Elastomeric articles, compositions, and methods for their production

Abstract

This application relates to synthetic elastomeric articles, such as gloves, comprising the cured product of a synthetic latex composition, the synthetic latex composition comprising a synthetic carboxylated polymer and a cross-linking composition, the cross-linking composition comprising an aqueous solution of a negatively charged multivalent metal complex ion having a pH of at least 9.0. Also described are compositions for forming the articles, and methods for making the articles, based on the use of the described cross-linking composition. The articles, compositions and methods contain a second cross-linking agent comprising either (a) sulphur and a sulphur donor, (b) a multivalent metal oxide or ionic cross-linking agent, (c) sulphur, a sulphur donor and an ionic cross-linking agent, or (d) sulphur donor.

Claims

1. A method of manufacturing a synthetic elastomeric article comprising: adding (i) a cross-linking composition comprising an aqueous solution of a negatively-charged multivalent metal complex ion having a pH of at least 9.0 and (ii) a second cross-linking agent comprising either: (a) sulphur and a sulphur donor, (b) a multivalent metal oxide or ionic cross-linking agent, (c) sulphur, a sulphur donor and an ionic cross-linking agent, or (d) sulphur donor, to an aqueous suspension of a synthetic carboxylated polymer having a pH of at least 9.0 to produce a synthetic latex composition, wherein a source of multivalent metal in the negatively charged multivalent metal complex ion is (A) a multimetal oxide of the multivalent metal, (B) a hydroxide of the multivalent metal, or (C) a salt of the multivalent metal; shaping the synthetic latex composition; and curing the synthetic latex composition so as to obtain the synthetic elastomeric article.

2. The method of claim 1, comprising incorporating at least one of sodium hydroxide, potassium hydroxide, and ammonium hydroxide into the cross-linking composition to provide pH control to stabilise the aqueous solution of the negatively charged multivalent metal complex ion prior to the addition of the cross-linking composition to the aqueous suspension of the synthetic carboxylated polymer.

3. The method of claim 1, comprising adding the cross-linking composition to the aqueous suspension of the synthetic carboxylated polymer when the concentration of the source of multivalent metal ions in the cross-linking composition is between about 0.01 and 5 parts by weight, per 100 parts by weight water in the cross-linking composition.

4. The method of claim 1, wherein the step of shaping the synthetic latex composition comprises a dipping a glove-shaped former into the latex composition, and the method is for the manufacture of a glove.

5. The method of claim 1, wherein the multivalent metal of the negatively-charged multivalent metal complex ion is aluminium.

6. The method of claim 1, wherein the source of multivalent metal in the negatively charged multivalent metal complex ion is sodium aluminate, and the method comprises forming the cross-linking composition by solubilising the sodium aluminate in water with heating.

7. The method of claim 1, comprising adding the cross-linking composition to the aqueous suspension of the synthetic carboxylated polymer in an amount to provide 0.01-0.5 phr of the source of the multivalent metal in the synthetic latex composition.

8. The method of claim 7, wherein the second cross-linking agent added to the aqueous suspension of synthetic carboxylated polymer is (c) sulphur, a sulphur donor and an ionic cross-linking agent, and each of the sulphur, sulphur donor and ionic cross-linking agent are added in an amount to provide not more than 1.0 phr of each of the sulphur, sulphur donor and ionic cross-linking agents.

9. The method of claim 8, wherein the ionic cross-linking agent is zinc oxide.

10. The method of claim 7, wherein the second cross-linking agent added to the aqueous suspension of synthetic carboxylated polymer is (b) the multivalent metal oxide or ionic cross-linking agent, and the second cross-linking agent is added in amount to provide 0.01-2.0 phr of the multivalent metal oxide or ionic cross-linking agent.

11. The method of claim 10, wherein the source of multivalent metal in the negatively charged multivalent metal complex ion is sodium aluminate, and the second cross-linking agent is zinc oxide.

12. The method of claim 1, wherein the amount of each second cross-linking agent that is added is not more than 1.0 phr.

13. The method of claim 4, comprising dipping the glove-shaped former into a coagulant composition prior to the step of dipping the glove-shaped former into the synthetic latex composition.

Description

(1) FIGS. 1-5 contain the images of the two films produced by a scanning electron microscope.

(2) FIGS. 1, 2 and 5 relate to the composition of Example 13-2 (previously numbered Example 9-2). In FIGS. 1 and 2, one peak possibly omitted was at 2.051 keV. FIG. 1 shows a cluster of white particles, being TiO.sub.2 particles, indicative of a non-solubilised metal oxide component (a pigment, rather than a cross-linking agent). The magnification in FIG. 1 is 15,000× magnification, with the scale bar indicated representing a distance of about 200 nm. FIG. 2 is of the same image at a different degree of magnification (5,000×, with the scale bar representing 1 μm). FIG. 5 is the same image but focusing on a different section, showing further clusters of white TiO.sub.2 particles. The magnification is 25,000×, and the scale bar represents 300 nm.

(3) The elements analysed in the SEM image for the Example 13-2 product were C, O, Al and Ti. In processing, all elements indicated were analysed (normalised). There was one iteration. These are based on standards for each element which were as follows: Carbon: CaCO.sub.3 Oxygen: SiO.sub.2 Aluminium: Al.sub.2O.sub.3 Titanium: Ti

(4) The % amounts of each detected for the composition of Example 13-2, based on atomic amounts, were as follows:

(5) TABLE-US-00042 Element Weight % Atomic % C K 34.05 50.59 O K 33.05 36.86 Al K 1.01 0.67 Ti K 31.88 11.88 Totals 100.00

(6) In the results in the table above, the SEM was focussed on a very small area, roughly 0.2 micron×0.2 micron width, where a cluster of undispersed TiO.sub.2 was found. The higher than expected Aluminium amount was due to the adherence of Aluminium to the TiO.sub.2 cluster. In normal cured elastomeric areas, the aluminium could not be detected.

(7) FIGS. 3 and 4 relate to the product of Example 13-1. In FIGS. 3 and 4, no peaks were omitted. FIG. 3 shows a uniform surface with proper and even distribution of the aluminium inside the elastomeric matrix. The visible dents are surface undulations. The magnification in FIG. 3 is 25,000×, with the scale bar indicated representing a distance of about 200 nm. FIG. 4 is of the same image at a different degree of magnification (15,000× magnification, with the scale bar representing 200 nm).

(8) The elements analysed were C, O, Al and Ti. In processing, all elements indicated were analysed (normalised) and those detected are indicated in the table below. There were 2 iterations. The elemental analysis was based on the following standards: Carbon: CaCO.sub.3 Oxygen: SiO.sub.2

(9) The % amounts of each detected for the composition of Example 13-1, based on atomic amounts, were as follows:

(10) TABLE-US-00043 Element Weight % Atomic % C K 88.71 91.28 O K 11.29 8.72 Totals 100.00
Items:

(11) 1. A synthetic elastomeric article comprising the cured product of a synthetic latex composition, the synthetic latex composition comprising a synthetic carboxylated polymer and a cross-linking composition, the cross-linking composition comprising an aqueous solution of a negatively charged multivalent metal complex ion having a pH of at least 9.0.

(12) 1(i) A synthetic elastomeric article comprising the cured product of a synthetic latex composition, the synthetic latex composition comprising a synthetic carboxylated polymer and a cross-linking composition, the cross-linking composition comprising an aqueous solution of a multimetal oxide of the multivalent metal, a hydroxide of the multivalent metal, or a salt of the multivalent metal producing an aqueous solution of negatively charged multivalent metal complex ion having a pH of at least 9.0, in which the amount of the multimetal oxide of the multivalent metal, the hydroxide of the multivalent metal, or the salt of is the multivalent metal is less than 0.3 phr.

(13) 1(ii). A synthetic elastomeric article comprising the cured product of a synthetic latex composition, the synthetic latex composition comprising a synthetic carboxylated polymer and a cross-linking composition, the cross-linking composition comprising an aqueous solution of a negatively charged multivalent metal complex ion having a pH of at least 9.0, the synthetic latex composition further comprising a second cross-linking agent comprising either (a) sulphur and a sulphur donor, (b) a multivalent metal oxide or ionic cross-linking agent, (c) sulphur, a sulphur donor and an ionic cross-linking agent, or (d) sulphur donor.

(14) 1(iii). A synthetic elastomeric article comprising the cured product of a synthetic latex composition, the synthetic latex composition comprising a synthetic carboxylated polymer and a cross-linking composition, the cross-linking composition comprising an aqueous solution of a negatively charged multivalent metal complex ion having a pH of at least 9.0, wherein the article is a glove having an average thickness of 0.2 mm or less and a modulus at 500% of less than 6.5 MPa.

(15) 1(iv). A synthetic elastomeric article comprising the cured product of a synthetic latex composition, the synthetic latex composition comprising a synthetic carboxylated polymer and a cross-linking composition, the cross-linking composition comprising an aqueous solution of a negatively charged multivalent metal complex ion having a pH of at least 9.0, the cross-linking composition further comprising a mechanical stabiliser or surfactant, or a combination thereof.

(16) 1(v). A synthetic elastomeric article comprising the cured product of a synthetic latex composition, the synthetic latex composition comprising a synthetic carboxylated polymer and a cross-linking composition, the cross-linking composition comprising an aqueous solution of a negatively charged multivalent metal complex ion having a pH of at least 9.0, wherein said cross-linking composition comprises a solution of a multimetal oxide of the multivalent metal, a solution of a hydroxide of the multivalent metal, or a solution of a salt of the multivalent metal, which is other than a solution of sodium aluminate.

(17) 1(vi). A synthetic elastomeric article comprising the cured product of a synthetic latex composition, the synthetic latex composition comprising a synthetic carboxylated polymer and a cross-linking composition, the cross-linking composition comprising an aqueous solution of a negatively charged multivalent metal complex ion having a pH of at least 9.0, wherein at least one of the following applies: i. the cross-linking composition comprises an aqueous solution of a multimetal oxide of the multivalent metal, a hydroxide of the multivalent metal, or a salt of the multivalent metal, such as sodium aluminate, in an amount of less than 0.3 phr of the multimetal oxide of the multivalent metal, the hydroxide of the multivalent metal, or the salt of the multivalent metal; ii. the synthetic latex composition comprises a second cross-linking agent comprising sulphur and a sulphur donor; iii. the synthetic latex composition comprises a second cross-linking agent comprising a multivalent metal oxide or ionic cross-linking agent; iv. the synthetic latex composition comprises a second cross-linking agent comprising sulphur, a sulphur donor and an ionic cross-linking agent; v. the synthetic latex composition comprises a second cross-linking agent comprising a sulphur donor; vi. the cross-linking composition comprises a mechanical stabiliser and/or surfactant; vii. the cross-linking composition comprises a solution of a multimetal oxide of the multivalent metal, a solution of a hydroxide of the multivalent metal, or a solution of a salt of the multivalent metal, which is other than a solution of sodium aluminate; viii. the article is a glove having an average thickness of 0.2 mm or less and a modulus at 500% of less than 6.5 MPa.

(18) 2. The synthetic elastomeric article of any of items 1 to 1(vi), wherein the synthetic carboxylated polymer comprises synthetic carboxylated polymer particles, and in the cured product the synthetic carboxylated polymer particles are bonded to each other through intra-polymer particle multivalent metal cross-links and inter-polymer particle multivalent metal cross-links, in which the intra-polymer particle and inter-polymer particle multivalent metal cross-links are uniformly distributed throughout the cured product.

(19) 3. The synthetic elastomeric article of item 1 or item 2, having a modulus at 500% of less than 7 MPa.

(20) 4. The synthetic elastomeric article of any one of items 1 to 3, having an elongation at break of at least 700%.

(21) 5. The synthetic elastomeric article of item 1 or item 2, having a modulus at 500% of less than 7 MPa and an elongation at break of at least 700%.

(22) 6. The synthetic elastomeric article of any one of the preceding items, wherein the article is in the form of a film.

(23) 7. The synthetic elastomeric article of any one of the preceding items, wherein the article is a glove.

(24) 8. The synthetic elastomeric article of any one of the preceding items, wherein the multivalent metal of the negatively-charged multivalent metal complex ion is an amphoteric metal.

(25) 9. The synthetic elastomeric article of any one of the preceding items, wherein the multivalent metal of the negatively-charged multivalent metal complex ion is selected from the group consisting of aluminium, beryllium, chromium, iron, cobalt, copper, zinc, lead, tin and bismuth.

(26) 10. The synthetic elastomeric article of any one of the preceding claims, wherein the multivalent metal of the negatively-charged multivalent metal complex ion is aluminium.

(27) 11. The synthetic elastomeric article of any one of the preceding items, wherein the cross-linking composition comprises a solution in water at a pH of at least of 9.0 of a multimetal oxide of the multivalent metal, a hydroxide of the multivalent metal or a salt of the multivalent metal.

(28) 12. The synthetic elastomeric article of item 11, wherein the cross-linking composition comprises a solution of the multimetal oxide of the multivalent metal or a solution of the multivalent metal hydroxide.

(29) 13. The synthetic elastomeric article of any one of the preceding items, wherein the cross-linking composition comprises a solution of sodium aluminate producing negatively-charged aluminium complex ions.

(30) 14. The synthetic elastomeric article of any one of the preceding items, wherein the cross-linking composition comprises alkali.

(31) 15. The synthetic elastomeric article of item 14, wherein the cross-linking composition comprises sodium hydroxide, potassium hydroxide or ammonium hydroxide.

(32) 16. The synthetic elastomeric article of any one of the preceding items, wherein the cross-linking composition comprises a stabiliser for maintaining the negatively-charged multivalent metal complex ions in solution.

(33) 17. The synthetic elastomeric article of item 16, wherein the stabiliser is selected from the group consisting of glycerine, maltodextrin, polysaccharide, polyglycerol and mixtures thereof.

(34) 18. The synthetic elastomeric article of any one of the preceding items, wherein the amount of multivalent metal in the synthetic latex composition is 0.01-5 phr.

(35) 19. The synthetic elastomeric article of any one of the preceding items, wherein the amount of multivalent metal in the synthetic latex composition is 0.01-0.5 phr.

(36) 20. The synthetic elastomeric article of any one of the preceding items, wherein the synthetic carboxylated polymer is selected from the group consisting of carboxylated nitrile butadiene rubber, carboxylated styrene butadiene rubber, carboxylated butyl rubber, carboxylated acrylic butadiene rubber, carboxylated polyisoprene, carboxylated polychloroprene, and mixtures or copolymers thereof.

(37) 21. The synthetic elastomeric article of any one of the preceding items, wherein the synthetic carboxylated polymer is carboxylated acrylonitrile butadiene rubber.

(38) 22. The synthetic elastomeric article of any one of the preceding items, comprising a second cross-linking agent.

(39) 23. The synthetic elastomeric article of item 22, wherein the second cross-linking agent is incorporated into the latex composition in solid form.

(40) 24. The synthetic elastomeric article of item 22 or item 23, wherein the second cross-linking agent comprises sulphur, a sulphur donor, or a combination thereof.

(41) 25. The synthetic elastomeric article of item 24, wherein sulphur is included in the latex composition in an amount of 0.1-5.5 phr.

(42) 26. The synthetic elastomeric article of item 24 or item 25, wherein a sulphur donor is included in the latex composition in an amount of 0.1-4.0 phr.

(43) 27. The synthetic elastomeric article of any one of items 22 to items 26, wherein the second cross-linking agent comprises an organic cross-linking agent.

(44) 28. The synthetic elastomeric article of item 27, wherein the organic cross-linking agent is present in the latex composition in an amount of 0.1-4.0 phr.

(45) 29. The synthetic elastomeric article of any one of items 22 to 28, wherein the second cross-linking agent comprises an ionic cross-linking agent selected from the group consisting of zinc oxide, magnesium oxide and combinations thereof.

(46) 30. The synthetic elastomeric article of item 29, wherein the amount of ionic cross-linking agent in the latex composition is 0.1-4.0 phr.

(47) 31. An elastomeric article-forming composition comprising: a synthetic carboxylated polymer, and a cross-linking composition, the cross-linking composition comprising an aqueous solution of a negatively-charged multivalent metal complex ion having a pH of at least 9.0.

(48) 31(i) An elastomeric article-forming composition comprising: a synthetic carboxylated polymer, and a cross-linking composition, the cross-linking composition comprising an aqueous solution of a multimetal oxide of the multivalent metal, a hydroxide of the multivalent metal, or a salt of the multivalent metal, producing a negatively-charged multivalent metal complex ion, and having a pH of at least 9.0, in which the amount of the multimetal oxide of the multivalent metal, the hydroxide of the multivalent metal, or the salt of the multivalent metal is less than 0.3 phr.

(49) 31(ii). An elastomeric article-forming composition comprising: a synthetic carboxylated polymer, a cross-linking composition, the cross-linking composition comprising an aqueous solution of a negatively-charged multivalent metal complex ion having a pH of at least 9.0, and a second cross-linking agent comprising either (a) sulphur and a sulphur donor, (b) a multivalent metal oxide or ionic cross-linking agent, (c) sulphur, a sulphur donor and an ionic cross-linking agent, or (d) sulphur donor.

(50) 31(iii). An elastomeric article-forming composition comprising: a synthetic carboxylated polymer, and a cross-linking composition, the cross-linking composition comprising an aqueous solution of a negatively-charged multivalent metal complex ion having a pH of at least 9.0,
wherein the composition can form gloves having an average thickness of 0.2 mm or less and a modulus at 500% of less than 6.5 MPa.

(51) 31(iv). An elastomeric article-forming composition comprising: a synthetic carboxylated polymer, and a cross-linking composition, the cross-linking composition comprising an aqueous solution of a negatively-charged multivalent metal complex ion having a pH of at least 9.0, and a mechanical stabiliser and/or surfactant.

(52) 31(v). An elastomeric article-forming composition comprising: a synthetic carboxylated polymer, and a cross-linking composition, the cross-linking composition comprising an aqueous solution of a multimetal oxide of the multivalent metal, a solution of a hydroxide of the multivalent metal or a solution of a salt of the multivalent metal, which is other than a solution of sodium aluminate, producing a negatively-charged multivalent metal complex ion having a pH of at least 9.0.

(53) 31(vi). An elastomeric article-forming composition comprising: a synthetic carboxylated polymer, and a cross-linking composition, the cross-linking composition comprising an aqueous solution of a negatively-charged multivalent metal complex ion having a pH of at least 9.0, wherein at least one of the following applies: i. the cross-linking composition comprises an aqueous solution of a multimetal oxide of the multivalent metal, a hydroxide of the multivalent metal, or a salt of the multivalent metal, such as sodium aluminate, in an amount relative to the synthetic carboxylated polymer to provide at least 0.01 phr and less than 0.3 phr of the multimetal oxide of the multivalent metal, the hydroxide of the multivalent metal, or the salt of the multivalent metal; ii. the composition further comprises a second cross-linking agent comprising sulphur and a sulphur donor; iii. the composition further comprises a second cross-linking agent comprising a multivalent metal oxide or ionic cross-linking agent; iv. the composition further comprises a second cross-linking agent comprising sulphur, a sulphur donor and an ionic cross-linking agent; v. the composition further comprises a second cross-linking agent comprising a sulphur donor; vi. the cross-linking composition comprises a mechanical stabiliser and/or surfactant; vii. the cross-linking composition comprises a solution of a multimetal oxide of the multivalent metal, a solution of a hydroxide of the multivalent metal, or a solution of a salt of the multivalent metal, which is other than a solution of sodium aluminate; viii. the composition can form gloves having an average thickness of 0.2 mm or less and a modulus at 500% of less than 6.5 MPa.

(54) 32. The elastomeric article-forming composition of any one of items 31 to 31(vi), wherein the multivalent metal of the negatively-charged multivalent metal complex ion is an amphoteric metal.

(55) 33. The elastomeric article-forming composition of any one of items 31 to 32, wherein the multivalent metal of the negatively-charged multivalent metal complex ion is selected from the group consisting of aluminium, beryllium, chromium, iron, cobalt, copper, zinc, lead, tin and bismuth.

(56) 34. The elastomeric article-forming composition of any one of items 31 to 33, wherein the multivalent metal of the negatively-charged multivalent metal complex ion is aluminium.

(57) 35. The elastomeric article-forming composition of any one of items 31 to 34, wherein the cross-linking composition comprises a solution in water at a pH of at least of 9.0 of a multimetal oxide of the multivalent metal, a hydroxide of the multivalent metal or a salt of the multivalent metal.

(58) 36. The elastomeric article-forming composition of item 35, wherein the cross-linking composition comprises a solution of the multimetal oxide of the multivalent metal or a solution of the multivalent metal hydroxide.

(59) 37. The elastomeric article-forming composition of any one of items 31 to 36, wherein the cross-linking composition comprises a solution of sodium aluminate producing negatively-charged aluminium complex ions.

(60) 38. The elastomeric article-forming composition of any one of items 31 to 37, wherein the cross-linking composition comprises alkali.

(61) 39. The elastomeric article-forming composition of item 38, wherein the cross-linking composition comprises sodium hydroxide, potassium hydroxide or ammonium hydroxide.

(62) 40. The elastomeric article-forming composition of any one of items 31 to 39, wherein the cross-linking composition comprises a stabiliser for maintaining the negatively-charged multivalent metal complex ions in solution.

(63) 41. The elastomeric article-forming composition of item 40, wherein the stabiliser is selected from the group consisting of glycerine, maltodextrin, polysaccharide, polyglycerol and mixtures thereof.

(64) 42. The elastomeric article-forming composition of any one of items 31 to 41, wherein the amount of multivalent metal in the composition is 0.01-5 phr.

(65) 43. The elastomeric article-forming composition of any one of items 31 to 42, wherein the amount of multivalent metal in the composition is 0.01-0.5 phr.

(66) 44. The elastomeric article-forming composition of any one of items 31 to 43, wherein the synthetic carboxylated polymer is selected from the group consisting of carboxylated nitrile butadiene rubber, carboxylated styrene butadiene rubber, carboxylated butyl rubber, carboxylated acrylic butadiene rubber, carboxylated polyisoprene, carboxylated polychloroprene, and mixtures or copolymers thereof.

(67) 45. The elastomeric article-forming composition of any one of items 31 to 44, wherein the synthetic carboxylated polymer is carboxylated acrylonitrile butadiene rubber.

(68) 46. The elastomeric article-forming composition of any one of items 31 to 45, comprising a second cross-linking agent.

(69) 47. The elastomeric article-forming composition of item 46, wherein the second cross-linking agent is in solid form.

(70) 48. The elastomeric article-forming composition of item 46 or item 47, wherein the second cross-linking agent comprises sulphur, a sulphur donor, or a combination thereof.

(71) 49. The elastomeric article-forming composition of item 48, wherein sulphur is included in the composition in an amount of 0.1-5.5 phr.

(72) 50. The elastomeric article-forming composition of item 48 or item 49, wherein a sulphur donor is included in the latex composition in an amount of 0.1-4.0 phr.

(73) 51. The elastomeric article-forming composition of any one of items 46 to 50, wherein the second cross-linking agent comprises an organic cross-linking agent.

(74) 52. The elastomeric article-forming composition of item 51, wherein the organic cross-linking agent is present in the composition in an amount of 0.1-4.0 phr.

(75) 53. The elastomeric article-forming composition of any one of items 46 to 52, wherein the second cross-linking agent comprises an ionic cross-linking agent selected from the group consisting of zinc oxide, magnesium oxide and combinations thereof.

(76) 54. The elastomeric article-forming composition of item 53, wherein the amount of ionic cross-linking agent in the composition is 0.1-4.0 phr.

(77) 55. A method of manufacturing a synthetic elastomeric article comprising: adding a cross-linking composition comprising an aqueous solution of a negatively-charged multivalent metal complex ion having a pH of at least 9.0 to an aqueous suspension of a synthetic carboxylated polymer having a pH of at least 9.0 to produce a synthetic latex composition; forming the synthetic latex composition into the shape of the synthetic elastomeric article; and curing the synthetic latex composition to form the synthetic elastomeric article.

(78) 55(i). A method of manufacturing a synthetic elastomeric article comprising: adding a cross-linking composition having a pH of at least 9.0 and comprising an aqueous solution of a multimetal oxide of the multivalent metal, a hydroxide of the multivalent metal, or a salt of the multivalent metal, which solution contains negatively-charged multivalent metal complex ions, to an aqueous suspension of a synthetic carboxylated polymer having a pH of at least 9.0, in an amount to provide less than 0.3 phr of the multimetal oxide of the multivalent metal, the hydroxide of the multivalent metal, or the salt of the multivalent metal, to produce a synthetic latex composition; forming the synthetic latex composition into the shape of the synthetic elastomeric article; and curing the synthetic latex composition to form the synthetic elastomeric article.

(79) 55(ii). A method of manufacturing a synthetic elastomeric article comprising: adding (i) a cross-linking composition comprising an aqueous solution of a negatively-charged multivalent metal complex ion having a pH of at least 9.0 and (ii) a second cross-linking agent comprising either: (a) sulphur and a sulphur donor, (b) a multivalent metal oxide or ionic cross-linking agent, (c) sulphur, a sulphur donor and an ionic cross-linking agent, or (d) sulphur donor, to an aqueous suspension of a synthetic carboxylated polymer having a pH of at least 9.0 to produce a synthetic latex composition; forming the synthetic latex composition into the shape of the synthetic elastomeric article; and curing the synthetic latex composition to form the synthetic elastomeric article.

(80) 55(iii). A method of manufacturing a synthetic elastomeric article comprising: adding a cross-linking composition comprising an aqueous solution of a negatively-charged multivalent metal complex ion having a pH of at least 9.0 to an aqueous suspension of a synthetic carboxylated polymer having a pH of at least 9.0 to produce a synthetic latex composition; forming the synthetic latex composition into the shape of the synthetic elastomeric article; and curing the synthetic latex composition to form gloves having an average thickness of 0.2 mm or less and a modulus at 500% of less than 6.5 MPa.

(81) 55(iv). A method of manufacturing a synthetic elastomeric article comprising: adding a cross-linking composition comprising an aqueous solution of a negatively-charged multivalent metal complex ion having a pH of at least 9.0 and a mechanical stabiliser and/or surfactant, to an aqueous suspension of a synthetic carboxylated polymer having a pH of at least 9.0 to produce a synthetic latex composition; forming the synthetic latex composition into the shape of the synthetic elastomeric article; and curing the synthetic latex composition to form the synthetic elastomeric article,

(82) 55(v). A method of manufacturing a synthetic elastomeric article comprising: adding a cross-linking composition having a pH of at least 9.0 and comprising an aqueous solution of multimetal oxide of the multivalent metal, a solution of a hydroxide of the multivalent metal, or a solution of a salt of the multivalent metal, which is other than a solution of sodium aluminate, which solution contains negatively-charged multivalent metal complex ions, to an aqueous suspension of a synthetic carboxylated polymer having a pH of at least 9.0, to produce a synthetic latex composition; forming the synthetic latex composition into the shape of the synthetic elastomeric article; and curing the synthetic latex composition to form the synthetic elastomeric article,

(83) 55(vi) A method of manufacturing a synthetic elastomeric article comprising: adding a cross-linking composition comprising an aqueous solution of a negatively-charged multivalent metal complex ion having a pH of at least 9.0 to an aqueous suspension of a synthetic carboxylated polymer having a pH of at least 9.0 to produce a synthetic latex composition; forming the synthetic latex composition into the shape of the synthetic elastomeric article; and curing the synthetic latex composition to form the synthetic elastomeric article,
wherein at least one of the following applies: i. the cross-linking composition comprises an aqueous solution of a multimetal oxide of the multivalent metal, a hydroxide of the multivalent metal, or a salt of the multivalent metal, and is added in an amount to provide less than 0.3 phr of the multimetal oxide of the multivalent metal, the hydroxide of the multivalent metal, or the salt of the multivalent metal; ii. a second cross-linking agent comprising sulphur and a sulphur donor is added to the synthetic carboxylated polymer; iii. a second cross-linking agent comprising a multivalent metal oxide or ionic cross-linking agent is added to the synthetic carboxylated polymer; iv. a second cross-linking agent comprising sulphur, a sulphur donor and an ionic cross-linking agent is added to the synthetic carboxylated polymer; v. a second cross-linking agent comprising a sulphur donor is added to the synthetic carboxylated polymer; vi. the cross-linking composition comprises a mechanical stabiliser and/or surfactant; vii. the cross-linking composition comprises a solution of a multimetal oxide of the multivalent metal, a solution of a hydroxide of the multivalent metal, or a solution of a salt of the multivalent metal, which is other than a solution of sodium aluminate; viii. the synthetic latex composition is cured to form gloves having an average thickness of 0.2 mm or less and a modulus at 500% of less than 6.5 MPa.

(84) 56. The method of any one of items 55 to 55(vi), wherein the cross-linking composition is added sufficiently slowly to the aqueous suspension of synthetic carboxylated polymer to avoid localised coagulation due to pH shock.

(85) 57. The method of item 56, wherein the pH of the cross-linking composition is within 1.0 units of the pH of the aqueous suspension of the synthetic carboxylated polymer.

(86) 58. The method of any one of items 55 to 57, comprising adding alkali to the aqueous suspension of the synthetic carboxylated polymer prior to the addition of the cross-linking composition to raise the pH of the aqueous suspension to at least 9.0.

(87) 59. The method of any one of items 55 to 58, comprising adding the cross-linking composition to the aqueous suspension of the synthetic carboxylated polymer when the concentration of multivalent metal ions in the cross-linking composition is between about 1% and 10% by weight of the cross-linking composition.

(88) 60. The method of any one of items 55 to 59, comprising adding the cross-linking composition in an amount of between about 1 and 20 parts per 100 parts by volume of the aqueous suspension of the synthetic carboxylated polymer.

(89) 61. The method of any one of items 55 to 60, comprising adding surfactant to the aqueous suspension of synthetic carboxylated polymer together with the cross-linking composition.

(90) 62. The method of any one of items 55 to 61, wherein the step of forming the latex composition into the shape of the synthetic elastomeric article comprises a dipping a former into the latex composition.

(91) 63. The method of item 62, wherein the former is a glove-shaped former, and the method is for the manufacture of a glove.

(92) 64. The method of item 62 or item 63, comprising dipping the former into a coagulant composition prior to the step of dipping the former into the latex composition.

(93) 65. The method of any one of items 55 to 64, wherein the multivalent metal of the negatively-charged multivalent metal complex ion is an amphoteric metal.

(94) 66. The method of any one of items 55 to 65, wherein the multivalent metal of the negatively-charged multivalent metal complex ion is aluminium.

(95) 67. The method of any one of items 55 to 66, comprising adding the cross-linking composition to the aqueous suspension of the synthetic carboxylated polymer in an amount to provide 0.01-5 phr of multivalent metal in the latex composition.

(96) 68. The method composition of any one of items 55 to 67, comprising adding the cross-linking composition to the aqueous suspension of the synthetic carboxylated polymer in an amount to provide 0.01-0.5 phr of multivalent metal in the latex composition.

(97) 69. The method of any one of items 55 to 68, comprising forming the cross-linking composition by solubilising a multimetal oxide of the multivalent metal, a hydroxide of the multivalent metal or a salt of the multivalent metal in water, and controlling the pH to be at least 9.0.

(98) 70. The method of item 69, comprising forming the cross-linking composition by solubilising sodium aluminate in water with heating.

(99) 71. The method of item 69 or item 70, wherein the step of forming the cross-linking composition comprises adding an alkali to raise the pH of the cross-linking composition to at least 9.0.

(100) 72. The method of any one of items 69 to 71, comprising adding a stabiliser to the cross-linking composition to maintain the multivalent metal complex ions in solution, to form a stabilised cross-linking composition, prior to addition of the cross-linking composition to the aqueous suspension of synthetic carboxylated polymer.

(101) 73. The method of item 72, wherein the stabiliser is selected from the group consisting of glycerin, maltodextrin, polysaccharide, polyglycerol and mixtures thereof.

(102) 74. The method of any one of items 69 to 73, comprising a step of diluting the cross-linking composition to obtain a multivalent metal ion concentration of between 1-10% by weight of the cross-linking composition, prior to the addition of the cross-linking composition to the aqueous suspension of a synthetic carboxylated polymer.

(103) 75. The method of any one of items 55 to 74, wherein the synthetic carboxylated polymer comprises synthetic carboxylated polymer particles, and the curing step results in the synthetic carboxylated polymer particles being bonded to each other through intra-polymer particle multivalent metal cross-links and inter-polymer particle multivalent metal cross-links, in which the intra-polymer particle and inter-polymer particle multivalent metal cross-links are uniformly distributed throughout the cured product.

(104) 76. The method of any one of items 55 to 75, wherein the synthetic carboxylated polymer is selected from the group consisting of carboxylated nitrile butadiene rubber, carboxylated styrene butadiene rubber, carboxylated butyl rubber, carboxylated acrylic butadiene rubber, carboxylated polyisoprene, carboxylated polychloroprene, and mixtures or copolymers thereof.

(105) 77. The method of any one of items 55 to 44, wherein the synthetic carboxylated polymer is carboxylated acrylonitrile butadiene rubber.

(106) 78. The method of any one of items 55 to 77, comprising adding to the latex composition particulate components selected from the group consisting of second cross-linking agents, plasticizers, anti-ozonants, stabilisers such as pH stabilisers, emulsifiers, antioxidants, vulcanising agents, pigments, fillers, colourising agents and sensitisers prior to forming the latex composition into the shape of the synthetic elastomeric article.

(107) 79. The method of item 78, wherein the particulate components comprise a second cross-linking agent.

(108) 80. The method of item 79, wherein the second cross-linking agent comprises sulphur, a sulphur donor, or a combination thereof.

(109) 81. The method of item 80, wherein sulphur is added into the latex composition in an amount of 0.1-5.5 phr.

(110) 82. The method of item 80 or item 81, wherein a sulphur donor is added into the latex composition in an amount of 0.1-4.0 phr.

(111) 83. The method of any one of items 79 to 82, wherein the second cross-linking agent comprises an organic cross-linking agent.

(112) 84. The method of item 83, wherein the organic cross-linking agent is added to the latex composition in an amount of 0.1-4.0 phr.

(113) 85. The method of any one of items 79 to 84, wherein the second cross-linking agent comprises an ionic cross-linking agent selected from the group consisting of zinc oxide, magnesium oxide and combinations thereof.

(114) 86. The method of item 53, wherein the ionic cross-linking agent is added into the latex composition in an amount of 0.1-4.0 phr.

(115) 87. An elastomeric article produced from the elastomeric article-forming composition of any one of items 31 to 54 or by the method of any one of items 55 to 86.

(116) 88. Elastomeric gloves produced from the elastomeric film-forming composition of any one of items 31 to 54 or by the method of any one of items 55 to 86.

(117) 89. A synthetic elastomeric article comprising cured synthetic carboxylated polymer particles bonded to each other through intra-polymer particle multivalent metal cross-links and inter-polymer particle multivalent metal cross-links, in which the intra-polymer particle and inter-polymer particle multivalent metal cross-links are uniformly distributed throughout the cured product.

(118) 90. The synthetic elastomeric article of item 89, and comprising the features of any one of items 1 to 30.