MXPA96006398A - Method and means to increase the effectiveness and durability to the washing of tele treated with insectic - Google Patents

Abstract

The present invention relates to the manufacture of fabric intended to be made into washable garments, and more specifically to the placement of an insecticide such as permethrin on the fabric by impregnation with polymeric binder and a crosslinking agent, or by coating of surface with a polymeric binder and a thickener to improve the effectiveness as an insect repellent and retention of permethrin in the fabric, as an effective insecticide through successive washes of the garments.

Description

"METHOD AND MEANS TO INCREASE THE EFFECTIVENESS AND DURABILITY TO LAVADA DE TELA TREATED WITH INSECTICIDE" FIELD OF THE INVENTION This invention relates to the finishing of a washable fabric intended to be made into clothing and more specifically to the finishing of this fabric with an insecticide, such as per etrine, by a process that increases the efficiency of felling and the retention of the insecticide. in the fabric through successive washings.

BACKGROUND OF THE INVENTION Permethrin is a synthetic pyrethroid that exhibits repellent activity as well as kill and kill against insects. Pyrethroids, including both naturally occurring compounds and their synthetically prepared analogues, effectively control a variety of pests, such as ticks, cockroaches, houseflies, mosquitoes, black flies, fleas and other flying or crawling insects. Pyrethroids are not harmful to plants, food, animals or humans and do not leave harmful residues.

Despite these highly favorable characteristics, permethrin has only had limited general utility due to its relatively short insecticidal activity. This is due to decomposition in a non-active, non-insecticidal product in the presence of oxygen and ultraviolet light. Mexican Patent Application Number 9300368 discloses a tent fabric with a water repellent and flame retardant coating that includes the insecticide permethrin. The patent discloses that placing permethrin in the coating on the inner surface of the tent allows the tent fabric and outer surface coating to protect the permethrin from oxygen and light ultraviolet and in this way provide an effective duration of more than six months for permethrin. 9 Mexican Patent Application Number 934287 discloses that permethrin can be conserved in insect repellent fabrics by placing a barrier on the permethrin to protect permethrin from degradation by ultraviolet light and oxygen. Another problem with the use of permethrin as the insect repellent in washable clothing is to retain permethrin in the washable garments through successive washing cycles.

U.S. Patent No. 5,089,298 offers a solution to the problem of retaining permethrin in clothes, through successive washing cycles. This patent discloses that permethrin is retained in garments impregnated with permethrin and amylopectin, a form of water-soluble starch through a considerably higher number of wash cycles than garments treated with permethrin alone. Mexican Patent Application Number 960894 discloses that an initial concentration in the fabric of approximately 1.25 grams of permethrin per square meter is strong enough to repel insects and also discloses that the addition of polyvinyl acetate as a binder for the Permethrin dispersion retains the efficacy of permethrin through more washes of the fabric than amylopectin from US Patent Number 5,089,298. The applicant's investigation has continued for the effective use of permethrin to repel mosquitoes and other insects, and applicants have found that polymeric binders other than polyvinyl acetate disclosed in Mexican Patent Application Number 960894, are effective. to prolong the durability of permethrin. Applicants have also found a process to apply permethrin to the fabric that effectively increases insect repellency and maintains the efficacy of permethrin after repeated washings of the treated fabric.

COMPENDIUM OF THE INVENTION Mexican Patent Application Number 960894 discloses the addition of polyvinyl acetate to permethrin by first impregnating the fabric with polyvinyl acetate and then impregnating the fabric in a second tank with a dispersion of permethrin which provides an initial concentration in the fabric of approximately 1.25 grams of permethrin per square meter, which is more than enough to repel insects. The applicants have now learned that a dispersion of permethrin and an effective polymeric binder can be applied effectively to the fabric by impregnation in a single tank. Applicants have also discovered that permethrin can be applied effectively to the fabric in a surface coating on only one side of the fabric. There are then two embodiments of the present invention: (1) impregnating the fabric with permethrin and (2) coating the surface on only one side of the fabric with permethrin.

In the first embodiment, the fabric to be made into washable garments is dyed and finished in the normal manner and then impregnated with a suitable polymeric binder and with a dispersion of permethrin, and sometimes a crosslinking agent. In the second embodiment, only one side of any desired fabric is coated on its surface with an insecticide and a thickening agent and sometimes an appropriate polymeric binder with or without a crosslinking agent. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a perspective view of the fabric that has been treated with permethrin impregnating the fabric 15 with a dispersion of permethrin and a polymeric binder; rj ^ ** Figure 1A is an enlarged sectional view taken essentially along the line 1 -1A in Figure i; Figure 2 is a perspective view of the fabric that has been treated with permethrin by surface coating on one side of the fabric with a dispersion of permethrin and a polymeric binder; Figure 2A is an enlarged sectional view # which is taken essentially by line 2 -2A in Figure 2; and Figures 3 and 4 are perspective views illustrating the apparatus and methods used to determine the efficacy of permethrin as an insect repellent.

DETAILED DESCRIPTION OF THE INVENTION The fabric or substrate with which this invention is used may be of any desired type. For example, the fabric can be a plain weave polyester fabric or a 65/35 blend of polyester and cotton suitable for the manufacture of clothes. Alternatively, but not exclusively, the cloth can be used for a military uniform made of either 100 percent ribbed knit cotton or 50 percent nylon and 50 percent cotton. A dispersion of permethrin that provides approximately 1.25 grams of permethrin per square meter on a selected fabric was used to find the effectiveness of the polymeric binders; and cross-linking agents as synergistic to prolong retention of permethrin in washable fabrics.

The exact amount of permethrin to be added depends on the type of fabric being treated. The different fabrics absorb or assimilate different amounts of the dispersion of permethrin. The exact amount of permethrin is determined by successive tests to find the amount necessary to provide an initial concentration in the selected fabric of approximately 1.25 grams of permethrin per square meter. That initial concentration has been found to ».. provides effective insecticidal properties and / or insect repellency.

THE FIRST MODALITY - IMPREGNATION Figures 1 and 1A illustrate a cloth 10 that has been impregnated with a solution containing a dispersion of permethrin and a polymeric binder. Permethrin and polymeric binder are indicated by dots 11 in Figure 1A. As seen in the sectional view of Figure 1A, the dots 11 are dispersed through the fabric 10. 20 Permethrin is dispersed through the fabric in the same manner when the permethrin is applied to the fabric by impregnation of the fabric. the fabric in a bath containing only permethrin. The fabrics have been impregnated with several solutions, each of which contains the same # dispersion of permethrin and the same percentage of different polymeric binders and / or crosslinking agents. The treated fabrics were then subjected to domestic washes - and the permethrin percentage remaining on the fabric was then measured to compare the effectiveness of the binders in retaining the permethrin in the fabric.

EXAMPLES OF IMPREGNATING THE FABRIC WITH PERMETRINE EXAMPLE I Example I is a comparison of Example I-A with Example I-B to determine the retention of permethrin in the fabric after a wash of the treated fabric. 15 Example I-A Impregnates the Fabric with Permethrin Only. Example I-B Permeables the Fabric with Permethrin and an Acrylic Binder. In this first example, the cloth substrate is a 65/35 cotton / polyester blend. In Example I-A, the fabric was impregnated with a dispersion of permethrin.

In Example 1-B, the fabric was impregnated with a dispersion of permethrin and with a solution of 74.90 grams per liter of acrylic copolymer as a binder.

Retention of Permethrin in Example I Example I-A 30.8 percent after 5 Washed in House; 11.9 percent after 10 Household Washes. 10 Example I-B 58.8 percent after 5 Washed in House; 47.1 percent after 10 Washes at Home.

Comment on Example I: The addition of an acrylic binder improves the retention of permethrin after the fabric is washed. ^ B ^^ EXAMPLE II Example II is a comparison of Example II-A with Example II-B to determine the retention of permethrin in the fabric after five washes of the treated fabric. Example II-A Impregnates the Fabric with Permethrin and Polyvinyl Acetate * Example II-B Impregnates the Fabric with Permethrin and Acrylic .

In the second example, the fabric substrate is a 65/35 cotton / polyester blend. In Example II-A, the fabric was impregnated with a dispersion of permethrin and with a solution of 74.90 grams per liter of polyvinyl acetate as a binder. In Example II-B the fabric was impregnated with a dispersion of permethrin and with a solution of 74.90 grams per liter of acrylic copolymer as a binder.

Retention of Permethrin in Example II 15 Example II-A 37.0 percent after 5 hours at home. Example II-B 58.8 percent after 5 Home Washes. 20 Comments on Example II: the use of an acrylic binder yields better wash durability than the use of a polyvinyl acetate binder.

EXAMPLE III Example III is a comparison of Example # III-A with Example III-B to determine the retention of permethrin in the fabric after five washes of the treated fabric.

Example III-A Impregnates the Fabric with Permethrin and Polyvinyl Acetate. Example III-B Impregnates the Fabric with Permethrin with Polyvinyl Acetate and with a Crosslinking Agent.

In this third example, the cloth substrate is a 65/35 cotton / polyether blend. In Example III-A, the fabric was impregnated with a dispersion of peritrin and with a solution of 74.90 grams per liter of polyvinyl acetate as a -ti ^ binder. In Example III-B, the fabric was impregnated with a dispersion of permethrin with a solution of 74.90 grams per liter of polyvinyl acetate as a binder, and 3.75 grams per liter of methylated melanin resin as a crosslinking agent. Permethrin Retention in Example III Example III-A 37.0 percent after 5 Home Washes. Example III-B 54.2 percent after 5 Home Washes.

Comment on Example III: the use of a polyvinyl acetate binder and a crosslinking agent yields better permethrin wash durability than the use of the polyvinyl acetate binder alone.

THE SECOND MODALITY - SURFACE COATING Figures 2 and 2A illustrate in a cloth 20 that it has been coated on its surface with a solution containing a dispersion of permethrin, a polymeric binder and a thickener. Permethrin, polymeric binder and thickener are indicated by dots 22 in Figure 2A, the points 22 are dispersed through the layer on only one major surface of the fabric 20. There are no stitches 22 in the body of the fabric 20. Similarly there is no permethrin in the fabric of the body that has been coated on its surface with permethrin. The fabrics have been coated on their surfaces only on one side with several solutions, each of the Which contains the same dispersion of permethrin and a thickener and the indicated concentrations of different polymeric binders and / or cross-linking agents. The treated fabrics were then washed at home and the percentage of permethrin remaining in the fabric was sent to compare the effectiveness of the binders in retaining the permethrin in the fabric.

EXAMPLES OF SURFACE COATING EXAMPLE IV Example IV is a comparison of Example IV-A with Example IV-B to determine the retention of permethrin in the fabric after five washes of the treated fabric. 15 Example IV-A Covers the Surface of the Fabric with i ^ f ^ Only Permethrin and Thickening Agent. Example IV-B Covers the Surface of the Fabric with Permethrin, a Thickener and a Binder Acrylic.

In the fourth example the fabric substrate is a 65/35 cotton / polyester blend. In Example IV-A, the fabric was coated on its surface with only one dispersion of permethrin and carboxymethylcellulose as a thickener. In Example IV-B, the fabric was coated on its surface with a dispersion of permethrin with a 10 weight percent weight solution of an acrylic copolymer emulsion as a binder, and with carboxymethyl cellulose as a thickening agent. of Permethrin in Example IV Example IV-A 25.2 percent after 1 Wash at Home. Example IV-B 42.9 percent after 1 Housewash. 15 Comments on Example IV: the addition of * an acrylic binder to permethrin and a thickener yields better washing durability than that obtained by simply adding a thickener to the permethrin.

EXAMPLE V Example V is a comparison of Example V-A 25 with Example V-B to determine the retention of the? [- permethrine in the fabric after five washes of the treated fabric.

Example V-A Covers the Surface of the Fabric with Permethrin, a Polyvinyl Acetate Binder and Thickening Agent. Example V-B Covers the Surface of the Fabric with Permethrin, a Polyvinyl Acetate Binder, Thickening Agent and Crosslinking Agent. In the fifth example, the fabric substrate is a 65/35 cotton / polyester blend. In Example V-A, the fabric was coated on its surface with a dispersion of permethrin with a percent solution by weight / weight of polyvinyl acetate for 3,785 liters as a binder and ß ^ W carboxymethylcellulose as a thickener. In Example V-B, the fabric was coated on its surface with a dispersion of permethrin with a percent by weight / weight solution of a polyvinyl acetate emulsion as a binder, with 0.5 weight percent / weight of a methylated melanin resin as a crosslinking agent and with carboxymethylcellulose as the thickening agent. 25 Retention of Permethrin in Example V Example V-A 63.3 percent after 5 Washed in House; 59.0 percent after 5 Washes at Home. Example V-B 65.2 percent after 5 Washed in House; 59.0 percent after 10 Washes at Home.

Comments on Example V: The addition of the crosslinking agent to the polyvinyl acetate binder in a thickened coating does not significantly increase the retention of permethrin in the fabric after repeated washing.

EXAMPLE VI Example VI is a comparison of Example VI-A with Example VI-B to determine the retention of permethrin in the fabric after a house wash of the treated fabric.

Example VI-A Covers the Surface of the Fabric with Permethrin, a Polyvinyl Acetate Binder and Thickening Agent.

# Example VI-B Covers the Surface of the Fabric with Permethrin, an Acrylic Binder and Thickener.

In the sixth example, the fabric substrate is a 65/35 cotton / polyester blend. In Example VI-A, the fabric was coated on its surface with a dispersion of permethrin, in a 10 percent by weight / weight polyvinyl acetate emulsion solution as a binder, and carboxymethylcellulose as a thickening agent. In Example VI-B, the fabric was coated on its surface with a dispersion of permethrin, with a 10 percent weight / weight solution of an emulsion of Acrylic copolymer as a binder with carboxymethylcellulose as a thickener.

Retention of Permethrin in Example VI Example VI-A 42.7 percent after 1 Washed at home. Example VI-B 42.9 percent after 1 Housewash.

* Comments on Example VI: the addition of an acrylic binder to a thickened surface coating does not significantly increase the durability to washing than the addition of a polyvinyl acetate binder.

EXAMPLE VII Example VII is a comparison of Example VII 10 to determine the retention of permethrin in the fabric after five washes at home from the fabric.

Example VII-A Covers the Surface of the Fabric with Permethrin, a Polyvinyl Acetate Binder and a Thickening Agent Example VII-B Covers the Fabric with Permethrin, a # Polyvinyl Acetate Binder, Thickening Agent and Crosslinking Agent.

In the seventh example, the cloth substrate is a 65/35 cotton / polyester blend. In Example VII-A, the fabric is coated on its surface with a dispersion of permethrin with a 10 percent by weight / weight solution of a polyvinyl acetate emulsion as a binder and carboxymethylcellulose as a thickening agent. In Example VII-B, the fabric was coated on its surface with a dispersion of permethrin, with a 10 weight percent / weight solution of a polyvinyl acetate emulsion as a binder, carboxymethylcellulose as the thickening agent and 0.5 by weight. one hundred in volume of a methylated melanin resin as a crosslinking agent. 10 Retention of Permethrin in Example VII Example VII-A 52.7 percent after 5 Home Washes. 15 Example VII-B 47.8 percent after 5 Washed at home. ft Comments on Example VII: the use of a crosslinking agent with the acetate binder Polyvinyl does not improve the durability of the wash in relation to the use of the polyvinyl acetate binder alone. EXAMPLE VIII Example VIII is a comparison of three surface coatings: Example VIII-A, Example VIII-B and Example VIII-C to determine the retention of permethrin in a 100 percent cotton knit ribbed fabric for a uniform after repeated washing of the fabric at home.

Example VIII-A is a Thickened Coating of Permethrin Only 10 Example VIII-B is a Thickened Coating of Permethrin with an Acrylic Binder. Example VIII-C is a Thickened Coating of Permethrin with an Acrylic Binder and a Crosslinking Agent. 15 In the eighth example, the cloth substrate is a 100 percent cotton knit ribbed fabric intended for a military uniform. In Example VIII-A, the fabric was coated on its surface with a dispersion * of permethrin and carboxymethylcellulose as a thickener. In Example VIII-B, the fabric was coated on its surface with a dispersion of permethrin, with a 10 weight percent / weight solution of an acrylic copolymer emulsion as a binder and carboxymethylcellulose as a thickening agent. In Example VIII-C the fabric was coated on its surface as a dispersion of permethrin, with a 10 weight percent / weight solution of an acrylic copolymer emulsion, the binder, carboxymethylcellulose as a thickening agent and 0.5 percent in weight / weight of a methylated melamine resin as a crosslinking agent. Retention of Permethrin in Example VIII After 1 Home Wash / After 5 Home Washings / After 10 Home Washings 15 Example VIII-A 59.5% 30.2% 4.76% Example VIII-B 86.4% 46.2% 18.2% Example VIII-C 74.8% 39.9% 23.8 % Comments on Example VIII: the use of a The acrylic binder significantly improves the washing durability of permethrin, and the addition of a crosslinking agent also improves the durability of permethrin washing.

EXAMPLE IX Example IX is a comparison of three surface coatings: Example IX-A, Example IX-B and Example IX-C to determine the retention of permethrin in a 50/50 nylon / cotton fabric for uniforms after of repeated home washings of the fabric.

Example IX-A is a Thickened Coating of Permethrin Only. Example IX-B is a Permethrin Thickened Coating with an Acrylic Binder. Example IX-C is a Thickened Coating of Permethrin with an Acrylic Binder and a Crosslinking Agent.

In the ninth example, the fabric substrate is a 50/50 nylon / cotton fabric intended for a Jßf uniform. In Example IX-A, the fabric was coated on its surface with a dispersion of permethrin, and carboxymethylcellulose as a thickener. In Example IX-B, the fabric was coated on its surface with a dispersion of permethrin, with a 10 weight percent / weight solution of an acrylic copolymer emulsion as the binder and carboxymethylcellulose as the thickener.

In Example IX-C, the fabric was coated on its surface with a dispersion of permethrin, with an emulsion of acrylic copolymer at 10 weight percent / weight as a binder, carboxymethylcellulose as a thickening agent and 5 volume percent of a methylated melamine resin as a crosslinking agent.

Retention of Permethrin in Example IX After 1 Housewash / After 10 Household Washes / After 20 Household Washes Example IX-A 47.4% Trace None Example IX-B 77.7% 29.9% 5.98% Example IX-C 66.4% 35.4% 8.85% Comments on Example IX: the use of a Wf. Acrylic binder significantly improves the durability when washing permethrin and the addition of a crosslinking agent also improves the durability to the washed out of permethrin.

EXAMPLE X Example 10 is a comparison of Example X-A 25 with Example X-B to determine the retention of permethrin in the fabric after five washes of the treated fabric.

Example X-A Impregnates the Fabric with Only 5 Permethrin. Example X-B Covers the Surface of the Fabric with Only Permethrin and Thickening Agent.

In the tenth example, the fabric substrate is a 65/35 cotton / polyester blend. In Example X-A, the fabric was impregnated with only one dispersion of permethrin. In Example X-B, the fabric was coated on its surface with only one dispersion of permethrin and carboxymethylcellulose as a thickener. r Retention of Permethrin in Example X Example X-A 30.8 percent after 5 20 Household Washes. Example X-B 39.7 percent after 5 Home Wash.

Comments on Example X: the surface coating of the permethrin on one side of the substrate of fabric with a thickening agent yields better durability to washing than the impregnation of the fabric with permethrin.

THE HOME WASHING PROCEDURE All the house washes in the aforementioned Examples were carried out in a KENMORE Ultra Fabric Care Heavy Duty 80 Washing Machine of the Residential Series. The sample was weighed and the fabrics were used to carry the weight of the load up to 1.82 kilograms. A beaker of 50 milliliters of detergent ALL was measured and added to the charge. The washing machine was programmed for its normal site at its regular graduation. The fabrics were washed in hot water (49 ° C) with a cold rinse. 15 After each wash cycle, the load was dried with medium heat for 20 minutes in a Dryer? Commercial HUEBSCH ORIGINATORS 30 Plus and cooled for 5 minutes.

THE TEST PROCEDURE The test instrument and procedure that was used to determine the amount of permethrin remaining in the fabric after the washings is disclosed below: Gas Chromatography (GC): Tre Metrics 541: Electron Capture Detector Column: 1,829 meters per 3.18 millimeter internal diameter of glass column packed with 3 percent OV 225 in 100/120 mesh of Chromium Gas Q or equivalent. Gas: 5 percent Methane, 95 percent Argon. Condition: Oven temperature: 245 ° C Injector temperature: 225 ° C Detector temperature: 350 ° C Injection volume: 2 microliters Flow rate of the carrier gas: 50 ml / minute Operating time: Approximately 20 minutes per sample TEST PROCEDURE 77.40 square centimeters of the test specimen are placed in a Soxhlet extraction thimble. This is prepared by cutting three layers of the test cloth with a matrix of 5.08 centimeters by 5.08 centimeters. 175 milliliters of the acetonitrile / methanol mixture and several boiling chips are added in a 250 milliliter heat-resistant flask. The Soxhlet extraction apparatus is assembled and the specimens impregnated with permethrin are extracted for 6 hours. After extraction, the extract will be diluted to a total volume of 200 milliliters in a volumetric flask. One microliter of the extract is injected to GC.

CALCULATIONS: A series of normal solutions of Permethrin are injected in GC, and two maximums of cis and trans are recorded. A linear trace of the integrated area of both cis and trans maximums versus the concentration is then created and the equation of the line is recorded. Using the equation of the line and the interaction area of the unknown maximums, extrapolation to an unknown concentration can be achieved. This should be repeated in units of grams per square meter. Note: If the linear stroke concentration axis is in units of grams per square meter, the extrapolation is accelerated.

THE INCREASED EFFICACY OF SURFACE COATING Fabrics that are coated on their surface with permethrin have a higher effectiveness of insect repellency than fabrics that are impregnated with equal amounts of permethrin. One reason is evident from a ^^^ comparison of the physical location of permethrin in the fabric of Figure 2A with the physical location of the permethrin in the fabric of Figure 1A. In Figure 2A, all permethrin is placed on only one major surface of the fabric. When that main surface becomes the outer surface of a garment, all of the permethrin is placed to contact the insects. At the same time, it is placed out of contact with the skin of the user In Figure 1A, the same amount of permethrin is dispersed through the body of the fabric. As a result, only the portion of the permethrin that is placed on the surface of. the fabric that turns on the outer surface of the garment is available for insect repellency. The remainder of the permethrin is dispersed through the fabric as shown in Figure 1A with an equal amount of permethrin inside a garment made of the fabric. as there is outside. Figures 3 and 4 illustrate the apparatus and procedure used in the actual test and has confirmed the increased efficiency of surface-coated permethrin for repelling insects. That test is the matter object of Examples XI and XII.

»As indicated in Figure 3, the test was carried out by placing an inverted petri dish cover 30 on a card 31 which is placed in sequence on differently treated pieces of fabric 32. A piece of the 32 fabric was treated according to Example 11 and another piece of fabric was treated according to Example XII. In each test ten mosquitoes 33 female aedes aegypti were restricted in cover 30 of the petri dish '^ BK' 10 as can be seen in Figure 3 and card 31 slid smoothly from under the cover of the petri dish allowing the mosquitoes to come into direct contact with the treated fabric 32. After the mosquitoes are exposed to the fabric 32 treated during a After the allotment time (from 5 to 60 minutes) the card 31 was gently returned to its initial position under the cover of the petri dish to terminate the exposure of the mosquitoes to the treated fabric. The demolition accounts are recorded at 15 and 60 minutes after that the mosquitoes were first exposed to the treated fabric by removing the card 31.

EXAMPLE XI IMPREGNATION 25 Formula Water 98 percent Permethrin: 2 percent Calculated concentration of permethrin 1.14 grams per square meter. Analyzed concentration of permethrin 1.17 grams per square meter. The face of the fabric was exposed to insects in a wrap for 5 minutes. After 15 minutes 25 percent of the aedes aegypti mosquitos had been knocked down. After 60 minutes, 80 percent of the Aedes aegypti mosquitoes had been knocked down.

EXAMPLE XIH COVERED ON ITS SURFACE Formula Water 92.5 percent Permethrin 5.5 percent Metocel 2.0 percent (thickener) Calculated concentration of permethrin 1.25 grams per square meter. Analyzed concentration of permethrin 0.85 grams per square meter. The face of the fabric was exposed to the insects in a wrap for 5 minutes. After 15 minutes, 50.0 percent of the osquitops aedes aegypti had collapsed. After 60 minutes, 95.0 percent of aedes aegypti mosquitos had been knocked down. ^ S "10 It is evident from this fact that the treatment of the surface creates a more effective pest control fabric which achieves faster and greater demolition than the impregnated cloth.15 Another advantage of the coated fabric on the surface intended for clothing is that the coating of s L the surface on the outside of the fabric decreases contact with the skin of the user and maximizes the location of permethrin for contact by the insects. In this way an improved method is provided to increase the durability of permethrin to repeated washes of a treated fabric and an improved method to increase the efficiency of an insecticide to repel insects. Although all the present examples have used permethrin as the insecticide, the described methods can be used with other insecticides within the scope of the invention. Even when specific terms have been used in describing the invention, they have been used in a descriptive sense only and not for the purpose of limitation.

^ Sm t

Claims (17)

R E I V I N D I C A C I O N S

1. A method for improving the effectiveness of a fabric for repelling insects before and after successive washings of the fabric, the method is characterized in that it comprises the steps of: (a) providing a solution containing a dispersion of an insecticide in a thickening agent; 4f (b) coating on its surface the solution not only on a main surface of the fabric, the thickener acting to essentially place the insecticide on only the main surface of the fabric that was coated.

2. A method according to claim 1, characterized in that the insecticide is permethrin. TS ?,

3. A method according to claim 1 or 2, characterized in that the solution includes a polymeric binder.

4. A method according to claim 3, characterized in that the polymeric binder is polyvinyl acetate.

5. A method according to claim 3, characterized in that the binder Polymeric is an acrylic copolymer.

6. A method according to any of the preceding claims characterized in that the thickener is carboxymethylcellulose.

7. A method according to any of the preceding claims, characterized in that the solution includes a crosslinking agent.

8. A method according to claim 7, characterized in that the crosslinking agent is methylated melamine resin.

9. A fabric intended for use in the manufacture of washable garments, the fabric contains permethrin and is characterized by a means of retaining the permethrin in the fabric as an effective insecticide after the fabric has been made into garments. and has 15 passed through successive washing cycles, and a medium comprising the polymeric acetate binder of ^ 5 ^ polyvinyl and a crosslinking agent.

10. A fabric that has a coating placed essentially on, but only on the surface The main one thereof functions as a means for repelling insects before and after successive washings of the coated fabric, characterized in that the coating has been derived from a solution containing a dispersion of an insecticide in a thickener, the thickener having operated to limit the placement of the insecticide on the main surface.

11. A fabric in accordance with claim 10 or 11, characterized in that the insecticide is permethrin.

12. A fabric according to claim 10 or 11, characterized in that the solution includes a polymeric binder.

13. A fabric according to claim 12, characterized in that the polymeric binder is polyvinyl acetate.

14. A fabric according to claim 12, characterized in that the polymeric binder is an acrylic copolymer.

15. A fabric according to any of claims 10 to 14 inclusive, characterized in that the solution includes a crosslinking agent.

16. A fabric according to claim 9 or 15, characterized in that the crosslinking agent is methylated melamine resin.

17. A fabric according to claim 9 and 16, characterized in that permethrin and means for retaining the permethrin in the fabric are impregnated in the fabric.