Preparation of modified polyesters containing triphosphorous and their applications to PU flame-retardant coatings.

Three phosphorous functional groups were introduced in one structural unit of polymer backbone to enhance the flame retardancy of PU coatings. In the first step, we synthesized tetramethylene bis(orthophosphate) (TBOP) that contained two phosphorus functional groups in one structural unit. In the next step, we synthesized modified polyesters (ATBTP-10, -20, -30) that contained triphosphorous groups by condensing polymerization of TBOP, 1,4-butanediol, trimethylolpropane, adipic acid, and phenylphosphonic acid (PPA). The amount of PPA in the ATBTPs was 10, 20, and 30 wt%. Then, flame-retardant PU coatings (AHFC-10, -20, -30) were prepared by curing ATBTPs with hexamethylene diisocyanate-biuret (curing agent) at room temperature. From the TGA analysis of diphosphorus-modified polyester (ATBT) and ATBTPs, the residues of ATBT, ATBTP-10, ATBTP-20, and ATBTP-30 were 24.6, 27.5, 29.2, and 31.9%, respectively. From this result, it was found that the residue increased in relation to the amount of PPA. Physical properties of the films of flame-retardant coatings were deteriorated with the addition of PPA (flame retarding component), however, all the films of flame-retardant coatings, except AHFC-30, met the required physical properties standard for coatings. Char lengths of the AHFCs measured by the 45[degrees] Meckel burner method were 2.9 ~ 4.8 cm, and LOI values were 28 ~ 31%, which indicates that the prepared AHFCs showed good flame retardancy.

Keywords: Gel permeation chromatography, polymerization, polyurethanes, cure, weatherability, packaging, titanium dioxide, esters, phosphate

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Among polyurethane (PU) coatings, the most popular one is a two-component polyol curing type coating, which is prepared by the addition reaction of polyols and isocyanates. (1,2) In the process of preparing flame-retardant PU coatings, flame retardancy is mainly provided by the polyols that contain flame-retarding components.

Almost all of the currently known flame-retardant PU coatings use polyols, in which chlorine or bromine is contained as a flame-retarding component. (3,4) However, there exists a problem of toxicity, because the halogen compounds emit toxic gases with fire. When a fire breaks out, toxic gases may cause more injury and death than the fire itself. Recently, a regulation on the emission of toxic gases of flame-retardant coatings, such as hydrogen fluoride or hydrogen bromide, has been made more strict. Therefore, there is a need to develop nontoxic flame-retardant coatings. It is known that coatings containing phosphorous are nontoxic, and exhibit two to four times higher flame retardancy than those containing halogen compounds. (5)

There exists some literature on the development of flame-retardant coatings that contain phosphorous. Ma et al. prepared intumescent PU flame-retardant coatings with a polyol that contained spirocyclic phosphate and examined their flame retardancy. (6) Weil and McSwigen (7) prepared flame-retardant coatings by blending melamine-phosphoric salt and resins. Blount (8) prepared PU flame-retardant coatings through the polymerization of polyether, amine-phosphoric salt, and an isocyanate that had more than two radicals. Park et al. synthesized flame-retardant modified polyesters that had one to two phosphorous functional groups in one structural unit; then, through the curing of the synthesized polyesters with isocyanate, flame-retardant coatings containing phosphorous could be prepared and examined. (9-11) Up to this day, there has been no report on the introduction of three phosphorous functional groups in one structural unit to provide stronger flame retardancy.

In this work, we introduced three phosphorous functional groups in one structural unit to produce stronger flame-retardant coatings. To do this, we first synthesized tetramethylene bis(orthophosphate) intermediate (TBOP) from pyrophosphoric acid and 1,4-butanediol. Then a prepolymer, modified polyester containing triphosphorous was prepared by condensing polymerization of the prepared TBOP, 1,4-butanediol as a diol, trimethylolpropane as a triol, and adipic acid as a two basic acid. Finally, PU flame-retardant coatings that cure at room temperature were prepared by blending the prepared prepolymer and hexamethylene diisocyanate-biuret at room temperature. Films were prepared with the prepared flame-retardant coatings, and the physical properties of the films were compared with nonflame-retardant coatings. Flame retardancy of the films was tested by the 45[degrees] Meckel burner method and limiting oxygen index (LOI) method.

EXPERIMENTAL

Materials

The monomers used were adipic acid (AA, Junsei Chemical Co.), trimethylolpropane (TMP, Tokyo Kasei Industry Co.), and 1,4-butanediol (1,4-BD, Sigma Chemical Co.). The adipic acid was recrystallized by acetone and dried at 120[degrees]C for two hours. The trimethylolpropane was also recrystallized by acetone and ether, and the 1,4-butanediol was dehydrated by [Na.sub.2]S[O.sub.4] and distilled at 107~108[degrees]C in a vacuum of 4 mm Hg. (12) The flame retarding reagents used were phenylphosphonic acid (PPA, first grade, Tokyo Kasei Industry Co.), pyrophosphoric acid (PYPA, first grade, Aldrich Chemical Co.) and tetramethylene bis(orthophosphate) (TBOP, synthesized and purified in our lab). (13) The curing agent used was hexamethylene diisocyanate-biuret (HDI-biuret, Desmodur N-100; solid content, 100%; NCO content, 22%; viscosity, 10,000 mPa * s at 23[degrees]C Leverkusen Co.). Ti[O.sub.2] (British Titan Product Co.) was used as a white pigment, BYK-320 (BYK-Chemie Co.) as a dispersant, BYK-066 (BYK-Chemie Co.) as an antifoaming agent, Tinuvin-384 (Ciba-Geigy Co.) as a UV absorber, Tinuvin-292 (Ciba-Geigy Co.) as a UV stabilizer, dibutyltindilaurate (Songwon Co.) as a curing catalyst, and Dow Corning-11 (Dow Chemical Co.) as a flow accelerator.

Synthesis of Diphosphorous-Modified Polyester

In order to synthesize diphosphorous-modified polyester, reactants, (listed in Table 1) for ATBT were introduced into a one-liter four-necked flask equipped with stirrer, dropping funnel, thermometer, nitrogen inducing tube, and refluxing condenser. Then, the reactor was heated in an environment of nitrogen; at 95[degrees]C all the reactants were solved completely. The temperature was raised from 100[degrees]C to 150[degrees]C at a rate of 20[degrees]C/hr, causing condensing polymerization of the reactants. Then, the mixture was held at 150[degrees]C for one hour to complete the reaction.

The product was purified by a precipitation method with a solution of excess distilled water and acetone, and the precipitate was dried at 40[degrees]C under a vacuum of 6 mm Hg and diluted with 20 g of toluene, producing a light brown transparent viscous copolymer, modified polyester prepolymer containing diphosphorous (ATBT).

Synthesis of Triphosphorous-Modified Polyester

The reactants listed in Table 1 for ATBTP-10 were introduced into a one-liter four-necked flask equipped with stirrer, dropping funnel, thermometer, nitrogen inducing tube, and refluxing condenser. The reactants were reacted and the product was purified by the same process mentioned in the previous section, producing a light brown transparent viscous copolymer, modified polyester prepolymer containing triphosphorous (ATBTP-10), which contained 10 wt% PPA.

In addition, ATBTP-20 and ATBTP-30, which contain 20 and 30 wt% PPA, respectively, were also produced by the same process used to produce ATBTP-10. ATBTP-20 and ATBTP-30 were also light brown transparent viscous copolymers.

Instrumental Analysis

FTIR (FTS-40, Bio-Rad) and [.sup.1]H-NMR (Unity-300, Varian) were used for the structural analysis of the products. Their molecular weights and molecular weight distributions were determined by gel permeation chromatography (GPC) (R-410, Waters). Thermal analysis was also carried out using thermogravimetric analysis (TGA) (TGA-50H, Shimazu) with temperature increasing at a rate of 10[degrees]C/min in air.

Preparation of Flame-Retardant Coatings

Two-component PU flame-retardant coatings were prepared by blending the prepared modified polyester prepolymers containing triphosphorous and HDI-biuret isocyanate in accordance with the ratio listed in Table 2. To prepare two-component PU flame-retardant coatings, 279.9 g of triphosphorous-modified polyester solution and 102.7 g of HDI-biuret curing solution were mixed. The prepared two-component PU flame-retardant coatings, ATBTP-10/HDI-biuret, ATBTP-20/HDI-biuret, and ATBTP-30/HDI-biuret, were designated as AHFC-10, AHFC-20, and AHFC-30, respectively. ATBT/HDI-biuret, which corresponds to a blank test, was designated as AHFC.

Physical Properties of Flame-Retardant Coatings

To test their physical properties, thin films of the prepared PU flame-retardant coatings were applied on some substrates: cold-rolled carbon steel plate (KS D 3512), tin plate (KS D 3516), and glass plate. Three specimens were prepared as follows. (11) For a cold-rolled carbon steel plate substrate, specimens were prepared according to KS M 5000-1111; for a tin plate, according to KS M 5000-1112; and for a glass plate, according to KS M 5000-1121. Viscosity of the coatings was measured by a Krebs-Stormer viscometer (Pacific Scientific Co.), pencil hardness was measured by a pencil hardness tester (Yasuda Seiki Seisakusho Co.), and 60[degrees] specular gloss was measured according to KS M 5000-3312. Impact resistance was tested according to JIS K 5400. Crosshatch adhesion was tested with the specimen prepared using a tin plate (KS D 3516), and flexibility was tested according to KS M 5000-3331. Pot life was measured by the time when the viscosity became 140 KU. For an accelerated weatherability test, Sunshine Weather-Ometer (SWO, Atlas Electric Devices Co., Ci65A) and QUV accelerated weathering tester (QUV, Q-Panel Co.) were employed.

[FIGURE 1 OMITTED]

Flame Retardancy Test

45[degrees] MECKEL BURNER METHOD. Flame retardancy was tested by the 45[degrees] Meckel burner method, according to JIS Z-2150. (14) Textiles used were acrylic textile (100%, Ne 2/36, Hanil Co.), nylon taffeta (70D/24F, Dongyang Nylon Co.), and polyester taffeta (75D/24F, Samyoung Textile Co.).

[FIGURE 2 OMITTED]

For a flame retarding treatment of the textiles, AHFC-10, -20, and -30 were dissolved in methanol and the textiles were treated with the solutions by one-dip and one-nip padding, and wet pick-up (15) conditions were controlled at 80% for acrylic textile and 60% for nylon taffeta and polyester taffeta. Then, the treated textiles were cured at 100[degrees]C for five minutes and were used to test physical properties.

LOI METHOD. Flame retardan-cy tested by the LOI method was examined with a flammability tester (ON-1, Suga Co.) according to ISO 4589. (16) This method employs a transparent drum in which a specimen (6.5 x 145 x 3) is kept vertically and is then ignited from the top. The minimum oxygen concentration at which the flame remained is measured.

[FIGURE 3 OMITTED]

[FIGURE 4 OMITTED]

RESULTS AND DISCUSSION

Identification of Synthesized Diphosphorous-Modified Polyester

We reported elsewhere on the synthesis of modified polyester, ATB, which does not contain a flame retarding component, that corresponds to a blank test in this study. (17) ATB was synthesized from AA, TMP, and 1,4-DB. The synthesis of diphosphorous-modified polyester, ATBT, which corresponds to another blank test, was performed with AA, TMP, 1,4-DB, and TBOP. The flame retardancy of ATBT stems from TBOP, which contains phosphorous. The moles of reactants for ATB and ATBT were calculated so as to fit the optimum OH contents or OH values, 6.5 or 215, respectively. (18)

The amounts of reactants, polymerization conditions, and yield are listed in Table 1. Figure 1 shows a scheme for ATBT synthesis. FTIR spectra and [.sup.1]H-NMR chemical shifts listed in Table 3 agree well with the molecular structure in Figure 1. Consequently, the formation of ATBT could be verified. GPC measurement results of ATBT are shown in Figure 2. The average molecular weights were [M.sub.n] = 3350 and [M.sub.w] = 8380, and polydispersity was 2.5. This indicates that the synthesized ATBT have a narrow distribution and a relatively low molecular weight.

Identification of Synthesized Triphosphorous-Modified Polyester

To get better flame retardancy, triphosphorous-modified polyester, which contains three phosphorous functional groups in one structural unit, was synthesized by the reaction of diphosphorous-modified polyester (synthesized above) and PPA. The synthesis scheme is shown in Figure 3, and the synthesis conditions and physical properties of ATBTP-10, -20, and -30 are listed in Table 1. As listed in Table 1, yield increased slightly with the content of PPA. FTIR spectra and [.sup.1]H-NMR chemical shifts listed in Table 3 agree well with the molecular structures of Figure 3. Consequently, the formation of ATBT could be verified. When comparing [.sup.1]H-NMR chemical shifts of ATBT and ATBTP, there existed a difference in peak at [delta]7.7 ppm, which corresponds to -CH=CH- of aromatic ring of O = P - [??] contained in PPA. From this comparison, the introduction of PPA was confirmed. The [.sup.1]H-NMR peak intensity at [delta]7.7 ppm was increased in the order of ATBTP-10<ATBTP-20<ATBTP-30, which indicates that the introduced amount of PPA was proportional to the order.

[FIGURE 5 OMITTED]

As shown in Figure 2, [M.sub.n], [M.sub.w], and the polydispersity of ATBTP-10 were 3090, 6800, and 2.2; [M.sub.n], [M.sub.w], and the polydispersity of ATBTP-20 were 2810, 5340, and 1.9; and [M.sub.n], [M.sub.w], and the polydispersity of ATBTP-30 were 2580, 4640, and 1.8. This shows that the molecular weight was decreased when the PPA content was increased. This may stem from the decrease in the homogeneity of monomers caused by the increase in the PPA concentration.

Thermal Stability of Triphosphorous-Modified Polyester

The thermal properties of modified polyesters containing halogen (3) and the thermal stability of modified polyesters containing phosphorous (19) are well known. However, there are no known papers on the thermal behavior of modified polyester containing three phosphoous functional groups in one structural unit.

TGA curves of ATBT, ATBTP-10, ATBTP-20, and ATBTP-30 are presented in Figures 4-7. When comparing these figures, in a range of 100-300[degrees]C, there are no remarkable differences in the curves between these four modified polyesters that contain phosphorous. However, in a range of 300-400[degrees]C, the amounts of residue were 31.9, 29.2, 27.5, and 24.6 for ATBTP-30, ATBTP-20, ATBTP-10, and ATBT, respectively. This indicates that the amount of residue increased with an increasing PPA content. This phenomenon agrees well with the report of Kuryla and Papa, (20) in which the introduction of phosphorous in PU resins facilitates char formation at a higher temperature.

[FIGURE 6 OMITTED]

[FIGURE 7 OMITTED]

[FIGURE 8 OMITTED]

Crosslinking of ATBTP and HDI-Biuret

Two-component PU flame-retardant coatings are composed of a resin solution and a curing solution. The main components of the resin solution and curing solution are phosphorous-modified polyester polyol and isocyanate, respectively. Through the crosslinking of these two components at room temperature, network structure is formed. (21)

Figure 8 shows the reaction mechanism of crosslinking ATBTP and HDI-biuret, in which the OH group of ATBTP and the NCO group of HDI-biuret were reacted with each other to form a urethane bonding. PU films obtained in this way show outstanding properties when compared with the films of other coatings, in properties of weatherability, close adherence, chemical resistance, and abrasion resistance.

Physical Properties of Flame-Retardant Coatings

Film specimens were prepared by the blending and curing of triphosphorous-modified polyester, HDI-biuret curing agent, and the chemicals listed in Table 2, at room temperature. The physical properties of the prepared specimens were examined. AFC (ATB/HDI-biuret) and AHFC (ATBT/HDI-biuret) were used for blank tests. AHFC-10, -20, and -30 indicates that the contents of PPA were 10, 20, and 30 wt%, respectively.

Physical properties are listed in Table 4. Viscosities of AFC and AHFC were larger than those of AHFC-10, -20, and -30, indicating that the addition of PPA decreases viscosity. The addition of PPA decreased the molecular weights of AHFCs, as shown in the section "Identification of Synthesized Triphos-phorous-Modified Polyester." Pot life (required value: more than four hours) and impact resistance were good for all except for AHFC-30. Pencil hardness (required value: harder than H) decreased with increasing PPA content. Cross-hatch adhesion (required value: more than 90) was good for all except AFC. The 60[degrees] specular gloss (required value: more than 80) was good for all except AHFC-10. Flexibility was good for all. In the SWO test, a method to test accelerated weathering resistances, color difference, yellowness index, and lightness index, the differences were good, while gloss retention became poor with increasing PPA content. In the QUV test, a more severe accelerated weathering test, all the properties became worse than the results of the SWO test. In Table 4, a positive sign (+) means getting bright and a negative sign (-) means getting dark.

From the results of physical properties tests, it was concluded that the physical properties of the films become slightly poor with increasing PPA content; however, all the physical properties of the films meet the requirement for coatings, except for AHFC-30.

Flame Retardancy of PU Flame-Retardant Coatings

Generally, flame-retardant coatings mean self-extinguishable coatings and consist mainly of halogen and/or phosphorous compounds. The halogen compounds in the flame-retardant coatings put out the fire by suppressing the flames of the pyrolysis gases, (22,23) while nontoxic phosphorous compounds extinguish the fire by suppressing the combustion of pyrolysis residue. (24)

Particularly, phosphorous compounds capture oxygen and hydrogen from the film during the fire and they are converted to phosphoric acid, meta-phosphoric acid, and poly-meta-phosphoric acid. These acid layers produced on the film block heat and oxygen flow, retarding the fire until it is extinguished. (20) Consequently, phosphorous compound can reveal its outstanding flame retardancy at even lower content through the shortening of afterflaming and afterglow. (24)

In the 45[degrees] Meckel burner method (JIS Z-2150), the char length testing method was chosen, and the testing conditions for various textiles were as follows. Textiles used were refined acrylic textile (100%, Ne 2/36), nylon taffeta (70D/24F), and polyester taffeta (75D/24F). The textiles were treated with pre-prepared AHFC solutions by one-dip and one-nip padding, and wet pick-up conditions were controlled at 80% for acrylic textile and 60% for nylon taffeta and polyester taffeta. Then the treated textiles were cured at 100[degrees]C for five minutes and were tested by the above-mentioned method.

The results of the flame-retardancy test are listed in Tables 5-7. As listed in Table 5, in the case of acrylic textile, char lengths were less than 3.9 cm, and afterflaming and afterglow were less than one minute with AHFC-20 and AHFC-30. These results prove that AHFC-20 and AHFC-30 are first grade flame-retardant coatings. Flame retardancy test results for nylon taffeta and polyester taffeta are listed in Tables 6 and 7. As listed in Tables 6 and 7, all the flame-retardant coatings revealed good flame retardancy.

The flame retardancy of the PU flame-retardant coatings was also tested by the LOI method. Figure 9 shows LOI values with respect to PPA content, in which LOI values increased from 25 to 31 while increasing the content of PPA from 0 to 30 wt%. When PPA content was more than 20 wt%, LOI values were in a range of 30 ~ 31, which indicates that the PU flame-retardant coatings were good in terms of flame retardancy. The reason why the LOI value at 0 wt% of PPA was 25 is that there already exists some amount of phosphorous groups in ATBT through the introduced TBOP. In the case of AFC, which contains no phosphorous groups, the LOI value was 17.

When comparing the thermal stability (third part of the Results and Discussion section) and flame retardancy, it may be concluded that the flame retardancy increases when the amount of residue increases by blocking heat and oxygen access. This result agrees well with the mechanism of flame retardancy mentioned above.

[FIGURE 9 OMITTED]

CONCLUSIONS

Triphosphorous-modified polyesters (ATBTP-10, -20, -30) were synthesized by condensing polymerization of tetramethylene bis(orthophosphate), 1,4-butanediol, trimethylolpropane, and phenylphosphonic acid (PPA). Film specimens were prepared by curing the prepared ATBTPs with hexamethylene diisocyanate-biuret (HDI-biuret) at room temperature, and were tested. The following results were obtained.

The optimum synthesis conditions for triphosphorous-modified polyesters (ATBTPs) were 100-150[degrees]C and a reaction time of 4.2-4.3 hr. Yields were 83 ~ 86%; number average molecular weight ([M.sub.n]) was 2580 ~ 3090; and weight average molecular weight ([M.sub.w]) was 4640 ~ 6800. The amount of residue for ATBTPs and ATBT increased in the order of ATBTP-30>ATBTP-20>ATBTP-10>ATBT, which indicates that the amount of residue increases when the PPA content increases. From the comparison of the physical properties of the films of flame-retardant coatings and nonflame-retardant coatings, we found that some physical properties of the films of flame-retardant coatings deteriorated in comparison with those of nonflame-retardant coatings; however, all the flame-retardant coatings, except AHFC-30, met the required physical properties for coatings. Char lengths of AHFCs measured by the 45[degrees] Meckel burner method were 2.9 ~ 4.8 cm, and the LOI values were 28 ~ 31%, which indicates that the prepared AHFCs showed good flame retardancy.

ACKNOWLEDGMENT

This work was supported by the RRC program of Most and Gyeonggi-do.

References

(1) Akkerman, J.M., Hall, R., Mestach, D., and Vandevoorde, P.M., "Small Change," Polym. Paint Colour J., 191, 17, 19 (2001).

(2) Tada, M., Otsuka, I., and Oguro, K., "Two-Component Curable Polyurethane Compositions and Surface-Coated Sealing Materials Using Them," Jpn. Patent, 363243A2 (2002).

(3) Park, H.S., Hahm, H.S., and Park, E.K., "Preparation and Characteristics of Two-Component Polyurethane Flame Retardant Coatings Using 2,3-Dibromo Modified Polyesters," J. Appl. Polym. Sci., 61, 421 (1996).

(4) Park, C.H., Wu, J.P., Park, H.S., and Kim, S.K., "Syntheses and Characterizations of Two-Component Polyurethane Flame Retardant Coatings Using 2,4-Dichloro Modified Polyesters," J. COAT. TECHNOL., 69, 875, 41 (1997).

(5) Nishizawa, H., The Technology and Application of Polymeric Materials: Market and Outlook, CMC Co. Ltd., Tokyo, p. 269, 1996.

(6) Ma, Z.L., Zhao, W.G., Liu, Y.F., and Shi, J.R., "Intumescent Polyurethane Coatings with Reduced Flammability Based on Spirocyclic Phosphate-Containing Polyols," J. Appl. Polym. Sci., 66, 471 (1997).

(7) Weil, E. and McSwigan, B., "Melamine Phosphate and Pyrophosphates in Flame Retardant Coatings," J. COAT. TECHNOL., 66, 839, 75 (1994).

(8) Blount, D.H., "Flame-Retardant Polyurethane Products," U.S. Patent 5,010,113 (1991).

(9) Park, H.S., Kim, D.W., Hwang, K.H., Yoon, B.S., Wu, J.P., Park, J.W., Hahm, H.S., and Im, W.B., "Preparation and Characterization of Polyurethane Flame-Retardant Coatings Using Pyrophosphoric Lactone-Modified Polyesters/Isophorone Diisocyanate-Isocyanurate," J. Appl. Polym. Sci., 80, 2316 (2001).

(10) Park, H.S., Choi, Y.H., Kim, D.W., Im, W.B., and Wu, J.P., Fire and Polymers: Materials and Solution for Hazard Prevention, ACS Sympo. Series, Washington, D.C, Chapt. 9, pp. 110-122, 2001.

(11) Park, H.S., Kwon, S.Y., Seo, K.J., Im, W.B., Wu, J.P., and Kim, S.K., "Preparation and Physical Properties of Polyurethane Flame Retardant Coatings Using Phosphorus-Containing Lactone Modified Polyesters," J. COAT. TECHNOL., 71, 899, 59 (1999).

(12) Perrin, D.D. and Armarego, W.L.F., Purification of Laboratory Chemicals, 3rd Ed., Pergamon Press, Oxford, 1988.

(13) Zech, J.D. and Ford, E.C., Jr., "Polyhydroxy Phosphate Esters," U.S. Patent 3,309,427 (1967).

(14) Kim, H.K., Keun, J.H., Hahm, H.S., Pyoun, M.S., and Park, H.S., "Preparation of Phosphate Type Softening Flame Retardant for Synthetic Fibers and Its Characterization," J. Korean Fiber Soc., 30, 752 (1993).

(15) Park, C.H., Kim, S.J., Kim, Y.G., and Park, H.S., "Synthesis of Silicone Softener for Permanent Press Finish and Its Characterization," J. Korean Oil Chem. Soc., 12, 29 (1995).

(16) Lutz, J.T., Jr. and Grossman, R.F., Polymer Modifiers and Additives, Marcel Dekker Inc., New York, pp. 179-180, 2001.

(17) Park, H.S., Keun, J.H., and Lee, K.S., "Syntheses and Physical Properties of Two-Component Polyurethane Flame-Retardant Coatings Using Chlorine-Containing Modified Polyesters," J. Polym. Sci. Part A, 34, 1455 (1996).

(18) Oldring, P.K.T. and Hayward, G., Resins for Surface Coatings, Selective Industrial Training Assoc. Ltd., London, Vol. III, pp. 109-122, 1987.

(19) Park, H.S., Wu, J.P., and Kim, H.K., "Syntheses and Physical Properties of Two-Component Polyurethane Coatings Using Bromine-Containing Aromatic Modified Polyesters," J. Ind. Eng. Chem., 3, 282 (1997).

(20) Kuryla, W.C. and Papa, A.J., Flame Retardancy of Polymeric Materials, Marcel Dekker Inc., New York, Vol. 3, pp. 1-61, 1980.

(21) Oldring, P.K.T. and Hayward, G., Resins for Surface Coatings, Selective Industrial Training Asso. Ltd., London, Vol. III, pp. 27-31, 1987.

(22) Park, E.K., "Studies on the Syntheses and Physical Properties of Two-Component Polyurethane Flame Retardant Coatings Using Modified Aliphatic Carboxylic Acid Polyesters," Ph.D. Dissertation, Myongji Univ., Yongin, Korea, 1994.

(23) Grand, A.F. and Wilkie, C.A., Fire Retardancy of Polymeric Materials, Marcel Dekker Inc., New York, pp. 245-284, 2000.

(24) Ibid., Marcel Dekker Inc., New York, pp. 147-170, 2000.

Hong-Soo Park, ([double dagger]) Hyuk-Jae You, Hye-Jin Jo, Il-Woo Shim, and Hyun-Sik Hahm -- Myongji University*

Seong-Kil Kim -- Sam-Hwa Paints Ind. Co. Ltd. ([dagger])

Young-Geun Kim -- Korea Institute of Construction Materials**

* Dept. of Chem. Eng., Yongin 449-728, Korea.

([dagger]) Ansan 425-110, Korea.

** Seoul 137-707, Korea.

([double dagger]) Author to whom correspondence should be addressed.

Table 1 -- Polycondensation Conditions and Yields for ATBT and ATBTPs

                                  Materials
          AA (a)  TMP (b)  1,4-BD (c)  TBOP (d)  PPA (e)  Toluene
Products  (g)     (g)      (g)         (g)       (g)      (g)

ATB       302.2   163.4    108.9       --        --       20
ATBT      200.3   209.5     69.8       97.8      --       20
ATBTP-10  151.9   208.2     69.4       97.2       50.0    20
ATBTP-20  103.6   206.9     69.0       96.6      100.0    20
ATBTP-30   55.3   205.6     68.5       95.9      150.0    20

                          Reactions
          Temp          Time  Dehydration  Yield
Products  ([degrees]C)  (hr)  (mL)         (%)

ATB       150~220       14.0  74.2         93
ATBT      100~150        4.1  76.3         80
ATBTP-10  100~150        4.2  75.7         83
ATBTP-20  100~150        4.2  75.1         85
ATBTP-30  100~150        4.3  74.9         86

(a) AA: adipic acid.
(b) TMP: trimethylolpropane.
(c) 1,4-BD : 1,4-buntanediol.
(d) TBOP: tetramethylene bis(orthophosphate).
(e) PPA: phenylphosphonic acid.

Table 2 -- Preparation of Flame Retardant Coatings Using Triphosphorus-
Modified Polyester/HDI-Biuret

Component                 Part

Part A (resin solution)
  Modified polyester      100
  3.6
  BYK-066                   0.6
  Ti[O.sub.2]              83.5
  Tinuvin-384               1.0
  Tinuvin-292               0.5
  Dibutyltindilaurate       1.0
  Dow Corning-11            1.2
  Butyl acetate            29.5
  Cellosolve acetate       29.5
  Ethyl acetate            29.5

Part B (curing solution)
  HDI-biuret               72.7
  Cellosolve acetate       15.0
  Xylene                   15.0

Part C
  Solid content (%)        67.0
  Pigment/binder           31.2/68.8
  NCO/OH ratio              1.2/1.0

Table 3 -- FTIR Spectra and [.sup.1]H-NMR Chemical Shifts of ATBT and
ATBTP-10

                                           [.sup.1]H-NMR
                                           (300MHz, CD[Cl.sub.3],
Products  FTIR(NaCl, [cm.sup.-11])         [delta] in ppm)

ATBT      3290 : free OH                   0.9 (C[H.sub.3]-C)
          2960 : C[H.sub.3]                1.4 (-C[H.sub.2]-C)
          1730 : C=O                       2.4 (C-C[H.sub.2]-CO-)
          1460 : -C[H.sub.2]-              3.6 (C-C[H.sub.2]-O-)
          1180 : C-O-                      4.0 (C-C[H.sub.2]-OCO-)
          1040 : P=O
          1010 : P-O-C
           780 : -(C[H.sub.2])[.sub.4]-O-
ATBTP-10  3250 : free OH                   0.9 (C[H.sub.3]-C)
          2960 : C[H.sub.3]                1.4 (-C[H.sub.2]-C)
          1730 : C=O                       1.6 (C-C[H.sub.2]-C)
          1460 : -C[H.sub.2]-              2.4 (C-C[H.sub.2]-CO-)
          1190 : C-O-                      3.6 (C-C[H.sub.2]-O-)
          1140 : P=O                       4.1 (C-C[H.sub.2]-OCO-)
          1000 : P-O-C                     7.7 (O=P-[??])
           780 : -(C[H.sub.2])[.sub.4]-O-

Table 4 -- Physical Properties of Two-Component PU Flame-Retardant
Coatings

Tests                          AFC     AHFC    AHFC-10  AHFC-20  AHFC-30

Viscosity (KU)                  65      60      57       53       50
Pot-life (min)                 480     350     310      240      150
Impact resistance
(30 cm/500 g)
  Direct                       good    good    good     good     poor
  Reverse                      good    good    good     good     poor
Pencil hardness                2H      H       F        HB       2B
Cross-hatch adhesion (%)        30     100     100      100      100
60[degrees] Specular gloss      99      85      71       80       91
Flexibility (1/8 in.)          good    good    good     good     good
Accelerated weathering
Resistance
SWO (120 hr)
  Gloss retention (%)          100.0    95.1    83.6     81.0     70.7
  Color difference ([DELTA]E)    0.41    0.48    0.70     0.86     0.93
  Yellowness index ([DELTA]N)    0.11   -0.30   -0.22    -0.31    -0.25
  Lightness index difference     0.29   -0.35   -0.63    -0.84    -0.99
    ([DELTA]L)
QUV (120 hr)
  Gloss retention (%)           65.7    41.2    60.5     35.9     32.4
  Color difference ([DELTA]E)    0.51    0.56    2.88     4.50     5.88
  Yellowness index ([DELTA]N)    0.19   +0.10   +2.23    +3.27    +4.80
  Lightness index difference     0.49   -0.54   -1.84    -2.39    -4.17
    ([DELTA]L)

Table 5 -- Flame Retardancy of Acrylic Fabrics Treated With Synthesized
Flame-Retardant Coatings

                           45[degrees] Meckel Burner Method
           Concentration  Char length  Afterflaming (a)  Afterglow (b)
Exp. No.     (wt%)          (cm)         (sec)             (sec)

Untreated  --             BEL (c)      --                --
AHFC-10    10             4.8          2.0               1.0
AHFC-20    20             3.9          0                 0
AHFC-30    30             3.2          0                 0

(a) Burning time after flame.
(b) Glowing time after flame.
(c) Burned entire length.

Table 6 -- Flame Retardancy of Nylon Taffeta Treated with Synthesized
Flame-Retardant Coatings

                             45[degrees] Meckel Burner Method
          Concentration  Char length  Afterflaming (a)  Afterglow (b)
Exp. No.    (wt%)          (cm)         (sec)             (sec)

B-1 (a)   --             8.8          0                 0
B-2 (b)   --             BEL          --                --
AHFC-10   10             3.6          0                 0
AHFC-20   20             3.4          0                 0
AHFC-30   30             3.1          0                 0

(a) Original fiber not treated with flame-retardant coating and resin.
(b) Fiber treated with resin only.

Table 7 -- Flame Retardancy of Polyester Taffeta Treated with
Synthesized Flame-Retardant Coatings

                             45[degrees] Meckel Burner Method
          Concentration  Char length  Afterflaming (a)  Afterglow (b)
Exp. No.    (wt%)          (cm)         (sec)             (sec)

B-1 (a)   --             7.6          2                 0
B-2 (b)   --             BEL          --                --
AHFC-10   10             3.5          0                 0
AHFC-20   20             3.2          0                 0
AHFC-30   30             2.9          0                 0

(a) Original fiber not treated with flame-retardant coating and resin.
(b) Fiber treated with resin only.