SU528366A1 - Method of preparation of paper pulp - Google Patents

Description

accelerates the swelling of the pulp during the grinding process, resulting in improved mechanical properties of the paper and reduced energy consumption for grinding (Tables 1-3). With an increase in the concentration of hydrotronic agents up to 2–3% or more, the grinding process is even more intensified, as a result of which, during the course of the long grinding, the cellulose can turn into a gel-like state (sappiness about 0), which makes it possible to use it for binding fibers in dry fiber. layer by iropitki last such a homogeneous substance.

With an increase in the concentration of hydrotropic additives, gironne impermeability and paper transparency increase, however, when their content in the ground mass is more than 2–3%, the strength of the paper sheet decreases due to a decrease in the mobility of the interfibre communication system in the sheet.

Increasing the effect of hydrotropic agents on cellulose (or reducing their effective concentrations) is caused in the alkaline environment by special substances, such as sodium zincate, Na2ZnO2, lithium zincate, LijZnOg, sodium stainate, Na2SnO2, and lithium nitrate, at a concentration of 0.05-0.6% by weight of fiber.

The presence in the paper pulp of a hydrotropic agent in combination with substances that enhance the hydrotropic effect on cellulose, leads to a qualitatively new effect. If a hydrotropic agent, especially in an alkaline medium, stimulates the swelling of cellulose during grinding, then in the presence of zinc, which forms a complex compound with cellulose, the accumulation becomes partial, or even complete dissolution. At the same time (which is especially important for paper mass of a high degree of iomol), the additives used make it difficult to dehydrate and do not require special techniques for fixing on the cellulose fiber. At the same time, urea (urea) is almost completely absorbed by the fiber, which has a positive effect on the characteristics of the effluent.

The urea retention under production conditions is 96-9i8%. The proposed substances are non-deformable and inexpensive reagents that have minimal toxicity or are non-toxic. Thus, zinc oxide is relatively cheap, low toxic and produced in large quantities in industry. Urea is also not a toxic substance, it is added to livestock feed, used in medicine to heal wounds and ulcers, and is used to fertilize fish ponds.

In the experiments with the use of urea in an alkaline and neutral environment, carried out under production conditions, a higher quality subpreg is obtained, as well as reduced power consumption for grinding.

The application of the proposed method for preparing paper pulp does not require the installation of special sophisticated equipment or a change in the technological mode. Use of hydrotropic agents & The preparation of paper mass improves the mechanical properties of the resulting paper, reduces the consumption of electrical energy for grinding, increases the transparency and grease resistance of the paper. These tools can be applied in the production of paper and paperboard in a wide range.

As shown in the table. 1, the addition of hydrotropic agents in an amount (0, 5%, solution) has a positive effect on the strength properties of the paper. At the same time, increasing the dosage to 2-3% concentration leads to a drop in the physico-mechanical characteristics.

As follows from the table. 2, grinding cellulose in the presence of a hydrotropic substance in an alkaline medium increases the mechanical performance of paper by an average of 10-30%. Thus, grinding cellulose in a urea environment has increased the breaking length of paper from 4070 to 4500 m,

5 resistance to fracture from 469 to 1917, resistance to extrusion increased from 2.6 to 3, 2 kg / cm. The grinding of cellulose in the environment of thiocarbamide resulted in a paper sheet with a breaking length of 9390 against 8420 m.

0 for the control experiment, fracture resistance 4211 versus 3107 and resistance to bursting 6.7 versus 6, 1 kg / cm. In tab. 3, in experiments 1, 2 and 5-8, sulphate unbleached pulp was used; in experiments 3, 4, sul5 was bleached.

As follows from the data table. 3, grinding the cellulose in a medium hydrotropic substance — the reinforcing substance makes it possible to obtain a paper sheet of increased mechanical strength. So, grinding in the medium zinc-carbamide increases the breaking length of paper from 7480 to 90i80. M, and the resistance to bursting from 5.0 to u, 6-kg / cm - for sulphate

5 cellulose, and a breaking length from 3,600 to 4,600 m, resistance to bursting from 1.9 to 2.2 kg / cm-ml sulfite bleached. Grinding sulphate unbleached pulp in stannate-urea medium increased breaking length

0 paper from 7Y20 to 9600 m, and resistance to bursting from 5.0 to 6.2 kg / cm-.

From the data table. 4 it follows that grinding cellulose in a water-urea-caustic soda medium at the consumption of these chemicals from 0.5 to 1.0% of the fiber weight significantly increases the grease resistance of the paper (from 30 to 180 s).

From the data table. 5 it follows that grinding of cellulose in an environment of hydrotropic substances with

60 consumption of the latter in the amount of 0.5-1.0% by weight of the fiber increases the transparency of the paper. Thus, in otsyty with the addition of urea, the transparency of paper increased from 31.7% to 37.2%, by 5.5%, i.e., by more than 17% of the initial value. Grinding sulphite bleached pulp in the presence of

Table 1 hydrotropic substances, the environment is neutral

Note. Thiourea cellulose turns yellow.

Milling of sulphate unbleached pulp in a laboratory mill in the presence of

hydrotropic agent, alkaline environment

table 2

T a b l and c a 3

Grinding pulp to the CRA mill in the medium

hydrotropic substances, in the presence of

enhancers

Table 5

The transparency of the paper obtained by grinding

bleached sulphite pulp in medium

hydrotropic substances