PRESERVATION OF WOOD, COMPOSITIONS AND METHODS THEREOF
The disclosure relates to compositions for wood preservation and methods of applying compositions for wood preservation. The compositions comprise nonionic surfactant mixtures and prepolymer. Compositions of nonionic surfactant mixtures and prepolymers can be used advantageously in methods to preserve wood by impregnation of the wood with preservatives at ambient atmospheric pressures.
This application is a continuation of U.S. application Ser. No. 14/176,339, filed Feb. 10, 2014, which is a continuation of U.S. application Ser. No. 13/142,976 filed Aug. 31, 2011, now U.S. Pat. No. 8,691,340, issued Apr. 8, 2014, which is a National Stage Application of PCT/US2009/069802, filed Dec. 30, 2009, which claims benefit of U.S. Provisional Application Ser. No. 61/141,920, filed Dec. 31, 2008, and which applications are incorporated herein by reference. To the extent appropriate, a claim of priority is made to each of the above disclosed applications.
FIELDThe disclosure relates to compositions for wood preservation and methods for using compositions of wood preservation at low pressures or atmospheric pressures.
BACKGROUNDTreatment of wood to extend serviceable life (preservation) has many applications. Treated wood is used in fence posts, utility poles, residential and commercial decking, railroad ties and the like. Additionally, woods that can be treated range from soft woods, such as for example pine, to hard woods such as for example oak or maple.
Methods used to treat wood can be energy and labor intensive. Presently, wood treatment of only sapwood can require subjecting wood to vacuum, followed by high pressure to impregnate wood with treatment compositions. Pressures in the range of 50-250 psig can be used for preservation of wood. Typically, the use of high pressure for wood treatment requires costly pressure containment vessels, controllers and pumps. Associated maintenance costs of those pressure containment vessels and pumps can be high to assure that the pressure vessels maintain integrity (e.g. do not leak) and thus can hold pressure/vacuum. Furthermore, energy requirements of pumps for evacuation and pressurizing the pressure vessels can be high and costly. U.S. Pat. Nos. 3,968,276 (Allen), 4,399,195 (Allen) and 4,433,031 (Allen) disclose wood treatment compositions and methods, and are incorporated herein by reference in their entirety.
With these requirements in mind, there is a need in the wood treatment industry for lower energy consumption methods and lower equipment and equipment maintenance costs for wood preservative applications.
SUMMARYEmbodiments of the present disclosure relate to a composition comprising a prepolymer and a nonionic surfactant for wood treatment. Further embodiments include a method for treating both sapwood and heartwood using said compositions.
Some embodiments in accordance with the present disclosure include a composition for preserving wood comprising:
a prepolymer comprising from about 4 wt % to about 20 wt % of the total composition; and
a nonionic surfactant mixture comprising alkylpolyglycosides and ethoxylated alcohols from about 0.1 wt % to about 1.0 wt % of the total composition;
wherein the pre-polymer has a weight average molecular weight (MWw) in the range of from about 125 to about 400 such that the pre-polymer impregnates wood with pressures from about ambient atmospheric pressure to about 15 psig.
Other embodiments include a method of preserving wood comprising:
(a) contacting a wood with a solution of a pre-polymer and nonionic surfactant; and
(b) curing the wood that has been contacted with the solution of prepolymer and nonionic surfactant; wherein
the method is conducted from about ambient atmospheric pressure to about 15 psig;
the solution of prepolymer and nonionic surfactant comprises from about 2 wt % to about 20 wt % of prepolymer of the total weight of solution of the prepolymer and nonionic surfactant; and
the curing step comprises heating the wood at temperatures above 25° C.
Composition and methods of the present disclosure allow for reduced energy expenditures for treatment of wood when compared with vacuum/pressure treatment methods presently used in the wood preservation industry. Certain embodiments of the present disclosure require simpler, less expensive equipment for affecting wood preservation, in that vacuum and pressure equipment can be eliminated, replaced for example, by fluid containing vessels and/or spray equipment that are operated at ambient or low pressure (for example, but not limited to 5 psig). Methods of the present disclosure can also reduce the inventory of treated wood on site at wood treatment centers.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTSAs used herein, the following definitions define the stated term:
A “prepolymer” is a composition of relatively low weight average molecular weight (MWw) which can be polymerized to produce a polymer. The prepolymer is typically soluble in water or a suitable solvent. Though not limiting, an example of a prepolymer can be the reaction product of formaldehyde and phenol with a weight average molecular weight (MWw) of from about 125 to about 400.
The term “impregnation” refers to a point in the preservation process of the present disclosure whereby the specific wood being treated can reach a refusal point whereby the wood cannot accept any further material under the given process and composition parameters.
The term “curing” refers to polymerization or crosslinking of a prepolymer by a method that induces polymerization or crosslinking of the pre-polymer. Curing can be induced by a combination of time and temperature for a temperature dependent polymerization system. Curing can induce polymerization with other like prepolymers. Curing can also be polymerization with pre-polymers and other reactive sites, such as reactive sites on cellulose. In some cases, curing can be a combination of polymerization with other like prepolymers and polymerization with reactive sites.
The term “low pressure” refers to process pressures between about atmospheric pressure and about 24 psig.
The term “preservative” refers to any material applied to the wood which can act as an insect repellant, a microorganism repellant, an insecticide, fire retardant, rot retardant, fire-proofing agent, a biocidal agent or combinations thereof.
Prepolymer
The prepolymer for wood preservation can be soluble in a suitable solvent. From an economic perspective and because water can be easily accessible at wood treatment sites, the prepolymer for treatment of wood in some embodiments can be a water soluble prepolymer composition. Solutions of compositions for wood preservation of the present disclosure can contain from about 2.0 wt % to about 20 wt % prepolymer. In other embodiments in accordance with the present disclosure compositions for wood preservation of the present disclosure can contain about 15 wt %, about 12 wt %, about 10 wt %, about 8 wt %, about 6 wt %, about 5 wt %, about 4 wt % or even about 3 wt % prepolymer, depending upon the density of wood being treated, the physical and chemical characteristics of the prepolymer being used and the desired impregnation level of the preservative.
The weight average molecular weight (MWw) of the prepolymer can be adjusted such that when the prepolymer solution contacts the wood to be treated, the prepolymer can impregnate the wood to an effective level to provide desired wood preservation. Generally, prepolymer compositions with low viscosity can be advantageous for ease of use. It can be advantageous in some embodiments of the present disclosure to provide a mixture of prepolymers to achieve a specific outcome, such as for example, but not limited to, preserving green lumber.
In some embodiments the prepolymer can be a condensation prepolymer. Examples of condensation prepolymers in accordance with the present disclosure include, but are not limited to, condensation prepolymers of urea derivatives and formaldehyde. The specific prepolymer resins that can be used include, but are not limited to urea formaldehyde, urea melamine formaldehyde, urea furfural, phenol formaldehyde or mixtures thereof. In other embodiments the prepolymer can be a condensation prepolymer of melamine derivatives and formaldehyde. In yet other embodiments the prepolymer can be a condensation prepolymer of phenolic derivatives and formaldehyde.
In other embodiments, the prepolymer comprises a phenol-formaldehyde prepolymer with a weight average molecular weight (MWw) in the range of from about 125 to about 400. In other embodiments the weight average molecular weight (MWw) can be less than about 350, less than about 300, less than about 250, less than about 200, or even less than about 140.
Nonionic Surfactants
Suitable nonionic surfactants for use in accordance with the present disclosure include alkoxylated surfactants in combination with alkyl polyglycosides. Suitable alkoxylated surfactants include EO/PO copolymers, capped EO/PO copolymers, alcohol alkoxylates, capped alcohol alkoxylates, mixtures thereof, or the like. Suitable alkoxylated surfactants for use as solvents include EO/PO block copolymers, such as the Pluronic and reverse Pluronic surfactants; alcohol alkoxylates, such as “DEHYPON LS-54” (R-(EO)5(PO)4) and DEHYPON LS-36″ (R-(EO)3(PO)6); and capped alcohol alkoxylates, such as “PLURAFAC LF221” and “TEGOTEN EC11”; mixtures thereof, or the like.
Nonionic surfactant mixtures employed in compositions of the present disclosure can be at concentrations higher than those conventionally employed as surfactants. For example, concentrated compositions can include from about 0.01 wt % to about 1.0 wt % of nonionic surfactants. In other embodiments, nonionic surfactant mixtures can include up to about 0.9 wt %, about 0.7 wt %, about 0.5 wt %, about 0.3 wt %, about 0.1 wt %, about 0.08 wt %, about 0.06 wt %, about 0.04 wt %, or even about 0.02 wt % of the composition.
Ethoxylated alcohols useful in some embodiments of the present disclosure include C12-C16 ethoxylated alcohols, “ALEX 12.0”, “ALEX 4.0”, “ALEX 6.0”, “ALFONIC 1216-1.3”, “ALFONIC 1216-22”, “BEROL 175”, “DEHYDROL LSS 5.5”, “ETHONIC 1214-2”, “ETHONIC 1214-6.5”, “GENAPOL 24/50”, “GENAPOL 24L50”, “GENAPOL 26L3”, “GENAPOL 26L80”, “GENAPOL LA 060”, “GENAPOL UD 030S”, “MERPOL HCS” and “NEONOL P 12-16-3.”
In some embodiments of the present disclosure alkylpolyglycosides such as D-glucopyranose, oligomeric, C10-C 16 alkyl glycosides and D-glucopyranose, oligomeric, decyl octyl glycosides (CAS-110615-47-9), linear alcohol alkoxylates (CAS-37251-67-5; 68551-12-2), and pareth 25-7 (CAS-68131-39-5), or mixtures thereof, can be used in surfactant mixtures of the compositions.
Examples of pareth 25-7 can include “ADEKATOL SO 160”, “AE 25-15A”, “AEO 40”, “AEO 9”, “ALFONIC 1012-40”, “ANAPOE C13E8”, “BIO-SOFT EN 600”, “C12-15 PARETH 3”, “C12-15 PARETH-9”, “DOBANOL 25-7”, “DOBANOX 25-7”, “EMERIST 7232”, “EMPILAN KCL 9”, “GENAPOL 26L45”, “GENAPOL LA 050”, “IMBENTIM C 125/094”, “LIALET 125/5”, “MARLIPAL 025/70”, “MULSIFAN RT 203/80”, “NEODOL 25-12”, “NEODOL 25-9” and “NEONOL P 1215-3.”
Additionally, examples of linear alcohol alkoxylates can include 2-methyl oxirane monodecyl ether, methyl oxirane monodecyl ether, ethylene oxide/propylene oxide copolymer monodecyl ether, polyethylene/polypropylene glycol monodecyl ether, “BIODAC 11009”, “BIODAC OP 1”, “EMALEX DAPE 0203”, “EMALEX DAPE 0230”, “ETHOX 1437”, “ETHOX 1449”, “EUSAPON LD 6031”, “FINESURF ELP 1608B”, “LUTENSOL XL 60”, “NOIGEN XL 60” and “PEGNOL D 218.”
Methods of Wood Preservation.
The prepolymer nonionic surfactant composition can be brought into contact with the wood to be treated using many different methods. The prepolymer nonionic surfactant composition can be sprayed onto the wood, dripped onto the wood, curtain-coated on the wood, atomized, sonicated, applied with a reciprocating arm (similar in action to a windshield wiper), wiped, and combinations thereof. In other embodiments of the method of wood treatment using the compositions of the present disclosure, the prepolymer nonionic surfactant compositions can be charged to a tank and the wood to be treated can be submerged in the prepolymer nonionic surfactant composition in the tank to allow intimate contact of the wood with the prepolymer nonionic surfactant composition treatment bath. The treatment bath can be stirred to ensure contact of the prepolymer nonionic surfactant mixture with the wood. The wood to be treated can be submerged in the bath without stirring. Alternatively, the wood to be treated can be partially submerged into the prepolymer nonionic surfactant mixture contacting bath with the wood rotated such that all surfaces of the wood are contacted with prepolymer nonionic surfactant mixture.
The wood treated with prepolymer nonionic surfactant compositions in accordance with the present application can be subjected to low pressure, for example, but not limited to pressures between about atmospheric and about 24 psig. In other embodiments, the treated wood can be subjected to pressures between about atmospheric and about 22 psig, between about atmospheric and about 20 psig, between about atmospheric and about 18 psig, between about atmospheric and about 16 psig, between about atmospheric and about 14 psig, between about atmospheric and about 12 psig, between about atmospheric and about 10 psig, between about atmospheric and about 8 psig, between about atmospheric and about 7 psig, between about atmospheric and about 6 psig, between about atmospheric and about 5 psig, between about atmospheric and about 4 psig, between about atmospheric and about 3 psig, between about atmospheric and about 2 psig or even in some cases between about atmospheric and about 1 psig.
Other methods of contacting wood to be preserved with the prepolymer nonionic surfactant mixture can include, but are not limited to, contacting only a portion of the wood to be treated with the prepolymer nonionic surfactant mixture. In one embodiment, such contact with portions of the wood can include dipping one or both ends of a utility pole or fence post vertically into a bath of prepolymer nonionic surfactant mixture. This method can preferentially treat and preserve the portion of the utility pole or fence post that would be buried and in contact with the ground. This preferential end-dipping application of preservative presents problem to applications that require vacuum and/or pressure, as the vacuum/pressurized treatment systems are horizontally disposed. Dipping the end of very long posts or telephone poles (e.g. 10, 30 or 100 feet long) would require major modifications to the horizontally disposed systems now used that require vacuum and high pressure for wood treatment.
The method of contacting wood to be preserved with the prepolymer nonionic surfactant mixture can be achieved by preparing aqueous solutions of prepolymer nonionic surfactant compositions. Measures can be taken to avoid curing the prepolymer solution or the prepolymer nonionic surfactant mixture composition before contact with the wood to be treated. Such measures include avoiding subjecting the prepolymer solution or the prepolymer nonionic surfactant mixture composition to temperatures over 40° F. for extended periods of time.
Curing
The resulting wood that has been contacted with the prepolymer nonionic surfactant mixture can be cured by a combination of time and temperature which has been chosen to optimize the particular polymer and size of wood being treated. For example, a 6 inch×6 inch fence post would take more time to cure than a 1 inch×6 inch board. This is due to the fact that the fence post is thicker than the board and can absorb more prepolymer, requiring a longer time or higher temperature to cure. The cure time can also be dependent upon the original water content of the wood before contact with the prepolymer mixture.
The treated wood can be cured by directly subjecting the treated wood to steam. In other embodiments, the treated wood can be cured by subjecting the treated wood to heat in an oven. Typically oven temperatures used to cure the treated wood include from about 110° F. to about 140° F. In some instances, the treated wood can be partially cured using steam or heated in an oven, and the remaining uncured treated wood can cure over long periods of time (e.g. days or months) in use at ambient temperature of about 72° F.
In some embodiments, curing the prepolymer nonionic surfactant composition can cause polymerization or crosslinking of the prepolymer composition with itself. For example, but not meant to be limiting, a phenol formaldehyde prepolymer can form a phenolic polymer. In other embodiments, curing can cause polymerization of the composition with sites on the wood which can be susceptible to reaction with the prepolymer. Sites on the wood which can be susceptible to polymerization include, but are not limited to, for example, hydroxyl groups on cellulose that can form ether linkages with the prepolymer or polymerized prepolymer. In yet other embodiments in accordance with the present disclosure curing can cause a combination of polymerization or crosslinking of the prepolymer with itself in combination with reaction of the prepolymer with sites on the wood which can be susceptible to reaction with the prepolymer nonionic surfactant composition.
It may be desirable that in some embodiments cure of the prepolymer nonionic surfactant composition is only partially performed using any of the means described above. The curing can be conducted at the preservation facility such that only a portion of the prepolymer is cured, and the remaining uncured prepolymer will be cured at ambient temperature as the preserved wood is put into use, for example, as a utility pole. This would allow for a shorter cure time at the preservation facility, thus reducing the time required for processing the preserved wood, while still allowing for ultimate full curing at ambient temperature of the preserved wood over a longer period of time once in the end use environment.
Other Benefits
Preserving wood with prepolymer compositions of the present disclosure also imparts dimensional stability, reduces hygroscopicity and gives protection from weathering. In some embodiments preserved wood with prepolymer compositions increases hardness, compression strength and modulus. The preserved wood with cured prepolymer can additionally have increased fastener holding power, such as, for example railroad spikes and other fasteners. Only a minor decrease in tensile strength can be observed in some species of wood. For example, the modulus of elasticity of phenol-formaldehyde treated wood increases from about 35 to about 40%. The rupture of phenol-formaldehyde treated wood increases from about 27 to about 43%, with a tensile strength decrease of only about 10%.
EXAMPLESIn Comparative Examples 1-2 and Example 1, each experiment was conducted using three Southern Yellow Pine (SYP) boards, at approximately 20% moisture content (one board was 1.5 inches thick×15.5 inches long×5.5 inches wide; two boards were 1.5 inches thick×15.5 inches long×3.25 inches wide).
Comparative Example 1To 20 parts by volume of prepolymer solution (phenol-formaldehyde prepolymer solution with 70 wt % solids; weight average molecular weight (MWw) in the range of 140-350 and a viscosity of 110 cps) was added 180 parts by volume of water. The boards were loaded into a pressure tank measuring approximately 2 foot length×1 foot diameter. A sufficient amount of prepolymer solution was added to the tank and boards to completely submerge the boards. The tank was closed and pressurized to 5 psig. After 30 minutes the tank pressure was relieved and the boards were removed and weighed. The dry weight of the prepolymer remaining in the boards was calculated using the theoretical percent solids of the prepolymer solution. The result dry weight for all three boards was 0.346 lbs of prepolymer/ft3 retention.
Comparative Example 2Comparative Example 2 was a duplicate run of the procedure described for Comparative Example 1. The result dry weight for all three boards was 0.355 lbs of prepolymer/ft3 retention.
Example 1The procedure described in Comparative Example 1 was repeated for Example 1, with the exception that 1 part by volume of nonionic surfactant aqueous solution containing deionized water (maximum about 72 wt %), pareth 25-7 (maximum about 22 wt %), linear alcohol ethloxylates (maximum about 9 wt %), “DOWICIL 75®” (maximum about 0.15 wt %), HCl (maximum about 0.05 wt %), butyrated hydroxytoluene (maximum about 0.015 wt %), D & C7 Green #5 (maximum about 0.002 wt %) and methylparaben (maximum about 0.001 wt %) was added to the pre-polymer solution. The result dry weight for all three boards was 0.47 lbs of prepolymer-surfactant/board ft3 retention.
Examples 2-6To 20 parts of prepolymer (phenol-formaldehyde prepolymer solution with 70 wt % solids; weight average molecular weight (MWw)=140-350 and a viscosity of 110 cps) was added 180 parts of water and 1.0 part of nonionic surfactant mixture containing alkylpolyglycoside (between 20-30% wt; CAS #110615-47-9 and CAS #68515-73-1) and ethoxylated alcohol (between 10-15% wt; CAS #68551-12-2), with the remainder being water. Twenty-five boards (green poplar; each board 1 inch×6 inch×16 ft; total of 0.67 ft3) were placed in a steel tank (approximate dimensions of 26 ft.×3.5 ft×3.5 ft). The boards were arranged such that boards designated with lower numbers (for example: Example 2; 4 boards) were closest to the bottom of the tank, with boards designated with higher numbers (for example: Example 6; 5 boards) being closest to the top of the tank. The ensuing prepolymer nonionic surfactant mixture composition was charged to the steel tank, submerging the boards in the prepolymer nonionic surfactant mixture composition. The boards were submerged in the solution for approximately 2 hours at atmospheric pressure. Table 1 lists the average wt % retention of prepolymer per cubic foot of board (on a dry basis).
The procedure described for Examples 2-6 above was used with the exception that the green poplar boards were replaced with debarked southern yellow pine (Air Dried) poles as described in Table 2.
The procedure described for Examples 2-6 above was used with the exception that the green poplar boards were replaced with green, debarked southern yellow pine poles as described in Table 3.
The procedure described for Examples 2-6 above was used with the exception that the green poplar boards were replaced with southern yellow pine boards (air dried) as described in Table 4.
The procedure described for Examples 2-6 above was used with the exception that the green poplar boards were replaced with green railroad ties as described in Table 5.
The procedure described for Examples 2-6 above was used with the exception that the green poplar boards were replaced with green railroad tie side boards as described in Table 6.
Claims
1. A method of preserving wood comprising:
- (a) contacting a wood with a solution of a pre-polymer and nonionic surfactant; and
- (b) curing the wood that has been contacted with the solution of prepolymer and nonionic surfactant; wherein
- the method is conducted from about ambient atmospheric pressure to about 15 psig;
- the solution of prepolymer and nonionic surfactant comprises from about 2 wt % to about 20 wt % of the total weight of solution of the prepolymer and nonionic surfactant;
- the prepolymer is water soluble and capable of impregnating the wood, and
- the curing step comprises heating the wood at temperatures above 25° C.
2. The method of claim 1, wherein the curing step comprises heating the wood at temperatures above 35° C.
3. The method of claim 1, wherein the solution of pre-polymer comprises an aqueous solution of phenol-formaldehyde prepolymer; wherein
- the weight average molecular weight (MWw) of the phenol-formaldehyde prepolymer is in the range of from about 125 to about 400.
4. The method of claim 1, wherein the nonionic surfactant comprises alkylpolyglycosides and ethoxylated alcohols.
5. The method of claim 1, wherein the pre-polymer is a water soluble pre-polymer in aqueous base.
6. The method of claim 1, wherein the method is conducted from about atmospheric pressure to about 10 psig.
7. The method of claim 1, wherein the method is conducted from about atmospheric pressure to about 5 psig.
8. The method of claim 1, wherein the method is conducted from about atmospheric pressure to about 1 psig.
9. The method of claim 1, wherein the solution of pre-polymer and nonionic surfactant comprises in the range from 5 wt % to 10 wt % of prepolymer.
10. The method of claim 1, wherein the solution of pre-polymer and nonionic surfactant comprises in the range from 6 wt % to 8 wt % of prepolymer.
11. The method of claim 1, wherein the wood comprises a utility pole.
12. The method of claim 11, wherein the solution of pre-polymer and nonionic surfactant is applied only to one end or both ends of the utility pole.
13. The method of claim 1, wherein the solution of pre-polymer and nonionic surfactant is applied by at least partially submerging the wood in the solution.
14. The method of claim 1, wherein contacting the wood with the solution of pre-polymer and nonionic surfactant comprises first applying the solution to the wood and then applying a pressure of up to 24 psig to the wood and applied solution.
15. The method of claim 1, wherein the solution of pre-polymer and nonionic surfactant is applied by at least partially submerging the wood in the solution.
16. The method of claim 1, wherein the contacting the wood with the solution of pre-polymer and nonionic surfactant comprises first applying the solution to the wood and then applying a pressure of up to 24 psig to the wood and applied solution.
17. The method of claim 1, wherein the curing comprises a first curing step and a second curing step, wherein during the first curing step the wood is heated to a temperature above 25° C., and during the second curing step the wood is maintained at ambient temperature.
18. The method of claim 1, wherein the curing has a duration of multiple days.
19. The method of claim 1, wherein during the curing some of the prepolymer crosslinks with reaction sites in or on the wood.
20. The method of claim 1, wherein the preserved wood has a modulus of elasticity that is about 35 to about 40% higher than a modulus of elasticity of the wood before preserving.
Type: Application
Filed: Apr 13, 2016
Publication Date: Aug 4, 2016
Inventor: Joseph L. Stark (Minneapolis, MN)
Application Number: 15/097,891
