<PAGE>

                                                                    EXHIBIT 10.9


                   MASTER PATENT GRANTBACK LICENSE AGREEMENT


     This Master Patent Grantback License Agreement (the "Agreement') is
effective as of March 31, 2001 (the "Effective Date"), between Millipore
Corporation, a Massachusetts corporation, having an office at 80 Ashby Road,
Bedford, Massachusetts 01730, ("MIL") and Mykrolis Corporation, a Delaware
corporation ("Mykrolis"), having an office at Patriots Park, Bedford,
Massachusetts 01730.

     WHEREAS, the Board of Directors of MIL has determined that it is in the
best interest of MIL and its stockholders to separate Millipore's existing
businesses into two independent businesses;

     WHEREAS, as part of the foregoing, MIL and Mykrolis, have entered into a
Master Separation and Distribution Agreement (as defined below) which provides,
among other things, for the separation of certain Mykrolis assets and Mykrolis
liabilities, the initial public offering of Mykrolis stock, the distribution of
such stock and the execution and delivery of certain other agreements in order
to facilitate and provide for the foregoing;

     WHEREAS, each of the parties have in the past used the same patented
technology in each of their businesses relating to membrane manufacture, filter
manufacture, filter design and other such commonly used inventions ("Commonly
Used Inventions");

     WHEREAS, the parties deem that it is necessary for the successful operation
of each entity after the separation for each party to have the right to practice
to the Commonly Used Inventions in certain fields of use; and

     WHEREAS in order to accomplish this, Mykrolis agrees to grant back a
license to MIL for the Licensed Patents (as defined below) to the Commonly Used
Inventions in certain fields of use after the separation of the Mykrolis
business.

     NOW, THEREFORE, in consideration of the mutual promises of the parties, and
of good and valuable consideration, it is agreed by and between the parties as
follows:


                                   ARTICLE 1
                                  DEFINITIONS

     For the purpose of this Agreement, the following capitalized terms are
defined in this Article 1 and shall have the meaning specified herein:
<PAGE>

     1.1  MASTER SEPARATION AND DISTRIBUTION AGREEMENT. "Master Separation
and Distribution Agreement" means the Master Separation and Distribution
Agreement between the parties.

     1.2  MIL Field of Use "means BIOPHARM including
pharmaceutical/biotechnology and genetic engineering companies as well as
manufacturers of cosmetics, medical devices, diagnostic products and clinical
analytical products; LAB & LIFE SCIENCE RESEARCH including government,
university and private research and testing analytical laboratories for
protenomic, genomic, microbiological, environmental and other such areas; and
FOOD & BEVERAGE including companies that manufacture or process foods and
beverages including dairy products, beer, wine, juice and soft drink
manufacturers and bottled water companies.

     1.3  MYKROLIS FIELD OF USE. "Mykrolis Field of Use" means IC
MANUFACTURERS including companies that manufacture integrated circuits,
semiconductors, semiconductor chips and other microelectronics components, flat
panel displays, solar cells and fiber optic cables, optical coatings, coated
optical lenses and coated optical fibers; IC OEM EQUIP & MATERIALS MANUFACTURING
including companies that manufacture equipment for the fabrication and
processing of semiconductors and integrated circuits for sale to IC
Manufacturing Companies as well as companies that integrate a number of
components into subsystems sold to OEM Equipment manufacturers for incorporation
into semiconductor fabrication equipment as well as Companies that manufacture,
process and supply liquids, gases, conductive materials and other advanced
materials to the IC Manufacturing Industry and which provide products and
systems to purify, monitor and control atmospheric conditions in clean room
manufacturing environments of the IC Manufacturing Industry and IC RESEARCH
LABORATORIES including university, government and commercial laboratories and
research operations that research and/or develop innovations in the structure
and composition of integrated circuits, the processes and materials used to
manufacture integrated circuits and new forms of integrated circuits.

     1.4  MYKROLIS LICENSED PATENTS.  "Mykrolis Licensed Patents" means those
Patents and Applications set forth in the Exhibit A hereto, any patents that
issue from any of the Applications or claiming priority from the Applications,
any related applications, divisionals, continuations, continuation-in-part,
reissues or reexaminations of the Patents and/or Applications.

     1.5  MYKROLIS OPTIONED PATENTS. "Mykrolis Optioned Patents" means those
Patents and Applications set forth in the Exhibit B hereto, any patents that
issue from any of the Applications or claiming priority from the Applications,
any related applications, divisionals, continuations, continuation-in-part,
reissues or reexaminations of the Patents and/or Applications.

     1.6  PERSON. "Person" means an individual, a partnership, a corporation, a
limited liability company, an association, a joint stock company, a trust, a
joint venture, an

                                       2
<PAGE>

unincorporated organization, and a governmental entity or any department, agency
or political subdivision thereof.

     1.7  SEPARATION DATE. "Separation Date" means March 31, 2001, or such
other date as may be fixed by the Board of Directors of Millipore Corporation.

     1.8  SUBSIDIARY. "Subsidiary" of any Person means a corporation or
other organization whether incorporated or unincorporated of which at least a
majority of the securities or interests having by the terms thereof ordinary
voting power to elect at least a majority of the board of directors or others
performing similar functions with respect to such corporation or other
organization is directly or indirectly owned or controlled by such Person or by
any one or more of its Subsidiaries, or by such Person and one or more of its
Subsidiaries; provided, however, that no Person that is not directly or
indirectly wholly-owned by any other Person shall be a Subsidiary of such other
Person unless such other Person controls, or has the right, power or ability to
control, that Person. For purposes of this Agreement, Mykrolis shall be deemed
not to be a subsidiary of MIL.

     1.9  THIRD PARTY.  "Third Party" means a Person other than MIL and its
Subsidiaries and Mykrolis and its subsidiaries.

     1.10 PRODUCTS "Products" shall mean any product made sold or otherwise
disposed of by MIL in the MIL Field of Use.



                                   ARTICLE 2
                                    LICENSES

     2.1  EXCLUSIVE LICENSE GRANT.  Mykrolis grants to MIL a personal,
irrevocable, exclusive, worldwide, fully-paid, royalty-free and non-transferable
(except as set forth in Section 8.10) license to use the Mykrolis Licensed
Patents (as set forth in Exhibit A) to make, have made, use, sell or otherwise
dispose of Products in the MIL Field of Use.

     2.2  OPTION TO LICENSE. Mykrolis grants to MIL a personal, irrevocable,
exclusive option for a period of five (5) years from the date of this agreement
to elect to obtain a license under one or more of the Mykrolis Optioned Patents
(as set forth in Exhibit B). It is contemplated that more than option election
may be exercised during this time period. If any such an option is exercised,
the license granted shall be personal, irrevocable, exclusive, worldwide, no
upfront fee, with a 5% royalty based on Net Sales and non-transferable (except
as set forth in Section 8.10) to use the Mykrolis Optioned Patent(s) to make,
have made, use, sell or otherwise dispose of Products in the MIL Field of Use.

                                       3
<PAGE>

     2.3  LICENSE RESTRICTIONS.

          (a) MIL shall not use the Mykrolis Licensed Patents in connection with
any products or services other than in the MIL Field of Use.

          (b) MIL shall not (i) misrepresent to any Person the scope of its
authority under this Agreement, (ii) incur or authorize any expenses or
liabilities chargeable to Mykrolis, or (iii) take any actions that would impose
upon Mykrolis any obligation or liability to a Third Party other than
obligations under this Agreement, or other obligations which Mykrolis expressly
approves in writing for MIL to incur on its behalf.

     2.4  RESERVATION OF RIGHTS.  Except as otherwise expressly provided in this
Agreement, Mykrolis shall retain all rights in and to the MMI Licensed Patents,
including without limitation:

          (a)  All rights of ownership in and to the Mykrolis Licensed Patents;

          (b)  The right to use (including the right of Mykrolis's Subsidiaries
               to use) the Mykrolis Licensed Patents, in all fields of use
               except for the MIL Field of Use; and

          (c)  The right to license Third Parties to use the Mykrolis Licensed
               Patents except in the MIL Field of Use.


                                   ARTICLE 3
                          PERMITTED SUBLICENSES BY MIL

     3.1  SUBLICENSES TO SUBSIDIARIES.  Subject to the terms and conditions of
this Agreement, MIL may grant sublicenses to its Subsidiaries to use the
Mykrolis Licensed Patents in accordance with the license grants in Sections 2.1
and 2.2 above; provided that (i) MIL enters into a written sublicense agreement
with each such Subsidiary sublicensee, and (ii) such agreement does not include
the right to grant further sublicenses other than in the case of a sublicensed
Subsidiary of MIL, to another Subsidiary of MIL.  MIL shall provide copies of
such written sublicense agreements to Mykrolis upon request.  If MIL grants any
sublicense rights pursuant to this Section 3.1 and any such sublicensed
Subsidiary ceases to be a Subsidiary, then the sublicense granted to such
Subsidiary pursuant to this Section 3.1 shall terminate 180 days from the date
of such cessation.

     3.2  ENFORCEMENT OF SUBLICENSE AGREEMENTS.  MIL shall take all appropriate
measures at MIL's expense promptly and diligently to enforce the terms of any
sublicense agreement or other agreement with any Subsidiary and shall restrain
any such Subsidiary from violating such terms, including without limitation (i)
monitoring the Subsidiaries' compliance with the terms and conditions of this
Agreement and causing any

                                       4
<PAGE>

noncomplying Subsidiary promptly to remedy any failure, (ii) terminating such
agreement and/or (iii) commencing legal action, in each case, using a standard
of care consistent with MIL's practices as of the Separation Date. In the event
that Mykrolis determines that MIL has failed promptly and diligently to enforce
the terms of any such agreement using such standard of care, Mykrolis reserves
the right to enforce such terms, and MIL shall reimburse Mykrolis for its fully
allocated direct costs and expenses incurred in enforcing such agreement, plus
all out-of-pocket costs and expenses, plus five percent (5%).


                                   ARTICLE 4
                         PROTECTION OF LICENSED PATENTS

     4.1  OWNERSHIP AND RIGHTS.  To the extent not contrary to applicable law,
MIL agrees not to challenge the ownership or validity of the Mykrolis Licensed
Patents or Mykrolis Optioned Patents. MIL shall not disparage or adversely
affect the validity of the Mykrolis Licensed Patents or Mykrolis Optioned
Patents.  MIL shall not acquire or assert any ownership rights therein.

     4.2  PROTECTION OF PATENTS.  MIL shall assist Mykrolis, at Mykrolis's
request and expense, in the procurement and maintenance of Mykrolis's
intellectual property rights in the Licensed Patents.  MIL will not grant or
attempt to grant a security interest in the Licensed Patents, or to record any
such security interest in the United States Patent and Trademark Office or
elsewhere, against any Mykrolis Licensed Patent.  Mykrolis makes no warranty or
representation that the Licensed Patents will be secured or maintained anywhere
within the world.

     4.3  INFRINGEMENT PROCEEDINGS. (a) In the event that the MIL Patent Counsel
learns of any infringement or threatened infringement of the Licensed Patents,
MIL shall notify Mykrolis or its authorized representative in writing giving
particulars thereof ("Notice"), and MIL shall provide necessary information and
assistance to Mykrolis or its authorized representatives at MIL's expense to
assist Mykrolis or its authorized representatives in determining whether
proceedings should be commenced.  Notwithstanding the foregoing, Mykrolis is not
obligated to monitor or police use of the Licensed Patents by Third Parties.

     (b)  Within sixty (60) days of the Notice, Mykrolis shall inform MIL in
writing of its decision whether to commence proceedings against the third party
for infringement of the Licensed Patent ("Decision").  If Mykrolis elects to
commence proceedings, it shall do so with ninety (90) days of its Decision. In
the event that Mykrolis commences proceedings, Mykrolis shall have exclusive
control of the decision whether to bring, maintain or settle any such
proceedings, said proceedings shall be at the exclusive option and expense of
Mykrolis, and all recoveries shall belong exclusively to Mykrolis. MIL shall
provide reasonable assistance to Mykrolis in the prosecution of the proceedings
as may be requested by Mykrolis or its authorized representatives.  Mykrolis
shall incur no liability to MIL or any other Person under any legal theory by
reason of Mykrolis's failure or refusal to prosecute or by Mykrolis's refusal to
permit MIL to prosecute, any alleged infringement by Third Parties, nor by
reason of any settlement to which Mykrolis may agree.

                                       5
<PAGE>

     (c)  In the event that Mykrolis in its Decision elects not to commence
proceedings or fails to commence proceedings within the ninety (90) days of the
Decision, then MIL may at its election, elect to initiate proceedings against
the third party in its own name ("Election"). MIL shall provide Mykrolis of
written notice of this Election at least thirty (30) days before commencing
proceedings. Mykrolis agrees to be named as a necessary party if required by law
and to provide reasonable assistance to MIL in the prosecution of the
proceedings as may be requested by MIL or its authorized representatives. MIL
shall have exclusive control of the decision whether to bring, maintain or
settle any such proceedings, said proceedings shall be at the exclusive option
and expense of MIL, and all recoveries shall belong exclusively to MIL. Any
settlement made by MIL that would affect any right outside of the MIL Field of
Use shall be approved by Mykrolis prior to the execution of such settlement with
agreed upon sharing of the settlement proceeds between MIL and Mykrolis based on
the fields of use. Mykrolis reserves the right to refuse to approve any
settlement which involves rights within the Mykrolis Field of Use.

                                   ARTICLE 5
                                  TERMINATION

     5.1  TERM.  This Agreement shall remain in effect until the last of the
patents licensed hereunder shall expire or otherwise be terminated, unless this
Agreement is earlier terminated as provided below.

     5.2  VOLUNTARY TERMINATION.  By written notice to Mykrolis, MIL may
voluntarily terminate all or a specified portion of the licenses and rights
granted to it hereunder by Mykrolis.  Such notice shall specify the effective
date of such termination and shall clearly specify any affected Licensed
Patents.

     5.3  SURVIVAL.  Any termination of licenses and rights of MIL under Section
5.2 shall not affect MIL's licenses and rights with respect to any Products made
or sold prior to such termination.

     5.4  OTHER TERMINATION. This Agreement, the Master Separation Agreement and
all other Ancillary Agreements may be terminated at any time prior to the IPO
Closing Date by and in the sole discretion of MIL without the approval of
Mykrolis. This Agreement may be terminated at any time after the IPO Closing
Date and before the Distribution Date by mutual consent of MIL and Mykrolis. In
the event of termination pursuant to this Section 5.4, no party shall have any
liability of any kind to the other party.


                                   ARTICLE 6
                               DISPUTE RESOLUTION

     6.1  USE AND INITIATION OF PROCEDURE. In the event of a dispute between the
parties arising out of or related to this Agreement (the "Dispute"), the parties
hereto agree to use the alternative dispute resolution procedures specified in
this section (the "Procedure") in good faith in order to resolve such dispute.
The Procedure may be
                                       6
<PAGE>

modified by written agreement of the parties at the time the Dispute arises. A
party seeking to initiate the Procedure shall give written notice to the other
party, describing briefly the nature of the dispute and its claim and
identifying an individual with authority to settle the dispute on its behalf.
The party receiving such notice shall have five (5) days within which to
designate, in a written notice given to the initiating party, an individual with
authority to settle the dispute on its behalf. Neither of such authorized
individuals shall have had direct substantive involvement in the matters
involved in the Dispute.

     6.2  UNASSISTED SETTLEMENT. The Authorized individuals shall make such
investigation as they deem appropriate and thereafter promptly (but in no event
later than thirty (30) days from the date of the initiating party's notice)
shall commence discussions concerning resolution of the Dispute.  If the Dispute
has not been resolved within thirty (30) days from the commencement of
discussions, it shall be submitted to alternative dispute resolution ("ADR") in
accordance with the provisions of Sections 6.3 through 6.10 hereof.

     6.3  SELECTION OF NEUTRAL.  The parties shall have ten (10) days
following the submission of the Dispute to ADR in accordance with Section 6.2
above to agree upon a mutually acceptable person not affiliated with either of
the parties (the "Neutral").  If no Neutral has been selected within such time,
the parties agree jointly to request the American Arbitration Association, the
Center for Public Resources, or another mutually agreed-upon provider of neutral
services to supply within ten (10) days a list of potential Neutrals with
qualifications as specified by the parties in the joint request.  Within five
(5) days of receipt of the list, the parties shall independently rank the
proposed candidates, shall simultaneously exchange rankings, and shall select as
the Neutral the individual receiving the highest combined ranking who is
available to serve.

     6.4  TIME AND PLACE FOR ADR. In consultation with the Neutral, the parties
shall promptly designate a mutually convenient time and place for the ADR (and
unless circumstances require otherwise, such time to be not later than forty-
five (45) days after selection of the Neutral).

     6.5  EXCHANGE OF INFORMATION. In the event either of the parties has
substantial need for information in the possession of the other party in order
to prepare for the ADR, the parties shall attempt in good faith to agree on
Procedures for the expeditious exchange of such information, with the help of
the Neutral if required.

     6.6  SUMMARY OF VIEWS. One week prior to the first scheduled session of the
ADR, each party shall deliver to the Neutral and to the other party a concise
written summary of its views on the matter in Dispute.

     6.7  STAFFING THE ADR. In the ADR, each party shall be represented by the
authorized individual and by counsel. In addition, each party may bring such
additional persons as needed to respond to questions, contribute information and
participate in the negotiations, the number of such additional persons to be
agreed upon by the parties in advance, with the assistance of the Neutral, if
necessary.

                                       7
<PAGE>

     6.8   CONDUCT OF ADR. The parties, in consultation with the Neutral, will
agree upon a format for the meetings, designed to assure that both the Neutral
and the authorized individuals have an opportunity to hear an oral presentation
of each party's views on the matter in Dispute, and that the authorized parties
attempt to negotiate a resolution of the matter in Dispute, with or without the
assistance of counsel or others, but with the assistance of the Neutral. To this
end, the Neutral is authorized to conduct both joint meetings and separate
private caucuses with the parties. The Neutral will keep confidential all
information learned in private caucus with either party unless specifically
authorized by such party to make disclosure of the information to the other
party.

     6.9   THE NEUTRAL'S VIEWS. The Neutral (i) shall, unless requested not to
do so by both parties, provide his opinion to both parties on the probable
outcome should the matter be litigated, and (ii) shall make one or more
recommendations as to the terms of a possible settlement, upon any conditions
imposed by the parties (including, but not limited to, a minimum and maximum
amount). The Neutral shall base his opinions and recommendations on information
available to both parties, excluding such information as may be disclosed to him
by the parties in confidence. The opinions and recommendations of the Neutral
shall not be binding on the parties.

     6.10  TERMINATION OF PROCEDURE. The parties agree to participate in the ADR
in good faith to its conclusion (as designated by the Neutral) and not to
terminate negotiations concerning resolution of the matters in Dispute until at
least ten (10) days thereafter. Each party agrees not to commence any other
proceeding or to seek other remedies prior to the conclusion of the ten-day
post-ADR negotiation period; provided, however, that either party may commence
                             --------  -------
litigation within five (5) days prior to the date after which the commencement
of litigation could be barred by an applicable statute of limitations or in
order to request an injunction to prevent irreparable harm, in which event, the
parties agree (except as prohibited by court order) to nevertheless continue to
participate in the ADR to its conclusion.

     6.11  FEES OF NEUTRAL; DISQUALIFICATION. The fees of the Neutral shall be
shared equally by the parties. The Neutral shall be disqualified as a witness,
consultant, expert or counsel for either party with respect to the matters in
Dispute and any related matters in any subsequent litigation or other proceeding
with respect to the Dispute.

     6.12  CONFIDENTIALITY.  The parties agree that the Procedure and the ADR
are compromise negotiations for purposes of the Federal Rules of Evidence and
the Rules of Evidence of any state of competent jurisdiction. The entire of the
Procedure and the ADR are confidential, and no stenographic, visual or audio
record shall be made. All conduct, statements, promises, offers, views and
opinions, whether oral or written, made in the course of the Procedure or the
ADR by either of the parties, their agents, employees, representatives, or other
invitees and by the Neutral (who will be the parties' joint agent for purposes
of these compromise negotiations) are confidential and shall, in addition and
where appropriate, be deemed to be work product and privileged. Such conduct,
statements, promises, offers, views and opinions shall not be discoverable or
admissible for any purposes, including impeachment, in any litigation or other
proceeding involving the parties, and shall not be disclosed to anyone not an
agent, employee, expert, witness, or

                                       8
<PAGE>

representative of either of the parties; provided, however, that evidence
                                         --------  -------
otherwise discoverable or admissible is not excluded from discovery or admission
as a result of its use in the ADR.

     6.13  ARBITRATION. Any Dispute which the parties cannot resolve through
mediation within ninety (90) days following the commencement of the Procedure,
unless otherwise mutually agreed, shall be submitted to final and binding
arbitration under the then current Commercial Arbitration Rules of the American
Arbitration Association ("AAA"), by three (3) arbitrators in Boston,
Massachusetts. Such arbitrators shall be selected by the mutual agreement of the
parties or, failing such agreement, shall be selected according to the aforesaid
AAA rules. The arbitrators will be instructed to prepare and deliver a written,
reasoned opinion stating their decision within thirty (30) days of the
completion of the arbitration. The prevailing party in such arbitration shall be
entitled to expenses, including costs and reasonable attorneys' and other
professional fees, incurred in connection with the arbitration (but excluding
any costs and fees associated with prior ADR, negotiation or mediation). The
decision of the arbitrator shall be final and non-appealable and may be enforced
in any court of competent jurisdiction. The use of any ADR procedures will not
be construed under the doctrine of laches, waiver or estoppel to adversely
affect the rights of either party.

     6.14  CONTINUITY OF SERVICE AND PERFORMANCE. Unless otherwise agreed in
writing, the parties will continue to provide service and honor all other
commitments under this Agreement and each Ancillary Agreement during the course
of dispute resolution pursuant to the provisions of this Article IX with respect
to all matters not subject to such dispute, controversy or claim.


                                   ARTICLE 7
                            LIMITATION OF LIABILITY

     IN NO EVENT SHALL MYKROLIS OR ITS SUBSIDIARIES BE LIABLE TO MIL OR ITS
SUBSIDIARIES FOR ANY SPECIAL, CONSIDQUENTIAL, INDIRECT, INCIDENTAL OR PUNITIVE
DAMAGES OR LOST PROFITS OR ANY OTHER DAMAGES, HOWEVER CAUSED AND ON ANY THEORY
OF LIABILITY (INCLUDING NEGLIGENCE) ARISING IN ANY WAY OUT OF THIS AGREEMENT,
WHETHER OR NOT MYKROLIS HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES;
PROVIDED, HOWEVER, THAT THE FOREGOING LIMITATIONS SHALL NOT LIMIT EACH PARTY'S
OBLIGATIONS EXPRESSLY ASSUMED IN THE SEPARATION AND DISTRIBUTION AGREEMENT;
PROVIDED FURTHER THAT THE EXCLUSION OF PUNITIVE DAMAGES SHALL APPLY IN ANY
EVENT.

                                   ARTICLE 8
                            MISCELLANEOUS PROVISIONS

     8.1   DISCLAIMER. MIL ACKNOWLEDGES AND AGREES THAT ALL LICENSED PATENTS ARE
LICENSED OR PROVIDED ON AN "AS IS" BASIS AND THAT NEITHER MYKROLIS NOR ANY OF
ITS SUBSIDIARIES MAKE ANY REPRESENTATIONS OR
                                       9
<PAGE>

EXTENDS ANY WARRANTIES WHATSOEVER, EXPRESS, IMPLIED OR STATUTORY, WITH RESPECT
THERETO INCLUDING WITHOUT LIMITATION ANY IMPLIED WARRANTIES OF TITLE,
ENFORCEABILITY OR NON-INFRINGEMENT. Without limiting the generality of the
foregoing, Mykrolis makes no any warranty or representation as to the validity
of any Licensed Patent licensed by it to MIL or any warranty or representation
that any use of any Licensed Patent with respect to any product or service will
be free from infringement of any rights of any Third Party.

     8.2  NO IMPLIED LICENSES.  Nothing contained in this Agreement shall be
construed as conferring any rights by implication, estoppel or otherwise, under
any intellectual property right, other than the rights expressly granted in this
Agreement with respect to the Mykrolis Licensed Patents and Mykrolis Optioned
Patents.  Mykrolis is not required hereunder to furnish or disclose to MIL any
information (including copies of the Patents), except as specifically provided
herein.

     8.3  INFRINGEMENT SUITS.  Mykrolis shall have no obligations hereunder to
institute any action or suit against Third Parties for infringement of any of
its Licensed Patents or to defend any action or suit brought by a Third Party
which challenges or concerns the validity of any of its Licensed Patents.

     8.4  PATENT MARKING Neither party is obligated to mark any of its Products
made under one or more of the Licensed Patents with the appropriate U S Patent
Number nor is either party obligated to acknowledge that the Products are made
under licenses provided by the other party.

     8.5  NO OTHER OBLIGATIONS.  NEITHER PARTY ASSUMES ANY RESPONSIBILITIES OR
OBLIGATIONS WHATSOEVER, OTHER THAN THE RESPONSIBILITIES AND OBLIGATIONS
EXPRESSLY SET FORTH IN THIS AGREEMENT OR A SEPARATE WRITTEN AGREEMENT BETWEEN
THE PARTIES.  Without limiting the generality of the foregoing, neither
Mykrolis, nor any of its Subsidiaries is obligated to (i) file any application
for patent of any invention not currently the subject of a patent application,
or to secure any rights in any Patents, (ii) to maintain any Licensed Patent, or
(iii) provide any assistance, except for the obligations expressly assumed in
this Agreement.

     8.6  ENTIRE AGREEMENT.  This Agreement, the Master Separation and
Distribution Agreement and the other Ancillary Agreements (as defined in the
Master Separation and Distribution Agreement) and the Exhibits and Schedules
referenced or attached hereto and thereto constitute the entire agreement
between the parties with respect to the subject matter hereof and thereof and
shall supersede all prior written and oral and all contemporaneous oral
agreements and understandings with respect to the subject matter hereof and
thereof.  To the extent there is a conflict between this Agreement and the
General Assignment and Assumption Agreement between the parties, the terms of
this Agreement shall govern.

     8.7  GOVERNING LAW.  This Agreement shall be construed in accordance with
and all Disputes hereunder shall be governed by the laws of the Commonwealth of

                                       10
<PAGE>

Massachusetts as applied to transactions taking place wholly within
Massachusetts between Massachusetts residents.  The Superior Court of Middlesex
County and/or the United States District Court for the District of Massachusetts
shall have jurisdiction and venue over all Disputes between the parties that are
permitted to be brought in a court of law pursuant to Article 7 above.


     8.8  DESCRIPTIVE HEADINGS. The headings contained in this Agreement, in any
Exhibit or Schedule hereto and in the table of contents to this Agreement are
for reference purposes only and shall not affect in any way the meaning or
interpretation of this Agreement. Any capitalized term used in any Exhibit or
Schedule but not otherwise defined therein, shall have the meaning assigned to
such term in this Agreement. When a reference is made in this Agreement to an
Article or a Section, Exhibit or Schedule, such reference shall be to an Article
or Section of, or an Exhibit or Schedule to, this Agreement unless otherwise
indicated.

     8.9  NOTICES.  Notices, offers, requests or other communications required
or permitted to be given by either party pursuant to the terms of this Agreement
shall be given in writing to the respective parties to the following addresses:

           if to MIL:
                                    MiIlipore Corporation
                                    80 Ashby Road
                                    Bedford, Massachusetts 01730

           With a copy to:
                                    General Counsel
                                    MiIlipore Corporation
                                    80 Ashby Road
                                    Bedford, Massachusetts 01730

           if to MYKROLIS:
                                    Mykrolis Corporation
                                    Patriots Park
                                    Bedford, Massachusetts 01730

           With a copy to:
                                    General Counsel
                                    Mykrolis Corporation
                                    Patriots Park
                                    Bedford, Massachusetts 01730

                                       11
<PAGE>

Or to such other address as the party to whom notice is given may have
previously furnished to the other in writing as provided herein.  Any notice
involving non-performance, termination, or renewal shall be sent by hand
delivery, recognized overnight courier or, within the United States, may also be
sent via certified mail, return receipt requested.  All other notices shall be
deemed to have been given and received on the earlier of actual delivery or
three (3) days from the date of postmark.

     8.10 NONASSIGNABILITY. MIL shall not, directly or indirectly, in whole or
in part, whether by operation of law or otherwise, assign or transfer this
Agreement, without Mykrolis 's prior written consent, and any attempted
assignment, transfer or delegation without such prior written consent shall be
void able at the sole option of Mykrolis; provided however, that MIL may assign
all of its rights and obligations under this agreement to its wholly owned
subsidiary, Millipore Investment Holdings Limited without the prior written
permission of Mykrolis. Notwithstanding the foregoing, MIL (or its permitted
successive assignees or transferees hereunder) may assign or transfer this
Agreement as a whole without consent to a Person that succeeds to all or
substantially all of the business or assets of such party as long as such Person
agrees to accept all the terms and conditions set forth herein. Without limiting
the foregoing, this Agreement will be binding upon and inure to the benefit of
the parties and their permitted successors and assigns.

     8.11 SEVERABILITY.  If any term or other provision of this Agreement is
determined by a court, administrative agency or arbitrator to be invalid,
illegal or incapable of being enforced by any rule or law or public policy, all
other conditions and provisions of this Agreement shall nevertheless remain in
full force and effect so long as the economic or legal substance of the
transactions contemplated hereby is not affected in any manner materially
adverse to either party.  Upon such determination that any term or other
provision is invalid, illegal or incapable of being enforced, the parties hereto
shall negotiate in good faith to modify this Agreement so as to effect the
original intent of the parties as closely as possible in an acceptable manner to
the end that the transactions contemplated hereby are fulfilled to the fullest
extent possible.

     8.12 FAILURE OR INDULGENCE NOT WAIVER; REMEDIES CUMULATIVE.  No failure or
delay on the part of either party hereto in the exercise of any right hereunder
shall impair such right or be construed to be a waiver of, or acquiescence in,
any breach of any representation, warranty or agreement herein, nor shall any
single or partial exercise of any such right preclude other or further exercise
thereof or of any other right.  All rights and remedies existing under this
Agreement are cumulative to, and not exclusive of, any rights or remedies
otherwise available.

     8.13 AMENDMENT. No change or amendment will be made to this Agreement
except by an instrument in writing signed on behalf of each of the parties to
such Agreement.

     8.14 COUNTERPARTS. This Agreement, including the Ancillary Agreements and
the Exhibits and Schedules hereto and thereto and the other documents referred
to herein or therein, may be executed in counterparts, each of which shall be
deemed to be an original but all of which shall constitute one and the same
agreement.

                                       12
<PAGE>

     8.15 AUTHORITY.  Each of the parties hereto represents to the other that
(a) it has the corporate or other requisite power and authority to execute,
deliver and perform this Agreement, (b) the execution, delivery and performance
of this Agreement by it have been duly authorized by all necessary corporate or
other actions, (c) it has duly and validly executed and delivered this
Agreement, and (d) this Agreement is a legal, valid and binding obligation,
enforceable against it in accordance with its terms subject to applicable
bankruptcy, insolvency, reorganization, moratorium or other similar laws
affecting creditors' rights generally and general equity principles.


  WHEREFORE, the parties have signed this Master Patent License Agreement
effective as of the date first set forth above.

Mykrolis Corporation                      Millipore Corporation


By: /s/ Jean-Marc Pandraud                By: /s/ Francis J. Lunger
    --------------------------                -------------------------

Name: Jean-Marc Pandraud                  Name: Francis J. Lunger
      ------------------------                  -----------------------

Title: President, Mykrolis Corporation    Title: Executive Vice President,
       -------------------------------           -------------------------
                                                 Millipore Corporation
                                                 ---------------------

                                       13
<PAGE>

                                   EXHIBIT A
                 TO MASTER PATENT GRANTBACK LICENSE AGREEMENT

                                      14
<PAGE>

            ASSIGN TO MICROELECTRONICS - LICENSE BACK TO MILLIPORE
            ------------------------------------------------------

<TABLE>
<CAPTION>
-------------------------------------------------------------------------------------------------------------------------
Wednesday, March 28, 2001                                Patent List                                            Page: 1
-------------------------------------------------------------------------------------------------------------------------
Case Number/Subcase           Case      Application         Publication         Patent              Status
Country Name                  Type      Number/Date         Number/Date         Number/Date         Expiration Date
-------------------------------------------------------------------------------------------------------------------------
<S>                           <C>       <C>                 <C>                 <C>                 <C>
MCA-131/                      ORD       60-504408           07-017782           2128513             Granted
Japan                                   08-Oct-1985         01-Mar-1995         25-Apr-1997         08-Oct-2005
                                             Title: Microporous Membranes of Ultrahigh Molecular Weight Polyethylene

-------------------------------------------------------------------------------------------------------------------------
MCA-131/2                     PCT       06-041793           7-48471             2727296             Published
Japan                                   08-Oct-1985         11-Mar-1998                             08-Oct-2005
                                             Title: Microporous Membranes of Ultrahigh Molecular Weight Polyethylene

-------------------------------------------------------------------------------------------------------------------------
MCA-131/                      ORD       US85/01936                              WO8602282           Granted
Patent Cooperation Treaty               08-Oct-1985                             24-Apr-1986
                                             Title: Microporous Membranes of Ultrahigh Molecular Weight Polyethylene

-------------------------------------------------------------------------------------------------------------------------
MCA-131/                      ORD       658600                                  4778601             ISSUED
United States of America                09-Oct-1984                             18-Oct-1988         18-Oct-2005
                                             Title: Microporous Membranes of Ultrahigh Molecular Weight Polyethylene

-------------------------------------------------------------------------------------------------------------------------
MCA-131/1                     DIV       192595                                  4828772             ISSUED
United States of America                09-May-1988                             09-May-1989         09-May-2006
                                             Title: Microporous Membranes of Ultrahigh Molecular Weight Polyethylene

-------------------------------------------------------------------------------------------------------------------------
MCA-262/                      PCT       2188649                                                     Pending
Canada                                  25-Apr-1997
                                             Title: Compositions and Processes for Separating and Concentrating Certain
                                                    Ions from Mixed Ion Solutions Using Ion-Binding Ligands Bonded to
                                                    Membranes
-------------------------------------------------------------------------------------------------------------------------
MCA-262/                      PCT       95193666.2                                                  Pending
China                                   25-Apr-1997
                                             Title: Compositions and Processes for Separating and Concentrating Certain
                                                    Ions from Mixed Ion Solutions Using Ion-Binding Ligands Bonded to
                                                    Membranes
-------------------------------------------------------------------------------------------------------------------------
MCA-262/                      PCT       PV 3097-96                                                  Pending
Czech Republic                          25-Apr-1995
                                             Title: Compositions and Processes for Separating and Concentrating Certain
                                                    Ions from Mixed Ion Solutions Using Ion-Binding Ligands Bonded to
                                                    Membranes
-------------------------------------------------------------------------------------------------------------------------
MCA-262/                      PCT       95916458.3                                                  Pending
European Patent Convention              25-Apr-1995
                                             Title: Compositions and Processes for Separating and Concentrating Certain
                                                    Ions from Mixed Ion Solutions Using Ion-Binding Ligands Bonded to
                                                    Membranes
-------------------------------------------------------------------------------------------------------------------------
</TABLE>
<PAGE>

<TABLE>
<CAPTION>
---------------------------------------------------------------------------------------------------------------------------------
Wednesday, March 28, 2001                                Patent List                                            Page: 2
---------------------------------------------------------------------------------------------------------------------------------
Case Number/Subcase           Case      Application         Publication         Patent              Status
Country Name                  Type      Number/Date         Number/Date         Number/Date         Expiration Date
---------------------------------------------------------------------------------------------------------------------------------
<S>                           <C>       <C>                 <C>                 <C>                 <C>
MCA-262/                      PCT       7-527746                                3100638             Granted
Japan                                   25-Apr-1995                             18-Aug-2000         25-Apr-2015
                                                     Title: Compositions and Processes for Separating and Concentrating Certain
                                                            Ions from Mixed Ion Solutions Using Ion-Binding Ligands Bonded to
                                                            Membranes
---------------------------------------------------------------------------------------------------------------------------------
MCA-262/                      PCT       706003/1996                                                 Pending
Korea, Republic of                      25-Apr-1995
                                                     Title: Compositions and Processes for Separating and Concentrating Certain
                                                            Ions from Mixed Ion Solutions Using Ion-Binding Ligands Bonded to
                                                            Membranes
---------------------------------------------------------------------------------------------------------------------------------
MCA-262/                      PCT       284360                                                      Pending
New Zealand                             25-Apr-1995
                                                     Title: Compositions and Processes for Separating and Concentrating Certain
                                                            Ions from Mixed Ion Solutions Using Ion-Binding Ligands Bonded to
                                                            Membranes
---------------------------------------------------------------------------------------------------------------------------------
MCA-262/                      ORD       US95/04833                                                  Pending
Patent Cooperation Treaty               25-Apr-1995
                                                     Title: Compositions and Processes for Separating and Concentrating Certain
                                                            Ions from Mixed Ion Solutions Using Ion-Binding Ligands Bonded to
                                                            Membranes
---------------------------------------------------------------------------------------------------------------------------------
MCA-262/                      PCT       9611821-1                                                   Pending
Singapore                               25-Apr-1995
                                                     Title: Compositions and Processes for Separating and Concentrating Certain
                                                            Ions from Mixed Ion Solutions Using Ion-Binding Ligands Bonded to
                                                            Membranes
---------------------------------------------------------------------------------------------------------------------------------
MCA-262/                      ORD       08/233640                               5547760             ISSUED
United States of America                26-Apr-1994                             20-Aug-1996          26-Apr-2014
                                                     Title: Compositions and Processes for Separating and Concentrating Certain
                                                            Ions from Mixed Ion Solutions Using Ion-Binding Ligands Bonded to
                                                            Membranes
---------------------------------------------------------------------------------------------------------------------------------
MCA-262/1                     DIV       08/685432                               5618433             Granted
United States of America                23-Jul-1996                             08-Apr-1997
                                                     Title: Compositions and Processes for Separating and Concentrating Certain
                                                            Ions from Mixed Ion Solutions Using Ion-Binding Ligands Bonded to
                                                            Membranes
---------------------------------------------------------------------------------------------------------------------------------
MCA-262/2                     DIV       08/745026                               5980987             Granted
United States of America                07-Nov-1996                             09-Nov-1999
                                                     Title: Compositions and Processes for Separating and Concentrating Certain
                                                            Ions from Mixed Ion Solutions Using Ion-Binding Ligands Bonded to
                                                            Membranes
---------------------------------------------------------------------------------------------------------------------------------
</TABLE>
<PAGE>

<TABLE>
<CAPTION>
---------------------------------------------------------------------------------------------------------------------------------
Wednesday, March 28, 2001                                Patent List                                            Page: 3
---------------------------------------------------------------------------------------------------------------------------------
Case Number/Subcase           Case      Application         Publication         Patent              Status
Country Name                  Type      Number/Date         Number/Date         Number/Date         Expiration Date
---------------------------------------------------------------------------------------------------------------------------------
<S>                           <C>       <C>                 <C>                 <C>                 <C>
MCA-262/3                     DIV       09/337837                                                   Pending
United States of America                22-Jun-1999
                                             Title: Compositions and Processes for Separating and Concentrating Certain
                                                    Ions from Mixed Ion Solutions Using Ion-Binding Ligands Bonded to
                                                    Membranes
---------------------------------------------------------------------------------------------------------------------------------
MCA-472/                      ORD                                                                   Pending
Patent Cooperation Treaty               28-Feb-2001
                                             Title: Disposable Fluid Separation Device and Manifold Assembly Design With
                                                    Easy Change-Out Feature

---------------------------------------------------------------------------------------------------------------------------------
MCA-472/                      ORD                                                                   Pending
Taiwan, Province of China               28-Feb-2001
                                             Title: Disposable Fluid Separation Device and Manifold Assembly Design With
                                                    Easy Change-Out Feature

---------------------------------------------------------------------------------------------------------------------------------
MCA-472/                      ORD       09/796038                                                   Pending
United States of America                28-Feb-2001
                                             Title: Disposable Fluid Separation Device and Manifold Assembly Design With
                                                    Easy Change-Out Feature

---------------------------------------------------------------------------------------------------------------------------------
MCA-489/                      ORD       US01/01293                                                  Pending
Patent Cooperation Treaty               12-Jan-2001
                                             Title: System and Method for Liquid Filtration Based on a Neutral Filter Material

---------------------------------------------------------------------------------------------------------------------------------
MCA-489/                      ORD       90100845                                                    Pending
Taiwan, Province of China               15-Jan-2001
                                             Title: System and Method for Liquid Filtration Based on a Neutral Filter Material

---------------------------------------------------------------------------------------------------------------------------------
MCA-489/                      ORD       09/759920                                                   Pending
United States of America                12-Jan-2001
                                             Title: System and Method for Liquid Filtration Based on a Neutral Filter Material

---------------------------------------------------------------------------------------------------------------------------------
</TABLE>