CN101962921A - Method for improving efficiency of fluorescent whitening agent in high yield pulp-containing paper - Google Patents

Abstract

The invention discloses a method for improving the efficiency of fluorescent whitening agent in high-yield pulp and paper. The polyacrylamide aqueous solution and the cationic starch aqueous solution are mixed evenly, and the sheets are sheeted on a standard sheet machine, squeezed by a press, and transferred to constant temperature and humidity for 24 hours; In terms of efficiency, after adding cationic starch, especially after adding 0.8%-1.2% cationic starch, relative to the control without adding cationic starch, the D65 whiteness increased by 0.5-0.7 units, and the CIE whiteness increased by 2- 3 units, fluorescence content increased by 1%. The method of the invention has simple process, low production cost and strong compatibility with wet end chemicals.

Description

A method for improving the efficiency of fluorescent whitening agent in high-yield pulp and paper

technical field

The invention belongs to the technical field of pulping and papermaking engineering, and in particular relates to a method for improving the efficiency of fluorescent whitening agents in high-yield pulp and paper.

Background technique

High-yield pulp, namely bleached chemical thermomechanical pulp (BCTMP), with its high yield and less pollution in the manufacturing process, can provide many functional advantages to paper, such as high bulk, high stiffness, and good printability etc. In recent years, it has been widely used in various paper and cardboard. However, compared with bleached kraft pulp, high-yield pulp has a certain yellow hue due to the presence of lignin and other colored substances, and the whiteness of pulp is relatively low. Improvement has received extensive attention from industry and research. Fluorescent whitening agent can absorb ultraviolet light with a wavelength of 300-400nm, which is invisible to the naked eye. After excitation, it can emit blue-violet fluorescence with a wavelength of 420-480nm that is visible to the naked eye. Complementary, at the same time, it can enhance the light sensitivity of total reflected light, thereby increasing the whiteness of paper, and is widely used in the wet end of papermaking to improve the whiteness of finished paper. However, during the chemical addition process in the wet end, the interaction between the fluorescent whitening agent and the cationic additive will cause the fluorescent whitening agent to produce a extinguishing effect and reduce its efficiency; The existence of will also reduce the efficiency of fluorescent whitening agent. For example, if 20% of high-yield pulp is added, the amount of fluorescent whitening agent will increase by about 50% compared with that without high-yield pulp. Therefore, the improvement of the efficiency of fluorescent whitening agent in high-yield pulp is extremely important. The improvement of the efficiency of fluorescent whitening agent can not only reduce the amount of fluorescent whitening agent, thereby reducing the content of anionic garbage in the entire papermaking system, saving the amount of cationic polymer added; Green dot effect, improve the printability of the finished paper. Therefore, the improvement of the efficiency of fluorescent whitening agent will play a positive role in the control of the chemical production cost of the whole wet end and the improvement of the paper quality.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies in the prior art, and provide a method for improving the efficiency of fluorescent whitening agents in high-yield pulp and paper materials with simple operation and standardized processes.

Technical scheme of the present invention is summarized as follows:

A method for improving the efficiency of fluorescent whitening agents in high-yield pulp and paper, comprising the steps of:

Measure the mixed slurry, stir it mechanically, add the fluorescent whitening agent aqueous solution with a mass concentration of 0.1%-1.2%, the light calcium carbonate aqueous solution with a mass concentration of 10%-30%, and the mass concentration of calcium carbonate at a time interval of 10-60s. 0.02%-0.1% cationic polyacrylamide aqueous solution and a cationic starch aqueous solution with a mass concentration of 5%-20% and then gelatinized at 90°C for 30 minutes, diluted with water to a mass concentration of 0.2%-2.0%, and mixed Uniformly, slice on a standard slicer, squeeze with a press, and transfer to constant temperature and humidity for 24 hours; the dry weight ratio of the mixed slurry to fluorescent whitening agent, light calcium carbonate, cationic polyacrylamide and cationic starch It is 1: 0.1%-1.2%: 10%-30%: 0.02%-0.1%: 0.2%-2.0%; the mixed slurry is composed of the following raw materials by mass percentage: beating in the PFI mill to the Canadian standard free 10%-50% softwood bleached kraft pulp with a density of 500-560mL, 20%-65% hardwood bleached kraft pulp beaten to a Canadian standard freeness of 300-500mL in a PFI mill, and a standard deflaker The 10%-50% high-yield pulp is decomposed to a freeness of 250-400mL, and the fluorescent whitening agent is a disulfonic acid type fluorescent whitening agent.

The method of the present invention can improve the efficiency of fluorescent whitening agent in high-yield pulp and paper. After adding cationic starch, especially after adding 0.8%-1.2% cationic starch, compared with the control sample without adding cationic starch, D65 The whiteness increased by 0.5-0.7 units, the CIE whiteness increased by 2-3 units, and the fluorescence content increased by 1%.

The method of the invention has simple process, low production cost and strong compatibility with wet end chemicals.

Detailed ways

The present invention will be more readily and more fully understood by reference to the following examples, which are given to illustrate the invention and not to limit it in any way.

Example 1

A method for improving the efficiency of fluorescent whitening agents in high-yield pulp and paper, comprising the steps of:

Measure the mixed slurry equivalent to 1.2g of absolute dry pulp, stir mechanically, and add successively 0.2% fluorescent whitening agent aqueous solution, 30% light calcium carbonate aqueous solution and 30% mass concentration at the time interval of 30s. 0.05% cationic polyacrylamide aqueous solution and cationic starch aqueous solution with a mass concentration of 10% and then gelatinized at 90°C for 30 minutes, diluted with water to a mass concentration of 0.2% cationic starch aqueous solution, mixed evenly, and sliced on a standard slicer. Squeeze with a press, transfer to constant temperature and humidity to dry for 24 hours; use an Elrepho spectrophotometer to measure the optical properties of the paper sheet. The dry weight ratio of the mixed slurry to the fluorescent whitening agent, light calcium carbonate, cationic polyacrylamide and cationic starch is 1: 0.2%: 30%: 0.05%: 0.2%;

The mixed pulp is composed of the following raw materials in terms of mass percentage: 35% softwood bleached kraft pulp beaten to a Canadian standard freeness of 560mL in a PFI mill, 55% softwood bleached kraft pulp beaten to a Canadian standard freeness of 500mL in a PFI mill Leaf wood bleached kraft pulp and 10% high-yield pulp with a freeness of 325 mL in a standard deflaker. The fluorescent whitening agent in this embodiment is a disulfonic acid type fluorescent whitening agent.

Using the same method as in Example 1, the ratio of mixed slurry to cationic starch dry weight is 1: 0.4%, 1: 0.8%, 1: 1.2% and 1: 2.0% to prepare the corresponding aqueous solution instead of mixing The dry weight ratio of slurry to cationic starch is 1: 0.2%, other materials and proportioning are the same as in Example 1, and sheet making, pressing, drying and performance measurement are carried out under the same conditions;

Using the same method as above, taking no cationic starch aqueous solution as a blank, carry out tablet making, pressing, drying and performance measurement under the same conditions.

The improvement effect of cationic starch on the efficiency of fluorescent whitening agent for high-yield pulp and paper materials is shown in Table 1. With the increase of cationic starch dosage, the D65 whiteness, CIE whiteness and fluorescence content of the paper are all on the rise. Under 10% high-yield pulp content, 0.2% fluorescent whitening agent dosage, D65 whiteness increased from 92.0% (no cationic starch added) to 92.7% (2.0% cationic starch); CIE whiteness increased by 2.7 units, fluorescence content increased by 1%.

Table 1 The amount of cationic starch on the improvement of the efficiency of optical brighteners in high-yield pulp and paper (10% high-yield pulp)

Example 2

A method for improving the efficiency of fluorescent whitening agent in high-yield pulp and paper, using 20% high-yield pulp to replace 10% of high-yield pulp in Example 1 (freeness is the same as in Example 1); 45% hardwood bleached kraft pulp replaces 55% hardwood bleached kraft pulp (freeness is the same as embodiment 1) in embodiment 1, and other is with embodiment 1;

See Table 2 for the effect of cationic starch on the efficiency of optical brighteners containing high-yield pulp and paper materials. Under 20% high-yield pulp content, 0.2% optical brightener dosage, D65 whiteness from 90.4% (without cationic starch Addition) increased to 91.2% (2.0% cationic starch); CIE whiteness increased by 2.2 units, fluorescence content increased by 0.9%.

The fluorescent whitening agent in this embodiment is a disulfonic acid type fluorescent whitening agent.

Table 2 Cationic starch content on the improvement of the efficiency of optical brighteners in high-yield pulp and paper (20% high-yield pulp)

Note: The content of high-yield pulp is 20%, the content of softwood bleached kraft pulp is 35%, and the content of hardwood bleached kraft pulp is 45%. The amount of fluorescent whitening agent is 0.2%, the amount of light calcium carbonate is 30%, and the amount of cationic polyacrylamide is 0.05%.

Example 3 Effects of different optical brightener additions on the efficiency of optical brighteners containing high-yield pulp and paper materials

Measure the mixed slurry equivalent to 1.2g of absolute dry pulp, stir mechanically, and add successively 0.2% fluorescent whitening agent aqueous solution, 30% light calcium carbonate aqueous solution and 30% mass concentration at the time interval of 30s. 0.05% cationic polyacrylamide aqueous solution and cationic starch aqueous solution with a mass concentration of 10% and then gelatinized at 90°C for 30 minutes, diluted with water to a mass concentration of 1.2%, mixed evenly, and sliced on a standard slicer. Squeeze with a press, transfer to constant temperature and humidity to dry for 24 hours; use an Elrepho spectrophotometer to measure the optical properties of the paper sheet. The dry weight ratio of the mixed slurry to the fluorescent whitening agent, light calcium carbonate, cationic polyacrylamide and cationic starch is 1: 0.2%: 30%: 0.05%: 1.2%;

The mixed slurry is composed of the following raw materials by mass percentage: 35% softwood bleached kraft pulp beaten in a PFI mill to a Canadian standard freeness of 560mL, 55% beaten in a PFI mill to a Canadian standard freeness of 500mL hardwood bleached kraft pulp and 10% high-yield pulp deflapped to a freeness of 325 mL in a standard deflaker.

Using the same method as in this example, the ratio of mixed slurry to fluorescent whitening agent by dry weight is 1: 0.4%, 1: 0.8%, and 1: 1.2% to prepare corresponding aqueous solutions to replace 0.2% fluorescent light. Brightener aqueous solution, under the same conditions for sheeting, pressing, drying and performance measurement;

Using the same method as above, the aqueous solution without fluorescent whitening agent is used as a blank, and the tablet making, pressing, drying and performance measurement are carried out under the same conditions.

The effect of cationic starch on the efficiency of fluorescent whitening agent for high-yield pulp and paper materials is shown in Table 3. Under the dosage of 0.2%-1.2% fluorescent whitening agent, cationic starch can effectively improve the efficiency of fluorescent whitening agent. That is to say, the paper added with cationic starch has higher D65 whiteness, CIE whiteness and fluorescence content.

The fluorescent whitening agent in this embodiment is a disulfonic acid type fluorescent whitening agent.

Table 3 The amount of fluorescent whitening agent on the improvement of the efficiency of fluorescent whitening agent in high-yield pulp and paper (10% high-yield pulp)

Note: The content of high-yield pulp is 10%, the content of softwood bleached kraft pulp is 35%, and the content of hardwood bleached kraft pulp is 55%. The amount of light calcium carbonate is 30%, the amount of cationic polyacrylamide is 0.05%, and the amount of cationic starch is 1.2%.

Example 4 Effect of Cationic Starch on the Physical Properties of High Yield Pulp Sheets

Measure the mixed slurry equivalent to 1.2g of absolute dry pulp, stir mechanically, and add successively 0.2% fluorescent whitening agent aqueous solution, 30% light calcium carbonate aqueous solution and 30% mass concentration at the time interval of 30s. 0.05% cationic polyacrylamide aqueous solution and cationic starch aqueous solution with a mass concentration of 10% and then gelatinized at 90°C for 30 minutes, diluted with water to a mass concentration of 0.2% cationic starch aqueous solution, mixed evenly, and sliced on a standard slicer. Squeeze with a press, transfer to constant temperature and humidity drying for 24 hours; measure the optical properties and physical properties of the paper;

The dry weight ratio of the mixed slurry to the fluorescent whitening agent, light calcium carbonate, cationic polyacrylamide and cationic starch is 1: 0.2%: 30%: 0.05%: 0.2%;

The mixed pulp is composed of the following raw materials in terms of mass percentage: 35% softwood bleached kraft pulp beaten to a Canadian standard freeness of 560mL in a PFI mill, 55% softwood bleached kraft pulp beaten to a Canadian standard freeness of 500mL in a PFI mill Leaf wood bleached kraft pulp and 10% high yield pulp deflapped to a freeness of 325 mL in a standard deflaker.

Using the same method as in this example, the ratio of mixed slurry to cationic starch dry weight is 1: 0.4%, 1: 0.8%, 1: 1.2% and 1: 2.0% to prepare the corresponding aqueous solution instead of 0.2 % cationic starch aqueous solution, under the same conditions for sheeting, pressing, drying and performance measurement;

Using the same method as above, without adding cationic starch aqueous solution as a blank, under the same conditions, tablet making, pressing, drying and performance measurement were carried out, and the results are shown in Table 4. Cationic starch improves the tensile index and tensile energy absorption of the paper, improves the internal bond strength of the paper, and slightly reduces the tear index.

The fluorescent whitening agent in this embodiment is a disulfonic acid type fluorescent whitening agent.

The impact of table 4 cationic starch on paper physical properties (10% high yield pulp)

Example 5

A method for improving the efficiency of fluorescent whitening agents in high-yield pulp and paper, comprising the steps of:

Measure the mixed slurry equivalent to 1.2g of absolute dry pulp, stir mechanically, and add successively at a time interval of 10s a fluorescent whitening agent aqueous solution of 0.1%, a light calcium carbonate aqueous solution of 10% in a mass concentration, and a mass concentration of 10%. 0.1% cationic polyacrylamide aqueous solution and cationic starch aqueous solution with a mass concentration of 5% and then gelatinized at 90°C for 30 minutes, diluted with water to a mass concentration of 0.2% cationic starch aqueous solution, mixed evenly, and sliced on a standard slicer , squeezed by a press, transferred to constant temperature and humidity drying for 24h; the dry weight ratio of the mixed slurry to fluorescent whitening agent, light calcium carbonate, cationic polyacrylamide and cationic starch is 1: 0.1%: 10%: 0.1 %: 0.2%; the mixed slurry is made up of the following raw materials by mass percentage: beating in the PFI mill to the 50% softwood bleached kraft pulp of Canadian standard freeness 500mL, beating in the PFI mill to the Canadian standard freeness 30% hardwood bleached kraft pulp at 300 mL and 20% high yield pulp in a standard deflaker to a freeness of 250 mL.

The fluorescent whitening agent in this embodiment is tetrasulfonic acid type fluorescent whitening agent.

Experiments have proved that the method of the present embodiment can effectively improve the efficiency of the fluorescent whitening agent, and the D65 whiteness and CIE whiteness and fluorescence content of the paper have been effectively improved, and the internal combination of the paper produced by the method of the present invention Increased strength with slightly reduced tear index.

Example 6

A method for improving the efficiency of fluorescent whitening agents in high-yield pulp and paper, comprising the steps of:

Measure 1.2g of mixed slurry equivalent to absolute dry pulp, stir mechanically, and add successively 1.2% fluorescent whitening agent aqueous solution, 20% light calcium carbonate aqueous solution and 20% mass concentration at time interval of 60s. 0.02% cationic polyacrylamide aqueous solution and cationic starch aqueous solution with a mass concentration of 20% and then gelatinized at 90°C for 30 minutes, diluted with water to a mass concentration of 2.0% cationic starch aqueous solution, mixed evenly, and sliced on a standard slicer , pressed by a press, transferred to constant temperature and humidity drying for 24h; the dry weight ratio of the mixed slurry to fluorescent whitening agent, light calcium carbonate, cationic polyacrylamide and cationic starch is 1: 1.2%: 20%: 0.02 %: 2.0%; the mixed slurry is made up of the following raw materials by mass percentage: beating in the PFI mill to the 10% softwood bleached kraft pulp of Canadian standard freeness 530mL, beating in the PFI mill to the Canadian standard freeness 65% hardwood bleached kraft pulp at 400 mL and 25% high yield pulp in a standard deflaker to a freeness of 400 mL.

The fluorescent whitening agent in this embodiment is tetrasulfonic acid type fluorescent whitening agent.

Experiments have proved that the method of the present embodiment can effectively improve the efficiency of the fluorescent whitening agent, and the D65 whiteness and CIE whiteness and fluorescence content of the paper have been effectively improved, and the internal combination of the paper produced by the method of the present invention Increased strength with slightly reduced tear index.

Example 7

The mixed pulp is composed of the following raw materials in terms of mass percentage: 30% softwood bleached kraft pulp beaten in a PFI mill to a Canadian standard freeness of 530mL, 20% softwood bleached kraft pulp beaten in a PFI mill to a Canadian standard freeness of 400mL Bleached kraft pulp of leaf wood and 50% high-yield pulp with a freeness of 400 mL in a standard deflaker, the others are the same as in Example 1.

Experiments have proved that the method of the present embodiment can effectively improve the efficiency of the fluorescent whitening agent, and the D65 whiteness and CIE whiteness and fluorescence content of the paper have been effectively improved, and the internal combination of the paper produced by the method of the present invention Increased strength with slightly reduced tear index.

Light calcium carbonate (PCC), produced by U.S. Albacar HO company;

Disulfonic acid type fluorescent whitening agent, Tinopal HW, produced by Ciba;

Cationic polyacrylamide (CPAM), Perco1292, produced by Ciba;

Cationic starch, C253, degree of substitution 0.03, produced by Roquette.

Experiments have proved that the present invention that adopts other commercialized raw materials with the above-mentioned names can also produce the same effect as the various embodiments.

Claims (1)

1. A method for improving the efficiency of fluorescent whitening agent in high-yield pulp and paper, characterized in that it comprises the steps of: measuring mixed slurry, stirring mechanically, and adding a mass concentration of 0.1% in time intervals of 10-60s -1.2% fluorescent whitening agent aqueous solution, light calcium carbonate aqueous solution with a mass concentration of 10%-30%, cationic polyacrylamide aqueous solution with a mass concentration of 0.02%-0.1%, and a solution with a mass concentration of 5%-20 % Then gelatinize at 90°C for 30 minutes, dilute with water to a cationic starch aqueous solution with a mass concentration of 0.2%-2.0%, mix evenly, make tablets on a standard tablet machine, press with a press, and transfer to constant temperature and humidity for 24 hours; The dry weight ratio of the mixed slurry to the fluorescent whitening agent, light calcium carbonate, cationic polyacrylamide and cationic starch is 1: 0.1%-1.2%: 10%-30%: 0.02%-0.1%: 0.2% -2.0%; the mixed pulp is made up of the following raw materials by mass percentage: 10%-50% softwood bleached kraft pulp beaten in a PFI mill to a Canadian standard freeness of 500-560mL, beaten in a PFI mill 20%-65% hardwood bleached kraft pulp to a Canadian standard freeness of 300-500mL and 10%-50% high-yield pulp to a freeness of 250-400mL in a standard deflaker. The whitening agent is a disulfonic acid type fluorescent whitening agent. the