AQUEOUS EMULSIONS OF HYDROCARBON RESINS AND PROCESS FOR PREPARING THE SAME

Abstract: An aqueous petroleum resin emulsion is realized by the slow addition of part of the water with vigorous agitation to a resin blended with up to 10 weight percent resinplast and in the presence from 3 to 10 weight percent of an emulsifier until inversion and thereafter adding the balance of the water at a low agitation and thereafter cooling said emulsion to a temperature at least about 20°C below the softening point of the mixture of emulsifier, resin and resinplast prior to terminating agitation.

Description: AQUEOUS EMULSIONS OF HYDROCARBON RESINS AND PROCESS FOR PREPARING THE SAME This invention relates to emulsions of hydrocar bon resins and more particularly to aqueous emulsions of resins prepared from steam cracked petroleum fractions. Many synthetic resins which may be formed by emulsion polymerization are well known in the art. It is not difficult to form stable aqueous dispersions of such resins by addition of the resin feed, an appropriate dis persing agent and catalyst to water with stirring. However, emulsification of resins produced by other poly merization techniques requires that the bulk polymer must be dispersed in water to obtain an aqueous dispersion. Such a type is hydrocarbon resin produced from steam cracked petroleum fractions. These hydrocarbon resins, i.e. petroleum resins, are defined herein as the thermoplastic resins obtained by polymerization, thermally or more frequently in the presence of. a catalyst of the Friedel-Crafts type, of steam cracked petroleum distillates, boiling in the range between about 300C and 2800C., or any fraction of these distillates boiling within the said range, or of mixtures of olefines and diolefins containing sufficient diolefins to obtain a resin and not an oil. This polymerization is performed at temperatures which range generally from 0 to 1200C., usually from 0 to 700C., and preferably from 300C to 550C. These resins are polydienic in character and can have a ring and ball softening point between about 380C and 1800C and the techniques of the present invention may be applied to any such resin although they are particular ly useful with the resins of higher softening points which are the more difficult to emulsify. Since these resins are solid at room temperature, numerous approaches have been utilized to produce aqueous emulsions of said resins for application as an adhesive, as a saturant or coating for paper or cloth or as a sizing or binding material in paper pulp. One approach was to solvate the resin in hydrocarbon solvent and then combine resin solution and water. Invariably some residual hydrocarbon solvent remains in the finished emulsion, and this is undesirable in certain applications. This has led to the development of solventfree dispersions (see U.S. Patent 2,809,948) and emulsions (see U.S. Patent 3,377,298) of petroleum resins. In both of these formulations, ionic emulsifiers have been utilized; in the former a mixture of cationic and nonionic surface active agents is used to achieve a resin dispersion; and, in the latter an ionic surfactant is used in combination with an aqueous gel of a swelling earth to produce an emulsion paste of a petroleum resin. Petroleum resin emulsions containing substantial amounts of plasticizers or diluents such as linseed oil and waxes and paraffins are taught in French Patent 1,452,875 and German Offen. 2014652 respectively. However, such large percentages of diluent can materially modify, not always favorably,the properties of the base resin. The resin emulsions of the present invention are particularly useful as tackifying components where they enhance the adhesive properties of an emulsion polymer system such as a natural or synthetic rubber used as an adhesive. It is highly desirable that raw materials added to the tackifier resin emulsion for primarily other than tack or adhesion enhancement, e.g. plasticizers or other diluents, emulsifiers, stabilizers, etc., be kept to an absolute -minimum. Such materials often have an adverse effect on the functional properties, e.g. -tack, adhesive properties, of the resin being emulsified. For a general discussion of resin emulsions for emulsion pressure sensitive adhesive use including its commercial aspects) see the published talk entitled Resin Dispersions for Water Based Pressure Sensitive Adhesives by Robert W. Wherry and presented at The Pressure Sensitive Tape Council Seminar on Water Based PSA Systems in June of 1979. This invention has for one of its objects the preparation of highly functional, relatively high softening point, non-polar petroleum resin emulsions without the use of volatile solvents and employing minimal plasticizers, diluents or other products constructive in emulsification but potentially deleterious to the emulsion end use. A further object is to provide an emulsion preparation method of an inversion type for the resins which effectively produces emulsions of small particle size and exceptional stability. A further object is provision of aqueous dispersions of hydrocarbon resins of high shelf life and mechanical stability. A further object is to provide petroleum resins in the form of a latex-like dispersion for application as a pressure sensitive adhesive which may be used as a tackifier in emulsion based adhesives such as those containing emulsions of natural and synthetic rubbers. The resin emulsions may also be used as a saturant or coating for paper or cloth, or as a sizing or binding-material in paper pulp. It has been discovered that an aqueous emulsion of a petroleum resin may be obtained when said resin is melt blended with an oil and an emulsifier and thereafter admixed with about 50 weight parts of water. The aqueous resin emulsion was made possible by initially slowly adding and dispersing with vigorous agitation boiling water in said melted blend of resin, naphthenic oil and emulsifier over a prescribed critical time length prior to inversion of the dispersion of water. Thus in accordance with the objects of this invention there is provided an aqueous emulsion of a hydrocarbon resin comprising 70 to 25 weight % of a mixture containing from 3 to l0'parts by weight of an emulsifier, from 3 to 10 parts by weight of a resinplast and from 80 to 94 parts by weight of said hydrocarbon resin, and 30 to 75 weight % of water. This emulsion is realized by admixture of a blend suitable for providing an aqueous emulsion of a hydrocarbon resin comprising from 3 to 10 parts by weight of an emulsifier of the class of nonionic polyoxyethylene alkyl aryl ethers, anionic alkyl aryl sulfonates and mixtures thereof blended with a mixture of from 3 to 10 parts by weight of resinplast and 80 to 94 parts by weight of said hydrocarbon resin with water through a novel inversion method. According to the invention there is also taught herein a method'four the production of a hydrocarbon resin in water emulsion comprising the sequential steps of admixing from 3 to 10 parts by weight of an emulsifier of the class consisting of nonionic polyoxyethylene alkyl aryl ethers, anionic alkyl aryl sulfonates and mixtures thereof with from 80 to 97 parts by weight of a molten hydrocarbon resin and from 0 to 10 parts by weight of a resinplast, heating said admixture above the softening point of the resin, emulsifier, resinplast mixture, slowly adding water heated to about 1000C to said heated admixture with vigorous stirring over a critical minimum period and until inversion occurs, adding sufficient additional water with agitation to provide an aqueous emulsion containing from 30 to 75 weight % water in the finished emulsion and thereafter cooling to a temperature less than about 200C below the softening point of the mixture of emulsifier, resin and resinplast prior to terminating agitation. As noted above, the hydrocarbon resins emulsified according to this invention are preferably petroleum resins prepared by homo and copolymerization of olefins, diolefins and aromatic components, predominantly C-5 and C-9 species, from distillates of cracked petroleum stocks. A Friedel-Crafts catalyst is typically employed. The resulting resin has an aliphatic, aromatic or mixed aliphatic/aromatic character, generally with a minimum ring and ball softening point of 300C. Although the methods described herein can be used to emulsify lower softening point resins, it is the higher softening point resins which are more difficult to emulsify and are thus especially addressed here. Broadly, the hydrocarbon resins are polymerized from petroleum cracked distillates boiling in the range of about 300C to 2800C or any fraction boiling within this range. The resins are prepared by thermal polymerization or, more usually, by treating the distillates with 0.25-2.5% of a Friedel-Crafts type catalyst such as aluminum chloride, aluminum bromide, boron trifluoride, and the like or solutions, slurries, or complexes thereof. The reactions are conducted at temperatures in the range of 0 to 1200C, preferably 0 to 700C, and more preferably 300 to 550C. Residual catalyst is quenched by suitable methods such as addition of methyl alcohol and subsequent filtration, water and/or caustic washing. The final solution is then stripped of unreacted hydrocarbons and low molecular weight oils by 'vacuum or steam distillation. In place of the petroleum cracked distillates, the feed to polymerization may consist of mixtures of a diolefin with an olefin. Sufficient diolefin must be present and incorporated in the polymer to give a resin having a suitably high melting point instead of an oil. For most resins a resinplast is admixed therewith in combination with the resin in amounts ranging up to 10% by weight (based on total weight excluding water), preferably in amounts ranging from 3 to 10 percent by weight. Preferably and especially with resins having a softening'point above 859C., the resinplast adjust the ball and ring softening point of the admixture to within 750C to 90or. The 95oC melt viscosity may range from 20,000 to 60,000 centipoises. The resinplast includes a wide variety of materials including petroleum oils ot the paraffinic, naphthenic and aromatic types, petroleum waxes, petrolatum, low molecular weight polyolefins such as low molecular weight, largely amorphous polyethylenes and similar materials. The resinplast must be compatible with the resin. By reducing the softening point and the melt viscosity of the resin, the resinplast promotes distribution of the water in the molten resin by making the resin softer and less cohesive, and thus more amenable to water addition and formation of small water droplets. Finally, the resinplast acts as a compatibilizer, making the resin more receptive to the emulsifier. An example of a preferred resinplast is naphthenic oils having a viscosity range of from 500 to 200Q SSU (at 1000F). The emulsifiers which have been found useful for producing the emulsions of the invention are a combination of a nonionic emulsifier with an anionic emulsifier. The nonionic emulsifier, for example, can be an ethoxylated alkyl phenol in which the alkyl group contains from 8 to 12, preferably about 9 carbon atoms. The-molar ratio-of ethylene oxide to alkyphenol is selected based on the chemistry of the particular resin. Useful ratios include 8 to 14, preferably 10 to 12 moles of ethylene' oxide per mole of alkyl phenol. Suitable anionic emulsifiers are the alkyl aryl sulphonates which are generally the alkali metal salts to make them water soluble. Highly useful for the practice of this invention is the sodium or calcium salt of dodecylbenzene sulfonic acid. In total amount as already indicated, the emulsifier ranges in weight from 3% to 10%, preferably 4% to 6%, by weight. Thus, in summary the non-water portion of the emulsion will have a concentration range of: resin ranging from 80% to 94% by weight; emulsifier ranging from 3% to 10%; resinplast ranging from 3 to 10%. The water content of the finished emulsion will range from 30 to 75 weight %. Any non-reactive additives may be used in the emulsion of this invention, for example, pigments, dyes and labeling agents. This invention also contemplates a method for the production of a hydrocarbon solid in water emulsion comprising the sequential steps of admixing, preferably by shearing agitation, from 3 to 10 parts by weight of an emulsifier preferably consisting of a nonionic polyoxyethylene alkyl aryl ether, anionic alkyl aryl sulfonate or mixtures thereof, with from 80 to 97 parts by weight of a molten hydrocarbon, preferably petroleum, resin and from 0 to 10 parts by weight of a resinplast, heating said admixture to above the softening point of the resin emulsifier, resinplast mixture, slowly adding water heated to about 1000C to said heated admixture with vigorous, high shear agitation over a time period, the length of which is critical, until inversion occurs, adding sufficient additional water with agitation to provide an aqueous emulsion containing from 30 to 75 weight % water and thereafter cooling to a temperature less than about 200C below the softening point of the mixture of emulsifier, resin and resinplast prior to terminating agitation. Finished emulsion is then typically strained using cheese cloth or a commercial filter bag or filter pack. As is indicated above, the water is dispersed in the resin admixture to form a water in oil emulsion using vigorous shearing agitation. The impeller design should maximize the portion of the mixing energy dissipation into the emulsion which is classified as shear. Various turbine impellers such as flat blade and disk type flat blade turbines and high shear proprietary design impellers such as the Fawcett mixed flow impeller are suitable. In the mixing procedure which has been detailed above, there appear to be certain critical aspects to this procedure which are hereinafter indicated. The mixing procedure involves, as indicated, the heating of the resin to a molten state and blending with the resinplast if used. Thereafter the emulsifier is added to the molten resin. This molten mix must be blended thoroughly to assure homogeneity. During this blending the admixture temperature is increased somewhat after which water at approximately 100or is metered into the admixture. Water addition can tend to reduce the temperature of the mixture. It is imperative that the temperature remain above the softening point of the resin-resinplast-emulsifier softening point, typically a minimum of SOC to 100C above, at all times prior to inversion. Further, high shear conditions should be used for the mixing, for example impeller rotational speed should be high (e.g. 550-700 rpm in a one liter laboratory unit) to ensure that the molten resin surface is continuously agitated and folded into the mix. During this time a water in oil emulsion is being obtained. When approximately 1/3 of the water addition is complete, it is highly desirable to terminate water addition for from 5 to 10 minutes while continuing vigorous agitation. It is essential that the critical time interval from first water addition to inversion be governed by short lapses in water addition in this manner. Such lapses are also useful to maintain mix temperatures, the importance of which is emphasized in the paragraph above. Mention has been made of the criticality of the time interval from first water addition to the point of emulsion inversion from water in oil to oil in water. Data indicate that for a given resin there is a mix time minimum, below which final resin emulsion particle size will be undesirably large. This critical mix time is dependent upon the power input to the mixture per unit volume of emulsion. Power input is directly related to impeller diameter and impeller rotational speed. This critical time interval can range from approximately 20 to 30 minutes in a small laboratory batch prepared employing the aforementioned very high impeller speeds to 2 plus hours in larger, plant units. It is within the skill of the art to determine the critical time and agitation requirement here for particular cases. Following inversion it is desirable to reduce the vigorous nature of the stirring to a slow stirring to minimize foam and to terminate batch heating. Water should now be added to the emulsion mix at a temperature materially reduced below boiling and continued until the desired solids level is obtained. The stirring is continued for from 5 to 10 minutes after completion of the water addition. Prior to terminating the stirring, the emulsion temperature must be reduced to a temperature of at least 200c below the resin-resinplast-emulsifier softening point in order to prevent particle size growth or skin development in the emulsion system. The aforementioned critical steps are vital to achieve excellent low particle size and the exceptional, unique stability exhibited by these hydrocarbon resin emulsions. Thus one may also produce an aqueous emulsion of a blend of a hydrocarbon resin having a ring and ball softening point of at least 900cm preferably 950C to 1250C and a hydrocarbon resin having a softening point less than 800C, said emulsion comprising from 3 to 10 parts by weight of an emulsifier of the class defined above, from 90 to 97 parts by weight of said bled bf hydrocarbon resins and the balance water. The emulsions of the present invention are useful as tackifiers in emulsion adhesive systems which generally contain emulsions of natural or synthetic rubber. Examples of synthetic rubber emulsions that are used are styrene butadiene rubber latexes which may or may not be carboxylated. Other suitable rubber emulsions are natural rubber emulsions such as neoprene emulsions. These adhesive formulations may be used for the production of labels, pressure sensitive adhesive tapes, contact adhesives and adhesives for use in the building industry and floor coverings. The example set forth below illustrates several embodiments of the invention and are not to be construed as limiting in any manner. EXAMPLE 1 85 parts by weight of a non-polar, 930C soften ing point petroleum resin, Escorez 2101 sold by Exxon Chemical Americas, Houston, Texas is heated to a tempera ture of about 1150C and admixed with 10 weight parts of naphthenic oil and 5 weight parts of Atlox 3404 F emul sifier sold by ICI Americas Inc. The Atlox 3404 F is reported to be a blend of polyoxyethylene alkyl -aryl ether and alkyl aryl sulfonate. The molten resin is blended with the naphthenic oil, then the emulsifier is stirred into the resin-resinplast blend until a complete and thorough blend of all three ingredients is achieved. The resin-resinplast-emulsifier admixed blend is heated at approximately 1200C at which time the first third of water is metered in at a temperature of approximately 100 C. Actual water addition will exceed 1/3 to make up for water evaporation. The metering in continues with fast blending speed, i.e. 550-700 rpm, so as to make certain that the resin admixture is continuously agitated and that the water is folded into the mix. The temperature during this initial metering is kept at about 88-930C in order to maintain a viscosity at appropriate levels to facilitate the mixing. When approximately 1/3 of the water has been added, the system is mixed vigorously for 5 to 10 minutes after which the hot water addition is resumed while main taining the temperature of the system at about Several additional, spaced water additions are utilized to prolong mixing and control batch temperature. Hot 1water addition continues until inversion occurs at which time the supply of heat to the system is terminated. The balance of the water is added at ambient temperature and the stirrer speed is reduced to minimize foam. Water addition continues with low stirring and upon its com pletion stirring continues from 5 to 10 minutes. Prior to terminating agitation it is necessary to cool the mixture to approximately 200C below the ring and ball softening point of the mixture of resin-resinplast-emulsifier or to about 600C. Upon terminating agitation the resin emulsion is passed through a cheese cloth so as to remove any large flakes or dried particles. In a laboratory mix typical times are as follows: resin melting and blending of resinplast and emulsifier - 30 to 45 minutes, water addition to the inversion point - 20 to 45 minutes, final dilution and cooling - about 15 minutes. The resulting emulsion is slightly off-white in color, smooth not gritty to the touch, dries to a very fine powder on the finger tips and will not separate even after months of shelf storage (unagitated). Particle sizes averaging 0.5 micron have been achieved which makes such emulsions excellent components for emulsion adhesives. EXAMPLE 2 90 parts by weight of a non-polar, 940C soften ing point petroleum resin, Escorez 1310 sold by Exxon Chemical Americas, Houston, Texas, is heated to a tempera ture of about 1150C and admixed with 5 weight parts of naphthenic oil and 5 weight parts of Atlox 3404 F emulsi fier sold by ICI Americas, Inc. Emulsion preparation pro cedures follow the same course as in Example 1. The resulting emulsion is white in color but otherwise similar :to that in Example 1 in appearance, feel and properties. This emulsion, too, is an excellent component for use in water based adhesives. As is apparent from the foregoing description, the emulsion preparation procedure has the advantage that it does not require either reduction or increase in pres sure to achieve the emulsion, i.e. the emulsion can be carried out at normal atmospheric pressure. EXAMPLE 3 Hydrocarbon resin prepared from feed having a boiling range between about 300C and 2000c and having a ring and ball softening point of about 600c is blended with a hydrocarbon resin prepared with feed having a boiling range between about 1000C and 2800C and having a softening point of 1150C, in a 70/30 ratio. The emulsifier used in the emulsification of this resin blend was an ethoxylated nonylphenol having 12 moles of ethylene oxide per mole of nonylphenol. This blend of resin was emulsified according to the procedure given below: Heat 250 grams of the blend of resins to a molten state in a 500 ml resin flask with a stirrer; Add 12.5 grams of an emulsifier to the molten resins (approximately at 1200C) and blend thoroughly; Maintain the resins at about 950C and begin metering in 1000C water at an addition rate of about 5 ml/min with continuous fast stirring at a speed of 500-600 rpm to ensure the resins surface is continuously agitated and folded.into the mix. Monitor and control the temperature to a minimum of 850C and preferably between 90 and 950C; After inversion, turn off heat and increase the water addition rate; and After the water addition is complete, the emulsion is stirred 5 more minutes and cooled to about 300C. The amount of water added can range in amounts to provide a solids content of 25 to 70 percent. EXAMPLE 4 50 parts of the resin emulsion produced according to Example 1 was mixed with 100 parts of various commercially available carboxylated styrene/butadiene rubber latices. The mixture was coated onto cellophane or polyester to produce an adhesive tape and the pressure sensitive adhesive properties were determined by the methods developed by the technical committee of the Pressure Sensitive Tape Council (PSTC) and more especially 1800C Peel Adhesion (PSTC-1 method) Tack Rolling Ball Method (PSTC-6), Polyken Tacks and Shear Adhesion (PSTC-7). The results were as follows: Latex 180 Peel Strength Ball Tack Polyken Tack Shear (PSTC-7) (g/cm) (cm) (g) (hours) Polysar PL 110 560 > 25 460 68 XE 222 620 > 25 880 4.2 XE 378 480 > 25 370 34.5 Amscores 6140 380 > 25 330 32.7 Revinex EL 8101 900 22 420 12.3 EL 8102 850 11 640 26.0 Bayer KA 8245 800 3 880 1.0 EXAMPLE 5 Example 4 was repeated except using the resin emulsion of Example 2 and the adhesive properties were as follows: : Latex 180 Peel Strength Ball Tack Polyken Tack Sheer (PSTC-7) (g/cm) (cm) (g) (hours) Polysar PL 110 300 > 25 260 > 200 XE 222 380 > 25 480 15 XE 378 255 > 25 180 62.3 Amscores 6140 140 > 25 80 > 300 Revinex EL 8101 500 > 25 660 30.7 EL 8102 500 19 490 47.2 Bayer KA 8245 500 6 630 44.0 It will be apparent from the foregoing that, although particular forms of the invention have been illustrated and described, various modifications can be made without departing from the spirit and scope of the invention. Accordingly it is not intended that the invention be limited except by the appended claims.

Claims: CLAIMS: 1. A blend suitable for providing a resin in water aqueous emulsion of a hydrocarbon resin by an inversion process comprising from 3 to 10 parts by weight of an emulsifier blended with a mixture of from 3 to 10 parts by weight of resinplast and 80 to 94 parts by weight of said hydrocarbon resin. 2. A blend according to claim 1 wherein said emulsifier is present in from 4 to 6 parts by weight. 3. A blend according to claims 1 or 2 wherein said resinplast is a naphthenic -oil. 4. A blend according to any of the preceding claims in which the hydrocarbon resin has a ring and ball softening point of at least 85eC. 5. A blend according to claim 3 wherein said emulsifier is present in about 5 parts by weight, said naphthenic oil is present in about 5 parts by weight and said resin is a petroleum resin having a softening point of from 900c to 95C and is present in about 90 parts by weight. 6. A blend according to any of the preceding claims having a ring and ball softening point of from 75C to 90-C and a 95*C melt viscosity ranging from 20,000 to 60,000 centipoises. 7. An aqueous emulsion of a hydrocarbon resin having from 30 to 75 weight % water and 70 to .25 weight % of a mixture comprising from 3 to 10 parts by weight of an emulsifier, 3 to 10 parts by weight of a resinplast and from 80 to 94 parts by weight of said hydrocarbon resin. 8. An aqueous emulsion of a hydrocarbon resin according to claim 7 in which the resin has a ring and ball softening point of at least 850 C. 9. An aqueous emulsion of a hydrocarbon resin according to claim 7 or claim 8 in which the emulsifier is a nonionic polyoxyethylene alkyl aryl ether, anionic alkyl aryl sulphonate or mixture thereof. 10. The use of an aqueous emulsion according to any of claims 7 to 9 as a tackifier in pressure sensitive adhesives and contact adhesives. 11. A method for the production of a hydrocarbon resin in water emulsion comprising the sequential steps of admixing from 3 to 10 parts by weight of an emulsifier with from 80 to 97 parts by weight of a molten hydrocarbon resin and from 0 to 10 parts by weigh; of a resinplast, slowly adding water heated to about 100it to said admixture whilst at a temperature above the softening point of the resin, emulsifier, resinplast mixture with stirring over a period of at least 20 minutes and until inversion occurs, and then adding sufficient additional water with agitation to provide an aqueous emulsion containing from 30 to 75 weight % water and thereafter cooling to a temperature at least about 200C below the softening point of the mixture of emulsifier, resin and resinplast prior to terminating agitation. 12. A method according to claim 11 in which the resin has a ring and ball softening point above 85'C. 13. A method according to claim 11 or 12 in which the emulsifier is a non ionic polyoxyethylene alkyl aryl ether, anionic alkyl aryl sulfonate or mixtures thereof. 14. A method according to any of claims 11 to 13 wherein said stirring is vigorous agitation and the temperature of said admixture is at least 50 - 100C above its softening point prior to inversion. 15. A method according to claim 11 in which the feed hydrocarbon resin is a blend of a hydrocarbon resin having a softening point in the range of about 95O to about 125µC and a hydrocarbon resin having a softening point below about 80'C. 16. A method according to claim 15 in which said first mentioned resin has a softening point of about 1250C.

Inventors: EVANS, MORRIS LEE, JAGISCH, FRANK CARL
Applicants: EXXON RESEARCH AND ENGINEERING COMPANY
Application year: 1983
Main classification: C08L101
IPC codes: C08J3, C08L57