Stock material or miscellaneous articles – Composite – Of silicon containing
Reexamination Certificate
2000-10-06
2002-06-04
Nakarani, D. S. (Department: 1773)
Stock material or miscellaneous articles
Composite
Of silicon containing
C428S451000
Reexamination Certificate
active
06399212
ABSTRACT:
DETAILED DESCRIPTION OF THE INVENTION
1. Technical Field of the Invention
The present invention relates to a silicon dioxide-coated polyolefin resin and a process for its production.
2. Prior Art
Polyolefin resins have a wide variety of uses arising from their excellent properties. For example, the polyolefin resin composed of a cyclopentene-based polymer described in Japanese Unexamined Patent Publication No. 168625 of 1994 has excellent electrical resistance and low water absorption, and therefore exhibits the feature of dimensional stability even under highly humid conditions. The polyolefin resin composed of a norbornene-based open-ring polymer described in Japanese Unexamined Patent Publication No. 152549 of 1998 has excellent optical properties, including transparency, water resistance and birefringence.
These polyolefin resins are widely used in optical parts, electronic parts, automobile parts and the like because of their excellent properties, but since they lack functional groups and therefore generally have low adhesion to other coatings or materials, it is difficult to form coating layers over their surfaces and this has hampered efforts to take full advantage of their excellent properties.
In particular, polyolefin resins offer considerable potential advantages for use in magnetic recording media and other electronic devices where their excellent properties such as low moisture absorption, heat resistance and chemical resistance are utilized, but formation of highly adhesive and durable coating layers could further increase their potential advantages as base materials for electronic devices and other devices having layers consisting of magnetic recording media additionally formed over the coating layers.
It is therefore an object of the present invention to establish a process for formation of an organic silicon-based coating with high adhesive property to polyolefin resins and high durability.
SUMMARY OF THE INVENTION
These objects of the invention can be achieved by the following construction.
Specifically, it is a process for production of a silicon dioxide-coated polyolefin resin wherein, after hydrophilic treatment of the surface of a polyolefin resin, it is coated with a primary coating composed of an organic silicon compound and the base is then contacted with a solution containing silicofluoric acid with silicon dioxide in a supersaturated state, to form a silicon dioxide coating on the primary coating.
The primary coating is preferably obtained by applying and subsequently drying a coating solution containing a silicon compound or its hydrolysate with an organic functional group represented by the following general formula (1)
R
1
n
Si(R
2
)
4−n
(1)
where R
1
is an organic functional group with a methacryloxy group,
R
2
is one or a plurality of hydrolyzable groups selected from among alkoxyl groups, acetoxyl groups and chlorine, and
n is an integer of up to 3.
The primary coating of the invention is even more preferably obtained by applying and subsequently drying a coating solution containing a plurality of different silicon compounds or their hydrolysates from among silicon compounds and their hydrolysates with an organic functional group represented by general formula (2)
R
3
n
Si(R
2
)
4−n
(2)
where R
3
is an organic functional group with a functional group selected from among methacryloxy, vinyl, allyl and amino groups,
R
2
is one or a plurality of hydrolyzable groups selected from among alkoxyl groups, acetoxyl groups and chlorine, and
n is an integer of up to 3.
When the primary coating of the invention is a primary coating obtained from a coating solution containing a plurality of silicon compounds of general formula (2), the properties such as adhesive property onto polyolefin resins is greater compared to using a primary coating obtained from a coating solution containing only a silicon compound of general formula (1).
The present invention also encompasses silicon dioxide-coated polyolefin resins obtained by the aforementioned production process.
[Function]
According to the invention, after hydrophilic treatment of a polyolefin resin, an organic silicon coating is formed and it is then immersed in a silicofluoric acid aqueous solution containing silicon dioxide in a supersaturated state, to form a silicon dioxide coating.
By laying an organic silicon film on the surface of a polyolefin resin by the method described above, it is possible to improve adhesive property between the polyolefin resin that has no functional groups, and silicon dioxide coatings. Here, providing an organic silicon film after hydrophilic treatment of the surface of the polyolefin resin to form a silicon dioxide coating can result in even more reliable improvement in adhesive property between the polyolefin resin and the silicon dioxide coating.
The polyolefin resin used as the base may be a polyalkene such as polyethylene or polypropylene, or a cycloolefin, including the cyclopentene-based open-ring polymer described in Japanese Unexamined Patent Publication No. 168625 of 1994 and the norbornene-based open-ring polymer described in Japanese Unexamined Patent Publication No. 152549 of 1998.
The hydrophilic treatment of the surface of the polyolefin resin base may be carried out by any method that allows hydrophilic treatment of resin base surfaces, and for example, corona discharge treatment, plasma treatment, UV ozone treatment, ozonized water washing and the like may be used for oxidation of the surface. Without this step it is not possible to form a satisfactory coating because of poor adhesive property, even though formation of a silicon dioxide coating is possible. UV ozone treatment, corona discharge treatment, plasma treatment by high frequency plasma discharge and other types of treatment or ozonized water washing can accomplish hydrophilic treatment without impairing the surface of the polyolefin resin. Such treatment methods also have the function of removing dirt and oil from the polyolefin resin surface, in addition to oxidation or activation of the surface. A concrete example of hydrophilic treatment will now be explained.
UV ozone treatment is carried out by irradiation for 1-20 minutes at 20 mW/cm
2
in an oxygen-containing atmosphere, with a distance of 20-50 mm between the polyolefin resin base and the UV lamp. The polyolefin resin base maybe rapidly subjected to hydrophilic treatment by heating at 30-100° C.
Corona discharge is accomplished by creating a corona discharge between the electrode and the base surface while maintaining a distance of 0.5-8 mm between the electrode and the polyolefin resin base and moving the base under the electrode at a speed of 1-100 mm/sec. The discharge is accomplished in air with application of a voltage of 10-30 kV at a cycle of 15 kHz.
Plasma treatment by high frequency plasma discharge is a method in which a glow discharge is created between the electrode and the base in a reduced pressure oxygen atmosphere, for hydrophilic treatment of the polyolefin resin surface.
Ozonized water washing is a method in which the base is immersed for a few minutes in water that has dissolved ozone having oxidizing property at about a few ppm, for hydrophilic treatment of the surface.
These types of treatment can accomplish hydrophilic treatment of the resin surface. Observation of the elemental composition of the surface by XPS reveals a larger amount of oxygen than before hydrophilic treatment, with the oxygen introduced only near the resin surface in the form of hydroxyl groups, carbonyl groups and carboxyl groups. These functional groups serve as bonding sites with the coating, allowing formation of a satisfactory coating. According to XPS, an elemental ratio of oxygen and carbon (O/C) of at least 0.08 allows formation of a coating with satisfactory adhesive property. The water droplet contact angle of the base surface after treatment has been confirmed to be no greater than about 60°. Incidentally, the water droplet contact angle of untreated polyolefin resin is around 90°.
The thic
Inomata Hiroyuki
Saito Yasuhiro
Sakai Yasuto
Dike Bronstein Roberts & Cushman
Nakarani D. S.
Nippon Sheet Glass Co. Ltd.
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