ADHESIVE COMPOSITION

Abstract: A resin useful in an adhesive for nylon is made by reaction of a phenol having a labile ring hydrogen (for example resorcinol) with a cyclic ketone for example cyclohexanone or a dialdehyde of at least 6 carbons. The obtained resin may be used in a 2 part adhesive by addition of curing agents or in a one part adhesive for nylon, wherein the resin cures by reaction with the amine of the nylon. Nylon gas pipes may be joined using the adhesives.

Description: ADHESIVE COMPOSITION TECHNICAL FIELD This invention relates to resin compositions having particular use for joining nylon pipes. BACKGROUND ART Extensive use is made of polya ide plastics, and in particular of various nylon plastics for a variety of engineering applications. An example is the use of Nylon 11 for pipes employed in gas distribution. There is a general need for improved adhesives for bonding polyamides and in particular for pipe connection. The adhesive currently favoured for connecting Nylon 11 gas pipes is a solution of Nylon 11 in m-cresol. M-cresol is toxic and is absorbed rapidly through the skin and by inhalation. Other solvent in which Nylon is sufficiently soluble at ambient temperature tend to be corrosive or toxic. Accordingly in joining nylon gas pipes there has been a need for an adhesive system which is non-toxic, which is gap filling when cured, which has a long shelf life and for preference which is a one part system or less preferably is a two part system in which the parts have a long pot life after mixing. OMPI The adhesive should result in a bond capable of passing pipe joint quality tests within 10 to 20 minutes of application and be resistant to environmental damage. An object of the present invention is to provide an improved method of, and compositions for, joining nylon pipes. Resins believed to be novel have been developed with that objective in view and those resins have novel properties suiting them for other purposes. ' DISCLOSURE OF INVENTION According to one aspect the invention consists in a method for manufacture of a resin comprising the steps of causing to react (1) a phenol or substituted phenol having a labile ring hydrogen, and (2) a compound selected from the group consisting of cyclic ketones having at least 6 ring carbons and dialdehydes of the formula CHO-(CR-) - C HO wherein n is a number greater than 3, AND R is hydrogen or an alkyl group. The invention also resides in a resin made by the method and in a method of joining parts by use of an adhesive including the resin. The term "phenol" is herein used generically and includes monohydric and polyhydric phenols. For preference the phenol is a dihydric phenol, more preferably resorcinol, and is reacted with cyclohexanone (a cyclic ketone having 6 ring carbons) to form a curable resin. The resin may be used as a two part adhesive by the addition of a curing agent, for example, paraformaldehyde or dia ine, or the resin may be cured by reaction with the amine groups of nylon and thus may be used as a single part adhesive for connecting nylon components or pipes. BEST MODE FOR CARRYING OUT INVENTION Various embodiments of the invention will now be described by way of example only. in accordance with the invention a phenol or substituted phenol having a labile ring hydrogen is caused to react with a cyclic ketone or a dialdehyde having at least 6 carbon atoms. Resorcinol is preferred as the phenol. However other polyhydric phenols and substituted phenols, which predictably have a labile proton on the ring group, may be used. In the following examples unless otherwise specified the reaction is performed in ethanol (99.7 to 100% V/V) and the resin is formed by reaction of resorcinol and cyclohexanone. The reaction may be conducted under acid or alkaline conditions. The means of controlling pH of the reaction mixture should be selected so as not to interfer with the reaction. For reaction in acid conditions Oxalic Acid dihydrate (HO CCO H.2H 0) is preferred. The reaction is generally conducted under reflux. A catalyst has been found to be desirable to reduce reaction times and to improve resin quality. Some of the compounds which catalyse the reaction include Lewis Acids (such as A1C1, or FeCl_,) , and organometallic compounds made from metal/resoncinol mixtures. These organometallics include compounds based on single or a combination of metals in combination with resorcinol. Up to 10 metals have been combined into one organometallic catalyst. The catalysts produced have a wide range of activities. The metals used include mercury, zinc, tin, iron, manganeze, cobalt, lead, nickel and aluminium in concentrations varying between 1 pp and 3,500 ppm (concentration of metal to final resin). Differences in reaction rates and quality of the final resin varies with the quantity and type of catalyst used. The procedure preferred for manufacture of the resins varies depending on the catalyst system (if any) used. Each system requires a different initial procedure in order to produce an alcohol solution of resorcinol, oxalic acid and the catalyst (if included) . Subsequently: 1. The solution is heated to reflux, and kept refluxing. 2. The cyclohexanone is added slowly to prevent the mixture from cooling. The reaction mixture must be kept refluxing during this addition, otherwise OMPI bumping of the solution will occur, resulting in an inferior quality product. 3. Refluxing is continued until no more colour change occurs. In the absence of a catalyst this may take one to two weeks. At any time during this period the mixture can be cooled and left, to be reheated later. In the event of cooling the reaction continues, but at a much lower rate. 4. When no more colour change occurs the reaction can 0 be considered to be completed. At this stage the solvent and the water of condensation are removed by distillation. 5. The product is then re-dissolved in ethanol (99.7 to 100% V/V) to yield a 20-50% w/W solution. EXAMPLE 1 A solution of resorcinol (50 g) in ethanol (50 ml) was heated to reflux and a solution of oxalic acid dehydrate (1.4 g) in water (9 ml) was added slowly. Cyclohexanone (approx. 33.4g 0.34M to 42.4g 0.43M) was , 0 ' then added dropwise. The mixture was refluxed a f rther 4 hours. The solvent and water of condensation were then removed and the resin product dissolved in ethanol to yield a 25-50% w/w solution. The resin was an alcohol soluble brown polymer which may precipitate as an oil, and which does not form crystals visible to the naked eye. EXAMPLE 2 Resorcinol (100G), Oxalic acid dihydrate (2.8G) OMPI WIPO and Aluminium chloride (0.2G) were dissolved in ethanol (200 ml). The mixture was heated to reflux. Cyclohexanone (between say 33.4 g, 0.34 M and say 42.4 g, 0.43 M) was added dropwise whilst refluxing. Their reaction was allowed to continue until no more change in colour was observed. At this stage, the resin was a dark brown colour and almost opaque to light. The mixture was distilled over flame until white smoke appeared above the residue. The residue was allowed to cool slightly before being opened to the atmosphere. When the temperature of the reaction mixture returned to 50°C, 25% W/V of ethanol (99.7 to 100% V/V) was added, and the reaction mixture allowed to assimilate the ethanol without major interference, i.e. stirring. This resin has been found to be especially suitable for adhesives for adhesion of nylon gas pipes. EXAMPLE 3 Table 1 shows various compositions according to the invention. The compositions were made by the method described but differed from each other in respect of the ratio by weight of cyclohexanone to resorcinol, the reflux time, and the pH of reaction. A filler or hardener was included in some samples. EXAMPLE 4 Table 2 is similar to Table 1 but includes resins according to the invention wherein one or more catalysts were used in the manufacture of the resin. In Table 2 reference to Catalyst type A is to a mixed metal solution of which the composition is shown in Example 5 hereinafter and catalyst type B is a mixed metal catalyst isolated as in Example 6 hereinafter. EXAMPLE 5 Example of Mixed Metals Catalyst for use in manufacture of resins according to the invention. Solution in one litre of water Concentration Metal Compound of Metal required Mass Required (ppm) (mg) Hg (CH 3 COO) 2 Hg 1.7 2.70 Zn ZnSO .7H 0 1 4.40 Sn Metal 1.4 6.0 Co CoCl .6H 0 2.4 9.69 Pb PB0 2 1.5 1.73 Ni NiCl 2 -6H 2 0 1.3 5.26 The catalyst was degassed with N« before use. EXAMPLE 6 Example of Mixed Metal Organometalic Catalyst for use in manufacture of resins according to the invention. Resorcinol (25g) was degassed under N_, and similarly treated ethanol (50ml) was added. The solution was heated to reflux under N-. Metal solution (25ml at the concentration listed in Example 5) was degassed and added whilst the mix was refluxing, and the resultant mixture refluxed for three hours and allowed to sit under nitrogen for 48 hours. Large pink crystals were isolated and washed with ether, and dried in the filter funnel. Resins according to the invention may be cured with a suitable curing agent for example formaldehyde (e.g. solid paraformaldehyde) or an amine (e.g. hexamine) . Of particular interest is that the resins may be cured by means of the amine groups of a nylon. The resins may thus be used is a single part adhesive for nylon. As a single part adhesive the resin has excellent shelf life. If solvent evaporates from the pot, the adhesive can be reactivated by the addition of solvent. The resin cures in contact with nylon but remains more soluble after curing than the two part adhesive system. When used as a two part system, i.e. with the addition of a curing agent, the resin has its greatest gap filling and strength properties. A typical pot life after adding curing agent is about 5 hrs. at 22°C. The resins were formulated for use as adhesives suitable for forming joints in nylon pipe systems. The data on tensile strength and pressure at failure shown in Tables 1 and 2 refers to comparative OMPI tests on 40 mm OD nylon pipes having a wall thickness of 1.21 - 1.33 mm. Prior art adhesives have a pressure at failure (kPa) of 1700-2000 on the comparative test. The tests show that the compositions of the invention are suitable for nylon pipe jointing, with the compositions of Table 2 being preferred. It is believed that the cyclohexanone chain breaks near the oxide group and forms a hexane chain attached to an initial resorcinol group. The hexane chain then attaches to another resorcinol group and chain building occurs. Adhesion to the nylon substrate is thought to be the result of a number of chemical reactions occurring concurrently. These reactions may include alkoxyalkylation of the nylon, cross linking between the resin and the substrate (chemical attachment of the adhesive to the substrate) , and nylon formation in ' situ. The resin is less brittle than for example resorcinol formaldehyde resin. It is believed that the hexanone chain separates the benzene rings of the resorcinol units in the polymer chain reducing brittleness in comparison with, for example, a resorcinol formaldehyde resin. Although resins of the invention have been exemplified with reference to manufacture from resorcinol those skilled in the art will understand that the phenolic hydroxy group is a powerful electron . repelling (and ortho para directing) group which tends OMPI to facilitate release of nuclear hydrogen atoms herein referred to as labile ring hydrogen permitting reaction with the ketone or aldehyde and that a substantially similar reaction can be conducted with substituted phenols such as the cresols or polyhydric phenols such as the 1,4 dihydric phenol and others in which a hydrogen is to an extent labile by virtue of the nuclear substituents. Similarly, while cyclohexanone is preferred and has the advantage that on -fission of the ring there is formed a chain reactive at each end, a similar result can be achieved for example by use of a straight chain dialdehyde. It is however important to select the aldehyde or ketone so that the bridge, for example a -(CH-) - bridge, between phenolic rings has at least 6 carbon atoms in order to obtain sufficient flexibility and other desired properties and therefore if a straight chain dialdehyde is used it should have at least 6 carbons including those to which the aldehyde oxygen is bonded. Although straight chain unsubstituted dialdehydes are preferred, those with alkyl or substituents may be used and preferably lower alkyl substituents. Resins according to the invention may find use as an adhesive for all nylon materials and components (especially for the more polar nylons such as nylon 11, 12, 610 or 612) . Resorcinol formaldehyde (RF) resins are used in the manufacture of laminated wood structures and in the manufacture of plywood. The brittle nature of cured RF adhesives can lead to problems in service of these structures. Resins according to the invention and especially when mixed with paraformaldehyde may prove suitable as a substitute for RF adhesives. As will be apparent to those skilled in the art adhesive compositions according to the invention may be provided with fillers, pigment like additives without departing from the scope of the invention herein described. TABLE 1 Composition # 1 2 3 4 5 6 7 Resorcinol (g) 10 10 10 10 10 10 10 Cyc1ohe anone (g) 7.14 7.58 7.14 7.58 8.03 8.48 6.68 Hardener % 0 0 0 0 0 0 0 Filler % 0 0 0 0 0 0 0 Reflux Time (h) 2 2 4 4 4 4 4 pH 1 1 1 1 1 1 9 h* t Tensile Strength 1.5- 1 (kN) 2.54 3.9 Yield Yield Yield Yield Yield Pressure at Failure (kPa) 600 400 1320 1200 1300 1300 1380 TABLE 1 (Conf'd) Composition # 8 9 10 11 12 13 Resorcinol (g) 10 10 10 10 10 10 Cyclohexanone (g) 6.68 6.68 6.68 6.68 6.68 6.68 Hardener % 15 20 15 0 0 12 Filler % 0 0 5* 0 0 0 Reflux Time (h) 4 4 4 4 4 4 pH 9 9 9 1 1 1 Tensile Strength I (kN) Yield Yield Yield Yield Yield Yield * LO Pressure at Failure (kPa) 1300 600 1050 1050 1370 N/T *Hexamine N/T - Not tested TABLE 2 Composition # 14 15 16 17 18 Resorcinol (g) 100 100 100 50 500 Cyclohexanone (g) 66.8 66.8 66.8 33.4 33.4 Catalyst Type A1C1 3 A AICI3 B AICI3 and Amount (g) 0.02 100 ml 0.02 2.50 0.2 Oxalic Acid (g) 2.8 2.8 2.8 1.4 14.2 (In 18ml H 2 0) (In 18ml H 2 0) Pre-Reaction (h) No Yes No Yes No (Isolated tr* A> Catalyst) Ethanol (ml) 100 100 200 50 1000 Tensile Strength Yield* Yield Yield Yield Yield (kN) Pressure At 1800 2150 2150 2000 1700 Failure (kPa) * Yield of substrate A For composition of mixed metals solution see Example 3 B Mixed metal catalyst made from solution - organometallic isolated see Example 4. TABLE 2 (Cont'd) Composition # 19 20 21 22 23 Resorcinol (g) 50 50 50 50 50 Cyclohexanone (g) 33.4 33.4 33.4 33.4 33.4 Catalyst Type AICI3 ZnCl2 ZnCl2 0. .02 FeCl2 Zn(Ac)2 and Amount (g) 0.02 0.2 AICI3 0..04 0.03 0.2 Oxalic Acid (g) 0.7 0.7 0.7 0.7 0.7 Pre-Reaction (h) Yes Yes Yes Yes Yes 48 h 48 h 48 h 48 h 48 h ** ** ** ** ** Ethanol (ml) 100 100 100 100 100 tr* U * l Tensile Strength 4.4 4.3 Yield Yield Yield (kN) Pressure At 1250 1300 1525 1780 2475 Failure (kPa) ** Reflux one hour under then stored under 2 for 48 hours at ambient temperature.

Claims: THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:- 1. A method for manufacture of a resin comprising the steps of causing to react (1) a phenol or substituted phenol having a labile ring hydrogen, and (2) a compound selected from the group consisting of cyclic ketones having at least 6 ring carbons and dialdehydes of the formula CHO-(CR^) - C HO wherein n is a number greater than 3 and R is hydrogen " or an alkyl group. 2. A method according to claim 1 wherein a polyhydric phenol is reacted with cyclohexanone. 3. A method according to claim 2 wherein the polyhydric phenol is resorcinol. 4. A method according to claim 3 wherein the reaction is conducted under acid conditions. 5. A method according to claim 4 wherein the reaction mixture is acidified with oxalic acid. 6. A method according to claim 4 wherein the reactants are heated under reflux. 7. A method according to claim 5 wherein refluxing is continued substantially until the reaction is completed. 8. A method according to claim 7 when conducted in a solvent comprising ethylalcohol. 9. A method according to claim 1 wherein catylised by means of a Lewis acid. 10. A method according to claim 1 when catylised by means of one or a combination of metals selected fr the group consisting of mercury, zinc, tin, iron, manganese, cobalt, lead, nickel, and aluminium and salts or compounds thereof. 11. A method according to claim 3 wherein the reactants are in the ratio of from 6.6 to 8.5 parts by weight cyclohexanone to 10 parts by weight of resorcinol. 12. An adhesive comprising a curable resin which is the reaction product of (1) a phenol or substituted phenol having a labile ring hydrogen, and (2) a compound selected from the group comprising cyclic ketones having at least 6 ring carbons and dialdehydes of the formula CHO-(CR ) - C HO wherein n is a number greater than 3, R is hydrogen or an alkyl grou . 13. An adhesive according to claim 12 wherein a polyhydric phenol is reacted with cyclohexanone. 14. An adhesive according to claim 13 wherein the phenol is resorcinol. 15. An adhesive according to claim 14 comprising from 6.6 to 8.5 parts by wt. of cyclohexanone reacted with 10 parts by wt. of resorcinol. 16. An adhesive according to claim 15 comprising a filler. 17. An adhesive according to claim 15 comprising a hardener or curing agent. 18. A method for adhering two parts comprising the steps of adding a curing agent to a curable resin which is a reaction product of (1) a phenol or substituted phenol having a labile ring hydrogen, and (2) a compound selected from the group comprising cyclic ketones having at least 6 ring carbons and dialdehydes of the formula CH0-(CR ) - C HO wherein n is a number greater than 3 and R is hydrogen or an alkyl group; applying the resin between the parts to be joined and allowing the resin to cure. 19. A method according to claim 18 wherein the resin is a reaction product of a polyhydric phenol and cyclohexanone. 20. A method according to claim 19 wherein the phenol is resorcinol. 21. A method according to claim 18 wherein the curing agent is paraformaldehyde or hexamine. 22. A method according to claim 18 wherein at least one of the parts is of Nylon. 23. A method of adhering two parts of which at least one is made of nylon comprising the step of applying between the parts a curable resin according to claim 12 and allowing the amine groups of the nylon to cure the resin. 24. A method according to claim 23 wherein the uncured resin is in an alcohol solvent. 25. A method according to claim 23 wherein the resin is a reaction product of a polyhydric phenol and cyclohexanone. 26. A method according to claim 23 wherein the polyhydric phenol is resorcinol.

Inventors: REYNOLDS GREGG, REYNOLDS, GREGG
Applicants: ESDAN EXTRUSION PTY LTD, ESDAN EXTRUSION PTY. LIMITED
Application year: 1983
Main classification: C08G8
IPC codes: C08G8, C08J5, C09J161