METHOD FOR PRODUCING AN ABLATIVE RESIN

Abstract

A method for producing an ablative resin by carrying out a reduction reaction for the reduction of a compound of formula A, followed by a polymerization reaction, formula A being the following:

##STR00001##

Claims

1. A method for producing a propulsion nozzle, wherein the nozzle is produced from a phenolic resin obtained by carrying out a production method comprising the following steps: a) reduction of a compound of formula A in order to obtain a hydroxybenzyl alcohol of formula B, formulae A and B being the following: ##STR00019## wherein: n.sub.1 is an integer between 0 and 4 and when n.sub.1 is greater than or equal to 2, the substituents R.sub.1 are identical or different, R.sub.1 is chosen from: —OH, —COOH, —CHO, the groups —O-Alk wherein Alk denotes a substituted or unsubstituted alkyl chain of 1 to 4 carbon atoms, saturated or unsaturated, substituted or unsubstituted hydrocarbon-based chains comprising between 1 and 20 carbon atoms, interrupted or not with one or more heteroatoms, and having or not having one or more carbonyl or carboxylic acid functions, substituted or unsubstituted, monocyclic or polycyclic, saturated, unsaturated or aromatic carbocyclic or heterocyclic groups having or not having one or more carbonyl or carboxylic acid functions, and substituted or unsubstituted aryl groups having or not having one or more carbonyl or carboxylic acid functions, and —R.sub.2 denotes —H or —OH, and b) polymerization reaction using the hydroxybenzyl alcohol of formula B obtained during step a) in order to obtain the phenolic resin.

2. The method as claimed in claim 1, wherein there is homopolymerization of the hydroxybenzyl alcohol of formula B during step b).

3. The method as claimed in claim 1, wherein there is reaction of the hydroxybenzyl alcohol of formula B with an aldehyde other than formaldehyde during step b).

4. The method as claimed in claim 3, wherein the aldehyde is chosen from benzaldehyde, terephthalaldehyde and trimesaldehyde or has one of the following two formulae C or D: ##STR00020## in formulae C and D, n.sub.3 is an integer between 0 and 4 and when n.sub.3 is greater than or equal to 2, the substituents R.sub.3 are identical or different, n.sub.4 is an integer between 0 and 5 and when n.sub.4 is greater than or equal to 2, the substituents R.sub.4 are identical or different and n.sub.5 is an integer between 1 and 6, the substituents R.sub.3 and R.sub.4 being chosen independently from one another from: —OH, —COOH, —CHO, the groups —O-Alk wherein Alk denotes a substituted or unsubstituted alkyl chain of 1 to 4 carbon atoms, saturated or unsaturated, substituted or unsubstituted hydrocarbon-based chains comprising between 1 and 20 carbon atoms, interrupted or not with one or more heteroatoms, and having or not having one or more carbonyl or carboxylic acid functions, substituted or unsubstituted, monocyclic or polycyclic, saturated, unsaturated or aromatic carbocyclic or heterocyclic groups having or not having one or more carbonyl or carboxylic acid functions, and substituted or unsubstituted aryl groups having or not having one or more carbonyl or carboxylic acid functions, R.sub.4 also denoting or not denoting a radical of formula C1 in formula C above or a radical of formula D1 in formula D above and R.sub.3 also denoting or not denoting a radical of formula C2 in formula C above, formulae C1, C2 and D1 being the following: ##STR00021##

5. The method as claimed in claim 1, wherein there is, during step b), reaction of the hydroxybenzyl alcohol of formula B with a phenolic compound other than said hydroxybenzyl alcohol.

6. The method as claimed in claim 1, wherein R.sub.2 denotes —OH and wherein the compound of formula A is formed, before step a), by a Kolbe-Schmitt carboxylation reaction using a compound of formula A1, the formula A1 being the following: ##STR00022## in the formula A1, R.sub.1 and n.sub.1 are as defined above.

7. The method as claimed in claim 1, wherein R.sub.2 denotes —OH and wherein the compound of formula A is formed, before step a), by a reaction for formylation of a compound of formula A1 or by a reaction for oxidation of a compound of formula A2, the formulae A1 and A2 being the following: ##STR00023## in the formula A2, X is a group forming —CHO after an oxidation reaction and, in the formulae A1 and A2, R.sub.1 and n.sub.1 are as defined above.

8. The method as claimed in claim 6, wherein the compound of formula A1 is chosen from: simple phenols, polyphenolic compounds, for example diphenolic compounds, hydroxybenzoic aldehydes, hydroxybenzoic acids, hydroxybenzyl alcohols, hydroxycinnamyl alcohols, hydroxycinnamic acids, phenylpropenes, coumarins, naphthoquinones, stilbenoids, flavonoids, isoflavonoids, anthocyans, lignans, lignins, condensed tannins, hydrolyzable tannins, depolymerized tannins, and resol and novolac resins.

9. The method as claimed in claim 1, wherein R.sub.1 is chosen from: —OH, —O-Alk wherein Alk denotes a substituted or unsubstituted alkyl chain of 1 to 4 carbon atoms, —CHO, —COOH, and substituted or unsubstituted aryl groups having or not having one or more carbonyl or carboxylic acid functions,

10. The method as claimed in claim 1, wherein n.sub.1 is between 0 and 3.

11. A method for producing a phenolic resin comprising the following steps: reduction of a compound of formula A in order to obtain a hydroxybenzyl alcohol of formula B, formulae A and B being the following: ##STR00024## wherein: n.sub.1 is an integer between 0 and 4 and when n.sub.1 is greater than or equal to 2, the substituents R.sub.1 are identical or different, R.sub.1 is chosen from: —OH, —COOH, —CHO, the groups —O-Alk wherein Alk denotes a substituted or unsubstituted alkyl chain of 1 to 4 carbon atoms, saturated or unsaturated, substituted or unsubstituted hydrocarbon-based chains comprising between 1 and 20 carbon atoms, interrupted or not with one or more heteroatoms, and having or not having one or more carbonyl or carboxylic acid functions, substituted or unsubstituted, monocyclic or polycyclic, saturated, unsaturated or aromatic carbocyclic or heterocyclic groups having or not having one or more carbonyl or carboxylic acid functions, and substituted or unsubstituted aryl groups having or not having one or more carbonyl or carboxylic acid functions, and R.sub.2 denotes —H or —OH, and polymerization reaction between the hydroxybenzyl alcohol and an aromatic polyaldehyde compound in order to obtain the phenolic resin.

12. A method for producing a propulsion nozzle, wherein the nozzle is produced from a phenolic resin obtained by carrying out the method of claim 11.

13. The method as claimed in claim 7, wherein the compound of formula A1 or A2 is chosen from: simple phenols, polyphenolic compounds, hydroxybenzoic aldehydes, hydroxybenzoic acids, hydroxybenzyl alcohols, hydroxycinnamyl alcohols, hydroxybenzoic acids, hydroxybenzyl alcohols, hydroxycinnamyl alcohols, hydroxycinnamic acids, phenylpropenes, coumarins, naphthoquinones, stilbenoids, flavonoids, isoflavonoids, anthocyans, lignans, lignins, condensed tannins, hydrolysable tannis, depolymerized tannis, and resol and novolac resins.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0075] Other characteristics and advantages of the invention will emerge from the following description with reference to the appended drawing, wherein:

[0076] FIG. 1 represents results of thermogravimetric analyses comparing the properties of resins obtained by means of a method according to the invention and of the Ablaphene RS 101 resin.

EXAMPLES

Example 1: Synthesis of a Phenolic Resin by Homopolymerization of 2-Hydroxybenzyl Alcohol

[0077] In a first step, 2-hydroxybenzoic acid was synthesized by carrying out the method described below.

[0078] Phenol (5 g, 1 eq., 53 mmol) and potassium carbonate (14.7 g, 2 eq., 106 mmol) are introduced into a 50 ml autoclave reactor equipped with a mechanical stirring system. The reactor is placed at 200° C. and carbon dioxide is gradually introduced until a pressure of 80 bar is reached in the reactor. After 6 hours of reaction, the reactor is gradually cooled to ambient temperature and then degassed. The medium is recovered and the pH is neutralized with a concentrated sulfuric acid solution at 1 mol/l. The 2-hydroxybenzoic acid product is purified by liquid-liquid extraction with EtOAc/H.sub.2O. The organic phases are recovered, dried over anhydrous magnesium sulfate and concentrated under reduced pressure. The product is purified by separative chromatography with a mixture of EtOAc/cyclohexane eluent: 10/90. 4.1 g of product are recovered. The product characterized by .sup.1H and .sup.13C NMR is pure. Appearance: White powder. Weight yield=55%. The reaction carried out is summarized below.

##STR00012##

[0079] 2-Hydroxybenzyl alcohol was then obtained by reduction of the 2-hydroxybenzoic acid previously obtained.

[0080] 2-Hydroxybenzoic acid (4 g, 1 eq., 29 mmol), copper triflate (0.52 g, 5% eq., 1.5 mmol) and 1,1,3,3-tetramethyldisilazane (15.5 g, 4 eq., 116 mmol) and 45 ml of 2-methyltetrahydrofuran are introduced into a 100 ml round-bottomed flask equipped with mechanical stirring, under a nitrogen atmosphere. The round-bottomed flask is placed on a bath of oil thermostated at 80° C. for 16 hours. At the end of this reaction, 120 ml of distilled water are added to the reaction medium. The product is purified by liquid-liquid extraction with EtOAc/H.sub.2O. The organic phases are recovered, dried over anhydrous magnesium sulfate and concentrated under reduced pressure. The product is purified by separative chromatography with a mixture of EtOAc/cyclohexane eluent: 30/70. 2.3 g of product are recovered. The product characterized by .sup.1H and .sup.13C NMR is pure. Appearance: White powder. Weight yield=64%. The reaction carried out is summarized below.

##STR00013##

[0081] A phenolic resin was then synthesized without phenol and without formaldehyde by homopolymerization of the 2-hydroxybenzyl alcohol previously obtained.

[0082] 2-Hydroxybenzyl alcohol (10 g, 1 eq., 80.6 mmol), sodium hydroxide in aqueous solution at 50% by weight (0.9 g, 03 eq., 0.23 mmol) and 8 ml of water are placed in a 50 ml round-bottomed flask equipped with a condenser, with magnetic stirring. The round-bottomed flask is immersed in a bath of oil thermostated at 130° C. for 4 hours. At the end of this reaction, the mixture is in homogeneous and viscous resitol form. It is recovered, placed in an aluminum dish and baked in an oven, under atmospheric pressure, according to a baking program consisting of an increase in temperature from 40° C. to 180° C. at the rate of 3° C./hour and of a stationary temperature phase of 24 hours at 180° C. The resite material obtained at the end of this baking is brown, rigid and totally insoluble in acetone. The polymerization carried out is summarized below.

##STR00014##

Example 2: Synthesis of a Phenolic Resin without Phenol and without Formaldehyde Using 2-Hydroxybenzyl Alcohol and Benzaldehyde

[0083] The 2-hydroxybenzyl alcohol obtained by carrying out example 1 (5 g, 1 eq., 40.3 mmol), benzaldehyde (2.14 g, 0.5 eq., 20.1 mmol) and sodium hydroxide in aqueous solution at 50% by weight (0.35 g, 0.2 eq., 9 mmol) are placed in a 50 ml round-bottomed flask equipped with a condenser, with magnetic stirring. The round-bottomed flask is immersed in a bath of oil thermostated at 130° C. for 30 minutes. At the end of this reaction, the mixture is in homogeneous and viscous resitol form. It is recovered, placed in an aluminum dish and baked in an oven, under atmospheric pressure, according to a baking program consisting of an increase in temperature from 40° C. to 180° C. at the rate of 3° C./hour and of a stationary temperature phase of 24 hours at 180° C. The resite material obtained at the end of this baking is black, rigid and totally insoluble in acetone. The polymerization carried out is summarized below.

##STR00015##

Example 3: Synthesis of a Phenolic Resin without Phenol and without Formaldehyde Using 2-Hydroxybenzyl Alcohol and Terephthalaldehyde

[0084] The 2-hydroxybenzyl alcohol obtained by carrying out example 1 (5 g, 1 eq., 40.3 mmol), terephthalaldehyde (1.35 g, 0.25 eq., 10.1 mmol) and sodium hydroxide in aqueous solution at 50% by weight (0.48 g, 0.3 eq., 12.1 mmol) are placed in a 50 ml round-bottomed flask equipped with a condenser, with magnetic stirring. The round-bottomed flask is immersed in a bath of oil thermostated at 130° C. for 15 minutes. At the end of this reaction, the mixture is in homogeneous and viscous resitol form. It is recovered, placed in an aluminum dish and baked in an oven, under atmospheric pressure, according to a baking program consisting of an increase in temperature from 40° C. to 180° C. at the rate of 3° C./hour and of a stationary temperature phase of 24 hours at 180° C. The resite material obtained at the end of this baking is black, rigid and totally insoluble in acetone. The polymerization carried out is summarized below.

##STR00016##

Example 4: Synthesis of a Phenolic Resin without Phenol and without Formaldehyde by Homopolymerization of Vanillyl Alcohol

[0085] In a first step, the vanillyl alcohol was synthesized.

[0086] Vanillin (5 g, 1 eq., 32.9 mmol) is dissolved in 10 ml of ethanol and this solution is poured into a 50 ml two-necked round-bottomed flask equipped with a condenser, with magnetic stirring and with a dropping funnel. Sodium borohydride (1.86 g, 1.5 eq., 49.3 mmol is dissolved in 5 ml of concentrated sodium hydroxide solution at 1 mol/l and this solution is poured into the dropping funnel. The round-bottomed flask is immersed in an ice bath and the sodium borohydride solution is added dropwise to the round-bottomed flask. At the end of the addition, the ice bath is removed and the reaction medium is left to stir at ambient temperature for one hour. At the end of this reaction, the pH of the reaction medium is slowly decreased to 6 by dropwise addition of a concentrated hydrochloric acid solution at 1 mol/l. The product is purified by liquid-liquid extraction with EtOAc/H.sub.2O. The organic phases are recovered, dried over anhydrous magnesium sulfate and concentrated under reduced pressure. 4.5 g of product are recovered. The product characterized by .sup.1H and .sup.13C NMR is pure. Appearance: Beige powder. Weight yield=89%. The reaction carried out is summarized below.

##STR00017##

[0087] A phenolic resin was then obtained without phenol and without formaldehyde by homopolymerization of the vanillyl alcohol.

[0088] Vanillyl alcohol (10 g, 1 eq., 64.9 mmol), sodium hydroxide in aqueous solution at 50% by weight (0.9 g, 0.3 eq., 0.23 mmol) and 8 ml of water are placed in a 50 ml round-bottomed flask equipped with a condenser, with magnetic stirring. The round-bottomed flask is immersed in a bath of oil thermostated at 130° C. for 2 hours. At the end of this reaction, the mixture is in homogeneous and viscous resitol form. It is recovered, placed in an aluminum dish and baked in an oven, under atmospheric pressure, according to a baking program consisting of an increase in temperature from 40° C. to 180° C. at the rate of 3° C./hour and of a stationary temperature phase of 24 hours at 180° C. The resite material obtained at the end of this baking is black and rigid.

##STR00018##

Example 5: Analysis of the Heat Stability and Carbonizing Properties of the Crosslinked Phenolic Resins Obtained

[0089] The measurements of the coke contents of the synthesized resites were carried out by thermogravimetric analyses (TGA) on a Q50 instrument sold by the company TA Instruments. A 30 mg sample of resite in monolithic form is placed on a platinum cradle and then heated, under a nitrogen stream (60 ml/min) according to the following program: [0090] Linear increase from 20° C. to 160° C. at the rate of 10° C./min. [0091] Stationary temperature phase for one hour at 160° C. (iw). [0092] Linear increase from 160° C. to 900° C. at the rate of 10° C./min. [0093] Stationary temperature phase for one hour at 900° C. (fw).

[0094] The coke content is calculated according to the following equation, wherein the parameters iw and fw represent the weights of the sample at the end of the stationary temperature phases at 160° C. and 900° C., respectively.

Coke content=fw/iw.

[0095] FIG. 1 represents the results obtained by TGA for the resins synthesized in examples 2 (benzaldehyde/2-hydroxybenzyl alcohol resite), 3 (terephthalaldehyde/2-hydroxybenzyl alcohol resite) and 4 (vanillyl alcohol resite) in comparison with the results obtained for the Ablaphene RS101.

[0096] The coke content and also the degradation temperatures at 10% by weight (Td10%) of the resins tested are reported in table 1 below.

TABLE-US-00001 TABLE 1 Coke Resite Td10% content Benzaldehyde/2-hydroxybenzyl 490° C. 62% alcohol Terephthalaldehyde/2- 548° C. 70% hydroxybenzyl alcohol Vanillyl alcohol 334° C. 51% Ablaphene RS101 370° C. 63%

[0097] These results show that the resins produced by means of the method according to the invention can have heat stability and carbonizing properties that are similar to, or even greater than, those of the Ablaphene RS101 reference resin. This method thus gives access to phenolic resins which can advantageously replace the conventional formo-phenolic resins for the production of aeronautical parts such as propulsion nozzles.

[0098] The expression “comprising/containing a” should be understood as “comprising/containing at least one”.

[0099] The expression “between . . . and . . . ” or “ranging from . . . to . . . ” should be understood as including the limits.