RU2333304C1 - Glue for cellulose materials processing - Google Patents

Abstract

FIELD: textiles, paper.

SUBSTANCE: glue is meant for cellulose materials processing and can be used in pulp and paper industry for production of paper and cardboard. The glue contains carbamide, formaldehyde and, as a modifying agent, melamine and cationic starch at certain rate of mixture.

EFFECT: improved quality of glue thanks to the increase in its hydrophobic property and stability.

1 tbl, 1 ex

Description

The invention relates to the pulp and paper industry and can be used in the manufacture of paper and cardboard.

Closest to the claimed is an adhesive based on urea-formaldehyde oligomers modified with starch (see Starch urea-formaldehyde adhesive for surface sizing of paper / I.N. Koverninsky et al. // Forest Journal. - 1990. - No. 2. - S.101-104 g )

The disadvantages of this method are: insufficiently high efficiency of urea-formaldehyde oligomers modified with native starches as strengthening agents; low water resistance and increased fragility of these oligomers and the material processed by them; low stability of their aqueous solutions during storage.

The problem solved by this invention is as follows: a significant increase in mechanical strength in the dry and wet state, as well as the hydrophobicity of the processed paper and cardboard; lack of fragility of the finished material; higher stability of the aqueous glue solution; the possibility of both surface treatment of cellulosic materials with the specified adhesive, and its introduction into the pulp before forming the paper web.

The solution to this problem is provided by the fact that in the adhesive for processing cellulosic materials, melamine and cationic starch are used as a modifier of urea-formaldehyde oligomers in the following ratio, wt.%:

Formaldehyde 47-48 Urea 36-37 Melamine 12-13 Cationic starch 2-5

The technical essence of the invention is as follows.

Schematically, the structural formula of the oligomer can be represented as follows:

This formula reflects the basic structural units of the carbamidelamino-formaldehyde oligomer modified with cationic starch, as well as the nature of the chemical bonds between them. The presence of a large number of hydroxyls (including those in the composition of methylol groups) and cross-links between glucopyranose starch units formed as a result of crosslinking with formaldehyde during oligomer synthesis is characteristic. The number of cationic groups is insignificant; their degree of substitution does not exceed 0.045 (i.e., approximately 4-5 substituted groups per 100 elementary starch units).

The use of melamine as a component of the urea-formaldehyde oligomer increases the stability of the aqueous solutions of the latter, and when processed with this oligomer of paper-cardboard materials it increases their hydrophobic properties. Cationic starch as a modifier of the urea-formaldehyde oligomer increases its affinity for cellulosic material due to the presence of a large number of hydroxyl groups and imparting cationic properties (positive charge) to the oligomer molecules, while the surface of the treated cellulosic material has a negative charge. This facilitates the attachment of the oligomer to the surface of the paperboard material.

The invention is illustrated by the following example.

A modified urea-melamine-formaldehyde oligomer is manufactured according to the following technology:

1. The ratio of components (in% by dry matter or in grams):

Formaldehyde - 48% (g, in the form of 37% formalin - 130 g);

Urea (main load, K1) - 22% (g);

Urea (additional charge, K2) - 15% (g);

Melamine - 13% (g);

Cationic starch (for example, Mylbond 143, manufactured by AMILUM GROUP, The Netherlands) - 2% (g, in the form of a 2% aqueous solution - 100 g; the content of modifier - cationic starch is minimal).

Production technology

In a 500 ml reaction flask equipped with a water bath, a mechanical stirrer, a reflux condenser and a thermometer, 2 g of cationic starch are charged, 98 g of water is poured, the stirrer is turned on and the water bath is heated. When the temperature of the mixture in the flask reaches 95 ° C, the mixture is incubated for 30 minutes. Then, 13 g of melamine, 22 g of urea (K1) are introduced into the flask and the temperature is allowed to drop to 40-50 ° C, while complete dissolution of melamine and urea should occur, and the pH of the mixture should be 7.5. After that, 130 g of 37% formalin, previously neutralized with an aqueous solution of NaOH to pH 8.5-9.0, is introduced into the flask. After that, the pH of the mixture in the flask should be 8.5 ± 0.2. If necessary, increase the pH by adding dropwise a 10% aqueous solution of NaOH. The mixture is heated to 60-65 ° C and maintained under these conditions for 1.5 hours

The second stage of the synthesis is carried out in a slightly acidic or neutral medium. For this, the pH of the mixture is reduced with a solution of HCl or NH ₄ Cl to a pH of 6.5-7.0 and maintained under these conditions for 2 hours.

After that, the pH in the flask was adjusted to 8.7 ± 0.2, 15 g of urea (K2) were introduced and the mixture was kept under these conditions for 30 minutes. It is necessary to ensure that during this time the pH in the flask is 8.7 ± 0.2.

If necessary, it is possible to concentrate the aqueous solution of the obtained oligomer by evaporation. The achievement of a concentration above 45% is undesirable, as this can lead to a loss of stability of the solution.

The stability of the obtained adhesive solution at a concentration of 25% and a pH of 8.5 is at least 4 months. (for the closest analogue - no more than 2 months.).

2. The ratio of components (in% by dry matter or in grams):

Formaldehyde - 47% (g, in the form of 37% formalin - 127 g);

Urea (main load, K1) - 22% (g);

Urea (additional load, K2) - 14% (g);

Melamine - 12% (g);

Cationic starch - 5% (g, in the form of a 3% aqueous solution - 167 g;

the content of the modifier - cationic starch - maximum).

The production technology is the same as in the 1st example. The difference in the properties of oligomers with a minimum and maximum content of cationic starch is that at its maximum content (5% by weight of dry matter) the concentration limit of the oligomer solution is 30%, above which concentration should not be carried out, since the stability of the solution is impaired and increases viscosity, which makes it difficult to use for processing cellulosic materials. The stability of both types of oligomer solutions (if the permissible concentration limit is not exceeded) is the same.

Technology of use in paper production

Offset paper No. 1 was made, weighing 100 g / m ² , ash content 22% with the following fiber composition: bleached softwood sulphate pulp - 50%, grinding degree - 30 ° SR; hardwood bleached pulp bleached - 50%, grinding degree - 32 ° SR. Production of offset paper No. 1 on a laboratory sheet-sieving apparatus includes the following steps:

1. Dissolution of the fibrous material (cellulose) in water with the formation of a water-fiber suspension.

2. Introduction to a water-fiber suspension of a mineral filler (kaolin).

3. Introduction to the water-fiber suspension of chemical additives in the following sequence and with the following costs for dry matter: rosin glue - 10 kg / t; aluminum sulfate - 30 kg / t.

4. Adjustment of the pH of the aqueous fiber suspension by the addition of sulfuric acid or sodium hydroxide to the desired value (pH 5.5).

5. The formation of the paper web, which consists in filtering a water-fiber suspension through a grid of a sheet-forming apparatus with the formation of a wet paper web on a grid.

6. Pressing the paper web, consisting in the mechanical extraction of water from it using a special roller.

7. Drying the paper web at a temperature of about 95 ° C for 7 minutes.

8. Surface treatment of paper with developed adhesive, which consists in passing the paper web through a bath with glue, followed by pressing on a laboratory twin-shaft press.

The properties of offset paper made using the developed glue and the closest analogue are presented in the table. The consumption of developed glue and the closest analogue is 20 kg / t of paper. After processing, additional drying of paper samples was carried out in an oven at t = 110 ° C for 15 min.

Physical and mechanical properties of offset paper The composition for processing Name of indicator Breaking length, m The degree of sizing, MM Surface Absorption, g / m ² Moisture resistance,% Plucking, m / s Kink No processing (blank option) 2300 1,2 thirty 7 1,1 3 K-min * 3100 2.0 eleven 24 2.2 5 K-max * 3200 2.0 10 19 2,3 6 The closest analogue 2900 1,5 12 eighteen 1.7 four ^* K-min, K-max - developed adhesive with minimum and maximum cationic starch content, respectively.

As can be seen from the data given in the table, when processing paper with developed glue, all its physical and mechanical properties increase significantly, including and compared with the closest analogue. We can say that glue with the maximum content of cationic starch gives a larger increase in the mechanical properties of paper, although insignificant, but when it is used, the moisture resistance is slightly reduced. In general, both types of glue surpass the nearest analogue in their properties according to the claimed solution.

Claims (1)

Adhesive for processing cellulosic materials, including a urea-formaldehyde oligomer and a modifier, characterized in that melamine and cationic starch are used as a modifier in the following ratio, wt.%: Formaldehyde 47-48 Urea 36-37 Melamine 12-13 Cationic starch 2-5