Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Patent
1994-02-04
1996-03-12
Yoder, Michele K.
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
156205, 1562722, 1562755, 1563809, B31F 124, B32B 3126
Patent
active
054983045
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to an improved method of bonding liner boards to corrugated mediums in the manufacture of corrugated board for box manufacture.
BACKGROUND OF THE INVENTION
Conventionally, in applying liners to corrugated medium the first liner is applied at the single facer to form a single faced board and this is achieved by applying adhesive to the flute tips while the medium is contained on the corrugating roll and then applying the liner under pressure and heat. The combination of heat from the corrugating roll and pressure roll and mechanical pressure itself forms the first liner to medium bond. Subsequently, the single face board is passed to a double facer or double backer where adhesive is applied to flute tips and the board passed over a series of steam heated platens to bond the second liner. Pressure is also applied by a transport belt on top of the board and a series of small rollers riding on that belt. Travel of the double face board through the double facer or double backer is assisted by sandwich belts after the steam heated platens.
The size of the plant and the length of the production floor is quite long in conventional plant for producing corrugated board. The heating platens are of extensive length to ensure sufficient curing of the adhesive bond as the board passes over the platens at speeds of up to 300 to 400 meters per minute.
Another characteristic of conventional corrugated board is that of "pressure lines" which result from the pressure applied by the pressure roll at the single facer. This is compounded by "washboarding" which is the effect of the adhesive, when drying, drawing the liner out of its linearity. These effects make the board unsuitable for high quality printing on that side.
SUMMARY OF THE INVENTION
It is an object of this invention to improve the quality of corrugated board and decrease the size of the plant required to produce board at commercially acceptable speeds.
To this end the present invention provides a method of forming corrugated paperboard in which at least one liner is applied to the corrugated medium using low mechanical pressure and the adhesive bonding is achieved with the application of radiant energy at a wavelength for which water, paper and adhesive have a low absorption coefficient. Preferably the wavelength is in the near infrared region of 1.0 to 2.1 microns more preferably 1.0 to 1.5 microns.
The selection of the wavelength range is critical to this invention. Radiant heaters have been proposed previously for curing adhesives in corrugated board and laminates but the wavelengths used have resulted in absorption of the radiant energy near the surface of the paperboard and the heat input into the adhesive layer has been by conduction through the paper. This did not radically improve the speed of bond development and there was little advantage compared to the use of conventional methods of heat input. For example U.S. Pat. Nos. 4,169,007 and 4,589,944 propose the use of I-R radiation in heating corrugated board and adhesives but without avoiding use of pressure or significantly reducing the curing time. U.S. Pat. No. 4,169,007 discloses the use of radiation with wavelengths within the range 2.6 to 3.5 microns for making single face board but without the aforesaid advantages of this invention.
Tabulated data supplied by IR equipment suppliers, show that the percentage energy radiated within the range 1.0 to 1.5 microns and 2.5 to 3.5 microns varies with the peak wavelength transmission as follows.
______________________________________ Source % Energy
Peak Temperature
% Energy in 1.0-1.5
in 2.5 to 3.5
wavelength
.degree.C. micron wavelength
micron range
______________________________________
3.04 675 1.0 17.5
2.64 816 2.2 23.8
2.35 954 4.0 24.5
1.75 1370 13.6 21.5
1.50 1650 19.4 18.2
1.23 2065 23.5 13.6
1.05 2480 28.9 9.2
______________________________________
An infra-red absorption spectrum, as supplied by the IR lamp suppliers, for a typical paper sheet of 185 gsm basis w
REFERENCES:
patent: H556 (1988-12-01), Tarko
patent: 3660200 (1972-05-01), Anderson et al.
patent: 4169007 (1979-09-01), Pray
patent: 4589944 (1986-05-01), Torti et al.
patent: 4950348 (1990-08-01), Larsen
patent: 5035045 (1991-07-01), Bowen et al.
Mutimer Frederick J.
Padanyi Zsolt V.
Shaw Neil W.
Amcor Ltd.
Yoder Michele K.
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