The use of calcium carbonate in an acidic aqueous medium

 

(57) Abstract:

Composition refers to the acid-stable suspension of calcium carbonate with a pH less than 7, preferably in the range of about 6 - 7. It contains water, calcium carbonate, and an acid stabilizer of the water-soluble calcium salt, a weak acid, a chelating agent, a weak acid capable helatirovat calcium ion, or mixtures thereof. The acid stabilizer is present in an amount sufficient to provide an aqueous suspension of calcium carbonate increased concentration of calcium ion and acidic pH. In the proposed acid-stable suspension of calcium carbonate with an acid stabilizer is present in a quantity sufficient to provide a concentration of calcium ion is from about 1 millimolar to about 5 molar, preferably about 1 to 120 millimolar. The invention also relates to a method for obtaining an acid-stable suspension of calcium carbonate of the invention, the method of manufacturing paper filled, which includes a stage of addition of the acid-stable suspension of calcium carbonate of the invention to wood pulp in the manufacturing process of acid paper, and paper with stuff that is in the paper. 4 C. and 20 C. p. F.-ly, 4 Il.

The scope of the invention

The present invention relates to acid-stable suspensions of calcium carbonate having a low pH, and to a method for producing the suspension. This acid-stable suspension of calcium carbonate useful as a filler for neutral or acidic paper to improve the optical properties of this paper.

The background to the invention

Typically, fillers are added to the paper during the paper manufacturing process to improve the optical properties of paper, such as white. Acid paper making, which is often used for making paper from wood pulp, wood pulp, the pH of this wood pulp, usually much below 7 and is typically in the range of from about 4 to about 6. For comparison, in the neutral papermaking pH is usually maintained within the range from about 6.8 to about 7.5. Therefore, when the acid paper making and in the neutral papermaking in certain conditions necessary filling material which is stable and resistant to acid conditions from subacid to acid.

As fillers for acid and nanosci titanium dioxide, are expensive and, thus, increase the cost of paper.

As the crushed natural and precipitated calcium carbonate is used as filler material for alkaline paper, usually of paper pulp with a pH of about 8. The resulting paper has improved optical properties, not counting the cost of more expensive fillers. However, calcium carbonate is usually decomposed in acidic aqueous environment and thus usually cannot be used as filler for acid paper, unless the filler of calcium carbonate is not acid-stable, i.e. resistant to decomposition at pH less than 7. Because alkaline conditions and alkaline fillers generally have a negative impact on the properties of paper from wood pulp, filler of calcium carbonate can be used for pulp wood pulp only if this is a filler made of calcium carbonate acid stabilized for use in acidic conditions.

The materials of the filler of calcium carbonate, as a besieged and natural shredded, processed or modified in the previous field for various purposes. In closedeye. Processing included the coating of particles of calcium carbonate directionspanel substance, such as a polysaccharide, fatty acid, or a resinous substance, and processing of particles of calcium carbonate or suspension of calcium carbonate of different weak acids and bases, salts and chelating agents.

In particular, in U.S. patent 4240870 disclosed the addition of at least one of phosphoric acid such as orthophosphoric acid, metaphosphoric acid, tripolyphosphoric acid, pyrophosphoryl acid, Metropolitana acid and exopolitica acid, or sodium, potassium or zinc salt of at least one of phosphoric acid to the aqueous suspension of calcium hydroxide as the first stage of the multistage process of obtaining precipitated calcium carbonate. Similarly, in U.S. patent 4244933 disclosed the addition of one of phosphoric acids or salts disclosed in 4240870, as an ingredient in either the first or the second-stage multi-stage process to obtain precipitated calcium carbonate.

In U.S. patent 4018877 described addition compleksoobrazuyuchee agent, such as a polyphosphate, such as sodium hexametaphosphate, during or after the end of the peo agent is added after completion of the deposition of mostly calcium carbonate. Differently, the complexing agent is added during subsequent ripening stages or carbonization.

In U.S. patent 4157379 disclosed the addition of a soluble metal salt such as a phosphate of an alkali metal, after the initial carbonation of aqueous suspension of calcium hydroxide.

In open Japanese patent application 090821/60 described a method of producing calcium carbonate, in which the condensed phosphoric acid or its salt is added to a viscous gelatinous emulsion, obtained by carbonation of aqueous dispersion of calcium hydroxide. Condensed phosphoric acid can be hexametaphosphate acid, pyrophosphoryl acid, tripolyphosphoric acid, polyphosphoric acid or ultrapetrol acid. In open Japanese patent application 090822/60 described a similar way with the addition of the magnesium-containing compound to the dispersion of calcium carbonate.

However, in all of the above references discloses methods, requiring the addition of phosphoric acid or phosphate salts during the process of obtaining precipitated calcium carbonate.

In U.S. patent 4793985 disclosed the addition of a dispersing agent such as water-soluble salt of poliya to improve the distribution of solids in a liquid, as part of the method of obtaining ultramega of calcium carbonate.

In U.S. patent 4610801 solved using polyphosphoric acid or polyphosphate suspension of mineral particles, such as calcium carbonate, for waste processing.

In U.S. patent 4219590 disclosed processing of calcium carbonate with an average particle size of not more than 20 μm, the acid gas that can interact with calcium carbonate.

In Japanese patent 030812/82 disclosed improving the surface of particles of calcium carbonate when added to aqueous suspensions of calcium carbonate aqueous solution of condensed phosphate, such as metaphosphate or pyrophosphate. As a result, particles of calcium carbonate are resistant to acid and pH of these particles is reduced by 0.1 to 5.0.

In U.S. patent 5043017 and 5156719 described the acid-stabilized calcium carbonate for use as a filler for paper from neutral to weak acid. In these patents claimed that the acid-stabilized calcium carbonate is able to resist decomposition in weakly acidic conditions due to the buffer action between the absorbed or reactive chelating calcium agent or conjugate base on the surface is And 5505819 disclosed a method of manufacturing a neutral paper containing wood pulp and a filler made of natural calcium carbonate. the pH of the mass is supported in the range from 6.7 to 7.3 by adding a reducing pH and BufferedReader agent, preferably phosphoric acid.

In U.S. patent 5531821 disclosed acid-resistant filler of calcium carbonate for use in the manufacture of paper from neutral to weak acid containing a mixture of calcium carbonate and from about 0.5 to 10 percent cationic salts and anionic salt based on the dry weight of calcium carbonate.

There is still a need for improved materials from the acid-stabilized calcium carbonate and methods of production of such materials for use in acid paper-making.

Brief description of the invention

The present invention is directed to a suspension of the acid-stabilized calcium carbonate with a pH less than 7, preferably from about 6 to about 7, which can be used as filler for the manufacture of acid paper with a filler, a suspension containing water, calcium carbonate, and an acid stabilizer of one of the water-soluble calcium salts, weak acids or chelating agent and some of their mixtures. The acid stabilizer is present in sufficient quantity DL is bonat calcium is present in the acid-stable suspensions of calcium carbonate of the invention in a quantity used in manufacturing processes of paper, usually from about 1 to about 40 weight percent, preferably from about 5 to about 30 weight percent, most preferably from about 15 to about 25 weight percent, and preferably is a precipitated calcium carbonate.

In the first variant embodiment of this invention the acid stabilizer is a water-soluble calcium salt and is usually present in a quantity sufficient to provide a concentration of calcium ions from about 1 millimolar to about 5 molar, preferably from about 1 to about 120 millimolar. Preferred salts include calcium sulfate, calcium acetate, calcium nitrate, calcium citrate, any halide of calcium, such as calcium chloride, and mixtures thereof.

In the second variant embodiment of the invention the acid stabilizer is a weak acid and is present in a quantity sufficient to provide a concentration of a weak acid is from about 0.1 to about 1000 millimolar, preferably from about 0.2 to about 100 millimolar. Preferred weak acids include carbonic acid, phosphoric acid, sulphurous acid, or carboxylic acid, and a lot of acid stabilizer may contain, in addition, water-soluble calcium salt in an amount sufficient to provide a concentration of calcium ions from about 1 millimolar to about 5 molar, preferably from about 1 to about 120 millimolar.

In an additional variant embodiment of the invention the acid stabilizer comprises a water-soluble calcium salt in an amount sufficient to provide a concentration of calcium ions from about 1 millimolar to about 5 molar, preferably from about 1 to about 120 millimolar, and chelating agent in a quantity sufficient to provide a concentration of the chelating agent is from about 0.01 to about 1000 millimolar, preferably from about 0.1 to about 100 millimolar. Preferred chelating agents include polycarboxylate, such as the sodium salt of ethylenediaminetetraacetic acid, or sodium polyacrylate, polyphosphates, phosphonates, polyphosphonates.

In the following variant embodiment of the invention the acid stabilizer contains a weak acid capable helatirovat calcium ion present in a concentration of from about 0.001 to about 1000 millimolar, preferably from about 0.01 to about 100 millimolar. Pre is lacrilube acid, acid, polyphosphorous acid, or any compound containing the group of carboxylic acids, such as ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), diethylenetriaminepentaacetic acid (DTPA), or any compound containing a phosphonic acid group, such as nitrilotri(methylene)triphosphonate acid.

The present invention relates also to a method of making paper with filler, which includes the addition of an acid-stable suspensions of calcium carbonate containing any of the above acid stabilizers, to the paper pulp during the manufacture of acid paper, and then drafting paper with filler on this way. In addition, the invention relates to a method of making an acid-stable suspensions of calcium carbonate by preparing a slurry of water, calcium carbonate and acid stabilizer of the water-soluble calcium salt, a weak acid, a chelating agent, a weak acid capable helatirovat calcium ion, or mixtures thereof. Water-soluble calcium salt, a weak acid, a chelating agent, a weak acid capable helatirovat calcium ion, or a mixture probablyone calcium and acidic pH less than 7. The preferred method aqueous suspension of calcium hydroxide initially carbonizer to obtain a suspension of precipitated calcium carbonate. This invention relates to acidic paper containing a filler obtained in accordance with the invention.

Fig. 1 is a graph showing the influence of calcium chloride and calcium acetate on the pH of the suspension of calcium carbonate.

Fig. 2 is a graph showing the effect of carbon dioxide and calcium ion on the pH of the suspension of calcium carbonate.

Fig. 3 is a graph showing the influence of calcium ion and a chelating agent at a pH of suspensions of calcium carbonate.

Fig. 4 is a graph showing the effect of compounds containing phosphonic acid, the pH of the suspension of calcium carbonate.

Detailed description of the invention

The present invention relates to acid-stabilized calcium carbonate, which can be used in neutral or acidic aqueous environment with little or no decomposition. Calcium carbonate may be either precipitated or crushed natural, but preferably is deposited. Unless crushed natural calcium carbonate.

The acid-stabilized calcium carbonate in accordance with the invention for use as filling material in a neutral or acidic paper are treated suspensions of calcium carbonate, which increases the concentration of calcium ions, CA2+in order to ensure the suspension of calcium carbonate having an acidic pH, but not alkaline pH of the untreated suspension of calcium carbonate. At present, it was found that lowering the pH of the suspension of calcium carbonate by increasing the concentration of calcium ion provides material of calcium carbonate is stable in neutral or acidic aqueous environment, like the one used in the paper machine, or method used for the manufacture of neutral or acidic paper. The material of the acid-stabilized calcium carbonate produced by adding to a suspension of calcium carbonate of at least one acid stabilizer of the water-soluble calcium salt, a weak acid, or a chelating agent, a mixture of water-soluble calcium salt and a weak acid, or a mixture of water-soluble calcium salt and a chelating agent. Adding to the suspension of calcium carbonate each hiszpanii of calcium carbonate.

In the first variant embodiment of the present invention as an acid stabilizer to the suspension of calcium carbonate is added a water-soluble calcium salt. The addition of soluble calcium ion lowers the pH of the suspension of calcium carbonate by lowering the concentration of soluble carbonate ion, CO32-. In addition, calcium ions are weakly acidic in aqueous solution. Preferred water-soluble calcium salts include the halides of calcium, particularly calcium chloride, calcium sulfate, calcium acetate, calcium nitrate and calcium citrate. However, in the present invention can be any water-soluble salt of calcium, is able to provide the concentration of calcium ion is from about 1 millimolar to about 5 molar, preferably from about 1 to about 120 millimolar. Alternative these salts can be obtained in situ by adding the appropriate amount of acid, which will interact with calcium carbonate, resulting in the desired concentration of the calcium salt. For example, you can add hydrochloric acid to produce calcium chloride, can be added nitric acid to produce calcium nitrate, or you can add acetic acid to the floor is lowered, and the concentration of calcium ion is increased when adding an acid stabilizer of a weak acid or a combination of a weak acid with a water-soluble salt of calcium. Weak acid stabilizes the suspension of calcium carbonate due to the creation of a buffer system with calcium carbonate having a low pH. The addition of calcium ion to this buffer system leads to a further decrease in the pH of the suspension of calcium carbonate in the manner described above. The present invention is useful in various weak acids. Preferred weak acids include carbonic acid, obtained by adding carbon dioxide to the aqueous solution or suspension, phosphoric acid, sulphurous acid and various carboxylic acids, such as acetic acid. As before, the invention is useful concentration of calcium ion is from about 1 millimolar to about 5 molar, preferably from about 1 to about 120 millimolar. The concentration of the weak acid should be from about 0.1 to about 1000 millimolar, preferably from about 0.2 to about 100 millimolar.

Acid-stable suspension of calcium carbonate with acid pH can also be obtained by adding water-soluble calcium salt and a chelating Jolee low pH values, than those that can only be obtained with the calcium ion. Preferred chelating agents include polycarboxylate, such as sodium salt of EDTA and sodium polyacrylate. Typically, the chelating agent is added in a concentration of from about 0.01 to about 1000 millimolar, preferably from about 0.1 to about 100 millimolar. The above-described water-soluble calcium salt is used in the usual and preferred concentrations given above.

In the following variant embodiment of acid-stable suspension of calcium carbonate with acid pH can be obtained by adding a weak acid capable of chelating calcium. The preferred weak acid capable helatirovat calcium include polycarboxylic acids, such as EDTA, NTA, DTPA, and polyacrylic acid, sulfonic acids, and polyphosphonate acid, phosphonic acid, or compounds containing phosphonic acid, such as nitrilotri(methylene)triphosphonate acid. The concentration of chelating calcium weak acids useful in the invention typically ranges from about 0.001 to about 1000 millimolar, preferably from about 0.01 to about 100 millimolar.

In each of the options volumeretrytimer in the form of water-soluble calcium salt, weak acid or chelating agent. The addition of weak acids usually leads to the generation of calcium ion in the reaction with calcium carbonate in suspension. This increase in the concentration of calcium ion lowers the pH by reducing the concentration of carbonate ion through a conventional ion effect. Chelating agents maintain the concentration of calcium ion and stabilize the system. In addition, a weak acid will usually bufferinput system with a stable low pH. In General, increasing either the concentration of calcium ion, or the concentration of weak acid lowers the pH of the suspension. Suspension of calcium carbonate with a stable low pH becomes when this acid-stable for use as filling material for neutral or acidic paper.

Being made, acid-stable suspension of calcium carbonate obtained in accordance with the present invention, can be added to neutral or acidic paper as the filling material during the process of making paper using any known in the field of method for making paper with filler. Accordingly, in the present invention includes a method of manufacturing ª the present invention to wood pulp in the manufacturing process of acid paper and drawing paper with filler on the way.

Examples

The following examples are only to illustrate the preferred variants of the present invention and should not be construed as limiting the invention, the scope of which is defined by the attached claims.

Example 1

The impact of adding soluble salts of calcium chloride and calcium acetate on the increase in the concentration of calcium ion or the addition of hydrochloric acid and acetic acid to generate the corresponding salts in situ at a pH of 5% slurry of calcium carbonate are presented in figure 1. Received a 5% suspension of calcium carbonate with a concentration of the calcium salt or calcium chloride or calcium acetate, in the interval from 0 to 250 millimolar. In each case, the pH was measured four days after the preparation of each suspension. As you can see from the graph in Fig. 1, increasing the concentration of the calcium salt leads to decrease the pH of the suspension. It is typical to add any water-soluble calcium salt or add to any suspension of the acid, which will lead to the formation of soluble salts of calcium carbonate. Despite the acidic pH of the obtained suspensions, suspensions were acid-Stevie decomposition of the carbonate.

Example 2

The effect of the addition of weak acids and weak acids and calcium ion at a pH of 5% slurry of calcium carbonate are presented in figure 2. a 5% suspension of calcium carbonate obtained and placed in an atmosphere of carbon dioxide at a pressure of one atmosphere. At one atmosphere of CO2the pH of the slurry can be maintained at pH 6 for at least 10 days without addition of calcium ion and at little or no decomposition of calcium carbonate in suspension. The addition of calcium ion to be added in the form of calcium chloride, leads to a further lowering of the pH of the suspension to 5.8 at 20 millimolar concentrations of calcium ion and to 5.4 at 200 millimolar concentration of calcium ion. As for suspensions with pH 6, pH slurries, acid-stabilized with carbon dioxide and calcium ion was stable for at least 10 days.

Example 3

The influence of a constant concentration of chelating agent is sodium hexametaphosphate (GMFN) at various concentrations of calcium ion at a pH of 5% slurry of calcium carbonate after three days are shown in figure 3. Were prepared with a 5% suspension of calcium carbonate from 0.7 millimolar concentration GMFN igure 3, the pH of the suspension of calcium carbonate decreases with increasing concentration of calcium ion. However, in the presence of a chelating agent, a pH lower than in the presence of calcium ion. For example, as shown in Fig. 1, the pH does not contain a chelating agent suspensions of calcium carbonate at 120 millimolar concentrations of calcium ions is about 6.3. The addition of a sufficient amount of calcium ion to obtain a suspension from 0.7 millimolar concentration of chelating agent GMFN lowers the pH further to 5.5.

Example 4

The effect of compounds containing a phosphonic acid group, i.e. nitrilotri(methylene)triphosphonate acid, at a pH of 5% slurry of calcium carbonate, presented in figure 4. Were prepared with a 5% suspension of calcium carbonate with 0.4, 4 and 40 millimolar concentration of acid. In each case, phosphonic acid interacted with a small portion of the calcium carbonate in suspension, increasing the concentration of calcium ions and reducing pH. In addition, the solution was stable due to the chelating effect of the resulting phosphonate and buffer the effects of acid, which was further reduced pH. Systems of this type are highly effective to reduce the pH of the suspension at 40 mil is ü the invention is well calculated to implement the previously stated goals, it is clear that the experts in this field can offer numerous modifications and variations of the embodiment. Therefore, it is implied that the accompanying claims cover all such modifications and variations of the embodiments that fall within the true spirit and scope of the present invention.

1. Acid-stable suspension of calcium carbonate for use in the manufacture of acid paper, which includes water, calcium carbonate, and an acid stabilizer selected from the group consisting of water-soluble calcium salts, weak acids, chelating agent, a mixture of water-soluble calcium salts and weak acids, mixtures of water-soluble calcium salt and a chelating agent, in which the stabilizer is present in an amount sufficient to provide an aqueous suspension of calcium carbonate increased concentration of calcium ions and pH less than 7.

2. Acid-stable suspension of calcium carbonate under item 1, in which the calcium carbonate is present in an amount of about 1 to 40 wt. %.

3. Acid-stable suspension of calcium carbonate under item 1, in which the calcium carbonate is precipitated calcium carbonate.

4. Acid-stable welding temperature, the water-soluble calcium salt, present in a quantity sufficient to provide a concentration of calcium ions from about 1 millimolar to about 5 molar.

5. Acid-stable suspension of calcium carbonate under item 4, in which the water-soluble calcium salt is present in a quantity sufficient to provide calcium ion concentration of about 1 to 120 millimolar.

6. Acid-stable suspension of calcium carbonate under item 4, in which the calcium salt is a calcium sulfate, calcium acetate, calcium nitrate, calcium citrate, calcium halide or a mixture thereof.

7. Acid-stable suspension of calcium carbonate under item 6, in which the calcium halide is a chloride of calcium.

8. Acid-stable suspension of calcium carbonate according to any one of paragraphs. 1-3, in which the acid stabilizer is a weak acid that is present in a quantity sufficient to provide a concentration of a weak acid is about 0.1 - 1000 millimolar.

9. Acid-stable suspension of calcium carbonate under item 8, in which the weak acid is added in sufficient quantity to provide a concentration of a weak acid is about 0.2 - 100 millimolar.

11. Acid-stable suspension of calcium carbonate according to p. 10, in which the water-soluble calcium salt is present in a quantity sufficient to provide a concentration of calcium ion is about 1 - 120 millimolar.

12. Acid-stable suspension of calcium carbonate under item 8, in which the weak acid is a carbonic acid, phosphoric acid, sulphurous acid or carboxylic acid.

13. Acid-stable suspension of calcium carbonate under item 1 or 3, in which the acid stabilizer comprises a water-soluble calcium salt in an amount sufficient to provide a concentration of calcium ion is from about 1 millimolar to about 5 molar, and a chelating agent at a concentration of about 0.01 - 1000 millimolar.

14. Acid-stable suspension of calcium carbonate under item 13, in which the water-soluble calcium salt is present in a quantity sufficient to provide a concentration of calcium ion is about 1 - 120 millimolar, and chelating agent in a concentration of about 0.01 - 100 millimolar.

15. Acid-stabilityof CLASS="ptx2">

16. Acid-stable suspension of calcium carbonate under item 15, in which polycarboxylate is a sodium salt of ethylenediaminetetraacetic acid or sodium polyacrylate.

17. Acid-stable suspension of calcium carbonate according to any one of paragraphs. 1-3, in which the acid stabilizer is a weak acid capable helatirovat calcium ion present in a concentration of about 0.001 to 1000 millimolar.

18. Acid-stable suspension of calcium carbonate under item 17, in which the weak acid is present in a concentration of about 0.01 - 100 millimolar.

19. Acid-stable suspension of calcium carbonate under item 17, in which the weak acid is a polycarboxylic acid, polyacrylic acid, acid, polyphosphorous acid or a compound containing phosphonic acid.

20. Acid-stable suspension of calcium carbonate according to p. 19, in which the weak acid is an ethylenediaminetetraacetic acid, nitrilotriacetic acid, diethylenetriaminepentaacetic acid or nitrilotri(methylene)triphosphonate acid.

21. A method of manufacturing paper filled with, vklyuchayuschimisya production of acid paper and manufacture of paper filled with the mentioned method.

22. A method of making an acid-stable suspension of calcium carbonate with a pH less than 7, including the formation of a suspension containing water, calcium carbonate, and an acid stabilizer selected from the group consisting of water-soluble calcium salt, a weak acid, a chelating agent, a mixture of water-soluble calcium salt and a weak acid, a mixture of water-soluble calcium salt and a chelating agent, in which the stabilizer is present in an amount sufficient to provide an aqueous suspension of calcium carbonate with a high concentration of calcium ion and pH less than 7.

23. The method according to p. 22, additionally comprising the primary carbonation of the aqueous suspension of calcium hydroxide with formation of a suspension of precipitated calcium carbonate.

24. Acidic paper with a filler containing a filler made in accordance with the method according to p. 22.

 

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