CH615443A5

CH615443A5 - Process for the manufacture of phenolic resins

Info

Publication number: CH615443A5
Application number: CH540476A
Authority: CH
Inventors: Daniel Hanton; Jean Davrou
Original assignee: Saint Gobain
Priority date: 1975-04-30
Filing date: 1976-04-29
Publication date: 1980-01-31
Also published as: NL180669B; ES447471A1; FI62109B; DE2618665C2; IE43622L; JPS6016449B2; ZA762315B; NL180669C; FR2309574B1; IT1062311B; AT351264B; IE43622B1; NO146641B; FR2309574A1; IL49492A0; ATA316576A; SE426837B; DE2618665A1; FI761169A; LU74858A1

Abstract

After having carried out the condensation of phenol with formaldehyde in two stages in the presence of sodium hydroxide, the reaction mixture is cooled and is acidified to a pH of 3 to 4 by addition of hydrochloric acid, after which the resin is allowed to deposit and is separated from aqueous phase. The resin thus obtained has a viscosity of 1100 to 4000 cPo in the case of a solids content of 70 to 74 % respectively. This viscosity range is suitable very particularly for the use of the resin for the manufacture of phenolic foams.

Description

A cet effet l'invention concerne un procédé pour la fabrication de résines phénoliques destinées notamment à l'obtention de mousses, lesdites résines ayant un extrait sec compris entre 70,0 et 74,0% et une viscosité comprise entre respectivement 1100 et 4000 cPo, selon lequel on condense en milieu aqueux un mélange de phénol et de formaldéhyde en présence d'un catalyseur alcalin, le formaldéhyde et le catalyseur alcalin étant ajoutés au phénol en deux stades successifs. Ce procédé est caractérisé en ce que l'on ajoute au milieu réactionnel, après l'avoir refroidi à la fin du dernier stade de condensation, une quantité d'acide suffisante pour obtenir un pH compris entre 3,0 et 4,0, de préférence entre 3,4 et 3,6 et l'on sépare la phase résineuse du milieu aqueux. To this end, the invention relates to a process for the manufacture of phenolic resins intended in particular for obtaining foams, said resins having a dry extract of between 70.0 and 74.0% and a viscosity of between 1100 and 4000 cPo respectively. , according to which a mixture of phenol and formaldehyde is condensed in an aqueous medium in the presence of an alkaline catalyst, the formaldehyde and the alkaline catalyst being added to the phenol in two successive stages. This process is characterized in that, after having cooled it at the end of the last stage of condensation, a quantity of acid sufficient to obtain a pH of between 3.0 and 4.0 is added to the reaction medium. preferably between 3.4 and 3.6 and the resinous phase is separated from the aqueous medium.

De préférence on refroidit le milieu réactionnel à une température comprise entre 30 et 35° C avant l'addition de l'acide. Preferably the reaction medium is cooled to a temperature between 30 and 35 ° C before the addition of the acid.

Selon le procédé antérieur décrit dans le brevet français n° 2 147 766, on refroidit le mélange réactionnel après la deuxième addition de formaldéhyde. Ce mélange contient un excès de NaOH. Selon ce procédé antérieur on ajoute alors de l'acide chlorhydrique à 35 % pour neutraliser le NaOH et on règle le pH à environ 7. According to the prior process described in French Patent No. 2,147,766, the reaction mixture is cooled after the second addition of formaldehyde. This mixture contains an excess of NaOH. According to this prior process, 35% hydrochloric acid is then added to neutralize the NaOH and the pH is adjusted to approximately 7.

Au lieu d'arrêter l'addition d'acide chlorhydrique lorsque le pH atteint la valeur de 7 environ, on poursuit selon l'invention l'addition jusqu'à un pH entre 3,0 et 4,0. On a constaté qu'un pH 3,5 est obtenu lorsque la quantité d'acide versée correspond stoechiométriquement à la quantité totale de soude utilisée comme catalyseur. Cela signifie que, à cette valeur du pH, tous les groupes OH phénoliques présents dans la résine et se trouvant précédemment â l'état de phénates de sodium, solubles dans l'eau, se trouvent libérés. Instead of stopping the addition of hydrochloric acid when the pH reaches the value of approximately 7, the addition is continued according to the invention up to a pH between 3.0 and 4.0. It has been found that a pH 3.5 is obtained when the quantity of acid poured corresponds stoichiometrically to the total quantity of sodium hydroxide used as catalyst. This means that, at this pH value, all the phenolic OH groups present in the resin and which were previously in the form of sodium phenates, soluble in water, are released.

On comprend dès lors que pour les valeurs de pH entre 3,0 et 4,0 la séparation de l'eau de la résine par décantation soit plus complète et que l'extrait sec de la résine séparée soit plus élevé que le cas de la neutralisation à pH 7,0 à 7,5. It is therefore understood that for the pH values between 3.0 and 4.0 the separation of water from the resin by decantation is more complete and that the dry extract of the separated resin is higher than the case of the neutralization at pH 7.0 to 7.5.

On a constaté d'autre part que, lors de la neutralisation à pH 7,0, la quantité d'acide versée correspond sensiblement à 58% seulement de la quantité d'hydroxyde de sodium utilisée au total comme catalyseur. D'où la rétention de l'eau par les groupes phénates de sodium restant dans la résine et empêchant d'obtenir pour celle-ci après soutirage un extrait sec élevé, même après centrifugation. It has also been found that, during neutralization at pH 7.0, the amount of acid poured corresponds substantially to only 58% of the amount of sodium hydroxide used in total as catalyst. Hence the retention of water by the sodium phenate groups remaining in the resin and preventing a high dry extract from being obtained for the latter, even after centrifugation.

Le domaine de pH d'acidification du présent procédé constitue une zone optimale. En effet, si l'on acidifie à des valeurs de pH inférieures à 3,0 on obtient des résines qui, après séparation présentent des viscosités beaucoup trop élvées. Il semble que The acidification pH range of the present process constitutes an optimal zone. In fact, if we acidify to pH values below 3.0, we obtain resins which, after separation, have viscosities which are much too high. It seems like

3 3

615 443 615,443

l'excès d'acide introduit catalyse même à la température peu élevée où on opère la condensation de la résine d'où l'accroissement de sa viscosité. Inversement si la valeur de pH atteinte est supérieure à 4,0, on n'obtient plus les viscosités et les extraits secs suffisamment élevés pour atteindre une cellularisation fine et homogène dans l'épaisseur des panneaux de mousse. the excess acid introduced even catalyzes at the low temperature, where the resin is condensed, thereby increasing its viscosity. Conversely, if the pH value reached is greater than 4.0, viscosities and dry extracts are no longer obtained high enough to achieve fine and homogeneous cellularization in the thickness of the foam panels.

L'invention est décrite plus en détail dans les exemples ci-après. The invention is described in more detail in the examples below.

Exemple 1 Example 1

On acidifie selon l'invention le mélange réactionnel d'une résine préparée selon le procédé en deux stades du B.F. The reaction mixture of a resin prepared according to the two-stage process of the B.F. is acidified according to the invention.

Formaldéhyde Formaldehyde

2 147 766 avec un rapport total moléculaire —j 2,147,766 with a total molecular ratio —j

de 1,4 avec une quantité totale de soude de 2% en poids par rapport au phénol et on obtient les valeurs correspondantes suivantes pour l'extrait sec et la viscosité: 1.4 with a total amount of sodium hydroxide of 2% by weight relative to the phenol and the following corresponding values are obtained for the dry extract and the viscosity:

pH d'acidification 3,0 3,4 3,6 4,0 acidification pH 3.0 3.4 3.6 4.0

de la résine resin

Extrait sec de la 74,0 72,5 71,5 70,0 Dry extract of 74.0 72.5 71.5 70.0

résine décantée et soutirée en % resin decanted and withdrawn in%

en poids in weight

Viscosité à 20° C en 4000 2000 1500 1100 Viscosity at 20 ° C in 4000 2000 1500 1100

cPo de la résine décantée et soutirée cPo of the decanted and withdrawn resin

Exemple 2 Example 2

Dans un réacteur de 150 litres en acier inoxydable, muni d'une double enveloppe pour chauffer et refroidir et d'un moyen d'agitation énergique, on introduit 63,45 kg (675 moles) s de phénol et 67,50 kg de formaldéhyde en solution aqueuse à 36% en poids (810 moles). On porte la température du mélange à 50° C et à cette température on ajoute progressivement 1268 g d'une solution à 50% en poids d'hydroxyde de sodium. 63.45 kg (675 moles) of phenol and 67.50 kg of formaldehyde are introduced into a 150 liter stainless steel reactor provided with a double jacket for heating and cooling and with vigorous stirring means. in an aqueous solution at 36% by weight (810 moles). The temperature of the mixture is brought to 50 ° C. and at this temperature is gradually added 1268 g of a 50% by weight solution of sodium hydroxide.

Le mélange est chauffé jusqu'à 70° C environ et la tempérait) ture s'élève d'elle-même jusqu'à 100° C et on maintient celle-ci à cette valeur pendant 1 heure en refroidissant légèrement. The mixture is heated to about 70 ° C and the temperature rises by itself up to 100 ° C and is maintained at this value for 1 hour while slightly cooling.

On refroidit ensuite jusqu'à 80° C et l'on ajoute alors 11,25 kg de solution aqueuse de formaldéhyde à 36% en poids 'soit 135 moles. La température du mélange étant maintenue à 15 80° C, on ajoute 1268 g d'une solution à 50% en poids d'hydroxyde de sodium et on maintient cette température pendant 30 minutes. Then cooled to 80 ° C and then added 11.25 kg of aqueous formaldehyde solution at 36% by weight, or 135 moles. The temperature of the mixture being maintained at 80 ° C., 1268 g of a 50% by weight solution of sodium hydroxide are added and this temperature is maintained for 30 minutes.

On refroidit alors la résine jusqu'à 30° C et on la partage en huit parties égales. Ces différents échantillons de résine sont 2o acidifiés séparément par de l'acide chlorhydrique à 18% en poids sous agitation jusqu'à obtenir des pH respectifs compris entre 2,0 et 7,4. The resin is then cooled to 30 ° C and divided into eight equal parts. These different resin samples are 2o acidified separately with 18% by weight hydrochloric acid with stirring until the respective pH is between 2.0 and 7.4.

Après acidification les échantillons de résine sont abandonnés pendant 6 heures à la décantation naturelle et l'on sépare 25 alors pour chacun d'eux la couche de résine et la couche aqueuse. Sur toutes ces couches on mesure les caractéristiques qui sont indiquées au tableau ci-dessous. En outre, les résines séparées après neutralisation à pH 5,0,7,0 et 7,4 sont concentrées sous pression réduite jusqu'à un extrait sec de 72% et leur so viscosité est alors mesurée à nouveau. After acidification, the resin samples are left for 6 hours to natural decantation and the resin layer and the aqueous layer are then separated for each of them. On all these layers we measure the characteristics which are indicated in the table below. In addition, the resins separated after neutralization at pH 5.0, 7.0 and 7.4 are concentrated under reduced pressure to a dry extract of 72% and their viscosity is then measured again.

L'ensemble des résultats obtenus figure au tableau siuvant. All the results obtained are shown in the following table.

pH d'acidification 2,0* 3,0 3,4 3,6 4,0 5,0* 7,0* 7,4* acidification pH 2.0 * 3.0 3.4 3.6 4.0 5.0 * 7.0 * 7.4 *

de la résine resin

Extrait sec de la (X) 74,0 72,5 71,5 70,0 68,2 66,3 64,5 Dry extract of (X) 74.0 72.5 71.5 70.0 68.2 66.3 64.5

résine séparée en % en poids resin separated in% by weight

Viscosité en cPo et >20 000 4000 2000 1500 1100 1040 900 810 Viscosity in cPo and> 20,000 4,000 2,000 1,500 1,100 1,040 900,810

à 20° C de la résine séparée mesurée après 24 heures at 20 ° C of the separated resin measured after 24 hours

Viscosité en cPo à 3200 4100 5600 Viscosity in cPo at 3200 4100 5600

20° C de la résine séparée et concentrée sous pression réduite jusqu'à 20 ° C of the resin separated and concentrated under reduced pressure up to

72% d'extrait sec 72% dry extract

(X) On obtient un f loculat de résine à très haute viscosité qui est inutilisable et difficile à séparer. * à titre comparatif. (X) A very high viscosity resin loculus is obtained which is unusable and difficult to separate. * for comparison.

C VS

Claims

615 443 2 CLAIMS

1. Process for the manufacture of liquid phenolic resins, intended in particular for obtaining foams, said resins having a dry extract of between 70.0 and 74.0% and a viscosity of between 1100 and 4000 cPo, respectively, according to which condenses in an aqueous medium a mixture of phenol and formaldehyde in the presence of an alkaline catalyst, formaldehyde and the alkaline catalyst being added to the phenol in two successive stages, characterized in that, after having cooled the reaction medium at the end from the last stage of the condensation, „a sufficient amount of acid is added to said medium to obtain a pH of between 3.0 and 4.0 and the resinous phase is separated from the aqueous medium.

2. Method according to claim 1, characterized in that a sufficient amount of acid is added to said medium to obtain a pH of between 3.4 and 3.6.

3. Method according to claim 1 or 2, characterized in that the phenol-formaldehyde mixture is produced in such a way that the formaldehyde / phenol molecular ratio is between 1.0 and 1.7, preferably between 1.0 and 1.6. 2n

4. Method according to one of claims 1 to 3, characterized in that the reaction medium is cooled to a temperature between 30 and 35 ° C before the addition of the acid.

5. Method according to one of claims 1 to 4, characterized in that it is acidified with concentrated hydrochloric acid.

6. Phenolic resin obtained by the process according to claim 1.

7. Phenolic resin according to claim 6, characterized in that its dry extract is between 71.5 and 72.5%.

8. Phenoline resin according to claim 6 or 7, charac-Sée in that its viscosity is between 1500 and 2000 cPo.

It is known according to French Patent No. 2,147,766 to manufacture phenolic foams from resols obtained by means of a condensation of formaldehyde and phenol, having the characteristic that the condensation reaction is carried out in two successive stages. 40

After this condensation, the reaction medium is neutralized until a pH of between 7 and 7.5 is obtained, then the resin is separated by decantation and withdrawal, and it is concentrated by elimination of water, for example by distillation under vacuum.

It is indeed essential to obtain panels of 45 foam, the cellularization of which is fine and homogeneous in thickness, to prepare the expandable dispersions from resins of which the viscosity is sufficient.

In the case where the viscosity of the resol is not high enough, the expandable dispersions which are obtained after the incorporation of the blowing agent, the surfactant and the curing catalyst also have viscosities. weak.

Consequently, the vapor bubbles formed by the blowing agent during its evaporation under the influence of the heat of the curing reaction at its beginning, tend to coalesce and to rise in the cream. Hence a coarse and heterogeneous cellularization in the thickness of the panels, the largest and most numerous pores being located near the upper face.

The resins obtained according to the method of patent no. 6o

2,147,766 after neutralization of the reaction medium, have for a range of dry extracts from 64 to 66%, at 20 ° C, viscosities of between 700 and 900 cPo.

However, these viscosities are such that the drawbacks mentioned above were encountered during the manufacture of foams.

This is why it was necessary to increase the viscosity of these resins, at the same time as their dry extract, by a fairly long additional operation of concentration under vacuum before the preparation of the expandable dispersions.

However, it was impossible, even when distilling at low temperature, under a sufficiently reduced pressure, to avoid during this concentration that the condensation of the resin does not continue, thereby increasing its viscosity in an exaggerated manner. Values of 4000 to 8000 cPo are thus reached at 20 ° C, for dry extracts respectively from 70 to 75%.

However, such viscosity values are troublesome for the preparation of expandable dispersions. Significant energy consumption is indeed obtained by the mixing devices, but also the mixing operation must be lengthened to obtain the necessary fineness of the dispersion. Hence the difficulty of manufacturing foams with reduced density.

Attempts have also been made to increase the viscosity by removing water by centrifugation. However the resin retained very strongly the water and even by an energetic centrifugation it was impossible to reach a dry extract of 70%.

It has now been found that these drawbacks and in particular the loss of time and energy of the concentration by distillation can be avoided. It is also possible to adjust very easily and at will the dry extract and therefore the viscosity of the resin, which greatly facilitates manufacturing.