from the surface followed by drying the said former in an oven at a temperature of 65° C.The said leached former is then vulcanized in an oven resulting in the said former having a blended layer of compounded natural rubber latex and synthetic latex at temperature of 115 degrees C in hot air. The said resultant former is then cooled and stripped to obtain a shell for a bladder for an inflatable ball. The stripped bladder shell is then washed with water to remove the extraneous material. The valve is fitted on the open end of the bladder shell to obtain a balanced bladder for inflatable balls. The subject invention as described herein should not be construed to restrict the broad scope of the invention.

Claims

WE CLAIM

1 A balanced bladder for inflatable balls comprising a shell and a valve fitted at the open end of the said shell wherein said shell comprises at least a layer of compounded synthetic latex and/or compounded natural rubber latex and a partial additional layer of synthetic latex and/or natural rubber latex provided diametrically opposite to the open end of the said shell characterized in that the said partial additional layer is superimposed on 2-20% of the circumference of the said shell, having the weight of the said superimposed layer conforming to the weight of the said valve.

2 A balanced bladder for inflatable balls comprising a shell and a valve fitted at the open end of the said shell wherein said shell comprises at least a pair of layers of compounded synthetic latex and/or compounded natural rubber latex and a partial additional layer of synthetic latex and/or natural rubber latex provided diametrically opposite to the open end of the said shell characterized in that the said partial additional layer is superimposed on 2- 20% of the circumference of the said shell, having the weight of the said superimposed layer conforming to the weight of the said valve.

3 A balanced bladder as claimed in claims 1 or 2, wherein the thickness of the said additional layer is from 0.1 mm to 2.0mm

4 A balanced bladder as claimed in claims 1 or 2 wherein the weight of the said additional layer is from 2 gms. to 14 gms.

5 An improved process for the manufacture of a balanced bladder for inflatable balls comprising a shell and a valve fitted at the open end of the said shell wherein said shell comprises at least a layer of compounded synthetic latex and/or compounded natural rubber latex and a partial additional layer of compounded synthetic latex and/or compounded natural rubber latex , comprising the steps of: a) cleaning the former; b) dipping the said cleaned former into a first coagulant bath at a temperature of 20°C -95°C to obtain a first coagulant coated former; c) drying the said first coagulant coated former; d) dipping the said dried coagulant coated former into a compounded synthetic latex and /or compounded natural rubber latex bath having 40-65% by weight water based solution for a period of 1 to 4 minutes depending upon the thickness required, at a temperature of 20°C -45° C to obtain a resulting layer of compounded synthetic latex and /or compounded natural rubber latex on said first coagulant coated former; e) dipping 2-20% of the said former having a layer of compounded synthetic latex and/or compounded natural rubber latex, into a compounded natural rubber latex and/ or compounded synthetic latex bath to form an additional layer having thickness of 0.1mm to 2.0mm f) drying the said former having layers of compounded synthetic latex and/or compounded natural rubber latex and said additional layer on 2-20% of the circumference of the said former ; g) leaching the said former having layers of said compounded synthetic latex and/or compounded natural rubber latex and said partial additional layer of compounded synthetic latex and/or compounded natural rubber latex, in hot water for 8 to 10 minutes to remove excess compounded material from the surface and drying the said former in an oven at a temperature of 55°C -115° C; h) vulcanising the said leached and dried former resulting in the said former having layers of said compounded natural rubber latex and/or said compounded synthetic latex and said partial additional layer at a temperature of 100°C -140° C; i) cooling the said resultant former; j) stripping the layers of compounded natural rubber latex, synthetic latex along with said additional superimposed layer from the said cooled resultant former to obtain a shell; k) washing the said stripped shell with water to remove any extraneous material, drying the washed shell in hot air room and post curing the said washed shell at 60°C -90 ° C for 8 to 12 hours, to obtain a resultant shell for bladder for an inflatable ball. I) fixing a valve at the open end of the said cured resultant shell to obtain a balanced bladder with true re-bounce properties.

6. An improved process for the manufacture of a balanced bladder for inflatable balls comprising a shell and a valve fitted at the open end of the said shell wherein said shell comprises at least a pair of layers of compounded synthetic latex and compounded natural rubber latex and a partial additional layer of compounded synthetic latex and/or compounded natural rubber latex , comprising the steps of: a) cleaning the former; b) dipping the said cleaned former into a first coagulant bath at a temperature of 20-95° C to obtain a first coagulant coated former; c) drying the said first coagulant coated former; d) dipping the said dried coagulant coated former into a compounded synthetic latex bath having 40-65% by weight water based solution for a period of 1 to 4 minutes depending upon the thickness required, at a temperature of 20°C - 45°C to obtain a resulting layer of compounded synthetic latex on said first coagulant coated former; e) drying the said former having layer of compounded synthetic latex; f) dipping the said dried former having layer of compounded latex into a second coagulant bath at a temperature of 20°C -95°C to obtain a coating of second coagulant on the layer of compounded synthetic latex on the former; g) drying the said second coagulant coated former; h) dipping the said dried second coagulant coated former into a compounded natural rubber latex bath having 40-65% by weight water based solution for a period of 1 to 4 minutes depending upon the thickness required, at a temperature of 20°C -45° C to obtain a layer of compounded natural rubber latex on second coagulant coated former; i) drying the said former having layers of compounded synthetic latex and compounded natural rubber latex; j) dipping the 2-20% of the said dried former having layers of compounded synthetic latex and compounded natural rubber latex in a bath having compounded natural rubber latex bath and /or compounded synthetic rubber latex to form an additional layer having thickness of from 0.1mm to 2.0mm k) drying the said former having layers of said compounded synthetic latex and said compounded natural rubber latex and said additional layer on 2-20% of the circumference of the said former ;

I) leaching the said former having layers of said compounded synthetic latex, said compounded natural rubber latex and said additional layer, in hot water for 8 to 10 minutes to remove excess compounded material from the surface and drying the said former in an oven at a temperature of 55°C - 1 15°C; m) vulcanising the said leached and dried former resulting in the said former having layers of said compounded natural rubber latex, said compounded synthetic latex and said partial additional layer at a temperature of 100°C -140° C; n) cooling the said resultant former; o) stripping the layers of compounded natural rubber latex, synthetic latex along with said partial additional layer from the said cooled resultant former to obtain a shell; p) washing the said stripped shell with water to remove any extraneous material, drying the washed shell in hot air room and post curing the said washed shell at 60°C -90 ° C for 8 to 12 hours, to obtain a resultant shell for bladder for an inflatable ball; wherein the said step of dipping the coagulant coated former in synthetic latex bath as defined in step (d) or natural rubber latex bath as defined in step (h) is reversible. q) fixing a valve at the open end of the said cured resultant shell to obtain a balanced bladder with true re-bounce properties.