Search Patents
  • Birefringent interference polarizer
    Patent number: 5612820
    Abstract: A birefringent interference polarizer which may be fabricated from readily available materials using established coextrusion techniques is provided. The polarizer has a level of light absorption near zero and can be fabricated to polarize and reflect light of specific wavelengths while transmitting light of other wavelengths. The polarizer includes multiple alternating oriented layers of at least first and second polymeric materials having respective nonzero stress optical coefficients which are sufficiently different to produce a refractive index mismatch between the first and second polymeric materials in a first plane which is different from the refractive index mismatch between the first and second polymeric materials in a second plane normal to the first plane. The refractive index mismatch in the first plane is preferably at least 0.03.
    Type: Grant
    Filed: May 30, 1995
    Date of Patent: March 18, 1997
    Assignee: The Dow Chemical Company
    Inventors: Walter J. Schrenk, Victor S. Chang, John A. Wheatley
  • Visibly transparent infrared reflecting film with color masking
    Patent number: 5233465
    Abstract: A polymeric multilayered film which reflects wavelengths of light in the infrared region of the spectrum while being substantially transparent to wavelengths of light in the visible spectrum without the effects of visibly perceived iridescent color is provided. The polymeric multilayered infrared reflecting film comprises at least two diverse, substantially transparent polymeric materials, with the layers having an optical thickness of between 0.09 .mu.m and 0.45 .mu.m and the polymeric materials having a different index of refraction such that light is reflected in the infrared portion of the spectrum. A color masking film is associated with the polymeric film which reflects light substantially uniformly over the visible portion of the spectrum to eliminate perceived iridescent color.
    Type: Grant
    Filed: May 27, 1992
    Date of Patent: August 3, 1993
    Assignee: The Dow Chemical Company
    Inventors: John A. Wheatley, Walter J. Schrenk
  • Birefringent interference polarization
    Patent number: 6583930
    Abstract: A birefringent interference polarizer which may be fabricated from readily available materials using established coextrusion techniques is provided. The polarizer has a level of light absorption near zero and can be fabricated to polarize and reflect light of specific wavelengths while transmitting light of other wavelengths. The polarizer includes multiple alternating oriented layers of at least first and second polymeric materials having respective nonzero stress optical coefficients which are sufficiently different to produce a refractive index mismatch between the first and second polymeric materials in a first plane which is different from the refractive index mismatch between the first and second polymeric materials in a second plane normal to the first plane. The refractive index mismatch in the first plane is preferably at least 0.03.
    Type: Grant
    Filed: December 23, 1998
    Date of Patent: June 24, 2003
    Assignee: 3M Innovative Properties
    Inventors: Walter J. Schrenk, Victor S. Chang, John A. Wheatley
  • Multilayer film for tamper indication by use of optical interference reflection
    Patent number: 5149578
    Abstract: A multilayer film including contiguous layers of two or more diverse thermoplastic materials of differing refractive indices whereby the film retains a permanent color change as evidence of tampering or an attempt at tampering when the yield point of at least one of the diverse materials has been at least equalled by the strain associated with such tampering or with such an attempt at tampering, and where before such yield point is at least equalled the wavelength of an unsuppressed reflectance of normally incident light is not within the visible spectrum while after such yielded point is at least equalled the reflectance is retained in the visible spectrum.
    Type: Grant
    Filed: December 23, 1991
    Date of Patent: September 22, 1992
    Assignee: The Dow Chemical Company
    Inventors: John A. Wheatley, Walter J. Schrenk
  • Formable reflective multilayer body
    Patent number: 5448404
    Abstract: A formable multilayer reflective polymeric body which has a substantially uniform broad bandwidth reflectance over substantially the entire range of the visible spectrum to provide a substantially uniform reflective appearance is provided. The body includes at least first and second diverse polymeric materials, the body comprising a sufficient number of alternating layers of the first and second polymeric materials such that at least 40% of visible light incident on the body is reflected. A substantial majority of the individual layers of the body have optical thicknesses in the range where the sum of the optical thicknesses in a repeating unit of the polymeric materials is greater than about 190 nm, and the first and second polymeric materials differ from each other in refractive index by at least about 0.03.
    Type: Grant
    Filed: May 13, 1994
    Date of Patent: September 5, 1995
    Assignee: The Dow Chemical Company
    Inventors: Walter J. Schrenk, Charles B. Arends, Conrad F. Balazs, Ray A. Lewis, John A. Wheatley
  • Method for producing blow molded multilayer plastic articles
    Patent number: 5540878
    Abstract: A blow molded multilayer plastic article having a large number of layers is formed. First and second diverse thermoplastic streams are extruded into a coextrusion feedblock. In the feedblock the streams are divided into multiple streams and arranged into a first composite stream having a substantially uniform distribution of the layers. The first stream is fed into an interfacial surface generator in which the stream is manipulated to form a second composite stream having even more layers of substantially uniform thickness. This second stream is then formed into a preform such as by injection molding and this preform is blow molded. The second composite stream and preform are formed so that the layers of first and second materials lie generally parallel to a critical surface and possess substantial uniformity when blow molded.
    Type: Grant
    Filed: September 27, 1994
    Date of Patent: July 30, 1996
    Assignee: The Dow Chemical Company
    Inventors: Walter J. Schrenk, Ranganath K. Shastri, Herbert C. Roehrs, Ralph E. Ayres
  • Scrapless forming of plastic articles
    Patent number: 3947204
    Abstract: Apparatus for rapidly making thermoplastic containers wherein the resultant containers can, if desired, be multilayered for vapor or gas barrier or other reasons, or be oriented for toughness and improved stress crack resistance. The apparatus takes a measured amount of thermoplastic material which is lubricated, heated and forged into a desired shape preform with a predetermined lip configuration. The center portion of each said preform is maintained at a forming temperature while the peripheral portion thereof is clamped and rapidly brought below the softening point of the plastic resin. The preform can then be immediately thermoformed into a container having a desired shape and size, and cooled. If desired, the preform can be forged, cooled and recovered for a subsequent thermoforming operation or can be a finished article itself.
    Type: Grant
    Filed: January 14, 1974
    Date of Patent: March 30, 1976
    Assignee: The Dow Chemical Company
    Inventors: Ralph E. Ayres, Kenneth J. Cleereman, Walter J. Schrenk
  • Container for food products and method for making same
    Patent number: 3977153
    Abstract: A plastic container for food products and method of making the container, the body of the container thermoformed from a sheet comprising a plurality of layers which are held together in a contiguous structure without being securely bonded together, said layers of the container body functionally secured in place after filling by an interlocking closure. At least one layer provides structural rigidity and a good water vapor barrier and at least one other layer provides a barrier to the transmission of oxygen and a supplementary water vapor barrier. The container is capable of withstanding retort temperatures. Separation of the scrap sheet from which the container body is formed and recycle of separate layer scrap from the container body thermoforming process can be accomplished since the layers forming the container body are not securely bonded together.
    Type: Grant
    Filed: July 1, 1974
    Date of Patent: August 31, 1976
    Assignee: The Dow Chemical Company
    Inventor: Walter J. Schrenk
  • Birefringent interference polarizer
    Patent number: 5486949
    Abstract: A birefringent interference polarizer which may be fabricated from readily available materials using established coextrusion techniques is provided. The polarizer has a level of light absorption near zero and can be fabricated to polarize and reflect light of specific wavelengths while transmitting light of other wavelengths. The polarizer includes multiple alternating oriented layers of at least first and second polymeric materials having respective nonzero stress optical coefficients which are sufficiently different to produce a refractive index mismatch between the first and second polymeric materials in a first plane which is different from the refractive index mismatch between the first and second polymeric materials in a second plane normal to the first plane. The refractive index mismatch in the first plane is preferably at least 0.03.
    Type: Grant
    Filed: November 26, 1990
    Date of Patent: January 23, 1996
    Assignee: The Dow Chemical Company
    Inventors: Walter J. Schrenk, John A. Wheatley, Victor S. Chang
  • Birefringent interference polarizer
    Patent number: 5872653
    Abstract: A birefringent interference polarizer which may be fabricated from readily available materials using established coextrusion techniques is provided. The polarizer has a level of light absorption near zero and can be fabricated to polarize and reflect light of specific wavelengths while transmitting light of other wavelengths. The polarizer includes multiple alternating oriented layers of at least first and second polymeric materials having respective nonzero stress optical coefficients which are sufficiently different to produce a refractive index mismatch between the first and second polymeric materials in a first plane which is different from the refractive index mismatch between the first and second polymeric materials in a second plane normal to the first plane. The refractive index mismatch in the first plane is preferably at least 0.03.
    Type: Grant
    Filed: December 18, 1996
    Date of Patent: February 16, 1999
    Assignee: Minnesota Mining and Manufacturing Company
    Inventors: Walter J. Schrenk, John A. Wheatley, Victor S. Chang
  • Multilayer polymeric reflective bodies for decorative and security applications
    Patent number: 5234729
    Abstract: A multilayered reflective polymeric body of alternating layers of polymers wherein at least a portion of the layers are in a folded-over relationship is provided along with a coextrusion apparatus and method of preparing the multilayer polymeric body. The reflective polymeric body includes at least first and second diverse polymeric materials having a sufficient number of alternating layers of the first and second polymeric materials such that a portion of the light incident on the body is reflected. The first and second polymeric materials differ from each other in refractive index by at least about 0.03. The reflective body is thermoformable and may be fabricated into wall panels, dishware, decorative trims, and the like, and may also find use in security applications such as credit cards, credit card emblems, or on currency.
    Type: Grant
    Filed: February 27, 1992
    Date of Patent: August 10, 1993
    Assignee: The Dow Chemical Company
    Inventors: John A. Wheatley, Walter J. Schrenk, David M. Wisniewski
  • Scrapless forming of plastic articles
    Patent number: 4005967
    Abstract: Apparatus for rapidly making thermoplastic containers wherein the resultant containers can, if desired, be multilayered for vapor or gas barrier or other reasons, or be oriented for toughness and improved stress crack resistance. The apparatus takes a measured amount of thermoplastic material which is lubricated, heated and forged into a desired shape preform with a predetermined lip configuration. The center portion of each said preform is maintained at a forming temperature while the peripheral portion thereof is clamped and rapidly brought below the softening point of the plastic resin. The preform can then be immediately thermoformed into a container having a desired shape and size, and cooled. If desired, the preform can be forged, cooled and recovered for a subsequent thermoforming operation or can be a finished article itself.
    Type: Grant
    Filed: January 21, 1976
    Date of Patent: February 1, 1977
    Assignee: The Dow Chemical Company
    Inventors: Ralph E. Ayres, Kenneth J. Cleereman, Walter J. Schrenk
  • Formable reflective multilayer body
    Patent number: 5568316
    Abstract: A formable multilayer reflective polymeric body which has a substantially uniform broad bandwidth reflectance over substantially the entire range of the visible spectrum to provide a substantially uniform reflective appearance is provided. The body includes at least first and second diverse polymeric materials, the body comprising a sufficient number of alternating layers of the first and second polymeric materials such that at least 40% of visible light incident on the body is reflected. A substantial majority of the individual layers of the body have optical thicknesses in the range where the sum of the optical thicknesses in a repeating unit of the polymeric materials is greater than about 190 nm, and the first and second polymeric materials differ from each other in refractive index by at least about 0.03.
    Type: Grant
    Filed: April 13, 1995
    Date of Patent: October 22, 1996
    Assignee: The Dow Chemical Company
    Inventors: Walter J. Schrenk, Charles B. Arends, Conrad F. Balazs, Ray A. Lewis, John A. Wheatley
  • Coextrusion of multilayer articles using protective boundary layers and apparatus therefor
    Patent number: 5269995
    Abstract: A process and apparatus for the coextrusion of a multilayer polymeric body is provided which incorporates protective boundary layers into the body, protecting the layers from instability and breakup during layer formation and multiplication. The process includes the steps of providing at least first and second streams of heat plastified extrudable thermoplastic material which are combined to form a composite stream having the first substreams and second substreams interdigitated. A third stream of heat plastified thermoplastic material is supplied to the exterior surfaces of the composite stream to form protective boundary layers adjacent the walls of the coextrusion apparatus through which the heat plastified polymer streams pass. Layer instability and breakup are avoided using process conditions which would otherwise adversely affect the optical and/or mechanical properties of the articles which are formed.
    Type: Grant
    Filed: October 2, 1992
    Date of Patent: December 14, 1993
    Assignee: The Dow Chemical Company
    Inventors: Ravi Ramanathan, Walter J. Schrenk, John A. Wheatley
  • Optically dissimilar composition for polymeric reflective bodies
    Patent number: 5278694
    Abstract: A multilayered reflective body which is thermoformable and capable of being fabricated into films, sheets and a variety of parts while maintaining a uniform reflective appearance is provided. The reflective polymeric body includes at least first and second diverse polymeric materials of a sufficient number of alternating layers of the first and second polymeric materials such that at least 30% of the light incident on the body is reflected. A substantial majority of the individual layers of the body have an optical thickness of not more than 0.09 micrometers or not less than 0.45 micrometers, and adjacent layers of the first and second polymeric materials differ from each other in refractive index by at least about 0.1. The reflective body may be fabricated into sheets, mirrors, noncorroding metallic appearing articles and parts, reflectors, reflective lenses, and the like.
    Type: Grant
    Filed: May 17, 1991
    Date of Patent: January 11, 1994
    Assignee: The Dow Chemical Company
    Inventors: John A. Wheatley, Walter J. Schrenk, Stephen E. Bales, Mark A. Barger, Charles A. Langhoff, Ravi Ramanathan
  • Method of producing a lamellar polymeric body
    Patent number: 5316703
    Abstract: A method for the production of a lamellar reflective polymeric body is provided and includes the steps of providing a first stream of a first heat plastified polymeric material and a second stream of a second heat plastified polymeric material, and encapsulating discrete portions of the first polymeric material in the second polymeric material by coextruding the polymeric materials to form a plurality of ribbon-like layers of the first polymeric material within a matrix of the second polymeric material to form the reflective polymeric body. The layers of the first polymeric material are arranged to have their major interfaces aligned substantially parallel to the major surfaces of the body such that at least 30% of light incident on the body is reflected. The ribbon-like layers may be further divided into a series of platelet-like layers to produce layers which are discontinuous in all major planar dimensions by passing the ribbon-like layers through a reciprocating feed plate or valve.
    Type: Grant
    Filed: January 19, 1993
    Date of Patent: May 31, 1994
    Assignee: The Dow Chemical Company
    Inventor: Walter J. Schrenk
  • Polymeric reflective bodies with multiple layer types
    Patent number: 5126880
    Abstract: A multilayered, highly reflective polymeric body comprising at least two types of optical layers which is thermoformable and capable of being fabricated into films, sheets and a variety of parts while maintaining a uniform reflective appearance is provided. The reflective polymeric body includes at least first and second diverse polymeric materials having a sufficient number of layers of the first and second polymeric materials such that at least 30% of light incident on the body is reflected. A portion of the layers have optical thicknesses between 0.09 and 0.45 .mu.m, and the remaining layers have optical thicknesses of not greater than 0.09 .mu.m or not less than 0.45 .mu.m. The first and second polymeric materials differ from each other in refractive index by at least about 0.03.
    Type: Grant
    Filed: December 18, 1990
    Date of Patent: June 30, 1992
    Assignee: The Dow Chemical Company
    Inventors: John A. Wheatley, Walter J. Schrenk
  • Multicomponent, multilayer polymeric reflective bodies
    Patent number: 5262894
    Abstract: A multicomponent, multilayered, highly reflective polymeric body which is thermoformable and capable of being fabricated into films, sheets and a variety of parts while maintaining a uniform reflective appearance is provided. The reflective polymeric body includes at least first, second, and third diverse polymeric materials having a sufficient number of alternating layers of the polymeric materials such that a portion of the light incident on the body is reflected. A sufficient number of the individual layers of the body have optical thicknesses of not more than 0.09 micrometers or not less than 0.45 micrometers, such that there is an absence of visibly perceived color in the body. The polymeric materials having the highest and lowest refractive indices differ from each other in refractive index by at least about 0.03. The reflective body may be fabricated into mirrors, noncorroding metallic appearing articles and parts, reflectors, reflective lenses, and the like.
    Type: Grant
    Filed: February 10, 1992
    Date of Patent: November 16, 1993
    Assignee: The Dow Chemical Company
    Inventors: John A. Wheatley, Walter J. Schrenk
  • Biaxially oriented thermoplastic container with or without molded tip periphery
    Patent number: 3995763
    Abstract: A scrap free process for rapidly making thermoplastic containers wherein the resultant containers can, if desired, be multilayered for vapor or gas barrier or other reasons, or be oriented for toughness and improved stress crack resistance. The containers can be formed from multilayered or homogeneous plastic sheets wherein a relatively thin thermoplastic blank is provided. This blank is lubricated, heated and forged into a desired shape preform with a predetermined lip configuration. The center portion of each said preform is maintained at a forming temperature while the peripheral portion thereof is rapidly brought below the softening point of the plastic resin. The preform is then immediately thermoformed into a container having a desired shape and size, and cooled. If desired, the preform can be forged, cooled and recovered from a subsequent thermoforming operation.
    Type: Grant
    Filed: May 27, 1975
    Date of Patent: December 7, 1976
    Assignee: The Dow Chemical Company
    Inventors: Ralph E. Ayres, Kenneth J. Cleereman, Walter J. Schrenk
  • All-polymeric ultraviolet light reflecting film
    Patent number: 5540978
    Abstract: An all-polymeric ultraviolet light reflective film which is lower in cost than previously used reflector materials, is weather resistant, and which does not absorb significant amounts of solar ultraviolet energy is provided. The film includes a sufficient number of alternating layers of at least first and second diverse polymeric materials which have an average percent transmission of greater than about 50% between wavelengths of 300-400 nm. A substantial majority of the individual layers of the film have optical thicknesses in the range where the sum of the optical thicknesses in a repeating unit of the polymeric materials is between about 0.15 .mu.m to about 0.228 .mu.m, and the first and second polymeric materials differ from each other in refractive index by at least about 0.03 in the wavelength range of from about 300-400 nm.
    Type: Grant
    Filed: May 11, 1994
    Date of Patent: July 30, 1996
    Assignee: The Dow Chemical Compny
    Inventor: Walter J. Schrenk
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