FI68283C - FOERFARANDE FOER PAPPERSTILLVERKNING - Google Patents

Description

Method for making paper 68283 Förfarande för papperstillverkning

The present invention relates generally to a process for making paper, and more particularly to a binder used in a papermaking process comprising a complex of cationic starch and colloidal silicic acid for producing paper having improved strength and other properties. In addition, such a binder provides greatly improved retention levels for both the added mineral materials and the fine fines of the fibers in the pulp. In addition, several features of the invention can be used to purify circulating water in papermaking.

10 There are currently a number of difficult problems in the paper industry. First, the price of cellulose-based pulp has risen sharply and the supply of high-quality pulp has gradually become more limited. Secondly, various problems, including those related to the removal of waste from papermaking and the ecological requirements imposed by different authorities, have substantially increased the cost of papermaking. Finally, the energy costs of papermaking have risen sharply. The result is that the industry and its customers are faced with two choices, namely that they either have to pay 20 higher costs or have to reduce the quantity and / or quality of cellulose-based fibers, in which case the quality of the finished paper product will also suffer.

Several attempts have been made in the industry to reduce the cost of paper products 25. The commonly used method is to add clay and other mineral-containing fillers to replace the fibers, but such additives have been shown to unsatisfactorily degrade the strength and other properties of the resulting paper. In addition, the addition of such mineral-containing fillers results in 30 poor filler retention, i. the filler passes through the wire to such an extent that the filler concentrations increase in the circulating water, making circulating water purification and material removal a real problem. Various binders have been used in 68283 experiments to alleviate the retention problem, but the effect of these binders has not been shown to be completely satisfactory.

Attempts have also been made to use pulp types which are cheaper and of inferior quality, but this of course leads to a deterioration in the properties of the paper and often to an excess of fine fibers which are not bound to the paper and which of course cause a circulating water purification problem.

It is therefore an object of the invention to provide a binder system and manufacturing method which improves the properties of the paper and which allows the use of a minimum amount of fibrous material to provide the necessary strength and other properties. Another object of the invention is to provide a binder system and a method using the same, wherein the system and method greatly improve the strength and other properties of paper compared to the strength and properties of similar paper made with known binders. Yet another object of the invention is to provide a binder and method for using the same, which binder or method maximizes the retention of mineral fillers and other materials in the prepared paper sheet when the binder is used in the grinding material entering the paper machine. Yet another object of the invention is to provide a paper having a high content of mineral filler and having acceptable strength and acceptable other properties. A final object of the invention is to provide a method for removing suspended solids from circulating water from a papermaking process.

Other objects and advantages of the invention will become apparent from the following description 35 and the accompanying drawings. The drawings show in Figure 1 a flow chart of a papermaking method utilizing various features of the invention. Figures 2 and 2A-2S show a diagram of a test run carried out in a paper machine according to Example 1 and the properties of the resulting paper, taking advantage of various features of the invention. Figure 3 shows a diagram graphically showing the results of Example 2. Figure 4 shows a flow chart of a papermaking process utilizing 68283 various features of the invention. Figure 5 shows a diagram of a test run performed on a paper machine, in which the manufacturing method took advantage of various features of the invention. Figure 6 shows a graph of the tensile index as a function of the amount of cationic starch added in one example of the papermaking process of the invention. Figure 7 shows a diagram of the settling rate of solids in a circulating water test and illustrates various features of the invention. Figures 8A-8G are diagrams graphically illustrating the results of Example 11.

The invention is based on a binder and a method of using the same, which binder or method greatly enhances the strength and other properties of the paper product and allows the use of substantial amounts of mineral fillers in the papermaking process while maximizing retention of filler and cellulose-based fibers in the sheet. The invention thus makes it possible to reduce the cellulosic fiber content in the paper sheet and / or to reduce the cellulosic fibrous quality in connection with a certain paper quality without unduly reducing the strength of the paper or deteriorating other properties of the paper. When the principles of the invention are utilized, the amount of mineral filler 20 can also be increased without unauthorized deterioration of the strength or other properties of the resulting paper product. By reducing the amount of pulp used to make a particular paper product or replacing the pulp as a mineral filler, the reduction in fiber content will also reduce the amount of energy required to make the pulp and the amount of energy required to dry the paper. In addition, it has been shown that the retention of the mineral filler and the finely divided material is high enough to minimize the circulating water problem.

It has also been found that the principles of the invention can be used to remove suspended fibers and mineral material in a circulating water system for papermaking.

Quite generally, the system of the invention comprises the steps of using a binder complex comprising two components, i.e. colloidal silicic acid and cationic starch. The weight ratio of cationic starch to SiO 2 in colloidal silicic acid is greater than 1 and less than about 25. Both components are passed to the pulp prior to the manufacture of the paper product in a paper machine. It has been shown that the paper has greatly improved strength properties after drying. When mineral fillers such as clay, chalk or the like are used in the grinding medium, it has also been shown that these mineral fillers remain effective on the paper and do not have the same detrimental effect on paper strength that can be observed when the binder system of the invention is not used.

10 Although the process that takes place in the grinding medium and paper formation and drying in the presence of a binder is not fully understood, it is assumed that cationic starch and anionic colloidal silicic acid form an agglomerate complex bound by anionic colloidal silicic acid and to the surface of a mineral filler that is either fully or partially anionic. The cationic starch is also incorporated into cellulose-based fibers and a fine-grained material, both of which are anionic. Upon drying, the joint between the agglomerate and the cellulosic fibers will produce 20 broad hydrogen bonds. This theory is supported in part by the fact that when the Z-potential of the anionic grinding material changes to zero when the binder complex of the invention is used, both the strength properties and the retention are improved. 1 2 3 4 5 6 7 8 9 10 11 s> '. * 1

It has also been found that the efficiency of the binder system when using 2 binder systems of the above type can be improved 3 by adding the colloidal silicic acid component in several 4 steps, i. first a portion of the colloidal silica is mixed with the pulp 5 and any mineral filler present, then 6 cationic starch is added and then, after the complex agglomerate 7 has formed from the pulp, any filler 8, part of the colloidal silicic acid into a grinding medium containing a complex 11 agglomerate. This approach of adding colloidal silica in two or more steps results in a certain improvement in paper strength and other properties, but the most obvious improvement 68283 is an increase in filler and fiber fines retention. Although the reason for these improvements has not been fully elucidated, it is assumed that they are the result of the development of complexes, agglomerates of filler, fibers and binder, which are more stable, i.

The final addition of colloidal silicic acid causes the initially formed agglomerates to be bonded together to form even more stable agglomerates that are less sensitive to mechanical forces and other forces in paper formation.

Based on the experiments and work done so far, it is assumed that the principles of the invention are applicable to the manufacture of all types and types of paper products such as printing paper grades, including newsprint, tissue paper, paperboard and the like.

15

It has been found that the greatest improvements are observed when the binder is applied to a chemical pulp, e.g. sulphate or sulphite pulp, made from both hardwood and softwood. Smaller but very significant improvements are obtained with thermomechanical and mechanical pulp. It has been found that the presence of excessive amounts of lignin in wood chips appears to affect the effectiveness of the binder, so that such pulps require either a higher amount of binder or additional blending of other low lignin pulp types to ensure the desired result (using the terms "cellulose" loose fibers "means chemical pulp, thermomechanical pulp and mechanical pulp, or wood chips and associated fibers).

The presence of cellulosic fibers is essential in order for the invention to provide improved results in cooperation or association between the agglomerate and the cellulosic fibers. Preferably, the finished paper should contain more than 50% cellulosic fibers, but paper with lower cellulosic fiber contents and greatly improved properties can be produced compared to paper made from similar grinding materials but without the binder agglomerate of the invention.

V

6,6283 Useful mineral fillers include any of the common mineral fillers that have at least partially anionic activity on the surface. Mineral fillers such as kaolin, bentonite, titanium oxide, chalk and talc can all be used with satisfactory results (the term "mineral filler" is used herein not only for the above materials but also for wollastonite and fiberglass as well as mineral-containing low density fillers). the binder complex shown, the mineral filler will remain in the paper product to a considerable extent, and the strength of the paper will not deteriorate to the same extent as when the binder is not used.

The mineral filler is usually added in the form of an aqueous slurry at the usual concentrations used with such fillers.

As mentioned above, the mineral filler in the paper may consist of a filler or contain a filler of low density or high mass. The ability to add such fillers to conventional paper milling materials is limited by factors such as retention of the filler on the wire, dewatering of the paper milling material on the wire, and the wet and dry strength of the finished paper product. It has now been found that the problems caused by the addition of such fillers can be prevented or mainly eliminated by using the binder complex according to the invention, which also allows higher amounts of fillers to be added than normally to obtain the special properties of the paper product. The binder complex according to the invention has thus made it possible to produce a paper product with low density and thus higher paper stiffness at the same basis weight 30, while maintaining or increasing the strength properties of the paper product (such as modulus of elasticity, tensile index, tensile strength and lifting resistance).

As already pointed out above, the binder consists of a combination of colloidal silicic acid 35 and cationic starch. The colloidal silicon pulp can take various forms, it can be e.g. polymeric silicic acid or a colloidal silicic acid sol, although the best results are obtained with the latter.

Polymeric silicic acid can be prepared by reacting water glass with sulfuric acid according to known methods to a molecular weight (calculated therein) of up to about 100,000. However, the resulting polymeric silicic acid is unstable and difficult to use and causes a problem, that the presence of sodium sulfate produces a corrosion problem and other problems in papermaking and circulating water removal. Sodium sulfate can be removed by ion exchange according to known methods, but the resulting polymeric silicic acid is unstable and without stabilization will deteriorate upon storage. Salt-free polymeric silicic acid can also be prepared by direct ion exchange of dilute water glass.

15

Although significant improvements in both strength and retention have been observed with a binder containing polymeric silicic acid and cationic starch, excellent results are obtained when cationic starch is used in combination with colloidal silicon-20 acid in the form of a sol containing about 2-60% by weight SiO preferably about 4-30% by weight SiO 2.

The specific surface area of the colloidal silicic acid in the sol is preferably n.

2 2 50-1000 m / g and especially about 200-1000 m / g, where the best results 2 25 have been found with a specific surface area of about 300-700 m / g. The silica sol is stabilized with alkali in a molar ratio of 10: 1 to 300: 1, preferably 15: 1 to 100: 1 (M is an ion from the group Na, K, Li and NH 4). It has been found that the size of the colloidal silica particles should be less than 20 nm and preferably the average particle size should be about 10-1 nm (the colloidal silica particle having a specific surface area of about 550 m / g corresponds to an average particle size of about 5.5 nm).

Preferably, it is best to try to use a silica sol with colloidal silica particles having a maximum active surface area and a well-defined small particle size of 4-9 nm at an average of 35.

Silica sols that meet the above properties are available on the market from various manufacturers, e.g., Nalco Chemical Company, Du Pont &

Nemours Corporation and EKA AB.

The cationic starch used in the binder may be made from starches derived from any conventional starch-producing materials, e.g. The best results are obtained when the degree of substitution (d.s.) is from about 0.01 to about 0.05, and preferably from about 0.2 to about 0.04, and especially above about 0.025 to less than about 0.04. Although several ammonium compounds, preferably quaternary, are used in the preparation of cationic starches for the binder of the invention, it is preferred to use cationic activated starch prepared by treating the starting starch with 3-chloro-2-hydroxypropyltrimethyl-dichloromethyltrimethylammonium chloride to produce cationic activated starch having a degree of substitution of 0.02 to 0.04.

20 In a papermaking process, a binder is added prior to forming the paper product in a paper machine. The two ingredients, the colloidal silicic acid component and the cationic starch can be mixed together to form an aqueous slurry of a binder complex of silicic acid and cationic starch, which slurry is then adjusted and mixed thoroughly with the grinding medium. However, this method does not produce maximum results. Preferably, a complex of silicic acid and cationic starch is formed in situ in the grinding medium. This can be accomplished by adding the colloidal silicic acid component as an aqueous sol and adding the cationic starch as an aqueous solution, both components being added separately to the grinding agent in a mixing tank or at a point in the system where adequate mixing occurs, so that both components are simultaneously distributed and will interact with each other and with the components of the powder.

Even better results are obtained if the colloidal silicic acid component is added to and thoroughly mixed with a portion of the grinding medium, after which the rest of the grinding medium is added and the cationic starch is added and mixed thoroughly to the grinding medium mixture before forming the paper product.

5

In the case where a mineral filler has to be added to the grinding agent, it has proved most advantageous to slurry the mineral filler in water together with the colloidal silicic acid component or, if this component is gradually added, with its initial part, and then lead the slurry of the filler and colloidal silica mixed with the pulp and cationic starch to form a grinding material.

When the colloidal silicic acid component is gradually added, the final or final portions of this component are then added, which are thoroughly mixed into the grinding medium after the initial agglomerate is formed but before the grinding medium is introduced or introduced into the head of the paper machine. The first or initial addition of colloidal silicic acid should comprise from about 20% to about 90% by weight of the total amount of colloidal silicic acid added, and then once the initial agglomerate has been formed, the remainder of the colloidal silicic acid must be added before forming the paper. Preferably, the initial amount comprises from about 30% to about 80% of the colloidal silicic acid component.

25

It has been found that the pH of the grinding medium in a papermaking process using the binder complex of the invention is not particularly critical and may be 4-9. However, a pH higher than 9 and a lower pH than 4 are not suitable. Other paper chemicals, such as glue, alum and the like, may be used, but care must be taken that the concentrations of these substances are not so high as to affect the formation of an agglomerate of silicic acid and cationic starch and that the concentrations of these additives in the circulating water are not become so large that they affect the formation of the binder agglomerate. For this reason, it is preferred to add chemicals at a point in the system after the binder agglomerate has formed.

^ · 68283

According to the invention, the weight ratio of cationic starch to colloidal silica component should be 1: 1 to 25: 1. Preferably, this weight ratio or ratio is 1.5: 1 to 10: 1 and especially 1.5: 1 to 4.5: 1.

5 The amount of binder used will vary depending on the desired effect and the properties of the various components selected for the preparation of the binder. For example, if the binder comprises polymeric silicic acid as a component of colloidal silicic acid, more binder may be required than if the component of colloidal silicic acid is composed of colloidal silicic acid having a specific surface area of 2 to 300-700 m / g. If the degree of substitution of the cationic starch is e.g. 0.025 compared to the degree of substitution 0.030, a correspondingly larger amount of binder may be required, assuming that the colloidal silicic acid component is the same.

15

When the grinding medium does not contain any mineral filler, the binder content may generally be 0.1-15% by weight, preferably 1-15% by weight based on the weight of the cellulosic fibers. As discussed above, the efficiency of the binder is higher on the chemical pulp, resulting in a lower amount of binder being required in these pulps to achieve the specified effect than when used on other pulp types. In the case where a mineral filler is used, the amount of binder may be based on the weight of the filler and may be 0.5 to 25% by weight, usually 2.5 to 15% by weight, based on the filler.

25

As discussed above, the binder can be added to the circulating water of the paper machine in a system where the binder system is not used to make the paper. The binder effectively forms an agglomerate together with the fines and suspended mineral soil material from the milling material, and this makes it possible to achieve effective precipitation or concentration of suspended solids to provide a relatively clear aqueous fraction which is fed back to the papermaking system and to obtain a fraction which is suspended. from which these can be removed by filtration or other means. The amount of binder system or complex required when using the above weight ratios (ratios) between cationic and SiO 2 can be relatively small and in most cases less than about 10% by weight, based on the dry weight of solids in the circulating water and the dry weight of the binder system. . The useful wide range of binder system or complex is from about 1% to about 20% by weight, preferably from about 2% to about 10% by weight.

The following specific embodiments illustrate how the binder, when used in a papermaking process, affects the retention of the mineral filler, the strength of the finished paper product, and the circulating water.

Example 1

A test run was performed to produce a base paper for the production of wallpaper, with a high clay content in the paper pulp. The run was performed on a flat wire machine with an estimated capacity of about 6000 kg / h.

2

The machine speed was about 250 m / min, and the intended basis weight was 90 g / m. Figure 1 shows a flow chart of the process.

20 The fibrous material of the grinding material consisted of a mixture of mechanical and chemical pulp. The mechanical pulp was unbleached and ground to a degree of grinding (CSF) of 100. The chemical pulp used was bleached hardwood sulphate pulp ground to a CSF of 400. Of course, suitable amounts of water were added to the pulp to achieve the desired consistency.

Kaolin and colloidal silicic acid were dispersed in water to form a slurry containing 5% by weight of kaolin. The particle size distribution of kaolin was about 0.5-10 μm. Colloidal silicic acid consists of 15% of a salt stabilized with alkali in a molar ratio of SiO 2: NaO 2 of 45: 1.

^. 2

The silica had a particle size of about 5-7 nm and a specific surface area of about 500 m / g. Colloidal silicic acid was added to give 2.86% SiO 2 based on the weight of kaolin. The pH of the slurry of kaolin and SiO 2 was about 8.

35

Figure 2 shows the dosing to the paper machine during the test run, expressed in kg / min at different times during the run. The consistency of the grinding material fed to the paper machine was about 6 to about 15 g / L, as seen in Figure 2A, and the times shown in Figure 2A are correlated with the times shown in Figure 2.

5 As can be seen from Figure 2, the test run started at 14.10 so that the chemical and mechanical masses were mixed in the proportions shown. At. At 14.40 the grinder valve was opened and the grinder flowed into the paper machine. The dashed line in Figure 2 shows how the grinder valve was adjusted while driving.

10

Initially, the grinding material fed to the machine consisted exclusively of a mixture of chemical and mechanical pulp. Kl. 14.50, however, a mixture of kaolin (clay) and colloidal silicic acid was introduced into a mixing box, and the paper machine was run with a grinding medium formed of fibers and clay until the ash content of the grinding medium and circulating water reached equilibrium. N. kl. At 15.35, a slurry of cationic starch was added and mixed thoroughly with the pulp, clay and colloidal silicic acid in a mixing box to form a grinding medium containing all the binder.

20 Kl. 15.35 was the added content of cationic starch of 7.14% by weight of the starch based on the weight of the clay, the ratio of cationic starch to colloidal silicic acid being 2.49 (this level or concentration of starch is sometimes referred to in the working example and drawings as "level 1"). Kl. At 16.25, the concentration of 25 cationic starches was increased to 8.57% by weight based on the weight of the clay, increasing the ratio of cationic starch to colloidal silicic acid to 2.99 (this level or concentration of starch is sometimes referred to as "level 2" in the example and drawings). Kl. On 17.02, the concentration of cationic starch-30 was increased to 11.43% by weight based on the weight of the clay, the ratio between cationic starch and colloidal silicic acid being 3.99 (this concentration or level of starch is sometimes referred to in the example and drawings as "level 3"). . At all times of the run, the pH of the grinding material fed to the machine was about 8.

35

The cationic starch was prepared by treating potato starch with 3-chloro-2-hydroxypropyltrimethylammonium chloride to give a degree of starch substitution of 0.03. The starting starch was dispersed in cold water at a concentration of about 4% by weight, heated for 30 minutes at about 90 ° C and then diluted with water to a concentration of about 2% by weight, after which the cationic starch prepared was prepared. was added to the mixing tank or box as shown in Figure 1.

For comparison, it was determined that after the addition or change was made in the mixing tank (the time of addition is indicated by the vertical arrows in Figure 2), it took about 15 minutes for the change to achieve stabilization on a paper machine (shown by the horizontal arrows in Figure 2).

After the addition of cationic starch to level 1, i. to 2.49 relative to silicic acid, the basis weight of the paper increased rapidly as the mineral content of the paper increased as a result of the increasing retention of the mineral material along with the fibers on the machine wire. The grinding valve was then adjusted to reduce the basis weight to 90 g / m 2, and by adjusting the grinding valve, the basis weight was kept relatively constant, while the ash content slowly increased. During this time period, the solids content in the circulating water decreased by about 50% due to the fact that more and more solids were retained.

25 As the concentration of cationic starch increased to level 2, i.e. at a ratio of 2.99 to silicic acid, the basis weight and ash content of the paper increased again, and the solids content of the circulating water continued to decrease as the retention rate increased again. 1 2 3 4 5 6

Then, when cationic starch was added to the system and increased clay retention was observed, it was found that the drying cylinders dried the paper too vigorously. The steam supply to the drying cylinders was reduced, and some of them were shut off due to faster drying. Despite the reduction in heat input to the drying cylinders, the paper occasionally became too dry. The reduction in steam consumption was the result of the fact that the fiber content of the paper decreased significantly as retention increased, and this weakened the drying process.

Although the mineral content of the paper (expressed as ash content) increased sharply, the paper machine was run at the same speed and 5 without changes in dewatering conditions during the test run.

The ratios and results of the test run are shown graphically in Figures 2A-2S.

Figure 2A shows the solids concentration of the grinding material at different times of the test run. It can be seen that the total solids concentration slightly exceeds the total fiber and ash content. This is because in the ash determination, the water of crystallization and other water present in the clay are removed.

Figure 2B shows the solids concentration of the circulating water. For the reasons given above, the total solids concentration in this case also exceeds the sum of the fiber and ash concentrations. In connection with Figure 2B, it should be noted that the ash content (in this case the one not retained in the material) increases rapidly until cationic starch is added at level 1 and has the potential to reach equilibrium in the system. As the concentration of cationic starch increased to level 2, a further significant decrease occurred.

The combination of colloidal silicic acid and cationic starch as a binder also increases the filtration rate of circulating water through the wire, as seen in Figure 2C. The dewatering time per unit volume increased until the composite binder was at level 1 and then decreased rapidly. With the addition of cationic starch to level 2, the reduction in dewatering time per unit volume was even stronger.

30

Figure 2D shows the Z-potential of the grinding medium, which decreases to zero upon addition of cationic starch. It can be said that the change corresponds to increasing retention and improved properties.

Figure 2E shows graphically the basis weight of paper in a test run. In the two cases shown, a web break occurred in the machine.

Kf ..

15 68283

Figure 2F shows the tensile index of a paper made according to an exemplary embodiment. It should be noted that the amount of clay in the paper is about 120% of the ash content shown because the water has been removed from the ash. It can be seen that the tensile index is significantly improved and that the clay causes an increase in the tensile index in the presence of a binder system consisting of colloidal silicic acid and cationic starch.

Fig. 2G shows, similarly to Fig. 2F, a diagram of the tensile index, except that the tensile index in this case is set in relation to the chemical pulp concentration.

Figure 2H shows that the Z-strength or delamination strength of the produced paper is improved despite the fact that the paper contains considerable amounts of clay.

Figures 2I-2S show diagrams of the various properties of the paper prepared according to the exemplary embodiment and the efficiency of a binder system consisting of silicic acid and cationic starch. In the case of Figure 2M 20, which shows the surface roughness of the paper, it should be noted that the paper occasionally became too strongly dried, as a result of which the conclusions that can be drawn from the surface roughness diagram may not be entirely correct. 1 2 3 4 5 6 i &

It is clear from the results of the test run and the properties of the produced paper that the use of a binder system causes the flocculation 4 of the mineral material, the cellulosic material and the binder 4 to provide a greatly improved retention and greatly improved paper properties. The binder thus allows significant mineral fillers to be introduced into the cellulosic pulp to achieve the same or better properties as can be achieved in a paper product containing a higher amount of cellulosic fibers and a smaller amount of mineral fibers when the binder of the invention is not used.

16 6 82 8 3

Example 2

In the form of laboratory paper, handmade sheets of paper were made from various grinding materials made from bleached softwood sulphate pulp with and without wollastonite used as a filler. Wollastonite consisted of needle-like crystals with a diameter of about 10 to 1 to 20 and a length of about 15 times the diameter.

The colloidal silicic acid used consisted of a silicic acid sol containing 2% colloidal silicic acid with a specific surface area of about 500 m / g.

The sol was alkali stabilized with a molar ratio of SiO 2: 2: Na 2 O of 40: 1.

The cationic starch (K.S.) used was the same as in Example 1 and had a degree of substitution of 0.03. The cationic starch was added in the form of a 4% by weight aqueous solution.

In preparation, a colloidal silica sol was added to the grinding agent prior to the cationic starch. In those examples containing wollastonite, a sol and cationic starch were added to the mineral to form a slurry of mineral and binder, which was then added to the cellulosic fibers. A standard amount of water was added to form a grinding material with the desired consistency of about 1% by weight solids. After the handmade sheets of paper were made, they were pressed and dried under substantially identical conditions. 1, '·

The table below shows the solids composition in each grinding material and the Z-strength (Scott Bond) measured to determine the properties of the resulting paper sheet after compression and drying.

17 68283 test mass wollastonite 4% K.S. 15% salt Z-strength n: ogggg (Scott Bond) 1 2.1 0 0 0 204 5 2 2.1 0.9 0 0 154 3 2.1 0 1.69 0 313 4 2.1 0.9 1 , 69 0 209 5 2.1 0 1.69 0.450 388 6 2.1 0 1.69 0.225 622 10 7 2.1 0 1.69 0.150 586 8 2.1 0 1.69. 0.113,568 9 2.1 0.9 1.69 0.450 266 10 2.1 0.9 1.69 0.225 291 11 2.1 0.9 1.69 0.150 380 15 12 2.1 0.9 1.69 0.133 410

Figure 3 is a graph showing the increased strength obtained with a binder system formed from silicic acid and cationic starch. It can be seen from the diagram in Figure 3 that the strength of Z-20 when using a binder system is higher in a paper sheet made of a grinding material with 30% wollastonite than in a paper sheet made exclusively of a grinding material consisting of cellulose fibers. Also, when a binder system was used in a sheet of paper containing exclusively cellulosic fibers, a significant change in the Z-strength of ai-25 was obtained.

Example 3

In the form of laboratory paper, handmade sheets of paper were made from 30 different grinding materials made from 2.0 g of bleached softwood sulfate pulp and 2.0 g of kaolin (English china clay Grade C). The kaolin was dispersed in an alkali-stabilized colloidal silica sol diluted from a solids content of 15% by weight to a solids content of 1.5% by weight, and the suspension was added to the mass in 500 ml of water in a laboratory decomposer. A 2% solution of cationic starch (d.s. - = 0.03) was added, and the resulting grinding medium was transferred to paper. The handmade sheets of paper 18 68283 were pressed and dried under substantially similar conditions.

Different silicic acid sols were used in the experiments, whereby the sols used had different specific surfaces and were stabilized with different molar ratios of alkali.

Sheets of paper having the following compositions were prepared, all containing the indicated amounts and types of silicic acid sol and cationic starch in addition to said 2 g pulp and 2 g clay.

10 The table shows the properties of handmade sheets of paper.

1.5% silicon molar 2% basis density tensile ash sol pon ratio KS metric kg / m3 indexing% g female pin- Si02i g weight si% 15 ta Νβ2θ g / m ^ (Scan m ^ / g P16: 76 1 2.3 900 20 8.5 153 780 21.5 3.5 37 2 3.3 900 40 7.5 170 780 19.7 4.0 40 20 3 1.7 900 40 8.7 151 760 22.8 5.0 36 4 2.3 650 40 8.5 190 830 17.7 4.5 47 5 3.8 550 20 7.1 196 810 18.0 5.0 48 6 3 .0 550 20 7.8 176 800 17.4 4.5 45 7 3.8 500 45 7.1 199 800 16.0 4.5 45 25 8 3.0 500 45 7.8 182 790 18.0 5 .0 43 9 3.3 350 45 * 7.5 185 840 15.7 6.0 46 10 3.3 200 100 7.5 170 730 16.5 6.0 33 11 5.0 200 100 7.5 165 730 16.5 5.5 37 12 0 - - 10.0 141 700 19.4 6.0 28 30 13 no SiO 2 no KS 200 800 5.5 2.5 41 alone 2.0 mass + 6 g kaolin

SiO 2 X Stabilized with ammonia instead of NaOH, molar ratio «- nh 3 35 From this example, it can be seen that the binder system formed from silicic acid sol and cationic starch greatly improves clay retention and in many cases results in almost 19 68283 complete retention. The example also shows that maximum clay retention is achieved when the colloidal silica particles 2 have a particle size such that the specific surface area becomes about 300 to 700 m / g. 5 Example 4

In the form of laboratory paper, handmade sheets of paper were prepared from various grinding materials containing polymeric silicic acid as a colloidal silicic acid component. 100 ml of water glass (R = SiO 2: 10 ^ E 0 = 3.3, and S 1 O 2 = 26.5% by weight) was diluted to 160 ml of water and slowly added to 130 ml of sulfuric acid (10%) with vigorous stirring. After the total amount of water glass was added, the pH was 2.7 and the S1O2 content was 8% by weight. This acidic sol was diluted to a 2% by weight SiO 2 concentration and added to kaolin (English china clay Grade C), followed by the addition of a 2% solution of cationic starch (d.s. = 0.03). The following suspensions were prepared: clay 2% 2% g sol g KS g 1 2 3 4 5 6 7 8 9 10 11 1 2.0 5.2 9.0 2 2 2.0 4.4 7.4 3 3 2, 0 4.4 7.4 4 4 2.0 2.9 7.1 5 5 2.0 2.9 7.1 6 7

Each of the suspensions 1, 2 and 4 was passed to a laboratory dispenser, already 8 ka containing 2.0 g of bleached softwood sulphate pulp in 500 ml of water, 9 and mixed thoroughly. Suspensions 3 and 5 were stored for 5 hours 10 before mixing as above. Immediately after mixing, handmade sheets of paper were prepared, pressed and dried. The sheets of paper had the following properties: 20 68283 square meter tensile index elongation ash weight. Nm / g% concentration g / m (Scan P16: 76)% 1 139 28.8 7.5 26 5 2 151 25.3 6.5 30 3 148 23.6 7.0 32 4 157 22.4 6, 5 28 5 154 21.2 7.0 31 10 Compared to the sheets of paper prepared in Example 3, the tensile index of the sheet of paper according to this embodiment was improved, but the retention of the mineral filler was not as high as in Example 3.

15 Example 5

In the form of laboratory paper, handmade sheets of paper were prepared from various grinding materials as follows: 20 l) 2.0 g of chalk with a particle size of n, 2-20 μm (main part about 5 μm), 2.0 g of water and 3.8 g of colloidal silicic acid (1.5% solids and a specific surface area of 500 m / g) were added in a laboratory diffuser to a grinding medium consisting of 2.0 g of fully bleached softwood sulphate pulp and 500 ml of water. To a grinding agent consisting of chalk, silica and pulp was added 7.1 g of a solution of cationic starch (a total of 2.0% solids, d.s.0.03). A sheet of paper was made from this grinding material in the form of laboratory paper, and the sheet was pressed and dried.

2) A sheet of paper was prepared from a grinding material corresponding to the above grinding medium except that the amount of colloidal silica sol was 5.7 g and the amount of cationic starch solution was 9.7 g.

3) The paper sheet was prepared from a grinding material corresponding to the above-mentioned grinding medium 1 except that the amount of the colloidal silica sol was 5.0 g and the amount of the cationic starch solution was 10.3 g.

• dr '· * 2i 68283 4) The same method was used to prepare a reference paper sheet without chalk, in which 3.8 g of colloidal lead acid sol was added to 2.0 g of mass in 300 ml of water, followed by 7.1 g of cationic starch solution.

5) The same method was used to prepare a reference paper sheet that did not contain any binder. 10 g of chalk was added to 2.0 g of mass in 500 ml of water, but no binder was added. The amount of chalk added was so large that the mineral pl-10 of the finished paper sheet, despite the poor retention observed, was approximately the same as when the binder was used.

6) Another sheet of paper was prepared from grinding albex consisting of 2.0 g of pulp in 500 ml of water and containing no additives.

The resulting sheets of paper had the properties shown in the table below: 20 Experiment No. _ 2 3 4 5 6 Weight per square meter g / m2 192 201 200 110 174 100 Density kg / m2 740 800 760 635 820 605 Tensile index SCAN P16: 76 25 Nm / g 16.0 20.0 17.3 50.7 10.5 31.4 Elongation X 7.5 5.5 4.0 5.5 6.0 7.5 Ash content X 50 47 48 4 45 1 This example shows the strength growth, which is the result of a binder system according to the invention with or without mineral fillers, and the example also shows the increased retention provided by the binder system. From the amounts of binder used relative to the pulp, it can be seen that substantially all of the mineral filler remained on the paper sheet in Experiments 1-3.

35

Example 6

A suspension prepared from 2.0 g of talc (Norwegian talc Grade 22 68283 IT Extra) with a particle size of about 1-5 μm, 8.0 g of water and 3.8 g of colloidal silicic acid (total 1.5% solids, self-2 female surface 480 m / g) were added in a laboratory diffuser to a grinding medium consisting of 2.0 g of fully bleached softwood sulphate pulp and 5,500 ml of water. To the grinding material thus obtained was added 5.9 g of cationic starch (a total of 2.4% solids, d.s. = 0.033). A sheet of paper was prepared in the form of laboratory paper, which was pressed and dried.

A comparative experiment was prepared in which 4.0 g of talc was added to 2 g of mass in 500 g of water, but no binder was added. (The amount of talc is higher to compensate for poor retention, so that the finished paper sheet has approximately the same mineral content as the paper sheet prepared as described above using binder-15).

with binder without binder 2 basis weight, g / m 198 214 density, kg / m ^ 825 715 20 tensile index SCAN P16: 76, Nm / g 16.5 3.1 elongation,% 6.5 3.0 ash content,% 48 51 25 As in Example 5, it can be seen from this example that the strength and retention of the paper sheet is clearly improved when a binder system is used in combination with a talc mineral filler.

Example 7 In this example, a binder system according to the invention was added to various grinding materials to show that the invention can also be used in grinding materials containing substantial amounts of fibers other than cellulose.

35

Fully bleached softwood sulphate pulp was used as the cellulose fibers, and glass fibers with a diameter of 25 6 8 2 8 3 about 5 μm and treated with phenolic resin were used as the non-cellulose fibers. The colloidal silica sol 2 contained silica particles having a specific surface area of about 400 m / g and the silica had an initial silica content of 15% by weight, but the sol was diluted with water to a silica content of 1.5% by weight before si-5 was used in the binder system. . The degree of substitution of the cationic starch used was 0.02 and was used as a solution of 2% by weight.

The following grinding agents were prepared (grindings Nos. 1 to 3 are 10 reference grinding agents): grinding cellulose glass silicic acid cation activity ratio fiber fibers 6 - - 2 1.6 0.3 - 3 1.6 0.3 - 1.12 4 1.6 0.3 0.187 1.12 8 20 5 1.6 0.3 0.372 1.12 4 6 1, 6 0.3 0.496 1.12 3 7 1.6 0.3 0.744 1.12 2

Sheets of paper were made from seven grinding materials in the form of laboratory-25 paper, the paper sheets thus obtained having the following properties: paper basis density tensile Z-strength elongation grinding weight kg / m 2 index (Scott- 30% of material g / in _ Nm / g Bond ) _ 1 68 650 55 135 9 2 91 530 33 84 11 3 88 520 40 120 10 4 90 520 44 132 10 35 5 85 520 44 138 11 6 94 540 48 152 12 7 93 550 47 149 11 24 68283 This example shows that the Z-strength decreased with the addition of glass fibers (cf. grinding agents 1 and 2) and then increased to approximately the original value (cf. grinding agents 1 and 4) with the addition of both silicic acid sol and cationic starch. Paper sheets made of grinding material 5, 6, 6 and 7 had a higher Z-strength than a paper sheet made of grinding material 1 without glass fibers.

Example 8 10

A commercial test run was performed to produce a coated, supercalendered 2 offset paper having a basis weight of 85 g / m 2.

The machine used was a double wire machine (Beloit "Bel-Baie") with a capacity of about 10,000 kg / h and a machine speed of 600 m / min. Coating was performed directly on the machine with 100 g / m calcium carbonate guided on both sides of the paper web. The cellulosic fibers consisted of 70% hardwood sulphate pulp and 30% softwood sulphate pulp, both pulps being fully bleached. The pH of the circulating water was about 8.5.

20

The quality requirements for the paper product made in this machine were very strict. As a result, a large portion of the finished coated Paper Product, about 25%, was classified as "waste" during normal use of the machine. The waste was unsatisfactory paper which was fed back into the grinding medium and reconstituted into paper. The pulverizer fed to the headbox of the machine thus contained a large amount of filler in the form of a reslurried coating mass from the waste paper. The proportion of waste paper was often as high as 50% of the total solids solids.

30 The presence of excess filler from the waste paper posed a real problem in the normal operation of the machine, since the retention of this filler on the wire of the paper machine is very poor and most of this filler was found again in the circulating water and gradually removed. Since the amount of waste always varies, the filler content of the base paper varies, which results in uneven properties of the paper web, with the result that countless interruptions occur during the manufacture of the paper web, which in turn leads to production losses.

Figure 4 shows a flow chart of a method of operating a test run according to the present example, in which the addition of colloidal silicic acid was gradually used according to the invention.

Both types of fully bleached sulfate pulp typically used in a paper machine, i. 70% hardwood pulp and 30% softwood pulp, mixed together and defibered into waste paper. In order to compensate for the variations in the amounts of filler in the grinding medium 10 caused by the variations in the amount of waste, measures were taken to increase the desired amount of excess filler (calcium carbonate). At this point, the amount of excess filler added depended on the ash content, which was continuously measured from the base paper in the machine, and sufficient calcium carbonate filler was added to maintain the ash content of the finished base paper at 15% by weight based on dry paper weight.

Additional colloidal silicic acid in the form of an aqueous solution containing 15% by weight of SiO 2 per metric ton of dry base paper (before coating) was added to mixing tank No. 1. The sol formed from colloidal silica was stabilized with alkali SiO 2 Na 2 O in a molar ratio of 45: 1. The silica had a particle size of 5-7 nm and a specific surface area of about 500 m 2 / g. 1 2 3 4 5 6 7 8 9 10 11

The materials were mixed thoroughly and fed to a mixing tank 2 2, where cationic starch was added to the grinding material in an amount equivalent to 10.2 kg of cationic starch 4 per metric ton of dry base paper. The cationic starch was prepared by treating potato starch with 3-chloro-6-hydroxypropyltrimethylammonium chloride to give a degree of substitution (d.s.) of 0.03. The starch was dispersed in cold water at a concentration of about 4% by weight, heated for 30 min. at about 90 ° C, 9 was diluted with cold water to a concentration of about 2% by weight and 10 was then added to the mixing tank 2.

11

After the cationic starch was thoroughly mixed, the grinding medium was fed to the mixing tank 3, where a second addition of colloidal silicic acid of the type described above was made to the grinding medium, the addition amount corresponding to 2.1 kg of SiO 2 and per metric ton of dry base paper.

From the mixing tank 3, the grinding medium was fed to the headbox of a paper machine, which was operated at normal speeds for the production of base paper, which paper was then dried, coated with a coating mass containing calcium carbonate and calendered in the same manner as before.

10

Figure 5 shows graphically the effects of the addition of colloidal silicic acid and cationic starch in the above manner. The left part of the diagram shows the conditions in the grinding medium and circulating water in a commercial run before the addition of colloidal silicic acid and cationic starch as described above. It can be stated that the total solids content of the grinding material in the paper former or headbox was about 15.5 g / l, of which 8.5 g / l was fiber and 7 g / l was ash. The base paper made from this grinding material contained about 3% ash.

20

As seen in Figure 5, the circulating water contained about 10.5 g / L solids, 6.0 g / L ash, and 4.5 g / L fibers in a commercial run before the addition of colloidal silicic acid.

The significant effect of the addition of colloidal silicic acid and cationic starch according to the above can be seen in the right part of Figure 5, where the total solids content in the headbox decreased by about 6 g / l, slightly less than 5 g / l fibers and about 1.5 g: n / l ash. The total solids content of the circulating water decreased to about 1 g / l, to about 0.5 g / l of fibers and to about 0.5 g / l of ash. The base paper contained about 15% ash, and the breaks in the paper web were substantially lower in machine use than in the commercial run, where the paper web contained only 3% ash.

Although the finished base paper prepared according to the above example had an increased filler content, i. growth n.

From 3% to about 15%, which normally degrades the properties of the paper, the test results showed that the excess filler did not cause any clear deterioration in the properties or weight of the paper. On the contrary, the prescribed properties clearly improved. Thus, the Z-strength, i.e. the delamination strength measured according to the Scott-Bond method, increased by 85% at a filler content of 15% compared to a filler content of 3% in commercial operation. Surface strength (as measured by the IGT Instituut Voor Grafische Techniek, Amsterdam) increased by 40% and puncture strength increased by 40%.

In a test run lasting a few weeks, it was found that it is possible to add 10 more waste to the grinding agent than before. Over a period of about 16 hours, all the grinding material consisted of waste. It was further found that the addition of additional filler made it possible to maintain the filler content of 15% in the base paper over a two week period and that the steady ash-15 level thus obtained increased the paper machine capacity due to less frequent web breaks and fiber savings.

It was also found that the coupling of increased retention and reduced abrasive concentration in the headbox resulted in a significant improvement in the dewatering rate of the abrasive on the wire. This, of course, means that machine speed can be increased, which in turn further increases production capacity.

The retention of fibers and fines on the paper machine wire was also greatly improved. Percent retention was determined by dividing the difference between the total solids concentration of the headbox and the total solids concentration in the circulating water by the total solids concentration of the headbox and multiplied by 100. Thus, the commercial run before 100% silicon sol and cationic active starch was 32%. The result using the invention was prcsentu- (g Q_ ^ Q \ aal retention increased by about 83% to -q * - x 100). This high level of retention simplified the purification and removal of the circulating water.

35 Example 9

To further illustrate the benefits of the two-stage addition, long-term test runs were performed under various conditions on the 28,682,83 machine shown in Example 8. The results of these runs are shown in the following table.

Run 1 illustrates the average use of the machine used in Example 8 in the production of coated, supercalendered printing paper over a long period of time. The cellulosic fibers consisted of 70% hardwood sulphate pulp and 30% softwood sulphate pulp, both pulps being fully bleached. Normal amounts of waste were fed back to the machine. The base paper was coated with 10 g / m calcium carbonate per side.

10

Driving 1 Driving 2 Driving 3 2 basis weight g / m 85 85 85 ash content% 17 28 24 tensile index 15 machine direction Nm / g 66.2 64.2 64.5 transverse direction Nm / g 21.7 22.5 26.8 puncture resistance kPa 214 294 310

lifting resistance IGT

20 top 73.4 92 112 wire side 68.7 83 112 delamination strength

Scott Bond J / m2 225,506,525 headbox concentration 25 g / l solids 15.5 10.1 6.3 circulating water concentration g / l solids 10.5 5.2 1.2 retention% 32.3 48.5 81.0 30 Run 2 depicts the averages of the machine used in Example 8 over a relatively long period of time to produce coated, supercalendered printing paper using the same fiber grinder and normal amounts of waste fed back to the machine, the colloidal silicic acid used consisting of 15% aqueous sol as in Example 8. features. This sol was added to mixing tank No. 1 in an amount of 3.8 kg of SiO 2 per metric ton of dry base paper. The cationic starch was added to the mixing tank No. 2 and the amount was 11.8 kg of cationic starch per metric ton of dry base paper, the cationic starch having the properties shown in Example 8 and using the addition methods described in Example 8. No additions were made to the mixing tank 3. After drying, the base paper was coated with a calcium carbonate account in an amount of 10 g / m 2 per side.

Run 3 was performed in the same manner as Run 2, except that the silicic acid sol was added in two steps. To the mixing tank 1 was added 2.9 10 kg of SiO 2 per metric ton of dry base paper. Starch was added to the mixing tank 2 in an amount of 13.7 kg of cationic starch per metric ton of dry base paper. A second addition of 1.5 kg of silica sol was made to the mixing tank 3 in an amount of 1.5 kg of SiO 2 per metric ton of dry base paper.

15

Example 10

To further elucidate the different degrees of substitution of the invention and the cationic starch component of the binder, two sets of handmade paper were prepared using a laboratory paper format and different grinding materials, all containing the same type and amount of colloidal silica sol but containing cationic active ingredients.

In this example, cationic starches prepared from two different starting starches (A and B) were used to achieve the degrees of substitution shown in the table below. 1 2 3 4 5 6

All grinding materials for handmade sheets of paper were prepared by mixing together 1.09 g of kaolin (English China Clay 3

Grade C) 2.72 g of colloidal silica sol (1.5% of total solids content and surface area 530 m / g) and feeding this slurry to a laboratory decomposer or disintegrator containing 1.63 g of full bleach. softwood sulphate in 500 ml of water. After mixing the components for 30 seconds, the cationic starch in question was added to the disperser. Stirring was then continued for about 15 s, 30 6 82 8 3 after which the grinding medium was poured into a paper former.

The degrees of substitution and addition rates of the different starches to the grinding materials as well as the properties of the prepared paper sheets are shown in Table 5 below.

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32 68283

The tensile index of the various paper products is plotted as a function of the amount of starch added (calculated as a percentage by weight of the sum of filler and fiber contents) in Figure 6, which clearly indicates that a lower degree of substitution (d.s.) requires a higher amount of starch to achieve maximum strength (tensile index). Thus, starch A with a degree of substitution of 0.033 produced a maximum strength increase of about 3.5%, while starch A with a degree of substitution of d.s. was 0.020, produced maximum strength in an increase of about 4.3%. The same is true for starch B, which at 10 degrees of substitution gave 0.047 the best strength at an addition rate of about 4.2% and at a degree of substitution 0.026 gave the best result at an addition rate of about 4.8%.

Example 11 This example relates to the utility of the invention in making lightweight fine paper.

A series of experiments were performed on a test paper machine to produce light fine paper having a basis weight of 75 g / m 2. The grinding material fed to the headbox of the machine consisted of 50% by weight of fully bleached hardwood pulp, 20% by weight of fully bleached softwood pulp and 30% by weight of filler, both pulps being sulphate pulps. Two types of filler were used, a conventional filler consisting of 25 grade papermaking chalk (CaCO 3) and a low density filler consisting of expanded perlite having a density of about 0.2 g / m 3 and a particle size of 99% less than 10 μm. In the control run (Run A), 0.2% by weight of a polyacrylamide retention aid was added to the grinding medium containing CaCO 3 as the sole mineral filler. In time 30B-E, the mineral filler was successively converted from chalk alone through mixtures of chalk and expanded perlite to perlite alone. At all times in this embodiment, the amount of binder was added in the same manner, i.e. 0.5% by weight of silicic acid sol (specific surface area approx. 500 m / m) and 1.5% by weight of cationic starch (degree of substitution 0.03) calculated as 353 solids in the binder and based on the weight of the grinding medium as a whole.

33 6 8 2 8 3

The results of the test runs are shown in the table below and in Figures 8A-8G, which graphically illustrate the determined results in the table.

comparison according to the invention

5 A__B C D E

CaCO3 wt.% 30 30 25 15 perlite wt.% - 5 15 30 density kg / nf * 630 645 610 570 500 10 stiffness (SCAN P29: 65) machine direction mN 4.7 4.2 4.6 5.4 6.4, 9 transverse direction mN 2.8 2.5 3.2 3.0 4.4 tensile index (SCAN P16: 76) machine direction 28 38 33 30 29 15 transverse direction 15 22 20 19 20 tensile breaking work _ machine direction J / in 27 48 41 35 32 o transverse direction J / m 18 37 30 25 23 lifting resistance (Dennison wax bond strength) top 9 16 12 12 10 wire side 12 18 12 13 12

As can be seen from the table and Figures 8A-8G of this embodiment, the binder complex of the invention has enabled the addition of substantial amounts of expanded per-connector and the achievement of the same or better properties of the paper product.

Figure 8A shows that the binder according to the invention has considerably improved the modulus of elasticity compared to the known additive (run A) both in the machine direction (curve M.D.) and in the transverse direction (curve C.D). The fact is that the modulus of elasticity at times C and D, to which expanded perlite had been added, was higher than in reference run A and was consistently approximately in the same plane in run E as in run A, despite complete replacement of the chalk with expanded perlite.

34 68283

Figures 8D, 8C, 8E and 8F show that the same good properties have been obtained in tensile index, tensile breaking work, paper stiffness and lifting resistance (expressed as Dennison wax tower strength).

Figure 8D shows the decrease in density obtained by replacing chalk with expanded perlite.

Figure 8G shows the surface roughness expressed as a surface roughness number according to Bendtsen (SCAN P-21) at different paper densities. The curves of the reference paper (run A) and the paper of run B (chalk as the sole mineral-containing additive using the binder complex according to the invention) were so close together that they had to be drawn as the only curve in the diagram. As can be seen from the diagram, the binder complex according to the invention and the filler consisting of expanded perlite 15 made it possible in large proportions to obtain smooth papers (low surface roughness values according to Bendtsen) at low densities.

Example 12 This example demonstrates that the invention can be used to make specialty papers from grinding materials containing both cellulosic and non-cellulosic fibers and continued with mineral-containing fillers, with very good results being obtained when using mineral-containing fillers with is a low density, extender.

Three different grinding agents were used. All grinding materials contained 50% by weight of fully bleached softwood sulphate pulp, 20% by weight of 30 mineral-containing fibers (mineral wool fibers), 1.43% by weight of colloidal silica sol (specific surface area approx. 500 m / g) and 3.57% by weight of cationic silica. active starch (degree of substitution 0.03). The remaining 25 weight-Z grinding material consisted of either chalk or expanded perlite or a mixture thereof. All percentages are calculated on dry solids and calculated on the ground material as a whole.

In the preparation of the grinding materials to be formed in the laboratory paper reformer, silica sol was used as a 1.5% solution and cationic starch as a 1% solution. In preparing the grinding materials for Experiments A and C, a mineral filler (chalk alone or freshly expanded perlite alone) was initially slurried in a silicic acid-5 sol solution. In preparing the grinding medium for Experiment B, the mineral fillers (15% chalk and 10% expanded perlite) were initially mixed together and then slurried in silicic acid sol solution. In all three cases, the mineral and sol slurry was added to the premixed mineral fiber sulfate pulp in 500 mL of water in a labora-10 thorium diffuser or disintegrator. After a mixing time of 30 seconds, various sheets of paper were formed in the dispenser in the form of 2 laboratory papers and pressed at a pressure of 5 kg / cm. The properties of the dried papers are shown in the table below.

15 tissue ABC

cellulose fibers% by weight 50 50 50 mineral fibers by weight 20 20 20 chalk by weight 25 15 0 expanded perlite by weight 0 10 25 20 binder silicic acid sol by weight 1.43 1.43 1.43 cationic act. starch weight% 3.57 3.57 3.57 2 basis weight g / m 315 325 320 thickness mm 0.62 0.72 0.77 3 density kg / m 510 450 415 tensile index Nm / g 12.6 12.9 11.7 Elongation% 6 6 6 Paper stiffness N 0.275 0.328 0.284 Ash content% 45.1 46.8 45.1 Retention, calculated on the ash content% 97.0 100 97.0 36 68283

Experiments A, B and C show that it was possible to replace part or all of the chalk with expanded perlite as a filler to reduce the density, leaving other properties consistently at the same level as when using chalk as the sole mineral-containing extender or filler. It should be noted that the retention, calculated from the ash content, was almost 100% in all experiments, which is high considering that the retention of the expanded perlite filler is low when the binder complex according to the invention is not used.

Example 13 This example relates to the purification of circulating water from a twin wire machine which was used to make wood-free coated paper. The circulating water tests were taken from the normal production run of the paper machine and analyzed for solids content and solids types. The solids content was 7 g / l and about 60% by weight of the solids consisted of kaolin and chalk.

Various amounts of cationic starch and silicic acid were added to the circulating water experiments. The degree of substitution of the cationic starch was 0.033 and it was used in the form of a solution containing 4% by weight of starch. The particle size of the colloidal silica sol was approx.

26 nm, specific surface area about 500 m / g and silicic acid concentration 15% by weight.

In each of the experiments shown in the table, 500 ml of circulating water was poured into a dish, and the indicated amounts of silica sol and cationic starch were added. The contents of the dish were stirred vigorously, and then stirring was stopped. After the time periods shown, 20 ml turbidity tests were taken with a pipette 5 mm below the surface of the surface from each tank. Turbidity measurement was performed according to the Swedish standard SIS in a turbidity meter (Hach model 21G0A) which gives the result in Formazine Turbidity Units (FTU). The lower the measured value, the better the cleaning achieved.

35 Additives for circulating water tests and test results are shown in the table below.

37 68283 rotation- 4% starch- 15% silicic acid weight gain turbidity

water kelysosol ratio (dry FTU

ml solution g R weight) test g% 15 s 1 min 5 min 5 1 500 - - xx 900 2 500 1.75 - 2 xx 550 3 500 1.17 0.15 2 2 x 580 270 4 500 2.93 0 .39 2 5 x 100 91 5 500 5.85 0.78 2 10 23 18 17

10 X not measurable, more than 1000 FTU

the addition is calculated on the one hand on the dry weight of the cationic starch added and on the silica sol added and on the other hand 3,5 g of solids present in a circulating water test with a volume of 500 ml R = weight ratio between cationic starch and silica sol 1 2 3 4 5 6

The results of the above table show that the addition of the binder system 2 according to the invention to the circulating water results in a higher settling rate for solids in the circulating water and thus a reduction in turbidity. The results also show that almost pure circulating water was obtained in Experiment 5, which is a significant improvement over the untreated circulating water in Experiment 1.

Example 14 This example relates to the purification of circulating water from a combined paperboard and printing paper mill. The circulating water test was taken from the mixed circulating water from the plant and analyzed for solids concentrations and solids types. The solids content was 1.1 g / l and about 25% of the solids consisted of pigment (mainly kaolin). A series of experiments were performed to determine the rate of settling and turbidity of circulating water by treatment with PERCOL® 1697 (a typical additive for circulating water treatment) and a binder according to the invention containing a silica sol and cationic starch.

Landing rates were determined using a graduated conical funnel with a diameter of 110 mm at its widest top and a height of 400 ml divided into degrees. Silica acid sol and cationic starch were added to 1200 mm circulating water test batches with vigorous stirring. The test batches were then poured into a graduated funnel and allowed to stand, while the interface between the 10 near-bright upper phase and the thick lower phase gradually decreased. The time at which this interface would pass every 50 ml or 100 ml mark was recorded, and the settling rates were calculated and plotted in Figure 7. The almost clear upper phase was almost free of flocs but audible due to different amounts of fine fiber fractions. and pigment particles. For this reason, turbidity was measured in an experiment taken from the upper end of the funnel well above the interface 15 min after the experiment was poured into the funnel. The experiments were also taken from the funnel to determine the solids content in the circulating water after this settling time.

20

Turbidity was measured according to the Swedish standard SIS in a turbidity tester (Hach modell 2100A), which produces an experiment in Formaz's Turbidity Units (FTU). The lower the FTU values, the better the cleaning. The experimental results are shown in the table below together with the solid 25 solids concentrations and settling rates. The settling rates in the table are calculated from the straight lines in Figure 7 between the 200 mml and 600 ml levels.

The comparative experiment was performed without additives, and the settling rate was determined and marked (Experiment A) in Fig. 7.

A series of comparative experiments were performed using PERCOL® 1697 as an additive (0.5% solution). To 1200 ml of circulating water were added 2 ml, 1 ml, 0.8 ml, 0.6 ml and 0.4 ml of 0.5% PERCOL® 1697 solution, 35 and thereafter settling times were determined. With this additive, an addition of 0.6 ml gave the best results (Experiment B is shown in Figure 7).

39 6 8 2 8 3 The experiment was then carried out with a binder according to the invention. The additions of silicic acid sol and cationic starch varied in the series of experiments and also the molar ratio (R) between starch and silicic acid sol varied. Two of the best results were obtained by the addition of 3.7 g of a 2% solution of cationic starch with a degree of substitution of 0.047 and 3.3 g of a 1.5% solution of silicic acid sol (Experiment C), and by the addition of containing 2.5 g of a 2% solution of cationic starch with a degree of substitution of 0.047 and 1.65 g of silicic acid sol (Experiment D). The weight ratios (R) between starch and SiO 2 were 1.5: 1 in Experiment C and 2.0: 1 in Experiment D, and in both cases the silica sol used consisted of an alkali-stabilized silica sol having a specific surface area of about 500 m / g and the initial concentration was 15%, although the silica sol was diluted to a concentration of 1.5% for use.

15 The results of the AD experiments are shown in the following table: experimental turbidity after 15 min solids settling-purification concentration rate Astex FTU mg / 1 mg / 1 20 A 80 580 340 52 B 38 320 400 73 C 23 280 - 77 D 20 270 690 78

X

25 solids content in the "clear phase" divided by an initial concentration of 1100 ml / g.

As can be seen from the table above, the best results were obtained with the invention, i.e. in experiments C and D, especially the latter -30 sa.

As seen above, a binder system consisting of colloidal silicic acid and cationic starch (especially a complex in which colloidal silicic acid is gradually added, some of which is added after the development of the original agglomerate) allows both substantial economics in papermaking and the production of a unique paper product. When the binder system is used on pulp alone, the strength of the resulting paper product can be improved to such an extent that mechanical pulp can replace substantial amounts of chemical pulp while maintaining the desired strength and other desired properties. If different strength properties are required, on the other hand, the basis weight of the paper can be reduced and still the desired properties can be maintained.

Similarly, the mineral filler can be used in significantly greater amounts than has hitherto been possible, while maintaining or improving the properties of the paper. Alternatively, the properties of the filler-containing paper can be improved.

When using the binder system according to the invention, increased retention of both the mineral-containing filler and the fine fractions of the fibers is achieved, as a result of which the problems of circulating water are minimal. As emphasized, the binder system according to the invention can also advantageously be used for agglomerating solids in the circulating water in order to facilitate the recirculation of the circulating water or the removal of the circulating water. Furthermore, since it is possible to reduce the basis weight of the paper to 20 meters or to increase the mineral filler content of the paper, it is possible to reduce the amount of energy required to dry the paper and produce pulp from wood fibers because a smaller amount of fibers can be used. Increased dewatering speed and increased wire retention also allow for faster machine speeds.

25

The binder system according to the invention also makes it possible to reduce the solids content in the circulating water and thus to reduce environmental problems also in a paper mill which does not use the binder system according to the invention as an addition to the pulp itself. The binder system thus improves the recovery of solids from the circulating water and improves the economics of the entire papermaking process.

Although the preferred embodiments are set forth herein, it is to be understood that this description is not to be construed as limiting the invention, which, however, encompasses all variations and alternatives within the scope of the following claims.

Claims (8)

1. A paper product containing cellulose fibers in an amount of at least 50 wt. a degree of substitution of about 0.01 to about 0.05, preferably from about 0.02 to about 0.04, wherein the ratio of cationic starch: SiO 2 is between 1: 1 and 25: 1, preferably between 1.5: 1 and 10. : 1st 10 2. A papermaking process for producing the paper product according to claim 1, wherein an aqueous pulp containing cellulose pulp is formed and dried, characterized in that the amount of cellulose pulp in the pulp is controlled to provide a finished paper of at least 50 by weight of cellulose fibers, and incorporating in the pulp prior to the formation of the paper a binder comprising colloidal silicic acid and cationic starch having a degree of substitution of free from about 0.01 to about 0.05, preferably from about 0.02 to about 0, 04, wherein the cationic starch and silicic acid are mixed in a weight-increasing cationic starch: SiO 2 of between 1: 1 and 25: 1, preferably between 1.5: 1 and 10: 1. 3. A process according to claim 2, characterized in that the colloidal silicic acid is supplied as a colloidal silicic acid sol with silicic particles having a specific surface of about 50 to about 2 1000 m / g, preferably from about 200 to about 1000 m / g and raised from about 300 to about 700 m 2 / g. 30 Method according to claim 1 or 2, characterized in that the pH of the pulp is adjusted to about 4-9. 5. A method according to claim 2, 3 or 4, characterized in that the binder is applied in a side amount to be bonded. «