A method of manufacturing paper

 

(57) Abstract:

Method for manufacturing paper. In the aqueous furnish containing fibrous material and an inorganic filler, introduced a water-soluble polysilicate the microgel and a water-soluble polymer. Is then formed and dried product. Using the microgel with an average particle size in the range from 20 to 250 nm with a surface area of more than 1000 m2/, Polysilicates the microgel is preferably polyaluminosilicate, especially one that has a molar ratio of alumina : silica is between 1:10 and 1: 1500. The use of such microgels leads to improved performance on the retention of filler and dehydration. 4 C. and 17 C.p. f-crystals, 4 tab., 5 Il.

The invention relates to methods of making paper, and particularly relates to such methods that involve the use of water-soluble polysilicate microgels, especially polyaluminosilicate microgels and aluminiumand polysilicate microgels as auxiliaries to improve uderzhivaemoi filler and enhance dewatering.

The background to the invention

Known to the formation of water-soluble poly is crovella and their use in paper production. In "Tappi journal" for December 1994 /T. 77, 12/ S. 133-138 provides an overview of such substances and their areas of application. In U.S. patent 5176891 disclosed is a method of obtaining polyaluminosilicate microgels consisting in the initial formation of microgel polysilicon acid followed by reaction of the microgel polysilicon acid with aluminate to form polyaluminosilicate. In addition, disclosed the use in paper production polyaluminosilicate microgels as superior substances to improve uderzhivaemoi filler and enhance dewatering. In U.S. patent 5127994 disclosed a method of making paper by education and dewatering a suspension of cellulose fibers in the presence of three compounds: aluminium salts, cationic polymer material to improve uderzhivaemoi filler and polysilicon acid.

The method of obtaining polyaluminosilicate microgels, disclosed in U.S. patent 5176891, contains three stages, namely: 1/ acidification of an aqueous solution of alkali metal silicate to form microgel polysilicon acid, 2/ introduction water-soluble aluminate in the microgel polysilicon acid for the formation of polyaluminosilicate and 3/ dilution of glia, during which the initially formed silicic acid will polimerizuet in a linear polysilicon acid and then in microglial structure, which is crucial for the properties polyaluminosilicate products. As described, the products have a surface area greater than 1000 m2/g, surface acidity greater than about 0.6 mEq/g, and the molar ratio of aluminum oxide/silicon dioxide is greater than 1:100, preferably between 1:25 and 1: 4.

In WO 95/25068 describes an improvement over the method described in U.S. patent 5176891, which is to combine the stages of acidification and plating. An unexpected and important get a useful effect is to substantially reduce the period of aging, necessary for the formation of microgel. Polydisperse polyaluminosilicate products obtained by the method according to this invention, immediately upon formation /without any period of aging/ have good activity as substances to improve uderzhivaemoi filler and to improve dewatering in paper production, and they reach their optimal properties for a shorter period of time than the products obtained by the previous spaa, necessary for the formation of the product, because they require additional or oversized equipment and is known to create problems, as, for example, the uneven quality of products. Thus, any reduction of the period of aging is an improvement in the method of production of paper and leads to improved product quality.

An important aspect of the method described in WO 95/25068 is the introduction of water-soluble aluminium salts in the acid used for acidification of a solution of silicate of an alkali metal. Thus, gidratirovannuyu aluminium hydroxide receive simultaneously with silicic acid, and during the polymerization of silicic acid in the polysilicon acid and formation of polydisperse microgel aluminum directly injected into the polymer accompanied by the formation of polyaluminosilicate. In this way you can get useful polyaluminosilicate /PAS/ in a wide range of compositions having a molar ratio of aluminum oxide/silicon dioxide in the range of about 1: 1500-1: 10, but is usually about 1:1000 or less, preferably 1:750-1:25 and most preferably 1: 500-1: 50. Due to low aluminum oxide/silicon dioxide total poulymenakou polysilicate microgels. At the same time anionic charge is maintained at a lower pH intervals than is observed with aluminiumalloy polysilicon acid.

The method according to WO 95/25068 can be implemented as a two-stage process, comprising:

a) acidification of an aqueous solution of alkali metal silicate containing 0.1-6 wt.% SiO2, to a pH of 2-10,5 using aqueous acidic solution containing an aluminium salt, and

b) dilution water of the product obtained at stage (a), prior to gelation of the content of SiO22 wt.%.

Choice after acidification stage, you can use the stage of aging to further improve the properties of the product. This aging period is not required, and it is partly prevents the positive effect obtained by this method, i.e., reducing the time needed to achieve maximal activity polyaluminosilicate products.

In this way you can use any water-soluble silicate salt, and the preferred alkali metal silicates, such as sodium silicate. For example, you can use sodium silicate, Na2O:3,2 SiO2weight.

You can use any acid with a pH value occhialini is sulfuric acid.

You can use any aluminum salts, which are soluble in the acid used. Suitable salts are sulfate, chloride, nitrate and acetate of aluminum. In addition, you can use the basic salts, such as sodium aluminate and chlorohydroquinone, Al(Oh)2CL. If you use the aluminates of alkali metals, they can first be turned into an aluminium salt by reaction with acid.

To implement the method according to WO 95/25068 dilute aqueous solution of alkali metal silicate containing about 0.1-6 wt.% SiO2, preferably about 1-5 wt.% SiO2and most preferably 2-4 wt.% SiO2quickly mix with the diluted aqueous acid solution containing the dissolved salt of aluminum, in order to obtain a solution with a pH in the range of approximately 2-10,5; and more preferably in the range of 7-10,5 and most preferably in the range of 8-10. Suitable acid concentrations are in the range of 1-50 wt.%, although concentrations may be smaller or larger, provided that there is adequate mixing. Generally preferred concentration equal to about 20 wt.% the acid. The amount of aluminium salts dissolved in the acidic solution may vary on the UB>/SiO2in polyaluminosilicate the microgels obtained by this method can vary widely from about 1:500 to 1:10 depending on the concentration of acid used, the amount of aluminum salts, dissolved in acid, and the pH of the resulting partially neutralized solution of the silicate. Acidification to lower pH values requires the use of more acid and can lead to the formation of polyaluminosilicate having a higher molar ratio of alumina/silica. Solubility data of the system Al2(SO4)3-N2SO4-N2O (Linke, "Solubility of Inorganic Compounds", 4th Ed. 1958, Vol.1) provide the basis for calculating the maximum relations Al2O3/SiO2attainable in polyaluminosilicate (in case of application of Na2O:3,2 SiO2as silicate) using sulphuric acid solutions containing 10-50 wt.% acid and saturated aluminium sulphate, for acidification of a solution of silicate to a pH of 9 (see table. 1A). (If the pH is neutralized to approximately 85% alkalinity Na2O:3,2 SiO2).

As shown, the method of obtaining polyaluminosilicate (PAS) microgels preferably carried out using acidic rilye solutions with pH around the preferred interval 8-10, concerned about 95-60 wt.%-Noah neutralization of Na2O:3,2 SiO2), you can get polyaluminosilicate the microgels with molar relationship Al2O3/SiO2from about 1:35 to 1:400. In the preferred range of concentrations and pH solutions polyaluminosilicate - transparent and after dilution to about 0.5 wt.% SiO2within approximately 24 h retain their activity in the processes of flocculation.

Although the method described in WO 95/25068, produce microgels PASSING, which is particularly useful in paper manufacture, it was unexpectedly found that even better results can be obtained with aluminiowymi or polyaluminosilicate the microgels having the average particle size (microgel) between 20 and 250 nanometers. According to the present invention proposes a method of making paper, in which:

a) add to the aqueous furnish containing fibrous material and, optionally, an inorganic filler, a water-soluble polydisperse polysilicates a microgel having a mean particle size from 20 to 250 nm and a surface area of more than 1000 m2/g, and a water-soluble cationic polymer, and

b) molded and dried product obtained in stage (STIs within 40-250 nm, more preferably 40-150 nm and most preferably 50-100 nm. They can be aluminiowymi polysilicate the microgels or microgels PAS obtained, for example, a two-step method described in WO 95/25068, at which stage after acidification, the product is subjected to aging for a period of time, depending on the selected mode process (i.e., pH concentration of silicon dioxide, aluminum concentration, temperature). To obtain particles of the desired size is usually possible to apply the aging duration 4-40 minutes, for example, 5-30 minutes. For example, if the duration of the aging of the order of 15 minutes, you can get a microgel having a mean particle size of about 100 nm.

The surface area of the microgels is at least 1000 m2/g, preferably 1360-2720 m2/,

As microgels preferably used polyaluminosilicate the microgels, especially those which have a molar ratio of alumina: silica is between 1:10 and 1:1500. Activity polyaluminosilicate microgels can be further improved, and this activity can be saved for longer periods of time, adjusting the pH of the microgel to about pH 1-4, before, p is clochette is the microgels can be stored at higher concentrations of silicon dioxide. Thus, it is possible to completely eliminate the stage of dilution depending on the concentration of silicon dioxide in aqueous acidic solution of an aluminum salt. Regulation of the pH to between about 1-4 allows you to store polyaluminosilicate the microgels with up to 4-5 wt.%. You can use any acid which will lower the pH of the microgel to about pH 1-4. Organic acids are preferred over inorganic mineral acids; most preferred is sulfuric acid.

Thus, according to a preferred variant of the invention, a method of manufacturing paper contains stage:

a) in the aqueous furnish containing fibrous material and, optionally, an inorganic filler, up to 1 wt.%, preferably 0.01 to 1 wt.% (calculated on the dry weight of the composition), introduced a water-soluble polydisperse polyaluminosilicate a microgel having a molar ratio of alumina: silica is between 1:10 and 1:1500 and obtained by the method containing the steps:

1) acidification of an aqueous solution of alkali metal silicate containing 0.1-6 wt.% SiO2, to a pH of 2-10,5, entering the waters of the making, and

2) adjusting the pH of the product obtained in stage (1), to between 1-4 before, after or simultaneously with the stage of dilution, but before gelation to achieve the content of SiO25 wt.%; and, at least, some of 0.001 wt.% (calculated on the dry weight of the composition) water-soluble cationic polymer; the microgel has an average particle size of 20 to 250 nm; and a surface area of more than 1000 m2/g;

b) shaping and drying of the product obtained at stage (a).

Regulation of pH on the above mentioned stages /a//2/ involves lowering the pH and acidification on the stage /and//1/ preferably gives a pH of 7-10,5, more preferably 8-10 and most preferably 8 to 8.5. A solution of silicate of an alkali metal preferably contains 2-3 wt.% SiO2.

Polysilicate used in this invention can be applied in a variety of processes of flocculation and paper production act as agents to improve uderzhivaemoi filler and to improve dehydration (used in amounts up to 1 wt.%, preferably 0.01 to 1 wt. % (based on dry weight of the composition of the paper). They can be used in combination with cationic polymers, such as cationic, Brahma orime) cationic polymers are present in amounts at least until about 0,001% by weight calculated on the dry weight of the composition. Thus, according to the invention it is also proposed a method of manufacturing paper, in which:

a) in the aqueous furnish containing fibrous material and, optionally, an inorganic filler, introduced a water-soluble polydisperse polyaluminosilicate the microgel, consisting essentially of:

1) microgels having a molar ratio of alumina: silica is between 1:25 and 1:1500, with aluminium ions are both intra-and intercalary, and the particles in the microgel have diameters of 1-2 nm; and

2) water, so that the microgels are present at 5 wt.% based on the content of SiO2and at pH 1-4; and at least about of 0.001 wt.% (calculated on the dry weight of the composition) water-soluble cationic polymer;

when the microgel has an average particle size of 20 to 250 nm; and

b) molded and dried product obtained in stage (a).

Anionic polymers, such as anionic polyacrylamide, anionic starches, anionic guar, anionic polyvinyl acetate and carboxymethyl cellulose, and its derivatives can also be successfully used together with polysilicate the microgels and cationic polymers. Depending on silikatnymi the microgels and high molecular weight cationic polymers. In systems containing large amounts of anionic impurities, you can enter, for example, low molecular weight cationic polymers with high charge density, such as polyethylenimine, polydiallyldimethyl and condensation products of amine and epichlorohydrin to more effectively achieve charge balance in the system and get the best results. Under certain conditions, to obtain the best results can be also introduced an additional amount of aluminum compounds in addition to those contained in the acidic solution, such as alum and sodium aluminate. They can be introduced into the composition for the manufacture of paper as a preliminary mixing with polysilicate the microgels according to this invention, and by adding separately.

Proposed water-soluble polydisperse polyaluminosilicate the microgel in water, consisting essentially of:

a) microgels having a molar ratio of alumina:silica is between 1:25 and 1:1500, with aluminium ions are both intra-and intercastes, the particles of the microgel have diameters of 1-2 nm and microgels have an average particle size of 20 to 250 nm and a surface area of more than 1000 m2/g;

b) water StoredProcedure has an average particle size within above.

The following examples are intended to illustrate, but not limit the invention.

Example 1

Prepare a solution of polyaluminosilicate (PAS), stirring 21 g of sodium silicate with respect 3,22 containing 28.5% SiO2with 260 g of deionized water. To the resulting 2.1% of the resultant solution of SiO2added 9,84 ml of a 5 n solution of H2SO4containing 0,052 g Al2(SO4)317H2About to obtain a pH of 8.6. Aliquot samples of the resulting 2 wt.%-aqueous solution of PAS (in terms of SiO2) was diluted and stabilized at a 0.125 wt.%-nom solution of PAS (per SiO2) and at pH of 2.5, diluting 0,0085 N. a solution of H2SO4at various times.

The average particle size of the microgel in the samples with 0.125 wt.%-aqueous solution of PAS (per SiO2) was determined using light scattering goniometer "Brookhaven Tool" model BI-200 SM. The measurements were carried out at room temperature using an argon laser with a wavelength of 488 nm, operating at a power of 200 mW. Different angles were measured intensity of light scattering and analyzed the data using the chart CIMA. The particle size distributions received average rasamee filler and enhance dewatering in paper production was determined by testing on the Canadian standard device for determining the degree of grinding, using the composition of bleached Kraft pulp from 0.3 wt.%-Noah consistency and pH 8, containing 35% pulp from hardwoods, 35% pulp from softwood and 30% precipitated calcium carbonate. Product properties were investigated by adding to the composition paper 9 kg/t (based on dry composition) of the cationic potato starch WWII-40 for 15 s prior to the introduction of 0.9 kg/t of solutions of PAS (per SiO2). Spent the stirring vessel Britta at 750 rpm, and then placed flocculating composition in the Canadian standard device for determining the degree of grinding and performed measurements of dehydration. Below in the table. 1 shows the results for determining the degree of milling (ml) and data on the average particle size of silicon dioxide in the microgel (in nanometers) in a time-dependent dilution.

Fixation of filler was determined using vessel Britta at 750 rpm, adding to the composition paper 9 kg/t of WWII-40 (see above) for 15 s prior to the introduction of 0.9 kg/t of solutions of PAS (per SiO2). After another 15 seconds stirring was started dehydration. Five seconds later, he started to collect the circulating water, and kept it up until there was not collected 100 ml of recycled water. Her left in the ash and figured fixation of filler. The results are also listed in table. 1. In addition, the results graphically shown in Fig.1, in which the degree of grinding plotted on a graph in relation to the size of the microgel particles, and Fig. 2, which is a graph of the relationship between fixation of the filler and the particle size of the microgel.

In addition, investigated the properties of solutions of PAS (using the above method of testing using the Canadian standard device for determining the degree of milling) in different compositions, paper production, namely:

1) in the furnish was added 4.5 kg/t of cationic potato starch WWII-40 for 15 s prior to the introduction of 0.11 kg/t cationic "Percol 182", after which 15 were injected with 0.45 kg/t of solutions of PAS;

2) in the furnish was added to 6.8 kg/t of cationic potato starch WWII-40 for 15 s prior to the introduction of 0.11 kg/t of alum (Al2O3after which 15 were injected with 0.45 kg/t of solutions of PAS;

3) in the furnish was added to 9 kg/t of cationic potato starch WWII-40 for 15 s prior to the introduction of 0.11 kg anionic "Percol 90L", after which 15 were injected with 0.45 kg/t of solutions of PAS.

The results of these three tests are graphically shown in Fig.3-5, where the degree n

Example 2

Prepare a solution of PAS, stirring 21 g of sodium silicate with respect 3,22 containing 28.5% SiO2with 260 g of deionized water. To the resulting 2.1 wt.%-the resultant solution was added the rate of 8.75 ml of a 5 n solution of N2SO4/ containing 0,80 g Al2(SO4)317H2About to obtain a pH of 8.5. Aliquot samples of the resulting 2 wt.%-aqueous solution of PAS (per SiO2) was diluted and stabilized at a 0.125 wt.%-nom solution of PAS (per SiO2) and at pH 2.0, diluting 0,0085 N. a solution of H2SO4at various times.

The average particle size of the microgel in the samples with 0.125 wt.%-aqueous solution of PAS (per SiO2) was determined as described above, and tested to determine the degree of grinding was performed as described in example 1. The results are shown in table. 2.

Example 3

To prepare the solution poluminimalnogo polysilicate (PS), stirring 21 g of sodium silicate with respect 3,22 containing 28.5% SiO2with 260 g of deionized water. To the resulting 2.1 wt.%-the resultant solution SiO2added 10 ml of a 5 n solution of H2SO4. Aliquot samples of the resulting 2 wt.%-aqueous solution of PS (calculated as SiO22SO4at various times.

Determined average particle size of the microgel and measured the degree of grinding as in example 1. The results are shown in table. 3.

As can be seen from these data, the size of the microgel particles in the range according to this invention, provides better performance in paper production (measured as the degree of grinding and uderzhivaemoi filler).

1. Method of making paper, which involves the following stages: (a) introducing into the aqueous furnish containing fibrous material and, optionally, an inorganic filler, a water-soluble polydisperse polysilicate microgel having a mean particle size from 20 to 250 nm and a surface area of more than 1000 m2/g, and a water-soluble cationic polymer and (b) shaping and drying of the product obtained at stage (a).

2. The method according to p. 1, in which as polysilicate microgel use polyaluminosilicate the microgel.

3. The method according to p. 2, in which polyaluminosilicate the microgel has a molar ratio of alumina: silica is between 1: 10 and 1: 1500.

4. The method according to p. 2 or 3, in which the polydisperse polyaluminosilicate, to a pH of 2-10,5 using aqueous acidic solution containing an aluminium salt, and b) dilution water of the product obtained at stage (a), prior to gelation of the content of SiO25 wt. %.

5. The method according to p. 4, which includes the aging of the product obtained at stage (a), in the course of from 4 to 40 minutes

6. The method according to p. 5, which includes the aging of the product obtained at stage (a), within 5 to 30 minutes

7. Method of making paper, which includes the stages of: a) introducing into the aqueous furnish containing fibrous material and, optionally, an inorganic filler to 1 wt. % (based on dry weight of the composition, of water-soluble polydisperse polyaluminosilicate microgel having a molar ratio of alumina: silica is between 1: 10 and 1: 1500, and obtained by the method containing the steps: 1) acidification of an aqueous solution of alkali metal silicate containing 0.1-6 wt. % SiO2, to a pH of 2-10,5, by addition of an aqueous acidic solution containing a sufficient amount of aluminum salts to provide the specified molar relationship; and 2) regulating the pH of the product obtained at stage (1) to values between 1-4 before, after or simultaneously with the stage of dilution, but before Goy weight of the composition of water-soluble cationic polymer, when the microgel has an average particle size of 20 to 250 nm and a surface area of more than 1000 m2/g; b) shaping and drying of the product obtained at stage (a).

8. The method according to p. 7, in which the acidification stage (a) (1) receive pH 7-10,5.

9. The method according to p. 7, in which the acidification stage (a) (1) obtain a pH of 8-10.

10. The method according to p. 7, in which the acidification stage (a) (1) receive pH 8-8,5.

11. The method according to any of paragraphs. 7-10, in which the solution of alkali metal silicate contains 2-3 wt. % SiO2.

12. Method of making paper, which includes the stages of: a) adding to the aqueous furnish containing fibrous material and, optionally, an inorganic filler, a water-soluble polydisperse polyaluminosilicate microgel, consisting essentially of: 1) microgels having a molar ratio of alumina: silica is between 1: 25 and 1: 1500, with aluminium ions are both intra-and intercalary, and the particles in the microgel have a diameter of 1-2 nm, and 2) water, so that the microgels are present at 5 wt. % (based on the content of SiO2and at pH 1-4; and at least about of 0.001 wt. % (based on dry weight of the composition of water-soluble cationic polymer, p).

13. The method according to any of paragraphs. 1-12, in which the composition of the paper introduce an additional amount of aluminum compounds.

14. The method according to any of paragraphs. 1-13, wherein the composition of the paper introduce anionic polymer.

15. The method according to any of paragraphs. 1-14, wherein the microgel has an average particle size in the range 40-250 nm.

16. The method according to p. 15, wherein the microgel has an average particle size in the range of 40-150 nm.

17. The method according to p. 16, wherein the microgel has an average particle size in the range of 50-150 nm.

18. The method according to p. 17, wherein the microgel has an average particle size in the range of 50-100 nm.

19. The method according to any of paragraphs. 1-18, wherein the microgel has a surface area 1360-2720 m2/,

20. Water-soluble polydisperse polyaluminosilicate the microgel in water, consisting essentially of (a) microgels having a molar ratio of alumina: silica is between 1: 25 and 1: 1500, with aluminium ions are both intra-and intercastes, the particles of the microgel have a diameter of 1-2 nm and microgels have an average particle size of 20 to 250 nm and a surface area of more than 1000 m2/g; b) water, so that the microgels are present at 5 wt. % (based on the content of SiO2

 

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