MODIFIED WOOD, MODIFICATION SOLUTION, METHOD OF MODIFICATION AND USE THEREOF

Abstract

Disclosed is a modification solution comprising -furfuryl alcohol; -a diluent; -a fire retardant, and -optionally a stabiliser, wherein the fire retardant comprises: -one or more nitrogen resins; and -phosphoric acid; a method of preparation thereof and wood modified therewith to achieve improve fire retardant and decay properties.

Claims

1. Modification solution comprising a total concentration of furfuryl alcohol of 10-40 weight %; a diluent; and a concentration of fire retardant of 10-40 weight %, wherein the fire retardant comprises: one or more nitrogen resins; and phosphoric acid.

2. Modification solution according to claim 1, wherein the nitrogen resin comprises a formaldehyde reaction product with one or more of melamine, dicyandiamide, guanylurea, trimethylol guanylurea, hexamethylol melamine, ammonia, urea, or a combination thereof.

3. Modification solution according to claim 2, wherein the nitrogen resin comprises a formaldehyde reaction product with melamine and dicyandiamide.

4. Modification solution according to claim 1, wherein at least a part of the furfuryl alcohol and at least a part of the nitrogen resin are in the form of an integrated furfuryl alcohol and nitrogen resin composition comprising oligomerised nitrogen resin dissolved in furfuryl alcohol.

5. Modification solution according to claim 1, wherein the diluent is water, an organic diluent or a mixture of water and an organic diluent.

6. Modification solution according to claim 1, wherein the total concentration of furfuryl alcohol is 10-40 weight-%.

7. Modification solution according to claim 1, wherein the concentration of fire retardant is 15-30 weight-%.

8. Modification solution according to claim 1, wherein the fire retardant consists of 35-50 weight-% phosphoric acid and the remainder up to 100% is one or more nitrogen resins, calculated based on the dry weight of nitrogen resin and phosphoric acid.

9. Method of preparation of a modification solution comprising furfuryl alcohol; a diluent; and a fire retardant, wherein the fire retardant comprises: one or more nitrogen resins; and phosphoric acid, wherein the method comprises a. preparing an integrated furfuryl alcohol and nitrogen resin composition by dissolving a formaldehyde in furfuryl alcohol; adding dicyandiamide to the first composition thereby forming a second composition; adding melamine or a melamine-formaldehyde oligomer to the second composition to form a third composition; and oligomerising the third composition thereby obtaining the integrated furfuryl alcohol and nitrogen resin composition; and b. adding water and phosphoric acid to the integrated furfuryl alcohol and nitrogen resin composition.

10. Method according to claim 9, wherein step c further comprises adding a nitrogen-containing stabilizer.

11. Modified wood characterised by being modified with a polymer formed by the polymerisation in wood of a modification solution comprising a total concentration of furfuryl alcohol of 10-40 weight % and a fire retardant comprising: one or more nitrogen resins; and phosphoric acid.

12. Modified wood according to claim 11, wherein the nitrogen resin comprises a formaldehyde reaction product with at least one of melamine, dicyandiamide, guanylurea, trimethylol guanylurea, hexamethylol melamine, ammonia, urea, or a combination thereof.

13. Modified wood according to claim 11, wherein the modified wood is fire retardant according to EN13823 and ISO 11925-2 and qualifies at least as class B.

14. Modified wood according to claim 11, wherein the modified wood is fire retardant according to EN13823 and ISO 11925-2 and qualifies as class B-s1,d0.

15. Modified wood according to claim 11, wherein the modified wood has a WPG compared to unmodified wood of 10-90%.

16. Method for modification of wood, wherein the method comprises impregnating the wood with a modification solution according to claim 1; optionally applying reduced or increased pressure or a combination thereof, and drying and curing the impregnated wood at a temperature between 60 and 160° C.

17. Method for modification of wood according to claim 16, wherein the drying and curing is performed for 24-170 hours.

18. (canceled)

19. (canceled)

20. A building material or a building product comprising modified wood according to claim 11.

21. Modification solution according to claim 1, further comprising a stabiliser.

22. Method according to claim 9, wherein the method further comprises adding additional furfuryl alcohol.

Description

EXAMPLES

Example 1—Preparation of Modification Solution WDM003.7N-Mix

[0109] A premix resin, or integrated furfuryl alcohol and nitrogen resin composition, was prepared in a batch reactor with reflux cooler and heating system by adding 1906 g of furfuryl alcohol and 256 g paraformaldehyde (solid) to the reactor. The reactor was heated to 100° C. for 120 minutes while stirring, until the paraformaldehyde dissolved and a clear liquid was obtained.

[0110] The reactor was cooled to 95° C. and 832 g water was added. Dicyan diamide was added gradually until the free formaldhyde concentration was reduced to 4.3 wt %, while the temperature was maintained at 95° C. for 80 to 90 minutes. Then, melamine was added gradually until the free formaldehyde concentration was reduced to 2.3%, while the temperature was maintained at 95° C. for 30 minutes.

[0111] The reactor was cooled to 30° C. and NH.sub.3 (24.5%) was added until the pH of the premix resin was between 9 and 10.

[0112] Activated modification solution was prepared in a batch reactor with cooling system. A mix of 142 g water and 224 g of premix resin was stirred at 25° C. until a clear, homogenous mixture was obtained. Slowly, 48 g of phosphoric acid (85%) was added while ensuring the temperature of the mixture did not exceed 35° C. The reaction was complete when no formaldehyde could be detected. The reactor was cooled to 20° C. or less at the end of the reaction.

[0113] The final activated solution, named WDM003.7N-P35, was characterized by a water content of 48%, pH value of 2.6, viscosity of 5 mPas @25° C. by Brookfield, and a solid yield of 32 to 33% at 140° C.

[0114] Optionally, impregnation solutions with different concentrations could be obtained by adding additional water and/or phosphoric acid and/or furfuryl alcohol to the final activated solution.

[0115] The storage stability of the final phosphoric acid activated solution was more than 2 months in which the resin remains an aqueous solution without precipitation. Furthermore, this stability was confirmed by the absence of reduction of acidity as the pH of the mixture gradually increased over a period of 69 days from a pH of 2.6 to 4.2.

Example 2—Preparation of Modification Solution WDM003.7C-Mix

[0116] A premix resin, or integrated furfuryl alcohol and nitrogen resin composition, was prepared in a batch reactor with reflux cooler and heating system by adding 1123 g of furfuryl alcohol and 224 g paraformaldehyde (solid) to the reactor. The reactor was heated to 100° C. for 120 minutes while stirring, until the paraformaldehyde dissolved and a clear liquid was obtained. The reactor was cooled to 95° C. and 490 g water was added. Dicyan diamide was added gradually until the free formaldhyde concentration was reduced to 4 wt %, while the temperature was maintained at 95° C. for 80 to 90 minutes. Melamine was added gradually until the free formaldehyde concentration was reduced to 1.8 wt %, while the temperature was maintained at 95° C. for 30 minutes. The reactor was cooled to 30° C. at a pH level of 7 to 8.

[0117] This premix resin differs from the premix resin of example 1 in that no ammonia is added.

[0118] Activated modification solution was prepared in a batch reactor with cooling system. A mix of 152 g water and 322 g of premix resin was stirred at 25° C. until a clear, homogenous mixture was obtained. Slowly, 38 g of phosphoric acid (85%) was added while ensuring the temperature of the mixture did not exceed 35° C. The reaction was complete when no formaldehyde could be detected. The reactor was cooled to 20° C. or less at the end of the reaction.

[0119] The final activated solution, named WDM003.7C-P30, was characterized by a water content of 48%, a pH value of 3, viscosity of 5 mPas @25° C. by Brookfield, and a solid yield of 36% at 140° C.

[0120] Optionally, impregnation solutions with different concentrations could be obtained by adding additional water and/or phosphoric acid and/or furfuryl alcohol to the final activated solution.

[0121] The storage stability of the premix resin was more than 2 months.

[0122] The storage stability of the phosphoric acid activated solution was about 10-14 days.

Example 3—Polymerisation

[0123] Following the same process as disclosed in example 1, a number of different impregnation mixtures were prepared and polymerised to provide information on the solid yield of each of the compositions. The composition of the dilute solutions in weight-% are provided in the table below. The first three rows disclose the amounts used for the preparation whereas the following four rows disclose the composition of the obtained mixtures. The mixtures were polymerised and dried at 140° C. to obtain the solid yield of each mixture.

TABLE-US-00001 TABLE 1 Composition and solid yield of N mix in weight-%. WDM-N- WDM-N- WDM-N- WDM-N- Code P25 P35 P45 P65 WDM003.7N-premix 62.29 56.48 51.65 44.12 Added H.sub.2O 25.74 32.67 38.42 47.40 Added H.sub.3PO.sub.4 (85%) 11.97 10.85 9.93 8.48 FA 31.15 28.25 25.83 22.07 N resin dry 13.72 12.44 11.37 9.72 Total H.sub.2O 43.16 48.47 52.87 59.74 H.sub.3PO.sub.4 (85%) 11.97 10.85 9.93 8.48 Solid yield 34 32.5 31 27 weight-%

[0124] The term “total H.sub.2O” as used here does not include the water included in H.sub.3PO.sub.4 (85%).

[0125] Similarly the solid yield of an impregnation mixture prepared according to example 2 was tested. A solid yield of 36 weight-% was obtained, with a composition comprising 28.9% furfuryl alcohol, 33.4% N-resin, 29.5% H.sub.2O and 8.2% H.sub.3PO.sub.4 (85%).

Example 4—Impregnation and Modification of Wood

[0126] Impregnation tests have been performed using impregnation solutions prepared according to the methods disclosed in examples 1, 2 and 3. The different N-mix solutions are labeled P25, P35, P45 and P65 corresponding to table 1. The higher label number refers to impregnation solutions containing larger amounts of water.

[0127] Wood

[0128] Scots pine and Radiata pine have been selected for the testing.

[0129] Scots pine (Pinus sylvestris) is sampled from a standard cladding product with a ship lap profile. The cladding had a cross sectional, over-all dimension of 21 mm×148 mm, with two rabbets, one on each side of the longest cross-sectional dimension. Profiling was done before treatment.

[0130] Radiata pine (Pinus radiata) was pre-moulded to an oversized shiplap profile (20×148 mm) before treatment. After treatment the product was once more moulded to the final dimension (19×148 mm). This was done to remove possible surface effects and to simulate claddings, which are profiled after treatment.

[0131] Impregnation Process

[0132] The wood boards were restricted to 2.5 m in length and arranged in the impregnation mixture under increased pressure for a selected duration. The wood was lifted out of the impregnation solution and cured in an oven for the selected duration sufficient to both cure and dry the wood.

[0133] For treatments that aimed at maximum uptake, long pressure times were used. Two different curing temperatures, 120° C. and 140° C. were used.

[0134] The general schedules aimed at maximum uptake used was: [0135] Scots pine: Impregnation pressure 10.5 bar for 20-24 hours, followed by curing at 120° C. or 140° C. for 45-46 hours [0136] Radiata pine: Impregnation pressure 10.5 bar for 5 hours, followed by curing at 120° C. or 140° C. for 43-47 hours

[0137] Impregnation was also performed at other pressures and for shorter time periods, as will be discussed in table 2, below.

[0138] Tests

[0139] Single Burning Item (SBI) EN 13823

[0140] The impregnated boards were cut to 1.5 m lengths for vertical testing and to 1.0 m or 0.5 m for horizontal testing.

[0141] Small Flame Test Samples, EN ISO 11925-2

[0142] 16 boards were randomly selected for this test. These samples were 250 mm long.

[0143] Decay Testing for Natural Durability, DS CEN TS 15083-1

[0144] Samples for this test were small blocks (15×25×50 mm). These were cut out of the treated boards. The test required 30 replicates for each treatment and each fungus. Preconditioning according to EN 84 were conducted before exposure to fungi. Untreated sapwood of Radiata pine and Scots pine was used as control samples.

[0145] Results

[0146] Key numbers from one set of treatments are presented in table 2. N is the number of wood elements treated. Pressure and time are the parameters applied for the impregnation. MC is the moisture content after drying and curing was done at 120° C. for 45 hours.

TABLE-US-00002 TABLE 2 Main test figures. Radiata Pine Scots Pine WDM WDM WDM WDM WDM WDM WDM WDM N-mix N-mix N-mix N-mix N-mix N-mix N-mix N-mix P25 P35 P45 P65 P25 P35 P45 P65 N 11 11 11 11 14 14 14 14 Pressure (bar) 8.0 8.0 8.0 8.0 8.0 8.0 9.0 7.0 Time (hour) 1.0 1.0 1.0 0.8 16.0 16.0 1.5 16.0 Uptake kg/m.sup.3 837.8 802.8 747.8 722.1 308.7 258.9 196.2 270.3 Stdev 18.0 34.4 37.3 47.5 102.9 161.8 78.3 127.7 Uptake (%) 200.3% 193.4% 139.7% 138.1% 65.1% 53.0% 37.0% 53.4% Stdev 14.6% 19.1% 19.0% 21.6% 28.7% 42.3% 14.9% 29.9% MC after cure (%) 3.6% 3.5% 8.2% 6.3% 4.9% 5,.6% 6.3% 6.2% WPG estimate (%) 92.0% 81.7% 47.8% 40.1% 29.7% 22.3% 10.4% 15.1% Stdev 7.4% 8.7% 10.1% 8.4% 14.1% 19.6% 5.0% 10.9% ROF 99.5% 95.1% 99.9% 95.4% 38.9% 33.5% 26.1% 35.1% Stdev 2.2% 3.5% 1.0% 3.2% 11.4% 18.6% 10.6% 15.3% Density (estimate) 420 417 536 520 492 532 534 524 Stdev 25 28 46 46 53 71 41 49 FIGRA (W/s) 9 10 26 25 128 183 113 199 THR (MJ) 1.3 1.4 1.9 2.5 5.3 8.3 7.3 8.3 Fire class B-s1, d0 B-s1, d0 B-s1, d0 B-s1, d0 C-s2, d0 C-s2, d0 B-s2, d0 C-s2, d0

[0147] Treatment of Radiata pine is consistent and straightforward. Uptake is correlated to the void volume of the wood tissue. Ratio of Filling (ROF) is a calculated value describing the actual liquid filling potential. ROF for Radiata pine is close to 100% and the standard deviation is low.

[0148] Impregnation of Scots pine has a large variation in liquid uptake, and the uptake is lower than for Radiata pine. This is mainly caused by variations in heartwood content and possibly raw material density. However, the treatment schedule will also influence the uptake. WDM P45 (table 2) was pressurized for 1.5 hours, compared to the other concentrations that had 16 hours of pressure duration at 8 bars. This difference might explain why the ROF value is only 26.1% for this group. Wood density was similar between the groups. However, WDM P25 had slightly lower density than the other groups and had the highest ROF value of 38.9%.

[0149] All the produced samples were subjected to SBI-tests. An important value is the FIGRA (Fire growth rate), which is presented in table 2. The limit for fire class B is FIGRA≤120 W/s and Total Heat Release (THR)≤7.5 MJ.

[0150] All treated Radiata pine panels passed the criteria for fire class B with a good margin.

[0151] The lowest FIGRA-value for Scots pine was 113 W/s, which is within class B. The FIGRA-values for the other tests were just above the limit for class B (ranging from 128 to 199 W/s) and hence, class C was achieved.

[0152] A further set of tests are presented in table 3. The wood was impregnated with compositions according to example 1 or 2, and the impregnations were aimed at maximum uptake, as discussed above.

[0153] Key values from these treatments and fire tests are summarized in table 3.

[0154] Treatment of Radiata pine with N- and C-mixes resulted in the best fire class achievable; B-s1,d0. The highest recorded FIGRA value was only 48.8 W/s, compared to the classification limit of 120 W/s. This was achieved with an N-mix with 65 parts water added.

[0155] Protection of Scots pine is more difficult than protection of Radiata pine. For Scots pine, the aim was to maximize chemical uptake in all treatments. Panel numbers (#) 11-14 in table 3 achieved fire class B-s2,d0. These panels had an uptake of 507.2 kg/m.sup.3.

[0156] Conclusions from SBI and small flame tests: [0157] Radiata pine, shiplap claddings (19×148 mm) was classified to Euroclass B-s1,d0, when treated with WDM003.7 N P-65 with average liquid uptake of 822 kg/m.sup.3. [0158] Scots pine shiplap cladding (21×148 mm) was classified to Euroclass B-s2,d0, when treated with WDM003.7 N P-35 with average liquid uptake of 507 kg/m.sup.3.

TABLE-US-00003 TABLE 3 Results from all SBI tests Uptake FIGRA THR FIRE Cure # Label N kg/m.sup.3 Uptake % Stdev Direction at SBI (W/s) (MJ) CLASS (° C.) WDM 003.7 N Scots Pine 11 P35 70 507.2 116% .sup. 39% Horizontal 103.9 5.2 B-s2, d0 140 12 Vertical 88 4 B-s1, d0 140 13 Horizontal 66.7 3.7 B-s2, d0 140 14 Horizontal 88.4 5.4 B-s2, d0 140 WDM 003.7 N Radiata Pine 15 P65 70 822 189.8%.sup.  25.7% Horizontal 48.8 2.4 B-s1, d0 140 16 Vertical 22.7 2.1 B-s1, d0 140 17 Horizontal 40.6 1.8 B-s1, d0 140 18 Horizontal 40.3 2.4 B-s1, d0 140 19 P65 70 837 193.7%.sup.  25.8% Horizontal 41.7 2.0 B-s1, d0 120 20 Vertical 14.4 1.8 B-s1, d0 120 21 Horizontal 36.0 1.8 B-s1, d0 120 22 Horizontal 36.0 2.1 B-s1, d0 120 WDM 003.7 C Scots Pine 23 P30 72 339 84.8%  28.1% Horizontal 135.5 6.0 C-s1, d0 140 24 Vertical 145.8 7.9 C-s2, d0 140 WDM 003.7 C Radiata Pine 25 P30 72 851 212% .sup. 34% Horizontal 21.7 1.6 B-s1, d0 140 26 Vertical 6.4 1.3 B-s1, d0 140

[0159] Decay Tests

[0160] Decay tests according to CEN/TS 15083-1:2005 and EN84 showed that a good decay protection was achieved. Samples #11, #15 , #23 and #25 in table 3 were tested with both Coniophora puteana and Poria placenta, and all samples were classified as durability class 1. Reference samples of untreated Radiata pine and Scots pine were classified as class 5, not durable.

[0161] Durability of Reaction to Fire Properties

[0162] Indicative weathering tests have shown that a durable fire-retardant effect is achievable.

[0163] Stability

[0164] The stability of the premix resins and the activated impregnation solutions have been tested. It was found that the premix resins had an acceptable shelf-life at ambient temperature (25° C.) of more than 1 month. The activated solutions remained applicable for impregnation with an acceptable shelf-life of at least 3 weeks at ambient temperature (25° C.). Also, the recyclability of the activated impregnation solutions was tested with acceptable results. This confirmed that the impregnation mixtures will be applicable in industrial processes.