KR100496704B1 - Process for the production of paper using cationic starch - Google Patents

Abstract

The present invention relates to a paper production method using cationic starch. Specifically, the process consists of dispersing the filler using white water or adding fine fibers to the filler diluted with fresh water, followed by adding cationic starch to preaggregate the filler, and adding the preaggregated filler to the paper. It relates to a paper manufacturing method. The paper manufacturing method of the present invention has the effect of reducing expensive pulp resources by increasing the ash content in the paper through not only improving the paper strength but also improving the retention of the filler.

Description

Process for the production of paper using cationic starch

The present invention relates to a paper manufacturing method that can improve the filler retention of the paper to increase the ash content without deteriorating the physical properties of the paper.

Retention degree is the ratio of pulp, fine fibers, fillers, and various chemicals contained in paper stock remaining on the wire to make paper, which is directly related to the economics of the papermaking process.

The fillers used in paper making are calcium carbonate, clay, talc, titanium dioxide, and up to 40% of the paper. Fillers improve the paper's opacity, whiteness, smoothness, printability, etc., and are cheaper than pulp, resulting in greater cost savings. However, when the amount of filler in the paper is increased in a general papermaking process, the retention of paper is lowered, and the paper workability is lowered. Therefore, there is an urgent need for a technique that can increase the amount of filler added without deteriorating the physical properties of paper.

Recently, research on filler preflocculation has been conducted as a technique to effectively hold a filler. Filler preaggregation refers to agglomerating fillers using cationic polymers before they are introduced into the pulp slurry to make them effective in retention. The size of the general filler is very fine to 0.5 ~ 10 ㎛ and difficult to hold on paper by the filter mechanism, it can be made easy to hold by increasing to 10 ~ 60 ㎛ by preaggregation technology.

The preaggregation technique reported in US Pat. No. 4,799,964 is to add a filler such as clay, calcium carbonate and titanium dioxide, and a cationic starch into a pulp slurry using a mixer specially designed to impart shear force. However, there is a disadvantage that a specially manufactured (Shear imparting device) must be used for the application of this technique. In addition, US patent 4,889,594, unlike the general pre-agglomeration technology, artificially prepared pulp fine powder and mixed with the filler, and then carried out coflocculation to aggregate the filler using a synthetic polymer. In this patent, similar to US Patent No. 4,799,964, a device suitable for preaggregation was designed and tested. Although various synthetic polymers were used as flocculants, cationic starch was not applied to precoagulation. Cationic starch was added to the pulp slurry in a general manner. . The technique reported in US Pat. No. 5,779,859 is to improve the retention by increasing the particle size of the filler by mixing the filler used in the process into the filler line, without directly adding the filler dispersed in fresh water to the pulp slurry.

In the present invention, a preaggregation technique of a filler using cationic starch, which is known to be effective for improving the strength of paper, has been developed. The filler is agglomerated to an appropriate size and directly applied to a papermaking process without any separate equipment as in US Pat. Nos. 4,799,964 and 4,889,594. can do. In addition, by using cationic starch, not only the retention of the filler can be improved, but also the strength of the paper can be improved, and the microfibers or the long fibers present in the process can be used to facilitate the aggregation of the fillers and harden them not to be broken by the shear force.

SUMMARY OF THE INVENTION An object of the present invention is to provide a paper manufacturing method that can reduce the cost of pulp resources by improving the retention of the filler to increase the amount of use thereof.

Another object of the present invention is to provide a paper manufacturing method that can improve the strength of paper in addition to improving retention.

The present invention provides a paper manufacturing method of increasing the ash content of paper without deteriorating the physical properties of the paper by injecting fillers such as calcium carbonate, titanium dioxide, clay and the like pre-aggregated to the pulp fibers using cationic starch.

Specifically, the present invention is to disperse the filler using the process white water or to add a fine fiber or long fiber to the filler diluted with fresh water and then add a cationic starch having a substitution degree of 0.04 ~ 0.4, preferably 0.1 ~ 0.3 The filler is preaggregated, and the preaggregated filler is added to the stock containing pulp, and the obtained suspension is dehydrated on a wire and press dewatered by press.

The preaggregation according to the invention consists of a mixture of cationic starch, process white water (or fresh water containing microfibers) and fillers. The term 'preaggregation' means aggregating the filler first before adding it to the stock containing pulp.

In the present invention, the 'material' refers to a mixture in the form of a slurry obtained by adding a retention agent, an intensifier, an internal additive size agent, etc., if necessary for the pulp or pulp.

'Process white water' refers to the process of dehydrating a suspension containing pulp on a wire and pressing and dehydrating it by pressing in a paper manufacturing process, and means that fine fibers or long fibers are included.

In the present invention, when the process white water is used to disperse the filler, not only the ash content in the paper can be increased but also the bond strength of the paper can be improved and the water can be saved.

When the process white water is not used in the present invention, dissociated microfibers or long fibers may be added to the filler slurry diluted with fresh water to improve the coagulation effect of the filler. The amount of microfibers or long fibers added in the preparation of the filler slurry is preferably 0.05 to 5% by weight relative to the filler.

'Clean water' refers to industrial water (water), which is commonly used in factories, and 'fine fiber or long fiber' refers to cellulose fibrous material derived from pulp. The fine fiber refers to pulp fibers of 76 um or less in length. Fibers larger than that are classified into long fibers.

In the present invention, the mixing ratio of the filler and the white water is 75:25 to 1:99 (w / w), preferably 50:50 to 20:80.

Cationic starch in the present invention can be prepared by treating a cationic agent such as corn starch, potato starch, tapioca starch, wheat starch, sweet potato starch, and the like in the art, for example, the method described in US Patent 4127563 Can be obtained according to. The cationizing agent refers to a substance having one end of a molecule capable of binding to a hydroxyl group on a starch molecule, and the other end having a cationic group, and a derivative containing a third amino group and a fourth ammonium ether group. And, quaternary ammonium-based amphoterics such as 3-chloro-2-hydroxytrimethylammonium chloride and 2,3-epoxypropyltrimethylammonium chloride are most preferred.

In preparing the paper, the ratio of the filler to the cationic starch is 99.9: 0.1 to 90:10 (w / w), and preferably, the cationic starch is added in an amount of 0.1 to 3% by weight relative to the filler. If the starch content is lower than 0.1% by weight compared to the filler, the efficiency of preaggregation decreases and the retention improvement or strength cannot be expected.If the starch content is more than 10% by weight, the production cost of paper is increased and cohesion is too high. There are disadvantages.

Preferred filler pre-aggregation sequence according to the present invention is to disperse the filler to 10 to 60% by weight with white water containing microfibers, add cationic starch to the dispersed filler reservoir, and then pre-aggregate the filler into the stock. . The input location of the preaggregated filler may be added to high density stocks such as mixing chests or stuff boxes or low density stocks at the inlet or outlet of the fan pump.

When the preaggregated filler is added to the stock, the ash retention of the paper is improved and the strength is excellent. Therefore, this technology means that it is easy to increase the ash content in the paper mill, and it is expected to increase the efficiency of cationic chemicals because it has the effect of reducing not only the ash unit but also the fines in the white water. It is expected to be advantageous for the production of high ash paper.

In the present invention, the production of papers is appropriately combined with the filler (talc, calcium carbonate, titanium dioxide, etc.) pre-aggregated to 0.5 to 5% pulp, which dissociates or breaks down the regenerated fibers derived from the chemical pulp or paper used for the paper. After that, if necessary, the strength enhancer, the internal additive size, and the like were added and diluted to 0.2-1.5% using white water of the process, followed by injection from the head box, dehydration on a wire, compression and dehydration by pressing, and drying. The present invention can be applied to paper such as printing paper, newspaper paper, liner paper, and cardboard.

Papermaking and property evaluation

In the present invention, the papermaking was performed using a vacuum dehydration papermaking machine FRET (Techpap, France), and the procedure was performed as shown in Table 1.

Time in seconds Stirring Speed (rpm) Drug addition 0 800 pulp 10 800 Filler addition 20 800 Add 0.18% of cationic PAM (holding agent) 30 1200 Increased stirring speed 40 800 0.25% silica sol (holding agent) added 55 800 water plant

In the present invention, the retention degree was measured using a Dynamic Draingage Jar (DDJ), and the internal bond strength was evaluated using a Scott Bond Tester (Scott Bond Tester, Precision Scientific, USA), and the ash content was based on the TAPPI method T211. Measured.

In the present invention, the ratio or% means weight ratio or weight% unless specifically limited.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following examples are illustrative of the present invention, and the content of the present invention is not limited by the examples.

Example 1

Four cationic starches were prepared for each degree of substitution to determine the effect of the degree of substitution of cationic starch on the ash retention of paper. Among these, three types of cationic starch (CS1, CS2, CS3) were used as fillers. Was preaggregated and then added to the stock to prepare a paper. Dispersion of fillers during paper production was performed using fresh water, and the stock composition was composed of hardened hardwood pulp (LBKP, Yeosu 400 mlCSF) and 20% calcium carbonate was added as a filler. As the retention agent, cationic PAM (polyacrylamide) and silica sol were added 0.18% and 0.25%, respectively.

Cationic starch was added to the corn starch as calcium hydroxide as a reaction catalyst, mixed with a cationic agent at 20% moisture condition for 10 minutes using a high speed mixer and aged for 3 days at 25 ℃. To prepare CS1, 0.48 g of calcium hydroxide was added to 200 g of corn starch, 10.94 g of water was added for moisture control, and 7.0 g (based on 100% solids) of a cationic agent. CS2, CS3 and CS4 are the same as CS1, with 200 g of corn starch in 0.96, 3.60 and 4.80 g in calcium, 9.95, 4.52 and 2.06 g in water and 14.05 and 52.67 in cationic agent (based on 100% solids), respectively. And 70.23 g were added. The degree of substitution of the finished product was analyzed using the Kjeldahl method.

The ash content in the paper and the physical properties of the paper were measured, and the results are shown in Table 2. Through filler preaggregation using cationic starch, the ash content in the paper was improved by 2% or more without decreasing the strength. It was more effective especially when cationic starch having substitution degree of 0.08 or more was applied.

Starch Degree of substitution Starch addition amount (%) Microdispersity (%) Ash content (%) Internal bond strength Blank - - 41.5 12.1 75.7 CS1 0.04 1.0 42.5 14.2 75.3 2.0 43.3 15.0 78.7 3.0 50.8 15.6 83.3 CS2 0.08 1.0 45.0 14.4 77.1 2.0 49.6 15.7 78.0 3.0 70.0 16.6 103.7 CS3 0.30 0.25 42.2 14.9 77.7 0.50 45.8 14.5 78.9 0.75 47.9 14.7 79.7

Example 2

In paper production, in order to grasp the effect of using white water on the strength and retention of paper, comparative experiments were conducted using fresh water and white water.

Filler preaggregation was performed using cationic starch CS3 and CS4 prepared in Example 1, respectively. The dispersion of the filler was dispersed at 30% (marked) using white water and fresh water of the papermaking process containing fine fibers. Cationic starch was added 0.5% of CS3 of Example 1 compared to the filler. The stock was used by diluting the mixing chest stock with white water before chemicals were added at the paper mill. The filler was added 20% calcium carbonate compared to the stock.

The results are shown in Table 3. It was found that the improvement of the strength and retention of paper was superior to that of fresh water when the process white water was used for preaggregation of the filler.

Starch water Ash content (%) Internal bond strength Blank clear water 17.1 108.0 CS3 (0.3 degree of substitution) clear water 18.8 116.710 Process white number6.79 19.359.88 120.3100.7 CS4 (degree of substitution 0.4) 15 Process White Number9.79 19.554.94 118.485.6

Example 3

In preparing paper, ash content and retention in the product were measured according to the concentration of filler. The stock was used as hardened pulp (LBSK, Yeosu 400 ml CSF), and calcium carbonate was used as a filler. The preparation of the filler was dispersed to 30% using the process white water, the amount of filler was adjusted to 0 ~ 30% compared to the stock, 0.5% of the cationic starch CS3 was added to the filler.

As shown in Table 4, when the filler was preaggregated with cationic starch and added to the stock, the ash retention was more than 20% higher than the average addition condition. Was higher. Nevertheless, the strength of the paper was found to be somewhat superior.

Starch Filler (%) Ash content (%) Ash retention (%) Internal bond strength Blank 0 0.18 - 115.2 General charging 10 6.79 59.88 100.7 15 9.79 54.94 85.6 20 12.35 52.08 82.5 25 14.94 48.76 79.0 30 16.86 42.00 75.00 CS3 10 8.27 75.63 101.4 15 12.95 77.70 90.7 20 16.42 75.23 88.0 25 19.23 73.41 81.3 30 25.52 75.80 74.2

In the paper manufacturing method according to the present invention, by adding a process white water containing cationic starch and microfibers, the preaggregated filler is added to the paper, thereby not only improving the paper strength but also increasing the ash content in the paper by improving the filler retention. This can reduce the cost of expensive pulp resources.

Claims (2)

Dispersing the filler using process white water containing fine fibers or adding fine fibers or long fibers to the filler diluted with fresh water and pre-aggregate the filler by adding a cationic starch having a substitution degree of 0.04 to 0.4, The pre-aggregated filler is added to a paper containing pulp. The method of claim 1 wherein the ratio of filler to cationic starch is 99.9: 0.1 to 90:10 (w / w).