Nitrile rubber article having natural rubber characteristics
View Patent ↗An improved process and material for making elastomeric nitrile rubber articles is disclosed. In particular, the process and material formulation can produce nitrile rubber based articles, which exhibit force-strain characteristics that are comparable to those of natural rubber latex articles, while maintaining the tensile strength properties of nitrile rubber. The process includes an accelerator composition at the pre-cure stage having a dithiocarbamate, a thiazole, and a guanidine compound. The invention also includes an elastomeric nitrile rubber product made by the process, such as examination, surgical, or work gloves.
1. An elastomeric glove comprising: a glove substrate formed from a formulation containing a carboxylated nitrile-butadiene random terpolymer composition having an acrylonitrile content of between about 17 wt. % to 45 wt. %, a carboxylic acid content of up to about 15 wt. %, and the remaining balance of the terpolymer being butadiene and having a glass transition temperature (Tg) in a range of about −15° C. to about −30° C., and in terms of parts per 100 dry parts of rubber consisting of the carboxylated nitrile-butadiene random 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, the glove substrate having a thickness of from about 0.05 to about 0.12 mm in a palm region of the glove, the glove substrate requiring a force of less than or equal to about 2.5 N to cause a 400 percent elongation (F-400) from initial dimensions and the glove substrate further exhibiting a substantially linear force-to-strain response up to about 300 percent elongation (F-300) from initial dimensions when tested in accordance with ASTM D412-98a.
2. The elastomeric glove according to claim 1 , wherein the alkali agent is selected from potassium hydroxide, ammonium hydroxide, or the like and combinations thereof.
3. The elastomeric glove according to claim 1 , wherein said formulation further includes, a stabilizer and, one or more accelerator from a group including a guanidine, dithiocarbamate, and optionally a thiazole compound.
4. The elastomeric glove according to claim 3 , wherein said accelerator comprises: zinc diethyldithiocarbamate (ZDEC), zinc 2-mercaptobenzithiazole (ZMBT), and diphenyl guanidine (DPG).
5. The elastomeric glove according to claim 3 , wherein said guanidine, dithiocarbamate, and thiazole, are in a ratio of about 2:1:1, respectively.
6. The elastomeric glove according to claim 1 , wherein said force at 300% elongation (F-300) of the glove substrate is up to about 1.5 N.
7. The elastomeric glove according to claim 1 , wherein the glove substrate may be extended up to about 500% elongation with a force of less than 3 N.
8. The elastomeric glove according to claim 1 , wherein said palm region of said glove has a thickness in the range from about 0.05 mm to about 0.10 mm.
9. The elastomeric glove according to claim 1 , wherein said force at 300% elongation (F-300) of the glove substrate is about 1.8 N.
10. The elastomeric glove according to claim 1 , wherein said force at 300% elongation (F-300) of the glove substrate is about 0.9 N.
11. The elastomeric glove according to claim 1 , wherein said F-400 is less than about 2.2 N.
12. The elastomeric glove according to claim 1 , wherein said F-400 is less than about 2.0 N.
13. The elastomeric glove according to claim 1 , wherein said glove substrate exhibits a force-to-break (F-BE) of at least about 6.5 N.
14. The elastomeric glove according to claim 1 , wherein said glove substrate exhibits a force-to-break (F-BE) of up to about 15 N.
15. The elastomeric glove according to claim 1 , wherein said glove substrate exhibits a tensile strength of about 30 MPa to about 58 MPa.
16. The elastomeric glove according to claim 1 , wherein said glove substrate has an elastic modulus in a range of from about 3 MPa to about 6 MPa at about 300% stretch elongation.
17. An elastomeric glove comprising: a glove substrate formed from a formulation containing a carboxylated nitrile-butadiene random terpolymer composition having a glass transition temperature (Tg) in a range of about −15° C. to about −30° C., and in terms of parts per 100 dry parts of rubber consisting of the carboxylated nitrile-butadiene random terpolymer, between 0-1.5 parts of an alkali agent providing a monovalent ion 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, the glove substrate having a thickness of from about 0.05 to about 0.12 mm in a palm region of the glove, the glove substrate requiring a force of less than or equal to about 2.5 N to cause a 400 percent elongation (F-400) from initial dimensions and the glove substrate further exhibiting a substantially linear force-to-strain response up to about 300 percent elongation (F-300) from initial dimensions at a force up to about 1.5 N when tested in accordance with ASTM D412-98.
18. The elastomeric glove according to claim 17 , wherein the alkali agent is selected from potassium hydroxide, ammonium hydroxide, or the like and combinations thereof.
19. An elastomeric glove comprising: a glove substrate formed from a formulation containing a carboxylated nitrile-butadiene random terpolymer composition having an acrylonitrile content of between about 17 wt. % to 45 wt. %, a carboxylic acid content of up to about 15 wt. %, and the remaining balance of the terpolymer being butadiene, and a glass transition temperature (Tg) in a range of about −15° C. to about −30° C., and in terms of parts per 100 dry parts of rubber consisting of the carboxylated nitrile-butadiene random terpolymer, between 0-1.5 parts of an alkali agent providing a monovalent ion 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, the glove substrate having a thickness of from about 0.05 to about 0.12 mm in a palm region of the glove, the glove substrate requiring a force of less than or equal to about 2.5 N to cause a 400 percent elongation (F-400) from initial dimensions and the glove substrate further exhibiting a substantially linear force-to-strain response up to about 300 percent elongation (F-300) from initial dimensions at a force up to about 1.5 N when tested in accordance with ASTM D412-98a.
20. The elastomeric glove according to claim 19 , wherein the alkali agent is selected from potassium hydroxide, ammonium hydroxide, or the like and combinations thereof.