COMPOSITION AND PROCESS FOR DETACKIFING PAINT

Abstract: Melamine-formaldehyde resin dispersions containing more free formaldehyde than is desirable for health and/or pollution reasons can be treated with diketo reagents or their nitrogen analogs to reduce the free formaldehyde content while not diminishing, and in some cases even enhancing, the ability of the dispersions to detackify paint. Preferably, the resin dispersions are also treated with urea, which allows considerably less acetoacetamide to be used to achieve the same amount of formaldehyde reduction.

Description: COMPOSITION AND PROCESS FOR DETACKIFING PAINT CROSS-REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of Application Serial No. 970,727 filed November 3, 1992. BACKGROUND OF THE INVENTION Field of the Invention This invention relates to the detackification of paint and similar materials en¬ trained in water, particularly circulating water in a conventional automobile plant spray booth. "Paint" as used herein is to be understood as a generic term which encompass¬ es all common varieties of water insoluble organic binder containing coatings common- ly applied in spraying operations, including but not limited to oil based paints, enam¬ els, lacquers, high solids solvent based automotive body base coat, high solids solvent based automotive body clear coat, water borne auto body base and clear coats, urethane polymer containing auto body top coats, and solvent and water borne primers. These paints may utilize asphaltic, acrylic, polyester, melamine-formaldehyde, isocyanate, epoxy, alkyd, melamine alkyd, and blocked polyurethane resins among others, along with appropriate solvents, pigments, and ancillary additives. Paint "overspray", the portion of the sprayed paint which does not fall on the surface(s) it is intended to pro¬ tect, if left untreated, readily adheres to the walls of spray booths and any other sur¬ faces that it contacts, such as the surfaces of water distribution piping, spray nozzles, and the like. Use of a process according to this invention converts the paint overspray to a non-sticky sludge suitable for convenient disposal. Statement of Related Art Ii is known in the art to use a melamine-aldehyde polymer, particularly a mel- amine-formaldehyde resin acid colloidal solution, as an effective treatment for detacki¬ fication. However, the previously known polymers of this type made from formalde¬ hyde usually contain substantial amounts of free formaldehyde. For example, most commercial liquid melamine-formaldehyde resins contain at least 0.2 % by weight of free formaldehyde. (Hereinafter, all percentages are to be understood as percentages by weight unless otherwise stated.) Formaldehyde is believed to be a carcinogen, so that use of materials containing more than a minimal amount of it is undesirable in general. It is an object of this invention to provide detackifying processes at least as ef¬ fective as those taught by the prior art while minimizing exposure of workers who use the process to free formaldehyde. DESCRIPTION OF THE INVENTION In this description, except in the claims and the specific examples and in other parts where expressly indicated to the contrary, all numbers specifying amounts of ma¬ terials or conditions of reaction or use are to be understood as modified by the term "about" in determining the broadest scope of the invention. Practice of the invention within the exact numerical limits given is generally preferred. Also, unless it is expli¬ citly stated to the contrary, wherever individual members of a class are described as suitable or preferred for a given purpose, it is to be assumed that mixtures of one or more members of the class are equally suitable or preferred for the same purpose. Summary of the Invention The disclosure in U. S. Patent 4,656,059 of April 7, 1987 to Mizuno et al. of melamine-formaldehyde resins and their use in detackification, except to the extent contrary to any explicit statement herein, is hereby incorporated herein by reference. It has been found that melamine-formaldehyde resins of the type disclosed in this Mizuno patent can be reacted with water soluble organic β-diketo compounds and their nitro¬ gen analogs (the abbreviation "DKA", from "diketo and analogs", being understood hereinafter to include both actual diketo compounds and their nitrogen analogs), that is, compounds containing a structure according to formula I: in which each of Q 1 and Q 3 independently is one of =O, =NH, or ≡N; Q 2 is N or C; and each of the free bonds except in the Q's can be bonded to any other moieties that do not interfere with the reaction with formaldehyde, to produce a modified resin with a free formaldehyde content that is no more than 80 % of the free formaldehyde content of the original melamine-formaldehyde dispersion reacted with the DKA modifying reagent and that is also no more than 0.20 % (and preferably is, with increasing preference in the order given, not more than 0.18, 0.17, 0.16, 0.15, 0.14, 0.13, 0.12, 0.1 1 , 0.10, 0.095, 0.090, 0.085, 0.080, 0.075, 0.070, or 0.066 %) and that the thus modified resin is still effective for detackifying paint. (Two molecules of the DKA compounds as defined above are believed to react irreversibly with one molecule of free formaldehyde to produce the following chemical structure: I I in which the formaldehyde formerly present is bound into a substantially nonvolatile form.) The content of free formaldehyde in a given volume of either the starting resin or the modified resin is defined as the product of the free formaldehyde concentration and the volume. The thus modified melamine-formaldehyde resins may advantageous¬ ly be combined with other materials, such as flocculants, defoamers, and the like, to maximize the practical value of their detackifying and flocculating effect, in a manner generally known per se in the art for using unmodified melamine-formaldehyde resins in detackification. Various embodiments of the invention include aqueous liquid compositions in¬ cluding modified dispersions of melamine-formaldehyde polymers that are useful in de¬ tackifying when added to the circulating water in spray booths, processes for making such modified dispersions, and detackifying processes using the compositions contain¬ ing the modified melamine-formaldehyde polymer dispersions. The detackifying pro¬ cesses are especially advantageously used as part of processes comprising steps of (I) O 95/26378 PC17US95/03768 detackifying and flocculating paint entrained in a circulating water based liquid to pro¬ duce a flocculated sludge, (II) separating detackified and flocculated paint solids from residual water based liquid, and (HI) using the residual water based liquid to entrain additional paint. However, detackifying may be achieved according to this invention in a variety of other ways which are generally, except for the particular detackifying agent used, known per se in the art and are all within the broad scope of this inven¬ tion. Description of Preferred Embodiments The most preferred water-soluble diketo compound for use in the invention is acetoacetamide, also known as β-ketobutyramide (CAS Registry No. 5977-14-0). An¬ other readily available and preferred water soluble nitrogen analog of a diketo com¬ pound is dicyandiamide, also known as cyanoguanidine. In the description below, acetoacetamide is often mentioned, but it should be understood that the invention is not limited thereby. Other suitable DKA modifying reagents include other β-keto- carboxylic acids and their salts, esters, amides, and the like, such as acetoacetic acid or its ethyl ester and β-diketones, such as acetylacetone. In an especially preferred embodiment of the invention, the use of DKA com¬ pounds or their nitrogen analogs is combined with urea. Urea itself has been previ¬ ously known to be capable of reducing the formaldehyde content of aminoplast resins to which it has been added. However, this use has been accompanied by a serious dis¬ advantage: a greatly increased likelihood of the formation of precipitates in resins to which urea has been added. The formation of precipitates during storage of resins of¬ ten gives rise to serious fouling of pumps and feed lines used for handling the resin on a large scale, necessitating expensive cleaning procedures and lost production. It has now been found, however, that urea and DKA compounds can be effect- ively used in combination. In this way, much of the desired reduction in formaldehyde content can be accomplished by urea rather than by the usually more costly DKA com¬ pounds, but precipitation is still avoided. The base melamine-formaldehyde polymer for use in this invention preferably is made by reacting melamine and formaldehyde, in a manner known in the art, with each other in a molar ratio of formaldehyde to melamine in the range from 6:1 to 1:1, preferably from 4:1 to 1:1, or more preferably from 3.0:1.0 to 1.0:1.0. For a concen¬ trate, the form in which a composition according to this invention would normally be shipped to the point of use, the concentration of dispersed polymer solids preferably is, with increasing preference in the order given, not less than 1, 3, 6.0, 7.0, or 8.0 %; in¬ dependently, the concentration of dispersed polymer solids preferably is, with increas¬ ing preference in the order given, not more than 20, 15, 12.0, 10.0, or 9.0 %. The con- centration of free formaldehyde preferably is, with increasing preference in the order given, not less than 0.10, 0.15, 0.16, 0.17, or 0.18 % and independently preferably is, with increasing preference in the order given, not more than 0.35, 0.30, 0.25, 0.22, 0.21, 0.20, or 0.19 . The pH preferably is, with increasing preference in the order given, not less than 1.0, 1.3, 1.5, 1.7, 1.8, or 1.9 and independently preferably is, with increasing preference in the order given, not more than 3.0, 2.8, 2.6, 2.3, 2.2, 2.1, or 2.0. (All the preferences in this paragraph are for the resin before treatment, but except for the formaldehyde concentration, they also apply to the modified resin after treatment.) If the concentration of melamine-formaldehyde resin is reduced to too low a value by the addition of large amounts of a DKA modifying reagent or of solvent such as water in which the DKA modifying reagent may be dissolved, the detackifying ef¬ fectiveness of the modified resin dispersion will suffer. On the other hand, when the amount of modifying reagent is within the preferred ranges, the detackifying effect¬ iveness in many cases is actually increased over that of the unmodified polymer dis- persion. The amounts of DKA compound and/or urea added should not be so large as to result in any visible formation of precipitate within 15 days after addition. Preferably, with increasing preference in the order given, compositions made according to this invention remain free of any visible precipitate for 20, 30, 40, 50, 60, 70, 80, 90, 100, 120, 150, or 180 days after the addition of DKA compounds and/or urea to the starting melamine-formaldehyde polymer containing dispersion. The amount of acetoacetamide added, when it is used without any urea, prefer¬ ably has, with increasing preference in the order given, a ratio by weight to the initial free formaldehyde content of the polymer dispersion reacted with it that is not greater than 135:1.0, 100:1.0, 85:1.0, 75:1.0, 67:1.0, 61:1.0, 55:1.0 or 52:1.0; independently, the amount of acetoacetamide added when used without urea preferably has, with in¬ creasing preference in the order given, a ratio by weight to the initial free formalde¬ hyde content of the polymer dispersion reacted with it that is not less than 6:1.0, 13:1.0, 18:1.0, 23:1.0, 27:1.0, 30:1.0, or 33:1.0. When acetoacetamide is used together with urea, the amount of acetoacetamide added preferably has, with increasing prefer¬ ence in the order given, a ratio by weight to the initial free formaldehyde content of the polymer dispersion reacted with it that is not greater than 50:1.0, 25:1.0, 20: 1.0, 15:1.0, 1 1 : 1.0, 8.0:1.0, 7.0: 1.0, 6.0:1.0, 5.0: 1.0, 4.0: 1.0, 3.0: 1.0, 2.5:1.0, 2.0: 1.0, 1.8: 1.0, or 1.65:1.0; independently, the amount of acetoacetamide added when used with urea preferably has, with increasing preference in the order given, a ratio by weight to the initial free formaldehyde content of the polymer dispersion reacted with it that is not less than 0.5:1.0, 0.8:1.0, 1.0:1.0, 1.2:1.0, 1.3:1.0, 1.4:1.0, or 1.5:1.0. When the DKA reagent is not acetoacetamide, the preferred amounts given above should be adjusted to provide the same number of units according to formula I above as do the specified amounts of acetoacetamide. The amount of acetoacetamide that provides the same number of units according to formula I above as some other DKA modifying reagent is defined for use later in this specification as the "stoichiometric equivalent as acetoacetamide" and abbreviated "SEA". Independendy, for any DKA modifying reagent, whether alone or in combina¬ tion with urea, the amount of modifying reagent added preferably is such as to result in a free formaldehyde content of the modified resin dispersion 24 hours after the addi¬ tion of the formaldehyde content modifying reagent(s) that is, with increasing prefer¬ ence in the order given, not greater than 65, 57, 50, 45, or 40 % of the free formalde- hyde content of the starting resin dispersion used to make the modified resin disper¬ sion; independently, the amount of modifying reagent added preferably is such as to re¬ sult in a free formaldehyde content of the modified resin dispersion 24 hours after the addition of the formaldehyde content modifying reagent(s) that is, with increasing pref¬ erence in the order given, not less than 5, 10, 15, 18, or 20 % of the free formaldehyde content of the starting resin dispersion used to make the modified resin dispersion. When urea is used, the ratio by weight of the amount of urea used to the SEA of DKA compound(s) used is, with increasing preference in the order given, not less than 1.0:100, 1.0:60, 1.0:30, 1.0:20, or 1.0:15, 1.0:8.0, 1.0:4.0, 1.0:2.0, 1.0:1.5, 1.0:1.3, 1.0:1.1, 1.0:0.95, 1.0:0.83, 1.0:0.75, 1.0:0.69, or 1.0:0.64; independently, the ratio by weight of the amount of urea used to the SEA of DKA compound(s) used is, with in¬ creasing preference in the order given, not greater than 1.0:0.40, 1.0:0.45, 1.0:0.50, 1.0:0.52, 1.0:0.54, 1.0:0.55, 1.0:0.56, 1.0:0.57, or 1.0:0.58. Independendy, it is preferred that the modified detackifying composition have a concentration of melamine-formaldehyde polymer solids that is at least 50, more pref¬ erably at least 62, or still more preferably at least 75, % of the concentration of mela¬ mine-formaldehyde polymer solids in the starting resin from which the detackifying composition is made. In a concentrate product to be added to water for detackification, the content of melamine-formaldehyde resin solids preferably is, with increasing preference in the order given, not less than 1.9, 2.7, 3.6, 4.0, 4.5, 4.8, or 5.0 % and independently pref¬ erably is, with increasing preference in the order given, not greater than 50, 35, 20, 17, 14, 11, 10, 9.0, 8.5, or 8.0 %. One major embodiment of the invention is a modified concentrated detackify¬ ing composition comprising, preferably consisting essentially of, or more preferably consisting of, water and: (A) dispersed melamine-formaldehyde polymer solids; (B) free formaldehyde; (C) products of reaction between free formaldehyde and water soluble DKA modifying reagent molecules; and, optionally one or more of the following, the first being preferred: (D) products of reaction between free formaldehyde and urea; (E) urea; and (F) unreacted DKA modifying reagent molecules. The free formaldehyde content for purposes of this invention is preferably mea¬ sured, and for the specific values given below was measured, by a method utilizing quantitative spectrophotometric absorbance of light with a wave length of 550 nano¬ meters (hereinafter "nra") in conjunction with commercially supplied reagents and ap- paratus which convert the formaldehyde in a sample to a colored reaction product. The needed reagents and apparatus are supplied by CHEMetrics, Inc. of Calverton, Virginia and are believed to be described in U. S. Patent 3,634,038. The Vacu-vials® needed have the Catalog No. K-4203 and employ a highly sensitive reagent called "Purpald®" which reacts with formaldehyde in alkaline solution to produce a purple color. With the aid of calibrating standards, the absorbance of the solution prepared as directed by the manufacturer of these Vacu-vials® can be converted directly to a free formaldehyde concentration, after appropriate quantitative dilution of the sample if nec¬ essary to bring the concentration of free formaldehyde in the photometric cell within the range of 0 to iO parts per million by weight (hereinafter "ppm") of free formalde¬ hyde. The reaction between acetoacetamide, other DKA modifying reagent, and/or urea and the formaldehyde containing polymer may be effected at any temperature at which the polymer dispersion is liquid. Normally, ambient human comfort temperature in the range from 20 - 30 ° C is preferred, both for convenience and because higher temperatures have been observed to increase the amount of free formaldehyde present in the starting melamine-formaldehyde resin and thereby require the addition of more of the modifying reagent(s). The normal time between commercial manufacture and use of the modified resins will be sufficient for reaction at ambient temperature, as will be apparent from the data in the examples below. Modification of polymer dispersions as contemplated by this invention includes not only the reduction of the initial free formaldehyde content but the retention within the modified polymer dispersion of any products of reaction between the free formal- dehyde initially present and the added modifying reagent(s), along with any unreacted modifying agent(s). For actual use, a modified melamine-formaldehyde polymer dispersion concen¬ trate according to this invention as described above is preferably added to water con¬ taining entrained paint to be detackified and/or flocculated, preferably in an amount to give a ratio by weight of solids content in the modified polymer dispersion to solids content of the paint to be detackified that preferably is, with increasing preference in the order given, not less than 0.01 :1.0, 0.03:1.0, 0.05:1.0, 0.07:1.0, 0.09:1.0, 0.11:1.0, 0.13:1.0, 0.14:1.0, or 0.15:1.0 and independently preferably is, with increasing preference in the order given, not more than 5.0:1.0, 2.5:1.0, 1.5:1.0, 1.0:1.0, 0.70:1.0, 0.50:1.0, 0.40:1.0, 0.35:1.0, 0.31:1.0, 0.28:1.0, 0.25:1.0, or 0.23:1.0. Detackified paint is then removed from the circulating water by any convenient means. The invention may be further appreciated by consideration of the following non-limiting examples and comparison examples. GROUP I - WITHOUT UREA Examples of Preparation of Modified Dispersions In these examples, the starting melamine-formaldehyde polymer dispersion was MAGNIFLOC™ 515C, a commercial product available from American Cyanamid Corp. with the following characteristics as described by its manufacturer: A specific gravity of 1.01 - 1.035; a pH value of 1.7 - 2.1, and a solids content of 8.2 - 8.6 %. The source of acetoacetamide used as the DKA modifying reagent was BKB™, commercially available from Eastman Chemical Co. and described by its supplier as a 30 % solution of acetoacetamide in water. These two ingredients, along with ad- ditional water in some cases, were mixed, with stirring for the first eight hours, and then maintained in loosely stoppered containers for time periods up to 40 days, with samples periodically removed for assay of the free formaldehyde content. Some results are shown in Table 1 below. These results indicate that within one day at the latest after mixing, the free formaldehyde content of the mixture had become low enough to qualify all these compositions as modified compositions within the meaning of this invention. Detackification Examples and Comparative Examples These processes were performed in a pilot scale spray booth apparatus. This uses 1041 liters of water in addition to all the other components shown below. The materials, other than paint, shown under the description of specific experiment numbers below are added to the circulating water of this spray booth, either by metering in with a controlled rate pump over a period of time or by "slug feeding" a substantial quantity of additive into an inlet port in the circulating water piping, while paint is being sprayed into it in a consistent manner that approximates very closely the practical use of a full scale spray booth. The resulting solid sludge is collected and separated by means conventional for practical spray booths. Example 2.1 The circulating water system was turned on and the pH was adjusted to the range 9.0 - 9.5 by adding 50 % NaOH solution in water as required. An amount of 230 milliliters (hereinafter "ml") of Composition 1.6 as described in Table 1 above was slug fed to the circulating system, and 2 minutes (hereinafter "min") later 30 - 40 grams (hereinafter "g") of paint (CMC™ "D03M Silver Slate Gray Metallic") was sprayed into the booth at a rate of 40 - 60 g/min. After 5 min of circulation, the circu¬ lation was halted long enough to determine that the paint was still tacky. Circulation was then resumed, and after 3 min an additional amount of 530 ml of Composition 1.6 was slug fed to the system. Two minutes after this addition, an additional 30 - 40 g of paint was sprayed into the booth, and 3 min later, circulation was stopped long enough to determine that the paint was still tacky. Table 1 COMPOSITIONS AND VARIATIONS OF FREE FORMALDEHYDE CONTENT WITH TIME IN MIXTURES LEADING TO MODIFIED COMPOSITIONS ACCORDING TO THIS INVENTION Composition Number 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 Parts by Weight in Initial Mixture of: MAGNIFLOC™ 515C 27 24 21 18 15 9 85 8 8 BKB™ 3 6 9 12 15 1 15 2 1 Additional Water 0 0 0 0 0 0 0 0 1 Free Formaldehyde Content of Mixture in ppm after: 10 minutes 1397 1 hour 1504 2 hours 1355 1520 1592 3 hours 1284 4 hours 1319 5.5 hours 1054 1340 6 - 6.5 hours 1279 1244 1637 7 hours 1387 8 - 8.5 hours 1249 Table 1 continued Composition Number 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 Free Formaldehyde Content of Mixture in ppm after: 1 day 1190 1500 2 days 980 1230 1000 1350 3 days 820 1260 4 days 810 5 days 750 599 375 187 102 7 days 900 570 1100 10 days 790 500 930 13 days 851 428 259 130 54 14 days 450 800 21 - 22 days 652 652 334 634 28 days 607 318 209 113 34 40 days 406 263 141 74 16 Notes for Table 1 The analytical method used for the free formaldehyde values shown has an average deviation of about + 5 %. Therefore, not all the digits given above are significant. The concentration of free formaldehyde in the MAGNIFLOC™ 515C starting material ranged from about 2050 to 2750 ppm in about ten different measurements taken over a period of several weeks, with most of the individual measurements in the range from 2050 - 2200 ppm. The concentration of free formaldehyde in the unmodified starting material was still at least 2000 ppm after 21 days and at least 1800 ppm after 40 days under the same storage conditions as those used to produce the data shown in tthis table. Empty cells indicate that no measurement was made at the indicated time. Circulation was immediately resumed, and after 2 min an additional 500 ml of Composition 1.6 was slug fed into the system. The pH of the circulating water was again measured and found to be 8.5. Most of the paint was now observed to have been detackified, but some was still tacky. An additional 500 ml of Composition 1.6 was added, and detackification was essentially complete, except for a slight amount of tacky paint on foam in the booth. The pH of the circulating water system was then 8.0. Example 2.2 and Comparison Example 2.2 In these examples the paint used was a DuPont Metallic Blue. In Example 2.2, the sequence of events was much like that of Example 2.1, with successive additions of Composition 1.6 and paint and additions of 50 % NaOH in water as needed to maintain the pH between 9.0 and 9.5, until virtually complete detackification of 936 g of paint was achieved with the addition of 427 ml of Composition 1.6. In Comparison Example 2.2, a composition made by mixing 9 parts by weight of MAGNIFLOC™ 515C with 1 part by weight of water, so that it contained the same concentration of dispersed melamine-formaldehyde polymer solids as Composition 1.6, was used instead of Composition 1.6. Much less effective detackification of a similar amount of the same kind of paint was achieved with a similar amount of this compari¬ son composition. Example 2.3 In this example, the modified Composition 1.8 as described in Table 1 was used as the detackifier, and the paint was a Du Pont red-blue metallic base blend with a viscosity of 24 seconds in a #2 Zahn Cup. The pH was initially adjusted to 9.25. Before any paint had been sprayed into the test booth, foaming was observed, so that 10 ml of a conventional hydrocarbon emulsion defoamer (P3™ Defoamer 2483, com¬ mercially available from Henkel Corporation) was added to the circulating water, and it was observed that the pH had fallen to 9.14. Continuously metered additions of Com¬ position 1.8, of a 0.1 % solution in water of a commercial polyacrylamide flocculant (Type 494C from American Cyanamid), and of 50 % NaOH in water ("alkalinizer") to the circulating water supply were then begun, and paint began to be sprayed into the booth at a rate of about 60 g/min. After five minutes, when amounts of 220 ml of Composition 1.8 and 150 ml of alkalinizer had been added, good detackification and substantially clear circulating water with a slight amount of entrained floe were ob- served. After two minutes, an additional 3 ml of the same defoamer was added. After an additional five minutes, an additional 200 ml of Composition 1.8 was added along with an additional 75 ml of the alkalinizer. Good detackification and clear water as before were observed to continue. During the next ten minutes, additions of the same materials were continued, so that the total inputs, twenty minutes after starting the run, had reached 820 ml of Composition 1.8, 315 ml of alkalinizer, 999 g of paint and 2.0 liters of the flocculant solution. The addition of alkalinizer was then discontinued, as the pH had risen to 9.8. Additions of Composition 1.8, of paint, and of flocculant were continued for another five minutes, one addition of 3 ml of the same defoamer as before was added during this interval, and the detackification and water clarity contin¬ ued to be satisfactory. At the completion of the run, after a total of 25 min of operation, the total ma¬ terials added were 880 ml of Composition 1.8, 315 ml of alkalinizer, 2550 ml of the flocculant solution, 1248 g of paint, and 16 ml of defoamer. GROUP H - EXAMPLES INCLUDING UREA AND COMPARISONS THEREWITH For this group, various formulations containing urea and acetoacetamide and/or dicyandiamide, some of which also contained other ingredients, and some comparison examples, were prepared, using the same MAGNIFLOC™ 515-C melamine-formalde¬ hyde resin and other tradenamed ingredients as before. The compositions and some results are shown in Table 2 below. These compositions, when they achieve sufficient reduction in formaldehyde content and freedom from precipitates, are used for detackification in the same general manner as illustrated in Group I. Table 2 Composi¬ Parts by Weight in Composition of: HCHO Precipi¬ tion No. Content, tate? 515-C BKB Urea DiCy NaHSO, Cit A H-O ppm II.1 99.25 0.25 0.50 850 yes II.2 99.0 0.5 0.5 770 yes II.3 98.5 0.5 0.5 0.5 790 yes II.4 99.0 0.5 0.5 770 yes II.5 99.5 0.5 870 yes II.6 99.5 0.5 1430 no II.7 99.5 0.5 2140 no II.8 99.0 0.5 0.5 1998 no II.9 99.0 0.5 0.5 1920 no 11.10 98.5 0.5 0.5 840 yes 11.11 98.9 1.0 0.1 1520 no 11.12 94.9 5.0 0.1 1170 no 11.13 98.8 1.0 0.2 1210 no 11.14 94.8 5.0 0.2 1000 no 11.15 98.9 1.0 0.1 1910 no 11.16 94.9 5.0 0.1 1600 no -Table continued on next page- - Table continued from preceding page -- Composi¬ Parts by Weight in Composition of: HCHO Precipi¬ tion No. Content, tate? 515-C BKB Urea DiCy NaHSO 3 Cit A H 2 O ppm 11.17 98.8 1.0 0.2 1940 no 11.18 94.8 5.0 0.2 1650 no 11.19 93.5 1.0 0.5 5.0 1720 no 11.20 93.5 1.0 0.5 5.0 820 no 11.21 94.7 5.0 0.3 1010 no 11.22 94.6 5.0 0.4 850 no 11.23 94.5 5.0 0.5 830 no 11.24 84.7 5.0 0.3 10.0 920 no σ. 11.25 84.6 5.0 0.4 10.0 740 no 11.26 84.5 5.0 0.5 10.0 650 no 11.27 99.0 0.5 0.5 780 no 11.28 99.9 0.1 1230 no 11.29 99.8 0.2 1050 no 11.30 99.0 1.0 1430 no 11.31 95.0 5.0 1250 no 11.32 100 0.1 1310 no -Table continued on next page-- -- Table continued from preceding page -- Composi¬ Parts by Weight in Composition of: HCHO Precipi¬ tion No. Content, tate? 515-C BKB Urea DiCy NaHSOj Cit A H 2 O ppm 11.33 100 0.2 1170 no 11.34 100 5.0 1180 no 11.35 100 5.0 0.1 1020 no 11.36 100 5.0 0.2 850 no 11.37 100 1.0 0.2 1040 no 11.38 100 1.0 1560 no Notes for Table 2 "515-C" means the melamine-formaldehyde resin described in detail as part of Group I, the particular lot used having a free formaldehyde content of 0.186 %; "DiCy" means dicyandiamide; "Cit A" means citric acid; and "HCHO Content, ppm" means the concentration of free formaldehyde determined twenty-four hours after mixing the composition as noted. In the column headed "Precipitate?", "yes" means pre¬ cipitate settled on the bottom of the container of the composition noted was visually observable within 15 days after mixing, "no" means no such precipitate was observable after 15 days of storage. In the columns under the "Parts by Weight ..." heading, blank spaces indicate no deliberate addition of the material in question, while in the two rightmost columns in the table, blank spaces indicate no measurement was made.

Claims: The invention claimed is: 1. A liquid composition suitable for adding to water containing entrained paint to detackify said paint, said composition consisting essentially of water and: (A) from about 1 to about 20 % of dispersed melamine-formaldehyde polymer solids; (B) from about 0.005 to about 0.20 % of free formaldehyde; (C) products of reaction between free formaldehyde and water soluble DKA modifying reagent molecules that include a structure according to formula I: in which each of Q 1 and Q 3 independently is one of =O, =NH, or ΞN; Q 2 is N or C; and (D) products of reaction between free formaldehyde and urea; and, optionally one or both of the following: (E) urea and (F) unreacted DKA modifying reagent molecules, the TSEA value, which is defined as the stoichiometric equivalent as acetoacetamide of the total of the unreacted DKA modifying reagent molecules and the products of reaction between free formaldehyde and DKA modifying reagent molecules, being from about 0.05 to about 17.5 % of the total composition and the TSEU value, defined as the total of urea and the stoichiometric equivalent as urea of the products of reaction between free formaldehyde and urea, being such that the ratio of the TSEU value to the TSEA value is from about 1.0:100 to about 1.0:0.40. 2. A composition according to claim 1, wherein the amount of free formaldehyde is from about 0.01 to about 0.16 % of the total composition, the TSEA value is from about 0.08 to about 6 % of the total composition, and the TSEU to TSEA ratio is from about 1.0:60 to 1.0:0.45. 3. A composition according to claim 2, wherein the concentration of melamine- formaldehyde polymer solids is from about 3 to about 15, the amount of free formalde¬ hyde is from about 0.022 to about 0.12 % of the total composition, the TSEA value is from about 0.15 to about 2.0 % of the total composition, and the TSEU to TSEA ratio is from about 1.0:30 to 1.0:0.50. 4. A composition according to claim 3, wherein the concentration of melamine- formaldehyde polymer solids is from about 6.0 to about 12.0 %, the amount of free formaldehyde is from about 0.027 to about 0.10 % of the total composition, the TSEA value is from about 0.22 to about 1.8 % of the total composition, and the TSEU to TSEA ratio is from about 1.0:20 to 1.0:0.52. 5. A composition according to claim 4, wherein the concentration of melamine- formaldehyde polymer solids is from about 6.0 to about 10.0 %, the amount of free formaldehyde is from about 0.030 to about 0.095 % of the total composition, the TSEA value is from about 0.22 to about 1.5 % of the total composition, and the TSEU to TSEA ratio is from about 1.0:15 to 1.0:0.54. 6. A composition according to claim 5, wherein the concentration of melamine- formaldehyde polymer solids is from about 6.8 to about 9.0 %, the amount of free formaldehyde is from about 0.030 to about 0.090 % of the total composition, the TSEA value is from about 0.27 to about 1.0 % of the total composition, and the TSEU to TSEA ratio is from about 1.0:5.0 to 1.0:0.55. 7. A composition according to claim 6, wherein the concentration of melamine- formaldehyde polymer solids is from about 6.8 to about 8.5 %, the TSEA value is from about 0.27 to about 0.50 % of the total composition, and the TSEU to TSEA ratio is from about 1.0:1.0 to 1.0:0.56. 8. A process of reducing the free formaldehyde content of a melamine-formalde¬ hyde resin dispersion in water, said process comprising steps of: (i) providing an initial aqueous dispersion containing from about 1 to about 20 % of dispersed melamine-formaldehyde polymer solids and from about 0.10 to about 0.35 % of free formaldehyde; (ii) mixing with the aqueous dispersion provided in step (I) (a) an amount of water soluble DKA modifying reagent molecules that include a structure according to formula I: t^C-Q^-OQ 3 (I) , I H in which each of Q l and Q 3 independently is one of =O, =NH, or ≡N and Q 2 is I N or C, such that the ratio of the stoichiometric equivalent as acetoacetamide of the total amount of DKA modifying reagent added ("TSEA") to the content of free formaldehyde of the resin provided in step (i) is from 0.5:1.0 to 50:1.0 and (b) an amount of urea such that the ratio by weight of urea to TSEA is from about 1:100 to about 1.0:0.50; and (iii) allowing the mixture formed in step (ii) to undergo spontaneous chemical reac¬ tion, at a temperature at which the mixture is liquid, to produce a modified resin dispersion in which the concentration of free formaldehyde is not greater than about 0.20 % and is not greater than about 80 % of the concentration of free formaldehyde in the resin provided in step (i). 9. A process according to claim 8, wherein the dispersion provided in step (i) con¬ tains from about 3 to about 15 % of dispersed melamine-formaldehyde polymer solids and has a pH in the range from about 1.0 to about 3.0, the ratio of TSEA to the free formaldehyde content of the resin provided in step (i) is from about 1.0:1.0 to 20:1.0, the ratio of urea to TSEA is from about 1.0:60 to about 1.0:0.5, the free formaldehyde content of the modified resin dispersion is from about 10 % of the concentration of free formaldehyde in the resin provided in step (i) to about 0.15 % of the total composition, and the pH of the modified resin dispersion is from about 1.0 to about 3.0. 10. A process according to claim 9, wherein the dispersion provided in step (i) con¬ tains from about 6.0 to about 12.0 % of dispersed melamine-formaldehyde polymer solids and has a pH in the range from about 1.5 to about 2.3, the ratio of TSEA to the free formaldehyde content of the resin provided in step (i) is from about 1.2:1.0 to about 11:1.0, the ratio of urea to TSEA is from about 1.0:20 to about 1.0:0.5, the free formaldehyde content of the modified resin dispersion is from about 15 % of the concentration of free formaldehyde in the resin provided in step (i) to about 0.11 % of the total composition, and the pH of the modified resin dispersion is from about 1.5 to about 2.3. 11. A process according to claim 10, wherein the dispersion provided in step (i) contains from about 7.0 to about 10.0 % of dispersed melamine-formaldehyde polymer solids, the ratio of TSEA to the free formaldehyde content of the resin provided in step (i) is from about 1.3:1.0 to 8.0:1.0, the ratio of urea to TSEA is from about 1.0:15 to about 1.3:1.0, and the free formaldehyde content of the modified resin dispersion is from about 15 % of the concentration of free formaldehyde in the resin provided in step (i) to about 0.10 % of the total composition. 12. A process according to claim 11, wherein the dispersion provided in step (i) contains from about 8.0 to about 9.0 % of dispersed melamine-formaldehyde polymer solids, the ratio of TSEA to the free formaldehyde content of the resin provided in step (i) is from about 1.3:1.0 to about 7.0:1.0, the ratio of urea to TSEA is from about 1.0:15 to about 1.4:1.0, and the free formaldehyde content of the modified resin dispersion is from about 18 % of the concentration of free formaldehyde in the resin provided in step (i) to about 0.095 % of the total composition. 13. A process according to claim 12, wherein the ratio of TSEA to the free formal¬ dehyde content of the resin provided in step (i) is from about 1.5:1.0 to about 1.8:1.0, the ratio of urea to TSEA is from about 1.0:1.0 to about 1.0:0.6, the free formaldehyde content of the modified resin dispersion is from about 20 % of the concentration of free formaldehyde in the resin provided in step (i) to about 0.090 % of the total composition, and the pH of the modified resin dispersion is from about 1.7 to about 2.1. 14. A process of detackifying paint entrained in a first aqueous liquid composition by mixing with said aqueous composition a detackifying effective amount of a second aqueous liquid composition comprising: (A) from about 1 to about 20 % of dispersed melamine-formaldehyde polymer solids; (B) from about 0.005 to about 0.20 % of free formaldehyde; (C) products of reaction between free formaldehyde and water soluble DKA modifying reagent molecules that include a structure according to formula I: ■ 2 I 3 I H in which each of Q 1 and Q 3 independently is one of =O, =NH, or -≡N; Q 2 is N or C; and (D) products of reaction between free formaldehyde and urea. 15. A process according to claim 14, wherein in said second aqueous liquid compo¬ sition the amount of free formaldehyde is from about 0.01 to about 0.16 % of the total composition, the TSEA value is from about 0.08 to about 6 % of the total composition, and the TSEU to TSEA ratio is from about 1.0:60 to 1.0:0.40; and the ratio of the amount of said second aqueous liquid composition added to the amount of paint entrained in said first aqueous liquid composition is from about 0.05:1.0 to about 1.5:1.0. 16. A process according to claim 15, wherein in said second aqueous liquid compo¬ sition the concentration of melamine-formaldehyde polymer solids is from about 6.0 to about 12.0, the amount of free formaldehyde is from about 0.022 to about 0.12 % of the total composition, the TSEA value is from about 0.15 to about 2.0 % of the total composition, and the TSEU to TSEA ratio is from about 1.0:30 to 1.0:0.45; and the ratio of the amount of said second aqueous liquid composition added to the amount of paint entrained in said first aqueous liquid composition is from about 0.09:1.0 to about 1.0:1.0. 17. A process according to claim 16, wherein in said second aqueous liquid compo¬ sition the amount of free formaldehyde is from about 0.027 to about 0.10 % of the total composition, the TSEA value is from about 0.22 to about 1.8 % of the total com¬ position, and the TSEU to TSEA ratio is from about 1.0:20 to 1.0:0.50; and the ratio of the amount of said second aqueous liquid composition added to the amount of paint entrained in said first aqueous liquid composition is from about 0.11:1.0 to about 0.70:1.0. 18. A process according to claim 17, wherein in said second aqueous liquid compo¬ sition the concentration of melamine-formaldehyde polymer solids is from about 6.0 to about 10.0 %, the amount of free formaldehyde is from about 0.030 to about 0.095 % of the total composition, the TSEA value is from about 0.22 to about 1.5 % of the total composition, and the TSEU to TSEA ratio is from about 1.0:15 to 1.0:0.52; and the ratio of the amount of said second aqueous liquid composition added to the amount of paint entrained in said first aqueous liquid composition is from about 0.13:1.0 to about 0.40:1.0. 19. A process according to claim 5, wherein in said second aqueous liquid compo¬ sition the concentration of melamine-formaldehyde polymer solids is from about 6.8 to about 9.0 %, the amount of free formaldehyde is from about 0.030 to about 0.090 % of the total composition, the TSEA value is from about 0.27 to about 1.0 % of the total composition, and the TSEU to TSEA ratio is from about 1.0:5.0 to 1.0:0.52; and the ratio of the amount of said second aqueous liquid composition added to the amount of paint entrained in said first aqueous liquid composition is from about 0.14:1.0 to about 0.31:1.0.- 20. A process according to claim 6, wherein in said second aqueous liquid compo¬ sition, the concentration of melamine-formaldehyde polymer solids is from about 6.8 to about 8.5 %, the TSEA value is from about 0.27 to about 0.50 % of the total composi¬ tion, and the TSEU to TSEA ratio is from about 1.0:1.0 to 1.0:0.54; and the ratio of the amount of said second aqueous liquid composition added to the amount of paint entrained in said first aqueous liquid composition is from about 0.15:1.0 to about 0.28:1.0.

Inventors: BELECK SCOTT J, BELECK, SCOTT, J.
Applicants: HENKEL CORP, HENKEL CORPORATION
Application year: 1995
Main classification: C08J7
IPC codes: C08K5, C08L61, C09D7