CA1128268A

CA1128268A - Panel based on polycondensable resin and a method for the manufacture of this panel

Info

Publication number: CA1128268A
Application number: CA318,839A
Authority: CA
Inventors: Claude Savey; Florent Laurent
Original assignee: Stratiforme SA
Current assignee: Stratiforme SA
Priority date: 1977-12-30
Filing date: 1978-12-29
Publication date: 1982-07-27
Also published as: DE2856717A1; FR2413198B1; JPS6053060B2; GB2013209B; GB2013209A; IT7831308A0; CH627124A5; FR2413198A1; BE872866A; IT1102450B; OA06162A; LU80679A1; JPS54160484A

Abstract

ABSTRACT

A panel comprising a phenolic resin covering fillers, the phenolic resin being an expanded phenolic resin having a system of closed cells. A process for producing such panel is also described The process comprises mixing a filler with a fluid mixture comprising at least one phenolic resin, a hardening agent, a surface active agent and a pore forming agent chosen such that it has a boiling point less than the polycondensation temperature of the mixture and greater than the ambient temperature during mixing.

Description

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'~'he present invention relates to a panel based on polycondensable re~in and a meth~d :Eo~ the manu~
.facture of this panel ~ he inven-tion r~ates more particularly to the manufacture O:e panels from a phenolic re~ln cornprisjng a filler such as balls of expanded polystyrene, or expanded clay, or microspheres of glass, or a similar material.
~hese panels, obtained by ~ixing the filler with a liquid ~ixture comprising the phenolic .resin, an a~ent for hardening this resin, have a certain number ~ of drawbacks in their present method of manufacture, due to their structure and to the fact that their manufacture is inadequately con-trolled.
One of these drawbacks resides in that under the conditions in which the manufac-ture is presently carried out, for obtaining a phenolic resin with open cells, on the one hand the latter is subject to infiltrations in particular of water and on -the other hand, burns easily owing to the presence of air which is trapped thereinO In addition, this resin having open cells lacks cohesion.
It is possible to minimise these drawbacks by p~cing the panel ob-tained between facings of a suitable type, for example steel facings, but it is only possible to envisage facings defining a casing around the panel, which casing has its own cohesion ~28;~8

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owing to the lack of cohesion of the panel itsel~.
In particular, it is not possible to produce fa¢inKs in the form of a Iayer of pol~tmerisable resin inte~ral with the panel over the entire surface area, this constraint limits the currently known use of pa~els based on phc-nolic resin.
Another drawback of these panel~ resides in their lack of homogeneity, fillers hàving a density less than the density of the resin tending ~o rise ~hen the resin .: .
- 10 has not been completel~ polycondensed and in particular . ,~ ~
at the time of an expansion ~hase~ whereas denser resin tends to dropD A cut made in ~ panel produced in the currently known manner reveals a much greater density ~- of filler on the upper part of~the panel ~han in its ; . .
- ~ 15 lower part~ the result being great friarbility of the panel in its upper part. It is also apparent that the :. .
xesin expands in a heterogeneous manner, expanding . .
much more freely towards the top of the panel than at the bottom, which detracts further ~rom the mechanical "20 properties of the panel in its upper part9 - ~urthermore, difficulties are encountered in working industrially with polystyxene balls and phenolic resin~ with their currently ~nown composition, owing to their short shelf life~ i.e~ the short period ~25 of time during which they can be used af~er prepaxationS
- considerably limits the quantity of resin which can be prepaFed ~nd consequentl~ used for a manu~acture.

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i ~'he present invention ~akes it possible to reTAqed~
all these drawbacks, both by a wise choice of the composition of the polycondensabLe mi~ture used and owing to control of the conditions, ln parti.cular

5 evolution of te~perature during the rnanufacture.
By dissoci.ating the expansion of th~-3 ~i~tu~ and its polycondensation, iOe. its hardening~ -the inventior ` makes it possible to cause a ~aximum expansion before the hardeningl i.e. to ensure co~ple-te fill;ng of the 1 10 mould in which the manufacture takes place, before ;~ hardening of the mix-ture, which results in obtaining s closed cells and an outer skin which is imper~eable and has a homogeneous appearance. If there has previously been placed against the inner sides o~this 15 enclosure, a particularly polycondensable material based on phenolic resin, possibly reinforced in order to cOnstitute a facing layer after polycondensation, this possibility of maximum expansion in a limited i enclosure also makes it possible to~ obtain good 20 interpenetration of the facing layer and of -the core of expanded phenolic resin in their adjacent areas~ which results in good attachment of the facing layer to the core of phenolic foam, which also has good cohesion owing to the closed cell strv.cture.
This dissociation o~ the expansion phase and of the hardening phase is obtained by a wise choice oi`
the pore forming agent (hereinafter also referred to as a porogenic agent~ in order that its boi.ling p~nt is lo~er than t-e polycondensation -tempera-ture of the ' ' ~
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~%~Z68 :, 5 mixture, but much higher than t~e ~mbient ternperature, ~ i~ order to prevent the beginning of an emul~iv~ d~ri.n~
l mixin~, which on -the one hand would re~uc~ the ~hel~
, life of the mixture and on the othe~ h~nd would limit t 5 the f~cility for subsequent expansion o~ the mi~ture.
i ~he me-thod of heati~g th~ mould aft~r t'ae introduction of the polycondensable mixture and of the fillers will be adapted according to the in~ention in order to effectively achieve dissociation of the expansion phase of the resin and of the polycondensation phase in . order to control tha reaction and. obtain a homo~elleou3 material. 'i~hen the balls have been coated with the i~ necessary quantity of resin, an expansion of the resin is caused in the region of eac~ ball, which expansion ¦ 15 manifests itself in the mould by pushin~ forces in all directions and in the region of each ball. According to . the invention9 heatin~ is in fact carried out such that the temperature rises progressively to a temperature close to the boiling point of the poroge~ic a~ent, ,l 20 then this temperature is kept virtually constant for a sufficient period of time to bring about maximum expansion of tlle mixture, under high stea!~ pressure of the poro~enic agent. The temperature is then increased o~ce more progressi~.ely to the polyconde~-satio~ temperature, in order to brin~ a~out thi~
polycondensa~ion when the exp~nsion is maximum, in vie~ of the limited volume of the ~ould i~ which it i~
'. carried ou~ his rise in temperature, from thè
temperature of the expansi.on.phase, i.e. the te~perature / llZ~IZ68

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close to the boiling point o~ the poroge~lc aL~en~
up to the polycondensation t~mper~ure, will t~ke place pro~,ressively in a preI'ex~r~d er~'~odiment~ in order to eliminate the wat~r vapour and formal~ehyde vapour more complet~l~ under the aoint ~1c~ion o~ the ~acuum. rrhis pro~ressive and therefore m~r~ complete elimination will make it possible to obtain a~
improved surfc~ce appearance in the case where one ; manu~a~tures a panel comprisin~ an outer coatin~ layer also of phenolic resin which is possibly reinforced.
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-' ' ,The ~omposition of the pol~condensable mixturel, is also chos~n in order to ensure ho~oge~eous coating of t~e filler~ i.e~ to fix a maximum quantit~ of mixture on this filler 9 in a ~omogeneous ma~ner 9 in ~' 15 order to cause the mc~ximum expansion, then polycon-- derlsation in the man~er a~ore-de~cribed~
`-,?, To this end, the proportion o~ surface active agents in the mixture is increased in order to provide better adhesion of the resin to the balls. The 20 ~ proportion of hardening agents will be reduced in oxder to decrease the effects'of starti~ of the polycondensation phase, which could occur simultaneousl~
with the expa~sion phase and this would be at the -chosen te~perature of the stage. ~he essential purpose 25 of these modifications in the propo~tio~s of the ~ixture ' ' with respect to the proportions used ~n X~ow~ m~nner i iB to ~i~e the viscosity of this mix-ture before expan-sion ~d to maintain thi~ viscosity duri~ expansion~

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at a ~alue which is sufficiently hi~h in order that the ~dhesion to the fillers is sufficie~t and . .
~uf~icientl~ moderate to pre~en~ the a~lom~r~i.on of an excessive quan~ity oi mixture around the ~ rs resulting in inadequate expansion for reason.s of wei~ht. ~s a non-limiting example, good re~ult~ have beon obtained by givin~ the quantity of hardeners in the polycondensable mixture a value o~ the order of i 5~k as against a ~alue of 10 to 15Y in the case o~
currently l~nown compositio~s which produce phenolic ~` resin ha~ing closed cells, and of i~creasin~ tha `' proportion of surface acti~e a~ents to approximately 2~, whi.c~l is of the order o~ ', in known compositions, ~he prooortion of porogenic a~ents normally of the order of 5 to 15,~G being raised to 2Q,q;'~ i.n order to increase the expansion capaci~y of the mixture, these . perce~ta~es bein~ understood in terms of weight per unit o~ weight of phenolic resin.
j ~he method according to the invention is ~onsequently charac~erised in that the fillers are.
mixed with a fluid mixture comprising at least one phenolic. resin, one hardening agentS one surface acti~e a~ent ~nd one porogenic agent chosen such that it has a . boiling point comprised betwee~ the ambient te:npera~ure 25 duri~s mixing and the polyconden~ation temperature of the ~.ixture, ~.~ter ha~in~ placed all ~he substances in the inner space o~ a closed mould, in a ~uantity such tha~ ere is a space in~ide the latter allowing a ~ubseq~ent e~pansion of the mixture, another cha*ac-.

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teristic of the method i~ that the tempera-ture of the mi~ture i~ raised progressively to a te~p~r~tu~e close to tl~e boiling poin~ o~ the po~og~nic ~ent, then ~h~
temperature is kept substantially c,onf~tarlt for a sufficient peri.od of ti~e in ord~r to hri.n~, about maximum exp~nsion of the mi.xture, then the temperature of the mixture is once more raised pro~re.ssively in order to caus~ polycondensation of the mixture expanded to the maximum exte~t.
Accordi~g to another feature of the method .~. ~ according to the-inventlon, the composition o~ the mixture is such that it is in the state of a gel up to - ~ said temperature close to t-he boilin~ point of the porogenic agent and less than the latter, in order to give this mixture a viscosity such that there is a maxim~ quantit~ around the fillers before and during expansion~
~ he panel according to the invention, comprising a phenolic resin coa-tin~ the fill~rs is in tuxn characterised in that the phènolic resin is an expanded phenolic resi~ having a sy~te.~ of closed cells O
; The inYention will be better unders-tood on xeferring to the ensuin~ description relatin~ to a non~limiting embodlment, as well as to the accompanying . drswings which ~orm an inte~ral part of this de~cription O

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Fi~ure 1 is a perspec-tive vi0w, ~Jith purt~
cut away, o~ nel accordin~ to the invcntio~9 ~ igur~s 2 to L~ illustrate three F,ucce.~;ive stages of the manufacture o~ this panel i~ a Mould, in sec~io~ through & vertical plan~ at right-a~le~
to the general horizontal plane of' this l~ould~
~ he same reference numerals have been used in these four fi~ures to designate the various -. constituents of the finished pc~nel (~ ures 1 ~n~ 4) and these various constituents as they exi~t cl~
the various stages of manufacture of the panel (fi~ures 2 and 3)~ ` `
its embodiment illustrated i~ figure 1, the panel according to the invention has ~n outer covering layer 1 of polycondensed phenolic resin, - preferably reinforcecl for example with a glass fibre fabric or other similar reinforcements, integral with the entixe surface area of the core produced ~rom ~
e~panded phenolic resin 2 having closed cells, coating the fillers and for example balls or microspheres oI
glass or an expanded materi~l such as expanded poly-st~rene 9 expanded clay etc. -': ' - ~he ~illers 3 ~re coated in the xesi~ 2 ; includin~ the side of the core in co~tact with the covering layer 1, where the resin 2 forms an impermeable s~in.
~ he panel accordin~ to the inveYlt-ion could also be devoid of the coverinO lay~r 1, this imper-~ ~ . .. .
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meable skin ens~ring lts water-ti.~ht~ess and : mechanical ~urface resistance, al~o provi~intr a ho~ogeneous appearance whe~ the panel i~
produced accordin~ to the invent:ionO
~o p:roduce ~uch a paneL~ the ~iller~ ~ are mixed with the mixture intended to form the resin 2 after expa~sion and polycondensatioll, whi~h mixture i8 also designated by the reference numeral 2 in , figures 2 to 4.
~his mixture w~ich is initially fluid, ~3 comp.rises at least one phenolic resin, a hardening gent, a sur~ace active agerlt and a porogenic agent~
As a non-limitin~ example, good results have ` been obtained by using a mixture comprising 5~
' 15 hardening a~e~t constituted b~ sulphuric acid to ' which alcohol 3nd w~ter ha~e been added, ~' of a . aurface active agent constituted `~y~ silicon oil and 2~y. of a porogenic a~ent co~stituted by a trichloro-tri~luoroethane~ these proportions being given 'in ~0 terms of mas~ per unit of weight of phenolic resin in the mixture. - .
- ~he'trichlorotrifluoroethane has a boiling po~nt of approximataly 47C9 which is an intermediate te~perature between the am'bie~t temperature at the time of mixing ~nd the polyco~dens~tion t~mperature oX the mi~ture, which is o~` the order of 60~ at 0.6 atmospheres~ this choice being according to one oX
the aims o~ the invention, which is to allow maxim~

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g~ ;2 8268 ~rexpansion he~ore polyconden~iation by con~rol~ing th~
rise in tempe~tu~e o~ the mix~u~ when it ie placed ~n the mould~
~ter mixin~ with the fillers in orde~ to provide t~e best distribution of the latter, the mould is placed in one of the hal~e,s 4 o~ a mould 5, if necesary after the inner ~ides of this half 4 and of the other half 6 of tlle mould have been coated with a layer o~ phenolic resin which pre~e~ably contains a reinforcing material such as a layer of . glass fibres, ~f one wishes to obtain a panel havin~
an outer phenolic covering layer 1 o~ the same type as the core. '~his stage of the manufacture of a panel is illustrated in figure 2.
i 15Preferablys the layer of phenolic resi.n 1 possibl~ comprising a reinforcement, is in the state of a pre~polymerised gel when the mixture 2-3 is introduced into the half ~ of the mould 5.
. ~he mould 5 is then sealed hermetically ~y folding the half 6 o~er on to the ha].f 49 then the ~pace 7 remaining free abo~e the mixture 2-3 inside the mould 5 closed in this way o~ing to the fact tha~
o~l~ the half 4 was initially ~illed with mixture 2-3, connected to a ~acu~m pump 8 which estab].ishe~ a ~
~acul~ at least during heati~g, shown dia~ra,lmatically by the arrow~ ~ in fi~ure 3, before and duriug the polycondensation followi.ng this hea'~ingO ~`he reduced pressure may ~emain sligh~ durinig t'~e sta~e of the .

1~ 8~6 12~, rise in temperature and the expan,sion sta~e, bu~ will b~ increased during the polycondensatlon ~tage in order to eli.minate an~ ~apoursO
Accordinæ to the inv~ntiorl, this heatin~r take.~
place in three st~ges the first of which 7 la~tin~ fvr 30 minutes for exaMple, progressively increa.ses the .
temperature of the mould and its contellts fror~ khe a~ient temperature to a temperature Or th~ order of ~0C for e~ample, i4 e. a temperature close to the ~ 10 boiling point o~ the poro~enic a~gent used. The ; - te,~perature is then l~ailltained at this value 9 for j èxa~ple of ~0C, ~or 30 ~inutes ~or example, during t~hich stage the mixture exp~nds under the hi~h pressure of ~apours comi~g fromothe poro~enic productO
~t the end of this expansion st-age1 the te~perat~lre is . then increased pro6ressivel~ from ~0C to 60C, ~t ., .
which point polyconde~sation occurs, the latter : heating lastin6 for approximately 120 minutes for example. -A polycondensation tempe:rature of the order of ~O~C makes i~ possible to use exDa~ded polystyrene . balls as ~illers 3, w~i~h should not be heated to a te,~pe~ature higher than 80C.
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~, Heating carried out under the~e conditions for the co~positio~ given above made it possible to obtain maximum expansioh before hardenin~, the entire inner 128~8 ~ 13 -space of the mould $ being filled by the expanded mate~ial applied under pressure against ~he surface coveriny 1, itself applied against the wall of the mould at the end of the expansion stage and before hardening as sh~wn diagram~
matically in figure 4. Furthermore, a homogeneous distribution of the filler 3 inside the panel is obtained.
Naturally, the composition given above and the operating conditions, linked with this composition, have been given solely by way of example and numerous variations could be made without diverging from the scope of the invention.
The mixture obtained with the afore-mentioned composition has a shelf life sufficient for carrying out manufacturing operations using a large quantity of mixture, this mixture being able to be used for up to one or two days.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AM EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process of making a panel which comprises:
forming a fluid mixture of phenolic resin, a hardening agent, a surface active event and a volotile liquid pore forming agent having a boiling point above ambient temperature during mix-ing and below the poly condensation temperature of said mixture, uniformly mixing said mixture with solid fillers in particulate form, partially filling a mould with said fluid mixture with said fillers therein and closing said mould, progressively raising the temperature of said mixture to a temperature in the vicinity of the boiling point of said pore forming agent and maintaining said mixture at said tempera-ture to produce expansion of said mixture to fill said mould, and thereafter progressively raising the temperature of said mixture to the polycondensation temperature of said mixture to ef-fect polycondensation of said mixture.

2. A process according to claim 1, in which said mould is evacuated during heating before and during polycondensation of said mixture.

3. A process according to claim 1, in which said mix ture is in the state of a gel up to said temperature to produce expansion of said mixture in order to give the mixture a viscosity to assure a maximum quantity of said mixture around said fillers before and during expansion.

4. A process according to claim 1, in which the walls of said mould are covered with a layer of phenolic resin prior to the introduction of said fillers and mixture into said mould.

5. A process according to claim 4, in which said layer of phenolic resin is in gel form prior to the introduction of said fillers and mixture into said mould.

6. A process according to claim 4 or 5, in which said layer of phenolic resin is reinforced with fiberglass fabric.

7. A process according to claim 1, in which said pore forming agent is a trichlorotrifluroethane having a boiling point of about 47 C.

8. A process according to claim 7, in which said mix-ture has a polycondensation temperature of about 60°C.

9. A process according to claim 1, in which the quantity of hardening agent in said mixture is about 5% of the quantity of phenolic resin.

10. A process according to claim 1, in which the quantity of surface active agent in said mixture is at least 20% of the tity of phenolic resin.

11. A process according to claim 1, in which the quantity of said pore forming agent in said mixture is at least about 20% of the quantity of phenolic resin.

12. A process according to claim 1, in which said fillers comprise small balls of glass, expanded polystyrene or expanded clay.