Thermoset foams, and method for manufacturing same from reducing sugars and amines

Abstract

A process for manufacturing a solid thermoset foam includes the following successive stages: (a) providing an expandable and thermosetting composition including a first reactant chosen from reducing sugars and a second reactant chosen from primary amines, primary amine acid addition salts, secondary amines, secondary amine acid addition salts, and ammonium salts of formula R.sup.n(NH.sub.4.sup.+).sub.n where n is an integer at least equal to 1 and R.sup.n represents the residue of an organic or inorganic acid; (b) introducing the expandable and thermosetting composition into a mold or applying the expandable composition to a support so as to form a film having a thickness at least equal to 1 mm; and (c) heating the expandable and thermosetting composition to a temperature at least equal to 140 C. to react the first reactant with the second reactant and to form, by polymerization and chemical foaming, a block of solid thermoset foam.

Claims

1. A process for manufacturing a solid thermoset foam, comprising the following successive stages: (a) making available an expandable and thermosetting composition containing: a first reactant chosen from reducing sugars, a second reactant chosen from primary amines, primary amine acid addition salts, secondary amines, secondary amine acid addition salts, and ammonium salts of formula R.sup.n(NH.sub.4.sup.+).sub.n where n is an integer at least equal to 1 and R.sup.n represents a residue of an organic or inorganic acid, the expandable and thermosetting composition containing less than 50% by weight of water, (b) introducing the expandable and thermosetting composition into a mold or applying the expandable and thermosetting composition on a support so as to form a film having a thickness at least equal to 1 mm, (c) heating the expandable and thermosetting composition to a temperature at least equal to 140 C., so as to react the first reactant with the second reactant and to form, by polymerization and chemical foaming, a block of solid thermoset foam.

2. The process as claimed in claim 1, wherein an amount of the expandable and thermosetting composition is such that the volume of the resulting block of solid thermoset foam is at least equal to 500 cm.sup.3.

3. The process as claimed in claim 1, wherein the thickness of the film is at least equal to 2 mm.

4. The process as claimed in claim 1, wherein the block of solid thermoset foam is a slab.

5. The process as claimed in claim 1, wherein the expandable and thermosetting composition contains at most 35% by weight of water.

6. The process as claimed in claim 1, wherein the first and second reactants represent, in total, at least 70% of the dry weight of the expandable and thermosetting composition.

7. The process as claimed in claim 1, wherein the first reactant is chosen from glucose and starch hydrolysates.

8. The process as claimed in claim 1, wherein the expandable and thermosetting composition additionally contains one or more surface-active agents.

9. The process as claimed in claim 1, wherein the expandable and thermosetting composition additionally contains up to 20% by weight, with respect to a total dry weight of the expandable and thermosetting composition, of one or more inorganic or organic fillers.

10. The process as claimed in claim 1, wherein the first reactant represents from 30 to 95% by weight and that the second reactant represents from 5 to 70% by weight of the total weight of the first and second reactants.

11. The process as claimed in claim 1, wherein an amount of the expandable and thermosetting composition is such that the volume of the resulting block of solid thermoset foam is at least equal to 0.01 m.sup.3.

12. The process as claimed in claim 1, wherein the thickness of the film is at least equal to 10 mm.

13. The process as claimed in claim 1, wherein the expandable and thermosetting composition contains at most 5% by weight of water.

14. The process as claimed in claim 1, wherein the first and second reactants represent, in total, at least 90% of the dry weight of the expandable and thermosetting composition.

15. The process as claimed in claim 7, wherein the starch hydrolysates have a dextrose equivalent (DE) of greater than 20.

Description

EXAMPLES

(1) Several expandable and thermosetting compositions are prepared by adding an aqueous solution of the second reactant to a powder of the first reactant. The mixture is stirred at ambient temperature until the powder has dissolved. The respective amounts of the first and second reactants, expressed as dry matter, and also the total solids content of the resulting compositions, are shown in table 1.

(2) Each of the compositions is introduced into a flat-bottomed aluminum dish (diameter of 5 cm) so as to form a film having a thickness of approximately 1 mm. The dishes are introduced into a drying oven heated to 200 C. After 20 minutes, they are removed and allowed to cool to ambient temperature and the thickness of the foam formed is observed.

(3) TABLE-US-00001 TABLE 1 Reactant 1 Reactant 2 Solids content Thickness of the foam 32.5 parts of 67.5 parts of 63% +++ D-glucose ammonium citrate monohydrate 85 parts of 15 parts of 75% +++++ D-glucose ammonium sulfate monohydrate 85 parts of 15 parts of 61% + maltodextrin ammonium sulfate (DE =3-20) 85 parts of 15 parts of 75% +++ D-glucose ammonium carbonate monohydrate : less than 0.5 cm +: 0.5 to 1 cm ++: 1.1 to 2 cm +++: 2.1 to 3 cm ++++: 3.1 to 4 cm +++++: more than 4 cm

(4) By way of comparison, a series of compositions identical to those of table 1, apart from the fact that the first reactant (reducing sugar) is replaced by a polyol not comprising a reducing group, is prepared. They are cured in a drying oven at 200 C. for 20 minutes. The results observed are recorded in table 2.

(5) TABLE-US-00002 TABLE 2 Polyglycerol Reactant 2 Solids content Foam Appearance 32.5 parts 67.5 parts of 63% Black crust ammonium citrate 85 parts 15 parts of 75% Beige-colored ammonium sulfate transparent film 85 parts 15 parts of 75% Colorless ammonium carbonate transparent

(6) Only the sample containing ammonium citrate seems to have reacted. Its color has changed and its consistency is hard but no foam formation is observed.

(7) For the other two samples containing, as second reactant, ammonium sulfate and ammonium carbonate, the color of the reaction mixture has virtually not changed. A transparent film which is very slightly colored is observed, but no foam formation.