|Title of Invention||
A PROCESS FOR MANUFACTURE OF WATER REDUCING AGENT FROM COAL TAR WASTE
|Abstract||A process for the manufacture of water-reducing agent from coal tar waste characterized by adding slowly under stirring 2 to 5 times sulphuric acid to coal tar oil maintained at a temperature in the range of 25-40°C for a minimum period of 2 hours to obtain sulphonated product, condensing the said sulphonated product by adding slowly under stirring 2-5% of formalin, neutralizing the sulphonate by adding 25-35% caustic soda to maintain pH at 7 to 8, diluting the resultant neutralized product to around 30-35% solid content|
|Full Text||The present invention relates to a process for the manufacture of water reducing agent from coal tar waste.
The present invention particularly relates to a process for preparing a water reducing agent from coal tar waste for improving workability of cement mortars/concrete at lower water-cement ratio. The water reducing agents/admixtures are the group of products which possess as their primary function the ability to produce workable mortars/concrete at lower water cement ratio.
The developed product of the present invention will be useful in improving the workability of cement mortars and concrete.
Coal tar is a black thick, oily liquid obtained by destructive distillation of coal tars. The actual composition of the tar varies with the nature of coal and temperature of destructive distillation. It has been found in addition to carbon particles, it contains a number of natural occurring neutral, acidic and basic compounds. Neutral substances are hydrocarbons* of aromatic series, such as benzene, toluene, naphthalene, anthracene, phenathrene. Important acidic substances are such as phenols and cresois. Basic substances include pyridine, quinoline and their homologues Coal tar is thus an important raw material for the manufacture of these substances. Tar obtained by low temperature carbonisation contains paraffins, naphthalenes, alkylated aromatic compounds etc. About 1 ton of coal produces 7.8 gal of coal tar. The organic solvents like benzene, toluene and naphthalene etc. are distilled alia the remaining tar which contain creosotes and undistilled naphthalene etc. is used for the development of water reducing agent.
According to BIS 9103 - 1979 the reduction of mixing water by use of these water reducing agents must be at least 5%. However, commercial water reducing agents can reduce mixing water upto 10 to 15% without significantly affecting. The setting characteristics of mortar/concrete. Normally by the addition of water reducing agent with a reduction in the water-cement ratio, a mortar/concrete having the same workability as the control mix can be obtained. This water reduced mortar/concrete has unconfined compressive strengths at all ages which exceed that of control. Secondly mortar/concrete with similar workability and strength development characteristics can be obtained at lower cement contents than control without adversely effecting the durability or engineering properties of mortar/concrete.
There are a number of formulations described in patents concerning water reducing agents. Usually the main components of these formulations are water soluble organic compounds. The earliest known published reference to the use of water reducers, in the thirties, refers to certain polymers of condensed naphthalene sulphonic acids for use in small amounts of about 0.1% by weight of cement. Reference may be made to H.L.Kennedy, Portland cement effects of catalysts and Dispersion, Industrial and Engineering chemistry, American Chemical Society Vol. 28, (1936) p 963-69. These polymers were never used as water-reducing agents or plasticizers on a large scale until the severities when they were rediscovered. The main compounds used in the manufacture of water reducers can be divided into four groups. The first on contains Ca, Na or NH4 salts of ligno sulphonic acids. The second groups contains the hydroxy Carboxylic acids generally Na, NH4 or tri-ethanolamine salts. The carbohydrates belong to the
third group. The last group comprises other compounds . Lignosulphonates are still the most widely used raw material in the production of water-reducing admixtures, though their use as water reducers was discovered in the thirties Lignosulphonates are produced from paper waste black liquor formed as a by-product containing a complex mixture of substances including 20-30% lignin Commercial lignosulphonates used in water reducing formulations contain up to 30% carbo-hydrates (reducing sugars). Reference may be made to Rixom, M.R., chemical Admixtures for concrete, E & F.N. spon Lts. (1978). Calcium and sodium salts are the most widely used cations in water reducer formulations. Sodium salts have higher degree of ionization. Reference may be made to F.M.Ernsberger and W.G.France. Some physical and chemical properties of weight-fractionated lignosulphonic acid, including the dissociation of ligno-sulphonates, J. of Physics & colloid chemistry Vol. 52, 1948, p. 267. In general, lignosulphonate based water reducing agents entrain a certain volume of air into the concrete. This could be considered as a desirable effect when air entrainment is required to increase frost resistance or to improve cohesion in lean mixes or in concrete containing coarse sand, but is often an unwanted side effect. Thus in the production of normal water-reducing agents, a small amount of air-detraining agent is added. The ligno-sulphonate molecule itself and, of course, the sugars present in the lignosulphonate materials do have a retarding influence on the hydration of cement, this is an undesirable effect. Salts of organic hydroxy carboxylic acids were developed as water-reducing agents or retarders in the fifties. Though their use has increased significantly, they are not used to the same extent as lignosulphonates, because water reducing agents developed from lignosulphonate were economical and easily available. Gluconic acid is perhaps the most widely
used admixture. Reference may be made to Davidsson, S. "Studies of the effect of some simple organic admixtures on the props, of Cement Paste", International Symposium on Admixture for Mortar and concrete, Vol. 2, 1967, p 57-68. Carbohydrate based water reducing agents synthesized include natural compounds, such as glucose and sucrose. Water reducing agent has also been synthesized from other organic compounds, such as glycerol, polyvinyl alcohol, sulfanilic acid. Reference may be made to Massazza, F and Testolin, M, "Latest Developments in the use of Admixtures for Cement and Concrete, II cemento Vol. 77 (1980) p 73-146. Water reducing agent from pure creosote obtained from the distillation of heavy coal tar has also been synthesized by Ito yoshilatea Manabe, Osamu, Hiyama. Sugai Chem. Ind. Co. Ltd. Japan, which has the ability to foam or entrain air. The product developed from pure creosote has the property of air entrainment which is only useful in the concretes for cold climate. Where as the water reducing agent prepared from coal tar solution is suitable for all weathers. The process of the present invention utilises waste of coal tar industry for making water reducing agent, where as the process reported by Ito yoshilatea Manabe, uses pure creosote and hence a different process. Other materials which are used commercially in the synthesis of water-reducing agents are Naphthalene and Melamine Sulphonates. Sulphonated Naphthalene formaldehyde condensate was referred as a water-reducing agent in literature in 1932 US Patent (1932) 643740. Recently it has found major application in admixture applications. Reference may be made to Rixom, M.R., Proceedings of the workshop on the use of chemical admixtures in concrete. Univ. of South wales 1975, p 153. The development of a water reducing agent from Melamine for application in concrete field was recognized in 1969, Reference may be made to British Patent 1969,
1169582. In addition to the five categories (Lignosulphonates, Hydroxy Carboxylic acids, Carbohydrates, Napthalene and Mclamine) for the formulation of water-reducing agents which account for the majority of commercially available products, water-reducing agent has also been developed from Insitol Japanese Patent 1972, 41897, Polyacrylenicde, Japanese Patent 1975, 36517, Polyacrylic acids, Japanese Patent 1973, , 71416. The normal water reducing admixtures added to mortar or concrete at the prescribed dosage, these admixtures have significant effect on the subsequent hydration of the cement. However, the improved dispersion of cement grains can cause a shortening of the stiffening time and enhanced early strength at a constant water/cement ratio. The water reducing agent reduces the amount of mixing water of mortar/concrete for a given workability. It improves the properties of hardened concrete and in particular, increases strength and durability. These water reducing agents are capable of reducing 10 to 15% water content. According to Indian Standard 9103/1979, specification for admixtures for concrete, minimum requirement for water reducing agents is 5%. For High range water reducing agents, known as superplasticizers which are capable of reducing water content by 20 to 30 percent. These super plasticizers are covered by several standard codes, mainly ASTM-C-494, BS 5075 Part III. All superplasticizers consists of high molecular weight, water soluble polyrhers, the majority being
synthetic chemicals (Naphthalene, Melamine and modified lignosulphonate etc.). As such these admixtures are costly and used only in specified projects. Though these are used extensively in Europe, Japan and USA. In India it is used in limited projects. The high cost of synthetic materials has led to the development of admixtures from natural occurring materials or industrial by-products. Lignosulphonate is being used extensively.
coal tar, an industrial waste obtained from the distillation of coal and after separation of petroleum products still contains number of natural occurring neutral, basic & acidic compounds. This waste has been used in the development of water reducing agent of the present invention.
The main object of the present invention is to provide a process for the manufacture of water reducing agent from coal tar waste.
Another object is to provide a process which allows manufacture of the water reducing agent from coal tar for mortars/concrete and is economical (~25%) as compare to the commercially available products and its shelf life is more than one year.
Accordingly the present invention provides a process for the manufacture of water-reducing agent from coal tar waste characterized by adding slowly under stirring 2 to 5 times sulphuric acid to coal tar oil maintained at a temperature in the range of 25-40°C for a minimum period of 2 hours to obtain sulphonated product, condensing the said sulphonated product by adding slowly under stirring 2-5% of formalin, neutralizing the sulphonate by adding 25-35% caustic soda to maintain pH at 7 to 8, diluting the resultant neutralized product to around 30-35% solid content.
In an embodiment of the present invention the coal tar oil used may be light and middle fractions containing various percentages of paraffins, naphthalenes, alkylated aromatic compounds, cresols.
In another embodiment of the present invention the sulphuric acid used is of commercial grade.
In yet another embodiment of the present invention sulphonation may be effected for a period of 2 to 6 hours.
In still another embodiment of the present invention, the formalin used is of laboratory grade.
In another embodiment of the present invention the neutralization may be effected using commercial caustic soda.
In another embodiment of the present invention the sulphonation and condensation steps may be repeated several times by adjusting the quantum of sulphuric acid and formalin.
The synthesis of water-reducing agent involves basically three steps i.e. The sulphonation, condensation and neutralisation. The light and middle fraction of the coal tar is sulphonated with commercial concentrated sulphuric acid. The sulphonated coal lar solution is condensed with formalin solution. This condensed product is neutralized with sodium hydroxide till
pH of 7 to 8 is obtained. The neutralize solution is adjusted to solid content for use.
The detailed process steps of the present invention are:
Known volume of coal tar oil is taken. To this oil concentrated commercial grade sulphuric acid is added slowly while stirring. The addition of sulphuric acid is maintained in such a way that the temperature of the oil remains in the range 25-40°C. This process of addition of H2SO4 is continued till we get a clear solution of the sulphonaled oil. This is checked by pouring a drop of sulphonated oil into a beaker containing water. If the sulphonalion is not complete the water will become milky otherwise, we get a clear brown solution. Once this sulphonation is complete. This is followed by condensation of the sulphonated oil by laboratory grade formalin solution. The formalin is added slowly under stirring. Precaution is taken that no lump is formed, so the addition of formalin is done carefully. To know whether the condensation is complete, there will be no smell of formalin from the reaction mixture. This condensed product is neutralized with commercial grade caustic soda so that pH of the solution remain within 7 to 8. This process of sulphonation, condensation is repeated several times by adjusting the amount of sulphuric acid and formalin, till we get maximum flow of mortar on the flow table. This neutralized product is diluted so that the solid content is around 30 percent, otherwise precipitation takes place. This diluted product is ready for use in mortars/concrete. The dose is adjusted accordingly. The product developed from pure creosote has the
property of air entrainment which is only useful in the concretes for cold climate. Where as the water reducing agent prepared from coal tar solution is suitable for all weathers. The process of the present invention utilises waste of coal tar industry for making water reducing agent, where as the other process reported by ito yoshilatea Manabe, uses pure creosote and hence a different process.
The following examples are given by way of illustration of the present invention and should not he construed to limit the scope of the present invention.
100 gms of light coal lar oil was taken in a plastic bucket. To this 380 gms of sulphuric acid was added slowly while stirring. This sulphonated coal tar oil was condensed with 29 cc of formalin solution (40%). Care was taken while adding formalin, that no lump formation lakes place, so the addition was carried out slowly. This condensed product was neutralized with 350 gms of caustic soda so that the pH was within 7 to 8. The solution was diluted with water so that the solid content was about 30 percent. The physical properties of the producl is given in table 1.
Table 1 :- Physical properties of the water reducing agent developed from Coal tar.
The water reducing agent has been tested for flow and compressive strength in 1:3 mortar at same water eement ratio and same flow, the results are given in tables (2-5).
Table - 2 Effect of Water-Reducing Agent on the flow of 1:3 Cement-
sand Mortar at 0.48 W/c Ratio.
Table -3 Effect of Water-Reducing Agent on the Setting time of Cement
* Indian Standard Initial lime 600 mins
(BIS 403 I - 1988)
Table 4 Compressive strength of 1:3 cement sand mortar at same water-Cement ratio (0.42)
Table 5 Compressive strength of 1:3 cement sand mortar at same flow-( 140mm) at various dose of water reducing agent
Example - 2
100 gms of coal tar oil was taken in a plastic bucket. To this 240 gms of concentrated sulphuric acid was added slowly while stirring. This sulphonated coal tar was condensed with-2Ice of formalin solution (40%). The condensed product was nutralized with 140 gms of commercial caustic soda, so that pH was around 7-8. The solution was diluted so that the solid content was around 35. The physical properties of the product is given in table 6 and the test results are given in table 7-10.
Table - 6 Physical Properties of the Water-Reducing Agent
Table - 7 Effect of Water-Reducing AGENT on the flow of 1:3 Cement-Sand Mortar a( 0.48 w/c. ratio
Table-8 Effect of Water-Reducing Agent on the Setting time of Cement
Table - 9 Compressive strength of 1:3 mortar at same vv/c ratio (0.42)
Table - 10 Compressive stength of 1:3 mortar at same flow
The conclusion drawn from the various physical properties such a How, setting time, comprcssive strength studied shows that the water
reducing agent has no deleterious cffect on the selling time of cement and compressive strength. At recommended dose of 0.6 to 0.8% (he initial and final setting limes have not changed appreciable and are well within the Indian Standard (Initial 600 mins.). The compressive strength at same flow show that at 3 and 7 day, the increase in strength is about 30%. This increased strength is beneficial for removing shuttering and grinding of floors, thus saving labour cost. Also it is clear that the shelf life of waler reducing agenl is more than one year. In commercial product the shelf life mentioned about one year. This is an added advantage of water reducing agent from coal tar.
The main advantages of the present invention are:-
1. Coal tar waste which is available in plenty lias been converted into
useful water- reducing agent for mortars/concrete.
2. The water reducing agent provides better workability and finish and mix
the mortar/concrete less permeable thereby enhancing the life of the
3. The use of water reducing agent will reduce the cost of labour. The
shuttering can be removed earlier. Also the grinding of floors is possible
at early age due to early strength.
4. The water-reducing-agent is approx. 20-25% cheaper than the
commercially available water-reducing agent.
5. The process does not require costly equipment and machinery which arc
essential for other chemical processes of manufacturing.
1. A process for the manufacture of water-reducing agent from coal tar waste
characterized by adding slowly under stirring 2 to 5 times sulphuric acid to coal tar
oil maintained at a temperature in the range of 25-40°C for a minimum period of 2
hours to obtain sulphonated product, condensing the said sulphonated product by
adding slowly under stirring 2-5% of formalin, neutralizing the sulphonate by
adding 25-35% caustic soda to maintain pH at 7 to 8, diluting the resultant
neutralized product to around 30-35% solid content.
2. A process as claimed in claim 1, wherein the coal tar used is light and medium tar
3. A process as claimed in claims 1-2 wherein the sulphonation is effected for a
period of 2 to 6 hours.
4. A process as claimed in claims 1-3, wherein the sulphonation and condensation
steps are repeated several times by adjusting the quantum of sulphuric acid and
5. A process for the manufacture of water reducing agent from coal tar waste
substantially as herein described with reference to the examples.
|Indian Patent Application Number||904/DEL/2000|
|PG Journal Number||34/2010|
|Date of Filing||06-Oct-2000|
|Name of Patentee||COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH|
|Applicant Address||RAFI MARG, NEW DELHI-110001, INDIA.|
|PCT International Classification Number||C04B 24/16|
|PCT International Application Number||N/A|
|PCT International Filing date|