Paper making and fiber liberation – Processes of chemical liberation – recovery or purification... – Waste paper or textile waste
Reexamination Certificate
1999-06-25
2001-09-18
Lithgow, Thomas M. (Department: 1724)
Paper making and fiber liberation
Processes of chemical liberation, recovery or purification...
Waste paper or textile waste
C162S055000, C162S056000, C162S189000, C209S164000
Reexamination Certificate
active
06290811
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for recycling of old corrugated container (OCC) using flotation and kneading treatment and more particularly, to a method for recycling of OCC, wherein OCC is treated with flotation and kneading treatment, and thereby removing fines and ink spots in the recycled pulp and improving the strength and drainage properties. As a result, it can be recycled similar to the expensive virgin unbleached kraft pulp.
2. Description of the Prior Art
The total paper production of Republic of Korea amounted to 8 million tons in 1997, and hence Korea became one of the top 10 largest production countries in the world. The production of the base paper for corrugated board essential for packaging goods accounts for more than 30% of the total paper production. Corrugated board used for packaging of goods, plays an important role in transfer and protection of goods, and improves the value of goods. So, it is an important packaging paper in the aspect of strength and appearance both. The base paper of corrugated board is; mainly manufactured from Korean old corrugated container (KOCC), and thus the recycling rate of KOCC is very high. However, KOCC used as main source material for the manufacture of corrugated board is already printed. Also, various printed matters other than corrugated board are contained in the waste paper, and since deinking has not been performed in the previous recycling process, the accumulation of ink is deepened as the recycling is repeated. Accordingly, since there remained ink spots cannot be removed by dyeing treatment in the recycling procedure, the base paper of the recycled corrugated board are distinguished apparently from the high-quality base paper of corrugated board, composed of unbleached kraft pulp, without spots.
The recycled pulp of OCC has the disadvantage of deteriorated appearance due to ink spots and poor drainage in papermaking and weak strength due to the high fines content. Currently used KOCC has the fines content more than half of the total paper compositions because of the repeated recycling treatments. And, the formation of fines is accelerated much more due to the hornification of fiber as the recycling treatment is repeated. Generally, fines refer to inorganic materials and fine fibers smaller than 75 &mgr;m, and they have been the main cause of the declination of productivity because they interfere draining of wet web in papermaking of the base paper.
However, the problem of drainage deterioration in papermaking due to the fines could not be settled by the conventional recycling treatment technique using KOCC as main source material. In addition, it was impossible to pulverize mechanically the said ink spots because the drainage deterioration due to the formation of fines hindered the sufficient treatment of hornified OCC pulp.
Although the technology comprising cleaning OCC with screen or cleaner, fractionating of long and short fiber portions, and improving the paper strength bad selectively disintegrating the long fiber portions, has been applied in developed countries [Bliss T.,
Pulp and Paper
, 88, 104 (1987); Clark L. E. and lannazzi F. D.,
Tappi
, 57, 59 (1974)], the said technology is only suitable for high quality OCC comprising good quality of unbleached kraft pulp and neutral sulfite semichemical pulp. The strength of the base paper of the corrugated board can not be improved, in case low-quality OCC, having more fines content than long fiber portions, is used for main material of the corrugated board, as in Korea.
For this reason, high-quality base paper for corrugated board with excellent: strength and without spots has been imported until now, and recently the imported amount of high quality base paper of corrugated board has increased rapidly from166,000 tons in 1995 to 193,000 tons in 1996 with the improvement of standard of living [Pulp & Paper International, 39, 65 (1997)]. As mentioned above, there was no alternative other than using 100%-imported unbleached kraft pulp as source material, and KOCC could not be used with the conventional technology. Actually, in 1996, the total quantity of unbleached kraft pulp imported for the manufacture of kraft paper and various corrugated board amounted to 270,000 tons [Pulp & Paper International, 39, 65 (1997)]. Accordingly, there is a serious demand for the development of new technology which improves the productivity, enhances the strength, removes ink spots in OCC, and reproduces to high-quality corrugated board by improving the drainage property of KOCC with high fines content.
SUMMARY OF THE INVENTION
As a result of earnest efforts to solve the said problems, the present invention was accomplished by confirming that the flexibility of fiber is improved and the ink spots are removed effectively without deteriorating the drainage of the base paper of OCC pulp, when the large quantity of inks and fines contained in OCC are separated effectively with the flotation treatment, and the long fiber portions and ink spots are treated with kneading treatment.
Accordingly, an object of this invention is to provide a method for recycling OCC which can substitute OCC for virgin unbleached kraft pulp used for the high-quality base paper of corrugated board by removing fines, ink spots, dusts, etc.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is a method for recycling OCC, wherein fines and inks are separated with the flotation treatment of OCC and then the same is treated with kneading treatment.
Hereunder is given a detailed explanation of each process of the present invention.
This invention is highly characterized by using flotation treatment applied previously in the deinking process of printed matter for separation of inks and fines of OCC.
The flotation treatment in a deinking process is conducted in order to separate the ink particles with different size and surface chemical properties from the stock. Although various kinds of deinking agents must be added for this flotation in deinking process to decrease the floating of wood fiber and promote desorption of ink particles and formation and stabilization of foams, the flotation process for OCC according to the present invention is fundamentally different from the flotation in a deinking process, in that it removes inks and it is conducted for the separation purpose only on the basis of size of fibers which have the same surface chemical property without using any chemical additives under relative low flow rate and air mixing condition. This is the excellence of the present invention.
The flotation treatment according to the present invention is carried out preferably under the condition of 0.5-2.0% OCC concentration, a temperature range of 40-70° C., a flow rate of 18-24 L/cm
2
/min, and an air mixing ration of 0.1-0.2 L/stock: L, and inks and fines cannot be separated effectively if the flotation treatment is carried out outside the above limiting ranges.
Subsequently, the kneading treatment process is performed in order to pulverize remaining ink spots larger than 200 &mgr;m which are not yet removed from the separated long fiber portion. It is desirable to perform the kneading treatment at the stock concentration of 15-30% and at the temperature of 60-90° C. If the temperature is lower than 60° C., the kneading treatment results in the formation of fines and induces the drainage load. The said kneading treatment may be treated just once, however the remaining ink spots can be removed effectively by conducting the treatment several times, preferably 2-5 times.
When the kneading treatment is conducted without flotation treatment, the drainage time of the kneaded stock increased rapidly, and thus sufficient mechanical treatment becomes impossible. However, if the flotation treatment is preceded according to the present invention, not only various strength properties but also drainage is improved after the kneading treatment.
As explained above, the present invention is especially useful for the recyclin
Ji Kyoung Rak
Ow Say Kyoun
Ryu Jeong Yong
Shin Jong-Ho
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Korea Research Institute of Chemical Technology
Lithgow Thomas M.
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