NO129230B - - Google Patents

Description

Pesticide preparation based on a polymeric carrier and a volatile, organic, phosphorus-containing pesticide.

This invention relates to a long-acting pesticide preparation containing a volatile, organic, phosphorus-containing compound, preferably dimethyl-2,2-dichlorovinyl phosphate (hereinafter also

called DDVP) as active ingredient.

It is generally known that the insecticide dimethyl-2,2-dichlorovinyl phosphate is slowly released when it is used together with a thermoplastic carrier, such as polyvinyl chloride, polymethyl methacrylate, etc. When the preparation is exposed to air, a slow release of the insecticide is obtained on the surface of the preparation. However, the initial release rate is relatively high compared to the release rate at the end of a three-month period, and the release of DDVP can be further improved.

When using the new preparations according to the invention, the ratio between the amount by weight of insecticide that is emitted into the atmosphere at the beginning, and the amount by weight that is emitted at the end of the three-month period (hereinafter called exponentiality E), can be reduced considerably, and the cumulative weight loss (KV) from the generator may also be generally higher than with the strip containing DDVP in thermoplastic carriers, and it may also occur that practically all of the DDVP has left the carrier.

It has now surprisingly been found that slow-release properties can be improved considerably by introducing the volatile, phosphorus-containing compound into a heterogeneous, polymeric system having at least 2 polymeric phases.

The invention can be defined as a slow-release pesticide preparation containing a volatile, organic, phosphorus-containing compound and a polymeric carrier. The preparation is characterized by the fact that the carrier is a heterogeneous, polymeric system with at least two polymeric phases, where one phase has a

J- le J» solubility parameter from 8.7 cal 2/ml 2 to 12.0 calml<2> and the

laugh. - The second phase has a solubility parameter below 8.7 calyml<2>

1- J-

or above 12.0 cal 2 /ml 2 , the weight ratio between the two polymeric phases being from 1:9 to 9:1. The values given here for solubility parameters are the calculated ones.

The solubility parameter { £) is defined as the square root of the cohesive energy density, both of which are defined in Journal of Applied Chemistry, Volume 3, (1953), pages 71 ff,

in the article "Some factors affecting the solubility of polymers".

The solubility parameter, cf , is expressed in cal/ml

Table II on page 76 of the aforementioned article shows the calculated and observed solubility parameters for a number of polymers.

This list can be extended with some other polymers, such as:

Since the 8.7 cal^/ml*5 value for the solubility parameter is considered critical for the purpose of determining whether a polymer will belong to the 8.7 cal to 12.0 ca group or not, the values for some polymers must be carefully evaluated.

Polystyrene must be considered to belong to the group of polymers

with a value of 8.7 cal^/ml*5 to 12.0 cal^/ml^. This also applies to polycarbonate (exactly 8.7 cal^/ml^) and neoprene.

The solubility parameter £ for DDVP has been experimentally determined to be approx. 9.0 cal^/mr<5> (calculated 10.3 cal^/ml^). The solubility of DDVP in polymers belonging to the group having an Γ of from 8.7 calVml 2 to 12.0 calVml 5 is generally excellent or good. The solubility of DDVP in other polymers is usually worse and they emit DDVP more quickly.

In general, the carrier system is heterogeneous in that two phases (three-dimensional networks) can be distinguished from each other with respect to differences in their compatibility with DDVP. The theory is that one, the most compatible, phase acts as a reservoir for the pesticide. The reservoir segments are considered to be partially or completely enclosed by the incompatible phase through which the pesticide must diffuse. to reach the surface of the generator. When the rate of diffusion through the highly compatible groundmass is low compared to the poorly compatible phase,

is the very compatible base mass release regulator (at the end of the release period). When, on the other hand, the rate of diffusion through the highly compatible phase is significantly higher than through the poorly compatible phase, the latter regulates the release (especially at the beginning).

The preferred representative compounds of the group

of polymers with an^on from 8.7 cal^/ml<*5> to 12.0 calVml^ are polystyrene, polycarbonate, polymethyl methacrylate, polyvinyl chloride, cellulose acetate and polyvinyl acetate.

To the second group of polymers with an £ below 8.7 calV belong polyethylene, polybutadiene, polyisoprene, cyclorubber, polyisobutene, ethylene-propylene-diene rubber, ethylene-vinyl acetate copolymer and styrene-butadiene rubber.

Preferred carrier systems are: polystyrene/polybutadiene,

polycarbonate/ethylene vinyl acetate copolymer, polystyrene/ethylene vinyl acetate copolymer, polymethyl methacrylate/ethylene vinyl acetate copolymer,

polyvinyl chloride/ethylene-vinyl acetate copolymer, S^B-S/ethylene-vinyl acetate copolymer,

S-B-S/polye tylen and

S-B-S/plasticized polyvinyl chloride.

The ratio between the amount of polymer having a solubility parameter from 8.7 cal*5/ml*5 to 12 cal^/ml35 to the amount of polymer with a solubility parameter below 8.7 cal/ml or above 12.0 cal /ml - , is from 1:;9 to 9:1, preferably from 1:4 to 4:1.

The carrier material is made up of a polymer (or irregular copolymer) with a £-value from 8.7 cal2/ml2 to 12.0 cal^/ml^ and the other ipolymer (or irregular copolymer) with a <f-value below 8 .7 cal Vml or over 12.0 cal /ml. However, the carrier can also be made up of more than 2 polymers (or irregular copolymers), provided that at least one polymer (or irregular copolymer) has a /-value, from 8.7, cal vml 2 to 12 cal 2/ml, and at least one polymer has a / value either below 8.7 cal vml 2 or above 12.0 cal 2 /ml 2 . E.g. the carrier material can be made up of styrene, butadiene and as a third polymer (or irregular copolymer) polyvinyl chloride, polyethylene or ethylene-vinyl acetate copolymer.

In general, a copolymer for this purpose can be considered as one polymer if the copolymer is built up of alternating or irregularly distributed monomer purity r. The copolymer has one ^" value, as is, for example, the case with ethylene-vinyl acetate copolymer. Completely different from the above copolymers are the block copolymers, since these contain long chains of the same units arranged in the molecule in blocks, such as styrene-butadiene-styrene block copolymers or styrene-isoprene-styrene block copolymers In this case, a block copolymer in* connection with the present invention can be considered as if the carrier is made up of 2 polymers.

As will be apparent from the following example VI, particularly favorable E values are achieved when a block copolymer is used, especially together with another polymer such as ethylene-vinyl acetate copolymer, polystyrene, polyethylene, polyvinyl chloride or chlorinated polyethylene. The preferred block copolymer has the general formula

A-B —— (A)0_1( A —-(B -A) 2_5 or A-B (B - A) 2_5 where both groups A are the same or different polymer blocks of a mono-alkenyl-substituted aromatic hydrocarbon, B is a polymer block of a conjugated diene hydrocarbon, and two adjacent polymer blocks B are considered as a single B bilayer, each block A having an average molecular weight in the range from 5,000 to 50,000, and polymer block B having an average molecular weight in the range from 40,000 to 500,000, and the amount of A is in the range from 10 to 65% by weight of the total block copolymer.

The block copolymers consist of blocks of polymeric units, and although the different blocks are chemically bound to each other, they can physically be considered a heterogeneous mixture, since it is possible to detect "islands" of different blocks by X-ray methods.

The block copolymer can have a linear, bundle-like or star-shaped configuration.

In the preferred block copolymers, polymer blocks A have an average molecular weight between 5,000 and 40,000, and polymer block B has an average molecular weight between 50,000 and 200,000, the amount of A being in the range from 10 to 50% by weight of the total block copolymer. Optimally, polymer block B has an average molecular weight between 50,000 and 125,000. The average molecular weights are determined by hplp of the limiting viscosity, osmotic measurements or by labeling with radioactive isotopes. The monomer for producing the polymer end blocks A is preferably styrene. Homologs of styrene can also be used as monomer component, such as alkylated styrene, e.g. alpha-methyl-styrene. The central block B is a polymer block of a conjugated diene hydrocarbon. The diene preferably contains 4 or 5 carbons per molecule, and butadiene is the preferred monomeric component. A preferred block copolymer is polystyrene-polybutadiene-polystyrene (SBS block copolymer).

Block copolymers with an A-B-A configuration can be prepared by sequential preparation of the polymer blocks by means of polymerization of the desired monomer in the presence of a lithium-based catalyst in a hydrocarbon solvent. In this way, a polystyrene-polybutadiene-polystyrene block copolymer can be produced by polymerizing styrene in the presence of butyllithium into a first polystyrene-lithium polymer block. Butadiene is added to the resulting solution of this "living" polymer block, and polymerization continues until a polystyrene-polybutadiene-lithium block copolymer intermediate is formed. The desired polystyrene-polybutadiene-polystyrene is finally obtained by adding the styrene .to the polystyrene-polybutadiene-lithium^block copolymer,.. and the pplymerization is continued..-; u

Und.is application of a coupling process; or; using a secondary function.il. initiator, the block copolymer used in the preparations according to the invention, is produced by means of a two-stage polymerization. ■■,■In the case of a coupling process, a desired end block A is first formed as described above, and the conjugated diene is then polymerized to half the molecular weight desired for the final polymer. In this way, the "living" block copolymer intermediate A-^B is formed, which is then coupled to itself by means of a suitable coupling agent, such as divinylbenzene or a dihaloalkane,

to form the desired block copolymer A-B-A. If a bi-functional initiator, such as dilithium naphthalene, is used, the central block is first formed by polymerization of a conjugated diene to form a polymer block Li-B-Li, which is "living" at both ends, and a vinyl aromatic hydrocarbon is then added, and the block copolymer A-B-A is formed again by means of continued polymerisation. - '-' '

In the preparation of a star-shaped block copolymer

from such monomers as styrene and butadiene, a lithium-terminated block copolymer of the configuration A-B-Li is first formed by polymerization of the relevant monomers in the presence of a lithium-based catalyst in a hydrocarbon solvent, bg the block copolymer- A-B-Li is then reacted with a diester of a monohydric alcohol and a dihydric carboxylic acid as coupling agent. The star-shaped block copolymers are represented by the configuration A-B-(B-A)2

The block copolymers described above can be mixed with another (co)polymer which is completely different from the block copolymers. The block copolymers can preferably be mixed with ethylene-vinyl acetate copolymer, polystyrene, polyethylene or polyvinyl chloride and used as carriers. In particular, S-B-S is mixed with ethylene-vinyl acetate copolymer or with softened polyvinyl chloride. The ratio between the amount of block copolymer and the amount of polyethylene, polyvinyl chloride or ethylene-vinyl acetate copolymer varies from 1:9 to 9:1, preferably from 1:3 to 3:1. If ethylene-vinyl acetate copolymer is used as additional polymer, the amount of vinyl acetate can vary considerably, e.g. from 10 to 75% by weight, preferably from 15 to 60% by weight, of the ethylene-vinyl acetate copolymer.

The amount of volatile, organic, phosphorus-containing compound, preferably DDVP, can vary within wide limits, namely from 5 to 75% by weight of the total preparation, preferably from 10 to 35% by weight of the total preparation.

Preferred compounds are volatile dialkyl vinyl phosphates of the formula

where R = methyl or

ethyl, X is oxygen or sulfur and Y is hydrogen or halogen, and Z is halogen.

The preparations may also contain fillers/oils, colourants, antioxidants, stabilisers, softeners, perfumes or deodorants.

The preparations can be produced by mechanical mixing of DDVP with the carrier, preferably a thermoplastic carrier» Mixing can be carried out by drum treatment of thermoplastic granules and liquid DDVP at room temperature or at a higher temperature.

The preparations can be cast, extruded or otherwise shaped into articles, such as strips, sheets, rods, granules or foam at a temperature of approx. 80°C or higher.

The preparations according to the invention act as generators for vapor phase dimethyl-2.,.2-dichlorovinyl phosphate.

Because of its high vapor pressure (1.2 x 10~^ mm Hg at 20°C), it evaporates from the surface of the preparation into the surrounding atmosphere. Since dimethyl-2, 2-diTorvinyl phosphate is a very active insecticide in the vapor phase, it is only necessary that small quantities be released for the preparations to be very active.

A concentration of 0.02-0.04 micrograms per liter in Tuften is e.g. fatal to insects such as mosquitoes. The preparations serve as long-lasting, continuous generators of fresh, unhydrolyzed insecticide even under conditions of high humidity. The preparations according to the invention discharge very well compared to the release of DDVP in the individual polymers. Depending on the carrier material, the depletion varies from 75 to practically 100% of the original content of DDVP. The preparations are used effectively in houses, warehouses, stables, factories etc. They are also suitable for use as animal collars and animal health preparations.

EXAMPLE 1.

Polymers or copolymers were mixed between two rollers, the softer material being added to the harder. The mixing was carried out for 10 minutes at a temperature of:

150°C for polystyrene-polybutadiene

o x) 170 C for polycarbonate-ethylene-vinyl acetate copolymer 150°C for polystyrene-ethylene-vinyl acetate copolymer 160°C for polymethyl methacrylate-ethylene-vinyl acetate copolymer

or xx)

150 C for polyvinyl chloride-ethylene-vinyl acetate copolymer.

x)'■ The ethylene-vinyl acetate copolymer contained 34% by weight

vinyl acetate and had a melt index condition E, ASTM D 1238-65T of 6 g/10 min.

<xx>^Polyvinyl chloride contained,

100 parts by weight PVC,

40 parts by weight of dioctyl adipate,

5 parts by weight of Ba-Cd stearate,

2.5 parts by weight organic phosphite.

The resulting sheets were granulated into particles with a diameter of 2 to 4 mm and soaked in dimethyl-2,2-dichloro-vinyl phosphate. The wet-through was carried out by drum treatment of granules and liquid dimethyl-2,2-dichlorovinyl phosphate for 24 hours at room temperature. A dry granule containing 20% by weight of dimethyl-2,2-dichlorovinyl phosphate was obtained.

The dry granules were homogenized in a masticator

for 12 minutes at a temperature 20°C below the above-mentioned roll temperature.

Strips were then made by pressurization, using a mold which had a temperature of 100°C and was under pressure, and the mold was cooled before being opened.

The die-cast strips (25 x 6.4 x 0.6 cm) had

a total weight of approx. 100 g and contained 20% by weight of dimethyl-2,2-dichlorovinyl phosphate.

The release rate of the samples was determined by weight loss measurements. The samples were freely suspended in a metal chamber with a cross section of 1.4 x 1.7 meters and a height of 1 meter

(volume approx. 2 cubic metres). An air current, which was even

distributed over the horizontal cross-section of this chamber, was introduced at the top of the chamber and exited at the bottom. The air flow consisted of fresh Tuft, regulated to a temperature of 23 ± 1°C and a relative humidity of 60 ± 5%. The volume of air passed through the chamber was T500 cubic meters per hour.

The values E and KV for the different strips are given below. The strips were treated for 90 days.

Strips containing dimethyl-2,2-dichlorovinyl phosphate as an insecticide and a styrene-butadiene-styrene block copolymer are prepared by first mixing liquid dimethyl-2,2-dichlorovinyl phosphate with styrene-butadiene-styrene (molecular weight 14,000-64,000-14,000) block copolymer powder in a weight ratio of 1:4. After 1% hour at 40°C, the liquid dimethyl-2,2-dichlorovinyl phosphate is absorbed into the powdery block copolymer, and stamps are then made by compression molding at 100°C . Elastic strips containing 20% by weight of dimethyl-2,2-dichlorovinyl phosphate are obtained. The die-cast strips (25 x 6.4 x 0.6 cm) had a total weight of approx. 100 g and contained 20 g of dimethyl-2,2-dichlorovinyl phosphate.

In the same way, strips containing styrene-butadiene-styrene block copolymer with different molecular weights for the blocks were made. A strip was made which, as a carrier for dimethyl-2,2-dichlorovinyl phosphate, contained a styrene-butadiene-styrene block copolymer with blocks with molecular weights 14,000 - 53,000 - 14,000 (total molecular weight 81,000) and with blocks with molecular weights 22,000 - 44,000 - 22,000 (total molecular weight 88,000) .

After 90 days of treatment in a ventilated room (at 23°C and 60% relative humidity), the weight loss in grams for the three different rubber strips was compared to the commercial strip with softened polyvinyl chloride.

The following results were obtained:

EXAMPLE III

An SBS-based strip and a polyvinyl chloride-based strip of the same thickness (0.6 cm) were examined to find the time at which dripping first occurs when treated at 28°C and 6CP/0 relative humidity.

The following results were obtained:

The above strip had the following composition:

EXAMPLE IV

Styrene-butadiene-styrene (S-B-S) block copolymer and ethylene-vinyl acetate copolymer were mixed between two rollers. Mixing was carried out for .10 minutes at a temperature of 160°C.

The S-B-S block copolymer had the following composition:

The ethylene-vinyl acetate copolymer contained 34% vinyl acetate by weight and had a melt index of 6 g/10 min. (condition E, ASTM p 1238-65T).

The resulting sheets were granulated into particles with a diameter of 2 - 4 mm and soaked in dimethyl-2,2-dichlorovinyl phosphate. The thorough moistening was carried out by drum treatment of granules and liquid dimethyl-2,2-dichlorovinyl phosphate for 24 hours at room temperature. A dry granule containing 20% by weight of dimethyl-2,2-dichlorovinyl phosphate was obtained.

The dry granules were homogenized in a masticator

1 12 minutes at a temperature of 140°C.

Strips were then made by compression molding using a mold at a temperature of 100°C and under pressure. The pressure-molded strips (thickness 1 cm) had a total weight of

of approx. 100 g and contained 20% by weight of dimethyl-2,2-dichlorovinyl phosphate.

The release rate of the sample was determined by weight loss measurements. The samples were freely suspended in a metal chamber with a cross-section of 1.4" x 1.7 m and a height of 1 m (volume approx. 2 cubic meters). An air stream, evenly distributed over the horizontal cross-section of the chamber, was introduced at the top of the chamber and led out at the bottom. The air flow consisted of fresh air, regulated to a temperature of 23 ± 1°C and a relative humidity of 60 ± 5%. The volume of air passing through the chamber was 1500 cubic meters per hour.

S-B-S/ ethylene-vinyl acetate copolymer as carrier

was compared with S-B-S (containing naphthenic oil, inorganic filler and antioxidant as mentioned above) and with ethylene-vinyl acetate copolymer.

EXAMPLE V

In the same manner as indicated in Example IV, strips containing a mixture of S-B-S block copolymer and polyvinyl chloride as carrier were made and examined.

The S-B-S block copolymer had molecular weights of 22,000 - 44,000 - 22,000. In one of the experiments it was used in mixed form (as in example IV) and in another experiment it was used without naphthenic oil, inorganic filler and anti-oxidation agent. The polyvinyl chloride contained 40 parts by weight. dioctyl adipate, 5 parts by weight of Ba-Cd stearate and 2.5 parts by weight of organic phosphite per 100 parts by weight polymer.

EXAMPLE VI

Strips containing a mixture of S-B-S block copolymer and ethylene-vinyl acetate copolymer as carrier were extruded.

The S-B-S block copolymer was mixed as in Example IV, and the ethylene-vinyl acetate copolymer contained 34% vinyl acetate by weight and had a melt index of 6 g/10 minutes. The preparation varied with regard to ethylene-vinyl acetate copolymer content.

The strips (thickness 0.5 cm) were exposed to air for 50 days.

EXAMPLE VII

In the same manner as set forth in Example IV, strips containing a mixture of S-B-S block copolymers with various amounts of ethylene vinyl acetate copolymer were prepared and examined.

The S-B-S block copolymer was mixed as in Example

IV.

The vinyl acetate content of the ethylene-vinyl acetate copolymer was 34% by weight, 27% by weight and 19% by weight of the copolymer, respectively.

The weight of the strips was approx. 100 g, thickness 2 cm, processing time 90 days.

EXAMPLE VIII

Strips of different thicknesses (1 cm, 1.5 cm and

2 cm) was made by compression molding.

In the same manner as stated in Example IV, strips containing a mixture of S-B-S block copolymer and 10% by weight polyethylene as carrier were made and examined.

The S-B-S block copolymer was a special type with molecular weights 22,000 - 44,000 - 22,000 and also contained oil, filler and some polystyrene.

The weight ratio between carrier and dimethyl-2,2-dichlorovinyl phosphate was 4:1, and each strip contained 20 g of active insecticide and had the same weight. in

The following results were obtained by treating the strips at 23°C and 60% relative humidity (90 days).

Claims (3)

1. Slow-release pesticide preparation containing a volatile, organic, phosphorus-containing pesticide and a polymeric carrier, characterized in that the carrier is a heterogeneous, polymeric system with at least two polymeric phases, where one phase has a solubility parameter from 8.7 cal^/ml ^ to 12.0 calVml2 and the second phase has a solubility parameter below about 8.7 or above 12.0 cal^/ml^, the weight ratio between the two polymeric phases being from 1:9 to 9:1. 2. Preparation as stated in claim 1, characterized in that the carrier is a block copolymer with the general formula where both blocks A are the same or different polymer blocks of a mono-alkenyl-substituted aromatic hydrocarbon, B is a polymer block of a conjugated diene hydrocarbon, and two neighboring polymer blocks B are considered a single block B, each block A having a average molecular weight in the range from 5,000 to 50,000, and polymer block B has an average molecular weight from 40,000 to 500,000, and the amount of A is in the range from 10 to 65% by weight of the total block copolymer. 3. Preparation as stated in claims 1 and 2, characterized in that the carrier is a mixture of a block copolymer as stated in claim 2 and of ethylene-vinyl acetate copolymer, polystyrene, polyethylene, polyvinyl chloride or chlorinated polyethylene.