Cocondensation of Urea with Methylolphenolsin Acidic Conditions

BUNICHIRO TOMITA 1. and CHUNG-YUN HSE2

Division of Chemistry of Polymer Materials, Department of Forest Products, Faculty of Agriculture, The University ofTokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113, Japan, 2USDA Forest Service, Southern Forest Experiment Station,2500 Shreveport Highway, Pineville, Louisiana 71360

SYNOPSIS

The reactions of urea with methylolphenols under acidic conditions were investigated using2- and 4-hydroxybenzyl alcohol and crude 2,4,6-trimethylophenol as model compounds.The reaction products were analyzed with 13C-NMR spectroscopy and GPC. From thereaction of urea with 4-hydroxybenzyl alcohol, the formations of 4-hydroxybenzylurea,N,N'-bis(4-hydroxybenzyl)urea, and tris (4-hydroXybenzyl) urea were confirmed and theformations of N,N-bis(4-hydroxybenzyl)urea and tetrakis(4-hydroxybenzyl)urea weresuggested. From the reaction of urea and 2-hydroxybenzyl alcohol, 2-hydroxybenzylureaand N,N'-bis (2-hydroxybenzyl) urea were identified. Further, the alternative copolymer ofurea and phenol could be synthesized by the reaction of urea with 2,4,6-trimethylolphenol.It was also found that the cocondensation between p-methylol group and urea prevailsagainst the self-condensation of the methylolphenol even at the low pH below 3.0, and thatp-methylol group has the stronger reactivity to urea than o-methylol group. @ 1992 JohnWiley & Sons, Inc.Keywords: urea . phenol. formaldehyde. cocondensation . hydroxybenzylurea

INTRODUCTION

Polymers of phenol or urea with formaldehyde havedominated such areas as the wood adhesives andmolding plastics for many years. Phenolic resins(PF) have demonstrated proven performance inproducing exterior quality composites while low-costurea-formaldehyde resins (UF) have performed wellin interior application. Nevertheless, the potentialscarcity and high cost of phenolic resins togetherwith concerns about rather low durability and form-aldehyde emission from UF resins have stimulatedefforts to develop a new resin system.

Recently, so-called "phenol-formaldehyde-ureacocondensed resins," which are generally made onlyby mechanical blending of UF resin and alkalinetype PF resins (resol) , have been used as adhesivesfor the manufacturing of wood products. However,

since these resins are cured with ammonium chloridewhich will react with free formaldehyde in the resinsto produce an acidic state gradually, the curing ofUF resin is considered to precede that of resol.Therefore the effective cocon<lensation cannot beexpected between them. In order to develop practicaluses it is necessary to introduce cocondensation be-tween phenol and urea at the time of resin prepa-ration. In our earlier work,I.2 the occurrence of co-condensation of phenol and urea/melamine byformaldehyde was determined with 13C-NMR spec-troscopy and it was concluded that a syntheticmethod of rer--ting methylolphenols with an exces-sive amount .If urea under acidic condition is effec-tive. Nevertheless, the information is still neededon the effects of various conditions on the acidiccocondensation of phenol and urea.

The purpose of this article is, therefore, focusedon elucidation of the chemical reactions of variousmethylolphenols with urea under acidic states to ea.tablish the effective cocondensation method andoptimum reaction conditions. Three kinds of melh.ylolphenols-4-hydroxybenzyl alcohol (p-methy-

'81~

. To whom all conespondence should be addreS8ed.

Joum8I of PoiyDIet' ScieI.ee: Part A: Polymer Cbemiotry. Vol. :.). 1615-1824 (1992)

It' 1992 John Wiley &. Sons, ltIC. CCC 0887.624X/92~1615-1(*>4.00

1818 TOMITA AND HSE

lolphenol, PMP), 2-hydroxybenzyl alcohol (0-methylolphenol, OMP) and 2,4,G-trimethylolphenol(TMP) -were used 88 model compounds to reactwith urea.

according to Freeman.3 After cooling to room tem-perature, 48.8 g (0.6 mol) of 37% formalin was addedto the solution, which was allowed to stand at roomtemperature for 1 week. The solution was pouredinto 500 mL of isopropyl alcohol. The white precip-itates formed were filtered off, washed with isopropylalcohol, and dried in a vacuum. 13C-NMR spectraof the precipitates both in alkaline solution andacidified solution showed the trimethylolphenol(sodium salt) as the main product.

EXPERIMENTAL

Reaction of Urea with 4-Hydroxybenzyl Alcoholand 2-Hydroxybenzyl Alcohol

Industrial grade urea and reagent grade 2- and 4-hydroxybenzyl alcohols (Aldrich Chemical Com-pany, Inc.) were used. Several reactions were per-fonned by changing the molar ratio of hydro~ybenzylalcohol to urea as well as the pH. In the case of theequimolar reaction (PMP IV = lor OMP IV = 1),e.g., each hydro~ybenzyl alcohol (20.7 g) and urea(10.0 g) were dissolved into 20 mL of warmed water,and the mixture was adjusted to the desired pH levelaby using 50% H2SO4 or AcOH and 1 N NaOH. Themixture was put in Erlenmeyer flask equipped withcondenser, and maintained at 85°C with magneticstirring. The pH was adjusted during reaction, andthe sample was taken every 10 min in the early stageand freeze-dried. Sometimes oily products began toseparate from water and precipitate after cooling.The precipitates were washed with water and dried..The kinds of experiments are listed in Table I.

Reaction of Urea with 2,4,6- Trimethylolphenol

Sodium 2,4,G-trimethylolphenate was dissolved inwater (20-30%, w/w), and acidified to pH 5.0 byH~4 and AcOH. After adding a calculated amountof urea, the pHs of the solutions were adjusted tothe target levels. Other reaction conditions were thesame as the reaction of urea with 0- or p-methylol-phenol.

Gel Permeation Chromatography, InfraredSpectroscopy and 13C-NMR Measurements

Each dried sample was dissolved into dimethyl-formamide (DMF) and analyzed by a liquid Chro-matograph ALC/GPC with R-401 Differential Re-fractometer (W aten A880Ciates). One Shodex GPC-AD-2002 column (Shows Denklo Co., Ltd.) was keptat GODC in a constant temperature bath. The flowrate ofDMF was 3.0 mL/min. The preparative GPCwas performed under the same conditions.

Synthesis of Sodium 2,4,6- Trimethylolphenate

Sodium hydroxide (8.0 g, 0.2 mol) was di88olved in20 mL of water and 8.8 g (0.2 mol) of phenol added

StartinICompound

Molar RatioMethylolphenol/U rea pW Remarks

p- Methylolphenol ~.o2.0

1.0

1.0

1.0

1.0

O.()

0.2

1.0

0.5

0.2

0.33

0.1

0.06

2.02.02.03.0 (AcOH)4.07.02.02.0

3.0 (AcOH)2.02.0

2.02.02.0

o-Methyloli-'henol

PrecipitatedPrecipitatedPrecipitatedCrystallizedCryatallizedC ryBtallizedCryatallizedCrystallized

SolutionPrecipitatedPrecipitated

PrecipitatedSolutionSolution

Trimethylolphenol

"ft88(:tiOD temperatuN: 86"C.~ The pH wa. adjuated by 50~ H,so. unleaa otherwise cited.

COCONDENSATION OF UREA WITH METHYLOLPHENOLS 1617

-1

M'U-O.2

IR spectra were taken with a 1420 Ratio Record-ing Infrared Spectroscopy (Perkin-Elmer) aftercasting the acetone solutions of samples on NaCIcell and drying in a vacuum.

NMR spectra were obtained in pyridine-ds or 020solution with a FT -BOA NMR spectrometer (V ar-ian) at a frequency of 20.0 MHz with the completedecoupling of proton. Chemical shifts were calcu-lated by defining the center of three signals of pyr-idine-ds that appeared in the upper magnetic fieldat 123.6 ppm, while by defining internal methanolat 50.0 ppm in 020 solution.

RESUL IS AND DISCUSSION

Reaction of Urea with 4-Hydroxybenzyl Alcohol

Identification of Products

The isolation of the reactants from urea and 4-hy-droxybenzyl alcohol by gel permeation chromatog-raphy was found to vary depending on differencesin reaction pH and molar ratio (PMP IV). as shownin Figures 1 and 2. The three peaks were observedat a low molecular-weight region except for thereactants at the higher molar ratio of PMP IV= 2.0. These three peaks were well isolated with the

45 . .~)

ELUTION VOlUME

Figure 2. Gel permeation chromatograms of the reac-tants from p-methylolphenol and urea at various molarratios (PMP IV). Reaction condition: 85°C, pH 2.0, 30min.

preparative GPC. Figure 3 shows each gel perme-ation chromatogram after the preparative GPC. Theproducts from peaks 1 and 2 were crystallized, re-spectively, while that from peak 3 was an amorphoussolid. Their IR spectra were simj1ar with that of the

_tJlrOlp1-..o1

Peak 1

Peak 2

J\ ,

4S 60 (111) 4S 60 (.1)

ElUTIIWI YOl"'E ElUTIOR YOlIJI:

Figure 1. Gel permeation chromatograms of the reac-tant from urea and p-methylolphenol at the molar ratioof PMP IV = 1 under various pH levels. Reaction tem-perature: 85°C.

~J\-v--"4~".'CO"(.1).

ELUTIOM VOlIJ£

Figure 3. Gel permeation chromatograms of isolatesby preparative GPC.

1618 TOMITA AND HSE

ISO

Figure 4.

100 50 ('PM)

13C-NMR spectra of isolates by preparative GPC in pyridine-d6

substitution of hydroxybenzyl carbon, the signal at44.3 ppm was assigned to the methylene carbon ofN,N'-bis (4-hydroxybenzyl) urea. Further the signalat 159.7 ppm indicated the carbonyl carbon of N,N'-disubstituted urea residue, because the second sub-stitution causes the downfield shift. Therefore it wasconcluded that the main component of the peak 2is N.N'-bis (hydroxybenzyl) urea.

The isolates of the peak 3 contained N.N'.bis (4-

tII--(Q}-C"z -1ItCOM"z4-h,droxJbeflzyl um

N.N-BiS(4-hydroXybenzyl)ure4

~~.~ /NC~

"'-@-C"z

self-condensate8 of 4-hydroxybenzyl alcohol. How-ever, strong absorption8 between 1640 and 1650 cm-lstrongly suggested the presence of amide group.

Figure 4 shows their 13C-NMR spectra mea8uredin pyridine-d6 solution, The chemical sbift8 of.methylene carbon due to the coconden88tion be-tween urea and p- or o-methylolphenol have beendetermined with the model experiment8},2 The peak1 W88 e88ily identified 88 4-hydroxybenzylurea bythe appearance of the 8ignal of the coconden8edmethylene carbon at 44.2 ppm. Furthermore, thesignal at 160.4 ppm indicated the presence of thecarbonyl carbon of the monosub8tituted urea re8i-due. The 8ub8titution of the aliphatic group to urearesidue was reported to cause a downfield 8hift ofthe carbonyl carbon8 from urea itself ( 162.5 ppm inpyridine-d6) ..,5

The NMR spectrum of the peak 2 shows also thestrong signal at 44.3 ppm as well 88 the small signalsdue to the self-condensation of 4-hydroxybenzyl al-cohol (35.9 ppm) and other impurities. The structureofN,N'-bis(hydroxybenzyl)urea W88 strongly sug-gested. In the case of urea-formaldehyde adducts,the chemical shifts of methylene carbons of N,N'-dimethylolurea (65.3 ppm) was quite similar withthat of monomethylolurea (65,0 ppm) " It had beenconcluded that the chemical shift of the carbon ofmethylol group is not greatly affected by the secondsubstitution to the other amide group of urea resi-dues. As this result was considered applicable to the

M.M-BIS(4-"ydroxybelllyl)

1«J~2.>~C"z-@--1«J-@-C"z

Tri.{4-hydro.y.nzyl)u...

ICI-@-(K C"z-@-CJ4Tetrakls(4-tlydroxybel\lyl lurea ~C*(

1CI-@-CII2 C112~

Figure 5. StnlctUl'eS of derivatives from the reactionof 4-hydroxybenzyl alcohol with urea in acidic condition.

COCONDENSATION OF UREA WITH METHYLOLPHENOLS 1619

Table II. Aliphatic 13C Chemical Shifts (ppm) of Hydroxybenzylureas Obtainedfrom the Reaction of Urea and Methylolphenols.

Methylene Carbon

Carbonyl Carbon ofUrea Residue

Monosubstitutedto Nitrogen

Oisubstituted toto NitrogenCompound

64.7

«.2«.3

100.4159.7100.0159.3

(159.3)

49.149.2

(49.2)«.7

61.140.640.6

(46.4)(46.4)

161.3160.6

UnknownUnknown

4-Hydroxybenzyl alcohol4- HydroxybenzylureaN,N l-bis(4-hydroxybenzyl)ureaN,N -bis( 4- hydroxyenzyl)ureaTris( 4-hydroxybenzyl)ureaTetrakis( 4- hydroxybenzyl)urea

2-Hydroxybenzyl alcohol2-HydroXybenzylureaN,N l-bis(2-hydroxybenzyl)ureaN ,N - bis( 2 - hydroxybenzyl )ureaTris( 2- hydroxybenzyl )urea

. The value in parenthesis is estimated.

calculated chemical shift of the disubstituted meth-ylene carbon to the same nitrogen atom is 50.3 ppmin the derivatives from 4-hydroxybenzyl alcohol and

hydroxybenzyl)urea as impurity as shown in theupper spectrum of Figure 4. The new signal at 49.2ppm was observed. It has been determined that the

Table m. Aromatic 13C Chemical Shifts (ppm) of Hydroxybenzylureas Obtained from the Reaction ofUrea and Methylolphenolsa

C-9 C-IO Coil C.laC4 c.7' c.aCo2 C-3 C-4 C-5Compound C-l

115.8116.3

157.3157.9

115.8116.3

129.1129.5

lU.O131.8

129.1129.5

116.3116.3 129.5 131.8 129.5158.0

129.6129.2

13t. 7131.5

129.6129.2

116.5116.3

158.3157.9

118.6118.3131.5 129.0 116.0167.6 116.0 129.0

116.4116.6

128.0128.5

129.3130.0

120.3120.3

129.4129.8

156.1156.2

4- Hydroxybenzyl alcohol

4-HydroxybenzyureaN.N1-bia( 4-hydroxy-

benzyl)ureaN.N-bia(4-hydroxy-

benzyl)ureaTria( 4-hydroxybenzyl)ureaTet1"8kja( 4-hydroxy-

benzyl)urea

2-Hydroxybenzyl alcohol2- HydroxybenzylureaN.N1-bia<2-hydroxy-

benzyl)ureaTria( 2- h ydroxybenzyl )urea

. Numbering of carmn is as follows:

Qi

~.'\Qt-CH.-NHCO-. .

Qi

~."~CH.,.., NCO-

.., /

"~CH.

JoK) -ra. CH.:-Nt-K:O--~. .

. .t«:)-'@.~ ".. 11.. /t«:)~~.. 11

~o-

"04

1620 TOMITA AND HSE

In the middle spectrum of Figure 4, the small sig-nal corresponding to the disubstituted methylenecarbons is observed at 49.1 ppm. This signal, how-ever, was not accompanied with the signal due tothe monosubstituted benzyl carbon of tria ( 4-hy-droxybenzyl) urea. Therefore, the presence of N,N-bis( 4-hydroxybenzyl) urea was strongly suggested inthe peak 2.

urea} ,2 This chemical shift was almost identical withthat observed in the present spectrum. Further, thissignal was accompanied with that at 44.7 ppm whichwas assigned to the monosubstituted methylenecarbon, as well as with the signal of the carbonylcarbon at 159.3 ppm. From this fact, it was concludedthat the main component of the peak 3 was tris ( 4-

hydroxybenzyl)urea.

COCONDENSATJON OF UREA WITH METHYLOLPHENOLS 1621

o_t",lol ratio of PMP / U = 1. It is obvious that the strongeracidic condition made the reaction time shorter toproduce condensates. In the state under pH 2.0, theoily reactant began to separate from the water layerwithin 10 min, and it was important that the prod-ucts mainly consisted of hydroxybenzylurea. Figure6 shows the NMR spectrum of the whole reactantunder pH 3 (AcOH), in which the self-condensationof 4-hydroxybenzyl alcohol was entirely negligiblebecause of the absence of the methylene signals at35.9ppm (o,p-linkage) and 40.5 ppm (p,p-linkage).

Figure 2 shows the changes of gel permeationchromatograms of the reactants by the differentmolar ratio (PMP /U) at the same pH (2.0) andreaction time (30 min). When the molar ratio wasbelow 1.0, only the three peaks identified in the pre-vious section could be recognized. On the other hand,the high molecular-weight part began to be observedin the chromatograms of the reactant at the molarratio of 2.0 and 4.0. Their GPC patterns, however,were different from that of the novolak synthesizedfrom 4-hydroxybenzyl alcohol at the same condition.Figure 7 shows the NMR spectra of the reactantsat PMP /U = 1 and 2, the latter of which the signalsdue to the self-condensation of 4-hydroxybenzyl al-cohol can be observed at around 35 and 40 ppm aswell as those due to the cocondensation at around44 and 49 ppm. Every 4-hydroxybenzylurea shownin Figure 5 has the free o-position to react with theother molecule. Therefore the formation of the con-densates involving both of the cocondensation andthe self-condensation was considered at the highermolar ratio of PMP /U, and the structures in whichone urea residue has several novolak-type substit-uents were proposed. .:

--is (.1)M

ELUTION VI]lIJC

FilUre 8. Gel penneation cbromatocrama of the mix-ture of urea and o-methylolphenol before (1) and after(2) reaction for 400 min under pH 3.0 (AcOH) at 85°C.Molar ratio: OMP IU = 1.

Figure 5 shows the structures of derivatives fromthe reaction of 4-hydroxybenzyl alcohol with ureain acidic condition.

The results of assignments on these derivativesare listed in Tables II and III including those ofaromatic carbons. It is extremely interesting thatthe formation of these hydroxybenzylureas wererecognized in the reaction of urea and p-methylol-phenol under acidic condition, and that the cacon-densation prevailed against the self-condensation ofmethylolphenol.

Effect of pH and Molar Ratio on Cocondensation

Figure 1 shows the effects of the pH on the reactionof 4-hydroxybenzyl alcohol with urea at the molar

1622 TOMITA AND HSE

@5..2""22-hydroxyWftzylurea

~c"z-~~N.N-BIS(2-h)droxybellZyl )um

N.N-8IS(2-hydroaybenzyl)u...

Tris(Z-hydroXybellZyl jure.

Figure 10. Structures of 2-hydroxybenzylureas.

Reaction of Urea with 2-Hydroxybenzyl Alcohol

Identification of Products

Figure 8 shows the changes of gel permeation chro-matogram on the equimolar reaction of urea and 2-hydroxybenzyl alcohol under pH 3.0 (AcOH) at85 °C. Though a large amount of urea still remainedunreacted after reacting 400 min, a considerableconsumption of 2-hydroxybenzyl alcohol was rec-ognized, and the 13C- NMR spectrum of the reactant

showed three signals at 35.8, 40.6, and 46.4 ppmshown in Figure 9. The signal at 35.8 ppm was as-signed to the carbon of o,p-methylene linkage of theself-condensed novolaks. Though the signal at 40.6ppm might be assigned to the carbon ofp,p-meth-ylene linkage in phenolic resins, its formation waseasily denied since the model compound had onlyo-methylol group. The chemical shift was identicalwith the value determined as methylene carbon of2-hydroxybenzylurea in previous studies.l.2 More-over the signal at 161.3 ppm was assigned to thecarbonyl carbon of2-hydroxybenzylurea. The smallsignal at 160.3 ppm was assigned to the carbonylcarbon of N,N'-bis(2-hydroxybenzyl) urea in a sim-ilar manner as the assignment of N,N'-bis(4-hy-droxybenzyl)urea. The methylene carbOn of N,N'-bis(2-hydroxybenzyl)urea will be overlapped withthat of 2-hydroxybenzylurea at 40.6 ppm. The smallsignal at 46.4 ppm implied the disubstituted meth-ylene carbons to amide group of tris(2-hydroxy-benzyl)urea or N,N-(2-hydroxylbenzyl)urea. Thedownfield shift by 5.8 ppm from the monosubstitutedmethylene carbon ( 40.6 ppm) was identical with thatobserved between tris (4-hydroxybenzyl) urea orN,N-bis(hydroxybenzyl)urea and 4-hydroxyben-zylurea as shown in Table II.

Figure 10 shows the structures of 2-hydroxyben-

zylureas.

COCONDENSATION OF UREA WITH METHVLOLPHENOLS 1623

150 I~ 50 I-I

13C-NMR Spectrum of crude 2,4.6-trimethylolphenol after acidification.Figure 12.

EHKfs of pH and Molar Ratio on Cocondensation

In Figure 9 the signal at 61.1 ppm was easily assignedto the unleacted methylol carbon of2-hydroxybenzylalcohol and that at 69 ppm was also assigned to thecarbon of dimethylene ether linkage.6.s When com-pared with 4-hydroxybenzyl alcohol (Fig. 6), thecocondensation of 2-hydroxybenzyl alcohol and urea... confirmed to be slow at pH 3.0 (AcOH). Gelpermeation chromatography on reactions of themolar ratios aMP IV = 0.2 or 0.5 at a strong acidiccondition of pH 2.0 showed that 2-hydroxybenzylalcohol was completely consumed after reacting from30 min to form polymeric materials. Figure 11 showsthe NMR spectra of the oily materials isolated fromboth reaction mixtures. The presences of the strongsignal at 35.8 ppm due to the o,p-methylene carbonand that at around 30 ppm due to the o,o-methylenecarbon indicated that the self-condensation of2-hy-droxybenzyl alcohol was the main reaction. The in-tensity of the cocondensed methylene carbon at 40.6ppm was about half of the self-condensed methylenecarbon. The formation of the cocondensed polymer,in .which urea residue was grafted by a novolak typesubstituents, was suggested besides the coexistenceof novolaks themselves.

phenol and monomethylolphenols in the samplewere denied by the NMR spectrum.

When the acidified solution was reacted with ureaat the molar ratio ofTMP IU = 0.33, the oily prod-ucts began to separate from water layer after react-ing under pH 2.0 at 85°C for 30 min. Its gel per-meation chromatogram (Fig. 13) shows the for-mation of polymeric materials. In the 13C-NMRspectrum (Fig. 14) three signals at 40.5, 44.3, and49.2 ppm are observed as well as the signal of un-reacted o-methylol groups at 61.5 ppm. Since thestarting materials had quite few free positions avail-able for reaction with a methylol group, the self-condensation by the methylene linkage was almostdenied, which was also con finned by the absence ofthe signal due to the o,p-linkage in the magneticfield of around 36 ppm. Therefore the signal at 40.5ppm was safely assigned to the cocondensed meth-ylene carbons between a-position and urea residue,

Reaction of Urea with 2,4,6- Trimethylolphenol

According to Freeman,3 sodium 2,4,6-trimethylol-phenate was obtained and its water solution wasused as 2,4,6-trimethylolphenol after acidification.Figure 12 shows the 13C-NMR spectrum oftbe acid-ified solution, where the presence of self-condensatesis almost negligible. Two large signals at 61.7 and64.6 ppm were easily assigned to the carbons of 0-and p-methylol groups of 2,4,6-trimethylolphenol,respectively.6,6 The small signal at 61.5 ppm was as-signed to the carbon of o-methylol group in 2,4-di-methvlolphenol.6 The presences of 2.6-dimethylol-

. . . . . . . . . . . . ..1. . .XI 45 60 (.1)

ELUTIC* VOlIM

Fipre 13. Gel permeation chromatOlr8m8 of ( 1) thereactant from urea and trimethylotphenot and (2) oilyprecipitates. Reaction condition: TMP / U = 0.33, pH 2.0,

85°C, 30 min.

1624 TOMITA AND HSE

and that at 44.3 ppm to those between p -positionand urea residue. Further N,N-disubstituted meth-ylene linkage was concluded to form mainly fromp-methylol group because of the presence of the sig-nal at 49.2 ppm. Therefore no self-condensation ofphenols were recognized.

From these results it was proved that this polymerwas the alternative copolymer of" urea ~d phenolthrough methylene linkage like as the structure rep-resented in Figure 15. It is particularly of significancethat the alternative copolymer can be synthesizedby the simple method under acidic condition.

more, it should be noted that the alternative copol-ymer could be synthesized from the reaction of 2,4,6-trimethylolphenol with urea. It was found that thecocondensation between p-methylol group and ureais faster than the self-condensation of p-methyloleven at the low pH « 3.0), and that p -methylolgroup has the stronger reactivity of urea than 0-

methylol group.This is the first time that the cocondensation be-

tween urea and phenol through formaldehyde hasbeen elucidated completely. We hope that these re-sults will develop not only the new urea/formal-dehyde / phenol resin system, but also the chemistryof the whole formaldehyde resins.

CONCLUSION This research was performed under the Research Agree-ment No. 19-87-076 between Faculty of Agriculture. TheUniversity of Tokyo and Southern Forest ExperimentStation. USDA Forest Service.

The reaction of urea with methylolphenols underacidic conditions were investigated using 2- and 4-hydroxybenzyl alcohol and crude 2,4,G-trimethylol-phenol as model compounds. Several new cocon-densed compounds between urea and phenol throughmethylene linkage have been identified. Further-

REFERENCES AND NOTES

1. B. Tomita and T. Matsuzaki. 1nd. Ens. Chern. Proc.Res. Dev.. 24, 1 (1985).

2. B. Tomita and T. Matsuzaki. ACS Poiyrn. Prepr..24(2).165 (1983).

3. J. H. Freeman. J. Chern. Soc., 6257 (1952).4. B. Tomita and S. Hotono. J. Poiym. Sci. Poiym. Chern.

Ed.. 18,2509(1978).5. A. J. J. de Breet. W. Dankelman. W. G. B. Huysmans.

andJ. de Wit. Angew. Makromol. Chern.. 82,7 (1977).6. H. Pasch. P. Goetzky. and H. Raubach. Acta Poiyrn..

32(1).14 (1981).

~ C)t ~

~ Hz

~~C"z-~-C"z~2~ -,

~_..AOL ~ ~C)t

- '-~-'l-~0!z.@:~~

Received January 29, 1990Accepted AUlUlt 5, 1991

Figure 15. Structure for the alternative copolymer fromurea and 2.4,6-trimethylolphenol. .