CH496644A - 4-hydroxy-3 5-dialkylbenzyl-carboxylic esters as - Google Patents

Abstract

esters of formula (I) are prepared by reacting Mannich bases (II) with carboxylic esters (III), in an anhydrous, inert organic solvent, in the presence of catalytic amounts of alkali or alkaline earth metal bases. CH2R3-COOR4 where R1 and R2 = alkyl groups, at least one alkyl group having 1-6 C atoms; R3 = CN or COOR4; and R4 = a straight chain, branched or cyclic or aryl-substituted alkyl-, thioether or ether group having a total of 1-20 C atoms; and R = a lower alkyl group.

Description

  

  
 



  Process for the preparation of (4-hydroxy-3,5-dialkylbenzyl) carboxylic acid esters and use of the same
The invention relates to a process for the preparation of (4-hydroxy-3, 5-dialkylbenzyl) carboxylic acid esters of the formula
EMI1.1
 in which R1 and R2 are identical or different, straight-chain or branched alkyl groups, of which at least one has 1-6 carbon atoms, R5 is -CN or -COOR4 and R4 is a straight-chain, branched, cyclic or aryl-substituted alkyl, thioether or ether - group with a total of 1-20 carbon atoms means, through conversion of Mannich bases of the formula:
EMI1.2
 in which R represents an alkyl group, with carboxylic acid esters of the formula:

  :
EMI1.3
 in the presence of catalytic amounts of alkali or alkaline earth bases in anhydrous, inert organic solvents.



   Preferably at least one of the alkyl groups R1 and R is bonded to the aromatic nucleus via a tertiary or quaternary carbon atom and R represents a lower alkyl group. The alkali or alkaline earth bases are preferably alkali or alkaline earth alcoholates, while aromatic hydrocarbons are used as preferred organic solvents will.



  Further examples of suitable solvents are the hydrocarbons in general and glycol ethers or other higher-boiling ethers. Furthermore, the alcohols corresponding to the radical R4 can be used as solvents.



   The compounds obtained by the process according to the invention are used to stabilize substances against decomposition by oxygen, light and heat. Antioxidants can also be used for stabilization, in particular an ester of thiodipropionic acid or a phosphite. Expediently, in the process according to the invention, 1 mol of Mannich base, which can easily be obtained by reacting phenols, formaldehyde and sec. Amines can be prepared with 1 mol of carboxylic acid ester (malonic ester, cyanoacetic acid ester) in the presence of 1 to 20 g of alkali or alkaline earth metal alcoholate in about 1 liter of toluene, preferably under nitrogen, for 2 to 3 hours under reflux and the resulting reaction solution in a manner known per se further worked up by removing the catalyst after cooling - z.

  B. by neutralization with dilute acid and shaking with water - the reaction mixture is dried, the solvent is distilled off and the residue z. B. is purified by recrystallization. The yield is about 70 to 95% of theory. Th.



   The smooth course of the reaction could not be foreseen, since according to H. Hellmann and G. Opitz u-Aminoalkylation (Verlag Chemie), page 284, phenol-Mannich bases only then smoothly C-alkylate; B. can be reacted with malonic esters if one starts from the ammonium salts of the phenol bases, but their preparation is difficult (loc. Cit.).



   The method according to the invention will be explained in more detail by the following example.



   example 1
Production of (4-hydroxy-3-methyl-5-tert-butyl-benzyl) -malonic acid distearyl ester) (stabilizer II)
22.1 g (0.1 mol) of (3-methyl-5-tert.-butyl-4-hydroxy banzyD-dimethylamine, together with 60.9 g (0.1 mol) of distearyl malonate and 1 g of magnesium ethylate in 75 cm3 Toluene refluxed for 3 hours under nitrogen After the solution had cooled, the magnesium ethylate was filtered off, the solvent was distilled off in vacuo and the residue was recrystallized from acetone, giving 71 g of (4-hydroxy-3-methyl-5-tert Butyl-benzyl) -malonic acid distearyl ester (90% of theory). Mp. 69-710 C.



   The compounds listed in Table 1, which - with reference to the general formula I - are characterized by their substituents, were prepared in an analogous manner. Its structure was determined based on the infrared spectra and the quantitative analysis. certainly.



  Table 1
EMI2.1


<tb> Stabilizer- <SEP> R1 <SEP> R2 <SEP> R3 <SEP> R4 <SEP> m.p. <SEP> yield
<tb> <SEP> No. <SEP> R1 <SEP> R2 <SEP> R3 <SEP> R4 <SEP> (oc) <SEP> (%)
<tb> <SEP> -CH3 <SEP> tert-butyl <SEP> CN <SEP> -C2Hs <SEP> 180-182 <SEP> 67
<tb> <SEP> -CH3 <SEP> tert-butyl <SEP> COOR4 <SEP> -CH3 <SEP> 191-193 <SEP> 72
<tb> <SEP> -CH3 <SEP> tert-butyl <SEP> GOOR4 <SEP> -CH # CHC4H9 <SEP> liquid <SEP> 84
<tb> <SEP> C2Hs
<tb> <SEP> -CH3 <SEP> tert-butyl <SEP> COOR4 <SEP> -CH2 # <SEP> liquid <SEP> 69
<tb> <SEP> -CH3 <SEP> tert-butyl <SEP> COOR4 <SEP> {i> <SEP> liquid <SEP> 73
<tb> <SEP> -CH3 <SEP> tert-butyl <SEP> COOR4 <SEP> -CH2CH2OC4Hg <SEP> liquid <SEP> 87
<tb> <SEP> -CH3 <SEP> tert-butyl <SEP> COOR4 <SEP> -CH2CH # -C15H37 <SEP> 60-62 <SEP> 75
<tb> <SEP> I <SEP> -CH3 <SEP> tert-butyl <SEP> COOR4 <SEP> -CloH21 <SEP> 40-42 <SEP> 92
<tb> <SEP> II <SEP> -CH3

   <SEP> tert-butyl <SEP> COOR4 <SEP> C18H57 <SEP> 69-71 <SEP> 90
<tb> <SEP> IIII <SEP> tert-butyl <SEP> tert-butyl <SEP> COOR4 <SEP> -CH2CH2SC1sH3s <SEP> 37-40 <SEP> 74
<tb> <SEP> IV <SEP> tert-butyl <SEP> tert-butyl <SEP> COOR4 <SEP> -C18H87 <SEP> 65-68 <SEP> 89
<tb> <SEP> V <SEP> Isopropyl <SEP> Isopropyl <SEP> COOR4 <SEP> -C18H37 <SEP> 68-70 <SEP> 80
<tb>
The compounds of formula I are particularly suitable for stabilizing polymeric plastics, e.g. B. polyolefins, polyamides, high-impact polystyrene containing copolymers of butadiene and styrene, ABS polymers (polymers of acrylonitrile, butadiene and styrene) of vegetable and animal fats, of plasticizers, e.g. B. phthalates, as well as mineral oils against decomposition by oxygen, light and heat.



   Particularly good stabilization results were achieved with compounds of the formula:
EMI2.2
 in which R: has the meaning given above and a total of 4-20 carbon atoms. In general, preference is given to the esters of higher alcohols, especially those which contain sulfur in an ether bond. These esters are well compatible with polymeric plastics, fats and mineral oils and, due to their low volatility, have a good stabilizing effect on these substances even after prolonged thermal exposure.



   The stabilizer compounds are usually used in an amount of 0.01 to 10%, based on the total weight of the substance to be stabilized.



   Known stabilizers against, z. B. the mixtures of alkylated phenols previously known from DAS No. 1 035 137 (as, for example, Example 5 shows), the thiobisphenols considered to be particularly effective and also the # - (hydroxy-alkyl -phenyl) -a1kan-carboxylic acid esters, the compounds used according to the invention have a superior stabilizing effect, as the examples show. Investigations have surprisingly shown that the type and number of methylene groups adjacent to the carboxylate group is decisive for the strength of the stabilizing effect. According to DAS No. 1 201 349, this was by no means to be expected.



   The compounds used according to the invention can also be obtained by reacting benzyl halides of the general formula:
EMI2.3
  with the alkali (e.g. sodium) derivatives of the carboxylic acid esters of the general formula:
EMI3.1
 or by reacting 2,6-dialkylated phenols with halogenated carboxylic acid esters of the general formula:
EMI3.2
 produce. Both processes are of manufacture from the phenols, formaldehyde and sec. Amines are inferior to easily accessible Mannich bases and carboxylic acid esters because the starting compounds of formulas V and VII are more difficult to access.



   The stabilizing effect of the compounds used according to the invention is intended to be illustrated in the following examples.



   Example 2
Stabilizing polypropylene
The stabilizers or stabilizer mixtures given in Table 2 were added to 100 parts of non-stabilized polypropylene powder (two different types were tested, which are designated in the table with A and B), all mixtures were rolled on a laboratory roller at 1800 ° C. for 10 minutes and the resulting mixtures Foils are pressed at a pressure of 200 atü and a temperature of 2100 C.



   5 strips were cut from the 1 mm thick plates obtained, subjected to accelerated aging by storage in a drying cabinet at 1500 ° C. and the time at which the oxidative degradation (onset of brittleness) could be determined according to the Brittle test was determined.



   Table 2 Pol lt Stb # l # t oxidative degradation yprnpyenyp aiisaor determined after
A 0.5 part of 4,4'-thiobis (6-tert-butyl-m-cresol) for 38 days
A 0.5 part of p- (3,5-di-tert-butyl-4-hydroxyphenyl) stearyl propionate for 38 days
A 0.5 part of stabilizer III for 66 days
B 0.2 part of 4,4'-thiobis (6-tert-butyl-m-cresol) for 49 days
0.3 parts dilauryl thiodipropionate (DLTDP)
B 0.2 part of p- (3,5-di-tert-butyl-4-hydroxyphenyl) stearyl propionate for 57 days
0.3 parts DLTPD
B 0.2 part of stabilizer II for 71 days
0.3 parts DLTDP
These results illustrate the superior effect of the stabilizers of the invention.



   Example 3
Stabilization of an ABS polymer
All four of the mixtures of 100 parts of ABS polymers listed in Table 3 (polymer of acrylonitrile, butadiene and styrene), 0.5 part of stabilizer and 2 parts of lubricant (1,2-bis-stearoyl-aminoethane) were on a laboratory roller at 1600 C rolled for 10 minutes and then the films obtained are pressed in a platen press at a pressure of 200 atm and at a temperature of 1800 C.



   5 strips were cut from the 1 mm thick plates thus obtained, subjected to accelerated aging by storage in a drying cabinet at 1100 ° C. and the stabilizing effect determined on the basis of the change in color and brittleness of the strips.



   The following results were obtained:
Table 3
Mixture of color after 10 days. Brittle after 100 parts of ABS resin
0.5 part of 2,6-di-tert-butyl-p-cresol light yellow for 37 days
0.25 part of 2,6-dimethylphenol
2 parts lubricant 100 parts ABS resin
0.5 part of 4,4'-thiobis (6-tert-butyl-m-cresol) brown for 42 days
2 parts lubricant
mixture
100 parts ABS resin
0.5 part stabilizer 1
2 parts lubricant
100 parts ABS resin
0.5 parts of stabilizer III
2 parts lubricant
As can also be seen from the table, the stabilizers I and III according to the invention surpass the stabilizing effect of the previously known products.



   Example 4
Stabilization of polyamide (condensation product of dicarboxylic acid and diamines)
All four of the mixtures of 100 parts of polyamide and 1 part of stabilizer listed in Table IV were used to produce sheets in an extruder at 2500 C, which were divided into 5 strips and allowed to age accelerated at 1400 C in a drying cabinet.



   The stabilizing effect was assessed according to the brittleness of the films. As can be seen from the table, the stabilizers used in accordance with the invention exceed the effect of known antioxidants. The addition of phosphite significantly improves the initial color of the extruded sheets.



   Table 4
Mixture Brittle after 100 parts of polyamide for 34 days
1 part 4,4'-thiobis- (6-tert-butyl m-cresol) 100 parts polyamide
1 part of stearyl ss- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate for 37 days, 100 parts of polyamide
1 part stabilizer IV 43 days 100 parts polyamide
1 part stabilizer III 48 days 100 parts polyamide
0.5 part of Stabilizer II for 60 days
0.5 part trinonylphenyl phosphite
Example 5
Stabilizing mineral oil
The following solutions were prepared from the same mineral oil: 1. 100 g mineral oil (Gardner color number 3-4,
Viscosity 144 cps at 200 C)
0.1 g of 4,4'-thio-bis (6-tert-butyl-m-cresol).



  2. 100 g of mineral oil
0.1 g of ss- (3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid aryl ester.



  3. 100 g of mineral oil
0.1 g stabilizer 1.



   Color after 10 days. Brittle after light yellow 46 days pale yellow 51 days 4. 100 g mineral oil
0.05 g stabilizer I.
0.05 g tri-nonyl phenyl phosphite 5. 100 g mineral oil
0.05 g of 2,4,6-tri-tert-butyl-phenol
0.05 g of 2,4-dimethylphenol.



  through which, under otherwise identical conditions (1900 C, 90 minutes), 5 liters of oxygen were passed and the degradation that occurred was assessed on the basis of the deepening of the color and the increasing viscosity.



   The following color numbers (FZ) and viscosities were measured:
Mixture 1: FZ 14 Viscosity: 165 cps at 200 C
Mixture 2: FZ 9 Viscosity: 192 cps at 200 ° C
Mixture 3: FZ 7 Viscosity: 180 cps at 200 C
Mixture 4: FZ 9 Viscosity: 165 cps at 200 ° C
Mixture 5: FZ 12 Viscosity: 188 #ps at 200 C
These results illustrate the good stabilizing effect of the stabilizers of the invention which is achieved especially when phosphites are mixed in.



   Example 6
Stabilizing edible oils and plasticizers
Olive oil and dioctyl phthalate (plasticizer) were stabilized and aged as in Example 5, and the deepening of color and increase in viscosity caused by the thermo-oxidative degradation were measured.



   The best results were always achieved with the stabilizers of the invention, especially in combination with tri-nonyl-phenyl-phosphite.



     PATENT CLAIMS
I. Process for the preparation of (4-hydroxy-3,5dialkylbenzyl) carboxylic acid esters of the formula:
EMI4.1
 in which R1 and R2 are identical or different, straight-chain or branched alkyl groups, of which at least one has 1-6 carbon atoms, R3 is -CN or -COOR4 and R4 is a straight-chain, branched, cyclic or aryl-substituted alkyl, thioether or ether group means with a total of 1-20 C atoms, characterized in that Mannich bases of the formula
EMI4.2
 

** WARNING ** End of DESC field could overlap beginning of CLMS **.



   

 

Claims (1)

** WARNING ** Beginning of CLMS field could overlap end of DESC **. mixture 100 parts ABS resin 0.5 part stabilizer 1 2 parts lubricant 100 parts ABS resin 0.5 parts of stabilizer III 2 parts lubricant As can also be seen from the table, the stabilizers I and III according to the invention surpass the stabilizing effect of the previously known products. Example 4 Stabilization of polyamide (condensation product of dicarboxylic acid and diamines) All four of the mixtures of 100 parts of polyamide and 1 part of stabilizer listed in Table IV were used to produce sheets in an extruder at 2500 C, which were divided into 5 strips and allowed to age accelerated at 1400 C in a drying cabinet. The stabilizing effect was assessed according to the brittleness of the films. As can be seen from the table, the stabilizers used in accordance with the invention exceed the effect of known antioxidants. The addition of phosphite significantly improves the initial color of the extruded sheets. Table 4 Mixture Brittle after 100 parts of polyamide for 34 days 1 part 4,4'-thiobis- (6-tert-butyl m-cresol) 100 parts polyamide 1 part of stearyl ss- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate for 37 days, 100 parts of polyamide 1 part stabilizer IV 43 days 100 parts polyamide 1 part stabilizer III 48 days 100 parts polyamide 0.5 part of Stabilizer II for 60 days 0.5 part trinonylphenyl phosphite Example 5 Stabilizing mineral oil The following solutions were prepared from the same mineral oil: 1. 100 g mineral oil (Gardner color number 3-4, Viscosity 144 cps at 200 C) 0.1 g of 4,4'-thio-bis (6-tert-butyl-m-cresol). 2. 100 g of mineral oil 0.1 g of ss- (3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid aryl ester. 3. 100 g of mineral oil 0.1 g stabilizer 1. Color after 10 days. Brittle after light yellow 46 days pale yellow 51 days 4. 100 g mineral oil 0.05 g stabilizer I. 0.05 g tri-nonyl phenyl phosphite 5. 100 g mineral oil 0.05 g of 2,4,6-tri-tert-butyl-phenol 0.05 g of 2,4-dimethylphenol. through which, under otherwise identical conditions (1900 C, 90 minutes), 5 liters of oxygen were passed and the degradation that occurred was assessed on the basis of the deepening of the color and the increasing viscosity. The following color numbers (FZ) and viscosities were measured: Mixture 1: FZ 14 Viscosity: 165 cps at 200 C Mixture 2: FZ 9 Viscosity: 192 cps at 200 ° C Mixture 3: FZ 7 Viscosity: 180 cps at 200 C Mixture 4: FZ 9 Viscosity: 165 cps at 200 ° C Mixture 5: FZ 12 Viscosity: 188 #ps at 200 C These results illustrate the good stabilizing effect of the stabilizers of the invention which is achieved especially when phosphites are mixed in. Example 6 Stabilizing edible oils and plasticizers Olive oil and dioctyl phthalate (plasticizer) were stabilized and aged as in Example 5, and the deepening of color and increase in viscosity caused by the thermo-oxidative degradation were measured. The best results were always achieved with the stabilizers of the invention, especially in combination with tri-nonyl-phenyl-phosphite. PATENT CLAIMS I. Process for the preparation of (4-hydroxy-3,5dialkylbenzyl) carboxylic acid esters of the formula: EMI4.1 in which R1 and R2 are identical or different, straight-chain or branched alkyl groups, of which at least one has 1-6 carbon atoms, R3 is -CN or -COOR4 and R4 is a straight-chain, branched, cyclic or aryl-substituted alkyl, thioether or ether group means with a total of 1-20 C atoms, characterized in that Mannich bases of the formula EMI4.2 in which R represents an alkyl group, with carboxylic acid esters of the formula: EMI5.1 be reacted in the presence of catalytic amounts of alkali or alkaline earth bases in anhydrous, inert organic solvents. II. Use of the (4-hydroxy-3,5-dialkylbenzyl) carboxylic acid esters obtained by the process according to claim I for stabilizing substances against decomposition by oxygen, light and heat. SUBCLAIMS 1. The method according to claim I, characterized in that at least one of the alkyl groups R1 and R2 is bonded to the aromatic nucleus via a tertiary or quaternary carbon atom. 2. The method according to claim I, characterized in that R represents a lower alkyl group. 3. The method according to claim I, characterized in that the alkali or alkaline earth bases are alkali or alkaline earth alcoholates. 4. The method according to claim I, characterized in that aromatic hydrocarbons are used as organic solvents. 5. Use according to fatent claim II, characterized in that antioxidants are used for stabilization. 6. Use according to dependent claim 5, characterized in that an ester of thiodipropionic acid or a phosphite is also used as the antioxidant.