Focus:

Studies on cyclohexanone formaldehyde- Styrenated CNSL coatings.

V D Athawale and N J Shetty

D e p a r t m e n t o f Chemistry, Universi ty o f Mumbai ,Vidyanagar i (East), Mumbai 400 098, India

Inlroduclion In parts of the world ketonic (cyclohexanone forn~aldehyde) resins, due to their high compatibility and solubility with a wide range of film-formers, >~ play a prime role in the field of coatings (paints, inks, varnish, and lacquer) as an excel- lent additive. However, meagre information r is available where ketonic (cyclohexanone formaldehyde) resin is used as a blend for the improvement of coating properties. Ketonic resin in a blend with another coating polymer may serve as a modifier for the other fihn-former, or it may be the principal f-tim-former, while the polymer may serve as a modifier to improve certain properties of the ketonic resin.

Summary Studies on cydohexanone Iormaldehyde - Styrenated CNSL blended coatings.

Commercial blends were prepared from Ketonic (Cyclohexanone Formaldehyde) - Cashew out shell liquid (CNSL)-slwenated resin and lheir cooling properlies such as drying lime, hardness, adhesion, flexibilily, gloss, skinning tendency, impact resistance and chemical resistance were studied for different compositions. The scope of the work was to produce a better combination of properties lhan lhose of lhe individual comonenls.

It was observed lhat lhe blend of of 50:50 percent (w/w) of ketonic (cyclohexanone formaldehyde) - slyrenated CNSL resin shows a notable improvement in cooling properlies over lhose of individual resins.

Studieu iiber Beschichlungsslofle aus Mischungen von Cydohexanon-Formaldehyd und styrolisiertes Cashewnuss~lbarzen.

Man stellte Kommerzielle Mischungen aus Keton (Cyldohexanon-Formddehyd) - Cnshewn~i~l-Slyrolen Harzen her und denen Beschichtungs ei@nschaften solch als Trockeazeit, Nrte, Adhiision, FlexibiltiJt, Glanz, Haulbildung,Sschl@esligkeit und Chemikoliea bestiindigkeit wurden bei verschiedenen Zusammensetzungen studiert. Der Neck dieser,%heit war die Schaffung eine bessere Komhination der Eigenschaften als de@nigen individuelles Komponents. Es wurde notiert, dass die Mischung van 50:50 proceatunler Gewichlsanteil der Ketun (Cyklohexanon-Formddehyd) und slyrolisiertes CosbewnessGIharze zeigt eine hetTiichltiche Verbesserung gegenOber denjenigen des iadividuellen Harzes.

Etudes sur revilements fi base de m&lmjes des r~sines de cyr el d'huile d'~cales d~ noix d'acajou stymlis~e.

On n pr~par~ des m61anges commercJelles des r~Jnes c~tunJques (cyclohexanone-formol) et d'huile d'~cales de noix d'acaju styrolJs~e et I'on a ~tudJ~, aux dJverses compositions, leurs coroct6ristiques en taut que rev~tements telles que temps de s~chage, duret6, adh6rence, flexiblJt6, brillant, formation de peau, r~sistance au choc et aux produils chJmJques. Le but de ces tTavaux ~taJt de r~aliser une meJlleure combination de proprJ~t~s que celles de chaque consfituant. On a remarqu~ que la 50:50 m~lage par pourcentage pond~rol des r6sines c6toniques (cyclohexanone-formol) et d'huile d'~cdes de noix d'aeajou met en 6vJdence une amelioration notable des caract~rJsliques du rev~tement en comNraison de cellos de chaque r~sJne JndJvJduelle.

Blending with 'coating resins' provides a variety of ways to improve the performance of ketonic resins.

Cashew mlt shell liquid (CNSL) containing 90% anacardic acid and 10% of a phendic compound, cardanol, is used in the preparation of resins, lacquers and varnishes. 8 The mod- ification of CNSL with styrene, improves the water and acid resistance of the coatings Hence, to produce a cost effec- tive, as well as a high performance coating system, a com- prehensive study of the effect of blended resins on the coat, hag properties was carried out.

Essentially, the present paper reports the effect of keton- ic (cyclohexanone formaldehyde) - styrenated CNSL (pre- pared from CNSL oil, styrene, and hexamine) resin blends on the coating properties such as drying thne, adhesion, hardness, flexibility, gloss, storage stability, impact resis- tance and chemical resistance.

Experimenlal Materials Ketonic (cyclohexanone formaldehyde) resin having the specification which appears in Table 1 was obtained from Hindustan Inks (IVlumbai, India). The structure of cyclohexa- none formaldehyde resin as suggested by Tilichemko 1~ is shown in Scheme I. CNSL refined oil as per Indian Standard (IS-840) was obtained from a local dealer of repute. Styrene and Hexamine (nRnhnum assay 99%) was purchased from Fluka, (Switzerland) and S D Fine Chem. Ltd, (Mumbai, India) respectively.

Table 1: Specifications of the ketonic (cydohexanone formaldehyde)resin.

Spedficat[on Value-Unit lesl Method

Melting point (%) 92-108 Gardner colour 50% in butyl acetate/ <2 n-butanol (85/15) Density at 20 ~ C ( g/cm t) 1.13-1.14 Acid value (rag KOH/g ) 03 Hydroxyl value ( mg KOH/g ) 330

Water content ( wt. % ) 4 max.

DIN 4625 ASTM D1544-80

DIN 53 479 DIN 53 402 DIN 53 240 ASTM E 222-67 DIN 51 777.part 1

Azoisobutyronitrile (AIBN) used as an hlitiator in the reac- tion was obtained from Fluka, (Switzerland). Solvents of minimum assay 99% (GC) were purchased from S D Fine Chem. Ltd, (Mumbai, India). All the solvents of analytical grade were used without further purification.

Synthesis The formulation used for the preparation of the resin appears in Table 2. The requisite quantity of CNSL was placed in a reaction kettle equipped with a thermometer,

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Sr 1: Synthesis of styrenated CNSL resin and [Is blend w[lh kelonk resin.

CH

~ C15H31 +

(Cardonol)

CtHsCH=CH 2

Styrene

AIBiq

(CH2)6N 4 + 3H20 Hexamine

OH

C15H31 CNSL (r

HCHO

..CH 2 OH

0 CH2~_ "10S "ill2 _n O

Ketonk (Cyclohexanone Formaldehyde) Resin

OH

~ CH2-CH2-C6H s

ClsH31 O-CNSL-Slyrene product

OH

CH2~fl2-f6fls P-CNSL-Slyrene product

4 NH 3 + 6 HCHO

+ 1

OH OH

water condenser, stirrer and ni t rogen inlet. The oil was heat- ed to 100~ and one fourth of the total required quantity of the initiator (AIBN) was a d d e d to the kettle. The requisite quantity of styrene containing half the total required quanti- ty of initiator was then a d d e d dropwise into the kettle through the Y-adapter. After the monomer addit ion was completed, the rest of the initiator was a d d e d and heat ing cont inued in an a tmosphere of ni t rogen until a reduct ion in the rate of reflux of the material was observed. Hexamine was added in small quantities in 10-15 minutes to the styre- na ted CNSL product, and the temperature was maintained at 135~176 after which it was raised slowly m 240~ and mainta ined at be tween 240~176 for 30 minutes. The resin formation was confirmed by IR analysis of the product. IR specn-um of CNSL styrene resin showed a band at 3000 cm -t attributed to alkene C-H stretching. The peaks at 1600, 1460, 920 and 700 cm -z are attributed to aromatic ring, vinyl group, mono, meta and symmetrical tri substitution with a r ing bend ing vibrat ion respectively. The resin obtained was dissolved in a solvent system (xylene, cyclohexanone, butanol in the ratio of 50:30:20 by volume respectively) to make 50% solution. The ketonic resin was also thinned to 50% solids by using the same solvent system utilised for CNSL-styrene resin.

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, Blend

Driers Driers used in the study were obta ined from Narchem Industries (Mumbai, India). The system used for the blends was of the following combination.

Driersw[lh theft metal cenlenl Perr by weighl of resin solid

Lead Napthenate (18%) 0.50 Copper Napthenate (6%) 0.20 Manganese Octoates (6%) 0.05

The percent of driers used were as pe r the resin solids.

Tests carried out for the study of coating propert ies

Drying Timer 2 Drying times for the b lend propor t ions were deternm~ed at 80% hmnidity and at 30~ temperature, The samples were appl ied onto mild steel panels using a 50p Sheen bar coater and the time noted for surface as well as tack-free drying.

Hardness: 13 Panels coated uniformly with the sample using bar coater were a l lowed to dry for a week before test. ing. A comparative measurement of hardness was achieved by rating the hardness with lead pencils,

Gloss: 14 The gloss of the film is assessed by measuring the reflectance of the coated panel. Glass panels were coated with different samples, and their gloss characteristics were measured using a Sheen gloss meter at an angle of 60 ~ .

Adhesion:13 Sample coated mild steel panels were a l lowed to mature for a week before undergoing the test. The cross-cut adhes ion me thod was

employed for the above adhesion test, Flexibility:l~ Flexibility of the film was measured by the

conical mandrel test, on tin plates that were a l lowed to dry for a week before checking flexibility on a conical mandrel (1/4").

Storage Stability: The storage stability of the samples was studied by storing them in cylindrical sample containers for four months, after which the condit ion of the surface was visually observed.

Impact Resistance: hnpact resistance is a measure of the ability of a n~aterial or structure therefrom to withstand the applicat ion of a sudden load without failure. It is measured using a falling weight type impact tester (Komal Scientific,

Table 2: CHSL-slyrene resin formulation for laboratory preparation.

Ingredients Wl. %

CNSL 50.00 Slyrene 35.00 Hexamine 04.00 AIBN (initiator) 03.00 Water 07.25 Curing agents 00.75

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Mumbai, India). The machine is driven by gravity. In this method a hemispherical indenter of known weight is dropped down on to the panel, which is fixed at the base of the instalment, An opening opposite to the indenter in the base support on which the panel rests permits deformation of the panel, The indenter is dropped from varying heights until the film cracks (The maximum height of the instrument is 48 inches and weight of the indenter is 2.82 k~. The direct impact test is carried out with the coated side facing upwards, and downwards for reverse knpact test, Prior to the testing of the above property the films were matured on mild steel panels for ten days.

Chemical resislance Water immersion test: Glass panels coated with samples of different proportions were allowed to dry for three days, The periphery of the glass panels was coated with wax in order to restrain the migration of water under the film from open ends. The panels were then dipped into water and were examined for the change in the appearance and disap- pearance after 24 hours.

Acid immersion test: Coated glass panels were prepared as mentioned in the water i~m~ersion test, These panels were dipped into 3 percent (w/w) sulphuric acid sdution and the change in the appearance was monitored after 24 hours.

Resulls and Discussion A detailed study was carried out on the coating properties of different blend ratios. When the blends were studied below 10% (w/w) concentration of the individual resin no signifi- cant changes were observed.

Drying Time: It was observed from Fig-ure 1, that surface drying and tack-free drying time improved remarkably with the increase in the concentration of the styrenated CNSL resin in the blends. Drying is explained as the intake of oxy- gen by the film former. The blending ratio of 50:50 (% w/w) shows a notable fast drying time, Ketonic (cyclohexanone formaldehyde) resin contains carbonyl groups in the poly- mer backbone chain. This carbonyl group activates the methylene group in the ketonic resin, Therefore, in the pres- ence of suitable driers, the oxygen activation of the methyl- ene group is further accelerated and that results in faster drying. The presence of the styrenated CNSL resin adds to this property of drying to a renmrkable extent, since styre- nated CNSL resin is a fast drying resin due to its high degree of unsaturation. Hence both these characteristics of the

Figure 1: Graph of drying time (minutes) against r of ketonic resin blend (wl%).

40

~ 30

~ 20

Surface , Drying tack free

0 10 20 30 40 50 60 70 80 90 100 Concenlration of Ketonic resin in the blend, wl.%

170

resins act simultaneously to increase the oxidative crosslink- ing and hence the drying time.

Hardness: Mild steel panels coated with different blends were tested for hardness using pencils graded from 5B to 5H. Table 3 reveals that poor hardness was shown by keton- ic resin. This is attributed to the aliphatic chain of the keton- ic resin (structure shown in Scheme I). Hardness remains constant for ketonic- styrenated CNSL resin blends up to 60:40 (% w/w) concentration. On increasing the percentage (w/w) of styrenated CNSL resin in the blend, a significant improvement in the hardness of the blends was observed. This is attributed to the aromatic nature of the styrenated CNSL resin. Hence, the compatible blend prepared pos- sessed aromaticity due m which the hardness increased.

labia 3: Pencil hardness end slorage stability of Ihe

ketonir styrenated CNSL resin blends

Kelanic CNSL-styrene Hardness Skinning tendency resin (percentage w/w) (lead pendls) (after four months)

100:0 HB 90:10 HB 80:20 HB 70:30 HB 60:40 HB 50:50 H 40:60 2H 30:70 3H 20:80 5H 10:90 5H 0:100 5H

no skinning no skinning no skinning no skinning skinning skinning skinning skinning skinning skinning skinning

Gloss: Gloss of the surface depends upon the amount of light reflected or absorbed by the coating material. Figure 2 shows a gradual decrease in the gloss of the blends with increase in the percentage (w/w) of the styrenated CNSL resin. Initially, the superior gloss was due to the low colour and excellent light stability of the ketonic resin. Colour does not affect gloss.

Adhesion and Flexibility: All the blends showed excellent adhesion. Table 4 shows that the ketonic as well as styrenat: ed CNSL resin exhibits 100% adhesion.

labia4: Adhesion and flexibility of Ihe kelonic - slyrenaled CHSL blends

Ketonic(HSL-styrene resin Adhesion (percentage) Flexibilily (percentage w/w)

100:0 1 O0 pass 90:10 100 pass 80:20 1 O0 pass 70:30 1 O0 pass 60:40 1 O0 pass 50:50 1 O0 pass 40:60 1 O0 fail 30:70 1 O0 fail 20:80 1 O0 fail 10:90 100 fail 0:1 O0 1 O0 fail

The blends up to 50:50 percent (w/w) concentration of ketonic-styrenated CNSL resin passed the 1/4 bend test. The ketonic resin composed of an aliphatic chain was soft, while

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Figure 2: Graph of gloss at 60 ~ against concentration of ketonic resin blend (wl%).

0 10 20 30 40 50 60 70 80 90 100

Concentration of Kelonic resin in the blend, wl.%

styrenated CNSL resin due t o its aromaticity was hard and brittle. Therefore, on increasing the percentage (w/w) con- centration of styrenated CNSL resin in the blends, the flexi- bility declined. This can be attributed also m the high cross- linking of the styrenated CNSL resin.

Storage stability: Ketonic and styrenated CNSL resins stored without driers showed no skhming tendency. The blend ratio up to 70:30 percent (w/w) concentration of ketonic-styrenated CNSL resin showed no skinning tendency as shown in Table 3. However, on increasing the concentra- tion of the styrenated CNSL resin in the blends the skinning tendency increased. The above observation revealed that on addition of driers the skinning tendency increases. This was because of the fast drying property of the styrenated CNSL resin, which was enhanced by the addition of the driers.

of the styrenated CNSL resin was increased, the films showed superior acid resistance as can be seen in Table 5. However, at 50:50 percent (w/w) blend neither blushing nor blistering were observed.

Therefore, 50:50 percent (w/w) concentration of ketonic- styrenated CNSL resin can be considered as the optinmm concentration at which both blushing and blistering were eliminated.

Impact resistance: From Table 8, it can be seen that the blend of ketone-styrenated CNSL resin ratio 50:50 (w/w) showed the highest impact resistance. As the percentage of

Table 6: Drying lime o[ Ihe kelonic-slyrenaled CNSL resin blends

KetanicG',lSL-styrene resin Surface dry (minules) Tack-free (minutes) (percentage w/w)

100:0 35 50 90:10 15 30 80:20 14 27 70:30 13 25 60:40 11 20 50:50 06 09 40:60 07 10 30:70 08 11 20:80 09 12 10:90 10 15 0:100 12 17

Table 7: Gloss of the ketonic-slyrenaled CHSL resin blends

Kelanic(BSL-slyrene resin (percentage w/w) Gloss at 60 ~

100:0

Chemical resislance 9o:1o Water immersion test: Water resistance of the blends 80:20 increased with the increase in the percentage of the styre- 70:30 nated CNSL resin, From Table 5 it can be seen that the 60:40 blends with the higher percentage of ketonic resin showed 50:50 marked blushing but no blistering. However, above 60:40 40:60 percent (w/w) composition of the blends the blushing effect 30:70 diminished. At 50:50 percent (w/w) composition of the

20:80 blends both blushing and blistering were not observed. Acid immersion test: The ~ass panels coated wdth 10:90

ketone-styrenated CNSL resin when inm~ersed in 3% sul- 0:100 phuric acid showed marked blushing for blends containing up to 70% ketonic resin. Whereas, when the concentration

TableS: Chemical resislance of Ihe ketonic- slyrenaled CNSL blends

KelanicCHSL-slyrene resin Add resislance Waler resislance (percentage w/w)

Heavy blush, no blistering Heavy blush, no blistering Heavy blush, no blistering Heavy blush, no blistering Slight blush, no blistering Unaffected no blistering Unaffected blistering Unaffected blistering Unaffected blistering Unaffected blistering Unaffected blistering

96 95 94 92 89 86 82 75 70 64 60

100:0 90:10 80:20 70:30 60:40 50:50 40:60 30:70 20:80 10:90 0:100

Table 8: Impacl resislance of Ihe ketonic-slyrenated r resin blends

KetanicG',lSL-styrene Impact resislance (Ibs inch*)

resin (percentage w/w)

100:0 90:10

Heavy blush, no blistering 80:20 Heavy blush, no blistering 70:30 Heavy blush, no blistering 60:40 Heavy blush, no blistering 50:50 Heavy blush, no blistering 40:60 Unaffected, no blisterin~

30:70 Slight blush, blisterin

20:80 Unaffected, blisterin

10:90 Unaffected, blisterin

0:1 O0 Unaffected, blisterin Unaffected, blisterin

Direct (passes) Reverse (passes)

25 25 50 25 75 50

100 75 100 100 125 125 125 100 100 100 75 75 75 50 50 50

~he values are arrived et by multiplvin~ weight of indenter in Ibs (6.251bs) with maximum height in if~ has from where indenter fells without any visible deme~e to the film.

Surface Coatings International 2000 (4) 171

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the styrenated CNSL resin increased, the films exhibited poorer impact resistance. Ttds is due to the hardness and brittleness of the styrenated CNSL resin that leads to crack- ing of the film. On the other hand, compared to styrenated CNSL resin, ketonic resin shows better knpact resistance owing to its stlucture.

Conclusions From the foregoing studies, it can be concluded that when Ketonic (cyclohexanone formaldehyde) resin was blended with styrenated CNSL resin in the optimum ratio of 50:50 (w/w) the blend exhibited excellent coating properties such as drying time, hardness, chemical resistance, impact resis- tance, adhesion, flexibility and moderate gloss, This can be attributed to the synergistic effect of the resins.

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55, 420, 1991, Chem. Abstr. 115: 210376w, 1991.

2. Bognar J, Kovacs L and Szabo L, Hungarian Patent HP 55, 421, 1991, Chem. Abstr. 115: 210377x, 1991.

3. Penc R and Cihlar J, Czech 153, 930 1974, Cheni. Abstr. 82: 45197d

4. Sailor Pen Co. Ltd, Jpn. Kokai Tokkyo Koho JP, 58 05, 381, 1983, Chem. Abstr. 99: 55184n.

5. Ttn'cu E, Bratalescu O, Filipache M and Ionita S, Romania RO 89, 433 1986, Chem. Abstr. 106: 215609y.

6. Bugrov GA, Gorin VP, Samokhvalov AI, Tikhonov VP, Levina FS, Gilyazetclinov LP, and Matishev VA, USSR SU 1,060, 662, 1983, Chem. Abstr. 100: 158359s

7. Athawale VD and Chamankar AV, JAOCS, "75, 887~89, 1998

8. Basu DS and Kar AK, Chemical Age of fndia, 24, 6, 341-344, June 1973.

9. Shirsalkar,MM and Sivasamban MA, Paint India, 25, 12, 17-20 (Eng.), Dec. 1975.

10. Tilichenko M and Zykova LV, 'Folyl~etone'EncylqOedia of Chemical Science and Technology, 11, 273-279. John Wiley and Sons, New York.

11. Gowri VS and Saxena M, tnd, J, Chem. TechnoL, 4, 145-149, 1997.

12. ASTM D, 1640~3, American Society for Testing and Materials, Philadelphia, Pa., 06.03, 1994.

13. Odell LB, Encyclopedia Of Industrial C~)emical Analysis, Enamels, Edited by Foster Dee Snell and Leslie S Ettre, Interscience Publishers a division of John Wiley & Sons, Inc. United States of America, 12, 170-192, 1971.

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15. ASTM D 522-93a, American Society for Testing and Materials, Philadelptda, Pa., 06.03, 1994.

16. ASTM D 1647-89, American Society for Testing and Materials, Vol. 06.03, 1994.

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