ROBUST POLYCARBOXYLATE WITH POLYALKYLENE OXIDE-BASED SACRIFICIAL SIDECHAIN LINKAGE AS MILLING AID FOR CEMENTITIOUS MATERIALS

Abstract

The present invention concerns a polycarboxylate ether polymer to be used as a grinding aid during the grinding of cementitious materials, said polymer having sacrificial linkages that preferentially break inside the cement mill. The polymer can have a polycarboxylate ether structure comprising free carboxylic acid groups, neutralized carboxylic acid groups, at least one side chain A and at least one side chain B. The at least one side chain A comprises a group (AlkO).sub.m and the at least one chain B comprises a group (AlkO).sub.n, where AlkO represents an alkylene oxide, and m and n are integers with m<n.

Claims

1. A polymer having a polycarboxylate ether structure comprising free carboxylic acid groups, neutralized carboxylic acid groups, at least one side chain A and at least one side chain B, wherein said at least one side chain A comprises a group (AlkO).sub.m and said at least one chain B comprises a group (AlkO).sub.n, wherein AlkO represents an alkylene oxide, and wherein m and n are integers with m<n.

2. A polymer according to claim 1, wherein AlkO is a C.sub.2 to C.sub.4 alkylene oxide.

3. A polymer according to claim 1, wherein (AlkO).sub.m and (AlkO).sub.n are independently chosen from the group consisting of polyethylene glycol, polypropylene glycol, polybutylene glycol, polyoxyethylene glycol, polyoxypropylene amine, and blends thereof.

4. A polymer according to claim 1, wherein m and n range from 2 to 120.

5. A polymer according to claim 1, wherein the degree of substitution of (AlkO).sub.m is 0.01 to 0.1.

6. A polymer according to claim 1, wherein the degree of substitution of (AlkO).sub.n is 0.1 to 0.4.

7. A polymer according to claim 1, wherein the polymer is represented by the formula (Z) below: ##STR00003## wherein R.sup.1, R.sup.2, R.sup.3 and R.sup.4, independently of one another, is a hydrogen atom or a methyl group. R.sup.5 is a hydrogen atom or C.sub.1 to C.sub.4 alkyl group, alkylaryl group or cycloalkyl group. R.sup.6 is a hydrogen atom or C.sub.1 to C.sub.4 alkyl group, alkylaryl group or cycloalkyl group or (AlkO).sub.pR.sup.8, wherein p is an integer ranging from 2 to 120 and R.sup.8 is a C.sub.1 to C.sub.2 alkyl group. R.sup.7 is R.sup.5 or is a bond to another polymer of formula (Z); providing that R.sup.7 is at least bond to one polymer of formula (Z). a, b, c and d represent the molar percentage of each of the monomers in the structure, and range as follows: a=25-85%; b=1-10%; c=10-40%, d=0-2%. M, independently, is an AlkO, hydrogen, alkali, or alkaline earth metal cation, ammonium, or any other organic amine group.

8. A polymer according to claim 1, wherein the polymer's backbone has an averaged molecular weight between 1000 and 20000 Da, more preferably between 2500 and 15000 Da, even more preferably between 5000 and 10000 Da.

9. A polymer according to claim 1, wherein the polymer's molecular weight is between 10000 and 100000 Da, more preferably 15000 and 80000 Da and even more preferably between 20000 and 65000 Da.

10. A method to use a polymer as a grinding aid during the manufacturing of cement, pozzolanic materials, or lime, that is characterized in: a) Providing a fresh feed to a cement mill; b) Adding a polymer according to claim 1; c) Grinding the material obtained in step b) until the material reaches the final desired fineness according to the final cementitious product being produced; d) Discharge the final product from the cement mill.

11. The method according to claim 10, wherein the polymer is added to the cement mill together with the fresh feed.

12. The method according to claim 10, wherein the polymer is added directly into the first chamber of the cement mill.

13. The method according to claim 10, wherein the polymer is added in an amount between 0.01 wt. % and 0.4 wt. % based on the dry weight of the cementitious material to be ground.

14. The method according to claim 10, wherein the residence time of the polymer inside the cement mill is between 1 and 10 minutes.

15. The method according to claim 10, wherein a defoamer can be added before or after the grinding process in a dosage ranging between 0.1 wt. % and 0.5 wt. %, based on the wet weight of the added polymer.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0057] FIG. 1 represents nine cement samples separately ground in a ball mill.

EXAMPLES

Material Preparation

[0058] In all examples, a closed circuit ball mill with the following characteristics was used:

TABLE-US-00001 TABLE 1 Experimental ball mill details Bond ball mill details Internal diameter (m) 0.3048 Internal length (m) 0.3048 Mill speed (rpm) 70 Mill speed (fraction of critical speed) 0.91 Ball load (% by volume) 19.27 Total mass of balls (g) 21125 Ball top size (mm) 36.38 Geometry of mill liner Smooth Grinding type dry

[0059] The grinding conditions of the closed circuit ball mill were: [0060] heating jacket set to 120? C.; [0061] 2.5 mL of water per hour being dripped into the raw materials feeder (an equivalent of 500 ppm on the 5 kg/hr production assumption);

[0062] In all examples, mortar preparation was done according to the EN-196 norm. Spreads at 5 (t.sub.5) and 30 (t.sub.30) minutes are measured on the EN flow table.

[0063] In all examples, the mortar mix design was made of 450 g of cement, 225 ml of water, and 1350 g of sand, according to the EN-196 norm.

Example 1

[0064] A raw meal was first homogenized with the use of an automatic homogenizer and then split into four samples, each sample intended to be milled separately and with one of four different grinding aids: [0065] 1) Polycarboxylate Ether (PCE) based on the molecular structure (Z) but without a sacrificial linkage, with a dosage 0.1 wt % based on the dry weight of the cementitious material to be ground (50% Active Solid Content (ASC)). [0066] 2) PCE with molecular structural (A) (two (Z) molecules connected by a sacrificial linkage): R.sup.1?R.sup.3=R.sup.4?R.sup.3?R.sup.4=hydrogen; R.sup.2?R.sup.1?R.sup.2=methyl group, m=17, n=70, a=a=80, b=b=3, c=c=16, d=d=1, Alk=ethylene, with a dosage 0.1 wt % based on the dry weight of the cementitious material to be ground (50% Active Solid Content (ASC)). [0067] 3) PCE with molecular structural (A) (same as sample 2)), with a dosage 0.2 wt % based on the dry weight of the cementitious material to be ground (50% Active Solid Content (ASC)). [0068] 4) Grinding aid based on lignosulfonate, with a dosage 0.1 wt % based on the dry weight of the cementitious material to be ground (50% Active Solid Content (ASC)).

[0069] The raw meal was composed of the following raw materials: [0070] 70% clinker [0071] 25% limestone [0072] 5% gypsum

[0073] The samples were ground until the final material had a fineness d.sub.90=45 ?m, where d.sub.90 means a particle dimension corresponding to 90% of the cumulative undersize distribution.

[0074] After grinding, water and sand were added to the samples, with a water/cement ratio of 0.5, and a defoamer tributylphosphate (0.1 wt % based on the wet weight of the added polymer) was also added.

TABLE-US-00002 TABLE 2 Results from Example 1 4) 1) 2) 3) Lignosul- PCE without PCE with PCE with fonate sacrificial sacrificial sacrificial (Formu- Sample linkage linkage linkage lation) w/c 0.5 0.5 0.5 0.5 PCE dosage 0.1% (as 0.1% (as 0.2% (as 0.1% (as (wt %) 50% ASC) 50% ASC) 50% ASC) 50% ASC) Defoamer dosage 0.1 0.1 0.1 0.1 (wt %) density [g/cm.sup.3] 2.226 2.222 2.209 2.202 t.sub.5 [mm] 180 19 186 186 t.sub.30 [mm] 169 185 178 173 Mill Energy [kWh/t] 33 27 31 32 Separator speed [rpm] 1495 1300 1375 1450

[0075] The spread was measured 5 minutes (t.sub.5) and 30 minutes (t.sub.30) after starting the mix.

[0076] As we see from

, the spreads in samples 2 and 3, using the PCE described in the present invention, have better values than in sample 1, without the sacrificial linkage, and sample 4 using a lignosulfonate formulation (with additions aiding the grinding process). Table 2 also provides us with the energy reduction that we are gaining when using the PCE described in the present invention. The energy needed to grind a sample without any additions (Reference blank cement, not reported in this table) was 40% (37 kWh/t) more compared to the milling performed with the PCE described in this invention.

Example 2

[0077] To simulate the conditions in the silos, and see if the polymer would decompose or the cement would show a different behavior, the first three cement samples ground in Example 1 were removed from the mill and kept for 60 hours in a curing chamber with a Relative Humidity of 80% and a temperature of 60? C.

[0078] After 60 hours, sand and water were added to the samples in a water-to-cement ratio of 0.5. Results are shown in Table 3.

TABLE-US-00003 TABLE 3 Results from Example 2 4) 1) 2) 3) Lignosul- PCE without PCE with PCE with fonate sacrificial sacrificial sacrificial (Formu- Sample linkage linkage linkage lation) w/c 0.5 0.5 0.5 0.5 PCE dosage 0.1% (as 0.1% (as 0.2% (as 0.1% (as (wt %) 50% ASC) 50% ASC) 50% ASC) 50% ASC) Defoamer dosage 0.1 0.1 0.1 0.1 (wt %) density [g/cm.sup.3] 2.203 2.207 2.210 2.185 t.sub.5 [mm] 189 196 193 182 t.sub.30 [mm] 178 188 186 176

[0079] The mortars prepared with the cement ground with the PCE of the invention present higher values for spread after 5 and 30 minutes, even after 60 hours in a curing chamber. This means that not only the PCE is stable, even after 60 hours in a curing chamber with a Relative Humidity of 80% and a temperature of 60? C., but its effect is enhanced when it is allowed to interact with the cement before being mixed in the mortar.

Example 3

[0080] For this example, nine cement samples were separately ground in the ball mill. The reference cement had the same composition as in example 1 (70% clinker, 25% limestone, 5% gypsum). The samples were ground until the final material had a fineness d.sub.90=45 ?m, where d.sub.90 means a particle dimension corresponding to 90% of the cumulative undersize distribution. Different polymers were added to the samples, at different stages of the process. The polymers were added in a dosage 0.1 wt % based on the dry weight of the cementitious material (50% Active Solid Content (ASC)) and the defoamer (tributylphosphate), when used, was added in a dosage 0.1 wt % based on the wet weight of the added polymer. [0081] Sample 1: Blank. Only cement (no polymer added at any stage of the grinding process); [0082] Sample 2: Reference cement ground alone. After exiting the mill, the PCE of the invention according to structure (A) (PCE I) was added to the cement, as well as the defoamer. [0083] Sample 3: Reference cement ground alone. After exiting the mill, the PCE of the invention according to structure (A) (PCE I) was added to the cement. No defoamer was used. [0084] Sample 4: Reference cement ground together with the PCE of the invention according to structure (A) (PCE I). After the material exited the mill, the defoamer was added. [0085] Sample 5: Reference cement ground together with the PCE of the invention according to structure (A) (PCE I). No defoamer was added. [0086] Sample 6: Reference cement ground alone. After exiting the mill, a commercial PCE was added to the cement, as well as the defoamer. [0087] Sample 7: Reference cement ground alone. After exiting the mill, a commercial PCE was added to the cement. No defoamer was used. [0088] Sample 8: Reference cement ground together with the commercial PCE. After the material exited the mill, the defoamer was added. [0089] Sample 9: Reference cement ground together with the commercial PCE. After the material exited the mill. No defoamer was used.

[0090] Nine mortar samples were mixed using each of the ground samples described above. Spread, air content, and strength at 1, 7, and 28 days were measured.

TABLE-US-00004 TABLE 4 Results from Example 3 PCE with Sacrificial sidechain linkage (PCE I) Traditional PCE (PCE II) BLANK 3. Reference 7. Reference 1. Reference 2. Reference Cement + 5. PCE I 6. Reference Cement + 9. PCE II Cement ? Cement + PCE I 4. PCE I Cement Cement + PCE II 8. PCE II Cement Blank PCE I (no def.) Cement (no def.) PCE II (no def.) Cement (no def.) w/c = 0.50 w/c = 0.50 w/c = 0.50 w/c = 0.50 w/c = 0.50 w/c = 0.50 w/c = 0.50 w/c = 0.50 w/c = 0.50 SPREAD t.sub.5 [min] 185 192 196 192 200 193 196 191 198 t.sub.30 [min] 174 182 179 186 182 183 180 180 181 AIR CONTENT Air [%] 4.19 3.04 5.99 2.55 6.25 2.27 5.65 2.34 5.98 STRENGTH 1 D 5.4 5.8 4.9 5.7 4.8 5.3 5.1 5.1 5.0 7 D 31.9 36.2 27.3 36.6 27.5 36.2 27.1 36.0 28.1 28 D 45.3 48.6 41.1 47.8 41.3 48.3 41.8 48.6 42.3

[0091] The results are shown in FIG. 1.

[0092] From the air contents, we see that the PCE according to the invention also acts as an air entrapper, like commercial PCEs. This is an advantage when applications with entrained air are needed. When this is not required, defoamers can successfully be used.

[0093] The spreads were comparable or even better than when the commercial PCE was used.

Example 4

[0094] To validate the invention, more samples were mixed and the data were compared. This cross-checking process further proves the advantage of the invention.

[0095] The samples consisted of: [0096] Sample 1: Blank. Only cement (no polymer added at any stage of the grinding process); [0097] Sample 2: Reference cement ground together with the PCE of the invention according to structure (A). [0098] Sample 3: Reference cement ground together with the PCE of the invention according to structure (A), and cured for 60 hours in a curing chamber (Relative Humidity of 80% and a temperature of 60? C.); [0099] Sample 4: Reference cement ground together with the PCE of the invention according to structure (A), and cured for 60 hours in a curing chamber (Relative Humidity of 80% and a temperature of 60? C.); [0100] Sample 5: Reference cement ground together with a PCE based on the molecular structure (Z) but without a sacrificial linkage. [0101] Sample 6: Reference cement ground together with a PCE based on the molecular structure (Z) but without a sacrificial linkage, and cured for 60 hours in a curing chamber (Relative Humidity of 80% and a temperature of 60? C.); [0102] Sample 7: Reference cement ground together with the commercial PCE (PEMA 300N).

[0103] The reference cement had the same composition as in example 1 (70% clinker, 25% limestone, 5% gypsum). The samples were ground until the final material had a fineness d.sub.90=45 ?m, where d.sub.90 means a particle dimension corresponding to 90% of the cumulative undersize distribution. The polymers were added in a dosage 0.1 wt % based on the dry weight of the cementitious material (50% Active Solid Content (ASC)), except in sample 4 where 0.2 wt % based on the dry weight of the cementitious material (50% Active Solid Content (AS2)) was used. A defoamer (tributy phosphate), in a dosage 0.1 wt % based on the wet weight of the added polymer, was added to all samples before mortar preparation.

[0104] After grounded, sand and water were added to the samples to prepare seven samples of mortars.

[0105] Table 5 reports the best results obtained.

TABLE-US-00005 TABLE 5 Results from Example 4 3. PCE 4. PCE 6. PCE (1000 ppm) (2000 ppm) (1000 ppm) 8. Traditional 2. PCE with with 5. PCE without PCE (1000 (1000 ppm) sacrificial sacrificial (1000 ppm) sacrificial ppm) with linkage linkage without linkage 7. Traditional Cement 1. Reference sacrificial Cement | Cement | sacrificial Cement | PCE (1000 | 60 h Cement ? linkage 60 h curing 60 h curing linkage 60 h curing ppm) curing Blank | Cement | chamber | chamber | Cement | chamber | Cement | chamber | w/c = 0.50 w/c = 0.50 w/c = 0.50 w/c = 0.50 w/c = 0.50 w/c = 0.50 w/c = 0.50 w/c = 0.50 SPREAD t.sub.5 [min] 185 192 196 193 182 187 191 194 t30 [min] 174 186 188 186 172 178 180 177 AIR CONTENT Air [%] 5.1 3.1 4.0 3.8 3.3 3.5 3.4 3.2

LIST OF DEFINITIONS

[0106] Admixture. Chemical species used to modify or improve concrete's properties in fresh and hardened state. These could be air entrainers, water reducers, retarders, superplasticizers, and others.

[0107] Air content. The volume of air voids in cement paste, mortar, or concrete.

[0108] Air entrainer. An admixture that ensures air bubbles are trapped inside the material.

[0109] Agglomeration. When particles stick to each other or surfaces they agglomerate, leading to buildup, caking, or lumping.

[0110] Aggregates. A broad category of fine to coarse particulate material used in construction, including sand or gravel. Also see the definitions for sand, fine and coarse aggregates.

[0111] Alkali. Basic, ionic salt of an alkali metal or an alkaline earth metal.

[0112] Alkaline. Material that has alkali or has a pH higher than 7.

[0113] Amide. Chemical compound with the general formula RC(?O)NRR, where R, R, and R represent organic groups or hydrogen atoms.

[0114] Backbone. The backbone of a polymer is the longest chain of covalently bonded atoms, forming the continuous chain of the molecule.

[0115] Binder. It is a material with cementing properties that sets and hardens due to hydration even underwater. Hydraulic binders normally also contain mineral additions like fillers, limestone, and supplementary cementitious materials (SCMs) like fly ash, slag, pozzolan, thermally or mechanically activated clay, etc.

[0116] Blaine. Is a standard test method for powdered material to measure the fineness of powdered material, such as cement, usually expressed as a surface area in square centimeters per gram.

[0117] Bond. A chemical connection that joins molecules.

[0118] Building material. Any material that can be used to build construction elements or structures. It includes concrete, masonries (bricksblocks), stone, ICF, etc.

[0119] Cement. It is a binder that sets and hardens and brings materials together. The most common cement is the ordinary Portland cement (OPC) and a series of Portland cements blended with other cementitious materials.

[0120] Cement mill. A cement mill is a piece of equipment used in the continuous cement grinding process to grind the clinker from the cement kiln into the fine grey powder that is cement.

[0121] Degree of substitution (DS). The DS of the polymer is the (average) number of substituent groups attached per monomeric unit.

[0122] Fresh feed. Stream of material that enters the ball mill. This material comprises mainly clinker but also gypsum and additions.

[0123] Cementitious materials. Materials that have the properties of cement. In the present invention, cementitious materials refer to cement and supplementary cementitious materials (SCMs).

[0124] Clinker. Also hereby mentioned as Portland clinker. Produced by heating limestone and aluminosilicate materials, such as clay, at temperatures of about 1,450? C. Portland clinker is the main component of Ordinary Portland Cement.

[0125] Coarse Aggregates. Manufactured, natural, or recycled minerals with a particle size greater than 8 mm and a maximum size lower than 32 mm.

[0126] Comb polymer. Class of branched polymers consisting of a linear backbone with grafted side chains.

[0127] Compressive strength. The capacity of a material or structure to withstand compressive load before fracturing.

[0128] Concrete. Building material that becomes hard upon hydration, made of a hydraulic binder, sand, fine and/or coarse aggregates, and water. Admixture can also be added to provide specific properties such as flow, lower water content, acceleration, etc.

[0129] Defoamer. A chemical additive that avoids or reduces the formation of foam in industrial process liquids.

[0130] Electrostatic interactions. The attractive or repulsive interaction between particles having electric charges.

[0131] Ester. A chemical compound with the general formula RCO.sub.2R, where R and R are the hydrocarbon parts of the carboxylic acid and the alcohol, respectively.

[0132] Ether. A chemical compound with the general formula ROR, where R and R represent the alkyl or aryl groups.

[0133] Fine Aggregates. Manufactured, natural, or recycled minerals with a particle size greater than 4 mm and a maximum size lower than 8 mm.

[0134] Fineness. Estimation of how fine a powdered material is. Normally measured by passing the material through sieves with different mesh sizes and registering how much of said particles are retained and how much passes through. Laser granulometry or Blaine test can also be applied to characterize fineness.

[0135] Flowability. The ability of a powder to flow under a specified set of conditions, for example, the pressure on the powder, the humidity, and the type of equipment where the powder is flowing.

[0136] Fluidity. The physical property of a substance that enables it to flow.

[0137] Fly ash. Ash produced from burning coal.

[0138] Granulated blast furnace slag. The product that is obtained by quenching molten iron slag from a blast furnace in water or steam.

[0139] Grinding or milling. The mechanical process used to reduce a material to a powder or small fragments by friction or abrasion (as in a mill).

[0140] Grinding medium. Objects, such as balls, used to refine material and reduce particle size.

[0141] Grinding aid. Also called a grinding agent or grinding additives. Chemical components that are added to the clinker to aid in the reduction process of the clinker into powder.

[0142] Humidity. A representation of the amount of water vapour in the atmosphere or in a gas.

[0143] Hydration. It is the mechanism through which Ordinary Portland Cement or other inorganic materials react with water to develop strength. Calcium silicate hydrates are formed and other species like ettringite, monosulfate, Portlandite, etc.

[0144] Imide. A chemical compound containing the group CONHCO, related to ammonia by replacement of two hydrogen atoms by acyl groups.

[0145] Kinetic energy. Kinetic energy is a property of a moving object or particle and depends not only on its motion but also on its mass. When the temperature of an object increases, the average kinetic energy of its particles increases.

[0146] Lime. A white caustic alkaline substance consisting of calcium oxide.

[0147] Limestone. A rock, mainly made of calcium carbonate or dolomite, used as building material and as raw material in cement production.

[0148] Linkage. Same as Bond. A connector between two atoms or molecules.

[0149] Mill. Same as Cement mill.

[0150] Molecule. A group of two or more atoms held together by chemical bonds or linkages.

[0151] Molecular structure. The location of the atoms, groups or ions relative to one another in a molecule.

[0152] Monomer. A molecule that can react with other monomer molecules to form an oligomer and then a polymer.

[0153] Mortar. A building material made of cement, sand and water, normally used between bricks or stones to held them together once it hardens.

[0154] Natural pozzolan. Raw or calcined pozzolan that is found in natural deposits.

[0155] Ordinary Portland cement (OPC). A hydraulic cement made from grinding clinker with gypsum. Portland cement contains calcium silicate, calcium aluminate, and calcium ferroaluminate phases. These mineral phases react with water to produce strength.

[0156] Pendant groups. Group of atoms attached to a backbone chain of a long molecule, usually a polymer.

[0157] Polycarboxylate ethers. Polymers widely used in concrete chemistry as water reducers.

[0158] Polymer. Material with a high molecular weight made of many monomers.

[0159] Pozzolan. Silicate-based materials that react with calcium hydroxide generated from the cement hydration process to form additional cementitious materials.

[0160] Raw meal. The mixture of the raw materials before entering the mill, such as clinker, limestone, fly ash, slag, clay, etc.

[0161] Sacrificial. According to the invention, a sacrificial linkage is designed to be destroyed in fulfilling the purpose of the invention.

[0162] Sand. Manufactured, natural, or recycled minerals with a particle size lower than 4 mm.

[0163] Sidechain. A group of atoms attached to the main part of a molecule.

[0164] Silo. A structure used to store and discharge powder materials.

[0165] Specific area. The total surface area of a material per unit of mass.

[0166] Spread. The extent, width, or area covered by the concrete or mortar.

[0167] Strength developmentsetting/hardening. The setting time starts when the construction material changes from plastic to rigid. In the rigid stage, the material cannot be poured or moved anymore. After this phase the strength development corresponding to the hardening of the material.

[0168] Superplasticizers. It relates to a class of chemical admixture used in hydraulic cement compositions such as Portland cement concrete having the ability to highly reduce the water demand while maintaining a good dispersion of cement particles. Superplasticizers avoid particle aggregation and improve the rheological properties and workability of cement and concrete at the different stages of the hydration reaction.

[0169] Supplementary cementitious materials. Materials that, when used together with cement, contribute to the properties of hardened concrete through hydraulic and/or pozzolanic activity.

[0170] Water reducer. Admixture added to concrete or similar construction material to reduce the amount of water needed in the mix design while achieving the same final properties.

[0171] Water requirement. The amount of water needed to hydrate per dry weight of product.

[0172] Water-to-binder ratio. Also described as w/b. Total free water (w) mass in Kg divided by the total binder mass (b) in Kg.

[0173] In summary, the polymer hereby disclosed provides advantages as a grinding aid during the milling of cementitious materials. Contrary to other polycarboxylate ethers, that are destroyed in the mill due to high humidity, temperature, and pH inside the mill, the polymer hereby disclosed is robust and endures the milling process of cementitious materials. As it combines with the cementitious particles, it also provides the final construction material (mortar or concrete) with properties given by superplasticizer PCEs, such as higher workability and strength gain.