Nitrile rubber article having natural rubber characteristics
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 monovalent salt and 0.5-1.5 parts of a metallic oxide wherein the total combined amount of the alkali monovalent salt 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 said formulation further includes, a stabilizer and, one or more accelerator from a group including a guanidine, dithiocarbamate, and optionally a thiazole compound.
3. The elastomeric glove according to claim 2 , wherein said accelerator comprises: zinc diethyldithiocarbamate (ZDEC), zinc 2-mercaptobenzithiazole (ZMBT), and diphenyl guanidine (DPG).
4. The elastomeric glove according to claim 2 , wherein said guanidine, dithiocarbamate, and thiazole, are in a ratio of about 2:1:1, respectively.
5. 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.
6. 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.
7. 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.
8. The elastomeric glove according to claim 1 , wherein said force at 300% elongation (F-300) of the glove substrate is about 1.8 N.
9. The elastomeric glove according to claim 1 , wherein said force at 300% elongation (F-300) of the glove substrate is about 0.9 N.
10. The elastomeric glove according to claim 1 , wherein said F-400 is less than about 2.2 N.
11. The elastomeric glove according to claim 1 , wherein said F-400 is less than about 2.0 N.
12. 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.
13. The elastomeric glove according to claim 1 , wherein said glove substrate exhibits a force-to-break (F-BE) of up to about 15 N.
14. The elastomeric glove according to claim 1 , wherein said glove substrate exhibits a force-to-break (F-BE) of from about 7 N to about 13 N.
15. The elastomeric glove according to claim 1 , wherein said glove substrate exhibits a force-to-break (F-BE) of about 9 N to about 11 N.
16. The elastomeric glove according to claim 1 , wherein said glove substrate exhibits a tensile strength of about 30 MPa to about 58 MPa.
17. The elastomeric glove according to claim 1 , wherein said glove substrate exhibits a tensile strength of about 35 MPa to about 55 MPa.
18. The elastomeric glove according to claim 1 , wherein said glove substrate exhibits a tensile strength of about 40 to 50 MPa.
19. 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.
20. 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 monovalent salt and 0.5-1.5 parts of a metallic oxide wherein the total combined amount of the alkali monovalent salt 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.
21. 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 monovalent salt and 0.5-1.5 parts of a metallic oxide wherein the total combined amount of the alkali monovalent salt 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.