Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Compositions to be polymerized by wave energy wherein said...
Reexamination Certificate
1999-08-30
2001-03-20
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Compositions to be polymerized by wave energy wherein said...
C522S148000, C522S110000, C522S109000, C522S129000, C525S477000, C252S06230Q, C252S06230R, C204S157150, C204S157600, C204S157640, C204S157450, C204S157750, C430S160000
Reexamination Certificate
active
06204305
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to diffusion barriers on polymeric articles, and to methods of preparing the diffusion barriers. According to the invention disclosed herein, a polymer blend alloy is prepared containing a high surface energy component and a low surface energy component. The article is then subjected to an ozone containing atmosphere in the presence of ultra violet radiation to form the diffusion barrier. The diffusion barrier is formed by the partial oxidation of the low surface energy component that has diffused to the surface. Exemplary low surface energy components are polysilanes, e.g., having —Si—Si-repeating units, exemplified by [—Si(CH
3
)
2
—] and the like, and polysiloxanes, e.g., having —Si—O-repeating units, exemplified by [—Si(CH
3
)
2
O—] and the like.
BACKGROUND OF THE INVENTION
For polymer blends, that is, physical mixtures of two or more polymers or copolymers that are not linked by covalent bonds, and that contain one or more components having lower surface energy than the bulk polymer, polymers, or copolymers, segregation of the low surface energy components to the surface can occur. This results in a hydrophobic surface and inhibits the ability to transfer materials (e.g., inks, paints, dyes) to the surface of an article comprising the blend. This segregation also may result in poor interfacial adhesion between applied layers, films, coatings, adhesives, and the like, and underlying articles comprising the blend.
In other cases, for a homogeneous polymer system, inward diffusion of moisture or other chemicals/materials into the bulk may be a problem. This can result in degradation of the properties of the article.
Thus, there exists a need for surface modification of articles fabricated of polymer blends or alloys to prevent segregation and hydrophobicity, and to enhance the wettability and bondability of the surface.
SUMMARY OF THE INVENTION
For polymer blends, the chemical transformation of the segregated material into a diffusion barrier has been achieved according to our invention. This transformation retards further segregation of the low surface energy component(s) to the surface.
In addition, the modified surface can act as a barrier to inward diffusion of moisture or other undesirable materials.
For a single polymer system, doping of the polymer with a component or components having lower surface energy than the bulk, followed by oxidation with ozone in the presence of ultra violet (uv) radiation will result in a diffusion barrier and a more stable surface with respect to reactions with the environment.
The polymeric body is treated with reactive oxygen (ozone) and UV radiation. The apparatus for this technique is quite modest, usually consisting of a UV source, e.g., a low-pressure mercury vapor lamp, and a chamber to house the UV source and the material being treated. The ozone is the photolysis product of oxygen in the presence of a source, as a mercury vapor light source, emitting 184.9 nanometer radiation. Treatment is almost always performed in air at atmospheric pressure to get ozone.
The method of this invention is particularly useful with organosilicon/organic polymer blends. By organosilicons are meant polysilanes and polysiloxanes, where polysilanes are polymers having —Si—Si-repeating units, exemplified by [—Si(CH
3
)
2
—] and the like, and polysiloxanes are polymers having —Si—O-repeating units, exemplified by [—Si(CH
3
)
2
O—] and the like. In these systems conversion of organosilicon materials to silicon oxides is a phenomenon that is well documented for exposure to oxygen plasma environments. Oxygen reactive ion etching of silicon-containing polymers results in an initial thickness loss and a gradual slowing of polymer erosion until etching ceases. During etching, it is believed that mobile silicon-containing monomer or polymer diffuses to the polymer surface where it is converted to SiO
2
or a suboxide thereof, and functions as an increasingly effective etching barrier.
According to our invention, UV/ozone treatment of organic polymers having organosilicon additives results in formation of a thin, protective barrier that inhibits diffusion of bulk material to the surface, inhibits diffusion of material from the environment into the bulk, and inhibits environmental contamination of the surface.
This is achieved by doping the bulk polymer or a surface portion thereof with a suitable organosilicon polymer or monomer additive at an appropriate concentration. The doped blend is then subjected to exposure in a UV/ozone environment such that a thin, stable, protective barrier is formed at the surface.
The method of this invention, and the resulting products are particularly useful, for example,
(1) to enhance printability and adhesion of inks to organosilicon containing polymers, for example, encapsulated products with organosilicon-containing encapsulants (e.g., Dexter Hysol 4450);
(2) to enhance the moisture and chemical resistance of polymers, such as encapsulants, in general, by doping with a suitable additive and treating in UV/ozone;
(3) to enhance the moisture and chemical resistance of other polymers used for a variety of applications requiring diffusion barriers and/or stable surface properties.
A further advantage is that unlike barriers produced by deposition processes, the method of the invention is self-patterning, i.e., the material that constitutes the protective barrier is formed only on the organosilicon-bearing material, not deposited on other areas of the substrate. Also, since the barrier formed by this method is, by the nature of the technique, incorporated as part of the organosilicon-bearing material, not as a separate, deposited layer, adhesion of the barrier to the bulk is high. In addition, the barrier, which is silicon dioxide or a suboxide thereof, is optically transparent (in the visible, and into the 185 nanometer ultraviolet and 1140 nanometer infrared bands) and hydrophilic. The method of the invention is also less expensive than conventional means of producing barrier films.
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Polymer Handbook, 4th ed, 1999., pp. VI 526, 531, and 540.*
Silane Coupling Agentsby Edwin Plueddemann, Published by Plenum Press 1982, p. 96.
Polymer Handbookedited by J. Brandrup/E.H. Immergut, Published by Interscience Pub. 1966, pp. III-113,114.
Egitto Frank Daniel
Matienzo Luis Jesus
Morrison, Jr. Bruce Otho
Fraley Lawrence R.
International Business Machines - Corporation
McClendon Sanza L.
Schmeiser Olsen & Watts
Seidleck James J.
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