WO2014064272A1

WO2014064272A1 - Wax-free rodenticidal bait block

Info

Publication number: WO2014064272A1
Application number: PCT/EP2013/072442
Authority: WO
Inventors: Lars Weichel; Roland Stephen TWYDELL; Sharon Hughes; Benjamin CHARNOCK
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2012-10-26
Filing date: 2013-10-25
Publication date: 2014-05-01
Anticipated expiration: 2015-04-26
Also published as: AR093167A1

Abstract

A rodenticidal bait block comprises a foodstuff for the rodent comprising edible seed and/or cereal, at least one rodenticide, and a polymeric binder wherein the polymeric binder comprises a polymer based on an acrylic ester and acrylonitrile and is present in an amount of from 1 to 18% by weight, preferably 1 to 10%, and more preferably from 1 to 5% by weight, based on the total weight of the bait block. The bait block is wax-free and preferred polymeric binders useful in the present invention comprise a polymer based on an alkyl acrylate, acrylonitrile and (meth)acrylic acid. The bait blocks of the invention are highly palatable to rodents, particularly rats, have an adequate hardness and high stability despite the use of only a low content of polymeric binder.

Description

WAX-FREE RODENT1CIDAL BAIT BLOCK

The present invention relates to a wax-free rodenticidal bait block, to method of manufacturing this and to its use in the control of rodents, particularly rats and mice.

Rodent populations, especially those of rats and mice, are controlled principally because of the economic damage they cause. Rats and mice are responsible for large scale food/feed consumption and spoilage and cause structural damage to buildings and other damage resulting from their habits of chewing and digging. Infestations by rats and mice are often controlled by the administration of poison formulations. Bait blocks are often used to avoid the scattering of poisoned bait and because they are generally more resistant to damp or wet conditions.

Rodenticidal block baits have traditionally been manufactured by dispersing feed materials and one or more rodenticides in a hard or semi-sofid wax, typically paraffin wax, binder. The mixture is then moulded or formed into suitably sized and shaped blocks which can be placed in a location close to signs of rodent activity but inaccessible to children and non-target animals or in tamper-proof bait stations.

Rodents have continuously growing incisors and the natural behaviour of rodents is to gnaw hard materials in order to wear down these teeth to keep them short. Conventional wax-based rodent blocks do not have sufficient hardness to satisfy the rodents' natural desire to gnaw.

It has been proposed in the prior art to use binder materials other than wax in the manufacture of bait blocks. GB-A-21 15698 discloses a rodenticidal block bait consisting essentially of brittle-hard polyvinyl acetate, or of a brittle- hard copolymer of vinyl acetate and acrylic acid ester, methacrylic acid ester and/or acrylonitrile, and a foodstuff treated with a rodenticidal poison and dispersed in the polymer carrier. According to the invention disclosed in GB- A-21 15698, the polymer component constitutes 4 to 30% by weight of the block bait and the actual examples described in the document describe baits comprising 20% by weight of polyvinyl acetate, or vinyl acetate/acrylic acid ester copolymer or vinyl acetate/acrylonitrile copolymer. According to GB-A- 21 15698 the block bait has adequate brittle hardness suitable for gnawing and has a high level of patentability.

WO-A-96/03037 discloses a rodenticidal bait in the form of agglomerated granules comprising a cereal base comprising a ground cereal, an anticoagulant rodenticide and water-soluble film-forming binder. The process of manufacture of the rodenticidal bait according to WO-A-96/03037 typically comprises mixing the dry ground cereals with rodenticide and then spraying the mixture with an aqueous solution of the film-forming binder. The wet granular mixture may then be formed into blocks and allowed to dry or, alternatively, may be dried and then mixed with molten fat or wax and then moulded into blocks which are then allowed to cool and solidify. Examples of film-forming binders, according to this document, include cellulose ethers, starch, polyvinyl alcohol, polyvinyl pyrrolidone, various gums such as guar, xanthan and locust bean gum, and polyacrylates although the preferred film- forming binder is said to be hydroxypropyl cellulose.

US-A-2005/0048095 discloses a pesticide consisting of disc-shaped pellets formed from a composition comprising, inter alia, starch and an aqueous dispersion of polyacrylate.

The bait blocks of the prior art and their methods of manufacture are found to suffer from various disadvantages. For instance, in GB-A-21 15698 a large amount, e.g. 20% by weight, of polymer is used to prepare a brittle-hard block. The hardness of the bait blocks in WO-A-96/03037 and in US-A- 2005/0048095 is not discussed. Bait blocks containing wax or fat not only fail to satisfy hardness requirements but also lack stability at elevated temperatures. Also, many of the bait blocks according to the prior art are still not sufficiently palatable to rodents to ensure that they retain an on-going interest in the bait. Furthermore, some processes for manufacturing prior art bait blocks require extended drying times or hardening times and are not sufficiently simple and/or reliable for industrial operation. It is the object of the present invention to provide rodenticidal bait blocks and a method for manufacturing these which overcome the disadvantages of the prior art.

In particular, the present invention provides wax-free bait blocks which contain low amounts of polymeric binder and which have good palatability and hardness properties and which have high temperature stability.

Accordingly, the present invention provides a rodenticidal bait block comprising a foodstuff for the rodent comprising edible seed and/or cereal, at least one rodenticide, and a polymeric binder wherein the polymeric binder comprises a polymer based on an acrylic ester and acrylonitrile and is present in an amount of from 1 to 18% by weight, preferably 1 to 10%, more preferably 1 to 5% by weight, based on the total weight of the bait block.

In an embodiment, the polymeric binder consists essentially of a polymer based on an acrylic ester and acrylonitrile, preferably one based on an alkyl acrylic ester, acrylonitrile and (meth)acrylic acid.

The bait block of the invention does not contain a wax binder. Accordingly, disadvantages noted in the prior art arising from the use of a wax binder are thereby avoided.

It has surprisingly been found that rodenticidal bait blocks according to the invention are highly palatable to rodents, particularly rats, yet and have adequate hardness and high stability despite the use of only a low content of polymeric binder.

The rodenticidal bait block of the present invention comprises a foodstuff for the rodent. The foodstuff contains edible seed or cereal or their mixtures. Examples of edible seeds include poppy seed, sunflower seed and sesame seed. By the term "cereal" we mean the edible grain or seed of crops, generally those of the family Poaceae, that are harvested for their dry grain or seed. Examples of cereals include, but are not limited to, wheat, barley, maize, sorghum, oats, rice, rye, millet and canary seed. Typically the bait block of the invention will contain more than one seed and/or cereal in order to present the rodent with different flavours in the same block. The cereal used in the bait block will be in the form of whole grains or seeds, ground grains or seeds, cut or comminuted grains or seeds and mixtures of these. Examples of cut or comminuted grains include pinhead oatmeal, cut wheat and corn grits. Typically, the bait block of the invention

5 will contain a mixture of whole grain or seed with ground or cut grain or seed in order to present the rodent with a variety of chew and bite textures in the same block. We have found that a mixture of canary seed with cut wheat grains presents the rodent with a mixture of flavours and textures which is sufficiently attractive to the rodent to retain interest.

10 The total content of cereal in the bait blocks is typically from 50 to 99% by weight, preferably from 70 to 98% and more preferably from 80 to 98% by weight.

The bait blocks of the present invention contain at least one rodenticidally-active substance. The rodenticidally-active substance may be i s an anticoagulant rodenticide or a non-anticoagulant rodenticide. Examples of anticoagulant rodenticides that may be used in the bait block of the invention include one or more of difenacoum, brodifacoum, flocoumafen, bromadiolone, difethialone, warfarin, coumatetralyl, chlorophacinone, diphacinone, coumachlor, coumafuryl and pindone. A preferred anticoagulant rodenticide 0 for use in the present invention is difenacoum. Examples of non- anticoagulant rodenticides that may be used in the bait block of the invention include vitamin D, including ergocalciferol (vitamin D₂) or cholecalciferol (vitamin D₃), and alphachlorolose. Preferably the non-anticoagulant rodenticide, if used, is ergocalciferol or cholecalciferol or a mixture thereof.5 Typically, the rodenticidally-active substance used in the bait block of the invention will be selected from difenacoum and vitamin D.

Typically, an anticoagulant rodenticide will be used in the present invention in an amount in the range of from 0.001 to 0.03% by weight, preferably 0.001 to 0.025% and more preferably 0.0025 to 0.025% by weight,0 based on the total weight of the bait block. If the bait block of the present invention contains Vitamin D (cholecalciferol) as the rodenticidally-active substance, this will typically be used in an amount of 500-1 OOOppm (0.05- 0.1 % by weight). The actual amount used will, of course, depend on the identity of the rodenticidally-active substance and on the target species.

In an embodiment of the invention the rodenticidally-active substance is provided, in the bait block, on or in the, or part of the, seed or cereal. It is generally known in the art to use, as a rodent bait, wheat grains or cut wheat grains treated with a rodenticide such as difenacoum. Thus, according to such an embodiment, the seed, grain or cut grain in the bait block is pre- treated with the rodenticidally-active substance prior to incorporation into the block.

It has been shown in WO 2007/031796 that the payability and efficacy of a rodent bait is increased by the presentation to the rodent of a mixture of a plurality of bait particles (i.e. particles containing rodenticide) with a plurality of non-bait particles (particles not containing rodenticide) wherein the non-bait particles have a flavour different from the flavour of the bait particles and wherein the non-bait particles are distinguished from the bait particles by at least one physical characteristic selected from size, shape, surface texture and internal texture. This concept may be utilised in the bait block of the present invention. According to an embodiment of the present invention, therefore, the bait block contains a plurality of bait particles, such as seed or cereal, treated with a rodenticide and a plurality of no n- bait particles, such as seed or cereal, which do not contain rodenticide, wherein the non-bait particles have a flavour different from the flavour of the bait particles and wherein the non-bait particles are distinguished from the bait particles by at least one physical characteristic selected from size, shape, surface texture and internal texture. Particulate rodent bait comprising such a mixture of bait and non-bait particles is available under the name "Fortec™" from BASF pic.

In the bait block of the invention the foodstuff comprising seed and/or cereal is bound together by a polymeric binder. The polymeric binder used in the present invention comprises a copolymer based on an acrylic ester and acrylonitrile. Preferably, the polymeric binder comprises a copolymer based on an acrylic ester, acrylonitrile and (meth)acrylic acid. Typically, the polymeric binder comprises at least 50% by weight of the acrylic ester component, preferably at least 70% and more preferably at least 80% by weight. The acrylonitrile component of the copolymer of the polymeric binder is typically present in an amount not greater than 40% by weight, preferably up to and including 20% and more preferably not greater than 15% by weight. The copolymer of the polymeric binder, as mentioned above, may also comprise (meth)acrylic acid. By the term "(meth)acrylic acid" we mean acrylic acid, methacrylic acid and mixtures thereof. When present, the (meth)acrylic acid component of the copolymer is typically present in the copolymer in an amount of not greater than 20% by weight, preferably not greater than 10% and more preferably not greater than 5% by weight.

In the above-described copolymer of the polymeric binder, the acrylic ester component is preferably a 1 to 12C alkyl ester of acrylic ester, more preferably a 1 to 6C alkyl ester. According to a particularly preferred embodiment of the invention, the acrylic ester component of the copolymer described above is n -butyl acrylate. We have found that particularly good results are obtained using, as the polymeric binder, a copolymer based on about 87% by weight of n-butyl acrylate, about 10% by weight of acrylonitrile and about 3% by weight of acrylic acid.

The polymeric binder, described above, is present in an amount of from 1 to 18% by weight based on the total weight of the bait block, preferably from 1 to 15% and more preferably 1 to 10% by weight. Since, as mentioned above, good hardness and high stability of the bait blocks of the present invention can be achieved using only a low content of polymeric binder, the polymeric binder is present, according to a particularly preferred embodiment of the invention, in an amount of 1 to 5% by weight based on the total weight of the bait block, especially 1 .5 to 4% and more especially 1 .5 to 3.5% by weight.

The bait block may also contain one or more components such as sweetening agents (e.g. sugar), vegetable oil, additional food components, pigments or dyes, flavouring agents, preservatives, taste deterrent (e.g. denatonium benzoate) and release agent (e.g. magnesium stearate). Such additional components are well known to the person skilled in the art. The bait block of the present invention may be manufactured by a process comprising mixing the seed and/or cereal together with the rodenticide and with an aqueous dispersion of the polymeric binder, moulding the mixture into a block and then drying the moulded block.

As mentioned above, in one embodiment the, or part of the, seed or cereal may be pre-treated with the rodenticidally-active substance before being mixed with the aqueous dispersion of the polymeric binder and any other components.

The polymeric binder, as described above, is added in the manufacturing process in the form of an aqueous dispersion. Typically, the aqueous dispersion will have a polymeric binder content (i.e. solids content) in the range of from 50 to 80% by weight, preferably 55 to 70%, more preferably 60 to 65% and most preferably 61 to 63% by weight and a pH in the range of from 5.5 to 6.5.

The aqueous dispersion is typically added in an amount such that final block contains 1 to 8%, preferably 1 to 15%, more preferably 1 to 10%, even more preferably 1 to 5%, especially 1 .5 to 4% and more especially 1.5 to 3.5% by weight of polymeric binder based on the total weight of the bait block. We have found that good results are obtained by the use of 3% by weight (based on the total weight of the formulation) of an aqueous dispersion containing 63% by weight of polymeric binder. Thus, in such a formulation the actual amount of polymeric binder is less than 2% by weight based on the total weight of the formulation.

Conveniently, the aqueous dispersion of the polymeric binder may be mixed with the other components of the bait block formulation in an industrial mixer or blender to ensure that the binder dispersion is distributed homogenously throughout the mixture. Mixers or blenders of this type that may be used in the invention are well known to the person skilled in the art. The mixture, when formed, may be fed to moulds of the desired dimensions or extruded and cut into blocks. The moulded, shaped or formed blocks will then be subjected to drying conditions to remove excess moisture. The drying stage may be carried out at room temperature or may be assisted by the application of heat, if desired.

The present invention further provides a method for controlling rodents which comprises placing a rodenticidal bait block according to any one of claims 1 to 11 in the vicinity of rodent activity.

Example

A wax-free rodenticidal bait block was made using the formulation shown in the table below.

*The Difenacoum was added in the form of cut wheat p retreated with difenacoum.

^**The binder aqueous dispersion is an aqueous dispersion containing 62% by weight of polymer composition comprising 87 wt% n-butyl acrylate, 10 wt% acrylonitrile and 3 wt% acrylic acid, having pH of about 6. The formulation above was mixed thoroughly and then compacted into a prepared mould. The moulded mixture was then removed from the mould and subjected to drying. The bait block, thus produced, possessed integrity and did not crumble or break easily.

Claims

A rodenticidal bait block comprising a foodstuff for the rodent comprising edible seed and/or cereal, at least one rodenticide, and a polymeric binder wherein the polymeric binder comprises a polymer based on an acrylic ester and acrylonitrile and is present in an amount of from 1 to 18% by weight, preferably 1 to 10%, and more preferably from 1 to 5% by weight, based on the total weight of the bait block.

A bait block according to claim 1 , wherein the polymeric binder consists essentially of a polymer based on an acrylic ester and acrylonitrile, preferably a polymer based on an acrylic ester, acrylonitrile and (meth)acrylic acid.

A bait block according to either claim 1 or claim 2, wherein the foodstuff comprises one or more edible seed selected from canary seed, poppy seed, sunflower seed and sesame seed.

A bait block according to any one of claims 1 to 3, wherein the foodstuff comprises one or more cereal selected form wheat, barley, maize, sorghum, oats, rice, rye and millet.

A bait block according to claim 4, wherein the cereal is whole grains or seed, ground grains or seed, cut or comminuted grains or seed or a mixture of any of these.

A bait block according to any one of claims 1 to 5, wherein the rodenticide is present in seed and/or cereal.

A bait block according to claim 6, which contains a plurality of bait particles containing a rodenticide and a plurality of non-bait particles not containing a rodenticide, wherein the non-bait particles have a flavour different from the flavour of the bait particles and wherein the non-bait particles are distinguished from the bait particles by at least one physical characteristic selected from size, shape, surface texture and internal texture.

8. A bait block according to any one of claims 1 to 7, wherein the rodenticide is an anticoagulant rodenticide.

9. A bait block according to claim 8, wherein the rodenticide is difenacoum.

10. A bait block according to any one of claims 1 to 7, wherein the rodenticide is a non-anticoagulant rodenticide.

1 1. A bait block according to claim 10, wherein the rodenticide is vitamin D.

12. A method of making the rodenticidal bait block of any one of claims 1 to 1 1 , comprising the steps of mixing the foodstuff comprising edible seed and/or cereal with the rodenticide and with an aqueous dispersion of the polymeric binder, moulding or shaping the mixture to form a block and then drying the block.

13. A method according to claim 12, wherein the aqueous dispersion of the polymeric binder has a polymer content of 50 to 80% by weight, preferably 55 to 70%, more preferably 60 to 65% and most preferably,

61 to 63% by weight.

14. A method for controlling rodents which comprises placing a rodenticidal bait block according to any one of claims 1 to 1 1 in the vicinity of rodent activity.