GB2276320A - Senko containing silicon carbide - Google Patents

Abstract

A senko, i.e. substance for volatilising an active ingredient by incomplete combustion, contains silicon carbide and shows a high active ingredient volatilisation rate. The active ingredient may be an insecticide or a perfume.

Description

SENKO The present Invention relates to a senko containing silicon carbide and a composition used as a material for the senko.

The term "senko" refers to a substance for volatilizing an active ingredient in the air by incomplete combustion. Usually, specific examples of the senko include an insecticidal senko called a mosquito coil, and a perfume-emitting senko called an incense stick which includes for example a senko for Buddhist mass called a joss stick.

Hitherto, various kinds of senko containing an insecticidal active ingredient or a perfume-emitting active ingredient have been used. Generally, a substantial part of these active ingredients contained in the senko is decomposed by combustion heat and the effectively volatilizing part is limited.

The present invention was made to improve the volatilization rate of the active ingredient in the senko, and it provides a senko containing, perhaps consisting of, silicon carbide and a composition used as a material for the senko.

The senko of the present invention contains silicon carbide usually in the form of a powder, and the content of silicon carbide may be 1 to 30 wt.%, preferably 1 to 20 ',.t of the total weight of the senko. The senko of the present invention comprises other materials commonly used for senko such as organic fillers, binders and additionally pigments and fungistats as necessary.

The active ingredient used in the insecticidal senko for killing flies, mosquitoes, etc., which is generally called a mosquito coil, includes pyrethroid compounds such as pyrethrin, allethrin, prallethrin, benfluthrin (transfluthrin), resmethrin, empenthrin, their active stereoisomers and mixtures of these stereoisomers. The active ingredient used in the perfume-emitting senko includes natural perfumes, synthetic perfumes and the like. The content of these active ingredients is generally 0.01 to 1.0 part by weight of the total weight of the senko.

These active ingredients are mixed with the materials for senko as they are or after formulated into emulsifiable concentrates, oil sprays, microencapsulated formulations, various inclusion complex formulations, etc. and if necessary diluted with a solvent or vegetable oil.

The solvent includes those having a boiling point of 100"C or more and a vapor pressure of 1 mmHg or more at 20"C, which are selected from the group consisting of liquid paraffin, aliphatic hydrocarbons having 10 or more carbon atoms, aromatic hydrocarbons, halogenated hydrocarbons having 3 or more carbon atoms, alcohols and esters having 3 or more carbon atoms.

The vegetable oil includes avocado oil, almond oil, persic oil, coconut oil, palm oil, olive oil, castor oil, peanut oil, rape seed oil, rice bran oil, sesame oil, cotton seed oil, corn oil, soybean oil, tung oil, linseed oil, perilla oil, torreya seed oil, safflower oil, bran oil, kapok oil, spicebush oil, sasanqua oil, tea seed oil, and camellia oil.

A preferred organic filler used as a material for senko includes those emitting little smoke or offensive odor by combustion at relatively low temperatures. It includes for example dry powders of woody parts of juniper, sandal wood, camphor tree, Japanese cedar, willow, Kalopanax pictus, Magnolia hypoleuca, lime tree, orange peel, fir, yellow poplar, Japanese Judas-tree, acacia, poplar, Tilia Miqueliana, Toisusu Urbaniana, Pterocarya rhoifolia, Thuja Standishii, paulownia, Fraxinus Spaethiana, lauan, white birch, citrus fruits, woods for shiitake fungus, etc.; dry powders of plants such as Compositae, Umbelliferae, Gramineae, Meliaceae, Thymelaeaceae, Myrtaceae, Moraceae, Oleaceae, Labiatae, Rubiaceae, Caprifoliaceae and rice chaff; and dry powders of plant extract such as Pyrethrum marc obtained by extraction of Pyrethrum.

These organic fillers may be used in mixture.

The binder used as a material for senko includes natural polymers such as starch, mannan, powdered algae extracts, Hibiscus Manihot powder, gum tragacanth, gum arabic, guar gum, powdered gambier extracts, powdered Machus thunbergii bark-extracts (called a tabu-powaer) and casein; and synthetic polymers such as polyvinyl alcohol, polyacrylamide, sodium polyacrylate, polyethylene oxide, polyvinyl pyrrolidone, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, the salt of carboxymethyl cellulose, the salt of carboxymethyl starch, dialdehyde starch and cationic starch.

These binders may be used in mixture.

The pigment used as a material for senko includes organic pigments (e.g. malachite green), inorganic pigments, dyes and the like. The fungistat used as a material for senko includes acids such as benzoic acid, sorbic acid and dehydroacetic acid and their salts, p-hydroxybenzoic acid esters, salts of propionic acid, o-phenylphenol and the like. These materials may be used in mixture of two or more of them.

The senko of the present invention may be produced by mixing the above materials for senko, kneading the mixture with water, extruding and stamping the kneaded product into optional forms with extruding and stamping machines, and then air-drying the product or drying it with driers.

Embodiments of the present invention will be illustrated more specifically with reference to the following examples, but it is not to be interpreted as being limited thereto.

Production Example 0.09 Part by weight of an emulsifiable concentrate containing prallethrin (pyrethroid insecticidal compound), [which comprises 0.088 part by weight of prallethrin, 0.01 part by weight of Hymal BLZ (a surface active agent produced by Matsumoto Yushi Seiyaku Co., Ltd.), 0.001 part by weight of Hymal 1002Z (a surface active agent produced by Matsumoto Yushi Seiyaku Co., Ltd.) and 0.009 part by weight of Solvesso 150 (a solvent produced by Exxon Chemical Co.)], 10.0 parts by weight of silicon carbide powder, 40.0 parts by weight of Pyrethrum marc, 30.0 parts by weight of tabu powder, 0.3 part by weight of malachite green and 0.2 part by weight of sodium dehydroacetate were mixed together, and the total weight of the mixture was made up to 100 parts by weight with Japanese cedar powder.

A proper amount of water was added to the resulting mixture which was then thoroughly kneaded, extrusionstamped and dried to obtain a mosquito coil.

Comparative Example A mosquito coil was obtained in the same manner as in Production Example except that 50.0 parts by weight of Pyrethrum marc was used in place of 10.0 parts by weight of silicon carbide powder and 40.0 parts by weight of Pyrethrum marc.

Test Example Using the mosquito coils obtained in the Production example and Comparative Example, the volatilization rate of prallethrin as an active ingredient was measured as follows.

The weighed sample is fixed to a senko-holder and burned in a measuring instrument (a wide-mouthed funnel). The smoke emitted by burning is caught by causing silica gel to adsorb the smoke while sucking the smoke by means of a suction pump. Thereafter, the measuring instrument, silica gel, etc. are washed with methanol, and the amount of prallethrin in the methanol washings is determined by gas chromatography.

The results of measurement of the volatilization rate are shown in Table 1.

Table 1

Sample Volatilization rate (t) Production Example 72 Comparative Example 59 The senko of the present invention can efficiently volatilize an active ingredient and may be used in various applications.

Claims (13)

1. A senko comprising silicon carbide.

2. A senko according to Claim 1 which comprises from 1 to 30 wtt silicon carbide.

3. A senko according to Claim 1 or 2, comprising an active ingredient which is an insecticide.

4. A senko according to Claim 3, wherein the active ingredient is a pyrethroid compound.

5. A senko according to Claim 4, wherein the active ingredient is a prallethrin.

6. A senko according to any preceding claim, which is in the form of a mosquito coil.

7. A senko substantially as hereinbefore described with reference to the Example.

8. A composition for producing a senko as claimed in any preceding claim, which composition comprises silicon carbide with an insecticidal active ingredient and/or with a perfume-emitting active ingredient.

9. A composition according to Claim 8 which comprises silicon carbide, an active ingredient, an organic filler and a binder.

10. A composition according to Claim 9, wherein the active ingredient is an insecticide.

11. A composition according to Claim 8 substantially as hereinbefore described with reference to the Example.

12. A method of improving the volatilization rate of an active ingredient in a senko, which method comprises adding an effective amount of silicon carbide to the senko.

13. Use of silicon carbide for improving the volatilization rate of an active ingredient in a senko.