DE102009000861A1 - Process for the preparation of cyanoacrylates - Google Patents

Abstract

The present invention relates to a process for the preparation of cyanoacrylic acid esters. The process is based essentially on a transesterification reaction, wherein the transesterification reaction is carried out in the presence of a transesterification catalyst which comprises at least one acid having a pks value ≰ 5 and at least one metal catalyst.

Description

The The present invention relates to a process for the preparation of Cyanoacrylates. The process is essentially based on a transesterification reaction, wherein the transesterification reaction in the presence a transesterification catalyst is carried out, the at least an acid with a pks value ≤ 5 and at least a metal catalyst.

polymerizable Adhesive compositions based on cyanoacrylates due to their ease of use and high curing speed and strength of the resulting adhesive bond is widely used found in both industrial and medical applications. It is known that monomeric forms of cyanoacrylates are extremely reactive and in the presence of even minute amounts of a polymerization initiator, including those contained in the air or on surfaces Polymerize moisture quickly. This is the initiation the polymerization by anions, free radicals, zwitterions or Ion pairs. Once the polymerization has started, the curing speed can be very high. polymerizable Adhesive compositions based on cyanoacrylic acid ester Therefore, for example, when joining plastics, rubbers, Glass, metals, wood and even biological tissues as attractive Solutions proved.

Like in US Patent 6,667,031 discloses the conventional synthesis of mono-cyanoacrylic acid esters based on a Knoevennagel condensation in which cyanoacetate is reacted with formaldehyde. The resulting prepolymer is depolymerized at high temperatures of 150 to over 200 ° C by thermal cracking, the separation of the monomers formed from the reaction solution is usually carried out by distillation. The thermal depolymerization succeeds only when this process proceeds in the presence of stabilizers or mixtures of stabilizers which can prevent both a radical and an anionic repolymerization of the monomers formed under the reaction conditions described. Stabilizers that prevent anionic repolymerization are usually, but not exclusively, Lewis acids, such as sulfur dioxide, nitric oxide or boron trifluoride or inorganic or organic Brønstedt acids, especially those having a pKa ≤ 5, such as sulfuric acid, phosphoric acid or organic sulfonic acids ,

Often leads the very high concentration used in the process the stabilizers that in the distillative separation of the Monomers from the reaction solution part of the stabilizer is dragged off. The resulting sometimes very high residual concentration of the stabilizer in the distilled cyanoacrylate monomer especially for sterically demanding cyanoacrylates to an overstabilization, whereby their rate of polymerization is reduced.

The preparation of Biscyanacrylaten has long been known and can be done as follows:
Analogously to the Knoevenagel condensation described above, formaldehyde and biscyanacetates are reacted. This results in a crosslinked polymer, which can hardly be thermally depolymerized.

Furthermore, the preparation of Biscyanacrylaten done in a retro-Diels-Alder reaction. Such as in the U.S. Patent 3,975,422 First, a monofunctional cyanoacrylate is blocked with dienes. The blocked monofunctional cyanoacrylate is saponified to the free acid. From the corresponding acid chloride, the ester is then prepared with a diol. After the biscyanoacrylate has been replaced by maleic anhydride, the pure biscyanoacrylate is finally obtained after repeated recrystallization from benzene. This production route thus comprises 5 stages and is therefore uneconomical.

An alternative possibility for the preparation of Biscyanacrylaten is in the European patent specification EP 0764148 B1 taught. The biscyanoacrylates are obtained by reaction of 2-cyanoacrylic acid or its alkyl ester with diols, the reaction preferably being carried out in the presence of sulfonic acids as catalyst in solution. The biscyanoacrylates are then isolated by fractional crystallization.

When A disadvantage of this method has been found to be relatively high Quantities of sulfonic acids must be used, to achieve an effective esterification or transesterification reaction. A complete separation of the sulfonic acids from the obtained Product is often difficult, which makes it especially bulky Biscyanacrylaten a significant reduction in the rate of polymerization of each monomer is observed, since the said sulfonic acids act as anionic polymerization inhibitors.

aim The present invention was therefore the development of an effective Process for the preparation of mono-, bis- and / or multicyanacryloic acid esters in high purity using as small amounts as possible on anionic polymerization inhibitors.

The Solution according to the invention is the claims refer to. It consists essentially in the transesterification of Mono-cyanoacrylic acid esters with monovalent and / or polyvalent ones Alcohols in the presence of a transesterification catalyst, the at least an acid with a pks value ≤ 5 and in addition comprises at least one metal catalyst. By use the at least one metal catalyst it is possible the amount of acids, in particular of acids with a pks value ≤ 5 compared to conventional Significantly minimize the process.

• a) Umesterung mindestens eines 2-Cyanacrylsäureesters der allgemeinen Formel (II),
  
  wobei R¹ ein verzweigter oder unverzweigter Alkylrest mit 1 bis 6 C-Atomen ist, mit mindestens einem Alkohol der allgemeinen Formel (III) [H-O-]_nR Formel (III)in Gegenwart eines Umesterungskatalysators, umfassend mindestens eine Säure mit einem pks-Wert ≤ 5 und mindestens einen Metallkatalysator und
• b) Isolierung des in Schritt a) erhaltenen Cyanacrylsäureesters der allgemeinen Formel (I), wobei n eine ganze Zahl von 1 bis 6 ist und R ein n-valenter Rest ist, der 1 bis 100 C-Atomen umfasst.

The present invention therefore provides a process for preparing at least one cyanoacrylic acid ester of the general formula (I), comprising the steps:

• a) transesterification of at least one 2-cyanoacrylic acid ester of the general formula (II),
  
  where R ^{1 is} a branched or unbranched alkyl radical having 1 to 6 C atoms, with at least one alcohol of the general formula (III) [HO-] _n R formula (III) in the presence of a transesterification catalyst comprising at least one acid having a pks value ≦ 5 and at least one metal catalyst and
• b) isolation of the obtained in step a) cyanoacrylic acid ester of the general formula (I), wherein n is an integer from 1 to 6 and R is an n-valent radical comprising 1 to 100 carbon atoms.

Under an n-valent radical R is within the meaning of the present invention an n-valent organic radical having 1 to 100 carbon atoms to understand that starting from the cyanoacrylic acid ester of the general formula (I) or Alcohol of the general formula (III) by the homolytic cleavage of carbon-oxygen bonds is formally formed.

The term of the n-valent radical will be explained in more detail below using the example of the trivalent alcohol TMP (n = 3):

By the formal homolytic cleavage of the three C-OH bonds in the TMP molecule This results in a 3-valent organic residue in the sense of the present Invention.

und/oder aus Biscyanacrylsäureestern der allgemeinen Formel (Ib)

und/oder aus Triscyanacrylsäureestern der allgemeinen Formel (Ic)

ausgewählt, wobei Rest R wie oben definiert ist.Depending on the alcohol used, both mono-cyanoacrylic acid esters and also higher cyanoacrylic acid esters can be prepared by the process according to the invention. In a preferred embodiment of the process according to the invention, the cyanoacrylic acid ester of the general formula (I) is therefore prepared from mono-cyanoacrylic acid esters of the general formula (Ia)

and / or from biscyanacrylates of the general formula (Ib)

and / or from triscyanoacrylic acid esters of the general formula (Ic)

wherein R is as defined above.

In a preferred embodiment of the process according to the invention, the radical R in formula (I), formula (Ia), formula (Ib), formula (Ic) and / or formula (III) comprises a C ₃ to C ₁₀₀ chain, preferably a C ₅ to C ₇₀ chain and in particular a C ₁₀ to C ₅₀ chain which is interrupted by at least one oxygen atom. The rest R can be linear, branched or cyclic. in particular In particular, radicals R are preferred which have at least one polyethylene glycol and / or at least one polypropylene glycol unit.

In a further embodiment of the invention Process comprises the radical R in formula (I), formula (Ia), formula (Ib), formula (Ic) and / or formula (III) 3 to 18, in particular 4, 8, 10 and / or 12 directly interconnected C atoms. The rest R can also be arranged linear, branched or cyclic be.

Of the Radical R can furthermore contain an aromatic group or in addition Hydrogen and carbon atoms also have at least one heteroatom, for example, selected from halogen, oxygen and / or Nitrogen atoms.

In the case of the alcohols of the general formula (III) [HO-] _n R formula (III) they are monohydric to hexahydric alcohols (n = 1-6), with mono-, di- and / or trihydric alcohols being preferred. From these alcohols, the above-shown mono-cyanoacrylic acid esters of the general formula (Ia), the Biscyanacrylsäureester of the general formula (Ib) and the Triscyanacrylsäureester of the general formula (Ic) are easily representable. The alcohols used in the process according to the invention are preferably primary or secondary alcohols, preference being given to primary alcohols, since these have a higher reactivity in the transesterification reaction. In general, any mixtures of different alcohols can be used.

The alcohol of the general formula (III) used in the process according to the invention is prepared in a preferred embodiment of the present invention from compounds of the general formula (IIIa) R ² COO (CH ₂ CH ₂ O) _m H formula (IIIa) in which R ² CO is a linear or branched acyl radical having 12 to 22 carbon atoms and m is a number from 5 to 30 and preferably 15 to 25. Typical examples are addition products of ethylene oxide with lauric acid, isotridecanoic acid, myristic acid, palmitic acid, palmitoleic acid, stearic acid, isostearic acid, oleic acid, elaidic acid, petroselinic acid, linoleic acid, linolenic acid, elaeostearic acid, arachidic acid, gadoleic acid, behenic acid and erucic acid, and their technical mixtures, which are e.g. B. in the pressure splitting of natural fats and oils or in the reduction of aldehydes from the Roelen oxo synthesis. Preferably, addition products of ethylene oxide are used to fatty acids having 16 to 18 carbon atoms.

Further preferred alcohols are preferably selected from Methyl glycol, methyl diglycol, hexanediol, octanediol, decanediol dodecanediol glycerin and / or trimethylolpropane and / or any of their mixtures.

wobei R¹ ein verzweigter oder unverzweigter Alkylrest mit 1 bis 6 C-Atomen ist.In the process according to the invention, the alcohols of the formula (III) are reacted with at least one 2-cyanoacrylic acid ester of the general formula (II)

where R ^{1 is} a branched or unbranched alkyl radical having 1 to 6 C atoms.

Methyl-2-cyanoacrylic acid esters or ethyl-2-cyanoacrylic are within the meaning of the present Invention preferred 2-cyanoacrylic, since in the Transesterification reaction resulting alcohol methanol or ethanol easily can be removed. It can also be mixtures of different 2-cyanoacrylates in the process of the invention be used, with mixtures of methyl 2-cyanoacrylic or ethyl 2-cyanoacrylic acid esters are preferred.

Of the at least one 2-cyanoacrylic acid ester of the general Formula (II) is used in the process according to the invention preferably used in excess. The molar ratio of 2-cyanoacrylic acid ester to the alcohol of the general In particular, formula (III) is at least 2.0: 1.0, preferably however, 2.5: 1.0, especially 2.2: 1.0.

The Transesterification is according to the invention Process in the presence of a transesterification catalyst, comprising at least one acid with a pks value ≤ 5 and at least one metal catalyst performed.

The pks value of the at least one acid is determined in aqueous solution at 25.degree. C., it also being easy for the person skilled in the art to derive the pKa values of acids from the corresponding literature. A compilation of different pKs values is for example in Holleman-Wiberg, Lehrbuch der anorganischen Chemie, 101st edition, pp. 237-238 and the literature cited therein.

Preferred acids are distinguished by a pKs value ≦ 4, in particular by a pKs value ≦ 3 or ≦ 2, and particularly preferably by a pKs value ≦ 1. The technical purpose In this case, the lower limit of the pKs value of the at least one acid is -20, with particular preference being given to acids which have a pKa value ≥ -16.

wobei R² für eine gegebenenfalls substituierte Arylgruppe oder eine Fluor-substituierte Alkylgruppe steht.In a particularly preferred embodiment of the process according to the invention, the acid having a pks value ≦ 5 is a sulfonic acid of the general formula (IV)

wherein R ^{2 is} an optionally substituted aryl group or a fluoro-substituted alkyl group.

wobei R³ für eine Methyl-, Methoxy-, Ethyl-, Ethoxy-, n-Propyl-, i-Propyl- oder n-Butylgruppe, und insbesondere für eine Methylgruppe steht.Preferably, R ² in formula (IV) is a trifluoromethane group or a group of general formula (V),

wherein R ^{3 represents} a methyl, methoxy, ethyl, ethoxy, n-propyl, i-propyl or n-butyl group, and especially a methyl group.

As already described above exercises at least one acid with a pKs ≤ 5 on the in the inventive Process produced cyanoacrylates a stabilizing Effect because the acid is an anionic polymerization of cyanoacrylic acid ester prevented. Be in the transesterification reaction used large amounts of the corresponding acid, can be an overstabilization of just a little reactive cyanoacrylates occur as a complete separation of the acid Of the product obtained is often difficult.

It is therefore particularly advantageous the amount of acid used with a pKs value ≤ 5 limit, which is why in a particular preferred embodiment of the invention Process the at least one acid with a pks value ≤ 5 in an amount of 0.0001 to 0.75 wt%, preferably 0.001 to 0.5% by weight, and more preferably from 0.01 to 0.2% by weight, respectively based on the total amount of 2-cyanoacrylic acid ester of the general formula (II).

Of the Transesterification catalyst used in the process according to the invention in addition to the at least one acid with a pKs value ≤ 5 also at least one metal catalyst which is suitable, the transesterification reaction to catalyze. Preferred metal catalysts are, for example, metal alcoholates and / or metal acetylacetonates.

Generally are also tin catalysts, chromium catalysts, titanium catalysts, Zirconium catalysts and / or lithium catalysts and / or their any mixtures preferred metal catalysts in the sense of inventive method.

suitable Metal catalysts from the group of tin catalysts are dialkyltin dicarboxylates, such as dibutyltin dicarboxylates, in particular dibutyltin diacetate, dibutyltin dilaurate, Dibutyltin diisoctoate, dibutyltin maleate and mixed dibutyltin dicarboxylates especially with longer-chain fatty acid residues, Dioctyltin dicarboxylates, in particular dioctyltin dilaurate, trialkyltin alkoxides, such as For example, tributyltin oxide, monoalkyltin compounds such as monobutyltin dihydroxychloride and monobutyltin dioxide, tin salts such as tin acetate, tin oxalate, and tin chloride, Tin oxides, such as. B. SnO.

Further suitable metal catalysts from the group of titanium catalysts are monomeric and polymeric titanates and titanium chelates such as tetraisopropyl orthotitanate, Tetrapropyl orthotitanate, tetraethyl orthotitanate, tetrabutyl orthotitanate, Tetraisobutyl orthotitanate, 2-ethylhexyl titanate, stearyl titanate, Cresyl titanate, titanium acetylacetonate, triethanolamine titanate, octylene glycol titanate, Isostearyl titanate, citric acid diethyl ester titanate and from the group of zirconium catalysts, zirconates and zirconium chelates such as tetrapropylzirconate, tetraisopropylzirconate, tetrabutylzirconate, Triethanolamine zirconate, citric acid diethyl ester zirconate, Zirconium (IV) acetylacetonate, as well as lithium catalysts such as lithium salts, Lithium alkoxides, and aluminum (III), chromium (III), iron (III) -, Cobalt (II), nickel (II) and zinc (II) acetylacetonate.

Prefers are dibutyltin diacetate, mixed dibutyltin dicarboxylates with long-chain fatty acid esters, dioctyltin dilaurate, Monobutyltin dihydroxychloride, monobutyltin dioxide, tin acetate, tin oxalate, Tin chloride, tetraisopropyl orthotitanate, tetrapropyl orthotitanate, Tetraethyl orthotitanate, tetrabutyl orthotitanate, tetrapropyl zirconate, and lithium salts and alkoxides and acetylacetonates listed above used.

Especially Dibutyltin diacetate, tetraisopropyl orthotitanate and / or are preferred Tetraethyl.

Of the At least one metal catalyst is dependent on the reactivity of the individual reactants and the chosen ones Reaction conditions preferably in amounts of from 0.01 to 10% by weight, preferably from 0.1 to 5% by weight and in particular from 1 to 3% by weight, in each case based on the total amount of 2-cyanoacrylic acid ester the general formula (II) used.

The inventive method is preferably in Presence of at least one radical polymerization inhibitor carried out, the required amount of one Professional can be easily determined.

suitable radical polymerization inhibitors are, for example, phenol compounds, such as hydroquinone, hydroquinone monomethyl ether, butylated hydroxyanisole (BHA), 2,6-di-tert-butyl-4-methylphenol (BHT), t-butyl catechinone, Catechol and p-methoxyphenol. Mixtures of said radical Polymerization inhibitors may also be used. A particularly preferred radical polymerization inhibitor is for the purposes of the present invention butylated hydroxyanisole (BHA) and / or hydroquinone monomethyl ether.

Farther the process of the invention is preferably in the presence of a gaseous acid at 22 ° C, in particular a Lewis acid, wherein For example, the acid is selected from sulfur dioxide and / or boron trifluoride.

The Transesterification can be carried out at normal pressure, but also at reduced or overpressure be carried out from 0.001 to 200 bar. The at the Transesterification of cleaved alcohol is preferably continuous or distilled off after completion of the reaction, the reaction in a suitable solvent, such as toluene, xylene or Toluoi / xylene mixtures can be performed. The process according to the invention is preferred carried out with the aid of a distillation column with high separation efficiency.

Of the obtained by the process according to the invention Cyanacrylsäureester of the general formula (I) can in highly pure form, in particular by distillation or crystallization be isolated, with product purities of greater 98% can be achieved.

The Cyanacrylsäureester produced by the present process can be used for bonding components, in particular for bonding of electrical and / or electronic components and for production of medical adhesives for the treatment of surgically cut or traumatically ruptured tissue.

embodiments

Representation of a Monocyanacrylats

In a three-necked flask, 91.3 g (1.2 mol) of absolute methylene glycol, 1.3 g of hydroquinone monomethyl ether, 1.3 g of tetraisopropyl orthotitanate and 0.1 trifluoromethanesulfonic presented and slowly covered with SO ₂ . Subsequently, 125 g (1 mol) of ethyl cyanoacrylate are metered in and the mixture is heated to 125 ° C., the resulting ethanol being passed through a dephlegmator set at 80 ° C. After completion of the ethanol release (control by determination of the refractive index), the reaction mixture is fractionally distilled. At a temperature between 110-152 ° C (0.06 mbar) 146 g Methylglykolcyanacrylat be obtained in a purity of 98%.

Preparation of a Biscyanacrylats

1,10-decanediol (348 mg, 2 mmol) and hydroquinone (5 mg, 0.045 mmol) are dissolved in absolute toluene (25 ml) submitted. The mixture is at 70 ° C with a Solution of ethyl cyanoacrylate (1.001 g, 1 ml, 8 mmol) in absolute toluene (3 ml) was added. Subsequently, will Tetraisopropyl orthotitanate (13.5 mg, 14 μl, 0.625 mmol) and trifluoromethanesulfonic acid (1.35 mg, 0.8 μl, 0.009 mmol) was added. The mixture is refluxed for 5 h heated. Subsequently, the toluene / ethanol is slowly azeotroped Mixture removed (about 17 ml). After cooling, the residue filtered off and the eluate (about 7 ml) with the same amount of heptane diluted. At a temperature of -20 ° C the biscyanoacrylate slowly falls as a white powder in a yield of 50%.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - US 6667031 [0003]
• US 3975422 [0006]
• - EP 0764148 B1 [0007]

Cited non-patent literature

• - Holleman-Wiberg, Lehrbuch der anorganischen Chemie, 101st edition, pp. 237-238 [0026]

Claims (12)

Process for the preparation of at least one cyanoacrylic acid ester of the general formula (I), comprising the steps:

a) transesterification of at least one 2-cyanoacrylic acid ester of the general formula (II),

where R ^{1 is} a branched or unbranched alkyl radical having 1 to 6 C atoms, with at least one alcohol of the general formula (III) [HO-] _n R formula (III) in the presence of a transesterification catalyst comprising at least one acid having a pks value ≦ 5 and at least one metal catalyst and b) isolating the cyanoacrylic acid ester of general formula (I) obtained in step a), where n is an integer from 1 to 6 and R is an n-valent radical comprising 1 to 100 carbon atoms. A method according to claim 1, characterized in that the cyanoacrylic acid ester of the general formula (I) is selected from mono-cyanoacrylic acid ester of the general formula (Ia)

and / or from Biscyanacrylsäureester of the general formula (Ib)

and / or from triscyanoacrylic acid esters of the general formula (Ic),

wherein the radical R comprises 1 to 100 C atoms. A method according to claim 1 and / or 2, characterized in that radical R in formula (I), formula (Ia), formula (Ib), formula (Ic) and / or formula (III) a C ₃ to C ₁₀₀ chain which is interrupted by at least one oxygen atom. Method according to claim 1 and / or 2, characterized the radical R in formula (I), formula (Ia), formula (Ib), formula (Ic) and / or formula (III) comprises 3 to 18 directly linked C atoms. Method according to at least one of claims 1 to 4, characterized in that the 2-cyanoacrylic acid ester of general formula (II) is selected from the group consisting of methyl 2-cyanoacrylic acid ester and ethyl 2-cyanoacrylic acid ester. Method according to at least one of claims 1 to 5, characterized in that the at least one organic acid having a pks value ≤ 5 is a sulfonic acid of the general formula (IV),

wherein R ^{2 is} an optionally substituted aryl group or a fluoro-substituted alkyl group. Method according to at least one of claims 1 to 6, characterized in that the at least one acid with a pks value ≤ 5 in an amount of 0.0001 to 0.75 Wt .-%, based on the total amount of 2-cyanoacrylic acid ester of the general formula (II). Method according to at least one of claims 1 to 7, characterized in that the at least one metal catalyst is selected from the group of tin catalysts, chromium catalysts, Titanium catalysts, zirconium catalysts and / or lithium catalysts. Method according to at least one of the claims che 1 to 7, characterized in that the at least one metal catalyst is selected from the group of metal alkoxides and / or metal acetylacetonates. Method according to at least one of claims 1 to 9, characterized in that the at least one metal catalyst in an amount of 0.01 to 10 wt .-%, based on the total amount of the 2-cyanoacrylic acid ester of the general formula (II), is present. Method according to at least one of claims 1 to 10, characterized in that the method in the presence at least a radical polymerization inhibitor and / or at least performed a gaseous acid becomes. Method according to at least one of claims 1 to 11, characterized in that the isolation of the at least one Cyanoacrylic acid ester of formula (I) by distillation or crystallization.