Nitrile rubber article having natural rubber characteristics
View Patent ↗An carboxylated nitrile-butadiene rubber latex formulation composed of a blend of a first acrylonitrile terpolymer and a second acrylonitrile terpolymer, wherein: the acrylonitrile content of the blended terpolymers is between 17 and 45% by weight, the methacrylic acid content of the blended termpolymers is less than 15% by weight, and the remaining balance of the terpolymers being butadiene. The invention also includes an elastomeric nitrile rubber article made from the formulation.
1. An elastomeric glove formed from a carboxylated nitrile-butadiene rubber latex formulation comprising a blend of a first acrylonitrile terpolymer and a second acrylonitrile terpolymer, wherein:
the acrylonitrile content of the blend is between 17 and 45% by weight,
the methacrylic acid content of the blend is less than 15% by weight, and
butadiene makes up the remainder of the blend;
wherein a ratio of the first and second acrylonitrile terpolymers ranges from 60:40 to 40:60, the first acrylonitrile terpolymer having a lower elastic modulus than the second acrylonitrile terpolymer.
2. The elastomeric glove of claim 1 , wherein the carboxylated nitrile-butadiene terpolymer latex formulation further comprises, in terms of parts per 100 dry parts of rubber consisting of the carboxylated nitrile-butadiene terpolymer, between 0-1.5 parts of an alkali agent that provides monovalent ions and 0.5-1.5 parts of a metallic oxide wherein the total combined amount of the alkali agent and metallic oxide is greater than 1.0 part per 100 dry parts of rubber.
3. The elastomeric glove of claim 1 , wherein the carboxylated nitrile-butadiene rubber latex formulation further comprises, in terms of parts per 100 dry parts of rubber consisting of the carboxylated nitrile-butadiene terpolymer, from 0.5-1.5 parts sulfur and 0.5-1.5 parts rubber accelerator.
4. The elastomeric glove of claim 1 , wherein the pH of the formulation during formation of the glove is 9 to 12.5.
5. The elastomeric glove of claim 1 , wherein the latex formulation is an emulsion containing 19-22% total solids content.
6. The elastomeric glove of claim 1 , wherein the acrylonitrile terpolymer comprises a random terpolymer of acrylonitrile, butadiene and carboxylic acid.
7. An elastomeric glove formed from a carboxylated nitrile-butadiene rubber latex formulation comprising a blend of a first random terpolymer of acrylonitrile, butadiene and carboxylic acid and a second random terpolymer of acrylonitrile, butadiene and carboxylic acid, the first and second random terpolymers in a compositional ratio ranging from 60:40 to 40:60, the first random terpolymer having a lower elastic modulus than the second random terpolymer, the blend including, in terms of parts per 100 dry parts of rubber consisting of the random terpolymers:
0-1.5 parts alkali hydroxide,
0.5-1.5 parts zinc oxide or other metal oxide,
0.5-1.5 parts sulfur, and
0.5-1.5 parts rubber accelerator,
wherein said glove has an elastic modulus in the range of 3 MPa to 6 MPa at 300% stretch-elongation, and a tensile strength at break in the range of 30 MPa to 55 MPa.
8. The elastomeric glove of claim 7 , wherein the glove has a palm thickness in the range of between 0.06 and 0.10 mm.
9. The elastomeric glove of claim 7 , wherein the glove has an elongation at break of 550-750%.
10. The elastomeric glove of claim 7 , wherein the alkali hydroxide is selected from potassium hydroxide and ammonium hydroxide.
11. The elastomeric glove of claim 7 , wherein the rubber accelerator comprises a rubber accelerator selected from the group consisting of zinc diethyldithiocarbamate (ZDEC), zinc 2-mercaptobenzithiazole (ZMBT), and diphenyl guanidine (DPG).