THERMOSET POLYESTER FOAMS AND MANUFACTURING METHOD

Abstract

A process for manufacturing a thermoset polyester foam includes the following successive steps: (a) providing an expandable and thermosetting composition containing a polyol component including at least one element selected from glycerol, diglycerol and glycerol oligomers; a polyacid component including citric acid; a surfactant selected from alkyl polyglycosides and mixtures of an anionic surfactant and a cationic surfactant, and an esterification catalyst; (b) introducing the expandable and thermosetting composition into a mold or applying the expandable composition to a support; and (c) heating the expandable and thermosetting composition at a temperature at least equal to 135 C. so as to react the polyol component with the polyacid component and form a block of thermoset polyester foam.

Claims

1. A process for manufacturing a thermoset polyester foam, comprising the following successive steps: (a) providing an expandable and thermosetting composition containing a polyol component comprising at least one element selected from glycerol, diglycerol and glycerol oligomers, a polyacid component comprising citric acid, a surfactant selected from alkyl polyglycosides and the mixtures of an, anionic surfactant and a cationic surfactant, and an esterification catalyst, (b) introducing the expandable and thermosetting composition into a mold or applying, the expandable composition to a support, and (c) heating the expandable and thermosetting composition at a temperature at least equal to 135 C. so as to react the polyol component with the polyacid component and form a block of thermoset polyester foam.

2. The process as claimed in claim 1, wherein the polyol component and the polyacid component represent together at least 60% of the dry weight of the expandable and thermosetting composition.

3. The process as claimed in claim 1 or, wherein the polyol component comprises at least 15% by weight of glycerol.

4. The process as claimed in claim 1, wherein the polyacid component comprises at least 50% by weight of citric acid.

5. The process as claimed in claim 1, wherein the surfactant as a mixture of sodium dodecyl sulfate (SDS) and tetradecyltrimethylammonium bromide (TTAB).

6. The process as claimed in claim 1, wherein the surfactant has a hydrophilic-lipophilic balance (HLB) of between 3 and 13.

7. The process as claimed in claim 1, wherein the polyol component represents from 15% to 60% by weight of the total, weight of the polyol and polyacid components

8. The process as claimed in claim 1, wherein the expandable and thermosetting composition contains at most 60% by weight of water.

9. The process as claimed in claim 1, wherein the esterification catalyst is selected from phosphorus-containing compounds.

10. The process, as claimed in claim 1, wherein the expandable composition also contains up to 30% by weight relative to the dry weight of the total expandable composition, of one or more inorganic or organic fillers.

11. A polyester foam capable of being obtained by the process as claimed in claim 1.

12. The polyester foam as claimed in claim 11, wherein the polyester foam has a density of between 20 and 80 kg/m.sup.3.

13. The polyester foam as claimed in claim 11, wherein the polyester foam has a closed porosity.

14. The solid foam as claimed in claim 11, wherein the mean diameter t f the pores determined by X-ray tomography is between 100 and 800 m.

15. A composition comprising a polyol component comprising at least one element selected front glycerol, diglycerol and glycerol oligomers, a polyacid component comprising, citric acid, a surfactant selected from alkyl polyglycosides and the mixtures of an anionic surfactant and a cationic surfactant, and an esterification catalyst, wherein the composition is an expandable and thermosetting composition for the manufacture of an insulating product of foam type.

16. The process as claimed in claim 1, wherein the temperature at which the expandable and thermosetting composition is heated is at least equal to 150 C.

17. The process as claimed in claim 1, wherein the polyol component and the polyacid component represent together at least 80% of the dry weight of the expandable and thermosetting composition.

18. The process as claimed in claim 1, wherein the polyol component comprises at least 25% by weight of glycerol.

19. The process as claimed in claim 1, wherein the polyacid component comprises at least 80% b weight of citric acid.

20. The process as claimed in claim 1, wherein the polyol component represents from 25% to 45% by weight of the total weight of the polyol and polyacid components.

Description

EXAMPLES

[0080] Several expandable and thermosetting compositions are prepared by adding powdered citric acid to an aqueous solution containing glycerol, diglycerol, oligoglycerol or a mixture thereof. Added next are the esterification catalyst (sodium hypophosphite monohydrate) in powder form, and then the surfactant, and the solids content of the mixture is adjusted to 66% by weight. The mixture is stirred at ambient temperature until the citric acid powder has dissolved. Table 1 indicates the respective amounts of the ingredients used, expressed as dry matter, and also the total solids content of the compositions obtained.

[0081] The reactive solution is then poured into rectangular molds, the bottom of which is covered with a sheet of aluminum. The thickness of the liquid film is around 1 mm. The molds are heated for 3 hours in a ventilated drying oven thermostated at 180 C.

[0082] After removing the molds from the drying oven>and cooling the foams formed to ambient temperature, the thickness of the foam formed is evaluated with the aid of the following rating scale:

[0083] : less than 0.5 cm

[0084] +: 0.5 to 1 cm

[0085] ++: 1.1 to 2 cm

[0086] +++: 2.1 to 3 cm

[0087] ++++: 3.1 to 4 cm

[0088] +++++: more than 4 cm

TABLE-US-00001 TABLE 1 Solids Thickness of Polyol Polyacid Catalyst Surfactant content the foam 34 parts of glycerol 66 parts of 5 parts of 5.1 parts of 66% +++++ citric acid HPS* TTAB/SDS** 42 parts of a 58 parts of 5 parts of 5.1 parts of 66% +++++ glycerol & citric acid HPS* TTAB/SDS** diglycerol & oligoglycerol mixture*** 41 parts of 59 parts of 5 parts of 5.1 parts of 66% +++ diglycerol citric acid HPS* TTAB/SDS** 41 parts of 59 parts of 5 parts of 5.1 parts of 66% ++ oligoglycerol**** citric acid HPS* TTAB/SDS** 34 parts of glycerol 66 parts of 5 parts of 2.55 parts of 66% +++++ citric acid HPS* TTAB/SDS** 34 parts of glycerol 66 parts of 5 parts of 5 parts of (C.sub.8-C.sub.14)alkyl 66% +++++ citric acid HPS* polyglycoside 34 parts of glycerol 66 parts of 5 parts of 2.5 parts of 66% +++++ citric acid HPS* (C.sub.8-C.sub.14)alkyl polyglycoside + 2.55 parts of TTAB/SDS** 34 parts of glycerol 66 parts of 10 parts of (C.sub.8-C.sub.14)alkyl 66% +++++ citric acid HPS* polyglycoside + 2.55 parts of TTAB/SDS** 42 parts of a 58 parts of 5 parts of 2.5 parts of 66% +++ glycerol & citric acid HPS* (C.sub.8-C.sub.14)alkyl diglycerol & polyglycoside oligoglycerol mixture*** 42 parts of a 58 parts of 5 parts of 3.75 parts of 66% +++++ glycerol & citric acid HPS* (C.sub.8-C.sub.14)alkyl diglycerol & polyglycoside oligoglycerol mixture*** 42 parts of a 58 parts of 5 parts of 5 parts of (C.sub.12-C.sub.14)alkyl 66% +++++ glycerol & citric acid HPS* polyglycoside diglycerol & oligoglycerol mixture*** 42 parts of a 58 parts of 5 parts of 7.5 parts of 66% +++++ glycerol & citric acid HPS* (C.sub.12-C.sub.14)alkyl diglycerol & polyglycoside oligoglycerol mixture*** 42 parts of a 58 parts of 5 parts of 7.65 parts of 66% +++++ glycerol & citric acid HPS* TTAB/SDS** diglycerol & oligoglycerol mixture*** 42 parts of a 58 parts of 5 parts of 10.2 parts of 66% +++++ glycerol & citric acid HPS* TTAB/SDS** diglycerol & oligoglycerol mixture*** *sodium hypophosphite hydrate **tetradecyltrimethylammonium bromide (TTAB) and sodium dodecyl sulfate (SDS) added in the form of 25% solution in water; TTAB/SDS weight ratio = 2 ***mixture containing around a third of each of the components ****polyglycerol-4 (CAS no. 25618-55-7) contains around 2% diglycerol, 43% triglycerol, 34% tetraglycerol, 14% pentaglycerol, 6% hexaglycerol

[0089] The foams obtained all have a fine and uniform porous structure. They are of ivory or beige color. FIGS. 1 and 2 show, by way of example, respectively a slab and a block of foam obtained. These tests show that the combined use of an esterification catalyst (sodium hypophosphite) and of a surfactant (cationic and anionic surfactant combination) makes it possible to obtain, foams in a single high-temperature step.

[0090] The test using polyglycerol-4 as polyol component appears to indicate s that the foaming is inhibited by the absence of glycerol monomer and the virtual absence of dimer. The presence of a certain amount of glycerol monomer and/or dimer appears to be important for the foaming.

[0091] The alkyl polyglycosides (neutral surfactants) give results comparable to the TTAB/SDS combination.

[0092] The Applicant carried out tests with an anionic surfactant (Disponil SUS 87 Spez.; disodium salt of an ethoxylated decyl alcohol ester), but this surfactant, used in the absence of a cationic surfactant, does not make it possible to obtain a foam.

[0093] The use of a nonionic surfactant having an HLB of 14 (Disponil PGE 110; polyglycolic diether of an aliphatic diol) does not result in a foam being obtained either.

[0094] Replacement of a Portion of the Glycerol by Other Polyols

[0095] Table 2 below shows the results obtained by tests carried out under the same conditions as those of table 1. Around a third of the glycerol/diglycerol/oligoglycerol was replaced by a different polyol (hydrophobic starch, trimethylolpropane, pentaerythritol).

TABLE-US-00002 TABLE 2 Solids Thickness Polyol Polyacid Catalyst Surfactant content of the foam 24 parts of glycerol + 66 parts of citric 5 parts 5.1 parts of 66% +++++ 10 parts of acid of HPS* TTAB/SDS** hydrophobic starch 24 parts of glycerol + 66 parts of citric 5 parts 5.1 parts of 66% +++++ 10 parts of acid of HPS* TTAB/SDS** trimethylolpropane 24 parts of glycerol + 66 parts of citric 5 parts 5.1 parts of 66% +++++ 10 parts of acid of HPS* TTAB/SDS** pentaerythritol *sodium hypophosphite hydrate **tetradecyltrimethylammonium bromide (TTAB) and sodium dodecyl sulfate (SDS) added in the form of 25% solution in water; TTAB/SDS weight ratio = 2

[0096] It can be observed that this partial replacement of the glycerol or of oligomers thereof in no way impairs the quality of the foams formed.

[0097] Total Replacement of Glycerol by Other Polyols

[0098] Table 3 below shows the results obtained by tests carried out under the same conditions as those of table 1, with the exception that all of the glycerol/diglycerol/oligoglycerol was replaced by a different polyol (hydrophobic starch, maltitol, isosorbide).

TABLE-US-00003 TABLE 3 Solids Thickness of Polyol Polyacid Catalyst Surfactant content the foam 34 parts of 66 parts of 5 parts of 5.1 parts of 66% EmCap*** citric acid HPS* TTAB/SDS** 48 parts of 52 parts of 5 parts of 5.1 parts of 66% maltitol citric acid HPS* TTAB/SDS** 54 parts of 46 parts of 5 parts of 5.1 parts of 66% isosorbide citric acid HPS* TTAB/SDS** *sodium hypophosphite hydrate **tetradecyltrimethylammonium bromide (TTAB) and sodium dodecyl sulfate (SDS) added in the form of 25% solution in water; TTAB/SDS weight ratio = 2 ***hydrophobic modified starch

[0099] It is observed that the total replacement of the glycerol or oligomers thereof prevents the formation of foams. The presence of glycerol, diglycerol or oligoglycerol therefore proves essential to the formation of foams.

[0100] Replacement of a Portion Or of All of the Citric Acid by Another Polyacid

[0101] Table 4 below shows the results obtained by tests carried out under the same conditions as those of table 1, with the exception that a portion or all of the citric acid was replaced by another polyacid.

TABLE-US-00004 TABLE 4 Solids Foam Polyol Polyacid Catalyst Surfactant content thickness 42 parts of a 58 parts of 5 parts 5 parts of 66% glycerol & tricarballylic acid of HPS* APG*** diglycerol & oligoglycerol mixture 42 parts of a 58 parts of 1,2,3,4- 5 parts 5 parts of 66% glycerol & tetrabutylcarboxylic of HPS* APG*** diglycerol & acid oligoglycerol mixture 42 parts of a 58 parts of itaconic 5 parts 5 parts of 66% glycerol & acid of HPS* APG*** diglycerol & oligoglycerol mixture 34 parts of glycerol 56 parts of citric 5 parts 5.1 parts of 66% +++++ acid + 10 parts of of HPS* TTAB/SDS** 1,2,3,4- tetrabutylcarboxylic acid 34 parts of glycerol 56 parts of citric 5 parts 5.1 parts of 66% +++++ acid + 10 parts of of HPS* TTAB/SDS** nonadioic acid *sodium hypophosphite **tetradecyltrimethylammonium bromide (TTAB) and sodium dodecyl sulfate (SDS) added in the form of 25% solution in water; TTAB/SDS weight ratio = 2 ***(C.sub.8-C.sub.14)alkyl polyglycoside (Glucopon 650 EC) added in the form of an aqueous solution having 52% by weight of solids

[0102] It is observed that the total replacement of the citric acid by other polyacids prevents the formation of foams. The partial replacement of citric acid does not impair the quality of the foams.

[0103] Esterification Catalyst

[0104] When a test is carried out under the same conditions as those of table 1 but omitting the sodium hypophosphite, the formation of foam is very greatly inhibited.

TABLE-US-00005 TABLE 5 Solids Foam Polyol Polyacid Catalyst Surfactant content thickness 34 parts of 66 parts of 5.1 parts of 66% + glycerol citric acid TTAB/SDS* *tetradecyltrimethylammonium bromide (TTAB) and sodium dodecyl sulfate (SDS) added in the form of 25% solution in water; TTAB/SDS weight ratio = 2

[0105] Thermogravimetric analysis (TGA) tests for an aqueous solution of citric acid containing sodium hypophosphite, in comparison with an identical solution without sodium hypophosphite, showed that the sodium hypophosphite catalyzes the decomposition of the citric acid to give aconitic acid and CO.sub.2.