PRODUCING RUBBER ARTICLES USING SAID FORMULATION

FIELD OF INVENTION

The present invention relates to a formulation of polymeric/inorganic composite particles and methods of producing rubber articles using said formulation.

BACKGROUND OF INVENTION

In industries where goods are being handled using rubber articles such as gloves, the gloves themselves can become a contaminant if a glove is tom during use. Usually these contaminants are very difficult to be detected. In fields such as food or pharma, these contaminants are highly undesirable for hygiene reasons.

High atomic weight elements and their compounds have been used in rubber articles due to their intrinsic property of absorbing ionising radiation which is useful for detection by ionising radiation or ionising radiation shielding. The use of blends of particulate inorganic compounds of high atomic weight elements and aqueous polymer dispersions has already been disclosed wherein the polymers are non-carboxylated polymers such as natural rubber, synthetic polyisoprene (PI) or polychloroprene rubber (CR). Natural rubber contains allergenic proteins and PI and CR are of high cost Another much more common type of polymer for glove making is carboxylated acrylonitrile /butadiene rubber (XNBR). However, the loading level of inorganic particles in common XNBR is limited, stiff or brittle films are formed due to ionic interaction between the rubber and the inorganic material.

A particular useful group of high atomic weight elements that absorb ionising radiation comprise of heavy metals, heavy metal oxides or other heavy metal compounds. Such materials have a very high density (usually above 8 g/cm ³ ) and thus aqueous dispersions tend to sediment rapidly. This leads to an inhomogeneous distribution of inorganic particles within rubber articles. The sedimentation problem can be mitigated by use of rheology modifiers as disclosed in

EP1644938B1 and WO 2004/114323 A1 by WRP Asia Pacific Sdn. Bhd. However, the two aforementioned patent documents describe the use of natural rubber or pre-vulcanised natural rubber which contain allergenic proteins which requires additional steps to remove those proteins, but such removal processes are not 100% reliable. Another shortcoming in the aforementioned disclosures lies in the use of modified cellulose based rheology modifiers which lead to rather high viscosities of the resultant mixture and causes the formation of thick films in a dip coating process and it hampers the escape of entrapped air which leads to the formation of pin-holes in the rubber article. One may choose to replace natural rubber with a synthetic analogue that is otherwise free from allergenic proteins but the issues arising from high viscosity would prevail

The sedimentation problem was also addressed by mechanical means as disclosed in US5001354

(Gould). Intense agitation or re-circulation is described while the mechanical mixing is stopped just before a mold is dipped into the formulation. This approach requires a low viscosity, which is also beneficial to allow air bubbles to escape from the formulation in order to prevent pin-hole defects. But due to high density of the dispersed tungsten particles (19.3 g/cm ³ ) sedimentation produces a concentration gradient of the heavy metal particles in the formulation within seconds.

Due to the nature of such blends, the concentration gradient results in a different ratio of polymer to inorganic material at the top and at the bottom of the container. In terms of quality control, there is no simple way to detect differences in the concentration of the inorganic particles, an articles ability to absorb ionising radiation sufficient for its intended use cannot be judged by the thickness of the article.

Therefore, there is a need for a new formulation using high density inorganic particles and also methods of producing rubber articles using said formulation. SUMMARY OF INVENTION

Accordingly, the present invention provides a polymeric/inorganic composite particle formulation, wherein the formulation includes (a) a polymer dispersion having a concentration of between 30.00 - 67.00% by dry volume, (b) a particulate inorganic material having a concentration of between 15.00 - 65.00% by dry volume, (c) a pH modifier having a concentration of between 0.30 - 3.00% by weight and (d) a dispersing agent having a concentration of between 0.25 - 5.00% by weight

Further, the present invention also provides a method of manufacturing a single layer rubber article from the polymeric/inorganic composite particle formulation, wherein the method includes (a) bringing a former in contact with a first formulation wherein, the first formulation includes, a wetting agent having a concentration between 0.10 - 2.00% by weight and a polyvalent metal salt having a concentration 0.50 - 30.00% by weight and a de-molding additive having a concentration 0.10 - 5.00% by weight, (b) drying tire former from step (a), (c) bringing the former from step (b) in contact with the polymeric/inorganic composite particle formulation, thereby coagulating the polymeric/inorganic composite particle formulation on the former to deposit a polymeric/inorganic composite film on the former, (d) curing the polymeric/inorganic composite film and (e) stripping the polymeric/inorganic composite film from the former to form the single layer rubber article.

Also provided is a method of manufacturing a multi-layer rubber article from the polymeric/inorganic composite particle formulation, wherein the method includes (a) bringing a former in contact with a second formulation wherein, the second formulation includes, a wetting agent having a concentration between 0.10 - 2.00% by weight and a polyvalent metal salt having a concentration 0.50 - 30.00% by weight and a de-molding additive having a concentration 0.10 - 5.00% by weight, (b) drying the former from step (a), (c) bringing the former from step (b) in contact with a latex formulation, thereby coagulating the latex on the former to deposit a film of latex on the former, (d) bringing the former from step (c) in contact with a third formulation wherein, the third formulation, includes, a wetting agent having a concentration between 0.10 -

2.00% by weight and a polyvalent metal salt having a concentration 0.10 - 30.00% by weight, (e) bringing the former of step (d) in contact with the polymeric/inorganic composite particle formulation, thereby coagulating the polymeric/inorganic composite particle formulation on the former to deposit a polymeric/inorganic composite film on the former, (f) bringing the former from step (e) in contact with the third formulation, (g) bringing the former from step (f) in contact with the latex formulation, thereby coagulating the latex on the former to deposit a film of latex on the former, (h) curing the deposited films and (i) stripping the deposited films off the former to form the multi-layer rubber article. Besides that; the present invention also provides a method of manufacturing a multi-layer rubber article from the polymeric/inorganic composite particle formulation, wherein the method includes (a) bringing a former in contact with a second formulation wherein, the second formulation includes, a wetting agent having a concentration between 0.10 - 2.00% by weight; a polyvalent metal salt having a concentration 0.50 - 30.00% by weight and a de-molding additive having a concentration 0.10 - 5.00% by weight, (b) drying of the former from step (a), (c) bringing the former from step (b) in contact with a latex formulation, thereby coagulating the latex on the former to deposited a film of latex on the former, (d) bringing the former from step (c) in contact with a third formulation wherein, the third formulation, includes, a wetting agent having a concentration between 0.10 - 2.00% by weight and a polyvalent metal salt having a concentration

0.10 - 30.00% by weight, (e) bringing the former from step (d) in contact with the polymeric/inorganic composite particle formulation, thereby coagulating the polymeric/inorganic composite particle formulation on the former to deposit a polymeric/inorganic composite film on the former, (f) bringing the former from step (e) in contact with the third formulation, (g) bringing the former from step (f) in contact with the latex formulation, thereby coagulating the latex on the former to deposit a film of latex on the former,

(h) curing the deposited films and (i) stripping the deposited films off the former to form the multi-layer rubber article. Further, there is provided a method of manufacturing a multi-layer rubber article the polymeric/inorganic composite particle formulation, wherein the method includes (a) bringing a former in contact with a second formulation wherein, the second formulation includes, a wetting agent having a concentration between 0.10 - 2.00% by weight; a polyvalent metal salt having a concentration 0.50 - 30.00% by weight and a de-molding additive having a concentration 0.10 -

5.00 by weight, (b) drying the former from step (a), (c) bringing the former in contact with a latex formulation, thereby coagulating the latex on the former to deposit a film of latex on the former,

(d) bringing the former in contact with a third formulation wherein, the third formulation. includes, a wetting agent having a concentration between 0.10 - 2.00% by weight and a polyvalent metal salt having a concentration 0.10 - 30.00% by weight, (e) bringing the former in contact with the polymeric/inorganic composite particle formulation, thereby coagulating the polymeric/inorganic composite particle formulation on the former to deposit a polymeric/inorganic composite film on the former; (f) bringing the former from step (d) in contact with a latex formulation, thereby coagulating the latex on the former to deposit a film of latex on the former, (g) curing the deposited films and (h) stripping the deposited films off the former to form the multi-layer rubber article.

Last but not least, the present invention also provides a method of manufacturing a multi-layer rubber article from the polymeric/inorganic composite particle formulation, wherein the method includes (a) bringing a former in contact with a second formulation wherein, the second formulation includes, a wetting agent having a concentration between 0.10 - 2.00% by weight; a polyvalent metal salt having a concentration 0.50 - 30.00% by weight and a de-molding additive having a concentration 0.10 - 5.00% by weight, (b) drying the former from step (a), (c) bringing the former in contact with a latex formulation, thereby coagulating the latex on the former to deposit a film of latex on the former, (d) bringing the former in contact with a third formulation wherein, the third formulation, includes, a wetting agent having a concentration between 0.10 -

2.00% by weight and a polyvalent metal salt having a concentration 0.10 - 30.00% by weight, (e) bringing the former in contact with the polymeric/inorganic composite particle formulation, thereby coagulating the polymeric/inorganic composite partide formulation on the former to deposit a polymeric/inorganic composite film on the former, (f) bringing the former in contact with the third formulation, (g) bringing the former from step (f) In contact with a latex formulation, thereby magulating the latex on the former to deposit a film of latex on the former, (h) curing the deposited films and 0) stripping the deposited films off the former to form the multi-layer rubber article.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1A is a cross-sectional view showing at least one layer of the polymeric/inorganic composite material of the rubber article;

Figure IB is a cross-sectional view showing at least one layer of the polymeric/inorganic composite material of the rubber article;

Figure 2A is a flow chart of the process of making thin rubber article using a polymeric/inorganic composite particle formulation; and

Figure 2B is a flow chart of the process of making thin rubber article using a polymeric/inorganic composite particle formulation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Broadly, the present invention relates to a polymeric/inorganic composite particle formulation, wherein the formulation includes (a) a polymer dispersion having a concentration of between

30.00 - 67.00% by dry volume, (b) a particulate inorganic material having a concentration of between 15.00 - 65.00% by dry volume, (c) a pH modifier having a concentration of between 0.30

- 3.00% by weight and (d) a dispersing agent having a concentration of between 0.25 - 5.00% by weight

The formulation may contain a rheology modifier having a concentration of between 0.15 - 2.00% by weight The formulation may contain sulphur having a concentration of up to 5.00% of dry weight rubber.

The formulation may contain a vulcanisation accelerator having a concentration of up to 2.00% of dry weight rubber.

The formulation may contain zinc oxide having a concentration of up to 1040.00% of dry weight rubber. The formulation may contain an anti-degradant with a concentration of up to 5.00% of dry weight rubber.

Particles in the polymer dispersion and the inorganic particles in the may be stabilised to form composite particles. The composite particles may move freely and do not sediment when the composite particles are agitated. A clear or translucent supernatant layer may be formed above a sediment of composite particles when not agitated.

The formulation may be used for manufacturing rubber articles such as single layer or multi-layer thin film rubber articles such as gloves, tubings, condoms, arm sleeves, cover skins and catheters. The polymer dispersion may be a carboxylated latex of acrylonitrile-butadiene rubber or styrene- butadiene rubber or polychloroprene rubber.

The polymer dispersion may be a non-carboxylated latex of acrylonitrile-butadiene rubber or styrene-butadiene rubber or polychloroprene rubber or butyl rubber. The polymer dispersion may be a natural rubber latex or a pre-vulcanised natural rubber latex.

The polymer dispersion may be a synthetic polyisoprene latex or a polyurethane dispersion.

The formulation may contain a wetting agent having a concentration of up to 5% by weight and the wetting agent may be a surfactant

The particulate inorganic material may be an ionising radiation absorbing material. The ionising radiation absorbing material may be a heavy metal powder. The ionising radiation absorbing material may be a mixture or alloy of various heavy metals. The ionising radiation absorbing material may be a heavy metal compound.

The particulate inorganic material may be a magnetic material.

The dispersing agent may be a polycarboxylic acid or polycarboxylic acid salt of molecular weight between 50,000 to 3,000, 000g/mol.

The pH modifier may be an alkaline solution.

The rheology modifier may be selected from xanthan gum, methyl cellulose, clay, polyamide, polyacrylate, polyurethane or a mixture thereof.

Further, the present invention also provides a method of manufacturing a single layer rubber article from the polymeric/inorganic composite particle formulation, wherein the method includes the steps of (a) bringing a former in contact with a first formulation wherein, the first formulation includes, a wetting agent having a concentration between 0.10 - 2.00% by weight, a polyvalent metal salt having a concentration 0.50 - 30.00% by weight and a de-molding additive having a concentration 0.10 - 5.00% by weight (b) drying the former from step (a), (c) bringing the former from step (b) in contact with the polymeric/inorganic composite particle formulation, thereby coagulating the polymeric/inorganic composite particle formulation on the former to deposit a polymeric/inorganic composite film on the former, (d) curing the polymeric/inorganic composite film and (e) stripping the polymeric/inorganic composite film from the former to form the single layer rubber article.

A step of drying the former from step (c) may be introduced before curing the polymeric/inorganic composite film of step (d). A step of beading the polymeric/inorganic composite film from step (c) may be introduced before curing the polymeric/inorganic composite film of step (d).

A step of leaching the polymeric/inorganic composite film from step (c) may be introduced before curing the polymeric/inorganic composite film of step (d).

The formulation may contain a rheology modifier having a concentration of between 0.15 - 2.00% by weight

The formulation may contain sulphur having a concentration of up to 5.00% of dry weight rubber.

The formulation may contain a vulcanisation accelerator having a concentration of up to 2.00% of dry weight rubber.

The formulation may contain zinc oxide having a concentration of up to 1040.00% of dry weight rubber.

The formulation may contain an anti-degradant with a concentration of up to 5.00% of dry weight rubber. Particles in the polymer dispersion and the particulate inorganic material may be stabilised to form composite particles. The composite particles may move freely and do not sediment when the composite particles are agitated. A clear or translucent supernatant layer may be formed above a sediment of composite particles when not agitated. The single layer rubber article is rubber articles such as gloves, tubings, condoms, arm sleeves and cover skins and catheter.

The polymer dispersion may be a carboxylated latex of acrylonitrile-butadiene rubber or styrene- butadiene rubber or polychloroprene rubber.

The polymer dispersion may be a non-carboxylated latex of acrylonitrile-butadiene rubber or styrene-butadiene rubber or polychloroprene rubber or butyl rubber. The polymer dispersion may be a natural rubber latex or a pre-vulcanised natural rubber latex. The polymer dispersion may be a synthetic polyisoprene latex or a polyurethane dispersion.

The formulation may contain a wetting agent having a concentration of up to 5.00% by weight and the wetting agent may be a surfactant The particulate inorganic material may be an ionising radiation absorbing material The ionising radiation absorbing material may be a heavy metal powder. The ionising radiation absorbing material may be a mixture or alloy of various heavy metals. The ionising radiation absorbing material may be a heavy metal compound.

The particulate inorganic material may be a magnetic material. The dispersing agent may be a polycarboxylic acid or a polycarboxylic acid salt of molecular weight between 50,000 to 3,000,000g/mol.

The pH modifier may be an alkaline solution. The rheology modifier may be selected from xanthan gum, methyl cellulose, clay, polyamide, polyacrylate, polyurethane or a mixture thereof.

The wetting agent in the first formulation may be a non-ionic surfactant

The polyvalent metal salt in the first formulation may be calcium chloride, calcium nitrate, aluminium chloride or aluminium nitrate or a mixture thereof.

The de-molding additive may be a stearic acid salt

Also provided is a method of manufacturing a multi-layer rubber article from the polymeric/inorganic composite particle formulation, wherein the method includes the steps of (a) bringing a former in contact with a second formulation wherein, the second formulation includes, a wetting agent having a concentration between 0.10 - 2.00% by weight; a polyvalent metal salt having a concentration 0.50 - 30.00% by weight and a de-molding additive having a concentration 0.10 - 5.00% by weight; (b) drying the former from step (a), (c) bringing the former from step (b) in contact with a latex formulation, thereby coagulating the latex on the former to deposit a film of latex on the former, (d) bringing the former from step (c) in contact with a third formulation wherein, the third formulation includes a wetting agent having a concentration between 0.10 - 2.00% by weight and a polyvalent metal salt having a concentration 0.10 - 30.00% by weight; (e) bringing the former of step (d) in contact with the polymeric/inorganic composite particle formulation, thereby coagulating the polymeric/inorganic composite particle formulation on the former to deposit a polymeric/inorganic composite film on the former, (f) bringing the former from step (e) in contact with the third formulation, (g) bringing the former from step (f) in contact with the latex formulation, thereby coagulating the latex on the former to deposit a film of latex on the former, (h) curing the deposited films and (i) stripping the deposited films off the former to form the multi-layer rubber article.

A step of drying the former from step (c) may be introduced before bringing the former from step (c) in contact with a third formulation of step (d). A step of drying the former from step (d) may be introduced before bringing the former of step (d) in contact with the polymeric/inorganic composite particle formulation of step (e).

A step of drying the former from step (e) may be introduced before bringing the former from step (e) in contact with the third formulation of step (f). A step of drying the former from step (f) may be introduced before bringing the former from step

(f) in contact with the latex formulation of step (g).

A step of drying the former from step (g) may be introduced before curing the polymeric/inorganic composite film of step (h).

A step of beading the polymeric/inorganic composite film from step (g) may be introduced before curing the polymeric/inorganic composite film of step (h).

A step of leaching the polymeric/inorganic composite film from step (g) maybe introduced before curing the polymeric/inorganic composite film of step (h).

The formulation may contain a rheology modifier having a concentration of between 0.15 - 2.00 by weight The formulation may contain sulphur having a concentration of up to 5.00% of dry weight rubber.

The formulation may contain a vulcanisation accelerator having a concentration of up to 2.00% of dry weight rubber.

The formulation may contain zinc oxide having a concentration of up to 1040.00% of dry weight rubber. The formulation may contain an anti-degradant with a concentration of up to 5.00% of dry weight rubber. Particles in the polymer dispersion and the particulate inorganic material may be stabilised to form composite particles.

The composite particles may move freely and do not sediment when the composite particles are agitated. A clear or translucent supernatant layer may be formed above a sediment of composite particles when not agitated.

The multi-layer rubber article may be rubber articles such as gloves, tubings, condoms, arm sleeves, cover skins and catheters.

The polymer dispersion may be a carboxylated latex of acrylonitrile-butadiene rubber or styrene- butadiene rubber or polychloroprene rubber. The polymer dispersion may be a non-carboxylated latex of acrylonitrile-butadiene rubber or styrene-butadiene rubber or polychloroprene rubber or butyl rubber. The polymer dispersion may be a natural rubber latex or a pre-vulcanised natural rubber latex. The polymer dispersion may be a synthetic polyisoprene latex or a polyurethane dispersion.

The formulation may contain a wetting agent having a concentration of up to 5.00% by weight The wetting agent may be a surfactant

The particulate inorganic material may be an ionising radiation absorbing material. The ionising radiation absorbing material may be a heavy metal powder or a mixture or alloy of different heavy metals or a heavy metal compound.

The particulate inorganic material may be a magnetic material. The dispersing agent may be a polycarboxylic acid or a polycarboxylic acid salt of molecular weight between 50,000 to 3,000,000 g/mol.

The pH modifier may be an alkaline solution. The rheology modifier may be a xanthan gum, metiiyl cellulose, day, polyamide, polyacrylate, polyurethane or a mixture thereof.

The wetting agent in the second formulation and third formulation may be a non-ionic surfactant

The polyvalent metal salt in the second formulation and third formulation may be calrium chloride, calcium nitrate, aluminium chloride or aluminium nitrate or a mixture thereof.

The de-molding additives may be a stearic add salt

The latex formulation may be one latex dispersion from non-carboxylated nitrile butadiene rubber (NBR), carboxylated nitrile butadiene rubber (XNBR), non-carboxylated styrene butadiene rubber (SBR), carboxylated styrene butadiene rubber (XSBR), polychloroprene, polyisoprene, polyvinyl chloride (PVC), polyurethane (PU), butyl rubber (IIR) or a mixture thereof.

The multi-layer rubber article may be a 3-layer rubber article comprising of an outer layer, an intermediary layer and an internal layer. The outer layer and the inner layer may be made from a polymer dispersion selected from non-carboxylated nitrile butadiene rubber (NBR), carboxylated nitrile butadiene rubber (XNBR), non-carboxylated styrene butadiene rubber (SBR), carboxylated styrene butadiene rubber (XSBR), polychloroprene, polyisoprene, polyvinyl chloride (PVC), polyurethane (PU), butyl rubber (IIR) or a mixture thereof.

The multilayer rubber article may be chlorinated or having its inner layer surface coated to reduce friction. Further, there is also provided a method of manufacturing a multi-layer rubber article from the polymeric/inorganic composite particle formulation, wherein the method includes the steps of (a) bringing a former in contact with a second formulation wherein, the second formulation includes, a wetting agent having a concentration between 0.10 - 2.00% by weight; a polyvalent metal salt having a concentration 0.50 - 30.00% by weight and a de-molding additive having a concentration 0.10 - 5.00% by weight, (b) drying of the former from step (a), (c) bringing the former from step (b) in contact with a latex formulation, thereby coagulating the latex on the former to deposited a film of latex on the former, (d) bringing the former from step (c) in contact with a third formulation wherein, the third formulation, includes, a wetting agent having a concentration between 0.10 - 2.00% by weight and a polyvalent metal salt having a concentration

0.10 - 30.00% by weight, (e) bringing the former from step (d) in contact with the polymeric/inorganic composite particle formulation, thereby coagulating the polymeric/inorganic composite particle formulation on the former to deposit a polymeric/inorganic composite film on the former, (f) bringing the former from step (e) in contact with the third formulation, (g) bringing the former from step (f) in contact with the latex formulation, thereby coagulating the latex on the former to deposit a film of latex on the former,

(h) curing the deposited films and (i) stripping the deposited films off the former to form the multi-layer rubber article. The deposited films on the former may be dried after step (c) is introduced but before step (d).

A drying step may be introduced after step (d) but before step (e).

The deposited films on the former may be dried after step (e) but before step (f).

A drying step is introduced after step (f) but before step (g).

The deposited films on the former may be dried after step (g) but before step (h). The deposited films may be beaded after step (g) but before step (h).

The deposited films on the former may be leached after step (g) but before step (h). The formulation may contain a rheology modifier having a concentration of between 0.15 - 2.00% by weight

The formulation may contain sulphur having a concentration of up to 5.00% of dry weight rubber.

The formulation may contain a vulcanisation accelerator having a concentration of up to 2.00% of dry weight rubber.

The formulation may contain zinc oxide having a concentration of up to 1040.00% of dry weight rubber.

The formulation may contain an anti-degradant with a concentration of up to 5.00% of dry weight rubber. Particles in the polymer dispersion and the particulate inorganic material may be stabilised to form composite particles. The composite particles may move freely and do not sediment when the composite particles are agitated. A clear or translucent supernatant layer may be formed above a sediment of composite particles when not agitated.

The multi-layer rubber article may be rubber articles such as gloves, tubings, condoms, arm sleeves, cover skins and catheters.

The polymer dispersion may be a carboxylated latex of acrylonitrile-butadiene rubber or styrene- butadiene rubber or polychloroprene rubber. The polymer dispersion may be a non-carboxylated latex of acrylonitrile-butadiene rubber or styrene-butadiene rubber or polychloroprene rubber or butyl rubber. The polymer dispersion may be a natural rubber latex or a pre-vulcanised natural rubber latex The polymer dispersion may be a synthetic polyisoprene latex or a polyurethane dispersion.

The formulation may contain a wetting agent having a concentration of up to 5.00% by dry rubber weight

The wetting agent may be a surfactant

The particulate inorganic material may be an ionising radiation absorbing material. The ionising radiation absorbing material may be a heavy metal powder or a mixture or alloy of different heavy metals or a heavy metal compound.

The particulate inorganic material may be a magnetic material.

The dispersing agent may be a polycarboxylic acid or a polycarboxylic acid salt of molecular weight between 50,000 to 3,000, 000g/mol.

The pH modifier may be an alkaline solution. The rheology modifier may be a xanthan gum, methyl cellulose, clay, polyamide, polyacrylate, polyurethane or a mixture thereof.

The wetting agent in the second formulation and third formulation may be a non-ionic surfactant The polyvalent metal salt in the second formulation and third formulation may be calcium chloride, calcium nitrate, aluminium chloride or aluminium nitrate or a mixture thereof. The de-molding additives may be a stearic add salt

The latex formulation may be one latex dispersion from non-carboxylated nitrile butadiene rubber (NBR), carboxylated nitrile butadiene rubber (XNBR), non-carboxylated styrene butadiene rubber (SBR), carboxylated styrene butadiene rubber (XSBR), polychloroprene, polyisoprene, polyvinyl chloride (PVC), polyurethane (PU), butyl rubber (IIR) or a mixture thereof.

The multi-layer rubber article may be a 3-layer rubber article comprising of an outer layer, an intermediary layer and an internal layer. The outer layer and the inner layer may be made from a polymer dispersion selected from non-carboxylated nitrile butadiene rubber (NBR), carboxylated nitrile butadiene rubber (XNBR), non-carboxylated styrene butadiene rubber (SBR), carboxylated styrene butadiene rubber (XSBR), polychloroprene, polyisoprene, polyvinyl chloride (PVC), polyurethane (PU), butyl rubber (IIR) or a mixture thereof.

The multilayer rubber article may be chlorinated or having its inner layer surface coated to reduce friction.

Also provided is a method of manufacturing a multi-layer rubber article from the polymeric/inorganic composite particle formulation, wherein the method includes the steps of (a) bringing a former in contact with a second formulation wherein, the second formulation includes, a wetting agent having a concentration between 0.10 - 2.00% by weight; a polyvalent metal salt having a concentration 0.50 - 30.00% by weight and a de-molding additive having a concentration 0.10 - 5.00 by weight; (b) drying the former from step (a), (c) bringing the former in contact with a latex formulation, thereby coagulating the latex on the former to deposit a film of latex on the former, (d) bringing the former in contact with a third formulation wherein, the third formulation, includes, a wetting agent having a concentration between 0.10 - 2.00% by weight and a polyvalent metal salt having a concentration 0.10 - 30.00% by weight; (e) bringing the former in contact with the polymeric/inorganic composite particle formulation, thereby coagulating the polymeric/inorganic composite particle formulation on the former to deposit a polymeric/inorganic composite film on the former, (f) bringing the former from step (d) in contact with a latex formulation, thereby coagulating the latex on the former to deposit a film of latex on the former, (g) curing the deposited films and (h) stripping the deposited films off the former to form the multi-layer rubber article.

The former from step (c) may be repetitively brought in contact with the latex formulation for not more than 5 times before step (d), thereby coagulating the latex on the former to deposit a film of latex on the former.

The former from step (e) may be repetitively brought in contact with the polymeric/inorganic composite particle formulation for not more than 5 times, before the multilayer rubber articled is formed, thereby coagulating the polymeric/inorganic composite particle formulation on the former to deposit a polymeric/inorganic composite film on the former.

The former from step (f) may be repetitively brought in contact with the latex formulation for not more than 5 times before step (d), thereby coagulating the latex on the former to deposit a film of latex on the former.

The deposited films on the former may be dried after step (c).

The deposited films on the former may be dried after step (d).

The deposited films on the former may be dried after step (e). The deposited films on the former may be dried after step (f) but before step (g).

The deposited films may be beaded after step (f] but before step (g). The deposited films may be leached after step (f) but before step (g).

The formulation may contain a rheology modifier having a concentration of between 0.15 - 2.00% by weight The formulation may contain sulphur having a concentration of up to 5.00% of dry weight rubber.

The formulation may contain a vulcanisation accelerator having a concentration of up to 2.00% of dry weight rubber. The formulation may contain zinc oxide having a concentration of up to 1040.00% of dry weight rubber.

The formulation may contain an anti-degradant with a concentration of up to 5.00% of dry weight rubber.

Particles in the polymer dispersion and the particulate inorganic material may be stabilised to form composite particles. The composite particles may move freely and do not sediment when the composite particles are agitated. A clear or translucent supernatant layer may be formed above a sediment of composite particles when not agitated.

The multi-layer rubber article may be rubber articles such as gloves, tubings, condoms, arm sleeves, cover skins and catheters. The polymer dispersion may be a carboxylated latex of acrylonitrile-butadiene rubber or styrene- butadiene rubber or polychloroprene rubber. The polymer dispersion may be a non-carboxylated latex of acrylonitrile-butadiene rubber or styrene-butadiene rubber or polychloroprene rubber or butyl rubber. The polymer dispersion may be a natural rubber latex or a pre-vulcanised natural rubber latex. The polymer dispersion may be a synthetic polyisoprene latex or a polyurethane dispersion.

The formulation may contain a wetting agent having a concentration of up to 5% by dry rubber weight

The wetting agent may be a surfactant

The particulate inorganic material may be an ionising radiation absorbing material. The ionising radiation absorbing material is a heavy metal powder or a mixture or alloy of different heavy metals or a heavy metal compound.

The particulate inorganic material may be a magnetic material.

The dispersing agent may be a polycarboxylic acid or a polycarboxytic acid salt of molecular weight between 50,000 to 3,000,000g/mol.

The pH modifier may be an alkaline solution.

The rheology modifier may be a xanthan gum, methyl cellulose, clay, polyamide, polyacrylate, polyurethane or a mixture thereof.

The wetting agent in the second formulation and third formulation may be a non-ionic surfactant The polyvalent metal salt in the second formulation and third formulation may be calcium chloride, calcium nitrate, aluminium chloride or aluminium nitrate or a mixture thereof.

The de-molding additives may be a stearic acid salt

The latex formulation may be one latex dispersion from non-carboxylated nitrile butadiene rubber (NBR), carboxylated nitrile butadiene rubber (XNBR), non-carboxylated styrene butadiene rubber (SBR), carboxylated styrene butadiene rubber (XSBR), polychloroprene, polyisoprene, polyvinyl chloride (PVC), polyurethane (PU), butyl rubber (IIR) or a mixture thereof.

The multi-layer rubber article may be a 3-layer rubber article comprising of an outer layer, an intermediary layer and an internal layer. The outer layer and the inner layer may be made from a polymer dispersion selected from non-carboxylated nitrile butadiene rubber (NBR), carboxylated nitrile butadiene rubber (XNBR), non-carboxylated styrene butadiene rubber (SBR), carboxylated styrene butadiene rubber (XSBR), polychloroprene, polyisoprene, polyvinyl chloride (PVC), polyurethane (PU), butyl rubber (IIR) or a mixture thereof.

The multilayer rubber article may be chlorinated or having its inner layer surface coated to reduce friction.

There is also provided a method of manufacturing a multi-layer rubber article from the polymeric/inorganic composite particle formulation wherein the method includes the steps of (a) bringing a former in contact with a second formulation wherein, the second formulation includes, a wetting agent having a concentration between 0.10 - 2.00% by weight; a polyvalent metal salt having a concentration 0.50 - 30.00% by weight and a de-molding additive having a concentration 0.10 - 5.00% by weight, (b) drying the former from step (a), (c) bringing the former in contact with a latex formulation, thereby coagulating the latex on the former to deposit a film of latex on the former, (d) bringing the former in contact with a third formulation wherein, the third formulation, includes, a wetting agent having a concentration between 0.10 - 2.00% by weight and a polyvalent metal salt having a concentration 0.10 - 30.00% by weight, (e) bringing the former in contact with the polymeric/inorganic composite particle formulation, thereby coagulating the polymeric/inorganic composite particle formulation on the former to deposit a polymeric/inorganic composite film on the former, (f) bringing the former in contact with the third formulation, (g) bringing the former from step (f) in contact with a latex formulation, thereby coagulating the latex on the former to deposit a film of latex on the former, (h) curing the deposited films and (i) stripping the deposited films off the former to form the multi-layer rubber article.

The deposited films on the former may be dried after step (c). A drying step may be introduced after step (d).

The deposited films on the former may be dried after step (e).

A drying step may be introduced after step (f).

The deposited films on the former may be dried after step (g).

The former from step (e) may be repeatedly brought in contact with the polymeric/inorganic composite particle formulation for not more titan 5 times before step (f), after bringing the former in contact with the third formulation, thereby coagulating the polymeric/inorganic composite particle formulation on the former to deposit a polymeric/inorganic composite film on the former. The former from step (g) may be repeatedly brought in contact with the latex formulation for not more than 5 times, before the multilayer rubber articled is formed, thereby coagulating the latex on the former to deposit a film of latex on the former. The deposited films on the former may be dried after step (g).

The deposited films on the former may be cured after drying the deposited films on the former.

The deposited films may be beaded after step (g).

The deposited films may be leached after step (g).

The formulation may contain a rheology modifier having a concentration of between 0.15 - 2.00% by weight

The formulation may contain sulphur having a concentration of up to 5.00% of dry weight rubber.

The formulation may contain a vulcanisation accelerator having a concentration of up to 2.00% of dry weight rubber.

The formulation may contain zinc oxide having a concentration of up to 1040.00% of dry weight rubber.

The formulation may contain an anti-degradant with a concentration of up to 5.00% of dry weight rubber. Particles in the polymer dispersion and the particulate inorganic material may be stabilised to form composite particles. The composite particles may move freely and do not sediment when the composite particles are agitated. A clear or translucent supernatant layer may be formed above a sediment of composite particles when not agitated.

The multi-layer rubber article may be rubber articles such as gloves, tubings, condoms, arm sleeves, cover skins and catheters.

The polymer dispersion may be a carboxylated latex of acrylonitrile-butadiene rubber or styrene- butadiene rubber or polychloroprene rubber.

The polymer dispersion may be a non-carboxylated latex of acrylonitrile-butadiene rubber or styrene-butadiene rubber or polychloroprene rubber or butyl rubber. The polymer dispersion may be a natural rubber latex or a pre-vulcanised natural rubber latex.

The polymer dispersion may be a synthetic polyisoprene latex or a polyurethane dispersion.

The formulation may contain a wetting agent having a concentration of up to 5.00% by dry rubber weight

The wetting agent may be a surfactant

The particulate inorganic material may be an ionising radiation absorbing material

The ionising radiation absorbing material may be a heavy metal powder or a mixture or alloy of different heavy metals or a heavy metal compound. The particulate inorganic material may be a magnetic material.

The dispersing agent may be a polycarboxylic acid or a polycarboxylic acid salt of molecular weight between 50,000 to 3,000,000g/mol.

The pH modifier may be an alkaline solution.

The rheology modifier may be a xanthan gum, methyl cellulose, clay, polyamide, polyacrylate, polyurethane or a mixture thereof.

The wetting agent in the second formulation and third formulation may be a non-ionic surfactant

The polyvalent metal salt in the second formulation and third formulation may be calcium chloride, calcium nitrate, aluminium chloride or aluminium nitrate or a mixture thereof.

The de-molding additives is a stearic acid salt

The latex formulation may be one latex dispersion from non-carboxylated nitrile butadiene rubber (NBR), carboxylated nitrile butadiene rubber (XNBR), non-carboxylated styrene butadiene rubber (SBR), carboxylated styrene butadiene rubber (XSBR), polychloroprene, polyisoprene, polyvinyl chloride (PVC), polyurethane (PU), butyl rubber (IIR) or a mixture thereof.

The multi-layer rubber article may be a 3-layer rubber article comprising of an outer layer, an intermediary layer and an internal layer. The outer layer and the inner layer may be made from a polymer dispersion selected from non-carboxylated nitrile butadiene rubber (NBR), carboxylated nitrile butadiene rubber (XNBR), non-carboxylated styrene butadiene rubber (SBR), carboxylated styrene butadiene rubber (XSBR), polychloroprene, polyisoprene, polyvinyl chloride (PVC), polyurethane (PU), butyl rubber (IIR) or a mixture thereof.

The multilayer rubber article may be chlorinated or having its inner layer surface coated to reduce friction.

The present invention will now be described in more specific details.

Specifically, the present invention provides thin rubber articles (≤ 0.2 mm palm thickness) that contain one or more layer of a polymeric/inorganic composite. Besides that, the present invention provides a compounding procedure to incorporate particulate inorganic materials into polymer dispersions resulting in low viscosity compounds that contain polymeric/inorganic composite particles.

The present invention provides a dipping procedure that allows controlling the thickness of rubber articles comprising of different layers one or more of which may contain a polymeric/inorganic composite.

The present invention provides methods for the manufacture of thin film rubber article consisting of at least two layers of controlled thickness. Each layer may comprise of a different base polymer such as or non-carboxylated nitrile butadiene rubber (NBR) or carboxylated nitrile butadiene rubber (XNBR), non-carboxylated styrene butadiene rubber (SBR) or carboxylated styrene butadiene rubber (XSBR), polychloroprene, polyisoprene, polyvinyl chloride (PVC) or polyurethane (PU). At least one layer (composite layer) contains a particulate inorganic material · comprising about 10-90% by volume (as referred as Layer 2 in Figures 1A and 1B). The composite layer thickness and the content of particulate inorganic material are determined by the application i.e. for detection by X-ray a lower thickness and/or content of a radiation absorbing material is required compared to radiation shielding. The degree of radiation absorption depends on the concentration of high atomic weight elements. the layer thickness, the density and the atomic weight (higher = better).

Carboxylated rubber is particular suitable for the manufacture of low dermatitis rubber articles in which the carboxylic acid functional groups serve as the primary crosslinking sites either by covalent or ionic crosslinking. Radiation shielding/detection requires such high loading of heavy metal or heavy metal oxides that the resulting ionomeric crosslinking becomes excessive, resulting in stiff or brittle films. Rubbers without carboxylation on the other hand exhibit much less interaction with these types of particulate inorganic materials but when use as the sole carrier curing additives for crosslinking are required. These curing additives can lead to Type IV allergies but without curing the filled non-carboxylated rubber would not exhibit enough physical strength that is required for a useful rubber article. It was found that by sandwiching the composite layer between layers of carboxylated rubber (support layer) an article with high content of particulate inorganic material can be made that has sufficient physical strength (Table

1) which is free from Type IV allergy causative agents. One problem that can arise from this approach is incompatibility of two different polymer types due to their differences in polarity.

Carboxylated polymers are much more polar that natural rubber or synthetic polylsoprene for example. The practical issue that arise from the differences poor inter-layer adhesion which leads to delamination under normal use conditions. The base polymer of the composite layer needs to be compatible with support layers, so that delamination of those layers can be avoided while the article is in use.

It was found that polychloroprene latex such as CL-750 from Showa Denko can be loaded with more than 65% (volume dry filler in dry polymer) of an Inorganic filler particles such as Bismuth Oxide (particle size d ₅₀ approximately 1.6 μm) while maintaining sufficient adherence to the support layer (Table 1 Part I). However, the Bismuth Oxide sediments rapidly so that vigorous agitation or a rheology modifier are required to ensure homogeneous distribution of the inorganic particles in the compound. The aforementioned mixture of chloroprene latex with Bismuth Oxide would be suitable as such for making gloves and it may contained a rheology modifier to reduce the sedimentation of the

Bismuth particles. Mechanical solutions such as agitation or pumping may also be employed to limit the sedimentation in such a way as to obtain a nearly homogeneously filled layer. The addition of dispersing agent; polycarboxylic acid salt of molecular weight (MW) between 50

000 to 3 000000 g/mol to the formulation as shown in Table 1 Part I leads to co-agglomeration of the inorganic particles and polychloroprene rubber particles forming an agglomerated latex

(AL) (Table 1 Part II). This is a surprising result as the polymer particles, the inorganic particles as well as the dispersant are of anionic character. At a pH greater than 7 the agglomeration is independent of the nature of inorganic material, it can be shown that ordinary sulphur powder

(particle size: 30 μm), zinc oxide powder (particle size: 1 μm, white seal) or titanium dioxide

(particle size: 300 nm) will form a dispersions of composite particles (Table 3). These examples demonstrate the general applicability of the method in terms of the nature of the particulate inorganic material. It can also be shown that the agglomeration can be achieved with various anionically stabilised polymer dispersions such as polychloroprene latex, carboxylated acrylonitrile/butadiene latex etc. Carboxylated polymer dispersions can principally be used to produce AL, however, depending on the concentration of the inorganic particles and the degree of carboxylation the resultant film will exhibit greater stiffness than films made with non- carboxylated polymers. Generally, below pH 7 coagulation predominates, composite particles of irregular shape and size are formed.

While AL still sediments it does so with the formation of a clear supernatant layer and the sediment has a homogeneous visual appearance throughout The agglomeration step has created composite particles consisting of the inorganic material and rubber. By using AL instead of the non-agglomerated dispersion homogeneity of the composite layer is ensured since the ratio of inorganic material to polymer are determined in the preceding formulating steps, the composite layer thickness and the amount of inorganic material are directly proportional therefore. AL is not found to form a hard sediment layer on standing which makes it suitable for storage, continuous agitation is required during dipping. It can be advantageous to add a small quantity of a rheology modifier such as xanthan gum, methyl cellulose or clay. It was also found that the rate of sedimentation without rheology modifier depends on the concentration of the dispersant The formation of a clear supernatant layer has the further advantage of preventing skinning under storage. The viscosity of AL without rheology modifier does not exceed 30 mPa-s which makes it suitable for continuous chain dipping (typical properties of AL as shown in Table 2).

As shown in Figures 2A and 2B, the article is formed, layer by layer employing a multiple dipping process. The initial step (Group A) is identical to conventional coagulant dipping using a coagulant formulation comprising of polyvalent metal salts, de-molding additives and wetting agents. The process of this invention deviates from the conventional process in that additional latex dips are performed with preceding coagulant dips (Coagulant Dips 2 and 3 in Figures 2A and 2B). The

Coagulant Dips 2 and 3, are performed using one or more auxiliary coagulant formulations comprising of wetting agent and polyvalent metal salts but without any de-molding additive whereby the polyvalent metal salt concentration is tailored to the composition of subsequent latex dip and the required layer thickness (example auxiliary coagulant formulations are shown in Table 4). After reaching the last step in Group B as shown in Figure 2A and 2B, additional layers can be built up by repeating the steps of Group B multiple times. Drying and leaching steps in each Group (A, B, C and D) are optional. By using the auxiliary coagulant dips one can easily achieve a sandwich structure of three or more layers, each of them having a defined thickness whereby it is feasible to use the same formulation for the 1 ^st and the 3 ^rd layer. Using auxiliary coagulant dips makes it particularly feasible to deposit a very thin layer of a polymeric/inorganic composite particle formulation followed by a much thicker support layer of conventional rubber. The absence of de-molding additive in the auxiliary coagulant formulations is important in order to prevent delamination of the individual layers of the article. Table 1. Polymeric/inorganic composite particle formulation

Table 2. Typical properties of a dispersion with polymeric/inorganic composite particles Table 3. Example inorganic materials that form composite particles, the amount is adjusted for constant volume fraction Example 1

L1: A ceramic glove former is cleaned, dried and coated with a standard coagulant formulation

(14% Calcium Nitrate) and then dried at 70°C The dry coated former is then dipped into a standard XNBR compound (total solid compound: 15%, pH: 10.0) with a total contact time of 7 seconds to form a 1 ^st layer. The former with the 1 ^st layer is then dried for 1 minute at 90°C, leached for 10 seconds in water at 60°C and dried for 60 seconds at 35°C.

L2: The dry former with layer LI is then dipped into the 1 ^st auxiliary coagulant formulation (Table

4, with Teric 320 as the wetting agent) with a total contact time of 14 seconds. The former is then dried at 70°C for 5 minutes and subsequently dipped into a polymeric/inorganic composite particle formulation as shown in Table 1 (using CL-750 as the non-carboxylated latex, sodium dodecylbenzene sulfonate as the wetting agent, Bismuth Oxide as the particulate inorganic material, no rheology modifier and Acumer 1510 from Dow Chemicals as the dispersing agent,

M _w = 60000 g/mol) with a total contact time of 7 seconds to deposit the 2 ^nd layer, followed by drying at 90°C for 1 minute, leaching for 10 seconds in water at 60°C and drying for 60 seconds at35«C.

L3: The dry former with layers L1+L3 is then dipped into the 2 ^nd auxiliary coagulant formulation (Table 4) with a total contact time of 14 seconds. The former is then dried at 70°C for 5 minutes and subsequently dipped into the same standard XNBR compound that was used for Layer LI with a total contact time of 7 seconds to deposit the 3 ^rd layer. The former with the three layers is then dried at 90°C for 1 minute and leached for 2 minutes at 60°C. After leaching the 3-layer film is beaded and dried at 90°C for 5 minutes and finally cured at 120°C for 20 minutes. After curing the glove is stripped off the former. The thickness of each layer is assessed at samples which have subsequent layers L2+L3 or L3 omitted. Table 4. Auxiliary coagulant formulations 1 + 2 (based on 100 parts dry coagulant)

Example 2

The steps of Example 1 were repeated but the formulation as shown in Table 1 was using 600 phr of the particulate inorganic material instead of 200 phr.

The physical properties of examples 1 and 2 are shown in table 6.

Example 3

The radiation polymeric/inorganic composite particle formulation that was used in example 3 was allowed to sediment and stored for 4 weeks at room temperature. The steps of Example 1 were repeated using the stored formulation after lh gentle agitation.

The attenuation results of examples 1-3 are shown in Table 5.

Example 4

The steps of Example 1 were repeated with the exception that the auxiliary coagulant dip after L2 was omitted. The thickness of the individual layers of Example 1-4 is shown in Table 7. It is clear that only with the use of auxiliary coagulant a desirable distribution of the layer thickness is obtained.

Table 5. Thickness and attenuation results of Examples 1-3 Table 6. Physical Properties of a Rubber Article that contains a polymeric/inorganic composite layer

Table 7. Thickness results of Example 4