GB2025769A

GB2025769A - Wood preservative composition

Info

Publication number: GB2025769A
Application number: GB7917185A
Authority: GB
Original assignee: SANYO WOOD PRESERVING; Sanyo Mokuzai Bofu KK
Current assignee: SANYO WOOD PRESERVING; Sanyo Mokuzai Bofu KK
Priority date: 1978-05-19
Filing date: 1979-05-17
Publication date: 1980-01-30
Also published as: GB2025769B; DE2919792A1; DE2919792C2

Abstract

A wood preservative composition is disclosed which can effectively control termites and woodworms as well as wood destroying fungi. The active ingredient is 2-mercapto- benzothiazole and/or salts thereof, preferably a water-soluble salt thereof. The composition may further contain an antioxidant selected from sulfites, acid sulfites, sulfides, hydrosulfides, hydrazines and thiosemicarbazides. A combination of a sulfite or acid sulfite and a sulfide, hydrosulfide, hydrazine or thiosemicarbazide is the most preferred antioxidant for stabilizing the active ingredient for an extended period of time.

Description

SPECIFICATION Wood preservative composition This invention relates to a wood preservative composition an active ingredient. The compositions are stable with low toxicity and have improved termite and woodworm controlling activity as well as a wood preservative effect.

Wood is an important resource and is used for telephone poles, house pillars and the like. Since wood tends to be rotted by the attack of various wood destroying fungi, it is necessary to treat wood with preservatives so as to prevent wood decay. Wood in the form of structural timbers is in use over a considerable number of years. Therefore, preservatives should be effective in wood for a long period of time. Preservatives are required to be stable with minimal volatility.

'A number of wood preservatives have been widely used which generally comprise organic or inorganic compounds as an active ingredient. For well known wood preservatives, mention may be made of copper-chromium-arsenic systems (to be abbreviated to "CCA", hereinafter), phenol-fluoride systems (to be abbreviated to "PF", hereinafter), pentachlorophenol and its sodium salt (to be abbreviated to "PCP" and "PCP soda", hereinafter), copper sulfate, creosote oil and the like.

Particularly, CCA, PF, PCP soda and copper sulfate are soluble in water. This means that water may be employed as an impregnating medium when wood is impregnated with these preservatives. Unlike organic solvents, the use of water as the impregnating medium is advantageous because water is inexpensive, easy to handle and safe. Creosote oil may be used as wood preservative liquid without dilution.

Although these conventional wood preservatives have sufficiently high preservative effect, they suffer from some disadvantages. The most undesirable disadvantage common to them is that these preservatives are or may provably be pullutive to the environment and deleterious to human health.

Specifically, CCA contains chromium and arsenic which are very harmful to the human body. It is thus necessary to closely monitor the health and working conditions of workers during preservative treatments. Further, a great care is required in disposing of treated timbers. PF contains highly toxic compounds such as sodium fluoride, dinitrophenol, dinitro-o-cresol and other compounds which are reported to be harmful to the human body. PCP and copper sulfate are well known toxic substances.

PCP and copper sulfate as well as dinitrophenol, dinitro-o-cresol and the like are highly injurious to plants and crops. Creosote oil is an ill-smelling contaminant suspected of carcinogenicity. Further, creosote oil treated wood articles cannot be coated with paint. The production and use of such harmful compounds have recently been regulated severely by governments. There have been proposed a number of less toxic organic wood-preservatives containing harmful heavy metals. However, none of these oil-soluble substances have been practically employed. Due to lack of inherent stability, these preservatives fail to satisfy the wood preservation requirements including long life.

There is a need for a water-soluble wood preservative which has a high, long lasting preservation action and causes no problem in view of human health and environmental pollution.

Furthermore, wood is often attacked by woodworms and termites. For the control of woodworms and termites, there have been widely used DDT (p,p'-dichlorodiphenyl trichloroethane), gamma-BHC (benzene hexachloride), dieldrin, PCP (pentachlorophenol), chlordane, borates and the like. Among these, DDT, gamma-BHC, dieldrin and PCP are unacceptably high in acute oral toxicity to rats and have Lid50 of 150, 125, 46 and 146 mg/kg, respectively. Even chlordane which are believed to be relatively safe has an LD50 of 283 mg/kg. Borates are less toxic, but have low termite controlling activity and are readily removed because they are highly soluble in water. Such borates can only be applied to a limited range. There is a need for compositions which are effective to control woodworms and termites, but are benign to the human body.

The inventors have found that 2-mercaptobenzothiazole and its salts have an LD, of about 2,300 mg/kg and show excellent woodworm and termite controlling activity.

According to this invention, there is provided a wood preservative composition with termite and woodworm controlling activity which comprises 2-mercaptobenzothiazole and/or its salts as an adtive ingredient.

In another embodiment of the present invention, the preservative composition comprises a salt, preferably a water-soiuble salt of 2-mercaptobenzothiazole as an active ingredient and an antioxidant, - preferably a water-soluble antioxidant for stabilizing the salt. The antioxidant is selected from the groups consisting of (i) alkali metal, alkaline earth metal and ammonium sulfites and acid alkali metal, alkaline earth metal and ammonium sulfites, (ii) alkali metal, alkaline earth metal and ammonium sulfides and alkali metal, alkaline earth metal and ammonium hydrosulfides, (iii) hydrazines, and (iv) thiosemicarbazides.

In a preferred embodiment of the present invention, the preservative composition contains a combination of two or more antioxidants, one being selected from the above-described group (i) and another being selected from the above-described groups (ii), (iii) and (iv).

The salts of 2-mercaptobenzothiazole used in the present invention include salts of metals, for example, alkali metals such as sodium and potassium, alkaline earth metals such as magnesium and calcium, and other metals such as copper and zinc; ammonium salt; and salts of amines for example, aliphatic amines, such as unsubstituted and substituted alkyl amines, typically 3-methoxy-propyl amine and 2-hydroxyethyl amine. Among these, the alkali metal salts, alkaline earth metal salts, ammonium salt, and amine salts are soluble in water. On the other hand, 2-mercaptobenzothiazole and its salts with metals other than alkali and alkaline earth metals, for example, copper and zinc salts are substantially insoluble in water.

The preferred examples of antioxidants (i) and (ii) are sodium sulfite, potassium sulfite, ammonium sulfite, sodium sulfide and the like. Examples of antioxidant (iii)-are hydrazine, hydrazine hydrate, and salts of hydrazine with maleic acid, tartaric acid and the like. Examples of antioxidant (iv) are thiosemicarbazide and thiosemicarbazide derivatives such as 1-phenyl-4-isopropylidene thiosemicarbazide.

In practicing the present invention, 2-mercaptobenzothiazole and its salts may be in the form of solution, suspension, emulsion, paste or the like by usual preparation processes using water or organic solvents. In the case of the water-soluble salts, solutions may readily be prepared by dissolving the salts in water. For the above-described reason, the water-soluble salts are the most preferred as the active ingredient according to the present invention. However, water-insoluble ingredients, i.e., 2 mercaptobenzothiazole and the other metal salts thereof described above may also be employed in the present invention. These water-insoluble ingredients may be prepared into emulsion using water and suitable surface-active agents.Organic solvents may also be used, for example, methanol, ethanol, isopropyl alcohol, chloroform, dimethylformamide, n-hexane, dioxane, benzene, toluene, ethyl ether and the like.

The composition generally contains 0.1 to 50 weight percent of 2-mercaptobenzothiazole or its salts. The form and concentration of the composition depend upon the solubility of the active ingredient used, wood to be treated, and application method. The preferred amount is 0.1 to 10 weight percent, especially 0.1 to 5 weight percent in pressure impregnating methods whereas 1 to 40 weight percent, especially 1 to 20 weight percent is preferred in brush coating.

The composition of the present invention generally uses water as a carrier for the salt of 2 mercaptobenzothiazole and the antioxidant. The amount of the antioxidant is 0.1 to 50 weight percent, preferably 0.1 to 5 weight percent of the aqueous solution. It is to be noted that the amount of the antioxidant largely depends upon the shelf life of the composition and the duration for which the composition should be kept effective.

It has been found for the wood preservative composition that the salt of 2-mercaptobenzothiazole is rendered highly stable in water in the presence of the antioxidant. The antioxidant serves to keep the salt of 2-mercaptobenzothiazole effective in wood for an extended period of time. The use of two or more of the above-described antioxidants enhances the stability of 2-mercaptobenzothiazole salt in water and in wood because their synergistic effect is obtained.

As far as the inventors know, it is described in the literature that sodium salt of 2 mercaptobenzothiazole is midew-proofing when applied to wood. The inventors have found that the salts of 2-mercaptobenzothiazole in water undergo chemical changes under the influence of light and air, forming a white or yellow-white precipitate of 2,2'-dithio-bisbenzothiazole or similar compounds.

Unlike 2-mercaptobenzothiazole, these precipitates exhibit substantially no wood preservative action.

Since 2-mercaptobenzothiazole chemically changes into 2,2'-dithiobisbenzothiazole, etc. slowly, it is effective to preserve wood and-to control termite and woodworms for a short period of time. However, the use of only 2-mercaptobenzothiazole or its salts is insufficient for protecting wood from wood destroying fungi, woodworms and termite over a number of years.

The use of the antioxidant in the composition of the present invention allows the salts of 2 mercaptobenzothiazole to retain their preservative activity over a long period of time. Therefore, wood treated with the composition of the present invention is protected from the attack of wood destroying fungi, woodworms and termites.

As described above, 2-mercaptobenzothiazoie and salts thereof are low in toxicity to the human being and domestic animals. Further, these compounds are not deleterious to plants or crops. Therefore, the wood preservative composition of the present invention- has a wider application than conventional preservatives which are deleterious to plants and crops. It is also possible to use the composition of the present invention as a soil treating agent.

The composition of the present invention may be prepared by dissolving a water-soluble salt of 2 mercaptobenzothiazole in water. When 2-mercaptobenzothiazole and water-insoluble salts thereof are to be used, the compound may be dispersed in water together with a surface-active agent. Organic solvents may also be used for these water-insoluble compounds.

In the preferred embodiment, a water-soluble antioxidant is mixed with a water-soluble salt of 2 mercaptobenzothiazole or an aqueous solution thereof. Alternatively, the antioxidant is first dissolved in water and then the salt is added thereto. The only requirement is that the final preservative solution contains both the water-soluble salt of 2-mercaptobenzothiazole and the antioxidant in water.

The composition of the present invention may be applied to wood by usual wood treatment methods well known in the art, for example, by dipping, spraying, coating and pressure impregnating method. The preferred application method is the pressure method. Alternatively, the composition may be incorporated into an adhesive which is used for the manufacture of plywood. By blending the preservative composition in the adhesive, plywood which is otherwise susceptible to borer attack may be rendered woodworm- and termite-proof.

Further, the composition of the present invention may include any of known preservatives and termite-controliing agents as well as any additives, if desired.

The following examples are included merely to aid in the understanding of the invention, and variations may be made by one skilled in the art without departing from the spirit and scope of the invention. In the examples, 2-mercaptobenzothiazole is abbreviated to "MBT" and sodium salt of 2mercaptobenzothiazole to "Na-MBT", for example.

EXAMPLE 1 In water were dissolved 22.6 g of sodium 2-mercaptobenzothiazole and then 10 g of sodium sulfite. The resulting solution was further diluted with water to a total volume of 1000 ml.

EXAMPLE 2 In water were dissolved 22.6 g of Na-MBT and then 10 g of hydrazine. The resulting solution was further diluted with water to a total volume of 1000 ml.

EXAMPLE 3 Example 2 was repeated except that sodium sulfide was used instead of hydrazine.

EXAMPLE 4 In water were dissolved 5.5 g of calcium hydroxide and then 20 g of MBT. Heat was applied to facilitate dissolution and salt formation. Thereafter, 10 g of hydrazine was added to the solution which was further diluted with water to a total volume of 1000 ml.

EXAMPLE 5 In water were dissolved 4.4 g of magnesium hydroxide and then 20 g of MBT. Heat was applied to facilitate dissolution and salt formation. Thereafter, 10 g of sodium sulfite was added to the solution which was further diluted with water to a total volume of 1000 ml.

EXAMPLE 6 Example 5 was repeated except that 13 g of 3-methyoxypropylamine was used instead of magnesium hydroxide.

EXAMPLE 7 Example 5 was repeated except that 6.7 g of monoethanolamine was used instead of magnesium hydroxide.

EXAMPLES 8-12 Wood preservative solutions were prepared according to the procedure of Example 1 or 4. The salt of MBT and the antioxidant used are shown in Table I.

STAB I LITY TEST A 200-ml portion of each of the solutions prepared according to Examples 1 to 1 2 was taken into a beaker and allowed to stand at room temperature. Observation was made at suitable intervals to ascertain any deposit.

PRESERVATION EFFECTIVENESS TEST Samples of 2cm x 2cm x 1 cm thick were prepared from Japanese cedar sap wood. Samples were impregnated with each of the solutions prepared according to Examples 1 to 12 and subjected to weathering for two months, (which corresponds to six years under natural conditions), by using a weatherometer of an ultraviolet light carbon-arc type. Thereafter, the samples were subjected to a decay test as prescribed in JIS A 9302. In this decay test, Poria vaporaria was used as a wood destroying fungus.

The results are shown in Table 1.

TABLE 1 Deposition 1) Effective-2) Example Ingredient 2 days 2 weeks 2 months 6 months ness 1 2.26% Na-MBT - - ++ ++++ 98 1% sodium salfite 2 2.26% Na-MBT - - - 98 1% hydrazine 3 2.26% Na-MBT - - - 97 1% sodium sulfide 4 Ca-MBT - - - 95 1% hydrazine 5 Mg-MBT - - - 95 1% sodium sulfite 6 amine-MBT - - - 96 1% sodium sulfite 7 amine-MBT - - - 98 1% sodium sulfide 8 2.26% NaMBT - - +++ ++++ 96 1% potassium sulfite 9 2.26% Na-MBT - - +++ ++++ 93 1% ammonium sulfite 10 2.45% K-MBT - - +++ ++++ 95 1% sodium sulfite 11 2.26% Na-MBT - + ++++ ++++ 88 1% thiosemicarbazide 12 2.26% Na-MBT - + ++++ ++++ 90 0.5% thiosemicarbazide 0.5% hydroxylamine hydrochloride 1) - no deposit + trace amount of deposit ++ minor amount of deposit +++ small amount of deposit ++++ large amount of deposit In Examples 1 and 8 - 12, the duration in the third column is 3 months.

EXAMPLES 1 322 In water was dissolved 22.6 g of Na-MBT. Then, stabilizers (a) and (b) as identified in Table II were added to the solution. Finally, water was further added to give a total volume of 1000 ml.

TABLE II Example Stabilizer (a) Stabilizer (b) 13 sodium sulfite 9 9 hydrazine hydrate 1 g 14 " 8 9 " 2 9 15 " 6 9 " 4 9 16 ,, 5 9 ,, 5 9 17 " 6 9 thiosemicarbazide 4 9 18 " 6 9 hydroxylaminehydrochloride 4 g 19 potassium sulfite 6 g hydrazinomaleic acid 4 g 20 ,, 6 g 1-phenyl-4-isopropylidene thiosemicarbazide 4 g 21 ammonium sulfite 6 g hydrazinotartaric acid 4 9 22 sodium sulfite 6 g thiosemicarbazide 2 9 hydroxylamine hydrochloride 2 9 EXAMPLES 23-26 In water was dissolved 24.5 g of K-MBT. Then stabilizers (a) and (b) as identified in Table III were added to the solution.Finally, water was further added to give a total volume of 1000 ml.

TABLE III Example Srabilizer (a) Stabilizer (b) 23 sodium sulfite 6 g hydrazine hydrate 4 9 24 " thiosemicarbazide 4 9 25 ,, hydroxylamine sulfuric acid 4 9 26 potassium sulfite 6 9 hydrazinotartaric acid 4 g The solutions prepared in Examples 1 3-26 were tested for stability and preservation effectiveness in the same manner as in Examples 1-12. The results are shown in Table IV.

TABLE IV Deposition 1) Example 2 days 2 weeks 3 months 6 months Effectiveness 2) 13-26 - - - - 100 1), 2) See Table I.

EXAMPLES 27-31 Sodium salt, calcium salt, magnesium salt, 3-methoxypropylamine salt, and monoethanol amine salt of MBT were dissolved in 1000 ml of water, respectively. The resulting solutions were tested for stability and preservation effectiveness in the same manner as described in Examples 1-12. The results are shown in Table V.

TABLE V Deposition 1) Example Ingredient 2 days 2 weeks 2 months Effectiveness2) 27 2.26% Na-MBT + +++ ++++ 54 28 2.4Z% Ca-MBT ++ ++++ +*++ 48 29 2.28% Mg-MBT ++ ++++ ++++ 52 30 3.15% amine-MBT ++ ++++ ++++ 67 31 2.71% amine-MBT + +++ ++++ 55 1), 2) See Table I.

EXAMPLE 32 Compositions I to V are prepared by blending MBT or MBT salt with water or an organic solvent and an optional surface-active agent. Formulation is shown in Table VI.

TABLE VI Composition Formulation, weight percent MBT 1 ethanol 99 II Na-MBT 0.2 water 98.8 III Ammonium-MBT 0.5 Water 99.5 IV MBT 5 dimethylformamide 2 surface-active agent 2 water 91 V Zn-MBT 1 ethanol 99 These compositions were tested for woodworm and termite controlling action.

Samples of 3cm x 3cm x 60cm were prepared from black pine sapwood and divided into fdur groups each including 1 0 samples. These groups were treated by the following procedures.

Procedure A: Composition I was applied to wood surface in an amount of 1 50 g/m2.

Procedure B: Composition II was pressure impregnated. Pre-evacuating at 600 mmHg for 30 min., pressurizing at 1 5 kg/cm2 for 3 hours, and post-evacuating at 600 mmHg for 30 min.

Procedure C: Samples were dipped in Composition IV for 3 min.

Procedure D: Composition V was applied to wood surface in an amount of 200 g/m2 and then the samples were air dried for 20 days.

TERMITE ATTACK TEST A field test was carried out by locating these treated samples and untreated samples alternately on a circle having a diameter of 3 m with a nest of a house termite, Coptotermes formosana at a center.

The samples were embedded into the ground for two thirds of their entire length. After one year, the samples were taken out of the ground and examined for the degree of attack. The results are shown in Table VII.

TABLE VII Degree of attack Treatment (average of ten samples) A ;O B O The Invention 0 C D O Dipped in kerosine solution of 2% chlordane for 3 min. 0 Control 3.9 Untreated *0: no attack 1: partial light attack 2: entire light attack 3: entire light attack with partial heavy attack 4: entire heavy attack 5: destroyed WOODWORM TEST Samples of 1cm x 5cm x 1 Ocm were prepared from Japanese oak sapwood and divided into four groups which were treated by Procedures A-D described above. Each sample was placed between two pieces of oak sapwood which were being attacked by a woodworm, Lyctus brunneus.An assembly made of a sample between woodworm attacked pieces was kept under cultivation conditions where the temperature was 27 + 1 OC and the humidity was to + 5%. After two months, the samples were examined for the degree of attack. The results are shown in Table VII I.

TABLE VIII Degree of attack Treatment (average of ten samples) A O B 0 The Invention C O D O Dipped in kerosine solution of 2% chlordane for 3 min 1 0.8 Control Pressure impregnated with aqueous solution of 2% sodium borate 0.9 Untreated 3.3 * See Table VII.

It has been found that Examples 1 to 26 show results superior to those of Examples 27-31 when subjected to the termite and woodworm attack tests.

The water-soluble salts of MBT in admixture with an antioxidant selected from group (i) to (iv) are sufficiently stable with high effectiveness as apparent from Examples 1 to 12. The water-soluble salts of MBT in admixture with a combination of antioxidants (i) and (ii), (iii) or (iv) are highly stable with maximum effectiveness as apparent from Examples 13 to 26.

The use of the MBT salts without any antioxidant is not so preferred in view of stability and preservation effectiveness as shown in Table V. However, Tables VII and VIII evidence that even such relatively less stable salts can provide excellent termite and woodworm control.

Claims

1. A wood preservative with termite and woodworm controlling activity comprising 2mercaptobenzothiazole and/or salts thereof as an active ingredient.

2. A wood preservative composition with termite and woodworrh controlling activity comprising 2-mercaptobenzothiazole and/or salts thereof as an active ingredient and a suitable carrier.

3. The composition of claim 2 wherein said active ingredient is a water-soluble salt of 2mercaptobenzothiazole selected from the group consisting of alkali metal salts, alkaline earth metal salts, ammonium salt and amine salts thereof, and said carrier is water.

4. The composition of claim 2 wherein said active ingredient is 2-mercaptobenzothiazole and said carrier is an organic solvent.

5. The composition of claim 2 wherein said active ingredient is a water-insoluble salt of 2mercaptobenzothiazole and said carrier is an organic solvent.

6. The composition of claim 2 wherein 2-mercaptobenzothiazole is dispersed in water, preferably using a surface-active agent.

7. The composition of claim 2 wherein a water-insoluble salt of 2-mercaptobenzothiazole is dispersed in water, preferably using a surface-active agent.

8. The composition of claim 2 which contains 0.1 to 50% by weight of the active ingredient.

9. A wood preservative composition comprising a water-soluble salt of 2-mercaptobenzothiazole as an active ingredient and a water-soluble antioxidant for stabilizing the salt.

10. The composition of claim 9 which further comprises water as a carrier.

1 The composition of claim 9 wherein said water-soluble salt of 2-mercaptobenzothiazole is selected from the group consisting of alkali metal salts, alkaline earth metal salts, ammonium salt and amine salts of 2-mercaptobenzothiazole.

12. The composition of claim 9 wherein said water-soluble antioxidant is selected from the group consisting of (i) alkali metal, alkaline earth metal and ammonium sulfites and acid alkali metal, alkaline earth metal and ammonium suIfites, (ii) alkali metal, alkaline earth metal and ammonium sulfides and alkali metal, alkaline earth metal and ammonium hydrosulfides, (iii) hydrazines, and (iv) thiosemicarbazides.

13. The composition of claim 10 which contains 0.1 to 50% by weight of the active ingredient and 0.1 to 50% by weight of the antioxidant.

14. The composition of claim 13 wherein the amount of the active ingredient is 0.1 to 20% by weight and the amount of the antioxidant is 0.1 to 5% by weight

15. A wood preservative composition comprising a water-soluble salt of 2-mercaptobenzothiazole as an active ingredient, said salt being selected from the group consisting of alkali metal salts, alkaline earth metal salts, ammonium salt and amine salts of 2-mercaptobenzothiazole, and a water-soluble antioxidant selected from the group consisting of (i) alkali metal, alkaline earth metal and ammonium sulfites and acid alkali metal, alkaline earth metal and ammonium sulfites, (ii) alkali metal, alkaline earth metal and ammonium sulfides and alkali metal, alkaline earth metal and ammonium hydrosulfides, (iii) hydrazines, and (iv) thiosemicarbazides.

1 6. A wood preservative composition comprising a water-soluble salt of 2-mercaptobenzothiazole as an active ingredient, said salt being selected from the group consisting of alkali metal salts, alkaline earth metal salts, ammonium salt and amine salts of 2-mercaptobenzothiazole, and a water-soluble antioxidant which is a combination of (a) at least one compound selected from the group consisting of alkali metal, alkaline earth metal and ammonium sulfites and acid alkali metal, alkaline earth metal and ammonium sulfites, and (b) at least one compound selected from the group consisting of alkali metal, alkaline earth metal and ammonium sulfides, alkali metal, alkaline earth metal and ammonium hydrosulfides, hydrazines, and thiosemicarbazides.

17. A wood preservative composition as claimed in any one of Claims 1,2, 9, 15 and 16 substantially as hereinbefore described with reference to any one of the Examples.