Printer Friendly

Co-condensates of resorcinols and methylol compounds for adhesive resins.

INTRODUCTION

The most important example of the practical use of formaldehyde co-condensates includes phenolresorcinol co-condensation resins for production of laminated timber. A similar resin has been successfully synthesized, substituting the resorcinol by oil-shale alkylresorcinols, containing about 50% of 5-methyl-resorcinol (1). The purpose of the synthesis is to obtain the maximum amount of co-condensates by the reaction of initially formed phenolic methylol derivatives with resorcinolic component.

13C NMR has been the most powerful analytical tool used to characterize phenol-formaldehyde resins and to a much lesser extent resorcinol-formaldehyde resins (2). The upfield shift of bridge carbon signals from pp[prime]-methylene to 2,2[prime]-methylene is influenced mainly by ortho-hydroxyl effects with the quite similar values for o,o[prime]- and 4,4[prime]-bridge carbons. Some of the 13C assignments are not specific also for co-condensate phenol-resorcinol resins (3), particularly in the presence of homocondensates. Quantitative applications are not very comprehensive. At the same time GPC/13C NMR analysis shows that the co-condensates of methylolphenols with resorcinol and 5-methylresorcinol are quite similar with dominating content of 4,o- and 4,p-methylenes.

The combined 1H and 13C NMR study was used mainly for investigation of phenol-formaldehyde resins (4, 5). It has been shown by a bromination method (6) that the reaction of o-methylolphenol with resorcinol is of second order assuming that the reaction product is trihydroxydiphenylmethane. An attempt has been made to determine the structural fragments by 1H NMR in acetylated phenol-resorcinol-formaldehyde resins (7).

Not devaluating the possibilities of 13C NMR, in this study we use 1H NMR as the more convenient method for quantitative determination of the content of various structural fragments in the course of formation of some co-condensates. We have experience with the co-condensation of some methylolxylenols and dimethylolcresols with resorcinol and 5-methylresorcinol (8). The complicated effect of the ortho-para-substituents distorts the well-known relative reactivities of ortho- and para-methylols and cannot be used directly in resin synthesis. As the sources of bound formaldehyde, we used ortho- and para-methylolphenols as the first-formed and most abundant compounds in the phenol-formaldehyde reaction. To draw more general conclusions about the co-condensation mechanism, some other methylol-derivatives are also included. The additional experimental results with N-methylolcaprolactam (9) are suitable to present here. According to Tomita, et al. (10) the incorporation of urea into the co-condensates occurs in the reaction with methylolphenols in the presence of acid catalysts. Methylol containing urea resins should be used in condensation with resorcinol (11). In this study methylol-N,N-diethylurea alongside of other methylolureas as the model compound was used.

Without discussing more thoroughly the solvent effects on 1H NMR, spectra obtained in pyridine are presented. The last one is a good solvent for phenolic and resorcinolic co-condensates and because of phenolic hydroxyl-pyridine hydrogen bonds the 1H signals of differently located methylols, dimethylene ethers and methylenes are better resolved.

EXPERIMENTAL

Materials

Commercial grade resorcinol (R) and 5-methylresorcinol (5MR) were recrystallized from benzene (m.p. 110.8 and 110.2 [degrees] C, correspondingly). 2,5-dimethylresorcinol (2,5DMR) was separated from oil shale alkylresorcinols by multiple crystallization from organic solvents (content of main substance 98.4%, m.p. 161.5 [degrees] C). Para-methylolphenol (p-MP) was synthesized by reduction of p-hydroxybenzaldehyde with NaB[H.sub.4] aqueous alkaline solution by cooling. After neutralization with [H.sub.2]S[O.sub.4] and filtration p-MP was recrystallized several times from ethyl acetate/hexane (3/1) (m.p. 124 [degrees] C, 1H NMR of C[H.sub.2]OH - 4.76 ppm in Py). A commercial grade ortho-methylolphenol (o-MP) was recrystallized several times from benzene/ethyl alcohol (20/1) (m.p. 84.0 [degrees] C, 1H NMR of C[H.sub.2]OH - 5.11 ppm in Py). N-methylolcaprolactam (MCL) was prepared from caprolactam and 37% aqueous solution of formaldehyde (molar ratio 1/1) in boiling benzene with continual removal of water. After distillation of benzene, MCL was recrystallized from diethyl ether (m.p. 67.3 [degrees] C, 1H NMR of C[H.sub.2]OH - 5.08 ppm in Py). Methylolurea (MMU) and N,N[prime]-dimethylolurea (DMU) were prepared in the presence of [Na.sub.2]HP[O.sub.4] from urea and 37% aqueous solution of formaldehyde (2/1 and 1/2 accordingly) by the reaction at 25 [degrees] C (2 h) and 0 [degrees] C (24 h). Solidified MMU and DMU were recrystallized twice from ethanol (m.p. 111 [degrees] C, 1H NMR of C[H.sub.2]OH - 5.05 ppm in Py and m.p. 136 [degrees] C, 1H NMR of C[H.sub.2]OH - 5.12 ppm in Py). Methylol-N,N-dlethylurea (MDEU) was synthesized from N,N-diethylurea and formaldehyde with equimolar ratio of reagents analogically, and after solidification was recrystallized from diethyl ether (m.p. 98.0 [degrees] C, 1H NMR of C[H.sub.2]OH - 5.06 ppm in Py).

Studied Systems

Co-condensation reactions of methylolphenols (MP) with resorcinols were performed in the melt at 120 [degrees] C in the presence of various catalysts (NaOH, Zn[(OCOC[H.sub.3]).sub.2], [C.sub.6][H.sub.5]COOH). The following molar ratios were used:

o-MP or p-MP/R = 1/1

o-MP or p-MP/5MR = 1/1

o-MP/p-MP/R or 5MR = 1/1/2

o-MP or p-MP/R/5MR = 1/1/1

o-MP/p-MP/R/5MR = 1/1/1/1

The quality of catalyst is expressed in moles per one mole of MP and is presented in tables (see Results).

Co-condensation reactions of MCL with resorcinols were performed in the melt at 70 [degrees] C in the presence of HCl as catalyst. The following molar ratios were used:

MCL/R or 5MR/HCl = 1/1/0.0005; 2/1/0.00075

MCL/R/5MR/HCl = 1/1/1/0.0005; 2/1/1/0.001; 4/1/1/0.0015

Co-condensation reactions of methylolureas with resorcinols were performed in the melt at 100 [degrees] C and in aqueous solution (20 moles) at 20 [degrees] C without catalyst and in the presence of 0.001 mole of para-toluenesulfonic acid (p-TSA). The following molar ratios were used:

MDEU/R or 5MR = 1/1 and 2/1

MMU/R or 5MR = 1/1 and 2/1 (1/4 in solution)

DMU/R or 5MR = 1/2 and 1/1 (1/8 in solution)

The samples were taken depending on the rate of methylol disappearance from the reaction mixture.

2,5DMR was condensed with methylol compounds in the melt. The following molar ratios and conditions were used:

o-MP or p-MP/2,5DMR = 1/1 and 2/1 without catalyst at 170 [degrees] C

MCL/2,5DMR/HCl = 1/1/0.001 and 2/1/0.001 at 80 [degrees] C

MDEU/2,5DMR/p-TSA = 1/1/0.001 and 2/1/0.001 at 100 [degrees] C

1H NMR Measurement

1H NMR spectra were obtained on a 100 MHz TESLA BS-567 spectrometer in pyridine-[d.sub.5] and also in DMSO-[d.sub.6] for some urea-containing samples. 1H chemical shifts were measured from internal hexamethyldisiloxane. Quantitative changes in methylol and methylene molar concentrations during the reaction were calculated from integral intensities of the corresponding 1H signals assuming no formaldehyde release throughout the reaction.

RESULTS AND DISCUSSION

Co-Condensation of Methylolphenols with Resorcinols

Spectral Assignments

According to the study of four two-component equimolar systems the methylene signals appear in the range of 4.08-4.55 ppm, but their spectra are quite different. This also makes it possible to study the reaction in three-component systems, containing the equimolar mixture of o-MP and p-MP with R or 5MR or the equimolar mixture of R and 5MR with o-MP or p-MP. Spectra of reaction products are presented in Fig. 1. Co-condensation of methylolphenols with resorcinols was practically the only reaction observed under the conditions used. There is no sign of formaldehyde release with subsequent reaction with resorcinols. Tendency to self-condensation of methylolphenols should be the greatest in the system p-MP/R but also in this case we can ascertain only about 5% of p,p-dimethylene ether (4.42 ppm). The absence of well-resolved signal of p,p-methylene at 3.76 ppm refers to the subsequent co-condensation of ether, mentioned. The alkaline catalyst influences only on the system o-MP/R enhancing the amount of self-condensate to 20%.

Spectral assignments (Table 1) clearly show the predominant substitution of R(5MR) at two equal positions (C4, C6). We can see [ILLUSTRATION FOR FIGURE 1 OMITTED] that the substitution with p-methylols in comparison with o-methylols gives the signals in the upper field (4.08-4.25 ppm and 4.28-4.55 ppm accordingly). The influence of R and 5MR reveals within the limits of regions mentioned. The signals of methylenes linked to 5MR appear in lower field. At the same time the disubstitution in comparison with monosubstitution in case of 5MR [TABULAR DATA FOR TABLE 1 OMITTED] gives the downfield shift of methylene signals. The upfield shift of methylene signals due to 4,6-disubstituted R occurs only in reaction with o-MP. In case of co-condensation with p-MP the methylene signals under discussion coincide.

The signals at 4.42-4.50 ppm are assigned to the methylenes substituted at C2 of the R or 5MR ring. Consequently, the hydroxyl effects have the decisive role to their chemical shift. In case of system o-MP/5MR they are overlapped by other signals. The extent of 2-substitution does not depend on the catalyst and forms about 10 and 15% of the total methylenes for R-containing systems and for p-MP/5MR accordingly. Hence, for the system o-MP/p-MP/R [ILLUSTRATION FOR FIGURE 1 OMITTED] we can quite successfully determine the relative amount of o-MP and p-MP that reacted at any moment with R. In case of o-MP/p-MP/5MR [ILLUSTRATION FOR FIGURE 1 OMITTED] we hope that we do not make a great mistake supposing that the signal in the region of 4.41-4.51 ppm involves also the overlapped signals of C2-methylenes with the intensity of 15% of total co-condensate methylenes. The same principles can be used for calculating the ratio of methylenes linked to R and 5MR in co-condensation of their mixture with o-MP or p-MP [ILLUSTRATION FOR FIGURE 1 OMITTED]. The four-component system gives the most complicated spectrum [ILLUSTRATION FOR FIGURE 1 OMITTED]. All signals assigned are present. Only the signal at 4.28 is overlapped by others, but in case of preferable reaction of 5MR it is not very probable that 4,6-disubstitution of R with o-MP really occurs. Because of the complicated character of methylene signals region, the quantitative calculation is not very reliable. At the same time it is clear that the reaction of 5MR is preferable, especially with p-MP, enhancing the content of 4,6-disubstituted compounds. The share of methylenes linked to R can be estimated to 30-35% from the total methylenes.

Surprisingly, only the alkaline catalyst and only in the case of o-MP has an influence on the composition of co-condensates with R and 5MR [ILLUSTRATION FOR FIGURE 2 OMITTED] enhancing the amount of 4,6-disubstituted rings. In other cases (without catalyst, Zn[(OCOC[H.sub.3]).sub.2], [C.sub.6][H.sub.5]COOH) the 1H NMR spectra of co-condensates do not depend on the type and amount of catalyst present.

The high melting point of 2,5DMR enables us to carry out the co-condensation with o-MP and p-MP in the melt at 170 [degrees] C. In both cases two co-condensate compounds are formed which methylene signals assignments give no problems (Table 1). The share of methylenes in 4,6-disubstituted compounds can be estimated at 45% in both cases and with equimolar ratio of reagents.

In conclusion, it is worth mentioning that the co-condensation is the predominant reaction in case of molar ratios used here and also in practical synthesis. In the conditions of great excess of methylolphenols the self-condensation of the latter becomes notable and formaldehyde released from dimethylene ether is used also for reaction with resorcinols.

Kinetic Measurements

Study of co-condensation process shows the linear dependence of the logarithm of methylol concentration on time. The difference in 1H shifts of ortho- and para-methylols (5.11 and 4.76 ppm) permits the determination of the reaction rate for both of them separately in their mixture. Some examples are presented in Fig. 3-5. It is notable that, regardless of C4, C6-disubstitution and the influence of C2-substitution, the methylol disappearance follows the first order during the whole process. The reaction in the most complicated four-component system is the best example [ILLUSTRATION FOR FIGURE 5 OMITTED]. The first order rate constants with respect to methylol concentration are presented in Tables 2 and 3. They are in good agreement, only the reaction with the mixture of methylols approaches their reaction rate to some extent with the exception of benzoic acid as catalyst.

Ratios of apparent rate constants quite clearly show the higher reactivity of p-MP in all the cases studied. The rate difference is obviously the result of a higher stability of the para-quinoidal canonical form of p-MP and of strong rate-retarding effect of intramolecular H-bond in o-MP. The reactivity difference is more pronounced in reaction with R and mainly because of the greater affinity of p-MP towards R. Alkaline and acid catalysts enhance the reactivity of p-MP. On the basis of molar concentration, the most effective catalyst is zinc acetate, enhancing the co-condensation rate of o- and p-MP with resorcinols equally. It can be explained by the similar configuration and higher strength of intramolecular H-bond and Zn-co-ordination bond in the case of o-MP in comparison with respective intermolecular bonds with p-MP.

Co-condensation rates with 5MR and R (Tables 2 and 3) allow one to predict preference of the latter in the co-condensation of o- and p-MP with the mixture of R and 5MR under the conditions used. It is quite different from the reaction of R and 5MR with formaldehyde and refers to the decisive factor of the reactivity of methylol electrophilic reagent on reaction rate. Actually, the overall reaction rate is quite similar to that observed for systems o-MP/R and p-MP/5MR (Table 2). Methylene distribution, according to above-mentioned calculation principles, shows that the reaction of 5MR is preferred. The amount of methylenes linked to R increases in the presence of catalysts, but in these conditions they never surpass the 40% level. We can only conclude that in concentrated systems the complicated physico-chemical interactions cause substantial changes in relative reactivities of R and 5MR when reacting them as a mixture.

Co-condensation of Methylolcaprolactam with Resorcinols

Different from the previous system, co-condensation with MCL needs highly selective catalytic conditions (9). Because of the equilibrium reaction of MCL formation in the case of equimolar mixture of reagents without catalyst, not more than 70% of co-condensate is formed. In the presence of alkaline catalyst only decomposition of MCL with subsequent reaction of formaldehyde with resorcinols occurs. Acetic acid as catalyst promotes the formation of resorcinolic resin and methylenedicaprolactam alongside co-condensate. Only a strong acid catalyst (here HCl) gives the quantitative amount of asymmetrical methylene cocondensates. The additional condition MCL/R(5MR) [less than or equal to] 2 is important to exclude the formation of methylenedicaprolactam entirely. The fastest reaction in all cases studied is self-condensation of MCL, but only to the equilibrium mixture with dimethylene ether (40-50%). In fact the co-condensation proceeds as electrophilic substitution by carbocation, sources of which can be MCL or ether, or both.

Spectral Assignments

We can see ([ILLUSTRATION FOR FIGURES 6, 7 OMITTED], and Table 1) that co-condensate methylene shifts depend not only on location of substitution in aromatic ring but also on structure of co-reagent. Caprolactam in comparison with phenol causes the co-condensate methylenes to give the signals in lower field (4.45-4.89 and 4.08-4.55 ppm accordingly). Also here the hydroxyl effects have the determining significance to the chemical shifts of methylenes substituted at C2. They are quite similar in case of R and 5MR and appear in the range of 4.53-4.63 ppm. In co-condensation of R/5MR mixture with MCL their quantitative amount can be considered as the total C2 substitution. Different from MP, the influence of MCL is very specific on methylene shifts in case of 5MR giving C4 and C6 signals in comparison with C2 signals in lower field (4.69-4.89 ppm). It is of great value for quantitative calculation in case of R/5MR mixture co-condensation with MCL. For all ten possible co-condensate compounds, specific [TABULAR DATA FOR TABLE 2 OMITTED] [TABULAR DATA FOR TABLE 3 OMITTED] methylene shifts are assigned, and only for C4 and C4C6 substituted R do the signals coincide.

Kinetic Measurements

The rate of co-condensate formation shows complicated kinetics [ILLUSTRATION FOR FIGURE 8 OMITTED]. Unlike the previous system, the main reason is the different rate of mono-, di- and trisubstitution in resorcinols. The disappearance of methylol and the initially formed ether from reaction mixture was not subjected to any kinetic order. Regardless, it is clear that the first-step high rate is connected with the formation of mono-substituted compounds. In equimolar mixtures the co-condensation slows because of advancing of disubstitution, but the three possible models of disubstitution have similar rates. In cases of excess MCL, the formation of trisubstituted compound by two possible models leads to the next slowing down. We can conclude that the co-condensation rate depends mainly upon the molar ratio of reagents, but not significantly on the type of resorcinolic component.

At the same time we have made some quantitative calculations of reaction mixtures composition observing the above-mentioned principles. According to the results presented in Tables 4 and 5, the affinity of resorcinols to C2 substitution is greater in reaction with MCL in comparison to that with MP. The other difference is the preferred formation of 2,4-disubstituted compounds in reaction with MCL (Table 6). In the case of equimolar mixture, the C2/C4 ratio does not change in the course of reaction (Table 4) despite the presence of 30-50% of methylenes in disubstituted compounds. The excess of MCL leads to the increase of C2 substitution (Table 5), which is due to 2,4- and 2,4,6-substituted compounds in products (Table 6).

A similar C2/C4 substitution ratio in co-condensation of R and 5MR with MCL is quite evident (Tables 4 and 5). In R/5MR mixtures it allows estimation of their relative reactivity only by C4 substitution. Analogous to the reaction with MP, the favorable co-condensation of 5MR can also be observed here. It is clear that the ratio of methylenes reacted with 5MR and R depends upon the conversion degree. The difference is greatest in case of preferred formation of monosubstituted compounds. The excess of MCL leads to a continual diminution of the ratio mentioned (Table 5). It means that in the final product, the amount of methylenes linked to R and 5MR is equal but the preferred reaction of 5MR in the first step is expressed through different composition of co-condensates (Table 6).

Co-Condensation of Methylolureas with Resorcinols

The main principle for successfully obtaining co-condensates is the initial binding of formaldehyde to reagent of lesser reactivity. It was obtained in two previous systems and also in co-condensation of methylolphenols with urea, This system is the most complicated because of the use of the higher reactivity methylol compound. It means that the co-condensation needs highly selective conditions. At the same time the importance of the methylol compound is not so great, as it can be formed in reaction mixture. However, in this study we used methylolureas, because of formation of co-condensates in greater amount. The alkaline catalyst was excluded because of the prevalence of resorcinolic resin in the products.

Co-Condensation with Methylol-N,N-Diethylurea

We expect that MDEU models the methylolurea type reagent in the co-condensation with resorcinols but because of monofunctionality gives products of better solubility and the interpretation is more adequate. Because of higher reactivity the self-condensation of MDEU is the main reaction in melt-condensation with R and 5MR without catalyst [ILLUSTRATION FOR FIGURE 9 OMITTED], giving the methylene compound with typical 1H signal at 4.81 ppm (triplet). The released formaldehyde reacts with resorcinolic component. As with MCL, the acidic catalyst is the obligatory condition to obtain co-condensates. The results of co-condensation with R and 5MR are similar. In melt-condensation at 100 [degrees] C in presence of p-toluenesulfonic acid as catalyst not more than 80-90% of co-condensate is obtained [ILLUSTRATION FOR FIGURE 9 OMITTED]. No self-condensate of MDEU is formed but the product contains about 10-15% of methylenes in resorcinolic resins.

The co-condensate methylenes give doublet signals due to the influence of amine hydrogen. C2 methylene signals appear in the lower field again because of hydrogen effects and they are not very specific depending [TABULAR DATA FOR TABLE 4 OMITTED] on R and 5MR (Table 1). The extent of 2-substitution is about 20% in case of the equimolar mixture. Co-condensate C4 and C4C6 methylenes are predominant in both cases. One resolved doublet signal allows quantitatively estimate the ratio of C4 and C4C6 substitution [ILLUSTRATION FOR FIGURE 9 OMITTED]. Signals of co-condensate methylenes, similar to other systems, appear in lower field for the condensation product with 5MR in comparison with R. Unlike other substituents here the C4C6 methylenes, in comparison with C4 methylenes, give the upfield shift of signals not depending on resorcinolic compound (Table 1). In case of 2,5DMR the shift enables us to estimate the presence of two compounds as well.
Table 5. Composition of Co-Condensates.

 Molar Methylene Distribution, %

 C2 R/5MR/MCL = 1/1/4

 C2 C4

Reaction R/MCL 5M/MCL
Time 1/2 1/2 R + 5MR R 5MR 5MR/R

5 min 26.7 23.2 21.0 26.5 52.5 2.0
0.25 hr 27.6 21.7 21.6 27.0 51.3 1.9
0.5 hr 25.0 22.2 20.0 26.7 53.3 2.0
1 hr 24.4 24.3 27.4 27.4 45.2 1.6
3 hr 27.8 25.8 30.2 32.3 37.5 1.2
6 hr 27.6 30.0 31.1 31.1 37.8 1.2
9 hr 29.1 30.5 30.6 34.7 34.7 1.0
12 hr 30.1 31.3 30.6 35.1 34.3 0.98
15 hr 29.0 31.7 - - - -
24 hr - - 30.4 35.1 34.5 0.98




[TABULAR DATA FOR TABLE 6 OMITTED]

The way to exclude the self-condensation reactions is to perform the co-condensation in aqueous solution at lower temperature [ILLUSTRATION FOR FIGURES 9 AND 10 OMITTED]. The quantitative co-condensation also promotes the change in product composition. Thus, the share of C4 monosubstitution is increased. The amount of C2 substitution diminishes, especially in case of reaction with R.

The tendency of MDEU in comparison with other methylol compounds to self-condensation appears in co-condensation with 2,5DMR in the melt [ILLUSTRATION FOR FIGURE 11 OMITTED]. The double amount of MDEU only slightly increases the quantity of co-condensate but evidently changes of C4C6/C4 substitution ratio in the co-condensate. Formaldehyde released in self-condensation of MDEU reacts with 2,5DMR but also the decomposition of MDEU is essential in the equimolar mixture. The lower reactivity of 2,5DMR towards formaldehyde in case of excess MDEU promotes the release of free formaldehyde from the system.

Co-Condensation with Mono- and Dimethylolurea

There are no problems to synthesize two methylol derivatives of urea under special conditions (see experimental). In condensation in melt or in aqueous solution with MMU, the formation of an equilibrium mixture from MMU, DMU and free urea occurs. Thus the products of co-condensation with resorcinols are not very specific depending on MMU or DMU. The high melting point of reagents (especially of DMU) allows the condensation in melt at a temperature where the decomposition of methylol compound is significant. The reaction of R or 5MR with MMU and DMU at 100 [degrees] C in melt without catalyst or in the presence of p-toluene sulfonic acid catalyst gives the mixtures of co-condensates with self-condensates. An interesting difference was ascertained. In reaction with DMU, the decomposition of the latter is favored and the preferred resorcinolic resins are formed. Because of high reactivity of free position of urea, the reaction with MMU leads to methylene derivatives of urea in a greater amount.

The co-condensation should be performed at a temperature lower than 100 [degrees] C and consequently in solution. One approach involves the use of great excess of R or 5MR [ILLUSTRATION FOR FIGURE 12 OMITTED]. The spectrum of reaction product with MMU is similar but no signal of methylenes of resorcinolic resin is present (4.25 ppm). The co-condensate methylenes give doublet signals at 4.43 and 4.47 ppm in both cases but with different ratio of intensity. They are assigned to methylenes linked to mono- or disubstituted urea and C4 substituted R. Both compounds can be isolated from reaction products with MMU and DMU by extraction (m.p. 133 [degrees] C and 112 [degrees] C accordingly).

The equimolar ratio of reagents or the excess of MMU leads to a different pattern of substitution. The spectra of some products are presented in Figs. 13 and 14. In conditions used, the decomposition of MMU is not very essential, and the multiple substitution in R or 5MR occurs. Owing to hydroxyl effects, the methylene signals of C2 substitution appear at lower field. The excess of MMU promotes C2C4 disubstitution [ILLUSTRATION FOR FIGURE 13 OMITTED]. The C4C6 substitution gives the methylene signals in a narrow region of 4.37-4.48 ppm (Py) and they are not very specific depending on R and 5MR.

The co-condensation of DMU with R and 5MR is the most complicated system because of the multifunctionality of both reagents. The appearance of broad multicomponent signal at 4.3-4.7 ppm (Py) can be ascertained as a sign of predominant formation of poly-co-condensates.

CONCLUSIONS AND SUMMARY

The study of co-condensation reaction of resorcinols with methylol compounds using 1H NMR spectroscopy is quite successful. In most cases the co-condensate methylene signals are specific, depending on location and number of substitution in aromatic ring and on structure of substituent used.

Catalytic conditions for co-condensation are different and depend mainly on affinity of co-reagents to formaldehyde and equilibrium of methylol formation. The tendency to co-condensation with resorcinols decreases in the following order: methylolphenols [greater than] N-methylolcaprolactam [greater than] methylolureas. In the two first cases melt-condensation can be used. The last system is the most complicated because of use of methylol of co-reagent of higher reactivity. The reaction in aqueous solution at lower temperature should be preferred. Only the acidic catalyst promotes the co-condensation with N-containing methylol compound.

The experience, obtained on model reactions, has been used to project the adhesive resins technology on the base of oil-shale alkylresorcinols. Co-condensates with phenol-formaldehyde prepolymers were successfully used for producing weather-proof laminated wooden constructions. Monofunctional N-methylolcaprolactam acts as molecular weight controlling end-group in polycondensate chains to modify rheological properties of synthesized adhesives. The urea-formaldehyde resins fortified with alkylresorcinols give low formaldehyde emission from particleboards with excellent mechanical properties.

REFERENCES

1. P. Christjanson, Adhesives and Bonded Wood Symposium, p. 267, Forest Products Society, Madison, Wis. (1994).

2. D. D. Werstler, Polymer, 27, 750 and 757 (1986).

3. H. Lippmaa, T. Valimae, and P. Christjanson, J. Adhesion Soc. Japan, 24, 255 (1987).

4. M. F. Grenier-Loustalot, S. Larroque, P. Grenier, J. P. Leca, and D. Bedel, Polymer, 35, 3046 (1994).

5. T. H. Fisher, P. Chao, C. G. Upton, and A. J. Day, Magnetic Resonance in Chemistry, 33, 717 (1995).

6. M. M. Sprung and M. T. Gladstone, J. Am. Chem. Soc., 71, 2907 (1949).

7. R. Anderson, A. H. Haines, and B. P. Stark, Angew. Makrom. Chem., 26, 171 (1972).

8. P. Christjanson and A. Koosel, J. Adhesion Soc. Japan, 25, 174 (1989).

9. P. Christjanson, Z. Arro, and A. Suurpere, J. Adhesion Soc. Japan, 25, 128 (1989).

10. B. Tomita and C. Y. Hse, Mokuzal Gakkaishi, 39, 1276 (1993).

11. E. Roffael, Adhasion, No. 12, 422 (1980).
COPYRIGHT 1997 Society of Plastics Engineers, Inc.
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1997 Gale, Cengage Learning. All rights reserved.

Article Details
Printer friendly Cite/link Email Feedback
Title Annotation:International Forum on Polymers - 1996
Author:Christjanson, Peep; Koosel, Arne; Siimer, Kadri; Suurpere, Aime
Publication:Polymer Engineering and Science
Date:Jun 1, 1997
Words:4668
Previous Article:International Forum on Polymers: status report 1996.
Next Article:Synthesis and properties of new esters of cellulose and inorganic polyacids containing phosphorus, molybdenum, tungsten and vanadium.
Topics:


Related Articles
Aromatic copolyester thermosets: high temperature adhesive properties.
Aliphatic/aromatic copolyester thermoset adhesives: synthesis and characterization.
Dow patents silicone resin emulsion process.
Eastman to expand resin production in the Netherlands, China.
Valspar patents low VOC coating.
NIGERIA - Resins.
Emulsion polymers.

Terms of use | Privacy policy | Copyright © 2018 Farlex, Inc. | Feedback | For webmasters