DE102005062315A1 - Antifoaming agent for aqueous fluid systems comprises finely dispersed shape-stable bodies with surface-active molecules arranged on and/or in their surfaces and dissolve completely or partially in aqueous solution - Google Patents

Abstract

An antifoaming agent comprises finely dispersed shape-stable bodies with surface-active molecules arranged on and/or in their surfaces and dissolve completely or partially in an aqueous solution.

Description

The The invention relates to a defoamer for aqueous fluid systems.

was standing of the technique

mechanistic cause defoamer the rapid coalescence of gas bubbles in fluid material systems and thus avoid foaming. Unless before adding the defoamer already Foam shares are present, they are destabilized. Dry defoamers have been in intensive use in a variety for several decades of product sectors (e.g., food, pharmaceutical, cosmetics, ceramics, Paper).

Most known defoamers like those in the US 6,605,183 . US 5,914,362 . US 5,846,454 and US 4,690,713 are based on proportions of silicone oil or silica particles. However, it is important to avoid silicone oil or silica particles in a large number of material systems, since other significant functionalities are disturbed by them. So-called water-based antifoams, which are oil-in-water emulsions or aqueous suspensions, as described for example by the US 4,976,888 and the US 5,429,718 were also found since the 50s of the last century industrial use. Another well-known group of defoamers, as for example in the US 5,346,511 describes ethoxylated polyether surfactants with polyhydric alcohol fatty acid esters. All patents describing these defoamers underline the very specific and narrowly limited fields of application of these known defoamers.

So far is the mechanism of defoaming by means of said "chemical" defoamer only little, in terms of physical parameters in processing / production processes of defoaming Fabric systems that the defoamer efficiency influence, almost nothing known.

Yet is in some publications the in water Phase insoluble Part of some defoamers for water-based Material systems relevant Meaning of the defoaming process attributed (e.g., Kerner, K.T., 1976, Foam Control Agents, Noy. Data Corportation, New Jersey). Such antifoams often form with the aqueous phase immiscible fluid drops or suspended solid particles out.

In Kerner a.a.O. (1976), patents on defoamers are mentioned in a broad overview and it should also be noted that the areas of application for known defoamers narrow and usually very specific tailored to the defoaming material system are. The defoamers are usually only in terms of their chemical nature and not described in terms of the mechanism of their action.

task

Of the Invention is based on the object, a defoamer of significantly improve the effectiveness of the assumed genre, in a wide range of applications.

solution

The The object is achieved by the reproduced in claim 1 features solved.

Some advantages

The defoaming Effect is inventively two in the defoamer system realized in a defined manner cooperating components (two-component mechanism): Component 1 corresponds to a deformation-stable finely dispersed body (Particles, drops), Component 2 of a molecular surfactant component (Surfactant), the first on the surface and / or inside the component 1 detachable from this and in aqueous solution going, is located. The particulate component 1 may be a solid particle with or without internal pores, a gel particle or a high-viscosity one Fluid drop with a preferred diameter according to the invention in Range from 1 to 10 microns. In the case of fluid drops has the fluid viscosity sufficiently high values of> 20 mPas or the viscosity ratio between Drop fluid and surrounding fluid is greater than 5, preferably greater than 20, and / or a sufficiently high interfacial tension is present to to ensure the extensive deformation stability of these drops.

Surprisingly, the particularly pronounced defoaming efficacy of a defoaming system of this type has been demonstrated when the surface-active molecule component detached from the surface of the component 1 and in solution in the fluid system to be defoamed, this process on the same time scale as the transport of the component 1 particles in the area of a foam lamella. If the surfactant component 2 molecules of component 1 particles dissolve too quickly, the former largely prove existing gas bubble interfaces and lead to their stabilization, so that the foam lamellae reduces or completely eliminates the destructive effect of the component 1 ponds in their "too late" reaching of the lamellar lamellae At matched kinetics, the surfactant molecule 1 release and component 1-particle transport into the foam lamellar regions on a comparable time scale, the component 1 particles are drawn into the fluid lamella located between the gas bubbles by a surface tension gradient arising at the approach of gas bubbles in the fluid system to be defoamed at the gas bubble interface. Partial detachment of the component 2 molecules from the component 1 particle surface partially hydrophobic surface character can be obtained. This causes a "puncturing" of the gas bubbles in the fluid lamella between the approximated gas bubbles, which in hydrophobic interaction with the component 1 particles also become hydrophobic / partially hydrophobic due to detachment of the component 2. Consequence is the gas bubble coalescence Since the thus enlarged gas bubbles by flotation The high degree of non-deformability of the component 1 particles avoids their deformation in the fluid lamella between two gas bubbles, which is of crucial importance for ensuring the "puncturing" of the gas bubbles.

To Defoamers developed according to these criteria work surprisingly according to the same two-component mechanism for a plurality of defoamers Substance systems in product areas such as food, Pharmaceuticals, cosmetics, paper and ceramics.

in principle there is also the possibility the described "two-component defoaming mechanism" with only one surfactant substance component (TYP2; special case). Here, this surfactant as highly viscous concentrate in droplet form be used. The highly viscous and thus dimensionally stable Drops takes over the task of "dimensionally stable Particles. "A thin surface layer of the concentrate drop is due to contact with the aqueous Environment soften and surfactant molecules in the fluid environment of the following substance system-specific solution kinetics, dismiss. Thus takes over this thin surface layer Concentrate drop the role of the TYP1 (two-component dimensionally stable Particle / surfactant) defoamer system at the particle surface isolated surfactant layer.

Other inventive refinements

Further inventive embodiments are in the claims 2 to 17 described.

In the drawing is the invention - partly schematic - for example It also illustrates other features and benefits result. Show it:

1 a schematic representation of a foam column for test experiments for defoaming efficiency under realistic conditions;

2 Reduction of the gas content in an aqueous foamable solution in the presence of defoamer concentrate (drops, TYP2, special case);

3 Reduction of the gas content in an aqueous foamable solution in the presence of surfactant concentrate in combination with dimensionally stable particles (TYP1 high surfactant (concentrate)) and

4 Reduction of the gas content in an aqueous foamable solution in the presence of an emulsion / suspension-based defoamer (dimensionally stable disperse, hydrophobic / partially hydrophobic particles and surfactant (TYP1 with surfactant layer on particle surface)).

Exemplary experiments for the verification of the defoamer capacity were carried out using a foam column, which is shown schematically in FIG 1 will be shown. In this is air / gas by means of a frit 4 at the bottom of the column 1 finely dispersed. The gas bubbles rise due to density difference in fluid 3 and form on the fluid surface, a foam layer of height h, and underneath a foaming zone of height z. The surface foam layer h increases with time as a function of the foam stability, ie stable, little "attacked / destroyed" foams form a thick foam layer 2 whereas the addition of efficiently effective defoamers results in significantly thinner foam layers. Both the height of the foaming zone z and the height of the surface foam layer h are measured as a function of time without and with the addition of defoamer. Leakage losses of air / gas and fluid are avoided by appropriate sealing of the components of the foam column.

• 1. 1 Liter des zu schäumenden/entschäumenden fluiden Basissystems (hier Modellsystem Polysorbat 20 (PS20) in Wasser) werden in der Schaumkolonne vorgelegt und der Fluidlevel registriert.
• 2. Luft/Gas wird mit definiertem Volumenstrom in das Fluid über die Gasdispergierfritte 4 eingeleitet, somit die Schaumbildung initiiert und die Höhe der gebildeten Schaumschicht als Funktion der Zeit registriert.
• 3. Der stationäre Gasgehalt des Schaumes wird in Kenntnis des vorgelegten Fluidanteils und des aus Fluid und Schaum bestehenden stationären Gesamtvolumens ermittelt.

Specifically, the foaming experiment is performed as follows:

• 1. 1 liter of the foaming / defoaming fluid base system (here model system polysorbate 20 (PS20) in water) are placed in the foam column and registered the fluid level.
• 2. Air / gas enters the fluid via the gas dispersion frit at a defined volume flow 4 initiated, thus initiating the foaming and registered the height of the foam layer formed as a function of time.
• 3. The steady state gas content of the foam is determined with knowledge of the fluid content presented and of the total stationary volume consisting of fluid and foam.

In the 2 to 4 becomes the escape mung effect for three different acting according to the principle of the invention defoamer represented ( 2 : Type2; 3 Mixed form type1 / type2 and 4 : Type1). On the ordinate axis in the 2 to 4 the height of the foam layer formed is shown, the abscissa corresponds to the time axis.

In 2 the operation of a defoaming system based on a concentrate of block copolymers is shown. At concentrations> 1 ppm the defoaming efficacy becomes visible. In this case, the defoamer is introduced as a block copolymer concentrate in drop form (type 1) in the material system to be defoamed. The block copolymer consists of an ethoxylated-propoxylated alcohol. The interfacial tension formed for such block copolymer co-concentrates with water is <40 mN / m, the viscosity of the concentrate is about 50 mPas (viscosity factor in a purely aqueous environment about 50). These drops with average diameters between 1 and 10 microns are drawn into the lamellar fluid film between two approaching gas bubbles due to the differences in concentration and resultant interfacial tension gradients at the gas bubble interface, as well as the previously described Form1 Particulate Complex 1 and Surfactant Component 2 type 1 defoamers There are no or few other surface-active molecules in the fluid environment and at the gas bubble interface. For this reason, the comparable time scale for the droplet transport into the fluid lamella between two gas bubbles 1 and the release of surfactant molecules from the surfactant droplet surface 2 is crucial here as well (for surfactant concentrate drops). The drops of surfactant form a bridge between the approximated gas bubbles, release further surface-active surfactant molecules into the fluid environment and cause the coalescence of the gas bubbles.

In 3 is a defoamer consisting of a block copolymer surfactant in combination with solid hydrophobic wax particles, in terms of its defoaming effect. The wax particles are embedded in the block copolymer concentrate. Thus, this defoamer can be understood as a combination of Type1 / Type2.

4 shows the effectiveness of a Type 1 defoamer, consisting of solidified fatty alcohol / fatty ester particles, which are coated with a surfactant layer of a non-ionic, water-soluble surfactant on its surface.

all indicated defoamer systems according to the invention is the previously described two-component mechanism of action in common.

All Surprisingly, examples presented above then work especially well good if the surfactant molecular surfactant components 2 according to the invention on the same Time scale from the interface the particle component 1 (in the case of type 2 defoamer, highly viscous droplet core) peel off. This obviously avoids that quickly gone into solution Component 2 surfactant molecules get to the gas bubble interface, These stabilize and thus first by the fluid flow between the approaching Gas bubbles induced surfactant concentration gradients so fast be compensated that the comparatively sluggish component 1 particles not efficiently retracted into the lamellar space between the bubbles where they are due to their hydrophobic / partially hydrophobic surface properties and their limited Deformability the "piercing" of the gas bubbles or a bridge formation cause bladder coalescence between them and subsequently.

Around such "pairings" of component 2 surfactant molecules sufficient according to the invention Release delay with have sufficiently dimensionally stable and hydrophobic surface properties To be able to find component 1 particles, according to the invention z. B. a special Wilhelmi plate interface test carried out. For this purpose, a shaping of the component 1 material in platelet form (with castable and temperature reduction solidifying materials) and coating (Coating) with the surface-active Component 2 surfactant. If such a plate over a thin wire with a sensitive Force transducer connected immersed in a fluid phase and off this pulled out again, then lets go over the before demolishing the over wetted perimeter of the platelet formed fluid lamella, measured maximum force the interfacial tension as the quotient of force per wetted circumferential length. Will this Test at defined time intervals or after defined immersion times in the continuous fluid phase Repeatable, then with removable component 2-surfactant molecules the measured interfacial tension increase (Thinning / removal of surfactant surface layer). Such an increase gets rid of quickly Component 2 Surfactant molecules be done quickly accordingly. From such a trial can thus a characteristic "peel-off time" of component 2 molecules be determined quantitatively. This allows compared to venting / foam destruction tests in the real system or in a foam column the system specific Determination of suitable component pairings 1 + 2 for the application according to the invention.

options the "adjustment" or "vote" of the two components 1 and 2 regarding the rate of release of surfactant molecules in the According to the invention, the surrounding fluid phase can be applied via and / or via a suitably adapted "binding strength" of the surfactant molecules in the "carrier" particles (component 1), which in Type 2 special case a high-viscosity drop of the surfactant itself corresponds, realize.

There the binding of surfactant molecules physically (Van der Waals forces, viscous friction ("adhesive") forces, steric Interactions) or chemically (H-bonds, covalent bonds, inclusion compounds), it is this Targeted interactions.

Inventive possibilities are: setting the temperature (i), adjusting the pore size (particles) in agreement with surfactant molecular size / morphology (ii), adjustment of viscosity (type 2 defoamers Concentrate drops) (iii), adjustment of gel network density (Type1 defoamers with gel-like particles (iv)).

The in the abstract, in the claims and in the description described as well as apparent from the drawing features can both individually as well as in any combination for the realization of the invention be essential.

1

column

2

foam layer

3

fluid

4

frit

H

Height foam layer, Surface foam layer

z

Height foam zone

Claims (17)

Antifoam for aqueous fluid systems, characterized in that it consists of finely dispersed, dimensionally stable bodies and surface-active molecules arranged on their surface and / or in their interior, the latter being able to change completely or partially into aqueous solution. defoamers according to claim 1, characterized in that the finely dispersed, dimensionally stable body with those on their surface or in the interior arranged surface-active molecules dispersed in an aqueous Phase in a concentration of> 5 %, where the concentration of the surfactant Molecules> 0.1%, based on the mass of dimensionally stable bodies, lies. defoamers according to claim 1, characterized in that the finely dispersed, dimensionally stable body with those on their surface or in the interior arranged surface-active molecules as dry or slightly moist powders with water content <5% are present. defoamers according to claim 1 or one of claims 2 and 3, characterized that the finely dispersed, dimensionally stable bodies correspond to particles, which under load conditions, as they are in the mixing in watery to pasty fluid systems occur (shear stresses> 1 Pa) over remain dimensionally stable for at least one second. defoamers according to claim 1 or one of claims 2 to 4, characterized that the finely dispersed, dimensionally stable bodies correspond to highly viscous drops, where the viscosity ratio is between Drop phase and continuous fluid phase> 5, preferably> 20, is. defoamers according to claim 1 or one of the following claims 2 to 5, characterized that the finely dispersed, dimensionally stable body capsules with fixed or semi-solid skin and fluid content. defoamers according to one or more of the preceding claims, characterized that the finely dispersed, dimensionally stable body semi-solid gel particles are. defoamers according to one or more of the preceding claims, characterized that the finely dispersed, dimensionally stable body drops out concentrated Surfactant solutions are, being on time scale of the defoaming process of up to 30 minutes surfactant molecules go into solution from the drop surface, the drop, however, remains sufficiently large and dimensionally stable. defoamers according to one or more of the preceding claims, characterized that the finely dispersed, dimensionally stable bodies have average diameters in the size range from 0.5 to 10.0 microns, preferably from 2 to 5 microns. defoamers according to one or more of the preceding claims, characterized that the finely dispersed, dimensionally stable bodies have pores through which in solution going surfactant molecules from the interior of the finely dispersed, dimensionally stable body to the outside interface and transportable to the surrounding continuous fluid phase are. defoamers according to one or more of claims 1 to 10, characterized that the interface-active molecules on the surface of the finely dispersed, dimensionally stable body or physically and / or chemically bound in these existing pores are arranged. defoamers according to one or more of claims 1 to 10, characterized that the interface-active molecules on the surface of the finely dispersed, dimensionally stable body or physically and / or chemically in these pores present that their rate of release into the surrounding aqueous system via the Pore size and / or over the Temperature is controllable. defoamers according to one or more of the preceding claims, characterized that as a chemical influence parameter for the adjustable binding the surface-active molecules on the surface the finely dispersed, dimensionally stable body or existing in these Pores the structure and size of the hydrophobic Part of the amphiphilic surfactant Surfactant molecules through appropriate selection or synthesis of these molecules are variable. defoamers according to one or more of the preceding claims, characterized that as a physical influence parameter for the adjustable bond the surface-active molecules on the surface the finely dispersed, dimensionally stable body or existing in these Pores the hydrophobicity the surface / pore surface of these bodies suitable choice of the material of these bodies or their coating, and / or the viscosity this body, and / or the adjustment of the temperature, and / or the surface morphology (e.g., roughness) of these bodies, is variable. defoamers according to one or more of the preceding claims, characterized that the defined setting of the binding of the surface-active molecules on the surface the finely dispersed, dimensionally stable body or existing in these Pores as required the surfactant molecule release rate, determined via Interfacial tension measurements between coated with the corresponding surfactant molecules platelet-shaped model bodies and pure Water takes place after different times. defoamers according to one or more of the preceding claims, characterized that the cessation of the binding of surfactant molecules on the surface the finely dispersed, dimensionally stable body or in these existing pores such happens that detachment and transport of the surfactant or surface-active molecules in the surrounding watery Fluid system on the same time scale, which also for the on Reason of surfactant concentration differences and resulting interfacial tension triggered Transport of the dimensionally stable body in the interlamellar space between gas / foam bubbles is needed. defoamers according to one or more of the preceding claims, characterized that on the surface or in the interior of the dimensionally stable, finely dispersed body arranged surfactant molecules any amphiphilic molecules, preferred however, fatty alcohols and / or block copolymers, the latter in turn preferably of the ethoxylated / propoxylated type Alcohols are.