Filed by Mykrolis Corporation

Pursuant to Rule 425 Under the Securities Act of 1933

And Deemed Filed Pursuant to Rule 14a-12

Under the Securities Exchange Act of 1934

Subject Company: Mykrolis Corporation

Commission File No. 001-16611

This filing relates to the proposed merger of equals transaction pursuant to the terms of that certain Agreement and Plan of Merger, dated as of March 21, 2005 (the “Merger Agreement”), by and among Entegris, Inc., a Minnesota corporation (“Entegris”), Mykrolis Corporation, a Delaware corporation (“Mykrolis”), and Eagle DE, Inc., a Delaware corporation and a wholly-owned subsidiary of Entegris (“Entegris Delaware”). The Merger Agreement is on file with the Securities and Exchange Commission (the “SEC”) as an exhibit to the Current Report on Form 8-K filed by each of Entegris and Mykrolis on March 21, 2005, and is incorporated by reference into this filing.

The following is a press release issued by Entegris relating to the adoption of a Share Rights Plan by Entegris Delaware in connection with the Merger Agreement.

ENTEGRIS SUBSIDIARY ADOPTS SHARE RIGHTS PLAN

CHASKA/MINNEAPOLIS, Minn., July 26, 2005 – Entegris, Inc., (Nasdaq: ENTG) announced today that, in accordance with the terms of its Merger Agreement with Mykrolis Corporation and as contemplated by the joint proxy statement of the companies regarding the merger, the Board of Directors of its wholly-owned subsidiary, Eagle DE, Inc. (“Entegris Delaware”), has adopted a share rights plan. The rights under the plan will not be issued until after the effective time of the merger.

Share Rights Plan

Under the share rights plan, the Board of Directors of Entegris Delaware has declared, subject to the merger becoming effective, a dividend of one preferred share purchase right on each share of common stock of Entegris Delaware that will be outstanding on August 8, 2005 to shareholders of record at the close of business on that date. The rights will expire on August 8, 2015. Each right will entitle shareholders of Entegris Delaware, the surviving corporation in the merger (which will be renamed Entegris, Inc.), to buy one-hundredth of a share of a series of preferred stock at an exercise price of $50, subject to adjustment. The rights will generally become exercisable only after a person or group acquires beneficial ownership of 15 percent or more of the common stock or announces a tender or exchange offer that would result in that person or group beneficially owning 15 percent or more of the common stock, subject to possible extension. If any person or group becomes an owner of 15 percent or more of the common stock, each right will entitle its holder – other than the 15 percent shareholder – to purchase, at the right’s then-current exercise price, shares of the corporation’s common stock having a value of twice the exercise price.

In addition, if the corporation is acquired in a merger or other business combination transaction or sells 50 percent or more of its assets or earnings power, each right will generally entitle its holder to purchase, at the right’s then-current exercise price, common shares of the acquiring company having a market value of twice the right’s exercise price.

In certain circumstances, the corporation may exchange the rights for shares of its common stock or delay or temporarily suspend exercisability of the rights. The corporation may redeem rights at $0.01 per right, subject to

adjustment, at any time before a person or group becomes the beneficial owner of at least 15 percent of the corporation’s common stock.

The rights dividend will be effective only if the merger is consummated. Following consummation of the merger, a letter will be sent out to shareholders of record on the record date outlining further details of the share rights plan.

ABOUT ENTEGRIS Entegris products and services protect and transport the critical materials enabling the world’s leading technologies. As a leading materials integrity management company, Entegris provides products and services used in key technology industries including the semiconductor, data storage, chemical processing, biopharmaceutical, medical device and fuel cell.

Entegris is ISO 9001 certified and has manufacturing or service facilities in the United States, France, Germany, Japan, Malaysia and Singapore. Its advanced research laboratories are located in Minnesota and Colorado, USA. Directly and through distributors, Entegris provides customer support on six continents. Additional information can be found at www.entegris.com.

Additional Information and Where to Find It

In connection with the proposed transaction, Entegris, Mykrolis and Eagle DE, Inc. (a newly formed corporation that will merge with Entegris to effect the reincorporation of Entegris in the State of Delaware in connection with the proposed transaction) will file a joint proxy statement/prospectus with the SEC. A registration statement on Form S-4 also will be filed with the SEC. Securityholders of each company and other investors are urged to read the registration statement and the joint proxy statement/prospectus (including any amendments or supplements to the joint proxy statement/prospectus) regarding the proposed transaction when they become available because they will contain important information about Entegris, Mykrolis and the proposed transaction. Stockholders will be able to obtain a free copy of the registration statement and the joint proxy statement/prospectus, as well as other filings containing information about Entegris and Mykrolis, without charge, at the SEC’s Internet site (http://www.sec.gov). Copies of the registration statement and the joint proxy statement/prospectus and the filings with the SEC that will be incorporated by reference in the joint proxy statement/prospectus can also be obtained, without charge, by directing a request to Entegris, 3500 Lyman Blvd, Chaska, MN 55318, Attention: Investor Relations Dept., telephone: (952) 556-8080, or at irelations@entegris.com or to Mykrolis, 129 Concord Road, Billerica, MA 01821, Attention: Investor Relations Dept., telephone (978) 436-6500, or at investor_relations@mykrolis.com. In addition, investors and security holders may access copies of the documents filed with the SEC by Entegris on Entegris’ website at www.entegris.com, and investors and security holders may access copies of the documents filed with the SEC by Mykrolis on Mykrolis’ website at www.mykrolis.com.

Participants in Solicitation

Mykrolis, Entegris and their respective directors and executive officers and other persons may be deemed to be participants in the solicitation of proxies in respect of the proposed transaction. Information regarding Mykrolis’ directors and executive officers is available in its proxy statement on Form DEF 14A filed with the SEC by Mykrolis on March 26, 2004 and in its Annual Report on Form 10-K filed with the SEC on March 11, 2005 (as amended by Form 10-K/A filed with the SEC on April 14, 2005) and information regarding Entegris’ directors and executive officers is available in its proxy statement on Form DEF 14A filed with the SEC by Entegris on December 15, 2004 and in its Annual Report on Form 10-K filed with the SEC on November 12, 2004. Other information regarding the participants in the proxy solicitation and a description of their direct and indirect interests, by security holdings or otherwise, will be contained the joint proxy statement/prospectus and other relevant materials to be filed with the SEC when they become available.

Forward-Looking Statements

Certain statements in this filing regarding Mykrolis Corporation, Entegris, Inc., the proposed transaction and the combined company after completion of the proposed transaction constitute “forward-looking statements” within the

meaning of the Private Securities Litigation Reform Act of 1995. Words such as “expect,” “feel,” “believe,” “may,” “anticipate,” “plan,” “estimate,” “intend,” “should,” and similar expressions are intended to identify forward-looking statements. These statements include, but are not limited to, financial projections and estimates and their underlying assumptions; statements regarding plans, objectives and expectations with respect to future operations, products and services; and statements regarding future performance. Such forward-looking statements involve known and unknown risks, uncertainties and other important factors that could cause the actual results, performance or achievements of Mykrolis, Entegris, and their respective subsidiaries or industry results, to differ materially from any future results, performance or achievements expressed or implied by such forward-looking statements. Such risks, uncertainties and other factors include, among others: the risks and factors described in the publicly filed documents of Mykrolis and Entegris, including their most recently filed Forms 10-K; general economic and business conditions and industry trends in the countries in which we operate; currency exchange risks; the continued strength of the industries in which we operate; uncertainties inherent in proposed business strategies and development plans; rapid technological changes; future financial performance, including availability, terms and deployment of capital; availability of qualified personnel; changes in, or the failure or the inability to comply with, government regulation in the countries in which we operate, and adverse outcomes from regulatory proceedings; changes in the nature of key strategic relationships with partners and joint venturers; competitor responses to the products and services of Mykrolis and Entegris, and the overall market acceptance of such products and services, including acceptance of the pricing of such products and services; the ability to achieve the cost savings and synergies contemplated by the proposed merger; the ability to promptly and effectively integrate the businesses of Mykrolis and Entegris; and the diversion of management time on merger-related issues. These forward-looking statements speak only as of the date of this filing. Mykrolis and Entegris expressly disclaim any obligation or undertaking to disseminate any updates or revisions to any forward-looking statement contained herein to reflect any change in the respective expectations of Mykrolis and Entegris with regard thereto or any change in events, conditions or circumstances on which any such statement is based. The transaction is subject to customary closing conditions, including regulatory, stockholder and other third-party consents and approvals.