Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Patent
1995-12-22
1998-04-07
Acquah, Samuel A.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
528272, 5282955, 528296, 528302, 528306, C08G 6348
Patent
active
057366225
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
Around the world the opinion for use of the recycled fibre is now growing. A number of countries have already legislated that a certain part of the total paper production shall be constituted of recycled fibre. The methods, which are used today at deinking are the flotation process and the washing process, where the later is mainly applied in North America. The flotation process, which is most common in Europe, technically originates from the mining industry and is the process being most interesting for our object.
The deinking can be divided in three different steps; 1) dissolution of recycled fibre and discharging printing-ink from the fibres, 2) dispersing printing-ink in the water phase and 3) separation of the printing-ink. These three steps are included in both flotation process and the washing process. The method, which one uses industrial depends on the requirements and conditions which are found where the activity is located. The object of the flotation process concerning the deinking is to remove the very most amount of printing-ink from a recycled fibre suspension. The first step is to solve the fibre and disengage the printing-ink. When this is accomplished the particles must be modified so that they obtain suitable physical and chemical characteristics so that they afterwards can be lifted to the surface and removed with help of air-bubbles.
Some parameters are important to be consider at the flotation, such as the size of the particle, airflow in the flotation cell, the size of the air-bubbles, temperature, flotation time, the concentration of the recycled fibres in the flotation cell, pH, the concentration of the chemicals as well as the degree of the hardness of the water.
The flotation process is carried out in such a manner that the recycled raw material of the fibre is poured out through mechanical treatment in combination with a concentration of the chemicals. Different methods concerning chemicals/the concentration of the chemicals and method to pour the raw material exist. The purpose of the mechanical treatment is that the fibres should be rubbed against each other and that one in that way, together with the chemicals, should get an efficient discharging of print-ink. However, a too strong mechanical influence causes great damages on the fibres and this is not desirable at the paper-making.
Then comes filtering, whereby the particle shaped impurities are separated, followed of a purification step, generally by means of a vortex cleaner, where very little and heavy particles are separated. In a dispersing step the discharge of printing-ink continues through mechanical treatment and chemical influence. Printing-ink and remaining small particles are separated subsequently in the flotation step. Different flotation technics exist and in the more contemporary ones, one can float all small particles by pressurizing the flotation cell. Small impurities are separated through washing and to increase the brightness of the pulp the bleaching is performed through hydrogen peroxide or hydro sulphite.
Following chemicals are used at the deinking:
Sodium hydroxide is used to adjust pH to the alkaline level and to saponificate and/or hydrolyse the resin in the printing-ink. The pH at, which the deinking occurs, 9.5-11.0, causes that the fibres swell and thereby become more flexible, Adding NaOH to the mechanical pulps makes the pulp to turn yellow and become dark. The concentration of NaOH must be optimized. The alkalinity must be high enough, as mentioned earlier, to obtain good saponification and hydrolysis of resins, which are included in the printing-inks. A sufficient high pH also gives a good fibre flexibility as well as an optimal function of the hydrogen peroxide. A quandary, as mentioned earlier, is that in the volumes with high lignin content the high alkali content give rise to chromophore groups. These chromophore groups are the reason for the pulp becoming yellow dyed. Experiments done show that the brightness increases with increasing pH when it is increase
REFERENCES:
patent: 4010126 (1977-03-01), Kuzma
patent: 4245059 (1981-01-01), Ichimura et al.
patent: 5344859 (1994-09-01), Eichen et al.
Paart Enn
W.ang.llberg Peter
Acquah Samuel A.
Bim Kemi AB
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