Coating processes – Direct application of electrical – magnetic – wave – or... – Pretreatment of substrate or post-treatment of coated substrate
Reexamination Certificate
1998-12-02
2001-02-20
Padgett, Marianne (Department: 1762)
Coating processes
Direct application of electrical, magnetic, wave, or...
Pretreatment of substrate or post-treatment of coated substrate
C427S491000, C427S539000, C427S540000, C427S492000
Reexamination Certificate
active
06190741
ABSTRACT:
CROSS REFERENCES TO RELATED APPLICATIONS
Not Applicable
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process and apparatus for treating a polymer coated paperboard material. Specifically, the present invention relates to a process and an apparatus for double corona treating a polymer coated paperboard material.
2. Description of the Related Art
The fabrication of a paperboard material for certain packaging usually undergoes a process on a laminator where a polyethylene is extruded onto both surfaces of the paperboard material. While on the laminator, one or both surfaces of the paperboard material are subjected to a corona treatment. On certain grades of polymer-coated paperboard material, usually those with a reflective average (hereinafter “RA”) of less that five which is mirror-like, it is very difficult to achieve an acceptable Dyne level from the corona treatment of the polymer-coated paperboard material. The smooth finish of the mirror pocket leaves the polyethylene very smooth making it difficult to print on the material at commercially acceptable levels. For comparison, a milk carton has a RA of 38 on the outside of the carton and 58 on the inside of the carton which are both relatively dull in comparison to a material having a RA of less than 5.
When processing a material with a RA of less than 5 on a laminator at a standard material speed of three hundred five meters per minute, a Dyne level of only thirty-eight Dyne per centimeter will be achieved on a conventional laminator. A Dyne level of at least forty-one Dyne per centimeter is required for printing at a commercially acceptable operating speed. In order to achieve such a Dyne level, the laminator would have to have its material speed reduced to less than one hundred eighty meters per minute, resulting in unacceptable (from a commercial perspective) laminator operating speeds. The Dyne level is a measurement of the surface tension of a material which is a mechanical force acting in the surface of the material.
Also, if the corona discharge has too great of power, the result will be pinholing in the material. Thus, there remains a need for producing a polymer-coated paperboard material with a Dyne level of at least 41 in a commercially viable manner.
BRIEF SUMMARY OF THE INVENTION
It is a primary object of the present invention to provide a method and apparatus for double corona treating a polymer-coated paperboard material.
It is an additional object of the present invention to provide a method and apparatus for producing a polymer-coated paperboard material with a predetermined Dyne level.
It is an additional object of the present invention to provide a method and apparatus for producing a polymer-coated paperboard material with a mirror-pocket finish of less than five RA, with a predetermined Dyne level.
It is an additional object of the present invention to provide a method and apparatus that increases production speed by as much as sixty-nine percent for producing a polymer-coated paperboard material with a mirror-pocket finish of less than five RA, with a Dyne level between 42-44.
One aspect of the present invention is a method for producing a polymer coated paperboard material with a predetermined Dyne level. The first step of the method is processing a paperboard material through a laminator at a predetermined speed. The method also includes extruding a first polymer layer onto a first surface of the paperboard material. The method also includes treating a surface of the first polymer layer of the paperboard material with a first corona treatment and treating the surface of the first polymer layer of the paperboard material with a second corona treatment subsequent to the first corona treatment. The first corona treatment and the second corona treatment impart a predetermined Dyne level to the surface of the first polymer layer. The predetermined Dyne level at least forty-one Dyne per centimeter.
Another aspect of the present invention is an apparatus for producing a polymer coated paperboard material with a predetermined Dyne level. The paperboard material is moved along a material pathway on the apparatus. The apparatus includes a gloss chill roll, a first extruder, a first corona treatment device, a second corona treatment device, a second extruder and a reel drum. The first extruder extrudes a first polymer layer onto the first surface of the paperboard material. The gloss chill roll imparts a predetermined level of gloss onto the first polymer layer of the paperboard material. The first corona treatment device is disposed subsequent to the first extruder along the material pathway and has a roller for exposing a surface of the first polymer layer of the paperboard material to a first corona treatment. The second extruder extrudes a second polymer layer onto a second surface of the paperboard material. The second extruder is disposed subsequent to the first extruder along the material pathway. The second corona treatment device is disposed subsequent to the first corona treatment device along the material pathway and has a roller for exposing the surface of the first polymer layer of the paperboard material to a second corona treatment. The reel drum is disposed at the end of the material pathway. The reel drum has a drive mechanism for rotating the reel drum at a predetermined speed and thereby moving the paperboard material at the predetermined speed. The first corona treatment and the second corona treatment impart a predetermined Dyne level to the surface of the first polymer layer of the paperboard material. The predetermined Dyne level is at least forty-one Dyne per centimeter. A preferred speed is at least three hundred meters per minute.
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Richard Lewis, Sr., Ed.,Hawley's Condensed Chemical Dictionary, Twelfth Edition; Van Nostrand Reinhold Co., N.Y., Excerpt p. 933, 1993 (no month).
Padgett Marianne
Tetra Laval Holdings & Finance SA
Welsh & Katz Ltd.
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