MXPA98007883A - Additives of ceme - Google Patents

Abstract

Substances useful as water reducing additives and superplasticizers are described for cement compositions which are formed through the reaction of carboxylic acid polymers with a polyether, preferably a mixture of monofunctional and difunctional polyethers, derivatives of C2-C4 epoxides, wherein the partial splitting of the polyethers and the esterification of the polyethers and their cleavage products are achieved through the other reagent. In one embodiment, a sulfonic acid is used to catalyze the reaction of polyacrylic acid, a monofunctional ethylene oxide-propylene oxide copolymer and a difunctional polypropylene glycol, at a temperature in excess of 140 g.

Description

CEMENT ADDITIVES BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to the use of polymeric additives composed of the reaction product of a carboxylic acid polymer such as polyacrylic acid and at least one polyether of one or more C2-C4 epoxides as in cement additives. The invention also relates to cement compositions containing these additives. The additives work as water reducers and superplasticizers, Description of the Prior Art Cement additives to increase the flowability of cement paste, mortar and concrete have been known and have been in use for many years. These additives are also known as water reducers since they allow less water to be used In a mortar or concrete without losing the settlement (a measure of consistency or workability) this class of cement additives' allows the use of less water to obtain the same settlement, or obtaining a settlement higher than a given water content, or the use of less Portland cement to obtain the same compressive strength. The operating requirements for water reduction mixtures are specified in ASTM Method C494-92, "Standard Specifications for Chemical Admixtures for Concrete". In ASTM C494-92, a water reduction mixture is defined as a mixture that reduces the amount of mixing water required to produce concrete of a given consistency of at least 5%. A large-scale water reduction mixture, also known as a superplasticizer, reduces the amount of mixing water required to produce concrete of a given consistency at 12% or more. Commercial water reduction mixtures include ligninsulfonates and naphthalene sulfonate-formaldehyde condensates. More recently, new classes of flow improvers or water reducers have been described. The patent of E. U. TO . 4, 814, 014, discloses a cement composition containing a graft copolymer containing a polymeric base structure portion and polymer straight chain portions wherein one of the polymer portions is a polyether portion and the other is a non-polyether formed through the polymerization of ethylenically unsaturated monomers. The patent of E. U. A. 5, 393, 433 discloses a cement composition containing an imidated acrylic polymer made, for example, by reacting a polyacrylic acid with a molecular weight of 2000 with a polyethylene oxide-polypropylene polymer with a finished molecular weight of 2000. at one end by a primary amine group and at the other end by a methyl group.

The compositions of the prior art, however, have not been completely satisfactory leaving much to improve.

BRIEF DESCRIPTION OF THE INVENTION In accordance with the present invention, it has been found that the reaction products of certain carboxylic acid polymers and certain polyethers are unexpectedly effective as water reducing additives or superplasticizers in cement. In contrast to other conventional superplasticizers based on polyethers, the reaction products of the present invention work well even at doses as low as 0.1% by weight of the cement, do not introduce air strongly, and do not substantially reduce in performance even when used in combination with a defoamer. Furthermore, at least in one embodiment of the invention, the total settlement loss time is much longer using the additive of the present invention as compared to conventional superplasticizers. This is an important advantage, since the cement remains in this way workable for a long period. A cementitious composition can be established before the composition is put in place if sufficient settlement can not be sustained for a sufficiently long period, with unfortunate consequences. According to a preferred embodiment of the present invention, a mixture of certain polyethers is employed. Through the use of said mixture, a reduction of air entry into the cement is achieved, as compared to the use of an individual polyether as described above.

DESCRIPTION OF THE PREFERRED MODALITIES The carboxylic acid polymers used in the preparation of the cement additives of the present invention are composed of, in whole or in part, one or more polymerizable acid monomers characterized by the presence of at least one polymerizable ethylenically unsaturated group together with a carboxylic acid, carboxylic anhydride or carboxylic ester group. "Acid" in this context refers in this manner to any portion capable of functioning as an equivalent of or precursor to a free carboxylic acid group. Said monomers include monomers corresponding to the structure: R1 O I II H2C = C- COR2 wherein R * 1 and R 1 are each independently hydrogen or C 1 -C 4 alkyl (for example methyl, ethyl, propyl, butyl). Other suitable monomers include cyclic unsaturated anhydrides and unsaturated dicarboxylic acids and their C 1 -C 4 alkyl esters. Preferred acid monomers include, but are not limited to, acrylic acid, methacrylic acid, methyl methacrylate, methyl acrylate. , maleic acid, maleic anhydride, and combinations thereof. The carboxylic acid is present in the salt form, ie, wherein R2 is replaced with an alkali metal, alkaline earth metal, ammonium, or the like. The carboxylic acid polymer in this manner can be in the acid salt form, partially neutralized, or completely neutralized. In certain embodiments of the invention, the polymer is composed of repeat units having the structure: neither - CH2 - C - I O - C I OR2 wherein R 1 is H or C 1 -C 4 alkyl and R 2 is H, C 1 -C 4 alkyl, alkali metal (for example Na, K), alkaline earth metal, or ammonium (for example NH 4, mono, di- or trialkylammonium or quaternary ammonium); or - CH - CH - C = O C = OR ORJ OR4 wherein R3 and R4 are the same or different and have the same meaning as R2 above; or - CH- CH O m C C = O In one embodiment of the invention, the carboxylic acid polymer consists essentially of the acid monomers in polymerized form (ie, the acid monomer can comprise up to 100% of the polymer). However, satisfactory results can also be obtained even when the acid monomer is copolymerized with a different type of polymerizable monomer such as ethylene, or another ethylenically unsaturated compound. Preferably, however, at least 25 mol% of the repeating units in the polymer are repeating units of the acid monomer. The homopolymer of acrylic acid. it is particularly useful in the present invention. Aqueous solutions of polyacrylic acid containing 30 to 70% solids and having molecular weights of between 1,000 and 4,000,000 are available from commercial sources such as BASF (under the trademark "Sokalan PA") and Aldrich Chemical Company. The polyacrylic acid is also commercially available in solid form. In another preferred embodiment of the invention, a copolymer of maleic acid and acrylic acid is used. Said materials are available in solid or aqueous BASF solutions under the trade name Sokalan CP (molecular weight = 3000 to 70,000). Other examples of carboxylic acid polymers suitable for use in the present invention include, but are not limited to, polyethylene-co-acrylic acid, polyethylene-co-methacrylic acid, polyethylene-co-maleic anhydride, and poly-co-methacrylic acid. methyl methacrylate. The precise molecular weight of the carboxylic acid polymer is not particularly critical and can be varied as desired to control the properties of the resulting cement additive. Typically, however, the polymer has a number average molecular weight of 500 to 2,000,000. In a preferred embodiment of the invention, the number average molecular weight ranges from 500 to 10,000. In one embodiment of the invention, the other reagent used in the synthesis of the cement additives of the present invention is a polyether composed of, in polymerized form, one or more C2-C epoxides. The polyether in this manner may be any homopolymer or copolymer having repeating units linked through ether linkages with two carbon atoms separating each ether linkage. Preferred polyethers are polyethers containing one or more terminal hydroxyl groups. Preferably, however, the polyether does not have a functionality greater than 2. That is, the use of polyethers having one or two terminal hydroxyl groups is desirable. The monofunctional polyethers are very preferred to be used, since the problems with the undesired gelation of the reaction product in this way are minimized. The precise molecular weight of the polyether reagent is not considered critical, but critically it can vary from 500 to 10,000 (average in number). Suitable polyethers in this manner include, but are not limited to, mono and difunctional propylene glycols, polyethylene glycols, and ethylene oxide-propylene oxide copolymers. The composition and molecular weight of the polyether are selected in a desirable manner so that the cement additive obtained from the polyether is soluble in water. In a second embodiment of the invention, a mixture of polyethers is used, each of which is composed of. in polymerized form, one or more C2-C4 epoxides. A polyether is monofunctional (ie it contains one hydroxyl group per molecule), while the other polyether is difunctional (ie it contains two hydroxyl groups per molecule). The polyethers can be derived from the same C2-C epoxide or mixture of C2-C epoxides; alternatively, different C2-C4 epoxides can be used to prepare the monofunctional and difunctional polyethers. The precise molecular weights of the polyether reagents are not considered critical, but typically vary from 500 to 20,000 (average in number). The compositions and molecular weights of the polyethers in the mixture are selected in desired form so that the cement additive obtained from polyether is soluble in water. It is desirable to control the amount of difunctional polyether relative to the monofunctional polyether in order to avoid excessive entanglement, which tends to reduce the solubility of the product derived therefrom in water. The weight ratio of the monofunctional polyether to the difunctional in this manner is typically maintained on a scale of 3: 1 to 25: 1. For the two aforementioned embodiments of the invention, the preferred C2-C4 epoxides include propylene oxide, ethylene oxide and mixtures thereof. For example, the molar ratio of repeating units of oxyethylene to oxypropylene in the polyethers can vary from 1: 99 to 99: 1. Generally speaking, the incorporation of higher proportions of oxyethylene repeating units in the polyether mixture will tend to increase the solubility of the ag ua of the resulting cement adit. However, the use of oxyalkylene repeating units derived from substituted epoxides such as propylene oxide and 1-butene oxide tends to increase the susceptibility of polyethers to undergo the desired partial cleavage during the reaction with the acid polymer. carboxylic The polyether may also contain repeat units other than those derived from C2-C4 epoxides. Copolymers of C2-C4 epoxides with other cyclic ethers such as oxetanes, oxolanes (e.g., tetrahydrofuran), and the like, can be used to have advantage, for example, of. In a preferred aspect of the embodiment of this invention, which employs a mixture of polyethers, the difunctional polyether is a homopolymer of propylene oxide (ie, polypropylene glycol). The polyethers corresponding to the above description are well known in the art and can be easily obtained from a number of commercial sources. Methods for their preparation include, for example, the catalyzed base reaction or catalyzed complex of double metal cyanide of C2-C4 epoxides with a suitable initiator having one or two active hydrogen atoms. In the aforementioned second embodiment of the invention, the monofunctional polyether can be obtained by polymerizing a C2-C4 epoxide on a monofunctional initiator (i.e., a compound having an individual active hydrogen atom such as a mono-alcohol) such as an aliphatic alcohol of C1-C10 (for example, methanol, ethanol, n-propanol); glycol ether (for example, propylene glycol monomethyl ether, diethylene glycol mono-t-butyl ether, tripopropylene glycol monomethyl ether), or the like. The difunctional polyether can be prepared by polymerizing a C2-C4 epoxide on a difunctional initiator (i.e., a compound having two active hydrogen atoms such as a di-alcohol) such as a glycol (eg, propylene glycol, ethylene glycol) , 1,4-butanediol, and the like) and their oligomers (for example, tripropylenic glycol, diethylene glycol). The polyethers can also be recirculated materials recovered through glycolysis or hydrolysis from a polyurethane foam or the like. The precise relative proportions of the above reagents are not critical, except that the number of equivalents of polyether or polyether mixture in reaction must be less than the number of equivalents of the carboxyl groups in the carboxylic acid polymer. That is, the number of hydroxyl groups in the initiator reagent per carboxyl group in the last reagent is selected to be less than 1., most preferably less than 0.5, and most preferably less than 0.3. The equivalent ratio of carboxyl groups in the carboxylic acid polymer to hydroxyl groups in the polyether or polyether mixture is preferably from 20: 1 to 2: 1. The above described polyether, or polyether mixture, and the carboxylic acid polymer react under effective conditions to obtain a partial cleavage of polyether or polyethers and the esterification of the polyether or polyethers and their cleavage products through the last reagent. Since the precise mechanism of said reaction and chemical structure of the resulting product is not known, it is believed that the cleavage of some, if not all, polyether ether ligatures or polyethers occurs, and that the resulting cleavage products finally they participate in the desired esterification of the acid groups originally present in the carboxylic acid polymer. When the polymerized acid monomer is present in the alkyl ester form, (ie, R2 in the above-described structure is C1-C4 alkyl), the esterification process can alternatively be described as interesterification, wherein the C1 alkyl group -C4 is displaced by the polyether or its cleavage products. It is preferred that most of the ether ligatures in the starting polyethers remain unfolded. In one embodiment of the invention, only about 1 to 25% of such ligatures exhibit cleavage. The desired reaction of the polyether and the carboxylic acid polymer is catalyzed, through a strong protic acid. Suitable protic acids are those substances that have a pKa less than 0. Generally, the acid will be a stronger acid than a carboxylic acid. Preferred strong protic acids include arylsulfonic acids, alkylsulfonic acids, and ion exchange resins of sulfonic acid. Inorganic as well as organic acids can be used; the acid can be soluble or insoluble in the reaction mixture. Other suitable acids are hydrogen halides, sulfuric acids, tetrafluoroboric acid, heteropolyacids, and sulfuric acid. Mixtures of different acids can be used. Illustrative examples of acids useful in the present invention include, but are not limited to, p-toluene sulfonic acid, trifluoromethane sulfonic acid, methane sulfonic acid, hydrochloric acid, phosphotungstic acid, "Nafion" resins, "Amberlyst 15" resin, and Similar. The protic acid can be added in the salt form (for example, zinc triflate), so that the acid is generated in. in situ through the interaction with the carboxylic acid polymer. The protic acid is used in an effective amount to promote the cleavage and esterification reactions mentioned above. The preferred amount that will be employed depends on many factors, including the desired reaction rate, the types of reagents and catalyst used, reaction temperature and other considerations. Generally, suitable amounts of protic acid are in the range of about 0.01 to 1% by weight based on the amount of the polyether or polyether mixture that will react. The process of the invention is conveniently carried out by combining the polyether or mixture of polyether, carboxylic acid polymer and the strong protic acid catalyst in any desired order or form and heating the mixture at a temperature sufficient for the desired cleavage and esterification Continue at speeds fast enough. The progress of the esterification reaction can be followed by measuring the acid number, which will be reduced as the esterification proceeds, through conventional wet chemical analytical techniques. In general, it will be advantageous to conduct said reaction until they are esterified from 1 to 50% (more typically from 2 to 20%) of the carboxyl groups initially present in the carboxylic acid polymer. When the polyether or polyether mixture is composed of repeating oxypropylene units derived from propylene oxide, the degree of polyether cleavage can be conveniently verified by inspecting the level of ether head-to-head ligatures in the polyether through NMR. Such head-to-head ligatures are apparently more susceptible to splitting than head-to-end ligatures. The degree of reaction (ie, esterification plus cleavage) can also be estimated through the measurement of the acid number. When a desired level of esterification and cleavage is achieved, the acid number will typically be less than the theoretical acid number (calculated from the relative proportions and functionalities of the starting materials), which can be obtained if the esterification of the original polyethers, but not of their splitting products, has been completed. The selected temperature must be high enough in order to promote both the desired cleavage and esterification. Since the minimum temperature required for that purpose will vary depending on a number of factors, it has been found that when the polyether or polyether mixture is derived wholly or in part from the propylene oxide, the carboxylic acid polymer is completely or partially derived. of acrylic acid, and strong protic acid is a sulfonic acid, temperatures in an excess of 140 ° C (most preferably 150 ° C to 250 ° C) are needed. In one embodiment of the invention, the reaction mixture is first heated to a slightly low temperature (eg, from 75 ° C to 140 ° C) for a sufficient period to obtain substantial esterification (but not a significant amount of cleavage). ) of the polyether or initially charged polyether mixture, followed by heating to an effective temperature to cause the cleavage of the polyether. Esterification can be favored by removing water or other by-products formed as a result of the esterification of the reaction mixture (as well as any water present in the reactants)., initially) through appropriate means such as distillation or the like. The application of vacuum or a spray of inert gas can be helpful. Once the appropriate degree of esterification and cleavage has been obtained (typically, from about 0.5 to 18 hours), the purification or further modification of the reaction product can be performed before use as a cement additive. For example, strong protic acid can be removed through any suitable method such as filtration, neutralization, or the like. The residual carboxylic acid groups in the additive can be left in acid form, or, if desired, converted in whole or in part to the salt form through the reaction with a suitable source of alkali metal (eg, hydroxide). sodium, potassium hydroxide), alkaline earth metal (eg, calcium hydroxide), ammonium (eg, ammonia, alkylamines such as triethanolamine and triisopropanolamine), or the like. The cation in the salt resulting in this manner can be an alkali metal cation. Ammonium as well as alkaline earth metal cations also serve as the cation for that purpose. If the acid monomer used to prepare the carboxylic acid polymer was in an anhydrous form, some or all of the anhydride groups, which may still be present in the polymer after the reaction with the polymer, can be converted to the form of free acid or salt through hydrolysis or other means using conventional methods in the art. The splitting hydrolysis of the ester bonds between the polyether and the carboxylic acid polymer must, however, be minimized by careful selection of the conversion conditions used. The cements with which the additives of the present invention can be used are hydraulic cements, significant cements which, when made in a paste with water, are fixed and hardened as a result of chemical reactions between water and cement. Suitable cements include ordinary Portland cements, fast hardening, and moderate heat, alumina cement, blast furnace slag cement, and vaporization cement. Of these, Portland cements of the ordinary and fast hardening types are particularly desired. The amount of additive used may vary with factors such as the degree of esterification and cleavage of the polyether obtained and the relative amount of the polyether or polyether mixture which reacts with the monocarboxylic acid polymer. The amount of additive that will be used according to the invention is usually in the range of 0.01 to 10%, preferably 0.05 to 2% based on the weight of dry cement. The amount of water that will be used to fix the cement is not critical; generally the weight ratios of water cement in the scale 0.25: 1 to 0.7: 1, preferably from 0.3: 1 to 0.5: 1, are satisfactory. When desired, an aggregate such as granite, gravel, sand, pumice or cooked pearlite or mixtures thereof may be employed in conventional amounts. The amount of aggregate, for example, typically can comprise from about 40 to 80% by volume of the total cement composition. Advantageously, the additives of this invention, which function as water reducing agents and / or superplasticizers, are used in combination with other known cement additives. Additional optionally employed additives include conventional hardening accelerators, for example, metal chlorides such as calcium chloride and sodium chloride, metal sulfates such as sodium sulfate, and organic amines such as triethanolamine; ordinary hardening retarders, for example, alcohols, sugars, starch and cellulose, corrosion inhibitors of reinforcing steel such as sodium nitrate and calcium nitrite, other water reducing agents such as salts of lignin sulphonic acid, as well as salts of oxycarboxylic acid and naphthalenesulfonic acid formalin condensates, air introducers, other superplasticizers, shrinkage reducing agents, strength improvers such as tisopropylamine, defoaming agents such as tributyl phosphate, air introduction mixtures, and the like. said optional ingredient or ingredients is usually from 0 to 6% by weight of the cement. The way of adding the additive of the invention to the cement can be the same as with ordinary cement mixtures. For example, the additive can be mixed with a suitable portion of water and the resulting solution mixed with the cement and the aggregate. As an alternative, a suitable amount of the additive can be added when the cement, aggregate and water are mixed. Another method to introduce the additive is by adding it to the dry cement before or after grinding. The additive may be added before, together with or subsequent to the addition of the other components of the cement composition. The concrete and the like incorporating the additive according to the invention can be applied in conventional ways. For example, it can be matched, filled in shapes, applied through spraying, or injected through a caulking gun. The hardening or curing of the concrete or the like can be through drying with air, moist air, water and any of the assisted healing techniques, (steam, autoclave, etc.). If desired, two or more of these techniques can be combined. The respective healing conditions can be the same as in the past.

EXAMPLES Example 1 Polyacrylic acid (200 g) was dissolved with a number average molecular weight of about 2000 in 200 g of distilled water and then mixed with a monofunctional polyether (800 g) having a number average molecular weight of about 2000 and acid p-toluenesulfonic (8 g). The monofunctional polyether was prepared by reacting methanol and ethylene oxide and propylene oxide (molar ratio 70:30) in the presence of alkali metal catalyst. The reaction mixture was heated to 180 ° C, while the water was taken in the upper part and then kept at 180 ° C for 3 hours. The resulting reaction product had an acid number of 77 and was found useful as a cement additive to increase the flowability of the cement, mortar or concrete paste, either in acid form or as an aqueous solution of the sodium salt .

Example 2 (Comparative) For comparative purposes, the procedure of the Exemplary, except that the reaction mixture was heated at 140 ° C for 4 hours, while the water was distilled in the upper part and then kept at 140 ° C for 1 hour more. The resulting reaction product had an acid number of 121, indicating that a lower degree of esterification was obtained than in Example 1.

Example 3 The reaction products of Examples 1 and 2 were tested in a completely neutralized sodium salt form (25% aqueous solutions) in mortar mixtures. The settlement was measured using a settlement cone of medium size; The air content was determined through ASTM method C185. The results, which are summarized in the following table, indicate that, the sodium salt form of the reaction product of Example 1 was able, even at low levels, to greatly increase the settlement of the mortar mixture at a water ratio / cement given with respect to the settlement observed in the absence of the additive. In addition, the results demonstrate that the water / cement ratio can be reduced to as much, 16%, by using the additive of the invention while maintaining an equivalent level of settlement. * 0.03% by weight, of tributyl phosphate (defoamer) additionally present.

Example 4 The reaction product of Example 1 was tested in the sodium salt form in a concrete mixture. The operation of the reaction product as a cement additive as compared to a control (without additive) and a commercially available superplasticizer is summarized in the following table. Adjusting for differences in air content, the reaction product of Example 1 gave a comparable settlement with the commercial plasticizer at half the dose level. The reaction product of Example 1 also maintained its settlement with a more effective time than the commercial superplasticizer. Fixation times with the reaction product of Example 1 were comparable with the control tests (without additive), but the compressive strength was improved too.

Example 5 A copolymer with a molecular weight of 3000 acrylic acid and maleic acid (50 g of a 50% aqueous solution) was combined with the monofunctional polyether used in Example 1 (100 g) and p-toluene sulphonic acid (1 g). The reaction mixture was heated to 10 ° C to remove the water at the top and then kept at 150 ° C for 1 hour. The resulting reaction product had an acid number of 1 33. The acid number value was slightly lower than the theoretical acid number (1 39) calculated based on the relative proportions of the reactants and the assumption that the presented the complete esterification (but not the splitting) of the monofunctional polyether. The lower acid number confirms that partial cleavage of the monofunctional polymer occurred and esterification of the resulting cleavage products through the acrylic acid-maleic acid copolymer. When tested in the sodium salt form according to Example 3 (% by weight of additive based on cement = 0.3, water / cement ratio = 0.42), a settlement of 72 mm and a high content was observed. of air of 8.0%. When the above reaction was repeated using a reaction time of 2 hours at 150 ° C, the product obtained had an acid number of 1 07 and produced a settling of 65 mm at an air content of 7.2%.

Example 6 Polyacrylic acid with a molecular weight of 2000 (39 g of a 65% aqueous solution) was combined with "Pluracol W5100N" (a monofunctional polyether terminated with n-butyl with a number average molecular weight of 3600 composed of about 58 % ethylene oxide and 42% propylene oxide sold by BASF, 100 g) and p-toluene sulphonic acid (1 g). The reaction mixture was heated to 10 ° C to remove the water, then kept at 180 ° C for 2 hours. The resulting reaction product had an acid number of 70. The acid number value was substantially lower than the theoretical acid number (14) calculated on the basis of the relative proportions of the reactants and the assumption that the the complete esterification of the original monofunctional polyether. The significantly lower acid number confirms that the partial splitting of the monofunctional polymer and the esterification of the cleavage products through the polyacrylic acid occurred. When tested in the sodium salt form according to Example 3 (0.3% by weight of additive, water / cement ratio = 0.42), a settling of 69 and an air content of 10.9% were observed.

Example 7 This example demonstrates the preparation of a cement additive according to the present invention using a mixture of monofunctional and difunctional polyethers. A mixture containing, (a) 309 g of a 65% by weight aqueous solution of polyacrylic acid having a number average molecular weight of about 2000 and an acid number, measured for the solution, of 388 mg of KOH solution / g, (b) 800 g of a monofunctional polyether ("MPI") having a number-average molecular weight of about 2000 corresponding to a hydroxyl number of 28 mg KOH / g, (c) 80 g of a difunctional polypropylene glycol having a number average molecular weight of about 4200, and (d) 8.6 g of p-toluenesulfonic acid monohydrate, it was heated in a 2 liter reaction vessel equipped with a mechanical stirrer and a top vapors collection with a condenser. The M P I was prepared by reacting methane! with ethylene oxide and propylene oxide (weight ratio 70: 30) in the presence of an alkali metal hydroxide catalyst. The optional polypropylene glycol was prepared using a double metal cyanide complex catalyst. . The mixture was heated at 125 ° C for 2 hours, while a stream of nitrogen was passed through the container and while the water was taken upwards. The mixture was then heated at 1 70 ° C for 5.5 hours. The product obtained had an acid number of 77 mg KOH / g. This is compared to the initial acid number of 12 mg KOH / g for the mixture, after the water was removed and a calculated acid number of 90 mg KOH / g if it was at its own that all the hydroxyl groups initially present in M PI and the polypropylene glycol reacted to form esters. The operation of the product obtained in this way was evaluated, both in the form of an acid and in an aqueous suspension of the sodium salt, as a cement additive.

Example 8 This example, like Example 7, also demonstrates the preparation of a cement additive according to the present invention using a mixture of polyethers. However, in this example a difunctional polypropylene glycol having a number average molecular weight of about 4000 prepared using the alkali metal hydroxide catalyst was used. A mixture containing 309 g of a 65% by weight aqueous solution of a polyacrylic acid with a molecular weight of 2000, 800 g of the monofunctional polyether MPI described in Example 7 and 8.6 g of p-toluene sulphonic acid, was heated to 120 g. ° C for 3 hours to remove the water, then it was heated for 13 hours at 170 ° C. Intermediate samples were taken, while the mixture was still heating at 170 ° C, with the sample taken at 7 hours having an acid number of 80 mg KOH / g and the sample taken at 10 hours having an acid number of 73 mg KOH / g. The final product had an acid number of 68 mg KOH / g.

I Examples 9-17 A series of reaction products were prepared using the general procedures and reagents described in Example 7, but using different monofunctional and difunctional polyethers. The details of the preparation are given in Table 1. In each case, the reaction mixture was heated to about 140 ° C to remove the water and then heated to the indicated temperature for the time shown. "MP2" was a monofunctional polyether having a number average molecular weight of about 2000 made by polymerizing a mixture of ethylene oxide and propylene oxide (weight ratio 30:70) on tripropylenic glycol methyl ether using a hexacyanocobalt complex catalyst of zinc. "DP 1" was a difunctional polypropylene glycol with a number average molecular weight of 2200 made using a zinc hexacyanocobalt complex catalyst; "DP2" was a difunctional polypropylene glycol with a number average molecular weight of 4200 made using a zinc hexacyanocobalt complex catalyst. "DP3" was a difunctional polypropylene glycol with an average molecular weight. in number 8200 made using a zinc hexacyanocobalt complex catalyst. "DP4" was a difunctional polypropylene glycol with a number average molecular weight of 4000 using an alkali metal hydroxide catalyst.

Example 18 (Comparative) This example demonstrates the preparation of a cement additive using only a monofunctional polyether. A mixture of 38.5 g of a 65% by weight aqueous solution of polyacrylic acid having a number-average molecular weight of 2000 was made with 100 g of monofunctional polyether MP1 and 1 g of p-toluenesulfonic acid monohydrate. The mixture was heated at 130 ° C for 2.5 hours to remove the water and then heated at 170 ° C-180 ° C for 3.5 hours to complete the reaction. The flow of nitrogen through the reactor was used to help remove the water, which was then condensed and collected in a receiver of higher vapors. The resulting product had a final acid number of 69 mg KOH / g. This is compared to the initial acid number of 121 in a water-free base assuming no ester formation and an acid number of 99 in a water-free base if all the hydroxyl groups initially present in the MP1 reacted to form ester groups .

Example 19 (Comparative) A larger batch of products was prepared using the procedures and reagents (including reagent ratios) described in Example 18. The reaction mixture was heated to 180 ° C-190 ° C and the water was collected in the top Example 20 'The reaction products obtained in Examples 7-19 were tested in mortar mixtures. The settlement was measured using a settlement cone of medium size; The air content was determined using ASTM method C185. The results obtained using Essroc cement are summarized in Table 2. The results obtained using Saylor cement are summarized in Table 3. To prepare these mixtures, the required amounts of water and reaction product (test sample) were loaded. in a mixing container; 1200 g of cement and 2700 g of sand were added (ASTM classification C778) according to the mixing procedures of ASTM C305. All the reaction products tested were able to greatly increase the settlement of the mortar mix at a given water / cement ratio with respect to the settlement observed in the absence of the additive. However, Comparative Examples 16, 18 and 19 demonstrate that products made in the absence of the difunctional polyether tend to introduce large amounts of air. Since the addition of a defoamer (TBP) generally helped reduce the amount of air introduced, it was still difficult to obtain acceptable air intake levels. The reaction products obtained in Examples 7-15 and 17, which were prepared using mixtures of monofunctional and difunctional polyethers, did not introduce an excess of air by themselves.

Example 21? The reaction products of Examples 7 and 19 were tested in a concrete mixture. The performance of the cement additive of these reaction products, compared to a control (without additive) and a commercially available superplasticizer, are summarized in Table 4. An air introduction mixture ("AEA") was also used in these tests. . The ability to control air is necessary to obtain a concrete with good freeze-thaw resistance. The reaction product of Example 19 introduced some air by itself. In this case, no defoaming was necessary to maintain the air level entered within the desired scale, although the variation of the cement used or the level of additive could result in excessive air introduction. Also, in the air gap size distribution it may not be the same as that provided by a conventional air introduction mixture. The reaction product of Example 7 did not itself introduce air; however, it was found to be fully compatible with the commercial air introduction mixture, so that the desired air level of introduced air can be easily obtained.

TABLE 1 TABLE 2 * comparative TBP = tri-phosphate used TABLE 3 comparative TBP = tributyl phosphate TABLE 4 > Comparative (a commercially available water reduction agent) A = Air Introduction Mix; Neutralized resin "Daravair", a commercial air introduction mixture, was used from W. R. Grace & Co.

Claims (4)

1 - . 1 - A cement additive containing carboxylic acid groups obtainable through the reaction of a carboxylic acid polymer composed of, in polymerized form, a polymerizable acid monomer characterized by the presence of at least one ethylenically active group unsaturated together with a carboxyl group selected from the group consisting of carboxylic acid, carboxylic anhydride and carboxylic ester groups, and a polyether composed of, in polymerized form, a C

2-C4 epoxide, under conditions effective to obtain partial cleavage of the polyether and the esterification of the polyether and its cleavage products through the carboxylic acid polymer. 2 - A cement additive according to claim 1, wherein the C2-C epoxide is selected from the group consisting of ethylene oxide, propylene oxide and mixtures thereof.

3 - A cement additive according to claim 1 or claim 2, wherein the polyether has a hydrological functionality of 1 or 2.

4 - A cement additive according to any of the claims. 1 to "3, wherein the polyether has a number average molecular weight of 200 to 1,000,000. A cement additive according to claim 1, characterized in that it is produced through the reaction of (a) ) a carboxylic acid polymer prepared by polymerizing a polymerizable acid monomer containing at least one ethylenically unsaturated group together with a carboxyl group selected from the group consisting of carboxylic acid, carboxylic anhydride and carboxylic ester groups, and (b) a polyether mixture comprising, (i) a monofunctional polyether prepared by first polymerizing an epoxide selected from the group consisting of C2-C4 epoxides and mixtures thereof on a monofun initiator and (ii) a difunctional polyether prepared by polymerizing a second epoxide selected from the group consisting of C2-C4 epoxides and mixtures thereof, which may be the same or different from the first epoxide, on a difunctional initiator, wherein ) and (b) are reacted under effective conditions to obtain partial cleavage of the polyether mixtures and esterification of the polyether mixture and its cleavage products through the carboxylic acid polymer. 6 - A cement additive according to claim 5, wherein the first epoxide is selected from the group consisting of ethylene oxide, propylene oxide and mixtures thereof, and the second epoxide is selected from the group consisting of of ethylene, propylene oxide, and mixtures thereof, which may be the same as b different from the first epoxide. < 7 - A cement additive according to claim 5 or claim 6, wherein the second epoxide is propylene oxide. 8 - A cement additive according to claim 5, claim 6, or claim 7, wherein the first epoxide is a mixture of ethylene oxide and propylene oxide. 9 - A cement additive according to any of claims 5 to 7, wherein the monofunctional polyether has a number average molecular weight of 500 to 20,000 and the difunctional polyether has a number average molecular weight of 200 to 20,000. 10. A cement additive according to any of claims 5 to 9, wherein the weight ratio of the monofunctional polyether to the difunctional polyether is from 3: 1 to 25: 1. 11. A cement additive according to any of claims 5 to 10, wherein the polymerizable acid monomer comprises acrylic acid, and (a) and (b) are reacted in the presence of an acid catalyst having a pKa less than 0. 12. A cement additive according to any of the preceding claims, wherein the acid monomer comprises at least 25 mol% of the carboxylic acid polymer. 13.- A cement additive according to the claim 12, wherein the carboxylic acid polymer consists essentially < of the polymerizable acid monomer in polymerized form. 14.- A cement additive according to the claim 13, wherein the carboxylic acid polymer is a homopolymer 15. A cement additive according to any of the preceding claims, wherein at least a portion of the carboxylic acid groups are in the salt form. 16. A cement additive according to any of the preceding claims, wherein the polymerizable acid monomer is selected from the group consisting of methyl acrylate, methyl methacrylate, maleic acid, maleic anhydride, and monomers having the structure : R1 O I H2C = C- COH wherein R 1 is hydrogen or C 1 -C 4 alkyl, and mixtures thereof. 17. A cement additive according to any of the preceding claims, wherein the carboxylic acid polymer has a number average molecular weight of 500 to 2,000,000. 18 - A cement additive according to any of the preceding claims, wherein the number average molecular weight of the carboxylic acid polymer is from 500 to 10,000. 19 - The cement additive according to any of the preceding claims, wherein the equivalent ratio of carboxyl groups in the carboxylic acid polymer to hydroxyl groups in the polymer is from 20: 1 to 2: 1. 20. A method for producing a cement additive containing carboxylic acid groups, which comprises reacting a carboxylic acid polymer composed of, in polymerized form, a polymerizable acid monomer wherein the presence of at least one ethylenically group unsaturated together with a carboxyl group selected from the group consisting of carboxylic acid, carboxylic anhydride and carboxylic ester groups, and a polyether composed of, in polymerized form, a C2-C4 epoxide, in the presence of a strong protic acid catalyst during a time and a temperature effective to achieve partial cleavage of the polyether and esterification of the polyether and its cleavage products through the carboxylic acid polymer to form the cement additive. 21. A method according to claim 20, wherein it comprises reacting: (a) a carboxylic acid polymer prepared by polymerizing a polymerizable acid monomer containing at least one ethylenically unsaturated group together with a carboxyl group selected from the group group consisting of carboxylic acid, carboxylic anhydride and carboxylic ester, and (b) a polyether mixture comprising: (i) a "monofunctional polyether prepared by polymerizing a first epoxide selected from the group consisting of C2-C epoxides and mixtures of the same on a monofunctional injector, and (ii) a polyether difu ncio l l prepared by polymerizing a second epoxide selected from the group consisting of C2-C4 epoxides and mixtures thereof, which may be the same or different from the first epoxide , on a difunctional initiator, in the presence of an acid catalyst having a pKa less than 0 at an effective temperature for or The partial cleavage of the polyether mixture and the esterification of the polyether mixture and its cleavage products through the carboxylic acid polymer. 22. A method according to claim 20 or claim 21, wherein the acid catalyst is selected from the group consisting of aryl sulfonic acids, alkyl sulphonic acids, ion exchange resins of sulfonic acid, and salts thereof . 23. A method according to any of claims 20 to 22, wherein the temperature is greater than 140 ° C. 24 - A method according to any of claims 20 to 23, characterized in that it comprises the additional step of converting at least a portion of the carboxylic acid groups. a l * a salt form. 25. A method according to any of claims 20 to 24, wherein the equivalent ratio of the carboxyl groups in the carboxylic acid polymer to the hydroxyl groups in the polyether is from 20: 1 to 2: 1. 26. - A method according to any of claims 20 to 25, wherein the polymerizable acid monomer has the structure: R1 O! II H2C = C- COH wherein R 1 is hydrogen or C 1 -C alkyl. 27. A cement composition composed of cement and a cement additive according to any of claims 1 to 19, or obtained by a method according to any of claims 20 to 26. 28 - A composition of cement according to claim 27, characterized in that it contains from 0.05 to 2% by weight, based on the dry weight of the cement, of the cement additive. 29. A cement composition according to claim 27 or claim 28, characterized in that it also comprises water. 30 - A cement composition according to claim 27, claim 28 or claim 29, characterized in that it also comprises an aggregate. 31.- A method for increasing the fluidity of a hydraulic cement composition that comprises adding to the hydraulic cement composition from 0.01 to 10% by weight, based on the weight of the dry cement, of a cement additive according to any of claims 1 to 19, or which is obtained by a method according to any of claims 20 to 26.