RESIN COMPOSITION

Abstract: Resin compositions for joining nylon pipes which comprises the reaction product of a resorcinol novolac and a polyamide homo-or co-polymer. The resin compositions are used in a 2 part system wherein curing agents selected from the group of amines, amides and aldehydes are added; or as a 1 part system wherein the resin cures by reaction with the amide groups of the nylon pipe. The resin composition can also be used as wood adhesives and in high speed bearing applications.

Description: RESIN COMPOSITION TECHNICAL FIELD This invention relates to resin compositions having particular use for joining nylon pipes and as a bearing material. BACKGROUND ART Extensive use is made of polyamide 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. A disadvantage of that adhesive is that m-cresol is toxic and is absorbed rapidly through the skin and by inhalation. Other solvents 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. Desirably the adhesive should adhere strongly to the substrate and 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 THE INVENTION - According to one aspect the invention consists in a resin comprising the product of reaction of (i) a resorcinol novolac and (ii) a polyamide homopolymer or copolymer. According to a second aspect the invention consists in a two part adhesive composition comprising the reaction product of a resin according to the first aspect with a suitable curing agent selected from the group comprising amines, amides, and aldehydes. According to a third aspect the invention consists in a method for joining parts of which at least one is made from a plastic having amide groups said method being characterized by the step of curing a resin according to the first aspect by reaction with amide groups of the plastic part. BEST MODE FOR CARRYING OUT THE INVENTION Various embodiments of the invention will now be described by way of example only. One reactant for manufacture of resins according to the invention is a resoncinol novolac. A novolac is a thermoplastic condensation product of the reaction between a phenolic species and an aldehyde. A novolac is typically formed when the phenolic is used in molar excess under usually acid 10 conditions. For use in the present invention a resorcinol-aldehyde novolac is desirably selected. For preference the aldehyde is a lower alkyl aldehyde, and more preferably is formaldehyde. The mole ratio of resorcinol to alkylaldehyde is selected having regard to the solvent to be used and the solubility of the novolac product. A ratio of 2 moles resorcinol to 1.0 or 1.5 moles of aldehyde general provides a novolac product soluble in a 20. compatible alcohol or alcohol/water mixture. In a preferred embodiment a novolac comprising 2.0 moles of resorcinol and 1.25 moles of formaldehyde in a 60% / solution in methanol/water is employed. A suitable commercially available alkaline novolac resin which may be used is "CASCOPHEN RS-224" available from BORDEN Chemical Co. Polyamides especially suitable for making resins -- '■■ £r according to the invention are the so called alcohol soluble nylons. These nylons consist of various combinations of nylon materials in alcohol soluble form. The selection of the most suitable nylon depends on a number of factors including performance of the final product, solvent-system compatibilities and the pH of the reactions. Typical of the nylons suitable for use in adhesive manufacture are Plata id copσly ers. Platamid Copolymers are available from Specialized Polymer Pty. Ltd., Oakleigh, Victoria. Typical Platamid nylons ares- Platamid 995 a mixture of copolyamide 6, 6/6 and 12 Solution - A solution most suitable for use with Cascophen RS-224 is 25% W/ nylon in ethanol (80%) and water (20%). Platamid 1276 a mixture of copolyamide 8 (33%), 11 (33%) and 12 (33%) Solution - A solution most suitable for use with cascophen RS-224 is 20% W/W in iso-propanol (80%) and water (20%) However other polyamide polymers and copolymers could be used provided that they can be solubilized in the Novolac/solvent system. The reaction of the novolac and the polyamide in accordance with the invention can be performed in acid or alkaline conditions. To change the pH of the system a very strong acid or alkali should be used which will provide minimal interference with the reaction. A typical acid would be sulphuric acid (36N) and a suitable alkali would be a saturated solution of NaOH. Table II describes by way of example only various compositions which differ from each other in respect of the polyamide polymer used, the percentage by weight of polyamide and rescorcinal-for aldehyde novolac and in respect of system pH. As shown in Table II a filler, for example, may optionally be included. As also shown in Table II a hardner, for example, may optionally be included. EXAMPLE OF MANUFACTURE OF RESIN SUITABLE FOR USE IN ADHESIVE. With reference to the compositions of Table II, a known amount of resorcinol novolac is heated and vigorously agitated or stirred. The temperature used depends on a number of factors including the novolac used, the type of nylon used and solvent-system interactions. The temperature used affects the quality of the product, but as a guide. temperatures in the range 50-80 C have been used successfully. Additional solvent is added to the hot resorcinol formaldehyde mixture whilst agitation continues. Preferred resins contain around 10% W/W of ethanol. The nylon powder or the nylon-alcohol solution or nylon/alcohol/water solution is added slowly whilst vigorous agitation and heating continues. This addition typically takes around one hour. Agitation and heating is continued for one to two hours after final addition of the nylon. Heat is removed and the mixture is allowed to cool slowly whilst the agitation continues. As the mixture cools its viscosity increases and agitation-stirring ip should be stopped when the consistency of the adhesive approaches the viscosity suitable for an adhesive. The resulting resins are generally an alcohol soluble dark red/purple solid. The novolac is capable of accepting a wide range of nylon types and concentrations. The most suitable nylons (Platamid 995 and 1276) performed best as a nylon adhesive for gas pipe when mixed from alcohol solutions at concentrations in the range up to 2% W/W of the novolac. Resins according to the invention with 20 concentrations above this level had reduced activity as a nylon adhesive. The resins may be used as a single part adhesive or as a two part adhesive and are capable of gluing all nylons (including polar or non-polar nylons).- The resins are very suitable for use in joining nylon pipes and will be described with reference to such pipes as an example. When used as a single part pipe adhesive the resin reacts with the amide group of the Nylon pipe to effect a cure. If the solvent evaporates from the adhesive pot, the adhesive can be reactivated by the addition of more solvent. As a single part adhesive preferred embodiments of the resin won't harden without reaction with the amide of the Nylon pipe. The single part adhesive is also more soluble when cured. This is also related to resin composition. Some single part resins remain water soluble when cured and experimentation may be necessary to screen those suitable for a particular use. When used as a two part adhesive the resins herein described are cured with an amine, amide or aldehyde, for example hexamethyl tetramine or para formaldehyde. The two part adhesive mixture has pot life of about 6 hours at 22 C. In contact with Nylon, the resin cures in about 1 hour. The cured resin is flexible when compared to an unmodified resorcinol-formaldehyde resin, but does have distinct elastic limits. For pipe joining the best combination of strength and flexibility comes with the Platamid 1276 nylon at a concentration of 1.5% in acid conditions. If this is cured with 12% w/w Paraformaldehyde, it yields the most flexible resin of those tested. Table I compares the tensile strength and Pressure at Failure of joints on pipe sections of 40 mm. OD (wall thickness 1.21-1.33 min. ) using an internal spigot as a joiner which expanded the pipe some 2% - 3% on diameter. Sample I was an unglued joint. Sample 2 was a solvent weld joint employing nylon dissolved in m-cresol according to the prior art. Sample 3 was a joint prepared using known resorcinol-formaldehyde resin for comparison purposes. TABLE I PERFORMANCE OF SAMPLE JOINTS MADE IN ACCORD WITH PRIOR ART Adhesive Ultimate Tensile Pressure at Strength Failure (kPa) Sample 1 Control 0.680 510-600 Sample 2 Prior Art Yield of substrate 1700-2000 (4.83-6.3) Sample 3 Yield of substrate 950-1220 Resorcinol-Formaldehyde Resin Table II gives the tensile strength and pressure at failure for a number of joints made from resins according to the invention, and shows that the joints have an acceptable tensile strength which in some cases is of comparable order.of magnitude as prior art. Other possible uses for resins according to the invention include use as a wood adhesive and as a bearing material. Resorcinol formaldehyde (RF) resins are known as wood adhesives. They are used primarily in making wood laminations, e.g. laminated girders or plywood manufacture. The advantage of RF resins for those purposes is that they require no heat for setting (phenol-formaldehyde resins require temperatures in excess of 140 C) but a lack of flexibility is a disadvantage. RF resins are very brittle when cured. It is believed that resins according to the present invention should be suitable for making wood laminations and provide a degree of flexibility to increase the resistance of the wood laminations to fracture under stress. Resin according to the invention may also find use as a bearing material. Phenolic bearings have been used for a number of years now and they are best when laminated with a fabric or paper to distribute vibration energy. They have a low co-efficient of friction, are very hard plastics and are suitable for very high speed lubricated and unlubricated bearing work. Unfortunately they suffer from a low abrasion resistance, possibly due to their brittle nature. The two-part adhesive detailed herein may be a substitute needing no laminations to produce vibration resistant bearing material. The resin described herein does not have a great affinity for steel, and cured resin can be very easily removed from flat plate. It would appear then, that the resins herein described may find use as a mould in place bearing material for high speed applications. TABLE II PLATAMID* 995 995 995 995 995 995 995 PH 9 9 9 9 9 9 1 Resorcinol Novolac % 84.5 84 83.5 83 98.5 79.5 83.5 Nylon % 0.5 1.0 1.5 2.0 1.5 1.5 1.5 Hardener % 15 15 15 15 15 0 15 Filler % 0 0 0 0 0 10 0 Tensile strength (M-J) 3.26 3.42 4.19 3.04 2.45 2.27 4.76 Pressure at Failure N/T* N/T N/T N/T Water N/T 500 (kPa) Soluble *PLATAMID 995 and PLATAMID 1276 are Trade Marks of Specialized Polymer Pty. Ltd. and identify nylon copolymers. TABLE II (Cont'd) PLATAMID* 995 1276 1276 1276 1276 pH 9 1 1 1 9 Resorcinol Novolac % 86.5 98.5 83.5 86.5 98.5 Nylon % 1.5 1.5 1.5 1.5 1.5 Hardener % 12 0 15 12 0 Filler % 0 0 0 0 0 t Tensile strength 3.10 4.01 4.76 Yield of Yield of (kN) Substrate Substrate Pressure at Failure 600 400 900 800 1,250 (kPa) *N/T - NOT TESTED *PLATAMID 995 and PLATAMID 1276 are Trade Marks of Specialized Polymer Pty. Ltd. and identify nylon copolymers.

Claims: - 13 - " "*~ - --- • - - . THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:- 1. A resin comprising the product of reaction of: (i) a resorcinol novolac, and (ii) a polyamide homopolymer or copolymer. 2. A resin according to claim 1 wherein the polyamide homopolymer or copolymer selected is soluble in alcohol or alcohol/water. 3. A resin according to claim 1 or claim 2 wherein the reaction is conducted under strongly acidic conditions. 4. A resin according to any one of the preceding claims wherein the resorcinol novolac is a resorcinol - formaldehyde novolac. 5. A resin according to claim 4 wherein the molar ratio of formaldehyde to resorcinol in the Novolac is in the range of from 0.5 to 0.8. 6. A resin according to claim 5 wherein the novolac is a solution in methyl alcohol. 7. A resin according to any one of the preceding claims wherein the polyamide is a copolymer. 8. A composition according to claim 1 comprising the product of reaction of: (1) from 79% to 99% by weight of the composition of a resorcinol formaldehyde novolac resin, (2) from 0.5 to 1.5% by weight of the composition of a copolyamide. 9. A resin according to claim 8 further including up to 15% by weight of a hardener. 10. A resin according to claim 9 further including a filler. 11. An adhesive composition comprising a resin according to any one of the preceding claims in combination with a curing agent. 12. An adhesive composition according to claim 11 wherein the curing agent is selected from the group comprising amines, amides and aldehydes. 13. An adhesive composition according to claim 8 or claim 9 when cured. 14. A method for joining parts comprising the steps of mixing a resin according to any one of claims ' 1-11 with an effective curing agent, applying the mixture to at least one of the parts, uniting the parts and permitting the resin to cure. 15. A method according to claim 14 wherein the parts are of Nylon 11. 16. A method for joining parts of which at least one is made from a plastic having amide groups, said method being characterised by the steps of curing a resin according to any one of claims 1-10 with amide groups of the plastic part. 17. A method according to claim 16, wherein the plastic part is a Nylon part. 18. A method according to claim 17 wherein the nylon is Nylon 11. 19. A method according to any one of claims 16-18 wherein the resin is dissolved in alcohol prior to application to the plastic part.

Inventors: REYNOLDS GREGG, REYNOLDS, GREGG
Applicants: ESDAN EXTRUSION PTY LTD, ESDAN EXTRUSION PTY. LIMITED
Application year: 1983
Main classification: C08G81
IPC codes: C08G81, C09J161, C09J177, F16C33, F16L47