JPH0337483B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an aqueous wood-suspended wood protection composition in which a micronized solid biocidal active substance is stably dispersed, and even when diluted with water, the biocidal active substance does not settle for a long period of time and maintains a good wood protection effect. The present invention relates to a composition for carrying out. A commonly used method to prevent mold from forming on the surface of sawn wood is to immerse the wood in an aqueous solution containing a fungicide diluted 20 to 200 times as much water for several minutes to several tens of minutes. This is the way to do it. Therefore, the characteristics required of a wood fungicide are that the biocidal active substance is maintained in a stable dispersion state for a long period of time when diluted with a large amount of water; that is, the biocidal active substance does not separate, settle, or One example is that crystal precipitation does not occur. By the way, most of the wood fungicides currently on the market contain 2,4,6-trichlorophenol, pentachlorophenol, 2,4,
6-tribromophenol, 2,4-dichloro-
It is an aqueous preparation in which a halogenated phenol such as 5-bromophenol is dissolved in an alkaline aqueous solution, and this aqueous preparation has an excellent antifungal effect, and
It has the advantage of being cost-effective as it does not require the use of surfactants. On the other hand, in addition to halogenated phenols, there are various biocide active substances that are effective as wood fungicides, but most of them are solids that are insoluble in water, so in order to formulate them, organic solvents are first used. After dissolving in
It is necessary to add a surfactant to provide water dilutability, making it difficult to achieve high concentrations as a formulation; there is a risk that crystals of the biocidal drug substance may precipitate when diluted with water; organic solvents are used; At present, it is hardly put into practical use because it has drawbacks such as being expensive, causing fire danger, and being inhaled toxic to humans and animals. One possible solution to these drawbacks is to formulate an aqueous suspension preparation, which is widely used in the field of agrochemicals and the like. In other words, an aqueous suspension preparation is a preparation in which a water-insoluble solid substance is stably dispersed in water with the help of surfactants, thickeners, protective colloids, etc., and is used as a wood fungicide. Possible water-insoluble solid biocidal drug substances can also be made into aqueous suspension formulations, similar to pesticide drug substances. However, the only problem with aqueous suspension preparations for agricultural chemicals is their stability as a distributed product, and the stability when diluted in water is not so important. It is sufficient that it has enough dispersibility to prevent sedimentation. However, in the case of wood fungicides, the solid biocidal active substance must be stably maintained in a dispersed state for a long period of time after being diluted with water. cannot fulfill its purpose. The present inventors focused on these circumstances and used a biocidal active ingredient for wood protection that is solid at room temperature and substantially water-insoluble, and the biocidal active ingredient remains stable for a long period of time in a dispersed state even when diluted in a large amount of water. Various studies have been carried out in an attempt to develop an aqueous suspension wood protection composition that can maintain the properties of wood. The present invention was completed as a result of such research, and consists of an aqueous suspension wood protection composition in which a biocidal active ingredient for wood protection is dispersed as an active ingredient in an aqueous dispersion medium. The biocide active substance for wood protection is solid at room temperature, has a solubility in the aqueous dispersion medium of 50 ppm or less, and has a true specific gravity and an average particle diameter (unit: μ
The gist is that the product of m) is 0.8 (μm) or less. In order to stably disperse a solid, water-insoluble biocidal substance in water, it is thought to be effective to improve the wetting and dispersion of solid particles using a surfactant, but there are other fundamental problems. It has also been confirmed that the true specific gravity and particle size of the biocidal substance and the specific gravity and viscosity of the dispersion medium are involved as problems. Among these, the specific gravity of the biocide active substance and the specific gravity of the dispersion medium cannot usually be changed, but it is possible to change the particle size of the biocide active substance and the viscosity of the dispersion medium. Therefore, in conventional aqueous suspension preparations, the particle size of the solid drug substance is made as small as possible and the viscosity of the dispersion medium is increased to prevent the biocidal drug particles from settling. However, when this aqueous suspension preparation is diluted with a large amount of water, the viscosity of the dispersion medium (water) becomes approx.
It becomes constant at 1 cp, and the biocidal drug particles, which were stable in the formulation state, quickly settle out. As a countermeasure to prevent sedimentation in this case, a method of reducing the particle size of the biocidal active substance under the above conditions can be considered.
The degree of reduction varies depending on the true specific gravity of the biocidal drug substance, but if it is generally about 0.2 to 0.5 μm, a product that is stable for a long period of time can be obtained even if diluted with water immediately after preparation.
However, depending on the type of biocidal drug substance, the stability of the preparation after long-term storage may be extremely poor when diluted with water. This is thought to be because the biocidal drug substance enlarges over time during storage of the preparation. It was confirmed that this tendency becomes stronger as the solubility of the biocidal substance in water increases. As described above, the stability of an aqueous suspension preparation of a biocidal drug substance when diluted in a large amount of water is significantly dependent on the true specific gravity and particle size of the biocidal drug substance, as well as its solubility in a dispersion medium. In the present invention, as a result of a detailed study of the interrelationship of the above-mentioned factors on the water dispersibility of the biocidal active substance, we found that the solubility in the dispersion medium is 50 ppm or less, and the product of true specific gravity and particle diameter (unit: μm) is 0.8 or less. The present invention was achieved based on the discovery that if a biocidal drug substance that satisfies the above requirements is used, the formulation itself exhibits extremely excellent stability not only when it is diluted with a large amount of water. The main component of the dispersion medium used in the present invention is water, but in addition, surfactants to promote the dispersion of the biocidal substance, alcohols for anti-freezing, Dalaicol, etc. Additives that dissolve the active biocidal substance well are often added, but in the present invention, the type and amount of surfactants and other additives are taken into consideration as long as the solubility of the active biocidal substance does not exceed 50 ppm. Must. The reason for this is that if the above-mentioned solubility exceeds 50 ppm, the biocidal drug substance particles will enlarge during storage of the preparation as described above, and the dispersion stability will decrease when diluted with a large amount of water. Furthermore, since the main component of the dispersant is water, when selecting a suitable biocidal substance, it can be judged that it is preferable if the solubility in water is 50 ppm or less. For example, the body is 2-
Benzimidazole methyl carbamate, 2-
(4'-thiazolyl)benzimidazole, N-1,
Examples include 1,2,2-tetrachloroethylthiotetrahydrophthalimide, tetrachloroisophthalonitrile, and the like, and these can be used alone or in combination of two or more types if necessary. In addition, another characteristic configuration of the present invention is [true specific gravity of biocidal substance x particle diameter (μm)] < 0.8 (μm)
m) is an essential requirement for maintaining good storage stability of the formulation itself and stability when diluted with water; for example, if the true specific gravity of the biocidal drug substance is 2.
If so, then the average particle size must be pulverized to 0.4 μm or less, and if the true specific gravity is 1.5, the average particle size must be pulverized to 0.53 μm or less before use. However, the above product is
If it exceeds 0.8 (μm), the dispersion stability of the preparation when diluted with water decreases, making it impossible to maintain its performance as a wood protection composition for a long period of time. The specific method for producing a wood protection composition that meets the above requirements is not particularly special, and a method similar to the production method for general aqueous suspension preparations can be adopted, for example. A method in which the wood biocidal active substance, which is solid at room temperature, is finely pulverized using a dry grinder such as an air mill or a hammer mill, and then dispersed in water using a surfactant, and the wood biocidal active substance is mixed with the surfactant and water. However, as a general method, it is recommended to finely pulverize the material using a wet pulverizer such as a vibration mill or a sand mill, and then disperse it in water. It is also effective to add an appropriate amount of a thickener, antifoaming agent, antifreeze agent, etc. in the above-mentioned preparation manufacturing process to improve dispersion stability and the like. Furthermore, if necessary, the aqueous suspension preparation according to the present invention may contain a small amount of a water-soluble biocide drug substance such as a halogenated phenol, or a liquid hydrophobic biocide drug substance emulsified and solubilized with a surfactant. can. As mentioned above, surfactants are effective in improving the dispersion stability of formulations and water dilution, but nonionic surfactants (e.g., polyoxyethylene alkyl phenyl ether, polyoxyethylene alkyl ether, polyoxyethylene phenol ether) The best results are obtained when a mixture of anionic surfactants (such as dialkyl sulfosuccinates, condensates of naphthalene sulfonic acid and formalin, polyoxyethylene alkyl allyl ether sulfates, etc.) is used. In addition, thickeners that are particularly effective for increasing dispersion stability during storage of formulations include:
For example, natural products such as guar gum and gum arabic, processed natural products such as sodium carboxymethylcellulose and alkali alginate, and synthetic products such as polyvinyl alcohol and polyvinylpyrrolidone are used. The present invention is constructed as described above, but the key point is that the storage stability of the formulation itself can be improved by appropriately adjusting the solubility of the biocidal raw material for wood in the dispersion medium and the product of true specific gravity and average particle diameter. In addition, the dispersion stability when diluted with water can be dramatically improved, and the performance as a wood preservative can be maintained at a high level for a long period of time. Next, Examples and Comparative Examples will be given to further clarify the effects of the present invention. The biocidal raw materials used in the following experimental examples and comparative examples were all dry-pulverized to 1 to 10 μm. Examples 1 to 3 Polyoxyethylene (20 mol) styryl phenyl ether and dioctyl sulfosuccinate are dissolved in water, and a biocide for wood is added and mixed. The mixing ratio was as follows. Biocidal active substance 30% by weight Polyoxyethylene (20 mol) - styryl phenyl ether 4 Dioctylsulfosuccinate Water Remainder 350 g of this mixture and 1000 g of crushed media (glass beads 1 mm φ) were milled in a pearl mill (90 mm φ x 160 mmh) with an inner capacity of 1. ) and pulverized and mixed at a circumferential speed of 4 m/sec for a predetermined period of time. The biocidal drug substance used and the grinding time were as follows.

[Table] Immediately after preparation of each obtained aqueous suspension, and
The samples stored at 45°C for 30 days were diluted with water, and the degree of sedimentation of the biocidal drug particles was measured. Comparative Examples 1 to 3 The grinding time of the mixture in the above examples was
Aqueous suspension compositions were prepared in the same manner as in Examples 1 to 3, except that BCM was used for 0.5 hours (Comparative Example 1), TBZ was used for 1 hour (Comparative Example 2), and TPN was used for 3 hours (Comparative Example 3). Similarly, the degree of sedimentation of the biocidal drug substance was measured. Comparative Examples 4 to 6 In the formulations of Examples 1 to 3, water was reduced by 5%,
Grinding and mixing were carried out in exactly the same manner except that ethylene glycol monomethyl ether was added instead. Biocidal drug substance 30% by weight Polyoxyethylene (20 mol) - styryl phenyl ether 4 〃 Dioctylsulfosuccinate 1 〃 Ethylene glycol monomethyl ethyl 5 〃 Water Balance Comparative example 4 using BCM as biocidal drug substance
Comparative Example 5 used TBZ and Comparative Example 6 used TPN, and the degree of sedimentation of the biocidal drug substance after dilution with water was similarly examined. Comparative Examples 7 and 8 Aqueous suspensions were prepared in the same manner as in Examples 1 to 3, except that the following biocide drug substance and grinding time were used, and the degree of sedimentation of the biocide drug substance was examined in the same manner. Ta.

[Average particle size of biocidal drug substance]

Particle size distribution analyzer model SA-CP2 (manufactured by Shimadzu Corporation)
Measured in. [True specific gravity of biocidal substance] Measured according to JIS K 0061-78 (Method for measuring specific gravity of chemical products). [Solubility of biocidal drug substance in dispersion medium] Average particle size of 1 to 10 μm in each dispersion medium (100 parts by weight)
Each biocidal active substance (1 part by weight) was added thereto, stirred at 25°C for 24 hours, and then allowed to stand for an additional 24 hours. A portion of this is centrifuged (10,000 RPM, 1 hour), and the concentration of the biocide drug substance in the supernatant is measured, and this is taken as the solubility of the biocide drug substance in the dispersion medium. [Sedimentation degree of biocidal drug substance when diluted with water] 1 part by weight of each of the obtained aqueous suspension compositions was diluted with 300 parts by weight of water, and poured into a 200 ml graduated cylinder with a stopper.
After adding 200 ml and leaving it for 7 days, collect the diluted liquid between the diluted liquid layers (the 100 ml position of the measuring cylinder), measure the concentration of the biocidal substance, and calculate the degree of sedimentation using the following formula. Sedimentation degree (%) = 100 - {Concentration of the biocidal drug substance in the middle part of the diluted solution after standing for 7 days / Concentration of the biocidal drug substance immediately after dilution with water x 100}

【table】

[Table] (A): Immediately prepared product
(B): Product stored at 45℃ for 30 days From the results in Table 1, the following can be considered. Since Examples 1 to 3 all meet all the requirements stipulated by the present invention, the sedimentation degree of the water diluted solution is 5 even when it is immediately prepared or after being stored at 45°C for 30 days. % or less, and excellent dispersion stability has been obtained. In all of Comparative Examples 1 to 3, the biocidal active substance was insufficiently pulverized, and the value of (average particle size x true specific gravity) exceeded 0.8, so the degree of sedimentation of the water diluted solution was low even immediately after preparation. high and poor dispersion stability. Comparative Examples 4 to 8 are comparative examples in which the solubility of the biocide drug substance in the dispersion medium exceeds 50 ppm, and the dispersion stability of the water diluted solution of the product immediately after preparation is good, but the biocide drug substance particles are removed during storage after formulation. It becomes enlarged, and when diluted with water, the dispersion stability becomes extremely poor.

Claims (1)

[Claims] 1 An aqueous suspended wood protection composition comprising a biocide active ingredient for wood protection dispersed as an active ingredient in an aqueous dispersion medium, wherein the biocide active ingredient for wood protection is solid at room temperature and An aqueous suspension wood protection composition having a solubility in an aqueous dispersion medium of 50 ppm or less, and a product of true specific gravity and average particle diameter (unit: μm) of 0.8 (μm) or less.