IL45712A - Hydrophilic copolymer salt and use thereof - Google Patents

Description

v bulk copolymerization of methyl methacrylate and acrylic acid are described and claimed in U. S. Patents 3,728,314 and 3,728,317, both in the name of Izhak Blank. Hydrogel copolymers which are hydrophilic are described in a number of prior art patents including U. S. 2,976,576--Wichterle et al, and U. S. 3,220,960--Wichterle.

The Wichterle et al and Wichterle patents describe hydrophilic materials which are hydrogels formed by the copolymerization, in the presence of water, of both monofunctional and di-functional materials. Included among the monofunctional materials which may be copolymerized, according to these patents, is dimethylaminoethyl methacrylate. However, both the Wichterle and Wichterle et al patents are directed to the formation of shape-retaining bodies, and, particularly because of the difunctional material present, cannot be truly employed for the formation of films.

Films formed of hydrophilic copolymeric material are extremely valuable in a variety of uses. For example, they can be used in application of agricultural chemicals so that the release of these materials is delayed and less of the chemical need be employed for a given use. Further, the use of a hydrophilic film is particularly valuable in combination with a chemically similar hydrophobic material, particularly when that hydrophobic material must come in contact with a member of the body where it may subjec It is frequently important, for these uses, that the material have adhesive properties or that it be useful over a wide pH range extending from the alkaline to the acid. The materials of the prior art have not been totally applicable for such uses, particularly for spray-on films with the desired properties and where the film must be compatible not only with aqueous vehicles but with organic solvent vehicles.

Summary of the Invention In accordance with the present invention a material useful in the formation of hydrophilic films has been developed. The material is formed by copolymerizing a monomer, which if polymerized alone, would be hydrophobic, with a second monomer which is potentially hydrophilic. Included among the first group of copolymers are methyl me hacrylate , styrene, acrylonitrile , vinyl acetate and other acrylate and methacrylate esters. Methyl methacrylate is the preferred material. The second group of monomers are those which contain an amine group. There should be from 60 to 90 percent, by weight, from the first group of monomers and from 10 to 40 percent, by weight, from the second group. The preferred amounts within the ranges are, to a degree, dependent upon the particular end use to which the product is to be put. Preferably, when the copolymer salt is to be employed as a spray-on adhesive, the amine material content should be less than 20 percent by weight, while when used for sustained release, the content shou Following copolymerization of the two monomer groups, some or all of the amino groups are neutralized, such neutralization being carried out with an acid. The acid employed can be organic, such as citric or acetic acid, or it may be inorganic, including such materials as hydrochloric acid and phosphoric acid. The amount of acid used, which determines the degree of neutraliza tion, will affect the compatibility of the copolymer material with aqueous and organic solvent solutions, through the effect on its hydrophilicity. Thus, this method of treatment can be employed to vary the particular properties of the material so as to render it useful in a variety of situations.

A particular advantage of the copolymeric material of the present invention is the fact that it is nontoxic. Thus, it can be used in many situations, including its employment in uses associated with the body. Solutions of the copolymeric salt material of the present invention are particularly useful as an adhesive film spray for dentures and for application of fine agricultural chemicals for sustained release. Similarly, the material is useful in other related applications for application of medical, cosmetic, and other materials.

Because of the combination of hydrophilic and hydrophobi properties present in the copolymer salt, a film cast from the material is capable of absorbing water, and yet remains insoluble and has good adhesion to hydrophobic surfaces.

Description of the Preferred Embodiments As previously explained, the material of the present invention is a salt formed through neutralization of a copolymer formed from a hydrophobic moiety and a moiety which is potentially hydrophilic. The hydrophobic moiety represents from approximately 60 to 90 percent, by weight, of the copolymer.. Preferably, the hydrophobic moiety is methyl methacrylate . However, up to about 30 percent of the methyl methacrylate, by weight, can be replaced with other hydrophobic materials including styrene, vinyl acetate, acrylonitrile, the corresponding acrylate, and similar materials, including other acrylate and methacrylate esters." The potentially hydrophilic moiety of the copolymer is an amino-substituted acrylate having the formula: where R is selected from the class consisting of hydrogen and methyl, R' and R" are independently selected from the class consisting of hydrogen and alkyl groups of from one to four carbon atoms, and n is from two to six. The lower alkyl groups which can be represented by R' and R" include both straight chain and isomeric alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, t-butyl, etc. This potentially hydrophilic moiety comprises from about 10 to 40 percent, by weight, of the copolymer.

The various monomeric materials, including one or more h dro hobic monomers and one or more potentially hydro hilic mono Further., the potentially hydrophilic comonomer can be formed in situ. In such a situation, acrylic or methacrylic acid is copolymerized with the hydrophobic comonomer with subsequent reaction of the copolymer with a material, such as ethylene imine, to yield the desired copolymer.

In solution polymerization, the solvent is generally selected so that it will be useful for application of the ultimately formed material. Solvents which can be so employed are acetone, which is preferred, acetone mixed with methanol, methyl ethyl ketone, mixtures of methyl ethyl ketone and methanol, mixtures of acetone and ethanol, and mixtures of methyl ethyl ketone with ethanol, among others. The solvent so employed can be particularly useful, for example, when the material is to be employed as an adhesive denture liner. The solvent polymerization step is carried out according to known techniques , generally with from about 40 to 60 percent solvent present, the remainder being the copolymeric materials.

In addition to the required hydrophobic monomer and potentially hydrophilic monomer, other monomers may be copolymerized to obtain particularly desirable properties. Normally, all of the monomers employed will be monoethylenically unsaturated so that the resulting copolymers are linear, rather than cross-linked. This allows them to be employed as films, rather than forming gels which are not useful for the same purposes.

In the copolymerization steps it is generally necessary to incorporate a free radical polymerization catalyst. In particular the catalyst can be *^ , c · -azodiisobutyronitrile.

Various other catalysts will be apparent to the skilled in the art. The amount of catalyst used can vary between about .1 percent and .5 percent of weight, based on the total weight of monomers being polymerized. Preferably the catalyst is employed in amounts ranging from about .2 percent to .3 percent by weight based on the combined weight of the monomer.

The copolymer obtained by the method just described is hydrophobic. However, by a neutralization of the amine groups of the copolymer, either partial or total, it can be rendered hydro-philic. The degree of hydrophilicity is determined by the amine group content and by the degree of neutralization of the amine groups which are present. Specifically, a higher content of amine group containing segments in the copolymer or a neutralization which more closely approaches total neutralization renders the copolymer salt more hydrophilic. As the copolymer becomes more hydrophilic, it becomes less compatible with nonpolar solvents, including organic solvents. The compatibility with nonpolar, organic solvents can be increased through a decrease in the amine content or through a lesser degree of neutralization. Thus, the properties of the copolymer salt can be tailored to specific uses.

Neutralization of the amine groups on the copolymers is accomplished employing an acid which may be either an organic acid or an inorganic, mineral acid. The amount of acid employed will, of course, be dependent upon the degree of neutralization desired. Among the acids which can be employed are organic acids, such as acetic and citric acids, or inorganic acids, such as hydro chloric and phosphoric acids. The amount of acid which is employed, regardless of type, should be sufficient for the film to achieve a water absorption rate of at least 20 percent. This will vary with the amine content, as previously indicated. As an example, with an amine content of approximately 30 percent, a partial neutralization of approximately 60 percent will provide the 20 percent water absorption capability. The neutralization can be carried out by adding the desired acid, in the necessary quantities, to the copolymer solution either before the copolymer has been cooled to room temperature, or after cooling, as desired. The determination of when the acid is added is affected more by safety considerations, than by the technical necessities for time of addition.

Following formation of the desired copolymer salt, through copolymerization of the monomers and neutralization of some or all of the amine groups, the solution is generally ready mixed with the solution for spraying, or the solution can be compounded with various materials to render the material useful as a fugitive adhesive for application to dentures. In the latter case, for example, the solution can be blended with such materials as astringents, propellants to render the material useful in spray formulations, disinfectants as are well known in the art, deodorants, flavors such as menthol, dyes and pigments such as calcium carbonate, medications such as Novocain, and bactericides such as benzalkonium chloride and neomycin sulfate. Should the concentration of the copolymer salt in the solution be greater than that which is desired for the end use, additional water or solvent, as desired, can be added.

In order that those skilled in the art may be better enabled to practice the present invention, the following examples are given by way of illustration and not by way of limitation. All parts in the following examples, unless otherwise indicated, are by weight.

Example 1 A copolymer of methyl methacrylate and dimethylamino-ethyl methacrylate was prepared by refluxing under stirring for seven hours 160 parts methyl methacrylate, 40 parts dimethylamino-ethyl methacrylate, 200 parts acetone, and 0.6 part c< , 1 -azo-diisobutyronitrile. The solution was found to contain 50.2 percen copolymer solids. To the solution, without cooling, 15.5 parts glacial acetic acid were added, with stirring, in order to neu Example 2 The copolymer solution of Example 1 was compounded with fluorocarbon propellant, additional acetone solvent, and small amounts of pigments and menthol to provide a copolymer salt content of three percent. Methyl methacrylate dentures were rinsed with water and dried with a paper tissue. The propellant solution just described was sprayed onto the denture on the gum side. A film of the copolymer salt was obtained and it was found that this film absorbed approximately 25 percent water. When placed in the mouth of the wearer, the dentures were found to be extremely comfortable.

Example 3 A copolymer salt was formed with the same materials and in the same manner as in Example 1, except that neutralization was carried out with the same quantity of hydrochloric acid. The resulting film, when sprayed onto methyl methacrylate dentures, was found to absorb approximately 50 percent water.

Example 4 A copolymer was formed in the same manner as in Example '. and with the same quantities, except that neutralization was carried out with the same amount of citric acid. When a film was formed by spraying this solution onto dentures, it was found that the film absorbed approximately 20 percent water.

Example 5 A copolymer was formed by refluxing for approximately eight hours 160 parts methyl methacrylate, 40 parts t-butylamino-ethylmethacrylate, 200 parts acetone, and 0.6 part ©< jO '-azodi-isobutyronitrile. The resulting solution was found to contain 48.7 percent copolymer solids. A quantity of 12.9 parts glacial acetic acid was added to the solution to neutralize amine groups and an aerosol was prepared in the same manner as in Example 2. This aerosol was sprayed onto methyl methacrylate dentures and the resulting film was found to absorb approximately 20 percent water.

Example 6 A copolymer was formed by refluxing for 4.5 hours 423 parts methyl methacrylate, two parts ethylhexyl acrylate, 90 parts acrylic acid, 320 parts acetone, 80 parts methanol, and 1.8 parts azodiisobutyronitrile . The resulting solution was found to contain 56 percent copolymer solids. A quantity of 145 parts ethanol was added to 100 parts of the copolymer solution and the resulting solution was heated so as to distill off all acetone present, 95 parts acetone being recovered at a final distillation temperature of 7 °C. A quantity of four parts ethylene imine in 20 parts ethyl alcohol was added over a period of one hour while maintaining solution temperature at 75 eC. Heating and stirring was continued for an additional 30 minutes and a quantity of 5.6 parts acetic acid film was cast directly from this polymer solution and was found to absorb 25 percent water.

Example 7 A copolymer was formed in the same manner as in Example but employing 140 parts methyl methacrylate and 20 parts styrene i place of the 160 parts methyl methacrylate. A film cast from this copolymer solution was found to absorb 25 percent water.

Example 8 A quantity of 0.1 part tannic acid was added to 100 part of the propellant solution of Example 2. This film was sprayed in the same manner and was found to have astringent' properties, in addition to the other desirable properties of the copolymer salt film.

Example 9 A copolymer was prepared by refluxing for eight hours 140 parts methyl methacrylate, 60 parts t-butylaminoethyl methacrylate, 200 parts acetone, and 0.6 part 0 ,o( ' -azodiisobutyro-nitrile. The copolymer solids content was found to be 51 percent. A quantity of 50 grams of this material was treated with 2.4 parts of acetic acid to neutralize the amine groups and a film was cast from the resulting solution. The film was found to absorb 60 part water.

The following examples illustrate the use of the copolym salts of the present invention in application of agricultural 4 provide a chemical compound for agricultural purposes at a locus, over a prolonged period. If, however, the compound is applied to the locus in pure form or in the presence of one of the conventional carriers, it will normally be present only for a short while before ambient conditions disperse it. However, if there i to be a sustained action, the material must generally be present in such large quantities, relative to that actually required, tha there is a resultant, undesirable pollution of the environment.

At present, for example, fine agricultural chemicals ar generally applied by spraying in the form of an aqueous solution, emulsion, or dispersion, or by dusting it onto plants or the soil surrounding the plants. Such materials, particularly pesticides, are generally only slightly soluble or substantially insoluble in water, though they are soluble in organic solvents. These materials are, therefore, generally applied from emulsifiable concentrates. Certain salts for the application of fine agri¬ the prcoont -inventi-oa.. While the salts disclosed in that «applica • im are useful for the intended purpose, they can be used only f alkaline or neutral media. On the other hand, the salts of the present invention can be used over a wide range of pH, particularly a range of from about 5 to 9.

The agricultural compositions which can be employed wit the copolymer salts of the present invention include pesticides, e.g. insecticides and other animal pesticides, fungicides, and herbicides, all as well known in the art. The salts are es eciall useful with the insecticides methyl and ethyl parathim. Because the solubility characteristics of the salts of the copolymers tan be so widely varied, great latitude is allowed in formulation Example 10 A copolymer was formed by heating, at reflux, for eigit hours a mixture of 980 parts methyl methacrylate, 420 parts dimethylaminoethyl methacrylate, 1400 parts acetone, and 4.2 pairts of, O * -azodiisobutyronitrile. The resulting polymer solution was cooled and was found to have a copolymer solids content of 48.5 percent. To the cooled solution a quantity of 162 parts acetic acid, which was sufficient to neutralize all of the amine group$., was added and the solution was stirred for an additional 30 minikte The resulting polymer solution was found to be completely miscible with a large number of solvents including xylene, toluene, ethariol e.g. insecticides and other animal pesticides, fungicides, and herbicides, all as well known in the art. The salts are especiall useful with the insecticides methyl and ethyl paratJr cn. Because the solubility characteristics of the salts of the copolymers can be so widely varied, great latitude is allowed in formulation of the ultimate agricultural compositions. For example, such compositions can be wettable powders or aqueous solutions, when the pesticide is water soluble. Alternatively, the salts can be made so as to form organic solvent solutions containing surface active agents so that emulsifiable or water-dispersible concentrates are formed that need only be mixed with water before application. The ultimate agricultural composition is, in any case, applied to a locus where controlled release of the contained agricultural chemical or chemicals is desired.

Example 10 A copolymer was formed by heating, at reflux, for eight hours a mixture of 980 parts methyl methacrylate, 420 parts dimethylaminoethyl methacrylate, 1400 parts acetone, and 4.2 parts of , 0< · -azodiisobutyronitrile. The resulting polymer solution was cooled and was found to have a copolymer solids content of 48.5 percent. To the cooled solution a quantity of 162 parts acetic acid, which was sufficient to neutralize all of the amine groups, was added and the solution was stirred for an additional 30 minute The resulting polymer solution was found to be completely miscible < s methyl ethyl ketone, and water. A quantity of the polymer solution was added to sufficient water to provide a ten percent polymer solution, which was found to be a convenient method of handling the material.

Example 11 A copolymer was prepared in the same manner and with the same amounts of material as in Example 10, except that t-butylaminc ethyl methacrylate was substituted for the dimethylaminoethyl methacrylate. The amount of acetic acid employed was 137 parts and the resulting copolymer solution was found to be miscible with the same solvents as the solution of Example 10.

Example 12 A copolymer solution was prepared under the same conditions as employed in Example 1 with 700 parts methyl methacrylate, 280 parts styrene, 420 parts dimethylaminoethyl methacrylate, 1400 parts acetone, and 4.2 parts ©( , 0< ' -azodiisobutyronitrile . The amine groups were neutralized with 137 parts acetic acid and the resulting polymer solution was found to be miscible with xylene, toluene, ethanol, and water.

Example 13 A copolymer solution was prepared by refluxing, for eight hours, a mixture of 222 parts methyl methacrylate, 78 parts dimethylaminoethyl methacrylate, 300 parts acetone, and 0.9 part °^ , σ( 1 -azodiisobutyronitrile. The resulting solution was cooled The amine groups were neutralized with 29.7 parts acetic acid, sufficient for neutralization of all of the amine groups, with 30 minutes of stirring being sufficient to accomplish the neutralization.

The resulting polymer solution was found to be completel) miscible with a large number of solvents including xylene, toluene, ethanol, methyl ethyl ketone, and water. This polymer solution was also diluted to a ten percent concentration through addition of the required amount of water, under rapid stirring, and this was found to be a convenient form for handling of the material.

One liter of the solution prepared according to Example 10 was mixed with one gram of Benomil with agitation sufficient to dissolve the Benomil. A film was cast from the resulting solution and was found to be clear and water absorbing.

Example 14 Solutions were made up to determine the effectiveness of aphid control employing copolymers of the present invention with agricultural fine chemicals when compared with the chemicals in the absence of the copolymer salts of the present invention. Five different areas were studied, spraying being with a knapsack sprayer, as follows: (a) Untreated control area; (b) 3.3 liters of 50 percent, effective concentration, Malathion in 300 liters water per hectare; (c) 3.3 liters of 50 percent, effective concentration, Malathion in 300 liters of water containing 1.25 percent of the copolymer salt of Example 10, per hectare; (d) Two liters of 35 percent, effective concentration, Thionex (endosulphan) in 300 liters of water, per hectare; and (e) One liter of 35 percent, effective concentration, Thipnex (endosulphan) in 300 liters of water containing 1.25 percent of the copolymer salt of Example 11, per hectare.

The various areas were tested over a 15-day period in April-May on a commercial plot of spring-planted pepper. Myzus Persicae (Sc.) was the dominant aphid. The results were as folr-lows : (a) A steady increase in the aphid population; (b) A steep decline in the aphid population to zero for the first six days, followed by a rapid increase to the original infestation level; (c) Good control of the aphid population over a 15-day period; (d) The full dosage (two liters in 300 liters of water) gave good control over the entire 15-day period; and (e) A half dosage (one liter in 300 liters of water) of Thionex, with the polymer, gave good control over the 15-day period.

Thus, it can be seen that inclusion of the copolymer sal Example 16 A cotton field infested with Prodenia, sown during the spring, was employed to check the effectiveness of insect control employing the copolymer salts of the present invention. Treatments were applied in August by spraying from the ;air, as follows: (a) Three kilograms of Parathion, 50 percent effective concentration, in 30 liters of water, per hectare, were applied to a four hectare plot; (b) Three kilograms of Parathion, 50 percent effective concentration, in 30 liters of water containing three percent of the copolymer salt of Example 10, per hectare, were applied to a separate four hectare plot.

A first spraying was carried out on August 8 and egg masses and larvae were examined daily after that. It was found that until August 28 a total of five sprays of treatment (a) were required to maintain adequate control, while adequate control was maintained with treatment (b) using no additional sprays. Thus, it is apparent that the inclusion of the copolymer salts of the present invention substantially increases the effective life of an insecticide treatment.

Example 17 According to this example, the effectiveness of fly control employing the copolymer salts of the present invention was demonstrated. Two cow-shed yards, both approximately 80 square employing a knapsack sprayer. Spraying took place on June 24.

The treatments were as follows : Amounts Spray Constituents Yard A Yard B Copolymer Salt of Example 10, 10 Percent in Water 2 Liters None Sugar 800 Grams 800 Grams Dimethoate, S.P. , 40 Percent Active 500 Grams 500 Grams Water To 20 Liters To 10 Liters The fly concentration was measured by placing a wooden screen with an area of 0.25 square meter at various places in the yard and counting the number of flies that covered the screen after two minutes. Approximately 12 such readings were taken each time and the average, multiplied by four, was used as the fly concentration, per square meter. The results are given in Table 1. Thus, a more persistent control of the fly concentration was obtained employing the copolymer of the present invention along with an agricultural chemical to prevent the accumulation of flies.

In accordance with the present invention a new and valuable copolymer salt has been described where the amount of one of the components, and the degree to which that component is neutralized after polymerization, can be varied to control compatibility with water and with nonpolar organic solvents. Inter alia, the material is extremely useful as a fugitive cushioning TABLE 1 Fly Concentration/Square Meter Days After Date Spraying Yard A Yard B June 24 0 (Before Spraying) 65 65 June 25 1 15 55 June 28 4 0 20 July 1 8 15 35 and adhesive agent for dentures, or other hydrophobic methacrylate plastics, and as an agent to extend the effective life of fine agricultural chemicals. The invention should not be considered as limited to the specific embodiments described and illustrated in the examples, but only as limited by the appended claims.

Claims (4)

1. 45712/2 WHAT IS CLAIMED IS : 1. A hydrophl Hc copolymer salt having from 60 to 90 percent, by weight, of units formed from a hydrophobic monomer and from 10 to 40 parts , by weight, of units of a potentially hydrophl Hc monomer having the formula: R 0 Ml CH2=C-C-0 £CnH2n} NR'R" where R 1s selected from the class consisting of hydrogen and methyl , R' and R" are Individual ly selected from the class consisting of hydrogen and al kyl radicals of from one to four carbon atoms , and n_ 1s from two to six, where a portion of the amine groups are neutralized with an add to provide at least 20 percent water absorption 1n the copolymer salt, wherein the hydrophobic comonomer 1s methyl methacrylate, or wherein up to 20 percent of the methyl methacrylate 1s replaced by a member sel ected from t he class consisting of styrene, acrylonltrl le, vinyl acetate, and acrylate and methacrylate esters .

2. The copolymer of claim 1 wherein the hydrophobic comonomer comprises from 70 to 80 percent and the hydrophi'Hc comonomer comprises from 20 to 30 percent.

3. The copolymer salt of claim 1 wherein the hydrophobic comonomer comprises from 80 to 90 percent and the hydrophlHc comonomer comprises from 10 to 20 percent. -22- comonome comonome zation o from the phosphor solvent 80 to 50 solvent methanol at least ants, pi life of copolyme formed f weight, where R methyl, R1 and R" are individually selected from the class - 'In 45712/2 consisting of hydrogen and alkyl radicals of from one to fourj carbon atoms, and. n is from two to six, where a portion of th amine groups are neutralized with an acid to provide at least percent water absorption in the copolymer salt. 15. The copolymer salt of claim 14 wherein the hyd phobic comonomer is methyl methacrylate. ΐ6. The copolymer salt of claim 15' wherein up to 2 percent of the methyl methacrylate is replaced by a member se from the class consisting of styrene, acrylonitrile, vinyl ac and acrylate and methacrylate esters. . 17. The copolymer of claim 14' wherein the hydropho comonomer comprises from 60 to 80 percent and the hydrophilic comonomer comprises from "20 to 40 percent*. ' 18 The copolymer salt of claim 1

4. wherein the neu tralization of the amine groups is accomplish ted with an acid selected from the class consisting of acetic, citric, hydroch and phosphoric. 19» A compos chemical comprising the of approximately ten pe of a fine agricultural s 20· . The comp fine agricultural chemi overall composition.