Decking

Abstract

Decking comprises: a support selected from the group consisting of: polymeric materials; marine engineering polymers, fiber reinforced polymers, polymer metal composites, metal or wood sheets or marine superstructure; an array of strips of polymer treated wood secured to the support by means of an adhesive; the adhesive being selected from the group consisting of: polyurethane adhesives, modified silyl polymer adhesives and epoxy resin adhesives; wherein the polymer treated wood comprises a wood species selected from the group consisting of: maple species impregnated with a wood compatible polymerizable monomer, preferably selected from furfuryl alcohol, bis hydroxymethyl furan and mixtures thereof and subsequently dried and cured.

Claims

1. Marine decking comprising: a support selected from the group consisting of polymeric materials; marine engineering polymers, fibre reinforced polymers, polymer metal composites, metal or wood sheets or marine superstructure; and an array of strips of polymer treated wood secured to the support by an adhesive, the array of strips forming an upper surface opposite the support, wherein the polymer treated wood includes a maple species impregnated with a polymer selected from the group consisting of furfuryl alcohol, bis hydroxymethyl furan, and mixtures thereof, and wherein the strips of polymer treated wood are oriented such that annual rings of at least some of the strips form a non-vertical angle with the upper surface.

2. The marine decking as claimed in claim 1 wherein the polymer treated wood has a hardness value of 3 to 8 on the Brinell scale.

3. The marine decking as claimed in claim 1, wherein the polymer treated wood has a bending modulus of rupture of between 100 and 130 MPa.

4. The marine decking as claimed in claim 1 wherein the wood surface exhibits a hardness of 4 to 7 on the Brinell scale.

5. The marine decking as claimed in claim 1 wherein a wood surface of the polymer treated wood exhibits a hardness of 5 to 6 on the Brinell scale.

6. The marine decking as claimed in claim 1 wherein the support further comprises a substrate selected from polyester sheeting, glass fibre, reinforced polyester, epoxy-wood composites, plywood, polyaramid sheet, carbon fibre composites or laminates, and solid wood or metal sheets.

7. The marine decking as claimed in claim 1 wherein the adhesive is selected from the group consisting of polyurethane adhesives, modified silyl polymer adhesives and epoxy resin adhesives.

8. The marine decking as claimed in claim 1 wherein the maple species is selected from Acer macrophyllum; Acer negundo; Acer nigrum; Acer rubrum; Acer saccharinum; Acer saccharum; Acer pseudoplatinus; Acer platanoides; Acer campestre.

9. The marine decking as claimed in claim 1 wherein edges of the strips include rebates.

10. The marine decking as claimed in claim 1 wherein a volumetric swelling of the polymer treated wood is 8 to 10% from oven dry to moisture saturated.

11. The marine decking as claimed in claim 1, the polymer treated wood having a modulus of elasticity between 10000 and 17000 MPa.

12. The marine decking as claimed in claim 1, the polymer treated wood having a density of 700 to 1000 kg.Math.m.sup.3.

13. A process for manufacture of marine decking as claimed in claim 1 comprising the steps of assembling a laminate comprising an array of the strips of polymer treated wood consisting of a maple species impregnated with a furfuryl alcohol polymer, the polymer being selected from the group consisting of furfuryl alcohol, bis hydromethyl furan, and mixtures thereof; securing the polymer treated wood to a sheet of polymeric material selected from the group consisting of marine engineering polymers, fibre reinforced polymers, polymer metal composites, metal or wood sheets, or superstructure by an adhesive selected from the group consisting of: polyurethane adhesives, modified silyl polymer adhesives, and epoxy resin adhesives; and applying pressure to the assembly and allowing the adhesive to cure.

14. The decking as claimed in claim 1, wherein the non-vertical angle is less than about 60 degrees.

15. A process for manufacture of a marine decking, the process comprising the steps of impregnating wooden strips including a maple species with a polymerizable composition comprising: (i) a polymer selected from the group consisting of furfuryl alcohol, bishydroxymethyl furan, and mixtures thereof; (ii) a catalyst; (iii) a solvent selected from the group consisting of water, C.sub.1-C.sub.4 alcohols, and mixtures thereof; and (iv) optionally one or more stabilisers or other ingredients; to produce impregnated decking strips; following impregnation, subjecting the impregnated decking strips to a water removal process comprising maintaining the impregnated decking strips in an atmosphere having a pressure of 10 kPa (0.1) to 50 kPa (0.5 bar), at a first temperature of 50 to 90 C., for a duration sufficient to cause removal of water from the impregnated decking strips; and following the water removal process, maintaining the impregnated decking strips at a second temperature higher than the first temperature to cure the polymerizable composition and form polymer treated decking strips.

16. The process as claimed in claim 15 wherein the polymerizable composition comprises 20 to 95 parts furfuryl alcohol, to 100 parts water.

17. The process as claimed in claim 15, wherein the polymerizable composition comprises about 70 to 100 parts polymer to about 100 parts solvent by volume.

18. The process as claimed in claim 15, further comprising: securing the polymer treated decking strips to a sheet of polymeric material selected from the group consisting of marine engineering polymers, fibre reinforced polymers, polymer metal composites, metal or wood sheets, and marine superstructure, by an adhesive selected from the group consisting of polyurethane adhesives, modified silyl polymer adhesives, and epoxy resin adhesives; and applying pressure to the polymer treated decking strips, sheet of polymeric material, and adhesive and allowing the adhesive to cure.

19. A process for the manufacture of a marine decking, the process comprising the steps of: impregnating wooden strips including a maple species with a polymerizable composition, the polymerizable composition including: a polymer selected from the group consisting of furfuryl alcohol, bishydroxymethyl furan, and mixtures thereof; a catalyst selected from the group consisting of maleic acid, malic acid, phthalic acid, benzoic acid, citric acid, organic anhydride, aluminum chloride, ammonium salt, and combinations thereof; and a solvent selected from the group consisting of water, C.sub.1-C.sub.4 alcohols, and mixtures thereof; to produce impregnated decking strips; following impregnation, drying the impregnated decking strips at a first temperature for a duration sufficient to cause removal of water from the impregnated decking strips; and following the drying process, curing the polymerizable composition by heating the impregnated decking strips to a second temperature higher than the first temperature to form polymer treated decking strips.

20. The process of claim 19, wherein the first temperature is about 50 to 90 C. and the second temperature is about 90 to 140 C.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is further described by means of example but not in any limitative sense with reference to the accompanying drawings of which:

(2) FIG. 1 is a schematic view of a timber impregnation plant in accordance with this invention;

(3) FIG. 2 illustrates the drying vessel of the plant;

(4) FIG. 3 illustrates decking in accordance with this invention; and

(5) FIGS. 4 to 6 illustrate test results showing physical properties of the decking.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(6) FIG. 1 is a schematic view of a timber impregnation plant. A supply of wood or wooden articles, for example planks (1), is organised into a separated stack (2) on a trolley or other carrier (not shown) using spacers separating horizontal layers of boards, allowing gases and vapour to flow between the wood layers. The stack is then moved on the trolley into an impregnation autoclave (3).

(7) The autoclave (3) is filled with an impregnating solution from buffer tanks (4,5) supplied from storage tanks (6,7,8) via a mixing and measuring tank (9).

(8) After impregnation, the impregnated wood or wooden articles are transferred to a drying chamber (10). The drying chamber is provided with a heat exchanger, or inlet for steam and a condenser (14) connected to an outlet for recycling condensate collected from the condenser (14) to the storage tank (7). Gases from the condenser are routed through an air purifier (15).

(9) After drying and curing the wood is sorted and stacked, machined if necessary, and packed for transportation and distribution.

(10) The wood or wooden articles may be impregnated by any conventional technique including application of pressure up to 15 bar, vacuum followed by pressure or by application of atmospheric or low pressure followed by higher pressure and a final vacuum step.

(11) The impregnating solution may comprise one or more monomers selected from furfuryl alcohol, bis hydroxymethyl furan, tris hydroxymethyl furan or oligomers of these compounds.

(12) Mixtures of monomers or of monomers and oligomers may be used, provided that they are sufficiently fluid to penetrate and impregnate the wood.

(13) A general method which may be used includes the steps of securing the wood so that it will not float; closing the autoclave and applying a partial vacuum; filling the autoclave with the treating mixture while maintaining the vacuum to submerge the wood; pressurizing the autoclave to a pressure in the range of 5-14 bar dependent on the wood species, dimensions of the wood or wooden articles and desired rate of impregnation. After impregnation the remaining liquid is removed and a final vacuum step is introduced for removal of excess liquid. Finally the treated wood is removed.

(14) A typical treatment solution may comprise:

(15) TABLE-US-00002 furfuryl alcohol 20 to 100 parts water 100 parts with optional further ingredients.

(16) A liquid uptake of 100% in relation to dry wood mass for maple sapwood may be achieved.

(17) Alternative impregnating solutions are disclosed in WO2004/011216 and WO2004/011214 the disclosures of which are incorporated into this specification by reference for all purposes.

(18) FIG. 2 is a diagrammatic view of a drying chamber (10) shown in FIG. 1. The chamber (10) includes nine fans (11) and an air inlet valve (12). An outlet (13) for evaporated water communicates with a condenser (14). A steam inlet (16) delivers steam which optionally may be superheated steam from a boiler (not shown) to supply heating and humidity to the chamber (10). Heat exchangers (17) circulate hot water from a heat exchanger (18) supplied by the steam inlet (19). In this way, dry heat is provided to the chamber as necessary.

(19) A condensate tank (20) serves to collect condensate from the bottom of the tank (10). The condensate is separated in separator (27).

(20) Condensate from the condenser (14) is delivered to measuring tanks (26) for measuring the amount of condensed water vapour. A pump tank (21) delivers the measured condensate to a pump (22) indicated with a water outlet (23) to a condensate storage tank. A gas water separator (24) separates gas from the condensed water. The condensed water is cooled by a heat exchanger (25).

(21) In use of the dryer, steam may be supplied directly to the tank (10) through inlets (16) and dry heat may be supplied by the heat exchangers (17) so that the temperature and humidity within the tank can be independently controlled.

(22) When the impregnated wood or wood articles have been placed within the drying chamber, a pre-vacuum is applied for a short period to remove any air from the chamber in order to prevent a risk of fire or explosion. The pressure during the pre-vacuum period may be up to 0.3 bar due to evaporation of water from the impregnated wood.

(23) The container is then heated to a temperature of about 70 C. over a period of 3-6 hours. During this heating up period the pressure may rise from the pre-vacuum pressure of less than 0.2 bar to between about 0.2 and about 0.4 bar, preferably about 0.3 bar.

(24) This pressure may be maintained for up to 120 hours. During this period the temperature remains approximately constant while the relative humidity decreases. After this drying stage the pressure is allowed to increase to about 1 bar as the temperature is raised to between 100 C. and 110 C. These conditions are maintained until the curing is complete.

(25) The relative humidity may be about 90%.

(26) The conditions within the container are maintained by control of pressure, injection of steam and external heating.

(27) The moisture content of the wood may be monitored by measurement of the amount of water collected from the container. The drying stage may be complete when the moisture content of the wood is about 15% or lower.

(28) After the drying stage is complete the pressure is allowed to rise to about 1 bar and the temperature is increased to about 100 to 140 C. preferably about 100 C. to 120 C. with the relative humidity increasing to about 60 to 80% by addition of steam to the container, in order to prevent cracking or deformation of the wood.

(29) The curing conditions may be maintained for about 6 to 24 hours dependent on the nature of the polymer composition and the thickness of the wood or wooden articles.

(30) When the curing is complete the polymer impregnated wood or wooden articles may be removed from the container for machining, package and distribution.

(31) The drying stage may last for about 120 hours. During this period the temperature is increased from 70 C. to 80 C. During this period the relative humidity decreases to below about 50% and the pressure to about 0.2 bar.

(32) Impregnated timber produced as described above may be cut and machined into boards, lamellas, strips etc. for manufacture of decking.

(33) FIG. 3 illustrates decking in accordance with this invention a substrate (31) composed of glass fibre reinforced polyester has a polyurethane adhesive (33) applied to the upper surface. Strips of polymer impregnated maple (34) are laid side by side upon the adhesive (33) and adhesive (35) is applied between adjacent strips to seal the gaps between the strips. A caulking adhesive (37) may be applied as a second step after completion of gluing of the planks to the support. The adhesive may be applied by vacuum gluing. After gluing, the planks may be sanded.

(34) The strips may have various dimensions for example dimension of 45 by 600 mm and a thickness of 5 mm and are profiled with rebate (38) extending along the long edges to form a channel between adjacent strips to receive a caulking composition (37). Strips of a maximum available length are preferably employed to provide unbroken decking.

(35) The adhesive (33) between the substrate and wood strips is a bedding adhesive selected to securely bond the impregnated wood (34) to the substrate (31). The adhesive (35) may have the same or different composition to the adhesive (33) and is selected to be flexible after curing to accommodate expansion or shrinkage of the wood during use.

(36) The wooden strips are selected so that the annual rings (40) of the strips have an angle (39) to the working surface (36) of the decking. Conventional wood which has not been treated usually has an angle (39) between 60 and 90 selected, to minimize horizontal movement due to swelling and shrinkage. If the annual rings are generally vertical (eg between 60 and 90) the main direction of swelling is vertical (tangentially to the annual ring direction). When using treated wood of the present invention the angle (39) may be selected to any convenient value and is less critical than if untreated wood is used. This allows more economical utilisation of timber resources.

(37) Decking in accordance with this invention does not swell to the same extent as untreated maple. Swelling properties of treated maple in accordance with this invention is similar to teak.

(38) The physical properties of decking in accordance with this invention were determined as described in the following examples:

Example 1

(39) Durability Against Rot

(40) The table below presents results from laboratory tests according to the American soil block method, E-10 (AWPA), for four different fungi and two different treatment levels of furfuryl alcohol. For all fungi the highest treatment level gives mass losses below 15% of the control losses, which corresponds to a high durability.

(41) TABLE-US-00003 E10 on Maple Mean corrected Mass loss (%) Durability Treating Retention Inven- Con- x- Test fungus solution (WPG) (kg/m.sup.3) tion trol value Class Coniophora 28% 22 144 5.4 30.3 0.18 2 puteana furfuryl Poria alcohol 22 144 17.4 47.5 0.37 3 placenta in Irpex lacteus solution 22 144 12.4 38.8 0.32 3 Coriolus 22 144 8.7 31.5 0.28 2 versicolor Coniophora 40% 31 209 2.5 29.2 0.09 1 puteana furfuryl Poria alcohol 31 209 6.6 48.0 0.14 1 placenta Irpex lacteus 31 209 4.6 40.4 0.11 1 Coriolus 31 209 1.0 33.5 0.03 1 versicolor

Example 2

(42) Adhesion Strength

(43) The glue-lines between the impregnated wood and polyester substrate were tested using the European test method EN 314-2. This method is intended for tests for gluing quality of plywood. Before the tests the specimens were divided into three groups pre-treated in three different ways: 1. Conditioning in an atmosphere of 20 C. and 65% relative air humidity. 2. Immersion for 72 hours in boiling water 3. V313-test according to EN 321. The specimens were submitted to a cyclic ageing of 3 days in water 20 C., 1 day in a freezer (12 C.) and 3 days in a heating cabinet 70 C. The cycle was repeated three times.

(44) After the pre-treatment the specimens were tested in tension shear with a constant rate of deformation. The speed was adjusted to get failure at 6030 sec. The maximum load for each specimen was recorded.

(45) FIG. 4 shows the results from tension shear tests of the glue-lines between impregnated wood and polyester. The mean values from 20 specimens were used.

(46) The percentage of wood failures in the specimens was very high, independent of the species or pre-treatment. All results from the tests are presented in FIG. 4.

(47) The sealant between the strips was tested with tension tests. The specimens were made from three ribs glued together with the adhesive sealant. This means that two joints were tested at the same time and the failure load represented the weaker of two glue lines. Also the stress represented the total stress from two joints and thus a conservative estimation of the ultimate stress. Since the tests are comparative between teak which have been proved to work in practice and impregnated Maple this was acceptable.

(48) Before the testing the specimens were submitted to three different pre-treatments: 1. Conditioning in a climate of 20 C. and 65% relative air humidity. 2. Immersion for 2 hours in boiling water 3. Immersion for 72 hours in boiling water

(49) Immersion for 72 hours in boiling water is a pre-treatment for determination of bonding strength for exterior plywood. Immersion for 2 hours in boiling water was selected based on pilot trials since there was a risk of total loss of strength of the sealant after 72 hours in boiling water.

(50) The results are shown in FIGS. 5 and 6.