DE3130508A1 - "METHOD FOR PRODUCING METHACRYL AND ACRYLAMIDES" - Google Patents

Description

S-

Process for the production of methacrylamides and acrylamides

In the production of the technically interesting amides of acrylic acid and methacrylic acid, there are in particular those procedures in the foreground that are easily accessible from technically Run out of raw materials.

Technically easily accessible starting products are e.g. the nitriles and the esters of acrylic or methacrylic acid and the acids themselves.

The Ctosetzung of organic carboxylic acids with alkylamines to the alkyl amides of the carboxylic acids at temperatures above 100 ⁰ C and below 350 ⁰ C, preferably at 150-250 ⁰ C, is already; in U.S. Patent 1,986,854. The amine is preferably added in the gaseous state at atmospheric pressure to the acid in the molten state and the amide formed is removed from the reaction batch by means of vacuum distillation. The amine should be added in a slight excess over the stoichiometrically required amount.

In US Pat. No. 2,719,177, it was demonstrated that after the process of the US-PS mentioned, for example, with dimethylamine as the gaseous amine component and acrylic acid in the molten state no N, N-dimethyl acrylamide is formed. The latter

Instead patent teaches a continuous gas phase reaction in the temperature range between 250 and 55Ö ^e C. ■ Dehydration catalysts. The conversion over aluminum oxide-containing catalysts with residence times between 1 and 7 seconds is shown to be advantageous. The ratio of acid to amine is ■ in the range from 1: 1 to 1: 2.5.

Also, a primary lAnsetzung in the gas phase · with acrylic acid or methacrylic acid and or secondary aliphatic or aromatic amines above 15O ⁰ C is taught by DE-AS 1,043,320, wherein phosphoric acid or phosphate-containing, wasserabspaltend acting catalysts are used.

In the case of the reaction with Ν, Ν-dialkylalkylenediamines with methacrylic acid, the stage of the Michael adduct, ie in this case the N- (dialkylaminoalkyl) -2-methyl-ßalanine, is deliberately included in the course of the reaction (US Pat. No. 3,652,671). The formation of the Michael adduct should therefore take place at 100-15O ⁰ C, the subsequent elimination reaction to methacrylamide at temperatures up to 23O ⁰ C, preferably at 180-220 ⁰ C and with the exclusion of oxygen. The corresponding reaction with acrylic acid, on the other hand, gave completely unsatisfactory results.

The prior art methods leave something to be desired in several respects. They are partly called Gas phase reaction carried out at relatively high temperatures in the presence of catalysts or they remain limited on the thermal decomposition of certain types of Michael adducts.

There was therefore the task of starting from the acrylic or the methacrylic acid provide a generally applicable process ai in which in the most economical way possible N-substituted acrylic or methacrylamides can be obtained, both from the product quality and from the yield satisfy her.

It has now been found that the requirements of the technology are largely met if, for the preparation of the N-substituted amides of acrylic or methacrylic acid in a first stage at normal pressure, the acid with the amine in stoichiometric amounts up to a slight excess of the amine at 75 - reacting 14O ⁰ C, with the proviso that it is carried in a homogeneous phase and in the second stage with removal of the water at 150-250 ⁰ C carried out the condensation and is subsequently worked up.

The invention relates in particular to a method of manufacture of acid amides of the formula I 20

CH ₂ = C - C NR ₂ R ₃ I.

R ₁ 0 -

where R- is hydrogen or methyl, R- is hydrogen or a saturated or unsaturated, optionally substituted alkyl radical or an optionally substituted aryl radical and R_ is a saturated or unsaturated, optionally substituted, optionally cyclic alkyl radical or an optionally substituted aryl or

denotes an aralkyl radical or an alkylenecarboxamido radical, or R ₂ and R ₃ together with the inclusion of the nitrogen form a heterocyclic ring, the acid of the formula II

CH ₀ = C - COOH II

L I

wherein R. has the above meaning with the amine of the formula III ■

mi in

^R 3

wherein R- and R- have the above meanings, is reacted in such a way that in the first stage the acid of the formula II with the amine of the formula III, preferably in stoichiometric amounts up to a slight excess of the amine at approx - 14O ⁰ C, preferably 80 - 130 ⁰ C, is brought to the reaction, with the proviso that the reaction mixture is a homogeneous phase and in the second stage with removal of the water formed at about 150 - 250 ⁰ C, preferably 160 - 24O ⁰ C, the condensation is carried out.

For workup, the unreacted acid of formula II is preferably converted with a suitable base such as calcium oxide, calcium hydroxide, potassium hydroxide, sodium hydroxide, in the salt, and then the amide t _he formula I preferably by distillation from the

3130S08

ι / Vi

-t9r ~

Won reaction batch.

In general, the desired product of formula I. the low-boiling portion, while the higher-boiling portion Shares the Michael adduct of the amine in the Λ, β-unsaturated Acid or an ß-unsaturated amide.

The meaning of the substituent R ₂ in the amine of the formula II includes a saturated or unsaturated, optionally branched, optionally substituted alkyl radical having 1 to 18 carbon atoms or an optionally substituted aryl radical, in particular a phenyl or naphthyl radical, the meaning of R ^ includes a saturated or unsaturated one , optionally substituted, optionally cyclic alkyl radical with 1 to 18 carbon atoms or an aralkyl radical or an optionally substituted aryl radical, in particular a phenyl or naphthyl radical or R- and R, together with the inclusion of nitrogen and optionally a further nitrogen, oxygen or Sulfur atom from a heterocyclic ring system.

Substituents which the 'radicals R ₂ or R- - as defined above - can have are, in particular, the carboxy, alkoxycarbonyl, (alkyl) carbamoyl, sulfo-,. Sulfonamido and especially the (alkyl) amino groups called. If the substituents contain alkyl radicals, they are preferably those with 1-6 carbon atoms. The amine of the general formula III can in the narrower sense compounds of the formula III '

3136508

vfr-

III ¹

where R has the meanings given above and A stands for a radical “CCR ₄ R ₅ ) or for a cyclohexyl, phenyl or naphthyl radical, where R. is hydrogen or an alkyl radical with 1 to 6 carbon atoms or a phenyl radical, R _{5 is} hydrogen or an alkyl radical with 1 to 6 carbon atoms, X is hydrogen or a group -COOH, -CONR ₆ R ₇ , -COOR ₈ , -SO ₃ H, - SO ₀ NR ₆ R ₇ or NR ^ and η is an integer of 1 to 18, with the proviso that η can only stand for 1, provided that X does not have the meaning -NRJRi and where R- and R ₇ and Ri and R ₇ ¹ independently of one another are hydrogen or an alkyl radical with 1 b 6 carbon atoms or A together with X forms an allyl or an alkenylcarboxamido radical.

The compounds of the general formula III thus include _Z .B. Amino acids, their esters and amides, such as glycine, alanine and alkylenediamines, for example ethylenediamine, propylenediamine, hexamethylenediamine, phenylenediamine, neopentanediamine and dimethylaminoneopentanamine, and sarcosine. If, in the context of the present invention, compounds of the general formula III are used which contain a second primary or secondary amino group, for example alkylenediamines, a reaction with two molecules of the ^ -unsaturated acid of the general formula II is possible. This type of conversion to a bis-amido compound is also included in the protection sought.

The reaction starting from compounds of acrylic acid (IL »methyl) and compounds of the formula III in which R _{7 is} not hydrogen, and the reaction starting from acrylic acid (R- = hydrogen) with the amines of the formula III is particularly preferred , and the implementation of both types of starting compounds of the formula II with unsaturated amines of the formula III, in particular allylamine and diallylamine.

These reactions have proven to be particularly advantageous, since the end products of the formula I are based on alternative ways only with difficulty or not in sufficient purity or with low yields or can generally not be produced inexpensively.

The implementation with branched ones is also of particular interest Alkylamines of the formula III, for example with isopropylamine. The implementation of the components of the formulas II and III is preferably carried out in a ratio of 1 mole of acid to T to 1.2 moles of amine.

To avoid polymerization losses, it is advisable to stop the reaction and work up the reaction product in the presence of polymerization inhibitors such as phenolthiazine, Hydroquinone, aromatic diamines such as N, N'-diphenyl-p-phenylenediamine, Iron compounds such as iron III acetylacetonate, copper compounds such as copper oleate etc. (cf. DE-OS 2 809 102).

In the case of the invention, which runs under normal pressure

3t3Ö? 08

Implementation, two reaction stages can be distinguished, each characterized by a specific temperature level. In this case, in the first in general between 75 ⁰ C and 14O ⁰ C, preferably 8.0 ⁰ C and 13O ⁰ C, extending step tf an accumulation of a portion of the amine to the <, ß-unsaturated acid of the formula It will be accepted. It appears to be of considerable importance. It is important that the reaction takes place in the first stage in the homogeneous phase; so there should be no crystal pulp.

It can be added in the presence of solvents such as xylene, mesitylene, isobutylbenzene, di-isoamyl ether, dichlorobenzene, .Decalin, cresol, i-bromo-4-chlorobenzene, nitrobenzene, resorcinol diethyl ether, but are preferably carried out without a solvent. In the first reaction phase, the acid is usually the amine is preferably added in the presence of the stabilizing agents. The duration is of course also based according to the size of the approach. As a guide value channel / 2 up to approx. 2 1/2 hours apply.

. In a transition phase, the temperature is raised to the temperature of the second reaction stage, ie up to approx. 165 ° C., a weak stream of gas, for example nitrogen, being expediently passed through, inter alia, to remove the water that forms during the condensation. The reaction is ₉ optionally continued with introduction of a gas at the temperature of the second reaction stage, for example over several hours, for example over 3 hours in the temperature range 160 - can be specifically left 18O ⁰ C at about 165 ⁰ C. In the second reaction stage, the water formed is expediently

3t3Ö508

removed by distillation. To complete the reaction, may finally even to a higher temperature, for example, be heated to ca.230 ⁰ C.

Alternatively, the amine (for example, 3 hours) within a few hours of about 165 ⁰ C to the upper temperature employed, so the range of 210 dm also gradually, ie after the addition - 23O ⁰ C to be heated. A very long treatment at temperatures above 21O ⁰ C should be avoided, however.

At the beginning of work-up, it is advisable to bind any acid that may still be present, for example by adding suitable ones Bases such as calcium oxide, calcium hydroxide, potassium hydroxide, etc.

The desired amides of the formula I are preferably isolated by fractional distillation, in particular vacuum distillation. The work-up _r -i-, ■.; -.-, by flash vacuum distillation or work-up on a thin-film evaporator has also proven successful. The low-boiling constituents — in general the desired amides, the high-boiling constituents — the Michael adducts that may still be present — to the un.ge, -; saturated acids of the formula II or the unsaturated amides I.

The following examples serve to illustrate the invention. according to the procedure.

3136S08

-η -

Be i s-ρ ie 1 e . · "

example 1

I ^m 1 1 four-necked flask were added 4 moles of methacrylic acid, 2 g Phenothiäzin and 0.5 g of hydroquinone at 90 ⁰ C within 45 min. With 4 moles of n-hexylamine. Under-a gentle stream of nitrogen (as a water entrainer) has now been Heist to 165 ⁰ G, the reaction mixture is kept 3 h at this temperature and distilling off the water of reaction thereby formed. Subsequently, the bottom temperature with simultaneous removal of water was further raised to 230 ⁰ C. Fractionated

^; Distillation of the reaction mixture in vacuo gave N-hexyl methacrylic acid amide in 72% yield.

· '

Examples 2-5

Methacrylic acid was prepared analogously to Example 1 in the presence of 50 ppm hydroquinone and 500 ppm iron (III) acetylacetonate or copper oleate implemented as stabilizers with various amines. The yields of the N-substituted methacrylamides obtained are listed in Table 1.

Unreacted methacrylic acid can easily be bound as a salt before working up by distillation (e.g. with CaO or KOH), as a result, the methacrylamides formed can be isolated very easily in high purity by distillation.

31.36.508

2 Methylamine 100 3 3. Isopropylamine 130 10 4th Allylamine 110 6th 10 5 Diallylamine 120 20th

Table 1

Example amine feed reaction yield of No. of the formula II temp. time b. 165- amide (% of theory) ( ⁰ C) 230 ° C (h)

57 75 58 31

Example 6

9 moles of acrylic acid were acetylacetonate along with 24 g of iron (III) and 2 per g of hydroquinone monomethyl ether, phenothiazine and Ν, Ν'-diphenyl-p-phenylenediamine at 110 - 130 ⁰ C are added with 9 moles of dimethylaminopropylamine. After the addition (2 hr) was heated for 3 hours from 165 ° C to 215 ⁰ C and distilling off the water formed. The reaction mixture was fractionally distilled in vacuo.

Yield of N- (dimethylaminopropyl) acrylic acid amide; j? 3% of the total Example 7-9

2 moles of acrylic acid were acetylacetonate with 5 g of iron (III) and 0.5 g of phenothiazine heated to 8O ⁰ C and at 80-120 ⁰ C within 30 min 2 moles of aniline was added.. The mixture was then ^{heated from 160 to 240 °} C. over the course of 4 h, and the resulting

Water of reaction distilled off.

Acrylic anilide was isolated in a 42 "yield. The analogous reaction in the presence of 0.1 mol of lithium hydroxide gave a yield of 46Λ of theory, in the presence of 0.1 mol of aluminum isopropoxide 44 % of theory.

Example 10

4 moles of methacrylic acid, S g Cu-oleate, and 0.5 g of hydroquinone 'were placed in 1 1 mesitylene and treated at 75 ⁰ C within 10 minutes with 4 moles of allylamine. (- C 165 ⁰ 160 sump) the water of reaction azeotropically (with methacrylic acid in the mixture and some amine) was then separated out at the boiling point. After a reaction time of 5 h, 40 % of theory formed on N-AlIylmethacrylamid.

Example 11

Reaction of methacrylic acid with methylamine as in Example 2 and work-up by flash vacuum distillation gave N-methyl methacrylic acid amide in 65% yield.

Claims (10)

3Ϊ30508 Process for the production of methacrylic and acrylamides patent claims 1.) Process for the preparation of acid amides of the formula I. CH, - C - C - NILR- I ώ ι H to R ₁ O wherein R _{1 is} hydrogen or methyl, R _{2 is} hydrogen or a saturated or unsaturated, optionally substituted alkyl radical or an optionally substituted aryl radical and R ₃ denotes a saturated or unsaturated, optionally substituted, optionally cyclic alkyl radical or an optionally substituted aryl or an aralkyl radical or an alkylenecarboxamido radical, or R ₂ and R- together form a heterocyclic ring with the inclusion of nitrogen, characterized in that 20 that the acid of the formula II Oi, = C - COOH II ώ ι R ₁
25th wherein R _{1 has} the above meaning with the amine of the formula III ■ I HN 'III wherein R ₂ and R- have the above meanings, is reacted in such a way that in the first stage at normal pressure the acid of the formula II with the amine of the formula III, preferably in stoichiometric amounts up to a slight excess of the amine at approx - 140 ⁰ C, is reacted, with the proviso that the resulting reaction mixture is a homogeneous phase and in the second stage with removal of the resulting water at about 150 - 25O ⁰ C, the condensation is carried out. 2. The method according to claim 1, characterized in that the unreacted acid of the formula II for work-up converted with a base into the salt and then the acid amide of the formula I by distillation from the reaction mixture is won. 3. The method according to claim 1, characterized in that at least one of the substituents R ₂ and R, in the amine of the formula III is an unsaturated alkyl radical. 4. Process according to Claims 1 and 3, characterized in that at least R ₂ in the amine of the formula III is an allyl radical. 5. The method according to claim 4, characterized in that R ^ and R, represent allyl radicals. 3130S08 6. The method according to claim 1, characterized in that at least one of the substituents R- or R- in the amine Formula III represents a branched alkyl radical. 7. The method according to claim 6, characterized in that at least one of the substituents R ₂ or R- a
Represents isopropyl radical. 8. The method according to claim 1, characterized in that R ₇ in the amine of the formula III is hydrogen and R _{3 is} an alkyl radical having 1-6 carbon atoms. 9. The method according to claim 8, characterized in that R ₇ in the amine of the formula III is hydrogen and R, a Represents methyl group. 10. The method according to claim 1, characterized in that the reaction and work-up in the presence of
Polymerization inhibitors performs.
20th