DE19534721A1 - Thickener reducing capillary water absorption and extending working life of synthetic resin plaster - Google Patents

Abstract

The use of thickener compsns. of cellulose ether (I) and synthetic hectorite (II) for producing synthetic resin plaster is claimed. Also claimed are the thickener compsn. and plaster per se.

Description

The invention relates to the use of a thickener composition for the production of Synthetic resin plasters as well as synthetic plasters that have such a thickener composition contain.

Natural and synthetic thickeners have long been known and are used in many Areas applied. The thickeners, also called rheological additives, generally increase the viscosity of solution systems or water-based ones Systems, depending on the type of additive. These usually exist Additives made from silicates, which can be organically modified, and organic or polymeric Thicken.

Of the latter derivatives of natural polymers, such as pectin, xanthan rubber, alginates, guar derivatives and in particular the various cellulose ethers such as Hydroxyethyl cellulose, carboxymethyl cellulose, methyl hydroxyethyl cellulose, and the ver various other modified celluloses are known to be dependent on their Chain length and concentration significantly increase the viscosity in aqueous media can increase.

It is also known that clay minerals, especially aluminum silicates or silicon oxide compounds such as montmorillonite, kaolin, saponite, bentonite, hectorite, atapulgite and other silicates, especially when bound to organic molecules, as ver can be used thicker. Non-organically modified silicates are used before used in water-based systems, the organically modified silicates in Solvent systems.  

The aforementioned thickeners can be used individually or in combination, for example as Thickeners, water retention agents, protective colloids, dispersants, stabilizers and binders can be used in many industrial applications.

For example, EP-A-0 445 653 describes a thickener composition for water systems containing a clay mineral and a modified cellulose. The preferred Clay mineral is a natural hectorite, the preferred cellulose is hydroxyethyl cellulose.

However, the thickener compositions known from the prior art become approximately used for the production of synthetic resin plasters, these synthetic resin plasters do not show for all processing criteria sufficiently good properties. In particular, the so-called "open processing time", i. H. the time when the consistency of the synthetic resin plaster ver work permits, in many cases not long enough.

It was therefore an object of the invention to provide a synthetic resin plaster that the does not have the aforementioned disadvantages and is particularly easy to use.

The invention thus relates to the use of cellu thickener compositions loose ethers and synthetic hectorite for the production of synthetic resin plasters.

A synthetic hectorite is particularly suitable for the use according to the invention formula

[Mg _6-x Li _x Si₈O₂₀ (OH) _4-y F _y ] ^{x (-)} x / z M ^{z (+)}

in which 0 x 1,2, 0y 4 and z is 1, 2 or 3.

A thickener composition is preferably used, the 25 to 75 wt .-% Cellu contains loose ether and 25 to 75 wt .-% synthetic hectorite.

The thickener composition 40 suitable for synthetic resin plasters particularly preferably contains up to 60% by weight of cellulose ether and 40 to 60% by weight of synthetic hectorite.  

The invention also relates to a thickener composition for synthetic resin plasters tend 25 to 75 wt .-% cellulose ether and 25 to 75 wt .-% synthetic hectorite.

The thickener composition preferably contains 40 to 60% by weight of cellulose ether and 40 to 60% by weight synthetic hectorite.

The invention also relates to a synthetic resin plaster containing a thickener composition according to the invention.

The synthetic resin plaster preferably contains 0.1 to 10% by weight of the inventive Thickener composition.

The synthetic hectorite used according to the invention for the thickener composition can be produced by the method described in EP-B-0 088 372. EP-B-0 088 372 describes a process for the production of a synthetic hectorite of the formula

[Mg _6-x Li _x Si₈O₂₀ (OH) _4-y F _y ] ^{x (-)} x / z M ^{z (+)}

in the 0 x 1.2, 0y 4 and z is 1, 2 or 3 and a cation with the valency z means be from an aqueous solution or suspension containing magnesium ions, a Na₂O source, a SiO₂ source, optionally with the addition of lithium - And / or fluoride ions, wherein the molar ratios 0.56 MgO / SiO₂ 0.75, 0 Li₂O / SiO₂ 0.2, 0 F / SiO₂ 1.25, 0.25 Na₂O / SiO₂ 2 are to be observed, in which an aqueous solution or suspension a magnesium salt is heated, optionally adding the lithium and / or fluoride ions to the solution or suspension of the magnesium salt before adding the other components, adding a source of SiO₂ and a source of Na₂O to the heated mixture, preferably with constant mixing, in the form of aqueous solutions with the proviso that the Na₂O source is not added before the SiO₂ source, the resulting mixture is kept for a long time at a higher temperature, the crystals of the synthetic hectorite formed in the N atri form separated from the mother liquor and optionally treated with an aqueous solution of a salt with the cation M ²⁺ and after the cation exchange, the bottom body is separated from the aqueous phase, characterized in that the addition of the components to the aqueous solution or suspension of the magnesium salt at temperatures from 120-373 ° C under pressure and the resulting mixture is kept for a long time in the temperature range of 110-373 ° C.

As cellulose ethers, for example methyl cellulose, methyl hydroxyethyl cellulose, methyl hydroxypropyl cellulose, hydroxyethyl cellulose, hydroxyethyl hydroxypropyl cellulose, Hy hydroxypropyl cellulose, ethyl hydroxyethyl cellulose, carboxymethyl cellulose, carboxy methylhydroxyethyl cellulose or also alkoxy-hydroxypropyl-hydroxyethyl cellulose and derivatives of cellulose ethers are used.

The quality of the synthetic resin plasters which are combined using the thickeners according to the invention were established using the following test methods.

consistency

24 hours after the plaster has been made, the consistency of the plaster is assessed using a stir bar Splits. It is determined whether the plaster has to be thinned for processing.

Wind up

The plaster is smoothed onto a surface primed with a suitable coating plaster raised. The winding up is assessed.

1 = easy
2 = moderate
3 = difficult
4 = very difficult

Rub

At certain intervals after plastering is applied, it is covered with a plastic disc grated to get structure. It is assessed how the plaster can be rubbed, with the Time must be noted.

1 = good / easy
2 = moderate
3 = bad / difficult
4 = very difficult

Open time

Table 2 shows the information "beginning" and "end". The beginning is that Time after which the plaster rubs with the plastic disc for the first time without greasing leaves. The end is the time after which the plaster just barely tears with the plastic disc ben lets. This period should be as long as possible.

Optical picture

After rubbing the plaster, the plaster is visually assessed.

1 = good picture
2 = moderate picture
3 = bad picture
4 = very bad picture

Capillary water absorption according to DIN 52617

The capillary water absorption was based on the Wacker method based on DIN 52617.

The following substances were used in the examples:

Mergal K9N

It is a preservative for aqueous systems. The manufacturer is the Riedel de Haen AG.

Agitan 280

It is a defoamer for aqueous systems, the liquid from a combination hydrocarbons, hydrophobic silica, synthetic copolymers and non-ionic gener emulsifiers. The manufacturer is Münzing Chemie GmbH.

Mowilith DM 21

It is an aqueous vinyl acetate dispersion with a solids content of 50%. Manufacturer is Hoechst AG.

Omyacarb BLP 2

It is a marble flour (CaCO₃). The manufacturer is Omya GmbH.

Tylose MH 600Oxp

Methylhydroxyethyl cellulose, normal powder (max. 180 µm), briefly delayed swelling, Viscosity level 6000 mPa · s (2% Höppler). The manufacturer is Hoechst AG.

Tylose MH 2000xp

Methylhydroxyethyl cellulose, normal powder (max. 180 µm), briefly delayed swelling, Viscosity level 2000 mPa · s (2% Höppler). The manufacturer is Hoechst AG.

The following products are compared in the test series:

• a) Attagel 40 (Attapulgit / Engelhard) Attapulgite is a palygorskite, a natural bandar layered silicate.
• b) Bentone EW (highly purified, natural layered silicate / Rheox)
• c) Laponite RD (synthetic hectorite / Laporte)
• d) SKS-21 (synthetic hectorite / Hoechst AG)

example 1

To produce a basic formulation, the components of Table 1 were given in the mixed order. Processing was carried out at room temperature commercially available dissolver mixers (Vollrath laboratory paste drivers of the type eentric EWTHX 0.5 from Vollrath, Hürth). The sum of the parts by weight corresponds to 100% by weight Product.

Table 1

Basic formulation for synthetic resin plasters

The results of the thickener systems used for the synthetic resin plasters are shown below given Table 2 reproduced.  

Table 2

Properties of synthetic resin plasters

As long as possible, processing time is required for synthetic resin plasters; the An The start time should therefore be as short as possible and the end time should reach a high value. Around To meet these criteria have so far been known in the prior art, low viscosity, i. H. short-chain cellulose ether used, because synthetic resin plasters with highly viscous, d. H. long chain Cellulose ethers show a tendency to smear and thus greatly reduce the processing time becomes. From an economic point of view, however, the use of more viscous cellulose ethers desirable, since much smaller amounts are required.

From Table 2 u. a. shows that the open processing time for resin plasters, the one Contain thickener system from higher viscous cellulose ethers and layered silicates with which open processing time of a synthetic resin plaster with a thickener system, which consists of low viscous cellulose ethers, is comparable. It is positive ten that the use of layered silicates marked the beginning of the open processing time (Start time) could be minimized.  

By combining higher-viscosity cellulose ethers with SKS-21 as a thickener system in synthetic resin plasters, in addition to the minimized initial time, becomes an essential one Increase in the total open processing time reached (difference end / start of the processed open processing time), which is comparable to the processing open times of Synthetic resin cleaning with low viscous cellulose ethers.

In addition, synthetic resin plasters with a thickener system according to the invention have the best SKS-21 and higher viscous cellulose ethers have no tendency to smear.

The thickener systems of synthetic layered silicates and cellulose eth according to the invention capillary water absorption. The capillary water absorption characterizes the Suction effect of a porous building material with or without coating. So that protection effect of a paint film against water determined; this is due to the water absorption represented coefficients. Paint films show very good water-repellent protection a water absorption coefficient of 0.1 [kg / (m²√ 24 h)].

Only through the combination of synthetic sheet silicates and Cellu according to the invention This high quality level can be achieved with loose ether. The use of SKS-21 as a synthetic layered silicate in such a thickener system leads to the best kapil laren water intake.

In addition, the results in Table 2 show that by using SKS-21 the amount of layered silicate can be significantly reduced.

Claims (8)

1. Use of thickener compositions from cellulose ethers and synthetic Hectorite for the production of synthetic resin plasters. 2. Use according to claim 1, characterized in that the synthetic hectorite of the formula [Mg _6-x Li _x Si₈O₂₀ (OH) _4-y F _y ] ^{x (-)} · x / z M ^{z (+)} corresponds in which 0 x 1,2, 0y 4 and z is 1, 2 or 3, and means a cation with the valence z. 3. Use according to claim 1 or 2, characterized in that the thickener composition 25-75% cellulose ether and 25-75% by weight synthetic hek contains torite. 4. Use according to claim 3, characterized in that the thickeners together setting 40-60% by weight cellulose ether and 40-60% by weight synthetic hectorite contains. 5. Thickener composition for synthetic resin plasters, containing 25-75% by weight cellulose ether and 25-75% by weight synthetic hectorite. 6. Thickener composition according to claim 5, containing 40-60 wt .-% cellulose ether and 40-60% by weight synthetic hectorite.   7. synthetic resin plaster containing a thickener composition according to any one of claims 5 or 6. 8. synthetic resin plaster according to claim 7, characterized in that it thickened 0.1-15 wt .-% composition contains.