Activation of swelling clays and processes using activated clay

 

(57) Abstract:

The invention can be used in the pulp and paper industry. The composition of dry clay contains a mixture of alkaline earth bentonite and an activating amount of a salt of an alkali metal or ammonium salt of the chemical substance. The last is selected from phosphonates, hydroxycarbonic acids, aminocarbonyl acids and di - or tricarboxylic acids. When this is mixed alkaline-earth bentonite from aqueous activating solution containing these compounds. The paper is prepared as follows: a dispersion of activated bentonite mix to the pulp suspension. Dehydrate with the formation of the raw sheet. The sheet is dried. The invention allows to improve the performance properties and stabilizes the aqueous dispersion of bentonite. 3 s and 5 C.p. f-crystals, 1 table.

This invention relates to the activation of bentonite and activated bentonite in the manufacture of paper.

Bentonite is usually obtained initially in the form of alkaline-earth compound, such as calcium and/or magnesium form of bentonite. That he had a satisfactory performance properties, for example, when proroga calcium and/or magnesium are replaced at ion of sodium or other alkali metal or ammonium ion

The usual way of carrying out this operation consists in mixing clay alkaline earth bentonite from aqueous activating solution, which contains a compound of an alkali metal or ammonium. For example, clay can be represented in the form of powder pre-mix clay with alkaline-earth metal compounds of an alkali metal or ammonium, and this pre-mixture can be mixed in water and left in this form in sufficient time to undergo ion exchange, after which it is diluted for use. Alternatively received in the career of alkaline-earth bentonite may be added directly to the aqueous activating solution under stirring.

In practice, the activating compound that is usually used is a sodium carbonate or sodium bicarbonate, typically in the amount of approximately from 5 to 10 weight %, based on the weight of the clay. The activation is carried out at neutral pH at variance, at pH approximately equal to 10.

Other electrolytes are described in JP-A-6445754 as added for promotion dispersion. It is also known according to U. S. 4,613,542 and 4,624,982 the inclusion of the poly is Ah ER 485124 and U. S. 5,266,538 and 5,391,228. Bentonite, which is introduced in these concentrated slurry may initially be in the form of sodium bentonite, but the EP 485,124 and U. S. 5,391,228 also mention getting slurries by mixing calcium bentonite and activator in the form of sodium carbonate with water and sodium chloride. Processes for the production of paper using bentonite with anionic organic polymer, are also described in the works(U. S. 5,015,334, 4753710).

One problem with the known activated bentonite (for example, activated bentonitovykh powders which are commercially available) is that the sodium carbonate or other activator, which is included in them, leads to the fact that the bentonite (when it is mixed with water creates a relatively high pH value, for example greater than pH 9 and often approximately pH 10. Accordingly, it is necessary to work with bentonite caution in regard to materials that can really create a pH of approximately pH 10.

Another problem is that commonly used activator in the form of sodium carbonate is subjected to ion exchange in the process of activation with the formation of calcium carbonate, the result is tigerbunny bentonites. This case, of course, especially is a problem when the water in which is dispersed bentonite, will be relatively hard.

Another difficulty with the known activated bentonitovykh powders is that sometimes you find that create a stable aqueous dispersion of powders is difficult. And again, it has been found that these difficulties in obtaining a stable dispersion increases with increasing water hardness. Thus, if is relatively hard water, for example, which has a hardness in excess of 10odH and in General in the range of 15odH 50odH, you may experience various problems.

In addition, the operational properties of bentonite, particularly when it is used in the manufacture of paper, can be less than satisfactory at lower pH than at high pH values, and in particular bentonite, activated commonly used method tends to be less effective at acid manufacturing processes of paper (for example, when the pulp suspension has a pH below 6.5 and often in the range from 4.2 to 5.5) in comparison with the case where the suspension to ileostomates improved performance properties.

In accordance with the first aspect of the present invention we provide a composition in the form of dry clay, containing a mixture of swelling clay alkaline earth bentonite and an activating amount of a salt of an alkali metal or ammonium insulating substance selected from phosphonates, hydroxycarbonic acids, aminocarbonyl acids and polycarboxylic acids.

In accordance with the second aspect of the present invention we provide a process of activation of swelling clay alkaline earth bentonite with the formation of swelling bentonite clay with alkali metal, which comprises mixing alkali-earth swelling clay with the aqueous activating solution which contains a salt of ammonium or alkali metal insulating substance selected from phosphonates, hydroxycarbonic acids, aminocarbonyl acids and di-, tri - or more carboxylic acids.

In both aspects of the present invention the insulating substance is preferably introduced as a sodium salt.

In both aspects of the present invention the insulating substance preferably is a sodium citrate.

The resulting activated bentonites have a NESCO is operating properties compared with the same bentonite, which was subjected to a commonly used activation using sodium carbonate at approximately pH 10. They can be used more efficiently in the paper production process, in which the commonly used activated bentonites less effective due to pH or the presence of hardness salts. Therefore, it is usually used bentonites tend to be less effective when the pulp suspension has a pH less than about 6.5, for example, in the range from 4.2 to 5.5, but activated bentonites obtained in the present invention can have very good performance properties of such suspensions without any appreciable loss of activity.

Commonly used activated bentonites can also have the worst performance properties when the pulp suspension is obtained by the use of relatively hard water, for example, having a hardness in excess of 10odH and usually in the range of 15odH 50odH. Improved performance properties are achieved with the use of activated bentonites obtained in the present invention, and in these hard waters. This improvement can be detected by enhanced near the SS activation may be carried out in the separate introduction of swelling clay and activator in the form of chemical substances in the water, for example, the addition of swelling clay in a solution of the activator or the result of adding the activator to the dispersion of swelling clay. In each of these alternatives swelling clay may be introduced in the form of powder or in the form of pulp.

It is preferable, however, that the process would be carried out by mixing pre-swelling mixture of clay and activator with the appropriate amount of water. Preliminary mixture preferably is a powder, but it can also be a liquid composition containing bentonite and activator.

The amount of water used during the process of activation, in the General case is such that the concentration of the swelling clay during a process is equal to from 2 to 8% or even up to 10%. Usually it is at least equal to 3%, and often it does not exceed about 5 or 6%, while often prefer 4 or 5%. These quantities are quantities that are typical of the processes of activation using sodium carbonate, and it is convenient that the same number can be used in the present invention.

However, an additional advantage of the activators used in the present invention, sostoi the shaft 8 to 14 or 15%. Despite the fact that clay, activated during this process, so it may become very viscous, the advantage of activators is that the resulting compositions still have the appropriate low viscosity and good properties in respect to fluid flow, so that they can easily be recycled.

In accordance with a third aspect of the present invention we provide a method for the production of paper, including the formation of a pulp suspension, the adulteration of dispersion of activated bentonite to the slurry, dewatering the suspension with the formation of the raw sheet and drying the sheet, in which the dispersion of activated bentonite obtained from the method according to p. 4, for which the choice should be thinning, or by mixing the compositions of p. 1 with water.

The insulating substance, apparently, in effect as a result of exchange with alkaline-earth ions and fixing exchanged with calcium ions or magnesium in a form that they can not be exchanged back into the bentonite. The insulating substance is usually located in the sodium form, due to the fact that sodium is the preferred cation, which is introduced in the ion about what I such as potassium or ammonium.

Suitable phosphonates, which can be used as an insulating substance may be selected from any of phosphonates, which are known for the ability to isolate ions of alkaline-earth metals, such as materials sold under the trademark Dequest.

Fit hydroxycarbonate acid, which can be used include materials such as tartrate or sodium gluconate, but the preferred material is sodium citrate. If necessary, can be used in the form of the free acid in the case of preferences, and not water-soluble salt.

Suitable aminocarbonyl acid include materials such as DTPA, NTA, and EDDHA and EDTA:

Di -, or three- (or more) carboxylic acid, which can be used include malonic acid, succinic acid, glutaric acid, adipic acid and oxalic acid, usually in the form of sodium salts. Acid (and all chemical substances) preferably represent materials with low molecular weight, for example having a molecular weight below 500, and usually they are Monomeric. The use of sodium polyacrylate with a high molecular missbreese.

The insulating substance shall be used in sufficient quantity to create activated in a particular system, and it is installed in the result of routine experimentation. Based on the weight of the quantities in the General case it is in the range from 1 to 20%, based on the dry weight of bentonite, most preferably in the range of from 3 to 15%.

All these quantities imply that the insulating substance is the only relevant activating material in the composition. Can be used mixtures of one or more insulating substances, and can be used, if necessary, mixtures of one or more insulating substances with other best activators, such as sodium carbonate. In that case, if you use sodium carbonate, then it would be possible to reduce the number of chemical substances that will be required. The number of insulating substances may need to be increased to a considerable extent, if present in sufficiently undesirable components such as sodium chloride, and accordingly it is preferred that there have been no intentional additions of simple electrolytes such as chloride, sulfate is that usually referred to as clay-type bentonite or bentonite. In General they are smectites or montmorillonite, while the latter is preferable. Suitable clays smectite or montmorillonite include violinski bentonite and fallerovo the earth, and various clays, which include those known under the chemical names of hectorite and bentonite. Clay will be in the alkaline-earth form, usually calcium or calcium and magnesium form.

The inclusion of bentonite in the manufacturing processes of paper for different purposes is very well known, and the present invention can be applicable to all these processes. For example, the bentonite may be included as a dispersant additive to bake.

One paper production process, which can be applied to the present invention, is a process in which the bentonite is added to the pulp suspension, usually in an amount of from 0.02 to 2% of dry weight, and then added to the polymer retaining Supplement with a medium or high molecular weight (for example, above 500000), in the General case, after the last point of high shear stress (for example, directly in front of the pressure box, directly in front of dehydration). Polymer with a high molecular weight can be neion the ssy or pulp with a relatively high demand for cations.

Processes of this type, which have a special importance are the processes in which the pulp has a relatively high demand for cations, and the polymer is essentially non-ionic or anionic, and paper products is primarily newsprint or material for corrugated cardboard. Processes of this type, in which the full content of the filler is relatively small, are described in the works of U. S. 4305781 and EP-A-17353, to which you should refer for additional details on a suitable non-ionic or weakly ionic polymers and suitable cellulosic suspensions, and which are included as references. Can be used more highly anionic or cationic polymers. These processes are of particular importance when the pulp suspension contains waste from which the removed ink. Suitable polymers and fillers (if the pulp has fillers) are also described in the works of EP-A-608989 and AU-A-63977/86.

The present invention is of particular value when it is applied to processes microcasting retention, in which the retaining polymer additive is added to the aqueous suspension, is after the last point of high shear stress, for example, right in front of the pressure box before dehydration. The polymer may be non-ionic or anionic, but often it is cationic.

The cationic polymer may be a natural material such as cationic starch, but preferably a substantially linear synthetic cationic polymer having a molecular weight greater than 500000. The amount of cationic polymer, which is present in the dispersion at the time of impact shift, must be sufficient to ensure that the result of adding the polymer would be formed flocculi and to flocculi destroyed would be due to shear effects with education microfocus, which would be resistant against further destruction in the feedback shift, but that would have sufficient charge to interact with the bentonite to provide better retention and/or molding in comparison with what can be obtained by adding only one polymer after the last point of high shear stress.

The shift may be caused by turbulent simply passing along a pipe or may be caused by passage through the centrifugal sorting, pump or other device, where PR is the commercial basis of the applicants under the trade mark Hydrocol, and preferred processes are described, for example, in U. S. patents 4753710, 4913775, 4969976, all of them are included here as reference. The optimum amount of polymer for any particular process can be determined by routine experimentation and will depend among other things on whether the entered cationic polymer with a low or medium molecular weight and/or polymer, durable in dry condition, in aqueous suspension at any earlier stage.

Activated bentonite present invention can be used everywhere where it can be useful bentonite, for example, in the dehydration of pulp, dewatering of paper sludge in the separation liquid/solid, with the clarification of sewage, the water-containing waste ink, and when you commit pitch (in the process of paper production). Activated bentonite can also be used in other industries that use activated bentonite, for example, upon receipt of bentonite for pelletizing iron ore, or for applications for the processing of other minerals.

Below are some examples.

Example 1.

5 weight parts of calcium bent Voditsa below. In each example, the amount of activator is expressed as a percentage, based on the dry weight of bentonite. Listed below are the products that were used.

And - sodium carbonate - 6%

With - sodium nitrate - 17%

D - sodium salt of EDTA - 21%

Example 2

Activated bentonites obtained in example 1 was used in a laboratory simulation of the paper production process described in US 4753710. In particular, the diluted mass to 0.5% of a fibrous composition bleached Kraft paper was added to 500 g/t of cationic polyacrylamide of high molecular weight (characteristic viscosity 6 DL/g) obtained from 40 weight % of dimethylaminoethylacrylate made Quaternary base with methyl chloride, and 60 percent by weight of acrylamide. The pulp suspension is subjected to shear exposure for 60 seconds at 1500 rpm, then with the specified dosage was added to the activated bentonite suspension was carefully mixed in the chamber Britta with partitions, and for draining 700 ml 1000 ml of diluted fibrous mass was recorded times of dehydration on the Shopper Rigler. In this test, the best result is the smallest possible columns labeled "bentonite" is expressed in g/t of dry weight, and the numbers in the columns labeled with the letter represent the times of dehydration in seconds for use with a specified number of activated bentonite specified in example 1.

In this table the column titled Ca, represents the results of the use of non-activated calcium bentonite.

These data show that citrate activation (column C) may give the same or better results compared with the activation of the sodium carbonate in the time of dehydration, and that adequate, but less satisfactory results can be obtained using EDTA (column D).

1. The composition of dry clay, containing a mixture of alkaline earth bentonite and an activating amount of a salt of an alkali metal or ammonium salt of an insulating substance selected from phosphonates, hydroxycarbonic acids, aminocarbonyl acids and di - or tricarboxylic acids.

2. The composition according to p. 1, wherein the salt is a sodium salt.

3. Composition under item 1 or 2, characterized in that the insulating substance is sodium citrate.

4. The method of activation of alkaline earth bentonite, including with the salt of an alkali metal or ammonium salt of the chemical substance, choose from a phosphonate, hydroxycarbonic acids, aminocarbonyl acids and di - or tricarboxylic acids.

5. The method according to p. 4, characterized in that the insulating substance is in the form of sodium salt.

6. The method according to p. 4, wherein the insulating substance is sodium citrate.

7. The method according to any of paragraphs.3 to 6, characterized in that it is carried out at a concentration of bentonite from 2 to 14%.

8. Method for the production of paper, including the formation of a pulp suspension, the adulteration of dispersion of activated bentonite to the slurry, dewatering the suspension with the formation of the raw sheet and drying the sheet, in which the dispersion of activated bentonite get way under item 4, for which the selection is followed by dilution, or by mixing the compositions of p. 1 with water.

 

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