AU2011213775A1

AU2011213775A1 - Fastenings and other components for use with treated timber

Info

Publication number: AU2011213775A1
Application number: AU2011213775A
Authority: AU
Inventors: Desmond Mark Ebejer; Yizheng Gong
Original assignee: Illinois Tool Works Inc
Current assignee: Illinois Tool Works Inc
Priority date: 2011-08-18
Filing date: 2011-08-18
Publication date: 2013-03-07
Anticipated expiration: 2031-08-18
Also published as: AU2016247115A1; AU2017258971B2; AU2016247115B2; AU2017258972A1; AU2011213775B2; NZ601854A; AU2017258971A1; NZ711830A; NZ621296A; AU2017258972B2

Abstract

C WRPonbl\DCC\PLW\3BIl233_l.DOC-18/0/2011 - 13 A fastening or other steel component for use in building construction, the component being coated with a base layer of zinc, and the zinc base layer having at least one polymer 5 coating.

Description

Regulation 3.2 AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT (ORIGINAL) Name of Applicant: Illinois Tool Works Inc. Actual Inventors: Yizheng Gong Desmond Mark Ebejer Address for Service: DAVIES COLLISON CAVE, Patent Attorneys, 1 Nicholson Street, Melbourne, Victoria 3000. Invention Title: "Fastenings and other components for use with treated timber" The following statement is a full description of this invention, including the best method of performing it known to us: C:\NRPonbI\DCC\PLW\3822578_ .DOC - 18/8/I1 C:NRPoribl\DCCPLW\ 311233_1.DOC-1078/2011 FASTENINGS AND OTHER COMPONENTS FOR USE WITH TREATED TIMBER 5 The present invention relates to fastenings and other components for use with treated timber, treated pine for example, in building construction. In building construction using external timber exposed to the weather, it is common to use timber treated with a preservative to improve its weather-resistance. Pine, a commonly 10 used timber for building construction, is widely available both in raw form and in a form in which it is treated with a wood preservative and this is usually referred to as "treated pine". A widely used preservative for this purpose is chromated copper arsenate (CCA) and preserves the wood from decay, fungi and wood-attacking insects. It has been used for many decades and is a very effective treatment although other copper-based treatments 15 which avoid the use of arsenic are now available. The copper primarily acts to protect the wood against decay and fungi, with other compounds acting as an insecticide (in CCA, it is the arsenic which provides the insecticidal function). An arsenic and chromium free alternative to CCA is available which uses copper and a quaternary ammonium compound (known as 'ACQ'). ACQ is also useful in protecting wood against fungi, termites and other 20 wood-boring insects. Conventionally, timber fastenings such as bolts or screws or other steel components for use in an external environment are coated against corrosion unless fabricated from stainless steel. A widely used anti-corrosion coating for components such as these is galvanising 25 involving the application of a zinc coating. A widely practised method of applying the zinc coating is to use a hot dip method which produces a thicker and less porous zinc coating than that which can be applied by other current methods such as mechanical pounding or electroplating. 30 For galvanised components which have been used with pine or other timber treated with a copper based preservative, the copper present in the preservative tends to attack the zinc C\NRPorb\DCC\PLW\3811233_1 DOC-17/08/2011 -2 coating and the rate of attack can be quite severe in certain environmental conditions for example moist or damp conditions and in some coastal situations. Although a hot dip zinc coating can be quite robust, such zinc coated products break down over a period of time as a consequence of attack from the copper used in the timber treatment (i.e., for instance, 5 either CCA or ACQ) , the underlying metal being subject to corrosion damage, and often quite severe damage. In order to overcome this shortcoming in the art the present invention relates to a polymer coating(s) to be applied to the zinc coating which thereby acts as a base layer, to shield that 10 zinc layer against attack by the copper in the treated timber. This additional coating does not adversely affect the ordinary performance of the fastening component and in some embodiments actually enhances the performance of the fastening component. According to the present invention there is provided a fastening or other steel component 15 for use in building construction, the component being coated with a base layer of zinc, and the zinc base layer having at least one polymer coating. In a further aspect the invention provides a method of forming a copper resistant zinc coated fastening or other steel component for use in association with copper treated wood; 20 said method comprising the step of coating the zinc coated fastening or other steel component with a polymer. Advantageously the polymer used for the coating is a thermosetting polymer preferably based on an epoxy resin system. 25 Embodiments of the invention will now be described in detail by way of example only. Preferred embodiments of the invention will be described in relation to a steel bolt coated with a base layer of zinc by a conventional hot dip process. Although for convenience the 30 embodiment is being described in relation to a coating applied to a bolt, it is to be understood that the invention is applicable to a range of other fasteners and other C.\NRPortbDCC\PLW\38 1233L DOC-17/08/201 -3 components as may be used in the building construction industry, such as nuts, washers, screws, nails, staples, nail plates, brackets, joist hangers, metal strap ties and so forth. It will be understood that in each case the component is basically fabricated from steel and after fabrication is coated with a zinc base layer using the hot dip coating method and then 5 the polymer coating as will be described in detail. Accordingly, in preferred embodiments the invention provides a method of forming a copper resistant zinc coated fastening or other steel component comprising: (i) subjecting the fastening or other steel component to hot-dip galvanising in 10 order to prepare a zinc coated fastening or other steel component; and (ii) coating the zinc coated fastening or other steel component with a polymer. The thickness of such a zinc coating achieved by the hot dip process in step (i) above is typically many times that which can be achieved by other galvanising methods and could 15 be as high as 80 microns. The polymer coating is preferably applied over the entirety of the zinc coating, although it will be appreciated that depending on the end use of the component, only part of the component may need to be polymer coated, for instance, any part which comes into contact with copper treated timber. 20 Although a primary use of the bolt is with treated pine or other treated timber, nevertheless the bolt with a polymer outer coating and zinc base layer also has significant utility in environments where an exposed outer coating layer of zinc would be exposed to salt-laden moist air as would typically be encountered in a coastal environment. In either case, the outer coating acts to shield the zinc base layer and thereby improves the corrosion 25 resistance of the bolt. In an embodiment the polymer coated fastening or other steel component of the present invention is used in conjunction with copper treated timber, and in particular either CCA or ACQ treated timber. 30 The Polymer Coating C:\NRPortblDCCPLW3811233_L.DOC-17/08/2011 -4 In an embodiment the polymer coating is based on a thermosetting polymer, for example, epoxy resins or phenol formaldehyde resins. 5 In an embodiment the polymer coating is a polymer composition comprising an epoxy resin based coating system. In the system described above the epoxy resins may be produced from a reaction between epichlorohydrin and bisphenol-A (or derivatives or analogues thereof). Other systems 10 involve the use of hardener or cross-linking components based on amines, guanidines, ureas, glycouril, or other nucleophilic nitrogen based compounds. Examples of suitable crosslinking/hardening components include triethylenetetraamine, hexamethylene, tetramine, methoxymethyl melamine as well as mixtures of the above. 15 It will be appreciated by those in the art that in relation to the aforementioned embodiment the "curing" step to form the epoxy resin based coating system can be controlled through temperature, choice of resin and hardener/crosslinking components and the ratio of resin to hardener/crosslinker. 20 Typically the ratio of epoxy resin: hardener/crosslinker is about 3:1 to about 4:1, and preferably about 3.5:1 to about 4:1. The curing process is typically conducted in an oven at temperatures between 180'-250 *C. Curing times may vary but are typically in the range of 7-20 mins. 25 The polymer coating compositions of the present invention may include additional components including: pigments and opacifers such as metal based pigments derived from aluminium, cadmium, cobalt, lead, mercury, titanium (e.g., TiO 2 ), zinc (e.g., zinc phosphate), and iron (e.g., sanguine, caput mortuum, oxide red, Venetian red, Prussian 30 blue, and iron oxide (clay earth) including yellow ochre, burnt and raw sienna, and burnt and raw umber; surface modifiers to control floating, flooding and silking, to enhance and C:\NRPonblDCC\PLW\381 2331 DOC-17/8/2OI I -5 improve flow and levelling, and to provide scratch and mar resistance, etc., such modifiers including polyether modified polydimethylsiloxanes, polyacrylates, polyesters, waxes (e.g., polyethylene, polypropylene, and mono- and bis amide based waxes), urea and amide based modifiers, and so on; defoamers (such as siloxanes); and solvents (such as propylene 5 glycol monomethyl ether acetate (PMA); 2-butoxyethanol (or BCS), dibenzyl ether, butyl alcohol, butyl acetate, xylene, toluene, trimethylbenzene, and the like which may also function as viscosity modifiers. In a preferred embodiment a bolt coated with a base layer of zinc is coated with the 10 polymer such that the resultant polymer coating does not impede the performance of the bolt. Preferably the coating is of a thickness of 10-40 microns, and preferably 25-30 microns. In relation to the embodiment where the polymer coating is a epoxy resin based coating 15 system, the resin components are mixed and shortly thereafter a bolt is coated with the coating composition. The coating process may involve dipping or immersing the bolt into the composition or spraying the bolt with the composition. Once coated the bolt is subjected to heat or UV curing. 20 In order to control coating thickness, the invention provides, in one embodiment, a double dipping (or immersion) method, whereby the zinc coated bolt is dipped into the polymer coating composition ('a primer coating') and subsequently cured, this sequence being repeated a further time to achieve the required coating thickness. In the first dip and cure process it is preferred that a coating thickness of between 8-10 microns is achieved. The 25 inventors have found that this double dipping technique with two layers of a primer coating ensures increased adhesion of the coating composition to the zinc surface of the bolt. In this embodiment, the primer coating (which is applied twice) is an epoxy resin based coating as described above. 30 A further process step between the coating and curing steps may involve a step to remove any unwanted coating on a bolt after the dipping (coating) process. For instance, this may C:\NRJorbl\DCC\PLW\3811233_.DOC17/08/2OlI -6 involve subjecting the bolt to centrifugal forces at high speed. Such a process may better ensure uniformity in coating thickness. Modifications of the above double dipping process would be apparent to the skilled person. 5 For instance, the first coating/curing step may be performed with a primer coating composition with slight variations compared to the subsequent coating composition which is used in the second coating/curing step. One of the variations may be the addition of polymer components (or differing amounts of polymer components) to aid in the adhesion quality of the primer coating composition to the zinc surface of the bolt. 10 In a preferred embodiment the coating/curing step is repeated a further third time with a "finishing coat". As this third finishing coat is intended to be the outer coating, it may be modified (relative to the first two coatings) by including components which, for example, provide enhancement in relation to wear (e.g., scratch resistance), weathering, colour 15 (which may be used to identify, for example, a particular sized bolt), and so on. Preferably the finishing coat is also an epoxy resin based coating. It will also be appreciated that the finishing coat may be applied in the same manner as the primer coating layer(s) described above. 20 Accordingly, in a further aspect the invention provides a method of forming a copper resistant zinc coated fastening or other steel component comprising: (i) coating a zinc coated fastening or other steel component with a polymer; 25 (ii) subjecting the resultant polymer coated zinc coated fastening or other steel component from step (i) to a further polymer coating process; (iii) applying a finishing polymer coat to the resultant polymer coated zinc fastening or other steel component from step (ii). 30 In relation to the above aspect it is preferred that at each stage the thickness of each coating does not exceed 10 microns.

C:\NRPortbl\CC LW\3811233 L.DOC- I7/20 l 1 -7 In a further preferred embodiment, which is based on the above aspect, the first two polymer coating layers in steps (i) and (ii) are based on the same epoxy resin based coating ('primer coating'), and the third finishing polymer coat is a modified epoxy resin based 5 coating (i.e., modified in relation to the "primer coating"). In other preferred embodiments, the second primer coating referred to earlier could form the outer finishing coat, or the finishing coat referred to earlier could be applied just to a single primer coating whereby in either case, the bolt has just two polymer layers over its 10 galvanised base layer. As a further recognised advantage the polymer coating on the fastening or other steel component functions to reduce friction when driving the fastener into timber, for instance, (i) into predrilled timber holes for fixing bolts or (ii) into pilot holes or directly into the 15 timber with "self-drilling" screws. Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps 20 but not the exclusion of any other integer or step or group of integers or steps. The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived 25 from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates. Examples 30 Formulation of epoxy coating C:\NRPonblDCCPLWG3811233 l.DOC.L7/08/20I -8 Raw Materials % I Epoxy Resin 20-40 2 Solvent 1.0-5.0 3 Wetting and dispersing Additives 0-2.0 4 TiO2 Pigment 5.0-15.0 5 Yellow Pigment 1.0-3.0 6 Chemical Resistance Pigment 5.0-15.0 7 Sealant 0-1.0 8 Solvent 1.0-5.0 9 Epoxy Resin 20-40 10 Amine Resin 1 2.0-12.0 11 Amine Resin II 2.0-12.0 12 Surface Additives 0-2.0 13 Leveling Additives 0-2.0 14 Solvent 0.1-5.0 15 Solvent 1.0-5.0 16 Color Paste 0-3.0 Total 100 Preparation of epoxy coating Process 1) Add the following raw materials 1, 2, 3, 4, 5, 6, 7 with middle speed 200 - 400 r/min , high speed 600-1000 r/min disperate 10-15min, send to three-roller mill in order to get thickness < 30 um, use 8 to clean 2) Add the following raw materials 9, 10, 11, 12, 13, 14 with C:\NRPonb\DCC\PLW8\3 I 233_LDOC-17/0/201 I -9 middle speed disperation about 10-20 min. 3) Use 15 to adjust viscosity, use 16 to adjust color, check viscosity and color, filtrate and packing. Coating Process 5 1) Bolts are dipped into coating formulation. 2) Excess coating is removed. 3) Coated bolts are cured in an oven at elevated temperatures for 5-20 mins. 4) The process (i.e., steps 1) - 3)) is repeated a further time. 5) The bolts are dipped into a finishing coat formulation which is a slightly modified 10 version of the coating formulation of 1). 6) Excess coating is removed. 7) Coated bolts are cured in an oven at elevated temperatures for 5-20 mins. 8) The total thickness of the combined polymer coats (i.e., resultant polymer coating) is between about 25-30 microns.

Claims

1. A fastening or other steel component for use in building construction, the component being coated with a base layer of zinc, and the zinc base layer having at least 5 one polymer coating.

2. A method of forming a copper resistant zinc coated fastening or other steel component for use in association with copper treated wood; said method comprising the step of coating the zinc coated component with a polymer. 10

3. A method according to claim 2 wherein the copper treated wood is CCA or ACQ treated wood.

4. A method of forming a copper resistant zinc coated fastening or other steel 15 component comprising: (i) subjecting the component to hot-dip galvanising in order to prepare a zinc coated component; and (ii) coating the zinc coated steel component with a polymer. 20

5. A component or method according to any one of claims 1 to 4 wherein the polymer coating is a thermosetting polymer.

6. A component or method according to claim 5 wherein the thermosetting polymer is an epoxy resin. 25

7. A component or method according to claim 6 wherein the epoxy resin comprises crosslinking components selected from amines or other nucleophilic nitrogen based compounds. 30

8. A component or method according to claim 7 wherein the crosslinking components are selected from triethylenetetraamine, hexamethylene, tetramine, C:\NU'orbI\DCC\PLW 8 I 233_I.DOC-17/08/201I methoxymethyl melamine and mixtures thereof.

9. A component or method according to claim 8 wherein the ratio of epoxy resin crosslinker components is about 3:1 to 4:1, preferably about 3.5:1 to about 4:1. 5

10. A method according to any one of claims I to 9 including a curing step which involves heat treatment, preferably at between 180*-250*C.

11. A component according to claim I wherein the polymer coating comprises one or 10 more of pigments or opacifers; modifiers to control floating, flooding and silking, or to enhance and improve flow and levelling, or to provide scratch and mar resistance; defoamers; and solvents.

12. A component according to claim 1 wherein the thickness of the polymer coating is 15 15-20 microns.

13. A method according to claim 2 wherein the step of coating the zinc coated component with a polymer, involves multiple coating/curing processes. 20

14. A fastening or other steel component for use in building construction, the component being coated with a base layer of zinc by hot-dip galvanising, and the component having at least one primer layer applied over the base layer, and an outer layer of a polymer coating. 25

15. A fastening or other steel component for use in building construction, the component being coated with a base layer of zinc by hot-dip galvanising, and the component having at least one epoxy layer applied over the base layer to provide resistance against copper which may be present in treated wood with which the component may be used. 30

16. A method of forming a copper resistant zinc coated fastening or other steel C:\NRJ-onb\DCC\PLW38 I 1233_ .DOC-17/OR/2011 - 12 component comprising: (i) coating a zinc coated fastening or other steel component with a polymer; (ii) subjecting the resultant polymer coated component from step (i) to a further 5 polymer coating process; and (iii) applying a finishing polymer coat to the resultant polymer coated component from step (ii).

17. A method according to claim 16 wherein the thickness of the coating at each step 10 does not exceed 10 microns.

18. A method according to claim 16 or 17 wherein the first two polymer coating layers from steps (i) and (ii) are based on the same epoxy resin and the finishing polymer coat is a modified epoxy resin. 15

19. A method according to any one of claims 16 to 18 wherein coating steps (i) - (iii) are conducted using a dipping (or immersion) method.