Application of nanotechnology in the wet end of papermaking

Abstract This paper briefly introduces the concepts of nanotechnology and papermaking wet-end chemistry, and the application of anionic colloidal silica (ACS) to generate nano-silica particles in the wet end of a paper machine and its practical results in high-speed paper machine production. .

Key words nanotechnology papermaking wet end chemistry anionic colloidal silica (ACS) silica nanoparticles cationic polymers

nanotechnology

The nanometer (code nm) is a small unit of length equal to one billionth of a meter, one-thousandths of a micrometer (μm), and a hair of about 10,000 nm in diameter. Scientific research has found that when the material structure unit is as small as 0.1 to 100 nm, the properties of many material materials are often surprisingly changed, so that the products of the micro structure have special application prospects. This has given rise to a new field in modern science and technology, namely, nanotechnology, a technology that studies the characteristics and applications of micro-structure materials below 100 nm. Some people think that nanotechnology has a promising future. It will be one of the priorities of the development of science and technology in the 21st century, and it may bring about a technological revolution and industrial revolution. This is worthy of attention of all industries.

Paper wet-end chemistry

The slurry entering the paper machine, in addition to the pulp fibers, often also contains a variety of fillers (eg, clay, talc, calcium carbonate, titanium dioxide, etc.), a variety of functional additives (such as sizing agent, retention aids, dry Wet enhancer) and chemical process aids. These components are blended according to the ratio of certain fiber raw materials and paper types needed to be produced. They are mixed into ingredients and suspended in production water. Water can be said to be in the ingredients. Another important component, but also a medium in the chemistry of all papermaking ingredients. In addition, impurities introduced into the water for production and impurities that are not part of the raw material production process of the fiber raw material may also enter the ingredients. Due to differences in molecular composition, morphological structure, charge properties and size, hydrophilicity and hydrophobicity, etc., these different components can generate flocculation, agglomeration, adsorption, neutralization, and colloidal ion formation ( Micella) and other complex effects, and these effects have important impacts on papermaking production process efficiency, paper quality and production cost, which cause papermakers to pay attention and in-depth study, this is the "paper wet end chemistry" Research areas.

From the general minimum specifications of the components of papermaking ingredients (except water), except for the fact that the fiber width is larger than 10-20 μm, the filler particles are generally 0.1-10 μm, and the remaining microfibers, non-fibrous fine substances, and soluble aggregates The particle size of the material is less than 1-2μm, and its specific surface area is about 0.6-600m2/g. Therefore, the overall surface is in a colloidal state. The interaction between the surface and the colloid plays an important role. It is also a surface and colloid chemistry.

Because the structure of many components in the papermaking wet ingredients is very small, the introduction of nano-components with special effects to exert the role of nano-technology and further improve the papermaking effect should be an inevitable trend in the development of papermaking wet-end chemistry.

Formation, Behavior and Effect of Nano-sized Silica Particles in the Wet-end of Paper Machine

According to the latest foreign data reports: In the ingredients of the modern high-speed paper machine wet section, a new generation of anionic colloidal silica (hereinafter referred to as ACS) and cationic polymers, such as cationic starch (C-starch) and cationic polycations are cited. When acrylamide (CPAM) is used in common, silicon oxide nanoparticles with a particle size of 3-5 nm and a specific surface area of ​​500-1000 m2/g can be produced in the wet part dosing system. Fine components, thereby improving the slurry structure and reduce the loss of fine components, to improve the operation of the paper machine and the formation of the paper, reduce the amount of additives in the slurry, can produce a very significant effect (see the figure). The following 3 cases are some comparisons of high-speed paper machine applications and the absence of ACS additives (ie, presence of nanoscale SiO2 particles).

Example 1 Forming machine for paper machine on the Internet: Scraper

Running speed: 1000m/min

Production varieties: 100-250g/m2 corrugated paper.

Slurry: 50% mixed waste paper + 50% OCC.

Wet condition: closed, pH 6-7, COD 25000ms/cm. Conductivity 11000ms/cm, Ca2+5000mg/L.

The effect of the operation is shown in Table 1.

Table 1



Compare items 0.1% CPAM+
0.1% PEI (without ACS
Control system
0.06% PAMT+
0.05% ACS
(There is nanometer SiO2 difference (%)
White water solids (g/L)
Filler retention (%)
Run Stability Paper Formation Strength 11.5
40


9.5
70


-17
+75
Significant improvement in uniformity improves paper strength

In this example, all waste paper was used as the raw material, and the wet part was completely closed and circulated. The COD in white water was as high as 25000 mg/L, and the Ca2+ content was as high as 5000 mg/L. However, after the ACS was used, the uniformity of the paper and the cleanliness were good. Min Good running at high speeds. It has important reference value for enterprises that use waste paper materials and close the water cycle of the wet department.

Example 2 The paper machine on-line forming machine: roller and scraper type clamp net.

Operating speed: 1460-1530m/min.

Production varieties: 40-48g/m2 newsprint.

Slurry: 100% deinked old newsprint and printing paper.

Wet state: pH 7.2, Ca 2+ 50 mg/L, conductivity 1500 ms/cm. The operating effect is shown in Table 2.

Table 2



Compare items 0.04% CPAM+
0.1% PEI (without ACS
Control system) 0.02% PAMT+
0.25% ACS
(including nano-SiO2) difference (%)
Speed ​​(m/min)
Paper ash content (%)
Filler margin (%)
Paper sheet opacity (%)
Whiteness %, ISO)
Number of wet paper breaks (times/d) 1460
4-4.5
20
90
57
4-81530
6.5-8
30-35
95
60
0-1+4.8
+45-100
+50-75
+16
+5.3
-75-100

Example 3: Paper machine on-line forming machine: Roller and scraper type clamp net.

Operating speed: 1250m/min.

Production varieties: uncoated 60-120g/m2 high-grade printing paper.

Slurry: 100% tropical mixed hardwood bleached chemical pulp plus 20% GCC (heavy calcium carbonate).

Wet state: pH 7.5, Ca 2+ 30 mg/L, conductivity 800 ms/cm.

The operating effect is shown in Table 3.

table 3



Compare items 0.05% CPAM+
1%C-starch+
0.15%-0.2%
Montnotilsniter
(Control system without ACS) 0.03% CPAM
+1%starch+
0.35% ACS
(with nano-SiO2 system) difference (%)
Sheet formation (kajjan)
Filler retention (%)
Starch content in water (mg/L)
CPAM usage (%)
Change variety and broke paper

Whiteness control 70
40
80
0.05

89
55
30
0.03

+27
+38
-62
-40

Easier


Outlook

From the above three cases, it can be seen that when using ACS to produce nano-scale SiO2 particles in the wet end of the paper machine, different ingredients are used for the high-speed paper machine. When the same product is produced, the stability, paper quality, and consumption are reduced. The obvious benefits.

However, it should be noted that the quality, amount of addition, sequence and location of various additives must be based on the basic theoretical principles of the paper machine wet-end chemistry careful research and necessary tests in order to achieve better results.

In recent years, several high-speed paper machines imported from abroad in recent years have been operating very well. In addition to the excellent performance of the paper machines and better quality of training and management personnel, they have generally adopted the recommendations of paper machine suppliers. Wet end additive. The highly effective ACS is worthy of analysis and research by companies and scientific research departments and is automatically developed to expand its application in the wet chemical field of papermaking.
references

1 Simonson P., S. Main. Tappi Journal, 1999, 82(4): 78

2 Dave Lovell, Patrik Simonsson. Pimas Asia Pacific Paper Maker, 2001, 11(3): 17-21

3 Translated by Cao Bangwei. The latest papermaking process (Chapter 7). Light Industry Press, 1999