Water-soluble copolymers based on olefinic sulfonic acids, method for the production thereof and use of the same

Water-soluble copolymers based on olefinic sulfonic acids, olefinic dicarboxylic acids, vinyl amides and vinyl ethers and/or allyl ethers and/or bisacryl derivatives are described as well as processes for their production and the use of these copolymers as water retention agents, thickeners or anti-segregation agents for aqueous building material systems that contain hydraulic binding agents such as cement, lime, gypsum, anhydrite etc. or for clay suspensions preferably based on bentonite.

The present invention concerns water-soluble copolymers based on olefinic sulfonic acids, olefinic dicarboxylic acids, vinylamides and vinyl and/or allyl ethers which can be used as water retention agents, thickeners or anti-segregation agents in plaster and cement mortars that are for example used in the form of plasters, and in clay suspensions.

Cement and plaster mortars are used in the building industry to bond various ceramic materials and surface coverings to the substrate or to cover surfaces (plaster). In this process the tempering water must be prevented from being removed from the mortar by capillary forces of porous substrates. This is achieved by adding water retention agents. These can either bind water per se due to their chemical structure (e.g. by means of hydrogen bonds) or they result in the formation of an impermeable filter cake of the mortar on the substrate. Thus for example mixtures of clay and guar are described as water retention agents in EP-A 1 090 889. The documents DE 195 43 304 A1 and U.S. Pat. No. 5,372,642 disclose cellulose derivatives as water retention agents.

Furthermore setting agents are often added to mortars to prevent the mortar from flowing out of cracks to be repaired or from vertical surfaces. This is often achieved by adding cellulose and/or starch derivatives. Thus setting agents which contain at least one cellulose ether and one starch ether are disclosed in EP-A 773 198. According to EP-A 0 445 653 and DE 195 34 719 A1 setting agents are described which contain the clay mineral hectorite in addition to cellulose derivatives. Thickener systems are known from EP-A 0 630 871 which contain at least one ionic or non-ionic surfactant in addition to a cellulose ether.

Suspensions of swellable clays are used in foundation and soil engineering to produce earth-supporting liquids for excavations. Examples of this are the construction of diaphragm walls, and the sinking of shafts, wells and caissons (see also: F. Weiss, “Die Standfestigkeit flüssigkeitsgestützter Erdwände” in “Bauingenieurpraxis” 70 (1967)).

The cellulose derivatives used according to the prior art have the disadvantage that they delay the stiffening of cement mortar. However, this is undesirable in many cases since a relatively rapid stiffening of the mortar is better for subsequent treatment. For this reason it is often necessary to additionally add accelerators to cement slurries which, however, is not unproblematic in practice due to the necessity of an exact dosage.

Hence the object of the present invention was to provide water-soluble copolymers which do not have the said disadvantages of the prior art, but can be produced in a technically simple manner and give the corresponding building material systems good application properties in the working and hardened state.

This object was achieved by the copolymers according to claim1.

It has surprisingly turned out that the water-soluble copolymers according to the invention can be used as water retention agents, thickeners or anti-segregation agents without prolonging the setting and stiffening times.

The copolymers according to the present invention consist of at least four structural units a), b), c) and d). The first-structural unit a) is derived from olefinic sulfonic acids of formula (Ia) and/or (Ib):

in whichR1=hydrogen or C1–C5alkyl,R2=C1–C20alkylene, carboxy-C1–C20-alkylene, carboamido-C1–C20-alkylene or phenyleneM=hydrogen, ammonium or a monovalent, divalent or trivalent metal cationandx=1 to 3.

Alkali ions and in particular sodium and potassium ions are preferably used as monovalent metal cations; alkaline earth ions and in particular calcium and magnesium ions are preferably used as divalent metal cations and aluminium or iron ions are preferably used as trivalent cations. According to a preferred embodiment R1=hydrogen and R2=—CO—NH—C(CH3)2—CH2— in formula (Ia).

The structural unit a) is derived from monomers such as 2-acrylamido-2-methylpropanesulfonic acid, styrenesulfonic acid, vinylsulfonic acid and methallylsulfonic acid and salts thereof. 2-Acrylamido-2-methylpropanesulfonic acid and salts thereof are particularly preferred.

The second structural unit b) corresponds to formula (IIa) and/or (IIb):

in whichR3and R4=—COO−(Mx+)1/xor are together

R5=—COO−(Mx+)1/xM=hydrogen, ammonium or a monovalent, divalent or trivalent metal cationandx=1 to 3.

Again alkali cations (Na, K) are preferred as monovalent metal cations, alkaline earth cations (Ca, Mg) are preferred as divalent metal cations and aluminium and iron ions are preferred as trivalent metal cations.

Maleic acid and salts thereof as well as maleic anhydride and also fumaric acid, itaconic acid or salts thereof are suitable as monomers which form the structure(s) (IIa) and/or (IIb).

The third structural unit c) corresponds to formula (III).

in whichR6=hydrogen or C1–C5alkylR7and R8=hydrogen, C1–C10alkyl or are together —(CH2)y— andy=3 to 7, in particular 3 to 5.

N-vinylcaprolactam, N-vinylpyrrolidone and also N-vinylformamide, N-vinylacetamide and N-methyl-N-vinylacetamide are preferably used as monomers that can form the structural unit c).

According to a preferred embodiment the C1–C20hydroxyalkyl, C7–C20hydroxyalkylaryl and C6–C10hydroxylaryl residues for R10and R4in formulae (IVa) and/or (IVb) have one or more e.g. 2 to 5 and in particular 2 to 3 hydroxyl groups.

Furthermore in formula (IVa), R9preferably represents hydrogen and R10represents a C1–C16hydroxyalkyl or a methyl- or hydroxyl-terminated mono- or poly-C2–C3alkyleneoxy residue.

Monomers which form the structural unit (IVc) are preferably bis-acrylamides and bis-acrylic acid esters which are linked together by means of alkylidene, phenylene, benzylidene, cyclohexylidene, hydroxyalkylene or oxyalkylene groups.

The fact that the copolymers contain 5 to 93 wt.-% of the structural units a), 1 to 50 wt.-% of the structural units b), 5 to 93 wt.-% of the structural units c) and 1 to 25 wt.-% of the structural units d) where the components a) to d) add up to 100 wt.-% is regarded as being fundamental to the invention.

Preferably used copolymers contain 40 to 83 wt.-% of the structural units a), 5 to 48 wt.-% of the structural units b), 5 to 53 wt.-% of the structural units c) and 1 to 10 wt.-% of the structural units d), where a), b), c) and d) amount to 100 wt.-%.

The number of repeating structural units in the copolymers according to the invention is unlimited. However, it has proven to be advantageous to adjust the number of structural units such that the copolymers have a molecular weight of 10,000 to 3,000,000 g/mol and in particular of 100,000 to 1,000,000 g/mol.

The copolymers according to the invention can be produced by a number of polymerization processes. Bulk, solution and inverse emulsion polymerization, as well as suspension polymerization in an organic continuous phase, precipitation polymerization and gel polymerization are suitable for their production. It is preferable to polymerize in solution or to use gel polymerization for their synthesis especially preferably in water as a solvent.

Hence the invention concerns a process for producing the copolymers according to the invention in which monomers of formula (Ia) and/or (lb)

in whichR1=hydrogen or C1–C5alkyl,R2=C1–C20alkylene, carboxy-C1–C20-alkylene, carboamido-C1–C20-alkylene or phenyleneM=hydrogen, ammonium or a monovalent, divalent or trivalent metal cationandx=1 to 3, especially in an amount of 5 to 93 wt.-% and of formula (IIa) and/or (IIb)

in whichR3and R4=—COO−(Mx+)1/xor are together

R5=COO−(Mx+)1/xM=hydrogen, ammonium or a monovalent, divalent or trivalent metal cationandx=1 to 3, especially in an amount of 1 to 50 wt.-%,and
of formula (III)

in whichR6=hydrogen or C1–C5alkylR7and R8=hydrogen or C1–C10alkyl or are together —(CH2)y—andy=3 to 7, especially in an amount of 5 to 93 wt.-%,
and of formula (IVa) and/or (IVb) and/or (IVc), especially in an amount of 1 to 25 wt.-%:

R16=H, CH3X=O, NHn=1 to 6r, s=0 to 5t=1 or 2u=1 to 50andR6has the above-mentioned meaning,
are polymerized in bulk or in solution at temperatures of −5 to 120° C.

For the inverse emulsion polymerization of the copolymers according to the invention, the monomers are dissolved in the aqueous phase and emulsified with the aid of a protective colloid in a standard organic solvent such as cyclohexane, toluene, heptane, petroleum ether or mineral oils and started with the aid of a commercial initiator that is soluble in organic solvents such as dibenzoyl peroxide or azoisobutyronitrile.

Suspension polymerization in an organic continuous phase differs from the inverse emulsion polymerization with respect to the selected initiator where a water-soluble initiator system is used. The polymer particles that are obtained in this process are often larger than in inverse emulsion polymerization.

If the copolymers according to the invention are synthesized by a precipitation polymerization process, then water-soluble C1–C5alkanols such as methanol, ethanol or tert.-butanol are particularly suitable as solvents. Especially the latter is preferred due to its low chain-transfer constant if it is intended to produce polymers having a large molecular weight. During the precipitation polymerization the polymer precipitates as a powder and can be isolated by simple filtration.

If it is intended to achieve high molecular weights, gel polymerization is particularly well suited. In this process the monomer is dissolved in a solvent and the monomer content of the aqueous solution is usually 25 to 75 wt.-%. Polymerization results in a high-molecular weight gel which can subsequently be reduced to small pieces and dried.

All polymerizations are started in a temperature range of −5 to 120° C. A start temperature between 5 and 90° C. is preferred. The reactions can be carried out under normal pressure or elevated pressure. Initiation and polymerization in an atmosphere of protective gas is advantageous in some cases.

The polymerization can be initiated in various ways. It can be started thermally by suitable initiators in which case azo compounds are preferably used. Initiation by initiators suitable for photochemical degradation is also possible. α-Substituted carbonyl compounds such as benzoin or benzil derivatives are preferably used. A photo-sensitizer can optionally be added to these light-sensitive initiators.

Many polymerization processes for producing the copolymers according to the invention result in high molecular weights. Lower molecular weights are obtained by adding substances with large chain-transfer constants to the reaction solution. Multi-functional amines such as tetraethylene pentamine, alcohols such as methanol, ethanol or isopropanol and mercaptans such as mercaptoethanol are preferred in this case. The use of allyl ethers as comonomers also results in products with comparatively low molecular weights.

Depending on the process used, the polymerizations can proceed with various degrees of exothermy. The heat generated at the start of polymerization can be reduced by adding suitable moderators in which case alkylamines are preferably used for this.

The polymer compounds according to the invention are excellently suitable as water retention agents, thickeners or anti-segregation agents for aqueous building material systems containing mineral binding agents such as cement, lime, gypsum and anhydrite etc. or for clay suspensions preferably based on bentonite.

The copolymers according to the invention are preferably and usually used in amounts between 0.05 and 5% by weight based on the dry weight of the building material system.

The copolymers according to the invention have excellent water retention, thickening and anti-segregation properties without prolonging the setting and stiffening properties.

The following examples are intended to further elucidate the invention.

EXAMPLES

Production Examples

11.9 g calcium hydroxide was suspended in 200 g tap water, 61.3 g AMPS and 3.2 g maleic anhydride were added and the pH was adjusted to 8 with additional calcium hydroxide. 7 g N-vinylpyrrolidone and 1.6 g 3-allyloxy-2,3-epoxypropane were subsequently added, the reaction solution was flushed with nitrogen and heated to 50° C. After adding 0.3 g 2,2′-azobis(N,N′-dimethyleneisobutyramidine)dihydrochloride, the reaction was stirred for 3 hours at 50° C.

11.9 g calcium hydroxide was suspended in 200 g tap water, 61.3 g AMPS and 1.6 g maleic anhydride were added and the pH was adjusted to 6 with additional calcium hydroxide. 8.6 g N-vinylcaprolactam was subsequently added, the reaction solution was flushed with nitrogen and heated to 50° C. After adding 4,4 g vinyloxy-butylene polyethylene glycol (MW ca. 500 g/mol) and 0.3 g 2,2′-azobis(2-amidinopropane)dihydrochloride, the reaction was stirred for 3 hours at 50° C.

14.34 g sodium hydroxide was suspended in 200 g tap water, 61.3 g AMPS and 2.9 g maleic anhydride were added and the pH was adjusted to 8 with additional sodium hydroxide. 15 g N-vinylacetamide and 21.3 g N-vinylformamide were subsequently added, the reaction solution was flushed with nitrogen and heated to 55° C. After adding 4.6 g of a 40% solution of 3-allyl-2-hydroxypropanesulfonic acid, sodium salt and 0.3 g 2,2′-azobis(2-amidinopropane)dihydrochloride, the reaction was allowed to stand for 3 hours at 55° C.

64 g calcium hydroxide was suspended in 800 g tap water, 245 g AMPS and 23 g maleic anhydride were added and the pH was adjusted to 8 with additional calcium hydroxide. 34 g N-vinylcaprolactam was subsequently added, the reaction solution was flushed with nitrogen and heated to 60° C. After adding 6 g hydroxybutylvinyl ether and 1.2 g 2,2′-azobis(2-amidinopropane)dihydrochloride, the reaction was stirred for 3 hours at 60° C.

11.6 g calcium hydroxide was suspended in 200 g tap water, 61.3 g AMPS and 1.2 g maleic anhydride were added and the pH was adjusted to 8 with additional calcium hydroxide. 25.8 g N-vinylcaprolactam and 1.4 g methylene bisacrylamide were subsequently added, the reaction solution was flushed with nitrogen and heated to 62° C. After adding 0.6 g tetraethylene pentamine and 0.85 g sodium persulfate, the reaction was stirred for 3 hours at 60° C.

Examples of Application

The copolymers according to the invention were examined with regard to their suitability as anti-segregation agents, thickeners and water retention agents for plaster pastes, cement slurries and clay suspensions.

The effect of the polymers according to the invention as anti-segregation agents for cement slurries was determined according to DIN EN 480-4. For this 1500 g cement CEM I 42.5 R was mixed with 900 g tap water and 7.5 g polymer, 900 ml was filled into a measuring cylinder, the bleed water was withdrawn after certain times and its mass in g was determined. The following accumulated values were obtained (table 1):

The polymers according to the invention are also suitable as water retention agents for cement slurries. The water retention capacity of the cement slurries treated with the polymers according to the invention was determined according to DIN 18 555. 350 g CEM I 42.5 R cement was mixed with 210 g tap water and 2.5 g polymer and homogenized. The results obtained are shown in table 2.

TABLE 2Water retention capacity of the described polymers according to theinvention in CEM I 42.5 R cement slurrieswater retention capacityPolymer(%)—64.8198.2298.4399.0497.8589.5

The thickening action of the polymers according to the invention on cement slurries was determined with the aid of the flow index. A commercial methyl cellulose was selected as the reference. 0.75 g polymer was dissolved in 180 g tap water and 300 g cement CEM I 42.5 R was subsequently added. The slurries were allowed to stand for 60 sec and afterwards stirred vigorously for 120 sec. The slurries were poured into a Vicat ring (H=40 mm, dsmall=65 mm, dlarge=75 mm) standing on a glass plate to the level of the rim. The Vicat ring was lifted 2 cm and held for about 5 sec above the slurries that flowed out. The diameter of the slurries that had flown out was measured in two axes which were perpendicular to one another. The measurement was repeated once. The arithmetic mean of all four measurements gives the flow index. The values obtained are shown in table 3.

TABLE 3Flow index of the CEM I 42.5 R cement slurries treated with thepolymers according to the inventionFlow indexPolymercm—26.0methyl cellulose22.0(reference)119.5221.5320.0523.0

The polymers according to the invention are suitable as water retention agents for plaster pastes. The water retention capacity of the plaster pastes treated with the polymers according to the invention was determined according to DIN 18 555. 350 g β-hemihydrate was mixed with 210 g tap water, 0.25 g Retardan®P (retarding agent for plasters from the Tricosal Company, Illertissen) and 2.5 g polymer and homogenized. The results obtained were compared with those for a commercial methyl cellulose. Results of the measurements are shown in table 4.

TABLE 4Water retention capacity of the described polymers according to theinvention in plaster pastesWater retention capacityPolymer(%)—73.2methyl cellulose98.7(reference)195.2295.1398.2

The thickening action of the polymers according to the invention in plaster paste was determined with the aid of a FANN rotation viscosimeter (rrotor=1.8415 cm, rstator=1.7245 cm, hstator=3.800 cm, dring gap=0.1170 cm, instrument constant K=300.0 (spring F1)). A commercial methyl cellulose was chosen as a reference. 0.25 g Retardan®P (retarding agent for plasters from the Tricosal Company, Illertissen) and 0.75 g polymer were dissolved in 245 g tap water and subsequently 350 g β-semi-hydrate was stirred in. The viscosity of the plaster paste was subsequently measured at a shear gradient y of 10.2 s−1. The values obtained are shown in table 5.

TABLE 5Vicosities of the polymers according to the invention in plaster pasteShear stress atViscosity aty = 10.2 s−1y = 10.2 s−1PolymerPamPas—6.1350methyl cellulose7.6440(reference)111.2650215.891038.2470

The thickening action of the polymers according to the invention on clay suspensions was determined with the aid of a FANN rotation viscosimeter (rrotor=1.8415 cm, rstator=1.7245 cm, hstator=3.800 cm, dring gap=0.1170 cm, instrument constant K=300.0 (spring F1)). For this 10.0 g bentonite was suspended in 350 ml tap water and 0.75 g polymer was subsequently added. The vicosity of the bentonite suspension was subsequently measured at a shear gradient of 10.2 s−1. The values obtained are shown in table 6.

The start and end of setting was determined according to Vicat (DIN EN 196-3). For this 500 g cement CEM 142.5 R was mixed with 210 g tap water and 2.5 g polymer. The mixture was homogenized and the cement slurries were subsequently measured. A commercial methyl cellulose was measured as a reference. The measured setting times are shown in table 7.

TABLE 7Start and end of setting determined according to DIN EN 196-3 of thecement slurries treated with the polymers according to the inventionStart of settingEnd of settingPolymer(h:min)(h:min)—4:005:30methyl cellulose7:008:45(reference)13:154:4524:005:0034:455:4544:155:45