Coating processes – Flame contact
Reexamination Certificate
2001-02-12
2004-03-16
Barr, Michael (Department: 1762)
Coating processes
Flame contact
C427S248100, C427S255230, C427S255260, C427S255270, C427S255280, C427S255600, C427S399000, C427S400000
Reexamination Certificate
active
06706320
ABSTRACT:
The present invention relates to a method and apparatus for modifying the surface of substrates comprising polymeric material.
BACKGROUND OF THE INVENTION
The surface properties of materials dictate the way in which they interact with their surroundings. This is particularly the case for surfaces containing solid organic polymers whose surface properties dictate to a large extent their useful applications. Some of the significant properties influenced by the structure and chemical properties of the surface include the quality of adhesion of adhesives, surface coatings, inks and other specialty or commodity materials, wettability, friction, permeability, gloss, corrosion, electrostatic and electroconductive properties and biocompatibility. Substrates exhibiting inert or insufficiently reactive surfaces such as polyolefins are particularly resistant to surface modification. Other types of polymeric materials containing more reactive functional groups often require additional surface modification in certain applications or to obtain optimum results.
There is a need for a processes and apparatus which will allow the surface properties of polymers to be tailored for a range of applications or applications or where special properties are required. The problem of inappropriate surface properties can in some instances be overcome by using a different material for construction of the substrate. In many instances, however materials that provide the desired bulk properties do not exhibit the required surface reactivity.
A number of processes have been developed for surface modification. Examples of surface modification techniques include:
(i) surface oxidation by methods such as electrical discharge, flame treatment, plasma, ozone, UV radiation, oxidizing or halogenating gases or liquids and excimer lasers;
(ii) surface functionalisation by: plasma treatment with reactive gases and/or reactive monomers and polymers; and
(iii) surface grafting, for instance by: (a) surface activation eg by the means of oxidation and/or other processes or means such as halogenation, and the deposition of specific graft chemicals, or by: (b) UV grafting and/or (c) other means known to those skilled in the art of surface modification.
Examples of such processes as listed in (i) to (iii) above are described in detail in our earlier inventions including U.S. Pat. Nos. 5,879,757; 5,922,161; 5,892,190, International Patent Applications: PCT/AU 00/01272 and another one based on Australian Provisional Patent Application PQ 5449, and Australian Patent Applications: PQ 8097, PN 3698 and PN our recently filed Australian provisional patent/application entitled “Composition and method for providing an electroconductive surface to a polymeric substrate”), the contents of which are incorporated by reference.
The present invention relates to a method and an apparatus for modifying the surface structure of a substrate by surface activation means and the deposition of specific surface modifying agents. The surface modifying agent may be of the type referred to in our previous applications and may include monomers, polymers and/or other macromolecules.
SUMMARY OF THE INVENTION
The invention provides a process for modifying the surface of a substrate containing a polymeric material by contacting the surface with the modifying agent to bond the modifying agent to the surface the process comprising providing a surface modifying agent composition comprising the surface modifying agent and optionally a carrier therefore and subjecting the surface modifying agent composition to a zone of elevated temperature to vaporize the surface modifying agent composition to provide diffuse contact between the modifying agent and the surface of the substrate.
The surface modifying agent composition may comprise undiluted surface modifying agent however it is preferred that the surface modifying agent composition further comprise a carrier such as a solvent for the surface modifying agent.
In accordance with a preferred aspect we provide a process for modifying the surface of a substrate containing a polymeric material by contacting the surface with the modifying agent to bond the modifying agent to the surface, the process comprising providing a solution of the surface modifying agent in a solvent and subjecting the solution of the modifying agent to a zone of elevated temperature to vaporize the solution of the surface modifying agent and provide diffuse contact between the modifying agent and the surface of the substrate.
We have found that the process of the invention has the significant advantage over conventional processes in that it provides bonded functional groups at the surface which significantly improve the quality of desired interaction of the surface with other materials with which it is to interact. The process provides diffuse contact between the surface modifying agent and substrate allowing precise and consistent application over an area of surface and establishes a strong bond with the surface. Without wishing to be bound by theory we believe the process produces an approximately monolayer of surface modifying agent reducing the incidence of weak boundary layers that may comprise excessive amount of adsorbed, instead of just chemically bound surface modifying agent which in turn can adversely interfere with the quality of attachment of other materials such as paints, inks, bioactive materials and others to the surface of the substrate modified by processes other than that of the current invention.
The composition of the modifying agent may be heated to a temperature above the boiling point of the composition. This may be above the boiling point of the solvent where present and/or above the boiling point of the modifying agent. The heating may occur prior to contacting the modifying agent with the surface of the substrate. Alternatively the of the modifying agent composition or may be heated to a temperature above the boiling point of the solvent and/or that of the modifying agent on or adjacent to the surface of the substrate. In some cases, for example where the substrate is sensitive to heat such as thin plastics firms the zone of elevated temperature may be at a suitable distance from the substrate.
The heating zone typically provides a temperature of at least 60° C. and less than 3000°. The heating zone will preferably provide a temperature of at least 120° C. and more preferably in the range of from 120 to 2300°. The optimal maximum will depend on the nature of the surface modifying agent and its decomposition temperature as well as the type of the carrier solvent used for diluting the modifying agent. If the solution of the modifying agent or an undiluted modifying agent is heated on the surface of the substrate then the effect of temperature on the substrate will also need to be considered.
The heating zone may be provided by a range of means including direct heating using a suitable heat exchanger or flame or other combustion method such as a standard combustion provided by a standard or modified flame treater comprising a standard flame burner or its multiplicity, or pulsed combustion burner or pulsed plasma torch, or by indirect heating means such as microwave or gliging arc otherwise known as corona jet, or laser treatment. The heating zone may be provided by a burner which can be of any known type and geometry such as but not limited to linear, curvilinear or cylindrical with the flame delivered through a singular or a plurality of continuous or individual flame zones of any shape and dimensions. Most preferably the heating zone is selected from the group consisting of a standard flame treatment zone and/or a pulse combustion burner or chamber and the associated flame treatment zone.
In a particularly preferred embodiment the invention provides a process for modifying the surface of a substrate wherein the modifying agent is applied to a heating zone adjacent to the surface of the substrate to produce vapor atmosphere in contact with the surface of the substrate. A flame or other suitable means may produce the he
Filippou Con
Gutowski Wojciech S
Proctor David
Spicer Mark
Barr Michael
Commonwealth Scientific and Industrial Research Organisation
Pillsbury & Winthrop LLP
Tsoy Elena
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