Patented May 6, 1952 2,595,954

UNITED STATES PATENT OFFICE 2,595,954 POLY WINY, ACETATE EMUSON CONTAIN ING AN ALPHATIC CARBOXYLIC ACID, AND BASE COATED THEREWITH Walter G. Kunze and Raymond Bertram Evans, Catonsville, Md., assignors to Le Page's Inc., Gloucester, Mass., a corporation of Massachu setts No Drawing. Application April 6, 1950, Serial No. 154,425 9 Claims, (C. 260-29.6) 2 This invention relates to emulsions of poly certain chromium salts, strong acids or highly mers which are suitable for use as coatings and as reactive aldehydes such as glyoxal, certain resins, adhesives. It is particularly concerned with toluene and peroxides. In most instances it was such an emulsion of polymers which is capable required that the Substances be added to the of providing a water-resistant bond or coating polymer emulsion immediately prior to use as and which at the same time retains the Stability, the resulting compositions were unstable and fluidity and the various other physical proper certain of the substances resulted in a progressive ties of such an emulsion which make it particu increase in the viscosity of the emulsion until a larly useful as a coating or adhesive. gel was formed. Gelling rendered the compo ... The use of melts and solutions of Water in 10 Sition unfit for use in adhesive applicator ma-. soluble artificial resins in the coating and ad chines operated at high speed. Additionally, the hesive art has been supplanted to a large ex modification effected by some of these substances tent by emulsions of such resins, particularly did not result in a substantial improvement in polyvinyl acetate emulsions, due to the improved the water-resistance of the coating or film de ease, economy and safety with which aqueous 15 posited from the emulsion, and often imparted emulsions of the resin may be employed. On the undesirable color and foaming characteristics to other hand, the usefulness of water insoluble the emulsion. polymer emulsions has been limited by the char Where thermo-plastic polymeric. material has acteristic lack of water-resistance of the coat been employed, it has been suggested that the ings and bonds deposited therefrom at room 20 water-resistance of the coating or bond deposited temperatures and the tendency of Such coatings from an emulsion of the material can be im and bonds to re-emulsify or disintegrate when proved by heating the coating or bond Sufficiently subsequently brought into contact with Water to cause coalescence of the material into a during the course of normal use of the object homogeneous mass. This procedure is obviously or article to which they have been applied. not suitable where the emulsion is employed as a This lack of Water-resistance has been Con quick-setting adhesive in high-speed mechanical sidered innate in the coatings and films de applicators, and in any event the drying and posited from such polymer emulsions inasmuch heating suggested often makes the use of Such as water-soluble emulsifying and bodying agentS emulsions economically prohibitive. are employed necessarily to establish and Stabi 30 A further suggestion directed to retaining the lize the emulsion. These agents are apparently advantages of working with the polymers in an carried into the film or bond deposited from the aqueous medium and at the same time avoiding emulsion upon application of the emulsion to a the inherent disadvantages of water-Sensitivity surface, and actively exhibit the emulsifying of the coatings or films deposited therefrom re effect on the polymer comprising the body of quired dispersing the polymer as extremely Small the coating or film and cause its redispersion particles. The coatings or films deposited from when the surface is brought into contact with Such emulsions do exhibit a satisfactory water water. resistance, but due to the fine particle size which Various proposals have been made to obviate imparts the water-resistance, the emulsions do the water-sensitivity of the coatings or bonds 40 not have the tack necessary to make them use deposited from such emulsions, but in general ful as quick-setting adhesives. these proposals have been directed to modifying It is an object of this invention to provide a emulsions of such polymers which have been pre composition comprising an aqueous emulsion of pared in a specific manner, or require treating a polymer, particularly a polymer of vinyl ace the emulsion with certain diluents immediately tate, alone or in combination with Small quan prior to its application due to the recognized tities of other monomers, which is stable through tendency of the suggested diluents to either break out long periods of storage, and which When en or gel the emulsion shortly after the addition of ployed as a coating or as an adhesive will de the diluent. posit a coating or bond which is highly Water Prior to the instant invention, for example, a resistant. A further object of the invention is to common expedient for increasing the water-re provide a process which is generally applicable sistance of a coating or film deposited from a to modify emulsions of polymers, particularly Water-insoluble polymer emulsion included the polyvinyl acetate, which have been polymerized addition of a quantity of one or more substances to different extents, or in different manners, and such as dimethylol urea, trimethylol melamine, which include various combinations of plasti 2,595,954 3 4. cizers and other diluents commonly employed to to thicken progressively until it is rendered use develop favored characteristics in the fillins Cl less. We have found that this difficulty can be coatings deposited from such emulsions. avoided in the practice of the instant invention We haye discovered that the Water-resistance by employing only the acids of the type specified of coatings or bonds deposited from an aqueous i which have an ionization constant which is less emulsion of polymers, particularly polyvinyl than about 6.6X10 at 25°C., which is the ioniza acetate emulsions, which are formulated, or modi tion constant of succinic acid which is effective fied, to have a tackiness rendering them suit in producing water-resistance. able for use as quick-setting adhesives, can be Active acids of this type, which include ifatty established by additions of one or more of a 0. acids having from 3 to 8 carbon atoms, are not certain group of organic compounds within sufficiently ionized to hydrolyze the vinyl acetate specific limits. These active compounds are ester, and consequently the erhulsions with which characterized by a particular balance between the these active compounds are incorporated are sta parts of the monomeric molecule, one part of ble over a long period of time. It was found that which is hydrophilic or polar in nature, and the 5 an emulsion treated with oxalic acid, which has Other part of Which is hydrophobic or non-polar. an ionization constant of 6.5x10-2 at 25° C., The effectiveness of the compounds in producing hydrolyzed after about 30 days. An emulsion Water-resistance in the coatings or bonds de treated with citric acid, which has an ionization posited from Such emulsions is apparently due constant of 8.4x104 at 25° C., decomposed and to the presence of both the polar and non-polar 20 thickened after a period of 6 to 9 weeks. In con groups within the molecule in the prescribed trast to the above results, an enlision treated balance. With the fatty acids having ionization constants Many of these active compounds exhibit solu leSS than that of succinic acid showed good sta bility, to various extents, in both water and in bility at the end of 3 months. For example, organic solvents such as mineral spirits, pe propionic acid, butyric acid and levulinic acid are troleum ether, toluene, castor oil, etc. This effective insolubilizers of the films and bonds de Solubility in both Water and organic solvents ap posited from polyvinyl acetate emulsions. The parently is due to the dual hydrophilic-hydro insolubilizing action of these acids is effected by phobic nature of the compound. As it has been the non-ionized portion of the acids added to the generally recognized that the presence of water 30 emulsions. The ionized portions of the com Soluble emulsifiers carried into the bonds and pounds may act to some extent to insolubilize the coatings deposited from emulsions of water-in films and bonds, but in the manner of the acid soluble polymers may later cause redispersion ions of the strong organic acids and with the same and disintegration of the bonds and coatings, it undesirable resultS, For this reason, the pre was particularly Surprising to find that incor 35 scribed ionization constant inlitation must be ob porating into the emulsion additional compounds served in Order to obtain Satisfactory resultS. Which are Water-soluble themselves will nullify Some of the active compounds within the pre the effect of the Water-soluble emulsifiers and Scribed class have a low Solubility in Water and thereby impart Water-resistance to the coatings effective quantities will not be solubilized by the and films deposited from such emulsions. 40 external Water phase of the emulsion. In the in For present purposes a polar or hydrophilic stances where the compounds are normally liquid group or radical may be considered to be one this nakes no material difference as such cona Which has a strong affinity for water and which pounds are taken up or combined in a manner When combined in compounds in which it is the which makes them effective in producing Water dominant functional group will cause the result resistance in the films deposited from the emul ing compound to be immiscible, or miscible to sion. Where the active compounds are normally a limited extent, in oil-type solvents. A non Solids they can be dissolved to obtain an effective polar or hydrophobic group, on the other hand, concentration, and the Solution thus formed may be considered to be one which has slight mixed with the emulsion. For example, it is ex affinity for water and a strong affinity for oil pedient to solubilize succinic and levulinic acid in type solvents. either water or alcohol, and add the acid Solution The carboxyl group, for example, is representa to the starting material emulsion. tive of a polar group. The hydrocarbon chains, The preferred range of quantities of one or ether chains and other arrangements which may more of the active compounds by weight with re include carbonyl groupS may be classified as ion Spect to the Solid content of the polyvinyl acetate polar groupS. emulsion has been found to be between about With regard to the carboxyl compounds which 4-25%. have the inter-molecular balance between polar The physical properties of a polyvinyl acetate and non-polar portions of the compound which emulsion such as the viscosity of the emulsion, make them effective in imparting water-resist 60 and the tensile strength, flexibility and heat seal ance to a polyvinyl acetate emulsion, we have ing temperature of the film or bond deposited found that certain of the organic acids which from the emulsion are determined in a large part contain 3 to 8 carbon atoms are active. The nao by the degree of polymerization of the vinyl ace lecular arrangement of the acids thus constituted tate monomer. A higher degree of polymeriza appears to be unimportant as either mono-basic, 65 tion results in increased bond Strength, a higher di-basic or tri-basic acids. Within the prescribed heat sealing temperature and a Somewhat higher limits are effective in producing water-resistance. initial water-resistance, which is, however, Con Further, the active compound may contain other siderably less than required commercially for a groups which are hydrophilic in nature as the water-resistant coating or bond. A lesser quan hydroxyl and carbonyl groups. For example, 70 tity of the active compounds is necessary to in levulinic acid has been found to be effective. part the desired water-resistance to the deposited As polyvinyl acetate is an ester it is Subject coatings or bonds when the relatively greater to hydrolysis in the presence of strong acids. water-resistant emulsions are employed as a The hydrolysis causes a slow decomposition of starting material. The age of the starting ma the ester and causes an emulsion of the ester 5 terial emulsion also determines in part the Sus 2,595,954 5 6 ceptibility of the emulsion to waterproofing, the In some instances care must be exercised to older emulsions, for example, emulsions 4 to 6 avoid breaking the emulsion by sudden heating, months old, show better water-resistance when or by extended heating above the temperature treated than those freshly made. specified. The critical temperature will vary, of For present purposes the polyvinyl acetate course, with the character of the particular start starting material emulsions having sufficient tack ing material emulsion employed. to be useful as quick-setting adhesives and suit Aging the composition tends to increase the able for improvement according to the instant water-resistance of the coatings or films deposit invention may be classified according to their ini ed therefron. tial water-resistance although in each instance O It will be apparent from the foregoing that in the water-resistance is negligible from the stand numerable possibilities for formulating the in point of minimum commercial requirements. stant water-resistance composition exist, and Such emulsions generally contain about 50-60% that the invention may be practiced to increase polyvinyl acetate by weight and a dried bond pro the water-resistance of any particular polyvinyl duced by the respective emulsions between two 6 acetate emulsion without materially interfering sheets of mildly calendered white sulphite paper with the versatility of the starting material will open up within 24 hours after immersion in. emulsion. It will be noted, however, that any of water at about 25° C. Such polyvinyl acetate the active compounds having the requisite polar emulsions include the commercially available non-polar balances in the molecules thereof and emulsions known as Elvacet No. 80-900, Elvacet 20 the stated ionization constant values are effective 81-900, Gelva, S-50 and Polyco 117H, Polyco in producing water-resistance when used in quan 117SS and Polyco 289. Within 3 hours after im tities within the range of 4-25% by weight of the mersion the bond shows less resistance than the solids present in the starting material polyvinyl wet strength of the paper, and upon separation acetate emulsion. The minimum amount of a of the bonded papers the bond disintegrates. 25 particular one of the active compounds depends The physical characteristics of the commer upon the factors discussed above, but in all in cially available polyvinyl acetate emulsions iden stances is within the range Specified. tified above may also vary to Some extent as a Compositions having up to 50% by weight of result of the emulsifiers and bodying agents em active compound with respect to the solid content ployed in producing the emulsions, and also as a of the polyvinyl acetate starting material emul result of particular plasticizers employed. In sions may be employed, especially where the general, however, the variations which tend to active compound has desirable plasticizing prop increase the relative initial water-resistance of erties and the cost thereof is not prohibitive. In the starting material emulsions lessen the quan most instances, however, the maximum Water tity of the active compounds required to effect 35 resistance is obtained with the least effect on complete water-resistance. other physical characteristics of the composition The amounts of active compound required to when a total of from 12-17% of active compound produce maximum water-resistance in a partic or compounds by weight of solids in the starting ular emulsion also varies with the quantity and material emulsion are employed. In the event the nature of the plasticizers, extenders, or other 80 plasticizers are also used in formulating the diluents which may be used to develop desired composition the same effect can be achieved with characteristics of fluidity or tackiness in the slightly lesser quantities of the active compounds. emulsion, or of flexibility, hardness, etc. in the Some of the numerous possibilities which exist coating or film deposited from the emulsion. In in formulating a water-resistant composition general, it has been found that the insoluble type 45 within the operable limitations specified above of plasticizers and resins in common use increase are illustrated in the following examples. the effectiveness of the active compounds, and The addition of the active compound to the that a lesser quantity of active compound. is starting material emulsion may result in a sub necessary to produce complete water-resistance stantial increase in the viscosity of the emulsion when such plasticizers are also present in the 50 to form a cohesive mass unless the active com emulsion. It should be noted, however, that in pound is added slowly with continuous agitation. each instance the emulsion containing the plasti In some instances rapid addition of the active cizers and various other diluents was not initially compound results in localized precipitation of water-resistant and that the addition of the the emulsion. The largest part of the increased active compound is necessary to effect any satis 55 cohesiveness and viscosity of the emulsion caused factory water-resistance, although as related by addition of the active compound at a suitable above, a lesser amount is necessary when insol rate disappears on agitation, or when the treated uble plasticizers are also present. emulsion is permitted to stand for a short period This enhancing effect of the insoluble plasti following the addition of the active compound. . cizers was particularly observed with respect to 60 In all of the following examples the composi dimethyl phthalate, dibutyl phthalate, chlo tion was prepared by stirring the starting ma rinated diphenyls, methyl abietate and tributyl terial emulsion with a high speed mixer contin phosphate, and appears to be characteristic of uously during the addition of the active com other common plasticizers such as di-carbitol pound thereto. The active compound was intro phthalate, dibutoxy-glycol phthalate, dimethoxy 65 duced into the emulsion at the rate of about 3% glycol phthalate, butyl phthalyl butyl glycolate, of the total weight of the active compound per methyl phthalyl ethyl glycolate, triglycol di-2- minute. ethylbutyrate, triglycol di-2-ethylhexoate, tri Each of the tacky starting material polyvinyl. cresyl phosphate and triphenyl phosphate. emulsions was applied as a coating on the sur On the other hand, the presence of a small 70 face of a moderately calendered and sized white amount of certain water-soluble thickeners such Sulphite paper and as a bond between two Such as polyvinyl alcohol and sodium carboxymethyl papers. The films and bonds thus formed were cellulose tend to increase the amount of active allowed to dry for 24 hours at room temperature compound necessary to effect maximum Water and Were thereafter immersed in Water at room resistance. 75 temperature for 24 hours. Upon removal from 2,595,954 7 8 the Water the wet strength of the paper ex were added. The films and bonds deposited ceeded the bond strength in all cases, and the from both these samples were found to be bond ruptured when the bonded papers were Waterproof when tested in the manner described Separated. The coatings in each instance had in Example 1. visibly disintegrated. These starting material Eacample 4 emulsions were, therefore, considered non-water resistant, and in the subsequent experiments, Three Samples Were prepared by adding to a Satisfactory water-resistance of a film or bond tacky polyvinyl acetate emulsion (110 grams to formed from an emulsion treated with an active each sample) having a solid content of about compound was considered fully indicated when 0 55%, 5, 10 and 20 grams, respectively, of butyric the strength of the bond exceeded the wet acid. . The addition of the acid Was made slow Strength of the paper after 24 hours innersion. ly While the acetate emulsion was being stirred It will be understood that the composition of continuously. A fourth Sample was prepared by the films and bonds deposited from the type of adding 3 grams of butyric acid and 5 grams of emulsion dealt with here is the same as that 5 dibutyl phthalate plasticizer to 110 grams of a of the emulsion except for the external Water polyvinyl acetate emulsion. The films and bonds phase which evaporates upon drying. deposited from all four compositions were test ed for WaterproofneSS in the manner described Ecample 1 in Example i and all were found to be waterproof. 7 grams of Succinic acid Were dissolved in about 20 25 cc. of Water and this solution was added slowly Eacample 5 to 110 grams of a polyvinyl acetate emulsion 5.5 grains of caprylic acid was mixed with 110 having about 55% solid content. The emulsion grams of a tacky polyvinyl acetate emulsion while Was stirred continuously during the addition of the emulsion was being continually stirred. A the acid. A second sample was prepared in 25 second sample was prepared by mixing 10 grams a similar manner using 15 grams of Succinic of caprylic acid with 110 grams of the same acid. In this instance a small amount of the starting material emulsion. A third sample was Succinic acid crystallized out as it was present prepared by the addition of 3 grams of caprylic in amounts in excess of its solubility limit. A acid, and 10 grams of dibutyl phthalate to 110 portion of each sample was applied to a moder 30 grams of the same starting material emulsion. ately sized and calendered white sulphite paper The additions were made slowly as the emulsion as both films and bonds. These were allowed to was constantly stirred. The films and bonds de dry for 24 hours and Were then immersed in posited from these compositions were tested for Water at room temperature for about 24 hours. waterproofness in the manner described in Ex At the end of this period the film and bonds 3. 5 ample 1 and all were found to be waterproof. Were still intact and the strength of the bonds It will be apparent that the Water-resistant exceeded the wet strength of the paper, i. e., compositions formulated according to the in when the bonded papers were separated the stant invention will considerably extend the use bond remained intact and portions of the papers fulness of aqueous emulsions of polyvinyl acetate adhered to the bond. 40 into the field in which high water-resistance of A third Sample was similarly prepared using the bond or coating deposited is necessary, and 4 grams of Succinic acid. To this 10 grams of Will find application in bonding or cementing for a dimethyl phthalate plasticizer were added. The cellulosic articles Such as paper cups or paper resulting mixture was stirred until it became bags which in the course of normal use are ex homogeneous. The composition was then applied posed to water, and for bonding surfaces of cellu as a film and bond in the manner described losic material to other surfaces of a hydrophilic above. Both the films and bonds deposited from character Such as masonry. These instant com this composition were waterproof. positions are particularly adapted for use as a Eacd.imple 2 sizing where water-resistance of the fabric or the paper to which it is applied is required. It may 12 grams of levulinic acid were dissolved in also be employed in the composition of printing about 30 cc. of water. This solution was added paste, as a finish for paper, paper-board, or foils to 220 grams of a tacky polyvinyl acetate emull and in the manufacture of formed or impreg Sion having a solid content of about 55%. The nated goods, as well as in distemper paints and addition was made slowly while the vinyl acetate 5 the like. was being stirred with a high speed mixer. A Having thus described the invention, what is Second sample was similarly prepared using 25 new and desired to be secured by Letters Pat grams of levulinic acid and enough additional ent is: Water to take the acid into Solution. A third 1. A composition Coimprising a tacky aqueous Sample was prepared by adding to a portion of the 60 emulsion of polyvinyl acetate and from 4 to 50% first Sample 5 grams of a chlorinated diphenyl by Weight of said acetate of an aliphatic saturated plasticizer and 5 grams of methyl abietate plasti Organic acid having an ionization constant of cizer. The films and bonds deposited from these leSS than about 6.6X 10-5, and 3 to 8 carbon samples were tested for Waterproofness in the atoms. manner described in Example 1. All were found 65 2. A composition comprising a tacky aqueous to be waterproof. emulsion of polyvinyl acetate and from 4 to 50% Eacample 3 by Weight of Said acetate of a saturated aliphatic monobasic organic acid having an ionization con 11 grams of propionic acid were added to 110 Stant of less than about 6.6x10-5 and 3 to 8 car grams of a tacky polyvinyl acetate resin having 70 bon atoms. about 55% solid content. The acid was added 3. A composition comprising an aqueous emul slowly and the vinyl acetate emulsion constant sion of polyvinyl acetate and from 4 to 50% by ly agitated during the addition. A second sam Weight of Said acetate of a polybasic organic acid ple was prepared in a similar manner and to having an ionization constant of less than about this 5 grams of dimethyl phthalate plasticizer 75 6.6X10-5. 2,595,954 10 4. A composition comprising tacky aqueous acetate of a saturated aliphatic polybasic organic emulsion of polyvinyl acetate and from 4 to 50% acid having an ionization constant of less than by weight of Said acetate of Succinic acid. about 6.6X105 and 3 to 8 carbon atoms. 5. A composition comprising tacky aqueous 9. A base having a Water resistant coating de emulsion of polyvinyl acetate and from 4 to 50% 5 posited thereon from a composition comprising by Weight of Said acetate of butyric acid. an aqueous emulsion of polyvinyl acetate and 6. A composition comprising tacky aqueous from 4-50% by weight of said acetate of an ali emulsion of polyvinyl acetate, a plasticizer for phatic Saturated organic acid having an ioniza Said acetate and from 4 to 25% by Weight of Said tion constant of less than about 6.6X105 and acetate of an aliphatic Saturated organic acid 3 to 8 carbon atoms. having an ionization constant of less than about WALTER, G. KUNZE. 6.6X105 and 3 to 8 carbon atoms. 7. A composition comprising a tacky aqueous RAYMOND BERTRAMI EVANS. emulsion of polyvinyl acetate, a plasticizer for Said acetate and from 4 to 25% by Weight of Said REFERENCES CITE) acetate of a Saturated aliphatic monobasic Or The following references are of record in the ganic acid having an ionization constant of less file of this patent: than about 6.6X105 and 3 to 8 carbon atoms. 8. A composition comprising a tacky aqueous UNITED STATES PATENTS emulsion of polyvinyl acetate, a plasticizer for Number Name Date Said acetate and from 4 to 25% by weight of said 0 244,396 Collins et al. ------June 29, 1948