Платэ Н.А., Сливинский Е.В. Основы химии и технологии мономеров
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701
Isolation of butadiene………………………………………….. 133
4.2.Isoprene…………………………………………………………………………135
4.2.1Тwo-step manufacture of isoprene from isobutylene and formaldehyde136
Reaction mechanism…………………………………………… 137
Transformation of 1,3-glycols into dioxanes…………………... 139
Formation of isopentene alcohols……………………………… 139
Transformation of 4,4-dimethyl-1,3-dioxane into isoprene …… 140
4.2.2. Manufacture of isoprene from isobutylene and formaldehyde via 3-methyl-
1,3-butanediol (MBD)……………………………………... ………..143
4.2.3. Manufacture of isoprene from isobutylene and methylal………….. 145
4.2.4. Manufacture of isoprene by dehydrogenation of hydrocarbons С
5
… 146
Two-step dehydrogenation of isopentane to isoprene………… 146
One-step dehydrogenation of isopentane to isoprene ………… 149
Two-step oxidative dehydrogenation of isopentane to isoprene.. 150
4.2.5. Manufacture of isoprene from propylene………………………….. 153
Dimerization of propylene……………………………………… 153
Isomerization of 2-methyl-1-pentene to 2-methyl-2-pentene …. 155
Cracking of 2-methyl-2-pentene ………………………………. 156
Synthesis of isoprene from ethylene and propylene…………… 159
4.2.6. Manufacture of isoprene from acetylene and acetone……………… 159
4.2.7. Manufacture of isoprene by liquid-phase oxidation of hydrocarbons 162
4.2.8. Manufacture of isoprene from 2-butenes and synthesis gas……….. 163
4.3. Diene monomers for the manufacture of ethylene-propylene-diene rubbers 165
4.3.1. Manufacture of nonconjugated dienes…………………………….. 166
Synthesis of dicyclopentadiene………………………………… 166
Synthesis of 1,4-hexadiene…………………………………….. 167
Synthesis of 1,5-cyclooctadiene……………………………….. 167
4.3.2. Manufacture of norbornene derivatives……………………………. 168
Synthesis of ethylidenenorbornene…………………………….. 168
Synthesis of methylenenorbornene…………………………….. 169
Synthesis of propenylnorbornene………………………………. 169
Synthesis of 5’-(buten-2-yl-4)-2’-norbornene…………………. 170
Synthesis of cyclopentadienyl-5-
endo-norbornen-2-yl-5’-methan 170
Chapter 5. Halogen-containing monomers…………………………………… 171
5.1. Chlorine-containing monomers…………………………………………….. 171
5.1.3
. Theoretical backgrounds of hydrocarbon chlorination……………. 171
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5.1.4 . Oxidative chlorination…………………………………………….. 173
5.1.5
Hydrochlorination………………………………………………….. 176
5.1.4. Dehydrochlorination ……………………………………………… 176
5.1.5. Manufacture of chloroorganic compounds………………………… 177
Gas-phase chlorination of hydrocarbons and chlorine derivatives 177
Liquid-phase chlorination of hydrocarbons……………………. 178
Gas-phase decomposition of chlorine derivatives …………….. 179
5.1.6. Manufacture of vinyl chloride……………………………………… 180
Balanced method of vinyl chloride synthesis from ethylene ….. 181
One-step of vinyl chloride synthesis from ethylene (Staffer proc.)185
Two-step synthesis of vinyl chloride from ethylene…………… 186
Synthesis of vinyl chloride from ethane……………………….. 187
Hydrochlorination of acetylene………………………………… 189
5.1.7. Manufacture of vinylidene chloride………………………………… 191
5.1.8. Manufacture of chloroprene………………………………………… 193
Preparative methods of obtaining chloroprene……………………193
Industrial methods for the synthesis of chloroprene……………………………. 194
5.1.9. Manufacture of epichlorohydrin…………………………………… 197
5.2. Fluorine-containing monomers……………………………………………… 199
5.2.1. Theoretical backgrounds of fluorination processes………………… 199
5.2.2. Mechanism of fluorination reactions……………………………….. 200
5.2.3. Methods of fluorination of alkanes ………………………………… 201
Metal fluoride process …………………………………………. 202
Cryogenic fluorination…………………………………………. 202
Electrochemical fluorination…………………………………… 203
5.2.4. Fluorinating agents…………………………………………………. 204
Molecular fluorine……………………………………………… 204
Hypofluorites…………………………………………………… 204
Hydrogen fluoride……………………………………………… 205
5.2.5. Manufacture of vinyl fluoride……………………………………… 206
5.2.6. Manufacture of vinylidene fluoride ……………………………….. 207
5.2.7. Manufacture of perfluoro-derivatives of hydrocarbons……………. 207
Synthesis of tetrafluoroethylene……………………………….. 207
Synthesis of hexafluorobutadiene……………………………… 208
Synthesis of perfluoroallenes………………………………….. 209
5.2.8. Manufacture of other fluoro-derivatives of hydrocarbons………… 209
Synthesis of trifluorochloroethylene…………………………… 209
Synthesis of sym-dichlorodifluoroethylene……………………. 209
Synthesis of 3,3,3-trifluoropropylene………………………….. 209
5.2.9. Manufacture of
chladones (freons)………………………………… 210
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Chapter 6. Vinylic monomers with aromatic and heterocyclic substituents
.. 212
6.1. Styrene and its derivatives…………………………………………………… 212
6.1.1. Manufacture of styrene ……………………………………………. 212
Preparative methods of obtaining styrene……………………… 213
Industrial methods for the manufacture of styrene ……………. 214
6.1.2. Manufacture of
-methylstyrene…………………………………… 218
6.2. Vinylpyridines………………………………………………………………. 219
6.2.1.
General aspects of basic methods for the synthesis of vinylpyridines 221
6.2.2. Industrial methods for the manufacture of vinylpyridines ………… 221
Synthesis of
2-methyl-5-vinylpyridine………………………… 220
Synthesis of 2- and 4-vinylpyridines and 2-vinyl-5-ethylpyridine 222
6.3. N-Vinylpyrrolidinone ………………………………………………... 223
6.3.1. Direct vinylation of
-pyrrolidinone by acetylene…………………. 224
6.3.2. Indirect vinylation of -pyrrolidinone ……………………………... 226
6.4. N-vinylcarbazole ……………………………………………………………. 228
6.4.1. Manufacture of N-vinylcarbazole through vinylation by acetylene… 229
6.4.2. Manufacture of N-vinylcarbazole by the vinyl exchange reaction… 230
6.4.3. Manufacture of N-vinylcarbazoles by multi-step processes………. 231
Decomposition of N-(2-hydroxyethyl)carbazole ……………… 231
Decomposition of 1-substituted N-ethylcarbazoles……………. 233
6.5. Other vinylic monomers…………………………………………………….. 234
6.5.1. Manufacture of ethylidenenorbornene……………………………… 234
6.5.2. Manufacture of vinyl toluene………………………………………. 235
6.5.3. Manufacture of vinyl ketones……………………………………… 236
Synthesis of vinyl methyl ketone……………………………… 236
Synthesis of isopropenyl methyl ketone………………………. 238
Synthesis of vinyl phenyl ketone……………………………… 239
Synthesis of vinylene carbonate………………………………. 239
Chapter 7. Acrylic monomers…………………………………………………. 241
7.1. Acrylonitrile………………………………………………………………… 242
7.1.1Synthesis of acrylonitrile via ethylene oxide and ethylene cyanohydrin243
7.1.2. Oxidative ammonolysis of propylene……………………………… 246
7.1.3. Synthesis of acrylonitrile from acetylene and prussic acid ……….. 249
7.1.4. Synthesis of acrylonitrile via acetaldehyde and hydroxynitryl……. 251
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7.1.5. Synthesis of acrylonitrile from propylene and nitrogen oxides…… 252
7.1.6. Synthesis of acrylonitrile by direct interaction of ethylene, prussic acid, and
oxygen………………………………………………………… 252
7.1.7. Oxidative ammonolysis of propane……………………………….. 252
7.2. Acrylamide…………………………………………………………………. 252
7.2.1. Preparative methods of obtaining acrylamide……………………... 253
7.2.2. Industrial methods for the manufacture of acrylamide …………… 254
7.3. Acrylic acid ………………………………………………………………... 255
7.3.1. Hydrolysis of acrylonitrile………………………………………… 255
7.3.2. Hydrocarboxylation of acetylene…………………………………. 257
7.3.3. Vapor-phase oxidation of propylene……………………………… 257
7.3.4. Hydrolysis of ethylene cyanohydrin……………………………… 260
7.3.5. Hydrolysis of
-propiolactone …………………………………… 260
7.3.6. Oxidative carbonylation of ethylene……………………………… 261
7.4. Methacrylic acid ………………………………………………………….. 261
7.4.1. Gas-phase oxidation of isobutylene………………………………. 262
7.4.2. Oxidation of methacrolein ……………………………………….. 262
7.4.3. Gas-phase oxidation of methacrolein…………………………….. 263
7.5. Acrylates…………………………………………………………………... 263
7.5.1. Manufacture of acrylates by esterification of acrylic
and methacrylic acids ………………………………………………….. 263
Esterification by alcohols in the presence of sulfuric acid…… 263
Esterification by alcohols in the presence of ion-exchange resins 264
Esterification by olefins……………………………………… 265
7.5.2. Manufacture of acrylates via transesterification…………………. 265
Transesterification in the presence of acidic catalysts……….. 265
Transesterification in the presence of ion-exchange resins….. 266
Transesterification in the presence other transesterification
catalysts……………………………………………………….. 266
7.5.3. Manufacture of acrylates from ethylene cyanohydrin…………….. 266
7.5.4. Manufacture of acrylates from acetylene by the Reppe reaction….. 267
BASF process…………………………………………………. 267
Rom and Haas process………………………………………… 267
7.5.5. Manufacture of acrylates from ketene and formal………………… 268
7.5.6. Manufacture of acrylates from acrylonitrile………………………. 268
7.6. Methacrylates………………………………………………………………. 269
7.6.1. Manufacture of methacrylate from acetone and cyanohydrin…….. 269
Synthesis of cyanohydrin (prussic acid)………………………. 269
Condensation of acetone and prussic acid ……………………. 270
Synthesis of methacrylamide sulfate………………………….. 270
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Hydrolysis or esterification of methacrylamide sulfate ………. 271
Commercial realization of the process………………………… 272
7.6.2. Manufacture of methyl methacrylate from tert-butyl alcohol……… 273
Oxidation of tert-butyl alcohol to methacrolein ………………. 273
Oxidation of methacrolein to methacroleinic acid…………….. 273
Esterification of methacrylic acid to methyl methacrylate…….. 274
7.6.4.
Manufacture of methyl methacrylate from isobutylene…………… 274
7.6.5.
New methods for the synthesis of methyl methacrylate…………… 277
Synthesis of methyl methacrylate via isobutyraldehyde………. 277
Carbomethoxylation of propylene……………………………... 278
Carbomethoxylation of methylacetylene……………………… 279
Methoxycarbonylation of allene and methylacetylene-allene
Fraction………………………………………………………… 280
7.6.5. Manufacture of other alkyl methacrylates…………………………. 281
Synthesis of methacrylamide………………………………….. 281
Synthesis of hydroxyethyl methacrylate………………………. 281
7.7. Oligoetheracrylates…………………………………………………………. 282
Chapter 8. Alcohols and vinyl ethers
…………………………………………. 283
8.1. Polyvinyl and polyallyl alcohols…………………………………………… 284
8.2. Backgrounds of vinylation processes ……………………………………… 286
8.3. Vinyl ethers………………………………………………………………… 289
8.3.1. Manufacture of vinyl ethers by vinylation of alcohols……………. 290
Vinylation of alcohols under atmospheric pressure…………… 290
Vinylation of alcohols under elevated pressure ………………. 292
Other methods for the synthesis of vinyl ethers…………….… 293
8.4. Vinyl esters. Vinyl acetate…………………………………………………. 294
Synthesis of
vinyl acetate from acetylene and acetic acid…….. 296
Synthesis of
vinyl acetate from acetaldehyde
and acetic anhydride…………………………………………… 298
Synthesis of
vinyl acetate from ethylene and acetic acid……… 300
Synthesis of
vinyl acetate from alternative sources…………… 304
8.5 Derivatives of polyvinyl alcohol – polyvinylacetals………………………… 311
Chapter 9.Monomers for polyethers…………………………………………. 313
9.1. Formaldehyde………………………………………………………………. 316
9.1.1 Mechanism and catalysts of oxidative dehydrogenation of methanol 316
Mechanism of oxidative dehydrogenation of methanol……….. 316
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Catalysts of oxidative dehydrogenation of methanol………….. 321
General aspects of the technology of oxidative
dehydrogenation of methanol………………………………….. 322
9.1.2. Manufacture of
formaldehyde……………………………………… 323
Synthesis of
formaldehyde with oxide catalysts………………. 323
Oxidation of natural gas and lower alkanes…………………… 324
9.2. Ethylene oxide …………………………………………………………….. 327
9.2.1. Manufacture of ethylene oxide via ethylene chlorohydrin………. 327
9.2.2. Direct oxidation of ethylene……………………………………… 329
9.3. Propylene oxide …………………………………………………………… 331
9.3.1 Manufacture of propylene oxide by direct oxidation with oxygen.. 333
Oxidation of propane………………………………………….. 333
Noncatalytic liquid-phase oxidation of propylene…………….. 333
Catalytic liquid-phase oxidation of propylene………………… 334
Liquid-phase oxidation of propylene by peroxides……………. 334
Epoxidation of propylene……………………………………… 336
9.3.2. Manufacture of propylene oxide by oxidation
of propylene via propylene
chlorohydrin……………………………… 337
9.4. Phenylene oxide…………………………………………………………….. 338
9.5. Allyl glycidyl ………………………………………………………………. 339
9.6. Epichlorohydrin ……………………………………………………………. 340
Manufacture of epichlorohydrin from glycerol……………….. 341
Manufacture of
epichlorohydrin from allyl chloride………….. 342
9.7. Sulfones……………………………………………………………………. 343
Part III
MONOMERS FOR POLYCONDENSATION POLYMERS
Chapter 10. Monomers for polyesters………………………………………… 346
10.1. Terephthalic acid and dimethyl terephthalate…………………………….. 347
10.1.1. Du Pont process………………………………………………….. 349
10.1.2. Witten process…………………………………………………… 350
10.1.3. Amoco process…………………………………………………... 351
Mechanism of
p-xylene oxidation…………………………….. 351
Intermediate and side products in oxidation of
p-xylene
to terephthalic acid ……………………………………………. 358
Technology of manufacture of terephthalic acid ……………… 360
10.1.4. One-step VNIPIM process……………………………………….. 361
10.1.5. Manufacture of aromatic and heterocyclic carboxylic
acids by thermal transformation of their alkali salts……………………... 361
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Transformations of alkali salts…………………………………. 362
Synthesis of terephthalic acid from toluene and xylenes………. 363
10.1.6. Mitsubishi process………………………………………………… 366
10.1.7. Manufacture of terephthalic acid from coal………………………. 367
10.2. Maleic anhydride…………………………………………………………... 368
10.2.1. Manufacture of maleic anhydride by gas-phase oxidation
of benzene………………………………………………………… 368
10.2.3.
Manufacture of maleic anhydride by oxidation of butane……….. 370
10.2.3. Manufacture of maleic anhydride by oxidation of
n-butenes……. 371
10.2.4. Isolation of maleic anhydride as a side product in
the manufacture of phthalic anhydride…………………………………… 372
10.3. Phthalic anhydride…………………………………………………………. 372
10.3.1. Vapor-phase oxidation of
o-xylene or naphthalene………………. 374
10.3.3.
Liqid-phase oxidation of o-xylene or naphthalene……………….. 375
10.3.3. VNIIOS process………………………………………………….. 375
10.4. Fumaric acid………………………………………………………………. 378
10.5. Dichloromaleic and dichlorofumaric acids and their derivatives…………. 379
10.5.1. Manufacture of dichloromaleic acid and its anhydride…………… 379
10.5.2. Manufacture of dichlorofumaric acid and its anhydride………….. 380
10.6. 2,6-Naphthalenedicarboxylic acid…………………………………………. 380
10.7. Thiophene-2,5-dicarboxylic acid………………………………………….. 381
10.8. Azelaic acid……………………………………………………………….. 382
10.9. Diols………………………………………………………………………. 383
10.9.1. Manufacture ethylene glycol…………………………………….. 383
Hydration of ethylene oxide…………………………………… 383
Other methods for the synthesis of ethylene glycol …………… 384
10.9.2. Manufacture of 1,2-propanediol………………………………….. 386
Hydration of propylene oxide…………………………………. 386
Other methods for the synthesis of 1,2-propanediol ………….. 388
10.9.3 Manufacture of 1,4-butanediol……………………………………. 389
Synthesis of 1,4-butanediol from acetylene and formaldehyde.. 390
Synthesis of 1,4-butanediol from propylene………………….. 391
Synthesis of 1,4-butanediol from renewable raw material
(Cvaker Oatz process)……………………………………….. 393
Propylene of 1,4-butanediol by acetoxylation
of butadiene (Mitsubishi process)……………………………. 393
Synthesis of 1,4-butanediol through chlorination
of butadiene
(Тоуо Soda process)…………………………….. 394
Synthesis of 1,4-butanediol through hydroformylation
of allyl alcohol (Кurare process)……………………………… 395
708
10.9.4. Manufacture of 1,4-dimethylcyclohexane……………………….. 398
Chapter 11. Monomers for polyamides……………………………………… 399
11.1. Monomers for polymerization polyamides …………………………….… 400
11.1.1. Manufacture of caprolactam……………………………………... 401
Methods for the synthesis of caprolactam…………………….. 401
Main stages in the
synthesis of caprolactam …………………. 405
Synthesis of caprolactam from toluene……………………….. 422
Photochemical synthesis of caprolactam……………………… 426
11.1.2. Manufacture of valerolactam…………………………………….. 427
11.1.3. Manufacture of 7-aminoheptanoic acid………………………….. 427
11.1.4. Manufacture of caprilolactam……………………………………. 429
11.1.5. Manufacture of 9-aminopelargonic acid ………………………… 429
11.1.6. Manufacture of 11-aminoundecanoic acid……………………….. 429
11.1.7. Manufacture of laurolactam………………………………………. 432
Trimerization of butadiene…………………………………….. 432
Heamisher Huls process……………………………………….. 433
Uber process…………………………………………………… 433
11.1.8. Manufacture of
-pyrrolidinone………………………………….. 434
Amination of
-butyrolactone………………………………….. 435
Noncatalytic synthesis of -pyrrolidinone…………………….. 435
Reductive amination of maleic anhydride……………………... 436
Other methods for the synthesis of
-pyrrolidinone…………… 437
11.2. Monomers for polycondensation polyamides derived from dicarboxylic
acids and diamines…………………………………………………………. 439
11.2.1 Manufacture of adipic acid………………………………………… 440
Synthesis of adipic acid from cyclohexane…………………….. 441
Synthesis of adipic acid from tetrahydrofurane……………… 442
Synthesis of adipic acid from phenol………………………….. 442
Other industrial methods for the synthesis of adipic acid……… 442
11.2.2. Manufacture of adiponitrile………………………………………… 443
Synthesis of adiponitrile from adipic acid……………………… 443
Synthesis of adiponitrile from butadiene………………………. 444
Synthesis of adiponitrile from acrylonitrile
by electrochemical method…………………………………….. 445
Catalytic dimerization of acrylonitrile…………………………. 446
709
11.2.3. Manufacture of hexamethylenediamine……………………………. 447
Synthesis of hеxamethylenediamine from adipic acid…………. 447
Synthesis of hеxamethylenediamine via 1,6-hexanediol………. 449
Synthesis of hеxamethylenediamine from butadiene………….. 449
Dimerization
of acrylonitrile…………………………………... 450
11.2.4 Manufacture of other monomers for the synthesis of polyamides .. 450
11.2.5. Manufacture of
m-xylylenediamine……………………………… 457
Bromination of xylene…………………………………………. 457
Oxidative ammonolysis………………………………………… 458
11.3. Monomers for other fiber-forming polyamides …………………………… 458
11.3.1. Manufacture of fiber-forming polyamides based on suberic
acid and 1,4-diaminomethylcyclohexane………………………….. 458
Synthesis of suberic acid ………………………………………. 459
Synthesis of 1,4-diaminomethylcyclohexane………………….. 459
11.3.2. Manufacture of fiber-forming polyamides based on
decanedicarboxylic acid and 4,4
-diaminodicyclohexylmethane…. 459
Synthesis of decanedicarboxylic acid………………………….. 460
Synthesis of 4,4
-diaminodicyclohexylmethane……………….. 460
11.4. Monomers for fully aromatic polyamides…………………………………. 461
11.4.1. Manufacture of aromatic acid chlorides………………………….. 461
Synthesis of acid chlorides from xylenes……………………… 461
Thionyl method………………………………………………... 462
11.4.2. Manufacture of monomers for fiber-forming polyamides by polycondensa-
tion of 4,4
-diaminodiphenyl sulfone………………. …………….. 463
11.4.3. Manufacture of 2,5-bis-(
p-aminophenyl)-1,3,4-oxadiazole………. 464
11.4.4.Manufacture of 5,5-bis(m-aminophenyl)-2,2-bis(1,3,4-oxadiazolyl)465
11.4.5. Manufacture of 4,4-bis-(p-aminophenyl)-2,2-dithiazole………… 465
11.4.6. Manufacture of bis-(
m-aminophenyl)-thiazolo(5,4-d)thiazole…… 466
11.4.7. Manufacture of monomers for polyamides based on
piperazine and diacids……………………………………………. 466
Synthesis of piperazine…………………………………………… 466
Synthesis of 4,4
-diphenyldicarboxylic acid………………………. 467
Chapter 12. Monomers for polyimides
……………………………………….. 470
12.1. Pyromellitic dianhydride………………………………………………….. 472
12.1.1. Manufacture of durene…………………………………………… 473
12.1.2. Manufacture of
pyromellitic dianhydride………………………... 475
12.2. Diphenyltetracarboxylic dianhydrides…………………………………….. 481
710
12.2.1. Manufacture of 2,2,3,3-diphenyltetracarboxylic dianhydride…… 481
12.2.2. Manufacture of 2,3,5,6-diphenyltetracarboxylic dianhydride…….. 482
12.2.3. Manufacture of 2,2
,6,6-diphenyltetracarboxylic dianhydride …… 483
12.2.4. Manufacture of 3,3,4,4-diphenyltetracarboxylic dianhydride ….. 484
12.3. Naphthalenetetracarboxylic dianhydrides…………………………………. 485
12.3.1. Manufacture of 1,4,5,8-naphthalenetetracarboxylic dianhydride … 485
12.3.2. Manufacture of 2,3,6,7-naphthalenetetracarboxylic dianhydride … 486
12.4. Benzophenone- and perylenetetracarboxylic dianhydrides………………... 486
12.4.1. Manufacture of 3,3
,4,4-benzophenonetetracarboxylic dianhydride 486
12.4.2. Manufacture of 3,4,9,10-perylenetetracarboxylic dianhydride …… 487
12.5. Aromatic diamines…………………………………………………………. 488
12.5.1. Manufacture of
o- and m-phenylenediamines…………………….. 488
12.5.2. Manufacture of
p-phenylenediamine……………………………… 489
12.5.3. Manufacture of benzidine…………………………………………. 493
12.5.4. Manufacture of 4,4’-diaminodiphenylmethane…………………… 493
12.5.5. Manufacture of 4,4
-diaminodiphenyl oxide……………………… 493
12.6. Aniline derivatives…………………………………………………………. 494
12.6.1. Manufacture of anilinophthalein…………………………………... 494
12.6.2. Manufacture of anilinofluorene…………………………………… 495
12.6.3. Manufacture of anilinoanthrone…………………………………… 495
Chapter 13. Monomers for polyurethanes
……………………………………. 496
13.1 Diamines……………………………………………………………………. 500
13.1.1 Manufacture of diamines by reduction of dinitriles…………………….. 500
13.1.2 Manufacture of diamines by reduction of aromatic
dinitro compounds………………………………………………… 501
Reduction of dinitro compounds by metals in acidic medium… 502
Reduction of dinitro compounds by metals in alkaline medium.. 503
Reduction of nitro compounds by sulfides …………………….. 504
Catalytic reduction of dinitro compounds……………………… 504
13.2
Diisocyanates and isocyanates……………………………………………… 505
13.2.1 Phosgenftion of amines……………………………………………. 506
13.2.2 Curtius, Hofmann and Lossen rearrangements……………………. 506
13.2.3
Manufacture of tolylene diisocyanates……………………………. 508
Reduction of dinitrotoluenes to tolylenediamine………………. 509
Phosgenation of tolylenediamine ……………………………… 509
Synthesis of phosgene…………………………………………. 509
Other industrial methods for the manufacture of
tolylene diisocyanates………………………………………….. 510