DE3704084A1 - Thickening agent - Google Patents

Abstract

The thickening agent described is based on swellably activated silicates with long-chain organic polyelectrolytes added, the polyelectrolyte being a polysaccharide having a total molecular weight of at least 2 million. The mixture of polysaccharide and sheet silicate (phyllosilicate) may additionally have been reacted with a.) primary or secondary amines, preferably diamines, and/or b.) a silane containing aminofunctional groups, preferably an aminoalkyltrialkoxysilane, and/or c.) a chelate complex, preferably a titanium chelate compound and/or a zirconium chelate compound. The field of application of the thickening agent described is unlimited. Using the thickening agent, it is possible to thicken or render thixotropic virtually any liquid system. The reactants can be added to the system in situ while stirring intensively or they can be mixed with water or another suitable solvent to form a paste and the paste can be added to the system.

Description

It is known that layered silicas activated to swell Kate such as bentonite, montmorillonite, illite, vermiculite and esp special smectite in numerous areas of technology as Ver Thickeners can be used, preferably in hydrated systems. The layered silicates are fine partial form using shear forces in the dis pergiert, whereby the individual layer platelets largely to completely separate from each other and in the system a colloi dale dispersion or suspension form, resulting in a gel structure leads. The gel framework can be added by adding long-chain organic polyelectrolytes such as starch degradation products, cellulose derivatives, pectins or gelatin, which adhere to the layer platelet store and build their own gel structure can be stabilized.

With the invention is an improved thickener proposed that is easy to use and high rheological effectiveness. This invention Thickener is based on a swellable activated layer silicates with an addition of long-chain organic polyelek trolyten and is characterized in that the polyelectrolyte is a polysaccharide, preferably a hetero-polysaccharide, which has a total molecular weight of at least 2 million.

All types can be used as polysaccharide in the invention be used with the required high molecular weight. This applies to the starch and cell oils known as additives losederivate (die - because their structure consists only of glucose units is built - also called homo-polysaccharides) in general not too. The so-called hetero- Polysaccharides made up of different monosaccharide units exist and usually achieve a higher molecular weight  Chen, which is usually above 2 million, but also has already been given as 30-50 million (the Un these values presumably depend on association phenomena rest). A typical example of such a hetero-polysaccharide is through Formula A

illustrated. This is a linear main chain (double helix) from 1,4-glycosidically linked glucose Units (G) with side chains made of mannose units (M) and Glucuronic acid units (S), the latter mixed as potassium, Sodium and calcium salts are present and certain mannose units still contain carbonyl groups (esters) and acetals. These Polysaccharides are not water-soluble, but swell in water and are relatively stable against mechanical forces. your With a content of 1% in water, the pH value is between 6 and 9.

The rheological effectiveness of the ver Thickening agent can be increased by the fact that the mixture made of polysaccharide and layered silicate with primary or secondary Amines is implemented. Diamines are preferred, since these contribute better to the formation of the gel state than  Monoamines. For example, have proven to be well suited (individually or in a mixture with each other)

Tolylene-2,6-diamine,
3,3′-dimethyl-4.4′-diamino-dicyclohexylmethane,
Ethylene-1,2-diamine,
Hexamethylene-1,6-diamine,
Xylylenediamine,
1.3.5-triisopropylbenzene-2,4-diamine,
Isophoronediamine.

But primary and secondary monoamines are also effective, such as. B. Butylamine, cyclohexylamine, octylamine, stearylamine, 2-ethylhexyl amine, dibutylamine and dicyclohexylamine. You can also use alcohol amines with the same carbon number as the corresponding amines be used.

A further increase in rheological effectiveness of the thickener according to the invention can thereby be achieved be that (if necessary with the primary or secondary amine for Implemented) mixture of polysaccharide and layered silicate also with an amino-functional silane, preferably one Aminoalkyltrialkoxysilan is implemented. Here, have proved to be well suited, for example (again individually or in Mixture with each other)

3-aminopropyl-triethoxysilane,
3-aminopropyl-methyl-diethoxysilane,
3-ureidopropyl-triethoxysilane,
3-aminopropyltrimethoxysilane,
3-aminopropyl-tris- (2-methoxy-ethoxy-ethoxy) -silane,
N-aminoethyl-3-aminopropyltrimethoxysilane,
N-aminoethyl-3-aminopropyl-methyl-dimethoxysilane

Implementation of the mixture of polysaccharide and Layered silicate with the amines and silanes can be made "in situ"  gene by the system to be thickened or thixotroped the individual reactants directly, for example, in the row order polysaccharide layered silicate amine silane are added. Likewise, the implementation can also be done so that the Reaction partner for yourself with water or another suitable Solvents are processed into a paste, which is then added to the thickening or thixotropic system as already finished Reaction product is added.

The thickener according to the invention can also still be implemented with a chelate complex, what to leads to a further increase in the rheological effectiveness. Appropriately, but not necessarily, the chelate complex subsequently added because this is the possibility an interaction with the reaction product from polysaccharide Layered silicate amine silane creates. Of course, that has to be done in advance setting that the reaction product is still active, for interaction contains groups capable of the chelate complex.

Titanium chelates are used as the chelate complex, but certain zirconium chelates such as potassium zirconium carbonate and mixtures of titanium chelates and zirconium chelates also have the same effect. The titanium chelates are complex compounds of titanium acid in which at least some of the hydrogen atoms of titanium acid are linked to organic radicals which can still form coordinative bonds with the titanium atom. In aqueous solutions they react to the so-called dimeric alkyl tanate. These can be titanium acid esters which have two alkoxy and two aminoalkoxy groups or even three or four aminoalkoxy groups per titanium atom. Titanium complexes of 2-hydroxy acids and their salts can also be used, as well as chelate from β- diketones and β- ketonic esters, which can react by alcoholysis in the enol form with lower alkyl esters of orthotitanic acid. The titanium chelates are difficult or not hydrolyzable. They contain between 3-10% Ti and are usually commercially available in solutions. The titanium chelate types available under the protected trade name "Tilcom" have proven to be very suitable.

The reaction mechanism underlying the invention is still unclear and because of the manifold possible reactions the substances used can hardly be precisely measured vote. In the order polysaccharide layered silicate amine Silane chelate of the reactants can be assumed that in Presence of water or another suitable solvent next by exchanging the interlayer cations an inter crystalline swelling of the layered silicate takes place. Can too become negative at a higher pH at the edge of the layer platelets Form charges that in turn hold interchangeable cations can. Under the influence of shear forces then separate individual layer platelets from each other, the original interlayer cations likely diffuse Form ion layers around the layer platelets and the repelling electrical charges between the ion layers that Stabilize the mixture. It can be assumed that another Stabilization takes place through the polysaccharide, that just if swells, attaches itself to the layer platelets and also can in turn build its own gel structure.

With regard to the other reactants, one of the Possibilities are that the carbonyl groups of the pre put polysaccharide with the amine or diamine to a makromo lecular poly (amino) amide react and then the remaining OH groups of the polysaccharide (hereinafter referred to as ROH, where R stands for the rest of the polysaccharide molecule) by the silane, for example, in the manner

are implemented, i.e. ultimately free instead of the OH groups  (Active) NH₂ groups arise. Since the preferred silanes trial are koxy-functional, they can be increased in this way Crosslinking of the polysaccharide contribute. Even the preferred ones Diamines can increase crosslinking, but they can also e.g. B. react with only one amino group and then give aminoamines, thus lead to additional NH₂ groups. If the order of Addition of the reactants can change, variations of these reaction options occur.

It can be assumed that according to the described possibilities reacted reactants via remaining NH₂-, NH or OH groups with the chelate complex for spatial interaction brought or on the active edges of the layer form interactions. This creates proportionately rapidly a highly cross-linked gel-like macromolecule that has thixotropic properties when the interaction bonds break up under the influence of shear forces and follow End of shear with a certain, quite he reversibly reverse the desired time delay.

The rheological effectiveness of the ver Thickening agent and the degree of thixotropy achieved themselves by selecting certain reactants and their relative Quantity ratios targeted according to the respective need control and from "not thixotropic" to the stages "slightly thixo trop "and" strongly thixotropic "until compact or solid adjust stand. An especially important for the compact state Another advantage is that the highly networked Makromo lekül no tendency to syneresis (leakage of water from the Gel without its structure breaking down).

The field of application of the thickener according to the invention is not limited, use is possible wherever Thickeners are common or may be useful.

The following examples are intended to illustrate the invention  explain. Unless otherwise noted, the quantities are given parts by weight (GT).

Example 1

In 27.5 pbw of a 2% aqueous polysaccharide solution, 5 pbw of a mica-like layered silicate of the smectite class intense stirred in and finely divided. Then 26 GT become one 50% colloid-free pure acrylic plastic dispersion under Stir mixed in. Then 39.0 pbw of one are mixed into the mixture Titanium dioxide paste (which is made by stirring quickly of 79.3 pbw of titanium dioxide, 4 pbw of emulsifier, 4.7 pbw of 1,2-propylene glycol and 12 pbw of water) and then add each other 0.46 pbw xylilendiamine, 0.46 pbw aminosilane and 0.6 pbw Titanium chelate added with vigorous stirring. There is one thixotropic color based on the usual application equipment a substrate can be applied.

Example 2

A pasta prepared with stirring, consisting of 16.0 GT a mica-like layered silicate of the smectite class and 84.0 pbw of water, in a 1: 1 ratio with a 2% aqueous solution Mixed polysaccharide solution. Then with intensive stirring 30 GT of this mixture with 30 GT of a colloid-free trade usual 50% styrene-acrylic dispersion and 39 pbw of a titanium dioxide paste mixed. Then 1 GT xylilies diamine and 0.6 GT titanium chelate added and finely divided. It results in a usable thixotropic color, which with the usual application devices can be applied to a substrate can.

Example 3

20 pbw of a mica-like clay mineral activated with soda are mixed intensively with 80 GT water. The mixture is called Pasta A.  

Furthermore, 20 pbw of the same clay mineral with 1.6 pbw poly saccharide and 78.4 GT water mixed intensively. This mixture is called Pasta B.

While pasta A is a zero sample, the state of the art Pasta B completed according to the following table and with the brought additives to the interaction.

table

All parts in parts by weight

General assessment of rheological behavior

Sample 1: supple; thixotropic Sample 2: higher viscosity than 1, but still supple; thixotropic Sample 3: higher viscosity than 2, but still supple; thixotropic Sample 4: higher viscosity than 3, strongly thixotropic Sample 5: higher viscosity than 4, strongly thixotropic Sample 6: higher viscosity than 4, strongly thixotropic

This example shows that each of the additives mentioned in a Increasing the rheological effectiveness of the thickener leads.

Claims (6)

1. thickener based on swellable fourth layered silicates with an addition of long-chain organic polyelectrolytes, characterized in that the polyelectrolyte is a polysaccharide, preferably a hetero-polysaccharide, which has a total molecular weight of at least 2 million. 2. Thickener according to claim 1, characterized in that that the mixture of polysaccharide and layered silicate with primary or secondary amines, preferably diamines for the reaction brought. 3. Thickener according to claim 1 or 2, characterized characterized in that the mixture with an amino functional Silane, preferably an aminoalkyl trialkoxysilane for reaction is brought. 4. thickener according to one of claims 1 to 3, characterized in that the mixture with a chelate complex, preferably titanium chelate and / or zirconium chelate for implementation brought.   5. Use of the thickener according to one of the An sayings 1 to 4 for thickening or thixotroping a liquid Systems, characterized in that the reactants in be added to the system in situ with vigorous stirring. 6. Use of the thickener according to one of the An sayings 1 to 4 for thickening or thixotroping a liquid Systems, characterized in that the reactants with Water or other suitable solvent to a paste be stirred and the paste is added to the system.