Any employer who promises in writing to make payments to an employee welfare plan, vacation plan, health plan, dental plan, insurance plan, supplemental unemployment benefit plan, profit sharing plan, pension plan or any employee welfare plan, either by contract with an individual employee, by a collective bargaining agreement or by agreement with such employee plan, and who with intent to defraud the employees or their beneficiaries fails to make such payments within 30 days after they become due and payable, is guilty of a business offense for the first such failure for which the penalty is a $100 fine, and is guilty of a Class B misdemeanor for the second and subsequent such failure.
     The provisions of this Act shall not be applicable until and unless an authorized representative of the plan shall give 30 days written notice to the employer at his principal office by registered mail of any default in payment. The employer shall have 30 days upon receipt of written notice to make proper payment.
     In any criminal proceeding brought to enforce this Section, it shall be an affirmative defense that the employer was prohibited from fulfilling the duty to make such payments by order of a court of competent jurisdiction or by reason of pendency of proceedings in bankruptcy or by reason of natural catastrophe.
     Nothing in this Act shall be construed to relieve an employer from civil liability for failure to make such payments.