GB2311519A - Methacrylated Or Arcrylated Cyanacetates - Google Patents

Description

METHACRYLATED OR ACRYLATED CYANOACETATES AND THE ADHES I VES AND POLYMERS THEREOF This invention relates to methacrylated or acrylated cyanoacetates and the adhesives and polymers thereof.

Cyanoacetic acid and its alkyl esters are used widely as raw materials for the synthesis of cyanoacrylate monomers and various pharmaceutical products.

The present invention provides methacryloyl or acryloyl derivatives of esters of cyanoacetic acid with formula

where R1 = H or CH3, R2 is alkyl, alkoxyalkyl, poly(oxyalkyl), cycloalkyl, alkynyl, aryl or an aromatic heterocyclic radical. R2 may also be one of the foregoing moieties substituted with one or more other of the moieties: this includes the case of a substituent itself being substituted. Group Ri may contain other compatible substituents, for example alkoxy, alkoxyalkoxy, carbalkoxyalkyl or halogen. The alkyl or alkenyl moiety may be cyclic and normally R2 contains from 1 to 16 carbon atoms and often is a lC, 2C, 3C, 4C, 5C, 6C, 7C or 8C group, more usually it is a lC-6C group. In the case of moieties containing a heterocycle, heteroatom ring members are normally counted as a carbon atom.

More preferably, R2 is alkyl, halogenated alkyl, alkenyl, alkynyl, phenyi, halogenated phenol, phenyalkyl, halogenated phenylalkyl, alkoxyalkyl, alkoxyalkoxyalkyl, poly(oxyalkyl), carbalkoxymethyl or alkylideneglyceryl, wherein the terms alkyl and "alkenyl" include the corresponding cyclic radicals. Uninterrupted carbon chains preferably contain 1, 2 or 3 carbon atoms.

Specific examples of R2 are:

- CH2CH20CH2 CH20CH2CH2 OCH2 CH20CH2 CH20CH2 CH2 - ama

The methacrylated or acrylated cyanoacetates of this invention are obtained by two routes.

One is the esterification of cyanoacetic acid with hydroxyl-terminated methacrylate or acrylate monomer. The esterification process is well known in the art. It is catalysed by inorganic or organic acids. The water produced as reaction by-product is removed from the reacting mixture with the help of azeotrope-forming solvent. This drives the equilibrium reaction in the desired direction. The use of azeotrope-forming solvent is also beneficial in maintaining low reaction temperature.

The other route is transesterification of lower alkyl cyanoacetate with hydroxyl-terminated methacrylate and acrylate monomers. The transesterification process is well known in the art. It is catalysed by acids, alkali, organometalic compounds. The low molecular weight alcohol produced as reaction by-product is distilled out of the reacting mixture, driving the equilibrium reaction in the desired direction.

A distinctive feature of the reactions for obtaining the compounds of the present invention is the polymerizability of the methacrylate or acrylate reactant, as well as the end product itself. Thus in order to avoid polymerization during the reactions phenolic-type inhibitors, like hydroquinone or p-methoxyphenol, in conjunction with air sparge of the reacting mixture are used.

If desired mixtures of two or more of the cyanoacetates of the present invention with themselves or other monomers or polymers could be used.

Usually the methacrylated or acrylated cyanoacetates of the present invention are stabilized with free-radical polymerization inhibitors, usually hydroquinone, pmethoxyphenol or t-butyl catehol for example. The inhibitors are normally used in small amounts of from 0.001% to 1% by weight of the monomer. It should be noted that the quantity of inhibitor will influence not only the stability in bulk but also the onset of polymerization of the compounds of the present invention and could be used as a means to control the set time.

The methacrylated or acrylated cyanoacetates of the present invention may contain polymerization initiators. Free radical initiators like methylethylketone peroxide, cyclohexyl peroxide, cumene hydroperoxide, dibenzoyl peroxide etc and redoxy systems for generating freeradicals, well known in the art of polymerizing acrylate and methacrylate monomers, could be such polymerization initiators. Compounds which generate radicals under KI'traviolet or electron beam irradiation could also be considered as suitable polymerization initiators of the monomers of the present invention. The various initiators could be used alone or in conjunction with each other.

In order to impart desired properties to the compounds of the present invention and to the properties of the resultant adhesive bond or polymer, as well as for economic considerations, further additives can be introduced. They can be, for example, any of the known polymeric thickness and viscosity regulators, rubbers, plasticizers and tougheners, compatibilizers, thixotropic agents, colourants, deodorants or perfumes, for example, used in cyanoacrylate adhesives and in acrylic and methacrylic ester compositions and polymers.

The compounds of the present invention may also contain other monomers containing a reactive double bond.

A distinctive feature of the methacrylated or acrylated cyanoacetates of the present invention is that they are easily polymerizable by heat, redoxy systems, ultraviolet or electron beam irradiation.

A distinctive feature of the methacrylated or acrylated cyanoacetates of the present invention is that due to the presence of the polar nitrile and carbonyl groups in their molecules the polymer formed interacts with the substrates it contacts during cure to form a strong adhesive bond.

A distinctive feature of the cyanoacetates or the present invention is that they contain an active methylene group which can react with ,-unsaturated carbonyl compound, as acrolein, for example, to produce more complex monomeric molecules with multiple unsaturations.

Application of the monomers of the present invention is in adhesives and coatings.

Another application of the compounds of the present invention is in modifying existing adhesives and polymers.

Another application of the compounds of the present invention is as reactants for more complex compounds in which they incorporate acrylic or methacrylic double bond, nitrile and carbonyl groups.

The above mentioned applications are only indicative and do not limit the scope of application of the methacrylated or acrylated cyanoacetates of the present invention as well as the applications of their adhesives and polymers.

The invention is illustrated by the following examples: Example 1 134g of hydroxyethyl methacrylate, containing 0.2g of predissolved hydroquinone is mixed with looms of heptane, 102g of cyanoacetic acid and 2g of sulfuric acid. An air flow of lOmlimin is forced through a capillary in the bottom of the flask and maintained during the reaction.

The temperature is brought to boiling and the reaction water is azeotroped into a Dean-Stark separator. The amount of removed water was used as measure of the completion of the reaction. 150 minutes after the start of reaction 17ml of water were separated. The reaction mixture was cooled to room temperature. It separated in two layers. The upper heptane layer was decanted and 150ml of methyl methacrylate were mixed with the product layer.

The resultant solution was washed with lOOml of 15% so dium chloride solution. The separated organic layer was neutralized to pH of 7 with 5% sodium carbonate solution and then washed again with lOOml of 15% sodium chloride solution. The organic layer was filtered and stripped from heptane residues and methyl methacrylate by heating up to 90"C under reduced pressure of 0.7 mm Hg. During the stripping stage an air sparge through a capillary was maintained. The residue was methacryloyloxyethyl cyanoacetate of which 192g were obtained. Its refractive index at 20 C was 1,4593 and was 999 pure by GC. The IR spectrium (Figure 1) confirms the chemical structure.

Example 2 74.4g of hydroxypropyl methacrylate, containing 0.2g of predissolved p-methoxyphenol, is mixed with 200g of chloroform, 85.9g of cyanoacetic acid and 3.4g of sulfuric acid. An air flow of Sml/min is forced through a capillary in the bottom of the flask and is maintained during the run of the reaction. The temperature is brought to boiling and the reaction water is azeotroped into a Dean-Stark separator. The amount of removed water was used as measure of the completion of the reaction. 5 hours and 40 minutes after the start of the reaction 9ml of water were separated. The reaction product was cooled to room temperature and consecutively washed with 200ml water, neturallzed to pH of 7 with 5% sodium hydroxide solution and then washed again with 200ml of water. The organic layer was filtered and stripped from the chloroform solvent and water residues by heating up to 90 C under reduced pressure of 0.7 mm Hg. During the stripping stage an air sparge through a capillary was maintained. The residue was methacryloyloxypropyl cyanoacetate of which 101 g were obtained. The refractive index at 20 C was 1,4552. The out was 98% pure b GC and contained two isomers. The IR spectrum (Figure 2) confirms the chemical structure.

Example 3 46.5g of hydroxyethyl acrylate, containing 0.lg of predissolved p-methoxyphenol is mixed with 118.6g of methyl cyanoacetate and 30g of toluene. The mixture is brought to boiling at reduced pressure of 40 mm Hg and the toluene is distilled off removing with it any moisture present in the reactants. Sample of the resultant reaction mixture analysed by Karl-Fisher titration, shows water content of 0.04%. One gram of titanium tetraisopropoxide is added to the mixture and dry air sparging of 4ml/min is initiated and maintained during the reaction. The mixture is brough to reflux at reduced pressure of 4G mm Hg. Methanol which is reaction by-product is removed from the reacting mixture by distillation. One hour after the reaction started the concentration of hydroxyethyl acrylate in the reacting mixture was reduced to 1% as determined by gas chromatograpahy. The heating was discontinued. 20g of water were added and the reaction product was cooled down te room temperature. The added water reacted with the titanium catalyst precipitating it out of the reaction mixture. The water layer was decanted and the organic layer was filtered. The product was isolated from the excess of methyl cyanoacetate by vacuum distillation of the latter. After the end of visible distillation the product was kept for 30 minutes at 90"C and 0.7 mm Hg. During the distillation and stripping stage a bleed of air was maintained through a capillary. The residue comprised of 61g of acryloyloxyethyl cyanoacetate with GC purity of 9.7. The refractive index at 200C was 1,4620 and the IR spectrum (Figure 3) confirms the chemical structure.

Example 4 87.7g of hexaethyleneglycol monomethacrylate, containing 0.2g of predissolved p-methoxyphenol is mixed with 100g of chloroform, 25.5g of cyanoacetic acid and 1.7g of methanesulfonic acid. The next steps are identical to those described in Example 2 with the difference that the duration of the reaction was 5 hours and 5 minutes and 4.0my of water were separated. The final yield of methacryloylhexa(oxyethyl) cyanoacetate was 86.4g and had refractive index of 1,4674 at 2odd. The IR spectrum (Figure 4) confirms the chemical structure.

Example 5 W light curable compositions were obtained by dissolving into various methacryloyl- and acryloylalkyl or polyoxyalkyl cyanoacetates obtained by the methods described in Examples I to 4 of 1% by weight of l-hydroxycyclohexyl-phenyl-ketone. A drop of the composition was spread between glass/glass or glass/steel surfaces and subjected to UV radiation with intensity of 7mW/cm2 at 365 nm and 4mW/cm2 at 310 nm for 2 minutes. Some of the joints were further aged at constant temperature for 24 hours.

The glass and steel surfaces were only degreased with methylene chloride prior to bonding. The glass/glass joints and the glass portion of the glass/steel joints were in turn bonded in larger areas to steel coupons (with cyanoacrylate adhesive) so that they rather than the fragile glass could be gripped in the testing machine. The testing procedure followed ASTM D 1002 and ASTM D 807 respectively for the shear and tensile strength determinations. Each reported value is average of 10 determinations. The obtained results are summarized in Table 1.

Table 1 Adhesive bond strength of joints bonded with UV-cured methacrylated and acrylated cyanoacetates

No Cyanoacetate Joint substrates Mode of Adhesive bond Mode of testing strength failure (kg/cm2) 1 methacryloyl- glass/glass tensile 78 cohesive oxyethyl shear > 20 substrate glass/steel tensile 78 cohesive shear > 20 substrate 2 methacryloyl- glass/glass tensile 36 cohesive oxypropyl shear @ substrate glass/steel tensile 43 cohesive shear > 20 substrate 3 acryloyl glass/glass tensile 11 adhesive oxyethyl shear 4 cohesive glass/steel tensile 10 adhesive shear 7 adhesive 4 acryloyl- glass/glass tensile @ adhesive oxypropyl shear 2 adhesive glass/steel tensile 8 adhesive shear 2 adhesive 5 methacryloyl- glass/glass tensile 9 cohesive hexa(oxyethyl) shear 10 cohesive glass/steel tensile 8 cohesive shear 9 cohesive 6 methacryloyl- glass/glass tensile 12 cohesive penta(oxypropyl) shear 11 cohesive glass/steel tensile 13 cohesive shear 12 cohesive Example 6 Adhesives based on pure ethyl 2-cyanoacrylate and ethyl 2cyanoacrylate containing 1 to 10% by weight of some acryloyloxyalkyl and methacryloyloxyalkyl cyanoacetates were used to bond steel joints. The steel surfaces were roughened with extra fine sandpaper and degreased with methylene chloride. No chemical treatment of the surface was performed. A drop of adhesive was placed on one surface to which the other was manually pressed for 1 minute. Adhesive strength was measured 24 hours later.

The specimen dimensions and testing procedure complied with ASTM D 897. Each reported value is average of iG determinations. The obtained results are summarized in Table 2.

Table 2 Tensile strength of steeUsteel joints bonded with ethyl 2cyanoacrylate compositions containing methacrylated and acrylated cyanoacetates

No Cyanoacetate Content in the Adhesive stength composition (kg/cm2) (%) 2 acryloyloxy- 1 227 ethyl 3 250 10 192 3 acryloyloxy- 1 305 propyl 3 280 10 89 4 methacryloyl- 1 310 I oxyethyl 3 319 10 273 5 methacryloyl- 1 290 oxypropyl 3 304 10 268

Claims (12)

1. CLAIMS 1. Methacryloyl or acryloyl derivatives of esters of cyanoacetic acid of the formula

   wherein R1 is H or CH3 and R2 is alkyl, alkenyl, alkynyl, alkoxyalkyl,, poly(oxyalkyl), aryl, cycloalkyl or heterocyclyc radical, or is one of these moieties substituted with one or more of the other moieties and could also contain halogens.
2. 2. Esters of Claim 1 wherein R2 is -CH2CH2-, -CH2CH2CH2-,
3. 3. Adhesives and polymers formed by the polymerisation of the esters of Claim 1.
4. 4. Adhesive and coating compositions containing esters of Claim 1.
5. 5. A method of synthesising the esters of Claim 1 by esterification of cyanoacetic acid with hydroxyl-tenninated methacrylate or acrylate monomer.
6. 6. A method of synthesising the esters of Claim 1 by transesterification of lower alkyl cyanoacetate with hydroxyl-terminated methacrylate or acrylate monomer.
7. 7. Esters of Claim 1 wherein they are stabilised against premature polymerisation with free-radical polymerisation inhibitors, including but not limited to hydroquinone, p-methoxyphenol, t-butyl catehol, in amounts of from 0.001 to 1%.
8. 8. Esters of Claim 1 wherein they contain polymerisation initiators as freeradical initiators including but not limited to methylethylketone peroxide, cyclohexyl peroxide, cumene hydroperoxide, dibenzoyl peroxide; as redoxy systems for generating free-radicals; and as compounds which generate radicals under ultraviolet or electron beam irradiation.
9. 9. Compositions based on esters of Claim 1 containing other monomers with a reactive bond, including but not limited to cyanoacrylates.
10. 10. Compositions based on esters of Claim 1 containing polymeric thickeners, viscosity regulators, plasticisers, thixotropic agents, compatibilisers, adhesion promoters, pigments, colourants, fillers, deodorants and perfumes.
11. 11. Application of esters of Claim 1 as reactants for synthesis of more complex molecules.
12. 12. Application of esters of Claim 1 as additives to adhesive and coating compositions and systems to improve adhesion.