The tested panels should be washed with gentle spray without disturbing the colonial growth of microorganisms. The follow video demonstrates how to clean the tested panel before taking up for microscopic examinations.
Do we need phosphating after sand blasting followed by powder top coat on hot rolled steel components?
No. It is not necessary if the salt spray resistance required is less than 550 hours. The purpose of sand blasting is to improve the surface profile of the component with a surface free from rust and heavy scales. Yet, the surface is not ready for powder coating if it contains oil and grease even after sand blasting.
One cannot expect complete removal of oil and grease just by sand blasting. It removes scales and rusts only. The oily components should be cleaned with some cleaning thinner or kerosene or MTO prior to sand blasting. This will help in preventing the agglomeration of sand or grit particles. Once sand blasted, the components need cleaning with solvent or thinners again. When the sand blasted and solvent cleaned surface is totally free from oil, grease, rust, scale and dust in any form, it is ready for powder coating.
How does one select a particular type metal pretreatment?
A job coater can expect the sheet metal components with the following surface conditions (Fig.1).
A) Thick oily, greasy, rusted steel with scales – In this case, sand blasting with or without metal pretreatment is recommended based on the salt spray resistance hours required. However, if the component is found to contain tool marks due to cutting or laser cutting and welding, that area should be smoothly buffed prior to sand blasting.
NOTE: Area with welding joints (Fig. 2) is more prone to electrochemical corrosion. It needs to be thoroughly buffed. That surface should be thoroughly cleaned with suitable solvent if there is any silicone based anti-spattering agent has been used.
B) Mild oily, rusted steel – 7 Stage phosphating followed by powder coating
C) Oily steel sheet with no trace of rust – Nano zirconia coating followed by powder coating. Nano zirconia coating serves the purpose of surface protection from corrosion and humidity after powder coating. This does the job similar to phosphating. This kind of coating enhances the salt spray resistance even after 600 hours. The greatest advantage of this Nanocoating is that there is no sludge formation and it can be coated at room temperature within 2 minutes.
Finally, one can select any kind of metal pretreatment based on the surface condition of the incoming sheet metal components. Yet, if the metal pretreatment is not done properly, the faulty coating by itself is detrimental to the performance of the top coat.
Suitable recommendations of finishing for heavy oiled and HR components with scales
Method – 1 (for Salt spray resistance < 600 h)
Solvent dip and cleaning -> Sand blasting -> solvent cleaning -> air blow. Make sure the sand blasted surface (Fig. 3) is totally free from rust, dust in any form or oil or grease before taking up for final coat of polyester epoxy powder followed by curing at 230o C.
Method – 2 (for Salt spray resistance > 600 h)
Solvent dip and cleaning -> Sand blasting -> solvent cleaning -> air blow -> Pre-degreasing -> alkaline degreasing -> Water rinse 1 -> Water rinse -2 -> Surface conditioning -> Phosphating -> DM water rinse-1 -> Fresh DM water rinse – 2 -> Pressurised air blow to drive water drops trapped in silent corners -> Water dry off oven at 110 o C. The phosphate coated surface should be free from water, oil, rust, or dust in any form (Fig.4). Within the shortest interval of time the polyester epoxy powder coat should be given followed by curing at 230 o C. Such type of powder coat with a perfect pretreatment will surely pass on cross hatch test (Fig. 5).
There should be always a clear understanding between the metal fabricator and job coater regarding the type of rust preventive oil used on the fabricated components and job coater should have a suitable cleaning thinner to remove the rust preventive oil. The interval between sand blasting or pretreatment and powder coating should be less than an hour in a dry and dust free atmosphere.
A technical write up on ethyl acetate
Government regulations and social concerns about environmental preservation and depletion of resource have made the solvents industry facing a major push towards green innovation. Solvents are integral components in a vast number of chemical processes and products, and are used in a wide variety of industrial applications such as paints and coatings, agrochemicals, printing inks, pharmaceuticals, and industrial & domestic cleaners. Since the thirty billion dollar solvent industry constantly undergoes scrutiny by regulatory bodies and end-users, nowadays, selection of solvent has become more complex.
Selection criteria of a solvent
Solvent consumers have to consider the following factors to select a solvent besides its physical parameters to perform the required function and periodical cost reduction.
- Environmental safety
- Labour safety
- Greenhouse gas emissions
- Flash point and Flammability
- Worker exposure limit
The term “green” is used to express the goal of minimising the environmental impact resulting from the use of a particular substance. However, the definition of “green” is rather used loosely and extensively in marketing materials. There are many criteria that form the basis upon which a solvent may be labelled “green”, including, but not limited to: a renewable feedstock, status as non-volatile organic compound (VOC) or functionally non-volatile organic compound (non-VOC) – a high flash point, non-toxic nature, biodegradability, and recyclability.
When a solvent may possess many or only one of these attributes, how can one measure the green qualities of a solvent to compare it with another? Nexant Solvent Sustainability Index (NSSI) is a method to quantitatively assess the relative “greenness” of solvents. The NSSI evaluates solvents on eight parameters: feedstock, toxicity, biodegradability, VOC status, odour, fire hazard, vapour pressure, and reactivity. A solvent with perfect greenness in all categories (e.g. water) will receive an NSSI of 100%. Less green alternatives are rated on a sliding scale down to zero. Ethanol is one of the oldest and most successful bio-renewable chemical products in commercial production. Besides its more pervasive end-uses in fuels and beverages, ethanol is an important solvent in detergents, cosmetics, lotions, soaps, shampoos, and other consumer products. Petrochemical ethanol has an NSSI rating of 44%; bioethanol is rated at 54%.
Government regulations have made a major industrial shift towards “greener” solvent use, through sustainable business initiatives and increased consumer awareness. Green solvents, at present represent around 10% of the total solvents market. However, maintaining process compatibility and solvent functionality will continue to be the top priority when selecting a green solvent replacement, but financial performance and environmental performance should not be mutually exclusive.
Ethyl acetate (ETAC) is considered as one of the least toxic industrial organic solvents. It is used in a wide range of applications such as paints, lacquers, enamels, dyes, printing inks, varnishes, car care chemicals, plastics, and rubber. ETAC has seen above-average growth in the solvents sector, as it has successfully been substituted for hazardous air pollutants (HAPs) such as methyl ethyl ketone (MEK) and toluene. ETAC has received an NSSI rating of 49 percent, with its bio-renewable counterpart 10 points higher.
- Ethyl ethanoate
- Acetic ester
- Ethyl acetate
- Abbreviated as ETAC
- Molecular Formula: CH3COOC2H5
Manufacture of Ethyl acetate
There are three methods employed to manufacture ethyl acetate.
- Fischer esterification reaction
- Tishchenko reaction
- Dehydrogenation of ethanol
Ethyl acetate is manufactured by two important processes viz. Fischer Esterification Reaction and dehydrogenation ethanol. Ethyl acetate is synthesised via the Fischer esterification reaction from ethanol and acetic acid, in the presence of concentrated sulphuric acid catalyst. This mixture converts to the ester at room temperature.
CH3CH2OH + CH3COOH → CH3COOCH2CH3 + H2O
(Ethanol) (Ethanoic acid) (Ethyl ethanoate) (Water)
In this method two equivalents of acetaldehyde are combined in the presence of an alkoxide catalyst.
2 CH3CHO → CH3COOCH2CH3
Silicotungstic acid is used to manufacture ethyl acetate by the alkylation of acetic acid by ethylene.
C2H4 + CH3COOH → CH3COOC2H5
Dehydrogenation of ethanol
A specialised industrial route entails the catalytic dehydrogenation of ethanol. This method is more cost effective than the esterification but is applied with surplus ethanol in a chemical plant. Typically, dehydrogenation is conducted with copper at an elevated temperature but below 250 °C.
Grades of Ethyl acetate
There are four grades of ethyl acetate.
- Urethane grade (Purity: 99.7 wt%)
- Spectro grade (Purity: 99.9 wt%)
- Food grade (99.85 wt%)
- Pharmaceutical grade (99.85 wt%)
Package of ethyl acetate
ETAC is generally available in various packings including plastic barrels.
Market of Ethyl acetate
Ethyl Acetate is one of the major organic chemicals produced in India. The main use of ethyl acetate is in the manufacture of a variety of coating preparations, such as epoxies, acrylics, urethanes, and vinyls. It is also used as a solvent in inks, adhesives, and a process solvent. Consumption of ethyl acetate in surface coatings depends heavily on constructions, automobile industry and refurbishment activity. Almost all the consuming sectors of ethyl acetate have witnessed attractive growth rate in the past 5 years, indicating a strong demand for ETAC. Coatings Sector is the largest consumer of ETAC. The printing and process solvent industries are other major consumers of ETAC in India. Western region of India is the largest hub of ETAC consumption, accounting for more than half of its domestic consumption. The market study firmly establishes a growing demand in India for ETAC, which has been constantly increasing over the years. Ethyl acetate demand is above three million tonnes per annum which is met through domestic production. Demand of ETAC is growing at a compound annual growth rate (CAGR) of 11.6% from fiscal year 2005-06 to 2016-17 and will be doubled over the period of 2016 to 2021 which will be met through domestic production.
Ethyl acetate demand is driven by its use as a solvent for printing inks, paints and in pharmaceuticals as well as exports. India also exports significant volumes of ethyl acetate. However, the production of Ethyl Acetate is not up to the full capacity because of the lower demand in the country in comparison to production. Laxmi Organics, JUBL and GNFC are the chief ETAC manufacturers in the Indian market. Though demand has seen an attractive growth for the past few years, it is still playing catch up to the domestic production. India’s excess domestic production mandates producers and exporters to export ETAC. Currently, China is the biggest importer of Indian ETAC, importing about 90% of total share. India needs to further expand its percentage of exports and increase the production up to its maximum capacity so as to increase the export market or to balance the domestic demand supply gap. Asia-Pacific is estimated to be the largest producer and consumer. Most of ethyl acetate capacities are concentrated in Asia Pacific region. Major ethyl acetate producing countries are China, India, United Kingdom, Japan and Brazil. China will keep the leading position in ethyl acetate market.
Alcohol and its Impact on Production of Ethyl acetate
Industrial alcohol is used as main raw material for the production of ethyl acetate. Industrial alcohol in India is based on sugarcane molasses. Once upon a time, molasses were wasted and sugar industries were finding it difficult to dispose molasses. Several committees appointed by Government of India examined the issue and concluded that the most value added use of alcohol is for the manufacture of chemicals and recommended setting up of alcohol based chemical units across the country. Development of alcohol based chemical industries has helped proper utilization of molasses in the production of alcohol.
Alcohol has two major uses:
- Potable use by diluting and blending etc.
- Industrial use for production of various chemicals like ethyl acetate, acetic acid, acetic anhydride, acetone, etc. These alcohol based chemicals provide feedstock for a variety of industries such as synthetic fibres, pesticides, pharmaceuticals, paints, Dyestuffs, adhesives, etc.
Alcohol is now also used for blending with motor spirit. Hence, the prices and distribution of molasses and prices of alcohol as regulated by the Central Government under the Molasses Control Order, 1961 and the Ethyl Alcohol (Price Control) Order, 1971 respectively up to 10thJune, 1993 have greater impact on the price of ethyl acetate and other related derivatives of ethanol. Both these Orders were issued under Section 18(G) of the Industries (Development and Regulation) Act, 1951. The rationale for this policy was that distilleries should obtain molasses at reasonable prices and thereby supply alcohol at controlled prices to chemical units based on alcohol. The implementation of these Orders was with the State Governments. The prices under these Orders were revised from time to time. Inter-State allocations were done by the Molasses Controllers of the States concerned.
The Central Government in the Department of Chemicals & Petrochemicals used to make Inter-State allocations of molasses and alcohol from surplus States to deficit States, on a non-statutory basis, on the advice of the Central Molasses Board (CMB) consisting of the Excise Ministers of all State/Union Territories and the representatives of the concerned Industry Associations.
This regime of controls was inhibiting the free movement of molasses and was not in keeping with the economic liberalization programme of the Government which was initiated during the early nineties. There were also reports about inordinate delays in obtaining allocations and consequent wastage of molasses. The downstream users of molasses were also not able to fully utilize their capacity. Taking all these factors into account and with a view to falling in line with the liberalization policy of the Central Government in other sectors of economy, the Molasses Control Order, 1961 and the Ethyl Alcohol (Price Control) Order, 1971 were rescinded on the 10th June, 1993.
There are about 300 distilleries with installed capacity of approx. 32,000 lakh litres. However, the capacity utilization is only about 55% with present production of approx. 17,000 lakh litres. The low capacity utilization is mainly due to non-availability of sufficient molasses.
The demand of alcohol is increasing in the following sectors three dimensionally.
- Industrial alcohol for the manufacture of ethyl acetate and other related derivatives.
- Potable alcohol which is often affected by political and social influences
- Alcohols blended with petrol
The production of alcohol in general has been showing a negative growth mainly due to adverse climatic conditions.
Acetic Acid is the main alcohol based chemical and is used in the production of Ethyl Acetate, Butyl Acetate, Acetic Anhydride, etc. The growth of Acetic Acid is much higher in Asia and it is estimated to rise by about 10% per year in China. The largest derivative Vinyl Acetate Monomer (VAM) accounts for 34% of Acetic Acid consumption. VAM is used in adhesives, textiles, paints and paper. Its growth is keeping pace with GDP growth. The second largest outlet for Acetic Acid is Purified Terephthalic Acid (PTA). The demand for PTA is driven by the boom in PET resins and polyester fibre. Worldwide 64% of PTA goes in polyester fibre and 31% in PET bottle resin and 5 % in film and other uses. PET resin production is growing very rapidly due to its success in penetrating the soft drinks and water bottles market.
Acetate Esters, which account for a total of 18% of acetic acid consumption, are used as solvents in a wide variety of paints, inks and other coatings. This sector is forecast to have a modest growth.
Industrial users of Ethyl acetate
The major industries using ethyl acetate are mentioned below:
- Synthetic fibres and synthetic yarn
- Drugs & pharmaceuticals
- Personal care products
- Dyestuffs, pigments, flavours & fragrances
- Textile processing
- Toiletries and perfumeries
- Paints and surface coatings
- Synthetic adhesives
- Plastics & polymers
- Solvents for inks & lacquer finishes
- Food preservatives
- Oilfield chemicals
- Leather chemicals
Consumption Pattern of Alcohol
The consumption pattern of alcohol has greater influence in the manufacture of ethyl acetate and allied industries.
Industrial Chemicals 9993 lakh litres 53%
Potable use 8571 lakh litres 45%
Other uses like blending with petrol 421 lakh litres 2%
There are about 20 major units engaged in the manufacture of alcohol based chemicals. The three largest users of alcohol are M/s. Jubilant Organosys Ltd., M/s. India Glycol Ltd. and M/s. Reliance Industries Ltd. These three companies account for 62% of the total requirement of industrial alcohol by the alcohol based chemical industries.
Demand of alcohol and ethyl acetate
The demand of industrial alcohol and ethyl acetate is higher than domestic availability and the gap is met through imports.
The size of alcohol based chemical industry is in the range of Rs. 4500 crores. A large number of alcohol based products are manufactured in India. Some of the important alcohol based chemicals are Acetic Acid, Ethyl acetate, Acetic Anhydride, Acetaldehyde, Ethylene Glycol, Glyoxal, Pyridine/Picoline, Pentaerythritol, etc.
Problems of Alcohol Based Chemical Industry:
- Sugar production is cyclical in nature; hence there is volatility in the prices of molasses and alcohol. This leads to severe fluctuations in prices of feedstock.
- Shortage of industrial alcohol. The new demand from the fuel sector has widened the gap.
- States prefer the movement of molasses/alcohol for potable sector.
- Price of industrial alcohol has increased considerably.
- Most States do not permit free Inter-State movement of industrial alcohol forcing the industry to purchase at higher prices locally.
- High export duty for Inter-State transfer.
- Some States charge higher sales tax on molasses compared to Petro-based raw materials putting the agro based route at a disadvantage. Besides, fees are charged under various heads viz. transport fee, purchase tax, vend fee, denaturalisation fee etc.
- Licencing /quota system followed by some States.
– Alcohol based chemicals like ethyl acetae are derived from renewable and replenishable agricultural source.
- Many of the Alcohol based chemicals are import substitutes and save foreign exchange worth Rs. 4000 crores.
- The industry not only caters to the domestic demand but also exports and earns substantial foreign exchange.
- Alcohol based chemicals offer good value addition.
- Major manufacturing units set up in or in the vicinity of rural areas provide scope for maximum employment potential.
- Alcohol based industry supports thousands of downstream industrial units for their feedstock and intermediates in the large, medium and small-scale sectors throughout India.
Usage of Ethyl acetate in Paints and Coating Industry
Due to its low toxicity and agreeable odour, ethyl Acetate has applications as a solvent in paints and inks, where its main function is to dissolve the resin, control the viscosity and enhance the drying rate. Ethyl acetate, due to its fast evaporating properties is also used in the flexible packaging industry at the screen printing stage in products such as polyester films and aluminium foil and as an auxiliary in the manufacture of glazed and transparent paper too. Asia-Pacific ranked as the world’s leading ETAC consumer with 70% share of the overall consumption volume. The solvents coatings industry was the major ETAC end-use sector, which consumed nearly 65% of the total production volume in 2012. The printings inks and process solvents industries are also important ETAC end-use sectors.
Worldwide, ETAC production is poised to grow by around 4.5% annually in the upcoming years, driven by the rising capacity utilization rates in the existing facilities. Asia is expected to maintain its leadership in the world ETAC market in the offing. Ethyl acetate is not soluble in water. This is another important characteristic of ethyl acetate and that is why it is used in Polyurethane thinners and acrylic lacquers.
Ethyl acetate is also used in the following industries – Pharmaceutic aid (flavor); artificial fruit essences; solvent for nitrocellulose, varnishes, lacquers, and aeroplane dopes; manufacture of smokeless powder, artificial leather, photographic films and plates, artificial silk, perfumes; cleaning textiles, etc.
Prolonged exposure may cause eye, noise and throat irritation. It causes drowsiness, dizziness and cause unconsciousness. In rare cases, it can cause skin eruption and can be fatal to human health. Severe human health associated issues may hamper market growth.
4. Organic Chemistry, I.L. Finar
5. Organic Chemistry, Morrison and Boyd