Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Patent
1984-09-24
1987-02-03
Foelak, Morton
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
521106, 521107, 521114, 521122, 521133, 521136, 521137, 521138, 521181, 521186, 523218, 523219, C08J 914
Patent
active
046409343
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to the preparation of cellular products and laminates based on furan prepolymers and having an excellent resistance to fire, good hardness properties and good insulating properties.
For this purpose, the invention relates to a process which makes it possible to ensure the progress of the polycondensation and to ensure cross-linking of the furan prepolymer at normal temperature and sufficiently rapidly to ensure virtually simultaneous hardening and, where relevant, expansion of this resin in very short times.
It is known in the art of expanded furan materials that furan resins can be expanded, by themselves or in association with other resins, in particular urea resins, using as the catalyst an acid, chiefly phosphoric acid. Acids are incorporated at high concentrations (10 to 15%) and the polymerisation reactions are slow and require post-curing in order to achieve complete polymerisation.
The Applicant Company has found that it is possible to accelerate the polymerisation reaction and to permit simultaneous hardening and expansion of furan resins by replacing some of the acid used as the catalyst with phosphorus oxychloride and/or silicon tetrachloride dissolved in a glycol phosphate or phenol phosphate, the reaction being carried out at normal temperature. Such a process is the subject of French Patent Application No. 2,508,918, filed by the Applicant.
The chlorine derivative is hydrolysed by the OH radicals present in the reaction medium and being formed as a result of the polycondensation of the furan products, and, since the hydrolysis is highly exothermic, the vigorous and rapid release of heat produced by the formation of H.sub.3 PO.sub.4 and HCl, in the case of OPCl.sub.3, and of SiO.sub.2 and HCl, in the case of SiCl.sub.4, has the effect of accelerating the crosslinking reaction and of allowing, at a very high rate, simultaneous hardening and expansion by vaporisation of the water included.
However, the addition of acids may lead, at trimerisation, to separation into two phases, with the consequence of a second exothermic reaction which in general causes destruction of the material by autocombustion.
In the course of its research, the Applicant Company has now discovered that a particular combination of furan resins associated with a well defined catalytic system makes it possible to obtain expanded furan materials with an increased heat resistance, the rates of expansion being even higher than those previously obtained.
The present invention thus relates to a process for the preparation of cellular products and laminates based on anhydrous furan prepolymers which possess free OH groups, which is carried out at normal temperature using small amounts of silicon tetrachloride and/or phosphorus oxychloride as the crosslinking and expansion agent, which comprises using, as the furan prepolymers, a combination of a furfuryl alcohol resin and/or a furfural/phenol (phenol or bisphenol A) resin with a bishydroxymethylfuran (BHMF) resin, without the use of an acid, the silicon tetrachloride and/or phosphorus oxychloride being used in amounts of 0.1 to 5% by weight, based on the resin employed.
The result of combining polymers and the catalytic system according to the invention is that expanded materials are obtained which are stable at 350.degree. C. and pass the muffle furnace test (15 minutes at 500.degree. C.) with a positive result, which was not the case with the formulations using acid which are described in Patent Application No. 2,508,918, filed by the Applicant Company.
The omission of the acid also provides the possibility of working with simpler machines, using two components instead of three.
Silicon tetrachloride and phosphorus oxychloride are extremely reactive products and their direct incorporation into the furan resins necessitates particular and meticulous precautions.
It is thus preferable to dissolve them in stable liquids which are inert under the reaction conditions or active in the reaction medium.
It has proved particularly useful to employ trichlorotr
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patent: 4548957 (1985-10-01), Hucke
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