EP2024295A1

EP2024295A1 - Use of polycarboxlate-based flow agents for anhydrite-based flow screeds

Info

Publication number: EP2024295A1
Application number: EP07723659A
Authority: EP
Inventors: Johann Plank; Dorina Vlad
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-03-29
Filing date: 2007-03-27
Publication date: 2009-02-18
Also published as: DE102006014529A1; WO2007112890A1; US20090111913A1

Abstract

The invention relates to the use of polycarboxylate-based flow agents, the polycarboxylate component being a water-soluble, branched-chain which comprises carboxyl groups and has at least one of the structural characteristics selected from the group of a nitrogen-functionalised lateral chain and an ester-linking, ether-linking and amid- and/or imid-linking as linking units between the primary and lateral chain. According to the invention, a) the molar ratio of monomers comprising acid groups to monomers comprising lateral groups in the polycarboxylate-component is > 2 : 1 and/or the lateral chain length n is < 25 and b) the flow screed has a sulphate content > 0,5 wt.-%, in relation to the total weight of the anhydrite fraction. The polycarboxylate component, which consists of a primary chain provided with anionically functional groups and at least one non-ionic lateral chain, has preferably an average molecular weight M<SUB>n</SUB> of between 5.000 and 250.000 g/mol. A particularly good liquefied effect is obtained by means of the flow agents in the powdery form, used in an amount between 0,1 - 5 wt.%, in relation to the content of mineral components in the flow screed.

Description

Use of polycarboxylate-based flow agents for anhydrite-based flow screeds

description

The present invention is the use of polycarboxylate-based flow agents for anhydrite-based flow screeds.

The addition of additives to hydraulic or latent hydraulic binders, for example cement or gypsum, is well known. An important group of additives is that of the flow agents. With their help, a liquid binder slurry is obtained with the addition of water, whereby overall improves the flowability and thus the processability is facilitated. Examples of building materials in which superplasticizers are used on a large scale are fluid concrete and liquid screed. For example, screed applications worldwide use approx. 5,000 t of plasticizer per year, and more than 500,000 t in concrete applications.

Anhydrite flow screeds (AFE) are screeds that are usually mechanically mixed in different mortar consistencies and pumped into the building due to their liquid consistency, which results in a considerable reduction in workload. Such screeds level largely independently or they can be leveled with little effort using a so-called. Schwabbelstange. Other advantages of AFE include its high flexural strength, a low tendency for so-called bowls, which means the shrinkage of the screed plate at the edges, as well as the possibility of laying even large surfaces without joints. In practice, such flow screeds are used in the form of wet and dry mortar systems. Wet mortars are mixed in a mixed form with truck mixers to the Construction site delivered, dry mortar are brought in silos or sacks to the site and mixed there.

As binders, especially anhydrites are used in this context. In the field of anhydrites, which chemically refers to CaSO ₄ , natural anhydrite, synthetic anhydrite and thermal anhydrite (so-called REA anhydrite) are known. In contrast to gypsum, namely stucco (chemically CaSO ₄ • Vz H ₂ O), anhydrite only binds very slowly after the addition of water, ie in a time that is not practical. Anhydrites therefore usually require so-called exciters to accelerate hydration. These consist either of alkali sulfates and in particular K ₂ SO ₄ or of cements or CaO-releasing substances. The cements are typical alkaline stimulants, whereas the potassium sulfate mentioned is considered to be salt-like exciters. In practice, a mixed excitation by sulfate and cements is often used.

In addition to pure anhydrite various mixtures of this type of binder are used, such. B. anhydrite / gypsum plaster mixed systems with a share up to 50 wt .-% burnt gypsum. The burnt plaster can in this case be made of natural or REA gypsum, but usually α-hemihydrate is used. Anhydrite / cement mixing systems are used as further binder mixtures based on anhydrite, although a compromise must be made between the low shrinkage values of the anhydrite and the water resistance of the cement. The cement content is therefore usually not more than one third of the total binder amount.

In the case of the above-mentioned superplasticizers, melamine-formaldehyde-sulfite-based polycondensate resins are currently used in approx. 90% of the applications in the anhydrite flow screed area. They are offered with different molecular weights and different molar ratios between the starting materials. Also can the particular flow agents used in the present Anhydritart be adjusted specifically. To a lesser extent, β-naphthalenesulfonic acid-formaldehyde polycondensation products are also used. Although these are cheaper compared to the melamine-based flow agents, but they have a brown-yellow color, which usually leads to unsightly discoloration of the screed surface. This is one of the reasons why the colorless melamine resins are used much more frequently.

But these melamine resins have disadvantages because they - as well as the Naphthalinfließmittel - in relatively high dosage amounts, namely in proportions between 0.3 to 0.7 wt .-%, based on the Additiveinwaage, must be added, which is the economic viability of their Application adversely affected. In addition, they have not negligible levels of free, so not chemically bound formaldehyde, which is released over time and thus pollutes the living room air.

The sulfates mentioned in connection with the exciters have little or no effect on the liquefaction effect of melamine and naphthalene resins. They are therefore considered to be extremely reliable flow agents for AFE. However, when polycarboxylate-based superplasticizers, which have only been on the market in powder form for a few years, have shown very different effects for identical products: In an AFE variant with polycarboxylate-based superplasticizers, even at extremely low doses of 0.05 Wt .-% very good liquefaction effects can be achieved, could with the identical flow agent in another AFE even with very high and thus uneconomical dosing of

1 wt .-% no sufficient flow effect can be achieved. For this reason, the polycarboxylate flow agents which have become widespread in cementitious systems in the AFE range have hitherto scarcely been commercialized. Polycarboxylates are polymers prepared by free-radical polymerization which have as their essential structural features an anionic-functional main chain and a non-ionic side chain. Because of these structural features that give the polymers the appearance of a comb, they are also referred to as comb or brush polymers.

In principle, four different polycarboxylate variants have hitherto been known. On the one hand, these are polymers which have ether linkages between the main chain and the side chain (s). Manufacturing methods and applications for these polymers are z. B. from the patents DE 196 53 524 A1 and US 6,176,921 known. Such polycarboxylates represent by far the most commonly used commercially agents because they are particularly accessible at extremely low cost. Examples of a further polymer variant in which the main and the side chains are linked to one another by ester linkages can be found in DE 100 48 139 A1 and EP 0 610 699 A1. Overall, in practice, polycarboxylates with ester linkages outweigh those with ether linkages. The third variant has amide or imide bonds as linkage type between main and side chain. Finally, WO 00/39045 A1 describes polycarboxylates which have nitrogen functions in the side chain. However, this variant is accessible only with great effort.

The use of polycarboxylates in the AFE range is described in DE 100 63 291 A1. Also known in this connection is the use of polycarboxylate flow agents based on maleic anhydride or (meth) acrylic acid, malonic or (meth) acrylic esters or vinyl ethers. These superplasticizers are characterized by a longer processability of the anhydrite-containing mass compared to melamine resins. Disclosed is also the use of sulfatic exciters, in particular extremely low potassium sulfate contents <0.8 wt .-% are given. Through this deliberately low selected sulfate amount are already discussed suppressed adverse effects, it should be noted that in practice, however, predominantly AFE formulations are used, the potassium sulfate contents are> 1 wt .-%.

Due to the described disadvantages of the prior art, the object of the present invention is to provide novel polycarboxylate-based superplasticizers which, due to their special structure and composition, also in sulfated AFE, regardless of the type of anhydride chosen and in particular also in the usual high concentrations of sulfatic exciters reliably unfold their liquefying effect. This should be possible in particular with economically justifiable quantities and also the setting behavior of the anhydrite should not be adversely affected in the form of a delay. It was also desirable that these flow agents are free of formaldehyde, which can be a burden of indoor air in residential buildings can be excluded. To meet these conditions, polycarboxylate-based fluxing agents suitable for anhydrite-based flow screeds were suitable. The polycarboxylate component is a water-soluble, branched-chain and carboxyl group-bearing copolymer which has at least one of the structural features selected from the series nitrogen-functionalized side chain and an ester linkage, ether linkage and amide linking unit between main and side chain - Has and / or imide linkage.

This problem has been solved by the use of the mentioned flow agents, which are essential to the invention in that

a) in the polycarboxylate component, the molar ratio of acid groups to pendant monomers> 2: 1 and / or the side chain length n <25, and b) the liquid screed has a sulfate content ≥ 0.5 wt .-%, based on the total weight of Andhydritanteils.

Surprisingly, it has been found in the use according to the invention that not only the task could be fully met, the flow agents with the features essential to the invention in various anhydrites and develop their beneficial effect together with different excitation types and concentrations. The liquefaction effect by the Polycarboxylatfließmittel is optimized in particular by the low side chain density at the same time high sulfate concentration. So z. For example, it has been found that polycarboxylates with a molar ratio of methacrylic acid to MPEG ester> 3: 1 remain fully effective with regard to their liquefaction effect even in the presence of potassium sulfate. Polycarboxylates having a high anionic charge density in the main chain have been found to be particularly effective in sulfated natural anhydrite. It was also surprising that polycarboxylate with a relatively short side chain of z. B. 8.5 even with a low proportion of methacrylic still show a liquefaction effect. The large number of positive effects was not to be expected due to the experience gained so far in sulphated anhydrite-based flow screeds.

The use of flow agents in which the polycarboxylate component consists of a main chain provided with anionic functional groups and at least one nonionic side chain has proven particularly advantageous.

With regard to the polycarboxylate component, the present invention particularly takes into account a variant in which the main chain has at least one of the structural features

(III)

wherein R ¹ = H, CH ₃ , NH ₂ , M or - ^ -CH ₂ - CH ₂ - 0 ^ CH ₃ with M = monovalent or divalent metal cation, in particular Na, or ammonium ion

R ² = H or an aliphatic C 1-20 _-hydrocarbon radical p = 5 - 150 X = O, NR ³ with R ³ = H or an optionally substituted with OH groups

Ci _-2 O hydrocarbon radical Y = H, CH ₃ or COOM _C with c = Y ₂ or 1 carries, as linking unit between the main and side chain of at least one of the structural features

(IV)

R ²

Y CH ₂

(VI)

wherein R ² and Y have the meaning mentioned R ⁴ = -H, -CH ₃

R ⁵ = -NH-R ⁶ , R ⁶ or -Of CH ₂ -CH ₂ -O ^ CH ₃ with p '= 5-35 and

or R ⁷ with R ⁷ =

O

-CH-CHrf NH-C- (CH ₂ ) ₄ -CN H-CH ₂ -CH ₂ VN Hf-CH ₂ -CH ₂ -OW-H o

and m = 3 to 150 n = 2 to 20 o = 5 to 50 and a and b independently of one another ≦ 300, where a: b = 1 to 10: 1

Such flow agents are described in particular in the already cited German patent application DE 100 63 291, which in terms of there said copolymers and the assemblies contained therein is a substantial part of the present invention.

With regard to the anhydrite component, the invention provides that this represents a sulphated and / or alkaline-excited anhydrite, which is preferably a natural anhydrite, a synthetic and chemical anhydrite and / or a thermal anhydrite. According to the invention, the leveling screed can also contain burnt gypsum, preferably in proportions of up to 50% by weight, and / or a cement component, preferably in proportions of up to 30% by weight, in addition to the anhydrite component.

It is to be regarded as essential to the invention that the floating screed has a sulphate content of> 0.5% by weight, based on the total weight of the anhydrite fraction. Surprisingly, since these high sulphate contents do not negatively influence the liquefaction effect of the flow agents in the anhydrite-containing system, the present invention also encompasses sulphate contents of the liquid screed which even> 0.8% by weight and in particular> 1.0% by weight, again in each case based on the total weight of the Anhydritanteils, are. As already mentioned, the tolerance to such high sulfate contents is surprising since usually the liquefaction effect of polycarboxylates is impaired especially by high sulfate excitation concentrations.

The mentioned sulphate content in the liquid screed should go back in particular to proportions of sulphates of alkali and subgroup metals, with iron, zinc, manganese and potassium sulphate being considered to be particularly preferred. In particular, the potassium sulfate may also be used as a double salt, such as. As syngenite, present (K ₂ SO ₄ • CaSO ₄ • H ₂ O). It is of course also possible that the syngenite is formed only in the liquid screed.

Polycarboxylate components which have an average molecular weight M _n of 5,000 to 250,000 g / mol have proven to be particularly suitable, with ranges between 15,000 and 150,000 and those between 30,000 and 100,000 g / mol are to be regarded as particularly preferred. In this context, it is worth noting that the individual side chains within a polycarboxylate molecule may, of course, be different from each other and, in particular, have different lengths. For example. For example, a polycarboxylate ether (PCE) molecule can be prepared from methacrylic acid and a mixture of MPEG esters with n _E o = 25 and 90. But it is also possible a purely physical mixture of polycarboxylates, each with different side chains (lengths) within a molecule or with each other.

From a practical point of view, the present invention also takes into account a flow agent which can be used in powder form. This variant facilitates not only the transport and storage, but also the dosages, since it can be added to the respective circumstances adapted to the liquid screed.

Finally, the present invention also takes into account that the flow agent in an amount of 0.01 to 5 wt .-%, based on the content of mineral constituents, is used in liquid screed.

In summary, it should be noted that the polycarboxylates used according to the invention in particular ensure a site-appropriate setting behavior of the Anhydritanteile in the flow screeds. In particular, the usual negative effect of high Sulfatahregermengen, which is due to a desorption of Polycarboxylatfließmittel by the sulfate ions, is not observed in the use according to the invention. This could be due to the fact that highly anionic polycarboxylates can not be desorbed from the anhydrite surface by sulfate anions and thus retain their effectiveness. The following examples illustrate these advantages of the present invention. Examples

Investigations with a wide variety of anhydrites and different stimulator types and concentrations showed that the liquefaction effect of polycarboxylates is impaired in particular by high sulfate excitation concentrations and only to a small extent by the stimulant cement. Further experiments have shown that polycarboxylates with high side chain density (ie, for example, at a molar ratio of methacrylic acid to MPEG-methacrylate ester 1: 1, 5) are greatly affected by high sulfate contents of the anhydrite component. Conversely, polycarboxylates with low side chain density (eg molar ratio of methacrylic acid to MPEG-methacrylate ester 3-6: 1) liquefy even at high sulfate concentrations (eg 1, 2% by weight K ₂ SO ₄ , based on anhydrite). still very good.

1. Table 1 shows experimental results with REA anhydrite. The liquefaction effect was measured by means of the so-called anhydrite spread measurement. It turns out that polycarboxylates with a molar ratio of methacrylic acid to MPEG ester> 3: 1 remain fully effective even in the presence of relatively large amounts of K ₂ SO ₄ .

Table 1: Liquefaction effect of polycarboxylates of different composition in Anhydritleim, measured by the dosage required for a slump of 26 ± 0.5 cm. (Blank value: 18 ±, 5 cm at a water / anhydrite ratio of 0.42).

Example Initiator Flow agent dosage [wt%] No. [wt%] MV * 1.5: 1 MV * 3: 1 MV * 6: 1

Invention:

Side chain length n _E o = 9

CEM I 42.5 R 0.3 0.2 0.2 [3% by weight]

K ₂ SO ₄ [1, 2 wt .-%] 0.75 0.3 0.2

Side chain length n _E o = 17

CEM I 42.5 R 0.25 0.2 0.2 [3% by weight]

K ₂ SO ₄ [1, 2% by weight] 0.50 0.2 0.2

Comparison:

Side chain length n _E o = 45

CEM I 42.5 R 1, 0.15 0.13 [3.3% by weight]

K ₂ SO ₄ [1, 2% by weight]> 2 0.25 0.1

¹ WV = molar ratio of methacrylic acid: methoxypolyethylene glycol methacrylate ester 2. Table 2 shows test results with sulfated natural anhydrite (exciter: 0.7% by weight K ₂ SO ₄ and 3% by weight CEM I 42.5 R. Blank value: 18 ±, 5 cm for a water / anhydride Ratio of 0.46).

Example Polycarboxylate dosage for slump 26 ± 0.5 cm

No. Composition [% by weight]

Invention:

4 8.5 PC 1, 5 ¹⁾ 0.2

5 8 5 PC 3 0.12

6 8.5 PC 6 0.10

7 17 PC 1, 5 0.23

8 17 PC 3 0.09

9 17 PC 6 0.09

10 45 PC 1, 5> 1

11 45 PC 3 0.16

12 45 PC 6 0.09

13 Comparison:

Melment F15G ²⁾ 0.4

Melment F17G ²⁾ 0,5

¹⁾ 8.5 PC 1, 5 means: 8.5 = number of ethylene oxide units in the side chain; 1, 5 = molar ratio of methacrylic acid: MPEG ester

²⁾ Commercial products of Degussa Construction Polymers GmbH based on melamine-formaldehyde sulphite

Table 2 confirms that polycarboxylates with high anionic charge density in the backbone (molar ratio methacrylic acid: MPEG methacrylate ester> 2) in sulfated natural anhydrite are particularly are effective. They liquefy at much more economical dosages than the currently commonly used melamine resins (comparative examples). Furthermore, it can be observed that PCE with short side chains (eg ri _E o = 8, 5 and 17) show good liquefaction even at low methacrylic acid content.

3. Comparable results were also obtained with synthesis anhydrite from hydrofluoric acid production.

Table 3 shows results on the liquefaction effect of polycarboxylates of different composition in synthesis anhydrite, measured on the dosage required for a slump of 26 ± 5 cm (blank: 18 ± 0.5 cm at a water / anhydrite ratio of 0.45; Excitator: 1, 2 wt .-% Syngenite, the anhydrite came from the hydrofluoric acid production (fluorochemistry Stulln)).

Example Polycarboxylate dosage for slump 26 ± 0.5

No. Composition cm [wt .-%]

14 8.5 PC 1, 5 ^v. 0.14

15 8.5 PC 3 0.087

16 8.5 PC 6 0.1

17 17 PC 1, 5 0.13

18 17 PC 3 0.07

19 17 PC 6 0.09

20 45 PC 1, 5 1.5

21 45 PC 3 0.1

22 45 PC 6 0.045

1) s. Table 2 Thermal calorimetric investigations show that the polycarboxylates according to the invention ensure a building-life-compatible setting behavior of the anhydrite.

Claims

claims

Use of polycarboxylate-based flow aids for anhydrite-based flow screeds, wherein the polycarboxylate component is a water-soluble, branched-chain, and carboxyl group-bearing copolymer having at least one of the structural features selected from the series of nitrogen-functionalized Side chain and as linking unit between the main and side chain an ester linkage, ether linkage and amide and / or imide linkage, characterized in that

a) in the polycarboxylate component, the molar ratio of acid groups to the pendant monomer ≥ 2: 1 and / or the side chain length n <25,

and

b) the liquid screed has a sulfate content ≥ 0.5 wt .-%, based on the total weight of the Anhydritanteils.

2. Use according to claim 1, characterized in that the polycarboxylate component consists of a main chain provided with anionic functional groups and at least one non-ionic side chain.

3. Use according to one of claims 1 or 2, characterized in that the polycarboxylate component in the main chain of at least one of the structural features

(H)

(III)

wherein R ¹ = H, CH ₃ , NH ₂ , M or - [-CH ₂ - CH ₂ - 0-Jr-CH ₃ with M = monovalent or divalent metal cation, in particular Na, or ammonium ion

R ² = H or an aliphatic C 1-20 _-hydrocarbon radical _p = 5 - 150 X = O, NR ³ with R ³ = H or an optionally substituted with OH groups C-ι- ₂₀ hydrocarbon radical, Y = H, CH ₃ or COOM _C with c = ₂ or 1 V

carries, as linking unit between the main and side chain of at least one of the structural features

(IV)

R ²

(V)

(VI)

wherein R ² and Y have the meaning mentioned R ⁴ = -H, -CH ₃ with P '= 5-35 and

or R ⁷ with R ⁷ =

O

and m = 3 to 150 n = 2 to 20 o = 5 to 50 and a and b are independently <300, where a: b = 1 to 10: 1

4. Use according to one of claims 1 to 3, characterized in that it is the anhydrite component is a sulfated and / or alkaline excited anhydrite and preferably a natural anhydrite, synthetic and chemical anhydrite and / or a thermal anhydrite.

5. Use according to one of claims 1 to 4, characterized in that the liquid screed in addition to the anhydrite component burnt gypsum, preferably in proportions up to 50 wt .-%, and / or a cement component, preferably in proportions up to 30 wt. %, contains.

6. Use according to any one of claims 1 to 5, characterized in that the sulphate content of the liquid screed> 0.8 wt .-% and in particular> 1, 0 wt .-%, each based on the total weight of the Anhydritanteils.

7. Use according to any one of claims 1 to 6, characterized in that the sulphate content of fractions of sulphates of alkali and subgroup metals and in particular iron, zinc, manganese, potassium sulphate and the double salt Syngenite K ₂ SO ₄ • CaSO ₄ • H ₂ O goes back.

8. Use according to one of claims 1 to 7, characterized in that the polycarboxylate component has an average molecular weight M _n of 5,000 to 250,000 g / mol.

9. Use according to one of claims 1 to 8, characterized in that the flow agent is used in powder form.

10. Use according to one of claims 1 to 9, characterized in that the flow agent in an amount of 0.01 to 5 Wt .-%, based on the content of mineral constituents in liquid screed is used.