CLIAMS:1. Cardanol based colour stable epoxy hardeners having
Formula I

wherein
R = CH2
R1 = ;
or
Formula II

wherein
R = CH2
R1 = ;
or
Formula III

wherein
R = CH2
R1 = .

2. Method for production of cardanol based colour stable epoxy hardeners comprising following steps
(a) Preparation of cardanol glycidyl ether:
i. taking distilled cardanol in a flask;
ii. adding epichlorohydrin to it along with sodium hydroxide flex;
iii. heating the mixture at 130- 180 °C for 4- 8 hrs and allowing it to be cooled;
iv. washing the resultant product with distilled water to remove excess of alkali and salt formed during the reaction;
v. removing the excess of epichlorohydrin by vacuum distillation;
vi. analyzing the produced cardanol glycidyl ether for its purity;
(b) Preparation of phenalkamine hardeners:
i. reacting the cardanol glycidyl ether prepared in step (a) with cycloaliphatic and polyethylene amines in a flask by slowly adding at temperature 25- 80 °C and adding solvent for making homogenous mixture;
ii. dissolving liquid epoxy resin in solvents;
iii. adding the epoxy liquid resin to mixture of step (ii) at temperature 25- 80 °C for producing the phenalkamine hardener;
(c) Preparation of phenalkamide hardeners:
i. reacting the Cardanol glycidyl ether prepared in step (a) with of cycloaliphatic and polyethylene amines by slowly adding at temperature 25- 60 °C;
ii. reacting the above reaction product to dimer fatty acid in a flask;
iii. dissolving liquid epoxy resin dissolved in solvents;
iv. adding to mixture of step (ii) at temperatures 25- 80°C for producing the phenalkamide hardener.

3. Method of production of cardanol based colour stable epoxy hardeners as claimed in claim 2 step (a) (i), wherein the amount of distilled cardanol taken is 40- 50 %.

4. Method of production of cardanol based colour stable epoxy hardeners as claimed in claim 2 step (a) (ii), wherein the amount of epichlorohydrin and sodium hydroxide flex taken is 50- 60 % and 15- 20%.

5. Method of production of cardanol based colour stable epoxy hardeners as claimed in claim 2 step (b) (i), wherein the amount of cardanol glycidyl ether taken is 60- 65 %.

6. Method of production of cardanol based colour stable epoxy hardeners as claimed in claim 2 step (b) (i), wherein the amount of polyfunctional amines and solvents taken are 35- 40 % and 2- 10%.

7. Method of production of cardanol based colour stable epoxy hardeners as claimed in claim 2 step (b) (ii), wherein the amount of liquid epoxy resin taken is 13- 18 %.

8. Method of production of cardanol based colour stable epoxy hardeners as claimed in claim 2 step (c) (i), wherein the amount of cardanol glycidyl ether taken is 60- 65 %.

9. Method of production of cardanol based colour stable epoxy hardeners as claimed in claim 2 step (b) (i), wherein the amount of cardanol glycidyl ether and polyfunctional amines taken is 60- 65 % and 30- 35 %.

10. Method of production of cardanol based colour stable epoxy hardeners as claimed in claim 2 step (c) (ii), wherein the amount of dimer fatty acid taken is 60- 65 %.

11. Method of production of cardanol based colour stable epoxy hardeners as claimed in claim 2 step (b) (iii), wherein the amount of liquid epoxy resin taken is 7- 10 %.

12. Method of production of cardanol based colour stable epoxy hardeners as claimed in claim 2 step (b) (i), wherein optionally 5- 30% of reactive diluents are added to the reaction along with cardanol glycidyl ether.

13. Method of production of cardanol based colour stable epoxy hardeners as claimed in claim 12, wherein the reactive diluents are selected from phenyl glycidyl ether, cresol glycidyl ether, C12-C14 glycidyl ether, 1-4 and 1-6 diglycidyl ether, Cardura E.

14. Method of production of cardanol based colour stable epoxy hardeners as claimed in claim 2 step (c) (i), wherein optionally 16- 28% of standard polyamide is added to the resultant product of to produce solvent free phenalkamide hardeners.

15. Method of production of cardanol based colour stable epoxy hardeners as claimed in claim 2 step (c) (ii), wherein optionally 5- 10% of monocarboxylic fatty acids are added along with dimer fatty acids is 60- 65 %.

16. Method of production of cardanol based colour stable epoxy hardeners as claimed in claim 15, wherein the monocarboxylic fatty acid is selected from soya fatty acid, safflower fatty acid and DCO fatty acid.

17. Method of production of cardanol based colour stable epoxy hardeners as claimed in claim 2, wherein the polyfunctional amines are selected from ethylene diamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, isophorone diamine, para-amino cyclohexylmethane, MACM (CAS No. 6864-37-5), metaxylelene diamine, 1-3 BAC, hexamethylene diamine and Vestamin TMD.

18. Method of production of cardanol based colour stable epoxy hardeners as claimed in claim 2 step (b) (i), wherein the solvents are selected from p-tertiary butyl phenol or p-nonyl phenol.

19. Method of production of cardanol based colour stable epoxy hardeners as claimed in claim 2, wherein the liquid epoxy resin are selected from EPON 828 and GY250. ,TagSPECI:FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)

1. TITLE OF THE INVENTION:
Cardanol Based Colour Stable Epoxy Hardeners
2. APPLICANT:

(a) NAME : BPC INNOVATION LLP
(b) NATIONALITY : Indian
(c) ADDRESS : 204, Siddharth Complex
R.C. Dutt Road, Alkapuri
Vadodara 390 007
Gujarat – India

3. PREMABLE TO THE DESCRIPTION:

The following specification particularly describes the invention and the manner in which it is to be performed.

Field of the invention
The present invention relates to cardanol based epoxy hardeners which have enhanced colour stability. More particularly the present invention deals with the cardanol based epoxy hardeners which do not develop colour upon long term sun and heat exposure.

Background and prior art of the invention
Cashew Nut Shell Liquid (CNSL), an agricultural renewable resource and the by-product of the cashew industry, holds a considerable promise in the different directions because it is the source of unsaturated hydrocarbon phenol, an excellent monomer for thermosetting polymers production. Vacuum distillation of CNSL yields a pure cardanol. The distilled cardanol will have major portion of cardanol and cardol and methyl cardol in small quantities.
They get oxidized rapidly and develop reddish brown colour in distilled cardanol in few days of storage. Heating of freshly distilled cardol containing cardanol also gives reddish colour. The cardanol has the following structure:

Removal of cardol, methyl cardol and its derivatives give pale coloured cardanol and is fractionally distilled to get light coloured cardanol. These light coloured cardanol hardeners are said to be colour stable because they do not change colour on storage, however, epoxy films cured with these hardeners tend to yellow in short time when exposed to weather.
This defect in cardanol based epoxy hardeners is seen due to the stearic hindrance at the Para position to the hydroxyl group because of the long side chain in Meta position which leads to auto-oxidation and develops colour. The hydroxyl group of the cardanol can be blocked by either epoxydation or ethoxylation. The epoxidation is done by reacting cardanol with epichlorohydrin under alkaline conditions. Ethoxylation can be done by reacting cardanol with ethylene oxide under high pressure and using suitable catalyst.
Also upon the weathering of the epoxy film having cardanol based curing agents the triene derivatives of various components of the distilled cardanol tend to develop colour. Epoxydation of the triene derivatives in cardanol have been done by reaction with organic peroxides. The cardanol based epoxy hardeners when used tend to chalking and darkening in colour upon exposure to the sun or heat.
Phenalkamine curing agents are a class of Mannich bases obtained by reaction of a cardanol-containing extract derived from cashew nutshell liquid, an aldehyde compound, such as formaldehyde, and an amine. Commercially available phenalkamines use ethylenediamine and diethyltriamine as the amine. When phenalkamine product available form Mannich reaction of cardanol-extract is reacted with fatty acids then the resultant product is called phenalkamide.
Due to the colouration of the cured coatings, epoxy resin compositions containing phenalkamine curing agents have been limited to use as primers and generally cannot be used as top coat material.
The US patent 6262148 claims production of a novel cardanol based phenalkamine compound using a Mannich base reaction. The reaction comprises of Mannich base reaction product obtained by combining an extract from cashew nutshell liquid with at least one aromatic or alicylic polyamine and at least one aldehyde compound. However, the use of an aldehyde in the manufacture process produces harmful byproducts and also the cardanol based phenalkamide hardener tends to chalk and forming a yellowish colour upon reaction with sunlight.
The other class of hardeners is Polyamides which have limitation for low temperature curing. The curing of epoxy composition with Polyamides and similar hardeners take very long time, sometimes several days, below 10°C temperature. The phenalkamine or phenalkamide hardeners available in the market are useful for low temperature curing. However, they can not be used in top coats in epoxy coating system for causing discoloration of epoxy films on weathering. The conventional cardanol based epoxy hardeners and the available prior art creates a major need for a class of colour stable cardanol based epoxy hardeners which may be used as top coat agents for the coating industries.

Object of the invention
The main object of the present invention is to provide cardanol based colour stable epoxy hardeners.
Another object of the present invention is to provide cardanol based colour stable epoxy hardeners which provide colour stability upon exposure to heat, U. V. radiation and sunlight.
Another object of the present invention is to provide cardanol based epoxy hardeners which are prepared by a reaction without addition of an aldehyde.
Yet another object of the invention is to provide cardanol based epoxy hardeners which have low curing temperature of upto 0°C.

Summary of the Invention
The present invention discloses cardanol based colour stable epoxy hardeners. In the present invention the cardanol glycidyl ether is used as a starting material for producing the cardanol based phenalkamine and phenalkamide hardeners. The cardanol based phenalkamine and phenalkamide epoxy hardeners have the property of colour stability for a long time. The present invention also claims low curing temperatures for the present hardeners, as low as 0°C.

Detailed description of the invention
The nature of the invention and the manner in which it is performed is clearly described in the specification. The invention has various components and they are clearly described in the following pages of the complete specification.
The present invention deals with the manufacture of cardanol based colour stable epoxy hardeners. The cardanol based epoxy hardeners are of the phenalkamine and phenalkamide varieties.
The defects seen in the prior art due to unoccupied para position to the hydroxyl group of the cardanol are overcome by reacting the hydroxyl group of cardanol with epichlorohydrin to convert it to a stable form of cardanol glycidyl ether by the following process:
(a) 40- 50% of distilled cardanol is taken in a flask.
(b) 50- 60% of epichlorohydrin is added to it along with 15- 20% of sodium hydroxide flex.
(c) The mixture is heated at 130 – 180 °C for 4-8 hrs and then cooled.
(d) The resultant product is washed with distilled water and the excess of epichlorohydrin is removed.

Also the hindrance caused by the triene derivatives of cardanol is solved by epoxydation by reaction with organic peroxides.
The reaction is given below:

The same processes to remove hydroxyl group and triene derivatives are used for the freshly distilled cardanol having cardol and methyl cardol.
The produced cardanol glycidyl ether is used as the starting product to produce the cardanol based colour stable epoxy hardeners.

Cardanol based phenalkamine hardeners
FORMULA I

Where, R = CH2
R1 =

The cardanol based phenalkamine epoxy hardeners are prepared by following process:
(a) 60- 65% of cardanol glycidyl ether is reacted with 35- 40 % of various aliphatic and cycloaliphatic amines at 25- 80 °C along with 2- 10% of p-tertiary butyl phenol or p-nonyl phenol to make homogenous mixture.
(b) The alternate step is carried out in step (a) by partly replacing cardanol glycidyl ether by other reactive diluents.
(c) Various other glycidyl ethers are also blended with cardanol glycidyl ether to produce polyamines.
(d) Polyamines produced above is further reacted with 13- 18% of liquid epoxy resin of EPON™ 828 or GY250; alone or mixed with reactive diluents at 25- 80 °C to make epoxy adducts of cardanol based colour stable phenalkamines.

The reaction to produce polyamines is given below:

The reaction to produce cardanol based phenalkamine hardeners is as follows:

Wherein
R = CH2
R1 =

Cardanol based phenalkamide hardeners
FORMULA II

Where, R = CH2
R1 =

Cardanol based solvent free phenalkamide hardeners
FORMULA III

Where, R = CH2
R1 =

The cardanol based phenalkamide epoxy hardeners are prepared by following process:
(a) 60- 65% of cardanol glycidyl ether is reacted with 30- 35% of cycloaliphatic and polyethylene amines in a flask at 25- 60°C.
(b) The alternate step is carried out in step (a) by partly replacing cardanol glycidyl ether by other reactive diluents.
(c) The resulting product is reacted with 32- 40% of dimer fatty acid alone or mixed with 5- 10% of mono carboxylic fatty acid to produce phenalkamides.
(d) An alternate step is carried out in step (c) by reacting the resultant product of step (a) with standard polyamides at specific temperature.
(e) The above phenalkamides are reacted with 7- 10% of liquid epoxy resin of EPON™ 828 or GY250 alone or mixed with reactive diluents to make epoxy adducts.

The reaction to produce cardanol based phenalkamide hardener is given below:

Wherein
R = CH2
R1 =

The alternate reaction to produce cardanol based phenalkamide hardeners by reacting with standard polyamides is as follows:

Wherein
R = CH2
R1 =

The aliphatic amines used in the present invention are selected from polyethylene amines viz. ethylene diamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), pentaethylenehexamine (PEHA) etc. While the cycloaliphatic amines are selected from viz. isophorone diamine (IPDA), para-amino cyclohexylmethane (PACM), MACM (CAS No. 6864-37-5) etc. Other amines like metaxylelene diamine (MXDA), 1-3 BAC, hexamethylene diamine and Vestamin® TMD are also used.
The diluents used in the reaction are selected from phenyl glycidyl ether (PGE), cresol glycidyl ether (CGE), C12-C14 glycidyl ether, 1-4 and 1-6 diglycidyl ether, Cardura™ E, etc. and are added in the range of 5 – 30%.
The mono carboxylic fatty acids employed in the preparation of phenalkamide hardeners are selected from soya, safflower, DCO fatty acids.
The present invention has an advantage that no aldehydes are used in the process to manufacture the phenalkamines and phenalkmides hardeners.
Further advantage is that the phenalkamine and phenalkamide hardeners produced in the invention possess physical properties which provide them lower curing temperature and enhanced colour stability which makes the use of the same in any weather and temperature and for the top surface coating.

The invention is illustrated more in detail in the following examples. The examples describe and demonstrate embodiments within the scope of the present invention. These examples are given solely for the purpose of illustration and are not to be construed as limitations of the present invention, as many variations thereof are possible without departing from the spirit and scope.

Example 1: Process to produce the cardanol glycidyl ether
(a) One mole of distilled cardanol was taken in a four necked flask fitted with stirrer and condenser.
(b) 3- 6 moles of epichlorohydrin was added to it along with 41.5 gm of sodium hydroxide flex.
(c) The mixture was heated at 130- 180 °C for 4- 8hrs and was allowed to be cooled.
(d) The resultant product was then washed with distilled water to remove excess of alkali and salt formed during the reaction. The excess of epichlorohydrin was removed by vacuum distillation.
(e) The product was analyzed for its purity.

Example 2:
Similar reaction as stated in Example 1 to produce cardanol glycidyl ether was repeated using one mole of distilled cardanol free of cardol and methyl cardol to get lighter cardanol glycidyl ether.

Example 3: Process to produce the cardanol based phenalkamine hardener
(a) One mole of the cardanol glycidyl ether (C.G.E.) prepared in Example 1 was reacted with 1.05 moles of tetraethylene pentamine (TEPA) in a four necked flask fitted with stirrer and reflux condenser by slowly adding at temperature 25- 60 °C.
(b) Two to ten parts by weight p-tert-butyl phenol was added in the above reaction product in hot condition to make homogenous mixture.
(c) 15.5 gm of liquid epoxy resin EPON™ 828 dissolved in 5 gm n-butyl alcohol and 18gm xylene was added to above mixture at temperatures 25- 60 °C to get the phenalkamine hardener.

Example 4: Process to produce the cardanol based phenalkamine hardener
The same process was carried out with an alternate step of reacting about two to ten parts of p-nonyl phenol in the step (b) of Example 3.

Example 5: Process to produce the cardanol based phenalkamine hardener
The same process was carried out with alternate step of adding calculated quantity of liquid epoxy resin GY250 in the step (c) of Example 3.

Example 6: Process to produce the cardanol based phenalkamide hardener
(a) One mole of the cardanol glycidyl ether (C.G.E.) prepared in Example 1 was reacted with 1.05 moles of tetraethylene pentamine (TEPA) by slowly adding at temperature 25- 60 °C.
(b) The above reaction product was further reacted to 520 gm of dimer fatty acid in a four necked flask fitted with stirrer and reflux condenser.
(c) 40 gm liquid resin GY250 dissolved in 2 gm n-butanol and 8 gm xylene were added to above mixture at temperatures 25- 60 °C to get the phenalkamide hardener.

Example 7, 8 and 9: Process to produce the cardanol based phenalkamide hardener
The same process was carried out with an alternate step of adding 5 to 10 % of mono carboxylic fatty acids soya / safflower / DCO respectively fatty acid mixed with dimer fatty acid in the step (b) of Example 6.

Example 10: Process to produce the Solvent free cardanol based phenalkamide hardeners
Sr.no. Ingredients Example 10 Example 11 Example 12
1. Reaction product prepared in example 6 step (a) 245 gm 375 gm 415 gm
2. Standard polyamide 40 gm 25 gm 25 gm
3. GY250 70 gm 57.5 gm 50 gm
4. Cardanol glycidyl ether 145 gm 42.5 gm 10 gm

Method of Preparation of Standard polyamide:
285 gm of dimer fatty acid and 35 gm of soya fatty acid were taken in a one litre four necked flask fitted with stirrer and reflux condenser. 180 g triethylenetetramine (TETA) was added to the mixture. The mixture was heated slowly upto 160 °C till water of reaction started to distill off. The heating was continued step by step upto 220 °C and further upto 270 °C. The produced standard polyamide was cooled.

General process for preparation of solvent free cardanol based phenalkamides
(a) The reaction product of Example 6 step (a) was further reacted to the standard polyamide prepared above in a four necked flask fitted with stirrer and reflux condenser with continuous stirring to get a homogeneous mixture.
(b) GY250 and cardanol glycidyl ether were added to the above said mixture at 25 to 60 °C for 3 to 4 hours.
(c) The reaction mixture was stirred for further 2 hours after completion of addition of GY250 and cardanol glycidyl ether.
(d) The produced solvent free cardanol based phenalkamide hardener was evaluated for its physical properties by comparison with the standard polyamides available in market viz. Versamid® 115, 125 and 140 by Huntsman, respectively.

RESULT:
(I) For solvent free phenalkamide prepared by process of Example 10
Sr.no. Physical Properties Solvent free phenalkamide Standard polyamide (Versamid® 115)
1 Viscosity @ 40°C
50000- 75000 50000- 75000
2 Amine Value
230- 260 230- 260
3 Color
10 max 10 max
4 Sp Gravity @ 25°C
0.95-0.97 0.95-0.97
5 Drying @ 25°C
4 hours 7- 8 hours
6 Drying @ 5°C
14 hours Does not dry for several days
7 Blush Resistance
1 hours recovery 1 hours recovery
8 Flexibility Passes extreme flexibility @ 130°C for 1 hr.
Passes extreme flexibility @ 130°C for 1 hr.

9 Gel time @25°C for 100gm mass
70 minutes 120 minutes
10 Adhesion Adhesion on MS Panel with 500 microns DFT paint film.
Satisfactory Adhesion on MS Panel with 500 microns DFT paint film.
Satisfactory.
11 Corrosion under Salt spray
B117; 75 Microns DFT.
( 500 HRS) No corrosion Few blisters on cross. Sl corrosion at the cross.

(II) For solvent free phenalkamide prepared by process of Example 11
Sr.no. Physical Properties Solvent free phenalkamide Standard polyamide (Versamid® 125)
1 Viscosity @ 40°C
8000- 12000 8000- 12000
2 Amine Value
330- 360 330- 360
3 Color
10 max 10 max
4 Sp Gravity @ 25°C
0.95- 0.97 0.95- 0.97
5 Drying @ 25°C
2.5 hours 5- 7 hours
6 Drying @ 5°C
13 hours Does not dry for several days
7 Blush Resistance
< 2 hours recovery 2 hours recovery
8 Flexibility Passes extreme flexibility @ 130°C for 1 hr.
Passes extreme flexibility @ 130°C for 1 hr.

9 Gel time @ 25°C for 100gm mass
40 minutes 80 minutes
10 Adhesion Adhesion on MS Panel with 500 microns DFT paint film.
Satisfactory Adhesion on MS Panel with 500 microns DFT paint film.
Satisfactory
11 Corrosion under Salt spray
B117; 75 Microns DFT.
(500 Hrs.) No corrosion No corrosion

(III) For solvent free phenalkamide prepared by process of Example 12
Sr. no. Physical Properties Solvent free phenalkamide Standard polyamide (Versamid® 140)
1 Viscosity @ 40°C
3000- 6000 3000- 6000
2 Amine Value
370- 400 370- 400
3 Color
10 max 10 max
4 Sp Gravity @ 25°C
0.95- 0.97 0.95- 0.97
5 Drying @ 25°C
3 hours 5-7 hours
6 Drying @ 5°C
14 hours Takes several days to dry
7 Blush Resistance
< 2 hours recovery 2 hours recovery
8 Flexibility Passes extreme flexibility @ 130°C for 1 hr.
Passes extreme flexibility @ 130°C for 1 hr.

9 Gel time @ 25°C for 100gm mass
35 minutes 100 minutes
10 Adhesion Adhesion on MS Panel with 500 microns DFT paint film.
Satisfactory Adhesion on MS Panel with 500 microns DFT paint film.
Satisfactory
11 Corrosion under Salt spray
B117; 75 Microns DFT.
(500 Hrs.) No corrosion No corrosion

Example 11:
The experiments were carried out by preparing the test panels by mixing the hardeners from Examples 3 and 10 along with epoxy glossy paint base for exterior exposure and for accelerated weathering as follows:

Method of Preparation of Epoxy glossy paint base:
The epoxy glossy paint base was prepared by using requisite amount of GY250, Araldite® 6071x75 of Huntsman, rutile TiO2, barytes, talc, BYK Additive, n-butanol and Bentone SD2.

Exterior exposure:
7.5 x 15 cm MS panels were abrasive blasted and primed with standard epoxy primer. These primed panels were applied with two coats with epoxy glossy paint prepared which has been prepared by mixing epoxy glossy base prepared with phenalkamine hardeners and phenalkamide hardeners produced in Example 3 and Example 10, respectively. The paint films were allowed to cure at 25 °C for 7 days in laboratory. The panels were then exposed to weathering by placing at 45° angle on the racks facing south.
The test panels for the phenalkamines, phenalkamides and polyamides available in the market were also prepared in the same fashion for comparison. The inspection was been done periodically to check yellowing of the exposed epoxy paint films.

Accelerated Weathering:
7.5 X 15 cm MS panels were thoroughly degreased using solvents. They were sanded with fine sand paper. Two coats of epoxy glossy white paint prepared by mixing epoxy glossy base with phenalkamine hardeners and phenalkamide hardeners produced in Example 3 and Example 10 respectively were applied to the surface. The painted panels were allowed to cure at 25 °C for 7 days in laboratory. The panels were subjected to artificial weathering in ATLAS weatherometer.
Similar panels were prepared using the phenalkamines, phenalkamides and polyamides available in the market as hardeners for comparison. The inspection was done periodically to check extent of yellowing of the exposed epoxy films.

RESULT:
The panels with the hardeners from Example 3 and Example 10 showed enhanced colour stability when compared to the phenalkamines and phenalkamides available in market, respectively. The same is shown in the figures 1 and 2 with visible colour darkening on the side of the phenalkamines and phenalkamides available in market.
Although the preferred embodiment as well as the preparation and use have been specifically described, it should be understood that variations in the preferred embodiment could be achieved by a person skilled in the art without departing from the spirit of the invention. The invention has been described with reference to specific embodiments which are merely illustrative and not intended to limit the scope of the invention as defined in the claims.