CA1079439A - Method for manufacturing phenolic resins - Google Patents

Abstract

?? ? No. 1079439 ?? ISSUED 800610 ?? CLASS 402-54 C.R. CL.
?? INT. CL.2 C08G 8/10 ?? ?? CANADIAN PATENT ??

?? METHOD FOR MANUFACTURING PHENOLIC RESINS

?? Hanton, Daniel; Davrou, Jean;
France Granted to Saint Cobain Industries, France ?? APPLICATION No. 251,000 ?? FILED 760426 ?? PRIORITY DATE France(7513570)750430 No. OF CLAIMS 8 - No drawing DISTRIBUTED BY THE PATENT OFFICE. OTTAWA.
CCA-274 (5-79)

Description

l~r:TllOD I~OR ~NUl~/~CTUI~] NG PrlJ~NOLIC r~rSIl~S

ABSTRACT OF THE I)ISCLOSURE
; ' ' .
A method of making phcnolic resins from the conden-sation of phenol with formaldehyde in the pres0nce of a basic S catalyst is disclosed. After the condensation reac~ion has pro-ceeded to a desired point, the reaction mass is acidified to a pl~ between 3 and 4. This facilitates removal of water from the phenolic resin. As a result, the viscosity of the resin obtained is sufficiently high so that when the resin is used in combination 1 10 with blowing agents, surfactants, and catalysts to form rigid j foams,-such foams have uniform cellularization.
.~, ; ~ . , .
11 .
.'~ '' .. .
, I .
1, ' ' ' ' :.

~ . ' ' ~
.,. . ' '~., . , : .
.

. i ' ' . ' , ~ ' ' .~ . . , . . . .. ' ..

107S~4~9 BACKGROUND OF THE INVENTION
Field of the Invention This invention relates to the manufacture of phenolic resins and particularly to phenolic resins that S are useful for making rigid foams.

Prior Developments Canadian Patent Application, S~rial No. 139,727, . . , . filed April 14, 1972, in the name of Daniel Hanton, dis- :
.:~ closes a method of making phenolic resin by the condensa~ 10 tion of phenol and formaldehyde, in which quantities of both the formaldehyde and a basic catalyst are added to the phenol in at least two successive steps. According . to the process disclosed in the above-identified applica-. tions, after the last stage of the condensation reaction has proceeded to a desired point, the ~, ~

,,. , ~
.
"~ .
.',,.; ' ~ `

,, :
1`':' . :
,~.

.'", ...
~; '. ' ',`'`'' 1 `.
' : `
:'~' ~, : ,, " - ~ ,, ~ 7 ~

rc~ction en~iroluncnt i~ ncutralizc~ by thc adc1ition oE
an acid. Sufficient ncid is a(tdc~ to bring the pll of the reaction cnvironmcnt to betwccn ~ and 7.5. Then thc reaction mass is allowed to rest an(l thc resin phasc and the aqueous phase separate. The resin is then decantcd from the reaction mass. After this decantationJ ~he resin is ~ubjected to at least one additional water r~moval step, for example, vacuum distillation, to increase its viscosity.

According to the above-idcntified applications, the phenolic resin thus obtained can be used to manufacture rigid phenolic foams, by mixing a blowing agent, a surfactant, and a hardening catalyst with the resin, The resins obtained according to the method just outlined above, i.e., in whicn the reaction environ-,nent is ?i 15 neutralized to a pH ranging between 7 and 7.5, have dry extracts of 64 to 66 per cent, and have viscosities ranging between 700 and 900 centipoises ~cp).
~. . .
.. . .
- It has been found that when using resins having viscosities in this ~range, the vapor bubbles formed by the blowing agent during its evaporatio~ under the influence of heat at the outset of the hardening reaction can have a tendency to coalesce and to rise in the resin-bubble disper-sion. This can result in a non-homogcnous cellularization throughout the thickness of the foam. Where there is coa-lescence of the bubbles,}eterogeneous cellularization occurs, with tlle largest and greatest number of cells being found on the side of the panel that is uppcrmost during produ~tion.

.
.

- ~07943~

This rcsults in a foam lulving a non-uniforln dcnsity ~nd poor mcchanical properties, especially in thc rcgions whcrc rclativcly lar~c cclls are located.

, It sllould be ~ointed out that thc blowing a~ents, ' 5 surfactants, and hardening catalys~s that are commonly ', uscd have a tcn~ency to a~gravate this problem as they ' ' tend to reduce the viscosity'of the expansible mixturc and -, thus increase tlle likelihood that a heterogeneous cellulari-zation will occur.

It has been determined that, in order to obtain ; -foams having small cells and a homogeneous cellularization '' 5 ,, throughout their thickness, it is necessary to use a resin ~; having a viscosity high enough to prevent migration and ' coalescence of the bubbles in the foam prior to the harder.-,',~ 15 ing of the resin. ' ' , One effort that was made to increase the viscosity of the resin involved removing water from the resin by means ,' of a relatively long duration vacuum distillation step. It was found to be extremely difficult, even when distilling at low temperatures under reduced pressure, to avoid the continuing condensation of the resin. Under, these conditions, '~
,~, viscosities of the resins reached 4,000 to 8,000 cp at 20C, ' ,i~ with dry extracts of 70 and 75 per cent, respectively. When -,~ ' resins having such und,uly high vis,cosities are used, the foam ~ 25 manufacturing process is adversely affected, especially fro~
"' an economic standpoint. This is so because, i'n order to mix ', .. . . .
~ ' the constit,uel-ts of the expallsible dispersion uniform~y in '', . ' "' , ~ ' : . .
, ' ' , ` ' , .

, 107943~

the higll viscosity rcsin, so that a low density foam having a homogencous cellularization of small bubbles is produced, the mixin~ device requires more power and the duration of the mixing step must be increased. This increases the total energy required by the process and thus increases the cost.
:
Another effort to increase the viscosity of the resin involved centrifuging of the resin to eliminate water.
However, the resin retained a significant amount of water, even after very high-speed centrifuging, and it was not . .
,~ possible to obtain resins having a dry extract of above 70 per cent.

~. .
. It has now been found that these disadvantages can be avoided, particularly the loss of time and energy involved in concentration by distillation or centrifugation. -Further, it has been found possible to regulate the dry b", extract of the phenolic resin, thus its viscosity, more easily and more precisely. This considerably facilitates the manufacture of phenolic foams having desired densities ;:, .
- 20 and cell distribution.
~,. . .
SUM~RY OF THE INVENTION

The invention concerns a method for the manufacture of phenolic resins, notably useful for manufacturing foams, from phenol and formaldehyde, by condensation in at least two successive stages in the presence of an alkaline catalyst.
After the reacting mixture has been cooled at the end of the , ~

: ! 4 .

1~75~43~

l~st sta~c o~ condcl1sntion, a ~ua11tity oE an acid su~ficient to ob~ain a pll rangi11g bctwccn about 3 to ~, and preferably betwecn about 3.4 and 3.6, is added to thc phenol-formalde11yde mixturc. Un~cr thcsc conditions, the resin is separated from : 5 its aqueous environmcnt so that it can be used to form ex-.pansible dispcrsions.

.
- According to one fcature of the invention, thc reacting mixture is cooled to a temperature ranging between 30 and 35C before the addition of acid.

. lO DESCRIPTION OF THE INVENTION
.

According to the.method described in the above-. idçntified Canadian patent application for making phenolic resins identified as Resole II bis, mixtures of phenol and ~ :
formaldehyde are.reacted in the presence of an alkaline . 15 catalyst. The mole ratio of formaldehyde to phenol in these reactions is between about l and 1.6 and does not exceed ~
~: l.7. The formaldehyde and a portion of the catalyst are . added to the phenol in successive steps and sometime after . the last addition of formaldehyde and catalyst to the reaction . 2~ mixture, the mixture is cooled. This mixt.ure contains an .~ excess of the basic catalyst tfor example, sodium hydroxide).
According to. this previous method, an acid, for example, hydrochloric acid, at 35 per cent concentration, is added to the mixture in order to neutralize the sodium hydroxide and to bring the pH of the mixture to about 7.
...

.
:. , - .

.~ , .

1079~3g ~ccording to the invention l1erein disclosed, instead of stopping th~ addition of the acid when the pH reaches about 7, an additional qu~lntity of acid is added to bring the pH to between about 3 and 4. It has been found that if a stoichiometric quantity of hydro-chloric acid is added in relation to the total quantity of sodium hydroxide used, a p~1 of about 3.5 is obtained.
~; This indicates that, at this pH value, all the phenolic-OH
groups present in the resin, which were previously found ` l0 to be water soluble in the sodium phenate state, are free.

The acid added to the reaction can be dilute or concentrated. For the purposes herein disclosed, hydro-chloric acid has been found to be especially useful.
' ' .

It has be~n foun~l that whe~ ~he pH of the reaction environment is between 3 and 4, a higher propor1ion of water separates from the resin and the dry extract of the separated resin is higher than in the case of neutraliza-; tion of the reaction environment to a pH of only 7 to 7.5.

, The range of acidification of t~e reaction mix-ture to a pH between 3 and 4 is considered to be optimal.
If the reaction mixture is acidified to values lower than about 3, the resins obtained after separation of water have much higher viscosities. It is believed that the excess acid introduced catalyzes the reactants, even at 2S - low temperatures, and thereby increases the v;scosity of ~ the resin.
,.
." .
; 6 . .
.
.. . - -, . . :

107~

Convcrs~ly, i the pl-l value is higher t]~an about 1 4, resins having viscosities sufficiently high to ensure l the attainment of fine, homogenous cellularization through-out the thickness of the foam are not obtained. For example ¦ 5 in one phenol-formaldehyde reaction, the quantity of hydro-chloric acid added to the reaction mixture to bring the ~ pH to about 7, corresponds to only about 58 percent of ¦ the total quantity of sodium hydroxide used as a catalyst.
Under these conditions, the sodium phenate groups retain j ]0 water and the desired resin viscosities after decantation, ~ and even after centrifuging, are not obtained.
.~ ' .
For purposes of further illustrating the invention, the following specific examples are g~iven.
- ,' '' -EXAMPLE l A reaction mixture was prepared, according to ~ -the method for preparing Resole II bis resins disclosed , in Canadian patent application, Serial No. 139,727, having a ~ .
. ::
; total mole ratio of formaldehyde to phenol of 1.4 and using an amount of sodium hydroxide catalyst equal to 2 per cent by weight of phenol. The following corresponding values ~ for the dry extract and the viscosity were obtained:
c .
. '.

,, ., , ' ,~ l ,~
,: -107943~
pH of the resin 3.0 3.4 3.6 4.0 dry extract of the resin decanted S and drawn o f f in ~ by w~ight 74.0 72.5 71.5 70.0 viscosity of the resin decanted ~ drawn off, in cp, at 20C 4000 2000 1500 1100 :: .

63.45 kg (675 moles) of phenol were placed in a ; 150 liter stainless steel reactor, having double wall con-. .
struction for the passage of a heating or cooling medium and having a means for agitating the contents of the reactor.
67.50 kg of formaldehyde in aqueous solution, having a con-centration of 36 per cent by weight (810 moles) were added to the phenol. The temperature of the mix was brought to 50C and at this temperature, 1268g of an aqueous solution of sodium hydroxide, having a concentration of 50 per cent by weight, was added to the reactor.
.

The mix was heated to about 70C to start the reaction. Because the reaction is exothermic the tempera-ture of the mix rose to 100C, and this temperature was maintained for one hour by circulating a coola~t between the walls of the reactor.

The mixture was then cooled to about 80C and 11.25 kg of an aqueous formaldehyde solution having a .. ...

107~439 .
concentration of 36 per cent by weight ti.e., 135 moles of formaldehyde) were added to the ~eactor. The tempera-ture of the mixture was maintained at 80C and 1268g of an aqueous solution of sodium hydroxide having a concen-tration of 50 per cent by weight was added to the reactor, and the 80C temperature was maint~ined for 30 minutes.

:
The mixture was then cooled to 30C and divided into eight equal parts. These eight parts of the mixture were separately acidified by dilute hydrochloric acid having a concentration of 18 per cent by weight, under - agitation, to pH values ranging from 2.0 to 7.4.

, . . .
'After acidification, all eight parts were left at rest for 6 hours so that in each of them, a resin laycr and an aqueous layer formed. Resin was obtained by decantation from each of the eight parts.
,., .,,~ , ` The dry extract and viscosity of the resin from - each of the eight parts were measured. Then, the resin taken from the parts in which the pH had been adjusted to 5.0, 7.0 and 7.4 were concentrated under vacuum to a .,.~, .
dry extract of 72 per cent and the viscosity was measured ~! again.
, 1., .
. I i . ~

~ ' , ' g . ' ' . ~
' ' ' ' ` ' . . . - . .
; .~ . ..
.
. .
.. .

Claims (5)

The results are presented in the following table:

(X) A resin flocculate of very high viscosity was obtained that was difficult to separate and that was not usable.

1. A method for making phenolic resins from the condensation of phenol with an aldehyde which comprises, in a first step, reacting phenol with an aldehyde in the presence of a basic catalyst, and allowing the reaction to proceed for a period of time to form a reaction mass having a resinous phase and an aqueous phase; in a second step, adding an additional quantity of an aldehyde and an addi-tional quantity of a basic catalyst to the reaction mass formed in the first step and allowing the reaction to pro-ceed for a period of time; near the end of the second step, adding a quantity of an acid to the reaction mass sufficient to adjust the pH of the reaction mass to a range of 3 to 4, and separat-ing the resinous phase from the aqueous phase.

2. The method according to Claim 1 wherein the quantity of acid added near the end of the second step is sufficient to adjust a pH of the reaction mass to a range between 3.4 and 3.6.

3. The method according to Claim 1 wherein the quantity of acid added near the end of the second step corresponds stoichiometrically with the total quantity of basic catalyst added to the reaction mass.

4. The method according to Claim 1 wherein the reaction mass is cooled to between 30°C to 35°C before the acid is added.

5. The method according to Claim 1 wherein the acid is concentrated hydrochloric acid.