GB2075522A

GB2075522A - Cyanoacrylate Adhesive Composition

Info

Publication number: GB2075522A
Application number: GB8106727A
Authority: GB
Original assignee: Henkel Teroson GmbH
Current assignee: Henkel Teroson GmbH
Priority date: 1980-03-10
Filing date: 1981-03-04
Publication date: 1981-11-18
Also published as: FR2477566A1; GB2075522B; JPH04208291A; ES500239A0; BR8101401A; IT1211003B; IT8120210A0; NL186644B; ES8302064A1; NL8101115A; AU4511585A; GB2085883A; AU6810181A; FR2477566B1; NL186644C; AU576605B2; JPH02167245A; AU546896B2; JPH0364490B2; GB2085883B

Abstract

A rapid setting alpha -cyanoacrylate based adhesive composition having an improved storage stability comprises a polymerization catalyst which is a polyethylene glycol derivative of the general formula <IMAGE> wherein A is a group linking the X's by one or two atoms, B is a tetravalent atom eg C or Si, R is a C1-C12 group free of hydroxy or amino, R<1> is H or lower alkyl, R<2> is lower alkyl, X and Y are oxygen or may be sulphur or -N-CH3 in compounds containing group A, and n m p and q are integers.

Description

SPECIFICATION Cyanoacrylate Adhesive Composition Background of Invention The present invention relates to a rapid-setting a-cyanoacrylate based adhesive composition having good storage stability and, in particular, to an adhesive composition having a very fast setting time on wood and other substrates with a porous/acid surface.

a-cyanoacrylates of general formula

are rapid-setting adhesives which are ideally suited for the adhesion of a large number of materials.

The parts can be joined in an extremely short time of only a few seconds and the adhesive joints produced in this way have good mechanical strength characteristics. The adhesives are hardened by anionic polymerization initiated by even small traces of extremely weak basic-acting compounds (Lewis bases) such as, for example, water or methanol.

When using such a-cyanoacrylates adhesives on wood leather and other porous/acid surfaces, there is the problem that the anionic polymerization of the a-cyanoacrylate is inhibited in spite of the high moisture content which should in fact aid the polymerization. As a result, the adhesive setting time is too long for practical use. In addition, such adhesives tend to penetrate the pores of the surfaces to be adhered to one another, so that in the case of porous material, the strength of the adhesive joint is impaired due to the protracted setting time.

However, because the distinct advantage of a-cyanoacrylate based adhesives is their short setting time, numerous measures have been attempted to reduce the setting times on wood and similar materials. One of these measures involves treating one of the wood surfaces to be joined with primer and the other with an a-cyanoacrylate adhesive composition. Polymerization occurs on contacting the treated surfaces together. The required added operation of applying a primer is a serious disadvantage to such process. Another measure involves reducing the quantity of acid stabilizers present for satisfactory storage stability of the a-cyanoacrylate adhesive compositions. However, although this reduces the setting time, such adhesive compositions have an increased tendency to prematurely harden during storage.

Therefore, polymerization catalysts have been proposed which are suitable for use in singlecomponent systems and which reduce the setting times of such a-cyanoacrylate adhesives without excessively impairing their storage stability. According to DE-OS 2,816,836 the setting time of acyanoacrylate adhesives is reduced by adding to the adhesive composition approximately 0.1 ppm or more of a macrocyclic polyether compound from the group of macrocyclic polyethers and their analogs. The most serious disadvantage of such accelerators relates to their synthesis which, even when the dilution principle is used, only supplies the desired product in low yields, because the tendency to produce intermolecular linkages which form chains is greater than that for intramolecular linkages which form macrocycles. Further, U.S.Patent 4,170,585 suggests the addition of approximately 0.0001 to 20% by weight of a polyethylene glycol with a degree of polymerization of at least 3 or a non-ionic surfactant with a polyethyleneoxy content (degree of polymerization also at least 3) or mixtures thereof to -cyanoacrylate based adhesive compositions. These compounds, however, have the disadvantage in that they have a great tendency to contain water and low molecular weight polyethylene glycol ether which are difficult to remove and spontaneously initiate polymerization when the compounds are added to a-cyanoacrylates.

The two specifications discussed above also describe in detail the disadvantages commonly associated with a-cyanoacrylate adhesives when used on wood, leather and other porous/acid surfaces as mentioned above.

It has now been surprisingly found that the above difficulties and disadvantages of the prior art polymerization catalysts can be obviated by the use of certain compounds described herein below as polymerization catalysts contained in a-cyanoacrylate-based adhesive compositions. These compounds can be easily prepared in high yield and purity, are free from polymerization-initiating substances, require only limited concentrations in the resulting adhesive compositions based on cr- cyanoacrylate and lead to greatly reduced setting times on wood and other porous/acid surfaces. It has also been found that the susceptibility to water can be still further reduced by the addition of suitable compounds described herein below which result in improved storage stability of such adhesive compositions.

Detailed Description of Invention The present invention is directed to adhesive compositions based on a-cyanoacrylate and which contain a polymerization catalyst and may contain conventional additives as described herein and in the appended claims.

The generally known ct-cyanoacrylates which serve as a basis for the adhesive composition according to the invention are of general formula:

wherein R is straight or branched-chain alkyl group such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, pentyl, hexyl, and the like as well as a halogen atom or alkoxy group substituted alkyl such as 2-chloroethyl, 3-chloropropyl, 2-chlorobutyl, trifluoroethyl, 2-methoxyethyl, 3-methoxybutyl, 2ethoxyethyl group and the like; a straight or branched-chain alkenyl group such as allyl, methallyl, crotyl and the like; a straight or branched-chain alkynyl group, such as propargyl and the like; cycloalkyl group such as cyclohexyl, and the like; an aryl group, such as benzyl, phenyl and the like; or an araikyl group, such as cresyl and the like.Further, German published application DE-OS 2,816,836 refers to a large number of suitable a-cyanoacrylates which are incorporated herein by reference. The adhesive compositions according to the invention may, in addition, contain conventional additives such as polymerization inhibitors, thickeners, plasticizers, perfumes, dyes, pigments, etc. These additives are conventionally known, form part of the prior art and examples of them are described in the herein above mentioned references.

The subject compounds found useful as polymerization catalysts in the adhesive compositions according to the invention are open-chain, podands having multiple arms each containing donor atoms.

The podands are compounds selected from the group of compounds of general formula:

wherein, with respect to compounds I, A represents a central chemical moiety capable of forming a one or two atom bridge between X units; and when A is the central chemical moiety, X represents oxygen, sulphur or N-CH3, preferably oxygen; Y represents oxygen, sulphur, N-CH3, or -N-, preferably oxygen; and R represents a short chain hydrocarbon terminal group.

The nature of the central group A of the subject podand compounds can be selected from chemical groups capable of linking the heteroatoms X by one or two atoms. Suitable groups include, for example, divalent alkyl groups of the general formula (CH2)n with n being 1 or 2; a divalent aryl group in which the linking bonds are ortho; a carbonyl group

with n being 1 or 2; a sulphonyl group

or a phosphonyl group, such as

In addition, compounds I have two short-chain terminal groups R which are free from hydroxyl and amino groups. The nature of the short-chain terminal groups R also have an important influence on the acceleration of the setting of a-cyanoacrylates obtainable through the use of presently disclosed multiple-armed podands.Suitable terminal groups are C, to C,2 hydrocarbon groups which may have hetero atom associated thereto but are free from hydroxyl and amino groups and are, in particular, C1-C4-alkyl groups and hereto or C1C4 hydrocarbon substituted or unsubstituted aryl groups with C1-C4-alkyl, phenyl, 1-naphthyl, 2-naphthyl, 2-methoxyphenyl, 2-nitrophenyl, 2-cyanophenyl and 2methoxycarbonyl groups being particularly suitable. When Y= -N- it has been found that phthaloyl groups are particularly suitable. The hetero atom substituted aryl can have a hetero atom of oxygen, nitrogen, sulphur in the form, for example, of methoxy, carbonyl, nitro and the like.

The compounds given in Table I below are illustrative of groups and compounds found particularly suitable according to the invention.

Table 1 Central Terminal group A X Y group B Compound class Synthesis

Transesterification of formaldehyde dimethyl acetal Formaldehyde-bis-(polyethylene glycol monoether)-acetal

Etherification according to Williamson.

Polyethylene glycol diether

Preparation according to the Gabriel synthesis α,#,bis-(phthalimidoyl)polyethylene glycol ether Central Terminal group A X Y group B Compound class Synthesis

Etherification according to Williamson Benzo-condensed polyethylene

thr -C- 0 0 CU - C 0 3 m o o o o=O o s o as / H o U v v o o Q Bis-(polyethylene glycol mono- Diethyl carbonate ether)-carbonate. transesterification.

N,N'-bis-(polyethylene glycol Alkylation of an monoether)-sulphamide N'N'-disubstituted sulphamide.

Central Terminal group A X Y group B Compound class Synthesis

Bis-(polyethylene glycol monoether)methane phosphate. Reaction of methane phosphonic acid dichloride with polyethyeleneglycol monomethyl ether in the presence of pyridine.

With respect to compounds II and III, B represents a central chemical moiety which is a four valenced or bond forming central atom, preferably a carbon atom or a silicon atom, R' represents a hydrogen atom or a short chain alkyl group; R2 are each independently selected from a short chain alkyl group. Generally, when R' and/or R2 are an alkyl group it is preferred that each group contain no more than 4 carbon atoms such that, for example each can independently be selected from methyl, ethyl, propyl, iso-propyl, n-butyl, isobutyl and the like. Further, it is preferred that when B is carbon R1 is hydrogen or alkyl and that when B is silicon R1 is alkyl. When B is the central chemical moiety of the subject podands, each X and Y of such podands represents oxygen. The central four-bond atom B is preferably a carbon or silicon atom.The preferred orthoester podands II and Ill are, therefore, ;orthoformic, orthoacetic, orthocarbonic, orthomethylsiliconic and orthosilicic acid esters, as well as mixtures thereof.

The podand compounds I, II and Ill can have arms which are formed from polyalkylene groups, such as ethylene which have oxygen associated therewith, and are, preferably polyethylene glycol chains. The chain length of each of the chains can vary widely. The setting time of the adhesive composition of the present invention is influenced by the podand chain length with the setting time being reduced with increased number of units, such as ethylene oxide units, in the podand chain as defined by n, m, p and q. However, if the number of donar atoms exceeds approximately 50 on each chain, there is no further significant acceleration of adhesion of the a-cyanoacrylate to wood or other porous/acid substances.

The symbols n, m, p and q as used herein above to define the podands I, II and Ill are each independently whole numbers between 2 and 50 and preferably between 3 and 20. With respect to n and m when associated with compound I, they each may be a whole integer such that n+m+4 has a value of between 5 and 100 and preferably between 5 and 50.

It has been unexpectedly found that the use of the adhesive compositions containing the polymerization catalyst according to the present invention cancels out the inhibition of polymerization of a-cyanoacrylates when used on wood and other substrates with porous/acid surfaces which otherwise occurs. Due to the advantageous action of the polymerization catalysts presently described, it is only necessary to add small quantities of 0.01 to 10% by weight and preferably 0.01 to 5% by weight (based on the total weight of the adhesive compositions) to the a-cyanoacrylate adhesives to obtain, for example, bonded wood joints with excellent mechanical strength. In the case of all the adhesive joints made and stored at room temperature for 24 hours, the break in the sample material took place in the wood during the tensile shear strength test.

In addition, it has been unexpectedly found that the storage stability of a-cyanoacrylate adhesive compositions is enhanced when they contain the polymerization catalysts according to the present invention. It is well known that -cyanoacrylate based adhesives tend to undergo premature polymerization and/or agglomeration to a greater or lesser extent. This behavior is particularly apparent when the adhesive is subjected to standardized accelerated aging tests at 700C. However, it has been found that a-cyanoacrylate based adhesives which contain the subject podands could undergo the standard accelerated ageing test (5 days at 700C.) without forming agglomerates or modifying viscosity or adhesive characteristics.

A further unexpected and highly desired advantage of the orthoester podands according to the present invention is that they can be easily synthesized. This takes place in a high yield from inexpensive, low molecular weight starting substances and is particularly economical due to the easy elimination of undesired by-products. DE-OS 2,062,034 and U.S. Patent 3,903,006 describe the synthesis of low molecular weight polyethylene glycol monoether esters of orthoformic acid and homologs thereof for use as constituents of hydraulic fluids.

The polyethylene glycol monoether esters of orthocarbonic acid, orthosilicic acid and alkyl sillonic acid of the present invention are novel compounds.

Synthesis of these new compounds can be performed using known process steps. Synthesis of the orthocarbonic acid esters can be carried out by acid catalyzed reaction of lower alkyl esters (methyl, ethyl esters and the like) of the relevant ortho acids, accompanied by azeotropic distillation of the lower alcohols formed by means of a suitable carrier (e.g. benzene, toluene). The corresponding chlorosilanes can be reacted with a polyalkylene glycol, such as polyethylene glycol monoethers to prepare the alkylsilionic acid esters and orthosilicic acid esters.

Advantageously, the multiple-armed podands used as polymerization catalysts can be introduced into the adhesive compositions according to the invention in the form of a solution formed with an organic solvent. For example, anhydrous aromatic hydrocarbons, such as benzene toluene, xylenes and the like are suitable solvents. It is also possible to use chlorinated hydrocarbons such as methylene chloride, chloroform or carbon tetrachloride without adverse influencing the storage stability. Other particularly suitable organic solvents are formed by the furane derivatives described hereinafter.

The properties of the adhesive compositions according to the invention can be further improved by adding furane derivatives. Suitable furan derivatives are 2,5-dihydro-5-alkoxy-furan-2-one and 2,5dialkoxy-2,5-dihydrofuran in accordance with the following general formulas:

in which each R3 stands for a straight or branched-chain alkyl or alkenyl radical, a cycloalkyl radical, a phenyl radical, a benzyl radical or an acetyl radical and R4and R5, independently of one another, stand for hydrogen, straight and branched-chain alkyl and alkenyl radicals, cycloalkyl radicals, phenyl radicals, benzyl radicals, acetyl radicals and halogen. Said alkyl, alkenyl, cycloalkyl, phenyl or benzyl radicals being those described herein above with respect to the podand compound.Preferably, R3 can stand for a methyl, ethyl, n-propyl, isopropyl, n-butyl, pentyl, hexyl, octyl, dodecyl or cyclohexyl radical and R4 and i independently of one another can stand for hydrogen, chlorine, bromine, methyl radicals or phenyl radicals. The preparation of these furane derivatives is known from the literature and can be performed using standard techniques. The adhesive compositions of the present invention can contain approximately 1 ppm to 20% by weight and preferably 10 ppm to 10% by weight of these furane derivatives based on the total weight of the adhesive composition.

The action of the above-described furane derivatives has been unexpectedly found to consist of a further considerable reduction in the susceptibility of the a-cyanoacrylate adhesive compositions to water, leading to an improvement of the storage stability and/or a simplification of storage. It has also been found that the addition of these furane derivatives to many substrates and in particular polyvinyl chloride (PVC), ethylene-propylene-diene (EPDM) and Styrene-Butadiene rubber (SBR) has an adhesion-imparting actiori. Thus, when producing an adhesive joint which includes'the addition of the furane cocatalyst, migration of the adhesive is further avoided through the immediate fixing on the substrate. Finally, the utilization of the cocatalysts offers the potential for subsequently correcting nonoptimum charges in such a way that they form a completely satisfactory product.

The following examples are given for illustrative purposes only and are not meant to be a limitation on the subject invention except as defined by the claimed appended hereto. All parts and percentages are by weight unless otherwise indicated.

Example 1 Podand Compound I Polyethylene glycol-400-dimethyl ether was synthesized by reacting polyethylene glycol 400 with metallic sodium in dioxan and alkylation of the resulting disodium salt with methyl iodide.

For this purpose, 53g of sodium (2.30 mol) were boiled in 500 ml of absolute 1 ,4-dioxan and finely dispersed by rapid stirring of the melted sodium. 400 g of polyethylene glycol 400 were added dropwise within a period of 30 minutes to the dispersion in boiling heat. This was followed by refluxing for 3 1/2 hours and the sodium almost completely reacted to the thus formed mixture. 355 g of methyl iodide (2.5 mol) were added dropwise within 30 minutes while stirring and was then refluxed for 1 hour. After cooling, the precipitated sodium iodide was removed by suction and the 1 4-dioxan distilled off. 419 g of crude polyethylene glycol-400-dimethyl ether were left behind as the residue (yellow oil, 98% theory).

347 g of pure polyethylene glycol-400-dimethyl ether were obtained by high vacuum molecular distillation at 10-3 mbar (colourless oil 81% theory).

An adhesive composition was prepared from 19.6 g of methyl-2-cyanoacrylate (thickened with - 8.7% by weight of polymethyl methacrylate and stabilized with 10 ppm of polyphosphoric acid) and 0.4 g of a 50% mixture of polyethylene glycol-400-dimethyl ether in absolute toluene. For comparison purposes, a mixture was prepared without adding the polymerization accelerator.

Using the above-described compositions overlapping adhesive joints were made on test pieces consisting of different wood species. The setting time was considered to be the value in which there is found to be a definite joining of the parts in a tensile test by hand. The results obtained are given in Table 2.

Table 2 Setting time of adhesive mixture at 200C in sec.

Without setting With setting Wood Species accelerator accelerator Balsa approx. 1 5 approx. 1 Limba approx. 80 5-6 Beech 180-210 15-20 Teak 240-300 20-25 Mahogany 1 50-180 1 5-20 Spruce approx. 240 15-20 Pine approx. 360 20-25 Oak approx. 360 20-25 The material break occurred in the wood with each test specimen when subjected they were each subjected to standard tensile tests after storing for 24 hours at room temperature. This behaviour was particularly marked with the soft woods tested, but also existed with the hard woods (beech, oak).

Example 2 The dependence of the setting time with respect to the number of donor atoms in each arm of the podands is illustrated by the following example. Podands of different chain lengths were synthesized.

The setting times of adhesive compositions based on a-cyanoacrylate as described in Example 1 above, containing in each case 1% by weight of the podand as the polymerization accelerator, were determined on limba.

Table 3 Setting time of the adhesive mixture containing 1% by Podand as setting No. ofdonor weight of the podand on Limba accelerator atoms (oxygen) at 20 OC in sec.

Tetraethylene glycol dimethyl ether 5 1 5 Polyethylene glycol 400-dimethyl ether approx. 10 5-6 Polyethylene glycol 600 dimethyl ether approx. 14 3-4 Polyethylene glycol 1 000-dimethyl ether approx. 22 2-3 Example 3 Podands I with different central groups were synthesized by conventionally known manners to illustrate the influence of the central group A. Adhesive compositions as described in Example 1, except based on ethyl-2-cyanoacrylate, were prepared, containing in each case 1% by weight of the podand as the polymerization accelerator and the setting times were determined on limba.

Table 4 Podand as setting accelerator Setting time of the adhesive mixture con taining 1% by weight of the podand on Limba at 200C in sec.

Formaldehyde-bis-(ll-methoxy-3,6,9 trioxyaundecyl)-acetal 5 - 6 Table 4 (cont.)

Polyethyl glycol-400-dimethyl ether 5 - 6

1,2-bis-(ll-methoxy-3,6,9--trioxa- undecyloxy-benzol

Bis-(ll-methoxy-3,6,9-trioxoundecyl) carbonate 10 Example 4 Podands I with different terminal groups were synthesized to illustrate the influence of terminal group R. The setting times on Limba were determined using the same a-cyanoacrylate adhesive composition as described in Example I above, containing, in each case, 1% by weight of the particular podand as stipulated in Table 5 below as the polymerization accelerator.

Table 5 Podand as setting accelerator Setting time ofqthe adhesive mixture containina 1% by weight of the podand on Limba at 200C in sec.

Tetraethylene glycol dimethyl ether

l,4,14-bis-(phenyloxy)-3,6,9,12tetraoxatetradecane

l,ll-bis-(2-methoxyphenyloxy)-3,6,9trioxaundecane Table 5 (cont.)

l,ll-bis-(2-nitrophenyloxy)-3,6,9-

trioxaundecane o L N' :(CH2)2 20 A o (CH2)2 20 - N7Q7 l,ll-bis-(phthalimidoyl)-3,6,9- trioxaundecane Example 5 Podand II 1 5.9g of trimethyl orthoformate, 1 00g of anhydrous tetraethylene glycol monomethyl ether,0.1 g of 4-methyl benzene sulphonic acid and 300ml of anhydrous toluene were refluxed with the aid of a packed column with the top fitted.The azeotropic mixture comprising methanol and toluene boiling at 64"C. was distilled until there was no further drop in the boiling point of toluene (1 1 OOC) on switching over to total reflux. At the end of the reaction, the reaction mixture was cooled, the toluene solution obtained was extracted by shaking with aqueous NaHCO3 solution, dried with Na2SO4 and the solvent was distilled off in vacuo. 99.3g (97.6% of theory) of crude tris-(tetraethylene glycol monomethyl ether)-orthoformate (colourless liquid) were obtained.

The crude product was distilled in high vacuum to remove unreacted tetraethylene glycol monomethyl ether. At a pressure of 8x 10-5 mbar and an evaporator temperature of 1300C.. firstly 11.89 of the colourless liquid were distilled off. The residue was again distilled off at 5 x 10-5 mbar/s50--2600C. and 84.99 (89.3%) of pure tris-(tetraethylene glycol monomethyl ether)orthoformate were obtained.

An adhesive composition was prepared from 9.89 of ethyl-2-cyanoacrylate (thickened with 8.7% by weight of polymethyl methacrylate and stabilized with 1 Oppm of polyphosphoric acid, 50ppm SO2 and 500ppm of hydroquinone) and 0.29 of a 50% solution of tris-(tetraethylene glycol monomethyl ether)-orthoformate in anhydrous toluene. For comparison purposes, the same mixture was prepared without the addition of the polymerization catalyst.

Using the presently prepared compositions, overlapping adhesive joints of testpieces with dimensions 80x25x6mm were produced from different wood species. The setting time was taken as the value at which there was a definite joining of the parts under manual tensile testing. The results obtained are given in the Table 6 below: Table 6 Setting time of adhesive composition at 23oC. in sec. on testpieces stored under ambient climatic conditions.

Without With polymerization polymerization Wood Species accelerator accelerator Limba 50-80 6-8 Beech 180-210 15-20 Spruce approx. 240 25-30 Oak approx. 360 20-25 The wood portion of all the testpieces fractured on determining the tensile and shear strength in the tensile test after storing for 24 hours at ambient temperature.

To determine the storage stability, the accelerated ageing of the present adhesive composition was performed at 700C. for 5 days. It was found that at the end of this time, which corresponds to the standard storage at ambient temperature of approximately 1 year, the adhesive composition containing the polymerization accelerator did not display a viscosity rise or an increase in the setting time.

Example 6 Podand Ill 37.39 of anhydrous polyethylene glycol-350-monomethylether, 2.99 of tetramethyl orthocarbonate, 1 50ml of anhydrous toluene and 50mg of 4-methyl benzene sulphonic acid were refluxed with the aid of a packed column with fitted top. The distillation of the reaction mixture was performed as in Example 1 above. 34.2 g (89.2%) of crude tetracis-(polyethylene glycol-350monomethyl ether)-orthocarbonate were obtained.

By high vacuum distillation at a pressure of 2x 1 0~5mbar and an evaporator temperature of 1 400C. 9.0g of a distillate were obtained which essentially comprised polyethylene glycol-350monomethyl ether. The distillation residue consisted of 24.19 of pure tetracis(polyethylene glycol-35monomethyl ether)-orthocarbonate.

The setting times and storage stability were determined as in Example 5 on an ethyl-2cyanoacrylate adhesive composition containing 2 per cent of a 50% solution of tetracis(polyethylene glycol-350-monomethyl ether)-orthocarbonate in the anhydrous toluene. The following values were obtained: Setting time of adhesive composition at 230C. in sec. on testpieces stored under ambient climatic conditions.

Without With polymerization polymerization Wood Species accelerator accelerator Limba 50-80 1-2 Beech 180-210 3-5 Spruce approx. 240 8-10 Oak approx. 360 5-8 The storage stability after 5 days at 700 C. was unchanged. The tensile and shear strength of testpieces tested after 24 hours as in Example 1 caused fracture of the material while the formed bond remained intact.

Example 7 289 of anhydrous polyethylene glycol-350-monomethyl ether were placed in a vessel and accompanied by stirring 3.4g of freshly distilled tetra-chlorosilane were added dropwise at 50C. within 5 minutes. The reaction mixture was stirred for an additional 10 minutes at 50C, then stirred for 3 hours at ambient temperature, and finally heated at 800C. for an additional 4 hours. The crude product obtained (28.6g, 100%) was freed from lower-boiling fractions in high vacuum.

At a pressure of 2 xlO-Smbar and an evaporator temperature of 1 700C., 3.29 of a colourless liquid were distilled off. The residue consisted of 24.19 (84.6%) of tetracis-(polyethylene glycol-350monomethyl ether)-orthosilicate.

An ethyl-2-cyanoacrylate adhesive composition, containing 1% of a 50% solution of tetracis (polyethylene glycol-350-monomethyl ether)-orthosilicate in anhydrous toluene gave the following values for the setting time on wood: Setting time of adhesive composition at 230C. in sec. on testpieces stored under ambient climatic conditions Without With polymerization polymerization Wood Species accelerator accelerator Limba 50-80 2-3 Beech 180-210 3-5 Spruce approx. 240 5-6 Oak approx. 360 10-12 The storage stability after 5 days at 700C. was unchanged. The tensile and shear strength was tested on testpieces after 24 hours in the same way as in Example 1. Each sample fractured in the wood leaving the formed bond intact.

Example 8 An ethyl-2-cyanoacrylate charge which, on storage in polyethylene bottles, had an agglomeration tendency in the gas chamber was thickened with 8.7% by weight of polymethyl methacrylate. In addition, 2% by weight of a 50% by weight solution of tetracis-(polyethylene glycol-350-monomethyl ether)-orthocarbonate was added to a portion of this mixture. Both the treated and untreated adhesive compositions were stored for 5 days at 700C. The adhesive composition containing no polymerization accelerator according to the invention revealed pronounced agglomeration on the vessel wall, while the adhesive composition containing the polymerization accelerator according to the invention was completely free of agglomerates.

While the invention has been described in connection with certain preferred embodiments, it is not intended to limit the invention to the particular form set forth, but, on the contrary, it is intended to cover such alternatives, modifications and equivalents as defined by the appended claims.

Claims

1. An -cyanoacrylate based adhesive composition having a catalytic amount of polymerization catalyst therein; said polymerization catalyst comprises at least one multi-armed podands selected from the group of podands of the general formula:

in which A is a central chemical group capable of linking each associated X by a single or two atom bridge; B represents a four-bond forming atom; R is a C1-C12 unsubstituted or substituted hydrocarbon group free of hydroxy or amino groups; R' represents hydrogen or a lower alkyl group; R2 each independently represents a lower alkyl;X and Y each represent a donor atom containing group wherein when said podands have an A central group X represents oxygen, sulphur or -N-CH3 and Y represents oxygen, sulphur, NCH3 or -N- wherein when said podands have a B central group X and Y are each oxygen; and n, m, p and q each represent a whole integer.

2. The -cyanoacrylate based adhesive composition of Claim 1 wherein said polymerization catalyst comprises at least one two-armed podand compound of the general formula:

in which X represents an oxygen atom, a sulphur atom or a N-CH3 group; Y represents an oxygen atom, a sulphur atom, a N-CH3 group or a -N-; R represents a C, to C,2 hydrocarbon groups which are free of hydroxy or amino groups; A represents a central group capable of linking each X to the other by one or two atom bridge; and n and m are each integers such that n+m+4 has a sum of from 5 to 100.

3. The adhesive composition of Claim 2 wherein the catalyst therein is at least one two arm podand compound having each podand chain in the form of a polyethylene glycol chain.

4. The adhesive composition of Claim 2 wherein the catalyst therein has a divalent central group, A, selected from -CH2-, -CH 2CH2-, arylene, carbonyl, dicarbonyl, sulphonyl or phosphonyl group.

5. The adhesive composition of Claim 2 wherein the catalyst therein has each terminal group R separately selected from a C1-C4 alkyl; an unsubstituted aryl; a C1-C4 substituted aryl; or a hetero atom substituted aryl.

6. The adhesive composition of Claim 2 wherein the catalyst therein is a two armed podand compound such that when Y is oxygen or sulphur, each R is independently selected from C1-C4 alkyl, phenyl, 1-naphthyl, 2-naphthyl, 2-methoxyphenyl, 2-nitrophenyl, 2-cyanophenyl or 2methoxycarbonylphenyl groups and when Y= -N- each terminal B group associated therewith is a phthaloyl group.

7. The -cyanoacrylate based adhesive composition of Claim 1 wherein said polymerization catalyst comprises at least one orthoester podand compound of the general formula:

in which B is a 4-bond forming atom, R' represents hydrogen or a lower alkyl group, each R2 separately represents a lower alkyl group and m, n, p, and q each represent a whole number of from about 2 to 50.

8. The a-cyanoacrylate based adhesive composition of Claim 7 wherein the orthoester podands of the polymerization catalyst have polyethylene glycol chains for which each of m, n, p and q represents a number from 3 to 20.

9. The a-cyanoacrylate based adhesive composition of Claim 7 wherein the central 4-bond forming atom is a carbon atom or a silicon atom.

10. The a-cyanoacrylate based adhesive composition of Claim 7 wherein the orthoester podands of the polymerization catalyst therein has R1 and R2 groups which are each independently a C1-C4 alkyl group.

11. The a-cyanoacrylate based adhesive of claim 7 wherein B is carbon and R1 is hydrogen or lower alkyl.

1 2. The -cyanoacrylate based adhesive of claim 9 wherein B is silicon and R1 is lower alkyl.

13. The adhesive composition of Claim 7 wherein the orthoester podands of the polymerization catalyst therein are esters of an acid selected from the group consisting of orthoformic acid, orthoacetic acid, orthocarbonic acid, orthomethyl siliconic acid and silicic acid.

14. The adhesive composition of any of Claims 1 to 13, wherein said composition contains from about 0.01 to 10 per cent by weight based on the total weight of the adhesive composition of said podands.

1 5. The adhesive composition of Claim 14 wherein said composition contains from about 0.01 to 5 per cent by weight based on the total weight of the adhesive composition of said podands.

1 6. The adhesive composition of Claims 1 to 1 5 wherein the polymerization catalyst further comprises a furan derivative of general formula

in which R1 stands for a straight or branched-chain alkyl or alkenyl radical, a cycloalkyl radical, a phenyl radical, a benzyl radical or an acetyl radical and R2 and R3, in dependently of one another, stand for hydrogen, straight and branched-chain alkyl and alkenyl radicals, cycloalkyl radicals, phenyl radicals, benzyl radicals, acetyl radicals and halogen.

1 7. The adhesive composition of any of Claims 1 to 1 6, wherein the cz-cyanoacrylate is of the general formula:

in which R is a straight or branched-chain alkyl or a halogen atom or alkoxy substituted alkyl group, a straight or branched chain alkenyl group, a straight or branched chain alkinyl group, a cycloalkyl group, an aralkyl group or an aryl group.

18. A compound having the general formula:

wherein B represents a carbon or silicon atom; R2 each independently represents a lower alkyl group; and n, m, p and q each independently represent an integer of from about 2 to 50.

1 9. The compound of Claim 1 6 wherein each of the lower alkyl groups is independently selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, iso-butyl and t-butyl.

20. A compound having the general formula:

wherein B represents a silicon atom, R1 represents a hydrogen atom or a lower alkyl group, RZ each independently represents a lower alkyl group and m, n and p each independently represents an integer of from about 2 to 50.

21. The compound of Claim 1 9 wherein each R1 and R2 group is independently selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, iso-butyl and t-butyl.

22. An adhesive composition according to Claim 1 substantially as claimed in any one of the foregoing Examples.

23. Method of bonding which comprises placing between two surfaces to be bonded an adhesive composition as claimed in any of Claims 1 to 17 or 22 and allowing the said composition to cure.

24. Method according to Claim 23 in which at least one of the surfaces to be bonded is of wood.