CA1224495A - Grinding aids for hydraulic cements - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Hydraulic cements such as Portland cement are interground with amine salts of aromatic group-containing carboxylic acids (e.g. triethanolamine benzoate) to enhance the efficiency of the grinding operation. In a preferred embodiment, a mixture of aromatic group-containing carboxylic acids obtained as a low cost by-product in a commercial process to produce phthalic anhydride, is utilized to prepare the amine salt grinding aid of the invention. The grinding aids of the invention also appear to inhibit the "pack-set" tendencies of the resulting ground cement particles.

Description

BACKGROUND OF THE INVENTION
This i.nvention relates to the grinding of hydraulic cements to recluce the part.icle size thereof, and more particularly to the addition of certain chemical addit;.ves to such cements during the grinding thereof to improve the efficiency of the grinding operation and also the "pack-set"
characteristics of the ground cementO
In the processing of Portland cement for example, a grinding operation is generally employed either in the unprocessed or semiprocessed state to reduce the cement to relatively small particle sizeO It is desirable in this grinding step to have as efficient an operation as possible, that is, to reduce the particular mineral to the desired size using as little energy as possible. Toward this end, it is customary to add chemicals known as "grinding aids" cluring the grinding operation which fac.ilitate the operation either by increasing the rate of production, or by increasing the fineness of the particles at the same rate of production, without having adverse effects on the properties o-f the ground productO
Cleavage of the cement particles during grinding exposes fresh or nas.cent surfaces ~hich have high energy. The surface forces of the ground particles persist for some time after grinding and can lead to compaction or

2~ "pack-set" and/or poor fluidity if they are not reduced. Cement particles ~hen compacted by vibration, eOg., when transported in a hopper car often become semirigid and will not flow until considerable mechanical effort has been applied to break up the compactionO It is desirable therefore if the "grinding a~d~ also acts to reduce this tendenc~ to compact or "pack~set"O
Many chemicals and chemical mixtures have been suggested ~or use as grinding aids and pack-set inhibitors for hydraulic cements such as Portland ~

cement. Examples of such chemicals Nhich have been successfully commercially applied include triethanolamine salts of acetic acid ~United States Patent 3l329,517 to Serafin) and tTiethanolamine salts o phenol (United States Patent

3,607,326 to Sera~in) D Also, the use of amine salts of alkyl benzene sulphonic acid and the diethanolamine sal~ of dodecyl benzene sulphonic acid in particular have been suggested as grinding aids for cements ~Japanese Patent NosO
7421408 and 7~21410 to H. Miyairi and M. Nakano).
SUMMARY OF THE INVENTION
The present invention is based upon the discovery that salts formed ~y reacting aromatic group-containing carboxylic acids with amînes are excellent grinding aids in the grinding of hydraulic cements such as Portland cement. The presence of such salts in the ground cement also acts to inhibit the tendency of ground cement to compact or ~pack-set~O Such salts moreover offer the advantage that the carboxylic acid reactant is obtainable commercially in many instances from starting materials (benzene, toluene, xylenes, etc.) produced in the distillation of coal, and therefore avoid the price fluctuations and shortages currently characteristic of chemicals derived solely from petroleum.
Most preferred as a grinding aid according to the invention is an aromatic group-containing carboxylic acid amine salt prepared by reacting an amine and an acid component ob~ained as a by-product in a commercial process to produce phthalic anhydrideO Tha by-product, which is principally a mixture of benzoic acid and phthalic anhydride, is economically available since uses for the by-product material are limited. ~oreover, the by-product is obtained ~rom a process which uses naphthalene as a starting material which is obtainable from coal tarsO

s DE LED DESCRIPTION
The grinding aids of the invention are prepared by mixing the aromatic group-containing carboxylic acid component and the amine to obtain ~n essentially neutral amine saltO The starting materials may be pure chemicals or chemical mixturesO
The amines employed in the present invention include primary, secondary and tertiary aliphatic or aromatic amines and preferably alkanolamines, as well as mixtures of such. Use~ul amines may be represented by the formulae:

I

~A) Rl _ N - R3 and ~B) R~N - R5 uherein Rl is hydrogen, an alkyl, alkanol, alkaryl or aryl radical; R2 is hydrogen, alkyl or alkanol radical; R3 is hydrogen, hydroxyl, alk~l, alkanol or aryl radical; R4N is pyrrolidinyl, pyrrolinyl J pyrrolyl, morpholinyl, piperdinyl, or piperazinyl radical and R5 is h~drogenj alkyl, or alkanol radicalO The term "aryl" as used herein is intended to refer to a phenyl or naphthyl radical~ One or more of the hydrogen atoms on the aryl radical may be replaced by a substituent group such as a nitro; halogen, preerabl~ chlorine, alkyl, preferably a 1 ~o 5 carbon group, more preferably methyl; aryl, amino and alkoxy, preferably a 1 to 5 carbon alkoxy groupO
In addition, pyridazine, pyrimidine and pyridine and such compounds wherein one or more hydrogen atoms are replaced wi~h hydrogen, hydroxy or alkyl ~L2~ 4~5 radicals are also useful in preparing additives within the scope of the present inventionO The terms pyrrolylJ pyrrolydil, morpholinyl and piperadyl, as used herein are intended to include the substituted radicals which are known to the art, e.gO~ N-meth~lmorpholine, and 4-~2-aminoethoxy) e thylmorpholineO
A particularly preferred amine component for reacting with the aromatic group-containing carboxylic acid to produce the additives of the invention is a residue product derived from commercial processes to produce alkanolamines such as that described in United States Patent NoO 3,329,517 to Dodson. The additive is derived from the residue obtained in preparing ethanolaminesO The residue product may be derived from a number of w011 known methods which are employed to synthesi~e ethanolaminesO It may be obtained from such reactions as the ammonolysis or amination of ethylene oxide, the reduction of nitro alcohols, the reduction of amino aldehydes, ketones and esters, and the reaction o halohydrins with ammonia or amines.
The exact composition of the residue product varies within certain limits, and, therefore, the term "ethanolamines" as used herein and in the claims refers to one or more mono-, di-, or triethanolamines, preferably between 4 to g5% by volume triethanolamineO In general the residue product is 2Q predominantly triethanolamineO A specific residue product which is employed in a particularly preferred embodiment of this invention is a mixture of mono , di~ and triethanolamine which is available commerciall~ and has the following chemical and physical properties:
Triethanolamine.00000000000~5 to 55% by volume Equivalent weightO.000~0000129 to 139 Tertiary amine.OOO.OOO.OOOO6~2 to 700 meq./gm.

WaterO.O.OOOOOOOOOOO00~OOOO0O5% by wgto, maximum Density.OOOOO.O J OoOOo~ooo.o9o~9 lbsO/gal lhe aromatic group~containing carboxylic acids reacted with the amines llereill include mono- and polycarboxylic aclds having one or more aro-matic groups in their molecular structureO The terms "aromatic" and "aryl" as employed herein include the unsaturated cyclic hydrocarbon radicals princip-ally, as exemplified by the phenyl, ben~yl, naphthyl, etcO~ radicalsO Such carboxylic acids could have groups (eOgO alkyl-, halo-, nitro-, hydroxy, etc., groups) in addition to, for example located uponJ such aromatic or aryl groups la so long as such do not deleteriously affect the intended use of the additive compound according to the invention. Illustrative of the aromatic group-containing carboxylic acids useable herein are aromatic carboxylic acids such as benzoic acid, phthalic acid and the alkyl benzene carboxylic acids. Also, aryl substituted aliphatic acids such as naphthaleneacetic acid and mandelic acid ~-hydroxyphenylacetic acid~O Mixtures of such acids ~ay also be used.
Moreover, anhydrides of such acids may be used herein but it may be necessary to first convert the anhydride to the acid prior to reaction with the amine componentO
A particularly preferred carboxylic acid component for reaction with the amines to produce the additives according to the invention is that obtain-ed from a by-product in commercial processes to produce phthalic anhydride by the oxidation af naphthalene, typically in the presence of catalyst, to phtha-lic anhydride. In the final stages of such processes~ the oxidation product is subjected to a distillation step towards recovery of the highly pure anhydride product. A by~product produced from such distillation, sometimes referred to in the industry as '~phthalic li~es," comprises a mixture of benzoic acîd and phthalic anhydrideO This by-product because of its impurity has limited usageO Also, its toxicity makes it disposal complicated. It has been found that such by-product, after treatment to convert the phthalic anhydride to the acid, is an ideal material to react with amine to produce the grinding aid additive of the inventionO The by-produc~ is economically available, and its use in hydraulic cement wherein it is ultimately encased ~in concretes, etcO), is an e.nvironmentally desirable disposal. Moreover, the by-product is obtained from a feedstock, naphthalene, obtainable from coal tar, and thus many of the problems associated with chemicals solely dependent upon petroleum for their availability are avoidedO
The "phthalic lites" by-product mixture as aforedescribed is prin~ipally comprised of a mixture of benzoic acid and phthalic anhydride.
The exact proportions of each of such ingredients in the mixture can vary widely, say from 99:1 to 1:99 benzoic acid to anhydrideO It has been found desirable to convert the anhydride in the by-product to the acid prior to reaction with the amine to produce the ~rinding aid of the lnvention. If the product is not so converted, esters are produced in the reaction with the amine, which leads to products uhich are less effecti.ve as grinding aids.
~ he preferred method for conversion of the "phthalic lites" by-2Q product mixture is by hydrolysis, hereinafter termed "hydrolyzed phthaliclites". In the preferred procedure, the by-product mix-ture is heated to a molten condition ~e,g. 110C.) which renders it easily transportable, pumpable, etc., and added to hot ~ater ~e.g. about 80C) to effect the conversion of the anhydride to phthalic acid. After cooling, the amine reactant is added to produce essentially a mixture of amine salt of benzoic acid and amine salt of phthalic acidO

~L2~

The amine salt addi-tive of the lnvention is interground with the cement in the grinding mill to provide increased grinding eEficiency as well as other advantageous results, e.g., inhibiting pack-set of bulk stored cement. Ihe additives of the invention are particularly preferred for use with Portland cement, a class of hydraulic cement comprised essentially of two calcium silicates and a lesser amound of calcium aluminate. These cements are produced by heating an intimate mixture of finely divided calcareous material (limestone) and argillaceous material ~clay) to form a clinker. The clinker is ground with the addition of about 2 percent gypsum~ or some other form of calcium sulfate, to obtain the desired setting qualities in the finished cementO It is to the clinker that the addi~ive of the invention is preferably added to increase grinding efficiency and to inhibit subsequent pack-set in the finished cementO
The additives of ~he present invention may be employed in either dry or liquid forma For convenience, the additive is in water solution to permit accurate metering into the mill stream. The addition is accomplished either prior to the grinding or the additive is introduced into the grinding mill simultaneously with the cementO If the additive is employed merely for the reduction of pack-set or for fluidizing purposes, it is added at any convenient point in the processing.
The additive of the invention is employed 0ffectively over a relatively ~ide rangeO The preferred range is about OoOOl to 1 percent based on the ~eight of the cement, i.e., the ~eight of additive solids based on the weight of the ce~ent solids ~herein referred to as "solids on solids"). In a particularly preferred embodiment, the amount of additive employed is about 0.004 to 0O04 percentO Higher levels are employed if grinding to a relatively ~2~5 high surface area, and the amount of additive is limited solely by the desired surface area and the degree of fluidity desiredO
As used herein, the term "pack-set" is intended to refer to the agglomeration or adheslon o~ particles by~ ~or example, storing or transport-ing in bulk. Adhesion results from surface forces~ the majority of which are believed to be created during the grinding of the cement.
Pack-set is determined în the following manner:
One hundred grams of the cement is placed in a 250 milliliter Erhlenmeyer flask set on top of a variable vibratorO The flask containing the cement is vibrated 15 seconds after which it is removed from the vibrator and set into a jig with the axis of the flask lying horizontally. Ihe flask is then rotated around its axis until the cement which is compacted in the bottom of the flask collapsesO The flask is twisted at 180 angles at approximatel~ 100 twists per minute The number of 180 twists required for the sample to collapse establishes the pack-set. Thus, the greater the energy required to break up the bed, the higher will be the pack-set~
The ~ollowing examples will serve to further illustrate the invent-ion.
EXAMPLE I
In experiments testing the effectiveness of chemicals as grinding aids for Portland cement, several aromatic acid components were first reacted with a t~iethanolamine mixture to form a salt thereo~, and test grinds made in a laboratory batch millO The triethanolamine mixture was a product obtained as a residue product o~ ethanolamine synthesis previously described. Several clinkers ("A" through "D" in Table I), each from a different manufacturing source, were used in the tests. In the tests3 3325 grams of clinker (-20 mesh 9~

size) ~ere ground along with 175 grams of gypsum (the latter is used in commercial production of "Portland cement")O The amine salts were added in various proportions ~salt solids on cement solids) to the clinker-gypsum mixture before grinding. For comparison, a "blank" control grind, that is, a grind of each of the clinkers "A" through "D" with gypsum and no grinding aicl was also per~ormedO Each grind ~ith respect to a single clinker was identical, that iSJ the mill was operated the same number of revolutions at 220F, and the surface area ("Blaine Surface Area") of the resulting ground product measured in centimeters square per gramO The exact number of revolutions varied between 5000 and 10~000 depending upon the particular clinker. The increase in fineness ~the increase in "Blaine SurfaGe Ar0a") evidenced by the ground test samples containing grinding aid was calculated as a percent oE the surface area measured for the "blank" control. This percentage is recorded as "Percent Improvement Over Blank" in Table I.
Duplicate, and in some cases triplicate, grinds were made of the grinding aids tested and the "Percent Improvement Over Blank" shown in Table I is an average value thereof. In Table I, the "Hydrolyzed Phthalic Lites" product was obtained as previously generally described, using in particular the "Procedure No. 1" of EXAMPLE II~ Fo-r further comparison, additional test grinds were 2Q made using a commercial grinding aid. The results are reported in Table I.

~ g --.

~2~

TABLE I

Percent Improvement Over Blank Addition Rate Run R~mRun Clinker Grinding Aid~O sos) #1 1~2#3 Average , A Triethanolamine Salt 0.025 6~78.6 7O3 7.5 of Phthalic Acid A Triethanolamine Salt 00014 3.5108 - 2.7 of Phthalic Acid A Commercial Product 0O025 9.87.8 9.3 9.O
A Commercial Product 0~013 2.2203 - 2.3 A Triethanolamine Salt 0.025 5O77.3 - 6.5 of Naphthaleneacctic Acid A Triethanolamine Salt 0.025 6098.5 - 7.7 Benzoic Acid A Triethanolamine Salt 0O015 3.1600 6.5 5.2 of Hydrol~zed Phthalic Lites A Commercial Product 0,015 6.36D3 8.1 6.9 L Triethanolamine Salt 0.015 8099.3 809 9.0 of Hydrol~zed Phthalic Lites B Commercial Product 0.015 5~88.3 10.7 8.3 C Triethanolamine Salt 0.015 6015.0 8O7 6.6 of Hydrolyzed Phthalic Lites C Commercial Product 0.015 7085.9 7O0 6.9 D Triethanolamine Salt 0~015 8.2805 7.1 7.9 of Hydrol~zed Phthalic Lites D Commercial Product 00015 6047O7 8.6 7.6 A Triethanolamine Sal~ 0.025 4O96.4 - 5.7 of Naphthalene Sulfonic Acid _ 10 -~z~

EXA~IPLE II
l'wo procedures may be used in the preparation of the triethanolamine sa.lt ~.rom "hydrolyzed phthalic lites", the method o choice being dictated prlmarily by the type of processing equipment available. The figures given In th:is example are based upon a 1000 gram batch although in practice batches as large as 500 lbsO have been prepared using both procedures.
Procedure #l . _ $tep 1: Melt 292 grams of phthalic lites and heat molten material to between 110 and 115C.
1~ Step 2: Add 20 grams of hot water (93 - 100 C) to the molten phthalic lites wlth vigorous stirringO
Step 3: Monitor the temperature of the reac~ion mixtureO Initially it will climb as the exothermic hydrolysis reaction takes p].ace, then become constant as thermal equilibrium is reached and finally fall after the hydrolysis step reaches completionO
Step 4: Upon completion of the hydrolysis ~as indicated by the decrease in reaction mixture temperature~ add 448 grams of triethanolamine with moderate stirringO
Step 5: When the reaction mixture temperature falls to below 90CO add 240 2Q grams of water.
Procedure #2 Step 1: Heat 260 grams of water to between 75 and 100Co Step 2: Add 292 grams of molten phthalic lite~ to the hot water with vigorous stirring. The temperature of the molten material should be between 110 and 115Co Step 3: Monitor the temperature of the reaction mixture as in Step 3 of Procedure 1~2 ~ContO) Procedure #l, Step 4: When the temperature of the reaction mixture falls to 70C begin a slow addition of 448 grams of triethanolamine with moderate agitation.
The rate of triethanolamine addition should be adjusted so that the temperature of the reaction mixture does not exceed 100Co EXAMPLE III
The ability of the grinding aid of the invention to also act as inhibitors of the "pack-set" of the ground product was testedO Table II shows the results of tests as described previously for ability to inhibit the "pack-set" tendencies of Por~land cement clinker mixtures "A", "B~ and "D".
The lower the "pack~set" number, the more effective the grinding aid is as an inhibitor of "pack~set"O

-. 12 TABLE II

Cement Addition Clinker Grinding AidRate ~% sos? Pack Set A None ~blank) - 30 A Triethanolamine Salt of 0.025 5 Naphthaleneacetic Acid A Triethanolamine Salt of 0.025 2 Benzoic Acid A Triethanolamine Salt of 00025 3 Phthalic Acid A Commercial Product 0O025 5 A Commercial Product 0.015 9 A Triethanolamine Salt of û.015 7 "Hydrolyzed Phthalic Lites"
B None ~blank) - 14 B Triethanolamine Salt of 0O015 "Hydrolyzed Phthalic Lites"
B Con~nercial Product 0.015 14 D None (blank) - 29 D Triethanolamine Salt of 0.015 11 I'Hydrolyzed Phthalic Lites"
D Commercial Product 0.015 8

Claims (16)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. The method of producing amine salts useful as additives to hydraulic cements comprising reacting an amine with a mixture of aromatic carboxylic acids obtained from the by-product produced in a process to produce phthalic anhydride.

2. The method of claim 1 wherein said by-product comprises a mixture of benzoic acid and phthalic anhydride.

3. The method of claim 2 wherein said by-product mixture is hydrolyzed to convert said anhydride to phthalic acid prior to reaction with said amine.

4. The method of claims 1 or 2 wherein said amine is alkanolamine or mixture of amines containing such.

5. The method of producing amine salts useful as additives to hydraulic cements comprising the steps of (a) hydrolyzing a mixture of benzoic acid and phthalic anhydride obtained as a by-product in a process to produce phthalic anhydride from naphthalene; and thereafter (b) reacting the hydrolyzed product from (a) with a mixture of amines obtained as a residue product of ethanolamine synthesis to produce said amine salts.

6. An amine salt useful as an additive to hydraulic cement produced by a process as recited in claims 1 or 5.

7. A Portland cement composition comprising Portland cement and, intimately mixed therewith, from about 0.001 to about 1 percent by weight of an amine salt of an aromatic group-containing carboxylic acid, said carboxylic acid being a mixture of aromatic carboxylic acids obtained from a by-product produced in a process for producing phthalic anhydride.

8. The composition of claim 7 wherein said mixture of acids comprises a mixture of benzoic and phthalic acids.

9. The composition of claims 7 or 8 wherein said mixture of acids is produced by hydrolysis of a by-product mixture containing benzoic acid and phthalic anhydride.

10. The composition of claims 7 or 8 wherein said by-product is obtained as a result of distilling an oxidation product obtained in a process to produce phthalic anhydride by the oxidation of naphthalene.

11. The composition of claims 7 or 8 wherein said amine comprises triethanolamine or a mixture of such with other amines.

12. The composition of claims 7 or 8 wherein said amine comprises a residue product of ethanolamine synthesis.

13. The method which comprises grinding a hydraulic cement in the presence of an amine salt of an aromatic group-containing carboxylic acid, said carboxylic acid being a mixture of acids obtained from a by-product from a process to produce phthalic anhydride.

14. The method of claim 13 wherein said cement is Portland cement.

15. The method of claims 13 or 14 wherein said amine is an alkanolamine or mixture of amines containing alkanolamine.

16. The method of claims 13 or 14 wherein said acid is benzoic acid, phthalic acid, naphthalene acetic acid, or mixture of such.