Progress in Organic Coatings 76 (2013) 966–971

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Bitumen paints, an old story with new approach, part-1, solvent based paints R. Aydemir a , M. Eren a,∗ , H. As¸kun a , A.E. Özbey a , M. Orbay a,b a b

Betek Boya ve Kimya San. A.S¸., Ankara Asfaltı, Hüseyin C¸elik Sok. No. 2, Bostancı, 34742 Istanbul, Turkey Department of Chemical Engineering, Faculty of Engineering, Istanbul University, Avcılar, 34320 Istanbul, Turkey

a r t i c l e

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Article history: Received 15 July 2012 Accepted 20 August 2012 Available online 17 November 2012 Keywords: Bitumen paint Solvent based Physical modification Chemical modification

a b s t r a c t Bitumen paints have lost their importance with the advent of modern polymers during the last century, but they are still used for large area applications such as tanks and pipelines. The main application of bitumen is as road paving binder and most of the research is devoted to improving properties by physical or chemical modification by polymers. Applying this approach to paints has shown that improvement in properties such as hardness and drying times without loss in adhesion and flexibility can be obtained by physical as well as physical followed by chemical modifications with EVA, reactive terpolymers and isocyanate prepolymers. Correct formulation with fortifying additives of asphaltene powder or hydrocarbon resin was another contributing factor. © 2012 Elsevier B.V. All rights reserved.

1. Introduction Naturally occurring bitumen was probably the one of the first bonding and waterproofing materials of mankind, the first application dating back up to 180,000 years in Syria [1]. The main application of bitumen is road paving, streets of Babylon being the first example, but modern use in Europe is recent as beginning of 18th century. Nowadays 95% of the bitumen is consumed in road paving, obtained entirely from vacuum distillation residue of petroleum. Rest is employed mainly for waterproofing membranes in emulsion form and an even smaller fraction, for paints. Bitumen is composed of n-heptane soluble maltene (MAL) and insoluble very high molecular weight polycyclic asphaltene (ASP) fractions, responsible for the flexibility and stiffness of the material, respectively. From the chemical point of view, again depending on their solubility in various solvents, MAL can be separated into saturates, aromatics and resins, with increasing molecular weights. Bitumen mainly consists of carbon (80–88 wt.%) and hydrogen (8–12 wt.%). In addition, sulfur (0–9 wt.%) in the form of sulfides, thiols and, to a lesser extent, sulfoxides, nitrogen (0–2 wt.%) as pyrrolic and pyridinic structures and quinolones and oxygen (0–2 wt.%) in the form of ketones, phenols and carboxylic acids [2]. During last decades, research on bitumen was concentrated on improving the adhesion, wear and rutting properties by various additives and chemical modifications. The most important contribution was physical modification by the addition of little amounts (1–10%) of elastomers or plastomers. Although

∗ Corresponding author. Tel.: +90 2626783321; fax: +90 2626783297. E-mail address: [email protected] (M. Eren). 0300-9440/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.porgcoat.2012.10.016

contributions of SBR: styrene butadiene rubber; SBS: styrene butadiene styrene; neoprene; styrene isoprene, scrap tire rubber, polyethylene, acrylics, EVA: ethylene vinyl acetate and many others were investigated, SBS and EVA were deemed to yield better results. They are very well summarized in two excellent reviews by Lesueur [2] and Yildirim [3]. When the polymer dissolves in the MAL fraction it swells up to 200–500% and depending on the amount added, a phase inversion may occur, from polymer rich phase dispersed in ASP rich matrix to ASP rich phase dispersed in polymer rich matrix. Along with this morphological transformation, which can be followed by optical and fluorescence microscopy, significant changes in physical properties occur. Usually the high concentration of ASP in ASP rich phase in a polymer rich matrix is considered to have reinforcing effect but the properties of matrix is dominant. Chemical modification is also possible, with ethylene terpolymers of ethylene, glycidyl metacrylate, and methyl, ethyl or butyl acrylate esters or with isocyanate containing prepolymers. The glycidyl group reacts mainly with the carboxylic groups in ASP, forming ester rings [4]. The other possibility is the employment of isocyanate prepolymers, –NCO groups react with most of the polar groups ( OH; SH; >NH; COOH) of asphaltenes and resins with the possibility of consequent crosslinking [5]. Bituminous paints have been abundantly employed in the first half of the last century but with the advent of modern polymers such as acrylics, urethanes and epoxy resins, their use is restricted to large area steel applications such as underground tanks and pipelines. Although they adhere well and offer corrosion protection, they are either too soft, or with high content of fillers, moderately hard, with consequent loss of adherence and flexibility. Research on improvement seems to be rare, last example being modification with cashew nut shell liquid-formaldehyde resin published in 2001 [6].

R. Aydemir et al. / Progress in Organic Coatings 76 (2013) 966–971

This paper deals with physical, chemical as well as physical followed by chemical modifications of 50–70 penetration grade bitumen (B50) and 70–100 penetration grade bitumen (B70) with EVA plastomer, styrene rapid alkyd, reactive terpolymers with glycidyl groups and reactive prepolymers with isocyanate groups, followed by preparation of paints from these modified bitumens with additives, to obtain satisfactory drying time, adhesion, hardness and flexibility properties. The results of water based paints prepared from modified bitumen emulsions shall be reported in a separate paper.

967

2. Experimental

by mandrel bending test (TS39/TS 8693). Gloss was determined according to TS 4318/EN ISO 2813. Dry to touch times were determined according to ASTM 1640. For the dry hard time, the more strict method of “coin mar test” was found to be more appropriate, since the main application of bitumen paints was pipes, which involved stacking as soon as possible. This was a “pass or fail” test, and it was found that when a pass was obtained, the coating had already reached the 7th degree of drying of DIN 53150. The light microscopy images were obtained from 60 ␮m dry films of modified bitumens on glass at 50× magnification by Nikon Eclipse LV 100. Fluorescence microscopy images were obtained by Olympus BX-51 TRF-5.

2.1. Materials

3. Results and discussion

All of the materials were technical grade. Bitumen samples were obtained from Türkiye Petrolleri A.S¸. and were 50–70 penetration grade (B50) and 70–100 penetration grade (B70). EVA was “Evatane 28-05” (E), with 27–29% vinyl acetate content. Glycidyl terpolymers were “Elvaloy AC 3427” (G-3), “Elvaloy AM” (G-5), “Elvaloy 4170” (G-9) with 3, 5, 9% glycidyl group contents, respectively. The isocyanate prepolymer was “Desmodur E 29” (I-24) with 24% NCO content. Styrene modified alkyd resin (SRA) was “MR 48 XT 60S” rapid alkyd (60% in toluene) Paint preparation binder support additives were asphaltene powder “Select 325” (softening point: 154–169 ◦ C, s.g.: 1.05) (S325) and hydrocarbon resin “Boracca B-120” (softening point: 116–125 ◦ C, s.g.: 1.09) (HR). The black pigments were iron oxide Bayferrox 318M (size: 0.2 ␮m, s.g.: 4.2) and carbon black Printex U. Fillers were Baser Baryte (size: 2.63 ␮m, s.g.: 4.3) and Talc D (size: 5 ␮m, s.g.: 2.89). Also various rheological and stabilizing additives and solvents were used. They are given below, in the paint preparation section.

A set of preliminary modification experiments was carried out with elastomers such as SBS, chlorinated rubber as well as some acrylic plastomers and paints were prepared. It was found that either the modifications did not provide the expected improvements to B50 and B70 bitumens or partial solubility–compatibility problems developed. Some further experiments with 10–20 and 160–200 grade bitumens indicated that the former yielded loss of flexibility and the latter yielded soft films. Thus only results of EVA, SRA, reactive acrylic terpolymers and isocyanate prepolymer modifications of B50 and B70 shall be reported here. Fig. 1 shows the radical morphological changes of modification with 3, 5 and 8% EVA copolymer. In case of 3% modification, the dark ASP rich phase separates from light the polymer rich one. With increased amounts of EVA, more MAL fraction is absorbed by the polymer, the size of the ASP rich phase globules decrease and the texture of swollen polymer rich phase changes. With 8% modification, the spongy polymer rich phase becomes the dominant matrix, with a dispersion of small size ASP rich phase. Table 1a shows the results of some preliminary experiments and Table 1b, the physically modified bitumen paints. It was found that

2.2. Bitumen modifications B50 and B70 grade bitumens were dissolved in toluene to yield 70 wt.% solutions and were used for modifications. The modifications were carried out under N2 flow in a 4 L reactor with stirrer and reflux system. For physical modifications, different amounts EVA was added portion wise, to solutions at 100–110 ◦ C and the mixture was further heated up to 3 h under stirring and reflux at a temperature about 130 ◦ C. In case of chemical modifications of unmodified or EVA modified bitumens, terpolymers and isocyanate prepolymers were again added at 100 ◦ C and the mixture was further heated for 3 h under stirring and reflux at a temperature about 130 ◦ C. All solutions were filtered and no significant amount of residue was observed. 2.3. Paint preparation

Table 1a Properties of the paints prepared from non modified bitumens. Experiment

1

2

3

9

Bitumen Modification Additive Dry to touch (min) Dry hard (h) Adhesion** Hardness (s) Gloss (60) Flexibility***

B50 None None 120

B50 None S 325 9% 40 30 0 9 20 0

B50 None S 325 14% 15 12 5 23 12 6

B70 None S 325 9% 60 72 0 18 14 0

* **

Paints were prepared in 2 L high speed dispersers followed by pearl mill grinding, to below 25 ␮m size. Base formulation was 15.23% modified bitumen (based on 100% solids), 9% S325 or HR, 5.6% Bayferrox 318M, 0.2% Printex U, 28% Baser baryte, 13% Talc D, 0.55% Antiterra 204 (Wetting agent), 0.2% MPA 60-X (solvent) and 0.4% Bentone SD-1 (rheological agent), 0.3% Baykanol N (stabilizer), 2% butylene glycol (solvent), 16.74% toluene (solvent) and 8.78% xylene (solvent). This formulation gave flat, black paints with PVC of 35.2%. 2.4. Tests and measurements The paints were applied on steel panels and the physical properties were determined after 1 week. Hardness was determined by König pendulum (TS6041/EN ISO 1522). Adhesion was determined by cross-cut test (TS4313/EN ISO 2409). Flexibility was determined

***

* *

3 10 *

Not determined. 0: best, 5: worst. 0: best, 6: worst.

Table 1b Properties of the paints prepared from physically modified bitumens. Experiment

4

5

6

7

8

10

Bitumen Modification Additive Dry to touch (min) Dry hard (h) Adhesion** Hardness (s) Gloss (60) Flexibility***

B50 E 5% None 180

B50 E 5% HR 9% 30 16 1 25 22 1

B50 E 3% S 325 9% 43 7 0 10 11 0

B50 E 5% S 325 9% 35 14 0 18 10 0

B50 E 8% S 325 9% 10 80 0 26 11 1

B70 E 5% S 325 9% 35 14 0 30 9 0

* ** ***

Not determined. 0: best, 5: worst. 0: best, 6: worst.

* *

3 12 *

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R. Aydemir et al. / Progress in Organic Coatings 76 (2013) 966–971

Fig. 1. Light microscopy images (50×) of B50 (a) unmodified, (b) 3% EVA modified, (c) 5% EVA modified, and (d) 8% EVA modified.

without the addition of S325 or HR, the paints did not reach dry hard stage and remained extremely soft and sticky (Exp. 1). Modification with 5% EVA did not provide an improvement (Exp. 4), and a series of experiments with 3, 5, 9, and 14% additives were carried out. Low amounts of additive did not bring satisfactory results and at 14% the paints lost flexibility completely. 9% additive was found to be optimal for both B50 and B70 bitumen paints, and although the HR increased the hardness better than S325, it also decreased the flexibility and adhesion slightly (Exp. 2, 3, and 5). The cost and contribution of S325 to paint color were also in favor, so the rest of paints (Exp. 6–25) were prepared with 9% S325. Since it dissolved in

toluene, it should be considered as a binder, not as filler. Combined with S325 addition, the hardness improved with EVA modification without harming adhesion and flexibility (Exp. 6–10). With low amounts of EVA, dry hard time was reduced, but at 8% EVA, swollen polymer rich matrix which did not release the solvent easily and the dry hard time increased. B70 modified with 5% EVA provided the best result for physical modification results (Exp. 10). Tables 2a and 2b summarize the results of chemical modifications by isocyanate prepolymers and reactive acrylic terpolymers with different amounts of glycidyl groups, respectively. Modification by isocyanate prepolymer improved drying times and hardness

Table 2a Properties of paints prepared from chemically modified bitumens (isocyanate prepolymer). Experiment

2

9

11

12

13

14

Bitumen Modification Additive Dry to touch (min) Dry hard (h) Adhesion* Hardness (s) Gloss (60) Flexibility**

B50 None 40 30 0 9 20 0

B70 None 60 72 0 18 14 0

B50 I-24 1% 10 6 5 19 10 3

B50 I-24 3% 15 3 4 25 7 3

B70 I-24 1% 10 3 3 22 14 0

B70 I-24 3% 10 7 4 30 7 2

* **

0: best, 5: worst. 0: best, 6: worst.

Table 2b Properties of paints prepared from chemically modified bitumens (reactive terpolymers). Experiment

15

16

17

18

19

20

Bitumen Modification Dry to touch (min) Dry hard (h) Adhesion* Hardness (s) Gloss (60) Flexibility**

B50 G-3 1% 13 12 4 25 15 0

B50 G-5 1% 9 24 4 28 11 1

B50 G-9 1% 11 18 5 20 14 3

B70 G-3 1% 16 18 3 29 11 2

B70 G-5 1% 25 12 0 21 17 2

B70 G-9 1% 12 24 0 19 17 0

* **

0: best, 5: worst. 0: best, 6: worst.

R. Aydemir et al. / Progress in Organic Coatings 76 (2013) 966–971

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Fig. 2. Fluorescence microscopy images of B70 (a) before modification and after modification by (b) 5% EVA, (c) 1% I-24, and (d) 5% EVA, followed by 1% I-24.

of paints for both grades of bitumen but impaired adhesion and flexibility (Exp. 11–14). In case of reactive terpolymers, modifications conveyed improvement of drying time and hardness properties but along with loss in adhesion and flexibility, in most cases (Exp. 15–20). Obviously chemical modification alone with these modifiers was not the best solution. Thus chemical modification of physically modified bitumens was carried out with isocyanate prepolymer. The change in morphology can be seen from Figs. 2 and 3. In case of fluorescence microscopy, some fluorescence was already present in B70 image, but contribution of modification by EVA, or isocyanate prepolymer (Fig. 2b and c, Exp. 10 and 13) is very distinct. Physical followed by chemical modification image (Fig. 2d, Exp. 24) illustrates the change in morphology due to crosslinking. Fig. 3 shows crosslinking with either isocyanate prepolymer or glycidyl acrylates forces the asphaltene rich phases separate to

appear and the effect of increase in reactive groups is also visible (Exp. 11–12 and 15–16). Similar behavior was observed for physical, followed by chemical modifications with EVA and isocyanate prepolymers (Table 3a) (Exp. 21–23). But the most dramatic change occurs when 8% EVA modified B50 is further modified with I-24 (Exp. 24). Crosslinking occurs mainly in the polymer rich phase, reducing the absorption of MAL, which swells the ASP rich phase, which can hardly be observed in the physically modified version (Fig. 1d, Exp. 8). Some improvement of drying times and hardness properties could be obtained with these multiple modifications, with slight impairment of adhesion and flexibility in some cases (Exp. 21–25). One of the last polymers to be tested was SRA. This alkyd is modified by addition of styrene polymer chains and is a well known primer of paint industry, with good hardness, short drying time and adequate flexibility to applications. It has enough double bonds for

Table 3a Properties of paints prepared from physically, followed by chemically modified bitumens (EVA-isocyanate). Experiment

21

22

23

24

25

Bitumen Modification Dry to touch (min) Dry hard (h) Adhesion* Hardness (s) Gloss (60) Flexibility**

B50 E 5% + I-24 1% 10 5 3 25 5 6

B50 E 5% + I-24 3% 30 3 0 22 8 1

B50 E 8% + I-24 3% 10 80 0 35 5 1

B70 E 5% + I-24 1% 15 6 1 47 5 0

B70 E 5% + I-24 3% 15 12 2 28 4 2

* **

0: best, 5: worst. 0: best, 6: worst.

Table 3b Properties of paints prepared from physically, followed by chemically modified bitumens (SRA and EVA-isocyanate combinations). Experiment

26

27

28

29

Bitumen Modification Dry to touch (min) Dry hard (h) Adhesion* Hardness (s) Gloss (60) Flexibility**

B50 SRA 5% 10 3 2 24 6 1

B50 SRA 10% 7 2 2 23 6 1

B70 SRA 5% 15 4 1 22 6 1

B70 E 5% + I-24 1% + SRA 5% 15 10 1 55 7 0

* **

0: best, 5: worst. 0: best, 6: worst.

970

R. Aydemir et al. / Progress in Organic Coatings 76 (2013) 966–971

Fig. 3. Light microscopy images (50×) of B50 modified by (a) 1% G-3, (b) 1% G-9, (c) 1% I-24, (d) 3% I-24 (e) 5% E followed by 1% I-24, (f) 5% E followed by 3% I-24, and (g) 8% E followed by 3% I-24.

air drying polymerization and hydroxyl groups available for further reactions. Thus blends with SRA were prepared (Table 3b, Exp. 26–28) and in one case an EVA-SRA physically modified sample was later modified with I-24 (Table 3b, Exp. 29). As seen from Table 3, some very satisfactory results such as increase in hardness accompanied by short drying times were achieved without impairment of other properties. SRA significant contribution was mainly due to crosslinking with I-24. 4. Conclusions While bitumen based paints have lost their importance due to superior properties of modern binders such as acrylics, modified alkyds, epoxy and urethane resins, they still survive due to their excellent adhesion and corrosion protection properties, as well

their incomparably cheap price, as binders for large area applications, such as pipelines. But available unsophisticated paints prepared from bitumen–filler–resin–solvent combinations show deficiencies in either in drying time and hardness or adhesion and flexibility. On the other hand, abundant recent research exists on modification of bitumen by polymers, for improving road paving applications. Although the requirements of these fields are quite different, the principle was applied to preparing bitumen paints from physically modified, chemically modified and physically followed by chemically modified 50–70 and 70–100 penetration grade bitumens. Since none of the unmodified bitumen paints dried at all and were very soft, a fortifying additive such as asphaltene powder or hydrocarbon resin had to be added to paint formulations to confer drying and hardness. Physical modification with EVA was

R. Aydemir et al. / Progress in Organic Coatings 76 (2013) 966–971

satisfactory, provided that both ASP rich and polymer rich phases exist, complete transformation to polymer rich matrix with higher amounts of EVA prolonging the dry hard times, due to reluctance of release of solvents from the paint film. Chemical modifications with glycidyl terpolymers and isocyanate prepolymer did provide some improvements but with slight impairment of flexibility and adhesion properties due to crosslinking of the matrix. Better results have been obtained when both modifications have been applied consecutively, especially in the case of multiple physical modifications by EVA and SRA, followed by chemical modification with isocyanate prepolymer. This work has shown that applying the principles of road paving bitumen research to surface coatings field can yield some exceptional results in improving the quality of present applications, as well as enhancing the application possibilities of this very cheap binder.

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Acknowledgments This work was supported by TÜBI˙ TAK-TEYDEB under project number 3090648. Authors are grateful to TEYDEB for financial support as well as Prof. Dr. I˙ smail Boz and I˙ SFALT A.S¸. Laboratories, I˙ stanbul, Turkey, for fluorescent microscopy. References [1] [2] [3] [4]

J. Connan, Phil. Trans. R. Soc. Lond. B 354 (1999) 33–50. D. Lesueur, Adv. Colloid Interface Sci. 145 (2009) 42–82. Y. Yildirim, Construct. Build. Mater. 21 (2007) 66–72. G. Polacco, J. Stastna, D. Biondi, F. Antonelli, Z. Vlachovicova, L. Zanzotto, J. Colloid Interface Sci. 280 (2) (2004) 366–373. [5] M.J. Martin- Alfonso, P. Partal, F.J. Navarro, M. Garcia-Morales, J.C.M. Bordado, A.C. Diogo, Fuel Process. Technol. 90 (2009) 525–530. [6] A.P. Kuriakose, S. Kochu Baby Manjooran, Surf. Coat. Technol. 145 (2001) 132–138.

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Title Bitumen paints, an old story with new approach, part-1, solvent based paints

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