WO2001038289A1

WO2001038289A1 - Method for acetoacetylation of nucleophilic compounds

Info

Publication number: WO2001038289A1
Application number: PCT/FI2000/001031
Authority: WO
Inventors: Tiina Lilja; Mervi YLÄ-JARKKO; Salme Koskimies; Petri MÄKIPEURA; Nina Heiskanen
Original assignee: Neste Chemicals Oy
Current assignee: Neste Chemicals Oy
Priority date: 1999-11-25
Filing date: 2000-11-27
Publication date: 2001-05-31
Anticipated expiration: 2002-05-25
Also published as: AU1866601A; FI19992519L; FI19992519A7

Abstract

The invention relates to a method for acetoacetylation of nucleophilic compounds with alkyl ketene dimers (AKD). In the method, the nucleophile is contacted with an alkyl ketene dimer either in the presence of a solvent, or without a solvent, optionally in the presence of a catalyst.

Description

Method for acetoacetylation of nucleophilic compounds

The present invention relates to a method for acetoacetylation of nucleophilic compounds, particularly of hydroxy functional nucleophilic compounds with alkyl ketene dimers (AKD). In the method, the nucleophile is contacted with an alkyl ketene dimer either in the presence of a solvent, or without a solvent, optionally in the presence of a catalyst.

Asetoacetate functionality is commonly utilized in the coating industry for crosslink- ing reactions. Coating made of acetoacetylated polymers have several improved properties in comparison with coatings obtained from the corresponding non- acetoacetylated polymers. Reactions favourable for the crosslinking of the acetoace- tylated polymers include reactions with activated olefins (the so-called Michael reaction), polyamines, melamines, and isocyanates. These reactions are rapid, they proceed at low temperatures, and are typically used for the curing of coatings, for instance. As disadvantages accompanying these methods may be mentioned the isocya- nate or epoxy type curing systems that are detrimental to health. Some acetoacetyla- tion methods useful in industrial scale have been developed and one of the best known is described in EP-376859 Al relating to the acetoacetylation of nucleophiles with β-dicarbonyl compounds, wherein the acetoacetylation runs via transesterifica- tion. At the end of the process, the alcohol formed as a by-product must be separated by distillation. In this transacetoacetylation method, a solvent is used for the removal of the alcohol from the reaction mixture. The solvent is usually selected to form an azeotropic mixture with the alcohol cleaved off, thus facilitating the removal of this alcohol by-product by distillation from the reaction mixture. The object of the invention is to provide a method for acetoacetylation of nucleophilic compounds with alkyl ketene dimers. Another object of the invention is to provide an improved method for acetoacetylation of nucleophilic compounds useful in industrial scale.

The characteristic features of the method of the present invention for acetoacetylation of nucleophilic compounds with alkyl ketene dimers are presented in the accompanying claims.

It has now been found that the above objects may be attained and the drawbacks of the prior art methods may be eliminated or substantially reduced with the method of the invention wherein the acetoacetylation of nucleophilic compounds is carried out with alkyl ketene dimers. In the method, a nucleophile is contacted with an alkyl ketene dimer or a mixture of alkyl ketene dimers either in the presence of a solvent, or without a solvent, and optionally in the presence of a catalyst.

In the acetoacetylation of nucleophiles, the alkyl ketene dimers used as starting materials may be produced by dehydrohalogenation of fatty acid halides in the presence of a tertiary amine, and an inert solvent. Straight chain or branched, saturated or unsatu- rated fatty acids suitable for such dehydrohalogenation reactions include C -C₂₀ fatty acids such as isostearic acid, decanoic acid, oleic acid, caprylic acid, palmitic acid, stearic acid, as well as the commercial tall oil fatty acid mixture and commercial vegetable oil fatty acid mixture. Acid chlorides prepared from fatty acids according to the Scheme 1 using several procedures are further converted with a tertiary amine to ketenes that are dimerized to form alkyl ketede dimers (AKD). In Scheme 1, the group R attached to the carbon chain represents a saturated or unsaturated alkyl group having a branced or a straight chain. Scheme 1

. COOH .COCl R-.

-HCl

According to the invention, alkyl ketene dimers prepared by means of the dimeriza- tion of ketene may be used as the reagents for the asetoacetylation of the nucleophiles. In this reaction, the β-lactone ring of the alkyl ketene dimer is opened as a result of the nucleophilic attac, and acetoacetate is obtained as the product.

Suitable nucleophiles to be acetoacetylated with alkyl ketene dimers include hydroxy functional saturated and unsaturated polyesters, primary and secondary polyols with the structure HO-R-OH and R(OH)_n, R representing a straight or branced chain alkyl, alkenyl, alkynyl, or allyl group, and n being more that 2, preferably 2 - 4. Examples of suitable nucleophiles comprising a hydroxy group include 1 ,4-butanediol, 2-butyl- 2-ethyl-l,3-propanediol (BEPD), trimethylol propane (TMP), 2,2-dimethyl-l,3- propanediol (NPG), 1 ,6-hexanediol (HD), ethylene glycol (EG), propylene glycol

(PG), ethyl hexanediol (ETHD), and pentaerythritol (PE).

Curing reaction may further be intensified by means of a crosslinking reaction by reacting a polyfunctional primary or secondary alkylamine having the structure H₂N-R- NH₂ or H₂N-R(R2NH₂)-NH₂, where the groups R and R₂ are identical or different alkenyl or alkyl groups, R and R₂ being suitably methyl, ethyl, octyl or a butyl group, with an acetylation product of a ketene dimer. Compounds with the above structures may be exemplified with 1 ,2-diaminopropane and 4-aminomethyl-l,8-octane diamide. Post-curing with a crosslinking reaction is particularly advantageous in coating applications.

Scheme 2 generally shows the reaction between a hydroxy functional nucleophile (I) and an alkyl ketene dimer (AKD) resulting in alkyl acetoacetate ester (II) as the reaction product. The group R is now a branched or straight chain saturated or unsaturated alkyl side chain having 1 - 8 carbons and the group Ri of the hydroxy functional nucleophile is a primary or secondary alkyl group.

Scheme 2

The reactivity between the alkyl ketene dimers and nucleophiles depends on the length of the alkyl side chains in the AKD used, and on the nucleophile used. AKDs with shorter chains such as a AKD made from caprylic acid chloride, acetoacetylate the hydroxy functional nucleophiles more quickly than alkyl ketene dimers having longer alkyl side chains. The reaction between alkyl ketene dimers having longer chains and nucleophiles may be accelerated by using catalysts such as tertiary amine catalysts, DMAP or 4-dimethyl amino pyridine. Other catalysts accelerating the acetoacetylation include tetramethyl ganide, triethyl amine, trimethyl amine, triethanol amine, N,N'-tetramethyl diamino compounds such as trans-N,N' -tetramethyl diamino-2-butene and cis-N, -tetramethyl diamino-2-butene, sulphonic acids, alkali metal salts such as alkali metal halides and alkali metal sulfates, α-chlorinated car- boxylic acids, sulphonic acid salts, tertiary phosphines, carboxylic acid betaines and sulphonic acid betaines. The increased reaction rate brought about by the catalyst also improves the selectivity of the reaction by reducing the amount of the reaction byproducts that are formed via hydrolysis and decarboxylation.

The method according to the invention for acetoacetylation of nucleophiles based on the acetoacetylating ability of alkyl ketene dimers may be carried out at a wide tem- perature range. The reaction is typically carried out at a temperature from 25 to 150

°C, preferably between 50 and 125 °C. Heating in not necessary when nucleophiles causing an exothermal reaction or AKDs having a shorter alkyl side chain are acetoacetylated. In this case, the reaction temperature may be controlled with the rate of addition of the nucleophile or AKD. Reaction times vary between 0.5 and 24 hours, depending on the acetoacetylating reagent and nucleophile used. An exothermal acetoacetylation reaction between the nucleophile and AKD will start immediately as the starting materials are contacted with one another. The use of a solvent in the acetoacetylation method carried out with AKD is optional. The use of a solvent is, however, preferable when hydroxy functional unsaturated or saturated polyesters, or nu- cleophiles with a very high melting point are acetoacetylated. In the production of acetoacetates, nearly any inert polar and non-polar organic solvent is a suitable optional solvent, including butyl acetate, ethyl acetate, methyl ethyl ketone and cyclo- hexanol. Although the use of a catalyst is not necessary for the succesful acetoacetylation, the use thereof is favourable for the selectivity and rate of the reaction when nucleophiles are acetoacetylated by means of alkyl ketene dimers having longer, branched or straight chain saturated or unsaturated alkyl side chains. The amount of the catalyst to be added depends on the catalyst used. Preferably, the catalyst is added in an amount from 0.01 to 0.10 mmol per millimole of the nucleophile. More prefera- bly, the catalyst is used in an amount of 1 % by weight or less, relative to the total amount of the reaction mixture.

The functionalization process of the invention is very simple and reactive. By con- trolling the structure of the AKD carbon chains (saturated/unsaturated), the solubility, viscosity and hardness properties of the product may be modified. It should especially be appreciated that no alcohol that should be removed separately is produced as a byproduct. A catalyst is not necessarily needed in the process, but it may be carried out directly owing to the acetoacetylating ability of the alkyl ketene dimers. Since the acetoacetylation is based on the reaction between the nucleophile and AKD, the reaction mixture will not contain any alcohol that would be produced as a by-product in transacetoacetylation. Thus, the acetoacetylation of the nucleophiles may be carried out without any need to distil alcohol off at the end of the synthesis. The method of the invention for the acetoacetylation of nucleophiles may be carried out both without a solvent and in the presence thereof. Since the acetoacetylation by using an AKD does not produce any alcohol that would be cleaved off, the selection of the solvent for the acetoacetylation method of the invention is more simple. With the method of the invention, isocyanate and epoxy type curing systems detrimental to health may be replaced. Accordingly, the invention is directed to an alternative method to carry out rapid reactions at low temperatures, these reactions being typically used for instance for curing of coatings. Moreover, by controlling the structure of the AKD carbon chains, the solubility, viscosity and hardness properties of the product may be modified as desired. Further, particularly in coating applications, post-curing may be intensified with crosslinking by means of polyfunctional amines.

To illustrate the method of the invention, the reactions between AKD mixtures and nucleophiles are described in more detail in the following synthesis examples without wishing to limit the invention thereto. EXAMPLE 1

Preparation of octanoic acid chloride from octanoic acid

14.3 g (0.104 mol) of phosphorous trichloride were added in a three-neck flask of 250 ml, equipped with a ball condenser, dropping funnel, nitrogen inlet and a magnetic stirrer. 30.0 g (0.208 mol) of dried octanoic acid were added to the phosphorous trichloride during 100 minutes. After the addition of the octanoic acid, the reaction mixture was further stirred for 120 minutes. The dropping funnel and the condenser comprised drying tubes containing silica to prevent the atmospheric moisture from entering the reaction. The reaction temperature was maintained at 55 °C with an oil bath. After the reaction, the octanoic acid chloride was separated from the phosphrous acid precipitated on the bottom of the flask by decantation. Based on the NMR analysis of the reaction mixture, the yield of the octanoic acid chloride was 97.8 %.

Preparation of alkyl ketene dimer from octanoic acid chloride

249 g (2.109 mol) of anhydrous n-butyl acetate and 172 g (1.704 mol) of anhydrous triethyl amine were added in a five-neck glass reactor of one liter, equipped with an oil mantle, thermometer, ball condenser, and a motor driven stirrer. A light nitrogen stream was bubbled through the mixture of n-butyl acetate and triethyl amine during 20 minutes before the reaction was initiated. Then, 249 g (1.530 mol) of octanoic acid chloride were added to the reaction mixture during 52 min. After the addition of the octanoic acid chloride, the reaction mixture was further stirred for 50 min. The condenser comprised thereon a drying tube containing silica. The reaction temperature was 45 °C. After the reaction, the triethyl ammoniumhydrogenchloride salt formed therein was filtered off. The solvent and any excess of triethyl amine were evaporated with a rotary evaporator. Based on the NMR analysis of the reaction mixture, the yield of the octyl ketene dimer was 97.3 %. EXAMPLE 2

Preparation of oleic acid chloride from oleic acid

2.43 g (0.018 mol) of phosphorous trichloride were added in a three-neck flask of 250 ml, equipped with a ball condenser, dropping funnel, nitrogen inlet and a magnetic stirrer. 10.0 g (0.035 mol) of dried oleic acid were added to the phosphorous trichloride during 26 minutes. After the addition of the oleic acid, the reaction mixture was further stirred for 85 minutes. The reaction apparatus was flushed with nitrogen before the reaction was started. The dropping funnel and the condenser comprised dry- ing tubes containing silica. The reaction temperature was maintained at 55 °C with an oil bath. After the reaction, the oleic acid chloride was separated from the phosphrous acid precipitated on the bottom of the flask by decantation. Based on the NMR analysis of the reaction mixture, the yield of the oleic acid chloride was 95.0 %.

Preparation of alkyl ketene dimer from oleic acid chloride

287.5 g (2.475 mol) of anhydrous n-butyl acetate and 106.35 g (1.051 mol) of anhydrous triethyl amine were added in a five-neck glass reactor of one liter, equipped with an oil mantle, thermometer, ball condenser, and a motor driven stirrer. A light nitrogen stream was bubbled through the mixture of n-butyl acetate and triethyl amine during 20 minutes before the reaction was initiated. Then, 288 g (0.035 mol) of oleic acid chloride were added dropwise to the reaction mixture during 120 min. After the addition of the oleic acid chloride, the reaction mixture was further stirred for 60 min. The condenser comprised thereon a drying tube containing silica. The reaction temperature was 45 °C. After the reaction, the triethyl ammoniumhydrogenchlo- ride salt formed therein was filtered off with suction. The solvent and any excess of triethyl amine were evaporated with a rotary evaporator. Based on the NMR analysis of the reaction mixture, the yield of the oleyl ketene dimer was 97.2 %. EXAMPLE 3

Preparation of isosteric acid chloride from isostearic acid

16.90 g (0.123 mol) of phosphorous trichloride were added in a three-neck flask of 250 ml, equipped with a ball condenser, dropping funnel, nitrogen inlet and a magnetic stirrer. 70.0 g (0.246 mol) of dried isostearic acid were added to the phosphorous trichloride during 168 minutes. After the addition of the isostearic acid, the reaction mixture was further stirred for 60 minutes. The reaction apparatus was flushed with nitrogen before the reaction was started. The dropping funnel and the condenser comprised thereon drying tubes containing silica. The reaction temperature was maintained at 55 °C with an oil bath. After the reaction, the isostearic acid chloride was separated from the phosphrous acid precipitated on the bottom of the flask by decantation. Based on the NMR analysis of the reaction mixture, the yield of the isostearic acid chloride was 93.3 %.

Preparation of alkyl ketene dimer from isostearic acid chloride 40.0 g (0.344 mol) of anhydrous n-butyl acetate and 17.78 g (0.146 mol) of anhydrous triethyl amine were added in a five-neck glass reactor of one liter, equipped with a ball condenser, a motor driven stirrer, dropping funnel, and a nitrogen inlet. A light nitrogen stream was bubbled through the mixture of n-butyl acetate and triethyl amine during 15 minutes before the reaction was initiated. Then, 40.0 g (0.136 mol) of isostearic acid chloride were added to the reaction mixture during 80 min. After the addition of the carboxylic acid chloride, the reaction mixture was further stirred for 60 min. During the reaction, a nitrogen stream was used and the condenser and the dropping funnel comprised thereon drying tubes containing silica. The reaction temperature was 45 °C. After the reaction, the triethyl ammoniumhydrogenchloride salt formed therein was filtered off with suction. The solvent and any excess of triethyl amine were evaporated with a rotary evaporator. Based on the NMR analysis of the reaction mixture, the yield of the isostearyl ketene dimer was 56 %. EXAMPLE 4

Acetoacetylation of 1,4-butanediol with AKD prepared from stearyl acid chloride and palmityl acid chloride according to Scheme 3

Scheme 3

(8)

BEPD

* (10)

R being either -(CH₂)_{] 5}CH₃ or -(CH₂)₁₃CH₃

To a three-neck flask of 100 ml equipped with a ball condenser, silica tube, dropping funnel, and a thermometer, 40.0 g of a mixture of alkyl ketene dimers (6) prepared from 75 % of stearyl acid chloride (purity 87.1 %), and 25 % of palmityl acid chloride were added. An oil bath was placed under the flask and the AKD mixture was melted by warming the flask in the oil bath. 3.5 g (3.88 mmol) of 1,4-butanediol (8) were added as a single portion to the melted AKD mixture by means of the dropping funnel and the temperature of the oil bath was raised to 125 °C. The mixture was boiled at about 116 °C under stirring with the magnetic stirrer for 18.0 h. The mixture of alkyl ketene dimers prepared from 75 % of stearyl acid chloride and 25 % of pal- mityl acid chloride acetoacetylates 85.4 % of the 1,4-butanediol to form the aceto- acetate ester having the structural formula (9).

EXAMPLE 5

Acetoacetylation of 2-butyl-2-ethyl-l,3-propanediol (BEPD) with AKD prepared from stearyl acid chloride and palmityl acid chloride according to Scheme 3

To a three-neck flask of 100 ml equipped with a ball condenser, silica tube, dropping funnel, and a thermometer, 40.0 g of a mixture of alkyl ketene dimers (6) prepared from 75 % of stearyl acid chloride (purity 87.1 %), and 25 % of palmityl acid chloride were added. The AKD mixture was melted by warming the flask in the oil bath. 6.2 g (3.86 mmol) of 2-butyl-2-ethyl-l,3-propanediol (BEPD) (10) were added as a single portion to the melted AKD mixture and the temperature of the bath was raised to 125 °C. The mixture was boiled under stirring with the magnetic stirrer for 22.5 h. The reaction mixture contained 88,9 % of the BEPD diacetoacetate having the structural formula (11).

EXAMPLE 6

EXEMPLARY CROSS LINKING REACTION

Scheme 4

(12) (13)

Equivalent amounts of acetoacetate (12) (5.0 g; 75 % by weight) synthesized with an acetoacetylation reaction between an alkyl ketene dimer prepared from caprylic acid chloride and 2-butyl-2-ethyl-l,3-propanediol (BEPD), and 4-aminomethyl-l,8- octanediamide (13) (0.65 g) were mixed together. From this mixture of compounds, a thin film was formed on a primed sheet with an applicator, and thereafter, the film was treated in an oven at 150 °C for 4.0 hours. A curing reaction was clearly seen.

Claims

1. Method for acetoacetylation of hydroxy functional nucleophilic compounds, characterized in that a nucleophilic compound is contacted with an alkyl ketene dimer, or a mixture of alkyl ketene dimers either in the presence of a solvent, or without a solvent, optionally in the presence of a catalyst, this nucleophilic compound being a saturated or unsaturated hydroxy functional polyester, or a primary or a secondary polyol with the structure HO-R-OH or R(OH)n, where R represents a straight or a branched chain alkyl, alkenyl, alkynyl, or allyl group, and n is more than 2, preferably from 2 to 4.

2. The method of Claim 1, characterized in that the nucleophilic compound is 1,4- butanediol, 2-butyl-2-ethyl-l,3-propanediol, trimethylol propane, 2,2-dimethyl- 1,3-propanediol, 1,6-hexanediol, ethylene glycol, propylene glycol, ethyl hexane- diol (ETHD), or pentaerythritol (PE).

3. The method of Claim 1 or 2, characterized in that the alkyl ketene dimer is produced by dehydrohalogenation of fatty acid halides in the presence of a tertiary amine and an inert solvent to form a ketene that is dimerized to an alkyl ketene dimer.

4. The method of Claim 3, characterized in that the fatty acid halides are produced from straight or branched chain saturated or unsaturated C₃-C₂₀ fatty acids.

5. The method of Claim 4, characterized in that the C₃-C₂₀ fatty acid is a isostearic acid, octanoic acid, stearic acid, decanoic acid, oleic acid, caprylic acid, palmitic acid, stearic acid, or a tall oil fatty acid mixture or a vegetable oil fatty acid mixture.

6. The method of any of Claims 1 - 5, characterized in that the catalyst used is a tertiary amine catalyst, an N,N' -tetramethyl diamino compound, a sulphonic acid, an alkali metal salt, an alkali metal halide, an alkali metal sulfate, an α- chlorinated carboxylic acid, a sulphonic acid salt, a tertiary phosphine, a carbox- ylic acid betaine, or a sulphonic acid betaine.

7. The method of any of Claims 1 - 6, characterized in that the reaction is carried out at the temperature from 25 to 150 °C, preferably at the temperature from 50 to 125 °C.

8. The method of any of Claims 1 - 7, characterized in that an inert polar or non- polar organic solvent such as butyl acetate, ethyl acetate, methyl ethyl ketone, or cyclohexanol is used in the reaction.

9. Method for boosting a post-curing reaction, characterized in that an acetylation product of a ketene dimer prepared with the method of any of Claims 1 - 8 is reacted with a polyfunctional primary or a secondary amine, preferably with a primary amine.

10. The method of Claim 9, characterized in that the polyfunctional amine is a primary or secondary alkyl amine with the structure H₂N-R-NH₂ or H₂N-R(R₂NH₂)- NH₂, where the groups R and R are identical or different alkenyl or alkyl groups, R and R₂ being preferably a methyl, ethyl, octyl, and a butyl group.

11. The use of the method of any of Claims 1 - 10 in a curing reaction of coatings.