JPH03152285A - Regeneration of white waste paper of good quality - Google Patents

Abstract

PURPOSE: To regenerate a waste white woodfree paper while improving its physical strength, without using fatty soap and saving the regeneration cost by adding natural polysaccharide and a disaggregation promoting agent in the disaggregation step and then using a frothing agent. CONSTITUTION: In the disaggragation step of the regeneration process of waste white woodfree paper printed with special ink and regular ink, (A) natural polysaccharide and (B) a disaggregation promoting agent are added to carry out the disaggregation in 8-15 wt.% pulp concentration at 40-80 deg.C and the pulp concentration is lowered and then the flotation is performed while using a frothing agent to remove the ink printed on the waste paper. Any one of algin, xylan and starch is preferably added to component A by 0.05-5% per the absolute dry weight of the waste paper and a surfactant of p-nonyl-phenol ethoxylate type is preferably added to component B by 0.005-0.05 wt.%.

Description

Detailed Description of the Invention (Technical Field) The present invention deinks white paper waste paper (i.e., high-quality waste paper) printed with special ink and ordinary ink using a deinking agent different from the conventionally used surfactants. The present invention relates to a method for recycling white paper used paper, which improves the physical strength of the recycled pulp obtained at the same time as deinking, and produces high-quality recycled pulp.

(Background Art) In the conventional method for deinking high-quality waste paper, alkalis such as sodium hydroxide, sodium carbonate, sodium silicate (water glass), surfactants, etc. are used during or after deinking the waste paper in a pulper. , an oxidizing agent such as hydrogen peroxide, a bleaching agent, and a PL + stabilizer as an auxiliary agent, a chelating agent, a dispersing agent, etc. are used to promote the detachment of ink particles from the pulp fibers, and the removal of ink particles from the pulp fibers is promoted. It is common to obtain deinked recycled pulp by removing ink particles by flotation or washing using a deinking agent containing fatty acid soap as a main component.

However, in recent years, various resins such as synthetic resins and phenolic resins have been increasingly used as vehicles for printing ink in response to demands for more beautiful printed matter, more robustness, and faster printing operations, and these resins have been collected. Deinking waste paper is becoming increasingly difficult. In particular, with the advancement of the information society, the usage of special information paper such as carbonless paper, xerographic paper, hot paper, and pressure-sensitive paper is rapidly increasing, and the proportion of specially printed waste paper mixed in with general waste paper is also high ( It has become.

These special printed waste papers cannot be completely deinked using conventional methods, so it is necessary to increase the concentration of chemicals such as alkali, lengthen the deinking time, or apply mechanical force using a kneader or divider. Methods for removing ink from fibers are being studied. What makes deinking particularly difficult is computer recording paper (LCPO: La5er pri), which is printed using a laser beam.
This paper is attracting attention as a raw material for recycling because it is easy to collect as waste paper and its quantity is increasing due to the computerization of office work. Since it cannot be recycled using the deinking method for white paper waste paper, it is mixed with a few percent of general white paper waste paper for deinking.

The reason why it is difficult to deink LCPO waste paper is that the composition of laser print ink uses styrene, acrylic, epoxy, polyester, polyolefin, and rubber resin as binders. Although it has good removability with alkali like mold ink, the ink film is strong and large ink particles are formed, so even though the ink has good hydrophobicity, normal deinking systems cannot solve the problem. There are some problems that cannot be resolved.

In addition, deinked pulp (DTP) is currently produced using the flotation method.
Recirculated water and wastewater issues are significant issues for companies that produce (deinked pulp). This is due to the use of calcium salt and water glass in combination to adjust the hardness of water when a fatty acid soap deinking agent is used in the flotation process.

These substances precipitate as their concentration increases during the water recovery process, causing blockages and pitch problems in paper machine wire piping, and dissolve into wastewater, increasing wastewater COD and BOD ( This increases the burden on wastewater treatment.

The present inventors discovered a phenomenon in which natural polysaccharides miniaturize giant ink particles that are detached during the difficult process of processing waste paper.
By introducing this into the deinking process of waste paper that is difficult to deink, such as CPO old paper, it is possible to easily remove ink, and also to produce high-quality deinked recycled pulp from ordinary white paper waste paper. The present invention was completed after confirming that it could be obtained.

The object of the present invention is to provide natural polymer II in the difficult process of waste paper without using surfactants conventionally used in the difficult process of waste paper and fatty acid soaps conventionally used in the flotation process.
It is an object of the present invention to provide a method for recycling white paper waste paper, which obtains high-quality deinked recycled pulp from white paper waste paper including waste paper that is difficult to be deinked, such as LCPO waste paper, using a similar method.

(Disclosure of the Invention) The present invention involves adding natural polysaccharides and refracturing promoters in the refracting process of waste paper, performing refracting at a temperature within the range of 40 to 80°C at a pulp concentration of 8 to 15% by weight, Next, the ink printed on the waste paper is removed by lowering the pulp density and performing flotation separation using a foaming agent.

Natural Polymer 1 used in the method of the present invention! For example, starch, galactomannan (vegetable rubber), xylan-algine, chitosan, etc. are quantitatively nonionic or anionic, and their molecular weights range from several hundred to several million. It is also often used as an additive for papermaking. When used as a papermaking additive, it has effects such as adding barrier properties, improving surface strength, preventing dusting, preventing ink penetration, and improving smoothness as well as sizing effects. In addition, when used in combination with pigments, it is known to have effects such as improving water retention, improving fluidity, and preventing pigment aggregation. Furthermore, natural polysaccharides are also used as water purifiers because they are non-toxic to humans and livestock as polymer flocculants and are easily decomposed. Natural polysaccharides are 0.05 to 5% per bone dry weight of waste paper.
It is preferable to add If it is less than 0.05% by weight, the deinking effect will be poor, and if it is more than 5% by weight, no improvement in the effect will be observed.

In the difficult step of the method of the present invention, it is preferable to use a pulp concentration of 8 to 15% by weight from the viewpoint of the effect of mechanical shearing force,
It is common to use temperatures within the range of 40-80°C.

LCP is currently known as waste paper that is difficult to deink.
In the case of deinking waste paper, when natural multi-wm is added as a deinking agent when deinking waste paper, and when using a nonionic P-nonyl phenoxylate type surfactant, which is currently most widely used as an ink agent. A certain Igebal-CO (Igeρal-CO, product name + T, G, Far
A comparative experiment was conducted to compare the deinking effect in the case where the deinking effect was added. In this experiment, the conditions of the conventional method described in Table 2 of Example 1 were used. The results are shown in Figure 1 (particle size distribution of ink particles) and Table 1 (number of remaining ink particles and remaining ink area).

As can be seen from Figure 1, the ink particles are
It can be seen that finer particles are made much finer by algin than by O. The longer the resolving time, the finer the ink particles become, and as the pulp fibers swell with the alkali and sodium hypochlorite, the ink is detached by dissolution or melting of the ink binder, and the giant ink particles that have been detached are formed. Natural polysaccharides have the effect of preventing agglomeration and re-adsorption to fibers, and on the other hand, shear forces are uniformly transmitted between fibers, between fibers and ink particles, and between ink particles, and mechanical frictional forces etc. It is thought that this makes the ink particles finer.

Table 1 Number of remaining ink particles and remaining ink As shown in Table 1, the number of remaining ink particles and the area of remaining ink are much smaller in the case of algin addition than in the case of image analyzer. This is because during the manufacture of handsheets, a significant portion of fine ink particles escape through the paper machine wires.

The pulp produced in the difficult step of the method of the present invention is diluted to a pulp concentration of, for example, 1% by weight, and the printed ink is removed from the waste paper by flotation separation using a foaming agent. The foaming agent is preferably of the polyoxyethylene alkylphenol ether type. It is preferable to add 0.005 to 0.05% by weight of Igebaru CO as a foaming agent based on the absolute dry weight of the waste paper and perform flotation separation for 3 to 5 minutes, thereby making it possible to completely deink the LCPO waste paper. Ta.

In this case, if 0.05% by weight or more of a foaming agent is added, too much foam will be produced and the deinking effect will be reduced. Also, 0
, 005% by weight, sufficient bubbles will not be generated for flotation separation.

(Example) Next, the present invention will be described with reference to an example. In the examples, all percentages shall mean percentages by weight.

Algin derived from seaweed was used as a natural polysaccharide. Algin is a hydrophilic colloidal anionic polyelectrolyte that dissolves in water and exhibits mucilaginous properties.

500g of LCPO waste paper, 1% sodium hydroxide, 0.
3% sodium hypochlorite and 0.2% alginic acid were added and the waste paper was refracted for 1 hour at a pulp consistency of 12%. Then, the pulp concentration was diluted to 1% and 0.00
Deinking was performed by flotation using 5% foaming agent (Igevar Co) for 5 minutes.

Handsheets manufactured using a standard paper machine from the recycled pulp obtained by this method (Table 2-A) and the recycled pulp obtained by the conventional method (Table 2-B) were analyzed for residual ink using an image analyzer, and the whiteness and specific tensile strength were measured.

Note that soap MT-90 is a brand name of a fatty acid soap manufactured by Stevens Brothers, UK.

Table 2 Comparison of difficult process and deinking process A: Example 1 B: Conventional method As can be seen from the analysis results in Table 3, the sheet obtained in Example 1 had significantly improved whiteness and strength; The deinking effect was improved by about 20 times in terms of the remaining ink area.

Table 3 Comparative test results Furthermore, the whiteness and strength were also significantly improved.

Table 4 Comparative test results In the same manner as in Example 1 except for L CP
O Waste paper was deinked and the deinking effect was compared with the conventional method. The results are shown in Table 4.

It has been found that when xylan is used, a deinking effect 50 times or more can be obtained compared to the conventional method.

Starch is widely distributed in seeds, fruits, bulbs, etc. of lower plants to higher plants, and the diameter, morphology, and properties of starch particles vary among them.

In this example, LCPO Kogi was deinked in the same manner as in Example 1 except that commercially available water-soluble starch was used instead of algin, and the deinking effect was compared with the conventional method. The starch used was soluble starch for reagents (manufactured by Hayashi Jun Kogyo Co., Ltd.).
As shown in Table 5, when starch was used, the deinking effect was about 10 times that of the conventional method, and the strength improvement effect was superior to when xylan and algin were used.

Table 5 Results of comparative tests. From Example 4, it can be seen that it is possible to sufficiently remove ink from mixed waste paper in which special ink-printed waste paper and general high-quality waste paper are mixed without sorting work.

Table 6 Results of Comparative Test A mixed waste paper in which LCPO waste paper and white ledger paper waste paper were mixed at a ratio of 40:60 was deinked in the same manner as in Example 1. As a result, as shown in Table 6, the addition of algin was much more effective. In addition,
The whiteness and strength were also improved, and the used ledger paper was deinked in the same manner as in Example 1 by adding algin. The results are shown in Table 7. It was found that the deinking effect was superior and the strength was improved compared to the conventional method.

Table 7 Results of Comparative Tests (Effects of the Invention) The advantages of the present invention are that it can be applied directly to the conventional deinking process, that it is not necessary to use any fatty soap in the flotation process, which reduces the production cost of recycled pulp, and that it reduces the production cost of white liquor. The problems caused by the use of water are improved, and the burden of wastewater treatment is reduced. In addition, the method of the present invention
Not only is it effective for deinking waste paper printed with special inks such as PO waste paper (it is also effective in deinking general white paper waste paper),
Since mixed waste paper of PO and general white paper can also be easily deinked, all the problems in the current deinking process of white paper waste paper can be solved. Furthermore, natural polysaccharides are
As it is used as a papermaking additive, it is added as it is or in modified form to the difficult process of waste paper, and since it also acts as a binder, it also has the effect of increasing paper strength.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the distribution of residual ink particles in waste paper after deinking by the method of the present invention in comparison with the conventional method.

Claims (1)

[Scope of Claims] 1. In recycling white paper waste paper printed with special ink and ordinary ink, in the refractory process of the waste paper, natural polysaccharides and a refractor accelerator are added, and 8 to 15% by weight are added. The method is characterized in that the ink printed on the waste paper is removed by carrying out inkling at a temperature within the range of 40 to 80 degrees Celsius at a pulp concentration of How to recycle used white paper. 2. The method according to claim 1, characterized in that the natural polysaccharide is one or more selected from the group consisting of algin, xylan, and starch. 3. 0.05 to 5% by weight of natural polysaccharides based on the bone dry weight of waste paper
3. The method according to claim 1 or 2, further comprising adding 4. As a foaming agent, use p-nonylphenol ethoxylate type surfactant at 0.005 to 0.0 per bone dry weight of waste paper.
The method according to claim 1, characterized in that 5% by weight is added.