Stable clay slurries

Abstract

A stable calcined clay slurry and method of preparing the same are provided by adding to a calcined clay suspension containing at least 50% clay in aqueous medium about 0.30% to 0.49% by weight of anionic polymer and about 0.007% to 0.011% by weight of cationic polymer by weight in the slurry.

Description

This invention relates to stable clay slurries and particularly to stable slurries of calcined kaolin which can be shipped in tank cars and trucks without deleterious effects of dilatant settling and which are readily pumped from the shipping tank by conventional means.

Kaolin is a well known inorganic pigment used as a filler in or a coating on paper, as a pigment in paints, rubber, resins and other materials. In its naturally occurring state it is in the form of a hydrated aluminum oxide of generally hexagonal plate-like configuration. Kaolin, in its natural hydrated form is used in large quantities. However, when calcined, kaolin loses its water of hydration and becomes brighter than naturally occurring hydrated kaolin and contributes a higher level of opacity to coatings made from it. Once kaolin has been dehydrated it does not return to the hydrated form on contact with water, but retains its new characteristics.

Since calcined kaolin is used in large tonnages, it would be desirable to ship it as high solids slurries in tank cars or tank trucks as many other pigments and extenders are shipped. Unfortunately, however, calcined kaolin is extremely dilatant in slurry form and only moderate solids levels can be achieved (50% to 65% solids). At these moderate solids levels, two very serious obstacles to slurry shipment of calcined kaolin occur. The first of these obstacles is dilatant settling when the slurries are allowed to stand without agitation. The second serious obstacle is that the slurries are too dilatant to be pumped from tanks by conventional means.

This problem has been the subject of considerable research and has been a long standing problem in the industry. Some of the attempts to solve this problem are represented in the patented art. For example, Tapper U.S. Pat. No. 3,846,147 attempted to solve this problem by adding to calcined clay suspensions of greater than 40% solids an alkalizing agent in amount sufficient to provide a pH of at least 8 and sufficient to stabilize and make the slurry pumpable. Among the alkalizing agents he proposes are sodium pyrophosphate (TSPP), potassium tripolyphosphate (KTPP), sodium carbonate (NaCO.sub.3) and certain anionic polymers. Eggers U.S. Pat. No. 4,017,324 attempted to solve the problem by adding 8% to 331/3% hydrated kaolin clay to the calcined clay along with a suspending agent such as bentonite clay, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose and a dispersing agent such as a non-ionic surfactant, an anionic surfactant or an alkanolamine. Unfortunately, none of the prior art methods have been completely successful in solving the problem. They are effective to a degree in some cases but totally ineffective in others.

We have discovered that the problems relating to dilatancy in calcined clays which have made slurry shipments unsatisfactory can be eliminated by using combinations of cationic and anionic polymers in the calcined clay slurries. This combination in appropriate amounts gives minimum settling of kaolin in the tank while minimizing the dilatancy effects so that the slurry is pumpable by conventional means, both of which have evaded prior art attempts at solution.

The significance of the present invention and its value can perhaps best be understood by the following examples showing prior practices and the present invention as applied to identical clay compositions. When no thickeners or suspending agents are used in the preparation of both fine particle size and coarse particle size calcined clays, the results which appear in the following Examples I and II are obtained.

EXAMPLE I

______________________________________ASTRA-PAQUE (Fine particle calcined clay) 50% solidsBrookfield ViscosityRPM c.P.s. Hercules Viscosity______________________________________10 50 18 dynes at 100 RPM20 3850 50100 68______________________________________

EXAMPLE II

______________________________________Glomax LL (Coarse particle calcined clay) 55% solidsBrookfield ViscosityRPM c.P.s. Hercules Viscosity______________________________________10 55 18 dynes at 150 RPM20 5050 52100 67______________________________________

As shown in Examples I and II, the fine particle size calcined clays cannot be made down at as high a solids content as coarse particle size calcined clays. Even though the fine particle size calcined clay was made down at lower solids, it exhibits greater dilatancy, as indicated by the Hercules viscometer reading.

Various non-ionic thickeners and suspending aids (cellulosics), cationic polymers and anionic polymers were compared alone and in various combinations with the present invention to illustrate the uniquely synergistic combinative effect obtained by compositions according to the invention.

In all of the following examples the slurries were made down using the following general procedure.

1. Slowly add calcined clay to appropriate amount of water and dispersant (stir 5 minutes). 2. Add in appropriate thickener and/or polymer (stir 10 minutes). Cellulosics were dissolved in the makedown water prior to clay addition. 3. Adjust pH if necessary.

EXAMPLE III

Table I Sample 1B

A coarse calcined clay slurry containing non-ionic thickener was prepared as follows:

1. To 123.0 g. water was added 25 g. of a 1% solution CMC-7 H (Hercules brand of Cellulose Gum, sodium carboxymethyl cellulose) and 0.05 g. sodium hexametaphosphate. 2. Added slowly 151.3 g. coarse calcined clay and stir 15 minutes. 3. The pH adjusted to 7.4 using NaOH. The results appear in Table I hereafter.

EXAMPLE IV

Table V Sample 4A

A fine calcined clay slurry was prepared as in Example III above using a 50% solids fine particle size using 137.5 g. water plus 25 g. of 1% solution of CMC-7H for every 137.2 g. of fine particle clay.

The results appear in Table V.

EXAMPLE V

Table II Sample 1C 1. To 123.0 g. water was added 0.20 g. of a Bentone LT (N.L. Industries brand of organo montmorillonite) while stirring. After Bentone LT was completely dispersed, added 15 g. of a 1% solution of CMC-7H (Hercules brand Cellulose Gum sodium carboxymethyl cellulose) plus 0.05 g. sodium hexametaphosphate. 2. Added slowly 151.3 g. of coarse calcined clay and stirred for 15 minutes. 3. The pH adjusted to 7.4 with NaOH. The results appear in Table II.

EXAMPLE VI

Table III Sample 2B 1. To 73 g. water was added 50 g. of a 1% solution Klucel G (Hercules brand of Cellulose Gum hydroxypropyl cellulose) and 0.05 g. sodium hexametaphosphate. Stirred to dissolve the polyphosphate completely. 2. Added slowly 151.3 g. of coarse calcined clay and stirred for 15 minutes. 3. After clay was completely wetted out and dispersed, added in 0.15 g. Daxad CP-1 (W. R. Grace Company brand water soluble cationic polymer).

The results appear in Table III.

EXAMPLE VII

Table III Sample 7A 1. To 87 g. of water was added 50 g. of a 1% of Natrosol 250 GR (Hercules brand Cellulose Gum, hydroxyethyl cellulose) and mixed. 2. Add slowly 136.5 g. of fine particle size calcined clay and stir for 15 minutes. 3. After clay is completely wetted out and dispersed, add in 0.2 g. of a 50% solution of Ionac PE-100 (Tanatex Sybron Corp. cationic polyelectrolyte of the quaternary polyamine type).

The results appear in Table III.

EXAMPLE VIII

Table IV Sample 1A 1. To 122.5 g. of water was added 0.05 g. sodium hexametaphosphate and stirred until completely dissolved. 2. Added slowly 150.8 g. of coarse particle size calcined clay and stirred for 15 minutes. 3. After clay was completely wetted out and dispersed, added in 1.62 g. of a 27.5% solids solution of Acrysol ASE-60 (Rohm & Haas Company brand of an acid containing crosslinked acrylic emulsion copolymer). Adjusted pH to 8.0 with NaOH.

The results appear in Table IV.

EXAMPLE IX

Table V Sample 4E 1. To 111.6 g. of water was added 25 g. of a 1% solution of CMC-7H (Hercules brand of Cellulose Gum, sodium carboxymethyl cellulose) and 0.05 g. sodium hexametaphosphate. Stirred to dissolve polyphosphate completely. 2. Added slowly 136.8 g. of fine particle size calcined clay and stirred for 15 minutes. 3. After clay was completely wetted out and dispersed, added 1.5 g. of a 27.5% solids solution of Acrysol ASE-60 (Rohm & Haas Company brand of an acid containing crosslinked acrylic emulsion copolymer). Adjust pH to 8.0 with NaOH.

The results appear in Table V.

EXAMPLE X

Table VI Sample 2A 1. To 133.5 g. of water slowly added 137 g. of fine particle size calcined clay. Stirred until clay is completely wetted out and dispersed (approximately 15 minutes). 2. Added 1 g. of a 1.0% solution Ionac PE-100 (Tanatex Sybron Corp. brand of 50% quaternary polyamine) slowly and stirred 10 minutes. 3. Added 1.5 g. of 27.5% solids solution of Acrysol ASE-60 (Rohm & Haas brand of an acid containing, crosslinked acrylic emulsion copolymer) and stirred 5 minutes. 4. Adjusted pH to 8.0 using NaOH.

The results appear in Table VI.

The foregoing and various other non-ionic thickeners and suspending aids (cellulosic), cationic polymers and anionic polymers were similarly used in varying amounts and combinations as appear hereafter in Tables I, II, III, IV, V and VI as follows:

TABLE 1__________________________________________________________________________Non-Ionic Thickeners Brookfield Viscosity cPsSamples 10 rpm 100 rpm Comments__________________________________________________________________________Coarse Clay Control at 55% solids 55 67 Extremely dilatant, settles to hard cake rapidly1 A 0.07% CMC-7H (based on dry clay) 300 104 Dilatant, hard cake on bottom in 1 day1 B 0.16% CMC-7H 1250 250 Dilatant, hard cake on bottom1 C 0.27% CMC-7H 1800 870 Dilatant, settled but cake not as hard1 D 0.33% CMC-7H 4200 2400 Dilatant, slight settling2 A 0.33% Natrosol 250 GR 1000 250 Dilatant, hard cake on bottom3 A 0.07% Natrosol HHR 650 145 Dilatant, hard cake on bottom4 A 0.16% Klucel G 460 116 Dilatant, hard cake on bottom4 B 0.33% Klucel G 560 138 Dilatant, hard cake on bottom5 A 0.07% Cellosize QP-15,000 960 180 Dilatant, hard cake on bottom6 A 0.07% Bentone LT 560 150 Dilatant, hard cake on bottom6 B 0.16% Bentone LT 1250 250 Dilatant, hard cake on bottom__________________________________________________________________________ CMC-7H = Hercules Cellulose Gum sodium carboxymethyl cellulose Natrosol 250 GR = Hercules Cellulose Gum hydroxyethyl cellulose Natrosol HHR = Hercules Cellulose Gum hydroxyethyl cellulose Klucel G = Hercules Cellulose Gum hydroxypropyl cellulose Bentone LT = NL Industries organo montmorillonite Cellosize QP15,000 = Union Carbide Company hydroxyethyl cellulose TABLE II__________________________________________________________________________Combinations of Non-Ionic Thickeners Brookfield Viscosity cPsSamples 10 rpm 100 rpm Comments__________________________________________________________________________Coarse Clay Control at 55% solids 55 67 Extremely dilatant, settles out rapidly1 A 0.07% CMC-7H + 0.07% Bentone LT 1000 270 Dilatant, hard cake on bottom1 B 0.07% CMC-7H + 0.16% Bentone LT 1500 350 Dilatant, hard cake on bottom1 C 0.10% CMC-7H + 0.13% Bentone LT 1650 415 Dilatant, hard cake on bottom2 A 0.33% Klucel G + 0.16% Bentone LT 1060 252 Dilatant, hard cake on bottom3 A 0.07% Cellosize QP-15,000 + 1550 275 Dilatant, hard cake on bottom 0.13% Bentone LT4 A 0.33% Natrosol 250 GR + 1400 390 Dilatant, hard cake on bottom 0.13% Bentone LT5 A 0.07% Natrosol HHR + 1400 280 Dilatant, hard cake on bottom 0.13% Bentone LT__________________________________________________________________________ TABLE III__________________________________________________________________________Cationic Polymers and Non-Ionic Thickeners Brookfield Viscosity cPsSamples 10 rpm 100 rpm Comments__________________________________________________________________________Coarse Clay Control at 55% solids 55 67 Extremely dilatant, settles out rapidly1 A 0.1% CMC-7H 750 320 Dilatant, hard cake on bottom1 B 0.1% CMC-7H + 0.04% Daxad CP-1 1250 600 Less dilatant, some settling1 C 0.09% Daxad CP-1 900 350 Dilatant, hard cake on bottom2 A 0.33% Klucel G 560 138 Dilatant, hard cake on bottom2 B 0.33% Klucel G + 0.04% Daxad CP-1 2200 332 Slight gel, little settling2 C 0.33% Klucel G + 0.09% Daxad CP-1 9000 1600 Gelled, but easily stirred3 A 0.07% Cellosize QP-15,000 960 180 Dilatant, hard cake on bottom3 B 0.07% QP-15,000 + 0.04% Daxad CP-1 7500 1300 Moderate gel, easily stirred4 A 0.33% Natrosol GR 1000 250 Dilatant, hard cake on bottom4 B 0.33% Natrosol GR + 0.04% Daxad CP-1 6400 1300 Moderate gel, easily stirred5 A 0.07% Natrosol HHR 650 145 Dilatant, hard cake on bottom5 B 0.07% Natrosol HHR + 0.04% Daxad CP-1 3200 620 Slight gel, easily stirred6 A 0.33% Klucel G 560 138 Dilatant, hard pack on bottom6 B 0.33% Klucel G + 0.04% Daxad CP-1 3200 640 Slight gel, easily stirred some settling6 C 0.33% Klucel G + 0.04% Reten 420 8400 1080 Hard gel, dilatant, difficult stirring6 D 0.33% Klucel G + 0.04% Reten 210 3800 1400 Moderate gel, dilatant, difficult stirringFine Clay at 50% solids 50 68 Extremely dilatant, settles out rapidly7 A 0.37% Natrosol 250 GR +0.07% 2400 480 Some settling, but not hard packed Ionac PE-1007 B 0.66% Natrosol 250 GR + 0.36% 3800 1400 Some settling, but not hard packed Ionac PE-1008 A 0.33% CMC-7H + 0.33% Natrosol 1850 460 Some settling, hard packed on bottom 250 GR8 B 0.33% CMC-7H + 0.33% Natrosol 2150 560 Some settling, but not hard packed 250 GR + 0.13% Ionac PE-1009 A 0.33% Klucel G + 11% 10,000 5300 Slight gel, but not settled Al.sub.2 (SO.sub. 4).sub.3 18 H.sub.2 O, pH 3.99 B 0.33% Klucel G + 11% 12,000 4850 Slight gel, but not settled Al.sub.2 (SO.sub.4).sub.3 18 H.sub.2 O, pH 4.19 C 0.33% Klucel G + 11% 13,000 5200 Slight gel, but not settled Al.sub.2 (SO.sub.4).sub.3 18 H.sub.2 O, pH 4.29 D 0.33% Klucel G + 11% 1100 290 Dilatant and some settling Al.sub.2 (SO.sub.4).sub.3 18 H.sub.2 O, pH 5.29 E 0.33% Klucel G + 11% 1100 270 Dilatant, hard pack on bottom Al.sub.2 (SO.sub.4).sub.3 18 H.sub.2 O, pH 6.7__________________________________________________________________________ Reten 420 = Hercules, Inc. nonionic high molecular weight acrylic polymer Daxad CP1 = W. R. Grace water soluble cationic polymer Ionac PE100 = Tanatex Sybron Corporation cationic polyelectrolyte of the quaternary polyamine type (50% quaternary aliphatic polyamine) Ionac PE110 = Tanatex Sybron Corporation 44% tertiary aliphatic polyamine Reten 210 = Hercules Incorporated high molecular weight cationic acrylic polymer (quaternized) Reten 300 = Hercules Incorporated high molecular weight strong cationic acrylic polymer (quaternized) TABLE IV__________________________________________________________________________Anionic Polymers Brookfield Viscosity cPsSamples 10 rpm 100 rpm Comments__________________________________________________________________________Coarse Clay Control at 55% solids 55 67 Extremely dilatant, settles out rapidly1 A 0.30% Acrysol ASE-60 pH 8.0 3000 820 Slight settling, some dilatancy1 B 0.40% Acrysol ASE-60 pH 8.0 5000 1360 No settling, weak gel, easily stirredFine Clay Control at 50% solids 50 68 Extremely dilatant, settles out rapidly2 A 0.22% Acrysol ASE-60 pH 8.0 4100 1000 Moderate settling2 B 0.44% Acrysol ASE-60 pH 8.0 7900 2000 Heavy gel, can be stirred__________________________________________________________________________ Acrysol ASE60 = Rohm & Haas Company an acrylic acidcontaining, crosslinke acrylic emulsion copolymer Acrysol G110 = Rohm & Haas Company ammonium polyacrylate TABLE V__________________________________________________________________________Combinations of Non-Ionic Thickeners and Anionic Polymers Brookfield Viscosity cPsSamples 10 rpm 100 rpm Comments__________________________________________________________________________Coarse Control at 55% solids 55 67 Extremely dilatant, settles out rapidly1 A 0.33% Klucel G 560 138 Dilatant, hard cake on bottom1 B 0.33% Klucel G + 0.11% 2200 480 Gelled, easily stirred Acrysol G-1102 A 0.17% CMC-7H 1300 520 Dilatant, hard cake on bottom2 B 0.17% CMC-7H + 0.15% 1400 620 Some settling, but easily stirred Acrysol G-1103 A 0.17% CMC-7H 1450 580 Dilatant, hard cake on bottom3 B 0.17% CMC-7H + 0.02% 850 390 Dilatant, decreasing hard cake on Acrysol ASE-60 bottom3 C 0.17% CMC-7H + 0.06% 1200 530 Dilatant, decreasing hard cake on bottom Acrysol ASE-603 D 0.17% CMC-7H + 0.11% 1700 710 Dilatant, decreasing hard cake on bottom Acrysol ASE-603 E 0.17% CMC-7H + 0.17% 2100 770 Dilatant, decreasing hard cake on bottom Acrysol ASE-603 F 0.17% CMC-7H + 0.22% 3300 1160 Soft settling Acrysol ASE-60Fine Clay Control at 50% solids 55 68 Extremely dilatant, settles out rapidly4 A 0.18% CMC-7H 700 230 Hercules viscosity, 18 dynes at 100 RPM, hard cake on bottom4 B 0.18% CMC-7H + 0.06% 850 285 Hercules viscosity, 18 dynes at 100 RPM, Acrysol ASE-60 pH 8.0 decreasing hard cake on bottom4 C 0.18% CMC-7H + 0.15% 1100 380 Hercules viscosity, 18 dynes at 100 RPM, Acrysol ASE-60 pH 8.0 decreasing hard cake on bottom4 D 0.18% CMC-7H + 0.30% 1300 440 Hercules viscosity, 18 dynes at 100 RPM, Acrysol ASE-60 pH 8.0 decreasing hard cake on bottom4 E 0.18% CMC-7H + 0.30% 2300 750 Hercules viscosity, 18 dynes at 200 RPM, Acrysol ASE-60 pH 8.0 soft settling5 A 0.18% CMC-7H + 0.30% 1350 550 pH adjustment made with NaOH, hard cake Acrysol ASE-60 pH 6.0 on bottom5 B 0.18% CMC-7H + 0.30% 1400 540 pH adjustment made with NaOH, decreasing Acrysol ASE-60 pH 6.5 hard cake on bottom5 C 0.18% CMC-7H + 0.30% 2000 685 pH adjustment made with NaOH, decreasing Acrysol ASE-60 pH 7.0 hard cake on bottom5 D 0.18% CMC-7H + 0.30% 1600 530 pH adjustment made with NaOH, decreasing Acrysol ASE-60 pH 7.5 hard cake on bottom5 E 0.18% CMC-7H + 0.30% 2100 740 Soft settling Acrysol ASE-60 pH 8.0__________________________________________________________________________ TABLE VI__________________________________________________________________________Combinations of Cationic and Anionic Polymers Brookfield Viscosity cPsSamples 10 rpm 100 rpm Comments__________________________________________________________________________Fine Clay Control at 50% solids 50 68 Extremely dilatant, settles out rapidly1 A 0.49% Acrysol ASE-60 pH 8.0 21,000 9500 No settling dilatant1 B 0.49% Acrysol ASE-60 + 0.004% 13,000 4600 No settling dilatant Ionac PE-1001 C 0.49% Acrysol ASE-60 + 0.007% 11,000 5000 No settling, dilatant Ionac PE-1001 D 0.49% Acrysol ASE-60 + 0.011% 3400 950 No settling, less dilatant Ionac PE-1001 E 0.49% Acrysol ASE-60 + 0.013% 1050 330 Soft settling, least dilatant Ionac PE-1002 A 0.30% Acrysol ASE-60 + 0.007% 3800 920 Little or no settling, Hercules Ionac PE-100 viscosity 18 dynes at 260 RPMCoarse Clay Control at 55% solids 55 67 Extremely dilatant, settles out rapidly3 A 0.45% Acrysol ASE-60 pH 8.0 8300 2510 No settling, but dilatant3 B 0.45% Acrysol ASE-60 + 0.007% 3000 820 Best with regard to dilatancy and Ionac PE-100 settling3 C 0.45% Acrysol ASE-60 + 0.007% 4100 1100 Slight settling, moderately dilatant Ionac PE-1003 D 0.45% Acrysol ASE-60 + 0.007% 5000 1310 Slight settling, moderately dilatant Reten 300__________________________________________________________________________

In all of the foregoing Examples the fine clay used was "Astra-Paque," Georgia Kaolin Company's brand of calcined fine clay having a particle size of 80% below 2 microns equivalent spherical diameter, 95% below 5 microns and 100% below 10 microns. The coarse clay used was "Glomax LL," Georgia Kaolin Company's brand of calcined coarse clay having a particle size of 52% below 2 microns equivalent spherical diameter, 85% below 5 microns and 95% below 10 microns.

The results of the foregoing tests show that:

1. If one or more non-ionic thickeners is used alone, viscosity can be increased sufficiently to prevent settling, but dilatancy of the slurry is increased rather than decreased. This is unsatisfactory. 2. Combinations of non-ionic thickeners and cationic polymers are used to control viscosity; hard cake settling can be decreased more efficiently than when using either the non-ionic thickeners or cationic polymers alone. Combinations of cellulosics and cationic polymers tend to increase thixotropy. 3. Anionic polymers, such as Acrysol ASE-60, tend to be similar to non-ionic thickeners but more thixotropic; and, thereby, prevent settling at lower viscosities. 4. Combinations of non-ionic thickeners and anionic polymers show no particular advantage over the use of these viscosity modifiers independently. 5. Combinations of cationic and anionic polymers result in the best calcined clay slurries. The appropriate combination gives minimum settling while minimizing dilatancy, as shown by Example X, Table VI, Sample 2 A.

The combination of cationic and anionic polymers appears to correct the deficiencies of each and to provide where the ratio of cationic polymer to anionic polymer is in the range of about 0.30% to 0.49% anionic polymer by weight in the slurry and about 0.007% to 0.011% cationic polymer by weight in the slurry.

In the foregoing specification we have set out certain preferred practices and embodiments of our invention, however, it will be understood that this invention may be otherwise embodied within the scope of the following claims.

Claims

1. A stable calcined clay suspension comprising at least 50% by weight of calcined clay in an aqueous medium in the presence of about 0.30% to 0.49% by weight of anionic polymer and about 0.007% to 0.011% by weight of cationic polymer in the slurry.

2. A stable calcined clay suspension as claimed in claim 1 wherein the anionic polymer is present at 0.30% by weight and the cationic polymer is present at 0.007% by weight.

3. A stable calcined clay suspension as claimed in claim 1 or 2 wherein the anionic polymer is an acid containing cross linked acrylic emulsion copolymer and the cationic polymer is a cationic polyelectrolyte of the quaternary polyamine type containing about 50% quaternary aliphatic polyamine.

4. A process for preparing a stable calcined clay suspension comprising the steps of:

(a) admixing calcined clay in water with a dispersant to provide a suspension containing at least 50% by weight of calcined clay,

(b) adding about 0.30% to 0.49% anionic polymer and about 0.007 to 0.011% cationic polymer by weight to the slurry of calcined clay with agitation of the slurry; and

(c) adjust the pH to about pH 7 to pH 8.

5. A process as claimed in claim 4 wherein the anionic polymer is added at 30% by weight and the cationic polymer at 0.007% by weight.

6. A process as claimed in claim 4 or 5 wherein the anionic polymer is an acid containing cross linked acrylic emulsion copolymer and the cationic polymer is a cationic polyelectrolyte of the quaternary polyamine type containing about 50% quaternary aliphatic polyamine.