Solvosol Paints Pvt. Ltd.

Background Why Polyurethane Coatings? A comparison between Apus-cured urethanes with two component urethanes & two component epoxies Apuscured Urethanes Moisture Cured Urethanes Apus-Cured Systems Apus-Cured Other Special Features   A Critical Comparison AC-TAR or AC-Zinc Vs COAL TAR Epoxy Uses Where AC Urethanes have Advantage

Background

K. Venkateswarlu

Graduate in Chemical Engineering from Andhra University and a Post Graduate from IIT, Kharagpur with specialisation in Petroleum Refinery Engineering and petrochemicals. Worked with the Paints Division of ICI for 12 years and then with Nagarjuna Group for 10 years, before resigning in 1992 as General Manager, Exports. Trained in U.S.A. and Malaysia on Polyurethane and Acrylic Coatings.

Travelled extensively abroad and all along associated with Corrosion and Corrosion protection through surface coatings. Participated in a number of seminars in the above field. A major part of the 22 years of industrial experience is devoted to special coatings like Polyurethanes, Epoxies and Acrylics. He was also a Consultant to Tata Exports Ltd.

Solvosol Paints Pvt. Ltd. is a company engaged in the manufacture of a variety of surface coatings, including coating systems on a turnkey basis for highly specialised applications.

The company promoted by Technocrat Entrepreneurs, has specialised in the Polyurethane, Acrylic, Epoxy and Alkyd Resin systems and makes coatings (paints) putties, sealants, caulking compounds, adhesives and customised coatings tailor-made for individual needs.

Summarising, we have developed and established the following successfully.

Conventional Two Pack Poly Urethanes Blocked Poly Urethanes Moisture Cured Urethanes Urethane Alkyds Polyols, Adducts & Urethane resin systems Heat Resistance Coatings up to 600°C Sealants & Adhesives Floor Coating Systems Ceramic Coatings Elastomers Both Isocyanate & Isocynurate foams Cathodic Depositable Water based Poly Urethanes Low Temperature Baking Water based Poly Urethanes Road marking coatings Coatings for the ID of the pipe lines Re-bar coatings Wood Lacquers and Laminates Coatings for effluent treatment plants

Why Polyurethane Coatings?

The following are the considerations of Polyurethane Coatings which show superior coating performance compared with epoxy coatings or fusion bonded epoxy coatings, so it was decided to formulate Polyurethane coatings:

Excellent resistance to atmospheric exposure Excellent adhesion Non-Chalking, Non-Yellowing Easy to clean Very good resistance to chemical and water Resistance to Mineral, Vegetable Oil, White Spirit, Paraffin, Petrol, etc Extremely tough and abrasion resistance Quick drying Wide choice of raw materials as compared to epoxy, including tightly bound rust and old paint Excellent application characteristics by brush roller or spray Resistance to Micro-organism is good because polyurethanes contain free isocyanate groups, which are poisonous to micro organisms Economical cost wise for longer period

A comparison between Apus-cured urethanes with two component urethanes & two component epoxies

S. No. Apus-Cured Urethanes Two Comp Urethanes Two Comp Epoxy 1 No pot life, no catallyzation, no mixing of plural components Short pot life Short pot life 2 Can be applied in humidity to 99% Not above 85% Not above 85% 3 No dew point restriction Must be a minimum 50F above dew point Must be a minimum 50F above dew point 4 Can cure down to 200F Not below 40-500F Not below 40-500F 5 Highly recommended for immersion. Can be immersed within 30 minutes Not recommended for immersion 2-6 days cure before immersion 6 Can be applied to damp Surfaces Not recommended Not recommended 7 Excellent colour and gloss typical of aliphatic urethanes Same Not recommended for exterior exposure w/o topcoat 8 Best corrosion resistance. Formulations available to give 20,000 hour ASTM salt spray resistance. Used only as top coat Not as good 9 Best Zinc-Rich Vehicle. Out performs inorganic Zinc when top coated Not recommended Not as good

Apuscured Urethanes

Popularly known as Moisture Cured Urethanes State of the Art Technology Technology not available in India Ideal for atmosphere where relative humidity is beyond 80%, where other coatings fail No sand blasting required

Moisture Cured Urethanes

MC Urethanes comes under ASTM Type II, single pack classification. These are NCO-terminated pre-polymers with the NCO percentage ranging from about 2 to 15%. Normally these are low solid coatings, solids varying from 40 to 60. The chemistry of the MC Urethanes involves the reaction of the diisocyanate with the hydrogen donors, leaving a slight excess of NCO available to react with the atmospheric moisture. These NCO groups react with any moisture available to form substituted or disubstituted ureas and biuret groups. These products are in use for almost 25 years. These coatings are most useful in any application calling for an extreme resistance to abrasion, for areas that require good elongation to withstand expansion and contraction of a substrate and for many chemical environments. Perhaps the major advantage of the MC Urethanes is that they are a one component material, ready to use as it is removed from the can. No mixing, measuring, weighing or additives are necessary.

The high relative humidity and presence of mono layer of moisture are two of the major problems associated with painting on marine installations. Most significantly these problems turn out to be assets for MC systems as they require a minimum relative humidity of 45% and up to 80% they perform exceptionally well.

Based on the literature available and our own R & D, we have evaluated Epoxy, Two Pack Conventional Urethanes and MC Urethanes for various applications in marine/saline atmospheres.

We have given importance to the following factors

High strength with matching elongation Very low permeability to air and moisture Excellent resistance to Marine atmosphere and sea water in alternate wet and dry conditions Very high adhesive strength and scratch resistance Faster turn around time Life spanning 3 to 5 years and 5 to 7 years depending on the end use Difficult working conditions like narrow spaces Low inventories

Apus-Cured Systems

Manual/Power Tool Cleaning One coal of Apus cured clear Two coats of Apus cured under coat Two coats of Aliphatic finish based on MIo/Plain On customer request we can replace MIO to give straight shades

Under Coats

Apus Cured Zinc Apus Cured Zinc MIO Apus Cured Tar Apus Cured MIO Tar Apus Cured Mastic

Finish Coats

Aromatic MIO finish Aromatic Plain finish Aliphatic MIO finish Aliphatic Plain finish Aromatic Aluminium Aliphatic Aluminium Ceramic Putty

Apus-Cured Other Special Features

Extremely hard, but flexible Very Low permeability, no substrate attack Exclusive formulations for PH above 7 and below 7

Of the above three, MC Urethanes appears to be the best. The MC Urethanes have shown outstanding properties compared to conventional Two Pack Urethanes. MC systems are used widely abroad, especially in USA.
AC Zinc outperforms inorganic zinc silicate in all respects.

A Critical Comparison AC-TAR or AC-Zinc Vs COAL TAR Epoxy

Advantages of…

S. No. AC-Tar or AC-Zinc Coal Tar Epoxy 1 AC-Tar and AC-Zinc can be applied at temperatures as low as -50C, humidity to 99%, no dew point restriction. Cannot be applied for humidity above 80-85%, or temperature below 70C. 2 AC-Zinc and AC-Tar can be immersed within 30 minutes. Required 2-8 days prior to immersion. 3 Both can be recoated or touched up at any time without special treatment. Cannot be recoated after 12-36 hour unless reblasted or used with a special tie coating. Field touch-up is always a problem. 4 All AC-Coatings are single component with no mixing, measuring or catalyzation and therefore have no pot life limitation. Plural components must be precisely mixed. Pot life can be very short. 5 AC-Tar and AC-Zinc have excellent urethane flexibility, weatherability and abrasion resistance. Epoxy tars are notoriously brittle and never as good as urethane for weathering and abrasion resistance. 6 AC-Tar is resistant to 800C continuous water immersion and intermittent temperatures up to 1150C. Epoxy tars blister with exposure to intermittent temperatures over 760C. 7 AC-Zinc/AC-Tar cannot undercut. Typical salt spray resistances over 20,000 hours. This system does not require holiday testing. Epoxy tar will undercut at mechanical damage or holiday, Epoxy tar requires holiday testing. 8 AC-Tar adheres to damp or green concrete. The concrete does not have to cure for 28 days. Epoxy tar requires very dry concrete with a concrete with a concrete cure of a least 28 days. Recoating a water blasted surface is always a problem. 9 AC-Tar and AC-Zinc comply with all current and proposed VOC and lead reduction legislation. Varies. 10 AC-Tar does not irritate skin and eyes of the applicator. AC-Coatings are isocyanate monomer free. AC-Tar contains only 20-25% refined tar. Epoxy tar is extremely irritating to applicators. Typical Epoxy tar contains up to 85% coal tar or refined tar. 11 AC-Tar contains micaceous iron oxide, which improves properties for abrasion, blistering, weathering, corrosion resistance & marine growth penetration. Does not contain micaceous iron oxide. 12 AC-Zinc/AC-Tar has a dramatic advantage for miscellaneous damaged, abraded, or driven. (This system will not undercut or creep at mechanically damaged site. Undercutting is limited to less than 1/8 inch for 10 years in sail-water splash zone). Epoxy tar will fail at every unrepaired damage point. 13 AC-Tar is always recommended at thinner films, 4-12 mils DFT. Epoxy tar usually requires a minimum of 18 mils DFT.

Uses Where AC Urethanes have Advantage

Bridges and Highways Concrete and Wooden Floors Marine and Harbour Pulp, Paper and Sugar Industry Production Plants & Equipments Storage Tanks Cross Country Pipelines Power Generation Facilities Water Works, Waste Water Pipelines Petroleum and Fertilizer Industry Pharmaceutical Industry Effluent Treatment Plants Amusements Parks