SU903436A1 - Method of making imitation parchment-paper - Google Patents

Description

(S) METHOD OF MANUFACTURING CHEMPER

one

This invention relates to the pulp and paper industry, in particular, to a method for manufacturing a harnesses,

A known method is to increase the ability of sulfite unbleached pulp to physico-mechanical parchmentation during grinding by applying low-temperature modes of deligni wood. With such cooking, the temperature in the boiler reaches 122 ° C slowly (over 9 hours), the stand at this temperature lasts 6-6 hours, and the total duration of cooking reaches 15 hours, not counting the time of loading the chips and unloading the semi-finished . From the obtained cellulose, which has a high content of pentosans (more than 6%), after its grinding, a low-fat permeability subparchment 1 is made ..

The disadvantage of this method is the long duration of the cooking process, due to

which he has not yet received industrial application.

There is also known a method of making parchment from standard sulfite unbleached softwood pulp by dissolving it at a mass concentration of 5.5 to 80-85 ° ShR, followed by pouring paper on a papermaking machine 21.

The disadvantage of this method is the need to use cellulose of a strictly specified brand - G-2 (cellulose sulphite unbleached from coniferous wood GOST 6501-73) with a pentosan content not lower than 5.3%, which is currently produced in a very limited quantity that does not meet the need production of parchment. Subparchment from other grades of cellulose has an increased fat permeability.

The purpose of the invention is the possibility of obtaining high-quality sub-parchment parchment from cellulose with reduced pentosan content. The goal is achieved by the fact that, according to the method of manufacturing a subparchment, including grinding unbleached sulphite pulp and pouring out a paper web, the pulp is ground before treatment with an aqueous or alkaline pentosan-containing extract at 50-80 ° C for 1-6 hours with constant mixing. Processing the pulp with a pento-containing extract results in the sorption of dissolved hemicelluloses, which are localized on the surface and in the submicroscopic capillaries of the walls of the cellulose fibers, with cellulose fibers. Hemicelluloses sorbed under the indicated conditions, due to hydrogen bonds, are firmly retained by the cellulose and retained on the fibers during the subsequent grinding of the cellulose, promoting their hydration and increasing the plasticity of the fiber. When forming a paper sheet, hemicelluloses perform the role of a binder between cellulose fibers, ensure the formation of a more dense sheet structure, which leads to a decrease in fat permeability and an increase in the mechanical properties of paper. The boundaries of the cellulose pulp processing temperature range are due to the fact that at temperatures below 50 ° C the diffusion of dissolved hemicelluloses and their serption by cellulose fibers slow down noticeably, and at temperatures above 80 ° C there is a significant destruction of hemicelluloses. The method for producing the asphalt consists of the following. Before grinding, sulphite unbleached pulp with any content of pentosans is treated in a mass basin with a stirrer with a pentosan-containing extract at the rate of kg of diluted hemicelluloses per 1 ton of cellulose. After processing, the pulp is ground on any type of grinding apparatus. The degree of grinding is established depending on the required fat permeability of the paper. As tests have shown, with the same duration of the processed and unprocessed pulp, the degree of grinding is higher than in the treated pulp. The ground mass is fed to a paper machine. The raw material for hemicellulose extract can be the waste of annual plant raw materials - cereal straw, oats for husks, sunflower husks, corn stalk, as well as cellulose prehydrolysates. Hemicellulose extraction from the indicated raw material is carried out by treating it with water or 0, sodium hydroxide solution at 120160 ° С 0.5-3 hours. Example 1. Air-dried sulphite unbleached pulp from H-C spruce wood (with pentosan content 5.051) for 2-3 minutes, diluted in water using a laboratory disintegrator, partially dehydrated on a Büchner funnel, and poured with a pentosan-containing extract obtained by high-temperature treatment of oat husks with water, calculated as O, g of dissolved hemicelluloses per 1 g air-dry yulozy. The mass is kept at 50 ° C, 75 ° C and 75 ° C for 3 hours with stirring, then washed and dried. The treated cellulose is further milled at a concentration of 6 in a TsRA mill at 150 rpm for minutes and manufactured on a sheet-pouring apparatus with a casting mass of 1 m. pushing through. The test results are presented in table 1. Example 2. Wet sulfite unbleached cellulose is treated as in Example 1, at 50 °, 60, 75 C with a pentosan-containing extract, obtained by high-temperature processing of oat husk 0, sodium hydroxide solution. Castings are made from the treated pulp and are tested as in Example 1. The results of the experiments are shown in Table. 1. Example 3. The initial sulphite unbleached pulp, which was used in examples 1 and 2, is filled with water for 2 hours at the rate of 6% concentration, then ground in a TsRA mill at 150 rpm

5EPOZ Zb6

within minutes Milled from 1 m and tested as in cellulose on a sheet-molding appara- example 1, a sample of a mass of g is cast. The results are presented in Table 1.

The content of pentosans,%

Fat permeability

mg

Kink resistance, number of double folds on average in two directions

Relative resistance to bursting, kPa

The degree of grinding of cellulose, SR Example 4. Sulfite unbleached cellulose from G-grade spruce wood (content of pentosans 4.10%) is dissolved in water using a laboratory disintegrator for 2-3 minutes, partially dehydrated and then filled with aqueous or alkaline pentosan-containing extract at the rate of 0.14 g of dissolved hemicelluloses per 1 g of air-dry cellulose. Mass for 3 hours table 1

9.02 9.97

5.05

11.00 8.00

2.90 2.10

1.20

1013 1118

930

tis

 "57 89

93

91 93 are stitched at, then washed and dried. The treated pulp and the raw pulp are then ground at a concentration of 6 in a TsRA mill at 150 rpm for 120 minutes. From the ground mass is made on a sheet-casting apparatus of a mass of 1 m 41-45 g and test them, as indicated in example 1. The test results are summarized in table 2.

table 2

Claims (1)

Claim A method of making parchment, which includes grinding unbleached sulphite pulp and pouring a paper web, characterized in that, in order to be able to produce high quality parchment from cellulose with a reduced pentosan content, before grinding, the pulp is treated with an aqueous or alkaline pentosan-containing extract at 50-80 ° C. 6 hours with constant stirring.