Tagged polymers and their synthesis by post polymerization (trans) amidation reaction

Abstract: Polymers tagged with pendant fluorescent groups are prepared by the (trans)amidation derivatization of pre-existing polymers having carbonyl-type pendant groups. Polymers having pendant amide groups wherein the amide nitrogen is substituted with fluorescent moieties, prepared by (trans)amidation derivatization, and polymers having pendant (sulfonated) napthalene moieties substituted to amide nitrogen are provided, with mer units of the Formula V: wherein R₄ is C n H 2n and n is zero or an integer of from 1 to about 10, R₁, R₂ and R₃ are independently hydrogen or a substituent other than hydrogen, wherein one of X₁ and X₂ is hydrogen and the other is an (alkylene) naphthalene having from 0 to 2 sulfonic acid substituents or salts thereof, or wherein X₁ and X₂ contain, separately or together, at least one organic fluorescent group.

Description: The present invention is in the technical field of polymer synthesis by the method of post-polymerization derivatization and polymers prepared thereby. More particularly, the present invention is in the technical field of synthesizing polymers having pendant fluorescent groups and polymers prepared thereby. In many fields that employ polymers it may be desirable to tag or mark such polymers to facilitate monitoring thereof. By the term "monitoring" is meant herein any type of tracing or tracking to determine the location or route of the polymers, and any type of determination of the concentration or amount of the polymer at any given site, including singular or intermittent or continuous monitoring. For instance, it may be desirable to monitor water treatment polymers in water systems, particularly industrial water systems, or to monitor polymers that may be present in waste fluids before disposal, particularly industrial waste fluids, or to monitor the polymer used for down-hole oil well applications, particularly the route taken after introduction down-hole, or to monitor polymers that may be present in fluids used to wash a manufactured product, for instance a polymer-coated product, to determine the amount of polymer washed or leached therefrom. By fluids or liquids as used herein generally is meant aqueous, non-aqueous, and mixed aqueous/non-aqueous fluid systems. As seen from the above list of possible applications of polymer monitoring, the purpose of such monitoring may be to trace or track or determine the level of the polymer itself, or to trace or track or determine the level of some substance in association with the polymer, or to determine some property of the polymer or substance in association with the polymer, for instance its leachability. Conventional techniques for monitoring polymers are generally time-consuming and labor intensive, and often require the use of bulky and/or costly equipment. Most conventional polymer analysis techniques require the preparation of calibration curves for each type of polymer employed, which is time-consuming and laborious, particularly when a large variety of polymer chemistries are being employed, and the originally prepared calibration curves lose their accuracy if the polymer structures change, for instance an acrylic acid ester mer unit being hydrolyzed to an acrylic acid mer unit. Direct methods wherein the level of functional groups present in a polymer is determined analytically are generally not practical for industrial use, particularly when it is desired to monitor a polymer on a frequent or continuous basis, or when rapid monitoring results are needed. Indirect methods of polymer monitoring may provide more rapid results using simpler techniques, but in many instances faster and/or more accurate determinations are desirable. Polymers tagged with pendant fluorescent groups are generally easily monitored, even when present at low concentrations. Highly fluorescent molecules, that is molecules which have a fluorescent quantum efficiency, or fluorescent quantum yield, within the range of from about 0.1 to about 1.0, and a light absorbance molar extinction coefficient of at least 1,000, are typically detectable at concentration ranges of parts per million ("ppm") to parts per billion ("ppb") or even less. The incorporation of such a highly fluorescent species into a polymer in the amount of one weight percent (based on polymer actives) will permit the detection of such polymer at polymer concentration levels down to 0.1 ppm or less, provided the fluorescent quantum yield and the light absorbance molar extinction coefficient of the fluorescent tagging agent arenot significantly adversely affected by its attachment to the polymer. US-A-4629566 describes the use of a fluorescent tagging agent to facilitate the monitoring of molecular weights of aqueous polymer solutions. The carboxyl functionality of the polymer is tagged with a fluorescein via a cyanide linkage. An aqueous solution of the tagged polymer can be separated by chromatography and monitored by fluorescence spectroscopy. The present invention provides a method of preparing polymers having pendant fluorescent groups by (trans)amidation derivatization of pre-existing polymers by reaction between certain pendant groups on such polymers and certain organic fluorescent derivatizing agents. More specifically, the pendant polymer groups derivatized by the (trans)amidation reaction are carbonyl-type groups of the Formula I: wherein R is -OR' or -NH₂, wherein R' is hydrogen or a substituent other than hydrogen, and salts thereof, and mixtures and combinations thereof. By salts is meant herein alkali metal salts, alkaline earth metal salts, amine salts, alkanol amine salts, and the like. By "substituent" is meant herein a single or multivalent group other than hydrogen covalently bonded to a carbon of an organic molecule. The pendant polymer group derivatized by the (trans)amidation reaction is contained in a polymer unit or mer unit (a portion of the polymer containing two adjacent backbone carbons) having the structure of Formula II: wherein R₄ is C n H 2n (wherein n is zero or an integer 1 to 10), R₁, R₂ and R₃ are independently hydrogen or a substituent other than hydrogen, and R is as defined above for Formula I, and salts thereof, and mixtures or combinations thereof. The organic fluorescent derivatizing agent is an organic fluorescent molecule that contains an amine group, preferably a primary amine group. Such an agent is represented by the Formula III: wherein one of R₅ and R₆ is hydrogen, and the other one of R₅ and R₆ includes a naphthalene ring system substituted by one to three sulfonic acid groups, or salts thereof. The (trans)amidation derivatization reaction proceeds as follows: wherein the structure designated Formula IV above is a (trans)amidation derivatized pendant group on the polymer. As seen from formula IV, the derivatized pendant polymer group is a pendant N-substituted amide group having an R₅ or R₆ fluorescent group. This reaction is an amidation reaction with R is -OR' and a transamidation reaction when R is NH₂, and hence the term "(trans)amidation" is used herein to specify either or both forms of the reaction. In preferred embodiments of the invention, the (trans)amidation reaction is conducted in an aqueous reaction mixture generally, employing a starting material polymer that is water soluble at the concentration used, or is introduced as held within a latex, and in addition, employing an organic fluorescent derivatizing agent that is water soluble. The reaction mixture preferably is fluid. The product polymer resulting from the (trans)amidation derivatization reaction may possibly have its solubility characteristics so altered by the incorporation of the fluorescent group that it precipitates, or partially precipitates, from the reaction mixture. The (trans)amidation reaction is conducted at elevated temperatures, and generally under pressures that exceed atmospheric pressure. In general it is desirable not to degrade the polymer to any significant extent during the derivatization reaction and generally a reaction in a closed vessel at a temperature of from 120 to 200° C., for a time period of from 1 to 8 hours, may be suitable, the presssure being dependent in part on the temperature. In preferred embodiment the reaction is conducted at from about 130 to about 155° C. In preferred embodiment the reaction is conducted over a time period of from about 1 to about 6 hours. Nonetheless, the reaction may proceed somewhat at temperatures as low as 75 or 80° C. The derivatization reaction may be conducted with air present in the reaction vessel at times, but it may be desirable to exclude oxygen, for instances by purging the reaction vessel with nitrogen gas prior to the reaction. When it is desirable to reduce the pressure that would otherwise be attained by reaction at a given temperature, the reaction vessel may have its internal pressure reduced prior to closing and raising the temperature for the transamidation reaction. The derivatization reaction may be conducted under varying pH conditions, for instance, at a pH of from about 3 to about 10 or possibly 11, but it is preferable, particularly to avoid hydrolysis or polymer degradation, to conduct the reaction at a moderate pH. Moreover, one of the advantages of the present invention is that the derivatization reaction proceeds at a moderate pH, which preferably is a pH of from about 5 to about 7. Another of the advantages of the present invention is that, for a suitable polymer starting material, the derivatization reaction may be conducted employing a high concentration of starting material polymer, which is particularly advantageous for the commercial use of the derivatization reaction. Commercially, a starting material polymer concentration of at least 10 weight percent is desirable, but if a low water solubility polymer is used, a lower concentration may be necessary to maintain a fluid reaction mixture. For water soluble polymers with weight average molecular weights of up to 50,000 to 200,000, or up to 50,000 to 100,000, starting material polymer concentrations of from about 10 to about 45 weight percent are desirable, and from about 30 to about 45 weight percent are very preferred. As noted above, the starting material polymer may be a polymer containing polymer units of the Formula II above. Such polymer units may be derived from acrylic acid, wherein the n of R₄ is zero, each of R₁, R₂ and R₃ are hydrogen, and R is -OH. Such polymer units may be derived from acrylamide, similar to acrylic acid except R is -NH₂. Such units may be methacrylic acid or methacrylamide wherein R₂ is methyl, or for instance itaconic acid wherein R₂ is -CO₂H, R₄ is -CH₂-, and R is -OH. Such polymer units may contain carboxylic acid esters, such as methylacrylate wherein R is -OR' and R' is methyl. It is believed that existing N-substituted amide pendant groups do not to any significant extent participate in the (trans)amidation reaction. The presence of nonparticipating pendant groups on the starting material polymer generally will not interfere with the (trans)amidation reaction, and hence the present invention may be used to tag a wide variety of pre-existing polymers. Only a very low level of fluorescent groups need to be incorporated into a polymer to provide fluorescent detectibility to the polymer. When highly fluorescent groups are employed, the fluorescent derivatizing agent may be required in amounts as low as 0.01 weight percent based on total weight of the polymer, and generally an amount of about 1 weight percent based on total weight of polymer should be sufficient. While the maximum amount of fluorescent groups that may be incorporated into the polymers is limited only by the reactive sites available for a given polymer, there is generally no practical purpose for excessively tagging a polymer. Since it is believed that the derivatization reaction does not, under the preferred and advantageous reaction conditions of the invention, proceed to the exhaustion of all fluorescent derivatizing agent and the exhaustion of all reactive sites on the polymer, it is preferred to employ a polymer having more reactive sites (pendant groups of the Formula I) than required for exhaustion of the fluorescent derivatizing agent used. Hence while a 1 to 1 mole ratio of polymer reactive sites to fluorescent derivatizing agent is possible, and in fact less polymer reactive sites could reasonably be employed, it is desirable to have an excess of polymer reactive sites, and a soluble polymer of any significant molecule weight will have such an excess generally. In preferred embodiment, the starting material polymers of the present invention are water soluble polymers having molecular weights of from about 2,000 to about 100,000, and more preferably to about 50,000. In further preferred embodiment, the starting material polymers of the present invention are water soluble polymers having at least 10 mole percent, and more preferably at least 30 or 50 mole percent of mer units of the Formula II. In every more preferred embodiment, such polymers have at least 70 mole percent of mer units of the Formula II. Nonetheless the (trans)amidation reaction of the present invention is believed to proceed with as little as about 1 weight percent of such mer units, particularly if excess derivatizing agent is used. In another preferred embodiment, the starting material polymers of the present invention are employed in the form of latices or emulsions, rather than aqueous solutions. Some polymers are manufactured in latex form, and for such polymers it is highly advantageous to utilize them in that form. High molecular weight polymers are often manufactured As water-in-oil latices, and this manufacturing technique is advantageous for polymers of such high molecular weight that solution polymerization is not practical. Lower molecular weight polymers could also be made in water-in-oil form, but generally there is no practical reason for employing this technique, which is more expensive generally than solution polymerization. Thus while there is no theoretical minimum molecular weight for a polymer employed in the present invention in latex form, in preferred embodiment such polymer has a molecular weight of at least 200,000, and more preferably at least 500,000, and even more preferably at least 1,000,000. The prescribed group of organic fluorescent derivatizing agents contain a naphthalene ring system, which ring system is substituted with at least one primary amine and one to three sulfonic acid groups. There are many compositions within this group that are commercially available at reasonable cost, and there are many compositions within this group, : distinguished from one another by the number of amine and sulfonic acid substituents and, for a given number of each substituent, by the position of each substituent on the naphthalene ring system. Below in Table I is a list of commercially available compositions within this group, identified as to number of substituents and ring positions, which list is not meant to be exhaustive of the compositions within this group. The amine-containing naphthalene compositions set forth in Table I above include amino naphthalene monosulfonic acids (Compositions a through k), amino naphthalene disulfonic acids (Compositions 1 through u), and amino naphthalene trisulfonic acids (Compositions v through aa), and various of these compositions are supplied as, or are available as, their sodium and/or potassium salt(s). There are numerous commercially available products that contain a fluorescent group and either a primary or secondary amine, or a plurality of same. For instance, Aldrich Chemical Company, InG., lists in excess of 50 of such products in addition to naphthalene derivatives. There is no need generally for the (trans)amidation reaction to proceed to extent where all of the organic fluorescent derivatizing agent is incorporated into the polymer. Residual fluorescent derivatizing agent is generally innocuous, and when desired may be separated from the product polymer, such as by selective precipitation of the polymer from the liquid system employed in the (trans)amidation reaction. In preferred embodiment, the product polymer has different spectral properties than the organic fluorescent derivatizing agent, and hence the presence of product polymer successfully tagged by the (trans)amidation reaction can be determined merely by the presence of its particular major fluorescent peak(s). The following Examples 1 through 37 demonstrate the advantages of the present invention, including without limitation the successful fluorescent tagging of pre-existing polymers without any deleterious effect on the polymer of any significance, using a wide variety of amine-containing fluorescent derivatizing agents. The derivatizing agents used were all commercially available, and many of such agents are commercially available at low cost. In some instances, noted in more detail below, the fluorescent spectras of the derivatized polymers differ from the fluorescent spectras of the derivatizing agents used, and hence one may confirm that fluorescent groups have been incorporated into the polymer by fluorescent spectral analysis without isolating the product polymer from any residual derivatizing agent that may be present. The synthesis method is exemplied using reaction mixtures containing high concentrations of polymer starting material, moderate pH conditions, a single reaction step, and generally low levels of derivatizing agent. The synthesis method proceeds successfully in short time periods. The polymers employed vary as to the amount of pendant groups of Formula I, and a number of the polymers employed have diverse pendant groups outside of Formula I. Exemplified are derivatizations using a single type of pendant group within Formula I, that is, an acrylic acid homopolymer, and a number of polymers containing both (meth)acrylic acid and acrylamide units. - The polymers employed as starting material polymers in Examples 1 to 37 each have more than 70 mole percent of mer units within Formula II and weight average molecular weights of less than 100,000. The following abbreviations are used for the polymer units of these and other Examples: AA Acrylic acid AcAm Acrylamide SMA Sulfomethylacrymalide VA Vinyl acetate MAA Methacrylic acid ACN Acrylonitrile It has been found that the (trans)amidation derivatization of the present invention may proceed together with other post-polymerization derivatization reactions that are feasible under the reaction conditions. For instance, in Examples 9, 10, 13, 20, and 22 to 32, a sulfomethylation derivatization reaction is conducted simultaneously using a formaldehyde-bisulfite (HOCH₂SO₃Na) derivatizing agent. In a number of the synthesis Examples that follow, sodium hydroxide is added to the reaction mixture for the purpose of neutralizing the fluorescent derivatizing agent by forming the salt form, which is more water soluble. In the following Examples 1 to 30, wherein about 140 to about 150 grams of aqueous solution of starting material polymer was employed, the reaction vessel used was a 300 m. Parr reactor. Example 1 To 150 grams of an aqueous solution containing about 55 grams of an AA/AcAm/SMA terpolymer was added 1.11 grams (2 wt. percent based on polymer weight) of 1-[(2-aminoethyl)amino]naphthalene-5-sulfonic acid, as the sodium salt (having a formula weight of 288). This admixture was placed in a Parr reactor, purged with nitrogen, and then heated to 150° C., and held at this temperature for 5 hours, and then cooled to room temperature and removed from the reactor. The polymer product was determined to have a weight average molecular weight of 15,500 and a polydispersity of 2.1, based on polyethylene glycol standards. The molecular weight of this polymer product was about the same as the starting material polymer. Based on size exclusion chromatography, the fluorescent intensity of this polymer was about 62 times that of the starting material polymer, the pendant fluorescent groups appeared to be uniformly distributed on the polymer and only a very small peak from residual fluorescent derivatizing agent was observed at very long elution times. Examples 2 to 6 The same procedure as described in Example 1 above was repeated except that different amine-containing fluorescent derivatizing agents were employed, and these were all employed as in Example 1, that is, in the amount of 1.11 grams or 2 weight percent based on total polymer weight. The resultant polymer product reaction mixture in each instance contained some residual derivatizing agent. The derivatizing agents employed and the characterization of the polymer products are set forth below in Table II. Examples 7 and 8 In each of these Examples, to 145 grams of an aqueous solution containing 50.75 grams of an AA/AcAm copolymer was added 20.35 grams of HOCH₂SO₃Na (20 mole percent based on total moles of mer units in total starting material polymer) and 1.22 grams of 1-amino-5-naphthalene sulfonic acid, as the acid, (having a formula weight of 223.25). These admixtures were each placed in a Parr reactor, purged with nitrogen, and then heated to an elevated temperature, and held at that elevated temperature for 5 hours. In Example 9 such elevated temperature was 150° C., and in Example 10 it was 137° C. After such period of heating, the reaction mixtures were cooled to room temperature and removed from the reactor. In each of Examples 7 and 8 the polymer product had a polydispersity of 1.9 and similar weight average molecular weights, i.e. , respectively 18,800 and 18,900. The fluorescent intensities of these polymer products were respectively 54.2 and 60.6 times greater than the starting material polymer. Residual fluorescent derivatizing agent was present in the reaction mixtures to a minor extent. The above Examples 7 and 8 exemplify the conducting of a second post-polymerization derivatization, adding pendant groups useful for scale inhibiting applications, simultaneously with the (trans)amidation reaction to incorporate the fluorescent derivatizing agent into the polymer. More particularly, the formaldehyde-bisulfite employed in the reaction provides sulfomethylation derivatization to polymer pendant groups of Formula I above wherein R is -OR' and has been shown to proceed under reaction conditions of the (trans)amidation reaction. In preferred embodiment, at least one mole of the formaldehyde-bisulfite is used per 100 moles of mer units in the starting material polymer, and in more preferred embodiment at least 5 mole percent formaldehyde-bisulfite is employed based on total polymer mer units. In further preferred embodiments, the starting material polymer is an acrylic acid polymer or copolymer with acrylamide, and is a polymer having a weight average molecular weight of from about 2,000 to about 200,000, or at least to about 50,000 to 100,000. Example 9 To 150 grams of an aqueous solution containing about 48.75 grams of an acrylic acid homopolymer was added 0.98 grams (about 2 wt. percent based on polymer weight) of 1-amino-5-naphthalene sulfonic acid, as the acid, (having a formula weight of 223.25). This admixture was placed in a Parr reactor, purged with nitrogen, and then heating to 150° C. for 5 hours, and then cooled to room temperature and removed from the reactor. The polymer product was determined to have a weight average molecular weight of 5,100 (as compared to about 4,500 for the starting material polymer) and a polydispersity of 1.5. The fluorescent intensity of this polymer product was about 366 times that the starting material polymer, and the pendant fluorescent groups appeared to be uniformly distributed on the polymer. Some residual derivatizing agent was observed in the gel permeation chromatograms. Example 10 The same procedure as described in the above Examples 1-6 was repeated (all of which, including the present example, employed an AA/AcAm/SMA starting material polymer) except that the fluorescent derivatizing agent employed was the 2-amino-1-naphthalene sulfonic acid, as the acid, and this was employed in the amount of 1.11 grams or 2 weight percent based on total polymer. Example 11 The procedure described in Example 8 above was repeated except that the amine-containing fluorescent derivatizing agent employed was the disodium salt of 1-amino-3,6,8-naphtalene trisulfonate (anhydrous formula weight of 427.34). The amount of this derivatizing agent employed was 1.22 grams. Example 12 To 150 grams of an aqueous solution containing about 52.5 grams of an AA/AcAm/VA terpolymer was added 1.05 grams (2 wt. percent based on polymer weight) of 1-amino-5-naphthalene sulfonic acid, as the acid, (having a formula weight of 233.25). This admixture was placed in a Parr reactor, purged with nitrogen, and then heated to 150° C., and held at this temperature for 5 hours, and then cooled to room temperature and removed from the reactor. The reaction mixture was a clear tan color having a pH of 4.6. The polymer was determined to be 58 mole percent anionic at pH of 10 by titration. Examples 13 and 14 Example 12 was repeated except that different starting material polymers were used. Example 13's starting material polymer was an AA/AcAm/MAA terpolymer and Example 14's starting material polymer was an AA/AcAm/ACN terpolymer. The reaction mixtures (after reaction) were respectively a turbid brown solution with solid material settled at the bottom and a clear brown solution, and respectively had pH's of 4.5 and 4.6. Example 13's product polymer was determined to be 56 mole percent anionic at pH of 10 by titration. Example 14's product polymer was determined to be 65 mole percent at pH 10 by titration. Examples 15 to 17 In each of these Examples, to 150 grams of an aqueous solution containing 52.5 grams of a starting material polymer (described below) was added 1.05 grams (2 wt. percent based on polymer weight) of 1-amino-7-naphthalene sulfonic acid, as the acid, (having a formula weight of 223.25). These admixtures were each placed in a Parr reactor, purged with nitrogen, and then heated to 150° C., and held at this temperature for 5 hours, and then cooled to room temperature and removed from the reactor. The starting material polymers and some product characteristics are set forth below in Table III. Example 18 The procedure described in Example 8 above was repeated except that the amine-containing fluorescent derivatizing agent employed was the 1-amino-7-naphthalene sulfonic acid employed as the acid, (formula weight of 223.25) and the amount of this derivatizing agent employed was 1.22 grams. Example 19 The procedure described in Examples 15 to 17 above was repeated except an AA/AcAm/SMA terpolymer was used as the starting material polymer. This terpolymer is like that used in Examples 1 to 6 and 10 above except that the pH of the aqueous polymer solution was about 11. Examples 20 to 22 In each of these Examples, to 145 grams of an aqueous solution containing 50.75 grams of an AA/AcAm copolymer was added 20.35 grams of HOCR₂SO₃Na (20 mole percent based on total moles of mer units in total starting material polymer) and 1.22 grams of 1-amino-3,6,8-naphthalene trisulfonic acid as the disodium salt (monoacid having an undetermined amount of water of hydration and an anhydrous formula weight of 427.34). The starting material polymers of each of these Examples were prepared in different polymerization batches. Each admixture was placed in Parr reactors, purged with nitrogen, heated to 137° C. and held at such elevated temperature for a period of 5 hours. Example 23 The procedure of Examples 20 to 22 above was repeated except that instead of the trisulfonic acid fluorescent derivatizing agent, 1.22 grams of 1-amino-7-naphthalene sulfonic acid was used. The product reaction mixture was a bright yellow solution having a pH of 5.0. Examples 24 to 26 The procedures of Examples 20 to 22 above was repeated except that in each of these Examples 26 to 28 a different fluorescent derivatizing agent was used and sodium hydroxide was added to each reaction mixture. The 50.75 grams of AA/AcAm copolymer starting material represents 0.710 moles of polymer mer units. In each of these Examples the amount of fluorescent derivatizing agent employed represented 0.005 moles, or 0.7 mole percent based on total moles of mer units, and 0.44 grams of 50 percent NaOH (0.005 moles) was added to each reaction mixture. The identities of the derivatizing agents used and the characterizations of the product reaction mixtures are set forth below in Table IV. Examples 27 to 30 The procedure of Examples 20 to 22 above was repeated except that in each of these Examples 27 to 30 a different fluorescent derivatizing agent was used and sodium hydroxide was added to each reaction mixture. The 50.75 grams of AA/AcAm copolymer starting material represents 0.710 mole of polymer mer units. In each of these Examples the amount of fluorescent derivatizing agent employed represented 0.004 moles, or about 0.56 mole percent based on total moles of mer units, and 0.28 grams of 50 percent NaOH (0.004 moles) was added to each reaction mixture. The identities of the derivatizing agents used and the characterizations of the product reaction mixtures are set forth below in Table V. The present invention also includes polymers wherein one of R₅ and R₆ is hydrogen and the other is an (alkylene)naphthalene which is further substituted on the naphthalene ring with one to three sulfonic acid groups or salts thereof. By "(alkylene)naphthalene" is meant herein both a naphthalene group directly bonded to the amine residue nitrogen or a naphthalene bonded to the nitrogen through an alkylene or partially alkylene group, or the alkylene group, or partial alkylene group, is bonded to the naphthalene ring through a functional group. In preferred embodiment the derivatizing agents are selected from those that a reasonably high "relative performance" for a given background. As noted above, a molecule is generally considered highly fluorescent when it has a fluorescent quantum efficiency, or fluorescent quantum yield, within the range of from about 0.1 to about 1.0, and a light absorbance molar extinction coefficient of at least 1,000. The magnitude of fluorescent signal, or relative fluorescence, is the product of the fluorescent quantum yield multiplied times the light absorbance molar extinction coefficient. Thus for instance if two compositions each had the minimal 1,000 light absorbance molar extinction coefficient, but one had a fluorescent quantum yield of 0.1 and the other had a fluorescent quantum yield of almost 1.0, the latter would have a ten-fold higher relative fluorescence. For a given application, however, that feature alone would not render the latter derivatizing agent the better choice, because the relative fluorescence determination does not take into considerationany fluorescent background characteristics of the medium (either natural or added by the system process) in which the tagged polymer is to be used, generally referred to as background fluorescence. The "relative performance", as this phrase is used herein, is the ratio of the relative fluorescence of a composition to the relative fluorescence of a given background medium. The fluorescence readings are typically measured at the excitation/emission wavelengths that represent major peaks for the given fluorescent tagged polymer. For a given process sample background, two compounds having similar relative fluorescence values, but at different excitation and/or emission wavelengths, may have diverse relative performance values because their relative performances are being measured at different wavelengths and the fluorescent intensity of the background at these diverse wavelengths may be significantly different. Some generalities may be considered. Industrial cooling waters generally have an overall higher fluorescent intensity than industrial boiler waters, and therefore a degree of polymer tagging that is reasonably high for use in boiler waters may not be sufficiently high for cooling waters, since of course the intensity of fluorescence must not be overwhelmed by the background fluorescence and the intensity of fluorescence is dependent on the concentration level of the fluorescent species. Similarly, a polymer that is to be used at high concentration levels in a given background medium need not be tagged to the same extent as one that is to be used at much lower concentration levels, other parameters being the same. Further, a derivatizing agent that is satisfactory for use in one type of background medium, for instance cooling waters, may not be suitable for tagging polymers that are to be used in a different medium, for instance waste water, because that agent's major- excitation/emission peaks may substantially coincide with the background fluorescence peaks of the waste water and hence have a low relative performance value for such a background. As noted above, the amino-naphthalene sulfonic acid derivatizing agents generally have different major fluorescent peaks than the product polymer tagged with such agent. While this spectral shift is obviously highly advantageous for determining the success of a derivatization and/or presence of residual agent, it of course renders the relative performance of the agent for a given background somewhat different than the relative performance of a polymer tagged with such agent because such relative performances are being measured in somewhat different spectral areas. Nonetheless this shift and its impact on relative performances is, for the purposes of using the agents per se in relative performance determinations against a given background, a minor effect that does not diminish the value of such determinations, particularly since the use of the fluorescence spectral data of the derivatizing agents in a given background permits a large number of agents to be screened without the burden of conducting a large number of derivatizing reactions. Thus in Example 31 below a survey of relative performance values of a number of fluorescent derivatizing agents against a cooling water background is given as representative of the use of such screening method for any other group of derivatizing agents and any other type of background. Example 31 The relative performances of a variety of fluorescent derivatizing agents were surveyed against a cooling water background as follows. An aqueous solution of each agent at a concentration level of 0.4 ppm (acid actives) and the fluorescent intensity of each agent at its fluorescence maximum was determined, in comparison to a fluorescence reference standard. The standard used was 1,5-naphthalene disulfonic acid, which is not a derivatizing agent for the purposes of the present invention because it has no amine functionality. This standard was also measured at its fluorescence maximum in an aqueous solution at a concentration of 0.4 ppm (acid actives) and its intensity was assigned a "relative intensity value" of 100%. The "relative intensity values" of each of the other compositions tested were assigned in relationship to the intensity of the standard. For instance, a composition that had twice the intensity of the standard (the standard and the composition each being measured at their own fluorescence maximums) would be given a relative intensity value of 200%. Then the relative intensity values of the various compositions were compared to that of the cooling water background at the fluorescent maximum (peak excitation/emission wavelengths) of the composition. The cooling water fluorescent intensity employed was the average relative intensity of ten representative cooling water formulations measured for combination of wavelengths of excitation-and emission within the range required for this survey. The relative performance for each composition thus is the value determined by dividing the relative intensity value determined for the fluorescence of each composition by the relative intensity value of the background fluorescence of cooling water at the same combination of wavelengths. The identities of the various compositions surveyed and thevalues determined are set forth below in Table VII. From the survey results set forth in Table VII above, it is noted that the 1-amino-8-naphthalene sulfonic acid did not provide detectable fluorescence. Beyond such composition, the survey results provide a good measure of which derivatizing agents may be preferred for tagging polymers to be used in cooling waters. Generally a relative performance value of at least 5 is preferred, a relative performance value of at least 10 is more preferred, and most preferred are those agents having a relative performance value of 15 and greater. A low performance value on a given survey, however, does not exclude a composition as a potential derivatizing agent generally. For instance, 1-amino-6-naphthalene sulfonic acid has a relative performance value in the survey of Table VII of only 3, but its relative intensity value is 74%. In comparison, the 4-amino-benzene sulfonic acid has a higher relative performance value of 8 and a lower relative intensity value of 26%. Thus while 1-amino-6-naphthalene sulfonic acid may not be a preferred tagging agent for cooling water polymers, its relative intensity is sufficiently high that it may well be a preferred agent for polymers to be used in an application with a different background fluorescence. In addition, those compositions shown to have low relative intensities may be sufficient for use in polymers to be used in mediums having lower background fluorescent intensities, and may be there the agent of choice for other reasons, such as cost, availability, efficiency of derivatization reaction, toxity, compatibility, or other reasons. Hence surveys as shown in Example 31 are a tool for making a reasonable selection of derivatizing agent for a given known purpose, and not an absolute categorization of potential usefulness of derivatizing agents in all applications. Example 32 Using the polymer derivatized as described in Example 5 above as a representative polymer suitable for cooling water treatment, the tolerance of the polymer, as to fluorescent intensity, upon exposure to chemical species generally present in industrial cooling waters was determined as follows. For each chemical species tested, an aqueous solution of the polymer (at a concentration level of 7.5 ppm as acid actives) and a certain amount of the chemical species was prepared and mixed for one minute, after which the fluorescent intensity was determined and compared to a sample of the same polymer, similarly diluted, but not exposed to any of the chemical species. The concentrations of the chemical species, which are set forth in Table VIII below, were 10 times or greater than the concentrations encountered in typical cooling waters. The results are reported as a percentage of fluorescent intensity, as compared to the polymer sample not exposed to any chemical species (the blank), which of course would be rated as 100%. The test results are set forth below in Table VIII. It is noted that an interference is commonly considered a chemical species or operating condition that produces a 10% change in the analytical response. These tests were designed to detect fluorescence quenching which would occur instantly, if at all. It is seen from Table VIII below that the various chemical species tested, except very high levels of ionic iron, do not produce an interference result even at the very high concentration levels employed. Given these test results, it is believed that none of the chemical species will have any significant effect on the fluorescent intesity of the tagged polymer in typical cooling water systems. Fluorescent intensity values that differ by 1% or less are considered equivalent, being within statistical error limits. Chemical Species Chemical Species Concentration Fluorescent Intensity (%) Ca⁺² 10,000 ppm (as CaCO₃) 100 Mg⁺² 10,000 ppm (as CaCO₃) 100 HCO 3 - 10,000 ppm (as CaCO₃) 102 SO 4 -2 10,000 ppm (as SO 4 -2 ) 99 Cl⁻ 10,000 ppm (as Cl⁻) 99 Na⁺ 10,000 ppm (as Na⁺) 102 Zn⁺² 10 ppm (as Zn⁺²) 97 Fe⁺²,⁺³ 10 ppm (as Fe⁺²,⁺³) 52 adjust to pH 3 96 adjust to pH 10 103 In addition, a polymer such as that prepared in Example 5, tagged with a sulfonate-containing derivatizing agent, is extremely tolerant, as to fluorescent intensity, to extremely high levels of bleach, a substance also found in industrial water systems, while the derivatizing agents themselves are much less tolerant. Example 33 Using the polymers derivatized as described in Examples 2, 5 and 8 above as representative of polymers suitable for cooling water treatment, the effect of the tagging on polymer performance was determined as follows. These three tagged polymers, and an underivatized AA/AcAm/SMA terpolymer of the same composition as employed in Examples 2, 5 and 8, were tested to determine their performances in a calcium phosphate threshold inhibition performance test using test conditions described in US-A-4,752,443. The calcium phosphate inhibition results are reported in percent inhibition as described in such patent. The test results are set forth below in Table IX. Polymer Preparation Example % Calcium Phosphate Inhibition Example 2 81 Example 5 83 Example 8 80 underivated AA/AcAm/SMA terpolymer 85 As seen from the results set forth in Table IX above, the fluorescent tagging of these polymers has not caused a detrimental response to the calcium phosphate inhibition performance of the polymers. The fluorescent derivatizing agents that have functionalities other than the aromatic ring system and the amine, for instance the amino-naphthaline mono- and disulfonic acids, have toxity levels, as reported in the literature for the LD50 test, oral administration on rats, that are favorably low, for instance in comparison to aniline (benzene amine). A sampling of such literature toxicity data is set forth below.in Table X. Derivatizing Agent Reported LD50 (oral/rats) Toxity Data (grams/kilogram) 2-amino-1-naphthalene sulfonic acid 19.4 2-amino-6-naphthalene sulfonic acid > 5.0 2-amino-4,8-naphthalene disulfonic acid > 5.0 2-amino-5,7-naphthalene disulfonic acid 2.0 2-amino-6,8-naphthalene disulfonic acid > 5.0 aniline 0.25 In the following Example 33 there is given a post-polymerization derivatization procedure suitable for polymers whose molecular weights are too high to be used as a water solution. The polymer starting material is of the type commercially available in the form of a water-in-oil emulsion or latex and the polymer is useful for industrial waste water treatment. Example 33 170.0 grams of a water-in-oil latex which contained 51.85 grams of a polymer was admixed with 5.05 grams of additional surfactant, a solution of taurine (2-aminoethanesulfonic acid) and a solution of 2-amino-8-naphthalene sulfonic acid, to form the reaction mixture. The polymer was a homopolymer of acrylamide having a weight average molecular weight of about 10,000,000 (a reduced specific viscosity of about 20). The polymer was formed in such water-in-oil latex form and such latex contains about 2 weight percent surfactant based on total latex. The additional surfactant employed was a nonionic surfactant commercially available from ICI Americas, Inc. under the tradename of Span 80 (Span is a registered trademark of ICI Americas, Inc.). The taurine solution was comprised of 9.12 grams taurine, 5.83 grams of 50% NaOH, and 1.63 grams of deionized water. The solution of 2-amino-8-naphthalene sulfonic acid was comprised of 1.04 g 2-amino-8-naphthalene sulfonic acid, 0.37 grams of 50% NaOH, and 8.99 grams of deionized water. The taurine solution was heated to dissolve the taurine and added slowly to the latex (with the additional surfactant) while stirring, and then the 2-amino-8-naphthalene sulfonic acid solution was added slowly while likewise stirring. The reaction mixture was transferred to a 300 ml. Parr reactor, which was then purged with nitrogen for about 30 minutes, and then the reactor was fully closed and heated to 140° C. for a four hour reaction period. The reaction product was substantially in latex form and analysis indicated that a degree of tagging had been accomplished, together with a post-polymerization transamidation reaction with the taurine. In the following Comparative Examples 34 to 37, the fluorescent derivatizing agents used were sulfanilic acid (4-aminobenzenesulfonic acid) and anthranilic acid (ortho-aminobenzoic acid or 2-aminobenzoic acid), and in some instances a concommitant post-polymerization derivatization with sodium formaldehyde bisulfite was conducted. Example 34 80 grams of an aqueous solution containing 35 weight percent of an AcAm/AA copolymer (50/50 mole percent, having a weight average molecular weight of about 13,000) was admixed with 0.69 grams of sulfanilic acid, and the admixture was transferred to a 300 ml. Parr reactor, which was then purged with nitrogen for about 30 minutes, and then sealed and heated to 150° C. for about 5 hours. The analysis of the reaction product indicated that a degree of fluorescent tagging of the polymer had occurred. Example 35 Example 34 was repeated except the sulfanilic acid charge was reduced to 0.67 grams, 11.22 grams of 93.5% HOCH₂SO₃Na was added to the reaction mixture, and the reaction temperature was reduced to 137° C. Analysis of the reaction product indicated that both derivatization reactions had occurred to some degree. Example 36 Example 35 was repeated except that 0.67 grams of anthranilic acid was substituted for the sulfanilic acid charge. Analysis of the reaction product indicated that both derivatization reactions had occurred to some degree. Example 37 150 grams of the 35% polymer solution described in Example 34 above was admixed with 1.26 grams of anthranilic acid, transferred to a 300 ml. Parr reactor, which was then purged with nitrogen for about 30 minutes, sealed, and heated to 138° C. for 5 hours. Analysis of the reaction product indicated that the fluorescent tagging of the polymer had occurred to some degree. It has been generally observed that the fluorescent intensities of the polymers prepared according to Examples 41 to 45 above were not as strong as that seen from solution derivatizations using various amino-naphthalene mono- and di-sulfonic acids, but such lesser fluorescent intensity is no deterrent to the use of such polymers in applications where the background fluorescent is less intense than cooling waters and/or where the polymers are used at higher concentration levels than is typical for cooling water treatment polymers. As discussed above, the successfully tagged polymers may be distinguished from unreacted derivatizing agent because these species have different fluorescent spectra, that is, different excitation/emission wavelengths at major peaks. In addition, it has been determined that the wavelengths of major absorption peaks are not dependent upon pH, that is, do not change when varying the pH from about 3 to greater than 5, while easily detectable shifts in the major absorption peaks occurs in the fluorescent derivatizing agent subjected to such a pH variation, and hence monitoring major peak excitation/emission wavelengths while so varying the pH of the medium in which the polymer and/or agent is disposed is another technique available for distinguishing these species. The present invention is applicable to any industry employing polymers, particularly water soluble polymers, wherein it is desired at times to have at least some of such polymer tagged with fluorescent groups for monitoring purposes, such as the water treatment industry.

Claims: A method of preparing a polymer having pendant fluorescent groups comprising: admixing an aqueous solution or latex of a polymer having mer units of the formula II wherein R is -OR' or -NH₂, R', R₁, R₂ and R₃ are independently hydrogen or a substituent other than hydrogen, and R₄ is C n H 2n wherein n is zero or an integer of from 1 to 10, and salts thereof and mixtures and combinations thereof, with an amine-containing organic fluorescent composition of the Formula III wherein one of R₅ and R₆ is hydrogen, and wherein the other one of R₅ and R₆ includes a naphthalene ring system substituted by one to three sulfonic acid groups or salts thereof; and heating said admixture for a sufficient period of time to accomplish a degree of (trans)amidation derivatization of said polymer. A method according to claim 1 wherein said admixture contains at least one post-polymerization derivatization agent in addition to said amine-containing organic fluorescent composition, and by said heating for said time period a post-polymerization derivatization reaction in addition to said (trans)amidation with said amine-containing organic fluorescent composition is accomplished. A method according to claim 2 wherein said post-polymerization derivatization agent in addition to said amine-containing organic fluorescent composition is formaldehyde-bisulfite. A method according to claim 1 wherein said aromatic ring system has 2 or 3 sulfonic acid substituents or salts thereof. A method according to any one of the preceding claims wherein said admixture is heated in a closed vessel at a temperature of from 120 to 200°C. A method according to any one of the preceding claims wherein said admixture contains at least 10 weight percent of said polymer. A method according to any one of the preceding claims wherein said amine-containing organic fluorescent composition is admixed with said polymer in an amount of at least 0.01 weight percent based on total weight of said polymer. A method according to any one of the preceding claims wherein said (trans)amidation derivatization of said polymer is accomplished to the degree of incorporating into said polymer at least 0.01 weight percent of said amine-containing organic fluorescent composition. A method according to any one of the preceding claims wherein said amine-containing organic fluorescent composition contains a primary amine. A method according to any one of the preceding claims wherein said polymer contains at least 10 mole percent of mer units of Formula II given and defined in claim 1. A method according to claim 10 wherein said polymer contains at least 50 mole percent of said mer units of said Formula II. A method according to claim 10 or claim 11 wherein said mer units are units of acrylic acid or acrylamide. A method according to any one of the preceding claims wherein said admixture has a pH of from 3 to 11. A method according to any one of the preceding claims wherein said admixture is heated for a time period of from 1 to 8 hours. A method according to any one of the preceding claims wherein said admixture is an aqueous solution of said polymer at a concentration of said polymer of from about 30 to about 40 weight percent, and said polymer has a weight average molecular weight of up to 100,000. A method according to any one of the preceding claims wherein said admixture is a water-in-oil latex of said polymer and said polymer has a weight average molecular weight of at least 200,000.

Inventors: FONG DODD W, HOOTS JOHN E, FONG, DODD W., HOOTS, JOHN E.
Applicants: NALCO CHEMICAL CO, NALCO CHEMICAL COMPANY
Application year: 1991
Main classification: C08F8
IPC codes: C08F8, C02F1, G01N21