CA1207952A

CA1207952A - Wood preservative composition

Info

Publication number: CA1207952A
Application number: CA000442340A
Authority: CA
Inventors: Stuart A. Eaton
Original assignee: Cloverdale Paint & Chemicals Ltd
Current assignee: Cloverdale Paint & Chemicals Ltd
Priority date: 1983-12-01
Filing date: 1983-12-01
Publication date: 1986-07-22

Abstract

ABSTRACT OF THE DISCLOSURE
A wood preservative composition comprises a wax, and a biocide dispersed in the wax. Preferably the biocide is selected from the group consisting of (2 thiocyanomethythio) benzothiazole, methylene bis thiocyanate, and 3-iodo-2-propyln butyl carbamate. The biocide is preferably in a weight concentration of bet-ween about .2% to .4%, and further preferably about .2%.
The wax preferably comprises a mixture of paraffin wax and polyethylene wax. Water is also preferably present, with a sufficient amount of amine based soap, preferably a morpholine based soap, so as to maintain the wax/biocide dispersion as an emulsion in the water.

Description

1~0~9S2 WOOD PRESERVATIVE CO~lPOSITION
This invention relates to a wood preservative composltion primarily intended to protect wood from mildew.
A large proportion of cut lumber is treated with a chemical compound to protect against rot and mildew ~which latter term is used to include fungi). For about the past 40 years, sodium penta and tetrach-lorophenates have been used in the lumber industry almost exclusively for the foregoing purpose. However, with the discovery of carcinogenic dioxins in the penta and tetrachlorophenates, it is becoming increasingly unde-sirable to use such compounds.
Aqueous wax emulsions have been also utilized in the past for treating cut lumber, the purpose of such treatment being primarily to coat such lumber with a layer of wax. Such a layer of wax helps the lumber main-tain a clean, bright appearance by repelling water and dirt, thereby keeping the lumber clean and dry par-; 20 ticularly during overland transport. Such compositions exhibit some mildewicide properties, which primarily arise by maintaining the wood dry so as to be less attractive to mildew attack, and by creating a barrier between the wood and spores. However, any such inciden-tal mildew protection offered by such compositions is unsatisfactory for most uses.

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The compound (2 thiocyanomethythio) benzothiazole (which is often abbreviated as T.C.M.T.B.) is a known mildewicide which can be utilized on cut lumber. However, such compound does not produce satis-factory mildew inhibition unless it is at a concentration in the solution in which the lumber is normally dipped, of at least about 1%, and preferably about 2%. Although T~CoM~T~B~ does not have the drawback of sodium penta and tetrachlorophenates as mentioned above, T.C.M.T.B. is considerably more expensive than the latter compounds and at the foregoing concentrations would result in a cost about 10 to 20 times higher, respectively, than suitable amounts of penta and tetrachlorophenates to obtain the same mildewicide effect.
It is desirable then, to have a wood preser-vative composition which can repel water and dirt, while at the same time acting as a mildewicide by virtue of the presence of preferably low concentrations of a suitable biocide (i.e. mildewicide) either than the sodium penta and tetrachlorophenates, and which is not overly expensive.
A wood preservative composition is provided, which comprises a wax, and a biocide dispersed in the wax. The foregoing biocide is usefully selected from the group consisting of (2 Thiocyanomethythio) benzothiazole, methylene bis thiocyanate, and 3-iodo-2-propyln butyl carbamate. Of the foregoing compounds, the (2-thiocyanomethythio) benzothiazole is preferred.
The wax usefully comprises a mixture of paraf-fin wax and polyethylene wax. The composition preferably additionally comprises water in which the wax/biocide dispersion is in turn dispersed, in the form of an emulsion.
Additionally, the composition usefully compri-ses a sufficient amount of an amine based soap so as to maintain the wax biocide dispersion as an emulsion in the water.
Preferably, the amine based soap is selected from the group consisting of morpholine and ethanolamine based soaps (which latter term includes monoethanolamine, diethanolamine, and triethanolamine based soaps). It is further preferred that a sufficient amount of a base be present so as to stabalize the emulsion of the wax/biocide dispersion in the water. Usefully, a defoamer is additionally preferably provided.
A method of producing the foregoing wood pre-servative is also provided, which comprises dispersing a biocide in a hot liquid wax, and adding a soap to the hot liquid wax. Then, the product of the foregoing steps is dispersed in water by adding hot water thereto and mixing, so as to produce an emulsion. A sufficient amount of a base is preferably provided, either before or 1207~5~

after adding of the hot water, so as to produce a com-position with a pH between about 10.4 and 10.6.
It has been found that when water emulsions of wax/biocide dispersions are used to coat cut lumber, a moisture repellancy is obtained as one would expect, but in addition a synergistic mildewicide activity is obtained, the composition as a whole being a more efEec-tive mildewicide -than either a water emulsion of the wax alone at the same concentration, or the biocide alone at the same concentration.
Table 1 below shows the components in a typical wood preservative composition of the present invention:

~Z0~795;2 Item Weight (lbs) Slack wax (i.e. last fraction of paraffin oils and first part of paraffin waxes) 234.87 Polyethylene wax 84.64 PAMAK W4 (a trade mark of Hercules Chemicals Ltd for a mixture of soya fatty acids) 27.27 T.C.M.T.B. 37.45 Caustic flake 3.55 Ethylene glycol 1.23 Morpholene 35.24 Boiling water 548.83 H-10 emulsion ~a trade mark of Dow Coini~g Chemicals for a silicone emulsion type defoamer) .28 NOPCO NDW ( a trade mark of Diamond Shamrock CoO for a mineral oil based emulsion defoamer) .50 TRITON CF-10 ( a trade mark of Rohm and Haas Co for a nonylphenyl surfactant) - 2.34 C888 yellow oxide C (a trade mark of Tenneco Canada Inc. for a water based pigment dispersion) 36.89 The above composition was made by heating and ; 25 mixing together all of the components in the table prior to the water, at a temperature of about 250F to produce a dispersion of the biocide, T.C.M.T.B. in the hot liquid ~LZ~t795~

wax (the word "dispersion" or the corresonding verb "dispersing" being used throughout this application to include the production of a solution or suspension). The boiling water was then added to, and mixed with, the foregoing product so as to produce an emulsion. It should be noted at this point that adding the hot liquid wax composition to boiling water does not produce a satisfactory emulsion. The remainder of the ingredients can be added following addition of the boiling water.
The polyethylene wax is utilized in the above composition in order to harden the overall mixture of the slack wax, which in itself is very soft, and polyethylene wax. During production the T.C.M.T.B. becomes dispersed in the mixture of the hot liquid wax. The soya fatty acids on the other hand react with the morpholene to pro-duce a morpholene based soap which acts as an emulsifier to maintain the wax/biocide dispersion in a water emulsion Eollowing addition of the water. The caustic flake is added so as to result in a final water emulsion which is alkaline so as to maintain the stability of the particular type of emulsion formed. Ethylene glycol is present to act as an anti-freeze in the final water emulsion, although it also acts somewhat as a solvent for the caustic flake when that compound is added prior to the boiling water. The defoamers serve the usual pur-pose, whi~e the TRITON CF-10 surfactant improves colour lZ0795~

acceptance (miscibility) of the pigment C888 yellow oxide C~ or any other pigment used, if any.
Various compositions analogous to that described in Table 1 above have been made and used for treating cut lumber. In particular, the biocide T.C.M.T.B. has been replaced by the biocide 3-iodo-2-propylene butyl carbamate (sometimes referred to in this application as 3-iodo-2-propylon butyl carbamate) sold under the trade mark POLYPHASE (a trade mark of Troy Chemical Co., New York), and methylene bis thiocyanate (often referred to in this application simply as M.B.T.). The weight percentage of the biocide in the above composition is changed simply by changing the weight of it added during production of the composition, with the weight of other components remaining the same.
A number of tests were conducted with cut lumber packages dipped in various mildewicide compositions as well as compositions analogous to that of Table 1 with the only exception being that the amount or type of biocide was varied as noted, and the TRITON CF-10 and C888 yellow oxide C were deleted. All of the lumber packages listed in Table 2 were created by utilizing lumber of mixed grade fir/hemlock two by fours which was purchased directly from a sawmill to ensure against any previous chemical treatment. In each case, the package was bundled in four foot lengths consisting of 16 pieces in rolls four wide. Each bundle was loosely strapped and , ~.

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dipped in the indica-ted solution for a period of one minute while being constantly rotated to avoid air pockets.

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_ckage No. Treatment Solution 1 .8% T.C.M.T.B.

2 1.0% T.C.M.T.B.

3 .8% polyphase (a trade mark of Troy Chemical Co, New York for 3-iodo 2-propyln butyl carbamate)

4 1.0% Polyphase .8~ M.B.T.
6 1.0% M.B.T.
7 .8~ WOOD BRITE 24 (a trade mark for sodium penta chlorophenate) 8 control (no treatment) 9 .015% KATHON (a trade mark of Rohn and Haas Company for 2-n-octyl-4 isothiazoline-3-one) .08% KATHON
11 .7% phenylmercuric acetate 12 Table 1 composition but with no biocide present.
13 Table 1 composition with .2%
T.C.M.T.B.
14 Table 1 composition with .4%
T.C.M.T.B.
Table 1 composition with .2%
polyphase 16 Table 1 composition with .4%
polyphase 17 Table 1 composition with .2%
M.B.T.
: 18 Table 1 composition with .4 M.B.T.

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Each of the above packages were then allowed to dry before being located in a grassy, damp location in Surrey, British Columbia, Canada so that the exterior of the packages were open to the environment. Each package was weighed and inspected prior to exposure for future weight loss calculation purposes. All of the packages were left in position for the same eight month test.
Commencing in February and concluding in October of the same year. Following termination of the tests, each package was opened and independently examined by three inspectors for incidents of sap stain (staining of the wood caused by mildew), mildew growth (which was examined for by both visual and microscopic scanning), and amount of free water remaining inside the package. The packages were categorized in two groups, group I consisting oE
packages 1 through 11, and group II consisting of packa-ges 12 through 18. The packages in each group were given a numerical rating in terms of their relative performance within their respective groups. That is, numbered 11 down to 1 for the best to worst packages in group I, and from 7 down to 1 or the best to worst packages in group II. In addition, each of the packages were assigned total points, which were in each case the weighted sum of points awarded by the inspectors for mildew resistance, stain resistance, weight loss, and water content. In the case of packages in group I, the weighting to establish total points was as follows:

~2079SZ

Mildew resistance 36~
Stain resistance 32%
Weight loss 18%
Water content 14%
With regard to group II, more emphasis was placed on weight loss and water content in establishing the total points, as customers using such a product would have a greater interest in these factors than they would if they were simply using a product of group I, since they would not be using the latter product in any event to inhibit water absorption. The weighting to establish total points in group II was as follows:
Mildew resistance 29%
Stain resistance 26%
Weight loss 26%
Water content 19%
The results obtained from the inspectors were averaged for each parameter, with the final average results being calculated in Table 4 on the following page.

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- lzc)7s~z It will be seen from Table 4 that the com-positions used in the packages of group II, on the average resulted in less absorption of water. In addi-tion though, it will be seen that in the case of each biocide used in the compositions for the packages of group II, far better stain and mildew characteristics are exhibited with the presence of .2% of the biocides indi-cated, then was exhibited with the presence of .8% of corresponding biocides in the compositions of group I, which lacked the presence of the wax. In addition though, it will be seen from Table 4 and bearing in mind the manner in which the weighted total points are calcu-lated, that the effect of combining .2% of the biocides with the remainder of the components of Table 1 in the manner described, produces a synergistic mildewicide effect. It will also be seen from Table 4, that in each of the biocides tested, the presence of .2~ of such biocide produced a better effect in the group II com-positions that did the presence of .4% of the same biocide.
Various alterations to the composition of Table 1, aside from those already mentioned, can be made and still result in a composition which has relatively useful mildewicide properties for cut wood. For example, another soap than that formed between the soya fatty acids and morpholene might be utilized. For example, a ``~'` 120795Z

soap formed between such fatty acids and triethanolamine produced a composition which worked but not as well as that described in Table 1. More fatty acid is necessary when triethanolamine is used to replace morpholene, since the pH of the former is higher. In addition, triethano-lamine is not as volatile as is morpholene, so that any excess triethanolamine does not readily vaporize and leave the composition after applied to lumber.
Morpholene on the other hand is volatile and any excess morpholine relativel~ readily vaporizes and diffuses out of the composition after it is applied to lumber. This is a particular advantage since morpholine and other ami-nes tend to be hydrophyllic to some extent, and the pre-sence of excess amine would tend to increase water absorption which in turn could result in increased mildew.
Diethanolamine in place of morpholine on the other hand, produces a water emulsion in the final pre-servative composition, which composition solidifies.
Monoethanolamine in place of morpholine produced a wood preservative composition emulsion, however such emulsion was heat unstable. Ammoniam h~droxide could also be used to replace morpholine, however due to the temperatures involved, as described in the above process, is difficult to handle and much of the ammonia vaporizes durin~ the process.

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Amino-methyl propanol was substituted for morpholine with some success, but the final preservative composition was in the form of a paste. Such a paste is difficult to break up and indicates a poorer emulsion.
Stearic acid was also utilized, however the final preser-vative composition solidified at room temperature. Some of the above, as well as further emulsifying systems were also attempted as shown below in Table 3. Each com-position in Table 3 was made up the same as that in Table 1, with the exception that the PAMAK W4 (soya fatty acids~ and morpholine were replaced with the amounts of ingredients listed in Table 3. Where the resulting com-position has a performance indicated as "separated", this means that the emulsion separated within a period of 7 days.

~07952 Wt. % Based On Trial Components Used Wax Solids Performance 1 Stearic Acid 20 Gelled Triethanolamine 7.6 2 Soya fatty acids 17.82 Stable but foamed exces-sively q~riethanolamine 23.28 3 REXOL 25 JWCl3.3 Separated Morpholine 19.2 4 INTERWET 332 3 Separated BUTYL CELLoSOLVE3 10 TRITON CF-104 2.0 Gelled on cooling TRITON X-100510.65 6 ATLOX 8404F6) Various Separated 7 PAMAK W_48 12.6 Stable emul-sion Monoethanolamine 17.3 8 PAMAK W_48 12.6 Stable emul-sion Mixed Isopropano- 17.3 lamines 9 TRITON GP-79 ) Separated TRITON N-10110) Various TRITON x-4511 ) 1 REXOL 25 JWC is a trade mark of Hart Chemical Co.
for nonyl phenoxy polyoxethylene ethanol.
2 INTERWET 33 is a trade mark of Interstab Chemicals Ltd. for a nonionic surfactant consisting of nonyl ~5 phenyl polyethoxy ~thanol, containing 68% ethylene oxide by weight.
3 BUTYL CELLOSOLVE is a trade mark is Union Carbide for an ethylene glycol mono butyl ether.

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4,5 TRITON CF-10 and TRITON X-100 are trade marks of Rohm and Haas Co. for respectively, a nonionic alky-laryl polyether and a nonionic isooctyl phenyl polyethoxy ethanal having 9 to 10 moles of ethylene oxide per mole of isooctyl phenyl.
6,7 ATLOX 3404F and ATLOX 3409F are trade marks of Atlast Chemical Company for anionic polyoxethylene derivatives, having respectively a low hydrophyllic lithophillic bonding, and a high hydrophyllic lithophillic bonding.
8 PAMAK W-4 is a trade mark of Hercules Chemicals Ltd.
for a mixture of soya fatty acids.
9,10,11 TRITON GP-7, TRITON N-101 and TRITON X-45 are trade marks of Rohm and Haas Company for respec-tively, an anionic dioct.yl sodium sulfosuccinate, a nonionic nonylphenyl polyethoxy ethanol having 9 to 10 moles of eth~lene oxide per mole of nonyphenyl, and a nonionic isooctyl phenyl polyethoxy ethanol having about 5 moles of ethy-lene oxide per mole of isooctyl phenyl.

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With regard to the pH of the preservative com-position, this can again be varied somewhat although the particular emulsion produced in the composition of Table 1, an alkaline solution is required in order that the emulsion is stable. For the emulsion to be stable for a period of about six to eight months, a pH of at least about 10.4 is required. A pH above about 10.4 would be even more desirable except that when the pH is larger than about 10.6, the wood to which the composition is applied, becomes discoloured. With regard to other variations, it will be noted that ethylene glycol can be omitted if antifreeze is not required, and particularly is the caustic flake is added after addition of the water.
As will be apparent to those skilled in the art in light of the foregoing disclosure, many alterations and rnodifications are possible in the practice of this invention without departing from the spirit or scope thereof. Accordingly, the scope of the invention is to be construed in accordance with the substance defined by the following claims.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are as follows:

1. A wood preservative composition comprising:
(a) a wax; and (b) a biocide dispersed in said wax, said biocide being selected from the group consisting of (2 thiocyanomethythio) benzothiazole and methylene bis thiocyanate.

2. A composition as described in claim 1 wherein said biocide is (2 thiocyanomethythio) benzothiazole.

3. A composition as described in claim 1 wherein said biocide is methylene bis thiocyanate.

4. A composition as described in claim 1 wherein said wax comprises a mixture of paraffin wax and polyethylene wax.

5. A composition as described in claim 2 wherein said wax comprises a mixture of paraffin wax and polyethylene wax.

6. A composition as described in claim 3 wherein said wax comprises a mixture of paraffin wax and polyethylene wax.

- Page 1 of Claims -

7. A composition as described in claim 1, 2 or 3 additionally comprising water in which the wax/biocide dispersion is dispersed in th form of an emulsion, and wherein the weight concentration of said biocide is between about .2% and about .4% wt.

8. A composition as described in claim 4, 5 or 6 additionally comprising water in which the wax/biocide dispersion is dispersed in the form of an emulsion, and wherein the weight concentration of said biocide is between about .2% and about .4% wt.

9. A composition as described in claim 1, 2 or 3 additionally comprising:
(a) water in which the wax/biocide dispersion is dispersed in the form of an emulsion;
and (b) a sufficient amount of an amine based soap so as to maintain the wax/biocide dispersion as an emulsion in said water.

10. A composition as described in claim 4, 5 or 6 additionally comprising:
(a) water in which the wax/biocide dispersion is dispersed in the form of an emulsion;
and - Page 2 of Claims -(b) a sufficient amount of an amine based soap so as to maintain the wax/biocide dispersion as an emulsion in said water.

11. A composition as described in claim 1, 2 or 3 additionally comprising:
(a) water in which the wax/biocide dispersion is dispersed in the form of an emulsion;
and (b) a sufficient amount of an amine based soap so as to maintain the wax/biocide dispersion as an emulsion in said water;
and wherein the weight concentration of said biocide is about .2%.

12. A composition as described in claim 4, 5 or 6 additionally comprising:
(a) water in which the wax/biocide dispersion is dispersed in the form of an emulsion;
and (b) a sufficient amount of an amine based soap so as to maintain the wax/biocide dispersion as an emulsion in said water;
and wherein the weight concentration of said biocide is about .2%.

- Page 3 of Claims -

13. A composition as described in claim 1, 2 or 3 additionally comprising an amine based soap selected from the group consisting of morpholine and ethanolamine based soaps.

14. A composition as described in claim 4, 5 or 6 additionally comprising an amine based soap selected from the group consisting of morpholine and ethanolamine based soaps.

15. A composition as described in claim 2, 5 or 6 additionally comprising:
(a) water in which the wax/biocide dispersion is dispersed in the form of an emulsion;
and (b) a sufficient amount of a morpholine based soap so as to maintain the wax/biocide dispersion as an emulsion in said water;
and wherein the weight concentration of said biocide is about .2%.

16. A composition as described in claim 2, 3 or 5 additionally comprising:
(a) a sufficient amount of a base so as to stabilize an emulsion of the composition in water; and - Page 4 of Claims -(b) an amine based soap selected from the group consisting of morpholine and ethanolamine based soaps.

17. A composition as described in claim 2, 3 or 5 additionally comprising:
(a) a sufficient amount of a base so as to stabilize an emulsion of the composition in water;
(b) an amine based soap selected from the group consisting of morpholine and ethanolamine based soaps; and (c) a sufficient amount of a base such that the pH of the composition is between about 10.4 to 10.6;
and wherein the weight concentration of said biocide is between about .2% to .4%.

18. A composition as described in claim 2, 3 or 5 additionally comprising:
(a) a sufficient amount of a base so as to stabilize an emulsion of the composition in water;
(b) an amine based soap selected from the group consisting of morpholine and ethanolamine based soaps;

- Page 5 of Claims -(c) a sufficient amount of a base such that the pH of the composition is between about 10.4 to 10.6; and (d) a defoamer;
and wherein the weight concentration of said biocide is about .2%.

19. A method of producing a wood preservative composition comprising:
(a) dispersing in a hot liquid wax a biocide selected from the group consisting of (2 thiocyanomethythio) benzothiazole and methylene bis thiocyanate;
(b) adding a soap to the hot liquid wax: and (c) dispersing the product of steps (a) and (b) in water by adding hot water thereto and mixing, so as to produce an emulsion.

20. A method as described in claim 19 wherein said biocide is methylene bis thiocyanate.

21. A method as described in claim 19 wherein said biocide is (2 thiocyanomethythio) benzothiazole.

22. A method as described in claim 19 wherein said wax comprises a mixture of paraffin wax and polyethylene wax.

- Page 6 of Claims -

23. A method as described in claim 21 wherein said wax comprises a mixture of paraffin wax and polyethylene wax.

24. A method as described in claim 19, 20 or 21 wherein the step of dispersing a biocide in the hot liquid wax comprises dispersing a sufficient amount of the biocide therein, so that the weight concentration of the biocide in the preservative composition is about .2%.

25. A method as described in claim 19, 20 or 21 wherein the step of dispersng a biocide in the hot liquid wax comprises dispersing a sufficient amount of the biocide therein, so that the weight concentration of the biocide in the preservative composition is about .2%
and wherein the soap is a morpholine based soap.

26. A method as described in claim 19, 20 or 21 wherein the step of dispersing a biocide in the hot liquid wax comprises dispersing a sufficient amount of the biocide therein, so that the weight concentration of the biocide in the preservative composition is about .2%, and wherein the soap is a morpholine soap, the method additionally comprising adding a sufficient - Page 7 of Claims -amount of a base to produce a composition with a pH
between about 10.4 and 10.6.

- Page 8 of Claims -