AMINO RESIN DISPERSION WITH REDUCED ALDEHYDE CONTENT, PROCESS THEREFOR, AND PAINT DETACKIFYING PROCESS THEREWITH

Abstract: Amino resins that contain more free formaldehyde than is desirable for health and/or pollution reasons can be treated with a mixture of diketo reagents (or their nitrogen analogs) and other compounds containing amino moieties to reduce the free formaldehyde content while not diminishing, and in some cases even enhancing, the ability of the resins to function according to their normal uses. The invention is especially useful for melamine-formaldehyde resin dispersions useful to detackify paint.

Description: AMINO RESIN DISPERSION WITH REDUCED ALDEHYDE CONTENT, PROCESS THEREFOR, AND PAINT DETACKIFYING PROCESS THEREWITH CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part of Application Serial No. 08/215,098 filed March 29, 1994, which was a continuation-in-part of Application Serial No. 970,727 filed November 3, 1992 and now abandoned., BACKGROUND OF THE INVENTION Field of the Invention In one of its embodiments, this invention relates to processes of reducing the aldehyde content of amino resins by a process that does not cause any instability, such as gelation or formation of a precipitate, to occur in the amino resin after treatment or reduce the utility of the resins for their intended ultimate purpose. In another embodi¬ ment, the invention relates to compositions, which can be added to amino resins which have higher aldehyde contents than is desirable, in order to reduce their alde¬ hyde content without (i) causing any instability, (ii) making the resin with reduced aldehyde less suitable for its intended use, or (ϋi) requiring any removal from the resin of the additive composition itself or any reaction products therefrom, in order to avoid impairing the intended useful properties thereof. Another embodiment of the inventions relates to amino resins that have had their aldehyde content reduced by a process according to the invention. Still another embodiment of the invention relates to the detackification of paint and similar materials entrained in water, particularly circulating water in a con¬ ventional automobile plant spray booth, with the use of a process or product accord¬ ing to the invention as described above. "Paint" as used herein is to be understood as a generic term which encompasses all common varieties of water insoluble organic binder containing coatings commonly applied in spraying operations, including but not limited to oil based paints, enamels, lacquers, high solids solvent based automot¬ ive 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 bome primers. These paints may utilize asphaltic, acrylic, polyes¬ ter, melamine-formaldehyde, isocyanate, epoxy, alkyd, melamine alkyd, and blocked polyurethane resins among others, along with appropriate solvents, pigments, and an¬ cillary additives. Paint "overspray", the portion of the sprayed paint which does not fall on the surface(s) it is intended to protect, if left untreated, readily adheres to the walls of spray booths and to any other surfaces that it contacts, such as the surfaces of water distribution piping, spray nozzles, and the like. Use of a process according to this embodiment of the invention converts the paint overspray to a non-sticky sludge suitable for convenient disposal. Statement of Related Art For the purposes of this description, the term "amino resins", unless specifical¬ ly limited, is to be understood to include (i) any collection of molecules that satisfies the following two conditions: (i.i) at least some of the molecules have been formed or could be formed by at least one addition reaction between a molecule containing a -CHO (aldehydo) moiety and a molecule containing an amino (i.e., -NH 2 ) moiety to form a single molecule product in which the nitrogen atom from the amino moiety has become covalently bonded to the carbon atom from the aldehydo moiety and (i.ii) the entire collection of molecules is capable of further reaction, without the addition of any outside ingredients, to form polymer molecules, each of which contains at least 10 nitrogen atoms and (ii) all liquid solutions and dispersions, in water or other com- pounds that are liquid at normal atmospheric pressure at a temperature of 20° C, of materials that are amino resins according to the definition of part (i) of this sentence. When necessary to distinguish between these two classes of amino resins, the latter class will be denoted herein as "amino resin dispersions" and the former class as "amino resins, solids basis". In commercially available amino resins, the aldehyde is almost always formal¬ dehyde, and most of the remainder of this specification will therefore be directed to- ward resins in which all or most of the aldehyde molecules from which the resin was or could be formed are formaldehyde molecules. However, this description is meant to apply, mutatis mutandis, to resins with other types of aldehydes. A much more diverse group of amino group containing compounds, many of which are themselves amino resins according to the definition given above, are used to form commercially available or otherwise previously known types of amino resins. These include, but are not necessarily limited to, urea, alkyl substituted ureas, thiour- ea and alkyl substituted thiourea, melamine, benzoguanamine, ethyleneurea (i.e., 2- imidazolidinone), dimethylolethyleneurea (i.e., l,3-bis[hydroxymethyl]-2,-imidazolid- inone), propyleneurea (i.e., tetrahydro-2-pyrmidinone), dimethylolpropyleneurea (i.e., l,3-bis[hydroxymethyl]tetrahydro-2-pyrmidinone), methylol urea, dimethylol urea, acetoguanamine, acrylamide, N-methylolacrylamide, aniline, toluene sulfonamide, N.N'-dimethylol derivatives of tetrahydro-5-alkyl-s-triazones, l,3-bis(methoxymeth- yl)uron, and 1.3,-bis(hydroxymethyl)-4,5-dihydroxy-2-imidazolidinone (also known as "dimethyloldihydroxyethyleneurea" or "DMDHEU"), and trimethylolmelamine and ethers thereof. Most of the remainder of the description will focus on melamine- formaldehyde resin, because they are particularly preferred in the specialized field of paint detackifying, to which one embodiment of this invention is directed. However, the description should be understood as applying, mutatis mutandis, to other arnine- aldehyde, and particularly other amine-formaldehyde, oligomers and polymers. It 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 detack- ification. 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 rninimal amount of it is undesirable in general. DESCRIPTION OF THE INVENTION General Principles of Description 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 materials 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 numerical limits given is generally preferred, however. Also, unless it is explicitly stated to the contrary, wherever individual members of a class are described as suitable or preferred for a given purpose, it is to be understood that mixtures of one or more members of the class are equally suitable or preferred for the same purpose. Summary of the Invention It has been found that the formaldehyde content of amino resins can be more advantageously reduced for many purposes by a combination of additives that react with formaldehyde rather than a single one. Specifically, preferred combinations ac¬ cording to this invention comprise, preferably consist essentially of, or more preferab¬ ly consist of: (A) a component consisting of at least one type of molecules that are soluble in the amino resin to be treated and are selected from the group consisting of organ- ic β -diketo moiety containing molecules and their nitrogen analogs, that is, molecules containing a structure according to formula I below: ( I ) Q 1 C-Q 2 -CQ 3 I H in which each of Q 1 and Q 3 independently is one of =O, =NH, or =N; Q 2 is C or N; and each of the free bonds shown in formula I can be bonded to any other moieties that do not interfere with reaction with aldehydes (the abbrevi- ation "DKA", from "diketo and analogs", being usually used hereinafter to in¬ clude both actual diketo compounds and their nitrogen analogs); and (B) a component selected from molecules that do not belong to component (A) but do contain at least one amino moiety that can react with an aldehyde molecule to form a single molecule product in which the nitrogen atom from the amino moiety has become covalently bonded to the carbon atom from the aldehydo moiety. Combinations according to the invention are especially advantageous because of a combination of economic and technical reasons: At least some compounds made up of molecules suitable for component (B) as defined above are relatively cheap per amount of formaldehyde to be reacted, but they are likely to cause slow but continu¬ ing formation of precipitates when added to amino resin dispersions. The formation of precipitates during storage of resins often gives rise to serious fouling of pumps and feed lines used for handling the resins on a large scale, necessitating expensive cleaning procedures and lost production. DKA additives are relatively expensive and require fairly large amounts of additive to remove any given amount of formaldehyde. (Two molecules of the DKA compounds as defined above are believed to react irre¬ versibly with one molecule of free formaldehyde to produce the following chemical structure: Q1 C _Q2_ C Q3 I H-C-H Q 1 C-Q 2 -CQ 3 in which the formaldehyde formerly present is bound into a substantially nonvolatile form.) However, these DKA additives have been found not to cause precipitates themselves, and also to be capable of preventing the formation of precipitates when used together with the less expensive materials of component (B). Hence the combi¬ nation is more practically valuable than either component alone. 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 either DKA additives or a combination of DKA and other compounds containing formaldehyde reactive amino moieties, 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 %, or 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 % of the total resin and that the thus modified resin is still effective for detackifying paint. The content of free formaldehyde in a given volume or mass of either the starting res- in or the modified resin is defined as the product of the free formaldehyde concentra¬ tion and the volume (or the mass, if the concentration has been measured per unit mass instead of unit volume). The thus modified melamine-formaldehyde resins may advantageously 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-formal¬ dehyde resins in detackification. Various embodiments of the invention include aqueous liquid compositions including amino resins modified to reduce their free formaldehyde content, particular- ly melamine-formaldehyde resins that are useful in detackifying when added to the circulating water in spray booths, processes for making such modified amino resins, and processes, including detackifying processes, using the compositions containing the modified amino resins. The detackifying processes are especially advantageously used as part of processes comprising steps of (I) detackifying and flocculating paint entrained in a circulating water based liquid to produce a flocculated sludge, (II) sepa- rating detackified and flocculated paint solids from residual water based liquid, and (HI) using the residual water based liquid to entrain additional paint. However, de¬ tackifying 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 invention. 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). Other suitable DKA modifying reagents include β-ketocarboxylic acids and their salts, esters, amides, and the like, such as acetoacetic acid or its ethyl ester and β-di- ketones, 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, which is normally the most preferred choice for component (B) as defined above, because it is low in cost and ef¬ fective in formaldehyde reduction. Most of the description will be specific to urea, but it is to be understood that other compounds containing formaldehyde reactive amino moieties can be substituted for urea. The base melamine-formaldehyde polymer for use in the embodiment of this invention relating specifically to paint detackification 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 concentrate, 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 pref¬ erence in the order given, not less than 1, 3, 6.0, 7.0, or 8.0 %; independently, the con¬ centration of dispersed polymer solids preferably is, with increasing preference in the order given, not more than 20, 15, 12.0, 10.0, or 9.0 %. The concentration 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 prefer- ence in the order given, not more than 3.0, 2.8, 2.6, 2.3, 2.2, 2.1, or 2.0. (All the pref¬ erences in this paragraph are for the resin before addition of formaldehyde reducing additives, but except for the formaldehyde concentration, they also apply to the modi¬ fied 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 and stor¬ age at normal ambient temperatures (20 to 30 ° C). Preferably, with increasing pref- erence 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-formalde¬ hyde polymer containing dispersion. The amount of acetoacetamide added, when it is used without any urea, pref¬ erably has, with increasing preference in the order given, a ratio by weight to the ini¬ tial free formaldehyde content of the amino resin 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; inde¬ pendently, the amount of acetoacetamide added when used without 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 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 increas¬ ing 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 50: 1.0, 25:1.0, 20:1.0, 15:1.0, 11:1.0, 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 disper- sion 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 accord¬ ing 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" of the other reagent and is abbrevi¬ ated "SEA" hereinafter, and the stoichiometric equivalent as acetoacetamide of the total of the unreacted DKA modifying reagent molecules and of the originally added but reacted DKA modifying reagent molecules is defined as the "TSEA" (for "total stoichiometric equivalent as acetoacetamide") value. Independently, 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 ad¬ dition of the formaldehyde content modifying reagent(s) that is, with increasing pref¬ erence in the order given, not greater than 65, 57, 50, 45, or 40 % of the free formal¬ dehyde 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 result 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 preference in the order given, not less than 5, 10, 15, 18, or 20 % of the free formalde¬ hyde content of the starting resin dispersion used to make the modified resin disper- sion. When component (B) as defined above is used, the compound(s) actually used as part of component (B), if not urea itself, are measured for purposes of this descrip¬ tion by the amount of urea that provides the same number of formaldehyde reactive amino moieties as the amount of the compound actually used, and this value for a single compound used as component (B) or the sums of all such values if more than one compound is used for component (B) is denoted herein as the "TSEU" value (from "total stoichiometric equivalent as urea". Any material within the scope of part (B) above that was originally added to an amino resin and later reacts is still consid¬ ered part of the TSEU value.) The ratio by weight of the TSEU value for component (B) to the TSEA value for component (A) preferably is, with increasing preference in the order given, not less than 1.0: 100, 1.0:60, 1.0:30, 1.0:20, 1.0: 15, 1.0: 12.0, 1.0: 10.0, 1.0:9.0, 1.0:8.0, or 1.0:7.6 and independently preferably is, with increasing preference in the order given, not greater than 1.0:0.40, 1.0:0.80, 1.0: 1.2, 1.0:1.6, 1.0:2.0, 1.0:2.4, 1.0:2.8, 1.0:3.2, 1.0:3.6, 1.0:4.0, 1.0:4.4; 1.0:4.8, 1.0:5.2, 1.0:5.6, 1.0:6.0, or 1.0:6.4. Independently, it is preferred that the modified detackifying composition have a concentration of melamine-formaldehyde polymer solids that is at least 50, more preferably at least 62, or still more preferably at least 75, % of the concentration of melamine-formaldehyde polymer solids in the starting resin from which the detacki- fying 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 modi- fying reagent molecules; and, optionally one or more of the following, the first being preferred: (D) products of reaction between free formaldehyde and urea; (E) unreacted urea; and (F) unreacted DKA modifying reagent molecules. The free formaldehyde content for purposes of this invention is preferably measured, and for the specific values given below was measured, by a method utiliz¬ ing quantitative spectrophotometric absorbance of light with a wave length of 550 nanometers (hereinafter "nm") in conjunction with commercially supplied reagents and apparatus which convert the formaldehyde in a sample to a colored reaction prod- uct. The needed reagents and apparatus are supplied by CHEMetrics, Inc. of Calver- ton, 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 pre- pared 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 necessary to bring the concentration of free formaldehyde in the photomet¬ ric cell within the range of 0 to 10 parts per million by weight (hereinafter "ppm") of free formaldehyde. 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 tempera- ture 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 manufac- ture and use of the modified resins will be sufficient for reaction at ambient tempera¬ ture, as will be apparent from the data in the examples below. Modification of polymer dispersions as contemplated by this invention in¬ cludes 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 formaldehyde initially present and the added modifying reagent(s), along with any un¬ reacted modifying agent(s). For actual use according to one preferred embodiment, a modified melamine- formaldehyde polymer dispersion concentrate according to this invention as described above is preferably added to water containing 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 pref¬ erably 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 in¬ dependently 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 MAGNTFLOC™ 515C, a commercial product available from American Cyana- mid Corp. with the following characteristics as described by its manufacturer: A spe- cific 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 additional 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 mean¬ ing 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 num¬ bers 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 prac¬ tical use of a full scale spray booth. The resulting solid sludge is collected and sepa¬ rated 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 CONCENTRATION 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 ω Free Formaldehyde Concentration 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 Notes for Table I 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 this 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 s 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 o 2.2, the sequence of events was much like that of Example 2.1, with successive addi¬ tions 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 s of MAGNIFLOC™ 515C with 1 part by weight of water, so that it contained the same concentration of dispersed melamine-formaldehyde polymer solids as Composi¬ tion 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 comparison composition. 0 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 5 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 Composition 1.8, of a 0.1 % solution in water of a commercial polyacrylamide floccu- lant (Type 494C from American Cyanamid), and of 50 % NaOH in water ("alkaliniz- er") 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 observed. 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 start¬ ing 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 continued to be satisfactory. At the completion of the run, after a total of 25 min of operation, e 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 Π - 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 compari¬ son examples, were prepared, using the same MAGNIFLOC™ 515-C melamine-for- maldehyde 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 -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 NaHS0 3 Cit A H,0 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 vo 11.24 84.7 5.0 0.3 10.0 920 no 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.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 t Notes for Table 2 O "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 deter¬ mined twenty-four hours after mixing the composition as noted. In the column headed "Precipitate?", "yes" means precipitate 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 die "Parts by Weight ..." heading, blank spaces indicate no deliberate addition of die 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 composition suitable for addition to liquid amino resins to reduce the free aldehyde content thereof without causing the development of a precipitated solid phase for at least 24 hours after addition, said composition consisting essentially of: (A) a component consisting of at least one type of molecules that are soluble in the amino resin to be treated and are selected from the group consisting of organic β -diketo moiety containing molecules and their nitrogen analogs, that is, from molecules containing a structure according to formula I below: ( I) Q 1 C-Q 2 -CQ 3 I H in which each of Q 1 and Q 3 independently is one of =O, =NH, or =N; Q 2 _ is C I or N; and each of the free bonds shown in formula I can be bonded to any other moieties that do not interfere with reaction with aldehydes (the abbrevi¬ ation "DKA" being used hereinafter to include both actual diketo compounds and their nitrogen analogs); and (B) a component selected from molecules that do not belong to component (A) but do contain at least one amino moiety that can react with an aldehyde molecule to form a single molecule product in which the nitrogen atom from the amino moiety has become covalently bonded to the carbon atom from the aldehydo moiety, wherein the ratio of the total stoichiometric equivalent as urea ("TSEU") of compon- ent (B) to the total stoichiometric equivalent as acetoacetamide ("TSEA") of compon¬ ent (A) is from about 1.0:15 to about 1.0:2.0. 2. A composition according to claim 1, wherein component (A) is acetoaceta¬ mide or dicyandiamide, component (B) is urea, and the ratio of urea to the TSEA of component (A) is from about 1.0:9.0 to 1.0:3.2. 3. A liquid amino resin composition consisting essentially of: (A*) amino resins, solids basis, (B') from about 0.005 to about 0.20 % of free aldehyde; (C) at least one product of reaction between free aldehyde and DKA modifying re- agent molecules; and (D 1 ) at least one product of reaction between free aldehyde and molecules that are not DKA molecules but do contain at least one formaldehyde-reactive amino moiety. 4. A composition according to claim 3 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) at least one product of reaction between free formaldehyde and water soluble DKA modifying reagent molecules; and (D 1 ) at least one product of reaction between free formaldehyde and molecules that are not DKA molecules but do contain at least one formaldehyde-reactive amino moiety; and, optionally one or both of the following: (E 1 ) unreacted DKA modifying reagent molecules; and (F) unreacted molecules that are not DKA molecules but do contain at least one formaldehyde-reactive amino moiety; the total stoichiometric equivalent as acetoacetamide ("TSEA") value in said compo¬ sition being from about 0.05 to about 17.5 % of the total composition; and the total stoichiometric equivalent as urea value ("TSEU") in said composition being such that the ratio of the TSEU value to the TSEA value is at least about 1.0:30, said composi¬ tion being suitable for adding to water containing entrained paint to detackify said paint. 5. A composition according to claim 4, wherein the concentration of melamine- formaldehyde polymer solids is from about 3 to about 15 %, the amount of free form- aldehyde 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 1.0:12.0 to 1.0:0.4. 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 1.0:9.0 to 1.0:3.2. 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 1.0:8.0 to about 1.0:4.0. 8. A process of reducing the free aldehyde content of an amino resin, said pro¬ cess comprising steps of: (i) providing an initial liquid amino resin containing from 0.10 to about 0.35 % of free aldehyde; (ii) mixing, either sequentially or simultaneously, with the liquid amino resin provided in step (I): (a) an amount of DKA modifying reagent molecules that are soluble in the amino resin and include a structure according to formula I: ( I ) Q C-QZ-CQ 3 I H in which each of Q 1 and Q independently is one of =O, = H, or =N; Q 2 is C or N, 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 aldehyde of the resin provided in step (i) is from 0.5: 1.0 to 50: 1.0; and (b) an amount of a component selected from molecules that do not belong to component (a) but do contain at least one amino moiety that can react with an aldehyde molecule to form a single molecule product in which the nitrogen atom from the amino moiety has become covalently bonded to the carbon atom from the aldehydo moiety, such that the ratio by weight of the TSEU of component (b) to the TSEA of component (a) is from about 1 :100 to about 1.0:0.40; and (ϋi) allowing the mixture formed in step (ii) to undergo spontaneous chemical re¬ action, at a temperature at which the mixture is liquid, to produce a modified amino resin in which the concentration of free aldehyde is not greater than about 0.20 % and is not greater than about 80 % of the concentration of free aldehyde in the resin provided in step (i). 9. A process according to claim 8 of reducing the free formaldehyde content of a melamine-formaldehyde 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) an amount of compon¬ ent (ii)(a) and an amount of component (ii)(b) such that the ratio by weight of the TSEU value of component (ii)(b) to the TSEA value of component (ii)(a) is from about 1 : 100 to about 1.0:0.40; and (iϋ) allowing the mixture formed in step (ii) to undergo spontaneous chemical re¬ action, 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). 10. A process according to claim 9, wherein: the dispersion provided in step (i) contains from about 6.0 to about 12.0 % of dispersed melamine-formaldehyde poly¬ mer 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 by weight of the TSEU value of component (ii)(b) to the TSEA value of component (ii)(a) is from about 1:20 to about 1.0:1.2; 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 compo¬ sition; 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 poly¬ mer 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 by weight of the TSEU value of component (ii)(b) to the TSEA value of component (ii)(a) is from about 1:9.0 to about 1.0:2.8; 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 by weight of the TSEU value of component (ii)(b) to the TSEA value of component (ii)(a) is from about 1.0:9.0 to about 1.0:2.4; 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, component (ii)(b) is urea, the ratio of urea to TSEA is from about 1.0:8.0 to about 1.0:4.0, 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 first aqueous composition a detackifying effective amount of a second aqueous liquid composition according to claim 4. 15. A process according to claim 14, wherein in said second aqueous liquid com¬ position 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 com¬ position, the TSEU to TSEA ratio is from about 1.0:30 to 1.0:1.6, and the ratio of the amount of said second aqueous liquid composition added to the amount of paint en- trained 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 com¬ position 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, the TSEU to TSEA ratio is from about 1.0:15 to 1.0:2.0; 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 com- position 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 1.0:12.0 to 1.0:2.8; 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 com¬ position the concentration of melamine-formaldehyde polymer solids is from about 6.0 to about 10.0 %, the amount of free formaldehyde is from about 0.0^30 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 1.0:9.0 to 1.0:4.0; 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 18, wherein in said second aqueous liquid composition 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 1.0:8.0 to 1.0:4.8; 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 19, wherein in said second aqueous liquid composition, 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 1.0:7.6 to 1.0:6.0; 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: 1996
Main classification: C08J3
IPC codes: C08G12, C08J3, C08L61, C09D7, C09D161