Rubber articles such as a glove, a finger cot and a dropper are produced by a method generally called “dip-forming”. Of these rubber articles, gloves are widely used in a household field and an industrial field. For these uses, it is required that the rubber articles are not broken even when they are used for a long period of time, and they have high resistance to solvents.
In recent years, the use of a glove is extended to a medical field including a surgical operation, and an electronic part-production field. In these uses, a glove of a relatively small size is worn in an expanded state to enhance its tight conformity to the skin of a wearer's hand. Therefore, the following characteristics are required for a glove: (i) ease in donning, i.e., capability of being well stretched and easily donned, (ii) good followability, i.e., capability of being easily stretched and shrunk so as to follow the movement of wearer's fingers so that, even when it is worn for a long time, it does not weary a wearer's hand, (iii) good and lasting tight conformity, namely, when it is distorted by the movement of wearer's fingers, it is loosened or creased with wrinkles only to a slight extent, and tight conformity to the skin of a wearer's hand lasts for a long time.
If a glove for surgical operation has pinholes or is broken during operation, infections tend to be caused by bacteria or virus. If a glove for electronic part-production has pinholes or is broken during operation, insulation failure is liable to occur due to electrolytes contained in sweat and grease from the human body with the result of malfunction of electronic parts. Therefore, it is required that a glove has no pin holes and is not easily broken during operation.
Natural rubber latex has heretofore been used for gloves for the above-mentioned uses. However, gloves made from natural rubber latex have a problem such that wearers acquire allergy thereto. An attempt is made for the removal of allergic substances, but the steps required are complicated and the production cost is increased.
As a substitute for natural rubber latex, a soft glove having high tensile strength and chemical resistance, which is comprised of a nitrile rubber composition containing no zinc oxide, has been proposed in international publication WO 97/48,765. However, examination of the nitrite rubber glove by the present inventors has revealed that the followability and lastingness of the tight conformity to the skin of a wearer's hand are insufficient.
A glove having characteristics such that modulus in tension at 100% elongation becomes substantially zero in 6 minutes from the start of elongation, which is comprised of a nitrile-butadiene rubber and a minor amount of zinc oxide, has been proposed in U.S. Pat. No. 5,014,362. However, this glove has poor lastingness of tight conformity.