Any employer maintaining a plan for furnishing disability insurance benefits to his employees for nonindustrial and nonoccupational injuries or sickness, under which plan the employer defrays 50 percent or more of the expense of such benefits, may secure a certificate of exemption from the commissioner under this article if such employer in respect to such plan otherwise complies with and is subject to the requirements of this article. Such compliance with this article need be only with respect to such plan and not in respect to other business of the employer.