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                                                                    Exhibit 3.15

                                                           STATE OF DELAWARE
                                                          SECRETARY OF STATE
                                                       DIVISION OF CORPORATIONS
                                                       FILED 03:00 PM 08/16/1996
                                                          960240919 - 2654109

                          CERTIFICATE OF INCORPORATION
                                       OF
                              MEDTECH PRODUCTS INC.


     FIRST: The name of the corporation is Medtech Products Inc.

     SECOND: The registered office of the corporation in the State of Delaware
is located at the Corporation Trust Center, 1209 Orange Street, in the City of
Wilmington, County of New Castle. The name of its registered agent at such
address is The Corporation Trust Company.

     THIRD: The nature of the business or purposes to be conducted or promoted
is to engage in any lawful act or activity for which corporations may be
organized under the General Corporation Law of Delaware.

     FOURTH: The total number of shares of all classes of stock which the
corporation shall have authority to issue is one thousand (1,000) shares of
Common Stock of the par value of one cent ($.01) per share.

     FIFTH: The name of the incorporator is J. Mark Metts and his mailing
address is c/o Vinson & Elkins L.L.P., 2300 First City Tower, 1001 Fannin,
Houston, Texas 77002-6760.

     SIXTH: In furtherance of, and not in limitation of, the powers conferred by
statute, the Board of Directors is expressly authorized to adopt, amend or
repeal the bylaws of the corporation. The number of directors of the corporation
shall be as specified in, or determined in the manner provided in, the bylaws.
Election of directors need not be by written ballot.

     SEVENTH: Whenever a compromise or arrangement is proposed between the
corporation and its creditors or any class of them and/or between the
corporation and its stockholders or any class of them, any court of equitable
jurisdiction within the State of Delaware may, on the application in a summary
way of the corporation or of any creditor or stockholder thereof or on the
application of any receiver or receivers appointed for the corporation under the
provisions of Section 291 of Title 8 of the Delaware Code or on the application
of trustees in dissolution or of any receiver or receivers appointed for the
corporation under the provisions of Section 279 of Title 8 of the Delaware Code
order a meeting of the creditors or class of creditors, and/or of the
stockholders or class of stockholders of the corporation, as the case may be, to
be, summoned in such manner as the said court directs. If a majority in number
representing three-fourths in value of the creditors or class of creditors,
and/or of the stockholders or class of stockholders of the corporation, as the
case may be, agree to any compromise or arrangement and to any reorganization of
the corporation as a consequence of such compromise or arrangement, the said
compromise or arrangement and the said reorganization shall, if sanctioned by
the court to which the said application has been made, be binding on all the
creditors or class of creditors, and/or on all the stockholders or class of
stockholders, of the corporation, as the case may be, and also on the
corporation.

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     EIGHTH: No director of the corporation shall be liable to the corporation
or its stockholders for monetary damages for breach of fiduciary duty as a
director, except for liability (i) for any breach of the director's duty of
loyalty to the corporation or its stockholders, (ii) for acts or omissions not
in good faith or which involve intentional misconduct or a knowing violation of
law, (iii) under Section 174 of the Delaware General Corporation Law, or (iv)
for any transaction from which the director derived an improper personal
benefit.

     NINTH: The corporation shall have the right, subject to any express
provisions or restrictions contained in the certificate of incorporation or
bylaws of the corporation, from time to time, to amend the certificate of
incorporation or any provision thereof in any manner now or hereafter provided
by law, and all rights and powers of any kind conferred upon a director or
stockholder of the corporation by the certificate of incorporation or any
amendment thereof are subject to such right of the corporation.

     I, the undersigned, being the incorporator hereinbefore named, for the
purpose of forming a corporation pursuant to the General Corporation Law of the
State of Delaware, do make this certificate, hereby declaring that this is my
act and deed and that the facts herein stated are true, and accordingly have
hereunto set my hand this 16th day of August, 1996.


                                                    /s/ J. Mark Metts
                                                    ----------------------------
                                                    J. Mark Metts