Dispersion comprising silicon dioxide and polycarboxylate ether

The invention relates to a dispersion based on silicon dioxide and a polycarboxylate ether, and its use as a concrete additive.

It has been known for a long time, for example from US 3135617, that an acceleration of setting can be achieved by means of finely divided amorphous silicon dioxide. This did not gain acceptance, however, since the workability of the fresh concrete was greatly restricted thereby.

In WO 02/070429, a composite material is disclosed which contains inorganic aggregates, ultrafine particles, a cement-containing binder and a concrete superplasticizer . The composite material allows the production of highly liquefied concrete, in which no bleeding occurs. The ultrafine particles employed are mainly "silica fume" particles, which are obtained in connection with the production of silicon metal. "Silica fume" particles, as a rule, are present as spherical individual particles having a diameter of 150 nm or more. In cement or concrete compositions, they show a strong filler effect, but are not very reactive here on account of their low specific surface area. Further particles of this order of magnitude which can be employed are argillaceous earth, fly ash, pozzuolana, calcium carbonate, aluminum oxide, barium sulfate and titanium dioxide. The particles specified have the disadvantage that they have a small specific surface area, which leads to a low nucleation rate of the strength- forming phases and thus to low early strengths. Early strength is understood within the context of the present text as meaning the strength of a concrete after < 48 h of cement hydration.

The proportion of the ultrafine particles, based on the total amount of the composite material, is 1 to 30% by

weight or about 10 to 25% by weight in the working examples, based on the sum of cement and ultrafine particles. Thus the necessary amount of ultrafine particles is very high.

In US 6752866, a process for the improvement of the early strength is disclosed in which an aqueous dispersion which contains a mineral filler and a special dispersant is added to cement. As mineral fillers, it is possible to employ calcium carbonate, barium carbonate, limestone, dolomite, talc, silicon dioxide, titanium dioxides, kieselguhr, iron oxide, manganese oxide, lime, kaolin, clay, mica, gypsum, fly ash, slag, calcium sulfate, zeolites, basalt, barium sulfate or aluminum trihydroxide . Preferably, calcium carbonate is employed. The disclosed, average particle diameters of the mineral fillers employed are in the range from about 2 to about 10 μm. A special dispersant is essential for the invention disclosed in US 6752866. This contains a copolymer which is obtained by free radical copolymerization of an alkoxypolyalkylene glycol urethane with an anionic or nonionic monomer. No actual details are given for the amounts of mineral filler, dispersant and cement necessary. From the working examples, it is to be inferred that the content of mineral filler is 10% by weight (silicon dioxide, Test number 12) or 30% by weight (silicon dioxide, Test number 17) and the content of dispersant 0.5 (Test number 17) or 0.75% by weight (Test number 12), based on silicon dioxide. These dispersions show only a low stability to sedimentation.

WO 01/90024 discloses a concrete composition which contains aggregates, a hydraulic binder, silica sol and a polycarboxylate . The BET surface area of the silica sol is preferably 300 to 900 m ² /g. Silica sols are individual particles having a diameter of 3 to 50 nm and are only stable in dispersion. In WO 01/90024, nothing is disclosed about the influence of the described silica sol on early

strength. However, it is known to the person skilled in the art that in the case of silica sol concentrations at which a significant increase in the early strength is achieved the workability is also markedly reduced, so high amounts of superplasticizer are necessary. It is presumed that this lies in the fact that silica sols dissolve very rapidly in the strongly alkaline cement or concrete compositions. The silica sols are thus only available to a small extent as a nucleus for the formation of the strength-forming calcium silicate hydrate phases.

WO 98/12149 discloses a concrete composition which contains aggregates, a hydraulic binder and silica sol having a BET surface area of less than 200 m ² /g, wherein the particle size distribution is such that the relative standard deviation of the numerical distribution of the silica sol is more than 30%, in the working examples about 45% to 70%. The invention aims at increasing the early strength without reducing the final strength. In the course of this, superplasticizers can be added to the concrete composition. The use of the superplasticizers disclosed in WO 98/12149, however, leads to a drastic reduction of the processing time in the presence of the silica sol. In WO 98/12149, it is explained that preferably 1-8% of particles and particularly advantageously 2% of particles based on the binder are needed in order to achieve an increase in the early strength. It is known to the person skilled in the art that in the case of such high silica sol concentrations the workability is markedly reduced and thus high amounts of superplasticizers are needed. Thus, Wagner and Hauck in Wiss. Z. Hochsch. Archit. Bauwesen. - Weimar 40 (1990), p.183 ff. show that on use of silica sol concentrations of > 1% of the cement content the amounts of superplasticizer have to be markedly over 1% of the cement content in order to obtain a readily processable concrete. High amounts of superplasticizer lead to high costs for the user and can

moreover often lead to adverse effects such as a stronger tendency to bleeding and a lower final strength.

In EP-A-I 607378 , additives based on pyrogenic metal oxides for cement-containing systems are described which contain at least one sorbent. The pyrogenic metal oxides can be present in the form of aqueous dispersions. Furthermore, a superplasticizer based on polycarboxylate can be employed. EP-A-1607378, however, contains neither details about the type of polycarboxylate, nor in which range of amounts the polycarboxylate must be added, nor about the manner in which process step the polycarboxylate is added. Furthermore, it is to be noted with regard to the additives described in EP-A-1607378 that they have a low stability to sedimentation in dispersion form.

In Wiss. Z. Hochsch. Archit. Bauwesen. - Weimar 40 (I ¹ p.183, Wagner and Hauck show that the sequence of addition of the various constituents in the production of a concrete has a significant influence on the early strength and the need of superplasticizer if oxides increasing early strength are employed. In the investigation, the oxide was added separately from the superplasticizer. As a result of the combination of flow agent and oxide in a concrete additive, the number of possible various sequences of the addition would be reduced and thus also the possibilities of error. A further advantage of the combination in one concrete additive is that only one addition device is needed, which represents a cost advantage for the user.

The prior art shows that there is a lively interest in developing concrete compositions which have a high early strength with, at the same time, good workability, without large amounts of superplasticizer having to be used. The prior art further shows that the presently available superplasticizers and particles in the cement or concrete composition are a sensitive system. For example, the sequence of the addition and the concentration of the

substances used have a crucial influence on the workability and the early strength of the concrete.

It is therefore the object of the invention to make available a concrete additive with which the disadvantages of the prior art can be minimized. In particular, the concrete additive should markedly increase the early strength of concretes with, at the same time, good workability.

The invention relates to a dispersion which contains silicon dioxide and at least one water-soluble polycarboxylate ether, wherein

— the silicon dioxide is a pyrogenic silicon dioxide which is present in the form of aggregated primary particles having a BET surface area of 50 to 250 m ² /g, where

- the aggregates in the dispersion have a mean diameter of less than 1 μm and

- the proportion of silicon dioxide is 5 to 50% by weight, based on the total amount of the dispersion,

- the water-soluble polycarboxylate ether is a copolymer based on at least one oxyalkylene glycol compound and at least one unsaturated monocarboxylic acid derivative or dicarboxylic acid derivative, - the weight ratio of polycarboxylate ether/silicon dioxide is 0.01 to 100.

In the present invention, the terms silicon dioxide and silicon dioxide particles designate the same substance.

The dispersion according to the invention is preferably an aqueous dispersion, that is the main constituent of the liquid phase is water. The liquid phase moreover contains the water-soluble polycarboxylate ether.

The dispersion according to the invention is free of binders. Here, binders are to be understood as meaning

inorganic substances, such as, for example, cement, or organic substances which are processable in the plastic state and harden in the course of a certain time and thereby combine other substances with one another.

Pyrogenic is to be understood as meaning silicon dioxide particles obtained by flame oxidation and/or flame hydrolysis. Starting substances for pyrogenic processes which can be employed are organic and inorganic substances. Silicon tetrachloride, for example, is particularly suitable. Suitable organic starting compounds can be, for example, Si (OR) 4 where R=CH3 or CH2CH3. The silicon dioxide particles thus obtained are to the greatest extent pore- free and have free hydroxyl groups on the surface. The silicon dioxide particles within the meaning of the present invention are at least partially present in the form of aggregated primary particles. As a rule, the silicon dioxide particles are to the greatest extent present in aggregated form.

The dispersion according to the invention can also contain pyrogenic mixed oxides with silicon dioxide as the first component and lithium oxide, sodium oxide, potassium oxide, magnesium oxide, calcium oxide, aluminum oxide or zirconium dioxide as the second component. Likewise, it is possible that a mixture of pyrogenic silicon dioxide is present with the abovementioned mixed oxides.

Preferred pyrogenic mixed oxides are those in which the mixed oxide component is introduced by means of an aerosol. These are, for example, silicon-potassium mixed oxide or silicon-lithium mixed oxide, which can be prepared, for example, according to DE-A-19650500 or the still unpublished European patent application having the application number 05024753.5 and the application date November 12, 2005. Furthermore, the dispersion according to the invention can contain silicon-aluminum mixed oxide, which can be prepared according to EP-A-995718. Said mixed

oxides are distinguished by only a low degree of coalescence of the primary particles.

Advantageously, the pyrogenic silicon dioxide can be selected from the group comprising: AEROSIL ^® 90, AEROSIL ^® 130, AEROSIL ^® 200, AEROSIL ^® TT600, AEROSIL® MOX 80,

AEROSIL® MOX 170, all from Degussa; CAB-O-SIL ^® LM-150, CAB-O-SIL ^® LM-150D, CAB-O-SIL ^® M-5, CAB-O-SIL ^® M-5P, CAB-O- SIL ^® M-5DP, CAB-O-SIL ^® M-7D, CAB-O-SIL ^® PTG, CAB-O-SIL ^® HP- 60, all from Cabot Corp.; HDK ^® S13, HDK ^® V15, HDK ^® V15P, HDK ^® N20, HDK ^® N20P, all from Wacker; REOLOSIL ^® QS-IO,

REOLOSIL ^® QS-20 REOLOSIL ^® QS-30 REOLOSIL ^® QS-40, REOLOSIL ^® DM-IO, all from Tokuyama.

The silicon dioxide according to the invention can also be present in surface-modified form. Thus, the surface can be surface-modified, for example, with haloorganosilanes, alkoxysilanes, silazanes, siloxanes, polysiloxanes . Preferably, the silanizing agents used can be trimethoxy- octylsilane [(CH ₃ O)S-Si-CsHi ₇ ], octamethylcyclotetrasiloxane or hexamethyldisilazane . Since the stability of the dispersion according to the invention is lower, as a rule, in the case of surface-modified silicon dioxide than in the case of unmodified silicon dioxide, the lastmentioned is given preference.

It is furthermore possible that the dispersion according to the invention contains the pyrogenic silicon dioxide as a sole solid. This can in particular be useful if the dispersion is to serve as a masterbatch for various applications .

The BET surface area of the silicon dioxide present in the dispersion according to the invention is restricted to values of 50 to 250 m ² /g. Preferably, the silicon dioxide has a BET surface area of 70 to 170 m ² /g.

Furthermore, the dispersion according to the invention has a mean diameter of the aggregates in the dispersion of preferably 50 to 500 nm and particularly preferably one of 70 to 300 nm. Values below 50 nm can only be realized industrially with difficulty based on pyrogenically produced silicon dioxides and do not have any more advantages in use.

Furthermore, it can be advantageous if the relative standard deviation of the numerical distribution of the aggregate diameters of the silicon dioxide is less than

30%, as a rule 15% to 25%. The relative standard deviation is a measure of the particle size distribution. It applies for the present invention that a distribution which is as narrow as possible, that is a standard deviation which is as low as possible, is advantageous. By means of a narrow distribution of the aggregate diameters it is possible to influence more specifically the development of strength of the concrete: the aggregate diameter can influence the point in time from when the acceleration of the hydration by the reactive silicic acids commences.

Figure 1 shows the distribution of the aggregate diameters of two silicon dioxides having 90 and 200 m ² /g BET surface area in a dispersion according to the invention. The determined relative standard deviation of the numerical distribution of the aggregate diameters is 23% or 25%.

These dispersions can be employed particularly preferably.

The proportion of silicon dioxide in the dispersion according to the invention is 5 to 50% by weight, based on the total amount of the dispersion. Dispersions according to the invention which have a silicon dioxide content of 10 to 30% by weight as a rule show a better stability than more highly filled dispersions and are therefore preferred. Dispersions containing less than 5% by weight of silicon dioxide are not economical on account of the high water content.

The weight ratio polycarboxylate ether/silicon dioxide in the dispersion according to the invention is 0.01 to 100. Preferentially, this ratio can be 0.05 - 5.

The pH of the dispersion according to the invention can vary within wide limits. As a rule, the pH can be between 2 and 12, where alkaline pHs of 8 to 12, in particular of 9 to 11.5, can be preferred in cementitic systems on account of the compatibility of the components. Furthermore, bases or acids can be added to the dispersion according to the invention. As bases, it is possible to employ, for example, ammonia, ammonium hydroxide, tetramethylammonium hydroxide, primary, secondary or tertiary organic amines, sodium hydroxide solution or potassium hydroxide solution. As acids, it is possible to employ, for example, phosphoric acid, sulfuric acid, hydrochloric acid, nitric acid or carboxylic acids.

Furthermore, aluminum salts can be added to the dispersion according to the invention. Suitable aluminum salts can be aluminum chloride, aluminum hydroxychlorides of the general formula Al(OH) _x Cl where x=2-8, aluminum chlorate, aluminum sulfate, aluminum nitrate, aluminum hydroxynitrates of the general formula Al (OH) _X NC>3 where x=2-8, aluminum acetate, alums such as aluminum potassium sulfate or aluminum ammonium sulfate, aluminum formates, aluminum lactate, aluminum oxide, aluminum hydroxide acetate, aluminum isopropylate, aluminum hydroxide, aluminum silicates and mixtures of the aforementioned compounds. The use of these aluminum compounds in the preparation of silicon dioxide dispersions is already described in DE-A-10238463.

Furthermore, it can be advantageous to add to the dispersion and/or predispersion a surface-active substance which is of nonionic, cationic, anionic or amphoteric type.

The dispersion according to the invention can contain a copolymer having the structural groups a) , b) , c) ,

preferably having the structural groups a) , b) , c) , and d) . Here, the proportion of the structural group a) is 25 to 95 mol%, of the structural group b) 1 to 48.9 mol%, of the structural group c) 0 to 5 mol% and of the structural group d) 0 to 47.9 mol%.

In particular the proportion of the structural group a) is 51 to 95 mol% and of the structural group c) is 0.1 to 5 mol% .

The first structural group a) is a mono- or dicarboxylic acid derivative having the general formula Ia, Ib or Ic.

COX

CH ₂ - CR ¹ - - CH ₂ — C — - CH ₂ - - C - CH ₂

COX CH ₂ O = C C = O \ / COX Y

Ia Ib Ic

In the monocarboxylic acid derivative Ia, R ¹ is hydrogen or an aliphatic hydrocarbon radical having 1 to 20 C atoms, preferably a methyl group. X in the structures Ia and Ib is - 0M _a and/or - 0 - (C _m H _2m O) _n -R ² or -NH- (C _m H _2m O) _n -R ² having the following meaning for M, a, m, n and R ² :

M is hydrogen, a mono- or divalent metal cation, ammonium, an organic amine radical and a = ^ or 1, depending on whether M is a mono- or divalent cation. As organic amine radicals, substituted ammonium groups are preferably employed which are derived from primary, secondary or tertiary Ci-20-alkylamines, Ci-20-alkanolamines, C5-8- cycloalkylamines and Cs-i-j-arylamines . Examples of the corresponding amines are methylamine, dimethylamine, trimethylamine, ethanolamine, diethanolamine, triethanol- amine, methyldiethanolamine, cyclohexylamine, dicyclohexyl- amine, phenylamine, diphenylamine in the protonated (ammonium) form.

R is hydrogen, an aliphatic hydrocarbon radical having 1 to 20 C atoms, a cycloaliphatic hydrocarbon radical having 5 to 8 C atoms, an aryl radical having 6 to 14 C atoms, which can optionally also be substituted, m can be = 2 to 4 and n = 0 to 200. The aliphatic hydrocarbons can in this case be linear or branched and saturated or unsaturated. Preferred cycloalkyl radicals are to be regarded as cyclopentyl or cyclohexyl radicals, preferred aryl radicals as phenyl or naphthyl radicals, which in particular can also be substituted by hydroxyl, carboxyl or sulfonic acid groups.

Instead of or in addition to the dicarboxylic acid derivative according to formula Ib, the structural group a) (mono- or dicarboxylic acid derivative) can also be present in cyclic form corresponding to formula Ic, where Y can be = 0 (acid anhydride) or NR (acid imide) having the meaning designated above for R ² .

The second structural group b) corresponds to formula II

— CH ₂ — CR ³ —

(CH ₂ )p - O - (C _m H _2m O) _n - R ² and is derived from oxyalkylene glycol alkenyl ethers, in which m, n and R ² have the meaning designated above. R ³ is in turn hydrogen or an aliphatic hydrocarbon radical having 1 to 5 C atoms, which can likewise be linear or branched or alternatively unsaturated, p can assume values between 0 and 3.

Formula II also comprises compounds shown in formula II A

-CH ₂ -CR ³ - (CH ₂ ) p-O- (CH ₂ ) 4-0- (C ₂ H ₄ O) _n' -R ²

HA

where

R ³ is hydrogen or an aliphatic hydrocarbon radical having 1 to 5 C atoms, p is 0 to 3, R ² is hydrogen, an aliphatic hydrocarbon radical having 1 to 20 C atoms, a cycloaliphatic hydrocarbon radical having 5 to 8 C atoms, an optionally substituted aryl radical having 6 to 14 C atoms n' is a value from 0 to 190.

According to the preferred embodiments, in the formula Ia, Ib and II m is = 2 and/or 3, so that the groups are polyalkylene oxide groups which are derived from polyethylene oxide and/or polypropylene oxide. In a further preferred embodiment, p in formula II is 0 or 1, i.e. they are vinyl and/or alkyl polyalkoxylates .

The third structural group c) corresponds to the formula IHa or IHb

R ⁴ R ² R ²

— CH — C — — CH — CH CH — CH —

S T (CH ₂ ) _Z V (CH ₂ ) _Z

Ilia 1Mb

In formula IHa, R ⁴ can be = H or CH ₃ , depending on whether acrylic or methacrylic acid derivatives are concerned. S can in this case be -H, -COOM _a or -COOR ⁵ , where a and M have the abovementioned meaning and R ⁵ can be an aliphatic hydrocarbon radical having 3 to 20 C atoms, a cyclo- aliphatic hydrocarbon radical having 5 to 8 C atoms or an aryl radical having 6 to 14 C atoms. The aliphatic hydrocarbon radical can likewise be linear or branched, saturated or unsaturated. The preferred cycloaliphatic hydrocarbon radicals are in turn cyclopentyl or cyclohexyl radicals and the preferred aryl radicals phenyl or naphthyl

radicals. If T = -COOR ⁵ , S is = C00M _a or -COOR ⁵ . For the case where T and S are = COOR ⁵ , the corresponding structural groups are derived from the dicarboxylic acid esters .

In addition to these ester structural units, the structural groups c) can also have other hydrophobic structural elements. These include the polypropylene oxide or polypropylene oxide-polyethylene oxide derivative where

T = — U ¹ — (CH — CH ₂ — O ) _x — (CH ₂ — CH ₂ — O) _y — R ⁶

x here assumes a value from 1 to 150 and y from 0 to 15. The polypropylene oxide (-polyethylene oxide) derivatives can in this case be linked via a group U ¹ containing the ethyl radical of the structural group c) corresponding to formula Ilia, where U ¹ can be = -CO-NH-, -0- or -CH ₂ -O-. These are the corresponding amide, vinyl or allyl ethers of the structural group corresponding to formula Ilia. R ⁶ can in thi s case in turn be R ² ( for meaning of R ² see above ) or

where U ² can be = -NH-CO-, -0-, or -OCH ₂ - and S has the meaning described above. These compounds are polypropylene oxide (-polyethylene oxide) derivatives of the bifunctional alkenyl compounds corresponding to formula Ilia.

As a further hydrophobic structural element, the compounds corresponding to formula Ilia can contain polydimethyl- siloxane groups, which in the formula scheme Ilia corresponds to T = - W - R ⁷ .

W in thi s case i s

(below called a polydimethylsiloxane group) , R ⁷ can be = R ^z and r can in this case assume values from 2 to 100.

The polydimethylsiloxane group can not only be bonded directly to the ethylene radical as in formula Ilia, but also via the groups

— CO — [NH- (CH ₂ ) ₃ ] _s — W — R' or — CO — O (CH ₂ ) _Z — W —R',

where R ⁷ is preferably = R ² and s can be = 1 or 2 and z = 0 to 4. R ⁷ can moreover also be

-[(CH ₂ ) _S -NH] _S -CO- C = CH or — (CH ₂ ) _Z —O — CO — C = CH

R ⁴ S R ⁴ S

The corresponding difunctional ethylene compounds corresponding to the formula Ilia are concerned here, which are linked to one another via the corresponding amide or ester groups and where only one ethylene group has been copolymerized.

The situation is similar with the compounds as in formula IHa having T = (CH ₂ ) _Z -V-(CH ₂ ) _Z -CH=CH-R ² , where z = 0 to 4, V can be either a polydimethylsiloxane radical W or an - O- CO-C6H4-CO-O- radical and R ² has the meaning indicated above. These compounds are derived from the corresponding dialkenylphenyldicarboxylic acid esters or dialkenyl- polydimethylsiloxane derivatives .

In the context of the present invention, it is also possible that not only one, but both ethylene groups of the difunctional ethylene compounds have been copolymerized. This corresponds essentially to the structural groups corresponding to the formula IHb

R R

— CH — CH CH — CH —

(CH ₂ )z V (CH ₂ ) _Z

1Mb

where R , V and z have the meaning already described.

The fourth structural group d) is derived from an unsaturated dicarboxylic acid derivative of the general formula IVa and/or IVb having the meaning indicated above for a, M, X and Y.

_CH CH _CH CH

COOMa COX c^ _/ C ^

O Y O

IVa IVb

Preferably, the copolymers contain 55 to 75 mol% of structural groups of the formula Ia and/or Ib, 19.5 to 39.5 mol% of structural groups of the formula II, 0.5 to 2 mol% of structural groups of the formula Ilia and/or IHb and 5 to 20 mol% of structural groups of the formula IVa and/or IVb.

According to a preferred embodiment, the copolymers according to the invention additionally contain up to 50 mol%, in particular up to 20 mol%, based on the sum of the structural groups a to d, of structures which are based, inter alia, on monomers based on vinyl- or (meth) acrylic acid derivatives such as styrene, methylstyrene, vinyl acetate, vinyl propionate, ethylene, propylene, isobutene, hydroxyalkyl (meth) acrylates, acrylamide, methacrylamide, N-vinylpyrrolidone, allylsulfonic acid, methallylsulfonic acid, vinylsulfonic acid, vinylphosphonic acid, AMPS, methyl methacrylate, methyl acrylate, butyl acrylate, allylhexyl acrylate.

The number of repeating structural units in the copolymers is not restricted. It has proven particularly advantageous, however, to set mean molecular weights of 1000 to 100 000 g/mol .

The copolymers can be prepared in various ways. It is essential here that 51 to 95 mol% of an unsaturated mono- or dicarboxylic acid derivative, 1 to 48.9 mol% of an oxyalkylene alkenyl ether, 0.1 to 5 mol% of a vinylic polyalkylene glycol, polysiloxane or ester compound and 0 to 55 mol% of a dicarboxylic acid derivative are polymerized with the aid of a free radical starter.

Unsaturated mono- or dicarboxylic acid derivatives employed which form the structural groups of the formula Ia, Ib or

Ic are preferably: acrylic acid, methacrylic acid, itaconic acid, itaconic anhydride, itaconic acid imide and itaconic acid monoamide.

Instead of acrylic acid, methacrylic acid, itaconic acid and itaconic acid monoamide, their mono- or divalent metal salts, preferably sodium, potassium, calcium or ammonium salts, can also be used.

Acrylic, methacrylic or itaconic acid esters used are especially derivatives whose alcoholic component is a polyalkylene glycol of the general formula HO- (C _m H _2m O) _n ~R ² where R ² = H, an aliphatic hydrocarbon radical having 1 to 20 C atoms, a cycloaliphatic hydrocarbon radical having 5 to 8 C atoms, an optionally substituted aryl radical having 6 to 14 C atoms, and m = 2 to 4 and n = 0 to 200.

The preferred substituents on the aryl radical are -OH, -COO or -SO3 groups.

The unsaturated monocarboxylic acid derivatives can only be present as monoesters, while in the case of the dicarboxylic acid itaconic acid diester derivatives are also possible.

The derivatives of the formula Ia, Ib and Ic can also be present as a mixture of esterified and free acids and are used in an amount of preferably 55 to 75 mol%.

The second component for the preparation of the copolymers according to the invention is an oxyalkylene glycol alkenyl ether, which is preferably employed in an amount of 19.5 to 39.5 mol%. In the preferred oxyalkylene glycol alkenyl ethers corresponding to the formula V

CH ₂ = CR ³ - (CH ₂ ) _P - O - (C _m H _2m O) _n - R ^{^} V

R ³ is = H or an aliphatic hydrocarbon radical having 1 to 5 C atoms and p = 0 to 3. R ² , m and n have the meaning already mentioned above. The use of polyethylene glycol monovinyl ether (p = 0 and m = 2) has proven particularly advantageous here, n preferably having values between 1 and 50.

The third component employed for the introduction of the structural group c) is preferably 0.5 to 2 mol% of a

vinylic polyalkylene glycol, polysiloxane or ester compound. Preferred vinylic polyalkylene glycol compounds used are derivatives corresponding to the formula VI,

CH = C — R"

I I

S U ¹ — (CH — CH ₂ — O) _x — (CH ₂ — CH ₂ — O) _y — R ⁶ Vl

where S can preferably be -H, or COOM _a and U ¹ = -CO-NH-, -0- or -CH ₂ O-, i.e. they are the acid amide, vinyl or allyl ethers of the corresponding polypropylene glycol or polypropylene glycol-polyethylene glycol derivatives. The values for x are 1 to 150 and for y = 0 to 15. R ⁶ can either in turn be R ¹ or

— CH ₂ — CH — U ² — C = CH R ⁴ R ⁴ S r

where U ² = -NH-CO-, -0- and -OCH ₂ - and S is = -C00M _a and preferably -H.

If R ⁶ = R ² and R ² is preferably H, the polypropylene glycol (-polyethylene glycol) monoamides or ethers of the corresponding acrylic (S = H, R ⁴ = H) , methacrylic (S = H, R ⁴ = CH ₃ ) or maleic acid (S = C00M _a , R ⁴ = H) derivatives are concerned. Examples of such monomers are maleic acid N- (methylpolypropylene glycol) monoamide, maleic acid N- (methoxypolypropylene glycol-polyethylene glycol) monoamide, polypropylene glycol vinyl ether and polypropylene glycol allyl ether.

If R ⁶ ≠ R ² , bifunctional vinyl compounds are concerned whose polypropylene glycol- (polyethylene glycol) derivatives are bonded to one another via amide or ether groups (-0- or -OCH ₂ -) . Examples of such compounds are polypropylene

glycol bismaleamic acid, polypropylene glycol diacrylamide, polypropylene glycol dimethacrylamide, polypropylene glycol divinyl ether, polypropylene glycol diallyl ether.

As a preferred vinylic polysiloxane compound, derivatives corresponding to the formula VII are used,

R"

CH ₂ = C VII

W-R'

where R ⁴ = - H and CH ₃ ,

and r = 2 to 100 and R ⁷ is preferably = R ¹ . Examples of such monomers are monovinylpolydimethylsiloxanes .

As further vinylic polysiloxane compounds, suitable derivatives are those corresponding to the formula VIII,

FT

CH ₉ = C VIII

CO — [NH — (CH ₂ ) ₃ ] _S — W — R ⁷

where s can be = 1 or 2 , R ⁴ and W have the abovementioned meaning and R ⁷ can be either = R ² or el se

— [(CH ₂ ) ₃ — NH] ₃ — CO — C = CH

R ⁴ S

and S is preferably hydrogen.

Examples of such monomers having a vinyl function (R ⁷ = R ² ) are polydimethylsiloxanepropylmaleamic acid or polydimethylsiloxanedipropyleneaminomaleamic acid. If R ⁷ ≠ R ² , they are divinyl compounds such as, for example, polydimethylsiloxane-bis (propylmaleamic acid) or polydimethylsiloxane-bis (dipropyleneaminomaleamic acid) .

As a further vinylic polysiloxane compound, a preferred derivative corresponding to the formula IX is suitable:

R ⁴

CH ₂ = C IX

CO — O — (CH ₂ ) _Z — W— R ⁷

where z can be 0 to 4 and R ⁴ or W have the abovementioned meaning. R ⁷ can be either R ² or else

— (CH ₂ ) _Z — O — CO — C = CH

R ⁴ S

S preferably being hydrogen. Examples of such monovinylic compounds (R ⁷ = R ¹ ) are polydimethylsiloxane- (l-propyl-3- acrylate) or polydimethylsiloxane- (l-propyl-3- methacrylate) .

If R ⁷ ≠ R ² , they are divinyl compounds such as, for example, polydimethylsiloxane-bis (l-propyl-3-acrylate) or polydimethylsiloxane-bis (l-propyl-3-methacrylate) .

As a vinylic ester compound in the context of the present invention, derivatives corresponding to the formula X are preferably employed,

CH = CH

S I CIOOR ^{5 χ}

where S is = COOM _a or - COOR ⁵ and R ⁵ can be an aliphatic hydrocarbon radical having 3 to 20 C atoms, a cycloaliphatic hydrocarbon radical having 5 to 8 C atoms and an aryl radical having 6 to 14 C atoms, a and M have the abovementioned meaning. Examples of such ester compounds are di-n-butyl maleate or fumarate or mono-n- butyl maleate or fumarate.

In addition, compounds corresponding to the formula XI can also be employed

xi

where z in turn can be 0 to 4 and R ² has the meaning already known. V can in this case be W (that is a polydimethylsiloxane group) , which corresponds to a dialkenylpolydimethylsiloxane compound such as, for example, divinylpolydimethylsiloxane . Alternatively to this, V can also be -O-CO-C6H4-CO-O-. These compounds are dialkenylphthalic acid derivatives. A typical example of such phthalic acid derivatives is diallyl phthalate.

The molecular weights of the compounds which form structural group c) can be varied within wide limits and are preferably between 150 and 10 000.

The fourth component which can be used for the preparation of the copolymers is preferably 5 to 20 mol% of an unsaturated dicarboxylic acid derivative (XII):

MaOOC - CH = CH - COX XII

having the meaning already indicated for a, M and X.

If X = 0M _a , the unsaturated dicarboxylic acid derivative is derived from maleic acid, fumaric acid, mono- or divalent metal salts of these dicarboxylic acids, such as the sodium, potassium, calcium or ammonium salt or salts with

an organic amine radical. Moreover, monomers used which form the unit Ia are polyalkylene glycol monoesters of the abovementioned acids having the general formula XIII:

MaOOC — CH = CH — COO — (C _m H _2m O) _n — R ²

having the meaning already indicated for a, m, n and R ² .

The fourth component can also be derived from the unsaturated dicarboxylic acid anhydrides and imides of the general formula XIV (5 to 20 mol%)

CH = CH

Y '

having the meaning indicated above for Y.

According to the invention, according to a preferred embodiment additionally up to 50, preferably up to 20 mol% of further monomers as described above based on the sum of the structural groups a) to d) can be employed.

The dispersion according to the invention can furthermore contain a copolymer whose basis is an oxyalkenyl glycol alkenyl ether and the copolymer contains the structural groups a) , b) and c) . Here, the content of structural group a) is 10 to 90 mol%, of structural group b) 1 to 89 mol%, of structural group c) 0 to 5 mol% and of structural group d) 0.1 to 10 mol%.

The first structural group a) is an unsaturated dicarboxylic acid derivative corresponding to the formula IVa or IVb.

- CH CH - CH CH

COO ₃ M COX ^ ^c _\ ^ ^c ^.

O Y O

IVa IVb

In the dicarboxylic acid derivative corresponding to formula Id, M is = hydrogen, a mono- or divalent metal cation, ammonium ion, an organic amine radical, and a = 1, or if M is a divalent cation, 1/2. There then results, together with a group likewise comprising M _a where a = 1/2, a bridge via M, which only exists theoretically as M _a where a = 1/2.

As a mono- or divalent metal cation, sodium, potassium, calcium or magnesium ions are preferably used. Organic amine radicals employed are preferably substituted ammonium groups which are derived from primary, secondary or tertiary Ci- to C2o-alkylamines, C _x - to C2o-alkanolamines, C ₅ - to Cs-cycloalkylamines and Cβ~ to Ci ₄ -arylamines . Examples of corresponding amines are methylamine, dimethyl- amine, trimethylamine, ethanolamine, diethanolamine, tri- ethanolamine, cyclohexylamine, dicyclohexylamine, phenyl- amine, diphenylamine in the protonated (ammonium) form. Moreover, X is likewise -0M _a or -0-(Cr ₁ H _2n O) _n -R ¹ where R ¹ = H, an aliphatic hydrocarbon radical having 1 to 20 C atoms, a cycloaliphatic hydrocarbon radical having 5 to 8 C atoms, an aryl radical having 6 to 14 C atoms, which can optionally also be substituted, m can be = 2 to 4 and n = 0 to 200. The aliphatic hydrocarbon radicals can in this case be linear or branched and saturated or alternatively unsaturated.

Preferred cycloalkyl radicals are to be regarded as cyclo- pentyl or cyclohexyl radicals, preferred aryl radicals as phenyl or naphthyl radicals, which can in particular also be substituted by hydroxyl, carboxyl or sulfonic acid

groups. Alternatively to this, X can additionally be -NHR and/or -NR ² ₂ , which corresponds to the mono- or disubstituted monoamides of the corresponding unsaturated dicarboxylic acid, where R ² can in turn be identical to R ¹ or instead can be -CO-NH ₂ .

Instead of the dicarboxylic acid derivative corresponding to formula IVa, the structural group a) (dicarboxylic acid derivative) can also be present in cyclic form corresponding to the formula IVb, where Y can be = 0 (= Ic acid anhydride) or NR ² (acid imide) and R ² has the meaning designated above.

In the second structural group corresponding to the formula II,

— CH ₂ — CR' —

I Ii

(CH ₂ )p — O — (C _m H _2m O) _n — R ¹

which is derived from the oxyalkylene glycol alkenyl ethers, R ³ is in turn hydrogen or an aliphatic hydrocarbon radical having 1 to 5 C atoms (which can likewise be linear or branched or alternatively unsaturated) . p can assume values between 0 and 3 and R , m and n have the abovementioned meaning. According to a preferred embodiment, in formula H p = O and m is = 2 or 3, so that these are structural groups which are derived from polyethylene oxide or polypropylene oxide vinyl ethers.

Formula II also comprises compounds shown in formula II A

-CH ₂ -CR ³ -

(CH ₂ ) p-O- (CH ₂ ) ₄ -O- (C ₂ H ₄ O) n _' -R ²

where

R ³ is hydrogen or an aliphatic hydrocarbon radical having 1 to 5 C atoms,

p i s 0 to 3 ,

R ² is hydrogen, an aliphatic hydrocarbon radical having 1 to 20 C atoms, a cycloaliphatic hydrocarbon radical having 5 to 8 C atoms, an optionally substituted aryl radical having 6 to 14 C atoms n' is a value from 0 to 190.

The third structural group c) corresponds to the formula IHa or IHb

R ⁴ R ² R ²

— CH — C — — CH — CH CH — CH —

S T (CH ₂ ) _Z V (CH ₂ ) _Z

Ilia 1Mb

In formula IHa, R ⁴ can be = H or CH ₃ , depending on whether acrylic or methacrylic acid derivatives are concerned. S can in this case be -H, COOM _a or -COOR ⁵ , where a and M have the abovementioned meaning and R ⁵ can be an aliphatic hydrocarbon radical having 3 to 20 C atoms, a cycloaliphatic hydrocarbon radical having 5 to 8 C atoms or an aryl radical having 6 to 14 C atoms. The aliphatic hydrocarbon radical can likewise be linear or branched, saturated or unsaturated. The preferred cycloaliphatic hydrocarbon radicals are in turn cyclopentyl or cyclohexyl radicals and the preferred aryl radicals phenyl or naphthyl radicals. If T = -COOR ⁵ , S is = COOM _a or -COOR ⁵ . If T and S are = COOR ⁵ , the corresponding structural groups are derived from the dicarboxylic acid esters.

In addition to these ester structural units, the structural groups c) can also have other hydrophobic structural elements. These include the polypropylene oxide or polypropylene oxide-polyethylene oxide derivatives where

T = — U ¹ — (CH — CH ₂ — O ) _x — (CH ₂ — CH ₂ — O) _y — R ⁶

CH ₃ x in this case assumes a value from 1 to 150 and y from 0 to 15. The polypropylene oxide (-polyethylene oxide) derivatives can in this case be linked via a group U ¹ to the ethyl radical of the structural group c) corresponding to formula Ilia, where U ¹ can be = -CO-NH-, -0- or -CH ₂ -O-. In this case, these are the corresponding amide, vinyl or allyl ethers of the structural groups corresponding to formula Ilia. R ⁶ can in this case in turn be R ¹ (for meaning of R ¹ see above) or

— CH ₂ — CH — U ² — C = CH R ⁴ R ⁴ S

where U ² can be = -NH-CO-, -0- or -OCH ₂ - and S has the meaning described above. These compounds are polypropylene oxide (-polyethylene oxide) derivatives of the bifunctional alkenyl compounds corresponding to formula Ilia.

As a further hydrophobic structural element, the compounds corresponding to formula Ilia can contain polydimethyl- siloxane groups, which in the formula scheme Ilia corresponds to T = -W-R ⁷ .

W in this case is

(called a polydimethylsiloxane group below) , R ⁷ can be = R ¹ and r can in this case assume values from 2 to 100.

In particular the proportion of structural groups of the formula Ilia or IHb is 0.1 to 10 mol%.

The polydimethylsiloxane group W cannot only be bonded directly to the ethylene radical as in formula Ilia, but also via the groups

— CO — [NH- (CH ₂ ) ₃ ] _s — W — R' or — CO — O (CH ₂ ) _Z — W —R',

where R ⁷ preferably i s = R ¹ and s can be = 1 or 2 and z = 0 to 4 .

R ⁷ can moreover additional ly be

— [(CH ₂ ) ₃ — NH] ₃ - CO — C = CH or — (CH ₂ ) _Z — O — CO — C = CH

R ⁴ S R ⁴ S

Here, the corresponding difunctional ethylene compounds corresponding to the formula Ilia are concerned, which are linked to one another via the corresponding amide or ester groups and where only one ethylene group has been copolymerized.

The situation is also similar with the compounds as in formula IHa having T = -(CH ₂ ) _Z -V-(CH ₂ ) _Z -CH=CH-R ¹ , where z = 0 to 4, V can either be a polydimethylsiloxane radical W or an -O-CO-C6H4-CO-O- radical and R ¹ has the meaning indicated above. These compounds are derived from the corresponding dialkenylphenyldicarboxylic acid esters or dialkenyl- polydimethylsiloxane derivatives .

It is also possible within the context of the present invention that not only one, but both ethylene groups of the difunctional ethylene compounds have been copolymerized. This corresponds essentially to the structural groups corresponding to the formula IHb

R ¹ R ¹

— CH — CH CH — CH —

(CH ₂ )z V (CH ₂ ) _Z

INb

where R ¹ , V and z have the meaning already described.

Preferably, these copolymers consist of 40 to 55 mol% of structural groups of the formula IVa and/or IVb, 40 to 55 mol% of structural groups of the formula II and 1 to 5 mol% of structural groups of the formula Ilia or IHb. According to a preferred embodiment, the copolymers additionally contain up to 50 mol%, in particular up to 20 mol%, based on the sum of the structural groups a) , b) and c) , of structural groups whose monomer is a vinyl, acrylic acid or methacrylic acid derivative.

The monomeric vinyl derivatives can preferably be derived from a compound which is selected from the group styrene, ethylene, propylene, isobutene or vinyl acetate. As a preferred monomeric acrylic acid derivative, the additional structural groups are in particular derived from acrylic acid or methyl acrylate. A preferred monomeric methacrylic acid derivative is to be regarded as methacrylic acid, methyl methacrylate and hydroxyethyl methacrylate .

The number of repeating structural elements of the copolymers is not restricted here, but it has proven particularly advantageous to adjust the number of the structural elements such that the copolymers have an average molecular weight of 1000 to 200 000.

The second component of the copolymers is an oxyalkylene glycol alkenyl ether, which is preferably employed in an amount of 40 to 55 mol%. In the preferred oxyalkylene glycol alkenyl ethers corresponding to the formula V

CH ₂ =CR ³ -(CH ₂ )p-O-(C _m H _2m O)n-R ¹ V

R ³ is = H or an aliphatic hydrocarbon radical having 1 to 5 C atoms and p is = 0 to 3. R ¹ , m and n have the meaning already mentioned above. The use of polyethylene glycol monovinyl ether (p = 0 and m = 2) has proven particularly advantageous here, n preferably having values between 2 and 15.

As the third component essential to the invention for the introduction of the structural groups c) , 1 to 5 mol% of a vinylic polyalkylene glycol, polysiloxane or ester compound is preferably employed. As a preferred vinylic polyalkylene glycol compound, derivatives corresponding to the formula VI are employed,

Vl

where S can preferably be -H or COOM _a and U ¹ = -CO-NH-, -0- or -CH ₂ O-, i.e. the acid amide, vinyl or allyl ethers of the corresponding polypropylene glycol or polypropylene glycol-polyethylene glycol derivatives.

The values for x are 1 to 150 and for y = 0 to 15. R ⁶ can in turn either be R ¹ or

-CH ₂ -CH-U ² -C = CH R ⁴ R ⁴ S,

where

U ² is = -NH-CO-, -0- and -OCH ₂ - and S is = -C00M _a and preferably -H.

If R ⁶ = R ¹ and R ¹ preferably = H, these are the polypropylene glycol (-polyethylene glycol) monoamides or ethers of the corresponding acrylic (S = H, R ⁴ = H) , methacrylic (S = H, R ⁴ = CH ₃ ) or maleic acid (S = COOM _a , R ⁴ = H) derivatives. Examples of such monomers are maleic acid N- (methylpolypropylene glycol) monoamide, maleic acid N- (methoxypolypropylene glycol-polyethylene glycol) monoamide, polypropylene glycol vinyl ether and polypropylene glycol allyl ether.

If R ⁶ ≠ R ¹ , these are bifunctional vinyl compounds, whose polypropylene glycol- (polyethylene glycol) derivatives are connected to one another by means of amide or ether groups (-0- or -OCH ₂ -) . Examples of such compounds are polypropylene glycol-bismaleamic acid, polypropylene glycol diacrylamide, polypropylene glycol dimethacrylamide, polypropylene glycol divinyl ether, polypropylene glycol diallyl ether.

As a preferred vinylic polysiloxane compound, derivatives corresponding to the formula VII are used, R ⁴

CH ₂ = C

W-R ⁷

VII

where R ⁴ = -H and CH ₃ , W=

and r = 2 to 100 and R ⁷ is preferably = R ¹ . Examples of such monomers are monovinylpolydimethylsiloxanes .

As a further vinylic polysiloxane compound, suitable derivatives are those corresponding to the formula VIII,

VIII

where s can be = 1 or 2, R ⁴ and W have the abovementioned meaning and R ⁷ can either be = R ¹ or else

and S is preferably hydrogen.

Examples of such monomers having a vinyl function (R ⁷ = R ¹ ) are polydimethylsiloxanepropylmaleamic acid or polydimethylsiloxanedipropyleneaminomaleamic acid. If R ⁷ ≠ R ¹ , they are divinyl compounds such as, for example, polydimethylsiloxane-bis (propylmaleamic acid) or polydimethylsiloxane-bis (dipropyleneaminomaleamic acid).

As a further vinylic polysiloxane compound, a suitable preferred derivative is one corresponding to the formula

^R CH ₂ = C

CO-O-(CH ₂ ) _Z -W-R ⁷

IX

where z can be 0 to 4 and R ⁴ or W have the abovementioned meaning. R ⁷ can either be R ¹ or else

-CH ₂ ) _Z -O-CO-C = C _{1 D 4 I}

where S is preferably hydrogen. Examples of such monovinylic compounds (R ⁷ = R ¹ ) are polydimethylsiloxane- (l-propyl-3-acrylate) or polydimethylsiloxane- (l-propyl-3- methacrylate) .

If R ¹ ≠ R ¹ , these are divinyl compounds, such as, for example, polydimethylsiloxane-bis (l-propyl-3-acrylate) or polydimethylsiloxane-bis (l-propyl-3-methacrylate) .

As a vinylic ester compound, in the context of the present invention derivatives corresponding to the formula X are preferably employed,

CH = CH

S COOR ⁵

X

where S is = COOM _a or -COOR ⁵ and R ⁵ can be an aliphatic hydrocarbon radical having 3 to 20 C atoms, a cycloaliphatic hydrocarbon radical having 5 to 8 C atoms and an aryl radical having 6 to 14 C atoms, a and M have the abovementioned meaning. Examples of such ester compounds are di-n-butyl maleate or fumarate or mono-n- butyl maleate or fumarate.

In addition, compounds corresponding to the formula XI can also be employed,

CH = CH CH = CH R ¹ (CH ₂ ) _Z -V-(CH ₂ ) _Z - (CH ₂ ) _Z R ¹ Xl

where z can in turn be 0 to 4 and R ¹ has the meaning already known. V can in this case be W (that is a polydimethylsiloxane group) , which corresponds to a dialkenylpolydimethylsiloxane compound, such as, for example, divinylpolydimethylsiloxane . Alternatively to this, V can also be -O-CO-C6H4-CO-O-. These compounds are

dialkenylphthalic acid derivatives. A typical example of such phthalic acid derivatives is diallyl phthalate.

The molecular weights of the compounds which form the structural group c) can be varied within wide limits and are preferably between 150 and 10 000.

Furthermore, additionally up to 50 mol%, in particular up to 20 mol%, based on the monomers having the structural groups as in the formulae II, III and IV of a vinyl, acrylic acid or methacrylic acid derivative can be copolymerized. As a monomeric vinyl derivative, styrene, ethylene, propylene, isobutene or vinyl acetate is preferably used, as a monomeric acrylic acid derivative acrylic acid or methyl acrylate is preferably employed, while as monomeric methacrylic acid derivatives finally methacrylic acid methyl methacrylate and hydroxyethyl methacrylate are preferably used.

The aforementioned copolymers are disclosed in EP-A-736553

The dispersion according to the invention can furthermore contain a copolymer whose basis is an oxyalkenyl glycol (meth) acrylic acid ester and the copolymer contains the following structural groups:

5-98% by weight of a monomer of the type (a) (alkoxy) polyalkylene glycol mono (meth) acrylic ester of the general formula XV

XV in which

R ¹ is a hydrogen atom or the methyl group,

R O is one type or a mixture of two or more types of an oxyalkylene group having 2-4 carbon atoms, with the proviso that two or more types of the mixture can be added either in the form of a block or in random form,

R ³ is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and

m is a value which is the average number of the added moles of oxyalkylene groups, where m is an integer in the range from 1 to 200. 95 to 2% by weight of a monomer of the (meth) acrylic acid type (b) of the general formula XVI

CH ₂ == CC ₁ -R ⁴

COOM ¹ XVI

in which

R ⁴ is a hydrogen atom or the methyl group, and M ¹ is a hydrogen atom, a monovalent metal atom, a divalent metal atom, an ammonium group or an organic amine group,

- and 0 to 50% by weight of another monomer (c) which is copolymerizable with these monomers, with the proviso that the total amount of (a) , (b) and (c) is 100% by weight .

Typical monomers (a) are: Hydroxyethyl (meth) acrylate,

Hydroxypropyl (meth) acrylate, polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, polybutylene glycol mono (meth) acrylate, polyethylene glycol-polypropylene glycol mono (meth) acrylate, polyethylene glycol-polybutylene glycol mono (meth) acrylate,

polypropylene glycol-polybutylene glycol mono (meth) acrylate, polyethylene glycol-polypropylene glycol-polybutylene glycol mono (meth) acrylate, methoxypolyethylene glycol mono (meth) acrylate, methoxypolypropylene glycol mono (meth) acrylate, methoxypolybutylene glycol mono (meth) acrylate, methoxypolyethylene glycol-polypropylene glycol mono (meth) acrylate, methoxypolyethylene glycol-polybutylene glycol mono (meth) acrylate, methoxypolypropylene glycol-polybutylene glycol mono (meth) acrylate, methoxypolyethylene glycol-polypropylene glycol- polybutylene glycol mono (meth) acrylate, ethoxypolyethylene glycol mono (meth) acrylate, ethoxypolypropylene glycol mono (meth) acrylate, ethoxypolybutylene glycol mono (meth) acrylate, ethoxypolyethylene glycol-polypropylene glycol mono (meth) acrylate, ethoxypolyethylene glycol-polybutylene glycol mono (meth) acrylate, ethoxypolypropylene glycol-polybutylene glycol mono (meth) acrylate and/or ethoxypolyethylene glycol-polypropylene glycol-polybutylene glycol mono (meth) acrylate .

Typical monomers (b) are: acrylic acid and methacrylic acid, mono- and divalent metal salts, ammonium salts and/or organic amine salts thereof. Typical monomers (c) are: esters of aliphatic alcohols having 1 to 20 C atoms with (meth) acrylic acid; unsaturated dicarboxylic acids such as maleic acid, fumaric acid, citraconic acid, mono- and divalent metal salts, ammonium salts and/or organic amine salts thereof; mono- or diesters of unsaturated dicarboxylic acids such as maleic acid, fumaric acid, citraconic acid with aliphatic alcohols of 1 to 20 C atoms, with glycols having 2 to 4 C atoms, with

(alkoxy) polyalkylene glycols of 2 to 100 added moles of the aforementioned glycols; unsaturated amides such as (meth) acrylamide and (meth) acrylalkylamide; vinyl esters such as vinyl acetate and vinyl propionate; aromatic vinyl compounds such as styrene; unsaturated sulfonic acids, such as (meth) allylsulfonic acid, sulfoethyl (meth) acrylate, 2-methylpropanesulfonic acid (meth) acrylamide, styrenesulfonic acid, mono- and divalent metal salts, ammonium salts and/or organic amine salts thereof. A further subject of the invention is a process for the preparation of the dispersion according to the invention, in which a) a polycarboxylate ether in the form of a powder or as an aqueous solution of the polycarboxylate ether is added with stirring to an aqueous starting dispersion of silicon dioxide, in which the aggregates have a mean diameter of less than 1 μm, and the mixture is optionally diluted further with water or b) a silicon dioxide powder is dispersed in an aqueous solution of a polycarboxylate ether by means of a suitable dispersing unit and is subsequently optionally diluted further with water or c) the silicon dioxide powder is dispersed in an aqueous phase, preferably in water, and subsequently the resulting dispersion is added to an aqueous solution of the polycarboxylate ether. The mixing in of the dispersion can in this case be carried out under very low shear energy, for example by means of a propeller stirrer.

Suitable dispersing units are understood as meaning those whose energy input suffices to disperse the silicon dioxide powder so that the aggregates have a mean diameter of less than 1 μm.

The dispersion of the silicon dioxide powder can be carried out at low degrees of filling in equipment which introduces a comparatively low shear energy into the system (e.g. dissolvers, rotor-stator systems) .

In order to achieve high degrees of filling, shear energies of > 1000 kJ/m ³ must be applied in order to obtain a stable dispersion of low viscosity. High shear energies can be achieved, for example, using stirred ball mills, high- pressure homogenizers or planetary kneaders .

In particular, the process disclosed in DE-A-10317066 can be employed.

Furthermore, a process disclosed in WO 2005/063369 can advantageously be employed, in which at least two streams of a predispersion are sprayed to a collision point by means of pumps, preferably high-pressure pumps, through in each case one nozzle into a milling space surrounded by a reactor housing, the milling space being flooded with the predispersion and it being removed from the milling space by means of overpressure of the predispersion flowing into the milling space. A process which is disclosed in German patent specification DE 10204470 is carried out in a similar manner. Here, at least two streams of a predispersion are sprayed to a collision point by means of pumps, preferably high-pressure pumps, through in each case one nozzle into a reactor space surrounded by a reactor housing and in the reactor space water vapor is introduced through an opening such that in the reactor space a vapor atmosphere prevails which consists predominantly of water vapor, and the finely divided dispersion and vapor and/or partially condensed vapor, which consists mainly of water, are removed from the reactor space by means of overpressure of the entering water vapor on the gas inlet side.

Optionally, using dispersing units which make available a lower energy input, for example a dissolver, a predispersion can initially be produced.

A further subject of the invention is the use of the dispersion according to the invention as a concrete additive .

A further subject of the invention is a cement-containing preparation which comprises the dispersion according to the invention .

Preferably, the content of silicon dioxide in the cement- containing preparation is 0.01 to < 2% by weight, based on the cement .

Examples

Analysis: Numerical distribution of the aggregate sizes determined by means of dynamic light scattering, measuring apparatus: Horiba LB-500, measuring range 0.003 μm to 6 μm, number of iterations: 800. The relative coarsely divided powder P2 is measured by laser diffraction according to ISO 13320-1.

The BET surface area is determined according to DIN 66131.

The preparation of standard mortar was carried out according to DIN EN 196. The testing of the strength was carried out according to DIN 1164 on prisms of size 4 x 4 x 16 cm.

Starting materials Silicon dioxide starting dispersions (SD) :

SDl: 32.5 kg of completely demineralized water are introduced into a 60 1 stainless steel batch container. Subsequently, 17.5 kg of AEROSIL 90 are drawn in with the aid of the suction head of the Ystral Conti-TDS 3 (stator slit: 4 mm ring and 1 mm ring, rotor/stator distance about 1 mm) under shear conditions. Afterward, the mixture is additionally resheared at 3000 rpm for 10 min. After milling has taken place, the mixture is adjusted to pH 10 using sodium hydroxide solution. The silicon dioxide particles have a d ₅ o value of 154 nm. The viscosity of the dispersion is 6 mPas at a shear rate of 10 s ^"1 and at 23°C.

SD2 : 32.5 kg of completely demineralized water are introduced into a 60 1 stainless steel batch container. Subsequently, 17.5 kg of AEROSIL 200 are drawn in with the aid of the suction head of the Ystral Conti-TDS 3 (stator slit: 4 mm ring and 1 mm ring, rotor/stator

distance about 1 mm) under shear conditions. Afterward, the mixture is resheared at 3000 rpm for 10 min. After milling has taken place, the mixture is diluted with completely demineralized water to a concentration which is something over 20% by weight. A pH of 10 is adjusted using sodium hydroxide solution. Afterward, the remaining water needed is added in order to achieve a silicon dioxide final concentration of 20% by weight. The silicon dioxide particles have a dso value of 81 nm. The viscosity of the dispersion is 40 mPas at a shear rate of 10 s ^"1 and at 23°C.

SD3: 36 kg of completely demineralized water and 104 g of 30% strength KOH solution are introduced into a 60 1 stainless steel batch container. 16.5 kg of 0.44% by weight potassium-doped silicon dioxide, prepared according to DE19650500, are sucked in with the aid of a dispersing and suction mixer from Ystrahl (at 4500 rpm) and coarsely predispersed. This predispersion is assisted by a rotor/stator flow-through homogenizer type Z 66 from Ystral having four processing rings, a stator slit width of 1 mm and speed of rotation of 3000 rpm. After the powder entry, the dispersion is completed using the rotor/stator flow-through homogenizer type Z 66 from Ystral at a speed of rotation of 11 500 rpm. During this 15-minute dispersion at 11 500 rpm, the pH is adjusted to a pH of 10.5 by addition of further KOH solution and held. A further 779 g of KOH solution were used here and a solids concentration of 30% by weight was adjusted by addition of 1.5 kg of water. The dispersion thus obtained is ground using a "Wet Jet

Mill", Ultimaizer System from Sugino Machine Ltd., model HJP-25050, at a pressure of 250 MPa and a diamond nozzle diameter of 0.3 mm and two milling passages. The dispersion has a content of doped silicon dioxide of 30% by weight. The silicon dioxide particles have a d ₅ o value

of 71 nm. The viscosity of the dispersion is 7.5 mPas at a shear rate of 500 s ^"1 and at 23°C.

Silicon dioxide powder (P) :

P4 : Pyrogenic SiO ₂ , doped with 0.1% by weight of Li ₂ O; having 90 m ² /g specific surface area

P5 : precipitated silicon dioxide having 165 m /g specific surface area, average aggregate diameter D ₅₀ (number- based) : 5 μm

P6: Silica fume having 20 m /g specific surface area average particle diameter D ₅₀ (number-based): 0.13 μm

Polycarboxylate ether (PCE) is prepared according to EP-A- 1189955, Example 2, the amounts being modified such that a 45 percent solution is obtained.

Dispersions (D) :

Dl (according to the invention) : 250 g of an aqueous solution of PCE (content of PCE: 45% by weight) are added to 1000 g of SDl with stirring.

D2 (according to the invention) : 183 g of an aqueous solution of PCE (content of PCE: 45% by weight) are added to 1000 g of SD2 with stirring. D3 (according to the invention) : 250 g of an aqueous solution of PCE (content of PCE: 45% by weight) are added to 1000 g of SD3 with stirring.

D4 (according to the invention) : First, 3.2 kg of water are added to 1000 g of an aqueous solution of PCE (content of PCE: 45% by weight) . Afterward, 1400 g of Pl are dispersed in the diluted PCE solution using a ball mill.

D5 (comparative example) : First, 4.4 kg of water are added to 1000 g of an aqueous solution of PCE (content of PCE:

45% by weight) . Afterward, 1100 g of P5 are dispersed in the diluted PCE solution using a ball mill.

D6 (comparative example) : First, 2.9 kg of water are added to 1000 g of an aqueous solution of PCE (content of PCE: 45% by weight) . Afterward, 1750 g of P6 are dispersed in the diluted PCE solution using a ball mill.

The ratio of PCE to silicon dioxide is adjusted such that on addition of the dispersion to a cement-containing preparation, the silicon dioxide content corresponds to 0.5% by weight, based on the cement content. The initial flow measurement of the mortar always lies in the range 24 cm +/- 1 cm.

The composition of the dispersions is shown in Table 1. D7 contains no silicon dioxide, but only PCE and is not a dispersion. For the sake of clarity, D7 is nevertheless displayed in Table 1.

The dispersions according to the invention show no noticeable change with respect to sedimentation stability and viscosity in the course of a period of time of 6 months.

Preparation of standard mortar

Cement: CEM I 52.5 Mergelstetten, temperature 20 ⁰ C. The dispersions corresponding to a silicon dioxide content of 0.5% by weight, based on the cement weight, are added to the mortar mixtures. The water/cement ratio was always 0.4. The results are summarized in Table 1. The results obtained show a marked increase in the early strength on using the dispersions according to the invention. Tests are furthermore carried out in a calorimeter. As cement, CEM I 42.5 Bernburg is used. The dispersions Dl, D2, and D3 according to the invention are used. The dispersions are added such that the content of silicon dioxide is 0.5% by weight based on the cement employed. The

water/cement ratio is constant at 0.5. Comparison to the dispersion D6 is carried out, which contains "silica fume" and D7, which contains no silicon dioxide but PCE. In all tests, the initial flow measurement was 24 +/- 1 cm. The curves obtained (Figure 2) show the liberated energy in J/g of CEM against the time in hours in the cement size test sample. The evolution of heat is to be attributed to the exothermic reaction of the silicate phases in the cement with water. This process is designated as cement hydration. The greater the evolution of heat up to a specific time of the hydration reaction, in general the greater also the strength of a building part at this time

The presentation clearly shows the higher reactivity of the mortar to which the dispersions according to the invention were added.

Table 1 : Dispersions and development of strength of mortar prisms prepared therewith

^r )Dl-D4: according to invention; D5-D7 comparative examples;