HU200304B - Process for producing gels of reversible capacity of water absorption and desorption from clay minerals and polymeres - Google Patents

Abstract

The present invention relates to a method for producing stabilized, reversible water uptake and water release gels from clay minerals and polymers. In accordance with the invention, unrefined or optionally treated up to 1.0% by weight of activating agent, based on the weight of the clay mineral, is at least about 8% by weight, preferably from about 10% to about 70% by weight of dry matter, of at least 0.6% by weight of dry matter, preferably 1, 5 to 15% by weight of a water-soluble polymer capable of reacting with clay, if desired, to reduce or remove the water content of the resulting material, and, if desired, to add at least 0, if necessary, water to the clay mineral content prior to use. 5% by weight, preferably between 1.0 and 5.0% by weight of the activating agent. Scope of the description: page 5, figure 0 HU 200304A -1-

Description

BACKGROUND OF THE INVENTION The present invention relates to an improved process for the preparation of gels with a stable structure having reversible water uptake and water retention properties from clay minerals.

Nos. 186,325 and 189,280. It is known from Hungarian patents that when thixotropic, triple-celled swellable smectites and / or swollen oily chain silicates are reacted with water-soluble polymers capable of reacting with a given clay, in activated state or in an activation medium, the polymeric clays.

Activation forms chemical bonds with the polymer at sites of clay mineral cleavage, largely disassembled into its elemental plates and chains, and is "attached" to the polymer chain and forms a gel with a stable structure. This gel loses the thixotropic character of the starting material, does not pepper in water, but at the same time swells well in water and is able to reversibly absorb and release water. Gels of this type can be used with good results as waterproofing layers and to improve the water balance of the soil.

As in the cited patents, a stable, irreversibly fixed structure capable of forming a reversible water uptake and release gel is a prerequisite for reacting the clay mineral with the polymer when activated or during activation.

Otherwise, if they are based on clay minerals that are "clumped", that is, not broken down into their elemental sheets or chains, the clay minerals "react" only on their surface, interacting loosely with sorption, but with little or no chemical bonding.

The structure and gelling properties of a product formed by the interaction of inactivated clay minerals and water-soluble polymers, composed of inorganic and organic macromolecules, are essentially determined by the particular characteristics of the inorganic component (i.e., clay mineral) and are modified to a greater or lesser extent by the gelling characteristics of the organic component.

For example, when thixotropic, triple-layered, swellable clay minerals are reacted with polymers in an inactive state, the resulting final product typically remains thixotropic for the parent clay mineral, and the polymer present merely modifies other gel properties (e.g., elasticity, hardness, swellability). .

The highest quality gels are obtained by reacting the activated clay minerals in a relatively dilute suspension with water-soluble polymers, otherwise the polymer will not be adequately dispersed due to the rapid reaction.

Thus, gels with a stable structure, reversible uptake and release of water are first formed in the form of a dilute suspension, which is expensive to transport and from which only some of the water can be removed by lengthy, energy-intensive drying operations. It is also possible to form a gel from a dense activated clay mass, but the gel thus formed is generally of a lower quality than that of the dilute suspension, and special, very powerful mixing equipment is required to react the clay mineral and the polymer. This method is therefore instrument-intensive and requires high process energy, which significantly reduces its cost-effectiveness.

There is a need for a process to overcome these drawbacks and adjust gels of impeccable quality in a more economical way than hitherto.

In our experiments, it has been surprisingly discovered that if the clay mineral is reacted in an inactive or partially activated state with the amount of water-soluble polymer required to form the gel, the resulting clay mineral / polymer complex is subsequently activated, preferably immediately before use, the cleavage of clay minerals on elemental plates or chains and the reactive sites of the clay mineral thus reacting directly with the polymer, resulting in a stable gel structure fixed by irreversible chemical bonds with reversible water uptake and release. This discovery is extremely surprising, since it could be expected that the polymer present in the unactivated clay mineral / polymer complex, fixed by sorption or loose chemical bonding on the surface of the clay 30, would completely prevent further activation.

The present invention relates to a process for the preparation of gels with reversible uptake and release properties of stabilized agents from clay minerals and polymers. According to the invention, the clay minerals are in an inactivated or optionally not more than 1.0% by weight, based on the weight of the clay, at least 8% by weight, preferably 10-70% by weight, based on the dry matter content. 0.6% by weight, preferably 1.5-15% by weight, of a water-soluble polymer capable of reacting with the clay, and then (i) at least 0.5, based on the clay mineral content of the resulting suspension of clay / polymer complex, preferably before use. wt%, preferably 1.0 to 5.0 wt% activator; or (ii) if necessary, reducing the water content of the mixture to at least 40% by weight, optionally granulating the resulting mass, and providing the resulting clay mineral / polymer complex, preferably prior to use, to at least 0.5% of the clay content. by weight, preferably 1.0-5.0% by weight, of an activating agent; or (iii) drying the resulting clay mineral / polymer complex to a maximum moisture content of 20% by weight, taking care not to permanently heat the surface of the solids to a temperature above 150'C, optionally pulverizing or granulating the dried material, and

-2HU? · · '·. 3 the resulting agar mineral / polyvinyl complex is preferably mixed with at least 0.5 wt.%, Preferably 1.0 to 5.0 wt.%, Of the activating agent, in the presence of the stomach prior to consumption.

As used herein and in the claims, the term "clay minerals" refers only to tri-layer swellable smectites and / or swellable chain silicates, and to rocks, mining products, and artificial mixtures containing at least 10% by weight of such clay minerals.

Examples of usable clay minerals include montmorillonite, beidellite, hectorite, nontronite, illite, allervedite, and paligoriccite, while bentonite is an example of clay mineral rocks.

The activating agent is an alkali metal and ammonium salts containing anions which form an insoluble precipitate with alkaline earth metal ions such as sodium carbonate, mono-, di- and trisodium phosphate, tripolyphosphate, sodium sulfate, lithium carbonate, lithium phosphate, lithium carbonate, lithium carbonate, or mixtures thereof.

In a particularly preferred embodiment, the activator is an overactivated, i.e., an excess of activator-pretreated smectites or smectite-containing rocks (e.g., overactivated bentonite).

The starting smectites may also be used in a pre-treated (i.e., pre-activated) form with a small amount of activating agent, if such a material is available.

However, the use of preactivated smectites is not necessarily required to form a final, stable structure, reversible water uptake and release gel, since the reaction will also occur with completely unactivated smectites upon subsequent activation.

Water-soluble polymers reacting with clay are known per se; examples of which are the reactive group -COOH, -COO'M ⁺ (M ^{+ is a} monovalent cation), -CONH2,

Water-soluble polymers having OH and / or -C-O-C- groups, as well as polymers containing modified (quaternary ammonium groups) acid amide groups. Examples of such polymers include: polyacrylamide, polymethacrylamide, polyacrylic acid, polymethacrylic acid, hydrolyzed polyacrylamide, acrylamide-acrylic acid copolymers, hydrolyzed acrylamide-acrylic ester copolymers, vinyl alcohol-acrylic acid copolymers, vinyl alcohol-acrylic acid copolymers, etc., and mixtures of the listed homo- and copolymers.

The polymers may also be graft copolymers, such as copolymers containing acrylic, methacrylic, acrylamide and / or methacrylamide side chains grafted onto the polysaccharide backbone,

The molecular weight of the polymers that can be used is generally between 50,000 and 20,000,000, preferably between 300,000 and 10,000,000. Our experience

It is believed that the higher the molecular weight of the polymer used, the smaller the amount of polymer sufficient for the reaction.

An essential feature of the process of the invention is that the clay mineral / polymer complex is subsequently activated, i.e., the clay mineral / polymer complex is mixed with an activating agent.

This operation is carried out in the presence of water. If the clay mineral / polymer complex does not contain enough water (for example, if the water content of the clay mineral / polymer complex has been reduced previously or the clay mineral / polymer complex has been previously dried), the dry matter content of the clay mineral / polymer complex is preferably at least 6% by weight.

Alternatively, the clay mineral / polymer complex may be suspended in water and added to the active agent, either solid or dissolved or suspended in water; alternatively, the clay mineral / polymer complex is admixed with an aqueous solution or suspension of the activator. If the clay mineral / polymer complex contains sufficient water (e.g., when the complex is an aqueous suspension), the amount of activating agent will vary depending on the type of starting mineral, but at least 0.5% by weight of the activating agent is required. The amount of activating agent is usually from 1 to 5% by weight, based on the weight of the starting clay mineral.

As a result of the addition of the activator, the polymer-coated smectite clumps "unexpectedly swell, partially disintegrating into their elemental sheets or bundles, whereby large amounts of new clay mineral surfaces (bonding sites) capable of reacting with the polymer are released.

The resulting bonding sites react immediately with the polymer present to form a stabilized, reversible gel uptake and release gel structure.

It is a significant advantage of the process according to the invention that it does not require the use of dilute suspensions, since the reaction of the unactivated clay mineral and the water soluble polymer can be carried out in a high solids mass or suspension.

This mass or slurry can be blended with significantly lower energy requirements than activated clay mineral masses with particular polymers.

The resulting clay mineral / polymer complexes are stable, can be stored unchanged for a long time, and are substantially cheaper to transport than dilute suspensions prepared in the known manner. The clay mineral / polymer complexes can be easily activated directly at the site of application (for example, it is sufficient to operate a known concrete mixer to mix the activator). By varying the amount and quality of the activating agent, the properties of the gels formed, such as gelation time, may be altered; Thus, a single intermediate can be used to form a final gel of various properties according to the particular local requirements.

-3HU 200304 A

The hit? ' The process of the present invention is described in more detail in the following examples without limiting the scope of the invention.

Example 1

Várkenő Mine Wet Bentonite (dry matter content 75% by weight) was crushed through a collar passage and then passed through two successive roller rolls, with decreasing particle size, to adjust the material to a mesh size of less than 0.1 mm.

Subsequently, the moisture content of the bentonite in the brain extruder is increased to 45% by weight with water, followed by the addition of 1.5% by weight aqueous hydrolyzed polyacrylamide (5%, average molar weight) in the extruder to 1/5 of the volume of the bentonite mass. 1.5 x 10 °).

The mixture of bentonite paste and polyacrylamide solution is extruded through a cylinder head 2 mm in diameter and the extrudate is cut into 5 mm long cylinders.

The granulate thus obtained is dried in a tumble dryer with flue gas at a countercurrent temperature of 300 ° C. The contact time of the flue gas and the granulate is set to about 5 minutes; Thus, the surface of the particles should not be permanently heated to temperatures above 150 ° C.

Hard, brittle fracture particles with a moisture content of 10% by weight of the rope are obtained.

The dried pellets are crushed using a hammer grinder and two different size fractions of the pellets are separated from the crushed pellets on a screen. The coarse fraction of coarse particles having a size of 0.3 to 1 mm is a highly dispersible granulate; the fine particle size fraction less than 0.3 mm is a fine powder.

g of the resulting powdery clay mineral / polymer complex in a solution of 0.16 g of sodium carbonate in 92 g of water with continuous stirring. After dispersion, the clay mineral / poly complex particles first swell vigorously and then form within about 10 minutes to form a pelleting gel mass.

Stirring is then stopped.

After another 1-2 hours, the gel particles swell completely to form a homogeneous gel with reversible uptake and release.

Example 2

Istenmezeje! Bentonite (72% by weight) of dry mineral origin (marketed by the National Ore and Minerals Company, Mad) is mixed with water in a laboratory kneading-kneading mixer so that the moisture content of the mass is 60% by weight.

The resulting mass is passed through a laboratory roller three times by adjusting the decreasing gap size, thereby reducing the particle size of inert pollutants (e.g. sand) in the mining product to less than 0.1 µm.

To a mass of 500 g of the product obtained above in a kneading kneading machine, a total of 100 g of a 5 wt% polyacrylamide solution (average weight: 3 x ^{10 6} ) was added in portions and the mixture was kneaded for 2 minutes.

100 g of the dough mass thus obtained are tossed into small pieces, the pieces are added to water in a household blender and mixed for 2 minutes. Thereafter, 3% by weight of sodium carbonate, based on the dry matter content, is added. After stirring for 2 minutes, the mixture forms a high quality gel.

Example 3

100 g of the dough-like clay mineral / polymer paste prepared according to Example 2 are placed in a laboratory mixer and then 3% by weight of trisodium phosphate, based on the dry matter content, in the form of a concentrated aqueous solution. After stirring for 2 minutes, the fluid resistance of the mixture is increased to eight times the initial value, confirming gel formation. The resulting gel has a media resistance of 70% greater than that of the same starting materials, otherwise prepared in the same manner, but with the same specification as 189,280. According to a Hungarian patent, a gel obtained from activated clay mineral prior to the addition of the polymer.

± _példa

A 1: 1 weight blend of crude calcium bentonite and lime ridge illite (commercially available from the National Mining Company, Mad) is prepared in a propeller mixer with a dry weight content of 35%. The suspension is then added with vigorous stirring to a 1: 1 weight ratio of sodium carbonate-trisodium phosphate in a weight ratio of 0.5% by weight.

After stirring for a minute, 6.5 wt% of an acrylamide-acrylic acid copolymer of 1.500,000 molar weight based on the dry matter content was added and the suspension was stirred for an additional 10 minutes.

After 1 day, the resulting slurry was diluted 1: 1 by weight with water with vigorous stirring in inhalation, and 3.0% w / w sodium carbonate was added to the slurry and the slurry was stirred for 10 minutes in a Labomix kneader. A gel with a stabilized structure is formed, which indicates that the suspension resistance of the suspension increases to 5.5 times the original value.

Example 5

5 liters of a 40 wt.% Dry matter slurry is prepared from a mixture of flour from the Divine fields (marketed by the National Ore and Minerals Company, Mad) using an Ultraturrax mixer. The suspension is divided into 5 equal portions and then the amount and quality of the polymer indicated in Table 1 and, if appropriate, the amount and quality of activator specified in Table 1 are added (for preactivation). Subsequently, the suspension was stirred with an Ultraturrax mixer for 3 minutes and then set aside.

Each suspension sample is then divided into two equal portions and mixed with one portion after 1 hour and the other after 1 month.

The amount and quality of activator specified in Table 1.

-4EN 200304 A

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Serial number of the pattern Elöaktiválószer name How much- Hungary * Polymer activator name How much- Hungary * name How much- Hungary * First - - polyacrylic amide 5.8 Sodium carbonate 2.6 Second trinátium- phosphate 0.4 acrylic acid -akrilamdi copolymer 6.5 mass ratio 2.3 sodium carbonate / trisodium phosphate mixture Third 1: 1 by weight sodium carbonate / trisodium phosphate mixture 0.3 The 100-** 3.4 Sodium carbonate 2.2 4th lithium carbonate 0.5 The 110-*** 6.8 lithium carbonate 2.2 5th disodium bidrogén- -phosphate 0.4 RboflocF5C 2.5 tripolyphosphate 3.0

♦ Weight% of dry matter content ♦♦ Hydrolyzed polyacrylamide, manufactured by American Cyanamid Comp. ♦♦♦ Hydrolyzed polyacrylamide, manufactured by American Cyanamid Comp.

Each suspension sample forms a gel with a reversible uptake and release of stabilized structure. The formation of stable structure gels is evidenced by the fact that the media resistance of the initial suspensions after mixing the activator increases 4 to 10 times the original value. The properties of the gels formed do not depend on how long the suspension is stored before mixing the activator.

Claims (5)

Claims CLAIMS 1. A process for the production of gels with reversible uptake and release properties of stabilized structure from clay minerals and polymers, characterized in that clay minerals are activated or optionally up to 1.0% by weight of clay minerals, preferably at least 8% by weight, at least 0.6% by weight, preferably 1.5-15% by weight on a dry weight basis, of a water-soluble polymer capable of reacting with the clay, and then (i) a suspension of the resulting clay mineral / polymer complex, preferably prior to use. at least 0.5% by weight, preferably 1.0-5.0% by weight, of the activator; or (ii) if necessary, reducing the water content of the mixture to at least 40% by weight, optionally forming granules from the resulting mass, and providing the resulting clay mineral / polymer complex, preferably prior to use, to at least 0.5% of its mineral content. by weight, preferably 1.0-5.0% by weight, of an activating agent; or (iii) drying the resulting clay mineral / polymer complex to a maximum moisture content of 20% by weight, ensuring that the surface of the dry matter is not permanently warmed to a temperature above 150 'during drying, optionally pulverizing or granulating the dried material; the clay mineral / polymer complex, preferably prior to use, in the presence of water, mixed with at least 0.5 wt.%, preferably 1.0 to 5.0 wt.%, of the activator. Process according to claim 1, characterized in that the activating agent is sodium carbonate, mono-, di- and tri-sodium phosphates, tripolyphosphate, lithium carbonate, lithium phosphates, sodium 20 sulfate, ammonium carbonate and ammonium phosphate. or over-activated smectites. The process according to claim 1 or 2, characterized in that the clay mineral / polymer complex is treated with a activator in the form of a slurry of at least 6% by weight. 4. A process according to any one of claims 1 to 5, characterized in that the clay mineral / polymer The activator is added to an aqueous suspension of 30 complexes. 5. A process according to any one of claims 1 to 3, wherein the clay mineral / polymer complex is added to an aqueous solution of the activator or 35