FI71802C - Paper containing chemically substituted cellulose. - Google Patents

Description

71802

Paper containing chemically substituted cellulose

The invention relates to a paper containing chemically substituted cellulose. According to the invention, the paper 1-5 la has particularly good rot resistance and wet 1 u u new. femininity. nights can be used, for example, as a raw material for seedling cultivation.

Rot-resistant papers are used for quite a number of purposes. In agriculture and forestry, they are used 10 as a material for the production of seedling nurseries, among other things.

Current production methods are based on mixing varying amounts of PVA fibers into the paper to provide the desired decay resistance to the paper. The disadvantage of this method is that relatively high price of fibers. It would be advisable to use rot-resistant paper based exclusively on natural fibers.

The addition of anti-rot agents to paper can provide some, but not sufficient, rot resistance. The potential toxic effects of anti-rot agents also limit their wider use.

There are several indications in the literature that by altering the chemical structure of cellulose it is possible to obtain long-term rot resistance. For example, 25 "Microbial decomposition of cellulose, Siu, R.G.H.,

Reinhold Publishing Corporation, New York (1951) »provides a theoretical basis for this method. Replacing the hydrogen groups of the hydroxyl groups of cellulose with other groups gives compounds

30 (C6H702 (0H) 3_y (0R) y) x I

where R = desired modification, x = DP; molecular chain length (number of glucose units) 35 y = DS; degree of substitution 71802

In order to obtain a sufficient rot resistance, it is necessary that the O-R bond be as stable as possible, so that any hydrolysis takes place very slowly.

5 In view of the strength properties of the paper, it is desirable that the reaction conditions be as mild as possible in the preparation of these derivatives.

It has now been found that paper containing 10 chemically substituted softwood cellulose fibers with dimethylol dihydroxyethylene urea (DMDHEU) has excellent rot resistance and wet strength. The term paper in this context also means cardboard, cardboard and other similar products. Dimethylol dihydroxyethylene urea has been found to form stable bonds with cellulose. Invention 15 is defined in more detail in the claims.

It is previously known from U.S. Pat. No. 3,858,273 to treat corrugated board made of semi-chemical hardwood cellulose with a dimethylol dihydroxyethylene groove to achieve wet strength. The recommended concentration is 5-6%. From Melliand Textilchemie 1/1965, 12-18, it is known to add 0.3-0.4% dimethylol dihydroxyethylene urea to cotton to counteract the action of fungi and bacteria.

The paper according to the invention is best produced by surface treatment of conventional paper.

When high temperatures or a particularly long reaction time are used, it is recommended to use a surface treatment which takes place in a unit separate from the paper machine. In principle, it is also possible to add the substances already in the gluing press of the paper-30 machine and to perform only the condensation in a separate unit.

An elevated temperature and evaporation of the water formed in the reaction are required to effect the reaction.

7180 2

In addition, a catalyst is required. Latent or potential acids can act as catalysts. A typical catalyst is M ^ ci · a suitable catalyst content is e.g. 20 γ> -% based on the reactive compound.

The temperature may be, for example, between 130 ° C and 200 ° C, preferably between 1 ° C and 180 ° C. The required conditioning time is temperature dependent. If a strongly acid catalyst and a high temperature are used, a very short condensation time can be achieved.

By varying the reactant concentrations of the solution or dispersion, the amount of reactant absorbed into the paner can simply be adjusted and thus affect the level of rot resistance of the paper.

The papers according to the invention are relatively inexpensive in their raw materials, can be prepared under rather mild conditions and, since only water-soluble or dispersible reagents are used in the preparation, the preparation is also easy to use.

The papers according to the invention have good rot-resistance and wet strength, the level of which can also be easily controlled by changing the degree of substitution or crosslinking of the cellulose. Dimethylol dihydroxyethylene urea also increases the dimensional stability and stiffness of paper products, which is an advantage, for example, in the manufacture and use of corrugated board.

25 Papers can in principle be used in all applications where good rot resistance or wet strength is required. Examples are packaging materials such as sacks, corrugated cardboard, boxes and barrels, paper cords and especially seedling growing cells and trays.

71802

In the manufacture of paper sacks, cords, barrels and other products, either the paper from which the the product is manufactured or molded product finished and process the finished product. However, the processing is always 5 the same. The paper is impregnated with a solution or dispersion containing dimethylol dihydroxyethylene urea, followed by drying and heat-demanding condensation. An intermediate form can be considered to be manufacturing in which the paper is impregnated, dried, molded. product and process the finished product with heat.

It is important in the manufacture of all these products that the degree of gluing of the paper is low and that resin adhesives are avoided. Thus, high concentrations of dimethylol dihydroxy-15 ethylene urea are not required to provide adequate rot resistance. On the other hand, embrittlement of the paper and deterioration of the properties of other papers are avoided.

Since hardwood] 1ulose is rich in carboxyl p η ....

groups are also formed by modifying Esters and Doks, which are not as stable as ether bonds. When made of softwood pulp-based paper with lebti-pulp-containing paper, paper is obtained which decays into holes, but still forms a frame when it remains strong. This ^ 5 can be used in seedling breeding cells.

Such a paper can be made, for example, by mixing in a bleached pine sulphate pulp under acidic conditions a resin-glued waste containing 50 to 100% by weight of birch fiber, lightly pulverized. From the pulp thus produced, paper with hardwood fiber flocs in a softwood fiber matrix is obtained, as long as care is taken to ensure that the flocs do not disintegrate in pumps or mixers.

Paper that decomposes to form holes can also be made by dispensing an agent containing carboxyl groups.

to certain areas of the paper. At these points, dimethylol-5 71 802 dihydroxyethylene urea reacts only with this "preservative" and cellulose remains unsubstituted. A suitable substance is, for example, carboxymethylcellulose (CMC). It is suitable to use a low-viscosity aqueous solution in order to obtain sufficient absorption of the substance. A suitable CMC content is e.g. 7%.

The substance containing carboxyl groups can be added to the paper, e.g. with a screen roll. After the aqueous solution is added, the water is removed by drying. In this way, the substance adheres to the fibers, and the spread of the substance outside the desired points is prevented.

In the manufacture of rot-resistant corrugated board, it is desirable that both the corrugated board and the liner be treated with dimethylol dihydroxyethylene urea prior to corrugation and the joining of the layers. Thus, sufficient impregnation is also achieved in the middle layer of the corrugated board. Corrugated board 1 slime must be water resistant. Such is, for example, a starch paste to which a synthetic resin such as urea-formaldehyde or resorcinol-formaldehyde has been added. The condensation of dimethylolediium hydroxyethylene urea 20 suitably takes place after corrugation.

The currently available liner and corrugated board grades can be used as corrugated board raw materials. However, it is important that the gluing degree of the liner is as low as possible, which facilitates saturation. There is also a risk of side reactions between carboxyl-containing resin adhesives and dimethylol dihydroxyethylene urea. Current corrugated board is often semi-chemical. However, such a grade is rich in carboxyl groups, which is why it is desirable to use also board made of, for example, softwood fibers (or perhaps recycled fibers) as corrugated board.

The durability of the papers according to the invention was tested by fermentation for 3 days in a solution of 2.5 l of a buffer solution 55 25 g of "Meicelase" powder (salulase enzyme) 0.7 g of "Triton" (foam norl) 31 g of lemon skin 0 g Na 2 HPO +: \ hL0 έ L | c- a 6 71802

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Claims (5)

Paper containing chemically substituted softwood cellulose, characterized in that the cellulose is substituted with dimethylol dihydroxyethylene urea and in that dimethylol dihydroxyethylene urea is 1-3% by weight of the paper. Paper according to Claim 1, characterized in that the paper contains sites containing unsubstituted cellulose. 3. A method for substituting cellulose from softwood cellulose-containing paper, characterized in that the paper is treated with an aqueous solution or dispersion of dimethylol dihydroxyethylene urea and dried at 130-200 ° C and that dimethylol dihydroxyethylene urea is used at 1-3% by weight of the paper. Process according to Claim 3, characterized in that a substance containing carboxyl groups is added to the paper at certain points before treatment with dimethylol dihydroxyethylene urea. 5. A process for preparing paper products from chemically substituted softwood cellulose-containing paper, characterized in that paper containing cellulose substituted with dimethylolidihydroxyethylene urea is used, in which dimethylolidihydroxyethylene urea is 1-3% by weight of the paper.