Method of improving strength properties of paper

Abstract

A method of improving strength properties of paper, where to strengthen paper an aqueous solution of chitosan and citric acid is used with the percentage concentration of chitosan in the solution of at least 0,1% and the percentage concentration of citric acid in the solution of at least 0,5%, where the solution is used in the paper strengthening process by adding it to the pulp in the ratio of at least ½ litre of the solution per 1 kg of dry paper according to patent PL237344, characteristic in that sodium benzoate is added to the concentrate in the amount of 0.001% to 30% as a preservative. The solution used in the strengthening process, obtained by diluting the concentrate, contains citric acid - with the concentration of at least 0,5%, chitosan with the concentration of at least 0,1% and sodium benzoate with the concentration of at least 0,001%.

Description

[0001] Method of improving strength properties of paper.

[0002] The subject of the application is a method of improving strength properties of paper using a solution of chitosan and citric acid according to patent PL237344, with the invention being improved by the use of sodium benzoate as a preservative for the biodegradable concentrate used to harden paper and, in particular, towel paper.

[0003] The international application WO2017075917A1 presents a solution disclosing a papermaking additive, a method of manufacturing paper and a tissue containing the papermaking additive. The papermaking additive is mainly formed by mixing and reaction of renewable biomass containing polysaccharide biomass with an acid solution. The papermaking method comprises adding the papermaking additive to paper pulp to produce mixed pulp and making paper. The papermaking additive can cause biodegradation and improve the wet strength and other physical properties of paper.

[0004] The Chinese patent description CN103882773A discloses an invention which relates to a chitosan wet strength enhancer and the method of making it. The chitosan wet strength enhancer comprises the following components in parts by weight: 6-7 parts of chitosan, 3-6 parts of hydroxypropyl methyl cellulose, 4-8 parts of isobutyl polyacrylate, 2-5 of parts myristyl benzene sulfonic acid sodium, 6-7 of parts butanediol, 1-2 of parts citric acid and of 205-215 parts of deionised water. The preparation process of the chitosan wet strength enhancer comprises the following steps: mechanical mixing of the various raw materials, mechanical stirring and such like. By using the prepared chitosan wet strength enhancer, the tear strength and tensile strength of paper can be improved, and the tear resistance and tensile performance of paper products are improved.

[0005] The subject of the application is a method of improving the strength properties of paper, using a solution of chitosan and citric acid. The strengthening mixture, which is an aqueous solution of chitosan and citric acid, is obtained by diluting a concentrate. The concentrate is obtained by diluting citric acid in water in such a quantity that its percentage concentration is 10%, followed by adding such a quantity of chitosan that its percentage concentration is 2%. The dissolution of chitosan is a lengthy process and can be accelerated by heating the solution. The resulting concentrate should be stored at the lowest possible temperature for no longer than 14 days. After appropriate dilution of the concentrate, a solution is obtained in which the concentration of chitosan should be at least 0.1% and the concentration of citric acid at least 0.5%, in the paper strengthening process, the solution should be dosed at the ratio of at least 1 / 2 litre of solution per 1 kilogram of paper. Using such a method to improve the strength properties of paper allows the desired result to be achieved with a much smaller amount of chitosan, which in turn translates into a significant reduction of the cost of strengthening paper.

[0006] The purpose of the invention is to reinforce the strength of paper by improving the solution of the paper strengthening mixture, which is an aqueous solution of chitosan and citric acid obtained by diluting the concentrate according to patent PL237344.

[0007] The concentrate is obtained by diluting citric acid in water in such an amount that its percentage concentration is 10%, followed by adding such an amount of chitosan that its percentage concentration is 2% and sodium benzoate, in such an amount that its percentage concentration is between 0.001% and 30%. The dissolution of chitosan is a lengthy process and can be accelerated by heating the solution. After appropriate dilution of the concentrate, a solution is obtained in which chitosan concentration is at least 0.1 %, with the citric acid concentration of at least 0.5 % and the sodium benzoate concentration of at least 0.001 %. In the paper strengthening process, the solution is dosed at the ratio of at least 1 / 2 litre of solution per 1 kilogram of dry paper according to the patent.

[0008] The essence of the invention is that sodium benzoate is additionally added in the amount of 0.001% to 30% to the concentrate prepared according to patent PL237344 as a preservative.

Claims

Patent claims1. A method of improving strength properties of paper, where to strengthen paper an aqueous solution of chitosan and citric acid is used with the percentage concentration of chitosan in the solution of at least 0,1% and the percentage concentration of citric acid in the solution of at least 0,5%, where the solution is used in the paper strengthening process by adding it to the pulp in the ratio of at least % litre of the solution per 1 kg of dry paper according to patent PL237344, characteristic in that sodium benzoate is added to the concentrate in the amount of 0.001% to 30% as a preservative.

2. A method according to claim 1, characteristic in that the solution used in the strengthening process, obtained by diluting the concentrate, contains citric acid - with the concentration of at least 0,5%, chitosan with the concentration of at least 0,1% and sodium benzoate with the concentration of at least 0,001%

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