ANTI-CORROSION PAINT BASED ON NATURAL CNSL (CASHEW NUT
SHELL LIQUID) RESIN FOR PIPING MEMBERS & THE PROCESS OF
PREPARATION THEREOF
FIELD OF INVENTION
[0001] The present invention relates to an anti-corrosive low VOC paint
composition based on Natural CNSL modified Resin and a method of production
thereof. More particularly, the present invention relates to cashew nut shell liquid
(CNSL) resin based paint with low VOC (Volatile Organic Compound) and
Bisphenol-A free for drinking water pipelines.
BACKGROUND ART
[0002] Cashew Nut Shell Liquid i.e. CNSL is a fairly abundant naturally
occurring low cost renewable substance consisting of alkyl-substituted phenols.
CNSL primarily consists of Anacardic Acid (3-n-pentadecylsalicylic acid) (70 %),
Cardnol (3-n-pentadecylphenol) (18 %) & Cardol (5-n-pentadecylresorcinol) (5
%). CNSL is a naturally occurring material in which a benzene ring bears one or
two hydroxyl groups, a carboxyl group, and in the meta position relative to the
hydroxyl group or groups, an unsaturated 15 carbon atom hydro-carbylene
group.
[0003] A CNSL based modified resin generally has advantageous
characteristics, such as good tensile and mechanical strength, high
adhesiveness and excellent resistance to abrasions, impacts, acids and
chemicals. Epoxy resins having such characteristics are widely used in various
industrial fields, such as shipbuilding, engineering works, construction, and
electric and electronic materials.
[0004] Additionally, the epoxy resins are increasingly in demand as corrosion-
inhibiting material used for suppressing corrosion of an easily corroding
material, such as an iron plate.

[0005] The use of CNSL has been known for many decades. For instance
cardnol polymerized via the unsaturated side chain, and after subsequent
formulation to form a cardnol-formaldehyde resin, (see inter alia U.S. Pat.
No.2,686,140, U.S. Pat. No. 3,227,249,FR 1573564 (U.S. Pat. No. 3,448,071),
U.S. Pat. No. 4,072,650). Cardanol, furthermore, is reacts with amines such as
ethylenediamine or diethyltriamine to form phenalkamines. Phenalkamines have
entered the art, by virtue of the lower cure temperature as compared with the use
of polyamides, as curing agents in the production of marine coatings and
adhesives, of solvent-free floor coatings, for coatings on agricultural equipment,
and for tank linings and pipe linings. They offer high resistance to moisture in the
course of curing, and both good chemical resistance and elasticity (see inter alia
US 2004048954, U.S. Pat. No. 5,075,034). More recently, CNSL-based curing
agents prepared by hydrosilylation have also become known (US 2008275204).
CNSL based phenolic resins serve as eco-friendly, acid-resistant anti-corrosion
coatings (CN 101125994); the chemical and mechanical properties of coatings
have been improved by chemically modified cardanol.
[0006] For example, an resin employed in shipbuilding and heavy-duty coatings
is required to have excellent dryness and wafer resistance. An resin composition
including a solid-state epoxy resin having a molecular weight of at least about
1,000 and an equivalent of about 500 g/eq, and a solvent capable of adjusting
the viscosity of the composition, has been used for the above purposes.
[0007] In order to reduce the viscosity of an resin composition, an reactive
diluent having a glycidyl ether type has been mixed with a compound, or a non-
volatile and non-reactive diluent, such as mortar, anhydroustar, pine oil, Hi-Sol
and/or Panasol has been used along with an compound.
[0008] However, the resin composition including such diluents exhibits as
substantially retarded curing rate and poor water resistance, since a cross-linking
density between the resin composition and a curing agent is very low.

[0009] Accordingly, there is still required an CNSL modified resin based anti
corrosive paint having low viscosity as well as excellent curability and water
resistance, along with low VOC (Volatile Organic Compound) and Bisphenol-A
free paint.
SUMMARY OF INVENTION
[0010] In order to overcome the lack of background art, the present invention
provides an environment friendly acid resistant corrosion coating for piping
members. The anti-corrosion coating is environment friendly, acid and wear-
resistant features.
[0011] There is a need for an economical, simpler, environment friendly process
of preparing paint composition.
[0012] Accordingly, an objective of the present invention is the preparation of
potent anti-corrosive, non-toxic, strong adhesion, water and chemical resistant
coatings in a single step at ambient conditions without using external reagents or
excessive energy for practical applications. Capitalizing on the versatility and
reliability of oils (such as oil-based paints), the present invention uses an
oxidative drying mechanism (lipid auto oxidation).
[0013] The technical solution adopted in the present invention is for the piping
members and the components meant for the transportation of drinking water. The
CNSL resin based anti-corrosion paint coatings according to weight percentage:
1. Natural resin CNSL modified 40-60 percent,
2. emulsifier 2-5%,
3. titanium dioxide and nontoxic colour pigments 10-20%,
4. anti-corrosion pigments viz. zinc phosphate, iron oxide 2-5 %,
6. fillers viz. silica powder, barites, talc, 15-25%,

5. xylene 3-10%,
6. DM (Demineralized) Water 20-25%,
10. bentone, fumed silica, defoamer, and driers 2-5%.
[0014] Another object of the present invention is to provide a CNSL resin based
anti corrosive paint having excellent curability, low viscosity, low VCO and
Bisphenol-A free suitable for air drying.
[0015] Another objective of the present invention is to provide a process of
preparing aforesaid paint composition in a single pack form. The said process for
the preparation of anti-corrosion low VOC natural Cashew Nut Shell Liquid
(CNSL) modified resin based paint comprising the steps of: mixing the pigments
with sufficient vehicle (Resin solution) to make the paste which has the correct
. consistency for grinding; grinding the paste in a mill until the aggregates are
broken down as indicated by the fineness of grinding test; letting down the
ground paste with the remainder materials in the formula; tinting the batch to the
required colour; testing and determination of physical properties and the
performance requirements of the paint; and staining, filling & packing wherein the
components of the paint is Natural resin CNSL modified 40-60 %, emulsifier 2-
5%, titanium dioxide and nontoxic colour pigments 10-20%, anti-corrosion
pigments 2-5 %, fillers 15-25%, xylene 3-10%, DM water .20-25%, bentone,
fumed silica, deformer, and driers 2-5%.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
[0016] Fig. 1 illustrates a chemical structure of partially cross linked CNSL
modified Phenolic resin in accordance with the present invention;
Fig. 2 illustrates chemical structure of the repeating unit of straight Phenolic resin
in accordance with the present invention;

Fig. 3(a) illustrates the salt spray test carried over samples painted with Bitumen
paint and disclosed CNSL based anti corrosive paint over 500 hrs in accordance
with the present invention;
Fig. 3(b) illustrates the Q.U.V. test carried over samples painted with Bitumen
paint and disclosed CNSL based anti corrosive paint over 100 hrs in accordance
with the present invention;
Fig. 3(c) illustrates the flexibility test results carried over sample painted with
disclosed CNSL based anti corrosive paint in accordance with the present
invention;
Fig. 3(d) illustrates the 1% NaOH test results carried over sample painted with
disclosed CNSL based anti corrosive paint for 150 hrs in accordance with the
present invention;
Fig. 3(e) illustrates the water test results carried over sample painted with
disclosed CNSL based anti corrosive paint for 800 hrs in accordance with the
present invention;
Fig. 3(f) illustrates the 1% HCI test results carried over sample painted with
disclosed CNSL based anti corrosive paint for 400 hrs in accordance with the
present invention;
Fig. 3(g) illustrates the scratch hardness test results carried over sample painted
with disclosed CNSL based anti corrosive paint in accordance with the present
invention;
DETAILED DESCRIPTION
[0017] CNSL is an economical agro-by product and renewable resource which
consists mainly of substituted phenols. By using CNSL in place of phenol, phenol

derived from petrochemicals can be conserved. One of the principal properties of
CNSL resin is the corrosion prevention. CNSL is treated and polymerized to
produce resins which can be used in manufacturing of anticorrosive protective
coatings. CNSL develops very high resistance to water and chemicals.
[0018] CNSL based paints are used in Industrial and marine coatings, and CNSL
oil is used as a key raw material in the production of curing agents for special
epoxy hardeners and epoxy resins.
[0019] In an exemplary embodiment, the present invention discloses an anti-
corrosion low VOC natural Cashew Nut Shell Liquid (CNSL) modified resin based
paint for drinking water ductile iron pipeline. The ductile iron piping members is
for water mains and distribution as a buried pipeline whereby the soil corrosion
resistance and antimicrobial properties of the same will be exploited.
[0020] The paint hereby disclosed consist of modified CNSL resin as a part,
fumed silica, bentone powder, non-silicone deformer as additives and titanium
dioxide, colour pigments, silica powder, calcium carbonate, emulsifier, DM water,
and xylene as main ingredients.
[0021] The paint form a non-toxic water potable film on ductile iron pipe with
improved acid resistance, alkali resistance, good water repellence and microbial,
termite, and insect repellent properties. It has the characteristics to form hard and
tough dry film thickness at >80 microns by two coats of spray application.
[0022] According to example embodiments of the present invention, a paint
composition includes a CNSL based resin composition having a synthetic resin
prepared by a reaction of a CNSL with a haloalkylene oxide, and a curing agent
including solvent vehicles such as benzol, gasoline, kerosene, naphtha, white
spirit and the like.

[0023] In an example embodiment of the present invention, when the paint
composition includes- less than about 60% by weight of the CNSL resin
composition, the curing rate of the paint composition is so fast that a curing
reaction may not be properly controlled while a coating layer is formed using the
paint composition. Physical and/or chemical characteristics of the coating layer
may also deteriorate. When the amount of the said resin composition is greater
than about 60% by weight, the curing rate of the paint composition may decrease
to retard drying of the coating layer. Therefore, the paint composition according
to an example embodiment of the present invention may include the CNSL based
anti corrosive resin composition in a range of about 40 to about 60%. by weight.
[0024] Examples of the curing agent that may be used in the paint composition
of the present invention may include an amine, an acid anhydride, an amide or
the like. These may be used alone or in a combination thereof.
[0025] In an example embodiment of the present invention, when the paint
composition includes less than 3% by weight of the curing agent, the curing rate
may decrease to retard drying of the coating layer formed using the paint
composition. When the amount of the curing agent is greater than about 8% by
weight, a curing rate is so fast that a curing reaction may not be properly
controlled and physical and/or chemical characteristics of the coating layer may
also deteriorate. Therefore, the paint composition according to an example
embodiment of the present invention may include the drying mechanism without
any such type of curing agent.
[0026] In an example embodiment of the present invention, the paint
composition may include an additive such as an inorganic filler viz. silica powder,
bariates etc, a viscosity-controlling agent or the like considering the use and
properties of the paint composition.
[0027] In an example embodiment of the present invention, when the viscosity
of the paint composition at about 25°C is about 100-120 sec/FC4/30 dc, In

another example embodiment the paint can be formulated in all kinds of available
colours and colour combination using specific available colour pigments as
known in the art.
[0028] According to the present invention, the paint composition may have a low
viscosity as compared with a conventional high-viscosity CNSL resin, and thus
may be used for forming a coating layer having excellent characteristics using a
solvent as a viscosity-dropping agent. The paint composition may also have high
working efficiency owing to the low viscosity. Furthermore, the paint composition
may have excellent water resistance and low-temperature curability to be usefully
employed as a coating agent in various industrial fields. In addition, the specific
gravity noted (gms/cc): 1.35.
[0029] According to the present invention, paint composition contain emulsifier,
anti corrosion pigments viz. zinc phosphates, iron oxides, silica of 2 - 5% , colour
pigments of 10-20% , deformers and driers 2 -5%.
[0030] The coating layer is made of low VOC (Volatile Organic Compound) and
Bisphenol-A free paint. To ensure the above test parameters, each ingredient
have been tested prior to use in the paint formulation during processing. The
paint manufacturing consists of the following basic procedures:
1) Mixing the pigments with sufficient vehicle (Natural resin CNSL modified) to
make the paste which has the correct consistency for grinding.
2) Grinding the paste in a mill until the aggregates are broken down as indicated
by the fineness of grinding test.
3) Letting down the ground paste with the remainder materials in the formula.
4) Tinting the batch to the required colour.
5) Testing and determination of physical properties and the performance
requirements of the paint.
6) Staining, filling & packing.

Drinking water pipe coating composition & the weight percentage formula
is:
• Natural resin CNSL modified 40-60 percent,
• emulsifier 2-5%,
• titanium dioxide and non toxic colour pigments 10-20%,
• anti-corrosion pigments viz., zinc phosphate, iron oxide 2-5 %,
• fillers viz., silica powder, barites, calcium carbonate 15-25%,
• xylene 3-10%,
• DM water 20-25%,
• bentone, fumed silica, defoamer, and driers 2-5%.
Drinking water pipe coated with the disclosed anti-corrosion modified
CNSL based paint has the following characteristic:
• Strong adhesion of the coating on Ductile Iron pipe.
• Very good mechanical and physical properties viz, adequate hardness,
flexibility and high impact resistant property.
• High chemical stability, water repellent and chemical resistant properties.
• Excellent protection against UV rays and corrosion resistant properties on
aging as per Q.U.V test report (as per ASTM Standards).
• Suitable for water potability.
• Acute oral toxicity test a non toxic level tested as per the guideline of Drinking
water health standard by the water soak for 1000 hrs tested & found satisfactory.
Hence the latest invention produced as a drinking water pipeline coating material
within the container which does not pollute the water quality.
Method of forming a Coating Layer
[0031] In example embodiments of the present invention, a coating layer is
formed on an object using the above-mentioned paint composition.

[0032] Particularly, the coating layer is formed on the object by coating the
object with the aforesaid paint composition including the CNSL based anti
corrosive resin composition and others with an uniform thickness of 50 - 100
microns and preferably 70 microns. The application of the paint composition is
done with an airless spray gun. The paint composition is previously described,
so any further explanations in this regard will be omitted herein for brevity.
[0033] The object, on which the coating layer is formed, is not limited to a type
or a material. All things that require water resistance may be the objects.
[0034] Examples of the object that may require corrosion inhibition may include
all sorts of pipes including ductile iron pipes, steel pipes or the like.
[0035] After forming the coating layer on the object, the coating layer is kept at
room temperature to cure the coating layer. The air drying may be carried out by
air spray. As a result, the coating layer having desired characteristics may be
obtained.
[0036] The following tests are carried out over the Paint composition applied
over a ductile, iron pipe following national and international standards such as IS
8329, BSEN545, BSEN 598, ISO 2531 etc with results tabulated as under:


1. Adhesion test as per ASTM D4541-06-07Mpa in DIP
2. Salt Fog (ASTM B117) - 1000 hrs - No rusting, cracking, rust creepage and
blistering
3. Hardness - (ASTM D 2240) - Shore D Hardness 50.
4. Flexibility - 5% Ring deflection - Passes, no effect of Paint film.
5. Impact resistance test (ASTM D 2794) - Passes 1x62 kg.cm.
[0037] The disclosed paint composition meet harmful substances enacted
mandatory national and international standards such as IS 8329, BSEN545,
BSEN 598, ISO 2531, ISO 7186 etc.
[0038] Although the foregoing description of the present invention has been
shown and described with reference to particular embodiments and applications
thereof, it has been presented for purposes of illustration and description and is
not intended to be exhaustive or to limit the invention to the particular
embodiments and applications disclosed. It will be apparent to those having
ordinary skill in the art that a number of changes, modifications, variations, or
alterations to the invention as described herein may be made, none of which
depart from the spirit or scope of the present invention. The particular
embodiments and applications were chosen and described to provide the best
illustration of the principles of the invention and its practical application to
thereby enable one of ordinary skill in the art to utilize the invention in various
embodiments and with various modifications as are suited to the particular use
contemplated. All such changes, modifications, variations, and alterations
should therefore be seen as being within the scope of the present invention as
determined by the appended claims when interpreted in accordance with the
breadth to which they are fairly, legally, and equitably entitled.

WE CLAIM:
1. An anti-corrosive low VOC natural Cashew Nut Shell Liquid (CNSL) modified
resin based paint comprising of:
Natural resin CNSL modified 40-60 %, emulsifier 2-5%, titanium dioxide and
nontoxic colour pigments 10-20%, anti-corrosion pigments 2-5 %, fillers 15-25%,
xylene 3-10%, DM water 20-25%, bentone, fumed silica, defoamer, and driers 2-
5%.
2. An anti-corrosive low VOC natural Cashew Nut Shell Liquid (CNSL) modified
resin based paint as claimed in claim 1, wherein anti-corrosion pigments
includes zinc phosphate, iron oxide.
3. An anti-corrosive low VOC natural Cashew Nut Shell Liquid (CNSL) modified
resin based paint as claimed in claim 1, wherein fillers includes silica powder,
barites, talc.
4. An anti-corrosive low VOC natural Cashew Nut Shell Liquid (CNSL) modified
resin based paint as claimed in claim 1, wherein said paint is free from
Bisphenol-A.
5. An anti-corrosive low VOC natural Cashew Nut Shell Liquid (CNSL) modified
resin based paint as claimed in claim 1, wherein the said paint at 25° C have a
viscosity of 100-120 sec / FC4/30 dc.
6. An anti-corrosive low VOC natural Cashew Nut Shell Liquid (CNSL) modified
resin based paint as claimed in claim 1, wherein the said paint is formulated in
all types of colour or colour combination.

7. An anti-corrosive low VOC natural Cashew Nut Shell Liquid (CNSL) modified
resin based paint as claimed in claim 1, wherein it includes the drying
mechanism without any curing agent.
8. An improved process for the preparation of anti-corrosion low VOC natural
Cashew Nut Shell Liquid (CNSL) modified resin based paint comprising the
steps of:
mixing the pigments with sufficient vehicle (Natural resin CNSL modified) to
make the paste which has the correct consistency for grinding;
grinding the paste in a mill until the aggregates are broken down as indicated by
the fineness of grinding test;
letting down the ground paste with the remainder materials in the formula;
tinting the batch to the required colour;
testing and determination of physical properties and the performance
requirements of the paint; and
staining, filling & packing wherein the components of the paint is Natural resin
CNSL modified 40-60 %, emulsifier 2-5%, titanium dioxide and nontoxic colour
pigments 10-20%, anti-corrosion pigments 2-5 %, fillers 15-25%, xylene 3-10%,
DM water 20-25%, bentone, fumed silica, defoamer, and driers 2-5%.
9. An improved process as claimed in claim 8, wherein anti-corrosive pigments
includes zinc phosphate, iron oxide.
10. An improved process as claimed in claim 8, wherein fillers includes
silica powder, barites, talc.
11. An improved process as claimed in claim 8, wherein said paint is free
from Bisphenol- A.

12. An improved process as claimed in claim 8, wherein the said paint at
25° C have a viscosity of 100-120 sec / FC4/30 dc.
13. An improved process as claimed in claim 8, wherein the said paint is
formulated in all types of colour or colour combination using colouring pigments.